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181.
以磁学参数作为环境重金属污染的一项指标,对西安市街道灰尘进行了系统的采样和测定.结果显示,磁化率可以反映西安市的整体污染水平.街道灰尘磁化率值较高、频率磁化率较低,二者呈显著负相关,表明街道灰尘磁性增强源于人类活动影响.磁化率随温度变化曲线表明,受电厂影响的样品主要含磁铁矿,而污染源较复杂的样品则含有磁赤铁矿、赤铁矿以及少量铁单质.磁化率与交通污染导致的Pb、Ba等元素及冶金行业带来的Cu、Cr等元素间有较好的相关性,表明西安市主要污染物来自交通污染及冶金行业排放.在局部范围内,磁化率与元素的相关性随元素种类的不同而具有明显的差异,表明不同区域内导致磁化率升高的人为活动存在差异. 相似文献
182.
讨论一种微波、毫米波电磁材料特性和参数宽频带测量方法——自由空间法。给出了该测量方法的测试原理和基于国产AV3630幅相接收机为基础的测试系统构成及系统扩频方法,论述了自由空间测试法需注意的关键技术问题。 相似文献
183.
184.
半干旱半湿润地区HSPF模型水文模拟及参数不确定性研究 总被引:9,自引:0,他引:9
本研究选取半干旱半湿润地区北京妫水河流域2005—2007年和2008年月径流数据为率定期和验证期,建立HSPF水文模型进行径流模拟,结合人工率定和PEST自动率定程序进行参数优选,并通过GLUE方法分析模型参数不确定性.通过Monte-Carlo随机采样得到30000组参数组合,分析参数与似然值散点图,把参数分为敏感参数(LZSN、AGWRC)、区间敏感参数(BASETP)和不敏感参数(AGWETP、INFILT、CEPSC、DEEPFR、UZSN、INTFW、IRC).针对比较敏感的参数LZSN、AGWRC和BASETP分析其相关性,发现LZSN和AGWRC相关性较强.模型存在大量"异参同效"现象,表明影响结果的是参数组合而不是单一参数.进一步计算90%置信度下的不确定性范围,发现不确定性范围与径流大小密切相关,径流愈大其不确定性范围愈大,反之亦然.本文对参数不确定的分析研究可为HSPF模型在区域尺度水文预测等提供参考和依据. 相似文献
185.
Roderick G. Eggert 《Resources Policy》1985,11(2):128-140
This article compares non-fuel mineral exploration in the USSR and the USA. It examines the organization of exploration; recent trends in the level and distribution of expenditures; exploration productivity; and planning and decision making. It shows that although the sequence of exploration stages and activities is very similar in both countries, substantial differences overshadow these similarities, largely because of different economic and political systems and mineral endowments. However, the article concludes that we still have much to learn before making a full comparison of Soviet and US exploration. 相似文献
186.
Ellen W. Stevens 《Journal of the American Water Resources Association》1992,28(6):1057-1068
ABSTRACT: The ability to predict extreme floods is an important part of the planning process for any water project for which failure will be very costly. The length of a gage record available for use in estimating extreme flows is generally much shorter than the recurrence interval of the desired flows, resulting in estimates having a high degree of uncertainty. Maximum likelihood estimators of the parameters of the three parameter lognormal (3PLN) distribution, which make use of historical data, are presented. A Monte Carlo study of extreme flows estimated from samples drawn from three hypothetical 3PLN populations showed that inclusion of historical flows with the gage record reduced the bias and variance of extreme flow estimates. Asymptotic theory approximations of parameter variances and covariances calculated using the second and mixed partial derivatives of the log likelihood function agreed well with Monte Carlo results. First order approximations of the standard deviations of the extreme flow estimates did not agree with the Monte Carlo results. An alternative method for calculating those standard deviations, the “asymptotic simulation” method, is described. The standard deviations calculated by asymptotic simulation agree well with the Monte Carlo results. 相似文献
187.
Louis H. Motz 《Journal of the American Water Resources Association》1990,26(2):233-239
ABSTRACT: A drain function and set of type curves were defined for the mathematical solution that represents one-dimensional flow under nonsteady conditions in a leaky aquifer for the constant drawdown boundary condition. A match point procedure was developed for determining the aquifer parameters transmissivity, storage coefficient, and leakance based on the drain function and type curves. Use of the procedure is illustrated by an example that utilizes simulated aquifer drawdowns and flowrate data. The drain function and type curves developed in this investigation include the effects of leakage for the constant drawdown boundary condition, which is not included in the existing drain function and type curve found in the literature. Thus, a new set of type curves was developed that can be used to analyze drawdowns for one-dimensional flow in a leaky aquifer with constant drawdown at a line sink. Applications would include flow to a canal or river, drainage of agricultural lands, and dewatering associated with strip mining operations. 相似文献
188.
金刚石钻进规程的实验室模拟及参数校核 总被引:3,自引:0,他引:3
金刚石钻进的钻进规程决定了钻进效率和钻头的使用寿命,也决定了钻进的安全性、可靠性和经济效益。因此,选择最佳的钻进规程尤其重要。本文通过智能微钻实验台对金刚石钻进的模拟钻进参数及其变化曲线、参数值,以及对应的钻进速度、进尺变化曲线、参数值进行分析,得到相应岩石条件下的最优钻进规程。 相似文献
189.
Li Xiuzhen Wu Kunjun Gong Peiyu Institute of Zoology Academia Sinica Beijing China 《环境科学学报(英文版)》1990,(4)
Population life tables of the army worm, Mythimna separata, were constructed and nutritional parameters of food for the larvae were examined at 5 temperatures from 16℃ to 32℃. The temperature suitable for growth and reproduction of the insect ranged from 20℃ to 28℃ with the optimum of 24℃. Their survivalship and fecundity were much poorer at 32℃ than at 16℃. Indices of population trend of the insect at these temperatures could well fitted with the parabolic curve which theoretically indicated that the population density would multiply by some 660 after one generation circle at the optimal temperature, 22.6℃, and it would decline at temperatures higher than 32.9℃ or lower than 12.3℃. Larval food intake and their AD tended to go up while their ECI and ECD to go down with a rise in temperature. These alterations in population size and feeding behavior caused by temperature would exert an important effect on their damage to crops. 相似文献
190.
镁渣配料煅烧硅酸盐水泥熟料的研究 总被引:8,自引:0,他引:8
研究了镁渣矿物组成和镁渣配料煅烧硅酸盐水泥熟料的反应动力在数和物理性能。结果表明:镁渣的主要矿物组成为γ-C2S、β-C2S、MgO、CF、C2F、FeO、CaF2等,并且镁渣可降低熟料形成反应表观活化能,加速熟料矿物的形成,提高熟料的强度。 相似文献