• Proceedings of the KWS Conference
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• 2010.05a
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• pp.95-95
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• 2010

자동차 산업에서 차체를 성형하는 프레스 금형 산업은 꾸준히 증가하고 있는 자동차 생산대수와 함께 성장해가고 있으며, 자동차 산업의 국제 경쟁이 심해지고 소비자들의 요구가 다양해짐에 따라 신제품 개발주기에 발맞추어 금형의 제작에도 단납기 및 비용절감을 위한 노력과 제품의 품질 향상을 위해 신기술, 신공법이 적용되고 있다. 한편 자동차 차체를 제작하는 프레스 금형가공은 박판소재를 원하는 형상으로 제작하는 공정으로써, 프레스의 상 하 운동을 이용하여 강판을 성형한다. 이러한 금형의 형태는 곧 자동차 차체 제품의 형태를 완성하므로 제품을 성형하는 도중에 금형과 소재의 마찰에 의해 금형의 마모나 마멸이 발생하여 제품의 품질을 저하시킬 우려가 있다. 따라서 금형의 내마모성 및 수명을 향상시키기 위한 방안들 중 표면경화처리가 행해지고 있으며, 그중 공정 속도가 빠르고 국부적인 열처리가 가능한 레이저 표면처리 방법이 많은 관심을 받고 있다. 본 연구에서는 이러한 금형의 성질을 향상시키기 위해 고출력 다이오드 레이저를 이용하여 프레스 금형공정 중 드로잉(drawing) 공정에의 적용을 위한 표면경화처리를 실시하였다. 최대출력 4.0kW의 다이오드 레이저를 사용하였으며, 6축 외팔보 로봇에 열처리용 광학계를 장착하여 열처리를 실시하였다. 또한 광학계 부근에는 적외선 온도센서가 부착되어있어 열처리시 시험편의 표면온도를 실시간으로 측정할 수 있도록 구성되어져있다. 시험편은 금형재료용 구상흑연 주철인 FCD550 소재를 사용하였으며, 공정변수에 따른 열처리 특성을 파악하고, 그 경화특성을 평가하였다. 실험 결과, FCD550 소재의 표면 열처리시 레이저 출력 3.5kW, 빔 이송속도 3mm/sec에서 최적의 열처리 특성을 나타내었으며, 이때의 최고 경도는 930Hv을 나타내며 모재에 비해 경도가 3배 정도 상승하는 우수한 경화특성을 보였다.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.24 no.1
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• pp.28-35
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• 2013

Objectives : The aim of this study was to examine attitudes of middle-school students toward happiness, suicide, and factors associated with suicide. Methods : A self-administered questionnaire was used in a cluster sample of 1,319 middle-school students (male 793, female 526). Data were obtained on a wide range of constructs regarding their attitude towards happiness, suicidal ideation and attempts, and factors associated with suicide. Results : Middle-school students choose 'love within family' as most important factor for their happiness. Subjective mental health status was mostly associated with happiness. Subjects in lower socioeconomic status tended to respond their mental health status was not good and have more suicidal idea. 48.7% of subjects had permissive attitudes toward suicide, especially, girls. However, 65.0% responded that suicide was preventable problem. Compared to older people, middle-school students perceived that environmental factors were more important than innate and personal factors for suicide. Conclusion : Results of the study indicate that middle-school students have permissive attitudes toward suicide, but positive attitudes for the prevention of suicide. This suggest that education in these age group could be effective for the prevention of suicide. Also, approaches to suicide prevention programs should be developed based on the family intervention. Especially, we should care about girls and adolescents in lower socioeconomic status.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.19-26
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• 2011

Compaction tests have been performed to investigate the compaction characteristics of sands and clays with organic mixture. Weathered granite soil, kaolinite, and granulated carbon were used as the alternatives of sand, clay, and organics, respectively. The soapy water which is a kind of surfactant solutions was also used as water substitute to see the engineering properties changes of each soil. As seen when water was used, the optimum moisture contents increased and the maximum dry unit weight decreased for the soil with surfactants as the percentage of the organic contents increased. Surfactants slightly improved the compaction efficiency at low compactive energy level for the weathered granite soil with organics. As the organic contents increased for clays with surfactants, the optimum moisture contents decreased and the maximum dry unit weight increased. Surfactants slightly improved the compaction efficiency of clays with organics at all levels of compaction energy.

• Composites Research
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• v.30 no.1
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• pp.15-20
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• 2017

In this study, LIPCA-S2 actuator with a piezoelectric single crystal layer and a carbon/epoxy layer was designed and evaluated to increase actuation performance of piezo-composite unimorph actuator. A curvature change model generated by the induced strain of a piezoelectric layer was used to predict the tip displacement of the piezo-composite unimorph cantilever. However, we found that there was big difference between the predicted and the measured tip displacement of LIPCA-S2 cantilever actuator when we used the previous linear prediction model. A new prediction model considering the change of piezoelectric strain coefficient and elastic modulus for the compression stress variation of the PMN-29PT single crystal layer was used and it was found that the difference between the predicted and the measured tip displacement reduced considerably.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.3
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• pp.219-224
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• 2000

Reproductive biology of the naked-headed goby, Faronigobius gymnauchen was investigated by means of histological methods. The ovary was consisted of several ovarian lamellae and the oogonia originated from the inner surface of the ovarian lamella. The testis was seminiferous tubule One in internal structure. Seminiferous tubule was consisted of many testicular cysts which contained numerous germ cells in a same developmental stage. The size of group maturity was 4.5 cm intotal length. Gonadosomatic index(GSI) of the female and male was the highest in June and July, respectively. Reproductive cycle could be classified into the growing ($January{\~}March$), maturation ($April{\~}May$), ripe and spent (June{\~}July$), and recovery and resting ($August{\~}December$). Oocyte development was group-synchronous, and yolk nucleus was observed in the early growing oocyte.

• The Journal of the Acoustical Society of Korea
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• v.22 no.1
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• pp.61-68
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• 2003

The guided wave has been widely employed to characterize thin plates and layered media. The dispersion curves of phase and group velocities are essential for the quantitative application of guided waves. In the present work, a fully automated system for the measurement of backward radiation of LLW has been developed. The specimen moves in two dimensional plane as well as in angular rotation. The signals of backward radiation of LLW were measured from an elastic plate in which specific modes of Lamb wave were strongly generated. Phase velocity of the corresponding modes was determined from the incident angle. The generated Lamb waves propagated forward and backward with the leakage of energy into water. Backward radiated LLW was detected by the same transducer and its frequency components were analyzed to extract the related information to the dispersion curves. The dispersion curves of phase velocity were measured by varying the incident angle. Moving the specimen in the linear direction of LLW propagation, group velocity was determined by measuring the transit time shift in the ultrasonic waveform.

• Journal of The Korean Association of Information Education
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• v.6 no.3
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• pp.266-278
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• 2002

The purpose of this study is to help cultivating Children's sensibility through the development of typing program which shows vocabulary of sensibility. The characteristic of this typing education program is designed to finish the game when the children get the certain point by typing the words on the screen(from the top to the bottom) within the limit of time. For examples, adjectives in the Korean dictionary, the words of modern & traditional children's songs, imitative words and echoic words through this game, the children are fully aware of the meaningful words without realizing it. Through this game, the children are fully a ware of the meaningful words without recognizing it. After application of this typing education program children were fully aware of meaningful words more than meaningless words. After examining the survey of children we could discover that this typing program help cultivating children's sensibility.

• Journal of The Korean Association of Information Education
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• v.7 no.3
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• pp.299-308
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• 2003

Programming education in the area of ICT instruction is usually considered as contributing to the improvement of one's analytical power, logic in thinking, and procedural problem-solving capabilities. However, it is hard to get access to adequate web coursewares in suit with their intellectual level of development of Korean elementary students. Most of the existing coursewares, if any, are dealing with high level and theory-oriented contents, and accordingly are quite difficult for the elementary students to understand them. In addition, it is very difficult to practice them on the Web. Drawing upon some ideas on the theories of Web-based design and learning, this study tries to develop and materialize a fresh learning courseware for Visual Basic. The Web courseware thus developed allows students to learn the basics of visual basic programming as well as the basic grammar. It also provides students with an environment that enables students to code and run programs on the Web.

• Journal of The Korean Association of Information Education
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• v.7 no.3
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• pp.285-298
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• 2003

According to the operation guide book concerning the educations of Information Communication, Art for Primary and Middle school issued by Ministry of Education, Korea, 2001, it revealed many things as to an Spread Sheet's paradigm, that is, as to an useful program in Science, Practical course, Moral, Physical education and Society. However it can be said that the existing Spread Sheet is more or less unconvenience to use for pupils. Because most of pupils generally feel constrained to the functional formula and also when a complicated menu of Spread Sheet would be made the most of it. Moreover, from a certain point of view, it is somewhat too difficult to use the program as they feel intuitionally taking a look at it. This very thesis in order to support a part of probability and statistics for pupils were observed sincerely.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2465-2472
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• 2015

Wireless Medium Access Control (MAC) and routing technologies are the basic building blocks making it possible the Internet of Things (IoT). These technologies have been the focus of substantial research in the last decade. Nevertheless, as new networking standards for IoT are being proposed and different solutions are patched together, evaluating the performance of the network becomes unclear. In this paper, a new overview of MAC and routing protocols for IoT and new interactions are given. The IEEE 802.15.4 MAC and Routing Protocol for Low-power Lossy Network (RPL) routing protocols are taken as reference to exemplify and illustrate the discussion. Experimental results show that contention-based access MACs may hurt the routing, unless these two are carefully designed together.