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Permanent Electric Dipole Moment of an Rb Atom

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Chinese Physics Letters 2002年第8期19卷 1038-1040页

作者：黄湘友游佩林 DepartmentofPhysics PekingUniversityBeijing100871 DepartmentofBasicSciences ZhanjiangOceanUniversityZhanjiang524025

We experimentally determine the conjecture that hydrogen-like atoms such as Rb and Cs may have large permanent electric dipole moments (EDMs). The saturated Rb vapour fills a cylindrical capacitor in the experiment. The influence of the vapour dielectric medium on capacitance is measured with a digital capacitance meter. Supposing that the measurement influence comes from the permanent EDMs of Rb atoms, from the experimental result we find that the EDM is large, i.e.dRb≥8.6e×10-9cm.

关键词： capacitance

Lateral Resolution and Signal to Noise Ratio in Electrostatic Force Detection Based on Scanning Probe Microscopy

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Chinese Physics Letters 2012年第7期29卷 42-46页

作者：张冬冬王小伟王锐王圣楠程志海裘晓辉 National Center for Nanoscience and Technology ZhongguancunBeijing 100190 Academy of Advanced Interdisciplinary Studies Peking UniversityBeijing 100871 Department of Physics Tsinghua UniversityBeijing 100084

The Lateral resolution (LR) and signal-to-noise ratio (SNR) are the essential factors in the applications of scanning probe microscopy in quantitative measurement of surface charge distribution,potential profile,and dielectric properties.We use a model system to comprise Au nanoparticles (NPs) embedded in a polystyrene (PS) matrix to study the effects of various experimental parameters,such as modulation bias voltage,tip-sample distance,and actual tip shape,on the electrostatic interactions between the tips and samples.The results show that LR and SNR decrease when the tip-sample distance increases,while SNR increases with tip modulation voltage.LR is less sensitive to tip modulation voltage,but shows complex dependence on the sample geometric structure.In combination with a numerical simulation based on the integral capacitance model,the electrostatic force interaction between tip and sample was quantitatively analyzed.

关键词： electrostatic Probe capacitance

Improving interruption performance of mechanical circuit breakers by controlling pre-current-zero wave shape

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High Voltage 2019年第2期4卷 122-129页

作者： Tim Schultz Benjamin Hammerich Lorenz Bort Christian M.Franck High Voltage Laboratory ETH ZurichPhysikstrasse 38092 ZurichSwitzerland

Mechanical circuit breakers(MCBs)are the limiting component for current injection HVDC circuit breakers.Improving their interruption performance reduces requirements for capacitance and inductance needed in the injection circuit and thus space use and costs.Higher performance can be achieved by creating a period of low current gradient before zero crossing in the MCB,e.***.by using a saturable inductor(SI).In this paper,the impact of duration and steepness during the low current-gradient phase is linked to arc parameters of the investigated model gas circuit breaker.It is shown in a scaled experimental setup that an optimum design of the SI can be derived from arc time constant and interruption limits for constant current gradients.This optimisation results in a considerable increase of interruption performance.The feasibility of implementing an SI in a full-scale HVDC circuit breaker is demonstrated using simulations.Using an improved injection scheme,the stresses for the MCB can be reduced significantly.Consequently,the injection circuit components can be scaled down,making the topology more economical.The reduced interruption requirements might also make it possible to use a single gas interrupter instead of a series connection of vacuum interrupters,reducing the complexity of the mechanical switch.

关键词： performance capacitance wave

Construction of WO_(3)/Ti-doped WO_(3)bi-layer nanopore arrays with superior electrochromic and capacitive performances

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Tungsten 2019年第3期1卷 236-244页

作者： Yingdi Shi Shujing Liu Yong Zhang Mingjun Sun Kai Tang Jiewu Cui Xia Shu Yan Wang Jiaqin Liu Yucheng Wu School of Materials Science and Engineering Hefei University of TechnologyHefei 230009China Key Laboratory of Advanced Functional Materials and Devices of Anhui Province Hefei 230009China Institute of Industry and Equipment Technology Hefei University of TechnologyHefei 230009China College of Materials Science and Engineering Taiyuan University of TechnologyTaiyuan 030024China

Crystalline WO_(3)/Ti-doped WO_(3)bi-layer nanopore arrays were constructed by the template synthesis of a WO_(3)nanopore layer modified by a magnetron sputtering of an amorphous Ti-doped/WO_(3)layer.The obtained bi-layer nanopore array shows a remarkable electrochromic performance with large dual-band optical modulation in both visible(VIS)and near infrared(NIR)regions(optical modulation of over 70%in the wavelength range from 600 to 1600 nm)and the fast response speed(coloring for 3.4 s and bleaching for 6.6 s).In addition,the bi-layer WO_(3)/Ti-doped WO_(3)nanopore array also present superior energy-storage properties(areal capacitance of 44.0 mF cm−2 and good rate capability),better than that of titanium-free thin films.The special bifunctional characteristics of electrochromism and pseudocapacitance can be ascribed to the large specific surface area provided by the architectural design,rich ion channels in the amorphous layer as well as proper titanium doping,which bestows the bi-layer nanopore array a great potential in clean energy applications.

关键词： Electrochromism capacitance Tungsten oxide Titanium doping

Ionic polymer-metal composite mechanoelectric transduction:effect of impedance

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International Journal of Smart and Nano Materials 2012年第4期3卷 275-295页

作者： Rashi Tiwari Mechanical and Aerospace Engineering Department Cornell UniversityIthacaNYUSA

Ionic polymer–metal composites(IPMCs)are commonly used as soft actuators due to their electromechanical response.However,the reverse phenomenon,i.e.IPMC’s ability to generate charge on application of mechanical strain(mechanoelectric response),is not very well understood.The concept of mechanoelectric transduction and its dependence on complex IPMC architecture comprising of electrode,polymer and composite layer is illustrated with a phenomenological model.The impedance model takes into account the charge transport inside the polymer and layer properties in terms of their impedances.The model lucidly indicates the significance of capacitance in IPMC transduction.The impedance model is used for studying IPMC step and frequency response and the effect of IPMC capacitance on its application as energy harvester.

关键词： ionic polymer-metal composite capacitance impedance mechanoelectric response

A Nonlinear Control Strategy for Vienna Rectifier Under Unbalanced Input Voltage

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Transactions of Nanjing University of Aeronautics and Astronautics 2019年第5期36卷 703-714页

作者： REN Xiaoyong CHEN Yu TONG Dan ZHANG Zhiliang CHEN Qianhong Aero-Power Sci-Tech Center College of Electronic EngineeringNanjing University of Aeronautics and Astronautics

The Vienna rectifier with unbalanced input voltage and load transient is analyzed.A nonlinear control strategy for Vienna rectifier under unbalanced input is proposed.From the view of positive and negative sequence components,the proposed nonlinear control strategy suppresses the twice frequency ripple and guarantees the dynamic response characteristic at the same time.Thanks to the proposed nonlinear control strategy,the DC bus capacitor can be reduced a lot since the voltage ripple and drop can be suppressed.A 10 kW Vienna rectifier is built to verify the proposed control strategy.After applying the proposed nonlinear control strategy,the voltage ripple is only7 V and decreases over 75%over the traditional PI control when the unbalanced degree is 20%.The voltage drop can be reduced about 80%than former control strategy which is helpful to reduce the DC bus capacitor and achieve higher power density.The volume of the capacitor can be reduced by 83.3%with the new control method.

关键词： Vienna rectifier radars unbalanced input voltage nonlinear control strategy DC bus capacitance

Responses of electrical properties of tea leaves to low-temperature stress

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International Journal of Agricultural and Biological Engineering 2015年第5期8卷 170-175页

作者： Lu Yongzong Hu Yongguang Zhang Xiliang Li Pingping School of Agricultural Equipment Engineering Jiangsu UniversityZhenjiang 212013China School of Mechanical Engineering Jiangsu UniversityZhenjiang 212013China College of Biology and the Environment Nanjing Forestry UniversityNanjing 210037China

Critical temperature is one of the most important parameters for the control of crop frost protection through airflow disturbance.It changes with complex weather conditions,thus it is difficult to be determined.A method of testing electrical property of tea leaves under cold stress was put forward to indicate critical temperature.The testing system was established to measure the capacitance,impedance,resistance and reactance of the samples under different air temperatures,air humidities and airflow velocities.The variation of the electrical property was also analyzed.The results show that at humidity below 70%and airflow velocity of 0 m/s the impedance and resistance increased slowly,while the reactance kept steady when air temperature decreased from 8.0°C to around−6.3°C,and then increased rapidly from around−6.3°C to−15.0°C.There were no significant differences of the above parameters and variation trend under different airflow velocities.There was an exponential relationship between the impedance and the temperature.The capacitance was rather small and almost no change occurred with air temperature under different conditions of air velocity and humidity,except a few abrupt peaks.The maximum peak capacitance was representative of its response at certain humidity and airflow velocity.The typical temperatures were close to a range,where the other three parameters began to increase rapidly.The typical temperature dropped to the lowest of−7.8°C at the airflow velocity of 0 m/s.Therefore,the characteristic response of the capacitance could indicate critical temperature of tea leaves.

关键词： low-temperature stress electrical property capacitance Camellia Sinensis critical temperature

Experimental Study on Wavy-Flow Pneumatic Conveying in Horizontal Pipe

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Journal of Thermal Science 2002年第2期11卷 114-120页

作者： Hua Xu Shi Liu Haigang Wang Fan Jiang Chinese Acad Sci Inst Engn Thermophys Beijing 100080 Peoples R China

Low-velocity pneumatic conveying systems have been developed to meet the requirement of low operation costs and have been widely used in chemical and process industries. However, the understanding of the mechanism is limited. This paper reports an experimental study on a slug-flow pneumatic conveying. Electrical capacitance tomography has been used to visualize plug shape and identify the flow pattern. Comparison was made between the experimental data of pressure drop with existed models.

关键词： pneumatic conveying wavy flow pressure drop electrical capacitance tomography.

Microscopic Insight to Nonlinear Voltage Dependence ofCharge in Carbon-Ionic Liquid Supercapacitors

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Energy Material Advances 2021年第1期2021卷 129-142页

作者： Aleksandar Y.Mehandzhiyski Xuehang Wang Candy Anquetil-Deck De Chen Brian A.Grimes Norwegian University of Science and Technology Department of Chemical EngineeringSem Sælandsvei 4N-7491 TrondheimNorway

The impact of cell voltage on the capacitance of practical electrochemical supercapacitors is a phenomenon observedexperimentally, which lacks a solid theoretical explanation. Herein, we provide combined experimental and molecular dynamicsinvestigation of the relation between voltage and capacitance. We have studied this relation in supercapacitor cells comprising ofactivated carbon material as the active electrode material, and neat ionic liquids (ILs), and a mixture of ILs as the electrolyte. Ithas been observed that the increase of accumulative charge impacts the conformation and packing of the cations in the anode,which determines its nonlinear behavior with increasing voltage. It has also been shown that for the mixture IL with two typesof cations, the contribution of each type of cation to the overall capacitance is highly dependent on the different pore sizes in thesystem. The smaller tetramethylammonium (TMA+) shows tendency for more efficient adsorption in the mesopores, while1-Ethyl-3-methylimidazolium (EMIM+) is found to be present almost exclusively in the micropores where TMA+ is presentin small quantities. Such microscopic insights from computer simulations of the molecular phenomena affecting the overallperformance in supercapacitors can help to design more efficient electrolytes and devices.

关键词： capacitance pores Nonlinear