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dielectric permittivity of Rigid Rapeseed Oil Polyol Polyurethane Biofoams and Petrochemical Foams at Low Frequencies

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Journal of Renewable Materials 2020年第9期8卷 1151-1170页

作者： Ilze Beverte Vairis Shtrauss Aldis Kalpinsh Uldis Lomanovskis Ugis Cabulis Irina Sevastyanova Sergejs Gaidukovs Institute for Mechanics of Materials University of LatviaRigaLV-1006Latvia Latvian State Institute of Wood Chemistry RigaLV-1006Latvia Faculty of Materials Science and Applied Chemistry Institute of Polymer MaterialsInstitute of Applied ChemistryRiga Technical UniversityRigaLV-048Latvia

Early investigations of dielectric permittivity of rigid polyurethane foams at low frequencies were made on petrochemical-origin foams,mainly by means of parallel plate *** the present investigation biopolyol was synthesized from Latvia-grown rapeseeds’oil by the transesterification method with triethanolamine,in an environmentally friendly process,without emission of harmful substances,at temperatures 175℃±5℃.Rigid,closed-cell rapeseed oil polyol polyurethane biofoams and petrochemical foams were made ensuring content of the renewable rapeseed oil polyol in ready foams 27 wt.%–29 wt.%.dielectric permittivity of the polyurethane foams and the underlying monolithic petrochemical-origin polyurethane and biopolyurethane was measured with a non-destructive dielectric spectrometer equipped with a capacitive sensor of one-side access type at 16 discrete frequencies distributed geometrically over the band 10 Hz,…,330 *** value of the gaseous phase in the closed-cells was estimated to beεg≈1.001 that corresponds to the values,characteristic for the most of *** permittivity of petrochemical polyurethane foams and the mentioned biofoams was compared with permittivity of polyurethane foams from industrial producers Sika JSC and General Plastics Manufacturing *** foams of the developed formulation exhibit competitive,low dielectric permittivity,not exceeding that of the foams from industrial producers:petrochemical foams up to 550 kg/m^(3) and the mentioned biofoams,comprising the renewable rapeseed oil polyol,up to densities 230–250 kg/m^(3).Considering petrochemical-origin polyurethane foams as a heterogeneous media“Polymer—gaseous phase”,the applicability of the rule of mixture and Maxwell–Garnett equation to model mathematically the dependence of effective dielectric permittivity on the volume fraction of phases was showed.

关键词： Polyurethane foams rapeseed oil polyol biofoams dielectric permittivity capacitive sensor one-side access low frequencies

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dielectric permittivity of dusty plasma in the Earth's mesosphere

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Earth and Planetary Physics 2021年第1期5卷 117-120页

作者： Hui Li Jian Wu National Key Laboratory of Electromagnetic Environment(LEME) China Research Institute of Radio Wave PropagationQingdao 266109China

This paper deals with the dielectric permittivity of dusty plasma in the earth’s *** give expressions for the complex dielectric permittivity of dusty plasma,taking into account the effects of the dust charging process and magnetic *** discuss the dielectric permittivity of dusty plasma in several cases,such as high frequency approximation,parallel propagation in MF/HF band,and effects of plasma ***,the expressions are employed to study the phenomenon of radar echoes from the polar summer *** report that dielectric permittivity caused by the dust charging process gives a radar cross section proportional to ω–4 and produces a number density of charged dust that agrees with measurements of mesopheric radar echoes.

关键词： dusty plasma dielectric permittivity polar summer mesosphere

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A new equation for dielectric permittivity of saturated soils based on polarization mechanics

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第3期9卷 293-302页

作者： Ren-peng CHEN Yun-min CHEN Wei XU Zhi-gang LIANG Wei FENG MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering Zhejiang University Hangzhou 31002 7 China Institute of Geotechnical Engineering Zhejiang University Hangzhou 310027 China Design Institute of Architecture of Hangzhou Hangzhou 310001 China Lexmark lnternational inc. Lexinton KY 40511 USA

Based on polarization mechanisms, such as electronic, ionic and orientational polarizations, a new equation for dielectric permittivity of soil is proposed to interpret the dielectric behavior of a mixture like soil, in terms of polarization process of its components and the interactions between its components. The dielectric permittivity is expressed in terms of a fre-quency-dependent part and a frequency-independent part. These two parts correspond to polarizations occurred at different fre-quency range. It is a new volumetric mixing model with theoretical background. Based on time domain reflectometry (TDR) measurements of saturated soil samples and test data from literature, comparisons of this model with some well established mixing models show that the curves for saturated sand soils and slurries resulted from the new equation, which agree well with TDR measurements, are close to those calculated from Birchak's model.

关键词： dielectric permittivity Saturated soils Polarization Time domain reflectometry (TDR)

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Enhanced dielectric permittivity of graphite oxide/polyimide composite films

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Journal of Central South University 2016年第11期23卷 2747-2753页

作者：李俊王亚李衡峰 School of Materials Science and Engineering Central South University

Graphite oxide(GO) was prepared by the pressurized oxidation method and incorporated into polyimide(PI) matrix to fabricate high-k composite films by in-situ polymerization and subsequent thermal treatment. The results show that the as-prepared GO had good dispersion and compatibility in PI matrix due to the introduction of abundant oxygen-containing functional groups during the oxidation. The residual graphitic domains and the thermal treatment induced reduction of GO further enhanced the dielectric permittivity of the resulting GO–PI composites. The dielectric permittivity of the GO–PI composites exhibited a typical percolation behavior with a percolation threshold of 0.0347 of volume ratio and a critical exponent of 0.837. Near the percolation threshold, the dielectric permittivity of the GO–PI composite increased to 108 at 10~2 Hz and was 26 times that of the pure PI.

关键词： graphite oxide pressurized oxidation polyimide dielectric permittivity percolation

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Temperature characterization of dielectric permittivity and AC conductivity of nano copper oxide-doped polyaniline composite

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Journal of Advanced dielectrics 2016年第3期6卷 27-33页

作者： L.N.Shubha P.Madhusudana Rao Department of Electronics St.Francis College for Women BegumpetHyderabad 500011TelanganaIndia Department of Physics Jawaharlal Nehru Technological University Hyderabad KukatpallyHyderabad 500085TelanganaIndia

The polyaniline/copper oxide(PANI/CuO)nanocomposite was prepared by mixing solutions of polyaniline and copper oxide nanoparticles in dimethyl sulfoxide(DMSO).The synthesized polymer nanocomposites were characterized by X-ray powder diffraction(XRD),scanning electron microscope(SEM)and UV-visible *** characteristic peaks in XRD and UV-visible spectra confirmed the presence of CuO in the polymer *** images indicated morphological changes in the composite matrix as compared to the pristine *** DC conductivity measurements were performed using two-probe method for various *** conductivity and dielectric response of the composites were investigated in the frequency range of 10^(2)-10^(6)Hz using LCR *** permittivityε′(w)and dielectric loss factorε″(w)were *** was observed thatε′(w)andε″(w)decrease with increase in frequency at all *** a particular frequency it is observed that bothε′(w)andε″(w)increase with increase in *** was also observed that AC conductivity increased with increase in frequency and temperature.

关键词： AC conductivity dielectric permittivity dielectric loss factor polyaniline composite

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CONTRIBUTION OF THE INTERPHASE INTERACTION TO THE dielectric permittivity OF COLLOID SYSTEMS

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Journal of Advanced dielectrics 2011年第2期1卷 169-178页

作者： V.S.BORISOV Department of Physics Irkutsk State University Boulevard Gagarina 20Irkutsk664003Russia

Specific features of the dielectric response of colloid systems with electrically interacting com-ponents(polar liquid matrix and solid spherical inclusions)have been revealed.A theory was developed to describe dielectric dispersion and anisotropy of the liquid phase caused by the electric field of surface charges on the solid *** was found that the local dielectric permittivity in diferent directions can vary over a wide range and strongly depends on the strength of the inner *** existence of the interphase interaction leads to the formation of thin structured liquid layers in the contact area of two phases and,therefore,to a decrease in the average dielectric permittivity of the considered *** structure of the polar liquid was taken into account while the derivation of a mixing formula which clearly demonstrates the contribution of the interphase interaction to the dielectric response of the investigated colloid system.

关键词： Colloids interphase interaction dielectric permittivity mixing formula

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Relative dielectric permittivity Variations during Compaction as a Mean of Compaction Quality Control: Case Study on Laterite Samples from Senegal

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International Journal of Geosciences 2023年第2期14卷 238-250页

作者： Mapathé Ndiaye Makhaly Ba Teophile Kiendrebeogo Linda E. Gaffo Foudjo Laboratoire de Mécanique et de Modélisation Université de Thiès Sénégal

This study explores an alternative to the classical use of direct methods, as water content and dry density measurements, for compaction quality control. For this purpose, the dielectric properties of lateritic materials are determined by radar method and are compared with the permittivity determined from the Topp formula and from the CRIM model. This approach allowed to establish a relationship between the geotechnical properties determined during compaction such as dry density, water content or porosity with dielectric permittivity. The obtained results made it possible to determine an optimum dielectric permittivity corresponding to the optimum dry density and the optimum water content that could be used for non-destructive in situ compaction testing. Such an approach should improve the implementation and effectiveness of in situ compaction quality control of geotechnical infrastructures.

关键词： Laterite Proctor Water Content Dry Density dielectric permittivity

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Lattice dynamics properties of chalcopyrite ZnSnP_2:Density-functional calculations by using a linear response theory

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Chinese Physics B 2017年第4期26卷 307-312页

作者：虞游董玉静沈艳红赵国栋郑小林盛佳南 College of Optoelectronic Technology Chengdu University of Information Technology School of Science and Technology Xinyang University

We present a first-principles study of the structural,dielectric,and lattice dynamical properties for chalcopyrite semiconductor *** structural properties are calculated using a plane-wave pseudopotential method of densityfunctional theory.A linear response theory is used to derive Born effective charge tensors for each atom,dielectric constants in low and high frequency limits,and phonon *** calculate all zone-center phonon modes,identify Raman and infrared active modes,and report LO-TO splitting of the infrared *** results show an excellent agreement with experiment and propose several predictive behaviors.

关键词： phonon Born effective charge dielectric permittivity linear response theory

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Comprehensive studies on dielectric properties of p-methoxy benzylidene p-decyl aniline with function of temperature and frequency in planar geometry: A potential nematic liquid crystal for display devices

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Chinese Physics B 2021年第6期30卷 329-333页

作者： Pankaj Kumar Tripathi Kunwar Vikram Mithlesh Tiwari Ajay Shriram Department of Physics Lovely Professional UniversityPhagwara-144411PunjabIndia Department of Allied Science Graphic Era(Deemed to be university)Dehradun-248002 India Department of Physics and Electronics Dr.Ram Manohar Lohia Avadh UniversityAyodhya-224001U.P.India School of Computer Science&Information Technology Jain(Deemed-to-be-University)Bengaluru-560069KarnatakaIndia

The dielectric properties of the nematic mesophase, p-methoxy benzylidene p-decyl aniline(MBDA), measured in planar geometry with a function of frequency and temperature are investigated in detail. The complex dielectric permittivity(ε' and ε'') is also studied at a bias voltage of 10 V for planar aligned sample cell of nematic mesophase. The dielectric permittivity with bias voltage attains a higher(> 2 times) value than that without bias voltage at a temperature of 56℃,which is due to the fact that the linking group of nematic molecules is internally interacted with an applied bias *** is supported by observing an enhanced dielectric permittivity of nematic liquid crystal(LC) in the presence of bias voltage, which can be fully explained as the increasing of the corresponding dipole moment. The dielectric relaxation behaviors of nematic LC are also demonstrated for planar aligned sample cell. The remarkable results are observed that the relaxation frequency shifts into low frequency region with the increase of the bias voltage applied to the planar aligned sample cells. The dielectric relaxation spectra are fitted by Cole–Cole nonlinear curve fitting for nematic mesophase in order to determine the dielectric strength.

关键词： dielectric permittivity dielectric loss relaxation frequency nematic mesogen

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Microstructural,magnetic and dielectric performance of rare earth ion(Sm^(3+))-doped MgCd ferrites

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Chinese Physics B 2022年第7期31卷 643-647页

作者： Dandan Wen Xia Chen Dasen Luo Yi Lu Yixin Chen Renpu Li Wei Cui Doctoral Research Station of Chongqing Key Laboratory of Optoelectronic Information Sensing and Transmission Technology Chongqing University of Post and TelecommunicationsChongqing 400065China State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu 610054China Chongqing Key Laboratory of Autonomous Navigation and Microsystem Chongqing University of Post and TelecommunicationsChongqing 400065China

The combined effects of Sm^(3+)substitution together with the addition of 3 wt%Bi_(2)O_(3)endow Mg Cd ferrites with excellent magnetic permeability and dielectric *** concentrations of Sm^(3+)(x=0,0.03,0.06,0.09,0.12and 0.15)were employed to modify the permeability(μ)and permittivity(ε)of the Mg Cd ferrites.X-ray diffraction,scanning electron microscopy(SEM),vibrating sample magnetometry and vector network analysis techniques were used to characterize the *** measurement results reveal that the ferrites processed a saturation magnetization of up to 36.8 emu/g and coercivity of up to 29.2 Oe via the conventional solid-state reaction *** surface morphology SEM confirms that with increasing Sm^(3+)concentration,the grain shape changes from a polygon to a ***,the dielectric permittivity can reach a value of *** excellent properties obtained in Sm^(3+)-substituted Mg ferrites suggest that they could be promising candidates for modern high-frequency antenna substrates or multilayer devices.

关键词： ferrites Sm^(3+)ions substitution magnetic permeability dielectric permittivity

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