• 한국재료학회지
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• 제15권9호
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• pp.560-565
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• 2005

The objective of this paper is to decide optimal of the slot angle to minimize stress concentration in rotating disc of diamond saw. The fracture phenomena of the slot are discussed by the theoretical and experimental approaches and then some recommendation are presented to prevent the fracture. The focus of this investigation is to evaluation the effect of the slot on stress distribution using optimum design technique and finite element method(FEM) analysis. Stress concentration of the slot with respect to the various parameter of the slot such position, size, number, rotation speed. From the experimental results, when the slot angle of diamond saw is located $8^{\circ}\~12^{\circ}$ from rotating direction, the maximum equivalent stress reduces.

• Human Ecology Research
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• 제53권5호
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• pp.475-488
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• 2015

Economic activity and social participation by women has recently increased; however, working mothers raising young children are under new stress due to the simultaneous combination of job and parenting responsibilities. This stress has resulted in social problems of career break and low fertility. This study investigates the effect of clinical art therapy on occupational stress and parenting stress of working mothers. We analyzed 34 working mothers in full-time employment (over 8 hours a day) who have preschool children (0-6 years old). They were divided into 17 subjects in the experimental group and 17 subjects in the control group. For the experimental group, 10 hours and a half sessions of group art therapy were participated in once a week from April to August in 2014. We perform Dan Occupational Stress Index by Ivancevich and Matteson, Parenting Stress Index/Short Form and salivary cortisol test before and after the group art therapy. For qualitative analysis, Kinetic House-Tree-Person (KHTP) drawing test was used. Using SPSS ver. 19.0, paired t -test or Wilcoxon signed rank test compared the pre and post analysis results. The results of this study are as follows. First, scores of 'occupational stress factor' subpart showed significant improvement in the Occupational Stress Index after the clinical art therapy. Second, scores of 'parental distress,' 'parent-child dysfunctional interaction,' and 'difficult child' subpart in Parenting Stress Index also showed a significant improvement. Third, a positive change was observed after the clinical art therapy in the KHTP drawing test. In conclusion, this study suggests that the clinical art therapy can be effective for occupational stress factors and the parenting stress of working mothers.

• Steel and Composite Structures
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• 제21권6호
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• pp.1227-1250
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• 2016

Most of the research work has been conducted on K-joints under static loading. Very limited information is available in consideration of fatigue strength of K-joints with concrete-filled chord. This paper aims to describe experimental and numerical investigations on stress concentration factors (SCFs) of concrete-filled circular chord and square braces K-joints under balanced axial loading. Experiment was conducted to study the hot spot stress distribution along the intersection of chord and braces in the two specimens with compacting concrete filled in the chord. The test results of stress distribution curves of two specimens were reported. SCFs of concrete-filled circular chord and square braces K-joints were lower than those of corresponding hollow circular chord and square brace K-joints. The corresponding finite element analysis was also conducted to simulate stress distribution along the brace and chord intersection region of joints. It was achieved that experimental and finite element analysis results had good agreement. Therefore, an extensive parametric study was carried out by using the calibrated finite element model to evaluate the effects of main geometric parameters and concrete strength on the behavior of concrete-filled circular chord and square braces K-joints under balanced axial loading. The SCFs at the hot spot locations obtained from ABAQUS were compared with those calculated by using design formula given in the CIDECT for hollow SHS-SHS K-joints. CIDECT Design Guide was generally quite conservative for predicting SCFs of braces and was dangerous for predicting SCFs of chord in concrete-filled circular chord and square braces K-joints. Finally SCF formulae were proposed for circular chord and square braces K-joints with concrete-filled in the chord under balanced axial loading. It is shown that the SCFs calculated from the proposed design equation are generally in agreement with the values derived from finite element analysis, which were proved to be reliable and accurate.

• 대한조선학회논문집
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• 제42권2호
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• pp.129-135
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• 2005

At present, fatigue design of welded structures is primarily based on a nominal stress or hot spot stress approach with a series of classified weld S-N curves. Although well accepted by major industries, the nominal stress based fatigue design approach is cumbersome in terms of securing a series of S-N curves corresponding to each class of joint types and loading modes. The hot spot stress based fatigue design has a difficulty of finding a proper stress through the global model, the midium size model, and the detail model of ship structure. Also, it is difficult to link proper displacements within three different mesh size models. Recently, the structural stress is proposed as a mesh-size insensitive structural stress definition that gives a stress state at weld toe with relatively large mesh size. However, this method requires an experimental validation in obtaining the fatigue strength of weldments. Therefore, in this study, a series of experiment is performed for various sizes of weldments.

• 대한조선학회지
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• 제20권4호
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• pp.17-24
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• 1983

In this study, it was investigated the distribution of residual stress in the direction of loading between the root and toe the load fillet welds for thick steel plate. Residual stress distributions are measured by sectioning method which is one of stress-relaxation technique in welded joint, and analyzed by two dimensional finite element method on thermo-elasto-plastic theory under plane stress condition. These are compared the results of F.E.M analysis with the experimental result by stress-relaxation techniques. As a results, the following conclusion were obtained. (1) In the no penetration fillet welded joint specimen using mild steel plate with 25mm in thickness, the residual stress of loading direction near the root was about $10kg/mm^2$ tensile. (2) The tensile residual stress has been observed in fillet region of the fillet joint by F.E.M. analysis method. (3) The range of compressive residual stress distribution from the root was largest in the case of 5mm root penetration.

• Geomechanics and Engineering
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• 제22권5호
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• pp.375-384
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• 2020

In this study, the application of conventional cubic law to a deep depth condition was experimentally evaluated. Moreover, a modified equation for estimating the rock permeability at a deep depth was suggested using precise hydraulic tests and an effect analysis according to the vertical stress, pore water pressure and fracture roughness. The experimental apparatus which enabled the generation of high pore water pressure (< 10 MPa) and vertical stress (< 20 MPa) was manufactured, and the surface roughness of a cylindrical rock sample was quantitatively analyzed by means of 3D (three-dimensional) laser scanning. Experimental data of the injected pore water pressure and outflow rate obtained through the hydraulic test were applied to the cubic law equation, which was used to estimate the permeability of rock fracture. The rock permeability was estimated under various pressure (vertical stress and pore water pressure) and geometry (roughness) conditions. Finally, an empirical formula was proposed by considering nonlinear flow behavior; the formula can be applied to evaluations of changes of rock permeability levels in deep underground facility such as nuclear waste disposal repository with high vertical stress and pore water pressure levels.

• 대한조선학회논문집
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• 제41권6호
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• pp.84-90
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• 2004

For the precise assessment of the effect of welding residual stresses on structural strength and fatigue crack growth behavior, new FE analysis algorithms for the estimation of residual stress relaxation due to external load and redistribution due to fatigue crack propagation were proposed in this paper. Initial welding residual stress field was obtained by thermal elasto-plastic analysis considering temperature dependent material properties, and the amount of residual stress relaxation and redistribution were assessed by subsequent elasto-plastic analysis In the analysis of fatigue crack propagation, the applied SIF(Stress Intensity Factor) range was evaluated by $\frac{1}{4}$-point displacement extrapolation method, and the effect of welding residual stresses on crack propagation was considered by introducing the effective SIF concept. The test results of crack propagations were compared with the predicted data obtained by the analysis.

• 한국가정과학회지
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• 제9권2호
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• pp.21-31
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• 2006

The purpose of this study is to investigate the differences in irrational faith and the school adaptation of elementary school students by experimental group and control group. To achieve these goals, the followings are setting the programs. The subjects are selected from grade 4, 5, 6 students from the elementary schools. The tools used for this study were Irrational faith Test and School adaptation Test. The followings are the results of the analysis of the collected data. First, in the analysis of irrational faith, there is no significant difference between experimental group and control group. Second, in the analysis of school adaptation, there is significant difference between experimental group and control group(t=.05, p<.05).

• 상하수도학회지
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• 제19권2호
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• pp.181-192
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• 2005

This study evaluated the effect of factors influencing the initial biofilm formation in drinking water distribution pipe by running experiments using a $2^{4-1}$ fractional factorial experimental design with a replicate. Important variables used for assessing biofilm formation included BDOC(biodegradable dissolved organic carbon), viable heterotrophic bacteria present in drinking water, water temperature, and shear stress at two levels each. Based on the statistical analysis of biofilm levels measured as attached HPC(heterotrophic plate count) and community-level assay, the main factors that have significant effects on biofilm formation were found to be viable heterotrophic bacteria and BDOC. Water temperature only exhibited significant effect on the levels of attached HPC, while shear stress was not a significant factor under given conditions. Moreover, the statistical analysis revealed that interactions between the important variables were not statistically significant at a 0.05 significance level.

• Journal of Ginseng Research
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• 제35권1호
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• pp.111-123
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• 2011

To investigate the effects of repeated immobilization-stress challenge on the the hypothalamic-pituitary-adrenal axis, the genomic transcriptome in the adrenal cortex of immobilization-stressed mouse was analyzed by using a cDNA microarray. Mice were subjected to immobilization stress for 2 h per day for 5 consecutive d. With a 4.0-fold cutoff of arbitrary criteria, the expression levels of 168 out of 41,174 genes were significantly modulated in the adrenal cortex by stress when comparing the control and experimental groups. These genes were related to apoptosis, cell cycle, immune response, inflammatory responses, and signal transduction, and thus may be used as potential targets for the development of therapeutics for chronic stress or depression. Six significant genes among these were selected for real time polymerase chain reaction analysis to confirm the change of their expression levels. The gene for phospho 1 was also further investigated because its expression showed the greatest fold-change.