• Journal of the Korean Electrochemical Society
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• v.8 no.4
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• pp.155-161
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• 2005

In this paper, commercial CFD program FLUENT v5.3 is used for simulation of MCFC stack. Besides using conservation equations included in FLUENT by default, mass change, mole fraction change and heat added or removed due to electrochemical reactions and water gas shift reaction are considered by adding several equations using user defined function. The stacks calculated are 6 and 25 kW class coflow stack which are composed of 20 and 40 unit cells respectively. Simulation results showed that pressure drop took place in the direction of gas flow, and the pressure drop of cathode side is more larger than that of anode side. And the velocity of cathode gas decreased along with the gas flow direction, but the velocity of anode gas increased because of the mass and volume changes by the chemical reactions in each electrodes. Simulated temperature profile of the stack tended to increase along with the gas flow direction and it showed similar results with the experimental data. Water gas shift reaction was endothermic at the gas inlet side but it was exothermic at the outlet side of electrode respectively. Therefore water gas shift reaction played a role in increasing temperature difference between inlet and outlet side of stack. This results suggests that the simulation of large scale commercial stacks need to consider water gas shift reaction.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.209-229
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• 2001

Simultaneous field measurements of short-period and long-period waves were made at five stations inside or outside Okkye Harbor, which is located in the east coast of Korea. Based on the measured data, spacial and temporal variations of the long-period wave energy were examined. Three smoothing methods were examined for the spectral estimates: fixed interval averaging method, incremental interval averaging method, and moving averaging method. It was shown that a proper smoothing method should be chosen depending on the period of first resonant mode and the length of data being used. By comparing the results obtained using the long-term data with those obtained using two-day data, we showed that it is necessary to analyze the data of calm seas and storm seas separately. The Helmholtz resonant period in Okkye Harbor was found to be about 9.6 minutes with its relative amplification ratio of 9 to 10, and local amplifications were apparent at the periods of 1.2 to 1.3 minutes and 0.7 minute. During calm seas, both at the harbor entrance and inside the harbor the energy of the waves of 9 minutes or longer period was larger than the infra-gravity wave energy by more than 100 times. However, during storm seas the energy level was very high all over the period band, and local amplification was larger than that during calm seas by more than 100 times, especially inside the harbor, Finally it was shown that the energies of the Helmholtz resonant mode and the infra-gravity waves of 1 to 2 minutes are proportional to the storm wave height.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.1
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• pp.7-14
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• 1995

As a part of the multidisciplinary oceanographic study for the productivity enhancement in Deukryang Bay, temperature and salinity were observed from 1992 through 1993. From the results, only the data in summer of two years are compared. Owing to the contrary meteorolgical conditions in both summers both of temperature and salinity had the patterns of horizontal distributions quite different from each other. In 1992 with low precipitation, there was a tendency of temperature increase and salinity decrease from the bay mouth towards the bay head. In 1993 when the air temperature was abnormally low, isotherms and isotherms tended to be parallel to the local u3s of the bay where the warmer and less saline water distributed along the western coast. Reduced solar radiation and increase in the relative importance of the distribution of properties along the current that was parallel to the axis of the bay could be responsible for this result. Vertical structures of both temperature and salinity were dependent on the stirring effect of tidal current. Stratification was destroyed during the spring tide while it was formed during the neap tide.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.1
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• pp.762-768
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• 2015

This study examined the integration value of a low level pilotis space, a component that has been often selected as an essential planning element of the recent high-rise apartment complex, and compared the main outdoor unit spaces with that of an average integration value of the individual complexes. Furthermore, this study provided the preliminary data for the next level of research, which is the observation of the pilotis space usage behaviors and the frequency of utilization. The results of this present research are as follows. First, from the main outdoor unit spaces of the high-rise apartment complexes including the pilotis space, a 'complex entrance' or a 'plaza' space showed the highest integration value. Second, the spatial integration value of a pilotis space in a high-rise apartment complex was generally lower that of the integration value of other main outdoor units. Third, from the pilotis spaces of the high-rise apartment complex, those with a 'projecting entry access + pilotis addition type' that did not provide an access to the individual units, had the lowest space utilization rate by the inhabitants; thus, had a high likelihood of the spaces becoming used for illegitimate activities or becoming vacant.

• Journal of Chest Surgery
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• v.30 no.3
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• pp.263-269
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• 1997

From April 1987 to May 1996, 13 infants underwent a Norwood operation for complex congenital heart diseases including hypoplastic left heart syndrome (n : 7), mitral stenosis with small VSD and subaortic stenosis (n : 1), mitral atresia with ventricular septal defect, coarctation of aorta, and subaortic stenosis (n = 1), interrupted aortic arch with ventricular septal defect and subaortic stenosis (n : 1), tricuspid atresia with transposition of the great arteries (n = 1), and complex double-inlet left ventricle (n : 2). All patients without hypoplastic left heart syndrome were associated wit hypoplasia of ascending aorta and arch. Age at operation ranged from 3 days to 8.7 months (mean 60.6 $\pm$ 71.6 days, median 39 days). The operative mortality( < 30 days) was 46% (6 patients). Late mortality was 15% (2 patients). All operative deaths occured during the Erst 24 hours after the operation as a result of cardiopulmonary bypass weaning failure (5 patients) and sudden hemodynamic instability postoperatively (1 patient). Late death was due to aspiration pneumonia in two cases. There are 5 long-term survivals (39%). Three of them have undergone a two-stage repair with a modified Fontan operation in two and total cavopulmonary shunt in one at 12, 17, 4.5 months after Norwood procedure with no mortality. Two patients have entered a three-stage repair strategy by undergoing a bidirectional cavopulmonary shunt at 3 and 5.5 months after initial operation with 1 operative death. The actuarial survival rate for all patients at the first-stage operation, including hospital deaths and ate death was 30.8% at 1 year. In conclusion, the operative mortality of Norwood operation was relatively high compared to other operation for major cardiac anomalies, continuing experience will lead to an improvement in result.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.1
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• pp.68-80
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• 1984

Garolim Bay is not only important fishing ground but also expected area for the tidal power plant. The construction and operation of tidal power plant will make change the ecosystem of this bay. Therefore, the actual fisheries stocks should be precisely understood for the effect estimation and overall utilization of the bay after the construction of the tidal power plant. During the study period from January through December in 1981, forty-six adult fishes species, 3 species of fish egg and 25 fishes larvae species have occurred in the bay. Considering the result on monthly distribution of eggs and larvae, the inner area of the bay seems to be important as nursing ground of larvae spawned at the outside bay in winter, e. g., Ammodytes personatus, and Enedrias sp. This inner bay is also major spawning ground for many species spawning in spring and summer, e. g., Gobiidae, Konosirus punctatus, Engraulis japonica, etc. Taking into consideration the annual mean production for three years($1978{\sim}1980$), there are two major fishing seasons. The one is in May-June for Enedrias larvae stock, and the another in October-November for big eyed herring stock. For the mariculture stocks, short necked clam, oyster and laver are important species. After construction of the tidal power plant, the migratory species, i. e., larvae of Enedrias and Ammodytes personatus, Mugil cephalus, Konosirus punctatus, etc. will be directly damaged by the interuption of migration route. On the otter hand, the change of physico-chemical factors of seawater will also affect the ecosystem of the bay. Consequently, for the overall utilization of the bay after construction, the actual ecosystem including the fisheries stocks, must bs precisely revealed, and the mechanical designs, e. g., sluice position and its demension, should be also considered with these biological characters of the bay.

• Journal of Advanced Marine Engineering and Technology
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• v.40 no.4
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• pp.270-274
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• 2016

The effect of the rib angle-of-attack on heat transfer in the convergent channel with ${\vee}/{\wedge}$-shaped ribs was examined experimentally. Four differently angled ribs (a = $30^{\circ}$, $45^{\circ}$, $60^{\circ}$, and $90^{\circ}$) were placed to only the one sided wall. The ribbed wall was manufactured with a fixed rib height (e) of 10 mm and rib spacing (p)-to-height (e) ratio of 10. The convergent channel had a length of 1,000 mm and a cross-sectional areas of $100mm{\times}100mm$ at inlet and $50mm{\times}100mm$ at exit. The measurement was conducted for the Reynolds numbers ranging from 22,000 to 75,000. The results show that the Nusselt number is generally higher at higher Reynolds number and that an angle-of-attack of $45^{\circ}$ at the ${\wedge}$-shaped rib produces the greatest Nusselt number.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.2
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• pp.171-179
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• 2012

Cooling of hot sections, especially the turbine nozzle and rotor blades, has a significant impact on gas turbine performance. In this study, the influence of precooling of the cooling air on the performance of gas turbines and their combined cycle plants was investigated. A state-of-the-art F-class gas turbine was selected, and its design performance was deliberately simulated using detailed component models including turbine blade cooling. Off-design analysis was used to simulate changes in the operating conditions and performance of the gas turbines due to precooling of the cooling air. Thermodynamic and aerodynamic models were used to simulate the performance of the cooled nozzle and rotor blade. In the combined cycle plant, the heat rejected from the cooling air was recovered at the bottoming steam cycle to optimize the overall plant performance. With a 200K decrease of all cooling air stream, an almost 1.78% power upgrade due to increase in main gas flow and a 0.70 percent point efficiency decrease due to the fuel flow increase to maintain design turbine inlet temperature were predicted.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.324-329
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• 2020

The emergency evacuation support system provides a safe means of evacuation by preventing the inflow of smoke through the formation of a smoke shield curtain in fire situations and pressurizing fresh air to the inside of the smoke shield curtain. In this study, numerical analysis was performed to examine the effects of the hole size on the flow inside the smoke curtain. As the air supply size decreased, the flow rate through the air supply was formed relatively uniformly from the inlet to the outlet length of the emergency support system. In addition, the size of the air supply hole was more than 20 mm, the flow rate was very low near the outlet, so the air supply hole size should be smaller than 20 mm. In addition, the minor loss of the air supply hole was calculated to be K = 1.5 from the numerical results. Therefore, the proper design of an emergency evacuation support system is possible using the flow characteristics according to the size and minor loss of the air supply hole.

• Journal of Chest Surgery
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• v.30 no.1
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• pp.48-54
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• 1997

Between 1987 and 1995, eleven patients with severe chronic corrosive stenosis of the hypopharynx and esophagus underwent surgical restoration of digestive continuity at Inje University Seoul Palk Hospital. There were 7 male and 4 female patients aged from 21 to 47 years (mean, 34 years). The caustic material was acid in 6 patients and alkali in 5 patients. The esophagus was reconstructed using the right colon In 9 and left colon in 2. The cervical approach and the side of proximal anastomosis depended on the status of the pyriform slnus of the hypopharynx. In the neck, J-formed incision was made along the sternocleidomastoid muscle. The sternohyoid and thyrohyoid muscles were divided transversely to expose the thyroid cartilage. Hypopharyngeal opening for proximal anastomosis was made by reverse triangular formed resection of the thyroid cartilage after elevation of perichondrium. Immediately after operation, dysphagia and aspiration into trachea were common, so training of swallowing was required. Feeding gastrostomy was usually maintained for 3 months until restoration of swallowing function was confirmed . There was graft necrosis in 3 patients, who were treated with jejunal free graft. Revisional procedures for stenosis of cervical anastomosis in B patients consisted of widening of pharyngocecostomy site in 2 and resection of adhesive band in one. Return of normal swallowing assuring normal nutrition was obtained in 10 of 11 cases.