• 대한금속재료학회지
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• 제50권8호
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• pp.569-573
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• 2012

In order to understand the difference in SiC deposition between the $CH_3SiCl_3-H_2$ and $C_3H_8-SiCl_4-H_2$ systems, we calculate the phase stability among ${\beta}$-SiC, graphite and silicon. We constructed the phase-diagram of ${\beta}$-SiC over graphite and silicon via computational thermodynamic calculation considering pressure (P), temperature (T) and gas composition (C) as variables. Both P-T-C diagrams showed a very steep phase boundary between the SiC+C and SiC region perpendicular to the H/Si axis, and also showed an SiC+Si region with a H/Si value of up to 6700 in the $C_3H_8-SiCl_4-H_2$, and 5000 in the $CH_3SiCl_3-H_2$ system. This difference in phase boundaries is explained by the ratio of Cl to Si, which is 4 for the $C_3H_8-SiCl_4-H_2$ system and 3 for the $C_3H_8-SiCl_4-H_2$ system. Because the C/Si ratio is fixed at 1 in the $CH_3SiCl_3-H_2$ system while it can be variable in the $C_3H_8-SiCl_4-H_2$ system, the functionally graded material is applicable for better mechanical bonding during SiC coating on graphite substrate in the $C_3H_8-SiCl_4-H_2$ system.

• 시스템엔지니어링학술지
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• 제14권2호
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• pp.24-32
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• 2018

System Complexity one of the most common cause failure of the projects, it leads to a lack of understanding about the functions of the system. Hence, the model is developed for communication and furthermore modeling help analysis, design, and understanding of the system. On the other hand, the text-based specification is useful and easy to develop but is difficult to visualize the physical composition, structure, and behaviour or data exchange of the system. Therefore, it is necessary to transform system description into a diagram which clearly depicts the behaviour of the system as well as the interaction between components. According to the International Atomic Energy Agency (IAEA) Safety Glossary, The safety system is a system important to safety, provided to ensure the safe shutdown of the reactor or the residual heat removal from the reactor core, or to limit the consequences of anticipated operational occurrences and design basis accidents. Core Protection Calculator System (CPCS) in Advanced Power Reactor 1400 (APR 1400) Nuclear Power Plant is a safety critical system. CPCS was developed using systems engineering method focusing on Departure from Nuclear Boiling Ratio (DNBR) calculation. Due to the complexity of the system, many diagrams are needed to minimize the risk of ambiguities and lack of understanding. Using Model-Based Systems Engineering (MBSE) software for modeling the DNBR algorithm were used. These diagrams then serve as the baseline of the reverse engineering process and speeding up the development process. In addition, the use of MBSE ensures that any additional information obtained from auxiliary sources can then be input into the system model, ensuring data consistency.

• Nuclear Engineering and Technology
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• 제55권10호
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• pp.3732-3753
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• 2023

The Real-time Analysis for Particle-transport and In-situ Detection (RAPID) Code System, developed based on the Multi-stage Response-function Transport (MRT) methodology, enables real-time simulation of nuclear systems such as reactor cores, spent nuclear fuel pools and casks, and sub-critical facilities. This paper presents the application of a novel fission matrix-based burnup methodology to the well-characterized JSI TRIGA Mark II research reactor. This methodology allows for calculation of nuclear fuel depletion by combination and interpolation of RAPID's burnup dependent fission matrix (FM) coefficients to take into account core changes due to burnup. The methodology is compared to experimentally validated Serpent-2 Monte Carlo depletion calculations. The results show that the burnup methodology for RAPID (bRAPID) implemented into RAPID is capable of accurately calculating the k_eff burnup changes of the reactor core as the average discrepancies throughout the whole burnup interval are 37 pcm. Furthermore, capability of accurately describing 3D fission source distribution changes with burnup is demonstrated by having less than 1% relative discrepancies compared to Serpent-2. Good agreement is observed for axially and pin-wise dependent fuel burnup and nuclear fuel nuclide composition as a function of burnup. It is demonstrated that bRAPID accurately describes burnup in areas with high gradients of neutron flux (e.g. vicinity of control rods). Observed discrepancies for some isotopes are explained by analyzing the neutron spectrum. This paper presents a powerful depletion calculation tool that is capable of characterization of spent nuclear fuel on the fly while the reactor is in operation.

• 방사성폐기물학회지
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• 제12권3호
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• pp.179-189
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• 2014

파이로 공정은 사용후핵연료 관리 이슈 해결과 유용자원 재활용 제고의 목적으로 개발되고 있다. 파이로 공정 중 전해환원 공정은 LiCl을 전해질로 사용하여 산화물을 금속으로 전환시키는 공정으로 금속 전환체에 잔류염이 포함되므로 후속 공정이 요구된다. 진공 증류 공정은 다양한 용융염계에서 적용되어 왔으며 금속 전환체에서도 활용될 수 있다. 전해환원 금속 전환체 잔류염은 LiCl과 알카리 및 알카리토 금속 염화물을 포함한다. 본 연구에서는 이들 염화물들의 증기압을 추산하여 진공 증류 공정에서 잔류 액체의 조성변화를 계산하였다. 증류된 기체가 일정하게 제거되는 조건에서 물질수지와 기-액 평형식을 결합한 모델을 개발하였으며 증기압을 이용하여 무차원 시간에 대한 액체 조성 변화를 계산하였다. 공정 조건 변화 모사를 위해 온도와 용융염 조성을 변화시켜 거동을 비교하였다. 잔류염의 증류는 주성분인 LiCl에 의해 지배되었으며 LiCl 보다 증기압이 높은 CsCl은 쉽게 제거될 것이 예상되었다. 증기압이 유사한 RbCl은 LiCl과 일정한 조성이 유지되었다. 반면 증기압이 낮은 $SrCl_2$와 $BaCl_2$는 시간에 따라 농축되며 초기 조성이 높은 경우 증류 과정에서 석출될 가능성이 있는 것으로 예상되었다.

• Asian-Australasian Journal of Animal Sciences
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• 제22권6호
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• pp.827-835
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• 2009

Insulin has crucial roles in energy metabolism in all mammals but has been less studied in ruminants. An experiment was conducted to investigate the effects of hypoinsulinemia induction on appetite, performance, carcass composition and blood metabolite levels in sheep. Treatments were intravenous injection of four doses of streptozotocin; 0, 25, 50 and 75 mg/kg BW named C, L, M and H, respectively. Twenty male lambs were divided into four treatment groups. Animals in group H could not continue the experiment because of abnormalities. The duration of the experiment was eight consecutive weeks, and injection was performed at the end of week 3. Feed and water intakes were measured weekly and weight changes of animals were recorded and used for calculation of other growth parameters. Blood samples were collected weekly via venipuncture at fasting and 2.5 h post-prandial and analyzed for hormones and blood metabolites. Results showed a marked hypoinsulinemia in group M with significant decrease in fasted and postprandial insulin concentrations and also fasted leptin concentrations vs. the control group C (p<0.05). Group M showed significant increases in blood glucose, triglycerides, cholesterol, total protein, blood urea nitrogen and ketone body levels vs. group C (p<0.05). After injection, animals in group M showed diabetic hyperphagia and enhanced water intake as compared to group C (p<0.05) but, despite increased feed intake, they did not gain more weight than controls (p<0.05), and consequently, their feed conversion ratio was greater. Protein and fat contents of meat and liver were not significantly different among groups (p>0.05). In conclusion, the results suggested a regulatory role of insulin in energy metabolism of ruminants by exerting two opposing effects; central catabolic and peripheral anabolic.

• 자원환경지질
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• 제26권3호
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• pp.363-370
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• 1993

옥천대에는 다양한 종류의 화산암이 산출하며, 특히 문경지역을 중심으로 다양한 두께의 조립현무암질 암상이 다수 관찰된다. 이런 암류에 대한 과거의 지구화학적 연구에서는 전암성분의 계통적인 변화를 마그마의 분별정출작용에 의한 것으로 해석하였다. 상내리지역에 분포한 조립현무암질 암상중 가장 잘 분화된 두번째 암상은 수직적으로 광물입자의 발달이 현저하게 변화하며, 그에 따라 전암성분도 계통적으로 변화한다. 이러한 성분변화가 마그마의 분별정출작용에 의한 것인지를 확인하기위하여 광물의 입출에 대한 최소자승법을 이용하였으며, Iwamori (1989)의 컴퓨터프로그램을 사용하였다. 계산 결과는 암상에서 보여준 선암성분의 변화는 분별정출작용에 의한 것이 아니라, 마그마의 관입전이나 관입직후에 만들어 졌을것으로 보여지는 반정들(감람석, 사장석, 단사휘석, 자철석)의 차별적 집적에 의한 것으로 나타났다. 또한 분화의 최종산물인 Patch 형태의 백색산성암은 분별작용의 결과임이 분명하다.

• 한국산학기술학회논문지
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• 제4권3호
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• pp.223-229
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• 2003

ICRP-60 신권고에 맞게 수정된 방사선피폭선량 계산프로그램인 K-DOSE 60을 4개 발전소 (고리, 월성, 울진, 영광)에 적용하여 주변주민 최대개인피폭선량을 평가하였다 핵종, 장기, 경로별로 결정변수값들을 도출한 결과, 경로는 성인의 경우 농작물, 유아의 경우 우유가, 핵종은 ³H, /sup 133/Xe, /sup 60/Co (고리 1,2발전소), /sup 14/C, /sup 41/Ar(월성 1,2발전소)로 나타났으며, 모든 장기에 대한 피폭선량차이가 매우 작았다. "출력 대 입력" 변동에 근거한 민감도 분석결과, 핵종의 화학적 형태가 타 입력변수들보다 10² factor만큼 높은 민감도를 보였으며, 전이/농축계수에 의한 민감도는 섭취량이나 방출량의 그것에 비하여 상대적으로 매우 낮았다. PCC를 이용한 상관성 민감도의 경우는 4가지 입력변수 모두 0.97 이상의 높은 상관성을 보였다.

• 소성∙가공
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• 제31권6호
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• pp.376-383
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• 2022

The potential damage region of a WC-Co cemented carbide die is investigated for cold forging process of a wheel-nut by numerical simulation with its chemical composition considered. Numerical simulation is utilized to calculate internal stress, especially for the WC-Co die, during the forging process. Finite element model is established, in which the elasto-plastic properties are applied to the work-piece of bulk steel, and elastic properties are considered for the lower die insert of the WC-Co alloy. This stress analysis enables to distinguish the potential damage regions of the WC-Co die. The regions from calculation are comparatively analyzed along with the crack area observed in the die after repetitive manufacturing. Effect of chemical composition of the WC-Co is also evaluated on characteristics of potential damage region of the die with variance of mechanical properties considered. Derived from Mohr-Coulomb fracture model, furthermore, a new stress index is presented and used for die stress analysis. This index inherently considers hydrostatic pressure and is then capable of deducing wide range of its distribution for representing stress state by modification of its parameter implying pressure sensitivity.

• Structural Engineering and Mechanics
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• 제78권4호
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• pp.473-484
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• 2021

Similar to other structures, ultimate strength values showing the maximum load that the structure can resist without damaging has great importance on ships. Therefore, increasing the ultimate strength values will be an important benefit for the structure. Low carbon steels used in ships due to their low cost and good weldability. Improving the ultimate strength values without interfering with the chemical composition to prevent of the weldability properties of these steels would be very beneficial for ships. Grain refinement via severe plastic deformation (SPD) is an essential strengthening mechanism without changing the chemical composition of metallic materials. Among SPD methods, equal channel angular pressing (ECAP) is one of the most commonly used one due to its capacity for achieving bulk ultrafine-grained (UFG) materials. When the literature is examined, it is seen that there is no study about ultimate strength calculation in ships after ECAP. Therefore, the mean purpose of this study is to apply ECAP to a shipbuilding low carbon steel to be able to achieve mechanical properties and investigate the alteration of ship hull girder grillage system's ultimate strength via finite element analysis approach. A fine-grained (FG) microstructure with a mean grain size of 6 ㎛ (initial grain size was 25 ㎛) was after ECAP. This microstructural evolution brought about a considerable increase in strength values. Both yield and tensile strength values increased from 280 MPa and 425 MPa to about 420 MPa and 785 MPa, respectively. This improvement in the strength values reflected a finite element method to determine the ultimate strength of ship hull girder grillage system. As a result of calculations, it was reached significantly higher ultimate strength values (237,876 MPa) compared the non-processed situation (192,986 MPa) on ship hull girder grillage system.

• 한국광물학회지
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• 제5권1호
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• pp.32-41
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• 1992

점토광물들은 지질환경에 따라 다양한 화학성분을 갖게되는데, 화학성분의 변화는 X-선 회절도형 회절선 intensity에도 영향을 미치기 때문에 점토광물들의 정확한 정량분석을 위하여서는 유사한 화학식을 표준시료를 필요로 하게 된다. 대부분의 경우 특정성분의 표준시료를 확보하기 어렵지만, X-선 회절도형 계산방법을 응용하면 표준시료를 사용하지 않고 점토광물들의 정량분석을 실시할 수 있다. 대부분 심해저 퇴적물은 smectite, illite, chlorite, kaolinite듣 점토광물들을 함유하고 있는데, 특정한 화학성분을 갖는 이러한 네가지 점토광물들의 X-선 회절도형을 NEWMOD 프로그램을 이용하여 계산하였다. smectite와 illite의 001 회절선, chlorite의 004회절선, kaolinite의 002회적선의 이론적 peak intensity들을 계산된 X-선 회절도형으로부터 구하여 각 광물들의 MIF(Mineral Intensity Factor)값을 결정하였다. 실험에서 얻어진 시료의 peak intensity는 MIF값을 이용하여 교정하면 peak intensity값과 각 광물들의 wt%가 비례하도록 된다. 각 광물들의 wt% 총합계는 100wt%가 되도록 설정한 후 각 광물들의 구성비율을 이용하여 정량화 하였다. 이러한 정량분석방법은 분석하려는 광물의 화학식과 거의 비슷한 표준시료를 준비하지 않아도 되기때문에, X-선 회절도형의 계산방법을 이용한 정량분석은 표준시료를 구할 수 없거나 구하기 힘든 경우 유용하게 사용될 수 있다. 회절도형계산을 이용한 정량분석 방법은 서로 비슷한 지질환경에서 산출된 점토광물들을 대량으로 빠른 시간내에 분석하는데 이용할 수 있다.