Support vector machines and generalized linear models for quantifying soil dehydrogenase activity in agro-forestry system of mid altitude central Himalaya     

Prashant K. Srivastava  Aradhana Yaduvanshi  Sudhir Kumar Singh  Tanvir Islam  Manika Gupta 《Environmental Earth Sciences》2016,75(4):299

  相似文献   

Simulating in-zone chemistry changes from injection time to longer periods of CO<Subscript>2</Subscript> storage     

Akand Islam  Alexander Sun  Jiemin Lu 《Environmental Earth Sciences》2016,75(20):1346

  相似文献   

Optimal error growth of South Asian monsoon forecast associated with the uncertainties in the sea surface temperature     

Siraj Ul Islam  Youmin Tang  Peter L. Jackson 《Climate Dynamics》2016,46(5-6):1953-1975

  相似文献   

Can an annual flood induce changes in channel geomorphology?     

Islam  Aznarul  Sarkar  Biplab  Saha  Ujwal Deep  Islam  Mainul  Ghosh  Susmita 《Natural Hazards》2022,111(1):1019-1046

The present study has been a pioneering effort examining the role of an annual flood as a potent stimulus inducing changes in channel geomorphology of the Mayurakshi River, India. Twenty cross sections have been considered for the measurement of various hydro-geomorphic attributes of the river in both the pre- and post-flood conditions in 2018. The study sensed an escalating trend for channel width, width/depth ratio, and wetted perimeter while the reverse was also detected for average depth, maximum depth, cross-sectional area, and hydraulic radius. For example, the width/depth ratio recorded an increase of?~?11%, and the hydraulic radius depicted a decrease of?~?8%. Furthermore, channel asymmetry, bed asymmetry and bed relief index experienced a decrease after the flood. The sudden hydraulic impulse during monsoon flood as manifested in velocity, discharge, specific stream power, Reynolds number, Froude number increases the erosivity of the fluid. Besides the hydraulic factors, bank material (massive sandbank susceptible to hydraulic action and mixed bank constituted by alternate bands of sand and silt, and vulnerable to failure by piping action) brings substantial changes in channel morphology. Moreover, anthropogenic interventions such as sand mining are found to play a significant role in channel behaviour. The role of the multiple factors driving the morphological changes of the cross sections has been unpacked using canonical component analysis.

  相似文献   

Assessing factors affecting drought,earthquake, and flood risk perception: empirical evidence from Bangladesh     

Mallick  Javed  Salam  Roquia  Amin  Ruhul  Islam  Abu Reza Md. Towfiqul  Islam  Aznarul  Siddik  Md. Nur Alam  Alam  G. M. Monirul 《Natural Hazards》2022,112(2):1633-1656

Natural Hazards - Understanding household disaster risk perception is crucial to formulate and apply disaster risk reduction strategies. Using survey data from 300 households from three highly...  相似文献   

Effect of Face Losses and Cover-to-Diameter Ratio on Tunneling Induced Settlements in Soft Clay,Using Transparent Soil Models     

Ads  Abdelaziz  Shariful Islam  Md  Iskander  Magued 《Geotechnical and Geological Engineering》2021,39(8):5529-5547

Geotechnical and Geological Engineering - Reliable prediction of surface and subsurface settlements&nbsp;induced by shallow tunnels is important to minimize the adverse effects which may take...  相似文献   

Ion migration in nepheline: a dielectric spectroscopy and computer modelling study     

A. Jones  D. Palmer  M. S. Islam  M. Mortimer 《Physics and Chemistry of Minerals》2001,28(1):28-34

 Using a combination of dielectric spectroscopy and atomistic computer simulation techniques, the dynamical behaviour of the loosely bound (Na⁺ and K⁺) channel ions in nepheline has been investigated. The low-frequency dielectric properties of a natural Bancroft nepheline have been studied from room temperature to 1100 K. At each temperature, the dielectric constant, conductivity and dielectric loss were determined over a range of frequencies from 100 Hz to 10 MHz. At high temperatures a distinct Debye-type relaxation in the dielectric loss spectrum was observed; the activation energy for this process was determined to be 1.38 ± 0.02 eV. Atomistic simulation techniques were used to elucidate the mechanism and energetics of cation migration. A mechanism involving the hopping of Na⁺ ions between oval sites and partially occupied hexagonal (K⁺) sites, via a bottleneck consisting of a distorted sixfold ring of (Al,Si)O₄ tetrahedra, was found to give a calculated energy barrier in very good agreement with the experimentally determined activation energy. These results confirm the nature of the process responsible for the observed dielectric behaviour. Overall, this study demonstrates the intrinsic, microscopic control of cation diffusion processes in rock-forming minerals. Identifying specific energy barriers and preferred diffusion pathways is fundamental to the prediction of diffusion energetics. Received: 8 May 2000 / Accepted: 21 July 2000  相似文献   

Spawning of major carps in the lower Halda River,Bangladesh     

Chu-fa Tsai  M. Nazrul Islam  Rezaul Karim MD  K. U. M. Shahidur Rahman 《Estuaries and Coasts》1981,4(2):127-138

Spawning biology and spawn fishery of three valuable species of Indian major carps,Catla catla, Labeo rohita andCirrhinus mrigala, in the lower Halda River, Bangladesh, were studied in 1978. The major carps spawned only in the Sonairchar oxbow-bend from April to June on or near the dates of the full moon and the new moon. The tide was then at its highest level, and there was heavy flood water runoff from the hill region with sharp increases in water level, turbidity and current velocity, as well as decreases in water temperature, dissolved oxygen, and hydrogen ion concentration. These three heterogeneric species, as a result of parallelism or convergence in evolution, overlap in their environmental requirements for spawning. The nursery ground of the major carp fry spawned in the Halda River was found to be in the Bay of Bengal. The brood stock origin is suspected to be at the Shankha River, 40 miles south of the Karnafuli River. The spawn fishery in the Halda River was intensive but inefficient. Engineering works and water management schemes are threatening the spawning habitat.  相似文献   

Alkali ion migration in albite and K-feldspar     

A.?JonesEmail author  D.?Palmer  M. S.?Islam  M.?Mortimer 《Physics and Chemistry of Minerals》2004,31(5):313-320

As part of a study of ion migration mechanisms in feldspars, the dynamical behaviour of the alkali metal cations ions in albite and K-feldspar has been investigated using a combination of dielectric spectroscopy and atomistic computer simulation techniques. The low-frequency dielectric properties of these minerals have been studied from room temperature to 1100 K. At each temperature, the dielectric constant, conductivity and dielectric loss were determined over a range of frequencies from 100 Hz to 10 MHz. At high temperatures a distinct Debye-type relaxation in the dielectric loss spectra was observed for both albite and K-feldspar; the activation energy for these processes was determined to be 1.33 eV in both albite and K–feldspar. Atomistic simulation techniques were used to elucidate the mechanism and energetics of the cation migration processes. Mechanisms involving the conventional hopping of Na⁺ and K⁺ ions between cation sites in the (010) plane were found to give calculated energy barriers in good agreement with the experimentally determined activation energies. These results assist in understanding the nature of the processes responsible for the observed dielectric behaviour.  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