• Journal of Radiation Industry
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• v.6 no.2
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• pp.165-169
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• 2012

This study was conducted to determine the prevention effect of poly-gamma-glutamic acid (${\gamma}-PGA$) on tissue damage induced by gamma irradiation for development of xenograft. Porcine tendons were treated at various doses of ${\gamma}-PGA$ (0.1, 0.5, 1 and 5%) and then gamma-irradiated (30 kGy). Prevention effects on tissue damage were measured as the result of tensile strength, hydroxyproline contents and viscosity of ${\gamma}-PGA$. Tensile strength was remarkably decrease in gamma-irradiated porcine ligament, but increased by ${\gamma}-PGA$ treated one. Among the ${\gamma}-PGA$ treatment doses, 1% treated group showed the highest values of tensile strength compared to non-treated group. Hydroxyproline contents was significantly increased by gamma irradiation, but decreased by the ${\gamma}-PGA$ treatment. Particularly, 1 and 5% ${\gamma}-PGA$ treated group were exhibited lower values of hydroxyproline contents than other group. In the result of viscosity, gamma-irradiated ${\gamma}-PGA$ (1%) was remarkably increased. Base on the results, it demonstrated that gamma irradiation induces severe alteration of mechanical property and collagen contents on porcine ligament, but ${\gamma}-PGA$ can effectively prevent these tissue damage.

• Computers and Concrete
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• v.24 no.1
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• pp.63-71
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• 2019

Thermal energy from high temperatures can cause concrete damage, including mechanical and chemical degradation. In view of this, the residual mechanical properties of high-strength fiber reinforced concrete with a design strength of 75 MPa exposed to $400-800^{\circ}C$ were investigated in this study. The test results show that the average residual compressive strength of high-strength fiber reinforced concrete after being exposed to $400-800^{\circ}C$ was 88%, 69%, and 23% of roomtemperature strength, respectively. In addition, the benefit of steel fibers on the residual compressive strength of concrete was limited, but polypropylene fibers can help to maintain the residual compressive strength and flexural strength of concrete after exposure to $400-600^{\circ}C$. Further, the load-deflection curve of specimen containing steel fibers exposed to $400-800^{\circ}C$ had a better fracture toughness.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.5
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• pp.199-203
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• 2004

Feasibility of 3Y-TZP for dental implant abutment was evaluated under the Hertzian cyclic fatigue by examining the extent of the indentation damage and strength degradation. Fatigue test was conducted at contact loads of 500 to 3000 N and up to $10^6$ cycles in exact in vitro environments. At 500 N, no strength degradation and crack generation was observed up to $5\times10^5$ contact cycles. As load rose, the dramatic reduction in strength was observed when the damage transition from ring to radial crack occurred. The. extent of strength degradation was more pronounced in vitro environment probably due to chemical corrosion of artificial saliva through cracks introduced during large numbers of contacts.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.10a
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• pp.139-142
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• 2002

This study presents a mathematical model predicting the stress-strain behavior of fiber reinforced (FMMCs) and fiber/particle reinforced metal matrix composites (F/P MMCs). MMCs were fabricated by squeeze casting method using Al2O3 short fiber and particle as reinforcement, and A356 aluminum alloy as matrix. The fiber/particle ratios of F/P MMCs were 2:1, 1:1, 1:2 with the total reinforcement volume fraction of 20 vol.%, and the FMMCs were reinforced with 10 vol,%, 15 vol. %, 20 vol. % of fibers. Tensile tests were conducted and compared with predictions which were derived using laminate analogy theory and multi-failure model of reinforcements. Results show that the tensile strength of FMMCs with 10 vol.% of fiber was well matched with prediction, and as the fiber volume increases, predictions become larger than experimental results. The difference between the prediction and experiment is considered to be a result of matrix allowance of fiber damage in tensile loading. As the fiber volume fraction in FMMCs increases, the fiber damage increases and so that the tensile strength is reduced. The strength of F/P MMCs approaches more closely to the prediction than FMMCs reinforced with 20 vol.% of fibers because F/P MMCs contains small quantity of fibers and thus has a positive effect in fiber strengthening.

• Journal of the Korean Society of Clothing and Textiles
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• v.2 no.2
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• pp.237-243
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• 1978

Dermatophytes such as Trichophyton mentagrophytes, Trichophyton rubrum and Epidermophyton floccosum are used in this study to confirm (a) The Dermatophytes could utilize the wool, cotton and nylon fiber as a nutrient source. (b) The degree of damage of fibers by the Dermatophytes growth. The results of the experiment are summarized as follows; 1. Dermatophytes could not utilize the wool, cotton and nylon fiber directly as a nutrient source without the exogenously applied nutrients. 2. It was presumed that Dermatophytes could utilize the knitted wool fabric as their nutrient source when nutrient was exogenously applied. since the knitted wool fabric was greatly damaged by T. mentagrophytes and T. rubrum growth. 3. The tensile strength of knitted wool fabric was significantly decreased by T. mentagrophytes and T. rubrum, but not by E. floccosum. However, the tensile strength of knitted nylon fabric was not particularly affected by the Dermatophytes. 4. The burst strength of knitted wool fabric was decreased by T. mentagrophytes ($77\%$). T. rubrum ($53\%$). and E. floccosum ($15\%$). Though the burst strength of knitted cotton fabric was decreased by Dermatophytes about $20\%$, that of knitted nylon fabric was not affected. 5. Observing the damaged wool fiber by scanning microscope, the inner part of wool fiber was permeated by T. mentagrophytes and T. rubrum.

• International Journal of Highway Engineering
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• v.16 no.6
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• pp.27-37
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• 2014

PURPOSES : The purpose of this study is to verify the causes of surface scaling at L-shoulder concrete structure. METHODS : From the literature reviews, mechanisms of frost damage were studied and material properties including strength, air void, spacing factor and scaling resistance of L-shoulder concrete structure were analyzed using core specimens taken by real fields. RESULTS : The spacing factor of air void has relatively high correlation of surface conditions : lower spacing factor at good surfacing condition and vice versa. If the compressive strength is high, even thought spacing factor does not reach the threshold value of reasonable durability, the surface scaling resistance shows higher value. Based on these test results, the compressive strength also provide positive effect on the surface scaling resistance. CONCLUSIONS : The main causes of surface scaling of L-shoulder could be summarized as unsuitable aid void amount and poor quality of air void structure. Secondly, although the compressive strength is not the governing factor of durability, but it shows the positive effect on the surface scaling resistance.

• Journal of the Korean Ceramic Society
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• v.40 no.7
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• pp.662-666
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• 2003

Hertzian cyclic fatigue properties of the alumina-glass dental ceramics were evaluated in exact in vitro environment at contact loads from 200 N to 1000 N and up to 10$\^$6/ cycles to investigate the indentation damage and strength degradation. At 200 N, no strength degradation and crack generation was observed up to 10$\^$6/ contact cycles. As load increased from 200 N to 1000 N, the drastic reduction in strength was found when the damage transition from ring to radial crack occurred. The extent of strength degradation was more pronounced in vitro environments probably due to chemical reaction of artificial saliva with glass phase through radial cracks introduced during large numbers of contacts.

• Composites Research
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• v.16 no.1
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• pp.13-18
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• 2003

Prediction of composite fatigue life is not a straightforward matter, depending on various failure modes and their interactions. In this paper, a methodology is presented to predict fatigue life and residual strength of composite materials based on Phenomenological Model(non-linear fatigue damage model). It is assumed that the residual strength is a monotonically decreasing function of the number of loading cycles and applied fatigue stress ratio and the model parameters(strength degradation parameter and fatigue shape parameter) are assumed as function of fatigue life. Then S-N curve is used to extract model parameters that are required to characterize the stress levels comprising a randomly-ordered load spectrum. Different stress ratios (${\sigma}_{min}/{\;}{\sigma}_{max}$) are handled with Goodman correction approach(fatigue envelope) and the residual strength after an arbitrary load cycles is represented by two parameter weibull functions.

• Journal of Ship and Ocean Technology
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• v.2 no.1
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• pp.58-70
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• 1998

Many bulk carrier losses have been reported of late, and one of the possible causes of such casualties is thought to be the structural failure of aging hulls in rough weather. Clearly, in such cases, vessels that start out belong adequate somehow become marginal later in life. Fatigue and corrosion related potential problems may be the most important factors affecting such age related vessel damage. With respect to fatigue, extensive studies have been done worldwide both experimentally and theoretically, and the results have been applied to some extent. However, in the case of corrosion effects, additional research is still needed to better understand, clarify and address the various strength uncertainties and their effects on structural behavior. This paper develops a probabilistic corrosion rate estimation model for the longitudinal strength members of bulk carriers. The model is based on available statistical data for corrosion of existing bulk carriers. The corrosion data collected are documented for future use.

• Structural Engineering and Mechanics
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• v.56 no.2
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• pp.201-221
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• 2015

The fatigue damage problems are frequently encountered in the design of civil engineering structures. A realistic and accurate fatigue life prediction is quite essential to ensure the safety of engineering design. However, constructing a reliable fatigue life prediction model can be quite challenging. The use of traditional deterministic approach in predicting the fatigue life is sometimes too dangerous in the real practical designs as the method itself contains a wide range of uncertain factors. In this paper, a new fatigue life prediction method is going to be proposed where the residual strength is been utilized. Several cumulative damage models, capable of predicting the fatigue life of a structural element, are considered. Based on Miner's rule, a randomized approach is developed from a deterministic equation. The residual strength is used in a one to one transformation methodology which is used for the derivation of the fatigue life. To arrive at more robust results, fuzzy sets are introduced to model the parameter uncertainties. This leads to a convoluted fuzzy based fatigue life prediction model. The developed model is illustrated in an example analysis. The calculated results are compared with real experimental data. The applicability of this approach for a required reliability level is also discussed.