• 한국멀티미디어학회논문지
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• 제18권2호
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• pp.158-167
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• 2015

This study presents a new method to improve the speed of high quality volume rendering. We improve the speed of ambient occlusion which is one of the global illumination techniques used in traditional volume visualization. Calculating ambient occlusion takes much time because it determines an illumination value of a sample by integrating opacities of nearby samples. This study proposes an improved method for this by using local statistics such as averages and standard deviations. We calculate local statistics for each volume block, a set of nearby samples, in pre-processing time. In the rendering process, we efficiently determine the illumination value by assuming the density distribution as a normal distribution. As the results, we can generate high quality images that combine ambient occlusion illumination with local illumination in real time.

• 한국정밀공학회지
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• 제17권7호
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• pp.74-79
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• 2000

Integrating a 3D solid modeler with a general purpose FEM code, an automatic nonlinear analysis system of the 3D crack problems has been developed. A geometry model, i.e. a solid containing one or several 3D cracks is defined. Several distributions of local node density are chosen, and then automatically superposed on one another over the geometry model by using the fuzzy knowledge processing. Nodes are generated by the bucketing method, and ten-noded quadratic tetrahedral solid elements are generated by the Delaunay triangulation techniques. The complete finite element(FE) model generated, and a stress analysis is performed. In this system, burden to analysts fur introducing 3D cracks to the FE model as well as fur estimating their fracture mechanics parameters can be dramatically reduced. This paper describes the methodologies to realize such functions, and demonstrates the validity of the present system.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.37-38
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• 2018

BIM(Building Information Modeling) in the architecture, VDC(Virtual Design and Construction) defined CIFE(Center for Integrated Facility Engineering) of Stanford university in USA, and Data-driven design definition issued by TECDOC-1284 of IAEA are doing data-level design generated by 3D CAD technology, integrating and managing related information based on the 3D model, and Using 3D models effectively during nuclear power plant life cycle. 3D model of domestic nuclear power industry is using interference review between design fields, 4D system linked 3D construction model and schedule activity, but the 3D model generated in the design phase is effectively not utilized during the construction, operation, decommissioning. therefore, This study is aimed to suggest 3D model LOD(Level of Detail) advancement method through the analysis of existing literature, 2D drawings, and 3D models throughout nuclear power plant lifecycle.

• 대한전기학회논문지:시스템및제어부문D
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• 제51권6호
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• pp.221-227
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• 2002

In this paper, the system model for the compensation of the low-cost personal navigation system is derived and the error compensation method using GPS is also proposed. WNS(Walking Navigation System) is a kind of personal navigation system using the number of a walk, stride and azimuth. Because the accuracy of these variables determines the navigation performance, computational methods have been investigated. The step is detected using the walking patterns, stride is determined by neural network and azimuth is calculated with gyro output. The neural network filters off unnecessary motions. However, the error compensation method is needed, because the error of navigation information increases with time. In this paper, the accumulated error due to the step detection error, stride error and gyro bias is compensated by the integrating with GPS. Loosely coupled Kalman filter is used for the integration of WNS and GPS. It is shown by simulation that the error is bounded even though GPS signal is blocked.

• Structural Engineering and Mechanics
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• 제13권5호
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• pp.569-589
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• 2002

In performing the dynamic analysis, the step size used in a step-by-step integration method might be much smaller than that required by the accuracy consideration in order to capture the rapid chances of dynamic loading or to eliminate the linearization errors. It was first found by Chen and Robinson that these difficulties might be overcome by integrating the equations of motion with respect to time once. A further study of this technique is conducted herein. This include the theoretical evaluation and comparison of the capability to capture the rapid changes of dynamic loading if using the constant average acceleration method and its integral form and the exploration of the superiority of the time integration to reduce the linearization error. In addition, its advantage in the solution of the impact problems or the wave propagation problems is also numerically demonstrated. It seems that this time integration technique can be applicable to all the currently available direct integration methods.

• Journal of the Optical Society of Korea
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• 제16권2호
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• pp.127-132
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• 2012

This study discusses photoresist forming using a composite grayscale to fabricate a Fresnel lens. Grayscale lithography is a common production method used to facilitate the forming of lenses with different curvatures and depths. However, this approach is time consuming and expensive. This study proposes a method for overcoming these obstacles by integrating a digital micromirror device and microscope to supplant the traditional physical grayscale mask. This approach provides a simple and practical maskless optical lithography system. According to the results, the two adjacent grayscales displayed substantial differences between the high grayscale and influence the low grayscale that ultimately affected photoresist formation. Furthermore, we show that change of up to 150% in the slope can be achieved by changing the grayscale gradient in the central zone and the ring profile. The results of the optical experiment show a focus change with different gray gradients.

• Journal of Computational Design and Engineering
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• 제2권3호
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• pp.165-175
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• 2015

One of the current challenges in the domain of the multicriteria shape optimization is to reduce the calculation time required by conventional methods. The high computational cost is due to the high number of simulation or function calls required by these methods. Recently, several studies have been led to overcome this problem by integrating a metamodel in the overall optimization loop. In this paper, we perform a coupling between the Normal Boundary Intersection - NBI - algorithm with Radial Basis Function - RBF - metamodel in order to have a simple tool with a reasonable calculation time to solve multicriteria optimization problems. First, we apply our approach to academic test cases. Then, we validate our method against an industrial case, namely, shape optimization of the bottom of an aerosol can undergoing nonlinear elasto-plastic deformation. Then, in order to select solutions among the Pareto efficient ones, we use the same surrogate approach to implement a method to compute Nash and Kalai-Smorodinsky equilibria.

• 대한인간공학회:학술대회논문집
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• 대한인간공학회 1997년도 추계학술대회논문집
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• pp.366-371
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• 1997

Although the concept of usability has been well defined in the software usability engineering area, it is not appropriate to apply the same concept directly to the consumer electronic products. A new concept of usability appropriate for evaluating consumer electronic consumer electronic products was suggested in this study. It is characterized by integrating both the performance and the impression factors. Based on the concept developed, a systematic and integrated methodology for usability evaluation was proposed. The methodology contains four major steps; the development of the measurement methods for evaluating usability attributes, the development of the analysis techniques for the human interface elements, the development of the evaluation method for the usability of human interface elements, and the development of the usability model. The results of this study can be applied to evaluate the usability of various electonic products in a systematic and efficent manner.

• 한국진공학회지
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• 제8권2호
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• pp.83-92
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• 1999

Pumping performance of a disk-type molecular drag pump for a hybrid molecular pump is numerically analyzed by the direct simulation onte-Carlo method. The flows in pumping channels are three-dimensional (3D) in a molecular transition regime. The main difficulty in modeling a 3D case comes from the rotating frame of reference. Thus, trajectories of particles ar no longer straight lines. In the present study, trajectories of particles are calculated by integrating a system of differential equations including the Coriolis and centrifugal forces. The null-collisions. The present numerical results molecular model is used for calculation of molecular collisions. The present numerical results significantly disagree with the previously known ones. This indicates that an actual pumping passage is very limited to a narrow region due to the significant backstreaming of molecules from the outlet.

• Journal of Power Electronics
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• 제14권5호
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• pp.859-865
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• 2014

This study presents an electromagnetic model for predicting shaft voltages in a 2-pole field-excited synchronous generator. After the first observations on shaft voltages were made more than a century ago, extensive work has been conducted on eliminating, mitigating, and integrating the aforementioned phenomena. Given that emphasis has been placed on modeling shaft- and bearing-induced voltages in AC motors driven by variable frequency drives, similar efforts toward a model that is dedicated to generators are insubstantial. This work endeavors to improve current physical interpretation and prediction methods for shaft-induced voltages in generators through semi-analytical derivation. Aside from the experimental validation of the model, investigations regarding the behavior of shaft voltages under varying machine complexities and operating conditions clarify previous uncertainties regarding these phenomena. The performance of the numerical method is also assessed for application in eccentricity fault diagnosis.