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基于改进介质微扰法的水膜厚度测量理论研究 预览
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作者 张淑娥 张天浩 曹宏沛 《天津大学学报:自然科学与工程技术版》 CSCD 北大核心 2020年第3期272-278,共7页
为了解决圆柱腔内壁水膜厚度的测量问题,对水膜厚度测量公式进行校正,分析了交变电场下电介质内的极化过程,推导了交变电场作用下电介质内电场的表达式.由于在交变电场作用下,谐振腔内壁水膜内的电场会发生变化,用准静态法近似介质微扰... 为了解决圆柱腔内壁水膜厚度的测量问题,对水膜厚度测量公式进行校正,分析了交变电场下电介质内的极化过程,推导了交变电场作用下电介质内电场的表达式.由于在交变电场作用下,谐振腔内壁水膜内的电场会发生变化,用准静态法近似介质微扰公式不再适用,基于推导的交变电场作用下电介质内的电场方程,对谐振腔介质微扰公式进行了改进.利用HFSS软件分别仿真分析了同轴腔和圆柱腔在不同频率、不同介质下微扰前后介质内电场大小的变化,将仿真数据和理论计算数据进行对比,证明了交变电场作用下电介质内电场方程的正确性.基于改进后的介质微扰公式,建立了圆柱腔内壁水膜厚度和谐振频偏之间的关系模型,将仿真数据与介质微扰公式改进前后理论数据进行对比分析,结果表明:在同一水膜厚度下,使用改进后微扰公式得到谐振频率较实际仿真数据更加吻合,谐振频率的理论与仿真误差至少提高了35.7%. 展开更多
关键词 交变电场 电介质 电场方程 介质微扰 水膜厚度
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高性能铁电吸波材料 预览
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作者 李雍 杨会静 +1 位作者 郝喜红 曹茂盛 《表面技术》 EI CAS CSCD 北大核心 2020年第2期41-55,共15页
铁电材料由于具有高极化以及良好的化学、热稳定性等性质,在微波吸收领域得到了广泛关注。过去二十年,开展了大量关于铁电吸波材料的研究。系统地综述了铁电材料微波吸收的损耗机制与几类典型铁电材料的微波吸收性能。在损耗机制方面,... 铁电材料由于具有高极化以及良好的化学、热稳定性等性质,在微波吸收领域得到了广泛关注。过去二十年,开展了大量关于铁电吸波材料的研究。系统地综述了铁电材料微波吸收的损耗机制与几类典型铁电材料的微波吸收性能。在损耗机制方面,详细论述了铁电材料的电损耗机制,包括介电损耗、电导损耗及界面损耗机制,同时对于多铁材料与铁电-磁杂化复合材料,分析了磁损耗机制以及磁-介电损耗协同机制,并对各类损耗的形成原因及作用机理进行了总结。在微波吸收性能方面,重点阐述了近些年BiFeO3基与BaTiO3基等铁电材料的微波吸收表现,包括单相材料、掺杂材料及复合材料,并对其在室温及高温下的微波吸收性能进行了比较,同时基于材料的结构、微结构与微波吸收强度及有效吸收带宽等参数的演变联系,对其微波响应机制进行了归纳。最后详细分析了影响铁电微波吸收材料发展所面临的关键问题,并对其未来的研究方向进行了展望。 展开更多
关键词 铁电 微波吸收 介电 损耗 电导 弛豫
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Broadband,High Gain,Narrow Width Rectangular Dielectric Resonator Antenna with Air Gap 预览
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作者 Ankit Kumar Roy Sukla Basu 《电子科技学刊:英文版》 CAS CSCD 2019年第1期90-96,共7页
The broadband,narrow width,rectangular dielectric resonator antenna(RDRA)of aluminum nitride(εr=8.6)was designed and the effect of inclusion of air gap at the bottom of the dielectric resonator antenna(DRA),above the... The broadband,narrow width,rectangular dielectric resonator antenna(RDRA)of aluminum nitride(εr=8.6)was designed and the effect of inclusion of air gap at the bottom of the dielectric resonator antenna(DRA),above the ground plane,was investigated.Gain around 7 dBi was obtained for DRA with air gap(DRAAG)over a broad bandwidth in upper X,Ku,and K bands.Further enhancement in gain could be obtained by placing a metal wall parallel to the length of DRA.However,due to the presence of metal wall,bandwidth was reduced.These structures with the metal wall are capable of operating over a wide band extending from Ku band to lower K band with the gain of around 10 dBi.CST Microwave Studio Software was used to simulate all these structures.Performance parameters of DRA with air gap were compared with several broadband DRA structures reported in recent literature.The proposed DRAAG with the metal wall in this paper is capable of operating over a wide bandwidth along with a significant gain. 展开更多
关键词 DIELECTRIC RESONATOR antenna(DRA) RECTANGULAR DIELECTRIC RESONATOR antenna(RDRA) wide band DIELECTRIC RESONATOR ANTENNA X Ku and K bands DIELECTRIC RESONATOR ANTENNA
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Fabrication of BaTiO3/Epoxy Composites Exhibiting Large Dielectric Constant, Low Dielectric Loss and High Flexural Strength
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作者 刘金鹏 YOU Xiaoqiang +1 位作者 陈楠 杜国平 《武汉理工大学学报:材料科学英文版》 SCIE EI CAS 2019年第6期1266-1273,共8页
BaTiO3/epoxy composites consisting of two three-dimensionally interpenetrating networks of BaTiO3 and epoxy phases were prepared using a new approach. The BaTiO3/epoxy composites exhibit a colossal dielectric constant... BaTiO3/epoxy composites consisting of two three-dimensionally interpenetrating networks of BaTiO3 and epoxy phases were prepared using a new approach. The BaTiO3/epoxy composites exhibit a colossal dielectric constant, low dielectric loss and high flexural strength. In the BaTiO3 networks, chemically bonded grain boundaries between neighboring BaTiO3 grains were established, and they are responsible for the colossal dielectric constant and high flexural strength of the BaTiO3/epoxy composites. Furthermore, unlike the conventional ceramic/polymer composites, this approach also makes high loadings of BaTiO3 contents possible for the BaTiO3/epoxy composites without compromising their high flexural strength. 展开更多
关键词 ceramic/polymer composite BaTi03/epoxy dielectric property colossal dielectric constant
Influence of test procedure on dielectric breakdown strength of alumina
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作者 Bjoern MIELLER 《先进陶瓷(英文版)》 CSCD 2019年第2期247-255,共9页
Dielectric strength testing of ceramics can be performed with various setups and parameters. Comparisons of results from different sources are often not meaningful, because the results are strongly dependent on the ac... Dielectric strength testing of ceramics can be performed with various setups and parameters. Comparisons of results from different sources are often not meaningful, because the results are strongly dependent on the actual testing procedure. The aim of this study is to quantify the influence of voltage ramp rate, electrode size, electrode conditioning, and sample thickness on the measured AC dielectric strength of a commercial alumina. Mean values, Weibull moduli, and failure probabilities determined in standardized short time tests are evaluated and related to withstand voltage tests. Dielectric strength values in the range from 21.6 to 33.2 kV·mm–1 were obtained for the same material using different testing procedures. Short time tests resulted in small standard deviations(< 2 kV·mm–1) and high Weibull moduli around 30, while withstand tests at voltage levels with low and virtual zero failure probability in short time tests resulted in large scatter of withstand time and Weibull moduli < 1. The strong decrease in Weibull moduli is attributed to progressive damage from partial discharge and depolarization during AC testing. These findings emphasize the necessity of a thorough documentation of testing procedure and highlight the importance of withstand voltage tests for a comprehensive material characterization. 展开更多
关键词 DIELECTRIC STRENGTH DIELECTRIC BREAKDOWN withstand VOLTAGE test high AC VOLTAGE testing
Effects on the thermal expansion coefficient and dielectric properties of CLST/PTFE filled with modified glass fiber as microwave material
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作者 Liu Zheng Jing Zhou +2 位作者 Jie Shen Yanyuan Qi Wen Chen 《中国化学快报:英文版》 SCIE CAS CSCD 2019年第5期1111-1114,共4页
Ceramic and polytetrafluoroethylene composites as dielectric materials have a low dielectric loss at high frequency and play an important role in the modern communication field.However,room temperature phase transform... Ceramic and polytetrafluoroethylene composites as dielectric materials have a low dielectric loss at high frequency and play an important role in the modern communication field.However,room temperature phase transformation of PTFE resins,which is accompanied by a large volume change(>400 ppm/℃),seriously affects the dimensional stability and performance stability of materials.The LD125 modified glass fiber(GF)was introduced to the CaO-Li2 O-Sm2O3-TiO2(CLST)/PTFE composite,to reduce the thermal expansion coefficient(CTE)of the composites.The tri-phase composites(CLST/PTFE/GF)show the low dielectric loss and excellent machine-ability.The effect of GF content on the dielectric properties and CTE was also investigated.The CLST/PTFE filled with 5%GF exhibits the best overall performance,which is a promising microwave dielectric material for microwave communication. 展开更多
关键词 MICROWAVE communication Thermal expansion COEFFICIENT CLST PTFE DIELECTRIC loss DIELECTRIC CONSTANT
Study on material of polymer-based electromagnetic shielding composites 预览
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作者 Hanwen Zhang Zhendong Qiu Huiping Wang 《材料物理与化学》 2019年第1期11-18,共8页
With the extensive application of electromagnetic resources in the information industry, electromagnetic interference has caused many hazards. Polymer-based electromagnetic shielding composite material as a new type o... With the extensive application of electromagnetic resources in the information industry, electromagnetic interference has caused many hazards. Polymer-based electromagnetic shielding composite material as a new type of material has good shielding effect on the electromagnetic wave. This paper mainly introduces the types of polymer-based electromagnetic shielding composite materials and the performance evaluation method of shielding materials. 展开更多
关键词 BENZOXAZINE DIELECTRIC properties COPOLYMERIZATION MODIFICATION
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Relation between etching profile and voltage-current shape of sintered SiC etching by atmospheric pressure plasma
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作者 D C SEOK S R YOO +2 位作者 K I LEE Y S CHOI Y H JUNG 《等离子体科学与技术:英文版》 SCIE EI CAS CSCD 2019年第4期137-144,共8页
Sintered silicon carbide(SiC)was etched by a dielectric barrier discharge source.A high voltage bipolar pulse was used with helium gas for the plasma generation.One stable filament plasma was generated and could be us... Sintered silicon carbide(SiC)was etched by a dielectric barrier discharge source.A high voltage bipolar pulse was used with helium gas for the plasma generation.One stable filament plasma was generated and could be used for SiC etching.As the processing gas(NF3)mixing rate increased,the width and depth of the etching profile became narrower and deeper.The differentiated V-Q Lissajous method was used for measuring the capacitances(Ceq)of the electrode after the plasma turned on.The width of the etching profile was proportional to Ceq.As the current peak value/smx of the substrate current in creased,the volume removal rate of SiC increased.The etch depth was proportional to the ratio of/smx to Ceq.Additionally,because of the different characteristics of the plasma disks on SiC substrate by the voltage polarity,the etching profile was unstable.However,in high NF3 mixing process,the etching profile became stable and deeper. 展开更多
关键词 dielectric BARRIER DISCHARGE silicon CARBIDE plasma etching、filament discharge surface CHARGE
Enhancing toluene removal in a plasma photocatalytic system through a black TiO2 photocatalyst
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作者 朱斌 张璐瑶 +2 位作者 闫妍 李猛 朱益民 《等离子体科学与技术:英文版》 SCIE EI CAS CSCD 2019年第11期77-85,共9页
An efficient toluene removal in air using a plasma photocatalytic system(PPS)not only needs favorable surface reactions over photocatalysts under the action of plasma,but also requires the photocatalysts to efficientl... An efficient toluene removal in air using a plasma photocatalytic system(PPS)not only needs favorable surface reactions over photocatalysts under the action of plasma,but also requires the photocatalysts to efficiently absorb light emitted from the discharge for driving the photocatalytic reactions.We report here that the PPS constructed by integrating a black titania(B-TiO2)photocatalyst with a dielectric barrier discharge(DBD)can effectively remove toluene with above 70%CO2 selectivity and remarkably reduced the concentration of secondary pollutants of ozone and nitrogen oxides at a specific energy input of 1500 J-I-1,while exhibiting good stability.Photocatalyst characterizations suggest that the B-TiO2 provides a high concentration of oxygen vacancies for the surface oxidation of toluene in DBD,and efficiently absorbs ultraviolet-visible light emitted from the discharge to induce plasma photocatalytic oxidation of toluene.The presence of B-TiO2 in the plasma region also results in a high discharge efficiency,facilitating the generation of large numbers of reactive species and thus the oxidation of toluene towards CO2.The greatly enhanced performance of the PPS integrated with B-TiO2 in toluene removal offers a promising approach to efficiently remove refractory volatile organic compounds from air at low temperatures. 展开更多
关键词 PLASMA PHOTOCATALYSIS BLACK TIO2 synergetic effect dielectric barrier discharge TOLUENE removal
Synthesis, Thermal Degradation and Dielectric Properties of Poly[octyl(triphenylethynyl)]silane Resin
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作者 WANG Yanli TAN Dexin 《高等学校化学研究:英文版》 SCIE CAS CSCD 2019年第6期1076-1081,共6页
Octyl(triphenylethynyl)silane monomer(OTPES)was synthesized with ethyl bromide,octyltrichlorosilane and phenylethylene by Grignard reaction.The molecular structure was confirmed by FTIR and NMR.The poly[octyl(tripheny... Octyl(triphenylethynyl)silane monomer(OTPES)was synthesized with ethyl bromide,octyltrichlorosilane and phenylethylene by Grignard reaction.The molecular structure was confirmed by FTIR and NMR.The poly[octyl(triphenylethynyl)]silane resin(POTPES)was prepared by thermal polymerization and the corresponding thermal degradation behavior wasstudied by thermogravimetric analysis(TG)combining with model and model-free fitted methods.The dielectric property of resin was also studied by vector network analyzer.The results show that the melt point of OTPES was 50℃ and the processing window was over 236℃.The resin degradation temperature of Td5 occurred over 433℃ and the char yield was over 60%at 800℃.Based on Kissinger,Flynn-Wall-Ozawa,Coats-Redfern,Achar,Vyazovkin-Wight and Tang methods,the reaction activity(E)was 155.51,152.97,150.82,146.02,148.38 and 148.77 kJ/mol,respectively.Dielectric properties analysis displayed that the real part(ε′)and the imaginary part(ε″)of the relative complex permittivity of POTPES was 2.5 and 0.05,respectively,and the dielectric loss tangent was between 0.03 and 0.25.The reflection loss of resin was more than−2.85 dB in all range of 1–5 mm thicknesses and 2–18 GHz frequency,which indicated that POTPES resin was a real wave-transparent resin matrix. 展开更多
关键词 Octyl(triphenylethyny1)silane Grignard reaction Thermal polymerization Thermal degradation behavior Dielectric property
一种三嗪类小分子铁电材料的合成及性能 预览
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作者 陈星晗 张小朋 刘建 《南昌大学学报:理科版》 CAS 北大核心 2019年第5期455-459,共5页
以1,3,5-均三嗪为合成砌块构建了一例中心对称的芳酸酯类铁电液晶小分子T-AE-C18。采用红外光谱、核磁氢谱和碳谱、元素分析等确定了目标化合物T-AE-C18的结构。通过差热分析、热重分析表征了材料的热学性能,并进一步测试了材料的铁电... 以1,3,5-均三嗪为合成砌块构建了一例中心对称的芳酸酯类铁电液晶小分子T-AE-C18。采用红外光谱、核磁氢谱和碳谱、元素分析等确定了目标化合物T-AE-C18的结构。通过差热分析、热重分析表征了材料的热学性能,并进一步测试了材料的铁电、介电和导电性质。结果表明,T-AE-C18在65℃时的剩余极化率达到最大值0.025μC·cm-2。本文为开发基于三嗪类衍生物的小分子光电材料具有一定的指导意义。 展开更多
关键词 三嗪 芳酸酯 铁电 介电
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Review of Soft Linear Actuator and the Design of a Dielectric Elastomer Linear Actuator
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作者 Xunuo Cao Mingqi Zhang +3 位作者 Zhen Zhang Yi Xu Youhua Xiao Tiefeng Li 《固体力学学报:英文版》 SCIE EI CSCD 2019年第5期566-579,共14页
Natural muscle provides excellent motilities for animals.As the basic unit of the muscle system,the skeletal muscle fibers function as a soft linear actuator.Inspired by the muscle fibers,researchers have developed va... Natural muscle provides excellent motilities for animals.As the basic unit of the muscle system,the skeletal muscle fibers function as a soft linear actuator.Inspired by the muscle fibers,researchers have developed various soft active devices with linear actuation.This paper reviews several soft linear actu ators,such as the dielec trie elastomer,t hermal responsive hydrogels,pneumatic artificial muscle,and conducting polymers.The actuation mechanisms and performances of these soft linear actuators are summarized.Based on the dielectric elastomer,we propose a design of a hybrid system with linear actuation,driven by both the electric motor and dielectric elasto mer cone.The elec tromechanical behaviors of the dielec trie elastomer cone have been investigated in both experiment and finite element analysis.This work may guide the further design of soft actuators and robots. 展开更多
关键词 Soft linear actu at or Dielectric elast omer Finite elemen t analysis
Experimental Investigations on the Out-of-Plane Sub-harmonic Vibration of a Circular Dielectric Elastomer Actuat or
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作者 Cheng Ma Meng Yang +1 位作者 Kun Jia Tongqing Lu 《固体力学学报:英文版》 SCIE EI CSCD 2019年第5期591-598,共8页
Dielectric elastomers have found interesting applications in soft loudspeakers,where vibrations subject to alternating electrical excitations are the key features.Although there are many t heore tical studies on the n... Dielectric elastomers have found interesting applications in soft loudspeakers,where vibrations subject to alternating electrical excitations are the key features.Although there are many t heore tical studies on the nonlinear vibrations of dielec trie elasto mers subject to electromechanical coupling loads,the systematic experimental research is rare.In this work,we design a simple experimental setup to observe the out-of-plane vibrations of a circular dielec trie elastomer actuator.We find that the dielec trie elastomer has different response modes including the harmonic,super-harmonic and sub-harmonic responses at different excitation frequencies.We analyze the responses by using the short-time Fourier transformation.We find that the equivalent voltage and the AC/DC ratio are the main parameters affecting the occurrence of sub-harmonic responses.The phenomenon of mode shift is also observed in our experiments.These experimental observations provide a deeper unders tanding of the dynamic responses of dielec trie elasto mer subject to electromechanical loads. 展开更多
关键词 Dielectric elastomer Nonlinear vibration Harmonic response Sub-harmonic response
Effects of newly devised plasma lice comb on human hair
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作者 Lars TEN BOSCH Andreas HUBER +3 位作者 Philipp SAUERBIER Robert KÖHLER Georg AVRAMIDIS Wolfgang VIÖL 《等离子体科学与技术:英文版》 SCIE EI CAS CSCD 2019年第12期78-84,共7页
A plasma device was developed showing high potential for a pesticide-free treatment of pediculosis. As a first safety assessment of the device was presented earlier, this present paper focuses on the damage introduced... A plasma device was developed showing high potential for a pesticide-free treatment of pediculosis. As a first safety assessment of the device was presented earlier, this present paper focuses on the damage introduced to human hair during a plasma treatment for pediculosis control. Therefore, human hairs were treated repeatedly to assess the possible occurring damage developing with increasing treatment durations. To analyse the inflicted changes on human hair examinations using x-ray photoelectron spectroscopy(XPS/ESCA), scanning nearfield optical microscopy(SNOM) and scanning electron microscopy were conducted, to compare the modifications of surface chemistry and mechanical alterations. The investigations revealed a mild impact on the surface chemistry(XPS/SNOM), while more distinct morphological changes on the hair surface could be observed. The authors conclude that an effect of the plasma comb device on the hair during a real-life treatment is negligible, due to the very short contact times during a standard combing procedure for pediculosis control. 展开更多
关键词 atmospheric pressure plasma dielectric barrier discharge pediculosis SEM SNOM ESCA XPS hair smoothing plasma based pest management
Synthesis of Organic Modified SiCw/PVDF Composite Membrane and Its Dielectric Properties under Low Temperature
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作者 许静 YU Ting +2 位作者 HAN Ding GUAN Xiaolin 雷西萍 《武汉理工大学学报:材料科学英文版》 SCIE EI CAS 2019年第6期1279-1287,共9页
Cetyltrimethylammonium bromide(CTAB) was incorporated into silicon carbide whiskers(SiCw) to improve their hydrophobicity. The solution casting method was employed to develop composite membranes of polyvinylidene fluo... Cetyltrimethylammonium bromide(CTAB) was incorporated into silicon carbide whiskers(SiCw) to improve their hydrophobicity. The solution casting method was employed to develop composite membranes of polyvinylidene fluoride(CTAB-SiCw/PVDF) with different feed ratios. FT-IR spectroscopic studies proved that CTAB was successfully incorporated into the SiCw. SiCw phase structure was maintained after modification by CTAB according to XRD results. SEM studies indicated that the surface became smoother with CTAB dispersal in the PVDF membrane. The dielectric properties of the composite membranes containing various amounts of CTAB-SiCw were measured at low temperature. It was found that the dielectric constant of the composite membranes with 13.0 wt% whiskers reached a maximum value of 25 at low frequency, and decreased to nine at high frequency(from 500 Hz to 1 MHz) at 0 ℃. The dielectric loss of each composite membrane increased with increasing temperature and reached a maximum value. The value shifted with corresponding frequency increases. In addition, the dielectric loss reached a maximum value of 0.2 when 16.7 wt% of CTAB-SiCw was fed at each frequency(from-30 ℃ to 10 ℃). At room temperature, the dielectric constant could be maintained at 42 and the loss factor decreased to 0.8 at 100 Hz when 13.0 wt% of CTABSiCw was incorporated. Additionally, TGA experiments indicated that the decomposition temperature of a PVDF membrane was increased by 10 ℃ and its heat resistance was improved by adding 13.0 wt% of CTAB-SiCw. This PVDF composite membrane has potential for use as an insulator and capacitor. 展开更多
关键词 silicon carbide whiskers PVDF MEMBRANE low temperature dielectric properties
Effects of Dielectric Barrier Discharge Plasma on the Combustion Performances of Reverse-Flow Combustor in an Aero-Engine
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作者 DENG Jun PENG Changxin +3 位作者 HE Liming WANG Shuai YU Jinlu ZHAO Bingbing 《热科学学报:英文版》 SCIE EI CAS CSCD 2019年第5期1035-1041,共7页
In order to apply plasma assisted combustion(PAC) into a reverse-flow aero-engine and verify the improvement of combustion performance, a feasible approach was proposed in this work. In this approach, based on the str... In order to apply plasma assisted combustion(PAC) into a reverse-flow aero-engine and verify the improvement of combustion performance, a feasible approach was proposed in this work. In this approach, based on the structure characteristics of the reverse-flow combustor, a parallel plate double dielectric barrier discharge(DBD) PAC actuator was designed to generate plasma. It was installed at the front of combustor. When the actuator is driven, the original air flow is not disturbed for the device’s structure and installation. Using aviation kerosene as fuel, the effects of plasma on ignition boundary and outlet temperature of the combustor were experimentally investigated at atmosphere pressures. Through the dual high voltage differential power supply, the large gap, large area and uniform plasma discharge was achieved. The results of PAC actuator discharge indicate that inlet air temperature has a small increase of 4–9 K. After PAC is applied, the combustion performances of reverse-flow combustor in an aero-engine are remarkably improved. Experimental results indicate that ignition boundary is widened by 3.7%–12.5% because of the impact of plasma. Outlet highest temperature of combustor is raised by 19–75 K;outlet temperature distribution coefficient is reduced by 11.1%–26.6%. This research provides an effective and practicable way to implement the application of PAC in aero-engine combustor and has some engineering application significance. 展开更多
关键词 AERO-ENGINE reverse-flow COMBUSTOR double dielectric BARRIER discharge plasma assisted combustion
Improved dielectric and electro-optical parameters of nematic liquid crystal doped with magnetic nanoparticles
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作者 Geeta Yadav Govind Pathak +4 位作者 Kaushlendra Agrahari Mahendra Kumar Mohd Sajid Khan V S Chandel Rajiv Manohar 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第3期223-229,共7页
This study investigates the effect of magnetic nanoparticles(NPs) on the weakly polar nematic liquid crystal(NLC).Different parameters of dielectric data were measured for both the homeotropic and planar aligned sampl... This study investigates the effect of magnetic nanoparticles(NPs) on the weakly polar nematic liquid crystal(NLC).Different parameters of dielectric data were measured for both the homeotropic and planar aligned samples as a function of frequency and temperature and the substantial changes have been noticed for the doped systems. Dielectric permittivity has been increased after the dispersion of magnetic NPs in the pure NLC. Dielectric anisotropy has also been influenced by incorporating the magnetic NPs with the NLC molecules. These results were attributed to the dipole–dipole interaction between the magnetic nanoparticles and nematic liquid crystal molecules. Electro-optical study indicated the faster rise time and fall time of the doped systems as compare to pure NLC. Threshold voltage has been calculated and found to be decreased for the doped systems. Moreover, we have also calculated the rotational viscosity and the splay elastic constant for pure and the doped systems. Both the rotational viscosity and splay elastic constant of the doped systems are found to be considerably lower than those of pure NLC. Change in these properties has been explained on the basis of molecular disturbances created by the interaction between the magnetic nanoparticle and LC director. This study reveals that the inclusion of magnetic NPs in weakly polar NLC can be useful to enhance the basic properties of the weakly polar NLC and make it a promising material for many display applications. 展开更多
关键词 magnetic nanoparticles DIELECTRIC PERMITTIVITY response time ROTATIONAL VISCOSITY
Effect of Sintering Temperature on Low Frequency Response Properties of Ba0.6Sr0.4TiO3 Ceramic
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作者 张悦 詹斌 WANG Xiaoying 《武汉理工大学学报:材料科学英文版》 SCIE EI CAS 2019年第6期1360-1364,共5页
Ba0.6Sr0.4TiO3 ceramic was synthesized by the sol-gel method combined with the solidstate reaction. Phase composition and microstructure analyses indicate that pure BST phase with aggregated nanograins can be achieved... Ba0.6Sr0.4TiO3 ceramic was synthesized by the sol-gel method combined with the solidstate reaction. Phase composition and microstructure analyses indicate that pure BST phase with aggregated nanograins can be achieved. The dielectric properties change with sintering temperature, and reach the maximum at suitable temperatures. The highest dielectric constant of 4351 is obtained at 100 Hz for 1 275 ℃ sintered sample that is 2 times greater than that of the original sample, which indicates the dielectric properties can be modulated by grain size and density. The results show that Ba0.6Sr0.4TiO3 is a promising candidate for microwave applications. 展开更多
关键词 BST sol gel dielectric property frequency spectrum
Effects of bismuth on structural and dielectric properties of cobalt-cadmium spinel ferrites fabricated via micro-emulsion route
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作者 Furhaj Ahmed Sheikh Muhammad Khalid +6 位作者 Muhammad Shahzad Shifa H M Noor ul Huda Khan Asghar Sameen Aslam Ayesha Perveen Jalil ur Rehman Muhammad Azhar Khan Zaheer Abbas Gilani 《中国物理B:英文版》 SCIE EI CAS CSCD 2019年第8期408-416,共9页
Spinel ferrites have a significant role in high-tech applications.In the present work nano-crystalline ferrites having general formula Co0.5Cd0.5BixFe2-xO4 with(x=0.0,0.05,0.1,0.15,0.2,and 0.25)are synthesized via mic... Spinel ferrites have a significant role in high-tech applications.In the present work nano-crystalline ferrites having general formula Co0.5Cd0.5BixFe2-xO4 with(x=0.0,0.05,0.1,0.15,0.2,and 0.25)are synthesized via micro-emulsion route.Powder x-ray diffraction(XRD)studies discover the FCC spinel structure.Crystalline size is calculated in a range of 11 nm-15 nm.Lattice parameter calculations are reduced due to its substitution which leads to the exchange of large ionic radius of Fe^3+for small ionic radius of Bi^3+.The x-ray density is analyzed to increase with doping.Fourier transform infrared spectroscopy(FTIR)is performed to analyze absorption band spectra.The two absorption bands are observed in a range of 400 cm^-1-600 cm^-1,and they are the characteristic feature of spinel structure.Thermo-gravimetric analysis(TGA)reveals the total weight loss of nearly 1.98%.Dielectric analysis is carried out by impedance analyzer in a frequency span from 1 MHz to 3 GHz by using the Maxwell Wagner model.Dielectric studies reveal the decrease of dielectric parameters.The alternating current(AC)conductivity exhibits a plane behavior in a low frequency range and it increases with the applied frequency increasing.This is attributed to the grain effects in a high frequency range or may be due to the reduction of porosity.Real and imaginary part of impedance show the decreasing trend which corresponds to the grain boundary action.The imaginary modulus shows the occurrence of peak that helps to understand the interfacial polarization.Cole-Cole graph shows a single semicircle which confirms that the conduction mechanism is due to the grain boundaries at low frequency.Dielectric studies reveal the applicability of these ferrites in high frequency equipment,microwave applications,high storage media,and semiconductor devices. 展开更多
关键词 CO-FERRITE NANOCRYSTALLINE ferrites XRD MICROEMULSION DIELECTRIC properties
一种微晶SOI的制作及电荷存储性能研究
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作者 黄志强 沈彦宇 +1 位作者 马雪涛 顾宇杰 《微电子学》 CAS 北大核心 2019年第6期847-851,857,共6页
运用高温熔凝工艺制作了一种Si-(SiO2-Ta2O5-B2O3-RO)-Si微晶SOI。实验结果显示,该SOI样品的顶层、底层的单晶硅片结合紧密,中间层为微晶结构,具有良好的绝缘、介电性能;恒压正负电晕充电可以在中间绝缘层建立无源空间电场,获得与栅压... 运用高温熔凝工艺制作了一种Si-(SiO2-Ta2O5-B2O3-RO)-Si微晶SOI。实验结果显示,该SOI样品的顶层、底层的单晶硅片结合紧密,中间层为微晶结构,具有良好的绝缘、介电性能;恒压正负电晕充电可以在中间绝缘层建立无源空间电场,获得与栅压相近的表面电位;热刺激放电曲线显示,电流峰位于T=513 K附近且呈正负对称,捕获电荷的能阱深度约为1.22 eV。这表明该微晶SOI是一种具有电荷存储能力的新型SOI复合材料。 展开更多
关键词 绝缘体上硅 复合材料 介电 电荷存储 热刺激放电
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