A Novel Statistical Technique for the Estimation of DC Stability in Higher-Order Σ-Δ A/D Converters

The existing techniques available for the statistical estimation of the dc input signal stability in general-order Σ-Δ analog-to-digital (A/D) converters are based on the assumption that the constituent quantizer input signal has a Gaussian distribution. However, empirical investigations reveal that this assumption holds adequately true only for the special case of conventional first-order Σ-Δ A/D converters. This paper presents an alternative technique for the accurate estimation of the dc input signal stability for higher-order Σ-Δ A/D converters. This estimation technique is based on the practical assumption that the constituent quantizer operates in its overload-free region, permitting the characterization of the quantizer output signal digit-pattern for the determination of the statistical moments of the corresponding quantizer input signal. The resulting statistical moments are subsequently incorporated in a Gram-Charlier series for an accurate quasi-linear modeling of the quantizer. A typical application example is given to demonstrate the accuracy of the proposed statistical technique for predicting the existence of multiple regions of instability and stability in the Σ-Δ A/D converter operation, and particularly for predicting the point where the A/D converter operation becomes unstable.     

Syntheses of 2,4‐diaryl‐2,3‐dihydro‐1,5‐benzothiazepines

The condensation of α,β‐unsaturated ketones with substituted o‐aminothiophenols, obtained by reductive cleavage of the corresponding disulfides in the presence of triphenylphosphine, is an effective method for the synthesis of 2,4‐diaryl‐2,3‐dihydro‐1,5‐benzothiazepines under neutral conditions.     

Detection of gas atoms via vibration of graphenes

The application of single-layered graphene sheets as mass sensors in detection of noble gases via a vibration analysis of graphenes is investigated using molecular dynamics simulations. An index based on frequency shifts of the graphenes attached by the distinct noble gas atoms is defined and examined to measure the sensitivity of the sensors. The dependence of number and location of gas atoms, size of graphene sheets, and type of restrained boundary of the sheets on the sensitivity is particularly studied. The simulation results indicate the resolution of a mass sensor made of a square graphene sheet with a size of 10 nm can achieve an order of ¹⁰−6 femtograms and the mass sensitivity can be enhanced with a decrease in sizes of graphenes.     

A fuzzy based threshold policy for a single server retrial queue with vacations

In this paper we deal with a single server retrial queue with vacations. The server serves the customers until the system becomes empty, then it takes a vacation. The system consists of two types of costs. The blocking cost is considered whenever a customer is blocked either because of the server is busy or off. There is also a cost each time the server is turned on. The problem is to find an effective policy for turning on the dormant server. We propose a Fuzzy Based Threshold Policy (FBTP) to control the server, substitute for conventional threshold policies. The FBTP is based on four input parameters, an inference stage and it is tuned up using a stochastic List Based Threshold Accepting (LBTA) algorithm. Simulation models are developed to validate the fuzzy controller. Numerical experiments are provided to show that the proposed method is superior to crisp threshold policies.     

A compensated PID active queue management controller using an improved queue dynamic model

Beside the major objective of providing congestion control, achieving predictable queuing delay, maximizing link utilization, and robustness are the main objectives of an active queue management (AQM) controller. This paper proposes an improved queue dynamic model while incorporating the packet drop probability as well. By applying the improved model, a new compensated PID AQM controller is developed for Transmission Control Protocol/Internet Protocol (TCP/IP) networks. The non‐minimum phase characteristic caused by Padé approximation of the network delay restricts the direct application of control methods because of the unstable internal dynamics. In this paper, a parameter‐varying dynamic compensator, which operates on tracking error and internal dynamics, is proposed to not only capture the unstable internal dynamics but also reduce the effect of uncertainties by unresponsive flows. The proposed dynamic compensator is then used to design a PID AQM controller whose gains are obtained directly from the state‐space representation of the system with no further gain tuning requirements. The packet‐level simulations using network simulator (ns2) show the outperformance of the developed controller for both queuing delay stability and resource utilization. The improved underlying model leads also to the faster response of the controller. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and X‐ray structural characterization of a bidendate phosphine (dppe) palladium(II) complex and its application in Stille and Suzuki cross‐coupling reactions

The synthesis, characterization, crystal structure and catalyst activity of the bidentate phosphine complex [1,2‐bis(diphenylphosphino)ethane]palladium(II) bromide, [PdBr₂(dppe)], are presented. Treatment of 1,2‐bis(diphenylphosphino)ethane with palladium(II) bromide under mild conditions resulted in the compound in high yield and purity. The characterization of the synthesized compound was performed using spectroscopic methods, such as Fourier transform infrared and NMR, CHN analysis and X‐ray crystallography. The structure of the compound was slightly distorted square planar. This compound was found to work as an efficient catalyst for both Stille and Suzuki cross‐coupling reactions of various aryl halides with triphenyltin chloride and/or phenylboronic acid. Also, the catalyst could be recovered and reused several times without significant loss of its catalytic activity. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis of nonlinear vibrations and stability of rotating asymmetrical nano-shafts incorporating surface energy effects

The objective of the present work is to investigate the nonlinear vibrations of the rotating asymmetrical nano-shafts by considering surface effect. In order to compute the surface stress tensor, the surface elasticity theory is used. The governing nonlinear equations of motion are obtained with the aid of variational approach. Bubnov–Galerkin is a very effective method for exploiting the reduced-order model of the equations of motion. The averaging method is employed to analyze the reduced-order model of the system. For this purpose, the well-known Van der Pol transformation in the complex form and angle-action transformation are utilized. The effect of surface stress on the forward and backward speeds, steady state responses of the system, fixed points, close orbits and stability of the solutions is examined. The preliminary results of the research show that the absolute values of forward and backward whirling speeds in the presence of surface effect with positive residual surface stress are higher than those of regarding the system without surface effect and in the presence of surface effect with negative residual surface stress. In addition, it is seen that the undamped rotating asymmetrical nano-shaft, for specified value of detuning parameter, in the absence or presence of surface effect has various number of stable and unstable periodic solutions. Besides, there is different number of separatrix (homoclinic orbit type). Furthermore, bifurcations, number of solutions and their stability for damped rotating asymmetrical nano-shaft are investigated. Also, the above results have been obtained for rotating symmetrical nano-shaft.     

Entanglement generation by electric field background

The quantum vacuum is unstable under the influence of an external electric field and decays into pairs of charged particles, a process which is known as the Schwinger pair production. We propose and demonstrate that this electric field can generate entanglement. Using the Schwinger pair production for constant and pulsed electric fields, we study entanglement for scalar particles with zero spins and Dirac fermions. One can observe the variation of the entanglement produced for bosonic and fermionic modes with respect to different parameters.     

A predictor-corrector interior-point algorithm for P ∗ ( κ ) -horizontal linear complementarity problem

We present a predictor-corrector path-following interior-point algorithm for \(P_*(\kappa )\) horizontal linear complementarity problem based on new search directions. In each iteration, the algorithm performs two kinds of steps: a predictor (damped Newton) step and a corrector (full Newton) step. The full Newton-step is generated from an algebraic reformulation of the centering equation, which defines the central path and seeks directions in a small neighborhood of the central path. While the damped Newton step is used to move in the direction of optimal solution and reduce the duality gap. We derive the complexity for the algorithm, which coincides with the best known iteration bound for \(P_*(\kappa )\) -horizontal linear complementarity problems.