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排序方式: 共有166条查询结果,搜索用时 15 毫秒
41.
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Energy transport in diffusion-wave fields is gradient-driven and therefore diffuse, yielding depth-integrated responses with poor axial resolution. Using matched-filter principles, we propose a methodology enabling these parabolic diffusion-wave energy fields to exhibit energy localization akin to propagating hyperbolic wave fields. This not only improves axial resolution but also allows for deconvolution of individual responses of superposed axially discrete sources, opening a new field of depth-resolved subsurface thermal coherence tomography using diffusion waves. 相似文献
43.
Jouybari Nima Fallah Lundström T. Staffan Hellström J. Gunnar I. 《Transport in Porous Media》2020,131(2):739-765
Transport in Porous Media - The aim of the present paper is to evaluate and compare the pore level hydrodynamic dispersion and effects of turbulence during flow in porous media. In order to compute... 相似文献
44.
Olsen RA Liu L Ghaderi N Johns A Hatcher ME Mueller LJ 《Journal of the American Chemical Society》2003,125(33):10125-10132
Pyridine carboxamides are a class of medicinal agents with activity that includes the reduction of iron-induced renal damage, the regulation of nicotinamidase activity, and radio- and chemosensitization. Such pharmacological activities, and the prevalence of the carboxamide moiety and the importance of amide rotations in biology, motivate detailed investigation of energetics in these systems. In this study, we report the use of dynamic nuclear magnetic resonance to measure the amide rotational barriers in the pyridine carboxamides picolinamide and nicotinamide. The activation enthalpies and entropies of DeltaH++ = 12.9 +/- 0.3 kcal/mol and DeltaS++ = -7.7 +/- 0.9 cal/mol K for nicotinamide and DeltaH++ = 18.3 +/- 0.4 kcal/mol and DeltaS++ = +1.3 +/- 1.0 cal/mol K for picolinamide report a substantial energetic difference for these regioisomers. Ab initio calculations of the rotational barriers are in good agreement with the experimentally determined values and help partition the 5.4 kcal/mol enthalpy difference into its major contributions. Of principal importance are the variations in steric interactions in the ground states of picolinamide and nicotinamide, superior pi electron donation from the pyridine ring in the transition state of nicotinamide, and an intramolecular hydrogen bond in the ground state of picolinamide. 相似文献
45.
S. M. M. Rasouli Mehrdad Farhoudi Nima Khosravi 《General Relativity and Gravitation》2011,43(10):2895-2910
We investigate the effects of a special kind of dynamical deformation between the momenta of the scalar field of the Brans–Dicke theory and the scale factor of the FRW metric. This special choice of deformation includes linearly a deformation parameter. We trace the deformation footprints in the cosmological equations of motion when the BD coupling parameter goes to infinity. One class of the solutions gives a constant scale factor in the late time that confirms the previous result obtained via another approach in the literature. This effect can be interpreted as a quantum gravity footprint in the coarse grained explanation. The another class of the solutions removes the big bang singularity, and the accelerating expansion region has an infinite temporal range which overcomes the horizon problem. After this epoch, there is a graceful exiting by which the universe enters in the radiation dominated era. 相似文献
46.
Levi Lustman Nima Geffen 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1979,30(4):637-645
Summary The theory of shocks evolving from weak discontinuities is applied to magnetogasdynamics and worked out in detail for two situations: a spherical disturbance propagating into a uniform magnetic field, and a planar disturbance propagating in the field of a current-carrying wire. For both cases, shock formation is delayed as the magnetoacoustic speed of propagation approaches the Alfvén speed. This agrees with the fact that Alfvén waves do not steepen to form shocks.
Research supported in part by Grant No. AFOSR-73-2561. 相似文献
Résumé On applique à la magnétogasdynamique la théorie des ondes de choc produites par l'évolution des discontinuités faibles. On présente des résultats sur la formation de chocs par des ondes magnétoacoustiques. Lorsque la vitesse de propagation de ces ondes se rapproche de la vitesse d'Alfvén, l'apparition des chocs est retardée, en accord avec le résultat bien connu que les ondes d'Alfvén ne se transforment pas pour former des chocs.
Research supported in part by Grant No. AFOSR-73-2561. 相似文献
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The cyclization of linear peptides from six to nine amino acids in length and containing between two and four pseudoproline turn inducers derived from serine or threonine was investigated to determine the effect of peptide length, amino acid composition and spacing between the pseudoproline residues on macrocyclization yield. 相似文献
49.
Mesgarani N Thomas S Hermansky H 《The Journal of the Acoustical Society of America》2011,130(1):EL14-EL18
A multistream phoneme recognition framework is proposed based on forming streams from different spectrotemporal modulations of speech. Phoneme posterior probabilities were estimated from each stream separately and combined at the output level. A statistical model of the final estimated posterior probabilities is used to characterize the system performance. During the operation, the best fusion architecture is chosen automatically to maximize the similarity of output statistics to clean condition. Results on phoneme recognition from noisy speech indicate the effectiveness of the proposed method. 相似文献
50.
Ebadi Ahmad Dastan Dara Azami Mojtaba Karimi Adibe Razzaghi-Asl Nima 《Structural chemistry》2017,28(3):849-857
Structural Chemistry - Chemokine receptor 2 (CCR2), a G-protein coupled receptor (GPCR), is a critical target for several inflammatory and autoimmune diseases. The main restriction on designing... 相似文献