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半潜式超大浮体连接器动力特性的一种时间序列分析方法 总被引：1，自引：2，他引：1
根据刚性模块弹性连接器 (RMFC)假设研究由 3个模块连接而成的半潜式超大浮体MobileOffshoreBase(MOB)的波浪载荷动力响应。模块和连接器动力响应根据时间序列法计算 ,这种方法包括海况模拟 ,波浪载荷计算和结构响应计算三个主要部分。通过对结构的适当简化 ,根据Airy波理论 ,Morrison公式以及流体中的结构运动方程、弹性连接器变形方程 ,计算求得MOB在不规则海况下的动力响应 ,并将其与相关文献中的结果进行比较 ,表明该方法有良好的精确性 相似文献
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手足口病（HFMD）是一种多发于儿童的常见传染病。近年来,中国HFMD发病人数逐年上升,疾病疫情也日益受到社会广泛关注。虽已有不少相关研究,但对于探测其时空异质性及量化潜在影响因子解释力的研究仍然较少。本文采用地理探测器及贝叶斯时空层次模型,对2009-2013年京津唐地区HFMD发病率的时空异质性进行分析,并量化各影响因子及其两两交互作用对HFMD发病率的解释力。结果表明：① HFMD的相对风险存在时间异质性,其发病风险在春夏季（5-7月）达到峰值,而冬季（12-次年2月）发病风险最低;② HFMD的相对风险存在空间异质性,在经济发达的地区HFMD发病率较高;③ 影响HFMD发病率时间异质性的主要气象因子为平均温度、累积降水、相对湿度,解释力分别为0.38,0.27,0.13,且交互作用都大于独自影响的作用,如平均温度和相对湿度、平均温度和降水,平均温度和风速两两交互的解释力分别为0.43, 0.40, 0.42。通过研究京津唐地区HFMD发病率的时空异质性以及影响因子的量化状况,为本地区HFMD的预防和控制提供理论依据。 相似文献
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本文以1：50000的地形图为工作底图，采用手持GPS技术、利用实地调查与分解森林资源分布图相结合的方法，对洞庭湖区植被分布状况进行了外业调绘的研究。建立了外业调绘过程中植被群落斑块最小面积和边界的确定原则及其斑块类型与编码。探讨了手持GPS实现WGS-84坐标系向1954北京坐标系的转化方法。并进行了精度估算，其点位误差≤5．8m，完全可以满足洞庭湖区植被分布外业调绘的精度要求。运用该方法进行植被分布的外业调绘，可以解决运用传统的定位测量方法在湖区定位难的问题，提高了外业作业效率。 相似文献
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《Limnologica》2020
We compared the capture efficiency of three traditional sampling methods, hand captures at day, hand captures at night and captures by commercial baited traps (“Pirat type”) with a coarse mesh size of 10 × 45 mm, for the native crayfish species Austropotamobius torrentium (stone crayfish) and Astacus astacus (noble crayfish). These capture types are applied regularly in monitoring programs. Additionally, we tested modified traps with fine mesh size to capture stone crayfish. We hypothesized that the capture efficiency of the methods is different between the two species, different sex and size classes and seasons and that modified traps with small mesh size were more effective in capturing juvenile stone crayfish than traps with coarse mesh size. Hand captures at night were found to be the most effective sampling method for both species. It generates the highest relative abundances and is the least biased method in relation to size and sex of crayfish specimen. Hand captures at day result in lower capture rates than hand captures at night. However, there is a tendency to gather more small individuals and females in comparison to the night captures. Baited traps turned out to be completely inappropriate for capturing stone crayfish; even traps modified with small mesh size were not a suitable capture method. For noble crayfish all three methods seem to be suitable, depending on the sampling purposes. The relative differences between the methods did not change significantly during the seasons. However, when capture rates of all three methods were combined, September was found to be the month where the highest capture rates were achieved as both sexes of both species were on the peak of their activity. 相似文献
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Many informal communities within urban areas in sub-Saharan Africa are heavily reliant on shallow hand-dug wells for water, but these are vulnerable to contamination from a range of sources. This paper assesses the heavy metal contamination and total coliform risk of unprotected shallow wells in Ndola, Zambia – a city struggling with contaminated surface waters from both bacteriological and potential mining waste products. One hundred and twenty three shallow wells were sampled across the Ndola, and these encompassed the three main lithologies of the city. All wells lacked an internal casing, however, some wells did have covers and/or pavements surrounding the wells, albeit of dubious efficacy. Despite the lack of protection, the quality of water used abstracted from these wells generally met the World Health (WHO) guidelines for heavy metals (with the exception of Al) and total coliforms (although, this was highly variable). The quality of shallow well water varied across Ndola relative to the underlying geology, where total recoverable concentrations were typically lowest in granite-gneiss. Dissolved load concentrations were lowest in dolomite-limestone, highlighting the role of aquifer geology in acting as a buffer against metal toxicity. Our study illustrates that shallow wells, within the appropriate geological units, may provide a safe and reliable source of drinking water. Well protection is, however, needed to ensure that the proliferation of shallow well use does not lead to regional degradation of the groundwater resource. There is an immediate need to invest in promoting internal well casing during the construction of shallow wells, concomitant with investment and education into protecting wells at the surface, despite the current relatively low level of contamination in wells without protection. 相似文献
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利用贝叶斯时空模型分析山东省手足口病时空变化及影响因素 总被引：1，自引：0，他引：1
手足口病是一种常见的传染病,多见于5岁以下儿童。近年来,中国手足口病发病人数逐年上升,疾病疫情也越来越受到公共卫生部门与社会大众的关注。虽然已有不少手足口病相关的研究,但对其时空变化及影响因素驱动效应的研究仍然较少。本文采用贝叶斯时空模型,对2008年山东省手足口病高发时间段（5-8月）的发病时空演变特征进行系统分析,并探究影响手足口病发病风险的气象因素。结果表明：① 空间上不同区县的手足口病发病风险存在一定差异,且区县间的发病风险随时间变化趋势也各不相同;② 5月和6月手足口病发病风险明显高于整个研究阶段（5-8月）平均发病风险;③ 对手足口病发病风险影响较大的气象因素依次是：周平均温度、平均风速和平均气压。本文针对山东省手足口病时空演化特征及气象影响因素的研究,能为高发时间段内手足口病的区域化防控提供科学依据。 相似文献
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The rural population of parts of northern and western Namibia uses hand dug wells for their domestic water supply, partly because no other source (e.g., deep tube wells) is available, but also as a substitute for pipeline water that is often perceived as being too expensive. The water quality of these wells is usually not monitored or controlled, thus a study has been carried out in four study areas in Namibia: southern Omusati/Oshana area, Okongo/Ohangwena area, Omatjete/Omaruru area, Okanguati/Kunene area. Hand dug wells have been tested for on-site parameters: electric conductivity, pH and temperature while samples were taken for major inorganic constituents and several minor and trace constituents including fluoride and nitrate. In addition a sampling campaign in 2010 included the determination of coliform bacteria and Escherichia coli. Results were classified according to the Namibian Water Guidelines. The constituents making the water unfit for human consumption are fluoride, nitrate, sulphate and total dissolved solids. Contamination by E. coli was indicated in nearly all wells that are used for livestock watering. For the Omatjete/Omaruru study area an isotope based study on the source of nitrate has indicated manure as a source. The range of recharge values obtained for the studied villages ranges from 1 mm/a to locally more than 100 mm/a. Overall the water resource in the shallow perched aquifers in the study areas is in many places inappropriate for human consumption. Treatment to improve the quality or introduction of protection measures is necessary to bring this resource to an acceptable quality according to national and/or international standards. 相似文献
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