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  • 126351.
    Zhao, Pengcheng
    KTH, School of Electrical Engineering (EES), Industrial Information and Control Systems.
    IEC 61850-9-2 Process Bus Communication Interface for Light Weight Merging Unit Testing Environment2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    IEC 61850 is an international standard for communication networks for substation [1]. As a part of the IEC 61850 series, IEC 61850 Part 9-2 was introduced in 2004 and updated to a stable version in 2011 [2]. Part 9-2 de nes the specfic communication service mapping for the transmission of sampled values from process equipment [3]. The interface between process equipment and bay level devices is named as Merging Unit (MU) [4].

    The 9-2 standard is a newly updated standard which has not yet been implemented in large scale. Therefore it is new or unfamiliar to many engineers working with substation automation systems. A project which is aimed to develop a light weight IEC 61850-9-2 MU testing environment is conducted in ICS department in KTH.

    The project can be also referred as "soft" MU project and consists of two parts. Part A is to implement conventional power system model, instrument transformer, and analog to digital converter [5]. This thesis project is Part B of the light weight merging unit (MU) testing tool project.

    This project is focusing on developing the 9-2 process bus communication interface for the "soft" MU project. The digitalized measurements such as current and voltage from Project A are encoded into 9-2 sampled values (SV) Ethernet stream by the process bus interface. The project is executed in the following steps. Firstly, the interface is programmed by C language under Linux environment. Secondly, the process bus communication interface is embedded into Matlab so that Part A and Part B can be combined as one system. To evaluate the light weight IEC 61850-9-2 MU testing environment, the "soft" MU is connected to a process bus network with one IED. The IED used in this thesis project is RET 670 which is a product of ABB Substation Automation. The four steps over current protection and two Windings transformer dierential protection in RET 670 is tested. The evaluation work is also demonstrated in this report.

  • 126352.
    Zhao, Pengran
    KTH, School of Information and Communication Technology (ICT).
    Inter-Application Communications Between IPTV Clients2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The master thesis: Inter-application communication in IPTV client was conducted at the Business Multimedia Unit in Ericsson.

    In the IPTV client side, there is a need to control another IPTV client remotely with a low latency. This functionality can be used in playing game and remote operation in IPTV. The current solution is that clients communicate through the portal (Ericsson’s Web based IPTV system) in remote location with high latency. The focus of this thesis work is designing, building and evaluating a communication mechanism among IPTV clients in a LAN.

    The major contribution of this thesis is analysis and design of a solution. The comparison between an implemented solution in this project and other possible solutions is also included in this thesis. The purpose of the solution is to improve the configuration and performance of Ericsson IPTV clients. In the thesis, a prototype of inter-application communication between IPTV clients was designed. The prototype includes a proxy server (Based on Node.js), UPnP applications (Based on open source UPnP stacks), communication components in portal system and an Android client. The prototype has achieved the goals of setting up fast and convenient communication in Ericsson IPTV client side, without using the IPTV server. UPnP applications allow two devices in a LAN find each other with no need to configure IP and port. A local proxy server, a couple of communication components in portal and an Android application are used to set up communication in a LAN. Also different solutions have been analyzed and designed in the project. And some related technologies have been investigated and introduced.

    Measurement and test shows that the communication between IPTV clients in a LAN is fast enough to replace the way of communication through the server. Security analysis shows some possible drawbacks, like the security vulnerability and compatibility. The security can be improved by some future work, part of which is proposed and designed in the thesis. Analysis also shows the advantages and disadvantages of on different service discovery technologies.

  • 126353. Zhao, R.
    et al.
    Lind, Johan
    KTH, Superseded Departments, Chemistry.
    Merenyi, Gabor
    KTH, Superseded Departments, Chemistry.
    Jonsson, Mats
    KTH, Superseded Departments, Chemistry.
    Eriksen, T. E.
    Reduction potentials and kinetics of beta-fragmentation reactions of 4-substituted benzoylthiyl radicals2000In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 104, no 37, p. 8524-8526Article in journal (Refereed)
    Abstract [en]

    By means of pulse radiolysis, the one-electron reduction potentials of 4-substituted benzoylthiolates E degrees(4-XPhC(O)S-./4-XPhC(O)S-), where X is CH3, CH3O, CF3, and CN, were measured in aqueous solutions. The kinetics of beta-fragmentation reactions of the 4-XPhC(O)S-. radicals to form the corresponding 4-XPh. radicals and COS (i.e., 4-XPhC(O)S-. --> 4-XPh. + COS) were also determined. The pK(a)s of the corresponding acids (4-XPhC(O)SH) were measured by a spectrophotometric method. Thus, the values of E degrees(4-XPhC(O)S-., H+/ 4-XPhC(O)SH) and the S-H bond strength of the 4-XPhC(O)S-H were calculated. The substituent effects on the redox potential, the pK(a), and the kinetics of their beta-fragmentation reactions were examined.

  • 126354.
    Zhao, Rong
    KTH, Superseded Departments, Chemistry.
    Thiyl radicals, reaction kinetics and redox chemistry1998Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    In focusing on the free radical chemistry of thiyl radicals,two importantclasses are dealt with, namely, the amino acidalkylthiyl and the acylthiyl radicals, where pulse radiolysisand steady state γ-radiolysis are applied.

    Amino acid thiyl radicals (RS•), are important in manybiological systems,as intermediates in the repair reactions ofthiols towards targeted carbon-centeredradicals and ascatalytic centers in many enzymatic reactions. Initially,thereactions following one-electron oxidation of cysteine(CysSH), homocysteine(HCysSH) and glutathione (GSH) in aqueoussolutions are observed, where kineticanalysis reveals thatintramolecular hydrogen abstraction by thiyl radicals fromtheα-amino-α-carboxyl C-H bonds is general for thethree investigated. Theintramolecular hydrogen abstraction of aglutathione thiyl radical from α-amino-α-carboxylC-Hbond discloses an equilibrium constant larger than 10 4 asevidencedby ammonia formation and thiol consumption. Thus,based on reduction potentialE°(RS•,H + /RSH) being1.36 V, E°(NH 2 (C•)RCO 2 ¯, H + /NH 2 CHRCO 2¯) andE°(NH 2 (C•)RCO 2 H, H + /NH 2 CHRCO 2 H)are derived as lower than 1.12 V and0.98 V vs NHE,respectively. These are, to my knowledge, the firstexperimentalvalues relating to C-H bond strengths of aminoacids with their biologicalimplications clearly appraised.

    Further, spectroscopic characteristics and one-electronreduction potential ofacylthiyl, including acetylthiyl,benzoylthiyl and 4-substituted benzoylthiylradicals arestudied. The kinetics and the thermodynamics of theß-fragmentationreactions, i.e. RC(O)S•——>R• + COS, for the CH 3 C(O)S•,PhC(O)S• and 4-X-PhC(O)S• radicals are observed,with experimental results compared andevaluated along withtheir oxygen counterparts CH 3 C(O)O•, PhC(O)O• and4-XPhC(O)O• radicals.

    Keywords:Thiyl, Glutathione,α-Amino-α-Carboxyl Carbon-Centered Radical,Acylthiyl,Aroylthiyl, Benzoylthiyl, 4-Substituted Benzoylthiyl Radical,PulseRadiolysis, Kinetics, One-Electron Reduction Potential,Bond Dissociation Energy, β-Fragmentation.

  • 126355. Zhao, Ruikai
    et al.
    Deng, Shuai
    Zhao, Li
    Liu, Yinan
    Tan, Yuting
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Energy Processes.
    Energy-saving pathway exploration of CCS integrated with solar energy: Literature research and comparative analysis2015In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 102, p. 66-80Article in journal (Refereed)
    Abstract [en]

    One of main technical barriers to a large-scale application of carbon capture and storage (CCS) technology is a significant amount of required energy, e.g., regeneration heat of solvent in the chemical absorption system. Thus, energy consumption and corresponding high operation cost become two primary challenges for the promotion of CCS technology. Meanwhile, energy from the solar source in various forms has already been successfully used as an effective alternative supply in the industrial section for drying, heating and even cooling. Thus, integrating solar energy utilization into the CCS process could be a reasonable option for a sustainable development. A comparative analysis of CCS integrated with solar energy was presented in this paper based on the existing researches. The current status on typical configuration structure, feature and energy-efficiency performance of integrating options is reviewed for post-combustion, pre-combustion and oxygen-combustion systems. Based on these typical CO2 capture systems, a theoretical analysis is conducted for an energy-efficient comparison. Then four typical structures of the post-combustion system, which are highlighted in the review, are chosen as comparative objects for energy-saving and techno-economic evaluation. The results show that systems with a solar-assisted thermal energy and power generation have comparative advantages in term of carbon emission intensity, but the economic cost is increased under the current conditions of the equipment price. Compared to that of baseline case, carbon emission intensity of the case integrated with solar Organic Rankine Cycle can be reduced with a maximum decline of 9.73%, meanwhile the levelized costs of electricity increases 0.01 USD/kW h correspondingly.

  • 126356.
    Zhao, Ruikai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Liu, Longcheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Zhao, L.
    Key Laboratory of Efficient Utilization of Low and Medium Grade Energy (Tianjin University).
    Deng, S.
    Key Laboratory of Efficient Utilization of Low and Medium Grade Energy (Tianjin University), Ministry of Education of China, Tianjin, 300350, China cInternational Cooperation Research Centre of Carbon Capture in Ultra-low Energy-consumption, Tianjin, 300350, China.
    Li, S.
    Key Laboratory of Efficient Utilization of Low and Medium Grade Energy (Tianjin University), Ministry of Education of China, Tianjin, 300350, China cInternational Cooperation Research Centre of Carbon Capture in Ultra-low Energy-consumption, Tianjin, 300350, China.
    Zhang, Y.
    Key Laboratory of Efficient Utilization of Low and Medium Grade Energy (Tianjin University), Ministry of Education of China, Tianjin, 300350, China cInternational Cooperation Research Centre of Carbon Capture in Ultra-low Energy-consumption, Tianjin, 300350, China.
    A comprehensive performance evaluation of temperature swing adsorption for post-combustion carbon dioxide capture2019In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 114, article id 109285Article in journal (Refereed)
    Abstract [en]

    Carbon dioxide capture from the post-combustion flue gas via temperature swing adsorption is supposed to be a valid technology to mitigate carbon emissions. With regard to the adsorbent development and process improvement, the technologies of temperature swing adsorption for post-combustion carbon dioxide capture have been reviewed and compared in terms of fixed bed, fluidized bed and moving bed. A comprehensive evaluation framework of fixed-bed temperature swing adsorption for CO2 capture has been established. In a four-step fixed-bed cycle, a shortcut model has been utilized. Four typical adsorbent materials, such as activated carbon, zeolite 13X, zeolite NaUSY and Mg-MOF-74, have been chosen in this assessment. The comparative study has been conducted under the same operating conditions, from four aspects using eight performance indicators. Results indicate that Mg-MOF-74 and zeolite 13X reveal excellent performance among the four selected adsorbents. Thereinto, Mg-MOF-74 performs well at four indicators including purity, productivity, specific thermal energy consumption and second-law efficiency; zeolite 13X excels in the other four indicators such as selectivity, recovery, minimum separation work and capture cost. Future work will complete a thorough assessment criterion in evaluating the TSA process for CO2 capture.

  • 126357.
    Zhao, Ruikai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Liu, Longcheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Zhao, Li
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China..
    Deng, Shuai
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China..
    Li, Hailong
    Malardalen Univ, Sch Business Soc & Engn, SE-72123 Vasteras, Sweden..
    Thermodynamic analysis on carbon dioxide capture by Electric Swing Adsorption (ESA) technology2018In: Journal of CO2 Utilization, ISSN 2212-9820, E-ISSN 2212-9839, Vol. 26, p. 388-396Article in journal (Refereed)
    Abstract [en]

    This study explores the impacts of materials, such as adsorbents and electrodes, on the energy efficiency of a 4-step ESA cycle for CO2 capture. Three types of adsorbents including activated carbon honeycomb monolith (ACHM) and two hybrid adsorbents are compared, and two kinds of electrodes such as aluminum and brass are combined for comparative analysis. Process description of ESA cycle, including feed, electrification, electrification with purge and cooling, is presented via the adsorption isotherm diagram. By the theory of thermodynamic carbon pump, sensitivity analysis of cycle parameters is evaluated in terms of the second-law efficiency (Eff(2nd)) and the electrical heating efficiency (Eff(ele)). The results show that Eff(2nd) of the employed adsorbents is in the range of 1.17%-6.15%, and Effele of the selected electrodes is between 27.46% and 60.91%. Among the three adsorbents, Eff(2nd) of ACHM is the lowest one compared to the others. Similarly, Effele of the combination with brass is superior to that of the groups with aluminum. However, the actual efficiency of ESA cycle is the production of both Eff(2nd) and Eff(ele), which is approximately 1.03%-3.66%. Typical measures are proposed to reduce the heat loss of the adsorbents and electrodes as well for future work.

  • 126358.
    Zhao, Ruikai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Liu, Longcheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Zhao, Li
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China..
    Deng, Shuai
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Li, Shuangjun
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Zhang, Yue
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    A comprehensive performance evaluation of temperature swing adsorption for post-combustion carbon dioxide capture2019In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 114, article id UNSP 109285Article in journal (Refereed)
    Abstract [en]

    Carbon dioxide capture from the post-combustion flue gas via temperature swing adsorption is supposed to be a valid technology to mitigate carbon emissions. With regard to the adsorbent development and process improvement, the technologies of temperature swing adsorption for post-combustion carbon dioxide capture have been reviewed and compared in terms of fixed bed, fluidized bed and moving bed. A comprehensive evaluation framework of fixed-bed temperature swing adsorption for CO2 capture has been established. In a four-step fixed-bed cycle, a shortcut model has been utilized. Four typical adsorbent materials, such as activated carbon, zeolite 13X, zeolite NaUSY and Mg-MOF-74, have been chosen in this assessment. The comparative study has been conducted under the same operating conditions, from four aspects using eight performance indicators. Results indicate that Mg-MOF-74 and zeolite 13X reveal excellent performance among the four selected adsorbents. Thereinto, Mg-MOF-74 performs well at four indicators including purity, productivity, specific thermal energy consumption and second-law efficiency; zeolite 13X excels in the other four indicators such as selectivity, recovery, minimum separation work and capture cost. Future work will complete a thorough assessment criterion in evaluating the TSA process for CO2 capture.

  • 126359.
    Zhao, Ruikai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry.
    Liu, Longcheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Zhao, Li
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China..
    Deng, Shuai
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China..
    Li, Shuangjun
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China..
    Zhang, Yue
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China..
    Li, Hailong
    Malardalen Univ, Sch Business Soc & Engn, SE-72123 Vasteras, Sweden..
    Techno-economic analysis of carbon capture from a coal-fired power plant integrating solar-assisted pressure-temperature swing adsorption (PTSA)2019In: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 214, p. 440-451Article in journal (Refereed)
    Abstract [en]

    This paper presents a techno-economic study to seek the feasibility about the proposed system that integrating solar-assisted pressure-temperature swing adsorption (PTSA) into an 800MWe coal-fired power plant. Solar energy has the potential to supply thermal energy demand for carbon capture, which can avoid the energy consumption of the traditional method such as the steam extraction. The performance of the proposed system is largely affected by the climatic conditions and solar collector's types. The assessment criteria include carbon emission intensity (CEO, levelized cost of electricity (LCOE) and cost of CO2 avoidance (COA). By the parametric analysis, the results show that CEI of the novel system with solar thermal collectors is approximately 2g/kWh lower than that of the referenced power plant with CO2 adsorption capture. In addition, CEI of the novel system can be further decrease with the decline of desorption temperature, adsorption pressure and desorption pressure. For the sake of lower LCOE and COA, the prices of the power plant capacity, adsorbents and solar collectors should be reduced. Specifically, LCOE of the system with evacuated tube collector will be lower than that of the reference system with CO2 capture as the price of solar field is lower than 46.08 USD/m2.

  • 126360.
    Zhao, Ruikai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Liu, Longcheng
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering.
    Zhao, Li
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Deng, Shuai
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Li, Shuangjun
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Zhang, Yue
    Tianjin Univ, Minist Educ China, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.;Int Cooperat Res Ctr Carbon Capture Ultralow Ener, Tianjin 300350, Peoples R China..
    Li, Hailong
    Malardalen Univ, Sch Business Soc & Engn, SE-72123 Vasteras, Sweden..
    Thermodynamic exploration of temperature vacuum swing adsorption for direct air capture of carbon dioxide in buildings2019In: Energy Conversion and Management, ISSN 0196-8904, E-ISSN 1879-2227, Vol. 183, p. 418-426Article in journal (Refereed)
    Abstract [en]

    Abrupt climate change such as the loss of Arctic sea-ice area urgently needs negative emissions technologies. The potential application of direct air capture of carbon dioxide from indoor air and outdoor air in closed buildings or crowded places has been discussed in this paper. From the aspects of carbon reduction and indoor comfort, the ventilation system integrating a capture device is of great value in practical use. For ultra-dilute carbon dioxide sources, many traditional separation processes have no cost advantages, but adsorption technologies such as temperature vacuum swing adsorption is one of suitable methods. Thermodynamic exploration has been investigated regarding minimum separation work and second-law efficiency at various concentrations in the air. The influence of concentration, adsorption temperature, desorption temperature and desorption pressure on the energy efficiency has also been evaluated. Results show that the minimum separation work for the level of 400 ppm is approximately 20 kJ/mol. The optimal second-law efficiencies are 44.57%, 37.55% and 31.60%, respectively for 3000 ppm, 2000 ppm and 1000 ppm. It means that a high energy-efficiency capture device in buildings merits attention in the exploration of the possibility of approaching negative carbon buildings.

  • 126361.
    Zhao, Ruikai
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemical Engineering. Tianjin Univ, Minist Educ, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China.
    Zhao, Li
    Tianjin Univ, Minist Educ, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China..
    Wang, Shengping
    Tianjin Univ, Sch Chem Engn & Technol, Key Lab Green Chem Technol, Tianjin 300072, Peoples R China..
    Deng, Shuai
    Tianjin Univ, Minist Educ, Key Lab Efficient Utilizat Low & Medium Grade Ene, Tianjin 300350, Peoples R China..
    Li, Hailong
    Malardalen Univ, Sch Business Soc & Engn, SE-72123 Vasteras, Sweden..
    Yu, Zhixin
    Univ Stavanger, Dept Petr Engn, N-4036 Stavanger, Norway..
    Solar-assisted pressure-temperature swing adsorption for CO2 capture: Effect of adsorbent materials2018In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 185, p. 494-504Article in journal (Refereed)
    Abstract [en]

    Because of the ability to utilize the low-grade solar thermal energy for regeneration, a CO2 capture system characterized by solar-assisted pressure temperature swing adsorption (SOL-PTSA) is studied on the effects of adsorbent materials. A detailed cycle description is firstly presented within the diagram of adsorption isotherm for the energy-efficiency analysis. Typical adsorbent materials, including zeolites and chemical adsorbent, are assessed in terms of sensible heat and latent heat, etc. Then, the energy consumption and the second-law efficiency, which can be considered as lumped indicators from such material parameters, are chosen as performance indicators as well. The influence of separation temperature, desorption temperature, CO2 concentration and CO2 adsorption pressure on system performance are finally obtained. For the chosen three adsorbent materials, the energy consumption of SOL-PTSA system is at the range of 25.96-87.76 kJ/mol, and the corresponding second law efficiencies are at the range of 9.18-26.89%. The effect of adsorbent materials on the energy-efficiency of SOL-PTSA system mainly depends on specific heat, CO2 working capacity and cycle design. In addition, the integration options of solar energy into PTSA technology are also discussed from the standpoint of the utilization of solar grade heat due to two energy loads required for PTSA's operation.

  • 126362.
    Zhao, Shiyu
    et al.
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield S10 2TN, S Yorkshire, England..
    Dimarogonas, Dimos V.
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, ACCESS Linnaeus Centre.
    Sun, Zhiyong
    Australian Natl Univ, Res Sch Engn, Canberra, ACT 0200, Australia..
    Bauso, Dario
    Univ Sheffield, Dept Automat Control & Syst Engn, Sheffield S10 2TN, S Yorkshire, England..
    A General Approach to Coordination Control of Mobile Agents With Motion Constraints2018In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 63, no 5, p. 1509-1516Article in journal (Refereed)
    Abstract [en]

    This paper proposes a general approach to design convergent coordination control laws for multiagent systems subject to motion constraints. The main contribution of this paper is to prove in a constructive way that a gradient-descent coordination control law designed for single integrators can be easily modified to adapt for various motion constraints such as nonholonomic dynamics, linear/angular velocity saturation, and other path constraints while preserving the convergence of the entire multiagent system. The proposed approach is applicable to a wide range of coordination tasks such as rendezvous and formation control in two and three dimensions. As a special application, the proposed approach solves the problem of distance-based formation control subject to nonholonomic and velocity saturation constraints.

  • 126363.
    Zhao, Shuang
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Analysis and Control Aspects of a PMSynRel Drive in a Hybrid Electric Vehicle Application2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals withmodeling and control of an electric drive equipped with a permanentmagnet assisted synchronous reluctance (PMSynRel) machine for a plug-in hybrid electric vehicle application.

    In the first part of the thesis, a special use of the PMSynRel machine in consideration, known as an integrated charger concept, is investigated. The integrated charger feature allows using the PMSynRel machine as a part of the vehicle’s on-board charging system when charging the battery from the grid. A finite-element based analysis is performed providing important insights into the machine operation during the charging process. Dynamic models are developed that facilitate the controller development and the estimation of the efficiency during charging.

    In the second part of the thesis, position sensorless control of the PMSynRel drive when applied in an automotive application is considered and analyzed thoroughly. First, a fundamental-excitation based rotor-position estimation technique is investigated. The study shows that the impact of current dynamics on the resulting torque dynamics has to be considered in some very demanding applications. Second, focus is put on signalinjection based sensorless control methods. Impacts of nonlinearities, such as magnetic saturation, cross-saturation and inductance spatial harmonics, on sensorless control performance are investigated and methods to improve the sensorless control quality are summarized and presented. An approach to determine the feasible region for operating sensorless at low-speeds without directly measuring the differential inductances is proposed. For the PMSynRel drive in consideration, the achievable maximum torque is limited when operating sensorless following the maximum-torque-per-ampere (MTPA) current reference trajectory at low-speeds. An optimization approach is therefore proposed which extends the output torque when operating sensorless while still maintaining a relatively high efficiency. To initialize the sensorless control correctly from standstill, the impact of the saturated magnetic bridges in the rotor is also investigated.

    Finally, torsional drive-train oscillations and active damping schemes are considered. An off-vehicle setup for implementing and evaluating different active damping schemes is proposed. Of particular interest for sensorless operation in automotive applications, the impact of slow speed estimation on the possibility to achieve good active damping control is investigated and a design approach that allows the implementation of an active damping scheme using estimated speed is suggested.

  • 126364.
    Zhao, Shuang
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Modeling and Control of a PMSynRel Drive for a Plug-InHybrid Electric Vehicle2011Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This thesis presents two transient models for a prototype integrated charger for use in a plug-in hybrid-electrical vehicle application. The models can be useful in order to develop control algorithms for the system or to recommend improvements to the machine design.

    A flux map based method, obtaining input data from simulations using the finite element method (FEM) is used to model the grid synchronization process. The grid side voltage can then be predicted by incorporating spatial flux linkage harmonics. The model is implemented in Matlab/Simulink and compared to stand alone FEM simulations with good agreement.

    The charging process is modeled using an inductance based model also requiring FEM simulations as input data. Since the flux linkages in the grid and inverter side windings are dependent on each other, the presented transient model is linearized around a specific operating point. This model is also implemented in a Matlab/Simulink environment.

    Sensorless control of a PMSynRel drive is also studied in this thesis. Focus is put on operating limits due to magnetic saturation when operating at low speeds. The rotating and pulsating voltage vector injection methods for sensorless control are studied in detail. A technique to map the feasible sensorless control region is proposed which utilizes the resulting position error signal rather than data of differential inductances. This technique is implemented experimentally and compared to corresponding FEM simulations with good agreement.

    The impact of spatial inductance harmonics on the quality of the position estimates is also studied. A method to predict the maximum position estimation error due to the inductance harmonics is proposed based on simplified analytical models. A technique is presented and experimentally verified which can compensate for this effect by injecting a modified rotating voltage carrier. Lastly, the impact of saturation in the rotor structure on the initial magnet polarity detection is investigated. The experimental results, in good agreement with the corresponding FEM simulations, indicate that the impact of saturation in the magnet bridges of rotor is the dominant phenomenon at lower peak current magnitudes.

  • 126365.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Haghbin, S.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics (closed 20110930).
    Lundmark, S.
    Carlson, O.
    Transient modeling of an integrated charger for a plug-in hybrid electric vehicle2011In: Proceedings of the 2011 14th European Conference on Power Electronics and Applications, EPE 2011, IEEE conference proceedings, 2011, p. 1-10Conference paper (Refereed)
    Abstract [en]

    This paper considers a permanent magnet assisted synchronous reluctance (PMSynRel) machine for an integrated charger application for use in a plug-in hybrid electric vehicle (PHEV). The integrated charger functionality means that the machine is also used when the battery is charged from the electrical grid. A finite element model (FEM) is presented from which a transient model of the complete system is derived. The resulting model can be used for simulating and tuning the algorithms needed to synchronize the machine to the electrical grid and controlling the charging process.

  • 126366.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Lasson, Anders
    Volvo Cars AB.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Off-Vehicle Evaluation of Active Oscillation Damping Schemes2014In: IEEE Journal of Emerging and Selected Topics in Power Electronics, ISSN 2168-6777, Vol. 2, no 2, p. 264-271Article in journal (Refereed)
    Abstract [en]

    Torsional drivetrain oscillations are a well-known problem in electrical or hybrid electric drivetrains and may greatly influence the driving comfort. An experimental testing setup that can be used to design and evaluate active oscillation damping schemes is proposed in this paper. Instead of an in-vehicle test, the drivetrain transmission is emulated from mathematic models, executed by a servo drive which is connected to the physical electrical drive system. The proposed setup functions as a hardware-in-the-loop simulator and can be easily adjusted to simulate any drive trains without additional cost.

  • 126367.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Torque dynamics in sensorless PMSM drives2012In: Electrical Machines (ICEM), 2012 XXth International Conference on, IEEE , 2012, p. 2273-2278Conference paper (Refereed)
    Abstract [en]

    In automotive drivetrains used in hybrid electric vehicles, the transmission connecting the electric machine(s) and the combustion engine often introduce non linear phenomena such as gear play and backlash. These non-ideal effects can result in drivetrain oscillations which, in turn, can be mitigated by a controller manipulating the torque reference of the electric machine. If a permanent-magnet synchronous machine (PMSM) is operated without using a position sensor (sensorless), the resulting torque dynamics (from the torque reference to the shaft torque) is different compared to the situation when the rotor position is known. Hence, it is desirable to know the torque dynamics for PMSMs operating sensorless when the drivetrain torque oscillation controller is tuned. This paper presents a number of models, evaluated using simulations, describing the torque dynamics of PMSM drives with and without the use of a position sensor.

  • 126368.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Analysis of a deeply saturated sensorless PMSynRel drive for an automotive application2011In: Proceedings of the 2011-14th European Conference on Power Electronics and Applications (EPE 2011), IEEE conference proceedings, 2011, p. 1-10Conference paper (Refereed)
    Abstract [en]

    This paper presents an method of mapping feasible region for a sensorless control PMSynRel drive using the resulting position error signal. Thanks to the rotor anisotropy, the rotor position can be detected at low speeds by means of injecting high frequency voltage, either a pulsating voltage vector in the estimated synchronous frame or a rotating vector in the stator frame, on top of the fundamental excitation. However, the resulting position error signal is degraded and distorted by magnetic saturation (including crosssaturation) and spatial inductance harmonics. Therefore, the feasible region is used to find the stable operating points. Instead of mapping the inductances, which is time consuming, position error signal is used to map the feasible sensorless control region. A prediction method of the maximum position estimation error is also presented by taking the spatial inductance harmonics into account. After that, some techniques are presented to compensate the cross-saturation and slot harmonic effects in order to improve the sensorless control quality. Additionally, it is shown how saturation in the rotor bridges affects the initial polarity detection required during startup.

  • 126369.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Damping of Torsional Drive-Train Oscillationsusing a Position Sensorless PMSynRel DriveIn: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059Article in journal (Other academic)
  • 126370.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Low-Speed Sensorless Control With Reduced Copper Losses for Saturated PMSynRel Machines2013In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 28, no 4, p. 841-848Article in journal (Refereed)
    Abstract [en]

    Permanent-magnet-assisted synchronous reluctance (PMSynRel) machines are generally well suited for sensorless operation at all speeds since the rotor topology possesses a magnetic saliency. However, magnetic saturation can result in a vanishing differential saliency which renders sensorless control at certain operating points difficult (or even impossible) at low speed. In this paper, an optimization procedure, based on results from finite-element (FEM)-based simulations, is proposed. As output, current reference trajectories are obtained in which copper losses are kept at minimum, while the capability for sensorless control is still maintained. The results from the FEM-based simulations are in good agreement with the corresponding experimental results. For the experimental prototype in consideration, the torque limit when operating sensorless at low speed is increased substantially from below 45% to around 95% of its rated value with only slightly increased copper losses. Additionally, the impact of position-dependent harmonics on the magnetic cross saturation (affecting the steady-state position estimation error) is found to be substantial. This highlights that this spatial variation should be taken into consideration for accurate prediction of performance during sensorless operation even if the winding of the machine is of the conventional distributed type.

  • 126371.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Lasson, Anders
    Off-Vehicle Evaluation of Active Oscillation Damping Schemes2013In: 2013 IEEE Energy Conversion Congress and Exposition, ECCE 2013, 2013Conference paper (Refereed)
    Abstract [en]

    Torsional drivetrains oscillations is a well known problem in electrical or hybrid electric drivetrains which may greatly influence the driving comfort. An experimental testing setup that can be used to design and evaluate active oscillation damping schemes is proposed in this paper. Instead of in-vehicle test, the drivetrain transmission is emulated from mathematic models, executed by a servo drive which is connected to the physical electrical drive system. The proposed setup functions as a hardware-in-the-loop simulator and can be easily adjusted to simulate any drivetrains without additional cost.

  • 126372.
    Zhao, Shuqi
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Self-Adaptive Algorithm for Warehouse Truck Speed Measurement with Accelerometer2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Warehouse trucks are now a practical equipment for lifting and moving

    goods in warehouses. The working situation for warehouse trucks

    is complicated. Spilling of machine oil or liquid product leads to low

    friction coefficient of the floor. Warehouse floors are normally made of

    concrete. Smooth concrete floors easily become slippery with liquid on

    the surface. With several tons of load on the fork, the braking distance is

    longer. An Anti-lock Braking System(ABS) for the truck control system

    is needed concerning the safety of the operator and people surrounding

    the truck. The warehouse truck braking is realized by controlling the

    motor torque. In order to control the torque, the truck wheel slip ratio

    is needed. With an accurate slip ratio, the control system will have

    accurate information regarding the vehicle status.

    To calculate the slip ratio, both the vehicle speed and wheel speed is

    needed. The wheel speed is derived from the motor speed. The vehicle

    speed is the challenge of this project. For normal passenger vehicles,

    sensors are installed on the trailer wheel where no slip occurs. In this

    case, the requirement is to use a lower number of sensors. There are

    two reasons of this requirement. It reduces the installation complexity

    and the cost of the control system.

    According to the literature study, a sensorless ABS system is impossible

    realize. Without sensor, it is not possible to estimate the vehicle

    status. One accelerometer is used in this project. An algorithm

    is designed and implemented in MATLAB. This algorithm solves the

    problem with zero-point drifting. Additional features are also added to

    the algorithm. The algorithm is a self-adaptive algorithm. It operates

    independently of the installation position of the accelerometer, without

    additional sensors. The result of the experiment with real measurements

    is very good. Future work on how to rewrite the algorithm from MATLAB

    programming to C programming is suggested in the end. Methods

    of implementation of the algorithm are also recommended.

  • 126373.
    Zhao, Tao
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Conifer chemical defense: Rugulation of bark beetle colonization and pheromone emission2011Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Terpenes and phenols are of importance in conifer defense against insects and pathogens. Knowledge about tree chemical defense is vital for developing practical methods to maintain healthy forests. With the aims of characterizing the defensive chemical induction in Norway spruce Picea abies and demonstrating its ecological function to spruce bark beetle Ips typographus, we measured the terpenoid and phenolic content in the bark of mature Norway spruce trees suffering windstorm, inoculated with Ceratocystis polonica, or treated with methyl jasmonate (MeJA), and investigated the colonization and pheromone emission of I. typographus.

    All three stressors altered the chemical profile in the bark of Norway spruce. Trees damaged by windstorm had lower proportions of (+)-3-carene and two unidentified stilbenes, and a higher taxifolin glycoside content than trees without apparent windstorm damage; C. polonica inoculation induced extremely strong quantitative terpene accumulation in the wound reaction zone, but only increased the levels of (+)-3-carene, sabinene and terpinolene in the bark near the reaction zone; MeJA treatment generally elicited quantitative terpene accumulation, but the induction differed extensively between individual trees. In addition, logs from MeJA-treated tree showed much stronger wounding response compared to control logs.

    The chemical profile of Norway spruce affected the colonization and pheromone emission of I. typographus. In response to fungal inoculation, terpene present in the reaction zone inhibited the colonization of I. typographus in a dose-dependent manner. Host defense elicited by MeJA treatment reduced emissions of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two key aggregation pheromone components of I. typographus, and altered the ratio between the two components.

  • 126374.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Axelsson, Karolin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Krokene, P.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fungal Symbionts of the Spruce Bark Beetle Synthesize the Beetle Aggregation Pheromone 2-Methyl-3-buten-2-ol2015In: Journal of Chemical Ecology, ISSN 0098-0331, E-ISSN 1573-1561Article in journal (Refereed)
    Abstract [en]

    Tree-killing bark beetles depend on aggregation pheromones to mass-attack their host trees and overwhelm their resistance. The beetles are always associated with phytopathogenic ophiostomatoid fungi that probably assist in breaking down tree resistance, but little is known about if or how much these fungal symbionts contribute to the beetles’ aggregation behavior. In this study, we determined the ability of four major fungal symbionts of the spruce bark beetle Ips typographus to produce beetle aggregation pheromones. The fungi were incubated on Norway spruce Picea abies bark, malt agar, or malt agar amended with 0.5 % 13C glucose. Volatiles present in the headspace of each fungus were analyzed for 7 days after incubation using a SPME autosampler coupled to a GC/MS. Two Grosmannia species (G. penicillata and G. europhioides) produced large amounts of 2-methyl-3-buten-2-ol (MB), the major component in the beetles’ aggregation pheromone blend, when growing on spruce bark or malt agar. Grosmannia europhioides also incorporated 13C glucose into MB, demonstrating that the fungi can synthesize MB de novo using glucose as a carbon source. This is the first clear evidence that fungal symbionts of bark beetles can produce components in the aggregation pheromone blend of their beetle vectors. This provides new insight into the possible ecological roles of fungal symbionts in bark beetle systems and may deepen our understanding of species interactions and coevolution in these important biological systems.

  • 126375.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Eerbilgin, Nadir
    Krokene, Paal
    Host resistance elicited by methyl jasmonate reduces emission of aggregation pheromones by the spruce bark beetle: Ips typographus2011In: Oecologia, ISSN 0029-8549, E-ISSN 1432-1939, Vol. 167, no 3, p. 691-699Article in journal (Refereed)
    Abstract [en]

    We treated Norway spruce (Picea abies) stems with methyl jasmonate (MeJA) to determine possible quantitative and qualitative effects of induced tree defenses on pheromone emission by the spruce bark beetle Ips typographus. We measured the amounts of 2-methyl-3-buten-2-ol and (S)-cis-verbenol, the two main components of the beetle's aggregation pheromone, released from beetle entrance holes, along with phloem terpene content and beetle performance in MeJA-treated and untreated Norway spruce logs. As expected, phloem terpene levels were higher and beetle tunnel length was shorter (an indication of poor performance) in MeJA-treated logs relative to untreated logs. Parallel to the higher phloem terpene content and poorer beetle performance, beetles in MeJA-treated logs released significantly less 2-methyl-3-buten-2-ol and (S)-cis-verbenol, and the ratio between the two pheromone components was significantly altered. These results suggest that host resistance elicited by MeJA application reduces pheromone emission by I. typographus and alters the critical ratio between the two main pheromone components needed to elicit aggregation. The results also provide a mechanistic explanation for the reduced performance and attractivity observed in earlier studies when bark beetles colonize trees with elicited host defenses, and extend our understanding of the ecological functions of conifer resistance against bark beetles.

  • 126376.
    Zhao, Tao
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Ganji, Suresh
    Schiebe, Christian
    Bohman, Bjorn
    Weinstein, Philip
    Krokene, Paal
    Borg-Karlson, Anna-Karin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Unelius, C. Rikard
    Convergent evolution of semiochemicals across Kingdoms: bark beetles and their fungal symbionts2019In: The ISME Journal, ISSN 1751-7362, E-ISSN 1751-7370, Vol. 13, no 6, p. 1535-1545Article in journal (Refereed)
    Abstract [en]

    Convergent evolution of semiochemical use in organisms from different Kingdoms is a rarely described phenomenon. Tree-killing bark beetles vector numerous symbiotic blue-stain fungi that help the beetles colonize healthy trees. Here we show for the first time that some of these fungi are able to biosynthesize bicyclic ketals that are pheromones and other semiochemicals of bark beetles. Volatile emissions of five common bark beetle symbionts were investigated by gas chromatography-mass spectrometry. When grown on fresh Norway spruce bark the fungi emitted three well-known bark beetle aggregation pheromones and semiochemicals (exo-brevicomin, endo-brevicomin and trans-conophthorin) and two structurally related semiochemical candidates (exo-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane and endo-1,3-dimethyl-2,9-dioxabicyclo[3.3.1]nonane) that elicited electroantennogram responses in the spruce bark beetle Ips typographus. When grown on malt agar with C-13 D-Glucose, the fungus Grosmannia europhioides incorporated C-13 into exo-brevicomin and trans-conophthorin. The enantiomeric compositions of the fungus-produced ketals closely matched those previously reported from bark beetles. The production of structurally complex bark beetle pheromones by symbiotic fungi indicates cross-kingdom convergent evolution of signal use in this system. This signaling is susceptible to disruption, providing potential new targets for pest control in conifer forests and plantations.

  • 126377.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Krokene, Paal
    Björklund, Niklas
    Långström, Bo
    Solheim, Halvor
    Christiansen, Erik
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    The influence of Ceratocystis polonica inoculation and methyl jasmonate application on terpene chemistry of Norway spruce, Picea abies2010In: Phytochemistry, ISSN 0031-9422, E-ISSN 1873-3700, Vol. 71, no 11-12, p. 1332-1341Article in journal (Refereed)
    Abstract [en]

    Constitutive and inducible terpene production is involved in conifer resistance against bark beetles and their associated fungi. In this study 72 Norway spruce (Picea abies) were randomly assigned to methyl jasmonate (MJ) application, inoculation with the bluestain fungus Ceratocystis polonica, or no-treatment control. We investigated terpene levels in the stem bark of the trees before treatment, 30 days and one year after treatment using GC-MS and two-dimensional GC (2D-GC) with a chiral column, and monitored landing and attack rates of the spruce bark beetle, Ips typographus, on the trees by sticky traps and visual inspection. Thirty days after fungal inoculation the absolute amount and relative proportion of (+)-3-carene, sabinene, and terpinolene increased and (+)-alpha-pinene decreased. Spraying the stems with MJ tended to generally increase the concentration of most major terpenes with minor alteration to their relative proportions, but significant increases were only observed for (-)-beta-pinene and (-)-limonene. Fungal inoculation significantly increased the enantiomeric ratio of (-)-alpha-pinene and (-)-limonene 1 month after treatment, whereas MJ only increased that of (-)-limonene. One year after treatment, both MJ and fungal inoculation increased the concentration of most terpenes relative to undisturbed control trees, with significant changes in (-)-beta-pinene, (-)-beta-phellandrene and some other compounds. Terpene levels did not change in untreated stem sections after treatment, and chemical induction by MJ and C polonica thus seemed to be restricted to the treated stem section. The enantiomeric ratio of (-)-alpha-pinene was significantly higher and the relative proportions of ( -)-limonene were significantly lower in trees that were attractive to bark beetles compared to unattractive trees. One month after fungal inoculation, the total amount of diterpenes was significantly higher in putative resistant trees with shorter lesion lengths than in putative susceptible trees with longer lesions. Thus, terpene composition in the stem bark may be related to resistance of Norway spruce against I. typographus and C. polonica.

  • 126378.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Krokene, Paal
    Hu, Jiang
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Christiansen, Erik
    Björklund, Niklas
    Långström, Bo
    Solheim, Halvor
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Induced Terpene Accumulation in Norway Spruce Inhibits Bark Beetle Colonization in a Dose-Dependent Manner2011In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 10, p. e26649-Article in journal (Refereed)
    Abstract [en]

    Background: Tree-killing bark beetles (Coleoptera, Scolytinae) are among the most economically and ecologically important forest pests in the northern hemisphere. Induction of terpenoid-based oleoresin has long been considered important in conifer defense against bark beetles, but it has been difficult to demonstrate a direct correlation between terpene levels and resistance to bark beetle colonization. Methods: To test for inhibitory effects of induced terpenes on colonization by the spruce bark beetle Ips typographus (L.) we inoculated 20 mature Norway spruce Picea abies (L.) Karsten trees with a virulent fungus associated with the beetle, Ceratocystis polonica (Siem.) C. Moreau, and investigated induced terpene levels and beetle colonization in the bark. Results: Fungal inoculation induced very strong and highly variable terpene accumulation 35 days after inoculation. Trees with high induced terpene levels (n = 7) had only 4.9% as many beetle attacks (5.1 vs. 103.5 attacks m(-2)) and 2.6% as much gallery length (0.029 m m(-2) vs. 1.11 m m(-2)) as trees with low terpene levels (n = 6). There was a highly significant rank correlation between terpene levels at day 35 and beetle colonization in individual trees. The relationship between induced terpene levels and beetle colonization was not linear but thresholded: above a low threshold concentration of similar to 100 mg terpene g(-1) dry phloem trees suffered only moderate beetle colonization, and above a high threshold of similar to 200 mg terpene g(-1) dry phloem trees were virtually unattacked. Conclusion/Significance: This is the first study demonstrating a dose-dependent relationship between induced terpenes and tree resistance to bark beetle colonization under field conditions, indicating that terpene induction may be instrumental in tree resistance. This knowledge could be useful for developing management strategies that decrease the impact of tree-killing bark beetles.

  • 126379.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Långström, Bo
    Performance of Tomicus yunnanensis and Tomicus minor (Col., Scolytinae) on Pinus yunnanensis and Pinus armandii in Yunnan, Southwestern China2012In: Psyche, ISSN 0033-2615, p. 363767-Article in journal (Refereed)
    Abstract [en]

    Pine shoot beetles, Tomicus yunnanensis Kirkendall and Faccoli and Tomicus minor Hartig (Col., Scolytinae), have been causing substantial mortality to Yunnan pine (Pinus yunnanensis Franch) in Yunnan, southwestern China, whereas only a few Armand pine (Pinus armandii Franch) were attacked by the beetles. In order to evaluate the suitability of P. armandii as host material for the two Tomicus, adults of both Tomicus were caged on living branches and felled logs of the two pines during shoot feeding and trunk attack phase, respectively. More beetles survived on the living branches of P. yunnanensis than on P. armandii. Tomicus yunnanensis and T. minor produced similar progeny in the logs of the two pines. The sex ratio and developmental period were not affected by host species, but the brood beetles emerging from Armand pine weighed less than those from Yunnan pine, suggesting that P. armandii are less suitable to be host of T. yunnanensis and T. minor.

  • 126380.
    Zhao, Tao
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Solheim, Halvor
    Långström, Bo
    Borg-Karlson, Anna-Karin
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Storm-induced tree resistance and chemical differences in Norway spruce (Picea abies)2011In: Annals of Forest Science, ISSN 1286-4560, E-ISSN 1297-966X, Vol. 68, no 3, p. 657-665Article in journal (Refereed)
    Abstract [en]

    Windstorm is one of the most destructive environmental disturbance factors on forests, but its influence on conifer defense chemistry and susceptibility to insects and diseases is not well understood.

  • 126381. 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.

  • 126382.
    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.

  • 126383.
    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.

  • 126384.
    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.

  • 126385.
    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.

  • 126386.
    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.

  • 126387.
    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.

  • 126388.
    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)
  • 126389.
    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.

  • 126390.
    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.

  • 126391.
    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).

  • 126392.
    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.

  • 126393.
    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.

  • 126394.
    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)
  • 126395.
    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.

  • 126396.
    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.

  • 126397.
    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.

  • 126398.
    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.

  • 126399.
    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.

  • 126400.
    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. 

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