• Advances in Computational Design
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• v.3 no.3
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• pp.289-302
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• 2018

The use of optimum content of supplementary cementing materials (SCMs) such as limestone filler (LF) to blend with Portland cement has been resulted in many environmental and technical advantages, such as increase in physical properties, enhancement of sustainability in concrete industry and reducing $CO_2$ emission are well known. Artificial neural networks (ANNs) have been already applied in civil engineering to solve a wide variety of problems such as the prediction of concrete compressive strength. The feed forward back propagation (FFBP) algorithm and Tan-sigmoid transfer function were used for the ANNs training in this study. The training, testing and validation of data during the backpropagation training process yielded good correlations exceeding 97%. A parametric study was conducted to study the sensitivity of the developed model to certain essential parameters affecting the compressive strength of concrete. The effects and benefits of limestone filler on hardened properties of the concrete such as compressive strength were well established endorsing previous results in the literature. The results of this study revealed that the proposed ANNs model showed a high performance as a feasible and highly efficient tool for simulating the LF concrete compressive strength prediction.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.14 no.3
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• pp.7-15
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• 2006

Aerodynamic analysis of an airfoil in the transonic region was automated in order to enable parametric study by using the journal file of the commercial analysis code FLUENT, pre/post process Gambit and computational mathematics code MATLAB. The automated capability was illustrated via NACA 0012 and RAE 2822 airfoils. This analysis was carried out at Mach numbers ranged from 0.70 to 0.80, angles of attack; 1$^{\circ}$, 2$^{\circ}$ and 4$^{\circ}$, Reynolds numbers; 4.0${\times}$106, 6.5${\times}$106. The analysis results of a pressure coefficient were verified by comparing with the experimental data which were measured in terms of chord length because the pressure coefficient of an airfoil surface is a good estimator of flow characteristics. The results of two airfoils show that this analysis code is useful enough to be used in the design optimization of airfoil.

• Journal of the Korea Concrete Institute
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• v.26 no.3
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• pp.401-409
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• 2014

This research develops tools and strategies for optimizing RC column sections applied in tall buildings. Optimization parameters are concrete strength and section shape, the objective function for which is subject to several predefined constraints drawn from the original structural design. For this purpose, we developed new components for StrAuto, a parametric modeling and optimization tool for building structure. The components receive from external analysis solvers member strengths calculated from the original design model, and output optimized column sections satisfying the minimum cost. Using these components, optimized sections are firstly obtained for each predefined concrete strength applied to the whole floors in the project building. The obtained results for each concrete strength are comparatively examined to determine the fittest sections which will also result in the fittest vertical zoning for concrete strength. The main optimization scenario for this is to search for the vertical levels where the identical optimized sections coincide for the two different concrete strengths in concern, and select those levels for the boundaries where a concrete strength will be changed to another. The optimization process provided in this research is a product of an intensive development designed for a specific member in a specific project. Thus, the algorithm suggested takes on a microscopic and mathematical approach. However, the technique has a lot of potential that it can further be extensively developed and applied for future projects.

• Journal of Audiology & Otology
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• v.23 no.3
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• pp.121-128
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• 2019

Background and Objectives: There is a scant evidence on the use of simulations in audiology (especially in Malaysia) for case-history taking, although this technique is widely used for training medical and nursing students. Feedback is one of the important components in simulations training; however, it is unknown if feedback by instructors could influence the simulated patient (SP) training outcome for case-history taking among audiology students. Aim of the present study is to determine whether the SP training with feedback in addition to the standard role-play and seminar training is an effective learning tool for audiology case-history taking. Subjects and Methods: Twenty-six second-year undergraduate audiology students participated. A cross-over study design was used. All students initially attended two hours of seminar and role-play sessions. They were then divided into three types of training, 1) SP training (Group A), 2) SP with feedback (Group B), and 3) a non-additional training group (Group C). After two training sessions, the students changed their types of training to, 1) Group A and C: SP training with feedback, and 2) Group B: non-additional training. All the groups were assessed at three points: 1) pre-test, 2) intermediate, and 3) post-test. The normalized median score differences between and within the respective groups were analysed using non-parametric tests at 95% confidence intervals. Results: Groups with additional SP trainings (with and without feedback) showed a significantly higher normalized gain score than no training group (p<0.05). Conclusions: The SP training (with/without feedback) is a beneficial learning tool for history taking to students in audiology major.

• Korean Journal of Audiology
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• v.23 no.3
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• pp.121-128
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• 2019

Background and Objectives: There is a scant evidence on the use of simulations in audiology (especially in Malaysia) for case-history taking, although this technique is widely used for training medical and nursing students. Feedback is one of the important components in simulations training; however, it is unknown if feedback by instructors could influence the simulated patient (SP) training outcome for case-history taking among audiology students. Aim of the present study is to determine whether the SP training with feedback in addition to the standard role-play and seminar training is an effective learning tool for audiology case-history taking. Subjects and Methods: Twenty-six second-year undergraduate audiology students participated. A cross-over study design was used. All students initially attended two hours of seminar and role-play sessions. They were then divided into three types of training, 1) SP training (Group A), 2) SP with feedback (Group B), and 3) a non-additional training group (Group C). After two training sessions, the students changed their types of training to, 1) Group A and C: SP training with feedback, and 2) Group B: non-additional training. All the groups were assessed at three points: 1) pre-test, 2) intermediate, and 3) post-test. The normalized median score differences between and within the respective groups were analysed using non-parametric tests at 95% confidence intervals. Results: Groups with additional SP trainings (with and without feedback) showed a significantly higher normalized gain score than no training group (p<0.05). Conclusions: The SP training (with/without feedback) is a beneficial learning tool for history taking to students in audiology major.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.2
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• pp.453-467
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• 2018

The excavation performance and the cutting tool wear prediction of shield TBM are very important issues for design and construction in TBM tunneling. For hard-rock TBMs, CSM and NTNU model have been widely used for prediction of disc cutter wear and penetration rate. But in case of soft-ground TBMs, the wear evaluation and the excavation performance have not been studied in details due to the complexity of the ground behavior and therefore few testing methods have been proposed. In this study, a new soil abrasion and penetration tester (SAPT) that simulates EPB TBM excavation process is introduced which overcomes the drawbacks of the previously developed soil abrasivity testers. Parametric tests for penetration rate, foam mixing ratio, foam concentration were conducted to evaluate influential parameters affecting TBM excavation and also ripper wear was measured in laboratory. The results of artificial soil specimen composed of 70% illite and 30% silica sand showed TBM additives such as foam play a key role in terms of excavation and tool wear.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.3
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• pp.310-316
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• 2016

We propose a novel contact-free transportation system in which an axial electrodynamic wheel is applied as an actuator. When the electrodynamic wheel is partially overlapped by a fixed conductive plate and rotates over it, three-axis magnetic forces are generated on the wheel. Among these forces, those in the gravitational direction and the lateral direction are inherently stable. Therefore, only the force in the longitudinal direction needs to be controlled to guarantee spatial stability of the wheel. The electrodynamic wheel consists of permanent magnets that are repeated and polarized periodically along the circumferential direction. The basic geometric configuration and the pole number of the wheel influence the stability margin of a transportation system, which would include several wheels. The overlap region between the wheel and the conductive plate is a dominant factor affecting the stiffness in the lateral direction. Therefore, sensitivity analysis for the major parameters of the wheel mechanism was performed using a finite element tool. The system was manufactured based on the obtained design values, and the passive stability of a moving object with the wheels was verified experimentally.

• Nuclear Engineering and Technology
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• v.28 no.1
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• pp.17-26
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• 1996

The in-reactor fuel rod support conditions against the fretting wear-induced damage can be evaluated by residual spacer grid spring deflection or rod-to-grid gap. In order to evaluate the impact of fuel design parameters on the fretting wear-induced damage, a simulation methodology of the in-reactor fuel rod supporting conditions as a function of burnup has been developed and implemented in the GRIDFORCE program. The simulation methodology takes into account cladding creep rate, initial spring deflection, initial spring force, and spring force relaxation rate as the key fuel design parameters affecting the in-reactor fuel rod supporting conditions. Based on the parametric studies on these key parameters, it is found that the initial spring deflection, the spring force relaxation rate and cladding creepdown rate are in the order of the impact on the in-reactor fuel rod supporting conditions. Application of this simulation methodology to the fretting wear-induced failure experienced in a commercial plant indicates that this methodology can be utilized as an effective tool in evaluating the capability of newly developed cladding materials and/or new spacer grid designs against the fretting wear-induced damage.

• Land and Housing Review
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• v.13 no.1
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• pp.113-129
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• 2022

A building's eco-friendliness is directly related to various values including the life cycle cost of a building. However, the conventional architectural design method has a limitation in that it cannot create an optimized case according to the surrounding environmental conditions. Therefore, the purpose of this research is to present a design assistance tool that can review planning cases optimized for the environmental conditions of the building site in the planning stage of architectural production. To achieve the purpose of the study, an algorithm for realizing 3D modeling of the region and analysis of the solar environment was produced based on the site contours, building, and road information from the digital topographic map provided by the National Geographic Information Institute. To examine the validity of the developed algorithm, a comparative experiment was conducted targeting the elevation direction of the existing building. As a result, it was found that the optimal elevation direction selected by the algorithm can receive higher insolation compared to the front facade of the main building.

• Structural Engineering and Mechanics
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• v.86 no.5
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• pp.589-605
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• 2023

This paper investigates the ductility demands of steel frames equipped with self-centring fuses under near-fault earthquake motions considering multiple yielding stages. The study is commenced by verifying a trilinear self-centring hysteretic model accounting for multiple yielding stages of steel frames equipped with self-centring fuses. Then, the seismic response of single-degree-of-freedom (SDOF) systems following the validated trilinear self-centring hysteretic law is examined by a parametric study using a near-fault earthquake ground motion database composed of 200 earthquake records as input excitations. Based on a statistical investigation of more than fifty-two (52) million inelastic spectral analyses, the effect of the post-yield stiffness ratios, energy dissipation coefficient and yielding displacement ratio on the mean ductility demand of the system is examined in detail. The analysis results indicate that the increase of post-yield stiffness ratios, energy dissipation coefficient and yielding displacement ratio reduces the ductility demands of the self-centring oscillators responding in multiple yielding stages. A set of empirical expressions for quantifying the ductility demands of trilinear self-centring hysteretic oscillators are developed using nonlinear regression analysis of the analysis result database. The proposed regression model may offer a practical tool for designers to estimate the ductility demand of a low-to-medium rise self-centring steel frame equipped with self-centring fuses progressing in the ultimate stage under near-fault earthquake motions in design and evaluation.