• Korean Journal of Cognitive Science
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• v.11 no.1
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• pp.47-65
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• 2000

Categorization systems of homepages in search engines are likely to be constructed considering system's efficiency only but not user-centered. This study I investigated user's mental model of superordinate and subordinate categories using category terms of major Korean search engines. From this result, we constructed two kinds of categorization system; redundant system and singular system. In the redundant system, for example, a subordinate category can belong to a number of superordinate categories, but in the singular system to only one superordinate category Three prototype categorization systems, with 'Simmani', were designed and search performances of each system were observed repetitively Overall results, with frequency of correct a answers, number of steps and time taken in solution taken into account, showed the redundant system was superior to the other two systems. This indicates that categorization search could be improved with appropriate categorizaton system. However. l in recognition test score in singular system was the best, which indicates that search performance and recognition memory of categorization reveal different aspects of categorization system learning. Issues of category organization. ways of interface, prior knowledge, exploratory learning, and application areas are discussed further.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.6 s.348
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• pp.1-8
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• 2006

In the asynchrous OFCDM(Orthogonal Frequency and Code Division Multiplexing) system, a three-step cell search algorithm is performed for the initial synchronization in the following three steps: OFCDM symbol timing, i.e., Fast Fourier Transform(FFT) window timing is estimated employing guard interval (GI) correlation in the first step, then the frame timing and CSSC (Cell Specific Scrambling Code) group is detected by taking the correlation of the CPICH(Common Pilot Channel) based on the property yeilded by shifting the CSSC phase in the frequency domain. Finally, the CSSC phase within the group is identified in the third step. This paper proposes a modification code(PCSSCG:Patial Cell Specific Scrambling Code Group) of the conventional CPICH based cell search algorithm in the second step which offers MS(Mobile Station) complexity reductions with the nearly same performance. The proposed method is to be compared and verified through the computer simulation.

• Journal of Nutrition and Health
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• v.35 no.1
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• pp.115-123
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• 2002

This study was carried out to investigate the utilization status of internet dietary information by gender(boys: 363, girls: 366) in adolescent(middle & high school students). The results were summarized as follows. The internet using frequency of 6-7times per week had 45.0% of subjects and the using time of internet per a time was shown mainly'<2hours(68.5%)'. The main place for internet use was home(79.0%) and favorite search engine was 'Yahoo'(45.7%) and 'Daum'(19.3%). As main purpose using internet were mentioned 'social intercourse'(45.0%) and data search'(24.8%). The organization that offer to reliable internet information was educational institution'(49.4%). The problems in using information site were 'poor information'(26.4%), 'slow connection speed'(22.6%), and 'don't arouse interest'(18.8%). The search experience about dietary information had only 27.9% of subjects and search purpose was 'for homework'(33.3%) and 'for health'(32.0). The satisfaction degree of dietary information was not high. The connection motive to dietary information was mainly 'by site navigation casualty'(55.7%). Only 7.7% of subjects had experience of nutrition counseling using internet, and the motive of nutrition counseling was also 'by site navigation causally'(55.8%). The purpose of counseling was 'for diet'(41.5%) and 'for health problem'(30.2%), and the satisfaction degree of counseling result was very low. As the ask of improvement for counseling site were pointed out 'poor in answer content'(44.8%) and 'lazy answer'(31.0%). The subjects wanted to get the dietary information about 'growth in status'(41.4%), 'diet related skin beauty'(14.6%), the update period less 1 month, and the way of 'free board'(32.3%), 'game'(21.1%) and 'animation'(19.3%) as offer tool. The results of this study showed that although the internet using percent and frequency of subjects was high, they used dietary information very seldom and they are dissatisfied with internet nutritional information. Therefore, the information donor should consider which dietary information was needed and what is the optimal tool for adolescent.

• The Journal of the Korea Contents Association
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• v.9 no.11
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• pp.54-62
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• 2009

To avoid the redundant investment on the project selection process, it is necessary to check whether the submitted research topics have been proposed or carried out at other institutions before. This is possible through the search engines adopted by the keyword matching algorithm which is based on boolean techniques in national-sized research results database. Even though the accuracy and speed of information retrieval have been improved, they still have fundamental limits caused by keyword matching. This paper examines implemented TFIDF-based algorithm, and shows an experiment in search engine to retrieve and give the order of priority for similar and redundant documents compared with research proposals, In addition to generic TFIDF algorithm, feature weighting and K-Nearest Neighbors classification methods are implemented in this algorithm. The documents are extracted from NDSL(National Digital Science Library) web directory service to test the algorithm.

• Korean Institute of Interior Design Journal
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• v.25 no.4
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• pp.80-89
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• 2016

The analysis of spatial search direction and its concentration through eye movement can produce some useful data in that it enables to know the features of space elements and their effects on one another. The results by analysing the search features and concentration of spatial sections through the eye-tracking in shops in a department store makes it possible to define the followings. First, the features of 'eye's in & out' could be estimated through the division of sections by the characteristics of those shops and the extraction of central point based on the decision of continuative observation. The decision of continuative observations enabled to analyse the frequency of observation data which can be considered to be 'things watched longtime' and the stared points that is equivalent to 'things seen very often', by which the searching characteristics of spatial sections could be estimated. Second, as with the eye's [in], the right shops had 0.6 times more (3.5%) than those left and as with the eye's [out] the left ones had 0.6 times more (3.5%). It indicates that [in, out] of the right and the left shops had the same difference, which lets us know that with starting point of the middle space, [in] and [out] were paid more attention to the right shops and the left shops respectively. Third, as with the searching directions by section, the searching times [2.9 times] from [B] to [A] were than that [2.6 times] from [A] to [B]. It was also found that the left shops had more searching direction toward [C, D] than the right ones and that those searching activities at the left shops were more active. Fourth, when the searching directions by section are reviewed, the frequency of searching from [B] to [A] was 2.9 and that of the other way 2.6. Also the left shops were found to have more searching direction toward [C, D] than the right ones and those searching activities at the left shops were estimated to be more active.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.6C
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• pp.480-486
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• 2008

The high peak-to-average power ratio (PAPR) of the transmitted signals is one of major drawbacks of the orthogonal frequency division multiplexing (OFDM). A partial transmit sequences (PTS) technique can improve the PAPR statistics of OFDM signals. However, in a PTS technique, the search complexity to select phase weighting factors increases exponentially with the number of sub-blocks. In this paper, a PTS technique with low computational complexity is presented, which adopts micro-genetic algorithm(${\mu}$-GA) as a search algorithm. A search on the phase weighting factors starts with a population of five randomly generated individuals. An elite having the largest fitness value and the other four individuals selected through the tournament selection strategy are determined, and then the next generation members are generated through the crossover operations among those. If the new generation converges, all the four individuals except the elite are randomly generated again. The search terminates when there has been no improvements on the PAPR during the predefined number of generations, or the maximum number of generations has been reached. To evaluate the performance of the proposed PTS technique, the complementary cumulative distribution functions (CCDF) of the PAPR are compared with those of the conventional PTS techniques.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.2
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• pp.19-25
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• 2008

When there are numerous wireless communication systems co-existing in the limited available frequency resource, an unexpected time delay can be caused during the system switching. So, in order to reduce this time delay, a mode selection method is required. In this paper, we propose a mode selection method to minimize the time delay for multi-system wireless communication systems. For the sake of efficiency, the mode selection method is designed by analyzing the preamble characteristics of different standards. Instead of performing a full search, we propose the preamble partial search to reduce the time delay to a minimum. Simulated with Matlab in an additive white Gaussian noise(AWGN) environment with a signal to noise ratio(SNR) of 10dB and bit error rate(BER) of $10^{-6}$, we evaluated and showed the performance improvement gained by using our proposed mode selection method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.1
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• pp.139-149
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• 2007

Asynchronous OFCDM(Orthogonal Frequency and Code Division Multiplexing) systems must have a cell search process necessarily unlike synch개nous systems. this process is hewn initial synchronization and a three-step cell search algorithm is performed for the initial synchronization in the following three steps: OFCDM symbol timing, i.e., Fast Fourier Transform(FFT) window timing is estimated employing guard interval (GI) correlation in the first step, then the frame timing and CSSC(Cell Specific Scrambling Code) group is detected by taking the correlation of the CPICH(Common Pilot Channel) based on the property yielded by shifting the CSSC phase in the frequency domain. Finally, the CSSC phase within the group is identified in the third step. This paper proposes a modification group code with two or three block of the conventional CPICH based cell search algorithm in the second step which offers MS(Mobile Station) complexity reductions. however, the effect of the reduction complexity leads to degradation of the performance therefore, look for combination to have the most minimum degradation. the proposed block type group code with suitable combinations is the nearly sane performance as conventional group code and has a complexity reduction that is to be compared and verified through the computer simulation.

• Journal of Magnetics
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• v.21 no.4
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• pp.509-515
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• 2016

We report on development of a ground-based bi-axial Search-Coil Magnetometer (SCM) designed to measure time-varying magnetic fields associated with magnetosphere-ionosphere coupling processes. The instrument provides two-axis magnetic field wave vector data in the Ultra Low Frequency or ULF (1 mHz to 5 Hz) range. ULF waves are well known to play an important role in energy transport and loss in geospace. The SCM will primarily be used to observe generation and propagation of the subclass of ULF waves. The analog signals produced by the search-coil magnetic sensors are amplified and filtered over a specified frequency range via electronics. Data acquisition system digitizes data at 10 samples/s rate with 16-bit resolution. Test results show that the resolution of the magnetometer reaches $0.1pT/{\sqrt{Hz}}$ at 1 Hz, and demonstrate its satisfactory performance, detecting geomagnetic pulsations. This instrument is scheduled to be installed at the Korean Antarctic station, Jang Bogo, in the austral summer 2016-2017.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.3C
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• pp.302-313
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• 2010

In this paper, we propose an enhanced AGC (Automatic Gain Control) structure and P-SCH detection method for initial cell search in 3GPP (3rdGenerationPartnershipProject) LTE (Long Term Evolution) FDD(Frequency Division Duplex) / TDD (Time Division Duplex) dual mode system. Since TDD frame structure consists of uplink subframe and downlink subframe, conventional AGC structure causes P-SCH detection performance degradation by increase of AGC variation due to signal power difference between uplink and downlink subframe. Also, P-SCH detection performance is degraded by distortion of P-SCH correlation characteristic in frequency offset and multipath fading channel environments. Therefore, we propose an AGC structure which can minimize P-SCH detection performance degradation with stable operation in 3GPP LTE TDD mode as well as FDD mode. Also we propose a P-SCH detection method which can reduce distortion of correlation chareteristics in frequency offset and multipath fading environments and obtain good P-SCH detection performance. Simulation results show that the proposed AGC structure and P-SCH detection method have stable AGC operation and excellent P-SCH detection performance for 3GPP LTE TDD / FDD dual mode downlink receiver in various channel environments.