A circuit modeling of SAGCM avalanche photodiode with additional layer and nonuniform electric field profile

This paper presents a new way to improve the speed of the separated absorption grading charge multiplication avalanche photodiode by adding a new thin charge layer between absorption and grading layers. In this method, we assume a nonuniform electric field in different regions of the structure. In addition, based on carrier rate equations, a circuit model of the proposed structure is extracted. Considering the trade-offs between thicknesses of layers, we try to acquire the optimum structure by setting the physical parameters. Finally, it is shown that, in comparison with the conventional structure, considerable improvements in the gain-bandwidth product and also breakdown voltage are achieved.     

On the conservation of the ideal focusing of a beam in a time-dependent electric field quadratic in one coordinate

It has been shown that ideal focusing of ions is conserved in a time-dependent electric field quadratic in one coordinate. Examples of application of this property have been considered.     

Thermally activated plastic flow of metals and ceramics with an electric field or current

The effects of high density electric current pulses (10³–10⁶ A cm⁻²) on the flow stress of metals at low homologous temperatures and of a modest external electric field on the flow stress of fine-grained oxides at high temperatures is presented. The results in both cases are evaluated in terms of thermally-activated plastic deformation processes. In the case of the metals, the influence of an electron wind on each of the parameters in the equation for the thermally-activated motion of dislocations was determined, the largest effect being on the pre-exponential. The derived electron wind push coefficient was one or more orders of magnitude larger than the value normally accepted for the electron drag coefficient. In the case of the oxides, the substantial effect of an applied electric field on the flow stress was evaluated in terms of its influence on the electrochemical potential of vacancies in the space-charge cloud adjacent to the grain boundaries. Both the derived space-charge cloud width and the electric potential/stress parameter Δ∅/Δσ are in reasonable accord with theoretical predictions.     

Discharge current and ultrashort avalanche electron beam current in a volume nanosecond gas discharge in inhomogeneous electric field

The moment of generation of an ultrashort avalanche electron beam (UAEB) relative to the discharge current pulse front has been determined in a volume discharge formed upon nanosecond breakdown of an air gap at atmospheric pressure in an inhomogeneous electric field. The UAEB current reaches maximum on the front of the discharge current pulse, ～100 ps before the peak of this current. Bias currents with amplitude above 1 kA have been observed. The amplitude of this current increases due to the charging of a capacitor formed by the flat metal anode and a dense discharge plasma expanding from the cathode.     

Effect of the retarding electric field on the critical electron-beam current for virtual cathode formation

The dependence of a critical current at which a virtual cathode (VC) is formed in an electron beam on the retarding electric field and the external focusing magnetic field have been studied. It is shown that, as the retarding field exceeds a certain threshold value, both stationary and nonstationary (oscillating) VCs can form in the interaction space.     

Thermoelectric current in a superconducting circuit

The problem of a thermoelectric current in a closed circuit of two different superconductors is considered. A solution is found that describes the distribution of field and currents about the cross section of a long nonuniformly heated, inhomogeneous cylinder. The generally accepted model for the current distribution (see Ref. 1 for a Review) is shown to be valid and the conclusions of Pickett to be erroneous. The connection of the theory to experiment is discussed.     

Effect of polyethylenimine on electrophoretic deposition of TiO2 nanoparticles in alternating current electric field

In this work, AC electric field was applied to deposit TiO₂ nanoparticles dispersed in Acetone on coplanar electrodes. The experiments were performed in presence and absence of an additive, polyethylenimine (PEI), at frequencies of 1 Hz and 10 kHz. It was revealed that deposition pattern changed dramatically by addition of PEI which makes particles to fill the inter electrode gap at both frequencies. When PEI is added, particles show different behavior. While they tend to fill the gap randomly at 1 Hz, they form chainlike pattern at 10 kHz. Chain formation of particles in the gap indicates presence of dielectrophoretic (DEP) forces. The ability of particles to polarize in both suspensions at 10 kHz are calculated by a multi-shell model in order to find DEP force. According to this model, the polarizability for particles in the suspension with PEI is more than the other, so DEP forces applied more strongly on them and promotes chain formation.     

Liquid crystal order in colloidal suspensions of spheroidal particles by direct current electric field assembly

DC electric fields are used to produce colloidal assemblies with orientational and layered positional order from a dilute suspension of spheroidal particles. These 3D assemblies, which can be visualized in situ by confocal microscopy, are achieved in short time spans (t < 1 h) by the application of a constant voltage across the capacitor-like device. This method yields denser and more ordered assemblies than had been previously reported with other assembly methods. Structures with a high degree of orientational order as well as layered positional order normal to the electrode surface are observed. These colloidal structures are explained as a consequence of electrophoretic deposition and field-assisted assembly. The interplay between the deposition rate and the rotational Brownian motion is found to be critical for the optimal ordering, which occurs when these rates, as quantified by the Peclet number, are of order one. The results suggest that the mechanism leading to ordering is equilibrium self-assembly but with kinetics dramatically accelerated by the application of the DC electric field. Finally, the crystalline symmetry of the densest structure formed is determined and compared with previously studied spheroidal assemblies.     

Electric field meter with dipole antenna in an alternating nonuniform electric field

Translated from Izmeritel'naya Tekhnika, No. 11, pp. 55–59, November, 1992.     

Temperature-dependent resistivity of a flat conductor and the temperature,current, and electric field patterns

Characteristic physical quantities have been determined as functions of the nonlinearity criterion and the frequency criterion for a flat conductor heated by a current having stationary and current distributions but temperature-dependent conductivity.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 29, No. 3, pp. 535–537, September, 1975.     

Simulating the effect of a high density electric current pulse on the stress field during plastic deformation

A certain pulse of electric current combined with plastic deformation is a powerful tool for improving the formability of hard-to-deform metal alloys. In recent years, much research has indicated that the current not only improves macro-mechanical properties but also influences microstructural-level phenomena such as recrystallization, local phase transformation, grain refinement, and even amorphous nanocrystallization. Despite the huge experimental dataset, virtually no focus has been placed on phenomenon??s computing. In this fashion, present paper concerned with the continuum-level numerical analysis of the pulse impact on the stress field during plastic deformation. Computation conducted herein has shown that a high density electric current pulsing weakens the stress field during plastic deformation. Ultimate results of the study should be useful in developing the novel metal processing technology.     

Computational thermodynamics in electric current metallurgy

Abstract

A priori derivation for the extra free energy caused by the passing electric current in metal is presented. The analytical expression and its discrete format in support of the numerical calculation of thermodynamics in electric current metallurgy have been developed. This enables the calculation of electric current distribution, current induced temperature distribution and free energy sequence of various phase transitions in multiphase materials. The work is particularly suitable for the study of magnetic materials that contain various magnetic phases. The latter has not been considered in literature. The method has been validated against the analytical solution of current distribution and experimental observation of microstructure evolution. It provides a basis for the design, prediction and implementation of the electric current metallurgy. The applicability of the theory is discussed in the derivations.     

Dual nanostructures in poly (3-hexylthiophene) based organic photovoltaics under alternative current electric field

Two-dimensional X-ray diffraction was employed, to provide a complete understanding of the energy efficiency improvement of organic photovoltaics by AC electric field alignment. Two distinguishable poly (3-hexylthiophene) (P3HT) nanostructures were found in the form of two separated layers, one of which is highly oriented and the other randomly distributed. The finding helps to analyze the crystallite arrangements not only in the interface in the bulk heterojunction, but also those closer to the substrate. The highly oriented P3HT layer, although located near the substrate, was found to enhance the device efficiency, by increasing the short circuit current and decreasing the series resistance.     

Electric field meter with a dipole antenna in an elliptically polarized electric field

A model of an electric field meter with a dipole antenna is analyzed. The model takes into account the fact that the meter incorporates other elements with a conducting surface in addition to the dipole antenna, viz.: a matching device, a signal cable, and a voltmeter. Alternative forms of the measurement equation are obtained, which differ in the error associated with the currents induced by the measured electric field on the braid of the signal cable and on the casing of the voltmeter. It is shown that this error can be eliminated partially or completely by performing additional measurements with the dipole antenna in different positions.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 45–48, February, 1994.     

Electric field meter with a dipole antenna in a nonuniform alternating electric field

Translated from Izmeritel'naya Tekhnika, No. 12, pp. 44–47, December, 1992.     

采用电流镜积分读出电路的X射线图像传感器

研制采用电流镜积分高性能读出电路的 X 射线图像传感器(CMI-X-IS),传感器像元由采用CMOS 工艺的光电二极管实现,利用电流镜将产生的光电流变成镜像并放大到积分电容中,经相关双采样电路抑制噪声后,由 CMOS 移位寄存器和多路开关电路输出视频信号。对 CMI-X-IS 要求的时序关系进行了分析。设计了 CMI-X-IS 的应用电路,并将其应用于一个实验系统中,得到了不同密度、不同尺寸材料的视频信号波形和清晰的目标物 X 射线图像。实验表明,CMI-X-IS具有较小的非均匀性(NU≤3.532%)、较低的暗噪声(Vn≤0.45mV)、较大的单位面积响应度(Ro=57.87×105V/Lx.S.cm2)、较高的输出电压(可达 5V)和较宽的动态范围(Dr ≥77dB),可以应用到 X 射线实时成像检测领域。     

Resistance of pollution in equivalent electric circuit of flashover

In flashover-modelling literature, researchers only take into account, the resistance of the pollution on the insulator, assuming that the current takes part in its totality and that the geometrical shape of its lines in the pollution does not have an influence on the phenomenon. In the paper, and after presentation of the equivalent electric circuit of flashover used in the literature, an experimental study and physical analysis are presented concerning this assumption in two sets of laboratory models: multidirectional models and circular-sector models. The results obtained allow us to confirm first that the form of the pollution and the distribution of leakage current lines are indispensable to flashover modelling; and secondly that flashover criteria and critical conditions in the literature are unjustified.     

Separation of long DNA molecules by quartz nanopillar chips under a direct current electric field

We have established the nanofabrication technique for constructing nanopillars with high aspect ratio (100-500 nm diameter and 500-5000 nm tall) inside a microchannel on a quartz chip. The size of pillars and the spacing between pillars are designed as a DNA sieving matrix for optimal analysis of large DNA fragments over a few kilobase pairs (kbp). A chip with nanopillar channel and simple cross injector was developed based on the optimal design and applied to the separation of DNA fragments (1-38 kbp) and large DNA fragments (lambda DNA, 48.5 kbp; T4 DNA, 165.6 kbp) that are difficult to separate on conventional gel electrophoresis and capillary electrophoresis without a pulsed-field technique. DNA fragments ranging from 1 to 38 kbp were separated as clear bands, and furthermore, the mixture of lambda DNA and T4 DNA was successfully separated by a 380-microm-long nanopillar channel within only 10 s even under a direct current (dc) electric field. Theoretical plate number N of the channel (380-1450 microm long) was 1000-3000 (0.7 x 10(6)-2.1 x 10(6) plates/m). A single DNA molecule observation during electrophoresis in a nanopillar channel revealed that the optimal nanopillars induced T4 DNA to form a narrow U-shaped conformation during electrophoresis whereas lambda DNA kept a rather spherical conformation. We demonstrated that, even under a dc electric field, the optimal nanopillar dimensions depend on a gyration radius of DNA molecule that made it possible to separate large DNA fragments in a short time.