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Heat Transfer Optimization for Air-Mist Cooling between a Stack of Parallel Plates

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journal of Thermal Science 2010年第3期19卷 253-260页

作者： roy j.Issa Mechanical Engineering Division Department of Engineering and Computer Science West Texas A&M University CanyonTexas 79016USA

A theoretical model is developed to predict the upper limit heat transfer between a stack of parallel plates subject to multiphase cooling by air-mist *** model predicts the optimal separation distance between the plates based on the development of the boundary layers for small and large separation distances,and for dilute mist *** results show the optimal separation distance to be strongly dependent on the liquid-to-air mass flow rate loading ratio,and reach a limit for a critical *** these dilute spray conditions,complete evaporation of the droplets takes *** results also show the optimal separation distance decreases with the increase in the mist flow *** proposed theoretical model shall lead to a better understanding of the design of fins spacing in heat exchangers where multiphase spray cooling is used.

关键词： Air-mist Multiphase Heat transfer Liquid-to-air loading

Atomic coordination dictates vibrational characteristics and thermal conductivity in amorphous carbon

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npj Computational Materials 2022年第1期8卷 525-531页

作者： Ashutosh Giri Connor j.Dionne Patrick E.hopkins Department of Mechanical Industrial and Systems EngineeringUniversity of Rhode IslandKingstonRI02881USA Department of Mechanical and Aerospace Engineering University of VirginiaCharlottesvilleVA22904USA Department of Materials Science and Engineering University of VirginiaCharlottesvilleVA22904USA Department of Physics University of VirginiaCharlottesvilleVA22904USA

We discuss the role of atomic coordination in dictating the vibrational characteristics and thermal conductivity in amorphous *** systematic atomistic simulations on amorphous carbon structures at varying mass densities show the significant role played by the ratio of sp2 to sp3 hybridized bonds in dictating the contributions from propagating(phonon-like)and non-propagating vibrational modes and their influence on the overall thermal conductivities of the ***,our results show that as the concentration of sp3-bonded carbon atoms increases,the thermal conductivity can be increased by four fold,which is attributed to enhanced contributions from propagating modes in these amorphous *** results shed more light into the role of atomic coordination on dictating heat transfer mechanisms in amorphous materials,and also provide a deeper understanding of the ability to tune the thermal conductivity of amorphous carbon structures through the control of the local atomic coordination.

关键词： amorphous conductivity thermal

Performance Prediction of a Multi-Stage Wind Tower for Indoor Cooling

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journal of Thermal Science 2012年第4期21卷 327-335页

作者： roy j. Issa Byungik Chang Department of Engineering and Computer Science West Texas A&M University Canyon

A theoretical model is developed to establish an indepth understanding of the performance of a three-stage wind tower with a bypass system for indoor cooling in rural dry and hot climates. Model simulations are presented for a wide range of ambient conditions that include inlet wind speed, inlet temperature and relative humidity. Simulation results provide an insight into the desirable water flow rates and air-to-water loadings for comfort zone tem-peratures and relative humidity levels at the exit of the wind tower. Simulations show wind towers with variable cross-sections provide an increase in the cooling power for the same inlet wind speed, inlet air temperature and relative humidity when compared to wind towers with a constant cross-section. The study shall lead to a better understanding to designing wind towers that are both environmentally friendly and energy efficient.

关键词： Wind tower Cooling power Cooling effectiveness Relative humidity

Mathematical modeling of nanoscale MOS capacitance in the presence of depletion and energy quantization in a poly-silicon gate

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journal of Semiconductors 2010年第11期31卷 5-8页

作者： Amit Chaudhry j.N.roy Institute of Engineering and Technology Panjab University Solar Semiconductor Pvt.Ltd.

A model has been developed to study the effect of depletion and energy quantization at the poly-silicon /oxide interface on the behavior of a nanometer scale n-MOSFET.A model of inversion charge density,including the inversion layer quantization using the variation approach in the substrate,has also been *** the exact calculations of the polygate potential under the depletion and quantization conditions,a C-V model has been developed. All the results have been compared with the numerical models reported in existing literature and they show good agreement.

关键词： BSIM inversion layers MOS devices quantization poly-depletion poly-quantization

Nanoscale strained-Si MOSFET physics and modeling approaches:a review

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journal of Semiconductors 2010年第10期31卷 19-23页

作者： Amit Chaudhry j.N.roy Garima joshi University Institute of Engineering and Technology Panjab University Solar Semiconductor Private Limited

An attempt has been made to give a detailed review of strained silicon technology. Various device models have been studied that consider the effect of strain on the devices, and comparisons have been drawn. A review of some modeling issues in strained silicon technology has also been outlined. The review indicates that this technology is very much required in nanoscale MOSFETs due to its several potential benefits, and there is a strong need for an analytical model which describes the complete physics of the strain technology.

关键词： mobility SiGe strained-Si technology CAD

SPICE compatible analytical electron mobility model for biaxial strained-Si-MOSFETs

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journal of Semiconductors 2011年第5期32卷 36-41页

作者： Amit Chaudhry j.N.roy S.Sangwan UIET Panjab UniversityChandigarhIndia Solar Semiconductro Pvt.Ltd HyderabadIndia

This paper describes an analytical model for bulk electron mobility in strained-Si layers as a function of strain. Phonon scattering, columbic scattering and surface roughness scattering are included to analyze the full mobility model. Analytical explicit calculations of all of the parameters to accurately estimate the electron mobility have been made. The results predict an increase in the electron mobility with the application of biaxial strain as also predicted from the basic theory of strain physics of metal oxide semiconductor （MOS） devices. The results have also been compared with numerically reported results and show good agreement.

关键词： mobility SiGe strained-Si phonon surface roughness columbic

Effect of calcination temperature on steam reforming activity of Ni-based pyrochlore catalysts

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journal of Rare Earths 2020年第7期38卷 711-718,I0002页

作者： Daniel j.Haynes Dushyant Shekhawat David Berry Amitava roy james j.Spivey National Energy Technology Laboratory U.S.Department of Energy3610 Collins Ferry RdMorgantownWV26507 USA Louisiana State University Cain Department of Chemical Engineering3307 Patrick Taylor HallBaton RougeLA70803USA

This work served as the second part of a study evaluating the effect of calcination temperature(700-1000℃) on Ni-based lanthanum zirconate pyrochlore catalysts for methane steam reforming.A previous study(Haynes et ***.2017(43) 16744) provided a thorough characterization of the material properties for the catalysts used here,and this study focuses on the evaluation of catalytic *** activity was assessed by two different experimental studies:the effect of reaction temperature using a temperature programmed surface reaction(TPSR),and the effect of reaction *** results demonstrate a complex interaction between the Ni particles and surface LaOx species under the methane steam reforming ***,the material calcined at the lowest temperature(700℃) possesses the highest activity and selectivity,which is attributed to smaller and more welldispersed Ni particles on the surface,and,more importantly,a lesser degree La enrichment at the *** catalysts were deactivated by steam to NiO under all conditions tested,but at certain low reaction pressure(p=0.23 MPa) conditions the materials calcined at 700-900℃ are able to completely recover equilibrium activity in-situ that is then robust and stable under both low and high reaction pressures(p=1.8 MPa) suggesting the formation of a synergistic relationship between Ni and La for syngas ***,exposure of a fresh material to high reaction pressures leads to a rapid and irreversible loss in both CH4 conversion and syngas selectivity whether in the fresh(no pretreatment),or pretreated(steam,H2 or Ar only at 800℃) form for any *** mechanism for deactivation appears to be due to the presence of LaOx species that become mobile,possibly by the formation of La-OH,and covers the active Ni particles and inhibits sites responsible for the CH4 decomposition.

关键词： Nickel Pyrochlore Methane Steam reforming Catalyst Lanthanum enrichment

A synchronous duty-cycled reservation based MAC protocol for underwater wireless sensor networks

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Digital Communications and Networks 2021年第3期7卷 385-398页

作者： Alak roy Nityananda Sarma Department of Information Technology Tripura UniversityWest TripuraIndia Department of Computer Science and Engineering Tezpur UniversityAssamIndia

To design an energy-efficient Medium Access Control(MAC)protocol for the Underwater Wireless Sensor Networks(UWSNs)is an urgent research issue since depleted batteries cannot be recharged or replaced in the underwater ***,the underwater acoustic channels are affected by hindrances such as long propagation delay and limited bandwidth,which appear in the design of the MAC protocol for the *** available MAC protocols for the terrestrial wireless sensor networks exhibit low performance in energy efficiency,throughput and reliability in the UWSNs,and cannot be used in the UWSNs directly because of their unique *** paper proposes a synchronous duty-cycled reservation-based MAC protocol named Ordered Contention MAC(OCMAC)*** basic mechanism of this protocol is to schedule data transmission by transmitters through the scheduling of Ready To Send(RTS)*** protocol eliminates the possible collision during data transmission and improves communication *** paper analyzes the performance in energy efficiency,throughput and reliability of the protocol by modeling the queuing behavior of OCMAC with a Markov Chain ***,the analytical model is validated through a simulation *** analysis results demonstrated that while providing good throughput and reliability,OCMAC can achieve energy saving.

关键词： Underwater wireless sensor networks MAC protocol Energy efficiency Throughput Reliability Acoustic communication OCMAC

Structural,optical,electrical,and dielectric relaxation properties of rare earth containing sodium bismuth titanate Na_(0.5)Bi_(0.5)TiO_(3) perovskite:Effect of ionic radius

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journal of Rare Earths 2024年第2期42卷 383-391,I0006页

作者： Rajdip roy Abhigyan Dutta Department of Physics The University of BurdwanBurdwan713104India

The main focus of this work is to study the effect of the ionic radius of different rare earth dopant cations RE^(3+)(RE=La,Sm,Dy,and Ho) on structural and various physical properties of sodium bismuth titanate(Na_(0.5)B_(0.5)TiO_(3),NBT) based perovskite *** X-ray diffraction data indicate the successful formation of the rhombohedral phase(space group R3c) of NBT nano perovskite incorporated with various rare earth ions in *** lattice parameters were found to increase linearly with the ionic radius of the dopant *** ionic radii and atomic mass of rare earth dopants appear to be essential factors in the grain growth of the prepared *** grain growth results in better crystallinity of the sample by reducing the microstrain with the increase of dopant ionic *** emission scanning electron microscopy and energy-dispersive X-ray spectra confirm the prepared compositions' phase purity and *** UV-Vis spectra reveal that La-doped NBT composition exhibits the lowest optical band gap,which unfolds the application of NBT-based perovskite as photoactive *** ac conductivity and complex impedance spectra unveil that the composition with the largest ionic radius,i.e.,La-doped NBT compound,exhibits the highest dc and bulk conductivity with the lowest activation *** frequency-dependent dielectric data follows Havriliak-Negami(HN) formalism and non-Debye type relaxation *** also indicate that La-doped NBT composition exhibits the highest dielectric strength ***,this study first elaborates that the increasing ionic radius of the rare earth dopant cation in the Bi-site of NBT perovskite improves its microstructural,optical,and electrical properties.

关键词： Rare earth doped NBT Microstructural analysis Optical band gap AC Conductivity Dielectric relaxation Rare earths