Polynomial Representation of NURBS and Its Application to High Frequency Scattering Prediction

This article presents a method that uses physical optics (PO) techniques to compute the monostatic radar cross section (RCS) of electrically large conducting objects modeled by non-uniform rational B-spline (NURBS) surfaces. At the beginning, a new algorithm to convert recursive B-spline basis function into piecewise polynomials in power form is presented. Then, algorithm computes the polynomial representation of B-spline basis functions and NURBS surface geometric parameters are obtained. The PO integral over NURBS surfaces of an electrically large conducting object is used to predict the object's RCS. The NURBS surface is divided into small piecewise polynomial parametric patches by isoparametric curves, and the PO integral expression over the parametric domain of each polynomial parametric patch is reduced to an analytical expression which permits an accurate and effective computation of the PO integral by using a modified Ludwig's algorithm. The RCS of the object can be obtained by adding up the PO integral contribution of each polynomial parametric patch. The effectiveness of this method is verified by numerical examples.     

Modeling and Experimental Investigation of Laser Drilling with Jet Electrochemical Machining

As two kinds of defects, recast layers and spatters, commonly accompanied by laser-drilled holes always prevent the laser drilling technique from extending its applications in aerospace and aircraft industries, therefore, a novel hybrid process incorporating laser drilling with jet electrochemical machining (JECM-LD) has been developed to solve these problems as well as improve the overall quality of laser-drilled holes. It is executed by directing an electrolyte jet coaxially aligned with a laser beam onto the workpiece surface. During the process, the electrolyte jet produces electrochemical reaction with the surface material, effective cooling of it and carries away the process scraps. A two-dimensional mathematical model is proposed to describe the shape of the holes machined by JECM-LD. The model is verified through comparison between the results from simulation and those from experiments conducted on the test pieces made of 321 stainless steel 0.5 mm thick processed by the pulsed Nd:YAG laser at second harmonic wavelength. An examination of the experimental results under an optical microscope discovers that, by contrast with the laser drilling in air, the JECM-LD has effectively removed the recast layers and spatters, but its efficiency dropped by about 30%.     

喷射成形高速钢内部组织研究

研究了喷射成形高速钢SFT15热处理前后的微观组织。结果表明,喷射成形制备的SFT15高速钢晶粒细小,无宏观偏析,组织致密,沉积坯平均体密度为8.208g/cm3,达到理论密度的99.8%。SFT15在热处理前的沉积坯硬度为56.5HRC,经热等静压和热处理后进一步提高到67HRC,冲击韧度达到11.8 J/cm2。采用SEM和TEM研究了SFT15的内部组织发现,热处理后SFT15高速钢组织主要为回火马氏体和碳化物。内部绝大部分为小于20μm的等轴晶,晶界和晶内分布许多M6C型的碳化物。     

超燃冲压发动机唇口气动热计算研究与分析

采用数值模拟方法,对超燃冲压发动机进气道唇口的气动热进行了计算和分析.依据唇口与前体激波所处相对位置的不同,分三种情形进行了计算研究.结果表明,三种情形下,进气道前缘驻点热流均大于头部.通过算例验证,证明该方法和结论的正确性.研究表明,激波干扰以及前体激波压缩后超声速来流使唇口热流增大,热防护和结构设计时应当予以充分考虑.      

电刺激大壁虎中脑对运动行为影响的研究

采用金属微电极对麻醉状态下的大壁虎（Gekko gecko）中脑脑区逐点施以电刺激,观测大壁虎中脑与运动的相互关系。结果发现,电刺激中脑不同脑区可分别诱导出张嘴、鸣叫及一些肢体动作,如：四肢动,脊柱对侧弯曲,脊柱同侧弯曲和脊柱S形弯曲等。这些结果为人工制导大壁虎运动打下一定的基础。     

基于观测器／滤波器结构的高精度转台自适应摩擦补偿

针对具有非线性动态摩擦的高精度转台系统,为了处理两种不同类型的摩擦参数不确定性,提出了两种自适应摩擦补偿方案。所提的两种方案均利用一种非线性观测器／滤波器结构来补偿转台系统中相应摩擦参数的不确定性。此外,第二种方案在双非线性滤波器中引入了可调增益,并通过调节滤波器增益来提高系统的位置跟踪性能。两种情况下,均采用基于Lyapunov的方法证明了整个闭环系统的全局渐近稳定性。仿真结果表明了所提方案的有效性。     

钎焊气氛对金刚石磨粒与钎料界面微观结构的影响

在真空和Ar气两种不同的氛围中,采用NiCr合金钎料,进行了炉中钎焊金刚石磨粒的试验研究。运用扫描电镜（SEM）、X-射线能谱仪（EDS）和X-射线衍射结构研究了不同钎焊气氛对NiCr合金钎料成分和金刚石磨粒与钎料界面微观结构的影响。结果表明：（1）在不同的钎焊气氛下,由于氧分压的不同导致了NiCr合金钎料的成分也不相同。在Ar气保护气氛下的炉中钎焊金刚石试样表面有B2O3生成。（2）在不同钎焊气氛中,在金刚石磨粒与合金钎料界面生成物都主要为铬的碳化物。但生成物表面形貌不同,在真空炉中焊后的金刚石磨粒表面生成物成放射状生长,而在Ar气保护炉中钎焊后的金刚石磨粒表面生成物如杂草一样生长且生成物组织较真空炉中细小。     

Interfacial Issues of All Solid State Lithium Batteries

All solid state lithium battery is a promising next-generation battery system with improved cycle life,energy density,especially safety.However,its development is greatly hampered by a large impedance between the solid state electrolyte/electrode interface.How to build an ideal electrolyte/electrode interface to improve the interfacial stability and reduce the interfacial resistance is a huge challenge for improving battery performance.This paper reviews interfacial problems and introduces the formation mechanism of different interface layers between electrodes and electrolytes.In addition,the strategies for improving interfacial contact and reducing interfacial resistance are described in detail.Finally,the research directions for engineering interfaces in all solid state lithium batteries are proposed.     

8m×6m风洞铰链力矩试验技术

介绍了8m×6m风洞近年来研究完善的全尺寸部件铰链力矩试验技术、大尺度模型舵面铰链力矩试验技术及全尺寸鱼雷舵面铰链力矩试验技术的优势和特点,给出了部分典型试验结果。8m×6m风洞进行的铰链力矩特性试验研究技术的不断发展和完善,为飞机及鱼雷操纵系统的改进设计提供了可靠的基础,为各类飞行器、航海器舵面铰链力矩测量与研究做出了积极贡献。     

广汉机场强对流天气潜势预报方法研究

利用2008-2010年6-8月共9个月的地面观测资料、高空观测资料和探空资料,分析发生强对流天气的天气形势,进行相关性分析并使用消空法筛选有利于强对流天气发生的物理量因子和指数.分析和检验结果表明:在系统性天气过程影响下K指数、沙氏指数(SI)、700hPa假相当位温(θse(700))和地面24小时变温(△T24)对广汉机场12小时强对流天气潜势预报有较好的指导作用.