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Groundwater fluoride contamination:A reappraisal

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Geoscience Frontiers 2015年第2期6卷 277-284页

作者： Amlan banerjee Geological Studies Unit Indian Statistical Institute

Dissolution of fluorite （CaF2） and/or fluorapatite （FAP） [Cas（PO4）3F], pulled by calcite precipitation, is thought to be the dominant mechanism responsible for groundwater fluoride （F） contamination. Here, one dimensional reactive-transport models are developed to test this mechanism using the published dissolution and precipitation rate kinetics for the mineral pair FAP and calcite. Simulation results correctly show positive correlation between the aqueous concentrations of F and CO2 and negative correlation between F- and Ca^2＋. Results also show that precipitation of calcite, contrary to the present understanding, slows down the FAP dissolution by 10G orders of magnitude compared to the FAP dissolution by hydrolysis. For appreciable amount of fluoride contamination rock-water interaction time must be long and of order 106 years.

关键词： Fluoride Contamination Dissolution Precipitation Reactive transport model

Mathematical Model of Relativistic Anisotropic Compact Stellar Model Admitting Linear Equation of State

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Communications in Theoretical Physics 2018年第11期69卷 585-592页

作者： Sumita banerjee Department of Mathematics Budge Budge Institute of Technology

In present paper, a static, spherically symmetric, anisotropic stellar object has been discussed by assuming a linear relationship between the matter density ρ and radial pressure pr. The interior solution is continuously matched with the exterior Schwarzschild vacuum solution at the junction interface. Various physical features viz. energy conditions,mass-radius relationship, stability are analyzed for our stellar model. By assigning some particular value to the arbitrary constants we have obtained a model of compact star of radius 6.7 km. and mass 1.148 M_⊙, which is very close to the observational data of the compact star Her X-1 proposed by Rawls et al. [Rawls, et al., Astrophys. J. 730(2011) 25].We have obtained that the model satisfies all the regularity conditions. We have found that our proposed model is stable as well as singularity-free.

关键词： compact anisotropic spherically symmetric singularity free

Molecular level biodegradation of phenol and its derivatives through dmp operon of Pseudomonas putida:A bio-molecular modeling and docking analysis

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Journal of Environmental Sciences 2015年第10期27卷 144-151页

作者： Sujay Ray Arundhati banerjee Department of Biochemistry and Biophysics University of Kalyani Department of Biotechnology Bengal College of Engineering and TechnologyShahid Sukumar SaraniBidhannagarDurgapur-713212West BengalIndia Department of Biotechnology National Institute of Technology

Participation of Pseudomonas putida-derived methyl phenol（dmp） operon and Dmp R protein in the biodegradation of phenol or other harmful, organic, toxic pollutants was investigated at a molecular level. Documentation documents that P. putida has Dmp R protein which positively regulates dmp operon in the presence of inducers; like phenols. From the operon,phenol hydroxylase encoded by dmp N gene, participates in degrading phenols after dmp operon is expressed. For the purpose, the 3-D models of the four domains from Dmp R protein and of the DNA sequences from the two Upstream Activation Sequences（UAS）present at the promoter region of the operon were demonstrated using discrete molecular modeling techniques. The best modeled structures satisfying their stereo-chemical properties were selected in each of the cases. To stabilize the individual structures, energy optimization was performed. In the presence of inducers, probable interactions among domains and then the two independent DNA structures with the fourth domain were perused by manifold molecular docking simulations. The complex structures were made to be stable by minimizing their overall energy. Responsible amino acid residues, nucleotide bases and binding patterns for the biodegradation, were examined. In the presence of the inducers, the biodegradation process is initiated by the interaction of phe50 from the first protein domain with the inducers. Only after the interaction of the last domain with the DNA sequences individually, the operon is expressed. This novel residue level study is paramount for initiating transcription in the operon; thereby leading to expression of phenol hydroxylase followed by phenol biodegradation.

关键词： Biodegradation dmp operon Docking simulations Modeling Phenol P.putida

Experimental verification of bridge seismic damage states quantified by calibrating analytical models with empirical field data

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Earthquake Engineering and Engineering Vibration 2008年第4期7卷 383-393页

作者： Swagata banerjee Masanobu Shinozuka Department of Civil and Environmental Engineering University of California

Bridges are one of the most vulnerable components of a highway transportation network system subjected to earthquake ground motions. Prediction of resilience and sustainability of bridge performance in a probabilistic manner provides valuable information for pre-event system upgrading and post-event functional recovery of the network. The current study integrates bridge seismic damageability information obtained through empirical, analytical and experimental procedures and quantifies threshold limits of bridge damage states consistent with the physical damage description given in HAZUS. Experimental data from a large-scale shaking table test are utilized for this purpose. This experiment was conducted at the University of Nevada, Reno, where a research team from the University of California, Irvine, participated. Observed experimental damage data are processed to identify and quantify bridge damage states in terms of rotational ductility at bridge column ends. In parallel, a mechanistic model for fragility curves is developed in such a way that the model can be calibrated against empirical fragility curves that have been constructed from damage data obtained during the 1994 Northridge earthquake. This calibration quantifies threshold values of bridge damage states and makes the analytical study consistent with damage data observed in past earthquakes. The mechanistic model is transportable and applicable to most types and sizes of bridges. Finally, calibrated damage state definitions are compared with that obtained using experimental findings. Comparison shows excellent consistency among results from analytical, empirical and experimental observations.

关键词： highway bridges nonlinear time history analysis fragility curves threshold damage limits mechanisticmodel calibration

Potentiality of semiconducting diamond as the base material of millimeter-wave and terahertz IMPATT devices

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Journal of Semiconductors 2014年第3期35卷 39-49页

作者： Aritra Acharyya Suranjana banerjee J.P.banerjee Institute of Radio Physics and Electronics University of Calcutta Academy of Technology West Bengal University of Technology

An attempt is made in this paper to explore the potentiality of semiconducting type-IIb diamond as the base material of double-drift region（DDR） impact avalanche transit time（IMPATT） devices operating at both millimetre-wave（mm-wave） and terahertz（THz） frequencies. A rigorous large-signal（L-S） simulation based on the non-sinusoidal voltage excitation（NSVE） model developed earlier by the authors is used in this study. At first,a simulation study based on avalanche response time reveals that the upper cut-off frequency for DDR diamond IMPATTs is 1.5 THz, while the same for conventional DDR Si IMPATTs is much smaller, i.e. 0.5 THz. The L-S simulationresultsshowthattheDDRdiamondIMPATTdevicedeliversapeakRFpowerof7.79Wwithan18.17%conversion efficiency at 94 GHz; while at 1.5 THz, the peak power output and conversion efficiency decrease to6.19mWand8.17%respectively,taking50%*** diamond and Si shows that the former excels over the later as regards high frequency and high power performance at both mm-wave and THz frequency bands. The effect of band to band tunneling on the L-S properties of DDR diamond and Si IMPATTs has also been studied at different mm-wave and THz frequencies.

关键词： diamond IMPATTs DDR large-signal simulation millimeter-wave terahertz

Effect of junction temperature on the large-signal properties of a 94 GHz silicon based double-drift region impact avalanche transit time device

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Journal of Semiconductors 2013年第2期34卷 19-30页

作者： Aritra Acharyya Suranjana banerjee J.P.banerjee Institute of Radio Physics and Electronics University of Calcutta92APC RoadKolkata-700009India Academy of Technology West Bengal University of TechnologyAdisaptagramHooghly-712121West BengalIndia

The authors have developed a large-signal simulation technique extending an in-house small-signal simulation code for analyzing a 94 GHz double-drift region impact avalanche transit time device based on silicon with a non-sinusoidal voltage excitation and studied the effect of junction temperature between 300 and 550 K on the large-signal characteristics of the device for both continuous wave （CW） and pulsed modes of operation. Results show that the large-signal RF power output of the device in both CW and pulsed modes increases with the increase of voltage modulation factor up to 60%, but decreases sharply with further increase of voltage modulation factor for a particular junction temperature; while the same parameter increases with the increase of junction temperature for a particular voltage modulation factor. Heat sinks made of copper and type-IIA diamond are designed to carry out the steady-state and transient thermal analysis of the device operating in CW and pulsed modes respectively. Authors have adopted Olson＇s method to carry out the transient analysis of the device, which clearly establishes the superiority of type-IIA diamond over copper as the heat sink material of the device from the standpoint of the undesirable effect of frequency chirping due to thermal transients in the pulsed mode.

关键词： admittance characteristics chirp bandwidth frequency chirping junction temperature large-signal analysis transient thermal analysis

Deforestation and forest fragmentation in the highlands of Eastern Ghats,India

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Journal of Forestry Research 2021年第3期32卷 1127-1138页

作者： Rakesh Paul Kakoli banerjee Central University of Orissa KoraputOdishaIndia

Tropical forest cover change along with increasing fragmentation has detrimental effects on the global *** the current study change in both forest cover and fragmentation of Koraput district have been assessed in the past three decades(1987-2017)and future decade(2017-2027),which has been modelled using logistic regression showing a gradual decrease in the forest cover and increase in *** long term deforestation rates from 1987 to 2017(current period)and from 1987 to 2027(predicted period)were found to be-0.018 and-0.012,*** of the total geographical area,2027 number of grids(1 km^(2))out of 8856 grids were found to have shown extinction of forest in the study *** conversion of forested lands into other land uses has been one of the major causes of deforestation in Koraput,especially because of the increasing mining activities and establishment of three major industries namely National Aluminium Company(NALCO),Damanjodi,Hindustan Aeronautics Limited(HAL),Sunabeda and Ballarpur Industries Limited(BILT).The forest fragmentation reveals a negative trend,recording highest conversion from large core fragments to edge(191.33 km2)and the predicted period has also shown the same trend of negative change,which poses serious danger to the structure of the *** of all the landscape matrices calculated,number of patches will increase to 214 in 2027 from 93 in *** the test between geographically weighted regression(GWR)and ordinary least square regression(OLS),GWR was the better fit model for drawing a spatial relationship between forest cover and fragmentation *** study confirmed that the forest cover change has impacted the forest fragmentation in the study *** programmes like REDD+should be implemented along with the experiences of Community Forest Management and the joint forest management should be intensified at community level in order to develop better management practices to conserve habitats in biodi

关键词： Forest cover Forest ecosystem Predictive model Forest fragmentation Grid based change Geographically weighted regression

Comparison and integration of CuInGaSe and perovskite solar cells

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Journal of Energy Chemistry 2023年第3期78卷 463-475,I0013页

作者： Weiguang Chi Sanjay K.banerjee Microelectronics Research Center Department of Electrical and Computer EngineeringThe University of Texas at AustinAustinTexas 78758USA

The rapidly developing perovskite solar cells(PSCs) provide a new and promising choice of thin film solar cells due to their attractive *** the commercialized thin film solar cells,CuInGaSe(CIGS)cells demonstrate higher efficiency than amorphous Si photovoltaic devices and lower toxicity than CdTe ***,a wide variety of studies have been conducted on ***,we elucidate CIGS materials and perovskites as absorber in thin film solar cells in terms of structure and optoelectronic ***,a comparison of PSCs and commercialized CIGS cells is made from the point of view of fabrication process,stability,and *** addition,the integration of CIGS devices and PSCs is elaborated based on tandem ***,prospects for the advancement of CIGS cells and PSCs are discussed.

关键词： CuInGaSe solar cells Perovskite solar cells Process Stability Toxicity Tandem

Heterojunction DDR THz IMPATT diodes based on Al_xGa_(1-x)N/Ga N material system

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Journal of Semiconductors 2015年第6期36卷 39-46页

作者： Suranjana banerjee Monojit Mitra Academy of Technology West Bengal University of Technology Indian Institute of Engineering Science and Technology

Simulation studies are made on the large-signal RF performance and avalanche noise properties ofhet- erojunction double-drift region （DDR） impact avalanche transit time （IMPATT） diodes based on AlxGal-xN/GaN material system designed to operate at 1.0 THz frequency. Two different heterojunction DDR structures such as n-Al0.4Ga0.6N/p-GaN and n-GaN/p-Al0.4Ga0.6N are proposed in this study. The large-signal output power, con- version efficiency and noise properties of the heterojunction DDR IMPATTs are compared with homojunction DDR IMPATT devices based on GaN and Al0.4Ga0.6N. The results show that the n-Al0.4Ga0.6N/p-GaN heterojunction DDR device not only surpasses the n-GaN/p-Al0.4Ga0.6N DDR device but also homojunction DDR IMPATTs based on GaN and Al0.4Ga0.6N as regards large-signal conversion efficiency, power output and avalanche noise performance at 1.0 THz.

关键词： A1GaN/GaN heterojuntion DDR IMPATTs avalanche noise terahertz frequency