• The KIPS Transactions:PartB
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• v.12B no.2 s.98
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• pp.137-142
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• 2005

Since wireless communication cost is relatively expensive, the mobile games using cellular phones or PDAs are mostly played after being downloaded unlike more updated types of phone-to-phone or online games. In particular, the upbringing games, in which garners foster virtual companion animals or vegetables as their avata, have been spotlighted. It is essential to supply variety of items for upbringing avatas. However, due to diverse tastes for avatas and limited storage of mobile terminals, game manias must download their desired items from homepages. In addition, game developers must inform users through SMS messages whenever a new item is created. To do so, they must link WEB server and WAP server to Call Back URL or ARS. This paper proposed a linkage method suitable for JAVA-based mobile phone operating system. The proposed method will consequently increase life cycle of a game and reinforce profitability.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.313-315
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• 2017

Recently, application fields using machine learning have been widely expanded. In addition to the spread of smart devices, application services using location-based services are also in demand. However, it is difficult to provide the application service through the positioning in the indoor environment such as the specific space where the disaster situation where the information for positioning can not be collected and the actual location location information can not be used. In this situation, using the spatial information composed of the marker information and the markers of the neighbor registered in the augmented reality environment, positioning at a specific situation or position becomes possible. At this time, it is possible to learn the operation that makes the configuration of the marker-based spatial information correspond to the actual position through the machine learning, and the optimal positioning result can be obtained by minimizing the error. In this paper, we study the positioning methods required in specific situations using machine learning for learning of augmented reality markers and spatial information.

• Journal of Practical Engineering Education
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• v.8 no.2
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• pp.103-109
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• 2016

In order to get the maintenance work for the normal operation of rail vehicles made safe maintenance training, which looked suffered direct physical train maintenance environment, gain experience to get out foster the practical skills, but experience the real maintenance in operational problems the maintenance procedures followed are difficult to be. So it can gain experience and knowledge of the actual maintenance work in safe conditions if you apply a simulation experience in a similar environment as possible to the actual train maintenance training can also reduce operational training costs. For a description of the current domestic and simulation programs of the railway sector it has been operating in overseas and is designed to train intensive training, maintenance and maintenance-related information is scarce situation. In this study, the contents of the theory of educational technology for effective training of train maintenance elements exhibit theory, theory of learning situations, designed to train maintenance training simulation through a previous study that investigated the problem-based learning theory.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.1 no.1
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• pp.23-26
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• 2000

In spot welded joint. Electronic Speckle Pattern Interferometry(ESPI) method using the Model 95 Ar laser a video system and an image processor was applied to measure the stress Unlike traditional strain gauges or Moire method, ESPI method has no special surface preparation or attachments and can be measured in-plane displacement with non-contact and real time. In this experiment, specimens are loaded in parallel with a load cell. The specimens are made of the cold rolled steel sheet with 1mm thickness, are attached strain. gauges. This study Provides an example of how ESPI has been used to measure stress and strain inspecimen. The results measured by ESPI are compared with the data which was measured by strain gauge method under tensile testing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.166-166
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• 2007

ZnO는 육방정계(wurtzite) 결정구조를 지니며 상온에서 3.37eV의 wide band gap을 갖는다. ZnO의 엑시톤 결합 에너지는 GaN에 비해 2.5배 높은 60meV로서 고효율의 광소자 적용 가능성이 높다. 또한 고품위의 박막합성이 가능하다. 이러한 특성 때문에 display소자의 투명전극, 광전소자, 바리스터, 압전소자, 가스센서 등에 폭 넓게 응용되고 있다. ZnO박막의 제조는 스퍼터링, CVD, 진공증착법, 열분해법 등이 있다. 본 논문에서는 RF 마그네트론 스퍼터에 의해 제작된 ZnO 박막에 CMP공정을 수행하여 연마율과 비균일도 특성 및 광투과 특성을 연구하였다. ZnO박막은 $2{\times}2Cm$의 Corning glass위에 증착되었다. 로터리 펌프와 유확산 펌프를 이용하여 초기진공을 $2{\times}10^{-6}$ Torr까지 도달시킨 후 Ar과 $O_2$를 주입하였다. 증착은 상온에서 이루어졌으며 공정압력은 $6{\times}10^{-2}$Torr이였다. 초기의 불안정한 상태의 풀라즈마를 안정시키기 위해 셔터를 이용하여 pre-sputtering을 하였다. CMP 공정조건은 플레이튼 속도, 슬러리 유속, 압력은 칵각 60rpm, 90ml/min, $300g/cm^2$으로 일정하게 유지하였으며 헤드속도는 20rpm에서 100rpm까지 증가시키면서 연마특성을 조사하였다. 실리카슬러리의 적합성을 알아보기 위해 DIW와 병행하여 CMP공정을 수행하고 비교 분석하였다. CMP공정 결과 광투과도는 굉탄화된 표면의 확보로 인해 향상된 특성을 보였다. 실리카 슬러리를 사용하여 CMP를 할 경우는 헤드속도는 저속으로 하여야 양호한 연마특성을 얻을 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.335-335
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• 2007

본 연구에서는 RF Magnetron Sputtering 법으로 94:6 wt%의 비율로 Sb가 첨가된 $SnO_2$ 타겟을 사용하여 실온에서 ATO(Antimony doped Tin Oxide) 박막을 증착하고, 열처리가 ATO 박막의 구조적, 전기적, 광학적 특성에 미치는 효과를 연구하고자 하였다. ATO 박막의 두께는 약 200 nm로 증착하였으며, 실험 조건으로는 Ar 유량을 100 seem, 진공도는 1, 5, 10 mTorr로 변화시켰으며 스퍼터링 파워는 100, 150, 200, 250 W로 조절하였다. 증착되어진 박막은 vacuum 상태에서 300, $600^{\circ}C$의 온도에서 열처리를 수행하였으며 결과적으로 스퍼터링 파워가 증가함에 따라 비저항이 감소하였고, 250 W의 파워와 10 mTorr의 공정압력 조건에서 $600^{\circ}C$로 열처리한 ATO 박막은 $5{\times}10^{-3}{\Omega}-cm$의 저항률과 85.3%의 높은 투과도를 가지는 우수한 투명 전도막을 얻을 수 있었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.336-337
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• 2007

현재 투명전극의 재료로 ITO, ZnO, $SnO_2$등의 재료가 주로 이용되며, 낮은 저항률을 장점으로 가지는 ITO 박막이 가장 널리 이용되고 있으나, 가격이 비싸다는 단점을 가지고 있다. 이 밖에도 ITO 박막보다 가격이 저렴한 ZnO박막에 대한 연구가 많이 진행되고 있으나, 고온에서의 열적 불안정성 등의 문제로 상용화되지는 못하고 있다. 그러나 $SnO_2$ 박막은 ITO와 ZnO 박막보다 저항률이 다소 높지만, 우수한 열적, 화학적 안정성과 저렴한 가격으로 ITO 박막을 대체할 투명전도막 재료로 주목받고 있다. 본 연구에서는 $SnO_2$박막의 저항률 향상을 위하여 ATO(Antimony doped Tin Oxide) 박막을 RF Magnetron Sputtering 법으로 Coming glass위에 증착하였으며, 박막 증착시 산소 유량의 변화가 ATO 박막의 구조적, 전기적 그리고 광학적 특성에 미치는 효과를 연구하였다. 본 실험에서는 동작압력을 10 mTorr, RF power를 250W로 고정하고 $O_2$ 유량을 부분적으로 변화시키면서 증착되어진 ATO 박막을 분석한 결과 Ar:$O_2$의 비가 90:10일 때 최적의 가스비율로써 우수한 구조적, 전기적 그리고 광학적 특성을 보임을 확인하였다.

• Korean Journal of Materials Research
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• v.25 no.3
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• pp.138-143
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• 2015

Aluminum nitride, a compound semiconductor, has a Wurtzite structure; good material properties such as high thermal conductivity, great electric conductivity, high dielectric breakdown strength, a wide energy band gap (6.2eV), a fast elastic wave speed; and excellent in thermal and chemical stability. Furthermore, the thermal expansion coefficient of the aluminum nitride is similar to those of Si and GaAs. Due to these characteristics, aluminum nitride can be applied to electric packaging components, dielectric materials, SAW (surface acoustic wave) devices, and photoelectric devices. In this study, we surveyed the crystallization and preferred orientation of AlN thin films with an X-ray diffractometer. To fabricate the AlN thin film, we used the magnetron sputtering method with $N_2$, NH3 and Ar. According to an increase in the partial pressures of $N_2$ and $NH_3$, Al was nitrified and deposited onto a substrate in a molecular form. When AlN was fabricated with $N_2$, it showed a c-axis orientation and tended toward a high orientation with an increase in the temperature. On the other hand, when AlN was fabricated with $NH_3$, it showed a-axis orientation. This result is coincident with the proposed mechanism. We fabricated AlN thin films with an a-axis orientation by controlling the sputtering electric power, $NH_3$ pressure, deposition speed, and substrate temperature. According to the proposed mechanism, we also fabricated AlN thin films which demonstrated high a-axis and c-axis orientations.

• Korean Journal of Materials Research
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• v.22 no.10
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• pp.562-568
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• 2012

Metal nanowires can be coated on various substrates to create transparent conducting films that can potentially replace the dominant transparent conductor, indium tin oxide, in displays, solar cells, organic light-emitting diodes, and electrochromic windows. One issue with these metal nanowire based transparent conductive films is that the resistance between the nanowires is still high because of their low aspect ratio. Here, we demonstrate high-performance transparent conductive films with silver nanofiber networks synthesized by a low-cost and scalable electrospinning process followed by two-step sequential thermal treatments. First, the PVP/$AgNO_3$ precursor nanofibers, which have an average diameter of 208 nm and are several thousands of micrometers in length, were synthesized by the electrospinning process. The thermal behavior and the phase and morphology evolution in the thermal treatment processes were systematically investigated to determine the thermal treatment atmosphere and temperature. PVP/$AgNO_3$ nanofibers were transformed stepwise into PVP/Ag and Ag nanofibers by two-step sequential thermal treatments (i.e., $150^{\circ}C$ in $H_2$ for 0.5 h and $300^{\circ}C$ in Ar for 3 h); however, the fibrous shape was perfectly maintained. The silver nanofibers have ultrahigh aspect ratios of up to 10000 and a small average diameter of 142 nm; they also have fused crossing points with ultra-low junction resistances, which result in high transmittance at low sheet resistance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.30 no.5 s.248
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• pp.413-421
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• 2006

The bubble dynamics induced by direct laser heating is experimentally analyzed as a first step to assess the technical feasibility of laser-based ink-jet technology. To understand the interaction between laser light and ink, the absorption spectrum is measured for various ink colors and concentrations. The hydrodynamics of laser-generated bubbles is examined by the laser-flash photography. When an Ar ion laser pulse (wavelength 488 nm) with an output power up to 600 mW is incident on the ink solution through a transparent window, a hemispherical bubble with a diameter up to ${\sim}100{\mu}m$ can be formed with a lifetime in a few tens of microsecond depending on the laser power and the focal-spot size. Parametric study has been performed to reveal the effect of laser pulse width, output power, ink concentration, and color on the bubble dynamics. The results show that the bubble generated by a laser pulse is largely similar to that produced by a thin-film heater. Consequently, the present work demonstrates the feasibility of developing a laser-actuated droplet generation mechanism for applications in ink-jet print heads. Furthermore, the results of this work indicate that the droplet generation frequency is likely to be further increased by optimizing the process parameters.