• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권3호
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• pp.1231-1245
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• 2015

People have transferred their business model from traditional commerce to e-commerce in recent decades. Both shopping and payment can be completed through the Internet and bring convenience to consumers and business opportunities to industry. These trade techniques are mostly set up based on the Secure Sockets Layer (SSL). SSL provides the security for transaction information and is easy to set up, which makes it is widely accepted by individuals. Although attackers cannot obtain the real content even when the transferred information is intercepted, still there is risk for online trade. For example, it is impossible to prevent credit card information from being stolen by virtual merchant. Therefore, we propose a new mechanism to solve such security problem. We make use of the disposable dynamic security code (DSC) to replace traditional card security code. So even attackers get DSC for that round of transaction, they cannot use it for the next time. Besides, we apply visual secret sharing techniques to transfer the DSC, so that interceptors cannot retrieve the real DSC even for one round of trade. This way, we can improve security of credit card transaction and reliability of online business. The experiments results validate the applicability and efficiency of the proposed mechanism.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.181-188
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• 2001

The present research is an experimental study of subcooled flow boiling behavior using flat, microporousenhanced square heater surfaces in pure FC-72. Two $1-cm^{2}$ copper surfaces, one highly polished (plain) and one microporous coated, were flush-mounted into a 12.7 mm square, horizontal flow channel. Testing was performed for fluid velocities ranging from 0.5 to 4 m/s (Reynolds numbers from 18,700 to 174,500) and pure subcooling levels from 4 to 20 K. Results showed both surfaces' nucleate flow boiling curves collapsed to one line showing insensitivity to fluid velocity and subcooling. The log-log slope of the microporous surface nucleate boiling curves was lower than the plain surface due to the conductive thermal resistance of the microporous coating layer. Both, increased fluid velocity and subcooling, increase the CHF values for both surfaces, however, the already enhanced boiling characteristics of the microporous coating appear dominant and require higher fluid velocities to provide additional enhancement of CHF to the microporous surface.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.13-13
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• 2009

We have investigated the fabrication and properties of bendable PZT film formed on plastic substrates for the application in flexible memory. These devices used the PZT active layer formed on $SiO_2/Si$ wafer by sol-gel method with optimized device layouts and Pt electrodes. After etching Pt/PZT/Pt layers, patterned by photolithography process. these layers were transferred on PET plastic substrate using elastomeric stamp. The level of performance that can be achieved approaches that of traditional PZT. devices on rigid bulk wafers.

• 설비공학논문집
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• 제10권4호
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• pp.475-482
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• 1998

In this paper, an experimental study was conducted to investigate the performance of the spherical ice particle production system which uses the technology of water spray in a vacuum chamber for increasing the heat transfer area. As a result, following conclusions were obtained. The diffusion-controlled evaporation model agreed relatively well with experiments. The spray flow rate influences the performance of the system rather than any other factors, for example, the spray nozzle position, the nozzle number. As the spray rate increases, the system efficiency increases. It is due to the entrainment of small droplets among the spray with the exhausted vapor. Thus the system should be designed and operated to prevent the entrainment. Assuming the compressor efficiency to be 70%, the COP of the system reaches highly up to 6 at a maximum spray rate. Under the conditions, however, the rigid ice layer is obtained because ice particles bond together with increase of the spray rate. Therefore, the spray rate should be controlled properly to make the spherical ice particles.

• 한국지반공학회지:지반
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• 제6권4호
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• pp.19-32
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• 1990

일반적으로 지반은 복잡하고 다양한 다층구조로 되어있다. 이러한 다층토 지반을 해석 하기 위 해 본문은 지반의 구성식,층의 구조와 두께, 각층의 강성, 재하조건 등을 변화시켜 수치해석 하였다. 기존의 다층토 지반은 Burmister의 2층계이론인 탄성해로 지중응력분포를 해석하였으나,여기서는 Biot방정식을 지배방정식으로하여 개발된 지반해석프로그램에 탄 .점소성구성식을 이용하여 층의 조건에 관계없이 2층이상의 모든 다층토지반의 지중응력분포를 해석 하고자 한다. 이들의 결과를 Burmister나 Fok의 결과와 비교하였으며, 서로 근접한 결과를 얻었다. 따라서, 본 연구는 다양한 다층토 지반을 전산 프로그램을 이용하여 실제에 가까운 응력전달기구 를 밝히려는 목적으로 수행된 것이다.

• Journal of applied mathematics & informatics
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• 제26권1_2호
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• pp.161-176
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• 2008

The effect of variable viscosity on MHD mixed convection Hiemenz flow over a thermally stratified porous wedge plate has been studied in the presence of suction or injection. The wall of the wedge is embedded in a uniform Darcian porous medium in order to allow for possible fluid wall suction or injection and has a power-law variation of the wall temperature. An approximate numerical solution for the steady laminar boundary-layer flow over a wall of the wedge in the presence of thermal diffusion has been obtained by solving the governing equations using numerical technique. The fluid is assumed to be viscous and incompressible. Numerical calculations are carried out for different values of dimensionless parameters and an analysis of the results obtained shows that the flow field is influenced appreciably by the magnetic effect, variable viscosity, thermal stratification and suction / injection at wall surface. Effects of these major parameters on the transport behaviors are investigated methodically and typical results are illustrated to reveal the tendency of the solutions. Comparisons with previously published works are performed and excellent agreement between the results is obtained.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.479-483
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• 2006

As high-definition television(HDTV) broadcasting were generalized, there have been many researches and developments about large storage capacity and fast data transfer rate in optical disk drives(ODD). Pickup actuators must have high flexible mode frequencies and gain margins. Flexible modes are caused by the flexibility of moving parts in the actuator and a servo bandwidth is limited by them. As a result, the system becomes unstable for high-speed operations in high density reading and recording. In this paper, we suggest improved modeling method that considers the bonding layer. And, flexible mode frequency of actuator is improved by Design of Experiment of lens holder. Magnet circuit is designed considering the relation with moving part. Through improving yoke design, the magnetic flux is changed and DC tilt is reduced. Consequently, we designed actuator which has high flexible mode frequency and gain margins.

• 한국표면공학회지
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• 제43권6호
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• pp.289-296
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• 2010

The effect of organic additives, thiourea (TU), on the copper electroplated layer of large rectangular size was investigated through physical and various electrochemical techniques. It was found that TU had strong adsorption characteristics on the Ni substrate and affected the initial electroplating process by inducing surface reaction instead of mass transfer in the bulk solution. TU additives had its critical micelle concentration at 200 ppm in copper sulphate solution and showed abrupt change in morphological and electrochemical impedance spectroscopic results around this concentration, which could be related with the destruction of adsorption structure of TU-Cu(I) complex formed at the Ni substrate surface. By conducting a commercial electroplating simulation, when TU additives was included at cmc in the plating solution, it acted as a depolarizer for copper electrodeposition and was effective to reduce the unevenness of copper deposits between centre and edge region at high current densities of 10 ASD.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1684-1685
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• 2011

This paper presents a theoretical and numerical analysis for thermal isolation of silicon micro-structures, especially for a large size with poor thermal conductivity, as well as straightforward solution for such an issue. Additional metal patterns underneath the silicon structures effectively reduces the thermal isolation. Heat transfer mechanism is analyzed using an equivalent circuit of thermal network including plasma, a heat source, heat capacitors, and thermal resistances. The FEM simulation was carried out to investigate the temperature change of silicon micro-structures according to process time. The temperature of silicon micro-structures with 2 ${\mu}m$ thick chrome layer at a steady state is $86^{\circ}C$, an approximately 40% decrease from the silicon microstructure without thin metal ($122^{\circ}C$)

• 한국전기전자재료학회논문지
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• 제22권12호
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• pp.1039-1044
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• 2009

Red color OLED has been fabricated by the doping method apply to CBP using co-evaporation, GDI4349 of phosphorescent dopant, and rubrene of fluorescent dopant. The OLED structure are multi-layer of ITO(150 nm)/ELM_HIL(50 nm)/ELM_HTL(30 nm)/CBP : Rubrene, GDI4349 (30 nm)/BAlq (30 nm)/LiF(0.7 nm)/Al (100 nm). Accomplished best result at 3 vol.% of rubrene when the OLEDs were made of 1, 3, 5, 7, 9 vol.% doped rubrene. The highest efficiency of 7.2 cd/A was resulted at 8 vol.% of GDI4349 when the OLEDs were made among 5, 8, 11, 14 vol.% of GDI4349. Obviously, the best concentration of rubrene at 3 vol.% and changing GDI4349 concentration to 5, 8, 11, 14 vol.% OLED dramatically enhanced characteristic of resulted 10.7 cd/A at 8 vol.% of GDI4349. This result would understand to analyse as the emission efficiency increases by energy transport efficiency increase using GDI4349 energy transfer when rubrene absorbs the energy from CBP of fluorescences host.