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  • 25301.
    Xie, Z Q
    et al.
    Hunan Normal Univ, Dept Math, Changsha 410081, Hunan Peoples R China.
    Gullikson, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Hägglund, R
    SCA.
    Determining the elastic constants of paper with optimization methods2002In: Inverse Problems in Engineering, ISSN 1068-2767, E-ISSN 1029-0281, Vol. 10, no 5, p. 393-411Article in journal (Refereed)
    Abstract [en]

    In this article we describe a method for determining the elastic constants for paper from a measured displacement field. Our model is based on the finite element method using quadrilateral elements. A method for finding the first and second order derivatives with respect to the unknown parameters plays a crucial role in the optimization process used to solve the inverse problems in this article. To reduce the influence of the noise of the input data, an efficient continuation method is used for the regularization term in the cost function. Some numerical results for synthetic data and measurement will verify the efficiency of our approach.

  • 25302.
    Xie, Ziqing
    et al.
    Dept of Mathematics, Hunan Normal Univ, China.
    Gulliksson, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Hägglund, Richard
    SCA Packaging Research, Sundsvall, Sweden.
    Determining the elastic constants of paper from measured displacements2001Report (Other academic)
  • 25303.
    Xin, Zhang
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Distributed Electronic Health Record System based on Middleware2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    With the fast development of information technology, traditional healthcare is evolving to a more digital and electronic stage. Electronic HealthRecord (EHR) is residents’ basic information and health care relatedinformation conforming to standard. It can not only provide usefulinformation to medical workers, but also exchange resources with otherinformation systems. But with the growing complexity of electronichealth record data sources, it becomes a big challenge to set up a structurewhich allows different types of data sharing and exchanging inmulti-platform applications. It’s even more important to find out amethod to support great amount of users from different applicationplatform to sharing and exchanging data at the same time.In this paper, we proposed a distributed electronic health record systembased on middleware to address the problem. Both permanent and realtimedata should pass through the middleware provided by the system,and will be transformed into standard format for storage. Multi-threadand distributed server group design will let the system be more flexibleand scalable, and will be able to provide service to users concurrently.The system creates a standard data format for data transferring andstorage. All raw data collected from different kinds of sensor system willbe formatted with application programming interface (API) or softwaredevelopment kit (SDK) system provided before upload to the system.Encryption methods are also implemented to ensure data security andprivacy protection.

  • 25304.
    Xiong, Ning
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Litz, Lothar
    Identifying flexible structured premises for mining concise fuzzy knowledge2003In: Interpretability Issues in Fuzzy Modeling, Berlin: Springer, 2003, p. 54-Chapter in book (Other academic)
  • 25305. Xiong, Shaojun
    et al.
    Johansson, Mats
    Hughes, Francine
    Hayes, Adrian
    Richards, Keith
    Nilsson, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Interactive effects of soil moisture, vegetation canopy, plant litter and seed addition on plant diversity in a wetland community2003In: Journal of Ecology, ISSN 0022-0477, E-ISSN 1365-2745, Vol. 91, no 6, p. 976-986Article in journal (Refereed)
    Abstract [en]

    1 We carried out a factorial experiment to examine how groundwater availability (low and high sites with intermediate or rare flooding), vegetation canopy, leaf litter and seed availability interacted to determine the species richness of a productive wet grassland community in Wicken Fen National Nature Reserve, Cambridgeshire, UK. Seeds of 18 species were added to half the plots in each of eight combinations of elevation, canopy and litter, and seedling emergence was observed for two growing seasons.2 Both individual and interactive effects on plant diversity and colonization were determined for all four examined factors. Interactive effects explained 41-63% of the total variation in both species richness and numbers of individuals growing from added seeds.3 Neither elevation nor vegetation canopy had significant individual effects on total species richness, but their interaction was significant. Litter addition limited seedling emergence at the low elevation but favoured it at the high elevation.4 The relative importance of vegetation canopy and plant litter in affecting plant community composition varied with the community parameter considered (species richness or number of seedlings), elevation and stage of vegetation development. In general, plant litter was more important in determining species richness, whereas the vegetation canopy was more important in determining seed germination and seedling emergence. Plant litter was also more important than vegetation canopy at an early stage of vegetation development and at low elevation.5 Seed availability was the most important factor in determining overall species richness in the studied community. The influence of the local seed bank was very limited. Seedling emergence and seedling species richness were generally enhanced by lower elevation and seed addition, but depressed by vegetation and litter addition.6 The complex relationships observed have considerable implications for ecological modelling and ecosystem restoration. Manipulation of one factor may produce unexpected effects on other factors, which may induce a series of consequences for the whole community. Further knowledge on how natural communities are organized and maintained is needed to guide the management of ecosystems.

  • 25306.
    Xiong, Shaojun
    et al.
    Umea Univ, Landscape Ecol Grp, Dept Ecol & Environm Sci, SE-90187 Umea.
    Nilsson, Christer
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Johansson, Mats E
    Umea Univ, Landscape Ecol Grp, Dept Ecol & Environm Sci, SE-90187 Umea.
    Jansson, Roland
    Umea Univ, Landscape Ecol Grp, Dept Ecol & Environm Sci, SE-90187 Umea.
    Responses of riparian plants to accumulation of silt and plant litter: the importance of plant traits2001In: Journal of Vegetation Science, ISSN 1100-9233, E-ISSN 1654-1103, Vol. 12, p. 481-490Article in journal (Refereed)
    Abstract [en]

    A 2-yr field experiment was used to determine the response of riparian plants to accumulation of litter or silt in a river flood-plain meadow in northern Sweden. Such disturbances occur regularly in free-flowing rivers but are likely to change as a result of global changes in land use or climate. We anticipated that plants with different traits would differ in their response to litter and silt accumulation. We quantified plant response as relative change in above-ground biomass, and regressed it on either litter mass or silt depth, and on plant traits such as lateral spread, plant height, relative growth rate, seed mass and seed persistence in soil. The relative changes in riparian plant biomass following litter or silt accumulation were negatively related to litter mass and silt depth, and positively related to most examined plant traits Such as seed mass. seed persistence and lateral spread. The vegetation recovery in the second season was largely determined by plant traits; litter or silt accumulation had no significant effect. Litter accumulation selected for large-seeded species, but silt accumulation selected for species with strong ability of lateral spread. Seed persistence was a useful variable in predicting species recovery from both litter and silt accumulation. Plant height was negatively related to plant recovery, but relative growth rate was not significantly related to relative change in plant biomass after silt or litter accumulation. Our results imply that plant traits are important variables to consider for predicting the responses of riparian vegetation to deposition of organic and inorganic matter.

  • 25307.
    Xiong, Wenjuan
    et al.
    Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, China.
    Jiang, Haojie
    Chinese Academy of Sciences, Beijing, China.
    Li, Tingting
    Chinese Academy of Sciences, Beijing, China.
    Zhang, Peng
    Chinese Academy of Sciences, Beijing, China.
    Xu, Qing
    Chinese Academy of Sciences, Beijing, China; University of Science and Technology of China, Hefei, People’s Republic of China.
    Zhao, Xuewei
    Chinese Academy of Sciences, Beijing, China; University of Science and Technology of China, Hefei, People’s Republic of China.
    Wang, Guilei
    Chinese Academy of Sciences, Beijing, China.
    Liu, Yaodong
    Chinese Academy of Sciences, Beijing, China.
    Luo, Ying
    Chinese Academy of Sciences, Beijing, China.
    Li, Zhihua
    Chinese Academy of Sciences, Beijing, China.
    Li, Junfeng
    Chinese Academy of Sciences, Beijing, China.
    Yu, Jinzhong
    Chinese Academy of Sciences, Beijing, China.
    Chao, Zhao
    Chinese Academy of Sciences, Beijing, China.
    Wang, Wenwu
    Chinese Academy of Sciences, Beijing, China.
    Radamson, Henry H.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design. Chinese Academy of Sciences, Beijing, China; University of Chinese Academy of Sciences, Beijing, People’s Republic of China.
    SiNx films and membranes for photonic and MEMS applications2020In: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 31, p. 90-97Article in journal (Refereed)
    Abstract [en]

    This work presents a novel process to form SiN x films and process for membranes with excellent mechanical properties for micro-electro-mechanical systems application as well as integration as IR waveguide for photonic application. The SiN x films were fabricated in SiNgen apparatus which is a single wafer chamber equipment compared to conventional low pressure chemical vapor deposition furnace process. The films showed low stress, good mechanical properties, but the synthesis also eradicates the issues of particle contamination. Through optimizing of the growth parameters and post annealing profile, low stress (40 Mpa) SiN x film could be finally deposited when annealing temperature rose up to 1150 °C. The stress relaxation is a result of more Si nano-crystalline which was formed during annealing, according to the FTIR results. The mechanical properties, Young’s modulus and hardness, were 210 Gpa and 20 Gpa respectively. For the waveguide application, a stack of three layers, SiO 2 /SiN x /SiO 2 was formed where the optimized layer thicknesses were used for minimum optical loss according to simulation feedback. After deposition of the first two layers in the stack, the samples were annealed in range of 900–1150 °C in order to release the stress. Chemical mechanical polish technique was applied to planarize the nitride layer prior to the oxide cladding layer. Such wafers can be used to bond to Si or Ge to manufacture advanced substrates.

  • 25308.
    Xiong, Ye
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Malaria infection in relation to reproductive success and secondary sexual traits in collared flycatcher: In new and old breeding areas2014Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Life-history theory is based on the idea that every individual face a limitation of energy, nutrients and time in its lifespan. This optimization problem is resulting in trade-offs between resource demanding tasks and traits. It has been shown that parasite resistance and specific immune response is reduced by increased reproductive effort in birds. Reproduction success and malaria infection state were tested on 434 individuals in two old and one new breeding area on Gotland. With a high accuracy and fast PCR method, three genera of protozoan haemosporidians, which are also known as avian malaria parasites, were analyzed in this study to detect host-parasite interactions. The reproduction success, indicated as lay-date and fledge, in Rums and OLD areas, Gotland, Sweden, did not show any significant relation to infection state. Instead, age (Young < 2yrs vs Old ≥ 2yrs) was found to be the most influential factor affecting reproduction success. A trade-off between infection state and patch size (secondary sexual traits) has not been shown in this study. However, there are still pieces missing in understanding how avian malaria parasites affect their host's fitness, such as the host bird immunity response to the blood parasite species and intensity levels, which need to be examined in future studies.

  • 25309.
    Xu, Chao
    et al.
    Stockholm Univ, Stockholm.
    Afewerki, Samson
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. Stockholm Univ, Stockholm.
    Tai, Cheuk-Wai
    Stockholm Univ, Stockholm.
    Cordova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. Stockholm Univ, Stockholm.
    Hedin, Niklas
    Stockholm Univ, Stockholm.
    Cyclopalladated Azo-linked Porous Polymers in C-C Bond Forming Reactions2016In: CHEMISTRYSELECT, ISSN 2365-6549, Vol. 1, no 18, p. 5801-5804Article in journal (Refereed)
    Abstract [en]

    We designed a new cyclopalladated porous polymer (cyclo-Pd (II)/PP-2) with up to 20.7 wt% of Pd and investigated it as a heterogeneous catalyst for C-C bond-forming transformations. It was also shown to be an effective scavenger for Pd2+ in solution. The palladacycles formed along the backbone of the azo-linked porous polymer (PP-2) with (Pd-N) and (Pd-C) bonds as were confirmed by a combination of spectroscopies. The cyclo-Pd(II)/PP-2 decomposed when used for Suzuki and Heck cross-coupling reactions, and acyclic-Pd/PP-2 formed with Pd nanoparticles (NPs) bound to the PP-2. The Suzuki couplings were highly efficient in water and exhibited excellent recyclability. The cyclo-Pd(II)/PP-2 was also an effective heterogeneous Lewis-acid catalyst for stereoselective carbocyclization reactions.

  • 25310.
    Xu, Chao
    et al.
    Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden.
    Deiana, Luca
    Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden.
    Afewerki, Samson
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Incerti-Pradillos, Celia
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Cordova, Oscar
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Guo, Peng
    Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden.
    Cordova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences. Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden.
    Hedin, Niklas
    Stockholm Univ, Berzelii Ctr EXSELENT Porous Mat, SE-10691 Stockholm, Sweden.
    The Use of Porous Palladium(II)-polyimine in Cooperatively-catalyzed Highly Enantioselective Cascade Transformations2015In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 357, no 9, p. 2150-2156Article in journal (Refereed)
    Abstract [en]

    Porous organic polymers have prospects as functional substrates for catalysis, with quite different molecular properties from inorganic substrates. Here we disclose for the first time that porous palladium(II)-polyimines are excellent catalysts for cooperatively catalyzed and enantioselective cascade reactions. In synergy with a chiral amine co-catalyst, polysubstituted cyclopentenes and spirocyclic oxindoles, including the all-carbon quaternary stereocenter, were synthesized in high yields. High diastereo- and enantioselectivities were achieved for these dynamic kinetic asymmetric transformations (DYKAT) of enals with propargylic nucleophiles.

  • 25311. Xu, Hongqi
    et al.
    Lindefelt, Ulf
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Electronic structure of neutral and charged vacancies in GaAs1990In: Physical Review B (Condensed Matter), ISSN 0163-1829, Vol. 41, no 9, p. 5979-5990Article in journal (Refereed)
  • 25312.
    Xu, Ting
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Systems and Technology.
    Integration and Evaluation of IoT Hardware and Software platforms2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The Internet of Things (IoT) is growing rapidly these years and the influence of IoT on everyday life and behavior are also increasing. It is a network that connects physical devices, vehicles, buildings, and other items and embedded with electronics, software, sensors, actuators, and network connectivity so that these objects can collect and exchange data. It has been utilized in lots of domains, such as transportation and logistics domain, healthcare domain, smart environment domain, personal and social domain. It is estimated that the IoT will consist of almost 50 billion objects by 2020. IoT Gateway is really important in IoT, which can bridge traditional communication networks with sensor networks to make the network communication easier. IoT communication is of vital importance in today’s life. This study has the aim of integrating and evaluating of IoT gateways and IoT communication systems. It proposes a scenario where the IoT gateway connects to an actuator in order to control the actuator and transmit the data via the IoT communication system, creates a demonstrator by setting up the communication between the IoT gateway platform and the IoT communication system, measures and evaluates the performance in terms of latency and throughput using the implemented scenario, and at last draws the conclusion.

  • 25313.
    Xu, Y S
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    CS-PRMA/AP: Carrier sense packet reservation multiple access with adaptive permission probability2000In: 2000 INTERNATIONAL CONFERENCE ON COMMUNICATION TECHNOLOGY PROCEEDINGS, VOLS. I & II / [ed] Ke G; Zhisheng N, BEIJING: PUBLISHING HOUSE ELECTRONICS INDUSTRY , 2000, p. 892-899, article id 889334Conference paper (Refereed)
    Abstract [en]

    In the paper a Carrier Sense Packet Reservation Multiple Access (CS-PRMA) protocol is proposed for Wireless Local Area Networks (WLAN). The proposed protocol can be viewed as a combination of CSMA with adaptive permission probability for contentions and TDMA for reserved transmissions. A mechanism for the sense of hidden transmitting terminals is described. As the original PRMA the CS-PRMA system has the properties of soft capacity, soft hand-over, and distributed slot assignment and selection. The basic feature that characterises CS-PRMA with respect to original PRMA is its very high channel efficiency. Simulation shows that a capacity of 2.50 conversations per slot is achievable for a broadband communication system with fast speech activity detectors. This capacity is close to the upper bound of the PRMA capacity, 2.78 conversations per slot. Furthermore the consecutive contention scheme is very flexible for different traffics with different priorities, such as voice, network control signals and data messages. This protocol is suitable for broadband WLANs, where a high degree of distributed system control is required.

  • 25314.
    Xu, Ye
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Kilowatt Three-phase Rotary Transformer Design for Permanent Magnet DC Motor with On-rotor Drive System2016Independent thesis Advanced level (degree of Master (Two Years)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of this thesis is to design a kilowatt three-phase step-down rotary transformer for

    a permanent magnet DC motor. The permanent magnet DC motor has an on-rotor drive

    system, and therefore requiring a power supply that can transfer power to its drive unit

    without mechanical contact. The rotary transformer has a detached magnetic coupling

    structure that qualifies it as a potential method for the wireless power transfer.

    This thesis studies the rotary transformer as a static device, focusing on its core loss.

    By using a transient finite element analysis of COMSOL Multiphysics and an iron loss

    prediction model, the rotary transformer was optimized in terms of efficiency and power

    density for the on-rotor drive system through proper material selection and geometry exploration.

    After this, a mechanical design, which based on a literature review of the

    influences of manufacturing processes on electrical steels, was proposed for realizing the

    core fabrication and the rotary transformer assembly.

    The results show that the rotary transformer can step down 400 V/50 Hz three-phase

    voltage to 13.15V in a Delta-wye connection and output 1.17kW power over an air-gap

    of 0.3mm with 95.94% overall efficiency. The proposed mechanical design enables the

    transformer to minimize the core loss and the manufacturing cost. Without using resonant

    inductive coupling, this transformer design simplifies the power supply for the motor,

    thereby decreasing the motor manufacturing and maintenance cost.

  • 25315.
    Xu, Ye
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bader, Sebastian
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Magno, Michele
    Dept. of Information Technology and Electrical Engineering, ETH Zurich.
    Mayer, Philipp
    Dept. of Information Technology and Electrical Engineering, ETH Zurich.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Energy-autonomous On-rotor RPM Sensor Using Variable Reluctance Energy Harvesting2019In: 2019 IEEE 8th International Workshop on Advances in Sensors and Interfaces (IWASI), IEEE, 2019, p. 175-180, article id 08791251Conference paper (Refereed)
    Abstract [en]

    Energy-autonomous wireless sensor systems have the potential to enable condition monitoring without the need for a wired electrical infrastructure or capacity-limited batteries. In this paper, a robust and low-cost energy-autonomous wireless rotational speed sensor is presented, which harvests energy from the rotary motion of its host using the variable reluctance principle. A microelectromechanical system (MEMS) gyroscope is utilized for angular velocity measurements, and a Bluetooth Low Energy System-on-Chip (SoC) transmits the acquired samples wirelessly. An analysis on the individual subsystems is performed, investigating the output of the energy transducer, the required energy by the load, and energy losses in the whole system. The results of simulations and experimental measurements on a prototype implementation show that the system achieves energy-autonomous operation with sample rates between 1 to 50 Hz already at 10 to 40 rotations per minute. Detailed investigations of the system modules identify the power management having the largest potential for further improvements.

  • 25316.
    Xu, Ye
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bader, Sebastian
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    A Survey on Variable Reluctance Energy Harvesters in Low-Speed Rotating Applications2018In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 18, no 8, p. 3426-3435Article in journal (Refereed)
    Abstract [en]

    Energy harvesting converts ambient energy to electrical energy that can be used to power, for example, sensors and sensor systems. Variable reluctance energy harvesting is a suitable candidate for the conversion of rotary kinetic motion, an energy form commonly found in industrial applications. The implementation of a variable reluctance energy harvester, however, has a significant effect on its performance and is not well studied. In this paper, we therefore conduct a survey on different structures of variable reluctance energy harvesters. Six existing structures, previously used in variable reluctance sensors, are presented and analyzed according to their approaches for magnetic flux change improvement. Together with a newly proposed structure, these structures are evaluated based on a finite element analysis, and their results are compared. It is demonstrated that the choice of structure considerably affects the power output of the harvester and is dependent on the improvement approaches the structure utilizes. The newly proposed structure outperforms all existing structures with respect to power output and power density, which comes at a cost of higher parasitic torque generation. A 53-fold power improvement over the reference and an 1.2-fold power improvement over the next best structure is observed. As a result, applications of variable reluctance energy harvesting become viable even at low angular velocities.

  • 25317.
    Xu, Ye
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Bader, Sebastian
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Electronics Design.
    Design, modeling and optimization of an m-shaped variable reluctance energy harvester for rotating applications2019In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 195, p. 1280-1294Article in journal (Refereed)
    Abstract [en]

    The variable reluctance principle can be used to convert rotational kinetic energy into electrical energy, creating a Variable Reluctance Energy Harvester (VREH) based on electromagnetic induction. This can be used to implement self-sustaining wireless sensors in rotating applications. In this paper, we present and investigate a novel design of a VREH with high volumetric power density that targets low-speed rotating applications. The design uses an m-shaped pole-piece and two opposing magnets. We theoretically analyze key design parameters that influence the VREH’s output power, and relate these parameters to geometrical design factors of the proposed structure. Key design factors include the coil height, the permanent magnet height and the tooth height. A method based on numerical simulations is introduced, enabling to determine the optimal geometrical dimensions of the proposed structure under given size-constraints. The results demonstrate that the method leads to optimal structure configurations, which has been evaluated for different cases and is verified experimentally. Good agreement between numerical simulations and experiments are reported with deviations in output power estimation below 3%. The optimized m-shaped VREH, moreover, provides output power levels sufficient for wireless sensor operation, even in low-speed rotating applications.

  • 25318. Xu, Youshi
    A concatenated random error and burst erasure decoding scheme for random noise and burst fading or interference channels1997In: Proceedings of IEEE International Symposium on Information Theory, 29 June-4 July 1997 , Ulm, Germany, New York: IEEE , 1997, p. 466-Conference paper (Refereed)
    Abstract [en]

    A concatenated random error correction and burst erasure recovering code scheme is proposed. This will significantly improve the performance of communication systems in some applications. This proposal is based on an efficient erasure decoding algorithm for binary block codes and an efficient application in the presence of fading or interference.

  • 25319. Xu, Youshi
    A modified Euclidean algorithm and the VLSI implementation1996In: 8th Mediterranean Electrotechnical Conference, 1996. MELECON '96., Bari, Italy, 13-16 May 1996. Vol. 3, 1996, p. 1324-1327Conference paper (Refereed)
    Abstract [en]

    The extended Euclidean algorithm is important in algebraic and symbolic computations, in error correcting codes, in code division multiple access and, in cryptology. We propose a modified algorithm and a recursive implementation. Both the time and space complexity of the implementation is better than conventional ones. The regular and modular construction implies that it can be implemented on VLSI chips. The implementation can be used in decoding BCH codes, RS codes and Goppa codes. A throughput of hundreds of megabits per second is achievable.

  • 25320.
    Xu, Youshi
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Efficient integration of voice and data services in wireless local area networks2000In: EEE Vehicular Technology Conference, IEEE conference proceedings, 2000, Vol. 2, p. 1395-1399Conference paper (Refereed)
    Abstract [en]

    We propose a new scheme of mixing speech information, network control message and data information with different priority in PRMA. This proposed PRMA can be viewed as a combined protocol of voice-only PRMA for voice terminals, carrier sense (CS)-slotted ALOHA for network control and CS-TDMA for data terminals. A mechanism for the sensing of hidden transmitting terminals is described. The integrated control packets and data packets do not have any influence on voice transmission. Simulation results show that the delay of network control packets and the channel throughput can be significantly improved, compared to all the other integrated PRMA protocols. This protocol distributes major control to the terminals, which may be extremely useful and important in the future.

  • 25321.
    Xu, Youshi
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Pure Binary BCH Concatenated Codes and the Applications for Fading Channels1996In: Radiovetenskap och Kommunikation, 3-5 June 1996, Luleå, Sweden, 1996Conference paper (Refereed)
  • 25322. Xu, Youshi
    et al.
    Nilsson, P
    Wiklund, H
    Packet Reservation Multiple Access for Joint Voice and Data1998In: 3rd International Symposium on Multi Dimensional Mobile Communications (MDMC'98), Menlo Park, CA, September 21, 1998, 1998Conference paper (Refereed)
  • 25323.
    Xu, Youshi
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Nilsson, Peter
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Wiklund, Håkan
    On the utilization of voice-unused resource for data transmission in PRMA systems1998In: IEEE 1998 International Conference on Universal Personal Communications, Florence, It., Oct 05-09, 1998. ICUPC '98. Vol. 2, IEEE , 1998, p. 1043-1047Conference paper (Refereed)
    Abstract [en]

    In the paper voice-unused resource in a voice-only PRMA system is analyzed. A mechanism for the detection of voice-unused resource is proposed. How to use the voice-unused resource for data transmission is proposed. Therefore, the voice subsystem is totally a voice-only PRMA system, and the existence of data transmission just improves the channel utilization efficiency, without any influence on the performance of voice communications. Simulation results show that a significant amount of data traffic can be supported by the voice-unused resource.

  • 25324.
    Xu, Youshi
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Zhang, Tingting
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    A VLSI Design for Universal Reed-Solomon Erasure Decoder2002In: International Conference on Signal Processing Proceedings, ICSP, IEEE conference proceedings, 2002, p. 398-401, article id 1181074Conference paper (Refereed)
  • 25325.
    Xu, Youshi
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Zhang, Tingting
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    An implementation of coding scheme for packet loss protection2001In: Proceedings of the 11th International Packet Video Workshop, 2001Conference paper (Other academic)
  • 25326.
    Xu, Youshi
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Zhang, Tingting
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Variable shortened-and-punctured Reed-Solomon codes for packet loss protection2002In: IEEE Transactions On Broadcasting, ISSN 0018-9316, Vol. 48, no 3, p. 237-245Article in journal (Refereed)
    Abstract [en]

    In this paper, techniques of Reed-Solomon (RS) codes to recover lost packets in digital video/audio broadcasting and packet switched network communications are reviewed. Usually, different RS codes and their corresponding encoders/decoders are designed and utilized to meet different requirements for different systems and applications. We incorporate these techniques into a variable RS code and present an encoding and decoding algorithm suitable for the variable RS code. A mother RS code can be used to produce a variety of RS codes and the same encoder/decoder can be used for all the derivative codes with adding/detecting zeros, removing a part of parity symbols, and adding erasures. A VLSI implementation for erasure decoding of the proposed variable RS code is described and the achievable performance is quantitatively analyzed. A typical example shows that the signal processing speed is up to 2.5 Gbits/second and the processing delay is less than one millisecond, when integrating the decoder on a single chip. Therefore, the proposed algorithm and the encoder/decoder can universally be utilized for different applications with various requirements, such as transmission data rate, packet length, packet loss protection capacity, as well as layered protection and adaptive redundancy protection in DVB/DAB broadcasting, Internet and mobile Internet communications.

  • 25327.
    Xu, Youzhi
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Zhang, Tingting
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    An adaptive redundancy technique for wireless indoor multicasting2000In: IEEE Symposium on Computers and Communications - Proceedings, Los Alamitos, Calif: IEEE Computer Society , 2000, p. 607-614Conference paper (Refereed)
    Abstract [en]

    In this paper we present an adaptive technique that combines forward error correction (FEC) with channel state estimation (CSE) and automatic repeat request (ARQ) for packet loss recovery in wireless indoor multicast systems. The novel aspect of the technique is its ability to achieve significant packet throughput with high data reliability, to avoid feedback acknowledgement (ACK) implosion, as well as to reduce and flexibly to limit delay for real-time applications. We suggest a set of criteria to measure the multicast performance and simulate a simple two-state indoor channel model. The simulation results show that the proposed technique significantly improves the communication quality and channel efficiency, to compare with traditional FEC and ARQ techniques.

  • 25328.
    Xuan, Lihua
    Mid Sweden University, Faculty of Human Sciences, Department of Business, Economics and Law.
    Factors affecting the adoption of mobile instant message: An empirical study of user acceptance of Wechat in China2014Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Nowadays, instant message has become a key tool for students to stay connected with existing friends and family, as well as to create new friendships. WeChat as a third party software that exists in the current market, is an instant messaging application that enables users to send voice, video, pictures and text to their contacts through mobile network. Being a new application, the user adoption of WeChat has not been studied. Therefore, the result of this study will be valuable to fill the knowledge gap about user adoption study of this mobile application, and future development of other similar instant messaging mobile application could also benefit from this study. This study focuses on WeChat users and answers to the following research question: What are the factors that affect the users’ adoption of WeChat?

    The purpose of this study is to explain factors that affect the users’ adoption of WeChat among WeChat users.

    This study adopts a theory testing approach. The research model will propose through UTAUT model and semi-structured interview. A survey was conducted subsequently to collect quantitative data. Hypotheses were tested through analyzing the quantitative data by using SPSS.

  • 25329.
    Xue, Ruidong
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Improved association rule mining to sensor time series2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 25330.
    Xue, Ruidong
    et al.
    Donghua Univ, Sch Comp Sci & Technol, Shanghai, Peoples R China.
    Zhang, Tingting
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Chen, Dehua
    Donghua Univ, Sch Comp Sci & Technol, Shanghai, Peoples R China.
    Le, Jiajin
    Donghua Univ, Sch Comp Sci & Technol, Shanghai, Peoples R China.
    Lavassani, Mehrzad
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Sensor Time Series Association Rule Discovery Based on Modified Discretization Method2016In: 2016 FIRST IEEE INTERNATIONAL CONFERENCE ON COMPUTER COMMUNICATION AND THE INTERNET (ICCCI 2016), IEEE, 2016, p. 196-202, article id 7778907Conference paper (Refereed)
    Abstract [en]

    Association rule discovery from sensor time series is a challenge. Because the time series has high dimensional, numerical and continuous nature. However the general association methods can only deal with data which are symbolic and discrete. And the general association methods have high processing time consumption when the data have high dimension. So a useful framework is proposed, which is pre-processing, representation, discretization and temporal association mining. In the discretization section, a modified discretization method is proposed which can combine the advantages of other methods, such as piecewise aggregate approximation (PAA), knee point selection, symbolic aggregate approximation (SAX) and monotonicity feature extraction. In the association section, a modified Apriori algorithm is proposed to discover special patterns and normal rules.

  • 25331.
    Xue, Shang
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Alternating Coding and its Decoder Architectures for Unary-Prefixed Codes2005Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The entropy coding of high peak, heavy-tailed probability distributions such as the Laplacian, Cauchy, and generalized Gaussian have been a topic of interest because they are able to provide good models for data in many coding systems, especially in image and video coding systems. This thesis studies the entropy coding of such high peak, heavy-tailed probability distributions. By summarizing the encoding of such distributions under the concept “Unary Prefixed Codes” (UPC), the thesis depicts the encoding via a different approach. By extending the concept of UPC, the thesis proposes a universally applicable coding algorithm “Unary Prefixed Huffman” (UPH) that could be applied to both finite and infinite sources. The code set resulting from the UPH algorithm has a coding efficiency which is upper-bounded by entropy + 2 given that the entropy is finite, and is able to provide sub-optimal encoding of the sources studied in the thesis. The thesis also proposes several different variations of UPCs that are simple in structure yet efficient for use for several variations of the high peak, heavy-tailed distributions that are commonly found in image and video coding systems. By applying the concept of the UPC, the thesis further proposes a coding method named the “Alternating Coding” (ALT) method. The ALT coding provides a coding pattern that is different from the conventional method which enables the extraction of special properties of the UPCs. Using the extraction of the special property of the UPCs, decoding could be greatly simplified and parallel decoding could be a possibility. Moreover, for the highly structured UPCs that are widely used in image and video coding systems, the ALT coding enables an error resiliency mechanism to be applied, which helps to improve the error tolerance of these UPC packets to a significant extent. Simulations and actual application results of the ALT coding are discussed in the thesis. By applying the ALT coding, the hardware architecture of the decoder changes accordingly. The ALT decoder is different to the conventional variable length decoders that have been applied in the decoding of UPCs, as it is able to utilize the special properties of the UPCs and thus simplify the decoder architecture. As shown in the thesis, the ALT decoders are smaller in size, faster in speed and consume much less power compared to the conventional decoders. This is particularly true for those highly structured UPCs that are commonly used in image and video coding systems. Actual realizations of several ALT decoders are discussed in the thesis, and comparisons are made to the conventional decoders. The improvements are shown to be very evident.

  • 25332.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    A Coding Method for UVLC Targeting Efficient Decoder Architecture2003In: Proceedings of the 3rd IEEE Internatioal Symposium on Image and Signal Processing and Analysis, Rome, Italy, September, 2003, 2003, p. 428-433Conference paper (Refereed)
    Abstract [en]

    Variable length code (VLC) is used in a large variety of lossless compression applications. A specially designed VLC, called "Universal Variable Length Code" (UVLC), is utilized in the latest video coding standard H.26L under development. In this work we propose a coding method that we call "Alternating Coding" (ALT coding) for UVLC. An efficient UVLC decoder is designed (ALT decoder) on the basis of it. ALT coding facilitates a much easier decoding scheme for UVLC. It frees the decoder from codeword tables and the sizes of the barrel shifters are reduced. The codeword tables and barrel shifters usually occupy the largest portion of the area in the traditional VLC decoders and they are also performance limiting in terms of speed and power consumption. We compare the ALT decoder with one of the most efficient VLC decoders called "VLC decoder using plane separation" (PLS). Our results show that the ALT decoder increases 25% in speed, decreases 41% in size, and consumes 45% power of the PLS decoder.

  • 25333.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Alternating Coding for Universal Variable Length Code2003In: Procceedings of the IEEE International Conference on Image Processing, Barcelona, Spain, September, 2003, IEEE , 2003, p. 477-480Conference paper (Refereed)
    Abstract [en]

    Variable length code (VLC) is used in a large variety of lossless compression applications. A specially designed VLC, called "Universal Variable Length Code" (UVLC), is utilized in the latest video coding standard H.26L under development. In this work we propose a new coding method under the name "Alternating Coding" (ALT coding) and apply it to the UVLC The ALT coded UVLC yields the same high coding efficiency as the original UVLC, but ALT coding also enables immediate decoding, immediate error detection and location in a UVLC packet. It improves the error resiliency and error robustness of the UVLC packet by applying an "error speculation". Results show that the ALT coded UVLC packet always outperforms the original UVLC packet in terms of error resiliency and robustness. Moreover the simple pattern of ALT coded UVLC can greatly simplify the UVLC decoder architecture and therefore enables small, fast, and low-power decoder design.

  • 25334.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Comparative study of low-voltage performance of standard-cell flip-flops2001In: ICECS 2001: 8TH IEEE INTERNATIONAL CONFERENCE ON ELECTRONICS, CIRCUITS AND SYSTEMS, VOLS I-III, CONFERENCE PROCEEDINGS, New York: IEEE , 2001, p. 953-957Conference paper (Other academic)
    Abstract [en]

    The static single-phase D flip-flop is the basic memory element in the standard cell based design methodology for digital integrated circuits. In low-power high-speed performance designs, pipelining in conjunction with voltage scaling has proven to be an efficient approach to achieve the targeted low-power performance. The efficiency of the flip-flop at low power supply voltages will therefore play an increasingly important role. In this paper a comparison of the efficiency of six different D flip-flops operating at different voltages are presented and discussed. All circuits in this paper have been designed in a 0.6 mum CMOS technology and the results have been obtained from analog simulation. This study shows that power savings are possible in power-driven synthesis by including different flip-flops that are based on different design styles in the standard cell library.

  • 25335.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Efficient VLSI Implementation of a VLC Decoder for Golomb-Rice Code using Alternating Coding2003In: IEEE Norchip´03, Riga, Latvia, November 2003, 2003Conference paper (Refereed)
  • 25336.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Efficient VLSI Implementation of a VLC Decoder for Universal Variable Length Code using Alternating Coding2003In: ISVLSI 2003: IEEE COMPUTER SOCIETY ANNUAL SYMPOSIUM ON VLSI, PROCEEDINGS - NEW TRENDS AND TECHNOLOGIES FOR VLSI SYSTEMS DESIGN, IEEE Computer Society, 2003, p. 207-208, article id 1183467Conference paper (Refereed)
    Abstract [en]

    Variable length code (VLC) is used in a large variety of lossless compression applications. A specially designed VLC, called "Universal Variable Length Code" (UVLC), is utilized in the latest video coding standard H.26L under development. In this work we develop an efficient decoder for UVLC by utilizing the special properties of UVLC which perform coding in an alternating way (ALT). We compare the ALT decoder with the decoder called "VLC decoder using plane separation" (PLS) which is claimed to be one of the most effective VLC decoders. Our results show that the ALT decoder is 1.34 times faster, 1.7 times smaller, and consumes 45% power in comparison to the PLS decoder

  • 25337.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Error Resilient coding of DCT coefficients using alternating coding of UVLC2003In: Norsig, Bergen, Norway,  October 2003, 2003Conference paper (Refereed)
  • 25338.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Parallel Variable-length Decoder Architecture for Alternated Coded GR-Codes2003In: IEEE Norchip´03, Riga, latvia, november, 2003, 2003Conference paper (Refereed)
  • 25339.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Unary Prefixed Huffman Coding for a Group of Quantized Generalized Gaussian Sources2006In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 54, no 7, p. 1164-1169Article in journal (Refereed)
    Abstract [en]

    We propose a coding algorithm called unary prefixed Huffman (UPH) coding for a family of infinite sources called quantized generalized Gaussian (GG) sources. Compared with the existing codes for these GG sources, the UPH algorithm provides a more adaptive approach, and its coding efficiency is upper bounded by entropy +2.

  • 25340.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Unary-Prefixed Encoding of the Lengths of Consecutive Zeros in a Bit Vector2005In: Electronics Letters, ISSN 0013-5194, E-ISSN 1350-911X, Vol. 41, no 6, p. 346-347Article in journal (Refereed)
    Abstract [en]

    A unary-prefixed encoding (UPE) algorithm for coding the lengths of zeros in a bit vector is proposed. While the lengths of consecutive zeros in a bit vector can be mapped to integer sources with a geometrical distribution (when the bits in the bit vector are independent of each other), the actual case, in a real-world situation, is more often that the distributions are exponential, with high peaks and heavier tails (when the bits in a bit vector are correlated). For the geometric distribution, the UPE code set can be proven to be optimal. For integer sources with high peaks and heavier tails, the UPE almost always provides better compression compared to existing suboptimal codes.

  • 25341.
    Xue, Shang
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Xu, Youzhi
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Oelmann, Bengt
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information Technology and Media.
    Hybrid Golomb codes for a group of quantised GG sources2003In: IEE Proceedings - Vision Image and Signal Processing, ISSN 1350-245X, E-ISSN 1359-7108, Vol. 150, no 4, p. 256-260Article in journal (Refereed)
    Abstract [en]

    The authors develop a class of codes for quantised generalised Gaussian (GG) sources. This new class of codes, that are called hybrid Golomb (HG) codes, are hybrids of Golomb-Rice (GR) codes and exp-Golomb (EG) codes. They integrate the properties of both GR and EG codes, which makes their performance more robust under variable source parameters. The efficiencies of the three classes of codes are compared and it is shown that the set of HG codes have efficiencies of approximately 70% or greater for a wide range of parameter values, whereas GR and EG codes can have efficiencies lower than 20%. The efficiencies of the set of HG codes are also compared with the set of EG codes that have the best performance under parameter scaling. It is shown that. this set of HG codes still achieve a higher efficiency.

  • 25342.
    Xyftilis, Georgios
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Information and Communication systems.
    Automatisering av Välkomstbrev: En webbapplikation med fokus på användbarhet2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [sv]

    Mittuniversitetet skapar "Välkomstbrev" för alla utbildningstillfällen vid varjeterminsstart, något som hittills gjorts manuellt. Det har dock på sistone uppkommit behov av att automatisera, förenkla och centralisera processengenom ett användarvänligt, webbaserat verktyg. Målet för detta projekt harvarit att presentera och utvärdera förslag till ett sådant verktyg som fyller deovan nämnda behoven. Verktyget är applikationen "Välkomstbrev" som skapatsmed tekniker, språk och moduler skrivna i öppen källkod som finns fritttillgängliga på nätet. De grundläggande språken som använts för konstruktionenär HTML5, CSS, JavaScript, PHP, SQL. Den arbetar emot databasen"kursprogrambrev" som innehåller all nödvändig data för publikationen avvälkomstbreven. Applikationen består av fyra olika gränssnitt som motsvararolika profiler: Lärare, Redaktör, Brevadministratör och Databasadministratör.Profilerna är lösenordsskyddade och åtkomliga för de av lärosätets personalsom berörs. Varje profil har sina konkreta uppgifter att sköta i applikationen ochinteragerar med de andra profilerna via databasen. Resultatet av profilernasinteraktion är att välkomstbreven skapas i PDF-format och placeras i utvaldkatalog. Eftersom användbarheten var av högsta prioritet från ledningens sidahar flera användartester gjorts för att utvärdera den slutliga produkten. Dessahar visat att målen överlag har uppnåtts, men att vissa aspekter måstevidareutvecklas i nära samråd med lärosätets ledning.

  • 25343.
    Yachin, Jonathan Moshe
    Mid Sweden University, Faculty of Human Sciences, Department of Tourism Studies and Geography. Dalarna University.
    The 'customer journey': Learning from customers in tourism experience encounters2018In: Tourism Management Perspectives, ISSN 2211-9736, E-ISSN 2211-9744, Vol. 28, p. 201-210Article in journal (Refereed)
    Abstract [en]

    For micro-tourism firms, customers are a readily-accessible and highly important knowledge source that often remains unutilised. This study explores firm–customer encounters along the customer journey as learning opportunities. Based on data collected through participant observations, interviews and a review of user-generated content, this case study provides an in-depth look into the customer journey, with a Swedish micro-tourism firm. The findings suggest that the possibility to generate knowledge about experiential purposes is conditioned by the firm's ability to bestow encounters with an experience-like quality and promote the customers' transformation into participants. This is facilitated by involving customers, adopting an experiential discourse and utilising in-situ supporting moments to socialise. Firms can also learn about customers' subjective perception of value from user-generated content. The study concludes that in the context of learning from customers, small size provides micro-tourism firms with an opportunity to engage in personal relationships with their customers.

  • 25344.
    Yachin, Jonathan Moshe
    Mid Sweden University, Faculty of Human Sciences, Department of Economics, Geography, Law and Tourism. Dalarna University.
    The entrepreneur–opportunity nexus: discovering the forces that promote product innovations in rural micro-tourism firms2019In: Scandinavian Journal of Hospitality and Tourism, ISSN 1502-2250, E-ISSN 1502-2269, Vol. 19, no 1, p. 47-65Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to investigate what sets in motion the process that results in product innovations in rural micro-tourism firms. The point of departure is to place entrepreneurship as a process that precedes innovations. This approach enables the application of the opportunity-based perspective, on the study of 40 new tourism products. Data were collected through in-depth interviews with owner-managers of micro-tourism firms in rural Sweden. The focus of the analysis is on the formation of the entrepreneur–opportunity nexus. The findings suggest that in forming the nexus, three types of forces are at play: internal, supply chain dynamics and reaction to changes. The notion of triggering forces adds a new dimension to the study of entrepreneurial opportunities. The theoretical contribution of this paper to tourism research is twofold. First, it points at the generating moment as a step towards theorising innovations, and second, the findings contribute to the growing knowledge base about entrepreneurial behaviour in micro-tourism firms in rural areas. Finally, in a practical manner, the findings of this study should encourage tourism entrepreneurs to invest in exploring the value chain, regard tourists as sources of knowledge and be attentive to changes in circumstances.

  • 25345.
    Yachin, Jonathan Moshe
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Economics, Geography, Law and Tourism. Dalarna University.
    Ioannides, Dimitri
    Mid Sweden University, Faculty of Human Sciences, Department of Economics, Geography, Law and Tourism.
    “Making do” in rural tourism: the resourcing behaviour of tourism micro-firms2020In: Journal of Sustainable Tourism, ISSN 0966-9582, E-ISSN 1747-7646, Vol. 28, no 7, p. 1003-1021Article in journal (Refereed)
    Abstract [en]

    We propose entrepreneurial bricolage as a framework that enables the description, explanation and exploration of the modus operandi of tour- ism micro-firms. Particularly, the notion of spatial bricolage constitutes fertile ground for further research and theoretical advances of sustain- able tourism entrepreneurship. The potential for rural tourism develop- ment is conditioned by entrepreneurs’ capability to utilise local physical and non-material resources sustainably. Thus, knowledge about the resourcing behaviour of micro-firms is paramount to understanding their role in promoting sustainable tourism. This study explores how rural micro-firms interact with their spatial environment to design tour- ism value propositions. Our analysis is based on interviews with eight- een owners-managers of tourism micro-firms in rural Sweden. We portray spatial bricolage as a resourcing behaviour that builds on the re-interpretation of existing resources, the unique features of the destin- ation and community involvement. The findings suggest that resource transfer facilitates sustainable development since it enables long-term planning and validates the entrepreneurs’ operation. Moreover, their small-scale enables rural tourism firms to utilise local resources in non- exploitative ways that minimise disturbance for other stakeholders.

  • 25346.
    Yahaya, Ismael
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. London Sch Hyg & Trop Med, London WC1, England.
    Uthman, O
    Univ Liverpool, Liverpool Sch Trop Med, Int Hlth Grp, Liverpool L3 5QA, Merseyside, England.
    Soares, Joaquim
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Karolinska Inst, Dept Publ Hlth Fdn Sci, Div Social Med, Stockholm, Sweden.
    Macassa, Gloria
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Karolinska Inst, Dept Publ Hlth Fdn Sci, Div Social Med, Stockholm, Sweden.
    Social disorganization and history of child sexual abuse against girls in Sub-Saharan Africa: A multilevel analysis2013In: BMC International Health and Human Rights, ISSN 1472-698X, E-ISSN 1472-698X, Vol. 13, no 33Article in journal (Refereed)
    Abstract [en]

    Background

    Child sexual abuse (CSA) is a considerable public health problem. Less focus has been paid to the role of community level factors associated with CSA. The aim of this study was to examine the association between neighbourhood-level measures of social disorganization and child sexual abuse CSA.

    Methods

    We applied multiple multilevel logistic regression analysis on Demographic and Health Survey data for 6,351 adolescents from six countries in sub-Saharan Africa between 2006 and 2008.

    Results

    The percentage of adolescents that had experienced CSA ranged from 1.04% to 5.84%. There was a significant variation in the odds of reporting CSA across the communities, suggesting 18% of the variation in CSA could be attributed to community level factors. Respondents currently employed were more likely to have reported CSA than those who were unemployed (odds ratio [OR] = 2.05, 95% confidence interval [CI] 1.48 to 2.83). Respondents from communities with a high family disruption rate were 57% more likely to have reported CSA (OR=1.57, 95% CI 1.14 to 2.16).

    Conclusion

    We found that exposure to CSA was associated with high community level of family disruption, thus suggesting that neighbourhoods may indeed have significant important effects on exposure to CSA. Further studies are needed to explore pathways that connect the individual and neighbourhood levels, that is, means through which deleterious neighbourhood effects are transmitted to individuals.

  • 25347.
    Yahaya, Ismail
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Childhood Sexual Abuse Against Girls in Sub-Saharan Africa: Individual and Contextual Risk Factors2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Background and objectives: Childhood sexual abuse (CSA) is a substantial public health and human rights problem, as well as a growing concern in sub-Saharan Africa (SSA). It has both short and long term effects on girls: physical and psychological, including negative sexual outcomes. Up to one-third of adolescent girls report their first sexual experience as being forced. Despite growing evidence supporting a link between contextual factors and violence, no studies have investigated the connection between CSA and contextual factors. It is therefore important to identify the extent of CSA and understand factors associated with it in SSA in order to develop interventions aimed to address the scale of the problem.

    Aim: The overall aim of this thesis is to assess the individual and contextual factors associated with CSA. In addition, the thesis aims to quantify the magnitude of CSA and describe the factors associated with CSA among women from SSA (Study I). This thesis also examines the independent contribution of individual and community socio-economic status on CSA (Study II). Moreover, it scrutinises the effect of social disorganisation on CSA (Study III) and explores the relationship between CSA and sexual risk behaviours as well as potential mediators (Study IV).

    Methods: This thesis used the Demographic and Health Survey (DHS) datasets conducted between 2006 and 2008 from six SSA countries. The thesis used multiple logistic regression models to describe and explore factors associated with CSA among 69,977 women (Study I).  It used multivariable multilevel logistic regression analysis to explore the effect of contextual level variables (neighbourhood socio-economic status) on CSA among 6,351 girls (Study II). Neighbourhood socio-economic status was operationalized with a principal component analysis using the proportion of respondents who were unemployed, illiterates, living below poverty level and rural residents. Study III applied multivariable multilevel logistic regression analysis on 6,351 girls and considered five measures of social disorganisation at the community level: neighbourhood poverty, female-headed households, residential mobility, place of residence, population density, and ethnic diversity. In study IV, 12,800 women from the Nigerian DHS were used. Structural equation modelling was applied using a two-step approach. The first step used a confirmatory factor analysis to develop an acceptable measurement model while the second step involved modifying the measurement model to represent the postulated causal model framework.

    Results: In study I, the reported prevalence of CSA ranged from 0.3% in Liberia to 4.3% in Zambia when the prevalence was based on all respondents aged between 15 and 49 years and who were present during the survey. None of the socio-economic factors were associated with CSA. In study II, where the data was restricted to permanent residents aged between 15 and 18 years, the prevalence ranged between 1.04% in Liberia to 5.8% in Zambia. At the individual level, there was no significant association between CSA and wealth status while at the community level, there was no significant association between CSA and socio-economic position. However, 22% of the variation in CSA was attributed to the community level factors. In study III, there was significant variation in the odds of reporting CSA across the communities, with community level factors accounting for 18% of the variation. In addition, respondents from communities with a high family disruption rate were 57% more likely to have reported sexual abuse in childhood. Study IV showed that there was a significant association between CSA and sexual risk behaviours and the association was mediated by alcohol and cigarette use.

    Conclusions: The study provides evidence that adolescents in the same community were subjected to common contextual influences. It also highlighted the significance of mediators in the relationship between CSA and sexual risk behaviours. It is therefore important that effective preventive strategies are developed and implemented that will cut across all socio-economic spheres in a context that both permits and encourages disclosure as well as identifying predisposing circumstances for recurrence.

  • 25348.
    Yahaya, Ismail
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    De Leon, Antonio Ponce
    Soares, Joaquim
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    Macassa, Gloria
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences.
    A comparative study of the socioeconomic factors associated with childhood sexual abuse in sub-Saharan Africa2012In: Pan African Medical Journal, ISSN 1937-8688, E-ISSN 1937-8688, Vol. 11, no 51, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Background: Childhood sexual abuse (CSA) is a problem of considerable proportion in Africa where up to one-third of adolescent girls report their first sexual experience as being forced. The impact of child hood sexual abuse resonates in all areas of health. The aim of this study was to describe the prevalence of childhood sexual abuse and variations across socioeconomic status in six sub-Saharan countries. Methods: Datasets from Demographic and Health Surveys (DHS) in six sub-Saharan African countries conducted between 2003 and 2007 were used to access the relationship between CSA and socio economic status using multiple logistic regression models. Results: There was no association between CSA and education, wealth and area of settlement. However, there was contrasting association between CSA and working status of women. Conclusion: This study concurs with other western studies which indicate that CSA transcends across all socio economic group. It is therefore important that effective preventive strategies are developed and implemented that will cross across all socio-economic groups. © Ismail Yahaya et al.

  • 25349.
    Yahaya, Ismail
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Centre for Evidence-Based Global Health, Nigeria.
    Ponce de Leon, Antonio
    Division of Social Medicine, Department of Public Health Sciences, Karolinska Institute, Sweden..
    A. Uthman, Olalekan
    Warwick - Centre for Applied Health Research and Delivery (WCAHRD), Division of Health Sciences, Warwick Medical School, The University of Warwick, Coven try, CV4 7AL, United Kingdom.
    Soares, Joaquim
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Division of Social Medicine, Department of Public Health Sciences, Karolinska Institute, Sweden.
    Macassa, Gloria
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Division of Social Medicine, Department of Public Health Sciences, Karolinska Institute, Sweden.
    Individual and community-level socioeconomic position and its association with adolescents experience of childhood sexual abuse: a multilevel analysis of sixcountries in Sub-Saharan Africa2013In: Journal of Injury and Violence Research, ISSN 2008-2053, E-ISSN 2008-4072, Vol. 6, no 1, p. 21-30Article in journal (Refereed)
    Abstract [en]

    BACKGROUND: Childhood sexual abuse (CSA) is a substantial global health and human rights problem and consequently a growing concern in sub-Saharan Africa. We examined the association between individual and community-level socioeconomic status (SES) and the likelihood of reporting CSA. METHODS: We applied multiple multilevel logistic regression analysis on Demographic and Health Survey data for 6,351female adolescents between the ages of 15 and 18 years from six countries in sub-Saharan Africa, between 2006 and 2008. RESULTS: About 70% of the reported cases of CSA were between 14 and 17 years. Zambia had the highest proportion of reported cases of CSA (5.8%). At the individual and community level, we found that there was no association between CSA and socioeconomic position. This study provides evidence that the likelihood of reporting CSA cut across all individual SES as well as all community socioeconomic strata. CONCLUSIONS: We found no evidence of socioeconomic differentials in adolescents’ experience of CSA, suggesting that adolescents from the six countries studied experienced CSA regardless of their individual- and community-level socioeconomic position. However, we found some evidence of geographical clustering, adolescents in the same community are subject to common contextual influences. Further studies are needed to explore possible effects of countries’ political, social, economic, legal, and cultural impact on Childhood sexual abuse.

  • 25350.
    Yahaya, Ismail
    et al.
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Centre for Evidence-Based Global Health, Nigeria.
    Ponce de Leon, Antonio
    Karolinska Institutet, Stockholm, Sweden.
    Uthman, Olalekan
    Warwick Medical School, The University of Warwick, Coventry, UK.
    Soares, Joaquim
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Division of Social Medicine, Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.
    Macassa, Gloria
    Mid Sweden University, Faculty of Human Sciences, Department of Health Sciences. Division of Social Medicine, Department of Public Health Sciences, Karolinska Institutet, Stockholm, Sweden.
    Childhood sexual abuse among girls and determinants of sexual risk behaviours in adultlife in sub-Saharan Africa2015In: Journal of Aggression, Conflict and Peace Research, ISSN 1759-6599, Vol. 7, no 2, p. 67-75Article in journal (Refereed)
    Abstract [en]

    Purpose – The purpose of this paper is to investigate the relationship between child sexual abuse and sexual risk behaviours as well as its potential mediators. Design/methodology/approach – This cross-sectional study used data from a cross-sectional study from 12,800 women between 15 and 49 years of age included in the 2008 Nigerian Demographic and Health Survey. Structural equation modelling (SEM) was applied to assess the association between childhood sexual abuse (CSA) and sexual risk behaviours. Findings – The authors found that CSA was directly associated with sexual risk behaviours. In addition, the association between CSA and sexual risk behaviour was also partially mediated by alcohol and cigarette use. Research limitations/implications – The results show that being abused in childhood is important for the subsequent development of sexual risk behaviours in adulthood and the association is mediated by alcohol and cigarette use. Practical implications – The results may be helpful for policy makers and health care planners in designing cultural sensitive public health intervention that will reduce the burden of CSA, its long-term effects (sexual risk behaviours) and intervening mediators that increase the risks. Social implications – These findings suggest that to reduce sexual risks, interventions to address sexual abuse needs to include other social problems (smoking, alcohol) that victims result to when faced with trauma. Originality/value – The current study is the only one so far in sub-Saharan Africa to have explored the relation between CSA and sexual risk behaviours using SEM.

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