• 한국항해항만학회:학술대회논문집
• /
• 한국항해항만학회 2012년도 추계학술대회
• /
• pp.160-161
• /
• 2012

The traditional theory regarding the pivot point of a ship during maneuvering, so called apparent pivot point, is located nearly at 1/3 ship's length from the bow when the ship is moving ahead, and between 1/4 ship's length from the stern and the rudder post when going astern. The pivot point is sometimes considered to be the centre of leverage for forces acting on the ship. However, the pivot point is located out of ship due to strong lateral force, such as current and it is very inconvenient to use during maneuvering a ship. In this paper firstly, pivot points due to ship's condition are investigated carefully. And then the center of lateral resistance used at the present are determined. While a new lateral force is added, we can compare the pivot point with the center of lateral forces. Finally, we will suggest the center of all lateral forces for maneuvering instead of pivot point. Especially, it will be very helpful for pilots to handle ships in simulation.

• Wind and Structures
• /
• 제11권2호
• /
• pp.153-178
• /
• 2008

Based on the empirical formulas for power spectra of generalized modal forces and local fluctuating wind forces in across-wind and torsional directions, the wind-induced lateral-torsional coupled response analysis of a representative rectangular tall building was conducted by setting various parameters such as eccentricities in centers of mass and/or rigidity and considering different torsional to lateral stiffness ratios. The eccentricity effects on the lateral-torsional coupled responses of the tall building were studied comprehensively by structural dynamic analysis. Extensive computational results indicated that the torsional responses at the geometric center of the building may be significantly affected by the eccentricities in the centers of mass and/or rigidity. Covariance responses were found to be in the same order of magnitude as the along-wind or across-wind responses in many eccentricity cases, suggesting that the lateral-torsional coupled effects on the overall wind-induced responses can not be neglected for such situations. The calculated results also demonstrated that the torsional motion contributed significantly to the total responses of rectangular tall buildings with mass and/or rigidity eccentricities. It was shown through this study that the framework presented in this paper provides a useful tool to evaluate the wind-induced lateral-torsional coupled responses of rectangular buildings, which will enable structural engineers in the preliminary design stages to assess the serviceability of tall buildings, potential structural vibration problems and the need for a detailed wind tunnel test.

• 대한정형외과스포츠의학회지
• /
• 제6권1호
• /
• pp.66-69
• /
• 2007

청소년기에 슬관절 부위에 스포츠 관련 손상은 흔하게 발생하며 이 시기에는 생리적 특성 때문에 골절이 인대손상보다 흔하다. 저자들은 청소년기의 축구 선수에서의 대퇴 외과 성장판 손상을 관절경을 이용하여 정복 및 고정을 하였다. 술 후 2년에 내고정물 제거를 동반한 이차 관절경 검사에서 관절면은 잘 치유되어 있었고, 하지 전장 방사선 촬영소견에서 하지 정열도 변형없이 잘 유지되어 있었다.

• Journal of Korean Neurosurgical Society
• /
• 제66권6호
• /
• pp.703-715
• /
• 2023

Objective : This retrospective study investigated the factors that affect cage obliquity angle despite orthogonal maneuvers performed during oblique lateral interbody fusion (OLIF) and assessed the relationship between cage obliquity angle and radiological outcomes post-surgery. Methods : Twenty-nine males who underwent L4-L5 OLIF for lumbar degenerative disease between 2019 and 2021 with a followup duration greater than 12 months were analyzed. Radiological parameters were measured including psoas muscle volume, total psoas area index (total psoas muscle area [cm²]/height squared [m²]), distance from the iliac artery to the origin of the psoas muscle (DIAPM), angle between the origin of the psoas muscle and the center of the vertebral disc (APCVD), iliac crest height, disc height, lumbar flexibility (lumbar flexion angle minus extension angle), cage location ratio, cage-induced segmental lumbar lordosis (LL) (postoperative index level segmental LL minus used cage angle), foraminal height changes, fusion grade. Results : DIAPM, APCVD, iliac crest height, postoperative index level segmental LL, and cage-induced segmental LL were significantly correlated with OLIF cage obliquity angle. However, other radiological parameters did not correlate with cage obliquity. Based on multiple regression analysis, the predictive equation for the OLIF cage obliquity angle was 13.062-0.318×DIAPM+0.325×1APCVD+0.174×iliac crest height. The greater the cage obliquity, the smaller the segmental LL compared to the cage angle used. Conclusion : At the L4-L5 level, OLIF cage obliquity was affected by DIAPM, APCVD, and iliac crest height, and as the cage obliquity angle increases, LL agnle achievable by the used cage could not be obtained.

• 대한정형외과스포츠의학회지
• /
• 제5권2호
• /
• pp.161-164
• /
• 2006

목적: 슬관절 손상의 많은 빈도를 차지하고, 가장 흔하게 수술의 원인이 되는 반월상 연골판 손상을 외래에서 쉽게 일차적으로 검사하는 관절선 압통의 유용성을 알아보고자 하였다. 대상 및 방법: 2005년 5월에서 2006년 6월까지 군병원에서 동일한 시술자에게서 반월상 연골판 손상이 의심되어 수술을 시행한 76명의 환자를 대상으로 관절선 압통(joint line tenderness)에 대한 민감도, 특이도, 정확도, 양성 예측율, 음성 예측율 등을 분석하였다. 결과: 관절선 압통의 민감도, 특이도, 정확도, 양성 예측을, 음성 예측율은 순서대로 78.8%, 32.6%, 52.6%, 47.3%, 66.7%로 나타났으며 외측과 내측 및 불안정성을 동반한 환자를 대상으로 동일하게 분석하여도 상기 결과와 비슷하게 높지 않은 결과를 나타내었다. 결론: 관절선 압통 단일 검사는 외래에서 손쉽게 행해지는 간편한 검사이나, 그 단독 검사로서는 유용성이 떨어지는 것으로 보인다. 그러므로, 여러가지 이학적 검사를 병행 시행하는 것이 좀 더 높은 진단율을 나타낼 것으로 보이고, 필요시에는 자기공명영상(MRI)이나 진단적 관절경 검사도 필요할 것으로 보인다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제7권4호
• /
• pp.201-208
• /
• 2003

철근콘크리트 코어 벽체와 외부 철골골조로 구성된 복합벽체시스템은 중앙 코아 전단벽 주변의 오픈공간을 갖는다. 이와 같은 복합 벽체시스템은 연결된 벽체가 대부분의 횡하중에 저항하고 벽체저면과 커플링 보에서 대부분의 에너지를 소산할 수 있는 설계기법을 개발하는 것이 필요하다. 본 연구논문은 커플링 보의 접합방식 및 층규모를 주변수로 수직하중 및 풍하중과 지진하중을 받는 복합 벽체시스템에 대하여 전단력, 전도모멘트, 최대 횡변위, 층간변위비 및 동적특성을 규명하였다.

• Tribology and Lubricants
• /
• 제18권1호
• /
• pp.1-8
• /
• 2002

Nano adhesion and friction between a $Si_{3}N_{4}$ AFM(atomic force microscope) tip and thin silver films were experimentally studied. Tests were performed to measure the nano adhesion and friction in both AFM and LFM(lateral force microscope) modes in various range of normal loads. Thin silver films deposited by IBAD (ion beam assisted deposition) on Si-wafer (100) and other Si-wafers of different surface roughness were used. Results showed that nano adhesion and friction decreased with the surface roughness. When the Si surfaces were coated by pure silver, the adhesion and friction decreased. But the adhesion and friction were not affected by the thickness of IBAD silver coating. As the normal force increased, the adhesion forces of bare Si-wafer and IBAD silver coating film remained constant, but the friction forces increased linearly. Test results suggested that the friction was mainly governed by the adhesion as long as the load was low.

• 한국자동차공학회논문집
• /
• 제16권2호
• /
• pp.183-190
• /
• 2008

This paper deals with the characteristics of idle vibration due to the type of constant velocity joints. Based on the kinematics model of constant velocity joints, a offset between the tripod center and tullip center plays a important role in generating unwelcome forces. Moreover, it induced additional forces in lateral direction of a vehicle movement according to the angle of the spider in idle vibration. The difference of mass for each constant velocity joint types affect the natural frequency of the driveshaft and the powertrain. When the static torque is applied to the constant velocity joints, the natural frequencies of the driveshaft are reduced nearby 50Hz. There will be a big opportunity that the dirveshaft and constant velocity joints would be a transfer path of idle vibration at D or R gear range. Experiments indicate that TJ type is better than SFJ and DOJ in idle vibration.

• 한국생산제조학회지
• /
• 제19권1호
• /
• pp.121-127
• /
• 2010

We consider the robust trajectory tracking control problem for a skid steering mobile robots. A dynamic model is derived accounting for the effects of wheel skidding. The control design utilizes the dynamic feedback linearization techniques, so as to obtain a predictable behavior for the instantaneous center of rotation thus preventing excessive skidding. The additive controller using the sliding mode type is then robustified against the unmodelled dynamics and parameter uncertainty. Simulation results show the good performances under excessively uncorrected estimations of the longitudinal forces and the lateral resistive forces caused by the skidding of the wheels in tracking trajectories.

• 한국정밀공학회지
• /
• 제19권11호
• /
• pp.65-74
• /
• 2002

This paper examines the usefulness of a Brake Steer System (BSS), which uses differential brake forces for steering intervention in the context of Intelligent Transportation Systems (ITS). In order to help the car to turn, a yaw moment can be achieved by altering the left/right and front/rear brake distribution. This resulting yaw moment on the vehicle affects lateral position thereby providing a limited steering function. The steering function achieved through BSS can then be used to control lateral position in an unintended road departure system. A 8-DOF nonlinear vehicle model including STI tire model will be validated using the equations of motion of the vehicle. Then a controller will be developed. This controller, which will be a PID controller tuned by Ziegler-Nichols, will be designed to explore BSS feasibility by modifying the brake distribution through the control of the yaw rate of the vehicle.