Experimental investigation of gas explosion in single vessel and connected vessels

Gas explosion in connected vessels usually leads to high pressure and high rate of pressure increase which the vessels and pipes can not tolerate. Severe human casualties and property losses may occur due to the variation characteristics of gas explosion pressure in connected vessels. To determine gas explosion strength, an experimental testing system for methane and air mixture explosion in a single vessel, in a single vessel connected a pipe and in connected vessels has been set up. The experiment apparatus consisted of two spherical vessels of 350 mm and 600 mm in diameter, three connecting pipes of 89 mm in diameter and 6 m in length. First, the results of gas explosion pressure in a single vessel and connected vessels were compared and analyzed. And then the development of gas explosion, its changing characteristics and relevant influencing factors were analyzed. When gas explosion occurs in a single vessel, the maximum explosion pressure and pressure growth rate with ignition at the center of a spherical vessel are higher than those with ignition on the inner-wall of the vessel. In conclusion, besides ignition source on the inner wall, the ignition source at the center of the vessels must be avoided to reduce the damage level. When the gas mixture is ignited in the large vessel, the maximum explosion pressure and explosion pressure rising rate in the small vessel raise. And the maximum explosion pressure and pressure rising rate in connected vessels are higher than those in the single containment vessel. So whenever possible, some isolation techniques, such as fast-acting valves, rotary valves, etc., might be applied to reduce explosion strength in the integrated system. However, when the gas mixture is ignited in the small vessel, the maximum explosion pressures in the large vessel and in the small vessel both decrease. Moreover, the explosion pressure is lower than that in the single vessel. When gas explosion happens in a single vessel connected to a pipe, the maximum explosion pressure occurs at the end of the pipe if the gas mixture is ignited in the spherical vessel. Therefore, installing a pipe into the system can reduce the maximum explosion pressure, but it also causes the explosion pressure growth rate to increase.     

The relationship between protective and risk characteristics of acting and experienced workload, and musculoskeletal disorder cases among nurses

PROBLEMS: Limited research is available on the acting (work characteristics) and experienced (perceived stress) workload of nurses. The relationship between risk and protective characteristics of work-related factors and the prevalence of musculoskletal symptoms in different body regions is also unclear. METHODS: The study was a cross-sectional design with 97 female registered nurses working in a hospital setting. Two surveys were used to document the workload exposure of the nurses. One survey consisted of 148 items aimed to measure the acting workload variables from the environment; the other survey included 33 items that were aimed to measure the nurses' experienced workload. The musculoskeletal outcomes were documented with a modified version of the Nordic Musculoskeletal Symptom Survey. RESULTS: Factor analyses revealed three factors that accounted for 56% of the total variance. Factor 1 (i.e., integrated experienced energy replenishment/expenditure) represented the psychological effects of work characteristics, effort, perceived risk, and performance. Factor 2 (i.e., acting energy replenishment/expenditure) consisted of non-physical variables of the work characteristics, while Factor 3 (i.e., acting energy expenditure) included both acting and experienced workload. Logistic regression analyses indicated that Factor 3 was significantly associated with the musculoskeletal symptoms of lower and upper back, hands/wrists, and knees/lower legs (odds ratios > 1.0). Factor 2 was significantly associated with the musculoskeletal symptoms of the upper back and knees/lower legs (odds ratios < 1.0). SUMMARY: Both the acting and experienced workloads exhibited associations with musculoskeletal outcomes in the lower back, upper back, hands/wrists, and knees/lower legs in terms of risk and protective effects.     

电除尘器控制系统中应用微机技术的研究

介绍了电除尘器系统微机控制的一种模式 ,就控制系统的组成、工作原理及特点作了论述 ,构成的系统具有一定的代表性。运行表明 :将微机技术应用于电除尘器控制系统中 ,实现生产过程的自动化和设备管理的现代化 ,取得了很好的效果     

基于CAN总线技术的智能火灾自动报警系统

介绍了以CAN总线技术为基础，以单片机为多机系统构成的通用智能火灾自动报警系统。CAN是一种快速的串行总线，它为传感器和传动机构之间提供了高效、可靠和经济的连接。CAN采用双绞线连接时，可以实现最多40个设备间的高达1Mbit／s的数据传输。本系统采用了先进的CAN总线技术，并利用诸多的智能特性为解决火灾自动报警系统存在的漏报和误报两大难题提供了新的方法和手段，提高了系统的可靠性和 准确性，并为工程设计施工提供了极大的方便。     

多管直流式旋风除尘器的研究与应用

简单介绍了多管直流式旋风除尘器的结构形式、除尘原理和研制过程及其在煤矿井下的实际应用情况。     

对开好单塔污水汽提粗氨精制系统的论述

介绍开好单塔污水汽提粗氨精制系统的必要性，以及技术改造和技术分析，通过技术改造后，产品液氨的质量得到了明显提高。     

平顶山市郊被动式太阳房单一系统可行性分析

本文主要分析了太阳能供热单一系统的经济效益参数和偿还年限，并结合实例进行推导、计算，论证在平顶山市郊推广单一系统的可行性。     

辽河铁岭段主要支流水质污染的综合决断

采用模糊集合理论，对辽河铁岭段的四条支流，西辽河、东辽河、招苏台河和条子河分别在枯水期、丰水期、平水期做出水质污染的综合决断，由结果可看出四条河流水质污染的不同性，为治理辽河污染提供了一定的理论依据。     

固定化微生物技术及其在生物脱氮中的应用

介绍了几种实用固定化微生物技术，对其进行了技术比较。简述了固定化微生物技术在生物脱氮技术中的应用，并提出一种基于颗粒污泥原理的微生物固定技术应用于单级生物脱氮。     

Cytogenetic abnormalities among perinatal deaths demonstrating a single umbilical artery

The presence of a single umbilical artery is associated with fetal congenital malformations and cytogenetic abnormalities. The incidence of chromosomal abnormalities in perinatal deaths complicated by a single umbilical artery is unknown. We studied the proportion of cytogenetic abnormalities associated with a single umbilical artery among perinatal deaths undergoing autopsy. Of 1078 autopsies, 42 (3·9 per cent) were identified with a single umbilical artery. Chromosome analysis was attempted in 21 of the 42 cases (50 per cent). There were 16 successful chromosome analyses, of which three (18·75 per cent) were abnormal. All the chromosomally abnormal fetuses had major congenital malformations. These data suggest that in a perinatal death, the presence of a single umbilical artery does not clinically alter the a priori risk of cytogenetic abnormalities.