Sharif Digital Repository

Purpose - Digital Delta Sigma Modulator (DDSM) is used widely in electronic circuits including Radars, class-D power amplifiers and fractional frequency synthesizers. The purpose of this paper is to propose an implementation for MASH DDSMs named as Multi Modulus Reduced Complexity (MMRC) architecture. Design/methodology/approach - This architecture will use a very simple pseudorandom Linear Feedback Shift Register (LFSR) dither signal with period N-d to randomize the digital MMRC modulator used for fractional frequency synthesizers. Using error masking methodology, the MMRC modulator can decrease the hardware consumption and increase accuracy of the fractional frequency synthesizer. Rules... 

A Digital Delta Sigma Modulator (DDSM) is a Finite State Machine (FSM); it is implemented using finite precision arithmetic units and the number of available states is finite. The DDSM always produces a periodic output signal when the input is constant. This paper proposes a novel method of applying periodic dither to a DDSM in order to obtain minimized spurious tones. The effects of adding the pseudorandom dither signal in different stages within the proposed Multi-Stage noise Shaping (MASH) modulator are expressed in the equations, and the results are compared. We present results regarding the periodicity of the quantization noise produced by a MASH modulator with a constant input and a... 

The contact line dynamics is an important phenomenon in natural and industrial processes and is still a challenging problem. The complexity of this problem in computational simulations is much more than theoretical and experimental works. In this paper, a color-gradient (CG) lattice Boltzmann method (LBM) for simulating wetting phenomena and the dynamics of contact line in two-phase flows with very high density-ratio (∼ 1000 was used. This method applies a multi-relaxation time (MRT) collision operator to enhance the stability of numerical scheme. Both static and dynamic contact angles were enforced at the wall through geometrical wetting boundary condition. Note, the main nobility of this... 

Micro-scale systems have gained considerable attention in recent years and a large amount of researches have been done in this field. In this study, the hydrodynamic interference of a droplet is comprehensively investigated under surface acoustic waves. This paper reveals the effects of some control parameters such as wave amplitude and wave frequency on the dynamical behavior of droplet. For these purposes, a two-dimensional multiple-relaxation-time color-gradient model lattice Boltzmann method is developed. This model is first validated by dynamical behaviors of a droplet subjected to shear flow. Moreover, displacement of a droplet affected by surface acoustic waves is comprehensively... 

Several types of research are performed on flow control and this fact highlights the importance of this topic. Over the last two decades, actuators based on acoustic waves have attracted much attention and have been used in widespread applications from mixing to pumping. This paper reveals the effects of some control parameters such as wave amplitude and wave frequency on the dynamical behavior of a sessile drop in order to change the flow characteristics. For this purpose, the removal of water from surfaces and drop movement against gravity are considered. Flow dynamics is simulated using lattice Boltzmann method. The results show that the drop can be removed from the surface in a short... 

The harmonic displacement response of a beam is utilized as the input signal function in wavelet analysis. Sudden changes in the spatial variation of transformed response identify the location of damages and defects. The damage incurred causes a change in the stiffness or mass of the beam. This causes a localized singularity which can be identified by a wavelet analysis of the displacement response. In this article, it is shown that using harmonic response is superior to the static deflection response and this approach is more effective in the presence of noise and more sensitive to the versatility of the applied harmonic loads. © 2007 SAGE Publications  

The gut-brain axis is believed to constitute a bidirectional communication mechanism that affects both mental and digestive processes. Recently, the role of the gut microbiota in cognitive performance has been the focus of much research. In this paper, we discuss the effects of gut microbiota and nutrition on spatial memory and learning. Studies have shown the influence of diet on cognitive capabilities such as spatial learning and memory. It has been reported that a high-fat diet can alter gut microbiota which subsequently leads to changes in spatial learning and memory. Some microorganisms in the gut that can significantly affect spatial learning and memory are Akkermansia muciniphila,... 

In this paper, a new constructive auto-associative neural network performing nonlinear principal component analysis is presented. The developed constructive neural network maps the data nonlinearly into its principal components and preserves the order of principal components at the same time. The weights of the neural network are trained by a combination of Back Propagation (BP) and Genetic Algorithm (GA) which accelerates the training process by preventing local minima. The performance of the proposed method was evaluated by means of two different experiments that illustrated its efficiency. ©2007 IEEE  

Selling correlated products faces the sellers with the cross-selling, which is a key factor in managing revenue and costs of the sellers. Cross-selling is a phenomenon which happens when the demands of products are correlated so that the demand for one of the correlated products automatically initiates demand of another. In these cases, different selling tactics such as bundling, tying, mixed bundling, etc. are applied to sell the items. In this paper, an integrated pricing-inventory model for two complementary products under three selling strategies is developed. In the first model, it is assumed that the seller sells the products separately while those are packed and sold as bundling in... 

Selling correlated products faces the sellers with the cross-selling, which is a key factor in managing revenue and costs of the sellers. Cross-selling is a phenomenon which happens when the demands of products are correlated so that the demand for one of the correlated products automatically initiates demand of another. In these cases, different selling tactics such as bundling, tying, mixed bundling, etc. are applied to sell the items. In this paper, an integrated pricing-inventory model for two complementary products under three selling strategies is developed. In the first model, it is assumed that the seller sells the products separately while those are packed and sold as bundling in... 

We have studied the relation between the spark-gap operation parameters and the plasma pinch and Neutron yield in our Filippov-type plasma focus, Dena, with 90kJ energy storage bank (25kV, 0.288mF). It has been found that better pinches with regard to their Neutron yield, generally are associated with a faster breakdown in the trigger-able spark-gap as well as higher current buildup rate. We have measured the current buildup speed at various operating conditions and derived the experimental primary ionization parameter and drift velocity of electrons, at extremely high field to pressure ratios. Also, an elaborate axisymmetric variational time-domain finite element simulation code has been... 

In the last decades, much attention has been paid to the design of multi-speaker voice conversion. In this work, a new method for voice conversion (VC) using nonlinear principal component analysis (NLPCA) is presented. The principal components are extracted and transformed by a feed-forward neural network which is trained by combination of Genetic Algorithm (GA) and Back-Propagation (BP). Common pre- and post-processing approaches are applied to increase the quality of the synthesized speech. The results indicate that the proposed method can be considered as a step towards multi-speaker Voice conversion. © 2007 IEEE  

Point Set Registration (PSR) of anatomic parts is used in different fields such as Patient Specific Implant (PSI) design in Computer Assisted Surgery (CAS) procedure. We designed a modified rigid PSR method based on student's-t mixture model. The proposed method is compared with Coherent Point Drift (CPD) registration method. Higher convergence speed and the lower error value are the advantages of the suggested algorithm in compare with CPD. In our method, the number of iterations decreases by about 69%, and the final error improvement was about 7% in comparison with CPD. The robustness of the proposed algorithm makes it beneficial to be used in the procedure of designing PSI in both... 

Controlling the safe distances between vehicles on freeways can be used to prevent many accidents. In this research, image-processing techniques have been used to develop an online system that calculates the longitudinal distances between vehicles. This system facilitates controlling safe distances between vehicles without the need for high technology devices. Our approach is real-time and simple, but efficient operations have been used to reduce the image occlusion problem. The main concept of this system is using simple, quick, and effective algorithms for calculating the position of each vehicle in each image. In this way, traffic parameters like speed and distances between vehicles can... 

The main purpose of this study is to provide the heating power for space heating and sanitary hot water for a residential house in sixteen stations located in Belgium using evacuated tube solar water (ETSW). A one-year dynamic simulation was performed using TSOL 5.5 software and Meteonorm 7.1 was used to obtain the climatic data. Technical and environmental studies as well as station rankings are the parameters that have been examined for the first time in the present study. The weighting results of using the Best-Worst method (BWM) revealed that total solar fraction and CO2 emission avoided have the highest and lowest weight, respectively. Station ranking was performed using ARAS technique... 

Network coding was first introduced in information theory for increasing the multicast rate in the networks with directed links. We can model many of the content distribution networks and overlay networks with such a network. Therefore, the solutions introduced in information theory can be used in these networks. In this paper, we analyze using of network coding in uncoordinated cooperative content distribution systems. Reaching the optimum performance in an uncoordinated system needs blocks of the system to be "equally important". In that case, we can retrieve the whole data without need of central controller or complex algorithms. In part of this paper, we exactly define the concept of... 

Abstract: Surface-nanostructured TiO2 nanorods were synthesized hydrothermally at 180 °C. Such nanorods have ‘crack-like’ surfaces that resemble burnt charcoal. Compared to nanorods with relatively smoother surfaces, the charcoal-like nanorods have higher-specific surface areas. By using the nanorods as a light-scattering layer in double-layered dye-sensitized solar cells, the cells based on the charcoal-like nanorods have 20 % higher dye loading and also higher diffuse reflectance compared with cells utilizing ‘smooth’ nanorods. The efficiency of a screen-printed double-layer dye-sensitized solar cell based on the charcoal-like nanorods is higher at 7.29 %. Electrochemical... 

Developing drug delivery systems with both antibacterial and anti-cancer effects is of importance in the treatment process of infection-associated cancers, especially prostate cancer. In this study, Span 60, Tween 60, and cholesterol were used to formulate doxycycline-loaded niosomes as a promising drug carrier system as either antibacterial or anticancer formulation. The formulation process was optimized by multi-objective response surface methodology (RSM), and then characterized. The developed niosomal formulation showed great storage stability for up to 2 weeks. In addition, they showed remarkable drug release in acidic solution (pH = 3) compared with physiological pH (7.4). The in-vitro... 

This paper aims at the investigation of acoustic streaming produced by surface acoustic waves (SAWs) in a drop. Computational simulation of acoustofluidic phenomenon, using lattice Boltzmann method (LBM), presenting acoustic applications in flow control, and a relatively complete parametric study are the motivations of this work. For this purpose, a computational fluid dynamics modeling based on multi-relaxation time multi-component multiphase color gradient lattice Boltzmann method was used. The simulations were carried out at wave frequencies ranging from 20 MHz to 271 MHz and wave amplitudes ranging from 0.5 nm to about 350 nm. First, the non-dimensional form of Navier-Stokes equations...