多段电容式锅炉液位测量系统设计

由于传统的锅炉汽包水位测量多采用差压式水位计、云母水位计等方法,测量过程中存在汽水分界面不明显,需要温度、压力补偿及投入麻烦等缺陷,为解决上述问题,提出了一种基于电容数字转换技术专用芯片Pcap01的智能多段式液位测量系统,并且应用HART通讯单元访问传感器的测量过程参数、设备组态、校准等信息。对多段电容式液位测量系统的总体方案、传感器设计、电容测量电路、HART通讯电路的设计进行了详细论述,同时设计了HART通讯软件和液位测量采集软件。对所设计的多段电容式锅炉液位测量系统经过试验表明,该液位计精度高、操作简单方便,解决了传统液位测量的缺陷,可以满足实际现场要求。     

Development of yttria-doped thoria solid electrolyte for use in liquid sodium systems

Electrolytic grade yttria-doped thoria (YDT) was synthesized by a novel combustion method. Sintering studies were carried out with polyvinyl alcohol as binder or ZnO as sintering aid to obtain high-density product. The sintering temperature has been optimized as 1,923 K. The results showed that when ZnO was used and sintered at 1,923 K, high-density YDT pellets were obtained, which met the required helium leak rate of the order of ∼10⁻⁹ std. l/s. Paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006     

Development of vulcanizable elastomers suitable for use in contact with liquid oxygen

For the past few years our research has been concerned with the preparation of polymers which are compatible with and have usable mechanical properties in the presence of liquid oxygen. These are stringent requirements and the need for oxidative stability necessitated investigation of halogen-containing polymers, in particular, polymers containing fluorine. Since only a few fluorocarbon monomers are commercially available, this study required an extensive synthesis program. A comprehensive search of the literature and an attempt to systematically study the effect of polymer structure on low-temperature properties directed our initial work toward the synthesis of some novel, highly fluorinated vinyl monomers and polymers. In this article the effect of structure on polymer glass transition temperatures will be discussed and the synthesis and characterization of some fluorocarbon vinyl ethers and their polymers will be described.     

浆氮电容式密度计及液位计的实验研究

采用电容式密度计及液位计来测量浆氮密度及液位的变化,使用整体屏蔽法对测量系统进行保护以减小寄生电容并提高其抗干扰能力。从理论上分析整体屏蔽法在提高测量系统性能上的作用,并通过实验加以验证。在实验中对密度计和液位计进行标定以提高其测量的精度,并使用密度计测量制备过程中浆氮密度的变化情况。     

Investigation of solid sodium reference electrodes for solid-state electrochemical gas sensors

Several types of solid reference electrodes for potentiometric gas sensors based on solid sodium ion conductors (e.g., Na⁺-/-Alumina or NASICON) are described and the observed experimental results are discussed in view of theoretical predictions. Defined sodium activities are established by appropriate equilibria of binary and ternary phases. The binary systems Na-Sb and Na-Bi, and the ternary systems Na-M-O (M is a transition-metal, Co or Ni) were found to show excellent kinetic performance and are capable to fix the chemical potential of sodium well defined over extended periods of time. Some of the sodium reference electrodes are even stable in air. The results are compared with the application of elemental sodium as reference electrode.     

超声波盐酸浓度计的研制

本文介绍了一种根据盐酸浓度、温度和声速三者之间的相互关系来进行在线检测的超声波盐酸浓度计。通过实验,作者精确地测定了不同浓度和温度的盐酸溶液中的超声波声速,给出了盐酸的声速浓度系数和声速温度系数。     

The structure factor for liquid nitrogen and liquid oxygen by neutron scattering

The structure factor S(Q) has been measured for liquid nitrogen at 77 K by neutron diffraction at four wavelengths. The effects of Placzek corrections on the self [1, 2] and interference [3] components of the observed differential scattering cross-sections at 0·35, 0·7, 0·84 and 1·06 Å [4] have been investigated. Effective molecular masses and internuclear bond lengths have been obtained by fitting a modified Placzek model to the observed data. It is concluded that after correction the different structure factors agree satisfactorily within the statistical errors of the measurements and the internuclear bond length is close to that measured in the gas phase.     

An electrochemical determination of oxygen adsorption on copper

The adsorption of oxygen on polycrystalline and thin film copper samples was studied with the solid state electrochemical cell: Cu,Cu₂O¦7.5wt%CaO/ZrO₂¦Cu in ultrahigh vacuum. The oxygen partial pressure in the bulk of the copper sample was controlled electrochemically by applying a voltage across the cell, while the oxygen coverage at the copper free surface was monitored by Auger Electron Spectroscopy (AES). This technique has enabled us to establish much lower oxygen partial pressures at high temperatures than normally attainable in ultrahigh vacuum. In this paper we report the results of reversible oxygen adsorption isotherms on polycrystalline copper at 928, 970 and 1093 K. The results agree reasonably well with the deductions of earlier surface energy measurements and indicate a surprising degree of stability for chemisorbed oxygen on polycrystalline copper. Isosteric heats of adsorption are calculated with and without the inclusion of the earlier surface energy measurements and are compared to previous differential heats of adsorption determined calorimetrically.     

Velocity autocorrelation in liquid sodium

The expression for the memory function of Corngold et al. has been modified using an effective potential for liquid sodium to calculate the velocity autocorrelation function and the coefficient of self diffusion. The results are found in good agreement with computer experiment results of Schiff.     

The structure factor for liquid nitrogen and liquid oxygen from neutron scattering studies

The structure factor, S(Q), has been measured for liquid nitrogen at 77 K and liquid oxygen at 84 K by neutron diffraction over a range of momentum transfer, Q, from 0·3 to 7·3 Å^-1. In the case of oxygen a correction for magnetic scattering has been included.

The liquid structure factor for nitrogen compares well with that obtained from X-ray diffraction measurements but there are significant discrepancies in the case of oxygen. These may be partially attributed to uncertainty in the form factor for paramagnetic scattering.

The data have been analysed in terms of several different models for the orientational correlation between neighbouring molecules. The results are particularly sensitive to uncertainties in the absolute normalization of the data, the inter-nuclear distance for the molecular structure and Placzek corrections; the effect of these errors is considered in detail. It is shown that some form of orientation correlation must exist but its precise nature could not be obtained from the present data.     

A theoretical equation of state for liquid and solid sodium

An equation of state is given having theoretical significance which uses the pressure as the independent variable and determines the volume. It is applied to the values of both solid and liquid sodium along the melting curve. Agreement with experimental data is excellent.     

Analysis of various optical pumping schemes for liquid oxygen lasers

Singlet oxygen generated by optical pumping in liquid oxygen/air medium has recently been reported as a potential gain medium for high power lasers at 1580 nm, by USA’s defense agency DARPA. However, the details with reference to the underlying physics of this laser and the potential pumping techniques for achieving lasing are still unclear. The present paper investigates numerically the population kinetics of both upper and lower lasing levels viz. O₂ and O₂ states in liquid oxygen and discusses the criticality involved in obtaining lasing with this medium. Isotopic liquid oxygen and liquid air medium where improved conditions for lasing are anticipated, as compared to that in natural liquid oxygen, have also been considered in the present study. The studies have been carried out for optical pumping by both continuous and pulsed mode lasers at 1064 nm and 634 nm wavelengths. The temporal variation of small signal gain in each case has been investigated along with limitations of the same from point of view of lasing. The available and extractable power from all three medium for an optimum pumping case has also been discussed. The studies reveal that liquid air has high potential for very high power lasers as compared to both natural and isotopic liquid oxygen. PACS 31.15.ag     

Performance of YSZ oxygen sensors protected by electrochemical filters

The performance of nernstian Yttria Stabilized Zirconia (YSZ) oxygen sensors can be seriously affected when in contact with some aggressive industrial furnace atmospheres. Longer life time can be obtained for sensors protected with electrochemical filters. The most relevant parameters determining the protected sensor performance are the ratio between the sensor and the filter oxygen electrochemical permeabilities, and the volume of the electrode protection chamber. The ratio between materials electrochemical permeabilities determines the sensor oxygen activity applicability domain and the deviation between the effective (steady state) and desirable (theoretical) sensor reading. The protected chamber volume will influence the time response behavior. Theoretical predictions on sensor performance are compared with experimental data obtained for protected YSZ sensors conceived for moderately oxidizing atmospheres (1 Pa<Po₂<21 kPa). Two different cases are studied including one single phase and one composite (ionic + electronic conductor) electrochemical filter. Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11–18 Sept. 1994.     

Turbulent diamagnetism in flowing liquid sodium

The nature of Ohm's law is examined in a turbulent flow of liquid sodium. A magnetic field is applied to the flowing sodium, and the resulting magnetic field is measured. The mean velocity field of the sodium is also measured in an identical-scale water model of the experiment. These two fields are used to determine the terms in Ohm's law, indicating the presence of currents driven by a turbulent electromotive force. These currents result in a diamagnetic effect, generating magnetic field in opposition to the dominant fields of the experiment. The magnitude of the fluctuation-driven magnetic field is comparable to that of the field induced by the sodium's mean flow.     

浮力式低温液位计的设计原理及运行工况分析

全超导磁约束核聚变实验装置EAST的13对磁体电流引线全部采用高温超导(HTS)。为保证其安全运行,特为其液氮储槽设计制作了浮力式液位计。经过几轮物理实验,证明这种深冷液位计能较准确地监视HTS电流引线液氮储槽的液面,从而保证HTS电流引线的安全运行。文中介绍浮力式深冷液位计的设计原理及其运行工况。     

一种简单高精度超声液位计系统的设计与实现

介绍了超声时延法测距的基本原理,设计并实现了一种基于DSP的超声液位计系统,改进国内同类产品精度和稳定度偏低的问题。利用选用的AD、DSP芯片特点,给出了一种简单高效率的超声换能器驱动电路和回波采集放大电路的实现方案;使用通用16位定点DSP芯片TMS320VC5502,实现测距算法,增强了后端数字信号处理能力;使用收发一体窄带超声换能器发射和接收超声信号,其中心频率20kHz,3dB带宽1kHz。实验结果表明,本系统测量范围为0.5～18m,测量精度可达到测量距离的0.5%。     

基于对数检波器的峰值功率计研制

针对北京正负电子对撞机重大改造工程(BEPCII)直线加速器的实际情况和具体需求,为了提高峰值功率计测量精度、进一步降低反射保护报警响应时间并提供实时波形检测手段,对基于集成电路的射频检波芯片进行了调研,研制了一种基于对数检波器、现场可编程门阵列(FPGA)、高速模数转换器(ADC)的新型峰值功率计。通过对不同工作频率下的多点校准,建立分段传递函数,实现功率计校准工作。对功率计样机进行了系统测试,实现了实验室功率测量误差±0.2 dB,BEPCII在线测试的反射保护响应时间2 μs的成绩,功率计已稳定上线运行一段时间。此外,新型峰值功率计具有宽线性动态范围、反射保护报警、内置双通道检波器、用户和工程师双界面、实时波形显示、波形任一点功率测量等特点。