Explicit solutions for the steady state distributions in M/PH/1 queues with workload dependent balking

We consider an M/PH/1 queue with balking based on the workload. An arriving customer joins the queue and stays until served only if the system workload is below a fixed level at the time of arrival. The steady state workload distribution in such a system satisfies an integral equation. We derive a differential equation for Phase type service time distribution and we solve it explicitly, with Erlang, Hyper-exponential and Exponential distributions as special cases. We illustrate the results with numerical examples.     

Dilute magnetic semiconductor nanowires

Semiconductor materials form the basis of modern electronics, communication, data storage and computing technologies. One of today’s challenges for the development of future technologies is the realization of devices that control not only the electron charge, as in present electronics, but also its spin, setting the basis for future spintronics. Spintronics represents the concept of the synergetic and multifunctional use of charge and spin dynamics of electrons, aiming to go beyond the traditional dichotomy of semiconductor electronics and magnetic storage technology. The most direct method to induce spin-polarized electrons into a semiconductor is by introducing appropriate transition-metal or rare-earth dopants producing a dilute magnetic semiconductor (DMS). At the same time the seamless integration of future spintronic devices into nanodevices would require the fabrication of one-dimensional DMS nanostructures in well-defined architectures. In this review we focus on recent advances in the synthesis of DMS nanowires as well discussing the structural, optical and magnetic properties of these materials. PACS 75.75.+a; 81.07.Vb; 68.65.La     

Can mobile shapes of fractals cause rate enhancement?

The notion of mobile shapes of a fractal object has been introduced to explain rate enhancements beyond the limits set by three-dimensional diffusion control. Allowing for mobilities of fractal shapes in the practical range, theoretical simulations for a model system show several hundred-fold variation in rates. The results of the analysis can have wide implications in understanding several biochemical as well as physical and chemical systems.     

The reactive states of ions: Antiaromatic seven-membered N-substituted-1H-azepines and isomeric aromatic substrates

Comparison of the electron impact and chemical ionization mass spectra of N-substituted-1H-azepines and isomeric aromatic substrates reveals significant differences. The data indicate that the substituted azepincs examined are stable to electron impact at low temperatures and retain their antiaromatic 8π electron seven-membered cyclic system prior to their fragmentation. The electron impact data are supported by low electron-volt and metastable scan techniques. Electron impact or chemical ionization induced transformation of azepines to aromatic substrates similar to the thermal transformation of neutral analogues is not observed at low temperatures. Chemical ionization mass spectra of N-ethoxycarbonyl-1H-azepines and N-phenylcarbamates were complicated owing to thermal decomposition reactions at high temperatures.     

Modifications in magnetic anisotropy of M—type strontium hexaferrite crystals by swift heavy ion irradiation.

Using vibrating sample magnetometery (VSM) 50 MeV Li³⁺ ion irradiation effects on magnetic properties of single crystals of SrGa_xIn_yFe_12−(x+y)O₁₉ (where x=0, 5, 7, 9; y=0, 0.8, 1.3, 1.0), are reported. The substitution of Ga and In in strontium hexaferrite crystals decreases the value of magnetization sharply, which is attributed to shifting of collinear magnetic order to a non-collinear one. Reduction of magnetization is also explained to be as a result of the occupation of the crystallographic sites of Fe³⁺ by Ga³⁺ and In³⁺. The Li³⁺ ion irradiation decreases the value of magnetization, irrespective of whether the crystals are Ga–In substituted or unsubstituted crystals of SrFe₁₂O₁₉. The result is interpreted in terms of the occurrence of a paramagnetic doublet in crystals replacing magnetic sextuplet as a result of irradiation. Substitution of Ga–In in Strontium hexaferrite decreases the value of anisotropy constant. Irradiation with Li³⁺ ions increases the values of anisotropy field for both substituted as well as unsubstituted crystals. Substitution with Ga–In also decreases the Curie temperature (T_c) but the irradiation with Li³⁺ ions does not affect the curie temperature of either Ga–In substituted or pure SrFe₁₂O₁₉ crystals.     

The characterization of modified silica-alumina catalysts active in the synthesis of picolines

The SiO₂–Al₂O₃ catalyst is modified by promoters like Pb, Cr, Cu. The SiO₂–Al₂O₃ catalyst is also modified using two elements by a simultaneous or stepwise impregnation method. The catalysts are characterized by XRD, IR and ESR techniques, and are useful in the synthesis of picolines.IICT Communication No. 3514, decicated to Dr. A.V. Rama Rao on his 60th birthday.     

Admission control of multi-class traffic with service priorities in high-speed networks

We consider a fluid model of a system that handles multiple classes of traffic. The delay and cell-loss requirements of the different classes of traffic are generally widely different and are achieved by assigning different buffers for different classes, and serving them in a strict priority order. We use results from the effective bandwidth of the output processes (see Chang and Thomas (1995)) to derive simple and asymptotically exact call-admission policies for such a system to guarantee the cell-loss requirements for the different classes assuming that each source produces a single class traffic. We compare the admission-control policies developed here with the approximate policy studied by Elwalid and Mitra (1995) for the case of two-class traffic. This revised version was published online in June 2006 with corrections to the Cover Date.     

Analysis of nonlinear systems arise in thermoelasticity using fractional natural decomposition scheme

The pivotal aim of the present study is to employ fractional natural decomposition method (FNDM) to find the solution for a nonlinear system arising in thermoelasticity. The considered coupled system is generalised many physical phenomena associated with the material with elastic characters and its temperature and also which is called a Cauchy problem. We consider the coupled system by incorporating the Caputo fractional operator and investigate three distinct cases for different initial values to illustrate the applicability and efficiency of the FNDM. With respect to fractional order, we capture the behaviour of the achieved solution cited in three different cases and exemplified with the aid of 2D and 3D plots for the particular value of the parameters in the model. Moreover, some interesting behaviours of the projected model are confirms the prominence of the employed fractional operator while analysing the nonlinear coupled equations exemplifying real-world problems and also shows the capability of the considered algorithm.