• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.5
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• pp.34-39
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• 2012

The DAS(Distribution Atomization System) determines a faulted section by using a FI(Fault Indicator) when the fault is occurred on the distribution networks. Sometimes FI is malfunction when the ground fault is occurred on a the distribution networks. As a result difficulties to make decision of faulted section. The cause of the FI malfunction is that the determination using the limited information of the installed area. In this study, a method is proposed to determine faulted section using the amount of the fault current instead of using the FI. This method is determinated faulted section using the fuzzy inference for the collected information from the all switches. The usefulness of the proposed algorithm is verified through the simulation test using PSCAD/EMTDC.

• 대한공업교육학회지
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• v.30 no.2
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• pp.23-32
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• 2005

The purpose of this study is to investigate and analyze the actual state of teaching and learning methods which are applied to the vocation inquiry section-related subjects of the College Scholastic Ability Test(CSAT) by the teachers who teach specialized subjects of vocational high schools. In order for us to get the background and feature of establishment in the area of vocation inquiry section of the CSAT, previous studies and literature was analyzed and sample survey on the 600 teachers who teach the vocation inquiry section-related subjects was made. The result of this survey is as shown below; First, the teachers who are in charge of vocation inquiry section-related subjects understand that theory and practice is in the ratio 60.76:39.24 and ratio of theory is higher than that of practice. Second, teaching and learning method which is the most relevant to the vocation inquiry section is in the order of lecture(83.9%), experiment & practice(50.4%), computerized learning(41.1%). Third, teaching and learning method which is the most used by the teachers who are in charge of vocation inquiry section-related subjects is in the order of lecture(85.8%), computerized learning(50.1%), experiment and practice(44.4%). Forth, the most desirable teaching and learning method which the teachers who are in charge of vocation inquiry section for this subject believe is in the order of lecture(62.7%) experience & practice(47.7%), computerized learning(44.4%). In light of this result, even though there were not so much difference among the teaching-learning methods which are the most consistent with the contents of the subject in relation to the vocation inquiry section, the most used teaching-learning method by the teachers who teach vocation inquiry section-related subjects and the most desirable teaching-learning method which the teachers who are in charge of vocation inquiry section believe, the most used teaching-learning method by the teachers who are in charge of the vocation inquiry section is lecture. Therefore, it is necessary for us to reinforce the contents in relation to the practice & experiment so that the experience and application can be accumulated and improved through practice which is the specialty of the course of the study in the vocational high school and various teaching and learning method should be developed in consideration of contents of the subject, capability & quality of the learners and status of a classroom.

• Journal of Ocean Engineering and Technology
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• v.18 no.2
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• pp.46-51
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• 2004

Natural frequencies of the transverse vibration of beams with step change in cross-section are obtained by using the asymptotic closed form solution. This closed form solution is found by using WKB method under the assumption of slowly varying properties, such as mass, cross-section, tension etc., along the beam length. However, this solution is found to be still very accurate even in the case of large variation in cross-section and tension. Therefore, this result can be easily applied to many engineering problems.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.128-131
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• 2004

This paper is to investigate the mock up test results of mass concrete for transfer girder using setting time difference with super retarding agent(SRA) to reduce hydration heat. According to test results, the temperature history of plain concrete without placing lift had a steep rising curvature, and plain concrete had a big temperature difference between surface and middle section of mass concrete, which may result in occurrence of temperature crack. However, considering placing method B, because setting time of middle section concrete was retarded with an increase in SRA contents, higher hydration heat temperature was observed at surface section concrete compared with that at middle section concrete at early age, which can lower the possibility of hydration heat crack. In case of placing method C, although peak temperature of hydration heat was much lower, at early age, high crack occurrence possibility of the hydration heat attributable to the big temperature difference between middle section and bottom section of concrete was expected at bottom section concrete. Therefore, the structure above the ground like transfer girder is not applicable to consider the placing method C.

• International Journal of Highway Engineering
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• v.16 no.5
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• pp.165-171
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• 2014

PURPOSES : The objective of this study is to find Percentile Speed($V_p$) for Appraisal of Road Section with Recurring Congestion. METHODS : Percentile Speed($V_p$) is determined by correlation analysis of CSI that proposed existing literature. and CSI(Consistency Service Index) is a index that subtract service fail frequency from 100 points, and service fail is defined as traffic situation is driving less than 80kph speed. In this study, We analyzed the highest correlation percentile speed associated with CSI. This speed is chosen as a delay decision speed. In order to verifying reliability, it performed a comparison with the previous method. RESULTS : As a result, 30 percentile speed($V_{30}$) was decided as index speed for judgement of recurring congestion section, and through comparison with existing methods, we demonstrated that 30 percentile speed can be useful for judgement of recurring congestion section. CONCLUSIONS : This method to Determine recurring congestion section using the percentile speed($V_{30}$) was proposed for the first time in this paper. This method can be applicated more quickly and easily than existing method for determining of recurring delay section.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.3
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• pp.16-24
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• 2007

The high-frequency analysis method of back-scattering cross section spectrum of rotating targets is established. The time history of the back-scattering cross section is calculated using a quasi-stationary approach, based on a physical optics and a physical theory of diffraction, combining an adaptive triangular beam method to consider the shadow effect. And the spectra of back-scattering cross section by the Doppler effect are analyzed applying a simple fast Fourier transform method to its time history. The numerical calculation for rotating targets, such as rotating metal plates and underwater propeller, are carried out. The time history appears to be periodic with respect to the number of wings. The backscattering cross section spectrum level and its frequency shift are dependent on the rotating speed, direction, and the shape of the targets.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.208-217
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• 2003

In order to construct the extrusion die surface of T -shaped sections, an automatic surface construction method based on NURBS surface and area mapping method is proposed in the present work. In the present study, a center point for area mapping is determined by introducing the mapping concept based on constant area proportionality between original billet and final product. The characteristic points of inlet profile are determined using the traditional area mapping method and the root finding numerical method. The inlet and outlet profiles are precisely described with NURBS curves using the characteristic points of entry and exit sections. For the construction of NURBS surface, an interpolation method for the pre-determined two section curves has been developed to be used in the generation of interior control points and weights. To show the validity of the proposed method, automatic die surface generation is carried out for the T-shaped section and T-shaped section with rounded corners.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06e
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• pp.247-250
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• 1998

The scattering of plane ultrasonic waves by the nuclear fuel pin of liquid metal reactor in sodium is studied. According to the internal composition in the cladding tube, the fuel pin has three cross sections, i.e. helium gas plenum, sodium-filled section, and fuel insertion section. The scattering spectra for each section of the fuel pin are different. The circumnavigating ultrasonic waves of each section are analyzed by the resonance scattering method. The whispering gallery wave modes are generated in the sodium-filled plenum section and the fuel rod insertion section with a sodium-gap. The circumferential wave modes are propagated in the cladding tube of the helium gas plenum section. The annular gap between the cladding tube and metal uranium pellet rod affects the scattering spectra. The different propagation characteristics can be utilized for the nondestructive method of detecting the unbonded area and measuring the level of the sodium-filled section of the fuel pin.

• 보존과학연구
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• s.27
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• pp.181-201
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• 2006

In this study, radiocarbon dating by the benzene synthesis method and liquid scintillation counting method were performed for the age determination of coal sample at the Cheongok-dong archaeologicalsite, Ulsan. The results of radiocarbon age(BP year) are section Ga #1 $2920\pm50$ BP year, section Ga #5 $3100\pm55$BP year, section Ga #6 $2820\pm60$ BP year, section Na #5 $2650\pm50$ BP year. These ages were converted to calibrated age(AD/BC year) using high precision curve. The products on the excavation of Cheongok-dong archaeological site, Ulsan, section Ga #1 BC 1260-980 BC, section Ga #5 BC1460-1200 BC, section Ga #6 BC 1110~830 BC, section Na #5 BC 920-760 BC. Comparison of samples with radiocarbon and archaeological ages for revealed the approximation.

• Journal of the Korea Concrete Institute
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• v.12 no.4
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• pp.91-101
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• 2000

As the computer related technology evolves a study for a practical use of real structure as well as its hteory for optimum design has been greatly advanced. But the study on optimum design of pre-stressed concrete beam(PSC-beam) bridge for the construction of national roads and highways in Korea is not sufficient. Since a standard section for the PSC-beam is proposed, it is practically used in designing the PSC-beam. It is noticed that the section using the current standard PSC-beam design to be an over-designed with its surplus safety factor. Therefore, it is necessary to consider economical PSC-beam section which automatically satisfies all requirement of design specifications. Thus, in this study, the optimum design methods of PSC-beam are carried out using the gradient-based search method and global search method. As a result of the optimum design method, it was confirmed that the design of PSC-beam has a serious properties to non-linearity and discontinuity. And the section that in economical and efficinet design methods than the current standard design method is proposed.