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Generation of Internal Tides: An Interaction of Tides with Variable Topography and Coastal Geometry
Himansu K. Pradhan,A. D. Rao,Sachiko Mohanty 한국해양과학기술원 2015 Ocean science journal Vol.50 No.2
The paper describes tide-topography interaction with changeable width and angle of continental shelf. Experiments are designed with MITgcm over a study area representative of the western Bay of Bengal with an idealized bathymetry. As the actual coastline consists of an irregular configuration, the experiments are set with different coastline geometry. The tidal forcing is incorporated in the model to generate internal tides by adding tidal components in the momentum equations. The density stratification represents the region during May and is kept invariant for all the experiments. Spectral analysis suggests that semi-diurnal internal tides possess the maximum spectral estimate. The peak semi-diurnal estimate is computed to understand its variation over the shelfslope region. The analysis demonstrates that the estimate is smaller for wider shelves against narrow continental shelves. The peak estimate is observed close to 100m local depth over the shelf regardless of the angle and width. Experiments are further continued to distinguish the effect of rotation and geometry of the coast as the shelf width and shelf angle are kept constant. Comparison of spectral estimate is performed without and with rotation for three different coastline configurations: concave, convex and straight. The estimate is noticed maximum in the concave and minimum in the convex shape of the coast. Significant contribution of the rotational effect is seen as an increase in the semi-diurnal peak estimate towards the north of the domain. In order to confirm the effect of the rotation, a similar experiment is performed for the southern hemisphere revealing an enhancement of the estimate towards the south of the domain.
Lee, S.,Park, Y.,Pradhan, D.,Sohn, Y. Korean Society of Industrial and Engineering Chemi 2016 Journal of industrial and engineering chemistry Vol.35 No.-
<P>The loading of AgX (X = Cl, Br and I) into BiOX nanoplates and microspheres was demonstrated, and then their adsorption and photocatalytic performances were studied using rhodamine B (RhB) and a more complicated mixed dye (methyl orange + RhB + methylene blue) system under UV and visible light. The adsorption performances were highly dependent on morphology, nature of material, dye system, and AgX-loading. Photocatalytic activity was also found to be dependent on the wavelength of incident light. The detailed approach to a more complicated system provides new insights that can aid in design of appropriate photocatalysts for a more complicated polluted target. (C) 2016 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.</P>
Nedumpallile Vasu, N.,Lee, S.R.,Pradhan, A.M.S.,Kim, Y.T.,Kang, S.H.,Lee, D.H. Elsevier Pub. Co 2016 Engineering geology Vol.215 No.-
An ever-increasing trend of extreme rainfall events in South Korea due to climate change is causing shallow landslides and shallow landslide induced debris flows in the mountains that cover 70% of the total land area of the nation. These catastrophic, gravity-driven processes cost the government several billion won in losses, and attendant fatalities, every year. The most common type of landslide observed is the shallow landslide occurring at 1-3m depth, which may mobilize into a catastrophic debris flow. A landslide early warning system encompassing different scale-based stages is used to predict potential areas for both the landslide types. Current study focusing on the first stage landslide hazard assessment at regional or medium scale requires the development of spatially evolving landslide hazard maps for both types of landslides based on the real-time rainfall. However, lack of complete landslide inventory data motivates the development of temporal and spatial models as independent components of the landslide hazard. Most of the existing temporal assessment schemes traditionally rooted in recurrence-based concepts does not consider soil factors and are not suitable to be incorporated in to the landslide early warning system since real-time rainfall cannot be considered. This motivated the development of a new probabilistic temporal model termed the extreme rainfall-induced landslide index. The probabilistic index was developed in Gangwon Province through a logistic regression using four factors; namely, continuous rainfall, 20-days antecedent rainfall, saturated hydraulic conductivity, and storage capacity. The developed model exhibited high area under the curve (AUC) values of 82% and 91% obtained for the training and validation curves, exhibiting good performance of the statistical index. Also, a high performance susceptibility model (training and validation AUC values of 96% and 94%, respectively) was developed using a logistic regression analysis, for Deokjeok-ri Creek, located in Gangwon province. Assuming the independence of the hazard components, a dynamic hazard index (DHI) was established through a joint probability of both the well validated models. The DHI was used to study the evolution of landslide hazard for the July 2006 extreme rainfall-induced landslide events in Deokjeok-ri Creek.
Review on bioleaching of uranium from low-grade ore
김동진,안종관,윤호성,Patra, A.K.,Pradhan, D.,Kim, D.J.,Ahn, J.G,Yoon, H.S. 한국자원리싸이클링학회 2011 資源 리싸이클링 Vol.20 No.2
본 총설은 광석으로부터 우라늄의 미생물 침출시 사용하는 Acidithiobacillus forrooxidans, Acidithiobacillus thiooxidans 그리고 Leptospirillum ferrooxidans 등에 역할과 침출반응에 관하여 기술하였다. 미생물에 의한 우라늄의 침출반응은 박테리아가 우라늄 광석과 직접 반응하기 보다는 박테리아가 $U^{4+}$를 산화시키는데 필요한 $Fe^{3+}$를 공급하고, $Fe^{3+}$가 우라늄 광석과 반응하는 간접반응기구(indirect mechanism)에 의하여 일어난다. 건식제련법과 같은 전통적인 금속회수 공정에 비하여 환경친화적이고 경제적인 장점 때문에 저품위 광물자원으로부터 유기금속을 회수하는데 미생물 제련법이 널리 활용되고 있다. 현재 우라늄은 heap, dump 그리고 in situ를 이용한 미생물 침출법으로 회수되고 있다. Bioheap의 공기 투입량, 교반반응용기의 디자인 및 조업 개선 분야에서 기술개발이 지속적으로 이루어졌으며 최근에는 미생물 침출반응에 투입된 박테리아의 특성 개선 및 균주수를 제어하기 위한 molecular biology 분야에서 활발한 연구가 진행되고 있다. This review describes the involvement of different microorganisms for the recovery of uranium from the ore. Mainly Acidithiobacillus forrooxidans, Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans are found to be the most widely used bacteria in the bioleaching process of uranium. The bioleaching of uranium generally follows indirect mechanism in which bacteria provide the ferric iron required to oxidize $U^{4+}$. Commercial applications of bioleaching have been incorporated for extracting valuable metals, due to its favorable process economics and reduced environmental problems compared to conventional metal recovery processes such as smelting. At present the uranium is recovered through main bioleaching techniques employed by heap, dump and in situ leaching. Process development has included recognition of the importance of aeration of bioheaps, and improvements in stirred tank reactor design and operation. Concurrently, knowledge of the key microorganisms involved in these processes has advanced, aided by advances in molecular biology to characterize microbial populations.
Varanasi, J.L.,Nayak, A.K.,Sohn, Y.,Pradhan, D.,Das, D. Pergamon Press 2016 ELECTROCHIMICA ACTA Vol.199 No.-
The anode of microbial fuel cell was impregnated with tungsten oxide (WO<SUB>3</SUB>) and platinum-tungsten oxide (Pt/WO<SUB>3</SUB>) nanocomposites to improve its power generation. The amended anodes were tested against pure and mixed culture type of biocatalysts. Improved performance was exhibited by the modified electrodes as compared to the uncatalyzed electrodes using both biocatalysts. However, pure culture showed higher power outputs as compared to the enriched mixed consortia. The maximum power density up to 0.15mWcm<SUP>-2</SUP> (1.46Wm<SUP>-2</SUP>) was obtained using pure culture which was almost 45% higher as compared to uncatalyzed electrodes. The anode modification also helped in lowering the charge transfer resistance and improving the coulombic efficiencies of the MFCs. High capacitance with nanostructure catalysts implied their role in holding an electric charge while SEM and epifluorescent images revealed enhanced bacterial adhesion. The high electrode conductivity, stability, and biocompatibility of the modified anodes make them more attractive for practical microbial fuel cell applications.