Aeroelastic tailoring and scaling using Bacterial Foraging Optimisation

Bacterial Foraging Optimisation (BFO) is investigated in an attempt to evaluate its use in solving complex optimisation problems for aeronautical structures. A hybrid variant of BFOA, which incorporates meta-modelling techniques, is also proposed and employed. The efficiency and effectiveness of the methods are tested for tailoring a rectangular composite wing, aiming to maximise the flutter speed and for scaling a joined-wing aircraft, targeting to match aeroelastic responses between the physical prototype and wind tunnel model. The obtained results are compared with those found using a range of other biologically inspired optimisation methods (GA, PSO, ACO), proving that the social foraging behavior of motile bacteria is an effective tool for aeroelastic optimisation.     

Aeroelastic tailoring using fiber orientation and topology optimization

This work presents a structural optimization aided design methodology for composite laminated plates subject to fluid-structure interaction. The goal of the optimization procedure is to increase the flutter speed onset through the maximization of natural frequencies related to the vibration modes involved in the phenomenon. The aeroelastic stability analysis is performed using ZAERO software system, which includes ZONA 6 unsteady lifting surface method. The finite element method is applied to solve the structural model equilibrium equations, the eigenvalues sensitivities with respect to design variables are calculated analytically, and sequential linear programming is applied. The maximization is accomplished using two methods; the first method uses an aeroelastic analysis to determine which eigenmode causes the flutter onset, and its eigenvalue is then maximized. In the second method, a forward finite difference method is applied and the flutter speed sensitivities with respect to the eigenvalues are calculated. This sensitivity is used to guide the optimization process. Finally, a topology optimization problem is formulated to reduce the plate mass under a minimum flutter velocity constraint, using density distribution as the design variable.     

Aeroelastic tailoring considering uncertainties in material properties

The robustness of aeroelastic design optimization with respect to uncertainties in material and structural properties is studied both numerically and experimentally. The model consists of thin orthotropic composite wings virtually without fuselage. Three different configurations with consistent geometry but varying orientation of the main stiffness axis of the material are investigated. The onset of aeroelastic instability, flutter, is predicted using finite element analysis and the doublet-lattice method for the unsteady aerodynamic forces. The numerical results are experimentally verified in a low-speed wind tunnel. The optimization problem is stated as to increase the critical air speed, above that of the bare wing by massbalancing. It is seen that the design goals are not met in the experiments due to uncertainties in the structural performance of the wings. The uncertainty in structural performance is quantified through numerous dynamic material tests. Once accounting for the uncertainties through a suggested reformulation of the optimization problem, the design goals are met also in practice. The investigation indicates that robust and reliable aeroelastic design optimization is achievable, but careful formulation of the optimization problem is essential.     

Maximization of buckling loads of composite panels using flexural lamination parameters

Unstiffened composite panels are optimized by using flexural lamination parameters as continuous design variables for the case in which the amounts of 0°, ±45°, and 90° plies are given. It is shown that for this case, the lamination parameters are located in a hexagonal domain. Continuous optimization is compared with genetic optimization for the stacking sequence that accounts for the discreteness of the design space and constraints on the number of contiguous plies of the same orientation. It is shown that only for very thin panels with low aspect ratios is there a significant difference between the continuous and discrete solutions.     

Optimum design of composite plate wings for aeroelastic characteristics using lamination parameters

The present paper treats the flutter and divergence characteristics of composite plate wings with various sweep angles. First, the effect of laminate configuration on the flutter and divergence characteristics is investigated for composite plate wings. To examine the effect of laminate configuration, the flutter and divergence characteristics are represented on the lamination parameter plane. Next, a minimum weight design of composite plate wings subjected to the constraints on the flutter and divergence speeds is conducted by using a genetic algorithm in which lamination parameters are used as design variables. The effectiveness of aeroelastic tailoring is demonstrated through the optimization results.     

Single-level composite wing optimization based on flexural lamination parameters

An optimization procedure based on flexural lamination parameters is used to integrate unstiffened composite panel design and wing structural design. The lamination parameters are constrained to a hexagonal domain when the amounts of 0°, ±45°, and 90° plies are given. The single-level optimization based on continuous flexural lamination parameters for the minimization of wing weight is compared with a two-level optimization using response surfaces of maximal buckling load for a simple wing box design example. Reasonable agreement between the two procedures indicates that the two-level approach leads to near-optimal designs.     

Optimization of coupled thermal-structural problems of laminated plates with lamination parameters

The behaviour of a laminated plate with given boundary temperatures and displacement constraints is optimized and the optimization problem is expressed in terms of lamination parameters. Because the thermal conductivity and structural properties of a laminate depend on the lamination parameters of the laminate, the analysis of the plate consists of solving a coupled-field problem. The strain energy, or certain displacements of the laminated plate due to given boundary temperatures and displacement boundary conditions, is optimized with respect to in-plane lamination parameters, and also buckling of the plate is considered. The buckling factors for thermal loading are expressed as a function of four in-plane and four bending lamination parameters, and the smallest factor is maximized with respect to these parameters. In addition to these thermal problems, the natural frequencies of the laminated plate are studied. Since transverse shear deformations are taken into account,the natural frequencies can be expressed as functions of two in-plane and four bending lamination parameters, with respect to which the lowest natural frequency of the plate is maximized. The lay-up for the laminate, corresponding to four optimal in-plane or bending lamination parameters, consists of three layers at most and can be determined using explicit equations. Explicit equations are derived for creating a lay-up having optimal bending lamination parameters. Received May 12, 1999     

Aeroelastic simulations using gridless boundary condition and small perturbation techniques

This paper examines the use of stationary Cartesian mesh for non-linear flutter computations involving complex geometries. The surface boundary conditions are implemented using reflected points which are determined via a gridless approach. The method uses a cloud of nodes in the vicinity of the surface to get a weighted-average of the flow properties using radial basis functions. To ensure computational efficiency and for local grid refinements, multigrid computations within an embedded grids framework are used. As the displacements of moving surfaces from their original position are typically small for flutter problems, a small perturbation boundary condition method is used to account for the moving surfaces. The method therefore does not require repeated grid re-generation for the deforming surfaces. The overall method is both accurate and robust. Computations of the well-known Onera M6 wing, RAE wing-body configuration, the AGARD 445.6 wing flutter test case show good accuracy and efficiencies. Simulations of the aeroelastic behavior of a complete fighter-type aircraft with wing tip missiles at high transonic speeds further demonstrate the practical usefulness of the present boundary conditions technique.     

Determining the real lay-up of a laminate corresponding to optimal lamination parameters by genetic search

A genetic algorithm search (GA) is employed for tailoring the thermomechanical properties of a laminated plate. Maximization of the strain energy, minimization of certain displacements and maximization of the first buckling factor due to given boundary temperatures and maximization of the lowest natural frequency of a graphite-epoxy plate with respect to the lay-up of the laminate are considered. Instead of computing these values during the GA iteration, lamination parameters giving the optima referred to above are employed in genetic searches. The fitness (objective) function consists of differences between target lamination parameters and lamination parameters of the current design, and thus no time-consuming global solution is needed. Two ways of coding the layers are applied: either orientations and relative thicknesses are coded separately, or commercial uni/multiaxial plies are coded. Received May 12, 1999?Communicated by J. Sobieski     

A semi-automated filtering technique for software process tailoring using neural network

It is widely known that implementation of the software development process to fit a given environment is the key to develop software at the lowest cost and highest quality. In general, applying an off-the-shelf software development process or an organizational process to a specific project can cause a lot of overhead if no effort is made to customize the given generic processes. Even though the process tailoring activities are done before starting a project, they are not given high importance. These activities depend on several process engineers who have a lot of experience and knowledge about process tailoring. Because of this dependence on human experience, it takes a long time to have a tailored process fit the project. To decide whether a specific task should be part of a given project or not is very time-consuming. Therefore, we suggest a semi-automated process tailoring method, which uses the artificial-neural network-based learning theory to reduce this time. We have demonstrated the effectiveness of our process filtering technique with a case study using process tailoring historical data as learning data.     

Low-stress fabrication of 3D polymer free standing structures using lamination of photosensitive films

Free-standing microstructures such as cantilevers, membranes or microchannels are building blocks of microfluidic systems and MEMS. As a complement to silicon, the large family of polymers offers many opportunities for micro and nanotechnologies. Their low temperature processing and the planarizing properties of many resists is a definitive advantage for system integration, paving the way to complete lab-on-chips. In this article, we investigate a fabrication process of polymeric free standing structures based on the lamination of SU-8, a thick epoxy photoresist. Our motivation is the hybrid integration of polymer microfluidic or MEMS components with silicon chips (e.g., integrated circuits or sensors). Compared to rigid substrates used in more conventional SU-8/SU-8 bonding process, the flexible photosensitive films used within this lamination technique allows a more homogeneous and reliable bonding at low pressure and temperature, and a 3D fabrication with an excellent level-to-level alignment. A parametric optimization of the lamination process is presented. The fabrication of a leakage-free 3D microfluidic network is demonstrated by stacking up to five layers. A polyethylene terephtalate layer has been employed to easily release the SU-8 devices. We show that this release layer also significantly decrease the curvature of the substrate by 32% and the related residual stress in a 100 μm SU-8 layer by at least 10%. Finally, we briefly describe the hybrid integration of a silicon sensor in a microfluidic network as a direct application of our lamination process to the fabrication of lab-on-chips.

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Aeroelastic applications of the Connection Machine

This paper describes the implementation of a dynamical systems approach to aeroelastic analysis using the Connection Machine model 2 (CM-2). Through numerical simulation, the regions of harmonic and chaotic behavior in the δ,R_x (velocity, in-plane load) plane have been examined in detail. These regions are of interest in evaluation of the fatigue life of fluttering plates. The CM-2 computer architecture allows the removal of many of the previous simplifying and limiting assumptions regarding the prediction of the stability regions maps. Owing to its high-speed prediction capability, the CM-2, with framebuffer, offers 'real-time' display of the solution as it evolves during the prediction process. This feature gives insight into the fundamental way in which the solution evolves. This is essential in defining the scenarios describing roads to chaotic behavior of the dissipative dynamical systems.     

Optimal tailoring of 2D volume-fraction distributions for heat-resisting functionally graded materials using FDM

Thermoelastic behavior of heat resisting functionally graded materials (FGMs), under given thermal loading and boundary conditions, is definitely characterized by the spatial distribution of volume fractions of constituent particles. Hence, the determination of volume-fraction distribution becomes a crucial step in tailoring an optimal heat-resisting FGM. In this paper, we address a two-dimensional volume-fraction optimization procedure for relaxing the effective thermal stress distribution. In order for the optimization efficiency and the volume-fraction continuity, we approximate the volume-fraction field with bilinear elements of n-times larger size than for the thermoelastic analysis. As well, the refined material-property estimate is employed to assure the design quality. Numerical experiments illustrating our theoretical work are also presented.     

基于服务模式规约的构件剪裁

构件剪裁是一种高效的提高构件可用性的方法,但是如何实施有效的构件剪裁一直是研究中的难点.对构件功能逻辑的准确理解有助于实施有效的构件剪裁.基于此,首先从构件提供者角度依据构件接口中方法间的关联性分析,给出了服务模式的概念和构件的服务模式规约.接着基于构件的服务模式规约,提供了一种便于使用者验证构件剪裁有效性的算法.最后结合详细的示例分析了算法的可行性.     

Mine detection using scattering parameters

The detection and disposal of antipersonnel land mines is one of the most difficult and intractable problems faced in ground conflict. This paper presents detection methods which use a separated-aperture microwave sensor and an artificial neural network pattern classifier. Several data-specific preprocessing methods are developed to enhance neural network learning. In addition, a generalized Karhunen-Loeve transform and the eigenspace separation transform are used to perform data reduction and reduce network complexity. Highly favorable results have been obtained using the above methods in conjunction with a feedforward neural network.     

Ontology tailoring in the Semantic Grid

This paper presents a Service Oriented Architecture (SOA) approach to a distributed framework for reusing, extracting and extending large domain ontologies in the Semantic Grid environment. The conceptual level of the framework describes how sub-ontologies are extracted and extended with new features, while the architectural level of the framework describes the components of the framework. These components allow the sub-ontology extraction and extension process to be performed using shared resources in the Semantic Grid environment. A prototype of the framework is built using Web Services and a complexity evaluation measure is presented. The results of several simulations show that the sub-ontology extraction and extension process in the Semantic Grid is a viable solution and can be optimized by using better quality, initial labeling set.     

On the modelling of time-interleaved sequential lamination micromixers

We develop a novel and simple theoretical model of time-interleaved sequential lamination micromixers that improves the model proposed by Nguyen and coworkers (Microfluid Nanofluid 1:373–375, 2005a, Lab Chip 5:1320–1326, b, J Phys Conf Ser 34:136–141, 2006) based on the Taylor–Aris dispersion theory. The Nguyen model takes into account the non uniform structure of the velocity profile through an effective dispersion coefficient. However, it is essentially a one-dimensional model that is not suitable to describe (i) neither the behavior of mixing occurring at short length-scales, and characterized by the growth of a mixing boundary layer near the channel walls, (ii) nor the exponential decay of the concentration field occurring at larger length-scales. The model we propose, which is based upon the theory of imaginary potential developed by Giona et?al. (J Fluid Mech 513:221–237, 2004, Europhys Lett 83:34001, 2008, J Fluid Mech 639:291–341, 2009a), is able to provide quantitative predictions on the evolution of the L ²-norm of the concentration fields as function of the axial coordinate ξ,?both for short and asymptotic lengthscales. The quantitative comparison with respect to the Nguyen model is illustrated and discussed. Finally, the coupling between parallel lamination and sequential segmentation is analyzed, and leads to unexpected and apparently counter-intuitive findings.