Farhang Daneshmand

Microtubules are the central part of the cytoskeleton in eukaryotic cells. The microtubules immersed in the cytoplasm are in contact with water and other cytoplasmic molecules. In this study, a mechanics model of microtubule vibration, considering the coupled effect of the ...

This article presents a system identification scheme to determine the geometric shape of a cavity with convective boundary condition in a heat-conducting medium using the measured temperatures on the surface of the object. The proposed algorithm is based on the nonlinear minimization of the squared errors between the measured temperatures and the calculated ones. In this article, a new approach based on non-boundary-fitted meshes and gradient smoothing technique is presented for the solution of the direct problem and shape ...

Microtubules are the central part of the cytoskeleton in eukaryotic cells. The microtubules immersed in the cytoplasm are in contact with water and other cytoplasmic molecules. In this study, a mechanics model of microtubule vibration, considering the coupled effect of the ...

ABSTRACT Non-stationary signals are frequently encountered in a variety of engineering fields. The inability of conventional Fourier analysis to preserve the time dependence and describe the evolutionary spectral characteristics of non-stationary processes requires tools which allow time and frequency localization beyond customary Fourier analysis. The spectral analysis of non-stationary signals cannot describe the local transient features due to averaging over the duration of the signal [1]. The Fourier Transform (FT) and the short time Fourier transform (STFT) have been often used to measure transient phenomena. These techniques yield good information on the frequency content of the transient, but the time at which a particular disturbance in the signal occurred is lost [2, 3]. Wavelets are relatively new analysis tools that are widely being used in signal analysis. In wavelet analysis, the transients are decomposed into a series of wavelet components, each of which is a time-domain signal that covers a specific octave band of frequency. Wavelets do a very good job in detecting the time of the signal, but they give the frequency information in terms of frequency band regions or scales [4]. The main objective of this paper is to use the wavelet transform for analysis of the pressure fluctuations occurred in the bottom-outlet of Kamal-Saleh Dam. The “Kamalsaleh Dam” is located on the “Tire River” in Iran, near the Arak city. The Bottom Outlet of the dam is equipped with service gate and emergency gate. A hydraulic model test is conducted to investigate the dynamic behavior of the service gate of the outlet. The results of the calculations based on the wavelet transform is then compared with those obtained using the traditional Fast Fourier Transform.

ABSTRACT This paper presents an analysis of flow parameters through a bottom outlet conduit with gated operation using physical and numerical models. A physical model of the regulating bottom outlet of Shahryar dam in Iran was used to investigate the hydraulic forces on the service radial gate and flow patterns within the conduit. The model was constructed from Plexiglas, and discharge and pressure data were recorded for different gate openings. The Froude law of similarity was satisfied in the hydraulic modelling, allowing for an investigation of the dynamic similarity of inertial and gravitational forces. The numerical scheme was based on using the natural-element method to study hydraulic forces and flow parameters within the conduit and the finite-element method to evaluate the natural frequencies of the radial gate. The results of the calculations for different radial gate openings showed good agreement with those from physical modelling for the pressure distributions throughout the flow domain and on the gate.

The boundary stabilization of a coupled fluid-structure system consisting of a vibrating parachute dam in contact with a fluid is studied in this paper. The parachute dam dynamics is presented by nonlinear partial differential equations. The fluid is assumed to be Newtonian, barotropic, and compressible. For the stability analysis of the coupled system, the boundary control method is used; a boundary feedback is constructed to stabilize the vibrations of the dam and the fluid simultaneously. The control force consists of the feedback from dam tension at its end. Moreover, the exponential stabilization of the parachute dam is achieved using a Lyapunov functional and boundary feedback.

The boundary stabilization of a coupled fluid-structure system consisting of a vibrating parachute dam in contact with a fluid is studied in this paper. The parachute dam dynamics is presented by nonlinear partial differential equations. The fluid is assumed to be Newtonian, barotropic, and compressible. For the stability analysis of the coupled system, the boundary control method is used; a boundary feedback is constructed to stabilize the vibrations of the dam and the fluid simultaneously. The control force consists of the feedback from dam tension at its end. Moreover, the exponential stabilization of the parachute dam is achieved using a Lyapunov functional and boundary feedback.

An analytical method is developed to consider the free vibration of an elastic bottom plate of a partially fluid-filled cylindrical rigid container with an internal body. The internal body is a rigid cylindrical block that is concentrically and partially submerged inside the container. The developed method captured the analytical features of the velocity potential in a non-convex, continuous, and simply connected fluid domain including the interaction between the fluid and the structure. The interaction between the fluid and the bottom plate is included. The Galerkin method is used for matching the velocity potentials appropriate to two distinct fluid regions across the common horizontal boundary (artificial horizontal boundary). Then, the Rayleigh–Ritz method is also used to calculate the natural frequencies and modes of the bottom plate of the container. The results obtained for the problem without internal body are in close agreement with both experimental and numerical results a...

This paper presents a methodology for solving shape optimization problems where the unknown is the shape of the problem domain. The proposed algorithm is based on minimization of the stress along the design boundary calculated by the Modiied Fixed Grid Finite Element Method (MFGFEM). Using MFGFEM eliminates mesh adaptation and re-meshing processes, as needed in the standard nite element method, and reduces the analysis cost signiicantly. In this study, a new approach for computing the stiiness matrix of boundary intersecting elements is also presented and the optimal shape of the problem domain is obtained via a simple optimization algorithm. The performance of the proposed approach is investigated for shape optimization problems. It is concluded that the results of the present method are in good agreement with other analytical and nite element solutions.

Particle Swarm Optimization (PSO) is a stochastic population based optimization algorithm which has attracted attentions of many researchers. This method has great potentials to be applied to many optimization problems. Despite its robustness the standard version of PSO has some drawbacks that may reduce its performance in optimization of complex structures such as laminated composites. In this paper by suggesting a new variation scheme for acceleration parameters and inertial weight factors of PSO a novel optimization algorithm is developed to enhance the basic version's performance in optimization of laminated composite structures. To verify the performance of the new proposed method, it is applied in two multi-objective design optimization problems of laminated cylindrical. The numerical results from the proposed method are compared with those from two other conventional versions of PSO-based algorithms. The convergancy of the new algorithms is also compared with the other tw...

ABSTRACT Remediation of contaminated sites requires an optimal decision making system to develop remediation techniques in a cost-effective and efficient manner. A coupled simulation-optimization solution approach, based on the finite element method (FEM) and a modified firefly algorithm (MFA), is developed in this study for optimal contaminated groundwater remediation design. A new modified firefly optimization algorithm is proposed by modifying the traditional firefly algorithm in three ways: (i) adding memory, (ii) preventing premature convergence to local optima and thus accelerating the optimization process, and (iii) proposing a new updating formula. Modifications performed in the present study improved the applicability and efficiency of the traditional metaheuristic firefly optimization algorithm, and led the MFA to outperform both its predecessor and conventional optimization methods (e.g., genetic algorithm). A hypothetical, unconfined contaminated field is considered and remediated by considering pump and treat and flushing methods. Pumping rates are considered as design variables while the number of pumps and pump locations, as well as the pumping period, are initially assumed. The coupled simulation-optimization model (FEM-MFA) proposed in this study constitutes an effective way to determine an optimal remediation design for a contaminated aquifer. The results of the present investigation will contribute to improve groundwater management in contaminated aquifers.

ABSTRACT Introducing carbon nanotubes (CNTs) into a polymer matrix can significantly improve the mechanical properties of nanocomposites. However regarding current processing techniques, there are several factors influencing the effective properties of carbon nanotube reinforced composites. Among these important factors, the interface, waviness, agglomeration, orientation and length of the nanotube are key parameters affecting the mechanical properties of nanocomposites. The effects of carbon nanotube length, waviness, agglomeration and distribution on the vibration behavior of functionally graded nanocomposite beams reinforced by single-walled carbon nanotubes (SWCNTs) are investigated in the present study. Monte-Carlo simulation is used to determine the effective elastic properties of wavy CNTs and a two-scale micromechanical model is developed to calculate the elastic properties of nanocomposites. The large scale model includes the CNT-free matrix and the clustered CNT/matrix inclusions. The small scale model addresses the property of the clustered inclusions containing the randomly oriented, transversely isotropic CNTs and matrix. Timoshenko beam theory is adopted to derive the governing equations and the finite element method is employed to discretize the model and obtain the numerical solution. The results show that the above mentioned parameters of nanotubes have significant effects on the vibrational behavior of functionally graded nanocomposite beams.

The heart rate signal contains information about the condition of the heart [1]. One of the features which information can be obtained from the heart rate signal is its chaotic behavior and it may be useful in disease diagnosis of the heart. It is known that a healthy heart, like many ...

Microtubules in mammalian cells are cylindrical protein polymers which structurally and dynamically organize functional activities in living cells. They are important for maintaining cell structures, providing platforms for intracellular transport, and forming the spindle during mitosis, as well as other cellular processes. Various in vitro studies have shown that microtubules react to applied mechanical loading and physical environment. To investigate the mechanisms underlying such phenomena, a mathematical model based on the orthotropic higher-order shear deformation shell formulation and Hamilton's principle is presented in this paper for dynamic behavior of microtubules. The numerical results obtained by the proposed shell model are verified by the experimental data from the literature, showing great consistency. The nonlocal elasticity theory is also utilized to describe the nano-scale effects of the microtubule structure. The wave propagation and vibration characteristics of the microtubule are examined in the presence and absence of the cytosol employing proposed formulations. The effects of different system parameters such as length, small scale parameter, and cytosol viscosity on vibrational behavior of a microtubule are elucidated. The definitions of critical length and critical viscosity are introduced and the results obtained using the higher order shell model are compared with those obtained employing a first-order shear deformation theory. This comparison shows that the small scale effects become important for higher values of the wave vector and the proposed model gives more accurate results for both small and large values of wave vectors. Moreover, it is shown that for higher circumferential wave number, the torsional wave velocity obtained by the higher-order shell model tend to be higher than the one predicted by the first-order shell model.

The Editor-in-Chief, Mehdi Ahmadian, and Associate Editors of Shock and Vibration journal extend their sincerest gratitude to the reviewers who have assisted with one or more papers during 1 November 2011 to 1 November 2012. We look forward to your continued contributions in the coming year. ... Shehata Abdel Raheem Adel Abdel-Wahab Mohammadhassan Abdollahi Sofla Maher Adam HJ Ahn Patricia Alexandrino Arzhang Alimoradi Reza Ansari Jerome Antoni Yoshikazu Araki Aurelio Araujo Kutluk Arikan Mark Arndt Jacques-André Astolfi Jan Awrejcewicz ...

Purpose – This paper seeks to extend the application of the natural neighbour Galerkin method to vibration analysis of fluid-structure interaction problems. Design/methodology/approach – The natural element method (NEM) which is a meshless technique is used to simulate the vibration analysis of the fluid-structure interaction systems. The method uses the natural neighbour interpolation for the construction of test and trial

ABSTRACT In this work, the numerical simulation of 2-D heat transfer problem is studied by using a meshfree method. The method is based on the local weak form collocation and the meshfree weak-strong (MWS) form. The goal of the paper is to find the temperature distribution in a rectangular plate. The results obtained are compared by those obtained by use of other numerical methods. Two types of boundary conditions are considered in this paper: Dirichlet and Neumann types. The Local Radial Point Interpolation Method (LRPIM) is used as the meshfree method. It is shown that the essential boundary conditions can be easily enforced as in the Finite Element Method (FEM), since the radial point interpolation shape functions posses the Kronecker delta property. It is also shown that the natural (derivative) boundary conditions can be satisfied by using the MWS method and no additional equation or treatment are needed. The MWS method as presented in this paper works well with local quadrature cells for nodes on the natural boundary and can be generated without any difficulty.

ABSTRACT The mechanical behavior of a eukaryotic cell is mainly determined by its cytoskeleton. Microtubules immersed in cytosol are a central part of the cytoskeleton. Cytosol is the viscous fluid in living cells. The microtubules permanently oscillate in the cytosol. In this study, two-dimensional vibration of a single microtubule in living cell is investigated. The Donnell’s shell theory equations for orthotropic materials is used to model the microtubule whereas the motion of the cytosol is modeled as Stokes flow characterized by a small Reynolds number with no-slip condition at microtubule-cytosol interface. The stress field in the cytosol induced by vibrating microtubule is determined analytically and the coupled vibrations of the microtubule-cytoplasm system are investigated. A coupled polynomial eigenvalue problem is developed in the present study and the variations of eigenvalues of coupled system with cytosol dynamic viscosity, microtubule circumferential Young’s modulus and circumferential wave number are examined.

ABSTRACT Micropolar theory constitutes extension of the classical field theories. It is based on the idea that every particles of the material can make both micro rotation and volumetric micro elongation in addition to the bulk deformation. Since this theory includes the effects of micro structure which could affect the overall behaviour of the medium, it reflects the physical realities much better than the classical theory for the engineering materials. In the micropolar theory, the material points are considered to possess orientations. A material point carrying three rigid directors introduces one extra degree of freedom over the classical theory. This is because in micropolar continuum, a point is endowed with three rigid directors only. A material point is then equipped with the degrees of freedom for rigid rotations, in addition to the classical translational degrees of freedom. In fact, the micropolar covers the results of the classical continuum mechanics. The micropolar theory recently takes attentions in fluid mechanics and mathematicians and engineers are implementing this theory in various theoretical and practical applications. In this paper the fluid-structure analysis of a vibrating micropolar plate in contact with a fluid is considered. The fluid is contained in a cube which all faces except for one of the lateral faces are rigid. The only non-rigid lateral face is made of a flexible micropolar plate and therefore, interacts with the fluid. An analytical approach is utilized to investigate the vibration characteristics of the aforementioned fluid-structure problem. The fluid is non-viscous and incompressible. Duplicate Chebyshev series, multiplied by boundary functions are used as admissible functions and the frequency equations of the micropolar plate are obtained by the use of Chebyshev-Ritz method. Also the vibration analysis of the plates modeled by micropolar theory has been done. This analysis shows that some additional frequencies due to the micropolarity of the plate appears among the values of the frequencies obtained in the classical theory of elasticity, as expected. These new frequencies are called micro-rotational waves. We also observed that when the micropolar material constants vanish, these additional frequencies disappear and only the classical frequencies remain. Specially, we observed that these additional frequencies are more sensitive to the change of the micro elastic constants than the classical frequencies. The frequencies and mode shapes of the coupled fluid structure interaction problem are obtained in the present study based on the micropolar and classical modeling. The numerical results for the problem are compared with those obtained by the analytical method for their differences and to confirm the proposed method. The microrotatinal wave frequencies and mode shapes are also developed. The results show that the natural frequencies and mode shapes for the transverse vibrations of the problem are in good agreement with the classical one and our knowledge from the physical nature of the problem.

Microtubules are key components of the cytoskeleton and perform a variety of functions, including chromosome movement during cell division, intracellular transport of materials, movement of organelles and intracellular tracking. A combination of essential and up-to-date methods is needed for investigating the biology of microtubules and understanding the mechanisms of microtubule-drug interaction. Coupled cytosol-microtubule mechanical vibrations of microtubules are studied in this article. Such investigations provide helpful insights on the functional mechanisms of microtubules and their interactions with other proteins and drugs. The viscous cytosol and the microtubule are coupled through the continuity condition across the microtubule-cytosol interface. The stress field in the cytosol induced by vibrating microtubule is analytically determined and the coupled circumferential vibrations of the cytosol-microtubule system are investigated by developing a coupled polynomial eigenvalue problem. Finally, the variations of vibration frequencies of a coupled system with cytosol dynamic viscosity, and microtubule circumferential Young's modulus are examined. Furthermore, the validity of the present analysis is confirmed by comparing the results with those obtained from the literature.

ABSTRACT A numerical procedure is proposed in this paper to study the response of an inclined beam subjected to sprung mass. The first-order shear deformation theory (FSDT) including rotary inertia is assumed for the beam element. The effects of inertial force as well as Coriolis and centrifugal forces induced by the moving sprung mass are considered in governing equations. The Newmark time integration method is adopted in solving equations. In this paper, the horizontal and vertical deformations of the beam, along with the Coriolis force and the inclined angle are investigated. The moving system is considered as a one degree of freedom system including two masses located at the ends of the moving load system, one spring and viscous damping. The effects of spring constant and damper ratio on the dynamic magnification factor (DMF) of the inclined beam are also studied. The results obtained from the present study show that the Coriolis force in lower speed has significant influence on the dynamic response of the beam.