• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.2
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• pp.35-41
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• 2014

A rotordynamic analysis is performed for a turbopump of 7 ton class liquid rocket engine considering bearing housing structural flexibility. Stiffness and damping characteristics of ball bearings and pump noncontact seals are reflected in a rotordynamic model. A dynamic model of bearing housing with lumped mass and stiffness is also applied to the rotordynamic analysis. Rotor critical speed and onset speed of instability are predicted from synchronous rotor mass unbalance response and complex eigenvalue analyses. The bearing housing structural flexibility effect on rotordynamic characteristics is investigated for both of bearing loaded and unloaded conditions respectively. From the numerical analysis, it is found that the effect of the housing structural flexibility significantly reduces the rotor critical speed and onset speed of instability.

• Journal of Nutrition and Health
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• v.35 no.9
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• pp.962-969
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• 2002

This study examined the effect of calcium supplementation and exercise on bone mineral density (BMD) and general characteristics, dietary intake and biochemical measurements for 45 healthy middle-aged women (40-57 years). Subjects were divided in to 4 groups; control group (G1), exercise group (G2), calcium supplementation group (G3), and calcium supplementation with exercise group (G4). The subjects were 45.8$\pm$ 0.66 years old. BMI(kg/$m^2$) was 23.31 $\pm$ 0.63 in Gl group, 22.92 $\pm$ 0.51 in G2 group, 23.64 $\pm$ 0.61 in G3 group, 23.40 $\pm$ 0.37 in G4 group, and BMI of all groups were in normal value. Energy intake was 1332.28㎉/day, 60% of RDA, so that may be unbalance of micronutrients. Especially, calcium intake was 62.8% of RDA that was very low level. Osteocalcine was not statistically significant but calcium supplementation group (G3) be showed increase. BMD was usually decreased by Aging, but in this study was increased in the all group, except control group. It showed increase of BMD for calcium supplementation and/or exercise. Overall results indicate that calcium supplementation and/or exercise increased BMD of middle-aged women, but long-term calcium supplementation and exercise will be able to more effect.(Korean J Nutrition 35(9) : 962~969, 2002)

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.22-29
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• 2011

Critical speed of high thrust liquid rocket engine turbopump is obtained through a rotordynamic analysis and a unloaded turbopump test is peformed for validation of the numerical model. The first critical speed predicted by the numerical analysis is correlated well with the test result for the bearing unloaded rotor condition only considering mass unbalance load. Using the previous rotordynamic model, critical speed variation is estimated as a function of varied bearing stiffness due to pump and turbine radial loads with relative angle difference. From the numerical analysis, it is found that the relative angle difference of pump and turbine radial loads greatly affects the critical speed. However, additional axial load reduces the effect derived from the relative angle difference of radial loads.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.05a
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• pp.65-66
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• 2010

To improve the gear noise quality, gear tooth grinding machine are widely used in automotive industry. While using the gear profile grinding machine to improve the gear tooth quality of the transmission, several defects such as chattering, tooth waves that cause the gear noise occasionally happened. But it is very difficult to solve that problem, because there is no one who knows the setting up the optimal grinding condition appropriately. The abnormal manufacturing conditions which make the gear noise make the engineer to spend a lot of time, effort, and money. Due to demands for solving the serious abnormal gear noise happened in the new FF 6th stage automatic transmission in the mass product stage, the vibration checking process in the worm wheel axis, work rotation and fixed axis of the grinding machine were adapted to find the root causes. As a result, gear profile wave are affected by the work rotation axis's unbalance which is caused by worm wheel feeding speed. And a primary and the secondary grinding feeding speed, cutting oil, work fixed forces are also proved as the important factors. After setting up the grinding condition reported in this paper, it was adapted successfully to the grinding machine to manufacture the new FF 6th speed automatic transmissions' output gear. The gear noise was dramatically disappeared and the process and results will offer good guides to the engineers who manufacture the gear with the grinding machine.

• Journal of Advanced Marine Engineering and Technology
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• v.38 no.3
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• pp.253-261
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• 2014

In this paper, vibration analysis of power differential gear train for 2.5MW wind turbine system is analyzed. which system is composed of two planetary gear set, one helical gear set and main shaft that connected by flange. Planetary gear set, helical gear set, main shaft are modeled in MASTA program and housing, torque arm, carrier, flange components are modeling by finite element method. Each models are combined by component mode superposition. To analysis of natural vibration characteristic about 2.5MW wind turbine gear train was performed and check about critical speed with wind load, mass unbalance, angle misalignment excitation frequency.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.7
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• pp.688-694
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• 2008

A rotordynamic analysis is performed for a high thrust class liquid rocket engine turbopump considering the dynamic characteristics of ball bearings and pump noncontact seals. Complex eigenvalue problems are solved to predict the rotating natural frequencies and damping ratios as a function of rotating speeds. Synchronous rotor mass unbalance response and time transient response analyses are also performed to figure out the rotor critical speed and the onset speed of instability. From the numerical analysis, it is found that the rear bearing stiffness is most important parameter for the critical speed and instability because the 1st mode is turbine side shaft bending mode. The pump seal effect on the critical speed is enlarged as the rear bearing stiffness decreases and the front bearing stiffness increases.

• Journal of Haehwa Medicine
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• v.9 no.2
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• pp.251-268
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• 2001

We arrived at the following conclusion after we have studied crohn's disease through the literatures of western and oriental medicine. 1. Crohn's disease has a characteristic of granulomatous necrosis and cicatricial inflammation which is called by segmental enteritis, granulomatous enteritis. This falls under the category of "Diarrhea", "Dysentery" and is similar to "small intestinal diarrhea", "acute temesmus", "splenic diarrhea" in oriental medicine. 2. In western medicine, the cause of crohn's disease indefinites, but it is presumed immunological unbalance of alimentary canal. In oriental medicine, it is summarized as the abnormal ascending and descending circulation of stomach and splenic energies, the hepatic stagnation, being the lower part of cleaning qi by exogenous disease, dyspeptic convulsion. 3. The presenting symptoms of crohn's disease are intermittent chronic diarrhea, fever, weight loss, abdominal spastic pain or abdominal discomfort. When anyone has a abdominal mass, a rectal abcess, and a rectal constriction by physical examination, we can doubt crohn's disease. 4. The methods of western medical treatment are a suppression of intestinal toxic contents and inflammatory mediator, a supply of nutritive substanceus to intestinal epithelial cell. Oriental medical treatments of these are "inducing diuresis", "warming kidney to reinforce yang", "nourishing qi to invigorate spleen", "eliminatin dampness by cooling" according to syndrome differentiations. As mentioned above, we can confirm possibility of oriental medical treatment that induces recovery of immunologic control function and we need advanced experiment, study, and clinical approach.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.7
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• pp.665-671
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• 2010

To improve the gear noise quality, gear tooth grinding machine are widely used in automotive industry. While using the gear profile grinding machine to improve the gear tooth quality of the transmission, several defects such as chattering, tooth waves that cause the gear noise occasionally happened. But it is very difficult to solve that problem, because there is no one who knows the setting up the optimal grinding condition appropriately. The abnormal manufacturing conditions which make the gear noise make the engineer to spend a lot of time, effort, and money. Due to demands for solving the serious abnormal gear noise happened in the automatic transmission in the mass product stage, the vibration checking process in the worm wheel axis, work rotation and fixed axis of the grinding machine were adapted to find the root causes. As a result, gear profile wave are affected by the work rotation axis's unbalance which is caused by worm wheel feeding speed. And a primary and the secondary grinding feeding speed, cutting oil, work fixed forces are also proved as the important factors. After setting up the grinding condition reported in this paper, it was adapted successfully to the grinding machine to manufacture the new automatic transmissions' gear. The gear noise was dramatically disappeared and the process and the results will offer good guides to the engineers who manufacture the gear with the grinding machine.

• Journal of the Korean Society of Propulsion Engineers
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• v.16 no.4
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• pp.42-49
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• 2012

Critical speed of high thrust liquid rocket engine turbopump is obtained through a rotordynamic analysis and a unloaded turbopump test is peformed for validation of the numerical model. The first critical speed predicted by the numerical analysis is correlated well with the test result for the bearing unloaded rotor condition only considering mass unbalance load. Using the previous rotordynamic model, critical speed variation is estimated as a function of varied bearing stiffness due to pump and turbine radial loads with relative angle difference. From the numerical analysis, it is found that the relative angle difference of pump and turbine radial loads greatly affects the critical speed. However, additional axial load reduces the effect derived from the relative angle difference of radial loads.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.6
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• pp.438-445
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• 2019

In this paper, we present a new approach to extract the g-sensitivity scale-factor error for a MEMS gyroscope. MEMS gyroscopes, based on the use of both angular momentum and the Coriolis effect, have a g-sensitivity error due to mass unbalance. Generally, the g-sensitivity error is not considered in general use of gyroscopes, but it deserves our attention if we are to develop for tactical class performance and reliability. The g-sensitivity error during vehicle flight increases navigation error; so it must be analyzed and compensated for the use of MEMS IMU for high dynamics vehicle systems. Therefore, we analyzed how to extract the g-sensitivity scale-factor error from the inertial sensor error model. Furthermore we propose a new method to extract the g-sensitivity error using flight motion simulator. We verified our proposed method with experimental results.