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991.
992.
993.
桑蚕蛹资源及其综合开发前景 总被引:5,自引:0,他引:5
我国有桑蚕蛹资源50万t/a,干蛹蛋白质高达48.98%.氨基酸种类齐全,8种必需氨基酸占41%。目前大部分蚕蛹仅作为饲料使用,高蛋白资源的浪费极大。蚕蛹可开发20多种保健食品、纺织、轻化工产品.综合开发经济效益高.具有广阔的开发前景。 相似文献
994.
城市可持续发展与城市政府职能 总被引:3,自引:0,他引:3
胡国亮 《中国人口.资源与环境》1999,9(1):14-17
城市作为我国行政区划中重要单元和区域经济活动的中心,城市经济、社会发展直接关系着全国的发展水平,城市可持续发展在我国可持续发展中占有重要的地位。城市政府是推动城市可持续发展的首位力量。本文分析了城市可持续发展面临的主要问题,阐述了城市政府五大主要职能,探讨了城市可持续发展与城市经济社会职能的关系。 相似文献
995.
996.
沿空窄煤柱锚网带支护的巷道稳定性研究 总被引:1,自引:1,他引:0
锚杆支护是煤矿采准巷道的重要支护方式 ,沿空留巷技术是回采巷道支护技术改革的主要方面。笔者将两种技术相结合 ,用于保证回采巷道的稳定。在现场矿压观测的基础上 ,讨论了支承压力分布规律和窄煤柱护巷机理 ,运用极限平衡理论计算出护巷煤柱宽度 ,同时结合数值分析和现场巷道变形以观测结果 ,实践证明 ,只要设计参数合理 ,施工质量满足要求 ,沿空窄煤柱锚网带支护技术就可以保证回采巷道的稳定 相似文献
997.
Stable sulfur isotope ratio indicates long-term changes in sulfur deposition in the Broadbalk experiment since 1845 总被引:1,自引:0,他引:1
Archived wheat (Triticum aestivum L.) grain and straw, and soil samples from the control plot of the Rothamsted Broadbalk Experiment, located in southeastern England and established in 1843, were used to investigate the effects of dramatically changing SO2 pollution inputs on the concentrations and stable isotope ratios (delta34S) of S in the samples. Representative coal samples from UK major coal fields were also determined for delta34S. Concentrations of S showed no clear trends in either grain or straw over the 155 years from 1845 to 1999. However, grain and straw delta34S decreased rapidly from 6 to 7/1000 in 1845 to -2 to -5/1000 in the early 1970s, and since then have increased to 0.5 to 2/1000 in the late 1990s. This pattern mirrored the trend of UK SO2 emissions over the 155 years. Both grain and straw delta34S correlated strongly and negatively with UK SO2 emissions (R2 > 0.89), but the relationships were different for the pre- and post-1970 data sets. Soil delta34S also decreased considerably, from 8.2/1000 in 1865 to 3.7 to 4.5/1000 during 1965-1999. A negative delta34S value was inferred for the anthropogenic S deposited at the experimental site before 1970, and further confirmed by negative delta34S values (-6 to -10/1000) found in the coal samples from southeastern England and southern Wales. Based on the S isotope ratios, we estimated that anthropogenic S contributed 62 to 78% of the S uptake by wheat at the peak of SO2 emissions, and accounted for 28 to 37% of the topsoil S in 1965. 相似文献
998.
A hydroponic experiment was carried out to investigate the effects of iodine species and solution concentrations on iodine uptake by spinach (Spinacia oleracea L.). Five iodine concentrations (0, 1, 10, 50 and 100 microM) for iodate (IO(3)(-)) and iodide (I(-)) were used. Results show that higher concentrations of I(-) (> or =10 microM) had some detrimental effect on plant growth, while IO(3)(-) had little effect on the biomass production of spinach plants. Increases in iodine concentration in the growth solution significantly enhanced I concentrations in plant tissues. The detrimental effect of I(-) on plant growth was probably due to the excessively high accumulation of I in plant tissues. The solution-to-spinach leaf transfer factors (TF(leaf), fresh weight basis) for plants treated with iodide were between 14.2 and 20.7 at different solution concentrations of iodide; TF(leaf) for plants treated with iodate decreased gradually from 23.7 to 2.2 with increasing solution concentrations of iodate. The distribution coefficients (DCs) of I between leaves and roots were constantly higher for plants treated with iodate than those treated with iodide. DCs for plants treated with iodide increased with increasing solution concentrations of iodide, while DCs for plants treated with iodate (around 5.5) were similar across the range of solution concentrations of iodate used in this experiment. The implications of iodine accumulation in leafy vegetables in human iodine nutrition are also discussed. 相似文献
999.
胡国亮 《长江流域资源与环境》1998,7(2):115-119
阐述了武汉市可持续发展战略提出的背景和可持续发展的远景目标,全面分析了影响武汉市可持续发展的六个主要问题:城市经济发展不够,产品市场不大;城市人口增长过快,人口素质仍然不高;管理城市水平有限,城市规划起点较低;交通设施建设滞后,居民住房严重不足;污染治理任务艰巨,生态环境不尽人意;洪涝威胁仍然较大,城市发展受长江制约。并就解决这些问题提出了对策措施,重点是转变政府职能,加快交通设施建设,贯彻“科教 相似文献
1000.
The stability in the energetic materials' thermal decomposition reaction is developed from both transient mass and heat transfer equations simultaneously. The derived equation is the sufficient and necessary condition for the reaction system's stability, which was expressed as:
In this stability equation, a modified Semenov number φ is the expressed function of three kinetic parameters, i.e., n, and β and two variables, i.e., x and θ, respectively. A reaction system is stable if its evaluated modified Semenov number satisfies this stability criterion. In the case of the minimum modified Semenov number φm, we can deduce the stability equation at critical condition as
The criteria of stability for the explosives TNT, RDX, PETN and HMX were evaluated using this formula, which was expressed θc as function of x at given n, η and various β as parameters. 相似文献