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21.
In a photonic crystal composed of anisotropic constituents we quantify the range of input angles and the degree of collimation of the beam inside the crystal. The optical properties of a photobleached 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) crystal are used in our model to demonstrate the efficacy of the self-collimation features. 相似文献
22.
Steffen Borchers Sandro Bosio Rolf Findeisen Utz-Uwe Haus Philipp Rumschinski Robert Weismantel 《Mathematical Methods of Operations Research》2011,73(3):381-400
This paper focuses on combinatorial feasibility and optimization problems that arise in the context of parameter identification
of discrete dynamical systems. Given a candidate parametric model for a physical system and a set of experimental observations,
the objective of parameter identification is to provide estimates of the parameter values for which the model can reproduce
the experiments. To this end, we define a finite graph corresponding to the model, to each arc of which a set of parameters
is associated. Paths in this graph are regarded as feasible only if the sets of parameters corresponding to the arcs of the
path have nonempty intersection. We study feasibility and optimization problems on such feasible paths, focusing on computational
complexity. We show that, under certain restrictions on the sets of parameters, some of the problems become tractable, whereas
others are NP-hard. In a similar vein, we define and study some graph problems for experimental design, whose goal is to support
the scientist in optimally designing new experiments. 相似文献
23.
通过高速撞击实验,探讨了采用小尺寸防护板的可行性。实验中采用的Whipple结构由尺寸变化的1 mm厚防护板(前板)和尺寸固定的3 mm厚舱壁板(后板)组成,防护板与舱壁板间隔10 cm。防护板为边长分别为8、12、16和20 cm的方形2A12铝合金板,舱壁板为边长为20 cm的方形5A06铝合金板。实验过程中均采用直径为4 mm的铝合金球形弹丸,撞击速度为1.45~1.71 km/s。实验结果表明:Whipple防护结构在舱壁板被击穿的概率大于0.8的条件下和击穿概率为0的条件下的极限速度以及舱壁板临界击穿条件下的速度都与防护板尺寸无关;并且,防护板前后表面击穿孔的直径及击穿孔侧壁的倾斜角也与防护板尺寸无关;但是,在速度相同的条件下随着板尺寸的增大,防护板板面的最大挠度增大,而且,防护板挠曲面的凸凹方向也由单一的凹向变成凸凹方向交替出现;随着速度的增加和板尺寸的增大,防护板最大挠度的增量减小。 相似文献
24.
Ultrashort-pulse fiber ring lasers 总被引:4,自引:0,他引:4
L.E. Nelson D.J. Jones K. Tamura H.A. Haus E.P. Ippen 《Applied physics. B, Lasers and optics》1997,65(2):277-294
Received: 18 February 1997/Revised version: 22 April 1997 相似文献
25.
The statistical dynamics of a particle scattered by randomly positioned stationary hard spheres are investigated. We examine the somewhat unusual long-wavelength, low-frequency fluctuation spectra resulting from the existence of an infinite set of mutually coupled conserved densities of which the number density and energy density are two members. The analytically soluble infinite-mode correlation functions are compared with the corresponding functions obtained by truncating the set of slow modes at successively increasing orders. Furthermore, we evaluate the long-wavelenght number density autocorrelation function for a fixed speed, υ0, in terms of a frequency-dependent diffusivity D(ω;υ0) and obtain the fluctuation spectra of all conserved densities by an additional velocity average with the appropriate canonical weights. The effect of the frequency-dependent diffusivity D(ω;υ0) on the density fluctuation spectra at frequencies small compared to the mean collision frequency is elucidated. 相似文献
26.
Pietro Baldi Emanuele Haus Riccardo Montalto 《Journal of Differential Equations》2018,264(3):1786-1840
We prove internal controllability in arbitrary time, for small data, for quasi-linear Hamiltonian NLS equations on the circle. We use a procedure of reduction to constant coefficients up to order zero and HUM method to prove the controllability of the linearized problem. Then we apply a Nash–Moser–Hörmander implicit function theorem as a black box. 相似文献
27.
We consider a generalization of the unsplittable maximum two-commodity flow problem on undirected graphs where each commodity ${i \in \{1, 2\}}$ can be split into a bounded number k i of equally-sized chunks that can be routed on different paths. We show that in contrast to the single-commodity case this problem is NP-hard, and hard to approximate to within a factor of α > 1/2. We present a polynomial time 1/2-approximation algorithm for the case of uniform chunk size over both commodities and show that for even k i and a mild cut condition it can be modified to yield an exact method. The uniform case can be used to derive a 1/4-approximation for the maximum concurrent (k 1, k 2)-splittable flow without chunk size restrictions for fixed demand ratios. 相似文献
28.
Non-relativistic configuration interaction (CI) ab initio calculations using large basis sets have been carried out to determine the potential curves of the first electronic states of Ne2 +, Ar2 + and Kr2 +. The spin—orbit interaction was treated assuming that the spin—orbit coupling constant is independent of the internuclear separation (R). For Ar2 +, calculated dissociation energies and equilibrium separations are in good agreement with experimental results. The calculations for Ne2 + suggest that the lowest vibrational level of the I(1/2u) ground state observed by threshold photoelectron spectroscopy by Hall et al. [1995, J. Phys. B: At. molec. opt. Phys., 28, 2435] and assigned to either ν = 0 or ν = 2 actually corresponds to ν = 4. The calculations also predict the I(1/2g) state of Ne2 + and Ar2 + to possess a double-well potential and that of Kr2 + to be repulsive at short range and to only possess a single shallow well at large internuclear separation. The ab initio calculations provide an explanation for the observation made by Yoshii et al. [2002, J. chem. Phys., 117, 1517] that Kr2 + and Xe2 + dissociate after photoemission from the II(1/2u) state to the I(1/2g) state whereas Ar2 + does not. 相似文献
29.
We investigate the dynamics of a 5-Gbit/s packet of ones and zeros loaded into a 0.5-kbit, phase-modulated optical fiber-ring buffer. A new mode of operation is explored in which the cavity length of the buffer is slightly detuned from the frequency driving the phase modulator. We examine the conditions for successful packet loading and the packet storage behavior. In addition, relaxation oscillations, which affected the storage time of previous high-speed optical ring buffers, are nearly eliminated with a cw holding beam, and significantly enhanced storage times are obtained. 相似文献
30.
Transport properties of membranes are closely related to morphological properties like surface porosity and variation of their inner pore structure. Scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM) are powerful tools to characterise the microscopical pore structure of membranes in a qualitative manner. In order to provide more quantitative data of surface and cross-sectional pores computer image analysis can be used. Parameters like ‘porous area fraction’ and ‘mean free path length’ have been selected to describe the pore distribution within porosity profiles in order to consider the effect that the pores within the cross-section are connected to each other. 相似文献