• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.553-558
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• 2003

The boundary estimation problem is used to estimate the shape of organic depend on the phase of the cardiac cycle or interested in the detection of the location and size of anomalies with resistivity values different from the background tissues such as nuclear reactor. And we can use the method to solve the optimal solution such as modified Newton raphson, kalman filter, extended kalman filter, etc. But, this method consumes much time and is sensitive to the initial value and noise in the estimation of the unknown shape. In the paper, we propose that multi-layer neural networks estimate the boundary of the unknown object using Fourier coefficient. This method can be used at the real time estimation and have strong characteristics at the noise and initial value. It uses voltage change; difference the homogeneous voltage to the non-homogeneous voltage, and change of Fourier coefficient change to train multi-layer neural network. After train, we can have real time estimation using this method.

• 동력기계공학회지
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• 제11권2호
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• pp.20-25
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• 2007

The performance of air-to-air heat exchanger has been investigated with rotating porous plates newly developed in this study. With an equal interval of 18 mm, the rotating porous plates are installed inside the heat exchanger where the hot and cold airs enter at opposite ends. When flowing in opposite directions by the separating plate installed in the center of the rotating porous plates, the airs give and receive the heat each other. Dry bulb temperature is set by adjusting heat supply at heater. In order to measure the temperature distribution of the hot air side inside heat exchanger, the thermocouples are inserted between the plates. The first location of thermocouple is 10mm downstream from the inlet of heat exchanger, and succeeding ten locations are aligned at an equal interval of 18mm. From the experiment of air-to-air heat exchanger with the rotating porous plates, the heat transfer rate increased as both air flow rate and RPM of the rotating porous plate increased. It was found that the overall heat transfer coefficient increased with the increase in RPM of porous plate at the conditions of the same air flow rate.

• 농촌계획
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• 제19권4호
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• pp.293-306
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• 2013

According to the increase of rural experience, that is important in satisfying needs of green tourism and vitalizing rural economy to use closed school in rural area as experience facility. For using closed school as experience facility, political and institutional assistants are needed in effective equipments and stable operation based on multi-perspective approach and analysis. In this study, we try to evaluate green-tourism accessibility of rural experience facility remodeled from closed school considering regional population and spatial characteristics. In evaluating process, gravity potential model are adapted with considering group size of customer and distance-friction coefficient. Distance-friction coefficient is a function of user restriction which depend on possible activity in each experience facility. Green tourism accessibility of experience facility is calculated with summation of accessibility to each region, and we analyzed it as a group by closed school type and location with application in Chungcheongnam-do. We found a correlation between green tourism accessibility of rural closed school and their income.

• The Plant Pathology Journal
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• 제29권3호
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• pp.344-349
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• 2013

Intraspecific variation in morphometry of pine wood nematodes Bursaphelenchus xylophilus and B. mucronatus in relation to geographical locations in South Korea was investigated using morphometric characters (body length, a, b and c ratio, stylet length, and spicule length for a male nematode and V (%) value for a female nematode). B. xylophilus was isolated from Pinus thunbergii in Jinju (1998), Ulsan (2000), Yangsan (2000), Mokpo (2001) and Jeju (2004), and from P. densiflora in Gumi (2001). B. mucronatus was isolated from P. thunbergii in Jinju (1991) and from P. densiflora in Milyang (2001). The body length of male and female B. xylophilus had the highest coefficient of variability and showed significant differences among geographical locations. The V (%) value for female B. xylophilus showed the lowest coefficient of variability, changing little with geographical area and host plant. All morphometric characters in B. mucronatus except for stylet length and female body length showed no significant differences between locations or hosts, suggesting they may not be affected by geographical area or host plant.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2007년도 학술발표회 논문집
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• pp.321-325
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• 2007

3개의 매개변수(location, scale, shape)로 이루어진 GEV와 GLO 분포는, 미국의 공식적인 홍수빈도 분포인 Log Pearson Type III와 함께 수문분야에서 중요한 위치를 차지하고 있다. 본 연구에서는 Monte Carlo 실험을 이용하여 GEV와 GLO 분포에서 서로 다른 두 지점의 유출량 자료를 생성하여 L-CV(L-moment Coefficient of Variation; $\tau_2$)와 L-CS(L-moment Coefficient of Skewness; $\tau_3$)를 추정하였으며, L-moment 추정값들 간의 교차상관$(\tau_2-\tau_2,\;\tau_3-\tau_3,\;\tau_2-\tau_3)$과 유출량 자료간의 교차상관의 관계를 Simple Power 함수를 이용하여 유도하였다. 실험 과정에서 GEV와 GLO 분포가 비현실적인 음수 유출량을 생성하여, 실험 결과에 큰 영향이 있음을 확인하여, 두 분포에서 생성된 유출량 자료에서 음수값을 제외한 GEV+와 GLO+ 분포를 이용하여 관계식을 유도하고 이를 GEV와 GLO 분포의 결과와도 비교하였다. 본 연구에서 도출된 관계식은 향후 Generalized Least Square 회귀식을 이용하여 홍수분포의 지역 매개변수를 추정하기 위해 활용성이 클 것으로 기대한다.

• 한국소음진동공학회논문집
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• 제22권11호
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• pp.1144-1151
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• 2012

A damage in structure alters its dynamic characteristics. The change is characterized by changes in the modal parameter, i.e., modal frequencies, modal damping value and mode shape associated with each modal frequency. Changes also occur in some of the structural parameters; namely, the mass, damping, stiffness matrices of the structure. In this paper, evaluation of changes in stiffness matrix of a structure is presented as a method not only for identifying the presence of the damage but also locating the damage. It is shown that changed stiffness matrix can be accurately estimated a sensitivity coefficient matrix derived from modifying mode shapes, First, with 4 story shear structure models, the effect of presence of damage in a structure on its stiffness matrix is studied. By using these analytical model, the effectiveness of using change of stiffness matrix in detecting and locating damages is demonstrated. To validate the predicted changing stiffness and its location, the obtained results are compared to the reanalysis result which shows good agreement.

• 대한가정학회지
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• 제36권2호
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• pp.91-104
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• 1998

The specific objectives of the study were (1) to determine the preferences for three home economics curriculum designs(HECD) categorized by Majorie Brown(Technical HECD, Self Actualization HECD, and Practical Reasoning HECD), (2) to determine the differences between middle school HE teachers and high school HE teachers on each curriculum element, and (3) to determine the relationships between preferences for three HECD by curriculum elements and personal and professional characteristics of HE teachers. For these objectives, the subjects were randomly selected from HE teachers of secondary schools in the areas of Seoul, In-Cho, and Keungi. The 300 data collected by mailed survey were analyzed into frequency, percentage, Chi-square, and contingency coefficient using SAS program. The major findings were as follows: 1) the majority of HE teacher respeondents preferred the Practical Reasoning HECD about the following curriculum elements: Purpose of HE education, knowledge, subject matter, teaching method, society and culture, learner, learning atmosphere, and HE teacher's role. 2) No significant difference emerged when Chi-square was applied to determine difference between the two groups(middle and high school HE teachers) on three HECD according to each curriculum element. 3) The contingency coefficient between preferences of HE education purpose for three curriculum designs and age was 21, years of teaching was 23, between preferences of learning atmosphere of three curriculum designs and location of school was. 17. These mean that the younger and more beginning teachers perferred HE purpose of the Practical Reasoning HECD, and HE teachers working in urban area more preferred learning atmosphere of Practical Reasoning HECD.

• KIEAE Journal
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• 제8권1호
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• pp.19-24
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• 2008

The wind-power among the new and renewable energies uses the wind, a limitless, clean and pure energy which is available at any place. It requires low installation cost compared to the generation of other renewable energies, and is easy to operate, and furthermore, can be automated for operation. Korea has been taking a great deal of interest in the development of renewable energy generating equipment, specifically wind power generation as the nation has a nearly total reliance on imported petroleum. A measuring poll 30m high was installed at a location with an altitude of 142m above the sea level in order to measure and analyze the wind power potentiality at H University's Asan Campus, and the wind velocity and wind direction were measured for 1 year. As for the wind power resource of the area adjacent to Asan campus, the Weibull Distribution coefficient was C=2.68, K =1.29 at H30m. Weibull Distribution coefficient was modified on the basis of compensated wind velocity (=3.1m/s) at H 60m, and the energy density was $42W/m^2$. AEP 223,750 KWh was forecast based on the simulation of an 800KW grade wind turbine. It is considered that the wind power generation has to be studied further in the inland zone with low wind velocity to cope with the possible exhaustion of fossil fuel and ensure a sustainable environmental preservation.

• 대한조선학회논문집
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• 제51권2호
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• pp.154-161
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• 2014

Naval ships have hull appendages which are more exposed to the outside because of its small block coefficient compared with commercial ships. These exposed hull appendages like skeg, strut and shaft line affect the maneuverability of a ship. The effect of hull appendages has considered at initial design stage to estimate more accurate maneuverability. In this paper, sensitivity analysis is used to analyze the effect on maneuverability by hull appendages. 3 DOF maneuvering equations based on Mathematical Modelling Group (MMG) model are used and propeller & rudder model are modified to reflect the characteristics of twin propeller & twin rudder. Numerical maneuvering simulations (Turning test, Zig-zag test) for benchmark naval vessel, David Taylor Model Basin (DTMB) 5415 are performed. In every simulation, it is calculated that stability indices and maneuverability characteristics (Tactical Dia., Advance, 1st Overshoot, Time of complete cycle) with respect to the parameters (area times lift coefficient slope, attachment location) of hull appendages. As a result, two regression formulas are established. One is the relation of maneuverability characteristics and stability indices and the other is the relation of stability indices and hull appendages.

• 한국군사과학기술학회지
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• 제22권6호
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• pp.773-783
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• 2019

A numerical analysis of a turbulent flow with a 'large-eddy breakup device(LEBU)' was performed to investigate the influence of the device on the drag of underwater vehicle using commercial CFD code, FLUENT. In the present study, the vehicle drag was decomposed to skin-friction coefficient(C_f) and pressure coefficient(C_p). The variation of the vehicle C_f and C_p were observed with changing location of the device and Reynolds number. As a result, the device decreased the vehicle C_f because it suppressed the turbulent characteristics behind the device. The larger Reynolds number, the higher reduction effect when the device was placed in front part of, and near the vehicle. On the other hand, the device increased/decreased the vehicle C_p with increasing/decreasing turbulent kinetic energy at recirculating flow region behind the vehicle. The total drag change by the device was caused by C_p rather than C_f.