• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.7-15
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• 2020

Recently, the fourth industrial revolution has been presented as a new paradigm and additive manufacturing (AM) has become one of the most important topics. For this reason, process monitoring for each cross-sectional layer of additive metal manufacturing is important. Particularly, deep learning can train a machine to analyze, optimize, and repair defects. In this paper, image classification is proposed by learning images of defects in the metal cross sections using the convolution neural network (CNN) image labeling algorithm. Defects were classified into three categories: crack, porosity, and hole. To overcome a lack-of-data problem, the amount of learning data was augmented using a data augmentation algorithm. This augmentation algorithm can transform an image to 180 images, increasing the learning accuracy. The number of training and validation images was 25,920 (80 %) and 6,480 (20 %), respectively. An optimized case with a combination of fully connected layers, an optimizer, and a loss function, showed that the model accuracy was 99.7 % and had a success rate of 97.8 % for 180 test images. In conclusion, image labeling was successfully performed and it is expected to be applied to automated AM process inspection and repair systems in the future.

• Archives of Plastic Surgery
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• v.40 no.1
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• pp.11-18
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• 2013

Background To minimize the inflammatory reaction and improve healing, a new modified dermal substitute composed of an atelocollagen, chondroitin-6-sulfate, and amniotic membrane (AM) was applied to full-thickness skin defects in a pig. Atelocollagen was extracted from bovine skin, and two modified dermal substitutes were generated according to the cross-linking type. Methods The AM-collagen dermal substitutes were characterized and compared with currently used dermal substitutes in a pig skin defect model. There were five experimental groups: dehydrothermal (DHT) cross-linking atelocollagen with the AM on the top (AM-DHT), DHT and chemical cross-linking atelocollagen with the AM on the top (AM-DHT/chemical), Terudermis, Integra, and AlloDerm. After $3{\times}3cm$ full-thickness skin defects on the back of a pig were created, each dermal substitutes dermal substitutes was randomly grafted on the defects. Two weeks after grafting, autologous partial-thickness skin was over-grafted on the neodermis. The take rate of the dermal substitutes, skin, and histological sections were all assessed at 1, 2, and 4 weeks postoperatively. Results More rapid healing and a higher take rate were evident in the AM-DHT and Terudermis groups. Histological examination revealed fewer inflammatory cells and more fibroblast hyperplasia in these two groups. Four weeks after surgery, the amount of newly formed collagen was significantly more appropriate in the AM-DHT group. Conclusions These observations provide supporting evidence that a newly developed amniotic-collagen dermal substitute may inhibit inflammatory reactions and promote wound healing.

• Nuclear Engineering and Technology
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• v.51 no.8
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• pp.1871-1885
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• 2019

The deterministic MOC code STREAM of the Computational Reactor Physics and Experiment (CORE) laboratory of Ulsan National Institute of Science and Technology (UNIST), was initially designed for the calculation of pressurized water reactor two- and three-dimensional assemblies and cores. Since fast reactors play an important role in the generation-IV concept, it was decided that the code should be upgraded for the analysis of fast neutron spectrum reactors. This paper presents a coupled code - TULIP/STREAM, developed for the fast reactor assembly and core calculations. The TULIP code produces self-shielded multi-group cross-sections using a one-dimensional cylindrical model. The generated cross-section library is used in the STREAM code which solves eigenvalue problems for a two-dimensional assembly and a multi-assembly whole reactor core. Multiplication factors and steady-state power distributions were compared with the reference solutions obtained by the continuous energy Monte-Carlo code MCS. With the developed code, a sensitivity study of the number of energy groups, the order of anisotropic P_N scattering, and the multi-group cross-section generation model was performed on the k_eff and power distribution. The 2D core simulation calculations show that the TULIP/STREAM code gives a k_eff error smaller than 200 pcm and the root mean square errors of the pin-wise power distributions within 2%.

• Journal of the Optical Society of Korea
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• v.12 no.2
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• pp.98-102
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• 2008

Optical Coherence Tomography (OCT) is an important noninvasive medical imaging technique that can reveal subsurface structures of biological tissue. OCT has demonstrated a good correlation with histology in sufficient resolution to identify morphological changes in articular cartilage to differentiate normal through progressive stages of degenerative joint disease. Current OCT systems provide individual cross-sectional images that are representative of the tissue directly under the scanning beam, but they may not fully demonstrate the degree of degeneration occurring within a region of a joint surface. For a full understanding of the nature and degree of cartilage degeneration within a joint, multiple OCT images must be obtained and an overall assessment of the joint surmised from multiple individual images. This study presents frequency domain three-dimensional (3-D) OCT imaging of degenerative joint cartilage extracted from bovine knees. The 3-D OCT imaging of articular cartilage enables the assembly of 126 individual, adjacent, rapid scanned OCT images into a full 3-D image representation of the tissue scanned, or these may be viewed in a progression of successive individual two-dimensional (2-D) OCT images arranged in 3-D orientation. A fiber-based frequency domain OCT system that provides cross-sectional images was used to acquire 126 successive adjacent images for a sample volume of $6{\times}3.2{\times}2.5\;mm^3$. The axial resolution was $8\;{\mu}m$ in air. The 3-D OCT was able to demonstrate surface topography and subsurface disruption of articular cartilage consistent with the gross image as well as with histological cross-sections of the specimen. The 3-D OCT volumetric imaging of articular cartilage provides an enhanced appreciation and better understanding of regional degenerative joint disease than may be realized by individual 2-D OCT sectional images.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.3
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• pp.203-209
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• 2012

In this paper, cross-sectional stiffnesses, static stresses, and dynamic natural frequencies are analyzed to examine the structural performance of wind turbine composite blades. The material properties of composite materials are based on room-temperature and radiation curing processes. The cross-sectional stiffnesses of composite blades are calculated by applying a beam theory with solid-profile cross sections. The wind turbine blades are modeled with a finite element program, and static analyses are carried out to check the maximum displacement and stress of the blades. In addition, dynamic analyses are performed to predict the rotating natural frequencies of the composite blades including the effects of centrifugal force. By comparing these analysis results, mainly owing to the material properties of composite materials, an improvement in the structural performance of the blades according to the curing process is investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.661-664
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• 2008

As architectures have recently become high-risers and megastructured, stable high strength products have been ensured. Accordingly, use of precast concrete accouplement has been increased in order to facilitate air compression and rationalize construction. Since not only external heating but also internal temperature rise caused by the accumulation of cement hydration heat in manufacturing process, precast concrete members with large cross-section used for high-rise mega-structure's columns and beams may exhibit different temperature history compared to the precast concrete members for wall and sub-floor with relatively small cross-sections. Therefore, this study aims to elucidate the characteristics of temperature history of mass concrete members cast with high-strength concrete for precast concrete application. In this study, large cross-sectional precast concrete mock-up, unit cement quantity, and temperature histories in manufacturing precast concrete member under different curing condition were inclusively investigated.

• Communications of Mathematical Education
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• v.24 no.3
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• pp.731-744
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• 2010

Nowadays in school mathematics, the skill and method for solving problems are often emphasized in preference to the theoretical principles of mathematics. Students pay attention to how to make an equation mechanically before even understanding the meaning of the given problem. Furthermore they do not get to really know about the principle or theorem that were used to solve the problem, or the meaning of the answer that they have obtained. In contemporary textbooks the conic section such as circle, ellipse, parabola and hyperbola are introduced as the cross section of a cone. But they do not mention how conic section are connected with the quadratic equation or how these curves are related mutually. Students learn the quadratic equations of the conic sections introduced geometrically and are used to manipulating it algebraically through finding a focal point, vertex, and directrix of the cross section of a cone. But they are not familiar with relating these equations with the cross section of a cone. In this paper, we try to understand the quadratic curves better through the analysis of the discussion made in the process of the discovery and eventual development of the conic section and then seek for way to improve the teaching and learning methods of quadratic curves.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.1
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• pp.36-44
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• 2019

The purpose of this study is to evaluate the structural performance of press-formed type asymmetric column to beam connections of steel-PC composite module frames. Most of the column sections of the joints making up the modular frame use a closed square steel section. The column-beam connection using the closed column section has difficulty in reducing the workability and securing the fire resistance. In order to overcome this disadvantage, concrete is filled in the asymmetrical open type cross section of the steel plate by press forming. A total of four specimens were fabricated to investigate the structural performance of press formed type asymmetric column to beam connections. The experimental results show that the structural performance and behavior of the asymmetric columns are different depending on whether the asymmetric column cross section is composited or the column width thickness ratio. The structural performance of the press formed type asymmetric column to beam connection was evaluated by comparing the experimental results with the theoretical formulas.

• The Korean Journal of Pain
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• v.34 no.1
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• pp.72-81
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• 2021

Background: In the literature, there have been debates as to whether smartphone use has negative effects on physical and mental health. The present study investigated the extent to which smartphone addiction impacts on musculoskeletal pain prevalence among university students. Methods: The questionnaire consisted of three sections: demographic information, the Smartphone Addiction Scale (SAS), and the modified Nordic Musculoskeletal Questionnaire. Results: A total of 249 participants were included in this cross-sectional study. The body parts that were reported with highest prevalence of musculoskeletal pain were the upper back (70.3%), neck (65.9%), and wrists/hands (68.7%). The SAS scores were correlated with duration of smartphone use on a typical day (P = 0.001), duration of owning a smartphone (P = 0.027), and musculoskeletal pain prevalence in the neck (P = 0.001), wrists/hands (P = 0.001), shoulders (P = 0.025), and upper back (P = 0.023). The SAS score was significantly associated with prevalence of musculoskeletal pain in the neck (odd ratio [OR], 1.08; 95% confidence interval [CI], 0.98-1.10; P = 0.002), wrists/hands (OR, 1.07; 95% CI, 0.97-1.09; P = 0.001), and upper back (OR, 1.10; 95% CI, 0.98-1.11; P = 0.033). Conclusions: The findings indicated that the upper back, neck, and wrists/hands have a higher prevalence of musculoskeletal pain among smartphone users, particularly those with a smartphone addiction. Smartphone addiction scores were correlated with duration of smartphone use on a typical day, duration of owning smartphone, and musculoskeletal pain prevalence in the neck, wrists/hands, shoulders, and upper back.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.545-552
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• 2020

This study evaluated the support performance of fiber-net integrated shotcrete in tunnel support system developed for the purpose of improving constructability and stability while fully performing its mechanical performance as a tunnel support materials by four-point bending test, two-dimensional numerical analysis, and cross-sectional analysis. As a result of evaluating the flexural performance through a four-point bending test, in the case of fiber-net reinforced shotcrete, the tensile performance of fiber-net resulted in a continuous increase in load after crack occurrence, unlike steel fiber reinforced shotcrete. Also, the results of the tunnel cross-sectional structure analysis for ground conditions and the cross-sectional analysis of fiber-net and steel fiber reinforced shotcrete showed that sufficient support performance can be exhibited even if the thickness of fiber-net reinforced shotcrete was reduced compared to the previous one. Additionally, through these results, the support pattern of fiber-net integrated shotcrete in tunnel support system, which can be applied efficiently to the construction sections requiring higher stability among the rock mass class III, was proposed.