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  • 122701.
    Zhu, Kun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Nordström, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Hammouri, A.
    Jordan University of Science and Technology .
    Examination of data delay and packet loss for wide-area monitoring and control systems2012Ingår i: 2012 IEEE International Energy Conference and Exhibition, ENERGYCON 2012, IEEE , 2012, s. 927-934Konferensbidrag (Refereegranskat)
    Abstract [en]

    Timely and synchronized phasor data at high resolutions holds a great promise for more responsible and advanced power grid operations. It is expected that the combined effort of developing new application paradigms and the supporting Information and Communication Technology (ICT) will enable the evolutionary change for future transmission grid operation. This paper addresses the design of the supporting ICT system for Wide-Area Monitoring and Control applications considering system performance. The major contribution that distinguishes this paper from previous research efforts in the same area is that this study quantifies the end-to-end data delay and the received packet rate with considerations of different levels of data concentrations. The analysis performed in this paper is not merely limited to the performance issues caused by communication networks but also provides means to view and analyze the overall data delay of the entire supporting ICT system.

  • 122702. Zhu, Kun
    et al.
    Ou, Haiyan
    Fu, Hongyan
    Remb, Edvin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP. KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    A Simple and Tunable Single-Bandpass Microwave Photonic Filter of Adjustable Shape2008Ingår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 20, nr 21-24, s. 1917-1919Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simple and tunable single-hand pass microwave photonic filter of adjustable shape is proposed and experimentally demonstrated. The filter is based on multiple sources (spectrum-sliced by a Mach-Zehnder interferometer) and two cascaded incoherent optical structures, namely, a dispersion medium of 50-km single-mode fiber and a fiber ring delay line. In the experimental range from 1.0 to 3.8 GHz, a discretely tunable single-hand pass filter with a high Q-factor or a flat-top response is achieved by carefully matching the transfer functions of the two individual optical structures.

  • 122703. Zhu, Kun
    et al.
    Ou, Haiyan
    Ye, Chenhui
    Fu, Hongyan
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    All-optical coherence-free microwave filter with switchable passbands based on phase and intensity hybrid modulation2011Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 284, nr 1, s. 140-143Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A simple all-optical coherence-free microwave notch filter is proposed and experimentally demonstrated. The filter with switchable passbands is based on a single-wavelength optical source and phase-intensity hybrid modulation scheme. The DC bias voltage applied to the Mach-Zehnder intensity modulator can be adjusted to switch signs of the tap coefficients, which affect the baseband response. Both lowpass and bandpass filtering responses are observed in the experiment and agree well with the simulated results.

  • 122704.
    Zhu, Kun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Song, Ji
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Chenine, Moustafa
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Nordström, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Analysis of phasor data latency in wide area monitoring and control systems2010Ingår i: 2010 IEEE International Conference on Communications Workshops, ICC 2010, Capetown, 2010Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Synchronized phasor measurement based Wide Area Monitoring and Control (WAMC) system is becoming a reality within international research and development both in academia and industry. Timely and accurate data with high resolutions holds great promise for more responsible and advanced grid control and operation. Currently, most of the research focuses on the different control schemes and applications. A relatively less addressed aspect is the dependency of the WAMC system on the performance of the Information and Communication Technology (ICT) infrastructure, without whose support the projected functionalities of the WAMC systems will be not achieved. Possible delays brought by the complex data transfer and processing processes in WAMC systems are addressed in the first part of this paper. Thereafter, simulations where delayed Phasor measurements are fed to the Static Var Compensator (SVC) are conducted iteratively to detect its maximum tolerated delay. Furthermore, performance requirements for the centralized computation and control actuation are researched and analyzed based on simulation results. It also includes a study on feasibility of compensations using local signal based Power System Stablizers (PSS) in situations with much phasor data delay. The paper is concluded by suggesting ICT architecture for WAMC systems aiming to improve its robustness.

  • 122705.
    Zhu, Kun
    et al.
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Yuan, Xu
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Honeth, Nicholas
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Nordström, Lars
    KTH, Skolan för elektro- och systemteknik (EES), Industriella informations- och styrsystem.
    Data Volume Estimation for CIM based Information Exchange2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    IEC 61970 and 61968, which are commonly referred as Common Information Model (CIM), are proposed to facilitate integration of EMS applications and information exchange between EMS systems with propitiatory data structures. To use communication network in an optimized manner, it is necessary to partition the potentially voluminous data into subsets given their sources, expected exchange frequency, and subscribing applications. In response to these requirements, the concept of CIM profiles is brought up by CIMug. In this paper, functions illustrating the dependency between exchange data volume and basic grid parameters for each data profile are presented. A CIM/XML/RDF file for a generally available 40 bus test system (CIM 13) and examples provided by standards are used as references. The method is validated by estimating the data sizes of similarly available 100bus and 60bus test systems that are modeled according to CIM 13 as well. The contribution of this paper is that it provides ICT system designers with a means to estimate the corresponding requirements for various CIM/XML based data exchange patterns. The estimations are performed based on commonly known grid parameters such as number of buses, branches, generators, transformers and loads together with execution frequency of particular grid planning and operation applications.

  • 122706. Zhu, L.
    et al.
    Ang, C. Y.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Nguyen, K. T.
    Tan, S. Y.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhao, Y.
    Luminescent color conversion on cyanostilbene-functionalized quantum dots via in-situ photo-tuning2012Ingår i: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 24, nr 29, s. 4020-4024Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Photo-responsive CdSe quantum dots functionalized with the cyanostilbene unit are synthesized. The as-prepared quantum dot hybrid reveals a photo-tunable dual fluorescent characteristic. White light emission can be generated in situ from the hybrid through photoirradiation to adjust the relative intensities of the two complementary emissions. Luminescent color conversion through yellow, white, and blue can be realized by varying the photoirradiation time.

  • 122707.
    Zhu, Lailai
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Numerical investigation of swimming micro-organisms in complex environments2012Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 122708.
    Zhu, Lailai
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll.
    Simulation of individual cells in flow2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this thesis, simulations are performed to study the motion ofindividual cells in flow, focusing on the hydrodynamics of actively swimming cells likethe self-propelling microorganisms, and of passively advected objects like the red bloodcells. In particular, we develop numerical tools to address the locomotion ofmicroswimmers in viscoelastic fluids and complex geometries, as well as the motion ofdeformable capsules in micro-fluidic flows.

    For the active movement, the squirmer is used as our model microswimmer. The finiteelement method is employed to study the influence of the viscoelasticity of fluid on theperformance of locomotion. A boundary element method is implemented to study swimmingcells inside a tube. For the passive counterpart, the deformable capsule is chosen as the modelcell. An accelerated boundary integral method code is developed to solve thefluid-structure interaction, and a global spectral method is incorporated to handle theevolving cell surface and its corresponding membrane dynamics.

    We study the locomotion of a neutral squirmer with anemphasis on the change of swimming kinematics, energetics, and flowdisturbance from Newtonian to viscoelastic fluid. We also examine the dynamics of differentswimming gaits resulting in different patterns of polymer deformation, as well as theirinfluence on the swimming performance. We correlate the change of swimming speed withthe extensional viscosity and that of power consumption with the phase delay of viscoelasticfluids. Moreover, we utilise the boundary element method to simulate the swimming cells in astraight and torus-like bent tube, where the tube radius is a few times the cell radius. Weinvestigate the effect of tube confinement to the swimming speed and power consumption. Weanalyse the motions of squirmers with different gaits, which significantly affect thestability of the motion. Helical trajectories are produced for a neutralsquirmer swimming, in qualitative agreement with experimental observations, which can beexplained by hydrodynamic interactions alone.

    We perform simulations of a deformable capsule in micro-fluidic flows. We look atthe trajectory and deformation of a capsule through a channel/duct with a corner. Thevelocity of capsule displays an overshoot as passing around the corner, indicating apparentviscoelasticity induced by the interaction between the deformable membrane and viscousflow. A curved corner is found to deform the capsule less than the straight one. In addition, we propose a new cell sorting device based on the deformability of cells. Weintroduce carefully-designed geometric features into the flow to excite thehydrodynamic interactions between the cell and device. This interaction varies andclosely depends on the cell deformability, the resultant difference scatters the cellsonto different trajectories. Our high-fidelity computations show that the new strategy achievesa clear and robust separation of cells. We finally investigate the motion of capsule in awall-bounded oscillating shear flow, to understand the effect of physiological pulsation to thedeformation and lateral migration of cells. We observe the lateral migration velocity of a cellvaries non-monotonically with its deformability.

  • 122709.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Brandt, Luca
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    The motion of a deforming capsule through a corner2015Ingår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 770, s. 374-397Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A three-dimensional deformable capsule convected through a square duct with a corner is studied via numerical simulations. We develop an accelerated boundary integral implementation adapted to general geometries and boundary conditions. A global spectral method is adopted to resolve the dynamics of the capsule membrane developing elastic tension according to the neo-Hookean constitutive law and bending moments in an inertialess flow. The simulations show that the trajectory of the capsule closely follows the underlying streamlines independently of the capillary number. The membrane deformability, on the other hand, significantly influences the relative area variations, the advection velocity and the principal tensions observed during the capsule motion. The evolution of the capsule velocity displays a loss of the time-reversal symmetry of Stokes flow due to the elasticity of the membrane. The velocity decreases while the capsule is approaching the corner, as the background flow does, reaches a minimum at the corner and displays an overshoot past the corner due to the streamwise elongation induced by the flow acceleration in the downstream branch. This velocity overshoot increases with confinement while the maxima of the major principal tension increase linearly with the inverse of the duct width. Finally, the deformation and tension of the capsule are shown to decrease in a curved corner.

  • 122710.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Do-Quang, Minh
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Lauga, Eric
    Dept. of Mechanical and Aerospace Engineering, University of California, San Diego, USA.
    Brandt, Luca
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Locomotion by tangential deformation in a polymeric fluid2011Ingår i: Physical Reivew E, ISSN 1539-3755, Vol. 83, nr 1, s. 011901-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In several biologically relevant situations, cell locomotion occurs in polymeric fluids with Weissenberg number larger than 1. Here we present results of three-dimensional numerical simulations for the steady locomotion of a self-propelled body in a model polymeric (Giesekus) fluid at low Reynolds number. Locomotion is driven by steady tangential deformation at the surface of the body (the so-called squirming motion). In the case of a spherical squirmer, we show that the swimming velocity is systematically less than that in a Newtonian fluid, with a minimum occurring for Weissenberg numbers of order 1. The rate of work done by the swimmer always goes up compared to that occurring in the Newtonian solvent alone but is always lower than the power necessary to swim in a Newtonian fluid with the same viscosity. The swimming efficiency, defined as the ratio between the rate of work necessary to pull the body at the swimming speed in the same fluid and the rate of work done by swimming, is found to always be increased in a polymeric fluid. Further analysis reveals that polymeric stresses break the Newtonian front-back symmetry in the flow profile around the body. In particular, a strong negative elastic wake is present behind the swimmer, which correlates with strong polymer stretching, and its intensity increases with Weissenberg number and viscosity contrasts. The velocity induced by the squirmer is found to decay in space faster than in a Newtonian flow, with a strong dependence on the polymer relaxation time and viscosity. Our computational results are also extended to prolate spheroidal swimmers and smaller polymer stretching are obtained for slender shapes compared to bluff swimmers. The swimmer with an aspect ratio of two is found to be the most hydrodynamically efficient.

  • 122711.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre. Ecole Polytech Fed Lausanne, Lab Fluid Mech & Instabil, CH-1015 Lausanne, Switzerland.;Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08540 USA.
    Gallaire, Francois
    Ecole Polytech Fed Lausanne, Lab Fluid Mech & Instabil, CH-1015 Lausanne, Switzerland..
    Bifurcation Dynamics of a Particle-Encapsulating Droplet in Shear Flow2017Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 119, nr 6, artikel-id 064502Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To understand the behavior of composite fluid particles such as nucleated cells and double emulsions in flow, we study a finite-size particle encapsulated in a deforming droplet under shear flow as a model system. In addition to its concentric particle-droplet configuration, we numerically explore other eccentric and time-periodic equilibrium solutions, which emerge spontaneously via supercritical pitchfork and Hopf bifurcations. We present the loci of these solutions around the codimension-two point. We adopt a dynamic system approach to model and characterize the coupled behavior of the two bifurcations. By exploring the flow fields and hydrodynamic forces in detail, we identify the role of hydrodynamic particle-droplet interaction which gives rise to these bifurcations.

  • 122712.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Lauga, Eric
    Dept. of Mechanical and Aerospace Engineering, University of California, San Diego, USA.
    Brandt, Luca
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Low-Reynolds number swimming in a capillary tube2013Ingår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 726, s. 285-311Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use the boundary element method to study the low-Reynolds-number locomotion of a spherical model microorganism in a circular tube. The swimmer propels itself by tangential or normal surface motion in a tube whose radius is of the order of the swimmer size. Hydrodynamic interactions with the tube walls significantly affect the average swimming speed and power consumption of the model microorganism. In the case of swimming parallel to the tube axis, the locomotion speed is always reduced (respectively, increased) for swimmers with tangential (respectively, normal) deformation. In all cases, the rate of work necessary for swimming is increased by confinement. Swimmers with no force dipoles in the far field generally follow helical trajectories, solely induced by hydrodynamic interactions with the tube walls, and in qualitative agreement with recent experimental observations for Paramecium. Swimmers of the puller type always display stable locomotion at a location which depends on the strength of their force dipoles: swimmers with weak dipoles (small alpha) swim in the centre of the tube while those with strong dipoles (large alpha) swim near the walls. In contrast, pusher swimmers and those employing normal deformation are unstable and end up crashing into the walls of the tube. Similar dynamics is observed for swimming into a curved tube. These results could be relevant for the future design of artificial microswimmers in confined geometries.

  • 122713.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Lauga, Eric
    Dept. of Mechanical and Aerospace Engineering, University of California, San Diego, USA.
    Brandt, Luca
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Self-propulsion in viscoelastic fluids: pushers vs. pullers2012Ingår i: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 24, nr 5, s. 051902-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We use numerical simulations to address locomotion at zero Reynolds number in viscoelastic (Giesekus) fluids. The swimmers are assumed to be spherical, to self-propel using tangential surface deformation, and the computations are implemented using a finite element method. The emphasis of the study is on the change of the swimming kinematics, energetics, and flow disturbance from Newtonian to viscoelastic, and on the distinction between pusher and puller swimmers. In all cases, the viscoelastic swimming speed is below the Newtonian one, with a minimum obtained for intermediate values of the Weissenberg number, We. An analysis of the flow field places the origin of this swimming degradation in non-Newtonian elongational stresses. The power required for swimming is also systematically below the Newtonian power, and always a decreasing function of We. A detail energetic balance of the swimming problem points at the polymeric part of the stress as the primary We-decreasing energetic contribution, while the contributions of the work done by the swimmer from the solvent remain essentially We-independent. In addition, we observe negative values of the polymeric power density in some flow regions, indicating positive elastic work by the polymers on the fluid. The hydrodynamic efficiency, defined as the ratio of the useful to total rate of work, is always above the Newtonian case, with a maximum relative value obtained at intermediate Weissenberg numbers. Finally, the presence of polymeric stresses leads to an increase of the rate of decay of the flow velocity in the fluid, and a decrease of the magnitude of the stresslet governing the magnitude of the effective bulk stress in the fluid.

  • 122714.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Rabault, Jean
    Brandt, Luca
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    The dynamics of a capsule in a wall-bounded oscillating shear flow2014Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The motion of an initially spherical capsule in a wall-bounded oscillating shear flow is studied via an accelerated boundary integral implementation. Neo-Hookean model is used as the constitutive law of the membrane of capsule. The lateral migration velocity of the capsule varies non-monotonically with its capillary number. It is negatively related with the initial height of the capsule above the wall. A positive correlation between the lateral migration velocity and normal stress difference is identified. The correlation becomes strongest for the capsule with the highest lateral migration velocity. For a fixed capillary number, the lateral migration velocity decreases linearly with the frequency of oscillating shear, and approaches an asymptotic value of zero for high frequency. The deformation of capsule displays a wave-like variation in time and its frequency is twice that of the underlying shear. A phase delay is observed between the variation of capsule deformation with that of the oscillatory flow, more pronounced for a more deformable capsule.

     

  • 122715.
    Zhu, LaiLai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Rabault, Jean
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. Ecole Polytech, F-91128 Palaiseau, France.
    Brandt, Luca
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    The dynamics of a capsule in a wall-bounded oscillating shear flow2015Ingår i: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 27, nr 7, artikel-id 071902Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The motion of an initially spherical capsule in a wall-bounded oscillating shear flow is investigated via an accelerated boundary integral implementation. The neo-Hookean model is used as the constitutive law of the capsule membrane. The maximum wall-normal migration is observed when the oscillation period of the imposed shear is of the order of the relaxation time of the elastic membrane; hence, the optimal capillary number scales with the inverse of the oscillation frequency and the ratio agrees well with the theoretical prediction in the limit of high-frequency oscillation. The migration velocity decreases monotonically with the frequency of the applied shear and the capsule-wall distance. We report a significant correlation between the capsule lateral migration and the normal stress difference induced in the flow. The periodic variation of the capsule deformation is roughly in phase with that of the migration velocity and normal stress difference, with twice the frequency of the imposed shear. The maximum deformation increases linearly with the membrane elasticity before reaching a plateau at higher capillary numbers when the deformation is limited by the time over which shear is applied in the same direction and not by the membrane deformability. The maximum membrane deformation scales as the distance to the wall to the power 1/3 as observed for capsules and droplets in near-wall steady shear flows.

  • 122716.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Stabilitet, Transition, Kontroll. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    Rorai, Cecilia
    Mitra, Dhrubaditya
    Brandt, Luca
    KTH, Skolan för teknikvetenskap (SCI), Mekanik, Fysiokemisk strömningsmekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW.
    A microfluidic device to sort capsules by deformabilityManuskript (preprint) (Övrigt vetenskapligt)
  • 122717.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Centra, SeRC - Swedish e-Science Research Centre. Laboratory of Fluid Mechanics and Instabilities, Switzerland .
    Rorai, Cecilia
    KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, Nordic Institute for Theoretical Physics NORDITA. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    Mitra, Dhrubaditya
    KTH, Centra, Nordic Institute for Theoretical Physics NORDITA.
    Brandt, Luca
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre.
    A microfluidic device to sort capsules by deformability: a numerical study2014Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, nr 39, s. 7705-7711Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Guided by extensive numerical simulations, we propose a microfluidic device that can sort elastic capsules by their deformability. The device consists of a duct embedded with a semi-cylindrical obstacle, and a diffuser which further enhances the sorting capability. We demonstrate that the device can operate reasonably well under changes in the initial position of the capsule. The efficiency of the device remains essentially unaltered under small changes of the obstacle shape (from semi-circular to semi-elliptic cross-section). Confinement along the direction perpendicular to the plane of the device increases its efficiency. This work is the first numerical study of cell sorting by a realistic microfluidic device.

  • 122718.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik. KTH, Skolan för teknikvetenskap (SCI), Centra, Linné Flow Center, FLOW. KTH, Centra, SeRC - Swedish e-Science Research Centre. Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA.
    Stone, Howard A.
    Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA..
    Propulsion driven by self-oscillation via an electrohydrodynamic instability2019Ingår i: Physical Review Fluids, ISSN 2469-990X, Vol. 4, nr 6, artikel-id 061701Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Oscillations of flagella and cilia play an important role in biology, which motivates the idea of functional mimicry as part of bioinspired applications. Nevertheless, it still remains challenging to drive their artificial counterparts to oscillate via a steady, homogeneous stimulus. Combining theory and simulations, we demonstrate a strategy to achieve this goal by using an elastoelectrohydrodynamic instability (based on the Quincke rotation instability). In particular, we show that applying a uniform dc electric field can produce self-oscillatory motion of a microrobot composed of a dielectric particle and an elastic filament. Upon tuning the electric field and filament elasticity, the microrobot exhibits three distinct behaviors: a stationary state, undulatory swimming, and steady spinning, where the swimming behavior stems from an instability emerging through a Hopf bifurcation. Our results imply the feasibility of engineering self-oscillations by leveraging the elastoviscous response to control the type of bifurcation and the form of instability. We anticipate that our strategy will be useful in a broad range of applications imitating self-oscillatory natural phenomena and biological processes.

  • 122719.
    Zhu, Lailai
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    Stone, Howard A.
    Princeton Univ, Dept Mech & Aerosp Engn, Princeton, NJ 08544 USA..
    Rotation of a low-Reynolds-number watermill: theory and simulations2018Ingår i: Journal of Fluid Mechanics, ISSN 0022-1120, E-ISSN 1469-7645, Vol. 849, s. 57-75Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent experiments have demonstrated that small-scale rotary devices installed in a microfluidic channel can be driven passively by the underlying flow alone without resorting to conventionally applied magnetic or electric fields. In this work, we conduct a theoretical and numerical study on such a flow-driven 'watermill' at low Reynolds number, focusing on its hydrodynamic features. We model the watermill by a collection of equally spaced rigid rods. Based on the classical resistive force (RF) theory and direct numerical simulations, we compute the watermill's instantaneous rotational velocity as a function of its rod number N, position and orientation. When N >= 4, the RF theory predicts that the watermill's rotational velocity is independent of N and its orientation, implying the full rotational symmetry (of infinite order), even though the geometrical configuration exhibits a lower-fold rotational symmetry; the numerical solutions including hydrodynamic interactions show a weak dependence on N and the orientation. In addition, we adopt a dynamical system approach to identify the equilibrium positions of the watermill and analyse their stability. We further compare the theoretically and numerically derived rotational velocities, which agree with each other in general, while considerable discrepancy arises in certain configurations owing to the hydrodynamic interactions neglected by the RP theory. We confirm this conclusion by employing the RP-based asymptotic framework incorporating hydrodynamic interactions for a simpler watermill consisting of two or three rods and we show that accounting for hydrodynamic interactions can significantly enhance the accuracy of the theoretical predictions.

  • 122720.
    Zhu, Lei
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Security Extensions of the OpenStack Platform2013Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The emergence of Cloud Computing has become one of hottest topics in IT industry. So, what is cloud computing? There are many definitions summarized by people from different areas in their perspectives. However, the US National Institute of Standard Technology (NIST) [1] defines cloud computing as a model for enabling ubiquitous, convenient, ondemand network access to a shared pool of configurable computing resources (e.g., networks, servers, storage, applications, and services) [2].

    Despite of all the benefits that Cloud Computing brings to the IT industry, there are increasing issues being pointed out about the security and privacy due to the currently immature cloud security status. NIST points out that there are several security and privacy issues in the area of public cloud computing including governance, authentication, access control, data protection and availability [3].

    This master thesis is intended to build security architecture for open-source cloud computing platform. This thesis work concentrates on providing strong authentication service between cloud provider and users, as well as delivering access control and Single- Sign-On (SSO) service to the users, which are provided by the central security system. The central security system, as the proposed solution for secure cloud-computing platform, comprises of different security components providing security services in the form of web services. OpenStack as an open-source cloud-computing platform is chose for the research.

  • 122721. Zhu, Liang-Liang
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi.
    Ji, Feng-Yuan
    Ma, Xiang
    Wang, Qiao-Chun
    Tian, He
    Photolockable Ratiometric Viscosity Sensitivity of Cyclodextrin Polypseudorotaxane with Light-Active Rotor Graft2009Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 25, nr 6, s. 3482-3486Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A prototype, based on light-active fluorescent rotor grafted to beta-cyclodextrin, shows a good solvent viscosity-sensitive behavior due to the environment-dependent nonradiative decay. With the reversible photoisomerization of the cyanostilbene unit, the viscosity sensitivity of the molecular rotor could be locked and activated, and the two switchable states can be distinguished by fluorescent signals. This cyclodextrin derivative was threaded to form a novel polypseudorotaxane. Such supramolecular assembly displays a lockable ratiometric fluorescent viscosity sensitivity with two emission channels: one aroused by fluorophore's intramolecular excimer without influenced by viscosity is used to gauge the concentration of the compound, while the other corresponding to the monomer's rotor fluorescence acts as a viscosity-sensitive signal and it can be shut off by UV irradiation.

  • 122722. Zhu, Liangliang
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Sanders, Samuel N.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Unimolecular Photopolymerization of High-Emissive Materials on Cylindrical Self-Assemblies2015Ingår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 48, nr 15, s. 5099-5105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report a novel self-assembly pathway from a bis(imidazolyl) diphenyl-diacetylene (DPDA) compound as a realization of self-templated photopolymerization with high polymerization degrees. The work takes advantage of a cylindrical self-assembly that strengthens the preorganization of the diphenyl-diacetylene moiety at the single molecular level. On this basis, photopolymerization of DPDA can be conducted smoothly to form high-molecular-weight polydiphenyl diacetylene. Such a cylindrical self-assembly is highly dependent on molecular structure, and control studies show that only oligomers can be formed on random self-assemblies from a monoimidazolyl or nonimidazolyl diphenyl-diacetylene compound. Moreover, the cylindrical self-assembly based systems bear aggregation-induced emission enhancement characteristics and are solution processable. The leading thin-film could afford a selectively tunable function in luminescent micropatterns.

  • 122723. Zhu, Liangliang
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Wu, Shaojue
    Nguyen, Kim Truc
    Yan, Hong
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhao, Yanli
    Chirality Control for in Situ Preparation of Gold Nanoparticle Superstructures Directed by a Coordinatable Organogelator2013Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, nr 24, s. 9174-9180Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Imposing chirality into nanoscale superstructures is a major step forward toward systematic understanding and utilization of nanomaterials. In an attempt to achieve tunable chirality during in situ preparation of hybrid nanomaterials, we here report a novel unimolecular strategy of employing a coordinatable organogelator for the realization of chirality control in the formation of gold nanoparticle superstructures. The work takes advantage of thermally reversible sol-gel transition of the chiral dispersion as template, which causes different micelle properties that can influence the coordination ability between the organogelator and Au(III) ions. Followed by a reduction reaction, gold nanoparticle superstructures with P-helicity were prepared from the sol form of the template through a coordination-induced chiral inversion, whereas those with M-helicity were obtained from the gel form with chiral holding. Such superstructures are solvent-stable and the chirality difference between them could be observed in many solvent environments.

  • 122724. Zhu, Liangliang
    et al.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhang, Quan
    Ma, Xing
    Li, Menghuan
    Zhang, Huacheng
    Luo, Zhong
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Zhao, Yanli
    Unimolecular Photoconversion of Multicolor Luminescence on Hierarchical Self-Assemblies2013Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, nr 13, s. 5175-5182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Facile tuning of photophysical properties is highly desirable for boosting the performance and versatility of photoluminescent materials. In an attempt to overcome the challenge of achieving the photoswitching of multicolor luminescence on unimolecular platforms, we here report a novel hierarchical self-assembly of a cyanostilbene-naphthalimide dyad as the realization of phototunable luminescence at the unimolecular level. The work takes advantage of the photoisomerization of the cyanostilbene moiety from the Z form to its E form, which causes a morphological disorder in the molecular self-assembly and gives rise to a dual fluorescent characteristic accompanied by a progressive luminescent color conversion from yellow to green and finally to blue. Such systems with convertible multicolor luminescence might exhibit application potentials for unimolecular selective imaging and labeling, as exemplified by the cell imaging studies presented in this work.

  • 122725. Zhu, Liangliang
    et al.
    Tran, Helen
    Beyer, Frederick L.
    Walck, Scott D.
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Ågren, Hans
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi.
    Killops, Kato L.
    Campos, Luis M.
    Engineering Topochemical Polymerizations Using Block Copolymer Templates2014Ingår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, nr 38, s. 13381-13387Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With the aim to achieve rapid and efficient topochemical polymerizations in the solid state, via solution-based processing of thin films, we report the integration of a diphenyldiacetylene monomer and a poly(styrene-b-acrylic acid) block copolymer template for the generation of supramolecular architectural photopolymerizable materials. This strategy takes advantage of non-covalent interactions to template a topochemical photopolymerization that yields a polydiphenyldiacetylene (PDPDA) derivative. In thin films, it was found that hierarchical self-assembly of the diacetylene monomers by microphase segregation of the block copolymer template enhances the topochemical photopolymerization, which is complete within a 20 s exposure to UV light. Moreover, UV-active cross-linkable groups were incorporated within the block copolymer template to create micropattems of PDPDA by photolithography, in the same step as the polymerization reaction. The materials design and processing may find potential uses in the microfabrication of sensors and other important areas that benefit from solution-based processing of flexible conjugated materials.

  • 122726.
    Zhu, Lin
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    DESIGN AND IMPLEMENTATION A BATTERY MANAGEMENT SYSTEM FOR A MULTI‐FUNCTION POWER CONVERTER2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This thesis work designed and implemented an advanced Battery Management System (BMS) for a battery package with 96 Lithium-ion battery cells connected in series. The focus of this thesis placed on battery model building, battery balancing algorithm developing, State-of-Charge (SOC) estimation algorithm developing, and implementing software in microprocessor.A set of simulation program is developed to verify the battery model and the algorithms. A battery simulator based on SPICE is built to implement a first order Thevenin dynamic electrochemical model. PID control algorithm is employed in balancing the battery cells. Meanwhile, Extended Kalman Filter (EKF) algorithm is used for estimating the SOC. An interactive web GUI application is also developed for easy control. Software running on STM32F103 microprocessor has been developed to adapt the existing BMS hardware.The simulation result proves that the first order Thevenin dynamic electrochemical model reflect the behavior of a real battery accurately, the PID balancing algorithm is effective to make the battery cells stay in balanced state and the error of EKF SOC estimation algorithm is below 5%.

  • 122727.
    Zhu, Lin
    KTH, Skolan för teknik och hälsa (STH), Naturvetenskap och biomedicin, Strukturell bioteknik.
    Structural studies of HDL and applications of EM on membrane proteins2017Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    A large number of proteins interact with biological membranes, either integrated in the membrane (PepTSo2), embedded on a membrane surface (5-lipoxygenase) or encircling a cutout of lipid bilayer (apolipoprotein1 (apoA-I). They function as transporters, receptors or biocatalysts in cellular processes like inflammation or cholesterol transport which are touched upon here. Malfunction of specific membrane proteins are the cause for several diseases or disorders.

    Knowledge of protein structure supports understanding of its mechanism of function. Here, transmission electron microscopy (TEM) was used for structure determination. To obtain structure information to high resolution for membrane proteins, normally surrounded by lipids, demands specific methods and materials for stabilization. Stabilized in detergent the structure of the bacterial transporter PepTSo2 was shown to form a tetramer even bound to substrate. However, with a protein based stabilizer, Salipro, the structure of PepTSo2 could be determined to high resolution.

    High density lipoprotein (HDL) in blood plasma, involved in the removal of cholesterol from peripheral tissues, have a central role in cardiovascular function, metabolic syndrome and diabetes.

    The HDL-particle is composed of two copies of ApoA1 and around hundred lipid molecules. From TEM data, for the first time the clearly discoidal shape could be shown by 3-dimendional reconstructions. These were used for modelling the ApoA1 protein dimer by a "biased fitting" procedure. The results indicate how ApoA1 folds around a lipid bilayer in a disc-shaped structure.

    Modified HDL called nanodiscs were here used to show the Ca2+ dependent binding of 5-lipoxygenase on the nanodisc bilayer and thereby increased production of the inflammatory mediator leukotrieneA4. Dimerization of 5-lipoxygenase inactivates these functions.

  • 122728.
    Zhu, Lin
    KTH, Skolan för teknik och hälsa (STH), Naturvetenskap och biomedicin, Strukturell bioteknik.
    Structural Studies of High Density Lipoprotein by Electron Microscopy and Flexible FittingManuskript (preprint) (Övrigt vetenskapligt)
  • 122729.
    Zhu, Lin
    et al.
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Strukturell bioteknik. Karolinska Institutet, Sweden.
    Petrlova, J.
    Gysbers, P.
    Hebert, Hans
    KTH, Skolan för teknik och hälsa (STH), Medicinsk teknik, Strukturell bioteknik. Karolinska Institutet, Sweden.
    Wallin, S.
    Jegerschöld, Caroline
    KTH, Skolan för teknik och hälsa (STH). Karolinska Institutet, Sweden.
    Lagerstedt, J. O.
    Structures of apolipoprotein A-I in high density lipoprotein generated by electron microscopy and biased simulations2017Ingår i: Biochimica et Biophysica Acta - General Subjects, ISSN 0304-4165, E-ISSN 1872-8006, Vol. 1861, nr 11, s. 2726-2738Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Background: Apolipoprotein A-I (apoA-I) in high-density lipoprotein (HDL) is a key protein for the transport of cholesterol from the vascular wall to the liver. The formation and structure of nascent HDL, composed of apoA-I and phospholipids, is critical to this process. Methods: The HDL was assembled in vitro from apoA-I, cholesterol and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) at a 1:4:50 molar ratio. The structure of HDL was investigated in vitreous samples, frozen at cryogenic temperatures, as well as in negatively stained samples by transmission electron microscopy. Low resolution electron density maps were next used as restraints in biased Monte Carlo simulations of apolipoprotein A-I dimers, with an initial structure derived from atomic resolution X-ray structures. Results: Two final apoA-I structure models for the full-length structure of apoA-I dimer in the lipid bound conformation were generated, showing a nearly circular, flat particle with an uneven particle thickness. Conclusions: The generated structures provide evidence for the discoidal, antiparallel arrangement of apoA-I in nascent HDL, and propose two preferred conformations of the flexible N-termini.

  • 122730. Zhu, M. -M
    et al.
    Zhao, P. -H
    Chen, Y. -L
    Bai, X. -S
    Fuchs, Laszlo
    KTH, Skolan för teknikvetenskap (SCI), Mekanik.
    The vorticity field of acoustic modulated free jets2012Ingår i: Kung Cheng Je Wu Li Hsueh Pao/Journal of Engineering Thermophysics, ISSN 0253-231X, Vol. 33, nr 10, s. 1811-1814Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The motivation of this paper is to investigate the effects of acoustic modulation on the structures of free jet. Large eddy simulation is performed on three dimensional free jet of Re number 2200 with multigrid method. Comparisons of the vorticity fields are made between the unmodulated jet and perturbed jets with different modulation frequencies. When the modulation frequency is near the preferred mode of the natural jet, the flow field changes significantly. The azimuthal vorticity rolls up into large vortex rings, and the jet spreads more widely. When the modulation frequency is about the twice of the preferred mode, vortex pairing happens and the subharmonic wave becomes dominant. The flow fields are almost the same as the natural jet when the modula-tion frequency is much higher than the preferred mode. The distribution of streamwise vorticity is examined for the modulated jet near the preferred mode, and agrees qualitatively with the experiments.

  • 122731. Zhu, M. Y.
    et al.
    Sichen, Du
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Modelling study of slag foaming phenomenon2000Ingår i: Steel research, ISSN 0177-4832, Vol. 71, nr 3, s. 76-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A one-dimensional model based on mass and momentum conservations has been developed to predict the heights of foams caused by gas injection. In the development of the model, a dimensionless number, N-foam = u(s)[(3C(d))/(4d(b)g)](1/2) has been deduced to characterise the foaming behaviour. According to the model, an increase in this dimensionless number results in an increase In foaming height. The validity of the model has been experimentally examined using silicon oils. The experiments have also shown that foamings can be classified into two types, namely one-layer foaming and two-layer foaming. The former type results in much larger height than the latter.

  • 122732. Zhu, M-Y
    et al.
    Jones, T
    Sichen, Du
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Mikro-modellering.
    Modelling study of slag foaming by chemical reactio2001Ingår i: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, s. 51-56Artikel i tidskrift (Refereegranskat)
  • 122733.
    Zhu, Ning
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Design, Fabrication and Characterization of Planar Lightwave Circuits Based on Silicon Nanowire Platform2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Optical devices based on Planar Lightwave Circuit (PLC) technology have well been studied due to their inherited advantages from Integrated Circuits (IC), such as: small size, high reliability, mass production and potential integration with microelectronics. Among all the materials, silicon nanowire platform gains more and more interest. The large refractive index difference between core and cladding allows tremendous reduction of the component size. This thesis studies theoretically and experimentally some integrated optical devices based on silicon nanophotonic platform, including echelle grating demultiplexers and photonic crystals.

    Some of the numerical methods are introduced first. Scalar integral diffraction method is efficient for calculating the diffraction efficiency of gratings. Beam propagation method and finite-difference time-domain method are also introduced, for simulating the light propagation along the devices.

    The fabrication technology and characterization methods are described. The fabrication steps involve: plasma assisted film deposition, E-beam lithography, RIE-etching. All these steps are proceeded under cleanroom environment. The characterization is mainly based on two methods: end-fire coupling and vertical grating coupling. The grating coupler is more efficient compared with the butt-coupling between fiber and nanowires, but is worse solution for final packaging.

    Two types of components have been realized and characterized with the above technology. The echelle grating demultiplexer is one of the key components in WDM networks. A method for increasing the diffraction efficiency based on total internal reflection is applied, and a significant improvement of the diffraction efficiency of more than 3dB is achieved. A novel cross-order echelle grating-based triplexer, a bidirectional transceiver for application in the Passive Optical Networks (PON), has been designed and fabricated, which can multi/demultiplex three channels located at 1310nm, 1490nm and 1550nm. Polarization dependence issue of echelle grating demultiplexers has been studied. Two polarization compensation schemes have been proposed, which are for the first time polarization insensitive designs of echelle grating demultiplexers based on silicon nanowire platform.

    Photonic crystal devices are also addressed in the thesis. There has been little research on the photonic crystal cavity based on pillar type. A silicon pillar type photonic crystal cavity has been fabricated with the measured Q value as high as about 104, and with an extremely high sensitivity for the changing of the background material or the effective diameter of the pillars. This kind of structure has the advantage on sensing applications compared to the air-hole type structure.

  • 122734.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Dai, Daoxin
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    A hybrid modeling for the theoretical analysis of reflections in a multimode-interference coupler based on silicon-on-insulator nanowires2008Ingår i: Optics Communications, ISSN 0030-4018, E-ISSN 1873-0310, Vol. 281, nr 11, s. 3099-3104Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A hybrid method combining the three-dimensional (3D) beam propagation method (BPM) and a 3D finite-difference time-domain (FDTD) method is presented for the simulation of multimode-interference (MMI) couplers based on silicon-on-insulator (SOI) nanowires. This hybrid method makes it possible to have a robust analysis for the reflection properties while avoiding a time-consumed computation with a simplex 3D-FDTD simulation. The reflected power is sensitive to both the length and the width of the MMI coupler and thus one should choose the optimal values for good self-imaging. Furthermore, the reflection could be reduced by introducing tapers between the MMI section and the access waveguides.

  • 122735.
    Zhu, Ning
    et al.
    E China Univ Sci & Technol, Key Lab Adv Mat, Shanghai 200237, Peoples R China.;E China Univ Sci & Technol, Inst Fine Chem, Shanghai 200237, Peoples R China..
    Li, Xin
    KTH, Skolan för bioteknologi (BIO), Teoretisk kemi och biologi. KTH Royal Inst Technol, Div Theoret Chem & Biol, Sch Biotechnol, SE-10691 Stockholm, Sweden..
    Wang, Yuan
    Chinese Acad Sci, Key Lab Photochem Convers & Optoelect Mat, Tech Inst Phys & Chem, Beijing 100190, Peoples R China..
    Ma, Xiang
    E China Univ Sci & Technol, Key Lab Adv Mat, Shanghai 200237, Peoples R China.;E China Univ Sci & Technol, Inst Fine Chem, Shanghai 200237, Peoples R China..
    Photo-responsive chiral cyclic molecular switches based on stiff stilbene2016Ingår i: Dyes and pigments, ISSN 0143-7208, E-ISSN 1873-3743, Vol. 125, s. 259-265Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two novel photo-responsive chiral cyclic molecular switches constituted of stiff stilbene and binaphthyl moieties connected through alkyl chains of different length were fabricated. The cyclization synthetic strategy employed herein made it convenient to obtain the pure Z isomers rather than Z/E isomer mixtures. The detailed photo-switching behaviors of target compounds were studied by the UV-Vis absorption and circular dichroism spectra in dichloromethane. The twist angles of the binaphthyl of the switches were able to be reversibly modulated by Z/E isomerization of stiff stilbene unit under alternative UV light stimuli and influenced by the length of alkyl chain to some extent.

  • 122736.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och Informationsteknik, IMIT. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Cross-Order Echelle Grating Triplexer Based on Amorphous Silicon Nanowire Platform2008Ingår i: 2008 7TH INTERNATIONAL CONFERENCE ON THE OPTICAL INTERNET (COIN), NEW YORK: IEEE , 2008, s. 37-38Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present fabrication and measurement results of an ultracompact silicon-on-insulator-based echelle-grating triplexer, which uses different diffraction orders to cover a large spectral range from 1.3 mu m to 1.5 mu m, with a footprint of 150 mu m x 200 mu m.

  • 122737.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Design of a polarization-insensitive echelle grating demultiplexer based on silicon nanophotonic wires2008Ingår i: IEEE Photonics Technology Letters, ISSN 1041-1135, E-ISSN 1941-0174, Vol. 20, nr 9-12, s. 860-862Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A polarization-insensitive design of an echelle grating (or etched diffraction grating) demultiplexer based on silicon nanowires is proposed in the present letter, by introducing a polarization compensation area in its free propagation region. The polarization-dependent wavelength shift of the present device has been compensated at the whole spectral range. For a design with nine channels and 10-nm channel spacing, when the wavelength shift at the central channel 1550 nm is. completely compensated, the wavelength shifts of the two edge channels are only 0.14 and 0.15 nm, which are acceptable.

  • 122738.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Etched diffraction grating demultiplexers based on amorphous silicon nanowire platform2008Ingår i: 2008 Asia Optical Fiber Communication and Optoelectronic Exposition and Conference, AOE 2008, 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present some theoretical and experimental results of Etched Diffraction Grating demultiplexer based on amorphous silicon nanowire platform, including issues with polarization sensitivity, diffraction efficiency and an application to triplexer.

  • 122739.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES).
    Total internal reflection type echelle grating demultiplexer based on amorphous silicon nanowire platform2008Ingår i: Proceedings of SPIE - The International Society for Optical Engineering, Hangzhou, 2008, Vol. 7134Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper we present measurement results of an ultracompact echelle-grating demultiplexer based on silicon-on-insulator nanowire platform, in which we introduced a total internal reflection design of the grating facets to improve the diffraction efficiency. An average increase of the diffraction efficiency with 3.7dB is observed for the 3 channels compared to a normal design.

  • 122740.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Song, Jun
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Kista Photonics Research Center, KPRC.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    He, Sailing
    KTH, Skolan för elektro- och systemteknik (EES), Elektroteknisk teori och konstruktion.
    Thylén, Lars
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik.
    Experimental demonstration of a cross-order echelle grating triplexer based on an amorphous silicon nanowire platform2009Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 34, nr 3, s. 383-385Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the design, fabrication, and characterization of an ultracompact silicon-on-insulator-based echelle grating triplexer. It is based on the cross-order design, which utilizes different diffraction orders to cover a large spectral range from 1.3 to 1.5 mu m with three channels located at 1310, 1490, and 1550 nm and with a footprint of 150 mu m X 130 mu m.

  • 122741.
    Zhu, Ning
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wang, Zhechao
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Wosinski, Lech
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP. KTH, Skolan för informations- och kommunikationsteknik (ICT), Centra, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    He, Sailing
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Bragg grating-assisted optical triplexer using two silicon nanowire-based directional couplers2009Ingår i: 2009 Asia Communications and Photonics Conference and Exhibition, ACP 2009, 2009, s. 5377094-Konferensbidrag (Refereegranskat)
    Abstract [en]

    A triplexer based on silicon nanophotonic wire structure consisting of two Bragg grating-assisted directional couplers is proposed. The device has low loss, low crosstalk, and a footprint of only 210 x40 μm, The 1-dB bandwidth for the three channels located at 1310, 1490 and 1550 nm are 110, 20, and 20 nm, respectively.

  • 122742.
    Zhu, Rui
    et al.
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    Gidofalvi, Gyözö
    KTH, Skolan för arkitektur och samhällsbyggnad (ABE), Samhällsplanering och miljö, Geodesi och geoinformatik.
    GPS-based Crowd Sourced Intelligent Traffic Information Hub2013Ingår i: Proceedings of the 26th International Cartographic Conference / [ed] Manfred F. Buchroithner, ICC International Cartographic Association , 2013, s. 669-670Konferensbidrag (Refereegranskat)
    Abstract [en]

    Congestion is a major problem in most metropolitan areas and given the increasing rate of urbanization it is likely to be an even more serious problem in the rapidly expanding mega cities. Some well know negative effects of congestion include: 1) the economic losses and quality of life degradation that result from the increased and unpredictable travel times, 2) the increased level of carbon footprint that vehicles idling in congestions leave behind, and 3) the increased number of traffic accidents that are direct results of the stress and fatigue of drivers that are stuck in congestion.

    One possible method to combat congestion is provide intelligent traffic management systems that can in a timely manner inform drivers about current or predicted traffic congestion that is relevant to them on their journeys. This this extent, the present paper proposes a scalable, grid-based intelligent traffic information hub that facilitates the manual definition and/or automatic detection of abnormal traffic condition events, e.g., accidents or congestion, and in advance informs drivers about events that will likely be relevant to them on their journey, thereby allowing the divers or their onboard navigation units to alter their paths as needed.

    The proposed system achieves the above described functionality through the following methodology. The system, without loss of generality, adopts a grid-based discretization of space, which by changing the resolution of the grid allows the system to scale in terms of it computation cost and the geographical level of detail of traffic information that it manages. The system derives traffic information from the continuous stream of grid-based position and speed reports that it receives from the vehicles. In particular, the system in an online fashion 1) summarizes Current (grid-based) Traffic Flow Statistics (CTFS), i.e., it records for each grid cell g from each neighboring grid cell n, the mean and standard deviation of the speeds of the vehicles that are currently located in g and have entered g from n; and 2) efficiently incorporates the CTFS into compressed Historical (grid-based) Traffic Flow Statistics (HTFS) using incremental statistics. Simultaneously, using a sliding window model, the system also 1) maintains the Recent (grid-based) Trajectories (RT) of the vehicles; 2) extracts Recent (gridbased) Mobility Statistics (RMS), i.e., it records for each destination grid cell d, for each neighboring grid cell n of g, and for each possible source grid cell s, the number of vehicles that (i) are currently in d, (ii) have entered d from n, and (iii) have a RT that has passed through s; and 3) efficiently incorporates the RMS into compressed Historical (grid-based) Mobility Statistics (HMS) using incremental statistics. To capture the temporal variability in traffic flow and mobility patterns at different scales, the system through temporal domain projections maintains day-of-week and hour-ofday based aggregations of HTFS and RMS. Then, the system classifies a grid cell g to be congested from the direction of a neighboring grid cell n if the current mean speed of vehicles that entered the grid cell g from the direction of n is below the normal according to the temporally relevant HFS. Finally, based on the temporally relevant HMS, the system sends out congestion notifications to vehicles that are likely to be effected in the future part of their journey by these congestions, i.e., the system sends out a congestion notification (g,n) to a vehicle v that is currently located in some grid cell s from which the likelihood of v moving to g through n within the prediction horizon is above a user-defined threshold.

    Extensive empirical evaluations on large sets of realistically simulated trajectories of vehicles illustrate that the above described methodology and its simple SQL-based implementation in a relational database system is scalable and effective. In particular, the execution time of- and the space used by the system scales linearly with the input size (number of concurrently moving vehicles) and the method’s mutually dependent parameters (grid resolution r and RT length l) that jointly define a spatio-temporal resolution. Within the area of a large city (40km by 40km), assuming a 60km/h average vehicle speed, the system, running on a single personal computer, can manage the described congestion detection and one-minute-ahead notification tasks within real-time requirements for 15 thousand and 2.5 million concurrently moving vehicles for spatio-temporal resolutions (r=62.5m, l=17) and (r=4km,l=2), respectively. Finally, the proposed method, for all spatio-temporal resolutions and prediction horizons, significantly outperforms in terms of notification accuracy the grid-based baseline method, which sends non-directional congestion notifications based on the recent linear movement tendencies of vehicles. 

  • 122743.
    Zhu Ryberg, Yingzhi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Wood Hydrolysate for Renewable Products2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

     

    Förnyelsebar biomassa har använts under lång tid för olika ändamål, från mat till industriprodukter. En stor familj av heteropolysackarider är hemicellulosa som har visat en potential i många applikationer, t. ex, inom medicin, jordbruket och förpackning industrin. För att utvinna renad hemicellulosa, krävs komplicerade processer, vilket är opraktiskt och för kostsant för många industriella tillämpningar. I detta arbete har vi använt ett hydrolysat som utvinns utan omfattande upprening från en flytande sidoström i massaindustrin. Detta barrveds hydrolysat är rikt på hemicellulosan, O-acetylerad galactoglucomannan (AcGGM) och innehåller även en del lignin.

    Filmer och beläggningar skapades genom blandning av detta hydrolysat med två andra polysackarider samkomponenter; karboximetylcellulosa (CMC) och kitosan. Olika formuleringar med varierade koncentrationer och kompositioner utvecklades. Dessutom framställdes motsvarande formuleringar av AcGGM. Filmerna och beläggningarna analyserades med avseende på mekaniska egenskaper, kemisk struktur, vattenånga- och syrebarriäregenskaper. Kitosan, som samkomponent, förbättrade de mekaniska egenskaperna bäst medan CMC gav bäst syrebarriäregenskaper vid såväl 50% som 80% relativ fuktighet. Hydrolysat-baserade filmer hade betydligt lägre syrepermeabilitet (OP) än AcGGM-baserade filmer. För att förstå varför mindre renat hydrolysat gav bättre syrebarriäregenskaper än upprenad AcGGM, utvecklades en kombinerat teoretisk-analytisk modell. Beräkningar baserade på Hansens löslighetsparametersteori (HSP) visade att det finns starka interaktioner mellan lignin och hemicellulosorna i hydrolysatet, och även att CMC var mer kompatibel med hydrolysat/AcGGM än kitosan, vilket ger en starkare affinitet mellan komponenterna och en mer kompakt molekylstuktur, och därmed mindre fri volym i matrisen. Denna tolkning verifieras av positron annihilation lifetime spectra (PALS), som visar att hydrolysat-baserade filmer har en mindre fri volym (hålstorlek) och högre homogenitet än AcGGM-baserade filmer. Även termiska analyser och FTIR verifierade inflytandet och arten av dessa interaktioner.

  • 122744.
    Zhu Ryberg, Yingzhi
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Wood hydrolysates- New concepts in renewable material design2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Hydrolysat är processvätskor från träindustrin. Istället för komplicerade utvinningsprocesser av ren hemicellulosa från processvätskor, används här det oförädlade hydrolysatet, som innehåller till största delen hemicellulosa och en del lignin. Den här avhandlingen beskriver hur vi framgångsrikt utvecklade detta hydrolysat till syrgasbarriärfilmer och bestrykningar som kan användas till matförpackningar samt hur modellering av strukturerna och interaktionerna mellan hydrolysatets komponenter kan förutsäga deras prestanda som barriärmaterial.

    Fristående filmer och bestrykningar skapades från blandningar av vedhydrolysat och en samkomponent: antingen kitosan eller karboximetylcellulosa (CMC). Filmerna hade utmärkta syrgasbarriäregenskaper som till och med var bättre än filmer beredda av motsvarande renade hemicellulosa. Hansens löslighetsparametersteori (HSP) påvisade och kvantifierade interaktioner mellan molekylerna i både hydrolysat och hydrolysat-baserade blandningar vilket ger en förståelse för de goda barriäregenskaperna. Vår hypotes var att dessa starka interaktioner ökade affiniteten i matrisen vilket leder till tät molekylär packning och därmed bra syrgasbarriäregenskaper. Med Positron annihiliation lifetime spectroscopy (PALS) uppmättes de fria volymerna i de hydrolysat-baserade matriserna. HSP resultaten, storlek och fördelning av fri volym, samt termisk analys, verifierade hypotesen väl.

    HSP-modellen användes sedan för att prediktera kompositionen hos syrgasbarriärbestrykningar från hydrolysat-baserade blandningar. Genom att använda HSP-modellen, kan interaktionerna mellan olika hydrolysat och CMC beräknas och interaktionerna i matrisen utvärderas. De fria volymerna uppmätta med PALS, syrepermeabilitet (OP)-resultaten var generellt överensstämmande med förutsägelserna från HSP-modellen, vilket visar potentialen för HSP- modellen som verktyg i formuleringen av barriärbestrykningarr för matförpackningar.

    För att utveckla en industriellt realistisk och effektiv process för produktion av hydrolysat-baserade bestrykningar provades flera angreppssätt. Först gjordes bestrykningar manuellt från hydrolysat-baserade blandningar och dessa hade utmärkta syrebarriäregenskaper. Sedan utvecklades en spraytorkningsbeläggningsteknik (SPD) som en reproducerbar, effektiv bestrykningsprocess för hydrolysat utan tillsatser eller andra samkomponenter. Dessutom förbättrade töjbarheten hos bestrykningarna genom tvärbindning med glyoxal vilket i sin tur förbättrade kvalitet och syrgasbariäregenskaperna för bestrykningen. SEM integrerat med en dragprovutrustning gjorde det möjligt att i realtid observeraytan av bestrykningen under deformationsprocessen. Detta gjorde det möjligt att studera de mekaniska egenskaperna för beläggningarna utan inverkan av substratet.

  • 122745.
    Zhu Ryberg, Yingzhi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Conceptual approach to renewable barrier film design based on wood hydrolysate2011Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, nr 4, s. 1355-1362Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Biomass is converted to oxygen barriers through a conceptually unconventional approach involving the preservation of the biomass native interactions and macromolecular components and enhancing the effect by created interactions With a co-component. A combined calculation/assessment model is elaborated to understand, quantify, and predict which compositions that provide an intermolecular affinity high enough to mediate the molecular packing needed to create a functioning barrier. The biomass used is a wood hydrolysate, a polysaccharide-rich but not highly refined mixture where a fair amount of the native intermolecular and intramolecular hernicelluloses-lignin interactions are purposely preserved, resulting in barriers with very low oxygen permeabilities (OP) both at 50 and 80% relative humidity and, considerably lower OPs than coatings based on the corresponding highly purified spruce hemicellulose, O-acetyl galactoglucomannan (AcGGM). The component interactions and, mutual affinities effectively mediate an immobilization of the chain segments in a dense disordered structure, modeled through the Hansen's solubility parameter concept and quantified on the nanolength scale by positron annihilation lifetime spectrum (PALS).

  • 122746.
    Zhu Ryberg, Yingzhi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Innovative Approaches for Converting a Wood Hydrolysate to High-Quality Barrier Coatings2013Ingår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, nr 16, s. 7748-7757Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An advanced approach for the efficient and controllable production of softwood hydrolysate-based coatings with excellent oxygen-barrier performance is presented. An innovative conversion of the spray-drying technique into a coating applicator process allowed for a fast and efficient coating process requiring solely aqueous solutions of softwood hydrolysate, even without additives. Compared to analogous coatings prepared by manual application, the spray-drying produced coatings were more homogeneous and smooth, and they adhered more strongly to the substrate. The addition of glyoxal to the aqueous softwood hydrolysate solutions prior to coating formation allowed for hemicellulose cross-linking, which improved both the mechanical integrity and the oxygen-barrier performance of the coatings. A real-time scanning electron microscopy imaging assessment of the tensile deformation of the coatings allowed for a deeper understanding of the ability of the coating layer itself to withstand stress as well as the coating-to-substrate adhesion.

  • 122747.
    Zhu Ryberg, Yingzhi
    et al.
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Edlund, Ulrica
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Albertsson, Ann-Christine
    KTH, Skolan för kemivetenskap (CHE), Fiber- och polymerteknik, Polymerteknologi.
    Retrostructural model to predict biomass formulations for barrier performance2012Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 13, nr 8, s. 2570-2577Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Barrier performance and retrostructural modeling of the macromolecular components demonstrate new design principles for film formulations based on renewable wood hydrolysates. Hardwood hydrolysates, which contain a fair share of lignin coexisting with poly- and oligosaccharides, offer excellent oxygen-barrier performance. A Hansen solubility parameter (HSP) model has been developed to convert the complex hydrolysate structural compositions into relevant matrix oxygen-permeability data allowing a systematic prediction of how the biomass should be formulated to generate an efficient barrier. HSP modeling suggests that the molecular packing ability plays a key role in the barrier performance. The actual size and distribution of free volume holes in the matrices were quantified in the subnanometer scale with Positron annihilation lifetime spectroscopy (PALS) verifying the affinity-driven assembly of macromolecular segments in a densely packed morphology and regulating the diffusion of small permeants through the matrix. The model is general and can be adapted to determine the macromolecular affinities of any hydrolysate biomass based on chemical composition.

  • 122748.
    Zhu, Shanying
    et al.
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China.;Minist Educ China, Key Lab Syst Control & Informat Proc, Shanghai 200240, Peoples R China..
    Chen, Cailian
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China.;Minist Educ China, Key Lab Syst Control & Informat Proc, Shanghai 200240, Peoples R China..
    Xu, Jinming
    Arizona State Univ, Ira A Fulton Sch Engn, Tempe, AZ 85281 USA..
    Guan, Xinping
    Shanghai Jiao Tong Univ, Dept Automat, Shanghai 200240, Peoples R China.;Minist Educ China, Key Lab Syst Control & Informat Proc, Shanghai 200240, Peoples R China..
    Xie, Lihua
    Nanyang Technol Univ, Sch Elect & Elect Engn, Singapore 639798, Singapore..
    Johansson, Karl H.
    KTH, Skolan för elektroteknik och datavetenskap (EECS), Centra, ACCESS Linnaeus Centre.
    Mitigating Quantization Effects on Distributed Sensor Fusion: A Least Squares Approach2018Ingår i: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 66, nr 13, s. 3459-3474Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, we consider the problem of sensor fusion over networks with asymmetric links, where the common goal is linear parameter estimation. For the scenario of bandwidth-constrained networks, existing literature shows that nonvanishing errors always occur, which depend on the quantization scheme. To tackle this challenging issue, we introduce the notion of virtual measurements and propose a distributed solution LS-DSFS, which is a combination of a quantized consensus algorithm and the least squares approach. We provide detailed analysis of the LS-DSFS on its performance in terms of unbiasedness and mean square property. Analytical results show that the LS-DSFS is effective in smearing out the quantization errors, and achieving the minimum mean square error (MSE) among the existing centralized and distributed algorithms. Moreover, we characterize its rate of convergence in the mean square sense and that of the mean sequence. More importantly, we find that the LS-DSFS outperforms the centralized approaches within a moderate number of iterations in terms of MSE, and will always consume less energy and achieve more balanced energy expenditure as the number of nodes in the network grows. Simulation results are presented to validate theoretical findings and highlight the improvements over existing algorithms.

  • 122749.
    Zhu, Shaoling
    KTH, Skolan för elektro- och systemteknik (EES), Reglerteknik.
    Experimental Study on Low Power Wireless Sensor Network Protocols with Native IP Connectivity for BuildingA utomation2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    The recent development of wired and wireless communication technologiesmake building automation the next battlefield of the Internet of Things. Multiplestandards have been drafted to accommodate the complex environmentand minimize the resource consumption of wireless sensor networks. This MasterThesis presents a thorough experimental evaluation with the latest Contikinetwork stack and TI CC2650 platform of network performance indicators,including signal coverage, round trip time, packet delivery ratio and powerconsumption. The Master Thesis also provides a comparison of the networkprotocols for low power operations, the existing operating systems for wirelesssensor networks, and the chips that operate on various network protocols. Theresults show that CC2650 is a promising competitor for future development inthe market of building automation.

  • 122750.
    Zhu, Wanning
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Kommunikationssystem, CoS.
    Multipoint Relay flooding: Network coding improvements2009Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Network coding is a new research area with potential to reduce network resources. With network coding, intermediate nodes forward packets that are linear combinations of previously received packets.

    The type of networks we consider are vehicle mounted mobile tactical radio networks. Tactical communication may be required in areas where pre-deployed base stations are unavailable. Mobile ad hoc networks satisfy this requirement. Due to low antenna heights, network resources are scarce inmobile networks without base stations. Broadcast traffic, which disseminates information network-wide, is very important in tactical mobile networks. Multipoint relay flooding is a well-known technique for efficient distribution of broadcast traffic. It is therefore interesting to evaluate how much network coding can reduce the number of transmissions in a mobile ad hoc network. In this thesis we show that it is possible to further reduce the number of transmissions for Multipoints Relay flooding by using network coding. However, this improvement is largely theoretical - there has been no effort to evaluate this approach in practice.

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