Sharif Digital Repository

This paper presents a new high speed current mirror with continuous gain adjustment. Based on this current mirror, a variable gain current amplifier is designed in 0.18μm CMOS technology. The current gain of the amplifier can be continuously varied from 0 dB to 20 dB while the bandwidth of the circuit remains above 1.00 MHz. The circuit consumes 0.9 mW from 1.5V supply. © IEICE 2007  

In this paper, a practical simulation method for optimizing of x-ray reflection of nano-multilayer mirrors in three different edge energies: Cr-Kα, Co-Kα, and Ti-Kα is discussed in order to obtain the most reflection based on quarter-wave thickness method (QW). In this method, the reflected x-ray will have a constructive interference, and a peak, called Brag peak, will appear in reflection curve when the tickness of the layer is an odd multiple of the quarter-wave thickness. The quarter-wave thickness is dependent to on the angle and energy of the entrance photon beam. In the mentioned edge energies, for different nano-multilayer mirrors, and for incident angle ranges from 0.5 to 8 degrees,... 

Given a simple polygon P with n vertices, the visibility polygon (VP) of a point q, or a segment pq‾ inside P can be computed in linear time. We propose a linear time algorithm to extend the VP of a viewer (point or segment), by converting some edges of P into mirrors, such that a given non-visible segment uw‾ can also be seen from the viewer. Various definitions for the visibility of a segment, such as weak, strong, or complete visibility are considered. Our algorithm finds every edge that, when converted to a mirror, makes uw‾ visible to our viewer. We find out exactly which interval of uw‾ becomes visible, by every edge middling as a mirror, all in linear time. In other words, in this... 

Empirical mode decomposition as a complete data driven method is typically employed to obtain constitutive components of all kinds of signal including non-stationary and nonlinear. Extracting modes using this method is normally associated with multiple sources of errors such as stop criteria, end effects, interpolation function and etc. In order to reduce end effects errors in this paper a modified method is proposed based on combination of auto regressive model and mirror method. In this combination method, to extract some of first intrinsic mode functions of a given signal, auto regressive model is initially implemented to forecast tails of maximum and minimum envelops for only a short... 

In the current article the effect of the Casimir force on the static behavior and pull-in characteristics of nano/micromirrors under capillary force is investigated. At the first, the dimensionless equation governing the static behavior of nano/micromirrors is obtained. The dependency of the critical tilting angle on the physical and geometrical parameters of the nano/micromirror and its supporting torsional beams is investigated. It is found that the Casimir effect can considerably reduce the pull-in instability limits of the nano/micromirror. It is also found that rotation angle of the mirror under capillary force highly depends on the Casimir force applied to the mirror. Finally the... 

A deterministic finite automaton (DFA) separates two strings w and x if it accepts w and rejects x. The minimum number of states required for a DFA to separate w and x is denoted by sep(w,x). The present paper shows that the difference |sep(w,x)-sep(wR,xR)| is unbounded for a binary alphabet; here wR stands for the mirror image of w. This solves an open problem stated in Demaine et al. (2011) © 2017 Elsevier B.V  

Given a simple polygon P with n vertices, the visibility polygon (V P) of a point q (V P(q)), or a segment (formula present) (V P(pq)) inside P can be computed in linear time. We propose a linear time algorithm to extend V P of a viewer (point or segment), by converting some edges of P into mirrors, such that a given non-visible segment (formula present) can also be seen from the viewer. Various definitions for the visibility of a segment, such as weak, strong, or complete visibility are considered. Our algorithm finds every edge such that, when converted to a mirror, makes (formula present) visible to our viewer. We find out exactly which interval of (formula present) becomes visible, by... 

In this paper, the effect of parametric amplifier pump phase noise on the cooling of a micromirror in an optomechanical system with an optical parametric amplifier inside the optical cavity is investigated theoretically. It has been demonstrated that the photon number distribution of a parametric amplifier near the threshold of instability leads to improved cooling of the micromirror. But due to the presence of the parametric amplifier, there is a resonance detuning frequency for transferring noise energy to the potential and kinetic energy fluctuations of the mirror which causes the mirror mechanical oscillation mode temperature to increase. In low quality factor cavities, this effect... 

The current paper uses the Extended Kantorovich Method (EKM) to analytically solve the problem of squeezed film damping in micromirrors. First a one term Galerkin approximation is used and following the extended Kantorovich procedure, the solution of the Reynolds equation which governs the squeezed film damping in micromirrors is reduced to solution of two uncoupled ordinary differential equation which can be solved iteratively with a rapid convergence for finding the pressure distribution underneath the micromirror. It is shown that the EKM results are independent of the initial guess function. It is also shown that EKM is highly convergent and practically one iterate is sufficient for... 

We provide a full quantum description of the optomechanical system formed by a Fabry-Pérot cavity with a movable micromechanical mirror whose center-of-mass and internal elastic modes are coupled to the driven cavity mode by both radiation pressure and photothermal force. Adopting a quantum Langevin description, we investigate simultaneous cooling of the micromirror elastic and center-of-mass modes, and also the entanglement properties of the optomechanical multipartite system in its steady state  

The objective of this work is to create an analytical framework to study the problem of squeezed film damping in micromirrors considering the bending of the supporting torsion microbeams. Using mathematical and physical justifications, nonlinear Reynolds equation governing the behavior of the squeezed gas underneath the mirror is linearized. The resulting linearized equation is then nondimensionalized and analytically solved for two cases of the infinitesimal and finite tilting angle of the mirror. The obtained pressure distribution from the solution of the Reynolds equation is then utilized for finding the squeezed film damping force and torque applied to the mirror. The results show that... 

In the present study, two novel annular photobioreactors (PBR) were developed to enhance microalgae growth. One of these photobioreactors used mirrors outside the PBR, while the other one utilized phosphorescence materials inside the PBR. The results of the study suggested that the use of mirrors and phosphorescence materials led to 70% and 30% increase, respectively, in the light intensity without any additional energy consumption. Further, the results revealed that when compared with the base case, the biomass concentration increased by 91% and 24% in PBR with mirrors and phosphorescence materials, respectively. In conclusion, an improvement in PBRs resulted in efficient light to biomass... 

We investigate the Fano profile in an optomechanical system with two vibrating mirrors. The detuning between their mechanical frequency, leads to the occurrence of double Fano resonances. The Fano profile can be controlled by adjusting the cavity parameters  

In this article, the static behavior of micromirrors under the effect of capillary force is studied. The dimensionless equations governing the static behavior and the pull-in state of the micromirror under capillary force are obtained, and the effects of different geometrical parameters on the pull-in angle of micromirrors are investigated. The static behavior of micromirrors is studied both numerically and analytically using the homotopy perturbation method. It is observed that with increasing the instability number defined in this article, the rotation angle of the micromirror is increased and suddenly the pull-in occurs. The results of the presented model are then verified by comparing... 

In this paper, the effect of van der Waals (vdW) force on the pull-in behavior of electrostatically actuated nano/micromirrors is investigated. First, the minimum potential energy principle is utilized to find the equation governing the static behavior of nano/micromirror under electrostatic and vdW forces. Then, the stability of static equilibrium points is analyzed using the energy method. It is found that when there exist two equilibrium points, the smaller one is stable and the larger one is unstable. The effects of different design parameters on the mirror's pull-in angle and pull-in voltage are studied and it is found that vdW force can considerably reduce the stability limit of the... 

In the current paper, a general theoretical model for the problem of micromirrors under the effect of capillary forces is presented. The presented model considers the coupling effect between torsion and bending of the torsion beams supporting the micromirror. First, the energy method, the principal of minimum potential energy is utilized for finding the equations governing the micromirror rotation and its deflection. Then using the implicit functions theorem, the equations governing the pull-in angle and pull-in displacement of the micromirror is derived. The results, shows that ignoring the bending effect in micromirrors under the effect of capillary forces, can cause a significant (up to...