Accuracy of a Bellows vacuum meter with an LC-generator

Errors of pressure measurement are considered. The error as a function of the pressure for a vacuum gauge rated at up to 1000 Pa is calculated as an example. It is 0.15 ≤ δp/p ≤ 0.2% over a pressure range of 14 ≤ p ≤ 1000 Pa and it increases hyperbolically up to 100% with p = 0.01 Pa. The parametric reliability of the instrument and its immunity to an accidental increase in pressure the atmospheric level is substantiated. __________ Translated from Izmeritel’naya Tekhnika, No. 9, pp. 37–41, September, 2006.     

Model of the Zero Drift of a Bellows Vacuum Gauge with an LC Oscillator and the Anomaly of the Axial Thermal Expansion of the Bellows

We have derived an equation of thermal perturbations by deduction from a physical model for deformation vacuum gauges with bellows as the elastic element. The model can be used to analyze the temperature zero drift of micropressure gauges, to divide the zero drift into components with regard to particular effects, and to eliminate or to diminish those effects. A zero drift of 0.1 Pa/K was obtained for a micropressure gauge rated at up to 1000 Pa (0.01 %/K). We have found that the temperature zero drift occurs mainly because with rising temperature the bellows expands to an anomalously large extent (1.5 to 2 times) along its axis as compared to the expansion of the alloy used to make the bellows.Translated from Izmeritel’naya Tekhnika, No.3, pp. 27–31, March, 2005.     

一种新型硅微机械粘滞型谐振真空计

在对静电激励硅微机械谐振真空传感器研究的基础上，实现了一种新型的粘滞型谐振真空计。并给出了理论分析和实验结果。测试表明，其有效量程为1～1．33×103Pa。     

压敏电阻用于低真空测量的研究

研究了将压敏电阻用于低真空的测量，包括规管和电路，研制成了新型DL-4型真空计。该计测量范围为102～105Pa，性能好，价格便宜。介绍了该真空计的原理、结构与特性。     

可变冷媒流量空调系统中变频技术和数码涡旋技术比较

从工作原理、能效比、综合部分负荷系数等等方面对可变冷媒流量空调系统中的变频技术和数码涡旋技术进行了分析和比较,指出了两种技术的异同点,供设计和运用这两种空调系统形式作参考。     

Digital sensor for linear displacements with an expanded temperature range

Construction of a linear displacement sensor with an expanded temperature range is presented. The structural layout of the converter is given and its operation is described. Static characteristics of the output signal and the procedure for correcting the temperature error of the sensor using a microcontroller are given __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 39–41, October, 2006.     

Breaking Reciprocity with Space‐Time‐Coding Digital Metasurfaces

Metasurfaces are artificially engineered ultrathin structures that can finely tailor and control electromagnetic wavefronts. There is currently a strong interest in exploring their capability to lift some fundamental limitations dictated by Lorentz reciprocity, which have strong implications in communication, heat management, and energy harvesting. Time‐varying approaches have emerged as attractive alternatives to conventional schemes relying on magnetic or nonlinear materials, but experimental evidence is currently limited to devices such as circulators and antennas. Here, the recently proposed concept of space‐time‐coding digital metasurfaces is leveraged to break reciprocity. Moreover, it is shown that such nonreciprocal effects can be controlled dynamically. This approach relies on inducing suitable spatiotemporal phase gradients in a programmable way via digital modulation of the metasurface‐elements' phase repsonse, which enable anomalous reflections accompanied by frequency conversions. A prototype operating at microwave frequencies is designed and fabricated for proof‐of‐concept validation. Measured results are in good agreement with theory, hence providing the first experimental evidence of nonreciprocal reflection effects enabled by space‐time‐modulated digital metasurfaces. The proposed concept and platform set the stage for “on‐demand” realization of nonreciprocal effects, in programmable or reconfigurable fashions, which may find several promising applications, including frequency conversion, Doppler frequency illusion, optical isolation, and unidirectional transmission.     

石英晶振真空度检测系统

随着科研及工业的不断发展, 对真空环境的要求越来越高, 相应的真空测量技术要求也越来越严格, 在精准测量的基础上对传感器的体积提出了更高的要求, 例如MEMS封装的真空设备将需要较小体积的传感器来完成真空度的测量。而目前常见的电阻真空规、液态式真空计、电容真空计、热传导真空计等都无法同时满足小体积、宽范围、高精度的测量要求。本文基于石英晶振在不同气压环境下振荡时其两端阻抗随环境中气压的改变而变化的原理, 设计了石英晶振振荡电路、信号隔离电路、差分放大电路、真有效值转换电路等, 并且将其前端信号利用STM32单片机进行处理, 通过编写对应的软件程序实现不同环境中真空度检测。在石英晶振振荡电路方面与已有研究有所不同, 本文采用石英晶振本身作为激励信号的自振荡电路, 相对于已有研究中的外加激励信号源而言频率稳定, Q值高, 因此能够产生非常稳定的正弦振荡, 可以有效的减小整个系统的测量误差, 提高测量精度。经过实际测试, 实验结果表明, 系统设计合理, 测量精度高, 达到预期测量效果。     

先进的数码涡旋制冷压缩机技术

介绍了空调系统中的压缩机几种能量调节技术:多级控制系统、变频技术和数码涡旋技术。详细地论述了数码涡旋制冷压缩机优越的特性。     

罗茨真空机组预抽阶段的抽气特性比较研究

针对罗茨泵真空机组在启动预抽阶段的三种工作模式——旁通式、直通式和变频式,分别建立了简化计算模型,推导得出罗茨泵进入正常稳态工作之前罗茨机组的有效抽速计算公式,以及被抽容器的抽气时间计算方法.通过一个计算示例,对比得出了三种不同启动预抽方式的压力-时间曲线,结果表明,直通式、旁通式、变频式工作模式下容器的抽气时间依次减...     

A micro-mechanics model for composites reinforced by regularly distributed particles with an inhomogeneous interphase

Based on the Mori–Tanaka method, a micro-mechanics model is developed to study the effective elastic properties of composites reinforced by regularly distributed particles. The spatial distribution of particles is supposed to be cube symmetric in the three-dimensional space, and the corresponding finite element method (FEM) computation has been performed through a unit cell model. Additionally, particle interaction and distribution are simultaneously taken into account by using the strain Green’s function, and the specified strain Green’s function is determined by utilizing the necessary conditions of geometric symmetry. In order to analyze particle size effect on the effective properties of composites, the Double-inclusion configuration and related theory are introduced to describe the role of the interphase between the matrix and particles. Finally, the overall elastic properties of the composite with regularly distributed particles are described by three independent elastic constants expressed in the explicit form, and the accuracy of the developed model is verified by comparing with FEM results.     

一种简易数字转速表电路

介绍了一种其电路原理与脉冲计数式仪表不同的数字转速表电路。它将输入脉冲经频率一电压转换器（PVC）变换成与之成正比的直流电压，采用数字电压表显示测量结果。文中详细地论述了FVC的工作原理，分析了整机电路，最后给出了实验结果。     

基于活塞式压力计和数字压力计的微小压力测量新方法

提出了一种微小表压力（差压）测量的新方法。采用1台活塞式压力计和1台精密的数字压力计,通过关断阀连接高低压端的特殊连接方式实现微小表压力（差压）测量,解决了活塞式压力计由于受其下限值的限制而不能实现微小压力测量的问题。利用数字压力计较好的短期稳定性以及活塞式压力计较低的不确定度,可以实现1~10kPa微小表压（差压）的校准,其校准结果的扩展不确定度为U=2.2Pa（k=2）。     

数码涡旋与变频涡旋空调系统性能比较

通过对变频涡旋压缩机和数码涡旋压缩机从工作原理上进行分析,指出了各自适合的应用范围;对当前市场上流行的变频和数码多联空调机组进行了综合比较,阐述了这两种空调机组各自的优势和不足;指出了进一步研究和推广两种空调系统需要解决的问题.     

Modelling the transient interaction of a thin elastic shell with an exterior acoustic field

Coupled finite and boundary element methods for solving transient fluid–structure interaction problems are developed. The finite element method is used to model the radiating structure, and the boundary element method (BEM) is used to determine the resulting acoustic field. The well‐known stability problems of time domain BEMs are avoided by using a Burton–Miller‐type integral equation. The stability, accuracy and efficiency of two alternative solution methods are compared using an exact solution for the case of a thin spherical elastic shell. The convergence properties of the preferred solution method are then investigated more thoroughly. Copyright © 2007 John Wiley & Sons, Ltd.     

A Surface‐Functionalized Ionovoltaic Device for Probing Ion‐Specific Adsorption at the Solid–Liquid Interface

Aqueous ion–solid interfacial interactions at an electric double layer (EDL) are studied in various research fields. However, details of the interactions at the EDL are still not fully understood due to complexity induced from the specific conditions of the solid and liquid parts. Several technical tools for ion–solid interfacial probing are experimentally and practically proposed, but they still show limitations in applicability due to the complicated measurements. Recently, an energy conversion device based on ion dynamics (called ionovoltaic device) was also introduced as another monitoring tool for the EDL, showing applicability as a novel probing method for interfacial interactions. Herein, a monitoring technique for specific ion adsorption (Cu²⁺ and Pb²⁺ in the range of 5 × 10^?6–1000 × 10^?6m ) in the solid–liquid interface based on the ionovoltaic device is newly demonstrated. The specific ion adsorption and the corresponding interfacial potentials profiles are also investigated to elucidate a working mechanism of the device. The results give the insight of molecular‐level ion adsorption through macroscopic water‐motion‐induced electricity generation. The simple and cost‐effective detection of the device provides an innovative route for monitoring specific adsorption and expandability as a monitoring tool for various solid–liquid interfacial phenomena that are unrevealed.     

变频与数码涡旋技术在空调系统中的应用

从工作原理、性能系数、温度与湿度调节功能、综合部分负荷系数等方面对空调系统中的变频技术与数码涡旋技术进行了分析与比较,并结合一些工程设计人员的经验,指出了两种技术各自的优势和不足。     

Methods of Checking Piezoelectric Vibration Sensors in Situ

Some methods for periodically checking piezoelectric vibration sensors in situ are considered. The use of the substitution method is analyzed and possible ways of increasing the metrological reliability and authenticity of such periodic checks are discussed.     

A reduced‐order representation of the Poincaré–Steklov operator: an application to coupled multi‐physics problems

This work investigates a model reduction method applied to coupled multi‐physics systems. The case in which a system of interest interacts with an external system is considered. An approximation of the Poincaré–Steklov operator is computed by simulating, in an offline phase, the external problem when the inputs are the Laplace–Beltrami eigenfunctions defined at the interface. In the online phase, only the reduced representation of the operator is needed to account for the influence of the external problem on the main system. An online basis enrichment is proposed in order to guarantee a precise reduced‐order computation. Several test cases are proposed on different fluid–structure couplings. Copyright © 2016 John Wiley & Sons, Ltd.