由骨骼中~(210)Pb含量估算~(222)Rn子体摄入量的方法

铀矿和某些非铀矿山的矿工往往受到较高浓度的~(222)Rn 及其子体的照射。本文介绍一种由骨骼中~(210)Pb 含量估算~(222)Rn 子体α潜能摄入量的方法。对加拿大28名铀矿工,用本方法估算的结果与国外文献给出的值基本相符合。     

Influence of surface pre-treatments on disturbed rolled-in subsurface layers of aluminium alloys

Rolling is known to alter the surface properties of aluminium alloys and to introduce disturbed subsurface layers. These layers are characterised by a refined grain structure, rolled-in oxide particles, a fine distribution of intermetallic particles, various voids and cracks.In this study, the effects of some surface pre-treatments, i.e., alkaline etching at various temperatures and chemical cleaning with Nabuclean and CrO₃/H₃PO₄, on these rolled-in layers are investigated by means of surface analytical techniques. The changes in composition and morphology of the (sub)surface are studied with scanning electron microscopy/energy dispersive X-ray analysis and backscattered electron imaging (SEM/EDX + BEI). The presence of incorporated oxide particles is evaluated by measuring the total reflectance. The (re-)distribution of alloying, impurity and trace elements upon these surface treatments is investigated with radiofrequency glow discharge optical emission spectrometry (rf-GDOES).     

ANALYSIS OF INTERNALLY GENERATED NOISE OF BIOELECTRIC AMPLIFIERS

This papenr deals with internally generated noise of bioelectric amplifiers that are usually used for processing of bioelectric events.The main purpose of this paper is to present a procedure for analysis of the effects of internal noise generated by the active circuits and to evaluate the output noise of the author‘s new designed bioelectric amplifier that caused by internal effects to the amplifier circuit itself in order to compare it with the noise generated by conventional amplifiers.The obtained analysis results of internally generated noise showed that the total output noise of bioelectric active circuits does not increase when some of their resitors have a larger value.This behavior is caused by the different transfer functions for the signal and the respective noise sources associated with these resistors.Moreover,the new designed bioelectric amplifier haws an output noise less than that for conventional amplifiers.The obtained analysis results were also experimentally verified and the final conclusions were drawn.     

化学纯VOSO_4对硫酸亚铁还原/重铬酸钾滴定测铀法的适用性研究

硫酸亚铁还原/重铬酸钾氧化滴定测铀法是美国新布伦士威克实验室(New Brunswick Laboratory)开发的精密测铀方法,现已被国际标准化组织(ISO)、美国、中国等作为测定U_3O_8、UO_2中铀含量的标准分析方法。在该法中,用重铬酸钾滴定之前必须加入分析纯VOSO_4作催化剂。但是,我国的分析纯VOSO_4产品很少应市,难以购得。为了能在没有分析纯VOSO_4     

谈谈高层建筑电气设计的主要内容及有关问题

建筑越来越多，高层建筑电气设计质量如何保证？高层建筑的主要内容及有关问题有哪些？本文根据多年对建筑电气设计经验结合规范做了初步探讨。     

影响铸铁热疲劳抗力的因素

在热交变应力的作用下，热疲劳是铸铁工件的主要失效形式之一。本文综述了影响铸铁热疲劳抗力的诸因素。     

A Study of Human Reactions to Emissions from Building Materials in Climate Chambers. Part II: VOC Measurements,Mouse Bioassay,and Decipol Evaluation in the 1–2 mg/m3 TVOC Range

Monitoring of human reactions to the emission of formaldehyde and volatile organic compounds (VOC) from four commonly used building materials was carried out. The building materials were: a painted gypsum board, a rubber floor, a nylon carpet, and a particle board with an acid-curing paint. The exposures were performed in climate chambers. The air quality was quantified on the decipol scale by a trained panel, measurements of formaldehyde and VOC being performed simultaneously. The irritating potency of the materials was measured by a mouse bioassay. The VOC measurements showed several malodorants and irritants. Some abundant VOC identified in the head-space analyses were absent in the climate chamber air. The rubber floor and the nylon carpet exhibited a marked increase in decipols compatible with a number of odorous VOC identified in the air. A high formaldehyde concentration (minimum 743μg/m³) was measured for the particle board coated with an acid-curing paint. This was not reflected by a corresponding relatively high decipol value but a long-lasting irritating potency was observed in the mouse bioassay. TVOC sampled on Tenax and expressed in mass per volume as well as in molar concentration, and decipol evaluation both have limitations and should be used with caution as indicators of (perceived) indoor air quality. Eye irritation expressed by means of the eye index reflecting the tear film quality index (comprised of break-up time, foam formation, thickness of the precorneal lipid layer of the tear film, and epithelial damage) was found to be insensitive to formaldehyde and a VOC mixture but sensitive to TVOC concentrations of 1–2 mg/m³. Lipophilic VOC may be the cause of reduced tear film quality by destabilization of the lipid multilayer of the tear film.     

Design principles for spray-roasted iron oxides for the manufacturing of ferrites

A range of high purity iron oxides are prepared by varying basic operation parameters of an industrial spray roasting process. These iron oxides are investigated in relation to their morphology and subsequently evaluated as raw materials for MnZn-ferrite preparation. It appears that the most important morphological parameters for determining the reactivity (defined as firing shrinkage at equal compaction density) of the high purity iron oxide, and consequently the final density and magnetic properties of the ferrite specimens, are the primary particle size and the number of primary particles per aggregate. As found, the specific surface area of the iron oxide is of no predictive value for the behavior of the iron oxide in a MnZn-ferrite manufacturing process. A small primary particle size is important for a high reactivity; however, when particles are packed together in large aggregates, they are not available for the prefiring reactions. As a result, reactive sintering takes place leading to high porosity and bad microstructure. As found by the characterization methods employed in this article, the optimum iron oxides for MnZn-ferrite preparation should have a primary particle size between 0.45 and 0.55 μm with an aggregate size below 1.60 μm.     

Optimizing the solar photo-Fenton process in the treatment of contaminated water. Determination of intrinsic kinetic constants for scale-up

The elimination of aromatic compounds present in surface water by photo-Fenton with sunlight as the source of radiation was studied. The concentrations of Fe³⁺ and H₂O₂ are key factors for this process. A solar simulator and a prototype parabolic collector were used as laboratory-scale reactors to find the parameters of those key factors to be used in the CPC (compound parabolic collector) pilot plant reactor. The initial mineralization rate constant (k_obs) was determined and evaluated at different Fe³⁺ and H₂O₂ concentrations to find the best values for maximum efficiency. In all the experiments the mineralization of an aqueous phenol solution was described by assuming a pseudo-first-order reaction. The intrinsic kinetic constants not dependent on the lighting conditions were also estimated for scale-up.     

Liquid phase benzoylation of arenes over iron promoted sulphated zirconia

The present work undertakes the preparation and physico-chemical characterisation of iron promoted sulphated zirconia (SZ) with different amounts of iron loading and their application to Friedel–Crafts benzoylation of benzene, toluene and xylene under different experimental conditions. XRD and laser Raman techniques reveal the stabilisation of the tetragonal phase of zirconia and the existence of iron in highly dispersed form as Fe₂O₃ on the catalyst surface. The surface acidic properties were determined by ammonia temperature programmed desorption (TPD) and perylene adsorption. The results were supported by the TGA studies after adsorption of pyridine and 2,6-dimethylpyridine (2,6-DMP). Strong Lewis acid sites on the surface, which are evident from TPD and perylene adsorption studies, explain the high catalytic activity of the systems towards benzoylation. The experimental results provide evidence for the truly heterogeneous nature of the reaction. The studies also establish the resistance to deactivation in the metal incorporated sulphated systems.