• New & Renewable Energy
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• v.8 no.1
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• pp.44-51
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• 2012

Due to a high tidal range of up to 10 m on the west coast of Korea, numerous tidal current projects are being planned and constructed. The turbine, which initially converts the tidal energy, is an important component because it affects the efficiency of the entire system. Its performance is determined by design variables such as the number of blades, the shape of foils, and the size of a hub. To design a turbine that can extract the maximum power on the site, the depth and duration of current velocity with respect to direction should be considered. Verifying the performance of a designed turbine is important, and requires a circulating water channel (CWC) facility. A physical model for the performance test of the turbine should be carefully designed and compared to results from computational fluid dynamics (CFD) analysis. In this study, a horizontal axis tidal current turbine is designed based on the blade element theory. The proposed turbine's performance is evaluated using both CFD and a CWC experiment. The sealing system, power train, measuring devices, and generator are arranged in a nacelle, and the complete TCP system is demonstrated in a laboratory scale.

• Journal of the Korean Society of Safety
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• v.21 no.5 s.77
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• pp.22-27
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• 2006

Even though the interior of urban transit vehicle has been changed as a preventing measure against fire to make it inflammable, there remains a possibility of fire breaking out in case of gasoline etc being brought in the subway. However, there is also the possibility that in case if fire toxic gas is generated and hot air spreads in carriage it will prove very dangerous for people sitting inside. This is a comparative study where we compare simulation results with model examining the time and direction the fire spreads when it breaks out. Also there is vertical distribution of temperature in carriage where the fire spreads out. This study is about demonstrating how to establish smokeless system in urban vehicle, about its necessity, and about vehicle system restructuring. This study also makes an effort to find more advanced method for efficient fire safety in trains. In existing vehicles, in case of fire, the smoke can't go out when doors are closed and hence it spreads in whole train. Even though the method of using ventilation or exhaust established inside the carriage to throw smoke out is much better than the way of opening end doors in each carriage, this study is trying to do research on second way. Through simulation we see that in second case, even though not as good as the first one, smoke can exit through gates. Even though the first method is better, the second can also be uses to let fire out. We can know that in the first case as the smoke can exit out faster, it provides more safety for people. So this system provides better fire safety condition.

• Journal of the Korean Geosynthetics Society
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• v.4 no.4
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• pp.3-11
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• 2005

In this study, a large-scale laboratory model test and 2-D numerical analysis were conducted to verify the reinforcement effect by utilizing geotextile bag on the railway roadbed. Static loading which simulated train load was applied on the geotextile-reinforced railway roadbed and also unreinforced railway roadbed. Computer program named Pentagon 2-D which is a part of FEM programs was used in the numerical analysis. Based on the results of laboratory test and 2-D numerical analysis, the effect of load distribution and settlement reduction was found to be depending on the geotextile characteristics, tensile strength of geotextile, and interface friction angle between geotextile bags. In general, the result of 2-D numerical analysis shows lower value than that of laboratory test.

• Composites Research
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• v.28 no.5
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• pp.327-332
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• 2015

In this research, a parametric study was carried out to design a metal-carbon fiber reinforced plastics (CFRP) hybrid pantograph for weight reduction of high speed train (KTX). To design a light-weight and high-stiffness pantograph, some parts of the original steel upper arm was replaced by CFRPs with appropriate stacking sequences. For the parametric study, steel was replaced by aluminium considering structure stiffness and weight of hybrid upperarm of a pantograph. Finite element analysis (FEA) was performed for checking the structure stiffness with varying design parameters. Static vertical load stiffness and weight changing ratio were derived from real CX-PG pantograph model analyses. From the FEA results, the geometries of high-stiffness, light-weight pantograph have been suggested.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.7-15
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• 2020

Recently, the fourth industrial revolution has been presented as a new paradigm and additive manufacturing (AM) has become one of the most important topics. For this reason, process monitoring for each cross-sectional layer of additive metal manufacturing is important. Particularly, deep learning can train a machine to analyze, optimize, and repair defects. In this paper, image classification is proposed by learning images of defects in the metal cross sections using the convolution neural network (CNN) image labeling algorithm. Defects were classified into three categories: crack, porosity, and hole. To overcome a lack-of-data problem, the amount of learning data was augmented using a data augmentation algorithm. This augmentation algorithm can transform an image to 180 images, increasing the learning accuracy. The number of training and validation images was 25,920 (80 %) and 6,480 (20 %), respectively. An optimized case with a combination of fully connected layers, an optimizer, and a loss function, showed that the model accuracy was 99.7 % and had a success rate of 97.8 % for 180 test images. In conclusion, image labeling was successfully performed and it is expected to be applied to automated AM process inspection and repair systems in the future.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.883-888
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• 2011

Laparoscopic surgery is being used in various surgical fields because it minimizes scarring. Laparoscopic operations require practical hand skills, so surgeons train on animals and via surgery training tool sets. However, these tool sets do not give the surgeon the sensation of touching real organs. A recently developed laparoscope simulator has a high friction force along the translational axis and a high gravity force along the pitch axis, and therefore it does not permit the operator to control his or her hands delecately. In the paper, the friction force along the axes is auumed to depend on the veolcity, and the gravity force on the angle and distance. We develop a compensation model that combines the gravity and friction force models.

• The Journal of the Korea Contents Association
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• v.16 no.3
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• pp.694-711
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• 2016

National Competency Standards (NCS) is a good resource for curriculum development and operations corresponding to the industrial damand. Recently, four-year colleges and universities are committed to a restructuring of the industry demand-driven training courses in order to strengthen competitiveness. However, NCS is focused to train the technical personnel in vocational training institutions(ex. College, Polytechnic University). Accordingly, NCS applications of four-year colleges and universities are hard to find. In this study, we propose a new model for NCS-based curriculum development and operations. Also, NCS was utilized to complement the existing curriculum. This paper includes the following contents; 1) NCS-based curriculum development process, 2) NCS-based course development and operation, 3) learner satisfaction analysis. Finally, this study provide practical implications to four-year colleges and universities to consider NCS application.

• Journal of Korea Multimedia Society
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• v.16 no.9
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• pp.1031-1043
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• 2013

Extracting hand region from images is the first part in the process to recognize hand posture and gesture interaction. Therefore, a good segmenting method is important because it determines the overall performance of hand recognition systems. Conventional hand segmentation researches were prone to changing illumination conditions or limited to the ability to detect multiple people. In this paper, we propose a robust technique based on the fusion of skin-color data and depth information for hand segmentation process. The proposed algorithm uses skin-color data to localize accurate seed location for region-growing from a complicated background. Based on the seed location, our algorithm adjusts each detected blob to fill up the hole region. A region-growing algorithm is applied to the adjusted blob boundary at the detected depth image to obtain a robust hand region against illumination effects. Also, the resulting hand region is used to train our skin-model adaptively which further reduces the effects of changing illumination. We conducted experiments to compare our results with conventional techniques which validates the robustness of the proposed algorithm and in addition we show our method works well even in a counter light condition.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.157-170
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• 2005

The combination of multiple antennas and multi-carrier code division multiple-access (MC-CDMA) is a strong candidate for the downlink of the next generation mobile communications. The study of such systems in scenarios that model real-life trans-missions is an additional step towards an optimized achievement. We consider a realistic MIMO channel with two or four transmit antennas and up to two receive antennas, and channel state information (CSI) mismatches. Depending on the mobile terminal (MT) class, its number of antennas or complexity allowed, different data-rates are proposed with turbo-coding and asymptotic spectral efficiencies from 1 to 4.5 bit/s/Hz, using three algorithms developed within the European IST-MATRICE project. These algorithms can be classified according to the degree of CSI at base-station (BS): i) Transmit space-frequency prefiltering based on constrained zero-forcing algorithm with complete CSI at BS; ii) transmit beamforming based on spatial correlation matrix estimation from partial CSI at BS; iii) orthogonal space-time block coding based on Alamouti scheme without CSI at BS. All presented schemes require a reasonable complexity at MT, and are compatible with a single-antenna receiver. A choice between these algorithms is proposed in order to significantly improve the performance of MC-CDMA and to cover the different environments considered for the next generation cellular systems. For beyond-3G, we propose prefiltering for indoor and pedestrian microcell environments, beamforming for suburban macrocells including high-speed train, and space-time coding for urban conditions with moderate to high speeds.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.119-128
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• 2004

With the growing traffic density and increasing comfort requirements, the automation of the drive train will gain importance in vehicles. The automatic clutch actuation relieves the drivers especially in urban driving and stop-and-go traffic conditions. This paper describes the dynamic modeling of a clutch actuator and clutch spring. The dynamic model of the clutch system is developed using MATLAB/Simulink, and evaluated by experimental data using a test rig. This performance simulator is useful to develop the clutch-by-wire (CBW) system for an automated manual transmission (AMT). The electro-mechanical type CBW system is also implemented as an automatic clutch for AMT. The prototype of CBW system is designed and implemented systematically, which is composed of an electric motor, worm gear and slider-crank mechanism. The test rig is developed to perform the basic function test of the automatic clutch, and the developed prototype is validated by the experimental data on the test rig.