2,334 research outputs found
Skin-Stiffener Separation in T-Stiffened Composite Specimens in Postbuckling Condition
No full textAn experimental and numerical investigation was conducted to study the skin-stiffener separation of single T-shape stiffener specimens in postbuckling condition. Three specimens were manufactured with a centrally located Teflon insert, and were loaded in compression until collapse. Deformation patterns and separation evolution were monitored during the tests. To measure the full-field displacements and the strain distributions of the specimens, a digital image correlation (DIC) system was used. Skin-stiffener separation was observed and measured with an ultrasound system. Finite-element (FE) analyses were conducted to capture interlaminar damage mechanism based on the virtual crack closure technique. The numerical analysis accurately predicted the postbuckling deformation and the skin-stiffener separation behavior. The close correlation between the experimental and numerical results allows for further exploitation of the strength reserve in the postbuckling region and wider design options for the next generation of composite aircraft designs.</p
Heck reaction of alkyl halides and α-selective heck reaction of styrenes
No full textMy graduate study has been focused on the development of transition metal-catalyzed reactions, especially Pd-catalyzed coupling reactions. In this thesis, we described two catalytic systems that solved challenging problems in the intermolecular Heck reaction.
In the first part, we disclosed a new catalyst – Pd/dnpf can efficiently catalyze the Heck reaction of aryl and vinyl triflates with aromatic olefins. In most cases, the aryl or vinyl groups insert selectively at α position in >95% purity and the minor isomers can be removed after purification by flash chromatography. We conducted both experimental and computational study to probe the origin of high internal selectivity. The study revealed that the generality and selectivity is attributed to the combination of electronic and steric effects derived from our new ligand – dnpf. The resulting rigid and congested coordination sphere sterically disfavors the terminal insertion. The initial results of aryl bromides unfolded the potential of the newly-developed ligand for more reactions.
In the second part, we disclosed an efficient catalyst – Pd/dppf for the intermolecular Heck reaction of alkyl halides, which is a challenging problem in palladium catalysis. The simple and easily accessible Pd/dppf catalyst showed good reactivity as well as good selectivity. The use of dppf as supporting ligand was crucial for our success in this reaction as other ligands failed to afford the product in a satisfactory yield. It can be applied to a broad spectrum of electrophiles including alkyl iodides, bromides and chlorides. Both primary and secondary alkyl halides bearing functional groups such as esters, amides and nitriles were tolerated in the catalytic system. Concerning the scope of olefins, vinylarenes of steric and electronic perturbations coupled well. We conducted mechanistic study to probe the reaction mechanism and the experimental data suggested that the reaction was initiated by a single electron transfer from Pd(0)-complex to alkyl halides.DOCTOR OF PHILOSOPHY (SPMS
Finite Element Methods and Their Convergence for Elliptic and Parabolic Interface Problems
No full textIn this paper, we consider the finite element methods for solving second order elliptic and parabolic interface problems in two-dimensional convex polygonal domains. Nearly the same optimal L 2 -norm and energy-norm error estimates as for regular problems are obtained when the interfaces are of arbitrary shape but are smooth, though the regularities of the solutions are low on the whole domain. The assumptions on the finite element triangulation are reasonable and practical. Mathematics Subject Classification (1991): 65N30, 65F10. A running title: Finite element methods for interface problems. Correspondence to: Dr. Jun Zou Email: [email protected] Fax: (852) 2603 5154 1 Institute of Mathematics, Academia Sinica, Beijing 100080, P.R. China. Email: [email protected]. The work of this author was partially supported by China National Natural Science Foundation. 2 Department of Mathematics, the Chinese University of Hong Kong, Shatin, N.T., Hong Kong. E-mail: [email protected]...
Metal salen coordination compounds: A new type of ambipolar charge transport materials
No full textA series of metal (Ni or Cu) salen coordination compounds were designed, synthesized and characterized. Their photophysical properties, electrochemical properties and thin film morphologies were studied. Their charge transport properties were measured by time of flight (TOF) technique. Compounds 1 and 1b showed hole transport properties, while compounds 2 and 3 exhibited balanced ambipolar mobilities. DFT calculation results were in good agreement with the experimental results and provided an explanation for the unexpected TOF results. Compound 3 showed the highest mobilities (10(-5) cm(2)/Vs) for both holes and electrons at ambient temperature, suggesting a promising candidate of ambipolar charge transport materials. (C) 2010 Elsevier B.V. All rights reserved.Materials Science, MultidisciplinaryPhysics, Condensed MatterPolymer ScienceSCI(E)EI2ARTICLE21-222299-230516
Hoe zou een publieke datadonatiepraktijk ten behoeve van gezondheid en welzijn eruit kunnen zien?
No full textDit boekje is verslag van het CHANGE! (Conscious Health dAta shariNg in movinG RottErdam!) project dat is uitgevoerd in 2021-22 in het kader van een Open Mind subsidie van het Convergence programma dat ten doel heeft samenwerking tussen TU Delft, Erasmus Universiteit Rotterdam en Erasmus Medisch Centrum te bespoedigen. Het stimuleert allianties van onderzoekers van de verschillende universiteiten om in samenwerking met publieke en private partners innovatieve bijdragen te leveren aan urgente en complexe maatschappelijke uitdagingen, zoals klimaatverandering, duurzaamheid, gezondheidszorg, verstedelijking en digitalisering.Dit (kleine, verkennende) interdisciplinaire project, uitgevoerd binnen het Health & Technology programma, betreft een onderzoek naar hoe een publieke datadonatiepraktijk ten behoeve van gezondheid en welzijn eruit zou kunnen zien. Het is een ultiem Convergence-project, omdat het grensoverschrijdend is voor elk van de participerende instituten en kennisdomeinen en expertise van het team. Binnen CHANGE! zijn onder andere de medische, ethische, sociaal-maatschappelijke, politieke en ruimtelijke (en niet strikt de technische) aspecten van het verzamelen en werken met gezondheidsdata verkend.Design Aesthetic
Wanted! Investigating how elements from the personal usage context affect Gen Z consumers' value-in-use experience and engagement with mobile service
No full textsponsorship: The research underlying this article has benefitted from a China Scholarship Council grant (No. 201508320285) to the first author. (China Scholarship Council|201508320285)status: Publishe
A contextual classification approach for forest land cover mapping using high spatial resolution multispectral satellite imagery – a case study in Lake Tahoe, California
No full textMaps of classified surface features are a key output from remote sensing. Conventional methods of pixel-based classification label each pixel independently by considering only a pixel’s spectral properties. While these purely spectral-based techniques may be applicable to many medium and coarse-scale remote sensing analyses, they may become less accurate when applied to high spatial resolution imagery in which the pixels are smaller than the objects to be classified. At this scale, there is a higher intra-class spectral heterogeneity. Detailed forest and vegetation classification is extremely challenging at this scale with both high intra-class spectral heterogeneity and inter-class spectral homogeneity. A solution to these issues is to take into account not only a pixel’s spectral characteristics but also its spatial characteristics into classification. In this study, we develop a generalizable contextualized classification approach for high spatial resolution image classification. We apply the proposed approach to map vegetation growth forms such as trees, shrubs, and herbs in a forested ecosystem in the Sierra Nevada Mountains.Submission published under a 24 month embargo labeled 'U of I only', the embargo will last until 2017-08-01The student, Yi Zou, accepted the attached license on 2015-07-17 at 13:20.The student, Yi Zou, submitted this Thesis for approval on 2015-07-17 at 13:27.This Thesis was approved for publication on 2015-07-20 at 13:48.DSpace SAF Submission Ingestion Package generated from Vireo submission #8535 on 2015-09-29 at 15:00:47Made available in DSpace on 2015-09-29T20:50:19Z (GMT). No. of bitstreams: 2
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Previous issue date: 2015-07-20Embargo set by: Seth Robbins for item 89495
Lift date: 2017-09-29T20:50:34Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 89495 on 2017-09-30T09:15:30Z
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