Sharif Digital Repository

We consider chaperone-assisted translocation of biopolymers with two distinct monomers or bases A and B, with the size of the chaperones being λα, where α is a monomer's size. The probability that A and B are neighbors in the biopolymer is PAB. A master equation is used, together with the detailed-balanced condition, in order to derive analytical results for the statistics of the first-passage times of the biopolymer as a function of PAB, λ, and the biopolymer's configuration. Monte Carlo simulations have also been carried out in order to compute the same quantities for biopolymers with 100-900 monomers and several λ. The results indicate nontrivial dependence of the variance of the... 

Previous studies of analysis and prediction of marine risers responses usually focus on vortex-induced vibration (VIV) of cross-flow (CF) direction rather than in-line (IL). Recent studies show that responses of IL direction tend to dominate in some cases. Responses of long riser due to biaxial bending of IL and CF VIV are investigated. Closed-form formulas are derived for estimating maximum normal stress due to the biaxial moment of CF/IL VIV and relations for estimating biaxial stress using CF values are presented. Analytical results are compared with numerical results of the time domain model and a good correlation is observed. It is shown that for tension and bending-controlled modes of... 

We propose and analyze a circularly polarized slot antenna built on a ferrite substrate which is saturated normal to its plane and metalized on both sides. The antenna is built by etching a circular slot in the top metal layer. The antenna operates in the frequency range where the effective permeability of ferrite is negative. An accurate analytical model is derived for the antenna by solving the integral equation for the electric field on the circular slot. The results obtained are in good agreement with numerical simulations. Using the analytical results, a practical antenna is designed that uses a microstrip feed line. For an antenna with inner and outer radii of 4.9 and 5.9 mm, the... 

In this paper, a size-dependent Timoshenko beam is developed on the basis of the couple stress theory. The couple stress theory is a non-classic continuum theory capable of capturing the small-scale size effects on the mechanical behavior of structures, while the classical continuum theory is unable to predict the mechanical behavior accurately when the characteristic size of structures is close to the material length scale parameter. The governing differential equations of motion are derived for the couple-stress Timoshenko beam using the principles of linear and angular momentum. Then, the general form of boundary conditions and generally valid closed-form analytical solutions are obtained... 

In this paper, we present a multi-user resource allocation framework using fragmented-spectrum synchronous OFDM-CDMA modulation over a frequency-selective fading channel. In particular, given pre-existing communications in the spectrum where the system is operating, a channel sensing and estimation method is used to obtain information of subcarrier availability. Given this information, some real-valued multi-level orthogonal codes, which are orthogonal codes with values of {±1, ±2, ±3, ±4,...}, are provided for emerging new users, i.e., cognitive radio users. Additionally, we have obtained a closed form expression for bit error rate of cognitive radio receivers in terms of detection... 

We present a new approach for analytical modeling and calculating the response of high-Tc superconductive transition edge sensors in a wide range of modulation frequencies for different configurations of the film patterns. The method used here is based on solving the heat transfer differential equation for two different time varying heat sources, which are related to the absorbed radiated power. The used method employs two-dimensional boundary conditions for describing meander-line patterned devices. The results from the applied method are in better agreement with those obtained from the frequency response measurements of the characterized samples, than the previously developed models. In...