• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.4
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• pp.52-62
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• 2017

The study for the performance characteristics of the nozzleless booster used in ramjet booster was carried out. Performances related to pressure and thrust for nozzleless booster are lower than classical motor those because of absence of convergent and divergent sections of nozzle. To solve this problem, it developed a high-performance propellant with maximum impulse density included Al as metal fuel. Using the nozzleless booster casted the propellant, ground test of it was carried out by varying the length-to-diameter ratio (L/D ratio) of the propellant. Specific impulse of nozzleless booster was limited to about 75 percents of its value compared with that of classical motor adapted nozzle in the same propellant and propellant length and will be estimated approximately 85 percents of its value compared with that of classical motor at same average pressure in terms of the curve fitting by our test results.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.117-121
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• 2012

Upper stage propulsion system designed for operation in the upper atmosphere should be tested under nozzle full flow conditions to verify its performance on the ground. KARI has carried out high altitude simulation test of KSLV-I kick motor using cylindrical supersonic exhaust diffuser. Also cold and hot flow test for the sub-scaled diffuser have been conducted to verify the design of real scale diffuser and to study its operating characteristics. This paper deals with the results obtained from these high altitude simulation tests.

• International Journal of Aerospace System Engineering
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• v.2 no.2
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• pp.58-61
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• 2015

Combustion instability in solid rocket motors is a long-term open problem since the first rockets were used. Based on the numerous previous studies, it is known that the limit cycle amplitude is one of the key characteristics of the nonlinear combustion instability in solid rocket motors. Flandro's extended energy balance corollary, aims to predict the limit cycle amplitude of complex, nonlinear pressure oscillations for rockets or air-breathing engines, and leads to a precise assessment of nonlinear combustion instability in solid rocket motors. However, based on the comparison with experimental data, it is revealed that the Flandro's method cannot accurately describe such a complex oscillatory pressure. Thus in this work we make modifications of the nonlinear term in the nonlinear wave equations which represents the interaction of different modes. Through this modified method, a numerical simulation of the cylindrical solid rocket has been carried out, and the simulated result consists well with the experimental data. It means that the added coefficient makes the nonlinear wave growth equations describe the experimental data better.

• Proceedings of the KIEE Conference
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• summer
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• pp.1118-1120
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• 2004

For the first time in Korea, a 100hp high Tc superconducting(HTS) motor has been designed, developed and successfully tested recently. The design was based on 2-dimensional electromagnetic field analysis of cylindrical coordinate. The field winding of rotor was wound with Bi-2223 tapes and tested after assembled with other rotor components. The stator had air-gap type armature windings which allow higher terminal voltage and more sinusoidal voltage waveform than conventional iron cored machines. Steady state open & short-circuit test and resistive load test were conducted also in generator mode. The fabrication and test results of this machine were discussed in this paper.

• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.1
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• pp.9-14
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• 2019

Hydroxy-terminated polybutadiene (HTPB) propellants of solid rocket motors age differently under different storage temperatures. The shelf life of a solid rocket motor depends on the aging ratio of the HTPB propellant; it can be estimated through the viscoelastic properties by an aging test. This study analyzed the initial and natural aging properties during long-term storage. The initial properties were obtained from characterization and accelerated test results. The test results were obtained by analyzing the strain on cylindrical grains when a thermal load was applied.

• 대한공업교육학회지
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• v.31 no.2
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• pp.364-380
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• 2006

This paper presents a procedure for designing command to maneuver flexible structure with very little residual vibration, even in the presence of modeling errors. For the open loop maneuver, the various shaped profiles using multiple step inputs delayed in time are considered for robustness and compared with the responses of rigid body and flexible body in virtue of simulations and experiments. Input shaping generates vibration-reducing shaped commands through convolution of an impulse sequence with the desired command. A flexible model with a cylindrical hub and four symmetric appendages is considered to examine the responses to real plant, and to illustrate the effectiveness of the proposed shapers. The appendages are long and flexible, leading to low frequency vibration under any control action. It is shown by a series of simulation that a properly designed feedback controller with input shaper performs well, as compared with open loop controller with input shaper. The control objective is to achieve a fast settling time of residual vibration to flexible structure and robustness (insensitivity)to plant uncertainty, to eliminate residual vibration.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.142-145
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• 2002

In order to develop a self-propelled microendoscope, the frictional resistance of the capsule-type endoscope inside the intestine should be understood. In this work the frictional resistance behaviors of capsules with different designs were experimentally investigated using a pig intestine. It was found that cylindrical capsule design had the least frictional resistance. Also, the resistance increased as the speed of the capsule motion was decreased. It is expected that the results of this work will be used to design the optimum propulsion system for the microendoscope.

• The Journal of Korea Robotics Society
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• v.5 no.4
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• pp.318-325
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• 2010

This paper proposes a new string controller for puppet which is optimized in terms of the number of motors and its size. To optimize the number of motors needed for generating the essential motions of puppet, the motion of bending a leg is implemented by one string and the walking motion by two legs is implemented by one motor. To minimize the space needed for the controller when generating the essential motions of puppet, cylindrical and articulated joints are used in the controller. The proposed controller is actually implemented to perform various puppet shows and it has been proved that the size of the controller is small enough for two puppets to stand close to shake hands and it is fast enough to simulate fast dance motions.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.427-430
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• 1999

This paper presents a S-FES(Superconducting magnetic bearing Flywheel Energy Storage System) for the purpose of replacing battery used to store the energy. Especially, the design elements of FES, such as the bearing, wheel material, and power converter, etc., is described. The design and manufacturing techniques of the controllable power converter are proposed to generate the sinusoidal output current in the high speed operation and to get the constant DC voltage in the regeneration mode. The cylindrical permanent magnet synchronous motor with halbach array of Nd-Fe-B permanent magnet which is the high coercivity material is used as the driver of FES. The proposed S-FES system shows the stable rotation characteristics at high speed range about 10,000 rpm. To verify the validity of proposed system, the comparative study with the conventional ball bearing system is proceeded and it is well confirmed with the result of the lower friction loss of S-FES system.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10a
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• pp.962-967
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• 1991

A counter balance valve is used as one part of hydraulic motor brake system. The function of this valve is to protect over-run or free falling of inertia load. But occasionally the brake system with counter balance valve makes some undesirable problems such as pressure surges or vibrations. In this study, for the purpose of easy estimation about dynamic characteristics of hydraulic system including counter balance valve, precise formulation describing fluid dynamics and valve dynamics under various boundary conditions were made. Dynamic characteristics were analysed by numerical integration using Runge-Kutta method, because the equations in this circuit with counter balance valve contain various nonlinear terms. Propriety of this analysis method is verified by experiment. For the purpose of obtaining fundamental data for preventing instability, this study experimented the effects of the spool taper, spring constant, cylindrical choke. And we developed double acting brake system integrated counter balance valve.