McCARD 연소계산을 이용한 하나로 냉중성자 장치 발열량 분석

학위논문(석사) -- 서울대학교대학원 : 공과대학 에너지시스템공학부, 2021.8. 심형진.The cold neutrons are used for research purposes such as cell observation and, the cold neutron source (CNS) has been operated in the HANARO reactor at KAERI since 2010. The CNS should be utilized at a low temperature. However, the nuclear heating in the CNS increases due to the fission neutrons and the gamma rays from the core. Thus, it is important to analyze accurately the nuclear heating in the CNS. The objectives of this study are to establish a nuclear heating analysis methodology in McCARD, and to analyze accurately the nuclear heating in the CNS during the cycle operation of 28 days by McCARD. The nuclear heating in the CNS is categorized into four types. These are neutron heating by fission neutrons, gamma heating from prompt gamma rays from fission reactions, gamma heating from delayed gamma rays by fission product decays, and beta heating produced by beta decays of Al-28 in the CNS tank. The flux conversion factor is used to convert a Monte Carlo output to one in real-scale. The flux conversion factor in McCARD changes with burnup steps, and it is the key factor to obtain the value of the nuclear heating in the CNS. McCARD burnup calculations are performed with constant power and constant flux maintaining criticality. The nuclear heating in the CNS increased by 6.54% from BOC to EOC in the constant power condition while that in the constant flux condition by 5.35%. The result of the constant flux condition is a more appropriate final result in this research because the HANARO reactor is a research reactor to maintain the constant flux. The flux conversion factor is consistent within the confidence interval (2σ) from BOC to EOC in the constant power condition while that in the constant flux condition decreases by 2.69%. From these results, it is demonstrated that the nuclear heating in the CNS did not increase due to the flux conversion factor. However, the flux in the CNS increased from BOC to EOC in both the constant power and the constant flux condition. To maintain criticality, the control rod between the core and the CNS was withdrawn from BOC to EOC. Therefore, it can be concluded that the nuclear heating in the CNS increased due to the increase of the neutron flux and the gamma flux from the core.냉중성자는 세포 관측 등의 연구 목적으로 사용되고, 그리고 냉중성자 장치는 한국원자력연구원의 하나로 원자로에서 2010년부터 운영하고 있다. 냉중성자 장치는 저온상태에서 운영해야 한다. 그러나, 노심에서 발생하는 핵분열 중성자와 감마선에 의해 냉중성자 장치의 발열량이 증가하게 된다. 따라서, 냉중성자 장치의 발열량을 정확하게 분석하는 것이 중요하다. 본 연구의 목표는 McCARD를 이용하여 발열량 분석 방법론을 구축하고, 그리고 이를 통하여 McCARD를 이용하여 원자로 한 주기 28일 동안 냉중성자 장치의 발열량을 정확하게 분석하는 것이다. 냉중성자 장치의 발열량은 네 가지로 분류하여 분석하였다. 핵분열 중성자에 의한 Neutron Heating, 핵분열 반응의 즉발 감마선에 의한 Gamma Heating, 핵분열 생성물 붕괴의 지발 감마선에 의한 Gamma Heating, 그리고 CNS Tank에서 Al-28의 베타 붕괴에 의한 Beta Heating으로 분류하였다. Flux Conversion Factor는 몬테칼로 코드의 아웃풋을 실제 스케일로 바꿔주기 위해 사용된다. McCARD의 Flux Conversion Factor는 연소단계에 따라 달라지고, 냉중성자 장치의 발열량을 계산하는 핵심 요소이다. McCARD 연소계산은 임계를 유지하는 상태에서 Power 일정 계산과 Flux 일정 계산으로 수행하였다. McCARD 연소계산 결과 냉중성자 장치의 발열량은 BOC 대비 EOC에서 Power 일정일 경우 6.54% 증가하였고 Flux 일정일 경우 5.35% 증가하였다. Flux 일정 결과가 최종결과에 더 적합한 결과인데 왜냐하면 하나로 원자로는 연구용 원자로이기 때문에 실제로 Flux 일정 방식으로 운전하기 때문이다. Fux Conversion Factor는 BOC 대비 EOC에서 Power 일정일 경우 신뢰구간 (2σ) 내에서 일정하고 Flux 일정일 경우 2.69% 감소한다. 이러한 결과로부터, 냉중성자 장치의 발열량은 Flux Conversion Factor 때문에 증가하지 않았다는 것을 알 수 있다. 그러나, 냉중성자 장치의 Flux는 BOC 대비 EOC에서 Power 일정 및 Flux 일정일 경우 모두 증가하였다. 임계를 유지하기 위해, 노심과 냉중성자 장치 사이의 제어봉이 BOC 대비 EOC에서 인출되었다. 따라서, 냉중성자 장치의 발열량은 노심에서 오는 Neutron Flux와 Gamma Flux의 증가 때문에 증가했다는 것을 알 수 있다.Chapter 1. Introduction 1 1.1. Research Background 1 1.2. Research Objectives 1 Chapter 2. Introduction to the HANARO Cold Neutron Source (CNS) 2 2.1. HANARO Core 2 2.2. HANARO CNS 3 Chapter 3. Monte Carlo (MC) Nuclear Heating Analysis Methodology 4 3.1 CNS Heatings by Radiations 4 3.2 Flux Conversion Factor in MC Eigenvalue Calculations 5 Chapter 4. McCARD Nuclear Heating Analyses for the HANARO CNS 7 4.1 Heating Analysis by Constant Power Operation Condition 7 4.2 Heating Analysis by Constant Flux Operation Condition 9 Chapter 5. Conclusion 11 References 12 초 록 13석

The analysis of detailed foot motion of the normal and hallux valgus during the gait through the development

의공학과/석사[한글] 인간의 보행에 있어 지면과 접촉을 이루는 발은 에너지를 저장, 방출하여 추진력 공급 및 균형 유지의 중요한 역할을 하는 복잡하고 정교한 인체 기관이다. 그러나 최근 다양한 발 질환이 급증하고 있고, 이는 보행에 이상을 가져오게 되어, 신체의 여러 부위에 연쇄적으로 나쁜 영향을 미친다. 발의 생체역학적 기전을 규명하기 위해 많은 연구들이 이루어져 왔지만 발의 여러 관절에 대한 분석이 없었고, 다양한 발 질환에 대한 운동특성의 분석이 미비하였다. 본 연구에서는 다양한 발 질환의 임상적 진단과 치료를 위해 기존의 단일체절 또는 3~4개의 다체절 발 모델의 단점들을 보완하는 9개 다체절 발 모델을 개발하고 개발된 모델을 정상인과 무지 외반증(hallux valgus) 환자군에 적용하여 보행 중 발의 세부 운동 특성을 분석하였다. 그리고 보행 시 발바닥에 작용하는 압력을 영역별로 나누어 보행주기에 따라 분석하고 이러한 분석 인자들과 관련하여 발의 주요 운동을 담당하는 근육들의 근활성도를 보행주기에 따라 분석하였다. 보행 시 발의 충격흡수 및 균형유지에 주요한 역할을 하는 활(arch)들의 변화들을 관찰하기 위해 중족골 부위를 내·외측으로 나누었고, 무지 외반증과 같은 발 질환의 적용을 위하여 발가락 부위를 엄지발가락, 내측 발가락, 외측 발가락 부위로 나누어 정의하였다. 또한 발꿈치뼈, 입방뼈, 목말뼈, 정강뼈를 각각 정의하여 총 9개의 체절의 발 모델을 개발하였다. 개발된 발 모델을 바탕으로 엄지발가락 허리관절, 내측 발가락 허리관절, 외측 발가락 허리관절, 목말밑관절, 발꿈치 입방관절, 발목관절의 총 8개 관절을 정의하고 총 19개의 마커를 해부학적으로 유의하게 위치시켜서 마커 O@V을 구성하고 다체절 모델링 프로그램을 사용하여 모든 체절과 관절들을 계층적으로 구속시켰다. 개발된 다체절 발모델을 사용하여 정상 성인군과 무지 외반증 환자군에 대한 발의 세부 운동특성을 분석하여 비교하였다. 시상면에서 엄지발가락 허리관절이 정상인의 경우 하중수용기에 급격한 굴곡을 한 후에 말기입각기에 급격한 신전을 하여 발이 지면을 차고 나가는 것을 보조하는 것에 반해 무지 외반증 환자군의 경우 전체적으로 굴곡과 신전의 운동크기가 매우 작고 특히 말기입각기시에 정상인의 운동 각도와 큰 차이를 보였다. 전두면에서는 말기입가기에 발목관절의 운동에서 정상인에 비해 환자군이 일찍 외반을 시작하는 특징과 목말밑관절의 입각기 초기에 과도한 외반을 하는 특징을 보였다. 횡단면에서는 보행주기 전체동안 발목관절과 엄지발가락 허리관절의 과도한 외회전의 특징을 보였다. 동적 발바닥 압력분포를 비교한 결과, 무지 외반증 환자군의 경우 정상인에 비해 외측으로 큰 압력을 받으면서 보행을 하고 상대적으로 내측 전족부와 엄지발가락부에 훨씬 작은 압력을 받는 것을 확인하였다. 보행 시 발의 운동에 관련된 근육들의 근활성도를 삼차원 운동특성 분석 결과 및 동적 발바닥 압력분포 결과와 연관하여 분석하여 다음과 같은 무지 외반증 환자군의 운동 특성을 찾았다. 1. 무지 외반증 환자는 대부분 환부가 제 1 중족골두에 위치하기 때문에 보행 시 환부에 가해지는 자극을 피해 발의 외측으로 보행을 하는 특성이 있다. 2. 그리하여 보행주기 전체적으로 발의 배굴 및 내반을 담당하고 있는 앞정강근의 과도한 활동을 유발하고 발 외측에 높은 압력을 분포시킨다. 3. 그리고 정상군에 비해 긴종아리근을 빨리 활성화 시켜서 회내 운동을 빨리 시작하여 제 2~3 중족골두로 압력중심이 지나가게 보행을 한다. 이와 같은 결과를 통하여 향후 다른 다양한 발 질환의 임상적 진단과 치료를 위한 운동특성 분석이 가능하고, 발 질환 환자들을 위한 특수 안창 및 특수화의 제작에 큰 도움이 될 것으로 생각된다. [영문]The foot, making contact with the ground, is essential in keeping the dynamic stability, while the body moves forward in human walking. But, various foot problems have been rapidly increasing in these days. These problems cause gait abnormalities, influencing on many other parts of the body. Many studies have been performed to determine biomechanics of the foot during locomotion. However, most previous studies focused on describing only ankle joint and there were few studies about the detailed foot motion of the various foot diseases. In this study, a multi-segment foot model which can make for the weakness of the previous foot model was developed for later clinical applications and then applied to the 3D motion analysis to determine detailed foot motions of normal and hallux valgus during the gait. And also we analyzed the areal plantar pressure of the foot and the muscle activity relating the foot movement along the gait cycle. A 9-segment foot model was defined to analyze the foot motion in sagittal, frontal and transverse planes during gait. Metatarsal bones were divided into medial and lateral parts to observe the change of the arch in the foot. There were three parts in the toes; hallux, medial toes and lateral toes. In addition, calcaneous, cuboid, talus and tibia were also defined. Based on the segmental definition, eight major joints in the foot were defined hallux metatarsophalangeal(MP) joint, medial MP joint, lateral MP joint, medial tarsometatarsal(TM) joint, lateral TM joint, subtalar joint, calcaneocuboid joint and talocrural joint. And totally nineteen 9mm reflective markers were attached at anatomical locations based the foot model. A user-defined motion analysis software was used for the modeling like that all markers were grouped, based on the foot anatomy and segmental coordinates, Euler angles were defined as well. The detailed foot motion of the normal and hallux valgus during the gait by using the developed multi-segment foot model was analyzed and compared. In sagittal plane, the hallux MP joint is rapidly dorsiflexed during the loading response and plantarflexed during the terminal stance for push-off process in the normal subject whereas, in the hallux valgus subject, the range of motion of the hallux MP joint is very small and specially there''s large difference in terminal stance as compared with the normal. In frontal plane, the hallux valgus sbject''s talocrural joint moved for the eversion early in the terminal stance and the subtalar joint is hyper-everted by comparison with the normal subject. In transverse plane, the talrocrural joint and the hallux MP joint moved for the hyper external rotation in hallux valgus subject. From the result''s of the comparison about the dynamic plantar pressure, we can also know that the hallux valgus walked under the large pressure in lateral side of the foot. The present multi-segment foot model would be very useful to diagnose and to treat other foot disease patients. And it also could be very helpful for the design of the special insole or shoes for the foot disease patients.ope

보행 장애인을 위한 맞춤 훈련 프로그램 기반 하이브리드 로봇형 보행훈련 시스템

Dept. of Biomedical Engineering/박사[한글] [영문]Gait, a method of locomotion, is a process that an animal moves itself from one position to another. The human gait serves an individual’s basic need to move from place to place. As such, the gait is the most common in all human movements. It also can provide independence and in the many activities of daily life. The importance of gait as an ability of humans has been emphasized for a long time by many researchers. The rapid-onset gait disorder represents the combined effects of more than one coexisting condition. Therefore, many kinds of gait training methods have been applied to recover or improve the walking abilities of patients with gait disorders. However, various conventional gait training methods have some limitations due to the inappropriateness and the ineffectiveness in the rehabilitation training. In this dissertation, a new hybrid robotic gait training system (HRGT) with an adaptive training program for the patients with a gait disorder was developed. Predefined joint motions of hip and knee were applied using robotic driving parts including AC servo motors and linear actuators. Functional-electrical-stimulation (FES) could be also applied to the system to control ankle dorsi/ plantarflexors based on the individual’s gait cycle during training. A graphic-user-interface (GUI) for the control algorithm and training program was also designed to provide patient information, personalized adaptive gait training pattern, and FES timing. Experimental validation was also conducted to assess the compatibility of the newly developed system for gait training. The kinematic validation confirms the correctness of the provided trajectory in static and dynamic conditions during gait training. The kinetic validation calculates joint moments provided by the developed gait training system. FES validation confirms the accuracy of the provided FES trigger signal during gait training. It is very difficult to measure various biomechanical parameters and the effects experimentally during gait training. Therefore, the gait training simulation was also performed to enable to estimate effects of gait training using CAD models of the RGT with the human musculoskeletal model and the multi-body dynamics. We expect that the developed HRGT system with FES could be applied very practically to recover walking abilities of patients with a gait disorder and the gait training simulation also could provide useful information and proper guidelines for the rehabilitation training of patients with a gait disorder.ope

Syntheses, surface modifications, and applications of supra quantum dots and magnetic nanoparticles

MasterThis thesis describes synthesis of nanoparticles which have novel electric or magnetic properties and their various applications through proper surface modifications. Nanoparticles have unique characteristics discriminated from bulk materials due to their nanometer scale dimension. Not only composing materials are critical to determine the characteristics of the nanoparticles, but the surface chemistries are also important. Nanoparticles are capped with surface ligands and stabilized in certain solvents. The ligands can be exchanged with other ligands to change solvents or perform additional surface treatments such as shell or film coating, and conjugation with other nanoparticles. Supra quantum dots (SQDs) are sphere nanoparticles that consist of hundreds of quantum dots (QDs) to construct large size three-dimensional self-assemblies. The size of SQDs is much larger than their Bohr radius, but SQDs maintain quantum confinement effect of individual QDs. SQDs were size-tunable and could be synthesized with various cadmium chalcogenide (II-VI) materials. SQDs could be dispersed in various solvents after surface modifications, which made it possible to perform facile solution process to fabricate solar cells. After pyridine exchange, SQD and nanorod solutions were blended and spin-coated onto ITO-patterned glasses and formed active layer films by thermal treatment. CdTe and CdSe nanocrystal solution blending and sequential deposition formed p-n nano-heterojunction structures of active layers. Fabrication of an all-inorganic type solar cell was completed with depositing aluminum electrodes onto the active layer films. The solar cell devices used SQDs with nanorods exhibited better performances compared with nanorod-only structure devices. The best performance device exhibited 3.03% of power conversion efficiency. Iron oxide nanoparticles (IONPs) are nanometer scale chemical compounds composed of iron and oxygen, which have superparamagnetic property. Water dispersed superparamagnetic nanoperticles can be utilized in biomedical applications such as contrast agent for magnetic resonance imaging (MRI) and targeted drug delivery in tumor therapy. Various sizes of IONPs were synthesized in organic solvent by thermal decomposition method, and dispersed in hydrophilic solvents after surface modifications. Catechol or pyrogallol ligands were selected to give binding affinity with iron oxide, and they also contained hydrophilic moiety such as carboxyl group. Original inorganic sizes and hydrodynamic sizes of IONPs were maintained after the ligand exchange with dihydroxyhydrocinnamic acid (DHCA), gallic acid (GA), and tannic acid (TA)

Development of Supra Quantum Dots and Their Photovoltaic Application

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Formation and Stepwise Self-assembly of Cadmium Chalcogenide Nanocrystals to Colloidal Supra-Quantum Dots and the Superlattices

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