复杂坝基重力坝抗滑稳定分析中应力状态研究

将有限元应力成果代入刚体极限平衡法中推求滑块稳定安全系数的强度校核法是一种有效的稳定分析方法,但线性和非线性应力分布所造成的差异是一个尚待深入研究的课题。通过对具有复杂坝基的重力坝的抗滑稳定进行分析,得出如下结论:采用强度校核法进行稳定分析时,应用弹性与非线性有限元的应力结果所得稳定安全系数相差不大,采用弹性有限元的结果能满足工程精度要求。     

九龙江流域台风期暴雨洪水预报方法探讨

通过研究九龙江流域的暴雨形成原因,分析登陆点与雨量、暴雨中心的关系等问题,对建立科学的台风期暴雨洪水预报体系,提高防汛抗旱的预见性具有重要意义。     

闹德海水库除险加固工程消能工设计

自建库以来,闹德海水库溢流坝下无任何消能工程,护坦下游20m处,形成一深度近6m、面积达1200m^2的冲坑,直接威胁大坝的安全。本次水库除险加固设计,根据水库的实际运行工况,结合下游地形和地质条件,通过多个方案的技术经济比较,最终采用了底流消力池设计解决消能问题,确保了水库的结构安全和运行安全。     

Antioxidative capacity produced by Bifidobacterium‐ and Lactobacillus acidophilus‐mediated fermentations of konjac glucomannan and glucomannan oligosaccharides

BACKGROUND: Konjac glucomannan (KGM) has been shown to stimulate the growth of bifidobacteria and lactobacilli in the human and rat colon. This study investigated the antioxidative effects produced after 48 h in vitro fermentation of unhydrolysed KGM and two hydrolysed KGM fractions (KH1 and KH2 with degree of polymerisation 10 and 5 respectively) by Bifidobacterium adolescentis, B. bifidum, B. breve, B. longum and Lactobacillus acidophilus respectively. The inhibitory effect on conjugated diene formation, ferric‐chelating capacity, α,α‐diphenyl‐β‐picrylhydrazyl (DPPH) radical‐scavenging ability and thiobarbituric acid‐reactive substances (TBARS) concentration produced by these fermentations were compared with those of oligofructose (OF) fermentation. RESULTS: The fermentation of KGM by each bacterial strain produced higher ferric‐chelating capacity of the culture supernatant compared with KH2 or OF fermentation. In contrast, the fermentation of KGM by each bacterial strain led to lower inhibition of conjugated diene formation and lower radical‐scavenging ability compared with KH2 fermentation. The fermentation of KH2 produced the lowest amount of TBARS. CONCLUSION: The fermentation of unhydrolysed KGM by colonic lactic acid bacteria in vitro produced antioxidative capacity mainly by preventing the initiation of ferrous ion‐induced peroxidation, whereas the fermentation of konjac oligosaccahrides did so by increasing the radical‐scavenging ability and eliminating lipid peroxide formation. Copyright © 2008 Society of Chemical Industry     

Rind of the rambutan, Nephelium lappaceum, a potential source of natural antioxidants

The rind of rambutan, which is normally discarded was found to contain extremely high antioxidant activity when assessed using several methods. Although having a yield of only 18%, the ethanolic rambutan rind extract had a total phenolic content of 762 ± 10 mg GAE/g extract, which is comparable to that of a commercial preparation of grape seed extract. Comparing the extract’s pro-oxidant capabilities with vitamin C, α-tocopherol, grape seed and green tea, the rind had the lowest pro-oxidant capacity. In addition, the extract at 100 μg/ml was seen to limit oxidant-induced cell death (DPPH at 50 μM) by apoptosis to an extent similar to that of grape seed. The extracts were not cytotoxic to normal mouse fibroblast cells or splenocytes while the powderised rind was seen to have heavy metals contents far below the permissible levels for nutraceuticals. Our study for the first time reveals the high phenolic content, low pro-oxidant capacity and strong antioxidant activity of the extract from rind of Nephelium lappaceum. This extract, either alone or in combination with other active principles, can be used in cosmetic, nutraceutical and pharmaceutical applications.     

Overland Flow along Stone Covered Slope Land Simulated with Semi-Analytical and Numerical Models

Overland flow is an important hydrological response of catchments to rainstorms and contributes to soil erosion and nutrient loss. The kinematic wave model is known to describe the transformation of rainfall to overland flow. Through this, field studies were conducted on a hillslope to simulate water scouring from upstream with a complex surface condition, which was covered with different sizes and percentages of stones. Existing semi-analytical and numerical models were adopted to describe the overland flow in the field. Results indicate that both semi-analytical and numerical models could be applied to describe the process of overland flow. Furthermore, predicted outflow rates by the semi-analytical and the numerical model showed strong correlation with the field measured outflow rates, respectively (NS?=?(0.926, 0.942, 0.992), RE?=?(5.5%, 4.7%, 1.7%) for the semi-analytical model, and NS?=?(0.817, 0.952, 0.992), RE?=?(5.5%, 5.5%, 2.1%) for the numerical model). Besides, hydraulic parameters (Reynolds number-Re, Froude numbers-Fr, Darcy-Weisbach-f, hydraulic shear stress-τ, stream power-ω, water wave celerity-v_w) at any time and distance could be described by the semi-analytical method, and the parameter n/h (an important factor indicating the energy of water and wave flow celerity) could successfully characterize the average hydraulic parameters, and all of the hydraulic parameters are fitted to the expression of y?=?a(n/h)^b.

     

劈裂灌浆技术在土质堤坝工程中的运用

福建省漳州市在中小型水库及堤防工程除险加固中采用劈裂灌浆技术取得了较好的效果。通过对已施灌的水库大坝、堤防运行情况进行观测,达到了预期目的。在实践中,对劈裂灌浆工艺要点进行了充实、完善,使其在治理大面积湿坡、漏水、渗水、降低浸润线,提高坝体质量,防止白蚁贯穿堤身等方面,发挥了显著效益。     

基于缝网扩展模拟的致密储层体积压裂水平井产能贡献分析

针对致密储层体积压裂缝网扩展预测和多重孔隙介质耦合流动模拟难度大的问题,开展了基于体积压裂裂缝扩展机理的致密储层流体流动规律研究,建立了多重介质不稳定渗流数学模型和多裂缝互相干扰条件下的压裂裂缝网络扩展模型,并采用有限单元法求解.以鄂尔多斯盆地致密油为例进行生产模拟,分析致密油藏体积压裂水平井不同孔隙介质产量贡献程度....     

油气并举再攀高峰——中国近海2010年勘探回顾及"十二五"勘探展望

近年来,中国近海油气勘探步入历史最好发展时期,有力地支持了"海上大庆油田"的建成,也为今后可持续发展奠定了坚实的基础.2010年,中国近海油气勘探成效显著,自营勘探储量发现再创历史新高,成熟区勘探拓展连获成功,勘探新区新领域不断开辟,石油和天然气勘探齐头并进.文中总结了中国近海2010年油气勘探取得的主要成果及其特点,并展望了"十二五"中国近海油气勘探前景.     

气相色谱法测定防老剂EPPD有效成分

利用气相色谱仪对橡胶防老剂EPPD有效成分进行了分析。结果表明,测定结果的准确度高,试样的相对标准偏差为0.283%～1.267%;标准溶液的回收率为98.91%～100.84%,相对误差为-1.09%～0.84%。