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排序方式: 共有194条查询结果,搜索用时 171 毫秒
81.
安徽省农业灾害系统的灾度预评估研究 总被引:2,自引:0,他引:2
本文从区域灾害系统的概念出发,选用16项指标对安徽省农业灾害系统(79个县、市)进行了灾度的R型因子分析预评估,并探讨了灾度指数空间分异的基本格局及其成因。 相似文献
82.
Titanium dioxide(TiO2) samples of different crystal forms were prepared by hydrolysis tetrbutyl titanate in various water to alkoxide ratios and sintering the hydrolysis product at different temperatures.The photocatalysts coated on hollow glass beads and loaded with platinum varying from 0.2% to 2.4% by weight.The photocatalytic degradation rate of sodium pentachlorophenolate (PCP-Na) depends on the preparing conditions such as:sintering temperatures,water to alkoxide ratios(R),platinum content and the size.The proper conditions of preparation photocatalysts are as follows:the ratio of tiO2:sodium silicate:hollow glass beads:platinum is 10:5:20:0.15(w/w),R is 100,sintering temperature is 650℃,and the size of hollow glass is 0.5-1mm.Under these conditions,the ratio between acatase and rutile of the photocatalyst is 2:1,and the photocatalytic activity is high. 相似文献
83.
饮用水生物处理中微生物量和活性的测定方法 总被引:4,自引:0,他引:4
微生物量和微生物活性是饮用水生物处理工艺设计与运行的重要参数。总结论述了适用于表示饮用水生物处理过程生物膜中微生物数量和活性的几种主要指标的测定方法。 相似文献
84.
With the popularity of refrigerants in the process industries, the potential safety problems caused by the use of refrigerants have attracted worldwide attention as people have realized their inherent explosion characteristics of refrigerants. This paper studied the explosion characteristics of refrigerant 2, 3, 3, 3–tetrafluoropropene (R1234yf) at different concentrations and initial pressures based on a 20 L experimental apparatus. The experimental results illustrated the peak overpressure of R1234yf increased with the rise of initial pressure. At a constant ambient temperature of 25 °C, the maximum rate of pressure rise and deflagration index showed an N-shaped trend with the increase of the refrigerant concentration from 6.8% to 10%. The maximum rate of pressure rise and deflagration index increased first and then decreased with the increase of the refrigerant concentration at atmospheric pressure, while they presented an M-shaped trend at pressurization condition. The peak overpressure, the maximum rate of pressure rise, and deflagration index reached 0.742 MPa, 4.04 MPa s−1, and 1.1 MPa.m.s−1 with a refrigerant concentration of 7.6%, respectively, which were less than those of refrigerant propane and difluoromethane (R32) at the optimal concentration. Furthermore, R1234yf exhibited better safety performance compared with refrigerant R32 in the same flammability classification. 相似文献
85.
人类只有一个地球,世界上任何资源都是稀缺的.因此对资源"减量化、再利用、再循环(5R)"的原则是每一位地球人所赋予的神圣职责.逆向物流是以环境保护为目的的物料回收,它包含产品返回、物品再利用、废弃物处置、再加工处理、维修与再造等物流活动.目前人们对逆向物流的认识,已经从单纯的废弃物回收,上升到资源"再利用和再循环"的高度. 相似文献
86.
87.
D301R树脂对铬(Ⅵ)的吸附性能研究 总被引:7,自引:0,他引:7
在pH=2.63的HAc-NaAc体系中,D301R树脂对Cr(Ⅵ)有较好的吸附性。树脂的静态饱和吸附容量为206mg/g。用 5%NH4CI和10%NH3·H2O的混合液能定量洗脱,测得吸附速率常数k298=2.52×10~(-4)/s。吸附过程遵守Freundlich等温式。298K 时测得吸附热力学参数△H=3.33kJ/mol、△G=-6.96kJ/mol、△S=34.5J/(mol·K)。树脂功能基与Cr(Ⅵ)的配位比为1:1。 相似文献
88.
The honeybee Apis mellifera has evolved in different environments and has developed different ecotypes. The objective of the Honeybee Genetic program in Argentina (MeGA) is to select honeybees adapted to different regions in the country using an important number of colonies as base population. In the last years, morphometric analyses are being incorporated into the Program as a tool for characterization of genetic materials; this fact has motivated the present work. A random sample of honeybee workers (250) was taken from 30 colonies situated in different regions in the country. The proboscis, right hind leg, right forewing and hind wing were placed on a slide and the following variables were measured: length and width of forewing and hind wing, different angles and length of wing veins, the length of the tibia, femur and metatarsi, the width of the metatarsi and the length of the proboscis. Thirty morphometrical variables were analyzed and the distribution and relation between them were recorded. 相似文献
89.
90.
Two kinds of disparities pervade China and threaten its well-being. The first, regional disparities focus on levels of economic development, which vary considerably across China. The second is largely a corollary of the first, referring to mismatch in energy supply and demand, with some places suffering severe shortages while others are blessed with significant surpluses. Western China enjoys the dubious distinction of recording the country's lowest levels of economic development while, paradoxically, being blessed with plentiful reserves of energy and non-energy minerals. Turning those surplus resources to good account through transferring them to minerals and energy-hungry Eastern China is seen by policy-makers as something of a panacea. Not only will such a strategy significantly boost Western China's economic prospects, but it will eliminate the resource shortages currently constraining the East's vibrant growth. The issues of regional disparities, energy mismatches and transfers of these resources are discussed, with attention given to both spatial and time perspectives. The paper concludes with a cautious endorsement of the policy initiatives that promote the strategy of mineral transfers. 相似文献