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Mechanical properties of Cu matrix composite fabricated by extrusion process 被引量:1
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作者 Ji-Hun PAK Gwi-Nam KIM +3 位作者 Sung-Gu HWANG Beom-Su KIM Jung-Pil NOH Sun-Chul HUH 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2016年第10期2679-2686,共8页
Carbon nanotube (CNT)was applied in various fields for itssuperior electrical, mechanical and thermal characteristics. After composites were fabricated by extrusion processusing ball-milledCu-CNT powders, mechanical... Carbon nanotube (CNT)was applied in various fields for itssuperior electrical, mechanical and thermal characteristics. After composites were fabricated by extrusion processusing ball-milledCu-CNT powders, mechanicalpropertiesofCu-CNT composites according to CNT fraction were reviewed. CNT (1%, 5% and 10%),Cu (d=100 nm), zirconia balls (90 g) and ethanol (20mL) were mixed and dispersed for5h at a speed of 500 r/minusing a planetary ball mill. A billet (d=50 mm, length=100 mm) was made with Cu, and the composite powderswerefilled up into billet using the uni-axial press. In the extrusion process, after the billet was heated at 880℃for1h, specimens were produced in the shape of a round bar using the billet by applying a load of 200 t. The composite powdersweremeasured for particle size byparticlesize distributionequipment. Then the specimen surface fabricated by extrusion was observed by SEM. Mechanicalpropertiesmeasured by the indentation equipment increased with increasing CNT content. The yield strength, tensile strength and hardness of theCu–CNTs composites canbeobviously improved. 展开更多
关键词 EXTRUSION MILLING INDENTATION MATRIX mechanical properties MICROSTRUCTURE
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CFD analysis of sound pressure in tank gun muzzle silencer 被引量:5
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作者 Hafizur Rehman Hanshik Chung +2 位作者 Taewhee Joung A.Suwono Hyomin Jeong 《Journal of Central South University》 SCIE EI CAS 2011年第6期2015-2020,共6页
The high pressure waves generated due to muzzle blast flow of tank gun during firing is a critical issue to examine. The impulsive noise from the gun has various negative effects such as damage of human bodies, damage... The high pressure waves generated due to muzzle blast flow of tank gun during firing is a critical issue to examine. The impulsive noise from the gun has various negative effects such as damage of human bodies, damage of structures, creating an environmental, social problem and also military problems such as exposure of location of troops. This high pressure impulsive sound, generated during the blast flow, was studied and attenuated. An axisymmetric computational domain was constructed by employing Spalart Allmaras turbulence model. Approximately 90% of pressure and 20 dB of sound level are reduced due to the use of the three baffle silencer at the muzzle end of the gun barrel, in comparison with the tank gun without silencer. Also, the sound pressure level at different points in the ambient region shows the same attenuation in results. This study will be helpful to understand the blast wave characteristics and also to get a good idea to design silencer for large caliber weapon system. 展开更多
关键词 baffle silencer muzzle blast impulsive noise DECIBEL tank-gun
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Experimental assessment of two-phase bubble pump for solar water heating 被引量:5
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作者 CHUNG Han-shik WOO Ju-sik +2 位作者 SHIN Yong-han KIM Jun-hyo JEONG Hyo-min 《Journal of Central South University》 SCIE EI CAS 2012年第6期1590-1599,共10页
The research goal is to develop a new solar water heater system(SWHS) that uses a solar bubble pump instead of an electric pump.The pump is powered by the steam produced from an evacuated tube collector.Therefore,heat... The research goal is to develop a new solar water heater system(SWHS) that uses a solar bubble pump instead of an electric pump.The pump is powered by the steam produced from an evacuated tube collector.Therefore,heat could be transferred downward from the collector to a hot water storage tank.The designed system consists of two sets of heat-pipe evacuated tube collectors,a solar bubble pump installed at an upper level and a water storage tank with a heat exchanger at a lower level.Discharge heads of 1 and 5 m were tested.The bubble pump could operate at the collector temperature of about 90-100 ℃ and vapor gage pressure of 80-90 kPa.It is found that water circulation within the SWHS depends on the incident solar intensity and system discharge head.Experimental investigations are conducted to obtain the system thermal efficiencies from the hourly,daily and long-term performance tests.The thermal performance of the proposed system is compared with conventional solar water heaters.The results show that the proposed system achieves system characteristic efficiency of 10% higher than that of the conventional systems using electric pump if taking the consumption of electric power into account.And the former is a zero carbon system. 展开更多
关键词 two-phase bubble pump solar water heater system (SWHS) zero carbon
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Heat transfer characteristics of nanofluid through circular tube 被引量:2
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作者 WUSIMAN Ku-er-ban-jiang CHUNG Han-shik +4 位作者 MD.J.Nine HANDRY Afrianto EOM Yoon-sub KIM Jun-hyo JEONG Hyo-min 《Journal of Central South University》 SCIE EI CAS 2013年第1期142-148,共7页
Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experimen... Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300<Re≤16 000). The forced convective heat transfer enhancement is available both in the laminar and turbulent flow with increasing the concentration. Especially, the enhancement rate increases dramatically in laminar flow regime, for instance, the heat transfer coefficient of Cu/water nanofluid increases by two times at around Re=2 000 compared with that of base fluid water, and averagely increases by 62% at 1% volume fraction. However, the heat transfer coefficient of Cu/water decreases sharply in the transition flow regime. Furthermore, it has the trend that the heat transfer coefficient displays worse with increasing the concentration. 展开更多
关键词 NANOFLUID heat transfer characteristic circular tube metallic particles
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A Metaheuristic Technique for Cluster-Based Feature Selection of DNA Methylation Data for Cancer
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作者 Noureldin Eissa Uswah Khairuddin +1 位作者 Rubiyah Yusof Ahmed Madani 《Computers, Materials & Continua》 SCIE EI 2023年第2期2817-2838,共22页
Epigenetics is the study of phenotypic variations that do not alter DNA sequences.Cancer epigenetics has grown rapidly over the past few years as epigenetic alterations exist in all human cancers.One of these alterati... Epigenetics is the study of phenotypic variations that do not alter DNA sequences.Cancer epigenetics has grown rapidly over the past few years as epigenetic alterations exist in all human cancers.One of these alterations is DNA methylation;an epigenetic process that regulates gene expression and often occurs at tumor suppressor gene loci in cancer.Therefore,studying this methylation process may shed light on different gene functions that cannot otherwise be interpreted using the changes that occur in DNA sequences.Currently,microarray technologies;such as Illumina Infinium BeadChip assays;are used to study DNA methylation at an extremely large number of varying loci.At each DNA methylation site,a beta value(β)is used to reflect the methylation intensity.Therefore,clustering this data from various types of cancers may lead to the discovery of large partitions that can help objectively classify different types of cancers aswell as identify the relevant loci without user bias.This study proposed a Nested Big Data Clustering Genetic Algorithm(NBDC-GA);a novel evolutionary metaheuristic technique that can perform cluster-based feature selection based on the DNA methylation sites.The efficacy of the NBDC-GA was tested using real-world data sets retrieved from The Cancer Genome Atlas(TCGA);a cancer genomics program created by the NationalCancer Institute(NCI)and the NationalHuman Genome Research Institute.The performance of the NBDC-GA was then compared with that of a recently developed metaheuristic Immuno-Genetic Algorithm(IGA)that was tested using the same data sets.The NBDC-GA outperformed the IGA in terms of convergence performance.Furthermore,the NBDC-GA produced a more robust clustering configuration while simultaneously decreasing the dimensionality of features to a maximumof 67%and of 94.5%for individual cancer type and collective cancer,respectively.The proposed NBDC-GA was also able to identify two chromosomes with highly contrastingDNAmethylations activities that were previously linked to cancer. 展开更多
关键词 CANCER clustering DNA methylation feature selection metaheuristic technique the cancer genome atlas
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Lignocellulosic Biocomposite Membranes for Air Filtration and Environmental Protection:A Review
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作者 Abiodun Abdulhameed Amusa Anwar Johari +4 位作者 Kamil Kayode Katibi Ibrahim Garba Shitu Abdulrahman Oyekanmi Adeleke Mohd Fairus Mohd Yasin Muhammad Thalhah Zainal 《Journal of Renewable Materials》 2025年第2期251-272,共22页
The increasing severity of air pollution necessitates more effective and sustained air filtration technology.Concurrently,the desire for more environmentally friendly,sustainable materials with better filtering perfor... The increasing severity of air pollution necessitates more effective and sustained air filtration technology.Concurrently,the desire for more environmentally friendly,sustainable materials with better filtering performance and less environmental impact drives the move away from conventional synthetic membranes.This review presents lignocellulosic biocomposite(LigBioComp)membranes as an alternative to traditional synthetic membranes.It focuses on their materials,fabrication,and functionalization techniques while exploring challenges and proposing methods for resourceful utilization.Renowned for their abundance and renewable nature,lignocellulosic materials consist of cellulose,hemicellulose,and lignin.Various applications can benefit from their antibacterial properties,large surface area,and remarkable mechanical strength.LigBioComp membranes are fabricated through casting,electrospinning,and freeze-drying,with advancements in fabrication techniques enhancing their performance and applicability.It is suggested to use solvent-free or low-solvent techniques such as Layer-by-Layer assembly to minimize environmental impact.Freeze-drying and electrospinning with green solvents can be used for achieving specific membrane properties,though energy consumption should be considered.Apply dry-wet spinning and solvent casting processes selectively.Functional groups,including carboxyl,hydroxyl,or amino groups,can significantly improve the membrane’s capacity to capture particulate matter.Chemical etching or the precise deposition of nanoparticles can further optimize pore size and distribution.The choice of chemicals and methods is critical in functionalization,with silane coupling agents,polyethyleneimine,and polydopamine.Future research should prioritize refining fabrication methods,advancing functionalization strategies,and conducting performance and recyclability assessments on hybrid and composite materials.This will enhance integrated systems and contribute to the development of smart filters. 展开更多
关键词 LIGNOCELLULOSE BIOCOMPOSITES renewable materials sustainable membranes environmental protection particulate matter removal air filtration technology
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Numerical assessment on improving multistage centrifugal impeller performance by changing inlet skew angle at impeller inlet 被引量:2
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作者 M.N.Labib Woo Ju-sik +4 位作者 Choi Du-youl T.Utomo B.Fajar Chung Han-shik Jeong Hyo-min 《Journal of Central South University》 SCIE EI CAS 2012年第4期953-961,共9页
Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics.The purpose of this work is to investigate the influences of lean angle at the blade tip of the ... Multistage centrifugal impellers with four different skew angles were investigated by using computational fluid dynamics.The purpose of this work is to investigate the influences of lean angle at the blade tip of the impeller inlet.Four variations of lean angles,that is,8°,10°,15° and 20°,were made at first stage impeller.Reynolds Average Navier Stokes equation was used in simulation together with a shear?stress transport(SST) k-w turbulence model and mixing-plane approach,respectively.Three dimensional fluid flows were simplified using periodic model to reduce the computational cost and time required.A good performance was expected that the secondary flow can be effectively reduced in the flow passage of the impeller without excessive increase in manufacturing cost caused by the secondary flow.The results show that secondary flow affects the main flow intricately to form vortices or having non-uniform velocity in the flow passage,which in turn results in substantial fluid energy loss not only in the impeller but also in the guide vane downstream of impeller.The numerical solutions were performed and allowed the optimum design and operating conditions to be obtained. 展开更多
关键词 computational fluid dynamics secondary flow blade inlet skew angle multistage centrifugal compressor
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Characterizing pressure fluctuation into single-loop oscillating heat pipe 被引量:3
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作者 PARK Yong-ho Md.Riyad Tanshen +2 位作者 Md.J.Nine CHUNG Han-shik JEONG Hyo-min 《Journal of Central South University》 SCIE EI CAS 2012年第9期2578-2583,共6页
The pressure characteristics inside single loop oscillating heat pipe (OHP) having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed. Distilled water was used as working fluid inside th... The pressure characteristics inside single loop oscillating heat pipe (OHP) having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed. Distilled water was used as working fluid inside the OHP with different filling ratios of 40%, 60% and 80% of total inside volume. Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency. And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60-96 ℃. Piezoresistive absolute pressure sensor (Model-Kistler 4045A5) was used to take data. The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio. 展开更多
关键词 oscillating heat pipe pressure fluctuation heat flow resistance filling ratio
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Liquid film falling behaviour on horizontal circular cylinder 被引量:3
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作者 CHUNG Han-shik K.Wusiman +5 位作者 KIM Seong-soo B.Nasan H.Afrianto Hafizur Rehman CHOI Du-youl JEONG Hyo-min 《Journal of Central South University》 SCIE EI CAS 2012年第5期1353-1358,共6页
The flow pattern behaviour of falling liquid film over three horizontal cylinders was evaluated.These flows can take three forms:discrete droplets,individual jets,and continuous sheet,and special attention is paid to ... The flow pattern behaviour of falling liquid film over three horizontal cylinders was evaluated.These flows can take three forms:discrete droplets,individual jets,and continuous sheet,and special attention is paid to the effects of the physical properties and geometrical parameters of the first two forms(droplets and jets) because these forms are more important in heat-transfer behaviour and less research has been published for these forms,The flow modes and experimental results were successfully compared with previous experimental literatures,and also the effects of liquid flow rate,tube diameter,and tube spacing on departure site spacing,in both drop and jet modes,were evaluated in the low Galileo number and high viscosity fluid(cooking oil),to help developing criteria for determining falling film modes and their transitions,and to understand the heat transfer characteristics associated with each mode. 展开更多
关键词 falling film flow mode CYLINDER
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Flow characteristics by particle image velocimetry in liquefied natural gas vaporizer model with several baffles 被引量:1
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作者 H.S.Chung S.M.Sayeed-Bin-Asad +2 位作者 Berkah Fajar Y.H.Shin H.M.Jeong 《Journal of Central South University》 SCIE EI CAS 2011年第5期1719-1725,共7页
Shell-and-tube vaporizers are the most commonly used and dominated types of vaporizers in liquefied natural gas (LNG) realm. Due to efficient performance, shell-side flow in this type of vaporizers has received cons... Shell-and-tube vaporizers are the most commonly used and dominated types of vaporizers in liquefied natural gas (LNG) realm. Due to efficient performance, shell-side flow in this type of vaporizers has received considerable attention and has been investigated extensively. However, the detailed flow structure in the shell needs to be determined for reliable and effective design. Therefore, the objective of this study was to clarify the flow structure in shell by particle image velocimetry (PIV). Experiments were conducted using two types of model; 15% baffle cut having inlet and outlet positions !n the direction of 90° to the cut and 30% baffle cut having inlet and outlet positions in the direction of 180° to the cut. Each test section is 169 mm in inner diameter and 344.6 mm in length. The flow features were characterized in different baffle cuts with regards to the velocity vector field and velocity distribution. The results show that the flow characteristics of 15% baffle cut type vaporizer are comparable to those of 30% baffle cut type vaporizer. 展开更多
关键词 particle image velocimetry liquefied natural gas VAPORIZER VORTEX TURBULENCE
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DPT‐tracker:Dual pooling transformer for efficient visual tracking
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作者 Yang Fang Bailian Xie +3 位作者 Uswah Khairuddin Zijian Min Bingbing Jiang Weisheng Li 《CAAI Transactions on Intelligence Technology》 SCIE EI 2024年第4期948-959,共12页
Transformer tracking always takes paired template and search images as encoder input and conduct feature extraction and target‐search feature correlation by self and/or cross attention operations,thus the model compl... Transformer tracking always takes paired template and search images as encoder input and conduct feature extraction and target‐search feature correlation by self and/or cross attention operations,thus the model complexity will grow quadratically with the number of input images.To alleviate the burden of this tracking paradigm and facilitate practical deployment of Transformer‐based trackers,we propose a dual pooling transformer tracking framework,dubbed as DPT,which consists of three components:a simple yet efficient spatiotemporal attention model(SAM),a mutual correlation pooling Trans-former(MCPT)and a multiscale aggregation pooling Transformer(MAPT).SAM is designed to gracefully aggregates temporal dynamics and spatial appearance information of multi‐frame templates along space‐time dimensions.MCPT aims to capture multi‐scale pooled and correlated contextual features,which is followed by MAPT that aggregates multi‐scale features into a unified feature representation for tracking prediction.DPT tracker achieves AUC score of 69.5 on LaSOT and precision score of 82.8 on Track-ingNet while maintaining a shorter sequence length of attention tokens,fewer parameters and FLOPs compared to existing state‐of‐the‐art(SOTA)Transformer tracking methods.Extensive experiments demonstrate that DPT tracker yields a strong real‐time tracking baseline with a good trade‐off between tracking performance and inference efficiency. 展开更多
关键词 human‐computer interfacing image motion analysis pattern recognition signal processing TRACKING
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