• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.6
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• pp.56-61
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• 2011

A class-D audio amplifier is widely used in coil speaker. This paper presented the technique for applying a class-D audio amplifier to the ceramic flat speaker. This technique can be achieved by employing a matching transmitter in order to replace class-G amplifier that is drven by voltage level to class-D amplifier employing power driving method. Consequently, the presented technique can improve the efficiency by making the voltage driving level a litter larger. We evaluate the sound-level efficiency using the various mediums such as wood, plastic, and paper. From the simulation results, the proposed technique employing a class-D audio amplifier rather than a class-G one showed a 10% improvement. The proposed system can be applicable for the mobile appliances as an external slim speaker.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.5
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• pp.373-380
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• 2014

Film flows applied to shell-and-tube heat exchangers in various industrial fields have been studied for a long time. One boundary of the film flow interfaces with a fixed wall, and the other boundary interfaces with a gaseous region. Thus, the flows become so unstable that wavy behaviors are generated on free surfaces as the film Reynolds number increases. First, high-amplitude solitary waves are detected in a low Reynolds number laminar region; then, the waves transit to a low-amplitude, high frequency ripple in a turbulent region. Film thickness is the most significant factor governing heat transfer. Since the wave accompanied in the film flow results in temporal and spatial variations in film thickness, it can be of importance for numerically predicting the film's wavy behavior. In this study, various turbulent models are applied for predicting low-amplitude ripple flows in turbulent regions. The results are compared with existing experimental results, and finally, the applied turbulent models are appraised in from the viewpoint of wavy behaviors.

• Journal of the Korean Society of Radiology
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• v.6 no.6
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• pp.477-481
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• 2012

An X-ray diffractometer which has various X-ray optics can give qualitative and quantitative information for a sample using a nondestructive analysis method. A parallel beam optic passes the parallel beam and removes divergent beam generated from an X-ray tube. The parallel beam optic used in the X-ray diffractometer was fabricated by wire cut and grading of stainless steel plates and was evaluated its performance using an X-ray imaging system. The measured parallelization of 6.6 mrad for the fabricated the parallel beam optic was a very close to the expected value of 6 mrad. An X-ray imaging technique for evaluating the parallel beam optics can estimate parallelization for each plate and can be used to other X-ray optics.

• The Journal of the Korea Contents Association
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• v.10 no.1
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• pp.122-137
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• 2010

Blogs are a new type of media that have recently become popular on the World Wide Web and have influence throughout society. The purpose of this study is to examine social motivations influencing intention of blog usage. Based on Technology Acceptance Model and Motivation Theory, this study considered perceived usefulness, perceived ease of use, reputation, reciprocity, enjoyment of helping, social identity as the determinants of influencing the intention to use of blog. The suggested model was empirically evaluated using online survey data collection from 342 users of popular blog site in Korea (NAVER Blog, Cyworld minihompy, Daum Blog, and Yahoo Blog). The results revealed that perceived usefulness, perceived ease of use, reciprocity, and social identity affect directly the intention of blog usage. Furthermore, social identity has moderate effect via reciprocity and enjoyment of helping on blog usage. This study contributes to a theoretical understanding of the factors as social motivation that affects the usage of blogs. Also, the results of this study provide blog service providers useful strategic insights and service guidelines to enhance user's intention of blogs practically.

• Journal of the Korean Society for Railway
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• v.14 no.4
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• pp.320-326
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• 2011

This paper proposes a baseline-free SHM technique in which the time-reversal process of Lamb waves and the imaging method are used. The proposed SHM technique has three distinct features when compared with the authors' previously proposed one: (1) It use the reconstructed signal for damage diagnosis, without need to extract the damage signal as the difference between reconstructed signal and initial input signal; (2) It use the imaging method based on the time-offlight information from the reconstructed signal, instead of using a pattern comparison method; (3) In order to make the damage image more clear, the modified mathematical definition of damage image in a pixel is used. The proposed SHM technique is evaluated through the damage detection experiment for an aluminum plate with damage at different locations.

• Journal of KIISE
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• v.44 no.4
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• pp.339-343
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• 2017

As the number of customers who write fake reviews is increasing, online shopping sites have difficulty in providing reliable reviews. Fake reviews are called review spam, and they are written to promote or defame the product. They directly affect sales volume of the product; therefore, it is important to detect review spam. Review spam detection methods suggested in prior researches were only based on an international site even though review spam is a widespread problem in domestic shopping sites. In this paper, we have presented new review features of the domestic shopping site NAVER, and we have applied the formerly introduced method to this site for performing an evaluation.

• The Journal of Information Systems
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• v.17 no.4
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• pp.301-319
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• 2008

The display market has been replaced by the FPD (Flat Panel Display) from the CRT (Cathode-Ray Tube) since the late 1990s. In the FPD production line, the most equipment has high price. Thus, when the equipment has multi-function, the repetitive process is arranged for the equipment. However, such disposition of equipment results in more complicated process flow owing to repetitive operations. This reduces the production capacity and increases lead-time in turn. In this paper, we develop an AutoMod simulation system that derives to information about the quantity, production lead-time, utilities of facilities, and occupation rates of racks. In this simulation system, we consider the situation where the equipment might be broken and suspended randomly. For the developed system, we first evaluate a production plan with current layout and then, propose a revised alternative plan. Using the same simulation scheme, we investigate comparing the production quantity and lead-time with the two plans. In addition, for a proposed alternative, we try to forecast the most adequate rule between the two job dispatching rules which are FOR (Fewest Operation Remaining) and FCFS (First Come First Serve) through simulation.

• KIISE Transactions on Computing Practices
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• v.22 no.5
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• pp.240-245
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• 2016

In this study, comments on restaurants, movies, and mobile devices, as well as tweet messages regardless of specific domains were analyzed for sentimental information content. We proposed a system for extraction of objects (or aspects) and opinion words from each sentence and the subsequent evaluation. For the sentiment analysis, we conducted a comparative evaluation between the Structural SVM algorithm and the Latent Structural SVM. As a result, the latter showed better performance and was able to extract objects/aspects and opinion words using VP/NP analyzed by the dependency parser tree. Lastly, we also developed and evaluated the sentiment detector model for use in practical services.

• Proceedings of the Korea Information Processing Society Conference
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• 2018.05a
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• pp.306-308
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• 2018

본 연구에서는 체중 감량을 위해 무분별한 다이어트 식품의 남용을 막고, 다이어트 보조 식품에 대한 정보를 제공하기 위해서 감성 분석을 활용하여 다이어트 보조 식품에 대한 온라인 후기를 분석하였다. 먼저, 다이어트 보조 식품을 그 특성에 따라 네 가지 종류로 분류하고 각 카테고리 별로 긍정 및 부정 점수를 계산하였다. 이를 위해 체중 감량에 대한 감성 사전을 다이어트 식품에 대한 후기를 텍스트 마이닝하여 구축하였다. 특히 부작용이 있는 식품에 대한 부정 점수에 가중치를 두기 위해서 WHO-ART 에서 정의한 부작용 용어에는 가중치를 두어 처리하였다. 분석 결과 단백질 보충 식품군이 긍정 점수가 가장 높게 나타났고, 이는 다이어트를 위한 목적 이외에도 운동을 전문적으로 하는 사람들에게 오랜기간 사용되어 왔기 때문인 것으로 해석된다. 또한 식욕 억제제 식품군이 긍정점수는 가장 낮고 부정 점수는 가장 높게 나타났는데, 이는 식욕억제제의 주성분인 펜타민에 의한 가능성이 클 것이라고 예측된다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.438-440
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• 2014

Recently it is used commercially to actively move the data from the SNS service. Therefore, we propose a method that can accurately analyze the information related to the reputation of companies and products in real time SNS environment in this paper.Identify the relationship between words by performing morphological analysis on the text data gathered by crawling the SNS scheme. In addition, it shows the visualization to analyze statistically through a established emotional dictionary morphemes are extracted from the sentence. Here, if the extracted word is not exist in sentimental dictionary. Also, we propose the algorithm that add the word to emotional dictionary automatically.