Queueing System with Potential for Recruiting Secondary Servers

In this paper, we consider a single server queueing system in which the arrivals occur according to a Markovian arrival process (MAP). The served customers may be recruited (or opted from those customers’ point of view) to act as secondary servers to provide services to the waiting customers. Such customers who are recruited to be servers are referred to as secondary servers. The service times of the main as well as that of the secondary servers are assumed to be exponentially distributed possibly with different parameters. Assuming that at most there can only be one secondary server at any given time and that the secondary server will leave after serving its assigned group of customers, the model is studied as a QBD-type queue. However, one can also study this model as a G I/M/1-type queue. The model is analyzed in steady state, and a few illustrative numerical examples are presented

Orbital overlap effects in electron transfer reactions across a metal nanowire/electrolyte solution interface

In this paper, we report on calculations of the orbital overlap between Fe(III) and Cr(III) aquacomplexes and different electrode surfaces: Cu(111), Ag (111), Au(111), Pt(111), and corresponding monatomic wires. The electronic structure of the monocrystalline surfaces and nanowires are described in terms of the electronic spillover and density of electronic states at the Fermi level obtained from periodic density functional theory (DFT) calculations. The transmission coefficients (κ) characterizing the first stage of outer-sphere electron transfer for the reduction of aquacomplexes are calculated on the basis of Landau–Zener theory as a function of electrode–reactant separation; the electronic transmission coefficients for the [Cr(H2O)6]3+/2+ redox couple were found to be smaller than those for [Fe(H2O)6]3+/2+. Two different intervals can be clearly distinguished for Cu, Au and Pt: “a catalytic region”, where κ(wire) > κ(Me slab) and “an inhibition region”, where κ(wire) < κ(Me slab). A similar behavior exhibits the coupling constant estimated for a hydrogen atom adsorbed at the Au(111) surface and the Au monatomic wire. These effects originate from some specific features of electronic density profile for metal nanowires: at short distances the electronic density of nanowires is higher compared with the (111) metal surfaces, while at larger separations it decreases more sharply.Fil: Nazmutdinov, Renat R.. Kazan National Research Technological University; RusiaFil: Berezin, Alexander S.. Kazan National Research Technological University; RusiaFil: Soldano, Germán. Universitat Ulm; Alemania. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Schmickler, Wolfgang. Universitat Ulm; Alemani

Analysis of Multiserver Retrial Queueing System with Varying Capacity and Parameters

A multiserver queueing system, the dynamics of which depends on the state of some external continuous-time Markov chain (random environment, RE), is considered. Change of the state of the RE may cause variation of the parameters of the arrival process, the service process, the number of available servers, and the available buffer capacity, as well as the behavior of customers. Evolution of the system states is described by the multidimensional continuous-time Markov chain. The generator of this Markov chain is derived. The ergodicity condition is presented. Expressions for the key performance measures are given. Numerical results illustrating the behavior of the system and showing possibility of formulation and solution of optimization problems are provided. The importance of the account of correlation in the arrival processes is numerically illustrated

Queueing System with Potential for Recruiting Secondary Servers

In this paper, we consider a single server queueing system in which the arrivals occur according to a Markovian arrival process (MAP). The served customers may be recruited (or opted from those customers&rsquo; point of view) to act as secondary servers to provide services to the waiting customers. Such customers who are recruited to be servers are referred to as secondary servers. The service times of the main as well as that of the secondary servers are assumed to be exponentially distributed possibly with different parameters. Assuming that at most there can only be one secondary server at any given time and that the secondary server will leave after serving its assigned group of customers, the model is studied as a QBD-type queue. However, one can also study this model as a GI/M/1-type queue. The model is analyzed in steady state, and a few illustrative numerical examples are presented

Multi-server retrial model with variable number of active servers

This paper deals with a multi-server retrial queueing model in which the number of active servers depends on the number of customers in the system. To this end, the servers are switched on and off according to a multithreshold strategy. For a fixed choice of the threshold levels, the stationary distribution and various performance measures of the system are calculated. In the case of equidistant connection levels, the optimum threshold level is numerically computed

Myxobolus pelecicola Voronin et Dudin 2015 is a junior synonym of Myxobolus ladogensis Rumyantsev et Schulman 1997 (Myxosporea: Myxobolidae) infecting the skeletal muscle of sichel Pelecus cultratus (Actinopterygii: Cyprinidae) in Russia

Myxobolus pelecicola Voronin et Dudin, 2015 was recently described from the skeletal musculature of sichel Pelecus cultratus. However, another species, Myxobolus ladogensis Rumyantsev et Schulman, 1997, was described previously from the same host, displaying identical tissue localization and spore morphology as in M. pelecicola. Unfortunately, M. ladogensis was overlooked when M. pelecicola was described, resulting in the superfluous description of the latter species, which, according to the International Code of Zoological Nomenclature, is a junior synonym of M. ladogensis. The description of M. ladogensis is supplemented with SSU rDNA sequence analysis supporting the conspecificity with M. pelecicola. The closest relatives of Myxobolus ladogensis (syn. M. pelecicola) include several muscle-infecting Myxobolus spp. with sequence similarity below 97%

Effect of extended defects on phonon confinement in polycrystalline Si and Ge films

We present Raman spectroscopy of the polycrystalline Si and Ge films deposited by molecular beam deposition on a dielectric substrate. The Raman study has been made using lasers with different wavelengths. Structural properties of the poly-films have been studied by XRD and TEM. The Raman spectra are characterized by appearance of the additional wide peaks around 500 cm–1 and 290 cm–1 in the main vibrational bands of TO(c-Si) and TO(c-Ge) phonons, respectively. It is shown that these peaks correspond to scattering in grain boundary area. For the poly–Si films, both a downward shift and an asymmetrical broadening of the vibrational band of TO(c-Si) near 520 cm–1 are observed, whereas there is only a symmetric broadening in the spectra of poly-Ge. The Raman line shape has been modeled within the framework of the phonon confinement theory taking into account the sizes of coherent scattering domains obtained using XRD. The model includes a symmetrical band broadening observed in polycrystalline films. It is shown that confinement of phonon propagation might be in the poly–Si films. The phonon dispersion and the density of phonon states have been simulated using density functional theory. It has been found that phonon confinement relates to grain boundaries rather than other extended defects such as twins (multiple twins, twin boundaries), the appearance of which does not lead to significant changes in phonon dispersion and density of phonon states

Robust and tunable itinerant ferromagnetism at the silicon surface of the antiferromagnet GdRh2Si2

Spin-polarized two-dimensional electron states (2DESs) at surfaces and interfaces of magnetically active materials attract immense interest because of the idea of exploiting fermion spins rather than charge in next generation electronics. Applying angle-resolved photoelectron spectroscopy, we show that the silicon surface of GdRh2Si2 bears two distinct 2DESs, one being a Shockley surface state, and the other a Dirac surface resonance. Both are subject to strong exchange interaction with the ordered 4f-moments lying underneath the Si-Rh-Si trilayer. The spin degeneracy of the Shockley state breaks down below ~90 K, and the splitting of the resulting subbands saturates upon cooling at values as high as ~185 meV. The spin splitting of the Dirac state becomes clearly visible around ~60 K, reaching a maximum of ~70 meV. An abrupt increase of surface magnetization at around the same temperature suggests that the Dirac state contributes significantly to the magnetic properties at the Si surface. We also show the possibility to tune the properties of 2DESs by depositing alkali metal atoms. The unique temperature-dependent ferromagnetic properties of the Si-terminated surface in GdRh2Si2 could be exploited when combined with functional adlayers deposited on top for which novel phenomena related to magnetism can be anticipated