• Journal of Information Processing Systems
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• v.7 no.4
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• pp.635-652
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• 2011

In ubiquitous environments, many applications need to process data with time and space dimensions. Because of this, there is growing attention not only on gathering spatiotemporal data in ubiquitous environments, but also on processing such data in databases. In order to obtain the full benefits from spatiotemporal data, we need a data model that naturally expresses the properties of spatiotemporal data. In this paper, we introduce three spatiotemporal data models extended from temporal data models. The main goal of this paper is to determine which data model is less complex in the spatiotemporal context. To this end, we compare their query languages in the complexity aspect because the complexity of a query language is tightly coupled with its underlying data model. Throughout our investigations, we show that it is important to intertwine space and time dimensions and keep one-to-one correspondence between an object in the real world and a tuple in a database in order to naturally express queries in ubiquitous applications.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1319-1320
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• 2007

본 연구는 ZnO 박막을 유도 결합 플라즈마를 이용하여, $BCl_3$/Ar 가스 혼합비, RF 전력, 직류 바이어스 전압과 공정 압력을 변경하면서 실험하였다. ZnO 박막의 최고 식각속도는 80%의 $BCl_{3}/(BCl_{3}+Ar)$에서 700 W의 RF 전력, -150 V의 직류 바이어스 전압, 15 mTorr의 공정 압력, $28^{\circ}C$의 기판 온도로 고정시켰을 때 50 nm/min 이었다. 이 조건에서 ZnO 박막과 $SiO_2$의 선택비는 0.75 이었다.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.5
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• pp.166-173
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• 2004

Axiomatic Design has been developed as a general design framework during past two decades and TRIZ has been developed for a design tool over 50 years. Axiomatic design is quite excellent in that the design should be decoupled. When a design matrix is established, the characteristics of the design are identified concerning the coupling properties. If the design is coupled, a decoupling process should be found. However, axiomatic design does not specifically indicate how to decouple. In this paper, a design method is developed to use TRIZ in the decoupling process. The decoupling ideas are extracted from the substance field analysis and various methods in TRIZ. The mettled is applied applied to the conceptual design of a beam splitter for the laser marker and the results are analyzed.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.7
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• pp.129-138
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• 1998

The objective of this study is to demonstrate the ability of a computer simulation of microstructural evolution in hot forging of C-Mn steels. The development of microstructure is strongly dependent on process variables and metallurgical factors that affect time history of thermodynamical variables such as temperature, strain. and strain rate during deformation. Then finite element method is applied for the prediction of microstructural evolution, and it should be coupled with heat transfer analysis to consider the change of thermodynamical properties during forming process. In this study, Yada's recrystallization model and rigid-thermoviscoplastic finite element method are employed in order to analyze microstructural evolution during hot forging process. To show the validity and effectiveness of the proposed method, experiments are accomplished and the results of experiments are compared with those of simulations.

• Journal of Ocean Engineering and Technology
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• v.27 no.5
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• pp.70-76
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• 2013

The present paper proposes a coupled volume-of-fluid (VOF) and level-set (LS) method for simulating incompressible two-phase flows that include surface tension effects. The interface of two fluids and its motion are represented by a VOF method designed using high-resolution differencing schemes. This hybrid method couples the VOF method with an LS distancing algorithm in an explicit way to improve the calculation of the normal and curvature of the interface. It is developed based on a rather simple algorithm to be efficient for various practical applications. The accuracy and convergence properties of the method are verified in a simulation of a single gas bubble rising in a three-dimensional flow with a large density ratio.

• Bulletin of the Korean Chemical Society
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• v.10 no.6
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• pp.568-572
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• 1989

Terphenyl dialdehyde 6 was obtained in 17.4% overall yield through oxidative coupling, methylation, and bisformylation reactions starting from p-cresol, and then coupled intermolecularly using McMurry reaction to give 22-membered macrocylic host 7 in 14.4% yield. In crystal structure host 7 has $C2_v$ symmetry with cis-cis configuration of two double bonds. Four methoxy groups adjacent to double bonds and the other two methoxy groups are directed opposite side, forming a cavity which can nest a guest. The cavity is filled by two inward-turned methyl groups out of four methoxy groups adjacent to double bonds. The kinetically controlled reaction mechanism leading to cis product was proposed. The cation binding properties of 7 were obtained using picrate extraction experiment from $D_2O\; into\; CDCl_3\; at\; 25^{\circ}C$. All the spherical cations (from $Li^+ to NH4^+)$ are complexed with free energies of $7.3{\pm}0.3$ kcal/mol.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.03a
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• pp.597-601
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• 2008

Three-dimensional structures of detonation wave propagating in circular tube were investigated. Inviscid fluid dynamics equations coupled with a conservation equation of reaction progress variable were analyzed by a MUSCL-type TVD scheme and four stage Runge-Kutta time integration. Variable-$\gamma$ formulation was used to account for the variable properties between unburned and burned states and the chemical reaction was modeled by using a simplified one-step irreversible kinetics model. The computational code was parallelized based on domain decomposition technique using MPI-II message passing library. The computations were carried out using a home made Windows based PC cluster having 160 AMD AthloxXP and Athlon64 processor. The computational domain consisted of through a roundshaped tube with wall conditions. As an initial condition, analytical ZND solution was distributed over the computational domain with disturbances. The disturbances has circumferential large gradient. The unsteady computational results in three-dimension show the detailed mechanisms of multi-cell mode of detonation wave instabilities resulting diamond shape in smoked-foil record.

• Structural Engineering and Mechanics
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• v.7 no.6
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• pp.575-588
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• 1999

A boundary element method is applied to the analysis of crack trajectory in materials with complex microstructure, such as discontinuously reinforced composite materials, and systems subjected to complex loading, such as indentation. The path followed by the crack(s) has non-trivial geometry. A study of the stress intensity factors and fracture toughness of such systems must therefore be accompanied by an analysis of crack trajectory. The simulation is achieved using a dual boundary integral method in planar problems, and a single boundary integral method coupled with substructuring in axisymmetric problems. The direction of crack propagation is determined using the maximum mechanical energy release rate criterion. The method is demonstrated by application to (i) a composite material composed of components having the elastic properties of aluminium (matrix) and silicon carbide (reinforcement), and (ii) analysis of contact damage induced by the action of an indenter on brittle materials. The chief advantage of the method is the ease with which problems having complex geometry or loading (giving rise to complex crack trajectories) can be treated.

• Coupled systems mechanics
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• v.3 no.1
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• pp.111-145
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• 2014

In this paper we present a new model for computing the nonlinear response of reinforced concrete frame systems subjected to extreme thermomechanical loads. The first main feature of the model is its ability to account for both bending and shear failure of the reinforced concrete composites within frame-like model. The second prominent feature concerns the model capability to represent the total degradation of the material properties due to high temperature and the thermal deformations. Several numerical simulations are given to confirm these capabilities and illustrate a very satisfying model performance.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2005.09a
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• pp.124-128
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• 2005

To produce a highly sensitive uncooled microbolometer, the development of a high-performance thermometric material is essential. In this work, amorphous vanadium-tungsten oxide was developed as a thermometric material at a low temperature of $300^{\circ}C$, and the microbolometer, coupled with the material, was designed and fabricated using surface micromachining technology. The vanadium-tungsten oxide showed good properties for application to the microbolometer, Such as a high temperature coefficient of resistance of over -4.0 $\%$/K and good compatibility with the surface micromachining and integrated circuit fabrication process due to its low fabrication temperature. As a result, the uncooled microbolometer could be fabricated with high detectivity over $1.0\;{\times}\;10^9\;cmHz^{1/2}/W$ at a bias current of $7.5\;{\mu}A$ and a chopper frequency of 10-20 Hz