• Computers and Concrete
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• v.3 no.5
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• pp.301-312
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• 2006

Experimental research revealed that the spatial dispersion of aggregate grains exerts pronounced influences on the mechanical and durability properties of concrete. Therefore, insight into this phenomenon is of paramount importance. Experimental approaches do not provide direct access to three-dimensional spacing information in concrete, however. Contrarily, simulation approaches are mostly deficient in generating packing systems of aggregate grains with sufficient density. This paper therefore employs a dynamic simulation system (with the acronym SPACE), allowing the generation of dense random packing of grains, representative for concrete aggregates. This paper studies by means of SPACE packing structures of aggregates with a Fuller type of size distribution, generally accepted as a suitable approximation for actual aggregate systems. Mean free spacing $\bar{\lambda}$, mean nearest neighbour distance (NND) between grain centres $\bar{\Delta}_3$, and the probability density function of ${\Delta}_3$ are used to characterize the spatial dispersion of aggregate grains in model concretes. Influences on these spacing parameters are studied of volume fraction and the size range of aggregate grains. The values of these descriptors are estimated by means of stereological tools, whereupon the calculation results are compared with measurements. The simulation results indicate that the size range of aggregate grains has a more pronounced influence on the spacing parameters than exerted by the volume fraction of aggregate. At relatively high volume density of aggregates, as met in the present cases, theoretical and experimental values are found quite similar. The mean free spacing is known to be independent of the actual dispersion characteristics (Underwood 1968); it is a structural parameter governed by material composition. Moreover, scatter of the mean free spacing among the serial sections of the model concrete in the simulation study is relatively small, demonstrating the sample size to be representative for composition homogeneity of aggregate grains. The distribution of ${\Delta}_3$ observed in this study is markedly skew, indicating a concentration of relatively small values of ${\Delta}_3$. The estimate of the size of the representative volume element (RVE) for configuration homogeneity based on NND exceeds by one order of magnitude the estimate for structure-insensitive properties. This is in accordance with predictions of Brown (1965) for composition and configuration homogeneity (corresponding to structure-insensitive and structure-sensitive properties) of conglomerates.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.6 no.4
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• pp.600-608
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• 1996

Specific structural properties of Li intercalation reaction into the spinel relatedmanganese dioxide, $Li_{x}Mn_{2}O_{4}(0.2{\leq}x{\leq}2.0)$, are investigated by X-ray diffractional and electrochemical studies of Li/1M $LiClO_{4}$-propylene carbonate solution/$Li_{x}Mn_{2}O_{4}$ cell. The effect of the chemical composition and the reaction temperature on electrochemical parameter of $Li_{x}Mn_{2}O_{4}$ are studied by the phenomena of phase-transition, analysis of crystal lattice, fine structure, and thermal analysis. Treatment of the spinel $Li_{x}Mn_{2}O_{4}$ with aqueous acid was found to result in conversiton of $Li_{x}Mn_{2}O_{4}$ to nearly pure $MnO_{2}$, as evidenced by a reduction in the lattice constant $a_{c}$ from 8.255 to $8.031\;{\AA}$. At a composition range of $0.2{\leq}x{\leq}0.6$ in $Li_{x}Mn_{2}O_{4}$ the reduction proceeded in a homogeneous phase, which was characterized by a constant voltage of 3.9~3.7 V together with a lattice constant of $8.255\;{\AA}$.

• Clean Technology
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• v.18 no.4
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• pp.432-439
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• 2012

The electrocatalytic oxidation of CO was studied using carbon-supported 20 wt% PtRu (PtRu/C) catalysts, which were prepared with different Pt : Ru atomic ratios from 7 : 3 to 3 : 7 using a colloidal method combined with a freeze-drying procedure. The bimetallic PtRu/C catalysts were characterized by various physicochemical analyses, including X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). CO stripping voltammetry measurements indicated that the addition of Ru with a Pt catalyst significantly improved the electrocatalytic activity for CO electrooxidation. Among the tested catalysts, the $Pt_5Ru_5/C$ catalyst had the lowest onset potential (vs.Ag/AgCl) and the largest CO EAS. Structural modification via lattice parameter change and electronic modification in the unfilled d band states for Pt atoms may facilitate the electrooxidation of CO.

• Earthquakes and Structures
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• v.13 no.1
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• pp.59-66
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• 2017

Modern seismic codes rely on performance-based seismic design methodology which requires that the structures withstand inelastic deformation. Many studies have focused on the inelastic deformation ratio evaluation (ratio between the inelastic and elastic maximum lateral displacement demands) for various inelastic spectra. This paper investigates the inelastic response spectra through the ductility demand ${\mu}$, the yield strength reduction factor $R_y$, and the inelastic deformation ratio. They depend on the vibration period T, the post-to-preyield stiffness ratio ${\alpha}$, the peak ground acceleration (PGA), and the normalized yield strength coefficient ${\eta}$ (ratio of yield strength coefficient divided by the PGA). A new inelastic deformation ratio $C_{\eta}$ is defined; it is related to the capacity curve (pushover curve) through the coefficient (${\eta}$) and the ratio (${\alpha}$) that are used as control parameters. A set of 140 real ground motions is selected. The structures are bilinear inelastic single degree of freedom systems (SDOF). The sensitivity of the resulting inelastic deformation ratio mean values is discussed for different levels of normalized yield strength coefficient. The influence of vibration period T, post-to-preyield stiffness ratio ${\alpha}$, normalized yield strength coefficient ${\eta}$, earthquake magnitude, ruptures distance (i.e., to fault rupture) and site conditions is also investigated. A regression analysis leads to simplified expressions of this inelastic deformation ratio. These simplified equations estimate the inelastic deformation ratio for structures, which is a key parameter for design or evaluation. The results show that, for a given level of normalized yield strength coefficient, these inelastic displacement ratios become non sensitive to none of the rupture distance, the earthquake magnitude or the site class. Furthermore, they show that the post-to-preyield stiffness has a negligible effect on the inelastic deformation ratio if the normalized yield strength coefficient is greater than unity.

• Journal of the Korean Institute of Gas
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• v.8 no.1 s.22
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• pp.37-47
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• 2004

Pressure swing adsorption (PSA) process using CMS as an oxygen purifier was developed to produce high purity oxygen over $99\%$ with high productivity. The cyclic performances such as purity, recovery, and productivity of PSA process were compared experimentally and theoretically under the non-isothermal condition. A binary ($O_2$/Ar 95:5 vol.$\%$) and two kinds of ternary ($O_2/Ar/N_2$ 95:4:1 and 90:4:6 vol.$\%$) mixtures were used as feed gases. The developed process with the consecutive two blowdown steps produced the oxygen with $99.8\%$ purity and $56\%$ recovery from $95\%$ oxygen containing feed. However, in the feed with $90\%$ oxygen, the $O_2$ Purity was decreased up to $97.3\%$. In addition, because the cyclic performances of the suggested process was significantly affected by the diffusion rate, the non-isothermal model with the the modified LDF model was applied for the process simulation. The concentration-dependent rate parameter of the applied rate model was incorporated with the Langmuir isotherm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.405-411
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• 2016

Given the importance of ensuring continued residency and maintenance of the 1st Planned New Town, which is the first of more than 20 such projects, this study aims to identify the factors determining the residents' living intention. The results show that age, gender, length of stay, and occupancy type are significant factors influencing their living intention. Among the environmental factors, the educational environment and shopping environment are crucial. This means that in order to achieve the "Ageing in Place" concept, it is necessary to improve the educational environment, provide a variety of commercial facilities and expand the living facilities. While it has no direct influence on the pros and cons of building remodeling, the results showed that when the living intention is used as a parameter, the transportation, educational, and shopping environment have an indirect influence on the pros and cons of building remodeling.

• Journal of Distribution Research
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• v.15 no.4
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• pp.87-117
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• 2010

'Entrepreneurship' which means spirit or activity seeking new value by challenging boldly the uncertainty is one of the most important concept in 21st century business environment. Franchise Industry taking a relationship with distribution industry also needs entrepreneurship. As franchise industry consists of small and medium enterprises, the entrepreneurship of franchisor's CEO is important for the franchisor's growth. The purpose of this study is to analyze the factors influencing on the entrepreneurship of franchisor's CEO, and the effect of the CEO's entrepreneurship on franchisor's performance. For this purpose, this study set CEO's psychological characteristics, market characteristics, and social-institutional characteristics as independent variables, CEO's entrepreneurship as parameter variables, and franchisor's performance as dependent variables. And to analyze this study model, this study collected questionnaires from 152 franchisors' CEOs, and uses SEM(Structural Equation Modeling). As the result, 'CEO's Entrepreneurship' influenced on both 'Franchisor's Financial Performance' and 'Franchisor's Non Financial Performance'. The results of this study provide some guides for franchisor's CEO and government policies.

• FLOWER RESEARCH JOURNAL
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• v.19 no.1
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• pp.68-76
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• 2011

This study was conducted to investigate customer taste related to satisfaction of a baby's first birthday party and re-visit of venues. General characteristics of customers were similar in male and female or the married and the unmarried. Mainstream age of respondents was from in their 20's to 30's. Among them, the number of university graduates were the largest in education level. Theoretical model was composed with seven significant variables of design style and composition and design harmony and color sense for flower decoration, accessibility, facility, service and price, satisfaction, and intention of re-visit based on the result of analysis on these factors. Exploratory factor analysis was performed using SPSS 14.0K. Structural equation modeling(SEM) for simultaneous measure of path coefficient in all casualty of study model, measurement model of AMOS 7.0 for evaluation of validity, and reliability and factor analysis method using technical statistics, frequency analysis, and Cronbach's Alpha for data analysis were used. The result of hypothesis verification showed that design style and composition was the most significant item in satisfaction of parameter and it was followed by design harmony and color sense. While service and price had positive effect on satisfaction, accessibility and facility had no relation to it. It means that the most crucial variable was a flower decoration in planning and representation of the celebration of baby's first birthday. In conclusion, the finding of this study suggests that the effective utilization of these variables will contribute to the enhancement of satisfaction affecting improvement service and price or intention of re-visit.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.8
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• pp.133-138
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• 2019

This study evaluated the tensile properties of SAPH440, a hot-rolled steel for automotive structural applications, based on GMAW lap welding, the welding current, the welding voltage, and the feed rate. Tensile tests were performed according to the joint parameters of the GMAW process, for which specimens were fabricated according to KS B ISO 9018 by lap welding. The bead appearance was observed in each condition, and the weldability was evaluated by the tensile test. Higher the welding current resulted in a deeper weld, but the tensile strength was not significantly different from when the parameter was fixed due to the fracture of the base material. When the current was higher than the voltage, as in the case of a welding current of 200 A and welding voltage of 17 V, a large amount of spatter is generated, the welding is unstable, and the welded part breaks. Higher the voltage resulted in the bead not causing defects in general, and it also affected the weldability. If the current and voltage were too low, the welding was not performed normally, and the tensile strength could not be measured. However, as the current increased, the increase of the voltage and the feed rate did not affect the tensile strength.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.4
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• pp.343-348
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• 2019

In this paper, a dual-band antenna is proposed for the autonomous vehicle as well as omni-directional. The proposed antenna operates in the 4G/LTE band (1,710~2,170MHz) and 5G/NR band (3,400~3,700MHz). In order to obtain the dual-band operation, the planar monopole antenna is proposed as the novel structure with single port of the 50ohm. To give the properties of dual-band, an additional antenna element with slit was added to the planar monopole antenna, and then a structural adjustment parameter was optimized for achieving the target performance in bands. The planar monopole antenna in the LTE band acts as the coupled feed for the added parasitic radiator in the 5G NR band. The proposed antenna has $38.5{\times}36.0{\times}1.0[mm^3]$ on a ground with diameter of 96mm. From the fabrication and measurement results, the impedance bandwidth (VSWR<2) of the proposed antenna covers 1,480~2,260MHz (LTE band: 1,710~2,170MHz) and 3,310~3,930MHz (5G NR band: 3,400~3,700MHz). The proposed planar monopole antenna also obtained the measured gain and radiation pattern of omni-directional radiation pattern in the anechoic chamber.