Sharif Digital Repository

The battery management system (BMS) in electric vehicles monitors the state of charge (SOC) and state of health (SOH) of lithium-ion battery by controlling transient parameters such as voltage, current, and temperature prevents the battery from operating outside the optimal operating range. The main feature of the battery management system is the correct estimation of the SOC in the broad range of vehicle navigation. In this paper, to estimate real-time of SOC in lithium-ion batteries and overcome faults of Extended Kalman Filter (EKF), the Square-Root Sigma Point Kalman Filter is applied on the basis of numerical approximations rather than analytical methods of EKF. For this purpose, the... 

The renewed attention paid to rammed earth materials in recent decades is related to their sustainability, high thermo-buffering capacity and relatively low cost. The energy performance of rammed earth materials can be enhanced with stabilization. However, some of thermal enhancement methods have destructive side-effects. In the current study, the effect of three different methods was investigated on thirteen different alternatives of rammed earth materials to improve energy efficiency of buildings. These methods include using phase change materials, cementitious admixtures and external insulators. Thermo-dynamic parameters such as time lag, thermal conductivity and heat flux were measured... 

In this paper, the vibration of a moderately thick plate to a moving mass is investigated. Pasternak foundation with a variable subgrade modulus is considered to tackle the shortcomings of Winkler model, and an analytical-numerical solution is proposed based on the eigenfunction expansion method. Parametric studies by using both CPT (Classical Plate Theory) and FSDT (First-Order Shear Deformation Plate Theory) are carried out, and, the differences between them are also highlighted. The obtained results reveal that utilizing FSDT without considering the rotary inertia leads to a smaller deflection in comparison with CPT pertaining to a thin plate, while it demonstrates a greater response for... 

The spatial sparsity of targets in the radar scene is widely used in multiple-input multiple-output (MIMO) radar signal processing, either to improve the detection/estimation performance of the radar or to reduce the cost of the conventional MIMO radars (e.g., by reducing the number of antennas). While sparse target estimation is the main challenge in such an approach, here, we address the design of a compressive-sensing-based MIMO radar, which facilitates such estimations. In particular, we propose an efficient solution for the problem of joint power allocation and antenna placement based on minimizing the number of transmit antennas while constraining the coherence of the sensing matrix.... 

This paper presents an evaluation of two distinct techniques to improve energy absorption capability of an accordion cellular structure with close-to-zero Poisson's ratio. For this purpose, fiber-reinforcement and foam-filling methods were employed to address the material enhancement and to obtain light and tough structures with high specific energy absorption. Employing an innovated additive manufacturing based on material extrusion process, specimens of glass fiber-reinforced PLA were produced in both in-plane directions to compare with the un-reinforced counterpart. In continue, some of the 3D printed samples were strengthened by means of polyurethane foam in their hollow structure. The... 

In the reliability analysis of systems, all system components are often assumed independent and failure of any component does not depend on any other component. One of the reasons for doing so is that considerations of calculation and elegance typically pull in simplicity. But in real-world applications, there are very complex systems with lots of subsystems and a choice of multiple components that may interact with each other. Therefore, components of the system can be affected by the occurrence of a failure in any of the components. The purpose of this paper is to give an explicit formula for the computation of the reliability of a system with two parallel active components and one spare... 

Electron guns are used as the electron sources in high-power electron tubes. The generated electron beam in electric guns passes through an aperture at the center of the anode. Since the electron beam has considerable kinetic energy, any collision between the electron beam and the anode aperture edge damages the electron gun. Therefore, electron guns are designed to meet the compatibility between the diameters of the electron beam and the anode aperture. However, this compatibility is disrupted during the transient time interval of the gun's power supply. In this article, the cause of failure of the electron gun of high-power electron tubes is investigated for the transient interval of the... 

In this paper, the elastic solution to the problem of an isotropic bi-material full-space reinforced by a perfectly bonded thin film across the media interface and subjected to arbitrary asymmetric interfacial loading is addressed. To not include any simplifications, the thin film is first considered as a layer having a finite thickness, and with the aid of Fourier expansion of Muki's potential functions in Hankel transformed space, the formulation of the problem is obtained for a tri-material full-space. Then, knowing that the flexural stiffness of the thin film is negligible, its thickness and shear modulus are assumed to tend to zero and infinity, respectively, such that its in-plane... 

Forced and free vibrational analyses of viscoelastic nanotubes containing fluid under a moving load in complex environments incorporating surface effects are conducted based on the nonlocal strain gradient theory and the Rayleigh beam model. To model the internal nanoflow, the slip boundary condition is employed. Adopting the Galerkin discretization approach, the reduced-order dynamic model of the system is acquired. Analytical and numerical methods are exploited to determine the dynamic response of the system. The impacts of geometry, scale parameter ratio, Knudsen number, fluid velocity, rotary inertia parameter, viscoelastic parameter, surface residual stress, surface elastic modulus, and... 

Derivation of the probability density evolution provides invaluable insight into the behavior of many stochastic systems and their performance. However, for most real-time applications, numerical determination of the probability density evolution is a formidable task. The latter is due to the required temporal and spatial discretization schemes that render most computational solutions prohibitive and impractical. In this respect, the development of an efficient computational surrogate model is of paramount importance. Recent studies on the physics-constrained networks show that a suitable surrogate can be achieved by encoding the physical insight into a deep neural network. To this aim, the... 

Supersonic turbulent high-pressure jet flows, which are discharging in low-pressure quiescent ambient, are recognized as imperfectly expanded turbulent jet. Steady-state imperfectly expanded jet flow has been already studied analytically; however, the transient flow has not been thoroughly studied. In the present study, the transient imperfectly expanded jet flow with focus on fuel spray in combustion is investigated analytically employing two-step separation of variables method and Fourier-Bessel expansion. The results are validated using available experimental data. The effects of different parameters such as eddy viscosity and pressure ratio on the behavior of the jet are studied. Results... 

Localization of radio-frequency (RF) transmitters using time difference of arrival (TDOA)-based methods is one of the conventional passive techniques that admits noncooperative source position finding, but suffers from challenging requirements such as precise intersensor synchronization and high-throughput transmission data links. A tradeoff governing the TDOA systems is in the sensor placement configuration. The more distance the sensors are placed, the more accurate localization is carried out, while the cost for the synchronization and data link increases, at the same time. In this work, a novel reconfigurable intelligent surface (RIS)-aided localization system is proposed that enjoys... 

Today, passenger and racing boats increasingly utilize surface-piercing propellers. This type of propeller operates in two distinct phases of water and air simultaneously. As a result, this propeller type has additional characteristics that must be investigated separately from conventional propellers. A new family of surface piercing propellers was investigated using experimental and numerical methods. The family consisted of five propeller models with varying geometric features operating at an immersion ratio of 0.7. Experiments were conducted in the Sharif University of Technology's hydrodynamic group's cavitation tunnel. Additionally, using Star-CCM + software, the numerical simulation... 

In the presented research, vibrational, and amplitude behaviors of a sandwich spinning disk made of two laminated layers and graphene nanoplatelets reinforced composite (GPLRC) core has been reported. The Coriolis and centrifugal impacts have been taken into account due to its rotational feature. The stresses and strains have been obtained through the high-order shear deformable theory (HSDT). The structure’s boundary conditions (BCs) are determined using laminated rotating disk’s governing equations employing energy methods and ultimately have been solved via a computational approach called generalized differential quadrature method (GDQM). The rotational disk’s vibrations with different... 

Accelerometers that work based on intensity modulation of light are more sensitive, economically feasible, and have a simpler fabrication process compared to wavelength modulation. A micro-opto-electro-mechanical-system accelerometer based on intensity modulation of light is designed and fabricated. A movable shutter that is attached to the proof mass is designed to change the intensity of light. Moreover, the mechanical part is designed to improve the overall sensitivity and linear behavior in the measurement range. The designed accelerometer is fabricated by a deep-reactive-ion-etching (DRIE) process. The DRIE process used in this report is based on a Bosch-like process, which uses SF 6... 

This study investigates the collapse resistance of the cable net structures. Compared to conventional structures, the analysis of the cable net structures is rather complicated due to the highly nonlinear behavior of the cables, which leads to large displacements and instabilities during the analysis. In this paper, 24 prototype structures are modeled with various force density levels, span lengths, and the number of spans. Several collapse scenarios, including the cable rupture, column removal, and restrain failure, are defined, and the prototype structures are analyzed considering 168 collapse scenarios. This paper aims to recognize the critical elements, the weak points, and other... 

Nondestructive tests and evaluations are robust techniques for inspecting different attributes of concrete configuration. However, most nondestructive techniques focused on an aspect of concrete configuration based on comparison to other samples. In this paper, an innovative inverse analysis technique was developed to inspect different attributes of concrete configuration simultaneously. The methodology was based on the scattering feature of the ultrasonic waves during propagation in heterogeneous media. The transition matrix method was employed to determine the scattered wavefield. This method considers the shape of objects, unlike most other numerical methods. Furthermore, a novel... 

In this article, a new mixed finite element formulation is presented for the analysis of two-dimensional compressible solids in finite strain regime. A three-field Hu–Washizu functional, with displacement, displacement gradient and stress tensor considered as independent fields, is utilized to develop the formulation in spatial configuration. Certain constraints are imposed on displacement gradient and stress tensor so that they satisfy the required continuity conditions across the boundary of elements. From theoretical standpoint, simplex elements are best suited for the application of continuity constraints. The techniques that are proposed to implement the constraints facilitate their... 

In this study, the nodal discontinuous Galerkin method is formulated in three-dimensions and applied to simulate three-dimensional non-cavitating/cavitating flows. For this aim, the three-dimensional preconditioned Navier-Stokes equations based on the artificial compressibility approach considering appropriate source terms to model cavitating phenomena are used. The spatial derivative terms in the resulting equations are discretized by utilizing the nodal discontinuous Galerkin method on tetrahedral elements and the derivative of the solution vector with respect to the artificial time is discretized by applying an explicit time integration method. An artificial viscosity method is formulated... 

An experimental setup has been developed to analyse the impact of cylinder transverse vibration caused by flow-induced vibration, and to improve wind energy harvesting from these vibrations. The setup consists of a cylinder mounted on four springs and is subjected to a uniform and steady flow of wind. In the first part, the effect of mounting a fixed cylinder as an obstacle with different diameters and distances from the downstream vibrating cylinder is investigated. It has been observed that the vibration amplitude on the wake of an unequal-sized obstacle is greatly amplified compared to the case of a single cylinder or an equal-sized cylinder. Numerical simulations has been conducted to...