试验用流速测试技术的新发展

流速测试技术是研究流场中气流流动特性的重要手段,了解现代流速测量仪器的原理和应用特点,对选择合适的仪器进行实验研究至关重要.本文介绍了国内外现代流速测试技术的原理和应用特点,并对各种测试仪器进行了流动速度测量的参数比较,依据比较结果给出了选取测量方式的若干原则,为气流流动实验选择合适的测量工具提供了有力的指导.     

血液粘性测量标准物质前期研究

探讨了聚乙二醇6000作为血液粘性测量标准物质的可行性。依据国际血液学标准化委员会2009年发布的血液流变学实验室技术的指导意见,分析了作为血液粘性测量标准物质的必要条件,选用高纯度的聚乙二醇6000配制了2种不同浓度的水溶液作为此标准物质的候选物,并使用英国马尔文仪器公司Gemini HR nano200高精密度高级旋转流变仪对这2种水溶液流变性进行了均匀性、稳定性检验。定值研究与不确定度评定的结果为:1号溶液(3.95±0.18 )mPa·s,2号溶液(10.03±0.56 )mPa·s,表明该物质可以满足血液粘性测量的质量控制需要,可作为标准物质候选物。     

The Development of a Standard for Contact Transient Methods of Measurement of Thermophysical Properties

Contact transient methods, some of which are available as commercial forms, are now widely used worldwide for thermal properties measurements on broad ranges of materials used in physical, chemical, and medical applications. However, in many cases the claimed measurement uncertainty has not been substantiated while in others – especially for the multiproperty techniques – internal inconsistencies in measured and/or derived values are clearly apparent. Following recommendations of participants of two workshops held on the subject in Würzburg (1999) and Cambridge, Massachussetts (2001), NPL agreed to coordinate a task to develop a standard test-method for these techniques. This involved using inputs provided by a small group of individuals from organizations in several European countries and also taking note of comments from other interested parties via the internet during the course of the development. Details are provided on the resulting document, which takes the form of a generic standard containing appropriate details and related information common to all techniques. These sections include the scope, theory, summaries of method, basic apparatus and experiment, the influencing factors, specimen requirements, procedure, and recommended approach for analysis of the experiment and calculation of the results. In addition, there are six annexes, each of which contains additional information that applies to a specific technique. Finally, the document proposes a recommended approach for verification of a technique together with a list of appropriate reference materials having known values for one or more properties. The status of intercomparison studies will also be reported. Paper presented as the Fifteenth Symposium on Thermophysical Properties, June 22–27, 2003, Boulder.     

Cellular Interactions of Liposomes and PISA Nanoparticles during Human Blood Flow in a Microvascular Network

A key concept in nanomedicine is encapsulating therapeutic or diagnostic agents inside nanoparticles to prolong blood circulation time and to enhance interactions with targeted cells. During circulation and depending on the selected application (e.g., cancer drug delivery or immune modulators), nanoparticles are required to possess low or high interactions with cells in human blood and blood vessels to minimize side effects or maximize delivery efficiency. However, analysis of cellular interactions in blood vessels is challenging and is not yet realized due to the diverse components of human blood and hemodynamic flow in blood vessels. Here, the first comprehensive method to analyze cellular interactions of both synthetic and commercially available nanoparticles under human blood flow conditions in a microvascular network is developed. Importantly, this method allows to unravel the complex interplay of size, charge, and type of nanoparticles on their cellular associations under the dynamic flow of human blood. This method offers a unique platform to study complex interactions of any type of nanoparticles in human blood flow conditions and serves as a useful guideline for the rational design of liposomes and polymer nanoparticles for diverse applications in nanomedicine.     

Measurement of Workability of Fresh Concrete Using a Mixing Truck

The main objective of this study is to evaluate the workability of fresh portland cement concrete while it is still in the mixing truck by determining fundamental rheological parameters (plastic viscosity and yield stress). Nine concrete mixtures with different values of yield stress and plastic viscosity were tested in a concrete truck. The measurements made with the truck were based on the typical method of determining the flow behavior in a traditional fluid rheometer; that is, the shear rate in the mixing truck was swept from high to low by varying the rotation speed of the drum. The results of these experiments are discussed and compared with data provided by the ICAR rheometer, a portable rheometer designed for measuring concrete rheology. The test results indicate that the mixing truck equipment is sufficiently sensitive to detect differences in yield stress, slump, and plastic viscosity. However, the plastic viscosity determined by the truck measurement did not correlate with plastic viscosity as measured by the ICAR rheometer, while the yield stress determined by the truck measurement did correlate well with the measured slump and the ICAR rheometer resultsSuggestions are given on how to improve the mixing truck for better use as a rheometer.     

A Comparative Study for the Assessment on Blood Flow Measurement Using Self-Mixing Laser Speckle Interferometer

We study a self-mixing laser diode (SM-LD) as a low-cost compact optical sensor for noninvasive blood flow measurement over the surface of the skin. We compare the SM-LD system with a commercially available Doppler flowmeter to assess the accuracy and feasibility of the SM-LD sensors for such applications. For the SM-LD flowmeter, we apply two different signal processing methods: (1) the counting method, i.e., counting the intensity fluctuations of the signal to obtain a frequency value, and (2) the autocorrelation method, i.e., measuring the autocorrelation time of the signal. In vitro measurements show good agreement with the commercially available flowmeter. In vivo measurements performed on test subjects revealed that the autocorrelation technique shows much better results. The results of in vitro and in vivo studies and the comparison with the commercial flowmeter confirm the applicability of the SM-LD flowmeter.     

微流量测量方法及其技术的发展

归纳了近五年来基于MEMS技术的微流量传感器结构及性能参数。根据国际上热门的研究方法推断微流量测量技术可能的发展方向与研究趋势,即集成两种或两种以上的测量方法,实现优势互补,提高测量精度或扩大量程比。最后基于现有的技术基础,提出了融合科氏效应与差压效应的微流量测量方法,阐述了传感器的工作原理与理论基础,并对其可行性进行了分析与论证。     

A Novel Technique of Flow Measurement for a Conducting Liquid

The flow rate of a conducting liquid is generally measured by an electromagnetic flowmeter, which requires a magnetization coil and a set of sensing electrodes. However, the size and cost of the flow head of this flowmeter generally become very high due to the large size of the magnetizing coil and core material. In this paper, a novel low-cost bridge-type technique of flow measurement of a conducting liquid has been described. In this technique, the lumped-parameter impedances among four electrodes placed at a radial distance apart in a flow-sensing tube form a Wheatstone bridge network. Each of these impedances is a combination of electrode polarization impedances and other impedances. Since the electrode polarization impedances are functions of the flow rate of the conducting liquid and some other parameters, the polarization impedances between two electrodes placed in two locations along the flow path of the conducting liquid may be taken as a measure of the flow rate of the liquid, with the other parameters remaining constant. The nonlinearity of these impedance variations with the flow rate is minimized by the proposed bridge-circuit near-balanced condition. The bridge is excited by a stabilized sinusoidal oscillator and balanced at the no-flow condition of the liquid. The output of the bridge network is converted into a 1- to 5-V dc signal in a signal conditioner circuit. The design aspects, theoretical analysis, and calibration data are presented in this paper. The experimental characteristic of the flowmeter is found to follow the theoretical equation and has good repeatability over the entire operating zone.      

竖直通道内降膜流动数值模拟

降膜蒸发是一种高效的传热技术,平均液膜厚度是考察降膜蒸发传热性能的一个重要影响因素。本文基于VOF算法,建立了水和空气沿二维竖直通道降膜流动的CFD模型,模拟研究了液膜速度、工质种类、同向和逆向气流对平均液膜厚度的影响。结果表明：提高液膜速度会增大平均液膜厚度;气相工质对液膜厚度影响不大,而液相工质对液膜厚度影响较大,液膜厚度随液相黏度增大而增大;同向气流对入口段和发展段的液膜厚度影响不大,稳定段液膜厚度会随着同向气流速度的增大而减小;平均液膜厚度随逆向气流速度增大而降低,当逆向气流速度达到2.5 m/s后,气流速度对液膜厚度的影响减小。     

基于两段法及改变落球高度的硝化棉落球粘度测量

为提高落球法测量硝化棉粘度的精确性,减小因小球在落球距离内做非匀速运动造成的误差,提出了一种基于两段法及改变落球高度的精确测量方法。采用PLC、光电传感器设计实验装置,选取5种粘度的试液,获得不同落球高度的计时值,拟合数据得到适宜落球高度。对比了传统固定高度与适宜落球高度方法的测量误差。实验表明,适宜落球高度和试液粘度之间存在负相关性;粘度大于60 300 mPa·s时,落球管口处即为适宜落球高度;粘度小于60 300 mPa·s时,在适宜落球高度释放小球能减小测量误差;粘度越低误差减小效果越明显。     

Flow Behavior of Fresh Portland Cement Pastes

Portland cement pastes prepared at various water/cement ratios were studied using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-oscillatory measuring device MV2P with serrated surfaces. The tests were performed under both continuous and oscillatory flow conditions. In this article, experimental shear stress and shear rate data were fitted very satisfactorily with a model proposed by the authors. Excellent results were achieved also by applying the Quemada equation. Oscillatory flow data gave further information on the workability of the pastes investigated. In addition, the influence of two different commercial superplasticizing agents (Concretan RX and Ergomix 1000, the first based on polycyclic copolymers with modified structures carrying hydroxylated side chains, the second on a modified polyacrylic resin) was studied with the aim of determining their optimum dosage. In the case of Ergomix 1000, agreement between the optimum dosage determined rheologically and that recommended by the producer was obtained.     

Flow Behavior of Fresh Portland Cement Pastes

Portland cement pastes prepared at various water/cement ratios were studied using the rate-controlled coaxial cylinder viscometer Rotovisko-Haake 20, system M5-oscillatory measuring device MV2P with serrated surfaces. The tests were performed under both continuous and oscillatory flow conditions. In this article, experimental shear stress and shear rate data were fitted very satisfactorily with a model proposed by the authors. Excellent results were achieved also by applying the Quemada equation. Oscillatory flow data gave further information on the workability of the pastes investigated. In addition, the influence of two different commercial superplasticizing agents (Concretan RX and Ergomix 1000, the first based on polycyclic copolymers with modified structures carrying hydroxylated side chains, the second on a modified polyacrylic resin) was studied with the aim of determining their optimum dosage. In the case of Ergomix 1000, agreement between the optimum dosage determined rheologically and that recommended by the producer was obtained.     

粘弹性材料的动态力学测试分析技术研究进展

本文对国内外粘弹性材料动态力学性能表征研究进行了综述，就如何获得声频范围（特别是在静压力条件下）粘弹性材料的动态力学性能参数进行了总结，并对粘弹性材料动态力学性能表征的发展进行了展望。     

关于应用“沉降原理”测定粒径几个问题的探讨

通过对斯托克斯沉降原理的分析与推导，对应用该原理测定颗粒粒径应注意的几个问题进行了分析探讨，提出了该原理可测的颗粒最大粒径和最小粒径的计算公式，对实际应用有一定的指导意义。     

滚动轴承滚针直径测量结果的不确定度评定

在立式光学计上测量滚动轴承滚针直径,利用量块尺寸作为标准,将测量装置调整为零位,然后测出滚针与量块标准尺寸的差值,求出被测滚针的直径尺寸。分析了温度误差、测量力误差、示值误差、标准量块极限误差、测量重复性和测量装置定位误差等对测量装置不确定度的影响,并给出了相应的不确定度的计算公式。