• Journal of the Korean earth science society
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• v.37 no.5
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• pp.286-294
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• 2016

Using a method suggested by Yanovskaya, we obtained Rayleigh wave group velocities with a resolution of $1.0^{\circ}{\times}1.0^{\circ}$ in a period range between 10 and 80 s in and around the Korean peninsula. Both regional and distant earthquake data sets were used together in analysis of group velocities. The resolution of the group velocity maps has been remarkably enhanced by the method, especially in the sparse/non-station region in the northern Korean peninsula. Some qualitative geophysical information was inferred from the group velocity maps. In the East Sea, the slow group velocities at periods longer than 40 s suggest the existence of an oceanic lithosphere at depths of 50-70 km, assuming 4 km/s of S wave velocity at a period of 40 s. On the other hand, a thick lithosphere can be inferred in the continental area from the fast group velocities at periods longer than 50 s. For most periods, the group velocities change rapidly over a short distance of about 200 km across the eastern coast of Korean peninsula, which may suggest a rapid change in the thickness of lithosphere in this area.

• Journal of Advanced Navigation Technology
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• v.10 no.1
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• pp.7-12
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• 2006

In this paper, we investigated performance for 5.8GHz dedicated short range communication system using OFDM which will be applied to Intelligent transportation system services. The maximum speed of a vehicle in DSRC channel is very fast as 180km/h, so a service time is very short to serve a various traffic information if hand-off is not occurred. Therefore higher bit rate is required to proved advanced and intelligent service to the drivers of various vehicle and the data transmission rate of the next generation DSRC system if being promoted over 10Mbps. The signals received in Racian channel have been simulated using the computer simulator. For performance improvement, BCH coding scheme are adopted.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.1
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• pp.421-433
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• 2015

Recently, there have been fast-growing social network services based on the Internet environment and web technology development, the prevalence of smartphones, etc. Social networks also allow the users to convey the information and news so that they have a great influence on the public opinion formed by social interaction among users as well as the spread of information. On the other hand, these social networks also serve as perfect environments for rampant malware. Malware is rapidly being spread because relationships are formed on trust among the users. In this paper, an effective patch strategy is proposed to deal with malicious worms based on social networks. A graph is formed to analyze the structure of a social network, and subgroups are formed in the graph for the distributed patch strategy. The weighted directions and activities between the nodes are taken into account to select reliable key nodes from the generated subgroups, and the Incremental PageRanking algorithm reflecting dynamic social network features (addition/deletion of users and links) is used for deriving the high influential key nodes. With the patch based on the derived key nodes, the proposed method can prevent worms from spreading over social networks.

• Geomechanics and Engineering
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• v.6 no.6
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• pp.531-544
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• 2014

Studies of earthquakes over the last 50 years and the examination of dynamic soil behavior reveal that soil behavior is highly nonlinear and hysteretic even at small strains. Nonlinear behavior of soils during a seismic event has a predominant role in current site response analysis approaches. Common approaches to ground response analysis include linear, equivalent linear and nonlinear methods. These methods of ground response analysis may also be categorized into time domain and frequency domain concepts. Simplicity in developing analytical relations and accuracy in considering soils' dynamic properties dependency to loading frequency are benefits of frequency domain analysis. On the other hand, nonlinear methods are complicated and time consuming mainly because of their step by step integrations in time intervals. In part Ι of this paper, governing equations for seismic response analysis of surcharged and layered soils were developed using fundamental of wave propagation theory based on transfer function and boundary conditions. In this part, nonlinear seismic ground response is analyzed using extended HFTD method. The extended HFTD method benefits Newton-Raphson procedure which applies regular iterations and follows soils' fundamental stress-strain curve until convergence is achieved. The nonlinear HFTD approach developed here are applied to some examples presented in this part of the paper. Case studies are carried in which effects of some influencing parameters on the response are investigated. Results show that the current approach is sufficiently accurate, efficient, and fast converging. Discussions on the results obtained are presented throughout this part of the paper.

• Journal of information and communication convergence engineering
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• v.21 no.2
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• pp.117-129
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• 2023

High-utility itemset mining (HIUM) has emerged as a key data-mining paradigm for object-of-interest identification and recommendation systems that serve as frequent itemset identification tools, product or service recommendation systems, etc. Recently, it has gained widespread attention owing to its increasing role in business intelligence, top-N recommendation, and other enterprise solutions. Despite the increasing significance and the inability to provide swift and more accurate predictions, most at-hand solutions, including frequent itemset mining, HUIM, and high average- and fast high-utility itemset mining, are limited to coping with real-time enterprise demands. Moreover, complex computations and high memory exhaustion limit their scalability as enterprise solutions. To address these limitations, this study proposes a model to extract high-utility frequent closed itemsets based on an improved cumulative summary list structure (CSLFC-HUIM) to reduce an optimal set of candidate items in the search space. Moreover, it employs the lift score as the minimum threshold, called the cumulative utility threshold, to prune the search space optimal set of itemsets in a nested-list structure that improves computational time, costs, and memory exhaustion. Simulations over different datasets revealed that the proposed CSLFC-HUIM model outperforms other existing methods, such as closed- and frequent closed-HUIM variants, in terms of execution time and memory consumption, making it suitable for different mined items and allied intelligence of business goals.

• The Journal of Korea Robotics Society
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• v.12 no.3
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• pp.350-355
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• 2017

UWB (Ultra Wide Band) refers to a system with a bandwidth of over 500 MHz or a bandwidth of 20% of the center frequency. It is robust against channel fading and has a wide signal bandwidth. Using the IR-UWB based ranging system, it is possible to obtain decimeter-level ranging accuracy. Furthermore, IR-UWB system enables acquisition over glass or cement with high resolution. In recent years, IR-UWB-based ranging chipsets have become cheap and popular, and it has become possible to implement positioning systems of several tens of centimeters. The system can be configured as one-way ranging (OWR) positioning system for fast ranging and TWR (two-way ranging) positioning system for cheap and robust ranging. On the other hand, the ranging based positioning system has a limitation on the number of terminals for localization because it takes time to perform a communication procedure to perform ranging. To overcome this problem, code multiplexing and channel multiplexing are performed. However, errors occur in measurement due to interference between channels and code, multipath, and so on. The measurement filtering is used to reduce the measurement error, but more fundamentally, techniques for removing these measurements should be studied. First, the TWR based positioning was analyzed from a stochastic point of view and the effects of outlier measurements were summarized. The positioning algorithm for analytically identifying and removing single outlier is summarized and extended to three dimensions. Through the simulation, we have verified the algorithm to detect and remove single outliers.

• Microbiology and Biotechnology Letters
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• v.19 no.2
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• pp.128-134
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• 1991

To study the reduced growth and synthesis, proeviously reported, of ${\beta}$-galactosidase of alkalophilic Bacillus sp. YS-309 at the higher lactose concentration of 0.5% (w/v) in the medium, lactose transport and utilization were examined. The results showed that lactose transport was influenced by the addition of four kinds of antibiotics, and tetracycline stimulated most but not valinomycin. PEP-potentials of the cells grown on lactose was estimated lower than the cells on glucose and on galactose. Thus, the transport of lactose was independent of intracellular PEP and phosphorylation reactions, and was thought to be uptaked directly or oxidized in part in the transport process. In the other hand, once lactose was uptaked into the cells, it was hydrolyzed by ${\beta}$-glactosidase to glucose and galactose. The former was metabolized fast but the latter was accumulated. Galactose and lactose were not utilized until glucose was mostly depleted in the medium. The ${\beta}$-galactosidase synthesis decreased in the presence of glucose over 0.2% and galactose over 0.05 to 0.1%, respectively. In conclusion, it was considered for glucose as a repressor and galactose as a inducer for ${\beta}$-galactosidase synthesis even though the mechanisms were not elucidated. Catabolite repression of glucose on the enzyme synthesis was not relieved by the addition of exogeneous cAMP.

• Journal of the Korean earth science society
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• v.25 no.4
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• pp.277-288
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• 2004

In this study, state of sea surface were analyzed comparatively for cases of low atmospheric pressure, which occurred in the middle area of China and moved eastward to the Korean Peninsula across the Yellow sea during April 9-12, 1999, and typhoons 'NEIL' May 1999 and 'OLGA' July 1999, which moved northward along the west coast of the Korean Peninsula. In cases of low pressure, wind speeds and phases were respectively stronger and faster in the center area than in the surrounding areas. The wave heights seem to a somewhat differing tendency from that of the wind speeds due to the influences of geometry. On the other hand, wave heights were lower under typhoon weather than under low pressures, except the instance of wave height over 5 m on Chilbal when typhoon Olga pass northward from the southern area. Storm surges also showed larger amplitudes under low pressures than under typhoons. The results suggest that wave sand storm surges may be larger for a slow passing synoptic low pressures than for a fast passing local typhoon.

• Proceedings of the IEEK Conference
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• 2001.10a
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• pp.526-531
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• 2001

LD slag, that is, a by-product of steel making process, has been mainly used as land construction materials. Recently, the seashore application of LD slag was tried in Japan and Korea tut the reaction between LD slag and seawater was not studied yet. We tried to clarify the leaching reaction and/or mechanism of LD slag and the reaction between seawater and LD slag. We tried to apply these results to the decarbonization of seawater for seawater magnesia process. At first, LD slag was milled and classified into 5 grades, that is, (ⅰ)45${\mu}{\textrm}{m}$ under, (ⅱ)0.25~0.5mm (ⅲ)0.5~1mm(ⅳ)1~2mm, (ⅴ)2.36~3.35mm. These slags were leached in the distilled water. In case of 45${\mu}{\textrm}{m}$ under, the pH of the leached solution was over 12. The chemical analysis of leached solution showed that the $Ca^{+}$$^2$was main component and the S $i^{+}$$^4$was very low. On the other hand, the content of S $i^{+}$$^4$in leached solution was decreased with the increase of pH of this solution. The nearly pure calcium solution was made and the ultra high purity MgO could be made with this calcium solution. The leaching behavior of LD slag was different between the fine particle and coarse particle. The calcium was leached by bulk dissolution in the coarse particle and by surface controlled reaction in fine particle. The leaching rate was slow in coarse particle and fast in fine particle. Therefore, the high pH solution, that is, over 12, was obtained in fine particle.cle.e.

• Journal of the East Asian Society of Dietary Life
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• v.22 no.2
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• pp.163-174
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• 2012

This study focused on the nutrition knowledge, food purchase behaviors, and dietary habits of 213 housewives (41 women under 39 years, 98 women 40~49 years, and 74 women over 50 years). Younger housewives held more special jobs, whereas older housewives worked as housewives or had no jobs ($p$<0.05). The average monthly income of the three family groups was 3,000,000~5,000,000 won, and the monthly dietary expenditure for all three groups was 200,000~500,000 won. Familial frames for the three groups was nuclear family (over 80%), but housewives younger than 39 years (19.5%) lived together with their parents and let them take care of their children. Housewives (over 50 years) prepared a balanced diet for every meal, utilized less drastic cooking methods to prevent loss of nutrients, and shopped at many places in order to save money on various food materials. Further, they purchased food materials that resulted in the least amount of left overs. On the other hand, housewives under 39 years visited large supermarkets and purchased cooked foods more than other groups. Housewives under 39 years considered nutrients content as the most important factor when purchasing food materials, whereas 74.5% of housewives between 40~49 years and 51.4% of housewives over 50 years put the most importance on flavor ($p$<0.05). Housewives under 39 years were interested in manufacture date, nutrient content, and food price, in decreasing order, whereas housewives between 40~49 years and over 50 years were interested in manufacture date, food prices, and nutrient content. Older housewives were interested in brown rice and fruits, whereas younger housewives under 39 years were interested in meat, fish, eggs, fried foods, and fast food. Older housewives over 50 years did not consume fried foods more than two times per week and consumed three regular meals more often than younger housewives. Accordingly, for younger housewives, it is necessary that healthy foods be cooked for their families.