Alleviating Effect of Calcium on Nickel Toxicity in Rice          下载免费PDF全文

Humera Aziz  Muhammad Sabir  Hamaad Raza Ahmad  Tariq Aziz  Muhammad Zia‐ur‐Rehman  Khalid Rehman Hakeem  Munir Ozturk 《洁净——土壤、空气、水》2015,43(6):901-909

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A Review of the Principles and Applications of the NMR Technique for Near-Surface Characterization   总被引：2，自引：0，他引：2  

Ahmad A. Behroozmand  Kristina Keating  Esben Auken 《Surveys in Geophysics》2015,36(1):27-85

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A new method of snowmelt sampling for water stable isotopes   总被引：1，自引：0，他引：1       下载免费PDF全文

D. Penna  M. Ahmad  S. J. Birks  L. Bouchaou  M. Brenčič  S. Butt  L. Holko  G. Jeelani  D. E. Martínez  G. Melikadze  J. B. Shanley  S. A. Sokratov  T. Stadnyk  A. Sugimoto  P. Vreča 《水文研究》2014,28(22):5637-5644

We modified a passive capillary sampler (PCS) to collect snowmelt water for isotopic analysis. Past applications of PCSs have been to sample soil water, but the novel aspect of this study was the placement of the PCSs at the ground‐snowpack interface to collect snowmelt. We deployed arrays of PCSs at 11 sites in ten partner countries on five continents representing a range of climate and snow cover worldwide. The PCS reliably collected snowmelt at all sites and caused negligible evaporative fractionation effects in the samples. PCS is low‐cost, easy to install, and collects a representative integrated snowmelt sample throughout the melt season or at the melt event scale. Unlike snow cores, the PCS collects the water that would actually infiltrate the soil; thus, its isotopic composition is appropriate to use for tracing snowmelt water through the hydrologic cycle. The purpose of this Briefing is to show the potential advantages of PCSs and recommend guidelines for constructing and installing them based on our preliminary results from two snowmelt seasons. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Stability of Pineapple Leaf Residue Chars Generated by Controlled Combustion and by Field Burning in Tropical Peat          下载免费PDF全文

Lee Yit Leng  Ahmad Husni Bin Mohd. Hanif  Samsuri Abdul Wahid 《洁净——土壤、空气、水》2014,42(5):648-656

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Wavelet-based multifractal analysis of earthquakes temporal distribution in Mammoth Mountain volcano,Mono County,Eastern California   总被引：1，自引：1，他引：0  

Ahmad Zamani  Amir Pirouz Kolahi Azar  Ali Akbar Safavi 《Acta Geophysica》2014,62(3):585-607

This paper presents a wavelet-based multifractal approach to characterize the statistical properties of temporal distribution of the 1982–2012 seismic activity in Mammoth Mountain volcano. The fractal analysis of time-occurrence series of seismicity has been carried out in relation to seismic swarm in association with magmatic intrusion happening beneath the volcano on 4 May 1989. We used the wavelet transform modulus maxima based multifractal formalism to get the multifractal characteristics of seismicity before, during, and after the unrest. The results revealed that the earthquake sequences across the study area show time-scaling features. It is clearly perceived that the multifractal characteristics are not constant in different periods and there are differences among the seismicity sequences. The attributes of singularity spectrum have been utilized to determine the complexity of seismicity for each period. Findings show that the temporal distribution of earthquakes for swarm period was simpler with respect to pre- and post-swarm periods.  相似文献   

Determination of aquifer geometry through geophysical methods: A case study from Quetta Valley, Pakistan     

Khurshaid Alam  Nasir Ahmad 《Acta Geophysica》2014,62(1):142-163

Due to increase in population and agricultural activities, the aquifer of Quetta Valley is under tremendous stress and the water table is declining at an increasing rate. This situation necessitates evaluation of the aquifer system, for which information about geometry of the aquifer is a prerequisite. However, there are no drilling-to-bedrock data available; therefore, electrical resistivity, seismic reflection and gravity methods were employed to determine geometry of the aquifer. Interpretation of vertical electrical soundings provided information about the depth-tobedrock at some specific points, whereas seismic reflection delineated bedrock topography along two lines. The depths to bedrock inferred from electrical resistivity and seismic reflection data were used as constraints in the modeling of gravity data. 2.75D gravity models were constructed along lines with a regular spacing. Map of depth-to-bedrock was prepared by contouring the depth given by the gravity models. Combination of these geophysical methods depicted the geometry of the aquifer. This example shows that in a similar geological setting proper integration of geophysical exploration methods can determine the aquifer geometry with an acceptable reliability and at an appropriate cost.  相似文献   

Observational constraints on the braneworld model with brane–bulk energy exchange     

M. Sadegh Movahed  Ahmad Sheykhi 《Monthly notices of the Royal Astronomical Society》2008,388(1):197-210

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Simulating low and high streamflow driven by snowmelt in an insufficiently gauged alpine basin     

Feiyun Zhang  Sajjad Ahmad  Hongqi Zhang  Xin Zhao  Xianwei Feng  Lanhai Li 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(1):59-75

Snowmelt and water infiltration are two important processes of the hydrological cycle in alpine basins where snowmelt water is a main contributor of streamflow. In insufficiently gauged basins, hydrologic modeling is a useful approach to understand the runoff formation process and to simulate streamflow. In this study, an existing hydrologic model based on the principles of system dynamics was modified by using the effective cumulative temperature (>0 °C) to calculate snowmelt rate, and the soil temperature to adjust the influence of the soil’s physical state on water infiltration. This modified model was used to simulate streamflows in the Kaidu River basin from 1982 to 2002, including normal, high, and low flows categorized by the Z index. Sensitivity analyses, visual inspection, and statistical measures were employed to evaluate the capability of the model to simulate various components of the streamflow. Results showed that the modified model was robust, and able to simulate the three categories of flows well. The model’s ability to reproduce streamflow in low-flow and normal-flow years was better than that in high-flow years. The model was also able to simulate the baseflow. Further, its ability to simulate spring-peak flow was much better than its ability to simulate the summer-peak flow. This study could provide useful information for water managers in determining water allocations as well as in managing water resources.  相似文献   

Application of singular value decomposition (SVD) and semi-discrete decomposition (SDD) techniques in clustering of geochemical data: an environmental study in central Iran   总被引：1，自引：1，他引：0  

Hamid Zekri  Ahmad Reza Mokhtari  David R. Cohen 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(7):1947-1960

Common multivariate clustering techniques are ineffective in identifying subtle patterns of correlation, and clustering of variables or samples within complex geochemical datasets. This study compares the combination of singular value decomposition (SVD) and semi discrete decomposition (SDD), with that of hierarchical cluster analysis (HCA), to examine patterns within a multielement soil geochemical dataset from an agricultural area in the vicinity of Pb–Zn mining operations in central Iran. SVD was used to both identify patterns of correlation between variables and samples and to “denoise” the data, and SDD to simultaneously cluster the samples and variables. The results reveal various spatial associations of mining waste-associated metals As, Ba, Pb and Zn, and within the remaining elements whose distribution is largely controlled by the major oxides. SVD–SDD was found to be superior to HCA, in its ability to detect subtle clusters in soil geochemistry indicative of mine-related contamination in the study area.  相似文献   

Response of a 2-story test-bed structure for the seismic evaluation of nonstructural systems     

Siavash?SoroushianEmail author  E.?“Manos”?Maragakis  Arash?E.?Zaghi  Esmaeel?Rahmanishamsi  Ahmad?M.?Itani  Gokhan?Pekcan 《地震工程与工程振动(英文版)》2016,15(1):19-29

A full-scale, two-story, two-by-one bay, steel braced-frame was subjected to a number of unidirectional ground motions using three shake tables at the UNR-NEES site. The test-bed frame was designed to study the seismic performance of nonstructural systems including steel-framed gypsum partition walls, suspended ceilings and fire sprinkler systems. The frame can be configured to perform as an elastic or inelastic system to generate large floor accelerations or large inter story drift, respectively. In this study, the dynamic performance of the linear and nonlinear test-beds was comprehensively studied. The seismic performance of nonstructural systems installed in the linear and nonlinear test-beds were assessed during extreme excitations. In addition, the dynamic interactions of the test-bed and installed nonstructural systems are investigated.  相似文献