• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.471-480
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• 2015

The building structure is planned to maximize the use of space in recent. It was developed of a hybrid OCB (Optimized Composite Beam) for trying to take advantage of the maximize space. The OCB is composed of the steel h-beam section reinforced by open strands in negative moment zone and the psc concrete section in positive zone. Flexural behaviors of typical architectural bybrid OCB section was investigated. The 15 m OCB specimen was tested under three point static loading system. Following results are obtained from the tests; 1) The OCB with 15 m span develop initial flexural crackings under the 171% of full service loading. 2) Overall deflections of OCB under the service loads are less than those of the allowable limit in KCI Code provision. 3) The crack patterns, failure mode and ultimate load capacity of test specimen and F.E. model in this paper and they are compared to each other. The OCB is verified of structural reliability from the experimental results.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.2
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• pp.34-41
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• 2011

Wrought nickel-base superalloys are being considered as the structural materials in very-high temperature gas-cooled reactors. To understand the effects of impurities, especially oxygen, in helium coolant on the mechanical properties of Alloy 617, creep tests were performed in high temperature flowing He environments with varying $O_2$ contents at 800, 900, and $1000^{\circ}C$. Also, creep life in static He was measured to simulate the pseudo-inert environment. Creep life was the longest in static He, while the shortest in flowing helium. In static He, impurities like $O_2$ and moisture were quickly consumed by oxidation in the early stage of creep test, which prevented further oxidation during creep test. Without oxidation, microstructural change detrimental to creep such as decarburization and internal oxidation were prevented, which resulted in longer creep life. On the other hand, in flowing He environment, surface oxides were not stable enough to act as diffusion barriers for oxidation. Therefore, extensive decarburization and internal oxidation under tensile load contributed to premature failure resulting in short creep life. Limited test in flowing He+200ppm $O_2$ resulted in even shorter creep life. The oxidation samples showed extensive spallation which resulted in severe decarburization and internal oxidation in those environments. Further test and analysis are underway to clarify the relationship between oxidation and creep resistance.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.501-509
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• 2004

The proposed model can predict the compressive behaviors of concrete confined with fiber reinforced polymer (FRP) jacket. To model confining concrete by FRP jackets, the hypoelasticity-based constitutive law of concrete In tri-axial stress states has been presented. The increment of strength of concrete has been determined by the failure surface of concrete in tri-axial states, and its corresponding peak strain is computed by the strain enhancement factor that is proposed in the present study, Therefore, the newly proposed model is a load-dependent confinement model of concrete wrapped by FRP jackets to compare the previous models which are load-independent confinement models. The behavior of FRP jackets has been modeled using the mechanics of orthotropic laminated composite materials in two-dimension. The developed model is implemented into the incremental analysis of compressive tests. The verification study with several different experiments shows that the model is able to adequately capture the behavior of the compression test by including better estimations of the axial responses as well as the lateral response of FRP-confined concrete cylinders.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.18 no.2
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• pp.224-235
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• 1996

Early implantation before sufficient ossification has taken place usually results in osseointegartion failure due to reduced bone-fixture interface area. However, various studies have shown successful osseointegration results following immediate implants concurrently with GTR. The clinical trends have been to shorten the patients' edentulous state by immediate implantation, and reduce the alveolar bone resorption. However, it may be difficult to attain the complete soft tissue coverage of the sites, increasing the chance of infection. Furthermore, there may be more studies needed on the clinical behaviors of e-PTFE membranes, various modofications in the membrane materials and bone graft materials. Various animal and clinical studies have been reported on the successful osseointagration following immediate implantation, but the long-term follow-up studies are limited. The present study investigated 16 immediately-implanted implants with GTR therapy with or without calcium carbonate grafting on 11 patients 3 years after installation and 24-30 months after functional loading. Based on the clinical, radiographic and histologic findings, the following results have been attained. 1. Clinically, stability has been shown on all 16 implants throughout the investigated periods. 2. Radiologically, the alveolar bone loss has progressed up to the polished neck portion but not beyond it, suggesting the progressive osseointegration from the GTR therapy. 3. The GTR method used in the present study is easy to use clinically, and may be appied in the regeneration of ossoeous defects around implants and in the immediate implantation. 4. The difficulty in complete tissue coverage may be avoided by delaying the installation for 2 to 3 weeks after the extraction allowing certain degree of soft tissue healing.

• Korean Journal of Community Nutrition
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• v.13 no.5
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• pp.640-652
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• 2008

Hypertension is among the most common and important risk factors for stroke, heart attack, and heart failure which is considered to be the leading cause of death in Korea. The prevalence rate of hypertension in Korea is 27.9%, according to the 2006 Korea National Health and Nutrition Survey. Since non-pharmacologic nutrition education is recommended as the first step in the management of hypertension, evaluation of nutrition program is needed to form strategies for improving patients' dietary adherence. This study was designed to evaluate the overall effectiveness of a hypertension nutrition education program (HNEP) for reducing the salt intake, at a public health center located in Gyunggi-province. The HNEP was offered for 16 weeks from May to September in 2007. Nutrition education activities included cooking classes, food preparation demonstrations, physical fitness programs, salty taste preference test sessions, games, case-study presentations, planning and evaluation of menus, etc. Forty patients participated fully in the program which had 47 female enrollees. Data about nutrient intake (24-hour recall), nutrition knowledge, food behavior were collected before (baseline) and after the program. Changes after program completion indicated the following: 1) diastolic blood pressure was decreased (p < 0.05), 2) sodium (salt) intake was also decreased (p < 0.01), especially baseline high salt intake group, 3) nutrition knowledge was improved (p<0.001), 4) dietary behaviors for maintaining a low salt diet was improved (p < 0.001), 5) participants preferred cooking class from nutrition education methods. As a conclusion, it appears that a nutrition education program for hypertensive female elderly for reducing the salt intake might effectively decrease blood pressure and salt intake. It also improves nutrition knowledge, dietary behavior, and finally adherence to a recommendable low-sodium diet.

• Journal of Embryo Transfer
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• v.26 no.1
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• pp.53-56
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• 2011

Infertility of the pig is directly affects on economic loss and failure of the embryo transfer. In the present case report, we show one rare case of porcine infertility resulted from oviductal obstruction. A gilt showing normal heat behaviors was selected as a recipient of embryo transfer. During the laparotomy surgery, abnormality of the reproductive tract was founded. Several large sized cyst-like structures were founded on infundibulum and body of uterus. Severe enlargement of oviduct represents that obstruction of the oviduct. Sign of fibrosis on the surface of uterus and other internal organs revealed that the obstruction was come arise from prior peritonitis. Mild neutropenia and elevated number of monocytes, eosinophils and platelets in blood smear represent that the peritonitis might be due to chronic parasitic infection. Ovarian function was seems to be normal due to blood progesterone concentration was higher than basal level. The pig was culled because she cannot be recovered by surgical or hormonal treatment.

• Journal of the Korea Concrete Institute
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• v.24 no.1
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• pp.79-86
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• 2012

Though steel reinforcing bars are the most widely used tensile reinforcement, corrosion problems are encountered due to the exposure to aggressive environments. As an alternative material to steel, the fiber reinforced polymers have been used as reinforcement in concrete structures. However, bond strength of FRP rebar is relatively low compared to steel rebar. It has been reported that fibers in matrix can resist crack growth, propagation and finally result in an increase of toughness. In this study, high-strength concrete reinforced with structural fibers was produced to enhance interfacial bond behavior between FRP rebar and concrete matrix. The interfacial bond-behaviors were investigated from a direct pullout test. The test variables were surface conditions of GFRP bars and fiber types. Total of 54 pullout specimens with three different types of bars were cast for bond strength tests. The bond strength-slip responses and resistance of the bond failure were evaluated. The test results showed that the bond strength and toughness increased according to the increased fiber volume.

• International Journal of Highway Engineering
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• v.6 no.2 s.20
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• pp.37-45
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• 2004

The asphalt concrete pavement takes various advantages of better riding quality, serviceability and easier maintenance. At the same time, it addresses a weak point of the premature failures due to rapid increasement of traffic volume, heavy vehicles and high temperature in summer. It increases the expenditure of maintenance and repair. In order to improve the performance of asphalt pavement avoiding this premature failure, the use reinforcements with geosynthetics have been considered. Geosynthetics are known as an effective reinforcement to restrain fatigue and reflective cracks in asphalt pavements. In this study, a comprehensive parametric study is conducted to capture the efficiency of geosynthetic-reinforcements using viscoelastic properties of the asphalt concrete(AC) layer. The investigated parameters were reinforcement location, AC layer thickness, temperature distribution across the AC layer and modulus of AC and base layer. As a result of observations, that reinforced asphalt concrete could be used effectively for improving resistance against fatigue cracks and permanent deformation. Especially, when a geogrid was placed at the interface between the asphaltic base and the subbase, tensile stress in the horizontal direction was significantly reduced.

• Composites Research
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• v.14 no.5
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• pp.46-53
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• 2001

In this research, damage behavior of singly oriented ply (SOP) fiber metal laminate (FML) subjected to concentrated load was studied. The static indentation tests were conducted to study fiber orientation effect on damage behavior of FML. During the static indentation tests, acoustic emission technique (AE) was adopted to study damage characteristics of FML. AE signals were obtained by using AE sensor with 150kHz resonance frequency and the signals were compared with indentation curves of FML. The damage process of SOP FML was divided by three parts, i.e., crack initiation, crack propagation, and penetration. The AE characteristics during crack initiation show that the micro crack is initiated at lower ply of the plate, then propagate along the thickness of the plate with creating tiber debonding. The crack grow along the fiber direction with occurring 60∼80dB AE signal. During the penetration, the fiber breakage was observed. As fiber orientation increases, talc fiber breakage occurs more frequently. The AE signal behaviors support these results. Cumulative AE counts could well predict crack initiation and crack propagation and AE amplitude were useful for the prediction of damage failure mode.

• Tribology and Lubricants
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• v.35 no.6
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• pp.356-361
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• 2019

The friction and wear between machine components directly influence the energy loss and failure in various machines. Therefore, there is always a demand for finding methods to reduce friction and wear. Of the possible methods, lubrication is a widely used method for reducing friction and wear. In the case of lubrication, it is important to analyze the tribological behavior in the boundary lubrication because most of friction and wear occurs in the boundary lubrication regime. Cast iron has been regarded as a good material for industrial applications due to the excellent mechanical properties and high productivity. Especially, nodular cast iron is a material that shows better mechanical properties and wear-resistance compared with cast iron due to inclusion of spheroidal graphite. In this work, we investigated the tribological characteristics of nodular cast iron with respect to different counter parts in boundary lubrication regime. Sliding tests were conducted with SUJ2, ZrO₂, Si₃N₄ balls as counter parts using a pin-on-disk type tribotester. The results showed different friction and wear behaviors with different counter parts. The case of ZrO₂ showed the lowest wear rate in specimen and no significant ball wear. In case of SUJ2, it showed similar wear rate with ZrO₂ case in specimen and the highest friction coefficient. The case of Si₃N₄ showed the lowest friction coefficient, 33% lower than the case of SUJ2. It showed 16.9 times larger wear rate in specimen and 43% larger wear rate in ball compared to that of the SUJ2 case.