• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.380-384
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• 2010

A disturbance flow at piping bands and discontinuous regions such as a valve, a header has a intense broadband internal pressure field and a sound field which are propagated through the piping system The fields becomes the source of a vibration of this piping system. Intense broadband disturbance flow at a discontinuous region such as elbows, valves or headers generates an acoustical pulsation. The pulsation becomes the source of structural vibration at the piping system. If it coincides with the natural frequency of the pipe system, excessive vibration results. High-level vibration due to the pressure pulsation affects the reliability of the plant piping system. This paper discusses the high vibration and the branch vent pipe's failure of condensate-water supply piping system due to the effect of acoustical pulsations by flow turbulence from the flow control valves of globe type in a power site.

• 한국가시화정보학회:학술대회논문집
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• 2005.12a
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• pp.111-116
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• 2005

An automobile engine has the Positive Crankcase Ventilation system (PCV system) for preventing air pollution as the environmental problem is important In this system, a PCV valve is the most important component to control the flow rate of Blowby gas which is generated by various engine powers. But, in the working place, the design of a PCV valve is very difficult because of interaction between fluid and solid motions. In this study, we investigated fluid flow characteristics using re-meshing method of a CFD technique to simulate spool behavior. As the results, a spool is periodically oscillated with time and is largely oscillated in proportion to the differential pressure between inlet and outlet. And, although the velocity at the orifice increases with the differential pressure, the flow rate of the outlet decreases. This research may give PCV designers visual flow information to help them

• Journal of computational fluids engineering
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• v.14 no.1
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• pp.78-85
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• 2009

A combined theoretical and numerical study is conducted to design a slit nozzle for large-area liquid coating. The objectives are to guarantee the uniformity in the injected flow and to provide the capability of explicit control of flow rate. The woking fluid is a dilute aqueous solution containing single-walled carbon nanotubes and its low viscosity and the presence of dispersed materials pose technical hurdles. A theoretical analysis leads to a guideline for the geometric design of a slit nozzle. The CFD-based numerical experiment is employed as a verification tool. A new flow passage unit, connected to the nozzle chamber, is proposed to permit the control of flow rate by using the commodity pressurizer. The numerical results confirm the feasibility of this idea. The optimal geometry of internal structure of the nozzle has been searched for numerically and the related issues are discussed.

• The Journal of Internal Korean Medicine
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• v.35 no.1
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• pp.24-36
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• 2014

Objectives : This study was performed to evaluate the effects of moxibustion on cerebral blood flow, peripheral blood flow and blood pressure. Methods : We designed a randomized, cross-over study that included 20 healthy, male volunteers who were randomly assigned to one of two groups (the moxibustion group or the control group). The initial trial was followed by a washout period of one week before the groups were switched and the trial repeated. The cerebral blood flow and peripheral blood flow of the volunteers in both groups were measured by mean velocity (Vm), peak systolic velocity (Vs), pulsatility index (PI), perfusion units (PU) and mean blood pressure (BP) before the intervention (baseline), 30 minutes after the intervention, and again 60 minutes after the intervention. Results : 1. The Vm increased significantly in the moxibustion group. The Vs also constantly increased in moxibustion group, but there was no significant difference. 2. The PI decreased significantly in the control group at 0-30 minutes and in the moxibustion group at 30-60 minutes. 3. The PU constantly decreased in moxibustion group. In control group, the PU decreased at 30 minutes and increased slightly at 60 minutes. 4. The mean blood pressure did not show any significant difference between the two groups. Conclusions : This study shows that moxibustion at CV12 increased the cerebral blood flow. Based on this result, we can suggest that moxibustion at CV12 might be helpful in improving the functional recovery of stroke patients. However, further research needs to be conducted on a larger numbers of subjects in order to confirm these effects.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3044-3050
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• 2015

The purpose of this study is to analyze the performance of the flow control oil pump for automatic transmission. The numerical model for analysis the performance of the flow control oil pump was develop and the characteristics of the internal flow, discharge flow rate, displacement of outer ring, driving torque, generation of cavitation was investigated according to rotating speed. As a result, the cavitation generation increased as the rotating speed increased. The volumetric efficiency was 90% for 2200 rpm and it decreased rapidly, then it decreased about 81% for 5000 rpm. Besides, the cavitation generation was 20%~30% for inlet of suction part, but it reduced below 13% owing to the compression. However, it shows higher cavitation generation for high rotating speed like 5000 rpm.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.553-558
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• 2011

This study have goal with conceptual design for offshore structures of high pressure drop control valve for localization valve for development accomplished with flow analysis based on provision of ANSI B16.34, ANSI B16.10, ANSI B16.25. In order to localize the Offshore structures high pressure drop control valve. This study is numerical analysis for zambil offshore project of high pressure drop control valve. The solver which ANSYS workbench used for offshore structures analysis. The working fluids assumed the glycerin(C3H8O3). The structural analysis used ANSYS which is a commercial code. Stress analysis result of internal pressure in valve showed lower than yield strength. This is expect to need more detail design and verification for stem and disk structure. In this study a multi-disk of high pressure drop control valve is designed and manufactured. Then, the flow rate and high pressure dorp of fluids flowing in the high pressure drop control valve is CAE. So, this system can be easily substituted for the existing zambil offshore project system. Finally, safety estimation for trim design of high pressure drop control valve for offshore structures.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.314-322
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• 2003

Pipe cooling method is widely used for reduction of hydration heat and control of cracking in mass concrete structures. However, in order to effectively apply pipe cooling systems to concrete structures, the coefficient of flow convection relating the thermal transfer between inner stream of pipe and concrete must be estimated. In this study, a device measuring the coefficient of flow convection was developed. Since a variation of thermal distribution caused by pipe cooling has a direct effect on internal forced flows, the developed testing device is based on the internal forced flow concept. Influencing factors on the coefficient of flow convection are mainly flow velocity, pipe diameter and thickness, and pipe material. Using experimental results from the developed device, the coefficient of flow convection was calculated. Finally, a general prediction model was proposed by theoretical procedures. The proposed prediction model is able to estimate the coefficient of flow convection with flow velocity and material properties of pipe. From comparison with experimental results, the coefficient of flow convection by this model was well agreed with those by experimental results.

• The Journal of Internal Korean Medicine
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• v.20 no.1
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• pp.222-231
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• 1999

Uwhangchungsimwon(UC) has been used in the treatment of a wide variety of conditions including stroke, hypertension, arteriosclerosis, autonomic imbalance, mental instablity, etc in Korean traditional hospitals, In particular it is often initialy chosen for emergency care of acute stroke. The aim of this study was to evaluate the effect of UC on cerebral hemodynamics. Using transcranial Doppler ultrasound, we studied changes of mean flow velocity and pulsatility index(PI) of middle cerebral arteries (MCAs) from 11 health young volunteers who were administrated with 1 pill UC and 11 health controls who were not. We obtained hypercapnia with breath-holding and evaluated cerebrovascular reactivity with breath-holding index(BHI). Systolic blood pressure, diastolic blood pressure, and heart rate were measured using ambulatory blood pressure monitoring(ABPM). In UC administration group, the evaluation was performed during basal condition. and repeated at 20, 40, and 60 min after administration. In controls, the evaluation was performed at corresponding time intervals. Mean flow velocity in middle cerebral artery, systolic blood pressure, diastolic blood pressure, and heart rate did not change during the observation period and were not different between these two groups. However, administration of UC was associated with decreases in PI by $3.6{\sim}12.4%$ in BHI by $17.9{\sim}24.8%$ compared with pre-administration period. Decreases in PI and BHI with UC were significantly different compared with control group (p<0.05). These results indicate that UC decreases PI and BHI in cerebral artery, which is due to a dilation of cerebral resistance vessels.

• The Journal of Internal Korean Medicine
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• v.19 no.1
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• pp.157-167
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• 1998

Background and Purpose : Cerebrovascular reactivity(CVR) can be estimated by measuring the change of cerebral blood flow that occurs during vasostimulation. To estimate the cerebrovascular reactivity, we investigated the change of flow velocity of the middle cerebral artery(MCA) during hyperventilation and hypoventilation with the transcranial doppler. So we studied whether the CVR measured by this method could show a significant difference between the normal and the cerebral infarction subjects and whether the CVR may decrease with age in normal subjects. Methods : Using transcranial doppler, we measured the mean velocity(Vm), the pulsatility index(P.I.) at the resting state, the end of breath-holding and the end of hyperventilation in 36 normal and 10 cerebral infarction subjects, so we calculated the percentile change of mean velocity(%${\Delta}$Vm) and P.I.(%${\Delta}$P.I.) after the vasostimulation. We estimated the change of Vm, P.I., %${\Delta}$Vm and %${\Delta}$P.I. by the age group and compared those parameters between the age-matched normal control and cerebral infarction subjects. Results : The Vm in MCA significantly decreased with age(p<0.05), but there was no significant difference in Vm and P.I. between normal and cerebral infarction subjects. The %${\Delta}$Vm and %${\Delta}$P.I. in response to hyperventilation significantly decreased with age in MCA and there was significant difference in $%{\Delta}Vm$ of MCA after breath-holding between the normal and cerebral infarction subjects. Conclusion : The breath-holding and hyperventilation tests could be non-invasive and useful methods in estimation of the cerebrovascular reactivity and could be applied in the basal and follow-up evaluation of the cerebrovascular reserve of the ischemic stroke patients.

• Tuberculosis and Respiratory Diseases
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• v.74 no.6
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• pp.264-268
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• 2013

Background: Idiopathic pulmonary fibrosis (IPF) is a lethal pulmonary fibrotic disease. In general, the exaggerated activation of the coagulation cascade has been observed during initiation or maintenance of the fibrotic disease. In our recent study, immunohistochemical expression of protease-activated receptor-2 (PAR-2), which plays a key role in coagulation cascade, was observed in surgical specimen of IPF patients, and associated with poor clinical outcome. The aim of this study was to evaluate the overexpression of PAR-2 in inflammatory cells from peripheral blood and bronchoalveolar lavage fluid in IPF patients. Methods: From May 2011 to March 2012, IPF patients and controls were enrolled in Seoul National University Hospital. Peripheral blood and bronchoalveolar lavage fluid were collected for analysis of PAR-2 expression. Flow cytometry and reverse transcription polymerase chain reaction were used for PAR-2 receptor and mRNA assessment. Results: Twelve IPF patients and 14 controls were included in this study. Among them, flow cytometry analysis was conducted from 26 peripheral blood (patient group, 11; control group, 13) and 7 bronchoalveolar lavage fluid (patient group, 5; control group, 2). The expression of PAR-2 receptor was not different between patient and control groups (p=0.074). Among all 24 population, PAR-2 mRNA assessment was performed in 19 persons (patient group, 10; control group, 9). The mRNA expression of PAR-2 was not significant different (p=0.633). Conclusion: In IPF patients, PAR-2 receptor and mRNA expression were not different from control group.