• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4A
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• pp.267-279
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• 2009

A numerical model that can simulate the nonlinear behavior of ultra high strength fiber reinforced concrete (UHSFRC) structures subjected to monotonic loading is introduced. The material properties of UHSFRC, such as compressive and tensile strength or elastic modulus, are different from normal strength reinforced concrete. The uniaxial compressive stress-strain relationship of UHSFRC is designed on the basis of experimental result, and the equivalent uniaxial stress-strain relationship is introduced for proper estimation of UHSFRC structures. The steel is uniformly distributed over the concrete matrix with particular orientation angle. In advance, this paper introduces a numerical model that can simulate the tension-stiffening behavior of tension part of the axial member on the basis of the bond-slip relationship. The reaction of steel fiber is considered for the numerical model after cracks of the concrete matrix with steel fibers are formed. Finally, the introduced numerical model is validated by comparison with test results for idealized UHSFRC beams.

• The korean journal of orthodontics
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• v.26 no.5 s.58
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• pp.581-590
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• 1996

Bone resorptiion was predominate in compression site, bone formation in tension site of periodontal ligament during tooth movement. The biologic response at compressiion site was different from tension site. Thus the CGHP immuno-positive nerve fiber will respond differently to mechanical force according to the area( compression or tension site). The purpose of this study was to investigate this response of CGRP immune-positive nerve fiber in the periodontal ligament according to the duration of applied force and the area (compression or tension site) during experimental tooth movement. The experimental animals were 7 week old male rat (approximately 200 gm). The orthodontic force was applied mesially to the right maxillary molar using the Ni-Ti coil spring during 12hours, 1, 3, 7, and 120days. Immunohistochemical staining using antibody against CGRP was performed after sacrifice. The results were as follows. The CGRP immune-positive nerve bundle showed reduced immunoreactivity and nerve fibers reduced in density after application of orthodontic force for 12 hours and 1day. The CGRP immune-positive nerve fibers showed many thin branches at the apical periodontal ligament after application of force for 3 days as compared with normal. The tension site in the apical periodontal ligament showed more branches than the compression site. In 7 day group, the CGRP immune-positive nerve fibers increased in terms of the number and had many thin branches in the apical periodontal ligament. The tension site had more branches than the compression site. In 12 day group, the CGRP immune-positive nerve fibers showed similar distribution to normal control at compression site of apical periodontal ligament, but the fibers at the tension site increased in number. The CGRP immuno-positive nerve fibers showed more increased at tension site than compression site after application of orthodontic force. Therefore it seems to have some relation to the bone remodeling besides the local inflammatory process.

• Magazine of the Korea Concrete Institute
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• v.6 no.2
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• pp.97-107
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• 1994

The objective of this study is to develop polymer-impregnated concrete(PIC), which is a newly developed composite material made by impregnating polymer impregnanls into hardened normal concrete, and to develop analytical techniques for its proper applications. Crystalline methyl methacrylate(MMA) is chosen as a monomer of polymer impregnants. The corrlpositions of polymer impregnants and producing processes are developed by analyzing the effects of penetration, polymerization, thermal safety, and strengthening characteristics. On t he basis of experimental results of this study, various strength characteristics and stress strain constitutive relations are formulated in terms of the compressive strength of normal concrete and the polymer loadings, which can be applied for analysis and design of PIC members. In order to provide a model for fracture analysis of flexural members, fracture toughness, fracture energy, critical crack width, and tension softening relations near crack tip are also formulated in terms of member depth, initial notch depth, and the flexural strength of normal concrete. The structural analysis procedure and the finite element computer program developed in the study are applicable to evaluate elastic behavior, ultimate strength, and tension softening behavior of MMA type PIC structural members subject to various loading conditions. The accuracy and effectiveness of the developed computer program is examined by comparing the anal ytical results with the experimental results. Therefore, it is concluded that the developed structural analysis procedure and the finite element computer program are applicable to analysis and design of in-situ and precast PIC structural members.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.104-109
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• 2002

In this paper, a statistical analysis of fatigue crack growth behavior under constant amplitude loads has been carried out. Fatigue crack growth tests were conducted on sixteen pre-cracked compact tension (CT) specimens of the pressure vessel (SPV50) steel in controlled identical load and environmental conditions. The assessment of the statistical distribution of fatigue crack growth experimental data obtained from SPV50 steel was studied and also the correlation of the parameter C and m in the Paris-Erdogan law was discussed. The probability distribution function of fatigue crack growth life seems to follow the 3-parameter Weibull. The fatigue crack growth rate seems to follow the 3-parameter Weibull and the log-normal distribution. The coefficient of variation (COV) of fatigue crack growth life was observed to decrease as the crack grows. A strong negative linear correlation exists between the coefficient C and the exponent m in Paris model. Fatigue crack growth rate data shows a normal distribution for both m and logC.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.6
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• pp.923-929
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• 2003

In this paper, an analysis of fatigue crack growth behavior from a statistical point of view has been carried out. Fatigue crack growth tests were conducted on sixteen pre-cracked compact tension (CT) specimens of the pressure vessel (SPV50) steel in controlled identical load and environmental conditions. The assessment of the statistical distribution of fatigue crack growth experimental data obtained from SPV50 steel was studied and also the correlation of the parameter C and m in the Paris-Erdogan law was discussed. The probability distribution function of fatigue crack growth life seems to follow the 3-parameter Weibull. The fatigue crack growth rate seems to follow the 3-parameter Weibull and the log-normal distribution. The coefficient of variation (COV) of fatigue crack growth life was observed to decrease as the crack grows. Fatigue crack growth rate data shows a normal distribution for both m and logC. A strong negative linear correlation exists between the coefficient C and the exponent m.

• Journal of the korean academy of Pediatric Dentistry
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• v.23 no.3
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• pp.729-735
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• 1996

Cleft lip and palate is the most common malformation in the craniofacial region. The patients with cleft lip and palate have functional problem such as, speech, feeding and respiratory as well as esthetic problem. So, treatment should be done by multidiciplinary team approach. The role of pediatric dentist in the team is advicement for feeding method, guidance of normal growth, caries control and preventive orthodontics. In cleft lip and palate patients, maxillary arch after cheiloplasty is usually collapsed by excessive tension of the scar. This collapse increase the difficulty of later orthodontic treatment. Therefore, the maxillary arch segments should be moved and retaind to normal position as soon as cheiloplasty is done to reduce the need and difficulty of orthodontic treatment. This concept is called by the early orthopedic treatment in cleft lip and palate. Also, this orthopedic appliance works as feeding applince to normal feeding and weight gain We reported two cases of early orthopedic treatment with favorable result in complete bilateral cleft lip and palate patients after cheiloplasty. Patients showed normal weight and their maxillary arch widths were increased.

• Journal of the Korean Society of Food Culture
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• v.35 no.2
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• pp.224-232
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• 2020

Glaucoma is one of the leading causes of blindness worldwide and is characterized by degeneration of the optic nerve. Elevated intraocular pressure (IOP) is the major contributing factor to optic nerve damage. However, some patients develop glaucoma even with normal IOP. Other factors, including age, race, myopia, and nutrition, can affect glaucoma risk. Dietary fat intake and serum fatty acid composition are closely related with the fatty acid profile of the retina and thus can modulate glaucoma risk. In this study, we collected serum samples from 34 glaucoma patients (26 primary open angle glaucoma (POAG) and 8 normal tension glaucoma (NTG)) and 45 healthy controls and analyzed their serum phospholipid fatty acid concentrations. The results show that the ratio of oleic acid to stearic acid (OA/SA), which is an indicator of stearoyl-CoA desaturase activity, was higher in POAG patients when compared to normal controls. The ratio of eicosapentaenoic acid to arachidonic acid (EPA/AA), which is an indirect marker of eicosanoid biosynthesis, was also higher in glaucoma patients (p=0.048). These results imply that dietary fatty acid intake and serum fatty acid profile can influence glaucoma risk. Additional study is necessary to identify the relationship between fatty acids and glaucoma.

• Smart Structures and Systems
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• v.19 no.2
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• pp.203-211
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• 2017

This paper provides a numerical solution for multiple confocal elliptic dissimilar cylinders. In the problem, the inner elliptic notch is under the traction free condition. The medium is composed of many confocal elliptic dissimilar cylinders. The transfer matrix method is used to study the continuity condition for the stress and displacement along the interfaces. Two cases, or the infinite matrix case and the finite matrix case, are studied in this paper. In the former case, the remote tension is applied in y- direction. In the latter case, the normal loading is applied along the exterior elliptic contour. For two cases, several numerical results are provided.

• Journal of the Korean Mathematical Society
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• v.49 no.5
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• pp.977-991
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• 2012

Let (M,F) and (M',F') be two foliated Riemannian manifolds with M compact. If the transversal Ricci curvature of F is nonnegative and the transversal sectional curvature of F' is nonpositive, then any transversally harmonic map ${\phi}:(M,F){\rightarrow}(M^{\prime},F^{\prime})$ is transversally totally geodesic. In addition, if the transversal Ricci curvature is positive at some point, then ${\phi}$ is transversally constant.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.79.2-79
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• 2002

1. the principal of a PSD(Position Sensitive Detector) 2. the optical system of the proposed method 3. signal processing 4. experimental result A mechanical engineer experiment on the tension test. In this experiment, they use the extensometer which can measure the extended distance of material. A normal extensometer is the contact type which means that the extensometer should attached to the specimen. It is not convenient to the user. The contacting type can also effect the characteristic of the specimen. So a extensometer is changed from contacting type to non-contacting type. Non-contacting type is not necessary to attach the extensometer to the specimen...