The first electric field pulse of cloud and cloud-to-ground lightning discharges     

Noor Azlinda Ahmad  M. Fernando  Z.A. Baharudin  M. Rahman  V. Cooray  Ziad Saleh  Joseph R. Dwyer  Hamid K. Rassoul 《Journal of Atmospheric and Solar》2010,72(2-3):143-150

In this study, the first electric field pulse of cloud and cloud-to-ground discharges were analyzed and compared with other pulses of cloud discharges. Thirty eight cloud discharges and 101 cloud-to-ground discharges have been studied in this analysis. Pulses in cloud discharges were classified as ‘small’, ‘medium’ and ‘large’, depending upon the value of their relative amplitude with respect to that of the average amplitude of the five largest pulses in the flash. We found that parameters, such as pulse duration, rise time, zero crossing time and full-width at half-maximum (FWHMs) of the first pulse of cloud and cloud-to-ground discharges are similar to small pulses that appear in the later stage of cloud discharges. Hence, we suggest that the mechanism of the first pulse of cloud and cloud-to-ground discharges and the mechanism of pulses at the later stage of cloud discharges could be the same.  相似文献   

Assessment of trace elements of groundwater and their spatial distribution in Rangpur district,Bangladesh     

A. R. M. Towfiqul Islam  Shuanghe Shen  Md. Bodrud-Doza  M. Atiqur Rahman  Samiran Das 《Arabian Journal of Geosciences》2017,10(4):95

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Drought analysis and its implication in sustainable water resource management in Barind area,Bangladesh     

A. T. M. Sakiur Rahman  Chowdhury Sarwar Jahan  Quamrul Hasan Mazumder  Md. Kamruzzaman  Takahiro Hosono 《Journal of the Geological Society of India》2017,89(1):47-56

The study analyzes drought using Standardized Precipitation Index (SPI) and Mann-Kendall (MK) Trend Test in the context of the impacts of drought on groundwater table (GWT) during the period 1971-2011 in the Barind area, Bangladesh. The area experienced twelve moderate to extreme agricultural droughts in the years 1972, 1975, 1979, 1982, 1986, 1989, 1992, 1994, 2003, 2005, 2009 and 2010. Some of them coincide with El Niño events. Hydrological drought also occurred almost in the same years. However, relationship between all drought events and El Niño is not clear. Southern and central parts of the area frequently suffer from hydrological drought, northern part is affected by agricultural drought. Trends in SPI values indicate that the area has an insignificant trend towards drought, and numbers of mild and moderate drought are increasing. GWT depth shows strong correlation with rainy season SPI values such that GWT regaining corresponds with rising SPI values and vice versa. However, 2000 onwards, GWT depth is continuously increasing even with positive SPI values. This is due to over-exploitation of groundwater and changes in cropping patterns. Agricultural practice in Barind area based on groundwater irrigation is vulnerable to drought. Hence, adaptation measures to minimize effects of drought on groundwater ought to be taken.  相似文献   

The interrelationship between travel behavior and life choices in adapting to flood disasters     

Qing-Chang Lu  Junyi Zhang  A. B. M. Sertajur Rahman 《Natural Hazards》2017,85(2):1005-1022

Disasters resulting from climate change are shown to be important determinants of people’s life choice decisions. In the literature, travel behavior choice and life choices are usually addressed separately under disasters such as flood and cyclone. However, travel behavior may be interdependent with other life choices, jointly shaping people’s adaptation decisions. To this end, the paper advances the literature by exploring the interrelationship between changes in travel behavior and job and residential location under flood disasters, while separating coastal and inland observations. For this purpose, a stated preference survey was conducted in 14 cities of Bangladesh in early 2013. An analysis approach based on structural equation modeling was developed to investigate the correlations between travel behavior change and job and residential location changes. Model estimation results suggest that flood impacts have significant influences on inland people’s life choices, while coastal people’s life choices are mainly affected by flood adaptation responses and attitudes. Significant correlations between travel behavior change and job and residential location changes are found for both observations. Moreover, both coastal and inland people tend not to change residential locations if changes in job location and travel behavior are made. Inland people may not change travel behavior if their job and/or residential locations are changed, but coastal people’s job and residential location changes are associated with changes in travel behavior. Travel behavior change is found to have more of an effect on residential location change than job location change in both regions. These findings conclude that the two-way relationship between travel behavior and life choices should be taken into account in future analyses, and thus adaptation policies to climate change disasters could be better linked with people’s behavioral responses.  相似文献   

A semi-analytical method for the wave-induced seabed response     

M. S. Rahman  Khalid El-Zahaby  John Booker 《国际地质力学数值与分析法杂志》1994,18(4):213-236

A general semi-analytical method is presented for the analysis of seabed response under wave action during a storm. The seabed is idealized as a poro-elastic medium filled with a single compressible fluid with anisotropic flow. The coupled process of fluid flow and deformation of soil skeleton is formulated in the framework of Biot's theory. The analysis for the response of homogeneous seabed of finite thickness under a plane progressive wave is developed first, followed by an extension for the case of a layered seabed. A generalization for three-dimensional response of seabed is also developed for a general wave field which provides the analyses for seabed response under short-crested or standing waves in the vicinity of a structure. Some numerical examples illustrating the proposed analyses are also presented.  相似文献   

Pollutant migration from deeply buried repositories     

M. S. Rahman  J. R. Booker 《国际地质力学数值与分析法杂志》1989,13(1):37-51

Semi-analytic solutions are developed for the migration of pollutants from cylindrical and spherical repositories buried deep in a homogeneous and isotropic soil in the presence of a uniform and unidirectional advection. The techniques adopted involves taking the Laplace transform of the governing equations, finding an analytic solution in transform space and then numerically inverting the transform to obtain the concentrations of the contaminants at selected positions and times. Numerical results are presented, and practical implications discussed.  相似文献   

A comparison of nearby incremental ground level and in plant concentrations of air pollutants emitted from electronics facilities     

P. L. Law M.Sc.  Ph.D.  S. C. Gracie Chong  A. Baharun B.Sc.  Ph.D.  A. Abdul Rahman M.Sc.  Ph.D. 《International Journal of Environmental Science and Technology》2006,3(3):243-250

Air dispersion modeling by was recently conducted to predict the incremental ground level and inplant concentrations of toxic organic chemicals due to stack and fugitive emissions from Sama Jaya Free Industrial Zone (SJFIZ), Kuching, Sarawak, Malaysia. Simulations of organic air pollutants emitted from industrial facilities in SJFIZ from years 1996 to 2001 were carried out in September 2004 by members of Faculty of Engineering, Universiti Malaysia Sarawak (UNIMAS). The results indicated that there were negligible amount of maximum incremental ground level concentrations of less than 3×10^?2 μg/m³ for 365-day average, and less than 18×10^?2 μg/m³ for 24 h. average. For in-plant maximum incremental concentrations, it is found that the simulated results were much lower than TWA values, except xylene. The predicted in plant concentration of xylene was 119.21 (parts per million) ppm as compared to ACGIH TLV-TWA of 100 ppm approximately 19% higher than ACGIH recommended values. From this study, it was concluded that both nearby population and in plant workers were not potentially at risk to exposing organic chemicals far lower than the threshold limit levels set by ACGIH.  相似文献   

Unplanned urbanization: Assessment through calculation of environmental degradation index     

Md. J. B. Alam  M. J. B. Alam  M. H. Rahman  S. K. Khan  G. M. Munna 《International Journal of Environmental Science and Technology》2006,3(2):119-130

Urbanization is an inevitable phenomena for the country like Bangladesh. The push and pull factors help to migrate people from rural area to urban area. As a result haphazard and unplanned urbanization create environmental degradation. Survey data reveals that inadequate solid waste disposal services, lack of adequate public water supply, traffic congestion, water logging, air pollution, noise pollution, hill cutting are the main problems in the city area. Concentration of dust as well as SOx, NOx exceeded the allowable limit at the selected points. Groundwater level of Sylhet city has a considerable lowering over the last few decades. It has lowered from 3380 mm below ground in 1982 to 7880 mm below ground. Sylhet is located in highly seismic risk zone but most of the buildings and other structures in this area are constructed without considering earthquake risk. Environmental degradation index was calculated based on economical condition of the country.  相似文献   

Chemical oxidation of N,N-diethyl-m-toluamide by sulfate radical-based oxidation: kinetics and mechanism of degradation     

K. S. Tay  N. A. Rahman  M. R. Bin Abas 《International Journal of Environmental Science and Technology》2013,10(1):103-112

A study was undertaken in order to understand the kinetics and mechanism of the chemical oxidation of N,N-diethyl-m-toluamide, an insect repellent, by sulfate radical. In this experiment, sulfate radical was generated using peroxymonosulfate with iron(II) and cobalt(II) as activator. The second-order rate constant for the reaction of the sulfate radical with N,N-diethyl-m-toluamide was found to be (1.9 ± 0.1) × 10⁹ M^?1 s^?1 at pH 7 and a temperature of 25 °C. Experiments for the chemical oxidation of N,N-diethyl-m-toluamide in river water and secondary wastewater revealed that the percentage of the removal of N,N-diethyl-m-toluamide was slightly influenced by the water matrices. However, the selected oxidation systems are not effective for the removal of N,N-diethyl-m-toluamide in seawater. Transformation by-products of N,N-diethyl-m-toluamide generated using peroxymonosulfate/iron(II) sulfate, peroxymonosulfate/iron(II) chloride, peroxymonosulfate/cobalt(II) sulfate and peroxymonosulfate/cobalt(II) chloride systems were identified. The results indicated that there are slight differences in the distributions of the transformation by-products detected depending on the activator. The common transformation by-products detected in all selected oxidation systems are N,N-diethylbenzamide, N-ethyl-m-toluamide, N,N-dimethyl-m-toluamide, N-ethyl-N-acetyl-m-toluamide, 2-(diethylamino)-1-m-tolylethanone, monohydroxylated N-ethyl-m-toluamide, and dihydroxylated N,N-diethyl-m-toluamide. Monohydroxylated N,N-diethyl-m-toluamide were detected only when the peroxymonosulfate/iron(II) system was applied. For the peroxymonosulfate/cobalt(II) systems, additional isomers of monohydroxylated N-ethyl-m-toluamide were detected. Peroxymonosulfate/cobalt(II) also transformed 2-(diethylamino)-1-m-tolylethanone into N-ethyl-N-(2-oxo-2-m-tolylethyl)acetamide and monohydroxylated 2-(ethyl(vinyl)amino)-1-m-tolylethanone as transformation by-products.  相似文献   

Ground Water Contamination of Arsenic in Ganges Plain     

Hiroaki Ishiga  Kaori Dozen  Md. Badrul Islam  Md. Hamidur Rahman  Md. Abdus Sattar  Chikako Yamazaki  Ahmed Faruque 《Gondwana Research》2001,4(4):636

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