Comparison of shear bond strength of orthodontic tube in glazed zirconia prostheses according to the surface treatment methods

치과대학/박사Current studies on zirconia bond strength mostly focus on “naked zirconia”, the inside of the zirconia crown. In the orthodontic field, tube bonding is required on the surface-“glazed” crown. In this study, shear bond strengths were measured and compared by bonding tubes not on “naked zirconia” but on “glazed zirconia” using various methods. A control group was established when bonding the tube on the glazed porcelain surface using the usual methods. After glazing one side of zirconia block and dividing the experimental groups into four random groups, the tubes were bonded by using different processing methods on each of the surfaces and using different primers. Control group : 50-µm Al2O3 + HF + Porcelain primer Experimental group 1 : 50-µm Al2O3 + HF + Porcelain primer Experimental group 2 : 50-µm Al2O3 + Zirconia primer Experimental group 3 : 30-µm silica-coated alumina particles + Porcelain primer Experimental group 4 : 110-µm silica-coated alumina particles + Porcelain primer Shear bond strength in each of the groups was measured by using a universal test machine. Surface characteristics were observed on the glazed surface by using SEM and a 3D optical profiler prior to applying primer, and specimens were classified according to the failure patterns. The results were as follows : 1. Shear bond strength of experimental group 2 was 10.59 MPa, which was significantly lower than all other groups (p < .05). 2. Two groups, the control group and experimental group 1 were clearly observed in the SEM images to have similar rough surfaces and cracks. However, experimental groups 2, 3 and 4 were observed as having particles attached. Experimental group 4 was observed as having bigger sized particles and more irregular rough surfaces compared to experimental groups 2 and 3. In addition, according to the results of analysis using a 3D optical profiler, the average surface roughness Sa value in experimental group 3 was significantly lower than the values for experimental groups 1, 2, 4 (p .05). 3. As for the failure type of debonding surface, only adhesive failure was manifest between zirconia block surface and resin cement interface in experimental group 2. In the rest of the groups, adhesive failure between resin cement and tube base interface was mostly manifest. Therefore, this reveals a significant difference between the experimental group 2 and the rest of the groups (p < .001). According to the results of this study, using porcelain primer after sandblasting with silica coating particles is clinically simpler, safer and more effective method in relation to glazed zirconia crown because it has a similar high shear bond strength compared to other methods without the need for hydrofluoric acid.ope

A Study on the Innovation Resistance and Usage Intention of Blockchain in the Shipping and Port field

Blockchain, one of the convergence technologies representing the Fourth Industrial Revolution era, is actively being introduced in the fields of finance, medical care, and logistics and distribution. Blockchain is a distributed data storage technology that stores data in blocks and connects them in chain form, replicating and storing them on numerous computers at the same time. It is also called a “public ledger.” Transaction records are sent to all the users participating in the transaction, without keeping them on a centralized server, and it is ensured that every transaction is free from data forgery or tampering by sharing the pertinent data among the users and allowing these to be compared with one another. Blockchain is also actively being promoted and introduced in the shipping and port field. In maritime transportation, which accounts for the majority of logistics transportation, the cost of handling trade-related documents is 20% of the total cost, and such task is inefficiently managed. Through the introduction of blockchain, it can be expected to become transparent and cost-cutting, with reduced disputes and increased dispute resolution cases as well as fewer cases of various types of fraud. Although blockchain has a high potential for utilization in the shipping and port field, the speed of its introduction in such field has not been accelerated as its effectiveness and safety have yet to be fully verified. Blockchain is currently known to the public only as bitcoin, and due to its vagueness, its introduction to certain fields as an innovation creates anxiety on the part of many, leading them to resist such innovation, thus hindering its wide usage. There has been insufficient research to date on innovation resistance, which serves as an obstacle to the successful introduction of blockchain in the shipping and port field, although there have been various studies of late on blockchain acceptance in academia. This study was conducted to investigate the degree and nature of the resistance to the introduction of blockchain in the shipping and port field on the part of many of its prospective users, so as to urge them to accept such innovation and to facilitate its successful introduction in the aforementioned field. This study was conducted as follows. First, the concept and characteristics of blockchain and the current status of its introduction in the shipping and port field sought to be understood through a review of the previous studies on blockchain. Second, the factors affecting the resistance to the introduction of blockchain in the shipping and port field were derived based on TAM (technology acceptance model), DOI (diffusion of innovation), the consumer characteristics theory, and the innovation resistance theory. Third, the research model to be used was empirically verified through a questionnaire survey among the workers in the shipping and port field. In this study, a research model was set up based on TAM. Seven items were selected as potential variables falling under three categories: relative benefits, compatibility, and perceived risks (variables related to the innovation characteristics); attitudes towards the existing products, innovativeness, and self-efficacy (variables related to the consumer characteristics); and cost rationality (variable related to the economic characteristics). Eight hypotheses were set and tested in this study: seven hypotheses to confirm the causal relationship between each of the aforementioned seven variables and the resistance to the introduction of blockchain in the shipping and port field, and one hypothesis to confirm the causal relationship between the said resistance and the blockchain usage intention. The survey for hypothesis testing was conducted for about 3 weeks among individuals engaged in or part of container terminal operations, shipping lines, public agencies and companies, inland transportation, international freight forwarders (3PL), and warehouse storage companies. A total of 300 questionnaires were distributed, and 239 valid accomplished questionnaires were collected. SPSS 21.0 was used for demographic analysis, and SmartPLS 3.0 was used for hypothesis testing and reliability and validity analysis. The results of this study are summarized as follows. First, the analysis of the three hypotheses on the innovation characteristics and innovation resistance showed that there was a negative (-) causal relationship between the relative advantage of introducing blockchain to the shipping and port field and the resistance to such innovation, and a positive (+) causal relationship between the perceived risk of its introduction and the resistance to such innovation. On the other hand, the causal relationship between compatibility and the innovation resistance was not verified. Second, the results of testing the three hypotheses on the consumer characteristics and innovation resistance were as follows. First, the more favorable the attitude towards the existing products was, the higher the resistance to the innovation, and the more innovative the users were, the lower their innovation resistance. On the other hand, no significant causal relationship was found between self-efficacy and innovation resistance. Third, in the case of cost rationality, a variable related to the economic characteristics, a lower degree of innovation resistance was found in the users who felt that the cost of the operation being undertaken was reduced through the introduction of blockchain. Finally, it was confirmed that the higher the innovation resistance was, the lower the intent to use the innovation. The implications of this study are as follows. First, the study is scholastically meaningful in that it deals with the two aspects of resistance and acceptance through a study of innovation resistance, a negative aspect that has not been dealt with in the previous studies related to the introduction of blockchain in the shipping and port field. In the practical aspect, this study confirmed the negative effect of innovation resistance on the intention to use the innovation, suggesting that the management of the innovation resistance is essential for the successful spread of blockchain. Therefore, efforts should be made to emphasize the functional benefits, innovativeness, and cost rationality of blockchain by establishing various channels for sharing information on it so as to control the resistance to its introduction in the shipping and port field. Also, as the perceived risks of blockchain introduction to the shipping and port field and the prospective users’ attitudes towards the existing products have been verified as negative factors for innovation resistance, it is believed that efforts should be made to come up with policies for ensuring information security, or with ways to dissolve the prospective users’ reluctance to embrace new technologies.초 록 ⅳ Abstract ⅶ 제1장 서 론 1 제1절 연구의 필요성 및 목적 1 제2절 연구의 방법 및 구성 4 제2장 이론적 배경 5 제1절 블록체인 기술 5 제2절 정보기술 사용의도 관련 이론 22 제3절 해운항만 분야의 블록체인 도입현황 48 제3장 연구 설계 53 제1절 연구모형의 설정 53 제2절 연구가설 설정 55 제3절 변수의 조작적 정의 및 측정 도구 61 제4절 자료수집 및 분석방법 64 제4장 실증분석 65 제1절 연구표본의 특성 65 제2절 측정 도구의 신뢰성 및 타당성 분석 68 제3절 가설 검정 73 제4절 분석 결과 76 제5장 결 론 79 제1절 연구결과 요약 및 시사점 79 제2절 연구의 한계점 및 향후 연구 방향 82 83 103Maste

울릉 분지의 성인과 구조에 대한 중력 자료의 분석과 섭입대에서의 아다카이트 생성에 관한 수치 모델링 연구

학위논문 (박사)-- 서울대학교 대학원 : 지구환경과학부, 2016. 2. 이상묵.This thesis presents the results of my studies concerning the tectonic evolution of the Ulleung Basin, East Sea using geological and geophysical data and the genesis of adakites and boninites by partial melting of oceanic crust in subduction zones. My thesis comprises two chapters and first is about the effect of time-varying subduction parameters on the Cenezoic adakites and boninites and next is the analysis of gravity measurements in the Ulleung Basin and its implications for the Moho depth variations. Chapter 1 addresses the effect of time-evolving slab age and convergence rate of the incoming oceanic plate on the genesis of adakites and boninites in the subduction zones. I made a series of two-dimensional numerical models using the time-dependent subduction parameters and compared with the geochemical evidence in each subduction zones. The results show that my model calculations successfully explained the adakites and boninites in some subduction zones. However, in the other regions such as Mariana and northeastern Japan subduction zones, the other tectonic settings of back-arc spreading, inflow of hot mantle and ridge subduction are needed to explain the partial melting of oceanic crust in subduction zones. Chapter 2 includes the analysis of gravity measurements in the Ulleung Basin and its implications for the crustal structure. I examined the gravity anomaly of the Ulleung Basin using more extensive data sets focusing on the crustal thickness and also calculated the effect of temperature on the gravity anomaly using a simple thermal model. My analysis shows that the Moho discontinuity is varied from 16 to 22 km, but within the central part of the basin, the variation is only about 10-20 %. Such finding appears to be consistent with previous studies using ocean bottom seismometers. Based on the gravity analysis, I provide the information of crustal structure and infer the important tectonic processes shaped the Ulleung Basin during post-rift period.Chapter 1 Effect of time-evolving age and convergence rate of the subducting plate on the Cenozoic adakites and boninites 10 Abstract 10 1.1. Introduction 12 1.2. Numerical model 15 1.3. Results 17 1.3.1. Izu–Bonin–Mariana (IBM) 17 1.3.2. Northeast Japan–Kuril 19 1.3.3. Tonga 20 1.3.4. Java–Sunda 21 1.3.5. Aleutians 23 1.4. Discussion 24 1.4.1. Implications of time-evolving subduction parameters to thermal structure 24 1.4.2. Other possible mechanisms responsible for adakites and boninites in arc volcanoes in the IBM, northeast Japan, Tonga, and southeastern Java–Sunda subduction zones 26 1.4.2.1. Izu–Bonin 27 1.4.2.2. Mariana 28 1.4.2.3. Northeast Japan 29 1.4.2.4. Tonga 30 1.4.2.5. Southeastern Java–Sunda 31 1.4.3. Caveats: mantle potential temperature and down-dip treatment in our model calculations 32 1.5. Summary 33 1.6. References 36 1.7. Figures 46 1.8. Table 55 Chapter 2 Analysis of marine gravity anomalies in the Ulleung Basin (East Sea/Sea of Japan) and its implications for the architecture of rift-dominated backarc basin 56 Abstract 56 2.1. Introduction 58 2.2. Regional Background 60 2.3. Data and Reduction 64 2.4. Result 66 2.5. Thermal Consideration 68 2.6. Discussion 69 2.7. Conclusions 73 2.8. References 75 2.9. Figures 80 Summary (in Korean) 90Docto

얍과 무사우 해구에서의 중력 이상 값과 유도된 섭입 작요에 대한 고찰

학위논문(석사) --서울대학교 대학원 :지구환경과학부,2007.Maste

Comparison of frictional forces between esthetic orthodonticcoated wires and self-ligation brackets

치의학과/석사최근 교정 치료에서의 심미적인 요구가 증대되면서 코팅 와이어의 사용이 점차 늘고 있지만, 코팅 와이어을 사용함으로써 생기는 마찰력 변화에 대해서는 아직 알려진 바가 적다. 이번 연구에서는 심미성을 증대시키기 위해 교정 치료 시 주로 사용되는 자가 결찰 브라켓을 이용하여, 코팅 와이어 중 polymer 코팅과 rhodium 코팅 와이어를 선택하여 코팅되지 않은 기존의 와이어와의 마찰력을 측정 비교함으로써 임상적인 효용성에 대해 평가하고자 하였다. 0.016 inch NiTi, 0.017 x 0.025 inch SS 두 종류의 와이어를 사용하였으며 브라켓과 와이어 간의 각도는 0°, 5°, 10°로 설정하고 Universal Testing Machine에 0.022 inch 슬롯의 상악 소구치용 브라켓(Clippy-C®, Tomy, Japan)을 부착 후 각각의 와이어를 고정, 5 mm/min 속도로 와이어 인장실험을 시행하여 최대 정지 마찰력과 운동 마찰력을 측정, 비교하여 다음과 같은 결과를 얻었다. 1.교정용 와이어는 코팅되지 않은 와이어보다 코팅 와이어가 같거나 더 큰 최대 정지 마찰력, 운동 마찰력을 나타내었다 (p <.05).2.최대 정지 마찰력은 0.016 inch NiTi 와이어를 사용하여 브라켓과 와이어 간 각도 5°인 조건에서와, 0.017 x 0.025 inch SS 와이어를 사용한 모든 각도에서 rhodium 코팅 와이어가 polymer 코팅보다 더 큰 마찰력을 나타내었다 (p <.05). 3.운동 마찰력은 0.016 inch NiTi 와이어를 사용하여 브라켓과 와이어 간 각도가 0°일 때를 제외한 모든 조건에서 rhodium 코팅 와이어가 polymer 코팅보다 더 큰 마찰력을 나타내었다 (p <.05). 4.교정용 와이어와 브라켓 간 각도가 증가할수록 더 큰 마찰력이 나타났으며, 0.016 inch NiTi 와이어의 경우 0°에서 5°로 변화할 때, 5°에서 10°로 변화하는 구간보다 2배 이상 큰 최대 정지 마찰력, 운동 마찰력의 증가량을 보였다 (p <.05). 심미성 보완을 위해 사용되는 코팅 와이어의 마찰력이 기존 와이어보다 같거나 큰 결과를 나타내었으나 임상적으로 의미 있는 차이인가에 대해서는 구강 내와 유사한 조건에서의 추가적인 마찰력 연구가 필요하며, 와이어의 선택에 있어서는 마찰력 뿐 아니라, 치아 색조와의 조화, 마모 저항성, 변색 등 다른 요인들도 고려하여야 할 것이다.ope

Nutritional directed regulation of nNOS expression in the rat paraventricular nucleus

의과학과/석사[한글] 본 연구에서는, 섭식상황에 따른 뇌시상하부 측뇌실핵에서의 nNOS 유전자 발현 조절의 분자기전을 추구하였다. 이를 위해, 금식 및 재급식시 측뇌실핵의 CREB 인산화 및 nNOS 발현 수준변화를 면역조직화학적 방법으로 조사하여, 이들과 당질코르티코이드 혈중 농도 변화 사이의 관련성을 검토하였다. 또한, 금식시 RU486투여에 의한 당질코르티코이드 수용체 봉쇄효과 및 재급식시 열량 배제효과를 조사함으로써, 측뇌실핵의 nNOS 유전자 발현 조절 기전에서 당질코르티코이드의 역할 및 열량의 효과를 규명하고자 하였다. 결과에서 혈장 코르티코스테론 수준은 48시간 금식시 유의하게 증가하였고, 재급식 5시간 후 다시 감소하는 것으로 관찰되었다. 한편 금식에 의해 감소되었던 nNOS유전자 발현은 재급식 후 다시 증가하였다. 당질코르티코이드 수용체의 길항제인 RU486처치는 금식에 의한 nNOS발현 및 CREB 인산화 감소를 봉쇄하였다. 재급식시, 정상 사료 공급군에서는 nNOS 발현 및 pCREB 수준이 증가하였으나, 열량이 배제된 혼합사료 공급군의 측뇌실핵에서는 nNOS 발현 및 pCREB 수준이 증가하지 않았다. 반면, 금식으로 증가했던 혈장 코르티코스테론 수준은 재급식시 열량의 유무에 관계없이 감소하였다. 이상의 결과로부터, 금식 또는 재급식시 혈장 당질코르티코이드는 그의 수용체를 매개로 하여 nNOS 발현의 변화를 억제적으로 조절하며, 이 과정에 CREB 인산화가 수반될 것임을 알 수 있었다. 또한, 측뇌실핵의 nNOS 유전자 발현 조절기전에서 음식으로부터 공급되는 열량이 유도 인자로 관여될 것이라 사료되었다. 아울러, 섭식상황에 따른 혈장 당질코르티코이드 수준 변화에는 열량 이외의 섭식 행동 인자가 관여할 것임을 알 수 있었다. [영문]Nitric oxide (NO) is an important biological messenger, especially in the hypothalamic paraventricular nucleus (PVN) of the brain, NO modulates a large number of neuronal, autonomic, and endocrine functions. nNOS expression in the rat PVN is decreased by food deprivation, increased by refeeding. The plasma level of glucocorticoids increases during food deprivation and decreases shortly after refeeding. Also it was reported that adrenalectomy abolishes fasting-induced down-regulation of PVN-nNOS and dexamethasone, a synthetic glucocorticoid, down-regulates the PVN-nNOS in intact rats. It is hypothesized that glucocorticoids may negatively regulate nNOS expression depending on the feeding conditions. However, its molecular mechanism is not known yet. Recently, in vitro experiments revealed that the nNOS promoter carries cAMP response element (CRE) in its upstream and nNOS expression is mediated by a CRE-binding protein (CREB) -dependent mechanism. In this study, we firstly examined if the fasting-induced nNOS down-regulationis is mediated by glucocorticoid receptors, and then if CREB phosphorylation is implicated in this regulatory pathway, and lastly, if changes in plasma glucocorticoids level and the PVN-nNOS expression is a nutritional-directed event. In the result, nNOS positive cells and pCREB positive nucleus in the PVN significantly decreased by 48 h food deprivation, and RU486, glucocorticoid receptor antagonist, prevented this reduction. This supports the idea that the elevated level of plasma glucocorticoids during food deprivation may exert an inhibitory role in the PVN-nNOS expression, and suggests that the fasting-induced nNOS down-regulation in this brain region is mediated by glucocorticoids receptor, and furthermore, CREB phosphorylation may be implicated in the regulatory pathway of nNOS expression. Additionally, 5 h of non-caloric refeeding following after 48 h food deprivation failed to increase nNOS expression and pCREB level, which increased by 5 h of chow refeeding. However, non-caloric refeeding decreased the plasma corticosterone level, so as chow refeeding did. These results indicate that calori supplement is required to induce nNOS expression in the PVN, and suggest that plasma glucocorticoid level may be influenced by post-ingestive factors, at least, other than calori.ope

Acute weight training bouts of different intensities and its effects on excess post-exercise oxygen consumption and energy expenditure

학위논문(석사)--서울대학교 대학원 :체육교육과,2005.Maste

에리히 케스트너의 아동 및 청소년문학 연구 : 작품 속에 구현된 교육관 분석 및 비판

학위논문(석사)--서울大學校 大學院 :外國語敎育科 獨語專攻,1997.Maste

Small area variation in rates of common surgery

학위논문(박사)--서울대학교 대학원 :보건학과 보건경제학전공,2003.Docto

Effects of breastfeeding empowerment program on exclusive breastfeeding

학위논문(박사)--서울대학교 대학원 :간호학과 간호학전공,2006.Docto