A multi-stage optimization technique is proposed to simultaneously reconstruct the infrared optical and thermophysical parameters in semitransparent media. The coupled radiative-conductive heat transfer in two-dimensi...
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A multi-stage optimization technique is proposed to simultaneously reconstruct the infrared optical and thermophysical parameters in semitransparent media. The coupled radiative-conductive heat transfer in two-dimensional absorbing, scattering and emitting medium is solved by the discrete ordinate method combined with finite volume method. The exit radiative intensity and temperature distribution on the boundary are served as input for the inverse analysis, and the sequential quadratic programming is used as the inverse technique. Since the measurement signals are much more sensitive to the infrared absorption and scattering coefficients than to the thermal conductivity of medium, the thermophysical property cannot be accurately reconstructed by the conventional method. The multi-stage optimization technique is developed to solve the inverse estimation tasks, through which the optical and thermophysical parameters are reconstructed in different stages based on different objective functions. All the retrieval results demonstrate that the multi-stage optimization technique is robust and effective in simultaneous estimation of absorption coefficient, scattering coefficient and thermal conductivity. The optical and thermophysical parameters can be reconstructed accurately even with measurement errors.
This paper presents an efficient hybrid optimization approach using a new coupling technique for solving the constrained optimization problems. This methodology is based on genetic algorithm, sequentialquadratic prog...
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This paper presents an efficient hybrid optimization approach using a new coupling technique for solving the constrained optimization problems. This methodology is based on genetic algorithm, sequential quadratic programming and particle swarm optimization combined with a projected gradient techniques in order to correct the solutions out of domain and send them to the domain's border. The established procedures have been successfully tested with some well known mathematical and engineering optimization problems, also the obtained results are compared with the existing approaches. It is clearly demonstrated that the solutions obtained by the proposed approach are superior to those of existing best solutions reported in the literature. The main application of this procedure is the location optimization of piezoelectric sensors and actuators for active control, the vibration of plates with some piezoelectric patches is considered. Optimization criteria ensuring good observability and controllability based on some main eigenmodes and residual ones are considered. Various rectangular piezoelectric actuators and sensors are used and two optimization variables are considered for each piezoelectric device: the location of its center and shape orientation. The applicability and effectiveness of the present methodological approach are demonstrated and the location optimization of multiple sensors and actuators are successfully obtained with some main modes and residual ones. The shape orientation optimization of sensors observing various modes as well as the local optimization of multiple sensors and actuators are numerically investigated. The effect of residual modes and the spillover reduction can be easily analyzed for a large number of modes and multiple actuators and sensors. (C) 2018 Elsevier Inc. All rights reserved.
This article introduces a new adaptive two-step optimization algorithm for finite element model updating with special emphasis on damage localization at supporting structures of offshore wind turbines. The algorithm c...
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This article introduces a new adaptive two-step optimization algorithm for finite element model updating with special emphasis on damage localization at supporting structures of offshore wind turbines. The algorithm comprises an enhanced version of the global optimization algorithm simulated annealing, the simulated quenching method that approximates an initial guess of damage localization. Subsequently, sequential quadratic programming is used to compute the final solution adaptively. For the correlation of numerical model and measurement data, both a measure based on eigenfrequencies and mode shapes and a measure employing time series are implemented and compared with respect to their performance for damage localization. Phase balance of the time signals is achieved using cross-correlation. The localization problem is stated as a minimization problem in which the measures are used in time and modal domain as the objective function subject to constraints. Furthermore, the objective function value of the adjusted model is used to distinguish correct from wrong solutions. The functionality is proven using a numerical model of a monopile structure with simulated damage and a lab-scaled model of a tripile structure with real damage.
This paper presents a novel gradient-free trust region assisted adaptive response surface method for aircraft optimization problems with expensive functions. A gradient-free trust region sampling space approach is dev...
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This paper presents a novel gradient-free trust region assisted adaptive response surface method for aircraft optimization problems with expensive functions. A gradient-free trust region sampling space approach is developed for design space reduction and sequential sampling, and response surface metamodel refitting enables the trust region assisted adaptive response surface method to possess higher optimization efficiency and better global convergence capability. Besides, an election sequential Latin hypercube sampling method is developed to improve the space-filling property and feasibility of the sequential samples. Moreover, the augmented Lagrangian method is employed to handle expensive constraints. The trust region assisted adaptive response surface method outperforms several adaptive response surface metamodel variants in the comparative study on a number of benchmark problems. Additionally, compared with several other well-known metamodel-based global optimization algorithms, the proposed algorithm also shows favorable performance in global convergence, efficiency, and robustness. Next, the trust region assisted adaptive response surface method is successfully applied to solve an airfoil aerodynamic optimization problem based on computational fluid dynamics simulation to demonstrate its effectiveness for real-world engineering problems. Finally, limitations of the proposed method and future work are discussed.
The continuous production of biodiesel is achieved through a sequence of stages such as reaction, absorption, decantation, and product distillation. These steps require certain performance criteria that must be optimi...
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The continuous production of biodiesel is achieved through a sequence of stages such as reaction, absorption, decantation, and product distillation. These steps require certain performance criteria that must be optimized. Several works have addressed the optimization of the design of biodiesel plants, and these have usually examined modifications to the dimensions and types of equipment or energy integration. However, there is only limited literature available on determining optimal operating conditions for existing processes. In this paper, the steady-state optimization of a soybean continuous biodiesel plant is proposed. To this end, a mathematical model to describe the chemical kinetics of soybean oil trans-esterification was developed and incorporated into a chemical process simulator. The optimization procedure is based on multidimensional sequential quadratic programming (SQP), in which the primary objectives were to minimize the plant's energy consumption subject to a minimum of 99 wt% biodiesel purity. The results reveal that the optimization of the current process allows a 4.45% reduction in energy consumption compared to the base case. Besides, the study also evidenced that the optimization approach can be applied to recalculate the optimal point when possible disturbances can deviate the system from a steady state. (C) 2019 Elsevier Ltd. All rights reserved.
Calculation of an optimal tariff is a principal challenge for pricing actuaries. In this contribution we are concerned with the renewal insurance business discussing various mathematical aspects of calculation of an o...
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Calculation of an optimal tariff is a principal challenge for pricing actuaries. In this contribution we are concerned with the renewal insurance business discussing various mathematical aspects of calculation of an optimal renewal tariff. Our motivation comes from two important actuarial tasks, namely (a) construction of an optimal renewal tariff subject to business and technical constraints, and (b) determination of an optimal allocation of certain premium loadings. We consider both continuous and discrete optimisation and then present several algorithmic suboptimal solutions. Additionally, we explore some simulation techniques. Several illustrative examples show both the complexity and the importance of the optimisation approach.
It is revealed that the local optimum is particularly prone to occur in multi-material topology optimization using the conventional SIMP method. To overcome these undesirable phenomena, reciprocal variables are introd...
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It is revealed that the local optimum is particularly prone to occur in multi-material topology optimization using the conventional SIMP method. To overcome these undesirable phenomena, reciprocal variables are introduced into the formulation of topology optimization for minimization of total weight with the prescribed constraint of various structural responses. The SIMP scheme of multi-phase materials is adopted as the interpolation of the elemental stiffness matrix, mass matrix and weight. The sensitivities of eigenvalue and weight with respect to design variables are derived. Explicit approximations of natural eigenvalue and weight are given with the help of the first and second order Taylor series expansion. Thus, the optimization problem is solved using a sequential quadratic programming approach, by setting up a sub-problem in the form of a quadratic program. The filtering technique by solving the Helmholtz-type partial differential equation is performed to eliminate the checkerboard patterns and mesh dependence. Numerical analysis indicates that it is beneficial to avoid the local optimum by using the reciprocal SIMP formulation. Besides, the structure composed of multi-materials can achieve a lighter design than that made from the exclusive base material. The effectiveness and capability of the proposed method are also verified by nodal displacement constraint and multiple constraints.
The main objective of this study is to develop an optimum mix design method for self-compacting concrete (SCC) based on experimental results. For this purpose, mix design of self-compacting concrete is formulated as a...
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The main objective of this study is to develop an optimum mix design method for self-compacting concrete (SCC) based on experimental results. For this purpose, mix design of self-compacting concrete is formulated as an optimization problem. Given the importance of manufacturing costs of concrete, the total cost of one cubic meter of self-compacting concrete is considered as the objective function in the optimization problem, which must be minimized. Limitation of the 28-day compressive strength and slump flow of self-compacting concrete are considered as the main inequality constraints. To ensure that sum of concrete components makes unit volume, an equality constraint is considered. To formulate the self-compacting concrete mix design optimization problem based on experimental data, forty-two different mix designs of self-compacting concrete are presented and three cylinder specimens are made and tested for each of them. Two mathematical models are developed to estimate the strength and the slump of the concrete and used to define the main constraints in the mix design optimization model. The concrete specimens are prepared in a construction site in Sanandaj in Iran. Considering importance of sand grading on the compressive strength of self-compacting concrete, stone powder is used to improve sand fineness modulus. The sequential quadratic programming is employed to solve the optimal mix design problem of self-compacting concrete based on proposed model. In order to verify the proposed method, the mix design problem is solved for several case studies and then the final optimal mix designs are made in laboratory and mechanical properties of specimens are evaluated. The results show that the proposed method satisfies the mechanical characteristics of the self-compacting concrete, besides minimizing the cost of the concrete and automating the mix design process. (C) 2018 Elsevier Ltd. All rights reserved.
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