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近年来,由于新材料及新技术的飞速发展,促使人们研制了多种新型的换能器及声基阵。新型换能器的换能机理均与能量转换材料有关,某些最有应用前途的换能器基本上取决于新材料的换能特性,因此本文将有一定数量的篇幅阐明新型换能材料的工作机理及其重要应用。  相似文献   

3.
按指向性因数部分值确定基阵指向性指数   总被引:2,自引:2,他引:0  
本文给出了一种按指向性因数的部分值经过严格数学处理求得实际基阵(real array)指向性指数的方法。特别指出复合阵的指向性指数并不是互相垂直的两个子阵的指向性指数的平均值。比较实例的理论计算和测试数据表明,这种处理方法是正确的和行之有效的。  相似文献   

4.
耿成德 《声学技术》1990,9(2):26-31
本文通过对宽带稀疏圆柱阵试验给出的测试结果与理论值的相当吻合这一点,验证了我们在设计圆柱阵中所采用的理论计算公式在工程上的实用性。文中还特别指出当选用适当的幅度加权因子对宽带稀疏圆柱阵中出现的大旁瓣(栅瓣)是能够进行有效抑制的。  相似文献   

5.
本文从互辐射的影响讨论了基阵设计中的一些问题。  相似文献   

6.
20多年来,所谓声波测井一直指的是利用双接收器下井仪检测首至波幅的压缩波声速测井。今天,声波测井技术能够利用声波形中包含的更多的声信息来获得切变波和斯通利波的速度以及幅度衰减特性。这需要使用能进行全波分析的信号处理技术。这种技术与标准的双接收器下井仪处理技术相比,通常需要对波场进行更多的空间抽样。为达到这一要求,我们设计了一种新型多接收器声波下井仪。 本文介绍一种新型声基阵下井仪,其基阵有8个接收器,接收器间隔为6英寸,基阵与两个发射器中较近者的距离为8英尺。本下井仪除增加了基阵检测能力之外,标准短源距和长源距声波测井是现有的。其中还加进了一个能够测量泥浆速度的特殊部分。井下电子装置能给出数字化波形采集,其有效分辨力为11位。 为了能从全波形中提取辅助信息,现已开发了一种慢度--时间相干(STC-slowness—time coherence)处理方法。STC处理根据相似技术可识别出通过基阵的相干到达信号。最后给出了由裸眼井和套管井得到的波形实例和经过处理的测井记录的例子,说明了本下井仪的性能。  相似文献   

7.
通过计算机辅助没计计算比较,对圆柱阵工作扇面水听器条引线采用分装几个接线盒的相间排布法,以提高水下声基阵在作战使命中的任务可靠性。同时指出用指向性系数近似公式定量估算失效的影响是不确切的。  相似文献   

8.
近年来由于大孔径非刚性基阵如拖曳线列阵、声呐浮标阵等的巨大潜在性能,人们对阵形非确知基阵或波阵面畸变情况下的声源方位估计问题日渐重视。本文提出了结构匹配的神经网络求解方法。由于该网络是高度内联的,具有高度并行处理能力、Robust性和学习能力,因而这一新的方位估计方法算法结构简单、运算量小,且有较好的跟踪能力,易于硬件实现。计算机模拟结果表明,利用神经网络方法解决阵形非确知基阵的方位估计问题是相当有效的。具有很大发展潜力,值得进一步研究探索。  相似文献   

9.
本文针对圆柱基阵换能器的多种实际排列计算了换能器幅相不一致性对基阵性能的影响。所得结论对工程设计有参考价值。  相似文献   

10.
水声换能器基阵的波束宽度及束控是声呐水下分机的重要性能要求,它又是影响声呐设备总体性能的重要指标;本文主要介绍一种仿制换能器基阵单元波束宽度及束控后波束宽度的测量。  相似文献   

11.
为了提高并联机床的加工精度,分析了并联机床的动力学特性对加工精度的影响。根据牛顿—欧拉方程,得到并联机床的动力学方程,解得连杆的驱动力;根据杆件轴向伸长量与受力之间的关系,得到连杆的长度误差;以无长度误差的连杆长度为优化目标,用优化的方法,得到动平台的位姿,并与连杆有长度误差时动平台的位姿比较,得动平台的位姿误差;根据刀具在动平台坐标系中位置,得刀具加工位置误差及对被加工零件精度的影响。结果表明:并联机床连杆的长度误差,引起刀具加工位置误差,使被加工零件产生形位误差和尺寸误差;并联机床电主轴偏心引起连杆的长度误差的扰动,产生刀具加工位置的扰动误差,影响被加工零件的表面粗糙度。  相似文献   

12.
Chen YS  Hsu YC 《Applied optics》1994,33(29):6818-6822
One way of testing color vision is with a color-blindness plate (CBP) consisting of a set of brilliant colored dots to form a pattern (a figure) and a set of other colored dots to form a background. Classification of such a type of color image into a pattern and a background with a traditional technique is difficult. Based on a self-organizing feature map and a labeling process as well as spatial distance computation, an effective approach to the segmentation of a CBP image is presented. We describe the principle of a CBP segmentation and then introduce the CBP. The proposed approach is described, and its experimental results are presented. We conclude that the method can segment the CBP image into a pattern and a background successfully.  相似文献   

13.
The effect of a thin adsorbed film on the fluctuational electromagnetic tangential force of interaction between a moving nanoparticle and a flat solid surface was theoretically studied for the first time in a nonrelativistic approximation. Particular calculations were performed for a metal film on a dielectric and for a dielectric film on a metal. In both cases, the nanoparticle is assumed to be made of a nonmagnetic metal. It is shown that, at a normal temperature, the presence of an adsorbed film may lead to an increase in the tangential friction force by one or two orders of magnitude for a certain relation between the particle distance from the surface and the film thickness. In the case of a dielectric film on a metal substrate, a decrease in the temperature is accompanied by exponential decrease in the viscous friction. For a metal film on a dielectric substrate, the tangential force exhibits a quadratic dependence on the temperature.  相似文献   

14.
Based on the data on the atomic density of a film and degree of its homogeneity during the formation of the interface between 3d transition metals (Cr, Co, Fe, or Cu) and silicon, a new concept of forming a contact between a reactive metal and a semiconductor has been justified. According to this concept, the low-temperature vapor-phase deposition of a metal onto a semiconductor is accompanied by the formation of a two-dimensional nanophase wetting layer of a metal or its mixture with silicon with a thickness of several monolayers, which significantly affects the interface formation and structure. This concept changes a perspective of forming a contact between a metal and a semiconductor substrate: it is necessary to take into account not only the formation of surface phases and clusters and/or the mixing process, but also the effect of elastic wetting of a substrate by the forming phases.  相似文献   

15.
The variational form of a mathematical model of a thermal explosion has been developed based on a variational formulation of a nonlinear problem of stationary thermal conductivity in a homogeneous solid body. The model takes the temperature dependence of the thermal conductivity of a solid body into account. The presented example of quantitative analysis of the model demonstrates a method for finding the combination of parameters for determining a thermal explosion in a plate with an exponential temperature dependence of the thermal conductivity. At the same time, the analysis allows one to identify the number of steadystate temperature distributions inside a body whose energy release intensifies with a temperature increase.  相似文献   

16.
A Product–Service System (PSS) is created by combing a tangible product and an intangible service into one integrated offering. Thus, a PSS can be achieved by a production company adding intangible services to a product using a servitisation strategy or by a service company adding a tangible product to a service by means of a productisation strategy. The focus of this paper is on the latter. Our work demonstrates a significant gap in the literature in this area. To address this, we adapt an existing PSS conceptual framework as a means to identify the driving and restraining forces considered by a service company as it explored the possibility of pursuing a PSS productisation strategy. The conceptual framework is applied in an exploratory case study with a 3PL service provider. Application of the framework reveals new driving and restraining forces not previously discussed in the literature. Furthermore, it allows a preliminary quantification of the driving and restraining forces using a force field analysis approach. Our work contributes towards the expansion of the empirical knowledge base in the area of PSS.  相似文献   

17.
It is generally acknowledged that product development involves a sequence of decision making under uncertainty, including setting target requirements for a new product, selecting product concept, and developing conceptual and detailed design of a chosen concept. To select a product concept, engineers need to assess the uncertainty of a future market share, market size, and a cost of concept (cost of the final product developed from a concept). This paper proposes a case-based reasoning (CBR) approach to model beliefs about the uncertainty of a cost of concept. The proposed CBR approach consists of storing information about various products in a knowledge-base, defining a new product concept, retrieving a cluster of products in the knowledge-base that are highly similar to the concept, and adapting the cost of the retrieved product to construct a distribution of the cost of concept. This paper illustrates the proposed approach using printers as an example.  相似文献   

18.
Original systems of singular integral equations of plane problems in the theories of elasticity, heat conduction and thermoelasticity for a solid containing a set of straight thermally isolated arbitrarily oriented cracks are developed.The problems such as those of a set of cracks in infinite and semi-infinite plates, a set of cracks in a circular disk and an infinite plane with a circular hole, a periodic and doubly periodic set of arbitrarily oriented cracks in an infinite plate, a periodic row of cracks in a half-plane are considered.Analytical solution of the equations obtained is performed by using a perturbation technique when cracks are wide apart or remote at a large distance from the boundary of a region; otherwise the equations are solved numerically.  相似文献   

19.
Duangrit Bunnag     
《设计新潮》2014,(5):55-60
用“人生赢家”来形容Duangrit Bunnag不为过,伦敦AA建筑学院毕业生,在金融危机的谷底逆市创立设计公司,设计亚洲数一数二的漂亮酒店:他开的餐厅,常客名单里有维珍航空创始人RichardBranson:他的公司集群在一个5,000多平方米的旧工厂遗址上,设计公司、餐厅、书店、咖啡馆、家具贩售中心、画廊,店都是他的,地也是他的。  相似文献   

20.
Similarity solutions for slender dry patches with thermocapillarity   总被引:2,自引:0,他引:2  
The lubrication approximation is used to investigate slender dry patches in an infinitely wide film of viscous fluid flowing steadily on an inclined plane that is either heated or cooled relative to the surrounding atmosphere. Four non-isothermal situations in which thermocapillary effects play a significant role are considered.Similarity solutions describing a thermocapillary-driven flow with a dry patch that is widening or narrowing due to either gravitational or surface-tension effects on a non-uniformly heated or cooled substrate are obtained, and examples of these solutions, when the substrate temperature gradient depends on the longitudinal coordinate according to a general power law, are presented. When gravitational effects are strong, the solution contains a free parameter, and for each value of this parameter there is a unique solution representing both a narrowing pendent dry patch and a widening sessile dry patch, whose transverse profile has a monotonically increasing shape. When surface-tension effects are strong, the solution also contains a free parameter, and for each value of this parameter there is both a unique solution representing a narrowing dry patch, whose transverse profile has a monotonically increasing shape, and a one-parameter family of solutions representing a widening dry patch, whose transverse profile has a capillary ridge near the contact line and decays in an oscillatory manner far from it.Similarity solutions are also obtained for both a gravity-driven and a constant-surface-shear-stress-driven flow with a dry patch that is widening or narrowing due to thermocapillarity on a uniformly heated or cooled substrate. The solutions in both cases contain a free parameter, and for each value of this parameter there is a unique solution representing both a narrowing dry patch on a heated substrate and a widening dry patch on a cooled substrate, whose transverse profile has a monotonically increasing shape.  相似文献   

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