双匹配层宽带超声换能器

超声换能器由支撑体、高介电常数和高声阻抗材料的压电层、第一阻抗匹配层和第二阻抗匹配层组成。第一匹配层为硅。     

超声换能器的“电感-变压器”阻抗匹配模型研究

在分析超声换能器阻抗特性和电路匹配的基础上,对传统纯电感电容匹配电路模型进行电路仿真和阻抗分析,证明该模型在谐振频率附近有大范围的电抗变化,存在电路不稳定和电阻调节精度低的问题;提出"电感-变压器"阻抗匹配模型,通过电感和变压器分别调节换能器电阻和电抗,实现电路的精确匹配,以提高超声换能器阻抗匹配的精度和稳定性,并给出了理想的匹配条件和匹配参数。利用匝数可调的变压器和电感制作了超声换能器的匹配电路,对20.8 k Hz的变幅杆换能器进行了阻抗匹配的实验测量,结果证明这种"电感-变压器"阻抗匹配模型在谐振频率附近具有较小的电抗变化范围、较低的电阻变化率和较高的电抗调节精度,在超声换能器的自动阻抗匹配中具有良好的应用前景。     

用于超声物位测量的换能器研究

本文介绍了两种用于超声物位测量的系列换能器──纵向振动夹心换能器和纵振动与圆盘弯曲复合振动的压电换能器。纵向振动夹心换能器的尺寸为４０和８０，外壳采用了防腐蚀的ＰＶＣ材料。从压电方程出发，计算了换能器的各部分振动元件的尺寸，然后通过实测，结果表明与计算值相吻合，当换能器距天棚２．５ｍ时。不经过放大器可接收到第一次回波为３００ｍＶｐ－ｐ，配以发射、接收电路盲区为０．５ｍ。另一类是采用纵向振动与圆盘弯曲振动的复合换能器，它具有尖锐的指向性、高的发射效率和接收灵敏度。但是受激圆盘作弯曲振动时，在其表面…     

一种新颖高温超声测厚实验系统研究(Ⅰ)--声系统及使用效果

介绍一种新颖高温超声测厚实验系统的理论研究和实测结果。阐述了它的原理、特点、５ＭＨｚ超声换能器系统及多种介质测厚使用效果。本测厚系统可在温度３２８℃介面上接触在线运行检测。当ＰＺＴ晶片夹角设置为２°、声波延迟块长２０ｍｍ时，则在０．２～１３ｍｍ测厚范围内有效，精度可达０．１ｍｍ。该机体积小、功耗低，且可适用于多种介质的测厚工作。     

B3 幅度加权曲面换能器的理论分析

Ｂ２超声换能器的宽带阻抗匹配器研究朱昌平，陈兆华，冯若，黄金兰，魏立升，李良学（荆州师专物理系湖北荆州·４３４１００）在功率超声领域，换能器的阻抗匹配占有相当重要地位，但有关在较宽频带内都能适用的匹配方案尚少见报道。为满足实验室工作需要，我们研制了两...     

B4 矩形超声换能器方阵的研究

Ｂ４矩形超声换能器方阵的研究孙福成，宋健，江以萍，朱峰（上海交通大学上海·２０００３０）在我们研制的超声加热治癌系统中为了增大加热面积和增大加热深度，我们选用９片方形压电晶片组成一个方阵（３×３），每片大小为３．０ｃｍ×３．０ｃｍ，这样可以方便地对不...     

传输线变压器的机理及宽带阻抗匹配的设计

传输线变压器具有频带宽、易于制作的特点，在通信领域得到了广泛的应用。但在超声换能器与超声信号源之间采用传输线变压器实现阻抗匹配的报道较少。文章对传输线变压器实现宽带阻抗匹配的机理进行了详细的分析，通过一个简单的等效电路阐明了传输线变压器如何巧妙地利用传输线间的分布电容，使其由影响高频能量传输的不利因素而转换为电磁能量转换必不可少的条件，从而达到宽频带传输的目的。以500kHz-2MHz范围内的超声换能器的阻抗匹配变压器的设计为例，具体给出了确定传输线变压器特性阻抗、线长、磁心、导线型号和匝数的方法。     

厚度振动换能器脉冲响应的研究

本文对厚度振动图片换能器的导纳、传递函数和脉冲响应进行了研究。利用换能器等效电路、基尔霍夫定律和傅里叶变换给出了导纳、传递函数和脉冲响应的表达式。通过在ＨＰ—１０００微机上进行大量的计算，得到了ＺＮＬ—２压电陶瓷圆片换能器在不同匹配层和背衬层材料的导纳，传递函数和脉冲响应，得出了匹配材料声阻抗分别为４， ６（ １０６ｋｇ／ｍ２· ｓ）和背衬材料声阻抗分别为 ７．５， １５．５（１０６ｋｇ／ｍ２·时左右比较理想，然后用ＨＰ阻抗分析仪、Ｘ—Ｙ３０３３记录仪和脉冲响应测试仪分别测出几个换能器的导纳和脉冲响应，从实验结果可知：理论和实验结果基本符合。所得结果可供工厂生产时参考。     

B3 用电流角分析超声换能器的匹配问题

所谓电流角是指流动换能器的电流超前换能器两端电压的角度，引入电流角的概念，可以简化超声换能器的匹配计算，同时，便于直观地表达各相关参量之间的关系。     

声波测井压电换能器多频点阻抗匹配技术研究

针对声波测井压电换能器的多频点阻抗匹配技术展开研究,首先采用多模态等效电路精确描述了换能器的导纳特性;然后通过分析多模态阻抗匹配理论,设计电感-电容复合阻抗匹配网络,并结合换能器等效电路进行参数优化和电路仿真。实验表明,相比于换能器没有阻抗匹配的测试结果,该阻抗匹配技术可大幅提高换能器在谐振频率附近多个频率处的有功功率,频带内的有功功率平均提高了30倍,从而改善换能器的激励带宽和激励效率,提高测井仪器的适应性、探测深度和分辨率。     

Effect of Permeable Crystalline Material on Steel Reinforcement Corrosion of Concrete

Permeable crystalline materialcan permeate into pores and cracks of concrete and catalyze the reaction between Ca(OH) 2and unhydrated cement to generate a great quantity needle non-soluble crystals, which can stop up the pores and cracks of concrete, and increase the impermeability of concrete. This paper reported the results of a study conducted to evaluate steel reinforcement corrosion of concrete specimens uncoated and coated with permeable crystalline material as well as mixed with the permeable crystalline material. The properties evaluated for corrosion test were water impermeability, water absorption, compressive strength and potential. The results of water impermeability, water absorption, compressive strength clearly showed that the permeable crystalline material could prohibit water, any soluble salts and moisture from penetrating the concrete to cause corrosion, leaking, and other problems, and it did increase the compressive strength, which was favorable for protection of corrosion of reinforcing steel. Moreover, it was concluded from the potential-time curve that the steel reinforcement of uncoated specimen was in the state of activation whereas that of other specimens coated and mixed with the permeable crystalline material was in the state of inactivation. Above all, it was indicated that the permeable crystalline materialis very effective to protect the steel reinforcement of concrete from corrosion.     

The Research and Application About "Dry Peeling Off" Technology for Airplane Surface Paint Layer

In this paper, the principle of spurting take off lacquer were introduced; and with orthogonal method the unsaturate polyester was prepared ;it was easy to peel airplane paint layer off with this material and equipment.     

Quality Study of Honeycomb Core Shaping Without Wax Stabilization

Sandwich panels utilizing honeycomb cores result in lightweight, high-strength units that are very rigid. Indeed, they give honeycomb panels the best strength-to-weight ratio of any construction type available. Conventionally, the wax is poured into the cell of the core to strengthen the structure and prevent the core from being crushed during milling. Much time and labor is required to wax, mill, and clean the cores. In this study, the process of pouring wax into the core was skipped. In other words, the cutter directly milled the core. Experiments showed that the compressive strength of the core produced without wax stabilization was only 3% lower than that of cores produced using the traditional method. In addition, the drum peel strengths of cores produced without wax stabilization were 38.4% higher than cores produced using the traditional method, in which residual wax seriously polluted the adhesive. It was also found that eliminating the wax process can reduce costs.     

In-process thermal treatment of polylactic acid in fused deposition modelling

Polylactic acid (PLA) is one of the most widely used open source fused filament fabrication materials due to its ease of extrusion, biodegradability, and mechanical strength. The mechanical strength of PLA largely depends on the proper growth of its semi-crystalline structure, which can be severely impaired by a low rate of crystallization, particularly in open source printers. This can be further aggravated by the non-uniform thermal distribution of heat that causes improper curing among the extruded beads of the printing material. As a result, PLA printed on open source printers does not achieve the best mechanical properties. This research, for the first time, proposes an additive-free solution implemented through a detailed set of experimentation to improve the curing rate through in-process temperature variations to cure the joints among the beads. Scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) spectroscopy is used to confirm the improvements in the bead joints. This work is conducted in two phases of experiments. In the first phase, a full factorial ANOVA is used to investigate various process parameters and the important variables are used in the second phase to print test specimens in four different sets.     

Investigation of the Corrosion Behaviors of HVOF-Sprayed Carbide Cernet Coatings in Molten Al-Zn-Si Alloy Bath

In continuous hot-dip galvanization process the corrosion and chemical stability of the sink roll in the galvanizing bath are important problem which effects on the quality and productivity. In order to protect the sink roll the carbide cermet and/or ceramic coatings were deposited on the surface of the sink roll. The WC-, Cr3 C2-cermet coatings were deposited by high velocity oxygen fuel (HVOF) spray, respectively. The coating samples were immersed in molten Zn-alloy containing 50 wt % aluminum at 833 K for 24 hr and 144 hr, respectively. The inter-diffusion and inter-reaction of Zn, Al and elements in coating and corrosion behaviors of these coatings were investigated by XRD, SEM and EPMA etc. The corrosion mechanisms of the carbide cermet coatings and ceramic coatings in molten High Al-Zn-alloy were approached.     

Fundamental study of adhesion of ice to cooling solid surface (Discussion on influence of copper oxide layer on ice adhesion force)

In many situations, ice often adheres to a cooling solid surface, frequently causing serious accidents. It is critical to clarify the mechanism of ice adhesion to the cooling surface in order to prevent ice adhesion. In a past study, the shearing stresses of two kinds of test plates with a copper surface having the higher thermal conductivity were measured. The shearing stress corresponds to ice adhesion force. Both shearing stresses were significantly different; however, the cause remains unclear.Therefore, the present study focuses on an oxide layer as the main factor causing the difference of both shearing stresses; the influence of the oxide layer formed on shearing stress was discussed. And in the removal and reformation processes of the oxide layer, the time variation of the shearing stress was clarified. Moreover, the relationship between the state of the copper surface and the shearing stress was also clarified by surface analysis.     

重塑标准推行格局 推动LED照明的普及（英文）

正When you are enjoying the green,energy-saving and healthy lighting of IKEA LED luminaire,you may not realize that most of IKEA’s LED bulbs are produced by the LED luminaire smart manufacturing system of Hangzhou Zhongwei Photoelectricity CO.,LTD(ZVISION).No longer enclosed in the laboratory,the product standards are brought into the factory workshop and even to the entire production process.Thus,the standards are promoted and applied in a favorable way by enterprises,benefitting consumers with high quality products.     

Chinese Experts Contribute to ISO＇s New Toy Standards

正The international standard,ISO 8124-6,Safety of toys–Part 6:Certain phthalate esters in toys and children’s products,was officially issued by ISO worldwide on August 15.It was the first time for Chinese experts to lead the ISO standard development in toys industry.The standard was drafted by a group of Chinese experts from SAC/TC for toys and relevant Chinese departments and finally completed by a dedicated international group of experts.ISO 8124-6 makes a substantive breakthrough in the aspects of the scope of toys,limitation of plasticizer types,control of test cost,accuracy of test,operation convenience,etc.,offering the operational guidance for toy manufactures and testing laboratories.     

中国质量(北京)大会(英文)

正Themed on"quality,innovation,development",the first China Quality Conference(Beijing)was held in the Great Hall of the People on September 15.Chinese Premier Li Keqiang delivered an important speech at the conference.State Councilor Yang Jing and Wang Yong attended the conference with over 600 domestic and international representatives from foreign,regional and international quality organizations     

National Working Meeting on Land and Resources Standardization

正The National Working Meeting on Land and Resources Standardization was held in Beijing on July 15,2014.Wang Min,the Deputy-Minister of the Ministry of Land and Resources,and Yin Minghan,the Chief-Engineer of SAC addressed the meeting.Representatives from relevant competent departments and technical committees were present.The meeting aims to summarize work,discuss existing problems and make clear working thoughts,promoting standardization work of land and resources to a new level.Wang Min pointed out that the standardization work of land and resources should be centered on the basic principles of"protecting land and resources dutifully,intensively and economically utilizing land and resources,and making all-out efforts to safeguard the public’s rights and interests",highlighted the