• Korean Journal of Hazardous Materials
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• v.6 no.2
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• pp.77-86
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• 2018

Interest in renewable energy is increasing for eco-friendly use of energy, and fuel cells are being used in various ways such as houses and buildings as power generation methods that have low emissions such as $NO_X$ and $CO_2$. As the supply of fuel cells expands, more and more boilers are installed in the existing buildings, but safety management is not being performed properly. Therefore, in this study, a prior study was conducted on the status of fuel cell-boiler complex installation and related criteria, and the risk factors were analyzed according to the installation environment and structure. Based on these standards, the safety performance of the fuel cell-boiler combined installation is assessed by conducting a demonstration using the starting product of the simulated operation to derive the installation criteria (proposal) for the fuel cell-boiler combined installation. The installation criteria (proposal) include the construction and connection method of the piping according to the fuel cell-boiler complex installation.

• Journal of Korea Multimedia Society
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• v.24 no.1
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• pp.75-94
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• 2021

The 4th industrial revolution needs a fusion of artificial intelligence, robotics, the Internet of Things (IoT), edge computing, and other technologies. For the fusion of technologies, cloud computing technology can provide flexible and high-performance computing resources so that cloud computing can be the foundation technology of new emerging services. The emerging services become a global-scale, and require much higher performance, availability, and reliability. Public cloud providers already provide global-scale services. However, their services, costs, performance, and policies are different. Enterprises/ developers to come out with a new inter-operable service are experiencing vendor lock-in problems. Therefore, multi-cloud technology that federatively resolves the limitations of single cloud providers is required. We propose a software platform, denoted as Cloud-Barista. Cloud-Barista is a multi-cloud service common platform for federating multiple clouds. It makes multiple cloud services as a single service. We explain the functional architecture of the proposed platform that consists of several frameworks, and then discuss the main design and implementation issues of each framework. To verify the feasibility of our proposal, we show a demonstration which is to create 18 virtual machines on several cloud providers, combine them as a single resource, and manage it.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.29-40
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• 2023

Xanthan gum and starch compound biopolymer (XS), an environmentally friendly soil-binding material produced from natural resources, has been suggested as a slope protection material to enhance soil strength and erosion resistance. Insufficient wet strength and the consequent durability concerns remain, despite XS biopolymer-soil treatment showing high strength and erosion resistance in the dried state, even with a small dosage of soil mass. These concerns need to be solved to improve the field applicability and post-stability of this treatment. This study explored the utilization of an alkaline-based cation crosslinking method using calcium hydroxide and sodium hydroxide to induce non-thermal gelation, resulting in the enhancement of the wet strength and durability of biopolymer-treated soil. Laboratory experiments were conducted to assess the unconfined compressive strength and cyclic wetting-drying durability performance of the treated soil using a selected recipe based on a preliminary gel formation test. The results demonstrated that the uniformity of the gel structure and gelling time varied depending on the ratio of crosslinkers to biopolymer; consequently, the strength of the soil was affected. Subsequently, site soil treated with the recipe, which showed the best performance in indoor assessment, was implemented on the field slope at the bridge abutment via compaction and pressurized spraying methods to assess feasibility in field implementation. Moreover, the variation in surface soil hardness was monitored periodically for one year. Both slopes implemented by the two construction methods showed sufficient stability against detachment and scouring, with a higher soil hardness index than the natural slope for a year.

• Journal of the Korean Institute of Gas
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• v.28 no.1
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• pp.65-72
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• 2024

Green Hydrogen demonstration complex is under conduction in Jeju island which is rich in renewable energy resources and will produces green hydrogen using a water electrolysis systems. In order to check durability of long-term operation, AST(accelerated stress test) was applied and the power pattern based on Jeju Island's wind power was applied. After 800 hours of repeated application of low current and high current, the performance of the PEM water electrolysis cell was reduced by up to 10% and by about 5.5% in operating conditions. As the result of impedance analysis, it can be seen that the electrode polarization resistance greatly increased than ohmic polarization resistance. In addition, when the durability evaluation was conducted by applying the wind power pattern of Jeju Island, the performance of the PEM water electrolysis cell showed up to 1.6% and a decrease of less than 1% in operating conditions. As a result of the impedance, it can be seen that the change of ohmic resistance and electrode polarization resistance is small.

• Journal of Astronomy and Space Sciences
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• v.32 no.4
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• pp.419-425
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• 2015

In this study, a new idea for developing a space scale for measuring mass in a microgravity environment was proposed by using the inertial force properties of an object to measure its mass. The space scale detected the momentum change of the specimen and reference masses by using a load-cell sensor as the force transducer based on Newton's laws of motion. In addition, the space scale calculated the specimen mass by comparing the inertial forces of the specimen and reference masses in the same acceleration field. By using this concept, a space scale with a capacity of 3 kg based on the law of momentum conservation was implemented and demonstrated under microgravity conditions onboard International Space Station (ISS) with an accuracy of ${\pm}1g$. By the performance analysis on the space scale, it was verified that an instrument with a compact size could be implemented and be quickly measured with a reasonable accuracy under microgravity conditions.

• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.454-459
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• 2003

We report the first demonstration of 10 Gb/s wavelength conversion in a Mach-Zehnder interferometric wavelength converter monolithically integrated with a loss-coupled DFB probe source. The integrated device is fabricated using a BRS (buried ridge stripe) structure with an undoped InP clad layer on the top of a passive waveguide to reduce high propagation loss. The device exhibited a static extinction ratio of 11 dB. Good performance at 10 Gb/s is obtained with an extinction ratio of 7 dB and a power penalty of 2.8 dB at a 10$^{-9}$ bit error rate.

• Journal of the Korean Society for Nondestructive Testing
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• v.13 no.1
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• pp.29-39
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• 1993

초음파탐상검사는 그 검사결과가 여타 비파괴검사법에 비해 검사자, 검사장비, 절차서 등 검사 시스템에의 의존도가 높으며, 이중에서도 특히 검사자의 능력과 숙련도에 크게 좌우된다. 따라서 검사결과의 신뢰도를 높이기 위해서는 무엇보다도 검사자에 대해 엄격한 자격인정(Qualification)이 필요하다. 초음파탐상검사는 원자력 발전소 기기의 가동전중검사시 가장 많이 적용하는 체적검사법으로써, 결함검출 및 평가의 신뢰도를 확보하기 위하여 최근 관련 기술기준에서는 검사자에 대해 보다 엄격한 자격인정을 요구함과 아울러 초음파탐상검사 시스템(검사자, 장비, 절차서)에 대한 기량검증(Performance Demonstration)까지를 요구하고 있다. 위의 두 가지 요건을 성공적으로 충족시킬 수 있다면, 초음파탐상기술의 신뢰도는 크게 향상될 것이다. 본고에서는 최근 보다 강화된 원전 가동전중검사 초음파탐상검사 요원의 자격인정요건에 대해 자세히 알아봄으로써 관련 국내 기술기준의 제정과 앞으로 국내 원전 초음파탐상 검사요원에 대한 본 자격인정요건의 적용에 대비코자 하였다. 한편, "초음파탐상검사 시스템에 대한 기량검증 요건"은 초음파탐상 검사요원의 자격인정 요건과 밀접한 관계가 있으므로 다음에 별도로 기술코자 한다.

• Journal of applied mathematics & informatics
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• v.8 no.1
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• pp.181-197
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• 2001

A heuristic method TABU-CSP using Tabu Search (TS) is described for solving Constraint Satisfaction Problems (CSPs). The method is started with a complete but inconsistent solution of a binary CSP and obtained in prespecified number of iterations either a consistent solution or a near optimal solution with an acceptable number of conflicts. The repair in the solution at each iterative step is done by using two heuristics alternatively. The first heuristic is a min-conflicts heuristic that chooses a variable with the maximum number of conflicts and reassigns it the value which leads to the minimum number of conflicts. If the acceptable solution is not reached after the search continued for a certain number of iterations, the min-conflict heuristic is changed and the variable selected least number of times is chosen for repair. If an acceptable solution is not reached, the method switches back to the min-conflict heuristic and proceeds further. This allowed the method to explore a different region of search space space for the solution as well as to prevent cycling. The demonstration of the method is shown on a toy problem [9]which has no solution. The method is then tested on various randomly generated CSPs with different starting solutions. The performance of the proposed method in terms of the average number of consistency is checked and the average number of conflicts is conflicts is compared with that of the Branch and Bound(BB) method used to obtain the same solution. In almost all cases, the proposed method moves faster to the acceptable solution than BB.

• Journal of the Korean School Mathematics Society
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• v.20 no.3
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• pp.303-323
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• 2017

This is a multiple-case study of how preservice secondary mathematics teachers teach a particular mathematics using a technological tool. In a performance interview, the preservice teachers demonstrated how they would teach a specific mathematical topic using Geometer's Sketchpad. The results of this study showed that the preservice teachers designed diverse types of lesson plans and implemented different pedagogical and technological techniques in their teaching demonstrations. The findings suggest that preservice teachers' pedagogical content knowledge is an important factor in the integration of technology into their mathematics teaching. Thus, mathematics teacher educators should help preservice teachers gain a robust pedagogical content knowledge in order to effectively teach mathematics with technological tools.

• Journal of environmental and Sanitary engineering
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• v.22 no.4
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• pp.33-44
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• 2007

Since the introduction of a new field of skin care to Korean market which was developed in 1980, a variety of skin care therapies have appeared in mid-1990s. Therefore, in particular, it is considered that aroma therapy is one of the most preferred methods for skin care. Therefore, previous studies focused just on clinical effects of aromatherapy while this study focuses on aestheticians by identifying whether performance of aromatherapy, and their contribution to income will influence on satisfaction in aestheticians and customers' intention to reuse aromatherapy service for positive demonstration. The results of the study are presented as follows: First, it is demonstrated that side-effect of aromatherapy, contribution to income, and customer satisfaction have significant effect on professional aestheticians. In particular, in respect to the aestheticians, this study obtains the results rather different from the estimation that customers are satisfied with the professional service though they have side-effect. Second, as the satisfaction in professional aestheticians after skin care service is a significant factor that influences on intention to reuse it, this study concludes that re-management on behaviors is required according to the degrees of satisfaction.