A 155 Mbps laser diode driver with automatic power and extinction ratio control

An integrated laser diode driver(LDD) driving an edge-emitting laser diode was designed and fabricated by 0.35 μm BiCMOS technology. This paper proposes a scheme which combines the automatic power control loop and temperature com-pensation for modulation current in order to maintain constant extinction ratio and average optical power. To implement tem-perature compensation for modulation current,a novel circuit which generates a PTAT current by using the injecting base current of a bipolar transistor in saturation region,and alternates the amplifier feedback loop(closed or not) to control the state of the current path is presented. Simulation results showed that programmed by choice of external resistors,the IC can provide modu-lation current from 5 mA to 85 mA with temperature compensation adjustments and independent bias current from 4 mA to 100 mA. Optical test results showed that clear eye-diagrams can be obtained at 155 Mbps,with the output optical power being nearly constant,and the variation of extinction ratio being lower than 0.7 dB.     

Study on hydrodynamic vibration in fluidic flowmeter

The characteristics of the fluidic flowmeter,which is a combination of impinged concave wall and bistable fluid amplifier,is investigated by experimental studies and numerical simulations. The numerical approaches are utilized to examine the time dependent flow field and pressure field inside the proposed flowmeter. The effect of varying structural parameters on flow characteristics of the proposed fluidic flowmeter is investigated by computational simulations for the optimization. Both the simulation and experimental results disclose that the hydrodynamic vibration,with the same intensity,frequency and 180° phase shift,occurs at axisymmetric points in the feedback channel of the fluidic flowmeter. Using the structural combination of impinged concave wall and bistable fluid amplifier and differential signal processing technique,a novel fluidic flowmeter with excellent immunity and improved sensibility is developed.     

The limit analysis in soil and rock： a mature discipline of geomechanics

The solution of a slope stability problem can be approached by its least upper-bound and maximum lower-bound with high accuracy. The limit equilibrium methods that employ vertical slices imply a lower bound of the factor of safety. It has been successfully extended to the area of active earth pressure analysis that accounts for different input of locations of earth pressure applications. Those methods that employ slices with inclined interfaces give an upper-bound approach to the stability analysis. It enjoys a sound mechanical background and is able to provide accurate solutions of soil plasticity. It has been successfully extended to the area of bearing capacity analysis in which various empirical coefficients are no longer necessary. The 3D upper- and lower-bound methods under this framework have been made possible and show great potential for solving various engineering problems.     

Effects of slag fineness on durability of mortars

In recent years, the usages of by-products and wastes in industry have become more important. The importance of the sustainable development is also of increasing. The utilizations of wastes, as mineral admixture or fine aggregate, reduce the consumption of the natural resources and improve the durability of concrete. In this study, the effect of the fineness on the high temperature and sulphate resistances of concrete mortar specimens, produced with ground granulated blast-furnace slag (GBFS) replacing cement, is investigated. The compressive and flexural strength test results for all series related to durability effects, exposing temperature and solutions, exposure times for these durability effects, slag content and fineness are discussed. Conse- quently, the optimum slag contents are determined for producing the sulphate and high temperature resistant mortars.     

Research on the operating characteristics of parallel 4-DOF electric platform with 4TPS-PS structure

The 4TPS-PS parallel platform designed for a stabilization and automatic tracking system is a novel lower-mobility parallel mechanism. In the first part of this paper, the structure of the platform is described and the kinematics model is built. The workspace of the platform is defined as the full reachable rotation workspace when the Z coordinate dimension of the upper plate varies continuously. A fast searching method of the full reachable workspace is presented, after which the inverse kinematics of the platform is deduced. The forward and inverse solutions of the speed and force of the platform are deduced. According to the characteristic of the 4TPS-PS platform’s structure, a fast searching algorithm of the maximum generalized speed and maximum generalized force output by the upper plate is put forward based on the forward and inverse solutions of the platform’s speed and force. The 4TPS-PS platform prototype built by the State Key Laboratory of Fluid Power Transmission and Control of China is taken as the research subject. The full reachable rotation workspace of the prototype is computed out and analyzed. The curves of maximum generalized speed and maximum generalized force of the prototype are computed out and plotted. Finally, the com- puting and analyzing results of the operating characteristics are confirmed through the experiment.     

中国远程教育评估方法的演进

中国远程教育评估随着远程教育发展而发展,同时远程教育评估也推动远程教育的发展.回顾远程教育评估方法包括评估的类型、指标、权重和目标的演进及意义;展望中国远程教育评估发展趋势,将向终身教育观、评估机构、成本效益、长效机制等方面发展.     

谈审计执法与处罚力度的强化

我国审计制度还处在不断完善的过程中,审计执法还存在不少问题,需要不断改进和加强。从贯彻依法治国的基本方略,规范经济秩序,促进国民经济健康发展,加强对权力制约的监督,促进廉政建设等方面阐述强化审计执法与处罚力度的重要性。分析了审计执法与处罚力度弱化的原因。对如何强化审计执法与处罚力度提出方案探讨。     

Influences affecting the soil-water characteristic curve

INTRODUCTION The soil-water characteristic curve (SWCC) gives the relationship between the amount of water in the soil (i.e. gravimetric or volumetric water content) and soil suction (i.e. matric suction at low suction and total suction at high suction). Many properties of a partially saturated soil such as the coefficient of permeability, shear strength and volume strain, pore size distribution, the amount of water contained in the pores at any suction, can be obtained from the SWCC. …     

仓储式商场管理信息系统及电子商城系统的设计

本文在研究了国内大量仓储式商场的经营管理模式和仓储式商场计算机信息管理现状的基础上，提出了仓储式商场计算机管理的信息系统模型。该模型不但解决了仓储式商场日常内部管理如柜台收费、库存商品管理、商品采购等一系列的问题，同时也提出了仓储式商场电子商务B—C模型，对提高企业管理水平和企业在消费者心目中的地位有一定的意义。