基于"功能-原理-结构"的计算机辅助概念设计模型

计算机辅助概念设计是产品设计早期阶段中的关键阶段.然而,传统的计算机辅助概念设计主要集中于产品几何设计阶段.因此,在产品设计初期,许多产品设计信息被忽略.建立了"功能-原理-结构"概念设计模型.初始产品设计信息存储于不同的模型层中.建立了功能、原理、结构数据库.在"功能-原理-结构"模型的帮助下,实现了由功能到原理再到结构的映射.建立了概念设计应用系统来验证"功能-原理-结构"求解模型.     

通带可调的吸收式频率选择表面设计

本文提出了一种具有透射窗口可调的双吸收带的吸收式频率选择结构,该结构可以实现电磁隐身通信一体化。该结构具有一个动态可调的传输窗口,且每个不同的传输窗口两边都具有一个吸收带。此频率选择结构是由具有吸收式频率选择反射特性的结构和具有传输特性的波导结构构成,其中吸收式频率选择反射结构包括上层加载集总电阻的有损层和下层加载变容二极管的无损层以及一层金属地层,三者结合实现了吸收-反射-吸收的频率选择反射的功能,波导结构是由一个矩形波导中间内部加载一个变容二极管组成,将两个结构组合而成实现了带内透射可调带外吸波特性的功能。仿真结果表明,该吸收式频率选择结构在反射率低于-10dB的频带范围内为4.8-16.7GHz,相对带宽为110.7%,透射窗口可以实现在11.04-7.7GHz范围内调谐,调谐带宽达到34.3%,并且插入损耗都小于1dB。     

多通道D/A转换器LTC2704-16及其应用

介绍一种新型的多通道16位D/A转换器LTC2704-16的特点和引脚功能,给出了LTC2704-16的应用方法。LTC2704-16的4个D/A转换通道都是独立的,并有独立的反馈调节功能。LTC2704-16结构简单,并带有回读功能,与控制器之间采用串行通讯的方式,可广泛应用于各种数据采集系统。     

CA-98系列调制器的结构分析与修理

CA - 98系列调制器是万利达公司生产的邻频中频处理调制器 ,有些调制器带有模拟卫星接收机或电视解调器 ,该产品的性能价格比较高 ,广泛应用于我国乡镇的中小型有线电视前端。1　CA - 98系列调制器的结构CA - 98系列调制器按功能将结构划分为 5个功能单元 :中频调制、中频处理、上变频、本机振荡、高频放大。其结构框图如图 1所示。图 1　调制器的结构框图中频调制 :其功能是把图像信号和声音信号调制成中频信号。从VIDEOIN输入的图像信号经过匹配、钳位电路 ,进入中频调制集成电路IC1(TDA5 6 6 6 )。由D1～D4 组成的钳位电路还可以…     

基于ARM核的IntelTMStrongARM嵌入式系统

介绍InteltTM StrongARM的起源以及SA -1110和SA -1111之间的关系 ,重点介绍了SA -1110处理器和SA -1111套片的结构、功能和接口特性 ,给出了这两种芯片的连接关系示意图。     

结构可变更、界面可配置的通用基础信息模型

针对关系数据库设计中潜在逻辑结构变更的需求,利用模板-实例思想,在关系数据库基础上设计实现一套对基础信息统一表达处理模型,以实现新旧逻辑结构数据共存、逻辑结构立即变更立即生效的目的;与通用信息模型相结合,针对广泛自定义输入界面需求,利用表格布局方式和浏览器交互功能,设计实现可配置界面功能;通过配置即可完成逻辑结构定义、输入输出界面编辑功能;模型的原型已应用于某单位人力资源决策辅助系统中。     

SINAMICS SM150在热轧主传动中的应用

交-交变频器传动系统是电压源型矢量控制技术产品,具有高功率因数,拥有灵活强大的通讯功能,结构简单紧凑,可靠性高,适合于低转速、大容量的场合。本文结合日照钢铁1580mm热连轧工程,介绍了交-交变频传动系统的组成、控制功能,着重介绍了矢量控制、速度控制和电流控制的主要控制功能。     

GNSS射频芯片中小数分频技术研究

针对GNSS射频前端PLL频率综合器中的低杂散小数分频问题,提出了分别基于累加器结构和MASH1-1-1Δ-∑结构的两种小数分频调制器实现方案。进而选取3.996 MHz为GNSS射频前端模拟中频频率,16.368 MHz为PLL频率综合器参考频率,在GPS L1和BD-2 B1频点上对30级累加器级联结构和MASH1-1-1Δ-∑结构的输出功率谱进行分析,并在此基础上对它们的小数杂散特性进行了对比研究。结果表明,MASH1-1-1Δ-∑结构具有噪声整形功能,可将小数杂散由低频段推至高频段,从而在低频段获得更优的杂散特性。由于高频段的杂散可被PLL环路滤波器滤除,故MASH1-1-1Δ-∑结构更适合用在基于PLL的频率综合器中。     

微纳技术

功能生物模仿光学器件=Functional　biomimetic opti-cal　devices[英]/Naik　R R,Brott L L…//Proc.SPIE.-2001,4590.-115～120 2002070440具有功能结构的三维微电机械系统= Three-dimen-sional MEMS devices withfunctional architectures[英]/Vajtai R,Wei B Q… //Proc.SPIE.-2001,4590.-131～141     

并联冗余UPS系统静态转换开关的设计与实现

文中主要介绍模块化并联冗余UPS系统静态转换开关的应用设计。转换开关采用并联组合式切换开关结构,在系统并联运行时,由DsP监控系统来统一集中控制主-旁路切换功能,实现快速切换和系统保护等一系列控制功能。功能样机的实验结果验证了该智能控制方案的有效性。     

Performance study on a novel variable area robotic fin

Fish fin possesses large deformations in its motion cycle assisting fish's swimming, in which its geometric parameters such as surface area, aspect ratio change greatly, and the complex deformations and motions result in complicated hydrodynamic response. In this paper, the dynamic change of surface area is concentrated to improve the propulsion performance of underwater propeller. A novel variable area robotic fin is developed and the effect of surface area change on the hydrodynamic forces is investigated quantitatively. The robotic fin composes two parts: a base fin with hand shaped holes and a cover fin that fits the shape of the holes. The change of the surface area of the robotic fin is realized by rotating the cover fin to shield the holes in the base fin. A crank-rocker-cam composite mechanism is designed to realize the fin pitching motion and surface change motion synchronously with one driving motor. Four control modes of surface area change in a motion circle are investigated, namely, complete traditional invariable fin, traditional invariable fin with smaller surface, fin with larger surface during in-strokes and fin with larger surface during out-strokes. The thrust force and efficiency of the four control modes with various swimming speeds are detailed experimented and discussed. It is found that the variable area fin achieves a remarkable different hydrodynamic response and the corresponding control modes affect much. For the variable surface area fin, they generate average thrust force between the complete invariable fin and invariable fin with smaller surface, in which the fin with larger surface area during in-strokes follows closely the complete traditional invariable fin, while the fin with larger surface area during out-strokes performs more like the traditional invariable fin with smaller surface. It is interesting that fin with larger surface during in-strokes can generate much larger average thrust force than the fin with large surface during out-strokes. For the efficiency, the fin with larger surface during in-strokes behaves the best. And the effect of the surface area change ratio and time is closely connected with the control modes. Besides, the influences of pitching frequency and amplitude are also studied. The results demonstrate that the propulsive performance can be indeed improved by proper surface area change in a motion cycle, which will be an inspiration to the design of novel underwater robot propulsive system.     

Mutual information-based rigid and nonrigid registration of ultrasound volumes

We investigated the registration of ultrasound volumes based on the mutual information measure, a technique originally applied to multimodality registration of brain images. A prerequisite for successful registration is a smooth, quasi-convex mutual information surface with an unambiguous maximum. We discuss the necessary preprocessing to create such a surface for ultrasound volumes. Abdominal and thoracic organs imaged with ultrasound typically move relative to the exterior of the body and are deformable. Consequently, four specific instances of image registration involving progressively generalized transformations were studied: rigid-body, rigid-body + uniform scaling, rigid-body + nonuniform scaling, and affine. Registration was applied to clinically acquired volumetric images. The accuracy was comparable with the voxel dimension for all transformation modes, although it degraded as the transformation grew more complex. Likewise, the capture range became narrower with the complexity of transformation. As the use of real-time three-dimensional ultrasound becomes more prevalent, the method we present should work well for a variety of applications examining serial anatomic and physiologic changes. Developers of these clinical applications would match the deformation model of their problem to one of the four transformation models presented here.     

Rectangular patch resonator with laminated ground plane

In this paper, we analyze the effect of a laminated ground plane on the resonance frequency of rectangular patch resonators. We model each lamina of the ground plane as an anisotropic layer and use a transition matrix to relate the tangential field components in different laminae. An integral equation is formulated in the spectral domain, and Galerkin's method is applied to solve the integral equation for the resonance frequencies of the patch resonator. A perturbation approach is also derived for comparison. The effects of substrate dielectric are studied. The resonance frequency variation thus obtained will be useful in designing patch resonators attached to composite laminated surfaces     

How Do Organizations Learn Lessons From Projects—And Do They?

The need to learn from one project to the next is clearly of vital importance, but is often neglected. Furthermore, there are fundamental issues within projects that inhibit such learning, such as the temporary nature of project organizations and the fundamental complexity of projects. This paper surveys the diverse literature that can help explain these factors and help projects to learn, and describes a large survey of project managers to look at what actual practice is and how successful it is perceived, as well as some empirical work. From this, a number of general conclusions are drawn as to how to create project organizations that are learning organizations.     

不锈钢-碳钢层合板激光弯曲试验研究

层状金属复合板以优良的材料和结构性能在舰船、汽车和飞行器等装备中显示了广阔的应用前景。为研究工艺因数对层状金属复合板激光弯曲成形的影响,以不锈钢-碳钢层合板为研究对象,对这种层状金属复合板的激光弯曲角度和规律进行了系统的试验研究。结果表明,不锈钢-碳钢层合板和不锈钢板激光弯曲存在共性,弯曲角度随着激光功率增加而增大,随着扫描速度增加而减小,随着扫描次数增加而增大,随着板厚增大而减小。同时二者也存在差异;随着不锈钢-碳钢层合板宽度的增加,弯曲角度先减小后增大;在相同工艺条件下,不锈钢-碳钢层合板弯曲角度大于不锈钢板的弯曲角度,并在一次固定安装下获得85.6°这一接近直角的极限弯曲角度。     

The Use of Computational Patient Models to Assess the Risk of Developing Radiation-Induced Cancers From Radiation Therapy of the Primary Cancer

Even with highly conformal treatment delivery techniques for radiation therapy, one cannot avoid the irradiation of healthy tissues surrounding the tumor. In treatment planning, absorbed dose constraints are defined for organs at risk visible in the patient's computed tomography scan in order to minimize side effects. However, scattered or secondary absorbed dose is also deposited in areas outside of the imaged volume. Although these doses are typically quite low (well below 1% of the therapeutic dose), there is the potential risk for patients to develop a radiation-induced second malignancy later in life. For a systematic analysis of scattered or secondary doses and their carcinogenic effects, accurate patient-specific organ dosimetry is necessary. Computational patient models are needed because low absorbed doses to organs away from the primarily irradiated target area cannot be measured easily. Monte Carlo simulations can incorporate the geometry and tissue properties of computational phantoms to simulate dose deposition events weighted with radiation weighting factors. Epidemiological models can then be applied to relate organ equivalent absorbed doses to cancer risks. This paper describes the use of computational phantoms in conjunction with Monte Carlo dose calculations and epidemiological risk models. We demonstrate how these simulations are applied with the purpose of estimating second cancer risks in radiation therapy and of improving existing epidemiological risk models.      

Propagation and coupling characteristics of microstrip lines withlaminated ground plane

In this paper, we analyze the effect of laminated ground plane on the propagation and coupling characteristics of microstrip lines. Each lamina is modeled as an anisotropic layer, and transition matrix is used to relate the tangential field components in different laminae. An integral equation is formulated in the spectral domain, and the Galerkin's method is applied to solve the integral equation for the phase and the attenuation constants of several microstrip line structures. The effects of substrate dielectric are also studied. The attenuation constant variation thus obtained will be useful in circuit board design and in studying signal transmission in lamina environment     

A Competing Risk Model: A One Organ Subsystem Plus a Two Organ Subsystem

A competing risk model is developed for an individual who is subject to two risks of death or failure. One risk is the failure of a single organ which has a constant hazard rate. The other risk is the failure of a two organ system in which one of the two organs must survive in order that the system not fail. Each organ in this two organ system has a constant hazard rate, and the hazard rate increases when only one organ is working. The two risks are assumed to operate independently. Maximum likelihood estimating equations are developed along with the formulas for the large sample variance-covariance matrix of the requisite parameters.