A series expansion method aided design of current mode second generation current conveyor based active control circuit

Current mode circuits are receiving considerable interest from engineering community due to their unique characteristics that are not found in their voltage mode counterparts. This paper presents a series method based design of a current conveyor active control circuit. An algorithm based on the principle of the series expansion of the pulse transfer function is employed for obtaining the transfer function of the controller. The controller is subsequently realized using the second generation current conveyors. The proposed methodology is used to design a CCII controller for a practical system, which is subsequently simulated using the AD844 IC’s in the NI’s Multisim simulation tool. Subsequently, the controller was designed and the comparisons are drawn between the experimental and simulation results in order to validate the approach.

     

Efficient prediction of exchange rates with low complexity artificial neural network models

In recent years forecasting of financial data such as interest rate, exchange rate, stock market and bankruptcy has been observed to be a potential field of research due to its importance in financial and managerial decision making. Survey of existing literature reveals that there is a need to develop efficient forecasting models involving less computational load and fast forecasting capability. The present paper aims to fulfill this objective by developing two novel ANN models involving nonlinear inputs and simple ANN structure with one or two neurons. These are: functional link artificial neural network (FLANN) and cascaded functional link artificial neural network (CFLANN). These have been employed to predict currency exchange rate between US$ to British Pound, Indian Rupees and Japanese Yen. The performance of the proposed models have been evaluated through simulation and have been compared with those obtained from standard LMS based forecasting model. It is observed that the CFLANN model performs the best followed by the FLANN and the LMS models.     

Application of FIR‐neural network on finite difference time domain technique to calculate input impedance of microstrip patch antenna

Finite impulse response artificial neural network (FIR‐ANN) is used for speeding up the FDTD. The FIR‐ANN based FDTD (Neuro FDTD) is used to calculate input impedance of coaxial fed stacked microstrip patch antenna. Input impedance obtained by Neuro FDTD and FDTD are compared. It has been observed that Neuro FDTD provides same result with less number of iteration than compared to FDTD. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

Optimal deflection and stacking sequence prediction of curved composite structure using hybrid (FEM and soft computing) technique

Engineering with Computers - The bending deflections and the corresponding optimal fiber angle sequences of the subsequent layers have been predicted in this article using a hybrid technique. The...     

The Temporal Precedence Problem

In this paper we analyze the complexity of the Temporal Precedence Problem on pointer machines. The problem is to support efficiently two operations: insert and precedes. The operation insert (a) introduces a new element a , while precedes (a,b) returns true iff element a was temporally inserted before element b . We provide a solution to the problem with worst-case time complexity O( lg lg n) per operation, where n is the number of elements inserted. We also demonstrate that the problem has a lower bound of Ω( lg lg n) on pointer machines. Thus the proposed scheme is optimal on pointer machines. Received February 5, 1998; revised October 21, 1998.     

Semiconductor quantum dots: Theory and phenomenology

Research in semiconductor quantum dots (q-dots) has burgeoned in the past decade. The size (R) of these q-dots ranges from 1 to 100 nm. Based on the theoretical calculations, we propose energy and length scales which help in clarifying the physics of this mesoscopic system. Some of these length scales are: the Bohr exciton radius (α_B*), the carrier de Broglie and diffusion length (λ_D andl _D), the polaron radius (α_p), and the reduction factor modulating the optical matrix element (M _x).R<α_B is an individual particle confinement regime, whereas the larger ones are exciton confinement regime wherein Coulomb interaction play an important role. Similarly a size-dependent dielectric constantε(R) should be used forR<α_p<α_B. An examination ofM _x reveals that an indirect gap material q-dot behaves as a direct gap material in the limit of very small dot size. We have carried out effective mass theory (EMT) calculations to estimate the charge density on the surface of the quantum dot. We present tight binding (TB) calculation to show that the energy upshift scales as 1/R ^x, wherex is less than 2 and the exponent depends on the orientation of the crystallite.     

Surface loads on granular material underlain by a rough rigid base

A general theoretical analysis with numerical evaluation for the complete distribution of stress within a granular layer underlain by a rough rigid base, and the surface displacements of the layer beneath the footing is presented. The cases of a point load, a uniformly loaded circular footing acting at the surface of the layer but transmitting three usual types of contact pressure, have been considered. It is considered that the material is elastic, cross-anisotropic in which the ratio $\text{E}\text{G}\text{> 2(1 + μ)}$. The effect of the material parameter $\text{E}\text{G}$ on stresses and displacements in granular materials has been presented in a non-dimensional form.     

A kinetic investigation of thermal degradation of poly(vinyl formals)

Several samples of poly(vinyl formal) having the same vinyl alcohol content (8–9%) but varying contents of vinyl acetate (6–22%) and vinyl formol (70–85%) were prepared and subjected to thermogravimetric analysis, in air and nitrogen atmospheres, employing both isothermal and dynamic methods. Kinetic parameters determined from both the isothermal and dynamic TGA data are compared. The activation energy is seen to be largely dependent on the degree of conversion, implying a complex degradation reaction. The activation energy is also much less for degradation in air than in nitrogen, which can be explained by a reaction with oxygen-producing structures favoring degradation. The activation energy is less sensitive to variation in polymer composition for degradation in air than in nitrogen. Thus, in the dynamic process, the activation energy value decreases (from 36 to 23 kcal/mole) with increasing acetate content (from 6 to 22%) in nitrogen atmosphere, while in air the activation energy value increases only moderately (from 21 to 27 kcal/mole) with increasing acetate content (from 6 to 22%). The order of reaction is nearly unity, irrespective of the composition of the polymer, both in air and nitrogen.     

Thermodynamics of the silver—silver chromate electrode in water + 10, + 20, + 30 and + 40 mass percent of dioxane at different temperatures

The emf of the cell: Ag, AgCl, NaCl(m)?Na₂CrO₄(m/2), Ag₂CrO₄, Ag in water + 10, + 20, + 30, and + 40 mass percent of dioxane has been measured at 5°C intervals over the temperature range 15–45°C. The values of the standard potentials of the silver—silver chromate electrode have been determined in these mixed solvent media at these temperatures. The standard thermodynamic quantities (ΔG°, ΔH°, and ΔS°) for the cell reaction in water + dioxane mixtures have been evaluated at these temperatures. The results are discussed in terms of the preferential solvation of the ions.     

Optimal design of flexible chemical processes

Practical ways are still needed for optimizing the design of chemical processes, with allowance for uncertain specifications and future changes in economic parameters. This problem fits the two-stage formulation of Dantzig[1]. Unfortunately, we found several practical difficulties in applying this two-stage analysis to realistic process design models. Some of these can be overcome by proper formulation of the process model or by improvements in the computational algotrithm. In the end, we obtained, for two realistic process models, optimal designs with improved flexibility compared to designs based on fixed parameters; the well-known inequalities were satisfied. More generally, the paper includes suggestions for practical efficient use of the two-stage approach in process design.