• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.37 no.1
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• pp.9-18
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• 2013

Two-phase vapor-liquid flows exist in many shell and tube heat exchangers such as condensers, evaporators, and nuclear steam generators. To understand the fluid dynamic forces acting on a structure subjected to a two-phase flow, it is essential to obtain detailed information about the characteristics of a two-phase flow. The characteristics of a two-phase flow and the flow parameters were introduced, and then, an experiment was performed to evaluate the pressure loss in the tube bundles and the fluid-dynamic force acting on the cylinder owing to the pressure distribution. A two-phase flow was pre-mixed at the entrance of the test section, and the experiments were undertaken using a normal triangular array of cylinders subjected to a two-phase cross-flow. The pressure loss along the flow direction in the tube bundles was measured to calculate the two-phase friction multiplier, and the multiplier was compared with the analytical value. Furthermore, the circular distributions of the pressure on the cylinders were measured. Based on the distribution and the fundamental theory of two-phase flow, the effects of the void fraction and mass flux per unit area on the pressure coefficient and the drag coefficient were evaluated. The drag coefficient was calculated by integrating the measured pressure on the tube by a numerical method. It was found that for low mass fluxes, the measured two-phase friction multipliers agree well with the analytical results, and good agreement for the effect of the void fraction on the drag coefficients, as calculated by the measured pressure distributions, is shown qualitatively, as compared to the existing experimental results.

• Economic and Environmental Geology
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• v.35 no.5
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• pp.407-420
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• 2002

The Buddhist Triad Cave in Gunwi (National treasure No. 109) consists of porphyritic biotite granite, and it has been deteriorated into microorganic smears, white films, brown rusts, granular decay, color changes, and joints by the same weathering factors as rain, moisture, temperature variation and microorganic living. Main origin is probably the rain that leaks into the cave along joints in Palgongsan granite, and then its moisture grows many microorganism and is frozen over during winter. The granites around the cave regularly develop two NEE and NWW joint sets that are conjugate to be a joint system. The NEE set extends far away with narrow joint spacings and affects the leakage of the rains, and is divided into 4 joint zones, among which J$_{m}$ and J$_{3}$ immediately affect the leaking water into the cave. An extensional Joint, in northern wall of the cave, was formed by toppling of the block between J$_{m}$and J$_{3}$joint zones from widening the Jm aperture by roots of a big pine tree, and passes through the J$_{m}$joint zone. This bypass allows no circulation of small rain, but a good circulation of heavy rain from influx to the cave for a long pathway. Many Joints and cracks, in the ceiling near the cave entrance, immediately get through the J$_3$ joint zone, and have a good circulation of small rain 10 mm. Both J$_{m}$and J$_{3}$ joint zones are, therefore, chief influxes that cause leakage of the rains.

• Korean Journal of Environmental Agriculture
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• v.10 no.1
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• pp.51-57
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• 1991

Field experiments were carried out to evaluate the utility of water hyacinth(Eichhornia crassipes Solm-Laub) for purifyng sewage water in paddy fields of $247m^2$(75 Pyung). A field was lined with PVC film at a depth of 30cm and sewage water for 40 days. The results obtained with the use of water hyacinth in the sewage water are summarized as follows : 1. The Sodium linear dodecyl benzene sulfonate content of sewage water on the inlet was 6.33 ppm, themiddle point was 3.50 ppm and the outlet was 1.37 ppm. 2. With the use of water hyacinth in the sewage and the distilled water, the L.A.S. content were decreased from 7.3 and 4.0 to 0, respectively. 3. Sterillization with 70% ethyl alcohol at the roots of the water hyacinth was reduced the degradation effect of L.A.S. 4. The COD and $NH_4^+-N$ content of the sewage decreased from 107 and 32.7 ppm to 32.6 and 16.2 ppm, respectively and the P, Na and Cl content also were reduced.

• Korean Journal of Environmental Biology
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• v.17 no.3
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• pp.271-278
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• 1999

In order to clarify water quality, dynamics and structure of phytoplankton communities, and red tides, the present study was carried out monthly from July to September 1998 at 19 stations in Deukryang Bay. Water temperature varied from 24.$0^{\circ}C$ to 28.6$^{\circ}C$, and salinities ranged from 25.0$\textperthousand$ to 28.6$\textperthousand$. During red tides in July, chlorophyll-$\alpha$ contents were rather high in August, it showed that phytoplankton controlled primary production in this bay. Phytoplankton was composed of 89 diatoms, 19 dinoflagellates, and 3 silicoflagellates. Phytoplankton standing crops varied from a minimum of 1.3$\times$10$^4$cells/ι(Sept., St. 17) to a maximum of 3.8$\times$10$^{6}$ cells/ι (July, St. 10). Red tides occurred in July when the standing crops averaged 1.8$\times$10$^{6}$ cells/ι. Leading the causative organisms of red tide were Prorocentrun minimum in the upper bay, Chaetoceros curvisetus in the mouth and middle part of the bay, Ceratium furca and Thazassio- sira sp. around Nokdong Harbour. Concentration of nutrients such as nitrogen was high in the upper bay, during red tides, water temperatures varied from 23.8$^{\circ}C$ to 29.7$^{\circ}C$ and salinity were 23.l$\textperthousand$ to 27.0$\textperthousand$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.27 no.5
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• pp.515-528
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• 1994

China Coastal Water(CCW) appeared in the neighbouring seas of Cheju Island has been analyzed and the results are as follows: The water with salinity below $32.20\%0$ in the neighbouring seas of Cheju Island in summer is thought CCW. During the period from April 1985 to August 1986, salinity of more than $34.00\%0$ was appeared in the Cheju Strait during January to mid May, but it decreased gradually from late May. CCW with salinity below $32.20\%0$ appeared in the Cheju Strait in early July and disappeared in October. The mean thickness of CCW in the Cheju Strait was about 25m and CCW had an influence of up to about 50m depth. And stratification structure of the Cheju Strait in summer was halocline between the surface and 50m depth and homogeneous salinity layer below 50m depth. It seems that although CCW appears in the wide area of neighbouring seas surface of Cheju Island in summer, the core of this CCW which has the lowest salinity flows into the Cheju Strait from the western seas of Cheju Island. This CCW flows out the east through the central part of the Cheju Strait and then seems to be transported further in the form of eddy.

• Proceedings of the KOR-BRONCHOESO Conference
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• 1981.05a
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• pp.39.3-40
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• 1981

Concerning the pathogenesis of acquired cholesteatoma in attic, there has been postulated theories by immigration from the Shrapnell's portion of the tympanic membrane, posterosuperior quardrant of the deep meatal skin and invagination of the margin of the central perforation. Otherwise, squamous metaplasia of the epithelium lining the middle ear cleft has been supported as a possible cause of cholesteatoma. Clinically, there has been known of the facts that cholesteatoma is formed in the attic but the pathogenesis concerning the acquired cholesteatoma is not still exactly reported. Recently, authors analyzed 170 cases of cholesteatomatous middle ear performed the operation to the middle ear cleft. On the operation finding, when the primary focus of the cholesteatoma was in the attic, we observed two types of perforation, marginal and central perforation in the Shrapnell's portion, and retraction to the Prussak's space, bony defect on the Rivinus notch. Among 36 cases of the cholesteatoma, the perforation of the Shrapnell's portion are 5 cases. Bony defect on the Rivinus notch and marginal perforation on the posterosuperior quadrant of the Shrapnell's portion are 21 cases. Among these cases, 3 cases are combined with central perforation of the Shrapnell's portion. Conclusively, the reasons that cholesteatoma is favorable site in the attic: 1) Excretion of the inflammatory discharge in the attic is difficult because of the distance of the E-tube. 2) The Shrapnell's portion has less collagen fiber than the pars tensa and it is thin because the elastic fibers are rich in it. It is easy to retract within the Prussak's space to the cases of keratinizing hyperplasia. 3) The epidermis attached at the Rivinus notch of the superior portion on the Shrapnell's portion is invaginated through the destructed bony wall of the Rivinus notch and the margin of the tympanic membrane in the response to the keratinizing hyperplasia.

• KIPS Transactions on Computer and Communication Systems
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• v.5 no.7
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• pp.159-172
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• 2016

This paper presents a novel algorithm for searching evacuation paths in indoor disaster environments. The proposed method significantly improves the time complexity to find the paths to the evacuation exit by introducing a light-weight Disaster Evacuation Graph (DEG) for a building in terms of the size of the graph. With the DEG, the method also considers load balancing and bottleneck capacity of the paths to the evacuation exit simultaneously. The behavior of the algorithm consists of two phases: horizontal tiering (HT) and vertical tiering (VT). The HT phase finds a possible optimal path from anywhere of a specific floor to the evacuation stairs of the floor. Thus, after finishing the HT phases of all floors in parallel the VT phase begins to integrate all results from the previous HT phases to determine a evacuation path from anywhere of a floor to the safety zone of the building that could be the entrance or the roof of the building. It should be noted that the path produced by the algorithm. And, in order to define the range of graph to process, tiering scheme is used. In order to test the performance of the method, computing times and evacuation times are compared to the existing path searching algorithms. The result shows the proposed method is better than the existing algorithms in terms of the computing time and evacuation time. It is useful in a large-scale building to find the evacuation routes for evacuees quickly.