高压取样放大器的研究

本介绍了一种在数字系统中有实用价值的取样放大器。它由输入和输出二级放大组成，且在输入与输出之间采用光电耦合器件，使其具有良好的高压隔离特性。本放大器具有良好的线性，已获得较好的实用效果。     

电荷放大器检定中的问题

本详细讨论了按照“普通电荷放大器检定规程”检定电荷放大器时，有可能出现新的误差，甚至无法检定高频段，并且提出了解决办法。     

前置光放大器实验研究：1994年10月27日收到

报道了在１４０Ｍｂ／ｓ光通信端机上采用国产１．３μｍ低噪声半导体光放大器作为前景光放大器的研究结果。理论分析和实验表明，必须采用窄带光学滤波器滤除光放大器自发辐射引起的各种噪声。     

前置光放大器实验研究

报道了在１４０Ｍｂ／Ｓ光通信端机上采用国产１．３μｍ低噪声半导体光放大器作为前置光放大器的研究结果。理论分析和实验表明，必须采用窄带光学滤波器滤除光放大器自发辐射引起的各种噪声。当光学滤波器为最佳带宽４ｎｍ，光放大器为最佳电流６５ｍＡ时（此时增益为１４ｄＢ），系统接收灵敏度改善５ｄＢ。前置光放大器噪声指数大约为３ｄＢ。     

声频放大器的动态指标及其对音质的影响

声频放大器的动态指标及其对音质的影响张维国前言声频放大器是放声系统的重要组成部分，它的技术指标基本上决定了放声系统的电性能。如何正确认识放大器这些指标并使其与听音评价标准尽量统一起来，以及如何提高这些指标，是放声系统中的重要问题。早在２０－３０年代，...     

一种新颖的瞬时浮点放大器

介绍了瞬时浮点放大器的原理及构成，并给出一种结构新的具有２５６阶的瞬时浮点放大器，可有效地提高数据采集系统的测量范围。     

单端A类放大器及场效应管（1）

音频功率放大器按所用放大器件可分为电子管放大器、晶体管放大器、集成电路放大器、场效应管放大器以及由上述所用器件两种或两种以上组成的混合放大器。各类放大器电路及所用元器件又是五花八门,千变万化,由此对音源的重放音质又各具特色,很难说哪一种放大器能以偏概全、技压群芳,成为万能放大器。     

分析放大器电路的设计方法

前置放大器在音频系统中的作用至关重要。本文首先讲解了在为家庭音：响系统或PDA设计前置放大器时，工程师应如何恰当选取元件。随后，详尽分析了噪声的来源，为设计低噪声前置放大器提供了指导方针。最后，以PDA麦克风的前置放大器为例，列举了设计步骤及相关注意事项。     

一种增益可调宽带放大器设计

近年来随着计算机和互联网的迅速普及，宽带放大器成为检测仪表、有线电视、无线通信等系统中必不可少的部分。本系统以可控增益放大器AD603为核心，外加STC89C58RD单片机的配合，实现了增益可调的宽带放大器。为解决宽带放大器自激及减小输出噪声，本系统采用多种形式的抗干扰措施，抑制噪声，改善放大器的稳定性。     

廉价靓声路：电子管音频放大器制作（一）

一、精控均衡前置放大器在ＣＤ机时尚的今天，平直（前级）放大器既简单又经济实用。但是那些存留的大量ＬＰ和ＳＰ也是一份宝贵的财产，因此含有均衡网络的前级放大器，会使软件的来源拓宽了许多，其商品机价格自然也贵了许多，就连国产的极典类机型等也是如此。ＳＰ和Ｌ...     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

From Industry 4.0 to Research 4.0. Development of High Performance Fibers in the Light of Digitization

We associate a variety of innovations with the term ＂Industry 4.0＂. The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di...     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Roman iron and steel: A review

ABSTRACT

The production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Synthesis of Alumina-Zirconia Nanocomposites by Solgel Process

Al₂O₃-ZrO₂ nanocomposites were developed starting with the solgel process. Composite alumina-zirconia nanopowders were synthesized from metallorganic precursors (Aluminium secondary butoxide and zirconium Iso propoxide) using the solgel process. The parameters affecting the synthesis—solvent, concentration of precursor, R/H ratio (i.e., dilution of water in solvent)—were varied as also the temperature and pH. BET and TEM were used to measure nanosize. Diffuse reflectance spectroscopy and also qualitative optical absorption led to identical particle size estimate. The variation of process parameters was used to study the effect and interdependence of process parameters. Artificial Neural Networks was used to rigorously analyze the process. Although this led to confirmation of interdependence of parameters, the presence of a single overwhelming solvent variable was also established. Then the optimal process was used to synthesize more nanopowder. To produce bulk nanocomposite the nanopowders were sintered by varying the temperature and time period. The sintered lithoids were probed with a vickers hardness tester to measure elastic modulus, hardness, and fracture toughness. The results showed high elastic modulus, modest hardness, and very high fracture toughness.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.