• Journal of the Korean Society for Heat Treatment
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• v.7 no.1
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• pp.17-24
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• 1994

The evaluation and analysis of diffusivity of lithium for coarsening and coarsening kinetics of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy aged at $170^{\circ}C$ have been investigated by transmission electron microscopy. With ageing time, ${\delta}^{\prime}$ precipitate coaesened to followed $\bar{\gamma}{\propto}t^{1/3}$ and coarsening kinetics was found to be obeyed to the Lifshitz-Slyozov-Wagner(LSW) theory and diffusivity of lithium for coarsening of ${\delta}^{\prime}$ precipitate in Al-Li-Cu-Mg-Zr alloy was obtained to be $5.85{\times}10^{-17}{\sim}1.53{\times}10^{-16}$ by experimental coarsening rate constant and various coarsening kinetic theory. Diffusivity of lithium measured by using various model but MLSW and Tsumuraya (VI) et al. model in Al-Li-Cu-Mg-Zr alloy is similar to that calculated by the Costas's diffusivity equation. It was, therefore, suggested that additing to the Cu, Mg and Zr element in Al-Li system have no great effect on diiffusivity of lithium for coarsening of ${\delta}^{\prime}$ This suggest that in matrix.

• Health Policy and Management
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• v.28 no.3
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• pp.233-239
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• 2018

A rapid decrease of total fertility rate to 1.08 in 2005 prompted the Korean government to plan and implement a '5-year plan for ageing society and population policy' starting from 2006. The 1st and 2nd 5-year plans had not shown any discernible impact on the fertility and the 3rd 5-year plan was launched in 2016. However, the fertility rate is going down further. The author reviewed the contents and assessment reports of the fertility promotion plan to suggest ideas for complementing the shortcomings of it. Author defined the major determinants of marriage and child birth as philosophy, politics, sense of value, social norm, culture, healthcare, and education. The plan was examined in view of these determinants. Transformation of Korea from an agricultural society to an industrialized society in a short period of time had brought about changes in most of the determinants of marriage and child birth; in particular philosophy and sense of value. These aspects were not put into consideration in the plan. Author suggested to launch a social education program for the general public to establish a sound philosophy of life, reform the sense of value on family, child birth and education, and cultivate the skill to draw a consensus through discussions on the social issues. A special program to promote marriage of women at the optimum age for child birth was proposed. The government should implement well balanced policy for economic development and labor. Multidisciplinary approach was recommended for these tasks.

• Advances in materials Research
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• v.4 no.1
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• pp.1-12
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• 2015

Low carbon steel of composition 0.05C - 0.18 Mn - 0.012 Si is intercritically annealed at temperatures $750^{\circ}C$, $775^{\circ}C$ and $800^{\circ}C$. The equilibrated alloys of different amounts of austenite with varying carbon contents are quenched in iced water. The same alloys are subcritically annealed at $675^{\circ}C$ and $700^{\circ}C$ for varying periods of times; the subcritically annealed alloy samples are quenched in iced water. Optical, scanning electron and transmission electron microscopy are carried out for all the samples. The dislocation structure, its distribution and density present in the above prepared duplex ferrite martensite steels are studied. The martensites are found to be highly dislocated due to lattice invariant deformation. At the same time ferrite adjoining the martensite areas also exhibits quite a high dislocation density. The high dislocation density is favorable for strain ageing and hence bakes hardenability. EDS analyses were carried out for both martensite and ferrite phases; it is found that the degree of supersaturation in ferrite together with carbon content in martensite varies with the process parameters. The microhardness test results show that the hardness values of different phases differ appreciably with process parameters. The microstructures and the corresponding microanalyses reveal that differently processed steels contain phases of varying compositions and different distribution.

• Journal of Magnetics
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• v.16 no.2
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• pp.173-176
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• 2011

Fe-Cr alloys with different Cr contents were prepared by an arc melting technique. The alloys were isochronally aged in the range from $400^{\circ}C$ to $900^{\circ}C$ with $50^{\circ}C$ steps with a holding time of 100 hours. The ageing produced embrittlement in the alloys due to either the formation of a Cr-rich ${\alpha}'$ phase or a $\sigma$ phase at high temperatures. Magnetic Hysteresis Loop (MHL) and Micro-Vickers hardness were measured at each step to correlate the magnetic and mechanical properties. Coercivity and hardness of the alloys were increased and remanence decreased up to 500-$550^{\circ}C$ due to formation of a Cr-rich ${\alpha}'$ phase. Beyond 500-$550^{\circ}C$ range, the coercivity and hardness decreased and remanence increased due to the coarsening or dissolution of the Cr-rich ${\alpha}'$ phase. In the Fe-48% Cr alloy, formation of the $\sigma$ phase at $700^{\circ}C$ reduced the maximum induction of the alloy significantly.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.231-234
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• 2009

The effects of annealing temperature and time on mechanical properties and microstructures were already investigated in cold drawn pearlitic steel wires. During annealing, the increment of the tensile strength at low temperatures found to be due to age hardening, while the decrease in the tensile strength at high temperatures was attributed to age softening, involving the spheroidization of lamellar cementite and recovery of lamellar ferrite. Since Between increase of tensile strength and the occurrence of the delamination would be closely related to the dissolution of cementite, the increase of drawing strain by lower annealing temperature caused the between higher tensile strength and the easier occurrence of the delamination in cold drawn pearlitic steel wires.

• Journal of Conservation Science
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• v.34 no.2
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• pp.129-135
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• 2018

Scientific investigation of cultural heritage can provide important information to understand the context of the object. To know the characteristics of the material is also an essential part of objects management and conservation. However, the identification and characterization of organic dyes used in archaeological and historical textiles are often limited by the restrictions in sampling. To cope with the difficulties, applications of high-performance techniques of surface analysis, such as Time of Flight-Secondary Ion Mass Spectra (TOF-SIMS) could be considered as a non or micro-destructive option. This study aims to examine the applicability of TOF-SIMS analysis to the detection of organic dyes from historical textiles. A group of silk fabrics dyed with vegetable dyes were artificially photo-aged to different degrees and analyzed with TOF-SIMS. Molecular and fragment ions from indigo were successfully detected from the aged samples; however, only some fragment ions were observed from gardenia and safflower dyed fabrics. Further studies with actual historical samples with extended examination scope would be necessary to assess the validity of this technique.

• Journal of the Korean Ceramic Society
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• v.25 no.6
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• pp.685-693
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• 1988

From leaching of Korean native halloysite with hot sulfuric acid, active species of siliceous aluminosilicate are obtained as residue, which gives the mole ratio of SiO2/Al2O3 10 and substantially removes most acid-soluble impurities. By dissolving the residue in sodium hydroxide at an ambient temperature sodium silicate solution is prepared, this is used for zeolite synthesis as one of starting materials. In order to prepare zeolite Type 4A thereform, addition of a proper aluminum source is made so that the composition of the reactant materials may be of the following mole ratios : Na2O/SiO2=1.2-1.5, SiO2/Al2O3=1.8-2.0 and H2O/Na2O=34-45 By careful control of ageing time and temperature, subsequent crystal growth is induced into microfine zeolite 4A, which gives optimum particle size distributjion being suitable for detergent builder. The zeolite products thus obtained and highly competitive with those from the use of the refined clay in comparison of their calcium exchange capacity, whiteness and particle size distribution. The present method shows a marginal advantage over the existing procedures requiring neitherseparate purification nor calcinating otherwise necessary for the raw clay ores in use.

• Journal of the Korean Society of Safety
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• v.27 no.3
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• pp.125-130
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• 2012

According to the Korea National Statistical Office data in 2010, the population over ages of 65 years would possess to 11.3% whole population of Korea in 2011 denoting Korea is already in the aging society. Old age is associated with inevitable time-dependent losses in physical capabilities. However the maintenance of physical capabilities is essential for continuing independence in old age. The work ability index(WAI) was constructed to reveal how well a worker is able to perform his work. This study focused on the discovery of an industrial and age-related influences on the work ability and job stress of workers in the shipbuilding, house managing, apartment construction industry. For this, the study conducted a job stress test using the Korean Occupational Stress Questionnaire Short Form, and employee performance evaluations using the Work Ability Index (WAI) of the Finnish Institute of Occupational Health (FIOH) on 3,228 workers in the shipbuilding, house managing and apartment construction industry. SPSS 12.0 K statistics program was used for statistics analysis and significance was verified with the Kruskal-Wallis test, a corporate body of nonparametric statistical analysis. As a result, employee performance had significant differences, depending on age, an industrial and years of service. The mean WAI score of the shipbuilding industry was lower than that of the other industry. Additionally, it was found that employee work ability decreased more as job stress increased.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.842-850
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• 2003

The suspension insulators are subjected to harsh environments in service for a long time. The long-term reliability of tile insulators is required for both mechanical and electrical performances. This study describes some basic performance tests and accelerated aging test by cool-heat cycling methods and thermal mechanical performance test methods on alumina porcelain insulators (new and aged) used for transmission line in KOREA. There was no fail in electrical and mechanical performance tests such as a high voltage strength, a flashover voltage, and an impact strength in all samples. But in the case of accelerating aging tests which have above 9$0^{\circ}C$ temperature gradient, fracture phenomena was happened by a thermal shock in tile aged sample(sample A) with low alumina porcelain body. It was indicated that sample A was more severely aged than other samples. According to results of HRB test and microstructural analysis, it was reasoned that insulator bodies with the matrix reinforced with alumina crystalline phase have advantages over the suppression of crack advance. And cool-heat aging and mechanical thermal ageing tests shows that a temperature gradient is more effective to accelerating than a cycling number.

• Proceedings of the KIEE Conference
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• 2003.07c
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• pp.1726-1728
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• 2003

The aging diagnosis method using partial discharge measurement detects discharge signals that critical cause of failure in insulation material operated a long time and can diagnose aging state of insulation materials with an aging analysis algorithm. The HFPD measurement method is a technique to analyze aging state of high voltage insulation materials and detect higher frequency signals than conventional PD measurement method therefore it takes less noise effect and could execute active line measurement. It is possible to analyze main discharge phenomena and obtain access to aging progress occurred in insulation materials through accumulation of HFPD signals during determined interval and expression of fractal dimension using statistical process of accumulated signals. The HFPD signals that occurred in each applied voltages are measured during 180 cycles and accumulated to the same phase of one cycle. These patterns that made by previous method are normalized with logarithm function and than inputted to neural networks. The aging diagnosis of insulation material was possible and the recognition ratio of neural network appeared very high.