滚动轴承故障诊断中精确转频的实用计算新方法

从滚动轴承故障特征频率的计算公式出发,分析了转轴的旋转频率在滚动轴承故障诊断中的重要性;阐述了由变频器频率估算的转频远远不能满足精度要求;提出基于时标脉冲信号的转频的计算方法,给出它的时域计算公式和频域计算公式,并推导出它们各自的适用条件;进一步建立隶属度函数和贴近度函数,以模糊数学为基本原理使用择近原则对转频进行精确调节,弥补了数据点数记录过程中可能存在的误差,消除了频率分辨率的影响,为以后的故障诊断工作做好充分的准备。     

可调间隙的半主动吸振器及其实现

为了扩展吸振器的工作带宽,提出一种实时调节弹性元件的半主动吸振器,并给出了吸振器的控制策略。分析了吸振器工作频段与系统参数间关系,介绍了吸振器的实现方案及实验。实验基于微机和TMS320C30芯片,根据测量的激励形成控制策略,用电磁离合器控制弹性元件的连接和断开,用步进电机调节弹性元件的间隙,使吸振器的特性跟踪激动频率和幅值的变化。实验表明,这种半主动吸振器的减振效果良好。     

On-line probe for fast electrochemistry/electrospray mass spectrometry. Investigation of polycyclic aromatic hydrocarbons

A newly invented probe accessory for fast electrochemistry/electrospray mass spectrometry (EC/ESMS) is presented and evaluated. The device features a low-volume, three-electrode electrochemical cell which has been designed with a minimum distance between the working electrode and the "Taylor cone" inherent to the electrospray process. This configuration limits the time between electrochemical generation of ions and mass spectrometric analysis to an absolute minimum. A fused-silica layer insulates the microcylinder working electrode from the sample solution until immediately prior to the electrospray region, postponing electrode processes until the last moment. The same fused-silica layer insulates the working electrode from the surrounding auxiliary electrode, a stainless steel capillary that also serves as the electrospray capillary. The performance and capabilities of the novel electrochemistry/electrospray mass spectrometry system have been evaluated using polycyclic aromatic hydrocarbons (PAHs) as test analytes. In the positive ion EC/ESMS mode, oxidized forms (one-electron removal) of PAHs are produced in high yield. The ability to analyze reaction products appearing subsequent to the initial oxidation is also demonstrated.     

A Glucose Biosensor Based on Immobilization of Glucose Oxidase in Electropolymerized o-Aminophenol Film on Platinized Glassy Carbon Electrode

A high-performance amperometric glucose biosensor has been developed, based on immobilization of glucose oxidase in an electrochemically synthesized, nonconducting poly(o-aminophenol) film on a platinized glassy carbon electrode. The large microscopic surface area and porous morphology of the platinized glassy carbon electrode result in high enzyme loading, and the enzyme entrapped in the electrodeposited platinum microparticle matrix is stabler than that on a platinum disk electrode surface. The response current of the sensor is 20-fold higher than that of the sensor prepared with a platinum disk electrode of the same geometric area. The experiments showed that the high sensitivity of the sensor is due not only to the large microscopic area but also to the high efficiency of transformation of H(2)O(2) generated by enzymatic reaction to current signal on the platinized glassy carbon electrode. The response time of the sensor is <4 s, and its lifetime is >10 months.     

Bidimensional spectroelectrochemistry

A new methodology is presented to offer the possibility of simultaneously obtaining two different spectroscopic signals in a single spectroelectrochemical experiment. Taking the plane of the electrode surface as a spatial reference, normal-beam and parallel-beam UV-vis absorbance signals are jointly analyzed, revealing important experimental differences between the two kinds of signals. Two different chemical systems are selected to show the possibilities of the bidimensional spectroelectrochemistry: a simple diffusive process and an adsorptive electrode reaction. Comparative results show clearly that the two kinds of spectroscopic signals, both normal and parallel to the electrode surface, have to be used together in the study of any electrode reaction scheme.     

Miniaturized electrochemical flow cells

Several novel types of miniaturized electrochemical flow cells are described. The flow cells are fabricated in fluorinated ethylene propylene using a novel technique where channels with inner diameters down to 13 microm are integrated with electrodes. The channel is formed by shrinking and simultaneous melting of a heat shrink/melt tubing around a channel template (a tungsten wire) and electrodes followed by removal of the channel template. The technique allows incorporation of different electrode materials of different sizes. The electrode configuration consists of one or two working electrodes inside the channel and a counter electrode located in the channel outlet reservoir. Electrode configurations with different channel and working electrode sizes, different electrode materials including carbon fibers, glassy carbon rods, poly(tetrafluoroethylene)/carbon composite material, and platinum wires, and different arrangements have been assembled. Hydrodynamic voltammograms in dual-electrode (generator-collector) experiments indicate good potential control for cells with 25-microm channels, while there is some iR drop in cells with 13-microm channels. Cells prepared with a cylindrical working electrode tangent and perpendicular to a flow channel show a flow rate dependence consistent with thin-layer cell behavior. Electrode areas can be made in the range of 10(-10)-10(-8) m2.     

Simultaneous electrochemical detection of nitric oxide and carbon monoxide generated from mouse kidney organ tissues

A planar-type amperometric dual microsensor for simultaneous detection of nitric oxide and carbon monoxide is presented. The sensor consists of a dual platinum microdisk-based working electrode (WE) and a Ag/AgCl counter/reference electrode covered with an expanded poly(tetrafluoroethylene) (Tetra-tex) gas-permeable membrane. The dual WE possesses two different platinized platinum disks (WE1 and WE2, 250 and 25 microm in diameter, respectively). The larger WE1 is further modified with electrochemical deposition of tin. Use of two sensing disks different in their size as well as in their surface modification produces apparently different sensitivity ratios of NO to CO at WE1 and at WE2 (approximately 2 and approximately 10, respectively) that are induced by favorable CO oxidation on the surface of tin versus platinum. Anodic currents independently measured at WE1 and at WE2 are successfully converted to the concentrations of NO and CO in the co-presence of these gases using the differentiated sensitivities at each electrode. The sensor is evaluated in terms of its analytical performance: respectable linear dynamic range (sub nM to microM); low detection limit (approximately 1 nM for NO and <5 nM for CO); selectivity (over nitrite up to approximately 1 mM); and sensitivity (sufficient for analyzing physiological levels of NO and CO). Using the NO/CO dual microsensor, real-time, simultaneous, direct, and quantitative measurements of NO and CO generated from living biological tissue (mouse, c57, kidney) surfaces, for the first time, are reported.     

Electrochemical characterization of parylene-embedded carbon nanotube nanoelectrode arrays

A novel parylene-embedded carbon nanotube nanoelectrode array is presented for use as an electrochemical detector working electrode material. The fabrication process is compatible with standard microfluidic and other MEMS processing without requiring chemical mechanical polishing. Electrochemical studies of the nanoelectrodes showed that they perform comparably to platinum. Electrochemical pretreatment for short periods of time was found to further improve performance as measured by cathodic and anodic peak separation of K(3)Fe(CN)(6). A lower detection limit below 0.1?μM was measured and with further fabrication improvements detection limits between 100?pM and 10?nM are possible. This makes the nanoelectrode arrays particularly suitable for trace electrochemical analysis.     

Miniaturized tris(2,2'-bipyridyl)ruthenium(II) electrochemiluminescence detection cell for capillary electrophoresis and flow injection analysis

The design and performance of a miniaturized chip-type tris(2,2'-bipyridyl)ruthenium(II) [Ru(bpy)3(2+)] electrochemiluminescence (ECL) detection cell suitable for both capillary electrophoresis (CE) and flow injection (FI) analysis are described. The cell was fabricated from two pieces of glass (20 x 15 x 1.7 mm), and the 0.5-mm-diameter platinum disk was used as working electrode held at +1.15 V (vs silver wire quasi-reference), the stainless steel guide tubing as counter electrode, and the silver wire as quasi-reference electrode. The performance traits of the cell in both CE and FI modes were evaluated using tripropylamine, proline, and oxalate and compared favorably to those reported for CE and FI detection cells. The advantages of versatility, sensitivity, and accuracy make the device attractive for the routine analysis of amine-containing species or oxalate by CE and FI with Ru(bpy)3(2+) ECL detection.     

A dynamic method of comparing frequencies

The problem of estimating the instantaneous frequency of a quasi-harmonic signal by means of the signal of a quantum standard is considered. A parametric method of determining the dynamic behavior of frequency using Tikhonov regularization in the class of functions of bounded variation and supplementary smoothing is proposed. Relationships for determining the frequency of a study signal are obtained and results of numerical simulation are presented. The method may be implemented on signal processors in real time.     

Ionic liquids as electrolytes for the development of a robust amperometric oxygen sensor

A simple Clark-type online electrochemical cell design, consisting of a platinum gauze working electrode and incorporating ionic liquids (IL) as electrolytes, has been successfully applied for the amperometric sensing of oxygen. Studying ILs comprising the bis(trifluoromethylsulfonyl)imide anion, the obtained analytical parameters were found to be strongly dependent on the choice of cation. Compared with a conventional Clark cell design based on an aqueous supporting electrolyte, the modified oxygen sensor achieves substantial improvements in performance and stability. A limit of detection for oxygen as low as 0.05 vol?%, linearity over an oxygen partial pressure between 0% and 20%, and a steady-state response time of 2 min was demonstrated, with a stable analytical response shown over the examined period of 90 days with no obvious fouling of the electrode surface. Based on the attractive physical attributes of ionic liquids (e.g., thermal stability beyond 150 °C), one can envision intriguing utility in nonstandard conditions and long-term online applications, as well as extension to the determination of other gases, such as methane and nitric oxide.     

ZrO_2氧传感器的电极制备及其响应特性研究

研究了电极浆料组成及烧结工艺等因素对电极性能的影响,利用汽车示波器获得的电势跃迁信号分析了氧传感器的响应性能,结果表明,造孔剂的加入和烧结温度对电极微观形貌影响很大。当Pt浆/造孔剂(质量比)比例最佳,选择合适的烧结温度时,电极电阻最小,且高电势跃迁大于800 m V,低电势跃迁小于100m V,响应时间小于200 ms,满足汽车氧传感器的实际使用要求。     

Calculation method of reflectance distributions for computer-generated holograms using the finite-difference time-domain method

The research on reflectance distributions in computer-generated holograms (CGHs) is particularly sparse, and the textures of materials are not expressed. Thus, we propose a method for calculating reflectance distributions in CGHs that uses the finite-difference time-domain method. In this method, reflected light from an uneven surface made on a computer is analyzed by finite-difference time-domain simulation, and the reflected light distribution is applied to the CGH as an object light. We report the relations between the surface roughness of the objects and the reflectance distributions, and show that the reflectance distributions are given to CGHs by imaging simulation.     

Large photocurrent-response observed at Pt/InP Schottky interface formed on anodic porous structure

A photoelectric-conversion device—based on an InP porous structure utilizing the large surface area inside pores and the low reflectance on the porous surface—is proposed. The InP walls inside the pores are covered with thin platinum films that form a Schottky barrier yielding an electric field that separates photo carriers generated under illumination. The coverage of the platinum film and its optical reflectance depended largely on the surface morphology of the porous structure. Removal of the irregular top layer formed at the initial stage of the pore formation effectively improved the coverage of the platinum film, which showed a very low optical reflectance (i.e., below 3.2%). According to current-voltage measurements under illumination, the platinum/porous InP showed larger photocurrents and higher responsivity than those of a reference planar sample.     

Ca10(PO4)6(OH)2-modified carbon-paste electrode for the determination of trace lead(II) by square-wave voltammetry

The analytical performance of hydroxyapatite Ca10(PO4)6(OH)2(HAp) screen-printed sensors designed for the detection of metals was evaluated. The hydroxyapatite plays an important role in modern analytical electrochemistry due to their usefulness for the preparation of sensors giving rise to improved responses from metals. The suitable HAp-modified carbon-paste electrode (HAp-CPE) for the electrochemical determination of lead is illustrated in this work using cyclic and square-wave voltammetry in the potential range between -0.3 and -0.8V. Perchlorate acid solution (1.0molL(-1)) was employed as the supporting electrolyte. The voltammetric measurements were carried out using as working electrode HAp-CPE, and a platinum electrode and an SCE electrode as auxiliary and reference electrodes, respectively. Under the optimized working conditions, calibration graph is linear for 5min of preconcentration time with the detection limit 7.68x10(-10)molL(-1). This detection limit is remarkably lower than those reported previously using other modified electrodes or amperometric detection. The results indicate that this electrode is sensitive and effective for the determination of Pb2+.     

Controlled frustration of total internal reflection by electrophoresis of pigment particles

A model based on geometrical optics has been developed to describe the photometric observations associated with a novel method to control the reflectance of a surface. In this new reflectance modulation approach, electrophoresis of pigment particles is used to absorb light reflected by total internal reflection (TIR). The pigment particles are sufficiently small that they substantially do not scatter light, but rather they modify the effective refractive index at the reflection interface. An incident light ray interacting with this modified effective index is attenuated in a spectrally selective manner. Although frustrated TIR has been understood and used in various applications for some time, in this case it is used to substantially modify the color of the reflected light, which to our knowledge has not been previously reported. A numerical model of the pigment particle distribution has been developed to describe the observations.     

Inspection of a Plasma Display Panel (PDP) Using Frequency Domain Analysis

A plasma display panel (PDP) consists of more than a thousand very thin parallel electrodes on a glass plate. It is quite probable that a PDP has defects such as midway broken electrodes. Therefore, inspecting defects in PDP electrodes is essential for minimizing the manufacturing costs and improving the product quality. In this paper, a new method for inspecting electrodes in a PDP using frequency domain analysis is presented. The transfer function of a PDP was modeled in the frequency domain, which is based on the lumped transmission line models. The effects of the electrode conditions on the frequency response were then analyzed by using the described model, and experiments were conducted with specimens to confirm the presented inspection method. The experimental results are in good agreement with the analytical results. Therefore, the presented method using frequency domain analysis was confirmed to be a good method for inspecting the electrode conditions in PDPs     

基于NIR的茶叶成分检测仪的设计与实现

本文提出了基于近红外光谱的荼叶成份检测仪的设计与实现.该检测仪采用干涉滤光片作为分光器件,其旋转样品池内嵌了漫反射标准白板,以实现快速交替检测样品及白板漫反射信号,使样品与白板的检测同步完成,简化仪器机械结构,提高了光谱稳定性和样品检测速度与精度.光电信号检测系统采用了InGaAs光电探测器,利用仪表放大器和24位A/D转换器分别完成信号调理和数据采集,以USB 2.0实现仪器与计算机的数据传输,再由计算机化学计量学软件完成吸光度计算及茶叶样品的成分分析.实验结果表明,本样机实测茶叶成份值与理化检验值的相对误差小于5%.     

Evanescent coupling in magneto-optical and phase-change disk systems based on the solid immersion lens

Results of numerical computations pertaining to evanescent wave coupling for near-field magneto-optical and phase-change disks based on the concept of the solid immersion lens are presented. We investigated the relation between the coupling efficiency and the width of the air gap in terms of the throughput of the recording process and the resolution of the readout signal. The simulations show a drastic decrease with a widening air gap of the coupling efficiency by means of evanescent waves into the recording medium. In magneto-optical readout, loss of the signal may be attributed to the reduction of magneto-optical interaction, the rise of reflectance, and the variation of the relative phase between the two components of polarization. In the phase-change readout the reduced reflectivity contrast between crystalline and amorphous marks is the cause of signal reduction.