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71.
Abstract Stress intensity factors are evaluated for a singly or doubly cracked fastener hole with frictional traction in an anisotropic plate, using a special kernel boundary integral equation (BIE) approach. The integration kernel (Green's function) used in this BIE approach has already taken the presence of the crack (or cracks) into account, thus.avoiding the need for element discretization to model the stress singularity at the crack tip. The Green's function employed is that of an infinite anisotropic plate containing an elliptical hole or crack, and subjected to an arbitrarily positioned point force. Several types of normal and shear traction conditions at the pinhole interface are considered. Numerical results are obtained for various geometrical and loading conditions and are compared with known solutions, where available, for their isotropic counterparts. 相似文献
72.
73.
Niranjan D. Parab Cang Zhao Ross Cunningham Luis I. Escano Kamel Fezzaa Wes Everhart Anthony D. Rollett Lianyi Chen Tao Sun 《Journal of synchrotron radiation》2018,25(5):1467-1477
The high‐speed synchrotron X‐ray imaging technique was synchronized with a custom‐built laser‐melting setup to capture the dynamics of laser powder‐bed fusion processes in situ. Various significant phenomena, including vapor‐depression and melt‐pool dynamics and powder‐spatter ejection, were captured with high spatial and temporal resolution. Imaging frame rates of up to 10 MHz were used to capture the rapid changes in these highly dynamic phenomena. At the same time, relatively slow frame rates were employed to capture large‐scale changes during the process. This experimental platform will be vital in the further understanding of laser additive manufacturing processes and will be particularly helpful in guiding efforts to reduce or eliminate microstructural defects in additively manufactured parts. 相似文献
74.
Bonanni S Aït-Mansour K Harbich W Brune H 《Journal of the American Chemical Society》2012,134(7):3445-3450
The catalytic activity of deposited Pt(7) clusters has been studied as a function of the reduction state of the TiO(2)(110)-(1 × 1) support for the CO oxidation reaction. While a slightly reduced support gives rise to a high catalytic activity of the adparticles, a strongly reduced one quenches the CO oxidation. This quenching is due to thermally activated diffusion of Ti(3+) interstitials from the bulk to the surface where they deplete the oxygen adsorbed onto the clusters by the formation of TiO(x) (x ? 2) structures. This reaction is more rapid than the CO oxidation. The present results are of general relevance to heterogeneous catalysis on TiO(2)-supported metal clusters and for reactions involving oxygen as intermediate. 相似文献
75.
In this paper, a new formulation of the Rubin's q-translation is given, which leads to a reliable q-harmonic analysis. Next, related q-positive definite functions are introduced and studied, and a Bochner's theorem is proved. 相似文献
76.
Azab HA Duerkop A Mogahed EM Awad FK Abd El Aal RM Kamel RM 《Journal of fluorescence》2012,22(2):659-676
This work describes the application of time resolved fluorescence in microtiterplates and electrochemical methods on glassy
carbon electrode for investigating the interactions of europium-3-carboxycoumarin with pesticides aldicarb, methomyl and prometryne.
Stern-volmer studies at different temperatures indicate that static quenching dominates for methomyl, aldicarb and prometryne.
By using Lineweaver-Burk equation binding constants were determined at 303 K, 308 K and 313 K. A thermodynamic analysis showed
that the reaction is spontaneous with ΔG being negative. The enthalpy ΔH and the entropy ΔS of reactions were all determined.
A time-resolved (gated) luminescence-based method for determination of pesticides in microtiterplate format using the long-lived
europium-3-carboxycoumarin has been developed. The limit of detection is 4.80, 5.06 and 8.01 μmol L−1 for methomyl, prometryne and aldicarb, respectively. This is the lowest limit of detection achieved so far for luminescent
lanthanide-based probes for pesticides. The interaction of the probe with the pesticides has been investigated using cyclic
voltammetry (CV), differential pulse polarography (DPP), square wave voltammetry (SWV) and linear sweep voltammetry (LSV)
on a glassy carbon electrode in I = 0.1 mol L−1 p-toluenesulfonate at 25 °C. The diffusion coefficients of the reduced species are calculated. The main properties of the
electrode reaction occurring in a finite diffusion space are the quasireversible maximum and the splitting of the net SWV
peak for Eu(III) ions in the ternary complex formed . It was observed that the increase of the cathodic peak currents using
LSV is linear with the increase of pesticides concentration in the range 5 × 10−7 to 1 × 10−5 mol L−1. The detection limit (DL) were about 1.01, 2.23 and 1.89 μmolL−1 for aldicarb, methomyl and prometryne, respectively. In order to assess the analytical applicability of the method, the influence
of various potentially interfering species was examined. Influence of interfering species on the recovery of 10 μmol L−1 pesticides has been investigated. 相似文献
77.
Energetic and spectral properties of triple photon downconversion in a phase-matched KTiOPO4 crystal
Dot A Borne A Boulanger B Segonds P Félix C Bencheikh K Levenson JA 《Optics letters》2012,37(12):2334-2336
We measured the spectrum and energy of infrared triple photons generated in a phase-matched KTiOPO4 crystal pumped by picosecond beams at 532 and 1662 nm. The experimental data are in good agreement with our model, taking into account the spectral linewidths of the incident beams as well as a parasitic Kerr effect. 相似文献
78.
Ismail MM Kamel MM Mohamed LW Faggal SI Galal MA 《Molecules (Basel, Switzerland)》2012,17(6):7217-7231
A series of new thiophene derivatives has been synthesized using the Gewald protocol. The acetylcholinesterase inhibition activity was assayed according to Ellman's method using donepezil as reference. Some of the compounds were found to be more potent inhibitors than the reference. 2-(2-(4-(4-Methoxyphenyl)piperazin-1-yl)acetamido)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (IIId) showed 60% inhibition, compared to only 40% inhibition by donepezil. 相似文献
79.
Sana Bannour Kamel Abderrazak Hatem Mhiri Georges Le Palec 《Optics & Laser Technology》2012,44(8):2459-2468
Laser welding processes are widely used for fabrications in many engineering applications such as aerospace and automotives. In this paper, a moving distributed heat source model based on Goldak's method [1] has been implemented into finite volume thermal simulations in order to predict temperature distributions during the welding process of a magnesium alloy and to study the effects of variations in thermal properties, absorption coefficient and gas shielding on the computed temperature distributions and weld pool dimensions. The main conclusion is the significant effects of varying the thermal conductivity and absorption coefficient of magnesium. Also, it has been seen that the shielding gas, besides its main role of protection against oxidation, has a significant effect on the width of the weld pool. Finally, the obtained results have been compared to the experimental ones and a satisfactory correlation has been observed, indicating the reliability of the model developed in this study. 相似文献
80.
A rotor-active magnetic bearing (AMB) system subjected to a periodically time-varying stiffness with quadratic and cubic nonlinearities
under multi-parametric excitations is studied and solved. The method of multiple scales is applied to analyze the response
of two modes of a rotor-AMB system with multi-parametric excitations and time-varying stiffness near the simultaneous primary
and internal resonance. The stability of the steady state solution for that resonance is determined and studied using Runge-Kutta
method of fourth order. It is shown that the system exhibits many typical non-linear behaviors including multiple-valued solutions,
jump phenomenon, hardening and softening non-linearities and chaos in the second mode of the system. The effects of the different
parameters on the steady state solutions are investigated and discussed also. A comparison to published work is reported. 相似文献