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  • Open Access

    ARTICLE

    A Deep Reinforcement Learning-Based Technique for Optimal Power Allocation in Multiple Access Communications

    Sepehr Soltani1, Ehsan Ghafourian2, Reza Salehi3, Diego Martín3,*, Milad Vahidi4

    Intelligent Automation & Soft Computing, Vol.39, No.1, pp. 93-108, 2024, DOI:10.32604/iasc.2024.042693

    Abstract For many years, researchers have explored power allocation (PA) algorithms driven by models in wireless networks where multiple-user communications with interference are present. Nowadays, data-driven machine learning methods have become quite popular in analyzing wireless communication systems, which among them deep reinforcement learning (DRL) has a significant role in solving optimization issues under certain constraints. To this purpose, in this paper, we investigate the PA problem in a -user multiple access channels (MAC), where transmitters (e.g., mobile users) aim to send an independent message to a common receiver (e.g., base station) through wireless channels. To this end, we first train… More >

  • Open Access

    EDITORIAL

    A Constantly Evolving Journal: Reflecting on 2023

    Une revue en constante évolution : retour sur l’année 2023

    Kristopher Lamore*

    Psycho-Oncologie, Vol.18, No.1, pp. 1-3, 2024, DOI:10.32604/po.2024.050518

    Abstract This article has no abstract. More >

  • Open Access

    ARTICLE

    Experimental Study of Heat Transfer in an Insulated Local Heated from Below and Comparison with Simulation by Lattice Boltzmann Method

    Noureddine Abouricha1,*, Ayoub Gounni2, Mustapha El Alami2

    Frontiers in Heat and Mass Transfer, Vol.22, No.1, pp. 359-375, 2024, DOI:10.32604/fhmt.2024.047632

    Abstract In this paper, experimental and numerical studies of heat transfer in a test local of side heated from below are presented and compared. All the walls, the rest of the floor and the ceiling are made from plywood and polystyrene in sandwich form ( plywood- polystyrene- plywood) just on one of the vertical walls contained a glazed door (). This local is heated during two heating cycles by a square plate of iron the width , which represents the heat source, its temperature is controlled. The plate is heated for two cycles by an adjustable set-point heat source placed just… More >

  • Open Access

    ARTICLE

    Effects of Viscous Dissipation and Periodic Heat Flux on MHD Free Convection Channel Flow with Heat Generation

    Mustafa Abdullah*

    Frontiers in Heat and Mass Transfer, Vol.22, No.1, pp. 141-156, 2024, DOI:10.32604/fhmt.2024.046788

    Abstract This study investigates the influence of periodic heat flux and viscous dissipation on magnetohydrodynamic (MHD) flow through a vertical channel with heat generation. A theoretical approach is employed. The channel is exposed to a perpendicular magnetic field, while one side experiences a periodic heat flow, and the other side undergoes a periodic temperature variation. Numerical solutions for the governing partial differential equations are obtained using a finite difference approach, complemented by an eigenfunction expansion method for analytical solutions. Visualizations and discussions illustrate how different variables affect the flow velocity and temperature fields. This offers comprehensive insights into MHD flow behavior… More >

  • Open Access

    ARTICLE

    HOT WATER COOLED HEAT SINKS FOR EFFICIENT DATA CENTER COOLING: TOWARDS ELECTRONIC COOLING WITH HIGH EXERGETIC UTILITY

    Peter Kastena, Severin Zimmermanna, Manish K. Tiwaria, Bruno Michelb, Dimos Poulikakosa,*

    Frontiers in Heat and Mass Transfer, Vol.1, No.2, pp. 1-10, 2010, DOI:10.5098/hmt.v1.2.3006

    Abstract Electronic data center cooling using hot water is proposed for high system exergetic utility. The proof-of-principle is provided by numerically modeling a manifold micro-channel heat sink for cooling microprocessors of a data center. An easily achievable 0.5l/min per chip water flow, with 60°C inlet water temperature, is found sufficient to address the typical data center thermal loads. A maximum temperature difference of ~8°C was found between the solid and liquid, confirming small exergetic destruction due to heat transport across a temperature differential. The high water outlet temperature from the heat sink opens the possibility of waste heat recovery applications. More >

  • Open Access

    ARTICLE

    LIQUID WATER DYNAMIC BEHAVIORS IN THE GDL AND GC OF PEMFCS USING LATTICE BOLTZMANN METHOD

    Li Chen, Hui-Bao Luan, Wen-Quan Tao*

    Frontiers in Heat and Mass Transfer, Vol.1, No.2, pp. 1-11, 2010, DOI:10.5098/hmt.v1.2.3002

    Abstract Multi-phase lattice Boltzmann method is applied to investigate liquid water transport in th GDL and GC. The liquid water transport processes in the GDL, near the GDL-GC interfaces and in the GC are discussed. The effects of channel land on liquid water dynamic behaviors and distribution in the GDL and GC are investigated. It is found that channel land covers the GDL-GC interface where liquid water reaches changes the water distribution near the GDL-GC interface and in the GC. While channel land is apart from the GDL-GC interface where liquid water reaches changes the effects of channel land is smaller. More >

  • Open Access

    ARTICLE

    VOLUME OF FLUID SIMULATION OF BOILING TWO-PHASE FLOW IN A VAPOR-VENTING MICROCHANNEL

    Chen Fang*, Milnes David, Anita Rogacs, Kenneth Goodson

    Frontiers in Heat and Mass Transfer, Vol.1, No.1, pp. 1-11, 2010, DOI:10.5098/hmt.v1.1.3002

    Abstract Vapor-venting microchannel heat exchangers are promising because they address the problems of high pressure drop, flow instability, and local dryout that are common in conventional two-phase microchannel heat sinks. We present a 3D numerical simulation of the vapor-venting process in a rectangular microchannel bounded on one side by a hydrophobic porous membrane for phase-separation. The simulation is based on the volume of fluid (VOF) method together with models for interphase mass transfer and capillary force. Simulation shows the vapor-venting mechanism can effectively mitigate the vapor accumulation issue, reduce the pressure drop, and suppress the local dry-out in the microchannel. Pressure… More >

  • Open Access

    ARTICLE

    NUMERICAL SIMULATION OF TURBULENT FLOW IN A RECTANGULAR CHANNEL WITH PERIODICALLY MOUNTED LONGITUDINAL VORTEX GENERATORS

    Pankaj Sahaa, Gautam Biswasa,b,*

    Frontiers in Heat and Mass Transfer, Vol.2, No.3, pp. 1-5, 2011, DOI:10.5098/hmt.v2.3.3008

    Abstract Detailed flow structure in turbulent flows through a rectangular channel containing built-in winglet type vortex generators have been analyzed by means of solutions of the full Navier-Stokes equations using a Large-Eddy Simulation (LES) technique. The Reynolds number of investigation is 6000. The geometry of interest consists of a rectangular channel with a built-in winglet pair on the bottom wall with common-flow-down arrangement. The winglet pair induces streamwise longitudinal vortices behind it. The vortices swirl the flow around the axis parallel to the mainstream direction and disrupt the growth of thermal boundary layer entailing enhancement of heat transfer. The influence of… More >

  • Open Access

    ARTICLE

    THERMOHYDRAULIC CHARACTERISTICS OF A SINGLE-PHASE MICROCHANNEL HEAT SINK COATED WITH COPPER NANOWIRES

    M. Yakut Alia,*, Fanghao Yanga, Ruixian Fanga, Chen Lia, Jamil Khana,†

    Frontiers in Heat and Mass Transfer, Vol.2, No.3, pp. 1-11, 2011, DOI:10.5098/hmt.v2.3.3003

    Abstract This study experimentally investigates single phase heat transfer and pressure drop characteristics of a shallow rectangular microchannel heat sink whose surface is enhanced with copper nanowires (CuNWs). The hydraulic diameter of the channel is 672 μm and the bottom wall is coated with Cu nanowires (CuNWs) of 200 nm in diameter and 50 μm in length. CuNWs are grown on the Cu heat sink by electrochemical synthesis technique which is inexpensive and readily scalable. The heat transfer and pressure drop results of CuNWs enhanced heat sink are compared with that of bare copper surface heat sink using deionized (DI) water… More >

  • Open Access

    ARTICLE

    CHAOTIC NATURAL CONVECTION IN AN ANNULAR CAVITY WITH NON-ISOTHERMAL WALLS

    H.E. Dillon, A.F. Emery, A.M. Mescher, O. Sprenger, S.R. Edwards

    Frontiers in Heat and Mass Transfer, Vol.2, No.2, pp. 1-14, 2011, DOI:10.5098/hmt.v2.2.3002

    Abstract The stability of free convection in an annulus is governed by the boundary conditions on the inner and outer walls of the annulus and the upper and lower boundaries. This paper explores the effect of free convection on the inner surface of the annulus, where the boundary conditions for the outer wall and the upper and lower boundaries are controlled. The temperature is measured in the center of the air cavity and just below the surface of the inner annular boundary. Experimental results are shown for a radius ratio of 0.40, aspect ratio of 20.7. These more recent experimental results… More >

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