Sharif Digital Repository

In this paper, a micromechanical study on rate-dependent behavior of connective tissues is performed. To this end, a hyper viscoelastic constitutive model consisting a hyperelastic part for modeling equilibrium response of tissues and a viscous part using a hereditary integral is proposed to capture the time-dependent behavior of the tissues. With regard to the hierarchical structure of the tissue, strain energy function are developed for modeling elastic response of the tissue constituents i.e. collagen fibers and ground matrix. The rate-dependency is incorporated into the model using a viscous element with rate-dependent relaxation time. The proposed constitutive model is implemented into... 

This paper presents a comparative performance analysis in more realistic scenario and more performance metrics of ADMR and ODMRP, two on-demand multicast routing protocols for Mobile Ad hoc Networks (MANETs) and Wireless Sensor Networks (WSNs). There are a few comparison works done between two multicast Ad hoc routing protocols, ADMR and ODMRP; these works are not complete in terms of both performance metrics and realistic scenarios. Simulation results show an unusual low number of control packets transmitted per data packet delivered in ADMR, this low number of control packet transmitted per data packet in ADMR has caused some comparison works to judge to better performance of ADMR than... 

Structures like beams, plates, shells, and sectors have a key role in different fields of science and engineering. Reliable design of structures requires detailed understanding of their behavior in different service conditions including statics, dynamics, and vibration. For instance, dynamics and vibration characteristics of structures such as natural frequencies, mode shapes, and damping ratios are among interesting properties. Furthermore, in most severe conditions, linear theories are not enough to accurately capture real structural behavior. Thus, investigation of nonlinear and/or large amplitude vibration of structures which is normally governed by system of nonlinear differential... 

Purpose: Many construction projects are implemented in open-environment job sites and can be significantly affected by various weather conditions. Evaluating the overall impacts of the weather conditions on a project can assist project managers to prepare effectively. Nevertheless, methods measuring the overall adverse impacts of the job sites’ weather condition on the project performance are still missing. This study aims to address this gap. Design/methodology/approach: In this investigation, a survey-based method was proposed to evaluate the overall impacts of the weather conditions on the construction project resources through a new indicator called job site weather index (JWI). The... 

Non-linear bending analysis of tapered functionally graded (FG) beam subjected to thermal and mechanical load with general boundary condition is studied. The governing equations are derived and a discussion is made about the possibility of obtaining analytical solution. In the case of no axial force along the beam, a closed form solution is presented for the problem. For the general case with axial force, the Galerkin technique is employed to overcome the shortcoming of the analytical solution. Moreover, the Generalized Differential Quadrature (GDQ) method is also implemented to discretize and solve the governing equations in the general form and validate the results obtained from two other... 

Here in this study, successful conversion of visible light into electricity has been achieved through utilizing microalgal pigments as a sensitizer of nanostructured photo-electrode of dye-sensitized solar cells (DSSCs). For the first time, photosynthetic pigments extracted from microalgae grown in wastewater is employed to imitate photosynthesis process in bio-molecule-sensitized solar cells. Two designs of photoanode were employed: 10μm nanoparticular TiO2 electrode and 20μm long self-ordered, vertically oriented nanotube arrays of titanium dioxide films. Microalgal photosynthetic pigments are loaded on nanostructured electrodes and their photovoltaic performances have been investigated.... 

In this study, free vibration analysis of moderately thick symmetrically laminated general trapezoidal plates with various combinations of boundary conditions is investigated. The governing partial differential equations and boundary conditions for trapezoidal plate are obtained using first order shear deformation theory (FSDT) together with proper transformation from Cartesian system into trapezoidal coordinates. Generalized differential quadrature (GDQ) method is then employed to obtain solutions for the governing equations. Results of the GDQ method are compared and validated with available results in the literature which show accuracy and fast rate of convergence of the method. Effect of... 

The quality of service in Wireless Multimedia Sensor Networks (WMSN) is related to congestion in network. Recently different studies have been done on developing efficient protocols in the transport layer for controlling packet loss in WMSN. However, all of these protocols are independent of the characteristics of multimedia content. In this paper, a novel transport layer protocol, called Energy Efficient Congestion Avoidance (EECA), is proposed to minimize the packet loss ratio in WMSN by predicting congestion in network, and adjusting the source nodes output rate before congestion happening. EECA adjusts the output video quality in source nodes to adjust the source nodes video quality. The... 

Stress analysis of thick walled functionally graded (FG) cylindrical pressure vessels subjected to uniform axisymmetric thermo-mechanical loads is presented using Bernstein polynomials. All thermal and mechanical properties except Poisson's ratio of the FG vessels vary through the thickness with arbitrary functions of the radial coordinate. Based on the thermo-elasticity theory, the first law of thermodynamics and axisymmetric assumption, the governing equations of the semi-coupled thermo-elasticity problem reduce to a set of second order boundary value problem. Galerkin method together with Bernstein polynomials is used to obtain solution for the governing equations. The presented method is... 

Ordinary frequently occur as mathematical models in many fields of science, engineering, differential equations (ODEs) and economy. It is rarely that ODEs have closed form analytical solutions, so it is common to seek approximate solutions by means of numerical methods. One of the most useful methods for the solution of ODEs is multi-step methods. Although the existing multi-step methods such as Adams—Moulton are accurate and useful, they also have their own limitations such as instability at large step sizes or weak performance in the case of stiff ODEs. Thus, multi-step methods that show better behavior compared to the existing methods are preferred, because they decrease the computational... 

In this paper, free vibration analysis of thin symmetrically laminated skew plates with fully clamped edges is investigated. The governing differential equation for skew plate which is a fourth order partial differential equation (PDE) is obtained by transforming the differential equation in Cartesian coordinates into skew coordinates. Based on the multi-term extended Kantorovich method (MTEKM) an efficient and accurate approximate closed-form solution is presented for the governing PDE. Application of the MTEKM reduces the governing PDE to a dual set of ordinary differential equations. These sets of equations are then solved with infinite power series solution, in an iterative manner until... 

This paper describes the concept and a sample design of a broadband loaded monopole antenna with a novel matching network integrated with the antenna body. The proposed monopole antenna is designed by loading three different lumped loads integrated on a wire antenna and a simple input matching network. Parameters of the matching circuits and the lumped loads optimized by using a genetic algorithm (GA). The proposed antenna loads and the matching network is integrated into the antenna body by the use of printed circuit technology making the antenna fabrication process easy. A prototype of the proposed 1.19-meter monopole antenna is fabricated and measured. The simulation and measurement... 

Electrocoagulation is an effective, fast, and economic method for treatment of industrial wastewaters. In this study, effects of different parameters including electrolysis time, voltage, and pH on the reduction of chemical oxygen demand (COD), lignin, and color in pulp and paper wastewaters were studied. Iron and aluminum were used as anode and cathode electrodes, respectively. Under the optimal conditions (pH 5, 60 min, 10 V), this treatment method led to 85% removal of COD and 78.5% removal of lignin. Furthermore, clear treated water with complete color removal was generated that suggests the application of electrocoagulation for industrial wastewater treatment, especially in pulp and... 

This study investigated the diesel and COD removal from oily wastewater by electrocoagulation. Experiments were conducted in a 2-l reactor using aluminum and iron electrodes. Effects of different parameters including pH (3–11), time (10–60 min), voltage (4.5–10.5 V), supporting electrolyte (NaCl concentration), electrode material and initial diesel concentration (3500–11,000 mg/L) were studied in order to evaluate the efficiency of electrocoagulation. Furthermore, the consumption of energy and the amount of sludge produced by this method were evaluated. The highest removal efficiency (COD removal of 99.1 ± 0.2 % and diesel removal of 98.8 ± 0.2 %) was observed under the following conditions:...