• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1663-1666
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• 2007

The finite element method is applied to analyze the deformation mechanisms in the closed-cell Al foam under the compression. The modeling of the real cellular structure proceeds with the concept of the reverse engineering. First of all, the small, $10{\times}\;10{\times}\;10mm^3$ sized specimens of the closed-cell Al foam are prepared. The micro focus X-ray CTsystem of SHIMADZU Corp. is used to scan the full structures of the specimens. The scanned structures are converted to the geometric surfaces and solids through the software for 3-D scan data processing, RapidFormTMof INUS Tech. Inc. Then the solid meshes are directly generated on the converted geometric solids for the finite element analysis. The large elastic-plastic deformation and 3-D contact problems for the Al cellular material are considered. The clear and successful analysis for the deformation mechanisms in the closed-cell Al foam is carried out through the comparison of the numerical results in this research with the referred experimental ones.

• Structural Engineering and Mechanics
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• 제22권1호
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• pp.17-32
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• 2006

The application of cellular materials in load-carrying and security-relevant structures requires the exact prediction of their mechanical behavior, which necessitates the development of robust simulation models and techniques based on appropriate experimental procedures. The determination of the yield surface requires experiments under multi-axial stress states because the yield behavior is sensitive to the hydrostatic stress and simple uniaxial tests aim only to determine one single point of the yield surface. Therefore, an experimental technique based on a uniaxial strain test for the description of the influence of the hydrostatic stress on the yield condition in the elastic-plastic transition zone at small strains is proposed and numerically investigated. Furthermore, this experimental technique enables the determination of a second elastic constant, e.g., Poisson's ratio.

• 한국산업융합학회 논문집
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• 제19권3호
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• pp.109-124
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• 2016

The objective of this paper is to find the density, stiffness, and strength of truss-wall diamond corrugation model combined with pinwheel truss inside space. The truss-wall diamond corrugation (TDC) model is defined as a unit cell coming from solid-wall diamond corrugation (SDC) model. Pinwheel truss-wall diamond corrugation (P-TDC) model is made by TDC connected with pinwheel structure inside of the space. Derived ideal solutions of P-TDC is based on truss-wall and pinwheel truss model at first. And then it is compared with Gibson-Ashby's ideal solution. To validate the ideal solutions of the P-TDC, ABAQUS software is used to predict the density, strength, and stiffness, and then each of them are compared to the ideal solution of Gibson-Ashby with a log-log scale. Applied material property is stainless steel 304 because of having cost effectiveness. Applied parameters for P-TDC are 1 thru 5 mm diameter within fixed opening width as 4mm. In conclusion, the relative Young's modulus and relative yield strength of the P-TDC unit model is reasonable matched to the ideal expectations of the Gibson-Ashby's theory. In nearby future, P-TDC model is hoped to be applied to make sandwich core structure by advanced technologies such as 3D printing skills.

• 한국식품과학회지
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• 제19권6호
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• pp.492-498
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• 1987

대두품종으로서 새알, 광교, 단엽을 온도별($10^{\circ}C,\;20^{\circ}C,\;30^{\circ}C,\;40^{\circ}C,\;50^{\circ}C$)로 침지과정중 침출액의 성분변화를 관찰하였다. 대두가 같은 무게의 수분량을 흡수한 시간은 $20^{\circ}C$에서 7.5시간, $50^{\circ}C$에서는 3.5시간이 걸렸다. 침지액의 pH변화는 온도가 상승할수록 낮아지는 경향을 보였다. 수용성 고형물의 함량변화는 침지 시간이 길수록, 온도가 상승할수록 많아져서 침지중 거의 직선적인 속도로 용출되었으며 24시간 침지 후 대두 100g당 $20^{\circ}C$에서는 $0.4{\sim}0.7g$정도, $50^{\circ}C$에서는 $10.2{\sim}15.0g$ 정도 용출되었다. 용출된 총 고형물 중 $12{\sim}25%$는 단백질이었으며 단백질 용출 비율은 침지 시간과 온도의 상승에 따라 증가했다. 24시간 침지 후 대두 100g당 $20^{\circ}C$에서는 80$\sim$200mg, $50^{\circ}C$에서는 $440{\sim}480mg$정도의 단백질이 용출되었다. 수용성 당의 용출은 24시간 침지 후 $20^{\circ}C$에서는 약 5%, $50^{\circ}C$에서 $83{\sim}100%$가 용출되었다. 그 중 sucrose, fructose, raffinose와 stachyose는 $20^{\circ}C$에서 24시간 침지 후 각각 3%, 3.8%, 2% 그리고 1%가, $50^{\circ}C$에서는 각각 87%, 150%, 80%, 77% 정도가 용출되어서 침지온도가 상승할수록 당의 용출량이 증가하였다.

• 대한수학회지
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• 제38권5호
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• pp.1069-1105
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• 2001

Regular maps and hypermaps are cellular decompositions of closed surfaces exhibiting the highest possible number of symmetries. The five Platonic solids present the most familar examples of regular maps. The gret dodecahedron, a 5-valent pentagonal regular map on the surface of genus 5 discovered by Kepler, is probably the first known non-spherical regular map. Modern history of regular maps goes back at least to Klein (1878) who described in [59] a regular map of type (3, 7) on the orientable surface of genus 3. In its early times, the study of regular maps was closely connected with group theory as one can see in Burnside’s famous monograph [19], and more recently in Coxeter’s and Moser’s book [25] (Chapter 8). The present-time interest in regular maps extends to their connection to Dyck\`s triangle groups, Riemann surfaces, algebraic curves, Galois groups and other areas, Many of these links are nicely surveyed in the recent papers of Jones [55] and Jones and Singerman [54]. The presented survey paper is based on the talk given by the author at the conference “Mathematics in the New Millenium”held in Seoul, October 2000. The idea was, on one hand side, to show the relationship of (regular) maps and hypermaps to the above mentioned fields of mathematics. On the other hand, we wanted to stress some ideas and results that are important for understanding of the nature of these interesting mathematical objects.

• 한국산업융합학회 논문집
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• 제20권2호
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• pp.133-140
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• 2017

This paper is a study of the central structural unit model of the sandwich core structure. The applied model is based on the honeycomb structure formed by the truss, the H-shaped honeycomb structure formed by adding the truss of H shape to the space of the center portion, and the honeycomb structure formed by the plate. Applied material property is AISI 304 stainless steel, which has cost effectiveness and easy to get near place. The truss diameter of the model is three different type: 1mm, 2mm and 3mm. ABAQUS software is obtained to do the analysis and applied test is quasi-static loading. Boundary conditions for the analysis are that vertical direction loading at top place without any rotation and bottom surface is fixed. The test results show that the H-truss model has the highest stiffness and yield strength. Therefore, it is hoped that more and more researching for the development of a unit model in sandwich core structure has been investigating and that the developed sandwich core model can be applied into various industrial fields such as mechanical or aerospace industries.

• 한국산업융합학회 논문집
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• 제22권4호
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• pp.387-394
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• 2019

This paper presents an analytical study on the strength and stiffness of various types of truss structures. The applied models are triangular-like opened truss-wall triangular model (OTT), closed truss-wall triangular model (CTT), opened solid-wall triangular model (OST), and hypercube models defined as core-filled or core-spaced cube. The models are analyzed by numerical model analysis using DEFORM 2D/3D tool with AISI 304 stainless steel. Then, the ideal solutions for stiffness and strength are defined. Finally, the relative elastic modulus of the core-spaced model is obtained as 0.0009, which is correlated with the cancellous bone for the relative density range of 0.029-0.03, and the relative elastic modulus for the core-filled model is obtained as 0.0015, which is correlated with cancellous bone for the relative density range of 0.035-0.036. For the relative compressive yield strength, the OTT reasonably agrees with the cancellous bone for the relative density of 0.042 and the relative compressive strength of 0.05. The CTT and OST are in good agreement at the relative density of 0.013 and the relative compressive yield strength of 0.002. The hypercube models can be used for the cancellous bone for stiffness, and the triangular models can be used for the cancellous bone for strength. However, none of the models can be used to replace the compact bone because it requires much higher stiffness and strength. In the near future, compact bone replacement must be further studied. In addition, previously mentioned models should be developed further.

• Asian-Australasian Journal of Animal Sciences
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• 제20권7호
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• pp.1156-1168
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• 2007

The somatotropic (GH-IGF-I) axis consists of many hormonal and nutritional factors that control GH release from the somatotrophs in the anterior pituitary. The GH-releasing substances are GHRH and GHS (GHRP or ghrelin), while the GH release-inhibiting substances are somatostatin (SRIF), insulin-like growth factor-I (IGF-I), leptin and glucocorticoids. However, there is evidence showing that nutrition is involved in the control of the somatotropic axis. In addition, weaning is a drastic event for neonates because their alimentary and endocrine circumstances are changed due to the switch, even if gradual, from a liquid milk diet to one composed of such solids as hay and grains. The biological role of ghrelin is one of the hormonal factors that have been focused on ever since ghrelin was discovered at the end of the last century. A 27-amino acid peptide that is mainly synthesized and released from the abomasum epithelium, ghrelin has not been fully evaluated in relation to the somatotropic axis of the ruminant. It has also proven difficult even to investigate the cellular mechanisms of ghrelin action, because this hormone exerts animal-species-dependent actions via a complex set of intracellular signaling pathways. This is also the case for the action of leptin. Another substance, IGF-I, shows a partial inhibitory action on GH secretion in the ruminant. The effect of nutrition is also different among animal species. This is evident by the fact that undernutrition suppresses the circulating GH levels in rodents, but increases it in ruminants and humans. Recently, weaning has been shown to change the postprandial GH responses in ruminants; milk feeding increases, but hay and concentrate feeding suppress, the postprandial circulating GH levels. Even if the postprandial GH level is increased, the ghrelin level is decreased by milk feeding. Macronutrients also possess stimulatory and inhibitory actions on GH secretion in vivo and in vitro. These findings indicate the complexity of the control mechanisms of the somatotropic axis. In the present review, we summarize recent findings on the factors controlling the axis of the ruminant.

• KSBB Journal
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• 제30권1호
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• pp.21-26
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• 2015

Plasma is an ionized gas mixture, consisting of neutral particles, positive ions, negative electrons, electronically excited atoms and molecules, radicals, UV photons, and various reactive species. Also, plasma has unique physical properties distinct from gases, liquids, and solids. Until now, non-thermal plasmas have been widely utilized in bio-medical applications (called bio-plasma) and have been developed for the plasma-related devices that are used in the medical field. Although numerous bio-plasma studies have been performed in biomedicine, there is no confirmation of the nonthermal effect induced by bio-plasma. Standardization of the biological application of plasma has not been evaluated at the molecular level in living cells. In this context, we investigated the biological effect of bio-plasma on living cells. Hence, we treated the fibroblasts with Dielectric Bauvier Discharge bio-plasma (DBD), and assessed the characteristic change at the molecular level, one of the typical cellular responses. Heat shock protein 70 (HSP70) regulates its own protein level in response to stimuli. HSP70 responds to heat shock by increasing its own expression at the molecular level in cells. Hence, we confirmed the level of HSP70 after treatment of mouse embryonic fibroblasts (MEFs) with DBD. Interestingly, DBD-plasma induced cell death, but there was no difference in the level of HSP70, which is induced by heat shock stimuli, in DBD-treated MEFs. Our data provide the basic information on the interaction between MEFs and DBD, and can help to design a molecular approach in this field.