压力传感器激励电源电压值的选择

由于压力传感器输出出现零点电漂移,不同激励电压零点便不同。本文介绍应怎样选择其激励电压值,同时分析了集成稳压电路的电压输入输出特性以及利用它对传感器供电消除热堆零点漂移同时又使零点偏移为零,并用实验加以验证。     

一种压力传感器的零点补偿电路

从压力传感器温度补偿问题出发,通过三种电阻桥零点输出补偿方法的温度误差对比,提出一种恒压供电的新型电阻桥零点输出补偿方法,主要特点是调节压力传感器(零点输出10mV以上)零点输出为零时,不会影响压力传感器的温度漂移,且较传统的电阻桥零点补偿方法,压力传感器的温度误差小的优点.     

压阻传感器的实用校正方法

本文详细介绍集成惠斯顿有源电桥压阻传感器的实用校正方法，有效克服半导体集成传感器输出的共模电压影响，调节静态和满程压力负载条件下的静态零点和满足程输出毫伏值，使传感器在流体或气体的测量线路设计中带业方便。     

GGY一20型高性能固态压力传感器(续)

六、温度补偿固态压力传感器受温度影响较大,这是人所共知的,因此除了在制作工艺上采取必要的措施以外,对传感器进行外电路补偿是必不可少的。这里采用的是一种常规的方法,其原理如图6所示。图6中,R_1、R_2、R_3、R_4为应变电阻;R_TZ为零点温度补偿电阻;R_Z为零点配平电阻;R_TS为灵敏度温度补偿电阻;V为桥电压;V_p为输出。 1.零点的温度补偿传感器零点随温度变化主要是由应变电阻的不一致性和应变电阻温度系数的不一致性引起的。因此对其补偿是通过改变一个桥臂的电阻值及其温度系数来实现的。如果温度变化了△T,电桥零点输出有了△V_po的变化,此时,零点温度系数为     

基于电网电压定向的光伏并网逆变器系统研究

针对传统的光伏并网系统逆变控制策略存在控制复杂、谐波含量多的问题,提出了一种基于电网电压定向的光伏并网逆变器直接电流控制方法,给出了以TMS320F2812为主控制器的三相光伏并网逆变器系统的硬件及软件设计。该逆变器直接电流控制方法采用过零检测电路测量电网电压的过零点时刻,得出过零点时刻的电网电压的旋转角度,从而得到逆变器输出电压的幅值和相位;采用SVPWM技术控制IPM的开断,使逆变器输出上述幅值和相位的电压,从而实现单位功率因数并网发电功能。实验结果表明,该逆变器直接电流控制方法简单,逆变器输出电流与电网电压基本保持相同的频率和相位,并网发电功率因数接近于1。     

新款101型电压放大器

美国Measurement Specialties公司现已推出一款信号调理器,能够为压力和振动的精准动态测量提供清洁传感器电源和输出放大。此新款101型三通道直流差分电压放大器具有直流到200kHz快速响应带宽,其离散信道可同时为三个传感器提供清洁传感器电源（0—12VDC）和输出放大（0～999增益）。     

可消除热零点漂移的双压阻半桥压力传感器

提出一种可消除热零点漂移的压阻式压力传感器。该传感器由两个压阻半桥构成。两个“半桥”受力时输出信号的极性相反,而零压时输出信号极性相同。两桥输出信号相减后,其压敏输出与一个压阻全桥的输出值相同,而随温度变化的零压输出则相互抵消。模拟实验显示出预期效果     

载体催化型瓦斯传感器输出电压与瓦斯体积分数函数关系研究

针对载体催化型瓦斯传感器的近似直线形的输出曲线存在非线性误差较大、准确度低的问题,提出了一种采用最小二乘法建立载体催化型瓦斯传感器输出电压与瓦斯体积分数函数关系的方法。以MJC4/2.9J型载体催化元件为实验对象,结合相应的实验数据得到输出电压与瓦斯体积分数的拟合曲线,该拟合曲线的结果表明,采用最小二乘法建立的瓦斯传感器输出电压与瓦斯体积分数函数关系非线性误差较小、准确度高,并将该函数关系应用到瓦斯检测仪的设计中。实际应用结果表明,该瓦斯检测仪具有较高的精度及稳定性。     

氮化硅薄膜传感器的平面加工工艺研究

介绍一种以氮化硅薄膜为压力敏感膜、多晶硅为电阻应变计的压力传感器。该压力传感器先后采用2种不同的平面加工工艺进行加工,实际结果表明:改进后的工艺比较好。通过采用对称分布在一个敏感膜上的4只多晶硅电阻应变计串联组成惠斯通电桥的一个桥臂,减少桥臂电阻的制作误差。制作传感器样品并对传感器的电压输出特性进行了测试。测试结果表明:恒流激励的传感器的电压输出特性非常好,传感器具有过载保护功能。     

LVDT位移传感器电压电流转换电路的设计

为使传感器输出信号能够远距离传输,设计了一种0～5 V到4～20 mA的电压电流转换电路。在Howland电流泵电路的基础上,增加电压跟随器和偏置直流放大器,实现电压电流的精确转换。仿真分析和实验测试结果表明:电路能够满足传感器电流输出的要求,并已成功应用于LVDT位移传感器调理电路。     

Transport for the elderly and the handicapped

This paper is a postcript to the International Conference on Transport for Elderly and Handicapped Persons held at Cambridge University from 4–6 April 1978. The author was one of the organisers and discusses in this paper the following issues which were of central interest at the conference: what is the rationale underlying the provision of transport for the elderly and the handicapped, how can the travel patterns of the elderly and the handicapped be characterised, what are the principal means of transport which the elderly and the handicapped use in urban areas, and what are their advantages and disadvantages from an economic, social and ergonomics point of view?The next International Conference on Transport for Elderly and Handicapped Persons will be held at Churchill College, Cambridge, from 14–16 July 1981. This paper will serve as a reference point for that conference and it will be interesting to see what advances, if any, have been made over the three years intervening between the two conferences, in understanding and solving the transport problems of the elderly and the handicapped.     

类Walsh变换的分析及其实现

利用二分技术设计了类Walsh变换的四种快速算法,并对这四种算法进行了计算机实现和比较。     

New results for the bounds of the solution for the continuousRiccati and Lyapunov equations

This paper presents upper and lower matrix bounds for the solution of the continuous algebraic matrix Riccati equation. Furthermore, a new lower matrix bound for the solution of the continuous algebraic Lyapunov equation is also developed. These are new results     

智能科学与技术专业毕业生情况分析与专业建设

针对南开大学"智能科学与技术"新兴本科专业,对首届学生的来源和去向进行整理和分析,根据毕业生的座谈与反馈情况,提出南开大学"智能科学与技术"专业的调整方向与后续建设目标。     

Evaluation of the DRM and the Time for Preventive Maintenance for Aging Software

An attempt to capture software aging and specify when to do preventive maintenance (PM) is presented in this paper. A composite measure termed the DRM, Deteriorating Response Measure, is defined. It is based on the analysis of the deteriorating speed of the software against time and load. This speed is characterized as follows: (1) It decays with increased load. (2) It does not increase again when the load decreases, this indicates loss of elasticity. The DRM is mathematically formulated based on a queueing system model.Specifying when to do preventive maintenance depends on the decision maker's perspective of the manifestation of aging. It is tried here to formalize this dependence. Three degrading performance metrics are defined for a DRM: (1) Decaying restored speed value. (2) Increasing speed offset ratio (recoverability index). (3) Increasing operation interval offset. These metrics can be used singly or aggregately in a DRM to specify when to do preventive maintenance. Results of model testing are also shown.This work can be part of an on-line procedure that calculates performance indexes for a server type software system like a web browser, an operating system, a database, and helps in the decision to do preventive maintenance for aging software.     

Interfaces for the ordinary and beyond

Several ways in which current computer interfaces discriminate against those who do not fit the accepted profile of the average user are described. A needs continuum for describing users' abilities and characteristics is presented. The parameters affecting a person's position within the continuum are discussed. The ways in which interface designers take into account a range of needs is also discussed     

Topologies for the digital spaces and

We show that there are only two topologies in and five topologies in whose connected sets are connected in the intuitive sense. Both topologies for are well known (e.g., one is presented in D. Marcus, F. Wyse et al., Amer. Math. Monthly 77 (1979) 1119, and the second in E. Khalimsky et al., Topology and its Applications 36 (1990) 1) and found applications in computer graphics and computer vision (e.g., A. Rosenfeld, Amer. Math. Monthly 77 (1979) pp. 621, and T.Y. Kong et al., Amer. Math. Monthly 98 (1991) 901). Two of the five topologies for are products of the topologies known from and . The remaining three topologies for are also generated from the two topologies for , however, they are not product topologies.     

一种对语义网上本体进行检索和排序新方法

提出了一种对语义网上的本体进行检索和排序的新方法ARRO(an Approach for Retrieval and Ranking for the On-tology),其核心思想是通过对本体进行解析产生逻辑三元组.再在三元组的基础上进行逻辑推理,形成概念的逻辑视图,然后通过排序公式对相关本体进行检索和排序.这种通过逻辑视图和三元组对本体进行检索和排序的方法可以有效的进行逻辑推理,并提高检索效率,从而解决在传统的基于关键字的信息检索中只能从句法上对关键字进行分析,无法将推理和检索相互结合,互相促进的问题.本文对ARRO进行了测试,结果验证了其实用性和有效性.