鹭鸶兰的核型分析

本文报道了鹭鸶兰的染色体数目和核型。结果如下:鹭鸶兰2n=56=2M 12m 32sm 10st。     

A complete sequence and comparative analysis of a SARS-associated virus(Isolate BJ01)

Severe Acute Respiratory Syndrome (SARS) is a newly identified infectious disease[1—5]. The global outbreak of SARS has been threatening the health of people worldwide and has killed 353 people and infected more than 5462 in 27 countries, as reported by WHO on April 29, 2003 (http://www.who.int/csr/sarscountry/en). Although it has been recognized that a variant of virus from the family of coronavirus might be the candidate pathogen of SARS[1—5], its identity as the unique pathogen sti…     

Instability of the shear layer in the near wake of a circular cylinder

The instability of the shear layer separated from a circular cylinder is studied with the Reynolds number (Re) of 3000～104 by numerically solving the two-dimensional Navier-Stokes equations. In the wake of the cylinder, primary vortex shedding with natural frequency fs occurs, and the instability of the shear layer with frequency ft develops, which leads to mixing layer eddies and interacts with the primary shedding vortices. However, there remains some uncertainties regarding to the variation of the shear layer characteristic frequency with the Reynolds number. Based on the previous experimental work, several relationships of ft/fs with Re has been proposed including ft/fs～Re0.5 by Bloor, ft/fs～Re0.87 by Wei and Smith and ft/fs～Re0.67 by Prasad and Williamson. The objective of this study is to predict reasonably the relation of the shear layer instability frequency with the Reynolds number based on the present accurate calculation with the high-order schemes and high-resolution spectrum analysis. According to our calculated results, a variation for the normalized shear-layer frequency of the form ft/fs～Re0.69 is predicted numerically, which is in good agreement with a recent experimental measurement of Re0.67 and physical prediction of Re0.7.     

一种新奇的Ru(Ⅱ)配合物[Ru(bpy)_3](dca)I_0.5(OH)_0.5·3H_2O的合成与晶体结构(英文)

合成了一种新奇的Ru(Ⅱ)配合物[Ru(bpy)3](dca)I0.5(OH)0.5·3H2O并进行了结构表征,该化合物属于六方晶系,P6/mcc晶胞群,晶格参数为a=1.3505(3)nm,b=1.3505(3)nm,c=2.1263(6)nm,α=90°,β=90°,γ=120°.在该化合物中,配体bpy和OH-离子之间以及dca和结晶水之间都存在较强的氢键作用。     

电弧喷涂铝及铝-锌涂层在动态腐蚀介质中的耐蚀性研究

对钢铁基体表面电弧喷涂铝及铝锌涂层进行了动态腐蚀实验 ,以失质量法计算了腐蚀速度 ,并探讨了腐蚀机理。采用SEM对铝及铝锌涂层腐蚀前后的外表形貌进行了观察 ,并对铝及铝锌涂层表面进行了能谱分析 ,采用电化学系统测试了涂层的自腐蚀电位。实验结果表明 ,在 3 %NaCl水溶液中铝涂层的耐蚀性优于铝锌涂层 ;其原因是铝涂层表面上氧化膜的自愈能力及自腐蚀电位高于铝锌涂层。研究还表明 ,铝及铝锌这些阳极涂层不仅能有效地保护它所覆盖的钢铁表面 ,还能保护暴露于腐蚀介质中的钢铁基体表面。在铝、铝锌涂层上刷涂有机涂料 ,有机涂料能渗透到金属涂层的孔隙中 ,将孔隙封闭。同时 ,有机涂层和金属涂层能构成复合涂层 ,其防腐效果更佳     

BP自适应网络在数值预报产品的释用

提出了动态指标库的概念，即不同时次采取不同的指标库，同时次在网络自适应时采取不断更新指标库的阈值，采取先建立消空指标库对样本进行消空，提高了降水样本在整体样本中的概率，然后利用BP(Back Propagation)网络作了大连短期的12h和24h降水有、无的预报，设计了网络的自适应算法，并在降水有、无预报中加以应用。结果表明，此方法比没有做消空样本和网络自适应的降水TS评分有所提高，在数值产品解释应用中更具有实际意义。     

Research on Precision Assembly Robot''''s Joint Torque Control Based on Current Measurement

A set of new current sensing device is used to realize joint torque control based on current measurement in a precision assembly robot's third joint. The output torque's model of the joint's brushless DC motor is founded. Disturbance factors and the compensated effect of the torque's closed loop based on current measurement are analyzed. Related simulations and experiments show that the system has good current tracking and anti-disturbances performance, which improve the force control performance of the robot in assembly.     

PCS网络中基于方向的自适应位置管理模型

研究了个人通信服务网络中的位置管理问题 ,提出了基于方向的自适应位置管理方法 (ADBU) ,该方法有效地减小了整个系统的位置管理总开销 .移动终端周期地检测其运动方向 ,当它的改变超过预先设定的阈值时 ,系统将更新它在数据库中的位置信息 .采用了高斯 -马尔科夫模型来模拟移动终端的运动方向 ,然后通过自适应反馈控制方法来调整移动终端的最佳方向阈值 ,从而减小其位置管理开销 .仿真结果表明ADBU的位置管理开销要明显小于基于距离的位置管理方法 ,也小于直线式寻呼位置管理方法 .     

螺杆技术及应用的探讨

本文主要讨论螺杆的挤压及输送的工作方式、螺旋叶片的展开和变化形式、螺杆组合的方法及螺杆技术的应用。     

基于比率的离散型捕食系统的周期解

针对一类基于比率的离散型捕食系统，利用重合度理论给出了该系统正周期解的存在性判据．