气相色谱仪检测溶解气H_2、He最佳观测条件的选择

通过色谱柱、固定相以及载气流速的选择性实验 ,提高了气相色谱仪在观测地下水中H2 、He分离效能和检测效能。本文对此作介绍 ,以期对使用气相色谱仪进行地下水H2 、He观测的台站能有所启发和借鉴     

垃圾场渗出污水厌氧处理的可行性研究

采用血清瓶静态试验法研究了垃圾渗出污水的厌氧处理的可行性。试验表明:垃圾渗出污水对厌氧发酵微生物无抑制作用,有良好的厌氧降解性,产气率为0.321/g·COD,污水中的大部份有机物都能被厌氧消化,COD_cr去除率为78.2%,发酵过程中还能获得能源——沼气。具有良好的应用前景。     

FINANCING PRIVATE WATER RESOURCE DEVELOPMENT: ANALYSIS OF A STATE LOAN PROGRAM1

ABSTRACT. A State loan program was analyzed for its effects on groundwater development in Wyoming. The analysis focused on the effects of low-interest State financing on the economic feasibility of investments in center-pivot sprinkler irrigation systems. The feasibility analysis indicated that investments in sprinkler systems for production of cash crops are highly profitable, and would frequently be carried out whether or not the State loan program were available. Investments in sprinklers for production of forage crops are perhaps frequently made attractive by the loan program. Thus, while the program appears to have accelerated the pace of private water resource development in Wyoming, it has also subsidized some investments that would have been carried out regardless of the program's existence. Further analysis indicated that sprinkler investments carried out with State financing contribute substantially to firm growth when cast crops are grown, but have less marked, and sometimes negative, effects on growth when forage crops are produced. Some positive effects of the loan program on southeast Wyoming's regional economy were noted, though a complete empirical analysis of regional impacts was beyond the scope of the study.     

Investigation the effect of adding graphene oxide into diesel/higher alcohols blends on a diesel engine performance

ABSTRACT

This article aims to study the influence of the addition of graphene oxide nanoparticles (GO) to diesel/higher alcohols blends on the combustion, emission, and exergy parameters of a CI engine under various engine loads. The higher alcohols mainly n-butanol, n-heptanol, and n-octanol are blended with diesel at a volume fraction of 50%. Then, the 25 and 50 mg/L concentrations of GO are dispersed into diesel/higher alcohols blends using an ultrasonicator. The GO structures are examined using TEM, TGA, XRD and FTIR. The findings show that there is a reduction in p_max. and HRR when adding higher alcohols with diesel fuel. Regarding engine emission, there is a significant improvement in emissions formation with adding higher alcohols. The addition of GO into diesel/higher alcohols blends improves the brake thermal efficiency by 15%. Moreover, the p_max. and HRR are both enhanced by 4%. The CO, UHC and smoke formation are reduced considerably by 40%, 50 and 20%, respectively, while NO_x level is increased by 30% with adding GO. Finally, adding high percentages of n-butanol, n-heptanol, and n-octanol with diesel fuel with the presence of GO has the potential to achieve ultra-low CO, UHC, and smoke formation meanwhile keeping high thermal efficiency level.     

中国经济实现持续增长面临的城市化滞后的挑战

我国人口城镇化滞后的根本原因在于计划经济体制下形成的二元经济结构和城乡隔离的户籍管理制度没有在工业化进程和市场经济体制建立进程中予以破除。而城镇化的滞后将给我国经济实现持续增长带来诸多挑战，包括有效需求不足、农业生产率低下、产业结构难以升级等。文章特别阐明通过包括户籍制度、就业制度和土地承包制度在内的制度创新，加快人口城镇化的步伐，促进经济持续稳定的增长。     

关于中国土地资源人口承载力问题的思考

土地资源的人口承载力问题也就是生存空间问题,它关系到人类未来的生存与发展问题,历来受学术界的注目。20世纪70年代联合国粮农组织(FAO)曾主持了一项大型的发展中地区土地资源人口承载力问题的研究,80年代后期,中国科学院—国家计委自然资源综合考察委员会也主持了一项大型的中国土地资源生产能力及人口承载量研究。相应地还有一系列有关中国未来的生存与发展和人口承载力问题的探讨。本文从中国人地关系变化的角度介入这一讨论,分析中国远期的土地资源是否超载的问题。     

吐鲁番地区粮食生产发展问题初探

吐鲁番盆地的特殊气候条件，为经济作提供了良好的生长环境，而粮食生产受气候条件和经济作物快速增长的双重制约，发展非常困难，本文分析了吐鲁番地区粮食生产增长态热及制约因素，并应用多种模型对未来粮食变化趋势作了定量和定性的，在此基础上提出了相应的对策。     

Prenatal measurement of the fetal cerebellum and cisterna cerebellomedullaris by ultrasound

The fetal cerebellum can be visualized with ultrasound throughout the second trimester. We describe a technique for measuring the transverse and anteroposterior cerebellar diameters and the measurement of the cisterna magna in the same plane between 14 and 32 weeks gestation. Nomograms for these measurements against gestational age showed good correlation, and narrow confidence limits for the transverse cerebellar diameter. The transverse cerebellar diameter was also measured directly in 79 fetuses after mid-trimester abortion and the measurements obtained were compared with the ultrasound TCD nomogram. Good correlation, was obtained between the post mortem measurements and the ultrasound TCD nomogram. Routine use of these measurements and nomograms should prove valuable in the diagnosis of congenital abnormality of the posterior fossa and may also be of use in assessing the effect of severe intrauterine growth retardation and other insults on cerebellar growth and development. The narrow confidence limits obtained with the TCD nomogram should enable it to be used with confidence in clinical practice.     

Effect of Grazing and Climatic Changes on Alpine Vegetation of Tungnath,Garhwal Himalaya,India

Effect of grazing and changing climate on vegetation composition of alpine pasture at Tungnath, Garhwal Himalaya was observed. Growth form pattern and phytosociological attributes were analyzed during 1988 under grazed (exposed to extensive grazing) and ungrazed (protected from grazing) conditions. These observations were repeated during 1998. It was observed that number of early growing species and long vegetative growth cycle species had increased at both sites in 1998 in comparison to 1988. Further, some species, viz., Poa alpina, Polygonum spp., Ranunculus hirtellus, Anemone spp., are predominantly found near the timberline-subalpine region. These species are less palatable and were present at both sites with higher dominance (TBC) and niche width in 1998 indicating wide distribution of the species along an altitudinal gradient. These observations indicated the migration of these species towards upper slopes of alpine. Species diversity was also higher after ten years. However, it is clear that climatic changes alone are not responsible for these vegetational shifts. In fact, human-induced changes are the main reason for habitat destruction and changes in vegetation composition of the alpine region of Garhwal Himalaya. Before final conclusions can be made, long-term studies on vegetation composition and changes are needed, especially in Himalayan region.