188,731 research outputs found
Nonlinear Ultrasonic Inspection of the Effect of Contaminants on Material Properties of Epoxy-Adhesive
No full textAdhesive joints have been an effective alternative to conventional mechanical fasteners for joining materials in the aerospace and automotive industries. Although adhesive joints have various advantages, including uniform stress distribution, lower weight, improved corrosion tolerance, and design flexibility, there can be various defects in adhesive joints, which have limited wider application. This paper investigates the effect of a contaminant on the chemical and mechanical properties of the epoxy-adhesive and seeks to determine if a SHG method can reliably detect and characterize the degree of contamination in the epoxy-adhesive. A contract based ultrasonic through-transmission method was used to measure nonlinearity and then the nonlinearity parameter was calculated using the measured fundamental and second harmonic frequency components in the signals. It was found that there is higher sensitivity to contaminant concentration, up to 1.5%, of the nonlinearity parameter than that for the sound velocity. These data were also found to correlate with changes in the mechanical hardness, which was measured by the Rockwell hardness testing, with different four levels of contamination. Differential scanning calorimetry (DSC) and the thermogravimetric analysis (TGA) were also conducted to assess the effect of the contaminant on thermal properties of the epoxy-adhesive. The DSC and TGA techniques were used to evaluate the curing reaction and the thermal stability of the epoxy-adhesive respectively.This is a preprint from Pyun, Do-Kyung, Lucas W. Koester, Daniel J. Barnard, and Leonard J. Bond. "Nonlinear ultrasonic inspection of the effect of contaminants on material properties of 2." Ultrasonics 35, no. 8 (1998): 573-580. doi: https://doi.org/10.21203/rs.3.rs-1502609/v1 Published as Pyun, Do-Kyung, Lucas W. Koester, Daniel J. Barnard, and Leonard J. Bond. "Nonlinear ultrasonic inspection of the effect of contaminants on material properties of epoxy-adhesive." Journal of Nondestructive Evaluation 41, no. 4 (2022): 75. doi: https://doi.org/10.1007/s10921-022-00904-y
Nondestructive characterization of contaminant-induced material softening in epoxy polymers using nonlinear ultrasonic measurements
No full textEpoxy polymer-based materials are widely used in structural assemblies due to their efficient and robust bonding capabilities. Nondestructive testing tools are needed to assess joint quality, and ideally strength, as contaminants, and some other defects, introduced during the manufacturing process can potentially cause material softening of the epoxy, leading to the degradation of the structural integrity of the bonded components. The application of the nonlinear response with ultrasonic methods used to characterize the epoxy material itself has been underexplored. This study investigates the use of an ultrasonic second-harmonic generation (SHG) method to characterize contaminant-induced material softening in epoxy polymers, with the contaminant being a release agent. The nonlinearity parameter associated with SHG was measured with varying contamination levels. To validate the effectiveness of the SHG method, nonlinear resonant ultrasonic spectroscopy (NRUS) was employed to independently assess the variation in material softening with the increase of contamination levels. Additionally, tensile testing was conducted on contaminated samples to establish a correlation between mechanical strength and the nonlinear parameter related to the degradation due to the material softening. This study demonstrated that the SHG technique is a promising nondestructive evaluation method for detecting contaminant-induced degradation in epoxy materials.This is a manuscript of an article published as Pyun, Do-Kyung, Daniel J. Barnard, and Leonard J. Bond. "Nondestructive characterization of contaminant-induced material softening in epoxy polymers using nonlinear ultrasonic measurements." NDT & E International (2025): 103364. doi: https://doi.org/10.1016/j.ndteint.2025.103364
Nonlinear ultrasonic inspection of cohesive failure in adhesive due to contaminants in the manufacturing process
No full textAdhesive joints have been an effective alternative to conventional mechanical fasteners for joining similar and dissimilar materials in the aerospace industry. Adhesive joints have various advantages, including uniform stress distribution, lower weight, and design flexibility, but quality issues and possible defects in these joints have limited wider use. In this study, contaminants mixed into the epoxy-adhesive, which cause cohesive failure, were investigated. In the manufacturing process there can be various contaminants, such as release agents, oils, and moisture. Since release agents are essential materials during the manufacturing process, these were used in this study. A nonlinear ultrasonic technique was employed to evaluate the micro-scale defects in the adhesive due to contaminants. The experiments measured the nonlinearity parameter, with varying the contamination level, at 0, 0.5, 1.0, and 1.5% of the total weight of the epoxy mixture. The nonlinearity parameter exhibited higher sensitivity than the sound velocity, which is a conventional linear ultrasonic parameter, for the differentiation of the contamination levels in the adhesive. Furthermore, differential scanning calorimetry (DSC) and Rockwell hardness testing were conducted to monitor changes in chemical and mechanical properties respectively, with varying degrees of the contamination. It is shown that using the correlation between the nonlinearity parameter and chemical, and mechanical properties of the adhesive, there is the basis for an advanced inspection system, which has potential to improve the detectability of micro-scale defects in adhesively jointed structures.This proceeding is published as Pyun, Do-Kyung, Lucas W. Koester, Daniel J. Barnard, and Leonard J. Bond. "Nonlinear ultrasonic inspection of cohesive failure in adhesive due to contaminants in the manufacturing process." In Nondestructive Characterization and Monitoring of Advanced Materials, Aerospace, Civil Infrastructure, and Transportation XVI, vol. 12047, pp. 75-82. SPIE, 2022.
DOI: 10.1117/12.2612271.
Copyright 2022 SPIE.
Posted with permission
순수 알루미늄과 알루미늄 합금의 수용액 부식의 예를 중심으로 수행한 전기화학 임피던스와 전기화학 노이즈 분석
No full text학위논문(박사) - 한국과학기술원 : 신소재공학과, 2007.2, [ xxii, 304 p. ]The present work involves an investigation of aqueous corrosion of pure aluminium (Al) and its alloys using electrochemical impedance spectroscopy and electrochemical noise (EN) measurement.
Chapter III-1 is concerned with the analysis of electrochemical impedance spectra of the anodised pure Al foil used for Al electrolytic capacitors. The capacitance of an Al electrolytic capacitor is mainly dependent on the surface area of Al foil. In this regard, several articles have been devoted to the study of increasing the surface area by the formation of etch tunnels. Since the ions in the electrolyte diffuse through the etch tunnel for charge saturation of the electrolytic capacitor, the electrochemical behaviour of the Al electrolytic capacitor will be affected by the tunnel length distribution. In this chapter, for the numerical calculation of the total impedance of the electrode, the transmission line model was modified to reflect the etch tunnel length distribution representing the contributions of the etch tunnel length to the total impedance. From the agreement of the numerically calculated impedance spectra with the experimentally measured spectra, it was concluded that the deviation of the impedance spectra from the ideal capacitive behaviour in the high frequency region originates from the characteristic frequency dispersion which itself it dependent upon the etch tunnel length distribution.
In chapter III-2, the effects of sulphate, thiosulphate and hydrogensulphate ion additives on the pitting corrosion of pure Al in 1 M NaCl solution were investigated as a function of solution temperature using double current step experiment. It is generally accepted that these ion additives have an essential role in increasing the surface area of Al foil used for Al electrolytic capacitors. From the analysis of the galvanostatic potential transients obtained from the double current step experiment, it was suggested that both sulphate and thiosulphate ions ret...한국과학기술원 : 신소재공학과
POR FORA DO PRÉ-MODERNISMO
No full textResumo:Este artigo propõe uma reflexão sobre a atuação intelectual do escritor Gustavo Barroso (1888-1959) e de sua relação com o Pré-modernismo brasileiro, considerando categorias como capital cultural e pessoal, conforme Pierre Bourdieu, e que demonstram de que modo o autor se coloca à margem do período, sem ser excluído propriamente.Palavras-chave: Pré-modernismo. Gustavo Barroso. Capital pessoal.Abstract: This article is a reflection about the intellectual activity of writer Gustavo Barroso (1888-1959) and his relationship with Brazilian Pre-modernism, considering categories such as personal and cultural capital, as in Bourdieu, showing how the author was marginalized in the period without being totally excluded.Keywords: Pre-modernism. Gustavo Barroso. Personal capital
Dam Kyung : Painting Sceneries Embodying Stories
No full text본 논문에서는 본인만의 그림을 그리기 위해서 『임천고치』에서 산수화의 본질을 찾고, 사의를 통한 진경산수의 표현법을 연구해본 내용에 대해 서술했다. 그 내용을 요약하면 『임천고치』의 ‘임천을 그리워하는 마음으로 그린 그림(산수화)’, 사의(寫意)의‘그림을 그리고 싶은 마음’과‘정신과 내용을 담아 실제보다 더 그곳 같은 느낌을 들게 하는 것’, 진경산수의 ‘직접 사생하며 경험한 내용을 그림으로 풀어가는 과정’이다. 산수를 직접 경험한 이야기를 감정에 따라 그리는 것, 이것이 본인이 산에 오르고 사생하게 된 이유고 ‘담경(談景)’이라는 작업방향을 갖고 작업하게 된 동기가 됐다.
본인이 표현하려는 ‘담경’은 ‘이야기가 있는 풍경(산수화)’을 그리는 것으로, 이야기에는 산세의 모습과 사람의 모습을 담으며 『임천고치』 와 사의의 이론을 바탕으로 산에서 겪은 경험과 감흥을 그려 산의 정취와 본인만의 시각을 담아낸다.
‘담경’을 담기 위해 나무와 바위가 있고 사람의 흔적이 있는 땅(평지, 地)과 울창한 숲이나 폭포, 산봉우리 등의 시선이 가는 경물(景物)의 모습(意)그리고 소탈하고 청산한 느낌을 위한 하늘(여백, 天)로 구성하고 표현법에서는 이야기 연출을 위해 불필요한 부분은 생략(축소)하고 인상적인 부분은 강조(확장)함으로써 산을 있는 그대로 그리는 것이 아닌 본인이 경험한 감흥에 맞게 산의 이야기를 구성하고 표현하게 한다.
이 연구를 통해 ‘담경’산수의 가능성을 탐구해 작업 방향을 설정하고, 이론에 뒷받침할 표현법을 키우기 위해 산수에 대한 관찰을 계속 하고자 한다.;This article outlines the author’s search of an autonomous expression of sceneries. This was pursued through her analysis of the Chinese medieval text of Imchungochi, through which she studied the essence of landscape art.
Imchungochi describes; portraying one’s nostalgia of the observed nature; using ‘the desire to paint’ and ‘the psyche’ to give one a feeling of being in the scene, even more so than while standing in the scene in reality; the narration of one’s own experience through painting.
“Walking into the sceneries and reliving the experience with such perceived emotion” was the author’s passion that led to her countless hiking journeys and her theme of Dam Kyung, which translates into ‘the views with stories.’
Using stories that portray the appearance and the behaviors of humans and the nature, the author applies the doctrines of Imchungochi to her work to present her very own experience and point of view through the painted landscape.
Dam Kyung composes of objects that attract and voids that exonerate. Objects include trees and rocks, ground with traces of people, dense forestry, waterfall, and mountains. The sky fills the void.
To express such, the perceived impressions are exaggerated [expand] and the rest is suppressed [contract].
The scenes are composed and expressed according to a subjective experience, as to recording factual elements. Through such, the art of Dam Kyung was realized.
With this in depth study of Dam Kyung, the author has set the direction of her work and established her own theory. The author will continue her endeavor to observe in order to further analyze her theme of Dam Kyung to practice her technical skills to achieve the goal.Ⅰ. 서론 1
A. 연구의 목적 1
B. 연구의 내용과 방법 3
Ⅱ. 이론적 배경 4
A. 곽희의 화론 4
B. 사의(寫意)와 진경산수(眞景山水) 10
1. 사의 속 진경산수 11
2. 정선이 그린 진경산수 12
C. 담경(談景) 17
Ⅲ. 조형적 표현 22
A. 담경을 담은 구도 23
B. 사생을 통한 생략과 강조 26
Ⅳ. 작품 분석 29
Ⅴ. 결론 58
참고문헌 60
ABSTRACT 6
Nonlinear ultrasonic techniques for evaluation of contaminant based micro-scale defects in adhesive joints
No full textAdhesive joints are extensively used in various engineering fields, including the aerospace, automotive, and marine industries. They are an alternative to using conventional mechanical fasteners and such joins have various advantages. Firstly, adhesive joints can provide a uniform stress distribution, and improve fatigue and corrosion tolerance. Second, adhesive joints have lower weight than mechanical fasteners, and when used in transportation structures, they provide design flexibility and enable higher fuel efficiency. However, ensuring and measuring joint quality and strength presents challenges. These adhesive joints can include manufacturing defects and material degradation in service.
For use of adhesive joints to increase it is necessary to have reliable and effective nondestructive methods for assessment. To improve joint QA/QC various diagnostic techniques have been investigated, including using conventional ultrasound techniques. Such techniques can characterize common macro-scale defects, such as large voids or delamination. However, there remains a critical need for detecting and characterizing micro-scale defects in adhesively jointed structures, such as contamination introduced during manufacturing process. Such contaminant based micro-scale defects can be categorized into two types, those where foreign materials are mixed into bulk adhesive and materials that collect, as a liquid state, at the interface between substrates and the adhesive. Contaminated bulk adhesive can induce material degradation, which can potentially cause cohesive failure. Contaminant based interfacial defects can weaken the bonding strength, which will cause the adhesive failure.
One potential novel technique for characterizing micro-scale contamination defects is nonlinear ultrasound. In this study, contaminant based micro-scale defects were characterized using two nonlinear ultrasound based approaches: second harmonic generation (SHG) and nonlinear resonance ultrasonic spectroscopy (NRUS). The research combined development and use of a finite element based numerical model, and experimental analyses. For the micro-scale bulk defects, the effects of contaminants on the material properties of epoxy-adhesive were investigated using SHG and NRUS. Supporting material characterization, such as thermal analyses and mechanical testing, was performed to quantify contaminant effects on adhesive properties. This work demonstrated that novel nonlinear ultrasound measurements can nondestructively detect and quantify the effect of a contaminant, a release agent at low concentration, on adhesive properties. A correlation between the ultrasonic nonlinearity parameters and the level of the material degradation was established.
For the micro-scale interfacial defects, a finite element model was developed to investigate the effects of the thickness of a contaminant inter-layer on the propagation of linear and nonlinear ultrasonic waves in layered structures. The model was validated using comparisons with the analytical solution, for ultrasound in layered structures and experiments. Model, experimental, and where available analytical results were in good agreement.
This study confirmed that conventional ultrasound techniques have limitations in terms of their capability to characterize contaminant based micro-scale defects in adhesive joints. It then demonstrated that nonlinear ultrasonic techniques, with the nonlinearity parameter (β'), have the capability to characterize contaminant based micro-scale defects in adhesively jointed structures
Variations on the Author
No full text“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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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