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1.
The aim of this work is to propose an original solution to the acoustic impedance mismatch between a PZT transducer and a water load. The characteristic acoustic impedance of the PZT is around 33 MRayl. Theoretically, a quarter-wave layer with characteristic acoustic impedance equal to 7 MRayl is necessary to match the transducer to water. In practice, it is difficult to find a material with this particular impedance. Two or more quarter-wave layers may also be used. The following proposed solution consists in using two matching layers where one of them is the glue. Moreover, their thicknesses are not equal to a quarter of their individual wavelength. Once the glue is taken as the first matching layer, the specific material of the second layer can easily be found. In this work, the second layer, which is also the front layer, is made of glass. The thickness of each matching layer is then calculated as a function of the characteristic acoustic impedance of the two layers. The influence of the thickness of these layers is discussed. The proposed matching configuration is analyzed and theoretical results have been carefully and successfully compared with measurements. 相似文献
2.
We present a simple glue method for fabricating membrane electrode assemblies (MEA) for direct methanol fuel cells (DMFC). Rather than the conventional “dry” hot-pressing method that relies solely on hot-pressing at a high pressure and temperature to form a MEA, the “wet” method developed in this work introduces a binding agent, consisting of Nafion® solution, between a polymer electrolyte membrane (PEM) and an anode/cathode. The introduced binding agent can provide a better adhesion and stronger binding force between a membrane and an electrode, thereby facilitating a better interfacial contact between the electrode and the Nafion® membrane, which has been proved by scanning electron microscopy (SEM) analyses to the cross-sectional morphology of the MEA after long-term operation. The cell performance characterization showed the MEA fabricated by the glue method was more stable in cell performance than that fabricated by the conventional hot-pressing method. Cyclic voltammetry (CV) results also demonstrated the MEA fabricated by the glue method exhibited a higher electrochemical surface area (ESA) as a result of the improved interfacial contact between the Nafion® membrane and the electrodes. Finally, the DMFC with the MEA fabricated by the glue method was characterized by the electrochemical impedance spectroscopy (EIS). 相似文献
3.
结合生产实践,通过典型事例介绍了乐泰胶在氧化铝行业设备检修中的应用,说明了乐泰胶在氧化铝行业设备检修中所起作用的多样化,指出了乐泰胶在此行业中的广泛应用前景。 相似文献
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N. Tuning S. BachmannY. Bagaturia M. BlomL. Ceelie D. van EijkCh. Färber T. HaasF. Jansen T. KetelM. Merk I. MousA. Nawrot A. PellegrinoO. van Petten T. du PreeN. Serra E. SimioniT. Sluijk B. StoraciM. Szczekowski U. UwerE. Visser D. Wiedner 《Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment》2011,656(1):45-50
The LHCb Outer Tracker straw tubes have shown to suffer from gain loss after irradiation in the laboratory at moderate intensities. Under irradiation an insulating layer is formed on the anode wire. The ageing is caused by contamination of the counting gas due to outgassing of the plastifier di-isopropyl-naphthalene in araldite AY103-1 used at construction. This paper presents irradiation results with and without the plastifier, together with the mass spectra of the glue samples. In addition, the effects of wire heating and large currents are presented. 相似文献
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Self‐tapping screws as reinforcement – new results. Self‐tapping continuously threaded screws can be used as elements for reinforcement or joints in timber construction because of their high axial strength and excellent bonding properties. The layout of the reinforcing or joining screws can be derived from strut‐and‐tiemodels which are common in concrete design and follow the internal flow of forces. Several series of tests in 2007 already showed the high potential of this construction method on various joint details and reinforced timber elements. Based on this success in 2008 further tests were taken out on joints and timber beams with altered and more sophisticated screw configurations. Hereby the load‐bearing capacity of timber beams reinforced with steel lamellas and rigid frame corners connected with self‐tapping screws was extraordinary and demonstrated once more the high potential of this design method. 相似文献
8.
挠性微加速度计是惯导系统的核心组件,主要采用胶粘接装配,因此研究胶层热传递和蠕变效应共同作用对揭示温度滞环对加速度计性能稳定性影响具有重要意义.本文针对因手工涂胶导致的胶层厚度、溢出和倾斜等误差因素进行仿真,结果表明,第1周期的滞环值明显高于第二及以后周期的,应采用分步补偿.胶层溢出对滞环值的影响较大,溢出量为0.03 mm时,第1周期最大可达260μg.胶层厚度在设计许可范围内,随厚度增加呈减小趋势.胶层倾斜量达到胶层厚度一半时,第1周期最大滞环值达120μg.上述研究结果可为加速度计装配工艺优化提供数据支撑. 相似文献
9.
电位滴定法测定107胶游离甲醛含量 总被引:1,自引:0,他引:1
提出了用电位滴定法测定107建筑胶中游离甲醛含量的方法。该法快速简便,条件易控制;与差减式碘量法进行比较,结果令人满意。 相似文献
10.
This paper presents a technique used to evaluate the shear and peel stiffness of an adhesive system that bonds fiber reinforced plastic (FRP) and steel sections. The technique combines experimental results and analytical solutions and involves the simulation of the shear and peel behavior of the adhesive through two continuous spring systems. The experiments involve shear lap testing of FRP sheets bonded to hollow steel sections. A closed form analytical solution was derived for both the in-plane and out-of-plane behavior of the tested FRP sheets. The measured in-plane load-displacement relations were incorporated into the closed form solution to evaluate the spring constant simulating the shear behavior of the adhesive. The out-of-plane behavior of the FRP sheets was identified experimentally through outer face strain and out-of-plane displacement measurements. A curve fitting approach in which the closed form analytical solution was fitted to the measured out-of-plane displacement profile was then used to evaluate the spring constant simulating the peel behavior of the adhesive. The study focused on a methacrylate adhesive system since preliminary investigation has shown it is suitable for applications involving bonding plastic and metal surfaces. The spring constants evaluated in this study can be used to perform detailed modeling of a bonded FRP/steel connection under a general state of loading. 相似文献