• Korean Journal of Metals and Materials
• /
• v.48 no.10
• /
• pp.957-963
• /
• 2010

The aging behavior of aluminum borate whisker ($Al_{18}B_4O_{33}$) reinforced AS52+Sr magnesium matrix composites was investigated with Vickers hardness measurements, bending tests, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Experimental results showed that aging is accelerated in the $AS52+Sr/Al_{18}B_4O_{33}$ composite compared with an unreinforced AS52+Sr alloy. The hardness of the alloy and composite increases monotonically as a function of the aging time before reaching its peak hardness and then gradually decreases. The composite reaches its peak hardness in 10 h, whereas the matrix alloy requires 30h, indicating accelerated age-hardening in the $AS52+Sr/Al_{18}B_4O_{33}$ composite compared with the unreinforced AS52+Sr alloy at $170^{\circ}C$. The interfacial reaction of $AS52+Sr/Al_{18}B_4O_{33}$ magnesium matrix composite is considered to play a dominant role in the strengthening mechanism, ultimately affecting the mechanical properties of the composite.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.32 no.1
• /
• pp.6-12
• /
• 2019

Bonding properties of epoxy-containing solder joints were investigated by a high temperature aging test. Specimens were prepared by bonding an R3216 standard chip resistor to an OSP-finished PCB by a reflow process with two basic types of solder (SAC305 & Sn58Bi) pastes and two epoxy-solder (SAC305+epoxy & Sn58Bi+epoxy) pastes. In all epoxy solder joints, an epoxy fillet was formed in the hardened epoxy, lying around the outer edge of the solder joint, between the chip and the Cu pad. In order to analyze the bonding characteristics of solder joints at high temperatures, a high-temperature aging test at $150^{\circ}C$ was carried out for 14 days (336 h). After aging, the intermetallic compound $Cu_6Sn_5$ was found to have formed in the solder joint on the Cu pad, and the shear stress on the conventional solder joint was reduced by a significant amount. The reason that the shear force did not decrease much, even though in epoxy solder, was thatbecause epoxy hardened at the outer edge of the supported solder joints. Using epoxy solder, strong bonding behavior can be ensured due to this resistance to shear force, even in metallurgical changes such as those where intermetallic compounds form at solder joints.

• Korean Journal of Metals and Materials
• /
• v.47 no.3
• /
• pp.175-181
• /
• 2009

Mechanical properties and precipitation behavior of backward extruded 6061 Al alloy for pressure vessel were investigated using tensile test, transmission electron microscopy (TEM) and differential scanning calorimeter (DSC). In this study, solution heat treatment (SHT) was performed at $535^{\circ}C$ for 30~90 min and aging treatment was conducted at 177 and $190^{\circ}C$ for 1~7 h. Maximum tensile strength of $36.6kgf/mm^2$ and yield strength of $33.29kgf/mm^2$ were achieved at the aging time of 5 h at $190^{\circ}C$. TEM observation showed that fine needle-like ${\beta}^{{\prime}{\prime}}$ phase which has 35~45 nm of length was uniformly distributed in the aged 6061 Al alloy specimen. From tensile test, TEM and DSC analysis, it is expected that aging time of 2~5 h at $190^{\circ}C$ is suitable for the extruded A6061 used as pressure vessels.

• Journal of Home Health Care Nursing
• /
• v.19 no.2
• /
• pp.112-118
• /
• 2012

Purpose: This study was examined to identify the correlation health-promoting behavior, self-esteem, and life satisfaction of the elderly. Method: The subjects consisted of 115 elderly. The data collected from Oct to Dec 2011 were analyzed using descriptive statistics, t-test, ANOVA, and Pearson correlation coefficients. Result: The mean scores of health-promoting behavior ($2.33{\pm}.34$), self-esteem ($2.87{\pm}.58$), and life satisfaction ($2.98{\pm}.44$) of elderly were the average. Health-promoting behavior was significantly different according to age, educational level, religion, spouse, living arrangement, economic status, and join groups. Self-esteem was significantly different according to religion, economic status, and join groups. Life satisfaction was significantly different according to age, economic status, and join groups. Significant correlations were found between health-promoting behavior, self-esteem, and life satisfaction. Conclusion: These findings indicate that health-promoting behavior, self-esteem, and life satisfaction may be necessities to pursue successful aging of elderly. In addition, above mentioned results will be reflected in improving the quality of life programs.

• Knowledge Management Research
• /
• v.21 no.2
• /
• pp.77-100
• /
• 2020

This study conducted a qualitative study on 23 seniors over 55 years old to understand the digital behavior of seniors in the online education acceptance environment. Grounded Theory methodology was applied to the initial enrollment behavior, login behavior, and utilization behavior of online education program. Through the process of open coding, axis coding, and selective coding, the framework in the online education environment of the senior generation was finally derived. As a causal conditions for the senior generation to participate in the online education environment, goal orientation, relationship orientation, leisure orientation and external compulsory were derived, and shadow work appeared as the central phenomenon. Also, contextual conditions resulted in social change, physical and cognitive aging, and psychological atrophy. The intervening conditions included digital device acceptance, educational attitudes, environmental factors, and self-efficacy. Based on this, the action/interactions strategy formed a positive and negative attitude toward shadow work. As a result, positive response behavior, compromising behavior, and shadow work avoidance behavior were shown. It is hoped that this study will be reflected in future researches for the use of digital devices of the elderly and the expansion of online education participation and government policy.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.38 no.5
• /
• pp.705-717
• /
• 2014

The interest and importance of appearance can be expanded by changes in social awareness about appearance, the extension of life expectancy, and the development of science, technology and technology and medicine. Especially, down-aging syndrome through a variety of mediums, amplifies consumer's interest in youth-pursing. This study discusses the relationship of youth-pursuing, appearance concern and appearance management behavior focused on the middle-aged. Data were collected from 300 females aged 40-65 in the areas of Seoul, Daejeon and Chungbuk areas. The data were analyzed by descriptive statistics, factor analysis, regression analysis, using the SPSS-WIN 20.0 program. Youth-pursuing formed social, psychological, and appearance factors. Each of these three dimensions influenced the appearance concern; consequently, appearance had the highest influence. Only appearance influenced appearance management behavior in the regression analysis of youth-pursuing and appearance management behavior. Appearance concern affected significantly appearance in the management behavior of the dimension regression analysis results for the appearance concern and appearance management behavior.

• Journal of Powder Materials
• /
• v.16 no.4
• /
• pp.275-279
• /
• 2009

The aging characteristics of gas atomized Mg-6 wt.% Al-1 wt.% Zn alloy were investigated and compared to those of cast Mg-6 wt.% Al alloy. The gas atomized Mg-6 wt.% Al-1wt.% Zn alloy powders had spherical morphology between 1 and 100 $\mu m$ in diameter. After compaction under the pressure of 700 MPa at $320^{\circ}C$ for 10 min, the Mg-6 wt.% Al-1 wt.% Zn alloy showed a grain size of approximately 40 $\mu m$ which is smaller than that of the cast Mg-6 wt.% Al alloy, and a relative compact density of approximately 93%. After ageing, the Mg-6 wt.% Al-1 wt.% Zn alloy showed much faster peak hardness than cast Mg-6 wt.% Al alloy. The Mg-6 wt.% Al-1 wt.% Zn alloy showed the new fine precipitations with ageing time, while the cast Mg-6 wt.% Al alloy was almost similar morphology.

• Architectural research
• /
• v.9 no.2
• /
• pp.1-9
• /
• 2007

As aging is notably developed, the elderly find it challenging to get around in housing chosen in their midlife, and seek for an alternative residential setting enabling them to continue the independent living. This research focuses on the residential mobility of the elderly who have recently moved to senior housing, and also is to investigate their residential satisfaction at previous residence. As a cross-sectional study, the research adopts the self-administered questionnaire survey. The questionnaires are mailed out, and one out of the two responses is retrieved. To investigate the residential mobility of the elderly, the research model is constructed based upon Morris and Winter's Housing Adjustment Theory. The result shows that the residential mobility of elderly from previous residence is a need-based choice, want-driven behavior and demand-oriented decision to maintain continued independence and utilize resources available during the aging process. Also, it is found that the vast majority of both co-op and rental households are satisfied with their previous residential environment. The previous residential satisfaction of co-op elderly is significantly influenced by household and housing characteristics, housing norm status, and environmental needs for independent living while only housing norm status is a significant predictor to explain the previous residential satisfaction of rental elderly.

• Journal of Korea Foundry Society
• /
• v.37 no.1
• /
• pp.14-20
• /
• 2017

The microstructure, electrical conductivity and hardness variation of an AZ91-5wt%Sn Mg alloy sample during a solid-solution and aging heat treatment were instigated by optical microscopy, scanning electron microscopy, X-ray diffraction and by Rockwell hardness techniques in this study. The XRD result shows that the main phases in the as-casted alloy are ${\alpha}$-Mg, $Mg_{17}Al_{12}$ and $Mg_2Sn$. From the SEM images of the AZ91-5wt%Sn Mg alloy after the solution treatment, the $Mg_{17}Al_{12}$ phases in the alloy were found to have dissolved into the matrix with an increase in the holding time during the solution treatment, but $Mg_2Sn$ phases were clearly observable. The highest peak hardness of the AZ91-5wt%Sn Mg alloy is 82HRE at an aging temperature of $200^{\circ}C$.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
• /
• 2011.04a
• /
• pp.271-277
• /
• 2011

Hanji(Korean traditional paper) is made from bark of paper mulberry(Broussonetia kazinoki). For a long time, Hanji has been used in various fields, such as paintings, printing paper, as specialty paper. The utilization of Hanji will become more and more diverse. One of the characteristic properties of Hanji is a long life time comparing to western paper. The mucilage which must be used in Hanji manufacturing should effect the conservation properties of Hanji. The effectiveness of the mucilage in aging of Hanji was evaluated in this paper. Strength properties of thermal aged Hanji made with synthetic mucilage decreased more slowly than those of Hanji made with natural mucilage. As prolonged aging time, all Hanji made mucilage increased oxidation index. But, Hanji made with PAM was most stable in oxidation of cellulose.