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Journal of Modern Physics 2013年第3期4卷 331-336页

作者： Kethireddy Narender Ammiraju Sowbhagya Madhusudhan Rao Kalvala Gopal Kishan Rao nallacheruvu gopi krishna CIC Kakatiya University Warangal India Department of Physics Kakatiya University Warangal India Varadha Reddy College of Engineering Warangal India

The gamma quanta attenuation studies have been carried out to determine mass attenuation coefficients of 7041, 7075 and 7095 wrought aluminum alloys. The temperature dependence of linear attenuation coefficient, density and thermal expansion of these wrought aluminum alloys in the temperature range 300 K - 850 K have been reported. The measurements were done by using a gamma ray densitometer designed and fabricated in our laboratory. The data on variation of density and linear thermal expansion with temperature have been represented by linear equations. Volume thermal expansion coefficients have been reported.

关键词： Density Thermal Expansion Linear Attenuation Coefficient Mass Attenuation Coefficient

Thermophysical Properties of NaCl, NaBr and NaF by <i>γ</i>-Ray Attenuation Technique

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Journal of Modern Physics 2013年第2期4卷 208-214页

作者： Ammiraju Sowbhagya Madhusudhan Rao Kethireddy Narender Kalvala Gopal Kishan Rao nallacheruvu gopi krishna Central Instrumentation Centere (CIC) Kakatiya University Warangal India Department of Physics Kakatiya University Warangal India

The γ-ray densitometer has been designed and fabricated in our laboratory and carried out studies on temperature dependent γ-ray attenuation and thermo physical properties of NaCl, NaBr and NaF. The linear attenuation coefficients (μl) for the pellets of NaCl, NaBr and NaF as a function of temperature have been determined. The coefficients of temperature dependence of density have been reported. The variation of density and thermal expansion of NaCl, NaBr and NaF in the temperature range of 300 K - 1000 K have been studied and compared with results available in the literature. The temperature dependence of density and thermal expansion has been represented by linear equations. Volume thermal expansion coefficients have been reported.

关键词： Linear Attenuation Coefficient Density Thermal Expansion γ-Ray Densitometer

Enhancing Stress Intensity Factor Reduction in Cracks Originating from a Circular Hole in a Rectangular Plate under Uniaxial Stress through Piezoelectric Actuation

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Materials Sciences and Applications 2024年第1期15卷 1-14页

作者： gopi krishna Konda Jens Schuster Yousuf Pasha Shaik Department of Applied Logistics and Polymer Sciences University of Applied Sciences Kaiserslautern Institute for Plastics Engineering West Pfalz (IKW) Pirmasens Germany

Circular holes are commonly employed in engineering designs;however, they often serve as locations where cracks initiate and propagate. This paper explores a novel approach to structural repair by utilizing piezoelectric actuators. The primary focus of this study is to investigate the influence of an adhesively bonded piezoelectric actuator patch placed above a circular hole on the stress intensity factor (SIF) in an aluminium plate. The plate is subjected to uniaxial tensile stress, while the piezoelectric actuator is excited with varying voltage levels. The analysis is conducted using the finite element method (FEM), a powerful numerical technique for simulating complex structures. The study assesses the stress distribution and employs the SIF as an adequate criterion for evaluating the impact of different patch configurations. The results indicate a strong correlation between the applied voltage and the SIF. Whether the SIF increases or decreases depends on the polarization of the piezoelectric actuator. Particularly noteworthy is the finding that rectangular patches in a horizontal orientation significantly reduce the SIF compared to other patch geometries. Moreover, double-sided patches exhibit a pronounced decrease in the SIF compared to single-sided patches. In summary, this research underscores the potential of piezoelectric actuators in mitigating stress intensity in structures with circular hole with crack initiation. It offers valuable insights into the influence of applied voltage, patch geometry, and patch placement on the SIF, thereby contributing to developing effective strategies for enhancing structural integrity.

关键词： Piezoelectric Actuators Stress Intensity Factor (SIF) Aluminium Plate Voltage Finite Element Method (FEM)

A threshold voltage model of short-channel fully-depleted recessed-source/drain(Re-S/D) SOI MOSFETs with high-k dielectric

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Chinese Physics B 2015年第10期24卷 604-611页

作者： gopi krishna Saramekala Sarvesh Dubey Pramod Kumar Tiwari Department of Electronics and Communication Engineering National Institute of Technology Shri Ramswaroop Memorial University

In this paper, a surface potential based threshold voltage model of fully-depleted（FD） recessed-source/drain（Re-S/D）silicon-on-insulator（SOI） metal-oxide semiconductor field-effect transistor（MOSFET） is presented while considering the effects of high-k gate-dielectric material induced fringing-field. The two-dimensional（2D） Poisson＇s equation is solved in a channel region in order to obtain the surface potential under the assumption of the parabolic potential profile in the transverse direction of the channel with appropriate boundary conditions. The accuracy of the model is verified by comparing the model＇s results with the 2D simulation results from ATLAS over a wide range of channel lengths and other parameters,including the dielectric constant of gate-dielectric material.

关键词： recessed-source/drain (Re-S/D) high-k gate-material fringing field and SCEs

Magnesium matrix composites for biomedical applications:A review

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Journal of Magnesium and Alloys 2019年第1期7卷 72-79页

作者： Vijay Kumar Bommala Mallarapu gopi krishna ChTirumala Rao Department of Mechanical Engineering Acharya Nagarjuna UniversityGuntur-522510Andhra PradeshIndia

In recent years,a new wave of bioactive,biocompatibility and biodegradable metallic materials were developed for orthopedic *** Magnesium,Magnesium alloys,Magnesium alloy-based composites are extensive material to the biomedical applications,by virtue of its high biocompatibility and reasonable *** magnesium,Magnesium alloys can corrode too fast during the physiological conditions and loses their properties before bone *** new era for the development of magnesium-based composites can satisfy the orthopedic ***-based composites,as bio-materials,can produce adjustable mechanical properties like Ultimate tensile strength,ductility,elastic modulus,and corrosion resistance in the physiological *** the Mg based composites,the matrix materials are biomedical magnesium alloys base like Mg-Ca,Mg-Al,Mg-Zn,and Mg-REE alloy and The reinforcements are based on hydroxyapatite(HAP),calcium polyphosphate(CPP),andβ-tricalcium phosphate(β-TCP)*** comprehensive review is focused on different grades of biodegradable magnesium matrix composites including their mechanical properties and corrosion resistance.

关键词： Magnesium composites Biodegradable Biocompatible Mechanical properties Biological corrosion

Analytical model for subthreshold current and subthreshold swing of short-channel double-material-gate MOSFETs with strained-silicon channel on silicon–germanium substrates

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Journal of Semiconductors 2014年第10期35卷 30-36页

作者： Pramod Kumar Tiwari gopi krishna Saramekala Sarvesh Dubey Anand Kumar Mukhopadhyay National Institute of Technology Rourkela Department of Electronics and Communication Engineering Faculty of Electronics and Communication SRM University

The present work gives some insight into the subthreshold behaviour of short-channel double-material- gate strained-silicon on silicon-germanium MOSFETs in terms of subthreshold swing and off-current. The formu- lation of subthreshold current and, thereupon, the subthreshold swing have been done by exploiting the expression of potential distribution in the channel region of the device. The dependence of the subthreshold characteristics on the device parameters, such as Ge mole fraction, gate length ratio, work function of control gate metal and gate length, has been tested in detail. The analytical models have been validated by the numerical simulation results that were obtained from the device simulation software ATLASTM by Silvaco Inc.

关键词： strained-Si channel Si1-xGex substrate dual-metal gate subthreshold current subthreshold swing

Chemical reaction effect of an axisymmetric flow over radially stretched sheet

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Propulsion and Power Research 2019年第1期8卷 79-84页

作者： B.Nayak S.R.Mishra G.gopi krishna Department of Mathematics Sikslia‘O’AnusandhanKhandagiriBhubaneswar 751030OdisaIndia Department of Mathematics Sri Venkateswara UniversityTirupatiIndia

A steady boundary layer flow over a porous flat plate has been considered in the present *** transfer analysis with first order chemical reaction is also considered instead of heat *** plate concentration is considered in the form of power law instead of taking *** goveming PDEs are transformed into ordinary differential equations using similarity transfomation and then these ODEs are solved by employing Runge-Kutta fourth order method associated with shooting technique.A parametric study of all involving parameters is obtained by the help of *** major findings are:(i)the concentration of the fluid in its boundary layer decrease with increase in heavier species,the reaction rate parameter and the power law exponent;(ji)the rate of mass transfer increases with an increase in reaction rafe parameter and power-law exponent.

关键词： Magnetohydrodynamic Mass transfer First order chemical reaction Runge-Kutta method Shooting technique

Swarm-LSTM: Condition Monitoring of Gearbox Fault Diagnosis Based on Hybrid LSTM Deep Neural Network Optimized by Swarm Intelligence Algorithms

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Computers, Materials & Continua 2021年第2期66卷 2041-2059页

作者： gopi krishna Durbhaka Barani Selvaraj Mamta Mittal Tanzila Saba Amjad Rehman Lalit Mohan Goyal School of Electrical and Electronics Sathyabama Institute of Science and TechnologyChennai600119India Department of Computer Science and Engineering G.B.Pant Government Engineering CollegeNew Delhi110020India Artificial Intelligence and Data Analytics(AIDA)Laboratory CCISPrince Sultan UniversityRiyadh11586Saudi Arabia Department of Computer Engineering J.C.Bose University of Science and TechnologyFaridabad121006India

Nowadays,renewable energy has been emerging as the major source of energy and is driven by its aggressive expansion and falling *** of the renewable energy sources involve turbines and their operation and maintenance are vital and a difficult *** monitoring and fault diagnosis have seen remarkable and revolutionary up-gradation in approaches,practices and technology during the last *** mostly do use a rotating type of machinery and analysis of those signals has been challenging to localize the *** paper proposes a new hybrid model wherein multiple swarm intelligence models have been evaluated to optimize the conventional Long Short-Term Memory(LSTM)model in classifying the faults from the vibration signals data acquired from the *** helps to analyze the performance and behavioral patterns of the system more effectively and efficiently which helps to suggest for replacement of the unit with higher *** results have demonstrated that the proposed hybrid modeling approach is effective in classifying the faults of the gearbox from the time series data and achieve higher diagnostic accuracy in comparison to the conventional LSTM methods.

关键词： Gearbox long short term memory fault classification swarm intelligence optimization condition monitoring

Complete oxidation of 1,4-dioxane over zeolite-13X-supported Fe catalysts in the presence of air

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Chinese Journal of Catalysis 2016年第2期37卷 240-249页

作者： C.Ramakrishna R.krishna T.gopi G.Swetha Bijendra Saini S.Chandra Shekar Anchal Srivastava 国防研发局、防化装备评估设备(CDEF) 印度那格浦尔MH-441108

Zeolite-13X-supported Fe（Fe/zeolite-13X） catalysts with various Fe contents were prepared by the wet impregnation *** catalysts were characterized by N2 adsorption-desorption isotherms to estimate the Brunauer-Emmett-Teller surface areas and Barrett-Joyner-Hanlenda pore size distributions.X-ray diffraction,scanning electron microscopy,temperature-programmed reduction,and temperature-programmed desorption of NH3 were used to investigate the textural properties of the Fe/zeolite-13 X *** catalytic activities were determined for the complete oxidation of1,4-dioxane using air as the oxidant in a fixed-bed flow reactor in the temperature range 100-400℃.The influences of various process parameters,such as reaction temperature,metal loading,and gas hourly space velocity（GHSV）,on the dioxane removal efficiency by catalytic oxidation were *** stability of the catalyst was tested at 400℃ by performing time-on-stream analysis for 50 *** Fe/zeolite-13 X catalyst with 6 wt%Fe exhibited the best catalytic activity among the Fe/zeolite-13 X catalysts at 400℃ and a GHSV of 24000 h^（-1）,with 97%dioxane conversion and95%selectivity for the formation of carbon oxides（CO and CO2）.Trace amounts（ 3%） of acetaldehyde,ethylene glycol monoformate,ethylene glycol diformate,1,4-dioxane-2-ol,1,4-dioxane-2-one,and 2-methoxy-1,3-dioxalane were also formed as degradation products.A plausible degradation mechanism is proposed based on the products identified by GC-MS analysis.

关键词： Iron Zeolite-13X 1 4-Dioxane Catalytic degradation Complete oxidation Degradation mechanism

Analog and radio-frequency performance analysis of silicon-nanotube MOSFETs

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Journal of Semiconductors 2016年第6期37卷 60-63页

作者： pramod kumar tiwari mukesh kumar ramavathu sakru naik gopi krishna saramekala Department of Electronics and Communication Engineering National Institute of TechnologyRourkela-769008OdishaIndia

This work presents a comparative study of the influence of various parameters on the analog and RF properties of silicon-nanotube MOSFETs and nanowire-based gate-all-around（GAA） *** important analog and RF performance parameters of SiNT FETs and GAA MOSFETs,namely drain current（/d）,transconductance to drain current ratio（g_m/I_d）,I_（on）/I_（off）,the cut-off frequency（f_T） and the maximum frequency of oscillation（/max） are evaluated with the help of Y- and H-parameters which are obtained from a 3-D device simulator,ATLAS^（TM）.It is found that the silicon-nanotube MOSFETs have far more superior analog and RF characteristics（g_m/I_d,f_T and /max） compared to the nanowire-based gate-all-around GAA *** silicon-nanotube MOSFET shows an improvement of ~2.5 and 3 times in the case of f_T and /max values respectively compared with the nanowire-based gate-all-around（GAA） MOSFET.

关键词： analog and RF SiNT MOSFETs GAA MOSFETs unity gain frequency unity power frequency