风险投资离你有多远

风险投资是指那些投入到具有巨大发展潜力的或年轻的高技术公司中去的资金,严格意义上的风险投资,是同技术创新形影相随,特指高技术产业中那些把高科技的创造发明第一次商品化、企业化的风险投资。     

几类群的混合自由积分解

讨论了有限实现群的混合自由积分解问题,证明了所有有限实现群皆可表示为其生成元个数不超过2的若干子群的混合自由积,并给出了 SL_n(Z)的具体的分解定理.     

广西洞穴金线鲃属一新种

描记采于广西天鹅县板么乡一洞穴的金线鲃属一新种，以采集地县名命名为天鹅金线鲃Sinocyclocheilus tianeensis Li,Xiao et Luo.sp.nov.新种与产于乐业的鸭嘴金线鲃S.anatirostris Lin et Luo相近，但有下列特征可明显区别：①新种体被密集细鳞，后者裸露无鳞；②新种眼虽退化，但仍能见到隐于膜下的小眼，后者眼已完全退化成盲眼；③新种体色紫褐色，后者无色呈半透明状。     

A Numerical Study of Vortex and Precipitating Cloud Merging in Middle Latitudes

We mainly focus on the study of precipitating cloud merging associated with vortex merging. The vortex and precipitating cloud merging are simulated by the cloud resolving model from 0000 21 to 1800 23 July 2003. The results show that the model well simulates vortex circulation associated with precipitating clouds. It is also proven that the vortex merging follows the precipitating cloud merging although vortices show the spatial and temporal differences. The convection vorticity vector is introduced to describe the merging processes. Two merging cases are identified during the 42-h simulation and are studied.     

Nitrogen Adatom Diffusion on a Ga－Rich GaN （0001） Surface

The diffusion of N adatoms on a Ga-rich GaN(O001) surface has been studied using density-functional theory.The configuration of Ga adatoms on a Ga-rich GaN surface has been identified. The first adlayer Ga adatoms are on top of the terminating substrate Ga atoms, and the outmost adlayer Ga adatoms exist randomly at the T4 or H3 sites. A very different diffusivity of N adatoms on a Ga-rich GaN(0001) surface has been found. The excess Ga adatoms on a GaN(0001) surface reduce the diffusion barrier by 0.75eV and influence the migration path. It seems that bilayer Ga adatoms are helpful for N atom diffusion.     

利用LNG冷(火用)的准零CO2排放循环探析

本文研究利用LNG冷(火用)来完善燃用它的热机性能,既提高了效率,又能回收用LNG燃料热机的唯一主要排放-CO2.这种系统的温度区间横跨大气温度,会有很多新的特点值得探索.作为前期研究,本文建议了两种新循环,分别基于Brayton循环与超临界Rankine循环,且分别适用于LNG超临界及亚临界汽化过程.文中对此两种循环进行了分析计算与讨论,说明建议是可行的,热机效率可达60%以上,且同时基本回收所有燃烧产生的CO2.     

Grinding Characteristics Of Directionally Aligned SiC Whisker Wheel-Comparison With Al2O3 Fiber Wheel

A unique SiC whisker wheel was invented,in which the whiskers were aligned normally to the grinding wheel surface.In this paper,grindabilities of the SiC whisker wheel are investigated and compared with those of other wheels of SiC grains,Al2O3 grains,as well as Al2O3 long and short fibres which were also aligned normally to the grinding wheel surface,respectively.The main research contents concern grinding characteristics of a directionally aligned SiC whisker wheel such as material-removal volume,wheel-wear rates,integrity of the ground surfaces,grinding ratios and grinding efficiency.Furthermore,grinding wheels of whiskers and fibres have a common disadvantage:they tend to load easily.The authors have proposed a simple method of loading-free grinding to overcome this propensity and investigate some related grinding characteristics under loading-free grinding conditions.     

燃气轮机考虑经济性和环保因素的热力分析

主要符号表人，从，C，H年运行小时数对热效率风，i二1，2价格方程的系数Hu燃料低位发热量雷压比c燃料含碳百分比d贴现率，温比CO投资额J单位质量C02罚款Cj年均燃料费M比例系数下标Cth年均运行维修费N电站容量0基准值COE发电成本。运行年限C发电成本E考虑变工况的系数P单位功率价格…最佳值G空气流量马单位能量燃料价格，热效率G，燃料流量产年投资费用率1概述在进行动力机械的循环热力分析时，结合经济因素与环保因素来定量进行，是实际生产的要求，也是热力循环分析的一次创新。本文将以燃气轮机发电机组为例，对此进行首次试探，…