基于逆向Stirling循环的制冷机中功转化为热的比率

以逆向Stirling循环为原理的理想气体的可逆制冷机中功转化为热的比率为η比率=-Q/W1=(T1-T2)/T1。在可逆制冷机中,实际气体和理想气体的功温比守恒。可逆过程的功温比是状态函数。文章提出了热力学第二定律的新表述,即不可能通过做功使之完全变为热量而不产生其它影响。可证明实际过程的功温比大于可逆过程的功温比,integral from n=j to i(δW)实际过程≥integral from n=j to i(δW)可逆过程。

可转换债券的特征及其核算方法

可转换债券的发行对投资者和筹资者都具有吸引力。它与一般公司债券相比具有以下基本特征 :( 1 )转换比率 ;( 2 )转换价格 ;( 3)转换价值 ;( 4)转换溢价。本文对可转换债券的发行价格。

Characteristic Change of Several Forest Landscapes Between 1896 and 1986 in Heilongjiang Province

Five forest landscapes in the maps of forest distribution in Heilongjiang Province in 1896 and 1986 were digitized and analyzed through GIS software. The results show that during the 90 years the total patch areas for Picea and Abies forest, Pinus sylvestris var. mongolica Litvin forest and Pinus koraiensis Sieb. et Zucc. forest had decreased about 87%, 40% and 84%, respectively. However, the total patch areas for broad leaved forest at the north of 51°N area had increased about 500%. The north frontier of broad leaved forest had moved towards northwest about 290 km. The fractal dimensions of Picea and Abies forest and mixed coniferous and broad leaved forest in 1986 were less than theirs in 1896, respectively. However, the fractal dimension of Pinus synvestris forest, Pinus koraiensis and broad leaved forest were more than theirs in 1896, respectively. Picea and Abies forest, Pinus synvestris forest, Pinus koraiensis and broad leaved forest became more fragmented. The transition percentages of Pinus sylvestris forest, Picea and Abies forest, Pinus koraiensis forest to themselves were less than the percentages to the mixed coniferous and broad leaved forest, respectively.

Hydrogenation of Silicon Tetrachloride in Microwave Plasma

This study investigated the hydrogenation of silicon tetrachloride （SIC14） in microwave plasma. A new launcher of argon （Ar） and hydrogen （Ha） plasma was introduced to produce a non-thermodynamic equilibrium activation plasma. The plasma state exhibited a characteristic temperature related to the equilibrium constant, which was termed ＂Reactive Temperature＂ in this study. Thus, the hydrogenation of SIC14 in the plasma could easily be handled with high conversion ratio and very high selectivity to trichlorosilane （SiHC13）. The effects of SiC14/Ar and H2/Ar ratios on the conversion were also investigated using a mathematical model developed to determine the op- timum experimental parameters. The highest hydrogenation conversion ratio was produced at a H2/SiCl4 molar ratio of 1, with mixtures of SICl4 and H2 to Ar molar ratio of 1.2 to 1.4. In this plasma, the special system pressure and incident power were required for the highest energy efficiency of hydrogenating SIC14, while the optimum system pressure varies from 26.6 to 40 kPa depending on input power, and the optimum feed gas （He and SiCI4） molar en- ergy input was about 350 kJ. mo1-1.

Optimization on cationic liposome-mediated cell transfection of plasmid DNA

Objective:The development of gene carriers for efficient gene delivery into cells has attracted growing attention in recent years.The aim of this study was to achieve a better outcome of AAV-293 cells transfection by plasmid DNA.Methods:We studied the optimal condition for higher efficiency of cationic lipid-mediated cell transfection.Four experimental groups were set.Plasmid DNA and liposome were mixed in each groups at different ratios(μg:μL),1:2.5,1:3.5,1:4.0 and 1:5.0,respectively.LacZ gene functioned as reporter gene,measuring the transfection efficiency of the four groups using the method of X-gal staining.Results:When the ratio was 1:3.5,the cell transfection rate was the highest.While the ratio of 1:2.5 recommended by product manual achieve the lowest transfection rate.Their difference had statistical significance.Conclusion:In order to obtain a higher transfection efficiency,optimization on conditions of the ratio of plasmid DNA to liposome is necessary in cell transfection.

深水气井水合物沉积预测新模型

由水合物聚结、沉积导致的井筒堵塞是气井测试中常见的安全隐患。预测水合物的生成与沉积规律,有利于控制事故风险、降低生产损失。通过对水合物颗粒在管流气核区和管壁附近的生成与运移机理分析的基础上,引入液滴沉积比率和转化比率,建立了一种适用于环雾流条件下的水合物沉积预测新模型,并参照实际工况设计了实验验证。实验结果表明,理论值与实验值趋势一致,平均偏差为4.9%,验证了模型的可靠性。以深水井X井为例,通过数值模拟探究了不同位置处水合物沉积规律。试算结果表明,水合物沉积堵塞过程可以划分为4个阶段,其中初始沉积阶段、临界沉积阶段所占时间比例较短,而沉积亚稳态生长阶段、沉积快速生长阶段所占时间比例较长。水合物堵塞主要发生在井筒偏上部分,尤其是井口附近。随着深度的增长,水合物沉积速率与沉积厚度逐渐减少,且减小幅度逐渐增大,堵塞风险减小。

Circulating Fluidized Bed Gasification of Low Rank Coal：Influence of O2/C Molar Ratio on Gasification Performance and Sulphur Transformation

To promote the utilization efficiency of coal resources,and to assist with the control of sulphur during gasification and/or downstream processes,it is essential to gain basic knowledge of sulphur transformation associated with gasification performance.In this research we investigated the influence of O_2/C molar ratio both on gasification performance and sulphur transformation of a low rank coal,and the sulphur transformation mechanism was also discussed.Experiments were performed in a circulating fluidized bed gasifier with O_2/C molar ratio ranging from 0.39 to 0.78 mol/mol.The results showed that increasing the O_2/C molar ratio from 0.39 to 0.78 mol/mol can increase carbon conversion from 57.65%to 91.92%,and increase sulphur release ratio from 29.66%to63.11%.The increase of O_2/C molar ratio favors the formation of H_2S,and also favors the retained sulphur transforming to more stable forms.Due to the reducing conditions of coal gasification,H_2S is the main form of the released sulphur,which could be formed by decomposition of pyrite and by secondary reactions.Bottom char shows lower sulphur content than fly ash,and mainly exist as sulphates.X-ray photoelectron spectroscopy(XPS)measurements also show that the intensity of pyrite declines and the intensity of sulphates increases for fly ash and bottom char,and the change is more obvious for bottom char.During CFB gasification process,bigger char particles circulate in the system and have longer residence time for further reaction,which favors the release of sulphur species and can enhance the retained sulphur transforming to more stable forms.