接收机整机最小噪声系数的实现

前级LNA的性能指标的好坏对接收机整体性能起主要作用。较流行的设计方法是用ADS等仿真软件在Smith圆图上作出LNA的等增益圆和等噪声圆，以确定LNA是否同时满足所要求的增益和噪声系数指标。这种方法虽然满足了设计要求，但往往不能获得整机噪声的最佳点。本文在符合设计指标后进一步对噪声和增益的关系进行分析，建立适用于常用接收机的简单模型，在此基础上获得基于整机噪声的最佳点。这种设计方法可以广泛应用于各种微波接收系统中,降低整机哭声系数.     

（E）-2-壬烯酸合成方法的改进

(E)-2-壬烯酸是有机合成的一种重要中间体,我们利用Knoevenagel反应机理,改进了(E)-2-壬烯酸的合成工艺,在不使用脱水剂条件下,使用少量吡啶作催化剂,获得了83%的反应收率。     

建筑工程投标报价优选模型

通过建立区间二次规划数学模型、灰色模型、多目标规划等模型，建立材料价格和用量的选择模型，提供投标单位一种便捷的调整工程造价和控制造价的手段。     

Experimental Study of Ice Jam Thickening under Dynamic Flow Conditions

River ice jams are a common occurrence on northern rivers, and their formation can present a severe flood risk to nearby communities. As more and more river regulation projects are developed to provide an alternative to fossil fuels for electrical power-generating capacity, our need to understand the mechanisms associated with ice jam formation under variable flow conditions becomes more vital. This is because, at present, hydropeaking operations are often severely curtailed during the ice-affected seasons due to concerns that sudden flow fluctuations might instigate ice jams and associated flooding. Here, an experimental investigation explores the effects of rapid increases in discharge on ice jam formation and evolution. It is found that the thickness of ice jams formed under highly dynamic flow conditions tend to be slightly thinner than those formed during steady carrier flows for comparable discharges. Also, despite the highly dynamic nature of these consolidation events, the resulting ice thicknesses appear reasonably well approximated by steady flow theory.     

汽车钢淬透性数学模型建立

在测定 2 0CrMnTi、4 0MnBH、2 0MnVBH钢淬透性及试样的化学成分基础之上 ,利用计算机采用逐步回归分析方法进行了回归运算 ,得到淬透性与化学成分的关系———回归方程 ,根据回归方程求出了不同窄淬透带规格所对应控制的化学成分范围     

土工带加筋地基处理施工技术

结合中铁十二局2号小区7号楼工程加筋地基处理的施工，介绍了加筋地基处理的材料要求，设计特点，施工工艺及施工要点，得出该施工技术简单易操作，质量易保证，造价低廉，效果良好。     

河流工程中的图形绘制与处理

在河流工程领域,不管是实体模型还是数学模型,对多样化的数据和丰富多彩的图形的需要越来越强烈,旧的表现形式已经被层出不穷的新的、信息量大而且地位高的2D、3D图形所取代,因此在工程中合理地选择绘图方式和开发软件就变得十分重要。以实际操作经验为基础,从基本操作类到二次开发类再到高端图形图像开发类,详细地讨论了在河流工程中各种图形的绘制和处理方法选择,具有一定参照价值。     

裂隙岩体边坡稳定性的渗流与应力耦合分析

用裂隙岩体渗流与应力耦合分析的四自由度全耦合法对岩质边坡进行耦合分析,通过强度折减有限元法求解岩体边坡的稳定安全系数。四自由度全耦合法建立了同时以渗流水压和位移为未知量的耦合方程组,使得渗流场与应力场的求解能够一次性完成,与两场交叉迭代分析方法相比达到了彻底的完全耦合。通过强度折减,整个系统达到不稳定状态,有限元计算将不收敛,此时的折减系数就是安全系数。算例表明由此求得的边坡稳定安全系数和滑动面都与传统方法十分接近。     

Mobile robot path planning based on hierarchical hexagonal decomposition and artificial potential fields

In this article, a new algorithm based on an artificial potential field and hierarchical cell decomposition technique is developed to solve the find-path problem for a mobile robot. The complete map of the workspace including obstacle locations is assumed to be known a priori. The basic cell structure used for decomposition is a hexagon. The artificial potential field is based on an attractive force from the goal position and repelling forces from the obstacles. Computer simulations of the algorithm for various obstacle scenarios are also presented. © 1994 John Wiley & Sons, Inc.     

Chemical mechanical polishing of polymer films

Strategies to reduce capacitance effects associated with shrinking integrated circuit (IC) design rules include incorporating low resistivity metals and insulators with low dielectric values, or “low-κ” materials. Using such materials in current IC fabrication schemes necessitates the development of reliable chemical mechanical polishing (CMP) processes and process consumables tailored for them. Here we present results of CMP experiments performed on FLARE™ 2.0 using a specialized zirconium oxide (ZrO₂) polishing slurry. FLARE™ 2.0 is a poly(arylene) ether from AlliedSignal, Inc. with a nominal dielectric constant of 2.8. In addition, we provide insight into possible removal mechanisms during the CMP of organic polymers by examining the performance of numerous abrasive slurries. Although specific to a limited number of polymers, the authors suggest that the information presented in this paper is relevant to the CMP performance of many polymer dielectric materials.