Topological Design of Survivable Mesh-Based Transport Networks

The advent of Sonet and DWDM mesh-restorable networks which contain explicit reservations of spare capacity for restoration presents a new problem in topological network design. On the one hand, the routing of working flows wants a sparse tree-like graph for minimization of the classic fixed charge plus routing (FCR) costs. On the other hand, restorability requires a closed (bi-connected) and preferably high-degree topology for efficient sharing of spare capacity allocations (SCA) for restoration over non-simultaneous failure scenarios. These diametrically opposed considerations underlie the determination of an optimum physical facilities graph for a broadband network provider. Standalone instances of each constituent problem are NP-hard. The full problem of simultaneously optimizing mesh-restorable topology, routing, and sparing is therefore very difficult computationally. Following a comprehensive survey of prior work on topological design problems, we provide a {1–0} MIP formulation for the complete mesh-restorable design problem and also propose a novel three-stage heuristic. The heuristic is based on the hypothesis that the union set of edges obtained from separate FCR and SCA sub-problems constitutes an effective topology space within which to solve a restricted instance of the full problem. Where fully optimal reference solutions are obtainable the heuristic shows less than 8% gaps but runs in minutes as opposed to days. In other test cases the reference problem cannot be solved to optimality and we can only report that heuristic results obtained in minutes are not improved upon by CPLEX running the full problem for 6 to 18 hours. The computational behavior we observe gives insight for further work based on an appreciation of the problem as embodying unexpectedly difficult feasibility apects, as well as optimality aspects.     

From Schrödinger’s equation to the quantum search algorithm

The quantum search algorithm is a technique for searching N possibilities in only O(√N) steps. Although the algorithm itself is widely known, not so well known is the series of steps that first led to it, these are quite different from any of the generally known forms of the algorithm. This paper describes these steps, which start by discretizing Schrödinger’s equation. This paper also provides a self contained introduction to quantum computing algorithms from a new perspective.     

Fabric phase sorptive extraction/GC‐MS method for rapid determination of broad polarity spectrum multi‐class emerging pollutants in various aqueous samples

A rapid extraction and cleanup method using selective fabric phase sorptive extraction combined with gas chromatography and mass spectrometry has been developed and validated for the determination of broad polarity spectrum emerging pollutants, ethyl paraben, butyl paraben, diethyl phthalate, dibutyl phthalate, lidocaine, prilocaine, triclosan, and bisphenol A in various aqueous samples. Some important parameters of fabric phase sorptive extraction such as extraction time, matrix pH, stirring speed, type and volume of desorption solvent were investigated and optimized. Calibration curves were obtained in the concentration range 0.05–500 ng/mL. Under the optimum conditions, the limits of detection were in the range 0.009 –0.021 ng/mL. This method was validated by analyzing the compounds in spiked aqueous samples at different levels with recoveries of 93 to 99% and relative standard deviations of <6%. The developed method was applied for the determination of the emerging contaminants in tap water, municipal water, ground water, sewage water, and sludge water samples. The results demonstrate that fabric phase sorptive extraction has great potential in the preconcentration of trace analytes in complex matrix.     

High pressure structural investigations on hexagonal YInO3

Hexagonal (space group P6₃cm) form of YInO₃ has been investigated under high pressure using synchrotron-based angle-dispersive X-ray diffraction and Raman scattering methods. Our experimental investigations suggest that it undergoes the phase transition to a new phase in the pressure range 12–15?GPa, while the ambient hexagonal phase is found to coexist with the new phase up to 29?GPa. DFT based calculations within the LDA approach on the hexagonal phase of YInO₃ showed that the unit cell volume matches well with the experimentally obtained volume at ambient pressure. As the pressure increases, theoretically obtained values of unit cell volume of the hexagonal phase were found to be significantly lower than that of experimentally obtained values. This discrepancy has been corrected using LDA?+?U_In(4d) (Hubbard interaction parameter between Indium 4d electrons) method. We have proposed the high pressure phase of YInO₃ to be orthorhombic with space group Pnma.     

Transverse vibrations in micro-scale viscothermoelastic beam resonators

In this article, the closed form expressions for the transverse vibrations of a homogenous isotropic, thermally conducting, Kelvin–Voigt type viscothermoelastic thin beam, based on Euler– Bernoulli theory have been derived. The effects of relaxation times, thermomechanical coupling, surface conditions, and beam dimensions on energy dissipation induced by thermoelastic damping in MEMS (micro-electromechanical systems) resonators are investigated for beams under clamped and simply supported conditions. Analytical expressions for deflection, temperature change, frequency shifts, and thermoelastic damping in the beam have been derived. Some numerical results with the help of MATLAB programming software in case of Silicon Nitride have also been presented. The computer-simulated results in respect of damping factor and frequency shift have been presented graphically.     

Dispersion managed dissipative solitons with higher order nonlinearity and frequency-selective feedback

We present the generation and interaction dynamics of dispersion managed soliton in a dissipative cubic-quintic nonlinear optical fiber coupled with frequency-selective feedback. Analytically, perturbative variational method is used to obtain evolution equations for different soliton parameters that are subsequently solved to study the propagation characteristics of the dispersion managed dissipative solitons (DMDS). The DMDSs show breather like characteristics and are found to be robust against certain level of initial noise. Both the standard Gaussian and more generic super-Gaussian pulse profile are shown to yield stable DMDS. Interaction of two DMDSs of same phase may lead to a bound state. By varying the temporal separation and phase difference between the DMDSs the bound state can be switched between low to high speed regime.     

Measurement and understanding of magnetization in AC and DC fields and the determination of intragrainH c1 in highT c RBa2Cu3O7 superconductors

We present DC and low frequency AC magnetization measurements on various RBa₂Cu₃O₇ superconductors. We identify features intrinsic to these compounds, and establish the features originating from intergranular links in sintered pellets. The isothermal magnetization curves, and the temperature dependence of magnetization in field-cooled and zero field-cooled states are shown to be consistent with the calculations done following a recent extension of Bean’s model. Low field anomalies predicted within this model are observed, and yieldH _c1 values of a few Oe. These values are shown to be consistent with the temperature variation of magnetization. A comparison is made with the other existing data and it is demonstrated that earlier quoted values ofH _c1 are gross overestimates.