1,722,005 research outputs found
압축응력 하에서의 시멘트와 뼈의 경계면의 전단 접착 강도에 관한 연구
No full text학위논문(석사) - 한국과학기술원 : 기계공학전공, 2002.8, [ v, 48 p. ]This study focuses on the experimental investigation of the shear bonding strength in the presence of normal stress of the cement-bone interface. For this study, special compressive and shear ‘biaxial’ jig was developed. The cement-bone interface is one of the most important factors in the aseptic failure. The experiments were performed with the small cement-bone specimens to verify the shear bonding strength in the interface. The author followed contemporary hip replacement surgery with a swine femur, prepared specimens by cutting into 10mm ×5mm×5mm (2.5mm: cement + 2.5mm: bone) specimens with low speed diamond cutter and tested it using INSTRON servo microforce system. The results showed that the cement-bone interface shear bonding strength increased with the increase of the normal stress based on the Hoffman’s multi-axial criteria diagram. From the regression equation, it is estimated that shear bonding strength increases 1.7 times (142%) as much as 1MPa incensement of normal stress. It is concluded that normal stress to the interface can decrease the shear failure.한국과학기술원 : 기계공학전공
A universally applicable 0D turbulence model based on the physical analysis of fundamental tumble behaviors in spark-ignition engines
No full textPredicting turbulence in a zero-dimensional (0D) simulation is an undeniably challenging task due to the complexity of in-cylinder charge motion. In that respect, a physics-based understanding of in-cylinder flow phenomena is of vital importance for establishing high-fidelity 0D turbulence models under diverse engine conditions. The proposed 0D model is hence built upon the kinetic energy analyses of tumble, evidenced by three-dimensional computational fluid dynamics. Specifically, the overall 0D turbulence model consists of an intake model, a spinning up model, and a turbulence production model. The major difference between this model and the existing 0D turbulence models is that this model is grounded on a kinetic energy perspective of tumble, as opposed to an angular momentum perspective of tumble. That is, the behaviors of tumble, such as spinning up and vortex breakdown, are interpreted and modeled based on the changes in the kinetic energy of tumble. This enables the proposed model to secure wider applicability at various engine conditions, which were otherwise difficult to achieve. Therefore, the 0D simulation in this study was able to predict turbulent intensities at the conditions, differing in valve strategy, engine geometry, and engine operation, without changing any validation constants. Furthermore, along with the validation points used in this study, better predictions of turbulent intensity were achieved using the proposed model compared to the existing state-of-the-art model.N
Solid oxide fuel cell-internal combustion engine hybrid system utilizing an internal combustion engine for anode off-gas recirculation, external reforming, and additional power generation
No full textA solid oxide fuel cell (SOFC)-internal combustion engine (ICE) hybrid system is proposed and analyzed. Although the existing SOFC-ICE hybrid system improves the efficiency of the SOFC stand-alone system by deriving additional power from the anode off-gas in the ICE, the proposed hybrid system further increases the system efficiency by utilizing the ICE for anode off-gas recirculation, external reforming, and additional power generation. Accordingly, we developed models for the SOFC and ICE and performed simulations to understand the operational characteristics of the hybrid system. Through simulation, the influence of each control parameter was analyzed, and the system operable ranges were determined according to the rate of system heat loss. When the heat loss considered is the least, a gross system efficiency of 66.9% is achieved at the optimum point. Thus, this study developed a high-efficiency SOFC-ICE hybrid system by combining methods that utilize the ICE as a recirculation blower, reformer, and power generator.N
Investigation of Fatigue Characteristics of Domain in Pb(Zr0.52Ti0.48)O3(PZT) Thin Films using Atomic Force Microscopy(AFM)
No full textFabrication and characterization of thin and smooth PZT nano films
No full text학위논문(박사) - 한국과학기술원 : 재료공학과, 2002.8, [ ix, 155 p. ]한국과학기술원 : 재료공학과
A study on the effect of the surface carbonation on the hydration of CaO
No full text학위논문(박사) - 한국과학기술원 : 재료공학과, 1991.2, [ iv, 92 p. ]한국과학기술원 : 재료공학과
Characterization of the Property Degradation of PZT Thin Films with Thickness
No full textThe property degradation of lead zirconate titanate (PZT) thin films with thickness was investigated. PZT thin films were fabricated under the optimum established conditions. PZT thin films with a thickness of less than 30 nm did not show the perovskite phase. When considering the thickness of the reacted layer between the PZT thin film and the Pt bottom electrode of about 10 nm in thickness, a thickness of 30 nm was considerable compared to the critical thickness (18 nm) over which PZT shows ferroelectricity. The degree of (001) orientation increased as the thickness increased due to the competition between the effect of the surface energy and that of the lattice mismatch with Pt(111). The degradation of the ferroelectricity with increasing PZT thickness was investigated. PZT thin films with a thickness of less than 30 nm did not show ferroelectric properties. The remnant polarization decreased and the coercive field increased as the PZT thickness decreased. We speculate that the increase in the residual stress and the decrease in the grain size with decreasing film thickness were the major factors in the decrease in the remnant polarization while the increase in the contribution of the low dielectric layer between the PZT and the bottom electrode contributed most to the increase in the coercive field. The leaky behavior of PZT thin films with thicknesses of less than 30 nm appeared to be due to the existence of metallic Pb at the PZT grain boundary, as observed by X-ray photoelectron spectroscopy
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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