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Paper No P01: Nonspecular Reflectors Using One-Step Spray Coating for Brightness Enhancement in Reflective Displays

SID Symposium Digest of Technical Papers 2015年第S1期46卷

作者： Su Pan Hoi-Sing Kwok State Key Lab on Advanced Displays and Optoelectronics Department of Electronic and Computer Engineering Hong Kong University of Science & Technology Clear Water Bay Kowloon Hong Kong

We proposed a novel method to fabricate nonspecular reflectors by spray coating system, which are applied to enhance brightness near normal view direction when light is obliquely incident. Fabrication parameters are o...

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Transformation thermodynamics: Heat flux control and device applications

Transformation thermodynamics: Heat flux control and device ...

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General Assembly and Scientific Symposium, URSI

作者： Yungui Ma Yichao Liu Wei Jiang Sailing He State Key Lab of Modern Optical Instrumentation Zheiianz University Hanazhou China Department of Electromagnetic Engineering Royal Institute of Technology Stockholm Sweden

Extended from its electromagnetic counterpart [1,2], transformation thermodynamics applied to thermal conduction equations can map a virtual geometry into a physical thermal medium, realizing the manipulation of heat flux with almost arbitrarily desired diffusion paths, which provides unprecedented opportunities to create thermal devices unconceivable or deemed impossible before [3,4]. In this talk we report our recent work on manipulation of transient heat flux employing this technique and showed two thermal devices: a heat flux cloak and an efficient plate heater. In the cloaking device we will show that heat flux can be guided by a transformed medium to flow around a vacuum obstacle and restore its diffusion direction as if nothing inhomogeneous exists in their trajectories [5]. In the second experiment we design an efficient plate heater that can transiently achieve a large surface of uniform temperature powered by a small thermal source [6]. As opposed to the traditional approach of relying on the deployment of a resistor network, our approach fully takes advantage of an advanced functional material system to guide the heat flux to achieve the desired temperature heating profile. Our research results are good examples of the powerful application of coordinate transformation on wave/flux manipulation and may help to broaden research in acquiring extraordinary ways to control and utilize heat energy or configure novel heat devices.

关键词： Heating Thermal engineering Heat engines electromagnetics Thermal conductivity Materials Thermodynamics

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Influencing factors study of armature current distribution at current ramp-up in railgun

Influencing factors study of armature current distribution a...

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electromagnetic Launch technology

作者： Liangliang Tang Junjia He Lixue Chen Shengguo Xia Deng Feng Jun Li Ping Yan State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Beijing Institute of Special Electromechanical Technology Beijing China Institue of Electrical Engineering Chinese Academy of Sciences Beijing China

Current ramp-up is an important stage for railgun electromagnetic launch system. In lots of launching experiments, a big chunk of deposit aluminum can be found on the rail surface at the start-up position of the armature-rail contact area, sometimes, erosion can even be turned up. The transition at current ramp-up is mainly related to local degradation of armature. The bigger value of maximum current densities at the rail/armature (A/R) interface lead armature local temperature to increase rapidly, which can deteriorate the material property of armature, degrade the static electrical contact performance, and significantly reduce the railgun lifetime. In this paper, for restraining startup transition, several influencing factors of armature degradation and melt are studied basis of current concentration. Rail resistivity, rail dimensions, armature resistivity and the shape of current supply are considered and simulated. At current start up, skin effect and induced current are analyzed, and which are considered as the direct factors of armature's current distribution. Armature current distribution and the maximum current density are obtained and compared for each factor. At last, launching experiments are carried out as the same condition with simulation, the deposition on the rail surface at the startup position of the A/R interface reflect that the different factors influence the current distribution on armature at the current ramp up, and the results are in reasonable agreement with simulation description.

关键词： Rails Conductivity Current density Armature Current distribution Surface treatment Aluminum

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Investigations on non-uniform coefficients of magnetic pressure distribution in railguns

Investigations on non-uniform coefficients of magnetic press...

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electromagnetic Launch technology

作者： Deng Feng Junjia He Shengguo Xia Lixue Chen Liangliang Tang Jun Li Ping Yan State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Beijing Institute of Special Electromechanical Technology Beijing China Institute of Electrical Engineering Chinese Academy of Sciences Beijing China

In the process of electromagnetic launching, the nonuniform contact pressure distribution on the armature-rail interface keeps changing with the armature moving on. At first, the contact pressure is mainly provided by the deformation of the trailing arm, from which it can keep a good metal-metal contact at the armature-rail interface. After the pulse current is constructed, the magnetic pressure will dominate the contact pressure because it is much larger than the mechanical interference pressure. In this paper, the 3-D modeling of magnetic pressure distribution is carried out with finite element method. In the simulation of 3-D contact calculations, the situation that current enters armature from the trailing edge is selected for using here. The electromagnetic force perpendicular to armature trailing arm is equivalent to uniform load on the inner surface of trailing arm. Typical contour pattern of non-uniform magnetic pressure distribution is acquired. Some nonuniform coefficients of magnetic pressure distribution are proposed and analyzed to evaluate the contact performances between armature and rails. A series of simulations are conducted under the conditions of different magnitudes of magnetic pressure, also with different armature structure parameters. The characteristics of the non-uniform coefficients are investigated and discussed. Dependences of the non-uniform coefficients on equivalent uniform load and armature structure parameters are obtained.

关键词： Armature Interference Load modeling Contacts Railguns Rails Finite element analysis

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Study on current concentration of large-caliber C-shaped armature at current ramp-up stage in square railgun

Study on current concentration of large-caliber C-shaped arm...

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electromagnetic Launch technology

作者： Liangliang Tang Junjia He Lixue Chen Shengguo Xia Deng Feng Jun Li Ping Yan State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Beijing Institute of Special Electromechanical Technology Beijing China Institute of Electrical Engineering Chinese Academy of Sciences Beijing China

Compared with small and medium caliber railguns, large caliber railguns (LCRs) could be applied in more occasions. Armatures for LCRs could be designed according to studies on small and medium caliber railguns, yet there are some unique features of the design. Current concentration is a special phenomenon in LCR systems, where it's more severe due to high energy density and large current. For a large-caliber armature that has the same muzzle speed as small-caliber armatures, which guarantees the identical velocity skin effect, the skin effect and the induced current are studied and have to be considered as the main influence factors. In this paper, the current distribution and concentration between large caliber armature (90 mm × 90 mm) and small caliber armature (20 mm × 20 mm) are studied and compared. The current distribution coefficients of these two armatures are obtained, it's shown that current density in large armature is more concentrated than the small one. The proportions of induced current to the total current for 90 mm × 90 mm and 20 mm × 20 mm armatures are obtained, which indicate that the induced current is the main reason for current concentration in large-caliber armature. At last, measures to improve current distribution in large-caliber armatures are discussed.

关键词： Current distribution Railguns Skin effect Rails Armature Conductivity

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Optimizing study on the concave arc surfaced C-shaped armature with medium and small caliber

Optimizing study on the concave arc surfaced C-shaped armatu...

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electromagnetic Launch technology

作者： Liangliang Tang Junjia He Lixue Chen Shengguo Xia Deng Feng Jun Li Ping Yan State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China Beijing Institute of Special Electromechanical Technology Beijing China Institute of Electrical Engineering Chinese Academy of Sciences Beijing China

Previous studies on solid armatures show that in a railgun system, concave arc surfaced C-shaped armature (ASCA) can improve the contact pressure and current distribution at the armature/rail (A/R) interface. However, concrete design or parameter study of the concave ASCA is rarely mentioned. In fact, besides the basic structural parameters for conventional C-shaped armatures, there are two more key structural parameters for concave ASCA, namely the radius (r) and the central angle (θ) of their surface arc. In this paper, three matching models of concave armature contacting with corresponding rail structure are discussed and compared, and consequently the best structure pattern of the contact is presented. Meanwhile, the radius and the central angle of the arc in the ASCA are proposed and analyzed. With a fixed railgun caliber and minimum thickness of armature trailing edge, the optimal θ and r are determined according to the current distribution obtained in simulation. The concave ASCAs for square-caliber railgun of 20 mm, 30 mm, 40 mm and 50mm calibers are discussed, and their optimal structural parameters are presented respectively.

关键词： Armature Rails Current density Structural engineering Railguns Current distribution Equations

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Dense matter with eXTP

arXiv

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arXiv 2018年

作者： Watts, Anna L. Yu, Wenfei Poutanen, Juri Zhang, Shu Bhattacharyya, Sudip Bogdanov, Slavko Ji, Long Patruno, Alessandro Riley, Thomas E. Bakala, Pavel Baykal, Altan Bernardini, Federico Bombaci, Ignazio Brown, Edward Cavecchi, Yuri Chakrabarty, Deepto Chenevez, Jérôme Degenaar, Nathalie Santo, Melania Del Salvo, Tiziana Di Doroshenko, Victor Falanga, Maurizio Ferdman, Robert D. Feroci, Marco Gambino, Angelo F. Ge, MingYu Greif, Svenja K. Guillot, Sebastien Gungor, Can Hartmann, Dieter H. Hebeler, Kai Heger, Alexander Homan, Jeroen Iaria, Rosario in’t Zand, Jean Kargaltsev, Oleg Kurkela, Aleksi Lai, Xiaoyu Li, Ang Li, XiangDong Li, Zhaosheng Linares, Manuel Lu, FangJun Mahmoodifar, Simin Méndez, Mariano Miller, M. Coleman Morsink, Sharon Nättilä, Joonas Possenti, Andrea Prescod-Weinstein, Chanda Qu, JinLu Riggio, Alessandro Salmi, Tuomo Sanna, Andrea Santangelo, Andrea Schatz, Hendrik Schwenk, Achim Song, LiMing Šrámková, Eva Stappers, Benjamin Stiele, Holger Strohmayer, Tod Tews, Ingo Tolos, Laura Török, Gabriel Tsang, David Urbanec, Martin Vacchi, Andrea Xu, RenXin Xu, Ypeng Zane, Silvia Zhang, Guobao Zhang, ShuangNan Zhang, Wenda Zheng, ShiJie Zhou, Xia Anton Pannekoek Institute for Astronomy University of Amsterdam Science Park 904 Amsterdam1098 XH Netherlands Shanghai Astronomical Observatory Shanghai200030 China Tuorla Observatory Department of Physics and Astronomy University of Turku Väisäläntie 20 PiikkiöFIN-21500 Finland Nordita KTH Royal Institute of Technology Stockholm University Roslagstullsbacken 23 StockholmSE-10691 Sweden Institute of High Energy Physics CAS Beijing100049 China Tata Institute of Fundamental Research Mumbai400005 India Columbia Astrophysics Laboratory Columbia University 550 West 120th Street New YorkNY10027 United States Institut für Astronomie und Astrophysik Tübingen Universität Tübingen Sand 1 TübingenD-72076 Germany Leiden Observatory Leiden University PO Box 9513 Leiden2300 RA Netherlands Research Center for Computational Physics and Data Processing Silesian University in Opava Bezrucovo nam. 13 OpavaCZ-74601 Czech Republic Physics Department Middle East Technical University Ankara06531 Turkey INAF Osservatorio Astronomico di Roma Via Frascati 33 Monteporzio CatoneI-00078 Italy New York University Abu Dhabi PO Box 129188 Abu Dhabi United Arab Emirates Dipartimento di Fisica Enrico Fermi University of Pisa PisaI-56127 Italy INFN Italian National Institute for Nuclear Physics Pisa Section Pisa56127 Italy Department of Physics and Astronomy Michigan State University East LansingMI48824 United States Department of Astrophysical Sciences Princeton University Peyton Hall PrincetonNJ08544 United States Mathematical Sciences and STAG Research Centre University of Southampton SouthamptonSO17 1BJ United Kingdom MIT Kavli Institute for Astrophysics and Space Research CambridgeMA02139 United States DTU Space Technical University of Denmark Elektrovej 327-328 Kgs Lyngby2800 Denmark INAF/IASF Palermo via Ugo La Malfa 153 PalermoI-90146 Italy Universita degli Studi di Palermo Dipartimento di Fisica e Chimica via Archira 36 Palermo90123 Italy

In this White Paper we present the potential of the Enhanced X-ray Timing and Polarimetry (eXTP) mission for determining the nature of dense matter;neutron star cores host an extreme density regime which cannot be replicated in a terrestrial laboratory. The tightest statistical constraints on the dense matter equation of state will come from pulse profile modelling of accretion-powered pulsars, burst oscillation sources, and rotation-powered pulsars. Additional constraints will derive from spin measurements, burst spectra, and properties of the accretion flows in the vicinity of the neutron star. Under development by an international Consortium led by the Institute of High Energy Physics of the Chinese Academy of Science, the eXTP mission is expected to be launched in the mid 2020s. Copyright © 2018, The Authors. All rights reserved.

关键词： Pulsars

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Photocurrent response of carbon nanotube-metal heterojunctions in the terahertz range

Photocurrent response of carbon nanotube-metal heterojunctio...

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作者： Wang, Yingxin Zhang, Guowei Qiao, Lingbo Wei, Jinquan Zhu, Jia-Lin Chen, Zhiqiang Zhao, Ziran Sun, Jia-Lin Key Laboratory of Particle and Radiation Imaging Tsinghua University Department of Engineering Physics Beijing 100084 China State Key Lab of Low-Dimensional Quantum Physics Department of Physics Tsinghua University Beijing 100084 China Key Lab for Advanced Materials Processing Technology of Education Ministry School of Materials Science and Engineering Tsinghua University Beijing 100084 China Collaborative Innovation Center of Quantum Matter Beijing China

We investigate the optoelectronic properties of a carbon nanotube (CNT)-metal heterostructure in the terahertz range. On the basis of terahertz time-domain spectroscopy characterization of a double-walled CNT (DWNT) film, we present and analyze the photocurrent measurement for a DWNT-nickel heterojunction illuminated by continuous-wave terahertz radiation. A significant current across the junction directly induced by terahertz excitation is observed and a negative photoconductivity behavior is found to occur in the device. The photocurrent shows a linear response to the bias voltage and the illumination power within the examined range. These phenomena support the feasibility of using CNT-metal heterojunctions as novel terahertz detectors © 2014 Optical Society of America.

关键词： Heterojunctions

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Adaptive sliding mode control for the speed regulation of PMSMs with load change

Adaptive sliding mode control for the speed regulation of PM...

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International Conference on Electrical Machines and Systems (ICEMS)

作者： Chaoxu Mu Wei Xu Changyin Sun School of Automation Southeast University Nanjin China School of Electrical and Automation Engineering Tianjin University Tianjin China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

ISBN: (纸本)9781479951635

This paper mainly studies the speed control for a permanent magnet synchronous motor system. The relationship between the reference quadrature axis current and the speed output is approximately considered as a second-order model. Based on this second-order model, an adaptive sliding mode controller is designed for the speed regulation, which can provide effective control for load torque change and parameter uncertainty. Simulation results are presented to veryfy the proposed method.

关键词： Observers Torque Stators Sliding mode control Uncertainty Load modeling Adaptation models

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Analysis of electromagnetic torque of induction machines with the load torque changes suddenly

Analysis of electromagnetic torque of induction machines wit...

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International Conference on Electrical Machines and Systems (ICEMS)

作者： Xinjian Cai Zhenxing Wu Le Sun State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology China School of Information Science and Engineering Fujian University of Technology China National Key Laboratory for Vessel Integrated Power System Technology China School of Electrical Engineering Xi'an Jiaotong University China

ISBN: (纸本)9781479951635

Since many Cascaded H-bridge multilevel (CHBML) inverters that are applied to drive high voltage machines can't transmit electric energy reversely, the electric energy transmitted from the machines may damage the inverters. This paper presents a transfer function to analyze the electromagnetic torque, when the load torque changes suddenly. Based on the achievements, the electric energy that flows between the machine and the inverter can be calculated. And then, a method is proposed to prevent the reversion of the direction of energy flow. Furthermore, the transfer function can be used to guide the design of the control system of induction machine. Simulation results verify the transfer function and the presented method.

关键词： Torque electromagnetics Induction machines Stators Rotors Load modeling Mathematical model

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