• Journal of Institute of Control, Robotics and Systems
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• v.22 no.7
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• pp.552-556
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• 2016

Obstacle detection is a key feature in the safe driving control of electric wheelchairs. The suggested obstacle detection algorithm was designed to provide obstacle avoidance direction and detect the existence of cliffs. By means of this information, the wheelchair can determine where to steer and whether to stop or go. A 3D depth camera (Microsoft KINECT) is used to scan the 3D point data of the scene, extract information on obstacles, and produce a steering direction for obstacle avoidance. To be specific, ground detection is applied to extract the obstacle candidates from the scanned data and the candidates are projected onto a 2D map. The 2D map provides discretized information of the extracted obstacles to decide on the avoidance direction (left or right) of the wheelchair. As an additional function, cliff detection is developed. By defining the "cliffband," the ratio of the predefined band area and the detected area within the band area, the cliff detection algorithm can decide if a cliff is in front of the wheelchair. Vehicle tests were carried out by applying the algorithm to the electric wheelchair. Additionally, detailed functions of obstacle detection, such as providing avoidance direction and detecting the existence of cliffs, were demonstrated.

• Journal of Welding and Joining
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• v.29 no.4
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• pp.67-72
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• 2011

The proportion of the welding in the production process of machinery, buildings and marine structures is increasing and the joining are mainly conducted by butt and fillet weld. In the case of fillet weld, the shape of structures is complicated depending on the constraint on the geometry of the structures, therefore, the full penetration is mostly difficult. Accordingly, it is necessary to establish safe and economical criteria of design of the structures through the strength based on the penetration state of the fillet weld. Patterns of fatigue failure in cruciform fillet weld jont appear in the form of the root, toe and mixed failure. In the case of toe and mixed failure, the fatigue strength is higher than root failure. Therefore, we have to make the enough depth of penetration or perform the welding work through improving the fatigue strength of cruciform joints in welded structures. So it is necessary to optimize the penetrated depth in the range of the possible mixed failure and find the way in the cost-effective design to lessen the amount of the welding work.

• Journal of the Korea Concrete Institute
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• v.11 no.4
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• pp.43-54
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• 1999

Shear tests are performed on four full-scale 12.5 m proto-type models, "least depth double tee," which are resulted from the optimization process. Domestic superimposed live load regulation, domestic material properties which is available to product. Korean building code requirements, construction environments and economy are considered as the main factors to establish the process. All of the specimens tested fully comply with the shear strength requirements as specified by ACI 318-95. The research has shown following results. 1) The development length requirement of ACI 318-95 does not seem a good predictor for the estimation of bond failure in a beam with the strands below the supports. 2) The load required for the first initial coner cracking in the dap end and first web shear cracking does not seem to have any relation with the dimension and shear strength of the section in the test beams. 3) The strand slip has a direct relationship with the web shear cracking. However, the coner cracking in the dap end does not give any help for the slip in anchorage. 4) Use of whole area for bearing steel at the bottom of dap end is desired for safe bearing pressure design in the precast prestressed double tee beams. 5) The deflection of beam influences directly on the amount of strand slip at the anchorage after initiation of it, and relationship between them are very linear.

• Journal of Ship and Ocean Technology
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• v.11 no.1
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• pp.36-46
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• 2007

The maintenance of a ship is essential for safe navigation and hence regular surveys are prescribed according to the rule of classification societies. A hull inspection is generally performed by professional divers, but it takes a long time and the efficiency is low in terms of time and cost. In this research, a ROV(Remotely Operated Vehicle) named as SNU-ROV(Seoul National University-ROV) is developed to replace the conventional inspection method. In this system, the ROV is intended to be used for inspecting ship and harbor because harbor inspection is merging as a safety measure against any possible terror actions. In order to increase the efficiency of inspection, the ROV must be able to measure the exact position of damages. SNU-ROV has a positioning system based on LBL(Long Base Line). In shallow water such as harbor, however, LBL has bad DOP(Dilution of Precision) in the depth direction due to the limited depth. Thus LBL only can not locate the exact depth position. To solve the DOP problem, a pressure sensor is introduced to LBL and a complementary filter is attached by using indirect feedback Kalman filter. Thus developed positioning system is verified by simulation and experiment in towing tank.

• Journal of the Korea Institute of Military Science and Technology
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• v.19 no.3
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• pp.395-403
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• 2016

A cylinder-type underwater vehicle for military use that is running near the free surface at the final homing stage to hit a surface ship target is affected by wave force and moment. Since wave can affect an underwater vehicle running at the depth less than half of the modal wave length, it is important to confirm that the underwater vehicle can work well in such a situation. In this paper, wave force and moment per unit wave amplitude depending on wave frequency, wave direction, and vehicle's running depth were calculated by 3-Dimensional panel method, and the numerical results were modeled in external force terms of six degrees of freedom equations of motion. Motion simulation of the underwater vehicle running in various speed, depth, and sea state were performed.

• Journal of the Society of Naval Architects of Korea
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• v.54 no.4
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• pp.301-311
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• 2017

Safety operational envelope (SOE) is the area which guarantees the safety of a submarine from the accident such as jamming and flooding. The maximum safe depth is set to prevent the damage to the hull from increasing water pressure with depth. A minimum safety depth is set to prevent a submarine from the exposure above the free surface and collision against surface ship. The prediction method for the SOE in the design phase is needed to operate the submarine safely. In this paper, the modeling and calculation methods of the SOE are introduced. Main ballast tank blowing modeling and propeller force modeling are conducted to simulate the accidents and the recovery process. The SOEs are established based on the crash stop and emergency rising maneuver simulation. From the simulation results, it can be known that the emergency rising maneuver is more effective recovery action than the crash stop.

• Journal of Korea Multimedia Society
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• v.24 no.8
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• pp.1026-1034
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• 2021

Tire wear and defect are important factors for safe driving condition. These defects are generally inspected by some specialized experts or very expensive equipments such as stereo depth camera and depth gauge. In this paper, we propose tire safety vision inspector based on deep neural network (DNN). The status of tire wear is categorized into three: 'safety', 'warning', and 'danger' based on depth of tire tread. We propose an attention mechanism for emphasizing the feature of tread area. The attention-based feature is concatenated to output feature maps of the last convolution layer of ResNet-101 to extract more robust feature. Through experiments, the proposed tire wear classification model improves 1.8% of accuracy compared to the existing ResNet-101 model. For detecting the tire defections, the developed tire defect detection model shows up-to 91% of accuracy using the Mask R-CNN model. From these results, we can see that the suggested models are useful for checking on the safety condition of working tire in real environment.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.4
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• pp.560-566
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• 2010

Port of Samcheonpo, designated as a Trading Port, is constructing New Port for the increase in trade and the requirement of maritime safety is growing. To meet these requirement for maritime safety, hydrographic surveying around south sea area of Samcheonpo using Multibeam Echo Sounder(MBES), DGPS etc was conducted. In this study, major item of hydrographic surveying such as sounding data was acquired and analyzed depth data comparing with vertical uncertainty in the special publication for hydrographic minimum specification published in Feb, 2008 by International Hydrographic Organization. By analyzing the depth data with 3 steps procedure, the port and starboard beam by removing the outskirts of the data processing could improve the efficiency and accuracy. The error of south sea were about 0.2m and the upper central part of the error were within 0.2m. Depth data of the study area are included in the 99% of 1st order and satisfied with a 100% tolerance of special order based on the international hydrograhic survey standard. This study will be a good case to support efficient decision-making for safe navigation, coastal management.

• Journal of the Korean Institute of Gas
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• v.17 no.1
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• pp.19-25
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• 2013

The joining methods of steel structures of gas facilities, bridges, ships etc. by welding are composed mostly of T-type or cruciform fillet welding and full penetration or partial penetration according to the uses and the shape of the structures. In this study, it was examined the characteristics of fatigue crack according to penetration depth in relation to material thickness in the cruciform fillet welded joints. From the results, it was investigated the safe design stresses within the range of infinite life. When the LOP length is long the range of infinite life is small with root failure and when the LOP length is short the range of infinite life is large with teo failure. For the specimen of material thickness, 20mm welded by 3 pass compared with 10mm, 15mm welded by 2 pass, the fatigue strength and the range of infinite life was more improved by increasing of notch toughness from formation of micro-ferrite acicular structure.

• Journal of the Korean Home Economics Association
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• v.40 no.2
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• pp.143-159
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• 2002

Consumer Education Policy for -Focusing on developing Social support System- The purpose of this research is to understand the change of future consuming environment and the characteristics of future potential consumer: the net generations. With those research results, we deduced our goal, content and method of consumer education for these net generations. Finally, I suggested a scheme of the social construction by demand of our future society. Literature review and depth interview are used for this research. The main factors of the change of our future consuming environment are Digitalization, globalization, improvement of consumer sovereignty, Sustainable consumption culture, the increasing pursuit of safe life. It is necessary to educate our future consumer, net generations, the information searching skills in order to be able to obtain right information. We also need to educate them how to practice the safe life and Sustainable consumption and how to get consumers sovereignty. The method of the education requires interchangeable communication. We need social networking system for the support of consumer education, in order to build this social system. We need an administrative support from the government and financial support from corporations. We have suggested that it is very desirable to share all the information developed among Academic field, Consumer related organizations and schools by this network be build.