• International Journal of Naval Architecture and Ocean Engineering
• /
• 제8권1호
• /
• pp.102-109
• /
• 2016

The hydrodynamic interaction between two large vessels can't be neglected when two large vessels are closed to each other in restricted waterways such as in a harbor or narrow channel. This paper is mainly concerned with the ship maneuvering motion based on the hydrodynamic interaction effects between two large vessels moving each other in curved narrow channel. In this research, the characteristic features of the hydrodynamic interaction forces between two large vessels are described and illustrated, and the effects of velocity ratio and the spacing between two vessels are summarized and discussed. Also, the Inchon outer harbor area through the PALMI island channel in Korea was selected, and the ship maneuvering simulation was carried out to propose an appropriate safe speed and distance between two ships, which is required to avoid sea accident in confined waters. From the inspection of this investigation, it indicates the following result. Under the condition of $SP_{12}{\leq}0:5L$, it may encounter a dangerous tendency of grounding or collision due to the combined effect of the interaction between ships and external forces. Also considering the interaction and wind effect as a parameter, an overtaken and overtaking vessel in narrow channel can navigate while keeping its own original course under the following conditions; the lateral separation between two ships is about kept at 0.6 times of ship length and 15 degrees of range in maximum rudder angle. On the other hand, two ships while overtaking in curved narrow channel such as Inchon outer harbor in Korea should be navigated under the following conditions; $SP_{12}$ is about kept at 1.0 times of ship length and the wind velocity should not be stronger than 10 m/s.

• 한국가시화정보학회:학술대회논문집
• /
• 한국가시화정보학회 2007년도 추계학술대회
• /
• pp.134-137
• /
• 2007

The temporal evolution of wake behind a circular cylinder oscillating rotationally with a relatively high forcing frequency has been investigated experimentally using a dynamic PIV technique. Experiments were carried out with varying the frequency ratio $F_R\;(=f_f/f_n)$ in the range from 0.0 (stationary) to 1.6 at oscillation amplitude of ${\theta}_A=30^{\circ}$ and Reynolds number of $Re=4.14{\times}10^3$. Depending on the forcing condition ($F_R$), the flow was divided into three regimes; non-lock-on ($F_R=0.4$), transition ($F_R=0.8$, 1.6) and lock-on regimes ($F_R=1.0$) with markedly different flow structure in the near-wake region behind the cylinder. When the frequency ratio was less than 1.0 ($F_R{\le}1.0$), the rotational oscillatory motion of the cylinder decreased the length of the vortex formation region and enhanced the mutual interaction between large-scale vortices across the wake centerline. The entrainment of ambient fluid seemed to play an important role in controlling the near-wake flow and shear-layer instability. However, the flow characteristics changed markedly beyond the lock-on flow regime ($F_R=1.0$) due to high-frequency forcing. At $F_R=1.6$, the mutual interactions between the vortices shed from both sides of the cylinder were not so strong. Thereby, the flow entrainment and momentum transfer into the wake center region were reduced. In addition, the size of the large-scale vortices decreased since the lateral extent of the wake was suppressed.

• Archives of Reconstructive Microsurgery
• /
• 제23권2호
• /
• pp.70-75
• /
• 2014

Purpose: Soft-tissue reconstruction in the knee area requires thin, pliable, and tough skin. The range of motion of the knee also acts as a limitation in using only local flaps for coverage. The author has successfully used various perforator flaps for soft tissue reconstruction around the knee while preserving its functional and cosmetic characteristics. Materials and Methods: Out of the twenty patients assessed from April 2009 to March 2011, seven received anterolateral thigh perforator flaps, four received medial sural perforator island flaps, four received lateral supragenicular perforaor perforator flaps, and five received medial genicular artery flaps. The age of the patients ranged from 44 to 79 and the size of the defects ranged from $4{\times}5cm$ to $17{\times}11cm$. Fifteen of the twenty patients had histories of total knee replacement (TKR) surgery. Results: There were no flap losses in any of the twenty patients assessed. Two patients showed partial losses in the distal area of the flap, but were treated through careful wound care. One patient presented with pedicle adhesion at the drainage site from a past TKR, but it did not hinder the flap survival. Primary closure at the donor site was possible in nine patients, while split skin graft was necessary for the other 13. Conclusion: In soft tissue reconstruction of the knee, various perforator flaps can be used depending on the condition of the preoperation scar, wound site, and size. It also proved to provide better functional and cosmetic results than in primary wound closure or skin grafts.

• Archives of Plastic Surgery
• /
• 제35권6호
• /
• pp.716-722
• /
• 2008

Purpose: Split or full thickness skin graft is generally used to reconstruct the palmar skin and soft tissue defect after release of burn scar flexion contracture of hand. As a way to overcome and improve aesthetic and functional problems, the authors used the preserved superficial fat skin(PSFS) composite graft for correction of burn scar contracture of hand. Methods: From December of 2001 to July of 2007, thirty patients with burn scar contracture of hand were corrected. The palmar skin and soft tissue defect after release of burn scar contracture was reconstructed with the PSFS composite graft harvested from medial foot or below lateral and medial malleolus, with a preserved superficial fat layer. To promote take of the PSFS composite graft, a foam and polyurethane film dressing was used to maintain the moisture environment and Kirschner wire was inserted for immobilization. Before and after the surgery, a range of motion was measured by graduator. Using a chromameter, skin color difference between the PSFS composite graft and surrounding normal skin was measured and compared with full thickness skin graft from groin. Results: In all cases, the PSFS composite graft was well taken without necrosis, although the graft was as big as $330mm^2$(mean $150mm^2$). Contracture of hand was completely corrected without recurrence. The PSFS composite graft showed more correlations and harmonies with surrounding normal skin and less pigmentation than full thickness skin graft. Donor site scar was also obscure. Conclusion: The PSFS composite graft should be considered as a useful option for correction of burn scar flexion contracture of hand.

• 한국운동역학회지
• /
• 제25권3호
• /
• pp.257-263
• /
• 2015

Objective : The purpose of this study was to investigate the effect of genu valgum on the body mass index, movement of lower limb joints, and ground reaction force. Methods : Gait patterns of 30 college students with genu valgum were analyzed and the static Q angle of the femur was measured for selecting genu valgum of the subjects. To analyze the kinetic changes during walking, the six-camera Vicon MX motion analysis system was used. The subjects were asked to walk 12 meters using the more comfortable walking method for walking. After they walked 12 meters more than 10 times, their most natural walking patterns were chosen three times and analyzed. Results : As a result of measuring a relationship between genu valgum and Q-angle, as the Q-angle increases, it showed a genu valgum also increased. Body Mass Index showed a significant difference between the groups was higher in the genu valgum group.(p<.001). The analysis result showed that genu valgum had a significant effect on the internal rotation moment in the hip joint(p<.05). Also, genu valgum had a significant effect on the internal rotation moment of the knee joint(p<.05). The comparative analysis of the Medial-Lateral ground reaction force in the genu valgum group showed a tendency to increase the medial ground reaction force(p<.05). The vertical ground reaction forces of the middle of the stance phase(Fz0) showed a significant increase in genu valgum group(p<.05), in particular the results showed a decrease in the early stance phase(p<.001). Conclusion : In conclusion, the change in body mass is considered to be made by proactive regular exercise for improvement of the genu valgum. In addition, the prevention of the deformation caused by secondary of the genu valgum in this study may be used as an indicator of the position alignment rehabilitation for structural and functional improvements. Applying a therapeutic exercise program for the next lap will require changes in posture alignment.

• 한국펄프종이공학회:학술대회논문집
• /
• 한국펄프종이공학회 2006년도 PAN PACIFIC CONFERENCE vol.1
• /
• pp.147-152
• /
• 2006

Restoration of historical documents and arts has become important to inherit cultural properties. Most of historical documents were recorded on paper. Therefore, restoration of ancient papers is demanded and techniques for this purpose must be developed and sophisticated. In our study, several nondestructive methods for analyzing ancient paper have been developed. Image analysis using fast Fourier transform with suitable modifications was applied to optical micrographs of traditionally-handmade Korean and Japanese papers. This analysis determines the angle and anisotropy of fiber orientation of paper surfaces. Fiber orientation of traditionally-handmade Korean and Japanese papers was found to show their own characteristics in accordance with the motion of a papermaking screen made of bamboo splints. Consequently, the information on fiber orientation was found to be possible to distinguish the flow-sheet forming typical of Japanese paper and still-sheet forming typical of Korean paper. Moreover, the anisotropy was always higher for the screen side than for the top side, thus meaning that surface fiber orientation is possible to distinguish the two sides of paper of which papermaking history is unknown. An application of this technique to actual historical documents evidenced that wrapping papers were used as envelops with a lateral side up, namely, after rotating 90 degrees. A variety of cultural habits in writing letters was revealed by discrimination of the two sides.

• Asian-Australasian Journal of Animal Sciences
• /
• 제24권2호
• /
• pp.181-189
• /
• 2011

Cryopreservation protocols induce partially irreversible damage to mammalian sperm plasma membranes. Previous studies have indicated that adding cholesterol to the plasma membrane, as cholesterol-loaded-cyclodextrins, improves cryosurvival of sperm. Therefore, the purpose of this study was to determine if treating sperm of Markhoz bucks with cholesterol-loaded-cyclodextrins (CLC) (0, 0.75, 1.5, 2.25 and 3 mg/ml diluted $240{\times}10^6$ sperm/ml) in Tris-citric acid-glucose diluents with and without egg yolk (containing 5% glycerol) would improve the post-thaw sperm quality. The motion characteristics were evaluated with a Computer Assisted System Analyzer (CASA); acrosome integrity and vitality were measured with the triple-stain technique. Samples were recovered before and after freezing by means of putting straws into $37^{\circ}C$ water for 30 sec and then parameters were assessed. The results showed that the treatments significantly affected motility, progressive motility, recovery rate, curvilinear velocity, beat cross frequency, live sperm with reacted acrosome, live sperm with unreacted acrosome, dead sperm with reacted acrosorne, and dead sperm with unreacted acrosome during freezing (p<0.05). However; no significant differences were found for average path velocity, straight line velocity, amplitude of lateral head displacement, straightness and linearity (p>0.05). The best results were observed for extender containing 2.25 mg/ml ($240{\times}10^6$ sperm/ml) CLC supplemented with 2.6% egg yolk. In conclusion, the findings of this study indicate improved Markhoz sperm viability and motility following treatment in the presence of egg yolk.

• 대한기계학회논문집A
• /
• 제34권4호
• /
• pp.431-437
• /
• 2010

본 연구의 목적은 편마비 환자와 같이 정상 보행이 아닌 경우의 보행 실험에서 힘측정판을 이용한 지면반발력의 측정이 매우 어려웠던 경험에서 출발하여 힘측정판을 사용하지 않고 운동학적 데이터만으로 보행 중 발생하는 지면반발력을 계산하는 것이다. 3차원 동작분석 시스템과 동기화된 힘측정판을 이용하여 보행실험을 실시하여 3차원 동작분석 시스템으로부터 보행의 운동학적 데이터를 추출하였고 이로부터 보행주기를 검출하였다. 인체를 13개의 체절로 모델링하고 각 체절의 거동이 추출한 운동학적 데이터를 따르도록 하였다. 각 체절의 질량과 질량 중심은 인체측정학의 자료를 이용하였다. 보행실험에서 측정한 지면반발력과 운동학적 데이터만을 이용한 계산 결과의 비교에서 크기가 가장 큰 수직방향은 잘 일치하였고 전후방향이나 횡방향도 유사한 경향을 보였다. 본 계산 결과는 보행에 관한 역동역학 해석의 기본 자료로 활용할 수 있다.

• 대한기계학회논문집A
• /
• 제37권6호
• /
• pp.731-738
• /
• 2013

본 논문은 6 륜 독립구동/독립조향 차량의 독립 스티어-바이-와이어 장치의 고장 안전 주행 제어방법을 제시하였다. 조향부 고장 휠의 횡방향 타이어 힘이 차량 선회 운동에 저항력으로 작용할 수 있으므로, 이를 줄이기 위하여 본 고장 안전 주행 제어 알고리즘은 조향부 고장 휠에 높은 슬립률이 발생하도록 토크 입력을 가한다. 고슬립으로 인한 조향부 고장 휠의 종방향 타이어 힘 증가를 고려하기 위하여 종방향 타이어 힘을 추정하여 고장나지 않은 휠의 구동력 최적 분배에 구속 조건에 포함시킨다. 개루프 조향 및 폐루프 조향 시뮬레이션 결과 조향부 고장이 발생한 차량의 주행시 고장을 고려하지 않은 최적 구동력 분배 제어에 비하여 본 알고리즘 적용시 차량의 주행 성능이 보정됨을 확인하였다.

• 한국콘텐츠학회논문지
• /
• 제11권10호
• /
• pp.488-493
• /
• 2011

한국과학기술정보연구원과 가톨릭대학교 의과대학 가톨릭응용해부연구소에서는 척추 연구자들이 쉽게 사용할 수 있는 기초 자료를 구축하고 있다. 척추 형상 정보를 제공하기 위해 60-80대 기증시신 20여 표본을 활용하여 고해상도 척추 (whole spine) CT (pixel dimension : 0.4x mm, thickness: 0.6mm)를 촬영하고 이를 3차원 모델링 소프트웨어(Mimics, Ver.14, Materialise, Belgium)를 사용하여 3차원 형상 모델(shell model, STL format)로 구축하고, 목, 등, 허리 척추의 주요 부위를 계측하여 수치화 하였다. 시신기반 자료의 한계를 극복하기 위해 고령자 호발 질환을 중심으로 대상 환자를 선정하여 X-Ray, CT, BMD 자료를 구축하여 보강하고 있다. 물리적 성질 정보 구축은 기증시신 10여 표본을 활용하여 임상적, 물리적 골밀도를 측정하고, 목척추(cervical), 등척추(thoracic), 허리척추(lumbar) 부분의 굽힘-폄(flexion-extension), 가쪽 굽힘(lateral bending), 회전(torsion), 압축(body/disc compression) 시험을 수행하여 작용력과 굽힘량의 관계를 구축하고 있다. 구축된 물성 시험 결과는 형상 모델과 함께 제공되어 자료의 활용도를 높이고 있으며, 이를 이용하여 한국인 특성이 반영된 척추 관련 연구 및 제품 개발에 활용 될 수 있다.