• International Journal of Control, Automation, and Systems
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• v.4 no.1
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• pp.77-86
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• 2006

A new method in robot path generation is presented using an analysis of the characteristics of multi-robot collision avoidance. The research is based on the concept of the collision map, where the collision between two robots is presented by a collision region and a crossing curve TLVSTC (traveled length versus servo time curve). Analytic collision avoidance is considered by translating the collision region in the collision map. The 4 different translations of collision regions correspond to the 4 parallel movements of the actual original robot path in the real world. This analysis is applied to path modifications where the analysis of collision characteristics is crucial and the resultant path for collision avoidance is generated. Also, the correlations between the translations of the collision region and robot paths are clarified by analyzing the collision/non-collision areas. The influence of the changes of robot velocity is investigated analytically in view of collision avoidance as an example.

• Ocean and Polar Research
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• v.43 no.4
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• pp.295-306
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• 2021

A field scale productivity analysis is required for the development of gas hydrate in marine sedimentary layers to verify the field applicability of production techniques and to improve productivity. In this study, the productivity resulting from the application of depressurization using multi-wells for the development of gas hydrate in the Ulleung Basin, East Sea of Korea, was determined. A numerical analysis model reflecting the conditions of candidate sites for the Ulleung Basin was constructed, and the productivity and dissociation behavior were comparatively analyzed. The pressure propagation and gas hydrate dissociation region by the multi-wells were wider and the productivity was higher than that of a single well. Different depressurization effects according to the spacing of multi-wells affected productivity. The results provide basic data for productivity analysis when establishing a field test production plan for the Ulleung Basin.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.18 no.2
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• pp.166-177
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• 2006

The accuracy impact of using high-order Boussinesq-type model as compared to the typical order model is examined in this paper. The multi-layer model developed by Lynett and Liu(2004a) is used for simulating of wave breaking over a shelf region. The nonlinearity of the waves tested, ${k_0}{A_0}$, ranges from 0.029 to 0.180. The overall agreement between the two-layer model and the hydraulic experiments are quite good. The one-layer model overshoals the wave near the breakpoint, while the two-layer model shoals at a rate more consistent with the experimental data.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.4
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• pp.161-169
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• 2003

The applications of SRM(Switched Reluctance motor) are dramatically increasing due to a simple mechanical structure, a high efficiency and a high speed drive characteristics. Energy recovery in the regenerative region is very important when SRM is used in traction drive. This is to reduce energy loss during mechanical braking and/or to have a high efficiency drive. To control excitation voltage during motoring and regenerating voltage in the generator operation in the SRM, multi-level voltage control is effective. This paper suggests multi-level inverter which is useful for motoring and regenerative operation. The proposed method is verified through simulations and experiments.

• Journal of Korea Multimedia Society
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• v.22 no.12
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• pp.1347-1355
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• 2019

Deep learning approach based on convolution neural network (CNN) has extensively studied in the field of computer vision. However, periocular feature extraction using CNN was not well studied because it is practically impossible to collect large volume of biometric data. This study uses the ResNet model which was trained with the ImageNet dataset. To overcome the problem of insufficient training data, we focused on the training of multi-layer perception (MLP) having simple structure rather than training the CNN having complex structure. It first extracts features using the pretrained ResNet model and reduces the feature dimension by principle component analysis (PCA), then trains a MLP classifier. Experimental results with the public periocular dataset UBIPr show that the proposed method is effective in person authentication using periocular region. Especially it has the advantage which can be directly applied for other biometric traits.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.6
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• pp.1207-1214
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• 2009

In this study, we propose a novel color-image segmentation algorithm to discern the teeth region utilizing RG intensity and its relevant RGB histogram features with resolving the variations of its maximum intensity in terms of peaks and valleys. Tooth candidates in a CCD image are first extracted by applying RGB color multi-threshold levels and consequently the successive morphological image operations and a Sobel-mask edge processing are performed to resolve the teeth region and its contour.

• International Journal of Air-Conditioning and Refrigeration
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• v.9 no.2
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• pp.8-18
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• 2001

The direct simulation Monte Carlo Method is applied to investigate the two-dimensional flow fields of a turbomolecular pump(TMP) in both molecular and transition flow regions. The pumping characteristics of the TMP are investigated for a wide range of the Knudsen number. The maximum of compression ratio and of pumping speed strongly depend on the Knudsen number in transition region, while they weakly depend on the Knudsen number in free molecular flow region. The present numerical results show good agreement with the previously known experimental data. Finally. the results of the single blade row in both molecular and transition regions are used to predict the overall performance of a TMP, which has three kinds of blade with 24-rows.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.5
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• pp.15-21
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• 2004

In this paper a new structure of BJT is proposed to improve the saturation voltage characteristics so that it can be used to the low power switching devices. In the case of the conventional finger transistor(FT), the saturation voltage is so high that it dose not satisfy the requirements for the low power device. So the other multi base island transistor(MBIT) is suggested and its saturation voltage is so low in the region of low current that it satisfy the requirement for the low power switching devices, but in region of the high current the saturation voltage tends to increase so that it does not satisfy the requirements for the low power switching devices. So in this paper a new structure of folded back electrode transistor(FBET) is proposed and the characteristics is investigated. When the new structure is applied the emitter area is increased by 35 % so the saturation voltage is reduced by 30 % at the low current region and the contact area is increased by 92 % so the saturation voltage is reduced by totally f % at the high current region with the reduction of 30 % by the increase of the emitter area and the reduction of 7 % by the increase of the emitter contact area.

• Structural Engineering and Mechanics
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• v.48 no.6
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• pp.775-789
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• 2013

The current paper proposes a boundary element formulation, applicable to 2-D and 3-D elastostatics problems using a unified approach for transformations of the domain integrals into boundary integrals. The method is applicable to linear problems encompassing both finite and infinite multi-region domains allowing non-vanishing body forces. Numerical results agree quite well with the analytical solutions; while the present method offers easy formulation with less numerical efforts in comparison to FEM or some BEM which need interior points to treat arbitrary body forces. It is demonstrated that the method has the potential to have profound impact on engineering design, notably in dam-foundation interaction.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.15 no.4
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• pp.38-44
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• 2007

This paper describes the structural safety of solid fuel in the Hybrid Rocket Motor (HRM). Hybrid rocket combustion has the distinct regression characteristics which include the process of thermal pyrolysis and fuel vaporization. Most of all, this regression characteristics would structurally affect the strength of the fuel having a multi-port configuration, and even may cause the breaking from the fuel grain. This problem would probably influence the performance and operating safety of HRM. Therefore, for the safe operation of HRM, the critical port radius which determines the structurally safe region was discussed from the heat analysis of the solid fuel.