International Journal of Engineering Systems Modelling and Simulation (6 papers in press)
Enhanced Monitoring of Batch Process Using Just-in-Time Learning Based Kernel Independent Component Analysis
by Li Wang
Abstract: A new method is developed for batch process monitoring in this paper. In the developed method, just-in-time learning (JITL) and kernel independent component analysis (KICA) are integrated to build JITL-KICA monitoring scheme. JITL is employed to tackle with the characteristics of batch process such as inherent time-varying dynamics, multiple operating phases, and especially the case of uneven length stage. According to new coming test data, the most correlated segmentation is obtained from batch-wise unfolded training data by JITL. Then, KICA serves as the principal components extraction approach. Therefore, the non-Gaussian distributed data can also be addressed under this modeling framework. The effectiveness and superiority of JITL-KICA based monitoring method is demonstrated through benchmark data of DuPont industrial batch polymerization reactor.
Keywords: batch process; process modeling; process monitoring; time varying dynamics; multiple operating phases; uneven length stage; non Gaussian distribution; kernel independent component analysis; just in time learning; online fault detection.
A Numerical Study of a Greenhouse CFD Simulation including Radiation Heat Transfer and Transpiration
by Karin Farber, Peter Farber, Jens Grabel, Sebastian Krick, Peer Ueberholz
Abstract: Radiation and transpiration are important physical phenomena in greenhouses. In this paper we present a 3D computational fluid dynamics (CFD) simulation of a system model of a small greenhouse to investigate heat fluxes due to radiation and transpiration. The system model of the greenhouse includes incoming radiation by the sun, radiation heat transfer exchange with the surrounding, convection heat transfer, an active ventilation, open windows, a porous media modeling tomato crop, and a transpiration model coupled to the porous medium of the tomato crop. All simulations were performed transient, modelling the global location of the city of Venlo in the Netherlands with the moving sun. The fine 5 million cell mesh allowed a high spatial discretization which, together with a moderate time discretization, showed details in transpiration and radiation absorption inside the crop as well as details of the humidity distribution inside and around the tomato crop.
Keywords: Computational Fluid Dynamics; Radiation Heat Transfer; Transpiration; Greenhouse; Tomato Crop.
Multi-Band Circular Polarizer Based on Periodic Metallic Strip Array
by Farman Ali Mangi, Shaoqiu Xiao, Ghulam Ali Mallah, Deedar Ali Jamro, Imran Memon, Ghulam Fatima Kakepoto
Abstract: The multi-band circular polarizer is proposed to convert linear-to-circular polarization using 3x3 metallic strips array. The metallic periodic strips are printed on both sides of the dielectric substrate that are subjected to enhance the axial ratio bandwidth at resonance frequencies. Firstly, the novel approach of fission transmission of electromagnetic waves is presented to obtain strong optical activity through the structure. It means that the incident linearly polarized wave is converted into two orthogonal components through lower printed metallic strips layer of the structure. Similarly, when two transmitted orthogonal components impinges on the upper printed strips, they converted into four orthogonal vector components at the end of structure. This projection and transmission sequence of incident and transmission wave sustain the chain transmission of electromagnetic wave and can achieve strong circular dichroism. Moreover, the axial ratio of Txx, Txy, is better than 1dB and the accumulative multi-band axial ratio bandwidth of 20.47% is obtained at frequency bands for circular polarization. This new concept and performance are theoretically investigated and verified by experimental results. Theoretical analysis and microwave experiments are presented to validate the performance of structure which realizes this idea successfully.
Keywords: Dual layer polarizer; circular polarization; quarter wave plate; metamaterial.
Main steam temperature control based on GA-BP optimized fuzzy neural network
by Zhongda Tian
Abstract: The high inertia and long time-delay characteristics of main steam temperature control system in thermal power plant will reduce the system control performance. In order to solve this problem, a GA-BP (genetic algorithm-back propagation) optimized fuzzy neural network control strategy is proposed in this paper. Gauss function is chosen as membership function and fuzzy neural network is designed. GA combined with BP algorithm is chosen for the offline parameters optimization of fuzzy neural network, and then BP algorithm is used for online parameters optimization. GA-BP optimization algorithm overcomes the shortcomings of GA algorithm or BP algorithm which is used to adjust the parameters of fuzzy neural network controller. The simulation experiment compared with cascade PID and fuzzy neural network is carried out. Simulation results show that the controller based on GA-BP optimized fuzzy neural network has faster response speed, smaller overshoot and error, better tracking performance, and reduces the lag effect of the control system under different load, working conditions and membership functions.
Keywords: main steam temperature; genetic algorithm; BP algorithm; fuzzy control; fuzzy neural network.
Identification of nonlinear dynamic systems described by Hammerstein state-space models with discontinuous nonlinearities
by Houda Salhi, Samira Kamoun
Abstract: The paper deals with the parameter estimation problem of Hammerstein state-space model with different nonlinearities. The basic idea is to develops a recursive algorithm which estimate jointly the system model parameter and the state variables by combining the adjustable model method, the least squares technique and the Kalman filter. A numerical example is provided to test the flexibility and the effectiveness of the proposed algorithm.
Keywords: Recursive algorithm; Parameter estimation; State estimation; Hammerstein model; discontinuous nonlinearities; Adjustable model; Least squares technique; Kalman Filter; Preaload and dead zone nonlinearity.
Shape optimization of 2-dimensional structures using Isogeometric Analysis (IGA).
by Vinay K. Ummidivarapu, Hari K. Voruganti
Abstract: Structural shape optimization is the important stage of a design process. It reduces the overall design cycle time, weight and cost of the structure. The main modules of structural shape optimization are geometric modelling, analysis technique and optimization procedure. Since shape optimization is an iterative process, it is recommended that all the three modules bear a similar framework. In the traditional FEA based shape optimization, the geometric modelling and analysis modules are based on different frameworks and lead to difficulties like meshing, remeshing, loss of geometric data, abnormal optimal shapes etc. Isogeometric analysis (IGA) would resolve the above issues by integrating both modelling and analysis into a unified framework. In this work, isogeometric analysis is applied for shape optimization of two-dimensional structures and the results are presented. The IGA optimized results show that the difficulties of FEA based shape optimization are eliminated. Numerical results indicate the applicability of the method.
Keywords: Isogeometric analysis; shape optimization; structural analysis; NURBS; finite elements; meshless method; genetic algorithm.