Numerical modelling of shear socketed piers

When a socketed pier embedded in a rock mass is pushed down, the concrete asperities slide over the matching rock asperities. Consequently, the normal stress across the rock–concrete interface increases due to the dilation of the rough contact. The objective of this paper is to model the behaviour of such rough interfaces analytically. A plasticity‐based interface model is developed and implemented in a finite element program. Various features of the model such as failure criterion, plastic potential, bond degradation and dilatancy are presented. Interface parameters obtained from laboratory tests are used to simulate the interaction between concrete and rock numerically. A comparison between laboratory observations and numerical predictions is presented. Copyright © 2000 John Wiley & Sons, Ltd.     

Linear and non-linear approaches to predict the Darcy-Weisbach friction factor of overland flow using the extreme learning machine approach

In modeling of overland flow and erosion, the overland flow friction factor (f), is a crucial factor. Due to the importance of a good understanding of f and its variability, the current study aimed to investigate the capability of non-linear approaches to estimate the Darcy-Weisbach friction factor of overland flow and its components (sediment transport, wave, form, and grain friction factors) through the Extreme Learning Machine (ELM) approach. Four datasets were used herein which were obtained from flume experiments done by different researchers. In order to investigate the effects of different parameters on the friction factor, numerous models consisting of various parameters were utilized to predict the friction factor using the ELM approach. The modeling procedure was established in two stages; the first stage aimed to model the overland flow friction factor and investigate the effect of the different parameters on the friction factor using non-linear separation via the ELM approach. In the second stage, the friction factor was linearly separated into different types of friction factors and then the separate components were estimated. Sensitivity analysis results confirmed the key role of Froude number (Fr) values for most of the models. On the other hand, the results obtained for estimated values of the friction factor were acceptable and outperformed available empirical approaches.     

Evaluating severity–area–frequency (SAF) of seasonal droughts in Bangladesh under climate change scenarios

Stochastic Environmental Research and Risk Assessment - Drought is considered to be one of the most devastating natural hazards, causing widespread environmental and social damage in many parts of...     

ROLE OF CONSTRUCTED WETLANDS IN NUTRIENT STRIPPING

1　INTRODUCTIONConstructedwetlandsplayanimportantroleinthereductionofnutrients,particularlyphosphorous,fromenteringintothewaterways .Excessivelevelsofphosphoroushavebeenidentifiedasamajorcon tributortoblue greenalgalbloomsinwaterways.Anumberofresearchprog…     

Distribution and generic composition of culturable marine actinomycetes from the sediments of Indian continental slope of Bay of Bengal

Actinomycetes population from continental slope sediment of the Bay of Bengal was studied. Samples were collected during two voyages of FORV Sagar Sampada in 2004 （May-June） and 2005 （July） respectively from 11 transects （each transect had ca. 200 m, 500 m, and 1 000 m depth stations）. The physicochemical parameters of overlying water, and sediment samples were also recorded. The actinomycete population ranged from 5.17 to 51.94 CFU/g dry sediment weight and 9.38 to 45.22 CFU/g dry sediment weight during the two cruises respectively. No actinomycete colony was isolated from stations in 1 000 m depth. Two-way analysis of variance showed significant variation among stations （ANOVA two-way, P〈0.05）, but no significance was found between the two cruises （ANOVA two-way, P〈0.05）. Populations in stations in 500 m depth in both cruises were higher than that of 200 m depth stations with statistically insignificant difference （ANOVA two-way, P〉0.05）. Three actinomycetes genera were identified. Streptomyces was found to be the dominating one in both the cruises, followed by Micromonospora, and Actinomyces. The spore of Streptomyces isolates showed the abundance in spiral spore chain. Spore surface was smooth. Multiple regression analysis revealed that the influencing physico-chemical factors were sediment pH, sediment temperature, TOC, porosity, salinity, and pressure. The media used in the present study was prepared with seawater. Thus, they may represent an autochthonous marine flora and deny the theory of land runoff carriage into the sea for adaptation to the salinity of the seawater and sediments.     

Semipermeable membrane devices link site-specific contaminants to effects: Part 1 - Induction of CYP1A in rainbow trout from contaminants in Prince William Sound, Alaska

Extracts from semi-permeable membrane devices (SPMDs) deployed on beaches in Prince William Sound (PWS), Alaska, were used to evaluate if complex contaminant mixtures from different sources can be distinguished by the resulting cytochrome P450 1A (CYP1A) activity in exposed test animals. Deployment sites included canneries, salmon hatcheries, and beaches where lingering oil remains from discharges during the 1964 earthquake or the 1989 Exxon Valdez oil spill. Other sites were selected at random to evaluate region-wide contaminant inputs or were located in salmon streams to evaluate contaminants carried and released by migrating salmon carcasses following reproduction. Following standard deployments of approximately 28 d, an aliquot of the accumulated contaminants was intraperitoneally injected without cleanup into juvenile rainbow trout (Oncorhynchus mykiss). After 2 d and 7 d, the activity of CYP1A was measured by the ethoxyresorufin-o-deethylase (EROD) assay. Exposure to extracts from the oiled sites and one hatchery site with numerous creosote pilings elicited strong EROD responses, whereas fish exposed to salmon stream extracts elicited weak but significant responses during late summer compared to late spring. Responses from the other sites were not significant, indicating contaminants from these sources are unlikely to cause CYP1A induction in resident biota. Rather than simply assessing extant contaminants, this method evaluates the potency of the different sites for bringing about aryl hydrocarbon receptor responses in resident biota.     

巴基斯坦穆斯林巴赫铬铁矿床成矿环境、 地质特征及控矿因素

巴基斯坦境内蛇绿岩广泛分布,且大多发育铬铁矿化。穆斯林巴赫铬铁矿床位于巴基斯坦中部,是新特提斯缝合带中大型豆荚状铬铁矿床之一,目前已经发现数百个矿体,储量超过4000 kt,是巴基斯坦境内最重要的铬铁矿产地。张洪瑞等（2013）总结了中部瓦济里斯坦-贝拉蛇绿岩带的地质特征和穆斯林巴赫铬铁矿床的产出特征,认为穆斯林巴赫铬铁矿床成因仍存在争议,其形成构造环境、控矿因素有待于进一步研究。本文论述穆斯林巴赫矿床的地质特征,通过矿床地球化学和铬尖晶石矿物化学等研究,结合我国典型的罗布莎豆荚状铬铁矿研究成果,分析了主要控矿因素,为巴基斯坦境内相同类型矿床的找矿勘查提供依据。