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排序方式: 共有833条查询结果,搜索用时 87 毫秒
521.
Matthew Ericson 《Safety Science》2010,48(5):537-543
Two-wheel tractors are known by different names: iron-ox; walking tractor; Kubota; mechanical ox; ox-machine; power tiller; rotary hoe, rotary plough, rotary tiller; Rotavator, tok-tok; and so on. They are increasingly common throughout rural areas in developing countries as they replace traditional ox-carts.This paper describes two-wheel tractors, including their dual function as an interchangeable agricultural implement and transport vehicle. Then an estimation of traffic accidents and casualties in Laos and Cambodia is presented, followed by results from a survey of 100 two-wheel tractor owners in Cambodia and Laos. The survey results include how, when and where two-wheel tractors are used as vehicles; the extent of drivers’ experience with motorised vehicles; vehicle safety standards and exposure data; and the income effects of two-wheel tractor operation. This paper is of interest to transport, agricultural and rural development authorities considering promotion and regulation of mechanised agriculture with particular regard to road safety. 相似文献
522.
Matthew F. Child 《Conservation biology》2009,23(2):241-243
523.
Bojan Gasic Matthew MacLeod Martin Scheringer Gerhard Lammel Aleksandar Pajovic Ivan Holoubek 《Environmental pollution (Barking, Essex : 1987)》2010,158(10):3230-3235
We present estimated emission source strengths of seven polychlorinated biphenyl (PCB) congeners for Banja Luka, a city that was affected by the civil war in Bosnia and Hercegovina (former Yugoslavia) in the 1990s. These emission estimates are compared to PCB emission rates estimated for the cities of Zurich, Switzerland, and Chicago, USA using an approach that combines multimedia mass balance modeling and measurement data. Our modeled per-capita emission estimates for Banja Luka are lower by a factor of ten than those for Zurich and Chicago, which are similar. This indicates that the sources of PCB emissions in Banja Luka are likely to be weaker than in the Western European and North American cities which show relatively high PCB emissions. Our emission rates from the three cities agree within a factor of ten with emission estimates from a global PCB emission inventory derived from production and usage estimates and emission factors. 相似文献
524.
James K. Sheppard Matthew Walenski Michael P. Wallace Juan J. Vargas Velazco Catalina Porras Ronald R. Swaisgood 《Behavioral ecology and sociobiology》2013,67(8):1227-1238
Populations of reintroduced California condors (Gymnogyps californianus) develop complex social structures and dynamics to maintain stable group cohesion, and birds that do not successfully integrate into group hierarchies have highly impaired survivability. Consequently, improved understanding of condor socioecology is needed to inform conservation management strategies. We report on the dominance structure of free-ranging condors and identify the causes and consequences of rank in condor populations by matching social status with the behavioral and physical correlates of individual birds. We characterized the hierarchical social structure of wild condor populations as mildly linear, despotic, and dynamic. Condor social groups were not egalitarian and dominance hierarchies regulated competitive access to food resources. Absence of kin-based social groups also indicated that condor social structure is individualistic. Agonistic interactions among condors were strongly unidirectional, but the overall linearity and steepness of their hierarchies was low. Although one aggressive male maintained the highest dominance rank across the 3-year observation period, there was considerable fluidity in social status among condors within middle and lower rank orders. Older condors were more dominant than younger birds and younger males supplanted older females over time to achieve higher status. Dominance rank did not predict the amount of time that a bird spent feeding at a carcass or the frequency that a bird was interrupted while feeding. Thus, younger, less dominant birds are able to obtain sufficient nutrition in wild social populations. 相似文献
525.
Willem M. Roosenburg William Cresko Michael Modesitte & Matthew B. Robbins 《Conservation biology》1997,11(5):1166-1172
The entrapment of diamondback terrapins ( Malaclemys terrapin) in crab pots frequently results in drowning and death of the trapped turtles. We determined the rate of capture, size, sex, and age of terrapins captured, and the potential impact crab pot mortality has on local terrapin populations. We estimated terrapin capture rates of 0.17 terrapins/pot/day in shallow water areas of Chesapeake Bay (Maryland, USA). The sex ratio of terrapins caught in crab pots was 3:2 male biased because female terrapins become too large to enter crab pots by the time they reach 8 years of age. Males, however, remain vulnerable to entrapment throughout their life. Our estimates of capture rates and local population size suggest that 15–78% of a local population may be captured in a single year. As a consequence, crab pots may be the major reason terrapins are extirpated in coastal, shallow water areas with heavy crab pot fisheries. Additionally, the selective removal of males may also contribute to female-biased sex ratios observed in this diamondback terrapin population. We developed and tested a modified crab pot that increases terrapin survival and does not reduce the number of crabs caught. Our modified crab pot maintained permanent access to air and prevented the drowning of terrapins. Additionally, our modified crab pot caught more crabs than standard commercial crab pots, suggesting that the modified crab pot could be a viable alternative to standard traps that result in terrapin mortality. 相似文献
526.
527.
《老子想尔注》认为实现理想社会的前提条件是"尊道"。道不仅是一个哲学概念,在这里被发挥成至高无上的太上老君,成为理想社会的掌控者。《老子想尔注》理想社会的理论在批判现实问题的基础上展开论述,主要讨论了君臣关系、伦理道德和贫富差异等。维系理想社会秩序的手段是道诫,道诫超越法律,内涵丰富。 相似文献
528.
529.
Flood Matthew T. D’Souza Nishita Rose Joan B. Aw Tiong Gim 《Food and environmental virology》2021,13(3):303-315
Food and Environmental Virology - Wastewater surveillance of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an emerging public health tool to understand the spread of Coronavirus... 相似文献
530.
Matthew T. Payne Mark Griffin Smith Clay J. Landry 《Journal of the American Water Resources Association》2014,50(6):1488-1500
Water scarcity presents an obstacle to economic development in the western United States. Water rights markets help improve water allocation, allowing states to derive the highest economic benefit from available resources, and supporting new uses and economic development. However, the implicit (marginal) prices of water rights attributes are uncertain. To address this problem, we apply econometric analysis to a unique dataset to estimate the implicit values that market participants place on the attributes of shares of ditch company water rights in Colorado's South Platte River Basin. Our analysis demonstrates that ditch company share buyers value proximity of water diversion, reliability of water deliveries, and temporal flexibility of water use. To assess reliability we introduce the use of the coefficient of variation to capture, in one variable, the randomness of supply from ditch company shares that are not a single water right, but a portfolio of rights with different appropriation dates. Finally, we test and correct for spatial autocorrelation for the first time in a study of water market prices. 相似文献