• Journal of the Korean Society for Heat Treatment
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• v.26 no.3
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• pp.126-131
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• 2013

In this study, effects of silicon addition on the spheroidizing annealing of hyper-eutectoid steel was investigated. Heat treatment at various temperatures in the ${\gamma}+{\theta}$ region was also conducted in order to systematically control the kinetics of undissolved cementite. It was found that small amount of Si addition could increase both $A_1$ and $A_{cm}$ transformation temperature by both the JMat Pro evaluation and dilatometric measurement. It was also revealed by the microstructural observation that the volume fraction of retained cementite during heat treatment increased with decreasing temperature as well as increasing Si content. Based on the results obtained, it could be suggested that spheroidization at relatively higher temperature above $950^{\circ}C$ could be achieved by small addition of Si.

• Journal of Ocean Engineering and Technology
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• v.32 no.4
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• pp.253-260
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• 2018

Recently, the application of non-steel materials in ships and offshore plants is increasing because of the development of various nonlinear materials and the improvement of performance. Especially, hyper-elastic materials, which have a nonlinear stress-strain relationship, are used mainly in marine plant structures or ships where impact relaxation, vibration suppression, and elasticity are required, while elasticity must be maintained, even under high strain conditions. In order to simulate and evaluate the behavior of the hyperelastic material, it is very important to select an appropriate material model according to the strain of the material. This study focused on the selection of material models for hyperelastic materials, such as rubber used in the marine and offshore fields. Tension and compression tests and finite element simulations were conducted to compare the accuracy of the nonlinear material models due to variations in the stretch ratio of hyper-elastic material. Material coefficients of nonlinear material models are determined based on the curve fitting of experimental data. The results of this study can be used to improve the reliability of nonlinear material models according to stretch ratio variation.

• Journal of Aerospace System Engineering
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• v.11 no.6
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• pp.34-41
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• 2017

As an alternative of the existing honeycomb shock absorbing device, the new approach on shock absorbing design using the extrusion of hyper-viscoelastic material such as silicon rubber is studied in this paper. The strain energy and stress-strain characteristic of viscoelastic material at extrusion process through the metered orifice has a similarity with the honeycomb core for maximizing shock absorbing capability. And in order to evaluate the design feasibility of this device and to understand the shock absorbing mechanism of energy transformation, finite element analysis and quasi-static compression test of the multi-stage extrusion shock absorber are examined in this paper.

• Journal of Internet Computing and Services
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• v.21 no.3
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• pp.103-111
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• 2020

Liver cancer is the most fatal cancer that occurs worldwide. In order to diagnose liver cancer, the patient's physical condition was checked by using a CT technique using radiation. Segmentation was needed to diagnose the liver on the patient's abdominal CT scan, which the radiologists had to do manually, which caused tremendous time and human mistakes. In order to automate, researchers attempted segmentation using image segmentation algorithms in computer vision field, but it was still time-consuming because of the interactive based and the setting value. To reduce time and to get more accurate segmentation, researchers have begun to attempt to segment the liver in CT images using CNNs, which show significant performance in various computer vision fields. The pixel value, or numerical value, of the CT image is called the Hounsfield Unit (HU) value, which is a relative representation of the transmittance of radiation, and usually ranges from about -2000 to 2000. In general, deep learning researchers reduce or limit this range and use it for training to remove noise and focus on the target organ. Here, we observed that the range of HU values was limited in many studies but different in various liver segmentation studies, and assumed that performance could vary depending on the HU range. In this paper, we propose the possibility of considering HU value range as a hyper parameter. U-Net and ResUNet were used to compare and experiment with different HU range limit preprocessing of CHAOS dataset under limited conditions. As a result, it was confirmed that the results are different depending on the HU range. This proves that the range limiting the HU value itself can be a hyper parameter, which means that there are HU ranges that can provide optimal performance for various models.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.3
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• pp.361-374
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• 2016

The material property of the rubber has been studied in order to improve the reliability of the finite element model of a lead rubber bearing (LRB) which is a typical base isolator. Rubber exhibits elastic behaviour even within the large strain range, unlike the general structural material, and has a hyper-elastic characteristics that shows non-linear relationship between load and deformation. This study represents the mechanical characteristics of the rubber by strain energy function in order to develop a finite element (FE) model of LRB. For the study, several strain energy functions were selected and mechanical properties of the rubber were estimated with the energy functions. A finite element model of LRB has been developed by using material properties of rubber and lead which were identified by stress tests. This study estimated the horizontal and vertical force-displacement relationship with the FE model. The adequacy of the FE model was validated by comparing the analytical results with the experimental data.

• Journal of Christian Education in Korea
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• v.71
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• pp.241-276
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• 2022

Due to the 4th industrial revolution, which started with the Smart Revolution in the early 21st century, Hyper-Connectivity, Hyper-Convergence and Hyper-Intelligence of our society is accelerating. These changes induced formation of Metaverse as a fused new space that crosses the perimeter of the physical space and virtual(digital) spaces beyond time and place. The characteristics of Metaverse are continuously spread by engaging with the characteristics of the MZ generation, which collects both Millennial generation (M Generation) and Z Generation. With outburst of Covid-19 pandemic, a variety of attempts have been made to utilize Metaverse, even in church education when it was impossible to worship directly. In other words, the usefulness of the Metaverse was confirmed as a new community space of the education of the church. In addition, Metaverse may provide a substantial, experiential and evolving space for church education. However, in order for church education to further develop, the development in the method of education is also required to move beyond mere concept of space. In particular, when the learner-centered education method, one of the common characteristics of the Metaverse and MZ generation, it is thought that the church education in the Metaverse era will be able to go in a more evolving direction.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.332-335
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• 2008

The purpose of this study is analysis of flow field where is around of injector of supersonic combustor which is bluff-body stabilized flame and hyper-mixer type of supersonic combustor injector by using hydrogen or hydrocarbon fuel. Various schemes are evaluated to supersonic backward step flow filed with massive separation region in validation step. Compounded scheme of 5th-order TVD-MUSCL, Roe FDS, S-A DES/DDES has a good performance in base and base-bleed flow.

• Journal of applied mathematics & informatics
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• v.27 no.3_4
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• pp.501-515
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• 2009

A second order nonlinear ordinary differential equation is obtained by solving the initial-boundary value problem of a class of elas-todynamics equations, which models the radially symmetric motion of a incompressible hyper-elastic solid sphere under a suddenly applied surface tensile load. Some new conclusions are presented. All existence conditions of nonzero solutions of the ordinary differential equation, which describes cavity formation and motion in the interior of the sphere, are presented. It is proved that the differential equation has singular periodic solutions only when the surface tensile load exceeds a critical value, in this case, a cavity would form in the interior of the sphere and the motion of the cavity with time would present a class of singular periodic oscillations, otherwise, the sphere remains a solid one. To better understand the results obtained in this paper, the modified Varga material is considered simultaneously as an example, and numerical simulations are given.

• Journal of the Korean Society of Industry Convergence
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• v.15 no.2
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• pp.59-63
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• 2012

Melatonin has been studied as a potential treatment of cancer, immune disorders, cardiovascular diseases, depression, seasonal affective disorder (SAD), circadian rhythm sleep disorders, sexual dysfunction and some forms of insomnia. Prolonged release melatonin has shown good results in treating insomnia in older adults. It may ameliorate circadian misalignment and SAD. Basic research indicates that melatonin may play a significant role in modulating the effects of drugs of abuse such as cocaine. A 2004 review found that melatonin significantly increased total sleep time in people suffering from sleep restriction. Therefore, in this study, in order to explain characteristics of melatonin, total energy, net charge, vibrational mode of melatonin are calculated by PM3 methods of HyperCam 6.0.

• Journal of the Korean Society of Industry Convergence
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• v.16 no.3
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• pp.69-74
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• 2013

Finasteride, ($5{\alpha}$, $17{\beta}$)-N-(1,1-dimethylethyl)-3-oxo-4-azaandrost-1-ene-17-carboxamide), is a 5a-reductase enzyme inhibitor. This enzyme converts testosterone to the more potent androgen, a-dihydrotestosterone. This molecules a logical medical treatment for benign prostatic hyperplasia (BPH), as it induced a reduction in serum dihydrotestosterone and prostatic specific antigen levels with a concomittant increase in blood testosterone concentration . Despite its widespread use, little has been published concerning its molecular properties. Therefore, in this study, in order to explain characteristics of finasteride, total energy, net charge, vibrational mode of melatonin are calculated by PM3 methods of HyperCam 8.0.