Theoretical and Empidcal Study on Urban Population Carrying Capacity:Case of Haidian District in Beijing

The measurement of urban population carrying capac- ity is the basis for cities' sustainable development.However,the traditional study on population carrying capacity which was based on food supply is not applicable to the single urban area.This paper built a model for the analysis of urban carrying capacity, and took Haidian District in Beijing as an example to calculate the urban carrying capacity of Haidian District in the future,which was the basis for the improvement of the population carrying capac...     

Integration of Case Studies on Global Change by Means of Qualitative Differential Equations

We present a novel methodology to integrate qualitative knowledge from different case studies on Global Change related issues into a single framework. The method is based on the concept of qualitative differential equations (QDEs) which represents a mathematically well-defined approach to investigate classes of ordinary differential equations (ODEs) used in conventional modeling exercises. These classes are defined by common qualitative features, e.g., monotonicity, signs, etc. Using the QSIM-algorithm it is possible to derive the set of possible solutions of all ODEs in the class. By this one can formulate a common, qualitatively specified cause–effect scheme valid for all case studies. The scheme is validated by testing it against the actually observed histories in the study regions with respect to their reconstruction by the corresponding QDE. The method is outlined theoretically and exemplary applied to the problem of land-use changes due to smallholder agriculture in developing countries. It is shown that the seven case-studies used can be described by a single cause–effect scheme which thus constitutes a pattern of Global Change. As a generally valid prerequisite for sustainability of this kind of land-use the presence of wage labor is shown to represent a decisive factor. This revised version was published online in July 2006 with corrections to the Cover Date.     

城市轨道交通危险因素分析

目前我国的城市轨道建设已经进入高潮期,城市轨道的安全问题也变得日益重要.笔者通过统计分析国内外历年发生的轨道交通事故,总结了轨道交通在施工期间、供电系统、车辆系统、通风/排烟系统、给/排水系统、通信/信号系统、公用工程及辅助设施等方面的事故分析了存在的危险因素,为确保地铁的安全运营提供依据.     

我国自然资源市场体系的建立与发展

文章以“东阳卖水—义鸟买水”这起全国首例水权交易的案例说明，必须清晰地界定自然资源的产权，同时减少有关自然资源交易过程中的费用，以尽快建立自然资源市场体系，发挥市场在配置自然资源方面的基础性作用。     

矿井用箱体防爆面加工安全技术研究

箱体零件是矿井机械中重要的基础零件。它的加工质量直接关系矿井设备的寿命、机器的性能和安全性。针对煤矿井下煤尘和瓦斯存在的环境特性、煤矿井用箱体防爆面加工的特殊要求,采用控制理论的信息流图,对工艺过程中传统方块图进行简化,使繁杂的方块图解采用信息流图表示工艺过程的工序(变量)之间关系。进而讨论箱体零件加工工艺过程误差转换模型、形状精度特征、传递图、描述方程、误差转换结构图;提出防爆面磨削工艺系统的数学模型;求解出振动特性、幅值和相位,得出了形状误差与工艺参数的关系曲线。实践证明,合理选择磨削参数,能够保证煤矿井下工作机械具有高的防爆性能,达到矿井安全生产的技术要求。     

Development of a limit state approach for design against gas explosions

The design of topsides against explosions requires the definition of a design over-pressure, however, these values are often treated as deterministic and there is a wide variation within the industry in the treatment and interpretation of the loads.

This paper advocates the adoption of a number of limit state for explosion loading. Events of different magnitudes are differentiated on the basis of frequency and linked to appropriate degree of reliability thus avoiding disproportionate effects from minor events.

The two principal limit states considered are a limit state for all the safety critical systems for relatively high frequency events and a survival condition for low probability events. Parallels are drawn from other branches of engineering where extreme loads have to be designed for.     

2014年1月沪渝高速公路汉宜段一次大雾个例分析

对2014年1月29~31日发生在沪渝高速公路湖北武汉—宜昌段(简称汉宜高速公路)的封路大雾过程气象要素进行分析。结果表明:(1)此次持续大雾过程发生时,近地层有逆温,地面处于高压底部前端的均压场,中纬度维持偏西气流,为大雾的形成和发展提供了有利的环流背景场条件;大雾消散后,地面处于冷高压控制;2)大雾造成的高速公路封路、解封前后,气象要素发生了较明显的变化。这些分析结果,对汉宜高速公路的大雾预警预报具有较好的指示意义。     

餐厨垃圾厌氧处理“碳中和”综合效益评价

为综合评估餐厨垃圾厌氧处理的环境影响与效益,对某餐厨垃圾厌氧处理工艺及其技术单元进行生命周期环境影响评价,并建立“碳中和”计算模型预测与验证实际碳排及耗能情况,综合“环境影响-碳排耗能-经济效益-社会效益”对实际案例进行评估.结果表明,沼肥加工和沼气提纯技术单元分别造成39%和59%总环境影响.另外,粗油提炼、沼气提纯以生物基产品回收形式大幅度削减碳排,分别占理论碳削减的9.7%和54.7%.餐厨垃圾处理厂需通过增加系统稳定性、完善气体监测体系、提高技术处理效率和优化设备额外耗能情况等方式,以减少理论与实际碳排能耗偏差.经综合评价,该餐厨垃圾处理厂模式具备实现“负碳”潜力,其工艺推广具有未来前景.     

基于遗传-BP算法的煤矿安全监控系统测试研究

针对煤矿监控系统的测试要求,提出了一种自动生成测试用例数据的方法用于煤矿监控系统的测试任务。该方法利用遗传算法和BP算法对要测试的功能模块和逻辑结构进行分析解读,通过全局寻优得出最佳测试路径和测试数据,对于提高测试的精准性和有效性有很大优势,而且相对与人工测试更加安全。新的测试用例生成算法结合遗传算法和BP算法,能充分发挥遗传算法的全局寻优能力和BP算法学习能力强的优势,使得数据生成更快捷可靠。选取煤矿监控系统的部分功能测试作为实验材料,与人工测试方法和利用遗传该算法生成测试数据进行了比较。结果表明,该新方法能够更好的检测出煤矿监控系统中的错误,发现错误的数量和时间都较人工测试要好,对于提高煤矿安全监控系统的准确性和稳定性有较好的帮助。     

Repetitive Strain in Nonrepetitive Work: A Case Study

In a Québec factory, a woman in a nontraditional job suffered from epicondylitis whereas her male coworkers were unaffected. A study was undertaken in order to enumerate the operations at risk for epicondylitis. Workers were interviewed in order to identify difficult operations and systematic observations were done over 4 work days. Although tasks were extremely varied, certain movements at risk for epicondylitis were repeated many times. Fifty-three valves were turned against resistance as part of this job, and one valve requiring a particularly difficult movement was turned 20 times in one day. There were at least 61 operations at risk for epicondylitis per day over a 4-day period. Strain on the elbow joint was particularly intense for the woman worker because the design of the workplace gave an advantage to taller workers with larger hands. Although this case study does not permit us to conclude that the worker’s epicondylitis was due to her job, it enables us to suggest that it would be wise to adapt the dimensions of relevant equipment and worksites to a wider range of potential worker sizes. We also raise some questions about the definition of repetitive strain in epidemiological studies. We suggest that it may be necessary to consider not only the cycle time but also the total of forces exerted on a joint in order to study workplace injuries to the musculoskeletal system.