• Wind and Structures
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• v.9 no.4
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• pp.255-270
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• 2006

Several analytical procedures available in literature, for the evaluation of wind induced fatigue damage of structures, either assume the wide band random stress variations as narrow band random process or use correction factors along with narrow band assumption. This paper compares the correction factors obtained using the Rainflow Cycle (RFC) counting of the measured stress time histories on a lamp mast and a lattice tower, with those evaluated using different frequency domain methods available in literature. A Bi-modal spectral method has been formulated by idealising the single spectral moment method into two modes of background and resonant components, as considered in the gust response factor, for the evaluation of fatigue of slender structures subjected to "along-wind vibrations". A closed form approximation for the effective frequency of the background component has been developed. The simplicity and the accuracy of the new method have been illustrated through a case study by simulating stress time histories at the base of an urban light pole for different mean wind speeds. The correction factors obtained by the Bi-modal spectral method have been compared with those obtained from the simulated stress time histories using RFC counting method. The developed Bi-modal method is observed to be a simple and easy to use alternative to detailed time and frequency domain fatigue analyses without considerable computational and experimental efforts.

• Bulletin of the Society of Naval Architects of Korea
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• v.9 no.1
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• pp.7-14
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• 1972

Recently, the matrix method has become almost universal tool to solve various engineering problems in conjunction with the rapid development of high speed electronic computers. The method also has been introduced to ship structure analysis in past few years. This paper treats a method to obtain an approximate solution for stress distribution in a web frame of oil tankers. The method is designed to use relatively small computer. The procedure consists of two steps. In the first step, the web frame is idealized to a plane frame of slender members as shown in Fig. 2. Then, the plane frame is analyzed with a matrix method to determine forces and moments in each members. In the second step, the original shape of the web frame is restored and any portion of the frame, in which the stress distribution is desired, is isolated as shown in Fig. 3. Then, again, a finite element method is used to determine the stress distribution in the isolated portion. In this work, IBM 1130 computer in the computation center, SUN has been used. A numerical example with scantlings of an actual ship is worked out to prove the validity of this method.

• Computational Structural Engineering
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• v.7 no.2
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• pp.121-129
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• 1994

The Finite Element Method(FEM), which is existing stress analysis method, requires substantial amounts of efforts for analysis of perforated plates. An equivalent solid plate analysis method is developed in this paper. A perforated plate is assumed to be an equivalent solid plate in this method. Stress analysis is performed for this equivalent solid plate using effective material properties, and then these stresses are converted to the actual stresses of the original perforated plate. A case study is conducted for a rectangularly arrayed perforated plate using the proposed method in this paper. Compared and analyzed with respect to those calculated by the existing stress analysis method, the result seems to be satisfied in terms of its practicality and more conservative with respect to margin in design application.

• Proceedings of the KWS Conference
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• 2002.10a
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• pp.372-377
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• 2002

Residual stress by welding should be reduced because that decreases the reliability on strength of welded structure. The reason is that the total stiffness of structure decreases by non-linear behavior of weldment under external load. The release of residual stress by mechanical loading and unloading is often performed in the fabrication of box structure for steel bridge. The proper degree of loading and unloading is significant at release method of residual stress by mechanical loading because that degree is changed by material and geometric shape of welded structure. Therefore, the simulation model that could exactly analyze the release of residual stress by mechanical loading is to be necessary. This simulation model should be established on the based of variable and accurate measurement data. In this study, the non-linear behavior of weldments under external loading and unloading, such as the decrease and increase of structure stiffness, was investigated by monitoring of nominal stress and strain. Tensile loading and unloading test under variable load was performed and the proper degree of stress relaxation was measured by sectioning technique using strain gauge.

• Korean Journal of Child Studies
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• v.33 no.2
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• pp.111-127
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• 2012

This study compared a number of related variables according to children's stress types using the data mining method. The sample population was taken from the Korean Youth Panel Survey (KYPS) data (2688, sixth-grade elementary students). The results of the decision tree model revealed that : (1) Parental expectations in terms of study, life satisfaction, self-esteem, parental attachment, aggression, the spousal relationship, other cognition (one's own misdeeds), and study related worries were all related to parent stress. (2) Life satisfaction, study related worries, admitting one's own misdeeds, gender, other cognition (one's own misdeeds), aggression, the spousal relationship, and a sense of alienation in the school were all related to appearance stress. (3) Study related worries, parental expectations in terms of study, aggression, life satisfaction, self-esteem, parental attachment, satisfying parental expectations, parental attachment, and teacher attachment were all related to academic stress. (4) A sense of alienation in the school, mixing with peers in the school, aggression, self-esteem, other cognition (one's own misdeeds), study related worries, parental abuse, and life satisfaction were all significantly related to friend stress. These results suggested that children's diverse conditions should be considered according to the stress types if we are to understand and cope with these stress types more efficiently.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.390-398
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• 2001

Welding process generates distortion and residual stress in the weldment due to rapid heating and cooling. Welding distortion and residual stress in the welded structure result in many troubles such as dimensional inaccuracies in assembling and safety problem during service. The accurate prediction of welding residual stress is thus very important to improve the quality of weldment and find the way to reduce itself. This paper suggests new analysis method to predict welding residual stress by considering solid phase transformation during welding process. Using the method, analysis is performed for medium and low carbon steel. The analysis result for medium carbon steel reveals that case considering phase transformation has compressive residual stress in contrast with the case neglecting phase transformation because of martensite formation. However, for the case of low carbon steel, residual stress shows little difference between the case considering phase transformation and the other case, because it has small transformation strain and recovers rapidly stress after phase transformation.

• Journal of Korean Academy of Nursing
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• v.34 no.2
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• pp.213-224
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• 2004

Purpose: This study was aimed to evaluate the effect of progressive muscle relaxation training using biofeedback on perceived stress, stress response, immune response and climacteric symptoms, Method: This was a crossover, pre-post test design, The study subjects are 36 middle-aged women who were selected at 2 public health centers, The independent variable was Biofeedback training for 4 weeks, twice a week and home training for 4 weeks, Dependent variables were perceived stress, stress response, immune response, and climacteric symptoms measured with Hildtch's scale (1996), Result: Progressive muscle relaxation training using biofeedback was not effective in reducing perceived stress, but it was shown to be effective in reducing physiological stress responses such as pulse rate and EMG, Though blood pressure and skin conductance were repeatedly down, and skin temperature slowly increased, there were no statistically significant differences. Progressive muscle relaxation training using biofeedback was not effective in reducing serum cortisol, enhancing immune responses, or decreasing climacteric symptoms. Conclusion: The findings point to a pressing need for further, well-controlled and designed research with consideration in selection of subjects and instruments, frequency of measurements, the sampling method, and intervention modalities.

• Journal of Welding and Joining
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• v.31 no.1
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• pp.51-57
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• 2013

Residual stress caused in the weldments with high restraint force are often observed during welding in the weldments of Inner and outdoor materials or radial tanks. The reason is that quantitative analysis about thermal stresses during laser welding is lacking for this weldments. To verify Finite Elements Method (FEM) theory, the temperature was measured with thermocouple in a real time in this paper. Also analysis of the thermal stress for welding condition is performed by Comsol program package on various welding condition in SCP1-S butt welding. The principal stress in laser welding process is seen through the width direction. Also, it was confirmed that a change in base metal by thermal expansion made the stress in width direction stronger. Base metal close to the weld bead as the process progresses to the tensile stress in the compressive stress was varied. It was shown that the change of stress was quantitative from the bead at a certain distance.

• International Journal of Korean Welding Society
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• v.2 no.1
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• pp.40-44
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• 2002

Residual stress by welding should be reduced because that decreases the reliability on strength of welded structure. The reason is that the total stiffness of structure decreases by non-linear behavior of weldment under external load. The release of residual stress by mechanical loading and unloading is often performed in the fabrication of box structure for steel bridge. The proper degree of loading and unloading is significant at release method of residual stress by mechanical loading because that degree is changed by material and geometric shape of welded structure. Therefore, the simulation model that could exactly analyze the release of residual stress by mechanical loading is to be necessary. This simulation model should be established on the based of variable and accurate measurement data. In this study, the non-linear behavior of weldments under external loading and unloading, such as the decrease and increase of structure stiffness, was investigated by monitoring of nominal stress and strain. Tensile loading and unloading test under variable load was performed and the proper degree of stress relaxation was measured by sectioning technique using strain gauge.

• Journal of Korean Academy of Nursing Administration
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• v.13 no.2
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• pp.184-190
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• 2007

Purpose: This study was undertaken in order to suggest self-leadership as a method for nurses to lower their job stress and enhance their job satisfaction. So the relations among self-leadership, job stress and job satisfaction were studied. Method: The subjects of study were 123 nurses who have been working in 2 general hospitals located in K city. The data were collected by Q & A and analyzed using descriptive statistics, Pearson's correlation coefficient, t-test, and ANOVA on SPSS Program. Result: Nurses got average 3.50, 2.64 and 3.12 points out of 5 in their self-leadership, job stress and job satisfaction respectively. The self-leadership was negatively correlated with job stress (r=-.429, p=<.001) while it is positively correlated with job satisfaction(r=.281, p=<.001). And job stress was negatively correlated with job satisfaction(r=-.574, p=<.001). Job stress had statistically significant differences according to age and marital status. Conclusion: In conclusion self-leadership is correlated with job stress and job satisfaction. It is recommend that hospital managers have to develop methods which enhance self-leadership of nurses.