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81.
A simple criterion that allows the efficient local coarsening of simplicial finite element meshes generated by bisections is devised and analyzed. Under a mild condition on the initial triangulation the proposed criterion allows to gradually reverse the entire refinement without employing its history explicitly. Numerical experiments underline the efficiency of the resulting algorithm. 相似文献
82.
Optimal power flow problems arise in the context of the optimization and secure exploitation of electrical power in alternating current (AC) networks. This optimization problem evaluates the flow on each line and to ensure that they are under line thermal limits. To improve the reliability of the power supply, a secure network is necessary, i.e., it has to be able to cope with some contingencies. Nowadays high performance solution methods, that are based on nonlinear programming algorithms, search for an optimal state while considering certain contingencies. According to the number of contingencies the problem size increases linearly. As the base case can already be large-scaled, the optimization time computation increases quickly. Parallelization seems to be a good way to solve quickly this kind of problem. This paper considers the minimization of an objective function and at least two constraints at each node. This optimization problem is solved by IPOPT, an interior point method, coupled with ADOL-C, an algorithmic differentiation tool, and MA27, a linear solver. Several results on employed parallelizing strategies will be discussed. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
83.
84.
Peng Cheng Ph.D. Michael A. Sutton Hubert W. Schreier Ph.D. Student Stephen R. McNeill 《Experimental Mechanics》2002,42(3):344-352
A full-field speckle pattern image correlation method is presented that will determine directly the complete, two-dimensional
deformation field during the image correlation process on digital images obtained using computer vision systems. In this work,
a B-Spline function is used to represent the object deformation field throughout the entire image area. This is an improvement
over subset-based image correlation methods by implicitly maintaining position and derivative continuity constraints among
subsets up to a specified order. The control point variables within the B-Spline deformation function are optimized iteratively
with the Levenberg-Marquardt method to achieve minimum disparity between the predicted and actual deformed images. Results
have shown that the proposed method is computationally efficient, accurate and robust. The general framework of this method
can be applied ton-dimensional image correlation systems that solve for multi-dimension vector fields. 相似文献
85.
R. Rehm M. Walther J. Schmitz J. Fleißner F. Fuchs J. Ziegler W. Cabanski 《Opto-Electronics Review》2006,14(1):19-24
The first fully operational mid-IR (3–5 μm) 256×256 IR-FPA camera system based on a type-II InAs/GaSb short-period superlattice
showing an excellent noise equivalent temperature difference below 10 mK and a very uniform performance has been realized.
We report on the development and fabrication of the detecor chip, i.e., epitaxy, processing technology and electro-optical
characterization of fully integrated InAs/GaSb superlattice focal plane arrays. While the superlattice design employed for
the first demonstrator camera yielded a quantum efficiency around 30%, a superlattice structure grown with a thicker active
layer and an optimized V/III BEP ratio during growth of the InAs layers exhibits a significant increase in quantum efficiency.
Quantitative responsivity measurements reveal a quantum efficiency of about 60% for InAs/GaSb superlattice focal plane arrays
after implementing this design improvement.
The paper presented there appears in Infrared Photoelectronics, edited by Antoni Rogalski, Eustace L. Dereniak, Fiodor F. Sizov, Proc. SPIE Vol. 5957, 595707 (2005). 相似文献
86.
Björn G. Walther 《Arkiv f?r Matematik》1999,37(2):381-393
For Ξ∈R n ,t∈R andf∈S(R n ) define $\left( {S^2 f} \right)\left( t \right)\left( \xi \right) = \exp \left( {it\left| \xi \right|^2 } \right)\hat f\left( \xi \right)$ . We determine the optimal regularitys 0 such that $\int_{R^n } {\left\| {(S^2 f)[x]} \right\|_{L^2 (R)}^2 \frac{{dx}}{{(1 + |x|)^b }} \leqslant C\left\| f \right\|_{H^s (R^n )}^2 ,s > s_0 } ,$ holds whereC is independent off∈S(R n ) or we show that such optimal regularity does not exist. This problem has been treated earlier, e.g. by Ben-Artzi and Klainerman [2], Kato and Yajima [4], Simon [6], Vega [9] and Wang [11]. Our theorems can be generalized to the case where the exp(it|ξ|2) is replaced by exp(it|ξ|a),a≠2. The proof uses Parseval's formula onR, orthogonality arguments arising from decomposingL 2(R n ) using spherical harmonics and a uniform estimate for Bessel functions. Homogeneity arguments are used to show that results are sharp with respect to regularity. 相似文献
87.
G.M. Kalvius E. Schreier M. Ekström O. Hartmann S. Henneberger A. Kratzer R. Wäppling E. Martin F.J. Burghart R. Ballou J. Deportes Ch. Niedermayer 《Hyperfine Interactions》2000,128(1-3):275-303
After a short introduction to μSR with respect to the study of magnetic properties, followed by a brief outline of the principle
of the high pressure-low temperature μSR spectrometer installed at the Paul Scherrer Institute, we discuss some measurements
on rare earth materials employing this instrument. They are concerned with: (1) The pressure dependence of the spin turning
process in ferromagnetic Gd. (2) The volume dependence of the internal magnetic field in the heavy rare earth metals Gd, Dy,
and Ho in their ordered magnetic states. (3) The response of the (first order) magnetic transition in the frustrated antiferromagnets
of type RMn2 (R = Y,Gd) to pressure. (4) The variation of magnetic parameters with pressure in La2CuO4 (powder sample), the antiferromagnetic parent compound of the high TC superconductors of type La2−x(Sr, Ba)xCuO4. In conclusion a short outlook on further developments is given.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
88.
89.
The outputs of two cw diode lasers are coupled into a flash-lamp-pumped Ti:sapphire laser cavity for regenerative amplification. Slices of each seed beam are simultaneously trapped in the cavity and amplified for approximately 33 round trips. The output is a 4.7-ns pulse, the total pulse energy is 110 mJ, and linewidths are only 50% greater than the Fourier-transform limit. The timing jitter between the pulses at the two wavelengths is less than +/-75 ps , and their relative energy is controlled by adjustment of the seed power of the cw diode lasers. Gain competition between the two frequencies does not lead to instabilities. 相似文献
90.