• Food Engineering Progress
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• v.13 no.4
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• pp.275-281
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• 2009

Sesame oils are partially mixed with other vegetable oils due to high price in a Korean market. To find out authentic sesame oil, a mass spectrometer-based electronic nose (MS-based E-nose) was used. Sesame oil (Se) was blended with soybean oil (So) or corn oil (Co) at the ratio (Se:So, Se:Co) of 97:3, 94:6, 91:9, 88:12 and 85:15, respectively. Intensities of each fragment from sesame oil by MS-based E-nose were completely different from those of soybean oil or corn oil. The obtained results were used for discriminant function analysis (DFA). Volatile organic components (VOC) of soybean oil or corn oil were similar to those of fresh air and DFA plot indicated a significant separation of pure sesame oil and pure other oil. The group of the mixed oil was seperated with that of sesame oil in DFA plot and the added amount of soybean oil to sesame oil was correlated with discriminant function first score (DF1). MS based E-nose system could be used as an efficient method to investigate the purity of sesame oil.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.387-392
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• 2019

A technique was researched to detect bolt looseness using a transfer impedance technique (the dual piezoelectric material technique) for monitoring the structural health of a bolt joint. In order to use the single piezoelectric material technique, an expensive impedance analyzer should be used. However, in the transfer impedance technique, low-cost fault detection can be performed using a general function generator and a digital multimeter. A steel plate frame test specimen composed of bolt joints was fabricated, and the tightening torques of the bolts were loosened step by step. By using the transfer impedance method, the damage index was obtained. It was found that the presence of faults could be reasonably estimated using the damage index, which increased with the degree of bolt looseness. An experiment was performed on the same specimen using the single piezoelectric material technique, and the results showed a similar tendency. It could be possible to estimate the damage of a bolt joint at low cost by eliminating the expensive impedance analyzer. This method could be used effectively for structural health monitoring after carrying out a study to estimate the fault location and severity.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.5
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• pp.477-484
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• 2021

Due to climate change, parts of Korea are experiencing large and small droughts every 2-3 years and extreme droughts every 7 years. Since most droughts occur mainly in areas where small water supply facilities in the tributaries or upstream are located, more research on technology for securing water in these areas is required. In this study, a drought evaluation using SPEI (Standardized Precipitation Evapotranspiration Index), SDI (Streamflow Drought Index), and WBDI (Water Budget-based Drought Index) was performed to investigate hydrological drought in the Mulrocheon watershed of Chuncheon, a vulnerable area in terms of water supply. As a result of calculating hydrological drought indices SPEI and SDI, examining each duration, it was confirmed that the common drought in 2014 did not recover and continued until 2015. In the hydrological drought index evaluation result by WBDI, a very severe drought condition was observed in the spring of 2015 following 2014, and that drought was the most severe at -1.94 in November 2017. As a result of deriving a SDF (Severity-Duration-Frequency) curve through frequency analysis by duration using the drought index calculated on a monthly basis from 2003 to 2019 (17 years), most droughts in the Mulrocheon watershed were found to have a return period of less than 10 years, but droughts that occurred in 2014, 2015, and 2019 were found to cover more than 20 years, respectively.

• Journal of the Korean GEO-environmental Society
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• v.12 no.1
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• pp.13-26
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• 2011

Because the allowable current loading of buried electrical transmission cables is frequently limited by the maximum permissible temperature of the cable or of the surrounding ground, there is a need for cable backfill materials to be maintained at a low thermal resistivity during the service period. Temperatures greater than $50^{\circ}C$ to $60^{\circ}C$ may lead to breakdown of cable insulation and thermal runaway if the surrounding backfill material is unable to dissipate the heat as rapidly as it is generated. This paper describes the results of studies aimed at the development of backfill material to reduce the thermal resistivity. A large number of different additive materials were tested to determine their applicability as a substitute material. The results of Dong-rim river sand (relatively uniform) show that as water content level increases, thermal resistivity tends to decrease, whereas the thermal resistivity on dry condition is very high value($260^{\circ}C-cm/watt$). In addition, other materials(such as Jinsan granite screenings, A-2(sand and gravel mixture), E-1(rubble and granite screenings mixture) and SGFC(sand, gravel, fly-ash and cement mixture)) are well-graded materials with low thermal resistivity($100^{\circ}C-cm/watt$ when dry). Based on this research, 4 types of improved materials were suggested as the environmentally friendly backfill materials with low thermal resistivity.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.33 no.3
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• pp.101-109
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• 2021

Wave observations using a marine X-band radar are conducted by analyzing the backscattered radar signal from sea surfaces. Wave parameters are extracted using Modulation Transfer Function obtained from 3D wave number and frequency spectra which are calculated by 3D FFT of time series of sea surface images (42 images per minute). The accuracy of estimation of the significant wave height is, therefore, critically dependent on the quality of radar images. Wave observations during Typhoon Maysak and Haishen in the summer of 2020 show large errors in the estimation of the significant wave heights. It is because of the deteriorated radar images due to raindrops falling on the sea surface. This paper presents the algorithm developed to increase the accuracy of wave heights estimation from radar images by adopting convolution neural network(CNN) which automatically classify radar images into rain and non-rain cases. Then, an algorithm for deriving the Hs is proposed by creating different ANN models and selectively applying them according to the rain or non-rain cases. The developed algorithm applied to heavy rain cases during typhoons and showed critically improved results.

• Journal of the Korea Society of Computer and Information
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• v.27 no.2
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• pp.43-51
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• 2022

In this paper, we suggest the method to improve the existing method leaning context-free grammar(CFG) using tabular representation(TBL) as a chromosome of genetic algorithm in grammatical inference and show the more efficient experimental result. We have two improvements. The first is to improve the formula to reflect the learning evaluation of positive and negative examples at the same time for the fitness function. The second is to classify partitions corresponding to TBLs generated from positive learning examples according to the size of the learning string, proceed with the evolution process by class, and adjust the composition ratio according to the success rate to apply the learning method linked to survival in the next generation. These improvements provide better efficiency than the existing method by solving the complexity and difficulty in the crossover and generalization steps between several individuals according to the size of the learning examples. We experiment with the languages proposed in the existing method, and the results show a rather fast generation rate that takes fewer generations to complete learning with the same success rate than the existing method. In the future, this method can be tried for extended CYK, and furthermore, it suggests the possibility of being applied to more complex parsing tables.

• Journal of Space Technology and Applications
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• v.1 no.2
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• pp.160-177
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• 2021

The Solar and Space Environment Division of the Korean Space Science Society investigated the use and possession of ground and satellite observations and models of solar and planetary data operated by domestic research institutes and universities. Based on the findings, we would like to introduce observational instruments, data, and models in solar and interplanetary fields in this paper to improve understanding and use of each data and explore opportunities for interdisciplinary research. The ground and satellite observations, which require a lot of investment, were mainly held by research institutes (National Meteorological Satellite Center, Polar Research Institute, Korean Space Weather, Korea Astronomy and Space Science Institute and KAIST Satellite Research Institute), and model development was overwhelmingly carried out at Kyung Hee University. In solar and interplanetary fields, we introduce Fast Imaging Solar Spectrograph (FISS), neutron monitors, and the analysis models [for the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) and Hinode/X-Ray Telescope (XRT) observations] in nonequilibrium ionization state as representatives. Survey on solar and interplanetary fields can be downloaded from the website of the Korean Space Science Society (http://ksss.or.kr/). The paper makes know the importance of long-term and continuous management of space science-related materials, and hopes to contribute to enhancing the status of domestic space science data by utilizing locally produced data by various personnel participating in space science research.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.4
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• pp.213-220
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• 2023

This paper presents a model simulating the folding process and collision dynamics of "ddakji", a traditional Korean game played using paper tiles (which are also referred to as ddakji). The model uses two A4 sheets as the base materials for ddakji. The folding process involves a series of boundary conditions that transform the wing part of the paper structure into a twisted configuration. A rigid plate boundary condition is also adopted for squeezing, establishing the shape and stress state of the game-ready ddakji through dynamic relaxation analysis. The gaming process analysis involves a forced displacement of the striking ddakji to a predetermined collision position. Collision analysis then follows at a given speed, with the objective of overturning the struck ddakji--a winning condition. A genetic algorithm-based optimization analysis identifies the optimal collision conditions that result in the overturning of the struck ddakji. For efficiency, the collision analysis is divided into two stages, with the second stage carried out only if the first stage predicts a possible overturn. The fitness function for the genetic algorithm during the first stage is the direction cosine of the struck ddakji, whereas in the second stage, it is the inverse of the speed, thus targeting the lowest overall collision speed. Consequently, this analysis provides optimal collision conditions for various compression thicknesses.

• Journal of the Korea Society for Simulation
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• v.19 no.4
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• pp.11-19
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• 2010

ZigBee is a standard for wireless personal area networks(WPANs) based on the IEEE 802.15.4 standard. It has been developed for low cost and low power consumption. There are two alternative routing schemes that have been proposed for the ZigBee standard: Ad-hoc On-Demand Distance Vector(AODV) and tree routing. The tree routing forwards packets from sensors to a sink node based on the parent-child relationships established by the IEEE 802.15.4 MAC topology formation procedure. In order to join the network, a sensor node chooses an existing node with the strongest RSSI(Received signal strength indicator) signal as a parent node. Therefore, some nodes carry a large amount of traffic load and exhaust their energy rapidly. To overcome this problem, we introduce a new metric based on link quality and traffic load for load balancing. Instead of the strength of RSSI, the proposed scheme uses the new metric to choose a parent node during the topology formation procedure. Extensive simulation results using TOSSIM(TinyOS mote SIMulator) show that the CFR scheme outperforms well in comparison to the conventional tree routing scheme.

• Environmental and Resource Economics Review
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• v.31 no.4
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• pp.451-480
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• 2022

The Japanese Flying Squid (Todarodes pacificus) is a commercially important species in South Korea and the most popular species among consumers. However commercial catches of Japanese Flying Squid have been declining since 2000. In this study, we conducted a stock assessment to identify stock status. This study differed from previous studies in two aspects: a greater amount of available fishing effort data was used, and data from China, Japan, and Korea were included. A CMSY (catch-maximum sustainable yield) model was used to estimate MSY, biomass and exploitation with Bayesian state-space implementation of the Schaefer (BSS) model for the method of stock assessment, and evaluated the species by dividing into two groups, 'Korea' and ' Korea·China·Japan'. In all cases, Japanese flying squid biomass showed a general decreasing trend. Additionally, the biomass estimated for 2020 was lower than the biomass necessary to achieve the maximum sustainable yield. To manage Japanese Flying Squid effectively, it is necessary to strengthen the resource management strategies of individual countries and prepare a cooperative plan among countries.