• 설비공학논문집
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• 제19권8호
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• pp.577-584
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• 2007

A variable-flow-rate balancing valve has been developed and optimized to apply to a distributor in a hot-water heating system. Fluid dynamic performance of the system was evaluated by comparing the results with the previous pressure difference control valve (PDCV) system. In view of the variations of pressure drop and flow rate according to the sequential closing of the control valves, the present system which is named "smart system distributor", is very stable without a certain flow rate concentration. The level of pressure drop variation is also low as compared with the previous system with a PDCV. In view of the occurrence of cavitation, the present system is quite superior to the previous system because the instantaneous pressures at all sections are much higher than the vapor pressure. On the other hand, the previous system has a possibility of cavitation when one or more control valves are closed.

• 한국유체기계학회 논문집
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• 제13권3호
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• pp.43-48
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• 2010

In this study rotordynamic characteristics of an air turbo-compressor (ATC) used in oxygen plant are analyzed and its operating-speed balancing is performed to solve the vibration trouble caused by rotor unbalance. Three dimensional model of the ATC rotor is completed and then analytical FE (finite element) model, which is verified by experimental modal testing, is developed. A rotordynamic analysis includes the critical map, Campbell diagram, and unbalance response, especially considering the pedestal housings supporting tilting pad bearings. A test run of operating-speed, using tilting-pad bearing of actual use, showed that the vibration level increased very sharply as approaching the rated speed. The operating-speed balancing specified by API 684 was carried out by using influence coefficient method. The results showed that the vibrations at the bearing pedestal housings represented good levels of 0.1 mm/s. From the test run and operating-speed balancing, the analytical results, that is, critical speeds are in good agreement with the test results and unbalance responses introducing the correction masses are similar to the as-is test responses in its aspect.

• Journal of Medicine and Life Science
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• 제17권1호
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• pp.16-20
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• 2020

Spontaneous hemopneumothorax is a rare disease, and it can cause life threatening condition. It is characterized by the accumulation of more than 400 mL of blood and air in the pleural cavity without any other apparent causes. A previously healthy 22-year-old female patient presented with acute chest pain and dyspnea. Chest X-ray and computed tomography revealed a massive hemopneumothorax in the left hemithorax. The images showed a completely collapsed left lung with right-sided tracheal deviation, several pleural adhesion bands, and fluid collection with air-fluid level. We emergently performed a closed thoracostomy, and then 560 mL of fresh bloods were initially drained. We considered an emergent video-assisted thoracoscopic surgery for pulmonary wedge resection and bleeding control because of the massive hemothorax. However, the patient's vital signs were stabilized after blood transfusion and supportive cares for re-expansion pulmonary edema. The patient discharged from the hospital on 11^th in-hospital day after removal of the chest tube, and there had not been any recurrence of the pneumothorax for 10 months. We suggest that treatment strategy should be decided upon individually based on the patient's condition and clinical course of the disease.

• 설비공학논문집
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• 제20권10호
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• pp.645-653
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• 2008

Spiral-jacketed thermal storage tanks can greatly simplify solar heating systems while maintaining the thermal performance at a similar level as conventional systems with an external heat exchanger. Proper design of the spiral-jacket flow path is essential to make the most of solar energy, and thus to maximize the thermal performance. In the present work, computational fluid dynamics (CFD) analysis was carried out for a spiral-jacketed storage tank installed in a solar heating demonstration system. The results of the CFD analysis showed a good agreement with experimentally determined thermal performance indices such as the acquired heat, collector efficiency, and mixed temperature in the storage tank. This verified CFD modelling approach can be a useful design tool in optimizing the shape of spiral-jacket flow path and the flow rate of circulating fluid for better performance.

• Journal of Chest Surgery
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• 제28권7호
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• pp.726-730
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• 1995

Congenital cystic adenomatoid malformation[CCAM of the lung is extremely rare. We have experienced an unusual case of congenital cystic adenomatoid malformation. The patient was 20-year-old male and had chest pain for 10 days. On simple chest x-ray and Thoracic CT scan, there was a large cystic mass surrounded with multiloculated round cysts with air fluid level on the right lower lobe of a lung. Right lower lobectomy was performed and the pathologic result was congenital cystic adenomatoid malformation.

• 한국농공학회논문집
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• 제55권6호
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• pp.135-144
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• 2013

Ventilation efficiency has an important role in agricultural facilities such as greenhouse and livestock house to keep internally optimum environmental condition. Age-of-air concept allows to assess the ventilation efficiency of an agricultural facility according to estimating the ability of fresh air supply and contaminants emission using LMA and LMR. Most of these methods use a tracer gas method which has some limitations in experiment like dealing unstable and invisible gas. Therefore, the aim of this study was to develop a straightforward method to calculate age-of-air values with CFD simulation which has the advantage of saving computational time and resources and these method can solve the limitations in experiment using tracer gas method. The main idea of LMA computation is to solve the passive scalar transport equation with the assumption that the production of the time scalar throughout the room is uniform. In case of LMR calculation, the transport of the time scalar was reversed compulsively using UDF. The methodology to validate the results of this study was established by comparing with preceding research that had performed a computing LMA and LMR value by laboratory experiments and CFD simulations using tracer gas. As a result, the error was presented similarly level of results of preceding research. Some big errors could be caused by stagnated area and incongruity turbulence model. while the computational time was reduced to almost one fourth of that by preceding research.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.183-190
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• 2002

In order to reduce NOx emissions in the 20kw class microturbines under development, the low NOx characteristics, as being an application to the lean premixed combustion technology, have been investigated. The study has been conducted at the conditions of high temperature and pressure. Air from a compressor with the temperature of 500K to 650K and the pressure of 0.3bar gauge to 0.7bar gauge, was supplied to the combustor through an air preheat-treatment. Sampling exhaust gases were measured at the immediate exit of the combustor. for the effect of temperature on NO and CO emissions. though NOx was increased, CO was decreased with increasing inlet air temperature. With increasing inlet air pressure, NOx and CO were increased also. NOx was decreased, but CO was increased with increasing inlet air mass flow rate. The test has been performed on the equivalent ratios of 0.10 to 0.25 in a lean region. NOx was increased with increasing equivalent ratios, but CO was decreased as an influence of flame temperature. In the very lean region of the equivalent ratio below 0.12, CO was increased suddenly, due to instability. As the results of this study, NOx and CO are found to be reduced to the similar level at the same time when operated at optimal conditions.

• 한국소음진동공학회논문집
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• 제17권2호
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• pp.168-176
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• 2007

The mixture sound speed in bubbly fluids is highly dispersive due to differences of the density and compressibility between bubbles and fluids. The dispersion range in bubbly fluids expands to a higher frequency than the resonance frequency of an air bubble. A theoretical model was developed to compute the reduction of radiation noise that is generated by a force applied on an infinite flat plate using a bubble layer as a compliant baffle. For evaluating the effectiveness of a bubble layer in reducing the structure-borne noise of an infinite elastic plate, the noise reduction levels for various parameters such as the thickness of bubble layers, the volume fractions and the distribution types of bubbly fluids are calculated numerically. The noise reduction effect of an air bubble layer on an infinite flat plate is considerable level and similar to the tendency of dispersion of bubbly fluids. It is recommended that the thickness of a bubble layer should be increased with keeping an appropriate volume fraction of an air bubble for the most effective reduction of the radiation noise.

• International Journal of Fluid Machinery and Systems
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• 제3권4호
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• pp.285-291
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• 2010

To provide required flow rates of cooling or circulating water properly, approach flow conditions of vertical pump systems should be in compliance with state of the art acceptance criteria. The direct inflow should be vortex free, with low pre-rotation and symmetric velocity distribution. Physical model investigations are common practice and the best tool of prediction to evaluate, to optimize and to document flow conditions inside intake structures for vertical pumping systems. Optimization steps should be accomplished with respect to installation costs and complexity on site. The report shows evaluation of various approach flow conditions inside a compact waste water pumping station. The focus is on the occurrence of free surface vortices and the evaluation of air entrainment for various water level and flow rates. The presentation of the results includes the description of the investigated intake structure, occurring flow problems and final recommendations.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 춘계학술대회논문집
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• pp.658-659
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• 2008

Numerical simulation is performed for a microdroplet deposition on the pre-patterned micro-structure. The liquid-air interface is tracked by level set method improved by incorporating the ghost fluid approach based on a sharp-interface representation. The method is further extended to treat the contact angle condition at an immersed solid surface. The present computation of a patterning process using microdroplet ejection demonstrates that the multiphase characteristics between the liquid-gas-solid phases can be used to overcome the patterning error.