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Erwin A. J. M. Bente Yohan Barbarin Martijn J. R. Heck Meint K. Smit 《Optical and Quantum Electronics》2008,40(2-4):131-148
In this paper a model and simulation results of integrated semiconductor passively modelocked ring lasers are presented. The model includes nonlinear effects such as two-photon absorption and a non-linear refractive index, a logarithmic gain-carrier relation, and concentration dependent radiative and non-radiative carrier recombination rates. The optical bandwidth of the system is controlled by a digital filter. The model has been used to simulate two geometries of ring modelocked lasers. The first is a symmetric design, where the two counter propagating pulses in the cavity experience the same amplification and absorption. The second is an asymmetric design where the differences for the two directions of pulse propagation are maximised. Simulation results show that a symmetrical cavity shows a several times wider window for its operating parameters for stable modelocking. 相似文献
23.
George EL Festen JM Houtgast T 《The Journal of the Acoustical Society of America》2008,124(2):1269-1277
Listening conditions in everyday life typically include a combination of reverberation and nonstationary background noise. It is well known that sentence intelligibility is adversely affected by these factors. To assess their combined effects, an approach is introduced which combines two methods of predicting speech intelligibility, the extended speech intelligibility index (ESII) and the speech transmission index. First, the effects of reverberation on nonstationary noise (i.e., reduction of masker modulations) and on speech modulations are evaluated separately. Subsequently, the ESII is applied to predict the speech reception threshold (SRT) in the masker with reduced modulations. To validate this approach, SRTs were measured for ten normal-hearing listeners, in various combinations of nonstationary noise and artificially created reverberation. After taking the characteristics of the speech corpus into account, results show that the approach accurately predicts SRTs in nonstationary noise and reverberation for normal-hearing listeners. Furthermore, it is shown that, when reverberation is present, the benefit from masker fluctuations may be substantially reduced. 相似文献
24.
Károly J. Böröczky Erwin Lutwak Deane Yang Gaoyong Zhang Yiming Zhao 《纯数学与应用数学通讯》2020,73(7):1406-1452
25.
We present a fully polynomial time approximation scheme (FPTAS) for a capacitated economic lot-sizing problem with a monotone
cost structure. An FPTAS delivers a solution with a given relative error ɛ in time polynomial in the problem size and in 1/ɛ. Such a scheme was developed by van Hoesel and Wagelmans [8] for a capacitated economic lot-sizing problem with monotone
concave (convex) production and backlogging cost functions. We omit concavity and convexity restrictions. Furthermore, we
take advantage of a straightforward dynamic programming algorithm applied to a rounded problem. 相似文献
26.
Flight gate scheduling with respect to a reference schedule 总被引:1,自引:0,他引:1
Ulrich?Dorndorf Florian?Jaehn Erwin?PeschEmail author 《Annals of Operations Research》2012,194(1):177-187
This paper considers the problem of assigning flights to airport gates. We examine the general case in which an aircraft serving
a flight may be assigned to different gates for arrival and departure processing and for optional intermediate parking. Restrictions
to this assignment include gate closures and shadow restrictions, i.e., the situation where certain gate assignments may cause
blocking of neighboring gates. The objectives include maximization of the total assignment preference score, a minimal number
of unassigned flights during overload periods, minimization of the number of tows, maximization of a robustness measure as
well as a minimal deviation from a given reference schedule. We show that in case of a one period time horizon this objective
can easily be integrated into our existing model based on the Clique Partitioning Problem. Furthermore we present a heuristic
algorithm to solve the problem for multiple periods. 相似文献
27.
The definition of Minkowski–Firey Lp-combinations is extended from convex bodies to arbitrary subsets of Euclidean space. The Brunn–Minkowski–Firey inequality (along with its equality conditions), previously established only for convex bodies, is shown to hold for compact sets. 相似文献
28.
Finite element approximation of spectral problems with Neumann boundary conditions on curved domains
This paper deals with the finite element approximation of the spectral problem for the Laplace equation with Neumann boundary conditions on a curved nonconvex domain . Convergence and optimal order error estimates are proved for standard piecewise linear continuous elements on a discrete polygonal domain in the framework of the abstract spectral approximation theory.
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G Carpintero E Rouvalis K Lawniczuk M Fice CC Renaud XJ Leijtens EA Bente M Chitoui F Van Dijk AJ Seeds 《Optics letters》2012,37(17):3657-3659
We report the generation of a 95?GHz carrier frequency by optical heterodyning of two wavelengths from adjacent channels from an arrayed waveguide grating-based multiwavelength laser. The extended cavity structure of the device provides low phase noise and narrow optical linewidth, further enhanced by the intracavity filter effect of the arrayed waveguide grating. We demonstrate that the generated RF beat note, at 95?GHz, has a -3 dB linewidth of 250?kHz. To the best of our knowledge, this is the narrowest RF linewidth generated from a free-running dual-wavelength semiconductor laser. The device is realized as a photonic integrated circuit using active-passive integration technology, and fabricated on a multiproject wafer run, constituting a novel approach for a compact, low-cost dual-wavelength heterodyne source. 相似文献