• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3035-3043
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• 2015

This study evaluates the thermal structural safety of the three-way catalyst(TWC) substrate for domestic passenger cars. Thermal-fluid boundary conditions on the TWC substrate were determined by D-optimal DOE. The thermal stresses on the TWC substrate were calculated by the temperature distribution obtained from the CFD results. The safety factors of the TWC substrate were determined by statistical strength and stress distributions and estimated to be 0.275. The thermal stresses for TWC substrate exceeded the strength of the material. Therefore, it is necessary to redesign the TWC substrate because it has much shorter service life than design life.

• Journal of Fashion Business
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• v.26 no.5
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• pp.91-104
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• 2022

In this study, a cycling smart wear for measuring cycling posture and motion was developed using a three-dimensional motion analysis camera and an IMU inertial sensor. Results were compared according to parts to derive the optimal smart device attachment location, enabling correct posture measurement and cycle motion analysis to design a pattern. Conclusions were as follows: 1) 'S-T8' > 'S-T10' > 'S-L4' was the most significant area for each lumbar spine using a 3D motion analysis system with representative posture change (90°, 60°, 30°) to derive incisions and size specifications; 2) the part with the smallest relative angle change among significant section reference points during pattern design was applied as a reference point for attaching a cycling smart device to secure detachable safety of the device. Optimal locations for attaching the cycling device were the "S-L4" hip bone (Sacrum) and lumbar spine No. 4 (Lumbar 4^th); 3) the most suitable sensor attachment location for monitoring knee induction-abduction was the anatomical location of the rectus femoris; 4) a cycling smart wear pattern was developed without incision in the part where the sensor and electrode passed. The wearing was confirmed with 3D CLO. This study aims to provide basic research on exercise analysis smart wear, to expand the smart cycling area that could only be realized with smart devices and smart watches attached to current cycles, and to provide an opportunity to commercialize it as cycling smart wear.

• The KSFM Journal of Fluid Machinery
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• v.17 no.1
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• pp.35-40
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• 2014

A multi-objective optimization of a regenerative fan for enhancing the aerodynamic and aeroacoustic performance was carried out using an integrated fan design system, namely, Total FAN-Regen$^{(R)}$. The Total FAN-Regen$^{(R)}$ was developed for non-specialists to carry out a series of design process, viz., computational preliminary design, three-dimensional aerodynamic and aeroacoustic analyses, and design optimization, for a regenerative fan. An aerodynamic analysis of the regenerative fan was conducted by solving three-dimensional Reynolds-averaged Navier-Stokes equations using the shear stress transport turbulence model. And, an aeroacoustic analysis of the regenerative fan was implemented in a finite/infinite element method by solving the variational formulation of Lighthill's analogy based on the results of the unsteady flow analysis. An optimum shape obtained by Total FAN-Regen$^{(R)}$ shows the enhanced efficiency and decreased sound pressure level as much as 1.5 % and 20.0 dB, respectively, compared to those of the reference design. The performance test was carried out for an optimized regenerative fan to validate the performance of the numerically predicted optimal design.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.435-442
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• 2017

A catadioptric optical system produces images by refraction and reflection. To improve the image quality, the shape of the secondary mirror supporters should be determined to ensure that the centering error and tilt of secondary mirror are very small, and the main mirror receives the maximum amount of light. Furthermore, random acceleration vibration has a severe effect on the optical system for observation reconnaissance. In order to obtain the best design under these circumstances, the volume of the secondary mirror supporter must be minimized while satisfying the constraints expressed in standard deviations of the centering error and tilt. It is difficult to analytically calculate the design sensitivities of the standard deviations, because they are statistically defined. Hence, after their second-order regression equations were determined using a response surface methodology, an optimal geometric design was obtained. As a result, it was found that the method proposed in this paper, which included a random vibration analysis, was effective in obtaining the optimal design for a secondary mirror supporter with robustness.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.4
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• pp.353-358
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• 2011

In this paper, we describe a process for optimally designing a ring-type permanent magnet thrust bearing. The bearing consists of two sets of permanent magnet rings. One set is located inside the other set. An axial offset between the two sets creates axial force, which results in a thrust bearing function. In order to realize an optimal design of the bearing where the required load capacity of the bearing is achieved with the least magnet volume, we derived analytical design equations by adopting the equivalent current sheet (ECS) method. We considered the following two types of magnet arrays: axial arrays and Halbach arrays. These two types of arrays are optimized using the analytical design equations. The results of the optimization are verified using three dimensional (3D) finite element analyses (FEA). The results show that the Halbach array can achieve the required load capacity with less amount of permanent magnet than the axial array does. The efficacy of the ECS method is also verified by using 3D FEA. It is found that the accuracy of ECS method is more sensitive to the underlying assumptions for the Halbach array than for the axial array.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1073-1081
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• 2005

This paper describes a 3.3 V 10 bit CMOS digital-to-analog converter with a divided architecture of a 7 MSB and a 3 LSB, which uses an optimal Thermal-to-Binary Decoding method. Most of Dfh converters with hiか speed current drive are an architecture choosing current switch cell, column, row decoding method but this decoding circuit is complicated, occupies a large chip area. For these problems, this paper describes a D/A converter using an optimal Thermal-to-Binary Decoding method. The designed D/A converter with an active chip area of $0.953\;mm^2$ is fabricated by using a 0.35um process. The simulation data shows that the rise/fall time, settling time, and INL/DNL are 1.92/2.1 ns, 12.71 ns, and a less than ${\pm}2.3/{\pm}58$ LSB, respectively. The power dissipation of the D/A converter with a single power supply of 3.3 V is about 224 mW.

• Journal of the Korean Association of Geographic Information Studies
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• v.6 no.3
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• pp.21-32
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• 2003

This paper discusses the design of location optimization visualization and feasibility of 3 dimensional visualization techniques. In generic GIS visualization of location analysis, 2 dimensional visualization techniques have been used to map location elements and model solution, such as displaying demand and supply points, drawing connecting lines(e. g. spider line) of optimal locations to their demands, and representing density of location variations. Nevertheless, current GIS and location analysis literatures have little attentions in 3D visualization applications for location optimization problems. Previous research has been neglected 3D visualization of solution performances and its evaluation of solution quality. Consequently, this paper demonstrates potential benefits of 3D visualization techniques and its appropriate GIS applications for location optimization analysis. The visualization effectiveness of 3D approaches is examined in terms of spatial accessibility, and solution performance of optimal location models is evaluated. Finally, this paper proposes extensive 3D visualization perspectives for location analysis and GIS research as a further research agenda.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1152-1155
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• 1995

An analytic model for the optimum design of the power MOSFET considering the degradation of the breakdown voltage by the three dimensional effect is proposed. The proposed method gives the optimum design parameters such as the lateral radius of window curvature and the doping concentration of the epi-layer, which does not minimize the on-resistance but also maintains the required breakdown voltage. The analytical results are verified by the quasi 3D simulation tools, MEDICI, and it is found that the proposed method may be a good guideline for the design of power MOSFET.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.12
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• pp.2361-2367
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• 2011

In this paper survey and analysis of recent trends in noise barriers and noise measurements and assessments were conducted for providing design basis of ANC barriers. Looking at the results, transparent barrier(glass) has received the most attention in domestic and foreign countries, because it has a harmony with the surrounding environment and easy installation in a small space. For optimal barrier design using computer simulation, reliability of simulation has been verified and classified into 5 groups, according to barrier's upper cross section. Evaluation results of barrier's performance and design using computer simulation are as follows : In the case of the "B-type" barrier, it has improved maximum 2.5dB(A) at each point(R1~R6) and have a good workability. Therefore, "B-type" Barriers applied to the next active noise barrier system will be possible.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1628-1633
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• 2016

This paper derives an effective shape of the ferromagnetic pole pieces (low-speed rotor) for the reduction of transmission torque ripple in a magnetic-geared machine based on a Box-Behnken design (BBD). In particular, using a non-linear finite element method (FEM) based on 2-D numerical analysis, we conduct a numerical investigation and analysis between independent variables (selected by the BBD) and reaction variables. In addition, we derive a regression equation for reaction variables according to the independent variables by using multiple regression analysis and analysis of variance (ANOVA). We assess the validity of the optimized design by comparing characteristics of the optimized model derived from a response surface analysis and an initial model.