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APPROXIMATION BY RATIONAL FUNCTIONS WITH POLYNOMIALS OF POSITIVE COEFFICIENTS AS THE DENOMINATORS 被引量:1
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作者 Dansheng Yu Songping Zhou 《Analysis in Theory and Applications》 2006年第1期65-71,共7页
The present paper proves that if(x) ∈ C[0,1], changes its sign exactly l times at 0 〈 y1〈 y2 … 〈 y1 〈 1 in (0, 1), then there exists a pn(x) ∈ Пn(+), such that |f(x)- p(x)/pn(x)|≤ Cωφ(f,n^... The present paper proves that if(x) ∈ C[0,1], changes its sign exactly l times at 0 〈 y1〈 y2 … 〈 y1 〈 1 in (0, 1), then there exists a pn(x) ∈ Пn(+), such that |f(x)- p(x)/pn(x)|≤ Cωφ(f,n^(-1/2)), where ρ(x) is defined by ρ(x)={^lПi=1(x-yi),if f (x)≥0 for x ∈(y1,1), {-^lПi=1(x-yi),if f (x)〈0 for x ∈(y1,1), which improves and generalizes the result of . 展开更多
关键词 polynomial with positive coefficients rational approzimation Ditzian-Totik modulus of smoothness
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ON CERTAIN CLASS OF MEROMORPHIC FUNCTIONS WITH POSITIVE COEFFICIENTS
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作者 J.Dziok G.Murugusundaramoorthy J.Sokól 《Acta Mathematica Scientia》 SCIE CSCD 2012年第4期1376-1390,共15页
In the present investigation we define a new class of meromorphic functions on the punctured unit disk A△^* := {z ∈ C : 0 〈 |z| 〈 1} by making use of the generalized Dziok-Srivastava operator Hm^l [α1]. Coef... In the present investigation we define a new class of meromorphic functions on the punctured unit disk A△^* := {z ∈ C : 0 〈 |z| 〈 1} by making use of the generalized Dziok-Srivastava operator Hm^l [α1]. Coefficient inequalities, growth and distortion inequalities, as well as closure results are obtained. We also establish some results concerning the partial sums of meromorphic functions and neighborhood results for functions in new class. 展开更多
关键词 meromorphic functions starlike function CONVOLUTION positive coefficients coefficient inequalities Dziok-Srivastava operator
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On the Coefficients of Polynomials with Positive Real Part in the Unit Disk
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作者 申大维 《Journal of Beijing Institute of Technology》 EI CAS 1995年第2期110+106-110,共6页
Let Q be the class of real coefficient polynomials of degree 2 with positive real part in the unit disk and constant term equal to 1. aam coefficient region of polynomials in Q is found and some sharp coefficient esti... Let Q be the class of real coefficient polynomials of degree 2 with positive real part in the unit disk and constant term equal to 1. aam coefficient region of polynomials in Q is found and some sharp coefficient estimates for the polynomials with positive real part in the unit disk are established in this paper. 展开更多
关键词 POLYNOMIALS coefficients/positive real part SUBORDINATION
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Oscillation in a Class of Neutral Differential Equations with Positive and Negative Coefficients
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作者 单文锐 葛渭高 郭彦平 《Journal of Beijing Institute of Technology》 EI CAS 2002年第3期321-324,共4页
The oscillatory behavior of neutral differential equation with positive and negative coefficients is investigated by mathematics analysis technique and the fixed point principle. Some sufficient conditions for oscilla... The oscillatory behavior of neutral differential equation with positive and negative coefficients is investigated by mathematics analysis technique and the fixed point principle. Some sufficient conditions for oscillation of neutral differential equation with positive and negative coefficients are obtained. 展开更多
关键词 neutral differential equation OSCILLATION fixed point principle positive and negative coefficients
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Preparation and study on performance of submicron nickel powder for multilayer chip positive temperature coefficient resistance 被引量:4
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作者 陈勇 龚树萍 +3 位作者 傅邱云 郑志平 黄日明 苏鹏 《Chinese Physics B》 SCIE EI CAS CSCD 2010年第11期571-575,共5页
Base metal nickel is often used as the inner electrode in multilayer chip positive temperature coefficient resistance (PTCR). The fine grain of ceramic powders and base metal nickel are necessary. This paper uses re... Base metal nickel is often used as the inner electrode in multilayer chip positive temperature coefficient resistance (PTCR). The fine grain of ceramic powders and base metal nickel are necessary. This paper uses reducing hydrazine to gain submicron nickel powder whose diameter was 200-300 nm through adjusting the consumption of nucleating agent PVP properly. The submicron nickel powder could disperse well and was fit for co--fired of multilayer chip PTCR. It analyes the submicron nickel powder through x-ray Diffraction (XRD) and calculates the diameter of nickel by PDF cards. Using XRD analyses it obtains several conclusions: If the molar ratio of hydrazine hydrate and nickel sulfate is kept to be a constant, when enlarging the molar ratio of NaOH/Ni^2+, the diameter of nickel powder would become smaller. When the temperature in the experiment raises to 70-80 ℃, nickel powder becomes smaller too. And if the molar ratio of NaOH/Ni2+ is 4, when molar ratio of (C2H5O)2/Ni^2+ increases, the diameter of nickel would reduce. Results from viewing the powders by optical microscope should be the fact that the electrode made by submicron nickel powder has a better formation and compactness. Furthermore, the sheet resistance testing shows that the electrode made by submicron nickel is smaller than that made by micron nickel. 展开更多
关键词 SUBMICRON nickel powder liquid-reduction process positive temperature coefficient (PTC)
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Characterization of the BaBiO_3-doped BaTiO_3 positive temperature coefficient of a resistivity ceramic using impedance spectroscopy with T_c=155℃ 被引量:3
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作者 袁昌来 刘心宇 +2 位作者 周昌荣 许积文 杨云 《Chinese Physics B》 SCIE EI CAS CSCD 2011年第4期543-550,共8页
BaBiO3-doped BaTiO3 (BB-BT) ceramic, as a candidate for lead-free positive temperature coefficient of resistivity (PTCR) materials with a higher Curie temperature, has been synthesized in air by a conventional sin... BaBiO3-doped BaTiO3 (BB-BT) ceramic, as a candidate for lead-free positive temperature coefficient of resistivity (PTCR) materials with a higher Curie temperature, has been synthesized in air by a conventional sintering technique. The temperature dependence of resistivity shows that the phase transition of the PTC thermistor ceramic occurs at the Curie temperature, Tc = 155℃, which is higher than that of BaTiO3 (≤ 130 ℃). Analysis of ac impedance data using complex impedance spectroscopy gives the alternate current (AC) resistance of the PTCR ceramic. By additional use of the complex electric modulus formalism to analyse the same data, the inhomogeneous nature of the ceramic may be unveiled. The impedance spectra reveal that the grain resistance of the BB-BT sample is slightly influenced by the increase of temperature, indicating that the increase in overall resistivity is entirely due to a grain-boundary effect. Based on the dependence of the extent to which the peaks of the imaginary part of electric modulus and impedance are matched on frequency, the conduction mechanism is also discussed for a BB-BT ceramic system. 展开更多
关键词 BaBiO3-doped BaTiO3 positive temperature coefficient thermistor impedance spectroscopy high Tc
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GLOBAL ATTRACTIVITY OF NEUTRAL DIFFERENCE EQUATIONS WITH POSITIVE AND NEGATIVE COEFFICIENTS 被引量:2
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作者 Li Xiaoping Jiang Jianchu Gao PingDept. of Math., Loudi Teacher’s College, Loudi 417000,China. 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2002年第3期258-266,共9页
A neutral difference equation with positive and negative coefficientsΔ(x n-c nx n-k )+p nx n-l -q nx n-r =0, n=0,1,2,...,is considered and a sufficient condition for the global attractivity of the ze... A neutral difference equation with positive and negative coefficientsΔ(x n-c nx n-k )+p nx n-l -q nx n-r =0, n=0,1,2,...,is considered and a sufficient condition for the global attractivity of the zero solution of this equation is obtained, which improves and extends the all known results in the literature. 展开更多
关键词 global attractivity neutral difference equations positive and negative coefficients.
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EXISTENCE OF POSITIVE SOLUTIONS FOR NEUTRAL DIFFERENCE EQUATIONS WITH POSITIVE AND NEGATIVE COEFFICIENTS 被引量:1
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作者 Luo Zhiguo Shen JianhuaDept. of Math., Hunan Normal Univ., Changsha 410081,China. 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 2002年第3期251-257,共7页
In this paper the sufficient conditions for the existence of positive solutions of the neutral difference equations with positive and negative coefficients are established. The results improve some known conclusions i... In this paper the sufficient conditions for the existence of positive solutions of the neutral difference equations with positive and negative coefficients are established. The results improve some known conclusions in the literature. 展开更多
关键词 positive solutions neutral difference equations positive and negative coefficients.
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Positive temperature coefficient of resistivity effects of semiconducting (Bi(1/2)Na(1/2)) TiO_3-CaTiO_3-BaTiO_3 ceramics sintered in air atmosphere
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作者 马季 朱兴文 +3 位作者 张芳 徐琼 姜文中 周晓 《Journal of Shanghai University(English Edition)》 CAS 2010年第6期452-455,共4页
Y^3+-doped (Bi 1/2 Na 1/2) TiO 3-CaTiO 3-BaTiO 3 (BNCBT) positive temperature coefficient of resistivity (PTCR) ceramics sintered in air atmosphere were investigated in this study. (Bi 1/2 Na 1/2) TiO 3 (BNT... Y^3+-doped (Bi 1/2 Na 1/2) TiO 3-CaTiO 3-BaTiO 3 (BNCBT) positive temperature coefficient of resistivity (PTCR) ceramics sintered in air atmosphere were investigated in this study. (Bi 1/2 Na 1/2) TiO 3 (BNT) component can remarkably increase the onset temperature T c of PTCR ceramics with the expense of the resistivity R 25 increase. CaTiO 3 (9–27 mol%) component can decrease the resistivity, and adjust the effects of BNT phase on the T c point. For the sample containing 3 mol% CaTiO 3 , T c raises from 122 ℃ to 153 ℃ when only 0.6 mol% BNT added, while for the ones with higher CaTiO 3 content (9–27 mol%), T c is only increased by a rate of 8–9℃/1.0 mol% BNT. The effects of BNT and CaTiO 3 components on R25/Rmin (negative temperature coefficient effect) are also discussed. 展开更多
关键词 lead-free materials positive temperature coefficient of resistivity (PTCR) (Bi 1/2 Na 1/2) TiO 3 CaTiO 3 negative temperature coefficient (NTC) effect
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A novel Na_(1−x)K_(x)TaO_(3)perovskite microwave dielectric ceramic with high permittivity and high positive temperature coefficient 被引量:1
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作者 Liu Tang Hongcheng Yang +1 位作者 Enzhu Li Chaowei Zhong 《Journal of Advanced Ceramics》 SCIE EI CAS CSCD 2023年第11期2053-2061,共9页
A novel Na_(1−x)K_(x)TaO_(3)(x=0,0.025,0.05,0.075,0.1,and 0.15)ceramic with high permittivity and high positive temperature coefficient was synthesized via the conventional solid-state method.All samples were determin... A novel Na_(1−x)K_(x)TaO_(3)(x=0,0.025,0.05,0.075,0.1,and 0.15)ceramic with high permittivity and high positive temperature coefficient was synthesized via the conventional solid-state method.All samples were determined to be pure phase orthorhombic NaTaO3 structure of space group Pmcn,and larger grain and lower porosity were observed after adding an appropriate amount of K+ions.The Q×f value is majored by the packing fraction and grain size,while the value ofτf is influenced by Ta–O bond valence.The Na_(0.95)K_(0.05)TaO_(3) ceramic possesses excellent dielectric properties ofεr=164.29,Q×f=9091 GHz(f=3.15 GHz),tanδ=3.46×10^(–4),τf=+809.52 ppm/℃,sintered at 1550℃.Compared with NaTaO_(3) ceramics,the Na_(1−x)K_(x)TaO_(3)ceramics prepared in this study demonstrate higher dielectric constants and higher positive temperature coefficients,which are promising for device miniaturization andτf compensators. 展开更多
关键词 Na_(1−x)K_(x)TaO_(3)ceramics high permittivity high positive temperature coefficient PEROVSKITE
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PTC/NTC Behavior of PVDF Composites Filled with GF and CF 被引量:3
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作者 WANG Xin-lei ZHANG Guo LI Ji-xin LI Zhuo-shi LIU Zhan-fang LIU Xiu-qi 《Chemical Research in Chinese Universities》 SCIE CAS CSCD 2008年第5期648-652,共5页
Conductive polyvinylidene fluoride(PVDF)matrix composites filled with graphited fiber(GF)or carbon fiber(CF)were prepared by the melt-mixing method.The breakage and length distribution of the fibers in the polym... Conductive polyvinylidene fluoride(PVDF)matrix composites filled with graphited fiber(GF)or carbon fiber(CF)were prepared by the melt-mixing method.The breakage and length distribution of the fibers in the polymer matrix were studied by scanning electron microscope(SEM)and optical microscope(OM)observations,respectively. The differences in the positive temperature coefficient(PTC)effects of the composites were mainly attributed to inter-fiber contact ability.The elimination of the negative temperature coefficient(NTC)effect for CF/PVDF composite was because of an increase in the viscosity of the polymer matrix.With the same filler content,CF could be more effective,to eliminate the NTC effect when compared with GF.Addition of 2%CF(mass fraction)in the PVDF composite with 7%GF(mass fraction)could effectively eliminate the NTC phenomenon of the composite. 展开更多
关键词 Polyvinylidene fluoride Graphited fiber Carbon fiber positive temperature coefficient effect Negative temperature coefficient effect
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Influence of sintering schedule on the electrical properties of Mn(NO_3)_2-doped Ba_(0.92)Ca_(0.08)TiO_3 PTCR ceramics 被引量:2
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作者 CAOMinghe YUANJun +1 位作者 CAOMingli ZHOUDongxiang 《Rare Metals》 SCIE EI CAS CSCD 2004年第3期274-278,共5页
The relationship of electrical properties of Mn-doped Ba_(0.92)Ca_(0.08)TiO_3PTCR (positive temperature coefficient resistance) ceramics with two sintering schedules wasdiscussed. Using TEM (transmission electron micr... The relationship of electrical properties of Mn-doped Ba_(0.92)Ca_(0.08)TiO_3PTCR (positive temperature coefficient resistance) ceramics with two sintering schedules wasdiscussed. Using TEM (transmission electron microscope) combined with EDS (energy dispersive X-rayspectrometer), the Mn ions distributed at grain boundaries were analyzed. The results show that thePTCR effect of Mn-doped PTCR ceramics is more dependent on the sintering schedule than those of Mnfree. The phenomenon may be caused by the valence states variance of Mn ions segregated at the grainboundaries. 展开更多
关键词 positive temperature coefficient resistance grain boundaries sinteringschedule SEGREGATION potential barrier
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Oscillation criteria for second order neutral dynamic equations of Emden-Fowler type with positive and negative coefficients on time scales 被引量:9
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作者 DENG XunHuan WANG QiRu ZHOU Zhan 《Science China Mathematics》 SCIE CSCD 2017年第1期113-132,共20页
We investigate oscillation of certain second order neutral dynamic equations of Emden-Fowler type with positive and negative coefficients. We use some different techniques and apply Riccati transformation to establish... We investigate oscillation of certain second order neutral dynamic equations of Emden-Fowler type with positive and negative coefficients. We use some different techniques and apply Riccati transformation to establish new oscillatory criteria which include two necessary and sufficient conditions. Moreover, we point out that how the power γ plays its role. Some interesting examples are given to illustrate the versatility of our results. 展开更多
关键词 neutral dynamic equations oscillation positive and negative coefficients Riccati transformation
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Studies on preparation and thermal control behavior of hybrid fillers/binary-polymer composites with positive temperature coefficient characteristic 被引量:1
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作者 YU AiMei LI Qiang 《Science China(Technological Sciences)》 SCIE EI CAS CSCD 2021年第7期1447-1458,共12页
Conductive polymer composites(CPCs) as the thermo-sensitive materials have attracted much attention in thermal control field due to their reliable self-regulating behaviors, high efficiency and mechanical flexibility.... Conductive polymer composites(CPCs) as the thermo-sensitive materials have attracted much attention in thermal control field due to their reliable self-regulating behaviors, high efficiency and mechanical flexibility. However, the development of these materials needs to manage the normal conflicting requirements, such as effective heating performance and good self-regulating capability. This paper presents a series of novel CPCs material having different amounts of hybrid fillers of multi-walled carbon nanotubes(CNTs) and carbon black(CB). The positive temperature coefficient intensity is enhanced to 105.2, and the roomtemperature resistivity is optimized to 320 ? cm. Besides, the Curie temperatures are regulated to room-temperature range by incorporating the low-melting-point blend matrix into the poly(ethylene-co-vinyl acetate)/CNTs/CB composite. The thermalcontrol experiment demonstrates that CPCs-heating elements can adjust the equilibrium temperature of controlled equipment near their Curie temperatures without any control methods. Compared with the ordinary resistor, the CPCs materials have the remarkable adaptive thermal control behavior. Furthermore, the temperature control capability is particularly prominent in the changing environment temperature. The CPCs as a safe and reliable adaptive heating element is potential to replace the conventional active thermal control means. 展开更多
关键词 positive temperature coefficient room-temperature Curie point adaptive thermal control CPCs materials
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A dual-gate and dielectric-inserted lateral trench insulated gate bipolar transistor on a silicon-on-insulator substrate 被引量:1
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作者 付强 张波 +1 位作者 罗小蓉 李肇基 《Chinese Physics B》 SCIE EI CAS CSCD 2013年第7期473-477,共5页
In this paper, a novel dual-gate and dielectric-inserted lateral trench insulated gate bipolar transistor (DGDI LTIGBT) structure, which features a double extended trench gate and a dielectric inserted in the drift ... In this paper, a novel dual-gate and dielectric-inserted lateral trench insulated gate bipolar transistor (DGDI LTIGBT) structure, which features a double extended trench gate and a dielectric inserted in the drift region, is proposed and discussed. The device can not only decrease the specific on-resistance Ron,sp , but also simultaneously improve the temperature performance. Simulation results show that the proposed LTIGBT achieves an ultra-low on-state voltage drop of 1.31 V at 700 A·cm-2 with a small half-cell pitch of 10.5 μm, a specific on-resistance R on,sp of 187 mΩ·mm2, and a high breakdown voltage of 250 V. The on-state voltage drop of the DGDI LTIGBT is 18% less than that of the DI LTIGBT and 30.3% less than that of the conventional LTIGBT. The proposed LTIGBT exhibits a good positive temperature coefficient for safety paralleling to handling larger currents and enhances the short-circuit capability while maintaining a low self-heating effect. Furthermore, it also shows a better tradeoff between the specific on-resistance and the turnoff loss, although it has a longer turnoff delay time. 展开更多
关键词 lateral trench insulated gate bipolar transistor specific on-resistance positive temperature coefficient turnoff characteristic
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Resistivity-temperature Characteristics of Conductive Asphalt Concrete 被引量:1
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作者 孙文州 LI Xu +1 位作者 杨群 ZHANG Hongwei 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2016年第2期367-371,共5页
The changes of resistivity of conductive asphalt concrete at different temperatures were studied,and positive temperature coefficient(PTC)modelwas established to estimate the influence of temperature on the resistiv... The changes of resistivity of conductive asphalt concrete at different temperatures were studied,and positive temperature coefficient(PTC)modelwas established to estimate the influence of temperature on the resistivity quantitatively,which eliminated the interference with conductivity evaluation brought by temperature variation.Finally,the analysis of temperature cycling test results proves that the changes of percolation network structure caused by temperature variation prompt the emergence of PTC of conductive asphalt concrete. 展开更多
关键词 conductive asphalt concrete electrical resistivity positive temperature coefficient percolation network
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Enhanced Reproducibility of Positive Temperature Coefficient Effect of CB/HDPE/PVDF Composites with the Addition of Ionic Liquid
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作者 Long Chen Xiao Wu +1 位作者 Xiao-Fang Zhang Jian-Ming Zhang 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 2021年第2期228-236,I0008,共10页
Developing an effective method for improving the reproducibility of positive temperature coefficient(PTC)effect is of great significance for large-scale application of polymer based PTC composites,owing to its contrib... Developing an effective method for improving the reproducibility of positive temperature coefficient(PTC)effect is of great significance for large-scale application of polymer based PTC composites,owing to its contribution to the security and reliability.Herein,we developed a carbon black(CB)/high density polyethylene(HDPE)/poly(vinylidene fluoride)(PVDF)composite with outstanding PTC reproducibility,by incorporating 1-octyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide([OMIm][NTf2])into the composite.After multiple repeated temperature cycles,the PTC performance of as-prepared material keeps almost unchanged and the varition of resistance at room temperature is less than 7%.Our studies revealed that[OMIm][NTf2]contributes to the improvement of PTC reproducibility in two ways:(i)it acts as an efficient plasticizer for refining the co-continuous phase morphology of HDPE/PVDE blends;(ii)it inhibits the crystallization of PVDF through the dilution effect,leading to more overlaps of the volume shrinkage process of HDPE and PVDF melt which results in the decrease of interface gap between HDPE and PVDF.This study demonstrated that ionic liquids as the multifunctional agents have great potential for improving the reproducibility in the application of the binary polymer based PTC composites. 展开更多
关键词 Conductive polymer composites REPRODUCIBILITY positive temperature coefficient Ionic liquid
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Dispersion of Polyacenic Semiconductor(PAS) in Polyethylene: Molecular Dynamics Simulation
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作者 SUNHai-zhu SHAOChen +3 位作者 HUDong-hua ZULong-min SUZhong-min ZHUYu-lan 《Chemical Research in Chinese Universities》 SCIE CAS CSCD 2005年第3期334-336,共3页
The dispersing process of polyacenic semiconductor(PAS) in polyethylene(PE) was simulated by using molecular dynamics(MD) methods. The results show that this process can be divided into three stages. In the first stag... The dispersing process of polyacenic semiconductor(PAS) in polyethylene(PE) was simulated by using molecular dynamics(MD) methods. The results show that this process can be divided into three stages. In the first stage, PAS particles in the crystal region of PE are expelled to the amorphous region; in the second stage, PAS particles aggregate due to small surface areas and PE chains are adjusted continuously, which makes the crystal region complete; PAS particles are separated from each other and the total energy increases in the third stage. During the whole dispersing process, PAS particles are more stable in the amorphous region than in the crystal region. All the simulation results are in good agreement with the experimental results. 展开更多
关键词 Molecular dynamics simulation Polyacenic semiconductor POLYETHYLENE positive temperature coefficient effect
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Conductive Behaviors of Carbon Nanofibers Reinforced Epoxy Composites
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作者 梅启林 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2008年第1期139-142,共4页
By means of ultrasonic dispersion, carbon nanofibers reinforced epoxy resin composite was prepared in the lab, the electrical conductivity of composite with different carbon nanofibers loadings were studied, also the ... By means of ultrasonic dispersion, carbon nanofibers reinforced epoxy resin composite was prepared in the lab, the electrical conductivity of composite with different carbon nanofibers loadings were studied, also the voltage-current relationship, resistance-temperature properties and mechano-electric effect were investigated. Results show that the resistivity of composite decreases in geometric progression with the increasing of carbon nanofibers, and the threshold ranges between 0.1 wt%-0.2 wt%. The voltage-current relationship is in good conformity with the Ohm's law, both positive temperature coefficient and negative temperature coefficient can be found at elevated temperature. In the course of stretching, the electrical resistance of the composites increases with the stress steadily and changes sharply near the breaking point, which is of importance for the safety monitor and structure health diagnosis. 展开更多
关键词 carbon nanofibers positive temperature coefficient negative temperature coefficient mechano-electric effect
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OSCILLATION AND EXISTENCE OF POSITIVE SOLUTIONS OF DIFFERENTIAL EQUATIONS WITH POSITIVE,NEGATIVE COEFFICIENTS
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作者 郭上江 黄立宏 《Annals of Differential Equations》 2002年第4期344-351,共8页
This paper is concerned with the existence of eventually positive solutions and oscillatory solutions of first-order neutral differential equation with positive and negative coefficients. The 'sharp' condition... This paper is concerned with the existence of eventually positive solutions and oscillatory solutions of first-order neutral differential equation with positive and negative coefficients. The 'sharp' conditions of oscillation for the equation have been obtained, i.e., the conditions are sufficient and necessary when all of the coefficients are constants. These conditions are distinguished from the previous criteria in the literatures, and also weaker than those existing results. 展开更多
关键词 neutral differential equation OSCILLATION positive and negative coefficients eventually positive solutions
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