The ‘Bayesics’ of Ranked Set Sampling

Ranked set sampling can be useful when measurements are expensive but units from the popu- lation can be easily ranked. In this situation one may draw k units from the population, rank them, select one on which to make the expensive measurement, draw another k units, rank them, select one, and so on. The method was originally suggested by McIntyre (1952) in connection with pasture yields and is obviously applicable in other situations as well. Dell and Clutter (1972) and Patil et al. (1994) explain the basics from a classical point of view. Our aim is to examine the procedure from a Bayesian point of view, determine whether ranked set sampling provides advantages over simple random sampling and explore some optimality questions     

Main particulate matter components in Saxony (Germany)

Aerosol filter samples have been collected nearby the industrialised basin of Leipzig in Saxony (Germany) at the research station Melpitz of the Institut für Troposphärenforschung e.V. (IfT). Time series (1992–1998) and a three year comparison (1995–1997) of two different aerosol filter sampling systems, the Sierra-Andersen-PM 10 high volume sampler (daily sample, PM 10 inlet) and the Rupprecht and Patashnik Co. Inc. Model Partisol 2000 (weekly sample, PM 10 and PM 2.5 inlet) are presented and discussed. The comparison of the different sampling systems and strategies yields small differences between the daily and weekly samples for mass and different ions, which may be influenced by sampling duration and flow rates. A general trend of change in aerosol composition was observed: Soot and Sulphate concentrations decreased whereas Nitrate and Ammonium concentrations increased. During summers the mass of coarse particles is higher than in other seasons. One reason could be found in the occurence of longer periods of dry ground surfaces enabling reemission of crustal and biological material. The time series have been integrated in a longer historical aerosol mass trend for Saxony and do show a good agreement. Since 1990 a significant downward trend in gravimetric mass concentration was found.     

南京市小型餐饮娱乐服务业废水排放系数计算

运用数理统计学的分层抽样法对南京市2001年-2003年小型餐饮娱乐服务业废水中具有相关性的主要污染因子的排放浓度进行了统计,并计算出排放系数,提出用计算的废水排放系数征收小型餐饮娱乐服务业的排污费,实例表明,在该行业运用这一方法征收排污费是可行的。     

长江江豚监测现状及展望

长江江豚(Neophocaena asiaeorientalis)是唯一淡水生活的鼠海豚类,近年来种群数量严重下降,2013年被世界自然保护联盟红色名录列为“极度濒危”,2021年升级为我国国家一级重点保护野生动物,2022年种群有所恢复。长江江豚是长江生态系统健康的指示物种,我国科学家自20世纪50年代开始监测至今,监测方法不断更新完善,对长江江豚现状的了解也越来越充分。该文回顾了截线抽样法、水下被动声学及自动实时监测系统、无人机、环境DNA等监测方法的应用及取得的成效,分析监测方法存在的不足,预测技术发展趋势,提出改进建议,为长江江豚的监测及保护提供基本参考。     

化学吸收法采集固定污染源氨气的影响因素探究

固定污染源氨气的手工监测,干扰因素较多,其中采样环节尤为关键。实验通过催化氧化-化学发光法考察不同采样管线材质对氨气的吸附效果,离子色谱法考察化学吸收法采集氨气的吸收瓶类型、采样流量、吸收液种类、吸收液浓度及体积等采样条件对氨气吸收效率的影响。实验表明,316 L不锈钢与聚四氟乙烯对氨气的吸附较小,氨气的采样流量不宜超过1.0 L/min,棕色气泡式吸收瓶更适用于氨气样品的采集,磷酸溶液作吸收液对氨气的吸收效率较好,对于低浓度的氨气样品,应采用低流量长时间采集。     

基于ANSYS-PDS的含缺陷压力容器可靠性分析

为更准确地分析含缺陷压力容器的可靠性,提出采用ANSYS软件中的PDS模块建模求解,从本质上克服API 581压力容器可靠性分析的局限性,采用将压力容器的内径、原始壁厚、缺陷深度、压力容器内压设置为服从正态分布的随机变量的方法,基于响应面法结合蒙特卡洛法抽样分析,通过编写APDL代码,探讨含缺陷压力容器的可靠性.结果表...     

基于随机抽样推测法的LPG储槽2次爆炸事故的模型研究

在借鉴LPG储槽2次爆炸事故后果不确定分析成果的基础上,对事故过程中的不确定参数进行重新分析与选择,将孔洞上方液位高度h0,气云的TNT当量系数α,泄漏开始到点火源出现之前的持续时间t亦作为不确定分析的参数,并利用随机抽样推测的不确定分析方法,对VCE与BLEVE 2次事故后果进行重新分析,获得了与前人研究成果差异较大的结果,并由此分析这些参数对于事故后果影响的显著性。同时对2次爆炸事故的伤害距离进行了研究与分析,由于LPG的闪蒸以及参数α的影响,本案例中LPG泄漏量为总量的80%-90%以上时,2次事故的死亡半径相等且达到最小。     

Improving construction site safety through leader-based verbal safety communication

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.     

Inexpensive substrate sampler for macroinvertebrates

Assessment of aquatic macroinvertebrates is a critical component of many watershed monitoring programs and passive samplers are often used to collect long-term site data, especially in environments where active sampling is not possible. However, standard passive samplers can be expensive and lost in extreme conditions. We developed a sampler using plastic soda bottles (PSB) filled with river rock and compared its effectiveness with standard Hester-Dendy samplers in both lotic and lentic environments. Abundance, taxa richness, and macroinvertebrate composition showed no significant differences between sampler types in either habitat type. PSB samplers, which can be constructed for less than one dollar each, collected the same number of organisms and represented the same diversity as Hester-Dendy devices that cost around $38 each. In studies where funds are limited, PSB samplers appear to be suitable for passive monitoring.     

运用经验公式分析BOD5

运用经验公式分析BOD5,节省时间、人力、财力,对污染源企业用此方法是可行的。