• KSTLE International Journal
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• v.8 no.2
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• pp.29-34
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• 2007

Recently, requirements relating to performance, environment and noise in the oil hydraulic system of the heavy construction equipment have been reinforced continuously. In order to solve these technical trends, studies on the system compactness, operation under high pressure and great rotating speed, electronic control, substitute oil, and noise reduction have been progressed briskly. Among these recent studies, the system operation under high pressure is quite difficult to carry into effect due to mechanical limitations; that is, for realizing the system operation in the hydraulic pump under high pressure, the improvements or innovations on the design techniques, the manufacturing techniques, and the lubrication performance of the working oil are required. Accordingly, in this study, the stress distribution and optimum design factors under the maximum pressure were discussed by using stress analysis on the cylinder block of the hydraulic axial piston pump, which is one of the most important relative sliding regions.

• Journal of the Semiconductor & Display Technology
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• v.22 no.3
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• pp.90-95
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• 2023

We describe an optimal alignment method for improving accuracy of dynamic spectroscopic polarimeter based on monolithic polarizing interferometer. The dynamic spectroscopic polarimeter enables real-time measurements of spectral ellipsometric parameters by using a spectral carrier frequency concept. However, the non-polarizing beam splitter used in the monolithic polarizing interferometer cannot maintain the polarization state perfectly due to phase retardation caused by optical anisotropic characteristics of the non-polarizing beam splitter, resulting in degraded measurement accuracy. The effect of the beam splitter can be minimized through optimal alignment of the polarizers used in the polarizing interferometer and the analyzer. We demonstrate how much the proposed alignment method can enhance the measurement accuracy by comparing with previous alignment approach.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.417-420
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• 2011

본 논문에서는 자전거의 구동 및 변속 창치인 스프라켓에 관한 연구이다. FEM을 이용하여 티타늄 소재 스프라켓의 구조해석을 수행하기 위해 10단 Cassette를 설계하였고, 사용자가 가장 많이 사용하는 단수인 4, 5, 6단을 티타늄 소재로 선정하였다. 티타늄 재료의 물성치를 실험을 통해 확보하였으며, 이를 이용하여 티타늄 스프라켓의 각 치형에 걸리는 Equivalent Stress를 구하였고 스프라켓 고정장치인 스파이더와의 체결 후의 Equivalent Stress를 구하여 티타늄 스프라켓의 안정성을 확보한다.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.413-416
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• 2011

Flip top cap은 경량성, 가공성, 내식성 우수하여 최근에 생활 용기 뚜껑으로 많이 활용되고 있다. Flip top cap은 사출성형에 의해 제작 되며 사출성형 과정에서 힌지부분에 웰드라인(Weldline)이 형성되어 기계적 강도가 떨어지게 된다. Flip top cap은 생활용기에 사용되며 실제생활에서 많은 작동을 요구하기 때문에 힌지부분의 웰드라인은 제품불량에 큰 원인이 된다. 또한 Flip top cap은 생산성을 높이기 위해 멀티캐비티(Multi-cavity) 사출방식을 선호한다. 멀티캐비티 방식은 높은 사출압력을 요구하기 때문에 사출품의 불량과 사출기에 많은 부하가 예상된다. 본 연구에서는 게이트 위치를 조정함으로써 사출품 힌지부분에서 발생할 수 있는 웰드라인을 품질에 영향이 없는 곳으로 이동시키고 최적의 사출 압력을 찾기 위한 유동해석을 통해 최적의 사출조건을 도출함으로써 Flip top cap의 기계적 품질과 제품생산성 향상을 위한 연구가 수행되었다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.220-223
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• 2005

The rapid prototyping (RP) technology has been advanced for various applications such as verification of design, functional test. However, many RP machines still have low accuracy and limitation of applications for various materials. In this research, a hybrid RP system was developed to improve precision of micro parts. This hybrid system consists of deposition and material removal process by mechanical micro machining to fabricate nano composites using photo-curable polymer resin with various nano particles. In this work, using hybrid RP process with Multi-Walled Carbon Nano Tube (MWCNT) and hydroxyapatite, micro parts were fabricated. The precision of parts was evaluated based on the original CAD design, and to see the effect of nano particles on mechanical properties, tensile strength was measured. From the results of experiments, it was confirmed that the part made by hybrid process had higher precision, and the addition of nano particles improved mechanical properties.

• Tribology and Lubricants
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• v.38 no.1
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• pp.1-7
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• 2022

Chemical-mechanical polishing (CMP) process is a semiconductor process that planarizes a wafer surface using mechanical friction between a polishing pad and a substrate surface during a specific chemical reaction. During the CMP process, polishing pad conditioning is applied to prevent the rapid degradation of the polishing quality caused by polishing pad glazing through repeated material removal processes. However, during the conditioning process, uneven wear on the polishing pad is inevitable because the disk on which diamond particles are electrodeposited is used. Therefore, the abrasion of the polishing pad should be considered not only for the variables during the conditioning process but also when designing the CMP conditioning system. In this study, three design variables of the conditioning system were analyzed, and the effect on the pad wear profile during conditioning was investigated. The three design variables considered in this study were the length of the conditioner arm, diameter of the conditioner disk, and distance between centers. The Taguchi method was used for the experimental design. The effect of the three design variables on pad wear and uniformity was assessed, and new variables used in conditioning system design were proposed.

• Proceedings of the Korean Vacuum Society Conference
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• 2008.08a
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• pp.48-48
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• 2008

• Proceedings of the Korean Vacuum Society Conference
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• 2008.08a
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• pp.53-53
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• 2008

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.4
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• pp.341-347
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• 2010

In this study, the efficiency of a solid-oxide fuel cell (SOFC) system with a steam reformer or prereformer was analyzed under various conditions. The main components of the system are the reformer, SOFC, and water boiling heat recovery system. Endothermic and exothermic reactions occur in the reformer and SOFC, respectively. Hence, the thermal management of the SOFC system greatly influences the SOFC system efficiency. First, the efficiencies of SOFC systems with a steam reformer and a prereformer are compared. The system with the prereformer was more efficient than the one with steam reformer due to less heat loss. Second, the system efficiencies under various prereformer operating conditions were analyzed. The system efficiency was a function of the heat requirement of the system. The efficiency increased with an increase in the operating temperature of the prereformer, and the maximum system efficiency was observed at $450^{\circ}C$ for a S/C of 2.0.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.12
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• pp.1573-1578
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• 2011

In this study, a novel electromagnetic microrobot system with locomotion and drilling functions in threedimensional space was developed. Because of size limitations, the microrobot does not have actuator, battery, and controller. Therefore, an electromagnetic actuation (EMA) system was used to drive the robot. The proposed EMA system consists of three rectangular Helmholtz coil pairs in x-, y- and z-axes and a Maxwell coil pair in the z-axis. The magnetic field generated in the EMA coil system could be controlled by the input current of the EMA coil. Finally, through various experiments, the locomotion and drilling performances of the proposed EMA microrobot system were verified.