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Frontiers of materials Science 2018年第3期12卷 247-263页

作者： m. mohamed Jaffer SADIQ U. Sandhya SHENOY D. krishna BHAT Department of Chemistry National Institute of Technology Karnataka Surathkal Mangalore-575025 India Department of Chemistry College of Engineering and Technology Srinivas University Mukka Mangalore-574146 India

Novel barium tungstate/nitrogen-doped reduced graphene oxide-graphi- tic carbon nitride （BaWO4/NRGO-g-C3N4） nanocomposite has been synthesized by a simple one-pot microwave technique. The synthesized nanocomposites are well characterized by diffraction, microscopic and spectroscopic techniques to study its crystal structure, elemental composition, morphological features and optical properties. The material prepared is tested for its performance as an electrocatalyst, photocatalyst and reduction catalyst. The nanocomposite catalyzed the photodegradation of methylene blue （mB） dye in 120 min, reduction of 4-nitro phenol （4-NP） to 4-amino phenol （4-AP） in 60 s, showed an impressive Tafel slope of 62 mV/dec for hydrogen evolution reaction （HER）. The observed results suggest that the nanocomposite acts as an efficient multifunctional catalyst. The reported approach provides fundamental insights which can be extended to other metal tungstate-based ternary composites for applications in the field of clean energy and environment in the future.

关键词： BaWO4/NRGO-g-C3N4 nanocomposites microwave irradiation hydrogen evolution reaction photocatalyst reduction

Improvement in hot corrosion resistance of dissimilar alloy 825 and AISI 321 CO2-laser weldment by HVOF coating in aggressive salt environment at 900℃

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International Journal of minerals,metallurgy and materials 2020年第11期27卷 1536-1550页

作者： S.m.muthu m.Arivarasu T.Hari krishna Supriyo Ganguly K.V.Phani Prabhakar Saurav mohanty School of mechanical Engineering Vellore Institute of TechnologyVelloreTamil Nadu 632014India Center for Innovative manufacture Research Vellore Institute of TechnologyVelloreTamil Nadu 632014India Welding Engineering and Laser Processing Centre Cranfield UniversityBedfordUnited Kingdom CLPm International Advanced Research Centre for Powder Metallurgy&New Materials(ARCI)HyderabadIndia Department of mechanical Engineering North Carolina State UniversityRaleighUSA

This study investigated the hot corrosion performance of a dissimilar weldment of Ni-based superalloy and stainless steel joined by CO2-laser welding and improved by high-velocity oxy-fuel(HVOF)coating in a Na2SO4-60wt%V2O5 environment at 900℃.A dissimilar butt joint of AISI 321 and alloy 825 was fabricated by CO2-laser welding with low heat input after obtaining the optimum welding parameters by bead-on-plate *** metallurgical and mechanical properties of the laser weldment were *** tensile test results indicated the occurrence of fracture in the base metal AISI 321 *** HVOF process was employed to coat Ni-20wt%Cr on the *** evaluate the surface morphology of the corrosion products formed on the uncoated and Ni-20wt%Cr-coated weldments,scanning electron microscopy(SEm)analysis was ***-dispersive spectroscopy(EDS)was used to determine the different elements present on the surface *** existence of oxide phases on the weldments was determined by X-ray diffraction(XRD).The cross sections of the weldments were characterized by SEm with EDS line mapping *** results indicated that the Ni-20wt%Cr-coated weldment exhibited superior hot corrosion resistance due to the development of Cr2O3 and NiCr2O4 protective oxide scales.

关键词： nickel-based superalloy dissimilar welding weldment corrosion high-velocity oxy-fuel coating corrosion kinetics

Study of Stability Analysis for a Class of Fourth Order Boundary Value Problems

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Applied mathematics 2014年第13期5卷 1887-1893页

作者： C. bala Rama krishna P. S. Rama Chandra Rao Department of mathematics Chaitanya Degree College (Autonomous) Warangal India Department of mathematics Kakatiya Institute of Technology & Science Warangal India

Fourth order differential equations are considered to develop the class of methods for the numerical solution of boundary value problems. In this paper, we have discussed the regions of absolute stability of fourth order boundary value problems. methods proposed and derived in this paper are applied to solve a fourth-order boundary value problem. Numerical results are given to illustrate the efficiency of our methods and compared with exact solution.

关键词： Numerical Differentiation Initial Value Problem Boundary Value Problem Absolute Stability multistep methods

Analysis of unlined pressure shafts and tunnels of selected Norwegian hydropower projects

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Journal of Rock mechanics and Geotechnical Engineering 2018年第3期10卷 486-512页

作者： Chhatra Bahadur Basnet krishna Kanta Panthi Department of Geoscience and Petroleum Norwegian University of Science and Technology

Norwegian hydropower industry has more than 100 years of experiences in constructing more than4000 km-long unlined pressure shafts and tunnels with maximum static head of 1047 m（equivalent to almost 10.5 mPa） reached at unlined pressure tunnel of Nye Tyin project. Experiences gained from construction and operation of these unlined pressure shafts and tunnels were the foundation to develop design criteria and principles applied in Norway and some other countries. In addition to the confinement criteria, Norwegian state-of-the-art design principle for unlined pressure shaft and tunnel is that the minor principal stress at the location of unlined pressure shaft or tunnel should be more than the water pressure in the shaft or tunnel. This condition of the minor principal stress is prerequisite for the hydraulic jacking/splitting not to occur through joints and fractures in rock mass. Another common problem in unlined pressure shafts and tunnels is water leakage through hydraulically splitted joints or pre-existing open joints. This article reviews some of the first attempts of the use of unlined pressure shaft and tunnel concepts in Norway, highlights major failure cases and two successful cases of significance, applies Norwegian criteria to the cases and reviews and evaluates triggering factors for *** article further evaluates detailed engineering geology of failure cases and also assesses common geological features that could have aggravated the failure. The minor principal stress is investigated and quantified along unlined shaft and tunnel alignment of six selected project cases by using threedimensional numerical model. Furthermore, conditions of failure through pre-existing open joints by hydraulic jacking and leakage are assessed by using two-dimensional fluid flow analysis. Finally, both favorable and unfavorable ground conditions required for the applicability of Norwegian confinement criteria in locating the unlined pressure shafts and tunnels for ge

关键词： Hydropower projects Unlined pressure shafts and tunnels minor principal stress Hydraulic jacking Water leakage

Investigations of Soret,Joule and Hall effects on mHD rotating mixed convective flow past an infinite vertical porous plate

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Journal of Ocean Engineering and Science 2019年第3期4卷 263-275页

作者： m.Veera krishna B.V.Swarnalathamma Ali J.Chamkha Department of mathematics Rayalaseema UniversityKurnoolAndhra Pradesh 518007India Department of Science and Humanities Stanley College of Engineering&Technology for WomenAbidsHyderabadTelangana 500001India Department of mechanical Engineering Prince Sultan Endowment for Energy and EnvironmentPrince Mohammad Bin Fahd UniversityAl-Khobar 31952Saudi Arabia RAK Research and Innovation Center American University of Ras Al Khaimah10021United Arab Emirates

We made an elaborate scrutiny on the Soret and Joule effects of mHD mixed convective flow of an incompressible and electrically conducting viscous fluid past an infinite vertical porous plate taking Hall effects into *** technique is used to solve the non-dimensional *** effects of the various non-dimensional parameters on velocity,temperature and concentration within the boundary layer are *** that,computational deliberations or discussions are also undertaken on the effects of the pertinent or significant parameters on the skin-friction coefficient and rates of heat and mass transfer in terms of the Nusselt and Sherwood numbers *** concentration distribution increases with increase in Soret effect and decrease with increase in chemical reaction *** increase in Prandtl number results to decrease the temperature *** the primary and secondary velocity components and temperature increases with increasing heat source *** friction coefficient decreases with an increase in permeability parameter,whereas it shows reverse effect for thermal and mass Grashof *** number increases with an increase in Prandtl *** number reduces with increasing Soret number.

关键词： Hall effects Soret number Porous medium Joules dissipation Chemical reaction

Rock-like behavior of biocemented sand treated under non-sterile environment and various treatment conditions

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Journal of Rock mechanics and Geotechnical Engineering 2021年第3期13卷 705-716页

作者： meghna Sharma Neelima Satyam krishna RReddy Discipline of Civil Engineering Indian Institute of Technology IndoreIndore453552India Department of Civil Materialsand Environmental EngineeringUniversity of Illinois at ChicagoChicagoILUSA

microbially induced calcite precipitation(mICP)is a recently developed technique for microbiological ground improvement that has been applied for mitigating various geotechnical ***,the major challenges,such as calcite precipitation uniformity,presence of different bacteria,cementation solution optimization for cost reduction,and implementation under non-sterile and uncontrolled field environment are still not fully explored and require detailed investigation before field *** study aims to address these challenges of mICP to improve the geotechnical properties of sandy *** series of experiments were conducted using poorly graded Narmada River(India)sand,which were subjected to various biotreatment schemes and tested for unconfined compressive strength(UCS),split tensile strength(STS),ultrasonic pulse velocity(UPV),hydraulic conductivity(after 6 d,12 d,and 18 d of treatment),and calcite *** microstructure of sand was examined through a scanning electron microscope(SEm).Initially,the sand was individually augmented with two non-pathogenic bacterial strains,***(S.)pasteurii and Bacillus(B.)*** stopped-flow injection method was adopted to provide cementation solutions at three different durations(treatment cycle)of 12 h,24 h,and 48 h and three different pore volumes(PVs)of 1,0.75,and *** pore volume here refers to the porosity which is expressed as a ratio,i.e.a porosity of 50%was used as *** results showed rock-like behaviors of biocemented sand with the UCS,STS,and UPV enhancement up to 2333 kPa,437 kPa,and 2670 m/s,*** hydraulic conductivity reduction of 96.6%was achieved by 12%of calcite formation after 18 d of treatment using Sporosarcina pasteurii,12-h treatment cycle,and one pore volume of cementation media in each ***,a 24-h treatment cycle and 0.5-pore volume cementation solution were found to be the optimal treatment which was effective and economical to achiev

关键词： Bacteria microbially induced calcite precipitation (mICP) Soil stabilization microstructure Calcite content

On the spatio-temporal variation in b-value after 25 April 2015 Gorkha,Nepal earthquake

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Geodesy and Geodynamics 2022年第5期13卷 525-533页

作者： Ram krishna Tiwari Harihar Paudyal Daya Shanker Central Department of Physics Tribhuvan UniversityKirtipurKathmanduNepal Birendra multiple Campus Tribhuvan UniversityBharatpurChitwanNepal Department of Earthquake Engineering Indian Institute of Technology RoorkeeRoorkeeUttarakhandIndia

In the present study,the spatial-temporal distribution of b-value along the five faults area(the Judi fault,Thaple fault,Kathmandu fault,motihari-Gauri Shanker fault,and motihari-Everest fault)was investigated after the Gorkha earthquake(m7.8).The earthquake catalog of 10,500 events was prepared by compiling the published *** study area is bounded in the central Himalaya from 26.5°to 29°in latitude direction and 84°to 87°in longitude *** frequency magnitude distribution shows the variation of the b-value along with fault areas from 0.45 to 0.69,indicating a common characteristic of aftershock *** particular,the Judi fault area,Thaple fault area,and motihari-Everest fault area are characterized by the low b-values of 0.45±0.02,0.48±0.02,and 0.55±0.04,*** regions could be the source region for future *** low b-value observed for fault areas are also consistent with the thrust faulting pattern in the region as indicated by the focal mechanism of mainshock and major *** temporal variation of b-value shows inevitable fluctuations during25 April to 12 may *** the area selected,the motihari-Everest fault area is in critical strain(mechanically locked)conditions,as indicated by the stepwise energy release pattern.

关键词： Frequency-magnitude distribution Time series analysis Thrust fault Stress Central Himalaya

Evaluation of WEPP versus EGEm and empirical model efficiencies in predicting ephemeral gully erosion around mubi area,Northeast Nigeria

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International Soil and Water Conservation Research 2021年第1期9卷 11-25页

作者： Ijasini John Tekwa John mathew Laflen Abubakar musa Kundiri Abdullahi bala Alhassan Department of Soil Science&Land Resources management Federal University WukariP.M.B1020Wukari Taraba StateNigeria USDA-ARS National Soil Erosion Research LaboratoryPurdue UniversityLafayetteINUSA Department of Soil Science Faculty of AgricultureUniversity of MaiduguriP.M.B1069Borno StateNigeria

Evaluation of prediction models is crucial to achieving valid information on erosion processes and their management *** model efficiency in predicting ephemeral gully(EG)erosion was recently tested and compared with both EGEm and empirical *** models abilities to predict EG erosion were validated using measured estimates at the 6 eroding locations around mubi area in Northeast Nigeria between April 2008 and October *** location consisted of 3 watersheds where data on soils,climate,slope,management practices,EG shapes and dimensions were *** on relevant soil properties were collected in the field and then analyzed in *** mass of soil loss(mSL)predicted by empirical,EGEm and WEPP models were compared with the measured using paired T-test,regression graphs(r^(2)-values),error analysis,and analysis of variance(ANOVA)in a completely ran-domized *** EG erosion losses varied significantly(P≤0.05)between sites and *** sig-nificant(P≤0.05)differences were observed between measured and the empirically predicted aggregate *** measured aggregate mSL strongly correlated with those predicted by empirical(r^(2)=0.67),than with EGEm(r^(2)=0.57),and WEPP(r^(2)=0.53)*** over and under-prediction instances against the measured erosion were noted with all the *** WEPP model was found to slightly over-predict mSL when compared to either the empirical or EGEm *** prediction quality of the models was generally *** works should focus more on local inputs such as climate,plants,management,and tillage data for use with WEPP.

关键词： Empirical EGEm WEPP Ephemeral gully erosion Soil loss mubi Northeast Nigeria

Joining of AZ91 mg alloy and Al6063 alloy sheets by friction stir welding

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Journal of magnesium and Alloys 2018年第1期6卷 71-76页

作者： B.Lakshmana prasad G.Neelaiah m.Gopi krishna S.V.V.Ramana K.Sai Prakash G.Sarika G.Pradeep Kumar Reddy Ravikumar Dumpala B.Ratna Sunil Department of mechanical Engineering Rajiv Gandhi University of Knowledge Technologies(AP-IIIT)Nuzvid 520201India Department of mechanical Engineering Vignana Bharathi Institute of TechnologyHyderabad 501301India Department of mechanical Engineering Visvesvaraya National Institute of TechnologyNagpur 440010India

In the present work,the effect of process parameters on joining of AZ91 mg alloy and Al6063 aluminum alloy sheets during friction stir welding(FSP)was studied.A successful joint was achieved at 1100 *** rotational speed and 25 mm/min tool travel *** of tool rotational speed and tool travel speed has observed a profound effect on the material flow mechanisms at the nugget *** the microstructural studies,the joint formation was observed as mainly due to mechanical mixing of the *** level of metallurgical continuity at the nugget zone was observed as poor and a sharp interface at the joint was *** microhardness measurements across the weld joint also revealed the lack of establishment of a perfect metallurgical bonding.X-ray diffraction analysis of weld zone showed presence of both magnesium and *** from the preliminary observations,it can be understood that the joining of AZ91 mg alloy and Al6063 alloy can be achieved by FSP;however,complex issues in material mixing still need further investigations.

关键词： Friction stir welding Dissimilar joints magnesium Aluminum Nugget zone

Effect of Sm^+ Rare Earth Ion on the Structural,Thermal,mechanical and Optical Properties of Potassium Hydrogen Phthalate Single Crystals

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Journal of materials Science & Technology 2014年第1期30卷 13-18页

作者： S.Sudhahar m.krishna Kumar V.Jayaramakrishnan R.muralidharan R.mohan Kumar Department of Physics Presidency College Department of Physics P.S.G.College of Arts and Science Department of Science and Humanities Vel Tech High Tech Dr.Rangarajan Dr.Sakunthala Engineering College

Rare earth Sm＋ ion doped potassium hydrogen phthalate （KHP） single crystal was grown by slow evaporation technique. Single crystal and powder X-ray diffraction analyses confirm the crystalline perfection of Sm＋ ion doped KHP crystal. The functional groups of pure and Sm＋ ion doped KHP crystals were identified by Fourier transform infrared spectroscopy （FTIR） spectral studies. Thermogravimetric and differential thermal analyses were carried out to study the thermal behavior of the grown crystals. UV-Vis studies explored the optical transmittance of the grown crystals in the entire visible region. The mechanical strength and etching studies were performed to assess the perfection of the pure and Sm＋ ion doped KHP crystals. The refractive index and birefringence properties of the grown crystal were analyzed. The second harmonic generation efficiency of Sm＋ ion doped KHP crystals was observed by Kurtz-Perry powder test.

关键词： Crystal growth Potassium hydrogen phthalate (KHP) single crystal Differential thermal analysis FTIR Hardness