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71.
Osman Ra?it I?ikMehmet Sezer Zekeriya Güney 《Applied mathematics and computation》2011,217(16):7009-7020
In this study, a new collocation method based on the Bernstein polynomials is introduced for the approximate solution of a class of linear Volterra integro-differential equations with weakly singular kernel. If the exact solution is polynomial, then the exact solution can be obtained. If the exact solution is not a polynomial, then an accurate solution can be obtained with a combination of choice in the number of nodes and the number of digits in the solver. In addition, the method is presented with error and stability analysis. 相似文献
72.
The ablation yield of polyethylene glycol is measured as a function of laser pulse energy and polymer molecular weight for both free running and Q-switched Er:YAG lasers. The results show that the deposition rate is dependent on the absorption coefficient in a way that is consistent with the blow-off ablation model but that the linear dependence of the efficiency on laser pulse energy is also consistent with a steady-state ablation model. The results for both lasers are remarkably similar given that the pulse durations are 350 μs and 85 ns, respectively. Furthermore, polystyrene thin films are deposited as well and it is found that the morphology depends on the THF/MeOH ratios in the matrices. The significance of these results is discussed as well as future directions for this research. 相似文献
73.
Barış Sevim Alemdar Bayraktar Ahmet Can Altunişik Sezer Atamtürktür Fatma Birinci 《Nonlinear dynamics》2011,63(4):755-770
Historic masonry arch bridges are vital components of transportation systems in many countries worldwide, ensuring the ready
access of goods and services to millions of people. The structural failure of these historic structures would severely and
adversely impact the economies of these nations due to the massive disruptions of transportation systems accompanying such
failures. To successfully maintain these aging masonry structures, performance assessment must incorporate the unique mechanical
characteristics of masonry. Therefore, the preferred analysis technique must go beyond a linear approach. This study assesses
the earthquake performance of a restored historical masonry arch bridge through nonlinear finite element analysis incorporating
the Drucker–Prager damage criterion. The case study structure is the Mikron Arch Bridge, a nineteenth century Ottoman Era
structure built over the Firtina River near Rize, Turkey, and restored in 1998. The Mikron Arch Bridge was first subjected
to ambient vibration testing, during which accelerometers were placed at several points on the bridge span to record the bridge
vibratory response. The investigators then used Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification
techniques to extract the experimental natural frequencies, mode shapes, and damping ratios from these measurements. Experimental
results were compared with those obtained by the linear finite element analysis of the bridge. Good agreement between mode
shapes was observed during this comparison, though natural frequencies disagree by 8–10%. The boundary conditions of the linear
finite element model of Mikron Arch Bridge are adjusted such that the analytical predictions agree with the ambient vibration
test results. By introducing the Drucker–Prager damage criterion, the calibrated linear FE model was next extended into a
nonlinear model. Nonlinear analysis of seismic behavior of Mikron arch bridge was performed considering the acceleration record
of Erzincan earthquake in 1992 that occurred near the Mikron Bridge region. The displacement and stress results were observed
to be allowable level of the stone material. Moreover, linear FE model calibrations elicited a significant influence on the
nonlinear FE model simulations. 相似文献
74.
The notion of μ-smoothness points of periodic functions of several variables is introduced and the rate of convergence of
the Gauss-Weierstrass means of relevant Fourier series at these points is investigated. 相似文献
75.
Ali Devin Sezer 《Optimization》2013,62(11):1399-1402
76.
A free-running Er:YAG laser is used to ablate polyethylene glycol and the ablation yield is studied as a function of molecular weight (1000-10,000 g/mol) and laser fluence (8-25 J/cm2). A steady-state ablation mechanism is proposed which includes recoil-induced expulsion as the primary contributor to the ablation yield. It is also proposed that the formation of a molten layer is a necessary part of the ablation mechanism because the calculated tensile strengths for the solid polymer are too large to permit fracture of the target due to the laser-induced stress transient. The ablation yield is found to depend in a sigmoidal fashion upon laser fluence, thus implying a variable ablation enthalpy. Finally, the current results are compared with that obtained previously with a free electron laser. 相似文献
77.
We consider the problem of testing two simple hypotheses about unknown local characteristics of several independent Brownian motions and compound Poisson processes. All of the processes may be observed simultaneously as long as desired before a final choice between hypotheses is made. The objective is to find a decision rule that identifies the correct hypothesis and strikes the optimal balance between the expected costs of sampling and choosing the wrong hypothesis. Previous work on Bayesian sequential hypothesis testing in continuous time provides a solution when the characteristics of these processes are tested separately. However, the decision of an observer can improve greatly if multiple information sources are available both in the form of continuously changing signals (Brownian motions) and marked count data (compound Poisson processes). In this paper, we combine and extend those previous efforts by considering the problem in its multisource setting. We identify a Bayes optimal rule by solving an optimal stopping problem for the likelihood-ratio process. Here, the likelihood-ratio process is a jump-diffusion, and the solution of the optimal stopping problem admits a two-sided stopping region. Therefore, instead of using the variational arguments (and smooth-fit principles) directly, we solve the problem by patching the solutions of a sequence of optimal stopping problems for the pure diffusion part of the likelihood-ratio process. We also provide a numerical algorithm and illustrate it on several examples. 相似文献
78.
Kılıç Önder Belivermiş Murat Sıkdokur Ercan Sezer Narin Akyıl Erentürk Sema Haciyakupoglu Sevilay Madadzada Afag Frontasyeva Marina 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(2):699-706
Journal of Radioanalytical and Nuclear Chemistry - This study presents the first data of 210Po and 210Pb activity concentrations using moss species Hypnum cupressiforme from Thrace region, the... 相似文献
79.
J.B.G. Frenk S. Javadi M. Pourakbar S.O. Sezer 《European Journal of Operational Research》2019,272(2):496-504
This paper studies the spare parts end-of-life inventory problem that happens after the discontinuation of part production. A final ordering quantity is set such that the service process is sustained until all service obligations expire. Also, the price erosion of substitutable or new generation products over time makes it economically justifiable to consider switching to an alternative service policy for repair such as swapping the old product with a new one. This requires the joint optimization of the final order quantity and the time to switch from repair to an alternative service policy. To the best of our knowledge, the problem has not been optimally solved yet either in its static or dynamic formulation. In the current paper, we solve its static version as a bi-level optimization problem. We investigate the convexity of the objective function and give a computationally efficient algorithm to find an exact optimal solution up to any given numerical error level ??>?0. We illustrate our approach on some numerical examples and compare our results with earlier works on this problem. 相似文献
80.
Müfit Sezer 《Journal of Pure and Applied Algebra》2006,205(1):210-225
We consider the ring of coinvariants for modular representations of cyclic groups of prime order. For all cases for which explicit generators for the ring of invariants are known, we give a reduced Gröbner basis for the Hilbert ideal and the corresponding monomial basis for the coinvariants. We also describe the decomposition of the coinvariants as a module over the group ring. For one family of representations, we are able to describe the coinvariants despite the fact that an explicit generating set for the invariants is not known. In all cases our results confirm the conjecture of Harm Derksen and Gregor Kemper on degree bounds for generators of the Hilbert ideal. As an incidental result, we identify the coefficients of the monomials appearing in the orbit product of a terminal variable for the three-dimensional indecomposable representation. 相似文献