激光光斑边缘提取算法应用研究

在以激光光斑为被测目标的光电测量系统中,对激光光斑边缘的提取是保证测量系统精度的首要前提.具体介绍了Sobel算子、Krisch算子、Robert算子、Canny算子及LOG算子的基本原理.对实际采集到的激光光斑图像首先进行中值滤波、二值化处理,用于滤除图像中的噪声.然后分别利用上述算子对预处理后的激光光斑进行边缘提取...     

空调用底盘组件定位螺栓点焊机理及其检验方法

通过对空调用底盘组件的定位螺栓点焊原理进行研究,了解螺栓点焊机理及其缺陷形成原因,为提高空调底盘组件的点焊质量提供了依据,并且通过抗压测试及破坏性试验评估点焊的质量。研究结果表明,合格的组件点焊后螺栓内、外侧有明显的凸点点焊痕迹,使用抗压测试及破坏性试验后螺栓与母材一起被拉掉。     

多片小尺寸Terfenol-D复合悬臂梁设计与实验

磁致伸缩式复合悬臂梁工作过程中,所粘贴的功能材料层承受张力。当弯曲挠度较大时易导致主动伸缩层断裂。针对这一问题,提出了一种新型的磁致伸缩式复合悬臂梁,采用多片小尺寸Terfenol-D薄片驱动,设计了磁路,并分别设置了提供偏置磁场的偏置线圈和提供驱动磁场的驱动线圈。对悬臂梁的动静态性能进行了测试,实验表明随着驱动频率的增高,悬臂梁磁滞环呈现增大趋势,但在一阶固有频率附近,即受共振影响区域,磁滞环反而会减小。     

3-D MOEMS mirror for laser beam pointing and focus control

A biaxial torsion scan mirror with a deformable membrane surface is described. The 700-mm-diameter optical surface can be tilted /spl plusmn/4/spl deg/ about two orthogonal axes and can be deformed to a parabola with greater than 3-mm sag at the membrane center. The surface, therefore, acts as a lens with variable focal length ranging from /spl infin/ to 10 mm. Mirror architecture and applications in three-dimensional beam pointing and scanning are discussed.     

激光粒度分析仪的关键技术及研究进展

激光粒度仪采用光散射原理测量颗粒的尺寸及其分布,可实现从亚纳米到微米测量范围的全覆盖。针对激光粒度仪的研究与应用热点,对光散射理论、测量技术、分形理论和传感器的优化设计等方面进行了深入的文献研究。阐述了静态光散射法和动态光散射法的原理及其适用条件;总结了国内外激光粒度测试技术研究的进展;分析了主要激光粒度仪产品的关键技术和性能指标。研究结果表明,激光粒度分析仪设计的关键技术是光学对中技术、激光检测器的优化设计及仪器校准技术、样品分散技术;激光粒度仪的发展趋势是测量准确度的提高、复杂信号的处理能力的增强,仪器设计的智能化和模块化水平的提高;最后指出了我国国产激光粒度检测仪发展的三大优势。     

激光粒度分析仪在铅粉分析检测中的应用

铅酸蓄电池行业测定铅粉粒径的方法有许多种,本文介绍了运用激光粒度分析仪分析检测铅粉粒径及粒径分布情况的一种准确、科学而快捷的方法。铅粉的粒径大小及其粒度分布情况对下道工序半成品质量会产生直接的影响,并对电池的性能产生最终影响。铅粉是生产铅酸蓄电池极板活性物质的基本原料。有关电池许多性能的"遗传密码"大部分隐藏在铅粉基料当中。所以制造性能稳定的铅粉是生产铅酸蓄电池非常重要的一道工序。     

Use of23Na MRS to discriminate viable from non viable tissue: experimental studies

3. Conclusion In experimental models, the use of²³Na MRI is an appropriate tool for the determination of infarct size as well as extra- and intracellular²³Na content. As stunned and hibernating myocardium show no increased²³Na content, the method could be used for discrimination of viable from non-viable myocardium.     

Analytical and experimental studies on the characteristics ofcomposite solid-state laser rods in diode-end-pumped geometry

In this paper, we report analytical and experimental studies on the characteristics of end-pumped composite laser rods with undoped end, using mainly Nd:YAG rods as an example. It is found that the peak temperature rise in a composite rod decreases to <70% of that in a noncomposite crystal. Thermal stress is dramatically reduced to <60% by employing the composite rod structure, We also demonstrate high-power operation of the diode-end-pumped composite Nd:YVO₄ rod and a maximum CW output power of 9.3 W was achieved, which is about 1.5 times higher than that in the noncomposite rod. This high-power performance of the composite rod is primarily attributed to the reduction of thermal stress inside the rod     

Combining hydro-generation and wind energy: Biddings and operation on electricity spot markets

Wind generation is growing rapidly in all the world, especially in Europe. The power produced by this kind of generation is difficult to predict and the predictions are not very accurate. In most systems these imbalances are costly. These penalties reduce the revenue for the wind generation company (WGENCOs). An option to solve this problem would be to work together with another agent. In this paper, a combined strategy for bidding and operating in a power exchange is presented. It considers the combination of a WGENCO and a hydro-generation company (HGENCO). The mathematical formulation for the optimal bids and for the optimal operation is presented, as well as results from realistic cases.     

IEEE Student Branch profile: To serve and connect

Service has been at the root of Rowan University in Glassboro, New Jersey, since the early 1900s. In 1917, when the state was suffering from a shortage of schools that provided training for teachers, Glassboro residents raised over US$7,000 to purchase 25 acres of land, which was offered to the state free of charge if the town was selected as the site of the planned twoyear teachers training school. That was quite a chunk of change then. Six years later, 236 young women arrived to christen the opening of Glassboro Normal School.     

Transmissive-detected laser speckle contrast imaging for blood flow monitoring in thick tissue:from Monte Carlo simulation to experimental demonstration

Laser speckle contrast imaging (LSCI) is a powerful tool to monitor blood flow distribution and has been widely used in studies of microcirculation, both for an...     

Free-electron lasers: reliability, performance, and beam delivery

The Vanderbilt free-electron laser (FEL) is a continuously tunable source of pulsed, mid-infrared radiation. FEL applications research has been underway for a decade. Recent experimental advances in FEL ablation of soft tissue indicate the potential for FEL-based protocols in surgery and medicine. In anticipation of these medical applications, the Vanderbilt FEL is being upgraded to meet the reliability and performance standards for a medical laser. Facilities for laser surgery have been constructed and equipped and medical delivery systems are being developed for pre-clinical and clinical research     

Er:YAG three-micron laser: performances and limits

Mathematical modeling is used to estimate the performances of the three-micron Er:YAG laser in various generation regimes. The model, based on simple rate equations, uses exclusively spectroscopic data and includes upconversion from both initial (/sup 4/I/sub 11/2/) and terminal (/sup 4/I/sub 13/2/) levels as well as the cross-relaxation from the pump level (/sup 4/S/sub 3/2/). Despite the unfavorable ratio between the lifetimes of the laser levels, the recirculation of the excitation on the metastable levels produced by the effective energy transfer processes at high erbium concentrations leads to rather high emission efficiency in the continuous wave (CW) regime. In contrast, in the Q-switch regime, the energy transfer processes are practically frozen during the giant pulse generation and the access to the stored energy is limited. In this paper, simple analytical expressions for emission efficiency in CW and Q-switch regimes are presented. Due to the growing interest in short laser pulses for medical applications, we discuss in more detail the Q-switch regime (pump conditions, co-doping, etc.).     

Space charge profile measurement techniques: recent advances and future directions

Some of the advances in space charge measurement techniques over the last 5 years are described. It is concluded that significant further improvements in spatial resolution are unlikely in the next 5 years, except in the case of the LIMM technique implemented using very short laser pulses, where spatial resolution approaching 100 nm might be achievable. It is suggested that existing space charge techniques be combined with conducting atomic force microscopy (CAFM), with the aim of correlating 3-dimensional space charge profiles and 2-dimensional conductivity maps and thus providing a more complete picture of charge transport through dielectrics, particularly in future work on nanodielectrics. Since CAFM samples are typically 5-10 nm thick, it would be necessary to operate the equipment at higher voltage (say 1000 V) so that samples not less than 10 /spl mu/m thick, e.g. polymers, could be investigated. This seems feasible.     

Nonlinear finite-element analysis of the role of dynamic changes inblood perfusion and optical properties in laser coagulation of tissue

A nonlinear finite-element program was developed to simulate the dynamic evolution of coagulation in tissue considering temperature and damage dependence of both the optical properties and blood perfusion rate. These dynamic parameters were derived based on the Arrhenius rate process formulation of thermal damage and kinetics of vasodilation. Using this nonlinear model, we found that the region of increased blood flow that formed at the periphery of the coagulation region significantly reduces the heat penetration. Moreover, increased scattering in the near-surface region prevents light penetration into the deeper region. Therefore, if the dynamic parameters are ignored, a relatively significant overestimation of the temperature rise occurs in a deeper area resulting in an overestimation in predicted depth of coagulation. Mathematical modeling techniques that simulate laser coagulation may not provide reliable information unless they take into account these dynamic parameters     

AC and DC conductivity studies in pulsed laser ablated (Ba,Sr)TiO3 thin films

Abstract

A comparison of the ac conductivity of laser ablated (Ba, Sr)TiO₃ thin films was made for films grown at different substrate temperatures. The ac conductivity was studied as a function of frequency and ambient temperature ranging from room temperature to 460°C. Conductivity results from ac and dc measurements were compared in their an respective Arrhenius plots revealing interesting coincidences. The value of the activation energies computed from the Arrhenius plot of à _ac with 1000/T ranged from 0.97 to 1.3 eV in the high temperature region to 0.36 to 0.54 eV in the low temperature region for different samples. The activation energies obtained from pure dc measurement for fields greater than 100 kV/cm across the samples were in the range of 1.06 to 1.32 eV for different samples. The similarity in results suggests a common origin in the de conduction process in the concerned temperature range and was attributed to ionic conduction resulting from oxygen vacancy motion which has been observed to be significant at high temperatures and high fields. For high temperature grown samples the value of activation energy computed from the Arrhenius plots was comparatively less than those grown at lower substrate temperatures. The difference was attributed to the microstructure and the effect of grain boundaries on the motion of oxygen vacancies leading to the conduction process.