• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.10
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• pp.2475-2482
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• 1993

The effects of the hole size(2R) and the specimen width(W) on the fatigue strength and the fatigue life in plain woven glass/epoxy composite plates are experimentally investigated under constant amplitude tensile fatigue loading. It is shown in this study that the notch sensitivity under fatigue loading is lower than that under static loading. It can be explained by the fact that the stress concentration is relaxed by the damage developed at the boundary of circular hole. To predict the fatigue strength at a specific cycle, the modified point stress criterion represented as a function of the geometry of the specimen(2R and W) is applied. It is found that the model used in the prediction of the notched tensile strength predicts the fatigue strength with reasonable accuracy. A model for predicting the fatigue life in the notched specimen, based on the S-$N_f$, curve in the smooth specimen, is suggested.

• Korean Journal of Social Welfare Studies
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• v.45 no.2
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• pp.375-402
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• 2014

The purpose of this study is to investigate the longitudinal change pattern of life satisfaction and the effect of social capital of people with disabilities. For this study, data were drawn from the panel data employment for the disabled from the second to the fifth. It includes 3,206 person with disabilities. The methodology adopted in this study is the latent growth curve modeling. The findings of this study are as follows: First, Life satisfaction has been decreased over years and the difference between individuals of life satisfaction of people with disabilities were statistically significant. Second, The intercept of life satisfaction in the disabled was positively associated with network, and slope of life satisfaction was negatively related to network. Third, social participation positively influences the intercept of life satisfaction but, no significant affect to the slope. Based on results of the study, practical implication and the political-approach to interventions for the better life satisfaction of the disabled are being discussed.

• East Asian mathematical journal
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• v.30 no.2
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• pp.149-172
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• 2014

The problems of optimization addressed in the high school curriculum are usually posed in real-life contexts. However, because of the instructional purposes, problems are artificially constructed to suit computation, rather than to reflect real-life problems. Those problems have thus limited use for teaching 'practicalities', which is one of the goals of mathematics education. This study, by utilizing 'GeoGebra', suggests the optimization problem solving related to the quadratic curve, using the contour-line method which contemplates the quadratic curve changes successively. By considering more realistic situations to supplement the limit which deals only with numerical and algebraic approach, this attempt will help students to be aware of the usefulness of mathematics, and to develop interests in mathematics, as well as foster students' integrated thinking abilities across units. And this allows students to experience a variety of math.

• Journal of Welding and Joining
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• v.33 no.6
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• pp.49-54
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• 2015

Welding process is of importance to assemble products or structures, but also the process is structural weakness due to stress concentration in welding joint. The fatigue design of welded joint requires time & labor consuming fatigue test because the fatigue life is various according to the depth of joint, joint type and load type etc. In fatigue design codes, they guide to classify welding joints with their shape( BS7608, IIW Documents) and provide fatigue assessment information. In terms of numerical method for fatigue analysis, it is also difficult to decide the stress peak in joint because of mesh sensitivity which means that stress value is varies with element type or size on stress concentration zone. Hot-spot method is used generally, but Battelle of United States proposed Master S-N Curve based on structural stresses converted by mechanical equilibrium theory. In this research, we extracted master S-N curve from Battelle's fatigue test DB including test data of various welding joints to apply on Non-Load-Carrying cruciform Joint. Comparing fatigue results between the case of using normal stress and case of structural stress cor the cruciform Joint, The suggested Battelle method showed successive results.

• Korea journal of population studies
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• v.6 no.1
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• pp.43-69
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• 1983

This study was conducted to make the life tables from specific causes of death in Korea. Both "Life tables of Korea in l978-79" and "the statistics on causes of death statistics in 1980" issued by Economic Planning Board were used as source of data for this study. Among the 58, 187 death certificates reported to the concerned authorities, 39, 801 causes were drawn for the purpose of this study. As a result, it is revealed that two thirds of men in Korea died from these 10 major causes of death. The summarized results are as follows: 1. According to recent statistics, 10 major causes of death in 1980 were shown in the order of 1) malignant neoplasms, 2) cerebrovascular disease, 3) accidents and adverse effects, 4)hypertensive disease, 5) ischaemic heart disease and heart attack, 6) chronic liver disease and cirrhosis, 7) tuberculosis, 8) pneumonia, bronchitis, emphysema and asthma, 9) suicide, 10) diabetes mellitis. 2. The major causes of death in Korea were very similar to those of developed countries such as West Germany, Denmark and Japan. This means that our pattern of death causes is almost approaching to that of developed countries. 3. Our crude death rate in 1980 was on the line of 6.6 per 1, 000 people. This is very low level, compared with 12.1 in West Germany and 10.0 in Denmark, however, our age sepcific death rate was on the verge of doubled level in each age category as to that of West Germany, Denmark and Japan. The fact tells us that our death rate is very high yet, especially in young and prime adult age, and the proportion of the aged is quite low. 4. Average ages of people died from malignant neoplasms, cerebro vascular diseases and hypertensive diseases were 63.1, 66.6, 67.3 respectively, however, that of accidents and adverse effect was only 42.5. This shows that accidents occur indifferently from age. 5. In the curve of eventual death probability, the curve of malignant neoplasms was the highest of all curves before 60 in age. However, the probability curve of eventually dying from accidents and adverse effects tends to decline with age. 6. In this study five life tables from major causes of death (four leading causes of death and of tuberculosis) were constructed for 1979. These life tables are reflecting accurately the effects of age distribution on the specific cause of death. In the surviving curje of these tables we can see that the curve of accidents is adversely related to age. While curves of neoplasms, hypertension and tuberculosis are not diminishing before 40 in age, they are going sharply downward after 50 in age.ard after 50 in age.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.39-40
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• 2006

• Journal of the korean Society of Automotive Engineers
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• v.12 no.6
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• pp.11-17
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• 1990

자동차용 변속기의 설계에 있어서 적용 Engine의 출력 및 차량 성능에 부합하는 동력전달 요소의 전달 용량 및 내구 수명을 고려해야 한다. 특히 자동차가 고속 경량화됨에 따라 변속기의 설계에 있어서도 동력전달 요소들의 소형 고용량화가 요구되며 이를 위해서는 설계시 동력전달 요소들의 정확한 강도 및 피로수명 예측이 필수적이다. 본 보고서에서는 Gear의 굽힘응력 계산식에 대한 고찰 및 Gear의 피로시험을 통하여 Helical 치차의 Bending stress에 대한 피로수명 곡선의 시험식을 도출하였다.

• Journal of Aerospace System Engineering
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• v.17 no.2
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• pp.62-70
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• 2023

We proposed a technique for predicting Stress-Life (S-N) curve or fatigue life using geometric features of a ply-overlap joint structure in which plies of two composite materials are partially or wholly laminated and bonded. Geometric features that could affect fatigue properties of a structure were selected as variables. By analyzing relationships between geometric variables and material constants of the Epaarachchi-Clausen model, a fatigue model for composites, relational expressions of these two factors were proposed. To verify the prediction accuracy of the proposed method, fatigue life of a CFRP/GFRP ply-overlap joint was predicted. Predicted life and life obtained by test data-based model were compared to actual life. High prediction accuracy was confirmed by calculating the coefficient of determination of the predicted S-N curve.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.479-487
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• 2007

Die life is generally estimated taking failure life and wear amount into consideration. In this study, the forging die life was investigated considering both of these two factors. The fatigue life prediction for the die was performed using the stress-life method, i.e. Goodman's and Gerber's equations. The Archard's wear model was used in the wear life simulation. These die life prediction techniques were applied to the die used in the forging process of the socket ball joint of a transportation system. A rigid-plastic finite element analysis for the die forging process of the socket ball was carried out and also the elastic stress analysis for the die set was performed in order to get basic data for the die fatigue life prediction. The wear volume of the die was measured using a 3-dimensional measurement apparatus. The simulation results were relatively in good agreement with the experimental measurements.

• Transactions of the Korean Society of Mechanical Engineers
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• v.7 no.1
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• pp.28-35
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• 1983

Quantitative analysis have been carried out on the micro-cracks on the surface and into the depth of unnotched smooth mild steel specimen under cyclic stains by rotating bending fatigue tests. Some of the results are; (1) Cracks initiate at the early stage of fatigue life N$_{I}$/ N$_{f}$=10 to 20%, and propagate during the rest of fatigue life. (2) Coalescence of highly crowded small fatigue cracks of random distribution seems to induce the final fracture at higher stress level. (3) The curves of crack initiation and the equal crack length on the graph of stress versus number of cycles are parallel to the S-N curve. (3) The curves of crack initiation and the equal crack length on the graph of stress versus number of cycles are parallel to the S-N curve. (4) The distributions of micro-surface crack length and depth show the composite Weibull distributions which are approximated to two straight lines separated by the value of transient region between stage I and stage II crack.k.k.