• Korean Journal of Metals and Materials
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• v.49 no.1
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• pp.40-45
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• 2011

Using the spark plasma sintering process (SPS process), the WC-6wt.%Co hard materials were densified using an ultra fine WC-Co powder. The WC-Co was almost completely dense with a relative density of up to 100% after the simultaneous application of a pressure of 60 MPa and the DC pulse current for 3 min without any significant change in the grain size. The average grain size of WC that was produced through this experiment was about $0.2{\sim}0.8{\mu}m$. The hardness and fracture toughness were about $1816kg/mm^2$ and $15.1MPa{\cdot}m^{1/2}$, respectively, for 60 MPa at $1200^{\circ}C$.

• Korean Journal of Materials Research
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• v.32 no.11
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• pp.489-495
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• 2022

This research investigated how adding Sb (0.75, 1.0, 2.0 and 5.0 wt%) to as-extruded aluminum alloys affected their microstructure, mechanical properties, electric and thermal conductivity. The addition of Sb resulted in the formation of AlSb intermetallic compounds. It was observed that intermetallic compounds in the alloys were distributed homogenously in the Al matrix. As the content of Sb increased, the area fraction of intermetallic compounds increased. It can be clearly seen that the intermetallic compounds were crushed into fine particles and homogenously arrayed during the extrusion process. As the Sb content increased, the average grain size decreased remarkably from 282.6 ㎛ (0.75 wt%) to 109.2 ㎛ (5.0 wt%) due to dynamic recrystallization by the dispersed intermetallic compounds in the aluminum matrix during the hot extrusion. As the Sb content increased from 0.75 to 2.0 wt%, the electrical conductivity decreased from 61.0 to 59.8 % of the International Annealed Copper Standard. Also, as the Sb content increased from 0.75 to 2.0 wt%, the ultimate tensile strength did not significantly change, from 67.3 to 67.8 MPa.

• Journal of Digital Convergence
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• v.17 no.11
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• pp.1-7
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• 2019

This study analyzed the effects of labor aging on labor productivity using panel statistics of 16 local governments from 1995 to 2017. The aging of the labor force, defined as the proportion of workers aged 60 or older in total employment, in the results of the panel regression analysis considering regional fixed effects and various adjustment variables, has a very consistent and significant negative effect on labor productivity. For every 1% increase in aging, labor productivity decreases by about 0.14 ~ 0.20%. In addition, the per capita capital stock and human capital considered as adjustment variables contributed to the increase of labor productivity, and the unemployment rate, which is a proxy variable of the economic fluctuation, has a significant negative effect on labor productivity as expected. The coefficient of the industrial structure, which represents the share of the service industry in the whole industry, was positive, but is not significant. The results of this study suggest that the design and construction of economic and educational policies that can maintain and expand human capital are necessary to curb the reduction in labor productivity expected by the aging workforce.

• Korean Journal of Metals and Materials
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• v.49 no.11
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• pp.845-852
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• 2011

The Spark Plasma Sintering(SPS) method offers a means of fabricating a sintered-body having high density without grain growth through short sintering time and a one-step process. A titanium compact having high density and purity was fabricated by the SPS process. It can be used to fabricate a Ti sputtering target with controlled parameters such as sintering temperature, heating rate, and pressure to establish the optimized processing conditions. The compact/target(?) has a diameter of ${\Phi}150{\times}6.35mm$. The density, purity, phase transformation, and microstructure of the Ti compact were analyzed by Archimedes, ICP, XRD and FE-SEM. A Ti thin-film fabricated on a $Si/SiO_2$ substrate by a sputtering device (SRN-100) was analyzed by XRD, TEM, and SIMS. Density and grain size were up to 99% and below $40{\mu}m$, respectively. The specific resistivity of the optimized Ti target was $8.63{\times}10^{-6}{\Omega}{\cdot}cm$.

• 전기의세계
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• v.40 no.1
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• pp.17-22
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• 1991

현대의 물질문명은 에너지와 밀접한 관계가 있다. 모든 산업설비와 우리 주위의 문명의 이기는 어떤 형태로든 전기 energy를 빼고는 생각할 수가 없는 것이며 그 양상은 날로 깊어져 가고 있는 것이다. 특히 동력원으로서의 전기 energy는 각종 생산설비의 구동력, 상하수도, 농업용수의 양수동력등 큰 용량의 동력으로부터 가정용 의학용으 소전력에 이르기까지 관련 안되는 곳이 없으며 최근에는 FA, OA등에 사용되는 극소형동력으로까지 그 이용이 심화되고 있는 것이다. 따라서 전기 energy의 기계 energy로의 변환장치인 전동기는 인류문명이 지속되는 한 사용될 것이며, 그 응용적 측면에서 앞으로의 수요는 꾸준히 늘어날 것으로 보아 본고에서는 우리나라 전동기사업을 기술적 측면과 기업적 측면에서 조명하여 현재의 위치를 확인하고 장래를 전망하고저 한다.

• Korean Journal of Metals and Materials
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• v.49 no.6
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• pp.488-492
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• 2011

Heat-treatable Al-Mg-Si-Cu alloy sheets, which are expected to have a growing demand, were fabricated by Cross rolling to improve their formability. The mechanical properties and texture of the sheets after the final annealing process were investigated by a tensile test, EBSD and XRD analysis. The grain size of the cross-rolled sheets was remarkably decreased compared to conventional rolled sheets, and the R-value of the cross-rolled sheets was notably increased by about one and a half times that of the conventional rolled sheet. Cube{001}<100> and cubic system orientations were strongly developed in conventional rolled sheets. However, randomized textures were formed in the cross-rolled sheets without specific texture. It is thought that much shear deformation was induced during the cross rolling. The results show that the cross rolling method is effective for improving the R-value of aluminum alloys sheets and their grain refinement. As a result, it is considered that cross rolling is effective for improving formability.

• Journal of Powder Materials
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• v.29 no.1
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• pp.28-33
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• 2022

Aluminum-based powders have attracted attention as key materials for 3D printing owing to their low density, high specific strength, high corrosion resistance, and formability. This study describes the effects of TiC addition on the microstructure of the A6013 alloy. The alloy powder was successfully prepared by gas atomization and further densified using an extrusion process. We have carried out energy dispersive X-ray spectrometry (EDS) and electron backscatter diffraction (EBSD) using scanning electron microscopy (SEM) in order to investigate the effect of TiC addition on the microstructure and texture evolution of the A6013 alloy. The atomized A6013-xTiC alloy powder is fine and spherical, with an initial powder size distribution of approximately 73 ㎛ which decreases to 12.5, 13.9, 10.8, and 10.0 ㎛ with increments in the amount of TiC.

• Journal of Digital Convergence
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• v.18 no.5
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• pp.25-31
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• 2020

This study analyzes the effects of aging workforce on human capital and the per capita gross regional domestic product, using regional panel statistics from 1995 to 2017. According to the results of the two-stage least-squares panel regression analysis reflecting the fixed effects by region, the aging of the labor force had no effect on the human capital employment ratio and per capita gross domestic product in the metropolitan cities, but reduced human capital and per capita gross domestic product in the provinces. The share of service businesses had a positive effect on human capital in metropolitan cities, but the effect was not significant in the provinces. Human capital significantly contributed to the increase in per capita gross regional domestic product in the metropolitan cities, but the physical capital stock significantly contributed to the increase in per capita gross regional domestic product in the provinces. The results of this study suggest that the human capital job policy and the per capita regional GDP growth policy due to the aging workforce may be different between metropolitan cities and provinces.

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.393-399
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• 2023

In this study, changes in the microstructure and mechanical properties of cast and extruded Al-2Li-1Ce alloy materials were investigated as the Mg content was varied. The density decreased to 2.485, 2.46 and 2.435 g/cm³ when the Mg content in the Al-2Li-1Ce alloy was increased to 2, 4 and 6 wt%, respectively. Intermetallic compounds of Al₁₁Ce₃ were observed in all alloys, while the β-phase of Al₃Mg₂ was observed in alloys containing 6 wt% of Mg. In the extruded material, with increasing Mg content the average grain size decreased to 84.8, 71.6 and 36.2 ㎛, and the fraction of high-angle grain boundaries (greater than 15°) increased to 82.8 %, 88.6 %, and 91.8 %, respectively. This occurred because the increased Mg content promotes dynamic recrystallization during hot extrusion. Tensile test results showed that as the Mg content increased, both the yield strength and tensile strength increased. The yield strength reached 86.1, 107.3, and 186.4 MPa, and the tensile strength reached 215.2, 285, and 360.5 MPa, respectively. However, it is worth noting that the ductility decreased to 27.78 %, 25.65 %, and 20.72 % as the Mg content increased. This reduction in ductility is attributed to the strengthening effect resulting from the increased amount of dissolved Mg, and grain refinement due to dynamic recrystallization.

• Journal of the Korean Geographical Society
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• v.34 no.2
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• pp.155-175
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• 1999

본 연구는 대구 섬유산업의 재구조화를 지역 내.외적 요인들의 관계적 관점에서 분석하고, 이에 기초하여 지역경제 발전전략의 정책적 함의를 도출하기 위해 수행되었다. 1970년대 이후 대구 섬유산업은 정부의 중화학공업 정책과 수출지향적 경제발전 정책에 힘입어 화학섬유 중심의 대량생산과 수출체제를 수립하였다. 노동력 공급의 부족현상이 나타남에 따라 노동력을 안정적으로 확보하기 위해 산업체 특별학급.부설학교와 섬유기술진흥원을 설립하였고 또한 기혼여성 노동력을 활용하기 시작하였다. 그리고 생산시설은 대구시 외곽지역에 집중적으로 입지하였다. 1980년대 중반 이후 대구 섬유산업은 국내.외 환경변화에 따라 구조전환을 시도하고 있다. 지역노동시장에서 저임금 노동력 확보가 어렵게 됨에 따라 자동섬유기계의 도입을 증대시키고 기혼여성과 외국인 노동력을 적극적으로 활용하고 있으며, 자본과 생산시설을 경북이나 해외로 이동시키고 있다. 대구 섬유산업의 재구조화 정책은 섬유업체간에 협력체제의 구축, 노.사공생의 노동제도 확립, 섬유업과 연관된 생산자 서비스업의 육성 등을 중심으로 추진되어야 할 것이다.