• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.1
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• pp.1-8
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• 2014

Using the level set and the meshfree methods, we develop a topological shape optimization method applied to linear elasticity problems. Design gradients are computed using an efficient adjoint design sensitivity analysis(DSA) method. The boundaries are represented by an implicit moving boundary(IMB) embedded in the level set function obtainable from the "Hamilton-Jacobi type" equation with the "Up-wind scheme". Then, using the implicit function, explicit boundaries are generated to obtain the response and sensitivity of the structures. Global nodal shape function derived on a basis of the reproducing kernel(RK) method is employed to discretize the displacement field in the governing continuum equation. Thus, the material points can be located everywhere in the continuum domain, which enables to generate the explicit boundaries and leads to a precise design result. The developed method defines a Lagrangian functional for the constrained optimization. It minimizes the compliance, satisfying the constraint of allowable volume through the variations of boundary. During the optimization, the velocity to integrate the Hamilton-Jacobi equation is obtained from the optimality condition for the Lagrangian functional. Compared with the conventional shape optimization method, the developed one can easily represent the topological shape variations.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.2
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• pp.133-144
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• 2006

In order to catch out such Bond Strength, the preceding researchers had ever examined the Bond Strength of FRP Plate through their experimentations by setting up of various fluent. However, since the experiment for research on such Bond Strength takes much of expenditure for equipment structure and time-consuming, also difficult to carry out, it is conducting limitedly. This Study purposes to develop the most suitable Artificial Neural Network Model by application of various Neural Network Model and Algorithm to the adhering experiment data of the preceding researchers. Output Layer of Artificial Neural Network Model, and Input Layer of Bond Strength were performed the learning by selection as the variable of the thickness, width, adhered length, the modulus of elasticity, tensile strength, and the compressive strength of concrete, tensile strength, width, respectively. The developed Artificial Neural Network Model has applied Back-Propagation, and its error was learnt to be converged within the range of 0.001. Besides, the process for generalization has dissolved the problem of Over-Fitting in the way of more generalized method by introduction of Bayesian Technique. The verification on the developed Model was executed by comparison with the resulted value of Bond Strength made by the other preceding researchers which was never been utilized to the learning as yet.

• Journal of Industrial Convergence
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• v.20 no.10
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• pp.121-129
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• 2022

The purpose of this study was to identify the factors affecting nursing practice of clinical nurses in the COVID-19 situation and provide basic data that could improve nursing practice in the pandemic situation. For this descriptive research, a survey was conducted to collect data from 119 clinical nurses in G City for six weeks from June 15 to July 20, 2022. Descriptive statistics, t-test, ANOVA, Pearson's correlation coefficient, and multiple regression were used. The results showed that infection control practice (r=.428, p<.001) and resilience (r=.324, p<.001) were statistically significantly correlated with nursing practice. As a factor affecting nursing practice of clinical nurses, infection control practice (B=.529, p<.001) had an explanatory power of 18.3%. This result is thought to be due to the fact that COVID-19 infection control acted as a new burden on nursing work in the COVID-19 pandemic, and recovery elasticity and job stress did not have an influence. It is however necessary to help clinical nurses relieve job stress and perform high-quality nursing through regular counseling for clinical nurses suffering severe job stress.

• The Journal of the Convergence on Culture Technology
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• v.9 no.6
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• pp.193-200
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• 2023

This study evaluate the quality characteristics and antioxidative properties of acorn mook containing seoritae powder(0%, 2%, 4%, 6%). Among them the results of moisture content, Hunter color system, Texture, and antioxidant activity by making a section different Acorn Mook. The moisture content of samples 70.83%~81.77%, as the Seoritae powder Level in the formulation increased. As the Seoritae powder Level in the formulation increased, L-value of samples decreased, a-value of samples 7.29~7.79 increased and b-value decreased. According to the texture evaluation results, as the Seoritae powder level in the formulation significant decreased, the hardness, adhesivness, chewiness and cohesiveness, chewiness of acorn mook decreased. Seoritae powder level in the formulation increased Total phenol contents increased, Total flavonoid contents, DPPH free radical scavenging activity and ABTS radical scavenging activity of acorn mook decreased. The sensory results, the 2% samples received high taste, color, elasticity, chewiness, overall acceptability scores. In addition the 4% added samples of Seoritae powder showed a good overall evaluation compared to the control samples, so if acorn mook is manufactured by adding 2%~4% of Seoritae powder, it is thought that there is a possibility of commercialization of Seoritae acorn mook. We have the above results adding Seoritae powder to make a traditional food mook will help to use it as basic data for making acorn mook with excellent antioxidant activity.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.6
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• pp.505-512
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• 2012

In this paper, an efficient yet accurate method for the thermal stress analysis using a first order shear deformation theory(FSDT) is presented. The main objective herein is to systematically modify transverse shear strain energy through the mixed variational theorem(MVT). In the mixed formulation, independent transverse shear stresses are taken from the efficient higher-order zigzag plate theory, and the in-plane displacements are assumed to be those of the FSDT. Moreover, a smooth parabolic distribution through the thickness is assumed in the transverse normal displacement field in order to consider a transverse normal deformation. The resulting strain energy expression is referred to as an enhanced first order shear deformation theory, which is obtained via the mixed variational theorem with transverse normal deformation effect(EFSDTM_TN). The EFSDTM_TN has the same computational advantage as the FSDT_TN(FSDT with transverse normal deformation effect) does, which allows us to improve the through-the-thickness distributions of displacements and stresses via the recovery procedure. The thermal stresses obtained by the present theory are compared with those of the FSDT_TN and three-dimensional elasticity.

• The korean journal of orthodontics
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• v.37 no.6
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• pp.432-439
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• 2007

The purpose of this study was to evaluate the influence of intraoral temperature changes on the orthodontic force level of a superelastic nickel-titanium alloy wire. Methods: Nickel-titanium archwires of $0.016"{\times}0.022"$ thickness were tested with a three point bending test setup, and temperature changes were applied. The force level changes according to temperature changes were measured at a 1.5 mm deflection during the loading phase and a 1.5 mm deflection during the unloading phase from a deflection to 3.1mm. Ten cycles of thermal cycling from baseline $(37^{\circ}C)$ to cold $(20^{\circ}C)$ or hot $(50^{\circ}C)$temperature were applied. Results: Alter thermal cycling, the force level during the loading phase decreased and the force level during the unloading phase increased even after the temperature was changed to the initial $37^{\circ}C$. Conclusions: The results suggest that the orthodontic force level can not return to the initial force level after temperature changes. When applying superelastic nickel-titanium archwires, we must consider that a lighter force than the loading force and a heavier force than the unloading force will be applied after intraoral temperature changes caused by eating and drinking.

• Journal of Korean Society of Forest Science
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• v.80 no.2
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• pp.210-219
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• 1991

This study is to diagnose the drought tolerance of twenty broad-leaved tree species by the pressure-volume(P-V) curves. As for the diagnosis of drought tolerance, the valuable water relations parameters obtained from P-V curves are the osmotic potential at full turgor, ${\Psi}_0{^{sat}}$, osmotic potential at incipient plasmolysis, ${\Psi}_0{^{tlp}}$, maximum bulk modulus of elasticity, $E_{max}$, and relative water content at incipient plasmolysis, $RWC^{tlp}$. Also, the figures related to the diagnosis of drought tolerance are the free water content (FWC) versus leaf water potential(${\Psi}_L$), volume-averaged turgor pressure ($P_{vat}$) versus leaf water potential (${\Psi}_L$), and H$\ddot{o}$fler diagram. In this study, the relatively high drought tolerant species are Fraxinus rhynchophylla, Quercus acutissima, Quercus serrata, Quercus aliena, and Populus alba${\times}$glandulosa ; the relatively low drought tolerant species are Fraxinus mandshurica, Betula platyphylla var. japonica, Populus euramericana, Kalopanax pictum, Carpinus loxiflora, Carpinus cordata, Prunus sargentii, Prunus leveilleana, and Cornus controversa ; medium species are Quercus mongolica, Acer mono, Acer triflorum, Acer pseudo-sieboldianum, Ulmus davidiana, and Zelkova serrata.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.61-69
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• 2004

The bridge piers under service suffered a brittle failure due to the deterioration of lap-spliced longitudinal reinforcement without developing its flexural capacity or ductility. The earthquake induced lateral force results in tension which causes bond-slip failure at the lap-spliced region in circular bridge piers. In this case, such a brittle failure can be controlled by the seismic retrofit using FRP laminated circular tube. The retrofitted piers using FRP laminated circular tube showed significant improvement in seismic performance due to FRP's confinement effect. This paper presents the analytical results on the seismic strengthening effect of circular bridge piers with poor lap-splice details and strengthened with FRP laminated circular tube. FRP's confinement effect is predicted by the classical elasticity solution for the laminated circular tube manufactured with several layers. The FRP laminated circular tube induces the flexural failure instead of a bond-slip failure of the circular reinforced concrete piers under seismic induced lateral forces. To investigate the correctness and effectiveness of analytical solution derived in this study, the analytical results were compared with the experimental data and it was confirmed that the results were correlated well each other, The effects on the confinement of FRP laminated circular tube, such as the number of layers, the fiber orientations, and the mechanical properties, were investigated. From the parametric study, it was found that the number of layers, the fiber orientations, and the major Young's modulus (E11) of the FRP laminated circular tube were the dominant parameters affecting the confinement of reinforced concrete circular bridge piers.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.2
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• pp.128-136
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• 2014

It is known that the best way to recycle fly ash is to use in concrete. It is impossible to bury in the ground this fly ash recently, so it is trying to use high volume fly ash concrete. Nevertheless, recent main research topics are focused in the part of material only. However, it is necessary to perform the researches about elasticity modulus, stress-strain relationship and structural behavior. Therefore, in this paper, 18 test members were manufactured with 3 test variables, namely fly ash replacement ratio 0, 35, 50%, concrete compressive strength 20, 40, 60MPa and 2 tensile steel ratio. 18 test members were tested for flexural behavior. From the test results, there were no differences between 35, 50% high volume fly ash cement concrete and ordinary concrete without fly ash (FA=0%). In order to evaluate the HVFAC flexural behavior, Analytical model was proposed and the computer program was developed. There were no differences between test results and analysis results. So, the proposed analytical model was reasonable.

• Tunnel and Underground Space
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• v.28 no.1
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• pp.59-71
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• 2018

Since the generalized Hoek-Brown (GHB) function predicts the strength of the jointed rock mass in a systematic manner by use of GSI index, it is widely used in rock engineering practices. In this study, a series of 2D elasto-plastic FE analysis, which adopts the GHB criterion as a yield function, was carried out to investigate the radial convergence characteristics of circular tunnel excavated in the GHB rock mass. The effect of the plastic potential function on the elasto-plastic displacement was also examined. In the analysis, the wide range of both the $K(={\sigma}_h/{\sigma}_v)$ and GSI values are considered. For each K value, the variation of the ratio of sidewall displacement to roof displacement was calculated with varying GSI values and the obtained displacement patterns were analysed. The calculation results show that the displacement ratio significantly depends not only on the K value but also on the range of GSI value. In particular, for lower range of GSI value, the displacement ratio pattern calculated in the elasto-plastic regime is opposite to that predicted by the elasticity theory. In addition, the variation of the radial displacement ratio with GSI value for different types of plastic potential function showed similar trend.