ISSUES ON CHINA′S ENERGY SECURITY

Energysupplyisadeterminantfactor to the developmentand the prosperity of a modern society. China is one ofthe largest energy consumers andproducersin the world,and energy supply and its security in the country aregreat issues concerned not onlybytheChina …     

EFFECTS OF WATER TABLE AND NITROGEN ADDITION ON CO_2 EMISSION FROM WETLAND SOIL

1IN T R O D U C T IO NCO2emissionfrom soiltoatmosphere,which isim por-tanttocontributetothecarbon balanceof ecosystem,isone of the largestfluxes in the global carbon cycle(SCHLESINGER and ANDREWS,2000).Further-more,thechange of CO2emission from soil,as a …     

伊犁牧业经济的战略开发问题

目前伊犁生态系统平衡失调:1.畜牧业的草畜不平衡和季节不平衡伊犁的夏场面积占53%,载畜量1,420万绵羊单位,春秋场面积占22%,载畜量182万,冬场面积占23%,载畜量457万。一九八四年全地区牲畜总数为787.26万绵羊单位。理论载畜量和实际载畜量出现了明显的不平衡,夏场富余,冬场不足,春秋场的紧张尤为突出,以致每年成畜平均死亡率达10%左右,灾害之年死亡率高达30%左右,草场的退化已十分严     

Interstellar cyanomethane

We have made an observational study of the newly identified cyanomethane radical CH2CN and the possibly related species CH3CN with the goals of (1) elucidating the possible role of reactions of the type CnHm(+) + N in astrochemistry, and (2) providing a possible test of Bates's models of dissociative electron recombination. We find a remarkably different abundance ratio CH2CN/CH3CN in TMC-1 and Sgr B2, which we deduce is a result of the large difference in temperature of these objects. Studies of CH2CN and CH3CN in other sources, including two new detections of CH2CN, support this conclusion and are consistent with a monotonic increase in the CH2CN/CH3CN ratio with decreasing temperature over the range 10-120 K. This behavior may be explained by the destruction of CH2CN by reaction with O. If this reaction does not proceed, then CH2CN and CH3CN are concluded to form via different chemical pathways. Thus, they do not provide a test of Bates's conjectures (they do not both form from CH3CNH+). CH2CN is then likely to form via C2H4(+) + N --> CH2CNH+, thus demonstrating the viability of this important reaction in astrochemistry. The T dependence of the CH2CN/CH3CN ratio would then reflect the increasing rate of the C2H4(+) + N reaction with decreasing temperature.     

Processing of refractory meteorite inclusions (CAIs) in parent-body atmospheres

The refractory meteorite inclusions known as CAIs (calcium-aluminum rich inclusions) display melted rims that were produced by thermal events of only a few seconds duration. We show that gas dynamic deceleration in a temporary atmosphere around an accreting parent body, produced by gas release during accretion, could provide a regime of sufficiently high gas density and small scale height to achieve partial melting of the CAIs. In addition, the presence of dust in the atmosphere would increase the gradient of pressure with height (i.e., effectively reduce the scale height), lower the rate of blowoff (thus keeping more gas around the body), as well as allow dust particles to become trapped in the partially melted material as is observed in some cases. Thus, CAIs may be regarded as probes of a primitive atmosphere by virtue of the thermal and mineralogical alteration that occurred upon their passage through the atmosphere.     

互联网信息特征研究综述

随着互联网的高速发展,网络上信息呈爆炸性增长.理解互联网上信息的特征对信息的快速获取具有重要意义.本文首先介绍了互联网信息载体的特征,然后分别按照互联网信息在时间上的演化特征、信息的大小特征、信息的内容特征以及信息的类型特征从不同的角度对互联网信息的特征进行了分析、归纳和总结,最后,对互联网信息特征潜在的应用给出了一个可能的实际例子.