• The KIPS Transactions:PartD
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• v.15D no.4
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• pp.485-494
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• 2008

Huge amounts of various web items such as keywords, images, and web pages are being made widely available on the Web. The popularities of such web items continuously change over time, and mining temporal patterns in popularities of web items is an important problem that is useful for several web applications. For example, the temporal patterns in popularities of search keywords help web search enterprises predict future popular keywords, enabling them to make price decisions when marketing search keywords to advertisers. However, presence of millions of web items makes it difficult to scale up previous techniques for this problem. This paper proposes an efficient method for mining temporal patterns in popularities of web items. We treat the popularities of web items as time-series, and propose gapmeasure to quantify the similarity between the popularities of two web items. To reduce the computation overhead for this measure, an efficient method using the Fast Fourier Transform (FFT) is presented. We assume that the popularities of web items are not necessarily following any probabilistic distribution or periodic. For finding clusters of web items with similar popularity trends, we propose to use a density-based clustering algorithm based on the gap measure. Our experiments using the popularity trends of search keywords obtained from the Google Trends web site illustrate the scalability and usefulness of the proposed approach in real-world applications.

• Journal of the Korea Society of Computer and Information
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• v.10 no.2 s.34
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• pp.1-10
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• 2005

In this Paper, we propose a new block matching a1gorithm that extracts motion vectors from consecutive range data. The proposed method defines a matching metric that integrates intensity, hue, and range. Our algorithm begins matching with a small matching template. If the matching degree is not good enough, we slightly expand the size of a matching template and then repeat the matching process until our matching criterion is satisfied or the predetermined maximum size has been reached. As the iteration proceeds, we adaptively adjust weights of the matching metric by considering the importance of each feature. In the experiments, we show that our block matching approach can work as a promising solution by comparing the proposed method with previously known method in terms of performance.

• Science of Emotion and Sensibility
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• v.3 no.1
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• pp.41-52
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• 2000

한·미 문화간 비교를 통하여 직물의 소리와 촉감이 주관적 감각에 미치는 영향을 고찰하고자 한국인과 미국인 각각 30명을 대상으로 의미분별척도에 의하여 서로 다른 8개 직물 소리의 주관적 감각(부드러움, 시끄러움, 유쾌함, 날카로움, 맑음, 거친, 높음)과 촉감의 주관적 감각 (딱딱함, 매끄러움, 성김, 시원함, 유연함, 까실거림, 무게, 두께)을 측정하였다. 직물 소리의 파라미터로 LPT(level pressure of total sound)와 Δf (frequency differences)를 계산하고, KES (Kawabata Evaluation System)을 이용하여 직물의 역학적 성질을 측정하였다. 직물의 소리에 대하여 ‘부드러움’의 점수가 높고 ‘시끄러움’과 ‘날카로움’, ‘거침’의 점수가 낮은 직물들이 주관적으로 유쾌하게 느껴지는 것으로 나타났다. 직물에 따른 소리의 시끄러움과 날카로움, 높음에 대한 주관적 감각은 한·미 간에 유사한 경향을 보였으나, 한국인은 미국인보다 모직물의 소리에 대하여 ‘부드러움’과 ‘유쾌함’의 점수가 높고, ‘거침’의 점수가 낮았으며, ‘맑음’에 대한 직물별 점수가 다양하였다. 직물의 촉감은 직물에 따른 차이가 더 다양하게 나타났다. ‘딱딱함’과 ‘매끄러움’의 직물 별 감각은 한 ·미 간에 유사한 경향을 보였는데, 한국인은 대체로 미국인보다 ‘성금’과 ‘까실거림’을 낮게, ‘시원함’을 높게 평가하였다. 직물 소리의 파라미터인 LPT와 ΔL이 양국인의 소리 감각에 영향을 미쳤는데, 한국인의 감각은 주로 LPT가, 미국인의 감각은 LPT와 ΔL이 함께 영향을 미치는 회귀식이 성립하였다. 촉감에서 ‘딱딱함’과 ‘매끄러움’, ‘유연함’, ‘까실거림’에 한·미 모두 표면 거칠기가 영향을 미쳤는데, 한국인의 촉감에 대한 회귀식이 더 많이 성립하였고 R2가 높게 나타났다.

• Membrane Journal
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• v.24 no.2
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• pp.123-135
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• 2014

The effects of pH, saturated oxygen, and back-flushing media were investigated in hybrid process of tubular ceramic microfiltration and $TiO_2$ photocatalyst-loaded PES (polyethersulfone) beads for advanced drinking water treatment, and compared results of water, nitrogen, or oxygen back-flushing in the viewpoints of membrane fouling resistance ($R_f$), permeate flux (J) and total treated water ($V_T$). $R_f$ decreased, and J and $V_T$ increased as decreasing pH. Turbidity treatment efficiencies were similar at water or nitrogen back-flushing independent of pH, but DOM (dissolved organic matter) treatment efficiency did not have a trend at water back-flushing. $R_f$ at NBF (no back-flushing) with SO (saturated oxygen) was the lower than that at NBF without SO. Also, the DOM treatment efficiency at NBF with SO was the lower than that at NBF without SO. It happened because OH radicals produced by reaction of SO and photocatalyst could dilute with water inside the module. The DOM treatment efficiency of gas back-flushing showed the larger than that of water back-flushing at back-flushig period 10 min. It proved that the adsorption or photo-oxidation of PES beads could be activated by the more effective bead-cleaning of gas back-flushing than water back-flushing.

• Membrane Journal
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• v.9 no.3
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• pp.178-184
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• 1999

A periodic backflushing was performed to reduce the membrane fouling of ultrafiltration for wastewater, and the effect and the optimum condition were investigated in this study. The alumina¬ceramic tubular membrane with pore size of 0.02${\mu}m$ was used for the wastewater treated by coagulation and sedimentation from two paper plants, of which A plant made toilet paper by recycling milk paper cartons and B plant recycled corrugated cardboards. And the effect of periodic backflushing to membrane fouling and quality of permeate were studied with a constant backflushing time of 3 sec. As results of measuring SS, TDS, and COD of source and permeate, the rejection rate of SS showed the highest value at the backflushing period of 15 see, which was the shortest time in these experiments, in case of waste¬water discharged from A plant. However, the rejection rate of COD had the highest value at the period of 30 sec for wastewater from both A and B plant. Then, the rejection rate of TDS was almost same at 30 and 60 sec for A plant wastewater, and the highest at 60 see for B plant. The effect of periodic back¬flushing to membrane fouling was investigated by change of permeate flux according to operating time. The permeate flux decreased slowly at the operation with backflushing, and was higher compared with that without backflushing in both case of A and B wastewater. But, the optimum period with the highest flux of A wastewater was different from that of B, because SS and COD of A was higher than those of Band TDS of B was higher than that of A.

• Korean Journal of Culture and Social Issue
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• v.23 no.2
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• pp.239-270
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• 2017

This study investigated the nature and dimensionality of the motives why employees showed the silence even though they could speak up their opinions. It aimed to develop the scales measuring employee silence. Thus, three studies were designed and particularly, two studies featured two different studies, totaling five studies. Study 1 conducted open-ended survey asking and 104 workers from a variety of work field answered. With the results of open-ended questions, a were developed, consisting of 60-items to measure employee silence motivation. Study 2 examined the scale developed and 481 workers from diverse work fields participated in. The exploratory factor and 'intra-ESEM' analyses were confirmed the construct of silence motivation, composing 5 factors(acquiescent, defensive, disengaged, opportunistic, relational silence) the 20-items was developed to measure the construct(Study 2-1). Furthermore, 'inter-ESEM' analysis was examined the discriminant validity of scale developed by the current study with general silence behavior and voice behavior. It found that the employee silence was distinguished from general silence behavior and voice behavior(Study 2-2). Study 3 was designed for validation of silence motivation scale which developed from Study 1 and Study 2. Based on these results, the implications and limitations of this study as well as the direction for future study were discussed.

• Journal of the Korea Society of Computer and Information
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• v.25 no.5
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• pp.99-106
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• 2020

The scalability problem inherent in collaborative filtering-based recommender systems has been an issue in related studies during past decades. Clustering is a well-known technique for handling this problem, but has not been actively studied due to its low performance. This paper adopts a clustering method to overcome the scalability problem, inherent drawback of collaborative filtering systems. Furthermore, in order to handle performance degradation caused by applying clustering into collaborative filtering, we take two strategies into account. First, we use fuzzy clustering and secondly, we propose and apply a similarity estimation method based on user preference for movie genres. The proposed method of this study is evaluated through experiments and compared with several previous relevant methods in terms of major performance metrics. Experimental results show that the proposed demonstrated superior performance in prediction and rank accuracies and comparable performance to the best method in our experiments in recommendation accuracy.

• Journal of the Korea Society of Computer and Information
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• v.27 no.7
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• pp.93-100
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• 2022

In the era of information overload on the Internet, the recommendation system, which is an indispensable function, is a service that recommends products that a user may prefer, and has been successfully provided in various commercial sites. Recently, studies to reflect the rating time of items to improve the performance of collaborative filtering, a representative recommendation technique, are active. The core idea of these studies is to generate the recommendation list by giving an exponentially lower weight to the items rated in the past. However, this has a disadvantage in that a time function is uniformly applied to all items without considering changes in users' preferences according to the characteristics of the items. In this study, we propose a time-aware collaborative filtering technique from a completely different point of view by developing a new similarity measure that integrates the change in similarity values between items over time into a weighted sum. As a result of the experiment, the prediction performance and recommendation performance of the proposed method were significantly superior to the existing representative time aware methods and traditional methods.

• Journal of Advanced Navigation Technology
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• v.16 no.3
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• pp.455-462
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• 2012

The loss due to caching replacement in the wireless mobile proxy caching structure has a significant effect on streaming QoS. This paper proposes a similarity-based caching loss minimization (SCLM) for minimizing the loss caused by the caching replacement. The proposed scheme divides object segments, and then it performs the similarity relation about them. Segments that perform the similarity relation generates similarity relation tree (SRT). The similarity is an important metric for deciding a relevance feedback, and segments that satisfy these requirements in the cache block for caching replacement. Simulation results show that the proposed scheme has better performance than the existing prefix caching scheme, segment-based caching scheme, and bi-directional proxy scheme in terms of QoS, average delayed startup ratio, cache throughput, and cache response ratio.

• Sleep Medicine and Psychophysiology
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• v.12 no.2
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• pp.133-138
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• 2005

Objectives: Narcolepsy is characterized by excessive sleepiness, cataplexy, sleep paralysis and hypnagogic hallucination. As there have been few researches on narcolepsy symptomatology in adolescents, we examined gender differences and prevalence of narcolepsy tetrad among students attending high school. Methods: Total 20,407 subjects, ages 14-19 years filled out Ullanlinna Narcolepsy Scale (UNS). Subjects whose UNS scores were equal to or more than 14 were interviewed by telephone using semi-structured questionnaire. Variables included questions to evaluate tetrad of narcolepsy. Results: UNS scores were higher in female than male ($11.1{\pm}5.2$ vs. $9.6{\pm}4.5$, p<0.001). Subjects scoring the UNS equal to or more than 14 were 4,535 (22.2% of all the participants), more frequently observed in female than in male (p<0.001). Excessive daytime sleepiness, cataplexy-like symptoms, sleep paralysis and hypnagogic hallucination in subjects of UNS ${\geq}14$ were significantly higher in female subjects than male ones. However, no significant gender difference was observed in the frequencies of severe sleep attack and cataplexy-like symptoms. Sleep paralysis was most frequently reported during sleep. There was significant correlation between sleep paralysis and hypnagogic hallucination (r=0.235, p<0.01). Conclusions: Our findings were that female adolescents complained more frequently narcolepsy symptoms than male subjects. Female adolescents might be more sensitive than male ones to physical complaints such as sleepiness or muscle weakness.