• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.536-537
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• 2010

If DC voltage adjustment can be controlled very easily, it is much more effective rather than AC in transmission efficiency. The main reason why DC is more effective than AC, DC has the same role as the 70[%] of AC whenever the same power send. In addition, AC streams the surface of electrical wire, but DC streams overall of electrical wire. Digital load, which is operated by DC, has increased in modern times. The step of convert of AC-DC has to be reduced. When we turn the dispersed AC-DC converters into the concentrated AC-DC converter, it can improve the effective of the whole system. Further more, if digital society develops more than now and the time of electric vehicle comes, the need of DC will increase much more than these days. This paper suggests that DC output of distributed power source and high efficient 3 phase PWM converter can control the adjustment of output voltage, harmonic restraint, power factor improvement and dump power.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2000년도 제15차 학술회의논문집
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• pp.314-314
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• 2000

This study deals with the analysis of the effectiveness of a safer belt in frontal crash. ATB, Articulated Total Body, program is used as a dynamics solver of the occupant model. ATB is a public code, however, the program is somewhat cumbersome to use due to lack of sufficient user interface. A preprocessor and a postprocessor are, therefore, developed for a user friendly graphic interface in Windows environment. Dialog boxes are used for an interface with GEBOD, Generator of Body Data, for human anthropometry and with ADAMS for vehicle dynamics. It is found through three test simulations that simulated results are in good agreement with those obtained by ATB. The effect of the initial slack of safety belt is investigated for frontal crash using the developed program.

• KIEE International Transactions on Power Engineering
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• 제2A권4호
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• pp.153-159
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• 2002

Power transformer protective relay should block the tripping during magnetizing inrush and rapidly operate the tripping during internal faults. Recently, the frequency environment of power system has been made more complicated and the quantity of 2nd frequency component in inrush state has been decreased because of the improvement of core steel. And then, traditional approaches will likely be maloperate in the case of magnetizing inrush with low second harmonic component and internal faults with high second harmonic component. This paper proposes a new relaying algorithm to enhance the fault detection sensitivities of conventional techniques by using a fuzzy logic approach. The proposed fuzzy based relaying algorithm consists of flux-differential current derivative curve, harmonic restraint, and percentage differential characteristic curve. The proposed relaying was tested with relaying signals obtained from EMTP simulation package and showed a fast and accurate trip operation.

• 한국신뢰성학회지:신뢰성응용연구
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• 제9권4호
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• pp.319-329
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• 2009

The airbag module is an inflatable restraint system that inflates within 0.05 seconds automatically in a collision to protect the occupants. The airbag fabrics used in the module are required to have the good resilience and strength and also to have retained at least 80% of mechanical properties after using longer than 10 years. In this study, we develop an accelerated test method in order to predict the lifetimes of airbag. In this test, we select temperature and humidity as environmental stresses by analyzing the failure mechanisms of coated and uncoated nylon 66 fabrics. It is found that the degradation of airbag fabrics is effectively accelerated under the combined conditions of high temperature and humidity. Analyzing the results of the accelerated test, the lifetimes of airbag fabrics are predicted to be longer than 10 years.

• 한국환경과학회지
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• 제19권6호
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• pp.737-746
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• 2010

Restraint to drying shrinkage is the most common cause of concrete cracking. In many applications, drying shrinkage cracks are inevitable. In this paper, the surface cracks of soil concrete caused by drying shrinkage were considered to become an one of concrete textures. So, laboratory shrinkage tests were conducted and the results were applied to the field applications. The study results were summarized as follows; First, the use of vinyl sheets and concrete polymers helped to control the concrete cracking. Second, crack propagation usually started at the interfaces of soil concrete slabs and the cracks grew to the inner slabs. Third, surface cracks of soil concrete slabs could be an one of good concrete textures

• 자동차안전학회지
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• 제12권1호
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• pp.39-45
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• 2020

The express/intercity bus models have been developing for wheelchair users to provide the preferable long-distance travels by the Korean government research. In the previous studies, evaluation method was set up for the wheelchair users' safety and the study for wheelchair occupants' safety was performed under various crash loadings mimic to real accidents, frontal crash, side impact and rollover, etc. This study was focused on the evaluation of occupant behaviors and injuries (head and chest) during vehicle impact loading cases in order to ensure the safety of wheelchair passengers in the bus. The occupant response and belt loading data during the sled FE simulation were compared with those of the sled test. The simulation results showed overall safety tolerances of wheelchair occupants under the severe frontal deceleration, side impact loading based on the FMVSS 214 configuration and bus rollover loading.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전력기술부문
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• pp.210-212
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• 2003

Conventional PDC relaying with 2nd harmonic restraint makes some doubt in reliability. It can contain second harmonic component to a large extent even during internal fault, and shows a tendency of relative reduction because of the advancement of transformer's core material. It is, therefore, necessary to develop a new algorithm as well as a new technique for the effective and accurate discrimination. This paper deals with advanced algorithm, fuzzy logic based relaying by using flux differential, and a new fault detection criterion logic scheme by using wavelet transform. To comparative analysis of proposed techniques, the paper constructs power system model including power transformer, utilizing the EMTP, and collects data through simulation of various internal faults and magnetizing inrush.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 추계학술대회 논문집 학회본부
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• pp.186-189
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• 1996

Convential inrush current detection method is used to harmonic restraint method by filtered second frequency component. Nowadays this technique must be modified because harmonics are occurred in steady state of power system. A purpose of this study is to develop of inrush current detection relaying algorithm for power transformer based on flux-current derivative curve method. We used the relaying signals obtained from EMTP simulation.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2008년도 정기총회 및 학술발표대회
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• pp.493-496
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• 2008

In case of collapsed or damaged Servicing infrastructure, such as a bridge, tunnel, dam, a severe loss may have to be incurred. Therefore, infrastructure should not be designed and constructed properly but also maintained impeccably. This paper tried to build an intelligent bridge maintenance system that warn the people on bridge and control traffic in the danger. For the purpose, diverse wireless sensor fields are composed and structure's database is established. Also the paper develops a bridge maintenance program. Developed programme is regarded as a good tool to provide the utmost bridge management scenario, which is exactly correspondent with the demand and restraint by improving the present bridge management strategy.

• Interaction and multiscale mechanics
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• 제5권2호
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• pp.105-114
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• 2012

The study of rigid roadway pavement under dynamic traffic loads with variable velocity is investigated in this paper. Rigid roadway pavement is modeled as a rectangular damped orthotropic plate supported by elastic Pasternak foundation. The boundary supports of the plate are the steel dowels and tie bars which provide elastic vertical support and rotational restraint. The natural frequencies of the system and the mode shapes are solved using two transcendental equations, obtained from the solution of two auxiliary Levy's type problems, known as the Modified Bolotin Method. The dynamic moving traffic load is expressed as a concentrated load of harmonically varying magnitude, moving straight along the plate with a variable velocity. The dynamic response of the plate is obtained on the basis of orthogonality properties of eigenfunctions. Numerical example results show that the velocity and the angular frequency of the loads affected the maximum dynamic deflection of the rigid roadway pavement. It is also shown that a critical speed of the load exists. If the moving traffic load travels at critical speed, the rectangular plate becomes infinite in amplitude.