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RISS 인기검색어
- 검색키워드
- 저자 : Massad, Alexander Ellis (검색결과 5 건)
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Massad, Nour Graduate School, Yonsei University 2021 국내석사
이번 연구의 목적은 세 가지 서로 다른 니켈 타이타늄 (Ni-Ti) 단일 파일 시스템을 사용하여 인공 근관 블록에서 근관 변위량 및 제거된 면적을 평가하는 것이었다. 90 개의 J 형태의 근관치료 실습 블록 (0.02 경사도, 16mm 길이)을 무작위로 3 개 그룹 (n = 30)으로 나눈 뒤, 각 그룹에 WaveOne Gold (Dentsply Sirona, Ballaigues, Switzerland), Trunatomy (Dentsply Sirona) 및 M3-L Platinum (United Dental Changzhou, Shanghai, China) 단일 나이타이 파일 시스템을 배정하였다. 이후, 각 그룹 내에 파일 크기 (small, primary, medium)에 따른 3 개의 하위 그룹에 각 10개의 블록을 배정하였다. 카메라가 내장된 광학 현미경을 사용하여 근관 성형 전 (염료 포함) 및 근관 성형 후 사진을 촬영한 뒤 Adobe Photoshop CC (Adobe Systems Inc, San Jose, CA, USA)를 이용하여 사진을 중첩하였다. 근관 내측, 외측에서 제거된 레진의 양과 근관 변위량은 근첨에서 1, 3, 5, 7mm 떨어진 위치에서 측정하였고 ImageJ 프로그램을 사용하여 분석하였다. 측정된 데이터는 일원배치 분산분석 및 터키 검증을 통하여 통계적으로 분석하였다. M3-L Platinum은 근관 변위량이 가장 많았고, Trunatomy는 가장 적었으며 일부 지점에서 통계적으로 유의미한 차이를 보였다. TRN, WOG, M3-L 순으로 제거된 면적의 양이 증가하였다. Medium 크기의 파일을 제외하고 WOG와 M3-L 간에 모든 군에서 유의한 차이를 보였다 (p <0.05). 결론적으로, 이번 연구에 사용된 세 가지 서로 다른 파일 시스템 모두에서 근관 변위량은 일반적으로 최소로 측정되었고, 근관 성형 능력은 만족스러웠다. 이번 연구를 통한 파일의 임상적 사용에 대한 제안은 다음과 같다. 좁은 근관에서 최소 침습적 근관 치료가 필요한 경우 Trunatomy 파일의 사용이 권장되고, 만곡이 심한 근관에서 사용하는 경우 주의를 기울여야 한다. WaveOne Gold 파일은 만곡이 있는 근관에서 안전하게 사용할 수 있으며, M3-L 파일은 비교적 만곡이 심하지 않은 근관에서 사용하는 것이 더 적합하다. Introduction: This study was aimed to evaluate root canal transportation and amount of removed area in artificial resin blocks with three different nickel titanium (NiTi) single-file systems. Material & Methods: Ninety J -shaped Endo-Training Blocks (0.02 taper, 16mm Length) were randomly divided into 3 groups (n=30) with each group having 3 sub-groups consisting of 10 samples for each file size (small, primary, medium) of the WaveOne Gold (Dentsply Sirona, Ballaigues, Switzerland), Trunatomy (Dentsply Sirona) and M3-L Platinum (United Dental Changzhou, Shanghai, China) NiTi single file systems. A preoperative (with dye) and postoperative images were taken of the samples using stereo microscope with build in camera, and the images were then layered using Adobe Photoshop CC (64 bit) (Adobe Systems Inc, San Jose, CA, USA), the amount of resin removed from both the inner and the outer sides of the canal and the amount of canal transportation was measured at the distance of 1, 3, 5 and 7 mm from the apex, as well as the amount of the canal in pre- and post-operative images using ImageJ program. One-way ANOVA and Tukey post hoc test were used to statistically analyze the data. Results: M3-L Platinum had the highest amount of canal transportation while Trunatomy had the lowest amount with statistically significant result at some but not all the levels, the amount of area of removed resin listed from smallest to largest came as follows (Trunatomy, WOG, M3-L), the result were significantly different. (p < 0.05) in all the groups except in medium file size between WOG, M3-L. Conclusions: Despite the differences between the systems, canal transportation was in general minimal, and so the shaping ability of these systems is proven to be satisfactory, some suggestions for the clinical use of these files are as follows; the use of Trunatomy files is recommended when minimally invasive endodontics is needed in narrow canals and if used with severely curved canals care must be taken. WaveOne Gold files can be used safely in curved canals while M3-L files are better suited to be used with less curved ones.
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Massad, Nelson Syracuse University 2003 해외박사(DDOD)
In the last few years, the Internet and World Wide Web (Web) have had a major effect on the way businesses and customers conduct business. The study aimed to enhance our understanding on how the transactions between customers and service providers take place on the Web. To accomplish this goal, the present study explored the antecedents of customer satisfaction with product-related services and pure services on the Web. Methodologically, the study implemented a self-administered Web survey instrument using the critical incident elicitation technique. The study identified three meta-categories, six categories, and 33 sub-categories as antecedents of satisfaction with online service encounters. The present research contributed at a theoretical level by (1) providing a deeper understanding of the transactions between customers and service providers on the Web; (2) providing an initial conceptual framework for future investigation of electronic service encounters; (3) pointing to novel forms of service encounters in the electronic environment. The present research contributed at a pragmatic level by (1) re-iterating the importance of the user-based approach; (2) presenting online service providers with a list of factors that customers deemed important in their purchasing experiences. This list can be used to improve their service to customers; (3) presenting online service providers with the means to improve customer-contact employees' skills in dealing with online customers.
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Macroscopic models for shape memory alloy characterization and design
Massad, Jordan Elias North Carolina State University 2003 해외박사(DDOD)
Shape memory alloys (SMAs) are being considered for a number of high performance applications, such as deformable aircraft wings, earthquake-resistant structures, and microdevices, due to their capability to achieve very high work densities, produce large deformations, and generate high stresses. In general, the material behavior of SMAs is nonlinear and hysteresic. To achieve the full potential of SMA actuators, it is necessary to develop models that characterize the nonlinearities and hysteresis inherent in the constituent materials. Additionally, the design of SMA actuators necessitates the development of control algorithms based on those models. We develop two models that quantify the nonlinearities and hysteresis inherent to SMAs, each in formulations suitable for subsequent control design. In the first model, we employ domain theory to quantify SMA behavior under isothermal conditions. The model involves a single first-order, nonlinear ordinary differential equation and requires as few as seven parameters that are identifiable from measurements. We develop the second model using the Muller-Achenbach-Seelecke framework where a transition state theory of nonequilibrium processes is used to derive rate laws for the evolution of material phase fractions. The fully thermomechanical model predicts rate-dependent, polycrystalline SMA behavior, and it accommodates heat transfer issues pertinent to thin-film SMAs. Furthermore, the model admits a low-order formulation and has a small number of parameters which can be readily identified using attributes of measured data. We illustrate aspects of both models through comparison with experimental bulk and thin-film SMA data.
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