• International Area Studies Review
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• v.20 no.3
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• pp.45-80
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• 2016

This paper examined, using three indicators, urban area rate, urbanization rate and urban population density upon the status of urbanization since the 2000s in Southeast Asia. This study also carried out an empirical analysis on the effects of urbanization on economic growth using the Williamson's inverted U-shape hypothesis. In addition, this study calculated the thresholds by which urbanization starts to have positive effects on economic growth by using estimated coefficients, and comparatively analyzed each Southeast Asian country's status. The empirical analysis results opposite to the Williamson's hypothesis. This means that the hypothesis asserting that urbanization has positive effects on economic growth in a country with low economic development phase and income level, but that urbanization can have negative effects on economic growth, if a country's income level is beyond a certain level(threshold), is not supported in this study. In summary, the economies of agglomeration represented as localization economy and urbanization economy is realized to some degree in terms of urbanization in Southeast Asia. Also, urbanization in Southeast Asia has positive effects on economic growth through knowledge spillover, the active exchange of ideas and productivity improvement. In examining the meaning of Southeast Asia's urbanization, policy consideration needs to be conducted, and efforts should be made to maximize the positive effects of the economies of agglomeration and knowledge spillover on economic growth.

• Journal of the Korean Ceramic Society
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• v.36 no.4
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• pp.343-353
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• 1999

Microwave(2.45 GHz) was used as energy source in hydrothermal reaction to fabricate ultrafine BaTiO3 powder. Using microwave of 700 W, crytal BaTiO3 began to fom after 5 min in microwave-autoclave sys-tem. The crystallinity was not noticeably increased with increasing longer reaction time than 10 min. On the other hand in microwave-reflux system crytal BaTiO3 began to form after 15min and the crystallinity was not noticeably increased with increasing longer reaction time than 1hr,. In either case particle size dis-tribution was considerably uniform due to the effect of homogeneous heating by microwave. In addition mi-crowave heating gave an extremely small degree of particle agglomeration compared to electric heating. Av-erage sizes of as-synthesized powders were 30-60nm. Ba/Ti ratio in sol played an important role in det-ermining the particle size. It seems that excess barium forms different phases such as Ba(OH)2 which makes thin layer on the surface of BaTiO3 powder. This thin layer would inhibit the agglomeration of Ba-TiO3 powders and keep the small grain size. In microwave-autoclave system tetragonal-BaTiO3 was formed directly by the reaction of only 15 min. In the case of microwave-reflux system tetragonal-BaTiO3 was formed by driyng over 25$0^{\circ}C$.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.3
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• pp.197-203
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• 2022

Urban space expansion is an important symbol of the urbanization process and has always been an important topic in urban studies. In addition, for sustainable city management, it is important to identify factors that can influence, such as the driving force and direction of urban space expansion, from the stage of establishing an urban development plan. To understand these factors, by observing the expansion process of a specific city, it is possible to sufficiently observe how the urban spatial dimension changes. Through a series of processes, the spatial growth characteristics of the city are analyzed, and the influence and results of important factors are analyzed. For this purpose, this paper examines the changes in the city's outer boundary and land use structure through monitoring data on urban areas of 14 cities in Hunan Province, China from 2000 to 2016. Temporal and spatial regularity according to the urban space expansion of these cities were analyzed, and a preliminary assessment was made on whether the urban space expansion is coordinated with the urban population growth. The assessment result showed: (1) The urban space of most cities has been extended rapidly in 2000-2015 however, the rate and the intensity of urban space expanding has been declining. (2) The construction of the industrial park is the core driving force of the urban space expanding, and the change of the urban space structure is manifested as enclave city expansion because that the industrial park is usually far away from the city center. (3) The population agglomeration is another driving force of the urban space expanding. At this time, the urban space expanding is like boundary extension. (4) Except Changsha city, all of the cities has a high urbanization-area-growth elastic coefficient. It means that most of the cities should enhance the land use degree.

• Korean Journal of Materials Research
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• v.27 no.2
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• pp.63-68
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• 2017

A black nickel oxide powder, one of the commercial nickel oxide ores, was reduced by hydrogen gas in a batch-type fluidized-bed reactor in a temperature range of 350 to $500^{\circ}C$ and in a residence time range of 5 to 120 min. The hydrogen reduction behavior of the black nickel oxide was found to be somewhat different from that of green nickel oxide ore. For the black nickel oxide, the maximum temperature (below which nickel oxide particles can be reduced without any agglomeration) was significantly lower than that observed for the green nickel oxide. In addition, the best curve fittings of the Avrami model were obtained at higher values of the overall rate constant "k" and at lower values of the exponent "m", compared to those values for the green nickel oxide. It may be inferred from these results that the hydrogen reduction rate of the black nickel oxide is faster than that of the green nickel oxide in the early stages, but the situation reverses in the later stages. For the black nickel oxide ore, in spite of the low temperature sintering, it was possible to achieve a high degree fluidized-bed reduction at lower temperatures and at lower gas consumption rates than was possible for the green nickel oxide. In this regard, the use of black nickel oxide is expected to yield a benefit if its ore price is sufficiently lower than that of the green nickel oxide.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.3
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• pp.118-122
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• 2018

Ceria ($CeO_2$) is a rare earth oxide, which has been widely investigated to improve the property. It is important to increase the surface area of $CeO_2$, because high surface area of $CeO_2$ can improve the catalytic ability. $CeO_2$ nanoparticles were synthesized by a solvothermal process. A discussion on the influence of solvent ratio and precursors on $CeO_2$ nanoparticles was performed. The size and degree of the agglomeration of the synthesized $CeO_2$ could be tuned by controlling those parameters. The average size and distribution of prepared $CeO_2$ powders was in the range of 3 to 13 nm and narrow, respectively. The XRD pattern showed that the synthesized $CeO_2$ powders were crystalline with cubic phase of $CeO_2$. The average particle size was calculated by Scherrer equation and FE-TEM images. The morphology of the synthesized $CeO_2$ particle was objected using FE-TEM and FE-SEM. Specific surface area of the synthesized $CeO_2$ was determined using BET (Brunauer-Emmett-Teller) equation.

• Advances in materials Research
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• v.2 no.2
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• pp.77-91
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• 2013

High quality nanoparticles of neodymium barium niobium ($NdBa_2NbO_6$) perovskites have been synthesized using an auto ignition combustion technique for the first time. The nanoparticles thus obtained have been characterized by powder X-ray diffraction, thermo gravimetric analysis, differential thermal analysis, Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopy. UV-Visible absorption and photoluminescence spectra of the samples are also recorded. The structural analysis shows that the nano powder is phase pure with the average particle size of 35 nm. The band gap determined for $NdBa_2NbO_6$ is 3.9 eV which corresponds to UV-radiation for optical inter band transition with a wavelength of 370nm. The nanopowder could be sintered to 96% of the theoretical density at $1325^{\circ}C$ for 2h. The ultrafine cuboidal nature of nanopowders with fewer degree of agglomeration improved the sinterability for compactness at relatively lower temperature and time. During the sintering process the wide band gap semiconducting behavior diminishes and the material turns to a high permittivity dielectric. The microstructure of the sintered surface was examined using scanning electron microscopy. The striking value of dielectric constant ${\varepsilon}_r=43$, loss factor tan ${\delta}=1.97{\times}10^{-4}$ and the observed band gap value make it suitable for many dielectric devices.

• Journal of the Korean Ceramic Society
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• v.36 no.7
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• pp.742-750
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• 1999

Nanosized TiO2 powders were synthesized using the chemical vapor conduensation (CVC) process with various precursor feeding rates (0.37 and 0.752 ml/min) and oxygen flow rates(1-2slm) conditions and powder characteristics were investigated in terms of formation of nanosized powder varying with the above processing conditions. For this study the main thermodynamic and fluid dynamic factors -supersaturation ratio collision frequency and residence time-were theoretically established and compared to the characteristics of formed TiO2 powder. The loosely combined anatase phase powders (including less than 3%of rutile phase) having 20-30nm crystallite size were obtained at overall conditions. The particle size and th degree of agglomeration for a precursor flow rate of 0.376 ml/min turn out to be smaller than for a flow rate of 0.742ml/min. And the decreasing of particles size and particle size distribution were observed with increasing oxygen flow rate as the residence time and collision frequency were reduced by increasing oxygen flow rate,. It appears that further scrutiny is needed to elucidate the influence of the individual thermodynamic and kinetic parameters mdependently.

• 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.

• Journal of the Korean Ceramic Society
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• v.41 no.4
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• pp.289-296
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• 2004

Whisker and short rod shaped hydroxyapatite (Ca$_{10}$(PO$_4$)$_{6}$(OH)$_2$ with stoichiometric composition (Ca/P=1.62 -1.67, molar ratio) has been synthesized by hydrolysis and hydrothermal reaction of aqueous $\alpha$-Ca$_3$(PO$_4$)$_2$($\alpha$-TCP) solution (pH 11), respectively. The shape of resultant HAp was mainly dependent on synthetic route and the microstructural development was on processing condition. In hydrolysis processing, the degree of intersection of whiskerlike particles and agglomeration in the apsis line increased with increasing reaction time. In hydrothermal synthesis, the reaction product obtained under excessive reaction time ($\geq$3 h at 20$0^{\circ}C$) was severely agglomerated without further grain growth above certain critical size (0.75 ${\mu}{\textrm}{m}$ in length, 0.3${\mu}{\textrm}{m}$ 11m in diameter).

• Journal of the Korean Regional Science Association
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• v.40 no.3
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• pp.95-108
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• 2024

This study analyzes the location determinants of newly established and relocated manufacturing firms in South Korea using the National Business Survey data from 2016 to 2019. Both new establishments and relocations are concentrated in the Seoul metropolitan area, Chungcheong, Yeongnam, and Daegyeong regions, with relocated firms showing a higher degree of spatial concentration. Employing a negative binomial regression model, we find that manufacturing concentration, population density, industrial diversity, and lower wage levels positively influence both new establishments and relocations. The proportion of highly educated workers, accessibility to producer services, and average land prices only positively affect the frequency of new establishments, suggesting that firms in the early stages of their life cycle, which are more dependent on human capital and producer services, demonstrate a higher willingness to pay for land use. Conversely, increased travel time to Seoul and improved transportation accessibility enhance the probability of attracting relocated firms. This implies that cost reduction incentives associated with distance from Seoul may outweigh the benefits of proximity to the capital in relocation decisions. Our findings suggest that strengthening agglomeration economies and improving transportation infrastructure efficiency could increase the likelihood of attracting relocated manufacturing firms to non-capital regions.