• KEPCO Journal on Electric Power and Energy
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• 제5권4호
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• pp.337-341
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• 2019

In this study, the effects of two materials, active alumina and CaO based inorganic binder, which cause the side reaction on the K₂CO₃-based solid CO₂ sorbents was investigated. K₂CO₃-based solid sorbents called KAM series was prepared by spray drying method and then measured its physical properties and CO₂ sorption capacity. Among the KAM series sorbents, KAM(0.5) maintained high CO₂ sorption capacity of 7.6 wt% after 3 cycle of sorption/regeneration reaction and showed very low attrition loss as low as 3.1 % which was measured by ASTM D5757-95.

• Industrial Engineering and Management Systems
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• 제14권1호
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• pp.58-72
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• 2015

A primary concern of national R&D plans is to encourage technological development in private firms and research institutes. For effective R&D planning and program support, it is necessary to assess technological impacts that may exist both directly and indirectly among technology areas within the whole technology system; however, previous studies analyze only direct impacts among technologies, failing to capture both direct and indirect impacts. Therefore, this study proposes an approach based on decision-making trial and evaluation laboratory (DEMATEL) to identifying specific characteristics of technology areas, such as technological impact and degree of cause or effect (DCE). The method employs patent co-classification analysis to construct a technological knowledge flow matrix. Next, to capture both direct and indirect effects among technology areas, it incorporates the modified DEMATEL process into patent analysis. The method helps analysts assess the technological impact and DCE of technology areas, and observe their evolving trajectories over time, thereby identifying relevant technological implications. This study presents a case study using Korean patents registered during 2003-2012. We expect our analysis results to be helpful input for R&D planning, as well as the suggested approach to be incorporated into processes for formulating national R&D plans.

• 한국환경과학회지
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• 제4권1호
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• pp.41-52
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• 1995

The effects of reaction temperature, SO2 and CO2 concentration in an air gas stream, particle sizes of limestone on the reactivity and capacity of SO2 removal have been determined in a thermogravimetric analyser(TGA). The apparent reaction order of sulfation reaction of pre-calcined lime(CaO) with respect to SO2 is found to be close to unity. The apparent activation energies are found to be 17,000 kcal/kmol for sulfation of pre-calcined lime and 19,500 kcal/kmol for direct sulfation of limestone(CaCO3). The initial sulfation reaction rate of pre-calcined lime increases with increasing temperature, whereas the sulfur capture capacity exhibits a maximum value at 90$0^{\circ}C$. In direct sulfation of limestone, sulfation reactivity and sulfur capature capacity of sorbent increase with increasing temperature and decreasing CO2 concentration in a gas bulk stream. The main pare of pre-calcined lime is shifted to the larger pore sizes and pore volume decreases with increasing sulfation time and temperature. The surface area of lime decreases with increasing calcination temperature under an air atmosphere, whereas is yearly constant under a CO2(5, 10%) atmosphere in a gas stream.

• 대한의용생체공학회:의공학회지
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• 제32권2호
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• pp.93-104
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• 2011

The purpose of this study was to investigate lower-limb joint torque of the two groups as it changed by somatosensory stimulation during the descent down three stairs of different heights and to describe the difference between the two groups, which are young people group and elderly people group. Subjects of each groups climbed down a stair at four stimulation conditions, which are non-stimulation, tibialis anterior tendon stimulation, achilles tendon stimulation, tibialis anterior - achilles tendon stimulation. Motion capture data were collected using 3D optoelectric motion tracking system that utilizes active infrared LEDs, near infrared sensor and force plate. The obtained motion capture data was used to build 3D computer simulation model. The results show that lower-limb joint torque of the two groups changed with somatosensory stimulation as they descended the stairs and the joint torque of the two groups differed from each other.

• Advances in nano research
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• 제12권1호
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• pp.101-115
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• 2022

Some researchers pointed out that the nonlocal cantilever models do not predict the dynamic softening behavior for nanostructures (including nanobeams) with clamped-free (CF) ends. In contrast, some indicate that the nonlocal cantilever models can capture the stiffness softening characteristics. There are substantial differences on this issue between them. The vibration analysis of porosity-dependent functionally graded nanoscale tubes with variable boundary conditions is investigated in this study. Using a modified power-law model, the tube's porosity-dependent material coefficients are graded in the radial direction. The theory of nonlocal strain gradients is used. Hamilton's principle is used to derive the size-dependent governing equations for simply-supported (S), clamped (C) and clamped-simply supported (CS). Following the solution of these equations by the extended differential quadrature technique, the effect of various factors on vibration issues was investigated further. It can be shown that these factors have a considerable effect on the vibration characteristics. It also can be found that our numerical results can capture the unexpected softening phenomena for cantilever tubes.

• 방사성폐기물학회지
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• 제21권2호
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• pp.205-224
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• 2023

The emission of off-gas streams from used fuel recycling is a concern in nuclear energy usage as they contain radioactive compounds, such as, ³H, ¹⁴C, ⁸⁵Kr, ¹³¹I, and ¹²⁹I that can be harmful to human health and environment. Radioactive iodine, ¹²⁹I, is particularly troublesome as it has a half-life of more than 15 million years and is prone to accumulate in human thyroid glands. Organic iodides are hazardous even at very low concentrations, and hence the capture of ¹²⁹I is extremely important. Dynamic adsorption experiments were conducted to determine the efficiency of sodium mordenite, partially exchanged silver mordenite, and fully exchanged silver mordenite for the removal of methyl iodide present at parts per billion concentrations in a simulated off-gas stream. Kinetic analysis of the system was conducted incorporating the effects of diffusion and mass transfer. The possible reaction mechanism is postulated and the order of the reaction and the values of the rate constants were determined from the experimental data. Adsorbent characterization is performed to investigate the nature of the adsorbent before and after iodine loading. This paper will offer a comprehensive understanding of the methyl iodide behavior when in contact with the mordenites.

• Communications for Statistical Applications and Methods
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• 제30권3호
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• pp.291-309
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• 2023

Longitudinal count data has been widely collected in biomedical research, public health, and clinical trials. These repeated measurements over time on the same subjects need to account for an appropriate dependency. The Poisson regression model is the first choice to model the expected count of interest, however, this may not be an appropriate when data exhibit over-dispersion or under-dispersion. Recently, Conway-Maxwell-Poisson (CMP) distribution is popularly used as the distribution offers a flexibility to capture a wide range of dispersion in the data. In this article, we propose a Bayesian CMP regression model to accommodate over and under-dispersion in modeling longitudinal count data. Specifically, we develop a regression model with random intercept and slope to capture subject heterogeneity and estimate covariate effects to be different across subjects. We implement a Bayesian computation via Hamiltonian MCMC (HMCMC) algorithm for posterior sampling. We then compute Bayesian model assessment measures for model comparison. Simulation studies are conducted to assess the accuracy and effectiveness of our methodology. The usefulness of the proposed methodology is demonstrated by a well-known example of epilepsy data.

• International Journal of Aeronautical and Space Sciences
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• 제17권1호
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• pp.8-19
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• 2016

This paper investigates the effects of inlet turbulence conditions and near-wall treatment methods on the heat transfer prediction of gas turbine vanes within the range of engine relevant turbulence conditions. The two near-wall treatment methods, the wall-function and low-Reynolds number method, were combined with the SST and ${\omega}RSM$ turbulence model. Additionally, the RNG $k-{\varepsilon}$, SSG RSM, and $SST_+{\gamma}-Re_{\theta}$ transition model were adopted for the purpose of comparison. All computations were conducted using a commercial CFD code, CFX, considering a three-dimensional, steady, compressible flow. The conjugate heat transfer method was applied to all simulation cases with internally cooled NASA turbine vanes. The CFD results at mid-span were compared with the measured data under different inlet turbulence conditions. In the SST solutions, on the pressure side, both the wall-function and low-Reynolds number method exhibited a reasonable agreement with the measured data. On the suction side, however, both wall-function and low-Reynolds number method failed to predict the variations of heat transfer coefficient and temperature caused by boundary layer flow transition. In the ${\omega}RSM$ results, the wall-function showed reasonable predictions for both the heat transfer coefficient and temperature variations including flow transition onset on suction side, but, low-Reynolds methods did not properly capture the variation of the heat transfer coefficient. The $SST_+{\gamma}-Re_{\theta}$ transition model showed variation of the heat transfer coefficient on the transition regions, but did not capture the proper transition onset location, and was found to be much more sensitive to the inlet turbulence length scale. Overall, the Reynolds stress model and wall function configuration showed the reasonable predictions in presented cases.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.1730-1738
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• 2011

Personal Rapid Transit(PRT)는 경쟁력 있는 건설비와 운영비로 보행중심의 환경을 제공함으로써 대중교통 중심의 지속가능한 사회를 위한 바람직한 교통수단으로 등장하였다. 본 연구에서는 PRT 도입시 PRT 이용경험이 없는 사람들의 교통수단선택 행태의 변화를 분석하였다. PRT 선택행태 분석의 핵심 이슈는 경험해보지 못한 교통수단에 대한 이용자들의 인지와 평가를 어떻게 효과적으로 측정하는 가이다. PRT 도입전후의 교통수단 선택에 대한 RP와 SP 자료를 설문조사를 이용하여 수집하였다. 설문지는 PRT 선호에 대한 bias를 최소화하도록 설계하였으며, 설문응답자의 성실한 답변을 방해하는 수많은 SP 설문항목을 획기적으로 줄일 수 있도록, 복잡한 fractional factorial 설계를 사용하지 않았다. 분석결과를 통해 본 연구에서 제안된 방법이 교통수단선택과 관련된 설명변수들을 효과적으로 측정하고 있음을 알 수 있다. 이산선택모형을 이용하여 다양한 PRT 시스템 특성과 운영방식하에서의 교통수단선택을 추정하였으며, 2개의 대상도시에 대해 PRT 이용수요를 예측하였다.

• 청정기술
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• 제18권3호
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• pp.229-249
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• 2012

산업 발달로 화석 연료 사용이 급증하고 이에 따른 지구 온난화 문제와 자원 고갈 문제가 대두되어 지속 성장을 위협하고 있다. 따라서 지속 성장을 위해서 두 문제를 모두 해결하여야 한다. 현재 이산화탄소의 처리 방법으로 인식되고 있는 이산화탄소 포집 및 저장 기술(carbon capture and sequestration, CCS)의 환경 논란으로 인해 사후 처리 기술의 필요성이 커지고 있다. 이에 해결책중 하나로 부각되고 있는 이산화탄소 포집 및 재활용 기술(carbon capture and utilization, CCU)에 대해서 알아보았다. 이산화탄소 전환 기술은 이산화탄소 배출량 감소에 따른 지구 온난화 문제의 해결 뿐 아니라 탄소원의 재활용이란 측면에서 자원고갈 문제의 해결책으로 제시될 수 있겠다. 이산화탄소 전환 기술은 기상 전환과 액상 전환으로 나눌 수 있으며 기상 전환의 경우 필요 에너지 공급원과 온화한 반응조건에서 전환이 이뤄져야 하고 저에너지 소비 생성물 분리 정제 기술의 개발이 필요하다. 액상 전환의 경우, 반응 속도를 높일 수 있는 촉매 및 광감응제 개발과 함께 촉매, 빛, 전기의 혼성 시스템의 개발이 요구되어진다. 이산화탄소 전환 기술은 신재생 에너지 및 바이오산업의 경쟁력 향상을 위한 연결 기술로 그 가치가 매우 크다.