- 标题
- 摘要
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- 实验方案
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Topology optimization of flextensional piezoelectric actuators with active control law
摘要： This work deals with the concept of Topology Optimization Method (TOM) applied to the design of a flextensional piezoelectric actuator (FPEA) targeting vibration attenuation of its dynamic response. On these actuators the piezoceramic shape is usually fixed and it is more advantageous to optimize the host structure topology. The flextensional actuator is formed by two piezo-ceramic layers that act as a sensor and an actuator coupled with a constant gain active velocity feedback control law (AVFC). The optimization procedure is fully described and implemented, with no simplification for the piezo-ceramic AVFC introduced to the model acts by modifying the damping matrix according to the measurements of the state variables of the system in time-domain. The dynamic equation analyzed throughout the response for the rectangular four-noded finite element (FE) analysis is obtained by the Newmark’s time-integration method, which is applied to the physical equation and to the adjoint equation needed for the sensitivity analysis. A gradient-based optimization method is applied to minimize the response signal energy of the FPEA under a transient mechanical load. Results are obtained for different control gain values to evaluate their influence on the final topology. The optimized host structure material topology for the nc-nodes model is compared with the collapsed nodes (c-nodes) model. In addition, the nc-nodes model is useful to future developments that intends to provide an external circuit to this FPEA structure aiming to intensify the AVFC damping effect.
关键词： Topology Optimization Method,Time domain transient analysis,Flextensional Piezoactuator,Active control law,Non-collapsed piezoelectric nodes
更新于2025-09-23 15:22:29
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Energy-Efficient QoS-based OCDMA Networks Aided by Nonlinear Programming Methods
摘要： One of the advantages of the optical code division multiple access (OCDMA) system networks over other multiple access methods is the ability to provide differentiated classes of quality of service (QoS) for different users. The performance of the OCDMA networks is mainly limited by the multi-access interference (MAI) coming from other users sharing the same spectral resources. The suitable resource allocation in OCDMA networks allows greater capacity and the reliable deployment of the available resources in the network. This work aiming at applying and analyzing four analytical optimization methods applied to energy efficiency (EE) maximization of OCDMA networks. Hence, such optimization methods were applied and their performance-complexity tradeoffs are compared, namely the augmented Lagrangian method (ALM) [18], sequential quadratic programming method (SQP), majoration-minimization (MaMi) approach [23], [24], as well as Dinkelbach’s method (DK). Tests were performed considering practical and realistic OCDMA networks with a wide range of nodes, typically K = {8; 16; 32} nodes. The evaluated optimization methods were able to achieve convergence and perform suitably to solve the optical EE-OCDMA optimization problem. However, in a few specific high loading system configurations, the DK method did not reach full convergence; besides DK processing time was much greater compared to the promising ALM, SQP and MaMi EE-OCDMA optimization approaches.
关键词： CvX,OCDMA networks,Energy efficiency,Majoration-minimization,Sequential quadratic Programming method,Augmented Lagrangian method,Dinkelbach’s fractional optimization method
更新于2025-09-23 15:21:01
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Design and Optimization Methodology of Coplanar Waveguide Test Structures for Dielectric Characterization of Thin Films
摘要： This paper describes an accurate design method of coplanar waveguide (CPW) test structures on characterizing dielectric properties of thin films with arbitrary thickness. Current CPW measurement method has difficulty in providing accurate dielectric properties of films with extremely small thickness. To address this issue, an optimized algorithm is presented to generate proper geometric parameters of CPW test structures for films with different thickness. To validate the accuracy of the proposed design methodology, various test cases of CPW structures with different dimensions have been designed and implemented, the extracted dielectric properties (e.g., dielectric constant and loss tangent) from the S-parameters of the different test cases are compared to the benchmark results simulated by accurate electromagnetic tool Ansys HFSS. It demonstrates the efficacy of the proposed optimized method on quickly producing correct dimensions of CPW test lines for accurate properties characterization of thin films.
关键词： Dielectric properties,Thin film,Coplanar waveguide test structure,Optimization method
更新于2025-09-23 15:21:01
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Optimized arrangement of vertical cavity surface emitting laser arrays to improve thermal characteristics
摘要： An optimization method for an arrangement of vertical cavity surface emitting laser (VCSEL) arrays to improve thermal characteristics of the arrays is presented. The method is based on the principle of minimum potential energy and is implemented by a self-organizing algorithm. The thermal and electrical properties of the active regions of the unoptimized and optimized arrays were obtained by a self-consistent thermoelectric simulation of the VCSEL structure based on the finite element method. The output characteristics of the unoptimized and optimized 4 × 4 square VCSEL arrays were studied theoretically and practically. The results showed that the optimized arrays have improved thermal characteristics.
关键词： VCSEL arrays,optimization method,thermal characteristics,self-organizing algorithm,finite element method
更新于2025-09-11 14:15:04
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Non-uniform distribution of sulfur vapor and its influence on Cu2ZnSnS4 thin film solar cells
摘要： Deep neural network with recurrent structure was proposed in the recent years and has been applied to time series forecasting. Many optimization algorithms are developed under the assumption of invariant and stationary data distributions, which is invalid for the non-stationary data. A novel optimization algorithm for modeling non-stationary time series is proposed in this paper. A moving window and exponential decay weights are used in this algorithm to eliminate the effects of the history gradients. The regret bound of the new algorithm is analyzed to ensure the convergency of the calculation. Simulations are done on short-term power load data sets, which are typically non-stationary. The results are superior to the existing optimization algorithms.
关键词： Recursive neural network,ADAptive Moment estimation,Time series forecast,Non-stationary data,Optimization method
更新于2025-09-11 14:15:04
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Wavelet Transform Subspace-based Optimization Method for Inverse Scattering
摘要： Inspired by the new fast Fourier transform subspace-based optimization method (NFFT-SOM), wavelet transform subspace-based optimization method (WT-SOM) that represents minor part of induced current by wavelet bases is proposed in this paper to solve the inverse scattering problem. This paper provides a guideline for choosing the appropriate bases for the minor part of induced current in the inverse problem, and it is shown that Daubechies 20 (D20) wavelet bases and Fourier bases are better choices than Daubechies 4 (D4) wavelet bases and Haar wavelet bases. Compared to NFFT-SOM, it is shown that WT-SOM can be used to improve the resolution of a specific region of a scatterer. By using only part of the detail coefficients, the convergence rate of the algorithm can be greatly accelerated compared to using all the detail coefficients. For a piecewise constant scatterer, additive total variation (TV) regularization is used together with WT-SOM. We prove that TV-regularized WT-SOM has exactly the same performance when the contrast is represented by no matter natural pixels bases, Fourier bases, or wavelet bases.
关键词： wavelet transform,optimization method,Fourier transform,inverse scattering
更新于2025-09-11 14:15:04