• Proceedings of the Korean Information Science Society Conference
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• 1998.10b
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• pp.407-409
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• 1998

루프 몸체를 복제하는 루프 펼침을 외부 루프에 대하여 적용하면, 루프 내포체의 데이터 지역성이 개선된다. 펼침 횟수 증가에 따른 루프 내포체의 데이터 지역성 변화를 예측하였고, 예측 결과를 행렬 곱셈 프로그램에 대하여 실행 시간과 개시 미스 변화를 측정하여 검증하였다. 펼침 횟수는 증가함에 따라, 초반에는 실행 시간과 캐시 미스가 급격히 감소하다 점점 감소폭이 줄어드는 기하급수적 변화를 보였다. 이 결과는 데이터 지역성 개선을 위한 외부 루프 펼침 변환을 적용 할 때, 작은 값(최대 405회)의 펼침으로 프로그램 성능 향상을 기대할 수 있음을 의미한다. 한편, 컴파일러에 의한 루프 펼침을 적용할 때, 불필요하게 많은 펼침 횟수의 펼침 효과에 대하여 분석 할 필요가 없음을 나타낸다

• Composites Research
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• v.28 no.5
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• pp.249-253
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• 2015

This paper reports a study on a method for achieving lightweight thermoplastic laminate composites referred to as tow spreading technology. Thickness of an unspread 12 K carbon fiber tow is reduced by increasing the tow width from 7 mm to 20 mm. The polypropylene (PP) film was used to stabilize and impregnate the spread tow, covering it into a partially consolidated prepreg: 12 K carbon fiber spread tow/PP. Laminates were fabricated from the spread tow prepreg and control laminate composites were produced from unspread tow prepreg consisting of 12 K carbon fiber and PP. The void content, tensile and flexural properties of the composite laminates were investigated. Consequently, the spread tow laminate composite exhibited lower void content and improved mechanical properties.

• Journal of the Korean Society of Radiology
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• v.3 no.2
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• pp.23-26
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• 2009

This study proposed an improved center array-sequencing phase unwrapping (ICASPU) algorithm. 2% agarose phantom dopped with 0.6mM/l MnCl2 was used with clinical 1.5T MRI system and commercial knee coil. Obtained k-space data(raw-data) was transmitted to PC and reconstructed into phase image with MATLAB software. Previous center array-sequence phase unwrapping algorithm wascompared with proposed ICASP algorithm using second order regression analysis. As a result, we found that the amount of error on proposed ICASPU method is less about 5 times than that of previous CASPU method. In this study, we exploit improved Center array-sequence phase unwrapping algorithm and expect to apply to images including phase informations.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.1
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• pp.91-96
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• 2012

The retract actuator makes the landing gear retract or extend during take-off and landing of an aircraft. To prevent folding of landing gear that has remained in the extended state because of an unexpected external disturbance, an internal locking device is applied to the retract actuator. The locking device is restrained with another internal component by oil pressure supplied to the retract actuator, and this restraint makes the locking of the actuator possible. Because locking and unlocking are repeated during retraction and extension of the landing gear, the locking device takes repeated identical loads, and the possibility of fatigue failure exists. In this study, the process and results of fatigue analysis for the locking device are presented, and the appropriateness of the analysis result is verified using a fatigue test.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.666-672
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• 2017

Our research team is developing a 6-DOF manipulator for narrow workspaces in press forming processes, such as placing PEM nuts on the bottom of a chassis. In this paper, kinematic analysis was performed for the position control of the manipulator, along with structural analyses for position accuracy with different payloads. First, the Denavit-Hatenberg (DH) parameters are defined, and then the forward and backward kinematic equations are presented using the DH parameters. The kinematic model was verified by visual simulation using Coppelia Robotics' virtual robot experimentation platform (V-REP). Position accuracy analysis was performed through structural analyses of deflection due to self-weight and deflection under full payload (5 kgf) in fully opened and fully folded states. The maximum generated stress was 22.05 MPa in the link connecting axes 2 and 3, which was confirmed to be structurally safe when considering the materials of the parts.

• Journal of the Korean earth science society
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• v.24 no.5
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• pp.467-476
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• 2003

For the seafloor acoustic image mapping of side scan sonar, the beginning step of the procedure is to fix the absolute sonar (tow-fish) position since the sonar is not hull mounted but towed astern. The technical algorithm used to calculate the actual sonar position without any other additional sub-system, i.e., the underwater acoustic position tracking system or the sonar attitude measuring device, was proposed. In the seafloor image mosaic mapping results using the sonar track (not ship track) developed in this study, any ambiguity or inconsistency of seafloor features was not found. The incidental effect from the sonar position determination procedure orients the towing direction of sonar to be smooth, consequently the swath pattern on the across-track direction becomes stable and the blanking phenomenon of the insonification area is reduced conspicuously. This technical method is considered to be an useful tool when applied toother underwater towing vehicle surveys.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.93-96
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• 2000

This study discusses a non-contact optical technique, phase shifting electronic speckle pattern interferometry, that is well suited for a deformation measurement. However, the phase shifting method has difficulties for determinating a deformation quantitatively beacuse of the characteristics of arctan function. In order to solve this problem, phase unwrapping methods has been studied during the last few years. In this study, using phase unwrapping based on line by line scanning phase shifted fringe patterns are studied to determinate a deformation quantitatively. Also least square fitting method is applied to reduce noise and improve image resolution.

• Journal of KSNVE
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• v.9 no.3
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• pp.509-516
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• 1999

The ESPI (Electronic Speckle Pattern Interferometry) algorithm has been simulated to calculate vibrational modes of a thin right-angled STS304 plate. The phase transformation of the reference wave of the ESPI is carried out only one time during vibration in order to clarify ESPI speckle patterns. Two dimensional vibrational modes are calculated from one ESPI pattern before vibration onset and two ESPI patterns during vibrations but with and without the phase transformation. The ESPI harmonic results are compared with those derived from the finite element method (FEM), and they agree very well. Additionally a phase unwrapping algorithm has been newly developed to derive a displacement map from an ESPI phase map.

• Journal of KIISE:Software and Applications
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• v.26 no.4
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• pp.557-567
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• 1999

본 논문은 데이터 캐시를 효과적으로 사용하기 위하여 개발된 원시 프로그램의 루프 변환체제에 대하여 논하고 있다. DIUS로 명명된 이 체계는 외부 루프 펼침을 중심으로 루프 분산, 교환이 선행되고 , 마직막에 스칼라화가 적용되는 변환체계이다. 루프 교환은 회전 공간이 루프 단위로 변형되어 전반적으로 캐시 재사용 기회를 높이지만 일부 배열 참조에 대해서는 오히려 재사용 기회를 감소시킨다. 본 연구에서는 이 문제를 외부 루프 펼침으로 해결하였다. 외부 루프 펼침과 루프 교환을 루프 몸체의 문장들에 선별적으로 적용하기 위하여 루프 분산을 도입하였다. 외부 루프 펼침을 적용하면 배열 참조를 스칼라 참조로 변환하는 스칼라화의 효과가 증대되어 레지스터 사용의 효율성이 높아진다. SPEC CFP95 벤치마크에 대하여 DIUS를 적용한 결과 기하학적 평균으로 속도 향상 1.10을 얻었으며, 특정 프로그램들은 모두 캐시 미스수가 줄어들었음을 확인하였다. 이와 같은 성능향상은사용된 루프 변환기법들이 갖는 캐시와 레지스터의 효율적인 사용에 기인한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2012.01a
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• pp.1-4
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• 2012

임베디드 시스템에서 최적화 기술의 성능은 크로스 컴파일러의 성능과 실행상황, 대상 하드웨어의 특징 등에 따라 좌우된다. 본 논문에서는 최적화 기술 중 루프 펼침과 형 변환을 이미지 처리 코드에 적용하여 성능을 측정하였다. 그 결과 기술을 적용하지 않은 성능을 기준으로 55%의 성능향상이 이루어졌다.