Sharif Digital Repository

A general three-dimensional aeroelastic solver is developed based on coupled finite element and boundary element methods and applied to investigate the flutter boundaries in supersonic flows. The boundary element method is applied to three-dimensional unsteady supersonic potential flow as the aerodynamic model and coupled with the finite element method for structural modelling, in order to construct the system of aeroelastic equations. The aeroelastic equations are solved for the flutter prediction using the frequency domain approach. Flutter boundaries for two types of wing planforms at supersonic speeds are determined and compared with the existing experimental results and previous... 

This study presents the application of the Proposed Modified Reduced-Order Aerodynamics Modelling approach for aeroelastic analysis based on the boundary element method (BEM) as a novel approach. The used BEM has the capability to capture the thickness effect and geometric complexity of a general three-dimensional model. In this approach the reduced-order aerodynamic model is defined through the eigenvalue problem of unsteady flow based on the unknown wake singularities. Based on the used aerodynamic model an explicit algebraic form of the aeroelastic equations is derived that reduces computational efforts and complexity. This special feature enables us to determine the aeroelastic... 

This paper presents a coupled flap-lag-torsion aeroelastic stability analysis and response of a hingeless helicopter blade in the hovering flight condition. The boundary element method based on the wake eigenvalues is used for the prediction of unsteady airloads of the rotor blade. The aeroelastic equations of motion of the rotor blade are derived by Galerkin's method. To obtain the aeroelastic stability and response, the governing nonlinear equations of motion are linearized about the nonlinear steady equilibrium positions using small perturbation theory. The equilibrium deflections are calculated through the iterative Newton-Raphson method. Numerical results comprising steady equilibrium... 

This paper presents an efficient reduced-order modelling approach based on the boundary element method. In this approach, the eigenvalue problem of the unsteady flows is defined based on the unknown wake singularities. By constructing this reduced-order model, the body quasi-static eigenmodes are removed from the eigensystem and it is possible to obtain satisfactory results without using the static correction technique when enough eigenmodes are used. In addition to the conventional method, eigenanalysis and reduced-order modelling of unsteady flows over a NACA 0012 airfoil, a wing with NACA 0012 section and a wing-body combination are performed using the proposed reduced order modelling... 

A new reduced-order modeling approach is presented. This approach is based on fluid eigenmodes and without using the static correction. The vortex lattice method is used to analyze unsteady flows over two-dimensional airfoils and three-dimensional wings. Eigenanalysis and reduced-order modeling are performed using a conventional method with and without the static correction technique. In addition to the conventional method, eigenanalysis and reduced-order modeling are also performed using the new proposed method, that is, without static correction requirement. Numerical examples are presented to demonstrate the accuracy and computational efficiency of the proposed method. Based on the... 

This paper presents a new reduced-order modeling approach based on boundary element method. In this approach the eigenvalue problem of the unsteady flows is defined based on the unknown wake singularities. By constructing this reduced-order model, the body quasi-static eigenmodes are removed from the eigensystem and it is possible to obtain satisfactory results without static correction technique when enough eigenmodes are used. In addition to the conventional method, Eigenanalysis and reduced-order modeling of unsteady flows over a NACA 0012 airfoil and a wing with NACA 0012 section are performed using this new ROM method. Numerical examples are presented that demonstrate the accuracy and... 

Simulation is the gold standard for training in aviation and trauma medicine. Now it is available for diseases diagnosis and treatment. With simulation, clinicians can practice their art in a realistic, consequence free environment, combining both theory and practice in a comprehensive program. Method and materials - In the virtual clinical environment of "VPsoft mentor" software, the practitioner reviews a patient's history, orders laboratory tests and procedures, interprets findings, renders diagnoses, and prescribes medication. Every diagnostic or treatment decision the clinician makes for the patient is analyzed by E-mentor, providing instant feedback.Results - This software have been... 

The use of Computer Science in order to categorize and store information, improve diagnostic and therapeutic procedures, patient education and the training of a skilled labor force, has taken important steps and there are constantly new developments in this area  

Determining the time of breakthrough of injected water is important when assessing waterflood in an oil reservoir. Breakthrough time distribution for a passive tracer (for example water) in percolation porous media (near the percolation threshold) gives insights into the dynamic behavior of flow in geometrically complex systems. However, the application of such distribution to realistic two-phase displacements can be done based on scaling of all parameters. Here, we propose two new approaches for scaling of breakthrough time (characteristic times) in two-dimensional flow through percolation porous media. The first is based on the flow geometry, and the second uses the flow parameters of a... 

Font recognition is one of the pre-processing steps in optical character recognition (OCR) systems that affects on their performance. In this paper two methods are proposed for Persian font recognition. In the first method, Gabor filter is used for feature extraction from the images, then principle component analysis (PCA) applied to reduce feature dimensions and finally, a multi-layer Perceptron (MLP) neural network is used for the classification. In the second techniques, random forest is utilized for recognizing fonts. For evaluation, a dataset includes 10 popular Persian fonts is used. The proposed Gabor-PCA-MLP method has achieved 98.70% of F-measure, and random forest resulted in of... 

This study is undertaken to evaluate the potential of a commercial molecular sieve to remove diverse sulfur compounds from condensate with high aromatic on an industrial scale. For the first part of this study, the adsorbent is characterized in detail using inductively coupled plasma optical emission spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, and Brunauer-Emmett-Teller analysis. For the second part, dynamic breakthrough experiments on an industrial scale are performed to assess the dynamic adsorption performance of a commercial molecular sieve. Dynamic experiments show that the adsorbent effectively removes the sulfur compound from condensate that has... 

Effect of alkaline metal salts on the solvent extraction of platinum from leached spent dehydrogenation catalysts (Pt/Al2O3) in aqua-regia by the Trioctylphosphine oxide (TOPO) has been investigated. Best salting out effect was achieved using KCl as the additive salt in which process upto 90% of Platinum extraction achieved. Response Surface methodology utilized in order to design the experiments, model the extraction process for platinum and aluminum as well as; optimize the whole process. It was shown that solvent extraction of platinum by TOPO was kinetically fast and the needed equilibrium time for it was less than 30 seconds. In the present study, proposed models for platinum and... 

This paper presents several efficient architectures of dynamic/static edge-triggered flip-flops with a compact embedded logic. The proposed structure, which benefits from the overlap period, fixes most of the drawbacks of the dynamic logic family. The design issues of setting the appropriate overlap period for this architecture are explained. The proposed overlap-based approach is compared with several state-of-the-art dynamic/static logic styles in implementing a 4-bit shift register and an odd-even sort coprocessor using different CMOS technologies. The simulation results showed that the overlap-based logic cells become much more efficient when the complexity of their embedded logic... 

In this research, data on liquid-liquid extraction of platinum from commercial spent catalysts by trioctylphosphine oxide (TOPO) in toluene were experimentally obtained. Alkaline metal salts were used to optimize the separation process. Best Salting-out effect was obtained by KCl which extracted up to 90% of platinum utilizing TOPO. Furthermore, extraction percentages of Pt and Al depending upon different factors were investigated. It was observed that the extraction process was kinetically fast and achieving the equilibrium time took less than 30 seconds. Optimized points obtained utilizing response surface methodology (RSM) by the "Design Expert" software in order to minimize the... 

Design and manufacturing of a high performance micro-hydro-kinetic turbine is discussed in the present paper. The main goal is manufacturing an equipped experimental model of hydro-kinetic turbine with highest energy absorption from water current. A multi-shape ducted turbine comprised of a multi-part diffuser was manufactured that can be converted to many experimental models for studying various diffuser enhancing effects. Turbine's rotor included a three-blade axial propeller and a mixed six-blade propeller with high power coefficient. Simple experiments on propeller were performed for flow visualization, torque measurement and illustrating dynamic balance at high speed rotation in air and... 

We show that a metal-organic framework (MOF) sustained by a nanosized Ag12 cuboctahedral node can be applied to selectively extract traces of lead(II) ion from environmental water samples. The MOF was characterized by thermogravimetric and differential thermal analysis, scanning electron microscopy, FTIR, and X-ray diffraction. The effects of pH value, flow rates, of type, concentration and volume of the eluent, of break-through volume and potentially interfering ions on the separation and determination of lead were evaluated. Following desorption with EDTA, Pb(II) was quantified by FAAS. The use of the MOF results in excellent analytical figures of merit including an analytical range from 2... 

In this paper, first, two new criteria, which are titled social welfare percent (SWP) and congestion cost percent (CCP), are defined for static transmission expansion planning in restructured power systems. Then by a simple example it will be shown that none of the already presented market-based criteria could completely and truly evaluate the transmission network expansion from market view. Hence the SWP and CCP criteria altogether are proposed to completely and truly evaluate the transmission network expansion. Then a least-investment cost expansion plan is searched that its SWP and CCP are in predefined acceptable limits. The results of applying of the proposed method are illustrated over... 

In this paper, first, two new criteria, which are titled social welfare percent (SWP) and congestion cost percent (CCP), are defined for static transmission expansion planning in restructured power systems. Then by a simple example it will be shown that none of the already presented market-based criteria could completely and truly evaluate the transmission network expansion from market view. Hence the SWP and CCP criteria altogether are proposed to completely and truly evaluate the transmission network expansion. Then a least-investment cost expansion plan is searched that its SWP and CCP are in predefined acceptable limits. The results of applying of the proposed method are illustrated over... 

Asphalt concrete is a complex mixture, the behavior of which is dependent on its components while showing different nonlinear behaviors under various conditions. Application of rest time between compressive loading cycles causes hardening-relaxation (H-R) behavior in the sample and increases the deformation potential of the sample. This process might induce changes in the microstructure and the pattern of the placement and rotation of the aggregates. These changes cause a relaxation in the hardening of the material, pose a higher potential of reception of viscoplastic strain in the following cycles, and increase the rate of accumulation of the permanent deformation in contrast with creep...