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71.
Danilo Babusci Giuseppe Dattoli Dario Sacchetti 《Central European Journal of Physics》2011,9(6):1381-1386
The Airy transform is an ideally suited tool to treat problems in classical and quantum optics. Even though the relevant mathematical
aspects have been thoroughly investigated, the possibilities it offers are wide and some features, such as the link with special
functions and polynomials, still contain unexplored aspects. In this note we will show that the so called Airy polynomials
are essentially the third order Hermite polynomials. We will also prove that this identification opens the possibility of
developing new conjectures on the properties of this family of polynomials. 相似文献
72.
Ademir Aparecido Constantino Dario Landa-Silva Everton Luiz de Melo Candido Ferreira Xavier de Mendonça Douglas Baroni Rizzato Wesley Romão 《Annals of Operations Research》2014,218(1):165-183
This paper tackles a Nurse Scheduling Problem which consists of generating work schedules for a set of nurses while considering their shift preferences and other requirements. The objective is to maximize the satisfaction of nurses’ preferences and minimize the violation of soft constraints. This paper presents a new deterministic heuristic algorithm, called MAPA (multi-assignment problem-based algorithm), which is based on successive resolutions of the assignment problem. The algorithm has two phases: a constructive phase and an improvement phase. The constructive phase builds a full schedule by solving successive assignment problems, one for each day in the planning period. The improvement phase uses a couple of procedures that re-solve assignment problems to produce a better schedule. Given the deterministic nature of this algorithm, the same schedule is obtained each time that the algorithm is applied to the same problem instance. The performance of MAPA is benchmarked against published results for almost 250,000 instances from the NSPLib dataset. In most cases, particularly on large instances of the problem, the results produced by MAPA are better when compared to best-known solutions from the literature. The experiments reported here also show that the MAPA algorithm finds more feasible solutions compared with other algorithms in the literature, which suggest that this proposed approach is effective and robust. 相似文献
73.
An integrated model for ranking scientific publications together with authors and journals recently presented in [Bini, Del Corso, Romani, ETNA 2008] is closely analyzed. The model, which relies on certain adjacency matrices H,K and F obtained from the relations of citation, authorship and publication, provides the ranking by means of the Perron vector of a stochastic matrix obtained by combining H,K and F. Some perturbation theorems concerning the Perron vector previously introduced by the authors are extended to more general cases and a counterexample to a property previously addressed by the authors is presented. The theoretical results confirm the consistency and effectiveness of our model. Some paradigmatic examples are reported together with some results obtained on a real set of data. 相似文献
74.
Dario Romano Efren Alberto Andablo‐Reyes Sara Ronca Sanjay Rastogi 《Journal of polymer science. Part A, Polymer chemistry》2013,51(7):1630-1635
The use of a hindered phenol to trap free trimethylaluminum (TMA) in methylaluminoxane (MAO) solutions has been reported to improve the performance of single‐site, homogeneous catalysts for olefin polymerization. In the present study, with the help of rheological analyses, we have investigated and compared the molecular weight, molecular weight distribution and entanglement density of ultrahigh molecular weight polyethylene synthesized with a single‐site catalyst activated by MAO and phenol‐modified MAO. While the number average molecular weight (Mn) of the obtained polymers remains the same for both activations, a higher yield and a higher entanglement density are found in the initial stages of polymerization on using phenol‐modified MAO as the cocatalyst. These results suggest that on using the phenol‐modified MAO as activator, a higher number of active sites are obtained. Surprisingly in the presence of untreated MAO, a tail in the higher molecular mass region is produced. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 相似文献
75.
76.
Antonio Pasini 《Geometriae Dedicata》1990,34(1):35-56
We give some contributions to the classification of geometries belonging to the following diagram: (Af. Cn) 相似文献
77.
Apparently, no rigorous results exist for the dynamics of a classical point particle interacting with the electromagnetic field, as described by the standard Maxwell-Lorentz equations. Some results are given here for the corresponding linearized system (dipole approximation) in the presence of a mechanical linear restoring force. We consider a regularization of the system (Pauli-Fierz model), and explicitly solve the Cauchy problem in terms of normal modes. Then we study the limit of the particle's motion as the regularization is removed. We prove that the particle's motion corresponding to smooth initial data for the field has a well-defined limit if mass is renormalized, while the motion is trivial (i.e. the particle does not move at all) if mass is not renormalized. Moreover, the limit particle's motion corresponding to an interesting class of initial data satifies exactly the Abraham-Lorentz-Dirac equation. Finally, for generic initial data the limit motion is runaway. 相似文献
78.
Dario Graffi 《Annali di Matematica Pura ed Applicata》1897,25(1):267-276
Sunto Mediante la trasformazione diLaplace, si stabilisce un teorema di reciprocità per le correnti elettriche che, comunque variabili nel tempo, percorrono una o più
reti di fili conduttori. Dal suddetto teorema, supposte nulle le condizioni iniziali, si deduce, in particolare, una formula
per il calcolo della corrente in un ramo della rete generata da una forza elettromotrice posta in un altro ramo, qualora sia
nota la corrente. in questo ultimo, generata da una forza elettromotrice continua o alternata posta nel primo.
Lavoro eseguito nel Seminario Matematico dell'Università di Bologna. 相似文献
79.
The paper studies a train scheduling problem faced by railway infrastructure managers during real-time traffic control. When train operations are perturbed, a new conflict-free timetable of feasible arrival and departure times needs to be re-computed, such that the deviation from the original one is minimized. The problem can be viewed as a huge job shop scheduling problem with no-store constraints. We make use of a careful estimation of time separation among trains, and model the scheduling problem with an alternative graph formulation. We develop a branch and bound algorithm which includes implication rules enabling to speed up the computation. An experimental study, based on a bottleneck area of the Dutch rail network, shows that a truncated version of the algorithm provides proven optimal or near optimal solutions within short time limits. 相似文献
80.
We present a new closure for the mean rate of stretching of a dissolved polymer by homogeneous isotropic turbulence. The polymer is modeled by a bead-spring-type model (e.g., Oldroyd B, FENE-P, Giesekus) and the analytical closure is obtained assuming the Lagrangian velocity gradient can be modeled as a Gaussian, white-noise stochastic process. The resulting closure for the mean stretching depends upon the ratio of the correlation time for strain and rotation. Additionally, we derived a second-order expression for circumstances when strain and rotation have a finite correlation time. Finally, the base level closure is shown to reproduce results from direct numerical simulations by simply modifying the coefficients. 相似文献