Electric Voltage Predictions and Correlation with Density Measurements in Green-State Powder Metallurgy Compacts

In this research we discuss an electrostatic measurement approach whereby electric current is injected into green-state compacts and the resulting surface voltages are recorded in an effort to determine density distributions. We present results for pure iron powder with and without lubricants compacted to various densities and their corresponding measured conductivity values, thereby clearly establishing correlation between these two entities. The electric conductivity recordings will ultimately be utilized to infer density distributions throughout the green-state P/M compact. The constant current is injected through point and aperture electrodes, and voltages are recorded along the surface of the compact. To gain confidence in the underlying physical concepts, the recorded voltages of the controlled cylindrical samples are compared with a mathematical Green's function model involving an analytical electrostatic solution of Poisson's equation.     

Intensity Modulation Produced by Crossed Electric and Magnetic Field Electron Image Deflection Systems

It was found that intensity fringes were produced in a crossed electric and magnetic field electron image deflection system. The origin of these fringes is discussed.     

Reconstruction of the Charge Density Wave State Under the Applied Electric Field

Charge density wave (CDW) under an applied electric field in constraint geometry experience stresses, which can easily exceed a plastic threshold. The stress is resolved by the ground state reconstruction which proceed via creation of topological defects like solitons and dislocations??the CDW vortices. These states can be observed experimentally either in average at macroscopic scales of X-ray and multijunction space resolved studies, at mesoscopic scales of coherent X-ray micro-diffraction and nano-junctions or individually as by the STM. Here, we report numerical modeling taking into account multiple fields in their mutual nonlinear interactions: the phase and the amplitude of the CDW order parameter, distributions of the electric field, of the density and the current of normal carriers. Following events of creation and the subsequent evolution of dislocations, we find that vortices are formed in the junction when the voltage across, or the current through, exceed a threshold. The number of vortices remnant in the reconstructed ground state increases stepwise??in agreement with experiments. The vortex core concentrates the voltage drop across the junction giving rise to observed peaks of the interlayer tunneling. The studied reconstruction in junctions of CDWs may be relevant to modern efforts of the field-effect transformations in other correlated electronic systems.     

光学多层膜减小电场强度的一种新设计方法

制作 损伤阈值光学薄膜不仅需要沉积工艺有所突破,而且需要膜系设计也有所改进,用于减少强激光对薄膜的损伤因素。本文提出了一种计算机算法用于改善光学多层膜内驻波场分布,肖弱电场强度对薄膜的损伤。其物理概念清清晰,理论推导,算法编程实用简单。     

Density and Thermal Conductivity Measurements for Silicon Melt by Electromagnetic Levitation under a Static Magnetic Field

The density and thermal conductivity of a high-purity silicon melt were measured over a wide temperature range including the undercooled regime by non-contact techniques accompanied with electromagnetic levitation (EML) under a homogeneous and static magnetic field. The maximum undercooling of 320 K for silicon was controlled by the residual impurity in the specimen, not by the melt motion or by contamination of the material. The temperature dependence of the measured density showed a linear relation for temperature as: ρ(T) = 2.51 × 10³−0.271(T−T _m) kg · m⁻³ for 1367 K < T < 1767 K, where T _m is the melting point of silicon. A periodic heating method with a CO₂ laser was adopted for the thermal conductivity measurement of the silicon melt. The measured thermal conductivity of the melt agreed roughly with values estimated by a Wiedemann–Franz law.     

浅谈磁感应强度和磁场强度

本文由磁场的存在和特斯拉计的检定引出了磁感应强度和磁场强度两个概念,分析了其区别和联系,并由此得出了该二者的正确用法.     

Intensity Correlation Measurements on a Schlieren Image

We determine the Fraunhofer and Fresnel diffraction patterns produced by a thin linear axicon when it is illuminated by a plane wavefront. An interferometric method of recording zone plates using linear axicons is presented.     

电力营销用户用电系统设计及应用

随着电网技术不断提高、电力建设的完善,最初的以人工为主的抄表方法已经无法满足系统的发展,国家电网自动抄表系统的建设工程全面开展,集中器这一核心设备的市场需求巨大,因此研究的价值也很大。本文主要介绍远程抄表系统的构成、详细讲述了电力抄表系统的采集方式,通过描述集中器的作用、原理,并结合相关集中器的招标技术协议,进行系统详细的分析,对目前系统在用的电力用户用电信息采集系统的应用情况进行分析,集中器的功能能够顺利的实现。系统的应用彻底的改变了传统费工费时的人工进行抄表的方式,有效的减少了抄表员劳动强度,实现快速、准确的智能表的数据抄读,同时也将因人为造成误抄率大大降低,因而提高国网公司工作的效率,具有非常好的前景。     

FM Receiver Measures Field Intensity

One of the limiting factors in measuring field intensity at the fringe area of an antenna is that the white noise level may be equal to or greater than the carrier signal. In addition, this noise level may vary with time of day, thereby rendering calibration for ambient-noise level an uncertain procedure. This paper describes a field-intensity measuring technique that overcomes this limitation. The silencing action of an FM receiver is used to accurately measure the magnitude of an RF signal regardless of the level of random noise present.     

Monitoring and Recording of Electric Power via the Electric Power Supply Networks

A solution of the problem of switching between the user and the segment of a high-speed network trunk line servicing him using data transmission over the electric power supply networks is proposed.     

Intensity Distribution Across a Source from Spectral Measurements

Abstract

The degree of spectral coherence (μ₁₂(ω)) over the plane of a double slit is determined from the measurement of spectral changes in Young's interference experiment using the spectral interference law. The experimental and theoretically calculated values of μ₁₂(ω)) for the experimental parameters agree well within experimental error, thus supporting the theoretical prediction of D. F. V. James and E. Wolf (1991, Phys. Lett. A, 157 6). The degree of spectral coherence determined is used for estimating the intensity distribution across a source. This new approach, being a simple spectral measurement technique, might find its application in astronomy, particularly for the study of intensity distribution across stars.     

Power Transformers Internal Insulation Design Improvements Using Electric Field Analysis Through Finite-Element Methods

Understanding the potential and electric field distribution in the insulation system of a transformer during transients is vital to its construction. Therefore, we have developed a method for electric field analysis inside a power transformer. The method consists of the following steps. (1) A lumped parameter equivalent model is constructed by dividing transformer windings into several blocks. (2) The electric circuit parameters of this model are calculated. (3) Employing the results of the transformer transient model analysis as boundary conditions, a 2-D asymmetrical electric field finite-element analysis is performed to determine electric fields through the windings. The method has been examined employing power frequency and impulse voltages. We have also demonstrated successful application of the method to a transformer and have verified the computed results by comparison with measured results.     

Hydrogen Density Measurements Using an Open-Ended Microwave Cavity

The density measurement of liquid hydrogen and two-phase mixtures of liquid and gaseous hydrogen is considered. This paper describes a complete prototype system that uses an open-ended microwave cavity for making dynamic density measurements of flowing hydrogen in a transfer line. The theory of operation along with test results for both the single- and two-phase cases are presented and discussed.     

Preparation and Certification of Novel Reference Material for Smoke Density Measurements

A novel type of reference material has been prepared and characterized for smoke density chamber calibration in the flame condition by Fire Protection Laboratory, National Institute of Standards, Egypt. The new reference material was fabricated by mixing modified magnesium hydroxide nanoparticles (MH-NP-OP) with acrylonitrile–butadiene–styrene copolymer (ABS). The reference material was certified for the physical properties of maximum specific optical density (D_m) and corrected maximum specific optical density (D_m·corr) using the analysis of two different competent laboratories. Preparation, characterization, homogeneity testing and certified value assignment for the developed reference material have been studied. It was clearly demonstrated that the smoke measurement of the two laboratories are harmonic which is an obvious prerequisite for the confidence assessment of the reference material. A metrological approach was followed to detect the statistical biases between different laboratories data to achieve an appropriate accuracy in smoke measurements. The obtained measurement results were statistically analyzed and the certified values of D_m and D_m·corr for reference material were estimated as 510.35 and 472.95, respectively as well as their expanded relative uncertainties at confidence level 95% were recorded 2.78 and 2.7%, respectively. The developed reference material are expected to be used to assist in validating smoke measurements of different materials to realize their fire hazard when be used in building.     

Analysis of the Electric Field and Ion Current Density Under Ultra High-Voltage Direct-Current Transmission Lines Based on Finite Element Method

The corona generated from high-voltage direct-current transmission lines can induce the ion around the lines, which will increase the electric field and the ion current density and influence the environment nearby. Based on the finite-element method, an iterative algorithm to analyze the electric field and the ion current density at the ground level generated from the bundled conductors of bipolar lines is proposed. After the validity of the method is testified, some examples are analyzed. The method has been used to design plusmn800 kV transmission lines system in China     

Probability Density Functions of Speckle Intensity Produced by Weak Diffusers

By using the discrete cell model for the rough surface of objects, a general expression is derived which gives the probability density function of speckle intensity produced by weak diffusers having an arbitrary phase distribution and an arbitrary cell number, N, of contributions for the formation of speckles. In some special cases, it gives the probability density functions which have been previously derived and are well known in the statistics of speckles. In the case of the small number N = 2, an analytical solution of the probability density function is obtained from that general expression. Some features on the probability density functions of speckles are discussed for the case of small roughness and small number N.