Pub Date : 2018-09-07DOI: 10.31534/ENGMOD.2018.1-2.SI.04_BDNY
D. Poljak, S. Šesnić, Ante Rubić, Enora Maze
The paper reviews some applications of the well-established analytical and domain discretisation methods (finite difference method-FDM, finite element method-FEM) in the modelling of the magnetohydrodynamics (MHD) phenomena for the fusion-related research and quantum structures for use in nanodevices. Hence, Grad-Shafranov Equation (GSE) for the plasma equilibrium has been implemented for certain simple excitation forms, and the results obtained for the rectangular plasma have been presented. Furthermore, the stationary Schrodinger equation is solved analytically and numerically via FDM and FEM, respectively.
{"title":"A note on the use of analytical and domain discretisation methods for the analysis of some phenomena in engineering physics","authors":"D. Poljak, S. Šesnić, Ante Rubić, Enora Maze","doi":"10.31534/ENGMOD.2018.1-2.SI.04_BDNY","DOIUrl":"https://doi.org/10.31534/ENGMOD.2018.1-2.SI.04_BDNY","url":null,"abstract":"The paper reviews some applications of the well-established analytical and domain discretisation methods (finite difference method-FDM, finite element method-FEM) in the modelling of the magnetohydrodynamics (MHD) phenomena for the fusion-related research and quantum structures for use in nanodevices. Hence, Grad-Shafranov Equation (GSE) for the plasma equilibrium has been implemented for certain simple excitation forms, and the results obtained for the rectangular plasma have been presented. Furthermore, the stationary Schrodinger equation is solved analytically and numerically via FDM and FEM, respectively.","PeriodicalId":35748,"journal":{"name":"International Journal for Engineering Modelling","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.31534/ENGMOD.2018.1-2.SI.04_BDNY","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46067901","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-09-07DOI: 10.31534/ENGMOD.2018.1-2.SI.03_BDNY
Marin Galic, D. Poljak, V. Doric
This paper outlines four different models for the assessment of the electric field radiated by the base station antenna system, thus featuring the Free Space Model (FS), Perfect Ground Model (PG), Fresnel Reflection Coefficient Model (RC) and Modified Image Theory Model (MIT). The results obtained with these approaches are compared to the results computed via Numerical Electromagnetics Code (NEC). Several variables have been varied to examine the accuracy of each calculation model. The calculations have been undertaken for the far field only. As many European countries perform the field assessment using the FS model, the final goal of this work is to come up with the most convenient model for the field calculation.
{"title":"Simple analytical models for the calculation of the electric field radiated by the base station antenna","authors":"Marin Galic, D. Poljak, V. Doric","doi":"10.31534/ENGMOD.2018.1-2.SI.03_BDNY","DOIUrl":"https://doi.org/10.31534/ENGMOD.2018.1-2.SI.03_BDNY","url":null,"abstract":"This paper outlines four different models for the assessment of the electric field radiated by the base station antenna system, thus featuring the Free Space Model (FS), Perfect Ground Model (PG), Fresnel Reflection Coefficient Model (RC) and Modified Image Theory Model (MIT). The results obtained with these approaches are compared to the results computed via Numerical Electromagnetics Code (NEC). Several variables have been varied to examine the accuracy of each calculation model. The calculations have been undertaken for the far field only. As many European countries perform the field assessment using the FS model, the final goal of this work is to come up with the most convenient model for the field calculation.","PeriodicalId":35748,"journal":{"name":"International Journal for Engineering Modelling","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.31534/ENGMOD.2018.1-2.SI.03_BDNY","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44110896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-09-07DOI: 10.31534/engmod.2018.1-2
M. Cvetković, H. Dodig, D. Poljak
This paper compares the numerical results for the induced electric field, the specific absorption rate (SAR), and the corresponding temperature increase in two detailed models of the human eye. The first model features the human eye placed in the free space, while the second one incorporates the eye model in the realistic head model obtained from the magnetic resonance imaging (MRI) scans. The electromagnetic model is based on the hybrid FEM/BEM formulation for the biological tissue, whereas the thermal dosimetry model is based on the bioheat equation solved by using the finite element method. The preliminary analysis showed a similar distribution of the induced electric field along the pupillary axis obtained in both models, however, the numerical results for the SAR and related temperature increase showed discrepancy between the two models, which can be attributed to the high values of induced field in the corneal and scleral regions obtained in the compound eye model.
{"title":"Numerical comparison of compound and extracted eye models for high frequency dosimetry","authors":"M. Cvetković, H. Dodig, D. Poljak","doi":"10.31534/engmod.2018.1-2","DOIUrl":"https://doi.org/10.31534/engmod.2018.1-2","url":null,"abstract":"This paper compares the numerical results for the induced electric field, the specific absorption rate (SAR), and the corresponding temperature increase in two detailed models of the human eye. The first model features the human eye placed in the free space, while the second one incorporates the eye model in the realistic head model obtained from the magnetic resonance imaging (MRI) scans. The electromagnetic model is based on the hybrid FEM/BEM formulation for the biological tissue, whereas the thermal dosimetry model is based on the bioheat equation solved by using the finite element method. The preliminary analysis showed a similar distribution of the induced electric field along the pupillary axis obtained in both models, however, the numerical results for the SAR and related temperature increase showed discrepancy between the two models, which can be attributed to the high values of induced field in the corneal and scleral regions obtained in the compound eye model.","PeriodicalId":35748,"journal":{"name":"International Journal for Engineering Modelling","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43081648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-09-07DOI: 10.31534/engmod.2018.1-2.ri.01_vjan
Saida Hamioud, S. Khalfallah
The paper describes free vibration of Timoshenko beam by using spectral element method. Based on the partial differential equation of motion, the dynamic stiffness matrix in the frequency domain is formulated. In this case, natural frequencies for simply supported beam are obtained for each mode of vibration. In this study, three solutions are presented: (1) the analytical solution, (2) the finite element method, and (3) the spectral element method. In the last method, the beam is described by one element only, but in finite element modelling, the number of elements varies in order to improve the quality of the solution. Numerical results obtained by these three methods are collected. The spectral element method displays high performance compared to the finite element approach, and is considered as interesting tool in the structural dynamic field.
{"title":"Spectral element analysis of free - vibration of Timoshenko beam","authors":"Saida Hamioud, S. Khalfallah","doi":"10.31534/engmod.2018.1-2.ri.01_vjan","DOIUrl":"https://doi.org/10.31534/engmod.2018.1-2.ri.01_vjan","url":null,"abstract":"The paper describes free vibration of Timoshenko beam by using spectral element method. Based on the partial differential equation of motion, the dynamic stiffness matrix in the frequency domain is formulated. In this case, natural frequencies for simply supported beam are obtained for each mode of vibration. In this study, three solutions are presented: (1) the analytical solution, (2) the finite element method, and (3) the spectral element method. In the last method, the beam is described by one element only, but in finite element modelling, the number of elements varies in order to improve the quality of the solution. Numerical results obtained by these three methods are collected. The spectral element method displays high performance compared to the finite element approach, and is considered as interesting tool in the structural dynamic field.","PeriodicalId":35748,"journal":{"name":"International Journal for Engineering Modelling","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.31534/engmod.2018.1-2.ri.01_vjan","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42662074","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-09-01DOI: 10.31534/ENGMOD.2018.1-2.SI.02_BDNY
I. Krolo, S. Vujević, Tonći Modrić
Novel approach for the high-accurate computation of Carson formulas is presented. Carson formulas are used for computation of per-unit length (pul) self and mutual impedances of infinitely long parallel conductors. Numerical algorithm described in this paper uses a piecewise approximation of the kernel function which appears in the Carson formula corrections. Approximated kernel function is multiplied by the rest of the integrands in the impedance correction expressions and analytically integrated. By using the proposed algorithm, highaccurate results with the desired computed n-digit accuracy can easily be obtained. Results computed by the proposed algorithm are compared with the two most commonly used approximation methods for large frequency range.
{"title":"Computation of Carson formulas using piecewise approximation of kernel function","authors":"I. Krolo, S. Vujević, Tonći Modrić","doi":"10.31534/ENGMOD.2018.1-2.SI.02_BDNY","DOIUrl":"https://doi.org/10.31534/ENGMOD.2018.1-2.SI.02_BDNY","url":null,"abstract":"Novel approach for the high-accurate computation of Carson formulas is presented. Carson formulas are used for computation of per-unit length (pul) self and mutual impedances of infinitely long parallel conductors. Numerical algorithm described in this paper uses a piecewise approximation of the kernel function which appears in the Carson formula corrections. Approximated kernel function is multiplied by the rest of the integrands in the impedance correction expressions and analytically integrated. By using the proposed algorithm, highaccurate results with the desired computed n-digit accuracy can easily be obtained. Results computed by the proposed algorithm are compared with the two most commonly used approximation methods for large frequency range.","PeriodicalId":35748,"journal":{"name":"International Journal for Engineering Modelling","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.31534/ENGMOD.2018.1-2.SI.02_BDNY","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45057781","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2017-03-17DOI: 10.20944/PREPRINTS201703.0127.V1
Jun He, Qinhua Zhang, Qingyang Hu, Guouxi Sun
In order to overcome the limitation of the traditional adaptive Unscented Kalman Filtering (UKF) algorithm in noise covariance estimation for state and measurement, we propose a hybrid adaptive UKF algorithm based on combining Maximum a posteriori (MAP) criterion and Maximum likelihood (ML) criterion, in this paper. First, to prevent the actual noise covariance deviating from the true value which can lead to the state estimation error and arouse the filtering divergence, a real-time covariance matrices estimation algorithm based on hybrid MAP and ML is proposed for obtaining the statement and measurement noises covariance, respectively; and then, a balance equation the two kinds of covariance matrix is structured in this proposed to minimize the statement estimation error. Compared with the UKF based MAP and based ML, the proposed algorithm provides better convergence and stability.
{"title":"A hybrid adaptive unscented Kalman filter algorithm","authors":"Jun He, Qinhua Zhang, Qingyang Hu, Guouxi Sun","doi":"10.20944/PREPRINTS201703.0127.V1","DOIUrl":"https://doi.org/10.20944/PREPRINTS201703.0127.V1","url":null,"abstract":"In order to overcome the limitation of the traditional adaptive Unscented Kalman Filtering (UKF) algorithm in noise covariance estimation for state and measurement, we propose a hybrid adaptive UKF algorithm based on combining Maximum a posteriori (MAP) criterion and Maximum likelihood (ML) criterion, in this paper. First, to prevent the actual noise covariance deviating from the true value which can lead to the state estimation error and arouse the filtering divergence, a real-time covariance matrices estimation algorithm based on hybrid MAP and ML is proposed for obtaining the statement and measurement noises covariance, respectively; and then, a balance equation the two kinds of covariance matrix is structured in this proposed to minimize the statement estimation error. Compared with the UKF based MAP and based ML, the proposed algorithm provides better convergence and stability.","PeriodicalId":35748,"journal":{"name":"International Journal for Engineering Modelling","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2017-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46564736","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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