• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권5호
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• pp.1618-1637
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• 2014

Clustering wireless sensor network is an efficient way to reduce the energy consumption of individual nodes in a cluster. In clustering, multihop routing techniques increase the load of the Cluster head near the sink. This unbalanced load on the Cluster head increases its energy consumption, thereby Cluster heads die faster and create an energy hole problem. In this paper, we propose an Energy Balancing Cluster Head (EBCH) in wireless sensor network. At First, we balance the intra cluster load among the cluster heads, which results in nonuniform distribution of nodes over an unequal cluster size. The load received by the Cluster head in the cluster distributes their traffic towards direct and multihop transmission based on the load distribution ratio. Also, we balance the energy consumption among the cluster heads to design an optimum load distribution ratio. Simulation result shows that this approach guarantees to increase the network lifetime, thereby balancing cluster head energy.

• 소성∙가공
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• 제9권1호
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• pp.52-58
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• 2000

Hot precision forging with a back pressure was investigated for manufacturing of compressor parts made of Al-Si alloy. Disk-shaped blank made of Al-Si alloy was hot forged, and ribs were formed by loading back pressure on their top. The influence of the back pressure and die temperature on forgeability and properties of parts made of Al-Si alloy were examined. Using the F.E.M. simulation, we found the optimum vallue of back-pressure. The prototypes of scroll parts were forged into the near-net shape and satisfied the required properties.

• ETRI Journal
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• 제36권4호
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• pp.643-653
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• 2014

To reduce interconnect delay and power consumption while improving chip performance, a three-dimensional integrated circuit (3D IC) has been developed with die-stacking and through-silicon via (TSV) techniques. The power supply problem is one of the essential challenges in 3D IC design because IR-drop caused by insufficient supply voltage in a 3D chip reduces the chip performance. In particular, power bumps and TSVs are placed to minimize IR-drop in a 3D power delivery network. In this paper, we propose a design methodology for 3D power delivery networks to minimize the number of power bumps and TSVs with optimum mesh structure and distribute voltage variation more uniformly by shifting the locations of power bumps and TSVs while satisfying IR-drop constraint. Simulation results show that our method can reduce the voltage variation by 29.7% on average while reducing the number of power bumps and TSVs by 76.2% and 15.4%, respectively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.457-461
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• 1996

An optimum design methodology for the power MOSFET's with a predetermined mask is proposed and verified by comparing with the results of MEDICI simulation and the data of commercially available devices. Optimization is completed by determining a doping concentration and a thickness of the epitaxial layer which satisfy a specific voltage and current rating requirements as well as a minimum on-resistance for the mask set. The commercial HEX-1 mask set with a die area of $40.4{\times}10^{-3}\;cm^2$ and a T0-220 package has the on-resistance of $1.5{\Omega}$ at 200 V/2.5 A rating while the M-1 mask from this study exhibits $0.6{\Omega}$ on-resistance at 200 V/6 A. The 60 % reduction in the on-resistance and 58 % enhancement in the current rating have been obtained by the proposed method.

• Design & Manufacturing
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• 제14권4호
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• pp.1-10
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• 2020

The seal plays a role in preventing oil leakage when the lip and the rotating shaft come into contact with the fluid and air pressure. Recently, micro dimples or micro pockets are processed and used on the lubrication surfaces of thrust bearings, mechanical bearings, and piston rings. Compared to a smooth surface, micro dimples reduce friction and increase the life of parts. This paper analyzed various kinds of micro dimple shapes on the sealing surface, i.e. circle, rectangle, triangle, and trapezoid. For this purpose, Introduced the design of experiments to work out a micro dimple configuration, unlikely to be damaged from cracks and low in contact stress. As a result, the triangular dimple showed the best results. Optimal factors were dimple size 0.15 mm, dimple depth 0.0383 mm, dimple density 40%, and the maximum equivalent stress was 9.1455 MPa, and the maximum contact pressure was 9.6612 MPa. This paper analyzed the optimal shape of dimples by finite element analysis. As a research project, experiments and comparative analysis of micro dimple shapes are needed.

• 한국산학기술학회논문지
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• 제15권7호
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• pp.4057-4064
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• 2014

본 연구는 본 연구에서 제안하는 근사 최적화 방법(메타모델 기반의 시뮬레이션 최적화)을 사용하여 저렴한 해석 비용으로 펀치 단조품의 예비성형체(preform)를 설계한다. 본 연구에서 사용한 설계목표는 유효변형률의 균일한 분포이고 설계변수는 예비성형체 치수이며, 구속조건으로 최대 미충진 비율을 사용한다. 이를 위해 먼저 예비성형펀치(반재), 마스터펀치(상부다이) 및 하부다이로 구성되는 단조성형 공정을 DEFORM 시뮬레이션에 의해 모사하고, 이 시뮬레이션 결과가 실제 단조 공정을 모사하고 있는지 확인하는 검증 방법에 관해 소개한다. 또한 본 연구에서 수행한 설계 최적화 과정, 즉 (i) 초기 메타모델의 생성, (ii) 메타모델의 최적화 수행, (iii) 메타모델 최적해의 검증, (iv) 메타모델의 개선에 관하여 상세히 기술한다.

• Design & Manufacturing
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• 제11권1호
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• pp.1-6
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• 2017

In these days, due to generalization of using smart mobile phone and wearable device such as smart watch, demand of Cover-glass and touch screen panel for protecting display increases. With increasing the demand of Cover-glass, slimming technique is promising for weight lightening, zero bezel. Cover-glass produced by this technique is required to decreasing thickness with increase strength. In the Cover-glass manufacturing process, mechanical processing and chemical processing has improve in the strength. Generally, Diamond electrodeposition wheel is used in mechanical process. Reinforced glass with the characteristics of the brittle and high hardness was manufactured by using a diamond electrodeposition wheel. At this time, Because of surface of the tool present non-uniform distribution of diamond particle, it has generate Loading of wheel and it has been decrease life of grinding tool, efficiency of grinding, quality and shape accuracy of workpiece. Thus Research is needed to controling particle distribution of diamond electrodeposition wheel uniformly. And it is necessary to study micro hole machining such as proximity senser hole, speaker hole positioned Cover-glass. Reinforced glass with the characteristics of the brittle and high hardness is difficult to machining. Processing of reinforced glass have generated wear of tool, micro cracks. Also, it is decreasing shape accuracy. In this paper, We conducted a study on how to control particle distribution uniformly about the diamond tool manufactured using elecetodeposition processing. It analyzed the factors that affect the arrangement of the particles in the electrodeposition process by design of experiment. And There is produced the grinding tool, which derives an optimum deposition conditions, for processing Cover-glass edge and the machinability was evaluated.

• 한국식품과학회지
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• 제20권3호
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• pp.303-309
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• 1988

Extruder 조작조건에 따른 extruder 내부물질의 온도변화는 제품의 물리화학적인 특성에 큰 영향을 미치는 요소이다. 자가발열형 single screw extruder를 사용하여 원료의 종류, 입자크기 수분함량과 같은 사입원료 조건과 사출구의 형태, breaker의 형태등과 같은 extruder의 구조적인 요소 및 냉각방법과 스크류 회전속도와 같은 작동조건을 달리했을 때의 작동초기 단계에서 열발생 속도와 평형상태에서 내부온도 분포를 관찰하였다. 쌀가루, 보리가루, 밀가루, 탈지대두분을 원료로 하여 각각 압출성형했을 때 바렐내부 발열상태를 보면 탈지대두분이 가장 급격한 온도증가를 나타내었으며 쌀가루가 가장 낮게 나타났다. 수분함량이 감소함에 따라 각 부위 온도 및 동력요구량은 증가했고, 입자크기가 작을 수록 표면적이 증가하여 압축부위 온도가 높았다. 스크류 회전속도가 증가함에 따라 각 부위의 온도가 높아졌다. 또한 바렐내부 온도분포가 계량부위>사출구부위>압축 부위 순서로 이루어질 때 extruder 작동상태가 가장 양호하였다.

• 소성∙가공
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• 제17권2호
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• pp.124-129
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• 2008

Net shape forging technologies give many effects into the costs and qualities for the finished products. So, the studies to reduce the additional machining amount are very important in forging industry. Specially, there are two main topics in cold forging industry, such as, tool life and precision forging. In this study, new forging technique was proposed to eliminate the machining process for fixing up the length and improve the lead accuracy of gear. The luck-up hub is manufactured through many processes, such as upsetting, piercing and direct extrusion. The gear is formed in direct extrusion process; however, lead accuracy of the gear is over allowance limit. Therefore, the additional sizing process must be added. In this study, process design for closed-die forging of a lock-up hub used for a component of automobile transmission was made using three-dimensional finite element simulations, and the strain distributions and velocity distributions are investigated through the post processor. The rigid-plastic finite-element method for back pressure forging has been used in order to reduce development time and die cost. Using the FEM simulation, we found the optimum value of back pressure. The prototypes of lock-up hub parts were forged into the net-shape. In the experiment, lead precision of tooth are measured by the CCMM(Contact Coordinate Measuring Machine). The dimensional accuracy of forged part was improved up to the 40% when back press was applied.

• 대한기계학회논문집A
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• 제25권9호
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• pp.1438-1443
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• 2001

The significance of the casting/forging process for reducing the production cost of large components is being noted in these days. This casting/forging process is a method of forging a workpiece preformed by casting into the final shape. In this study, the casting/forging process has been applied in manufacturing a large aluminum flange in order to reduce press capacity and material cost. Firstly, a hot compression test was performed with cast cylindrical billets in order to determine the optimum forging condition of the aluminum flange. The optimum range of forging temperature of Al 5083 was from 420$\^{C}$ to 450$\^{C}$. The suitable strain rate was 1.5 sec(sup)-1. The deformation amount of a preform of a preform in a forging process is a key role in the mechanical properties of casting/forging products. In order to find the change of mechanical properties according to effective stain of cast aluminum billets, a hot upsetting test were performed with rectangular blocks and then a uniaxial tensile test was performed with specimens cut from the upsetted billets. The tensile strength and the elongation of cast/upsetted aluminum billets were increased largely until the effective strain was 0.7. FE analysis was performed to determine the configurations of case preform and die for an aluminum flange. In the FE analysis, the forging load-limit was fixed 1500ton for low equipment cost. The cast preform was designed so that the effective stain around the neck of a flange exceeded 0.7. From the result of FE analysis, optimal configurations of the cast preform and the die were designed for a large flange. The filling and solidification analysis for a sound cast-preform was carried out with MAGMA soft. In the forging experiment for an aluminum flange, it was confirmed that the optimal configuration of the cast preform predicted by FE analysis was very useful. The cast/forged products using designed preform were made perfectly without any defects.