• Korean Journal of Cognitive Science
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• v.29 no.4
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• pp.265-281
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• 2018

This study examines the effect of present and future situation on the temporal distance estimation to the future. The effect of present and future situation on time expression was verified. In Experiment 1, an experiment was conducted to investigated the effects of positivity/negativity situation of the present and the future on the judgment of subjective the distance to a certain future time. The results are as follows. When the present is positive and the future is negative, the future looks closer than the objective temporal distance and comes faster, When the present is negative and the future is positive, the future looks farther and comes slower. On the other hand, when the present and the future are both negative, the future looks coming slower. And when the present and the future are both positive, the future is expected to come faster. In Experiment 2, the cognitive and emotional aspects of subjective time through time expressions. It can be said to be 'the time of perseverance' in the sense of time for effort. On the other hand, when the present is positive compared to the future, the time seems go fast and we generally prefer to use cognitive expressions such as 'fast' and emotional expressions such as 'near' and 'pleasant' and 'flutter'. It is 'the time of availability', which means the time to enjoy and utilize.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.683-690
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• 2003

This purpose of this research is an attempt to measure and comparatively analyze the efficiencies and RTS(Returns to Scale) using panel data of OECD countries including Korea. In order to achieve this purpose, at first this study used efficient production frontier estimation combined with DEA for obtaining parameter estimates of a efficient production frontier. secondly using estimated results, measured R&D productivity and RTS(Returns to Scale) on all of the OECD countries. thirdly using time-series data related to R&D activity of korea, measured R&D productivity and RTS(Returns to Scale). Finally based on the results of R&D productivity and RTS(Returns to Scale) using efficient production frontier, some policy implications for enhancing the R&D competitiveness and the technological capabilities are discussed.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.157.5-157
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• 2001

Generally, the application of Programmable Logic Controller PLC is emphasized on the Process Control. This paper presents Neurofuzzy application, Which can estimate the distance to a fault by means of PLC and based up on the Electrical Power System theory and ground resistance. The case study refers to the distribution lines of the Provincial Electricity Authority (PEA). Also, the thesis is supposed to be of much benefit: saving time both to go to the scene and to clear fault, reducing unpleasant impacts on customers and stabilizing reliability of the distribution lines.

• Journal of Information Technology Services
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• v.18 no.1
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• pp.173-186
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• 2019

Recently, as the amount of fine dust has risen rapidly, our interest is increasing day by day. It is virtually impossible to remove fine dust. However, it is best to predict the concentration of fine dust and minimize exposure to it. In this study, we developed a mathematical model that can predict the concentration of fine dust using various information related to the weather and air quality, which is provided in real time in 'Air Korea (http://www.airkorea.or.kr/)' and 'Weather Data Open Portal (https://data.kma.go.kr/).' In the mathematical model, various domestic seasonal variables and atmospheric state variables are extracted by multiple regression analysis. The parameters that have significant influence on the fine dust concentration are extracted, and using ANN (Artificial Neural Network) and SVM (Support Vector Machine), which are machine learning techniques, we proposed a prediction model. The proposed model can verify its effectiveness by using past dust and weather big data.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.20-28
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• 2014

In this paper, based on the characteristics of proportional navigation, a composite guidance law is proposed for impact angle control of passive homing missiles maintaining the lock-on condition of the seeker. The proposed law is composed of two guidance commands: the first command is to keep the look angle constant after converging to the specific look angle of the seeker, and the second is to impact the target with terminal angle constraint and is implemented after satisfying the specific line of sight(LOS) angle. Because the proposed law considers the seeker's filed-of-view(FOV) and acceleration limits simultaneously and requires neither time-to-go estimation nor relative range information, it can be easily applied to passive homing missiles. The performance and characteristics of the proposed law are investigated through nonlinear simulations with various engagement conditions.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2019.10a
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• pp.76-76
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• 2019

The purpose of this study was to evaluate the antioxidant and whitening action of Fagopyrum esculentum and F. tataricum buckwheat seeds depending on their germination time. In a previous study, we reported significant changes in sprout yield and phytochemical content in ethanol extracts from F. esculentum and F. tataricum seeds with increase in germination times. DPPH radical scavenging activities of F. tataricum increased with increasing germination time, whereas that of F. esculentum decreased. Next, we investigated anti-melanogenic activities of these species by estimation of melanin content and tyrosinase activity. Inhibition of melanin production in ${\alpha}-MSH$ (${\alpha}$-melanocyte stimulating hormone)-induced B16F10 cells by extracts from these seeds were analyzed. Among the two, F. tataricum extracts were characterized by higher inhibitory activity against melanin production. In addition, when B16F10 cells were incubated with L-DOPA for detection of in situ tyrosinase activity, F. tataricum and F. esculentum extracts were observed to reduce melanin production in cells. Taken together, these results indicate that extracts from buckwheat seeds could influence cellular processes via modulation of tyrosinase activity. Hence, buckwheat seeds could be utilized as whitening agents in the cosmetic industries and as therapeutics for hyperpigmentation disorders in a clinical setting.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.5
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• pp.501-510
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• 2016

Capabilities of several beamforming techniques are compared for estimating the position of a moving source. Beamforming has enabled to widen our perspective of aeroacoustics in wind tunnel experiments and has provided useful approach in array measurements. Meanwhile beamforming techniques have been developed in a way to improve estimation accuracy and to save ing effort at the same time. In order to achieve reasonable outcome from aeroacoustic measurement, it is important to identify the spectral characteristics of source and to select an appropriate beamformer. Though aeroacoustic sources normally generates broadband noises, many array signal processing have been focused on narrowband processing which makes calculation numerically efficient. However, calculation in frequency-domain requires selection of single frequency of interest which affects spatial resolution and sidelobe level as a consequence. To be able to localize broadband noise source, it is proposed to use broadband beamforming. The formulas implements the deletion of diagonal term from cross spectral matrix. In this study, trajectory of flying source emitting broadband noise was simulated and several beamformers are applied.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.7
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• pp.3433-3446
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• 2019

Aiming at the high complexity of traditional single-channel demodulation algorithm for PCMA signals, a new demodulation algorithm based on neural network is proposed to reduce the complexity of demodulation in the system of non-cooperative PCMA communication. The demodulation network is trained in this paper, which combines the preprocessing module and decision module. Firstly, the preprocessing module is used to estimate the initial parameters, and the auxiliary signals are obtained by using the information of frequency offset estimation. Then, the time-frequency characteristic data of auxiliary signals are obtained, which is taken as the input data of the neural network to be trained. Finally, the decision module is used to output the demodulated bit sequence. Compared with traditional single-channel demodulation algorithms, the proposed algorithm does not need to go through all the possible values of transmit symbol pairs, which greatly reduces the complexity of demodulation. The simulation results show that the trained neural network can greatly extract the time-frequency characteristics of PCMA signals. The performance of the proposed algorithm is similar to that of PSP algorithm, but the complexity of demodulation can be greatly reduced through the proposed algorithm.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.69-74
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• 2016

A technique for improving estimation accuracy is introduced in order to locate the impact position of artillery shell during the weapon scoring test. Study on localization of impacts using acoustic measurement has been conducted and the usability of sensor array is verified with experiments. When the blast occurs above the ground in the firing range, the acoustic sensor above the ground can measure the directly propagated sound with the ground-reflected one. In this study, a method for reducing estimation error by using the reflection signal measurements based on the time difference of arrival method. Considering the reflection sound works as same as placing a virtual sensor symmetrically through the ground. This idea enables a virtual three-dimensional array configuration with a two-dimensional plane array above the ground as such. The time difference between the direct and the reflected propagations can be estimated using cepstrum analysis. Performance test has been made in the simulation experiment in the football size area.

• Geomechanics and Engineering
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• v.27 no.5
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• pp.433-445
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• 2021

Artificial ground freezing (AGF) is a commonly used geotechnical support technique that can be applied in any soil type and has low environmental impact. Experimental and numerical investigations have been conducted to optimize AGF for application in diverse scenarios. Precise simulation of groundwater flow is crucial to improving the reliability these investigations' results. Previous experimental research has mostly considered horizontal seepage flow, which does not allow accurate calculation of the groundwater flow velocity due to spatial variation of the piezometric head. This study adopted vertical seepage flow-which can maintain a constant cross-sectional area-to eliminate the limitations of using horizontal seepage flow. The closure time is a measure of the time taken for an impermeable layer to begin to form, this being the time for a frozen soil-ice wall to start forming adjacent to the freeze pipes; this is of great importance to applied AGF. This study reports verification of the reliability of our experimental apparatus and measurement system using only water, because temperature data could be measured while freezing was observed visually. Subsequent experimental AFG tests with saturated sandy soil were also performed. From the experimental results, a method of estimating closure time is proposed using the inflection point in the thermal conductivity difference between pore water and pore ice. It is expected that this estimation method will be highly applicable in the field. A further parametric study assessed factors influencing the closure time using a two-dimensional coupled thermo-hydraulic numerical analysis model that can simulate the AGF of saturated sandy soil considering groundwater flow. It shows that the closure time is affected by factors such as hydraulic gradient, unfrozen permeability, particle thermal conductivity, and freezing temperature. Among these factors, changes in the unfrozen permeability and particle thermal conductivity have less effect on the formation of frozen soil-ice walls when the freezing temperature is sufficiently low.