Farhang Daneshmand

Optimal groundwater remediation design of pump and treat systems via a simulation-optimization approach and firefly algorithm

In the present study, an optimization approach based on the firefly algorithm (FA) is combined with a finite element simulation method (FEM) to determine the optimum design of pump and treat remediation systems. Three multi-objective functions in which pumping rate and clean-up time are design variables are considered and the proposed FA-FEM model is used to minimize operating costs, total pumping volumes and total pumping rates in three scenarios while meeting water quality requirements. The groundwater lift and contaminant concentration are also minimized through the optimization process. The obtained results show the applicability of the FA in conjunction with the FEM for the optimal design of groundwater remediation systems. The performance of the FA is also compared with the genetic algorithm (GA) and the FA is found to have a better convergence rate than the GA.

Wave propagation in protein microtubules modeled as orthotropic elastic shells including transverse shear deformations

Wave propagation along the microtubules is one of the issues of major concern in various microtubule cellular functions. In this study, the general wave propagation behavior in protein microtubules is investigated based on a first-order shear deformation shell theory for orthotropic materials, with particular emphasis on the role of strongly anisotropic elastic properties of microtubules. According to experimental observation, the first-order shear deformation theory is used for the modeling of microtubule walls. A general displacement representation is introduced and a type of coupled polynomial eigenvalue problem is developed. Numerical examples describe the effects of shear deformation and rotary inertia on wave velocities in orthotropic microtubules. Finally, the influences of the microtubule shear modulus, axial external force, effective thickness and material temperature dependency on wave velocities along the microtubule protofilaments, helical pathway and radial directions are elucidated. Most results presented in the present investigation have been absent from the literature for the wave propagation in microtubules.

Mitigating Socio-Economic-Environmental Impacts During Drought Periods by Optimizing the Conjunctive Management of Water Resources

Multi-period optimization of conjunctive water management can utilize reservoirs and aquifer carry-over to alleviate drought impacts. Stakeholders’ socio-economic and environmental indices can be used to minimize the socio-economic and environmental costs associated with water shortages in drought periods. The knowledge gap here is the evaluation and inclusion of the socio-economic and environmental value of conjunctive water management in terms of its drought mitigation capability. In this paper, an integrated water quantity-quality optimization model that considers socio-economic and environmental indices is developed. The model considers and integrates reservoir and aquifer carry-over, river-aquifer interaction and water quality with stakeholders’ socio-economic indices of production, net income and labor force employment to evaluate the socio-economic and environmental value of conjunctive water management. Total dissolved solid (TDS) is used as the water quality index for environmental assessments. The model is formulated as a multi-period nonlinear optimization model, with analysis determining the optimal decisions for reservoir release and withdrawal from the river and aquifer in different months to maximize the socio-economic indices of stakeholders within the environmental constraints. The proposed model is used in Zayandehrood water resource system in Iran, which suffers from water supply and pollution problems. Model analysis results show that conjunctive water use in the Zayandehrood water basin reduces salinity by 50 % in the wetland and keeps water supply reduction during a drought under 10 % of irrigation demand.

Hybrid sliding mode control of semi-active suspension systems

In order to design a controller which can take both ride comfort and road holding into consideration, a hybrid model reference sliding mode controller (HMRSMC) is proposed. The controller includes two separate model reference sliding mode controllers (MRSMC). One of the controllers is designed so as to force the plant to follow the ideal Sky-hook model and the other is to force the plant to follow the ideal Ground-hook model; then the outputs of these two controllers are linearly combined and applied to the plant as the input. Also, since the designed controller requires a knowledge of the terrain input, this input is approximated by the unsprung mass displacement. Finally, in the simulation section of this study, the effect of the relative ratio between the two MRSMCs and the knowledge of the terrain on the performance of the controller is numerically investigated for both steady-state and transient cases.

Combined strain-inertia gradient elasticity in free vibration shell analysis of single walled carbon nanotubes using shell theory

In this paper, a gradient elasticity shell formulation is presented for free vibration analysis of single-walled carbon nanotube placed on Winkler/Pasternak foundation. The proposed formulation is based on the combined strain-inertia gradient elasticity. The combined strain-inertia gradient elasticity provides an extension to the classical equations of elasticity with additional higher-order spatial derivatives of strains and two material length scale parameters related to the inertia and strain gradients, which enable formulation to investigate the size effect on the dynamic behavior of nanotubes. The effects of the length scale parameters, aspect ratio of single-walled carbon nanotube and foundation parameters on the fundamental frequencies for different values half-axial wave number and circumferential wave number are investigated. The natural frequencies obtained from the proposed shell formulation show the effects of size-dependent properties. It can be concluded that a continuum model enriched with higher-order inertia terms has been proposed as alternative to the continuum description obtained with classical elasticity theory.

A higher-order mathematical modeling for dynamic behavior of protein microtubule shell structures including shear deformation and small-scale effects

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 Hamiltons 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.

Inverse geometry heat conduction analysis of functionally graded materials using smoothed fixed grid finite elements

A shape identification scheme is developed in this article to determine the shape of the inaccessible parts of a two-dimensional object made of functionally graded material using the measured temperatures on its accessible parts. The proposed method is based on minimization of the differences between measured and calculated temperatures. The smoothed fixed grid finite element method which is a new approach based on the non-boundary-fitted meshes and the gradient smoothing technique are used for the solution of direct problem and shape sensitivity analysis. The boundary parameterization technique using splines is also adopted to manipulate the shape variations. The conjugate-gradient method is used as the optimization algorithm and some numerical examples are solved to evaluate the applicability of the proposed method in the context of functionally graded materials.

Cavity-Shape Identification with Convective Boundary Conditions Using Non-Boundary-Fitted Meshes

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 sensitivity analysis. In this method, the domain boundary can be moved independently from the mesh, and the solution of the variable-domain problems can be found easily. The domain parameterization technique using cubic splines is adopted to manipulate the shape variation of the cavity. The conjugate gradient method is used as the optimization algorithm. Some numerical examples are solved to evaluate the applicability of the proposed method in the solution of inverse-geometry problems. In the examples, the effects of mesh size, measurement errors, cavity-shape, cavity size, and the initial guess are examined.

Asymptotic stabilization of vibrating composite plates

This paper presents a solution to the boundary stabilization problem of free vibration of composite plates. It is assumed that an object such as a flange which has mass and mass moment of inertia can be attached to the free portion of the boundary of the plate. Both cases of with and without boundary object have been analyzed for other types of plates by many researches. In the presence of boundary mass and mass moment of inertia, two ordinary differential equations govern their motion. For both cases, the plate dynamics is presented by a linear fourth order partial differential equation (PDE). Linear boundary control laws are constructed to stabilize the composite plates asymptotically. The control forces and moments consist of feedbacks of the velocity and normal derivative of the velocity at the boundaries of the plate. Asymptotic stabilization of free vibration of composite plates in both cases (i.e. with and without boundary object) is achieved via boundary actions. Finally, it is shown that exponentially stability of the hybrid system cannot be fulfilled (in the other words the asymptotical stability is the best). Our main tools in this article are semigroup techniques, spectral theory of the linear operators and Lyapunov stability method.

Optimal Remediation Design of Unconfined Contaminated Aquifers Based on the Finite Element Method and a Modified Firefly Algorithm

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.