• Journal of the Korea Institute of Building Construction
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• v.9 no.5
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• pp.127-133
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• 2009

It is important to increase the strength of binders in order to enhance the strength of concrete. However, when the mineral admixture used for high strength concrete is incorporated individually, its dispersibility decreases due to the phenomenon of compaction, which reduces its fluidity and results in insufficient strength being created. To solve this problem, we can pre-mix each binder in advance to disperse a mineral admixture among binders, which will strengthen the fluidity and strength of concrete. Therefore, this study analyzed the properties of high strength concrete depending on the mix method used, to determine the effect of pre-mix cements ranging from W/B 15 to 35%. It was found that the fluidity of pre-mix increased to a level higher than that of individual mix due to its dispersion and ball bearing effect. The air content was slightly decreased from the result of individual mix due to the micro filler effect, which causes fine particles of silica-fume to fill the voids among cement particles, while the setting time of pre-mix was shorter than that of individual mix, because enhanced dispersion of pre-mix affects hydration heat time. The compressive strength of pre-mix increased due to the phenomenon of compaction of gap structure, and the variation of coefficient decreased by 1.69% on average in strength variation.

• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.39-46
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• 2017

In this research, considering the practical conditions at field, thermal cracking reducing method was suggested based on the comparative analysis between predicted value and actual value obtained from the actual structure member with optimum mix design. The optimum mix design was deduced from the various mix designs with various proportions of cementitious binder for upper and lower placement lifts of mat-foundation mass concrete. Therefore, before field applications, the mix designs were obtained from the theoretical analysis obtained by MIDAS GEN for upper lift was OPC to FA of 85 to 15, and for lower lift was OPC to FA to BS of 50 : 20 : 30. Based on this mix design, the actual concrete for field was determined and all concrete properties were reached within the predicted range. Especially, the temperature properties of mass concrete at core was approximately $39^{\circ}C$ of temperature difference for low-heat mix design, while approximately $54^{\circ}C$ was shown for normal mix design currently used. Additionally, in the case of cracking index, the low heat mix design showed about 1.4 of relatively high value while the normal mix design showed 1.0. Therefore, it can be stated that applying low heat mix design and different heating technique between upper and lower placement lifts for mass concrete are efficient to control the thermal cracking.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.292-298
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• 2016

In this research, considering the practical situation of separated placing method for mass concrete structure, an efficient method of controlling the heat of hydration is suggested by comparing between the simulated values and actual measurements conducted with the optimum mix design obtained from the various mix conditions with different types and amount of supplementary cementitious materials(SCMs). As the result of the research, firstly, the optimum mix designs for top and bottom layers were determined by Midas gen as OPC to FA of 85 to 15, and OPC to FA to BS of 50 to 20 to 30, respectively. The concrete mixtures prepared with the mix designs determined from the simulation satisfied the target performance range in slump, air content and compressive strength. Additionally, from temperature measurement for the actual mass concrete placed during spring, the maximum temperature difference between surface and core was about $10^{\circ}C$ with 59 and $49^{\circ}C$ for top and bottom layers, respectively, and 1.4 of cracking index was obtained. Therefore, considering the practical conditions of mass concrete construction, it is considered that the different heat of hydration method using different mix designs with SCMs can be an efficient method for controlling thermal cracking and settling cracking of mass concrete.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.4
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• pp.522-533
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• 2012

This paper presents an adaptive strategy of GENCOs for reducing the greenhouse gas by fuel mix change. Fuel mix stands for generation capacity portfolio composed of different fuel resources. Currently, the generation sector of power industry in Korea is heavily dependent on fossil fuels, therefore it is required to change the fuel mix gradually into more eco-friendly way based on renewable energies. The generation costs of renewable energies are still expensive compared to fossil fueled resources. This is why the adaptive change is more preferred at current stage and this paper proposes an optimal strategy for capacity planning based on multiple environmental scenarios on the time horizon. This study used the computer program tool named GATE-PRO (Generation And Transmission Expansion PROgram), which is a mixed-integer non-linear program developed by Hongik university and Korea Energy Economics Institute. The simulations have been carried out with the priority allocation method in the program to determine the optimal mix of NRE(New Renewable Energy). Through this process, the result proposes an economic fuel mix under emission constraints compatible with the greenhouse gas mitigation policy of the United Nations.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.5
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• pp.50-57
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• 2009

The Kyoto Protocol finally entered into force in 2008. In this respect, it is imperative to explore different options to reduce greenhouse gas emissions for developing countries under the framework of the Kyoto Protocol. One of the main sources of $CO_2$ gas emission is fossil fueled power plants, thereby emission reduction could be achieved by substituting fossil fuel by non-fossil fuel sources on electric power generation sector. This paper presents the method for evaluating the effectiveness of emissions trading by fuel mix change. The cost of Fuel mix is formulated considering the economic effects of emission trading in electricity market. And the optimal fuel mix is proposed under the given emission constraints.

• Journal of Internet Computing and Services
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• v.21 no.6
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• pp.51-56
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• 2020

Cryptocurrencies, including Bitcoin, has decentralization, distribution and P2P properties unlike traditional currencies relies on trusted central party such as banks. All transactions are stored transparently and distributively, hence all participants can check the details of those transactions. Due to the properties of cryptographic hash function, deletion or modification of the stored transations is computationally not possible. However, cryptocurrencies only provide pseudonymity, not anonymity, which is provided by traditional currencies. Therefore many researches were conducted to provide anonymity to cryptocurrencies such as mix-based methods. In this paper, I will propose more efficient hybrid mix-based method for anonymity than previous mix-based one.

• Journal of the Korean Society of Clothing and Textiles
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• v.26 no.9
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• pp.1354-1365
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• 2002

With the appearance of many new types of fashion stores in Korea, competitions among fashion store types art fiercer than ever before. As consumers alternatives in fashion store selection increase, they select different store types to purchase different product types. Therefore, the probability of patronage mix behavior according to product type increases. Understanding consumers patronage mix behavior, finding out the determinant attributes of fashion stores for each product type, and analyzing competitive structures among fashion stores are important to retailers and marketers for building a successful merchandising and marketing strategies. An empirical study was conducted to analyze the competitive structure among the store types by consumers' patronage mix behavior. A questionnaire was developed and data were collected from 464 adult women living in Seoul area in Korea. Factor analysis, paired t-test, ANOVL Duncan test, and discriminant analysis were employed to analyze the data. Data regarding patronage mix behavior by product type proved that certain store types had ‘natural dominance’ in a particular product type as Hirschman(l978) pointed out. Also, a new analytic method of the competitive structures among fashion store types was suggested in the study, by which a specific store type retailer can analyze his/her own customers' patronage mix behavior by product type. The analysis will enable retailers to distinguish which of their competitors are substitutive, selling same product types, and which are complementary, selling different product types. Retailers have to concentrate on the strategies for the substitutive competitors rather than complementary competitors because their marketing abilities and resources are limited.

• Journal of Korea Society of Industrial Information Systems
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• v.12 no.5
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• pp.183-200
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• 2007

This study examines the relationships between typical anticipated benefit factors of introducing online business activities by traditional brick-and-mortar shipping and port logistics companies and their performance in marketing mix and global competitiveness. Three major benefit factors were derived including improved trust, information acquiring and limitation of offline business activities. The three empirically derived critical synergy factors were then used to examine how they improve the firms performance in marketing mix and global competitiveness. The results of structural equation modeling method show that the anticipated benefit factors significantly influence the firms' performance in marketing mix. Subsequently, marketing mix significantly influence the firms' global competitiveness. The results provide useful guidelines for the shipping and port logistics firms to develop appropriate marketing mix strategies to improve their global competitiveness.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.561-572
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• 2010

This paper is a study about application of recently proposed Performance Based Mixture Design (PBMD) for design of high strength concrete (HSC) to obtain HSC mix proportion that satisfies required performances. The PBMD method which uses Satisfaction curve based on a Bayesian method is a performance oriented concrete mix proportion design procedure easily applicable to any condition and environment for a possible replacement to the current prescriptive design standards. Based on extensive experimental results obtained for various materials and performance parameters of HSC, the application feasibility of the developed PBMD procedure for HSC has been verified. Also, the proposed PBMD procedure has been used to perform application examples to obtain desired target performances of HSC with optimum concrete mixture proportions using locally available materials, local environmental conditions, and available concrete production technologies. The validity and precision of HSC mix proportion design obtained using the PBMD method is verified with the experimental and ACI presented results to check the feasibility for actual design usage.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.1-15
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• 2009

Surface of exposed aggregate concrete pavements is consists of exposed coarse aggregate by removing upper 2$\sim$3mm mortar of concrete slab. Exposed aggregate concrete pavements have advantages of maintaining low-noise and adequate skid-resistance level during the performance period. In order to provide the successful exposed concrete aggregate pavement, uniform distribution of the coarse aggregate on pavement surface through adequate the mix design and exposing method. The mix design in concrete pavement is generally designed on the basis of strength, but mix design of exposed aggregate pavement employed in this study includes the consideration of noise and skid resistance, as well as strength. Smaller of maximum coarse aggregate is known to be effective for reduce noise level. Optimum mix design and exposing method of fine-size exposed aggregate portland cement concrete pavement that can reducing the noise and maintain the adequate level of skid resistance are proposed in this study. To consider the variation of optimum exposing time due to the hardening speed of mortar by climatic condition, quantitative is also suggested measurement of hardening state.