385 research outputs found
Coupled adjoint aerostructural wing optimization using quasi-three-dimensional aerodynamic analysis
No full textThis paper presents a method for wing aerostructural analysis and optimization, which needs much lower computational costs, while computes the wing drag and structural deformation with a level of accuracy comparable to the higher fidelity CFD and FEM tools. A quasi-threedimensional aerodynamic solver is developed and connected to a finite beam element model for wing aerostructural optimization. In a quasi-three-dimensional approach an inviscid incompressible vortex lattice method is coupled with a viscous compressible airfoil analysis code for drag prediction of a three dimensional wing. The accuracy of the proposed method for wing drag prediction is validated by comparing its results with the results of a higher fidelity CFD analysis. The wing structural deformation as well as the stress distribution in the wingbox structure is computed using a finite beam element model. The Newton method is used to solve the coupled system. The sensitivities of the outputs, for example the wing drag, with respect to the inputs, for example the wing geometry, is computed by a Ali Elham [email protected] Michel J. L. van Tooren [email protected] 1 Faculty of Aerospace Engineering, Delft University of Technology, Delft, Netherlands 2 McNair Center for Aerospace Research and Innovation, University of South Carolina, Columbia, South Carolina, USA combined use of the coupled adjoint method, automatic differentiation and the chain rule of differentiation. A gradient based optimization is performed using the proposed tool for minimizing the fuel weight of an A320 class aircraft. The optimization resulted in more than 10 % reduction in the aircraft fuel weight by optimizing the wing planfor
Advanced Directives in Older Adults with Dementia: Ethical Challenges and Advocacy Role of Nurses
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Corresponding Author: Elham Navab
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Long-Range Surface Plasmon Polariton Active Structures Based on Optically-Pumped Dye-Doped Polymer Gain Media
No full textSolid state organic gain medium using optically-pumped dye molecules doped in a polymer host is considered as the top cladding of a long-range surface plasmon polariton (LRSPP) structure to enable active plasmonic devices with interesting applications operating in the near-infrared.The gain media is a thin film of PMMA (poly (methyl methacrylate)) doped with ~ 0.9 wt% organic dye molecules of IR-140 and is pump optically using 8 nsec laser pulses at 810 nm to enable stimulated emission by excited dye molecules to the LRSPP mode at ~ 880 nm.The gain media was modeled through rate equations for a four-level energy system, relating the small signal gain coefficient to the dye photo-physical parameters, dye concentration and pump irradiance. Distributed Bragg reflector (DBR) and distributed feedback (DFB) lasers were proposed using Bragg reflectors based on modulation of the metal stripe width, forming a stepped-in-width Bragg grating in the LRSPP waveguide. Single mode surface plasmon DFB and DBR lasers were designed at 882 nm, by applying coupled-mode theory and transfer matrix method (TMM).The IR-140 doped PMMA gain medium was experimentally characterized. The maximum available material gain was identified for various pump intensities and two possible pump polarization in the gain media using the variable stripe length (VSL) method. The maximum available material gain agreed well with the theoretical gain modeling performed previously.The DFB lasers and passive Bragg gratings were fabricated in the microfabrication laboratories at Center for Research in Photonics in University of Ottawa. Main fabrication processes included electron beam lithography to create stepped-in-width Bragg grating patterns with sharp corners and edges, with features as small as 150 nm.Passive Bragg gratings were successfully characterized by my colleague showing a clear dip in the transmittance spectra (~ 40%) at the designed Bragg wavelength 882 nm.DFB lasers were characterized and successfully demonstrated a highly narrowed (FWHM ~ 0.2 nm) single mode lasing peak at 882 nm. The mode profile from the DFBs’ output facet was captured by an infrared camera showing a tiny bright spot surrounded with dim spontaneous emission
Multi-fidelity wing aerostructural optimization using a trust region filter-SQP algorithm
No full textA trust region filter-SQP method is used for wing multi-fidelity aerostructural optimization. Filter method eliminates the need for a penalty function, and subsequently a penalty parameter. Besides, it can easily be modified to be used for multi-fidelity optimization. A low fidelity aerostructural analysis tool is presented, that computes the drag, weight and structural deformation of lifting surfaces as well as their sensitivities with respect to the design variables using analytical methods. That tool is used for a mono-fidelity wing aerostructral optimization using a trust region filter-SQP method. In addition to that, a multi-fidelity aerostructural optimization has been performed, using a higher fidelity CFD code to calibrate the results of the lower fidelity model. In that case, the lower fidelity tool is used to compute the objective function, constraints and their derivatives to construct the quadratic programming subproblem. The high fidelity model is used to compute the objective function and the constraints used to generate the filter. The results of the high fidelity analysis are also used to calibrate the results of the lower fidelity tool during the optimization. This method is applied to optimize the wing of an A320 like aircraft for minimum fuel burn. The results showed about 9 % reduction in the aircraft mission fuel burn
Trajectory driven multidisciplinary design optimization of a sub-orbital spaceplane using non-stationary Gaussian process
No full textThis paper presents the multidisciplinary optimization of an aircraft carried sub-orbital spaceplane. The optimization process focused on three disciplines: the aerodynamics, the structure and the trajectory. The optimization of the spaceplane geometry was coupled with the optimization of its trajectory. The structural weight was estimated using empirical formulas. The trajectory was optimized using a pseudo-spectral approach with an automated mesh refinement that allowed for increasing the sparsity of the Jacobian of the constraints. The aerodynamics of the spaceplane was computed using an Euler code and the results were used to create a surrogate model based on a non-stationary Gaussian process procedure that was specially developed for this study.Aerodynamics, Wind Energy & PropulsionAerospace Engineerin
CIM a current inverting metamutator and its application to universal filters among others
No full textMinayi, Elham (Dogus Author) -- Conference full title: 2017 40th International Conference on Telecommunications and Signal Processing (TSP); Barcelona; Spain; 5 July 2017 through 7 July 2017.A new kind of metamutator namely “Current Inverting Metamutator,” its realizations using different types of active blocks and some of its applications are given in this paper. As a classical application of the metamutator simulation of a memristor and, as an original application, several schemes realizing universal filters are proposed. The post-layout characteristics of both applications, using TSMC 0.13 μm process parameters with ±0.75 V power supply voltage, are presented to confirm the theoretical analysis
A rectifier circuit using add-differentiate IC with a minimal number of CMOS transistors
No full textMinayi, Elham (Dogus Author) -- Conference full title: 25th IEEE International Conference on Electronics Circuits and Systems, ICECS 2018; Bordeaux; France; 9 December 2018 through 12 December 2018.Using the recently developed Add-Differentiate 5-terminal Integrated Circuit, AD-IC (which possess 12 CMOS transistors only), augmented with two diodes, a new rectifier configuration is presented. Transistor level circuit and its layout are provided and the rectifier is simulated with parameters extracted from the layout showing very good conformity with desired rectifier behavior. Finally, a table of comparison of the proposed rectifier with fourteen others, existing in the literature, is included to conclude the paper
ATLAS pixel cluster splitting using Mixture Density Networks
No full textThe high energy and luminosity of the LHC allows to study jets and hadronically decaying tau leptons at extreme energies with the ATLAS tracking detector. These topologies lead to charged particles with an angular separation smaller than the size of the ATLAS Inner Detector sensitive elements and consequently to a reduced track reconstruction efficiency. In order to regain part of the track reconstruction efficiency loss, a neural network (NN) based approach was adopted in the ATLAS pixel detector in 2011 for estimating particle hit multiplicity, hit positions and associated uncertainties. Currently used algorithms in ATLAS will be briefly summarized. An alternative algorithm based on Mixture Density Network (MDN) is currently being studied and the initial performance is promising. As MDN can provide an estimate of position and uncertainty at the same time, the execution can be faster compared to current ATLAS NNs. Overview of MDN algorithm and its performance will be highlighted in the poster. At the same time comparison will be made with the currently used NNs in ATLAS tracking
Aerodynamic Shape Optimization Using Symbolic Sensitivity Analysis
No full textThe least-squares finite element method is used to solve the compressible Euler equations around airfoils in transonic regime. The symbolic analysis method is used to generate the element stiffness and force matrices. The equations of the element matrices are derived symbolically based on the flow primitive variables and the position of the element nodes. The symbolic analysis is also used to compute the exact derivatives of the residuals with respect to both design variables (e.g. the airfoil geometry) and the state variables (e.g. the flow velocity). The symbolic analysis allows to compute the exact Jacobian of the governing equations in a computationally efficient way, which is used for Newton iteration. Besides, using the symbolic analysis the sensitivities of the outputs, such as the airfoil drag, with respect to the design variables, such as the airfoil geometry, are computed using the discrete adjoint method without the need for automatic differentiation. This makes the analysis and optimization computationally more efficient
Toward Wing Aerostructural Optimization Using Simultaneous Analysis and Design Strategy
No full textThe application and computational efficiency of wing aerostructural optimization us- ing simultaneous analysis and design (SAND) strategy is investigated. A coupled adjoint aerostructural analysis method based on quasi-three-dimensional aerodynamic analysis is used for this research. Two different optimization problems are tested. In the first case a wing aeroelastic optimization is performed using both nested analysis and design (NAND) and SAND strategies. In this optimization the wing box structure is optimized to achieve minimum wing weight. In the second optimization the wing structure as well as the outer aerodynamic shape are optimized to achieve minimum aircraft fuel weight. The results of both SAND and NAND optimizations have been compared based on accuracy and compu- tational cos
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