• Applied Chemistry for Engineering
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• v.31 no.4
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• pp.383-389
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• 2020

Mesoporous silica solid catalysts modified with sulfonic acid were prepared for cationic ring-opening polymerization of octamethylcyclotetrasiloxane (D₄). Two sets of MCM-41 (1.7 and 2.8 nm) and SBA-15 (8.1 and 15.9 nm) with different pore sizes were used as catalyst supports. The surface of silica materials was modified with (3-mercaptopropyl)trimethoxysilane by silylation reaction and oxidized to sulfonic acid. The structures of the prepared catalysts were examined by X-ray diffraction and nitrogen adsorption-desorption. The pore size, specific surface area, and pore volume of the modified solid catalysts decreased slightly. In addition, the modification of the sulfonic acid on the silica surface was confirmed by using infrared spectroscopy and nuclear magnetic resonance spectroscopy. To observe the effect of the particle size on the catalytic activity, it was observed with a scanning electron microscope. The catalysts were used to synthesize PDMS through a ring-opening polymerization of D₄, and the conversion and polymerization rate of the polymerization reaction depended on the pore size, specific surface area, particle size, and particle agglomeration of the catalysts. In order for the polymerization rate, the catalyst prepared with SBA-15 of 8.1 nm pore size had the fastest reaction rate and showed the best catalytic activity.

• Journal of the Economic Geographical Society of Korea
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• v.6 no.1
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• pp.45-60
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• 2003

As the process of economic globalization deepens market uncertainty and severe competition, modern companies are tend to rely on non-market, socio-economic mechanisms such as trust, collaboration, and interdependence, They are being more influenced by cultural economic mechanisms like networks, embeddedness, and placeness rather than explicit cost-reductions. This paper analyzes the characteristics of industrial clusters, the formation of social capital, and the process of institutionalization by comparing two distinctive types of clusters, say Teheran and East-Gate Valleys in Seoul, Korea. The one is mainly consisted of IT industries with increasing vertical integration supported by venture capitals and favorable business infrastructures. The other cluster has long been a traditional CBD frame of Seoul and has transformed to the most dynamic and productive area, characterized by one-stop 'R&D-production-distribution-consumption-after sales services'. The study of the developmental trajectory and key characteristics for these kinds of clusters can give us insight for the cluster theory. This paper firstly reviews the similarities and differences between the social capital in general and that of industrial clusters. It then profiles the growth of the two clusters over the past decade, and compares the current spatial and business structure of the two clusters, focusing on transactions costs, the creation and flow of information, and the local institutions. The paper concludes with some comments about the prospects and perils of the two types industrial clusters of Seoul.

• Journal of the Korean Academic Society of Industrial Cluster
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• v.4 no.1
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• pp.14-50
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• 2010

This study focused on the competitiveness analysis of industrial cluster using econometric method and competency analysis method to measure the situation of Seocho-gu industrial cluster and Yangjae R&D cluster at Seoul. The econometric method used the data such as the number of firms, the number of employee, GRDP. The competency analysis method measured the level of agglomeration of cluster for years through LQ(Location quotient) index. In addition, the characteristics and structure of each industry in Secho-gu and Yangjae-dong R&D cluster. The circumstance of location and business, the competency of potential ability of industries were analysed by SWOT. In sum, this study has the following conclusion. First, Seocho-gu and Yangjae-dong region has an advantage in the circumstance for R&D related industry and man power. Second, Seocho-gu and Yangjae-dong region has a good potential for development in R&D related industries. These region has a good relationship the four major R&D related industry of Seoul. Third, these region also has a advantage in the potential development of R&D related researchers in the corresponding industries.

• Journal of the Korean association of regional geographers
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• v.11 no.1
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• pp.83-100
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• 2005

The Seoul Metropolitan Area's economy has undergone structural changes since the 1990s. With recent structural changes in the Korean economy in mind, this paper employs a decomposition analysis of Gross Regional Domestic Product per head and labor productivity to examine how the region's economic performance has changed relative to that of Korea since the 1900s. There are some findings. First, a strong cumulative causation process, derived from industrial linkages and agglomeration effects, has oocurred in the Seoul Metropolitan Area, widening economic disparities between the Seoul Metropolitan Area and the other regions especially since the Korean financial crisis in 1997 mainly due to Gyeonggi province's overwhelming cumulative GRDP growth relative to the national average. Second, the Seoul Metropolitan Area has begun w display good economic performance in terms of labour productivity relative w the national average since the late 1990s, with the region's industrial upgrading being implemented. Finally, manufacturing, financial intermediation and communications have made sensitive contributions to relative Seoul Metropolitan Area's labor productivity growth.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.500-507
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• 2008

By Using various grinding mill in powder cosmetics manufacturing process; screen milt and pin mill, jet mill, properties of the powder and grinding mills were studied; talc, mica, nylon powder, silica, titanium dioxide. Besides, the experiments fur evaluation of grinding were performed by using iron oxides those are tracers. In powders of plate shape, they were grinded more vertically than horizontally at the screen mill and pin mill, although were all grinded vertically and horizontally at the jet mill. The spheric powders became the primary particles or aggregation by electrostatic interaction at the screen mill and pin mill. But, at the jet mill, they resulted the agglomeration or transformation or damage up to 2bar. Titanium dioxides became the primary particles by all grinding mill. Pin mill has an excellent result in experiments which is a change of the tone of color by grinding. From these results, suggest that the jet mill is used to pre-treat of powders of plate shape in practical cosmetic manufacturing process, and the screen mill and pin mill are used to match the color of powder cosmetics. If industrial process condition is taken into consideration, suggest that 4times of grinding is excellent on grinding effect by the screen mill, and twice grinding by the pin mill and grind air pressure of 1bar by the jet mill.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.2
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• pp.120-125
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• 2006

By employing a rapid solidification method and atmospheric annealing at $450^{\circ}C-1hr$, we were able to manufacture inexpensively granular CuCo alloy ribbons with thickness of $20{\mu}m$ showing giant magnetoresistance (GMR) ratio of more than 5% at a high magnetic field of 0.5T. To verify maximum MR effect, the MR ratio, saturation magnetization, and microstructure change were investigated with Co contents between 5 and 30 at%. It was possible to obtain GMR ratios of 5.2% at 1.2T, and 3% at 0.5T, which implies an appropriate MR for industrial purpose at a Co content of $8{\sim}l4%$. MR ratio was reduced rapidly at a Co content below 5% due to superparamagnetic effect and at a Co content above 20% due to agglomeration of Co clusters. Surface oxidation during rapid solidification and atmospheric annealing did not have much affect on MR ratio. Our result implies that our economic CuCo granular alloy ribbons may be appropriate for high magnetic field sensor applications with wide content range of $8{\sim}14$ at%Co.

• 대한공업교육학회지
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• v.32 no.2
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• pp.188-198
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• 2007

Platinum nanoparticles loading on carbon nanotube was carried out by impregnation of hexachloro platinate(IV) from hydrogen hexachloro platinate(IV) hydrate dissolved solution without using reduction agents, and heating the hexachloro platinate(IV) impregnated carbon nanotube up to $400^{\circ}C$. The amounts of impregnated hexachloro platinate(IV) on to carbon nanotube were measured with UV-visible spectrophotometer. The TG, XRD, and TEM analysis were performed to confirm the platinum particles loading and distribution on carbon nanotube. The average platinum particles size on carbon nanotube was under 2 nm by heating the hexachloro platinate(IV) up to $400^{\circ}C$ in spite of non-using reduction agents, while the average size increased due to the agglomeration of some particles by heating them up to $800^{\circ}C$. Therefore, uniformly distributed platinum nanoparticles loading on carbon nanotube can be obtained from simple impregnation of hexachloro platinate(IV) from solution and heating it up to $400^{\circ}C$.

• Journal of the Korean Regional Science Association
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• v.34 no.3
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• pp.43-54
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• 2018

This paper analyzes the effects of population aging on regional differentiation from the New Economic Geography perspective. The addition of old-age population variable affects the price index, income, nominal wage, and real wage derived in the short-run equilibrium. Using the new model, we can better explain industrial agglomeration patterns corresponding to the new long-run equilibrium. As the real wage criterion does not properly take the old-age group into account, we employ the indirect utility function as an additional condition for equilibrium. We further consider tax as a policy tool for achieving a better long-run equilibrium. This would enable the government to direct the economy toward a particular equilibrium desired in the face of population aging.

• Korean Journal of Materials Research
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• v.21 no.8
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• pp.425-431
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• 2011

The industrial manufacturing of YSZ products can be summarized as a three step process: a) hydrolysis of zirconyl chloride and mixing of other solutions, b) precipitation, and c) calcination. The addition of ammonia or OH- is essential in the precipitation process. However, a strong agglomeration was observed in the results of an ammonia or OH- addition. Thus, it is necessary to disperse the powders smoothly in order to improve the mechanical strength of YSZ. In this study, YSZ was synthesized using the urea stabilizer and hydrothermal method. YSZ powders were synthesized using a hydrothermal method with Teflon Vessels at $180^{\circ}C$ for 24 h. The mole ratio of urea to Zr was 0, 0.5, 1, and 2. The crystal phase, particle size, and morphologies were analyzed. Rectangular specimens ($33\;mm{\times}8\;mm{\times}1{\pm}0.5\;mm$) for three-point bend tests were used in the mechanical properties evaluation. The crystalline of YSZ powders observed a tetragonal phase in the sample with a ratio of Zr:urea = 1:2 addition and a hydrothermal reaction time of 24 h. The average primary particle size of YSZ was measured to be 9 nm to 11 nm. The agglomerated particle size was measured from 15 nm to 30 nm. The three-point bending strength of the YSZ samples was 142.47 MPa, which is the highest value obtained for the Zr:urea = 1:2 ratio addition YSZ sample.

• Journal of the Economic Geographical Society of Korea
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• v.15 no.2
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• pp.292-303
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• 2012

The main purpose of this study is to analyze R&D networks and spatial implications in Qingdao consumer electronics industry agglomeration in China. The characteristics of R&D networks in Qindao consumer electronic industry are as follows. There is a cluster central around large enterprises led by the government and their subcontracting enterprises. However, the degree of collaborative networks in intra-firm, inter-firm, firm-research institutes(including university lab.) is relatively low. Therefore, Large enterprises in Qingdao has stimulated research collaborations with firms and research institutes located in other regions rather than within region. It is likely to show that R&D networks of consumer electronics industry has not been stimulated in Qingdao. Therefore, collaborative R&D networks among firms, research institutes and governments should be stimulated to build regional innovation systems central around consumer electronics industry in Qingdao.