• Steel and Composite Structures
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• v.6 no.4
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• pp.285-302
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• 2006

This paper describes the design and behaviour of cold-formed stainless steel slender circular hollow section columns. The columns were compressed between fixed ends at different column lengths. The investigation focused on large diameter-to-plate thickness (D/t) ratio ranged from 100 to 200. An accurate finite element model has been developed. The initial local and overall geometric imperfections have been included in the finite element model. The material nonlinearity of the cold-formed stainless steel sections was incorporated in the model. The column strengths, load-shortening curves as well as failure modes were predicted using the finite element model. The nonlinear finite element model was verified against test results. An extensive parametric study was carried out to study the effects of cross-section geometries on the strength and behaviour of stainless steel slender circular hollow section columns with large D/t ratio. The column strengths predicted from the parametric study were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. It is shown that the design strengths obtained using the Australian/New Zealand and European specifications are generally unconservative for the cold-formed stainless steel slender circular hollow section columns, while the American Specification is generally quite conservative. Therefore, design equation was proposed in this study.

• Journal of the Korean Society of Industry Convergence
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• v.13 no.2
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• pp.77-84
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• 2010

Recently, the concept of structural design against instability has been proposed in the chassis parts. The design considerations of lower control arm of chassis parts under the buckling and durability strengths are the general. More precisely, this paper considers a specific application and associated optimization problem for two strengths, where the design variables are the physical or geometric dimensions for skins and stiffeners. The objective is the minimization of the total weight, while optimization constrains involve reserve or improve factors for the buckling and durability strengths. The most important features are related to the numerical simulations for the estimation of buckling factor and their sensitivities by means of nonlinear and linear finite element analyses. The bucking and durability strength analyses, and the morping geometries are directly included in the optimization problem and the modified design is formulated. As a result, the optimal structure with stable behavior is obtained or increases the buckling and durability strengths of parts. Most of design problems for structures exposed to elastic instability can be formulated and solved.

• Advances in concrete construction
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• v.3 no.1
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• pp.55-69
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• 2015

Tailing Material (TM) and Fly Ash (FA) are obtained as waste products from the mining and thermal industries. Studies were carried out to explore the possibility of utilizing TM as a part replacement to fine aggregate and FA as a part replacement to cement, in concrete mixes. The effect of replacing fine aggregate by TM and cement by FA on the standard sized specimen for compressive strength, split tensile strength, and flexural strengths are evaluated in this study. The concrete mix of M40 grade was adopted with water cement ratio equal to 0.40. Concrete mix with 35% TM and 65% natural sand (TM35/S65) has shown superior performance in strength as against (TM0/S100, TM30/S70, TM40/S60, TM50/S50, and TM60/S40). For this composition, studies were performed to propose the optimal replacement of Ordinary Portland Cement (OPC) by FA (Replacement levels studied were 20%, 30%, 40% and 50%). Replacement level of 20% OPC by FA, has shown about 0-5% more compressive strength as against the control mix, for both 28 day and 56 days of water curing. Interestingly results of split tensile and flexural strengths for 20% OPC replaced by FA, have shown strengths equal to that of no replacement (control mix).

• Steel and Composite Structures
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• v.21 no.6
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• pp.1327-1345
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• 2016

$Al_2O_3$/SiC particulate reinforced (Metal Matrix Composites) MMCs which were produced by using stir casting process, bending strength and hardening behaviour were obtained using an analysis of variance (ANOVA) technique that uses full factorial design. Factor variables and their ranges were: particle size $2-60{\mu}m$; the stirring speed 450 rpm, 500 rpm and the stirring temperature $620^{\circ}C$, $650^{\circ}C$. An empirical equation was derived from test results to describe the relationship between the test parameters. This model for the tensile strength of the hybrid composite materials with $R^2$ adj = 80% for the bending strength $R^2$ adj = 89% were generated from the data. The regression coefficients of this model quantify the tensile strength and bending strengths of the effects of each of the factors. The interactions of all three factors do not present significant percentage contributions on the tensile strength and bending strengths of hybrid composite materials. Analysis of the residuals versus was predicted the tensile strength and bending strengths show a normalized distribution and thereby confirms the suitability of this model. Particle size was found to have the strongest influence on the tensile strength and bending strength.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.911-919
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• 2021

In this paper, the design stress intensity values for the plate-type fuel assembly for research reactor are presented. Through a tensile test, the material properties of the cladding (aluminum alloy 6061) and structural material (aluminum alloy 6061-T6), in this case the yield and ultimate tensile strengths, Young's modulus and the elongation, are measured with the temperatures. The empirical equations of the material properties with respect to the temperature are presented. The cladding undergoes several heat treatments and hardening processes during the fabrication process. Cladding strengths are reduced compared to those of the raw material during annealing. Up to a temperature of 150 ℃, the strengths of the cladding do not significantly decrease due to the dislocations generated from the cold work. However, over 150 ℃, the mechanical strengths begin to decrease, mainly due to recrystallization, dislocation recovery and precipitate growth. Taking into account the uncertainty of the 95% probability and 95% confidence level, the design stress intensities of the cladding and structural materials are established. The presented design stress intensity values become the basis of the stress design criteria for a safety analysis of plate-type fuels.

• Journal of Family Relations
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• v.20 no.4
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• pp.3-24
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• 2016

Objectives: The main purpose of this study was to examine how family strengths affect friend attachment and psychological well-being among college students and to analyze the relative influence of these two variables on psychological well-being. Method: Data were collected by self-administered questionnaire method from 362 university students in four different regions. The data were analyzed through various statistical methods such as t and F tests, Pearson's correlation analyses, and multiple regression analyses. Results: First, there were significant differences in the level of psychological well-being according to gender and the monthly family income, showing that males and higher family income group reported greater psychogocal-well-being level. Males also reported lower level of anxious attachment. Second, correlational analyses results indicated that college students' psychological well-being was positively related with family strengths and secure attachment, and was negatively correlated with avoidant and anxious attachment. Finally, the results of hierarchical multiple regression analyses indicated that college student's psychological well-being was influenced by family communication, secure attachment, and anxious attachment, showing that anxious attachment was the most influential variable. Conclusions: This study suggests the importance of providing education and/or counseling services focusing on strengthening the positive relationship with their friends and on increasing the family communication for college students' psychological well-being.

• Journal of the Korean Physical Society
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• v.73 no.9
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• pp.1310-1314
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• 2018

Non-Maxwellian distributions are found in the laboratory and space plasmas. For an accurate study of plasmas, the Kappa-averaged collision strengths of silicon VIII ion for $4^0S_{3/2}-2^0D_{3/2}$, $4^0S_{3/2}-2^0D_{5/2}$ and $2^0D_{3/2}-2^0D_{5/2}$ transitions are calculated for Kappa distributions with ${\kappa}=2$, 3 and 5 and for temperatures from $10^{4.5}K$ to $10^{6.5}K$. Results indicate that significant differences occur between the averaged collision strengths for the Maxwellian and the Kappa distributions. Fuythermore, and for each ${\kappa}$ value, the Kappa-averaged collision strengths vary in a complicated way with temperature for the $4^0S_{3/2}-2^0D_{3/2}$ and $4^0S_{3/2}-2^0D_{5/2}$ transitions while they decrease with increasing temperature for the $2^0D_{3/2}-2^0D_{5/2}$ transition. The calculation is significant if plasmas are to be studied for a non-Maxwellian distribution.

• Journal of the Korean Society of Safety
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• v.36 no.4
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• pp.29-36
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• 2021

The allowable strength based on experiments and the design allowable strength calculated using the design criteria were compared, which suggested a ratio between the allowable strengths for the reused vertical members of the system scaffolding and system support. By investigating a total of 421 certification reports for reused vertical members, the experimental allowable strengths were collected. Using design criteria such as the road bridge design and KDS 14 30 10, the design allowable strengths were calculated for various slenderness ratios. For the system scaffolding, the average ratio between the experimental and design allowable strengths was calculated to be 0.880 by assuming a normal distribution for all specimens. However, by analyzing the strength ratio according to the slenderness ratio, the lowest average strength ratio was found to be at least 0.844. Therefore, it is reasonable to assume that the allowable strength of the reused vertical members was 80-84% of the design allowable strength. In addition, assuming the allowable strength to be 85% of the design allowable strength is a possible method for reused vertical members of system supports.

• Steel and Composite Structures
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• v.47 no.4
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• pp.455-466
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• 2023

To investigate the load bearing capacity of axially preloaded circular hollow section (CHS) stub columns strengthened by carbon fiber reinforced polymer (CFRP), theoretical analysis is carried out. The yield strength and the ultimate strength of a CFRP strengthened preloaded CHS stub column are determined at the yielding of the CHS tube and at the CFRP fracture, respectively. Theoretical models are proposed and corresponding equations for calculating the static strengths, including the yield strength and the ultimate strength, are presented. Through comparison with reported experimental results, the theoretical predictions on the static strengths are proved to be accurate. Through finite element (FE) analyses, parametric studies for 258 models of CFRP strengthened preloaded CHS stub columns are conducted by considering different values of tube diameter, tube thickness, CFRP layer and preloading level. The static strengths of the 258 models predicted from presented equations are proved to be in good agreement with FE simulations when the diameter-to-thickness ratio is less than 90ε². The parametric study indicates that the diameter and the thickness of the steel tube have great effects on CFRP strengthening efficiency, and the recommended ranges of the diameter and the thickness are proposed.

• Journal of the Korean Home Economics Association
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• v.43 no.2
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• pp.115-126
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• 2005

Environmentally and human compatible chitosan were pretreated on cotton fabrics which were then dyed with 100% persimmon juice. The chitosan concentration was 1% and the chitosan types were high molecular weight chitosan (1980cps), low molecular weight chitosan (18첸), chitosan oligomer and water soluble chitosan. The properties of the fabric surfaces, the dyeabilities, the color fastnesses, the antibacterial activities, the strengths, the elongations and the drape stiffnesses were evaluated. The properties of the chitosanpretreated, persimmon juice-dyed cotton fabrics (CLP) were compared to those of the untreated (CN), chitosan treated (CL) and persimmon juice-dyed fabrics (CP). The results were as follows. The fibers extruded from the surface of CN decreased on CP. The air between the fibers within CN were substituted by chitosan solution or persimmon juiceand decreased within CLP according to SEM observations. The effects of chitosan treatment, the chitosan molecular weights and the degrees of deacetylation of chitosan on the dyeabilities of the persimmon juice-dyed cotton fabric were not distinct. The curing after chitosan padding improved the dyeabilities of CLP compare to noncuring. The strengths of CP decreased and those of CL increased, compared to those of CN. The strengths of CLP were greater than those of CP. The elogations of CP and CL were greater than those of CN. The strengths and elongations of CLP were greater than those of CN. The chitosan treatments improved the strengths but not the elongations. The drape stiffnesses of CL, CP and CLP were greater than those of CN. The antibacterial activites of chitosan pretreated, persimmon juice-dyed cotton fabrics against Staphylococcus aureus were increased by more than 98% by persimmon juice.