Search results for "Amination"
showing 10 items of 1702 documents
MULTIPLE CRACKS LOCALIZATION FOR THIN COATING FILM LAYERS IN PURE BENDING
2018
Recently, accurate small scale four-point bending flexural tests, for superalloy specimens with multiple ceramic type external coating film layers, have shown that under high loading, the failure mechanism is characterized by the development of complex multiple surface cracks, followed by interior interlayers debonding mechanisms. The final stage is then the complete debonding of the fragmented thermal coating, which leave the interior superalloy completely uncoated. The mechanical problem has an high technological relevance, since failure, or just severe damage, of the ceramic coating, can jeopardize the functionality of structural elements working at high temperature and under severe load…
US-Elastography for Breast Lesion Characterization: Prospective Comparison of US BIRADS, Strain Elastography and Shear wave Elastography
2020
To evaluate the diagnostic performance of strain elastography (SE) and 2 D shear wave elastography (SWE) and SE/SWE combination in comparison with conventional multiparametric ultrasound (US) with respect to improving BI-RADS classification results and differentiating benign and malignant breast lesions using a qualitative and quantitative assessment. In this prospective study, 130 histologically proven breast masses were evaluated with baseline US, color Doppler ultrasound (CDUS), SE and SWE (Toshiba Aplio 500 with a 7-15 MHz wide-band linear transducer). Each lesion was classified according to the BIRADS lexicon by evaluating the size, the B-mode and color Doppler features, the SE qualit…
Experimental Tests of Fatigue Induced Delamination in Gfrp and Cfrp Laminates
2007
This work deals with the experimental analysis of the delamination phenomena in various composite materials under different loading conditions. Quasi-static and fatigue tests are performed on specimens made of glass-fibre reinforced plastic (GFRP) and carbon-fibre reinforced plastic (CFRP). In particular, under both quasi-static and fatigue loading, single fracture modes I and II (using standard DCB and ENF test configurations) and mixed modes I+II (using the MMB test configuration) with several mode mixtures, have been analysed. Further experiments of delamination growth with mode mixture that varies with the crack length, will be performed.
Mixed mode energy release rates for bonded composite joints
2011
Abstract: Analytical formulae developed by Luo and Tong (2009) to determine the mixed mode strain energy release rates of laminated and co-cured composite structures and joints are reviewed. The effects of varying loading conditions and geometries on the mode mixity found analytically are investigated via a parametric study. A critical evaluation of the analytical formulae indicates that the formulae are robust in calculating the total strain energy release rate, but may underestimate the mode II component compared with the finite element analysis and experimental results. Possible reasons for this discrepancy are discussed, including the effect of stress concentrations and singularities at…
Competition between the buckling-driven delamination and wrinkling in compressed thin coatings
2012
Abstract The competition between two common failure modes of a thin coating under in-plane compression, the surface wrinkling and the buckling-driven delamination, is studied to assess the critical strain when the mechanical instability may occur at given geometrical and material parameters. A buckling map is constructed based on results of a finite element analysis, which relates the critical applied strain for the onset of instability to the interface adhesion and elastic properties of materials. An approximate scaling relation is derived for the energy release rate of buckling-driven delamination of a coating deposited on a compliant substrate.
Crack growth analysis at adhesive–adherent interface in bonded joints under mixed mode I/II
2008
The propagation of an interface crack subjected to mixed mode I/II was investigated for two 2024-T351 aluminum thin layers joined by means of DP760 epoxy adhesive produced by 3M©. On the basis of beam theory, an analytical expression for computing the energy release rate is presented for the mixed-mode end loaded split (MMELS) test. The analytical strain energy release rate was compared by finite element (FE) analysis using the virtual crack closure technique (VCCT). Several fatigue crack growth tests were carried out in a plane bending machine to compare the experimental energy release rates to those of the analytical and FE solutions. Experimental results showed the relationship between t…
Technique of CT Examination
1981
The three study groups used the same CT systems during the investigation period : the EMI Mark I head scanner from 1975 until June 1977 and the EMI CT 1010 head scanner from the middle of 1977, with the Diagnostic Enhancement Package since March 1980. Special studies of the base of the skull were performed with an EMI CT 5005 body scanner (Department of Radiology, Klinikum Steglitz, Free Universityof Berlin).
Use of a bulky phosphine of weak σ-donicity with palladium as a versatile and highly-active catalytic system: allylation and arylation coupling react…
2005
Abstract Carbon–carbon(sp2–sp2 and sp1–sp2) and carbon–nitrogen (nucleophilic allylation) coupling processes are promoted by a catalytic system containing [PdCl(η3–C3H5)]2 with the new ferrocenyl bis(difurylphosphine) 1,1′-bis[di(5-methyl-2-furyl)phosphino]ferrocene, Fc[P(FuMe)2]2. Starting from aryl bromides or allylic acetates this versatile catalyst system may be used at low palladium loadings (10−1–10−4 mol%) in some Heck, Suzuki, Sonogashira and allylic amination reactions to give cross-coupled products in excellent yield. Remarkably high activity is obtained in allylic substitution reactions, providing a significant impetus for the development of bulky phosphines possessing weak σ-don…
N1-Functionalized Indole-Phosphane Oxazoline (IndPHOX) Ligands in Asymmetric Allylic Substitution Reactions
2012
N-Functionalized IndPHOX ligands bearing various groups have been synthesized and the effects of the N1-substituent on the reaction rate, yield, and asymmetric induction in a palladium-catalyzed allylic substitution reaction are reported. The presence of an oxygen atom in the ligands, namely an N-MOM or N-THP group, led to enhancement of the enantioselectivity in the allylic amination reaction. In addition, a ligand with a chiral oxazoline ring at C-1 and a phosphane substituent at C-2 provided high enantioselectivity in good yield in an asymmetric allylic alkylation reaction.
ChemInform Abstract: N1-Functionalized Indole-Phosphane Oxazoline (IndPHOX) Ligands in Asymmetric Allylic Substitution Reactions.
2012
N-Functionalized IndPHOX ligands bearing various groups have been synthesized and the effects of the N1-substituent on the reaction rate, yield, and asymmetric induction in a palladium-catalyzed allylic substitution reaction are reported. The presence of an oxygen atom in the ligands, namely an N-MOM or N-THP group, led to enhancement of the enantioselectivity in the allylic amination reaction. In addition, a ligand with a chiral oxazoline ring at C-1 and a phosphane substituent at C-2 provided high enantioselectivity in good yield in an asymmetric allylic alkylation reaction.