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  • 124301. Zhao, W.
    et al.
    Li, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Li, Xiaoqing
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Gong, S.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sun, Z.
    Thermo-mechanical properties of Ni-Mo solid solutions: A first-principles study2019In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 158, p. 140-148Article in journal (Refereed)
    Abstract [en]

    The mechanical strength of Ni-based single-crystal superalloys under service condition is related to the thermo-mechanical properties of the disordered γ matrix. Here we use density functional theory and quasi-harmonic approximation to determine the temperature-dependent bulk moduli and generalized stacking fault energies (GSFEs) of Ni-Mo solid solutions. We show that the increasing temperatures between 1000 K and 1400 K cause evident reductions in the bulk moduli and planar fault energies of Ni-Mo alloys. Furthermore, their negative slopes versus temperature are gradually diminished with increasing Mo concentration except that of the unstable stacking fault energy. Adopting recent theoretical models for twinning based on GSFE, increasing temperature enhances the twinnability of low-Mo alloys but has limited influences in the case of high-Mo alloys. The composition-dependent thermal expansion, the thermal electronic excitation and the magnetic transition are shown to be the main factors rendering the complex variations in the elastic properties and twinning behavior of Ni-Mo solid solution with temperature.

  • 124302.
    Zhao, Wang
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Hu, JianHao
    Xiong, Xing Zhong
    Song, Jie
    Non-data-aided timing acquisition for asynchronous IDMA systems2012In: Wireless personal communications, ISSN 0929-6212, E-ISSN 1572-834X, Vol. AprilArticle in journal (Refereed)
    Abstract [en]

    Sample-timing error can cause significant performance degradation for the interleave-

    division multiple-access systems (Wang et al.2009). In this paper, we propose a nondata-aided timing acquisition scheme tomitigate sample-timing error due to the asynchronoustransmission of random allocated user ends (UEs) on the uplink.Aclosed-loop timing control scheme is constructed for the asynchronous IDMA system in this paper.We use the extrinsic information generated during the iterative detection algorithm with signal noise ratio  volution to estimate the timing offset for the asynchronous uplink in the base station (BS) receiver. The BS receiver returns the timing control bits, which is generated with estimated timing offsets, to the corresponding UE. And the UE uses the timing control bits to adjust local transmission time to guarantee the sampling performance at the BS receiver. The simulation results show that the proposed acquisition scheme based on feedback loop can provide high acquisition probability and low false alarm probability. The proposed scheme can overcome the bit-error-rate performance bottleneck, which is caused by the sample-timing error in BS receiver due to the asynchronous signals in the uplink.

  • 124303.
    Zhao, Wang
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Wang, Chao
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    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.
    On the achievable degrees of freedom of partially cooperative X networks with delayed CSIT2012In: 2012 IEEE Global Communications Conference (GLOBECOM), New York: IEEE , 2012, p. 2450-2454Conference paper (Refereed)
    Abstract [en]

    We investigate the achievable degrees of freedom (DoF) in K-user X networks (K × K X networks) with delayed channel state information at transmitters (CSIT), where partial cooperation (i.e. message sharing) is potentially allowed among transmitters. We consider two possible cooperation scenarios. In the first scenario one of the transmitters serves as a super node which can obtain the messages of the other transmitters. By proper interference alignment (IA) design, we prove that a DoF 2K over K+1 can be achieved almost surely. In the second scenario, there is no super node but each transmitter shares its message to its left-side neighbor. We show that when K = 3, DoF 7 over 5 is achievable. In both cases, the achieved DoF are shown to be improved compared with non-cooperative X networks. Moreover, we use a simple example to show that sharing a subset of messages may also improve DoF.

  • 124304.
    Zhao, Wang
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Wang, Chao
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    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.
    The two-hop MISO broadcast network with quantized delayed CSIT2013In: 2013 IEEE Wireless Communications and Networking Conference (WCNC), IEEE Communications Society, 2013, p. 3022-3027Conference paper (Refereed)
    Abstract [en]

    We consider a downlink two-hop MISO broadcast network with a 2-antenna source communicating to 2 singleantenna destinations, assisted by 2 single-antenna intermediate relays. We investigate spectrally efficient transmission schemes and their achieved sum degrees of freedom (DoF), with quantized delayed channel state information (CSI) feedback. Assuming Grassmannian vector quantization, we study two feedback scenarios according to the feedback range limit, namely global-range feedback, i.e., the source can receive the feedback signals from both the relays and the destinations, and one-hop-range feedback, i.e., each node can only attain the feedback information of its upcoming hop. We establish a sum DoF lower bound for each case. Our results reveal that when the quantization rate at relays BR= α1log2(SNR) and at destinations BD = α2log2(SNR) for min 1, α2} ≥ 1, the optimal sum DoF 4/3 can be achieved with finite-rate delayed feedback.

  • 124305.
    Zhao, Wang
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    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), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Poor, H. Vincent
    Princeton University.
    Secrecy degrees of freedom of wireless X networks using artificial noise alignmentManuscript (preprint) (Other academic)
    Abstract [en]

    The problem of transmitting confidential messages in $M \times K$ wireless X networks is considered, in which each transmitter intends to send one confidential message to every receiver. In particular, the secrecy degrees of freedom (SDOF) of the considered network achieved by an artificial noise alignment (ANA) approach, which integrates interference alignment and artificial noise transmission, are studied. At first, an SDOF upper bound is derived for the $M \times K$ X network with confidential messages (XNCM) to be $\frac{K(M-1)}{K+M-2}$. By proposing an ANA approach, it is shown that the SDOF upper bound is tight when either $K=2$ or $M=2$ for the considered XNCM with time/frequency varying channels. For $K,M \geq 3$, it is shown that an SDOF $\frac{K(M-1)}{K+M-1}$ can be achieved, even when an external eavesdropper appears. The key idea of the proposed scheme is to inject artificial noise to the network, which can be aligned in the interference space at receivers for confidentiality. Moreover, for the network with no channel state information at transmitters, a blind ANA scheme is proposed to achieve the SDOF $\frac{K(M-1)}{K+M-1}$ for $K,M \geq 2$, with reconfigurable antennas at receivers. The proposed method provides a linear approach to handle secrecy coding and interference alignment.

  • 124306.
    Zhao, Wang
    et al.
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Wang, Chao
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Skoglund, Mikael
    KTH, School of Electrical Engineering (EES), Centres, ACCESS Linnaeus Centre. KTH, School of Electrical Engineering (EES), Communication Theory.
    Degrees of freedom of two hop MISO broadcast network with mixed CSIT2014In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 13, no 12, p. 6982-6995Article in journal (Refereed)
    Abstract [en]

    A downlink two-hop MISO broadcast network is considered, with a two-antenna source communicating to 2 single-antenna destinations, via multiple single-antenna relays in between. The sum degrees of freedom (DOF) of the network with mixed channel state information at the transmitter (CSIT) is investigated. The mixed CSIT consists of accurate delayed CSIT and inaccurate instantaneous CSIT, and its availability is limited within each hop, i.e. the source is oblivious to the channels of the second hop. Given a transmission power P and a real value α in [0,1], if the variance of the error for instantaneous CSIT decreases as O(P-α), it is shown that the sum optimal DOF of the considered network is d = when there exist at least 3 intermediate relays. The result can be extended to the MIMO and multiple-hop cases. The proposed achievable schemes essentially combine the concept of retrospective interference alignment based on delayed CSIT and linear beamforming based on inaccurate instantaneous CSIT into an integrated form. Our results show that, in multi-hop MISO broadcast networks, delayed CSIT and inaccurate instantaneous CSIT can be exploited simultaneously to benefit network DOF.

  • 124307.
    Zhao, Wei
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Functional Materials, FNM. KTH Royal Institute of Technology.
    Evaluation of Zinc Oxide Nano-Microtetrapods for Biomolecule Sensing Applications2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Zinc oxide (ZnO) is a well-known II-VI semiconductor material that has gained renewed interest in the past decade due to the developments of growth technologies and the availability of high-quality ZnO bulk single crystals. Owing to a wide direct band gap (3.37 eV), large exciton binding energy (60 meV), and high electron mobility (440 cm2 V-1 s-1), ZnO has been used for applications including actuators, optoelectronics, and sensors. ZnO nanoparticles can be synthesized in a broad variety of morphologies, such as nanotetrapods, nanotubes, and nanowires. Among these nanostructures, the tetrapods have attracted significant attention due to their unique morphology consisting of four legs connected together in a tetrahedral symmetry. Recently, it has been reported that nano-microstructured ZnO tetrapods (ZnO-Ts) can be synthesized by flame transport synthesis (FTS) in a rapid and up-scalable approach. Compared to conventional ZnO nanoparticles, the nano-microstructured ZnO-Ts can reduce cellular uptake, while still exhibiting specific nanomaterial properties due to the nanoscale tips. Moreover, the anisotropic ZnO-Ts have the advantages of multiple electron transfer paths, chemical stability, and biocompatibility, which make the ZnO-Ts promising candidates for biomolecule sensing applications.

    This work herein reports a systematical study on the structural, optical and electrochemical properties of the ZnO-Ts, which were synthesized by FTS using precursor Zn microparticles. The morphology of the ZnO-Ts was confirmed by scanning electron microscopy (SEM) as joint structures of four single crystalline legs, of which the diameter of each leg is 0.7-2.2 μm in average from the tip to the stem. The ZnO-Ts were dispersed in glucose solutions to study the photoluminescence as well as photocatalytic activity in a mimicked biological environment. The photoluminescence (PL) intensity in the ultraviolet (UV) region decreased with linear dependence on the glucose concentration up to 4 mM. The ZnO-Ts were also attached with glucose oxidase (GOx) and over coated with Nafion® to form the active media for electrochemical glucose sensing. The active layers were confirmed by Fourier transform infrared spectroscopy (FT-IR). Furthermore, the current response of the active layers to glucose was studied by cyclic voltammetry (CV) in various glucose concentration conditions. Stable current response to glucose was detected with linear dependence on the glucose concentration up to 12 mM, which confirms the potential of ZnO-Ts for biomolecule sensing applications.

  • 124308.
    Zhao, Wei
    et al.
    Ericsson Research.
    Andersson, Loa
    Ericsson AB.
    Sköldström, Pontus
    Acreo AB.
    Prototyping MPLS-TP forwarding and OAM2009In: 5th International Conference on IP + Optical Network, 2009Conference paper (Refereed)
  • 124309.
    Zhao, Wei
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Acreo Swedish ICT AB, Sweden.
    Zhao, Yichen
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Karlsson, Mikael
    Wang, Qin
    Toprak, Muhammet S.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Evaluation of Zinc Oxide Nano-Microtetrapods for Biomolecule Sensing Applications2015In: MICRO+NANO MATERIALS, DEVICES, AND SYSTEMS, SPIE - International Society for Optical Engineering, 2015, article id UNSP 966833Conference paper (Refereed)
    Abstract [en]

    Zinc oxide tetrapods (ZnO-Ts) were synthesized by flame transport synthesis using Zn microparticles. This work herein reports a systematical study on the structural, optical and electrochemical properties of the ZnO-Ts. The morphology of the ZnO-Ts was confirmed by scanning electron microscopy (SEM) as joint structures of four nano-microstructured legs, of which the diameter of each leg is 0.7-2.2 mu m in average from the tip to the stem. The ZnO-Ts were dispersed in glucose solution to study the luminescence as well as photocatalytic activity in a mimicked biological environment. The photoluminescence (PL) intensity in the ultraviolet (UV) region decreased with linear dependence on the glucose concentration up to 4 mM. The ZnO-Ts were also attached with glucose oxidase (GOx) and over coated with a thin film of Nafion to form active layers on Si/SiO2/Au substrate for electrochemical glucose sensing. The attachment of GOx and the coating of Nafion onto ZnO-Ts were confirmed by Fourier transform infrared spectroscopy (FT-IR). Furthermore, the current response of the active layers based on ZnO-Ts was investigated by cyclic voltammetry (CV) in various glucose concentration conditions. Stable current response of glucose was detected with linear dependence on the glucose concentration up to 12 mM, which confirms the potential of ZnO-Ts for biomolecule sensing applications.

  • 124310.
    Zhao, Weifeng
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. Sichuan University.
    Chemical Pathways to Electrically Conductive Hemicellulose Hydrogels2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hydrogels have been extensively explored and are widely used in diverse biomedical applications, such as scaffolds for tissue engineering and vehicles for drug delivery. As one type of important natural polymer-based hydrogel, hemicellulose hydrogels have interesting attributes, including being renewable, non-toxic, biocompatible, biodegradable, and abundantly available. A prominent way to extend their potential is by combining them with desirable properties from other materials. The focus of this thesis is to develop a new family of electrically conductive hemicellulose-based hydrogels (ECHHs) using O-acetyl-galactoglucomannan (AcGGM) and aniline oligomers through different chemical pathways.

    A first approach to synthesize the ECHHs includes two steps: first, carboxylated AcGGM (C-AcGGM) is dissolved with glycidyl methacrylate, followed by polymerization initiated by ammonium persulfate; second, the resulting hydrogels are covalently coupled to varying amounts of aniline tetramer (AT), which is homogeneously distributed throughout the network. The swelling ratios of C-AcGGM hydrogels decrease as the degree of substitution of maleic anhydride increases. The swelling ratios and conductivities of ECHHs are tuned by the AT content.

    To develop a simpler and greener approach to synthesize ECHHs under ambient conditions, AcGGM is in-situ cross-linked in the presence of aniline pentamer (AP) in basic water. Hydrogel equilibrium swelling ratios (ESRs) vary from 12.7 to 10.4, regulated by cross-linker concentration. The ESRs are also tuned from 9.6 to 6.0 by changing the AP contents from 10 % (w/w) to 40 % (w/w) while simultaneously altering conductivities from 9.05×10-9 to 1.58×10-6 S/cm.

    ECHHs with controllable conductivity, tunable swelling behavior and acceptable mechanical properties extend the applications of hemicellulose to include e.g. biosensors and electronic devices.

  • 124311.
    Zhao, Weifeng
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. College of Polymer Science & Engineering, Sichuan University.
    Engineering and Functionalization of Hemicellulose Hydrogels2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Hemicellulose is the second most abundant component in wood and is an important renewable resource  that is used in films, paper composites and biofuels.  Hemicelluloses  have  several  advantages,  including  their abundance,  degradability  and  renewability.  O-acetyl-galactoglucomannan (AcGGM) is a type of hemicellulose that is predominantly found in softwood specimens. In the recent drive to engineer functional hydrogels with stimuli-responsive  properties,  functional  AcGGM-derived  hydrogels  are  highly interesting alternatives. In  the  first  part  of  this  thesis,  a  combination  of  the  electro-activity  of conducting oligomers and AcGGM was used to design a robust pathway to generate  electrically  conductive  hemicellulose  hydrogels  (ECHHs)  using AcGGM  and  a  conductive  aniline  tetramer.  Subsequently,  in  order  to fabricate  ECHHs  using  a  greener  and  more  facile  approach,  a  one-pot reaction  was  performed  in  which  AcGGM  was  cross-linked  with epichlorohydrin in the presence of a conductive aniline pentamer in water at ambient  temperature.  To  impart  other  functionalities  to  the  hemicellulose hydrogels,  magnetic  field-responsive  hemicellulose  hydrogels  (MFRHHs) were  fabricated  by  simultaneous  in  situ  formation  of  magnetic  Fe 3 O 4   and cross-linking of AcGGM. These MFRHHs exhibited  a controlled release of the  protein  bovine  serum  albumin.  Finally,  a  facile,  fast  and  functional chemical  methodology  to  prepare  stimuli-responsive  hemicellulose  micro-gels was developed that offers the potential for fabricating hydrogels using a green  processing  technique.  The  micro-gels  were  shown  to  have  a  rapid response to electrochemical stimuli, pH alterations and a magnetic field, as well  as  good  blood  compatibility,  which  is  required  for  biomedical applications.  All  these  stimuli-responsive  hemicellulose  hydrogels  demonstrated controllable  aqueous  swelling  behavior  and  combine  the  renewability  of hemicellulose  and  stimuli-responsiveness  of  functional  molecules,  thereby opening new potential routes to fabricate biomaterials with a wide range of applications  (e.g.,  biosensors,  nerve  system  repair,  and  controlled  drug release).

  • 124312.
    Zhao, Weifeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Glavas, Lidija
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    A robust pathway to electrically conductive hemicellulose hydrogels with high and controllable swelling behavior2014In: Polymer, ISSN 0032-3861, E-ISSN 1873-2291, Vol. 55, no 13, p. 2967-2976Article in journal (Refereed)
    Abstract [en]

    A robust pathway to synthesize electrically conductive hemicellulose hydrogels (ECHHs) based on O-acetylgalactoglucomannan (AcGGM) and conductive aniline tetramer (AT) is presented. These ECHHs were obtained by functionalizing carboxylated AcGGM with glycidyl methacrylate (GMA) and subsequently covalently immobilizing AT onto GMA. Hydrogel swelling ratios (SRs) were regulated by the degree of substitution (DS) of the carboxylated AcGGM, the maximum varied as follows: SRDS=1.14 < SRDS=0.60 < SRDS=0.24. The SR can also be tuned from 548% to 228% by changing the AT contents from 10% (w/w) to 40% (w/w) while simultaneously altering conductivities from 2.93 x 10(-8) to 1.12 x 10(-6) S/cm. Free-standing ECHHs with tunable conductivity and degree of swelling, as presented herein, have a broad potential for biomedical applications.

  • 124313.
    Zhao, Weifeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. Sichuan University, China .
    Glavas, Lidija
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Albertsson, Ann Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Facile and Green Approach towards Electrically Conductive Hemicellulose Hydrogels with Tunable Conductivity and Swelling Behavior2014In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, no 14, p. 4265-4273Article in journal (Refereed)
    Abstract [en]

    A one-pot reaction to synthesize electrically conductive hemicellulose hydrogels (ECHHs) is developed via a facile and green approach in water and at ambient temperature. ECHHs were achieved by cross-linking O-acetyl-galactoglucomannan (AcGGM) with epichlorohydrin in the presence of conductive aniline pentamer (AP) and were confirmed by infrared spectroscopy (IR) and elemental analysis. All hydrogels had macro-porous structures, and the thermal stability of ECHHs was improved by the addition of AP. Hydrogel equilibrium swelling ratios (ESRs) varied from 13.7 to 11.4 and were regulated by cross-linker concentration. The ESRs can also be tuned from 9.6 to 6.0 by changing the AP content level from 10 to 40% (w/w) while simultaneously altering conductivity from 9.05 x 10(-9) to 1.58 X 10(-6) S/cm. ECHHs with controllable conductivity, tunable swelling behavior, and acceptable mechanical properties have great potential for biomedical applications, such as biosensors, electronic devices, and tissue engineering.

  • 124314.
    Zhao, Weifeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Han, Zhiyuan
    Zhao, Changsheng
    Super anti-coagulant dual-network hydrogels with controllable conductivity, tunable swelling and mechanically strong properties2017In: Journal of Controlled Release, ISSN 0168-3659, E-ISSN 1873-4995, Vol. 259, p. E137-E137Article in journal (Refereed)
  • 124315.
    Zhao, Weifeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. Sichuan University, China.
    He, Chao
    Nie, Chuanxiong
    Sun, Shudong
    Zhao, Changsheng
    Synthesis and Characterization of Ultrahigh Ion-Exchange Capacity Polymeric Membranes2016In: Industrial & Engineering Chemistry Research, ISSN 0888-5885, E-ISSN 1520-5045, Vol. 55, no 36, p. 9667-9675Article in journal (Refereed)
    Abstract [en]

    A universal mold casting approach for the preparation of cation-exchange membranes (CEMs) and anion-exchange membranes (AEMs) with ultrahigh ion-exchange capacities (IECs) is developed based on in situ cross-linking polymerization of acrylic acid (AA) and 2-vinylpyridine (2VP), respectively. This new method produced ultrahigh IECs of 7.88 mequiv g(-1) for CEM and 6.27 mequiv g(-1) for AEM, which are 8.8 and 7.0 times that (0.89 mequiv g(-1)) of Nafion 117, respectively. Also, the prepared membranes demonstrate excellent thermal and chemical stability and acceptable conductivity. As a consequence, the membranes show relatively high performance for ion-exchange application and methanol barrier, exhibiting ion permeabilities of 2.06 x 10(-7) cm(2) s(-1) for Na+, 2.57 x 10(-7) cm(2) s(-1) for Ca2+, 1.45 x 10(-7) cm(2) s(-1) for Cu2+ regarding CEMs, and 7.72 x 10(-7) cm(2) s(-1) for methanol regarding AEMs. These results indicate that the CEMs and AEMs fabricated from the universal mold casting approach are promising candidates for targeting ultrahigh ion-exchange capacity membranes.

  • 124316.
    Zhao, Weifeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. Sichuan Univ, Peoples R China.
    Huang, Xuelian
    Wang, Yilin
    Sun, Shudong
    Zhao, Changsheng
    A recyclable and regenerable magnetic chitosan absorbent for dye uptake2016In: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 150, p. 201-208Article in journal (Refereed)
    Abstract [en]

    A recyclable and regenerable magnetic polysaccharide absorbent for methylene blue (MB) removal was prepared by coating magnetic polyethyleneimine nanoparticles (PEI@MNPs) with sulfonated chitosan (SCS) and further cross -linked with glutaraldehyde. The driving force for coating is the electrostactic interaction between positively charged PEI and negatively charged SCS. Infrared spectra, zeta potential, thermal gravimetric analysis and X-ray diffraction demonstrated the successful synthesis of magnetic polysaccharide absorbent. The self-assembly of polysaccharide with magnetic nanopartices did not alter the saturation magnetization value of the absorbent confirmed by vibrating sample magnetometer. The nanoparticles showed fast removal (about 30 min reached equilibrium) of MB. In particular, the removal ability of MB after desorption did not reduce, demonstrating an excellent regeneration ability. Our study provides new insights into utilizing polysaccharides for environmental remediation and creating advanced magnetic materials for various promising applications.

  • 124317.
    Zhao, Weifeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology. Sichuan University, China.
    Nugroho, Robertus Wahyu. N.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    Zhao, Changsheng
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Polymer Technology.
    In Situ Cross-Linking of Stimuli-Responsive Hemicellulose Microgels during Spray Drying2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 7, p. 4202-4215Article in journal (Refereed)
    Abstract [en]

    Chemical cross-linking during spray drying offers the potential for green fabrication of microgels with a rapid stimuli response and good blood compatibility and provides a platform for stimuli-responsive hemicellulose microgels (SRHMGs). The cross-linking reaction occurs rapidly in situ at elevated temperature during spray drying, enabling the production of microgels in a large scale within a few minutes. The SRHMGs with an average size range of similar to 1-4 mu m contain O-acetyl-galactoglucomannan as a matrix and poly(acrylic acid), aniline pentamer (AP), and iron as functional additives, which are responsive to external changes in pH, electrochemical stimuli, magnetic field, or dual-stimuli. The surface morphologies, chemical compositions, charge, pH, and mechanical properties of these smart microgels were evaluated using scanning electron microscopy, IR, zeta potential measurements, pH evaluation, and quantitative nanomechanical mapping, respectively. Different oxidation states were observed when AP was introduced, as confirmed by UV spectroscopy and cyclic voltammetry. Systematic blood compatibility evaluations revealed that the SRHMGs have good blood compatibility. This bottom-up strategy to synthesize SRHMGs enables a new route to the production of smart microgels for biomedical applications.

  • 124318.
    Zhao, Weifeng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology. Sichuan University, China.
    Odelius, Karin
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Edlund, Ulrica
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Zhao, Changsheng
    Albertsson, Ann-Christine
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    In Situ Synthesis of Magnetic Field-Responsive Hemicellulose Hydrogels for Drug Delivery2015In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, no 8, p. 2522-2528Article in journal (Refereed)
    Abstract [en]

    A one-pot synthetic methodology for fabricating stimuli-responsive hemicellulose-based hydrogels was developed that consists of the in situ formation of magnetic iron oxide (Fe3O4) nanoparticles during the covalent cross-linking of O-acetyl-galactoglucomannan (AcGGM). The Fe3O4 nanoparticle content controlled the thermal stability, macrostructure, swelling behavior, and magnetization of the hybrid hydrogels. In addition, the magnetic field-responsive hemicellulose hydrogels (MERHHs) exhibited excellent adsorption and controlled release profiles with bovine serum albumin (BSA) as the model drug. Therefore, the MFRHHs have great potential to be utilized in the biomedical field for tissue engineering applications, controlled drug delivery, and magnetically assisted bioseparation. Magnetic field-responsive hemicellulose hydrogels, prepared using a straightforward one-step process, expand the applications of biomass-derived polysaccharides by combining the renewability of hemicellulose and the magnetism of Fe3O4 nanoparticles.

  • 124319.
    Zhao, Weijie
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Corrosion initiation induced by sodium sulfate and sodium chloride particles on Cu and the golden alloy Cu5Al5Zn at simulated atmospheric conditions2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Effects of sodium sulfate (Na2SO4) particle deposition on the atmospheric corrosion of copper (Cu) metal and a Cu-based alloy (Cu5Al5Zn) used in architectural applications were investigated at laboratory conditions compared with effects induced by sodium chloride (NaCl) and to some extent ammonium sulfate (NH4)2SO4 induced corrosion. Pre-deposited surfaces were exposed to repeated wet/dry conditions in a climatic chamber and the formation of corrosion products were assessed using light optical microscopy (LOM), scanning electron microscopy with elemental analysis (SEM/EDS), Fourier transform infrared techniques (FTIR microscopy) and cathodic reduction (CR). Na2SO4 induced corrosion resulted in corrosion cells locally over the surface on both Cu and Cu5Al5Zn, of increased oxygen content in the anodic area of the cells (center of pre-deposited area). The main corrosion products formed on Cu metal are basic copper sulfates and cuprite (Cu2O), while basic sulfates (copper and/or zinc) and Cu2O were the main corrosion products formed on Cu5Al5Zn. A combined deposition of Na2SO4 + NaCl was carried out on the Cu5Al5Zn alloy using two different deposition methods to investigate the possible interplay from a corrosion initiation perspective between the two salt particles. For short time exposed Cu5Al5Zn (1 cycle), two different corrosion cells formed, mainly induced by Na2SO4 and NaCl. Corrosion products formed in anodic areas of a Na2SO4 induced corrosion cell were similar to findings observed for Cu5Al5Zn pre-deposited with Na2SO4 only, whereas peripheral cathodic areas primarily were affected by NaCl dissolution and predominantly composed of Cu2O that was the main corrosion product with small amount of hydroxides and carbonates of the NaCl induced corrosion cells. After relatively longer exposure periods (2 and 6 wet/dry cycles), NaCl dominated the corrosion of the entire surface with the formation of more Cu2O, hydroxides and carbonates. Cathodic reduction findings revealed a negative interplay on corrosion for the mixed salt after short time exposures (1 and 2 cycles), whereas a slight synergistic effect was evident after a longer exposure period (6 cycles), compared with corrosion induced by single salts.

  • 124320.
    Zhao, Weijie
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Johnson, C. Magnus
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science.
    Nano Infrared Microscopy: Obtaining Chemical Information on the Nanoscale in Corrosion Studies2019In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 166, no 11, p. C3456-C3460Article in journal (Refereed)
    Abstract [en]

    In this perspective article, the novel technique "nano infrared microscopy" is introduced as a valuable tool in the field of corrosion science to obtain chemical information with a spatial resolution of around 10 nm. Accordingly, the resolution is well below the diffraction limit, in contrast to conventional vibrational microscopy techniques. Thus, studies of corrosion initiation, localized corrosion, and thin protective films can be performed in greater detail than before. There are a few different types of nano infrared microscopes, but they all have in common that they are based on a combination of infrared (IR) spectroscopy and atomic force microscopy (AFM). In this article the theory of the different techniques is discussed, and some results are highlighted to show the ability of the technique in the field of corrosion science. Future possibilities of the technique in studies of corrosion and degradation of materials are also discussed. 

  • 124321.
    Zhao, Weiwei
    KTH, School of Computer Science and Communication (CSC).
    Flowers for a Witness – E-Commerce Case Study following the Pirate Bay Trial February 2009.2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The aim of this master thesis is to analyze how the Pirate Bay Trial could result in a boom for the online flower e-commerce business in Stockholm and the underlying factors explaining how a non-profit e-commerceClike website could be created and run successfully and effectively in a very short time. The prerequisite of the snowball effect in terms of common interests is discussed to deduce relevant implications regarding the e-commerce business. A SWOT analysis focusing on social media and traditional media facilitates the understanding of the role of social media in the case and how it can be applied in e business. The relationship between the online community and social media technology is analyzed, resulting in the conclusion that social media is the catalyst for the snowball effect and the online community is the roll booster.

    The Peer Production phenomenon and Open source concept in the networked information economy are used to study information products and information production. Long tail theory can be applied into e business to increase revenue. E-business transaction models and logistics integration are analyzed to make predictions regarding an ideal combination mode for the e-commerce business. A comparative study of the current commercial e-commerce website Amazon and some other internet phenomena are also used to analyze the Pirate Bay Flower for Wallis case study.

    Implementation of the information product industry is used to illustrate the necessity to change business model to create a new market space. At the end of the thesis, a concrete proposal is presented to exemplify innovation in terms of designing a new websites structure to achieve effective advertisements arrangements, with the aim of generating the snowball effect, illustrated in the Wallis Flower case, in networked e-commerce.

    Key words: pirate bay trial, flower, snowball effect, common interest, social media, information product, peer production, e-commerce, open source, online community, advertisement

  • 124322.
    Zhao, Wenquan
    KTH, School of Computer Science and Communication (CSC).
    Deep Active Learning for Short-Text Classification2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this paper, we propose a novel active learning algorithm for short-text (Chinese) classification applied to a deep learning architecture. This topic thus belongs to a cross research area between active learning and deep learning. One of the bottlenecks of deeplearning for classification is that it relies on large number of labeled samples, which is expensive and time consuming to obtain. Active learning aims to overcome this disadvantage through asking the most useful queries in the form of unlabeled samples to belabeled. In other words, active learning intends to achieve precise classification accuracy using as few labeled samples as possible. Such ideas have been investigated in conventional machine learning algorithms, such as support vector machine (SVM) for imageclassification, and in deep neural networks, including convolutional neural networks (CNN) and deep belief networks (DBN) for image classification. Yet the research on combining active learning with recurrent neural networks (RNNs) for short-text classificationis rare. We demonstrate results for short-text classification on datasets from Zhuiyi Inc. Importantly, to achieve better classification accuracy with less computational overhead,the proposed algorithm shows large reductions in the number of labeled training samples compared to random sampling. Moreover, the proposed algorithm is a little bit better than the conventional sampling method, uncertainty sampling. The proposed activelearning algorithm dramatically decreases the amount of labeled samples without significantly influencing the test classification accuracy of the original RNNs classifier, trainedon the whole data set. In some cases, the proposed algorithm even achieves better classification accuracy than the original RNNs classifier.

  • 124323. Zhao, Wenyan
    et al.
    Wang, Xi Vincent
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Yang, Jianxin
    Li, Bo
    Wang, Lihui
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    A CLOUD-BASED APPROACH TO SUPPORT THE MOBILE PHONE RECYCLING INDUSTRY IN CHINA2016In: ASME 2016 11th International Manufacturing Science and Engineering Conference, MSEC 2016, American Society of Mechanical Engineers , 2016Conference paper (Refereed)
    Abstract [en]

    In recent years, the waste mobile phones are generated in large quantity in China. Those e-wastes gain more and more attention because of both the sharp increase in quantity and the recyclable resources they contain. Furthermore, the mobile phone recycling industry has experienced a trend of rapid growth as well. However, due to the lack of national policies and legislations, the recycling industry is now facing problems in recycling processes. Thus in this paper, mobile phone recycling industry in China is systematically analyzed and a Cloud-based approach is developed which integrates tracking, interaction and coordinator mechanism through the recycling processes. With the integration of various stakeholders, the system can provide integrated data system throughout the whole life cycle of the mobile phones for the policy maker, and provide guidance for the operations during recycling service for the recycling stakeholders.

  • 124324.
    Zhao, Wenyue
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Li, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Sun, Z.
    Gong, S.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Tuning the plasticity of Ni-Mo solid solution in Ni-based superalloys by ab initio calculations2017In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 124, p. 100-107Article in journal (Refereed)
    Abstract [en]

    The generalized stacking fault energies of face centered cubic Ni-Mo solid solutions are calculated using the exact muffin-tin orbital method in combination with coherent potential approximation. The alloying of Mo in Ni is found to decrease the intrinsic stacking fault energy of the solid solution from 150 mJ/m2 (pure Ni) to 50 mJ/m2 (17.5 at.% Mo) almost linearly. At the same time, the unstable stacking fault energy (the unstable twin fault energy) of the Ni-based solid solution increases (decreases) in a small extent with increasing Mo concentration. Three different twinnability measures are adopted and all indicate a substantially enhanced twinning mechanism in Ni-Mo solid solutions with increasing concentration of Mo. The weaker Ni-Ni bonding at high Mo concentrations is considered to be the main mechanism behind the disclosed phenomena. Segregation of Mo to the fault plane is proved to have strong effect on the generalized stacking fault energy of Ni-based solid solution.

  • 124325. Zhao, W.L.
    et al.
    Yang, S.Y.
    Wang, J.
    Xiao, J.M.
    Lu, X.X.
    KTH, School of Industrial Engineering and Management (ITM). College of Oceanography and Earth Science, Xiamen University, Xiamen, China.
    Lin, J.
    Huang, P.
    Cai, M.G.
    Load estimation and assessment of land-based pollution for Quanzhou Bay and their relevance to the Total Quantity Control of Pollutants Discharged into the Sea (TQCPS) Program in China2015In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 166, no Part B, p. 230-239Article in journal (Refereed)
    Abstract [en]

    The Total Quantity Control of Pollutants Discharged into the Sea (TQCPS) Program belonged to the Public Science and Technology Research Funds Projects of Ocean in China, launched in 2008. As one of the most important and typical demonstration cases of the TQCPS Program, a full investigation of the land-based pollutions discharges around Quanzhou Bay, China developed the total input for three main environmental factors (NH<inf>3</inf>-N, TP, COD) which were estimated and quantified in 2008 and 2012, respectively. Combined with the trend of seawater quality changes in Quanzhou Bay in the same periods, the effects of the program’s implementation were then evaluated. On the whole, by using the basic survey data and export coefficient method, the total amounts of NH<inf>3</inf>-N, TP and COD discharged into the bay were estimated to be approximately 888.3, 130.6 and 14527.4t/a in 2008, and 1518.6, 558.8 and 19986.7t/a in 2012, respectively, where the percentage of the discharge from domestic sources (46.5% in 2008 and 45.2% in 2012) was generally higher than that from the other sources. Based on the characteristic of geography and administrative division, the land areas around the bay were divided into three parts: the south coast region (SCR), the west coast region (WCR), and the north coast region (NCR). The SCR and WCR accounted for 59.2 and 35.4% of the COD loads, and 49.2 and 48.0% of NH<inf>3</inf>-N loads in 2008. The NCR contributed less of the industrial pollution, but most to domestic pollution (54.1%), followed by 26.2% in the SCR in 2012. The contributions of the discharge from different land areas to the pollution of Quanzhou Bay were found to be differed in 2008 and 2012. Due to the difference in the levels of the economic development among these three areas, the discharge of pollutants from the north coast was much lower than that from the other two parts in 2008; however, following our suggestion of the moderation and optimization of the industrial distribution and the sewage discharge around Quanzhou Bay, the contribution of the west coast decreased while that of the north coast increased significantly in 2012. Furthermore, to a great extent, because of some marine ecological rehabilitation projects, which were also suggested by our TQCPS Program and finally adopted by local government and then developed recently in Quanzhou Bay, the seawater qualities there were improved by in 2012. A longer time and greater efforts are needed to reduce the discharge of land-based pollutants and to improve the marine ecological health and sustainability further. Based on the demonstration results of the research and practice of the TQCPS Program in Quanzhou Bay, some recommendations were suggested. These require further implementation and management and can be transferred to similar estuaries and bays in southeastern coastal areas of China.

  • 124326. Zhao, X. Y.
    et al.
    Gharizadeh, B.
    Hjelmstrom, P.
    Pirskanen, R.
    Nyrén, Pål
    KTH, Superseded Departments, Biochemistry and Biotechnology.
    Lefvert, A. K.
    Ghaderi, M.
    Genotypes of CCR2 and CCR5 chemokine receptors in human myasthenia gravis2003In: International Journal of Molecular Medicine, ISSN 1107-3756, E-ISSN 1791-244X, Vol. 12, no 5, p. 749-753Article in journal (Refereed)
    Abstract [en]

    The aim of this study was to examine the association of human autoimmune myasthenia gravis (MG) with two DNA polymorphisms of the chemokine receptors CCR5-Delta32 and CCR2-64I. CCR2 and CCR5 interact primarily with the human CC family ligands CCL2 (formerly called monocyte chemoattractant protein; MCP-1), CCL3 and CCL4 (macrophage inflammatory protein-1alpha and -1beta; MIP-1alpha/beta), and their main function is to recruit leukocytes from circulation into the tissues, thus playing an important role in human inflammatory disorders. A PCR-based genotyping method was used to determine the genetic variation at the CCR5 gene and an automated real-time Pyrosequencing technology was employed for the analysis of G-->A point mutation at the CCR2 gene. Results obtained from 158 patients and 272 healthy controls demonstrate no evidence of association between genetic variants of CCR2 and CCR5 with MG and its clinical manifestations. CCR2-64I and CCR5-Delta32 genotypes are thus unlikely to be involved in protection or predisposition to MG.

  • 124327. Zhao, Xiaogang
    et al.
    Zhou, Yi
    Zhao, Jianyu
    KTH, School of Architecture and the Built Environment (ABE).
    Zhan, Guo
    Yang, Peng
    Safety Prediction of Soleplate Corrosion State in Petroleum Storage Tank Based on Grey Theory Model2016In: 3rd International Conference on Applied Engineering, AIDIC - associazione italiana di ingegneria chimica, 2016, p. 271-276Conference paper (Refereed)
    Abstract [en]

    The corrosion protection of petroleum storage tank is important for safety work in petroleum depot. Precise prediction of soleplate corrosion may reflect the security state of a storage tank, and it can provide scientific references to the anti-corrosion and maintenance in safety management. Grey Model GM (1,1) in the Grey Theory is a good prediction method based on small volume of original data, and it is introduced and applied to predict the soleplate corrosion of No. G-2 petroleum storage tank in Luquan oil depot. In order to improving the calculation speed, the GM (1,1) model is programmed by MATLAB and is further utilized in data processing. Compared with the measurements, the prediction results meet them very well, which shows that this model is practical. Meanwhile, the prediction results also reflect the status and the corrosion rate of a petroleum tank which is of great importance for the future safety management and maintenance works. Meanwhile, the GM (1,1) is suitable for wide applications in other relative fields in oil depots.

  • 124328.
    Zhao, Xiaoyu
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.).
    Condition Monitoring of Hydraulic Systems2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The purpose of this project is to investigate and propose a system for condition monitoring and analysis of the hydraulic system of a forestry machine based on available on-board oil quality sensor data. The sample machine used was Scorpion King from Ponsse. This machine is equipped with an Icount PDR particle sensor from Parker. A two weeks long field test was conducted by Skogforsk. The data measured by the particle counter was collected, and breaks longer than five minutes were recorded as well as the reason for each break. The main results from the thesis are the relations between three factors: number of particles in the oil, machine operations, and machine breaks. The thesis also aims at proposing how the operator could use the Icount PDR data to manage the maintenance of the machine.

  • 124329.
    Zhao, Xin
    et al.
    KTH.
    Haller, Philipp
    KTH.
    Observable atomic consistency for CVRDTs2018In: AGERE 2018 - Proceedings of the 8th ACM SIGPLAN International Workshop on Programming Based on Actors, Agents, and Decentralized Control, co-located with SPLASH 2018, Association for Computing Machinery (ACM), 2018, p. 23-32Conference paper (Refereed)
    Abstract [en]

    The development of distributed systems requires developers to balance the need for consistency, availability, and partition tolerance. Conflict-free replicated data types (CRDTs) are widely used in eventually consistent systems to reduce concurrency control. However, CRDTs lack consistent totally-ordered operations which can make them difficult to use. In this paper, we propose a new consistency protocol, the observable atomic consistency protocol (OACP). OACP enables a principled relaxation of strong consistency to improve performance in specific scenarios. OACP combines the advantages of mergeable data types, specifically, convergent replicated data types, and reliable total order broadcast to provide on-demand strong consistency. By providing observable atomic consistency, OACP avoids the anomalies of related protocols. We provide a distributed implementation of OACP based on Akka, a widely-used actor-based middleware. Our experimental evaluation shows that OACP can reduce coordination overhead compared to other protocols providing atomic consistency. Our results also suggest that OACP increases availability through mergeable data types and provides acceptable latency for achieving strong consistency.

  • 124330.
    Zhao, Xin
    et al.
    Nanyang Technol Univ, Sch Mat Sci & Engn, 50 Nanyang Ave, Singapore 639798, Singapore..
    Hu, Jun
    Nanyang Technol Univ, Sch Mat Sci & Engn, 50 Nanyang Ave, Singapore 639798, Singapore.;Northwest Univ, Sch Chem Engn, Xian 710069, Shaanxi, Peoples R China..
    Wu, Bo
    Nanyang Technol Univ, Sch Phys & Math Sci, Singapore 637371, Singapore..
    Banerjee, Amitava
    Uppsala Univ, Mat Theory Div, Dept Phys & Astron, S-75120 Uppsala, Sweden..
    Chakraborty, Sudip
    Uppsala Univ, Mat Theory Div, Dept Phys & Astron, S-75120 Uppsala, Sweden..
    Feng, Jianyong
    Nanyang Technol Univ, Sch Mat Sci & Engn, 50 Nanyang Ave, Singapore 639798, Singapore..
    Zhao, Zongyan
    Kunming Univ Sci & Technol, Fac Mat Sci & Engn, Kunming 650093, Yunnan, Peoples R China..
    Chen, Shi
    Nanyang Technol Univ, Sch Phys & Math Sci, Singapore 637371, Singapore..
    Ahuja, Rajeev
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. Uppsala Univ, Mat Theory Div, Dept Phys & Astron, S-75120 Uppsala, Sweden.
    Sum, Tze Chien
    Nanyang Technol Univ, Sch Phys & Math Sci, Singapore 637371, Singapore..
    Chen, Zhong
    Nanyang Technol Univ, Sch Mat Sci & Engn, 50 Nanyang Ave, Singapore 639798, Singapore..
    Simultaneous enhancement in charge separation and onset potential for water oxidation in a BiVO4 photoanode by W-Ti codoping2018In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 6, no 35, p. 16965-16974Article in journal (Refereed)
    Abstract [en]

    Efficient charge separation of photo-generated electrons and holes is critical to achieve high solar to hydrogen conversion efficiency in photoelectrochemical (PEC) water splitting. N-type doping is generally used to improve the conductivity by increasing the majority carrier density and enhance the charge separation in the photoanode. However, minority carrier transport is also very important in the process of charge separation, especially in materials that possess inadequate minority carrier mobility. Herein, we take a BiVO4 PEC water splitting cell as an example to demonstrate how to analyze the limiting factor and to formulate the corresponding solutions to improve the hole mobility. The benefits and problems caused by n-type doping (W-doping here) of BiVO4 are analyzed. Codoping with Ti further enhances the charge separation by improving the hole transport and leads to a cathodic shift of the photocurrent onset potential. A high charge separation efficiency (79% at 1.23 V-RHE) in a compact BiVO4 photoanode has been achieved without any nanostructure formation. Theoretical results show that W-Ti codoping has decreased the hole polaron hopping activation energy by 11.5% compared with mono-W doping, and this has resulted in a hole mobility increase by 29%. The calculated adsorption energy and reaction Gibbs free energies indicate that the Ti site is energetically more favorable for water splitting. Moreover, the Ti site possesses a lower overpotential in the W-Ti codoped sample compared with the mono-W doped sample. The current study indicates that in order to improve the solar energy conversion efficiency, there should be a balanced charge transport of both majority and minority charge carriers. This can be achieved by simply choosing appropriate codoping elements.

  • 124331.
    Zhao, Xin
    et al.
    Guangzhou Med Univ, Sch Pharmaceut Sci, Key Lab Mol Target & Clin Pharmacol, State Key Lab Resp Dis, Guangzhou 511436, Guangdong, Peoples R China.;Guangzhou Med Univ, Affiliated Hosp 5, Guangzhou 511436, Guangdong, Peoples R China.;Chinese Acad Sci, Guangzhou Inst Biomed & Hlth, Guangzhou 510530, Guangdong, Peoples R China.;Univ Arizona, Coll Pharm, Dept Pharmacol & Toxicol, Tucson, AZ 85721 USA..
    Li, Runfeng
    Guangzhou Med Univ, Guangzhou Inst Resp Hlth, Affiliated Hosp 1, Natl Clin Res Ctr Resp Dis,State Key Lab Resp Dis, Guangzhou 510120, Guangdong, Peoples R China..
    Zhou, Yang
    AlbaNova Univ Ctr, Royal Inst Technol KTH, Sch Biotechnol, Div Theoret Chem & Biol, SE-10044 Stockholm, Sweden..
    Xiao, Mengjie
    Guangzhou Med Univ, Sch Pharmaceut Sci, Key Lab Mol Target & Clin Pharmacol, State Key Lab Resp Dis, Guangzhou 511436, Guangdong, Peoples R China.;Guangzhou Med Univ, Affiliated Hosp 5, Guangzhou 511436, Guangdong, Peoples R China.;Chinese Acad Sci, Guangzhou Inst Biomed & Hlth, Guangzhou 510530, Guangdong, Peoples R China..
    Ma, Chunlong
    Univ Arizona, Coll Pharm, Dept Pharmacol & Toxicol, Tucson, AZ 85721 USA.;Univ Arizona, BIO5 Inst, Tucson, AZ 85721 USA..
    Yang, Zhongjin
    Guangzhou Med Univ, Sch Pharmaceut Sci, Key Lab Mol Target & Clin Pharmacol, State Key Lab Resp Dis, Guangzhou 511436, Guangdong, Peoples R China.;Guangzhou Med Univ, Affiliated Hosp 5, Guangzhou 511436, Guangdong, Peoples R China..
    Zeng, Shaogao
    Chinese Acad Sci, Guangzhou Inst Biomed & Hlth, Guangzhou 510530, Guangdong, Peoples R China..
    Du, Qiuling
    Guangzhou Med Univ, Guangzhou Inst Resp Hlth, Affiliated Hosp 1, Natl Clin Res Ctr Resp Dis,State Key Lab Resp Dis, Guangzhou 510120, Guangdong, Peoples R China..
    Yang, Chunguang
    Guangzhou Med Univ, Guangzhou Inst Resp Hlth, Affiliated Hosp 1, Natl Clin Res Ctr Resp Dis,State Key Lab Resp Dis, Guangzhou 510120, Guangdong, Peoples R China..
    Jiang, Haiming
    Guangzhou Med Univ, Guangzhou Inst Resp Hlth, Affiliated Hosp 1, Natl Clin Res Ctr Resp Dis,State Key Lab Resp Dis, Guangzhou 510120, Guangdong, Peoples R China..
    Hu, Yanmei
    Univ Arizona, Coll Pharm, Dept Pharmacol & Toxicol, Tucson, AZ 85721 USA.;Univ Arizona, BIO5 Inst, Tucson, AZ 85721 USA..
    Wang, Kefeng
    Guangzhou Med Univ, Sch Pharmaceut Sci, Key Lab Mol Target & Clin Pharmacol, State Key Lab Resp Dis, Guangzhou 511436, Guangdong, Peoples R China.;Guangzhou Med Univ, Affiliated Hosp 5, Guangzhou 511436, Guangdong, Peoples R China..
    Mok, Chris Ka Pun
    Guangzhou Med Univ, Guangzhou Inst Resp Hlth, Affiliated Hosp 1, Natl Clin Res Ctr Resp Dis,State Key Lab Resp Dis, Guangzhou 510120, Guangdong, Peoples R China.;Univ Hong Kong, HKU Li Ka Shing Fac Med, Sch Publ Hlth, HKU Pasteur Res Pole, 5 Sassoon Rd, Hong Kong, Peoples R China..
    Sun, Ping
    Guangzhou Med Univ, Sch Pharmaceut Sci, Key Lab Mol Target & Clin Pharmacol, State Key Lab Resp Dis, Guangzhou 511436, Guangdong, Peoples R China.;Guangzhou Med Univ, Affiliated Hosp 5, Guangzhou 511436, Guangdong, Peoples R China..
    Dong, Jianghong
    Chinese Acad Sci, Guangzhou Inst Biomed & Hlth, Guangzhou 510530, Guangdong, Peoples R China..
    Cui, Wei
    Wang, Jun
    Univ Arizona, Coll Pharm, Dept Pharmacol & Toxicol, Tucson, AZ 85721 USA.;Univ Arizona, BIO5 Inst, Tucson, AZ 85721 USA..
    Tu, Yaoquan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Yang, Zifeng
    Guangzhou Med Univ, Guangzhou Inst Resp Hlth, Affiliated Hosp 1, Natl Clin Res Ctr Resp Dis,State Key Lab Resp Dis, Guangzhou 510120, Guangdong, Peoples R China..
    Hu, Wenhui
    Guangzhou Med Univ, Sch Pharmaceut Sci, Key Lab Mol Target & Clin Pharmacol, State Key Lab Resp Dis, Guangzhou 511436, Guangdong, Peoples R China.;Guangzhou Med Univ, Affiliated Hosp 5, Guangzhou 511436, Guangdong, Peoples R China.;Chinese Acad Sci, Guangzhou Inst Biomed & Hlth, Guangzhou 510530, Guangdong, Peoples R China..
    Discovery of Highly Potent Pinanamine-Based Inhibitors against Amantadine- and Oseltamivir-Resistant Influenza A Viruses2018In: Journal of Medicinal Chemistry, ISSN 0022-2623, E-ISSN 1520-4804, Vol. 61, no 12, p. 5187-5198Article in journal (Refereed)
    Abstract [en]

    Influenza pandemic is a constant major threat to public health caused by influenza A viruses (IAVs). IAVs are subcategorized by the surface proteins hemagglutinin (HA) and neuraminidase (NA), in which they are both essential targets for drug discovery. While it is of great concern that NA inhibitor oseltamivir resistant strains are frequently identified from human or avian influenza virus, structural and functional characterization of influenza HA has raised hopes for new antiviral therapies. In this study, we explored a structure-activity relationship (SAR) of pinanamine-based antivirals and discovered a potent inhibitor M090 against amantadine-resistant viruses, including the 2009 H1N1 pandemic strains, and oseltamivir-resistant viruses. Mechanism of action studies, particularly hemolysis inhibition, indicated that M090 targets influenza HA and it occupied a highly conserved pocket of the HA(2) domain and inhibited virus-mediated membrane fusion by "locking" the bending state of HA(2) during the conformational rearrangement process. This work provides new binding sites within the HA protein and indicates that this pocket may be a promising target for broad-spectrum anti-influenza A drug design and development.

  • 124332.
    Zhao, Xingwang
    et al.
    Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, Tianjin 300072, Peoples R China..
    Liu, Wei
    Zhejiang Univ, ZJU UIUC Inst, Sch Civil Engn, Haining 314400, Peoples R China..
    Lai, Dayi
    Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, Tianjin 300072, Peoples R China..
    Chen, Qingyan
    Tianjin Univ, Sch Environm Sci & Engn, Tianjin Key Lab Indoor Air Environm Qual Control, Tianjin 300072, Peoples R China.;Purdue Univ, Sch Mech Engn, W Lafayette, IN 47907 USA..
    Optimal design of an indoor environment by the CFD-based adjoint method with area-constrained topology and cluster analysis2018In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 138, p. 171-180Article in journal (Refereed)
    Abstract [en]

    An indoor environment should be designed to provide occupants with a desirable level of thermal comfort and air quality. The optimal design of an indoor environment can be achieved by using the computational fluid dynamics (CFD)-based adjoint method to determine the size, locations, and shape of air supply inlets, and the air supply parameters (i.e., velocity, temperature, and angle). However, the optimal design may involve a large number of air supply inlets, which would be impractical to implement. This investigation developed an area-constrained topology and cluster analysis to consolidate multiple air supply inlets into a limited number and to determine their size and locations. The desired indoor environment can be maintained by further optimizing the air supply inlet shape and parameters. This investigation demonstrated the method's capability by applying it to a two-person office and a single-aisle, fully-occupied aircraft cabin. The optimal thermal comfort conditions around the occupants can be achieved with a limited number of air supply inlets at appropriate locations.

  • 124333.
    Zhao, Xueqian
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Network on Chip: Performance Bound and Tightness2015Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Featured with good scalability, modularity and large bandwidth, Network-on-Chip (NoC) has been widely applied in manycore Chip Multiprocessor (CMP) and Multiprocessor System-on-Chip (MPSoC) architectures. The provision of guaranteed service emerges as an important NoC design problem due to the application requirements in Quality-of-Service (QoS).

    Formal analysis of performance bounds plays a critical role in ensuring guaranteed service of NoC by giving insights into how the design parameters impact the network performance. The study in this thesis proposes analysis methods for delay and backlog bounds with Network Calculus (NC). Based on xMAS (eXecutable Micro-Architectural Specification), a formal framework to model communication fabrics, the delay bound analysis procedure is presented using NC. The micro-architectural xMAS representation of a canonical on-chip router is proposed with both the data flow and control flow well captured. Furthermore, a well-defined xMAS model for a specific application on an NoC can be created with network and flow knowledge and then be mapped to corresponding NC analysis model for end-to-end delay bound calculation. The xMAS model effectively bridges the gap between the informal NoC micro-architecture and the formal analysis model. Besides delay bound, the analysis of backlog bound is also crucial for predicting buffer dimensioning boundary in on-chip Virtual Channel (VC) routers. In this thesis, basic buffer use cases are identified with corresponding analysis models proposed so as to decompose the complex flow contention in a network. Then we develop a topology independent analysis technique to convey the backlog bound analysis step by step. Algorithms are developed to automate this analysis procedure.

    Accompanying the analysis of performance bounds, tightness evaluation is an essential step to ensure the validity of the analysis models. However, this evaluation process is often a tedious, time-consuming, and manual simulation process in which many simulation parameters may have to be configured before the simulations run. In this thesis, we develop a heuristics aided tightness evaluation method for the analytical delay and backlog bounds. The tightness evaluation is abstracted as constrained optimization problems with the objectives formulated as implicit functions with respect to the system parameters. Based on the well-defined problems, heuristics can be applied to guide a fully automated configuration searching process which incorporates cycle-accurate bit-accurate simulations. As an example of heuristics, Adaptive Simulated Annealing (ASA) is adopted to guide the search in the configuration space. Experiment results indicate that the performance analysis models based on NC give tight results which are effectively found by the heuristics aided evaluation process even the model has a multidimensional discrete search space and complex constraints.

    In order to facilitate xMAS modeling and corresponding validation of the performance analysis models, the thesis presents an xMAS tool developed in Simulink. It provides a friendly graphical interface for xMAS modeling and parameter configuring based on the powerful Simulink modeling environment. Hierarchical model build-up and Verilog-HDL code generation are essentially supported to manage complex models and conduct simulations. Attributed to the synthesizable xMAS library and the good extendibility, this xMAS tool has promising use in application specific NoC design based on the xMAS components.

  • 124334.
    Zhao, Xueqian
    et al.
    KTH. Natl Univ Def Technol, Peoples R China.
    Lu, Zhonghai
    KTH, School of Information and Communication Technology (ICT), Electronics.
    A Tool for xMAS-Based Modeling and Analysis of Communication Fabrics in Simulink2017In: ACM Transactions on Modeling and Computer Simulation, ISSN 1049-3301, E-ISSN 1558-1195, Vol. 27, no 3, article id 16Article in journal (Refereed)
    Abstract [en]

    The eXecutable Micro-Architectural Specification (xMAS) language developed in recent years finds an effective way to model on-chip communication fabrics and enables performance-bound analysis with network calculus at the micro-architectural level. For network-on-Chip (NoC) performance analysis, model validation is essential to ensure correctness and accuracy. In order to facilitate the xMAS modeling and corresponding analysis validation, this work presents a unified platform based on xMAS in Simulink. The platform provides a friendly graphical user interface for xMAS modeling and parameter setup by taking advantages of the Simulink modeling environment. The regulator and latency-rate sever are added to the xMAS primitive set to support typical flow and service behaviors. Hierarchical model build-up and Verilog-HDL code generation are essentially supported to manage complex models and to conduct cycle-accurate bit-accurate simulations. Based on the generated simulation models of xMAS, this tool is applied to evaluate the tightness of analytical delay bound results. We demonstrate the application as well as the work flow of the xMAS tool through a two-agent communication example and an all-to-one communication example with a tree topology.

  • 124335.
    Zhao, Xueqian
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Lu, Zhonghai
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Backlog bound analysis for virtual-channel routers2015In: 2015 IEEE Computer Society Annual Symposium on VLSI, Institute of Electrical and Electronics Engineers (IEEE), 2015, Vol. 07, p. 422-427Conference paper (Refereed)
    Abstract [en]

    Backlog bound analysis is crucial for predicting buffer sizing boundary in on-chip virtual-channel routers. However, the complicated resource contention among traffic flows makes the analysis difficult. Because conventional simulation-based approaches are generally incapable of investigating the worst-case scenarios for the backlog bounds, we propose a formal analysis technique. We identify basic buffer use scenarios and propose corresponding analysis models to formally deduce per-buffer backlog bound using network calculus. A topology independent analysis technique is developed to convey the per-buffer backlog bound analysis step by step. We further develop an algorithm to automate the analysis procedure with polynomial complexity. A case study shows how to apply the technique and the analytical bounds are tight.

  • 124336.
    Zhao, Xueqian
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Lu, Zhonghai
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Empowering study of delay bound tightness with simulated annealing2014In: Proceedings -Design, Automation and Test in Europe, DATE, 2014Conference paper (Refereed)
    Abstract [en]

    Studying the delay bound tightness typically takes a practical approach by comparing simulated results against analytic results. However, this is often a manual process whereas many simulation parameters have to be configured before the simulations run. This is a tedious and time-consuming process. We propose a technique to automate this process by using a simulated annealing approach. We formulate the problem as an online optimization problem, and embed a simulated annealing algorithm in the simulation environment to guide the search of configuration parameters which give good tightness results. This is a fully automated procedure and thus provide a promising path to automatic design space exploration in similar contexts. Experiment results of an all-to-one communication network with large searching space and complicated constraints illustrate the effectiveness of our method.

  • 124337.
    Zhao, Xueqian
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Lu, Zhonghai
    KTH, School of Information and Communication Technology (ICT), Electronics and Embedded Systems.
    Heuristics-Aided Tightness Evaluation of Analytical Bounds in Networks-on-Chip2015In: IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, ISSN 0278-0070, E-ISSN 1937-4151, Vol. 34, no 6, p. 986-999, article id 7038204Article in journal (Refereed)
    Abstract [en]

    Studying the tightness of analytical delay and backlog bounds is critical for network-on-chip designs, since formal analysis predicts the boundary of communication delay and buffer dimensioning. However, this evaluation process is often a tedious, time-consuming, and manual simulation process whereas many simulation parameters have to be configured before the simulations run. We formulate the tightness evaluation as constrained optimization problems for delay bound and backlog bounds, respectively. The well-defined problems enable a fully automated configuration searching process, which can be guided by a heuristic algorithm with cycle-accurate simulations integrated. This is a fully automated procedure and thus provides a promising path to automatic design space exploration in similar contexts. Experimental results over various topologies and traffic patterns indicate that our method is effective in finding the configuration for best tightness up to 98%, even when up to 50 parameters are configured in a multidimensional discrete search space under complex constraints.

  • 124338.
    Zhao, Xueqian
    et al.
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Lu, Zhonghai
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Per-flow delay bound analysis based on a formalized microarchitectural model2013In: 2013 7th IEEE/ACM International Symposium on Networks-on-Chip, NoCS 2013, IEEE , 2013, p. 6558411-Conference paper (Refereed)
    Abstract [en]

    System design starting from high level models can facilitate formal verification of system properties, such as safety and deadlock freedom. Yet, analyzing their QoS property, in our context, per-flow delay bound, is an open challenge. Based on xMAS (eXecutable Micro-Architectural Specification), a formal framework modeling communication fabrics, we present a QoS analysis procedure using network calculus. Given network and flow knowledge, we first create a well-defined xMAS model for a specific application on a concrete on-chip network. Then the specific xMAS model can be mapped to its network calculus analysis model for which existing QoS analysis techniques can be applied to compute end-to-end delay bound per flow. We give an example to show the step-by-step analysis procedure and discuss the tightness of the results.

  • 124339. Zhao, Y. J.
    et al.
    Persson, Clas
    Lany, S.
    Zunger, A.
    Why can CuInSe2 be readily equilibrium-doped n-type but the wider-gap CuGaSe2 cannot?2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, no 24, p. 5860-5862Article in journal (Refereed)
    Abstract [en]

    The wider-gap members of a semiconductor series such as diamond-->Si-->Ge or AlN-->GaN-->InN often cannot be doped n-type at equilibrium. We study theoretically if this is the case in the chalcopyrite family CuGaSe2-->CuInSe2, finding that: (i) Bulk CuInSe2 (CIS, E-g=1.04 eV) can be doped at equilibrium n-type either by Cd or Cl, but bulk CuGaSe2 (CGS, E-g=1.68 eV) cannot; (ii) result (i) is primarily because the Cu-vacancy pins the Fermi level in CGS farther below the conduction band minimum than it does in CIS, as explained by the doping limit rule; (iii) Cd doping is better than Cl doping, in that Cd-Cu yields in CIS a higher net donor concentration than Cl-Se; and (iv) in general, the system shows massive compensation of acceptors (Cd-III,V-Cu) and donors (Cl-Se,Cd-Cu,In-Cu).

  • 124340. Zhao, Y. S.
    et al.
    Yang, W. S.
    Xiao, D. B.
    Sheng, X. H.
    Yang, X.
    Shuai, Z. G.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Yao, J. N.
    Single crystalline submicrotubes from small organic molecules2005In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 17, no 25, p. 6430-6435Article in journal (Refereed)
    Abstract [en]

    The single crystalline submicrotubes of a small organic functional molecule, 2,4,5-triphenylimidazole (TPI), were successfully prepared with a facile method. A series of characterizations indicated that the tubes were obtained from the rolling followed by seaming of a preorganized two-dimensional sheet-like structure, whose formation was due to the efficient cooperation of several molecular recognition elements. The length and diameter of the TPI tubes can be readily controlled by adjusting the experimental conditions. The as-prepared submicrotubes have intensive luminescence and size-dependent optical properties, which allows them to find potential applications in novel optical and optoelectronic devices together with their single crystalline structure and good stability. The strategy described here should give a useful enlightenment for the design and fabrication of tubular structures from small organic molecules.

  • 124341. Zhao, Y.
    et al.
    Xiong, D. -B
    Qin, Haiying
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Gao, F.
    Inui, H.
    Zhu, Bin
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
    Nanocomposite electrode materials for low temperature solid oxide fuel cells using the ceria-carbonate composite electrolytes2012In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, no 24, p. 19351-19356Article in journal (Refereed)
    Abstract [en]

    Low temperature solid oxide fuel cell (LTSOFC, 300-600 °C) is one of the hot areas in recent fuel cell developments. In order to develop high performance LTSOFCs, compatible electrodes are highly demanded. We used NANOCOFC (nanocomposites for advanced fuel cell technology) approach to develop nanocomposite electrodes based on metal oxides Ni-Cu-Zn-oxide and samarium doped ceria (SDC). It was found that the materials consist of individual metal oxide and SDC phase, indicating the material as a composite with a homogenous distribution for all constituent components. Highly homogenous distribution of the particles enhanced the catalyst function for electrode applications in LTSOFC devices. We constructed the devices using the SDC-carbonate nanocomposite (NSDC) as the electrolyte and above as prepared composite as electrodes in a symmetrical configuration. We found that the prepared composite electrodes had good catalytic function for both H2 and O2, to prove its anode and cathode functions. Based on the material properties, the LTSOFC devices have reached a power output more than 730 mW cm-2 at 550 °C.

  • 124342.
    Zhao, Yadong
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Towards Large-scale and Feasible Exploitation of Tunicate Cellulose and Cellulose Nanocrystals for Different Applications2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Tunicates are a group of filter-feeding animals that live in the ocean. They are widely distributed throughout the world and are a major contributor to the fouling problem in aquaculture. In addition to their natural abundance, large-scale farming will further render them readily available in high quantities, and they should instead be providing us food, energy, chemicals and materials. As tunicates are the sole known animal group synthesizing cellulose, the primary target for this bioresources exploitation should be cellulose preparation and application. Moreover, cellulose exploitation should be conducted in both a technically and economically feasible manner.

    Among the tunicates, Ciona intestinalis (termed Ciona hereafter) is one of the most abundant species in Norwegian and Swedish coastal waters. Upon comprehensive quantification of the principal chemical compositions, cellulose has been confirmed to exist as cellulose-protein fibrils cemented by non-cellulose glycans and lipids and is almost exclusively present in the Ciona tunic fraction. Using the tunic as raw material, Ciona cellulose was prepared following a unique prehydrolysis-kraft cooking-bleaching sequence with a yield of 21.64% and by a modified Updegraff method with a yield of 23.65% on a dried ash-free mass basis. To improve the Ciona cellulose dispersibility and processability, Ciona cellulose nanocrystals (CNs) were prepared using different processes, namely acid hydrolysis, 2,2,6,6‑tetramethylpiperidine-1-oxyl (TEMPO)-mediated oxidation and enzymatic hydrolysis as well as acid hydrolysis followed by TEMPO-mediated oxidation. The CN preparation yield was 30.0-73.4%, depending on the process applied.

    By conducting comprehensive characterizations, it was found that the Ciona cellulose was nearly 100% pure, with a large weight average degree of polymerization (DPw=4200), a high surface area (133 m2/g), a large aspect ratio (length of several micrometres and diameter of ~16 nm), a high crystallinity (89%) in the form of nearly pure Iβ crystals, and a good thermal stability (onset degradation temperature of 226 ºC). When obtained in membrane form, the cellulose preserved the native interwoven microfibril network structure in the original tunic. It had a high ductility (tensile strain of 19.24%) in the wet state and good mechanical strength (tensile strength of 41.19 MPa and Young’s Modulus of 1.98 GPa) when dried. The CNs obtained were smaller in DPw, shorter in morphological size (length), similar or higher in crystallinity and more thermally stable than the starting cellulose to different extents and with different charged structures and charge contents dependent on the method/procedure used.

    Several applications have been examined. First, the Ciona cellulose in pulp form was utilized in the fabrication of sponge cloth to replace cotton, and the product obtained was of similar quality to the commercial one made from cotton. Second, the Ciona cellulose in membrane form was tested in the cultivation of human umbilical vein endothelial cells and mouse NIH‑3T3 cells for evaluations of cell proliferation performance and medical application potential. The performance was very positive. Third, the Ciona cellulose membrane and two CNs were applied as the matrix for high-quality zinc-blende CdSe/CdS core/shell nanocrystal quantum dots (QDs) for the development of mechanically strong and high-performance fluorescent material. The QDs were firmly attached to the Ciona CNs with uniform monolayer distribution and a high packing density. The obtained composites preserved both the high-quality optical properties from the QDs and the matrix morphology and thus expectedly the excellent mechanical properties from the cellulose. Finally, the Ciona CNs were processed to composite films cemented by konjac glucomannan for material development. Newly introduced hydrogen bonds between these two compatible polysaccharides and thus strong cementing effects were observed. The composite films showed excellent mechanical properties in addition to improved transparency, thermal stability and hydrophobicity compared with the CN’s neat films.

    Feasible tunicate cellulose exploitation demands the sound large-scale farming of Ciona for the highest possible cellulose content in the farmed animal, the exploitation of species other than Ciona, the complete utilization of fractions other than the tunic used and the value-added productions of other by-products. Composition quantification of the adult Ciona specimens collected from different farms showed that the carbohydrate content was linearly correlated with the body weight, which in turn was affected by the farm location, deployment time and sub-sea depth of the settling structures. Through analysing the Ciona intestinal content, it was found that both eukaryotes and prokaryotes contributed to the diet of the animal, and their quantities were positively correlated with the animal size (body weight). The tunics of three other tunicate species, Halocynthia roretzi, Styela plicata, and Ascidia sp., have been examined for tunicate cellulose preparation following the prehydrolysis-kraft cooking‑bleaching procedure. They were all found to be good sources for similar quality tunicate cellulose exploitation, thus verifying the universal applicability of the procedure. Based on more detailed chemical composition analyses, all the fractions other than the tunic, termed the inner body tissues fraction, from all four tunicate species were found to have excellent nutritional values: a high protein content with good quality amino acids and high contents of omega-3 (n-3) fatty acids and essential elements. Their toxic element contents were under the regulated limits for human food. They should therefore all be explored as human food sources. Furthermore, many different chemical structures, many of which were found for the first time, were present in the tunicate animals studied, ranging from collagens, glycosaminoglycans, and sterols to phospholipids. These structures should be explored as various bioactive by‑products during tunicate cellulose exploitation. For example, the prepared Ciona lipids had a high content of n-3 fatty acids, which presented mainly in the form of phospholipids. They should be an excellent alternative to markedly high value fish oils, but with a higher bioavailability.

    The techniques and knowledge obtained by this study will provide a basis for the promising large-scale and feasible exploitation of tunicate cellulose and cellulose nanocrystals for different applications.

  • 124343.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ascidian bioresources: common and variant chemical compositions and exploitation strategy examples of Halocynthia roretzi, Styela plicata, Ascidia sp and Ciona intestinalis2016In: Zeitschrift für Naturforschung C - A Journal of Biosciences, ISSN 0939-5075, E-ISSN 1865-7125, Vol. 71, no 5-6, p. 165-180Article in journal (Refereed)
    Abstract [en]

    To explore abundant marine ascidian bioresources, four species from two orders have been compared in their chemical compositions. After a universal separation of the animal body into two fractions, all tunics have been found rich in carbohydrate contents, while all inner body tissues are richer in proteins. Cellulose is present almost exclusively in the tunics and more in the order Stolidobranchia, while more sulfated polysaccharides are present in Phlebobranchia species. Almost all proteins are collagens with a high essential amino acid index and high delicious amino acid (DAA) content. All fractions also have high contents of good-quality fatty acids and trace minerals but low toxic element contents, with different sterols and glycosaminoglycans. There are species-specific characteristics observed for vanadium accumulation and sterol structures which are also meaningful for ascidian chemotaxonomy and resource exploitation. It is suggested that in addition to the present utilizations of tunics for cellulose production and of some species' inner body tissues as human food, one should explore all species' inner body tissues as human foods and all tunics as food or animal feed with the contained cellulose as dietary fiber. Collagens, sulfated polysaccharides, glycosaminoglycans, sterols and trace elements could be explored as byproducts for, e.g. pharmaceutical and chemical industries.

  • 124344.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Comprehensive comparison between woody and tunicate celluloses2014In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 247, p. 95-CARB-Article in journal (Other academic)
  • 124345.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Comprehensive lipid classification and its structural characterization of Tunicate Ciona intestinalis2013In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 245Article in journal (Other academic)
  • 124346.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Excellent chemical and material cellulose from tunicates: diversity in cellulose production yield and chemical and morphological structures from different tunicate species2014In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 21, no 5, p. 3427-3441Article in journal (Refereed)
    Abstract [en]

    The high crystallinity and the high microfibrils aspect ratio of tunicate cellulose (TC) indicate TC's excellent chemical and material applications. However, its quantity and quality from different species have never been systematically reported and compared. In this study, the tunics of Ciona intestinalis (CI), Ascidia sp. (AS), Halocynthia roretzi (HR) and Styela plicata (SP) were processed to TC after an identical prehydrolysis-kraft cooking-bleaching sequence, while the tunicate fibrils were chemically and structurally characterized in situ and during the sequence. All tunics studied were composed of crystalline cellulose embedded with protein, lipids, sulfated glycans and mucopolysaccharides. The native composite structures are all very compact. However, the tunics from Phlebobranchia order (CI and AS) are soft, while those from Stolidobranchia, HR and SP, are hard. Fibrous cellulose could be prepared after removing the lipids, sulfated glycans and mucopolysaccharides through prehydrolysis, protein removal through kraft cooking and a final purification by bleaching. The final product is similar to 100 % pure cellulose which is in large molecular masses, composed of highly crystalline I-beta crystals, in elementary microfibrils form, with high specific surface area and thermal stability. There were lower TC yields from the soft tunics than from the hard ones. The cellulose fibrils had a section shape of lozenges with higher crystallinity. This study demonstrates that TC could be obtained in different yields and exhibited different chemical and morphological structures depending on the species. There is a great potential of tunicate resources for preparing excellent chemical and material cellulose.

  • 124347.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Li, Liebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Ascidian bioresources: common and variant chemical compositions and exploitation strategy- Examples of Halocynthia roretzi, Styela plicata, Ascidia sp. and Ciona intestinalisManuscript (preprint) (Other academic)
    Abstract [en]

    Four ascidian species have been compared on chemical compositions. All animal tunics have rich carbohydrate contents, while all inner body tissues are richer in proteins. Cellulose is present almost exclusively in the tunics and more in the order Stolidobranchia, while more sulfated polysaccharides are present in Phlebobranchia species. Almost all proteins are collagens with a high essential amino acid index and high delicious amino acid content. All fractions also have high contents of good-quality fatty acids and trace minerals but low toxic element contents, with different sterols and glycosaminoglycans. Therefore, in addition to the present utilizations of tunics for cellulose production and of some species’ inner body tissues as human food, one should explore all species’ inner body tissues as human foods and all tunics as food or animal feed with the contained cellulose as dietary fiber. Collagens, sulfated polysaccharides, glycosaminoglycans, sterols and trace elements could be explored as byproducts.

  • 124348.
    Zhao, Yadong
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Moser, Carl
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Henriksson, Gunnar
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology.
    Transparent Composites Made from Tunicate Cellulose Membranes and Environmentally Friendly Polyester2018In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 11, no 10, p. 1728-1735Article in journal (Refereed)
    Abstract [en]

    A series of optically transparent composites were made by using tunicate cellulose membranes, in which the naturally organized cellulose microfibrillar network structure of tunicate tunics was preserved and used as the template and a solution of glycerol and citric acid at different molar ratios was used as the matrix. Polymerization through ester bond formation occurred at elevated temperatures without any catalyst, and water was released as the only byproduct. The obtained composites had a uniform and dense structure. Thus, the produced glycerol citrate polyester improved the transparency of the tunicate cellulose membrane while the cellulose membrane provided rigidity and strength to the prepared composite. The interaction between cellulose and polyester afforded the composites high thermal stability. Additionally, the composites were optically transparent and their shape, strength, and flexibility were adjustable by varying the formulation and reaction conditions. These composites of cellulose, glycerol, and citric acid are renewable and biocompatible and have many potential applications as structural materials in packaging, flexible displays, and solar cells.

  • 124349.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Moser, Carl
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Lindström, Mikael E
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Cellulose Nanofibers from Softwood, Hardwood, and Tunicate: Preparation-Structure-Film Performance Interrelation2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 15, p. 13508-13519Article in journal (Refereed)
    Abstract [en]

    This work reveals the structural variations of cellulose nanofibers (CNF) prepared from different cellulose sources, including softwood (Picea abies), hardwood (Eucalyptus grandis × E. urophylla), and tunicate (Ciona intestinalis), using different preparation processes and their correlations to the formation and performance of the films prepared from the CNF. Here, the CNF are prepared from wood chemical pulps and tunicate isolated cellulose by an identical homogenization treatment subsequent to either an enzymatic hydrolysis or a 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO)-mediated oxidation. They show a large structural diversity in terms of chemical, morphological, and crystalline structure. Among others, the tunicate CNF consist of purer cellulose and have a degree of polymerization higher than that of wood CNF. Introduction of surface charges via the TEMPO-mediated oxidation is found to have significant impacts on the structure, morphology, optical, mechanical, thermal, and hydrophobic properties of the prepared films. For example, the film density is closely related to the charge density of the used CNF, and the tensile stress of the films is correlated to the crystallinity index of the CNF. In turn, the CNF structure is determined by the cellulose sources and the preparation processes. This study provides useful information and knowledge for understanding the importance of the raw material for the quality of CNF for various types of applications.

  • 124350.
    Zhao, Yadong
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Moser, Carl
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Wood Chemistry and Pulp Technology. Valmet AB, Sundsvall, Sweden..
    Lindström, Mikael
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Li, Jiebing
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Film formation and performance of different nanocelluloses obtained from different cellulose sources after different preparation processes2017In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 253Article in journal (Other academic)
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