• Health Policy and Management
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• v.21 no.4
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• pp.511-526
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• 2011

This study aims at surveying how Koreans look upon and prepare for the age of longevity("age of 100 years") drawing near at hand, analyzing factors affecting such a perception and behavior. To this end, a telephone survey was launched for 1200 persons sampled to evenly comprise the young, middle-aged, and elderly groups. Our findings indicate that more Koreans looked upon the upcoming "age of 100 years" as a 'disaster' rather than a 'blessing.' The sense of combined uneasiness over the aged life being further elongated while they are unprepared for it, anxiety over maintaining health and so forth came into play. However, the better a person is prepared by way of health management, savings for retirement, preparation for leisure activities and employment for the later life, the more positively he or she looked upon the "age of 100 years". An analysis by group indicates that women rather than men, the elderly rather than the young, the less educated rather than the highly educated, the low-income bracket rather than the high-income bracket looked upon the "age of 100 years" more negatively. Under such circumstances, it is suggested that the nation's social system tailored to a life expectancy of 80 years should be readjusted, tailored to a 'longevity paradigm' and that to this end social systems should be reoriented toward the direction where 'healthy aging' and 'active aging' are fully supported.

• Journal of the Korean Society for Heat Treatment
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• v.22 no.6
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• pp.345-353
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• 2009

The precipitates of $L2_1$-type $Ni_2AlHf$ phase in B2-ordered NiAl system has been observed by using transmission electron microscope (TEM). The hardness of as-quenched NiAl-Hf alloys is high due to the larger strengthening. However, age hardening of this alloy is not main effect to increase hardness compared to the large microstructural variations during aging. At the beginning of aging, the $L2_1$-type $Ni_2AlHf$ precipitates keep a lattice coherency with the NiAl matrix. The orientation relationship between the $Ni_2 AlHf$ precipitate and the NiAl matrix is <100>$_{Ni2AlHf}$//<100>$_{NiAl}$, {001}$_{Ni2AlHf}$//{001}$_{NiAl}$. By aging treatment for long time $Ni_2AlHf$ precipitates lost their coherency and change their morphology to the spherical ones surrounded by misfit dislocations. The orientation relationship between the NiAl matrix and the $Ni_2AlHf$ precipitates, however, has been kept even after longer aging time. The lattice misfit between the $Ni_2AlHf$ precipitate and the NiAl matrix has been calculated by the selected electron diffraction patterns, and the spacings of misfit dislocations is about 4.5% at 1173 K.

• Journal of Korea Association of Health Promotion
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• v.2 no.2
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• pp.187-197
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• 2004

Owing to continuous economic growth, an increased standard of living, and improvements to health care in Korea, the life expectancy of Koreans rose from 69.0 years in 1985 to 71.3years in 1990. It continued to rise throughout the 1990s, and, by 2002, had reached 76.5years for the general population and 80.0 years for Korean females. Similarly, the percentage of the Korean population that is 65 years of age or older increased from 3.1 in 1970 to 7.1in 2000, and is expected to reach approximately 14,0 in 2019. Thus, according to this estimate, Korea will have evolved from an "aging society" to an "aged society" in only 19years. In the case of other countries, this same transformation has generally taken 2 to 5times longer. One of the major issues related to Korea's rapidly aging population relates to the health problems of the elderly. According to the 2002 National Health Survey Report, 87,6 percent of the elderly were reported to Have at least one chronic disease. In other words, almost 9out of every 10 elderly persons in Korea were suffering from a chronic illness, This, clearly, places a significant economic burden on Korean society in the form of increased health care Costs. This paper examines the increasing prevalence of chronic diseases within Korea's rapidlv aging population and offers some possible short- and long-term solutions to cope with the increased burden being placed on Korea's health care system. These include the basic services at local health centers for the elderly and the national life-long health promotion programs that aim to correct unhealthy behavior, such as smoking, the excessive use of alcohol, and poor eating and exercise habits.

• Journal of Ocean Engineering and Technology
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• v.27 no.2
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• pp.75-79
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• 2013

This study was carried out to investigate the precipitation behavior of the ${\chi}$ phase and the impact toughness of 25%Cr-7%Ni-2%Mo-4%W super duplex stainless steel. The ${\chi}$ phase was precipitated in the early stage of aging, and with the increasing aging time. However, after reaching a maximum value, the number decreased as a result of the gradual transformation of the ${\chi}$ phase into the ${\sigma}$-phase. It was proved that the ${\chi}$ phase was an intermetallic compound, which represented a lower nickel concentration, higher chromium and molybdenum concentrations, and very higher tungsten concentration compared to the matrix phases. It also showed higher molybdenum and tungsten concentrations than the ${\sigma}$ phase. The decomposition of the ferrite phase into the ${\gamma}_2$ and ${\sigma}$ phases was retarded by W substitution for Mo. Thus, the number of ${\chi}$ phases increased. The impact value was decreased by the substitution of W for Mo. The impact toughness rapidly decreased with time when the ${\chi}$ phase began to precipitate in the initial stage of aging. The impact toughness was, therefore, greatly influenced for the precipitation of the ${\chi}$ phase.

• The Journal of Advanced Prosthodontics
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• v.8 no.1
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• pp.30-36
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• 2016

PURPOSE. The aim of this study was to evaluate the fracture resistance and fracture behavior of monolithic zirconia crowns in accordance with the preparation design and aging simulation method. MATERIALS AND METHODS. An upper first molar was prepared sequentially with three different preparation designs: shoulderless preparation, 0.4 mm chamfer and 0.8 mm chamfer preparation. For each preparation design, 30 monolithic zirconia crowns were fabricated. After cementation on Cr-Co alloy dies, the following artificial aging procedures were performed: (1) thermal cycling and mechanical loading (TCML): 5000 cycles of thermal cycling $5^{\circ}C-55^{\circ}C$ and chewing simulation (1,200,000 cycles, 50 N); (2) Low Temperature Degradation simulation (LTD): autoclave treatment at $137^{\circ}C$, 2 bar for 3 hours and chewing simulation; and (3) no pre-treatment (control group). After artificial aging, the crowns were loaded until fracture. RESULTS. The mean values of fracture resistance varied between 3414 N (LTD; 0.8 mm chamfer preparation) and 5712 N (control group; shoulderless preparation). Two-way ANOVA analysis showed a significantly higher fracture loads for the shoulderless preparation, whereas no difference was found between the chamfer preparations. In contrast to TCML, after LTD simulation the fracture strength of monolithic zirconia crowns decreased significantly. CONCLUSION. The monolithic crowns tested in this study showed generally high fracture load values. Preparation design and LTD simulation had a significant influence on the fracture strength of monolithic zirconia crowns.

• Nuclear Engineering and Technology
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• v.47 no.6
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• pp.712-718
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• 2015

Cast duplex stainless steels are susceptible to thermal aging during long-term service at temperatures ranging from $280^{\circ}C$ to $450^{\circ}C$. To analyze the effect of thermal aging on leak-before-break (LBB) behavior, three-dimensional finite element analysis models were built for circumferentially cracked pipes. Based on the elasticeplastic fracture mechanics theory, the detectable leakage crack length calculation and J-integral stability assessment diagram approach were carried out under different bending moments. The LBB curves and LBB assessment diagrams for unaged and thermally aged pipes were constructed. The results show that the detectable leakage crack length for thermally aged pipes increases with increasing bending moments, whereas the critical crack length decreases. The ligament instability line and critical crack length line for thermally aged pipes move downward and to the left, respectively, and unsafe LBB assessment results will be produced if thermal aging is not considered. If the applied bending moment is increased, the degree of safety decreases in the LBB assessment.

• Journal of Korea Foundry Society
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• v.22 no.2
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• pp.89-96
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• 2002

This study examined the effects of adding Zn to Sn-3.5Ag solder on the microstructure changes and behavior of interface reaction of the solder joint with Cu substrate. The solder/Cu joints were examined with microscope to observe the characteristics of microstructure changes and interfacial reaction layer with aging treatment for up to 120 days at $150^{\circ}C$. Results of the microstructure changes showed that the microstructures were coarsened with aging treatment, while adding 1%Zn suppresses coarsening microstructures. The Sn-3.5Ag/Cu had a fast growth rate of the reaction layer in comparison with the Sn-3.5Ag-1Zn at the aging temperature of $150^{\circ}C$. Through the SEM/EDS analysis of solder joint, it was proved that intermetallic layer was $Cu_6Sn_5$ phase and aged specimens showed that intermetallic layer grew in proportion to $t^{1/2}$, and the precipitate of $Ag_3Sn$ occur to both inner layer and interface of layer and solder. In case of Zn-containing composite solder, $Cu_6Sn_5$ phase formed at the side of substrate and Cu-Zn-Sn phase formed at the other side in double layer. It seems that Cu-Zn-Sn phase formed at solder side did a roll of banrier to suppress the growth of the $Cu_6Sn_5$ layer during the aging treatment.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.20 no.1
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• pp.56-65
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• 2024

Cast austenitic stainless steels (CASS) and austenitic stainless steel weldments with a ferrite-austenite duplex structure are widely used in nuclear power plants, incorporating ferrite phase to enhance strength, stress relief, and corrosion resistance. Thermal aging at 290-325℃ can induce embrittlement, primarily due to spinodal decomposition and G-phase precipitation in the ferrite phase. This study evaluates the effects of thermal aging by collecting and analyzing various mechanical properties, such as Charpy impact energy, ferrite microhardness, and tensile strength, from various literature sources. Different model expressions, including hyperbolic tangent and phase transformation equations, are applied to calculate activation energy (Q) of room-temperature impact energies, and the results are compared. Additionally, predictive models for Q based on material composition are evaluated, and the potential of machine learning techniques for improving prediction accuracy is explored. The study also examines the use of ferrite microhardness and tensile strength in calculating Q and assessing thermal embrittlement. The findings provide insights for developing advanced prediction models for the thermal embrittlement behavior of CASS and the weldments of austenitic steels, contributing to the safety and reliability of nuclear power plant components.

• Korean Journal of Materials Research
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• v.10 no.12
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• pp.793-798
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• 2000

The age-hardening behavior of unreinforced 6061 Al alloy and SiCp/6061 Al alloy composites reinforced with different size of SiC particle (average diameter ; 0.7$\mu\textrm{m}$ and 7.0$\mu\textrm{m}$) was investigated by hardness measurement, calorimetric technique and transmission electron microscopy. At 17$0^{\circ}C$ isothermal aging treatment, the peak aging time of 0.7$\mu\textrm{m}$SiCp/6061Al alloy composite and 7.0$\mu\textrm{m}$SiCp/6061Al alloy composite is shorter than that of unreinforced 6061Al alloy, and the aging of 7.0$\mu\textrm{m}$SiCp/6061Al alloy composite is accelerated more than that of 0.7$\mu\textrm{m}$SiCp/6061Al alloy composite. This acceleration is due to the increase of dislocation density by the compositeness with SiCp and the SiC particle size. In the peak aged condition, the major strengthening phase of these materials is intermediate $\beta$ phase(Mg$_2$Si), and the activation energy for the formation of $\beta$ phase is considerably decreased by the compositeness with SiCp and the increasing of SiC Particle site.

• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.13 no.2
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• pp.79-84
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• 2007

Purpose: The data was performed to evaluate the effect of conservative treatment in 30 patients aging from 21 to 71 with lumbar back pain. Methods: The effect of conservative treatment was analyzed with use of pain behavior scale, pain self assessment scale by Million Index in according to age, occupation, duration of symptom, symptom. Results: The occupation were desking job 43.4%, standing job 33.3%, house wife 23.3%. Duration of symptoms in over 2-5 months was 40.0%. The pain in below 1 months, classified by duration of symptoms, was reduced from 2.1 to 3.0 in pain behavior scale, 6.0 to 2.2 in pain self assessment scale(p<0.05). The pain in only lumbar back pain, classified by symptoms, was reduced from 2.0 to 3.0 in pain behavior scale, 6.6 to 2.4 in pain self assessment scale(p<0.05). Conclusion: The pain in over 9 months. classified by duration of physical therapy, was increase 2.0 in pain behavior scale, 4.0 in pain self assessment scale (p<0.05).