• Journal of the Society of Naval Architects of Korea
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• v.41 no.6
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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.

• Korean Journal of Occupational Health Nursing
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• v.20 no.2
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• pp.105-112
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• 2011

Purpose: The purpose of this study was to investigate the effect of foot bath therapy on post-operation pain, stress, HRV of hand replantation patients. Methods: Quasi-experimental study design and non-equivalent control group pre & post test repeated measure design were employed for this experiment. 47 subjects were selected for this study. 25 subjects of experimental group participated in foot bath program had foot bath 11 times for 2 weeks; 22 subjects of control group didn't have foot bath. Pain was digitized numerically by using Visual Analogue Scale, stress was measured by stress perception questionnaire, and HRV was measured by using Cnopy9 (IEMBIO). Results: The collected data were analyzed by using SPSS 17.0 Win program. (1) The difference between experimental group and control group was shown statistically significant in aspect of pain (p<.05). (2) The difference between experimental group and control group was shown statistically significant in aspect of stress (p<.05). (3) The difference between experimental group and control group was not shown statistically significant in aspect of HRV (p>.05). Conclusion: Foot bath program was an effective intervention for pain loss and perception of stress reduction. But it wasn't effective for HRV.

• Journal of Korean Public Health Nursing
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• v.24 no.1
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• pp.105-114
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• 2010

Purpose: To investigate the effect of smoking cessation expectation and on the stress for subjects in smoking cessation clinic and effect of self-efficacy in the relationship between expectancy and stress, with the aim of establishing an effective management smoking cessation strategy. Methods: Current smokers (n=161) >30-years-of-age who were residents of G city completed a questionnaire. Results: Concerning the effect of self-efficacy and the expectancy on stress, they were significantly effective in first, second and third stage, and appeared 8.3% in first stage, 13.8% in third stage, showing self-efficacy has a controlling effect on stress. Conclusion: Smoking cessation expectancy and self-efficacy significantly influence stress, and must be taken into account in development of smoking-cessation strategies and programs.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.1
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• pp.62-69
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• 1986

Fatigue surface crack growth was studied in 7075-T651 aluminum alloy plates subjected largely to bending loads. The surface crack length and its depth were measurement by the unloading elastic compliance method. The surface crack growth rate dc/dN, on the surface and da/dN, in the depth direction were obtained by the secant method. The stress intensity factor range .DELTA.K was computed by means of Newman and Raju equation. The aspect ratio a/c was presented in form of a/c=0.815-0.853(a/T). The effect of the stress ratio on the stable surface crack growth rates under increasing .DELTA.T is larger in lower .DELTA.K, while the relation between dc/dN, da/dN and the effective stress intensity factor range .DELTA.K$_{eff}$ is weakly dependent on the stress ratio.o.

• Journal of the Society of Naval Architects of Korea
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• v.39 no.2
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• pp.61-68
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• 2002

From the viewpoint of linear fracture mechanics, the crack propagation behavior of two different structures having the same K-a relationship could be considered identical. In this study the stress distribution in an infinitely wide cracked plate with the same K-a relationship as in a real structure is defined as the equivalent stress distribution. Fatigue life of a real structural element can be predicted by applying the equivalent stress distribution to a simple structural element, and performing a fatigue crack propagation analysis. The K-a relationship for a structural member can be estimated by a finite element method or a simplified prediction method. The validity to obtain effective crack driving stresses by using the equivalent stress-distribution is examined.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.938-946
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• 1989

Using the CT specimen of carbon steel(SM45C), we estimated the fatigue crack propagation behavior in stable crack propagation range. Furthermore the fatigue crack propagation rate, Acoustic Emission(AE) count rate, and fractography characteristics were also compared among others. The following results were confirmed by experimental observation. Near-threshold stress intensity factor range(.DELTA. $K_{th}$) is influenced by stress ratio but not at the upper limit of stable crack propagation range. As stress intensity factor range(.DELTA.K) and(or) stress amplitude increase (s), both crack propagation rate(da/dN) and AE count rate(dn/dN) increase. Effective stress intensity factor range(.DELTA. $K_{off}$) determined from the crack closure point measurement by AE method is useful for the evaluation of fatigue crack propagation rate. Fractography in stable crack propagation range showed striation, and agreed with the crack propagation rate obtained either by experiment of by the results of microscopic measurements.s.

• Journal of Ocean Engineering and Technology
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• v.35 no.2
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• pp.161-171
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• 2021

For the fatigue design of offshore structures, it is essential to understand and use the S-N curves specified in various industry standards and codes. This study compared the characteristics of the S-N curves for five major codes. The codes reviewed in this paper were DNV Classification Rules (DNV GL, 2016), ABS Classification Rules (ABS, 2003), British Standards (BSI, 2015), International Welding Association Standards (IIW, 2008), and European Standards (BSI, 2005). Types of stress, such as nominal stress, hot-spot stress, and effective notch stress, were analyzed according to the code. The basic shape of the S-N curve for each code was analyzed. A review of the survival probability of the basic design S-N curve for each code was performed. Finally, the impact on the conservatism of the design was analyzed by comparing the S-N curves of three grades D, E, and F by the five codes. The results presented in this paper are considered to be a good guideline for the fatigue design of offshore structures because the S-N curves of the five most-used codes were analyzed in depth.

• 한국초등상담교육학회:학술대회논문집
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• 2004.01a
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• pp.137-168
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• 2004

The purpose of this study is to find the effect of group counseling program based on reality therapy that is developed by researcher and to investigate whether the program can decrease the academic stress of elementary school students. For this study, firstly a framework for academic stress decrease programs is established and a program is developed in accordance with the framework. Secondly, in order to verify the effect of the program, both quantitative and qualitative methods were applied to 6th grade students through a academic stress test. Experimental group and control group is composed of 18 students, each. During a two month-experimental period, group counseling program based on reality therapy was implemented to the experimental group for 10 sessions but not to the control group. The program included nicknaming, recreation activities to promote friendliness among participants and other various activities to decrease the academic stress. The results of the quantitative and statistical research are as follows: First, group counseling program based on reality therapy is effective to decrease of elementary school students' academic stress. Second, sub factor(such as perceptions of academic stress cause, symptoms of academic stress)of academic stress is significantly decreased in experimental group. But no significant difference is found in control group. Third, for some sub factor(career, friend-relationship, house-environment, behavior-symptom), an independent-sample test and a paired-sample test showed different results: the paired-sample test showed no significant differences in experimental group while the independent-sample test showed significant decrease of academic stress. The results of the qualitative research based on student commentaries on the program is as follows: First, experimental group students report that the program based on reality therapy was effective to decrease of academic stress. Second, experimental group students' commentaries shows that students could remember the WDEP, 'act' factor and acquire the solution of academic stress. Third, for a group counseling, students reported the interest about positive feedback, searching on themselves, growth of human-relationship. This means that the program developed on this study is suitable for group counseling program. In conclusion, this study proves that group counseling program based on reality therapy is effective to decrease of elementary school students' academic stress by increasing individual internal-control. Therefore, it is necessary that we should develop and apply similar program to elementary school students in other to decrease students' academic stress. school students in other to decrease students' academic stress.

• Restorative Dentistry and Endodontics
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• v.25 no.3
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• pp.321-337
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• 2000

Dental caries, one of the most frequent dental disease, become larger because it can be thought as a simple disease. Further more, it can progress to unexpected root canal therapy with fabrication of crown that needs reduction of tooth structure. Base is required in a large caries and ZOE, ZPC, glass ionomer are used frequently as base material. They, with restorative material, can affect the longevity of the restoration. In this study, we assume that the mandibular 1st molar has deep class I cavity. So, installing the 3 base material, 3 kinds of fillings were restored over the base as follows; 1) amalgam only, 2) amalgam with ZPC, 3) amalgam with ZOE, 4) amalgam with GI cement, 5) gold inlay with ZPC, 6) gold inlay with GI cement, 7) composite resin only, 8) composite resin with GI cement. After develop the 3-dimensional model for finite element analysis, we observe the distribution of stress and temperature with force of 500N to apical direction at 3 point on occlusal surface and temperature of 55 degree, 15 degree on entire surface. The analyzed results were as follow : 1. Principal stress produced at the interface of base, dentin, cavity wall was smallest in case of using GI cement as base material under the amalgam. 2. Principal stress produced at the interface of base, dentin, cavity wall was smaller in case of using GI cement as a base material than ZPC under gold inlay. 3. Composite resin-filled tooth showed stress distributed over entire tooth structure. In other words, there was little concentration of stress. 4. ZOE was the most effective base material against hot stimuli under the amalgam and GI cement was the next. In case of gold inlay, GI cement was more effective than ZPC. 5. Composite resin has the small coefficient of thermal conductivity. So, composite resin filling is the most effective insulating material.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.2 s.245
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• pp.120-127
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• 2006

The fatigue behavior of LIPCA was so sensitive to the manufacturing condition, the environmental factors and the change of the test apparatus. Therefore, we could be considering not only the relationship between the stroke range $({\Delta}h)$ and actuating frequency but also the relationship between the stroke range $({\Delta}h)$ and the total effective moment $(M^E)$. Thus, this study proposed the calculation method of the applying $M^E$ when the $({\Delta}h)$ of LIPCA was increased from 1.mm to 20mm. To estimate the relationship between the total effective moment $(M^E)$ and the Bernoulli-Euler bending moment (M) was reviewed. And the residual stress distribution of LIPCA and THUNDER using the CLT was evaluated. In conclusions, converting the $({\Delta}h)$ of LIPCA to the radius of curvature (p) and calculating the $(M^E)$, it was found that the p by the $M^E$ changed similarly as the $({\Delta}h)$. It was found that the $M^E$ was 2.2 times as the M. While CFRP and PZT of LIPCA, which had the superior compressive characteristic, had the compressive residual stress, GFRP was subject to the tensile residual stress. Since this reversed configuration between the compressive residuals stress and the tensile one was made, the requirement of the stroke range $({\Delta}h)$ increase was satisfied.