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  • 51.
    Bakar, Muhammad Abu
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Alam, Farhan Muhammad
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Modeling and Characterization of Series Connected Hybrid Transformers for Low-Profile Power Converters2020Inngår i: IEEE Access, E-ISSN 2169-3536, Vol. 8, s. 53293-53306Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Compact and low profile power converters are the main business of today's power industry. A significant volume of a power converter is occupied by the power transformer. This article proposes a unique solution that would make the power converters low profile. Instead of designing a power converter by using a single bulky transformer, the solution proposed is to split the main bulky transformer into a number of low profile transformers. This not only reduces the total weight and volume of the converter but also the total transformer losses. The use of more than one transformer in series reduces the applied voltage on the transformers, which minimizes the required turns ratio and decreases the stress on the secondary rectifiers and filter elements. Moreover, the decrease in the applied voltage reduces the proportional loss per transformer and makes it possible to design a hybrid transformer by combining Litz wire and traces of a printed circuit board. The reduced copper loss and lower heat dissipation per transformer simplify thermal management. An analytical comparison is made between the utilization of a single transformer or a number of transformers. The procedure of splitting a volume of a single transformer into a number of small transformers has been comprehensively discussed. The idea is investigated both experimentally and in computer simulation for an example application of a phase shifted full bridge dc-dc converter. The converter is characterized up to a load power of 2.2 kW at Vin = 400 Vdc and Vout = 48 Vdc. To make the approach more practical, the transformers are modeled using the traditional analytical method. The design of the example application using the split transformer approach reduces the total transformer weight by 45%, compared to the traditional approachwith a single transformer. The converter also shows good performance with a maximum efficiency of 96%.

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  • 52.
    Bakar, Muhammad Abu
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Alam, Farhan Muhammad
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Das, Moumita
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Barg, Sobhi
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Reconfigurable three state dc-dc power converter for the wide output range applications2019Inngår i: IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society, Lisbon: IEEE, 2019, s. 4911-4916Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Improving the dc voltage gain of power converters has been the primary focus of the current and past research in the area of power electronics. This work presents another solution to widen the range of the output voltage. It proposes three reconfigurable steps for the output voltage. The range of theoutput voltage varies up to four times the base level. These configurations together vary the output voltage from 15 to 96 volts. A soft switched dc-dc power converter is built with the traditional topology of phase shifted full bridge converter along with improved characteristics. For better management of thetransformer loss, a configuration of four transformers has been employed. The proportional gate drive approach is implemented to obtain four similar isolated blocks of the output voltage. This makes it possible to either configure these blocks all in series,parallel or in series/ parallel combination of two. The concept is verified in a low-profile prototype. The hardware is characterized up to the load power of 1kW for the input voltage of 400Vdc. The converter reports better efficiency over the complete range of output voltage.

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  • 53.
    Bakar, Muhammad Abu
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Alam, Farhan Muhammad
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Majid, Abdul
    COMSATS University Islamabad.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Dual-mode stable performance Phase-Shifted Full-Bridge converter for wide-input and medium power applications2021Inngår i: IEEE transactions on power electronics, ISSN 0885-8993, E-ISSN 1941-0107, Vol. 36, nr 6, s. 6375-6388Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Power converters with an extended range of line voltage are the main requirement in today's industrial applications like photovoltaic and supercapacitors based energy systems. The variation in the line voltage severely degrades the performance of power converters, because of the extended freewheeling interval, more circulation current, narrow range of zero voltage switching and increased EMI. This work suggests a modified Phase-Shifted Full-Bridge converter that cuts the freewheeling interval and minimizes these problems. It extends the input voltage range by keeping the operational duty cycle of the converter high over the wide range of input voltage while maintaining the performance stable. The proposed converter consists of four low profile transformers having reconfigurable interconnection structure. There are two distinct reconfigurable modes, a series mode and a parallel mode, which can be configured with changes in the operational conditions. The operation of the proposed converter with high switching frequency improves power density. Additionally, the use of multiple transformers minimizes heat management efforts and reduces the overall volume of the converter. The proposed work is validated in hardware characterization for a wide range of input voltage 100-400Vdc and up to the load power of 1kW. The measured energy efficiency of the proposed converter remains stable over the complete range input voltage 100-400Vdc.

  • 54.
    Bakar, Muhammad Abu
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Alam, Farhan Muhammad
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Shalchi Alishah, Rasoul
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Characterization of phase shifted full bridge converter along with GaN devices and series-connected hybrid transformers for medium power applications2020Inngår i: / [ed] IEEE, 2020, s. 1058-1064Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Compact power converters are the major concern of today’s power industry. This article proposes GaN devices based isolated dc-dc phase shifted full bridge converter along with the configuration of four series-connected hybrid transformers. The series connection of transformers reduces the applied volt-second on each transformer which reduces the proportional losses and simplify thermal management. This configuration also reduces the required turn’s ratio as well as bringing down the stress on the secondary devices and filters. The converter is characterized in a compact prototype up to the load power of 2.2 kW for Vout=48 Vdc at Vin=400 Vdc. The converter reports satisfactory performance with a maximum efficiency of 96%.

  • 55.
    Bakar, Muhammad Abu
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Alam, Farhan Muhammad
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Wårdemark, Mats
    Powerbox International AB, SWEDEN.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    A 2x3 Reconfigurable Modes Wide Input Wide Output Range DC-DC Power Converter2021Inngår i: IEEE Access, E-ISSN 2169-3536, Vol. 9, s. 44292-44303Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is an increasing demand for efficient and low-profile power converters in almost all industrial applications. Some require stable performance over a wide range of input voltages, whereas others require converters with a stable performance over a wide range of output voltages. In this regard, little work has been done to combine both requirements into one solution. This work suggests a unique solution that addresses both requirements at once. A power converter with 2x3 reconfigurable modes has been presented, able to operate with DC gains of 1, 2 and 4, which can be further extended to 8. The converter shows stable performance for the extended range of both input and output voltage. The flexible reconfigurable feature of the proposal can be applied in a variety of applications. Two reconfigurable modes on the input side can be configured following the variation in the line voltage to maintain a stable performance, and three reconfigurable modes for the output voltage, which raises the output voltage from 24V to 48V and 96V. The proposal is applied in an example application of a phase shifted full bridge converter. The converter is characterized for Vin = 100-400Vdc, Pout = 1kW. CCBY

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  • 56.
    Bakar, Muhammad Abu
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    A Modified Higher Operational Duty Phase Shifted Full Bridge Converter for Reduced Circulation Current2020Inngår i: IEEE Open Journal of the Industrial Electronics Society, ISSN 2644-1284, Vol. 1, s. 82-96Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Besides many advantages, the reduction in the operational duty of traditional phase shifted full converter limits its scope in applications where a wide range of input voltage is the main requirement. Operation with low duty cycle extends freewheeling interval, which results in degraded performance such as more circulation current, increased conduction loss in power devices, narrow range of zero voltage switching and increased EMI. To overcome these drawbacks, this work suggests a modified phase shifted full bridge converter that keeps the operational duty of the converter high for a wide range of input voltage. This cuts the freewheeling interval and improves performance. The proposed converter consists of four low profile transformers having reconfigurable interconnection structure. There are two distinct reconfigurable modes, a low gain mode and a high gain mode, which can be adopted in accordance with the variation in line voltage. The proposed work is validated in LTspice simulation and hardware characterization for a wide range of input voltage 100-400Vdc/12Vout and up to the load power of 1.2kW.

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  • 57.
    Bakar, Muhammad Abu
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Haller, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Contribution of Leakage Flux to the total Losses in Transformers with Magnetic Shunt2021Inngår i: International journal of electronics (Print), ISSN 0020-7217, E-ISSN 1362-3060, Vol. 108, nr 4, s. 558-573Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    To execute soft switching methods in resonant power converters, transformers with larger leakage inductance are getting more attention. Many papers have constructed various concepts in this regard. However, a discussion about, how the transformer efficiency is affected is lacking in the literature. This paper analyses the effects of the increased leakage inductance on the performance of the transformer. A transformer for increased leakage inductance is modelled and constructed to investigate the losses. The model discusses the effects of increased leakage inductance either by increasing the inter-winding spacing or by integrating the magnetic shunt within the transformer. The investigations show that increasing the leakage inductance by inserting a magnetic shunt can have severe degrading effects on the performance of the transformer, if not designed adequately. Additional losses are also calculated and the effects are verified by the experiments.

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  • 58.
    Balliu, Enkeleda
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Power Scaling of Highly Compact Single-Frequency Yb-Doped Fiber Amplifiers2022Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Both scientific interests and industrial applications have stimulated the advance of single-frequency laser technology. The high spatial and temporal coherence of this technology has facilitated many applications such as gravitational wave detection, high-precision fiber sensors, high-resolution spectroscopy, holography, and nonlinear optical conversion. However, this is currently achieved through large footprint lasers with limited portability and mobility. Therefore, there is a need to reduce the size of these lasers into a compact format. Power performance of hundreds of watts in the near-infrared spectrum and tens of watts in the visible and UV spectra for continuous (CW) operation mode and pulse energies up to several tens of mJ in pulsed operation mode are needed. 

    An amplification structure for single-frequency lasers that meets these requirements is the master oscillator power amplifier (MOPA). However, compactness imposes several constraints on the MOPA design. The main challenge is the limited output power of the single-frequency fiber MOPA due to the onset of stimulated Brillouin scattering (SBS) in the amplifier fiber. SBS arises from the interaction of acoustic phonons with the propagating signal wave and is converted into a frequency-shifted, backward-propagating wave. SBS is manifested through high-intensity pulses propagating in the backward direction, which can be very harmful for optical components and the seed laser itself. Hence, the suppression of SBS is crucial to the power optimization of the MOPA. This thesis therefore focuses on investigating different SBS suppression techniques that fit a compact MOPA design. More specifically, this is implemented by studying the efficiency of the strain distribution technique applied to the amplifier fiber and the use of custom and commercial highly Yb- doped fibers both in CW and pulse operating MOPAs. Using highly Yb-doped fibers presents challenges with respect to the composition of the fiber material and in high- power operation that can have undesirable degradational effects, such as photodarkening and thermal load generation, and these have been investigated and discussed in this thesis. 

    As a result of the different mitigation approaches, output power approaching 100 W in CW mode operation and pulse energies near mJ in pulse mode operation are demonstrated in only one amplification stage, showing the feasibility of a MOPA design with high performance and a small footprint. This may facilitate many applications in the visible and UV spectral ranges that require mobility and portability. 

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  • 59.
    Balliu, Enkeleda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Boetti, Nadia G.
    LINKS Foundation - Leading Innovation and Knowledge for Society, Via P. C. Boggio 61, 10138, Torino, Italy.
    Pugliese, Diego
    DISAT - Politecnico di Torino and RU INSTM, C.so Duca degli Abruzzi 24, 10129, Torino, Italy.
    Lousteau, Joris
    CMIC - Politecnico di Milano, Via Mancinelli 7, 20131, Milano, Italy.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Milanese, Daniel
    DIA - Università di Parma and RU INSTM, Parco Area delle Scienze 181/A, 43124, Parma, Italy.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Single-frequency, pulsed Yb3+-doped multicomponent phosphate power fiber amplifier2020Inngår i: Journal of Optics, ISSN 2040-8978, E-ISSN 2040-8986, Vol. 22, nr 11, artikkel-id 115606Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-power, single-frequency, pulsed fiber amplifiers are required in light detection and ranging, coherent laser detection, and remote sensing applications to reach long range within a short acquisition time. However, the power-scaling of these amplifiers is limited by nonlinearities generated in the optical fibers, in particular by stimulated Brillouin scattering (SBS). In this regard, the use of multicomponent phosphate glasses maximizes the energy extraction and minimizes nonlinearities. Here, we present the development of a single-stage, hybrid, pulsed fiber amplifier using a custom-made multicomponent Yb-doped phosphate fiber. The performance of the phosphate fiber was compared to a commercial Yb-doped silica fiber. While the latter showed SBS limitation at nearly 6.5 kW for 40 cm length, the maximum achieved output peak power for the multicomponent Yb-doped phosphate fiber was 11.7 kW for 9 ns pulses using only 20 cm with no sign of SBS.

  • 60.
    Balliu, Enkeleda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Digonnet, Michel J. F.
    Coetzee, Riaan. S.
    Elgcrona, Gunnar
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Compact single-frequency mopa using a silica fiber highly doped with yb3+2021Inngår i: Applied Sciences, E-ISSN 2076-3417, Vol. 11, nr 21, artikkel-id 9951Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on a single-frequency fiber master oscillator power amplifier utilizing a polarization-maintaining step-index fiber with an Al/Ce/F core-glass composition doped with a very high Yb concentration (0.25 at.%). This design made it possible to use a very short fiber (~1 m) and to coil it in a tight radius (4 cm in the amplifier, while 2 cm gave similarly negligible bending loss) so that the packaged system is one of the most compact reported to date (~0.6 L). The use of a short fiber increased the threshold for stimulated Brillouin scattering well above 100 W while maintaining near-ideal beam quality. The fiber was pumped with a diode-pumped solid-state laser and cooled passively by spooling it on a grooved aluminum mandrel. The amplifier produced a strongly linearly polarized output at 1064 nm in the fundamental mode (M2 ≤ 1.2) with a 150 kHz linewidth and a power of 81.5 W for 107 W of launched pump power. No deleterious effects from the elevated thermal load were observed. The residual photodarkening loss resulting from the high Yb concentration, found to be small (~0.7 dB/m inferred at 1064 nm) with accelerated aging, reduced the output power by only ~20% after 150 h of operation. 

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  • 61.
    Balliu, Enkeleda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Digonnet, Michel J. F.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Quasi‐cw pumping of a single‐frequency fiber amplifier for efficient shg in ppln crystals with reduced thermal load2022Inngår i: Applied Sciences, E-ISSN 2076-3417, Vol. 12, nr 1, artikkel-id 285Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Single‐frequency lasers are essential for high‐resolution spectroscopy and sensing applications as they combine high‐frequency stability with low noise and high output power stability. For many of these applications, there is increasing interest in power‐scaling single‐frequency sources, both in the near‐infrared and visible spectral range. We report the second‐harmonic generation of 670 μJ at 532 nm of a single‐frequency fiber amplifier signal operating in the quasi‐continuous‐wave mode in a 10‐mm periodically poled Mg‐doped lithium niobate (MgO:PPLN) crystal, while increasing compactness. To the best of our knowledge, this is the highest pulse energy generated in this crystal, which may find applications in the visible and UV such as remote Raman spectroscopy. 

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  • 62.
    Balliu, Enkeleda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    A compact, single-frequency, high-power, SBS-free, Yb-doped single-stage fiber amplifier2019Inngår i: Proceedings of SPIE - The International Society for Optical Engineering / [ed] W. Andrew Clarkson and Ramesh K. Shori, SPIE - International Society for Optical Engineering, 2019, Vol. 10896, s. 6pp-, artikkel-id 1089618Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Interest in compact, single-frequency fiber amplifier has increased within many scientific and industrial applications. The main challenge is the onset of nonlinear effects, which limit their power scaling. Here we demonstrate a compact, high-power, single-frequency, polarization-maintaining, continous-wave fiber amplifier using only one amplification stage. We developed the fiber amplifier using a master oscillator fiber amplifier architecture, where a low-noise, single-frequency, solid-state laser operating at 1064 nm was used as a seed source. We evaluated the amplifier's performance by using several state-of-the-art, small-core, Ytterbium (yb)-doped fibers, as well as an in-house-made, highly Yb-doped fiber. An output power of 82 W was achieved with no sign of stimulated Brillouin scattering. A good beam quality and a polarization extinction ratio (PER) of > 25 dB were achieved. The compact fiber amplifier can be a competitive alternative to multi stage designed fiber amplifiers.

  • 63.
    Balliu, Enkeleda
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Thontakudi, Anjali
    Monta Vista High School, Cupertino, CA USA.
    Knall, Jenny M.
    Stanford University, Stanford, CA USA.
    Digonnet, Michel J. F.
    Stanford University, Stanford, CA USA.
    Predictive comparison of anti-Stokes fluorescence cooling in oxide and non-oxide fiber hosts doped with Er3+, Pr3+, or Yb3+2019Inngår i: Proceedings of SPIE - The International Society for Optical Engineering: Photonic Heat Engines: Science and Applications, SPIE - International Society for Optical Engineering, 2019, Vol. 10936, artikkel-id 109360JKonferansepaper (Fagfellevurdert)
    Abstract [en]

    A comprehensive study was performed to quantify anti-Stokes-fluorescence (ASF) cooling in fibers of various host compositions (telluride, fluorozirconates, fluorophosphates, phosphates, and chalcogenides) doped with Yb3+ or Er3+. Published expressions were used to calculate the maximum heat that can be extracted per unit length and time from a single-mode fiber in the limit of negligible absorptive loss, and the associated cooling efficiency. These expressions consider host- and ion-dependent parameters, namely the absorption and emission cross-section spectra, the radiative and nonradiative lifetimes, and the critical concentration for quenching. Using these expressions with published values for these parameters, the maximum extractable heat was calculated for a large-mode-area fiber (NA = 0.05) doped with either Yb3+ or Er3+ in a variety of hosts. The results show that for a given ion, the maximum heat that can be extracted depends strongly on the host due to the strong dependence of quenching on host composition. In contrast, the cooling efficiency (ratio of extracted heat to pump power absorbed) depends very weakly on the host. The cooling efficiency is also almost twice as high for Er3+ (average of 3.8%) than for Yb3+ (average of 2.2%) due to the larger gap between the pump and mean fluorescence energy in Er3+. Of the limited number of materials for which a full set of data was found in the literature, the highest extractable heat for Yb3+ is in phosphate (-51.5 mW/m), and for Er3+ is in chalcogenide (-10.3 mW/m). This work provides a simple methodology to evaluate the quantitative cooling performance of these and other rare-earth ions in any amorphous host, a procedure that should guide researchers in the selection of optimum materials for ASF cooling of fibers.

  • 64.
    Barg, Sobhi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Alam, Farhan Muhammad
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Modeling of the Geometry Effect on the Core Loss and Verification with a Measurement Technique Based on the Seebeck Effect and FEA2019Inngår i: IECON 2019 - 45th Annual Conference of the IEEE Industrial Electronics Society / [ed] IEEE, IEEE, 2019, s. 1832-1837Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper, the effect of the core geometry of non-toroidal magnetic cores on the magnetic loss is investigated. A frequency dependent core material-geometry loss factor is developed. This factor is function of the change in the non-toroidal core section and the Steinmetz parameter “β”. In addition, the temperature effect is included in the developed loss model for wide range of frequency and magnetic flux density. The model is applied for ER core and 3C92 ferrite material. The core loss measurements are performed using a Peltier cell. The principle of operation of the Peltier cell is based on the Seebeck effect, which convert the heat flow due to the temperature difference into electric power.  The calibration of the Peltier cell is validated with a resistive load and a relative error lower than 1% is achieved. The accuracy of the developed model is assessed with FEA and the experimental results. A maximum error of 10% is registered of the developed core loss model.

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  • 65.
    Barg, Sobhi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Alam, Farhan Muhammad
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Optimization of High Frequency Magnetic Devices with Consideration of the Effects of the Magnetic Material, the Core Geometry and the Switching Frequency2020Inngår i: 2020 22nd European Conference on Power Electronics and Applications, EPE 2020 ECCE Europe, IEEE, 2020, artikkel-id 9215860Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents an optimization approach of high frequency transformers based on the calculation of the optimum number of turns. The relationship between the volume, the power and the frequency is also investigated. The design approach considers the skin and proximity effects, the core geometry and the magnetic material. 

  • 66.
    Barg, Sobhi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Core Loss Calculation of SymmetricTrapezoidal Magnetic Flux Density Waveform2021Inngår i: IEEE open Journal of Power Electronics, E-ISSN 2644-1314, Vol. 2, s. 627-635Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Existing empirical core loss models for symmetric trapezoidal flux waveform (TzFW) stillsuffer some issues such as the inaccuracy and the complexity. These issues are mainly due to the lack ofan accurate model of the relaxation loss generated during the off-time. This paper aims to understand therelaxation loss and develop an accurate model using the superposition technique. The developed model givesan accurate prediction of the on-time loss and the relaxation loss and shows the dependency of each on theduty cycle. The research shows that the core loss at low duty cycle is several times the core loss at full dutycycle. The developed model is verified with experimental results and compared to the Improved Steinmetzequation (ISE). The model error is reduced to lower than 15% compared to 50% of the ISE. Finally, an easymethod using multiplication factors with the ISE model is given to simplify the developed model.

    Fulltekst (pdf)
    Core Loss Calculation of SymmetricTrapezoidal Magnetic Flux Density Waveform
  • 67.
    Barg, Sobhi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Core Loss Modeling and Calculation for Trapezoidal Magnetic Flux Density Waveform2021Inngår i: IEEE Transactions on Industrial Electronics, ISSN 0278-0046, E-ISSN 1557-9948, Vol. 68, nr 9, s. 7975-7984Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This paper proposes a novel approach in order to understand the different kinds of core loss of the trapezoidal flux waveform. The proposed approach is based on the theory of magnetism and assessed with the experimental results to show that the total loss is composed by two terms: the effective triangular loss during the on-time resulting from the flux variation and the relaxation loss during the off-time which is due to the magnetic after-effect phenomenon. The study shows that the relaxation loss depends on the off-time and it has a maximum at a particular off-time-to-on-time ratio which depends on the magnetic material. In addition to that, two models with accuracy higher than 96% and with reduced number of parameters compared to the existing models were developed to predict the relaxation loss. The models are verified with previous experimental results and new experiments performed in this work.

  • 68.
    Barg, Sobhi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Multi‑objective Pareto and GAs nonlinear optimization approach for fyback transformer2019Inngår i: Electrical engineering (Berlin. Print), ISSN 0948-7921, E-ISSN 1432-0487, Vol. 101, nr 3, s. 995-1006Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Design and optimization of high-frequency inductive components is a complex task because of the huge number of variables to manipulate, the strong interdependence and the interaction between variables, the nonlinear variation of some design variables as well as the problem nonlinearity. This paper proposes a multi-objective design methodology of a 200-W flyback transformer in continuous conduction mode using genetic algorithms and Pareto optimality concept. The objective is to minimize loss, volume and cost of the transformer. Design variables such as the duty cycle, the winding configuration and the core shape, which have great effects on the former objectives but were neglected in previous works, are considered in this paper. The optimization is performed in discrete research space at different switching frequencies. In total, 24 magnetic materials, 6 core shapes and 2 winding configurations are considered in the database. Accurate volume and cost models are also developed to deal with the optimization in the discrete research space. The bi-objective (loss–volume) and tri-objective (loss–volume–cost) optimization results are presented, and the variations of the design variables are analyzed for the case of 60 kHz. An example of a design (30 kHz) is experimentally verified. The registered efficiency is 88% at full load.

    Fulltekst (pdf)
    fulltext
  • 69.
    Barg, Sobhi
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Torrico, Grover
    A Novel Concept to Optimize Core Loss in Planar Magnetic Based on an Unbalanced-Flux-Approach2022Inngår i: 2022 24th European Conference on Power Electronics and Applications (EPE'22 ECCE Europe), IEEE conference proceedings, 2022Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper presents a new method to design planar magnetics. Unlike existing magnetics which have a balanced-flux distribution, the proposed method is based on the principle of unbalanced-flux distribution. The Steinmetz model, derived for this design principle, shows that the unbalanced-flux method reduces the core loss by more than 50%. The core loss reduction brings several benefits to planar magnetics such as: high magnetic power factor, better thermal performance and larger safe operating area (SOA). The proposed method is experimentally evaluated and compared with the balanced-flux method. The obtained results confirmed the advantages of the unbalanced-flux method found from the theoretical study. The core loss is decreased by more than 50%, the magnetic power factor is increased by 73% and the SOA is much larger.

  • 70.
    Beganovic, Nejra
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Moulik, Bedatri
    Amity University.
    Ali M., Ahmed
    University of Duisburg-Essen.
    Söffker, Dirk
    University of Duisburg-Essen.
    Lifetime Model Development for Integration in Power Management of HEVs By Terms of Minimizing Fuel Consumption and Battery Degradation2019Inngår i: Proceedings of the Annual Conference of the PHM Society 2019, PHM Society , 2019, Vol. 11, s. 1-8, artikkel-id 784Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Along with increasingly frequent use of electric and hybrid electric vehicles, the constraints and demands placed on them become stricter. The most noticeable challenge considering Hybrid Electric Vehicles (HEVs) is to provide an optimal power flow between multiple electric sources alongside provided as less as possible aging of energy storage components. To provide efficient battery usage with respect to battery life, it becomes unavoidable to develop battery lifetime models, which not only reflect the State-of-Heath (SoH) but also allow battery lifetime prediction. The lifetime-oriented battery models have to be integrated into power management. To be used efficiently and to provide optimal power split ensuring mitigation of battery degradation without sacrificing desired power consumption, accurate modeling of battery degradation is of utmost importance. This implies that gradual battery degradation, which is directly affected by applied loading profiles, has to be monitored and used as additional control input. Moreover, the lifetime model developed in this case has to provide model outputs also in the timeframe of power management. In this contribution, a machine state-based lifetime model for electric battery source was developed. In this particular case, different degradation states as well as machine state transitions are identified in accordance with current operating conditions. Here, the change in charge / discharge rate (C-rate), overcharging / undercharging of the battery (depth-of-discharge), and the temperature are taken into consideration to define machine model states. The End-of-Lifetime (EoL) is defined as the deviation between nominal and current ampere-hour (Ah) throughput. The proposed machine state-based lifetime model is verified based on existing battery lifetime models using simulation setup. The developed lifetime model in this way serves as a prerequisite for its integration into power management with an aim to provide the trade-off between aforementioned conflicting objectives; fuel consumption and battery degradation.

    Fulltekst (pdf)
    PHM784_OpenAccess
  • 71.
    Bergsten, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Tillståndsbaserad dynamisk korrigering av produktionsvärde2020Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Detta arbete har med hjälp av logiska samband tagit fram en matematisk formel samt logiska villkor för att tillämpa en dynamisk offset för ett felvisande produktionsvärde. Arbetet grundar sig i hur en känslig konsistensgivare påverkas vid avsaknad av tillräcklig blandning av pappersmassa, liksom hur en dynamisk offset kan korrigera produktionsvärdet och vara en temporär lösning tills en mer långsiktig lösning kan implementeras i produktionen. Konsistensen på massan används för att få fram koncentrationen fibrer, vilket i sin tur är en del av uträkningen för produktionsvärdet i pressen. Genom att analysera vilka parametrar som identifierar en stabil produktion kunde ett tillstånd hittas där produktionsvärdet ska vara densamma som i produktionen för föregående press. Om en parameter ändrar sig så kommer inte värdet att korrigeras utifrån produktionsvärdet i pressen innan. Behovet av ett korrekt produktionsvärde är kritiskt då det används senare i processen för en korrekt blandning av kemikalier och spädvätska, med hjälp av denna metod har den uppmätta produktionsskillnaden mellan press 6 och 7 minskar med cirka ≈ 16 ton/h i snitt till enbart ≈ 0,200 ton/h.

     

    Fulltekst (pdf)
    fulltext
  • 72.
    Björklund, Johannes
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    PLC-simulering: Virtuell balningslinje i felsökningssyfte2019Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Eftersom Valmet inte har någon metod för att testa styrsystemen för transportörerna de levererar med sina balningslinjer går mycket tid åt till att felsöka på plats. De söker därför en metod som gör det möjligt att simulera styrsystemen för att hitta och lösa fel innan leverans. Tryckt litteratur och artiklar publicerade i vetenskapliga journaler har varit grunden till den studie som utförts under arbetet. Ett tillhandahållet styrsystem innehållande en typ av transportör har studerats för att få förståelse för dess funktion. För att simulera krävs en modell som representerar och uppför sig som systemet i fråga. Om simuleringen ska vara användbar måste modellen vara tillräckligt exakt. En väl fungerande simulering är till väldigt stor fördel då denna kan förhindra förseningar, ge bättre arbetsvillkor, spara pengar och öka säkerheten. Utifrån arbetets mål togs ett koncept fram för simuleringen av styrsystemet. Det framtagna konceptet skriver över värdena av de fysiska ingångarna innan de går in i styrlogiken. Varje transportör simuleras enskilt där de har en funktion som sparar positionen för de virtuella massabalarna på det egna bandet. Simuleringen visualiseras via ett HMI där balarnas förflyttning kan följas. Det framtagna konceptet visade sig fungera bra för att simulera det tillhandahållna styrsystemet. Stora delar kan med säkerhet återanvändas för andra typer av transportörer. Huruvida konceptet faktiskt kan hitta fel i styrsystem är däremot inte fastställt, men högst sannolikt. Slutsatsen som kan dras av det framtagna konceptet är att det har god potential för att simulera verkliga styrsystem om det vidareutvecklas, varigenom uppstartstiden kan förkortas.

     

    Fulltekst (pdf)
    fulltext
  • 73.
    Björklund, Lars
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Automatisering av pH-mätning vid plantskola2021Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Plantskolan i Friggesund önskade utveckla sitt bevattningssystem. Önskemålet var att ta fram en lösning där vattnets pH loggas samt eventuellt regleras till en konstant nivå för att säkerställa ett optimalt näringsupptag samt ett kostnadsförslag. I nuläget sker ingen mätning av pH och tillsats av gödsel sker manuellt. Målet med detta examensarbete är att kunna presentera ett kostnadsförslag samt ett förslag som med hjälp av pH-mätning kan förbättra bevattningsprocessen. Detta för att förbättra hanteringen av gödsel i bevattningsvattnet för att kunna optimera tillväxten av plantorna samt minimera utsläppen av gödningsmedel i naturen. Målet är även att detta skall kunna utgöra en grund till en bättre automatiserad anläggning där hela bevattningssystemet kan kopplas samman för att verka i symbios. I en studie utförd år 2003 visas ett samband mellan tallplantans aminosyraupptag och dess pH-beroende. Bäst upptag uppmättes vid ett pH 4–5. Två pH-givare och en temperaturgivare skall installeras i vattenledningen från vattentanken i pumprummet för att kunna mäta samt logga dessa data. För att möjliggöra datainsamlande samt framtidssäkra anläggningen togs ett kostnadsförslag fram baserat på utvärdering av befintligt styrsystem kontra ett nytt, baserad på en PLC. I resultatet presenteras ett kostnadsförslag samt flödesschema över tänkt installation. Författaren föreslår som en ytterligare vinst för plantskolan efter installation av PLC att även genomföra automatisering av frilanden genom att använda sig av jordfuktsmätare i frilandet och som ansluts till den PLC som styr bevattningen vid frilandet. Om installationen genomförs kan detta utmynna i att ytterligare forskning på området kan utföras.

  • 74.
    Bond, Luke
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Minimising Size of Laser-Active Nanoparticles Synthesised via Laser Ablation in Liquid2022Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Laser ablation in liquid (LAL) allows the synthesis of various sizes and structures of nanoparticles via alterations of laser, bulk, and solvent parameters with a “green” one-step process. This report involves the utilization of a femto-second laser, achieving ultrashort heating of the substrate surface, for processing of laser-active crystals, namely: Yb:YAG, Yb:YLF and Yb:VO4. The laser was operated with the maximum pulse energy capacity to maximise productivity for future doping of host materials with improved optical properties. The main objective of this experiment was to reduce the size of the synthesised laser-active nanoparticles, without compromising on productivity. This was achieved via the use of an extensive library of solutes ranging from surfactants to chelating agents with varying concentrations to prevent nanoparticle agglomeration, capping the size. Initial analysis was performed via dynamic light scattering (DLS) with secondary confirmation utilizing scanning electron microscopy (SEM). This research may be further explored via expansion of bulk materials, solvents and pulse energies with differing ablation periods and target areas. This allows for further confirmation on productivity optimisation for LAL of laser-active crystals.

  • 75.
    Brandt, Filippa
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Soft sensor for snow density measurements2022Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    The aim of this project was to examine if a machine learning model could be used to predict snow density from six different weather parameters. These were artificially generated snow density, air temperature, ground temperature, relative humidity, windspeed and the snow depth change. The questions asked were what parameters correlates to the snow density, what model will perform best and could this approach be a better alternative to measure snow density manually. The research was performed in the application Regression Learner in MATLAB by testing five different premade machine learning models on a dataset. The premade models were, Linear Regression, GPR Matern 5/2, SVM Medium Gaussian, Wide Neural Network and Trilayered Neural Network. Also, the project includes data collection, data cleaning, data modification, data generation, training, testing, and evaluating the models. The results show that air temperature and windspeed overall are the most important parameters and the GPR Matern 5/2 and the Wide Neural Network had the highest performance. Lastly, it was concluded that the machine learning model could be a better alternative to measuring snow density with a real sensor. 

    Fulltekst (pdf)
    fulltext
  • 76.
    Brugés, Javier Mauricio
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Surface characterization methods for quality assessment of polyethylene-coated paperboard2021Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In manufacturing processes, the quality of a product often depends on its surface, and careful control of surface properties is critical to meet customer requirements. A thin layer of polyethylene (PE) is applied to paperboard to increase barrier functionality and high optical quality of the product. For PE-coated paperboard, product quality inspection is performed at the end of the manufacturing process by taking a portion of the reel to the laboratory for quality inspection. These associated offline characterization methods are destructive and time consuming and are representative of only a small portion of the product.

    The overall goal of this thesis is to provide new methods to characterize the Surface properties of PE-coated paperboard. Specifically, to determine imaging techniques for measuring surface parameters that affect its barrier functionality and surface roughness.

    In this thesis, two methods for surface characterization of PE-coated paperboard are presented to quantify the two most important product-related quality parameters, i.e. barrier functionality and optical quality, which are affected by the presence of defects in the coating and by the surface roughness of the product, respectively. First, a full-Stokes imaging polarimeter (FSIP) is used to detect the presence of PE-coated material and to distinguish between coated and uncoated samples at the pixel level. Second, a three-dimensional scanning electron microscope (3D SEM) is employed to calculate the Surface roughness of PE-coated paperboard. These surface characterization techniques offer an advantage over the industry standard due to the high speed and non-contact nature of the measurement, while increasing the throughput of the sample surface parameters studied.

    A classification accuracy of 99, 74% is achieved using a FSIP to distinguish between PE- and non-PE-coated paperboard at pixel level. Using the 3D SEM technique to measure the topography of PE-coated samples results in a faster method that is comparable in accuracy to a chromatic confocal microscope (CCM). The surface roughness measured with the 3D SEM differs from the standard method by up to 6% and good agreement with statistical parameters is found.

    In general, surface analysis of PE-coated is often a complex and difficult task for imaging techniques and suitable methods need to be evaluated for their sensitivity to measure the desired surface parameters. The presented characterization techniques inspect larger areas of PE-coated paperboard compared to current industry standards. These methods provide a quantitative solution for surface characterization to inspect the surface parameters necessary to assure the product’s quality.

    Fulltekst (pdf)
    fulltext
  • 77.
    Brugés Martelo, Javier Mauricio
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Lundgren, Jan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi.
    Paperboard Coating Detection Based on Full-Stokes Imaging Polarimetry2021Inngår i: Sensors, E-ISSN 1424-8220, Vol. 21, nr 1, artikkel-id 208Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The manufacturing of high-quality extruded low-density polyethylene (PE) paperboard intended for the food packaging industry relies on manual, intrusive, and destructive off-line inspection by the process operators to assess the overall quality and functionality of the product. Defects such as cracks, pinholes, and local thickness variations in the coating can occur at any location in the reel, affecting the sealable property of the product. To detect these defects locally, imaging systems must discriminate between the substrate and the coating. We propose an active full-Stokes imaging polarimetry for the classification of the PE-coated paperboard and its substrate (before applying the PE coating) from industrially manufactured samples. The optical system is based on vertically polarized illumination and a novel full-Stokes imaging polarimetry camera system. From the various parameters obtained by polarimetry measurements, we propose implementing feature selection based on the distance correlation statistical method and, subsequently, the implementation of a support vector machine algorithm that uses a nonlinear Gaussian kernel function. Our implementation achieves 99.74% classification accuracy. An imaging polarimetry system with high spatial resolution and pixel-wise metrological characteristics to provide polarization information, capable of material classification, can be used for in-process control of manufacturing coated paperboard. 

    Fulltekst (pdf)
    fulltext
  • 78.
    Brugés Martelo, Javier Mauricio
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Thim, Jan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Andersson, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi.
    Liguori, Consolatina
    Department of Industrial Engineering (DIIn), University of Salerno, Fisciano, SA, Italy .
    Three-dimensional scanning electron microscopy used as a profilometer for the surface characterization of polyethylene-coated paperboard2021Inngår i: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, Vol. 36, nr 2, s. 276-283Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In food packaging, low-density polyethylene (PE) coating is applied to paperboards to act as a functional barrier and to provide the smoothness required to enhance printability. These characteristics are related to the material’s surface roughness, the parameter monitored during the manufacturing process. Measurement of surface roughness using optical profilometry has gained importance in the paper industry. The optical instruments used to measure surface roughness are limited spatially by the relationship with the light wavelength at which they operate. A scanning electron microscope (SEM) is an alternative for overcoming the spatial resolution limitation, and the use of stereo-photogrammetry on SEM images can be seen as an alternative profilometry technique to measure surface roughness. In this investigation, the surface topography of industrially manufactured high-quality PE-coated paperboard was studied, comparing the SEM stereo-photogrammetry technique with a reference profilometry method, i. e., chromatic confocal microscopy (CCM). We found close agreement between the calculated surface roughness and the results of the techniques used and compared them according to the new ISO 25178 Geometric Product Specifications. We concluded that SEM stereo-photogrammetry provides comparable accurate alternative profilometry method for characterizing the surface roughness of PE-coated paperboard in the micrometer scale.

    Fulltekst (pdf)
    fulltext
  • 79.
    Burgos, Marcelo
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Smarta nivåmätningar av dagvatten i realtid: Med en ny metod baserad på Time-of-Flight LiDAR sensorn VL53L1X2022Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Dagvatten transporteras via dagvattenbrunnar in i ledningsnät och bort från betongytor. Problem uppstår då dessa sätter igen vilket leder till att vägar och bostäder kan översvämmas. Detta medför ett behov att övervaka när dagvattenbrunnarna sätter igen. Sundsvalls kommun har tillsammans med Mittuniversitet använt sig av differentiella tryckgivare för att mäta vattennivåer i syfte att detektera när dagvattenbrunnarna sätter igen. Tryckgivaren fungera bra under sommartid men ger felaktiga utslag under vintern. Det har därmed föreslagits en kontakt fri lösningsmetod som omfattar ToF LiDAR sensorn VL53L1X. ToF LiDAR sensorer används för att bestämma avstånd till objekt, eftersom dessa inte vanligtvis appliceras inom vattennivåmätningar är detta en ny metod i det området. Syftet med arbetet var att utreda ifall ToF LiDAR sensorn VL53L1X kunde användas för att mäta vattennivåer samt avgöra om den kan tillämpas för övervakning av dagvatten under sommar- och vintertid. Övergripande mål var att utreda ifall sensorn kunde implementeras i en nod. Ett flertal förstudier gjordes för att utreda vilka faktorer som påverkade mätresultatet och för att karakterisera sensorns konfigurering för att anpassa sensorn för vattennivåmätningar i avsikt att effektivisera mätmetoden. Det framgick av förstudierna att faktorerna vattengrumlighet, solljus och avstånd till mätobjektet påverkade mätningarna så att mätresultatet försämrades. Det har konstaterats med arbetet som underlag att sensorn kan mäta vattennivåer och kan tillämpas för att övervaka dagvattennivåer. Mätresultat vid vattennivåmätningar kan åstadkommas med en mätnoggrannhet på ca 28 mm och ett mätfel på ca 46 mm. Mätresultatet gäller under omständigheterna att vattnet är rent, under påverkan av solljus samt att sensorns höjdposition är maximalt 90 cm.

    Fulltekst (pdf)
    fulltext
  • 80.
    Caldeborn, Daniel
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Skogsklang: En studie om skogsmiljöers akustiska reflektioner2022Independent thesis Basic level (university diploma), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Denna studie har tittat på hur olika skogsmiljöer kan påverka efterklangen. Studien har genomförts med inspelningar av impulsrespons i tre testmiljöer och analyserat dessa inspelningar. Syftet var att undersöka hur efterklangen karaktäriseras i olika typer av skog och hur detta sedan kan tillämpas i postproduktion av ljud. De undersökta miljöerna är: Skogstyp 1: Planterad averkningsredo gallrad tallskog. Skogstyp 2: Blandskog med naturskogstatus (gran, tall, björk och asp). Skogstyp 3: Fjällnära gammelskog (gran). Det framgår i studien att skogstyp 2 var den främst användbara skogstypen för postproduktion. Detta då dess efterklang hade det bredaste frekvensspektra samt en lång reverbtid. Det finns flera sätt att applicera en sådan klang, allt ifrån musik och filmproduktion. En av de främsta orsakerna till detta var skogens täthet. De kala konvexa stammarna reflekterade ljudet och sprider det i miljön. Det bildades även ett tätare lövverk vilket i sin tur kunde bidra till reflektionerna. Skogstyp 1 var också användbar men den hade en betydligt tunnare karaktär. Dessa planerade produktionsskogar är 2 mycket vanliga och i många svenska filmer förekommer just denna skog. En slutsats av undersökningen är att om man vill eftersträva realism i svenska filmer inspelade i produktionsskog bör denna efterklang inte ha mycket botten. Förslagsvis ett högpassfilter på ungefär 350–400 Hz och sedan ett lågpassfilter vid 1400 Hz. Skogstyp 3 var den skog med absolut kortast efterklang. Detta beror på att det var mycket glest mellan träden samt att stammarna var täckta med lågt hängande grenar vilket också fungerade som absorbenter.

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    fulltext
  • 81. Carratu, M.
    et al.
    Gallo, V.
    Liguori, C.
    Pietrosanto, A.
    O'Nils, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Lundgren, Jan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    A CNN-based approach to measure wood quality in timber bundle images2021Inngår i: 2021 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), IEEE, 2021Konferansepaper (Fagfellevurdert)
    Abstract [en]

    At present, the Smart Industry is becoming a field of great interest for many worldwide researchers since it allows to experiment and research new advanced techniques. One of the most common explored approaches in operations where image processing has already been a milestone is the use of Convolutional Neural Networks (CNN). Those networks have enhanced the current image processing algorithms, achieving an improvement in decision processes usually based on human experience, where an analytical model is not always available. This paper proposes a novel approach for measuring the number of rotted logs in timber bundles using a CNN trained on thousands of timber log images extracted from bundles. Today, the Swedish forest industry bases the selling price of timber bundles on the evaluation of a visual inspection. This operation is based on human experience to evaluate and measure timber bundles' features, which is necessary to categorize them. The proposed approach has shown promising results compared to the actual visual inspection made by operators showing an F1 score with the best CNN architecture of 0.89. 

  • 82.
    Carratu, Marco
    et al.
    University of Salerno, Italy.
    Liguori, Consolatina
    University of Salerno, Italy.
    Pietrosanto, Antonio
    University of Salerno, Italy; SPRING OFF srl, Italy.
    O'Nils, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Lundgren, Jan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Data Fusion for Timber Bundle Volume Measurement2019Konferansepaper (Fagfellevurdert)
  • 83. Carratù, M.
    et al.
    Liguori, C.
    Paciello, V.
    Pietrosanto, A.
    Russo, D.
    Sommella, P.
    Lundgren, Jan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    A Sound Level Meter featured with automatic estimation of the measurement uncertainty2022Inngår i: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 188, artikkel-id 110409Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the area of measuring the environmental noise the equivalent sound pressure level LA,eq is adopted and compared with legal thresholds in order to characterize the site of interest. The paper describes an innovative Sound Level Meter (SLM) able to provide information about the measurand contribution to the measurement uncertainty estimation. This measurement technology is made possible thanks to an approach based on bootstrap method for selecting the suitable measurement episode for an estimation of LAeq. The firmware implementation of the developed SLM is disclosed with reference to a low-cost platform for real-time execution of the proposed methodology. Finally, a metrological characterization of the prototype performed in laboratory is reported as well as the performance comparison with a class 1 SLM in a real scenario. As a result, the smart features of the new SLM may be easily implemented by including commercial devices into the instrument schematics. 

  • 84.
    Carratù, Marco
    et al.
    University of Salerno.
    Ferro, Matteo
    University of Salerno.
    Paciello, Vincenzo
    University of Salerno.
    Sommella, Paolo
    University of Salerno.
    Lundgren, Jan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    O'Nils, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Wireless Sensor Network Calibration for PM10 Measurement2020Inngår i: 2020 IEEE International Conference on Computational Intelligence and Virtual Environments for Measurement Systems and Applications (CIVEMSA), IEEE, 2020Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The proposal of an Advanced Metering Infrastructure based on short-range communication is suggested for the continuous monitoring of Particulate Matter. A prototype of Automatic Measurement System (AMS), including a low-cost off-the-shelf PM sensor, has been developed as a remote node to be adopted in the radio Local Area Network. The results of the system calibration and comparison with the data quality requirements of the PM measurement according to European regulations, as well as the simulation of a typical Smart City scenario in terms of communication performance, confirm the feasibility of the proposed distributed AMS for an effective adoption within an urban area.

  • 85.
    Carratú, Marco
    et al.
    University of Salerno.
    Liguori, Consolatina
    University of Salerno.
    Pietrosanto, Antonio
    University of Salerno.
    O'Nils, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Lundgren, Jan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    A novel IVS procedure for handling Big Data with Artificial Neural Networks2020Inngår i: 2020 IEEE International Instrumentation and Measurement Technology Conference (I2MTC), IEEE, 2020Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In recent times, thanks to the availability of a large quantity of data coming from the industrial process, several techniques based on a data-driven approach could be developed. Between all the data-driven techniques, as Principle Component Regression, Support Vector Machines, Artificial Neural Networks, Neuro-Fuzzy Systems, and many others, the data on which they rely should be analyzed to find correlations and dependencies that could improve their design. For this reason, the Input variable Selection (IVS) process has become of great interest in the recent period. The classical IVS relies on classical statistics, as Pearson coefficients, able to discover linear dependencies among data; today, due to the significant amount of data available, the challenge of also discovering non-linear dependencies appears to be a necessary skill, mainly for the design and development of a neural network. This paper proposes the use of a novel statistical tool named Maximal Information Coefficient (MIC) for developing an IVS procedure able to discover dependencies in a considerable dataset and guide the IVS designer to the selection of input variables in a data-driven application. As a case study, the procedure will be applied to a real application developed in the context of the Swedish forest industry, in order to choose the input variables of a neural network able to estimate the timber bundles volume, which represents an expensive parameter to measure in this context.

  • 86.
    Chen, Jialei
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Active Infrared light power supply for indoor wireless sensor nodes2020Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In order to expand the energy source in energy harvesting, this thesis explores the feasibility of using infrared light source as the energy source. Firstly, the thesis investigated the current energy harvesting solution and the way of using infrared light energy, and determined the use of crystalline solar panels as energy harvesters. By testing the illu-mination characteristics of the infrared light source, a wireless sensor node based on active infrared light energy is designed to verify the reliability of the energy harvesting system. The node uses the BQ25505 as a power management circuit to store energy in the supercapacitor and power the system load through the boost convertor of the TPS61020. The load is a CMWX1ZZABZ wireless module based on LoRa network communication. The thesis measures the energy conversion efficiency of each part of the system. Through data analysis and evaluation, it is considered feasible to use the infrared light source as the energy source of the wireless sensor node.

    Fulltekst (pdf)
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  • 87.
    Chen, Zhiqiang
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Evaluating the performance of a vibration energy harvester under complex excitation2020Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    In recent years, vibration energy harvesting has become a research hotspot in the field of energy harvesting. Energy harvester output power is the most important parameter in a vibration energy harvesting system. Assessing the harvester output power in different vibration environments is an important study issue to study. This thesis proposed a research method for harvester output based on the complex vibration environment simulated in the laboratory, a closed-loop control experimental system for the simulated vibration environment was established, the system can simulate a vibration environment with specific vibration frequency and acceleration, and automatically measure the harvester output power. Using FFT methods to analyse the harvester output voltage waveform, research the relationship between the harvester output power and the noise vibration signal frequency. Polynomial fitting modelling method is used for the harvester output power prediction in the 62.5Hz dominant frequency vibration environment. At the same time, researching the harvester output power in different dominant frequency and same vibration acceleration vibration environment which containing noise signal. Through the analysis of harvester output power, it was found that, for the case of the vibration environment dominant frequency is 62.5Hz, all noise frequency component of the vibration signal will reduce the output power of vibration energy harvester modelD, especially when the noise frequency is around 57.5Hz and67.5Hz, the output power of vibration energy harvester modelD is quite lower than the output power of harvester under the pure sinusoidal excitation signals. For the case of the vibration environment dominant frequency is not 62.5Hz, if the noise frequency component of the vibration signal close the harvester resonance frequency, it has a great impact on output power, and the output power of harvester is higher than the output power of harvester under the pure sinusoidal excitation signals. The presented research methods apply to most such studies, which can help user to analyse the effect of vibration noise on the harvester output and helps increase the harvester's output power. Research conclusions can provide user a reference in harvester selection.

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  • 88.
    Claeson, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Mixing strings of Lithium-Ion and Lead-Acid in parallel2020Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [en]

    The purpose of this survey has been to test and analyse the behaviour of battery systems mixing parallel strings of lithium and lead acid.

    The underlying theory of why batteries of different chemistries behaves together was investigated in order to understand the resulting tests.

    Several tests were made with different products, loads and chargers in order to confirm this theory and to discover cases where the system works good and where it works bad.

    Based on this understanding a script was made in order to find a point of the least annual cost. Annual cost was then compared with systems of Lead acid only and Lithium only.

    The final goal for the script was so that a salesman can input known parameters for a backup site. Script is then adding a small Lithium battery in parallel with a fixed Lead acid battery and, increasing Lithium in size and estimating depth of discharge for Lithium and Lead acid at each step, until desired breakpoint.

    A point of minimum system cost together with Li size is then represented together with the recommended current limits.

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  • 89.
    Correa, J.
    et al.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany; CFEL Center for Free-Electron Laser Science, Hamburg, Germany.
    Wunderer, C. B.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany; CFEL Center for Free-Electron Laser Science, Hamburg, Germany.
    Marras, A.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany; CFEL Center for Free-Electron Laser Science, Hamburg, Germany.
    Okrent, F.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany; CFEL Center for Free-Electron Laser Science, Hamburg, Germany.
    Lange, S.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany; CFEL Center for Free-Electron Laser Science, Hamburg, Germany.
    Kuhn, M.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany; CFEL Center for Free-Electron Laser Science, Hamburg, Germany.
    Niemann, M.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany; CFEL Center for Free-Electron Laser Science, Hamburg, Germany.
    Gottlicher, P.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany.
    Shevyakov, I.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany.
    Zimmer, M.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany.
    Krivan, F.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany.
    Boitrelle, B.
    DESY (Deutsches Elektronensynchrotron), Hamburg, Germany; CFEL Center for Free-Electron Laser Science, Hamburg, Germany; Synchrotron SOLEIL L'Orme des Merisiers, Gifsur- Yvette Cedex, France.
    Guerrini, N.
    RAL (Rutherford Appleton Laboratory) / STFC, OX, U.K.
    Marsh, B.
    RAL (Rutherford Appleton Laboratory) / STFC, OX, U.K.
    Nicholls, T.
    RAL (Rutherford Appleton Laboratory) / STFC, OX, U.K.
    Sedgwick, I.
    RAL (Rutherford Appleton Laboratory) / STFC, OX, U.K.
    Cautero, G.
    Elettra Sincrotrone Trieste, Trieste, Italy.
    Giuressi, D.
    Elettra Sincrotrone Trieste, Trieste, Italy.
    Menk, R. H.
    Elettra Sincrotrone Trieste, Trieste, Italy.
    Pinaroli, G.
    Elettra Sincrotrone Trieste, Trieste, Italy; Universita degli Studi di Udine, Udine, Italy.
    Stebel, L.
    Elettra Sincrotrone Trieste, Trieste, Italy.
    Greer, A.
    DLS (Diamond Light Source), OX, U.K.
    Pedersen, U.
    DLS (Diamond Light Source), OX, U.K.
    Tartoni, N.
    DLS (Diamond Light Source), OX, U.K.
    Hyun, H. J.
    PAL (Pohang Accelerator Laboratory), Pohang, Korea.
    Kim, K. S.
    PAL (Pohang Accelerator Laboratory), Pohang, Korea.
    Rah, S. Y.
    PAL (Pohang Accelerator Laboratory), Pohang, Korea.
    Graafsma, Heinz
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. DESY (Deutsches Elektronensynchrotron), Hamburg, Germany; CFEL Center for Free-Electron Laser Science, Hamburg, Germany.
    The PERCIVAL soft X-ray Detector2018Inngår i: 2018 IEEE Nuclear Science Symposium and Medical Imaging Conference, NSS/MIC 2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, artikkel-id 8824727Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The PERCIVAL collaboration to develop a soft X-ray imager able to address the challenges of high brilliance light sources, such as new-generation synchrotrons and Free Electron Lasers, has reached one of its major milestones: a full 2-MegaPixel (P2M) system (uninterrupted 4 × 4 cm2 active area) has already seen its first light.Smaller prototypes of the device, a monolithic active pixel sensor based on CMOS technology, have already been fully characterised, and have demonstrated high frame rate, large dynamic range, and relatively high quantum efficiency.The PERCIVAL modular layout allows for clover-leaf like arrangement of up to four P2M systems. Moreover, it will be post-processed in order to achieve a high quantum efficiency in its primary energy range (250 eV to 1 keV).We will present the P2M system, its status and newest results, bring these in context with achieved prototype performance, and outline future steps. 

  • 90.
    Croci, Gabriele
    et al.
    Univ Milano Bicocca, Milan, Italy.
    Muraro, Andrea
    CNR, Milan, Italy.
    Cippo, Enrico Perelli
    CNR, Milan, Italy.
    Grosso, Giovanni
    CNR, Milan, Italy.
    Hoglund, Carina
    European Spallat Source ESS AB, Lund.
    Hall-Wilton, Richard
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. European Spallat Source ESS AB, Lund.
    Murtas, Fabrizio
    Ist Nazl Fis Nucl, Frascati, Italy.
    Raspino, Davide
    Rutherford Appleton Lab, Didcot, Oxon, England.
    Robinson, Linda
    European Spallat Source ESS AB, Lund.
    Rhodes, Nigel
    Rutherford Appleton Lab, Didcot, Oxon, England.
    Rebai, Marica
    CNR, Milan, Italy.
    Schooneveld, Erik
    Rutherford Appleton Lab, Didcot, Oxon, England.
    Defendi, Ilario
    TUM, Garching, Germany.
    Zeitelhack, Karl
    TUM, Garching, Germany.
    Tardocchi, Marco
    CNR, Milan, Italy.
    Gorini, Giuseppe
    Univ Milano Bicocca, Milan, Italy.
    I-BAND-GEM: a new way for improving BAND-GEM efficiency to thermal and cold neutrons2019Inngår i: The European Physical Journal Plus, E-ISSN 2190-5444, Vol. 134, nr 4, artikkel-id 166Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    .The BAND-GEM detector represents one of the novel thermal neutron detection devices that have been developed in order to fulfil the needs of high intensity neutron sources that, like ESS (the European Spallation Source), will start operation in the next few years. The first version of this detector featured a detection efficiency of about 40% for neutrons with a wavelength of 4 angstrom, a spatial resolution of about 6mm and a rate capability in the order of some MHz/cm(2). The novelty of this device is represented by an improved 3D converter cathode (10 cm thick) based on (B4C)-B-10-coated aluminum grids positioned in a controlled gas mixture volume put on top of a Triple GEM amplifying stage. The position where the neutron interacts in the converter depends on their energy and it was observed that the first version of the detector would suffer from an efficiency decrease for long (>5 angstrom) neutron wavelength. This paper describes how the new 3D cathode allowed improving the detection efficiency at long neutron wavelengths while keeping all the benefits of the first BAND-GEM version.

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  • 91.
    Das, Moumita
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Barg, Sobhi
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Haller, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bakar, Muhammad Abu
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Rezaee, Ali
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    State of Art of Designing Power Electronics Converter for Low Voltage Motor Drives for Electric Vehicle2020Inngår i: 2020 IEEE International Conference on Power Electronics, Smart Grid and Renewable Energy (PESGRE2020), IEEE, 2020Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In recent times, the boom in electric vehicle (EV) is increasing due to the development of highly efficient power converters and to reduce the fossil fuel dependency. Hence, the progress in both electric and hybrid vehicles are rising. However, the safety become an issue in EVs for operating at high voltage level. Therefore, the application of the low voltage motor in EVs is proposed. This helps to increase the safety in the vehicle and reliability of the system. The proposed voltage for such low voltage motor drives is 48V. This voltage level is also beneficial for integration of battery and ultra-capacitors (UCs). This paper proposes the state of art of designing power converters for low voltage motor drives. Additionally, a novel bi-directional DC-DC converter with reconfigurable transformer is proposed for driving low voltage motors. The proposed bi-directional converter can operate with wide input (12V-4SV) and wide output voltage (1.5V-24V) ranges for power level of 1. 2kW. Analysis of this system and operating principle of the novel converter are also included for different output voltage and current levels. The presence of UCs in the system helps to improve the control response required during accelerating and braking. The simulation results of the system are included in the paper for different voltage and speed levels. The preliminary experiment result is included in the paper.

  • 92.
    Das, Moumita
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Bertilsson, Kent
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    GaN Based Converters for Battery Charging Application of Electric Vehicle2019Inngår i: IECON2019: 45th Annual Conference of the IEEE Industrial Electronics Society, IEEE, 2019Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The high frequency capability and low on-state losses of Gallium Nitride (GaN) transistors offer the potential to increase converter efficiency and/or reduce heatsink and passive component size. This paper investigates the use of GaN technology to enhance the performance of power factor correction (PFC) and LLC converters for battery charging applications. First the efficiency performance of non-isolated PFC converters using GaN transistors is compared by simulation, the asymmetric bridgeless PFC converter is shown to achieve the best efficiency, with a predicted figure of 99% in a 1MHz, 200W design. The predictions are validated by an experimental prototype using a GS66502B, GaN Systems E-mode GaN transistor. Then the efficiency comparison of the PFC and LLC converter using GaN devices for battery charging applications is included in the paper. The experimental results of the PFC converter with GaN devices are also included. Additionally, this paper includes the analysis and design of a common mode input filter for the GaN-based high frequency converters for battery charging application. The size of both the converters using GaN devices is reduced by 40% than the converters based on Si devices. The switching loss comparison of GaN and Si devices are also included in the paper.

  • 93.
    Dian, E.
    et al.
    Hungarian Acad Sci, Budapest, Hungary; European Spallat Source ESS ERIC, Lund; Budapest Univ Technol & Econ, Budapest, Hungary.
    Kanaki, K.
    European Spallat Source ESS ERIC, Lund.
    Khaplanov, A.
    European Spallat Source ESS ERIC, Lund.
    Kittelmann, T.
    European Spallat Source ESS ERIC, Lund.
    Zagyvai, P.
    Hungarian Acad Sci, Budapest, Hungary; Budapest Univ Technol & Econ, Budapest, Hungary.
    Hall-Wilton, Richard
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. European Spallat Source ESS ERIC, Lund.
    Suppression of intrinsic neutron background in the Multi-Grid detector2019Inngår i: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 14, artikkel-id P01021Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    One of the key requirements for neutron scattering instruments is the Signal-toBackground ratio (SBR). This is as well a design driving requirement for many instruments at the European Spallation Source (ESS), which aspires to be the brightest neutron source of the world. The SBR can be effectively improved with background reduction. The Multi-Grid, a large-area thermal neutron detector with a solid boron carbide converter, is a novel solution for chopper spectrometers. This detector will be installed for the three prospective chopper spectrometers at the ESS. As the Multi-Grid detector is a large area detector with a complex structure, its intrinsic background and its suppression via advanced shielding design should be investigated in its complexity, as it cannot be naively calculated. The intrinsic scattered neutron background and its effect on the SBR is determined via a detailed Monte Carlo simulation for the Multi-Grid detector module, designed for the CSPEC instrument at the ESS. The impact of the detector vessel and the neutron entrance window on scattering is determined, revealing the importance of an optimised internal detector shielding. The background-reducing capacity of common shielding geometries, like side-shielding and end-shielding is determined by using perfect absorber as shielding material, and common shielding materials, like B4C and Cd are also tested. On the basis of the comparison of the effectiveness of the different shielding topologies and materials, recommendations are given for a combined shielding of the Multi-Grid detector module, optimised for increased SBR.

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  • 94.
    Drewniak, Sabina
    et al.
    Department of Optoelectronics, Silesian University of Technology, 2 Krzywoustego St., 44-100 Gliwice, Poland.
    Procek, Marcin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. Department of Optoelectronics, Silesian University of Technology, 2 Krzywoustego St., 44-100 Gliwice, Poland (marcin.procek@polsl.pl).
    Muzyka, Roksana
    Institute for Chemical Processing of Coal, 1 Zamkowa St., 41-803 Zabrze, Poland.
    Pustelny, Tadeusz
    Department of Optoelectronics, Silesian University of Technology, 2 Krzywoustego St., 44-100 Gliwice, Poland.
    Comparison of Gas Sensing Properties of Reduced Graphene Oxide Obtained by Two Different Methods2020Inngår i: Sensors, E-ISSN 1424-8220, Vol. 20, nr 11, artikkel-id 3175Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, the sensitivity of reduced graphene oxide structures (rGO) to the action of selected gases (especially hydrogen, but also nitrogen dioxide and ammonia) was examined. Two sensing structures, based on rGO structures, obtained by different methods of oxidation (the modified Hummers, and the modified Tour’s method respectively), were investigated. We show here that the method used for the oxidation of rGO influences the sensitivity of the sensing structure during contact with various gaseous atmospheres. We performed our experiments in the atmosphere, containing hydrogen in a concentration range from 0 to 4% in nitrogen or synthetic air, both in dry and wet conditions. The temperature range was from 50 °C to 190 °C. Finally, we checked how the resistance of the samples changes when the other gases (NO2, NH3) appear in tested gas mixtures. The gas investigations were supplemented by the characterization of rGOs materials using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and N2 sorption method.

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  • 95.
    Du, Shiyu Sandy
    et al.
    Beihang University, Beijing, China.
    Wong, Kainam Thomas
    Beihang University, Beijing, China.
    Song, Yang
    Nanyang Technological University, Singapore.
    Nnonyelu, Chibuzo Joseph
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Wu, Yue Ivan
    Sichuan University, Chengdu, Sichuan, China.
    Higher-order figure-8 microphones/hydrophones collocated as a perpendicular triad—Their “spatial-matched-filter” beam steering2022Inngår i: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 151, nr 2, s. 1158-1170Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Directional sensors, if collocated but perpendicularly oriented among themselves, would facilitate signal processing to uncouple the azimuth-polar direction from the time-frequency dimension—in addition to the physical advantage of spatial compactness. One such acoustical sensing unit is the well-known “tri-axial velocity sensor” (also known as the “gradient sensor,” the “velocity-sensor triad,” the “acoustic vector sensor,” and the “vector hydrophone”), which comprises three identical figure-8 sensors of the first directivity-order, collocated spatially but oriented perpendicularly of each other. The directivity of the figure-8 sensors is hypothetically raised to a higher order in this analytical investigation with an innocent hope to sharpen the overall triad's directionality and steerability. Against this wishful aspiration, this paper rigorously analyzes how the directivity-order would affect the triad's “spatial-matched-filter” beam's directional steering capability, revealing which directivity-order(s) would allow the beam-pattern of full maneuverability toward any azimuthal direction and which directivity-order(s) cannot.

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  • 96. Du, Y.
    et al.
    Kong, Z.
    Toprak, M.
    Wang, G.
    Miao, Y.
    Xu, B.
    Yu, J.
    Li, B.
    Lin, H.
    Han, J.
    Dong, Y.
    Wang, W.
    Radamson, Henry H.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. Chinese Academy of Sciences; University of Chinese Academy of Sciences; Guangdong Greater Bay Area Institute of Integrated Circuit and System; .
    Investigation of the heteroepitaxial process optimization of ge layers on si (001) by rpcvd2021Inngår i: Nanomaterials, E-ISSN 2079-4991, Vol. 11, nr 4, artikkel-id 928Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This work presents the growth of high-quality Ge epilayers on Si (001) substrates using a reduced pressure chemical vapor deposition (RPCVD) chamber. Based on the initial nucleation, a low temperature high temperature (LT-HT) two-step approach, we systematically investigate the nucleation time and surface topography, influence of a LT-Ge buffer layer thickness, a HT-Ge growth temperature, layer thickness, and high temperature thermal treatment on the morphological and crystalline quality of the Ge epilayers. It is also a unique study in the initial growth of Ge epitaxy; the start point of the experiments includes Stranski–Krastanov mode in which the Ge wet layer is initially formed and later the growth is developed to form nuclides. Afterwards, a two-dimensional Ge layer is formed from the coalescing of the nuclides. The evolution of the strain from the beginning stage of the growth up to the full Ge layer has been investigated. Material characterization results show that Ge epilayer with 400 nm LT-Ge buffer layer features at least the root mean square (RMS) value and it’s threading dislocation density (TDD) decreases by a factor of 2. In view of the 400 nm LT-Ge buffer layer, the 1000 nm Ge epilayer with HT-Ge growth temperature of 650◦C showed the best material quality, which is conducive to the merging of the crystals into a connected structure eventually forming a continuous and two-dimensional film. After increasing the thickness of Ge layer from 900 nm to 2000 nm, Ge surface roughness decreased first and then increased slowly (the RMS value for 1400 nm Ge layer was 0.81 nm). Finally, a high-temperature annealing process was carried out and high-quality Ge layer was obtained (TDD=2.78 × 107 cm−2 ). In addition, room temperature strong photoluminescence (PL) peak intensity and narrow full width at half maximum (11 meV) spectra further confirm the high crystalline quality of the Ge layer manufactured by this optimized process. This work highlights the inducing, increasing, and relaxing of the strain in the Ge buffer and the signature of the defect formation. 

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  • 97. Du, Y.
    et al.
    Wang, G.
    Miao, Y.
    Xu, B.
    Li, B.
    Kong, Z.
    Yu, J.
    Zhao, X.
    Lin, H.
    Su, J.
    Han, J.
    Liu, J.
    Dong, Y.
    Wang, W.
    Radamson, Henry H.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. Chinese Academy of Sciences, Beijing; University of Chinese Academy of Sciences, Beijing; Guangdong Greater Bay Area Institute of Integrated Circuit and System, Guangzhou, 510535, China .
    Strain modulation of selectively and/or globally grown ge layers2021Inngår i: Nanomaterials, E-ISSN 2079-4991, Vol. 11, nr 6, artikkel-id 1421Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents a novel method to grow a high-quality compressive-strain Ge epilayer on Si using the selective epitaxial growth (SEG) applying the RPCVD technique. The procedures are composed of a global growth of Ge layer on Si followed by a planarization using CMP as initial process steps. The growth parameters of the Ge layer were carefully optimized and after cycle-annealing treatments, the threading dislocation density (TDD) was reduced to 3 × 107 cm−2 . As a result of this process, a tensile strain of 0.25% was induced, whereas the RMS value was as low as 0.81 nm. Later, these substrates were covered by an oxide layer and patterned to create trenches for selective epitaxy growth (SEG) of the Ge layer. In these structures, a type of compressive strain was formed in the SEG Ge top layer. The strain amount was −0.34%; meanwhile, the TDD and RMS surface roughness were 2 × 106 cm−2 and 0.68 nm, respectively. HRXRD and TEM results also verified the existence of compressive strain in selectively grown Ge layer. In contrast to the tensile strained Ge layer (globally grown), enhanced PL intensity by a factor of more than 2 is partially due to the improved material quality. The significantly high PL intensity is attributed to the improved crystalline quality of the selectively grown Ge layer. The change in direct bandgap energy of PL was observed, owing to the compressive strain introduced. Hall measurement shows that a selectively grown Ge layer possesses room temperature hole mobility up to 375 cm2/Vs, which is approximately 3 times larger than that of the Ge (132 cm2/Vs). Our work offers fundamental guidance for the growth of high-quality and compressive strain Ge epilayer on Si for future Ge-based optoelectronics integration applications.

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  • 98.
    Du, Yijun
    et al.
    Univ Sci & Technol China, Hefei, Anhui, Peoples R China.
    Wu, Xiaopo
    Univ Sci & Technol China, Hefei, Anhui, Peoples R China.
    Sidén, Johan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Wang, Gang
    Univ Sci & Technol China, Hefei, Anhui, Peoples R China; Chinese Acad Sci, Beijing, Peoples R China.
    Design of ultra-wideband antenna with high-selectivity band notches using fragment-type etch pattern2020Inngår i: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 62, nr 2, s. 912-918Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    By specifying objective functions defining the two bands to be notched with high roll-off criteria (ROCs), optimization searching for the best fragment-type etch pattern on ultra-wideband (UWB) antenna is implemented by using multi-objective optimization. The optimization with too many objective functions requires special treatment to improve the searching efficiency. In this design, two slits are preset on appropriate positions on different sides of the UWB radiator to constrain the decision space for etch pattern searching and yield two initial notched bands to speed up the optimization. For demonstration, a UWB patch antenna is designed with dual-band notches of ROC = 0.63 at WiMAX band and ROC = 0.65 at WLAN band. Both the simulation and measurement results indicate that there is significant improvement of the selectivity of the dual-band notches.

  • 99.
    Du, Yong
    et al.
    Chinese Acad Sci, Inst Microelect, Key Lab Microelect Devices & Integrated Technol, Beijing 100029, Peoples R China..
    Xu, Buqing
    Chinese Acad Sci, Inst Microelect, Key Lab Microelect Devices & Integrated Technol, Beijing 100029, Peoples R China.;Univ Chinese Acad Sci, Inst Microelect, Beijing 100049, Peoples R China..
    Wang, Guilei
    Chinese Acad Sci, Inst Microelect, Key Lab Microelect Devices & Integrated Technol, Beijing 100029, Peoples R China..
    Miao, Yuanhao
    Chinese Acad Sci, Inst Microelect, Key Lab Microelect Devices & Integrated Technol, Beijing 100029, Peoples R China.;Guangdong Greater Bay Area Inst Integrated Circui, Res & Dev Ctr Optoelect Hybrid IC, Guangzhou 510535, Peoples R China..
    Li, Ben
    Guangdong Greater Bay Area Inst Integrated Circui, Res & Dev Ctr Optoelect Hybrid IC, Guangzhou 510535, Peoples R China..
    Kong, Zhenzhen
    Chinese Acad Sci, Inst Microelect, Key Lab Microelect Devices & Integrated Technol, Beijing 100029, Peoples R China.;Univ Chinese Acad Sci, Inst Microelect, Beijing 100049, Peoples R China..
    Dong, Yan
    Chinese Acad Sci, Inst Microelect, Key Lab Microelect Devices & Integrated Technol, Beijing 100029, Peoples R China..
    Wang, Wenwu
    Chinese Acad Sci, Inst Microelect, Key Lab Microelect Devices & Integrated Technol, Beijing 100029, Peoples R China.;Univ Chinese Acad Sci, Inst Microelect, Beijing 100049, Peoples R China..
    Radamson, Henry H.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. Chinese Acad Sci, Inst Microelect, Key Lab Microelect Devices & Integrated Technol, Beijing 100029, Peoples R China.;Guangdong Greater Bay Area Inst Integrated Circui, Res & Dev Ctr Optoelect Hybrid IC, Guangzhou 510535, Peoples R China.
    Review of Highly Mismatched III-V Heteroepitaxy Growth on (001) Silicon2022Inngår i: Nanomaterials, E-ISSN 2079-4991, Vol. 12, nr 5, artikkel-id 741Artikkel, forskningsoversikt (Fagfellevurdert)
    Abstract [en]

    Si-based group III-V material enables a multitude of applications and functionalities of the novel optoelectronic integration chips (OEICs) owing to their excellent optoelectronic properties and compatibility with the mature Si CMOS process technology. To achieve high performance OEICs, the crystal quality of the group III-V epitaxial layer plays an extremely vital role. However, there are several challenges for high quality group III-V material growth on Si, such as a large lattice mismatch, highly thermal expansion coefficient difference, and huge dissimilarity between group III-V material and Si, which inevitably leads to the formation of high threading dislocation densities (TDDs) and anti-phase boundaries (APBs). In view of the above-mentioned growth problems, this review details the defects formation and defects suppression methods to grow III-V materials on Si substrate (such as GaAs and InP), so as to give readers a full understanding on the group III-V hetero-epitaxial growth on Si substrates. Based on the previous literature investigation, two main concepts (global growth and selective epitaxial growth (SEG)) were proposed. Besides, we highlight the advanced technologies, such as the miscut substrate, multi-type buffer layer, strain superlattice (SLs), and epitaxial lateral overgrowth (ELO), to decrease the TDDs and APBs. To achieve high performance OEICs, the growth strategy and development trend for group III-V material on Si platform were also emphasized.

  • 100.
    Duan, Jiatong
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Optimization and development of the welding system for fiber-optic duct joints2019Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    At present, the fiber optic ducts are connected by a mechanical type of joint. In this method, two ducts cut in the right angle are pushed in from both sides of the

    joint, and takes approximately one second to joint ducts together. The problem with the existing joint technology is that if there is water inside of the joint, it will be damaged when the water freezes into ice, and then may cause leakage. There is a risk of explosion when compressed air to blow the fiber. Thus, a joint protection device (silicone rubber sleeve) was developed to seal the joint for protection utterly. However, this will cause the larger size of the entire joint and limit the number of single-duct joints next to each other in a multi-duct joint. Fiber optic ducts are made of High-Density Polyethylene, which is the best plastic for remelting and can be welded by using the electro-fusion welding method. Based on the thermoplasticity of this material, this thesis developed a plastic joint with a built-in conductive metal wire inside. The applied voltage will heat the wire, then remelt the duct surfaces to weld them together through the joint. The welding system uses a portable battery operating system, so there is no need to connect it to the grid. To prevent the battery

    from being damaged by supplying too much current, a capacitor bank is used to store high energy for the preheating joints. The system uses a microcontroller to control and monitor current and voltage to ensure uniform heating of the metal wire.

    Theemphasisof this thesis isplacedon the implementation of basic experiments to run the welding system. Multiple welding experiments show that the welding system can manually set parameters to control the welding current of different joints, thereby ensuring the welding quality. Using a 2.5Ω joint to weld ducts will approximately consume 120J from the battery, so a fully charged 42V, 4.4AH rechargeable battery can perform almost 5600 times of welding. The suitable range of joint resistance will decrease as the required energy consumption increases/ the welding time decreases.

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