• Korean Journal of Optics and Photonics
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• v.34 no.2
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• pp.76-83
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• 2023

In this paper, the results of analyzing the frequency lock-in breaking characteristics of a ring laser gyroscope with random dithering through numerical experiments are presented. By observing the variant features in the frequency lock-in characteristics according to the dithering amplitude noise, it was possible to analyze the minimum noise condition that causes the frequency lock-in to be broken. It was confirmed that the result is closely related to the relative difference between the dynamic frequency lock-in corresponding to the average dithering amplitude and the frequency determined by the Sagnac effect corresponding to an input rotational angular velocity.

• Clinics in Shoulder and Elbow
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• v.14 no.2
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• pp.229-235
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• 2011

Purpose: To compare the clinical and radiological result of arthroscopic Mattress Locking suture repair to that of a Simple suture repair with small and medium-sized rotator cuff tears. Materials and Methods: Among 92 patients who were followed up after arthroscopic repair in patients with small and medium-sized rotator cuff tear from April 2007 to October 2010, 27 patients who took Arthroscopic Mattress Locking suture were set as group I and 65 patients who took Simple suture were set as Group II. The average age of patients were 58 years old and average follow-up period was 30 months. For analysis, VAS, ASES and KSS were used to analyze the range of joint movement and pain. And, for the image result, MRI performed after operation were evaluated. Results: The average VAS, KSS, UCLA score and ASES prior to surgery improved in the last follow-up (p<0.001), while was no difference in two groups (p>0.001). In MRI follow-up examination, the 2 cases (7.41%) of group 1 showed increased rupture lesions with improved symptoms. And the 12 cases (18.47%) of group 2 showed increased rupture lesions with improved symptoms. Retears in the group I were significant less than the group II (p<0.001). Conclusion: Comparing patients with small and medium-sized rotator cuff tear who took arthroscopic mattress locking suture repair to those who took simple suture repair after over one year follow up period, the clinical result showed no significant difference between two groups. However, Mattress Locking suture repair showed excellent radiological result compared to simple suture repair when comparing rerupture.

• 한국전산유체공학회:학술대회논문집
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• 2008.03b
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• pp.126-129
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• 2008

In this study the aerodynamic characteristics of a canard-controlled missile with freely spinning tailfins were investigated by using a CFD code. The aerodynamic coefficients and roll-rate of freely spinning tailfins were calculated by an analysis of 6-DOF and the Euler code. Results were in good agreement with experimental data, and the roll-rates of freely spinning tailfins were also in good agreement with the experimental data for the roll and yaw canard control inputs. This indicates that the CFD Euler code can be applied to predict the canard-controlled missile with freely spinning tailfins.

• Journal of the Korean Society for Marine Environment & Energy
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• v.14 no.4
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• pp.264-272
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• 2011

Shipbuilders carry out the operation test to check the conditions of the main propulsion system and auxiliaries for moored vessel in the quoy before the sea trial. The estimation of the thrust and torque for the partially submerged propeller should be prepared to ensure the safety of mooring line and the ship. In this paper, the variations of the thrust and torque according to the shaft submergence and the propeller rotating speed in bollard pull condition are investigated with the model test and the numerical analysis. Based on these resaearch, the empirical formula representing the physical phenomena of the partially submerged propeller is derived and validated through comparison to measurement results of full-scale propellers under the quoy operation test.

• Journal of computational fluids engineering
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• v.14 no.4
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• pp.48-55
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• 2009

In this study, roll lock-in phenomena of freely spinning tailfins were investigated by a CFD code. To analyze a motion of freely spinning tailfins, this research use a Chimera method, an Euler code and a 6 degrees of freedom analysis. The numerical results of aerodynamic characteristics and roll rates of a canard-controlled missile with freely spinning tailfins show a good agreement with wind tunnel test results. Using the roll rates calculation result of freely spinning tailfins, roll lock-in phenomena is confirmed. Roll lock-in phenomena and Roll lock-in states can be predicted through effects of the induced vortex of the canards control and the analysis of the rolling moments of tailfins due to the bank angle.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.9
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• pp.849-855
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• 2010

This paper investigated the roll lock-in phenomena of a canard-controlled missile with freely spinning tailfins by applying Falanga's roll-rate equation. To confirm and validate the accuracy of the results of the roll-rate and roll lock-in prediction for freely spinning tailfins, the results were compared with Blair's wind tunnel test data. For calculation of the roll-rate of freely spinning tailfins, rolling moment coefficients of the tailfins were obtained from the wind tunnel test data and roll-damping coefficients were calculated by missile DATCOM. The roll-rate and roll lock-in of the freely spinning tailfins were calculated by applying these values to the roll-rate equation for freely spinning tailfins. The calculation results showed good agreement with the wind tunnel test data, and the roll lock-in could be anticipated as well.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.760-763
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• 2011

본 논문의 목적은 효율적인 3절점 판 유한요소를 개발하는 것이다. Hellinger-Reissner 범함수에 근거한 혼합정식화(mixed formulation)를 사용한다. 잠김현상을 일으키는 전단변형률장을 독립적으로 분리한 후, MITC(Mixed Interpolation of Tensorial Components)방법을 이용하여 대체전단변형률장(assumed transverse shear strain field)을 구성한다. 추가적으로 회전된 반변기저벡터(contravariant base vector)로 정의된 근사전단변형률장(approximated transverse shear strain field)에 미지수(unknowns)를 도입하여 혼합정식화를 완성시키고 정적응축(static condensation)을 통해 최종 강성행렬을 구성한다. 거짓영에너지모드시험(spurious zero energy mode test), 조각시험(patch test), 등방성시험(isotropic test) 등을 실시하였으며, 4변 완전구속 정사각형 판 구조물과 60도 기울어진 단순지지 판 구조물 등 예제들을 해석하여 MITC3판 유한요소와 수렴성능을 비교하였다.

• Clinics in Shoulder and Elbow
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• v.16 no.1
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• pp.27-32
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• 2013

Purpose: The purpose of this study is to evaluate the clinical and radiological outcomes of treatment of humerus shaft simple fracture by minimally invasive percutaneous osteosynthesis (MIPO) technique using locking compression plate (LCP). Materials and Methods: Six patients who were operated for humerus shaft simple fracture from August 2010 to May 2011 were enrolled for this study. We checked the cause of injury and the accompanying injuries and evaluated the operation time, the clinical and radiological period of union, postoperative range of motion of the shoulder and elbow joint, pain, activities in daily living, radiologic alignment, and other complications. Results: The clinical period of bone union was 7.2 weeks on average, and the radiologic period of bone union was 8 weeks on average. Follow-up period was more than 12 months in all cases. The angulation through postoperative alignment was 2.8 degrees in AP view and 2 degrees in lateral view. The postoperative range of motion was 167 degrees in forward flexion, 50 degrees in external rotation, and thoracic vertebra 12 level in internal rotation. The average value of visual analogue scale (VAS) was 1.2 and that of KSS was 91.3. The American Shoulder and Elbow Surgeons' score (ASES) was 26.5 and the UCLA score was 31.5. Conclusion: MIPO technique for the humerus shaft simple fracture showed good functional and radiological outcomes and may be considered as one of the treatment options for humerus shaft simple fracture.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.6
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• pp.2284-2291
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• 2010

In this paper, we investigate the vibration analysis of plates, using an 8-node shell element that accounts for the transverse shear strains and rotary inertia. The forced vibration analysis of plates subjected to arbitrary loading is investigated. In order to overcome membrane and shear locking phenomena, the assumed natural strain method is used. To improve an 8-node shell element for forced vibration analysis, the new combination of sampling points for assumed natural strain method was applied. The refined first-order shear deformation theory based on Reissner-Mindlin theory which allows the shear deformation without shear correction factor and rotary inertia effect to be considered is adopted for development of 8-node assumed strain shell element. In order to validate the finite element numerical solutions, the reference solutions of plates are presented. Results of the present theory show good agreement with the reference solution. In addition the effect of damping is investigated on the forced vibration analysis of plates.

• Korean Journal of Optics and Photonics
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• v.3 no.1
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• pp.27-36
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• 1992

Frequency modulation spectroscopy of the super-cavity, of which finesse is app. 40,000 has been demonstrated by using a sigle mode He-Ne laser. In-phase and quardrature components of frequency modulation signals (FM signal) were obtained by using the 1.5 MHz-driven-electrooptic phase modulator. The vector locus of the FM signa in the phase space, which is consisted of in-phase and quardrature components of the FM signal, was observed and analyzed for the dependence of FM signal upon the phase of the reference signal of a phase-sensitive-detector. According to rotating the phase of the reference signal, the vector locus was observed to rotate with the same phase angle as the reference signal. The in-phase component of the FM signals will be used to stabilize the frequency of the He-Ne laser to the resonant frequency of the super-cavity.