Titanomagnetites prepared at different oxidation conditions: Influence of magnetite-rich inclusions     

A.A. Rahman  L.G. Parry 《Physics of the Earth and Planetary Interiors》1980,21(1):15-21

Synthetic titanomagnetites prepared at 1300°C at different oxidation potentials, although giving only spinel-type X-ray reflections, were found to contain a small amount of included material with a Curie point above that for the bulk material. Specimens, comprising either dispersed sized grains, or polycrystalline spherical aggregates of grains, develop thermoremanent moments which are dependent upon the presence of the inclusions. The magnetization of the inclusions is revealed by thermal demagnetization experiments, and the experimental results are compared with the effects expected to arise from magnetic shielding by the matrix titanomagnetite.  相似文献   

Response of saturated and nearly saturated porous media: Different formulations and their applicability     

M. B. C. Ulker  M. S. Rahman 《国际地质力学数值与分析法杂志》2009,33(5):633-664

The response of saturated porous medium is of significant interest in many fields ranging from geomechanics to biomechanics. Biot was the first to formulate the basic equations governing the process of coupled flow and deformation in porous media. Depending on the nature of loading vis‐à‐vis the characteristics of the media, different formulations (fully dynamic, partly dynamic, quasi‐static) are possible. In this study, analytical solutions are developed for the response of saturated and nearly saturated porous media under plane strain condition. The solutions for different formulations are developed in terms of non‐dimensional parameters. The response is studied for various conditions and the regions of validity for various formulations are identified in a parametric space. An assessment of the needed formulation for few important problems is also presented. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Seismic hazard assessment for Mymensingh,Bangladesh     

Jiban K. Sarker  Mehedi Ahmed Ansary  Md. S. Rahman  A. M. M. Safiullah 《Environmental Earth Sciences》2010,60(3):643-653

Mymensingh municipality lies in one of the most earthquake-prone areas of Bangladesh. The town was completely destroyed during the Great Indian Earthquake of 12 June 1897, for which the surface-wave magnitude was 8.1. In this study the 1897 Great Indian Earthquake was used as a scenario event for developing seismic microzonation maps for Mymensingh. For microzonation purposes SPT data from 87 boreholes were collected from different relevant organizations. To verify those data ten boreholes of depth up to 30 m were drilled. Intensity values obtained for different events were calibrated against attenuation laws to check applicability to the study area. Vibration characteristics at diverse points of the study area were estimated by employing the one-dimensional wave-propagation software SHAKE. SHAKE discretizes the soil profile into several layers and uses an iterative technique to represent the non-linear behavior of the soil by adjusting the material properties at each iteration step. The required input information includes depth, shear wave velocity, damping factor, and unit weight of each soil layer. The liquefaction resistance factor and the resulting liquefaction potential were estimated to quantify the severity of liquefaction. Quantification of secondary site effects and the weighting scheme for combining the various seismic hazards were heuristic, based on judgment and expert opinion.  相似文献   

Socio-economic drivers of deforestation in Roghani Valley,Hindu-Raj Mountains,Northern Pakistan   总被引：1，自引：1，他引：0  

Fazlur RAHMAN  Fazlul HAQ  Iffat TABASSUM  Ihsan ULLAH 《山地科学学报》2014,11(1):167-179

Deforestation and associated ecological disturbances are the issues of global concern.Researchers have investigated a number of driving forces which accelerate the rate of deforestation at local and regional levels.These include poverty,population growth,market demand and prices,political instability,agricultural expansion and changes in property right and ownership regimes.This paper seeks to explore the impacts of population growth,changing tenure system and other socioeconomic factors on the forest cover of Roghani Valley,located in Hindu Raj Mountains,Northern Pakistan.The present study is mainly based on information collected through participatory observation,selfadministered interviews and questionnaire survey.Geographical Information System（GIS） database is also used for mapping and quantification.The results reveal that in the past three to four decades the study area has been subjected to severe deforestation and about half of the forest area has been converted into barren land.Thus,the area under natural forests decreased from 2099 to 1444 hectares in four decades.This large-scale deforestation is attributed to both proximate and under lying causes particularly traditional land tenure system and demographic development.Consequently,forest resources have been degraded and a number of plant species have disappeared from the forests of the study area while several others are in the process of disappearance.  相似文献   

Partitioning of dioxins (PCDDs/Fs) in ambient air at urban residential locations     

Md. M. Rahman  Z.-H. Shon  C.-J. Ma  R. J. C. Brown  S. K. Pandey  C. G. Park  I. S. Bae  J. R. Sohn  H.-O. Yoon  K.-H. Kim 《International Journal of Environmental Science and Technology》2014,11(7):1897-1910

In this work, 17-polychlorinated dibenzo-p-dioxin/furan (PCDD/Fs) isomers were measured in ambient air at four urban sites in Seoul, Korea (from February to June 2009). The concentrations of their summed values (ΣPCDD/Fs) across all four sites ranged from 1,947 (271 WHO₀₅ TEQ) (Jong Ro) to 2,600 (349 WHO₀₅ TEQ) fg/m³ (Yang Jae) with a mean of 2,125 (± 317) fg/m³ (292 WHO₀₅ TEQ fg/m³). The sum values for the two isomer groups of ΣPCDD and ΣPCDF were 527 (30 WHO₀₅ TEQ) and 1,598 (263 WHO₀₅ TEQ) fg/m³, respectively. The concentration profile of individual species was dominated by the 2,3,4,7,8-PeCDF isomer, which contributed approximately 36 % of the ΣPCDD/Fs value. The observed temporal trends in PCDD/F concentrations were characterized by relative enhancement in the winter and spring. The relative contribution of different sources, when assessed by principal component analysis, is explained by the dominance of vehicular emissions along with coal (or gas) burning as the key source of ambient PCDD/Fs in the residential areas studied.  相似文献   

Yield Forecasting of Spring Maize Using Remote Sensing and Crop Modeling in Faisalabad-Punjab Pakistan     

Ishfaq Ahmad  Umer Saeed  Muhammad Fahad  Asmat Ullah  M. Habib ur Rahman  Ashfaq Ahmad  Jasmeet Judge 《Journal of the Indian Society of Remote Sensing》2018,46(10):1701-1711

Real time, accurate and reliable estimation of maize yield is valuable to policy makers in decision making. The current study was planned for yield estimation of spring maize using remote sensing and crop modeling. In crop modeling, the CERES-Maize model was calibrated and evaluated with the field experiment data and after calibration and evaluation, this model was used to forecast maize yield. A Field survey of 64 farm was also conducted in Faisalabad to collect data on initial field conditions and crop management data. These data were used to forecast maize yield using crop model at farmers’ field. While in remote sensing, peak season Landsat 8 images were classified for landcover classification using machine learning algorithm. After classification, time series normalized difference vegetation index (NDVI) and land surface temperature (LST) of the surveyed 64 farms were calculated. Principle component analysis were run to correlate the indicators with maize yield. The selected LSTs and NDVIs were used to develop yield forecasting equations using least absolute shrinkage and selection operator (LASSO) regression. Calibrated and evaluated results of CERES-Maize showed the mean absolute % error (MAPE) of 0.35–6.71% for all recorded variables. In remote sensing all machine learning algorithms showed the accuracy greater the 90%, however support vector machine (SVM-radial basis) showed the higher accuracy of 97%, that was used for classification of maize area. The accuracy of area estimated through SVM-radial basis was 91%, when validated with crop reporting service. Yield forecasting results of crop model were precise with RMSE of 255 kg ha^?1, while remote sensing showed the RMSE of 397 kg ha^?1. Overall strength of relationship between estimated and actual grain yields were good with R² of 0.94 in both techniques. For regional yield forecasting remote sensing could be used due greater advantages of less input dataset and if focus is to assess specific stress, and interaction of plant genetics to soil and environmental conditions than crop model is very useful tool.  相似文献   

Effects of over-consolidation history on flow instability of clean and silty sands     

Lashkari  Ali  Shourijeh  Piltan Tabatabaie  Khorasani  Seyed Saeid Sahebkar  Irani  Nazanin  Rahman  Md. Mizanur 《Acta Geotechnica》2022,17(11):4989-5007

Acta Geotechnica - This article presents an experimental program under the constant volume condition to investigate the influence of over-consolidation on flow instability of clean and silty sand...  相似文献   

Design flood estimation in ungauged catchments using genetic algorithm-based artificial neural network (GAANN) technique for Australia   总被引：2，自引：0，他引：2  

K. Aziz  Sohail Rai  A. Rahman 《Natural Hazards》2015,77(2):805-821

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Exploratory experiments to determine the effect of alternative operations on the efficiency of subsurface arsenic removal in rural Bangladesh     

M. M. Rahman  M. Bakker  S. C. Borges Freitas  D. van Halem  B. M. van Breukelen  K. M. Ahmed  A. B. M. Badruzzaman 《Hydrogeology Journal》2015,23(1):19-34

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Analytical solutions for tidal propagation in a rectangular basin     

M. Rahman 《Advances in water resources》1983,6(1):44-53

The tidal propagation in a rectangular basin of an estuary has been studied in this paper. The dynamic response of the tidal current and elevation inside the basin has been obtained using the concept of Kelvin waves and spectrum of Poincare waves. In this study, we have found that initial tidal elevations are amplified near the closed end of the basin or at the tidal barrier site.  相似文献