Sharif Digital Repository

Electrical analogy (Lumped method) is an easy way to model human cardiovascular system. In this paper Lumped method is used for simulating a complete model. It describes a 36-vessel model and cardiac system of human body with details that could show hydrodynamic parameters of cardiovascular system. Also this paper includes modeling of pulmonary, atrium, left and right ventricles with their equivalent circuits. Exact modeling of right and left ventricles pressure increases the accuracy of our simulation. In this paper we show that a calculated pressure for aorta from our complex circuit is near to measured pressure by using advanced medical instruments  

A new analytical method is introduced for the analysis of wave propagation in one-dimensional tapered transmission lines. Based on the analytical extension of ordinary transfer matrix into differential transfer matrix, this approach can be used for calculating reflection and transmission coefficients. Different numerical test cases are thoroughly studied and in each case an excellent agreement between the results of our differential transfer matrix method and exact solutions is observed. It is also shown that our approach is superior to the more common small reflection method  

The present article aims to investigate the Graetz-Nusselt problem for blood as a non-Newtonian fluid obeying the power-law constitutive equation and flowing inside the axisymmetric tube subjected to non-uniform surface heat flux. After the flow field is determined by solving the continuity and the momentum equations, the energy equation is handled by employing the separation of variables method. The resulting Eigen functions and Eigen values are numerically calculated using MATLAB built-in solver BVP4C. The analysis is first conducted for the situation of constant heat flux and subsequently generalized to apply to the case of sinusoidal variation of wall heat flux along the tube length,... 

Background: Codon degeneracy and codon usage by organisms is an interesting and challenging problem. Researchers demonstrated the relation between codon usage and various functions or properties of genes and proteins, such as gene regulation, translation rate, translation efficiency, mRNA stability, splicing, and protein domains. Researchers usually represent segments of proteins responsible for specific functions or structures in a family of proteins as sequence patterns or motifs. We asked the question if organisms use the same codons in pattern segments as compared to the rest of the sequence. Methods. We used the likelihood ratio test, Pearson's chi-squared test, and mutual information... 

Gas porosities and entrapped double oxide film (hereafter: oxides) are known to be the most detrimental defects in cast Al-Si-Mg alloys. This study investigated the effects of dissolved hydrogen (hereafter: H) and oxides on reproducibility of tensile properties in Al-7Si-0.35 Mg alloys. Also the effects of H and oxides content on the morphology of defects were studied. Four different casting conditions (low oxide-low H, low oxide-high H, high oxide-low H, high oxide-high H) were tested using tensile test bars that were cast in a metallic mold. Results of tensile test that were obtained for each casting condition were analyzed using Weibull two-parameter analysis. Microstructure and fracture... 

A new genetic algorithm (GA) based method for direct calibration of 2-D hot-wire probe and other instruments that can measure 2-D flow properties is introduced. This new method is an alternative for the previous QR method that is commonly used for calibration of the X-probe hot wires. The proposed GA method resulted in a much smaller error in the velocity estimation while preserving the number of sentences in its calibration equation format. In addition, it preserves the magnitude of its error even when the number of sentences in the calibration equation is decreased while the error in the QR method increases substantially for the same situation. Furthermore, the results were much closer to... 

Dynamic gait planning for humanoid robots encounters difficulties such as stability, speed, and smoothness. In most of previous studies, joints' trajectories are calculated in 3D Cartesian space, then, introducing boundary conditions and using polynomials, the first and second derivatives of the motion are ensured to be continuous. Then, the stability of the motion is guaranteed using Zero Moment Point (ZMP) stability criterion. In this study, a trajectory planner is presented using the semi-ellipse equations of the motion; the continuity of the derivatives is preserved. Stabilization of motion is attained through using ZMP criterion and 3d inverted pendulum equations in three slope... 

Gas porosities and Fe-rich phases and entrapped double oxide films (hereafter: oxides) are known to be the most detrimental defects in cast Al-Si-Mg alloys. The effects of H (gas porosities) and Fe (Β-Al5FeSi phase) on reproducibility of tensile properties in Al-7Si-0.35Mg alloy have been investigated in this study. Four different casting conditions (Low H-Low Fe, Low H-High Fe, High H-Low Fe and High H-High Fe) were studied. In each case, 30 tensile test samples were prepared by casting in a metallic mold and machining (total of 120 tensile test samples). Results of tensile test were analyzed by Weibull three-parameter analyses. The microstructures of samples were studied by optical... 

The effects of melt quality and the placement of a filter in the filling system on Weibull distributions of tensile strength and elongation of Al-7%Si-Mg alloy castings were investigated. Three different combinations of melt quality and filtering were used: (a) unstirred, with filter in the filling system, (b) stirred to produce and entrain surface oxide films with no filter in the filling system to emulate poor initial melt preparation and melt handling, and (c) stirred and with a filter placed in the filling system. The results showed that the highest elongation and tensile strength values were obtained from the unstirred, filtered condition and lowest values were from stirred and... 

An efficient circuit model is proposed for studying the electromagnetic characteristics of rectangular plasmonic cavities. The proposed model comprised a finite size transmission line terminated by scalar load impedances at its both ends. It is capable of the fast extraction of resonance frequencies, quality factors, and mode profiles of plasmonic resonators made by carving rectangles in metallic medium. The accuracy of the proposed model is assessed using the fully numerical finite difference time domain technique. It is employed for analysis and design purposes  

A simple and efficient transmission line model is proposed here to study how the transmission characteristics of photonic crystal waveguides are tailored by introduction of stubs patterned in the photonic crystal lattice. It is shown that band-pass and band-stop optical filters can be easily designed and optimized when stubs of appropriate length are brought in. Since the lengths of the designed stubs are not necessarily integer multiples of the photonic crystal lattice constant, a geometric shift in a portion of the photonic crystal structure is shown to be essential. The proposed model is verified by using a rigorous numerical method. An excellent agreement is observed between the... 

In this paper, enhanced spatial and temporal shifts in the reflection of Gaussian wave packets from twodimensional photonic crystal waveguides supporting above-the-light-line leaky modes are studied, for the first time to our best knowledge. Particular attention is given to two important special cases, namely, harmonic Gaussian beams and Gaussian-pulse uniform plane waves. Analytical expressions are given for enhanced spatial and temporal shifts when the stationary phase approximation holds and the incident wave excites above-the-light-line leaky modes. The enhanced spatial and temporal shifts of Gaussian wave packets are thereby related to each other via the group velocity of the excited... 

Radio frequency identification (RFID) technology is a prominent technology which has been used in most authentication and identification applications. Above all, recently RFID systems have got more attention as an interesting candidate to implement in the internet of things systems. Although RFID systems provide useful and interest services to users, they can also threat the security and the privacy of the end-users. In order to provide the security and the privacy of RFID users, different authentication protocols have been proposed. In this study, we analyze the privacy of three RFID authentication protocols that proposed recently. For our privacy analysis, we use a formal RFID privacy... 

The scattering of graphene surface plasmons normally incident on a line discontinuity in graphene surface conductivity is investigated. The effect of the length of the transition region on the reflection and transmission coefficients is studied. It is shown that the reflection coefficient is reduced by widening the transition region. Based on the results obtained, a transmission line model is derived for the graphene sheet in which the discontinuity is represented by a simple circuit. This model is next used to design graphene-based bandpass and bandstop filters with arbitrary bandwidth in the terahertz regime  

Noise reduction is a major concern in digital image processing systems, which have been investigated by several techniques. One kind of important noises in images is known as Salt & Pepper, which may have different causes. In this paper a new approach for eliminating this type of noise is presented. The approach is different from all previous works in this field, and is based on classification. More precisely, it tries to classify pixels of an image to one of two categories: noisy or not noisy. Afterward, it employs a median filter for pixels which have been classified as noisy, and remains others unchanged; hence, edges and other fine details are kept. Experimental results show this... 

Cyclic loading on asphalt concrete materials with a longer relaxation time and lower remaining stress lead to higher viscoelastic strain recovery. Consequently, more aggregate reorientation occurs and the rate of viscoplastic strain increases in subsequent cycles. The present study proposes a hardening relaxation constitutive relationship (fHR) as a function of accumulated recovered viscoelastic strain εrve based on experimental observation. This model captures the initiation and evolution of hardening-relaxation during the relaxation time and/or stress reduction under cyclic loading. The model was then coupled with viscoelastic, viscoplastic and viscodamage constitutive relationships. The... 

Active behavior in skeletal muscle soft tissue is affected by electrical, chemical and mechanical parameters. More realistic model of skeletal muscle demands detailed formulation which is able to involve other parameters in addition to mechanical ones. In this paper a new formulation for considering Ca2+ level (as the most important chemical factor) along with mechanical parameters in force producing process of skeletal muscle is introduced and validated comparing simulated results with some experimental data. Prepared skeletal muscle behavior is able to predict the maximum generated force in muscle according to the concentration of intracellular Ca2+ level and muscle contraction velocity... 

This work offers an extensive framework for the techno-economic evaluation of the subsurface and surface components of low-grade geothermal (< 100 °C) desalination systems, that is based on validated hydrogeological, thermodynamic, and economic considerations. Additionally, this work incorporates a recently developed advanced multi-effect distillation (MED) process for an improved utilisation of the geothermal heat sources. The analysis focuses on a pre-feasibility study for Western Australia, the influence of the different cost drivers, especially the often overlooked geothermal well field parameters like permeability, so as to permit rational assessments of potential application sites. For... 

The Calcium ion Ca2+ plays a critical role as an initiator and preserving agent of the cross-bridge cycle in the force generation of skeletal muscle. A new multi-scale chemo-mechanical model is presented in order to analyze the role of Ca2+ in muscle fatigue and to predict fatigue behavior. To this end, a cross-bridge kinematic model was incorporated in a continuum based mechanical model, considering a thermodynamic compatible framework. The contractile velocity and the generated active force were directly related to the force-bearing states that were considered for the cross-bridge cycle. In order to determine the values of the model parameters, the output results of an isometric simulation... 

A rigorous, fast and efficient method is proposed for analytical extraction of guided defect modes in two-dimensional photonic crystals, where each Bloch spatial harmonic is expanded in terms of Hermite-Gauss functions. This expansion, after being substituted in Maxwell's equations, is analytically projected in the Hilbert space spanned by the Hermite-Gauss basis functions, and then a new set of first order coupled linear ordinary differential equations with non-constant coefficients is obtained. This set of equations is solved by employing successive differential transfer matrices, whereupon defect modes, i.e. the guided modes propagating in the straight line-defect photonic crystal...