2009年中国GPS市场呼唤行业领头羊

随着2009年1月1日起燃油税改革的正式实施和1月20日起1.6L小排量汽车购置税减半政策的出台,沉寂了许久的汽车市场受到了激发,各个品牌的4S店都是一派繁荣景象,许多车型都要预定并等上一两个月才能提到车.汽车行业的复苏也为与之休戚与共的GPS市场带来了转机.在汽车销量增幅的带动下,截止09年4月,GPS销量同比去年增加了8%.     

反常二重积分收敛性的判定

华东师范大学数学系编《数学分析(下册)》教材在第21.8节介绍了反常二重积分收敛的定义、判定定理,作者发现教材中对本节内容的处理不够清晰,特别是没有给出定理21.19关于反常二重积分收敛等价于绝对收敛的直观解释.本文优化了该节的内容,理顺了反常二重积分收敛的判定方法,证明了无界区域上的二重积分转化为累次积分的定理,构造例子说明了反常一重积分收敛与反常二重积分收敛的本质区别.通过分析例子表明,在本文框架下判定反常二重积分收敛性及计算积分值是非常有效的.     

从偏导数恒等式变换到偏微分方程求解

从高等数学教材课后习题的偏导数恒等式变换求解,引导学生讨论一类偏微分方程的求解.在拓展课程内容、应用和常微分方程变量分离方法的基础上,巩固多元复合函数求导法则,常系数线性微分方程求解方法和傅里叶级数的相关理论与方法.     

混合型渐近非扩张映射合成隐迭代序列的收敛性定理

在一致凸Banach空间中,研究了有限族渐近非扩张自映射和渐近非扩张非自映射的新的合成隐迭代序列的强收敛和弱收敛定理.得到的结果改进和推广了许多作者的相应结果.     

R~N上具有渐近线性项的奇异椭圆问题的研究（英文）

本文通过变分方法,证明包含Hardy位势的奇异椭圆问题-Δu(x)-μ/|x|2u(x)=K(x)f(u),x ∈RN,x在u∈D1,2(RN)中至少有一个非平凡解,其中N≥3,0≤μ≤∶=((N-2)/2)2,f(t)是在R上的连续函数并且在无穷远处渐近线性.     

环状硅酸盐图的友好指数集

Let G be a graph with vertex set V(G) and edge set E(G). A labeling f : V(G) →Z2 induces an edge labeling f*: E(G) → Z2 defined by f*(xy) = f(x) + f(y), for each edge xy ∈ E(G). For i ∈ Z2, let vf(i) = |{v ∈ V(G) : f(v) = i}| and ef(i) = |{e ∈ E(G) : f*(e) =i}|. A labeling f of a graph G is said to be friendly if |vf(0)- vf(1)| ≤ 1. The friendly index set of the graph G, denoted FI(G), is defined as {|ef(0)- ef(1)|: the vertex labeling f is friendly}. This is a generalization of graph cordiality. We investigate the friendly index sets of cyclic silicates CS(n, m).     

米波雷达阵地选择要素分析

简要回顾了米波雷达发展历程,阐述了米波雷达反隐身的有效性,从理论上分析了影响其作战效能的地形遮蔽、同频段干扰、地面反射影响等几种主要因素,并分别进行仿真,给出了仿真结果以及阵地选择建议。     

Optimized power simulation of AlGaN/GaN HEMT for continuous wave and pulse applications

An optimized modeling method of 8 × 100 μm AlGaN/GaN-based high electron mobility transistor (HEMT) for accurate continuous wave (CW) and pulsed power simulations is proposed. Since the self-heating effect can occur during the continuous operation, the power gain from the continuous operation significantly decreases when compared to a pulsed power operation. This paper extracts power performances of different device models from different quiescent biases of pulsed current-voltage (I-V) measurements and compared them in order to determine the most suitable device model for CW and pulse RF microwave power amplifier design. The simulated output power and gain results of the models at V_gs = -3.5 V, V_ds = 30 V with a frequency of 9.6 GHz are presented.     

A 3.16–7 GHz transformer-based dual-band CMOS VCO

A dual-band, wide tuning range voltage-controlled oscillator that uses transformer-based fourth-order(LC) resonator with a compact common-centric layout is presented. Compared with the traditional wide band(VCO), it can double frequency tuning range without degrading phase noise performance. The relationship between the coupling coefficient of the transformer, selection of frequency bands, and the quality factor at each band is investigated. The transformer used in the resonator is a circular asymmetric concentric topology. Compared with conventional octagon spirals, the proposed circular asymmetric concentric transformer results in a higher qualityfactor, and hence a lower oscillator phase noise. The VCO is designed and fabricated in a 0.18- m CMOS technology and has 75% wide tuning range of 3.16–7.01 GHz. Depending on the oscillation frequency, the VCO current consumption is adjusted from 4.9 to 6.3 m A. The measured phase noises at 1 MHz offset from carrier frequencies of 3.1, 4.5, 5.1, and 6.6 GHz are –122.5, –113.3, –110.1, and –116.8 d Bc/Hz, respectively. The chip area, including the pads, is 1.20.62 mm2 and the supply voltage is 1.8 V.