排序方式: 共有49条查询结果,搜索用时 15 毫秒
1.
Mingbao Zhang Raymond Reeves Cheng Bi Robert Dally Gaetan Ladouceur William Bullock Jefferson Chin 《Tetrahedron letters》2004,45(27):5229-5231
Three novel, optically active, 6-substituted 2-(aminomethyl)chromans were synthesized from readily available chroman 2-carboxylic acid precursors. These chroman-containing primary amines are useful building blocks for the synthesis of chroman-derived pharmaceutical agents. 相似文献
2.
We analyze isolated resonance curves (IRCs) in single-degree-of-freedom systems possessing nonlinear damping. Through the combination of singularity theory and the averaging method, the onset and merging of IRCs, which coincide to isola and simple bifurcation singularities, respectively, can be analytically predicted. Numerical simulations confirm the accuracy of the analytical developments. Another important finding of this paper is that we unveil a geometrical connection between the topology of the damping force and IRCs. Specifically, we demonstrate that extremas and zeros of the damping force correspond to the appearance and merging of IRCs. Considering a damping force possessing several minima and maxima confirms the general validity of the analytical result. It also evidences a very complex scenario for which different IRCs are created, co-exist and then merge together to form a super IRC which eventually merges with the main resonance peak. 相似文献
3.
K. R. Jayaprakash Yuli Starosvetsky Alexander F. Vakakis Maxime Peeters Gaetan Kerschen 《Nonlinear dynamics》2011,63(3):359-385
We study standing waves (nonlinear normal modes—NNMs) and band zones in finite granular chains composed of spherical granular
beads in Hertzian contact, with fixed boundary conditions. Although these are homogeneous dynamical systems in the notation
of Rosenberg (Adv. Appl. Mech. 9:155–242, 1966), we show that the discontinuous nature of the dynamics leads to interesting effects such as separation between beads, NNMs
that appear as traveling waves (these are characterized as pseudo-waves), and localization phenomena. In the limit of infinite
extent, we study band zones, i.e., pass and stop bands in the frequency–energy plane of these dynamical systems, and classify
the essentially nonlinear responses that occur in these bands. Moreover, we show how the topologies of these bands significantly
affect the forced dynamics of these granular media subject to narrowband excitations. This work provides a classification
of the coherent (regular) intrinsic dynamics of one-dimensional homogeneous granular chains with no pre-compression, and provides
a rigorous theoretical foundation for further systematic study of the dynamics of granular systems, e.g., the effects of disorders
or clearances, discrete breathers, nonlinear localized modes, and high-frequency scattering by local disorders. Moreover,
it contributes toward the design of granular media as shock protectors, and in the passive mitigation of transmission of unwanted
disturbances. 相似文献
4.
We review the important features of the right-angle X-junction diffraction model and discuss both its theoretical framework and its validity range. In addition, we present explicit new results from BPM calculations that show that the analytical model aptly describes the dominant physical processes involved and provides bounds on the numerical results. We also address some misinterpretations of the model that have recently appeared in the literature. 相似文献
5.
Gaetan?KerschenEmail author Alexander?F.?Vakakis Young?S.?Lee D.?Michael?Mcfarland Jeffrey?J.?Kowtko Lawrence?A.?Bergman 《Nonlinear dynamics》2005,42(3):283-303
The purpose of this study is to highlight and explain the vigorous energy transfers that may take place in a linear oscillator
weakly coupled to an essentially nonlinear attachment, termed a nonlinear energy sink. Although these energy exchanges are
encountered during the transient dynamics of the damped system, it is shown that the dynamics can be interpreted mainly in
terms of the periodic orbits of the underlying Hamiltonian system. To this end, a frequency-energy plot gathering the periodic
orbits of the system is constructed which demonstrates that, thanks to a 1:1 resonance capture, energy can be irreversibly
and almost completely transferred from the linear oscillator to the nonlinear attachment. Furthermore, it is observed that
this nonlinear energy pumping is triggered by the excitation of transient bridging orbits compatible with the nonlinear attachment being initially at rest, a common feature in most practical applications. A parametric
study of the energy exchanges is also performed to understand the influence of the parameters of the nonlinear energy sink.
Finally, the results of experimental measurements supporting the theoretical developments are discussed.
This study was carried out while the author was a postdoctoral fellow at the National Technical University of Athens and at
the University of Illinois at Urbana-Champaign. 相似文献
6.
We present two algorithms to compute the endomorphism ring of an ordinary elliptic curve E defined over a finite field Fq. Under suitable heuristic assumptions, both have subexponential complexity. We bound the complexity of the first algorithm in terms of , while our bound for the second algorithm depends primarily on log|DE|, where DE is the discriminant of the order isomorphic to End(E). As a byproduct, our method yields a short certificate that may be used to verify that the endomorphism ring is as claimed. 相似文献
7.
Guo Q Brodzeli Z Pozhidaev EP Fan F Chigrinov VG Kwok HS Silvestri L Ladouceur F 《Optics letters》2012,37(12):2343-2345
The electro-optical behavior of deformed helix ferroelectric liquid crystal in reflective mode is described in this paper. The electrically controlled reflectance has been measured at subkilohertz driving voltage frequency for different polarizations of the incident light and compared quite successfully with the simulation results. 相似文献
8.
The excess loss across an acute-angle symmetric X-junction composed of two weakly guiding single-mode buried channel waveguides of square core cross-section is shown to be very small provided the junction angle is greater than a few degrees. Numerical and approximate analytical results are presented, as well as a simple criterion for the onset of cross-talk as the junction angle decreases. 相似文献
9.
Nicolas Lebegue Gaetan Charrier Pascal Carato Saïd Yous Pascal Berthelot 《Tetrahedron letters》2004,45(52):9509-9511
The decarbalkoxylations of disubstituted geminal diesters by water–DMSO with added salts (KCN or NaCN) is a convenient preparative route leading to the corresponding monoesters. Herein, we described an efficient and very simple methodology for the preparation of 2-(ethylsulfanyl)aniline derivatives through the unexpected ring opening of the corresponding N-substituted-2(3H)-benzothiazolones in the presence of disubstituted geminal diester, KCN, and water–DMSO. 相似文献
10.
Jean Michel Sellier Kristina G. Kapanova Jacob Leygonie Gaetan Marceau Caron 《International journal of quantum chemistry》2019,119(23):e26017
Recently neural networks have been applied in the context of the signed particle formulation of quantum mechanics to rapidly and reliably compute the Wigner kernel of any provided potential. Important advantages were introduced, such as the reduction of the amount of memory required for the simulation of a quantum system by avoiding the storage of the kernel in a multi-dimensional array, as well as attainment of consistent speedup by the ability to realize the computation only on the cells occupied by signed particles. An inherent limitation was the number of hidden neurons to be equal to the number of cells of the discretized real space. In this work, anew network architecture is presented, decreasing the number of neurons in its hidden layer, thereby reducing the complexity of the network and achieving an additional speedup. The approach is validated on a onedimensional quantum system consisting of a Gaussian wave packet interacting with a potential barrier. 相似文献