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Journal of Central South University 2021年第11期28卷 3354-3367页

作者： hamid-reza bahrami Department of Mechanical Engineering Qom University of TechnologyQom 37195Iran

The backward-facing step is a critical problem existing in many engineering and industrial *** this study,a semi-porous baffle(the root of the baffle is a porous medium and the tip is solid) is placed behind the *** effects of the length of the porous part,and the baffle location on the energy transfer and pressure drop are studied in different Reynolds numbers(Re=100,200,300,400,500).The effect of the Darcy number of the porous medium on the aforementioned parameters is also *** the local maximum and average relative Nusselt numbers(divided by the Nusselt of the base case with no baffle at the same Reynolds) and relative pressure drop(calculated as the relative Nusselt number) are *** results show that by adoption of the proper length of the porous medium,the average relative and maximum local Nusselt numbers could be enhanced by 20% and 90%,*** permeable porous media give better energy *** example,porous media with Da=10^(-5) give 30% better maximum local Nusselt number and about 7% higher average Nusselt number with respect to the same case with Da=10^(-2).

关键词： porous media enhanced heat transfer baffle backward-facing step two-dimensional channel

Dropwise condensation heat transfer enhancement on surfaces micro/nano structured by a two-step electrodeposition process

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Journal of Central South University 2019年第5期26卷 1065-1076页

作者： hamid reza TALESH bahrami Alireza AZIZI hamid SAFFARI School of Mechanical Engineering Iran University of Science and Technology

Condensation is an important regime of heat transfer which has wide applications in different industries such as power plants,heating,ventilating and air conditioning,and *** occurs in two different modes including filmwise (FWC) and dropwise (DWC) *** occurring on hydrophobic and superhydrophobic surfaces has a much higher heat transfer capacity than ***,wide investigations have been done to produce DWC in recent *** surfaces have micro/nano structures with low surface *** this study,a two-step electrodeposition process is used to produce micro/nano structures on copper *** surface energy of specimens is reduced by a self-assembled monolayer using ethanol and 1-octadecanethiol *** results show that there is an optimum condition for electrodeposition *** example,a surface prepared by 2000 s step time has 5 times greater heat transfer than FWC while a surface with 4000 s step time has nearly the same heat transfer as *** surfaces of the fabricated specimens are examined using XRD and SEM *** SEM analyses of the surfaces show that there are some micro-structures on the surfaces and the surface porosities are reduced by increasing the second step electrodeposition time.

关键词： dropwise condensation heat transfer electrodeposition micro/nano structure porosity

Numerical analysis on forced convection enhancement in an annulus using porous ribs and nanoparticle addition to base fluid

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Journal of Central South University 2019年第5期26卷 1089-1098页

作者： Majid SIAVASHI hamid reza TALESH bahrami Ehsan AMINIAN hamid SAFFARI School of Mechanical Engineering Iran University of Science and Technology

Miniaturization of electronic equipment has forced researchers to devise more effective methods for dissipating the generated heat in these *** this study,two methods,including porous media inserting and adding nanoparticles to the base fluid,are used to improve heat transfer in an annulus heated on both *** study porous media insert,porous ribs are used on the outer and inner walls *** results show that when porous ribs are placed on the outer wall,although the heat transfer enhances,the pressure drop increment is so considerable that performance number (the ratio of heat transfer enhancement pressure increment,PN) is less than unity for all porous rib heights and porous media permeabilities that are *** the other hand,the PN of cases where porous ribs were placed on the inner wall depends on the Darcy number (Da).For example,for ribs with Da=0.1 and Da=0.0001,the maximum performance number,PN=4,occurs at the porous ribs height to hydraulic diameter ratios H/Dh=1 and H/Dh=*** these conditions,heat transfer is enhanced by two orders of *** is found that adding 5% nanoparticles to the base fluid in the two aforementioned cases improves the Nusselt number and PN by 10%–40%.

关键词： nanofluid porous media annulus heat transfer enhancement internal flow

User Selection and Precoding Schemes Based on Partial Channel Information for Broadcast MIMO Systems

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International Journal of Communications, Network and System Sciences 2010年第4期3卷 339-349页

作者： hamid reza bahrami Tho Le-Ngoc 不详

Due to the large number of users and the time-varying characteristics of wireless channels, it is very tough to inform the transmitter of full channel information in real multi-user MIMO broadcast systems. On the other hand, the capacity of multi-user systems greatly depends on the knowledge of the channel at the transmitter while this is not always the case in single-user MIMO systems. In this paper, we investigate combined user selection and zero-forcing precoding schemes that use partial channel information, i.e., very low amount of channel information at the base station. We show that while greatly reducing the complexity and channel knowledge feedback load, the proposed schemes preserve the optimality of zero-forcing scheme in term of achievable ergodic sum capacity in limit of large number of active users.

关键词： Broadcast Channel Multi-User System Partial Channel Information Precoding

Maximum Ratio Combining Precoding for Multi-Antenna Relay Systems

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Communications and Network 2010年第2期2卷 97-103页

作者： hamid reza bahrami Tho Le-Ngoc 不详

This paper addresses the design of practical communication strategies for multi-antenna amplify-and-forward and decode-and-forward relay systems. We show that simple linear techniques at the source and destination in conjunction with maximum ratio combining can provide an optimal transmission strategy in terms of received SNR without imposing a huge computational load over the relay node(s). Besides, the structures of precoding matrices are very similar at the source and relay nodes, which reduces the complexity as all nodes can play the role of source and relay nodes without changing their transmission structure. Numerical results show that the proposed transmission and reception techniques can improve the received SNR, and hence enhance the ergodic capacity.

关键词： Cooperation Relay System Linear Precoding Maximum Ratio Combining

Characteristics of turbulent flow in 3-D pools in the presence of submerged rigid vegetation in channel bed

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Journal of Hydrodynamics 2024年第1期36卷 158-169页

作者： Kourosh Nosrati Hossein Afzalimehr Jueyi Sui hamid reza Reisifar Natural Disasters Prevention Research Center Faculty of Civil EngineeringIran University of Science and TechnologyTehranIran School of Engineering University of Northern British ColumbiaPrince GeorgeCanada

In this study,the interaction between 3-D bedforms and submerged rigid vegetation has been *** laboratory experiments were conducted to study the distribution of flow velocity,Reynolds shear stress,turbulent kinetic energy,and skewness coefficients for a constant density of *** showed that the velocity profile in the pool section deviates from those in the upstream section of the *** has been found that the dip parameter varied between 0.6H and 0.9H depending on various factors including bed roughness,vegetation distribution,and pool entrance/exit ***,scattered vegetation in the pool and differences in slopes created non-uniform flow ***,in the wake region behind each vegetated element,flow velocity reduced significantly,and small-scale eddies are formed,causing increased *** decreasing the entrance slope and bed roughness,relatively uniform flow and weaker turbulence was resulted,but the random distribution of vegetated elements counteracted this balance and intensified *** the decrease in the pool entrance slope,the contribution of sweep event decreased and the contribution of ejection event increased.

关键词： Submerged rigid vegetation 3-D pool Reynolds shear stress skewness coefficients

Effects of heat stress and long photoperiod on the prostate of rats

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Asian pacific Journal of Reproduction 2024年第4期13卷 187-196页

作者： hamid reza Ghaffari Javad Poursamimi Department of Basic Sciences School of MedicineZabol University of Medical SciencesZabolIran Department of Immunology Faculty of MedicineZabol University of Medical SciencesZabolIran

Objective:To examine light and heat effects on the morphological,histological,and micrometric structure of the prostate of ***:Thirty adult male rats were divided into three *** control group was kept under 20℃-22℃ and an artificial 12 h/12 h day/night cycle;the temperature group was under normal light and at(42±1)℃ heat for 4 to 5 h daily,and the light group was exposed to 8 h/16 h day/night cycle with 20℃-22℃.Rats were weighed five times(at the beginning of the study and every seven days).Five milliliters(mL)of their peripheral blood were *** tissue staining was performed using the hematoxylin-eosin(H&E)stain and periodic acid-Schiff(PAS).In the following,tissue and cellular reactions to the PAS were ***:Folds were located entirely on the surface of the anterior lobe and periphery of the other *** secretory units in the anterior lobe were more than the lateral lobe.A strong reaction of the secretory cells to the PAS was *** serum levels of the light group also significantly increased compared to the control group(P<0.05).The most histometric changes of the lobes were established in the lateral *** stress resulted in a significant decrease in testosterone levels and transformed prostate *** epithelium and parenchyma to scaffold ratio in the temperature group ***:Maximum and minimum changes in the ventral lobe happened under the ascent of temperature and light,*** ventral lobe in the study of prostatic hyperplasia should be more considered.

关键词： Prostate Heat stress Photoperiod Histology Testosterone Rat

Evaluating the characteristics of geological structures in karst groundwater inflow, Nowsud Tunnel

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Journal of Mountain Science 2024年第10期21卷 3434-3452页

作者： BAYAT Narges SADEGHI Erfan NASSERY hamid reza Department of Minerals and Groundwater Resources Faculty of Earth SciencesShahid Beheshti UniversityEvin AveTehran ***Iran Ministry of Energy Kordestan ExpyTehran ***Iran

Highly permeable geological structures such as dissolution channels, open fractures, and faults create environmental challenges regard to hydrological and hydrogeological aspects of underground construction, often causing significant groundwater inflow during drilling due to the limitations of empirical and analytical methods. This study aims to identify the geological factors influencing water flow into the tunnel. High-flow zones' geological features have been identified and examined for this purpose. According to the geological complexity of the Nowsud tunnel, presence of different formations with different permeability and karstification have led to a high volume of underground inflow water (up to 4700 L/s) to the tunnel. The Nowsud tunnel faces significant geological and hydrogeological challenges due to its passage through the Ilam formation's LI2 unit, characterized by dissolution channels, faults, and fractures. The highest inflow rate (4700 L/s) occurred in the Hz-9 zone within the Zimkan anticline. The relationship between geological features and groundwater inflow indicates that anticlines are more susceptible to inflow than synclines. Additionally, different types of faults exhibit varying hydraulic effects, with strike-slip faults having the most significant impact on groundwater inflow, thrust faults conducting less water into the tunnel, and inflow through normal faults being negligible compared to the other two types of faults. The novelty of this paper lies in its detailed analysis of geological features influencing groundwater inflow into the Nowsud tunnel, providing empirical data on high-flow zones and differentiating the hydraulic effects of various fault types, which enhances the understanding and prediction of groundwater inflow in underground constructions.

关键词： Geological structures Groundwater inflow Hydrogeology Nowsud tunnel Karst

Effect of CO_(2)exposure on the mechanical strength of geopolymerstabilized sandy soils

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第2期16卷 670-681页

作者： hamid reza Razeghi Armin Geranghadr Fatemeh Safaee Pooria Ghadir Akbar A.Javadi School of Civil Engineering Iran University of Science and TechnologyTehran***Iran Department of Engineering University of ExeterExeterEX44QFUK

In recent years,there has been growing interest in developing methods for mitigating greenhouse effect,as greenhouse gas emissions continue to contribute to global temperature *** the other hand,investigating geopolymers as environmentally friendly binders to mitigate the greenhouse effect using soil stabilization has been widely ***,the effect of CO_(2)exposure on the mechanical properties of geopolymer-stabilized soils is rarely *** this context,the effect of CO_(2)exposure on the mechanical and microstructural features of sandy soil stabilized with volcanic ash-based geopolymer was *** factors were concerned,for example the binder content,relative density,CO_(2)pressure,curing condition,curing time,and carbonate *** results showed that the compressive strength of the stabilized sandy soil specimens with 20%volcanic ash increased from 3 MPa to 11 *** was also observed that 100 kPa CO_(2)pressure was the optimal pressure for strength development among the other *** mechanical strength showed a direct relationship with binder content and carbonate ***,in the ambient curing(AC)condition,the mechanical strength and carbonate content increased with the curing ***,the required water for carbonation evaporated after 7 d of oven curing(OC)condition and as a result,the 14-d cured samples showed lower mechanical strength and carbonate content in comparison with 7-d cured ***,the rate of strength development was higher in OC cured samples than AC cured samples until 7 d due to higher geopolymerization and carbonation rate.

关键词： Soil stabilization CO_(2)effect Geopolymer

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伊朗传统医学的诊断方法

国际中医中药杂志 2009年第5期31卷 476-477页

作者： Hoda Azizi hamid reza bahrami-Taghanaki 薛晓欧北京中医药大学东直门医院妇科北京100700 Mashhad University of Medical Sciences Mashhad 91375-345 Iran

伊朗传统医学在理论基础、诊断和治疗方法等都有其特点。本文介绍伊朗传统医学的诊断方法。

关键词：传统医学诊断方法伊朗