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971.
为研究系统故障演化过程中,通过原因事件得到的结果事件发生可能性与直接试验得到的结果事件发生可能性不同的问题,定义系统故障演化过程的不连续现象,研究不连续现象出现的原因和消除方法。根据不连续现象的程度将原因分为3层,第1层是基本的原因事件、结果事件或传递的概率错误造成的不连续;第2层是因素对应错误造成的概率错误;第3层是演化结构不清造成的错误。针对这些错误提出消除方法,基本方法包括试验法、结构分析法和逻辑推理法;第2层次使用空间故障树和因素空间等方法;第3层使用三值逻辑等方法。研究结果表明:导致不连续的原因是演化过程的结构性问题,消除的方法应根据实际情况进行选择和变化。 相似文献
972.
近年来,生态足迹作为可持续发展的有效度量工具之一,获得了广泛关注。在参阅相关文献的基础上,系统总结了生态足迹核算方法及其应用特点和趋势,结果表明,(1)在核算方法上尚存争议,目前主要的核算方法有3种:传统土地足迹法;能值足迹法;投入产出足迹法。(2)从静态足迹核算朝时间序列足迹分析和动态情景足迹预测演化。(3)尽管在各个尺度上都有应用,但生态足迹目前仅被看作是交流工具,用于决策分析的意义不大。拓展其在企业及其产品系统的应用,将是其应用价值体现的一个突破口。(4)生态足迹作为一系列指标的一部分时,发挥作用更大。(5)生态足迹应加强与现有核算体系(如GDP)的衔接,增加其被决策者接纳的可能性。 相似文献
973.
首先,阐述了美国ACI318-08规范中钢筋混凝土受弯、受压构件的设计原理和基本假定。与我国混凝土结构设计规范不同,ACI318-08规范是根据构件的受力破坏形态来确定名义抗压和抗弯承载力的折减系数的,相对于延性破坏,脆性破坏构件的承载力折减较多。然后,由平衡条件、平截面假定及Newton迭代格式,推导出林聪悟-直线法的计算公式。编制程序实现该算法时,须根据最大、最小配筋率的规定对迭代区域进行限定;在确定P-M相关曲线上的拐点位置的基础上,实现中性轴高度在曲线上的分段迭代。通过在曲线拐点处设置微小增量及自动调整中性轴高度等方法,解决了程序计算时可能出现的迭代发散问题。算例表明,所编制程序的计算结果具有很高的精度。 相似文献
974.
Succession of aquatic microbial communities as a result of the water quality variations in continuous water 总被引:1,自引:0,他引:1
The changes of structural and functional parameters of aquatic microbial communities in continuous water on campus of Tsinghua University, China are investigated by polyurethane foam unit(PFU) method. The measured compositions of the communities include alga, protozoa, and some metazoa (such as rotifers). The measured indicators of water quality include water temperature, pH value, dissolved oxygen (DO), potassium permanganate index(CODMn), total nitrogen(TN), total phosphorus(TP) and chlorophyll- a(Chla). The trophic level, expressed by the trophic level indices(TL/c), is assessed with analytic hierarchy process and principal component analysis (AHP-PCA) method. The changing trends of the structural and functional parameters of aquatic microbial communities, such as Margalef index of diversity(D), Shannon-weaver index of diversity (H), Heterotropy index (HI), number of species when the colonization gets equilibrium(Seq), colonizing speed constant(G) and time spent when 90 percent of Seq colonized in PFU ( T90% ), are also analyzed. The experimental results showed the succession of aquatic microbial communities along the water flow is consistent with the water quality changes, so the parameters of microbial community can reflect the changes of water quality from the ecological view. 相似文献
975.
976.
Kines P Andersen LP Spangenberg S Mikkelsen KL Dyreborg J Zohar D 《Journal of Safety Research》2010,41(5):399-406
Background
The construction industry is one of the most injury-prone industries, in which production is usually prioritized over safety in daily on-site communication. Workers have an informal and oral culture of risk, in which safety is rarely openly expressed. This paper tests the effect of increasing leader-based on-site verbal safety communication on the level of safety and safety climate at construction sites. Method: A pre-post intervention-control design with five construction work gangs is carried out. Foremen in two intervention groups are coached and given bi-weekly feedback about their daily verbal safety communications with their workers. Foremen-worker verbal safety exchanges (experience sampling method, n = 1,693 interviews), construction site safety level (correct vs. incorrect, n = 22,077 single observations), and safety climate (seven dimensions, n = 105 questionnaires) are measured over a period of up to 42 weeks. Results: Baseline measurements in the two intervention and three control groups reveal that foremen speak with their workers several times a day. Workers perceive safety as part of their verbal communication with their foremen in only 6-16% of exchanges, and the levels of safety at the sites range from 70-87% (correct observations). Measurements from baseline to follow-up in the two intervention groups reveal that safety communication between foremen and workers increases significantly in one of the groups (factor 7.1 increase), and a significant yet smaller increase is found when the two intervention groups are combined (factor 4.6). Significant increases in the level of safety are seen in both intervention groups (7% and 12% increases, respectively), particularly in regards to 'access ways' and 'railings and coverings' (39% and 84% increases, respectively). Increases in safety climate are seen in only one of the intervention groups with respect to their 'attention to safety.' No significant trend changes are seen in the three control groups on any of the three measures. Conclusions: Coaching construction site foremen to include safety in their daily verbal exchanges with workers has a significantly positive and lasting effect on the level of safety, which is a proximal estimate for work-related accidents. It is recommended that future studies include coaching and feedback at all organizational levels and for all involved parties in the construction process. Building client regulations could assign the task of coaching to the client appointed safety coordinators or a manager/supervisor, and studies should measure longitudinal effects of coaching by following foremen and their work gangs from site to site. 相似文献977.
PBXN-5传爆药安全可靠性试验方法研究 总被引:1,自引:0,他引:1
为满足引信传爆序列对高可靠性、高安全性火工药剂的需求,通过小隔板试验及升降法试验对PBXN-5传爆药的输出能力和冲击波感度作了分析和研究,小样本试验发现:当施主药柱装药相同,随施主与受主间隔板厚度增加,可靠起爆概率明显降低;但随受主药柱的装药尺寸的减小,传爆概率却增大。总之,受主药柱直径越小,隔板越薄,使用可靠性越高,结合安全使用性,计算得到合适的可靠度数据,为微型火工品装药提供参数依据。 相似文献
978.
生物群落中物种多度分布(species abundance distribution)呈典型的倒J形,即其中存在许多稀有种、少量常见种.物种多度分布模型研究有助于解决森林生态恢复中的物种配置等实际问题.本研究考察了一种过分散(over-dispersion,或称超分布,即方差大于均值)的离散型分布,即具有λ和α两个参数... 相似文献
979.
980.
Roukaya Bouyakhsass Soukaina Bouaouda Abdeslam Taleb Abdelaziz Madinzi Michel Baudu Salah Souabi 《环境质量管理》2023,32(4):237-246
The estimation of leachate quantities produced in landfills is necessary to dimension the treatment plants allowing to reduce the polluting load of these effluents and consequently avoid their negative impacts on the environment. Different leachate quantification methods were used in this study to assess the leachate volume produced at the Oum Azza landfill. The water balance method give comparable estimations of leachate production to the Ouled Berjal landfill ratio. The first method showed average values between 487 and 495 m3/day for 2015, 2018, and 2019, and at the same time, the second method gave values between 470 and 477 m3/day for the same years. In contrast, the World Bank ratio showed high values that vary between 2260 and 2295 m3/day for 2015, 2018, and 2019. The on-site data and the statistical analysis showed us that the World Bank ratio is not adapted for the estimation of the leachates produced in Oum Azza landfill, while the water balance and the ratio of Ouled Berjal landfill allowed to give comparable results to reality. 相似文献