• Steel and Composite Structures
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• v.47 no.4
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• pp.523-537
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• 2023

This paper proposed a new self-centering brace (SCB), which consists of four post-tensioned (PT) high strength steel strands and energy absorbing steel plate (EASP) clusters. First, analytical equations were derived to describe the working principle of the SCB. Then, to investigate the hysteretic performance of the SCB, four full-size specimens were manufactured and subjected to the same cyclic loading protocol. One additional specimen using only EASP clusters was also tested to highlight the contribution of PT strands. The test parameters varied in the testing process included the thickness of the EASP and the number of EASP in each cluster. Testing results shown that the SCB exhibited nearly flag-shape hysteresis up to expectation, including excellent recentering capability and satisfactory energy dissipating capacity. For all the specimens, the ratio of the recovered deformation is in the range of 89.6% to 92.1%, and the ratio of the height of the hysteresis loop to the yielding force is in the range of 0.47 to 0.77. Finally, in order to further understand the mechanism of the SCB and provide additional information to the testing results, the high-fidelity finite element (FE) models were established and the numerical results were compared against the experimental data. Good agreement between the experimental, numerical, and analytical results was observed, and the maximum difference is less than 12%. Parametric analysis was also carried out based on the validated FE model to evaluate the effect of some key parameters on the cyclic behavior of the SCB.

• Structural Engineering and Mechanics
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• v.83 no.4
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• pp.475-493
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• 2022

The results of research focusing on the experimental and numerical performance of ferrocement RC beams with openings reinforced with welded steel mesh, expanded steel mesh, fiber glass mesh, and polyethylene mesh independently are presented in this article. Casting and testing of fourteen reinforced concrete beams with dimensions of 200×100×2000 mm under concentric compression loadings were part of the research program. The type of reinforcing materials, the volume fraction of reinforcement, the number of mesh layers, and the number of stirrups are the major parameters that change. The main goal is to understand the impact of using new appealing materials in reinforcing RC beams with openings. Using ANSYS-16.0 Software, nonlinear finite element analysis (NLFEA) was used to demonstrate the behavior of composite RC beams with openings. A parametric study is also conducted to discuss the variables that can have the greatest impact on the mechanical behavior of the proposed model, such as the number of openings. The obtained experimental and numerical results demonstrated the FE simulations' acceptable accuracy in estimating experimental values. Furthermore, demonstrating that the strength gained of specimens reinforced with fiber glass meshes was reduced by approximately 38% when compared to specimens reinforced with expanded or welded steel meshes is significant. In addition, when compared to welded steel meshes, using expanded steel meshes in reinforcing RC beams with openings results in a 16 percent increase in strength. In general, when ferrocement beams with openings are tested under concentric loadings, they show higher-level ultimate loads and energy-absorbing capacity than traditional RC beams.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.793-815
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• 2023

The current study looks at the experimental and numerical performance of ferrocement RC channel slabs reinforced with welded steel mesh, expanded steel mesh, and fiber glass mesh individually. Ten RC channel slabs with dimensions of 500 mm×40 mm×2500 mm were subjected to flexural loadings as part of the testing program. The type of reinforcing materials, the number of mesh layers, and the reinforcement volume fraction are the key parameters that can be changed. The main goal is to determine the impact of using new inventive materials to reinforce composite RC channel slabs. Using ANSYS -16.0 Software, nonlinear finite element analysis (NLFEA) was used to simulate the behavior of composite channel slabs. Parametric study is also demonstrated to identify variables that can have a significant impact on the model's mechanical behavior, such as changes in slab dimensions. The obtained experimental and numerical results indicated that FE simulations had acceptable accuracy in estimating experimental values. Also, it's significant to demonstrate that specimens reinforced with fiber glass meshes gained approximately 12% less strength than specimens reinforced with expanded or welded steel meshes. In addition, Welded steel meshes provide 24% increase in strength over expanded steel meshes when reinforcing RC channel slabs. In general, ferrocement specimens tested under flexural loadings outperform conventional reinforced concrete specimens in terms of ultimate loads and energy absorbing capacity.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.1
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• pp.31.2-31.2
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• 2021

To estimate the contribution of quasars on keeping the IGM ionized, building a quasar luminosity function (LF) is necessary. Quasar LFs derived from multiple quasar surveys, however, are incompatible, especially for the faint regime, emphasizing the need for deep images. In this study, we construct quasar LF reaching M₁₄₅₀~-21.5 AB magnitude at z ~ 5, which is 1.5 mag deeper than previously reported LFs, using deep images from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP). We trained an artificial neural network (ANN) by inserting the colors as inputs to classify the quasars at z ~ 5 from the late-type stars and low-redshift galaxies. The accuracy of ANN is > 99 %. We also adopted the Bayesian information criterion to elaborate on the quasar-like objects. As a result, we recovered 5/5 confirmed quasars and remarkably minimized the contamination rate of high-redshift galaxies by up to six times compared to the selection using color selection alone. The constructed quasar parametric LF shows a flatter faint-end slope α=-127^+0.16_-0.15 similar to the recent LFs. The number of faint quasars (M₁₄₅₀ < -23.5) is too few to be the main contributor to IGM ionizing photons.

• Earthquakes and Structures
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• v.25 no.4
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• pp.235-247
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• 2023

Bingöl, a city in eastern Türkiye, is located at a very close distance to the Karlıova Region which is a junction point of the North Anatolian Fault Zone and Eastern Anatolian Fault Zone. By bilateral step over of North Anatolian Fault Zone and Eastern Anatolian Fault Zone each other there occurred NorthWest-SouthEast extended right-lateral and NorthEast-SouthWest extended left-lateral fault zones. In this paper, a typical school building located in Bingöl Çeltiksuyu was selected as the case study. Information on the school building and Bingöl Earthquake (2003) have been given in the paper. This study aimed to determine the fragility curves of the school building according to HAZUS 2022, Turkish Seismic Codes 1998, 2007 and 2018. These codes have been introduced in terms of damage limits. Incremental dynamic analysis is a parametric analysis method that has recently emerged in several different forms to estimate more thoroughly structural performance under seismic loads. Fragility analysis is commonly using to estimate the damage probability of buildings. Incremental Dynamic Analysis have performed, and 1295 Incremental Dynamic Analysis output was evaluated to obtain fragility curves. 20 different ground motion records have been selected with magnitudes between 5.6M and 7.6M. Scaling factors of these ground motions were selected between 0.1g and 2g. Comparison has been made between HAZUS 2022 and Turkish Seismic Codes 1998, 2007 and 2018 in terms of damage states and how they affected fragility curves. TSC 1998 has more conservative strictions along with TSC 2018 than TSC2007 and HAZUS moderate and extensive damage limits.

• Advances in nano research
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• v.15 no.4
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• pp.367-384
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• 2023

Natural frequency behavior of graphene platelets reinforced composite (GPL-RC) joined truncated conical-cylindrical- conical shells resting on Winkler-type elastic foundation is presented in this paper for the first time. The rule of mixture and the modified Halpin-Tsai approach are applied to achieve the mechanical properties of the structure. Four different graphene platelets patterns are considered along the thickness of the structure such as GPLA, GPLO, GPLX, GPLUD. Finite element procedure according to Rayleigh-Ritz formulation has been used to solve 2D-axisymmetric elasticity equations. Application of 2D axisymmetric elasticity theory allows thickness stretching unlike simple shell theories, and this gives more accurate results, especially for thick shells. An efficient parametric investigation is also presented to show the effects of various geometric variables, three different boundary conditions, stiffness of elastic foundation, dispersion pattern and weight fraction of GPLs nanofillers on the natural frequencies of the joined shell. Results show that GPLO and BC3 provide the most rigidity that cause the most natural frequencies among different BCs and GPL patterns. Also, by increasing the weigh fraction of nanofillers, the natural frequencies will increase up to 200%.

• Educational Technology International
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• v.25 no.1
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• pp.1-25
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• 2024

This study aims to analyze the impact of learners' usability perceptions of topic modeling-based visual feedback and generative AI interpretation on reflection levels in online discussions. To achieve this, we asked 17 students in the Department of Korean language education to conduct an online discussion. Text data generated from online discussions were analyzed using LDA topic modeling to extract five clusters of related words, or topics. These topics were then visualized in a network format, and interpretive feedback was constructed through generative AI. The feedback was presented on a website and rated highly for usability, with learners valuing its information usefulness. Furthermore, an analysis using the non-parametric Mann-Whitney U test based on levels of usability perception revealed that the group with higher perceived usability demonstrated higher levels of reflection. This suggests that well-designed and user-friendly visual feedback can significantly promote deeper reflection and engagement in online discussions. The integration of topic modeling and generative AI can enhance visual feedback in online discussions, reinforcing the efficacy of such feedback in learning. The research highlights the educational significance of these design strategies and clears a path for innovation.

• Communications for Statistical Applications and Methods
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• v.31 no.2
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• pp.179-189
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• 2024

In multivariate regression with a high-dimensional response Y ∈ ℝ^r and a relatively low-dimensional predictor X ∈ ℝ^p (where r ≥ 2), the statistical analysis of such data presents significant challenges due to the exponential increase in the number of parameters as the dimension of the response grows. Most existing dimension reduction techniques primarily focus on reducing the dimension of the predictors (X), not the dimension of the response variable (Y). Yoo and Cook (2008) introduced a response dimension reduction method that preserves information about the conditional mean E(Y | X). Building upon this foundational work, Yoo (2018) proposed two semi-parametric methods, principal response reduction (PRR) and principal fitted response reduction (PFRR), then expanded these methods to unstructured principal fitted response reduction (UPFRR) (Yoo, 2019). This paper reviews these four response dimension reduction methodologies mentioned above. In addition, it introduces the implementation of the mbrdr package in R. The mbrdr is a unique tool in the R community, as it is specifically designed for response dimension reduction, setting it apart from existing dimension reduction packages that focus solely on predictors.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7331-7339
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• 2014

As the Korean government initiates the Han-style campaign, the efforts and expectations for the modernization and industrialization of Hanok are growing. Accordingly, a major R&D project sponsored by the government is in progress for the development of related technologies, in which the development of a Hanok design support system based on Building Information Modeling(BIM) technology is included as one of the major subjects. However, the development of design tools for Hanok so far has not focused on the windows and doors, which is another major element of Korean traditional architecture. Therefore, this study developed a BIM-based design tool for Hanok windows and doors as an approach to the integrated design of various Hanok elements and their applications to modern buildings. To this end, the characteristics of Hanok windows and doors were analyzed first in terms of the location, opening method, style, components, and the over-all construction. A design tool was then developed with the parametric modeling functions of the $ArchiCAD^{(R)}$system. The applicability and efficiency of the developed tool were verified with design simulations. This is expected to contribute to not only the application of Hanok windows and doors to modern buildings but also to the further development of an integrated Hanok design system.

• Environmental and Resource Economics Review
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• v.21 no.3
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• pp.743-776
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• 2012

This study utilizes the meta-analysis for the benefits transfer (MA-BT) approach to measure social costs the 7 target sites in the City and County of Honolulu. The estimated MA models (MA-1 and MA-1) were evaluated in terms of validity and reliability criteria. This study utilized a parametric t-test and a non-parametric sign rank test for checking validity. A transfer error measured by an absolute percentage difference was utilized to check reliability their similarity. The GIS was utilized for data collection in order to measure social costs for each target site. The results clearly demonstrated that social costs were substantially higher thant direct costs and varied market conditions and different methods used. In terms of validity and reliability criteria, MA models were preferred to the mean transfer value approach. MA-BT approach is desirable for measuring social costs for a project designed to measure social costs for these 7 proposed landfill sites with inaccessible data, on short time frames, and with little money. If researchers and planners have enough time and money, they can implement primary research. If not, the meta-analysis for the benefits transfer approach can be much better than no framework. The use of a GIS can help to identify secondary data within a specific radius of each target site.