对建设中国先进文化的几点认识

充分认识文化和先进文化的本质特征,领会“三个代表”重要思想中关于“代表中国先进文化前进方向”的深刻内涵,研讨我国先进文化建设面临的新课题,努力实践“三个代表”,积极发展先进文化。     

A high-efficiency CMOS +22-dBm linear power amplifier

Modern wireless communication systems require power amplifiers with high efficiency and high linearity. CMOS is the technology of choice for complete systems on a chip due to its lower costs and high integration levels. However, it has always been difficult to integrate high-efficiency power amplifiers in CMOS. In this paper, we present a new class of operation (parallel A&B) for power amplifiers that improves both their dynamic range and power efficiency. A prototype design of the new amplifier was fabricated in a 0.18-/spl mu/m CMOS technology. Measurement results show a PAE that is over 44% and the measured output power is +22 dBm. In comparison to a normal class A amplifier, this new design increases the 1-dB compression point (P1dB) by over 3 dB and reduces dc power consumption by over 50% within the linear operating range.     

钢坯修磨金属切除率数学模型的研究

从分析修磨过程运动学和单个磨粒切削入手,建立了磨削深度与磨削过程诸参数(如工艺、材料性能、砂轮性能等)的关系表达式,从而建立起金属切除率与各单项参数的定量关系,为改善或提高修磨效率和修磨过程控制提供了有意义的根据。理论分析与实验结果吻合良好。     

BC—1型白平衡仪的原理与实践

ＢＣ－１型白平衡仪是一种光电积分式测色仪器，它通过颜色传感器获取屏幕的红，绿，蓝三条色信号，与预先存储在仪器中的标准信号值相比较通过ＬＥＤ条形显示器显示两者之偏差，用以直接指导彩电生产线的白平衡调整，仪器采用Ｉｎｔｅｌ１８０９８单片微机为系统核心，内藏信号发生器，仪器可任选红，绿，蓝作为基准色，具有基色亮度自动调整功能，该仪器的定标方法简单，快捷，可方便地存储８套基准白场标准数据，该仪器已可靠在应     

Finite-element analysis of hyperelastic thin shells with large strains

The objective of this contribution is the development of theoretical and numerical models applicable to large strain analysis of hyperelastic shells confining particular attention to incompressible materials. The theoretical model is developed on the basis of a quadratic displacement approximation in thickness coordinate by neglecting transverse shear strains. In the case of incompressible materials this leads to a three-parametric theory governed solely by mid-surface displacements. The material incompressiblity is expressed by two equivalent equation sets considered at the element level as subsidiary conditions. For the simulation of nonlinear material behaviour the Mooney-Rivlin model is adopted including neo-Hookean materials as a special case. After transformation of nonlinear relations into incremental formulation doubly curved triangular and quadrilateral elements are developed via the displacement method. Finally, examples are given to demonstrate the ability of these models in dealing with large strain as well as finite rotation shell problems.The present study is supported by a research grant of the German National Science Foundation (DFG) under Ba 969/3-1.dedicated to Prof. Dr. Dr. Erwin Stein for his 65th birthday anniversary     

(+)-CC-1065 as a structural probe of Mu transposase-induced bending of DNA: overcoming limitations of hydroxyl-radical footprinting

Phage Mu transposase (A-protein) is primarily responsible for transposition of the Mu genome. The protein binds to six att sites, three at each end of Mu DNA. At most att sites interaction of a protein monomer with DNA is seen to occur over three minor and two consecutive major grooves and to result in bending up to about 90 degrees. To probe the directionality and locus of these A-protein-induced bends, we have used the antitumor antibiotic (+)-CC-1065 as a structural probe. As a consequence of binding within the minor groove, (+)-CC-1065 is able to alkylate N3 of adenine in a sequence selective manner. This selectivity is partially determined by conformational flexibility of the DNA sequence, and the covalent adduct has a bent DNA structure in which narrowing of the minor groove has occurred. Using this drug in experiments in which either gel retardation or DNA strand breakage are used to monitor the stability of the A-protein--DNA complex or the (+)-CC-1065 alkylation sites on DNA (att site L3), we have demonstrated that of the three minor grooves implicated in the interaction with A-protein, the peripheral two are 'open' or accessible to drug bonding following protein binding. These drug-bonding sites very likely represent binding at at least two A-protein-induced bending sites. Significantly, the locus of bending at these sites is spaced approximately two helical turns apart, and the bending is proposed to occur by narrowing of the minor groove of DNA. The intervening minor groove between these two peripheral sites is protected from (+)-CC-1065 alkylation. The results are discussed in reference to a proposed model for overall DNA bending in the A-protein att L3 site complex. This study illustrates the utility of (+)-CC-1065 as a probe for protein-induced bending of DNA, as well as for interactions of minor groove DNA bending proteins with DNA which may be masked in hydroxyl radical footprinting experiments.     

PbO－Bi_2O_3－B_2O_3－SiO_2系重金属氧化物玻璃的结构与光学性

通过密度、可见光光谱、红外吸收光谱、Ｃｏ－６０辐照损伤试验及荧光光谱的测试，研究了ＰｂＯ－Ｂｉ２Ｏ３－Ｂ２Ｏ３－ＳｉＯ２玻璃系的光学性能与结构．密度最高可达８．４６４ｇ／ｃｍ３其紫外吸收达截止波长随Ｐｂ２＋及Ｂｉ３＋含量升高而红移．玻璃熔化温度低达８５０℃．在ＰｂＯ－Ｂｉ２Ｏ３－Ｂ２Ｏ３系玻璃中加人ＳｉＯ２可使玻璃结构更致密．室温下该系统玻璃在３６０ｎｍ有一个宽的激发峰，能产生４１８ｕｍ及４３８ｕｍ两个弱的发射峰．该系统玻璃的结构是由［ＳｉＯ４］４－、［ＢＯ３］３－、［ＢＯ４］５－、［ＰｂＯ４］６－及［ＢｉＯ６］９－构成．其中部分Ｐｂ２＋及Ｂｉ３＋以网络外体进入玻璃．     

Synthesis of polyurethane elastomers hypercross-linked by partially hydrated polyhydroxylated C60

Utilization of polyhydroxylated C₆₀ (fullerenols) in a condensation reaction with diisocyanated oligo(tetramethylene oxide) led to the successful fabrication of elastomeric poly (urethane-ether) networks. These polymer networks exhibit interesting thermal behavior at low temperatures, improved tensile strength and elongation at ambient temperatures, and enhanced thermal mechanical stability at high temperatures, as compared with those of the parent linear polyurethane analogues; or with the conventional oligo (tetramethylene oxide)-derived polyurethane elastomers cross-linked by trihydroxylated reagents (1,I,1-trismethylol propane) or tetrahydroxylated reagents (pentaerythritol). The presence of a limited quantity of water molecules in the condensation reaction of fullerenols with diisocyanated prepolymers modified the physical properties of the resulting elastomeric products with a notable increase in tensile strength, modulus, and Ts over those of elasotmers prepared under anhydrous conditions. These water molecules contributed effectively to the increase of the number of cross-linking centers during the reaction.