• 열처리공학회지
• /
• 제36권2호
• /
• pp.77-85
• /
• 2023

In this study, the mechanical properties of the Al-Mg-X (X=Cr, Si) alloy, which clearly showed the influence of the specimen and grain size, were investigated by changing the specimen size extensively. In addition, the effect on the specimen size, grain size and aging condition on the mechanical properties of the grain refining alloy according to the addition of Cr was clarified, and the relationship between these factors was studied. As the specimen size decreased, the yield stress decreased and the fracture elongation increased. This change was evident in alloys with coarse grain sizes. Through FEM analysis, it was confirmed that the plastic deformation was localized in the parallel part of specimen S2. Therefore, when designing a tensile specimen of plate material, the W/L balance should be considered along with the radius of curvature of the shoulder. In the case of under-aged materials of alloys with coarse grain size, the fracture pattern changed from intergranular fracture to transgranular fracture as W/d decreased, and δ increased. This is due to the decrease in the binding force between grains due to the decrease in W. In the specimen with W/d > 40 or more, intergranular fracture occurred, and local elongation did not appear. Under-aged materials of alloys with fine grain size always had transgranular fracture over a wide range of W/d = 70~400. As W/d decreased, δ increased, but the change was not as large as that of alloys with coarse grain sizes. Compared to the under-aged material, the peak-aged material did not show significant dependence on the specimen size of σ_0.2 and δ.

• International Journal of Advanced Culture Technology
• /
• 제3권1호
• /
• pp.46-51
• /
• 2015

The mechanical and electrical properties of aluminium alloy 6061 are reported in this present work. Aluminium alloys were homogenized at $550^{\circ}C$, for 5 hours and cooled in the furnace. The different thickness reductions of 60-90% on homogenized aluminium alloy plates were achieved by cryo-rolling. Later, the as rolled samples were aged by solution treatment at the temperatures of $520^{\circ}C$ for 1 hour, water quenched; subsequently aged at $160^{\circ}C$ for 8-24 hours and partial aged (not solution treatment) at $160^{\circ}C$ for 8- 24 hours. Mechanical and electrical properties of samples were investigated. The experimental result showed that the microhardness of cryo-rolled samples were increase with increasing the percentage of the thickness reduction. Moreover, the microhardness of cryo-rolled, aged by solution treatment samples were higher than those of the cryo-rolled and cryo-rolled, partial aged samples. The cryo-rolled alloys subjected to full aged at $160^{\circ}C$ for 24 hours exhibited the hardness of 125 HV and electrical conductivity values was 45.76 %IACS and the cryo-rolled alloys subjected to partial aged at $160^{\circ}C$ for 20 hours exhibited the hardness of 67 HV and electrical conductivity values was 49.67 %IACS.

• 비파괴검사학회지
• /
• 제25권5호
• /
• pp.377-383
• /
• 2005

석유화학 및 정유설비는 고온이나 고압에서 폭발 위험성을 지닌 유체를 사용하기 때문에 방재기술에 관한 관심이 높다. 이들 설비 중에서도 고압반응기는 특히 고온/고압 하에서 사용되므로 안전성이 요구된다. 본 연구에서는 석유화학 플랜트의 고압반응기 소재로 많이 사용되고 있는 2.25Cr-1Mo강을 대상으로 하였으며, 3가지 온도조건에서 열화시간을 달리하여 총 8 종류의 인공열화 시험편을 준비하였다. 열화는 고압반응기의 사용온도인 $391^{\circ}C$보다 약간 높은 온도에서 둥온 열처리하였다. 미열화재를 포함하여 인공열화재에 대해 비커스경도값과 전기비저항값을 측정하였으며, Larson-Miller parameter와의 상관관계로부터 master curve를 작성하였다. 그리고 현장의 고압반응기에서 비커스경도와 전기비저항을 측정하여 실험실에서 작성한 master curve와 비교하였다. 전기비저항법을 이용한 고압반응기의 현장에서의 열화평가 가능성을 검토하였으며, 현장에서 측정한 전기비저항은 비슷한 열화수준에서의 인공열화재의 전기비저항값과 비슷하였다.

• Journal of Preventive Medicine and Public Health
• /
• 제39권1호
• /
• pp.46-52
• /
• 2006

Objectives: This study was performed to investigate the relationship between regional material deprivation and the standardized mortality ratios(SMRs) of community residents aged 15-64 in Korea. Methods: SMRs were investigated using the registered death data from 1995 to 2000 that was obtained from the Korean National Statistics Office with the denominators being drawn from the 1995 to 2000 census. Material deprivation was measured using the Townsend score that was calculated from the 1995 to 2000 census. The relationship between the regional material deprivation and the SMRs of the community residents aged 15-64 was investigated by using ANOVA, Spearman's rank correlation analysis and Pearson's correlation analysis. The trends in mortality inequality were investigated using the concentration index. Results: On the ANOVA, the SMRs of the men and women residents in the least deprived areas were the smallest and those in the most deprived areas were the largest. Spearman's rank correlation analysis, Pearson's correlation analysis and the concentration index revealed that significant positive relationships exist between the regional material deprivation and the SMRs of the community residents aged 15-64. Conclusions: This study suggests that there are mortality inequalities among the communities in Korea and part of this difference is due to the material deprivation of the community. Strategies aimed at reducing mortality inequalities among the communities will be needed to address economic inequalities. Further studies are needed to explore the mechanisms of how the regional deprivation influences on health and how the other factors of the community influence on the health of the community residents.

• 한국의류산업학회지
• /
• 제15권4호
• /
• pp.583-595
• /
• 2013

In the women's clothing industry that targets middle aged-women, there is increased interest on middle-aged women and their appearance management and diet. It is believed that the body type of middle-aged women is becoming thinner. This study examines if middle-aged women body types have changed based on data from the $5^{th}$ and $6^{th}$ Size Korea that objectively analyzed the aspects of middle-aged women's body size change and the related fashion industry that recognize changes in middle-aged women body types by suggesting foundational data for clothing designs. According to research results, middle-aged women's body type shows an increase in items related to height and that measurement values related to obesity (such as weight and BMI index) tend to decrease. Height has increased and weight has decreased compared to the past. Most items related to width or depth tend to show decreased values and we can assume that the present middle-aged women's body type is changing more dynamically than before. It will be possible to design proper clothes for consumer body type and trends if we design clothes that afford multilateral attention to the patterns, design, or material in clothing design by applying the aspects of middle-aged women's body size and body type change.

• 한국전기전자재료학회논문지
• /
• 제31권6호
• /
• pp.372-376
• /
• 2018

The effects of off-state bias stress on the characteristics of p-type poly-Si TFT were investigated. To reduce the gate-induced drain leakage (GIDL) current, the off-state bias stress was changed by varying Vgs and Vds. After application of the off-state bias stress, the Vgs causing GIDL current was dramatically increased from 1 to 10 V, and thus, the Vgs margin to turn off the TFT was improved. The on-current and subthreshold swing in the aged TFT was maintained. We performed a technology computer-aided design (TCAD) simulation to describe the aged characteristics. The aged-transfer characteristics were well described by the local charge trapping. The activation energy of the GIDL current was measured for the pristine and aged characteristics. The reduced GIDL current was mainly a thermionic field-emission current.

• 대한조선학회논문집
• /
• 제60권2호
• /
• pp.65-75
• /
• 2023

Ships operated at sea for a long time are subjected to various kinds of loads, which may cause various types of damage. Such damages will eventually reduce the strength of hull structures. Therefore, it is necessary to estimate and evaluate the residual strength and remaining fatigue life of aging ships in order to secure structural safety, establish a reasonable maintenance plan, and make a judgment of life extension. For this purpose, the corrosion damage and local denting damage should be measured, fatigue damage estimation should be performed, and material properties of aged steel should be identified. For this study, in order to investigate the mechanical properties of aged steel, steel plates were obtained from a naval ship that reached the end of her life span. The specimens were manufactured from the obtained steel plates, and static and dynamic tensile tests, fatigue tests, and metallographic tests were performed. The mechanical properties obtained from the aged steel plates were compared with those of new steel plates to quantify the aging effect on the mechanical properties of marine steel materials.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1997년도 가을 학술발표회 논문집
• /
• pp.621-626
• /
• 1997

Recently, TYFO glassfibers have been used for strengthening n aged RC bridge slabs because of low material cost and easy repairing work. The purpose of this study is to experimentally and analytically investigate the effect of TYFO glassfibers for enhancing the capacity of aged RC bridge slabs. Tes result shows that yield and ultimate strength of RC slabs with TYFO are increased as 11~18% and 25~35% comparing with those for RC slabs without TYFO, respectively, Also, ductility of RC slabs strengthened with TYFO have been significantly increased. Further tests have been performing on aged RC bridge slabs strengthened with carbon fiber strips.

• Safety and Health at Work
• /
• 제9권2호
• /
• pp.184-191
• /
• 2018

Background: Due to an increasing number of workers aged 50 years and above, the number of those employed is also on the rise, and those workers aged 50 and over has exceeded 50% of the total fatal occupational injuries. Therefore, it is necessary to implement the selection and concentration by identifying the characteristics of high-risk groups necessary for an effective prevention against and reduction of fatal occupational injuries. Methods: This study analyzed the characteristics of high-risk groups and the occupational injury fatality rate per 10,000 workers among the workers aged 50 and over through a multi-dimensional analysis by sex, employment status of workers, industry and occupation by targeting 4,079 persons who died in fatal occupational injuries from January 2007 to December 12. Results: The share of the workers aged 50 years and above is increasing every year in the total fatal occupational injuries occurrence, and the high-risk groups include 'male workers' by sex, 'daily workers' by worker's status, 'craft and related-trades workers' by occupation, and 'mining' by industry. Conclusion: The most frequent causal objects of fatal occupational injuries of the workers aged 50 years and above are found out to be 'installment and dismantlement of temporary equipment and material on work platforms including scaffold' in the construction industry and 'mobile crane, conveyor belt and fork lifts' in the manufacturing industry.

• 지역사회간호학회지
• /
• 제20권1호
• /
• pp.49-58
• /
• 2009

Purpose: Purpose: The purpose of this study was to explore the yangsaeng level in a health management way of an aged women in rural area, and to offer basic material for the development of community's public health service. Methods: The subjects were 144 aged women who participated voluntarily in the questionnaire. The data were collected from January to February, 2008 with a self-administered questionnaire. Data were analyzed by SPSS 13.0 win program for finding frequency, percentage, mean, standard deviation, ANOVA and Tukey. Results: The average age of workers was 72. Total yangsaeng level was $3.08{\pm}.33$, highest yangsaeng factor was Activity & Rest Yangsaeng of $3.55{\pm}.46$ and lowest yangsaeng factor was Season Yangsaeng of $2.43{\pm}.75$. The total Yangsaeng level was the significant difference in monthly incomes(F=4.046, p=.047). Conclusion: Considering the results above, the yangsaeng level of aged women is affected by the age, education level, a monthly income etc. Therefore, for health promotion plan of aged women, consider that their age, educational level, economic level ect, and systematic education for promotion of health is necessary.