• 방사성폐기물학회지
• /
• 제21권2호
• /
• pp.283-294
• /
• 2023

APro, developed in KAERI for the process-based total system performance assessment (TSPA) of deep geological disposal systems, performs finite element method (FEM)-based multiphysics analysis. In the FEM-based analysis, the mesh element quality influences the numerical solution accuracy, memory requirement, and computation time. Therefore, an appropriate mesh structure should be constructed before the mesh stability analysis to achieve an accurate and efficient process-based TSPA. A generic reference case of DECOVALEX-2023 Task F, which has been proposed for simulating stationary groundwater flow and time-dependent conservative transport of two tracers, was used in this study for mesh stability analysis. The relative differences in tracer concentration varying mesh structures were determined by comparing with the results for the finest mesh structure. For calculation efficiency, the memory requirements and computation time were compared. Based on the mesh stability analysis, an approach based on adaptive mesh refinement was developed to resolve the error in the early stage of the simulation time-period. It was observed that the relative difference in the tracer concentration significantly decreased with high calculation efficiency.

• 한국분말재료학회지
• /
• 제30권5호
• /
• pp.436-441
• /
• 2023

Molybdenum-tungsten (Mo-W) alloy sputtering targets are widely utilized in fields like electronics, nanotechnology, sensors, and as gate electrodes for TFT-LCDs, owing to their superior properties such as high-temperature stability, low thermal expansion coefficient, electrical conductivity, and corrosion resistance. To achieve optimal performance in application, these targets' purity, relative density, and grain size of these targets must becarefully controlled. We utilized nanopowders, prepared via the Pechini method, to obtain uniform and fine powders, then carried out spark plasma sintering (SPS) to densify these powders. Our studies revealed that the sintered compacts made from these nanopowders exhibited outstanding features, such as a high relative density of more than 99%, consistent grain size of 3.43 ㎛, and shape, absence of preferred orientation.

• Structural Engineering and Mechanics
• /
• 제85권1호
• /
• pp.55-64
• /
• 2023

Energy-based seismic design and evaluation methods are promising to be involved in the next generation design codes. Accordingly, determining the distribution of earthquake input energy demand among floor levels is quite imperative in order to develop an energy-based seismic design procedure. In this paper, peak floor input energy demands are achieved from relative input energy response histories of several reinforced concrete (RC) frames. A set of 22 horizontal acceleration histories selected from recorded near-fault earthquakes and scaled in time domain to be compatible with the elastic acceleration design spectra of Turkish Seismic Design Code are used in time history analyses. The distribution of the computed input energy per mass values and the arithmetic means through the height of the considered RC frames are presented as a result. It is found that spatial distribution of input energy per mass is highly affected by the number of stories. Very practical yet consistent formulation of distributing the total input energy to story levels is achieved, as a most important contribution of the study.

• 한국가금학회:학술대회논문집
• /
• 한국가금학회 2000년도 제17차 정기총회 및 학술발표
• /
• pp.94-96
• /
• 2000

The experiment was conducted to determine the effects of dietary supplementation of enzyme(Endopower) into corn-soybean meal diet on the performance of broiler chicks. Three hundred sixty 3 day-old male broiler chicks(Ross) were divided into 4 groups with 3 replicates of 30 birds per replicate and assigned at random to each of four treatment groups for two energy levels(3100 and 2980 kcal TMEn/kg) with 0 or 0.1% Endopower in the diet. The body weight gain of birds fed the low energy diet with 0% Endopower was lower significantly than the other groups(P<0.05). There were no significant differences in feed intake and feed conversion rate among the treatments. The relative sizes(% B. wt) of the liver and leg muscle were not different significantly among the treatments. The breast muscle weights of the low energy diet birds were higher than those of the high ones, and those of the lower energy group with 0.1% Endopower were highest. The intesinal lengths(cm/B.wt) of low energy diet group without Endopower were lower than those of the others. No significant differences in the relative jejunum and ileum weights were found, but % duodenum weights of high energy group were higher than those of the low energy group. The villi of the ileum of birds fed corn-soybean diet without Endopower were shortened and thickened compared to those of the birds fed with Endopower diet regardless of energy level. The results demonstrated that dietary Endopower improved body weight gain reduced abdominal fats and developed intestinal villi. Therefore it can be concluded that dietary supplementation of Endopower improves nutritive value of corn-soybean diet in broiler chicks.

• 신재생에너지
• /
• 제17권2호
• /
• pp.50-58
• /
• 2021

We proposed an MEA development methodology that accurately measures intrinsic MEA performance while considering the uneven reaction environments formed inside a large-area BP. To facilitate measurement of the inherent MEA performance, we miniaturized the active area of the MEA to 3 cm², and prepared two MEAs with different ionomer contents of 0.65 and 0.80 (I/C). By simulating the operating conditions of a 100 cm² BP at the inlet (I), center (C), and outlet (O), the oxygen concentration and relative humidity were determined to be 20.7, 13.8, 11.7%, and 50, 66.1, and 70.1% respectively. We measured the performance and electrochemical analysis of the prepared MEAs under the three simulated conditions. Based on the results of statistical analysis of the evaluated MEA performance data, I/C 0.65 MEA had a higher average performance and lower performance deviation than I/C 0.80 MEA. Hence, it can be concluded that an I/C 0.65 MEA is a more effective MEA for large-area BP. Based on the above research process, we confirmed the effectiveness of the proposed MEA development methodology.

• 신재생에너지
• /
• 제9권3호
• /
• pp.14-19
• /
• 2013

Comparative evaluation of offshore wind retreival software, which use the satellite images taken by Synthetic Aperture Radar sensor; SARTools of CLS-SOPRONO, France and SpaceEye of London Research and Development Corporation, Canada is carried out. For a reference satellite image, ENVISAT ASAR imagery of Jeollanam-do Wan-do area when the winter-time northwestern wind prevails is processed by CMOD_IFR2, CMOD4, CMOD5 algorithms. Wind speed difference and its relative ratio are calculated to evaluate uncertainty of software selection.

• International Journal of Fluid Machinery and Systems
• /
• 제2권1호
• /
• pp.80-91
• /
• 2009

In this study, a prediction theory for specific noise that is the overall characteristic of the fan has been proposed. This theory is based on total pressure prediction and broadband noise prediction. The specific noises of two forward curved fans with different number of blades were predicted. The flow around the impeller having 120 blades (MF120) was more biased at a certain positions than the impeller with 40 blades (MF40). An effective domain of the energy conversion of MF40 has extended overall than MF120. The total pressure was affected by the slip factor and pressure loss caused by the vortex flow. The suppression of a major pressure drop by the vortex flow and expansion of the effective domain for energy conversion contributed to an increase in the total pressure of MF40 at the design point. The position of maximum relative velocity was different for each fan. The relative velocity of MF120 was less than that of MF40 due to the deviation angle. The specific noise of MF120 was 2.7 dB less than that of MF40 due to the difference in internal flow. It has been quantitatively estimated that the deceleration in the relative velocity contributed to the improvement in the overall performance.

• 한국해양공학회지
• /
• 제25권6호
• /
• pp.9-16
• /
• 2011

The feasibility of wave energy extraction from a heaving truncated cylinder and the corresponding response of the linear electric generator (LEG) composed of spring, magnet, and coil has been investigated in the frame of three-dimensional linear potential theory. The heaving motion of a circular cylinder is calculated by means of the matched eigenfunction expansion method. Further, the analytical results are validated by numerical results using the ANSYS AQWA commercial code. By the action of a heaving circular cylinder, the magnet suspended by a spring can slide vertically inside the heaving cylinder. The mechanical power is extracted from the magnet motion relative to the coil/stator which is attached to the cylinder. The coupled ODE of a heaving cylinder and LEG system in waves is derived to obtain the magnet motion relative to a cylinder. To maximize the relative motion of the magnet, both the buoy draft and the LEG system parameters (spring stiffness, damping) should be selected properly for generating the double resonance considering the peak frequency of the target spectrum.

• 마이크로전자및패키징학회지
• /
• 제7권1호
• /
• pp.35-40
• /
• 2000

Teflon-like fluorocarbon thin film was deposited on various substrates by vapor deposition using PFDA (perfluorodecanoic acid). The fluorocarbon films were characterized by static/dynamic contact angle analysis, VASE (Variable-angle Spectroscopic Ellipsometry) and AFM/LFM (Atomic/Lateral Force Microscopy). Based on Lewis Acid/Base theory, the surface energy ($S_{E}$) of the films was calculated by the static contact angle measurement. The work of adhesion (WA) between de-ionized water and substrates was calculated by using the static contact data. The fluorocarbon films showed very similar values of the surface energy and work of adhesion to Teflon. All films showed larger hysteresis than that of Teflon. The roughness and relative friction force of films were measured by AFM and LFM. Even though the small reduction of surface roughness was found on film on $SiO_2$surface, the large reduction of relative friction farce was observed on all films. Especially the relative friction force on TEOS was decreased a quarter after film deposition. LFM images showed the formation of "strand-like"spheres on films that might be the reason far the large contact angle hysteresis.

• 한국수자원학회논문집
• /
• 제56권4호
• /
• pp.285-299
• /
• 2023

증발산량을 산정하는 것은 수자원 관리에서 매우 중요한 요소이고, 많은 연구자들에 의해서 FAO Penman-Monteith (FAO P-M) 식이 기준증발산량을 산정을 위해 적용되고 있다. 하지만 FAO P-M 식에는 다양한 입력 변수들이 적용되어서, 이들 입력변수들의 영향력을 파악하는 것은 필요하다. 따라서 본 연구에서는 우리나라 56개 연구지역을 대상으로 8개의 기상요소들(최고기온, 최저기온, 풍속, 상대습도, 일사량, 증기압부족, 순복사량, 지중열유동)과 FAO Penman-Monteith (FAO P-M) 기준증발산식의 에너지항과 공기동력항, 그리고 고도의 변화에 따른 FAO P-M 기준증발산량 산정에 미치는 영향을 분석하였다. 이를 위해 다른 변량들은 고정한 상황에서 각 특정 변량을 10% 증가시킴에 따른 기준증발산량의 변화를 평가하기 위해 상대 민감도분석을 실시하였다. 또한 5개 대표 지역을 선정하여 그 지역들에 대해서 월별 민감도분석을 실시하고자 군집분석을 이용하여 56개 연구지역을 5개로 분류하였다. 분석결과에 의하면 56개 연구지역에서 8개의 기상요소 중에서 순복사량이 가장 민감한 것으로 나타났고, 다음으로 상대습도, 일사량, 최고기온, 증기압부족, 풍속, 최저기온 순으로 나타났다. 지중열유동은 가장 덜 민감한 요소인 것으로 나타났다. 지표면 특성의 경우, 고도는 매우 낮은 양의 상대 민감도를 보였다. FAO P-M 기준증발산식의 에너지항과 공기동력항의 상대적 민감도는 에너지항이 0.707, 공기동력항이 0.293을 보여서 에너지항이 공기동력항보다 기준증발산량 산정에 기여도가 더 큰 것으로 나타났다. 월별 민감도분석에 의하면 기상 요소별 민감도는 계절적인 영향을 보이는 것으로 나타났고, 고도의 상대민감도는 지역 간 서로 다른 양상을 보였다. 따라서 FAO P-M 식 적용을 위해서는 입력변수의 지역적, 계절적 민감도 차이를 고려해야할 것으로 판단된다.