基于TF-熵权法的矿井通风系统可靠性可拓评价

为准确评价煤矿通风系统可靠性,提高可靠性评价的客观性与准确性,有效防止因通风系统故障而引起的煤矿安全事故,提出基于三角模糊数(TF)-熵权法的矿井通风系统可靠性可拓评价模型,首先利用德尔菲法从通风动力、通风网络等6个方面,选取29个评价指标确定矿井通风系统可靠性评价指标体系;然后,通过三角模糊数与熵权法相结合的方式确定...     

儒家“天人合一”观：构建可持续发展理论的源泉

本文从可持续发展的目标、动力、方式、调控四个方面,分析“天人合一”观巨大的道德指导价值,并从儒家的“天人合一”观出发,对可持续发展的四个方面进行新的思考和定位。     

中国可持续发展进展及其理论研究的若干思考

用可持续发展理论指导实践,建立理论与实践互动关系,是当前我国实施可持续发展战略的重要问题,本文总结了我国可持续发展理论与实吓的重要进展,指出了近期理论研究的重要内容,并提出了相应的建议。     

Urban Environmental Management in Botswana: Toward a Theoretical Explanation ofPublic Policy Failure

For the last three and half decades, Botswana has been widely acclaimed to be one of sub-Saharan Africa's longest and most stable liberal democracies, coupled with and sustained by a growing economy. One of the major contradictions, however, within this development scenario, has been the neglect of environmental problems in the country in general, and urban environmental issues in particular. Part of the problem fueling the misconception of environmental issues in Botswana is the state's domination of the country's environmental agenda. This is linked to the power disjunction in decision-making and policy processes between state and nonstate actors over the most appropriate course of action to tackle the problems. Without adopting appropriate analytical frameworks, it is possible that the problem of urban environmental mismanagement in Botswana will persist. This article examines some of the major urban environmental issues in Botswana from neighborhood, citywide, and urban–rural interface perspectives. Further, the elite theory of public policy is used to explain constraints on policy change in the urban environmental management arena in Botswana.     

Estimating the biogenic enhancement factor of weathering using an inverse viability method

To determine the influence of the biosphere on weathering we use a dynamic model of the global carbon cycle. It takes into account the most important processes for the long-term evolution of the Earth. The model is solved under a slowly changing environment of increasing solar luminosity and volcanic activity and continental area. By comparing the model results for the global average temperature with data derived from δ¹⁸O values from cherts it is possible to quantify the biogenic enhancement factor of weathering. For this purpose a newly developed inverse viability method is applied, which allows for calculating the range of possible biogenic enhancement factors consistent with the data. We find that in the Precambrian the weathering was 5.4 times lower than in the Phanerozoic era. This supports the hypothesis that the Cambrian explosion was caused by a positive feedback between the spread of biosphere, increased silicate weathering, and a consequent cooling of the climate.     

The influence of social experience on cooperative behaviour of rats (Rattus norvegicus): direct vs generalised reciprocity

Cooperation among non-kin has been attributed sometimes to reciprocal altruism: Two or more individuals exchange behaviour that benefits the respective partner. According to direct reciprocity, cooperation is based on past behaviour of a known partner. In contrast, in generalised reciprocity, cooperation is based on anonymous social experience where the identity of the partner is irrelevant. In a previous study, female Norway rats (Rattus norvegicus) were found to cooperate according to a generalised reciprocity mechanism. In this study, we tested whether Norway rats would also cooperate as predicted by a direct reciprocity mechanism and whether direct reciprocity would cause a higher propensity to cooperate than generalised reciprocity. Focal animals were experimentally manipulated to receive social experience from known or unknown, helpful or defecting partners in an instrumental cooperative task. Our first experiment shows that rats are more helpful towards a partner from which they had received help before than towards a partner that had not helped (i.e. direct reciprocity). Our second experiment revealed that after receiving help by others, rats were more helpful towards a partner from which they had received help before than towards a new partner (i.e. direct reciprocity generated a higher cooperation propensity than generalised reciprocity). We conclude that in female Norway rats, the tendency to cooperate is influenced by partner-specific information. To our knowledge, this is the first study to demonstrate direct reciprocity in rodents, and it is the first study testing direct vs generalised reciprocity in animals.     

Time stress,predation risk and diurnal–nocturnal foraging trade-offs in larval prey

Insect larvae increase in size with several orders of magnitude throughout development making them more conspicuous to visually hunting predators. This change in predation pressure is likely to impose selection on larval anti-predator behaviour and since the risk of detection is likely to decrease in darkness, the night may offer safer foraging opportunities to large individuals. However, forsaking day foraging reduces development rate and could be extra costly if prey are subjected to seasonal time stress. Here we test if size-dependent risk and time constraints on feeding affect the foraging–predation risk trade-off expressed by the use of the diurnal–nocturnal period. We exposed larvae of one seasonal and one non-seasonal butterfly to different levels of seasonal time stress and time for diurnal–nocturnal feeding by rearing them in two photoperiods. In both species, diurnal foraging ceased at large sizes while nocturnal foraging remained constant or increased, thus larvae showed ontogenetic shifts in behaviour. Short night lengths forced small individuals to take higher risks and forage more during daytime, postponing the shift to strict night foraging to later on in development. In the non-seasonal species, seasonal time stress had a small effect on development and the diurnal–nocturnal foraging mode. In contrast, in the seasonal species, time for pupation and the timing of the foraging shift were strongly affected. We argue that a large part of the observed variation in larval diurnal–nocturnal activity and resulting growth rates is explained by changes in the cost/benefit ratio of foraging mediated by size-dependent predation and time stress.     

A Graph-Theory Framework for Evaluating Landscape Connectivity and Conservation Planning

Abstract:  Connectivity of habitat patches is thought to be important for movement of genes, individuals, populations, and species over multiple temporal and spatial scales. We used graph theory to characterize multiple aspects of landscape connectivity in a habitat network in the North Carolina Piedmont (U.S.A).^. We compared this landscape with simulated networks with known topology, resistance to disturbance, and rate of movement. We introduced graph measures such as compartmentalization and clustering, which can be used to identify locations on the landscape that may be especially resilient to human development or areas that may be most suitable for conservation. Our analyses indicated that for songbirds the Piedmont habitat network was well connected. Furthermore, the habitat network had commonalities with planar networks, which exhibit slow movement, and scale-free networks, which are resistant to random disturbances. These results suggest that connectivity in the habitat network was high enough to prevent the negative consequences of isolation but not so high as to allow rapid spread of disease. Our graph-theory framework provided insight into regional and emergent global network properties in an intuitive and visual way and allowed us to make inferences about rates and paths of species movements and vulnerability to disturbance. This approach can be applied easily to assessing habitat connectivity in any fragmented or patchy landscape.     

低温等离子体技术在环境工程中的研究进展

低温等离子体技术是一种用来处理环境污染问题的高新技术。介绍了低温等离子体的概念和去除污染物的机理,阐述了该技术在国内外环境工程中的应用现状,分析其存在的问题,并指出今后的发展方向。     

杭州西湖水体富营养化的控制

本文综述了杭州西湖水体富营养化的状况,并为西湖水体富营养化的控制提出了建议和对策。