Study of van der waals interactions in graphene

Ahn, Sungjoon Sungkyunkwan university 2017 국내박사

(A) stochastic modeling of traffic breakdown for freeway merge bottlenecks and variable speed limit control strategies using connected automated vehicles

한영준 ProQuest LLC 2017 국내박사

Diagnosis of Canine Chronic Mitral Valve Insufficiency by Evaluating Growth Differentiation Factor 11 and Interventricular Septal Wall Excursion

Ahn, Sung Taek Kangwon National University 2018 국내박사

국문초록 GDF 11과 ISWE의 평가를 통한 개의 CMVI에 대한 진단 안 성 택 강원대학교 대학원 수의학과 CMVI(Chronic mitral valve insufficiency)는 일반적으로 개, 특히 소형견에서 가장 흔한 심장병의 하나이며, 만성적인 이첨판의 점액변성으로 이첨판 폐쇄부전을 유발하여 울혈성 심부전(congestive heart failure, CHF)을 초래한다. GDF 11(Growth differentiation factor 11)은 BMP(bone morphogenetic protein) 계열의 일종이며, 배아 및 성인 조직 모두에서 세포 성장과 분화를 조절하는 인자이다. 또한, GDF 11이 SERCA-2 의 발현 증가를 통해 심근 확장 기능을 향상시키는 연구보고가 있으며, 마우스 연구에 있어 GDF 11 혈청농도는 나이들수록 낮아지고 심장질환을 가진 개체에서도 낮은 농도를 나타냈다. CMVI도 노화와 연관된 심장질환으로 GDF 11의 농도가 낮을 수 있다는 것을 유추할 수 있다. 본 연구의 가설은 CMVI를 가진 개에서 혈청 GDF 11농도가 낮아지며, 심장병의 진행이 더 빠르게 진행될 수 있다는 것이다. 이는 GDF 11의 혈청 농도는 CMVI를 가진 개를 진단할 수 있는 좋은 지표가 될 수 있다는 근거가 된다. 본 실험을 위해 11마리의 건강한 개와 CMVI가 있는 69마리의 개가 선발되었으며 연령,체중등의 신체검사 및 혈액검사,심장초음파검사등의 임상검사를 통해서 CMVI그룹은 ISACHC기준에 따라 심부전을 분류했다. 연령과 심부전에 따른 혈청 GDF 11농도를 평가하고 분석한 결과,혈청 GDF 11농도는 심장질환을 나타내는 여러 indices 및 연령과 상관관계가 없게 나타났다. 따라서 마우스실험에서 확인된 심장병이 있는 나이든 마우스의 혈청 GDF 11농도가 감소한다는 이론은 CMVI를 가진 개의 실험에서는 확인되지 않았다. 좌심실과 우심실사이에 있는 중격벽의 움직임인 ISWE는 이전의 사람 및 동물 실험을 통에서 좌심실의 부하가 증가할 때나 심박수가 급격하게 증가할 때 과잉움직을 보이는 것을 알아냈다.이러한 과잉움직임은 만성심장병을 가진 개에 있어 대상부전을 의미하기도한다.개의 CMVI는 만성적으로 좌심실의 부하가 증가하는 심장병이다.이는 CMVI를 가진 개에 있어 ISWE가 증가하며 심부전이 진행될수록 증가할 수 있다는 것을 유추할 수 있다.본 실험은 CMVI를 가진 개에 있어 ISWE가 증가하며 심부전이 심해질수록 증가한다는 가설을 세워 진행했다.이는 ISWE가 CMVI의 진단을 위한 좋은 지표가 될 수 있다는 근거가 된다.본 실험을 위해 18마리의 건강한 개와 CMVI를 가진 51마리의 개가 선발되었으며 연령.체중등의 신체검사 및 임상검사를 통해서 CMVI그룹은 ISACHC기준에 따라 심부전을 분류했다.심장초음파 검사를 통해서 ISWE를 평가하고 분석한 결과 심장질환을 나타내는 심장초음파지표 및 바이오마커와 상관성이 높은 것으로 밝혀졌다.따라서 ISWE는 CMVI진단 및 중증도를 평가하는 데 있어 우수한 지표가 될 수 있다. □ 핵심주제어 바이오마커, 성장분화인자 11(GDF 11), 개, 만성이첨판폐쇄부전, 심실간 중격 벽 유출 Diagnosis of Canine Chronic Mitral Valve Insufficiency by Evaluating Growth Differentiation Factor 11 and Interventricular Septal Wall Excursion Sung-Taek Ahn Department of Veterinary Medicine, Graduate School, Kangwon National University ABSTRACT In general, chronic mitral valve insufficiency (CMVI) as a cardiac disease is commonly found in dogs, in particular, small breed. CMVI takes place because of chronic myxomatous mitral valvular degeneration. It triggers mitral regurgitation, which consequently leads to the congestive heart failure (CHF). Growth differentiation factor 11 (GDF 11) is one of bone morphogenetic proteins (BMP). It is a regulator of cell growth and differentiation in both embryonic and adult tissues. In addition, other studies report that GDF 11 improved myocardial diastolic function through the increase in the manifestation of SERCA-2. In case of a study using mice, it was indicated that the serum level of GDF 11 became lower as the age of mice was higher. In this sense, since CMVI as a cardiac disease is related to aging, it infers that the serum level of GDF 11 might be lower. This study hypothesizes that dogs with CMVI would have the low serum level of GDF 11 and the progression of heart disease might be more quickly accelerated. Therefore, it is the evidence that the serum level of GDF can be a good marker to diagnose dogs with CMVI. 11 healthy dogs and 69 dogs with CMVI were examined for this study. All selected dogs' age and body weight were investigated. Physical examination, blood test and echocardiography for CMVI dogs were conducted. The degree of cardiac insufficiency in CMVI dogs was sorted out by the criteria of ISACHC. The result from evaluating and analyzing the serum level of GDF 11 depending on age and heart failure showed that there was no correlation between the serum level of GDF 11, age, and various indices representing heart disease. Thus, the hypothesis that the serum level of GDF in an old mouse with heart disease decreases was not identified in dogs with CMVI. Previous studies with clinical tests and animal experiments found that interventricular septal wall excursion (ISWE) located in the gap between the left ventricle and the right ventricle excessively moved when the load of the left ventricle increased or heart rate dramatically increased. These excess movement of ISWE in dogs with CMVI represents a decompensatory response. Dogs' CMVI refers to heart disease that the load of the left ventricle chronically increases. It infers that dogs with CMVI have an increase in ISWE, and ISWE can rise as cardiac insufficiency deteriorates. The experiment for this study was conducted with the hypothesis that ISWE in CMVI dogs increases and the increment in ISWE takes place when cardiac insufficiency deteriorates. It provides the evidence that ISWE could be a good index to diagnose CMVI dogs. 18 healthy dogs and 51 dogs with CMVI were investigated for this study. All dogs' age and body weight in this study were examined. Physical examination and a medical test were conducted. The degree of cardiac insufficiency in CMVI dogs was classified by the criteria of ISACHC. The result from evaluating and analyzing ISWE by echocardiography indicated that ISWE was closely correlated with echocardiographic indices representing heart disease and a cardiac biomarker. Accordingly, ISWE can be a good indicator to diagnose CMVI dogs and evaluate the severity level of CMVI. □ Key words biomarker, growth differentiation factor 11 (GDF 11), dog, chronic mitral valve insufficiency (CMVI), interventricular septal wall excursion (ISWE)

Thermophysical property and material compatibility of accident-tolerant UO2-U3Si2 composite fuel

Jungsu Ahn Ulsan National Institute of Science and Technology 2023 국내박사

One of the important lessons learned from the Fukushima accident was the low thermal conductivity of UO2 is not something supposed to be overlooked, at least not any longer. The most widely used commercial nuclear fuel, UO2, in fact has the lowest thermal conductivity among all major types of nuclear fuel including U-Zr, U-Mo, UN, UC, and U3Si2. After the accident, many accident-tolerant fuel (ATF) concepts, usually with enhanced thermal conductivity, have been resuscitated and newly suggested; however, after over a decade of research, most of them are still in the testing phase. Uranium sesquisilicide (U3Si2) is a strong candidate material for ATF since it can simultaneously provide 4-8 times higher thermal conductivity and ~16% higher fissile density than UO2 unlike other non-fissile higher thermal conductivity additives considered for nuclear fuel. Similar benefits could be expected by adopting uranium mononitride (UN) and uranium monocarbide (UC); however, their corrosion resistance in for water-cooled reactor is generally considered unacceptable. The corrosion resistance under water/steam environment is also an outstanding issue for U3Si2, but perhaps considerably manageable. For instance, shorter fuel rod design with reduced fuel pellet diameter has been suggested mainly by Westinghouse Electric Company (WEC) to mitigate the consequence of cladding rupture; however, it will certainly increase the fuel cost. The in-reactor corrosion issue of U3Si2 could be more economically handled by adopting UO2-xU3Si2 (x < ~50 wt%) composite fuel. In this approach, the concerns are laid on the potential microstructural defect formation between UO2 and U3Si2, e.g., micro-crack and secondary phase formation, which may deteriorate the fuel thermal conductivity and the corrosion resistance, which are the main subject of this dissertation. A comprehensive experimental investigation on UO2-xU3Si2 (x = 10, 30, and 50 wt%) composite has been conducted in particular order to examine its applicability as an accident-tolerant fuel for water-cooled reactors. Firstly, the fuel manufacturing process was developed, for both conventional sintering (CS) and spark plasma sintering (SPS), using a surrogate material (CeO2-xCeSi2) to minimize radioactive waste generation during the development phase. Then, the UO2-U3Si2 pellets using UO2.02 and UO2.15 powder have been prepared and characterized using X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), and laser flash analysis (LFA). The stoichiometric UO2.02-U3Si2 was selected as as-fabricated or beginning-of-cycle (BOC) composite fuel since the interaction layer (IL) formation between UO2 and U3Si2 has to be suppressed during the fabrication. In contrast, hyper-stoichiometric UO2.15-U3Si2 was considered as an end-of-cycle (EOC) composite fuel assuming a significant discharge burnup that might be challenged for advanced reactor designs. Finally, with the fully characterized fuel pellets, the oxidation resistance of UO2-U3Si2 was evaluated under high temperature air and pressurized water environment using thermogravimetric analysis (TGA). Diffusion couple study of UO2-U3Si2 with a selected ATF cladding material, FeCrAl alloy, was also carried out to glimpse the material compatibility of the composite fuel. From the surrogate tests (CeO2 instead of UO2, and Ce3Si2 for U3Si2), spark plasma sintering was selected over conventional sintering based on simultaneously obtained higher pellet density and homogeneous microstructure; thus, all UO2-U3Si2 composite pellets used for this study were spark plasma sintered. In the SPS-ed UO2-xU3Si2 (x = 10, 30, 50 wt%) pellets, the formation of U3Si inclusions and USi phase regions was confirmed, which was more significant in high temperature (> 1400 °C) SPS-ed pellets. With increasing U3Si2 composition and sintering temperature, the SPS-ed pellet density per theoretical density was monotonically increased up to ~93%TD. The thermal conductivity of UO2-U3Si2 composite was decreased with increasing temperature, while the amount of decrement was decreased with increasing U3Si2 composition. Hyper-stoichiometric UO2.15-50wt% U3Si2 pellets exhibited 5-7% lower thermal conductivity than that of UO2.02 due to significant secondary USi phase zone formation. In contrast, stoichiometric UO2-50 wt%U3Si2 exhibited up to 100% higher thermal conductivity than UO2, which may suggest progressively accelerated formation of interaction layer and secondary phase with increasing burnup. Significantly enhanced oxidation and corrosion resistance of UO2-U3Si2, compared to U3Si2, was concluded from the following results: (1) ~130 ℃ higher onset temperature in dynamic oxidation in air, (2) ~50% less weight gain for isothermal oxidation at 300 ℃ in air, and (3) noticeably mitigated pellet degradation under high temperature pressurized water. The diffusion couple study on UO2-U3Si2 composite with an FeCrAl alloy showed the formation of 5-10 μm thick U-Si-O layer after 100 h annealing at 600 ℃. With further elevated annealing temperature of 800 ℃, U and Si infiltration to FeCrAl matrix was also observed after 100 h annealing, which may potentially limit the reactor operating temperature or the use of the FeCrAl alloy with the composite fuel. This series of metallurgical and thermophysical investigations partially demonstrated the feasibility of UO2-U3Si2 composite as an accident-tolerant fuel, which might be an only option to offer both higher thermal conductivity and higher fissile density at the same time. It also indicated that suppressing the formation of secondary phases (U3Si and USi) with lower melting temperature and/or thermal conductivity during the fuel fabrication and reactor operation is a key to the successful utilization of the type of inhomogeneous composite fuel. Thus, concerning irradiation-accelerated interaction layer formation between UO2 and U3Si2, further experimental demonstration of the safety and performance of the composite fuel needs to be carried out as a future study, which could utilize, if not in-pile test in a research reactor, in-situ heating ion-beam irradiation under various mechanical stress and temperature conditions matching to an advanced reactor design under consideration.

Forms and functions of English tag questions : a corpus-based study

안소영 Chonnam National University 2018 국내석사

Korean learners have shown weaknesses in practical communication applications, while they have excellent grammatical and lexical skills. This is because they show much strength in mechanical learning on syntactic and semantical aspects of tag questions but have been experiencing a lot of difficulties in applying tag questions in actual use. Therefore, it is imperative to analyze the various forms and functions used in authentic situation. In addition to the strategic role and function of tag questions to facilitate communication, a study on practical use that has been somewhat neglected in the education field. Although the study of typical tag questions in the use of English texts have been relatively active, there have been few studies on exceptionally diverse uses. Moreover, in Korean schools, tag questions which have the same polarity or inconsistent verb with the main clause are accepted as the wrong grammatical form. This was found to be significantly different from actual use. Therefore, this study analyzes the use of various forms of tags through the corpus analysis study and examines the functions according to them. To do this, Three research tasks have been presented and studied: Firstly, what the most frequently used English tag questions; secondly, How tag questions appears in various forms in terms of polarity, subject, auxiliary value; and lastly, what functions tag questions exhibit in utterance situations. As a result of the analysis, it was confirmed that the tag questions on the corpus was not consistent with the verb or subject of the sentence, unlike the normative grammar. Although the grammatical elements are specified, the actual use of tag questions does not fit into this framework and it shows various forms depending on various practical use. Especially in case of polarity, it was observed that the tags in the same polarity shows high proportion of all tags. It was also found that tag questions are used in various forms in terms of subject and auxiliary value through data. In addition, it was indicated that there exist a wide range of functions of tag questions. Consequently, it was advised that pedagogical effort should be made to make students apply tag questions into practical use. Through the authentic practice of tag questions, it is expected that the overall english speaking ability will be improved as well.

A study of sponge sulfur ZIF 67 wrapped in rGO as cathode material for Lithium Sulfur Battery

NEEMA CYRIL KARIMA 순천향대학교 2022 국내박사

Anti-melanogenic and Anti-inflammatory effect of novel synthetic compounds

Sehwan Ahn 광주과학기술원 대학원 2019 국내석사

The demand for novel anti-melanogenic compounds is increasing due to the weak efficacy and unwanted side effects of present medication. To identify effective anti-melanogenic compounds for cosmetic discovery, we used zebrafish as an animal model. Synthesized compounds were evaluated for their ability to anti-melanogenic effects in the zebrafish model. We identified compounds that affected the pigmentation of developing melanophores in zebrafish. Among them, compound 3d, a novel sulfoxide isoquinoline as an anti-melanogenic agent, which strongly inhibits melanin synthesis in the developing melanophores of zebrafish. Thus, compound 3d has a potential for use in skin-whitening cosmetics. Compound 2i, a synthetic sulfide isoquinoline was first screened for its anti-melanogenic effect using zebrafish larvae. In this study, we also examined its anti-inflammatory activities in vitro using lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Among them, compound 5h and compound 5i, a synthetic 4-fluorophenyl sulfoxide purine and pyrrolo pyrimidine show enhanced the anti-inflammatory effect and Phase 1 liver microsomal stability. These results demonstrated that compound 5h and compound 5i may be effective as anti-inflammatory agents.

Gene-embedded coronary stent for treatment of post-angioplasty restenosis

처후이롄 Chonnam National University 2015 국내박사

Antiangiogenic and antitumor constituents from vietnamese medicinal plants and their analogues : Nam, Nguyen-hai

Nam, Nguyen-hai 충남대학교 대학원 2002 국내박사

Analysis of the factors affecting e-waste recycling intention focusing on the role of information publicity using integrated NAM-TPB

Walimuni Arachchilage Chathuri Sugandika Muthukuma Graduate School Jeju National University 2023 국내석사

This research aims to investigate how information publicity effects residents' e-waste recycling intentions. This study extends the norm activation model (NAM) and the theory of planned behaviour (TPB) by including external information components, such as information publicity, in order to analyse Korean residents' intentions and actual behaviour regarding garbage classification and the factors influencing it. The researcher collected a total of 500 valid samples from mainland Korea and Jeju Island, Korea. The primary data was analysed using partial least squares structural equation modelling (PLS-SEM) to validate the model. The results indicate that while information publicity cannot directly affect residents' behaviour intentions toward e-waste recycling, it can affect them indirectly via two mediating variables: recycling attitude and moral norms. Furthermore, the findings show that information publicity has a direct influence on perceived behavioural control, but that perceived behavioural control does not perform a mediating role. With this finding, this study can conclude that, people are aware of the convenience of recycling infrastructure, but this awareness is insufficient to change residents' intentions to recycle. The study's findings suggest that present information and publicity on recycling e-waste are insufficient or that their substance does not encourage recycling behaviour. In order to increase the regularity of publicity events, government need concentrate on their content.