• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.205-208
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• 2006

Damage of hydraulic concrete structures by the abrasion and erosion process is very severe and it indicates that the necessity of considering the influence of this process while designing concrete mixtures. Abrasion wear of concrete in hydraulic structures is caused by the movement of particles, water-borne debris. The resistance against erosion for high-strength self-consolidating concrete(SCC) was examined in this paper. A newly designed testing method is presented in order to quantitatively estimate the erosion of concrete. It was shown that loss of volume in abraded concrete can be explained as function of material parameters such as the amount of fly ash and blast furnace slag. Those admixtures have been widely used to reduce heat of hydration and improve resistance against sulfate attack. The results of current study can be used as a guideline in selecting the composition of concrete exposed to abrasion-wear.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.04a
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• pp.766-770
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• 1996

In this study, a CAD/CAM system for axisymmetric deep drawing processes has been developed. An approach to the system is based on the knowledge based system. Under the environment of CAD/CAM software of Personal Designer, the system has been written in UPL. The geometries of intermediate and final object in deep drawing process, including processes parameters are input for the CAD/CAM system. The input data can be obtained from the results of Pro-Deep. The parts drawing of die sets for each process is generatedin tool design module of the CAD/CAM system. Also, the die assemblydrawings can be obtained. NC commands for machining of the part can be generated in the developed CAD/CAM system.

• Korean Journal of Remote Sensing
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• v.24 no.5
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• pp.517-524
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• 2008

In order to classify an satellite imagery into geospatial features of interest, the supervised classification needs to be trained to distinguish these features through training sampling. However, even though an imagery is classified, different results of classification could be generated according to operator's experience and expertise in training process. Users who practically exploit an classification result to their applications need the research accomplishment for the consistent result as well as the accuracy improvement. The experiment includes the classification results for training process used VITD polygons as a prior probability and training parameter, instead of manual sampling. As results, classification accuracy using VITD polygons as prior probabilities shows the highest results in several methods. The training using unsupervised classification with VITD have produced similar classification results as manual training and/or with prior probability.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.6
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• pp.139-146
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• 2019

The modular building system is a type of prefabricated construction method, and is an industrialized building system that transports, assembles, and completes a three-dimensional module manufactured in a factory to the site. The economics of a modular building system where 50 to 80% of the entire process takes place in a modular factory is dominated by productivity of the factory manufacturing process. Since the building of the module is finished by the combination of unit parts produced by each material, it is necessary to manage the process in each module unit. However, currently marketed process control programs do not reflect the features of these modular methods. In this paper, we introduce Modular Factory Design software(MFD 2019) that can make modular unit production plan which reflects production base(modular factory) and production target(application and number of modular units). In order to verify software compatibility and reliability, two production plans with different production methods were formulated and simulated.

• Korean Chemical Engineering Research
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• v.49 no.2
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• pp.256-262
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• 2011

Amine can undergo irreversible reactions by $O_{2}$ and high temperature in amine scrubbing process and these phenomena are called "degradation". Degradation causes not only a loss of valuable amine, but also operational problems such as foaming, corrosion and fouling. In this study, using various chemical absorbents(MEA; monoethanolamine, AMP; 2-amino-2-methyl-1-propanol, DAM; 1,8-diamino-p-menthane), we examined the following variable. I) loading ratio of $CO_{2}$ at $50^{\circ}C$ and $120^{\circ}C$, ii) concentration variation and initial degradation rate constant of absorbent in $CO_{2}$ and $CO_{2}/O_{2}$ system, and iii) effect of degradation by $O_{2}$. The $CO_{2}$ loading of 20 wt% DAM was 400% and 270% higher than that of 20 wt% MEA and AMP at 50, respectively and was the largest the difference of $CO_{2}$ loading between absorption $(50^{\circ}C)$ and regeneration $(120^{\circ}C)$ condition. The initial degradation rate constant of 20 wt% DAM was $2.254{\times}10^{-4}cycle^{-1}$ which was slower than that of MEA $(2.761{\times}10^{-4}cycle^{-1})$ and AMP $(2.461{\times}10^{-4}cycle^{-1})$ in $CO_{2}$ system. Also, it was increased 30% by $O_{2}$ that effects on the degradation by $O_{2}$ was less than 100% increased. these degradation reactions was able to identify by formation of new peak in GC and FT-IR spectrum analysis.

• Journal for History of Mathematics
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• v.21 no.3
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• pp.53-66
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• 2008

The concepts of ratio and proportion are familiar with students but have difficulties in use. The purpose of this paper is to identify the meanings of the concepts of ratio and proportion through investigating the historical development process of the meanings and representations of them. The early meanings of ratio and proportion were arithmetical meanings, however, geometrical meanings had taken the place of them because of the discovery of incommensurability. After the development of algebraic representation, the meanings of ratio and proportion have been growing into algebraic meanings including arithmetical and geometrical meanings. Through the historical development process of ratio and proportion, it is observable that the meanings of mathematical concepts affect development of symbols, and the development of symbols also affect the meanings of mathematical concepts.

• Carbon letters
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• v.21
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• pp.51-60
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• 2017

Isotropic pitch-based fibers produced from coal tar pitch with the melt-blowing method were carbonized at temperatures ranging from 800 to $1600^{\circ}C$ to investigate their crystalline structure and physical properties as a function of the carbonization temperature. The in-plane crystallite size ($L_a$) of the carbonized pitch fiber from X-ray diffraction increased monotonously by increasing the carbonization temperature resulting in a gradual increase in the electrical conductivity from 169 to 3800 S/cm. However, the variation in the $d_{002}$ spacing and stacking height of the crystallite ($L_c$) showed that the structural order perpendicular to the graphene planes got worse in carbonization temperatures from 800 to $1200^{\circ}C$ probably due to randomization through the process of gas evolution; however, structural ordering eventually occurred at around $1400^{\circ}C$. For the carbonized pitch powder without stabilization, structural ordering perpendicular to the graphene planes occurred at around $800-900^{\circ}C$ indicating that oxygen was inserted during the stabilization process. Additionally, the shear stress that occurred during the melt-blowing process might interfere with the crystallization of the CPF.

• Journal of Korea Water Resources Association
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• v.53 no.5
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• pp.383-393
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• 2020

The main objective of this study is to provide a robust model for estimating parameters of the Clark unit hydrograph (UH) using the observed rainfall-runoff data in the Soyangang dam basin. In general, HEC-1 and HEC-HMS models, developed by the Hydrologic Engineering Center, have been widely used to optimize the parameters in Korea. However, these models are heavily reliant on the objective function and sample size during the optimization process. Moreover, the optimization process is carried out on the basis of single rainfall-runoff data, and the process is repeated for other events. Their averaged values over different parameter sets are usually used for practical purposes, leading to difficulties in the accurate simulation of discharge. In this sense, this paper proposed a hierarchical Bayesian model for estimating parameters of the Clark UH model. The proposed model clearly showed better performance in terms of Bayesian inference criterion (BIC). Furthermore, the result of this study reveals that the proposed model can also be applied to different hydrologic fields such as dam design and design flood estimation, including parameter estimation for the probable maximum flood (PMF).

• Journal of Wetlands Research
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• v.22 no.2
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• pp.130-138
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• 2020

As of 2017, the sewerage penetration rate of Seoul and metropolitan cities is more than 90%, and the number of domestic sewage treatment plants increased by 25% from 3,064 in 2010 to 4,072 in 2017. Among them, sewage treatment plant operated by SBR system is 585, which is 17% higher than 2010. In order to improve the water quality of the water source and improve the operation of the small sewage facilities, the improvement of the process was studied by applying the modelling to 49 facilities of the sewage treatment plant in Andong Imha dam area with more than 500㎥/day 3 places and 46 places less than 500㎥/day. As an improvement plan for modelling, candidate data were derived by reviewing operation data for 5 years. 49 facilities are operated by 12 types of operating processes. Among them, 1 place mort than 500㎥/day with SBR method and 9 facilities with less than 500㎥/day were selected by dividing 46 sites into 3 types. As a result of applying modelling to more than 500㎥/day, it was possible to improve the quality of discharged water through SRT control and it was found that applying model to sites of small scale treatment plants can improve the removal efficiency of TP by up to 14.4%. As a result, the data of this study could be used to improve and improve the operation of sewage treatment plants and RCSTP(Rural Community Sewage Tratment Plant).

• Journal of Korea Water Resources Association
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• v.47 no.7
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• pp.573-585
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• 2014

In this study, we propose a consensus-building support system to engage various stakeholders, transparently disseminate information, ensure objective decision-making, and reflect the view of each stakeholder as a methodology or tool for resolving conflicts that may arise in the process of implementing water environment policies and plans. The system suggests ways to resolve issues by engaging all interested actors and not just a few influential groups of stakeholders imposing their solutions upon local users. The system provides an environment where stakeholders can find solutions to conflicts through their own efforts, mediating competing interests through the interactions such as negotiations and conciliation to reach a consensus. To verify the applicability of the proposed consensus-building support system, simulated role-playing albeit restricted was conducted on the case of the Hantangang Dam construction. The simulation validated that open discussions and negotiations with the local community or NGO by the government increased the efficacy of negotiations.