• Korean Chemical Engineering Research
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• 제57권6호
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• pp.804-811
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• 2019

본 연구는 매체형 전동밀(전동 볼 밀)에서 매체선정에 관한 공정조건 최적화를 위하여, 직경과 재질이 각각 다른 3가지 종류의 분쇄매체를 이용, 매체의 움직임을 실제 촬영하고 DEM 시뮬레이션을 병행하여 비교 연구하였다. 시뮬레이션에서는 밀의 회전속도, 매체의 재질, 매체의 운동속도, 매체와 포트 벽면과의 마찰계수 등을 실제 실험조건과 동일하게 조건을 맞추었다. 다양한 종류의 분쇄매체의 움직임을 실제 촬영된 사진 및 시뮬레이션에서 해석된 스냅샷 사진 위에, 본 연구에서 정의한 분쇄장을 설정하여 해석함으로써 그 값을 정량적으로 측정하였다. 또한, 정량적으로 측정된 값과 분쇄시료의 변화된 모습을 관찰하여 그 상관관계를 검토하였다. 따라서 특정 실험조건에서 분쇄장에 가장 큰 영향을 주는 분쇄매체의 최적화를 제언 하고자 하였다.

• ETRI Journal
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• 제36권4호
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• pp.519-527
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• 2014

An integrated multi-beam satellite and multi-cell terrestrial system is an attractive means for highly efficient communication due to the fact that the two components (satellite and terrestrial) make the most of each other's resources. In this paper, a terrestrial component reuses a satellite's resources under the control of the satellite's network management system. This allows the resource allocation for the satellite and terrestrial components to be coordinated to optimize spectral efficiency and increase overall system capacity. In such a system, the satellite resources reused in the terrestrial component may bring about severe interference, which is one of the main factors affecting system capacity. Under this consideration, the objective of this paper is to achieve an optimized resource allocation in both components in such a way as to minimize any resulting inter-component interference. The objective of the proposed scheme is to mitigate this inter-component interference by optimizing the total transmission power - the result of which can lead to an increase in capacity. The simulation results in this paper illustrate that the proposed scheme affords a more energy-efficient system to be implemented, compared to a conventional power management scheme, by allocating the bandwidth uniformly regardless of the amount of interference or traffic demand.

• 한국자원식물학회:학술대회논문집
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• 한국자원식물학회 2002년도 춘계 학술발표대회
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• pp.43-44
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• 2002

• 대한치과기공학회지
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• 제43권4호
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• pp.145-152
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• 2021

Purpose: This study aimed to produce resin prosthetics using a dental barrel finishing machine. For dental resin grinding, the ingredients of the barrel finishing media were analyzed, and surface residues of the resin were observed. Methods: Two types of barrel finishing media for dental resin grinding were tested. Specimens were made from thermal polymerized, auto polymerized, and photopolymerized resins. Finishing media were analyzed through energy-dispersive X-ray spectroscopy (EDS) component analysis and inductively coupled plasma-optical emission spectrometry (ICP-OES) component analysis. Then, the prepared specimen was barrel finished for 25 minutes using two types of barrel finishing media, and scanning electron microscope was photographed to observe the surface residues. Results: As a result of EDS component analysis, both types of finishing media were analyzed for the components of C, O, Zr and Al elements, and industry media (IM) was further analyzed for the components of Si and Mg elements. In the ICP-OES component analysis, Cd and As, which are harmful elements, were detected in IM, and no harmful elements were detected in manufacturing media (MM). Because of observation of surface residues, no residues were observed in the three types of resin specimens that were barrel finished with two types of finishing media. Conclusion: Surface residue wasn't observed on the specimens polished using two types of finishing media. However, in IM, Cd and As, which are harmful elements, were detected, making it inappropriate for clinical use. In MM, harmful elements were not detected; therefore, clinical use will be possible.

• Korean Chemical Engineering Research
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• 제55권4호
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• pp.456-466
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• 2017

이 연구는 교반볼밀을 이용한 금속기반 복합재 제조공정에 있어서 분쇄매체의 차이에 의한 입자형상의 변화를 관찰하고, 볼 거동의 DEM시뮬레이션을 행하였다. 교반볼밀에서 볼 거동의 3차원 시뮬레이션을 통해 분쇄메커니즘을 규명하기 위하여 분쇄매체의 힘, 운동에너지, 매체 운동속도 등을 계산하였다. 또한 복합재 제조를 위한 실험조건을 이전의 다른 볼밀에서에 같이 교반볼밀 회전속도를 변화시켰고, 볼 재질, 운동속도, 마찰계수 등도 동일한 조건으로 변화시키면서 투입되는 에너지의 변화량도 계산하였다. 교반볼밀의 회전속도가 증가함에 따라, 분쇄매체와 매체, 매체와 벽면, 그리고 매체와 교반기 사이의 충격에너지가 증가하는 것을 정량적으로 계산 할 수 있었다. 또한 같은 실험 조건에서 입자형상 변화를 명확하게 분석 할 수 있었으며, 볼 거동이 입자형상 변화에 매우 큰 영향을 미치는 것을 알 수 있었다.

• 한국재료학회지
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• 제28권3호
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• pp.148-158
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• 2018

This study investigated the effect of the grinding media of a ball mill under various conditions on the raw material of copper powder during the milling process with a simulation of the discrete element method. Using the simulation of the three-dimensional motion of the grinding media in the stirred ball mill, we researched the grinding mechanism to calculate the force, kinetic energy, and medium velocity of the grinding media. The grinding behavior of the copper powder was investigated by scanning electron microscopy. We found that the particle size increased with an increasing rotation speed and milling time, and the particle morphology of the copper powder became more of a plate type. Nevertheless, the particle morphology slightly depended on the different grinding media of the ball mill. Moreover, the simulation results showed that rotation speed and ball size increased with the force and energy.

• 인터넷정보학회논문지
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• 제19권2호
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• pp.69-75
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• 2018

Over the years, the types of media and media usage patterns have rapidly changed and communication channels in society have diversified. The courses in the universities on "media" have accordingly been altered to adapt to these changes. To investigate the ways in which the higher learning institutions in Korea have adapted to the changes in the media environment, this study analyzed the curriculum provided by the communication/media departments in the areas of Seoul and Gyeonggi-do. For the curricula analysis,names of the course soffered at the selected universitie swere analyzed; then keywords were extracted from morphological analysis of thes enames. Also, to investigate the changes over time, the courses offered in the years 2008 and 2017 were selected. The network analysis was done by using Netminer; the shape, main components, and major nodes of the network were compared. The results showed that firstly, overall shape of network from 2008 and 2017 looked similar. Due to the existence of concentrations within the major, the overall shape of the network showed several independent components, rather than one network. However, the analysis revealed differences in major nodes in the 2008 case from 2017. In the 2008 case, 'programming,' 'media,' 'introduction' among others were the major nodes; in 2017, 'editing' was the most important node. This signifies that in 2017, the curricula in the selected universities emphasized more practical and technical media education. In other words, the universities have adapted to the changing environments by including new topics, paying more attention to video media, and providing students with more direct field experiences.

• Journal of electromagnetic engineering and science
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• 제9권4호
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• pp.188-193
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• 2009

A K-band low-power miniaturized planar-type hyperthermia system was developed to replace massive and expensive equipment. The system consists of a VCO with a buffer amplifier, a high-power amplifier module, a 20-dB-coupled line coupler, a chip circulator and two power detectors for signal generation, amplification and power monitoring. All these components have been implemented in planar form on two module blocks. The total size of the hyperthermia system was less than $10\times6.5\times3\;cm^3$. In order to verify the system performance, ablations were carried out on nude mice xenografted with human breast cancer. Ablation results show performance comparable to the massive components-based system. This work shows the feasibility of a low-cost miniaturized hyperthermia system for practical clinical applications.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.184-188
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• 2009

To interactively share High Definition (HD)-quality visualization over emerging ultra-high-speed network infrastructure, several lossless and low-delay real-time media (i.e., uncompressed HD video and audio) transport systems are being designed and prototyped. However, most of them still rely on expensive hardware components. As an effort to reduce the building cost of system, in this paper, we propose the integration of both transmitter and receiver machines into a single bi-directional transport system. After detailed bottleneck analysis and subsequent refinements of embedded software components, the proposed integration can provide Real-time Transport Protocol (RTP)-based bi-directional transport of uncompressed HD video and audio from a single machine. We also explain how to interface the Gbps-bandwidth display output of uncompressed HD media system to the networked tiled display of 10240 $\times$ 3200 super-high-resolution. Finally, to verify the feasibility of proposed integration, several prototype systems are built and evaluated by operating them in several different experiment scenarios.

• The Journal of Asian Finance, Economics and Business
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• 제7권11호
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• pp.381-391
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• 2020

This research article investigates the way eWOM in social media influences the formation of destination image through development of trust and satisfaction for the potential tourist. The research involved administering an 18-point questionnaire taking online reviews, tourist involvement, and eWOM, destination image components of trust and satisfaction as variables. Data was collected from 554 individuals forming a cross-section of social media users and analyzed using multi-variate techniques (Reliability, CFA, and SEM). Results indicate a positive and significant relationship between all except online review and destination trust and satisfaction. Indirect and direct effects indicate that eWOM fully mediates the relationship between destination satisfaction and involvement and partially mediates the relationship between destination trust and involvement. In the case of online reviews, eWOM acts as a full mediator between destination trust and destination satisfaction for the future traveler using social media. The study proposes that components of image vary depending upon the degree of involvement, volume online reviews and eWOM generated also termed as 'virality' and these in turn influence the intention to revisit or recommend a destination. The study highlights its utility for National Tourist Organizations (NTOs) and online travel intermediaries to enhance destination marketing efforts.