• 한국철도학회:학술대회논문집
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• 한국철도학회 1999년도 추계학술대회 논문집
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• pp.360-367
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• 1999

An inverter-driven induction motor is used as the traction motor for a high speed drive system that required safety, reliabillity, performance, compact size owing to the space and weight alloted for attaching to train, etc. particularly it is possible to happen the saturation effects of flux density at constant voltage-frequency region and then increase very higher than the at lowed capacity of no-load current and temperature in any case. therefore the optimum design of core, optimum voltage-frequency ratio, adoption of high grade magnetic core have been developed and researched for preventing these problems. this paper show the saturation effects of traction rotor by measuring the induced voltage of search coil at stator teeth and presents optimum voltage-frequency ratio as well as optimum core design through the comparison with efficiency, power factor, load current and no-load current for korea high speed train.

• Structural Engineering and Mechanics
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• 제72권4호
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• pp.525-540
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• 2019

The purpose of the present work was to study the dynamic instability of a three-layered, symmetric sandwich beam subjected to a periodic axial load resting on nonlinear elastic foundation. A higher-order theory was used for analysis of sandwich beams with soft core on elastic foundations. In the higher-order theory, the Reddy's third-order theory was used for the face sheets and quadratic and cubic functions were assumed for transverse and in-plane displacements of the core, respectively. The elastic foundation was modeled as nonlinear's type. The dynamic instability regions and free vibration were investigated for simply supported conditions by Bolotin's method. The results showed that the responses of the dynamic instability of the system were influenced by the excitation frequency, the coefficients of foundation, the core thickness, the dynamic and static load factor. Comparison of the present results with the published results in the literature for the special case confirmed the accuracy of the proposed theory.

• Steel and Composite Structures
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• 제44권1호
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• pp.91-104
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• 2022

The purpose of the present work is to study the parametric nonlinear vibration behavior of three layered symmetric laminated plate. In the analytical formulation; both normal and shear deformations are considered in the core layer by means of the refined higher-order zig-zag theory. Harmonic balance method in conjunction with Galerkin procedure is adopted for simply supported laminate plate, to obtain its natural and damping properties. For these aims, a set of complex amplitude equations governed by complex parameters are written accounting for the geometric nonlinearity and viscoelastic damping factor. The frequency response curves are presented and discussed by varying the material and geometric properties of the core layer.

• Nuclear Engineering and Technology
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• 제55권5호
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• pp.1533-1540
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• 2023

Self-Powered Neutron Detectors(SPNDs) are used to calculate core power distributions, an essential factor in the safe operation of nuclear power plants. Some detectors may fail during normal operation, and signals from failed detectors are isolated from intact signals. The calculated detailed power distribution accuracy depends on the number of available detector signals. Failed detectors decrease the operating margin by enlarging the power distribution measurement error. Therefore, a thorough reconstruction of the failed detector signals is critical. This note suggests a compressive sensing based methodology that rationally reconstructs the readings of failed detectors. The methodology significantly improves reconstruction accuracy by sorting signals and removing high-frequency components from conventional compressive sensing methodology.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.145-146
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• 2023

One of the causes of recent construction site collapses was that the compressive strength of concrete was less than half of the allowable design standard strength range. In the safety diagnosis of structures, the compressive strength of concrete is a factor that determines the durability of a building. Therefore, in this study, we aim to examine the characteristics of compressive strength according to the particle size distribution of coarse aggregate among the compressive strength factors using small-diameter cores. To avoid problems when collecting cores, core specimens with diameters of 100×200, 50×100, and 25×50 (mm) were manufactured directly. As a result of measuring the compressive strength of concrete for each diameter, the larger the core diameter, the higher the compressive strength. has increased.

• 대한전기학회논문지:전력기술부문A
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• 제48권2호
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• pp.119-126
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• 1999

Current transformer (CT) saturation may cause a variety of protective relays to malfunction. The conventional CT is designed that it can carry up to 20 times the rated current without exceeding 10% ratio error. However, the possibility of CT saturation still remains if the fault current contains substantial amounts of ac and/or dc components. This paper presents a design method of iron-cored CTs for use with protective relays to prevent CT saturation. The proposed design method determines the core cross section of the CT; it employs the transient dimensioning factor to consider relay's operating time (duty cycle) and dc component as well as ac components contained in the fault current, and symmetrical short-circuit current factor to consider as well as ac components contained in the fault current, and symmetrical short-circuit current factor to consider the biggest fault current. The method designs the cross section of CTs in cases of reclosure and no reclosure.

• 영재교육연구
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• 제24권4호
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• pp.509-541
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• 2014

21세기 지식 기반 사회가 추구하는 가치나 비전에 따른 과학 영재 교육의 새로운 방향으로서 핵심 역량 중심의 교육을 고려해 볼 필요가 있다. 따라서 이 연구에서는 향후 핵심 역량 중심의 과학 영재 교육을 위한 선결 요건으로서 과학자의 핵심 역량 모델을 개발하고, 타당성을 검토하였다. 이를 위하여 논문, 도서, 신문 기사, 행동사건면접에 대한 분석을 바탕으로 설문 문항을 개발한 후 설문 조사를 실시하였다. 그리고 설문 조사 결과를 바탕으로, 탐색적 요인분석을 실시하였다. 그 결과, 5개의 역량군, 15개의 하위 역량으로 구성된 잠재적인 핵심 역량 모델을 구성할 수 있었고, 확인적 요인분석을 통해 탐색된 핵심 역량 모델의 신뢰도와 수렴타당도, 판별타당도 등을 확보할 수 있었다. 과학자의 핵심 역량 모델에서 '인지' 역량군은 '창의적 사고', '종합적 사고', '탐색적 사고', '분석적 사고', '개념적 사고'의 5개 하위 역량으로 구성되었다. '성취지향' 역량군은 '주도성', '준비 및 문제해결력', '전략적 영향력'의 3개 하위 역량으로 구성되었고, '과학적 태도' 역량군은 '유연한 사고와 태도', '연구 열정', '과학에 대한 견해'의 3개 하위 역량으로 구성되었다. '개인 효과성' 역량군은 '풍부한 경험과 체험', '글로벌 자세'의 2개 하위 역량으로 구성되었으며, 마지막으로, '네트워킹' 역량군은 '대인이해', '의사소통'의 2개 하위 역량으로 구성되었다. 이 연구 결과는 과학자의 핵심 역량 모델을 과학 영재 교육에 소개하고, 핵심 역량 중심의 과학 영재 교육을 위한 프로그램 개발이나 전략 마련 등을 위한 기초 자료를 제공해 줄 수 있을 것으로 기대된다.

• 대한안전경영과학회:학술대회논문집
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• 대한안전경영과학회 2010년도 추계학술대회
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• pp.113-129
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• 2010

Proper pre-safety training is one of core mandatory in order to reduce injuries at the construction fields. In this study, we investigate the employee's opinions of safety training, safety recognition, the actual conditions of safety through survey. As a result of study, incident factors are roughly divided into technical factor, managerial factor, and educational factor. We confirmed that the educational factor led by deficiency of safety awareness and knowledge was the major factor. It needs to be resettled or revised properly to match with the incident trends and the safety training curriculum should also be improved and drastically revised with special quality. The managerial workers' safety recognition is lower than the site ones regarding the correct understanding of the importance of the training.. It suggest that the education method and system in construction fields might have fundamental problems.

• 건설안전기술
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• 통권51호
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• pp.75-83
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• 2010

In terms of deregulation requests from business, incidents at construction sites are rapidly increasing after reducing the regular safety training hours. Especially, to prevent incidents through safety trainings for construction site workers, who have lots of hazardous tasks than general manufacturing, is not only to protect property of both the companies and the country but also to increase their profits. That is why there are loud voices regarding that the safety training is a core mandatory to prevent industrial incidents. But, most companies, as soon as the deregulation for safety training is implemented, mitigated conducting safety trainings to prevent incidents. With this, theincidents are currently to be increased and caught in a vicious circle of many incidents at the smaller companies because of their absentmindedness regarding safety training due to their poorness as subcontractors of major companies, comparing to major companies. This study explains that incident factors are roughly divided into technical factor, managerial factor, and educational factor. And, we confirmed that the educational factor led by deficiency safety awareness and knowledge was the major factor.

• Nuclear Engineering and Technology
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• 제52권5호
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• pp.869-877
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• 2020

A 24-month Advanced Power Reactor 1400 (APR1400) core with a very-low-boron (VLB) concentration has been investigated for an inherently safe and high-performance PWR in this work. To develop a high-performance APR1400 which is able to do the passive frequency control operation, VLB feature is essential. In this paper, the centrally-shielded burnable absorber (CSBA) is utilized for an efficient VLB operation in the 24-month cycle APR1400 core. This innovative design of the VLB APR1400 core includes the optimization of burnable absorber and loading pattern as well as axial cutback for a 24-month cycle operation. In addition to CSBA, an Er-doped guide thimble is also introduced for partial management of the excess reactivity and local peaking factor. To improve the neutron economy of the core, two alternative radial reflectors are adopted in this study, which are SS-304 and ZrO₂. The core reactivity and power distributions for a 2-batch equilibrium cycle are analyzed and compared for each reflector design. Numerical results show that a VLB core can be successfully designed with 24-month cycle and the cycle length is improved significantly with the alternative reflectors. The neutronic analyses are performed using the Monte Carlo Serpent code and 3-D diffusion code COREDAX-2 with the ENDF/B-VII.1.