Sharif Digital Repository

In this paper a new least mean square (LMS) based adaptive weighting algorithm is proposed. It is appropriate for antenna array systems with moving targets and mobile applications. The essential goal of this algorithm is to reduce the complexity of weighting process and to decrease the time needed for adjusting the antenna radiation pattern. The main lobe of antenna will be adjusted in the direction of desired signal (main signal) and nulls pointed in the direction of undesired signals (interference signals). By predicting the relative velocity of source, the next location of the source will be estimated and the array weights will be determined using LMS algorithm before arriving to the new... 

Reducing the computational complexity as well as convergence time is the main task of adaptive antenna array processing. This article proposes an improved algorithm for estimating the weights of adaptive array elements based on Constant Modulus Algorithm (CMA). In this new type of algorithm, those weights that have higher effect on the radiation pattern will be estimated and antenna pattern will be adjusted by changing these weights. In this research, 3 new algorithms are proposed. By simulating these algorithms and comparing them with conventional full weight CMA, finally new algorithm that has a reduced complexity and an acceptable performance at different signal to noise ratios (SNRs) is... 

This paper focuses on cross-layer transmission based on rateless coding for relay channels. In the proposed method, rateless coding is used at packet level and a separate physical layer coding is used at the physical layer. As rateless codes are originally designed and optimized for erasure channels, using these codes at the physical layer can lead to significant performance degradation. The proposed scheme has the advantage of a cross-layer design which uses a rateless code at the packet level modeled by an erasure channel. Based on the analysis and simulation results provided in this paper, there is an exact tradeoff between physical layer code rate and rateless code depth, and the optimum... 

The focus of the paper is on cross-layer transmission based on rateless coding for relay networks. In the proposed method, rateless coding is used at the packet level and a separate physical layer coding is used at the physical layer. As rateless codes are originally designed and optimized for erasure channels, using these codes at the physical layer can lead to significant performance degradation. The proposed scheme has the advantage of a cross-layer design which uses a rateless code at the packet level modeled by an erasure channel. Based on the analysis and simulation results provided in this paper, the cross-layer scheme results in earlier successful decoding at the destination  

In this article, a novel cooperative secondary voltage/frequency control considering time-varying delays and noises in fading channels is presented for an autonomous alternating current (AC) voltage sourced-based converter (VSC)-based microgrid (MG), including inverter-interfaced distributed generations (DGs). Fading phenomenon makes complex random fluctuations on the voltage and frequency of every DG received from its neighbor DGs. In multi-agent cooperative systems, in addition to the total additive noise and time-variant delay, a multiplicative complex random variable is considered to model the main received signal and its replicas due to multipath propagation. The proposed... 

In order to restrain ferroresonance in coupling capacitor voltage transformers (CCVT), two kinds of ferroresonance suppression circuits (FSCs) , are proposed in this paper: the resonant type, the fastsaturation reactor type which are connected to secondary side of CCVTs. Frequency domain analyses, for voltage ratio magnitude, are carried out for CCVTs to obtain preferable FSC. Furthermore, using surge suppressors such as metal oxide varistors (MOV) to improve the performance of the FSCs is investigated. Time domain simulations demonstrate that ferroresonance can be cleared in few cycles in presence of FSCs. The Electromagnetic Transients Program (EMTP) is used for modeling and fine-tuning... 

In this study the ability of artificial neural network (ANN) in forecasting the daily NASDAQ stock exchange rate was investigated. Several feed forward ANNs that were trained by the back propagation algorithm have been assessed. The methodology used in this study considered the short-term historical stock prices as well as the day of week as inputs. Daily stock exchange rates of NASDAQ from January 28, 2015 to 18 June, 2015 are used to develop a robust model. First 70 days (January 28 to March 7) are selected as training dataset and the last 29 days are used for testing the model prediction ability. Networks for NASDAQ index prediction for two type of input dataset (four prior days and nine... 

In this research, multi-walled carbon nanotubes (MWCNTs) were modified by dendritic macromonomer. Herein, polyamidoamine with acrylamide end groups was incorporated on MWCNTs. Afterwards, poly(N-isopropylacrylamide), (PNIPAM), was grafted on polyamidoamine in a facile synthesis. Then, doxorubicin as anticancer drug was loaded on this nanocarrier. The drug release was studied at below and above the lower critical solution temperature of PNIPAM, (LCST 32 °C), 27 °C and 37 °C, respectively. At 37 °C (body temperature) the polymer shell dehydrated and the drug release increased. The profile of drug release was expressed by Higuchi's equation which indicated that the drug release mechanism was... 

The success of restoring images degraded by motion blur highly depends on precise estimation of parameters such as motion direction and length that were involved in the motion blur function. In this paper we suggest a method which uses Radon transform to estimate motion direction and for estimating motion length we used curve fitting methods to provide an equation that could model the behaviour of Fourier transform of images that were degraded with different motion lengths. The input to this model is a property found to be available in the Fourier transform of the degraded image and its output is an estimate for the motion length. Our method was tested on a wide range of different type of... 

Motion blur is one of the most common blurs that degrades images. Restoration of such images are highly dependent to estimation of motion blur parameters. Many researchers have developed algorithms to estimate linear motion blur parameters. These algorithms are different in their performance, time complexity, precision and their robustness in noisy environments. In this paper we have presented a novel algorithm to estimate linear motion blur parameters such as direction and extend by using Radon transform to find direction and fuzzy set concepts to find its extend. The most benefit of this algorithm is its robustness and precision in noisy images. Our method was tested on a wide range of... 

Motion blur is one of the most common blurs that degrades images. Restoration of such images are highly dependent to estimation of motion blur parameters. Many researchers since 1976 have developed algorithms to estimate linear motion blur parameters. These algorithms are different in their performance, time complexity, precision and their robustness in noisy environments. In this paper we have presented a novel algorithm to estimate linear motion blur parameters such as direction and extend by using Radon transform to find direction and power spectrum modeling to find its extend. The most benefit of this algorithm is its robustness and precision in noisy images. This algorithm is a... 

Results of the seismic performance assessment of a new structural system that has been used in a 54-story reinforced concrete building are presented. The structure, which is still under construction, and has a 'Y-shape' form, utilizes a special structural system that does not include any beams or columns. Instead, walls and slabs are used for carrying both gravitational and lateral loads. The general distinctions of the system are discussed. The structural efficiency of the system is compared with other conventional systems in some existing tall buildings. The seismic responses and dynamic behavior of the structure that were achieved by conducting various analyses are presented. The effects... 

The effect of dielectric cladding on the waveguiding characteristics of an array of metallic pillars on a metal plane in the sub-terahertz band is explored. Firstly, a 2D structure made up of a metallic grating of infinite lateral width with various dielectric overlays is analytically studied to get more insight into the problem. Then the ideas inferred from the 2D structure are applied to the realistic 3D structure that has a finite lateral width. It is shown that by proper design of the dielectric medium surrounding the metallic structure the modal field confinement can be enhanced in a broad frequency band resulting in a low bending loss. Especially, by integrating the pillars into a... 

Platinum extraction from spent reforming catalysts in iodine solutions under atmospheric pressure and at temperatures up to 95°C was previously investigated in our group. In this system, platinum is oxidized from the spent catalyst with tri-iodide. In some of the experiments, it was observed that platinum extraction peaked and then decreased. This indicates that a precipitation reaction slowly occurs that removes the dissolved Pt ions from the solution. Power-law rate equation for the Pt extraction to PtI6 2- and the precipitation of the dissolved platinum to PtI 4(s) was implemented to model the experimental Pt extraction data. The activation energies for the platinum dissolution reaction... 

The site-selectivity and regioselectivity of Diels-Alder reactions of allenyl aryl ethers with cyclopentadiene and acrolein were studied. While cyclopentadiene (as an electron-rich diene) only reacted with the external double bond of allenyl aryl ethers to provide the site-selective normal electron demand Diels-Alder cycloadducts, acrolein (as an electron-deficient diene) reacted with the C1-C2 π bond of allenyl aryl ethers to provide the site- and regioselective hetero-Diels-Alder cycloadducts as exclusive products  

Palladium nanoparticles immobilized on the magnetic nanoparticles@2-amino-N-(2-aminoethyl) benzamide (MNPs@A-N-AEB.Pd0) have been presented as an efficient, and reusable magnetically heterogeneous catalyst for the C-O coupling reaction, namely Ullmann condensation reactions in an aqueous medium. This heterogeneous catalyst shows superior reactivity for the C-O arylation of different aryl halide (chloride, bromide, and iodide) with phenol derivatives to afford the desired products in good to excellent yields within short reaction time. Moreover, the catalyst can be easily recovered and reused for seven runs without loss of catalytic activity. The catalyst was characterized by several...