• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.05a
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• pp.183-186
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• 2008

Both structural analysis and hydraulic test have been conducted to confirm the burst characteristics of filament wound solid motor case. Failure criteria have been defined with bursting above 150% of MEOP and failure in the cylinder. The results of analysis showed that filament fiber in the cylinder should be broken at about 2088psig. From a hydraulic test the same failure mode and the level of 2200psig of burst pressure have been proved. With these results, it is verified that a filament wound case meets burst requirements.

• International Journal of Concrete Structures and Materials
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• v.10 no.3
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• pp.307-323
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• 2016

The nonlinear behaviors of recycled aggregate concrete (RAC) frame structure are investigated by numerical simulation method with 3-D finite fiber elements. The dynamic characteristics and the seismic performance of the RAC frame structure are analyzed and validated with the shaking table test results. Specifically, the natural frequency and the typical responses (e.g., storey deformation, capacity curve, etc.) from Model 1 (exclusion of strain rate effect) and Model 2 (inclusion of strain rate effect) are analyzed and compared. It is revealed that Model 2 is more likely to provide a better match between the numerical simulation and the shaking table test as key attributes of seismic behaviors of the frame structure are captured by this model. For the purpose to examine how seismic behaviors of the RAC frame structure vary under different strain rates in a real seismic situation, a numerical simulation is performed by varying the strain rate. The storey displacement response and the base shear for the RAC frame structure under different strain rates are investigated and analyzed. It is implied that the structural behavior of the RAC frame structure is significantly influenced by the strain rate effect. On one hand, the storey displacements vary slightly in the trend of decreasing with the increasing strain rate. On the other hand, the base shear of the RAC frame structure under dynamic loading conditions increases with gradually increasing amplitude of the strain rate.

• Journal of the Korean Society of Costume
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• v.59 no.10
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• pp.111-123
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• 2009

This study investigated the multifaced country image. The casual relationships among the multifaced country image, attitudes toward a country, and purchase emotion and purchase intention of fashion products with Korean images were also investigated. To conduct a quantitative analysis, we collected data from 296 Korean female consumers. SPSS 12.0 and AMOS 5.0 packages were used for statistical analysis. The results of this study as follows. To identify components of country image of Korea, exploratory and confirmatory factor analyses were conducted. This procedure produced five components such as culture, technique/product, ethical values, nationality, and space. Structural equational model was used to analyze the relationships among the country image, attitudes toward a country, purchase emotion, and purchase intention of fashion products with Korean image. The proposed model was verified.

• Composites Research
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• v.29 no.2
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• pp.66-72
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• 2016

Porosity in polymer matrix composites increases rapidly during thermochemical decomposition at high temperatures. The generation of pores reduces elastic moduli and failure strengths of composite materials, and gas pressures in internal pores influence thermomechanical behaviors. In this paper, micromechanical finite element analysis is carried out by using two-dimensional representative volume elements for unidirectionally fiber-reinforced composites with porous matrix. According to the state of the pores, effective elastic moduli, poroelastic parameters and failure strengths of the overall composites are investigated in detail. In particular, it is confirmed that the failure strengths in the transvers and through-thickness directions are predicted much more weakly than the strength of nonpored matrix, and decrease consistently as the porosity of matrix increases.

• Advanced Composite Materials
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• v.18 no.2
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• pp.121-134
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• 2009

The present study investigated, both experimentally and numerically, the improvement of low-velocity impact damage resistance of carbon fiber reinforced plastic (CFRP) laminates due to through-the-thickness stitching. First, we conducted drop-weight impact tests for stitched and unstitched laminates. The results of damage inspection confirmed that stitching did improve the impact damage resistance, and revealed that the improvement effect became greater as the impact energy increased. Moreover, the stitching affected the through-the-thickness damage distribution. Next, we performed FEM analysis and calculated the energy release rate of the delamination crack using the virtual crack closure technique (VCCT). The numerical results revealed that the stitching affected the through-the-thickness damage distribution because the stitch threads had a marked effect on decreasing both the modes I and II energy release rate around the bottom of the laminate. Comparison of the results for models that contained delaminations of various sizes revealed that the energy release rate became lower as delamination size increased; therefore the stitching improved the impact resistance more effectively when the impact energy was higher.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.1886-1895
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• 1999

The delamination behavior of multidirectional carbon-fiber/epoxy composite laminates under 10NA intermediate and high rates of test, up to rate of about 11.4m s has been investigated using the double cantilever beam specimens. The mode I loading under rates above l.0m/s showed considerable dynamic effects on the load-time curves and thus higher values of the average crack velocity than that expected from a simple proportional relationship with the test rate. The modified beam analysis utilizing only the opening displacement and crack length exhibited an effective means for evaluating the dynamic fracture energy $G_{IC}$. Based on the assumption of constant flexural modulus, values of $G_{IC}$ at the crack initiation and arrest were decreased with an increase of the test rate up to 5.7m/s, but the maximum $G_{IC}$ was increased at 11.4m/s.

• The Korean Journal of Food And Nutrition
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• v.22 no.1
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• pp.92-96
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• 2009

Comparisons of the physico-chemical characteristics between white Atlantic potatoes and violet Bora Valley potatoes were performed. According to the results, Bora Valley had 7% higher moisture content than Atlantic, but there were no differences in crude fat and crude ash contents. Bora Valley, however, had about 3% less crude protein content than Atlantic. In a vitamin C analysis by HPLC, the Atlantic and Bora Valley potatoes contained 14% and 39% vitamin C, respectively, indicating that Bora Valley contained about twice as much of the vitamin as Atlantic. In a vitamin C analysis by HPLC, the Atlantic and Bora Valley potatoes contained 14% and 39% vitamin C, respectively, The dietary fiber content of Bora Valley was 3.12 g per 100 g higher than that of the Atlantic variety. While Atlantic contained neither glucose nor fructose, both sugars were measured in the Bora Valley potatoes, and there was no difference in sucrose content between the cultivar.

• Steel and Composite Structures
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• v.7 no.1
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• pp.19-34
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• 2007

This paper presents results of a non-linear finite element analysis of axially loaded slender hollow structural section (HSS) columns, strengthened using high modulus carbon-fiber reinforced polymer (CFRP) longitudinal sheets. The model was developed and verified against both experimental and other analytical models. Both geometric and material nonlinearities, which are attributed to the column's initial imperfection and plasticity of steel, respectively, are accounted for. Residual stresses have also been modeled. The axial strength in the experimental study was found to be highly dependent on the column's imperfection. Consequently, no specific correlation was established experimentally between strength gain and amount of CFRP. The model predicted the ultimate loads and failure modes quite reasonably and was used to isolate the effects of CFRP strengthening from the columns' imperfections. It was then used in a parametric study to examine columns of different slenderness ratios, imperfections, number of CFRP layers, and level of residual stresses. The study demonstrated the effectiveness of high modulus CFRP in increasing stiffness and strength of slender columns. While the columns' imperfections affect their actual strengths before and after strengthening,the percentage gain in strength is highly dependent on slenderness ratio and CFRP reinforcement ratio, rather than the value of imperfection.

• Steel and Composite Structures
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• v.8 no.6
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• pp.457-473
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• 2008

Yielding of the internal steel reinforcement is an important mechanism that influences the Intermediate Crack-induced debonding (IC debonding) behavior in FRP-strengthened RC members since the FRP is required to carry additional forces beyond the condition of steel yielding. However, rational design practice dictates an appropriate limit state is defined when steel yielding is assured prior to FRP debonding. This paper proposes a criterion which correlates the occurrence of IC debonding to the formulation of a critical steel yielding length. Once this length is exceeded the average bond stress in the FRP/concrete interface exceeds its threshold value, which proves to correlate with the average bond resistance in an FRP/concrete joint under simple shear loading. This proposed IC debonding concept is based on traditional sections analysis which is conventionally applied in design practice. Hence complex bond stress-slip analyses are avoided. Furthermore, the proposed model incorporates not only the bond properties of FRP/concrete interface but also the beam geometry, and properties of steel and FRP reinforcement in the analysis of IC debonding strength. Based upon a solid database, the validity of the proposed simple IC debonding criterion is demonstrated.

• Journal of the Korean Home Economics Association
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• v.43 no.1 s.203
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• pp.167-176
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• 2005

This study was intended to investigate the wearing conditions of shirts, and examine the preferred subjective sensation for shirt fabrics. A questionnaire survey was conducted on 469 university students (male students $45.3\%$, female students $54.7\%$) in the Cheongju area, Korea. Frequency, descriptive analysis, $\x^2$ and t-tests were used for data analysis. The results were as follows: Regardless of gender, most owned 4 shirts in the autumn, which were each worn once or twice week. Generally, patterned shirts were less favored than those with solid colors, regardless of gender, but the color of the shirts differed slightly according to gender. Most students gathered items from those displayed in the store as their source of information on shirts, and tended to purchase items worth $30,000\~50,000$ won at franchised stores with friends of the same gender. They almost always looked carefully at the size and brand, but the care label and fiber content were rather neglected during the purchase. While purchasing their shirts, the following elements were considered, in this order of importance: size; color; fitness; comfort; price; tactile sensation. Light, dense, soft, warm, wrinkle-free, dry and strong sensation of the shirt fabrics were the strongest preferences for a purchase. There were partially significant gender differences in the subjective sensation of shirt fabrics.