• Journal of Astronomy and Space Sciences
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• v.26 no.2
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• pp.171-186
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• 2009

Various Earth-Moon transfer trajectories are designed and analyzed to prepare the future Korea's Lunar missions. Minimum fuel trajectory solutions are obtained for the departure year of 2017, 2020, 2022, and every required mission phases are analyzed from Earth departure to the final lunar mission orbit. N-body equations of motion are formulated which include the gravitational effect of the Sun, Earth and Moon. In addition, accelerations due to geopotential harmonics, Lunar J2 and solar radiation pressures are considered. Impulsive high thrust is assumed as the main thrusting method of spacecraft with launcher capability of KSLV-2 which is planned to be developed. For the method of injecting a spacecraft into a trans Lunar trajectory, both direct shooting from circular parking orbit and shooting from the multiple elliptical intermediate orbits are adapted, and their design results are compared and analyzed. In addition, spacecraft's visibility from Deajeon ground station are constrained to see how they affect the magnitude of TLI(Trans Lunar Injection) maneuver. The results presented in this paper includes launch opportunities, required optimal maneuver characteristics for each mission phase as well as the trajectory characteristics and numerous related parameters. It is confirmed that the final mass of Korean lunar explorer strongly depends onto the initial parking orbit's altitude and launcher's capability, rather than mission start time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.126-132
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• 2016

This study numerically investigates the characteristics of chemical reactions and thermal deformation in a steam reformer. These phenomena are significantly affected by the high-temperature burner gas and the process gas conditions. Because the high temperature of the burner gas ranges from 800 to 1000 K, the reformer tubes undergo substantial thermal deformation, eventually resulting in structural failure. Thus, it is necessary to understand the characteristics of the reaction and thermal deformation under the operating conditions to evaluate the reformer tubes for sustainable, stable operation. Extensive numerical simulations were carried out using commercial CFD code (ANSYS FLUENT/MECHANICA Ver. 13.0) while considering three-dimensional turbulent flows and combined heat transfer including conduction, convection, and radiation. Structural analysis considering conjugated heat transfer between solid tubes and fluid flows was conducted using the Fluid-Solid Interaction (FSI) method. The results show that when the injection temperature of the process gas and burner gas decreased, the hydrogen production rate decreased significantly, and thermal deformation decreased by at least 15 to 20%.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2013.11a
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• pp.26-27
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• 2013

산림생태계의 에너지, 물질, 정보의 교환 과정과 그 변화를 이해하려면 먼저 생태계의 구조와 기능이 어떻게 상호작용하는지를 이해해야 한다. 생태계의 기능은 한, 두 가지의 특징에 의해서만 이루어지는 것이 아니다. 그렇기 때문에 그 기능을 파악하고 적절히 이용하거나 대응하기 위해서는 한 생태계와 주변 환경 전체를 바라볼 수 있는 시스템 사고가 필요하다. 이에 우리는 생태계의 '구조'를 파악함으로써 생태계의 '상태'를 이해하고자 한다. 본 연구에서는 Ruddell and Kumar (2009)의 접근법을 따라, 어떻게 한 생태계의 상태를 파악할 수 있는가라는 질문을 광릉활엽수림에 적용하여 답하고자 한다. 즉, 우리는 산림생태계가 열린 복잡계라고 가정하고, 생태계 내에서 다양한 프로세스들 간의 시시각각 변하는 네트워크의 구조가 각 시점의 시스템의 상태를 나타내는 지표가 될 수 있다고 가정하였다. 이 연구에서는 그 구조적 특징을 정량화하여 나타내는데 초점을 맞추었다. 각각의 프로세스를 대표하는 상태 변수들 간의 정보 흐름의 양과 방향, 시간 규모를 계산해냄으로써 네트워크 구조를 파악하고자 하였다. 온대 산악지형 활엽수림인 GDK의 2008년 순생태계교환량(NEE), 총일차생산량(GPP), 생태계호흡량(RE), 현열플럭스(H), 잠열플럭스(LE), 하향단파복사(Rg), 강수량(Precipitation), 기압(Pressure), 기온(T), 포차(VPD)의 시계열 자료를 월별로 나누어 최장 18 시간 규모의 정보 흐름을 계산하였다. 정보 흐름의 구조를 파악하기 위하여 변수들 간의 전이엔트로피(Transfer entropy)와 상호정보(Mutual Information)를 계산하는 방법을 사용하였다. 또한 시계열 자료를 이용함으로써 변수들 간에 정보가 전달되는 시간 규모의 특성을 파악할 수 있었다. 최종적으로, 계산한 정보 흐름을 시각화하여 프로세스 네트워크 구조를 나타내었다. 결과는 월별로 생태계의 정보 흐름의 종류, 방향과 시간 규모, 그에 따른 프로세스 간 상호 작용의 특징 등을 보여준다. 이를 통해 계절적 환경 변화에 따라 시스템의 네트워크 구조와 상태가 어떻게 변화하는지 이해할 수 있을 것이다. 이 연구는 추후 우리 연구실에서 생산한 8 년 자료에 적용함으로써 다양한 날씨 및 기후변화와 환경 변화에 따라 생태계의 구조와 상태가 어떻게 변화하는지 연구하는 시작점이 될 것이다. 이 접근법은 단위나 차원에 무관하게 다양한 종류의 자료에 적용할 수 있는 반면에, 일관성 있게 정의된 시스템의 상태 및 그 상태를 구성하는 주요 하부 시스템들의 네트워크 상태를 이해하는데 이용될 수 있다. 본 연구는 비평형 열역학과 복잡계의 관점에서 바라 본 시스템 사고를 적용하려 하는 여러 연구 분야에 새로운 도전을 촉발할 좋은 선행연구가 될 것이라 기대된다.

• Journal of Climate Change Research
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• v.4 no.1
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• pp.41-49
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• 2013

Recent findings have revealed that black carbon is one of the substantial materials affecting climate change along with greenhouse gases. Usually, black carbon is generated by incomplete combustion of biomass and deposited on snow and ice surface, resulting in increasing adsorption of radiant energy and accelerating ice melting. However, it is still questionable what the emission characteristics of black carbons from biomass combustion is. We investigated the emission characteristics of black carbon generated from a wood stove in this study. We found that the emission of black carbon was highly dependent upon combustion temperature and the amount of combustion air supplied. The emission factors were 1.01 g-BC/kg-Oak for fireplace wood burning under incomplete combustion, 0.37 g-BC/kg-Oak for fireplace wood burning under complete combustion and 0.29 g-BC/kg-Oak for small wood-stove burning.

• Korean Journal of Remote Sensing
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• v.34 no.6_2
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• pp.1273-1282
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• 2018

Recently, active research on the Arctic Ocean has been conducted due to the influence of global warming and new Arctic ship route. Although previous studies already calculated quantitative extent of sea ice using passive microwave radiometers, melting at the edge of sea ice and surface roughness were hardly considered due to low spatial resolution. Since Sentienl-1A/B data in Extended Wide (EW) mode are being distributed as free of charge and bulk data for Arctic sea can be generated during a short period, the entire Arctic sea ice data can be covered in high spatial resolution by mosaicking bulk data. However, Sentinel-1A/B data in EW mode, especially in HV polarization, needs significant radiometric correction for further classification. Thus, in this study, we developed algorithms that can correct thermal noise and scalloping effects, and confirmed that Arctic sea ice and open-water were well classified using the corrected dual-polarization SAR data.

• Science of Emotion and Sensibility
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• v.24 no.2
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• pp.81-92
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• 2021

In this study, we investigated the effects of five EMS lumbar back pressure belts produced on an anatomical basis on lumbar spine stabilization. Five core muscles were selected, including the urinal, vertebral column, endotracheal, external abdominal, and large back muscles, and patterns were designed using a conductive fabric considering the appropriate muscle shape and pain-causing points. We experimented with four motions to examine the effects of different EMS abdominal compression belts on lumbar spine stabilization. Five healthy men in their 20s were selected. The selection conditions include no back pain history for the past three months, no restricted movements through pre-inspection, and the muscular strength of the body should belong to the normal grade. Using SLR, the sequence of experimental actions was chosen from the following but not limited to left-hand, body-hand, and back-line forces. Resting between movements lasted for 2 min, and the experiments were conducted after wearing the EMS abdominal pressure belt. Electrical stimulation was applied for 10 min to increase blood flow and muscle activation. The statistics of the experimental results were analyzed for specific differences by conducting the Wilcoxon and Friedman tests with nonparametric tests. The ranking results of each pattern were successfully assessed in the order of 5, 4, 3, 1, 2 for the five patterns, and we could identify slightly more significant results for experimental behavior associated with each muscle movement. Patterns produced based on anatomy showed differentiated effects when electric stimulation was applied to each muscle in different shapes, which could improve the stabilization of the lumbar spine in everyday life or training to the public. Based on these results, subsequent research would focus on developing smart healthcare clothing that is practical in daily life by employing different anatomical mechanisms, depending on the back pain, to utilize trunk-type tights.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.88-88
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• 2021

최근 수자원과 수질관리 분야에 자료기반 머신러닝 모델과 딥러닝 모델의 활용이 급증하고 있다. 그러나 딥러닝 모델은 Blackbox 모델의 특성상 고전적인 질량, 운동량, 에너지 보존법칙을 고려하지 않고, 데이터에 내재된 패턴과 관계를 해석하기 때문에 물리적 법칙을 만족하지 않는 예측결과를 가져올 수 있다. 또한, 딥러닝 모델의 예측 성능은 학습데이터의 양과 변수 선정에 크게 영향을 받는 모델이기 때문에 양질의 데이터가 제공되지 않으면 모델의 bias와 variation이 클 수 있으며 정확도 높은 예측이 어렵다. 최근 이러한 자료기반 모델링 방법의 단점을 보완하기 위해 프로세스 기반 수치모델과 딥러닝 모델을 결합하여 두 모델링 방법의 장점을 활용하는 연구가 활발히 진행되고 있다(Read et al., 2019). Process-Guided Deep Learning (PGDL) 방법은 물리적 법칙을 반영하여 딥러닝 모델을 훈련시킴으로써 순수한 딥러닝 모델의 물리적 법칙 결여성 문제를 해결할 수 있는 대안으로 활용되고 있다. PGDL 모델은 딥러닝 모델에 물리적인 법칙을 해석할 수 있는 추가변수를 도입하며, 딥러닝 모델의 매개변수 최적화 과정에서 Cost 함수에 물리적 법칙을 위반하는 경우 Penalty를 추가하는 알고리즘을 도입하여 물리적 보존법칙을 만족하도록 모델을 훈련시킨다. 본 연구의 목적은 대청호의 수심별 수온을 예측하기 위해 역학적 모델과 딥러닝 모델을 융합한 PGDL 모델을 개발하고 적용성을 평가하는데 있다. 역학적 모델은 2차원 횡방향 평균 수리·수질 모델인 CE-QUAL-W2을 사용하였으며, 대청호를 대상으로 2017년부터 2018년까지 총 2년간 수온과 에너지 수지를 모의하였다. 기상(기온, 이슬점온도, 풍향, 풍속, 운량), 수문(저수위, 유입·유출 유량), 수온자료를 수집하여 CE-QUAL-W2 모델을 구축하고 보정하였으며, 모델은 저수위 변화, 수온의 수심별 시계열 변동 특성을 적절하게 재현하였다. 또한, 동일기간 대청호 수심별 수온 예측을 위한 순환 신경망 모델인 LSTM(Long Short-Term Memory)을 개발하였으며, 종속변수는 수온계 체인을 통해 수집한 수심별 고빈도 수온 자료를 사용하고 독립 변수는 기온, 풍속, 상대습도, 강수량, 단파복사에너지, 장파복사에너지를 사용하였다. LSTM 모델의 매개변수 최적화는 지도학습을 통해 예측값과 실측값의 RMSE가 최소화 되로록 훈련하였다. PGDL 모델은 동일 기간 LSTM 모델과 동일 입력 자료를 사용하여 구축하였으며, 역학적 모델에서 얻은 에너지 수지를 만족하지 않는 경우 Cost Function에 Penalty를 추가하여 물리적 보존법칙을 만족하도록 훈련하고 수심별 수온 예측결과를 비교·분석하였다.

• Journal of Animal Environmental Science
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• v.10 no.3
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• pp.141-154
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• 2004

The solar powered water pump is very ideal equipment because solar power is more intensive when the water is more needed in summer and it is very helpful in the rural area, in which the electrical power is not available. The average so]ar radiation energy is 3.488 kWh/($m^2{\cdot}day$) in Korea. In this study, the automatic control logic and system of the water pump driven by the radiation energy were studied, designed, assembled, tested and analyzed for realizing the solar powered water pump. The experimental system was operated automatically and the cycle was continued. The average quantity of the water pumped per cycle was about 5,320 cc. The cycle time was about 4.9 minutes. The thermal efficiency of the system was about $0.030\%$. The pressure level of the n-pentane vapour in flash tank was 150$\%$450 hPa(gauge) which was set by the computer program for the control of the vapour supply. The pressure in the condenser and air tank during cycles was maintained as about 600 hPa and 1,200 hPa respectively. The water could be pumped by the amount of 128kg/($m^2{\cdot}day$) with the efficiency of $0.1\%$ and the pumping head of 10 m for the average solar energy in Korea.

• Journal of Nutrition and Health
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• v.43 no.2
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• pp.197-206
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• 2010

Now a days, people eat outside of the home more and more frequently. Menu labeling can help people make more informed decisions about the foods they eat and help them maintain a healthy diet. This study was conducted to develop menu labeling system using Nutri-API (Nutrition Analysis Application Programming Interface). This system offers convenient user interface and menu labeling information with printout format. This system provide useful functions such as new food/menu nutrients information, retrieval food semantic service, menu plan with subgroup and nutrient analysis informations and print format. This system provide nutritive values with nutrient information and ratio of 3 major energy nutrients. MLS system can analyze nutrients for menu and each subgroup. And MLS system can display nutrient comparisons with DRIs and % Daily Nutrient Values. And also this system provide 6 different menu labeling formate with nutrient information. Therefore it can be used by not only usual people but also dietitians and restaurant managers who take charge of making a menu and experts in the field of food and nutrition. It is expected that Menu Labeling System (MLS) can be useful of menu planning and nutrition education, nutrition counseling and expert meal management.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2003.05a
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• pp.181-186
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• 2003

The satellite navigation system is widely used for identifying a user's position regardless of weather or geographic conditions and also make effect on new technology of marine LBS(Location Based Service), which has the technology of geographic information such as the ENC. Generally, there are conceivable systems of marine LBS such as ECDIS, or ECS that use the ENC itself with powerful processor in installed type on ships bridge. Since the ENC is relatively heavy structure with dummy format for data transfer between different systems, we should reduce the ENC to small and compact size in order to use it in mobile platform. In this paper, we assumed that the mobile system like PDA, or Webpad can be used for small capability of mobile platform. However, the ENC should be updated periodically by update profile data produced by HO. If we would reduce the ENC without a consideration of update, we could not get newly updated data furthermore. As summary, we studied considerations for ENC reduction with update capability. It will make the ENC be useful in many mobile platforms for various applications.