• Journal of Korea Water Resources Association
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• v.37 no.10
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• pp.823-836
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• 2004

Using the simple geometry for the idealized catchment consisting of two plane surfaces and a stream between them, runoff was analysed for the moving storms based on the kinematic wave equation. The storm velocity applied in this study was 0.25∼2.0 m/s moving up, down and cross direction of catchment. Applied rainfall distribution types are uniform, advanced, delayed, intermediate type. The results indicate that the moving storms of cross direction generate the largest peak runoff, and the smallest runoff appears in the case of up stream direction. The sensitivity of runoff to rainfall distribution types decreases as storm velocity increases. It is clear that faster storm velocity generates faster peak time and becomes thin hydrographs rapidly.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.04a
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• pp.1071-1074
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• 2015

본 논문은 진공을 이용한 흡착방식과 바퀴형 이동방식을 이용하고 환경 탐지용 센서를 부착한 벽면 이동형 로봇의 물리적 해석을 통한 이동 성능 개선에 관한 연구로서, 대형 구조물의 안전 검사 및 위험한 시설물의 보수 작업등을 보조하기 위한 목적이 있다. 로봇의 무게에 따른 중력을 견딜 수 있는 강력한 진공흡착방식과 고성능 모터 제어에 의한 바퀴 이동방식을 혼합하고 효율적으로 평형을 유지 또는 제어하기 위하여 로봇에 미치는 다양한 힘과 모멘트를 분석하고 수식화 하였으며 기존의 수직이동 속도를 개선하기 위한 로봇의 물리적 변수를 추출하여 변수와 이동력간의 관계를 고찰하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.260-263
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• 2019

Recently, the need of researches and developments about WSN(Wireless Sensor Network) technologies, which can be applied to services to regions where the access is difficult or services that require continuous monitoring, has gradually increased due to its expansion and efficiency of the application areas. In this paper, we analyze existing researches which focused on reducing packet loss rate and increasing lifetime of sensor nodes. Then, we conduct studies about performance improvement factors where some schemes - clustering and location-based approaches - are applied and compare our study results with existing researches. Based on our studies, we are planning to conduct researches about a new scheme that could contribute to improve WSN's performance in terms of packet loss rate and network lifetime.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.3
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• pp.197-209
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• 2018

In this study, numerical analyses on Quad Tilt Rotor(QTR) are carried out to investigate the interference effect of components and effect of operating condition during forward flight. Actuator Surface Method(ASM) which is implemented in an open source CFD code, OpenFOAM, is used to calculate the flow field around QTR with high computational efficiency. The lift of the front and rear wing is found to increase or decrease depending on the rotation direction of the rotor. At the rear wing, the interference effects of the front and rear rotor appear as a combined manner. Performance change due to the phase difference is found to be insignificant. For both rotors, the locally higher thrust is generated by the blockage effect of the wing. The interference effect of wake from the front nacelle contributes to higher local thrust for the rear rotor compared to the front rotor. And it is observed that the amplitude of thrust oscillation can decrease depending on the phase difference between the rotors. Aerodynamic performances of both rotors and the entire aircraft were compared and analyzed for various operating conditions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.5
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• pp.443-448
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• 2015

Obstructive sleep apnea (OSA) is a syndrome characterized by the repetitive episodic collapse of the upper airway. Maxillomandibular advancement surgery is one of the most effective surgical treatment methods in treating obstructive sleep apnea. The advancement of both maxill and mandible can enlarge the cross-sectional areas and volumes of the postero-superior airway. The purpose of this study is to analyze flow patterns in the upper airway before and after maxillomandibular advancement surgery. Here, we analyzed flow phenomena of inspiration and expiration to prevent obstructive sleep apnea patient from happening side effect. Modeling of the upper airway carried out from clinical CT scanned images. We used time-dependent values for boundary condition. CFD analyses were performed and evaluated section of minimum area (SMA), compared with patient inside upper airway before and after maxillomandibular advancement surgery in SMA, and negative pressure effects. The study showed the greatest enlargment of the section of minimum cross-sectional area. Moreover, the velocity and the negative airway pressure were decreased. According to the result of this study, the maxillomandibular advancement surgery stabilizes the airflow in the postero-superior airway of OSA patients.

• Journal of the Korean GEO-environmental Society
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• v.9 no.2
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• pp.47-59
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• 2008

Application of mechanically stabilized earth wall (MSEW) abutment has been rapidly increasing in United States of America, Pennsylvania since 2002. MSEW is effective for reducing construction cost and period compared to general concrete reinforced wall. In the paper, theoretical background and conventional criterion of MSEW abutment that is widely used abroad are analyzed. Based on the results, application of suitable MSEW abutment to domestic bridge type is examined. For the application of MSEW abutment in Korea, load interacting with upper shoe in domestic bridge types and structural analyses of beam seat and pile are investigated. As a result, all applications are possible except for PSC BOX Bridge that has heavy self-weight of girder. Through two and three dimensional numerical analyses, horizontal behaviour mechanisms between pile and MSEW were analyzed and field tests are also carried out for seven piles behind earth walls. From results of field tests, it is confirmed that an angle of internal friction of backfill material needs to be greater than 34 degree to use H-Pile as foundation of MSEW.

• The Journal of the Korea Contents Association
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• v.10 no.5
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• pp.303-313
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• 2010

The purpose of this study is to evaluate the performance efficiency and productivity change of the regional public hospital in Korea. We use DEA(Data Envelopment Analysis) for CCR, BCC model, and MPI(Malmquist Productivity Index). DEA is a useful nonparametric technique for measurement of efficiency of a DMU(Decision Making Unit) and MPI is a evaluation method to measure DMU's productivity change. We utilize 34 regional public hospital's time-series data over 6 years from 2003 to 2008.The results of this study were as follows. First, technical efficiency(TE) shows that approximately 3.6% of inefficiency exists on the regional public hospitals and it reveals that the cause for technical inefficiency is due to scale inefficiency. Second, MPI's results show that regional public hospital made effort to improve total factor productivity change to raise technical efficiency. In order to raise efficiency, the regional public hospitals should deploy internal innovation and the government should support welfare policies.

• Analytical Science and Technology
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• v.23 no.4
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• pp.357-362
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• 2010

Phthalate plasticizer is not human carcinogens which has been classified as environmentally hazardous substance. Phthalates are absorbed into the body and cause tumors and ecological mutation to human potentially as reproductive toxic substances. For this reason, in some countries the use of phthalates in products for children has been banned. In this study, we proposed the analytical method of phthalate content and migration rate for children's product which was compared and reviewed to the analytical method of various countries, United States, Japan, European Union. The children's product on the proposed analytical method was analysed to consider of the correlation between the phthalate content and migration rate, but there was no correlation both of them.

• The Korean Journal of Mycology
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• v.18 no.3
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• pp.164-177
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• 1990

This study was carried out to obtain some useful data for increasing an effective ginseng production. There was a direct relationship (r=0.2645) between spore germination of Fusarium solani and soil pH, and (r=0.315) between Cylindrocarpon destructans and soil pH. On the other hand, there was a direct relationship (r=0.19) between relative hyphal growth of Rhizoctonia solani and soil pH. There was a direct relationship (r=0.21) between number of total bacteria and F. solani, (r=0.37) between actinomycetes and F. solani and (r=0.20) between celluloytic bacteria and F. solani. However, there was an inverse relationship (r=-0.20) between number of total fungi and F. solani. There was a direct relationship (r=0.24) between number of actinomycetes and R. solani. Each ginseng pathogen-suppressive soil screened was 40 in F. solani, 20 in C. destructans and 9 soil samples in R. solani among 146 soil samples, respectively. The mean contents of K, Ca and Mg were fairly lower in each ginseng pathogen-suppressive soil than conducive soil, whereas Na were somewhat lower. The mean contents of organic matter were over 2 times higher in each ginseng pathogen-suppressive soil than conducive soil. The mean contents of phosphate were fairly lower in F. solani and R. solani-suppressive soil than conducive soil and, on the other hand, were somewhat higher in C. destructans-suppressive soil than conducive soil. The mean soil pH was somewhat lower in each ginseng pathogen-suppressive soil than conducive soil. The mean contents of sand were about 2 times higher in each ginseng pathogen­suppressive soil than conducive soil, whereas silt and clay were somewhat lower. The microbial numbers of total bacteria, total fungi and celluloytic fungi were higher in F. solani-suppressive soil than conducive soil, whereas actinomycetes and celluloytic bacteria were lower. Each microbial number of total bacteria or total fungi indicated a significant difference (p=0.05) between F. solani­suppressive and conducive soil, and the microbial number of actinomycetes was a highly significant difference (p=0.01) between F. solani-suppressive and conducive soil. The microbial numbers of total bacteria, total fungi, actinomycetes and celluloytic fungi were higher in C. destructans-suppressive soil than conducive soil, whereas celluloytic bacteria were about 2 times lower. On the other hand, the microbial numbers of total fungi were higher in R. solani-suppressive soil than conducive soil, whereas total bacteria, actinomycetes, celluloytic bacteria and celluloytic fungi were lower. Fourteen of 16 F. solani-suppressive soils tested were suppressive to ginseng root rot, whereas fifteen of 16 C. destructans-suppressive soils were suppressive. Ginseng root rots of ginseng disease-suppressive soils were in the range of 1.0-17.4% in F. solani-suppressive soil and 0.2-20.4% in C. destructans-suppressive soil, respectively.

• Korean Journal of Remote Sensing
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• v.30 no.1
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• pp.13-24
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• 2014

Satellite remote sensing data have been valuable tool for volcanic ash monitoring. In this study, we present the results of application of satellite remote sensing data for monitoring of volcanic ash for three major volcanic eruption cases (2008 Chait$\acute{e}$n, 2010 Eyjafjallaj$\ddot{o}$kull, and 2011 Shinmoedake volcanoes). Volcanic ash detection products based on the Moderate Resolution Imaging Spectro-radiometer (MODIS) observation data using infrared brightness temperature difference technique were compared to the forward air mass trajectory analysis by the HYbrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model. There was good correlation between MODIS volcanic ash image and trajectory lines after the volcanic eruptions, which support the feasibility of using the integration of satellite observed and model derived data for volcanic ash forecasting.