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991.
通过分析安徽省地质环境特点,选取其中8个地质环境因子建立了地质环境评价指标体系,采用专家打分法确定权重,利用层次分析法进行了地质环境承载能力综合评价。结果显示,安徽省地质环境承载能力总体较强;仅大别山区、黄山市、池州市-铜陵市-芜湖市等矿山集中开采区承载能力较弱,面积占比4.78%。根据安徽省地质环境承载能力特征,提出了针对对大别山区、皖南山区开展地质环境保护和针对安徽省地下水超采区进行修复的建议,为国土空间开发提供科学参考。  相似文献   
992.
Due to its large heat transfer area and stable thermal performance,the middle-deep coaxial borehole heat exchanger (CBHE) has become one of the emerging technologies to extract geothermal energy. In this paper,a numerical modeling on a three-dimensional unsteady heat transfer model of a CBHE was conducted by using software FEFLOW,in which the model simulation was compared with the other studies and was validated with experimental data. On this basis,a further simulation was done in respect of assessing the influencing factors of thermal extraction performance and thermal influence radius of the CBHE. The results show that the outlet temperature of the heat exchanger decreases rapidly at the initial stage,and then tended to be stable; and the thermal influence radius increases with the increase of borehole depth. The heat extraction rate of the borehole increases linearly with the geothermal gradient. Rock heat capacity has limited impact on the heat extraction rate,but has a great influence on the thermal influence radius of the CBHE. When there is groundwater flow in the reservoir,the increase of groundwater velocity will result in the rise of both outlet temperature and heat extraction rate. The heat affected zone extends along with the groundwater flow direction; and its influence radius is increasing along with flow velocity. In addition,the material of the inner pipe has a significant effect on the heat loss in the pipe,so it is recommended that the material with low thermal conductivity should be used if possible.  相似文献   
993.
Livestock grazing is one of primary way to use grasslands throughout the world, and the forage-livestock balance of grasslands is a core issue determining animal husbandry sustainability. However, there are few methods for assessing the forage-livestock balance and none of those consider the dynamics of external abiotic factors that influence forage yields. In this study, we combine long-term field observations with remote sensing data and meteorological records of temperature and precipitation to quantify the impacts of climate change and human activities on the forage-livestock balance of alpine grasslands on the northern Tibetan Plateau for the years 2000 to 2016. We developed two methods: one is statical method based on equilibrium theory and the other is dynamic method based on non-equilibrium theory. We also examined the uncertainties and shortcomings of using these two methods as a basis for formulating policies for sustainable grassland management. Our results from the statical method showed severe overgrazing in the grasslands of all counties observed except Nyima (including Shuanghu) for the entire period from 2000 to 2016. In contrast, the results from the dynamic method showed overgrazing in only eight years of the study period 2000-2016, while in the other nine years alpine grasslands throughout the northern Tibetan Plateau were less grazed and had forage surpluses. Additionally, the dynamic method found that the alpine grasslands of counties in the northeastern and southwestern areas of the northern Tibetan Plateau were overgrazed, and that alpine grasslands in the central area of the plateau were less grazed with forage surpluses. The latter finding is consistent with field surveys. Therefore, we suggest that the dynamic method is more appropriate for assessment of forage-livestock management efforts in alpine grasslands on the northern Tibetan Plateau. However, the statical method is still recommended for assessments of alpine grasslands profoundly disturbed by irrational human activities.  相似文献   
994.
995.
水资源是制约干旱、半干旱区社会经济发展的关键因素,结合联合国可持续发展目标(SDGs)指标和美丽中国评价指标,以水资源承载力为核心,从水资源系统、社会系统、经济系统、生态环境系统、协调系统5个方面构建指标体系,基于熵权法确定权重,评价2001-2017年黑河流域各县区水资源承载力及时空分布。结果表明:(1)当前水资源利用效率水平下,2010年以来黑河流域大多数县区GDP均超过最大承载能力,而人口则在2010年以前已超载。(2)从水资源承载综合评价结果来看,2001-2015年随着生态输水工程的进一步实施,水资源承载力有所好转,但中下游波动较大,水资源形势依然十分严峻。(3)控制不断扩展的绿洲面积,减少高耗水农作物种植面积,实施合理用水总量控制和定额管理措施,是减缓水资源压力的重要措施。  相似文献   
996.
This paper studies the magnetic hysteresis and refrigeration capacity of Ni--Mn--Ga alloys in detail during heating and cooling isothermal magnetisation processes. The Ni--Mn--Ga alloys show larger magnetic hysteresis when they transform from austenite to martensite, but smaller magnetic hysteresis when they transform from martensite to austenite. This behaviour is independent of either the pure Ni--Mn--Ga alloys or the alloys doped with other elements. Because of the existence of the magnetic hysteresis, the relation between the magnetic entropy change and refrigeration capacity is not simply linear. For practical consideration, magnetocaloric effect of Ni--Mn--Ga alloys should be investigated both on cooling and heating processes.  相似文献   
997.
This paper provides an analytical review of the development of distant water fisheries and the implementation of vessel monitoring systems (VMS) in Taiwan. Taiwanese distant water fisheries have gone through several stages in development: rebirth from the damage of World War II up until the early 1970s, stagnation during the mid-1970s to early 1980s, unbridled growth in the late 1980s to a peak in the 1990s–early 2000s, and a stage of disruption and transformation since the mid-2000s. There were two major fisheries in this stage: tuna and squid, both of which rank between the world's first and third largest. Development was mainly driven by national promotion programs and vessel-building restricting policies; and international influences such as oil crises, declaration of exclusive economic zones, and legal arrangements that stimulated strengthening of international management measures. Growth in Taiwan's over-developed fisheries has outpaced the incommensurately scaled Taiwanese fisheries management sector that has not expanded in parallel with the fisheries. Monitoring of vessel activities remains a major management issue. VMS, which can provide both national and international bodies with an essential monitoring capability for ensuring resource management, was found to be one of the important solutions to this issue. The system, however, was initially unacceptable to the fishers, and the government has transformed external pressures arising from international arrangements and management measures into a force for promoting installation of VMS on Taiwanese fishing vessels. This has occurred in stages: a trial period during 1989–1992; initial development during 1994–1996; expansion during 1996–2004; and a more mature stage of enhanced implementation from 2005 to the present.  相似文献   
998.
自升式平台桩脚在含硬壳层地基中的插深分析   总被引:1,自引:0,他引:1  
存在硬壳层的层状地基承载能力分析是自升式钻井平台桩脚插深分析的关键,但是目前对硬壳层承载能力的确定还没有成熟可行的理论计算方法。一般的针对非均质层状地基的承载力计算方法,因参数较多,计算步骤繁琐,很难广泛应用于实际的平台桩脚入泥深度分析中。文中主要介绍了存在硬壳层的层状地基承载力的分析方法与过程,根据应力扩散原理推导并做适当的简化得到硬壳层承载力修正方法。简化后的修正方法能满足一般硬壳层承载力分析的需要,并使平台插桩深度分析计算过程变得简便。通过在实际工程的应用,得到的实测结果与理论计算值也较为一致,说明了用此方法分析硬壳层地基的平台插桩是合理、实用的。  相似文献   
999.
音乐欣赏是人们对音乐本身产生认识、发生共鸣获得审美愉悦的过程,在音乐欣赏中,人们必须学会倾听音乐、体验音乐情感,掌握一定的音乐基础知识,懂椁音乐欣赏技巧,才能培养音乐审美能力并提升音乐艺术的审美情趣。  相似文献   
1000.
A fundamental element of sustainable development is that humans live within nature's biological capacity. Quantifying this, however, remains a significant challenge for which there are many emerging tools. The concept of the Ecological Footprint is one such accounting tool for comprehensive assessment of the status of sustainable development, based on integration of resource consumption and land capacity, reflecting the human impact on the environment. A region's development is defined as unsustainable when the Ecological Footprint surpasses the biological capacity. In this paper, the Ecological Footprint concept Was applied in assessing the development of Yunnan Province, China in a period between 1988 and 2006. The results showed that the Ecological Footprint per capita in Yunnan rose from 0.854 gha in 1988 to 2.11 gha in 2006. Ecological deficit, defined as when the human demand on the land surpasses the regions biological productive capacity, emerged in 1991 and quickly increased from 0.02 gha in 1991 to 1.05 gha in 2006. The increase in the ecological deficit is primarily a result of the rapid increase in population and consumption level. To achieve sustainable development in Yunnan, production and consumption rates need to be modified.  相似文献   
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