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911.
912.
机器振动对厂房结构影响的检测及分析 总被引:5,自引:0,他引:5
应用振动测试方法,对机器振动对厂房结构的影响进行检测及分析.检测结果分析表明,在机器振动产生的动荷载作用下,厂房结构振动响应不满足工程结构安全要求.分析了其原因并提出应采取的有效措施,为对厂房结构进行安全评价提供了可靠的科学依据. 相似文献
913.
B. Bobee P. Boucher H. Demard 《Journal of the American Water Resources Association》1980,16(4):729-737
ABSTRACT: The importance of estimating peak water demands for determining the dimensions of pipe size and meters which provide household water to multifamily residences is examined. Several methods utilized in North America and Europe are examined. The analysis makes clear the necessity of studying the peak water demand through statistics based on local data concerning multifamily residences. For different periods of return, the peak demand of a given apartment building is related to its size (the number of apartments) in order to compare the results obtained with existing formula. By use of Ridge-regression technique, the relationship between peak water demand, and building size (number of apartments) and available pressure is established. It can be concluded that peak demand can be estimated with the square root of number of apartment units in the building and the cube root of water pressure. 相似文献
914.
915.
Effects of uncertainty, transmission type, driver age and gender on brake reaction and movement time
PROBLEM: Braking time (BT) is a critical component in safe driving, and various approaches have been applied to minimize it. This study analyzed the components of BT in order to assess the effects of age, gender, vehicle transmission type, and event uncertainty, on its two primary components, perception-reaction time and brake-movement time. METHOD: Perception-reaction time and brake-movement time were measured at the onset of lights for 72 subjects in a simulator. The six experimental conditions were three levels of uncertainty conditions (none, some, and some + false alarms) and two types of transmission (manual and automatic). The 72 subjects, half male and half female, were further divided into three age groups (mean of 23, 30, and 62 years). Each subject had 10 trials in each of the three levels of uncertainty conditions. RESULTS: Transmission type did not significantly affect either perception-reaction time or brake-movement time. Perception-reaction time increased significantly from 0.32 to 0.42 s (P < .05) as uncertainty increased but brake-movement time did not change. Perception-reaction time increased (from 0.35 to 0.43 s) with age but brake-movement time did not change with age. Gender did not affect perception-reaction time but did affect brake-movement time (males 0.19 s vs. females 0.16 s). IMPACT ON INDUSTRY: At 90 km/h, a car travels 0.25 m in 0.01 s. Consequently, even such small effects multiplied by millions of vehicle-kilometers can contribute to significant savings in lives and damages. 相似文献
916.
针对炭素焙烧炉含尘低浓度高温沥青烟,优化设计方案,采用干式、湿式预处理和静电净化两级处理,先除去大粒径烟尘,降低烟尘温度,降低电阻率,后静电净化沥青烟。系统具有自动控制,节电节能,除尘效率高等特点。 相似文献
917.
中国科技人才资源的地区和部门分布具有明显的区域差异.在三大地带间、地区内和各省市间差异程度不同且有扩大趋势,在三个重要部门中配置也表现出明显的地域差异.根据科技人才资源赋存状况及部门配置的区位熵值,将各省市区分成5种类型:科技人才资源高度型、中高度型、中度型、中低度型、低度型,这些区域类型与我国的区域经济发展格局相适应. 相似文献
918.
我国石油矿场普遍使用重锤式防碰天车装置,针对其使用过程中存在的问题,经改进设计后,生产出结构简单而新颖的双重锤式防碰天车装置。经现场试验表明,该装置具有刹车灵敏、安全、可靠性高、寿命长、限位调整方便、制造成本低和技术经济效益和社会效益显著等优点,深受现场使用者的欢迎 相似文献
919.
Aristeo Renzoni 《Environmental management》1992,16(5):597-602
Following the Minamata events, an extraordinary number of studies concerning mercury toxicity and human health have been undertaken.
Particular attention has been given to the evaluation of the dose-response relationship, i.e., the body burden at which (evaluated
through the mercury analyses in blood or hair) the risk of poisoning begins. The results of a comparative study concerning
levels of mercury in the hair of fishermen living in small islands who eat seafood more than four times per week show that
in two areas only, and only in a few cases in these areas, the mercury in the hair exceeds the limit at which a possible risk
could exist. In fact, the limit of 50 mg/g of total mercury in the hair (indicated as the lower limit above which a possible
risk could occur) is surpassed by nine fishermen out of a total of 39 at station 1 and by four fishermen out of a total of
26 at station 3. The average value at station 1 is 36.38 mg/g and that at station 3 is 30.31 mg. Many countries have set legal
limits of mercury for seafood, but evidently the system does not offer a true protection for man. Only the provisional tolerable
weekly intake (PTWI), as repeatedly suggested by WHO, should be considered the best guideline to prevent possibly harmful
consequences. 相似文献
920.
Small mammals are important predators of gypsy moths (Lymantria dispar L.), which are major defoliators of deciduous forests in the northeastern United States. Abundance and habitat relationships
of small mammals were studied during summers 1984 and 1985 on forested sites at Moshannon and Rothrock state forests in two
physiographic regions of Pennsylvania (Allegheny High Plateaus Province and Valley and Ridge Province, respectively) that
varied in potential susceptibility to defoliation. The white-footed mouse (Peromyscus leucopus), which is a major vertebrate predator of gypsy moths, was the most common small mammal on all sites. Of the four common
species, northern short-tailed shrews (Blarina brevicauda), southern red-backed voles (Clethrionomys gapperi), and white-footed mice were more abundant at Moshannon compared to Rothrock State Forest, but masked shrews (Sorex cinereus) were more abundant at Rothrock. Elevation was a major factor affecting abundance and distribution of small mammals. Because
of the greater abundance of small mammals and more suitable physiographic features at Moshannon compared to Rothrock State
Forest, small mammals may be more effective as predators on gypsy moths in the Allegheny High Plateaus than the Valley and
Ridge Province of Pennsylvania. 相似文献