• Journal of the Society of Naval Architects of Korea
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• v.47 no.6
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• pp.843-849
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• 2010

This paper presents definition of symmetry of a ship section where three symmetries are proposed: material, geometric, and load symmetries. Precise terminologies of centroid, moment plane, and neutral axis plane are also defined. It is suggested that force vector equilibrium as well as force equilibrium are necessary condition to determine new position of neutral axis due to translational and rotational mobility. It is also stated that new reference datum of ENMP(elastic neutral moment plane), PNMP(fully plastic moment plane), ENAP(elastic neutral axis plane), and INAP(inelastic neutral moment plane) are required to define asymmetric section properties such as second moment of area, elastic section modulus, yield moment, fully plastic moment, and ultimate moment. Since collision-induced damage and flooding-induced biaxial bending moment produce typical asymmetry of section, the section properties are calculated for a typical VLCC. Geometry asymmetry is determined from ABS and DNV rules and two moment planes of 0/30 degs are assumed for load asymmetry. It is proved that the property reduction ratios directly calculated from second moment of area are usually larger than area reduction ratio. Reduction ratio of ultimate moment capacity shows almost linearly proportional to area reduction ratio. Mobility of elastic and inelastic neutral axis planes is visually provided.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.1
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• pp.15-24
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• 2008

The data delivery confirmation method of MIL-STD-188-220C, which is a tactical wireless mobile Ad-Hoc communication protocol, is that a source node requires the end-to-end ack from all destination nodes and the data-link ack from 1-hop neighboring destination nodes and relaying nodes, regardless of the hop distance from a source node to destination nodes. This method has the problem to degrade the whole communication network performance because of excessive data traffic due to the duplicate use of end-to-end ack and data-link ack, and the collision among end-to-end acks on the wireless network in the case of confirming a data delivery within an 1-hop distance. In order to solve this problem, this paper has proposed the method to perform the data delivery confirmation with the improvement of communication network performance through the data traffic reduction by achieving the reliable data delivery confirmation requiring the only data-link ack within an 1-hop distance. The effects of the proposed method are analyzed in the two aspects of the data delivery confirmation delay time and the data delivery confirmation success ratio.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.6
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• pp.782-789
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• 2010

It is important to satisfy the requirements and standards for the protections of passengers in a car accident. There are lots of studies on the crushing energy absorption of a structure member in automobiles. In this paper, we have studied to investigate collapse characteristics and moisture absorption movements of CFRP( carbon fiber reinforced plastics) structure members when CFRP laminates are under the hygrothermal environment. In particular, the absorbed energy, mean collapse load and deformation mode were analyzed for CFRP members which absorbed most of the collision energy. Also, variation of stacking angle is important to increase the energy absorption capability. The purpose of this study is to evaluate the strength reduction and moisture absorption behavior of CFRP hat shaped member. Therefore we have made a impact collapse experiment to research into the difference of absorbed energy and deformation mode between moisture absorbed specimen and non-moisture absorbed. As a result, the effect of moisture absorption and impact loads of approximately 50% reduction in strength are shown.

• Journal of the Society of Disaster Information
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• v.19 no.2
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• pp.421-431
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• 2023

Purpose: The purpose of this study is to analyze the safety and disaster prevention effects of the Smart Safety System used to prevent safety accidents in construction machinery and demonstrate its safety. Method: Among construction machines, the behavioral patterns of workers according to the presence or absence of a smart safety system were analyzed for excavators with high risk and frequent accidents. Result: When the smart safety system was installed in the construction machine, the safety of workers from accidents caused by constriction and collision with the construction machine was secured. Conclusion: It is judged that the smart safety system installed in construction machinery can increase the effectiveness of disaster reduction and major disaster prevention related to construction machinery.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.3
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• pp.30-35
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• 2008

As demands for being economical, precise drilling process is on the increase. Therefore, the objective of this study is to develop a step cutter that can be controllable through micro dimension and can be changed from separate manufacturing processes of drilling and boring into an integrated one. In order to attain this object the step cutter is designed with a 3D geometric modeling and the design could be modified easily by using parametric modeling methodology. Also, collision is not occurred during manufacturing process because of cutting simulation. The step cutter is assembled by parts made up of 5-axis machining and sintering. Validation tests are accomplished. They show that developed cutter has characteristics such as reduction of machining time as well as the good surface roughness of the machined hole. Indeed, reliability could be obtained from a durability test.

• Aerospace Engineering and Technology
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• v.2 no.2
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• pp.179-185
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• 2003

In this study, considerations for establishing RVSM airspace and requirements for RVSM operating aircraft are verified. The purpose of RVSM is to reduce vertical separation minimum for aircraft which operate between FL290~FL410 inclusive in regional airspace, and to increase airspace capacity by providing additional flight levels. To introduce RVSM, it is necessary to estimate quantatively airborne collision risk due to the reduction in vertical separation minimum. Aircraft operating through RVSM airspace is required to verify that height keeping performance is above specific standards.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.6
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• pp.67-72
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• 2012

Novel Front End Module(FEM) with improved pedestrian protection is very important to reduce the severity of pedestrian injury. The FEM needs to have enough space from hood to absorb the energy from any pedestrian collision. In this study, the cooling performance of the FEM to cool the engine was investigated under 25% height reduction. The results indicated that the cooling performance analysis was about 86% level compared to that of the conventional FEM. Also, good qualitative agreement between CFD predictions and experimental measurements was found. This FEM needs the cooling performance enhancement for changed air flow path at the frontal part of vehicle. Therefore, we showed an improved performance using air guide setup and shape modification under the high load condition.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.1495-1500
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• 2004

The interface link for railway signaling systems is generally point-to-point communication scheme, but there have been several efforts to apply the network technology to these interface link in overseas country. However general Ethernet scheme has several drawbacks, so this scheme cannot meet the very high reliability, safety and real-time properties. To overcome these drawbacks, there have been studies reduction and modeling of data collision probability for this ethernet at the industrial and academic world. Therefore, in this paper we analyzed describe a interface trend using network technology between railway signaling equipments and will describe a major technology and framework of a network for railway signaling system.

• 제어로봇시스템학회:학술대회논문집
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• 1999.10a
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• pp.25-28
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• 1999

In this article, a new performance index is proposed to re-duce the collision impulsive force by controlling the null motion of redundant manipulators. First, we define the normalized impact ellipsoid in the viewpoint of instantaneous velocity change. Then, we propose a new impact performance index based on velocity direction for null motion to reduce initial impulsive effects. It gives some advantage for the case of unknown environment. The optimization of this index is that the successional impact forces are reduced. The performance of the proposed index is demonstrated by simulation study.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1999.03b
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• pp.30.2-34
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• 1999

The hydroforming technology has gained in importance over the last few years, because of its potential for substantial weight avings costs reduction and quality improvement such as collision property, shape fixability and rigidity of white body. However, in comparison with the traditional sheet forming process, the hydroforming is much younger and the main development efforts were made in the last 15 years. The new technology, high pressure tublar hydroforming in particular, involves many process parameters to be optimized. This paper covers a brief overview of the hydroforming simulator as well as design of die and tools. The effects of typical parameters such as internal pressure and axial compression stroke are presented. Moreover, the conditions of forming failure occurrences such as fracture and wrinkle are examinated.