抓斗式疏浚设备对底泥污染物释放规律的研究

抓斗式疏浚设备如何进行效率高、底泥污染物释放少的疏浚是环保疏浚面临的难题。根据环保疏浚的要求和三峡库区常年回水区的具体情况,要解决库区淤积和一般疏浚工程带来的二次污染问题,必须从减少扰动,防止泥沙悬浮等方面寻求最优参数。采用传统的抓斗式疏浚设备通过抓斗开度、飘斗角、抓泥频率等参数的控制模拟三峡库区常年回水区底泥疏浚,以寻找底泥污染物释放量最小的参数组合。建议三峡库区常年回水区疏浚以试验最优参数组合为基础,结合实际通航要求进行工程疏浚。     

平跑速度对我国男子跳远运动员成绩的影响

本文通过中外优秀男子跳远运动员在助跑速度、平跑速度、腾起角、速度利用率等运动学参数对比分析,指出提高我国男子跳远运动员成绩的关键是提高平跑速度。     

六自由度动态模拟环境试验系统

六自由度动态模拟环境试验是考核车辆、舰船等运输工具在复线路面谱或海浪谱的运动条件和不同气候环境条件同时作用下的性能可靠性和行驶安全性及其使用寿命的重要模拟试验方法。本文详细介绍了为满足这一试验而研发的六自由度动态模拟环境试验系统。     

旋风除尘器灰环磨损与锥体角度关系的研究

提出在普通锥体型旋风除尘器中,回转性灰环是造成锥体部位磨损的重要原因之一.通过对锥体内粉尘颗粒的受力分析,从理论上推导出了减低灰环磨损的锥体角度的表达式.通过对理论分析提出了旋风除尘器锥体设计中应注意的问题,为旋风除尘器的设计提供一定的参考依据.     

基于有限元与极限平衡分析的露天矿边坡角优化

为保证露天边坡的安全稳定,提出用有限元与极限平衡综合分析法分析其稳定性并优化边坡角。利用数值分析软件ABAQUS模拟出边坡潜在滑动面和张裂缝的位置,再根据极限平衡法计算出不同边坡角下的安全系数值,绘制安全系数随边坡角的变化曲线,最后得到安全稳定条件下的最终边坡角的优化值。采用该方法对某露天矿的边坡进行优化,最终边坡角由原设计的53.5°提高至55.4°,能同时降低剥离工程量,保证边坡的稳定性。     

Spatial and temporal patterns of soil erosion in the Tibetan Plateau from 1984 to 2013北大核心CSCD

Soil erosion has a critical effect on ecological security and socioeconomics, which may deteriorate ecosystem services and common human well-being. The revised universal soil loss equation (RUSLE) was applied to assess soil erosion from 1984 to 2013 in the Tibetan Plateau and analyzed the temporal and spatial variation of soil erosion intensity. Furthermore, the temporal and spatial variation rates of soil erosion were explored across different ecosystems. The results indicated that the annual soil erosion fuctuated in the Tibetan Plateau, the soil erosion intensity decreased from south to north, and the most serious soil erosion was mainly distributed in the southern Tibetan Plateau (Xigaze and Changdu regions, Lhasa, and north of the Shannan region). The soil erosion intensity was higher in shrub, alpine meadow, and sparse vegetation ecosystems. The highest soil erosion was found in alpine meadow (2.17 × 1010 t), followed by alpine grassland (1.59 × 1010 t) and sparse vegetation (1.30 × 1010 t) ecosystems. Meanwhile, although the most serious soil erosion intensity was found in the regions of 3 000-4 000 m altitude, the soil erosion was mainly observed in the regions of 4 000-5 000 m altitude. In the three most recent decades, annual soil erosion decreased at a rate of-1.78 × 108 t/a. Additionally, soil erosion mainly increased in south of the Qiangtang Plateau and in the periphery of the Qaidam basin. Decreased soil erosion was mainly found along the Hengduan Mountains, central Himalayas. Although the increased annual normalized difference vegetation index (NDVI) had positive effects for soil protection, changes in soil erosion was mainly controlled by the change of annual precipitation. Thus, the fragility of ecological systems and increased rainfall erosivity accounted for the obviously increased soil erosion in the alpine grassland ecosystem (1.19 × 10 t/a). However, increased ecosystem stability and decreased rainfall erosivity contributed to the decreased soil erosion in forest and shrub ecosystems, by-0.77 × 10 t/a and-1.65 × 10 t/a, respectively. The slightly decreased rainfall erosivity accounted for a decrease of soil erosion in the sparse vegetation ecosystem (-0.44 × 10 t/a). Meanwhile, soil erosion has decreased in the alpine meadow ecosystem over the past 30 years, which may owing to the relatively higher NDVI that neutralized the increase of rainfall erosivity to some extent. This study revealed serious soil erosion regions and ecosystems in the Tibetan Plateau and explored possible reasons for variations in soil erosion in different ecosystems, which may provide a scientific reference for soil erosion conservation and control in the near future. © 2018 Science Press. All rights reserved.     

Accelerating progress on salt iodisation in Sudan: time for action

This paper uses a public health approach to examine briefly: (a) the progress of universal salt iodisation (USI) in Sudan; (b) the roles of the main actors involved; and (c) the main issues around accelerating USI. The literature, especially that coming from the UN agencies, is analysed and experiences from the recently revitalised USI programme, and related relevant meetings, are distilled. In Sudan the prevalence of goitre is 22 per cent. It is assumed that productivity among the people affected is reduced by 5–25 per cent. Little apparent progress has been made with USI. The Government of Sudan, UN multilateral agencies, international consultative groups, bilateral agencies, global and national non-governmental organisations and, increasingly, the private sector must work together to find innovative approaches to increase awareness of the broader social, public health and nutritional contexts, and to advocate for increased national nd international funding.     

基于CCD成像的多角度激光散射探测技术

介绍了基于CCD成像的多角度激光散射的探测技术。本技术采用数字图象、神经网络等处理技术，对不同的燃烧方式设定相应的灵敏度，能准确识别灰尘、飞虫和水蒸汽等非火灾的干扰因素，实现了在复杂环境中稳定可靠的超早期的火灾探测和报警，改变了现有探测技术在提高灵敏度后却只能用于洁净环境、对恶劣环境只能通过提高报警阈值等手段来解决的被动局面。     

某山坡露天矿边坡稳定性的FLAC3D研究

某山坡露天矿,原设计的最终边坡角约为46°。为了探索最终边坡角的合理性,应用快速拉格朗日有限差分法FLAC3D在摩尔-库伦准则下搜索该岩质山坡露天边坡的潜在受拉区,判定其稳定性。结果表明:经济合理的最终边坡角是50°38';应用8 m长的锚索加固局部台阶可减小其潜在受拉区中的拉应力;并段将减小边坡的稳定性;爆破开挖时的同段最大装药量与爆距对边坡稳定性影响明显。该方法确定最终边坡角技术可行,它适用于研究岩质边坡的稳定性,克服了用极限平衡法研究边坡稳定性必须事先假定滑动面的弱点。     

软煤样断裂韧性加载速率效应实验研究*

为探究加载速率对软煤样Ⅰ型断裂韧性的影响,对取自云南老厂的煤样开展压入硬度实验及不同加载速率条件下的断裂韧性实验,分析加载速率及割理角度对软煤样断裂特性的影响。结果表明:实验老厂煤岩压入硬度分布在51.84～125.03 MPa之间,按压入硬度划分属于软岩类别;实验岩样Ⅰ型断裂韧性分布在0.009 9～0.208 2 MPa·mm^0.5之间,平均值为0.096 5 MPa·mm^0.5;在0.2～1.1 mm/min的位移加载速率范围内,实验软煤岩Ⅰ型断裂韧性值随加载速率的增大呈现先增大后降低的规律,割理角度对软煤岩Ⅰ型断裂韧性有较大影响,Ⅰ型断裂韧性与割理角度的关系呈现为负线性相关性。低加载速率条件下,软煤岩表现为韧性断裂,高加载速率条件下,软煤岩表现为脆性断裂,加载速率的变化导致软煤岩断裂类型的变化。