铝合金型材的等效简化计算

目前,铝合金型材结构被广泛地应用于铝合金车体的轻量化设计中。在车体结构的初始设计阶段,需要对初始设计进行力学性能评估,但如果对车体结构建立详细的三维有限元模型,需要花费很长时间,这会显著增加设计周期。一种可行的方案是将车体结构做适当的等效和简化。据此,介绍了一种等效方法,将铝合金型材结构等效为正交各向异性材料的单层板壳,该方法在保证了计算精度的同时极大地提高了计算效率。     

介质埋藏平面蝶形天线的设计

采用了介质埋藏的形式将平面蝶形天线埋藏于介质中,并设计了渐变的平面微带巴伦给平面蝶形天线馈电,实现了不平衡到平衡的转换;还设计了三角形微带巴伦和微带传输线一起的结构形式,进行阻抗匹配。使用电磁仿真软件Ansoft HFSS对该天线进行了优化设计和仿真实验,与制作的实物天线性能进行对比。仿真和实测结果表明,该天线S11≤-10 dB仿真的相对带宽达到88.7%而实测的相对带宽为79.3%,具有超宽带特性;在工作频率处,仿真增益为 6.9 dB,实测增益为5.8 dB。该天线满足某工程项目的需要,可作为探地雷达系统的收发天线。     

一种Ka波段混合集成的单平衡混频器

本文介绍了一种由正交E面折叠魔T与鳍线混合集成的Ka波段单平衡混频器的研制概况,混频器使用国产W121封装的带状引线混频二极管。介质基片采用国产的仿RT-Duroid5880,经测试该混频器的最小单边带噪声为5.7dB(不包括前中噪声),射频与本振的隔离度均优于20dB,整体尺寸为32×19×14(mm)。     

一种用于ASIC芯片测试的多接口CPU模型的VHDL设计

为了对具有不同CPU接口的VHDL语言实现的ASIC芯片进行仿真测试，降低芯片测试的复杂性及成本，本文设计了一个专门用于芯片测试的CPU模型。模型用VHDL语言实现，设计采用了分层次、模块化的设计思想。与现有的VHDL实现的CPU模型相比较，该模型具有结构简单、多接口、高效率、调试使用方便等特点，本文对此CPU模型的设计思想，结构作了介绍和分析。     

一种高线性短波宽带混频器的设计

采用双平衡场效应管结构和阻抗匹配技术设计了一种适用于短波宽带接收机的高线性 混频器,通过调整场效应管的沟道宽度和偏置电压优化了混频器的性能指标。该混频器射频 输入频率为15～30 MHz,本振输入频率为715～100 MHz,中频输出频率为70 MHz。测试结果表明：输入三阶截点高于40 dBm,变频损耗小于7 dB,1 dB 压缩点高于12 dBm,单边带噪声系数小于7 dB。     

VaR方法及其对我国的适用性研究

本文讨论了度量金融风险的VaR方法的概念和参数VaR的计算方法及其运用,并探讨了该方法的简化模型以及在我国的适用性问题。     

综合法设计单片晶体滤波器的简化方法

单片石英滤波器的综合已经简化到直接采用公式。该方法是建立在描述两对电极耦合的简化弹性方程的基础之上。     

利用改进简化PSO优化设计多层吸波材料

现有的粒子群优化算法（PSO）在传统多层平板吸波材料的优化过程中收敛速度慢，寻优精 度低。为了改善设计的收敛速度和寻优精度，利用改进简化粒子群优化方法（ISPSO）在传 输线法计算模型基础上对多层吸波材料进行了优化设计。优化设计结果表明，在08～6 GHz范围内，5层吸波材料的反射系数在-22.98 dB以下，得到的结果比现有文献好。     

用ANSYS对航空发动机风扇叶片进行模态分析

模态分析技术是用于对机械系统、土建结构、桥梁等工程结构系统进行动力学分析的现代化方法和手段．模态分析是识别出系统的模态参数，为结构系统的振动特性分析、振动故障诊断及预报和结构动力特性优化设计提供依据。论文通过应用大型通用有限元软件ANSYS8．0对航空发动机风扇叶片的简化模型进行模态分析，计算风扇叶片模型的模态参数——固有频率和振型。通过模态分析可以降低风扇叶片的设计成本。缩短设计时间。     

一种快速,低运算量的信道辨识算法

在离散多音频（ＤＭＴ）系统中，保证通信正常进行的关键之一是完成收发信机的时域和频域均衡器的正确设置。一般的均衡器训练算法计算量较大。为了降低对计算量的要求，同时保证的精确度，本文提出一种基于信道辨识的均衡器训练算法。该算法将信道等效为一个ＡＲＭＡ（自回归滑动平均）模型，应用正交最小二乘法（ＯＬＳ）可快速估计出这个ＡＲＭＡ模型的阶数和参数，同时也就得到了均衡器系数的值。实验结果证明，本算法计算量较小     

Sinosteel：Extraordinary Moves in Industry Chess

Among the Fortune 500 firms,more and more images from China emerge out.On the 2008 list,Sinosteel Corporation,a landmark group of China industries quietly squeezes into the candidate line.As the largest steel service ＆ trade enterprise,its sales reached at RMB 111.24 billion,with a year-on-year increase of 83.03 percent,and the profit grew by 180.03 percent.On the Sinosteel 2008 Work Meeting,the president Huang Tianwen uttered,＂In the coming year,we will work for US$20 billion sales,and look forward to getting a position in Fortune 500 firms for ourselves.＂     

Walk Through Unusual Five Years—— An Exhibitor＇s Canton Fair Course

When the 103rd Canton Fair is approaching, an old friend of Canton Fair, Li Ying from Jiangsu prov-ince recollected his past five years＇ experiences to the grand trade meeting. Each year is special, with some unforgettable memories colored by the year.     

China's Auto Industry Steps Forward

Last year,the volume of China's auto trade reached US$66.878 bil- lion,of which imports accounted for US$25.982 billion,a year-on- year increase of 24.45 percent;while ex- ports totaled US$40.896 billion,growing by 45.31 percent.The China Association of Automobile Manufacturers(CAAM) predicts that the number of autos sold in 2008 will break the 1 million barrier for the first time in history,representing an increase of about 20 percent.     

Wisdom and Wealth Go First in a Harmonious Society——The Announcement of "2007 China Top Ten Wealthy and Intelligent People"

In order to implement the strategy "strengthening country on talent", and to form an good environment of respecting knowledge,talent, and fortune, in 2007 December, Bejing Cultural Development Research Institute, China National Condition Research Association, Fortune Times Press, China Election website,and some other institutes jointly elect 2007 China Top Ten Wealthy and Intelligent People, on the principle of"Contribution, creation, and power".     

Next Target Market for China Automakers?——China Autos Displayed in 101st North American International Auto Show 2008

As a top international show,the North American International Auto Show(NAIAS)is among the most prestigious auto shows in the world.On January 13,2008,in Detroit,the 101st NAIAS unveiled the first auto show of 2008.With the developing strategy of"Going Out"and the innovation on research and technology,China automakers achieved great progress in recent years.In this show,China five automakers including:BYD Auto,Changfeng Group,Geely International Corp,Li Shi Guang Ming Auto Design CO.Ltd,and ZXAuto China(Hebei Zhongxing)attended the NAIAS on January 13 to 27,2008.Changfeng Motor Group and Geely International Corporation made return visits to Detroit while BYD Auto Co.,Chamco and Li Shi Guang Ming appeared for the first time.     

Increasing Inflationary Pressure

China＇s CPI rose to 8.7 percent in February after hitting 7.1 percent in January,creating a 12-year high, the National Bureau of Statistics said.The figure exceeded market expectations,as the Bank of China,the country＇s second- largest lender,     

Sister Cities Flourish

Building sister city relation, also known as friendship city, is a common channel for cities in different countries to keep a closertie and communication. According to the statistics from China International Friendship Cities Association, up to the end of 2007, 1087 provinces and states and 314 cities from 120 countries in the world have found their sister cities in China. Among them, Japan has the largest amount of Chicapital history.     

Export Rebates on Grain Finished

A ccording to the State Statistics Bureau, China＇s consumer price index（CPI） jumped by 6.9 percent year-on-year last November, approaching the high levels seen at the end of 1996, one of the largest areas of increase was the price of grain, which rose by 6.6 percent.     

China,More than Self-Sufficient

At the moment,the whole world faces the most severe inflation in food prices in history,as grain and soybean prices climb to all-time highs.Although some observers blame the weather for the decrease in crop yields and that the growing demand for cereals used for bio-fuel production has conspired toward continuous price rises on world grain ma ket;others regard it simply as a matter of demand outpacing supply.In seven of the last eight years,world grain production has fallen behind rates of consumption.     

Sound Security,Safe Beijing

With the approach of the longawaited event, Chinese authorities have geared up to intensify security prepa-rations. In line with the ＂people-oriented＂ and ＂athletes-centered＂ ideas, Beijing will spare no efforts to provide quality services and to build a safe and comfortable environment that will satisfy all the Games＇ participants.