用边界元法和状态空间梯度投影法进行两维形状优化

本文应用边界元法和状态空间梯度投影法对平面应力状态下的弹性体进行形状优化,并且较好地处理了应用中出现的问题.如全部边界力已知,同时给定位移约束,由边界元法会得到一组矛盾方程应如何处理;优化中设计灵敏度分析矢量如何计算,以及约束相关问题等等.     

Surface Structure of Large Synthetic Diamonds by High Temperature and High Pressure

With NiMnCo and FeCoNi alloys as solvent metals, large single-crystal diamonds of about 3mm across are grown by temperature gradient method （TGM） under high temperature and high pressure （HPHT）. Although both {100} and {111} surfaces are developed by a layer growth mechanism, some different characteristic patterns are seen clearly on the different surfaces, no matter whether NiMnCo or FeCoNi alloys are taken as the solvent metals. For {100} surface, it seems to have been melted or etched greatly, no dendritic patterns to be found, and only a large number of growth hillocks are dispersed net-likely; while for {111} surface, it often seems to be more smooth-faced, no etched or melted traces are present even when a lot of depressed trigonal growth layers. This distinct difference between {111} and {100} surfaces is considered to be related to the difference of surface-atom distribution of different surfaces, and {111} surfaces should be more difficult to be etched and more steady than {100} surfaces.     

Measurement of Electrical Conductivity of Porous Titanium and Ti6A14V Prepared by the Powder Metallurgy Method

Porous titanium and Ti6A14V are produced by the powder metallurgy method. Dependence of the electrical conductivity on the porosity and pore size is investigated and the experimental results are correlative and compared with several earlier models. A newly modified Mori-Tanaka relationship based on the effective field method is proposed, which is successfully applied to describe the dependence of the electrical conductivity of porous titanium and Ti6A14V on the porosity. The pore size has a minor effect on the electrical conductivity of both samples.     

Influences of Temperature on Proton Conductivity in the Hydrogen-Bond Molecular Systems with Damping

Influences of temperature of medium on proton conductivity in hydrogen-bonded systems exposed in an electricfield are numerically studied by the fourth-order Runge-Kutta method with our model. The results obtained show that the proton soliton is very robust against thermal perturbation and damping of medium, and is thermally stable in the temperature range T ≤ 273 K. From the simulation we find out that the mobility （or velocity） of proton conduction in ice crystal is a nonmonotonic function of temperature in the temperature range 170-273 K： i.e., it increases initially, reaches a maximum at about 191 K, subsequently decreases to a minimum at about 211 K, and then increases again. This changed rule of mobility is qualitatively consistent with its experimental data in ice in the same temperature range. This result provides an evidence for existence of solitons in the hydrogen-bonded systems.     

EuBO3的低温水热合成及光谱可调性质研究

采用低温水热法合成了稀土硼酸盐EuBO3的纯相样品.利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱仪(XPS)和荧光光谱仪(PL)对样品的结构、形貌、价态及发光性质进行了研究.结果表明,该样品属六方晶系,在不同的矿化剂和碱度下呈现不同的自组装形貌.当以NaOH或NH3.H2O为矿化剂时,该样品分别沿着(100)和(002)晶面生长.因为Eu离子以混合价态形式存在,样品表现出光谱可调性,当激发波长为270～360 nm时,样品荧光由红色转为橙色,经粉紫光变为蓝光.     

爆炸驱动铁电体电源快脉冲产生技术

以发展轻小型高电压脉冲驱动源为出发点,提出采用爆炸驱动铁电体作为初级电源,通过电感储能与电爆炸丝断路开关进行脉冲压缩和功率放大,探索基于爆炸驱动铁电体电源的小型化高电压快脉冲产生技术。从爆炸驱动铁电体电源的全电路模型和铁电陶瓷材料特性出发,通过理论分析和仿真研究,分别对大电流模式和高电压模式的爆炸驱动铁电体电源的物理参数进行了设计,获得了铁电体电源工作模式和电路参数对产生高电压脉冲的影响规律,认为铁电体电源高电压模式更适合于与断路开关技术结合产生高电压快脉冲,并通过实验对该技术原理进行了验证。实验中铁电体电源输出电流约360 A、脉宽约3.8 μs,对17.5 nF电容器充电至75 kV,电容器放电后在电爆炸断路开关中产生峰值大于12 kA的脉冲电流,最终在X射线二极管负载上获得了电压峰值大于180 kV、前沿3 ns、脉宽30 ns、电流峰值3.4 kA的高电压快脉冲。     

二十世纪最多产的“流浪”数学家——厄多斯

他一生发表过1475篇数学论文,各国数学家都以与他合作研究为荣;他游历于世界各地的大学和研究所,在一个城市停留的时间不超过一个月;他没有结婚,没有固定住所,没有信用卡,只有两个简单的行李箱;他的研究涉及到数论、集合论、组合数学、图论、概率论、实变函数论、无究级数理论等;他70岁高龄获数学界的最高奖“沃尔夫”奖．他就是20世纪的天才数学家——厄多斯（Erdos,1913—1996）．     

一类4pq(p>q≠3)阶群的构造

在有限群理论中,确定n阶群的构造是一个分类问题.利用了超可解群的性质,通过群的扩张理论解决了在p 1(modq)时4pq(p>q≠3)群的构造,即证明了下面的定理:当p/≡1(modq)时4pq(p>q>3)阶群的构造:①10种,p/≡1(mod 4),q/≡1(mod 4)时;②16种,p≡1(mod 4),q≡1(mod 4)时.③12种,p≡1(mod 4),q/≡1(mod 4)时;④12种,p/≡1(mod 4),q≡1(mod 4)时.     

搜索引擎行业竞争策略

2011年,我国互联网广告市场规模达512．9亿元,预计2012年网络广告规模将达800亿元,超过平面媒体并且逼近电视广告规模。然而,随着2012年宏观经济增速放缓,企业主们在广告投放预算上显然变得更加谨慎,互联网搜索引擎广告也难独善其身。     

氢化物发生-原子荧光光谱法测定大米与圆白菜中痕量铅

建立了氢化物发生-原子荧光光谱法(HG-AFS)测定经HNO3-HClO4-H2O2湿法消解的大米与圆白菜等样品中痕量铅的方法,系统地优化了灯电流等仪器参数条件,探讨了载流、还原剂、样品酸度、氧化剂的最佳浓度,考察了掩蔽剂去干扰的情况。实验表明:在选定载流浓度HCl 2%(V/V)、还原剂KBH4浓度2%(m/V)[KOH恒为0.5%(m/V)]、样品酸度HCl 1%(V/V)、氧化剂K3Fe(CN)60.4%(m/V)、掩蔽剂H2C2O40.2%(m/V)及优化设置灯电流等参数的最佳实验条件下,测定铅的检出限为0.07μg/L,在0.00—50.00μg/L范围呈良好的线性关系,样品测定变异系数小于等于6.22%。该方法简便、干扰少、灵敏度高,应用于大米、圆白菜等样品中Pb的测定,结果与参考值相符,是一种切实可行的方法。