• Journal of Astronomy and Space Sciences
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• v.21 no.2
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• pp.153-166
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• 2004

Interplanetary trajectories using the gravity assists are studied for future Korean interplanetary missions. Verifications of the developed softwares and results were performed by comparing data from ESA's Mars Express mission and previous results. Among the Jupiter exploration mission scenarios, multi-planet gravity assist mission to Jupiter (Earth-Mars-Earth-Jupiter Gravity Assist, EMEJGA trajectory) requires minimum launch energy ($C_3$) of 29.231 $Km^2$/$S^2$ with 4.6 years flight times. Others, such as direct mission and single-planet(Mars) gravity assist mission, requires launch energy ($C_3$) of 75.656 $Km^2$/$S^2$ with 2.98 years flight times and 63.590 $Km^2$/$S^2$ with 2.33 years flight times, respectively. These results show that the planetary gravity assists can reduce launch energy, while EMEJGA trajectory requires the longer flight time than the other missions.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.493-494
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• 2015

전원설비 투자계획은 주어진 기간 하에서 최적 발전기 투입용량 및 시기를 결정하는 문제이다. 전원설비의 준공일정은 다양한 사회적 요인의 영향으로 불확실성에 노출되어 있다. 본 논문에서는 전원설비 준공 불확실성을 고려한 전원설비 계획 문제를 제시한다. 발전설비의 준공지연 불확실성은 이산 확률론적 밀도함수를 갖는 확률변수로 표현된다. 최적화 문제에서 확률변수를 고려하기 위해 2단계 확률론적 계획법이 도입된다. 주문제-부문제로 분해된 최적화 문제는 쌍대함수 정보를 교환하는 반복연산을 수행하여 최적 전역해에 도달할 수 있다.

• Korean journal of applied entomology
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• v.15 no.4 s.29
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• pp.185-191
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• 1976

This study was conducted to evaluate the performance of 2,4-D amine salt (2,4-dichlorophenoxy acetic acid) 40EC in broadleaf weeds control under diverse conditions of rate and time of application and soil type in fall barley field. The results obtained were summarized as follows: 1) At the rate of 70cc prod./10a, 2,4-D amine salt treated during the fully tillered stage of barley was effective for the control of most broadleaf weeds without crop injury. 2) The fully tillered stage was a optimun time lot the application of 2,4-D amine salt in fall barley. Earlier(zero-to four-leaf stage) or late. (boot stage to flowering) application than this stage caused a crop injury and resulted in yield reduction. 3) It was possible to safely use 2,4-D amine salt in fall barley regardless of soil types if applied the rate of 70cc prod./10a at the fully tillered stage.

• Journal of Energy Engineering
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• v.24 no.4
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• pp.166-174
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• 2015

This study examined combustion characteristics by selecting the fuel which have a different physical properties compared to gasoline in order to examine the effects of vehicle performance and environment depending on the physical properties. The experiment examined the combustion characteristic in the optimum ignition timing according to the physical properties change and the lean burn by performing control about ignition timing and air-fuel ratio for each fuel, and it was also evaluated the exhaust gas according to the experiment. We used a single-cylinder engine for the experiment, and tested for gasoline properties change by selecting a fake fuel that beyond the fuel quality standards in 석대법. As a result, in the case of the selected fuel showed a difference in Octane and distillation characteristics, vapor pressure and it was also found to unstable combustion, and leads to a large amount of harmful exhaust gas.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.30-30
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• 2016

환경창(EWs; Environmental Windows)이란, 준설 및 준설토 처리에 대한 부정적인 영향이 최소가 되는 기간을 정하고, 그 기간에 준설 및 준설토 처리를 수행하게끔 지정된 기간을 의미한다. 1970년대부터 미국을 중심으로 개발되어, 2001년을 기준으로 미국의 모든 준설사업의 약 80% 이상을 관리하고 있다. 준설이 가능하도록 규정된 환경창과 준설이 가능하지 않은 계절적 제한(seasonal restrict)으로 구성되어 있으며, 계절적 제한 기간에 준설을 수행하고자 하는 경우에는 준설과 관련된 의사결정권자, 이해관계자 및 전문가들의 협의가 이루어져야 한다. 그러나 현재 환경창에서 제공하고 있는 정보는 준설 수행의 가능/불가능의 양자택일에 대한 정보만을 제시하고 있으며, 이러한 문제는 의사결정권자 및 이해관계자에게는 정량적인 정보를 주지 못해 의사결정이 어려워지는 단점이 있다. 이러한 단점을 극복하기 위해서 통계학적 기법을 이용하여 사회 환경적인 측면에서 준설의 부정적인 영향을 수치화하여 정량적인 정보를 제공할 수 있도록 환경창 지수를 개발하였다. 환경창 지수를 적용한 환경창의 검증을 위해 미국의 샌프란시스코 만에 적용하였으며, 적용결과와 현재 샌프란시스코 만에서 운영 중인 환경창과 비교 분석을 수행하였다. 본 연구에서 개발된 환경창은 샌프란시스코 만에서 운영하고 있는 환경창과 동일한 환경창 기간을 제공함은 물론, 정량적인 환경창 지수를 제공함으로써 보다 간편한 의사결정이 가능함을 보였다. 또한 낙동강에 위치한 다기능보 중, 강정고령보에 적용하여 환경창을 개발하고 최적 준설시기 및 기간을 산정하였다. 개발된 환경창에 의하면 3월에 환경창 지수가 가장 높은 수치를 보임에 따라 가장 준설의 부정적인 영향이 작은 환경창 기간이라고 할 수 있으며, 가장 부적절한 환경창 기간은 5월인 것으로 나타났다.

• 한국생물공학회:학술대회논문집
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• 2005.04a
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• pp.203-206
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• 2005

TGE (Transmissible Gastroenteritis) caused by a virus belonging to family coronavirus, results in an acute infection of the small intestine of the pig. The optimum operation variables such as multiplicity of infection (MOI), infection time and harvest time were investigated for TGE vaccine production by immobilized ST(swine testicle) cells. In the culture supplemented with 5% serum, maximum virus titer of $1.2{\times}10^6pfu/ml$ was obtained at the conditions of 0.01 MOI, 2day infection time, and 1 day harvest time. Serum is a potential source of bacterial, mycoplasmal and viral contamination, and it has a possibility of the introduction of serum proteins, prion and pyrogens into the final product. For these reasons, much attention has been focused on the development of serum-free media. A new serum-free media (SFM) has been developed in order to produce TGE vaccine of high quality with low cost. The performance of SFM developed was compared with other commercially available serum-free media and serum supplemented media in terms of virus productivity. The cultures with serum-free media showed higher titer than that with serum supplemented media. Among various serum-free media tested, CHO-S-SFMII showed highest virus titer.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.56 no.3
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• pp.273-278
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• 2011

The contents of starch, moisture, crude protein, crude fat, crude fiber, and ash of different varieties of potatoes were analyzed. The average starch contents of Go-woon, Ha-ryoung, Dae-seo, Jo-won, Ga-won potatoes were $17.9{\pm}0.2$, $18.0{\pm}1.7$, $17.7{\pm}0.5$, $14.8{\pm}0.4$, and $16.2{\pm}1.0%$, respectively. The ground powder of each starchy substrate was suspended in distilled water, and then liquefied, saccharified, and fermented by Saccharomyces cerevisiae ATCC26603 at $30^{\circ}C$ for 4 days. By statistical analysis, the effectiveness of the contents of the different components of the potato tubers on the ethanol production were examined. The results showed that the starch content positively affected the ethanol production. while moisture content affected negatively the ethanol production. Ethanol production from the 5 different varieties of potato tubers harvested on different time were examined and the results indicated that both of potato variety and the harvesting-time significantly affected the ethanol production. Among the several varieties of potato, Ha-ryoung produced the highest yield of ethanol as much as $94.3{\pm}1.9$ L/ton or $3111{\pm}62.7$ L/ha.

• Smart Media Journal
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• v.8 no.1
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• pp.74-81
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• 2019

Recently, machine learning technology has had a significant impact on society, particularly in the medical, manufacturing, marketing, finance, broadcasting, and agricultural aspects of human lives. In this paper, we study how to apply machine learning techniques to foods, which have the greatest influence on the human survival. In the field of Smart Farm, which integrates the Internet of Things (IoT) technology into agriculture, we focus on optimizing the crop growth environment by monitoring the growth environment in real time. KT Smart Farm Solution 2.0 has adopted machine learning to optimize temperature and humidity in the greenhouse. Most existing smart farm businesses mainly focus on controlling the growth environment and improving productivity. On the other hand, in this study, we are studying how to apply machine learning with respect to harvest time so that we will be able to harvest fruits of the highest quality and ship them at an excellent cost. In order to apply machine learning techniques to the field of smart farms, it is important to acquire abundant voluminous data. Therefore, to apply accurate machine learning technology, it is necessary to continuously collect large data. Therefore, the color, value, internal temperature, and moisture of greenhouse-grown fruits are collected and secured in real time using color, weight, and temperature/humidity sensors. The proposed FPSML provides an architecture that can be used repeatedly for a similar fruit crop. It allows for a more accurate harvest time as massive data is accumulated continuously.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.4
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• pp.427-435
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• 2023

Changes in flowering time due to weather fluctuations impact plant growth and ecosystem dynamics. Accurate prediction of flowering timing is crucial for effective forest ecosystem management. This study uses a process-based model to predict flowering timing in 2023 for five major tree species in Korean forests. Models are developed based on nine years (2009-2017) of flowering data for Abeliophyllum distichum, Robinia pseudoacacia, Rhododendron schlippenbachii, Rhododendron yedoense f. poukhanense, and Sorbus commixta, distributed across 28 regions in the country, including mountains. Weather data from the Automatic Mountain Meteorology Observation System (AMOS) and the Korea Meteorological Administration (KMA) are utilized as inputs for the models. The Single Triangle Degree Days (STDD) and Growing Degree Days (GDD) models, known for their superior performance, are employed to predict flowering dates. Daily temperature readings at a 1 km spatial resolution are obtained by merging AMOS and KMA data. To improve prediction accuracy nationwide, random forest machine learning is used to generate region-specific correction coefficients. Applying these coefficients results in minimal prediction errors, particularly for Abeliophyllum distichum, Robinia pseudoacacia, and Rhododendron schlippenbachii, with root mean square errors (RMSEs) of 1.2, 0.6, and 1.2 days, respectively. Model performance is evaluated using ten random sampling tests per species, selecting the model with the highest R². The models with applied correction coefficients achieve R² values ranging from 0.07 to 0.7, except for Sorbus commixta, and exhibit a final explanatory power of 0.75-0.9. This study provides valuable insights into seasonal changes in plant phenology, aiding in identifying honey harvesting seasons affected by abnormal weather conditions, such as those of Robinia pseudoacacia. Detailed information on flowering timing for various plant species and regions enhances understanding of the climate-plant phenology relationship.

• Journal of The Korean Society of Grassland and Forage Science
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• v.40 no.1
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• pp.66-72
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• 2020

This study aimed to discuss the optimal seeding and harvesting dates with growing degree days(GDD) via meta-data of whole crop maize(WCM). The raw data (n=3,152) contains cultivation year, cultivars, location, seeding and harvesting dates collected from various reports such as thesis, science journals and research reports (1982-2012). The processing was: recording, screening and modification of errors; Then, the final dataset (n=121) consists of seeding cases (n=29), and harvesting cases (n=92) which were used to detect the optimum. In addition, the optimal periods considering tolerance range and GDD also were estimated. As a result, the optimum seeding and harvesting periods were 14th April ~ 3rd May and 15th August ~ 4th September, respectively; where, their GDDs were 23.7~99.6℃ and 1,328.7~1,602.1℃, respectively. These GDDs could be used as a judge standard for selecting the seeding and harvesting dates.