• 대한수학회보
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• 제37권3호
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• pp.537-542
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• 2000

When A is a subalgebra of a $C^*$-algebra, the spatial numerical range of element of A can be described in terms of positive linear functionals on the $C^*$-algebra.

• Structural Engineering and Mechanics
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• 제15권6호
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• pp.629-651
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• 2003

Current design specifications prescribe that the upper and lower reinforcement mat is required in the same amount to resist negative and positive moment in bridge decks. This design concept is primarily based on the unrealistic assumption that the girder plays a role of rigid support against deck deflection. In reality, however, girders are flexible and the deflection of girders affect the behavior of deck slabs. In the present study, an analytical method was developed to take the effect of the girder flexibility on the deck behavior into account. The method was formulated based on the slope-deflection equations of plates and harmonic analysis. Unlike the conventional finite element analysis, the input and output schemes are simple and convenient. The validity of the presented study was verified by a series of comparative studies with finite element analyses and experimental tests. It was shown from the analyses that the negative transverse moments of decks were significantly reduced in many cases when the girder flexibility were appropriately taken into consideration whereas the positive moments tend to increase. This poses a strong need to improve the conventional design concept of decks on rigid girders to those on flexible girders.

• Steel and Composite Structures
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• 제20권6호
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• pp.1369-1389
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• 2016

This paper investigates the flexural stiffness of simply supported steel-concrete composite I-beams under positive bending moment through combined experimental, numerical, and different standard methods. 14 composite beams are tested for experimental study and parameters including shear connection degree, transverse and longitudinal reinforcement ratios, loading way are also investigated. ABAQUS is employed to establish finite element (FE) models to simulate the flexural behavior of composite beams. The influences of a few key parameters, such as the shear connection degree, stud arrangement, stud diameter, beam length, loading way, on the flexural stiffness is also studied by parametric study. In addition, three widely used standard methods including GB, AISC, and British standards are used to estimate the flexural stiffness of the composite beams. The results are compared with the experimental and numerical results. The findings have provided comprehensive understanding of the flexural stiffness and the modelling of the composite beams. The results also indicate that GB 50017-2003 could provide better results in comparison to the other standards.

• Structural Engineering and Mechanics
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• 제36권5호
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• pp.575-598
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• 2010

The shape and size of the plastic zone around the crack tip are analyzed under pure mode I, pure mode II and mixed mode (I+II) loading for small scale yielding and for both plane stress and plane strain conditions. A new analytical formulation is presented to determine the radius of the plastic zone in a non-dimensional form. In particular, the effect of T-stress on the plastic zone around the crack tip is studied. The results of this investigation indicate that the stress field with a T-stress always yields a larger plastic zone than the field without a T-stress. It is found that under predominantly mode I loading, the effect of a negative T-stress on the size of the plastic zone is more dramatic than a positive T-stress. However, when mode II portion of loading is dominating the effect of both positive and negative T-stresses on the size of the plastic zone is almost equal. For validating the analytical results, several finite element analyses were performed. It is shown that the results obtained by the proposed analytical formulation are in very good agreements with those obtained from the finite element analyses.

• 한국수학사학회지
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• 제21권1호
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• pp.1-16
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• 2008

중국의 산학서 산학계몽은 산학의 훌륭한 입문서로 조선 산학에 지대한 영향을 끼쳤다. 이의 편제와 내용을 본받은 조선 산학서 묵사집산법은 많은 문제와 별해를 추가하고 산학계몽에서 다루지 않은 산학의 몇 가지 주제도 보완해서 교육적 개선을 시도하였다. 그러나 묵사집산법은 정부술을 배제시킴으로써, 전통적인 방정술을 이용할 수 없었다. 또 천원술도 회피함으로써, 일반적인 승방(다항 방정식)의 표현과 풀이에도 큰 제약을 받았다.

• Journal of Platform Technology
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• 제8권1호
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• pp.33-40
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• 2020

본 연구의 목적은 교양 ICT활용 과정의 서술형 강의 평가에 대해 텍스트 마이닝의 토픽모델링 분석을 실시하여 수강생의 강의 선택 요인과 강의에 대한 긍정적·부정적 요소 파악을 하고자 하는데 있다. 이를 위해 M 대학교의 2019년 2학기에 개설된 ICT활용 과정 강의에 대해 '강의를 신청한 이유', '강의에서 개선되어야 할 점'과 '강의에서 좋았던 점'에 대한 데이터 전처리부터 키워드 빈도 분석, 워드 클라우드 시각화 및 토픽 모델링 분석을 실시하였다. 연구결과 M 대학의 2019년 2학기 ICT활용 과정은 자격증 취득을 위해 강의를 신청하며, 동시에 자격증을 취득할 수 있어 강의가 좋았다는 긍정적 분석을 알 수 있다. 부정적 요소로 강의실 사용 환경 불편에 대한 것을 알 수 있다.

• Structural Engineering and Mechanics
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• 제62권3호
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• pp.303-310
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• 2017

The model updating problems, which are to find the optimal approximation to the discrete quadratic model obtained by the finite element method, are critically important to the vibration analysis. In this paper, the structured model updating problem is considered, where the coefficient matrices are required to be symmetric and positive semidefinite, represent the interconnectivity of elements in the physical configuration and minimize the dynamics equations, and furthermore, due to the physical feasibility, the physical parameters should be positive. To the best of our knowledge, the model updating problem involving all these constraints has not been proposed in the existed literature. In this paper, based on the semidefinite programming technique, we design a general-purpose numerical algorithm for solving the structured model updating problems with incomplete measured data and present some numerical results to demonstrate the effectiveness of our method.

• 디지털산업정보학회논문지
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• 제6권2호
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• pp.209-224
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• 2010

This study is focus on consumer innovativeness. The purpose of this study is to explore variable that affect users' perceived value of mobile advertising and actual response intension to analyze relationship among variables. We built research new model based on the Technology Acceptance Model(TAM) and the Ducoffe's model(1996). The result of this study can be summarized as below. First, consumer innovativeness had a positive effect on convenience, the entertaining element and informativeness. Second, credibility and convenience had a positive effect on mobile advertising value. Third, Mobile advertising value had a positive effect on actual response intention to mobile advertising. As shown in the result of this study, the relation between perceived value of mobile advertising and actual response intention, depending on innovativeness in accordance with mobile advertising characters elements.

• 한국화재소방학회논문지
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• 제23권5호
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• pp.196-205
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• 2009

전자모기향 매트는 배선피복의 손상, 반단선, 과부하 및 트래킹 등 다양한 원인에 의하여 발화 할 수 있다. 본 연구에서는 전자모기향 매트의 구조, 발열체인 PTC서미스터(Positive temperature coefficient thermistor) 및 화재현장에서 수거한 전자모기향 매트 잔해의 현상학적 특징을 관찰하고 동일 제품의 PTC 서미스터를 재현 발화 실험을 한 후 각각에 대하여 비교 분석한 결과 발열판의 용융형태와 PTC서미스터의 파열형태 등이 동일하다는 것을 확인하였다.

• 전력전자학회논문지
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• 제20권4호
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• pp.305-312
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• 2015

In this study, inter-turn short fault models of interior permanent magnet synchronous motors (IPMSM) are developed by adding saliency modeling to surface-mounted permanent magnet motor models. The saliency model is obtained using the deformed flux models based on both fault-winding flux information and inductance variations caused by cross-flux linkages that depend on the distribution of the same phase windings. By assuming the balanced three-phase current injection, we obtain the positive and negative sequence voltages and the fault current in the positive and the negative synchronous reference frames. The output torque model is developed by adding the magnet and the reluctance torque, which are derived from the developed models. To verify the proposed IPMSM model with an inter-turn short fault, finite element method-based simulation and experimental measurement results are presented.