Potential Hydrodynamic Performance Enhancement of Hydrokinetic Turbine with Hydrophobic Coatings

China Ocean Engineering - Hydrokinetic energy is a promising technology to harness predictable renewable energy from free-flowing water, tides and ocean currents. Many studies have been conducted...     

华南花岗岩残积土红土化程度的地带性与香港该类土不发育的原因

从华南花岗岩残积土红土化程度的地域变化规律出发 ,通过香港与华南沿海各地花岗岩残积土的化学成分及红土化指标对比 ,作者发现香港花岗岩残积土无论厚度、类型 ,还是红土化程度都具有与所处气候环境不协调的特点。文章进一步讨论了香港花岗岩残积土不发育的原因和对工程性质的影响.     

Distribution of relict permafrost features in the Pannonian Basin,Hungary

Wedge structures and involutions suggest that Late Pleistocene frozen ground, either permafrost or deep seasonal frost, extended at least as far south as latitude 47°N in central Europe (the Pannonian Basin). Optically stimulated luminescence dating of the sand infill from a number of wedges indicates that emplacement of the sand infill occurred during the Late Pleistocene (22.2–15.7 ka). This suggests that during this time the mean annual air temperature was depressed by at least ～15°C relative to the present. Either continuous or discontinuous permafrost was probably present in the north and NW of the Pannonian Basin. The subsequent thaw of frozen ground is indicated by the widespread occurrence of deformed sediments. The presence of soil (ground) wedges suggests conditions of deep seasonal frost probably existed during the period when climate ameliorated following the Last Permafrost Maximum (LPM).     

Consumption tradeoff vs. catastrophes avoidance: implications of some recent results in happiness studies on the economics of climate change

Recent discussion of climate change focuses on the trade-off between present and future consumption and hence correctly emphasizes the discount rate. Stern (2007) favours immediate and strong actions of environmental protection, but this has been questioned as the discount rate used is much lower than the market or commonly used rates. Focussed only on consumption trade-off, the use of these higher discount rates completely reverses the need for strong actions. However, an even more important problem has been largely neglected. This is the avoidance of catastrophes that may threaten the extinction of the human species. But ??we lack a usable economic framework for dealing with these kinds of ... extreme disasters?? (Weitzman, J Econ Lit 45(3):703?C724, 2007, p. 723). To analyse this, the comparison of marginal utility with total utility is needed. As happiness studies suggest a low ratio of marginal to total utility and as scientific and technological advances (especially in brain stimulation and genetic engineering) may dramatically increase future welfare, immediate and actions stronger than proposed by Stern may be justified despite high discount rates on future consumption, as discount rates on future utility/welfare should be much lower.     

香港国家地质公园粮船湾组火山岩岩石学研究

在香港国家地质公园西贡火山岩园区,核心地质景观是白垩纪粮船湾组(Kkh)火山岩优美的六方形石柱(柱状节理),它们的岩石类型长期存在熔岩和火山碎屑岩之争。笔者等经野外调查和薄片岩石学研究,确认粮船湾组火山岩实属一种特殊的熔岩——流纹质碎斑熔岩,以普遍的柱状节理、斑晶具有碎斑结构和珠边结构、基质发育霏细结构和流动构造为特征;它们不仅代表了香港地区中生代最晚期火山喷发的产物,而且构成了西贡破火山机构的中央侵出相岩穹。推断粮船湾组火山岩石柱是地球上已知面积最大的流纹质碎斑熔岩石柱群(～150 km2),目前所见的火山岩石柱仅是长期剥蚀后的残余部分。     

Large-scale environmental controls on the seasonal statistics of rapidly intensifying North Atlantic tropical cyclones

This study is concerned with the connections between the large-scale environment and the seasonal occurrence of rapid intensification (RI) of North Atlantic tropical cyclones. Physically-motivated statistical analysis using observations and reanalysis products suggests that for tropical cyclones over the open tropical North Atlantic, the interannual variability of the probability of storms undergoing RI is influenced by seasonal large-scale atmospheric and oceanic variables, but not so for storms over the Gulf of Mexico and western Caribbean Sea. We suggest that this differentiated response is due to the former region exhibiting a strong negative correlation between the seasonal anomalies of vertical wind shear and potential intensity. Differences in the mean climatology and subseasonal variations of the large-scale environment in these regions appear to play an insignificant role in the distinctive seasonal environmental controls on RI. We suggest that the interannual correlation of vertical wind shear and potential intensity is an indicator of seasonal predictability of tropical cyclone activity (including RI) across the tropics .     

Rainfall-induced landslides in Hulu Kelang area, Malaysia

Hulu Kelang is known as one of the most landslide-prone areas in Malaysia. The area has been constantly hit by landslide hazards since 1990s. This paper provides an insight into the mechanism of rainfall-induced landslide in the Hulu Kelang area. Rainfall patterns prior to the occurrences of five selected case studies were first analyzed. The results showed that daily rainfall information is insufficient for predicting landslides in the area. Rainfalls of longer durations, i.e., 3–30 days prior to the landslides should be incorporated into the prediction model. Numerical simulations on a selected case study demonstrated that both matric suction and factor of safety decreased steadily over time until they reached the lowest values on the day of landslide occurrence. Redistribution of infiltrated rainwater in the soil mass could be a reason for the slow response of failure mechanism to rainfall. Based on 21 rainfall-induced landslides that had occurred in the area, three rainfall thresholds were developed as attempts to predict the occurrence of rainfall-induced landslide. The rainfall intensity–duration threshold developed based on the local rainfall conditions provided a reasonably good prediction to the landslide occurrence. The cumulative 3- versus 30-day antecedent precipitation index threshold chart was capable of giving the most reliable prediction with the limiting threshold line for major landslide yielded a reliability of 97.6 %.     

A modified analytical solution of soil stress distribution for XCC pile foundations

X-section cast-in-place concrete pile (XCC pile) is a new type of pile foundation, which has an X-shaped cross section. Compared to the traditional circular pile of the same cross-sectional area, the bearing capacity of an XCC pile is higher due to increased cross-sectional perimeter. Since Geddes solution is based on St. Venant’s principle, leading to the results independent of the cross-sectional geometry and size, large differences are induced when estimating the soil stress distribution for XCC pile foundations. This paper derives a modified analytical solution, which is dependent on the cross-sectional geometry of XCC pile, from Geddes solution. Validation of this modified solution was conducted through three-dimensional numerical analysis and proven more suitable for XCC pile foundations. Parametric study on three geometrical parameters is conducted using this modified solution. The results indicate that the stress in founding soil due to skin friction decreases with increasing pile radius and central angle of concave, but increases with increasing length of flat side. The stress due to end-bearing decreases with increasing pile radius and length of flat side, but increases with increasing central angle of concave. From the parametric studies, the recommended dimensions of XCC pile radius, length of flat side, and central angle of concave are recommended ranges from 200 to 600 mm, 30 to 60 mm, and 90° to 150°, respectively.     

Distribution, classification, petrological and related gochemical (SRA) characteristics of a tropical lowland peat dome in the Kota Samarahan-Asajaya area, West Sarawak, Malaysia

Petrographic studies indicate that lateral variations in the decomposition levels of peat are associated with the predominantly occurring peat macerals. Source Rock Analyzer (SRA) results indicate lateral variation in peat organic matter types from type II to III and back again to type II, occurring laterally within the top 0-m to 0.5-m layer at the basin margin to the midsection and further towards the near-center areas of the peat dome. This variation is most likely caused by a combination of factors: (a) Horizontal zonation and lateral variation of the dominant species of plant assemblages (b) Fibric (marginal) peats and hemic to sapric peats associated with type II organic matter (kerogen). Sample organic matter (coal-equivalent kerogen) typing indicates that the relative abundance of phytoclasts and palynomorphs generally supports the organic matter classification obtained by the SRA method. Lateral variations in the peat organic matter types may support the lateral vegetation variation concept. The classification of peat organic matter types (interpreted from visual analyses of palynological slides) occurring from the basin periphery to the mid-section and further towards the basin center yields organic matter of type II to type III and mixed types II to III (coal kerogen-equivalent), respectively.