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  • 1551.
    Zhang, Congcong
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    A Distributed Range Query Framework for Internet of Things2014Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    With the rapid development of information technology, applications referring to the Internet of things are booming. Applications that gather information from sensors and affect the context environment with actuators can provide customized and intelligent behaviour to users. These applications have become widely used nowadays in daily life and have initiated the multi-dimensional range query demand referring to the Internet of things. As the data information is fully distributed and the devices like sensors, mobile phones, etc., has limited resources and finite energy, supporting efficient range query is a tough challenge. In this paper, we have proposed a distributed range query framework for Internet of things. In order to save energy costs and reduce the network traffic, we suggest a reporting data range mechanism in the sensing peers, which choose to report a data range and report again only when the peer senses an abnormal data instead of the common moving data method. In addition, we selected some strong peers to be used as the super peers to create a data index by collecting the reporting data range, which will be used for performing range queries. The study has shown that our proposal framework could reduce resource costs in the less strong peers like sensors and mobile phones, and reduce network traffic among all the peers within the network, as well as support a range query function. According the evaluation results, the reporting data range method could greatly reduce the data migration times and save energy costs, and the data index could significantly reduce accessing unnecessary peers and diminish the network traffic.

  • 1552.
    Zhang, Han
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Design of a high gain filter system for Marker Locator2015Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    This paper introduces a high-gain, low-noise band-pass filter system for detection/amplification of small signals. In addition, related theory and methodology are described for a specific design implementation. Simulation and experimental results are presented and discussed. The purpose of the implemented design was to construct a band-pass filter system with 102 dB gain and with an output noise level of less than 0.8V.

    The design of the high-gain band-pass filter system was achieved mainly with the help of Filter Pro, LTSpice IV, and Multisim 12.

    The thesis provides important support for the project Marker Locator and constitutes a valuable reference for future active filter system design and small signal detection/amplification.

  • 1553.
    Zhang, Hao
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    A Peer to Peer Security Protocol for the Internet of Things: Secure Communication for the SensibleThings Platform2014Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    With the rapid development of the Internet connected technologies and applications, people are keen on embracing the convenience and practi-­‐‑ calities they brings. As all kinds of technologies improve, the Internet of Things matures and is able to provide more advanced services to people, which connects a variety of devices, systems and applications beyond traditional machine-­‐‑to-­‐‑machine. However, it covers a variety of devices, protocols and applications, which makes it much more complex than a normal network. Nevertheless, equipped with appropriate security solutions, the Internet of Things is promising to bring us more conven-­‐‑ iences and be widely applied in our daily life. And like the main appli-­‐‑ cation areas, wireless sensor networks with a frequent but short com-­‐‑ munication character, it requires an efficient and flexible protocol to protect the information. To protect the traffic of the Internet of Things is the focal point of this research work. Although many protocols for the Internet have been put forward, it is still not enough to meet the increas-­‐‑ ingly complex requirements from applications. Many of them are not efficient enough to adapt the device diversity and timely communica-­‐‑ tion environment. This research work is trying to address this problem, by proposing a peer-­‐‑to-­‐‑peer security protocol to satisfy this varied environment. Secure communication is implemented on an open sourced platform for the Internet of Things. The philosophy of the platform it implemented on is also inherited to this protocol and the implementation. It avoids unnecessary handshakes between entities, which makes it more efficient in a wireless sensor network. Modulariza-­‐‑ tion and unit test are adapted in implementation to enhance the robust of the system. Its dynamic security level adjustment feature satisfies the realistic demand on one platform this protocol is implemented on. Finally, with a comparison test and an analysis using the BAN logic, the result shows that the proposed protocol is efficient to meet the specific goals and applicable for the platform. 

  • 1554.
    Zhang, Heng
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Efficient database management based on complex association rules2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    The large amount of data accumulated by applications is stored in a database. Because of the large amount, name conflicts or missing values sometimes occur. This prevents certain types of analysis. In this work, we solve the name conflict problem by comparing the similarity of the data, and changing the test data into the form of a given template dataset. Studies on data use many methods to discover knowledge from a given dataset. One popular method is association rules mining, which can find associations between items. This study unifies the incomplete data based on association rules. However, most rules based on traditional association rules mining are item-to-item rules, which is a less than perfect solution to the problem. The data recovery system is based on complex association rules able to find two more types of association rules, prefix pattern-to-item, and suffix pattern-to-item rules. Using complex association rules, several missing values are filled in. In order to find the frequent prefixes and frequent suffixes, this system used FP-tree to reduce the time, cost and redundancy. The segment phrases method can also be used for this system, which is a method based on the viscosity of two words to split a sentence into several phrases. Additionally, methods like data compression and hash map were used to speed up the search.

  • 1555.
    Zhang, Renyun
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Hummelgård, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Örtegren, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Yang, Ya
    Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, PR China; University of Chinese Academy of Science, Beijing, PR China.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Balliu, Enkeleda
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Blomquist, Nicklas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Olsen, Martin
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Wang, Zhong Lin
    Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, PR China; University of Chinese Academy of Science, Beijing, PR China; Georgia Institute of Technology, Atlanta, GA, USA.
    Olin, Håkan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap.
    Sensing body motions based on charges generated on the body2019Inngår i: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 63, artikkel-id 103842Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The sensing of body motions is of great importance in areas such as healthcare, rehabilitation, and human-computer interactions. Different methods have been developed based on visual or electrical signals. However, such signals are acquired by external devices and are not intrinsic signals that are created on the body. Here, we report a new universal body motion sensor (UBS) to detect motions based on the intrinsic contact electrification (CE) of the skin or electrical induction (EI) of the body. The CE or EI generates charges on the body, leading to potential differences between the body and ground that can be measured to identify different body motions, such as motions of the head, arms, fingers, waist, legs, feet and toes. Proof-of-concept experiments have demonstrated that the UBS can be used to monitor the conditions of people with Parkinson's disease (PD) and to quantitatively monitor the recovery of those with a leg injury, suggesting great potential for healthcare applications.

  • 1556.
    Zhang, Weiting
    et al.
    Beijing Jiatong University, China.
    Yang, Dong
    Beijing Jiatong University, China.
    Wang, Hongchao
    Beijing Jiatong University, China.
    Zhang, Jun
    Beijing Jiatong University, China.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationssystem och –teknologi.
    AESGRU: An Attention-based Temporal Correlation Approach for End-to-End Machine Health Perception2019Inngår i: IEEE Access, E-ISSN 2169-3536, Vol. 7, s. 141487-141497Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Accurate and real-time perception of the operating status of rolling bearings, which constitute a key component of rotating machinery, is of vital significance. However, most existing solutions not only require substantial expertise to conduct feature engineering, but also seldom consider the temporal correlation of sensor sequences, ultimately leading to complex modeling processes. Therefore, we present a novel model, named Attention-based Equitable Segmentation Gated Recurrent Unit Networks (AESGRU), to improve diagnostic accuracy and model-building efficiency. Specifically, our proposed AESGRU consists of two modules, an equitable segmentation approach and an improved deep model. We first transform the original dataset into time-series segments with temporal correlation, so that the model enables end-to-end learning from the strongly correlated data. Then, we deploy a single-layer bidirectional GRU network, which is enhanced by attention mechanism, to capture the long-term dependency of sensor segments and focus limited attention resources on those informative sampling points. Finally, our experimental results show that the proposed approach outperforms previous approaches in terms of the accuracy.

  • 1557.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    A review on biofuels for transportation2006Inngår i: Asia Biofuels Conference & Expo IV, 2006, Beijing., 2006Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Energy use in the transport sector is heavily dependent on crude oil which is running out in a limited time. Under the pressure of oil dependency and climate change, the possibility of producing transportation fuels from biomass and wastes has been a more and more attractive subject. The first generation of biofuels for transportation, such as bioethanol, biodiesel and biogas produced from agricultural activities have been successfully introduced into the transport market in a number of countries. From the viewpoint of fuel potential, economics, environment, land use, water use and chemical fertilizer use, there is a strong preference for the use of woody biomass and various forest/agricultural residues as the feedstock. Thus, the production of second generation of biofuels i.e. synthetic transportation fuels such as methanol, DME, FT-diesel and hydrogen through biomass gasification seems promising. This paper is trying to review the present market of the first generation of bio-automotive fuels and the technology development of the second generation of bio-automotive fuels. It can be concluded that the second generation of bio-automotive fuels is on the way to a breakthrough in the transport markets of industrial countries especially for those countries with a strong forest industry. The first generation will remain as favourable bio-automotive fuels in the developing countries.

  • 1558.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för naturvetenskap, teknik och matematik.
    Automotive fuels from biomass via gasification2010Inngår i: Fuel processing technology, ISSN 0378-3820, E-ISSN 1873-7188, Vol. 91, nr 8, s. 866-876Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There exists already a market of bioautomotive fuels i.e. bioethanol and biodiesel produced from food crops in many countries. From the viewpoint of economics, environment, land use, water use and chemical fertilizer use, however, there is a strong preference for the use of woody biomass and various forest/agricultural residues as the feedstock. Thus, the production of 2nd generation of bioautomotive fuels i.e. synthetic fuels such as methanol, ethanol, DME, FT-diesel, SNG and hydrogen through biomass gasification seems promising. The technology of producing synthetic fuels are well established based on fossil fuels. For biomass, however, it is fairly new and the technology is under development. Starting from the present market of the 1st generation of bio-automotive fuels, this paper is trying to review the technology development of the 2nd generation bio-automotive fuels. The production of syngas is emphasized which suggests appropriate gasifier design for a high quality syngas production. A number of bio-automotive fuel demonstration plant will be presented, which gives the state of the art in the development of BTS (biomass to synthetic fuels) technologies. It can be concluded that the 2nd generation bio-automotive fuels is on the way to a breakthrough in the transport markets of industrial countries especially for those countries with a strong forest industry.

  • 1559.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    PROCESS SIMULATION OF CIRCULATING FLUIDIZED BEDS - mid term assessment report 2000Rapport (Annet vitenskapelig)
  • 1560.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    PROCESS SIMULATION OF CIRCULATING FLUIDIZED BEDS - yearly report1999Rapport (Annet vitenskapelig)
  • 1561.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    PROCESS SIMULATION OF CIRCULATING FLUIDIZED BEDS - yearly report: reporting the JOR3CT980306 project of 4th EU-framework Programme2000Rapport (Annet vitenskapelig)
  • 1562.
    Zhang, Wennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    TRANSPORTATION FUELS FROM BIOMASS VIA GASIFICATION: 2nd World Conference and Exhibition on Biomass for Energy and Industry, May 2004, Rome, Italy2004Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    There exists already a market of transportation fuels i.e. bioethanol and biodiesel produced from food crops in several countries. From the viewpoint of economics, environment, land use, water use and chemical fertilizer use, however, there is a strong preference for the use of woody biomass and various forest/agricultural residues as the feedstock. Thus, the production of transportation fuels through biomass gasification seems the most promising. The technology of producing liquid fuels such as methanol and FT-diesel is well established based on fossil fuels. For biomass, however, it is fairly new. This paper critically reviews a number of transportation fuels such as methanol, DME, FT-fuels etc. with respect to four criteria: efficiency, economy, environmental impact and end use with emphasis on well-to-wheel efficiency. The production of syngas required is discussed which suggests appropriate gasifier design for a high quality syngas production. It is supposed that ethanol is the best choice to substitute gasoline while FT-diesel is the best choice to substitute diesel.

  • 1563.
    Zhang, Wennan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Dai, X
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Wu, C
    Further test on the Sanya 6MW biomass CFB gasifier2004Inngår i: 2nd World Conference and Exhibition on Biomass for Energy, Industry and Climate Protection. Rome, Italy, 10 - 14 May 2004, 2004Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Following a preliminary test on the 6 MW Sanya biomass CFB gasifier (reported in the last conference at Amsterdam), a further test has been carried out focusing on the use of in-bed dolomite in order to reduce the tar content in the product gas. The gas composition and tar contents in the product gas at different temperatures were measured and analyzed. The results show that there is no big difference between two cases with and without dolomite at low temperature of 700C. However, at high temperature of 900C, the tar content was reduced significantly by the addition of in-bed dolomite. Temperature has a strong effect on the efficiency of dolomite catalyst

  • 1564.
    Zhang, Wennan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Dai, X.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Wu, C.
    Luo, X.
    A PRELIMINARY TEST ON AN INDUSTRIAL BIOMASS CFB GASIFIER 2002Inngår i: 12th European Biomass Conference: Vol. 1, 2002, s. 745-748Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    A test was carried out on an 6 MW industrial biomass atmospheric CFB gasifier in a power plant. The gas composition, NH3 and tar contents in the product gas at different temperatures were measured and analyzed. Ash (char in the present case) analysis was also made to make mass balance of chemical element in solid and gas phases during gasification based on Si balance analysis. The measurement results show that a gas productivity of 2 Nm3/kg (daf biomass) with gas LHV of 5MJ/Nm3 can be achieved at 750℃.The conversion of fuel-bound nitrogen (FBN) to NH3 ranges from 6 wt% to 70 wt% depending on temperature. Tar content in the product gas ranges from 2.5 to 16.7 g/m3. Small fractions of H, O, N, Cl and S contents in fuel remain in the ash while most of mineral metal element remains in the ash.

  • 1565.
    Zhang, Wennan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Forsman, B.
    Söderlind, U.
    Biofuels in Sweden2005Inngår i: Proceedings of the 7th World Congress on Recovery Recycling and Reintegration, 2005Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    Biomass residual from forest has been utilized in a large scale in Sweden after full speed development over the past decade, which contributes about 20% of the total energy consumption. This is a big event for an industrial country to shift fossil fuel-based society to a sustainable society. The well established biofuel market in Sweden is, in principle, attributed to the good synergy of a strong forest industry with the energy sector, to a good district heating system, and to a favorable tax system. In this paper, the authors are trying to present a picture of how biomass residual is shaping the Swedish energy system in the past and for the future. The production of heat, electricity and transportation fuels will be discussed. A number of critic points associated to biofuel potential, economy, environmental impact, end-use, as well as to biomass conversion technologies such as combustion, gasification and biological processes will be discussed. The advances of research and technology development in Sweden will be overviewed. Swedish bioenergy industry shows a good example in the world regarding biomass residual utilization as a renewable energy. The practices and experiences might be useful to other countries.

  • 1566.
    Zhang, Wennan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Johnsson, F
    Johnsson, H
    Leckner, B
    Time-dependent fluctuation characteristics of particle flow in a circulating fluidized bed boiler2001Inngår i: Fluidization X : proceedings of the Tenth Engineering Foundation Conference on Fluidization, Beijing, People Republic of China, May 20 - 25, 2001: Conference on Fluidization <10, 2001, Beijing>, New York: United Engineering Foundation , 2001, s. 818-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Measurements of the fluctuations in solids flow in a circulating fluidized bed (CFB) boiler has been carried out with emphasis on the layer of downflowing particles at the furnace walls. Signals of local fluctuations in particle downflow, global pressure drop fluctuations in the upper and bottom zones of the furnace, and in absolute pressure in air plenum, were simultaneously sampled. Spectral and probability analyses on the signals suggest a regular slow fluctuation of the particle suspension flow passing through the core and falling at the wall. The flow of particles in the wall-layer has a wide distribution of densities. The transfer of particles from the core to the wall is the dominant process for the formation and evolution of the wall-layer in the furnace of CFB boilers.

  • 1567.
    Zhang, Wennan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Leckner, Bo
    PROCESS SIMULATION OF CIRCULATING FLUIDIZED BEDS WITH COMBUSTION/GASIFICATION OF BIOMASS - The project final report: reporting the JOR3CT980306 project of 4th EU-framework Programme2001Rapport (Annet vitenskapelig)
  • 1568.
    Zhang, Wennan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    A review on transportation fuels from biomass syngas: 7th World Congress on Recovery, Recycling and Reintegration, Beijing2005Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    There exists already a market of transportation fuels i.e. bioethanol and biodiesel produced from food crops in several countries. From the viewpoint of economics, environment, land use, water use and chemical fertilizer use, however, there is a strong preference for the use of woody biomass and various forest/agricultural residues as the feedstock. Thus, the production of transportation fuels through biomass gasification seems the most promising. The technology of producing liquid fuels such as methanol and FT-diesel is well established based on fossil fuels. For biomass, however, it is fairly new. This paper critically reviews a number of transportation fuels such as methanol, DME, FT-fuels etc. with respect to four criteria: efficiency, economy, environmental impact and end use with emphasis on well-to-wheel efficiency. The production of syngas required is discussed which suggests appropriate gasifier design for a high quality syngas production. It is supposed that ethanol is the best choice to substitute gasoline while FT-diesel is the best choice to substitute diesel.

  • 1569.
    Zhang, Wennan
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Yu, C
    Tabikh, A
    Dai, X
    Söderlind, Ulf
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Adanes, J
    de Diego, L
    García-Labiano, F
    Gayán, P
    Aibeo, A
    Pinho, C
    Andersson, Bertil
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för teknik, fysik och matematik.
    Brus, E
    Nordin, A
    Fjällström, T
    Process simulation of circulating fluidized beds with combustion/gasification of biomass.2002Inngår i: Twelfth European Biomass Conference - Biomass for Energy, Industry and Climate Protection: European Conference on Biomass for Energy, Industry and Climate Protection 12, 2002, Amsterdam>, Florence: ETA , 2002, s. 1503-Konferansepaper (Fagfellevurdert)
    Abstract [en]

    This paper briefly presents the work carried out for the 4th framework Joule project under the contract JOR3CT980306. The project is to build up an integrated mathematical model to predict reactor performance of biomass circulating fluidized bed boiler/gasifier when reactor design, operating conditions and fuel properties are defined. For CFB boilers, the sub-models of combustion, heat transfer, ash deposition on a heat transfer surface and NOx/N2O emission have been developed, and evaluated against the 12 MW Chalmers CFB boiler. For CFB gasifiers, the sub-models of gasification, heat transfer, NH3/HCN emission, alkali ash and tar emissions from the gasifiers are developed. The results have been checked on Sanya 6MW industrial biomass CFB gasifier.

  • 1570.
    Zhang, Ye
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    On The Importance of Light Source Classification in Indoor Light Energy Harvesting2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Indoor light energy harvesting plays an important role in field of renewable energy. Indoor lighting condition is usually described by level of illumination. However, measured data alone does not by classification of different light sources, result is not representative. Energy harvesting system needs to be evaluated after classification to obtain more accurate value. This is also importance of different light source classification. In this thesis, a complete set of indoor light energy harvesting system is introduced, two models are proposed to evaluate energy, robustness is improved by mixing complex light condition during data collection. Main task of this thesis is to verify importance of indoor light classification. Main contribution of this thesis is to fill a gap in energy evaluation, and built a model with superior performance. In terms of collecting data, this thesis researches influence factor of data collection to ensure reliability of accuracy. This work can more accurately collect spectral under different light conditions. Finally, light energy is evaluated by classification of indoor light. This model is proven to be closer to true energy value under real condition. The result shows that classified data is more accurate than direct calculation of energy,it has a smaller error. In addition, performance of classifier model used in this thesis has been proven to be excellent, classifier model can still carry on high-accuracy classification when measurement data are not included in training data set. This makes it a low-cost alternative to measuring light condition without spectrometer.

  • 1571.
    zhang, zhennan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Camera Node for Conical Volumetric Surveillance2014Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Generally  cameras  are  used  for  area  based  surveillance,  but  with  advancement  in  technology, cameras  can  be  employed  for wide  area  space  surveillance  (volumetric space surveillance). The volumetric systems require a number of cameras in order to cover a large area. Single panoramic cameras  do  not  provide  required  functionality  for  wide  area  space  surveillance  and Pan-Tile-Zoom (PTZ) cameras do not either cover wide areas.   To  meet  this challenge,  we  propose  a  cost  effective smart volumetric  surveillance system  which utilizes smaller number of cameras in order to provide a coverage of 360 degree. A test case used for this system includes detection of birds in the wind farms. The proposed approach provides a solution  for recording/preventing collision  of  birds  with  wind turbine. To  realize  the  system, a model is developed with two camera nodes. This model provides a 360 degree conical volumetric space coverage. The  system is  utilizing  a  servo  motor  with  capability  of  changing  speed  and arduino  embedded  platform for  controlling  different  functionality. After  triggering  the  camera nodes from arduino, software perform the image analysis.  This  cost  effective  and  wide  area  surveillance  system  consumes at  least half lower  power as compared  to traditional  linear  systems with  eight  cameras. It  is  worth  noting  that  the system provides  conical  shaped  area coverage  of  200  square  meters  with  height ranging  from approximately 40 to 100 meters. The system would capture images in raw format in local storage and  the test  results  show  that  saving  images  with  PNG  format  requires a small  memory  size  as compared  to BMP  and TIFF.    Experiment  results  indicate  that  surveillance  system  can  be effectively employed for detecting birds in opening places.

  • 1572.
    Zhao, Jing
    et al.
    Beijing Jiatong University.
    Yang, Dong
    Beijing Jiatong University.
    Qin, Yajuan
    Beijing Jiatong University.
    Zheng, Tao
    Beijing Jiatong University.
    Duan, Junqi
    Beijing Jiatong University.
    Gidlund, Mikael
    ABB Corporate Research.
    Issues of Routing Protocol for Wireless Industrial Sensor Networks2012Konferansepaper (Fagfellevurdert)
    Abstract [en]

    With the success of wireless technologies and the number of wireless devices increasing, the wireless coverage footprint expands and removes the needs of wired networks for industrial applications. Wireless industrial sensor networks (WISNs) are a type of wireless sensor networks (WSNs), which dedicate to industrial applications. The WISNs bring several advantages over traditional wired industrial networks for detection and control, include flexibility, scalability, remote maintenance, and rapid deployment. However, some technical issues and routing design principles need to be noticed in terms of the stringent requirements of industrial applications. In this paper, we firstly introduce the characteristics and some routing issues of WISNs. Then we discuss existing routing protocols for WISNs and analysis their performances. Finally, we outline several future research directions.

  • 1573.
    Zhao, Jingbo
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Color Segmentation on FPGA for Automatic Road Sign Recognition2012Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
  • 1574.
    Zhao, Mingxuan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Paper Printing Circuit Based on Inductively Coupled Wireless Transmission2018Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This report is about how to design and fabricated a wireless energy

    transfer system which is printed on flexible photo paper. That is a

    technology used to print conducting tracks on paper, or even entire

    circuit system.

    The circuit of wireless energy transmission is half bridge converter with

    spiral coil as the inductance which are etching in primary side and

    printing in secondary side.The procedure of fabrication will be

    introduced.

    While realizing the feasible simulation circuit, the optimal transmission

    energy system components are mounted according to the requirements.

    While looking for the best efficiency, it’s also neccessary to consider the

    appropriate size of the system. In the end of this report there will be

    some analysis which is aimed to identify where the largest electrical

    losses are located.

    Compared with ordinary PCB circuit board, printed circuit on paper

    makes the whole system very flexible and portable. When the primary

    side as close with secondary side, The efficiency is almost 72% while the

    60Ω as the load. The output power is 10.68w.

    On the other hand, the ink of printed circuit on paper has high resistivity,

    which affects the efficiency of radio power system. However, for different

    paper substrates, the efficiency of wireless charging system will not be

    affected.

  • 1575.
    Zhao, Xuewei
    et al.
    University of Science and Technology of China, Hefei, Anhui, China; Chinese Academy of Sciences, Beijing, China.
    Moeen, M.
    KTH Royal Institute of Technology, Stockholm.
    Toprak, M. S.
    KTH Royal Institute of Technology, Stockholm.
    Wang, G.
    Chinese Academy of Sciences, Beijing, China.
    Luo, J.
    Chinese Academy of Sciences, Beijing, China.
    Ke, X.
    Chinese Academy of Sciences, Beijing, China.
    Li, Z.
    Chinese Academy of Sciences, Beijing, China.
    Liu, D.
    Chinese Academy of Sciences, Beijing, China.
    Wang, W.
    Chinese Academy of Sciences, Beijing, China.
    Zhao, C.
    Chinese Academy of Sciences, Beijing, China.
    Radamson, Henry H.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion. Chinese Academy of Sciences, Beijing, China.
    Design impact on the performance of Ge PIN photodetectors2020Inngår i: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 31, s. 18-25Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    This article presents the impact of epitaxial quality, contact resistance and profile of Ge PIN photodetectors (PDs) on dark current and responsivity. The PD structures were processed with either selectively grown Ge with integrated waveguides on SOI wafer or globally grown Ge on the entire wafer. The contact resistance was lowered by introducing NiGe layer prior to the metallization. The n-type doped Ge PIN structure was formed by ion implantation and the contact resistivity was estimated to 2.6 × 10 −4  Ω cm 2 . This value is rather high and it is believed to be due to fomation of defects during implantation. The results show a minor difference in dark currents for selectively and globally grown PDs but in both types, it depends on detector area and the epitaxial quality of Ge. For example, the threading dislocation density (TDD) in non-selectively grown PDs with thickness of 1 µm was estimated to be 10 6  cm −2 yielding relatively low dark currents while it dramatically changes for PDs with thinner Ge layers where TDD increases to 10 8  cm −2 and the dark current levels increase almost by 1.5 magnitude. Surprisingly, for selectively grown PDs with Ge thickness of 500 nm, TDD was still low resulting in low dark currents. The dark current densities at − 1 V bias of non-selectively and selectively grown PDs with optimized profile were measured to be 5 mA/cm 2 and 47 mA/cm 2 , respectively, while the responsivity of these detectors were 0.17 A/W and 0.46 A/W at λ ~ 1.55 µm, respectively. Excellent performance for selectively grown PD shows an appropriate choice for detection of 1.55 µm wavelength. 

  • 1576.
    Zhao, Yi
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Discovery of temporal association rules in multivariate time series2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    This thesis focuses on mining association rules on multivariate time series. Com-mon association rule mining algorithms can usually only be applied to transactional data, and a typical application is market basket analysis. If we want to mine temporal association rules on time series data, changes need to be made. During temporal association rule mining, the temporal ordering nature of data and the temporal interval between the left and right patterns of a rule need to be considered. This thesis reviews some mining methods for temporal association rule mining, and proposes two similar algorithms for the mining of frequent patterns in single and multivariate time series. Both algorithms are scalable and efficient. In addition, temporal association rules are generated from the patterns found. Finally, the usability and efficiency of the algorithms are demonstrated by evaluating the results.

  • 1577.
    Zheng, Tao
    et al.
    Beijing Jiatong University.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Åkerberg, Johan
    ABB Corporate Research.
    Wireless Arbitration: A Priority-Based Deterministic Media Access Technique for Industrial Wireless Sensor Networks2013Konferansepaper (Fagfellevurdert)
  • 1578.
    Zhu, Sainan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Creating a NoSQL database for the Internet of Things: Creating a key-value store on the SensibleThings platform2015Independent thesis Advanced level (degree of Master (One Year)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Due to the requirements of the Web 2.0 applications and the relational databaseshave a limitation in horizontal scalability. NoSQL databases have become moreand more popular in recent years. However, it is not easy to select a databasethat is suitable for a specific use. This thesis describes the detailed design, im plementation and final performance evaluation of a key-value NoSQL databasefor the SensibleThings platform, which is an Internet of Things platform. Thethesis starts by comparing the different types of NoSQL databases to select themost appropriate one. During the implementation of the database, the algorithms for data partition, data access, replication, addition and removal ofnodes, failure detection and handling are dealt with. The final results for theload distribution and the performance evaluation are also presented in this pa per. At the end of the thesis, some problems and improvements that need betaken into consideration in the futures.

  • 1579.
    Ziegler, A.
    et al.
    Microscopy and Microanalysis Unit, The University of the Witwatersrand, 1 Jan Smuts Ave., Johannesburg, 2000, South Africa .
    Graafsma, Heinz
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Detectors for Electron and X-ray Scattering and Imaging Experiments2014Inngår i: In-situ materials characterization: across spatial and temporal scales / [ed] Ziegler, A; Graafsma, H; Zhang, XF; Frenken, J, Berlin Heidelberg: Springer, 2014, nr 1, s. 207-250Kapittel i bok, del av antologi (Fagfellevurdert)
    Abstract [en]

    Suitable detectors for these expensive and highly complex experimental instruments described in the previous chapters are a key factor to consider, primarily because if one cannot visualize or record the experimental results with an appropriate detector, any experiment will fail. The general challenge for all position-, energy-, and time-resolving detector systems is the fulfillment of stringent requirements for direct X-ray and electron detection experiments. These include a priori a high detection sensitivity and efficiency, but most important is coping with extremely high flux (1012 highly energetic X-ray photons or 108 300 kV electrons per second), exhibiting appropriate radiation hardness to maintain proper detection sensitivity and operability, low electronic noise for finest energy resolution in single-photon counting mode, and high frame rates for high time resolution. Parameters such as the Modulation Transfer Function (MTF), the Detector Quantum Efficiency (DQE), the dynamic range, pixel size, sensitivity, linearity, uniformity, background noise, read out speed, and reliability (or life time) among other characteristics will need to be considered to decide which detector design is best for what application. There are a variety of designs in the development and/or prototype stage. Costs are high, because most are produced using expensive wafer fabrication processes. A point of consideration is flexibility, adaptability, and how swift detector parameters can be changed. The trend at high-end, multi-national, multi-user scientific research facilities (Synchrotrons, FELS) however, is to operate dedicated, non-transferable detectors for specialized applications, whereas the medium to small scale research facilities may well decide for a more versatile, multi-purpose detector. The following sections will address detectors for electrons and detectors for X-ray photons separately. Development efforts for these detector types overlap, in part due to the high costs involved, and in part due to the compatibility of some developmental stages and components for both detector types. © Springer-Verlag Berlin Heidelberg 2014.

  • 1580.
    Zimic, Sheila
    et al.
    Västernorrland County, R&D Unit.
    Dalin, Rolf
    Västernorrland County, R&D Unit.
    Systematical Follow-up in Social Work Practices2016Inngår i: Computers & society, ISSN 0095-2737, E-ISSN 2167-3055, Vol. 45, nr 3, s. 159-166Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this paper, we explore the meaning of a specific follow-up system in different social work practices. We want to gain understanding about if the system can be an empowering tool for the practitioners to learn in their professional work. We interviewed four practitioners in different teams in order to find out how they describe the follow-up system as a tool, how they describe the knowledge they produce with help of it and what this means to them.

    We have found that the practitioners describe the tool as an easy way to present results which are often described as 'facts'. The teams mainly use their specific follow-ups to present their work to others and in relation to that the tool serves a purpose for the team to gain credibility and be considered as professional. Their use can be understood in light of Evidence Based Practice and performance measurement as a discourse which sets limits and have effects on professional learning.

  • 1581. Åberg, Daniel
    et al.
    Edvardsson, Sverker
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Direct calculation of optical absorption amplitudes for trivalent rare-earth ions in LiYF42002Inngår i: Physical Review B, ISSN 1098-0121, Vol. 65, nr 4, s. 045111-1Artikkel i tidsskrift (Fagfellevurdert)
  • 1582. Åberg, Daniel
    et al.
    Edvardsson, Sverker
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    The crystal dependent open-shell polarizability of f-elements: higher order contributions2000Inngår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 303-304, nr 24 May, s. 345-348Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    It has earlier been shown that the use of a self consistent multipole electrostatic model to derive the crystal field parameters (CFP) actually gives the correct curve shape when the CFP are plotted against the various rare-earth ions (S. Edvardsson, M. Klintenberg, The use of CI calculated polarizabilities to study rare-earth CFP dependencies in the laser host RE:YLF. Mater. Sci. Forum, 1999;315-317:407). It is also known that the electrostatic contribution is important for the lower order parameters. In this connection; our primary interest is to revisit this model and investigate theoretically some aspects of the dipole polarizability (alpha(D)). A few approximations were done in the earlier calculations: the treatment of unfilled shells, the neglect that also higher order terms of the type A(10)r(t)C(0)(t) contribute with t odd (not only the A(10)r(1)C(0)(1) term), correlation effects and second order contributions in perturbation theory. The solutions of the inhomogeneous Schrodinger equation are solved by a powerful numerical method. The problem is reformulated and results instead in a simple linear equation system (symmetric tridiagonal matrix) which is stable and fast to solve. The various theoretical results will be used in future applications.

  • 1583.
    Åberg, Daniel
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Edvardsson, Sverker
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Engholm, Magnus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Direct calculation of correlated absorption amplitudes for Nd:LiYF42003Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, nr 19, artikkel-id 195105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The correlation contribution to the transition amplitudes are investigated in the case of Nd:LiYF4. By using many-body perturbation theory, we derive expressions for an effective dipole operator. The operators considered are Omega(es)((1)dagger)DOmega(cf)((1)), Omega(cf)((1)dagger)DOmega(es)((1)), Omega(es-cf)((2)dagger)D, and DOmega(es-cf)((2)). In contrast to third-order spin-orbit and crystal-field modified amplitudes, inclusion of correlation modifies the standard second-order amplitudes significantly. A model cluster is optimized to experimental energy levels. This approach is then used to compute consistent odd and even crystal-field parameters needed for theoretical absorption spectra. As expected, it is observed that transitions occurring at small wavelengths are quite heavily influenced by correlation. The overall agreement between experimental and theoretical spectra below 600 nm (above 17000 cm(-1)) is greatly improved when correlation is taken into account.

  • 1584.
    Åberg, Ludvig
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Parallelism within queue application2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    The aim of this thesis was to modify an existing order queue application which was unable to execute orders in a queue in parallel which in turn could lead to a bad user experience due to the increased queue delay. The thesis proposes two queue structures to allow parallel execution within a queue. One of the two is selected for implemented in the modified order queue application. The implementation was carried out in Java EE and used different types of frameworks such as JPQL. Some parts of the order queue application had to be modified to be able to handle the new queue structure. New attributes that defines dependencies of the orders are used to find a suitable parent for each order in the queue. The queue structure was visualized making it possible to see the execution in real time, and a test server was implemented to test the queue structure. This resulted in a working prototype able to handle dependencies and parallel orders. The modified order queue application was performance measured and compared to the original order queue application. The measurement showed that the modified order queue application performed better than the original order queue application in terms of execution time below a certain number of queues. Future work includes optimizing the methods and queries in the implementation to increase the performance and to handle parallelism within the orders.

  • 1585.
    Åhman, Stefan
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Robust Issue Tracking Application (RITA): Developing an issue tracker using modern web technologies2017Independent thesis Advanced level (degree of Master (Two Years)), 20 poäng / 30 hpOppgave
    Abstract [en]

    Issue tracking is one of the vital parts in maintaining computer  systems.  It is utilized in anything from small independent companies to large enterprises. The tracking does not just provide developers and other personnel with crucial information regarding their systems current state, but additionally stores useful documentation if any error reoccurs in the future. However, if the tracking issue would be deficient in some way, the complete process of developing or maintaining a system could affected negatively in great extent. This thesis work has looked into a scenario where the tool has been to slow, overly complicated and obsolete. It has made a large negative impact on the work force that uses the tool and made tracking issue to a discouragement. The thesis work has thence investigated features of the existing tool, suggested a better solution to use based upon these findings, followed by the development of a web application. When the application was finished, its usability was tested by the intended staff and performance tests were conducted. The test results showed that the application had been implemented successfully in many aspects. Unfortunately, due to deficient technical choices, the project did struggle with implementing all features as expected. The thesis work did consequently learn the hard way the importance of a choosing development techniques very thoroughly.

     

  • 1586.
    Åkerberg, Johan
    et al.
    ABB Corporate Research.
    Gidlund, Mikael
    ABB Corporate Research.
    Björkman, Mats
    Mälardalen University.
    Future Research Challenges in Wireless Sensor and Actuator Networks targeting Industrial Automation2011Inngår i: IEEE International Conference on Industrial Informatics (INDIN), IEEE conference proceedings, 2011, s. 410-415Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A growing trend in the automation industry is to use wireless technologies to reduce cable cost, deployment time, unlocking of stranded information in previously deployed devices, and enabling wireless control applications. Despite a huge research effort in the area of wireless sensor networks (WSNs), there are several issues that have not been addressed properly such that WSNs can be adopted properly in the process automation domain. This article presents the major requirements for typical applications in process automation and we also aim to outline the research direction for industrial wireless sensor networks (IWSNs) in industrial automation. The major issues that need to be addressed are safety, security and availability before industrial wireless sensor networks will be adopted in full scale in process automation.

  • 1587.
    Åkerberg, Johan
    et al.
    ABB Corporate Research.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informations- och kommunikationssystem.
    Lennvall, Tomas
    ABB Corporate Research.
    Landernäs, Krister
    ABB Corporate Research.
    Björkman, Mats
    Mälardalen University.
    Design Challenges and Objectives in Industrial Wireless Sensor Networks2013Inngår i: Industrial Wireless Sensor Networks: Applications, Protocols, Standards, and Products / [ed] V. C. Gungor and G. P. Hancke, CRC Press, 2013Kapittel i bok, del av antologi (Fagfellevurdert)
  • 1588.
    Åkerberg, Johan
    et al.
    ABB Corporate Research.
    Gidlund, Mikael
    ABB Corporate Research.
    Lennvall, Tomas
    ABB Corporate Research.
    Neander, Jonas
    ABB Corporate Research.
    Björkman, Mats
    Mälardalen University.
    Efficient Integration of Secure and Safety Critical Industrial Wireless Sensor Networks2011Inngår i: EURASIP Journal on Wireless Communications and Networking, ISSN 1687-1472, E-ISSN 1687-1499Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Wireless communication has gained more interest in industrial automation due to flexibility, mobility, and cost reduction. Wireless systems, in general, require additional and different engineering and maintenance tasks, for example cryptographic key management. This is an important aspect that needs to be addressed before wireless systems can be deployed and maintained efficiently in the industry.

    In this paper, we take an holistic approach that addresses safety and security regardless of the underlying media. In our proposed framework we introduce security modules which can be retrofitted to provide end-to-end integrity and authentication measures by utilizing the black channel concept. With the proposed approach, we can extend and provide end-to-end security as well as functional safety using existing automation equipment and standards, such as Profisafe, Profinet IO, and WirelessHART. Furthermore, we improve the WirelessHART standard with periodic and deterministic downlink transmissions to enable efficient usage of wireless actuators, as well as improving the performance of functional safety protocols.

  • 1589.
    Åkerberg, Johan
    et al.
    ABB Corporate Research.
    Landernäs, Krister
    ABB Corporate Research.
    Gidlund, Mikael
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier. ABB Corporate Research.
    Dynamic assigning of bandwidth to field devices in a process control system2012Patent (Annet (populærvitenskap, debatt, mm))
  • 1590.
    Åkerberg, Johan
    et al.
    ABB Corporate Research.
    Reichenbach, Frank
    ABB Corporate Research.
    Gidlund, Mikael
    ABB Corporate Research.
    Björkman, Mats
    Mälardalen University, Västerås.
    Measurement on an Industrial Wireless HART network Supporting PROFIsafe: A Case Study2011Konferansepaper (Fagfellevurdert)
  • 1591.
    Åkerdahl, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Felbortkoppling: Gasturbinanläggning2016Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Detta examensarbete har utförts på uppdrag av konsultföretaget Rambölls energiavdelning i Sundsvall.

    Gasturbinanläggningars uppgift idag är att agera effektreserv för tillfällen då behov av extra effekt uppstår. Gasturbinanläggningen i Hallstavik byggdes under 70-talet, men har under en period varit avställd med mycket efterstatt underhåll som följd. Den kunskap som funnits om anläggningen har till stor del försvunnit med de personer som tidigare arbetat på anläggningen. Arbetet syftar till att formulera en felbortkopplingsfilosofi för anläggningstypen.

    Detta arbete redogör för de krav som ställs på gasturbinanläggningar, genom studie av de lagtexter som finns för området. Teoretiska beskrivningar av reläskyddssystemet och dess funktioner tillsammans med de felbortkopplingskarv som finns ligger till grund för beräkning av de inställningsvärden som görs i reläskydden.

    Felbortkoppling av produktionsanläggningar har visat sig ha grunden i de tekniska begränsningarna som finns för generator och turbin, detta lämnar ett stort ansvar till de som sköter inställningarna för att säkerställa att lagkrav uppfylls.

  • 1592.
    Åkerlind, Marcus
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för elektronikkonstruktion.
    Elnätsplanering i framtida bostadsområden: Med påverkan från solceller och elbilsladdare2019Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    Målet med detta arbete var att undersöka hur mikroproduktion med solceller och laddning av elbilar i våra hushåll kommer att se ut i framtiden och om elkvalitén, kapaciteten i distributionsnätet, utlösningsvillkoren och elnätsdimensioneringen i nya bostadsområden påverkas av detta. Två olika scenarier har tagits fram, där det som skiljer dem åt är hur många procent av hushållen som har elbilsladdare och solcellsproduktion. De två scenarierna jämförs sedan med hur det ser ut i dagsläget för att få en uppfattning om vad som krävs vid fram-tidens elnätsdimensioneringar. Två extremfall används där maximal produktion och minimal konsumtion sommartid jämförs med maximal konsumtion och ingen produktion vintertid.

    Arbetet visar att den totala effektförbrukningen ökar med procentökningen av elbilsladdare och solcellsanläggningar vilket leder till att nya bostadsområden måste dimensionernas för högre belastningsström-mar. Detta resulterar i att större transformatorer och att kablar med grövre ledarareor måste användas för att klara av den ökade belastningsströmmen. Spänningsvariationerna ökar vilket gör att acceptans-gränserna i vissa fall inte kan hållas. Vid simulering och beräkningar visade det sig att utlösningsvillkoren för alla sammankopplingspunkter och anslutningspunkter mot bostäder låg inom gränsvärdet fem sekunder samt att selektiviteten var god i de delsträckor som testades.

  • 1593. Öberg, J.
    et al.
    O'Nils, Mattias
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Jantsch, A.
    Postula, A.
    Hemani, A.
    Grammar-based Design of Embedded Systems2001Inngår i: Journal of systems architecture, ISSN 1383-7621, E-ISSN 1873-6165, Vol. 47, nr 3-4, s. 225-240Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Grammars define syntax of languages and as such have not been commonly considered as methods for design, despite well-known applications in computer science. Only in recent years grammar-based design has become a promising research field and the first commercial tools have appeared on the market. This paper reviews the basic concepts of applying grammars to electronic design - in particular to the device driver synthesis of communication protocols for embedded software, to the design of custom-hardware, and to the virtual prototyping of DSP systems. The paper shows the power of these methods, presents the latest research results and discusses future developments in this field.

  • 1594.
    Öhlund, Thomas
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Örtegren, Jonas
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Andersson, Henrik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Nilsson, Hans-Erik
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Sintering Methods for Metal Nanoparticle Inks on Flexible Substrates2009Inngår i: NIP 25: DIGITAL FABRICATION 2009, TECHNICAL PROGRAM AND PROCEEDINGS, The Society for Imaging Science and Technology, 2009, s. 614-617Konferansepaper (Fagfellevurdert)
    Abstract [en]

    In this paper a number of selective sintering methods suitable for inkjet printed nanoparticles are demonstrated on two different coated papers. The selective methods demonstrated here are electric current heating, microwave sintering and photonic curing. As a reference, conventional heat chamber sintering is also included. Conductivity measurements and studies of sintered structures with optical and scanning electron microscopy are performed, as well as a qualitative evaluation of how the heat-sensitive substrates are affected. The purpose is to analyze characteristics of each method and gain insight in how different process parameters affect overall performance and reliability. With heat chamber sintering the best achievable conductivity without substrate deformation corresponded to less than 20% of pure silver. With some selective methods, conductivity reached well above 50% of pure silver.

     

     

  • 1595.
    Öst, Albert
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för informationssystem och -teknologi.
    Evaluating LoRa and WiFi Jamming2018Independent thesis Basic level (degree of Bachelor), 10 poäng / 15 hpOppgave
    Abstract [en]

    Internet of Things changes our world with everything we have around us, our everyday things will be connected to the Internet. According to experts, in two years there will be up to 29 billion devices connected to the Internet. With all of the information that is produced it is important to keep the communication secure, otherwise there can be serious problems in the future. Therefore the objective with this study has been to investigate the area of jamming attacks on wireless communication for Internet of Things, more specifically on LoRa and WiFi technologies. This was made by a literature study to research about Internet of Things, the industrial side of it, the two communication technologies and wireless jamming of them. Additionally to this a small scale test bed system consisting of two LoRa nodes (an Arduino and a LoRa gateway), two WiFi nodes (a laptop and router) and a software defined radio frequency jammer (a HackRF One) were set up. Jamming was performed on the system and evaluated form the perspective of a typical industrial Internet of Things scenario. The testing on the system was done by measuring the received signal strength index, round trip time for a message and packet losses. The study showed that the WiFi communication broke down completely while the LoRa communication stood strong up to the jammer. This concluded that LoRa communication is secure for a typical Internet of Things scenario, from this particular jamming device, or a similar one.

  • 1596.
    Österberg, Patrik
    et al.
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    Zhang, Tingting
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Institutionen för informationsteknologi och medier.
    A Bandwidth-Allocation Policy Taking Layered Video Multicast into Consideration2004Inngår i: Proceedings of the Eighth IASTED International Conference on Internet and Multimedia Systems and Applications, Acta Press , 2004, s. 347-352Konferansepaper (Fagfellevurdert)
    Abstract [en]

    As multicast is slowly gaining in support, the concept of multicast fairness is starting to attract some attention. Should multicast flows be favored at the expense of unicast flows, and if so to what extent? Allocating link bandwidth in proportion to the logarithm of the number of receivers of a flow has been proposed. That kind of policies favors multicast flows, without totally starving unicast flows. A problem of maintaining such policies emerges if layered multicast flows are introduced, since each layer is transmitted to a separate multicast IP address and will therefore be treated as an individual flow. Layered multicast flows will consequently be allocated too much bandwidth. In this paper, a logarithmic bandwidth-allocation policy that copes with layered multicast is proposed and evaluated through simulations. The results confirm that the proposal meets the expectations by preserving the intended fairness properties in scenarios with layered multicast traffic.

  • 1597.
    Öström, Daniel
    Mittuniversitetet, Fakulteten för naturvetenskap, teknik och medier, Avdelningen för elektronikkonstruktion.
    Styrning av värmepanna med PLC: Från relästyrning till digital styrning2017Independent thesis Basic level (professional degree), 10 poäng / 15 hpOppgave
    Abstract [sv]

    På det kommunalägda energiföretaget Sala Heby Energi AB pågår arbetet med att konvertera styrningen av en värmepanna från relästyrning och analog övervakning till digital styrning med PLC. Inom ramarna för detta examensarbete studeras tre specifika delar av denna konvertering: en teoretisk studie med syfte att kartlägga fördelar och nackdelar med konverteringen, en undersökning huruvida det finns möjlighet att förbättra en-skilda styrfunktioner i samband med konverteringen och upprättande av ett principschema eller översiktsbild över värmepannan som ska fungera som underlag till dess implementering i kraftvärmeverkets SCADA-system. En fördel med relästyrningen är att den kan vara kostnadseffektiv för att klara enskilda enkla styruppgifter. Dock, överlag och i synnerhet för styrning av större mer komplexa processer talar det mesta till den digitala styrningens fördel. Detta i form av kostnadseffektivitet för större system, möjligheter till mer effektiv larmhantering och möjligheten till loggning av driftdata. Två enskilda funktioner studeras: reglering av värmepannans siktskärm i förhållande till ångdomstrycket och styrning för bränslehanteringen. För reglering av siktskärmens höjd jämförs två alter-nativ med hjälp av simuleringar i Simulink. Konventionell PID-reglering jämförs mot en egenkonstruerad fuzzy-regulator. Mycket på grund av en bristfälligt underbyggd modellering av processen går inte fuzzy-regulatorns eventuella fördelar mot PID-regulatorn att fastställa. Framtida studier av fuzzy-regulatorn skulle potentiellt kunna ändra på detta förhållande. Vidare diskuteras styrningen av funktioner i bränslehantering och då främst autentisering av chaufförer som ska bränslefylla. För att de ska få tillgång till bränslehanteringens funktioner när kraftvärmeverket är obemannat föreslås det en lösning med nyckelbrytare för att aktivera aktuella styrfunktioner. Slutligen tas en ny digital översiktsbild fram över systemet för värmepannan. Denna innehåller mindre uppdateringar och anpassningar jämfört med två översiktsbilder som finns uppritade på de gamla styrskåpen.

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