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  • 121901.
    Xiao, Ming
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Multiple-User Cooperative Communications Based on Linear Network Coding2010In: IEEE Transactions on Communications, ISSN 0090-6778, E-ISSN 1558-0857, Vol. 58, no 12, p. 3345-3351Article in journal (Refereed)
    Abstract [en]

    We propose a new scheme for cooperative wireless networking based on linear network codes. The network consists of multiple (M >= 2) users having independent information to be transmitted to a common basestation ( BS), assuming block-fading channels with independent fading for different codewords. The users collaborate in relaying messages. Because of potential transmission errors in links, resulting in erasures, the network topology is dynamic. To efficiently exploit the diversity available by cooperation and time-varying fading, we propose the use of diversity network codes (DNCs) over finite fields. These codes are designed such that the BS is able to rebuild the user information from a minimum possible set of coded blocks conveyed through the dynamic network. We show the existence of deterministic DNCs. We also show that the resulting diversity order using the proposed DNCs is 2M - 1, which is higher than schemes without network coding or with binary network coding. Numerical results from simulations also show substantial improvement by the proposed DNCs over the benchmark schemes. We also propose simplified versions of the DNCs, which have much lower design complexity and still achieve the diversity order 2M - 1.

  • 121902.
    Xiao, Ming
    et al.
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    M-user Cooperative Wireless Communications Based on Nonbinary Network Codes2009In: ITW: 2009 IEEE INFORMATION THEORY WORKSHOP ON NETWORKING AND INFORMATION THEORY, NEW YORK: IEEE , 2009, p. 316-320Conference paper (Refereed)
    Abstract [en]

    We propose a new method of applying network coding for cooperative wireless networks. The network consists of multiple (M >= 2) users having independent information to be transmitted to a common base station (BS). These users form partners and relay information for each other. The transmission blocks are subject to block-fading with independent fading coefficients for each block. Designed non-binary network codes over finite fields are used on top of channel codes. Assuming perfect error detection, erroneous blocks out from channel decoders are discarded (erasure). Thus, relaying nodes may not have information messages of some partners (erasure in inter-user channels), and the BS may not decode some blocks correctly either. The network topology from the point of view of network coding is dynamic. To improve performance, we propose dynamic-network codes (deterministic codes for dynamic networks) for the cooperative networks. The codes are designed such that the BS can rebuild user information from a minimum possible set of coding blocks. In this sense, dynamic-network codes achieve the min-cut for cooperative networks with a dynamic topology. For block fading channels, the proposed scheme obtains high asymptotic performance. For two-user networks, we calculate the resulting outage probabilities. We also present simulations with specific channel codes. Numerical results show substantial improvement over previous schemes. Then, we generalize the results to multiple-user (M > 2) networks. We investigate the existence of deterministic dynamic-network codes for multiple-user networks, and show that the diversity order of the proposed scheme can achieve 2M - 1.

  • 121903.
    Xiao, Ming
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Communication Theory. KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre.
    On network coding with finite channel state information2011In: 2011 8th International Symposium on Wireless Communication Systems (ISWCS), IEEE , 2011, p. 487-491Conference paper (Refereed)
    Abstract [en]

    We study network coding for wireless networks with finite channel state information (CSI) at intermediate nodes (relays). Based on the CSI of the relay-sink channels, we adapt the network codes at the relays. For a specific network with two sources, four relays and two sinks, the analytic results show that one bit CSI of all relay-sink channels (global CSI) can reduce complexity (field size), and simultaneously decrease the erasure probability. Then, we generalize the results to relay networks with M users, N relays and J sinks. We show that fixed network codes without CSI cannot achieve instantaneous min-cut, i.e., min-cut under current channel state. We also show that with one bit global CSI, we can achieve instantaneous min-cut by adapting the network codes using an alphabet size L, where L is the number of sinks connecting to a relay. Yet, the fixed MDS network codes use an alphabet size L(M-1N-1). For the networks with perfect or imperfect source-relay channels, adaptive network codes with one bit global CSI have lower erasure probability than the codes without CSI. Thus, one bit global CSI can reduce the erasure probability, and simultaneously reduce coding complexity.

  • 121904.
    Xiao, Qian
    KTH, School of Architecture and the Built Environment (ABE), Architecture.
    Climate resilient city2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 121905. Xiao, S. H.
    et al.
    Shen, L. F.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    A novel directional coupler utilizing a left-handed material2004In: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 16, no 1, p. 171-173Article in journal (Refereed)
    Abstract [en]

    A novel directional coupler with a left-handed material (LHM) layer between two single-mode (SM) waveguides of usual material is introduced. The coupling system is analyzed with the supermode theory. It is shown that such an LHM layer of finite length can shorten significantly the coupling length for the two SM waveguides. An LHM layer with two slowly tapered ends is used to avoid the reflection loss at the ends.

  • 121906. Xiao, S. S.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    FDTD method for computing the off-plane band structure in a two-dimensional photonic crystal consisting of nearly free-electron metals2002In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 324, no 01-4, p. 403-408Article in journal (Refereed)
  • 121907. Xiao, S. S.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Lin, Q. C.
    Shen, L. F.
    Defect mode computation in two-dimensional photonic crystals consisting of nearly-free-electron metals2001In: Chinese Physics Letters, ISSN 0256-307X, E-ISSN 1741-3540, Vol. 18, no 9, p. 1218-1221Article in journal (Refereed)
  • 121908. Xiao, S. S.
    et al.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Zhuang, F.
    Guided modes in a two-dimensional photonic crystal waveguide consisting of nearly-free-electron metals2001In: Chinese Physics Letters, ISSN 0256-307X, E-ISSN 1741-3540, Vol. 18, no 10, p. 1363-1365Article in journal (Refereed)
  • 121909. Xiao, S. S.
    et al.
    Liu, L.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Resonator channel drop filters in a plasmon-polaritons metal2006In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 14, no 7, p. 2932-2937Article in journal (Refereed)
    Abstract [en]

    Channel drop filters with ring/disk resonators in a plasmon-polaritons metal are studied. It shows that light can be efficiently dropped. Results obtained by the finite difference time domain method are consistent with those from the coupled mode theory. It also shows, without considering the loss of the metal, that the quality factor for the channel drop system can be very high. The quality factor decreases significantly if we take into account the loss, which also leads to a weak drop efficiency.

  • 121910. Xiao, S. S.
    et al.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Doppler effects in a left-handed material: A first-principles theoretical study2005In: Microwave and optical technology letters (Print), ISSN 0895-2477, E-ISSN 1098-2760, Vol. 47, no 1, p. 76-79Article in journal (Refereed)
    Abstract [en]

    The Doppler effects for the reflected wave from moving media are systemically analyzed in this paper. The theoretical formula for the Doppler shift in left-handed material, which is described by Drude's dispersion model, is presented. This formula is examined by first-principles numerical experiments, which are in agreement with the theoretical results.

  • 121911. Xiao, S. S.
    et al.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Study of transmission properties for waveguide bends by use of a circular photonic crystal2005In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 340, no 06-maj, p. 474-479Article in journal (Refereed)
    Abstract [en]

    We study the transmission properties for the waveguide bends composed by a circular photonic crystal. Two types (Y and U type) of the waveguide bends utilizing the circular photonic crystal are studied. It has been shown, compared with the conventional photonic crystal waveguide bends, transmission properties for these bends can be significantly improved. Over a 6.4% bandwidth, less than 1-dB loss/bend are observed. U bent waveguide, i.e., 180 degrees bend, can be easily realized with low loss using the circular photonic crystal.

  • 121912. Xiao, S. S.
    et al.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Surface-mode microcavity2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 11Article in journal (Refereed)
    Abstract [en]

    Optical microcavities based on zero-group-velocity surface modes in photonic crystals are studied. It is shown that high quality factors can be easily obtained for such microcavities in photonic crystal slabs. With increasing of the cavity length, the quality factor is gradually enhanced and the resonant frequency converges to that of the zero-group-velocity surface mode in the photonic crystal. The number of the resonant modes with high quality factors is mainly determined by the number of surface modes with zero-group velocity.

  • 121913. Xiao, S. S.
    et al.
    Shen, L. F.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    A plane-wave expansion method based on the effective medium theory for calculating the band structure of a two-dimensional photonic crystal2003In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 313, no 01-2, p. 132-138Article in journal (Refereed)
  • 121914. Xiao, S. S.
    et al.
    Shen, L. F.
    He, Sailing
    Large complete band gap at low and high frequencies in a two-dimensional anisotropic photonic crystal2002In: Wuli xuebao, ISSN 1000-3290, Vol. 51, no 12, p. 2858-2864Article in journal (Refereed)
  • 121915.
    Xiao, Sanshui
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Liu, Liu
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Qin, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Channel drop filters realized in a surface plasmon-polaritons metal2006In: Optoeletronic Materials and Devices, Pts 1 and 2 / [ed] Lee, YH; Koyama, F; Luo, Y, 2006, Vol. 6352, p. U23-U30Conference paper (Refereed)
    Abstract [en]

    Channel drop filters with ring/disk resonators in a plasmon-polaritons metal are studied. It shows that light can be efficiently dropped. Results obtained by the finite difference time domain method are consistent with those from the coupled mode theory. It also shows, without considering the loss of the metal, that the quality factor for the channel drop system can be very high. The quality factor decreases significantly if we take into account the loss, which also leads to a weak drop efficiency.

  • 121916. Xiao, Sanshui
    et al.
    Mortensen, Niels Asger
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Enhanced transmission through arrays of subwavelength holes in gold films coated by a finite dielectric layer2007In: Journal of the European Optical Society - Rapid Publications, ISSN 1990-2573, E-ISSN 1990-2573, Vol. 2, p. 07009-Article in journal (Refereed)
    Abstract [en]

    Enhanced transmissions through a gold film with arrays of subwavelength holes are theoretically studied, employing the rigid full vectorial three dimensional finite difference time domain method. Influence of air-holes shape to the transmission is firstly studied, which confirms two different resonances attributing to the enhanced transmission: the localized waveguide resonance and periodic surface plasmon resonances. For the film coated with dielectric layers, calculated results show that in the wavelength region of interest the localized waveguide resonant mode attributes to sensing rather than the periodic gold-glass surface plasmon mode. Although the detected peak is fairly broad and the shift is not too pronounced, we emphasize the contribution for sensing from the localized waveguide resonant mode, which may opens up new ways to design surface plasmon based sensors.

  • 121917.
    Xiao, Sanshui
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    High-Q microcavities realized in a circular photonic crystal slab2005In: Photonics and Nanostructures-Fundamentals and Applications, ISSN 1569-4410, Vol. 3, no 2-3, p. 134-138Article in journal (Refereed)
    Abstract [en]

    A series of microcavities in circular photonic crystal slabs are studied in this paper. It is shown that high quality factors can be obtained for such microcavities. For a cavity with three inner layers of air holes missing, Q factor larger than 105 can be obtained. It is also worth noting there exists resonant modes with high quality factors, even for the defect-free circular photonic crystal slab, due to gradual change of the average effective index.

  • 121918. Xiao, Sanshui
    et al.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Optical microcavities based on surface modes in two-dimensional photonic crystals and silicon-on-insulator photonic crystals2007In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 24, no 5, p. 1225-1229Article in journal (Refereed)
    Abstract [en]

    Surface-mode optical microcavities based on two-dimensional photonic crystals and silicon-on-insulator photonic crystals are studied. We demonstrate that a high-quality-factor microcavity can be easily realized in these structures. With an increasing of the cavity length, the quality factor is gradually enhanced and the resonant frequency converges to that of the corresponding surface mode in the photonic crystals. These structures have potential applications such as sensing.

  • 121919. Xiao, Sanshui
    et al.
    Qiu, Min
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Theoretical study of the transmission properties of a metallic film with surface corrugations2007In: Journal of Optics. A, Pure and applied optics, ISSN 1464-4258, E-ISSN 1741-3567, Vol. 9, no 4, p. 348-351Article in journal (Refereed)
    Abstract [en]

    Transmissions through a metallic film at near-infrared wavelengths with different surface corrugations on both sides are systemically studied. The calculations are performed by the three-dimensional finite-different time-domain method. Calculated results show that the transmissions are strongly dependent on the surface structures. Compared with other structures, the transmission for a film periodically drilled by cross air grooves are relatively larger. Transmission is enhanced more with symmetric conditions on both layers than the asymmetric case. The enhanced transmission can be explained by a competition between the absorption in the metal and enhanced transmission due to coupled surface plasmon resonance.

  • 121920.
    Xiao, Sanshui
    et al.
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Qiu, Min
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Ruan, Z. C.
    He, Sailing
    KTH, Superseded Departments, Electromagnetic Theory.
    Influence of the surface termination to the point imaging by a photonic crystal slab with negative refraction2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 19, p. 4269-4271Article in journal (Refereed)
    Abstract [en]

    Point imaging by a photonic crystal slab due to the negative refraction is studied theoretically. By investigating the transfer function of the imaging system, the influence of the surface termination to the imaging quality is analyzed. It is shown that an appropriate surface termination is important for obtaining an image of good quality.

  • 121921.
    Xiao, Shuang
    et al.
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Wang, Zhan
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS.
    Folkesson, John
    KTH, School of Computer Science and Communication (CSC), Centres, Centre for Autonomous Systems, CAS. KTH, School of Computer Science and Communication (CSC), Computer Vision and Active Perception, CVAP.
    Unsupervised robot learning to predict person motion2015In: Proceedings - IEEE International Conference on Robotics and Automation, IEEE conference proceedings, 2015, no June, p. 691-696Conference paper (Refereed)
    Abstract [en]

    Socially interacting robots will need to understand the intentions and recognize the behaviors of people they come in contact with. In this paper we look at how a robot can learn to recognize and predict people's intended path based on its own observations of people over time. Our approach uses people tracking on the robot from either RGBD cameras or LIDAR. The tracks are separated into homogeneous motion classes using a pre-trained SVM. Then the individual classes are clustered and prototypes are extracted from each cluster. These are then used to predict a person's future motion based on matching to a partial prototype and using the rest of the prototype as the predicted motion. Results from experiments in a kitchen environment in our lab demonstrate the capabilities of the proposed method.

  • 121922.
    Xiao, Xiang
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    Zhang, Wenbin
    KTH, School of Industrial Engineering and Management (ITM), Industrial Economics and Management (Dept.), Sustainability and Industrial Dynamics.
    The Study of Battery Electric Vehicle DiffusionConsidering  Technology Development Impact: A model based study of Swedish market2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Battery Electric Vehicle as an environmental friendly transportation alternative has already emerged as well as fade out of the market twice. It has been reintroduced along with the increasing concern about the environment issue. This recent diffusion is surrounded by lots of dynamic changes and uncertainties. However, most current studies focus on political, financial as well as infrastructure factors but neglect factors like the technology especially how people perceived it. Therefore, this study mainly research into how the technology development impact on the diffusion of battery electric vehicle.To achieve this aim, a model based study was conducted targeting Swedish electric vehicle market. In the research, customers are considered to be the target objective because they are the one  who perceive the technology and make decision for adoption directly. In order to know the relationship between them, researches have been conducted through qualitative and quantitative approach. Empirical work including interviews and survey were conducted through tripartite aspect to investigate the customer needs and related technology. The investigation indicates the environmentally friendly performance is the key driving force perceived by the early adopters. Meanwhile, range issue, total cost of ownership and safety & technology reliability are identified as the top three critical concerns that  hold back customer purchasing decision. A modified classic model for the innovation diffusion has been proposed which is used to evaluate the technology’s perception based on historical data. Two BEV- related technologies were chosen as examples to prove and illustrate the relationship between technology development and electric vehicle diffusion.The results showed that the BEV-related technologies, which have potential ability to address critical customer demand, are able to impact on the customer adoption positively through valid perception by customer. Taking technology development and perception into consideration, the diffusion process should be accelerated to some extent. Technologies which can be more easily perceived tend to have more impact in the diffusion process.

  • 121923. Xiao, Y. Y.
    et al.
    He, Sailing
    A new design approach to MMI-based (de)multiplexers2004In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 239, no 01-3, p. 85-90Article in journal (Refereed)
  • 121924. Xiao, Y. Y.
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    An MMI-based demultiplexer with reduced cross-talk2005In: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 247, no 04-6, p. 335-339Article in journal (Refereed)
  • 121925. Xiao, Ya
    et al.
    Kedem, Yaron
    KTH, Centres, Nordic Institute for Theoretical Physics NORDITA. Stockholm Univ, Sweden.
    Xu, Jin-Shi
    Li, Chuan-Feng
    Guo, Guang-Can
    Experimental nonlocal steering of Bohmian trajectories2017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 13, p. 14463-14472Article in journal (Refereed)
    Abstract [en]

    Interpretations of quantum mechanics (QM), or proposals for underlying theories, that attempt to present a definite realist picture, such as Bohmian mechanics, require strong non-local effects. Naively, these effects would violate causality and contradict special relativity. However if the theory agrees with QM the violation cannot be observed directly. Here, we demonstrate experimentally such an effect: we steer the velocity and trajectory of a Bohmian particle using a remote measurement. We use a pair of photons and entangle the spatial transverse position of one with the polarization of the other. The first photon is sent to a double-slit-like apparatus, where its trajectory is measured using the technique of Weak Measurements. The other photon is projected to a linear polarization state. The choice of polarization state, and the result, steer the first photon in the most intuitive sense of the word. The effect is indeed shown to be dramatic, while being easy to visualize. We discuss its strength and what are the conditions for it to occur.

  • 121926. Xiao, Yan
    et al.
    Takwa, Mohamad
    KTH, School of Biotechnology (BIO), Biochemistry.
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Koning, Cor E.
    Heise, Andreas
    Martinelle, Mats
    KTH, School of Biotechnology (BIO), Biochemistry.
    Systematic Comparison of HEA and HEMA as Initiators in Enzymatic Ring-Opening Polymerizations2009In: Macromolecular Bioscience, ISSN 1616-5187, E-ISSN 1616-5195, Vol. 9, no 7, p. 713-720Article in journal (Refereed)
    Abstract [en]

    Two initiators (HEA and HEMA) containing a cleavable ester bond were compared in the lipase-catalyzed ROP of CL and PDL. HEA and HEMA displayed similar reaction efficiencies as initiators (acyl acceptors) in the enzymatic ROP. However, transacylation reactions were found to be 15 times faster on the HEA-initiated polyesters as compared with the HEAAA initiated polyesters (HEA/HEMA moieties as acyl donors). While in both cases the amount of HEA- and HEMA-initiated polymers could be maximized by H short reaction times, a well-defined (meth)acrylation by this approach was not possible. Our results show that trans esterification reactions are present at high rates throughout the enzyme-catalyzed ROP.

  • 121927.
    Xiao, Ying
    KTH, Superseded Departments, Physics.
    Basic studies of advanced magneto-optic media and MAMMOS- modulated magnetically amplified M-O system1998Doctoral thesis, comprehensive summary (Other scientific)
  • 121928.
    Xiao, You-Cai
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Silaborative Carbocyclizations of 1,7-Enynes. Diastereoselective Preparation of Chromane Derivatives2016In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, no 2, p. 308-311Article in journal (Refereed)
    Abstract [en]

    Palladium(0)-catalyzed carbocyclization of 1,7-enynes mediated by (chlorodimethylsilyl)pinacolborane proceeds with 1,8-addition of the silicon and boron functions to give functionalized cyclohexane derivatives with boron attached to the exocyclic olefin. A variety of chromane dervatives are accessible by this method. In contrast to the analogous reactions with 1,6-enynes, the configuration of the newly formed stereogenic center is controlled by a stereogenic center present in the substrate.

  • 121929.
    Xiaofeng, Yu
    et al.
    State Key Lab. for Novel Software Technol., Nanjing Univ., Nanjing.
    Sommestad, Teodor
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    Fung, Casey
    Boeing Phantom Works, USA.
    Hung, Patrick C. K.
    University of Ontario Institute of Technology, Canada.
    Emergency Response Framework for Aviation XML Services on MANET2008In: Proceedings of the IEEE International Conference on Web Services, ICWS 2008, IEEE , 2008, p. 304-311Conference paper (Refereed)
    Abstract [en]

    A XML service is a software component that supports interoperable application-to-application interaction over a network. Each service makes its functionality available through well-defined or standardized XML interfaces. Aviation XML services refer to the services that make operating an airplane in air and on ground possible. In this paper, we present an emergency response framework to organize the aviation XML services to work cooperatively on mobile ad-hoc networks (MANETs). A MANET is defined as a self-organized and rapidly deployed network of XML services in order to exchange information without using any pre-existing fixed network infrastructure. Note that the framework does not have to be limited to the aviation sector. The methodology can also be adopted into other MANET computing scenarios including: natural disaster communications (e.g., tsunami, earthquakes), emergency relief scenarios, car-based networks, and the provision of wireless connectivity in remote areas.

  • 121930. Xiao-ling, Cao
    et al.
    Zheng-ren, Pi
    Shao-jian, Jiang
    Weihong, Yang
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Blasiak, Wlodzimierz
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Energy and Furnace Technology.
    Dynamic simulation of drum level sloshing of heat recovery steam generator2013In: J CENT SOUTH UNIV, ISSN 2095-2899, Vol. 20, no 2, p. 413-423Article in journal (Refereed)
    Abstract [en]

    Drum level sloshing is the latest discovery in the application of heat recovery steam generator (HRSG) in combined cycle, and shows certain negative influence on drum level controlling. In order to improve drum level controlling, influence factors on the drum level sloshing were investigated. Firstly, drum sub-modules were developed using the method of modularization modeling, and then the model of drum level sloshing was set up as well. Experiments were carried out on the experimental rig, and the model was validated using the obtained experimental results. Dynamic simulation was made based on the model to get a 3-D graph of drum level sloshing, which shows a vivid procedure of drum level sloshing. The effect of feed-water flow rate, main-steam flow rate and heating quantity on the drum level sloshing was analyzed. The simulation results indicate that the signals with frequency higher than 0.05 Hz are that of drum level sloshing, the signals with frequency of 0.0-0.05 Hz are that of drum level trendy and "false water level", and variation of the feed-water flow rates, main-steam flow rates and heating quantities can change the frequency of drum level sloshing, i.e., the frequency of sloshing increases with the increase of feed-water flow rate, or the decrease of the main-steam flow rate and the heating quantity. This research work is fundamental to improve signal-to-noise ratio of drum level signal and precise controlling of drum level.

  • 121931. Xiaoming, Zhang
    et al.
    Wenhong, Cao
    Qingchao, Guo
    Sihong, Wu
    KTH, School of Architecture and the Built Environment (ABE), Land and Water Resources Engineering.
    Effects of landuse change on surface runoff and sediment yield at different watershed scales on the Loess Plateau2010In: INTERNATIONAL JOURNAL OF SEDIMENT RESEARCH, ISSN 1001-6279, Vol. 25, no 3, p. 283-293Article in journal (Refereed)
    Abstract [en]

    Erosion and sediment yield from large and small watersheds exhibit different laws. Variations in surface runoff and sediment yield because of landuse change in four watersheds of different scales from 1 km(2) to 73 km(2) were analyzed. Due to reforestation and farmland terracing, surface runoff and sediment yield reduced by 20-100% and 10-100% respectively. Reductions in surface runoff were differed significantly under different precipitation regimes. For the large watershed (73 km(2)) landuse change had similar effects on surface runoff regardless of changing of precipitation. For the small watershed (1 km(2)) landuse change had fewer effects on surface runoff under high precipitation. The relative changes of sediment yield in the four watersheds under reforestation and farmland terracing decreased as precipitation increased from 350 mm to 650 mm, then increased as precipitation increased from 650 mm to 870 mm. Where initial forest coverage rate was below 45%, sediment yield decreased dramatically as forest coverage rate increased. Watershed management with aiming at reducing both surface runoff and sediment yield should be conducted both on sloping surfaces and in channels in large watersheds.

  • 121932.
    Xiaoqing, Li
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Mechanical Properties of Transition Metal Alloys from First-PrinciplesTheory2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of the thesis is to investigate the alloying and temperature effects on the mechanical properties of body-centered cubic (bcc) random alloys. We employ the all-electron exact muffin-tin orbitals method in combination with the coherent-potential approximation. The second-order elastic constants reflect the mechanical properties of materials in the small deformation region, where the stress-strain relations are linear. Beyond the small elastic region, the mechanical properties of defect-free solids are described by the so called ideal strength. These two sets of physical quantities are the major topic of my investigations.

    In part one (papers I and II), the elastic constants and the ideal tensile strengths (ITS) are investigated as a function of Cr and Ti for the bccV-based random solid solution. We find that alloys along the equi-composition region exhibit the largest shear modulus and Young’s modulus, which is a resultof the opposite alloying effects obtained for the two cubic shear elastic constants C′ and C44. The classical Labusch-Nabarro solid-solution hardening (SSH) model extended to ternary alloys predicts a larger hardening effect in V-Ti than in V-Cr alloy. By considering a phenomenological expression for the ductile-brittle transition temperature (DBTT) in terms of Peierls stress and SSH, we show that the present theoretical results can account for the observed variations of DBTT with composition. Under uniaxial [001] tensile loading, the ITS of V is 12.4 GPa and the lattice fails by shear. Assuming isotropic Poisson contraction, the ITSs are 36.4 and 52.0 GPa for V in the [111] and [110] directions, respectively. For the V-based alloys, Cr increases and Ti decreases the ITS in all principal directions. Adding the same concentration of Cr and Ti to V leads to ternary alloys with similar ITS values as that of pure V. We show that the ITS correlates with the fcc-bcc structural energy difference and explain the alloying effects on the ITS based on electronic band structure theory.

    In part two (paper III), the alloying effect on the ITS of four bcc refractory HEAs based on Zr, V, Ti, Nb, and Hf is studied. Starting from ZrNbHf, we find that the ITS decreases with equimolar Ti addition. On the other hand, if both Ti and V are added to ZrNbHf, the ITS is enhanced by about 42%. An even more captivating effect is the ITS increase by about 170%, if Ti and V are substituted for Hf. We explain the alloying effect on the ITS based on the d-band filling. We explore an intrinsic brittle-to-ductile transition, which arises due to an alloying-driven change of the failure mode under uniaxial tension. Our results indicate that intrinsically ductile HEAs with high intrinsic strength can be achieved by controlling the proportion of group four elements to group five elements.

    In part three (papers IV and V), the ITS of bcc ferromagnetic Fe-based random alloys is calculated as a function of compositions. The ITS of Fe is calculated to be 12.6 GPa under [001] direction tension, which is in good agreement with the available theoretical data. For the Fe-based alloys, we predict that V, Cr, and Co increase the ITS, while Al and Ni decrease it. Manganese yields a weak non-monotonic alloying behavior. We show that the previously established ideal tensile strengths model based on structural energy differences for the nonmagnetic V-based alloys is of limited use in the case of Fe-bases alloys, which is attributed to the effect of magnetism. We find that upon tension all investigated solutes strongly alter the magnetic response of the Fe host from the unsaturated towards a stronger ferromagnetic behavior.

    In part four (paper VI), the temperature effect on the ITS of bcc Fe and Fe0.9Co0.1alloy is studied. We find that the ITS of Fe is only slightly temperature dependent below∼500K but exhibits large thermal gradients at higher temperatures. Thermal expansion and electronic excitations have an overall moderate effect, but magnetic disorder reduces the ITS with a pronounced 90% loss in strength in the temperature interval∼500 - 920K. Such a dramatic temperature effect far below the magnetic transition temperature has not been observed for other micro-mechanical properties of Fe. We demonstrate that the strongly reduced Curie temperature of the distorted Fe lattices compared to that of bcc Fe is primarily responsible for the onset of the drop of the intrinsic strength. Alloying additions, which have the capability to partially restore the magnetic order in the strained Fe lattice, push the critical temperature for the strength-softening scenario towards the magnetic transition temperature of the undeformed lattice. This can result in a surprisingly large alloying-driven strengthening effect at high temperature as illustrated in our work in the case of Fe-Co alloy

  • 121933.
    XiaoTeng, Ma
    et al.
    Shandong Univ, Inst Thermal Sci & Technol, Jinan 250061, Shandong, Peoples R China.
    YuCheng, Deng
    KTH, School of Engineering Sciences (SCI).
    Zheng, Cui
    Shandong Univ, Inst Thermal Sci & Technol, Jinan 250061, Shandong, Peoples R China.
    Transient heat transfer analysis in packed beds: Entropy generation model and multi-objective optimization2019In: SCIENCE CHINA-TECHNOLOGICAL SCIENCES, ISSN 1674-7321, Vol. 62, no 11, p. 1999-2008Article in journal (Refereed)
    Abstract [en]

    Due to the important role of the unsteady heat transfer process of packed beds in industrial production, the construction of the transient heat transfer model is of great significance for the operation and optimization. The present study performs a transient thermal analysis of packed bed, in which the convective heat transfer and conductive thermal resistance within the particles are considered simultaneously. A mathematical model is established of the total entropy generations (0-t) contributed by viscous dissipation and heat transfer; the influence of particle diameter, air flow rate, and pressure drop, is then investigated. Because of the time cost, these results present some different trends from the steady-state process. Furthermore, for a laboratory heat transfer system, with the aid of the genetic algorithm we adopt a multi-objective genetic algorithm model and modified expressions of the entropy generations are set as objective functions. Finally, optimal operational and structural parameters are obtained for different fan power settings. When the fan power is 300 W, the optimal particle diameter and inlet wind speed are 14 mm and 2.4 m/s, respectively. The results also suggest that the time cost is reduced with increasing fan power consumption.

  • 121934.
    Xiaotian, Yang
    KTH, Superseded Departments, Chemistry.
    Spectrophotometry in process analytical chemistry: applications to kraft liquors2000Licentiate thesis, comprehensive summary (Other scientific)
  • 121935.
    Xiaowan, Su
    KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL.
    Acoustics of parallel baffles muffler with Micro-perforated panels2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Micro-perforated panels (MPP) have a good acoustic damping performance and a potential to be used in mufflers [1, 2]. This thesis aims to investigate the acoustic performance of a parallel baffles muffler, which consists of MPP baffles. The work is both experimental and numerical, i.e., a model is developed for a MPP baffles muffler with local reaction. The prototype MPP mufflers tested in the thesis were all produced by the Swedish company Sontech. First, the experiments were based on the procedure for experimental characterization of heat exchangers described in Ref. [5]. The transmission loss and flow generated sound are tested at four flow speeds for seven kinds of parallel baffles. Second, the mathematical modeling is built on the basis of the standard models of a locally reacting liner muffler [13]. The impedance for the Micro-perforated panels is computed using the models described by Maa [1] and Guo [2].

  • 121936.
    Xiaoyi, Wang
    KTH, School of Information and Communication Technology (ICT).
    Growth and Characterization of Polycrystalline Indium Phosphide on Silicon2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    III-V thin film solar cells attract large interest among the scientific community as a highly efficient solar energy source. High cost of the III-V materials, however, is the fundamental limitation for using these materials as a household energy source. Integrating these materials on low cost and large area Si wafer both for photovoltaic and photonics application is a field of research that draw intense attention of the scientific community. The fundamental challenge to fabricate III-V materials directly on silicon wafers arises from the disparity in polarity, large lattice and thermal mismatch between the III-V semiconductors and Si.

    In this work, we introduce a method to synthesize polycrystalline InP directly on silicon wafer by using In2O3 or In as intermediate material. The crystal quality and conversion degree of the intermediate material and the final poly-InP were analyzed by Powder X-ray Diffraction. Depending on the type of the intermediate material and substrate orientation (Si (100) or Si (111)), the crystallite size was found to be varying from 739 to 887 nm. The surface morphology of poly-InP was studied by using Atomic Force Microscopy. The root mean square surface roughness of the InP thin film was found to be varying from 314 to 1944 nm. Structural and optical qualities of intrinsic and sulfur doped InP layers were compared at different growth conditions (growth time, growth temperature, PH 3 source flow), intermediate material type(In2O3 and In) and substrate type (Si (100) and Si (111)). Within the investigated experimental parameter range, the higher PH 3 source flow at longer growth time improved the structural quality of InP layer grown on In 2O3 coated on silicon substrate, which also result in good optical quality. Comparison of structural and optical qualities of InP grown from In and indium oxide precoated substrates show that the former gave better quality InP. These achievements will be helpful in the realization of the high efficiency III-V solar cell on silicon substrate as a low cost option.

  • 121937.
    Xiaoyu, Wei
    et al.
    Ericsson Research, Isafjordsgatan 14E, 164 93 Kista, Sweden.
    Larsson, Peter
    Ericsson Research, Isafjordsgatan 14E, 164 93 Kista, Sweden.
    A Joint Power and Rate Control Algorithm and Fairness Enhancement for Multiuser OFDM System2008In: 68TH IEEE VEHICULAR TECHNOLOGY CONFERENCE, FALL 2008, 2008, p. 1872-1876Conference paper (Refereed)
    Abstract [en]

    A joint adaptive power and adaptive rate (APAR) control algorithm for OFDM systems that aims at sum-rate maximization, subject to certain power and rate constraints, is presented in this paper. In the basic optimization framework, the overall system throughput is the main objective, but as such it lacks user fairness consideration. Two scheduling schemes that allow adjusting the trade-off between fairness and throughput are proposed and combined with the APAR scheme for fairness enhancement. Simulation results show that enhanced system performance and balanced efficiency-fairness trade-off can be achieved by the proposed schemes in downlink.

  • 121938.
    Xie, Binbin
    KTH, School of Electrical Engineering (EES).
    The application of D2D communication in 60 GHz millimeter wave transmissions2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Motivated by the increase of traffic load in cellular network and the associated increase of traffic through the network, device-to-device (D2D) communication with 60GHz millimeter wave (mmWave) is a possible solution to manage this future task. In this research project, our investigation focuses on the benefits of combining D2D links and conventional links with 60 GHz mmWave.  Our investigation is performed in two phases. At first, we consider a network that has only two users, to provide a better understanding of the performance of different communication schemes with 60 GHz mmWave in simplified circumstances. Subsequently, from the realistic point of view, a multi-users system is introduced in latter to detect the relation between system throughput, antenna beamwidth, and interference model. Meanwhile, to ensure the accuracy of system performance, an accuracy improvement algorithm based on iterative algorithm is purposed in the project either.  Simulation results show that, the system with D2D communication and conventional communication together improves performance of system with pure conventional system under 60 GHz mmWave. The capacity can improve more than 13 times with 60 GHz mmWave under highly directional antenna compared with 5 GHz transmission, and system performance highly depends on antenna beamwidth and traffic load. Meanwhile, interference analysis indicates that the interference is not a significant factor for 60 GHz mmWave communication. Finally, the ratio for D2D links under different propagation conditions describes the appropriate environment of using D2D communication in network. Key words: 60 GHz millimetre wave, D2D communication, antenna beamwidth, traffic load, Interference analysis, and accuracy improvement algorithm.

  • 121939. Xie, Fei
    et al.
    Lu, Hongduo
    Nylander, Tommy
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Forsman, Jan
    Theoretical and Experimental Investigations of Polyelectrolyte Adsorption Dependence on Molecular Weight2016In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 32, no 23, p. 5721-5730Article in journal (Refereed)
    Abstract [en]

    This work focuses on adsorption of polyions onto oppositely charged surfaces and on responses to the addition of a simple monovalent salt as well as to the polyion length (degree of polymerization). We also discuss possible mechanisms underlying observed differences, of the adsorbed amount on silica surfaces at high pH, between seemingly similar polyions. This involves theoretical modeling, utilizing classical polymer density functional theory (DFT). We furthermore investigate; how long- and-short-chain Versions of the polymer adsorb onto carboxymethylatect cellulose, carrying a high negative charge. Interestingly enough, comparing results obtained for the two different surfaces, we observe an opposite qualitative response for the molecular weight. The large polymer adsorbs more strongly at a silica surface, but for cellulose at low salt levels, there are indications that the trend is opposite. Another difference is the very slow adsorption process observed for cellulose, particularly with short polymers; in fact, with short polymers, we were sometimes unable to establish any adsorption plateau at all. We speculate that the slow dynamics is due to a gradual diffusion of short polymers into the cellulose matrix. This phenomenon could also explain why short-chain polymers seem to adsorb more strongly than long-chain ones, at low salt concentrations, provided that the latter then are too large to enter the cellulose pores. Cellulose swelling at high salt concentrations might diminish these differences, leading to more similar adsorbed amounts or even a lower adsorption for short chains.

  • 121940. Xie, Fei
    et al.
    Nylander, Tommy
    Piculell, Lennart
    Utsel, Simon
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Wågberg, Lars
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Fibre Technology. KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center.
    Åkesson, Torbjörn
    Forsman, Jan
    Polyelectrolyte Adsorption on Solid Surfaces: Theoretical Predictions and Experimental Measurements2013In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 29, no 40, p. 12421-12431Article in journal (Refereed)
    Abstract [en]

    This work utilizes a combination of theory and experiments to explore the adsorption of two different cationic polyelectrolytes onto oppositely charged silica surfaces at pH 9. Both polymers, poly(diallyldimethylammonium chloride), PDADMAC, and poly(4-vinyl N-methylpyridinium iodide), PVNP, are highly charged and highly soluble in water. Another important aspect is that a silica surface carries a relatively high surface charge density at this pH level. This means that we have specifically chosen to investigate adsorption under conditions where electrostatics can be expected to dominate the interactions. Of specific focus in this work is the response of the adsorption to the addition of simple salt (i.e., a process where electrostatics is gradually screened out). Theoretical predictions from a recently developed correlation-corrected classical density functional theory for polyelectrolytes are evaluated by direct quantitative comparisons with corresponding experimental data, as obtained by ellipsometry measurements. We find that, at low concentrations of simple salt, the adsorption increases with ionic strength, reaching a maximum at intermediate levels (about 200 mM). The adsorption then drops but retains a finite level even at very high salt concentrations, indicating the presence of nonelectrostatic contributions to the adsorption. In the theoretical treatment, the strength of this relatively modest but otherwise largely unknown nonelectrostatic surface affinity was estimated by matching predicted and experimental slopes of adsorption curves at high ionic strength. Given these estimates for the nonelectrostatic part, experimental adsorption data are essentially captured with quantitative accuracy by the classical density functional theory.

  • 121941.
    Xie, Fei
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden..
    Pearce, Mark
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden.
    SPHiNX, Collaboration
    A Study of Background Conditions for Sphinx-The Satellite-Borne Gamma-Ray Burst Polarimeter2018In: Galaxies, E-ISSN 2075-4434, Vol. 6, no 2, article id 50Article in journal (Refereed)
    Abstract [en]

    SPHiNX is a proposed satellite-borne gamma-ray burst polarimeter operating in the energy range 50-500 keV. The mission aims to probe the fundamental mechanism responsible for gamma-ray burst prompt emission through polarisation measurements. Optimising the signal-to-background ratio for SPHiNX is an important task during the design phase. The Geant4 Monte Carlo toolkit is used in this work. From the simulation, the total background outside the South Atlantic Anomaly (SAA) is about 323 counts/s, which is dominated by the cosmic X-ray background and albedo gamma rays, which contribute similar to 60% and similar to 35% of the total background, respectively. The background from albedo neutrons and primary and secondary cosmic rays is negligible. The delayed background induced by the SAA-trapped protons is about 190 counts/s when SPHiNX operates in orbit for one year. The resulting total background level of similar to 513 counts/s allows the polarisation of similar to 50 GRBs with minimum detectable polarisation less than 30% to be determined during the two-year mission lifetime.

  • 121942.
    Xie, Guoxin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Forslund, Mattias
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Direct Electrochemical Synthesis of Reduced Graphene Oxide (rGO)/Copper Composite Films and Their Electrical/Electroactive Properties2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 10, p. 7444-7455Article in journal (Refereed)
    Abstract [en]

    Electrical contact materials with excellent performances are crucial for the development and safe use of electrical contacts in different applications. In our work, reduced graphene oxide (rGO)/copper (Cu) composite films, as potential electrical contact materials, have been synthesized on copper foil with one-step electrochemical reduction deposition method. Cyclic voltammetry (CV) was used to define the deposition conditions, and confocal Raman microscopy (CRM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to characterize the chemical compositions, molecular and micro- and nano-structures of the composite films. Atomic force microscopy/scanning Kelvin probe force microscopy (AFM/SKPFM), conductive AFM (C-AFM) as well as impedance analysis were employed to evaluate the electroactive/electrical properties of the prepared composite films, respectively. The CRM and XPS results suggest that the rGO/Cu composite films can be synthesized through one-step electrochemical codeposition using suitable precursor solutions. Within a short deposition period, the growth of discrete nanograins in the composite film predominates, whereas pine-tree-leaf nanostructures are formed in the composite film when the deposition period is long, due to the chelating role of GO or rGO to regulate the growth rate of metallic copper nanograins. The electrical resistivity of the composite films is lower than the polished Cu foil and the electrodeposited Cu film, probably due to the higher conductivity (enhanced transfer of charge carriers) of the rGO incorporated in the composite films. The Volta potential variation in the rGO/Cu composite film is quite different from that in the electrodeposited Cu film. The electroactivity of the rGO/Cu composite films is higher than the electrodeposited Cu film, but lower than polished Cu foil, and the underlying mechanisms have been discussed.

  • 121943.
    Xie, Guoxin
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science. Tsinghua Univ, State Key Lab Tribol, Peoples R China.
    Zhang, Fan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Pan, Jinshan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Surface and Corrosion Science.
    Adsorption and friction of Mussel Adhesive Protein (MAP) films under polarization2015In: PROCEEDINGS OF MALAYSIAN INTERNATIONAL TRIBOLOGY CONFERENCE 2015, 2015, p. 19-20Conference paper (Refereed)
    Abstract [en]

    Mussel Adhesive Protein (MAP) is an adhesive protein derived from blue mussel byssus, and has promising applications for a variety of functional coatings. In this work, different analytical techniques including cyclic voltammetry, chronocoulometry experiments, and microtribometer have been used to investigate the interfacial structures and the frictional properties of MAP film on the platinum (Pt) substrate under polarization. MAP adsorption could change electrostatically after polarization. The friction of adsorbed MAP film can be tuned effectively in a suitable potential range, which is promising for future active control over the adsorption and friction of MAP films.

  • 121944. Xie, H.
    et al.
    Fan, Ting
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Lei, Q.
    Fang, W.
    New progress in theoretical studies on palladium-catalyzed C−C bond-forming reaction mechanisms2016In: Science China Chemistry, ISSN 1674-7291, p. 1-16Article in journal (Refereed)
    Abstract [en]

    This review reports a series of mechanistic studies on Pd-catalyzed C−C cross-coupling reactions via density functional theory (DFT) calculations. A brief introduction of fundamental steps involved in these reactions is given, including oxidative addition, transmetallation and reductive elimination. We aim to provide an important review of recent progress on theoretical studies of palladium-catalyzed carbon–carbon cross-coupling reactions, including the C−C bond formation via C−H bond activation, decarboxylation, Pd(II)/Pd(IV) catalytic cycle and double palladiums catalysis.

  • 121945. Xie, H
    et al.
    Lekarp, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    The Influence of Moisture Content on Mechanical Performance of Unbound Granular Materials - A Literature Review2001Report (Other academic)
  • 121946. Xie, H
    et al.
    Lekarp, Fredrik
    KTH, School of Architecture and the Built Environment (ABE), Transport Science, Highway and Railway Engineering.
    The Influence of Moisture Content on Mechanical Performance of Unbound Granular Materials - A Literature Review2001Report (Other academic)
  • 121947. Xie, H.
    et al.
    Liu, C.
    Yuan, Y.
    Zhou, T.
    Fan, Ting
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Lei, Q.
    Fang, W.
    Oxidation of phenyl and hydride ligands of bis(pentamethylcyclopentadienyl)hafnium derivatives by nitrous oxide via selective oxygen atom transfer reactions: Insights from quantum chemistry calculations2016In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 45, no 3, p. 1152-1159Article in journal (Refereed)
    Abstract [en]

    The mechanisms for the oxidation of phenyl and hydride ligands of bis(pentamethylcyclopentadienyl)hafnium derivatives (Cp∗ = η5-C5Me5) by nitrous oxide via selective oxygen atom transfer reactions have been systematically studied by means of density functional theory (DFT) calculations. On the basis of the calculations, we investigated the original mechanism proposed by Hillhouse and co-workers for the activation of N2O. The calculations showed that the complex with an initial O-coordination of N2O to the coordinatively unsaturated Hf center is not a local minimum. Then we proposed a new reaction mechanism to investigate how N2O is activated and why N2O selectively oxidize phenyl and hydride ligands of. Frontier molecular orbital theory analysis indicates that N2O is activated by nucleophilic attack by the phenyl or hydride ligand. Present calculations provide new insights into the activation of N2O involving the direct oxygen atom transfer from nitrous oxide to metal-ligand bonds instead of the generally observed oxygen abstraction reaction to generate metal-oxo species.

  • 121948.
    Xie, Hailian
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    On Power-system Benefits, Main-circuit Design, and Control of StatComs with Energy Storage2009Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Static synchronous compensation (StatCom) is an application that utilizes a voltage source converter (VSC) to provide instantaneous reactive power support to the connected power system. Conventionally, StatComs are employed for reactive power support only. However, with the integration of energy storage (ES) into a StatCom, it can provide active power support in addition to the reactive power support. This thesis deals with the integration of ES into StatComs. The investigation involves the following aspects: possible benefits for power systems, main circuit design, and control strategies.

    As the basis of the investigation, a control scheme is proposed for two-level VSCs. It is a novel flux modulation scheme combined with the well-known deadbeat current control. The current controller is capable of controlling the positive sequence, the negative sequence, and the offset components of the converter current. With flux modulation, all the three above-mentioned components of the bus flux are controllable. This differs from the conventional voltage modulation scheme, in which only the positive and negative sequence components of the bus voltage are controllable. The difference between the proposed flux modulation scheme and the voltage modulation scheme is investigated regarding saturation of transformers in the connected system during fault recovery. The investigation shows that by controlling the offset component of the bus flux, the transformer saturation problem can be mitigated to a certain extent.

    The possible benefits of the additional active power support of StatComs are investigated through several case studies. Different active power compensation schemes are proposed. First, active power compensation for sudden load changes in weak systems is investigated. The proposed control strategies are verified through computer simulations and through experiments in a real-time simulator. It is shown that with active power compensation, both the phase jumps and magnitude variations in the voltage at the PCC can be reduced significantly. Secondly, the power compensation of cyclic loads is investigated. The results show that the power quality at the connection point can be improved regarding both phase jumps and magnitude variations. In the third case study, the fault-recovery performance of an example system is investigated, showing that improved performance can be achieved by the additional active power support.

    ES devices such as capacitors, supercapacitors, and batteries exhibit considerable variation in the terminal voltage during a charging/discharging cycle. A direct connection of ES devices to the dc side of a VSC requires a higher voltage rating of the VSC. Thus, the cost of the VSC has to be increased. In this thesis, a dual thyristor converter topology is proposed to interface ES devices with the dc side of the VSC. First, a cost comparison is performed to compare the total cost of the whole system with and without the proposed interface topology. A cost comparison between various types of ES is also presented, providing a guideline for the choice of ES at energy levels where several alternatives exist. Then, the dynamics of systems with the proposed interface topology are investigated. Control strategies are proposed and verified by computer simulations. Two different control methods for the dual-thyristor converter are compared.

  • 121949.
    Xie, Hailian
    KTH, School of Electrical Engineering (EES).
    Voltage Source Converters with Energy Storage Capability2006Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    This project deals with voltage source converters with energy storage capability. The main objective is to study the possible benefits of energy storage to a power system with a VSC as the interface between them.

    First of all, a converter control system is proposed for a two level VSC. In the conventional converter control, the control system usually takes the voltage measured at the point where the converter is connected and calculates the reference voltage for the converter; with a modulation system the converter then produces the required 'average voltage'. In this project, a novel flux modulation scheme, combined with the deadbeat current control strategy, is proposed. The current controller is capable of controlling both positive and negative sequence current components. With flux modulation, the control system measures the bus flux and commands the converter to generate the required flux.

    Based on the proposed control strategies, several application studies have been carried out.

    The first application study investigates the effect of energy storage on the power quality at the point of common coupling when a system is subject to load disturbances. The voltage at PCC in a weak network is very sensitive to load changes. A sudden change in active load will cause both a phase jump and a magnitude fluctuation in the bus voltage, whereas reactive load changes mainly affect the voltage magnitude. With the addition of energy storage to a StatCom, it is possible to compensate for the active power change as well as providing reactive power support. In this thesis, some effective active power compensation schemes are proposed. Simulations and experiments have been performed to verify the compensation schemes. The results show that a StatCom with energy storage can significantly reduce phase jumps and magnitude deviations of the bus voltage.

    pact of the energy storage on the performance of weak systems under fault conditions has been investigated. The investigation was done by studying an example system. The system model was established based on a real system, in which some induction motors driving pumps along a pipeline are fed from a radial transmission line. Studies show that for a weak system with induction motor loads, a StatCom with certain energy storage capacity will effectively improve the system recovery after faults. Although this incurs extra cost for the increasing dc voltage rating and size of the dc side capacitor, the overall rating of the converter can be reduced by utilization of the proposed active power compensation scheme.

    The last case study investigates the possible use of a StatCom with energy storage to improve the power quality at the point of common coupling where a cyclic load is connected. Studies show that by providing both fast reactive and fast active power support to the network, not only the voltage magnitude can be well controlled, but also the voltage phase jump can be reduced significantly.

  • 121950.
    Xie, Hailian
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Ängquist, Lennart
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    A Converter Topology Suitable for Interfacing Energy Storage with the dc Link of a StatCom2008In: 2008 IEEE INDUSTRY APPLICATIONS SOCIETY ANNUAL MEETING, 2008, p. 1916-1919Conference paper (Refereed)
    Abstract [en]

    Voltage Source Converters (VSC) have been widely utilized to provide instantaneous reactive power support to power systems, an application referred to as Static synchronous Compensators (StatCom). Integration of energy storage (ES) into a StatCom makes it possible for the StatCom to provide a certain amount of active power as well as reactive power support. The possible benefit of the additional active power support of a StatCom can be power oscillation damping capability, mitigation of phase-jump related disturbance, etc. Direct connection of ES device to the dc link of the VSC incurs unnecessary high voltage rating of the VSC due to the considerable voltage swing associated with the ES device. This paper proposes a thyristor converter topology as the interface between the ES device and the VSC dc link. With the proposed interface, the dc voltage of the VSC can be kept constant and thus lower the VSC rating and cost.

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