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751.
Conditions for reproduction of the red king crab Paralithodes camtschatica (Tilesius) on scallop plantations in Primorye have been studied. It has been found that the settling of larvae and the growth of juveniles to the size sufficient for their survival take place only in the cleanest water areas of Peter the Great Bay. Solar activity (expressed as the Wolfer number) is one of the most important abiotic factors affecting P. camtschatica reproduction. The population dynamics of juvenile crabs are characterized by fluctuations with two-year and five-year cycles.  相似文献   
752.
Phenotypic diversity in populations of Polyommatus icarus Rott. (Lepidoptera, Lycaenidae) is regarded as a component of the ecocenotic strategy of the species, trends in which may serve as markers characterizing the state of natural populations.  相似文献   
753.
沈阳市生态城市建设对策探讨   总被引:1,自引:0,他引:1  
介绍了国内外生态城市建设情况,介绍了沈阳生态市建设现状,从政府引导、环保机制完善、生态产业培植以及生态文化建设等方面提出对策。  相似文献   
754.
在滇池生态安全调查与评估研究成果的基础上,进一步阐述了滇池流域存在的生态…安全问题,以社会经济调控、水土资源调控、水环境污染控制、水生态调控、管理支撑体系为核心内容构建滇池流域生态安全保障策略,同时对滇池流域生态安全保障策略进行了目标可达性分析。  相似文献   
755.
PM2.5是指大气中动力学直径≤2.5μm的颗粒物,也称为可入肺颗粒物。北京的大气污染是我国在快速发展过程中出现的典型的城市大气环境问题的代表,具有明显的烟煤型污染与光化学污染相结合的复合型污染特征,北京市PM2.5的污染已经相当严重。为了进一步研究北京市PM2.5的特性,对北京市PM2.5的污染特征、化学组成、源解析方面进行探讨,并提出了相应的防治对策。  相似文献   
756.
基于BP神经网络的导弹环境适应性评估及对策   总被引:1,自引:1,他引:0  
论述了转型期海军战术导弹开展环境适应性研究的必要性和紧迫性,分析了环境因素的影响。选取典型型号的海军战术导弹为研究对象,给出了8种严重影响导弹的环境适应性因子。结合BP神经网络算法建立了环境适应性模型,并对环境适应性水平进行了仿真评估分析。仿真结果表明,该模型具有良好的评估效用。根据仿真结果,针对不同时期的导弹提出了相应的环境适应性对策。  相似文献   
757.
虚拟水是解决水资源短缺和粮食安全问题的新途径,是目前国际新兴的研究热点。文中系统地阐述了虚拟水的概念和内涵,归纳总结了关于产品的虚拟水含量的计算方法,包括基于不同产品类型区别计算的方法和产品生产树的方法。并且介绍了虚拟水的应用情况,还对今后的研究方向进行了探讨。  相似文献   
758.
Abstract

With the further development of socialist market economy, the mobility of factor markets in China, especially the labor market, is strengthened. Externalities interacts with the agglomeration of productive factors. Under the framework of new economic geography, this article presents a theoretical model involving the endogenous population density affected by urban externalities. Results show that the population density is more concentrated around the center because the degree and extent of interaction between individuals intensifies when the distance from the center decreases. When there are several externalities resources, the aggregation of externalities changes the configuration of spatial factor allocation. These results fit well with the empirical facts about the decreasing density of floating population along the cities of Guangzhou, Dongguan and Shenzhen in Guangdong Province which is situated in the eastern coast of the Pearl River Delta. We find that under the impacts of externalities released from Hong Kong into the coast, floating population was more concentrated around Shenzhen and Dongguan, which are more adjacent to Hong Kong compared with Guangzhou City.  相似文献   
759.
Abstract

The measurement of urban population carrying capacity is the basis for cities’ sustainable development. However, the traditional study on population carrying capacity which was based on food supply is not applicable to the single urban area. This paper built a model for the analysis of urban carrying capacity, and took Haidian District in Beijing as an example to calculate the urban carrying capacity of Haidian District in the future, which was the basis for the improvement of the population carrying capacity. This study would also provide a reference to the measurement of the urban population carrying capacity for other cities and districts in China.  相似文献   
760.
The economic marketability of a brachiopod, Lingula was studied at three coastal mangrove sites, specifically based on socioeconomic parameters from 10 villages that utilized Lingula along Pearl Bay, Beilun Estuary Marine Nature Reserve, China. The significantly highest density of Lingula was at Jiao Dong (48.2 ± 35.14 individual/m2) whereas the biomass of Lingula was highest (0.76 ± 0.22 g/individual) at Gui Lao Bu. The shell size of the largest specimen was still less than that in other references. The socioeconomic study of the population related to Lingula involved a small group, and no relationship could be determined among the parameters of age range, education level, occupation, and financial status. The total economic value (320,927.4 Yuan) was based on the value of consumption whereas the value from sales was very low as recorded from Shan Xin over a three-month season. Analysis of the results to determine strengths, weaknesses, opportunities, and threats was undertaken to identify the potential of Lingula sp. to be promoted and supported in the market as a novel source of income for the local community who are associated with mangrove resources; and also to examine its potential as a new food source for the rapidly growing population of China.  相似文献   
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