Heavy metals in maternal and cord blood

Heavy metal concentrations have been determined in maternal and cord blood samples collected from mothers in the age group 20-25 years with full-term neonates (37-40 weeks). The concentrations of Pb, Cd, Cu and Zn were found to be low in cord blood as compared to mother's blood and the ratio between cord blood and maternal blood for the respective elements was found to be approximately 0.80, 0.86, 0.47 and 0.40. On the other hand, the concentrations of Fe and Mg in the mother's blood were found to be lower than those in the cord blood. Prenatal exposure to lead in Mumbai, though low (5.1 microg/dl), is approximately 2-3 times higher than that observed in Canada or Italy. A strong correlation (r = 0.79) between the maternal and cord blood lead levels has been observed during the present study.     

ROBOT软件在特种结构计算中的应用

结合实例介绍有限元结构分析软件ROBOT在特种结构空间分析中的应用。     

Development of passive viscoelastic damper to attenuate excessive floor vibrations

Recent changes in the construction of building floors have included the use of light material composite systems and long span floor systems. Although these changes have many advantages, such floor systems can suffer from excessive vibration due to human activities. This problem is exacerbated in office buildings due to the reduction in inherent damping associated with modern fit outs. Excessive floor vibrations are often realised after the completion of construction or following structural modifications and normally arise due to inadequate knowledge of the damping values in the design process. Thus rectification measures are normally required to reduce floor accelerations. This paper proposes a new innovative passive viscoelastic damper to reduce floor vibrations. This damper can be easily tuned to the fundamental frequency of the floor and can be designed to achieve various damping values. The paper discusses the analytical development of the damper with experimental results presented on a prototype to demonstrate its effectiveness.     

Seismic methods for study of soil building properties

Bulletin of Engineering Geology and the Environment - Information about distribution of elastic wave propagation velocities Vp, Vs in the subsurface zone of a soil mass can be obtained rapidly and...     

Stable lead isotopes and lake sediments--a useful combination for the study of atmospheric lead pollution history

Analysis of stable lead isotopes and lead concentrations in lake-sediment deposits, not least in varved (annually-laminated) sediments, is a useful method to study lead pollution history. This paper presents details from a study of 31 lakes in Sweden. Using a strong acid digestion of sediment samples and ICP-MS analyses, we have found that Swedish lake sediments have a high natural (pre-pollution) 206[Pb]207[Pb] ratio (mean 1.52+/-0.18, range 1.28-2.01, n=31 lakes). In contrast, atmospheric lead pollution derived from metal smelting processes, coal burning and from alkyl-lead added to petrol has a lower ratio (< 1.2). Consequently, when pollution lead deposition began approximately 3500 years ago, the lead isotope ratio of the sediments started to decline, and in modern sediments it is typically < 1.2. Using the isotope and concentration values and a mixing model, the relative contribution of pollution and natural lead in sediment samples can be calculated. The pollution lead records of the Swedish lake sediments show a consistent picture of the atmospheric lead pollution history. Some noticeable features are the Roman peak (approx. 0 AD), the large and permanent Medieval increase (approx. 1000 AD), peaks at approximately 1200 and 1530 AD, the rapid increase after World War II, the peak in the 1970s, and the large modern decline.     

A quadratic complementarity problem related to the optimal design of a pipeline freely resting on a rough sea bottom

A submarine pipeline resting on a rigid, frictionless seabed assumes an equilibrium configuration which can be determined by solving a unilateral contact problem, i.e. a quadratic program or a variational inequality.When the sea bed is irregular, its profile along the sealine can be modified, in present offshore technology, by means of costly trench excavations or artificial supports, in order to avoid excessive bending moments in the pipe. Thus, the problem arises of determining the minimum cost of the profile changes provided that a specified curvature is nowhere exceeded.This optimal design problem is solved by assuming a quadratic cost function and reducing it to a sequence of convex quadratic programming problems leading to the optimal design situation. Upper and lower bounds on the absolute minimum cost and optimality conditions are established. A suitable algorithm for solving the problem in a finite number of steps is developed. Its generalization to allow for ‘fixed charges’ due to the equipment mobilization cost is presented. Two numerical examples illustrate the optimum (minimum cost) proposed design method.     

The Italian national survey of indoor radon exposure

An investigation is being developed by the Camitato Nazionale per la Ricerca e per lo Sviluppo dell'Energia Nucleare e delle Energie Alternative, ENEA, to assess the indoor exposure of the Italian population. The programme, which started in 1982, includes regional and local surveys in all the administrative districts and intensive investigations of factors which influence indoor radon levels. The survey is organized by statistical areas of sampling to obtain representative samples of houses. The definition of the areas takes into account basic parameters e.g. geolithological environments, radon soil gas from underlying soils and rocks, specific activities of local building materials, climatic and seasonal variations, building technology, types of houses and town planning. The collected data may also be used for the compilation of radon risk maps to plan special monitoring and remedial actions if needed. Preliminary results concerning the above items are discussed.     

Prediction of the effectiveness of rolling dynamic compaction using artificial neural networks and cone penetration test data

Rolling Dynamic Compaction(RDC),which is a ground improvement technique involving non-circular modules drawn behind a tractor,has provided the construction industry with an improved ground compaction capability,especially with respect to a greater influence depth and a higher speed of compaction,resulting in increased productivity. However,to date,there is no reliable method to predict the effectiveness of RDC in a range of ground conditions. This paper presents a new and unique predictive tool developed by means of artificial neural networks(ANNs) that permits a priori prediction of density improvement resulting from a range of ground improvement projects that employed 4-sided RDC modules;commercially known as"impact rollers". The strong coefficient of correlation(i.e. R0.86) and the parametric behavior achieved in this study indicate that the model is successful in providing reliable predictions of the effectiveness of RDC in various ground conditions.     

Glowing connections

This paper gives the results of a series of experiments and how they shed light on problems of electrical fires. Experimental glowing connections were made by allowing wires to make poor contact with another object in series in a circuit. Note: The information in this paper was presented in the course “Electrical fires” at the University of Wisconsin—Extension, Madison, Wisconsin, April 1982.