• Smart Structures and Systems
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• v.12 no.2
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• pp.137-155
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• 2013

Brittle fracture of structures excited by earthquakes can be prevented by adding a tuned mass damper (TMD). This TMD must be optimum and suitable to the physical conditions of the structure. Compressive strength of concrete is an important factor for brittle fracture. The application of a TMD to structures with low compressive strength of concrete may not be possible if the weight of the TMD is too much. A heavy TMD is dangerous for these structures because of insufficient axial force capacity of structure. For the preventing brittle fracture, the damping ratio of the TMD must be sufficient to reduce maximum shear forces below the values proposed in design regulations. Using the formulas for frequency and damping ratio related to a preselected mass, this objective can be only achieved by increasing the mass of the TMD. By using a metaheuristic method, the optimum parameters can be searched in a specific limit. In this study, Harmony Search (HS) is employed to find optimum TMD parameters for preventing brittle fracture by reducing shear force in additional to other time and frequency responses. The proposed method is feasible for the retrofit of weak structures with insufficient compressive strength of concrete.

• Journal of Navigation and Port Research
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• v.30 no.5 s.111
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• pp.357-362
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• 2006

This paper describes two kinds of personal hand-held electronic devices to enhance marine leisure safety. The one is Radar response-type safety device triggering by the pulse signal from a commercial 9GHz-band Radar to provide quick search and rescue with combined civilian-government-military fleets. The other one is M-RFID (Marine Radio Frequency IDentification) based safety electronic device using 900MHz Tx/Rx with spread spectrum frequency hopping and GPS. Through the field tests at sea using Korea Coast Guard's warship the operating performances are verified. Further plan for practical use of each device was also discussed.

• International Journal of Advanced Culture Technology
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• v.12 no.1
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• pp.270-275
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• 2024

Introduction. In this study, purpose is to analize the types of golf tourism, inbound or outbound, by using big data and see how movement of industry is being changed and what changes have been made during and after Covid-19 in golf industry. Method Using Textom, a big data analysis tool, "golf tourism" and "Covid-19" were selected as keywords, and search frequency information of Naver and Daum was collected for a year from 1 st January, 2023 to 31st December, 2023, and data preprocessing was conducted based on this. For the suitability of the study and more accurate data, data not related to "golf tourism" was removed through the refining process, and similar keywords were grouped into the same keyword to perform analysis. As a result of the word refining process, top 36 keywords with the highest relevance and search frequency were selected and applied to this study. The top 36 keywords derived through word purification were subjected to TF-IDF analysis, visualization analysis using Ucinet6 and NetDraw programs, network analysis between keywords, and cluster analysis between each keyword through Concor analysis. Results By using big data analysis, it was found out option of oversea golf tourism is affecting on inbound golf travel. "Golf", "Tourism", "Vietnam", "Thailand" showed high frequencies, which proves that oversea golf tour is now the re-coming trends.

• Journal of Internet Computing and Services
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• v.18 no.4
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• pp.109-119
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• 2017

This paper is to analyse empirically using the data collected from Korea portal Naver's ad management system and show online ad platform may not be two-sided market. It is aim of this study to propose the appropriate approach to define the market, based on the empirical result. Here are two research questions to be reviewed. First, is there any consistency between business model of search advertising and definition of two-sided market which Rochet-Tirole proposed in 2006? Second, do indirect network externalities exist significantly in search advertising market? if so, this study is going to estimate the level of it through empirical measurement. Based on Luchetta's paper which suggested that google may be one-sided market, it performed the correlation & regression analysis to prove his suggestion. The result is that online search advertising costs increased by more than 50 won when advertisers increased by one unit. However, there was no significant correlation and regression between the search frequency and online search advertising cost. It means that there is little possibility to identify two-sidedness in online search advertising service(market) because of no(or little) indirect network externalities which are a necessary condition for two-sided market. This result has three implications, such as the availability to adapt traditional market definition tools to online search advertising market, the possibility enhancement to find the fundamental competition elements in defined market and promotion of the powers of persuasion in competitive market reality. It is significant that the gap between legal scholars including regulatory practitioners and economists can be overcome to some extent. who have shown the different perspective on the two-sided market.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.248-251
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• 2006

This paper provides the basic theory and numerical results of shell design optimization considering the appearance of close natural frequencies in optimization process. In this study the fundamental natural frequency to be maximized is considered as the objective function and the initial volume of structures is used as the constraint function. In addition, the constraints related to natural frequency is also adopted to avoid the natural frequency closeness phenomenon during the optimization iteration. The Coon's patch is used to represent the shape and thickness distribution of shells. A degenerated shell finite element is adopted to calculate the fundamental natural frequency of the shells. The SQP available in the optimizer DoT is used to search optimum solution. From numerical results, the introduction of the frequency constraint into shell design optimization can deeply affect on the final optimum shape of shells although it is likely to be used to avoid the frequency closeness phenomenon.

• Journal of IKEEE
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• v.22 no.4
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• pp.1158-1162
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• 2018

A fast-lock multiplying delay-locked loop (MDLL)-based digital clock frequency multiplier with an anti-harmonic lock capability is presented. The proposed digital frequency multiplier utilizes a new most-significant bit (MSB)-interval search algorithm to achieve fast-locking time without harmonic lock problems. The proposed digital MDLL frequency multiplier is designed in a 65nm CMOS process, and the operating output frequency range is from 1 GHz to 3 GHz. The digital MDLL provides a programmable fractional-ratio frequency multiplication ratios of N/M, where N = 1, 4, 5, 8, 10 and M = 1, 2, 3, respectively. The proposed MDLL consumes 3.52 mW at 1GHz and achieves a peak-to-peak (p-p) output clock jitter of 14.07 ps.

• Journal of Information Technology Services
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• v.19 no.4
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• pp.49-61
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• 2020

Prior studies on technology predictions attempted to predict the emergence and spread of emerging technologies through the analysis of correlations and changes between data using objective data such as patents and research papers. Most of the previous studies predicted future technologies only from the viewpoint of technology development. Therefore, this study intends to conduct technical forecasting from the perspective of the consumer by using keyword search frequency of search portals such as NAVER before and after the introduction of emerging technologies. In this study, we analyzed healthcare technologies into three types : measurement technology, platform technology, and remote service technology. And for the keyword analysis on the healthcare, we converted the classification of technology perspective into the keyword classification of consumer perspective. (Blood pressure and blood sugar, healthcare diagnosis, appointment and prescription, and remote diagnosis and prescription) Naver Trend is used to analyze keyword trends from a consumer perspective. We also used the ARIMA model as a technology prediction model. Analyzing the search frequency (Naver trend) over 44 months, the final ARIMA models that can predict three types of healthcare technology keyword trends were estimated as "ARIMA (1,2,1) (1,0,0)", "ARIMA (0,1,0) (1,0,0)", "ARIMA (1,1,0) (0,0,0)". In addition, it was confirmed that the values predicted by the time series prediction model and the actual values for 44 months were moving in almost similar patterns in all intervals. Therefore, we can confirm that this time series prediction model for healthcare technology is very suitable.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7A
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• pp.733-742
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• 2008

In 3GPP LTE downlink system, initial cell search is essential for mobile station to connect to base station. In order to obtain information of the base station, the mobile station detects frame timing, frequency offset, and cell identification using primary synchronization channel(PSC) and secondary synchronization channel(SSC), which are defined in downlink OFDMA specification. In this paper, we analyze various detection algorithms in practical environment of inter-cell-interference, frequency offset, and multi-path fading channel and propose the optimal algorithm. Simulation results show that partial correlation method (for PSC acquisition) and interference cancellation method (for SSC detection) are the most superior algorithms among the applicable algorithms. Employ these two algorithms for receiver design, initial cell search is performed with 99% probability within 70ms in the channel environment considered.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.43 no.1 s.307
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• pp.39-44
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• 2006

In this paper, search result list synthesis method is proposed using borda count method for still image retrieval based on MPEG-7 descriptors. MPEG-7 standardizes descriptors that extract feature information from media data. In many cases, using a single descriptor lacks of correctness, it is suggested to use multiple descriptors to enhance retrieval efficiency. In this paper, retrieval efficiency enhancement is achieved by combining multiple search results which are from each descriptor. In combining search result, newly calculated borda count method is proposed. Comparing current frequency compensated calculation, rank considered frequency compensation is used to score animage in database. This combining method is considered in Content based image retrieval system with relevance feedback algorithm which uses high level information from system user. In each relevance iteration step, adoptive borda count method is used to calculate score of images.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.10 s.101
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• pp.995-1002
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• 2005

An orthogonal frequency division multiplexing(OFDM) system has the problem of the peak-to-average power ratio(PAR). In general, in order to obtain optimal PAR reduction using the partial transmitted sequence(PTS), the total search for the number of sub-blocks and the rotation factors must be accomplished. As the number of sub-blocks and rotation factors increases, PAR reduction improves, such that complexity increases exponentially and the process delay occurs simultaneously. Therefore a technique that reduces PAR, which is almost close to optimal, and the amount of calculation is desired. In this paper a new method using genetic algorithm(GA), which is widely used to search for a point that is globally optimal in many problems, is proposed to search for a rotation factor that reduces simultaneously both the PAR and the amount of calculation, such that the complexity of calculation and the process time are reduced at the same time, Comparison is performed between the proposed method and the various techniques developed previously. The superiority of proposed method is presented by demonstrating the reduction of complexity while a similar PAR reduction is obtained.