• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.1
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• pp.161-167
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• 2022

Ocean waves passing through the underwater bar at a shallow depth experience a shoaling effect caused by decreasing water depth, a nonlinear interaction therein owing to steepening wave slope, and a wave dispersion effect as the water depth increases again. Because this problem includes many complicated phenomena, it is used as a good example of validating a theoretical development or a CFD method for ocean wave applications. Validation is performed mainly for regular waves by comparing the wave elevation patterns in the time domain with the experimental results. In this study, the spectral evolution of wave spectrum is investigated in the frequency domain when a CFD method such as OpenFOAM is applied for this problem. In particular, the effects of initial phase conditions as well as the nonlinear interaction among harmonic waves are studied.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.12
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• pp.1904-1913
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• 2021

With the proliferation of smart phones and the development of IoT technology, it has become possible to collect personal data for public purposes. However, users are afraid of voluntarily providing their private data due to privacy issues. To remedy this problem, mainly three techniques have been studied: data disturbance, traditional encryption, and homomorphic encryption. In this work, we perform simulations to compare them in terms of accuracy, message length, and computation delay. Experiment results show that the data disturbance method is fast and inaccurate while the traditional encryption method is accurate and slow. Similar to traditional encryption algorithms, the homomorphic encryption algorithm is relatively effective in privacy preserving because it allows computing encrypted data without decryption, but it requires high computation costs as well. However, its main cost, arithmetic operations, can be processed in parallel. Also, data analysis using the homomorphic encryption needs to do decryption only once at any number of data.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.515-524
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• 2022

In this study, the on-site hydrogen production process for refueling stations that were not energy-optimized was improved through exergy analysis and heat exchange network synthesis. Furthermore, the process was scaled up from 30 Nm3/h to 150 Nm3/h to improve hydrogen production capacity. Exergy analysis results show that exergy destruction in the SMR reactor and the heat exchanger accounts for 58.1 and 19.8%, respectively. Thus, the process is improved by modifying the heat exchange network to reduce the exergy loss in these units. As a result of the process simulation analysis, thermal and exergy efficiency is improved from 75.7 to 78.6% and 68.1 to 70.4%, respectively. In conclusion, it is expected to improve the process efficiency when installing on-site hydrogen refueling stations.

• The Journal of the Korea Contents Association
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• v.21 no.5
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• pp.755-764
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• 2021

This study aimed to examine the effects of the character education program applying mindfulness diary in 'H' girls' middle school, which is implemented as a practical character education at the school level while supplementing the limitations of existing character education programs. To achieve this, the pre- and post-design of a single treatment group in which data were collected over three time periods over two years for all 182 enrolled students was conducted. As a result of repeated measures of ANOVA to examine the significant mean change in the data, this program significantly improved the level of self-control, prosocial behavior, and gratitude of students. This was not only showing a significant improvement one year after the start of the program, but also showing a continuous significant improvement even one year later. Based on the above results, the implications and suggestions of this study were discussed.

• Smart Media Journal
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• v.12 no.9
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• pp.103-115
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• 2023

A Korean Tea-Historical Literature DB was constructed, collating information related to tea from eight historical texts, including the Annals of the Joseon Dynasty. Data were gathered from existing historical literature DB and web services. After processing, verification, and tag input, 53,679 historical literature data entries related to tea were created. This DB construction centralizes previously dispersed reading services into a single web service. Features such as literature title, time, and tag-based search functionality; assignment of attribute tags to data; search linkage through original source links; and a bookmark function were incorporated to enhance user convenience. The outcomes of this research support studies in the related fields, and it is believed that by accumulating and improving accessibility to tea-related literature, contributions can be made to the preservation and education of Korean traditional tea as a food resource and cultural heritage.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6B
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• pp.731-741
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• 2008

Previous studies on the numerical simulation at the tidal reach of Han River tend to restrict downstream boundary as Jeon-ryu station due to difficulties in gaining cross section data and tidal elevation values at Yu-do. But, in this study, geometries beyond the confluence of Gok-reung stream and Im-jin River are constructed based on the numerical sea map; tidal elevation at the downstream boundary, Yu-do is estimated by harmonic analysis of In-cheon tide gage station so that hydrodynamic and diffusion behavior have been analyzed. The domain ranging from Shin-gok submerged weir to Yu-do is selected (which is 36.8 km in length). RMA-2 and RAM4 developed by Il Won Seo (2008) are applied to simulate flow and diffusion behavior, respectively. Numerical results of flow characteristic are compared with the measured data at Jeon-ryu station. Simulation is carried out from June 23 to 25 in 2006 on the ground that hydrologic data is satisfactory and tidal difference is huge during that period. The result shows that reverse flow occurs 5 times according to the tidal elevation at Yu-do and the maximum reverse flow is observed up to Jang-hang IC, which is 32.9 km in length. Also analysis is focused on the process of generation and disappearance of reverse flow, the distribution of water surface elevation and velocity along the maximum velocity line, and the transport of nonconservative pollutant. Pollutant injected from Gul-po stream spreads widely across the river; however, the size of BOD cloud entering from Gok-reung stream is relatively small because water depth at the mid and left side becomes deeper and maximum velocity occurs along the right bank so that transverse mixing is completed quickly. Finally, mixing characteristic of horizontal salinity distribution is obtained by estimating the salinity input with analytical solution of 1D advection-dispersion equation.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.43 no.1
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• pp.61-68
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• 2017

The key quality attributes of the pressed powder, one of base makeup products, are skin-affinity and spreadability. In general, there was a limit to meet skin-affinity and spreadability simultaneously, which are opposite attributes each other. In this study, air jet mill process was tried to satisfy two main properties. Skin-affinity was improved by a wet coating of sericite with a mixture of lauroyl lysine (LL) and sodium cocoyl glutamate (SCG). The application of mono-dispersed polymethyl methacrylate (PMMA) and diphenyl dimethicone/vinyl diphenyl dimethicone/silsesquioxane crosspolymer (DDVDDSC) improved both qualities. Air jet mill process has been mainly applied in the pharmaceutical and food industries, and is a method used for processing powder materials in cosmetic field. In this study, we were able to complete makeup cosmetics with an optimum particle size $6.8{\mu}m$ by combining the air jet mill process at the manufacturing stage. It was confirmed that the Ti element was uniformly distributed throughout the cosmetics by EDS mapping, and that the corners of the tabular grains were rounded by SEM analysis. It is considered that this can provide an effect of improving the spreadability when the cosmetic is applied to the skin by using a makeup tool. LL with excellent skin compatibility and SCG derived from coconut with little skin irritation were wet coated to further enhance the adhesion of sericite. SEM images were analyzed to evaluate effect of the dispersion and uniformity of PMMA on spreadability. With the spherical shapes of similar size, it was found that the spreading effect was further increased when the distribution was homogeneously mono-dispersed. The dispersion and spreadability of PMMA were confirmed by measuring the kinetic friction and optimal content was determined. The silicone rubber powder, DDVDDSC, was confirmed by evaluating the hardness, spreading value, and drop test. Finally, it was found that the dispersion of PMMA and silicone rubber powder affected spreadability. Such makeup cosmetics have excellent stability in drop test while having appropriate hardness, and good stability over time. Taken together, it is concluded that air jet mill process can be utilized as a method to improve skin-affinity and spreadability of the pressed powder.

• Korean Journal of Remote Sensing
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• v.35 no.6_2
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• pp.1117-1132
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• 2019

Forest covers 30% of the Earth's land area and plays an important role in global carbon flux through its ability to store much greater amounts of carbon than other terrestrial ecosystems. The Gross Primary Production (GPP) represents the productivity of forest ecosystems according to climate change and its effect on the phenology, health, and carbon cycle. In this study, we estimated the daily GPP for a forest ecosystem using remote-sensed data from Moderate Resolution Imaging Spectroradiometer (MODIS) and machine learning algorithms Support Vector Machine (SVM). MODIS products were employed to train the SVM model from 75% to 80% data of the total study period and validated using eddy covariance measurement (EC) data at the six flux tower sites. We also compare the GPP derived from EC and MODIS (MYD17). The MODIS products made use of two data sets: one for Processed MODIS that included calculated by combined products (e.g., Vapor Pressure Deficit), another one for Unprocessed MODIS that used MODIS products without any combined calculation. Statistical analyses, including Pearson correlation coefficient (R), mean squared error (MSE), and root mean square error (RMSE) were used to evaluate the outcomes of the model. In general, the SVM model trained by the Unprocessed MODIS (R = 0.77 - 0.94, p < 0.001) derived from the multi-sites outperformed those trained at a single-site (R = 0.75 - 0.95, p < 0.001). These results show better performance trained by the data including various events and suggest the possibility of using remote-sensed data without complex processes to estimate GPP such as non-stationary ecological processes.

• Journal of Korean Society of Forest Science
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• v.66 no.1
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• pp.82-94
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• 1984

The variation of stomatal density and stomatal length of four species of oaks was studied for the purpose of examining the differences among populations and among individual trees within population. Nine populations of Quercus mongolica, four populations of Q. serrata and Q. variabilis respectively, and three populations of Q. acutissima were selected in the natural stands of oaks distributed through the whole country. Twelve leaves were sampled from each of 20 trees from each population. The length of 20 stomata and ten replications of stomatal density were measured from collodion replicas of each leaf under a microscope. Average stomatal densities and lengths ranged through $600-1000/mm^2$ and $19-26{\mu}m$ respectively in all of the species studied. The stomatal densities and lengths presented significant differences statistically at the level of 1 or 5% among populations and among individual trees within population in all the species. Quercus mongolica, especially, showed large variation among populations, while Q. variabilis did very narrow variation compared to the other species. The coefficients of variation of stomatal densities and lengths among individual trees within population exhibited small values of 3.7-12.0% and 1.4-5.3% respectively in all the populations of the species. The average stomatal densities of Q. mongolica showed statistically significant correlation of multiple correlation coefficient of $R_{df{\cdot}2.6}=0.868^*$ and multiple regression equation of $Y=0.041X_1(G.M.T.S.)+0.489X_2(G.M.H.S.)+22.37$ with the sum of growing season mean daily temperature and the sum of growing season mean daily humidity of the stand studied. However the average stomatal lengths showed no relation with the same meteological variables. The figures of frequency distribution of the measurements of leaves or the mean values of individual trees did not show normal distribution curves in some populations. The curves, as well as the results of ANOVA, exhibited the differences among populations.

• Journal of KIISE:Computer Systems and Theory
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• v.34 no.5_6
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• pp.257-266
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• 2007

In On-Chip bus, the arbitration scheme is one of the critical factors that decide the overall system performance. The arbitration scheme used in traditional shared bus is the master-side arbitration based on the request and grant signals between multiple masters and single arbiter. In the case of the master-side arbitration, only one master and one slave can transfer the data at a time. Therefore the throughput of total bus system and the utilization of resources are decreased in the master-side arbitration. However in the slave-side arbitration, there is an arbiter at each slave port and the master just starts a transaction and waits for the slave response to proceed to the next transfer. Thus, the unit of arbitration can be a transaction or a transfer. Besides the throughput of total bus system and the utilization of resources are increased since the multiple masters can simultaneously perform transfers with independent slaves. In this paper, we implement and analyze the arbitration schemes for the Multi-Layer AHB BusMatrix based on the slave-side arbitration. We implement the slave-side arbitration schemes based on fixed priority, round robin and dynamic priority and accomplish the performance simulation to compare and analyze the performance of each arbitration scheme according to the characteristics of the master and slave. With the performance simulation, we observed that when there are few masters on critical path in a bus system, the arbitration scheme based on dynamic priority shows the maximum performance and in other cases, the arbitration scheme based on round robin shows the highest performance. In addition, the arbitration scheme with transaction based multiplexing shows higher performance than the same arbitration scheme with single transfer based switching in an application with frequent accesses to the long latency devices or memories such as SDRAM. The improvements of the arbitration scheme with transaction based multiplexing are 26%, 42% and 51%, respectively when the latency times of SDRAM are 1, 2 and 3 clock cycles.