• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2009.11a
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• pp.395-398
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• 2009

Currently, a new generation of ducted fan UAVs (Unmanned Aerial Vehicles) is under development for a wide range of inspection, investigation and combat missions as well as for a variety of civil roles like traffic monitoring, meteorological studies, hazard mitigation etc. The current study presents extensive results obtained experimentally in order to investigate the tip clearance effects on performance characteristics of a ducted fan for small UAV systems. Three ducted fans having different tip clearance gap and with same rotor size were examined under three different yawed conditions of calibrated slanted hot-wire probe. Three dimensional velocity flow fields were measured from hub to tip at outlet of the ducted fan. The analysis of data were done by PLEAT (Phase locked Ensemble Averaging Technique) and three non-linear differential equations were solved simultaneously by using Newton -Rhapson numerical method. Flow field characteristics such as tip vortex and secondary flow were confirmed through axial, radial and tangential velocity contour plots. At the same time, the effects of tip clearance on axial thrust and input power were also investigated by using wind tunnel measurement system. For enhancing the performance of ducted fan, tip clearance level should be as small as possible.

• Nuclear Engineering and Technology
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• v.55 no.6
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• pp.1959-1965
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• 2023

The objective of this study was the establishment of clearance method that can ensure radiological safety and reasonably minimize radioactive waste when demolishing contaminated buildings at KRR-1&2. By reviewing Korean and international laws related to decommissioning, the method for clearance of contaminated buildings presented in this study is to first decontaminate the building and then conduct a radiological safety assessment, such as measuring residual radioactivity, to determine whether the radiation dose criteria for clearance are satisfied. The measurement results meet the radiation dose criteria, the contaminated buildings are regarded as clearance and can be converted into the general buildings. The demolition of the cleared buildings is carried out using conventional demolition methods. The waste generated during the demolition is classified as general construction waste and is disposed of according to relevant laws. The proposed method significantly optimized the number of samples analyzed and reduced the time and cost associated with the decommissioning. The established method will be applied to the ongoing decommissioning of contaminated buildings at KRR-1&2, and its application will be verified by regulatory bodies. The study suggests that this method could be used for the decommissioning of contaminated buildings at other Korean nuclear facilities in the future.

• Korean Journal of Applied Biomechanics
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• v.28 no.2
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• pp.79-85
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• 2018

Objective: This study aimed to create a strategic training method to enhance optimal athletic ability using information from 1H to 10H rhythmic units. Method: Top three world class athletes and three national winners of 110-m hurdle finals from the 2010 Daegu International Athletics Competition and 2017 National Athletics Championship, respectively, were selected. To analyze the kinematic variables, Dartfish 9.0 was used for two-dimensional analysis. Results: Regarding the interval time from the start to the finish line, the national athletes took less time during the pure acceleration phase (start to 1H) than the foreign athletes. The horizontal velocity increase was slower after 1H; the national athletes showed a lack of ability to accelerate at the interval phases. Moreover, the hurdle clearance time between phases was longer in the national athletes than in the foreign athletes and lacked consistency. Conclusion: The national athletes lacked the ability to accelerate at the transition, maximum rhythm, rhythm maintenance, and re-acceleration phases and showed a longer hurdle clearance time. If technical improvements and strategic training methods using rhythmic units are applied for hurdling motions, the national athlete's hurdling abilities, performance, and consistency could improve.

• Proceedings of KOSOMES biannual meeting
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• 2017.11a
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• pp.47-47
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• 2017

• The Journal of Internal Korean Medicine
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• v.1 no.1
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• pp.92-97
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• 1976

Upon feeding dried Ginseng to rats of either low-protein or high protein diet ethanol was administered intraperitoneally and disappearance rate blood alcohol was enzymatically measure. In terms of residual blood alcohol after a time lapse of 3.5 hours between intraperitonial administration and blood withdrawal neither ginseng nor ginseng plus 40% casein did improve the rate, of alcohol clearance but sexual difference was clearly demonstrated in favor of female rats. In the case of blood withdrawn only 2 hours after intraperitoneal injection of alcohol, the tendency of female superiority in alcohol clearance rate is demonstrated when a comparison is made among the groups fed with ginseng and this was particularly true is groups of rats fed with basal diet plus 1 percent ginseng residual blood ethanol being 15.4 mg/ml vs. 8.8 mg/ml. Liver homogenate alcohol dehydrogenase activity measured in terms of residual ethanol content after in vitro reaction on which a known amount of alcohol was added clearly demonstrated a male superiority in alcohol clearance.

• Journal of Physiology & Pathology in Korean Medicine
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• v.30 no.5
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• pp.347-354
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• 2016

This study evaluated the effects of Fructus Corni Officinalis water extract (FCE) on congnitive impairment and Aβ clearance induced by beta amyloid Aβ (1-42) injection in the hippocampus of rat. Aβ (1-42) was injected into the hippocampus using a Hamilton syringe and micropump (5 ㎍/5 ㎕, 1 ㎕/min, each hippocampus bilaterally). FCE was administered orally once a day (100, 250, 500 mg/kg) for 4 weeks after the Aβ (1-42) injection. The acquisition of learning and retention of memory were tested using the Morris water maze. Aβ accumulation and Aβ clearance in the hippocampus were observed using immunostaining. Aβ (1-42) level in plasma was confirmed using enzyme-linked immunosorbent assay (ELISA). FCE significantly shortened the escape latencies during acquisition training trials. FCE significantly increased the number of target heading to the platform site and significantly shortened the time for the 1^sttargetheadingduringtheretentiontesttrial.FCEsignificantlyattenuatedtheAβ accumulation in the hippocampus produced by Aβ (1-42) injection. FCE significantly increased LRP-1 expression around vessels in the hippocampus and Aβ (1-42) levels in plasma. The results suggest that FCE improved cognitive impairment by ameliorate Aβ clearance and Aβ accumulation in the hippocampus. FCE may be a beneficial herbal formulation in treating cognitive impairment including Alzheimer's disease.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.2_spc
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• pp.291-303
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• 2020

The Kori-Unit 1 nuclear power plant, which is scheduled to be decommissioned after permanent shutdown, is expected to generate large amounts of various types of radioactive waste during the decommissioning process. Among these, nuclear reactors and internal structures have high levels of radioactivity and the dismantled structure must have the proper size and weight on the primary side. During decommissioning, it is important to prepare an appropriate and efficient disposal method through analysis of the disposal status and the legal restrictions on wastes generated from the reactors and internal structures. Nuclear reactors and internal structures generate radioactive wastes of various levels, such as medium, very low, and clearance. A radiation evaluation indicates that wastes in the clearance level are generated in the reactor head and upper head insulation. In this study, a clearance waste safety evaluation was conducted using the RESRAD-RECYCLE code, which is a safety evaluation code, based on the activation evaluation results for the clearance level wastes. The clearance scenario for the target radioactive waste was selected and the maximum individual and collective exposure doses at the time of clearance were calculated to determine whether the clearance criteria limit prescribed by the Nuclear Safety Act was satisfied. The evaluation results indicated that the doses were significantly low, and the clearance criteria were satisfied. Based on the safety assessment results, an appropriate metal recycle and disposal method were suggested for clearance, which are the subject of the deregulation of internal structures of nuclear power plant.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.65 no.4
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• pp.262-267
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• 2016

This paper describes a design of a hair drier to improve its performance. the performance of the hair drier can be improved by increasing the wind velocity of its discharge port. the design of the hair drier is accomplished by using the CFD. the validity of design results were verified by comparison with the dry change of the hair drier. In this paper, the initial condition of the applied hair drier is as follows, the number of the blade is 9, the diameter of the suction port is 40[mm], the tip clearance is 12.5[mm], the con angle is $28.5^{\circ}$ and the fan angle is 27.5R. From design results, the enhanced condition of the hair drier can be obtained as follows, the number of the blade is 3, the diameter of the suction port is 50[mm], the tip clearance is 10.5[mm], the con angle is $21.5^{\circ}$ and the fan angle is 75R. At the enhanced condition of the hair drier, the wind velocity of the hair drier is 29[%] increase, and the dry time is 40[%] increase compare to the initial condition of the hair drier.

• Tuberculosis and Respiratory Diseases
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• v.43 no.2
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• pp.173-181
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• 1996

Background : Several studies have suggested that impaired mucociliary clearance plays a role in the pathophysiology of bronchial asthma. Cough productive of mucoid sputum is common, and mucous plugs in the airways are frequently observed. These clinical features are in keeping with the histologic lesions of asthma, which involve primarily the epithelial and mucous-producing structures of the conducting airways. Some studies have shown that the mucociliary clearance is impaired in adult asthma, but it has not been studied in childhood asthma. The objectives of this study were to examine whether the mucociliary clearance is impaired in childhood asthma and to estimate the degree of impairment in comparison with that of immotile cilia syndrome. Method : Thirteen children with mild stable asthma and eight patients with immotile cilia syndrome completed this study. Ten healthy children were recruited as a normal control group. The whole-lung mucociliary clearance was measured by the radioaerosol technique. Aerosols, tin colloid particles tagged with the radionuclide technetium-99m($^{99m}Tc$), were generated by means of nebulizer, and inhaled via a mouthpiece. The retention of radioactivity was measured at 30, 60, 90 and 120 minutes by gamma camera, and mucociliary clearance was calculated as percent retention at each time. Results: 1) In each subject, the percent retention decreased variably with the lapse of time. 2) The percent retention of radionuclide decreased at each time in order of normal control, bronchial asthma and immotile cilia syndrome and the percent retention of immotile cilia syndrome was significantly higher than that of normal control at each time(p<0.05). 3) At two hours, the percent retention of bronchial asthma($65.0{\pm}1.8$(SE)%) was significantly higher than that of the normal control($54.4{\pm}3.5%$, p<0.05), and significantly lower than that of immotile cilia syndrome($73.3{\pm}1.4%$, p<0.01). 4) When the percent retention was analyzed according to $PC_{20}$ in the children with bronchial asthma, they had no relationship with each other. Conclusion: Mucociliary clearance in the children with bronchial asthma was significantly lower than normal control. This finding indicates that impaired mucociliary clearance operates in childhood asthma as well, and suggests that it may be one contributing factor in the pathogenesis of asthma. The degree of impairment, however, was not so severe as immotile cilia syndrome.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.5
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• pp.1083-1091
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• 1988

Vacuum brazing is the most modern brazing process and is at present, far from being completely understood. By brazing under high vacuum, in an atmosphere free of oxidizing gases, a superior product with greater strength, ductility and uniformity can be obtained. In this study, the influence of brazing parameters such as base metal characteristics, joint clearance and brazing time were described in relation to the metallurgical phenomena and shear strength of vacuum-brazed joints between carbon steels and 304 stainless steel (SUS 304) brazed by copper filler metal. In copper brazing of SUS 304 to a medium carbon steel(M.C.S) the columnar Fe-Cr-Ni-Cu-C alloy structure was formed and grew from the M.C.S side and at the same time, the surface of M.C.S. was decarbonized. The driving force for the formation and growth of columnar structure was the difference of carbon content between base metals. As the joint clearance is narrower and brazing time is longer, the formation and growth of columnar phase and decarburization of carbon steels were more noticeable. Because of decarburization of carbon steels, the shear strength of brazed joints were reduced as the formation of columnar structure was increased.