Sharif Digital Repository

In this article we propose a novel mechano-optical switch and dual channel transmitter based on photonic crystal. The device consists of two waveguides and an elliptical cavity in a square lattice structure. Two optical signals at separate wavelengths are inserted in the input waveguide. The elliptical cavity can be rotated using a mechanical force, which results in the control of transmission efficiency at each of the wavelengths. In addition, rotation of the cavity can be considered as a switching action, which changes on-off states of the output signals  

In this paper, we introduce a modified optical integrator based on suitably designed metamaterial blocks. The integration is performed on an impinging wave pattern as it propagates through these blocks. So far, various metamaterial-based optical integrators have been implemented with appropriate performance in the case of zero- DC input signals. However, these integrators suffer from low accuracy when fed by signals rich in low-frequency contents. The latter property arises from truncation of low-frequency contents of the input wave in the Fourier domain. To solve this shortcoming, we propose a new metasurface-based structure which reflects low-frequency parts of the input signal in the... 

In Analog to Digital Converters, the sampled values are not necessarily sampled in the desired time. Sampling may occur before or after the desired time because of using non ideal converters; therefore the output signal of converters contains a noise related to this inexact sampling time. In this paper, signal to noise ratio according to practical sampling of continuous signal will be estimated. For this estimation, we have assumed the continuous signal as a band limited, zero-mean real signal which is wide sense stationary (wss). Sampling rate is also considered equal or more than Nyquist sampling rate. It will be concluded that what condition should be applied in order to have any... 

In this letter, we explore blind interference alignment (BIA) for the K-user single-input and single-output interference channel. We show that if we implement the structure of reconfigurable antennas at the receivers, by increasing the number of reception modes, the chance of finding proper channel conditions to align most part of interference signals will increase. Throughout this letter, we use the antenna structure of media-based modulation as reconfigurable antenna structure of the receivers. In this method, the receivers try to find proper channel states to align interference signals in an opportunistic manner. The results of this letter show that our proposed method has higher capacity... 

In this paper, an optical fiber multi-intruder sensor based on polarization maintaining optical fiber (PMF), without any interferometric fiber loop, is introduced. To map the local coordinates of intruders on the beating spectrum of the output modes, radiation from a ramp frequency modulated laser is injected at the input of PMF optical fiber sensor. It is shown that the local coordinates and some characteristics of intruders can be obtained by the measurement of the frequencies and amplitudes of the output mode beating spectrum. Generally the number of beating frequencies is more than the number of intruders. Among the beating frequencies, a group with maximum signal to noise ratio is... 

Design of a classical controller is based on output feedback and structure of the controller. From modern control point of view, the information of input signals, output signals and internal behavior of the system are presented in state space model. In this paper, modern control is used to increase small-disturbance stability of power systems. Although many of existing power plants prefer to use classical Power System Stabilizers (PSS), these controllers have their own problems. Digital implementation of modern controllers is considered as a good advantage of modern PSS. In this paper, a modern control based PSS is designed for Bistun power plant and its output results are compared to the... 

In this paper the problem of chaos control in single mode lateral oscillations of spinning disks is studied. At first, using the harmonic balance method, one of the periodic orbits of system is evaluated. Then proposing a nonlinear feedback strategy a control law is presented for chaos elimination by tracking the mentioned periodic solution. It is shown that although the system is not input-state feedback linearizable, by defining an output signal and using the input-output linearization method, the objective of complete periodic orbit tracking is achieved. The sufficient condition for this purpose is presented, and the performance of proposed method is examined by numerical simulation. ©... 

A new technique for the laminar-turbulent intermittency measurement based on the surface hot-film data is presented. The existing techniques require data acquired from the calibrated hot-films which leads to the real wall shear stress values. However, calibration of the hot-films is usually very complex. In the proposed method, a technique based on the probability distribution function (PDF) of the acquired data using the uncalibrated hot-film sensors is presented and evaluated. The PDF is prepared for a reduced form of the quasi-wall shear stress value instead of the real shear stress value one. This leads to a standard normal distribution curve for the PDF in the turbulent flow region and... 

The performance of degree of polarization (DOP) is investigated as a control signal in polarization-mode dispersion (PMD) compensation systems aided by polarization scrambling. The relation between the input and output polarization states of a signal propagating through a polarization scrambler and a PMD-induced optical fiber is described by a 3 × 3 Stokes transfer matrix. The average DOP of the output signal over a period of polarization scrambling is derived as an alternative to the conventional DOP-based control signal, i.e., minimum DOP. In the presence of first- and all-order PMDs, the performance of the average and minimum DOPs in monitoring of differential group delay (DGD) for... 

Functional magnetic resonance imaging (fMRI) is widely-used for detection of the brain's neural activity. The signals and images acquired through this imaging technique demonstrate the human brain's response to pre-scheduled tasks. Several studies on blood oxygenation level-dependent (BOLD) signal responses demonstrate nonlinear behavior in response to a stimulus. In this paper we propose a new mathematical approach for modeling BOLD signal activity, which is able to model nonlinear and time variant behaviors of this physiological system. We employ the Nonlinear Auto Regressive Moving Average (NARMA) model to describe the mathematical relationship between output signals and predesigned...