• Proceedings of the KIEE Conference
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
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• pp.1317-1321
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• 1987

A new type of motor-driven Total Artificial Heart(TAH) system with rolling cylinder mechanism has been developed. Brushless DC motor was chosen as energy converter and controlled by PI controller according to the given velocity profile under the highly time-varying load. Computer simulation was also performed to calculate the optimal gains of PI controller which minimize the input power, one of the most important parameter in artificial heart system.

• Tribology and Lubricants
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• 제27권1호
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• pp.25-33
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• 2011

Rolling contact ball bearings are utilized almost exclusively for liquid propellant rocket engine turbopump. Turbopump ball bearings are required to endure high speed and high load for a poor lubricated condition in cryogenic environment. To evaluate bearing heat generation performance, friction torque is investigated as a function of rotation speed, bearing load and cooling flow rate through an experimental study using water coolants. Radial and axial loads are simultaneously applied to the test bearing by gas pressurized cylinder rod. Endurance performance of bearing has been also verified under the bearing required load for operating condition during total accumulated test time 2,100 sec.

• Journal of Chest Surgery
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• 제22권2호
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• pp.202-211
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• 1989

We experienced a series of animal experimental studies of the total artificial heart in 1988. So called, "Korean Heart* was used in this study, which is developed and fabricated in the Department of Biomedical Engineering, College of Med., S.N.U.. "Korean Heart" is a Rolling-Cylinder Motor-Driven type which is a newly developed electromechanical heart over the shortcomes of the previous artificial hearts, especially pneumatic type. The advantages of the "Korean Heart" are total implantability, quiet and smooth movement, small size fittable in oriental people, etc. The animal experiments were performed two times, as an assist device in sheep and total artificial heart implant experiment in calf weighing 100 kg. After total implantation, the artificial heart was well functioned in movement and hemodynamic control. So that, the calf was recovered excellently, which was able to stand up by herself and take an oral intake. Total survival time was 100 hours and the cause of death was a sudden pumping failure [electrical connection problem]. Several postoperative laboratory results almost within normal limits and no hemolysis, but in autopsy, the multiple thromboembolic findings were seen at the lung and kidney.n at the lung and kidney.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• 제13권8호
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• pp.763-770
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• 2001

The high pressure side rotary compressor is investigated in this study. The temperatures at 29 points of main components and the refrigerant and the performance of the instrumented compressor are measured at various operating conditions. The complex heat transfer mechanism between the components, such s cylinder, suction pipe and stator of motor, is fairly clarified. It is also confirmed that the achievement of a high efficiency by reducing the heat transfer loss in the rotary compressor is possible.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 한국해양공학회 2001년도 춘계학술대회 논문집
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• pp.139-143
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• 2001

Ring-stiffened cylinders are widely used as the pressure hull of submarines and underwater vehicles. For large ring-stiffened cylinders cylindrical shells are fbricated by cold rolling of flat plates and then welding of curved shells. After forming cylinders ring-stiffeners are welded on th the cylinders. Due to these cold roiling and welding initial shape imperfections and residual stresses exists in fabricated ring-stiffened cylinders. It is well known that the initial shape and material imperfections affect the ultimate strength of ring-stiffened cylinders significantly. In this paper previous researches on the effects of initial shape imperfections and residual stresses are briefly reviewed Recently a numerical analysis computer program was developed to predict the ultimate strength of ring-stiffened cylinders subjected to hydrostatic pressure, which is based on the Dynamic Relaxation technique. This program was employed to numerically investigate those effects. The numerical predictions were substantiated with relevant experimental results.

• Bulletin of the Society of Naval Architects of Korea
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• 제17권4호
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• pp.13-20
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• 1980

The integral equation method to solve the boundary-value problem of a 2-dimensional body oscillating in the presence of a free surface generally breaks down at and near irregular frequencies due to the hypothetical flow inside the body. In this paper singularity distributions were extended to an inner free surface to remove the irregular frequency as Ohmatsu's work in 1978, and the solution for the above problem was found by using stream function. For various bodies including Lewis form cylinders, the hydrodynamic forces were calculated numerically at various wave numbers. From the results we concluded that the irregular frequencies can be removed even for the Lewis form cylinder as Ohmatsu done for circular cylinders, and calculated hydrodynamic forces by the present method are little higher than those of Ohmatsu's when the singularities are put on the inner free surface of the body. We specially point out that the solution for heaving motion converges in an oscillatory manner but not for swaying and rolling motions.

• Journal of the Korea Fashion and Costume Design Association
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• 제8권3호
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• pp.27-34
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• 2006

Flexibility, love of symbols, small size-these are all qualites that accompany the proclivity towards compactness in Japanese culture. They developed and have been refined to an unusual level in Japan partly out of the necessity to use limited space economically, but these qualities also characterize the aesthetic preferences of the people. Because space is so precious, it receives a great deal of attention in every aspect of life. Over the centuries Japanese have devised innumerable ways to use space that are ingenious in their successful combination of pragmatism, harmony, and beauty. Folding, stacking, rolling, nesting, carrying, consolidating, miniaturizing and transforming are some of the techniques for living that have created the compact culture. Folding allows a one-dimensional object to be placed in prescribed small space. Stacking objects of the same shape makes use of vertical space, saving valuable horizontal space. Rolling an object reduces it to a tidy cylinder without creasing it, creating yet another form of repose for functionally flat things. Nesting several identically shaped objects of graduated sizes is known as ireko. Carrying things by hand makes them available for any occasion, by plan or on impulse. Consolidating is to bring together the multifarious systems of living into an integrated whole. Miniaturizing things is a way to bring even the universe down to the scale of a human hand. Transforming the face of things is another notable propensity in the Japanese life style. Each one is put to use in countless ways, suggesting principles and conceptions that encapsulate the wisdom of tradition. In this study I wishes to investigate the principals of Japanese traditional design and the applied case in fashion goods.

• Journal of the Korean Society for Railway
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• 제17권1호
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• pp.14-18
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• 2014

Wheel/rail contact is a significant problem in railway dynamics. In this paper, the wheel/rail contact is examined analytically and numerically as a contact problem between two cylinders where torque and friction have effect. Furthermore, the contact of a real wheel and rail is investigated numerically where the normal and shear force act. This study demonstrates that the wheel/rail contact is a process that generates traction force through creep where rolling and sliding occurs simultaneously depending on the shape of the wheel and rail, and the friction coefficient between them.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제17권8호
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• pp.624-629
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• 2016

A brake lever in a basic railway brake system is an important safety device that delivers braking force from the brake cylinder to the brake pad. The safety guidelines for designing rolling stock only qualitatively describe that the brake lever should have sufficient strength. Each train has a different type of brake lever. One brake lever that was designed with a factor of safety of 1.27 has failed, so the material was changed to increase the strength. Therefore, the stress distribution and weak points of the lever were identified by theoretical analysis. and structural analysis. Different brake lever designs were examined for KTX high-speed trains, which have a split-type structure, as well as for electric locomotives, which use an electric multiple unit (EMU) with a unity-type structure. A fracture test was also done to look at the relationship between the vertical stress and the bending stress during braking. The results were used to find a safety factor to apply to each train and suggest quantitative minimum guidelines. We also looked at changing the unity-type EMU brake lever to the split type under the same conditions and analyzed how much the design change affected the factor of safety.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 한국추진공학회 2007년도 제29회 추계학술대회논문집
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• pp.114-118
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• 2007

Design and fabrication of a 30-tonf-class full-scale regenerative cooling combustion chamber of a liquid rocket engine for a ground hot firing test are described. It has chamber pressure of 60 bar and nozzle expansion ration of 12 and manufactured to have a single welded structure of· the mixing head and the chamber. The material of the mixing head is STS316L which has excellent mechanical property in cryogenic condition. The chamber comprise of the cylinder, nozzle throat, and 1st/2nd nozzle parts. The material of the inner jacket is copper alloy/STS329J1/STS316L and that of the outer jacket is STS329J1. The components of· the combustor were manufactured by mechanical processing including lathing, milling, MCT, rolling and pressing. The machined components were integrated to a single body by means of general welding, electron beam welding(EBW), and brazing.