Inversion of quasi-3D DC resistivity imaging data using artificial neural networks   总被引：2，自引：0，他引：2  

Ahmad Neyamadpour  W. A. T. Wan Abdullah  Samsudin Taib 《Journal of Earth System Science》2010,119(1):27-40

The objective of this paper is to investigate the applicability of artificial neural networks in inverting quasi-3D DC resistivity imaging data. An electrical resistivity imaging survey was carried out along seven parallel lines using a dipole-dipole array to confirm the validation of the results of an inversion using an artificial neural network technique. The model used to produce synthetic data to train the artificial neural network was a homogeneous medium of 100Ωm resistivity with an embedded anomalous body of 1000Ωm resistivity. The network was trained using 21 datasets (comprising 12159 data points) and tested on another 11 synthetic datasets (comprising 6369 data points) and on real field data. Another 24 test datasets (comprising 13896 data points) consisting of different resistivities for the background and the anomalous bodies were used in order to test the interpolation and extrapolation of network properties. Different learning paradigms were tried in the training process of the neural network, with the resilient propagation paradigm being the most efficient. The number of nodes, hidden layers, and efficient values for learning rate and momentum coefficient have been studied. Although a significant correlation between results of the neural network and the conventional robust inversion technique was found, the ANN results show more details of the subsurface structure, and the RMS misfits for the results of the neural network are less than seen with conventional methods. The interpreted results show that the trained network was able to invert quasi-3D electrical resistivity imaging data obtained by dipole-dipole configuration both rapidly and accurately.  相似文献   

Clustering of non-point mass system of galaxies in the expanding Universe     

Farooq Ahmad  Abdul Wahid  Ajaz Ahmad 《Astrophysics and Space Science》2010,330(1):115-121

We derive the cosmic energy equation for the non-point mass system of galaxies (galaxies with halos) by using the adiabatic approximation for the growth of gravitational clustering of galaxies in the expanding Universe. The cosmic energy equation so derived represents the general form of conservation of energy for the expanding volume. Using the derived form of cosmic energy equation we try to study the evolution of correlation potential energy of the system. We also try to explore the condition under which the approximation of extensivity may be applied to the infinite gravitating non-point mass system of galaxies.  相似文献   

Deterioration of groundwater quality in the vicinity of an active open-tipping site in West Malaysia   总被引：3，自引：0，他引：3  

Bahaa-eldin E. A. Rahim  I. Yusoff  A. R. Samsudin  W. Z. W. Yaacob  A. G. M. Rafek 《Hydrogeology Journal》2010,18(4):997-1006

There is an urgent need for characterization of leachate arising from waste disposal to ensure a corresponding effective leachate management policy. Field and laboratory studies have been carried out to investigate the impact of municipal landfill leachate on the underlying groundwater at a site in West Malaysia. The solid waste was disposed of directly onto an unprotected natural soil formation. This situation was made worse by the shallow water table. The hydrochemical composition of groundwater in the vicinity of the site (background) is a dilute mixed cation, bicarbonate water. The high ionic balance error of ~13.5% reveals that the groundwater body underneath the site was a highly contaminated leachate rather than contaminated groundwater. Elevated concentration of chloride (355.48 mg/L), nitrate (10.40 mg/L as NO₃), nitrite (14.59 mg/L), ammoniacal-N (11.61 mg/L), sodium (227.56 mg/L), iron (0.97 mg/L), and lead (0.32 mg/L) measured downgradient indicate that the contamination plume has migrated further away from the site. In most cases, the concentration of these contamination indicators, together with the ranges of sodium percentage (66.3–89.9%) and sodium adsorption ratio (10.1–19.7%), were found to be considerably higher than the limit values of safe water for both domestic and irrigation purposes, respectively.  相似文献   

Trace element geochemistry of groundwater from Quetta Valley,western Pakistan   总被引：1，自引：0，他引：1  

Shuhab D. Khan  Khalid Mahmood  Mohamed I. Sultan  Abdul S. Khan  Yingqian Xiong  Zhanay Sagintayev 《Environmental Earth Sciences》2010,60(3):573-582

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Recent changes in extreme rainfall events in Peninsular Malaysia: 1971–2005     

Wan Zawiah Wan Zin  Suhaila Jamaludin  Sayang Mohd Deni  Abdul Aziz Jemain 《Theoretical and Applied Climatology》2010,99(3-4):303-314

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Stormflow generation involving pipe flow in a zero‐order basin of Peninsular Malaysia     

J. N. Negishi  S. Noguchi  R. C. Sidle  A. D. Ziegler  Abdul Rahim Nik 《水文研究》2007,21(6):789-806

Hydrological responses in a zero‐order basin (ZOB), a portion of whose discharge emerged via preferential flow through soil pipes, were examined over a 2‐year period in Peninsular Malaysia to elucidate primary stormflow generation processes. Silicon (Si) and specific conductance (EC) in various runoff components were also measured to identify their sources. ZOB flow response was dependent on antecedent precipitation amount; runoff increased linearly with precipitation during events >20 mm in relatively wet antecedent moisture conditions. Runoff derived from direct precipitation falling onto saturated areas accounted for <0·2% of total ZOB flow volume during the study period, indicating the predominance of subsurface pathways in ZOB flow. ZOB flow (high EC and low Si) was distinct from perennial baseflow via bedrock seepage (low EC and high Si) 5 m downstream of the ZOB outlet. Pipe flow responded quickly to ZOB flow rate and was characterized by a threshold flow capacity unique to each pipe. Piezometric data and pipe flow records demonstrated that pipes located deeper in the soil initiated first, followed by those at shallower depths; initiation of pipe flow corresponded to shallow groundwater rise above the saprolite‐soil interface. Chemical signatures of pipe flow were similar to each other and to the ZOB flow, suggesting that the sources were well‐mixed soil‐derived shallow groundwater. Based upon the volume of pipe flow during storms, the combined contribution of the pipes monitored accounted for 48% of total ZOB flow during the study period. Our results suggest that shallow groundwater, possibly facilitated by preferential flow accreted above the saprolite–soil interface, provides dominant stormflow, and that soil pipes play an important role in the rapid delivery of solute‐rich water to the stream system. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Water and sediment quality, partial mass budget and effluent N loading in coastal brackishwater shrimp farms in Bangladesh   总被引：2，自引：0，他引：2  

Shahidul Islam M  Jahangir Sarker M  Yamamoto T  Abdul Wahab M  Tanaka M 《Marine pollution bulletin》2004,48(5-6):471-485

The present study aimed to quantify the water and sediment quality and growth and production parameters and to establish nutrient budgets for an average of five selected semi-intensive shrimp ponds in Bangladesh over a growing cycle. Physico-chemical parameters of water and sediments were measured and analyzed by standard methods. Gross yield (kg ha-1) of shrimp was calculated from the stocking and harvesting data. Finally, a partial nutrient mass budget for N and P was calculated. Most of the parameters of water and sediments correlated significantly with each other suggesting a high degree of interactions between different parameters in the system. Significantly higher concentrations of all species of nitrogenous nutrients were recorded in the effluent waters than that entering into the ponds. Therefore, a high loading and net output of nitrogenous nutrients in effluent waters was documented. The study also indicated a net discharge of solids and minerals through effluent loading. However, significantly lower concentrations of phosphorus in the effluent water indicated a net retention and trapping of phosphatic nutrients in the environment. Total production ranged between 532.0 and 697.0 kg ha-1 cycle-1 and P. monodon production between 484.0 and 562.0 kg ha-1 cycle-1. Ponds gained nitrogen primarily from intake water (55%) and fertilizers (29%), and nitrogen was lost primarily from water exchange (78%) and harvested shrimp (12%). Phosphorus gain occurred mostly from intake water (52%) and fertilizers (25%), and phosphorus was lost primarily from water exchange (52%) and harvested shrimp (3.3%). About 10% of input nitrogen and 44% of phosphorus were not accounted for in measured losses, and presumably were fixed or metabolized in the system. On average, 78 g N was discharged to and 25 g P was removed from the surrounding water by the system for each kilogram of shrimp produced. Mean conversion of feed nitrogen and phosphorus to shrimp flesh averaged 74% and 40%, respectively. It was concluded that semi-intensive systems serve as net supplier of N to and net remover of P from the surrounding water.  相似文献   

Holocene faulting and earthquake recurrence along the Serghaya branch of the Dead Sea fault system in Syria and Lebanon   总被引：3，自引：0，他引：3  

Francisco Gomez  Mustapha Meghraoui  Abdul Nasser Darkal  Fouad Hijazi  Michel Mouty  Youssef Suleiman  Reda Sbeinati  Ryad Darawcheh  Riad Al-Ghazzi  Muawia Barazangi 《Geophysical Journal International》2003,153(3):658-674

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结合遥感和气象数据的森林火险监测研究——以马来西亚半岛为例   总被引：4，自引：1，他引：3  

彭光雄  陈云浩  李京 《地球信息科学学报》2007,9(5):99-104

结合遥感和气象数据,基于可燃物引燃能量的物理概念,利用火灾敏感性指数(FSI)进行森林火险监测和评估。计算FSI只需要两个参数,即可燃物的温度和湿度,两者均可以从遥感和气象数据获得。利用遥感数据进行可燃物类型制图,并根据可燃物易燃性对FSI的值进行调整计算。利用MODIS探测的火点数据对马来西亚半岛火灾前9天的FSI进行了比较分析,发现随着火灾发生日期的接近,FSI的值逐渐升高,这个趋势在火灾发生的前4天中表现的尤其明显。结果表明,FSI将遥感数据和气象数据两者紧密结合在一起,能够很好地对森林火险进行监测和预警,是一种性能优越的火险评价指数。FSI可用于计算可燃物的点燃概率以及在不同的生态系统中进行火险的比较,并且因其灵活性和可扩展性,有利于不同类型火险模型的集成和发展。  相似文献   

Cretaceous Environments of Afghanistan:A Synthesis Based on Selected Sections     

Abdul Rahman Ashraf  Ashok Sahni 《世界地质(英文版)》2003,6(1)

The Cretaceous of Afghanistan is marked by great facies diversity. The evolution of Cretaceous basins is part of a complex accretionary history involving three distinct tectonic units namely the Asian (Russian) Block separated from the Indian plate by a rather well defined transcurrent fault (Chaman-Nuski). The southwestern component is representedby the Iran-Afghanistan plate. The Lower Cretaceous of the Asian Block is represented by the Red-Grit Series which isconformable to the underlying Upper Jurassic sequences. The transition is marked by evaporitic facies dominated by salt,gypsum and marl deposits. In south Afghanistan volcanic rocks occur at Farah, with the emplacement of plutonics inwest-central Afghanistan. The Upper Cretaceous of north Afghanistan is marked by richly fossiliferous, lime stone-dominated sequences. The Upper Cretaceous of southern Afghanistan is marked by strong ophiolitic magrmatism.  相似文献