• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2181-2188
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• 1992

Two-dimensional natural convection within a circular trapezoidal cavity with parallel cylindrical top and bottom walls at different temperatures and two adiabatic side walls has been solved by finite-difference methods. This study has been conducted to evaluate the effects of aspect ratio and inclination in the natural convection for various Rayleigh numbers. The minimum average Nusselt number occurs at the point of transition from a conductive heat transfer to a convective heat transfer. Numerical results are compared to experimental results with qualitatively good agreement.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.4 no.1
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• pp.11-19
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• 1992

The natural convection heat transfer within a trapezoidal enclosure with parallel cylindrical top and bottom walls at different temperatures and two adiabatic side walls are studied. A finite-difference method has been used to solve the governing equations numerically. The range of parameters studied herein are Prandtl number 0.7, aspect ratio from 0.5 to 4.0, Rayleigh number from $10^3$ to $3{\times}10^4$, enclosure tilt angle from 22.5 to 157.5 degrees. Mean and local Nusselt numbers are presented for discussing heat transfer characteristics within the enclosure. The heat balances for the hot and cold walls are differed by less than 1% for converged solutions, so these results appear to be reasonable.

• Solar Energy
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• v.13 no.1
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• pp.31-38
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• 1993

A numerical study of natural convection heat transfer confined by circular parallel walls at different temperatures and flat adiabatic walls is investigated for Rayleigh numbers from $10^3$ to $10^5$and sectorial angles from $30^{\circ}$ to $180^{\circ}$. It is used by a finite difference method to solve the governing equations. The results show velocity and temperature distributions. Mean Nusselt numbers are shown by $\overline{Nu}=C(Ra_L)^m$.

• Journal of the Economic Geographical Society of Korea
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• v.24 no.1
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• pp.76-101
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• 2021

This paper analyzes two cases of space tokenization, Meridio and QuantmRE, to explore the potential of tokenization as a new means of space financialization. Space tokenization is based on blockchain technology and security token offering (STO). Although some financial geographers noted the possible impact of blockchain technology on space financialization, it has not been examined in depth. Therefore, this paper demonstrates space tokenization cases in detail. Meridio and QuantmRE suggest financial structures that convert space into tokens based on fractional ownership transactions. QuantmRE, specifically, allows a homeowner to secure cash without either debt or ownership relinquishment through sales of tokenized home equity. As this method takes a form of sale transaction rather than a loan, it enables financial institutions to circumvent strengthened regulation on loans after the 2008 global financial crisis. Moreover, even "house poor" households, who own houses but lack cash due to excessive loans, can cash out from their properties through QuantmRE. As such, space tokenization enables financial institutions to overcome constrained conditions after the global financial crisis, thereby reproducing space financialization. Space tokenization also has the potential to geographically expand space financialization through stimulating investment in the depressed housing market.

• The Journal of the Korea Contents Association
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• v.19 no.9
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• pp.280-292
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• 2019

This study was carried out for the Centum Shinsegae Department Store, to grasp the indoor rest space and furniture design status, this study analyzes the characteristics of visitors' use behavior centered on furniture. The purpose of this study is to provide basic data for commercial rest space design by understanding the characteristics of resting space in commercial space and whether the furniture can support the behavior of visitors. The research method is to carry out on-site inspection, including the location of the rest space on each floor, the type and design characteristics of the furniture design, and the characteristics and patterns of the users on each were analyzed. The results of the study are as follows. As a result of analyzing the rest space and furniture, the furniture is brown, it has been provided with various designs such as fan-shaped, arched bench, sofa, chair type, and comfortable colors of lightness ranging from light gray to black, and appropriately supported the most common usage patterns.However, in the case of Shinsegae Department Store, it is necessary to consider the safety and convenience of the vulnerable groups.

• Journal of Korea Society of Industrial Information Systems
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• v.14 no.5
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• pp.1-9
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• 2009

Relay-assisted multiple input technique has become a promising candidate for next generation broadband wireless communications. In this paper, we propose channel selective relay-based multiple input transmission system. In the proposed system, single carrier frequency division multiple access (SC-FDMA) and orthogonal frequency division multiple access (OFDMA) are adopted for uplink and downlink transmissions, respectively. The performance of relay-based system can be improved by using the subcarriers selectively based on the channel condition between relay station (RS) and mobile station, or between RS and base station. Simulation results show that the proposed relay-based system considerably outperforms the conventional relay-based system.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.48 no.4
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• pp.53-60
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• 2011

In order to augment the robustness of OFDM system to Rayleigh multipath fading, there exist two smart antenna algorithms, namely, Pre-FFT smart antenna and Post-FFT smart antenna. After the mathematical modeling of both smart antenna algorithms, computer simulations have been carried to compare and analyze the performance of generalized eigen problem based Pre-FFT algorithm and the performance of Wiener solution based Post-FFT algorithm. It has been shown that the Post-FFT smart antenna far outperforms the Pre-FFT smart antenna due to the computational complexities. Especially it is so when the multipath signal arrives at beyond the guard interval and a rich co-channel interferer is introduced. Performance of a subcarrier clustering method proposed to lessen the computing load has been compared to that of a typical Wiener solution based Post-FFT smart antenna. Performance comparison between MRC(Maximum Ratio Combining) diversity based Post-FFT algorithm and typical Post-FFT algorithm has also been carried.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.3 no.4
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• pp.249-260
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• 1998

To understand the attachment of micro algae and their subsequent growths on artificial surfaces immersed in seawater, the relationship between attachment of diatoms on the immersed artificial substrates and species pool in the surrounding water was investigated. We used acryl slides for the study of diatom attachment and examined the surrounding water samples collected in Incheon Harbour from July 1995 to February 1997. Variations of species composition and abundances by exposure time in seawater were investigated during the early phase of biofilm formation on various substrates, e.g. glass, acryl, titanium, copper and antifouling paint-treated slides. Immigration rates of diatoms to acryl slides during spring and winter were significantly correlated with the abundance of benthic diatoms in surrounding water ($r^2$=0.78, p<0.01, n=42), suggesting that immigration rates were affected by variations of benthic diatom abundances in surrounding water. Immigration coefficient of monoraphid diatoms was 5 times higher than that of biraphid diatoms, but relative abundance of monoraphid diatoms was 3 times lower than that of biraphid diatoms on acryl slides in spring. In winter, immigration coefficient and relative abundance of centric diatoms were higher compared to other raphe forms. These results suggest that the attachment of diatoms seems to be caused by the abundance and immigration coefficients of benthic diatoms in surrounding water. Pennate diatoms predominantly attached to all artificial surfaces throughout all experimental periods. Interestingly, centric diatoms predominantly attached to all artificial surfaces in winter. Hantzschia virgata, Licmophora abbreviata and Melosira nummuloides appeared dominantly on antifouling paint-treated slides, probably being tolerant of the antifouling paint. During incubations, the abundance of attached diatoms increased exponentially on glass, titanium and acryl slides with exposure time. The maximum abundance was highest on glass slide, followed by acryl, titanium, copper and antifouling paint-treated slides. The growth rates of attached diatom community on all artificial surfaces were higher at temperature of $24-25^{\circ}C$ than that of $2-3^{\circ}C$. The growth rate of attached diatoms on glass slide was generally higher compared to other slides during the study period. Dominant morphotypes of observed species with exposure time in seawater were prostrate form Amphora coffeaeformis, fan shape Synedra tabulata, stalk type Licmophora paradoxa and chain type M. nummuloides. A micro-succession in the attached microalgal community was observed. The composition of dominant species seems to be the result of species-specific response to gradually limited space with development of microalgal film.