A high-resolution digital time-interval measurement instrument

A new method for time-interval measurements is described and the results of measurements on a prototype are given. This method uses a virtually periodic exponential signal as the reference clock and consists of measuring both the phase deviation and the number of cycles of this clock signal between the beginning and the end of the unknown time-interval. The use of two auxiliary sinusoidal signals in order to measure the phase of the corresponding periodic exponential signal is discussed, also considering the main causes of error. The functional block diagram of the prototype is described in detail and the measurement results show that a resolution improvement of two orders of magnitude with respect to the period of the clock signal can easily be obtained.     

Design of a compensated signal rod for low magnetic moment sample measurements with a vibrating sample magnetometer

A zero-signal sample holder is proposed for the measurement of weak magnetic signals with vibrating sample magnetometers. With proper shape of the support rod, a nearly vanishing signal can be obtained as a function of the magnetic field and the temperature. In particular, it is shown that the addition of an extra part to a standard glass sample holder can reduce the diamagnetic signal by more than three orders of magnitude with no noise increase. The proposed method is applicable to field, temperature, and angular measurements; it is also ideally suited to direct measurement of nanometer thick magnetic layers deposited on much thicker diamagnetic substrates.     

Note: An adhesion measurement setup for bioinspired fibrillar surfaces using flat probes

Current adhesion measurement setups designed for experiments on bioinspired fibrillar surfaces, either commercial or constructed in-house, do not allow adhesion measurements with in situ visualization, high resolution, high force range, and controlled alignment at the same time. In this paper a new adhesion tester is presented, which enables contact experiments with controlled tilt angle (accuracy of ±0.02°). This allows the use of flat probes and thus greatly simplifies the determination of experimental parameters such as pull-off strength or Young's modulus. The deflection of a double-clamped glass beam is measured by laser interferometry with an accuracy of ±60 nm, which yields a precise force measurement over three orders of magnitude force range without changing the glass beam. Contact formation and detachment events can be visualized in situ. The current adhesion tester is designed for force measurements in the range of 1 μN to 1 N and fills the gap between macroscopic tests and atomic force microscopy measurements.     

Development of a laboratory EXAFS facility

The EXAFS technique is a powerful new structural tool, particularly useful for studies of disordered or otherwise complex materials for which x-ray diffraction techniques are difficult or unfeasible. At the present time, most EXAFS experiments are carried out at a synchrotron facility because of the larger fluxes available. We have developed an in-laboratory apparatus utilizing a focusing crystal technique which increases available fluxes two to three orders of magnitude over previous laboratory facilities, so that EXAFS measurements can be carried out quickly and accurately in the laboratory. We will discuss the principles of the focusing monochromator and we will also illustrate the experimental method with examples, including studies of chemical solutions, defect crystalline solids, and high-temperature superconductors.     

Characterization of instrument drift using a spherical artifact

Drift is a common and inevitable error source in measurements. Currently there are two main approaches to address instrument drift in image or area-based measurements, drift calibration with target tracking and active feedback correction. We propose an alternative approach to drift calibration for profilometers, particularly high speed instruments such as confocal microscopes or scanning white light interferometers. The method is based on sequential measurements of a spherical artifact whose diameter is larger than the field of view. A best fit sphere algorithm is used to determine the movement of the spherical artifact's center over time. This reduces drift measurement uncertainty because it uses height data over the full field of view, compared to target tracking strategies that involve tracking small features. Simulation results show that under practical conditions, e.g. with typical noise levels and typical drift rates, this method is quite effective and can yield measurements with low uncertainty. The measurement is demonstrated on a commercial confocal microscope to determine drift rate magnitude and direction.     

新的消光起伏信号数据处理模型

窄光束照射含颗粒两相流时,透过率会产生起伏。透过率起伏信号可用来测量颗粒粒径和浓度。由于在测量原理和结构上非常简单,这种方法可用来实现在线、实时测量。本文对Gregory提出的模型讨论,指出其中不足之处并提出一种新的数据处理模型。模拟计算和实测表明,新的模型在颗粒粒径范围和浓度范围均有扩展。     

实时采集道路车流量信息的视频新方法

本文介绍了一种实时采集道路车流量信息的视频新方法.该方法采用2个新的视频参数作为道路车流量检测的参数,分别称它们为对比度失真和亮度失真参数.分析表明:以视频的对比度失真作为采集道路车流量信息的检测参数对阴影干扰有着很好的抑制作用,从而可利用它来很好地解决传统道路车流量视频检测方法中存在的阴影干扰问题;亮度失真非常适合于实时更新道路背景的视频图像模板,以作为对比度失真参数的补充来提高道路车流量视频检测的准确性;此外,利用这2个参数还可以在很大程度上缓解困扰传统视频检测方法的车距过近问题.大量不同道路、不同车流量和天气情况的实验结果表明:本文提出的视频方法采集车流量的准确率可以达到97.27%.     

氨基酸直接分析法原理及应用

本文介绍一种新型氨基酸分析方法——离子交换色谱、积分脉冲安培法(HPC-IPAD),详细讨论了方法的原理和应用,该方法与传统方法比较,无须进行柱后或柱前衍生反应,可以对氨基酸直接进行分析,灵敏度高,大多数氨基酸的最小检测限均小于1pmol,线性范围可以达到3个数量级以上。     

氨基酸直接分析法原理及应用

本文介绍一种新型氨基酸分析方法-离子交换色谱-积分脉冲安培法（HPIC-IPAD）,详细讨论方法的原理和应用,该方法与传统方法比较,无须进行柱后或柱前衍生反应,对氨基酸可以直接进行分析,灵敏度高,大多数氨基酸的最小检测限均小于1pmol,线性范围可以达到3个数量级以上。     

A Method of Quantitative Measurement of Fluorescence Intensity by Confocal Laser Scanning Microscopy

We present a method of quantitative measurement, by laser scanning microscope, of intensity of fluorescence in assays on concentration of fluorochromes in a sample. This method can be used to evaluate the DNA content or the concentration of any protein, marked by an appropriate fluorescent dye, in single cells or groups of cells, isolated or in a tissue. Confocal laser scanning microscopy provides optical serial sections through thick biological sample that give accurate information about the intensity of fluorescence. The method we propose consists in scanning the sample by juxtaposition of optical sections and displaying it as a suitable projection. Multiplying the fluorescence intensity in such projection by the number of sections we obtain an estimate of the concentration of fluorochrome in the sample. We tested this method on fluorescent beads and on biological samples stained for DNA. We evaluated and corrected the measure for the photobleaching effect and for the beam theoretical distortion. Our results show that this method is accurate and suitable to compare samples of variable thickness and for multiple stained samples, and is less time consuming than the method based on the scanning of the sample according to the Nyquist principle.     

Novel non-contact torque measurement using the magnetomechanical effect

With the recent developments in science and technology, torque measurements have been widely used in many fields. However, present torque measurement methods have limitations for long-term applications. Therefore, a new method of non-contact torque measurement based on the magnetomachanical effect is reported that may be used in reducing fatigue for long-term measurements. The theory of the changes in magnetization with torque are analyzed to construct a model. Hence, an experiment platform was constructed that includes an excitation coils, shaft, and Gauss meter. The relationship between the magnetic induction and the torque was measured using this apparatus. The results show that the experimental measurements are in agreement with mathematical models obtained using magnetomechanical concepts. The results also show that the maximum nonlinearity error of the system is 0.6% and the maximum repetitive error is 3.125%. Additionally, this proposed method meets the requirements for long-term torque measurements and may also be used for the non-contact characterization of the torque of watercraft and airplanes.     

The estimation of measurement uncertainty of small circular features measured by coordinate measuring machines

This paper examines the measurement uncertainty of small circular features as a function of the sampling strategy; i.e., the number and distribution of measurement points. Specifically, we examine measuring a circular feature using a three-point sampling strategy in which the angular distance between the points varies from widely spaced, 120°, to closely grouped, a few degrees. Both theoretical and experimental results show that the measurement uncertainty is a strong function of the sampling strategy. The uncertainty is shown to vary by four orders of magnitude as a function of the angular distribution of the measurement points. A conceptual framework for theoretically estimating the measuring uncertainty is described, and good agreement with experiments is obtained when the measurements are consistent with the assumptions of the theoretical model. This paper is an expansion of a previous internal report1 with additional material on analog probes and probe lobing models.     

A system for time-fluctuating flow rate measurements in a single-blade pump circuit

Commonly used flow rate measurement systems provide an accurate and stable output value of the quasi-stationary flow rate. In some pump types as e.g. single-blade pumps significant flow rate fluctuations may occur even in steady operation points due to rotor-stator interaction. For the analysis of the time-resolved flow rate a new measurement and evaluation method is presented based on an electromagnetic flow meter. Internal averaging of the flow meter is deactivated and the raw signal is evaluated directly with a sampling rate of 3 kHz. With ensemble-averaging in combination with an impeller position detection, interfering signals acting on the time-resolved measurement signal are filtered out. Accompanying numerical simulations of the pump flow circuit are carried out with a 1D method of characteristics and validated against well-established time-resolved pressure measurements of the pump flow. Experiment and simulation show a resembling trend of pressure as well as flow rate fluctuations over the entire operation range of the pump. Thus, by the combined utilisation of measurement and simulation technique, we assure the validity of the ensemble-averaged flow rate fluctuation results. We find that the flow rate fluctuations show a consistent phase shift to the pressure fluctuations that increases towards overload. The flow rate amplitude is an order of magnitude smaller than the amplitude of the pressure fluctuations.     

Analysis of diffusion and binding in cells using the RICS approach

The movement of macromolecules in cells is assumed to occur either through active transport or by diffusion. However, the determination of the diffusion coefficients in cells using fluctuation methods or FRAP frequently give diffusion coefficient that are orders of magnitude smaller than the diffusion coefficients measured for the same macromolecule in solution. It is assumed that the cell internal viscosity is partially responsible for this decrease in the apparent diffusion. When the apparent diffusion is too slow to be due to cytoplasm viscosity, it is assumed that weak binding of the macromolecules to immobile or quasi immobile structures is taking place. In this article, we derive equations for fitting of the RICS (Raster‐scan Image Correlations Spectroscopy) data in cells to a model that includes transient binding to immobile structures, and we show that under some conditions, the spatio‐temporal correlation provided by the RICS approach can distinguish the process of diffusion and weak binding. We apply the method to determine the diffusion in the cytoplasm and binding of Focal Adhesion Kinase‐EGFP to adhesions in MEF cells. Microsc. Res. Tech., 2009. © 2008 Wiley‐Liss, Inc.     

五点法测量机床主轴轴向及倾角的运动误差

提出了测量机床主轴的轴向及倾角运动误差的端面五点法。在轴端面绕轴心的某一圆周上,垂直于轴端面,按通过误差分析优化确定的位置,布置五个测头,在主轴回转一圈中同时测得主轴的轴向及倾角运动误差以及端面基准的形状误差,并将测头的读数及定位误差的影响降至最低程度。本方法可用于机床主轴回转精度的实时测量,试验表明其测量精度可达亚微米级。     

An instrumentation system for multi-parameter measurements of gas-solid two-phase flow based on Capacitance-Electrostatic sensor

In this paper, an instrumentation system for the measurements of local solid volumetric concentration, local solid velocity, local solid mass flowrate and solid mass flowrate in gas-solid two-phase flow system is developed. It is based on a new type of a Capacitance-Electrostatic sensor (CES). The CES sensor is mainly composed of a capacitance electrode array and two electrostatic electrode arrays. The optimum design of the sensor is achieved by finite element method. The capacitance electrode array is employed to detect the solid distribution over the cross-section of the pipe, and the local solid volumetric concentration measurement is further derived. The electrostatic electrode arrays are used to measure the local solid velocities in conjunction with cross-correlation method. From the local solid velocity and local volumetric concentration, the solid mass flowrate and the local solid mass flowrate can be achieved. The developed system for the local solid volumetric concentration measurement is verified through analogue simulation experiments and static experiments. Finally, the system is employed to measure the local solid volumetric concentration, local solid velocity, local solid mass flowrate and solid mass flowrate on a belt conveyor. The experimental results show that the measurement error of the local solid volumetric concentration measurement results are less than 10.43% for solid local volumetric concentration ranging from 0.02 to 0.56, the standard deviations of the local solid velocity measurement results are less than 0.42 for solid velocity ranging from 3.5 m/s to 15.0 m/s, and the relative error of the solid mass flowrate is within −19.6% to +14.9% for solid mass flowrate ranging from 0.006 kg/s to 0.103 kg/s, indicating that the system is capable of achieving multi-parameters measurement in gas-solid two-phase flow system.     

Low-Speed Atomistic Simulation of Stick–Slip Friction using Parallel Replica Dynamics

Atomic stick–slip friction has been predicted by molecular dynamics simulation and observed in experiments. However, direct quantitative comparison of the two has thus far not been possible because of the large difference between scanning velocities accessible to simulations and experiments. In general, the slowest sliding speeds in MD simulations are at least five orders of magnitude larger than the upper limit available to experimentalists. To take a step toward bridging this gap, we have applied parallel replica dynamics, an accelerated molecular dynamics method, to the simulation of atomic stick–slip. The method allows molecular simulations to run parallel in time in order to extend their duration, thereby enabling lower scanning velocities. We show here that this method is able to predict atomic stick–slip friction accurately and efficiently at scanning speeds several orders of magnitude slower than standard molecular dynamics simulations. The accuracy and usefulness of this method is illustrated by correct prediction of the logarithmic dependence of friction on velocity.     

Toward a better modulus at shallow indentations—Enhanced tip and sample characterization for quantitative atomic force microscopy

Approximations of the geometry of indenting probes, particularly when using shallow indentations on soft materials, can lead to the erroneous reporting of mechanical data in atomic force microscopy (AFM). Scanning electron microscopy (SEM) identified a marked change in geometry toward the tip apex where the conical probe assumes a near linear flat-punch geometry. Polydimethylsiloxane (PDMS) is a ubiquitous elastomer within the materials and biological sciences. Its elastic modulus is widely characterized but the data are dispersed and can display orders of magnitude disparity. Herein, we compare the moduli gathered from a range of analytical techniques and relate these to the molecular architecture identified with AFM. We present a simple method that considers sub-100 nm indentations of PDMS using the Hertz and Sneddon contact mechanics models, and how this could be used to improve the output of shallow indentations on similarly soft materials, such as polymers or cells.     

气固两相流质量流量测量的新方法

文提出了一种采用电容传感器测量气固两相流质量流量的新方法。通过电容传感器对固相浓度的测量,可以求出气固两相流的固气比,结合气固混合之前所测得的载气流量,便可测出固相的质量流量。实测结果显示,测量误差小于5     

Continuous Scan, a method for performing modal testing using meaningful measurement parameters; Part I

This paper presents the first part of a work about modal testing using meaningful measurement parameters. Scanning Laser Doppler Vibrometer (SLDV) systems are becoming largely used both in industry and university for performing vibration measurements. A reason for the success of SLDV systems can be found in their capability of measuring vibration remotely and under different environmental conditions which, when hostile, can inhibit other transducers to work correctly. Hence, SLDV system can be very practical and useful in many engineering applications. SLDV systems are being used as a contactless transducer measuring vibrations from a discrete number of measurement positions marked on the specimen whenever an optical access to it is available. Hence, the advantage of a modal test carried out using accelerometers and one carried out using a SLDV system can be: (i) the automation of the measurements and (ii) the increase of the spatial resolution of the measured modes. This suggests that SLDV systems can be used as a practical replacement of accelerometers operating the same measurement method. Continuous Scanning method is a novel approach of using contactless transducers for measuring vibrations. The most important difference between a discrete and a continuous approach is the method of measuring a vibration pattern. A discrete method measures the level of vibrations at discrete positions on a structure whereas a continuous method captures the modulation of the vibrations produced by the excited modes. This is possible when a transducer can travel across a vibrating surface. This first part of the work presents a new approach of continuous scanning measurement method using a multi-tonal excitation waveform. The paper starts from a comparison between a step and continuous scan mode to introduce a novel approach of continuous scan and multi-tonal excitation waveform. The objective of this first part of work is to present and understand that measurement parameters, such as measurement positions, and can be carefully chosen to improve the measurement technique. A laboratory test piece and a helicopter tail cone are used as examples for the application of this new measurement method approach.