Coupling effects of the explosion shock wave and heat radiation on the dynamic response of a fixed-roof tank

The occurrence of leakage in large tank farms or oil deposits can lead to fire or explosion accidents. Coupling effects of fire and explosion loadings can cause considerably more damage to adjacent tanks or buildings than either loading individually does. In this study, the combined loadings of the explosion shock wave and heat radiation from a pool fire on a neighboring empty fixed-roof tank were numerically investigated. The effects of the explosion shock wave intensity and relative height of the explosion center [the ratio of the height of the explosion center to the height of the tank (h_r)] were analyzed. The results indicate that tanks damaged by explosion shock waves have decreased fire resistance and critical buckling temperature. Moreover, the thermal buckling deformation of the predamaged tank largely depends on the explosion shock wave. With an increase in the explosion shock wave intensity or a decrease in h_r, the explosion shock wave has greater influence on the fire resistance of the tank, and the critical buckling temperature decreases. This paper can provide an understanding of the dynamics of a tank under explosion shock wave loading, and of the critical failure criterion and failure modes of a target tank under the coupled loading of the explosion shock wave and an adjacent pool fire.     

紫外线B对海洋生态系统的影响

近年来随着臭氧损失现象日益严重，到达地球表面的紫外线B辐射不断加强，海洋生态系统受到了前所未有的威胁。UV-B的增强改变了生物体赖以生存的水体环境，影响了浮游植物对营养盐的吸收同化，抑制了浮游植物的光合作用，从而减少了海洋对CO2的吸收能力，其结果直接增加了温室效应。同时UV-B也直接影响生态系统食物链的各个营养级，伤害海洋病毒、细菌和浮游植物，降低浮游动物和仔稚鱼的成活率，进而影响到整个海洋生态系统的结构和功能。     

Comparison of the daily global solar radiation from different data sources in Northwest China climate

The solar radiation data are of high importance to the solar energy systems. Conventional methods to obtain the solar radiation data are from weather stations, solar radiation models, commercial software databases, and field measurements. In the present study, a new daily global solar radiation model is proposed, by combining the quadratic function of sunshine fraction and sine function of the day of the year. The solar radiation model calculated data are then compared with China Meteorological Data Sharing System (CMDSS) data, TRNSYS data, and field-measured data in Northwest China climate. It is found that the newly proposed solar radiation model has better performance than the other nine solar radiation models in the literature. The solar radiation model calculated data fit well with the CMDSS annually average data. The TRNSYS data are a bit larger than the CMDSS annually average data in summer half year and a little smaller than those in winter half year. The solar radiation model and the CMDSS annually average data have the best correlation, whereas the TRNSYS data and the field-measured data have the worst correlation. The solar radiation model calculated data have the best correlation with the other three data sources.     

核电燃料元件厂环境辐射监测与评价

本文对 1994～ 1998年核电燃料元件生产所排放的放射性流出物及环境辐射进行了监测分析。结果表明 ,在正常生产运行情况下 ,放射性流出物对周围公众造成的年最大个人有效剂量当量是 7 2 6× 10 -2 mSv ,远低于公众剂量限值。评价半径为80km范围内的集体有效剂量当量为 4 70× 10 -2 人·Sv/a。     

电磁辐射测量仪对测量结果的影响分析

目前国内外对环境电磁波的测量仪器主要分为两类,分别是选频式和非选频式。选频式仪器由各类测量接收机或频谱分析仪和接收天线组成,其不适于非周期信号测量。非选频式仪器由各类全向型探头和主机组成,适用于周期和非周期信号的环境电磁波测量,但这类仪器动态范围不高。本文采用了两种不同的测量仪器,分别以单频连续波和调制脉冲为激励信号进行比较分析。结果表明：随着测量信号电平增加,两种仪器测量结果数据趋于一致。而在用两种标准的不同方法计算某一频段的复合场强时,其数值有较大差异。     

电磁辐射污染及防护探索

电子设备、仪器的广泛使用产生的电磁辐射已成为当今的重要污染之一。电磁辐射分为天然和人为两种,严重危害和影响着人类的生活和生产。人们要重视电磁辐射,从行政、科学技术、个人生活方面加强对电磁辐射的防范。     

Effect of 450 MHz Microwave Modulated with 217 Hz on Human EEG in Rest

Summary This study focuses on discrimination of changes, produced by low-level microwave exposure in intensity and time variability of the human EEG at rest. The power spectral density (PSD) method and nonlinear scaling analysis of the length distribution of low variability periods (LDLVP) were selected for analysis of the EEG signal. During the study, 19 healthy volunteers were exposed to a microwave (450 MHz) of 217 Hz frequency on-off modulation. The field power density at the scalp was 0.16 mW/cm². The experimental protocol consisted of ten cycles of repetitive microwave exposure. Signals from frontal, temporal, parietal and occipital EEG channels on EEG theta, alpha and beta rhythms were analysed. Exposure to microwave causes average increase of EEG activity. LDLVP analysis discriminated significant effect in time variability for 2 subjects (11%). PSD method detected significant changes in intensity for 4 subjects (21%). The effect of low-level microwave exposure is stronger on EEG beta rhythm in temporal and parietal regions of the human brain.     

A Parallel Study of SAR Levels in Head Tissues for Three Antennas Used in Cellular Telephones: Monopole, Helix and Patch

Summary This paper is a comparative study of several antennas commonly used in cellular telephones. These include a monopole, a helix-monopole and a patch antenna. Each one of these structures is modeled and numerically tested using finite-difference time-domain simulation and human models based on magnetic-resonance images, which allow for inclusion of details of the human body in the simulation. The testing procedure involves antenna simulation in the proximity of the human head. The behavior of each antenna is evaluated for variable distances from the head geometry (0, 1, 2, 4, 8 and 16 mm). Continuous waveform, representative of the sources used in mobile telephones, (250 mW, 1.8 GHz) is used as the form of the antenna excitation. The simulation outputs used as measures for this comparative study include transmitting and receiving antenna characteristics and the specific absorption rate (SAR). The SAR levels for the head tissues are calculated for and with accordance to the two currently accepted standards: Federal Communications Commission (FCC) and International Commission on Non-Ionizing Radiation Protection (ICNIRP). The computed SAR levels within each of the considered tissues vary for the three antennas under investigation and are within the determined health safety standards. Results suggest that the patch antenna may be the structure of choice when considering safety standards, as its radiation yields the lowest local SAR in the head tissues.     

热真空设备中与温度相关的试验技术探讨

以RZHM-1400-AB型热真空试验箱为实例,简述设备主要工作原理。强调其温度传递方式及航天产品在热真空试验中温度参数的重要性。以无数试验数据为依据,着重论证何种类型测温传感器与实际设备相匹配,同时论证选取何种外形的测温传感器为最佳温度测量工具。同时,进一步介绍几种在热真空试验中使用这些测温传感器的方法,以减少不必要的人为测量误差。     

电磁辐射污染投诉原因分析及解决办法探讨

近年来,随着经济的发展,高压输变电工程和移动通信基站越来越多地落户于大型居民小区,由此引发的环境投诉和纠纷呈快速上涨趋势。电磁辐射污染投诉产生的原因主要是:电磁辐射环境管理法制不健全,思想上不重视,项目环保审批环节脱节,环保与规划部门信息交流不畅,公众维权意识增强,寻求其他经济利益;针对原因提出的预防和解决办法为:加强法制建设、强化现场监管,理顺项目审批和监管程序,建立与规划部门的联动机制,加强宣传,引导司法解决。