• 한국과학교육학회지
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• 제13권2호
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• pp.257-271
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• 1993

Four science concepts were selected from high school earth science textbook to investigate the differences in students knowledges activated in laboratory and earth environmemtal contexts. Two items, one is for laboratory and the other for earth environmental contexts, were develped for each selected concept. Students' responses were analyzed in terms of 'Common Activated Knowledges' (CAK), 'Specific Activated Knowledges'(SAK) across students' cognitive frames, grades and sexes. As contextual differences of the problems increased, gender contributed more than other variables to the frequencies of activating CAK and SAK. Context effects were also reported across cognitive frames for CAK, but SAK became more avtivated when the contextual differences of the items become smaller. As a whole, students with laboratory cognitive frames showed more significant context effects than others. Students in 11th grade, with scientific frames and with earth science cognitive frames showed relatively small context effects. The results of the study showed that sciene concepts learned in a laboratory context are not usually transferred spontaneously to earth environmental contexts. Special instructional strategies should developed to overcome the context effects.

• Steel and Composite Structures
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• 제36권3호
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• pp.273-291
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• 2020

Two-storey X-bracings are currently very popular in European practice, as respect to chevron and simple X bracings, owing to the advantages of reducing the bending demand in the brace-intercepted beams in V and inverted-V configurations and optimizing the design of gusset plate connections. However, rules for two-storey X braced frames are not clearly specified within current version of EN1998-1, thus leading to different interpretations of the code by designers. The research presented in this paper is addressed at investigating the seismic behaviour of two-storey X concentrically braced frames in order to revise the design rules within EN1998-1. Therefore, five different design criteria are discussed, and their effectiveness is investigated. With this aim, a comprehensive numerical parametric study is carried out considering a set of planar frames extracted from a set of structural archetypes that are representative of regular low, medium and high-rise buildings. The obtained results show that the proposed design criteria ensure satisfactory seismic performance.

• Structural Engineering and Mechanics
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• 제64권3호
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• pp.301-310
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• 2017

For further development of passive control systems to dissipate larger seismic energy and prevent the structures from earthquake losses, this paper proposes an innovative two-level control system to improve behavior of chevron braced steel frames. Combining two Knee Braces, KB, and a Vertical Link Beam, VLB, in a chevron braced frame, this system can reliably sustain main shock and aftershocks in steel structures. The performance of this two-level system is examined through a finite element analysis and quasi-static cyclic loading test. The cyclic performances of VLB and KBs alone in chevron braced frames are compared with that of the presented two-level control system. The results show appropriate performance of the proposed system in terms of ductility and energy dissipation in two different excitation levels. The maximum load capacity of the presented system is about 30% and 17% higher than those of the chevron braced frames with KB and VLB alone, respectively. In addition, the maximum energy dissipation of the proposed system is about 78% and 150% higher than those of chevron braced frames with VLB and KB respectively under two separate levels of lateral forces caused by different probable seismic excitations. Finally, high performance under different earthquake levels with competitive cost and quick installation work for the control system can be found as main advantages of the presented system.

• Structural Engineering and Mechanics
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• 제44권6호
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• pp.763-774
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• 2012

Reinforced concrete frame structures with masonry infill walls constitute the significant portion of the building stock in Turkey. Therefore it is very important to understand the behavior of masonry infill frame structures under earthquake loads. This study presents an experimental work performed on reinforced concrete (RC) frames with different types of masonry infills, namely standard and locked bricks. Earthquake effects are induced on the RC frames by quasi-static tests. Results obtained from different frames are compared with each other through various stiffness, strength, and energy related parameters. It is shown that locked bricks may prove useful in decreasing the problems related to horizontal and vertical irregularities defined in building codes. Moreover tests show that locked brick infills maintain their integrity up to very high drift levels, showing that they may have a potential in reducing injuries and fatalities related to falling hazards during severe ground shakings.

• 한국기계가공학회지
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• 제12권6호
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• pp.93-100
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• 2013

This paper presents the development process for a bicycle monocoque frame using bolt fastening. Traditionally, bicycle frames have been constructed with metal tubes joined at their ends by welding. These frames have been brazed or soldered onto metal lugs, forming the frame. Because stress loads become greatest at the joint of the bicycle tube frame, joint construction strongly influences frame design and construction. To avoid the inherent problems of material discontinuity at frame joints, numerous designers have attempted to reduce or eliminate the number of joints in tube frames. Nevertheless, the manufacture of high quality, reliable, one-piece and jointless frames has proven difficult and expensive. In this study, a new monocoque frame adapted to a hybrid bike is proposed. The advantage of the monocoque frame, is theat is has a rechargeable battery system that is built into the frame; as a result, the emotional quality for the customer is improved. In order to estimate the design compatibility compared with that of tube frames, structural analysis is performed using finite element method. A prototype based on a modified design has also been made and stability testing has been carried out.

• Steel and Composite Structures
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• 제33권4호
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• pp.525-535
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• 2019

The seismic performance of steel frames equipped with a particular type of bending dissipative braces (BDBs) having U elements, which has recently been introduced and tested by the authors, is investigated. For this purpose, two structural systems, i.e., simple and dual steel building frames, both with diagonal BDBs and different number of stories, are considered. After providing a design method of this new BDB, the detailed structural models are developed in the OpenSees platform to perform nonlinear dynamic analyses. Seismic performance factors like ductility, overstrength, response modification and deflection amplification factors are calculated using incremental dynamic analysis (IDA). In addition, to assess the damage probability of the structural models, their seismic fragilities are developed. The results show high energy dissipation capacity of both structural systems while the number of U elements needed for the bracing system of each story in the moment frames are less than those in the corresponding non-moment (simple) frames. The average response modification and deflection amplification factors for both structural schemes are obtained about 8.6 and 5.4, respectively, which are slightly larger than the corresponding recommended values of ASCE for the typical buckling-restrained braces (BRBs).

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.254-257
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• 2009

In this paper, we propose a learning-based super-resolution algorithm. In the proposed algorithm, a multi-resolution wavelet approach is adopted to perform the synthesis of local high-frequency features. To obtain a high-resolution image, wavelet coefficients of two dominant LH- and HL-bands are estimated based on wavelet frames. In order to prepare more efficient training sets, the proposed algorithm utilizes the LH-band and transposed HL-band. The training sets are then used for the estimation of wavelet coefficients for both LH- and HL-bands. Using the estimated high frequency bands, a high resolution image is reconstructed via the wavelet transform. Experimental results demonstrate that the proposed scheme can synthesize high-quality images.

• 인터넷정보학회논문지
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• 제11권6호
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• pp.31-39
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• 2010

영상에서 원을 찾을 때 정확도가 높은 일반화 허프 변환 (Generalized Hough Transform: GHT) 알고리즘이 가장 많이 사용된다. 그러나 GHT는 영상의 모든 가능한 픽셀에 대해 가능한 모든 원의 크기를 확인해야하기 때문에 많은 계산 시간을 요구한다는 단점을 가지고 있다. 또한 동영상에서 원을 찾는다면, 매 프레임마다 이러한 GHT를 실행해야하므로 계산 속도는 더욱 느리게 된다. 본 논문에서는 동영상의 연속된 프레임 사이에서 변화되는 부분이 적고 대부분 이전 영상과 유사하다는 점을 이용하여, GHT의 정확도를 유지하면서 계산 속도를 줄이는 알고리즘을 제안한다. 제안하는 알고리즘은 동영상의 현재 프레임과 이전 프레임을 비교하여 움직임이 크면 본래의 GHT를 수행하는 변화 기반 방법과 움직임이 작으면 이전 프레임에서 검출한 원의 정보로 GHT의 후보영역과 후보 원들만을 이용하여 GHT를 수행하는 경로 기반 방법을 사용하였다. 이는 동영상에서의 GHT 수행에 영향을 미치는 프레임 수, 에지 수, 원의 개수를 줄임으로써 속도를 향상시킬 수 있다. 실험결과는 제안하는 알고리즘이 고정된 카메라나 이동 카메라에 대해 정확도의 손실이 없으면서, 수행 시간을 줄이고 있음을 보여준다.

• 인터넷정보학회논문지
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• 제10권4호
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• pp.1-11
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• 2009

대규모 인간 동작 데이터베이스에서 고차원의 데이터를 처리하는 것이 큰 비용을 요구하기에, 최근 데이터베이스 및 그래픽스 학계는 인간 동작 데이터 질의 및 접근에 큰 관심을 가지게 되었다. 특히, 인간 동작 데이터를 위한 효과적인 유사도(거리) 측정 방법이나 질의 처리는 여전히 많은 연구진들이 도전하고 있는 문제이다. 이에, 본 연구진은 SMoFinder 라고 명명한 동작 질의 처리 시스템을 제안한다. SMoFinder는 새롭게 고안된 운동학적 거리 측정 그리고 적응적 프레임 세그멘테이션에 기반하는 효율적인 인덱싱을 사용하여 동작 질의를 처리한다. 이를 위해, SMoFinder에서는 인간 동작을 다연결 물리 운동으로 간주하고 새로운 가중치 Minkowski 함수를 정의했다. 또한, 효율적인 인덱싱을 위해 모든 프레임을 저장하지 않고 유사한 프레임들 중에서 대표 프레임을 뽑아서 저장하는 적응적 세그멘테이션을 고안했다. 그리고, 효율적인 검색을 위해 이들 대표 프레임들만 가지고 k-근접 이웃 질의를 수행하는 새로운 방법을 제안한다. 마지막으로, SMoFinder가 데이터베이스 용량이 크게 줄지만(1/25배), 검색 능력은 다른 시스템과 동일하거나 우월하다는 것을 실험을 통해 보여주고자 한다.

• Steel and Composite Structures
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• 제34권5호
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• pp.625-641
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• 2020

The realistic modeling of the beam-column semi-rigid connection in steel frames attracted the attention of many researchers in the past for the seismic analysis of semi-rigid frames. Comparatively less studies have been made to investigate the behavior of steel frames with semi-rigid connections under different types of earthquake. Herein, the seismic behavior of semi-rigid steel frames is investigated under both far and near-field earthquakes. The semi-rigid connection is modeled by the multilinear plastic link element consisting of rotational springs. The kinematic hysteresis model is used to define the dynamic behavior of the rotational spring, describing the nonlinearity of the semi-rigid connection as defined in SAP2000. The nonlinear time history analysis (NTHA) is performed to obtain response time histories of the frame under scaled earthquakes at three PGA levels denoting the low, medium and high-level earthquakes. The other important parameters varied are the stiffness and strength parameters of the connections, defining the degree of semi-rigidity. For studying the behavior of the semi-rigid frame, a large number of seismic demand parameters are considered. The benchmark for comparison is taken as those of the corresponding rigid frame. Two different frames, namely, a five-story frame and a ten-story frame are considered as the numerical examples. It is shown that semi-rigid frames prove to be effective and beneficial in resisting the seismic forces for near-field earthquakes (PGA ≈ 0.2g), especially in reducing the base shear to a considerable extent for the moderate level of earthquake. Further, the semi-rigid frame with a relatively weaker beam and less connection stiffness may withstand a moderately strong earthquake without having much damage in the beams.