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为实现水资源的循环利用与国民经济的可持续发展,必须对工业废水进行处理。在过去的几十年中,工业废水的任意排放给水资源环境和人民的身体健康带来了巨大的危害,为了杜绝这种现象的再次出现,本文对工业废水的处理方法做了如下的探讨。 相似文献
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135.
高填方路基诱发滑坡机理分析 总被引:1,自引:0,他引:1
通过对上三高速公路K92滑坡工程地质条件、滑坡特征及滑坡稳定性的分析,采用不分离接触数值模型模拟边坡的变形破坏,初步揭示了松散覆盖土层上厚度较大的高填方路基是诱发滑坡的内在机理。该类型滑坡的产生是由于路基堆载使坡体产生垂直方向的压缩变形,也使坡体向坡脚方向产生一定的挤出变形,最后诱发了推动式滑坡。 相似文献
136.
目的研究航空用继电器的失效机理。方法通过对电磁继电器进行振动与工作载荷单独施加以及二者综合加载情况下的试验方法及性能退化行为研究,实时监测继电器内部触点间接触电阻等性能参数的变化趋势,并对不同条件下触点表面的微观形貌进行对比分析。结果发现相比较工作载荷单独施加而言,振动应力的加入使得继电器的寿命大幅度降低,并使得触点表面呈现"雪花"一般的形貌。结论振动环境导致了触点之间电弧的变化,以及触点表面接触压力、接触面积和接触超程等,并通过燃弧时间和超程时间的变化趋势对其进行了验证。 相似文献
137.
北京市天然气公交车的发展现状及前景 总被引:2,自引:0,他引:2
随着石油资源短缺、城市空气污染问题的日益严重,天然气汽车作为一种实用的低排放汽车逐渐得到了重视和应用。本文首先通过汽车与能源、汽车与环境两个方面,分析说明了北京市发展天然气汽车的重要性;然后简要介绍了北京市天然气公交车的发展现状、未来几年的发展规划,最后指出了实现发展规划的条件和政策。 相似文献
138.
Ninon F. V. Meyer Ricardo Moreno Christopher Sutherland J. Antonio de la Torre Helen J. Esser Christopher A. Jordan Melva Olmos Josué Ortega Rafael Reyna-Hurtado Samuel Valdes Patrick A. Jansen 《Conservation biology》2020,34(1):207-219
Habitat fragmentation is a primary driver of wildlife loss, and establishment of biological corridors is a common strategy to mitigate this problem. A flagship example is the Mesoamerican Biological Corridor (MBC), which aims to connect protected forest areas between Mexico and Panama to allow dispersal and gene flow of forest organisms. Because forests across Central America have continued to degrade, the functioning of the MBC has been questioned, but reliable estimates of species occurrence were unavailable. Large mammals are suitable indicators of forest functioning, so we assessed their conservation status across the Isthmus of Panama, the narrowest section of the MBC. We used large-scale camera-trap surveys and hierarchical multispecies occupancy models in a Bayesian framework to estimate the occupancy of 9 medium to large mammals and developed an occupancy-weighted connectivity metric to evaluate species-specific functional connectivity. White-lipped peccary (Tayassu pecari), jaguar (Panthera onca), giant anteater (Myrmecophaga tridactyla), white-tailed deer (Odocoileus virginianus), and tapir (Tapirus bairdii) had low expected occupancy along the MBC in Panama. Puma (Puma concolor), red brocket deer (Mazama temama), ocelot (Leopardus pardalis), and collared peccary (Pecari tajacu), which are more adaptable, had higher occupancy, even in areas with low forest cover near infrastructure. However, the majority of species were subject to ≥1 gap that was larger than their known dispersal distances, suggesting poor connectivity along the MBC in Panama. Based on our results, forests in Darien, Donoso–Santa Fe, and La Amistad International Park are critical for survival of large terrestrial mammals in Panama and 2 areas need restoration. 相似文献
139.
Jennifer E. Smith Sandra K. Memenis Kay E. Holekamp 《Behavioral ecology and sociobiology》2007,61(5):753-765
When social partners vary in their relative value, individuals should theoretically initiate partnerships with conspecifics
of the highest value. Here, we tested this prediction in a wild population of spotted hyenas (Crocuta crocuta). Crocuta live in complex, fission–fusion societies structured by dominance hierarchies in which individuals vary greatly in their
value as social companions. Because patterns of association among Crocuta reflect social preferences, we calculated association indices (AIs) to examine how social rank influences intrasexual partner
choice among unrelated adults of both sexes. The highest-ranking individuals were generally most gregarious in both sexes.
Females associated most often with dominant and adjacent-ranking females. Females joined subgroups based on the presence of
particular conspecifics such that subordinates joined focal females at higher rates than did dominants. Dominants benefit
from associations with subordinates by enjoying priority of access to resources obtained and defended by multiple group members,
but the benefits of these associations to subordinates are unknown. To investigate this, we tested three hypotheses suggesting
how subordinates might benefit from rank-related partner choice among unrelated females. We found that subordinates who initiated
group formation benefited by gaining social and feeding tolerance from dominants. However, rates at which dominants provided
coalitionary support to subordinates did not vary with AIs. Overall, our data resemble those documenting patterns of association
among cercopithecine primates. We consider our results in light of optimal reproductive skew theory, Seyfarth’s rank attractiveness
model, and biological market theory. Our data are more consistent with the predictions of Seyfarth’s model and of biological
market theory than with those of skew theory. 相似文献
140.
Abstract: Concerns have been raised regarding the potential adverse effects on biological diversity of the use of living modified organisms (LMOs, which are commonly known by similar terms such as genetically modified organisms). At the international level these concerns are addressed in part by an agreement known as the Cartagena Protocol on Biosafety and include potential toxic effects of insect-resistant crops on nontarget organisms and potential ecological effects of gene flow from modified crops, fish, microorganisms, or insects to wild species or counterparts. We reviewed the protocol's main provisions, including those dealing with risk assessment and risk management, decision making on imports, documentation accompanying shipments, and liability resulting from damages caused by LMOs. A medium-term program of work has been adopted by the parties, which includes the potential contribution of conservation biologists to delivering capacity building, developing risk assessment guidance, evaluating mechanisms of potential ecological damages from LMOs, and other issues. Conservation biologists and other experts have opportunities to influence the negotiations and implementation of the protocol by providing inputs at meetings, offering expertise to governments and organizations, and participating in or developing relevant projects and initiatives. Involvement of conservation biologists in the implementation and further development of the protocol would contribute to its effectiveness. 相似文献