• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.5 s.51
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• pp.11-23
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• 2006

This paper evaluates the seismic response of multi-span prestressed concrete girder bridges typically found in the New Madrid Seismic Zone region of the central United States. Using detailed nonlinear analytical models and synthetic ground motion records for Memphis, TN, nonlinear response history analyses are performed for two levels of ground motion: 10% probability of exceedance (PE) in 50 years, and 2% probability of exceedance (PE) in 50 years. The results show that the bridge performance is very good fur the 10% PE in 50 years ground motion level. However, the performance for the 2% PE in 50 years ground motion is not so good because it results in highly inelastic behavior of the bridge. Impact between decks results in large ductility demands on the columns, and failure of the bearings that support the girders. It is found that making the superstructure continuous, which is commonly performed for reducing dead load moments and maintenance requirements, results in significant improvement in the seismic response of prestressed concrete girder bridges.

• The Mathematical Education
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• v.56 no.3
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• pp.341-363
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• 2017

This case study contributes to the efforts on identifying the essential features of responsive teaching practice where students' mathematical thinking is central in instructional interactions. We firstly conceptualize responsive teaching as a type of teachers' instructional decisions based on noticing literature, and agree on the claim which teachers' responsive decisions should be accounted in classroom interactional contexts where teacher, students and content are actively interacting with each other. Building on this responsive teaching model, we analyze classroom observation data of a 7th grade teacher who implemented a lesson package specifically designed to respond to students' mathematical thinking, called Formative Assessment Lessons. Our findings suggest the characteristics of responsive teaching practice and identify the relationship between noticing and responsive teaching as: (a) noticing on students' current status of mathematical thinking by eliciting and anticipating, (b) noticing on students' potential conceptual development with follow-up questions, and (c) noticing for all students' conceptual development by orchestrating productive discussions. This study sheds light on the actual teachable moments in the practice of mathematics teachers and explains what, when and how to support teachers to improve their classroom practice focusing on supporting all students' mathematical conceptual development.

• Structural Engineering and Mechanics
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• v.68 no.1
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• pp.67-80
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• 2018

Recently, U-section decks have been more and more used in metro and light rail bridges as an innovative concept in bridge deck design and a successful alternative to conventional box girders because of their potential advantages. U-section may be viewed as a single vent box girder eliminating the top slab connecting the webs, with the moving vehicles travelling on the lower deck. U-section bridges thus solve many problems like limited vertical clearance underneath the bridge lowest point, besides providing built-in noise barriers. Beam theory in mechanics assumes that plane section remains plane after bending, but it was found that shearing forces produce shear deformations and the plane section does not remain plane. This phenomenon leads to distortion of the cross section. For a box or a U section, this distortion makes the central part of the slab lagging behind those parts closer to the webs and this is known as shear lag effect. A sample real-world double-track U-section metro bridge is modelled in this paper using a commercial finite element analysis program and is analysed under various loading conditions and for different geometric variations. The three-dimensional finite element analysis is used to demonstrate variations in the transverse bending moments in the deck as well as variations in the longitudinal normal stresses induced in the cross section along the U-girder's span thus capturing warping and shear lag effects which are then compared to the stresses calculated using conventional beam theory. This comparison is performed not only to locate the distortion, warping and shear lag effects typically induced in U-section bridges but also to assess the main parameters influencing them the most.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.6A
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• pp.794-801
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• 2000

In this paper, the efficient new performance evaluation method for digital communication channels is suggested and verified its efficiency in terms of simulation run-tim for the digital satellite broadcasting satellite TV channel. In order to solve the difficulties of the existing Importance Sampling(IS) Technics, we adopted the discrete probability mass function(PMF) in the new method for estimating the statistical characteristics of received signals from the measured Nth order central moments. From the discrete probability mass function obtained with less number of the received signal than the one required in the IS technic, continuous cumulative probability function and its inverse function are exactly estimated by using interpolation and extrapolation technic. And the overall channel is simplified with encoding block, inner channel performance degra-dation modeing block which is modeled with the Uniform Random Number Generator (URNG) and concatenated Inverse Cummulative Pr bility Distribution function, and decoding block. With the simplified channel model, the overall performance evaluation can be done within a drastically reduced time. The simulation results applied to the nonlinear digital satellite broadcasting TV channel showed the great efficiency of the alogrithm in the sense of computer run time, and demonstrated that the existing problems of IS for the nonlinear satellite channels with coding and M-dimensional memory can be completely solved.

• The Journal of Art Theory & Practice
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• no.3
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• pp.9-34
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• 2005

Contemporary Korean art in the 1960s and the 1970s reflects the social and political contexts in Korea from the 5 16 revolution through the Yoo Shin period. This paper investigates whether art has been free from power or not. It examines the power embedded in contemporary Korean art in the 1960s and the 1970s. This paper examines the historical moments of the Korean Art Exhibition, focusing on the complications between the abstract and figurative artworks of the 1960s. One of the significant art exhibitions since the 8 15 liberation of Korea, the Korean Art Exhibition witnessed conflict among Korean artists who wanted to have power in the art world of Korea. Institutional contradiction based on factionalism and conservatism prevailed in the Korean Art Exhibition was attacked by the avant-garde young artists in the 1960s. With the contact of Abstract Expressionism, young artists' generation participated in the The Wall Exhibition. This exhibition challenged and established moral principles and visualized individual expression and creation similar to the Informal movement in the West. In the world of the traditional painting of Korea, the Mook Lim Exhibition of 1960, organized by young artists of traditional painting, advocated the modernization of Soo Mook paintings. Additionally, abstract sculptures in metal engraving were the new trends in the Korean Art Exhibition. In the 1970s, the economic development and establishment of a dictatorial government made the society stiffen. Abstract expression died out and monochrome painting was the most influential in the 1970s. After the exhibition of Five Korean Artists, Five White Colors in the Tokyo Central Art Museum in 1976, monochrome paintings were formally discussed in Korea. 'Flatness' 'physicality of material' 'action' 'post-image' 'post-subjectivity' and 'oriental spirituality' were the critical terms in mentioning the monochrome paintings of the 1970s. 'Korean beauty' was discussed, focusing on the beauty of white which was addressed by not only Yanagi Muneyoshi but also the policy of national rehabilitation under the Yoo Shin government. At this time, the monochrome paintings of the 1970s in Korea, addressing art for art's sake, cutting of communication with the masses, and elitism, came to be authorized.

• Journal of English Language & Literature
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• v.58 no.1
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• pp.43-67
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• 2012

My essay aims at illustrating Whitman's homosexual vision of utopia with a close reading of his representative homosexual text, Calamus. His expansive self is based upon his intimate contact with the world and is almost always drawn to a wider vision of community in which different individuals share the locus of commonness and reach beyond their empirical boundaries. While foregrounding the contingent and the singular, Whitman forges bonds with other people through a series of ecstatic moments that carry us into the public sphere and common interests. Contrary to the current Whitman studies, his homosexual text doesn't repress contingency in order to celebrate the universal, but fully develops the commensurability among diverse historical agents. Whitman knows well the social taboos and inhibitions at the time of national crisis and expansion, but keeps imagining the world where homosexuality plays a central and significant role in founding a democratic solidarity and achieving a desirable social structure. His ideal of America is not a deferred wish for the future, but a concrete vision that can be achieved here and now, realized by the spontaneous bonding and instant attraction among free men. Instead of interpreting history or suggesting practical alternatives, he keeps questioning the dominant ideologies and the given orders of social control, and suggests a free and open relationship among men where no exterior power or mediating other intervenes. His utopian vision is radical as well as ideal, in that it rejects the interventions of the power structure and its institutions and courageously inscribes his homosexuality in the process of writing about and reading his contemporary America. As a predecessor of a homosexual utopian vision of America, Whitman has inspired many later poets, showing a possibility of infusing a homosexual identity into a radical imaging of the nation and its future.

• The Journal of Korean Academy of Prosthodontics
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• v.41 no.5
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• pp.674-688
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• 2003

Statement of Problem : With increasing demand of the implant-supported prosthesis, it is advantageous to use the different platform width of the fixture according to bone quantity and quality of the patients. Purpose : The purpose of this study was to assess the loading distributing characteristics of two implant designs according to each platform width of fixture, under vertical and inclined loading using finite element analysis. Material and method : The two kinds of finite element models were designed according to each platform width of future (4.1mm restorative component x 11.5mm length, 5.0mm wide-diameter restorative component x 11.5mm length). The crown for mandibular first molar was made using UCLA abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction, 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction and 200N at the buccal cusp in a 300 transverse direction individually Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment screw. Results : The stresses were concentrated mainly at the cortex in both vertical and oblique load ing but the stresses in the cancellous bone were low in both vertical and oblique loading. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading. Increasing the platform width of the implant fixture decreased the stress in the supporting bone, future and abutment screw. Increased the platform width of fixture decreased the stress in the crown and platform. Conclusion : Conclusively, this investigation provides evidence that the platform width of the implant fixture directly affects periimplant stress. By increasing the platform width of the implant fixture, it showed tendency to decreased the supporting bone, future and screw. But, further clinical studies are necessary to determine the ideal protocol for the successful placement of wide platform implants.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.1
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• pp.1-14
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• 2005

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis of internal connection system(ITI system) according to position and direction of load, under vertical and inclined loading using finite element analysis (FEA). The finite element model of a synOcta implant and a solid abutment with $8^{\circ}$ internal conical joint used by the ITI implant was constructed. The gold crown for mandibular first molar was made on solid abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric cusp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant under both vertical and oblique loading but stresses in the cancellous bone were low under both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. So, the relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 4. In this internal conical joint, vertical and oblique loads were resisted mainly by the implant-abutment joint at the screw level and by the implant collar. Conclusively, It seems to be more important that how long the distance is from center of rotation of the implant itself to the resultant line of force from occlusal contact (leverage). In a morse taper implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. This type of implant-abutment connection can also distribute forces deeper within the implant and shield the retention screw from excessive loading. Lateral forces are transmitted directly to the walls of the implant and the implant abutment mating bevels, providing greater resistance to interface opening.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.6
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• pp.53-60
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• 2008

The cross-sections of continuous multi-span beams sometimes suddenly increase, or become stepped, at the interior supports of continuous beams to resist high negative moments. The three-dimensional finite-element program ABAQUS (2007) was used to analytically investigate the inelastic lateral-torsional buckling behavior of stepped beams subjected to linear moment gradient and resulted in the development of design equations. The ratios of the flange thickness, flange width, and stepped length of beam are considered for the analytical parameters. Two groups of 27 cases and 36 cases, respectively, were analyzed for doubly and singly stepped beams in the inelastic buckling range. The combined effects of residual stresses and geometrical imperfection on inelastic lateral-torsional buckling of beams are considered. First, the distributions of residual stress of the cross-section is same as shown in Pi and Trahair (1995), and the initial geometric imperfection of the beam is set by central displacement equal to 0.1% of the unbraced length of beam. The new proposed equations definitely improve current design methods for the inelastic lateral-torsional buckling problem and increase efficiency in building and bridge design.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.1-9
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• 2009

This paper investigates inelastic lateral-torsional buckling of stepped beams subjected to uniformly distributed load and end moments. A three-dimensional finite-element program ABAQUS (2007) and a regression program MINITAB(2006) were used to analytically develop new design equation for singly and doubly stepped beams with simple boundary condition. The flanges of the smaller cross-section in the stepped beams were fixed at 30.48 by 2.54 cm, whereas the width and thickness of the flanges of the larger cross-section varied. The web thickness and height of the beams were kept at 1.65 cm and 88.9 cm, respectively. The ratios of the flange thickness, flange width, and stepped length of beam are considered with analytical parameters. Two groups of 27 cases and 36 cases, respectively, were analyzed for doubly and singly stepped beams in the inelastic buckling range. The combined effects of residual stresses and geometrical imperfection on inelastic lateral-torsional buckling of beams are considered. The distributions of residual stress of the cross-section is same as shown in Pi and Trahair (1995) and the initial geometric imperfection of the beam is set by central displacement equal to 0.1% of the unbraced length of beam. The comparisons between results from proposed equations and the results from finite element analyses were presented in this paper. The maximum differences of two results are of 13% for the doubly stepped beam and 10% for the singly stepped beam. The proposed equations definitely improve current design methods for the inelastic lateral-torsional buckling problem and increase efficiency in building and bridge design.