Design of a rail-to-rail operational amplifier for implantable neural signal regeneration systems

为满足治疗中枢神经损伤的植入式神经信号再生系统的低压低功耗要求,设计了该微电子系统的中间级放大和激励的核心电路——恒跨导轨到轨运算放大器.根据系统满摆幅和低功耗的特点,在电路设计中采用了工作在亚阈值区的电流开关跨导控制电路作为输入级,改进的前馈AB类放大器作为输出级.芯片采用中芯国际0.18μm 1P6MCMOS工艺设计完成.仿真和测试结果表明,芯片实现了满摆幅动态范围,跨导恒定,可用于对探测得到的微弱神经信号的放大和激励,满足神经信号再生系统的要求.此芯片电路功耗和体积都很小,满足生物体植入式器件的要求.     

低功耗无源超高频射频识别应答器芯片的射频电路设计与实现

提出了一种符合ISO/IEC 18000-6B标准的高性能低功耗无源超高频(UHF)射频识别(RFID)应答器芯片的射频电路.该射频电路除天线外无外接元器件,通过肖特基二极管整流器从射频电磁场接收能量.其构成包括本地振荡器、时钟产生电路、复位电路、匹配网络和反向散射电路、整流器、稳压器以及AM解调器等几个主要模块.该射频电路芯片采用支持肖特基二极管和EEPROM的chartered 0.35μm 2P4M CMOS工艺进行流片,测试结果表明其读取距离大于3m,在915MHz ISM频带下工作时其电流小于8μA,该芯片核心面积为300μm×720μm.     

磁粉离合器励磁与退磁系统

本文针对磁粉离合器传递的转矩与励磁电流呈线性关系这一特性,设计了一种磁粉离合器励磁与退磁系统。包括系统主电路结构、系统软件设计以及对开关器件浪涌电流的抑制措施。     

开关电源系统稳定性补偿电路的设计

开关电源系统往往由于电压电流双环控制的使用而导致一些扰动,扰动的产生一定程度上影响着开关电源的稳定性,开关电源系统稳定性状态关键是取决于系统电流是否对扰动如何作出收敛响应,而系统电流收敛的发生一般有两种途径,一是在空占比(D)小于0.5时产生收敛,一是空占比(D)大于0.5时产生收敛,而D小于0.5时,电流扰动量即电流发生的误差Δin将会慢慢的衰减一直到零,从而使得系统趋于稳定;D大于0.5时,误差将会逐渐变大,使得系统不能正常工作,造成不稳定状态,因此,在扰动发生之后,通过补偿电路以确保空占比在0.5以下,来确保系统的稳定,将从开关电源系统不稳定性的分析入手,探讨斜波补偿的过程,并提出一些建议。     

SCR软启动技术在变频空调中的应用

通过分析SCR软启动技术的工作原理,提出一种新的控制电路及控制方法,给出由专用的双核MCU组成的低功耗系统的硬件设计原理和软件设计方法。测试结果表明,采用差分电路、基准零点电路和移相PWM技术后,变频空调的启动电流大大减小,启动性能提高,保证变频空调的可靠性。     

CPLD技术在微型化过载存测仪中的应用

本文结合实验研究工作,研究设计了用于某型号巡航导弹模拟侵彻钢靶的过载参数测试系统.该研究选用xilinx公司的最新产品coolrunner cpld系列可编程器件,详细介绍了 cpld型号的选择,系统的组成和工作原理,测试系统电路框图及系统工作状态图,任意分频器及具接口电路.并研究了其低功耗的实现.     

基于单矢量水听器弱信号值班检测系统

采用平均声强作为检测量,设计出一种基于单个矢量水听器的低功耗弱信号值班检测系统。针对矢量信号特有的 90°相移、指向性零点、相乘再积分、正负双极性等问题,设计了宽带全通 90°移相网络、双通道检测、1Bit模数混合乘法器、定时放电、绝对值检测等功能电路。系统设计中兼顾高增益、低功耗、稳定可靠等实际需要,并选用微功耗模拟器件。系统仿真研究显示,该系统作用距离超过 2km。初步设计制作的实验电路板,工作带宽达到1. 8kHz,工作电流 5mA,稳定可靠。     

基于LCD便携式设备低功耗的研究

随着LCD便携式设备性能的不断发展与完善,其对低功耗的要求日趋严峻。针对这些问题,本文提出了一种LCD及其背光电路低功耗的硬件与软件方案。硬件电路分析了LCD及其背光驱动电路的工作原理;软件设计则利用S3C2440的定时器产生PWM信号,系统通过软件对背光的实时调节完成了驱动程序设计。最终通过ARM-Linux系统平台测试LCD运行与休眠时的耗电情况。将两者进行对比,结果表明该设计方案有效地提高了效率,降低了能耗,并延长了系统运行时间。     

基于PWM控制的电磁流量计脉冲励磁系统分析与研制

为了提高励磁频率和减少发热,使电磁流量计能够更好地用于浆液流量测量和灌装流量测量,并长期稳定、可靠地工作,研究了基于PWM控制的脉冲励磁方案,分析其工作原理,计算各种参数,研制实际系统,进行测试和实验。结果表明,该系统能实现更高的励磁频率,产生稳定的励磁电流,极大地减小了励磁系统的功耗,能去除微分干扰对流量信号测量的影响,水流量检定准确度优于0.5级。     

一种高效率的开关稳压电源的设计

本设计是一个大电流、小电压的开关稳压电源的设计。设计中主要是通过尽量减少电路的损耗来完成。通过单片机和脉宽调整电路来稳定输出电压、电流,并通过单片机的控制对整个电路进行过流保护,排除过流故障后,电源能自动恢复为正常状态。其中模拟部分由隔离变压器、整流滤波电路、DC-DC变换器组成,数字电路控制部分使用高性能低功耗的增强性51单片机,电路简洁、控制精度高低功耗。     

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.     

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.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Brainstorming for ISO Strategy 2016-2020

正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from     

CNAS Passes APLAC's PTP Review

正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively.