Multipoint laser vibrometer for modal analysis

Experimental modal analysis of multifrequency vibration requires a measurement system with appropriate temporal and spatial resolution to recover the mode shapes. To fully understand the vibration it is necessary to be able to measure not only the vibration amplitude but also the vibration phase. We describe a multipoint laser vibrometer that is capable of high spatial and temporal resolution with simultaneous measurement of 256 points along a line at up to 80 kHz. The multipoint vibrometer is demonstrated by recovering modal vibration data from a simple test object subject to transient excitation. A practical application is presented in which the vibrometer is used to measure vibration on a squealing rotating disk brake.     

Multipoint diffraction strain sensor with variable sensitivity

In our earlier work, a multipoint diffraction strain sensor using a microlens array was developed for measurement of whole-field strains. The method is extended to a system with variable sensitivity and measurement range. In the present system, two collimated laser beams, 3 mm in diameter, symmetrically strike the grating attached to the specimen surface at prescribed angles. The diffracted wavefronts, magnified by a microscope objective, are sampled by a lenslet array with each microlens acting as an individual strain sensor. In-plane strain components over the full field can be measured by what is to our knowledge a new sensor with variable sensitivity by changing the distance from the microscope objective to the microlens array. Both a theoretical explanation and experimental verification are provided.     

Amplitude Estimation by a Multipoint Interpolated DFT Approach

This paper focuses on the amplitude estimation by a multipoint interpolated discrete Fourier transform (DFT) method. Accurate results are obtained using the weighted multipoint interpolated DFT (WMIpDFT) method with maximum sidelobe decay windows. In addition, using the WMIpDFT method with maximum sidelobe decay windows, it is mathematically proven that the systematic errors affecting the amplitude estimation decrease as the number of interpolation points and/or the window order increases. Computer simulations confirm the accuracy of the derived expressions. Moreover, the influence of white Gaussian noise on the amplitude estimations has been analyzed by means of computer simulations.     

Multipoint approximation development: thermal structural optimization case study

Function approximation is one of the most important fields of research in design optimization. Accurate function approximation reduces the repetitive cost of finite element analysis. Many local approximations, such as one‐ and two‐point local approximations, are already available. These are, however, only valid in a small domain and require stringent move‐limits on design variables. The objective of this research is to achieve an efficient and accurate multipoint approximation to constraints by integrating the most accurate segment of all local approximations previously constructed. The proposed multipoint approximation is constructed by combining weighting functions with local function approximations. With function and gradient information at a series of points, local approximations are established at those points. Once established, all local approximations are blended into a multipoint approximation by use of a weighting function. Function and gradient values of this multipoint approximation correspond directly with exact counterparts at the points where the local approximations were generated. Finally, the multipoint approximation is applied to a plate and wing box thermal‐structural optimization. Published in 2000 by John Wiley & Sons, Ltd.     

Multipoint support technology for mirror milling of aircraft skins

Mirror milling is a new efficient and green technology of aircraft skin processing. Currently, the support head of mirror milling system is mostly a metallic sphere and the support area is smaller than the milling area, which results in the deformation error of workpiece. To solve this problem, a new multipoint support device is proposed. The purpose of this research is to optimize the support location of multipoint support in mirror milling of aircraft skin parts. The simulation and experimental studies indicate that the deformation of workpiece is reduced by increasing the support points. To obtain the good thickness consistency of workpiece, the distribution of the support points should make the rigidity distribution of the workpiece consistent with the change of milling force, not as close as the milling trajectory. The workpiece deformation error can be reduced only by changing the support locations.     

Multipoint temperature-independent fiber-Bragg-grating strain-sensing system employing an optical-power-detection scheme

A temperature-independent fiber-Bragg-grating strains-sensing system, based on a novel optical-power-detection scheme, is developed and analyzed. In this system a pair of fiber Bragg gratings with reflection spectra either partially or substantially overlapping is placed side by side to form a temperature-independent strain-sensor unit. Conventional wavelength-interrogation techniques are not used here, and instead an optical-power-detection scheme is proposed to directly calibrate the measurand, i.e., the strain. Unlike the conventional approach in a multiplexed sensing system, the presented power-detection-based interrogation method does not need the fiber-Bragg-grating sensors to be spectrally separate. The only requirement is that the spectra of the two fiber Bragg gratings of each sensor unit in a multiplexed system be identical or slightly separate (slightly overlapping spectra would also work in the sensing scheme) and the source's optical power be sufficient for sensitive measurement. Based on a three-sensor-unit system, we demonstrate simple strain measurements of high linearity (+/- 0.4%), good sensitivity [2 microstrains (microS)], high thermal stability (+/- 0.8%), and zero cross talk. The effects of light source spectral flatness and fiber bending loss on measurement accuracy are also discussed.     

Multipoint Thomson scattering system for the extrap Z-pinch experiment

A Thomson scattering system for simultaneous measurements of the electron temperature and density at three different positions and at two different times during a single plasma shot has been developed for a Z-pinch experiment. The plasma in the pinch is characterized by densities in the range from 5 × 10²⁰ to 10²² m⁻³, temperatures up to 30 eV and a pinch radius of the order of 1 cm. The spatial resolution of three points with 3 mm between points is obtained by imaging the plasma onto a matrix of quartz optical fibres at the output slit of the spectrometer. Thus only one spectrometer is used together with 15 PM-tubes to detect the scattered radiation as well as the background radiation. Due to the relatively dense plasma prevailing in this Z-pinch discharge the number of scattered photons is large and the photon to electron conversion noise is small. Therefore the background radiation is the most important factor limiting the accuracy of the measurements.     

多点源光热法表征液体的热学性质

1引言 液体物质热物理性质的准确测量一直是物理学领域中的研究热点之一.液体材料在受热时会产生较强的对流和辐射等物理特性,因此采用传统的接触式测量方法不易精确测定液体材料的热学参量.由于光学方法具有快速、非接触式等特性,近二十年来已先后有多种光学方法应用到液体物质的热学参量的表征[1,2],其中较为突出的是利用激光在液体中激发的热栅技术.本文在此基础上,并根据调制多点阵源激光在凝聚态物质中激发调制多点阵热源的光热实验,提出了利用多点源光热法表征液体材料热学性质的方法,建立了相应的理论模型并进行了数值分析.     

Multipoint cure monitoring of CFRP laminates using a flexible matrix sensor

Since a carbon fiber reinforced plastic (CFRP) structure is complicated in the adoption of integral molding, local molding faults such as under curing and dry spots are liable to occur. To solve this problem, the distribution of the degree of curing for the entire composite structure must be measured. In the present study, we propose a patch-type flexible matrix sensor based on permittivity measurements. Multiple electrodes and wirings are readily fabricated simultaneously using a photolithographic process. Moreover, the sensor has only m + n wirings for m × n sensors, and is thereby suitable for multipoint cure monitoring. We also constructed a method for estimating the degree of curing considering the effect of frequency dependence of the permittivity of resin and viscosity variation due to temperature change. Experiments of multipoint cure monitoring are carried out using a CFRP plate and an actual aircraft structure. As a result, we confirmed the effectiveness of this method by comparing with results using a conventional differential scanning calorimeter.     

多点耦合包装系统动态逆子结构理论试验验证

将产品-包装-运载体系统作为整体考虑,建立了二级多点动态逆子结构理论与模型。推导了用系统水平FRF来预测部件水平FRF的表达式。用弹簧-质量块组成的实际模型进行了实验验证。实验结果验证了用系统水平FRF预测部件水平FRF的可行性与准确性。     

The Strategic Resources

“The reason I pay close attention to and am very concerned about standards is that fiom my point of view standards are very important resources or even strategic resources.The meteorological work is highly professional and requires standards in every aspect.With disjoint standards,businesses,services and scientific researches cannot be properly done.”     

Sectoral Innovation Patterns And The Rise Of New Competitors: The Case Of Civil Aerospace In Asia

This paper examines the internationalization of the civil aerospace industry, and particularly the rise of the industry in the Asia-Pacific region. The argument developed is that aerospace has been treated uncritically as yet another “high technology” sector, and susceptible to the same public policy effects is other high technology industries like IT. The paper argues, by contrast, that the aerospace sector has particular economic and political characteristics, which suggest that European and American firms enjoy considerable, and possibly persistent advantages over new competitors.     

Strategic Technology Management

ABSTRACT

The explosion in the literature in the area of technology management indicates a need for some integration of concepts and issues. This article defines and discusses a Strategic Technology Management System (STMS), which meets this need. The STMS delineates a systems life cycle approach to technology management, which includes eight phases: creation, monitoring, assessment, transfer, acceptance, utilization, maturity, and decline. Each phase includes critical issues that must be managed in order for a firm to successfully control its product/service and process technology projects and programs. These critical issues are defined, and a number of industry examples are given to substantiate the STMS life cycle concept. Finally, several key performance factors for STMSs are discussed.     

基于广播中继的自组网组播路由协议改进(ODMRP-MPR)

提出一种对ODMRP协议的改进,即ODMRP-MPR路由协议。该协议继承了ODMRP协议对拓扑频繁变化的良好适应性,并采用广播中继机制MPR(Multipoint Relay),优化了组播转发网格并减少了协议开销,提高了协议对网络规模的可扩展性和吞吐量,并且提供拥塞控制,有效地解决单向链路问题,增强了协议的健壮性。通过对ODMRP-MPR和ODMRP协议的模拟仿真实验比较,验证了ODMRP-MPR协议的改进效果。     

Restructuring for Strategic Outcomes

Restructuring in higher education is ultimately based on the need to continuously improve the learning experience for students and to prepare them for a constantly changing job market. Engineering programs are expected to prepare their graduates for success and leadership in business, industry, consulting, government, and education. Such preparation, of necessity, must display agility in responding to changing needs during times of uncertain and dwindling resources. For this reason, the College of Engineering and Science of Louisiana Tech University has been restructured to achieve significant improvement in accomplishing its objectives. This article describes the rationale and process of restructuring the college, aligning the budget according to the new structure, and developing a strategic plan in the context of an integrated structure and with the goal of achieving strategic outcomes. Early measurable successes in undergraduate curriculum reform, graduate curriculum, and research activity are reported.     

标准化科学攻坚的战略高地

本文在解释了什么是标准化战略高地及其极端重要性之后,着重论述了传统标准化面临的一系列挑战,提出了向现代标准化转型的问题。作者认为虽然模块化和综合标准化能发挥一定作用,但不能满足现代社会发展对标准化的要求,必须加快建设现代标准化。研究现代标准化理论,探索现代标准化方法,创造标准化的新形式是摆在当代标准化工作者面前的历史任务。