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81.
On a recursive method for the estimation of unknown parameters of partially observed chaotic systems
We investigate a recently proposed method for on-line parameter estimation and synchronization in chaotic systems. This novel technique has been shown effective to estimate a single unknown parameter of a primary chaotic system with known functional form that is only partially observed through a scalar time series. It works by periodically updating the parameter of interest in a secondary system, with the same functional form as the primary one but no explicit coupling between their dynamic variables, in order to minimize a suitably defined cost function. In this paper, we review the basics of the method, and investigate its robustness and new extensions. In particular, we study the performance of the novel technique in the presence of noise (either observational, i.e., an additive contamination of the observed time series, or dynamical, i.e., a random perturbation of the system dynamics) and when there is a mismatch between the primary and secondary systems. Numerical results, including comparisons with other techniques, are presented. Finally, we investigate the extension of the original method to perform the estimation of two unknown parameters and illustrate its effectiveness by means of computer simulations. 相似文献
82.
Push-pull dithiafulvenes with reduced bond length alternation (BLA) and high optical nonlinearities have been prepared. The interplay between the proaromaticity of the donor and the structural and optical properties of these merocyanines is discussed. The donor ability of dithiafulvenes can reach that of ferrocene or dialkylaminophenyl groups. 相似文献
83.
The aim of this article is to derive stable generalized sampling in a shift-invariant space by using some special dual frames in L2(0,1). These sampling formulas involve samples of filtered versions of the functions in the shift-invariant space. The involved samples are expressed as the frame coefficients of an appropriate function in L2(0,1) with respect to some particular frame in L2(0,1). Since any shift-invariant space with stable generator is the image of L2(0,1) by means of a bounded invertible operator, our generalized sampling is derived from some dual frame expansions in L2(0,1). 相似文献
84.
Ana L. Montero Luis A. Montero Ricardo Martínez S. Spange 《Journal of Molecular Structure》2006,770(1-3):99-106
A quantum chemical model (Abinitio HF-MO and DFT-B3LYP) of polyfurfuryl alcohol crosslinking is shown. Two pathways were considered: (a) a Diels–Alder (D–A) reaction between a dihydrofuran moiety and a furan ring; (b) the addition reaction of electrophilic specimens on conjugated double bonds. The ability for the formation of D–A adducts (dienes and dienophiles) was investigated by the frontier molecular orbital (FMO) theory. Energy gaps between the FMO's of diene and dienophile structures suggest that the occurrence of the D–A reaction is possible. The results suggest that the carbons of the exo double bonds attached to dihydrofuran rings are the sites most likely to be attacked by electrophilic species, while the C3 and C4 atoms display the opposite tendency due to their low HOMO electron densities. Results of a thermochemical approach to these reactions at the MP2 level was in agreement with reactivity modelled by MO predictions. 相似文献
85.
Zbigniew Jaskólski 《Communications in Mathematical Physics》1991,139(2):353-375
Following the general scheme of the convariant path integral quantization of gauge systems, two alternative formulations of
the first quantized closed bosonic string in a position representation are presented. In both approaches the covariant path
integral representations of the propagator and of the higher order off-shell amplitudes are constructed. For a wide class
of gauges the explicit formulae for off-shell amplitudes are obtained. This paper is the continuation of our previous work
where the corresponding problems in the open string case were considered [20]. 相似文献
86.
M. Olivares-Marín C. Fernández-González V. Gómez-Serrano 《Applied Surface Science》2006,252(17):5980-5983
Using cherry stones, the preparation of activated carbon has been undertaken in the present study by chemical activation with potassium hydroxide. A series of KOH-activated products was prepared by varying the carbonisation temperature in the 400-900 °C range. Such products were characterised texturally by gas adsorption (N2, −196 °C), mercury porosimetry, and helium and mercury density measurements. FT-IR spectroscopy was also applied. The carbons prepared as a rule are microporous and macroporous solids. The degree of development of surface area and porosity increases with increasing carbonisation temperature. For the carbon heated at 900 °C the specific surface area (BET) is 1624 m2 g−1, the micropore volume is 0.67 cm3 g−1, the mesopore volume is 0.28 cm3 g−1, and the macropore volume is 1.84 cm3 g−1. 相似文献
87.
We consider a retrial queue with a finite buffer of size N, with arrivals of ordinary units and of negative units (which cancel one ordinary unit), both assumed to be Markovian arrival
processes. The service requirements are of phase type. In addition, a PHL,N bulk service discipline is assumed. This means that the units are served in groups of size at least L, where 1≤ L≤ N. If at the completion of a service fewer than L units are present at the buffer, the server switches off and waits until the buffer length reaches the threshold L. Then it switches on and initiates service for such a group of units. On the contrary, if at the completion of a service
L or more units are present at the buffer, all units enter service as a group. Units arriving when the buffer is full are not
lost, but they join a group of unsatisfied units called “orbit”. Our interest is in the continuous-time Markov chain describing
the state of the queue at arbitrary times, which constitutes a level dependent quasi-birth-and-death process. We start by
analyzing a simplified version of our queueing model, which is amenable to numerical calculation and is based on spatially
homogeneous quasi-birth-and-death processes. This leads to modified matrix-geometric formulas that reveal the basic qualitative
properties of our algorithmic approach for computing performance measures.
AMS Subject Classification: Primary 60K25 Secondary 68M20 90B22. 相似文献
88.
Given a constant of motion for the one-dimensional harmonic oscillator with linear dissipation in the velocity, the problem to get the Hamiltonian for this system is pointed out, and the quantization up to second order in the perturbation approach is used to determine the modification on the eigenvalues when dissipation is taken into consideration. This quantization is realized using the constant of motion instead of the Hamiltonian.
PACS: 03.20.+i, 03.30.+p, 03.65.−w,03.65.Ca 相似文献
89.
Jaime Pfretzschner Pedro Cobo Francisco Simón María Cuesta Alejandro Fernández 《Applied Acoustics》2006,67(1):62-73
Microperforated panels (MPPs) coupled to a rigid wall have been proposed recently as an alternative to porous absorbers in situations having concerns with bacterial contamination and small particles discharge, like food, pharmaceutical and microelectronic industries. There exists also an increasing interest for MPP absorbers in the transportation industry and civil engineering. In general, an optimally designed MPP with good broadband absorption requires many submillimetric holes distributed over a panel of also submillimetric thickness. Such thin plates or foils become so fragile that they need to be protected from mechanical damage. In this paper, an alternative strategy is investigated which allows the design of MPPs with panels of millimetric thickness while maintaining their acoustic performance. These absorbers, named microperforated insertion units (MIUs), avoid the structural problems of the classical MPPs. An assessment of the sound absorption properties of these structures is presented. Comparisons between calculations and measurements are also made under two experimental conditions: plane waves at normal incidence (impedance tube) and free field (anechoic room). 相似文献
90.
Our object of study is the asymptotic behavior of the sequence of polynomials orthogonal with respect to the discrete Sobolev
inner product <formula> \langle f, g \rangle = ∈t_{E} f(ξ) \overline{g(ξ)} ρ(ξ) |d ξ|+ f(Z) A g(Z)^H, </formula> where E is a rectifiable Jordan curve or arc in the complex plane
f(Z) = (f(z_1), \ldots, f^{(l_1)}(z_1) , \ldots , f(z_m) , \ldots ,f^{(l_m)}(z_m)),
A is an M \times M Hermitian matrix, M l
1
+ ⋅s + l
m
+ m , |d ξ| denotes the arc length measure, ρ is a nonnegative function on E , and z
i
∈Ω,
i=1,2,\ldots,m , where Ω is the exterior region to E .
July 23, 1999. Dates revised: September 11, 2000 and February 16, 2001. Date accepted: February 26, 2001. 相似文献