Nonuniform Lines Research Articles

ATP-EMTP simulation of lightning protection system for multi-storey building

Multi-storey buildings with occupied highly technological instruments have more attraction possibilities of a lightning stroke than ordinary residential buildings. A protection system against lightning is necessary for these buildings and the level of the protection system performance is an issue to be examined. In this study, a protection system for a three-storey building is simulated in Alternative Transient Program-Electromagnetic Transients Program (ATP-EMTP). Distributed-parameter line models are used for the conductors of the protective system by modelling vertical conductors as nonuniform lines. The currents flowing in the critical conductors and the voltages at some critical points resulting by a lightning stroke are computed. The conventional lighting parameters required for structural protection such as lightning peak current, current rise time and time interval for the current flowing are determined. The effect of the radius of conductors in the protection system on the surge response is investigated.

Realization of double uniform line self-focusing of elliptical Airyprime beams

Double line self-focusing characteristics of elliptical Airyprime beams (EAPBs) with different elliptical vertical-axis factor β are investigated by varying the main ring radius r0. Overly large or small r0 results in the inhomogeneous distribution of light intensity at one linear focus of the double line self-focusing. Only when r0 is appropriate and β is within a certain range, can double uniform line self-focusing happen to the EAPB. Moreover, the self-focusing ability of the second line self-focusing is weaken than that of the first line self-focusing. Under the premise of our selected values of beam parameters, the EAPB can achieve double uniform line self-focusing when r0 = 0.3 mm and β = 0.58∼0.71. The focal length of the first line self-focusing, the lengths of double linear focus, and the self-focusing abilities of the double uniform line self-focusing can be regulated by varying β within the range of 0.58∼0.71. If β is smaller than 0.58 or larger than 0.71, it will lead to nonuniform line self-focusing. An explanation of the physical mechanism behind the double uniform line self-focusing of the EAPB is proposed. Finally, the experimental measurements of the line self-focusing of the EAPB confirm the validity of the above conclusions. This research provides a new solution on how to generate double uniform line self-focusing and new insights into the practical application of elliptical self-focusing beams.

THE USE OF TWO FREQUENCY VARIABLES IN THE DISTRIBUTED CIRCUITS SYNTHESIS.

One of the approaches to the design of filters from segments of non-uniform lines is the use of NLs connected by a quadrupole between the generator and the load. In this case, the required characteristic of selectivity is achieved by changing the wave resistance of the line according to a certain law. However, the input op of the NL loaded with an active resistance cannot be purely reactive at real frequencies, so the reflection coefficient cannot be equal to unity at any of them. Therefore, it is fundamentally impossible to obtain a significant attenuation at least at one point outside the passband of the filter. Only by choosing a certain class of complex loads can significant attenuation be achieved outside the passband. Another principle of filter construction is based on the use of the simplest heterogeneous lines that perform the functions of resonators. The necessary selective characteristic of the filter is achieved by selecting the parameters of resonators and communication circuits. This method of building filters is more rational. In addition, in the process of synthesis, you can use ideas and techniques characteristic of circles from segments of uniform lines. It is shown that in the synthesis of distributed circuits based on transmission lines, complex functions of two frequency variables should be used, which allows the construction arbitrary circuit functions and fully cover the classes of physically realized transfer functions. A description of the elements "inductance" and "capacitance" in the class of functions of two complex frequency variables was obtained, which allows synthesizing circuits using the ideas and methods of Richards’s circuit theory.

An Implicit Adaptive FDTD Mesh Generation Techniquebased on Tetrahedrons

A novel implicit adaptive FDTD mesh generation method based on tetrahedrons is proposed in this paper. According to the vertex coordinates of tetrahedrons which make up an object, non-uniform grid lines are generated first. These grid lines are constrained by the structure of the object and follow three rules mentioned in the paper. The first rule is to find demarcation points of the object and drop grid lines on these points. The second rule is to make sure all mesh sizes are less than one-tenth of the wavelength by adding more grid lines. The last rule is to densify mesh at the fine structure of the object. Then by comparing the positional relationship between center points of Yee cells and tetrahedrons, the object can be discretized by Yee cells. Finally, numerical examples are given to verify the validity and accuracy of this novel method.

Numerical analysis of lossy nonuniform interconnect lines in modern integrated circuits by multistep θ-method and Runge-midpoint method

Numerical analysis of lossy nonuniform interconnect lines in modern integrated circuits by multistep θ-method and Runge-midpoint method

Design of T-shaped non-uniform microstrip lines for reducing crosstalk in high-speed PCBs

High-speed and high-density PCB circuit layout design faces serious signal integrity problems. Crosstalk is one of the key problems affecting signal quality. Periodic non-uniform differential microstrip lines have the possibility of reducing crosstalk. This paper proposes a T-shaped non-uniform microstrip line, which adds the T-shaped bump on the inner side of the parallel microstrip lines. The microstrip line adopts the minimum batch production process linewidth to maintain high density, which is suitable for occasions where the line spacing is three times the linewidth. The principle of crosstalk mitigation for T-shaped microstrip lines is explained, and the evolution process of T-shaped microstrip lines is given, compared with parallel microstrip lines and tabbed lines with the same density. The simulation resulting in the time domain and frequency domain shows that the transmission performance of the T-shaped microstrip line is good, and crosstalk can be effectively suppressed in a high-frequency band, even better in some specific frequencies due to the crosstalk fluctuation with frequency.

A Lattice-Boltzmann-based modelling chain for traffic-related atmospheric pollutant dispersion at the local urban scale

Urban traffic-related air pollution is a major source of environmental and health damage and is difficult to quantify due to its inherent physical complexity. We construct a CFD-based simulation framework coupling an efficient numerical method for turbulent fluid flows with a microscopic traffic model and an emissions model to simulate road transport pollutant dispersion at the urban microscale. We improve the open-source Lattice-Boltzmann based CFD software OpenLB to overcome its original stability deficiencies for high Reynolds number flows. A stable recursive regularization procedure with a double distribution function approach is proposed to solve an advection diffusion equation for passive scalar transport at high Reynolds number. The code is successfully validated on three reference cases of increasing complexity and the traffic model SUMO along with a physical engine emissions model are coupled with OpenLB to simulate traffic-induced pollution from a road network in a realistic complex geometry. Transient flow features are analysed and the time-averaged concentration levels in different neighbourhoods of the considered geometry are evaluated: high concentration levels are observed close to the streets but also inside specific building infrastructures due to complex wind dynamics. Analyses of altitudinal concentration variations show that flow recirculations located close to traffic lights can drive pollutant over the buildings and increase concentration levels inside inner courtyards. Time-averaged concentration maps are constructed using both spatially uniform and non-uniform line sources and it is shown that using uniform sources leads to up to 20% local concentration overestimations inside the urban canopy.

Cross-stream migration of a vesicle in vortical flows.

We use numerical simulations to systematically investigate the vesicle dynamics in two-dimensional (2D) Taylor-Green vortex flow in the absence of inertial forces. Vesicles are highly deformable membranes encapsulating an incompressible fluid and they serve as numerical and experimental proxies for biological cells such as red blood cells. Vesicle dynamics has been studied in free-space or bounded shear, Poiseuille, and Taylor-Couette flows in 2D and 3D. Taylor-Green vortex are characterized with even more complicated properties than those flows such as nonuniform flow line curvature, shear gradient. We study the effects of two parameters on the vesicle dynamics: the ratio of the interior fluid viscosity to that of the exterior one and the ratio of the shear forces on the vesicle to the membrane stiffness (characterized by the capillary number). Vesicle deformability nonlinearly depends on these parameters. Although the study is in 2D, our findings contribute to the wide spectrum of intriguing vesicle dynamics: Vesicles migrate inwards and eventually rotate at the vortex center if they are sufficiently deformable. If not, then they migrate away from the vortex center and travel across the periodic arrays of vortices. The outward migration of a vesicle is a new phenomenon in Taylor-Green vortex flow and has not been observed in any other flows so far. Such cross-streamline migration of deformable particles can be utilized in several applications such as microfluidics for cell separation.

On an improved PDE-based elliptic parameterization method for isogeometric analysis using preconditioned Anderson acceleration

Constructing an analysis-suitable parameterization for the computational domain from its boundary representation plays a crucial role in the isogeometric design-through-analysis pipeline. PDE-based elliptic grid generation is an effective method for generating high-quality parameterizations with rapid convergence properties for the planar case. However, it may generate non-uniform grid lines, especially near the concave/convex parts of the boundary. In the present work, we introduce a novel scaled discretization of harmonic mappings in the Sobolev space H1 to remit it. Analytical Jacobian matrices for the involved nonlinear equations are derived to accelerate the computation. To enhance the numerical stability and the speed of convergence, we propose a simple and yet effective preconditioned Anderson acceleration framework instead of using computationally expensive Newton-type iteration. Three preconditioning strategies are suggested, namely diagonal Jacobian, block-diagonal Jacobian, and full Jacobian. Furthermore, we discuss a delayed update strategy of the preconditioner, i.e., the preconditioner is updated every few steps to reduce the computational cost per iteration. Numerical experiments demonstrate the effectiveness and efficiency of our improved parameterization approach and the computational efficiency of our preconditioned Anderson acceleration scheme.

Ultra-Wideband 3-D Microwave Absorbers With Composite Slotlines and Microstrip Lines: Synthetic Design and Implementation

This article proposes a class of ultra-wideband 3-D microwave absorbers with composite slotlines and microstrip lines from synthetic design to practical implementation. Firstly, the general equivalent transmission line (TL) model of the proposed 3-D absorber element is formed based on two sets of shunt short-ended stubs and an i-section nonuniform connecting line. Then, the synthetic procedure is theoretically investigated using the equivalent TL model, aiming to construct an ultra-wide absorption band with the Chebyshev equal-ripple response. According to the prescribed absorptive performance, such as maximum reflection coefficient (C) and fractional bandwidth (FBW), the relevant parameters of the TL model can be directly calculated by the established synthesis approach. To validate the proposed concept, two prototypes, namely, absorber-I (i=1) and absorber-II (i=2), are designed, fabricated, and measured. Each prototype element applies a simple 3-D structure composed of slotlines, microstrip lines, and only one absorptive load, which are all etched on a single-layered substrate. Measured results agree well with synthetizations and simulations. For absorber-I, the measured bandwidth of 95.5% in a frequency range from 5.08 to 14.44GHz is successfully realized. Absorber-II obtains a measured FBW of 111.1% in a range from 4.48 to 15.68GHz. Average absorption ratios within the operating band are higher than 95.5% and 93.8% for absorber-I and absorber-II, respectively. Besides, the proposed 3-D absorbers are angularly stable within 600 oblique incidence. Therefore, such ultra-wideband 3-D microwave absorbers with simple structures possess the attractive potential for effectively absorbing electromagnetic waves.

Static Magnetic Shielding of a Perfectly Electric Conducting Circular Disk: Exact Analytical Solution Considering Radius of Emitting Loop

This letter proposes an accurate analytical formulation for the shielding problem of a perfectly electric conducting disk against the static magnetic field of a circular current loop placed coaxially with the disk. The key is to convert this problem into an electric field problem: the circular disk is grounded and is excited by nonuniform line charges distributed on the loop. The latter can be solved through the known Green function. Then, we obtain the accurate solution in integral form for magnetic vector potential at any field point and the accurate analytical solution for the magnetic field on the central axis of the disk. Also, the solution for the magnetic field is extended to the whole space when the loop radius is approaching zero.

Revisiting the [C ii] 158 μm line-intensity mapping power spectrum from the EoR using non-uniform line-luminosity scatter

Abstract Detecting the line-intensity mapping (LIM) signal from the galaxies of the epoch of reionization is an emerging tool to constrain their role in reionization. Ongoing and upcoming experiments target the signal fluctuations across the sky to reveal statistical and astrophysical properties of these galaxies via signal statistics, e.g. the power spectrum. Here, we revisit the [C ii]$_{158 \, \mu \text{m}}$ LIM power spectrum under non-uniform line–luminosity scatter, which has a halo-mass variation of statistical properties. Line–luminosity scatter from a cosmological hydrodynamic and radiative transfer simulation of galaxies at $z$ = 6 is considered in this study. We test the robustness of different model frameworks that interpret the impact of the line-luminosity scatter on the signal statistics. We use a simple power-law model to fit the scatter and demonstrate that the mean luminosity–halo mass correlation fit cannot preserve the mean intensity of the LIM signal (hence the clustering power spectrum) under non-uniform scatter. In our case, the mean intensity changes by ∼48 per cent compared to the mean correlation fit in contrast to the general case with semi-analytical scatter. However, we find that the prediction for the mean intensity from the most-probable fit can be modelled robustly, considering the generalized and more realistic non-uniform scatter. We also explore the possibility of diminishing luminosity bias under non-uniform scatter, affecting the clustering power spectrum, although this phenomenon might not be statistically significant. Therefore, we should adopt appropriate approaches that can consistently interpret the LIM power spectrum from observations.

ВИМІРЮВАННЯ КОЕФІЦІЄНТА ПІДСИЛЕННЯ АНТЕН ДОВІЛЬНОЇ ПОЛЯРИЗАЦІЇ ДЗЕРКАЛЬНИМ МЕТОДОМ

Requirements to characteristics and parametres of modern aerials, especially to electromagnetic compatibility, constantly grow. The effective utilisation of antenna technics is impossible now without development and perfection of means and ways of measurement of electric characteristics and parametres. Experimental study of antenna characteristics is the most important technological process during their development and manufacture. Results of measurements of characteristics of aerials allow to check up reliability of calculations and modelling, correctness of a choice of a design and materials, accuracy of manufacturing, and also conformity to requirements of electromagnetic compatibility. The article analyzes the current mirror methods for determining the characteristics of elliptical and circular polarization antennas. On the basis of the analysis (features of the considered methods) necessity of their perfection is proved. The block diagramme of measurement of factor of strengthening of the aerial of any polarisation is offered by a mirror method. It is distinguished by the presence of a polarizing screen with a rectangular foam plate on which thin metal conductors are applied, the distance between which is less than a quarter of the wavelength in air. The circuit also includes: a panoramic voltage standing wave ratio meter, an indicator, a matching transformer, an antenna for research, a mirror image of the antenna. Measurement strengthening factor is spent taking into account its communication with the diagramme of an orientation of the aerial. The settlement and experimentally removed schedules of diagrammes of an orientation of aerials of circular polarisation in planes Е and Н accordingly are resulted: rectangular wave guide with round cracks and square aerials with a dielectric plate on which from two parties non-uniform slot-hole lines are put. Comparison of the calculation and experimental results showed the possibility of using the mirror image method to measure the characteristics of circularly polarized antennas. Feature of an advanced mirror method of measurement of factor of strengthening is that the direction of rotation of a vector of intensity of electric field at reflexion does not change on opposite, it is not necessary to measure parametres of a polarising ellipse, has no value how excitation of an electromagnetic wave of rotating polarisation is provided, you can measure the parameters of antennas with linear polarization.

An experimental and numerical investigation into the effects of bond line thickness variations on the strength of composite bonded joints

The structural integrity of adhesive joints used in the attachment of laminated composite panels has received considerable attention over the past few decades. Of particular concern and the topic of this paper is the effect that a nonuniform bond line thickness has on the load carrying capacity of a bonded joint. To this end, carbon fiber adherends were joined in a single lap joint configuration using a two-part epoxy adhesive. The joints were initially fabricated and tested with various uniform bond line thickness in a single lap joint configuration to establish a benchmark. Bonded single lap joints with linearly varying bond line thickness were then investigated. A finite element study was performed to predict bond strength of the uniform and linearly varying bond lines using the Critical Zone method. The failure strength of the uniform bond line thickness specimens was found to decrease with an increase in the bond line thickness. In the case of linearly varying bond line thickness specimens, the bond strength decreased as the bond thickness at one end of the bonded joint overlap deviated from its intended value. The finite element model using the Critical Zone method was able to predict the failure strength of the joints in both uniform and linearly varying bond thickness configurations. The reduction in failure strength was attributed to an increase in the stresses in the adherend ply adjacent to the bond line as determined through the finite element stress analysis.

The relationship between slip behavior and dislocation arrangement for large-size Mo-3Nb single crystal at room temperature

The slip behavior and mechanism of large-size Mo-3Nb single crystal have been investigated and disclosed comprehensively at room temperature by quasi-static compression with various strains. With the increase of deformation, the slip traces change from shallow non-uniform slip lines to dense and uniform slip bands. Different slip traces in the same deformation condition were observed, suggesting that the slip traces in the single crystal are controlled by different types and arrangement mechanisms of mobile dislocation. To clarify the relationship between slip behavior and dislocation arrangement, TEM and AFM analyses were performed. Significant discrepancy between the mobility of screw segments and edge segments caused by double cross-slip multiplication mechanism is the reason why different slip features were witnessed. During the whole slip deformation process, screw dislocations play a dominant role and they are inclined to form wall-substructures by interaction and entanglement. With the development of dislocation accumulation, the entangled dislocation walls evolve into dislocation cells with higher stability.

Experimental Study of the Characteristics of Band-Passed Ultra-High Frequency Filters with Increased Protective Band in the Interest of Ensuring Electromagnetic Compatibility

The article presents the structure of the method for the synthesis of microwave bandpass filters (BPF) on non-uniform lines, which makes it possible to select the structure and parameters of the BPF that provide the maximum length of the stop band to meet the requirements of electromagnetic compatibility (EMC) with given restrictions on the attenuation characteristics in the passband and barrier bands. and the established design and technological limitations on the drop in wave resistance and manufacturing tolerances. The results of experimental studies of the characteristics of ultrahigh-frequency bandpass filters with an increased protective band in order to ensure EMC are presented

Artificial intelligence–based design optimization of nonuniform microstrip line band pass filter

AbstractDesign optimization of many electromagnetic and multiphysics problems have multiscale issues that require a fast, efficient, and accurate surrogate‐based model to be used. Recently, in microwave engineering field, artificial intelligence–based models are being used for modeling of complex microwave stages. In all the studies, the main aim is to form models inner structure parameters, by using the given data to predict the linear/nonlinear relationships between given inputs and outputs. Herein, a surrogate‐based model of a nonuniform microstrip transmission line (NTL) with a typical application of design optimization of a band‐pass filter for ISM band application using deep learning (DL) and meta‐heuristic optimization has been presented. In order to have a computationally efficient and accurate optimization process, firstly a 3D EM unit element model of NTL has been designed. The training and test data sets are created based on different sampling methods. A DL regression model modified multilayer perceptron M2LP have been used for prediction of scattering parameters (S) of the NTL, with respect to the variation of geometrical design parameters. The proposed S‐parameters will then be used to calculate the equivalent S‐parameters of the cascading NTL to be used to calculate the NTL‐based microstrip band‐pass filter S‐parameter response. The optimal design parameters of each line used in the filter design have been determined using a fast and powerful optimization algorithm differential evolutionary algorithm.

A continuous analytical solution for the load sharing and friction torque of involute spur and helical gears considering a non-uniform line stiffness and line load

In this work a continuous analytical model for the estimation of the mesh stiffness, load sharing and friction torque for parallel axis involute spur and helical gears is presented. The model has no limitations in the admissible range for the overlap and contact ratios. The main novelty of the work lies on the mathematical approach that allows the continuous description of the gearing phenomena without using functions by domains. At first, a model for the mesh stiffness and load sharing ratio for spur gears is developed. Then, a more advanced approach is used to tackle the same problem for helical gears. Both models consider a non-uniform contact line stiffness sharing function. Afterwards, assuming a constant friction coefficient, two friction torque models are developed, one for spur and the other for helical gears, while considering a non-uniform contact line load. The influence of the model parameters in the mesh stiffness, load sharing and friction torque is evaluated. Finally three gears of different types are selected and compared with reference results.

Electromagnetic transient modeling of form-wound stator coils with stress grading system under PWM excitation

The insulation system of a machine coil includes several layers made of materials with different characteristics. The effective insulation design of machine coils, especially in the machine end winding, depends upon an accurate model of the stress grading system. This paper proposes a modeling approach to predict the transient overvoltage, electric field, and heat generation in machine coils with a stress grading system, considering the variation of physical properties in the insulation layers. A non-uniform line model is used to divide the coil in different segments based on material properties and lengths: overhang, stress grading and slot. The cascaded connection of chain matrices is used to connect segments for the representation of the complete machine coil. The resulting model is able to simulate the transient overvoltages due to the application of fast rise time pulses such as those observed with pulse width modulation from adjustable speed drives, considering coils with different insulation topologies and under pulses with different rise times. The parameters in each coil region are calculated using the finite element method (FEM). Additionally, the resistive heat and electric field distribution in the machine coil are calculated for excitations with different rise times by means of 3-dimensional FEM simulations.

Application of an Sb Surfactant in InGaAs Nano-ridge Engineering on 300 mm Silicon Substrates

Nano-ridge engineering (NRE) is a novel heteroepitaxial integration approach for III–V devices on Si substrates. It starts with selective area growth in narrow trenches for misfit defect trapping. Growth is then continued out of the trenches to engineer the nano-ridges (NRs). Different device concepts such as lasers and transistors have been demonstrated using box-shaped NRs. To widen the field of applications, NRE is extended to the alloy In0.53Ga0.47As. The In and Ga incorporation depends strongly on the exposed NR facets; hence, composition fluctuation has to be limited to avoid misfit defect formation. Growth conditions, which typically ensure the formation of a box-shaped NR, result in nonuniform InGaAs NR lines. For the first time, an Sb surfactant was applied in NRE to achieve uniform and box-shaped InGaAs NRs. A detailed structural investigation shows that the presence of Sb improves the In-distribution in the NR but reduces the gliding efficiency of threading dislocations, which is essential for the misfit defect reduction inside the trench. A two-step growth approach was developed to overcome this drawback and to still benefit from the desired impact of a surfactant on the InGaAs box-formation, which ensures InGaAs NRs with high crystal quality.