• Resources Recycling
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• v.30 no.5
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• pp.17-24
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• 2021

Natural aggregate regular exploitation has led to environmental and resource depletion issues; consequently, construction waste has become an important raw material in the supply of aggregate smoothly. The recycled aggregate produced in the most of recycled aggregate processing company in Korea has a high adhesion ratio of cement paste and mortar, which affects the water absorption ratio and density. Therefore, the quality of recycled aggregate needs to be improved. In this study, we improved the quality of recycled aggregate through the use of a multistage separation ball mill. This ball mill has a sieve which protects the ball mix and improves the motion. Products produced by using multistage separation ball mill were compared with various quality standard for utilization as recycle aggregate. Finally, we confirmed that the multistage separation ball mill can efficiently separate cement paste and mortar from natural aggregate and that it is suitable for the production of recycled aggregates.

• Resources Recycling
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• v.29 no.6
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• pp.98-103
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• 2020

In this study, the depression behavior of zinc sulfate on the sphalerite with the addition of potassium butyl xanthate was investigated to clear the relationship between zinc sulfate and xanthate in depression of sphalerite. As a result of the experiment, it was confirmed that the depress effect of zinc sulfate on the sphalerite declined with the increase of its addition amount. From the results of SEM-EDS and FT-IR analysis, it was found out that the amorphous precipitate of metal xanthate (Zn-BX) was formed in sphalerite concentrate, when the solubility product of [Zn+]·[BX] in the pulp solution exceeded 3.71×10-11, which is the solubility of Zn-butyl xanthate. It is considered that the Zn-butyl xanthate had a negative effect on the depression of sphalerite.

• Journal of Marine Bioscience and Biotechnology
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• v.12 no.2
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• pp.75-80
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• 2020

In the present study, the estrogenic activity and anti-osteoclastogenic activity of the Myelophycus simplex extract were evaluated using T47D-Kbluc cells and bone marrow-derived macrophages (BMMs). As a result of the measurement of the estrogenic activity in the T47D-Kbluc cell line, the Myelophycus simplex extract showed increased estrogenic activity in a dose-dependent manner in association with its concentration. To confirm the regulatory effect of the Myelophycus simplex extract on the estrogen-responsive gene, the Myelophycus simplex extract showed a similar tendency to estradiol: the expression of estrogen receptor 1 (ESR1) was significantly decreased while the expression of estrogen receptor 2 (ESR2) was increased. Furthermore, the Myelophycus simplex extract exhibited an inhibitory effect on osteoclast differentiation. In conclusion, these Myelophycus simplex extracts might be regarded as candidates for further studies or the development of functional food products or medicine to prevent or avoid postmenopausal symptoms for women.

• Journal of Korean Society of Water and Wastewater
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• v.34 no.6
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• pp.411-423
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• 2020

To remove phosphorus from the effluent of public wastewater treatment facilities, hundreds of enhanced phosphorus treatment processes have been introduced nationwide. However, these processes have a few problems including excessive maintenance cost and sludge production caused by inappropriate coagulant injection. Therefore, the optimal decision of coagulant dosage and automatic control of coagulant injection are essential. To overcome the drawbacks of conventional phosphorus removal processes, the integrated sedimentation and dissolved air flotation(SeDAF) process has been developed and a demonstration plant(capacity: 100 ㎥/d) has also been installed. In this study, various jar-tests(sedimentation and / or sedimentation·flotation) and multiple regression analyses have been performed. Particularly, we have highlighted the decision-making algorithms of optimal coagulant dosage to improve the applicability of the SeDAF process. As a result, the sedimentation jar-test could be a simple and reliable method for the decision of appropriate coagulant dosage in field condition of the SeDAF process. And, we have found that the SeDAF process can save 30 - 40% of coagulant dosage compared with conventional sedimentation processes to achieve total phosphorus (T-P) concentration below 0.2 mg/L of treated water, and it can also reduce same portion of sludge production.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.6
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• pp.261-270
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• 2010

As the usage of social network service(SNS) increases recently, great attention has been shown to the information security in SNS. However, there has been little investment in SNS environment for security while preferential investment to attract subscribers has been made so far. Moreover, there is still a lack of confidence for investment effect and an absence of framework to analyze the threat factors of information security in SNS. In this paper, we propose to model for decision-making standard of SNS information security investment by the AHP. The result shows that 'service image' is the most important criterion for the decision of SNS information security. It also shows that 'Profile-squatting and reputation slander through ID thefts' and 'Corporate espionage' are important threat factors in SNS information security.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.165-174
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• 2021

The purpose of this study is to compare the differences in national R&D research outcomes in science and technology according to gender. For this purpose, the analysis was conducted by mapping WoS SCI(E) papers from 1990to 2018 and NTIS R&D papers from 2007 t0 2016. As a result of examining the differences in research achievements in science and technology according to gender based on three bibliometic indicators - average Times cited, Time-lag, and Impact factor - we found that the overall topography of research achievement was still male-centered, and the differences in the main research area between male and female were also very prominent. On the other hand, in top 10 research areas, it was confirmed that female researchers' outcomes were higher in the number of Times cited and Impact factor.

• Journal of Aerospace System Engineering
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• v.16 no.3
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• pp.10-22
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• 2022

According to the Space Development Promotion Basic Plan, more than 110 satellites are expected to be deployed by 2031. Accordingly, the operation concept and technology for satellites constellation are required, compared to the existing few multi-satellite operations. It is essential to automate and optimize the mission operation system, for efficient operation of the satellite constellation, and preparations are urgently needed for the operation of satellite constellation in domestic as well. In this study, the development direction and strategy of the mission operation system applying automation and optimization for efficient operation of the satellite constellation are proposed. The framework for evaluating the automation level and priority of the mission operation system was developed, to identify the tasks to which automation should be applied preferentially.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.5
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• pp.557-565
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• 2022

The effect of flow configuration in ammonia-fed solid oxide fuel cell are investigated by using a three-dimensional numerical model. Typical flow configurations including co-flow and counter-flow are considered. The ammonia is directly fed into the stack without any external reforming process, resulting in an internal decomposition of NH3 in the anode electrode of the stack. The result showed that temperature profile in the case of counter-flow is more uniform than the co-flow configuration. The counter-flow cell, the temperature is highest at the middle of the channel while in the case of co-flow, the temperature is continuously increased and reached maximum value at the outlet area. This leads to a higher averaged current density in counter-flow compared to that of co-flow, about 5%.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.31 no.4
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• pp.617-635
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• 2021

Internet of Things (IoT) devices connected to the network without appropriate security solutions have become a serious security threat to ICT infrastructure. Moreover, due to the nature of IoT devices, it is difficult to apply currently existing security solutions. As a result, IoT devices have easily become targets for cyber attackers, and malware attacks on IoT devices are actually increasing every year. Even though several security solutions are being developed to protect IoT infrastructure, there is a great risk to apply unverified security solutions to real-world environments. Therefore, verification tools to verify the functionality and performance of the developed security solutions are also needed. Furthermore, just as security threats vary, there are several security solution s that defend against them, requiring suitable verification tools based on the characteristics of each security solution. In this paper, we propose an high-speed malware propagation tool that spreads malware at high speed in the IoT infrastructure. Also, we can verify the functionality of the security solution that detect and quickly block attacks spreading in IoT infrastructure by using the high-speed malware propagation tool.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.558-567
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• 2022

The evolution of temperature and thermal stress in a granite specimen is studied via heating experiment in the context of a high-level radioactive waste repository. A heating condition based on the decay-induced heat is applied to a cubic granite specimen to measure the temperature and stress distributions and their evolution over time. The temperature increases quickly due to heat conduction along the heated surfaces, but a significant amount of thermal energy is also lost through other surfaces due to air convection and conduction into the loading machine. A three-dimensional finite element-based model is used to numerically reproduce the experiment, and the thermo-mechanical coupling behavior and modeling conditions are validated with the comparison to the experimental results. The most crucial factors influencing the heating experiment are analyzed and summarized in this paper for future works.