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  Subjects -> ENGINEERING (Total: 2167 journals)
    - CHEMICAL ENGINEERING (184 journals)
    - CIVIL ENGINEERING (168 journals)
    - ELECTRICAL ENGINEERING (94 journals)
    - ENGINEERING (1173 journals)
    - HYDRAULIC ENGINEERING (55 journals)
    - INDUSTRIAL ENGINEERING (57 journals)
    - MECHANICAL ENGINEERING (81 journals)

CIVIL ENGINEERING (168 journals)                  1 2     

ACI Structural Journal     Full-text available via subscription   (Followers: 8)
Acta Polytechnica : Journal of Advanced Engineering     Open Access  
Acta Structilia : Journal for the Physical and Development Sciences     Open Access   (Followers: 2)
Advances in Civil Engineering     Open Access   (Followers: 30)
Advances in Structural Engineering     Full-text available via subscription   (Followers: 18)
Ambiente Construído     Open Access   (Followers: 2)
American Journal of Civil Engineering and Architecture     Open Access   (Followers: 22)
Architectural Engineering     Open Access   (Followers: 5)
Archives of Civil Engineering     Open Access   (Followers: 8)
Archives of Hydro-Engineering and Environmental Mechanics     Open Access   (Followers: 2)
ATBU Journal of Environmental Technology     Open Access   (Followers: 1)
Australian Journal of Structural Engineering     Full-text available via subscription   (Followers: 5)
Baltic Journal of Road and Bridge Engineering     Full-text available via subscription   (Followers: 3)
BER : Building and Construction : Full Survey     Full-text available via subscription   (Followers: 10)
BER : Building Contractors' Survey     Full-text available via subscription   (Followers: 4)
BER : Building Sub-Contractors' Survey     Full-text available via subscription   (Followers: 3)
BER : Survey of Business Conditions in Building and Construction : An Executive Summary     Full-text available via subscription   (Followers: 4)
Berkeley Planning Journal     Open Access   (Followers: 5)
Bioinspired Materials     Open Access  
Bridge Structures : Assessment, Design and Construction     Hybrid Journal   (Followers: 15)
Building and Environment     Hybrid Journal   (Followers: 13)
Building Women     Full-text available via subscription  
Built Environment Project and Asset Management     Hybrid Journal   (Followers: 15)
Canadian Journal of Civil Engineering     Full-text available via subscription   (Followers: 15)
Case Studies in Engineering Failure Analysis     Open Access   (Followers: 4)
Case Studies in Nondestructive Testing and Evaluation     Open Access  
Case Studies in Structural Engineering     Open Access  
Cement and Concrete Composites     Hybrid Journal   (Followers: 12)
Change Over Time     Full-text available via subscription   (Followers: 3)
Civil and Environmental Engineering     Open Access   (Followers: 1)
Civil And Environmental Engineering Reports     Open Access  
Civil and Environmental Research     Open Access   (Followers: 15)
Civil Engineering     Hybrid Journal   (Followers: 13)
Civil Engineering = Siviele Ingenieurswese     Full-text available via subscription   (Followers: 5)
Civil Engineering and Architecture     Open Access   (Followers: 4)
Civil Engineering and Environmental Systems     Hybrid Journal   (Followers: 5)
Civil Engineering and Technology     Open Access   (Followers: 5)
Civil Engineering Dimension     Open Access   (Followers: 5)
Cohesion and Structure     Full-text available via subscription   (Followers: 2)
Composite Structures     Hybrid Journal   (Followers: 145)
Computer-aided Civil and Infrastructure Engineering     Hybrid Journal   (Followers: 9)
Computers & Structures     Hybrid Journal   (Followers: 26)
Concrete Research Letters     Open Access   (Followers: 2)
Constructii : Journal of Civil Engineering Research     Open Access   (Followers: 10)
Construction Engineering     Open Access   (Followers: 4)
Construction Management and Economics     Hybrid Journal   (Followers: 29)
Construction Science     Open Access   (Followers: 1)
Constructive Approximation     Hybrid Journal  
Curved and Layered Structures     Open Access  
DFI Journal : The Journal of the Deep Foundations Institute     Hybrid Journal  
Earthquake Engineering and Structural Dynamics     Hybrid Journal   (Followers: 13)
Enfoque UTE     Open Access   (Followers: 1)
Engineering Project Organization Journal     Hybrid Journal   (Followers: 4)
Engineering Structures     Hybrid Journal   (Followers: 14)
Engineering Structures and Technologies     Hybrid Journal   (Followers: 2)
Engineering, Construction and Architectural Management     Hybrid Journal   (Followers: 16)
Environmental Geotechnics     Open Access   (Followers: 2)
European Journal of Environmental and Civil Engineering     Hybrid Journal   (Followers: 5)
Fatigue & Fracture of Engineering Materials and Structures     Hybrid Journal   (Followers: 14)
Frattura ed Integrità Strutturale : Fracture and Structural Integrity     Open Access  
Frontiers of Structural and Civil Engineering     Hybrid Journal   (Followers: 6)
Geomaterials     Open Access   (Followers: 2)
Geosystem Engineering     Hybrid Journal   (Followers: 3)
Geotechnik     Hybrid Journal   (Followers: 1)
Géotechnique Letters     Hybrid Journal   (Followers: 4)
HBRC Journal     Open Access   (Followers: 2)
Hormigón y Acero     Full-text available via subscription  
HVAC&R Research     Hybrid Journal   (Followers: 1)
Indoor and Built Environment     Hybrid Journal   (Followers: 1)
Infrastructure Asset Management     Full-text available via subscription  
Ingenio Magno     Open Access  
Insight - Non-Destructive Testing and Condition Monitoring     Full-text available via subscription   (Followers: 7)
International Journal for Service Learning in Engineering     Open Access  
International Journal of 3-D Information Modeling     Full-text available via subscription   (Followers: 1)
International Journal of Advanced Structural Engineering     Open Access   (Followers: 6)
International Journal of Concrete Structures and Materials     Open Access   (Followers: 7)
International Journal of Condition Monitoring     Full-text available via subscription  
International Journal of Construction Engineering and Management     Open Access   (Followers: 6)
International Journal of Geosynthetics and Ground Engineering     Full-text available via subscription   (Followers: 1)
International Journal of Protective Structures     Full-text available via subscription   (Followers: 6)
International Journal of Steel Structures     Hybrid Journal   (Followers: 4)
International Journal of Structural Engineering     Hybrid Journal   (Followers: 7)
International Journal of Structural Integrity     Hybrid Journal  
International Journal of Structural Stability and Dynamics     Hybrid Journal   (Followers: 5)
International Journal of Sustainable Built Environment     Open Access   (Followers: 3)
International Journal of Sustainable Construction Engineering and Technology     Open Access   (Followers: 10)
International Journal on Pavement Engineering & Asphalt Technology     Open Access   (Followers: 2)
Journal of Accessibility and Design for All     Open Access   (Followers: 6)
Journal of Advanced Research in Civil and Environmental Engineering     Open Access   (Followers: 1)
Journal of Bridge Engineering     Full-text available via subscription   (Followers: 18)
Journal of Building Engineering     Hybrid Journal  
Journal of Building Materials and Structures     Open Access  
Journal of Building Performance Simulation     Hybrid Journal   (Followers: 5)
Journal of Civil Engineering and Construction Technology     Open Access   (Followers: 3)
Journal of Civil Engineering and Management     Hybrid Journal   (Followers: 7)
Journal of Civil Engineering and Science     Open Access   (Followers: 13)
Journal of Civil Engineering Research     Open Access   (Followers: 12)
Journal of Civil Society     Hybrid Journal   (Followers: 3)
Journal of Civil Structural Health Monitoring     Hybrid Journal   (Followers: 3)
Journal of Composites     Open Access   (Followers: 42)

        1 2     

Journal Cover   Structural and Multidisciplinary Optimization
  [SJR: 1.825]   [H-I: 61]   [5 followers]  Follow
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1615-1488 - ISSN (Online) 1615-147X
   Published by Springer-Verlag Homepage  [2281 journals]
  • Hierarchical model calibration for designing piezoelectric energy
           harvester in the presence of variability in material properties and
    • Abstract: Abstract Piezoelectric energy harvesting which scavenges electric power from ambient vibration energy has received significant attention as an ultimate solution to realize self-powered wireless sensors. For designing a piezoelectric energy harvester, it is of great importance to develop a high-fidelity electromechanical model which predicts the output power under various vibration conditions. To the best of our knowledge, however, there has been no systematic approach to account for variability in the material properties and geometry of a piezoelectric energy harvester. This paper thus presents (1) the hierarchical model calibration to improve the predictive capability of the electromechanical model and (2) the design of energy harvesting (EH) skin to maximize the output power to reliably operate self-powered wireless sensors. In this study, the hierarchical model calibration infers statistical information of unknown model variables (compliance, piezoelectric strain coefficient, and relative permittivity). The calibrated electromechanical model is then used to design EH skin based on the piezoelectric material segmentation to avoid voltage cancellation. The output power predicted by the calibrated electromechanical model is statistically compared with the measured one. Finally, it is concluded from the feasibility demonstration that EH skin can sufficiently generate the output power to realize self-powered wireless sensors without batteries.
      PubDate: 2015-08-29
  • A multi-objective, multidisciplinary design optimization methodology for
           the conceptual design of a spacecraft bi-propellant propulsion system
    • Abstract: Abstract Space propulsion systems play an increasingly important role in planning of space missions. The traditional method for design of space propulsion systems includes numerous design loops, which does not guarantee to reach the best optimal solution. Multidisciplinary Design Optimization (MDO) is an approach for the design of complex systems that considers a design environment with multiple disciplines. The aims of this study are to implement and compare Multidisciplinary Feasible and Collaborative Optimization architectures for the multi-Objective optimization of a bi-propellant space propulsion system design. Several disciplines such as thrust chamber, cooling, and structure were exploited in a proper combination. The main optimization objectives in the MDO frameworks were to minimize the total wet mass and maximize the total impulse by considering several constraints. Furthermore, Genetic Algorithm and Sequential Quadratic Programming are employed as the system-level and local-level optimizers. The presented design methodology provides an interesting decision making approach to select the best system parameters of space propulsion systems under conflicting goals.
      PubDate: 2015-08-22
  • Multidisciplinary dynamic optimization of horizontal axis wind turbine
    • Abstract: Abstract The design of physical (plant) and control aspects of a dynamic system have traditionally been treated as two separate problems, often solved in sequence. Optimizing plant and control design disciplines separately results in sub-optimal system designs that do not capitalize on the synergistic coupling between these disciplines. This coupling is inherent in most actively controlled dynamic systems, including wind turbines. In this case structural and control design both affect energy production and loads on the turbine. This article presents an integrated approach to achieve system-optimal wind turbine designs using co-design, a design methodology that accounts directly for the synergistic coupling between physical and control system design. A case study, based on multidisciplinary simulation, is presented here that demonstrates a promising increase (up to 8%) in annualized wind turbine energy production compared to the results of a conventional sequential design strategy. The case study also revealed specific synergistic mechanisms that enable performance improvements, which are accessible via co-design but not sequential design.
      PubDate: 2015-08-22
  • Actuator placement optimization for adaptive trusses using a two-level
           multipoint approximation method
    • Abstract: Abstract Parameters in adaptive trusses considering placements of actuators, control gains as well as structure cross-sectional sizes, have been simultaneously optimized to suppress vibrations and to maintain stringent shape specifications. Since the placements of actuators are treated as (0,1) variables but the control gains and structural member sizes are continuous, the studied problem then becomes mixed (0,1)-continuous optimization, which is difficult to be tackled with conventional optimization methods since they are often encountered with local optimal solutions or numerous computational costs. A two-level multipoint approximation strategy combined with genetic algorithm, which proved to be applicable in truss topology-size optimizations involving discrete-continuous design variables, has been developed to address the current actuator placement problem. To enhance the efficiency of this method, a branched multi-point approximation function was introduced to construct the first-level approximation problem. Besides, a new fitness function as well as adaptive crossover and mutation operators were adopted to prevent the optimization process from too early converging to local optimal solutions. Numerical results were presented to illustrate the efficacy of this strategy in dealing with actuator placement problems.
      PubDate: 2015-08-22
  • Microstructural topology optimization of viscoelastic materials for
           maximum modal loss factor of macrostructures
    • Abstract: Abstract The geometric layout and physical properties of a viscoelastic damping material have a significant influence on the damping performance of a passive constrained layer damping (PCLD) structure. This paper presents a two-scale optimization method and aims to find the optimal microstructural configuration of the viscoelastic material (i.e., the optimal effective properties of the material) with maximum modal loss factors of the macrostructures. The modal loss factor is obtained by using the Modal Strain Energy (MSE) method. The material microstructure is assumed to be homogeneous in the macro-scale, i.e., the macrostructure is composed of periodic unit cells (PUC). In the optimization formulation, the relative densities are introduced as the design variables for the material microstructure design, based upon the idea of the Solid Isotropic Material with Penalization (SIMP) method of topology optimization. The modal loss factor of the structure is assigned as the objective function. All the sensitivities of the modal loss factor with respect to the design variables are derived analytically and the optimization problem is solved by Method of Moving Asymptote (MMA) method. Several examples of the design optimization of viscoelastic cellular materials are presented to demonstrate the validity of the method. The effectiveness of the design method is illustrated by comparing a solid and an optimized cellular viscoelastic material as applied to a cantilever beam with the PCLD treatment.
      PubDate: 2015-08-19
  • Bridging topology optimization and additive manufacturing
    • Abstract: Abstract Topology optimization is a technique that allows for increasingly efficient designs with minimal a priori decisions. Because of the complexity and intricacy of the solutions obtained, topology optimization was often constrained to research and theoretical studies. Additive manufacturing, a rapidly evolving field, fills the gap between topology optimization and application. Additive manufacturing has minimal limitations on the shape and complexity of the design, and is currently evolving towards new materials, higher precision and larger build sizes. Two topology optimization methods are addressed: the ground structure method and density-based topology optimization. The results obtained from these topology optimization methods require some degree of post-processing before they can be manufactured. A simple procedure is described by which output suitable for additive manufacturing can be generated. In this process, some inherent issues of the optimization technique may be magnified resulting in an unfeasible or bad product. In addition, this work aims to address some of these issues and propose methodologies by which they may be alleviated. The proposed framework has applications in a number of fields, with specific examples given from the fields of health, architecture and engineering. In addition, the generated output allows for simple communication, editing, and combination of the results into more complex designs. For the specific case of three-dimensional density-based topology optimization, a tool suitable for result inspection and generation of additive manufacturing output is also provided.
      PubDate: 2015-08-05
  • Design optimization based on state problem functionals
    • Abstract: Abstract This paper presents a general mathematical structure for design optimization problems, where state problem functionals are used as design objectives.It extends to design optimization the general model of physical theories pioneered by Tonti (1972, 1976) and Oden and Reddy (1974, 1983). It turns out that the classical structural optimization problem of compliance minimization is a member of the treated general class of problems. Other particular examples, discussed in the paper, are related to Darcy-Stokes flow and pipe flow models. A main novel feature of the paper is the unification of seemingly different design problems, but the general mathematical structure also explains some previously not fully understood phenomena. For instance, the self-penalization property of Stokes flow design optimization receives an explanation in terms of minimization of a concave function over a convex set.
      PubDate: 2015-08-01
  • Discrete sizing optimization of steel trusses under multiple displacement
           constraints and load cases using guided stochastic search technique
    • Abstract: Abstract The guided stochastic search (GSS) is a computationally efficient design optimization technique, which is originally developed for discrete sizing optimization problems of steel trusses with a single displacement constraint under a single load case. The present study aims to investigate the GSS in a more general class of truss sizing optimization problems subject to multiple displacement constraints and load cases. To this end, enhancements of the GSS are proposed in the form of two alternative approaches that enable the technique to deal with multiple displacement/load cases. The first approach implements a methodology in which the most critical displacement direction is considered only when guiding the search process. The second approach, however, takes into account the cumulative effect of all the critical displacement directions in the course of optimization. Advantage of the integrated force method of structural analysis is also utilized for further reduction of the computational effort in these approaches. The proposed enhancements of GSS are investigated and compared with some selected techniques of design optimization through six truss structures that are sized for minimum weight. The numerical results reveal that both enhancements generally provide promising solutions with an insignificant computational effort.
      PubDate: 2015-08-01
  • The effect of ignoring dependence between failure modes on evaluating
           system reliability
    • Abstract: Abstract Assuming independence between failure modes makes system reliability calculation simple but it adds approximation error. Interestingly, error due to ignoring dependence can be negligible for a highly reliable system. This paper investigates the reasons and the factors affecting the error. Error in system probability of failure (PF) is small for high reliability when tail-dependence is not very strong or the ratio between individual PFs is large. We created various conditions using copulas and observed the effect of ignoring dependence. Two reliability-based design optimization problems with a 2-bar and a 10-bar trusses are presented to show the effect of error on the optimum design and the system PF calculation. For the 10-bar truss, there were 5 % error in system PF and mass penalty less than 0.1 % in the optimum design for a target system PF of 10−7 even though five truss failures were strongly correlated.
      PubDate: 2015-08-01
  • Extension of concurrent subspace optimization to structural optimization
           of product families
    • Abstract: Abstract This paper discusses the problem of structural optimization of product families with predefined platforms. The main challenge lies in the increased design variables and constraints, and providing an optimal tradeoff for individual products performance in the family which are competitive with each other. The Concurrent Subspace Optimization for multidisciplinary problem is extended to product family design with predefined platforms. The main advantage of the proposed approach is that the system level owns the ability to catch the global tendency of the true design space and the number of evaluations required is reduced by using surrogate models. Each subspace optimization problem has the freedom to specify the unique variables for one family member, and the system level optimizes the product platform using the surrogate models created based on subspace optimizations. The process is solved in an iterative way, and the improving surrogate models guide the optimization to the global optimal design. Results from a truss family example with small design space confirm the ability and efficiency of the extended Concurrent Subspace Optimization to address product family problem by compared with ATC approach. Then the proposed method is successfully applied to a family of unmanned aircraft wing structures, which is more complicated and related to practical implementation issues.
      PubDate: 2015-08-01
  • Structural mass reduction by integrating active material in direct drive
           generator design
    • Abstract: Abstract Permanent magnet synchronous generator technology is known for its low power to mass ratio. Its heavy structural design results from the need to ensure a small air-gap at a large diameter between stator and rotor parts. Numerous options for lowering structural mass are considered. In this paper, an overall mass reduction strategy which entails the integration of the magnetically active parts with the support structure are presented. Two three megawatt generator designs, one with a single bearing and the other with double bearing lay-up, are considered. These models comprise three-dimensional elements, isotropic and orthotropic materials, linear static extreme hub loads, and magnetic stresses. Shape and size optimisations are applied in calculation of structural mass saving incurred from structural integration and the altering of rotor and stator yoke thicknesses. The results show that total generator mass reduction is possible through the integration of the active material.
      PubDate: 2015-08-01
  • Thickness filters for gradient based multi-material and thickness
           optimization of laminated composite structures
    • Abstract: Abstract This paper presents a new gradient based method for performing discrete material and thickness optimization of laminated composite structures. The novelty in the new method lies in the application of so-called casting constraints, or thickness filters in this context, to control the thickness variation throughout the laminate. The filters replace the layerwise density variables with a single continuous through-the-thickness design variable. Consequently, the filters eliminate the need for having explicit constraints for preventing intermediate void through the thickness of the laminate. Therefore, the filters reduce both the number of constraints and design variables in the optimization problem. Based upon a continuous approximation of a unit step function, the thickness filters are capable of projecting discrete 0/1 values to the underlying layerwise or ”physical” density variables which govern the presence of material in each layer through the thickness of the laminate. Combined with an in-plane density filter, the method enables manufacturers to control the length scale of the geometry while obtaining near discrete designs. Together with the applied manufacturing constraints it is now possible for manufacturers to steer the design towards a higher level of manufacturability. The method is demonstrated for mass minimization with displacement and manufacturing constraints. The results show that the method indeed is capable of obtaining near discrete designs which obey the governing constraints.
      PubDate: 2015-08-01
  • A two-stage stochastic PDE-constrained optimization approach to vibration
           control of an electrically conductive composite plate subjected to
           mechanical and electromagnetic loads
    • Abstract: Abstract A new two-stage stochastic partial differential equation (PDE)-constrained optimization methodology is developed for the active vibration control of structures in the presence of uncertainties in mechanical loads. The methodology relies on the two-stage stochastic optimization formulation with an embedded first-order black-box PDE-constrained optimization procedure. The PDE-constrained optimization procedure utilizes a first-order active-set algorithm with a conjugate gradient method. The objective function is determined through solution of the governing PDEs and its gradient is computed using automatic differentiation with hyper-dual numbers. The developed optimization methodology is applied to the problem of post-impact vibration control (via applied electromagnetic field) of an electrically conductive carbon fiber reinforced composite plate subjected to an uncertain, or stochastic, impact load. The corresponding governing PDEs consist of a nonlinear coupled system of equations of motion and Maxwell’s equations. The conducted computational study shows that the obtained two-stage optimization solution allows for a significant suppression of vibrations caused by the randomized impact load in all impact load scenarios. Also, the effectiveness of the developed methodology is illustrated in the case of a deterministic impact load, where the two-stage strategy enables one to practically eliminate post-impact vibrations.
      PubDate: 2015-08-01
  • Predictive quantification of surrogate model fidelity based on modal
           variations with sample density
    • Abstract: Abstract It is generally challenging to quantify the fidelity of surrogate models without additional system evaluations. Standard error measures, such as the mean squared error and cross-validation error, often do not adequately capture the fidelity of the model trained using all available sample points. This paper introduces a new model-independent approach to quantify surrogate model fidelity, called Predictive Estimation of Model Fidelity (PEMF). In PEMF, intermediate surrogates are iteratively constructed over heuristic subsets of sample points. The median and the maximum errors estimated over the remaining points are used to determine the respective error distributions at each iteration. The estimated modes of the error distributions are represented as functions of the density of intermediate training points through nonlinear regression, assuming a smooth decreasing trend of errors with increasing sample density. These regression functions are then used to predict the expected median and maximum errors in the final surrogate model (trained using all available sample points). A Monotonic Trend criterion is defined to statistically test if the regression function is reasonably reliable in predicting the model fidelity, failing which a stable implementation of k-fold cross-validation (based on modal error) is used to predict the final surrogate error. To compare the accuracy and robustness of PEMF with that of the popular leave-one-out cross-validation, numerical experiments are performed using Kriging, RBF, and E-RBF models. It is observed that the model fidelities estimated by PEMF is up to two orders of magnitude more accurate and statistically more stable compared to those based on cross-validation.
      PubDate: 2015-08-01
  • Efficient global robust optimization of unconstrained problems affected by
           parametric uncertainties
    • Abstract: Abstract A novel technique for efficient global robust optimization of problems affected by parametric uncertainties is proposed. The method is especially relevant to problems that are based on expensive computer simulations. The globally robust optimal design is obtained by searching for the best worst-case cost, which involves a nested min-max optimization problem. In order to reduce the number of expensive function evaluations, we fit response surfaces using Kriging and use adapted versions of expected improvement to direct the search for the robust optimum. The numerical performance of the algorithm is compared against other techniques for min-max optimization on established test problems. The proposed approach exhibits reliable convergence, is more efficient than previous methods and shows strong scalability.
      PubDate: 2015-08-01
  • A variational growth approach to topology optimization
    • Abstract: Abstract This paper presents a new approach to topology optimization that is based on observations of natural biological systems in which growth processes are initialized during high mechanical loading. A compliance parameter is introduced that serves as an internal variable and for which evolution equations are derived using the variational principle of the minimum of the dissipation potential. The well-known problem of checkerboarding is faced with regularization techniques on the Helmholtz free energy. The final procedure uses only the Helmholtz free energy as input. Several numerical examples are given for demonstration purposes.
      PubDate: 2015-08-01
  • L-dominance: An approximate-domination mechanism for adaptive resolution
           of Pareto frontiers
    • Abstract: Abstract In Evolutionary Multi-objective Optimization (EMO), the mechanism of 𝜖-dominance has received significant attention because of its ability to guarantee convergence near the Pareto frontier and maintain diversity among solutions at a reasonable computational cost. A noticeable weakness of this mechanism is its inability to vary the resolution it provides of the Pareto frontier based on the frontier’s tradeoff properties. We therefore propose a new mechanism—L-dominance, based on the Lamé curve—as an alternative to 𝜖-dominance in EMO. The geometry of the Lamé curve naturally supports a greater concentration of Pareto solutions in regions of significant tradeoff between objectives. This variable resolution of solutions allows an algorithm using L-dominance to generate fewer solutions to describe the Pareto frontier as a whole while maintaining a desired concentration of solutions where the frontier requires greater detail. The L-dominance mechanism is analyzed theoretically and by simulation on five test problems, and is shown to result in increasingly significant computational gains as the dimensionality of problems increases.
      PubDate: 2015-08-01
  • Sensitivity analysis and optimization of eigenmode localization in
           continuum systems
    • Abstract: Abstract A model problem arising from optical design of photonic bandgap structure is investigated. That is, the optimization problem is to find the material inhomogeneity in a domain so that a particular eigenmode governed by the scalar Helmholtz equation is localized. The continuum sensitivity analysis of the objective function including the eigenmode is carried out. The derivative of the objective function with respect to the density function is obtained by the sensitivity problem and the adjoint problem in continuum systems. When the multiplicity of eigenmode happens, our strategy is to select the closest eigenmode to the current eigenmode. Four numerical examples in a square domain are studied, with different weight functions and initial density distributions. The numerical results illustrate the validity of the algorithm based on the continuum sensitivity analysis.
      PubDate: 2015-08-01
  • Probability of failure sensitivity with respect to decision variables
    • Abstract: Abstract This note introduces a derivation of the sensitivities of a probability of failure with respect to decision variables. For instance, the gradient of the probability of failure with respect to deterministic design variables might be needed in RBDO. These sensitivities might also be useful for Uncertainty-based Multidisciplinary Design Optimization. The difficulty stems from the dependence of the failure domain on variations of the decision variables. This dependence leads to a derivative of the indicator function in the form of a Dirac distribution in the expression of the sensitivities. Based on an approximation of the Dirac, an estimator of the sensitivities is analytically derived in the case of Crude Monte Carlo first and Subset Simulation. The choice of the Dirac approximation is discussed.
      PubDate: 2015-08-01
  • Automatic penalty continuation in structural topology optimization
    • Abstract: Abstract Structural topology optimization problems are often modelled using material interpolation schemes to produce almost solid-and-void designs. The problems become non convex due to the use of these techniques. Several articles introduce continuation approaches in the material penalization parameter to reduce the risks of ending in local minima. However, the numerical performance of continuation methods has not been studied in detail. The first purpose of this article is to benchmark existing continuation methods and the classical formulation with fixed penalty parameter in structural topology optimization. This is done using performance profiles on 225 minimum compliance and 150 compliant mechanism design problems. The results show that continuation methods generally find better designs. On the other hand, they typically require a larger number of iterations. In the second part of the article this issue is addressed. We propose an automatic continuation method, where the material penalization parameter is included as a new variable in the problem and a constraint guarantees that the requested penalty is eventually reached. The numerical results suggest that this approach is an appealing alternative to continuation methods. Automatic continuation also generally obtains better designs than the classical formulation using a reduced number of iterations.
      PubDate: 2015-07-28
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