基于非本征珐布里-泊罗干涉仪的多路复用应变测量传感技术

非本征珐布里-泊罗干涉传感器(EFPl)已经被证明适用于压力和温度的精确测量.我们介绍一种基于白光干涉仪的路径匹配完全测量方法.该系统从参考间隔到EFPI的感应间隔都适用.当这两个波长差在光源的相干长度内时,在系统输出中会产生一个强度包络.相应的路径失谐明确的指出传感器间隙的大小,压力便可以确定.这种应用大量EFPl传感器的多路技术的测量方法是可行的,并且给出四个多分复用设备的实验数据.文中也给出系统优化的理论设想.     

激光干涉仪的计量保证方案研究

首先简要介绍了计量保证方案的基本实施过程,在此基础上提出了针对激光数字波面移相干涉仪的计量保证方案,内容包括核查标准和传递标准的设计,过程统计参数的建立,测量不确定度评定等三个方面。该方案的运行极大地增强了实验室对干涉仪性能状况的了解,提高了测试结果的可信度。     

Grease Degradation in Constant Velocity (CV) Joints

Constant velocity (CV) joints have been widely used for modern vehicles. The sealed grease of CV joints must provide low friction and wear protection for the lifetime use of the vehicle. Grease performance affects the vibration and noise level in the vehicle. Vehicles that have traveled long distances may suffer mechanical and thermal overloads, thus causing the grease to degrade due to changes in its physical and chemical properties. In this article, the grease degradation phenomenon in CV joints is investigated by collecting grease samples from both tripod joints and Birfield joints in actual vehicles that traveled various ranges of distance. In order to analyze the property changes of grease, grease penetration and oxidation induced time are measured using a penetration meter and infrared (IR) spectrometer, respectively. Where oxygen induced time (OIT) is the point that the oxidation occurs in grease. The performance variations of grease are investigated by measuring the friction and wear using linear-oscillation (SRV, Schwingung (oscillation) Reibung (friction) Verschleiss (wear)) test machine as well as the four-ball wear tester. Degradation of properties as well as performance in CV joint grease due to physical and/or chemical changes is identified.     

Enhancing chemi-mechanical transduction in microcantilever chemical sensing by surface modification

The use of chemically selective thin-film coatings has been shown to enhance both the chemical selectivity and sensitivity of microcantilever (MC) chemical sensors. As an analyte absorbs into the coating, the coating can swell or contract causing an in-plane stress at the associated MC surface. However, much of the stress upon absorption of an analyte may be lost through slippage of the chemical coatings on the MC surface, or through relaxation of the coating in a manner that minimizes stress to the cantilever. Structural modification of MC chemical sensors can improve the stress transduction between the chemical coating and the MC. Surfaces of silicon MC were modified with focused ion beam milling. Sub-micron channels were milled across the width of the MC. Responses of the nanostructured, coated MCs to 2,3-dihydroxynaphthalene and a series of volatile organic compounds (VOCs) were compared to smooth, coated MCs. The analytical figures of merit for the nanostructured, coated MCs in the sensing of VOCs were found to be better than the unstructured MCs. A comparison is made with a previously reported method of creating disordered nanostructured MC surfaces.     

DZ系列纺锭轴承振动(速度)测试方法

对纺锭轴承振动(速度)测试方面进行了初步研究,介绍了纺锭轴承振动(速度)测试的原理及方法,并对测试结果进行了分析与探讨.     

Tip-tilt mirror suspension: beam steering for advanced laser interferometer gravitational wave observatory sensing and control signals

We describe the design of a small optic suspension system, referred to as the tip-tilt mirror suspension, used to isolate selected small optics for the interferometer sensing and control beams in the advanced LIGO gravitational wave detectors. The suspended optics are isolated in all 6 degrees of freedom, with eigenmode frequencies between 1.3 Hz and 10 Hz. The suspended optic has voice-coil actuators which provide an angular range of ±4 mrad in the pitch and yaw degrees of freedom.     

Velocity vector (3D) measurement for spherical objects using an electro-optical device

The present paper describes a procedure to measure the velocity vector (3D) of a spherical object using an electro-optical device configured as a single large detection area optical barrier. The proposed procedure allows a measurement accuracy up to 0.1% in some cases and presents several advantages in relation to other measurement procedures like image processing, doppler-radar and some other electro-optical devices. The procedure is independent of the relative position of the measurement device in relation to the object trajectory. The fact of using a single optical barrier reduces the space required in the movement direction and increase the cases where the device can be used. A prototype has been built and tested.     

粒子图像测速（PIV）技术在烟丝流量检测中的研究

粒子图像测速技术（PIV）是一种全新的非接触式的,瞬时的,全场流速测量方法,广泛应用于流体力学中。本研究将PIV技术引入烟丝运动研究是一个尝试,旨在为烟丝流量的检测提供一个新的测量手段。通过分析烟丝在风送管道内的运动,利用PIV技术并结合PTV技术,采用图像处理得到烟丝的运动速度。粒子图像测速技术具有一定的优势,可以克服传统测量手段的不足。     

Velocity measurements in developing narrow open-channel flows with high free-stream turbulence: Acoustic Doppler Velocimetry (ADV) vs Laser Doppler Anemometry (LDA)

A developing narrow open-channel flow has been investigated using Acoustic Doppler Velocimetry (ADV) and Laser Doppler Anemometry (LDA). The objectives were to first characterize the flow environment with the LDA system alone, then quantify the intrusion effect of the ADV sensor immersion, and finally compare ADV-LDA measurements. The main features of the flow have been described. The turbulence levels measured in the outer flow region are high and almost isotropic due to the specificities of the flow (3D, narrow, developing). This contributes to a flattening of the mean streamwise velocity profile in this region. The intrusion effect of the ADV sensor is found to be dependent on Froude number ($Fr=U_0/\sqrt{gH}$ with $U_0$ the discharge velocity, $H$ the flow depth, and $g$ the gravity acceleration). Vertical flow below the sensor is amplified while the streamwise component of the flow is enhanced for “low” Fr ($\le 0.6$) and reduced for “high” Fr ($\ge 1.1$). On the other hand, turbulence quantities are not affected by the sensor presence. Compared to the LDA, the ADV is shown to underestimate the mean flow and turbulence intensities, while not affecting Reynolds shear stress measurements. The underestimation of the turbulence intensities can be attributed to the lower sampling rate and larger sampling volume of the ADV, but the underestimations of the mean velocities are more likely linked to a constant bias that the ADV seems to have or to some type of ADV-intrinsic noise. Some implications for practical application are discussed.     

Measurement and analysis of flow behaviour in complex geometries using the Ultrasonic Velocity Profiling (UVP) technique

In this project a non-Newtonian CMC model fluid was tested in two different complex geometries using Ultrasonic Velocity Profiling (UVP). Velocity profiles were measured at three different positions at the center (contraction) of a specially manufactured 50% open diaphragm valve. The complex geometry coordinates and velocity magnitudes were analysed and compared to the bulk flow rate measured using an electromagnetic flow meter. The difference between the calculated and measured flow rates varied from 15% to 25%. A complete flow map in the axial direction from developed to contracting flow was also measured by scanning the transducer along a hyperbolic contraction using a high precision robotic arm set-up. Experimental results obtained using UVP showed good agreement (10%) with theoretical predictions. Results showed that it was possible, for the first time, to measure quantitative velocity data for non-Newtonian flow in a complex geometry, such as a diaphragm valve. It was found that the most important problem in order to increase measurement accuracy is the estimation of wall interface positions, which is due to the ultrasonic transducer’s near field. This problem can be eliminated by the introduction of a next generation transducer, which is currently under development.     

Chemical modification of poly(tetrafluoroethylene) micropowder — basis for special lubricant additives

This contribution presents results of the chemical coupling reaction between the poly(tetrafluoroethylene) (PTFE) micropowder and oils. For the preparation of such dispersions, the reaction between the perfluoroalkyl(peroxy) radicals, which are generated by irradiation of PTFE in presence of oxygen, and the olefinic unsaturated groups of the oils was used. The modified and charged PTFE micropowder particles prevent the agglomeration by repulsion and therefore also the sedimentation. Processes of structural formation in the dispersions were studied by rheological characterisation and observed into dependence of the PTFE concentration and the chosen kind of PTFE. The tribological characterisation should explore the influence of the chemical coupling reaction between PTFE and oil in the dispersions. In addition, the tribological effect of the dispersions as an additive in a synthetic lubricant was investigated. The results obtained were discussed from rheological and tribological point of view taking into account the effect of the chemical coupling in dependence of the oils used and the chosen PTFE type. Copyright © 2012 John Wiley & Sons, Ltd.     

A modification of microglia impregnation (author's transl)]

A modification of the Weil and Davenport (1933) silver carbonate method for microglia impregnation is described. Formalin-dextran-CaCl2 solution was used as a fixation solution. The technique is simple, reproducible and improved. The staining method includes the demonstration of as well resting as progressive microglia.     

Improvement of impact properties for Nb/MoSi2 laminate composites by the interfacial modification (II)

The thermodynamical estimation of the interfacial reaction and the impact properties of Nb/MoSi₂ laminate composites containing SiC, NbSi₂ or ZrO₂ particles are investigated. Laminate composites, which comprise alternating layers of MoSi₂ with the particle and Nb foil, were fabricated by the hot press process. It is clearly found out that the interfacial reaction of Nb/MoSi₂ can be controlled by the addition of ZrO₂ particle to the MoSi₂ phase. The addition of ZrO₂ particle increases both the impact value and the sintered density of Nb/MoSi₂. The suppression of the interfacial reaction is caused by the formation of ZrSiO₄ in MoSi₂−ZrO₂ matrix mixture.     

MELLT3 protects against cerebral ischemia-reperfusion (I/R) injury through up-regulation of m6A modification

Ischemic cerebrovascular disease is a leading cause of death globally and is often exacerbated by cerebral ischemic/reperfusion injury (CIRI). The exact mechanisms underlying I/R injury are unclear. In this study, we aimed to determine the role of m⁶A-modified methylase complex methyltransferase-like 3 (METTL3) in cerebral ischemia-reperfusion (I/R) injury. We found that m6A and METTL3 levels increased in OGD/RX-induced mouse astrocytes-cerebellar (MA-C) and the brain of middle cerebral artery occlusion (MCAO) model mice. METTL3 siRNA treatment reduced OGD-RX-induced MAC cell viability and proliferation, which increased with METTL3 over-expression. Flow cytometry analysis showed that silencing METTL3 significantly enhanced OGD/RX-induced MAC apoptosis, which was significantly reduced with METTL3 up-regulation. In an MCAO model, METTL3 overexpression significantly reduced cerebral infarction area and decreased brain cell apoptosis, indicating that METTL3 OE treatment could ameliorate brain edema and injury. Thus, METTL3 could be used as a target to treat I/R injury.     

Vibration modeling and modification of cutting platform in a harvest combine by means of operational modal analysis (OMA)

Vibration in combine cutting platform causes increase in grain loss, reduction of vehicle lifetime and driver’s comfort, and also affects the machine working precision. In order to determine vibration behavior of a mechanical structure, the model which relates acting forces on the structure with the resulting responses of it plays a significant role. For a great deal of mechanical structures, only response data are measurable while the actual loading conditions are unknown. Therefore, the system identification process will need to build on the output-only data. The use of such processes allows the identification of modal models of structures which are excited by unknown ambient vibration. In this contribution, controlled vibration experiments were conducted on cutting platform of a combine in order to recognize and reduce its vibration problem. A finite element model is constructed representing the vibration behavior of the cutting platform. Also, the frequency domain decomposition (FDD) technique is used to estimate the modal parameters of vibrating structures in operational conditions. Then, the finite element model is successfully updated by comparing the estimated results of the operational modal analysis. It is found that there is a resonance condition around 50 Hz. Then, the mass change strategy is used to estimate the scaling-factor and frequency response function (FRF) matrix. Finally, the resonance condition and subsequently vibration of cutting platform is reduced by the structural modification technique. As a result of this modification, natural frequency of fifth mode shape (50 Hz) of the combine cutting platform is shifted to 48 Hz.     

Influence of amount and modification of resin on fade and recovery behavior of non-asbestos organic (NAO) friction materials

Phenol formaldehyde resin is one of the most important ingredients in friction materials that binds the other multiple ingredients firmly. The type and amount of resin in the friction material is very critical for structural integrity of the composite. Present work focuses on the influence of resin percentage and modification of straight phenolic resin by cashew nut shell liquid (CNSL) on fade and recovery behavior of friction composites developed in the laboratory. These composites were based on variation in amount of CNSL modified resin (10, 12.5, and 15 wt.%) keeping other ingredients same. Fade and recovery studies on these composites were done according to ECE R-90 regulation. The friction coefficient (μ) (all types viz. performance, fade, and recovery), extent of fade and recovery, increase in counterface temperature, wear and mechanical properties were significantly influenced by the variation in amount of resin. It was observed that with increase in amount of resin all types of μ decreased and extent of fade increased. Most of the mechanical properties and wear, however, improved with increase in percentage of resin. Since μ is more important for friction materials rather than wear, it was concluded that 10 wt.% CNSL resin was an optimum amount for best friction performance in severe operating conditions. The performance properties of these composites when compared with similar composites based on unmodified resin in earlier work, it was revealed that the modification of phenolic resin by CNSL deteriorated the fade and recovery performance.     

Reduction of erosion rate by particle size distribution (PSD) modification of hematite as weighting agent for oil based drilling fluids

Natural hematite (Fe₂O₃) and barite (Ba₂SO₄) are usually employed as weighting agents for oil based drilling fluids in several venezuelan fields. Hematite has shown some physico-chemical advantages with respect to barite: a greater specific gravity and solubility in acid media and lower attrition rate. However, the most challenging issue related to hematite field applications has been to reduce its high erosive potential. Effects of particle size distribution (PSD) have been evaluated with four different samples of hematite (48, 38, 30 and 18 μm based on the statistical parameter D_(v,0.9)) respect to commercial barite. These samples were used to prepare fluids with a density of 1977 kg/m³. An erosion test loop was used to expose different samples of AISI 1020 flat steel to the erosive action of jet fluid. Wear of metallic samples was measured by weight lost and wear mechanisms were identified by laser profilometry, SEM and EDS. The investigation showed that the erosion rate (E) produced by hematite decreases potentially with size grain reduction (D_(v,0.9)) and depends on the morphology and angularity of the particle in comparison with barite. Laboratory results were validated on field tests with drilling fluids formulated with hematite of different PSD.     

Complex surface modification of carbide tool by Nb + Hf + Ti alloying followed by hardfacing (Ti + Al)N

The surface of the WC/Co carbide tool was modified by an electron beam with the magnetron sputtering of Nb + Hf + Ti alloy to obtain a gradient interlayer before hardfacing with (Ti + Al)N. The results of investigations of the composite using a scanning electron microscope equipped with a device for X-ray energy dispersion spectroscopy are given. The results of the comparative mechanical tests show reduced wear rate.