On the Sizing Accuracy of Laser Optical Particle Counters

The performance of a narrow-angle and a wide-angle, forward scattering laser aerosol spectrometer has been studied as a function of particle size and refractive index. The results have been compared with theoretical calculations based on light scattering theory. The results indicate that for the narrow-angle instrument, the scattered-light intensity is not a monotonic function of particle size for transparent particles (a monotonic relationship is required for unambiguous particle size measurement) above 0.7 μm. The instrument is therefore limited in its useful range to size distribution measurement between 0.2 μm – its lower particle size limit – and 0.7 μm for transparent particles. In the case of the wide-angle instrument, the instrument output is a monotonic function of particle size for transparent particles, but the output is severely attenuated for light absorbing particles above 0.3 μm. The instrument, therefore, cannot be used for accurate size measurements above 0.3 μm for light absorbing particles.     

Simultaneous, single particle, magnetization and size measurements of micron sized, magnetic particles

Single particle magnetization and size measurements of micron and nano sized, magnetic particles were made using a previously described device referred to as Cell Tracking Velocimetry, CTV. Three types of commercially available, and commonly used, magnetic particles were studied in this report. While the CTV instrument provides individual particles measurements, the average magnetization and size measurements were found to have reasonable agreements with reported values from instruments which measure bulk values. In addition, the CTV instrument, using electromagnets, can also determine magnetization curves, which also proved to have reasonable agreement with other published studies. Given that magnetic separation and analysis technology is dependent on the quality of the magnetic particles used, studies such as this one using CTV provide not only average data, but also provides information with respect to the distribution of the properties such as magnetization and size. For example, the spread of the data in magnetic and settling velocities were found to be predominately due to the size distribution of the analyzed particles.     

Time-resolved multi-channel optical system for assessment of brain oxygenation and perfusion by monitoring of diffuse reflectance and fluorescence

Time-resolved near-infrared spectroscopy is an optical technique which can be applied in tissue oxygenation assessment. In the last decade this method is extensively tested as a potential clinical tool for noninvasive human brain function monitoring and imaging. In the present paper we show construction of an instrument which allows for: (i) estimation of changes in brain tissue oxygenation using two-wavelength spectroscopy approach and (ii) brain perfusion assessment with the use of single-wavelength reflectometry or fluorescence measurements combined with ICG-bolus tracking. A signal processing algorithm based on statistical moments of measured distributions of times of flight of photons is implemented. This data analysis method allows for separation of signals originating from extra- and intracerebral tissue compartments. In this paper we present compact and easily reconfigurable system which can be applied in different types of time-resolved experiments: two-wavelength measurements at 687 and 832 nm, single wavelength reflectance measurements at 760 nm (which is at maximum of ICG absorption spectrum) or fluorescence measurements with excitation at 760 nm. Details of the instrument construction and results of its technical tests are shown. Furthermore, results of in-vivo measurements obtained for various modes of operation of the system are presented.     

Fundamental aspects of pulse phase-locked loop technology-based methods for measurement of ultrasonic velocity.

A new instrument based on a constant frequency pulse phase-locked loop concept has been developed to accurately measure the ultrasonic phase velocity in condensed matter. Measurements of the sound velocity in ultrapure water are reported in which both damped and undamped transducers are used with the instrument together with reflectors of various thicknesses placed in the sound propagation path. An analysis of measurements made with the new instrument and similar measurements, taken under identical experimental conditions, using a popular variable frequency pulsed-phase-locked loop instrument is reported. Uncertainties in both measurement systems are analyzed and discussed. A method for measuring inherent phase shifts, not addressed by previous investigators, within the variable frequency pulsed phase-locked loop system and a derivation of the equations that govern the overall use of variable frequency systems using phase-sensitive comparisons are presented. The effects of a finite pulse length on the measurements of phase velocity in dispersive media are addressed in detail.     

An international round-robin calibration protocol for nanoindentation measurements

Nanoindentation has become a common technique for measuring the hardness and elastic-plastic properties of materials, including coatings and thin films. In recent years, different nanoindenter instruments have been commercialised and used for this purpose. Each instrument is equipped with its own analysis software for the derivation of the hardness and reduced Young's modulus from the raw data. These data are mostly analysed through the Oliver and Pharr method. In all cases, the calibration of compliance and area function is mandatory. The present work illustrates and describes a calibration procedure and an approach to raw data analysis carried out for six different nanoindentation instruments through several round-robin experiments. Three different indenters were used, Berkovich, cube corner, spherical, and three standardised reference samples were chosen, hard fused quartz, soft polycarbonate, and sapphire. It was clearly shown that the use of these common procedures consistently limited the hardness and reduced the Young's modulus data spread compared to the same measurements performed using instrument-specific procedures. The following recommendations for nanoindentation calibration must be followed: (a) use only sharp indenters, (b) set an upper cut-off value for the penetration depth below which measurements must be considered unreliable, (c) perform nanoindentation measurements with limited thermal drift, (d) ensure that the load-displacement curves are as smooth as possible, (e) perform stiffness measurements specific to each instrument/indenter couple, (f) use Fq and Sa as calibration reference samples for stiffness and area function determination, (g) use a function, rather than a single value, for the stiffness and (h) adopt a unique protocol and software for raw data analysis in order to limit the data spread related to the instruments (i.e. the level of drift or noise, defects of a given probe) and to make the H and E(r) data intercomparable.     

Optimized energy dispersive X‐ray fluorescence analysis of atmospheric aerosols collected at pristine and perturbed Amazon Basin sites

Elemental composition of aerosols is important to source apportionment studies and to understand atmospheric processes that influence aerosol composition. Energy dispersive X‐ray fluorescence spectroscopy was applied for measuring the elemental composition of Amazonian atmospheric aerosols. The instrument used was a spectrometer Epsilon 5, PANalytical B.V., with tridimensional geometry that reduces the background signal with a polarized X‐ray detection. The measurement conditions were optimized for low‐Z elements, e.g. Mg, Al, Si, that are present at very low concentrations in the Amazon. From Na to K, our detection limits are about 50% to 75% lower than previously published results for similar instrument. Calibration was performed using Micromatter standards, except for P whose standard was produced by nebulization of an aqueous solution of KH₂PO₄ at our laboratory. The multi‐element reference material National Institute of Standards and Technology–2783 (air particulate filter) was used for evaluating the accuracy of the calibration procedure of the 22 elements in our standard analysis routine, and the uncertainty associated with calibration procedures was evaluated. The overall performance of the instrument and validation of our measurements were assessed by comparison with results obtained from parallel analysis using particle‐induced X‐ray emission and another Epsilon 5 spectrometer. The elemental composition in 660 samples collected at a pristine site in the Amazon Basin and of 1416 samples collected at a site perturbed by land use change was determined. Our measurements show trace elements associated with biogenic aerosols, soil dust, biomass burning, and sea‐salt, even for the very low concentrations as observed in Amazonia. Copyright © 2014 John Wiley & Sons, Ltd.     

Resolution in the far-infrared Fourier transform spectroscopy with a pulsed synchrotron source

The effect of the pulse width on the resolution in the Fourier transform spectroscopy with a pulsed synchrotron source has been studied. The instrument line shape function is obtained as a function of the pulse width for both the boxcar and Gaussian pulses. It is shown that the amplitude of the interference fringes produced by a transparent disk serves as a sensitive test of the resolution. Interference fringes due to a single crystal silicon disk were measured with the synchrotron radiation from the UVSOR facility at IMS (Okazaki). The lower bounds of the pulse width were estimated from the fringe amplitude and were consistent with the value obtained by direct measurements of the pulse width.     

Detection of moisture content in high-purity ammonia by means of diode-laser spectroscopy

The aim of this work was the development of an as-simple-as-possible instrument for trace moisture concentration measurements in high-purity ammonia. A near-infrared diode-laser-based instrument has been applied to measure the humidity in a process of on-line detection of water in ammonia during industrial purification. The results of water concentration measurements were compared with alternative techniques (primarily dew-point detection) and good agreement was achieved. The long-term sensitivity of such a diode-laser-based instrument was estimated to be 5 ppm. The calculation of the water concentration from measurements of the integrated volume of water contained in the heavy fraction, extracted during the purification process, yields an even lower detection limit of less than 0.1 ppm, depending on the initial ammonia purity. PACS 42.55.Px; 42.62.Cf; 42.62.Fi     

Mechanical response measurements of real and artificial brass players lips

Mechanical frequency responses of human and artificial lips in brass instrument playing have been measured using a high-speed digital video technique, in an attempt to classify the true nature of the "lip-reed." Four semiprofessional human players were used, and three notes played on a trombone were studied. All measurements revealed a strong mechanical resonance with "outward striking" behavior; the played note always sounded above this frequency. Several measurements also showed a weaker second resonance, above the played frequency, with "inward striking" behavior. The Q values of the dominant resonances in human lips were lower than those typical of artificial lips.     

The Use of Streak Photography,X-Ray Radiography,and Radiometric and Spectrometric Measurements to Study Plasma Bunches Generated under Gyroresonant Interactions

Results of experimental studies of relativistic plasma bunches obtained under gyromagnetic autoresonance (GA) and confined in a magnetic mirror trap are provided. The main attention is paid to observations of the radiation generated by plasma bunches at different stages of their lives in different spectral ranges using streak photography and X-ray imaging techniques. The original method of accounting for the instrument function in X-ray spectroscopic analysis and radiometric measurements is applied within the quantum energy range of 0.2–2 MeV to take account of considerable distortion caused by the Compton scattering in the detector.     

Experimental characterization of instrument panel buzz, squeak, and rattle (BSR) in a vehicle

Among the various elements affecting a customer’s evaluation of automobile quality, buzz, squeak, and rattle (BSR) are considered to be major factors. We propose an integrated experimental method that can be used to reduce BSR in an instrument panel module in a vehicle cabin, especially during the early design stage of vehicle development. We devised a vibration triggering system consisting of a fixture and an electromagnetic shaker to generate an input load reproducing the excitation signal from the road to the instrument panel without distortion. Potential source regions for BSR were localized using a near-field acoustic holography map obtained from near-acoustic-field visualization equipment consisting of 48 intensity-type microphones, a data-acquisition system, and its analysis software. Finally, a sound quality evaluation of BSR from the detected potential source regions was performed using sound quality metrics. These experimental procedures were applied to characterize BSR from the instrument panel in a passenger vehicle. Based on our measurements and analysis, typical main source regions for BSR on the instrument panel were identified and quantitatively evaluated in terms of physical levels and sound quality metrics. These results revealed that the proposed experimental procedure can be used as a test procedure to identify BSR issues at an early stage in the vehicle development cycle, which could ultimately reduce production costs.     

光学传递函数测量仪刀口和狭缝两种扫描方法比较分析

GC 2 11光学传递函数分析仪是北京理工大学光电工程系自行研制的一台能对折轴、潜望等复杂光学系统进行测量的大型精密测量仪。其测量采用了刀口扫描和狭缝扫描两种方式。但实际应用时 ,用刀口扫描方式得到的光学传递函数值总是小于理论值。通过分析计算 ,得出在相同条件下 ,刀口扫描法比狭缝扫描法抗干扰能力差的结论 ,弄清了长期以来刀口扫描测试数值偏小的问题。     

Limits of coherence-based aeroacoustic analysis in the presence of distributed sources

Coherence-based analysis techniques utilizing a small number of microphones are often applied in aeroacoustic measurements. These techniques can remove statistically incoherent noise, electronic or hydrodynamic, from acoustic signals measured by microphones, at significantly lower cost than array methods. However, the assumptions involved in the usage of the ordinary coherence function technically limit analysis to a single-source field. In the presence of multiple sources the coherence function breaks down and ordinary analysis techniques under-predict true acoustic levels. This phenomenon is demonstrated mathematically and illustrated using experimental trailing edge noise data.     

Raman and fluorescence lidar measurements of aircraft engine emissions

Laser induced Raman and fluorescent measurements were made in the exhaust of a gas turbine engine with a new field portable instrument devised specifically for gas turbine exhaust measurements. The gas turbine exhaust was analyzed by conventional instruments for CO, CO₂, NO, NO_x, total hydrocarbons, smoke and temperature, and these data were used as a ‘calibration’ standard for the evaluation of the laser Raman instrument. Results thus far indicate good correlations for CO₂, O₂, smoke, hydrocarbons and temperature. The instrument was not sensitive enough for NO detection but the data analysis indicates that 100 ppm may be detectable with instrument improvements. CO analysis was not attempted, but it is expected that CO could be detected with further research. NO₂ (or NO_x) was not attempted because theoretical and experimental laboratory analysis indicated severe interference with CO₂. The conclusion was that laser Raman shows a good potential for aircraft gas turbine emission analysis.     

An improved high-resolution solar reference spectrum for earth's atmosphere measurements in the ultraviolet, visible, and near infrared

We have developed an improved solar reference spectrum for use in the analysis of atmospheric spectra from vacuum wavelengths of 200.07 through 1000.99 nm. The spectrum is developed by combining high spectral resolution ground-based and balloon-based solar measurements with lower spectral resolution but higher accuracy irradiance information. The new reference spectrum replaces our previous reference spectrum, and its derivatives, for use in a number of physical applications for analysis of atmospheric spectra, including: wavelength calibration; determination of instrument transfer (slit) functions; Ring effect (Raman scattering) correction; and correction for spectral undersampling of atmospheric spectra, particularly those that are dilute in absorbers. The applicability includes measurements from the GOME, SCIAMACHY, OMI, and OMPS satellite instruments as well as aircraft-, balloon-, and ground-based measurements.     

Development of Low-Cost Instrumentation for Single Point Autofluorescence Lifetime Measurements

Autofluorescence lifetime measurements, which can provide label-free readouts in biological tissues, contrasting e.g. different types and states of tissue matrix components and different cellular metabolites, may have significant clinical potential for diagnosis and to provide surgical guidance. However, the cost of the instrumentation typically used currently presents a barrier to wider implementation. We describe a low-cost single point time-resolved autofluorescence instrument, exploiting modulated laser diodes for excitation and FPGA-based circuitry for detection, together with a custom constant fraction discriminator. Its temporal accuracy is compared against a “gold-standard” instrument incorporating commercial TCSPC circuitry by resolving the fluorescence decays of reference fluorophores presenting single and double exponential decay profiles. To illustrate the potential to read out intrinsic contrast in tissue, we present preliminary measurements of autofluorescence lifetime measurements of biological tissues ex vivo. We believe that the lower cost of this instrument could enhance the potential of autofluorescence lifetime metrology for clinical deployment and commercial development.     

HFC-32饱和气导热系数的实验研究

1研究背景自《蒙特利尔议定书》签定后，特别是1992年11月哥本哈根会议以来，HCFCS的替代日程已经确定。目前以含有HFC－32的混合物替代HCFC－22的呼声很高，而且国外正开始着手应用。有关HFC－32的饱和气的导热系数现在还没有见文献报导。在本文中，作者自行开发设计了一套双热线法测量导热系数的实验装置，并对HFC－32的饱和气的导热系数进行了测量，经分析测量结果是令人满意的。2实验装置及实验原理热线法是测量导热系数的瞬态方法之一，其基本原理是Carslaw提出的半径趋于零的无限长线热源在无限大介质中的导热方程的解山文献…     

Amplitude modulation excitation for cancellous bone evaluation using a portable ultrasonic backscatter instrumentation

The ultrasonic backscatter (UB) has the advantage of non-invasively obtaining bone density and structure, expected to be an assessment tool for early diagnosis osteoporosis. All former UB measurements were based on exciting a short single-pulse and analyzing the ultrasonic signals backscattered in bone. This study aims to examine amplitude modulation (AM) ultrasonic excitation with UB measurements for predicting bone characteristics. The AM multiple lengths excitation and backscatter measurement (AM-UB) functions were integrated into a portable ultrasonic instrument for bone characterization. The apparent integrated backscatter coefficient in the AM excitation (AIB_AM) was evaluated on the AM-UB instrumentation. The correlation coefficients of the AIB_AM estimating volume fraction (BV/TV), structure model index (SMI), and bone mineral density (BMD) were then analyzed. Significant correlations (|R| = 0.82-0.93, p < 0.05) were observed between the AIB_AM, BV/TV, SMI, and BMD. By growing the AM excitation length, the AIB_AM values exhibit more stability both in 1.0-MHz and 3.5-MHz measurements. The recommendations in AM-UB measurement were that the avoided length (T1) should be lower than AM excitation length, and the analysis length (T2) should be enough long but not more than AM excitation length. The authors conducted an AM-UB measurement for cancellous bone characterization. Increasing the AM excitation length could substantially enhance AIB_AM values stability with varying analyzed signals. The study suggests the portable AM-UB instrument with the integration of real-time analytics software that might provide a potential tool for osteoporosis early screening.     

微束微区X荧光探针分析仪的矿物定量分析

介绍了微束微区X荧光探针分析仪的工作原理,该探针分析仪能够对样品表面约50μm范围内进行多元素定性与定量分析.在定量分析中,建立线性校准方程,采国家标准样品对微束微区X荧光该探针分析仪进行校准曲线的系数标定.以Fe、As和Ti元素所制定的校准曲线为例,定量分析出的元素含量与标准含量相对误差低于9.62％.结果显示微束微区X荧光探针分析仪具有较高的能量的分辨率,可以快速鉴定矿石的物质成分.定量分析结果的准确度低于地质样品分析的误差标准.表明该探针分析仪可以应用于野外条件下矿石微区成分的定性与定量分析.     

基于猝灭荧光素的一种TCSPC仪器响应函数测量方法

根据荧光物质的动态猝灭作用原理,将碘化钠饱和水溶液与碱性荧光素水溶液按照特定的比例混合,利用时间分辨设备测量猝灭后的荧光素荧光寿命。实验观察到随着碘化钠饱和溶液浓度的增加,测量得到的荧光寿命逐步从4 ns减小至24 ps左右。如将猝灭荧光素作为仪器响应函数的标准样品,与通常作为标准样品的二氧化硅纳米颗粒悬浮液进行对比,实验结果显示两者非常吻合,表明猝灭荧光素可以作为荧光衰减测试中的标准样品,进一步研究发现这种新的标准样品一方面避免了传统测量手段中需要在不同探测波长反复测量仪器时间响应函数的问题,更有效地减小了实验中颜色效应造成的实验误差。有望在时间分辨荧光光谱和荧光寿命成像等研究中得到应用。