• Nuclear Engineering and Technology
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• 제46권3호
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• pp.363-372
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• 2014

In this study, we proposed a newly designed sulfuric acid transfer system for the sulfur-iodine (SI) thermochemical cycle. The proposed sulfuric acid transfer system was evaluated using a computational fluid dynamics (CFD) analysis for investigating thermodynamic/hydrodynamic characteristics and material properties. This analysis was conducted to obtain reliable continuous operation parameters; in particular, a thermal analysis was performed on the bellows box and bellows at amplitudes and various frequencies (0.1, 0.5, and 1.0 Hz). However, the high temperatures and strongly corrosive operating conditions of the current sulfuric acid system present challenges with respect to the structural materials of the transfer system. To resolve this issue, we designed a novel transfer system using polytetrafluoroethylene (PTFE, $Teflon^{(R)}$) as a bellows material for the transfer of sulfuric acid. We also carried out a CFD analysis of the design. The CFD results indicated that the maximum applicable temperature of PTFE is about 533 K ($260^{\circ}C$), even though its melting point is around 600 K. This result implies that the PTFE is a potential material for the sulfuric acid transfer system. The CFD simulations also confirmed that the sulfuric acid transfer system was designed properly for this particular investigation.

• 한국전자통신학회논문지
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• 제15권3호
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• pp.487-494
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• 2020

본 논문에서는 정적소비전력을 줄이며, 전류 모드 신호처리의 장점을 최대로 올릴 수 있는 전류 메모리 회로 설계를 제안한다. 제안하는 전류 메모리 회로는 기존의 전류 메모리 회로가 갖는 Clock-Feedthrough와 Charge-Injection 등으로 인해 데이터 저장 시간이 길어지면서 전류 전달 오차가 심해지는 문제를 최소화하며, 저전력 동작이 가능한 Current Transfer 구조에 밀러 효과(Miller effect)를 극대화하는 Support MOS Capacitor를 삽입하는 설계로, 저장 시간에 따르는 개선된 전류 전달 오차를 보였다. 매그나칩/SK하이닉스 0.35㎛ 공정으로 칩 제작을 통한 실험 결과, 저장 시간에 따르는 전류 전달 오차가 5% 이하로 개선되는 것을 검증하였다.

• Journal of Astronomy and Space Sciences
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• 제41권1호
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• pp.43-60
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• 2024

Korea Pathfinder Lunar Orbiter (KPLO) is South Korea's first space exploration mission, developed by the Korea Aerospace Research Institute. It aims to develop technologies for lunar exploration, explore lunar science, and test new technologies. KPLO was launched on August 5, 2022, by a Falcon-9 launch vehicle from cape canaveral space force station (CCSFS) in the United States and placed on a ballistic lunar transfer (BLT) trajectory. A total of four trajectory correction maneuvers were performed during the approximately 4.5-month trans-lunar cruise phase to reach the Moon. Starting with the first lunar orbit insertion (LOI) maneuver on December 16, the spacecraft performed a total of three maneuvers before arriving at the lunar mission orbit, at an altitude of 100 kilometers, on December 27, 2022. After entering lunar orbit, the commissioning phase validated the operation of the mission mode, in which the payload is oriented toward the center of the Moon. After completing about one month of commissioning, normal mission operations began, and each payload successfully performed its planned mission. All of the spacecraft operations that KPLO performs from launch to normal operations were designed through the system operations design process. This includes operations that are automatically initiated post-separation from the launch vehicle, as well as those in lunar transfer orbit and lunar mission orbit. Key operational procedures such as the spacecraft's initial checkout, trajectory correction maneuvers, LOI, and commissioning were developed during the early operation preparation phase. These procedures were executed effectively during both the early and normal operation phases. The successful execution of these operations confirms the robust verification of the system operation.

• Journal of Radiation Protection and Research
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• 제31권4호
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• pp.211-217
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• 2006

원자력 시설의 가동에 따른 한국인의 식품 섭취 피폭 선량을 보다 현실적으로 평가하기 위해서는 농작물에서의 핵종 이동 계수에 대해 국내 생산 자료를 사용할 필요가 있다. 본 논문에서는 과거 수년간 한국원자력연구소에서 수행된 우리나라 주요 농작물의 핵종 이동 인자에 관한 결과를 분석하고 이를 외국의 사례와 비교하여 이를 사용할 때 선택할 수 있는 근거를 제시하고자 하였다. 이동인자의 경향은 실험의 횟수가 많을 경우 대체로 평균에 대해 정규분포를 이루는 경향을 보였으나 일부 핵종은 실험의 환경, 작물 및 토양의 종류에 따라 큰 변이를 보였다. 이러한 이동 인자들은 원자력 시설의 가동전이나 정상가동 중 또는 사고 시에 작물체내 방사성 핵종의 농도를 예측하고 평가하는 데 목적이나 환경에 따라 적절히 활용될 수 있다. 여기에 제시된 모든 인자는 대부분 온실 실험을 통하여 얻은 것이어서 몇 가지는 실험상의 제약으로 인하여 보수적이거나 단편적인 결과를 얻을 가능성이 있다. 따라서 본 논문에서 제시된 인자를 사용할 경우 각각의 의미와 한계를 충분히 숙지하고 평가의 목적이나 모델의 특성에 맞게 사용해야 하며, 그럴 경우 외국의 모델에서 제시된 인자를 사용할 때보다 현실적인 평가가 될 것으로 여겨진다.

• 환경영향평가
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• 제4권1호
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• pp.9-15
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• 1995

For the purpose of saving the waste disposal cost a self-governing community on the whole reclamates the wetland and uses it as a landfill site. During the operation period of site, the environmental impact by the leachate is usually neglected. Therefore, to predict the environmental impact and dispersion of leachate, the wetland adjacent to the South Han River in Chungju is selected as a site of case study. The main content of this article is to apply the simulation model CONMIG to leachate transfer in the ground water and to derive the impact by the leachate. A kind of non-reacting conservative material, chloride ion is used as a tracer to quantify impacts by the leachate.

• 대한산업공학회지
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• 제35권1호
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• pp.73-86
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• 2009

This paper discusses a method of determining the optimal design of a block. A horizontal layout of blocks is assumed in which transfer points are located at a side of the block. Each block has several transfer points (TPs) each of which is assigned to a group of adjacent bays and located at the center of the assigned group. The goal is to find the optimal size of a block and the optimal number of TPs while minimizing the total cost consisting of the fixed and operational cost of yard cranes (YCs), the operational cost of internal trucks, and the installation cost of TPs. Constraints on the maximum expected system time of trucks are imposed for the optimization. Formulas for estimating handling operation cycle times of a YC are derived analytically. Numerical experiments are conducted to illustrate optimal block designs for a given set of data.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(3)
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• pp.149-152
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• 2000

In the Internet, multimedia data transfer is hard to guarantee the characteristics of the Real-Time because of the Best-Effort of the nature of IP, then additional mechanism is applied to multimedia application for real-time data. In this paper, we introduce the nature of multimedia and the necessary facility for real-time protocol. We propose protocol layer, which has necessary function above mentioned and offer the end-to-end transfer far real-time data. Also, the proposed protocol perform a next low operation: 1) a required information for QoS control by using Feedback mechanism is obtained from sender, 2) divided a transferred packet by delay and loss priority. 3) recognized the low service models, and 4) decided a bandwidth and QoS according to a network state

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.345-348
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• 2009

Maintaining proper membrane humidity is crucial to ensure optimal operation of a PEMFC system. A gas-to-gas membrane humidifier is popular technology for external humidification of PEMFC reactant gases. Characteristics of heat and water transfer in shell-and-tube Nafion membrane humidifiers has been experimentally investigated for various dry side inlet temperature of membrane humidifier. The results show that heat flux decreases linearly with dry side inlet temperature of membrane humidifier. The water flux through the membrane varies nonlinearly with the temperature elevation.

• Structural Engineering and Mechanics
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• 제2권1호
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• pp.49-62
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• 1994

Based on the transfer matrix approach and integral transforms, a solution method is developed for the stress analysis of axisymmetrically loaded transversely isotropic elastic media with generalized interlayer and support conditions. Transfer functions (Green's functions in the transformed domain) are obtained in explicit integral form. For several problems of practical interest with different loading and support conditions, solutions are worked out in detail. For the inversion operation, an efficient technique is introduced to remedy the slow convergence of numerical integrals involving oscillating functions. Several illustrative examples are considered and numerical results are presented.

• 산업경영시스템학회지
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• 제35권1호
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• pp.154-160
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• 2012

This paper reviewed the two proposed hypotheses. The first hypothesis is to test the relationship between knowledge management and incremental innovation, and the second hypothesis is to test the moderating effect of firm-size on that relationship. Data were gathered from 434 employees in service industry, and multiple regression analysis was used to test two proposed hypotheses. In the first hypothesis, it was appeared that knowledge acquisition and knowledge transfer have positive effects on all incremental innovation factors (process innovation, operation innovation, service innovation). In the second hypothesis, it was appeared that firm-size has an positive interaction effect on incremental innovation in knowledge transfer, but not in knowledge acquisition. It means that knowledge transfer has more positive effect on incremental innovation in large firm-size than in small firm-size.