We report the observation of unidirectional plasmon propagation in metallic nanowires over distances >10 μm. Through control of the incident excitation wavelength and rod composition, we demonstrate the selective coupling of photons into the plasmon mode of a 20 nm diameter nanowire. This mode then propagates in a nonemissive fashion down the wire length before being emitted as an elastically scattered photon at the distal end. As expected from previous studies of plasmon excitation in nanoparticles and thin films, we observe a strong wavelength and material dependence of this phenomenon. This metal-dependent plasmon propagation is exploited to produce a wire through which plasmons propagate unidirectionally. A bimetallic wire with a sharp Au/Ag heterojunction is shown to display both wavelength dependence and unidirectionality with respect to plasmon propagation across the heterojunction. It is expected that these results will contribute to the growing interest in optical energy transport in molecular-le...

Unidirectional Plasmon Propagation in Metallic Nanowires

Neural networks

The Riemann-Liouville fractional integral for repeated fractional integration is expanded in block pulse functions to yield the block pulse operational matrices for the fractional order integration. Also, the generalized block pulse operational matrices of differentiation are derived. Based on the above results we propose a way to solve the fractional differential equations. The method is computationally attractive and applications are demonstrated through illustrative examples.

Numerical solution of fractional differential equations using the generalized block pulse operational matrix

The present work proposes a complementary pair of orthogonal triangular function (TF) sets derived from the well-known block pulse function (BPF) set. The operational matrices for integration in TF domain have been computed and their relation with the BPF domain integral operational matrix is shown. It has been established with illustration that the TF domain technique is more accurate than the BPF domain technique as far as integration is concerned, and it provides with a piecewise linear solution. As a further study, the newly proposed sets have been applied to the analysis of dynamic systems to prove the fact that it introduces less mean integral squared error (MISE) than the staircase solution obtained from BPF domain analysis, without any extra computational burden. Finally, a detailed study of the representational error has been made to estimate the upper bound of the MISE for the TF approximation of a function f ( t ) of Lebesgue measure.

A new set of orthogonal functions and its application to the analysis of dynamic systems

Solving nonlinear mixed Volterra-Fredholm integral equations with two dimensional block-pulse functions using direct method

The present work proposes a method based on block pulse function ( BPF) analysis for the determination of cross-/ auto-correlation of time-varying signals. These results are used subsequently to evaluate power spectral densities ( PSD) of a few codes for communication. Two Lebesgue integrable time-varying functions are represented by means of their respective equivalent BPF spectra. The BPF spectral coefficients are used to develop positive and negative correlation matrices of an operational nature. These matrices, when combined, result in a correlation matrix that is used to determine cross-/ auto-correlation of the input functions over the entire time scale. The results thus obtained in the BPF domain are utilized to determine the PSDs of a few communication codes employing the well-known fast Fourier transform algorithm. Numerical experiments are carried out to establish the validity of the proposed method and the results are found to be in close agreement with the exact solutions

Cross-/auto-correlation of time-varying signals using block pulse functions and determination of power spectral densities

It has been shown by Chen and Chung (1987) that the use of the conventional kintegral operational matrix P in block pulse function (BPF) analysis is equivalent to evaluating the BPF coefficients of the integrated function by the well known trapezoidal rule. They have improved upon P by employing a three-point interpolation polynomial in the Lagrange form to develop a new integral operational matrix P 1 (say). In the present paper, it has been established that once a function f(t) is represented by a BPF series, application of P to integrate f(t) in the staircase form is exact. Also, the method proposed by Chen and Chung (1987) is merely an extension of the trapezoidal rule wherein only one term of the remainder has been considered. Consideration of two terms from the remainder improves upon the integral operational matrix P 1 further and this improved operational matrix P 2 (say) has been employed to illustrate its superiority. Inclusion of still further terms from the remainder will improve upon P 2 further, but the rate of improvement will diminish gradually as evident from the illustrative examples.

On improvement of the integral operational matrix in block pulse function analysis

A method for tracking power line frequency with millihertz resolution and high/low cut-off

A microprocessor based load shedding controller (LSC) with Kalman filter is presented. The filter helps in reducing noise of the accessed data. The novelty of the LSC lies in its algorithm which considers not only the deviation in the power line frequency and its rate of change, but also the second derivative of the frequency. The proposed LSC uses a modified Kalman Filtering technique to reduce the operating time of the controller with no degradation in its effectiveness. The LSC could be used to prepare strategic load shedding schedules in addition to its basic job of monitoring and control.

Microprocessor Based Improved Load Shedding Controller (LSC) with Kalman Filter

The authors present a microprocessor based control scheme for an industrial motor with interrupt driven cause/effect protection. The scheme requests service from the microprocessor only under unhealthy conditions. The scheme also takes care of the causes as well as the effect of the fault. Under healthy conditions, the microprocessor generates the required control signals based upon the desired logic sequence. This arrangement increases the efficiency of the microprocessor, throughput of the system and also reduces the software complexity. The interrupt driven protection scheme allows the microprocessor to run other programs under normal operating conditions. >

Sunit K. Sen

Papers

Cross-/auto-correlation of time-varying signals using block pulse functions and determination of power spectral densities

On improvement of the integral operational matrix in block pulse function analysis

A method for tracking power line frequency with millihertz resolution and high/low cut-off

Microprocessor Based Improved Load Shedding Controller (LSC) with Kalman Filter

Microprocessor based industrial motor control and protection using interrupt