复合材料补片胶接修补剥蚀金属结构技术研究

建立了复合材料补片单面胶接修理含孔剥蚀损伤铝合金试件的三维有限元模型,分析了修理结构的应力分布情况,对中性轴偏离导致的弯曲变形及固化过程中形成的残余热应力对修理效果的影响进行了评估。结果表明,复合材料补片单面胶接修理是一种有效的修理方法,复合材料补片可以对含孔剥蚀损伤铝合金试件补强。     

Increased egg estradiol concentration feminizes digit ratios of male pheasants (<Emphasis Type="Italic">Phasianus colchicus</Emphasis>)

The length ratio between individual digits differs between males and females in humans, other mammals, lizards, and one bird species. Sexual dimorphism in digit ratios and variation among individuals of the same sex may depend on differential exposure to androgens and estrogens during embryonic life. Organizational effects of sex hormones could cause the observed correlations between digit ratios and diverse phenotypic traits in humans. However, no study has investigated experimentally the effect of prenatal estrogens on digit ratios. We analyzed the effect of estradiol injection in ring-necked pheasant (Phasianus colchicus) eggs on digit ratios. Males from control eggs had higher ratios between the second or third and the fourth digit of the right foot compared to females. Estradiol-treated eggs produced males with lower (feminized) right foot second to fourth digit ratio. Thus, we provided the first experimental evidence that prenatal exposure to physiologically high estrogen levels affects bird digit ratios.     

基于DEM的白云山区域三维景观模型的建立和应用

数字高程模型DEM是对地形地貌的一种离散的数字表达,是构建三维模型的基础数据。DEM的一种数据格式GRID通过二维的格网灰度描述地形的起伏,另一种数据格式TIN通过连续三角面模拟地形表面。文章根据DEM对地形高程变化敏感这一特性,选取地形起伏大和地貌类型多样的山地丘陵地区—白云山区域作为研究区,在ARCGIS环境下将二维等高线数据转化为三维地形表面,以TIN为基准高程叠加区域内的矢量图层和遥感影像图,最终构建区域环境的三维景观模型.并以模型为基础,假设区域内的磨刀坑水库在无源淹没的情况下,应用三维分析功能计算水库淹没地形的表面积和体积。     

地下水曝气修复过程的三维数值模拟

地下水曝气法是去除挥发性有机污染物的重要原位修复方法之一,目前已得到广泛应用,但其现场设计主要依据经验,缺乏系统的设计标准.为深入了解曝气去除污染物过程,并为现场设计提供重要参考依据,针对地下水曝气过程开展了数值模拟研究.水气两相渗流数值模型以水压力和气压力作为基本未知量,利用达西定律和质量守恒原理可以建立水气两相渗流过程的控制方程.利用Van Genuchten(VG)模型及Mualem公式,建立渗透系数-饱和度-基质吸力(K-S-P)三者之间的关系.污染物的去除过程则是在水气两相渗流的基础上,引入污染物的溶质运移、相间交换及生物降解模型.采用开发的有限元数值模型,对地下水曝气过程及污染物去除过程进行三维数值模拟,并将三维数值模拟的结果与二维数值模拟的结果进行对比.结果表明,三维模型的曝气影响区域偏小,在曝气口附近,水有效饱和度最小;在曝气口上方,水饱和度先增大后减小.考虑气体所受的浮力作用或不考虑气体可压缩性均会使计算得到的曝气影响区域偏小.污染物去除边界与曝气影响区域的边界基本一致,在曝气区域内,溶质交换过程大大促进了污染物的去除速率;在曝气区域外,污染物的去除主要通过生物降解作用,去除较慢.结果表明实际工程地下水曝气修复系统设计时,应使得曝气影响区域覆盖污染区域以得到较好的修复效果.研究结果表明,两相渗流模型结合污染物迁移转化模型的三维有限元数值模拟可以较好地模拟地下水曝气法去除污染物的全过程,对地下水曝气的设计、应用与效果评价具有重要指导意义.     

Green research and development (R&D) investment and its impact on the market value of firms: evidence from South African mining firms

The importance of global corporate green research and development (R&D) investment is gaining momentum and South Africa is no exception. This paper examines growing economic perceptions that green financial and stock-market systems result in heightened corporate hyperopia and therefore increase long-term and future green investment associated with R&D. It reports on the findings of a survey of 14 South African mining firms listed on the Johannesburg Stock Exchange SRI index. The study found, that, these firms’ market value showed a positive association with Green R&D. It also revealed increased Green R&D activity among large mining firms in the country and that they are highly likely to maintain their level of such investment in the coming years. The study's outcomes thus add to the body of empirical knowledge on firm hyperopia in relation to corporate greening initiatives.     

An energetic life cycle assessment of C&D waste and container glass recycling in Cape Town,South Africa

This study presents the results of a comparative life cycle assessment (LCA) on the energy requirements and greenhouse gas (GHG) emission implications of recycling construction and demolition (C&D) rubble and container glass in Cape Town, South Africa. Cape Town is a medium sized city in a developing country with a growing population and a rising middle class, two factors that are resulting in increased generation of solid waste. The City is constrained in terms of landfill space and competing demands for municipal resources.The LCA assessment was based on locally gathered data, supplemented with ecoinvent life cycle inventory data modified to the local context. The results indicated that recycling container glass instead of landfilling can achieve an energy savings of 27% and a GHG emissions savings of 37%, with a net savings still being achieved even if collection practices are varied. The C&D waste results, however, showed net savings only for certain recycling strategies. Recycling C&D waste can avoid up to 90% of the energy and GHG emissions of landfilling when processed and reused onsite but, due to great dependence on haulage distances, a net reduction of energy use and GHG emissions could not be confidently discerned for offsite recycling. It was also found that recycling glass achieves significantly greater savings of energy and emissions than recycling an equivalent mass of C&D waste.The study demonstrated that LCA provides an important tool to inform decisions on supporting recycling activities where resources are limited. It also confirmed other researchers’ observations that strict adherence to the waste management hierarchy will not always result in the best environmental outcome, and that more nuanced analysis is required. The study found that the desirability of recycling from an energy and climate perspective cannot be predicted on the basis of whether such recycling conserves a non-renewable material. However, recycling that replaces a virgin product from an energy-intensive production process appears to be more robustly beneficial than recycling that replaces a product with little embodied energy. Particular caution is needed when applying the waste management hierarchy to the latter situations.     

土壤气抽提多井方案的数值模拟研究

以存在石油烃污染的北京市某加油站场地为研究对象,设计了土壤气抽提(SVE)原位修复系统,应用AIR3D软件对SVE作用下土壤包气带的气压场进行数值模拟.划定以土壤气压强低于或等于101.122kPa的区域为抽气影响区域.模拟结果显示,单井的抽气影响区域不能满足要求;多井抽气时,井间区域土壤气体真空度受多井共同作用,扩大了抽气的影响区域.抽气井不同布置情况下井间距大小对相互作用效果存在影响.研究发现,井间相互作用随着井间距的增大而减小,井间距存在临界值.井间距临界值与抽气井的布置形式相关.对于本研究中的2眼井、3眼井、4眼井情景,此临界值分别在3~5m、5~8m、8~10m区间.超过此临界值时井间相互作用将显著减弱,并导致抽气影响区域不能覆盖整个井间范围.     

抗滑桩加固三维多地层边坡最小势能稳定性分析

为了分析抗滑桩加固边坡的稳定性,基于最小势能原理,考虑桩土之间的相互作用和滑面储存的剪切势能,提出了抗滑桩加固多地层边坡的三维稳定性分析方法。将该方法与其他方法进行对比验证,并分析了抗滑桩相关参数对边坡稳定性的影响。结果表明:该方法是合理可行的;当抗滑桩位于边坡中部时,对边坡的稳定性更好;当抗滑桩的桩间距大于8 m时,抗滑桩间距的变化对边坡安全系数的影响较小。     

近岸海域多环芳烃生态系统动力学模型及生境影响

利用生态动力学模型Delf3D,对大连葫芦山湾海域多环芳烃(PAHs)在海洋中的理化及生态动力学过程进行耦合,并以大连葫芦山湾实际监测数据及相关文献资料为基础,确定了一套适用于该近岸海域PAHs生态动力学过程的特征参数,模拟研究了PAHs在近岸海域生态动力学过程.以浮游植物生长率作为指示近岸海域生态系统健康程度的指标,将PAHs含量的数值模拟结果与浮游植物生长率的动力学响应方程相拟合,定量的评估了PAHs对海洋生态系统的影响.结果显示:排污口选址于水深大、流速快、水动力强处,对PAHs污染物扩散、水质改善具有显著作用,反之造成PAHs大规模富集.PAHs富集作用对该湾生境影响较显著,湾顶水动力作用微弱,浮游生物生长率削减度高达18%.ArcGIS分析显示,浮游生物生长率削减程度与PAHs时空分布并不完全一致,体现海湾生态系统的动力复杂性与结构稳固性.