Proposed Modeling Technique Research Articles

Constitutive Material Model for the Compressive Behaviour of Engineered Bamboo

The mechanical properties of the structural components (i.e., columns and beams produced from engineered bamboo products), such as, bamboo scrimber (also known as parallel bamboo strand lumber, PBSL) and Laminated Bamboo Lumber (LBL), have attracted considerable attention from researchers in recent years. In previous studies, researchers reported on the stress-strain behaviour of bamboo scrimber, LBL and glue laminated bamboo under compression and proposed some empirical and semi-empirical models, based on their individual studies. However, a generic constitutive model for engineered bamboo products is still not available. The compressive stress-strain curves of bamboo scrimber and LBL are reported to show a similar behaviour with three distinct stages i.e., a linear elastic stage followed by a nonlinear plastic stage and a plateau. As part of the current study, the previously proposed models for bamboo scrimber were carefully studied and all available material test results on engineered bamboo were used to develop a generic constitutive model, based on the Ramberg-Osgood (RO) formulation considering its suitability to capture its material nonlinearity. Based on the test results, it was observed that 1% proof stress can be used in a compound RO model to predict an accurate material response for bamboo scrimber. The proposed modelling technique has also been applied to predict the compressive behaviour of LBL. This paper proposes the RO coefficients for both bamboo scrimber and LBL that can be used to develop accurate nonlinear models for engineered bamboo products.

The bearing capacity of arch cover structures made of thin-walled cold-formed profiles

Introduction. The article is focused on evaluating the stress-strain state of nonreinforced arch cover structures made of thin-walled cold-formed profiles and arch cover structures reinforced by arch frames made of triangular trusses and girders. The relevance of the study is backed by the need to reinforce arch covers in the event that the design area of operation of a structure is different from the actual area of operation, which is confirmed by the recent cases of collapse of these structures. To reduce the labour input into simulation, the authors suggest a 3D modelling methodology presented using the case of a hangar reinforced by orthotropic plates and rods.
 Materials and methods. A 2D analysis of an arch was performed using the parameters of the reduced cross-section and a 3D analysis of the same arch was performed using a combined cross-section of plates and rods to verify the methodology. The 2D arch and 3D models were subjected to snow loading in compliance with the regulatory document document SP 20.13330.2016 “Loads and impacts”. Parameters of reduced straight sections and stresses, arising in the 2D arch, were analyzed on the basis of identified internal forces and the regulatory document SP 260.1325800.2016 “Thin-walled steel structures made of cold-formed galvanized profiles and corrugated sheets”. A reduction in the rigidity of corrugated sections is taken into account by assessing the rigidity subjected to the effect of a single force. Finite element modeling was conducted in SCAD Office software; stresses and displacements were calculated automatically.
 Results. The 3D calculation method involving orthotropic plates and rods showed satisfactory convergence with the calculation made in the two-dimensional formulation. Maximum stresses arising in a 3D model are 2 % lower than in a 2D arch, and maximum displacements are 21 % lower thanks to a more accurate FEM analysis of the 3D behaviour of the whole hangar.
 Conclusions. The proposed modeling technique reduces the labor intensity of structural modeling and is suitable for evaluating the joint behaviour of basic and reinforced structures of any type.

A Unified Rule-Based Small-Signal Modelling Technique for Two-Switch, Non-Isolated DC–DC Converters in CCM

The inherent non-linear behavior of switch-mode power supplies complicates the task of computing their linear models, which are essential for a model-oriented control design of DC–DC converters. In a model-oriented control design approach, the accuracy of the plant model directly influences the performance of the control system as the plant parameters tend to be linked to the controllers’ gains. Moreover, the extractions of linear dynamic models of high-order non-linear plants such as DC–DC converters are laborious and mathematically intractable. Therefore, in this paper, a generalized expression that represents either the audio-susceptibility or the control-to-output voltage transfer function for voltage-mode control is proposed. The proposed generalization reduces the task of computing the small-signal model of a given converter to simple calculations of coefficients of generalized transfer function/expression. It is shown that the coefficients of the generalized model can be deduced by inspection, directly from the circuit diagram, allowing the whole model to be computed by inspection. Additionally, the proposed modelling technique will be shown to have secondary use of verifying accuracy even when conventional modelling techniques such as state-space averaging or circuit averaging are used.

Parameter Extraction Technique for Evaluation of Inductive and Capacitive Elements of Three-Winding Coupled Inductor

Wide-bandgap devices have enabled miniaturization of magnetic components to enhance the power density of the converter. However, parasitic components become dominant at higher switching frequencies that actuate unwanted electromagnetic interference issues. Therefore, it is critical to model and evaluate them in compact magnetic structures. Since multiwinding coupled inductive structures are essential part of multiphase converters, this article introduces a measurement method to compute the parasitic elements of a three-winding coupled inductor. Results of the proposed method are verified by measuring the high-frequency emissions of the high-step-up converter with two inductor structures. Both inductors had similar inductances but different physical dimensions. With application of the proposed measurement methodology, parasitic capacitances of both inductors were computed. Results showed that one inductor structure has higher parasitic capacitance than the other. Since high-frequency emissions of the converter directly depend on the parasitic capacitance of the inductor structure, the emission profile of the converter showed that the converter indeed had lower noise peaks when the inductor with lower capacitance was employed. Hence, these results validate the capacitance trend as predicted by the proposed modeling technique. This method can be employed to any multiwinding coupled inductor to compute its parasitics to optimize the required electromagnetic interference filters.

Model of Series-Parallel Photovoltaic Arrays Using Double-Diode Model and Parallel Computing

Several applications require to estimate the power production of photovoltaic (PV) systems under partial shading conditions. For example, dynamic reconfiguration of the array connections is needed to maximize the power production under partial shading conditions, which requires estimating the power generated by the PV array in several possible configurations. Therefore, a fast and accurate modeling technique is needed to perform those calculations in practical times and with low estimation errors. To address those kinds of problems, this paper proposes a modeling approach based on the double-diode model to provide high accuracy at low voltage and low irradiance conditions, which are important for partial-shading analysis. Moreover, the proposed modeling technique is designed to be implemented in parallel processing devices; thus, the calculation time is much shorter in comparison with classical serial solutions. The proposed model is tested in terms of accuracy and speed, obtaining satisfactory results. Finally, the applicability of the parallel model in reconfiguration applications is demonstrated using an application example.

A General Approach to Sampled-Data Modeling for Ripple-Based Control—Part I: Peak/Valley Current Mode and Peak/Valley Voltage Mode

This article is aiming to unify the modeling methods for various ripple-based control schemes. It is divided into two parts, and the first part presents a sampled-data modeling method for the peak/valley current mode (PCM/VCM) control and the peak/valley voltage mode (PVM/VVM) control. It is pointed out that due to the high bandwidth of the dc–dc converter under PCM/VCM or PVM/VVM control, the sideband effect cannot be ignored in the modeling process. Meanwhile, with the small-signal assumption, the feedback perturbation signal has a discontinuity of the first kind at each sampling instant, so the perturbation value at this instant should be obtained according to the Dirichlet conditions, which is equal to half of the sum of the limit values on the left and right sides of the signal. Then, by using Shannon's sampling theorem, the transfer functions of the modulator and the loop gain are derived, and they are used to analyze the influence of the sideband components on the converter stability. Finally, the experimental results from a PCM controlled buck converter validate the proposed modeling technique.

A new approach to modelling closed cell nanofoams and analysis of their mechanical properties

A new approach which is based on the discreet element method and can be used for modelling closed cell nanofoams is revealed in this study. Atomistic models of closed cell nanofoams with five different types of porosity are generated with the help of a proposed modelling technique in order to examine the role of the porosity. Following the generation of atomistic models, the mechanical behaviour is investigated by performing molecular dynamic analyses. The findings signify that such mechanical properties as elastic moduli, ultimate and yield stresses rise with decreasing porosity for both loading types. Additionally, dislocation extraction algorithm (DXA) analysis is carried out to observe the evolution of the deformation mechanism of atomistic models. Dislocation analyses show that the Shockley partial dislocation plays a huge role in the deformation mechanism.

Proposing an Adaptive Neuro-Fuzzy System-Based Swarm Concept Method for Predicting the Physical Properties of Nanofluids

This paper employs dispersed nanoparticles (NPs) to build an adaptive neuro-fuzzy system (ANFIS) for predicting their thermal conductivity (TC) and viscosity according to the most important input data including concentration, size, the thickness of the interfacial layer, and intensive properties of NPs. In this regard, we gather an extensive and comprehensive data set from different sources. Here, the ANFIS model factors are optimized by using the particle swarm optimization (PSO) technique. Afterward, the obtained results are compared with previously published models which did a better job in predicting target values. In the following, to investigate the validity of our proposed model, statistical and graphical techniques are employed and it was proved that this model is efficient to evaluate the output values. Amounts of results obtained from the PSO-ANFIS model evaluation are 0.988 and 0.985 for the R2 and 0.0156 and 0.0876 for root mean squared error (RMSE) of TC ratio and viscosity ratio values, respectively, letting out a valid forecast of targets. Finally, by performing various statistical analyzes, it can be said that this model shows a high ability to predict target values and can be considered a good alternative to previous models.

Improved behavioral modeling using augmented LSTM networks for ultra‐broadband mmWave PA

AbstractIn this article, a new behavioral modeling method based on augmented long‐short term memory (ALSTM) networks for ultra‐broadband millimeter‐wave power amplifiers (mmWave PAs), is proposed. The basic theory and modeling procedure of this technique are provided. Different optimization cores of the models are tested, and the optimal algorithm is chosen. Tradeoffs have been made to fix the optimal topology for the proposed modeling technique. To validate the proposed method, a 4‐carrier 320 MHz modulated signal was employed to excite a mmWave PA with the center frequency located at 41 GHz. Experimental results show that the proposed ALSTM model has better predictive capability when compared with the traditional and other existing machine learning modeling techniques.

Spatially referenced Bayesian state-space model of total phosphorus in western Lake Erie

Abstract. Collecting water quality data across large lakes is often done under regulatory mandate; however, it is difficult to connect nutrient concentration observations to sources of those nutrients and to quantify this relationship. This difficulty arises from the spatial and temporal separation between observations, the impact of hydrodynamic forces, and the cost involved in discrete samples collected aboard vessels. These challenges are typified in Lake Erie, where binational agreements regulate riverine loads of total phosphorus (TP) to address the impacts from annual harmful algal blooms (HABs). While it is known that the Maumee River supplies 50 % of the nutrient load to Lake Erie, the details of how the Maumee River TP load changes Lake Erie TP concentration have not been demonstrated. We developed a hierarchical spatially referenced Bayesian state-space model with an adjacency matrix defined by surface currents. This was applied to a 2 km-by-2 km grid of nodes, to which observed lake and river TP concentrations were joined. The model generated posterior samples describing the unobserved nodes and observed nodes on unobserved days. We quantified the impact plume of the Maumee River by experimentally changing concentration data and tracking the change in in-lake predictions. Our impact plume represents the spatial and temporal variation of how river concentrations correlate with lake concentrations. We used the impact plume to scale the Maumee River spring TP load to an effective Maumee River TP spring load for each node in the lake. By assigning an effective load to each node, the relationship between load and concentration is consistent throughout our sampling locations. A linear model of annual lake node mean TP concentration and effective Maumee River load estimated that, in the absence of the Maumee River load, lake concentrations at the sampled nodes would be 23.1 µg L−1 (±1.75, 95 % CI, credible interval) and that for each 100 t of spring TP effective load delivered to Lake Erie, mean TP concentrations increase by 11 µg L−1 (±1, 95 % CI). Our proposed modeling technique allowed us to establish these quantitative connections between Maumee TP load and Lake Erie TP concentrations which otherwise would be masked by the movement of water through space and time.

Dead Time Optimization in a GaN-Based Buck Converter

A gallium nitride (GaN) field effect transistor can provide superior performance over a Si- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> due to its low <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> -state resistance and low junction capacitances. However, a GaN-based converter exhibits higher dead time loss during reverse conduction. Thus, to improve the efficiency, dead time optimization is required. This article proposes simple models for dead time optimization in a GaN-based buck converter under different load conditions. The proposed models are analytical in nature compared to the conventional models available for Si-based converters. A buck converter prototype is designed using a 100 V GaN device (GS61008P from GaN Systems) and the proposed analytical model-based dead time optimization techniques are validated experimentally. The proposed modeling techniques can be extended for other GaN-based dc–dc converters.

Particle-in-cell model of a relativistic magnetron system driven by a pulse forming network Marx generator

A three dimensional particle-in-cell (PIC) model of a relativistic magnetron (RM) is established using CST Studio Suite. As we adopted a novel technique to imitate pulse forming action of pulser, simulation domain is now fully extended to include a pulser, a transmission line, and a magnetron tube. This feature enables the model to describe a dynamic power coupling process between the pulser and RM in a self-consistent manner. It is demonstrated that model accuracy is strongly dependent on user-defined parameters for an explosive electron emission model. Particularly, emission rise time for space charge formation influences significantly on an initial mode competition phase. Compared to a previous excitation method using a step voltage pulse, the new model gives more reliable results as the intrinsic impedance of the pulser is now considered. Our model is able to estimate the major RM characteristics over a wide range of an external magnetic field. As a result of dynamic power coupling, the RM impedance, the gap voltage, the excitation frequency, and the output power tend to increase at a higher external magnetic field condition. It is suitable to adopt a proposed modeling technique for the virtual assemble and simulation of the system. Hence, it will suggest a practical way to implement and verify complicated structures or innovative designs that could not be solved by existing PIC codes.

Seismic performance of superimposed RC shear walls with concealed bracings using different horizontal connections

To enrich the horizontal connection method and to further study the seismic performance of superimposed RC shear walls with concealed bracings (SRCBSWs) using different horizontal connections, three specimens including SRCBSW with horizontal connection by steel plate bolt kit (SPBK), SRCBSW with horizontal connection by U-ring buckle insert (URBI) and cast-in-place shear wall with concealed bracings were tested under quasi-static loading test. Test results indicated that SRCBSWs exhibited the seismic performance close to that of cast-in-place specimen. The horizontal connection of URBI not only enabled achieve the goal of equivalent cast-in-place connection, but had a beneficial effect on the energy consumption. Due to the fact that the steel plates of SPBKs slipped relative to the contact concrete, the horizontal connection by SPBK was not conducive to energy dissipation and stiffness degradation of the wall, while the load-bearing capacity and deformation characteristic could be enhanced due to the cooperative work of steel plates and concrete in later loading. Finite element analysis of SRCBSWs by Abaqus was conducted based on the proposed modelling techniques, and the reasonable accuracy of the numerical method was verified. The parametric analysis results showed that the axial load ratio, volumetric ratio of the X-shaped steel plate bracings and longitudinal reinforcement ratio in hidden column had obvious effect on the load-bearing capacity and elastic stiffness of SRCBSWs. Taking displacement ductility into account, the axial load ratio of SRCBSWs should be reasonably restricted in practice. Moreover, appropriate thickness of steel plates in SPBKs should be determined according to actual demand, but at least one set of SPBK needed to be arranged in the middle of the wall along the height direction when conducting the layout of SPBK. Besides, the inserted reinforcement ratio in URBI could be reinforced in accordance with the constructional requirements.

Analytical modelling of synchronous reluctance motor including non‐linear magnetic condition

This paper presents an analytical modelling technique based on modified winding function and co-energy analysis, for characterisation of synchronous reluctance machines, in conjunction with a hybrid algorithm for mapping of the machine's operating point on BH curve and the corresponding performance parameters in non-linear magnetic condition. The model successfully provides the mean torque and the torque profiles of a synchronous reluctance motor as a function of input current and load-angle in the magnetic linear and non-linear conditions. The obtained results of this proposed model are compared with finite-element-analysis (FEA) based commercial design software Simcentre-MAGNET. The comparison proves this model's capability to estimate the machine's performance parameters with considerable accuracy from an already established design analysis technique, FEA. The proposed modelling technique requires only a fraction of simulation runtime when compared to other design analysis techniques. Considering the accuracy of this modelling technique and the least requirement of computation resources and simulation time, this model can be used as an initial iterative-design tool for mass personalised, additively manufactured electrical machines where rapidness of the iterative design analysis tool is of paramount importance.

A New Approach to Model Machine Learning by Using Complex Bipolar Intuitionistic Fuzzy Information

Many industries are developing robust models, capable of analyzing huge and complex data by using machine learning (ML) while delivering faster and more accurate results on vast scales. ML is a subfield of artificial intelligence, which is broadly defined as the capability of a machine to imitate intelligent human behavior. ML tools enable organizations to swiftly identify profitable opportunities and potential risks. Besides these uses, ML also has a wide range of applications in our daily lives. So, the development in ML is most important in this age of digital system to solve more complex problems. In order to further develop ML and diminish the uncertainties to improve accuracy, an innovative concept of complex bipolar intuitionistic fuzzy sets (CBIFSs) is introduced in this article. Further, the Cartesian product of two CBIFSs is defined. Moreover, the complex bipolar intuitionistic fuzzy relations (CBIFRs) and their types with suitable examples are defined. In addition, some important results and properties are also presented. The proposed modeling techniques are used to study different ML factors and their interrelationship, so that the functionality of ML might be enhanced. Furthermore, the advantages and benefits of proposed methods are described by their side to side comparison with preexisting frameworks in the literature.

Cyclic Behavior of All-steel BRBs with Bolted Angle Restrainers: Testing and Numerical Analysis

ABSTRACT This study presents the sub-assemblage tests on six all-steel buckling-restrained braces (ABRBs) with bolted angle restrainers. The clearance between the core and restrainers, the core configurations, and the position of stoppers were varied in the experiments. ABRBs with stopper welded in the elastic segments and a higher clearance exhibited higher cumulative ductility. The specimen with perforated core plates showed a stable hysteretic response even for a smaller gap width. Numerical modeling was conducted to predict their hysteretic response and the core fracture of ABRBs. The proposed modeling technique successfully predicted the hysteretic response and the core fracture of braces.

Вплив накопичуваної пошкоджуваності на експлуатаційний ресурс барабана котлоагрегата теплоелектростанції

Goal of the work is to develop a methodology for researching the possibility of further exploitation of drums of boiler units of thermal power plants after exhausting their park resource. Significance. During long-term operation of the drums of boiler units of TPP power units, which work under the action of high pressure, elevated temperature, repeatedly changing cyclic loads, the influence of a corrosive-active working environment, a water-steam mixture, the stressed metal of the drums degrades, various kinds of defects are formed in the vicinity of the stress concentrators and damage that can lead to failure and even large-scale catastrophic destruction. The proposed method makes it possible to establish the residual operational resource of the drums and outline the ways of their more economical operation. Method. The method of computer modeling of the processes of deformation of the drum of a high-pressure boiler under different modes of its operation is built on the basis of spatial-three-dimensional thermoelasticity ratios using the finite element method. Results. The developed technique makes it possible to establish the total value of the parameter of the accumulated damage of the metal of the drum and its residual operational resource. Scientific novelty. A methodology for researching the condition of drums of boiler units of thermal power plants according to the level of accumulated metal damage has been developed, taking into account the determined maximum stresses under different modes of their industrial operation. Practical significance. The proposed modeling technique will make it possible to establish the remaining operational resource of the drums of boiler units of thermal power plants and outline the ways of their more economical operation.

Determining the State of a Nonlinear Flexible Multibody System Using an Unscented Kalman Filter

This paper describes an estimator incorporating the Unscented Kalman Filter (UKF) technique and multibody system dynamics, to determine the state of the flexible multibody applications. The dynamic equation of the flexible mechanism is formed using a set of non-linear equations as functions of reference and modal coordinates. Since both reference and modal coordinates have no physical meaning, their information is not able to be obtained directly from sensors. Thus, a novel technique is proposed in this work that can successfully translate physical measurements collected by sensors into non-physical modal coordinates. To validate the performance of the proposed modeling technique to apply a UKF to determine the state of a nonlinear flexible multibody system, simulation were carried out for a four-bar mechanism case study to compare the simulation data and UKF data.

Prediction of residual stresses in high-strength S690 cold-formed square hollow sections using integrated numerical simulations

In general, residual stresses are induced in structural members during various fabrication processes, such as welding, bending, press-braking, folding, flame cutting and punching. The presence of those residual stresses in cold-formed square hollow sections (CFSHS) primarily caused by i) transverse bending (or cold-forming), and ii) longitudinal welding, is widely considered to have modified both initial stress and strain conditions of these steel members significantly. Hence, these residual stresses are widely considered to have significant adverse effects onto the structural performance of these CFSHS under various actions.In order to examine and quantify both magnitudes and distributions of these residual stresses in S690 CFSHS, an investigation is undertaken to measure residual stresses due to transverse bending and longitudinal welding. Moreover, an approach of integrated numerical simulations is adopted in which a total of three co-ordinated finite element models are established together with various element types and block data transfers to generate compatible meshes for the following three analyses: i) two-dimensional plane-strain bending analyses with large plastic deformations and springback, ii) three-dimensional heat transfer analyses for transient temperature distributions under a heat source, and iii) three-dimensional thermomechanical analyses for welding-induced residual stresses.The predicted results of these three analyses have been carefully calibrated against various experimental data, such as surface temperatures during welding, and residual stresses and strains after welding. Good comparisons between the measured and the predicted data of these S690 CFSHS are demonstrated. The complete residual stress distributions within typical S690 CFSHS due to transverse bending and longitudinal welding are illustrated in three-dimensional plots while simplified residual stress patterns of these sections with specific values and parameters are also provided for subsequent advanced structural analyses and design.The proposed modelling technique for transverse bending and longitudinal welding with compatible meshes of two-dimensional and three-dimensional models with various element types and block data transfers is demonstrated to be highly effective. The technique is readily applicable to simulate residual stresses of all fabricated sections manufactured with transverse bending and longitudinal welding, and, thus, the simulated residual stresses can be employed in subsequent structural analyses of all fabricated members.

Ensemble‐based surrogate modeling of microwave antennas using XGBoost algorithm

AbstractWith respect to the ever‐increasing performance needs in communication technologies, the need for accurate and computational efficient design optimization methods for high‐end microwave designs are also increased. Many studies had been proposed for the last decades for creating numerical modeling methods for having high accurate, stable, and computation efficient solutions suitable to be used in the design optimization process. Ensemble learning is a technique that the models are strategically created and combined to solve a specific computer intelligence challenge and primarily employed to boost the efficiency of a model or to lower the risk of a weak learner collection. Herein, XGBoosting‐based ensemble learning had been used for having surrogate models for three different microwave designs. In the first and second study cases, two microwave designs from the literature are taken into consideration for testing the performance of the proposed model with existing methods. Furthermore, a novel antenna design had been studied as a third study case with sparse training samples, to test the performance of the proposed modeling technique. As a result, the proposed method had achieved a remarkable performance for all the mentioned study cases both based on its own performance measures and its comparison with the counterpart algorithms.