Search results for "ALLOYS"
showing 10 items of 1689 documents
UV photoexcitation of a dissolved metalloid Ge9 cluster compound and its extensive ultrafast response.
2015
Femtosecond pump-probe absorption spectroscopy in tetrahydrofuran solution has been used to investigate the dynamics of a metalloid cluster compound {Ge9[Si(SiMe3)3]3}(-). Upon UV photoexcitation, the transients in the near-infrared spectral region showed signatures reminiscent of excess electrons in THF (bound or quasi-free) whereas in the visible part excited state dynamics of the cluster complex dominates.
Correction of B-scan distortion for optimum ultrasonic imaging of backwalls with complex geometries
2020
Ultrasound undergoes refraction and reflection at interfaces between media of different acoustic refractive indices. The most common ultrasonic method (pulse-echo) monitors the reflected energy to infer the presence of flaws, whereas the lower amplitude of refracted signals is ignored. When the reflector is orientated normally with respect to the ultrasonic beam, the received echo signal shows the maximum amplitude. The pulse-echo method also relies on monitoring the amplitude of the backwall echo to identify or confirm the presence of defects. This works well for parts with constant thickness and with planar backwalls. Unfortunately, parts with complex backwalls are common to many industri…
Unprecedented use of silver(I) N-heterocyclic carbene complexes for the catalytic preparation of 1,2-bis(boronate) esters.
2005
Catalytic diboration of internal and terminal alkenes with Ag(I) N-heterocyclic carbene complexes leads to 1,2-bis(boronate) esters as single intermediates, that can be oxidised towards the corresponding diols. Sanau Torrecilla, Mercedes, Mercedes.Sanau@uv.es
Training Deep Neural Networks with Novel Metaheuristic Algorithms for Fatigue Crack Growth Prediction in Aluminum Aircraft Alloys
2022
Fatigue cracks are a major defect in metal alloys, and specifically, their study poses defect evaluation challenges in aluminum aircraft alloys. Existing inline inspection tools exhibit measurement uncertainties. The physical-based methods for crack growth prediction utilize stress analysis models and the crack growth model governed by Paris’ law. These models, when utilized for long-term crack growth prediction, yield sub-optimum solutions and pose several technical limitations to the prediction problems. The metaheuristic optimization algorithms in this study have been conducted in accordance with neural networks to accurately forecast the crack growth rates in aluminum alloys. Through ex…
X-ray powder diffraction study of the stability of solid solutions in LaO(Cl1−xBrx)
1997
Abstract The formation of solid solutions in the LaO(Cl 1− x Br x ) series was studied by X-ray powder diffraction (XPD), Rietveld profile refinement and bond valence calculations. The LaO(Cl 1− x Br x ) (0 ≤ x ≤ 1, step 0.2, and x = 0.5) powder samples were prepared by the solid state reaction between La 2 O 3 and a mixture of ammonium chloride and bromide. The X-ray powder diffraction patterns were collected at room temperature between 5 and 125° in 2Θ using Cu K α 1 radiation (λ = 1.5406 A). The XPD data between 20 and 90° were analyzed with the DBWS-9006PC Rietveld profile refinement program. All the LaO(Cl 1− x Br x ) phases studied crystallize in the tetragonal PbFCl-type structure wi…
VEH electronic structure of Si60
1993
Abstract We present a valence effective Hamiltonian (VEH) theoretical investigation on the electronic structure of Si60. The VEH one-electron energy level distribution calculated for Si60 is used to predict the ionization potential (7.86 eV), electron affinity (6.62 eV) and HOMO-LUMO energy gap (1.24 eV) of Si60. We also report the first allowed electronic transitions of Si60. The results are compared with other theoretical levels and with those calculated for C60.
Valence electronic structure of C60: Theoretical analysis of photoemission data
1993
Abstract We present a theoretical investigation of the valence band photoemission spectra of C 60 using the nonempirical valence effective Hamiltonian (VEH) method. The VEH-DOVS curves calculated for the C 60 molecule are found to be in excellent agreement with synchrotron-radiation photoemission spectra reported for C 60 films. A detailed interpretation of all the photoemission bands is performed in the light of the VEH results.
Theoretical study on the effect of backbone conformation on the electronic structure of poly(di-n-butylsilane)
1993
Abstract We present the results of valence effective Hamiltonian (VEH) calculations on the electronic structure of poly(di-n-butylsilane) in its all-trans and 7/3 conformations. The band structure of all-trans conformation is analyzed in detail and the effects of the backbone conformation on the electronic and optical properties are studied. The VEH results for the 2/1 and 7/3 conformations are in excellent quantitative agreement with photoemission and UV-absorption data and show the reliability of the VEH method to deal with organopolysilanes.
Valence instabilities and inhomogeneous mixed valence in some ternary europium compounds
1997
Abstract Photoemission spectra and TB-LMTO-ASA band structure calculations of some mixed valency europium compounds hve been studied. The band structures are compared with the band structures of the isostructural lanthanum and strontium compounds. Surprisingly a 4f density of states in the vicinity of the Fermi level is observed in inhomogenous mixed valency EuPd 3 B, Eu 3 S 4 , and EuPdP. Indeed a van Hove Singularity (vHS) derived from the d states of La and Pd or p states of boron or phosphorous are found in La 3 S 4 , LaPd 3 B and SrPdP. The valence instability in the Eu compounds is thus not necessarily due to Eu 4f states. The results also provide some ground for the assumption that i…
Photomagnetic effect in a cyanide-bridged mixed-valence {FeII2FeIII2} molecular square
2012
The self-assembly of [Fe(III)(Tp)(CN)(3)](-) and [Fe(II)(bik)(2)(S)(2)](2+) affords the cyanide-bridged mixed valence {Fe(III)(2)Fe(II)(2)}(2+) molecular square, which exhibits a photomagnetic effect under laser light irradiation at low temperature and also shows thermal spin-state conversion near ambient temperature.