• 한국전문물리치료학회지
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• 제20권4호
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• pp.16-21
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• 2013

The purpose of this study was to determine the effect of contralateral hip adduction (CHA) on the muscle activity of lumbar stabilizers and the angle of pelvic lateral tilting during hip abduction in side lying. Twenty healthy male subjects with no medical history of lower extremity or lumbar spine disorders were recruited for the study. Subjects randomly performed preferred hip abduction (PHA) and hip abduction with contralateral hip adduction in side lying. The muscle activities of the dominant side rectus abdominis, external oblique, internal oblique, quadratus lumborum, gluteus medius, and non-dominant side hip adductor longus were measured during PHA and CHA by using a surface electromyography (EMG) system. Pelvic lateral tilting motion was measured by using a three-dimensional motion analysis system. Data on EMG and pelvic motion were collected at the same time during PHA and CHA. A paired t-test was used to compare EMG activity and the angle of pelvic lateral tilting in the two exercises. The study found that the EMG activities of all muscles were more increased significantly in CHA than PHA condition. The angle of pelvic lateral tilting was more decreased significantly in CHA than PHA condition. These findings suggest that CHA could be recommended as a hip abduction exercise for activating lumbar stabilizers and decreasing compensatory pelvic lateral tilting motion.

• 천문학논총
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• 제7권1호
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• pp.19-23
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• 1992

We investigated the "tilting" of the Universe, i.e., a non-Doppler origin of the dipole moment of the cosmic background radiation (CBR). Superhorizon-sized isocurvature, rotational and true vacuum bubble perturbations are considered. We show that the more natural way of the "tilting" the Universe is via the true vacuum bubble perturbation. Nevertheless, due to the small filling fraction of the bubbles of viable extended inflationary models, we find that the probability of the real occurrence in the Universe is quite insignificant.

• 한국정밀공학회지
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• 제32권7호
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• pp.661-666
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• 2015

This paper presents control performance improvement by modifying center of gravity (COG) of an underwater robotic platform. To reduce the oscillation or to increase the positioning accuracy, it is important to accurately know the COG of an underwater robotic platform. The COG is determined by the three measured tilting angles of the platform in different postures. The tilting angle is measured while the platform is hanged by two strings. Using coordinate transformation, the plane of intersection is defined from the angle of the platform and the position of the string. The COG of the robotic platform is directly calculated by the intersected point in three defined planes. The measured COG is implemented to the control algorithm that is pre-designed in the previous research, and the empirical result on tilting gives 48.26% improved oscillation performance comparing to the oscillation result with the ideal COG position.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.2151-2155
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• 2008

The tilting train express (TTX) is able to tilt its body toward to the center of the turning radius on curved railways. TTX can travel at higher speed than the existing normal railway vehicles due to the tilting mechanism decreasing centrifugal force. Also, a new suspension system is required for TTX which has proper stiffness constants and damping ratios because it has different suspension characteristics with the others. Therefore, the suspension systems need to be optimized to maximize dynamic characteristic of the railway vehicle. To optimize the dynamic characteristics of TTX, sensitivity analysis should be onde to identify design variables. In this paper, Design of Experiments(DOE) is used for the sensitivity analysis of TTX.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.796-805
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• 2005

The tilting pad journal bearings have been widely used to support high pressure/high rotating turbine rotors owing to their inherent dynamic stability characteristics. However, fatigue damages in the upper unloaded pads and the break of locking pins etc. by pad fluttering are continuously taken place in the actual steam turbines. The purpose of this paper is to develop a new bearing model that can prevent bearing problems effectively by pad fluttering in a tilting pad journal bearing. A new bearing model which has a wedged groove is suggested from the studies of fluttering mechanism performed by previously research works. The fluttering characteristics of the upper unloaded pad are studied experimentally in order to verify the reliability of a new bearing model. It can be known that the phenomenon of pad fluttering nearly does not occurred in the new bearing model under the various experimental conditions. And it is observed that any kinds of bearing failures by pad fluttering does not detect in the application of acture steam turbines.

• Tribology and Lubricants
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• 제30권2호
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• pp.77-85
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• 2014

This study set out to predict the load capacity and rotordynamic coefficients of tilting-pad journal bearings, taking the pivot stiffness into account. The analysis uses rocker-back (cylindrical) and ball in socket (spherical) pivot models, both of which are based on Hertzian contact stress theory. The models ascertain the non-linear elastic deformation of the pivots according to the applied load, pivot geometry, and material properties. At present, the Reynolds equation for an isothermal, isoviscous, and incompressible fluid is used to calculate the film pressure by using the finite-element method, after which the Newton-Raphson method is used to simultaneously find the journal center location, pad angles, and pivot deflections. The bearing analysis, excluding the pivot models, is validated using predictions those are readily available in the literature. As the rotor speed increases, the predicted journal eccentricity and damping coefficients decrease, but the stiffness coefficients increase, as expected. Most importantly, the implementation of the pivot models increases the journal eccentricity but significantly decreases the stiffness and damping coefficients of the tilting-pad journal bearings.

• International Journal of Fluid Machinery and Systems
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• 제6권2호
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• pp.49-55
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• 2013

Water lubricated guide bearing was newly released and has been applied to actual hydro turbines with vertical shaft. As a result, they can have not only high bearing performance but environmental advantages in meeting the demand for reducing river pollution by oil leakage from oil lubricated guide bearing. The PTFE composite guide bearing was tested by experimental equipment operated under conditions similar to those of actual hydro turbines. Circumferential and axial tilting bearing segments help to improve the bearing performance and efficiency due to low friction loss in the bearing system. Furthermore, bearing cooling systems could be eliminated and maintenance periods could be extended, thus the initial investment and operating costs of the hydroelectric power plant are reduced.

• 대한의용생체공학회:의공학회지
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• 제28권1호
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• pp.117-126
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• 2007

In this paper, we propose an early rehabilitation training system for the improvement of postural balance with multi-modality on a tilting bed. The integration of the visual, somatosensory and vestibular functions is significant to for maintaining the postural control of the human body. However, conventional rehabilitation systems do not provide multi-modality to trainees. We analyzed the characterization of postural control at different tilt angles of an early rehabilitation training system, which consists of a tilting bed, a visual feedback, a computer interface, a computer, and a force plate. The software that we developed for the system consists of the training programs and the analysis programs. To evaluate the characterization of postural control, we conducted the first evaluation before the beginning of the training. In the following four weeks, 12 healthy young and 5 healthy elderly subjects were trained to improve postural control using the training programs with the tilting bed. After four weeks of training, we conducted the second evaluation. The analysis programs assess (center of pressure) COP moving time, COP maintaining time, and mean absolute deviation of the trace before and after training at different tilt angles on the bed. After 4 weeks, the COP moving time was reduced, the COP maintaining time was lengthened, and the mean absolute deviation of the trace was lowered through the repeated use of vertical, horizontal, dynamic circle movement training programs. These results show that this system improves postural balance and could be applied to clinical use as an effective training system.

• 대한방사선기술학회지:방사선기술과학
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• 제44권4호
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• pp.367-373
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• 2021

A quality assurance of computed tomography(CT) have done seven items that were water attenuation coefficient, noise, homogeneity, spatial resolution, contrast resolution, slice thickness, artifact using by standard phantom. But there is no quality assurance items and methods for CT simulator at domestic institutions yet. Therefore the study aimed to access the CT dose index(CTDI), table tilting, image distortion, laser accuracy, table movement accuracy and CT seven items for CT simulator quality assurance. The CTDI at the center of the head phantom was 0.81 for 80 kVp, 1.55 for 100 kVp, 2.50 for 120 mm, 0.22 for 80 kVp at the center of the body phantom, 0.469 for 100 kVp, and 0.81 for 120 kVp. The table tilting was within the tolerance range of ±1.0° or less. Image distortion had 1 mm distortion in the left and right images based on the center, and the laser accuracy was measured within ±2 mm tolerance. The purpose of this study is to improve the quality assurance items suitable for the current situation in Korea in order to protect the normal tissues during the radiation treatment process and manage the CT simulator that is implemented to find the location of the tumor more clearly. In order to improve the accuracy of the CT simulator when looking at the results, the error range of each item should be small. It is hoped that the quality assurance items of the CT simulator will be improved by suggesting the quality assurance direction of the CT simulator in this study, and the results of radiation therapy will also improve.

• Radiation Oncology Journal
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• 제12권1호
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• pp.117-121
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• 1994

연구목적 : 국소재발을 줄이면서 합병증을 최소화하기 위한 방법으로 제안된 수술중 방사선 치료(IORT)는 육안으로 치료 범위를 확인 할 수 있는 이점이 있으나 조사 선축의 각도와 치료과 치료면의 거리 등이 조금만 틀려도 조사야의 선량에 차이가 있을 뿐 아니라 조사방사선의 동질성(Homogeneity)에도 영향을 미치게 된다. 직장암의 경우 조사 부위가 대부분에서 3차적인 경사면을 가진 골반벽이 됨으로 치료 cone의 정확한 Set-up은 적절한 gantry의 회전과 치료대(treatment couch)의 tilting이 조화되어야만 가능하다. gantry의 회전은 어느 기계에서나 가능하나 치료대의 tilting은 대부분에서 불가능함으로 영남대학교 의료원 치료 방사선과에서는 상하로의 tilting이 30$ ^{\circ} $까지 가능할 뿐 아니라 기존 치료대에 장착과 탈거가 5분이내에 쉽게 될수 있는 치료대를 개발하기 위함. 재료 및 방법 : IORT 치료대는 2cm 두께의 bekelite로 2cm 두께의 sponge를 leather로 싸서 수술대에 피나 기타용액이 스며들지 못하게 하였고 전체의 무게가 45kg을 넘지 않도록 하여 치료대의 양끝에 장착할 경우, 치료대의 수평이 유지되도록 하였다. 상하 경사각은 30$ ^{\circ} $를 유지토륵 하였고 lithotomy position에서도 side handle을 사용하여 경사각 조절이 가능토록 하였다. 결과 및 결론 : 1992년 9월부터 1993년 3월까지 여러번의 수정을 거친 후 대장 직장암의 IORT에 사용하고 있으며, 3차원적인 골반벽에의 정확한 접근(approach)이 가능할 뿐 아니라 기존 방사선 치료대에 장착과 탈거가 5분 이내에 가능하며, 상하 경사각 30$ ^{\circ} $ 정도로의 조절이 수술이나 마취에 전혀 영향을 주지 않는 상태에서 자유로이 조절 되므로 향후 대장직장암의 IORT에 크게 공헌할 수 있을 것으로 사료됨.