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Lumped passive elements are usually lossy because parasitic resistances dissipate the power transferred from the source to the load; thus, this loss influences the performance of the matching network. Furthermore, the impedances that need to be matched are usually complex‐valued. In this paper, we described an optimization design method for lossy three‐element network to achieve impedance matching between complex source and load impedances. We first determined the efficiency formulas for lossy Π and T networks via a generalized quality‐based equation. Next, two methods were introduced to design the lossy Π and T networks with maximum efficiency. Finally, to validate the effectiveness of the designed lossy three‐element networks, we conducted a series of numerical analysis and simulations, which indicates that the designed lossy Π and T networks exhibits excellent impedance matching performance at the desired frequency. For some instances, the lossy Π network with three elements exhibits a higher efficiency than a multistage matching network with more elements. [ABSTRACT FROM AUTHOR]

In this paper, we adopt the discontinuous Galerkin finite element method and the enriched Crouzeix‐Raviart finite element method to study the magnetohydrodynamic (MHD) Stokes eigenvalue problem describing the flow of a viscous and electrically conducting fluid in a duct under the influence of a uniform magnetic field. We give the convergence and error analysis for the approximations, and the theoretical analysis and numerical experiments show that the methods are effective and can be applied to general domains. We also explore the influence of the Hartmann number on the eigenpairs and the consequential variation of the eigenstructure with the magnetic field by numerical experiments. [ABSTRACT FROM AUTHOR]

In this paper, a delayed mosquito population suppression model with stage and sex structure is constructed incorporating periodic releases of the sterile mosquito and its sexual lifespan. Sterile mosquitoes are released periodically into the field to suppress the wild mosquito population, and only sexually active sterile mosquitoes are included in the interaction system of these two populations. According to the relationship between the release period T$$ T $$ and the sexual lifespan T1$$ {T}_1 $$, we study the dynamic behaviors of the system, such as the existence of positive periodic solutions and the stability of extinction equilibrium in three cases. A series of numerical simulations are performed, which not only verify the reliability of the theoretical results but also make a numerical analysis of the open problems raised in the theoretical research. [ABSTRACT FROM AUTHOR]

In this paper, improving the thermal performance of flat plate solar water heater systems by inserting different tube configurations inside the riser pipes has been numerically and experimentally studied. This study is focused on increasing the moving of energy from riser pipes to the operating fluid within the riser pipes. To achieve that, the diameter of the riser pipes was increased along with the insertion of different tube configurations within them, namely, smooth, helical, and wavy tubes, keeping the same amount of the operating liquid. A comparison was performed to determine the best in terms of coefficient of heat transfer of the operating liquid, mass flow rate of the operating liquid, pressure drop, and water temperature in the storage tank, as a thermal performance indication of the system under study. The findings show the model consisting of a straight tube inside the riser pipe provides the best thermal performance. In terms of thermal performance, the straight model outperforms the conventional model by 12.3%. An experimental and numerical comparison between the optimum model (straight model) was conducted. The study proves that the average difference between numerical results and experimental findings is 7.2%. [ABSTRACT FROM AUTHOR]

It is difficult to separate Luer lock adapters during the external ventricular drainage (EVD) since they are often connected by a threaded connection, and the infusion needle put into the patient's body gets pulled out when extubation occurs unexpectedly. The paper described a new magnetic connection assembly made up of ring magnetic permanents and a Hall sensor that could be used to replace Luer lock adapters for quicker disconnection and reconnection of the drainage catheter. For the design and analysis of the device, the finite element method magnetics (FEMM) was used to estimate the size of magnetic permanents and the best detection site of the Hall sensor for detecting whether the magnetic permanents were closely attracted and/or pulled apart. Then an experiment was conducted to confirm our findings. Both simulation and experiment revealed that a pair of hollow cylindrical magnetic permanents, each with height 10 mm, outer diameter 8 mm, and inner diameter 4 mm, could achieve the same force as the Luer lock adapters held, and that the best Hall sensor detection position was in the middle of the permanent magnets, with a radial distance of about 2 mm. [ABSTRACT FROM AUTHOR]

This paper numerically investigates three typologies of Gerber saddle in existing ordinary and post‐tensioned girder concrete bridges. The main goals of this work concern the evaluation of the effective load‐bearing capacity of Gerber saddles, and the identification of weak points (i.e., lack of enough diagonal reinforcement, loss of pretension in tendons) of existing dapped‐end connections, which lead to the re‐entrant corner diagonal crack, typical of these kinds of structural elements. At this aim, two analytical approaches, with different level of approximations, are used. First, different strut‐and‐tie models are arranged for each typology of Gerber saddle considered, and the global safety factor is estimated for several cases. Second, using nonlinear finite‐element method, the results obtained by strut‐and‐tie models are compared. In addition, several information about the condition of Gerber saddle at collapse are obtained (deformation and stress of concrete and steel rebar, crack patterns) also taking into account the corrosion‐damage effects. Moreover, the results of analyses allow identifying the potential modes of crisis of the dapped‐end connections and their critical aspects. [ABSTRACT FROM AUTHOR]

The effect of openings left in reinforced concrete shear walls due to functional requirements or architectural reasons is an important issue that should not be underestimated mainly since shear walls are considered as one of the most critical load‐carrying members in a structure owing to playing an active role against seismic forces. In this paper, a parametric study was carried out by creating a nonlinear finite element model to determine the effects of openings in reinforced concrete shear walls on the maximum shear force bearing capacities, initial stiffness, displacement ductility ratios, and energy dissipation capacities of the shear walls. The variables examined in the study were the size of the openings left in the reinforced concrete shear walls, opening location, the number of openings, and the concrete compressive strength used in the production of the shear walls. In the first part of the study, nonlinear finite element models of three experimental shear wall test elements: one with no opening (solid), and two with openings: were created using ABAQUS finite element software package, then verified by comparing the numerical analysis results with the experimental results. In the second part of the study, a nonlinear finite element model of 44 reinforced concrete shear walls, including the parameters planned to be investigated, was created by using the verified model, and finite element model (FEM) analyses were performed. As a result of numerical analyses, a capacity reduction coefficient proposal has been developed to calculate the shear force capacities of reinforced concrete shear walls with openings. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical behavior of 10 and 14 vol.% SiCp/Al composites was studied with both experiments and numerical analysis. A 3D macrostructure model based on modified Gurson–Tvergaard–Needleman (GTN) model was developed to predict the elasto‐plastic response and fracture behavior of particle reinforced aluminum matrix composites (PRAMCs). The particle size effects on the plastic strengthening induced by geometrically necessary dislocations (GNDs) were introduced, and the size distribution of the SiC particles was obtained according to the statistical analysis of the microstructure. The material parameters for GTN model were determined with a parameter identification process, and the validity of the numerical results was validated by the agreement of the experimental stress–strain curve. Results reveal that particle size randomness plays an important role in the fracture morphologies. Highlights: Establish a macro‐mechanical model to predict failure behavior of PRAMCs.Modify the GTN damage model to introduce the effect of particle failure and decohesion.Identify the parameters for the modified GTN model and validate the model by comparing with experimental results.Find that particle size randomness plays an important role in fracture morphologies. [ABSTRACT FROM AUTHOR]

Linear operators with off‐diagonal decay appear in many areas of mathematics including harmonic and numerical analysis, and their stability is one of the basic assumptions. In this paper, we consider a family of localized integral operators in the Beurling algebra with kernels having mild singularity near the diagonal and certain Hölder continuity property, and prove that their weighted stabilities for different exponents and Muckenhoupt weights are equivalent to each other on a space of homogeneous type with Ahlfors regular measure. [ABSTRACT FROM AUTHOR]

The present paper is dedicated to the mechanical and fracture characterization of a specific earthen material, that is, the shot‐earth 772. Although such a material has been recently characterized from a microstructural, chemical and physical point of view, the knowledge of its mechanical and fracture properties (essential for extending its use in construction industry) is still lacking. Such characterizations are here performed both experimentally, through laboratory tests, and numerically, through a FE model. The experimental tests (i.e., flexural, compression, and fracture tests) are carried out on shot‐earth specimens according to recommendations available for concrete and a method proposed by the present authors, named Modified Two‐Parameter Model. The numerical analyses are performed by employing a micromechanical model (implemented in a nonlinear 2D FE homemade code), which allows to simulate both flexural and fracture behavior of the shot‐earth examined. Finally, the obtained numerical results are compared with the experimental ones. Highlights: The mechanical and fracture characterization of shot‐earth 772 is performed.Flexural, compression and fracture tests are carried out on the shot‐earth specimens.Numerical analyses are performed by using a homemade micromechanical finite element model.Flexural behavior and fracture behavior of shot‐earth 772 are numerically simulated. [ABSTRACT FROM AUTHOR]

In this paper, heat transfer induced in smooth and wavy channels in the presence of two phases (air and steam) was conducted and discussed. Two configurations have been studied according to the geometrical shape of the channel walls. The thermal and hydrodynamic fields in the channel have been predicted using the single‐fluid approach with a solver based on the finite volume method. Explicit formulation of the volume of fluid was used to track the interface between both fluids. The mesh in the wavy channel was treated with a curvilinear mesh grid. Local Nusselt evolution, isothermal distribution, streamlines, and other parameters have been shown at different times of simulation. It was found that weak air phase velocities and wave patterns of the channel walls play a destabilizing role in the interface evolution between both fluid phases. In addition, results show that channels with wavy walls can be an effective solution to ensure higher heat transfer in two‐phase flows. [ABSTRACT FROM AUTHOR]

This paper presents a novel perspective on fully distributed adaptive protocol design for bipartite consensus under directed communication graphs. It is revealed that the fully distributed protocol is indeed a PI‐gain design approach. Based on such PI‐gain method, fully distributed observer‐based protocols are proposed to solve the consensus problem of nonlinear multi‐agent systems over directed cooperative‐antagonistic networks, where the neural network approximation is introduced to tackle the unknown nonlinearity. Fully distributed continuous protocols are further presented by modifying the sign function with a decaying variable, which takes the advantage of avoiding chattering problem. Theoretical analysis and numerical simulations are given to support our main results. [ABSTRACT FROM AUTHOR]

Unlocking the biomechanical effects of cervical spine positioning rotation manipulation in the treatment of patients with neck pain. In this paper, the safety of the cervical positioning rotation manipulation is analyzed by experimentally obtaining head kinematic data, importing them into a finite element model that has been developed and validated, and calculating and analyzing the angular displacements, disc pressures, and articular surface contact forces in the normal and pathological models. The results show that the cervical spine positioning rotation technique is more effective in adjusting the position and applying force to the cervical spine C5–C6 "tendon out of the groove and bone misalignment" pathological model. Also, the cervical positioning rotation manipulation is applied with less variation in disc nucleus pulposus pressure than in the non‐positioning situation. Thus, in patients with disc degeneration, cervical positioning rotational manipulation has a more direct mechanical effect and is safer than non‐positioning rotational manipulation. The cervical spine positioning rotation manipulation is a safe method that can effectively treat patients with neck pain. It has been well demonstrated in the computational analysis of the pathological model. [ABSTRACT FROM AUTHOR]

Millimetre wave (mmWave) communications, that is, 30 to 300 GHz, have intermittent short‐range transmissions, so the use of reconfigurable intelligent surface (RIS) seems to be a promising solution to extend its coverage. However, optimizing phase shifts (PSs) of both mmWave base station (BS) and RIS to maximize the received spectral efficiency at the intended receiver seems challenging due to massive antenna elements usage. In this paper, an online learning approach is proposed to address this problem, where it is considered a two‐phase multi‐armed bandit (MAB) game. In the first phase, the PS vector of the mmWave BS is adjusted, and based on it, the PS vector of the RIS is calibrated in the second phase and vice versa over the time horizon. The minimax optimal stochastic strategy (MOSS) MAB algorithm is utilized to implement the proposed two‐phase MAB approach efficiently. Furthermore, to relax the problem of estimating the channel state information (CSI) of both mmWave BS and RIS, codebook‐based PSs are considered. Finally, numerical analysis confirms the superior performance of the proposed scheme against the optimal performance under different scenarios. [ABSTRACT FROM AUTHOR]

In this paper, we proposed a modified marker and cell (MMAC) method for solving the steady‐state Stokes equations with Dirichlet boundary condition. We reconstruct the marker and cell (MAC) schemes by using the quadratic Lagrange extrapolation method to approximate the value of ghost points near the boundary. First, we prove the stability of the proposed scheme rigorously. Then, we obtain the second‐order superconvergence for pressure in the discrete L2$$ {L}^2 $$ norm and velocity in the discrete H1$$ {H}^1 $$ norm by constructing auxiliary functions and discretizing parameters. Meanwhile, we present two MMAC schemes for the time‐dependent Stokes equations by a similar method. Finally, we provide some numerical experiments to confirm our theoretical analysis. [ABSTRACT FROM AUTHOR]

We analyze a mathematical model of a tumor that includes the interactions among tumor cells (live or dead), macrophages, endothelial cells, and the cytokines based on a system of partial differential equations which describes inhibition of tumor growth by granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) treatment. The aim of the model is to predict the growth of the tumor volume under partial blocking of hypoxia‐inducible factor (HIF)‐1 or stabilization of HIF‐2, with injection of GM‐CSF. It was assumed that tumor is a spherical and the treatment by GM‐CSF is not optimized. In this paper, we do not assume that tumor is a spherical model and we develop a dual dynamic programming approach to formulate a verification condition of an approximate treatment for an injection of GM‐CSF. Next, we analyze numerically an ε$$ \varepsilon $$‐optimal treatment. [ABSTRACT FROM AUTHOR]

Since the pioneering work of Turing, it has been known that diffusion can destablise a homogeneous solution that is stable in the underlying model in the absence of diffusion. The destabilisation of the homogeneous solutions leads to the generation of patterns. In recent years, techniques have been developed to analyse so‐called localised spatial structures. These are solutions in which the spatial structure occurs in a localised region. Unlike Turing patterns, they do not spread out across the whole domain. We investigate the existence of localised structures that occur in two predator‐prey models. The functionalities chosen have been widely used in the literature. The existence of localised spatial structures has not investigated previously. Indeed, it is easy to show that these models cannot exhibit the Turing instability. This has perhaps led earlier researchers to conclude that interesting spatial solutions can therefore not occur for these models. The novelty of our paper is that we show the existence of stationary localised patterns in systems which do not undergo the Turing instability. The mathematical tools used are a combination of Linear and weakly nonlinear analysis with supporting numerical methods. By combining these methods, we are able to identify conditions for a wide range of increasing exotic behaviour. This includes the Belyckov‐Devaney transition, a codimension two spatial instability point and the formation of localised patterns. The combination of spectral computations and numerical simulations reveals the crucial role played by the Hopf bifurcation in mediating the stability of localised spatial solutions. Finally, numerical solutions in two spatial dimensions confirms the onset of intricate spatio‐temporal patterns within the parameter regions identified within one spatial dimension. [ABSTRACT FROM AUTHOR]

Millimetre wave (mmWave) communications, that is, 30 to 300 GHz, have intermittent short‐range transmissions, so the use of reconfigurable intelligent surface (RIS) seems to be a promising solution to extend its coverage. However, optimizing phase shifts (PSs) of both mmWave base station (BS) and RIS to maximize the received spectral efficiency at the intended receiver seems challenging due to massive antenna elements usage. In this paper, an online learning approach is proposed to address this problem, where it is considered a two‐phase multi‐armed bandit (MAB) game. In the first phase, the PS vector of the mmWave BS is adjusted, and based on it, the PS vector of the RIS is calibrated in the second phase and vice versa over the time horizon. The minimax optimal stochastic strategy (MOSS) MAB algorithm is utilized to implement the proposed two‐phase MAB approach efficiently. Furthermore, to relax the problem of estimating the channel state information (CSI) of both mmWave BS and RIS, codebook‐based PSs are considered. Finally, numerical analysis confirms the superior performance of the proposed scheme against the optimal performance under different scenarios. [ABSTRACT FROM AUTHOR]

It is well‐known that when the geometry and/or coefficients allow stable trapped rays, the outgoing solution operator of the Helmholtz equation grows exponentially through a sequence of real frequencies tending to infinity. In this paper we show that, even in the presence of the strongest possible trapping, if a set of frequencies of arbitrarily small measure is excluded, the Helmholtz solution operator grows at most polynomially as the frequency tends to infinity. One significant application of this result is in the convergence analysis of several numerical methods for solving the Helmholtz equation at high frequency that are based on a polynomial‐growth assumption on the solution operator (e.g. hp‐finite elements, hp‐boundary elements, and certain multiscale methods). The result of this paper shows that this assumption holds, even in the presence of the strongest possible trapping, for most frequencies. © 2021 The Authors. Communications on Pure and Applied Mathematics published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper presents a tri‐level stochastic coordinated transmission and distribution system expansion (CTDS) planning considering the deployment of energy hubs (EHs) across the distribution systems (DSs). The first level of the proposed optimization approach deals with transmission system expansion planning (TEP), while the second level develops distribution system expansion planning (DEP). Market clearing is done in the third level to update the locational marginal prices (LMPs) for different distribution system operators (DSOs). The EHs include photovoltaic cells (PVs), wind turbines (WTs), combined heating and power units (CHPs), boilers, and electrical and absorption chillers. The proposed tri‐level approach is solved with an iterative algorithm based on the diagonalization approach and tested on the modified IEEE 30‐bus transmission systems (TS) with several DSOs. Each DSO includes 18‐bus electrical, heating, and cooling energy systems. The numerical analysis shows that the total cost of the transmission system operator (TSO) is not changed with implementing the uncoordinated approach. However, the total cost of the whole system is reduced by 6.54% with accommodation of the EHs in the uncoordinated approach. Moreover, the total cost of the TSO as well as the whole system are reduced by 41.11% and 16.96%, respectively, with the proposed (CTDS) planning. [ABSTRACT FROM AUTHOR]

Wireless power transfer (WPT) has been attracting a lot of attention in recent years for its ability to greatly improve the convenience of our lives. Moreover, WPT for Electric Vehicles (EVs) has become an important key to the spread of EVs. The efficiency of WPT using magnetic field resonant coupling can be evaluated by the kQ product, but the optimal coil design method to maximize the kQ product at a specific frequency has not yet been established. In this paper, taking the Test station GA‐WPT1 and the Test station VA‐WPT1/Z3 of SAE J2954, which is officially defined as the standard for WPT while the electric vehicle is stationary in October 2020, as examples, the coil parameters that maximize the kQ product in the case of the coreless are determined according to the proposed method. An efficiency of 99.13% was obtained with a transmission distance of 200 mm and the number of turns of N1 = 34 and N2 = 30. Also, since all analyses can be derived immediately except for the analysis of the Litz wire to be used, the optimization time could be reduced significantly compared with the electromagnetic field analysis. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

In this review paper, a critical assessment of the main degradation processes in three key components of solid oxide fuel cells and electrolysers (negative and positive electrodes and the interconnect) is undertaken, attempting prioritization of respective degradation effects and recommendation of the best approaches in their experimental ascertainment and numerical modeling. Besides different approaches to quantifying the degradation rate of an operating solid oxide cell (SOC), the latest advancements in microstructural representation (3D imaging and reconstruction) of SOC electrodes are reviewed, applied to the quantification of triple‐phase boundary (TPB) lengths and morphology evolution over time. The intrinsic degradation processes in the negative (fuel) electrode and the positive (oxygen) electrode are discussed, covering first the composition and governing mechanisms of the respective electrodes, followed by a comprehensive evaluation of the most important factors of degradation during operation. By this systematic identification of dominant degradation processes, measurement techniques, and modeling approaches, the foundations are laid for the definition of meaningful accelerated stress testing of SOC cells and stacks, which will help the technology achieve the constantly more demanding durability targets in market applications. [ABSTRACT FROM AUTHOR]

Improvements in technology for the production of microbial biomass from natural gas, which have been gaining importance in recent years, require the development and optimization of energy‐efficient bioreactor designs. The most advanced methods for developing and scaling up industrial biotechnological processes rely on detailed hydrodynamic modeling, in addition to classical approaches, as the main tool for analysis and large‐scale transfer of experimental information. This paper presents the results of a simulation of flows in a bioreactor circuit using the latest mathematical methods and numerical flow analysis tools for two‐phase bubble flows based on experimental data. [ABSTRACT FROM AUTHOR]

The numerical techniques required to prove the single‐photon emission from any type of quantum emitter (QE) after being coupled to any nanostructure are presented in this paper. The Purcell effect modifies the emission characteristics of QEs, such as color centers in nanodiamonds, for example, nitrogen‐vacancy (NV) centers, silicon vacancy (SiV) centers, and so forth, or semiconductor quantum dots. Our numerical approach is based on the unique QEs' experimental photophysics parameters and numerical analysis software, which are MATLAB and Quantum Toolbox in Python (QuTiP). Our results show a comparable g(2) (τ) behavior between our proposed numerical model and the other two experimental results for the QE before and after coupling to a plasmonic waveguide with subwavelength dimensions. Our proposed method is essential to prove the single‐photon emission of modeled single‐photon source (SPS) in an on‐chip polarization‐dependent quantum key distribution system (QKD). [ABSTRACT FROM AUTHOR]

The effect of the boundary conditions, defined as the thermal expansion restraint imposed by the external uniaxial compressive load in plain concrete subjected to high temperatures, is discussed. A numerical mesoscopic investigation uncoupled the load induced thermal strain (LITS) into three main components (aggregates and matrix strain contributions and the effect of the thermal expansion restraint). The analyses demonstrate that LITS depends on the materials properties (viscous‐plastic behavior) and also on the boundary conditions, which is function of the test setup and seems to be not related to the material properties. In this paper, the role of the boundary conditions on 1‐phase (homogeneous) and 2‐phase (matrix + aggregates) numerical analyses are investigated. A LITS semi‐empirical model is incorporated in the numerical modeling to account for the stiffness degradation. It is demonstrated that in 1‐phase models, the effect of the boundary conditions is absent, which is not true for mesoscale analyses. In this case, the effect of the boundary conditions should be taken into account and subtracted from the results to avoid an overestimation of the material response. It is important mentioning that the analyses of concrete behavior at elevated temperatures and transient creep experimental procedures completely neglect the role of the boundary conditions. [ABSTRACT FROM AUTHOR]

This paper deals with a Finite Element (FE) numerical analysis of an electromagnetic stirring system for composite plastic materials with ferromagnetic particles. The electromagnetic stirring process is ensured by the magnetic forces acting on the ferromagnetic particles spread in the plastic matrix. These forces are produced by the rotating magnetic field of the stator of a three‐phase induction motor supplied from an inverter. The analysis is carried out using the professional software package Flux for electromagnetic field computation based on the FE method. The 2D computations allowed to estimate the magnetic forces and their orientation acting on micrometric particles spread in a fluid plastic material. A preliminary experimental setup is also built for studying the proposed solution. [ABSTRACT FROM AUTHOR]

In this paper, we study the finite difference/iterative method for the fractional telegraph equation with Hadamard derivatives. The model is first transformed into an equivalent fractional integro‐differential equation, then the technic of exponential type meshes is adopted. The resulting discrete coefficients of Hadamard fractional integral own several graceful properties, which are crucial in numerical analysis. To conquer the difficulty caused by weak regularity, we also propose iterative schemes. The error estimate is equal to O(logt)n+γ,1

This paper analyses the performance of the experimental setups to assess the punching strength of slab‐column connections in continuous flat slabs under vertical and horizontal loading. In the last years, several experimental campaigns have been performed to investigate the punching strength of slab‐column connections, but most of the experimental tests concerned isolated slab‐column connections. Among the few setups aimed at reproducing the eccentric punching failure in continuous flat slabs, the setup developed at the NOVA School of Science and Technology in Lisbon is considered in this paper. The performance of the Lisbon setup is assessed through nonlinear finite element analyses, calibrated on experimental data, by comparison with numerical results of a theoretical continuous setup. Then, the performance of the isolated setups, used in many researches and at the base of some international codes, is also evaluated through the same finite element model. Numerical analyses highlight that the setup developed in Lisbon could provide reliable ultimate rotations of continuous flat slab connections, but it underestimates the punching strength. Despite isolated setups lead to similar results when compared with the Lisbon setup, the latter seems to provide a better representation of a continuous slab‐column connection. The numerical analyses presented in this paper have been performed assuming monotonic lateral loading. [ABSTRACT FROM AUTHOR]

The present numerical investigation has focused on the magnetohydrodynamics flow of a viscous nanofluid over a stretching wedge with the boundary convective conditions, thermal radiation, and ohmic heating. Buongiorno's two‐component nonhomogeneous nanoscale model was used and a dilute nanofluid with spherical type particles is considered. Similarity transformations are used to render the system of governing partial differential equations into a system of coupled similarity equations. The transformed equations are solved numerically with the BVP4C method. Validation of solutions with previous studies based on special cases of the general model is included. The salient features of fluid velocity profile, temperature as well as concentration profiles are discussed in a graphical manner for various values of selected governing factors. The skin friction coefficient, mass, and heat transfer rates are calculated and summarized. It is worthwhile noticing that the validation results exhibit an excellent agreement with already existing reports. The modeling of the present problem is useful in the thermal processing of sheet‐like substances that is a necessary operation in paper procurement, wire drawing, drawing of plastic films, polymeric sheets, and metal spinning. [ABSTRACT FROM AUTHOR]

By installation in district heating and cooling systems, large volumetric sensible heat storage tank is a technology that can reduce CO2 emissions into the atmosphere, ensure the integration of renewable energy sources into district heating and cooling systems, overcome the mismatch between production and demand and increase reliability and efficiency of entire systems. Such tanks operate on the principle of temperature stratification. In this paper, the processes of charging and discharging the heat storage tank used in district heating systems depending on the geometric and process parameters are analyzed and the thermal efficiency of each of these processes is calculated. The thermal efficiency of the tank charging process is calculated based on the distribution of the warmer water temperature in the tank after the complete tank charging process and varies between 53.85% and 96.75%. The thermal efficiency of the tank discharging process was calculated based on the warmer water outlet temperature and varies between 87.83% and 96.00%. Validation of mathematical model was achieved by comparing the data obtained by measuring the water temperature in the heat storage tank installed in the city thermal power plant‐heat plant and the results of numerical calculation. [ABSTRACT FROM AUTHOR]

Detection and tracking of small targets in sea clutter using a high-resolution radar is a challenging problem as the sea surface constantly moves in a complex manner, with rough seas creating strong target-like returns. Recently, a Bernoulli track-before-detect (TBD) filter has been developed for an airborne scanning radar in the maritime domain. Its purpose is to detect and track short-exposure targets by using the radar in a fast scanning mode. The current paper investigates the potential improvement in detection and tracking performance of the Bernoulli TBD filter by incorporating a backward smoothing step. The developed algorithm, referred to as the Bernoulli TBD forward-backward smoother (FBS) for maritime radar, is making a delayed decision by taking into account multiple future scans of radar data. A numerical analysis of a joint detection and tracking error with a fixed-lag smoothing is presented, as a function of the number of delay lags, signal-to-interference ratio and the sea clutter spikiness. [ABSTRACT FROM AUTHOR]

We study in this paper the well‐posedness and stability of three structures with interfacial slip and two infinite memories effective on the transverse displacement and the rotation angle. We consider a large class of kernels and prove that the system has a unique solution satisfying some regularity properties. Moreover, without restrictions on the values of the parameters, we show that the solution goes to zero at infinity and give an information on its speed of convergence in terms of the growth of kernels at infinity. A numerical analysis of the obtained theoretical results will be also given. [ABSTRACT FROM AUTHOR]

This paper discusses the numerical solutions of the nonlinear Klein–Gordon–Zakharov model by the use of five recent numerical schemes (Adomian decomposition, El‐kalla, cubic B‐spline, extended cubic B‐spline, and exponential cubic B‐spline). The object of this numerical analysis is to demonstrate the accuracy of the analytical solutions obtained using the generalized Khater system and also to display the accuracy of the five numerical schemes mentioned above. This mathematical model explains the development in plasma physics of efficient Langmuir turbulence. We use computational solutions to assess the original and boundary conditions which require the numerical schemes to be implemented. Many distinct sketches are given to demonstrate the exactness of the numerical solutions measured. [ABSTRACT FROM AUTHOR]

The purpose of operating a radar system multistatically is to acquire information about targets of interest more quickly and reliably than would be possible using disparate radars, which fuse data and track post‐detection. This paper identifies and addresses the critical issues for designing a coherent multistatic radar system using conventional coherent radars and proposes a set of design principles for configuring a coherent multistatic radar network with the aim of maximising the utility of information while constraining system cost and complexity. The issues discussed are as follows: the localisation of targets in three dimensions; eliminating the inevitable spatial ambiguities arising from sparse spatial sampling while exploiting the large aperture for high resolution; the achievement of spatial coherent processing gain for target detection; the effect of phase centre localisation, phase and frequency errors on synchronisation; the incorporation of three‐dimensional Doppler estimation for slow‐time coherent integration. The arguments presented are physically‐based and complemented by mathematical analysis and numerical experimentation using non‐linear sparse estimation, the sparse algorithm being critically important for resolving spatial ambiguities. An optimal configuration is identified, which has sufficiently many nodes to overcome spatial ambiguities and achieves significant spatial coherent processing gain, while simultaneously constraining the overheads of inter‐node synchronisation and communication. [ABSTRACT FROM AUTHOR]

This paper presents several methods for performing two types of static load model conversion: exponential to ZIP & ZIP to exponential model conversion. In general, these conversions are inaccurate due to non‐equivalence of exponential and ZIP (second‐order polynomial) models. A numerical analysis is conducted using generated datasets of load models to analyse the error and to compare the accuracy of the presented methods. The results of the analysis indicate that the optimal selection of conversion method depends on a number of factors, including normalisation of load models, ZIP model type (accurate or constrained) and expected use of the converted model. In addition, a case study is conducted to analyse the impact of conversion error on load flow results. The results of the case study indicate that a significant difference in load flow results can occur when the load models are converted. Recommendations for conversion method selection are given in the discussion section of the paper. [ABSTRACT FROM AUTHOR]

We consider a fractional‐order nerve impulse model which is known as FitzHugh–Nagumo (F–N) model in this paper. Knowing the solutions of this model allows the management of the nerve impulses process. Especially, considering this model as fractional‐order ensures to be able to analyze in detail because of the memory effect. In this context, first, we use an analytical solution and with the aim of this solution, we obtain numerical solutions by using two numerical schemes. Then, we demonstrate the walking wave‐type solutions of the stated problem. These solutions include complex trigonometric functions, complex hyperbolic functions, and algebraic functions. In addition, the linear stability analysis is performed and the absolute error is occurred by comparing the numerical results with the analytical result. All of the results are depicted by tables and figures. This paper not only points out the exact and numerical solutions of the model but also compares the differences and the similarities of the stated solution methods. Therefore, the results of this paper are important and useful for either neuroscientists and physicists or mathematicians and engineers. [ABSTRACT FROM AUTHOR]

The paper presents the tridimensional numeric model of an inner slab‐column connection of reinforced concrete, which was previously tested against the punching shear in the lab of the University of Brasília. The numerical analysis has been carried out by the finite element method, using the software ABAQUS. To evaluate the sensitivity of the main factors that influence the responses of the model, a parametric investigation was conducted as per the finite element mesh, mechanical properties of the concrete and plastic parameters of the assumed model for the concrete, named by concrete damaged plasticity model (CDPM). The results of the resistance capacity, displacements, strains, cracking pattern, and failure mode were compared with those obtained experimentally. From this comparison, it was concluded that the numerical model was able to reproduce the punching shear phenomenon with a high level of precision. [ABSTRACT FROM AUTHOR]

Summary: Millimeter wave (mmWave) massive multiple‐input multiple‐output (MIMO) channels are cosparse in nature. These cosparse channels share common cosparsity properties, which is interesting when it comes to estimating a large number of mmWave mMIMO channels. Therefore, the channel estimation (CE) problem can be solved by exploiting the cosparsity and common cosupport properties. Specifically, the CE problem can be formulated as a cosparse signal recovery problem, which can be solved using an analysis operator (AO) and the iterative hard thresholding (IHT) algorithm. Prior analysis‐based compressive sensing (ACS) CE techniques adopt an overcomplete AO, which leads usually to a suboptimal solution that cannot guarantee CE accuracy. In this paper, we firstly propose a projected subgradient (PSG) scheme for AO learning. Then, using the previously learned AO, we propose an iterative Newton hard thresholding (INHT)‐based ACS‐CE algorithm. The effectiveness of the proposal has been proven by computational complexity analysis and numerical simulations. [ABSTRACT FROM AUTHOR]

This paper suggests a simple loading configuration for conducting the SCB (semi‐circular bend) tests on brittle materials to produce mixed mode I/III loadings. In the suggested test setup, the SCB specimen containing an inclined crack is loaded using a conventional three‐point bending fixture, but the bottom supports touches nearly half of the specimen thickness rather than the entire thickness. It is found that various mixed mode I/III loadings can be provided by rotating the crack, and especially the SCB specimen experiences pure mode III when the crack angle is set to be 90°. Different values of the crack length, span and crack angle are then considered in the numerical analyses to further study the proposed SCB test setup. Finally, several experiments are successfully conducted on the rock samples under various mixed mode I/III and pure mode III loadings to evaluate the SCB test setup in practical point of view. Research highlights: A simple loading configuration is suggested for conducting the SCB tests.Mixed mode I/III and pure mode III tests can be performed using the SCB specimen.Effects of crack length, span and crack angle in the SCB tests are numerically explored.Mode III has a negative effect on the fracture resistance of rock materials. [ABSTRACT FROM AUTHOR]

In this paper, the problem of opportunistic spectrum sharing for the next generation of wireless systems empowered by the cloud radio access network (C‐RAN) is studied. More precisely, low‐priority users employ cooperative spectrum sensing to detect a vacant portion of the spectrum that is not currently used by high‐priority users. The authors' aim is to maximize the overall throughput of the low‐priority users while guaranteeing the quality of service of the high‐priority users. This objective is attained by optimally adjusting spectrum sensing time, with respect to target probabilities of detection and false alarm, as well as dynamically allocating C‐RAN resources, that is, powers, sub‐carriers, remote radio heads, and base‐band units. To solve this problem, which is non‐convex and NP‐hard, a low‐complex iterative solution is proposed. Numerical results demonstrate the necessity of sensing time adjustment as well as effectiveness of the proposed solution. [ABSTRACT FROM AUTHOR]

As one kind of jacketed vessels, half‐pipe jacketed vessels are widely used in engineering owing to the structural and heat transfer advantages. But for the design of half‐pipe jacketed vessels, there are limitations in codes ASME VIII‐1 and ASME VIII‐2. In this paper, a new design method based on numerical limit‐load analysis is proposed to design half‐pipe jacketed vessels. The scheme and advantages of the method are presented through a design of half‐pipe jacketed vessel. It is found that by performing limit‐load analysis, problems of the codes ASME VIII‐1 and ASME VIII‐2 about the structural limitation of the half‐pipe jacketed vessels and loading limitation are solved. In addition, by performing limit‐load and parametric analysis, the strength weakness areas on the vessels can be found, and the rational strength design of a structure can be achieved. [ABSTRACT FROM AUTHOR]

Generalized inverses of tensors play increasingly important roles in computational mathematics and numerical analysis. It is appropriate to develop the theory of generalized inverses of tensors within the algebraic structure of a ring. In this paper, we study different generalized inverses of tensors over a commutative ring and a noncommutative ring. Several numerical examples are provided in support of the theoretical results. We also propose algorithms for computing the inner inverses, the Moore–Penrose inverse, and weighted Moore–Penrose inverse of tensors over a noncommutative ring. The prowess of some of the results is demonstrated by applying these ideas to solve an image deblurring problem. [ABSTRACT FROM AUTHOR]

This paper presents a refined full‐domain model for the fluidic‐thermal coupled analyses of a 15‐kW 30,000‐rpm high‐speed permanent magnet synchronous machine (HS‐PMSM) considering the heat generation and dissipation of the bearing components. In order to analyse the heat dissipation capacities of the bearing components, firstly, the fluid flow conditions inside the bearings with different revolution and rotation ratios are researched, and the most serious case is taken in the full‐domain calculations. Secondly, the three‐dimensional (3D) full‐domain model is established, and the fluidic‐thermal analyses are conducted based on the basic principles of numerical heat transfer and CFD. During calculations, in order to obtain the temperature rise precisely, the angular contact ball bearings are well modelled with all the internal components including the oil films, and the frictional loss in the bearings are computed by the Palmgren model. A 15‐kW 30,000‐rpm HS‐PMSM prototype is established and tested to verify the full domain thermal modelling methodologies and indirectly validate the bearing performance calculations. Finally, a self‐ventilated structure is employed to prevent the bearing temperature rise, and the cooling effectiveness is validated by numerical calculations. [ABSTRACT FROM AUTHOR]

In this paper, the issue of output feedback finite‐time stabilization is investigated for a class of p‐norm stochastic systems with output constraints. A novel tan‐type barrier Lyapunov function (BLF) is constructed to cope with the constraint on the system output, and a finite‐time state feedback controller is subsequently designed by the adding a power integrator technique. Then, based on the designed state feedback controller and a devised nonsmooth observer for the unmeasurable state, the output feedback finite‐time stabilizer is obtained. Both the theoretical analysis and numerical example demonstrate that the proposed scheme guarantees the finite‐time stability of the considered system without violating the prespecified output constraint. [ABSTRACT FROM AUTHOR]

Intrinsic localized mode (ILM) can be generated in multiple mass‐spring systems using nonlinear springs, and ILM has attracted a lot of attention due to its special vibration modes that are not found in linear systems. However, the difficulty of creating nonlinearity remains a barrier to ILM research. In this paper, we propose a rotating magnetic spring based on magnetic nonlinearity. The nonlinear restoring properties of the proposed magnetic spring are confirmed by finite element method (FEA). Finally, using the restoring properties obtained from FEA, it is shown that ILM can be excited by MATLAB numerical analysis. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This paper describes PWLFIT+, an extension to the frequency domain of PWLFIT, a new paradigm in time‐domain macromodeling for linear multiport systems, based on a piecewise‐linear (PWL) behavioral representation of the S‐parameters step response. While the impulse response of each S‐parameter is approximated as sum of delayed rectangles (rect) functions, its spectrum is interpolated as sum of the corresponding delayed cardinal sine (sinc) functions. Exploiting this correspondence, the model building is performed by an iterative procedure where the PWL macromodels can be determined in order to meet defined accuracy goals on the spectrum. At runtime, waves at macromodels ports are calculated using the Segment Fast Convolution (SFC) algorithm within the Digital Wave Simulator (DWS) framework. The proposed method is characterized by its simplicity, stability, speed and scalability, all features that are emphasized when it is used in the DWS framework. After an analysis of the excellent numerical features of SFC in the Z‐domain, clearly differentiated with respect conventional macromodeling methods based on poles and residues, two suitable application examples are presented to demonstrate the unique features of PWLFIT+. [ABSTRACT FROM AUTHOR]

In this paper, we consider the time‐dependent Stokes problem in a three‐dimensional domain with mixed boundary conditions. The discretization relies on spectral methods with respect to the space variables and Euler's implicit scheme with respect to the time variable, then by the second order BDF method. A detailed numerical analysis leads to a priori error estimates for each numerical scheme. [ABSTRACT FROM AUTHOR]

In this paper, we apply the characteristic finite volume method (CFVM) for solving a convection‐diffusion problem on two‐dimensional triangular grids. The finite volume method is used to discretize the equation while the finite element method is applied to estimate the gradient quantities at cell faces. The numerical analysis of the convergence has been implemented for the CFVM in one‐dimension. The approximate L2 norm of the error is derived to determine the errors for the approximate solution. The accuracy of four piecewise linear reconstruction techniques, namely, Frink, Holmes‐Connell, Green‐Gauss, and least‐squares methods are investigated on structured triangular grids. Numerical evidence shows that the least‐squares method is the most accurate of all methods for smooth initial condition problems. For discontinuous initial condition problems, the Frink and the Holmes‐Connell methods give a spurious oscillating solution in the vicinity of the discontinuity upstream of the discontinuity, and the Green‐Gauss and least‐squares methods give a spurious oscillating solution in the vicinity of the discontinuity downstream of the discontinuity. Moreover, the amplitude of the oscillation could be amplified on the finer grid sizes. [ABSTRACT FROM AUTHOR]

Inclusion is one of the main causes for unqualified wire. However, the forming mechanism of drawing fracture due to inclusions is still unclear. Therefore, it is significant to figure out the forming mechanism of wire drawing fracture with inclusions for designing and manufacturing high‐quality wires. In this paper, a physical model of wire with inclusion is established based on experimental observations. Multipass drawing is simulated by using finite element method (FEM) with the developed numerical damage modeling. Numerical results demonstrate that the damage increases with the development of drawing progress, and the damage caused by high elastic modulus of inclusion is greater than that of low elastic modulus. Pen‐tip shaped fracture of wire with inclusions is mainly caused by the superposition of core and external V‐shaped damage. Furthermore, the core V‐shaped crack will propagate along the external V‐shaped damage area. [ABSTRACT FROM AUTHOR]

Control of optical fields at the nanoscale holds the promise of fast, efficient imaging methods, but is elusive due to the diffraction limit. This paper investigates how a single metasurface patch in the near field of a sample plane may be used to create a wide variety of intensity patterns by applying different illumination profiles from the far field. Numerical analysis shows that one metasurface patch may be used to generate complete bases of illumination patterns on a grid as fine as λ/16. The limits of control are explored in terms of degrees of freedom on the illumination side and spatial resolution on the sample side. These illumination patterns are expected to enable sub‐wavelength structured illumination microscopies, compressive imaging and sensing. Quantitative analysis of how the engineered fields may be used for detection of small scattering particles demonstrates the potential the approach holds for nanoscale optical sensing. [ABSTRACT FROM AUTHOR]