• Journal of Power System Engineering
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• v.6 no.4
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• pp.49-55
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• 2002

In this paper, the elevated temperature tensile properties and short-time creep rupture characteristics were investigated for the friction welded joints of dissimilar materials, Cu-1%Cr-0.5%Zr and STS316L. The joining tests on Cu-1%Cr-0.5%Zr/STS316L by friction welding were performed, and optimum joining conditions of the friction welded joints were determined. The characteristics of the elevated temperature tensile strength, hardness, fractographs were examined, and the creep rupture characteristics for the optimum welded joints were investigated under uniaxal static load at 300, 400 and $500^{\circ}C$.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.4
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• pp.54-61
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• 2002

Inconel 690 alloy has widely been used in power plant and high temperature facilities because it has high thermal resistance and toughness. But we have little design data about the creep behaviors of the alloy. Therefore, in this study, an apparatus has been designed and built for conducting creep tests under constant load conditions. A series of creep tests on Inconel 690 alloy have been performed to get the basic design data and life prediction of inconel products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become bigger. thirdly, the constant of Larson-Miller Parameters on this alloy is estimated about 10. And last the fractographs at the creep rupture show both the ductile and the brittle fracture according to the creep conditions.

• Journal of the Korean Home Economics Association
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• v.42 no.2
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• pp.213-227
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• 2004

This study was attempted to investigate the sensory and textural characteristics of mungbean starch gels with soy bean oil and sucrose fatty acid ester(SE) addition during room temperature storage. Freshly prepared mungbean starch gels, with and without soy bean oil and SE, were stored at 25$^{\circ}C$ for 24, 48 and 72 hours. The color value, syneresis, texture and sensory properties of the gels were measured. The lightness(L) of the gels with soy bean oil and without additives was similar whereas that with SE was lower than that without additives. Syneresis of the gels with soy bean oil and SE was lower than that without additives. Rupture stress, rupture strain and rupture energy of the freshly prepared gel with 2∼4% soy bean oil were increased, but there were no differences in rupture properties between the gel with soy bean oil and that without additives. Rupture stress, rupture stain and rupture energy of all the gels with SE were decreased. Addition of soy bean oil to the gel did not change the texture profile of the gel, whereas hardness, springiness and chewiness of the gel with SE were decreased. In sensory evaluation, the acceptability of freshly prepared gel with soy bean oil was similar to that without additives, whereas that of the gel with 2% soy bean oil stored for 24 hours was higher than that without additives. The acceptability of the gel with SE was decreased significantly.

• The korean journal of orthodontics
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• v.28 no.3 s.68
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• pp.419-429
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• 1998

This study was carried out in order to study early histologic changes and repair reaction appling to extrusive force for 3rd premolar of adult dogs. After 1 week of extrusive force with elastic chain, one of dogs was sacrified and after 3 weeks retention period, another dog was sacrified. The paraffin sections of samples were stained with Hematoxylin - Eosin and Masson's Trichrome and were examed by light microscopy . The obtained results as follows 1. In Hematoxylin - Eosin and Masson Trichrome stain of control group , the periodontal ligament width was constant from apical third to cervical third of the root and periodontal fiber arrangement was horizontal or oblique in cervical third. oblique in middle third, oblique in apical third of root. in alveolar bone, smooth appearance was shown 2. In Group 1, all periodontal fiber arrangement was oblique toward tooth, and the periodontal ligament width increased Partially PDL was ruptured in apex. In MT stain, immature bone formation was seen at alveolar crest area. Active bone formation was observed along the one side of alveolus, and apical portion of pulp was involved with blood vessel rupture , vacuolization of pulp tissue and hyperemia 3. In Group 2, most periodontal ligament arrangement and PDL width was repaired and fiber density increased. In MT stain, mineralization of immature bone on the alveolar crest was progressed. In pulp, vacuole and hyperemia was diminished and fibrotic change was diminished 4. After 3 week periodontal ligament has more repair ability than pulp tissue. pulp was involved with vacuolization and fibrosis, so it takes more time for repair.

• Journal of Veterinary Clinics
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• v.20 no.3
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• pp.278-285
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• 2003

This study was performed to compare early stage changes following the administrations of Conjugated Linoleic Acid (CLA), Carprofen and their combinations in the experimental canine cranial cruciate ligament rupture. Twenty five mongrel dogs were divided into five groups; Groups 1, 2, and 3 received a sectioning the cranial cruciate ligament (CCL) of the right stifle joint, and were administered CLA (250 mg/kg/day/orally), carprofen (4.4 mg/kg/day/orally), and their combinations for 4 weeks beginning 4 weeks postsurgery, respectively. Group 4 received sectioning CCL and no treatment. Group 5 was composed of unoperated normal dogs. The macroscopic observation of cartilage erosions on both the condyles and plateaus were evaluated, and the severity of the cartilage lesions and synovial inflammation was examined histologically at eight weeks after surgery. Histological examinations including hematoxylin and eosin stain, standard toluidine blue method, PAS technique and Masson trichrome technique, hematologic and radiographic evaluation were perfonned after experimental surgery. Slight yellowish discoloration of the surface was found in some of the experimental dogs. However macroscopic findings showed no significant differences among the groups. In radiographic findings, cranial displacement of the proximal tibia relative to the femoral condyles in all groups was observed but no significant differences among the groups was seen. This study showed that oral administration of CLA, carprofen and their combinations revealed no early stage change in the canine stifle joint following experimental rupture of the cranial cruciate ligament.

• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.135-144
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• 2007

Recently, fiber-reinforced plastic(FRP) wraps are blown as an effective material for the enhancement and rehabilitation of aged concrete structures. The purpose of this investigation is to experimentally investigate behavior of concrete cylinder wrapped with FRP materials. Experimental parameters include compressive strength of concrete cylinder, FRP material, and confinement ratio. This paper presents the results of experimental studies on the performance of concrete cylinder specimens externally wrapped with aramid, carbon and glass fiber reinforced Polymer sheets. Test specimens were loaded in uniaxial compression. Axial load, axial and lateral strains were investigated to evaluate the stress-strain behavior, ultimate strength ultimate strain etc. Test results showed that the concrete strength and confinement ratio, defined as the ratio of transverse confinement stress and transverse strain were the most influential factors affecting the stress-strain behavior of confined concrete. More FRP layers showed the better confinement by increasing the compressive strength of test cylinders. In case of test cylinders with higher compressive strength, FRP wraps increased the compressive strength but decreased the compressive sham of concrete test cylinders, that resulted in prominent brittle failure mode. The failure of confined concrete was induced by the rupture of FRP material at the stain, being much smaller than the ultimate strain of FRP material.

• Journal of Chest Surgery
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• v.35 no.6
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• pp.407-419
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• 2002

Atherosclerosis is a chronic inflammatory disease of the arterial wall characterized by progressive accumulation of lipids, cells, and extracellular matrix. Matrix metalloproteinases(MMPs) and tissue inhibitor of metalloproteinases(TIMPS) contribute to vascular matrix remodeling in atherosclerosis, and some cytokines may play role in the synthesis or activation of MMPs or TIMPs. Material and Method： We produced experimental atherosclerotic plaques in 9 rabbits by atherogenic hypercholesterol diet for 12 weeks, and 10 other rabbits were used as control group with standard laboratory chow, At that time, 19 rabbits were sacrificed and aorta, coronary arteries and blood specimens were prepared. The expressions of MMP-9, TIMP-2 and interleukin(IL)-18, and the bioactivity of IL-6 were investigated with H&E stain, immunohistochemical stain, immunoblotting(Western blot analysis), and bioassay. Result： Serum cholesterol in the experimental group increased up to 1258$\pm$262 mg/dL(control group： 41$\pm$7 mg/dL). All experimental group showed well-developed atherosclerotic plaques in aorta and coronary artery. The expression of MMP-9 in aorta and coronary artery of the experimental group showed significant increase than that of the control group by immunohistochemistry. Among the experimental group, complicated lesions with intimal rupture or complete luminal occlusion, demonstrated stronger expression of MMP-9. Interestingly, there was no difference in expression of TIMP-2 between the experimental and the control group. These findings were confirmed by Western blot analysis. The bioassay revealed significant up-regulation of serum bioactivity of IL-6 in the experimental group(4819.60$\pm$2021.25 IU/$m\ell$) compared to that of IL-6 in the control group(27.20 $\pm$ 12.19 IU/$m\ell$). IL-18 was expressed in all atherosclerotic plaques, whereas little or no expression was detected in the control group. Conclusion： The increased MMP-9 expression along with the unchanged TIMP-2 expression seem to be contributory factors in extracellular matrix degradation in atherosclerosis. Focal overexpression of MMP-9 may promote plaque destabilization and cause complications of atherosclerotic plaques such as thrombosis with/without acute coronary syndrome. Elevation of IL-6 and IL-18 may be more than just markers of atherosclerosis but actual participants in lesion development. Identification of critical regulatory pathway is important to improve the understanding of the cellular and molecular basis of atherosclerosis and may open the way for novel therapeutic strategies.