山西北部一次飑线大风的多普勒雷达特征

利用山西省北部大同地区多普勒雷达的基本反射率因子、组合反射率因子、速度剖面图、垂直液态含水量、回波顶及VWP产品,结合环流形势和自动站分钟数据资料,对2010年6月16日发生在大同地区的飑线天气过程进行了分析。结果表明:这次飑线过程发生在高中低三层的冷涡环流形势和地面冷锋前的暖区;飑线过境时压、风、温三要素出现剧烈变化;研究极大风速≥16.8 m.s-1的台站时发现:飑线过境时两个站出现的速度极大值与外流边界的影响时间相吻合,四个站出现的速度极大值与强回波下沉气流影响时间相对应;冷涡携带的冷空气使飑线后部入流不断得到补充,而前侧暖湿气流沿着后部入流爬升,不断产生新的单体,是飑线能够维持、发展的主要原因。     

Line intersect sampling: Ell-shaped transects and multiple intersections

The probability of selecting a population element under line intersect sampling depends on the width of the particle in the direction perpendicular to the transect, as is well known. The consequence of this when using ell-shaped transects rather than straight-line transects are explicated, and modifications that preserve design-unbiasedness of Kaiser's (1983) conditional and unconditional estimators are presented. A case against treating multiple intersections as multiple probabilistic events is argued on the basis, also, of preserving design-unbiased estimation.     

一种识别低压电力线载波通信系统中随机脉冲噪声的新方法

目的从电力线载波通信系统中提取随机脉冲噪声并分析其来源。方法建立一个简单的检测随机噪声的测试系统。结果 FSV方法可以成功地识别热水壶在电力线上造成的随机脉冲噪声,同时也证明了统计分析的方法对于识别随机脉冲噪声效果不佳。结论可以通过对MAFFSV方法结果设定阈值来识别低压电力线载波通信系统中的随机脉冲噪声,进而可以确定低压电力线网络拓扑结构的改变。     

城市防洪的一种方法—纳潮

本文介绍一种城市防洪的方法－纳潮。即以合理的调度运行，充分利用圩区的调蓄能力，降低风暴潮引起的高潮位，用以应付超标准风暴潮。通过纳潮效果与纳潮闸位置，调蓄面积，操作方式等因素的关系分析，表明纳潮是一种可行且有效的方法。本文阐述的基本规律，为工程设计、运行操作提供参考依据。     

The steel industry, abiotic resource depletion and life cycle assessment: a real or perceived issue?

Time and again, there has been a hue and a cry that the world is running out of natural resources and the most prominent among those is the famous study entitled ‘The Limits to Growth’ by the ‘Club of Rome’. Since then the fear of scarcity of abiotic resources has been challenging human societies around the globe, particularly the research community. In this paper we will examine the case of the steel industry to argue how and why mineral resources depletion is an issue that needs to be addressed through life cycle assessment in more detail. This paper shows that a more comprehensive understanding about the current production trends of iron ore and steel, which also requires several vital metals such as copper, manganese, nickel and so on, can provide useful insights in assessing the potential future threat of shortages due to depletion of abiotic mineral resources.     

Change of Flood Patterns in China under the Influences of Climate Change and Human Activities

Abstract

Based on the flood affected area (FA) data of the provinces in China from 1950 to 2005, the article discusses the change of the flood patterns in China, and investigates its relationship with climate change and human activities. The flood center shifted from North China and the Yangtze–Huaihe basin in the 1950s towards the south, north and west of China, and located in the south of the Yangtze River and South China after the 1990s. The FA in the western provinces was continuously on the rise since the 1950s. There are two characteristics for the future flood pattern in China. The pattern of “flood in the south and drought in the north” depends on the north–south shift of the maximum rainfall region in eastern China. The flood intensification to the west of Hu Huanyong’s line mainly results from the increase of rainfall, extreme precipitation and the melting of glaciers under the background of human activity magnification.     

国家化学事故应急咨询专线接警情况统计分析

基于国家化学事故应急咨询专线2002年-2011年10年间接到的1100起化学品事故咨询电话,从事故发生时间、事故发生地域、事故类型、事故发生环节、事故引发物质等进行统计分析,结果表明,自2007年起应急电话的使用频率呈现逐年递增的趋势,5月-8月是化学品事故高发季节,危险化学品企业分布越多的地域发生事故的机率越大,人身伤害事故占的比例最高,使用环节的事故咨询电话起数最多;农药是引发事故最多的物质。从加强化学品安全知识普及教育、建立完善的立法和执法机制、继续大力推行危险化学品登记制度、进一步加强应急电话宣传等方面提出了预防和减少化学品事故的对策建议。     

苯胺对小鼠成纤维细胞L929的体外毒性评价

探讨不同浓度的苯胺化合物对小鼠成纤维细胞L929的体外毒性作用,为满足危险化学品分类鉴定和风险评估需求、更好地预防环境化合物对人体健康的损害提供理论依据。体外培养L929细胞,分别将不同浓度的苯胺化合物(0、0.001、0.01、0.1、1、10μg·mL~(-1))加入培养基中处理细胞,在不同时间点分别取材,MTT检测细胞增殖率,AO/PI染色检测细胞存活率,Annexin V-PI染色后流式细胞仪检测细胞凋亡,相关检测试剂盒测定细胞内活性氧(ROS)的含量及总谷胱甘肽的含量。结果表明,高浓度(1、10μg·mL~(-1))的苯胺化合物对L929细胞的生长和增殖具有显著的抑制效应。即使浓度降低至0.1μg·mL~(-1),在处理48 h后,细胞的存活数量显著下降,说明其对细胞增殖具有浓度和时间的累积效应和依赖性。同时,对各组细胞采用流式细胞仪测定细胞凋亡,发现低浓度的苯胺对细胞凋亡影响并不明显,但高浓度的苯胺处理后,细胞凋亡和坏死数量显著增加。ROS含量和GSH含量检测结果显示,较低浓度的苯胺对细胞氧化应激反应并无显著影响,但浓度至0.1μg·mL~(-1)时,细胞较对照组出现明显的氧化应激反应,说明细胞已受损,再继续培养将会导致细胞死亡。上述研究结果提示,高浓度苯胺化合物可显著影响L929细胞存活率,且具有时间和浓度累积效应。其毒性机制可能与细胞内活性氧增加、谷胱甘肽耗竭有关。     

力学学科在安全工程专业课程体系中的设置与探讨

在安全工程专业的培养计划中,如何设置力学类课程,使其在安全工程专业各研究分支领域发挥应有的作用,是安全教育工作者所关注和深思的问题。笔者通过调研国内若干大学安全工程专业,力学类基础和专业基础课程的设置情况,对资料与数据的统计分析与对比,认为力学类课程与安全工程技术、职业安全检测技术、劳动保护与器材、安全人机工程等研究方向有紧密关系;提出了力学学科是安全工程和技术科学的重要基础的观点;同时指出力学类课程作为基础和专业基础课,在安全工程专业培养计划中有其重要性;还对安全工程专业各具体分支的力学类课程的设置与教学侧重点提出了建议和探讨。     

Getting of the seeds-and-tools treadmill with CRS seed vouchers and fairs

The free distribution of seeds and tools is the standard approach to agricultural recovery. The predominance of this approach is partly attributable to the: (1) perception that farmer seed quality is poor, (2) insistence on seed certification, (3) promotion of researcher varieties, (4) misdiagnosis of unavailability, (5) difficulty accessing farmer seed, and (6) support for the commercial seed sector. This paper presents a Seed Security Assessment Framework to distinguish among the causes of seed insecurity and focuses on three principal concepts: seed availability; access to seed; and factors associated with seed utilisation. Using this diagnostic framework, Catholic Relief Services (CRS) has developed a better approach to promoting seed system-based agricultural recovery. It involves a combination of seed voucher distribution and the organization of seed fairs, which bring together a range of sellers from whom the holders of vouchers may purchase seed. This approach is advantageous because it: strengthens farmer seed procurement systems; is cost efficient; in economic terms, has a multiplier effect in the community; is straightforward to plan and implement; allows commercial sector participation; provides an opportunity to promote improved varieties for farmer evaluation; brings together different communities.