• Korean Journal of Optics and Photonics
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• v.12 no.2
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• pp.135-142
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• 2001

Recently, plastic optical fiber draws a lot of attention as a new transmission medium for local area network (LAN) and home network applications. As PMMA based GI-POF (Graded Index Plastic Optical Fiber) has very low loss at about 500 nm and 650 nm wavelengths, it is very important to have a compact ultra short optical pulse source at these wavelength windows. In this paper, we have investigated detailed characteristics of gain switched laser system by using a commercially available low cost RF devices and an InGaAlP Fabry Perot semiconductor laser operating at 650 nm wavelength. The shortest optical 'pulse obtained was 33 psec with 1 GHz repetition rate. Depending on the DC bias current and the modulation frequency, the FWHM and the pulse energy of the gain switched pulses show 33.3-82.8 psec and 0.97-9.69 pI respectively. Also, the spectral bandwidths for CW and gain switched operations are 0.44 nm and 1.50 nm. We believe that these results are quite useful for high bit rate optical transmission applications with PMMA based plastic optical fibers in addition to estimate properties of ultra fast optical components and electro-optic devices. vices.

• Journal of Korea Ship Safrty Technology Authority
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• s.28
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• pp.19-35
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• 2010

본 연구에서는 2톤 미만 소형선박에 대한 효율적인 안전관리를 위하여 RFID(Radio Frequency IDentification)시스템의 실제 해양환경에서의 도입타당성을 검증하였다. 이를 위하여 FRP Fiber Glass Reinforced Plastic 선박을 중심으로 목선과 알루미늄선에 태그를 부착하고 이동형 Reader를 활용하여 태그정보를 확인하는 실제 해양환경 인식실험을 실시하였다. 해양환경 인식실험을 위하여 4종의 태그를 선정하였으며 다양한 각도에서 인식률 및 인식거리를 측정하여 그 특성을 파악하고자 하였다. 특히, 선박에 설치된 무선설비로 인한 전파장애, 염분, 수분, 온도 등 열악한 해양환경에서 무선인식(RFID)기술의 기술적 환경적 문제점 유무를 분석하였으며, 2톤 미만 소형선박 소유자의 편의성 제고를 위하여 유관기관과의 관련정보 공유를 통한 연계방안으로 무선인식(RFID)기술을 적용한 효율적인 선박안전관리체계 구축방안을 강구하여 선박등록 및 검사업무에서의 활용방안을 제시하였다.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.3
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• pp.232-237
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• 2001

The purpose of this study was to find the clinical features of periapical lesions. A total of 130 periapical lesions which were obtained from biopsy and diagnosed histopathologically as periapical cyst, periapical abscess, and periapical granuloma at the Department of Dentistry in Hanyang University Hospital were throughly analysed according to the distribution and incidence of age, sex, location, and so on. The following results were obtained : 1. Out of 130 periapical lesions, 88 cases(67.7%) were periapical cysts, 30 cases(23.1%) were periapical abscesses, and 12 cases(9.2%) were periapical granulomas. 2. The periapical lesions occurred most frequently in the third decade, and followed by the fourth, fifth, sixth, and second decade. The periapical cysts occurred most frequently in the third decade(26.1%), the periapical granulomas in the fourth decade(33.3%) the periapical abscesses in the sixth decade(26.7%). 3. The periapical lesions were more frequent in men than in women with the ratio of men to women of 1.4 : 1. The radio of men to women of periapical cysts was 1.6 : 1, that of periapical granulomas was 0.5 : 1, and that of periapical abscesses was 1.3 : 1. 4. The periapical lesions were more frequent in maxilla than in mandible with the ratio of 1.2 : 1. The ratio of maxilla to mandible of periapical cysts was 1.5 : 1, that of periapical granulomas was 0.5 : 1, that of periapical abscesses was 1 : 1. 5. The most commonly involved location of the periapical lesions was maxillary anterior teeth(40.8%), and followed by mandibular molars, mandibular premolars, and mandibular anterior teeth and maxillary molars. The most frequent location of the periapical cysts was maxillary anterior teeth(48.9%), that of periapical granulomas was mandibular molars(50.0%), that of periapical abscesses was mandibular molars(40.0%).

• Journal of the Korean Vacuum Society
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• v.13 no.4
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• pp.175-181
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• 2004

We investigated the stability of the DLC film coated on 304 stainless steel substrate by Radio frequency assisted chemical vapor deposition method. Fracture and spallation behaviour of the coating was observed during micro-tensile test of the fil $m_strate composite. As the tensile deformation progressed, the cracks of the film were observed in the perpendicular direction to the tensile axis. Further deformation resulted in the plastic deformation with $45^{\circ}$ slip bands on the substrate surface. Spallation of the film occurred with the plastic deformation, which was initiated at the cracks of the film and was aligned along the slip directions. We found that both the cracking and the spallation behaviors are strongly dependent on the pre-treatment condition, such as Ar plasma pre-treatment. The spallation of the film was considerably suppressed in an optimized condition of the substrate cleaning by Ar glow discharge. We observed the improved stability with increasing duration of Ar plasma pre-treatment.nt.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.18 no.4
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• pp.59-66
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• 2010

Aerospace structures need high stability and long life because many personal injuries can result from an accident and securing structural integrity for various external environments is more important than any other thing. So first of all we must prove the destruction properties for operating environment, have prediction technology about damage evolution and life, and develop an economical non-destructive technology capable of detecting structure damage. Acoustic emission (AE) have no need of artificial environment like ultrasonic inspection or radio fluoroscopy to emit a certain energy, is a testing technique using seismic signal resulting from interior changes of solids, and enables to observe if any fault is appeared and it grows seriously or not while running. In this study we suggest the method of structural integrity evaluation for aerospace structures through the acoustic emission technique, for which a model plane was manufactured and an actual operation test was conducted.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.535-544
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• 2008

Unlike MS(Magnetic Stripe), SMART CARD is equipped with COS(Chip Operating System) consisting of the Microprocessor and Memory where information can be stored and processed, and there are two types of cards according to the contact mode; the contact type that passes through a gold plated area and the contactless one that goes through the radio-frequency using an antenna embedded in the plastic card. the contactless IC card used for the transportation card was first introduced into local area buses in Seoul, and expanded throughout the country so that it has removed the inconvenience such as possession of cash, fare payment and collection. Focusing on the Seoul metropolitan area in 2004, prepaid and pay later cards were adopted and have been used interchangeably between a bus and subway. The card terminal compatible between a bus and subway is Proximity Integrated Circuit Card(PICC) as international standards(1443 Type A,B), communicates in the 13.56MHz dynamic frequency modulation-demodulation system, and adopts the Multi Secure Application Module(SAM). In the second half of 2009, the system avaliable nationwide will be built when the payment SAM standard is implemented.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.214-215
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• 2008

Zinc-oxide(ZnO) films were deposited on PC(polycarboanate) and PES(polyethersulphone) substrates by using RF(radio-frequency)sputter with various rf sputtering Power at a room temperature. The effects of rf sputtering Power on the structural and optical properties of ZnO films were investigated by using atomic force microscopy, X-ray diffraction, and UV spectrophotometer. The most excellent structural and properties of a ZnO film are obtained in the condition of an rf-power of 150 W. This film shows larger Grain size and lower surface roughness and a higher optical transmittance of over 80 % in the visible range than other films deposited in the different conditions of rf- power. Regardless of substrate types, The presence of a strong diffraction peak indicates that films have a (0 0 2) preferred orientation associated with the hexagonal phase.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.115-116
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• 2012

The demand for flexible electronic systems such as wearable computers, E-paper, and flexible displays has increased due to their advantages of excellent portability, conformal contact with curved surfaces, light weight, and human friendly interfaces over present rigid electronic systems. This seminar introduces three recent progresses that can extend the application of high performance flexible inorganic electronics. The first part of this seminar will introduce a RRAM with a one transistor-one memristor (1T-1M) arrays on flexible substrates. Flexible memory is an essential part of electronics for data processing, storage, and radio frequency (RF) communication and thus a key element to realize such flexible electronic systems. Although several emerging memory technologies, including resistive switching memory, have been proposed, the cell-to-cell interference issue has to be overcome for flexible and high performance nonvolatile memory applications. The cell-to-cell interference between neighbouring memory cells occurs due to leakage current paths through adjacent low resistance state cells and induces not only unnecessary power consumption but also a misreading problem, a fatal obstacle in memory operation. To fabricate a fully functional flexible memory and prevent these unwanted effects, we integrated high performance flexible single crystal silicon transistors with an amorphous titanium oxide (a-TiO2) based memristor to control the logic state of memory. The $8{\times}8$ NOR type 1T-1M RRAM demonstrated the first random access memory operation on flexible substrates by controlling each memory unit cell independently. The second part of the seminar will discuss the flexible GaN LED on LCP substrates for implantable biosensor. Inorganic III-V light emitting diodes (LEDs) have superior characteristics, such as long-term stability, high efficiency, and strong brightness compared to conventional incandescent lamps and OLED. However, due to the brittle property of bulk inorganic semiconductor materials, III-V LED limits its applications in the field of high performance flexible electronics. This seminar introduces the first flexible and implantable GaN LED on plastic substrates that is transferred from bulk GaN on Si substrates. The superb properties of the flexible GaN thin film in terms of its wide band gap and high efficiency enable the dramatic extension of not only consumer electronic applications but also the biosensing scale. The flexible white LEDs are demonstrated for the feasibility of using a white light source for future flexible BLU devices. Finally a water-resist and a biocompatible PTFE-coated flexible LED biosensor can detect PSA at a detection limit of 1 ng/mL. These results show that the nitride-based flexible LED can be used as the future flexible display technology and a type of implantable LED biosensor for a therapy tool. The final part of this seminar will introduce a highly efficient and printable BaTiO3 thin film nanogenerator on plastic substrates. Energy harvesting technologies converting external biomechanical energy sources (such as heart beat, blood flow, muscle stretching and animal movements) into electrical energy is recently a highly demanding issue in the materials science community. Herein, we describe procedure suitable for generating and printing a lead-free microstructured BaTiO3 thin film nanogenerator on plastic substrates to overcome limitations appeared in conventional flexible ferroelectric devices. Flexible BaTiO3 thin film nanogenerator was fabricated and the piezoelectric properties and mechanically stability of ferroelectric devices were characterized. From the results, we demonstrate the highly efficient and stable performance of BaTiO3 thin film nanogenerator.

• Korean Journal of Materials Research
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• v.24 no.11
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• pp.625-631
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• 2014

To investigate the deformation properties of TiC-(5-20) mol% Mo solid solution single crystals at high temperature by compression testing, single crystals of various compositions were grown by the radio frequency floating zone technique and were deformed by compression at temperature from 1250K to 2270K at strain rates from $5.1{\times}10^{-5}$ to $5.9{\times}10^{-3}/s$. The plastic flow property of solid solution single crystals was found to be clearly different among a three-temperature range (low, intermediate and high temperature ranges) whose boundaries were dependent on the strain rate. From the observed property, we conclude that the deformation in the low temperature range is controlled by the Peierls mechanism, in the intermediate temperature range by the dynamic strain aging and in the high temperature range by the solute atmosphere dragging mechanism. The work softening tends to become less evident with an increasing experimental temperature and with a decreasing strain rate. The temperature and strain rate dependence of the critical resolved shear stress is the strongest in the high temperature range. The curves are divided into three parts with different slopes by a transition temperature. The critical resolved shear stress (${\tau}_{0.2}$) at the high temperature range showed that Mo content dependence of ${\tau}_{0.2}$ with temperature and the dependence is very marked at lower temperature. In the higher temperature range, ${\tau}_{0.2}$ increases monotonously with an increasing Mo content.

• The Research Journal of the Costume Culture
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• v.4 no.3
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• pp.427-445
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• 1996

According as the fashion at the latter half part of the 20th century is diversified and made into high-class gradually, it is demanding the individuality of each one. Especially, since the beginning of 1980s, fashion came to represent the restoration mood in a modern style because of the popularization of post-modernism. And with this, it came to result in the reappearance of minimalism which was one of anti-culture in 1960s. In this study, this researcher grasped the appearance background, concept and structural concept of minimalism, and tried to study the influence that he minimalism had on fashion in the flow of fashion over the first half period of the 20th century. Minimalism is the fine art trend of American characteristic which quicked by the meeting of European culture and American culture, according as the new avant-grade art of Europe moved to America after World War II Minimalism which appeared, refusing the mechanisation, industrialization and mass production of America and the falsehood of consciousness and sensitivity under existing system remained obscure by the pop art which is the commercial fine art of same period, but it came to expand the domain of work possibility of modern fine art, and it became the basis of appearance of post-modernism. Minimalism has 4 kinds of structural features which are nonside nature, repetitiousness and environment nature with 3 dimensional feature which is issue nature. Minimalism is appearing in the exfcellent and future-oriented fashon of Andre Kureju t the time of 1960 well. Then science revolution and minimalism aroused the mini-revolution, and they made the compact radio in electric home appliances and the miniskirt in fashion appear. The features of minimal fashion as Retro '60' which appeared in the decedent mood with the 21st century just before on are as follows: First, the are the pursuit of concise plastic line. Second, it is the use of high tech material Third, the miniaturization in size amy be enumerated. Minimal fashion will appear s the positive confrontation from of mankind as the optimistic viewpoint about feature in the situation hat environment was destroyed and the resources were exhausted.