Comparison of two dust collection methods for reservoir indoor allergens and endotoxin on carpets and mattresses

Variable methods of dust collection may lead to uncertainty in the measurement of biomarkers. The purpose of this study was to examine the effect of two different dust collection devices on dust weight, Der p 1, Fel d 1, and endotoxin levels. We compared: (1) a nylon mesh sock inserted between the furniture attachment and the vacuum hose (the reference method) and (2) the ALK device. Duplicate dust samples were collected for 2 min from 2 m(2) of 37 living room floors and from each longitudinal half of 37 mattresses. Measurement of Der p 1 and Fel d 1 were by double monoclonal antibody enzyme-linked immunosorbent assay (ELISA) and endotoxin by a Limulus Amobocyte Lysate assay. Geometric mean ratios (95% confidence intervals) were calculated to show the differences between sampling devices for each measurement. Compared with the ALK device, the reference method collected significantly more dust from floors (sevenfold) and mattresses (threefold) and more total Der p 1, Fel d 1, and endotoxin in both sites. Floor, but not mattress, Der p 1 concentrations were also significantly higher (threefold) using our reference method. We recommend that, in order to minimize sampling device bias, allergen and endotoxin are expressed as a concentration, and that the bed is considered the major source of allergen exposure. Practical Implications Dust sampling equipment can influence the dust yield. In order to have confidence in comparisons of allergen and endotoxin reservoir levels between centers, standardization in the use of sampling equipment is important.     

Flutter reliability analysis of suspension bridges

A reliability analysis method is proposed in this paper through a combination of the advantages of the response surface method (RSM), finite element method (FEM), first-order reliability method (FORM) and the importance sampling updating method. The method is especially applicable for the reliability evaluation of complex structures of which the limit state surfaces are not known explicitly. After the accuracy and efficiency of the method are demonstrated through numerical examples, the method is used to estimate the flutter reliability of a suspension bridge. The uncertainties such as material properties, geometric parameters, structural damping ratio, flutter derivatives and extreme wind velocity at the bridge site are considered. The example suspension bridge is the Jiang Yin Bridge with a main span length of 1385 m built in China. The results show that the proposed method based on an empirical formula in which the limit state function is explicitly represented as a function of variables overestimates the flutter reliability of suspension bridges. The actual flutter reliability should be more accurately analyzed using the proposed method based on the deterministic finite element method in which the limit state function is implicitly represented as a function of variables. Finally, the most influential random variables on flutter reliability of suspension bridges are identified by using a sensitivity analysis.     

北山花岗岩裂隙地下水循环属性试验研究

 中国高放核废物预选场址位于甘肃省北山花岗岩体中。北山3号试验钻孔(BS03)位于旧井地段，地处区域性地下水系统的径流区。该钻孔是专门为场址评价而开凿的。首次采用钻孔双栓塞水文地质试验系统由该钻孔采集到分别来自144.00～156.77，208.00～238.00，430.51～445.72 m这3个层段的代表性地下水样。稳定同位素(d 2H，d18O)测试分别采用铬还原和CO2平衡法制备并且在MAT253质谱上测试。结果表明，地下水补给为本地降水，与前人关于祁连山补给的观点不同。氚采用蒸馏与电解富集流程(20倍)制备并且在QUANTLUS1220上测试。氟利昂(CFCs)采用带德国制富集装置的气相色谱测试。结果表明，3个层段地下水样品中均不含1951年以来人工热核试验带来的氚或1940年以来人类工业化带来的氟利昂，属于年龄在60 a以上的老水。     

利用统计学原理调查建筑能耗

了解建筑能耗现状,是开展建筑节能工作的基础。面对种类繁多、数量巨大的建筑物,为了使调查数据具有代表性,建议采用统计学原理进行调查。就调查方式、抽样方法和样本容量的计算进行了探讨。利用模拟结果代替试验抽样数据,得到了样本容量与建筑总量的变化关系,为样本容量的计算提供了帮助。     

Computational methods for accounting of structural uncertainties, applications to dynamic behavior prediction of piping systems

Computational probabilistic methods enable us to incorporate and propagate uncertainties in mechanical models. However, in some cases, classical methods, such as FORM/SORM methods and Monte-Carlo methods, can be computationally expensive or inaccurate. An efficient importance sampling method is then suggested to yield sufficiently accurate results with acceptable computational cost in an industrial context. The method is an importance sampling method based on a second order asymptotic approximation combined with the HyperCube Latin method. A clustering method is used to solve the global optimization problem which arises to find the points of maximum likelihood. The efficiency of the method compared to classical methods is illustrated with several examples. Considerable reduction of the statistical error of the estimated failure probability can be achieved. The interest of the method is assured provided the points of local maximum likelihood are not too numerous and uniformly distributed. The paper presents two vibratory test cases, the second one is an industrial piping system.     

取样扰动对土的工程性质指标影响的试验研究

本文报道了取样扰动对土的工程性质指标影响的一批研究成果。采用100mm和75mm两种直径的取土器取样作对比试验以研究取土器扰动的影响。试验证明取土器直径对试样的孔隙比、压缩系数、超固结比和天然强度等指标都有明显的影响。采用两种预固结处理的方法以恢复原生应力状态,用不固结不排水试验比较了应力状态对天然强度的影响。对取土过程中土体应变的分布及其对土样扰动的影响用有限元方法进行了模拟。     

备样方法对标准吸湿含水率的影响

利用室内试验手段研究了不同备样方法对标准吸湿含水率的影响。研究结果表明：原状样和调制样的试验结果大于风干样和烘干样；原状样与其他3种备样方法的试验结果呈线性关系，相关系数的平方为0．94～0．97，说明在原状样缺乏时可采用其他备样方法的试验结果来代替，但必须对其进行修正。     

软土地基取土质量控制与分析

本文叙述了杭州湾跨海大桥南岸接线高速公路软基试验段工程中钻孔取土所用的机具与水压式固定活塞薄壁取土器的应用情况,介绍了室内试验的土样制作情况,对软土试样无侧限抗压强度试验的结果进行了统计分析,得到四层土共105个试样的平均破坏应变只有5.4%,说明本工程取土质量是好的,室内土工试验结果可用于工程效果的判断和理论分析计算。     

静压平衡等速采样技术在转炉煤气测尘的应用

介绍了采用静压平衡等速取样技术测定煤气含尘量的原理、装置与方法。取样时通过控制采样流量，使样气流速模拟取样点管道中煤气流速达到等速取样的条件。该技术操作简单、取样时间短且准确度高，适用于周期性回收转炉煤气的测尘。     

Fire detection in computer facilities

A recent fire in a computer center in Canberra, Australia, prompted an investigation of the installed smoke detection system. The opportunity was also taken to evaluate alternate detection equipment in the actual center under operational conditions. One device tested was VESDA, a new highly sensitive smoke detector developed in Australia for clean occupancies such as computer rooms and telephone exchanges. Details of the test program and the effects of high room airflows on all forms of detectors are presented. The effectiveness of VESDA in giving very early warning of fire is demonstrated. Reference: Peter F. Johnson, Fire Detection in Computer Facilities,Fire Technology, Vol. 22, No. 1, February 1986, p. 14. Note: This paper is a modified version of a CIRL Major Report No. 251, 1984, prepared for Department of Housing and Construction, Canberra, Australia.