• 정보교육학회논문지
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• 제24권2호
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• pp.147-155
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• 2020

SWEET 사업은 초등교원양성 기관의 교육과정을 SW 교육으로 개선하고, 컴퓨터 교육 심화전공의 내실화를 갖추는 것을 목적으로 진행되었다. 본 연구는 SWEET 사업이 시작된 2018년도를 기준으로 예비교사의 SW 교육 역량을 향상시키기 위해 변화된 내용을 살펴보고, 사업의 효과성을 분석하는 것이다. 분석은 SWEET 사업이 적용된 전국 교육대학교와 교육대학 11개 기관의 SW 교육 관련 필수로 이수하는 교양, 교과, 실기의 교육과정을 대상으로 하였다. 연구결과, 초등교원양성 기관의 SW 교육과 관련된 학점은 평균적으로 교양이 2.2학점, 교과 2.3학점, 실기 0.6학점을 운영하고 있는 것으로 분석되었다. 교육과정의 년도별 추이를 분석한 결과, SW 교육관련 교과의 학점과 시수 비중은 늘리고 교양과 실기의 비중은 감소하는 것으로 분석되어, SWEET 사업의 효과라고 해석할 수 있다. 하지만, 이수학점이 평균적으로 SW 교육이 5.1학점인 것에 반하여 수학 6.5학점, 과학 7.8학점인 것으로 분석되어 향후 SW 교육을 위한 교육과정의 개선에 시사하는 바가 크다고 할 수 있다.

• 자원환경지질
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• 제46권3호
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• pp.247-256
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• 2013

재해위험지구 정비사업의 질적 수준제고를 위하여 재해위험지구 정비 사업을 대상으로 비용 대비 편익을 분석하였다. 최근의 재해이력을 고려하여 8개의 분석대상 지구를 선정하였고, 비용편익비(B/C)를 사용하여 투자효과를 분석하였다. 편익 산정은 해당지역의 과거재해이력을 활용하였으며, 비용은 총사업비로 평가하였다. 8개의 분석대상 지구에 대한 분석결과는 영향범위, 할인율 등의 인자에 따라 다른 범위에서 1보다 큰 B/C를 보여주고 있다. 분석결과에 따르면, 4% 할인율과 5 km 영향거리 조건에서 8개 대상 지구에 대한 평균 B/C는 4.1로 1이상을 나타내는 것으로 확인되었다. 이러한 결과로 볼 때 재해위험지구 정비 사업은 비용 대비 효율이 높을 것으로 판단된다.

• Computers and Concrete
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• 제15권5호
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• pp.771-794
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• 2015

This paper proposes an innovative method for selection of measurement sets in static parameter identification of concrete or steel bridges. This method is proved as a systematic tool to address the first steps of Structural System Identification procedures by observability techniques: the selection of adequate measurement sets. The observability trees show graphically how the unknown estimates are successively calculated throughout the recursive process of the observability analysis. The observability trees can be proved as an intuitive and powerful tool for measurement selection in beam bridges that can also be applied in complex structures, such as cable-stayed bridges. Nevertheless, in these structures, the strong link among structural parameters advises to assume a set of simplifications to increase the tree intuitiveness. In addition, a set of guidelines are provided to facilitate the representation of the observability trees in this kind of structures. These guidelines are applied in bridges of growing complexity to explain how the characteristics of the geometry of the structure (e.g. deck inclination, type of pylon-deck connection, or the existence of stay cables) affect the observability trees. The importance of the observability trees is justified by a statistical analysis of measurement sets randomly selected. This study shows that, in the analyzed structure, the probability of selecting an adequate measurement set with a minimum number of measurements at random is practically negligible. Furthermore, even bigger measurement sets might not provide adequate SSI of the unknown parameters. Finally, to show the potential of the observability trees, a large-scale concrete cable-stayed bridge is also analyzed. The comparison with the number of measurements required in the literature shows again the advantages of using the proposed method.

• Wind and Structures
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• 제26권6호
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• pp.369-382
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• 2018

Tornadoes are vertical swirling air formed because of the existence of layers of air with contrasting features of temperature, wind flow, moisture, and density. Tornadoes induce completely different wind forces than a straight-line (SL) wind. A suitably designed building for an SL wind may fail when exposed to a tornado-wind of the same wind speed. It is necessary to design buildings that are more resistant to tornadoes. In tornado-damaged areas, dome buildings seem to have less damage. As a dome structure is naturally wind resistant, domes have been used in back yards, as single family homes, as in-law quarters, man caves, game rooms, storm shelters, etc. However, little attention has been paid to the tornadic wind interactions with dome buildings. In this work, the tornado forces on a dome are computed using Computational Fluid Dynamics (CFD) for tornadic and SL wind. Then, the interaction of a tornado with a dome and a prism building are compared and analyzed. This work describes the results of the tornado wind effect on dome and prism buildings. The conclusions drawn from this study are illustrated in visualizations. The tornado force coefficients on a dome building are larger than SL wind forces, about 120% more in x- and y-directions and 280% more in z-direction. The tornado maximum pressure coefficients are also higher than SL wind by 150%. The tornado force coefficients on the prism are larger than the forces on the dome, about 100% more in x- and y-directions, and about 180% more in z-direction. The tornado maximum pressure coefficients on prism also are greater those on dome by 150% more. Hence, a dome building has less tornadic load than a prism because of its aerodynamic shape.

• Korea-Australia Rheology Journal
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• 제21권4호
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• pp.225-233
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• 2009

In various attempts to relate the behaviour of highly-elastic liquids in complex flows to their rheometrical behaviour, obvious candidates for study have been the variation of shear viscosity with shear rate, the two normal stress differences $N_1$ and $N_2$, especially $N_1$, and the extensional viscosity $\eta_E$. In this paper, we shall be mainly interested in 'constant-viscosity' Boger fluids, and, accordingly, we shall limit attention to $N_1$ and $\eta_E$. We shall concentrate on two important flows - axisymmetric contraction flow and "splashing" (particularly that which arises when a liquid drop falls onto the tree surface of the same liquid). Modern numerical techniques are employed to provide the theoretical predictions. It is shown that the two obvious manifestations of viscoelastic rheometrical behaviour can sometimes be opposing influences in determining flow characteristics. Specifically, in an axisymmetric contraction flow, high $\eta_E$ can retard the flow, whereas high $N_1$ can have the opposite effect. In the splashing experiment, high $\eta_E$ can certainly reduce the height of the so-called Worthington jet, thus confirming some early suggestions, but, again, other rheometrical influences can also have a role to play and the overall picture may not be as clear as it was once envisaged.

• 한국수학교육학회지시리즈E:수학교육논문집
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• 제26권2호
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• pp.205-220
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• 2012

이 연구에서는 수렴하는 자연 수 수열의 사례를 구성하는 것을 목표로 특별한 패턴의 자연수 수열을 찾아 연구하였다. 자연수 수열의 수렴과 관련하여 다음 두 가지를 조사 분석하였다. 첫째, 극한에 대한 일상의 언어지만 수학적 의미를 내포한 고등학교 직관적 정의를 자연수 수열의 수렴성에 대한 이해의 토대가 되는 상수 수열을 포함한 기본적인 수열들에 어떻게 적용하는지를 수학교육전공의 대학생을 중심으로 살펴보았다. 둘째, 자명하지 않으며 특수한 패턴을 가진 수렴하는 자연수 수열의 사례로 전자항의 각 자릿수의 제곱의 합이 후자항을 결정하는 자연수 수열들에서 찾았다. 이 수열들의 탐구를 위해 꼬리의 개념을 사용하였고, 지필의 환경에서 이 수열들의 극한과 관련된 속성들이 쉽게 관찰되지 않아 원활한 탐색을 위해 스프레드시트를 활용하였다. 여기서 스프레드시트는 실험과 관찰을 도모하고 수학적 패턴의 발견을 도울 뿐 아니라 추론과 증명을 뒷받침하는 자료 추출의 도구가 될 수 있다는 시사점올 준다.

• Advances in Computational Design
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• 제5권2호
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• pp.127-146
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• 2020

Building Information Modeling (BIM) is increasingly used throughout the facility's life cycle for various applications, such as design, construction, facility management, and maintenance. For existing buildings, the geometry of as-built BIM is often constructed using dense, three dimensional (3D) point clouds data obtained with laser scanners. Traditionally, as-built BIM systems do not contain the material and textural information of the buildings' elements. This paper presents a semi-automatic method for generation of material and texture rich as-built BIM. The method captures and integrates material and textural information of building elements into as-built BIM using thermal infrared sensing (TIS). The proposed method uses TIS to capture thermal images of the interior walls of an existing building. These images are then processed to extract the interior walls using a segmentation algorithm. The digital numbers in the resulted images are then transformed into radiance values that represent the emitted thermal infrared radiation. Machine learning techniques are then applied to build a correlation between the radiance values and the material type in each image. The radiance values were used to extract textural information from the images. The extracted textural and material information are then robustly integrated into the as-built BIM providing the data needed for the assessment of building conditions in general including energy efficiency, among others.

• 한국수학교육학회지시리즈A:수학교육
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• 제56권4호
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• pp.387-405
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• 2017

The purpose of this study is to investigate the change of students 'perception and expression about the motion of object following distance function $={x \atop 3}$ and distance function $y=\frac{x^3}{3}+3$ according to the necessity of research on students' perception and expression about integral constant. In this paper, we present the recognition and the expression of the difference of the constant in the relationship between the distance function and the speed function of the students, while examining the process of constructing the speed function and the inverse process of the distance function. This provides implications for the relationship between the derivative and the indefinite integral corresponding to the inverse process. In particular, in a teaching experiment, a constructive activity was performed to analyze the motion of two distance functions, where the student had a difference of the constant term. At this time, the students used the expression 'starting point' for the constants in the distance function, and the motion was interpreted by using the meaning. This can be seen as a unique 'students' mathematics' in the process of analyzing the motion of objects. These scenes, in introducing the notion of the relation between differential and indefinite integral, it is beyond the comprehension of the integral constant as a computational procedure, so that the learner can understand the meaning of the integral constant in relation to the motion of the object. It is expected that it will be a meaningful basic research on the relationship between differential and integral.

• Spatial Information Research
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• 제17권4호
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• pp.455-462
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• 2009

원격탐사 영상에서 압축을 위한 근최적의 PSNR 값을 찾는 방법을 연구하였다. 예상 웨이블릿쌍은 다양한 영상에서 최적의 결과로 나타났다. 영상처리를 위한 최고의 웨이블릿쌍을 찾는 규칙은 없다. 제시된 알고리즘에 따라 예상 웨이블릿쌍이 다양한 종류의 영상에서 최적의 결과를 나타냈다. 먼저 세 개의 웨이블릿 패밀리에서 PSNR 값의 변화를 분석하였다. 직교 웨이블릿 패밀리에서는 많은 경우에 웨이블릿 필터의 길이가 길수록 높은 PSNR 값을 나타내지만, 그 증가 비율이 점차로 작아졌다. 연산비용의 측면에서 중간 필터길이의 웨이블릿을 제안한다. 쌍직교 웨이블릿 패밀리에서는 필터의 길이와 PSNR값의 관계를 예측하기는 어려웠다. 다차원 웨이블릿 분석에서는 세 개의 웨이블릿 패밀리가 3단계까지 처리되었다. 쌍직교 웨이블릿 패밀리는 최대 PSNR 값에서 불규칙한 패턴을 보였지만, 직교 웨이블릿 패밀리는 규칙적 패턴을 나타냈다. 직교 웨이블릿 패밀리는 1단계 결과로부터 근최적의 웨이블릿쌍을 예상할 수 있었다.

• Steel and Composite Structures
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• 제19권2호
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• pp.369-384
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• 2015

This work presents a free vibration analysis of functionally graded metal-ceramic (FG) beams with considering porosities that may possibly occur inside the functionally graded materials (FGMs) during their fabrication. For this purpose, a simple displacement field based on higher order shear deformation theory is implemented. The proposed theory is based on the assumption that the transverse displacements consist of bending and shear components in which the bending components do not contribute toward shear forces and, likewise, the shear components do not contribute toward bending moments. The most interesting feature of this theory is that it accounts for a quadratic variation of the transverse shear strains across the thickness, and satisfies the zero traction boundary conditions on the top and bottom surfaces of the beam without using shear correction factors. In addition, it has strong similarities with Euler-Bernoulli beam theory in some aspects such as equations of motion, boundary conditions, and stress resultant expressions. The rule of mixture is modified to describe and approximate material properties of the FG beams with porosity phases. By employing the Hamilton's principle, governing equations of motion for coupled axial-shear-flexural response are determined. The validity of the present theory is investigated by comparing some of the present results with those of the first-order and the other higher-order theories reported in the literature. Illustrative examples are given also to show the effects of varying gradients, porosity volume fraction, aspect ratios, and thickness to length ratios on the free vibration of the FG beams.