• Proceedings of the KSME Conference
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• 대한기계학회 2003년도 추계학술대회
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• pp.986-991
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• 2003

A turbulent wake generated by a cylinder in nozzle contraction affects to the jet flow characteristics. In this study, a computational work to investigate the effect of the turbulent wake on two-dimensional subsonic jet was carried out with three different kinds of nozzle. Computations are applied to the two-dimensional unsteady, Navier-Stokes equations. Several kinds of turbulent models and wall functions are employed to validate the computational predictions. It was known that the wake flow enhanced the spread of the jet flow, compared with no wake flow condition. It was also found that the jet core is shortened by the wake flow developed from a control cylinder.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2005년도 연구개발 발표회 논문집
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• pp.441-447
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• 2005

The present study is aimed at understanding the flow physics associated with a safety valve applied to LNG ship engines. One-dimensional gasdynamic analyses and axisymmetric, compressible Navier-Stokes computations have been carried out to provide a qualitative and quantitative knowledge base for an effective design of the safety valve. Gasdynamic forces and thrust coefficients are obtained regarding a change in chamber pressure and distance between the nozzle exit and valve sheet which are major parameters to offer a variation in the flow feature. The present results show that the control of the passage area between the nozzle exit and valve sheet can attenuate the strength of shockwave generated in front of the valve sheet, which causes harm to stable system operation.

• The Journal of Internal Korean Medicine
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• 제29권3호
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• pp.582-594
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• 2008

Objective : The purpose of our study was to investigate the effect of JinlnWhaChul-tang-ga-wasong (JIN) on NDEA-induced liver tumorigenesis. Materials and Methods : We investigated the possible protective effects of Jininwhachul-tang-ga-wasong (JIN) as an anticancer against NDEA-induced liver injury in mice. Experimental mice were classified into 3 groups; normal, saline administered group (control group), and JIN extract (0.15g/kg/every other day) administered group (JIN group) after being injected with NDEA over 12 weeks. We examined the state of differentiation of these tumors and the effects of JIN after 6 weeks. To confirm the induction of apoptosis, the cells were analyzed by terminal deorynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, acridine orange staining and flow cytometric analysis. To investigate inhibitory effect on the expression of COX-2 by JIN, we performed COX-2 immunohistochemistry and reverse transcription polymerase chain reaction analysis. Results : Body weights significantly decreased in the control and JIN groups compared with the normal group. The levels of cholesterol, hemoglobin and testosterone decreased in the control compared with the normal group. The level of estradiol significantly increased in the control compared with the normal group. The control group reacted with TUNEL assay more than the normal and JIN groups. Upon naked eye, light and electron microscopic examination, JIN improved the morphological and histopathological changes of the liver caused by NDEA-induced hepatic neoplasm. COX-2 immunoreactivity decreased in the JIN group compared with the control group, mRNA expression of the control group was greater than the normal and JIN groups. Conclusion : these results suggest the possibility that JIN may exert an anti-tumor effect on NDEA-induced liver tumorigenesis.

• Transactions of the Korean Society of Automotive Engineers
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• 제9권2호
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• pp.192-201
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• 2001

Analyzing internal structure, flow rate and dynamic behavior characteristics of electronically controlled shock absorber, damping performance limit is identified to comprise the two reciprocal characteristics of ride comfort and handling safety. Regardless of its lower performance than the active suspension control system, the semi-active suspension control system has been taking interest because of its absolutely higher performance than passive suspension system. Since the pervious studies have been concentrated mostly on analytic aspect and survey on the internal structure of the shock absorber remain insufficient, the main discourse of this paper is focused on analyzing the nonlinear shock absorber which varies the damping force of semi-active suspension system and the dynamic characteristics of the solenoid valve, a sort of pressure valve, and proposing the design factors of importance.

• The Journal of Internal Korean Medicine
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• 제27권1호
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• pp.114-125
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• 2006

objective : The purpose of this research is to examine the effects of Scutellaria Radix(SR) extract on immune cells and cytokines in ovalbumin(OVA)-induced asthmatic mice. Methods : In vivo, C57BL/6 mice were sensitized and handicapped by OVA for 9 weeks. In this experiment, one group was not treated, and the other group was treated with SR extract for six weeks(five times per week) and analyzed by ELISA and flow cytometer. Results : In vivo, there were significant decreases in eosinophils, IL-4, IL-13 in BALF (bronchoalveolar lavage fluid) compared with that of control group. However,$IFN{\gamma}$ in the SR group increased significantly compared with that of control group. Additionally, the population of $CD3e^-/CCR3^+,\;CD69^+/CD3e^+,\;IgE^+/B220^+,\;CD11b^+/Gr-1^+$ cells in the SR group decreased compared with that of control group. conclusion : The results of this study support a role for SR as an effective treatment for asthma in its experimental success in significantly decreasing inflammation and asthma reactions, and in increasing $IFN{\gamma}$, Which helps prevent such reactions.

• Journal of Digital Convergence
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• 제15권2호
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• pp.121-133
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• 2017

The propose of study is to examine the characteristics of companies with high possibility to form an internal control weakness using forecasting model. This study use the actual listed/unlisted companies' data from K_financial institution. The first conclusion is that discriminant model is more valid than logit model to predict internal control weak companies. A discriminant model for predicting the vulnerability of internal control has high classification accuracy and has low the Type II error that is incorrectly classifying vulnerable companies to normal companies. The second conclusion is that the characteristic of weak internal control companies have a low credit rating, low asset soundness assessment, high delinquency rates, lower operating cash flow, high debt ratios, and minus operating profit to the net sales ratio. As not only a case of listed companies but unlisted companies which did not occur in previous studies are extended in this study, research results including the forecasting model can be used as a predictive tool of financial institutions predicting companies with high potential internal control weakness to prevent asset losses.

• Journal of Advanced Marine Engineering and Technology
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• 제26권3호
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• pp.299-306
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• 2002

The load frequency control(LFC) of power system is one of important subjects in view of system operation and control. That is, even though the rapid load disturbances are applied to the given power system, the stable and reliable power should be supplied to the users, converging unconditionally and rapidly the frequency deviations and the tie-line power flow ones of each area into allowable boundary limits. Nonetheless of such needs, if the internal parameter perturbation and the sudden load variation are given, the unstable phenomena of power systems can be often brought out because of the large frequency deviation and the unsuppressible power line one. So, an optimal modulation controller for UC of multi-area power system is designed by a recursive algorithm that determines the state weighting matrix Q of a linear quadratic performance criterion. The optimal modulation controller is based on optimal control and can obtain the exact dynamic response of the UC of multi-area power system in the time domain. The performances of the resultant optimal modulation control, that is, the steady-state deviations of frequency and tie-line power flow and the related dynamics, were investigated and analyzed in detail by being applied to the UC of multi-area power system in the perturbations of predetermined internal parameters. Through the simulation results tried variously in this paper for disturbance of stepwise load changes, the superiorities of the proposed optimal modulation controller in robustness and stability were proved.

• Journal of KSNVE
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• 제10권2호
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• pp.280-290
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• 2000

The paper deals with vibration suppression and dynamic stability of a vertical cantilevered pipe conveying an internal flowing fluid and having an attached mass. Real pipe systems may have some valves or mechanical attached parts, which can be regarded as attached lumped masses. The effect of attached mass on the dynamic stability of a cantilevered pipe conveying fluid is investigated for different locations and magnitudes of the attached mass. The flow rate was controlled through motor pump output and measured by a flow meter. Experimental resutls in the vicinity of flutter fluid velocity were compared with theoretical predictions. It has been found that the experimental results are in substantial agreement with the theoretical predictions. Finally, in order to suppress the vibration of the pipe subjected to a disturbance, and control technique using an internal flowing fluid is introduced.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• 제17권12호
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• pp.1223-1229
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• 2007

Flow traveling over a cavity opening forms a vortex due to unstable shear layer and induces an aerodynamic pressure excitation from the diffusion of the vortex convecting out of the trailing edge of the opening. The interaction between the excitation force and the cavity response sustains resonance in the resonator(cavity) and locked-in vortex shedding at the leading edge of the opening. The aerodynamic excitation force can be described from the diffusion of the vortex over the trailing edge and the level of its diffusivity is related to the strength of vorticity seeded at the leading edge. In this study, the control scheme of the internal pressure oscillation was proposed from regulating the vorticity at the leading edge by use of an oscillating spoiler. It was found that the relative motion between the spoiler and the air mass at the cavity opening influenced vorticity strength and the control was achieved by direct feedback of the cavity pressure fluctuation to the actuator.

• The Journal of Korean Medicine
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• 제19권1호
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• pp.251-270
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• 1998

The effects of Gamigunshimtang on the isolated perfused ischemic heart in rats, heart rates, left ventricular pressure, cardiac blood flow and cardiotoxicity were stu.died in H9C2 myoblast cell, myocardial slice culture The results were as follows: 1. The administration of Gamigunshimtang to the rat recovered effectively heart rate, left ventricular pressure and flow rate from the experimental ischemia in perfused rat heart. The release of lactic dehydrogenase after the ischemia also decreased compared to the control group. 2. The administration of Gamigunshimtang to H9C2 myoblast culture enhanced the cell proliferation and protected against doxorubicin and allylamine induced release of the lactic dehydrogenase into the culture medium. It also protected effectively against doxorubicin and allylamine induced decrease of Ca ATPase activity and the increase of NADPH-cytochrome C reductase activity in the microsome. 3. The administration of Gamigunshimtang to the rat myocardial slice culture protected effectively against doxorubicin and allylamine induced decreases of protein synthesis and ATP content, and increases of cvtosolic enzyme, creatin kinase into the medium and lipid peroxidation.