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  • 121251.
    Zhang, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Jin, Lebing
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Evaluation of Modular Integrated Electric Drive Concepts for Automotive Traction Applications2017In: IEEE Transactions on Transportation ElectrificationArticle in journal (Other academic)
    Abstract [en]

    In order to achieve compactness and realize a certain level of fault tolerance in integrated motor drives, a number of integrated modular motor drive concepts have been proposed in recent years. In this paper, converter topology candidates suitable for an IMMD are considered with particular focus on the stacked polyphase bridges cconverter; the parallel-connected polyphase bridges converter, and the modular high frequency converter. A comparative evaluation of the studied topologies is presented and discussed in terms of machine design aspects, power losses, capacitor energy storage requirements, costs, and cell redundancy using the conventional two-level three-phase drive system as reference.

  • 121252. Zhang, Hui
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Zhang, Duo
    Zhang, Liang
    Kapilashrami, Mukes
    Sun, Tao
    Glans, Per-Anders
    Zhu, Junfa
    Zhong, Jun
    Hu, Zheng
    Guo, Jinghua
    Sun, Xuhui
    Comprehensive electronic structure characterization of pristine and nitrogen/phosphorus doped carbon nanocages2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 103, p. 480-487Article in journal (Refereed)
    Abstract [en]

    The electronic structures of carbon nanocages (CNCs) and nitrogen/phosphorus doped carbon nanocages (N-CNCs/P-CNCs) have been studied by X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS), X-ray emission spectroscopy (XES) and resonant X-ray emission spectroscopy (RXES). The doping configurations for N/P dopants are identified from the experiments. The results have shown that there are three major doping configurations for nitrogen but only one doping configuration for phosphorus. The nitrogen doping reveals the complex coexistence of graphite-like, pyridine-like and pyrrole-like configurations that are proved by density functional theory (DFT) simulations, while the phosphorus doping presents only the "graphite-like" configuration. The different configuration profiles result in less atomic structure ordering of N-CNCs than that of P-CNCs. XAS spectra obtained from both surface and bulk sensitive detection suggest different chemical environments between the interior and shell for all types of nanocages. The electronic structure modifications show significant difference between nitrogen and phosphorus doping from the DOS calculations. (C) 2016 Elsevier Ltd. All rights reserved.

  • 121253.
    Zhang, Hui
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Evaluation of winding arrangements in electric machinery for modular electric drives2016In: 2016 IEEE 8th International Power Electronics and Motion Control Conference, IPEMC-ECCE Asia 2016, IEEE conference proceedings, 2016, p. 2820-2825Conference paper (Refereed)
    Abstract [en]

    This paper considers different winding connection configurations for a modular electric drive based on series/ parallel connected polyphase bridges converter. Suitable stator winding connection configurations are identified to adapt to the converter topologies considered. Particular focus is put on the post-fault performance. Selected winding layouts are evaluated using 2D-FEM simulations.

  • 121254.
    Zhang, Hui
    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.
    An iterative FEA-based approach for the design of fault-tolerant IPM-FSCW machines2015In: 2015 17TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'15 ECCE-EUROPE), IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    This paper presents an iterative finite-element analysis (FEA) approach for the design of integrated electric drives comprising of interior permanent magnet fractional-slot concentrated winding (IPM-FSCW) machines and the stacked poly-phase bridges (SPB) converter. Particular focus is put on fault tolerance to handle a shorted converter submodule and the level of fault tolerance versus compactness (torque density) and power factor is quantified in the form of a case study considering a 30 kW, 2000 rpm machine.

  • 121255.
    Zhang, Hui
    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.
    On fault tolerance for IPM-FSCW machines adopting a modular converter2014In: 2014 17th International Conference on Electrical Machines and Systems, ICEMS 2014, 2014, p. 1633-1638Conference paper (Refereed)
    Abstract [en]

    This paper investigates the fault-tolerant capability of a number of 30 kW permanent magnet (PM) machines with fractional-slot concentrated windings (FSCWs) when connected to two types of modular type converters recently proposed in the literature. Due to the strong PM rotor magnetization when using NdFeB-type magnets, the resulting short-circuit currents during a converter submodule short-circuit was found to be larger than the rated current which, potentially, may cause the machine to overheat. Reducing the PM rotor magnetization will reduce the short-circuit current but also affect the constant power speed range (CPSR). The results further highlight the importance of a tailored design specification when designing FSCW PM machines in automotive applications.

  • 121256.
    Zhang, Hui
    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.
    Norrga, Staffan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Harnefors, Mojgan
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Jin, Lebing
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Machine design considerations for an MHF/SPB-converter based electric drive2014In: 2014 The 40th Annual Conference of the IEEE Industrial Electronics Society, IECON 2014, 2014, p. 3849-3854Conference paper (Refereed)
    Abstract [en]

    This paper identifies suitable phase/slot/pole combinationsfor fractional-slot concentrated winding (FSCW)permanent-magnet machines when forming an integrated electricdrive together with a modular high frequency (MHF) converteror a stacked polyphase bridge (SPB) converter.

  • 121257.
    Zhang, Huimin
    et al.
    School of Electro-Mechanical Engineering, Xidian University, Xi'an China.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Li, Zhiwu
    School of Electro-Mechnical Engineering, Xidian University, Xi'an China.
    A learning-based synthesis approach to the supremal nonblocking supervisor of discrete-event systems2018In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 63, no 10, p. 3345-3360Article in journal (Refereed)
    Abstract [en]

    The paper presents a novel approach to synthesize supremal nonblocking supervisors of discrete-event systems (DES), when the automaton models of specifications are not available. Extending the L* learning algorithm, an S* algorithm is developed to infer a tentatively correct supervisor. If the tentatively correct supervisor is nonblocking, it is indeed the supremal nonblocking supervisor with respect to the plant and specifications. Otherwise, the blocking automaton is regarded as a new plant, and the specification is the nonblocking property. Then, the supremal nonblocking supervisor with respect to the new problem is computed using supervisory control theory of DES. Two simplification rules are introduced to the S* algorithm to decrease the computational cost. Finally, the S* algorithm is implemented based on the LearnLib framework, and experiments are performed to verify the proposed approach.

  • 121258. Zhang, Huimin
    et al.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Machine Design (Div.). KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Embedded Control Systems. KTH, School of Industrial Engineering and Management (ITM), Centres, Innovative Centre for Embedded Systems, ICES. KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Li, Zhiwu
    Control of Black-Box Embedded Systems by Integrating Automaton Learning and Supervisory Control Theory of Discrete-Event Systems2019In: IEEE Transactions on Automation Science and Engineering, ISSN 1545-5955, E-ISSN 1558-3783, p. 1-14, article id 10.1109/TASE.2019.2929563Article in journal (Refereed)
    Abstract [en]

    The paper presents an approach to the control of black-box embedded systems by integrating automaton learning and supervisory control theory (SCT) of discrete-event systems (DES), where automaton models of both the system and requirements are unavailable or hard to obtain. First, the system is tested against the requirements. If all the requirements are satisfied, no supervisor is needed and the process terminates. Otherwise, a supervisor is synthesized to enforce the system to satisfy the requirements. To apply SCT and automaton learning technologies efficiently, the system is abstracted to be a finite-discrete model. Then, a C* learning algorithm is proposed based on the classical L* algorithm to infer a Moore automaton describing both the behavior of the system and the conjunctive behavior of the system and the requirements. Subsequently, a supervisor for the system is derived from the learned Moore automaton and patched on the system. Finally, the controlled system is tested again to check the correctness of the supervisor. If the requirements are still not satisfied, a larger Moore automaton is learned and a refined supervisor is synthesized. The whole process iterates until the requirements hold in the controlled system. The effectiveness of the proposed approach is manifested through two realistic case studies.

  • 121259.
    Zhang, Huimin
    et al.
    School of Electro-Mechanical Engineering, Xidian University.
    Feng, Lei
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Wu, Naiqi
    Institute of Systems Engineering, Macau University of Science and Technology.
    Li, Zhiwu
    School of Electro-Mechanical Engineering, Xidian University.
    Integration of Learning-Based Testing and Supervisory Control for Requirements Conformance of Black-Box Reactive Systems2018In: IEEE Transactions on Automation Science and Engineering, ISSN 1545-5955, E-ISSN 1558-3783, Vol. 15, no 1, p. 2-15Article in journal (Refereed)
    Abstract [en]

    A fundamental requirement of the supervisory control theory (SCT) of discrete-event systems is a finite automaton model of the plant. The requirement does not hold for black-box systems whose source code and logical model are not accessible. To apply SCT to black-box systems, we integrate automaton learning technology with SCT and apply the new method to improve the requirements conformance of software reuse. If the reused software component does not satisfy a requirement, the method adds a supervisor component to prevent the black-box system from reaching ''faulty sections.'' The method employs learning-based testing (LBT) to verify whether the reused software meets all requirements in the new context. LBT generates a large number of test cases and iteratively constructs an automaton model of the system under test. If the system fails the test, the learned model is applied as the plant model for control synthesis using SCT. Then, the supervisor is implemented as an executable program to monitor and control the system to follow the requirement. Finally, the integrated system, including the supervisory program and the reused component, is tested by LBT to assure the satisfiability of the requirement. This paper makes two contributions. First, we innovatively integrate LBT and SCT for the control synthesis of black-box reactive systems. Second, software component reuse is still possible even if it does not satisfy user requirements at the outset.

  • 121260. Zhang, Huotian
    et al.
    Liu, Yiting
    Lu, Haizhou
    Deng, Wan
    Yang, Kang
    Deng, Zunyi
    Zhang, Xingmin
    Yuan, Sijian
    Wang, Jiao
    Niu, Jiaxin
    Zhang, Xiaolei
    Jin, Qingyuan
    Feng, Hongjian
    Zhan, Yiqiang
    Zheng, Lirong
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits. Fudan University, China.
    Reversible air-induced optical and electrical modulation of methylammonium lead bromide (MAPbBr(3)) single crystals2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 111, no 10, article id 103904Article in journal (Refereed)
    Abstract [en]

    The photoluminescence (PL) variations of organic-inorganic hybrid lead halide perovskites in different atmospheres are well documented, while the fundamental mechanism still lacks comprehensive understandings. This study reports the reversible optical and electrical properties of methylammonium lead bromide (MAPbBr(3) or CH3NH3PbBr3) single crystals caused by air infiltration. With the change in the surrounding atmosphere from air to vacuum, the PL intensity of perovskite single crystals decreases, while the conductivity increases. By means of first-principles computational studies, the shallow trap states are considered as key elements in PL and conductivity changes. These results have important implications for the characterization and application of organic-inorganic hybrid lead halide perovskites in vacuum.

  • 121261.
    Zhang, Igor Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Jiang, Jun
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Gao, Bin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xu, Xin
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    The RRS-PBC Method: Bridge Finite Cluster to Crystalline Bulk SolidIn: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448Article in journal (Other academic)
  • 121262.
    Zhang, Igor Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. Fudan University Shanghai, China.
    Jun, Jiang
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. University of Science and Technology of China Hefei, China.
    Bin, Gao
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xin, Xu
    Fudan University Shanghai, China.
    Yi, Luo
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology. University of Science and Technology of China Hefei, China.
    RRS-PBC: a molecular approach for periodic systems2014In: Science China Chemistry, ISSN 1674-7291, Vol. 57, no 10, p. 1399-1404Article in journal (Refereed)
    Abstract [en]

    Technically, when dealing with a perfect crystal, methods in k-(reciprocal) space that impose periodic boundary conditions (PBC) in conjunction with plane-wave basis sets are widely used. Chemists, however, tend to think of a solid as a giant molecule, which offers a molecular way to describe a solid by using a finite cluster model (FCM). However, FCM may fail to simulate a perfect crystal due to its inevitable boundary effects. We propose an RRS-PBC method that extracts the k-space information of a perfect crystalline solid out of a reduced real space (RRS) of an FCM. We show that the inevitable boundary effects in an FCM are eliminated naturally to achieve converged high-quality band structures.

  • 121263.
    Zhang, Igor Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Xu, Xin
    State Key Laboratory of Physical Chemistry of Solid Surfaces, College of Chemistry and Chemical Engineering, Xiamen University.
    Basis set dependence of the doubly hybrid XYG3 functional2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 133, no 10, p. 104105-Article in journal (Refereed)
    Abstract [en]

    In the present study, we investigated the basis set dependence of XYG3, a newly developed doubly hybrid functional [Y. Zhang, X. Xu, and W. A. Goddard III, Proc. Natl. Acad. Sci. U.S.A. 106, 4963 (2009)], in prediction of (1) heats of formation (HOFs), (2) bond dissociation enthalpies (BDEs), (3) reaction barrier heights (RBHs), and (4) nonbonded interactions (NBIs). We used basis sets of triple-zeta quality starting from 6-311+G(d,p) with increasing completeness of the polarization functions to the largest Pople-type basis set 6-311++G(3df,3pd) and found that there was a continued improvement with larger basis sets. We showed that while HOF predictions were prone to basis set deficiencies, the basis set dependences in calculating BDEs, RBHs, and NBIs were mild. All of them converged fast with the increase of basis set size. We extended XYG3 to propose the XYG3o functional which was specifically optimized for a particular basis set in order to enhance its performance when using basis set of moderate size. With the 6-311+G(2df,p) basis set, XYG3o led to MADs of 2.56 kcal/mol for HOFs of the G3/99 set, 1.17 kcal/mol for BDEs of the BDE92/07 set, 1.11 kcal/mol for RBHs of the NHTBH38/04 and HTBH38/04 sets, and 0.40 kcal/mol for NBIs of the NCIE31/05 set, being comparable to those obtained by using XYG3/6-311++G(3df,3pd).

  • 121264.
    Zhang, Igor Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry.
    Xu, Xin
    XYG3s: Speedup of the XYG3 fifth-rung density functional with scaling-all-correlation method2010In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 132, no 19, p. 194105-Article in journal (Refereed)
    Abstract [en]

    Recently, we proposed a new version of doubly hybrid functional, XYG3 [Y. Zhang, X. Xu, and W. A. Goddard III, Proc. Natl. Acad. Sci. U.S.A. 106, 4963 (2009)], which not only has a nonlocal orbital-dependent component in the exchange term (Hartree-Fock-like exchange), but also contains information about the unoccupied Kohn-Sham orbitals in the correlation part (PT2 double excitation). In the present work, we examine the frozen-core approximation and Truhlar's scaling-all-correlation (SAC) method in order to accelerate the PT2 evaluations. We adopt the SAC idea and extend XYG3 to propose XYG3s that uses a uniform scaling parameter for the PT2 correlation. We conclude that XYG3s is both fast and accurate for thermochemistry, bond dissociation enthalpies, reaction barrier heights, and nonbonded interactions of main group molecules. In addition, the accuracy remains nearly constant with system size.

  • 121265.
    Zhang, Igor Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Wu, Jianming
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xu, Xin
    Accurate Bond Dissociation Enthalpies by Using Doubly Hybrid XYG3 Functional2011In: Journal of Computational Chemistry, ISSN 0192-8651, E-ISSN 1096-987X, Vol. 32, no 9, p. 1824-1838Article in journal (Refereed)
    Abstract [en]

    In this work, we examine the performance of XYG3, a newly developed doubly hybrid density functional (Zhang, Xu, and Goddard III, Proc Natl Acad Sci USA 2009, 106, 4963), to calculate covalent bond dissociation enthalpy (BDE). We use 5 atoms, 32 molecular radicals, and 116 closed-shell molecules to set up 142 bond dissociation reactions. For the total of 148 heats of formation (HOFs) and 142 BDEs, XYG3 leads to mean absolute deviations (MADs) of 1.45 and 1.87 kcal/mol, respectively. In comparison with some other functionals, MADs for HOFs are 2.31 (M06-2X), 2.98 (B2PLYP-D), 3.04 (BMK), 3.96 (B3LYP), 4.47 (B2PLYP), 5.42 (B2GP-PLYP), 6.46 (PBE0), and 29.93 kcal/mol (B3P86), and the corresponding errors for BDEs are 2.06 (M06-2X), 2.25 (BMK), 2.51 (B2PLYP-D), 2.89 (B2GP-PLYP), 3.30 (B3P86), 3.44 (B2PLYP), 3.87 (PBE0), and 6.14 kcal/mol (B3LYP). (C) 2011 Wiley Periodicals, Inc. J Comput Chem 32: 1824-1838, 2011

  • 121266.
    Zhang, Igor Ying
    et al.
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Wu, Jianming
    Luo, Yi
    KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512).
    Xu, Xin
    Trends in R-X Bond Dissociation Energies (R-center dot = Me, Et, i-Pr, t-Bu, X-center dot = H, Me, Cl, OH)2010In: Journal of Chemical Theory and Computation, ISSN 1549-9618, E-ISSN 1549-9626, Vol. 6, no 5, p. 1462-1469Article in journal (Refereed)
    Abstract [en]

    Trends for R X bond dissociation energies have been examined with density functional methods of B3LYP, BMK, M06-2X, MC3MPW, B2PLYP, MCG3-MPW, and XYG3, as well as 03, MCG3/3, G3X, and 04 theories as functions of alkylation (i.e., IT = Me, Et, i-Pr, (-Bu) and X' substitution (i.e., X' = H, Me, Cl, OH). The results highlight the physical origin of success or failure of each method and demonstrate the good agreement with experimental results for G4, MCG3-MPW, and XYG3. The last holds great promise as a reliable method that is applicable to larger systems.

  • 121267. Zhang, J.
    et al.
    Ellison, A.
    Danielsson, O.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Henry, A.
    Janzen, E.
    Epitaxial growth of 4H SiC in a vertical hot-wall CVD reactor: Comparison between up- and down-flow orientations2002In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 241, no 4, p. 421-430Article in journal (Refereed)
    Abstract [en]

    The CVD growth of 4H SiC is investigated in a vertical hot-wall reactor in both up-flow (the chimney reactor) and down-flow (the inverted chimney) orientations. The growth rate and the nitrogen doping are studied for comparison. Under the investigated process conditions the growth mechanism is shown to be similar in these two reactor orientations. Only slight difference is observed in the temperature effect depending on the flow direction. Both reactor types have produced epilayers with high growth rates (10-35 mum/h) and low residual n-type doping (low 10(16) down to mid 10(13) cm(-3)) with comparable morphology. Dimensionless flow numbers are used to provide a qualitative analysis of the flow and heat transfer mechanisms in the vertical hot-wall system. Two-dimensional numerical simulation in a cylindrical geometry is conducted to demonstrate the flow and temperature profile with selected process parameters. Comparison of the experimental results in the chimney and the inverted chimney is performed to give insight into the fast epitaxial hot-wall growth.

  • 121268. Zhang, J
    et al.
    Ellison, A
    Henry, A
    Linnarsson, M K
    KTH, School of Information and Communication Technology (ICT).
    Janzen, E
    Nitrogen impurity incorporation behavior in a chimney HTCVD process: pressure and temperature dependence1999In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 61-2, p. 151-154Article in journal (Refereed)
    Abstract [en]

    Experimental results are presented for residual nitrogen incorporation in both Si and C face 4H SiC epilayers using the high temperature chemical vapor deposition (HTCVD) process in a chimney reactor. The influence of total pressure, process temperature and input C/Si ratio on the residual nitrogen doping is studied. The results are further confirmed by intentional nitrogen doping experiments. Activation energies of 200 kcal/mol for Si face and 108 kcal/mol for C face samples are obtained for nitrogen incorporation. Possible incorporation mechanisms related to both surface and gas phase kinetics are discussed. (C) 1999 Elsevier Science S.A. All rights reserved.

  • 121269. Zhang, J.
    et al.
    Ellison, A.
    Henry, A.
    Linnarsson, Margareta K.
    KTH, Superseded Departments, Microelectronics and Information Technology, IMIT.
    Janzen, E.
    Nitrogen incorporation during 4H-SiC epitaxy in a chimney CVD reactor2001In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 226, no 03-feb, p. 267-276Article in journal (Refereed)
    Abstract [en]

    Nitrogen incorporation is studied during epitaxial chemical vapour deposition (CVD) of 4H-SiC in a vertical, hot-wall CVD reactor. The nitrogen doping dependencies on input C/Si ratio, growth temperature and process pressure are investigated under the process conditions leading to growth rates in the range of 15-30 mum/h. The nitrogen incorporation is observed to be a thermally activated process with a higher apparent activation energy for the Si-face than for the C-face. The site-competition principle is well followed at C/Si ratios higher than 0.3, whereas the nitrogen doping becomes less sensitive to the C/Si ratio on both the Si- and the C-faces at C/Si ratios below 0.3. The pressure has a strong effect on the nitrogen incorporation efficiency, allowing lower doping at the lower pressure. The influence of the growth parameters on the nitrogen incorporation is closely related both to the epitaxial growth mechanisms and to the surface kinetics on the different polarity SiC faces. The doping mechanisms are analysed taking into account the gas-phase chemistry and the surface kinetics.

  • 121270. Zhang, J. G.
    et al.
    Lin, Y. J.
    Hillert, Mats
    KTH, Superseded Departments, Materials Science and Engineering.
    Selleby, Malin
    KTH, Superseded Departments, Materials Science and Engineering.
    Shi, H. S.
    Yan, B.
    Zhang, H.
    Luo, G. M.
    Li, X. J.
    Wang, J.
    Microstructure and mechanical properties of spray formed ultrahigh-carbon steels2004In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 383, no 1, p. 45-49Article in journal (Refereed)
    Abstract [en]

    The microstructure and mechanical properties of the spray formed 1.25C-3.0Si-1.5Cr ultrahigh-carbon steel (UHCS) were described. The 1.25C-3.0Si-1.5Cr UHCS was processed by spray forming to break up carbide networks. The fine pearlites with average interlamellar spacing of 0.20 mum was observed in the as-sprayed microstructure. The ultimate tensile strength and the pearlite spacing can be related by the Hall-Petch equation. The as-sprayed 1.25C-3.0Si-1.5Cr UHCS consisting of fine lamellar pearlites has been shown to exhibit superplastic behavior at elevated temperature. The dramatic change of microstructure from fine lamellar pearlites to equiaxed grains stabilized by spheroidized particles during superplastic deformation has been observed. The estimation on the basis of thermodynamics shows that the content of chromium of 1.54 wt.% is needed to inhibit graphite formation in the l.25C-3.OSi-1.5Cr UHCS.

  • 121271. Zhang, J.
    et al.
    Guo, C.
    Liu, L.
    He, Sailing
    KTH, School of Electrical Engineering and Computer Science (EECS), Electromagnetic Engineering.
    Hong, X.
    Demonstration of a visible light communication system based on filter bank spread OFDM/OQAM2017In: Optics InfoBase Conference Papers, OSA - The Optical Society , 2017Conference paper (Refereed)
    Abstract [en]

    We propose and experimentally demonstrate a 2.2Gbit/s visible light communication system based on filter bank spread (FBS-) OFDM/OQAM. Both low peak-to-average power ratio and high diversity gain are achieved by FBS, which improves transmission performance. © 2017 OSA.

  • 121272. Zhang, J.
    et al.
    Guo, H. -W
    Wu, J.
    Gao, G. -J
    Kou, Z. -M
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Design and analysis of flexure revolute joint based on four-bar mechanism2018In: Acta Astronautica, ISSN 0094-5765, E-ISSN 1879-2030, Vol. 151, p. 420-431Article in journal (Refereed)
    Abstract [en]

    In order to avoid the stress concentration and increase rotational angle of a flexure joint, the method of partial separation of storage elements in the motion transmission elements is proposed. A type of flexure revolute joint with large rotational angle is designed based on the block approach. By setting a 4-bar mechanism as the intermediate block which connects the outer ring and the inner ring of the revolute joint, and replacing the rigid bar by a flexible beam, large rotational angles of the joint can be achieved. The basic size of the joint is designed by setting the initial and the constraint condition of the 4-bar mechanism. Then, influence analyses of the size of the linkage joint and large flexible beam on the stress, the torque, and the torsional stiffness are conducted by using nonlinear static analysis method. Based on the requirements for torque and rotational stiffness, the size of the flexure revolute joint is defined. Experiments on the joint, which can rotate 90° are conducted. 

  • 121273. Zhang, J.
    et al.
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang University, China.
    Cladding-free efficiently tunable nanobeam cavity with nanotentacles2017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 11, p. 12541-12551Article in journal (Refereed)
    Abstract [en]

    We propose a cladding-free, efficiently tunable, high-quality factor (Q) nanobeam cavity with subwavelength-period nanotentacles (NT), adequately investigate the performance of the cavity, and study the directional heat transfer. By virtue of the excellent heat transfer of Si nanotentacles, a tuning range of more than 6 nm wavelength, with 24mW and 10 KHz switching rate, and 13 μs raising time is experimentally obtained. This result is about twentyfold better than the previous work by Fegadolli [ACS Photon. 2, 470-474 (2015)]. A potential 12nm tuning range with identical power is also theoretically suggested by modifying the silicon structure. With an optimized design, these nanotentacles are demonstrated to have a minimal effect to the cavity and are available to serve as photonic waveguides. This cladding-free design, with a simple fabrication process, is comparable to other proposals in which deep etching, suspended treatment, and troublesome heterogeneousintegration may be needed. Finally but importantly, this smart design can be applied to other photonic cavities, particularly cavities such as ring/disk resonators, in which we reasonably predict a better tuning efficiency due to the thermal circulation. We believe this design is fairly suitable for applications in which light-matter interaction is of primary importance, such as sensing, particle trapping, cavity quantum electrodynamics (CQED), and III-V/Si hybrid lasers with external cavities.

  • 121274. Zhang, J.
    et al.
    Henriksson, Gunnar
    KTH, Superseded Departments, Pulp and Paper Technology.
    Johansson, G.
    Polygalacturonase is the key component in enzymatic retting of flax2000In: Journal of Biotechnology, ISSN 0168-1656, E-ISSN 1873-4863, Vol. 81, no 1, p. 85-89Article in journal (Refereed)
    Abstract [en]

    Seven commercial enzyme mixtures were tested for their ability to perform retting of flax (i.e. to separate flax fibers by partly removal of middle lamella) and were assayed for hydrolysis of xylan, cellulose and four kinds of pectin. The only activity that showed correlation to the ability to perform retting was the degradation of low esterfied pectin. A purified Aspergillus niger polygalacturonase was also shown to be able to perform retting. From this data it is hypothesized that degradation of the smooth regions (i.e, non-methylated polygalacturonase) in the middle lamella pectin is the most important step in enzymatic retting.

  • 121275. Zhang, J.
    et al.
    Henriksson, H.
    Szabo, I. J.
    Henriksson, Gunnar
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology, Wood Chemistry and Pulp Technology.
    Johansson, G.
    The active component in the flax-retting system of the zygomycete Rhizopus otyzae sb is a family 28 polygalacturonase2005In: Journal of Industrial Microbiology & Biotechnology, ISSN 1367-5435, E-ISSN 1476-5535, Vol. 32, no 10, p. 431-438Article in journal (Refereed)
    Abstract [en]

    The zygomycete Rhizopus oryzae sb is a very efficient organism for retting of flax, the initial microbiological step in the process of making linen. An extracellular polygalacturonase, when isolated could perform retting, and therefore probably is the key component in the retting system of R. oryzae. This was purified and characterized. The purified enzyme has a molecular mass of 37,436 Da from mass spectrometric determination, an isoelectric point of 8.4, and has non-methylated polygalacturonic acid as its preferred substrate. Peptide sequences indicate that the enzyme belongs to family 28, in similarity with other polygal-acturonases (EC. 3.2.1.15). It contains, however an N-terminal sequence absent in other fungal pectinases, but present in an enzyme from the phytopathogenic bacterium Ralstonia solanacearum. The biochemical background for the superior retting efficiency of R. oryzae sb is discussed.

  • 121276. Zhang, J.
    et al.
    Hong, X.
    Liu, L.
    He, Sailing
    KTH, School of Information and Communication Technology (ICT), Centres, Zhejiang-KTH Joint Research Center of Photonics, JORCEP.
    Asynchronous multiple access in visible light communication system based on DFT spread OFDM/OQAM2015In: Asia Communications and Photonics Conference, ACPC 2015, 2015Conference paper (Refereed)
    Abstract [en]

    A multiuser asynchronous visible light communication system adopting DFT spread (DFS-) OFDM/OQAM is proposed and experimentally demonstrated. Both high spectral locality and low peak-to-average power ratio are achieved with DFTS-OFDM/OQAM, which improves system's transmission performance. © 2015 OSA.

  • 121277. Zhang, J.
    et al.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Yang, L.
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, M. B.
    Vlachopoulos, N.
    Kloo, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Boschloo, G.
    Johansson, E. M. J.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, A.
    The Role of 3D Molecular Structural Control in New Hole Transport Materials Outperforming Spiro-OMeTAD in Perovskite Solar Cells2016In: Advanced Energy Materials, ISSN 1614-6832, Vol. 6, no 19, article id 1601062Article in journal (Refereed)
  • 121278. Zhang, J.
    et al.
    Johansson, Karl H.
    KTH, Superseded Departments, Signals, Sensors and Systems.
    Lygeros, J.
    Sastry, S.
    Zeno hybrid systems2001In: International Journal of Robust and Nonlinear Control, ISSN 1049-8923, E-ISSN 1099-1239, Vol. 11, no 5, p. 435-451Article in journal (Refereed)
  • 121279. Zhang, J.
    et al.
    Natarajan Arul, Murugan
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Tian, Y.
    Bertagnin, C.
    Fang, Z.
    Kang, D.
    Kong, X.
    Jia, H.
    Sun, Z.
    Jia, R.
    Gao, P.
    Poongavanam, V.
    Loregian, A.
    Xu, W.
    Ma, X.
    Ding, X.
    Huang, B.
    Zhan, P.
    Liu, X.
    Structure-Based Optimization of N-Substituted Oseltamivir Derivatives as Potent Anti-Influenza A Virus Agents with Significantly Improved Potency against Oseltamivir-Resistant N1-H274Y Variant2018In: Journal of Medicinal Chemistry, ISSN 0022-2623, E-ISSN 1520-4804, Vol. 61, no 22, p. 9976-9999Article in journal (Refereed)
    Abstract [en]

    Due to the emergence of highly pathogenic and oseltamivir-resistant influenza viruses, there is an urgent need to develop new anti-influenza agents. Herein, five subseries of oseltamivir derivatives were designed and synthesized to improve their activity toward drug-resistant viral strains by further exploiting the 150-cavity in the neuraminidases (NAs). The bioassay results showed that compound 21h exhibited antiviral activities similar to or better than those of oseltamivir carboxylate (OSC) against H5N1, H5N2, H5N6, and H5N8. Besides, 21h was 5- to 86-fold more potent than OSC toward N1, N8, and N1-H274Y mutant NAs in the inhibitory assays. Computational studies provided a plausible rationale for the high potency of 21h against group-1 and N1-H274Y NAs. In addition, 21h demonstrated acceptable oral bioavailability, low acute toxicity, potent antiviral activity in vivo, and high metabolic stability. Overall, the above excellent profiles make 21h a promising drug candidate for the treatment of influenza virus infection.

  • 121280. Zhang, J.
    et al.
    Pelton, R.
    Wågberg, Lars
    Rundlof, M.
    The effect of molecular weight on the performance of paper strength-enhancing polymers2001In: Journal of Pulp and Paper Science (JPPS), ISSN 0826-6220, Vol. 27, no 5, p. 145-151Article in journal (Refereed)
    Abstract [en]

    The influence of dextran molecular weight (77 000 to 2 000 000) on the strength of fibre-fibre bonds was investigated. A series of cationic dextrans with different molecular weights, from 77 000 to 2 000 000, was prepared and the adsorption behaviour on fibre was characterized. The maximum amount of adsorbed dextran increased with decreasing molecular weight, while the adsorbed layer thickness on colloidal silica increased with increasing molecular weight. At saturation coverage, the molecular weight of dextran did nor affect the tensile strength of handsheets made from unbeaten bleached kraft pulp. The strength improvement with polymer addition did not correspond to increased optical bonded area (opacity). The external surface of fibre accessible to dextran of molecular weight 2 000 000 was estimated as 35 m(2)/g.

  • 121281. Zhang, J.
    et al.
    Yu, Z.
    Zhang, K.
    Lu, Z.
    Jantsch, Axel
    KTH, School of Information and Communication Technology (ICT), Electronic Systems.
    Efficient distributed memory management in a multi-core H.264 decoder on FPGA2013In: 2013 International Symposium on System-on-Chip, SoC 2013 - Proceedings, IEEE Computer Society, 2013, p. 6675256-Conference paper (Refereed)
    Abstract [en]

    Memory management is a challenging issue of multicore architecture. With growing core numbers, Distributed Shared Memory (DSM) is becoming a general trend. In this paper, a DSM based multi-core architecture is explored and evaluated via an H.264 decoder application. The memory access and communication over Network-on-Chips is managed by the Data Management Engine (DME). Experimental results realized on an Altera Strati x VI show that 9-node distributed memory system increases performance by 1.5x compared to centralized memory. Moreover, the performance of proposed DSM architecture grows linearly with the number of cores deployed.

  • 121282. Zhang, Jia Ming
    et al.
    Ji, Qinglei
    State Key Laboratory for Turbulence and Complex Systems, Department of Mechanics and Engineering Science, BIC-ESAT, College of Engineering, Peking University, Beijing, 100871, China.
    Liu, Ying
    Huang, Jianyong
    Duan, Huiling
    An integrated micro-millifluidic processing system.2018In: Lab on a chip, ISSN 1473-0197, Vol. 18, no 22, p. 3393-3404Article in journal (Refereed)
    Abstract [en]

    The development of integrated microfluidic systems/platforms concerns many fields. Current remarkable integrated systems based on stacking multi-layer polydimethylsiloxane (PDMS) require complicated fabrication and operation and still remain challenging. We propose a novel micro-millifluidic processing system (MPS) comprising three core modules: a motherboard, a control panel and microfluidic chips. Fluids are handled in sub-millichannels in a motherboard and functional operations occur in microchannels in microfluidic chips. A motherboard with versatile functional units for fluid handling was monolithically fabricated via multimaterial 3D printing, which avoids multi-layer structures, and the major disadvantage of current 3D printing, i.e. low resolution, has been overcome by integrating novel microfluidic chips based on our developed maskless lithography platform. Both numerical and experimental studies were conducted to validate our system. Potential applications such as droplet generation and distribution, microfluidic mixing and simple bacterial resistance tests have been demonstrated via our MPS.

  • 121283.
    Zhang, Jian
    KTH, School of Information and Communication Technology (ICT).
    Equilibrium design for multi-channel random access networks with selfish users2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Recently, there has been increasing research in the inefficency in spectrum utilization, which is mainly caused by fixed spectrum allocation policies. There are some proposed approaches to solve this inefficiency, like Dynamic Spectrum Access (DSA), which allows users to share spectrum resources. Implementing DSA in a distributed way can avoid problems with system complexity that can arise in centralized DSA systems; however, it can create incentives for the users to behave selfishly. Selfish behavior reduces the sfficiency of the DSA system, and it causes the system to end up in one of many possible operating points, which makes the performance analysis difficult.

    In this work, we study a multichannel random access system with selfish users and we propose two mechanisms in which the access point charges users for transmissioon. We analyze the performance of these mechanisms using Game Theory. Results show that by charging users for transmission, we can reduce the possible operating points of the system to a single one. Of the two proposed mechanisms, the per-channel cost mechanism performs rather well, bringing the system sum utility close to that of scheduling systems.

  • 121284.
    Zhang, Jian
    et al.
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Poongavanam, Vasanthanathan
    Univ Southern Denmark, Dept Phys Chem & Pharm, DK-5230 Odense M, Denmark.;Uppsala Univ, Dept Chem BMC, Box 576, SE-75123 Uppsala, Sweden..
    Kang, Dongwei
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Bertagnin, Chiara
    Univ Padua, Dept Mol Med, Via Gabelli 63, I-35121 Padua, Italy..
    Lu, Huamei
    Shandong Acad Agr Sci, Inst Poultry Sci, 1 Jiaoxiao Rd, Jinan 250023, Shandong, Peoples R China..
    Kong, Xiujie
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Ju, Han
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Lu, Xueyi
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Gao, Ping
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Tian, Ye
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Jia, Haiyong
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Desta, Samuel
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Ding, Xiao
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Sun, Lin
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Fang, Zengjun
    Shandong Univ, Hosp 2, 247 Beiyuan Ave, Jinan 250033, Shandong, Peoples R China..
    Huang, Boshi
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Liang, Xuewu
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Jia, Ruifang
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Ma, Xiuli
    Shandong Acad Agr Sci, Inst Poultry Sci, 1 Jiaoxiao Rd, Jinan 250023, Shandong, Peoples R China..
    Xu, Wenfang
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Natarajan Arul, Murugan
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Loregian, Arianna
    Univ Padua, Dept Mol Med, Via Gabelli 63, I-35121 Padua, Italy..
    Huang, Bing
    Shandong Acad Agr Sci, Inst Poultry Sci, 1 Jiaoxiao Rd, Jinan 250023, Shandong, Peoples R China..
    Zhan, Peng
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Liu, Xinyong
    Shandong Univ, Sch Pharmaceut Sci, Minist Educ, Dept Med Chem,Key Lab Chem Biol, 44 West Culture Rd, Jinan 250012, Shandong, Peoples R China..
    Optimization of N-Substituted Oseltamivir Derivatives as Potent Inhibitors of Group-1 and-2 Influenza A Neuraminidases, Including a Drug-Resistant Variant2018In: Journal of Medicinal Chemistry, ISSN 0022-2623, E-ISSN 1520-4804, Vol. 61, no 14, p. 6379-6397Article in journal (Refereed)
    Abstract [en]

    On the basis of our earlier discovery of N1-selective inhibitors, the 150-cavity of influenza virus neuraminidases (NAs) could be further exploited to yield more potent oseltamivir derivatives. Among the synthesized compounds, 15b and 15c were exceptionally active against both group-1 and -2 NAs. Especially for 09N1, N2, N6, and N9 subtypes, they showed 6.80-12.47 and 1.20-3.94 times greater activity than oseltamivir carboxylate (OSC). They also showed greater inhibitory activity than OSC toward H274Y and E119V variant. In cellular assays, they exhibited greater potency than OSC toward H5N1, H5N2, H5N6, and H5N8 viruses. 15b demonstrated high metabolic stability, low cytotoxicity in vitro, and low acute toxicity in mice. Computational modeling and molecular dynamics studies provided insights into the role of R group of 15b in improving potency toward group-1 and -2 NAs. We believe the successful exploitation of the 150-cavity of NAs represents an important breakthrough in the development of more potent anti-influenza agents.

  • 121285.
    Zhang, Jianan
    KTH, School of Electrical Engineering and Computer Science (EECS).
    Anti-Islanding Protection in Distribution Grids2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The growing number of distributed generation in the electrical system increasesthe risk of unintentional islanding. Power system islanding is the eventthat a part of the grid is continuously powered by the distributed generation,while it is already electrically separated from the power grid[1]. Several consequencescan be caused by unintentional islanding, such as endangerment ofpersonnel, uncontrolled voltage and frequency operation and equipment damagedue to unsynchronised reclosing. Therefore, it’s important to detect islandingevents quickly and reliably.The main objective of this thesis was to investigate the performance ofthree passive islanding detection methods for Ellevio’s 50kV distribution network.These detection methodswere under/over voltage, under/over frequencyand rate of change of frequency (ROCOF). Aiming at the objective, a dynamicmodel was built in MATLAB/Simulink for Ellevio’s distribution network,where the three methods were implemented and applied to the DGs.Moreover, the performance of the methods was evaluated by the non detectionzone (NDZ) and detection time, and it was studied under several simulations.Firstly, a NDZ of each method was found for a Single Machine Infinite Bus(SMIB) system and compared with the results obtained in Ellevio’s network.Besides, the detection time was measured under various islanding conditionsto evaluate the response speed of the detection methods. Apart from the sensitivityand response speed, the reliability of the detection methods was alsoinvestigated because the detection methods should not mistakenly operate inthe case of non-islanding events. Thus, the load switchings and short-circuitfaults were simulated as the disturbance events to test the reliability of detectionmethods. In the end, all three methods were compared, and their advantagesand disadvantages were summarized.

  • 121286.
    Zhang, Jianbo
    KTH, School of Information and Communication Technology (ICT).
    Readout Circuits for a Z-axis Hall Sensor with Sensitivity Drift Calibration2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Hall effect magnetic sensors have gradually gained dominance in the market of magnetic sensors during the past decades. The compatibility of Hall sensors with conventional CMOS technologies makes monolithic Hall sensor microsystem possible and economic. An attractive application is the contactless current sensor by using Hall sensors to measure the magnetic field generated by the electrical current. However, Hall sensors exhibit several non-idealities, i.e., offset, noise and sensitivity drift, which limit their precision. Therefore, effective techniques to reduce these imperfections are desired.

    This thesis presents the design of a new readout scheme for Hall magnetic sensor with low offset, low noise and low sensitivity drift. The Hall sensor is realized in N-well as Hall plate and modeled in Verilog-A for the purpose of co-simulation with interface circuits. The self-calibrated system is composed of two identical Hall plates, preamplifiers and a first-order ΣΔ modulator, which can be fully integrated monolithically. Four-phase spinning current technique and chopper stabilization technique have been employed to reduce the offset and 1/fnoise of Hall platesand OTA, respectively. Integrated coils are used to generate the reference magnetic field for calibration. The preamplifiers amplify the signal and separate the Hall voltage and reference voltage. The ΣΔ modulator reduces the thermal drift by using Hall voltage as the modulator input and reference voltage as the DAC output. This new calibration technique also compensates the thermal drifts of the biasing current and readout circuits.

    The overall system is implemented in NXP140nm CMOS process with 1.8V supply. The Virtuoso/Spectre simulation results show residual drifts lower than 10ppm/ ̊C, which are 3-5 times lower than the state of the art. The input magnetic field and temperature range are ±100mT and -40 ̊C to 120 ̊C, respectively.

  • 121287. Zhang, Jiangbo
    et al.
    Hong, Yiguang
    Hu, Xiaoming
    KTH, School of Engineering Sciences (SCI), Mathematics (Dept.), Optimization and Systems Theory.
    MULTIAGENT OPINION DYNAMICS OF BOUNDED CONFIDENCE WITH NONLOCAL AGGREGATIVE INTERACTION2017In: SIAM Journal of Control and Optimization, ISSN 0363-0129, E-ISSN 1095-7138, Vol. 2017, no 55, p. -2573, article id 4Article in journal (Refereed)
    Abstract [en]

    In this paper, we propose nonlocal aggregative opinion interactions for a bounded-confidence opinion model to demonstrate the fluctuation mechanism, and then study this opinion fluctuation mechanism by both theoretical analyses and numerical simulations. In this proposed agent-based opinion model, there are stubborn agents and regular agents: while each stubborn agent never changes its opinion, a regular agent updates his/her opinion based on selected agents' opinion values and his/her confidence bound. At first, we show that the global fluctuation for opinions of regular agents occurs almost surely if and only if the confidence bound of regular agents is larger than a critical value. Next, we give an estimated probability bound of the local fluctuation for regular agent opinions when the confidence bound is sufficiently small. Finally, we provide upper and lower bounds on the fluctuation strength and the regular agent opinion mean in the case when the global fluctuation occurs almost surely.

  • 121288. Zhang, Jianhao
    et al.
    Liu, Weixi
    Shi, Yaocheng
    He, Sailing
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering. Zhejiang Provincial Key Laboratory for Sensing Technologies, Zijingang Campus, Zhejiang University, China.
    High-Q side-coupled semi-2D-photonic crystal cavity2016In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 26038Article in journal (Refereed)
    Abstract [en]

    High-Q semi-2D-photonic crystal cavities with a tapered edge and side-coupled bus waveguide are demonstrated. With a quadratic design, the unloaded cavity presents a theoretical ultrahigh quality factor up to 6.7 x 10(7) for the condition that there are mere 34 holes in the propagated direction, which is pretty close to the 2D and 1D counterpart. Combined with a side-coupled bus waveguide, an all-pass-type cavity with a loaded quality factor (Q) of over 2.4 x 10(4) and an extinction ratio over 10 dB are experimentally demonstrated. An experimental loaded Q up to 1.1 x 10(5) are also achieved by tuning the coupling between the cavity and the bus waveguide, which is much larger than any reported surface-mode cavity. This cavity is quite suitable for sensors, filters and especially optomechanical devices thanks to the mechanical stability of the cavity and flexibility of the bus waveguide.

  • 121289. Zhang, Jianjun
    et al.
    Huang, Yongming
    Wang, Jiaheng
    Ottersten, Björn
    KTH, School of Electrical Engineering (EES), Signal Processing. University of Luxembourg.
    Yang, Luxi
    Per-Antenna Constant Envelope Precoding and Antenna Subset Selection: A Geometric Approach2016In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 64, no 23, p. 6089-6104Article in journal (Refereed)
    Abstract [en]

    Constant envelope (CE) precoding can efficiently control the peak-to-average power ratio (PAPR) and improve the power efficiency of power amplifiers in large-scale antenna array systems. Antenna subset selection (ASS), combined with CE precoding, can further improve power efficiency by using a part of antennas to combine the desired signal. However, due to the inherent nonlinearity, the joint optimization of CE precoding and ASS is very challenging and satisfactory solutions are yet not available. In this paper, we present new methods for CE precoding and ASS optimization from a geometric perspective. First, we show the equivalence between the CE precoder design and a polygon construction problem in the complex plane, thus transforming the algebraic problem into a geometric problem. Aiming to minimize the computational complexity, we further transform the CE precoder design into a triangle construction problem, and propose a novel algorithm to achieve the optimal CE precoder with only linear complexity in the number of used antennas. Then, we investigate the joint optimization of ASS and CE precoding to minimize the total transmit power while satisfying the QoS requirement. Based on the geometric interpretation, we develop an efficient ASS algorithm, which, using only addition and comparison operations, is guaranteed to find the globally optimal solution and provides robustness to channel uncertainty. The complexity of the proposed ASS algorithm is at most quadratic in the number of antennas in the worst case. The optimality and superiority of the proposed geometric methods are demonstrated via numerical results.

  • 121290.
    Zhang, Jianjun
    et al.
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Huang, Yongming
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering and Computer Science (EECS), Information Science and Engineering.
    Wang, Jiaheng
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Yang, Luxi
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Energy-Efficient Cooperative Hybrid Precoding for Millimeter-wave Communication Networks2018In: 2018 IEEE Global Communications Conference, GLOBECOM 2018 - Proceedings, Institute of Electrical and Electronics Engineers (IEEE), 2018, article id 8647975Conference paper (Refereed)
    Abstract [en]

    Millimeter wave (mmwave) communication operating in the band of 30-300 GHz is promising to provide Gbps data rates owing to its abundant spectrum resource, and has attracted increasing attention. Cooperative transmission, by converting undesired interferences into useful signals, is able to further improve performance of mmwave systems. In this paper, we propose a novel cooperative transmission scheme for mmwave communication networks, where each mobile user is cooperatively served by multiple access points (APs) that use hybrid precoders. Our goal is to maximize the system energy efficiency, which leverages on a joint design of the hybrid precoders of all APs. The formulated problem is a difficult nonlinear fractional programming subject to unit modulus constraints. We propose an efficient algorithm by incorporating penalty decomposition and block coordinate descent methods. Numerical results are provided to confirm the effectiveness of the proposed algorithm and reveal some important insights.

  • 121291.
    Zhang, Jianjun
    et al.
    Southeast Univ, Natl Mobile Commun Res Lab, Nanjing 210096, Jiangsu, Peoples R China..
    Huang, Yongming
    Southeast Univ, Natl Mobile Commun Res Lab, Nanjing 210096, Jiangsu, Peoples R China..
    Yu, Tianyuan
    Sichuan Univ, Sch Elect & Informat Engn, Chengdu 210096, Sichuan, Peoples R China..
    Wang, Jiaheng
    Southeast Univ, Natl Mobile Commun Res Lab, Nanjing 210096, Jiangsu, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering (EES).
    Hybrid Precoding for Multi-Subarray Millimeter-Wave Communication Systems2018In: IEEE Wireless Communications Letters, ISSN 2162-2337, E-ISSN 2162-2345, Vol. 7, no 3, p. 440-443Article in journal (Refereed)
    Abstract [en]

    This letter studies analog and digital hybrid precoding for millimeter wave communication systems with multiple subarray architecture. To reap the benefit of multiple subarrays with less number of RF chains, subarray selection needs to be jointly optimized, which leads to a mixed integer nonlinear problem and hard to solve. To find a good solution, we propose an efficient hybrid precoding algorithm by leveraging the constraint-introducing-and-penalty (CIP) approach. Simulation results show that the spectral efficiency achieved by the proposed algorithm is larger than that of existing hybrid precoding algorithms.

  • 121292.
    Zhang, Jianjun
    et al.
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Huang, Yongming
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Zhang, Cheng
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    He, Shiwen
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Xiao, Ming
    KTH, School of Electrical Engineering (EES), Communication Theory.
    Yang, Luxi
    Southeast Univ, Sch Informat Sci & Engn, Nanjing 210096, Jiangsu, Peoples R China..
    Cooperative Multi-Subarray Beam Training in Millimeter Wave Communication Systems2017In: Globecom 2017 - 2017 IEEE Global Communications Conference, Institute of Electrical and Electronics Engineers (IEEE), 2017Conference paper (Refereed)
    Abstract [en]

    This paper studies beam training design for a codebook-based beamforming millimeter wave (mmwave) system where multiple antenna arrays are employed and each array is capable of beamforming independently. To reduce the training overhead and the complexity of subsequent beam direction search, we propose a cooperative multi-subarray beam training method. Specifically, from the perspective of excluding non-effective beam direction combinations and thus reducing search space, method and criterion of beam superposition are proposed to construct a wide beam from multiple narrow beams corresponding to multiple subarrays. Then, a cooperative multi-subarray beam training scheme is proposed based on the proposed criterion. Finally, simulation results show that the proposed scheme achieves a spectral efficiency close to that of the optimal exhaustive search scheme, while has greatly reduced training overhead and computational complexity.

  • 121293.
    Zhang, Jianrong
    KTH, School of Information and Communication Technology (ICT).
    Characterizing the Scalability of Erlang VM on Many-core Processors2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    As CPU chips integrate more processor cores, computer systems are evolving from multi-core to many-core. How to utilize them fully and efficiently is a great challenge. With message passing and native support of concurrent programming, Erlang is a convenient way of developing applications on these systems. The scalability of applications is dependent on the performance of the underlying Erlang runtime system or virtual machine (VM). This thesis presents a study on the scalability of the Erlang VM on a many-core processor with 64 cores, TILEPro64. The purpose is to study the implementation of parallel Erlang VM, investigate its performance, identify bottlenecks and provide optimization suggestions. To achieve this goal, the VM is tested with some benchmark programs. Then discovered problems are examinedmore closely with methods such as profiling and tracing.

    The results show that the current version of Erlang VM achieves good scalability on the processor with most benchmarks used. The maximum speedup is from about 40 to 50 on 60 cores. Synchronization overhead caused by contention is a major bottleneck of the system. The scalability can be improved by reducing lock contention. Another major problem is that the parallel version of the virtual machine using one core is much slower than the sequential version with a benchmark program containing a huge amount of message passing. Further analysis indicates that synchronization latency induced by uncontended locks is one of the main reasons. Low overhead locks, lock-free structures or algorithms are recommended for improving the performance of the Erlang VM. Our evaluation result suggests Erlang is ready to be used to develop applications on many-core systems.

  • 121294.
    Zhang, Jiateng
    et al.
    Tianjin University.
    Lian, Binbin
    KTH, School of Industrial Engineering and Management (ITM), Machine Design (Dept.), Mechatronics.
    Song, Yimin
    Tianjin Univeristy.
    Geometric error analysis ofan over-constrained parallel tracking mechanism using screw theory2018In: Chinese Journal of Aeronautics, ISSN 1000-9361Article in journal (Refereed)
  • 121295. Zhang, Jiayi
    Design and Implementation of AXI-based Network-on-Chip Systems for Flow Regulation2009Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In Network-on-Chip (NoC), controlling Quality-of-Service is crucial in order to build predictable systems. In this project, we design and implement an AXI-based system on the Nostrum NoC, which features a 2D mesh topology and deflective routing. The main components we add to the Nostrum NoC are master and slave interfaces. The master interface conducts packetization, queuing and multiplexing. The slave interface performs de-packetization, queuing, de-multiplexing and, in particular, reordering of transfers. We also build master and slave modules to serve as traffic generators and sinks. One particular feature of the master module is that it can regulate traffic burstiness while generating traffic. All these models are implemented in VHDL at the RTL. The interface protocol of masters and slaves is the AXI from ARM. With the above components, we designed experiments to show the effect of traffic regulation. Our results show that higher burstiness traffic results in larger transfer delay and bigger backlog. We can conclude that the transfer delay and backlog can be controlled to some degree in a best-effort network via regulating the traffic burstiness.

  • 121296. Zhang, Jie
    et al.
    Long, Zhengwei
    Liu, Wei
    Chen, Qingyan
    Strategy for Studying Ventilation Performance in Factories2016In: Aerosol and Air Quality Research, ISSN 1680-8584, E-ISSN 2071-1409, Vol. 16, no 2, p. 442-452Article in journal (Refereed)
  • 121297.
    Zhang, Jinbao
    et al.
    Monash Univ, Dept Mat Sci & Engn, Clayton, Vic 3800, Australia..
    Daniel, Quentin
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry.
    Zhang, Tian
    Monash Univ, Dept Mat Sci & Engn, Clayton, Vic 3800, Australia..
    Wen, Xiaoming
    Swinburne Univ Technol, Ctr Microphoton, Melbourne, Vic 3122, Australia..
    Xu, Bo
    Uppsala Univ, Phys Chem, Dept Chem, Angstrom Lab, Box 523, S-75120 Uppsala, Sweden..
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD. KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116012, Peoples R China..
    Bach, Udo
    Monash Univ, Dept Chem Engn, Clayton, Vic 3800, Australia.;CSIRO Mfg, Clayton, Vic 3168, Australia.;Melbourne Ctr Nanofabricat, Clayton, Vic 3800, Australia..
    Cheng, Yi-Bing
    Monash Univ, Dept Mat Sci & Engn, Clayton, Vic 3800, Australia.;Wuhan Univ Technol, State Key Lab Silicate Mat Architectures, Wuhan 430070, Hubei, Peoples R China..
    Chemical Dopant Engineering in Hole Transport Layers for Efficient Perovskite Solar Cells: Insight into the Interfacial Recombination2018In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 12, no 10, p. 10452-10462Article in journal (Refereed)
    Abstract [en]

    Chemical doping of organic semiconductors has been recognized as an effective way to enhance the electrical conductivity. In perovskite solar cells (PSCs), various types of dopants have been developed for organic hole transport materials (HTMs); however, the knowledge of the basic requirements for being efficient dopants as well as the comprehensive roles of the dopants in PSCs has not been clearly revealed. Here, three copper-based complexes with controlled redox activities are applied as dopants in PSCs, and it is found that the oxidative reactivity of dopants presents substantial impacts on conductivity, charge dynamics, and solar cell performance. A significant improvement of open- circuit voltage (V-oc) by more than 100 mV and an increase of power conversion efficiency from 13.2 to 19.3% have been achieved by tuning the doping level of the HTM. The observed large variation of V-oc for three dopants reveals their different recombination kinetics at the perovskite/HTM interfaces and suggests a model of an interfacial recombination mechanism. We also suggest that the dopants in HTMs can also affect the charge recombination kinetics as well as the solar cell performance. Based on these findings, a strategy is proposed to physically passivate the electron- hole recombination by inserting an ultrathin Al2O3 insulating layer between the perovskite and the HTM. This strategy contributes a significant enhancement of the power conversion efficiency and environmental stability, indicating that dopant engineering is one crucial way to further improve the performance of PSCs.

  • 121298.
    Zhang, Jinbao
    et al.
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    Hao, Yan
    Uppsala Univ, Angstrom Lab, Dept Chem, Box 523, SE-75120 Uppsala, Sweden..
    Yang, Li
    Uppsala Univ, Dept Engn Sci, Nanotechnol & Funct Mat, Uppsala, Sweden..
    Mohammadi, Hajar
    Univ Isfahan, Dept Chem, Esfahan 8174673441, Iran..
    Vlachopoulos, Nick
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, CH G1 523, CH-1015 Lausanne, Switzerland..
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, CH G1 523, CH-1015 Lausanne, Switzerland..
    Sheibani, Esmaeil
    Univ Isfahan, Dept Chem, Esfahan 8174673441, Iran..
    Electrochemically polymerized poly (3, 4-phenylenedioxythiophene) as efficient and transparent counter electrode for dye sensitized solar cells2019In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 300, p. 482-488Article in journal (Refereed)
    Abstract [en]

    A new conducting polymer poly (3, 4-phenylenedioxythiophene) is synthesized by the electrochemical polymerization technique with different solvents. We find that solvents used in electrochemical polymerization play important roles for the catalytic activity and morphology of the formed conducting polymers. The obtained poly (3, 4-phenylenedioxythiophene) is for the first time employed as counter electrode electrocatalyst in dye sensitized solar cells with cobalt-based electrolytes. We demonstrate that a polymer prepared from a mixed acetonitrile-dichloromethane solvent exhibit higher catalytic activity for redox reactions, as compared to that from a single solvent, dichloromethane. The devices based on this mixed solvent-based polymer from a mixed solvents show a high power conversion efficiency of 5.97%. An additional advantageous feature of the electrochemically polymerized poly (3, 4-phenylenedioxythiophene) for solar cell applications is the high transparency in the visible and nearinfrared region. We also investigate the beneficial effect of the poly (3, 4-phenylenedioxythiophene) layer thickness on device performance, and concluded that the series resistance and charge transfer resistance are greatly influenced by the thickness of polymer, as evidenced by electrochemical impedance spectroscopy measurements. The optimal thickness for poly (3, 4-phenylenedioxythiophene) is about 100 nm. Furthermore, the high catalytic activity and transparency of the new conducting polymer as counter electrode shows great promise for other optoelectronic applications.

  • 121299. Zhang, Jinbao
    et al.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Malin B.
    Hadadian, Mahboubeh
    Baena, Juan Pablo Correa
    Liu, Peng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Hua, Yong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Vlachopoulos, Nick
    Johansson, Erik M. J.
    Boschloo, Gerrit
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Hagfeldt, Anders
    Constructive Effects of Alkyl Chains: A Strategy to Design Simple and Non-Spiro Hole Transporting Materials for High-Efficiency Mixed-Ion Perovskite Solar Cells2016In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 6, no 13, article id 1502536Article in journal (Refereed)
  • 121300. Zhang, Jinbao
    et al.
    Xu, Bo
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Malin B.
    Vlachopoulos, Nick
    Boschloo, Gerrit
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Johansson, Erik M. J.
    Hagfeldt, Anders
    Strategy to Boost the Efficiency of Mixed-Ion Perovskite Solar Cells: Changing Geometry of the Hole Transporting Material2016In: ACS Nano, ISSN 1936-0851, E-ISSN 1936-086X, Vol. 10, no 7, p. 6816-6825Article in journal (Refereed)
    Abstract [en]

    The hole transporting material (HTM) is an essential component in perovskite solar cells (PSCs) for efficient extraction and collection of the photoinduced charges. Triphenylamine- and carbazole-based derivatives have extensively been explored as alternative and economical HTMs for PSCs. However, the improvement of their power conversion efficiency (PCE), as well as further investigation of the relationship between the chemical structure of the HTMs and the photovoltaic performance, is imperatively needed. In this respect, a simple carbazole-based HTM X25 was designed on the basis of a reference HTM, triphenylamine-based X2, by simply linking two neighboring phenyl groups in a triphenylamine unit through a carbon-carbon single bond. It was found that a lowered highest occupied molecular orbital (HOMO) energy level was obtained for X25 compared to that of X2. Besides, the carbazole moiety in X25 improved the molecular planarity as well as conductivity property in comparison with the triphenylamine unit in X2. Utilizing the HTM X25 in a solar cell with mixed-ion perovskite [HC(NH2)(2)](0.85)(CH3NH3)(0.15)Pb(I0.85Br0.15)(3), a highest reported PCE of 17.4% at 1 sun (18.9% under 0.46 sun) for carbazole-based HTM in PSCs was achieved, in comparison of a PCE of 14.7% for triphenylamine-based HTM X2. From the steady-state photoluminescence and transient photocurrent/photovoltage measurements, we conclude that (1) the lowered HOMO level for X25 compared to X2 favored a higher open-circuit voltage (V-oc) in PSCs; (2) a more uniform formation of X25 capping layer than X2 on the surface of perovskite resulted in more efficient hole transport and charge extraction in the devices. In addition, the long-term stability of PSCs with X25 is significantly enhanced compared to X2 due to its good uniformity of HTM layer and thus complete coverage on the perovskite. The results provide important information to further develop simple and efficient small molecular HTMs applied in solar cells.

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