基于20 L球罐的多相混合物扩散模拟

为更好地探索多相混合物的爆炸特性，以铝粉、乙醚、空气为研究对象，基于20 L球型爆炸罐建立三维计算模型，对气固两相和气液固三相混合物的分散过程进行数值模拟，以分析不同多相混合物分散过程的差异，并为测量多相混合物爆炸下限时的点火延迟时间设定提供参考。监测分析铝粉浓度粒子分布、流场内部湍流动能以及液相体积百分数等的演化过程，讨论混合物分散效果的差异，并确定测量爆炸下限的点火延迟时间。研究结果表明:实验工况下，液相的存在会降低粉尘云团的湍流动能、降低其扩散速度，并使粉尘云内部浓度更均匀。测量多相混合物爆炸下限时，三相混合物的最佳点火延迟时间早于气固两相混合物10~20 ms。     

Internal and External Factors Influencing Time-Related Injury Risk in Continuous Shift Work

Time-related accident risk in shift work may be attributed to internal factors, such as fatigue, level of performance, sleep propensity, and to some external factors, like shift system, physical and social environment. Six hundred and sixty-eight events in the metallurgical industry have been analysed in terms of time of day, time on task, consecutive day of the shift block, day of the week, and season.

The injury rate was similar on all shifts but more severe accidents happened in the nighttime. Somewhat more injuries occurred in the second half of the shift, in the second part of a shift block, and in summer compared with winter. There were fewer injuries at weekends.     

单洞双线铁路隧道火灾人员疏散安全性分析

为了分析单洞双线铁路隧道火灾人员疏散安全性，基于单洞双线铁路隧道结构特点，分析不同火灾场景下人员疏散模式，利用火灾动力学模拟软件FDS，建立隧道火灾模型，分别研究火源位于车头和列车中部车厢内时可用安全疏散时间。利用Pathfinder软件，模拟人员折返路线与不同疏散口间距下人员疏散过程，分析必需安全疏散时间及其影响因素。研究结果表明:隧道发生火灾时，人员可用安全疏散时间与火源位置有关，必需安全疏散时间受疏散总人数、疏散口选择、疏散口间距等因素影响很大。在设计隧道疏散系统时，可通过减小疏散口间距和设置明显的疏散设施指示标识，减少人员疏散所用时间。     

Use of residence time distribution for evaluation of gaseous pollutant volatilization from stored swine manure

Abstract

A quantification analysis for evaluation of gaseous pollutant volatilization as a result of mass transfer from stored swine manure is presented from the viewpoint of residence time distribution. The method is based on evaluating the moments of concentration vs. time curves of both air and gaseous pollutants. The concept of moments of concentration histories is applicable to characterize the dispersal of the supplied air or gaseous pollutant in a ventilated system. The mean age or residence time of airflow can be calculated from an inverse system state matrix [B]‐1 of a linear dynamic equation describing the dynamics of gaseous pollutant in a ventilated airspace. The sum elements in an arbitrary row i in matrix [B]‐1 is equal to the mean age of airflow in airspace i. The mean age of gaseous pollutant in airspace i can be obtained from the area under the concentration profile divided by the equilibrium concentration reading in that space caused by gaseous pollutant sources. Matrix [B]‐1 can also be represented in terms of the inverse local airflow rate matrix ([W]‐1), transition probability matrix ([P]), and air volume matrix ([V]) as, [B]‐1 =[W]‐1[P][V]. Finally the mean age of airflow in a ventilated airspace can be interpreted by the physical characteristics of matrices [W] and [P]. The practical use of the concepts is also applied in a typical pig unit.     

Could we remain simply applying discount rate to evaluate the life quality of our future generations?

When we try to estimate future environmental costs resulting from our current economic activities,we usually calculate the present value of the consequences for our future generations by utilizing a discount rate as a standard economic procedure.The popularity of this procedure is solely supported by its simplicity which assumes:(1)a perfect financial market over even 100 years,and(2)existence of a stable time preference between two consecutive periods for an individual consumer.An apparent deficiency of this approach is that the present value of life quality of future generations varies to a large extent along an arbitrarily chosen discount rate.As a matter of fact,the discount rate,which could reflect the time preference as2%or 5%,matters when we predict current strategies of environmental protection for future generations.Simply applying a discount rate to evaluate the quality of our future generation,without clarifying the actual production mechanism behind this,is almost to the same as ignoring the fact that all of the goods are produced through an actual production process and that environmental degradation reduces the efficiency of that process.The greatest concern for our future generations should not be given by an assumed discount rate,since the discount rate itself is determined by financial market conditions at certain points in time.     

The Comparative Approach on Outdoor Leisure Behavior of Urban Elderly People: A Case Study in Beijing

Abstract

With the income increase of elderly people in Beijing and the improvement of leisure facilities since 2000, the quality of elderly people leisure life in Beijing has obviously increased compared to ten years ago. According to the investigation and comparative analysis on more than 900 elderly people, who usually exercise in public parks in Beijing City, we have found out several new features of elderly people’s outdoor recreation in Beijing: the increase of the leisure time, the expansion of leisure space, the individuation of interest and the diversification of consumption. The leisure life quality evaluation index system of urban elderly people can be built based on these analyses. In order to accommodate the development tendency of elderly people’s demand for leisure diversification, we should strengthen the organization and management of elderly people’s leisure activity in urban construction, and pay more attention to function complementation between communities and parks.     

一种新型泡沫凝胶成胶时间及灭火特性的实验研究

为研究新型无氨泡沫凝胶的胶凝特性和灭火特点,采用倾斜试管法分别测试了不同反应物浓度、温度、pH值和发泡剂浓度等参数对新型泡沫凝胶成胶时间的影响,同时通过灭火实验对泡沫凝胶的消防特性进行了研究。结果显示：当水玻璃与促凝剂的质量比在1．33—4．0时材料成胶时间满足煤矿灭火要求;pH值在6．9—8．5时成胶最快;成胶时间随温度升高而减小;发泡剂浓度对成胶时间影响不大;泡沫凝胶灭火效果良好且有效延长了复燃周期。因此泡沫凝胶在矿井消防中有很强的实用价值,并且可通过限制反应物浓度、pH值、温度等参数,更高效的控制成胶时间。     

Computer Usage With Cold Hands; An Experiment With Pointing Devices

Computers are used in the outdoors and in connection with cold store work. Cold hand and fingers limit data input, as studied here. Six input devices; trackballs, pens, and a mouse were tested by 19 participants in a Fitts’ target acquisition task with 2 target sizes under 2 experimental conditions; warm and cold right hand. Measures were acquisition times, number of errors, participant’s preferences, and observed handling of the devices. Effects of device, target size, and cold were significant. Learning and attempts to improve handgrip were confirmed. Large enough targets, a thick pen, and a mouse make computer work practicable in the cold. Direct visual feedback, as with pen on template with target images, shortened acquisition times by half a second.     

Resistance of Medical Gloves to Permeation by Methyl Methacrylate (MMA), Ethylene Glycol Dimethacrylate (EGDMA), and 1,4-Butanediol Dimethacrylate (1,4-BDMA)

Gloves afford hand protection by minimizing skin contact. The effectiveness of medical gloves to protect against permeation of the monomers, methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDMA), and 1,4-butanediol dimethacrylate (1,4-BDMA), was assessed focusing on permeation rates and degradation of glove materials caused by monomer contact. Fifteen different brands of gloves were tested using a European Standard procedure. Surface images of glove materials before and after exposure to the monomer mixture were obtained using a scanning electron microscope. The standard is not applicable as the only method for estimating the safety of gloves, but it is useful as guideline together with the cumulative permeation of acrylic monomers. Monomer contact on the outside resulted in substantial swelling of most glove materials, and structure changes of the inside surface.     

活性炭复合床层对动活性的影响试验

本文通过对KZ1床层、KZ2床层、KZ1和KZ2复合床层在不同床层厚度条件下,对氯化氰蒸气的动活性进行对比试验,并对试验结果进行分析,得出了后者并非前两者之和,而有了大幅提高的结论。