汽车变速器模糊综合评价系统的研究

运用模糊综合评价方法对汽车变速器的燃油经济性、动力性、寿命和噪声目标进行了总体评价,结合CA141 汽车变速器对该评价系统进行验证,其结果能客观地反映汽车变速器的性能等级     

An ultrasonic array-based system for real-time inspection of carbon-epoxy composite plates

A real-time ultrasonic imager operating at a frequency of 3.5 MHz to test composites in immersion has been developed. It is based on linear array transducers and provides either B-scan or transmission images of composite plates of a few centimeters thickness. The electronic scanning has a pitch of 1.25 mm and an amplitude of 80 mm, and the electronic focusing as well as the acoustic lens on the arrays are set to work at a depth of 40 mm in water. Tests made on composite and plastic plates of 5 to 17 mm thickness show that the system allows the detection of different types of defects and that the interpretation of the ultrasonic signals can be performed on line.     

Fatigue load monitoring in steel bridges with Rayleigh Waves

Fatigue load monitoring is a useful tool for safety assessment of highway bridges. Monitoring has been conventionally done using strain gages. Installation of these gages is labor-intensive and requires safety precautions. Noncontact electromagnetic-acoustic transducers (EMATs) offer an attractive alternative. EMATs were used to transmit and receive Rayleigh Waves (RW). Changes in time of flight of RW due to the acoustoelastic effect can in principle be used to monitor stresses resulting from vehicular traffic. We have performed proof-of-concept experiments to demonstrate the feasibility of this approach. Specimens were subjected to bending to simulate the load environment in bridges. RW EMATs were used to measure the relatively low stresses (less than 14 MPa) typically experienced by bridge girders. The signal-to-noise ratio achievable with our system should allow adequate stress resolution for fatigue load monitoring. Factors which could impede technology transfer were considered. The primary obstacle appears to be variability in time of flight (TOF) due to magnetostriction. If the magnetic state is changed (e.g., by scanning of the EMATs) the TOF can change, even at constant stress. We have characterized this effect. If a proper installation procedure is followed, fatigue load monitoring with RW EMATs is feasible.Contribution of the National Institute of Standards and Technology.     

压电晶体-固体-液体结构中IDT的体声波激励

对压电晶体－固体（层）－液体结构中叉指换能器的体声波激励效应进行了深入探讨，通过引入压电晶体－固体层界面的界面有效介电常数，研究了叉指换能器的体声波激励效应与晶体切向、电边界条件及固体层归一化厚度之间的关系。数值分析表明，电边界条件对叉指换能器体声波激励效应的影响可忽略；体声波激励效应与压电晶体切向和固体层归一化厚度密切相关；通过选择恰当的晶体切向、固体层归一化厚度和慢度，叉指换能器仅向液体中激励体声波，且可确定出最强体声波激励时的结构参数。文中所得结果，为有关液体声传感器结构的优化设计奠定了基础。     

Flow imaging for multi-component flow measurement

For pseudo-homogeneous flows, measurements of density and mean velocity can give the component mass flow rate of a two-component mixture. However, for accurate measurement of non-homogeneous flow rate, the density and velocity distribution across the cross-section of the pipe must be known. The most practical way of obtaining this information is by using the flow imaging technique.

A recently developed capacitance system gives 60 frames per second images of oil/water flow in a 78 mm pipe. The target spatial resolution is one part in 20 by distance (one in 400 by area). The electrical properties of each imaged boundary are functionally related to the imaged value, so the component ratio of a two-component mixture within a boundary can be measured, although individual particles cannot be imaged. Design data shows how the basic system can be part of a complete system for component mass flow measurement.     

Modelling of attenuation of Lamb waves using Rayleigh damping: Numerical and experimental studies

In this study, the Lamb mode attenuation constants were derived in terms of the attenuation coefficient, group velocity and central frequency of excitation of the Lamb mode, using the Rayleigh damping model. Attenuation of Lamb waves, both fundamental symmetric and anti-symmetric modes, propagating through viscoelastic media (cross-ply glass/epoxy laminate) was modelled using the Finite Element Method. Numerically simulated attenuation of Lamb waves using Lamb mode attenuation constants was found to be in good agreement with the assumed attenuation. Experiments were performed on a quasi-isotropic laminate, employing air-coupled ultrasonic transducers, to measure the attenuation coefficient. Lamb mode attenuation constants, computed using the attenuation coefficient, were used to model the attenuation of the Lamb mode in quasi-isotropic laminates. Numerically simulated amplitude variation was found to be in good agreement with that computed from experiments.     

面波法检测地基波速中振源与测点的布置方法

在地面竖向简谐集中力作用下,利用轴对称有限元-无限元耦合模型计算了地表动力响应的相频特性,并由此系统地考察了由两点相位差确定R波速度的影响因素及其规律性。对匀质弹性地基的研究结果表明,为保证由不作P波和S波滤波处理的实测地表信号相位差求出的R波速度具有足够高的精度,点-源距和测点间距必须满足一定的要求;对高饱和度地基及当测点间距较小时,目前对振源和测点布置的常见做法会使检测结果出现较大的误差。结论对地基波速检测的面波法现场工作方法具有重要的指导意义。     

爆电换能用反铁电材料

采用爆炸冲击波作用于贮存有电极化能量的铁电体，迫使其转变成反铁电体，可释放出巨大电能量，用于一次性的高压、大功率脉冲电源。本工作研究了锆钛酸铅反铁电材料在电场、压力、温度作用下的反铁电一铁电相变性质，介绍了在爆炸冲击波作用下铁电向反铁电转变过程中电量的输出特性。     

The prediction and measurement of axial forces, bending moments and accelerations in an engine connecting rod

An engine connecting rod was fitted with two accelerometers, an axial force bridge and a bending moment bridge. These transducers enabled the acceleration components (along the connecting rod axis and perpendicular to it), the axial force and the bending moment, to be measured at the transducer locations.
A theoretical method of analysis was carried out and a computer programme was developed, for use on a PET computer, to execute the repetitive calculations of the above mentioned quantities.
The connecting rod was fitted into a Ford two-litre OHC automotive engine. A few components were manufactured to complete the test rig.
Three engine tests were conducted using combinations of engine load and cylinder gas pressure. The outputs from the transducers were recorded on photographic film from a galvanometer recorder. The traces were then analysed to reveal the variation of the dynamic properties with crankshaft angle.
The experimental and theoretical results of the three tests were compared. The experimental accelerations and axial force were in close agreement with the predicted results. However, the experimental and the predicted bending moment distribution, did not agree at all well.     

"Explorations in Ecological Psychology": Erratum.

Reports an error in the original article by Roger G. Barker (American Psychologist, 1965, 20, 1-14). The captions for Figures 1 and 2 on pages 2 and 3, respectively, are correct and follow text, but the figures have been interchanged. (The following abstract of this article originally appeared in record 1965-08912-001.) The "great diversity of coupling between psychologists and psychological phenomena can be divided into 2 types which produce data of crucially different significance for the science of psychology." (1) Psychologists as Transducers--T Data: The psychologist transforms data and in effect is a translating machine. (2) Psychologists as Operators--O Data: The psychologist "achieves control which allows him to focus upon segments and processes of particular concern to him, via data that refer to events which he, in part, contrives." Psychologists "as operators and as transducers are not analogous, and . . . the data they produce have fundamentally different uses within science. A central problem of our science is the relation between ecological events (the distal stimuli) at the origin of E-O-E [environment-organism-environment] arcs and the succeeding events along these arcs." There "are a number of reasons for avoiding the role of transducer in psychological research . . . . The skills and personality attributes required of a successful transducer are different from those of a successful operator . . . . The techniques of the transducer are in many respects more difficult than those of the operator." (PsycINFO Database Record (c) 2010 APA, all rights reserved)