• Composites Research
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• v.13 no.4
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• pp.75-82
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• 2000

A small diameter steel-ball impact experiment was performed to study the impact resistance of the surface of glass plates bonded with glass fabric/epoxy lamina. Five kinds of materials were used in this study: soda-lime glass plates, glass/epoxy lamina(one layer)-bonded and unbonded glass plates, glass/epoxy lamina(three layers)-bonded and unbonded glass plates. The range of impact velocity was 40 120m/s. The maximum stress and absorbed fracture energy were measured on the back surface of glass plates. With increasing impact velocity, various types of surface cracks such as ring, cone, radial and lateral cracks took place in the interior near the impacted site of glass plates. The cracks drastically decreased with glass/epoxy lamina coating. The surface fracture behavior could be evaluated using the maximum stress and the absorbed fracture energy.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.2
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• pp.65-74
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• 2015

In order to design an advanced composite materials drainage pipe structures for an undersea tunnel, mechanical properties for the lamina types of the structural member must be predetermined. It is also reported that the size effect of the specimen is significant. In this study the tensile tests for the lamina types of the structural member are conducted at the room temperature ($20^{\circ}C$) and the seawater temperature ($0^{\circ}C$). In addition, the mechanical properties are predicted by theory based on the rule of mixtures and elasticity solution technique. The predicted mechanical properties are compared with test results obtained by a test method. In the design of an advanced composite materials drainage pipe structural members for an undersea tunnel, the used mechanical properties must be applied at the room temperature with considering the modified factors. These are to be offered the datum for the design an advanced composite materials drainage pipe structures for an undersea tunnel.

• Journal of Nutrition and Health
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• v.30 no.10
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• pp.1123-1131
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• 1997

This study examined the effect of dietary lipids and guar gum on lipid metabolism in ovariectomized rats. The experimental animals received ovarietomy (OVX). Lipids sources were divided into 3 groups (soybean oil(SB), beef tallow(BT)) and fish oil(FO)) and guar gum was supplemented to each lipid diet (SBG, BTG, FOG). Experimental diets were fed to therats for 16 weeks. Serum triglyceride (TG) levels were higher in the BT group and lower in the FO group as compared to the SB group .Serum total cholesterol (Tc) and HDL-C levels were lower in the FO group as compared to the SB group. Serum LDL-C and phospholipid levels were lower in the FO group as compared to the SB group. Serum lipids levels were lowered by guar gum supplement. Serum SFA(saturated fatty acids) contents were not significantly influenced by dietary lipids and guar gum. Serum MUFA(monounsaturated fatty acids) contents were the lowest in the SB group. Fecal weight was highest in the beef tallow group and lowest in the fish oil group. Fecal weight was increased by guar gum supplement in all lipid groups. Total bile acid content in feces was increased by guar gum supplement in the soybean oil and beef tallow groups. The endothelial cells of the beef tallow group changed from a flat shape to distorted round and enlarged shapes. The subendothelial layer was the thickness the thickest in the beef tallow group ; the interspace between elastic lamina was widened and elastic lamina was straightened and partly disrupted . The fish oil group showed more porminient endothelial cells and subendothelial layer. Internal elastic membrane and elastic lamina exhibited regularly wavy shapes. Guar gum supplement showed positive effects in all lipids groups. Based on the above results , it is suggested that beef tallow increased serum TG levels and injured the wall of the aorta. On the other hand, fish oil , which decreased serum lipid levels, has a positive effect on the walls of the aorta. Guar gum protects the aorta from injury by reducing the serum lipid levels. Therefore, it is suggested that soybean oil and beef tallow consumed with guar gum is beneficial.

• Composites Research
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• v.22 no.4
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• pp.33-40
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• 2009

Fiber orientation effects on the impact surface fracture of the glass plates coated with the glass fiber/epoxy lamina layer were investigated using a small-diameter steel-ball impact experiment. Four kinds of materials were used: soda-lime glass plates, unidirectional glass fiber/epoxy layer(one ply, two plies)-coated, crossed glass tiber/epoxy layer (two plies)-coated glass plates. The maximum stress and absorbed fracture energy were measured on the back surface of glass plates during the impact. With increasing impact velocity, various surface cracks such as ring, cone, radial and lateral cracks appeared near the impacted site of glass plates. Cracks in the plate drastically diminished by glass fiber coating. The tiber orientation guided the directions of delamination and plastic deformation zones between the tiber layer and the glass plate. Impact surface-fracture indices expressed in terms of the maximum stress and absorbed energy could be used as an effective evaluation parameter of the surface resistance.

• Journal of the Korean Wood Science and Technology
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• v.43 no.4
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• pp.463-469
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• 2015

In this study, to improve bending strength performance of Korean white pine, we made the curved composite glulam that was reinforced with glass fiber materials and larch lamina. Five types of Korean white pine curved glulams were made depending on whether they had been reinforced or not and how they had been reinforced. Type-A, reference specimen, was produced only with Korean white pine lamina, and Type-B was with larch lamina in the same thickness. Type-C was made by inserting a glass fiber cloth of textile shape between the each layer. Type-D was reinforced with two glass fiber cloths, which were placed inside and outside of the outermost lamina. Type-E was reinforced with GFRP sheet in the same way as Type-D. As a result of this bending strength test, the modulus of rupture (MOR) of Type-B, Type-C and Type-E were increased by 29%, 6%, and 48% in comparison with Type-A. However, MOR of Type-D was decreased by 2% in comparison with Type-A. In the failure modes, Type-A, Type-B and Type-C were totally fractured at the maximum load. However, load values of Type-D and Type-E decreased slowly because of reinforcement of fracture suppression, and the GFRP sheet (Type-E) had better reinforcing effect on compressive stress and tensile stress than the glass fiber cloth (Type-D).

• Journal of the Korean Wood Science and Technology
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• v.48 no.6
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• pp.791-806
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• 2020

In this study, a block shear strength test was conducted to compare and analyze the strength and failure mode on the glued laminated timber, CLT, and Ply-lam CLT, which are mainly used for the construction of wood construction as engineering wood. Through this, the Ply-lam CLT manufacturing conditions for optimum production, such as the type of lamina, plywood, adhesive, and layer composition, were investigated. The results are as follow. Through block shear strength test, it showed high strength in the order of glued laminated timber, Ply-lam CLT and CLT. In particular, the shear strength of Ply-lam CLT, which is made of a composite structure of larch plywood and larch lamina, passed 7.1 N/㎟, which is a Korean industrial standards for block shear strength of structural glued laminated timber. In addition, in this study, there was no different in shear strength according to the adhesive type used for glulam, CLT, and Ply-lam CLT adhesion. However, in the case of Ply-lam CLT, the difference in shear strength of Ply-lam CLT was shown according to the type of lamina and plywood. The results showed high strength in the order of Larix kaempferi > Mixed light hardwood ≒ Pinus densiflora, sieb, et, Zucc plywood. The optimal configuration of Ply-lam CLT is when larch plywood and larch lamina are used, and it is decided that the adhesive can be used by selecting PRF and PUR according to the application. The results of block shear strength failure mode by type of wood based materials were analyzed. The failure mode showed shear parallel-to-grain for glulam, rolling shear for CLT, and shear parallel-to-grain and rolling for ply-lam CLT. This is closely related to shear strength results and is decided to indicate higher shear strength in Ply-lam CLT than in CLT due to rolling shear.

• Journal of the Korean Wood Science and Technology
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• v.37 no.6
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• pp.546-555
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• 2009

To study an effective use of woods, three-ply hybrid laminated woods instead of crosslaminated woods which are composed of spruce in the face and three kinds of wood-based boards (MDF, PB, OSB) in the core were manufactured, and the effect of constitution elements for the core laminae on bending strength performances was investigated. Bending modulus of elasticity (MOE) of hybrid laminated woods had the highest values for the hybrid laminated wood types arranging OSB laminae in the core, and had the lowest values for those arranging MDF laminae in the core. These values were higher than those of various cross-laminated woods. The estimated bending MOEs of the hybrid laminated woods which were composed of perpendicular-direction lamina of spruce in the faces were similar to their measured values, regardless of wood-based boards in the core. However, those of the hybrid laminated woods which were composed of parallel-direction lamina of spruce in the faces had much higher values than those of their measured values, and it was necessary to revise the measured values. Bending modulus of rupture (MOR) of the hybird laminated woods had the highest value for those arranging OSB laminae in the core, and had the lowest values for those arranging PB laminae in the core unlike the bending MOE. By hybrid laminating, the anisotropy of bending strength performances was markedly decreased, and the differences of strength performances among wood-based boards were also considerably decreased.

• Korean Journal of Ichthyology
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• v.17 no.4
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• pp.241-247
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• 2005

To observe the respiratory system in relation to the air-breathing organ in Iksookimia longicorpa, micro-anatomical investigation was performed on the epidermis and on intestinal tract fragments. The epidermis was distinguished by two types of skin glands, a small mucous cell and a large club cell. The mucous cell was acid sulfomucins (some sialomucins), but the club cell did not give any histochemical tests for mucosubstances. The presence of a well defined lymphatic system with small lymphocytes was established in the stratum germinativum layer of the epidermis. A large number of blood capillaries run very close to each other just below the basement membrane. The straight intestinal tract is divided into an intestine and rectum, which consisted of a mucosa (epithelial layer), lamina propria-submucosa, muscularis, and serosa. The intestine and rectum have shorter mucosal folds and a thinner wall. The majority of the epithelial mucous cells contain acid sulfomucines. Based on the above results, I. longicorpa adapts to poor dissolved oxygen conditions by using an additional respiratory system using air through the epidermis, not the intestines.

• Composites Research
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• v.29 no.6
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• pp.321-327
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• 2016

In this study, tests and finite element analyses were performed regarding compression after impact strength for laminated composite structures of unidirectional carbon fiber reinforced plastic widely used in structural materials. Two lay-up sequences of composite laminates were selected as test specimens and four impact energy conditions were applied respectively. Impact and compressive strength tests were conducted in accordance with ASTM standards. Impact damages in test specimens were analyzed by using non-destructive inspection method of C-Scan, and compression after impact strengths were calculated with compressive test results. Progressive failure analysis method that can progressively simulate damages and fractures of fiber/matrix/lamina/laminate level was used for impact and compressive strength analyses. All analysis results including contact force, deflection, impact damages, compressive strengths, etc. were compared to test results, and the validity of analysis method was verified.