Uniform Theory Research Articles

Scalable Modeling of Human Blockage at Millimeter-Wave: A Comparative Analysis of Knife-Edge Diffraction, the Uniform Theory of Diffraction, and Physical Optics Against 60 GHz Channel Measurements

Scalable Modeling of Human Blockage at Millimeter-Wave: A Comparative Analysis of Knife-Edge Diffraction, the Uniform Theory of Diffraction, and Physical Optics Against 60 GHz Channel Measurements

A Radio Propagation Model for a Rainforest–River Environment Using UTD and Geometrical Optics

This paper describes a radio propagation model for a mixed environment formed by rainforest and river in Brazil's Amazon region. The model uses Geometrical Optics and the Uniform Theory of Diffraction for the calculation of the electric field at the receiver, accounting for the different transmitted, reflected and diffracted components in each of the environments. Simulation results are compared with measurements performed in Belem (Para) at 521 MHz, showing a good fit, with an average Root Mean Square Error (RMSE) over all measured paths of 3.3 dB and a maximum one of 4.2 dB. The proposed model performs much better than the ITU-R P. 1546 and the Okumura Hata ones, where the comparison with measurements leads to an RMSE higher than 8 dB. In addition, by using Genetic Algorithms, the electrical parameters for the dense forest are obtained, enabling to slightly decrease (0.14 dB on the average of all measured paths) the RMSE of the proposed model.

Research on Heat Dissipation of Multi-Chip LED Filament Package.

By studying the substrate material, structure, chip distribution, and array form of the multi-chip light-emitting diode (LED) package, the heat-dissipation capacity of the LED package is improved. Finite element analysis and steady-state thermal analysis are used to simulate and analyze LED packages with different materials and structures. Using the theory of LED illuminance and uniformity, the illuminance of some structures is computed. The results show that the change of substrate material and structure can greatly impact heat dissipation, while changing array forms has little effect on heat dissipation. By improving the spatial distribution of the chip, the temperature superposition problem of the substrate is solved, and the illuminance and uniformity are improved while dissipating heat. The LED filaments of the combined, equidistant, chip-distribution mode have improved heat dissipation. The S-type equal difference has the highest illumination and high illumination uniformity.

Equivariant uniform Alexander-Spanier cohomology theory

In this paper we construct an equivariant cohomology functor with a contravariant coefficient system from the category of pair of uniform G spaces and G maps to the category of abelian groups, where G is a finite group. We call this Equivariant Uniform Alexander-Spanier Cohomology functor as our construction generalizes the construction of Uniform Alexander-Spanier Cohomology functor [1] on uniform spaces. We show that on the category of pair of precompact uniform G spaces, this cohomology functor satisfies all the Eilenberg-Steenrod axioms for an equivariant cohomology theory including the dimension axiom.

A Ray-Tracing Model for Millimeter-Wave Radio Propagation in Dense-Scatter Outdoor Environments

The future saturation of the electromagnetic spectrum currently allocated for mobile communications has led the scientific and technical communities to consider the use of the vast millimeter-wave frequency band. However, there are technical obstacles limiting the immediate use of this band. In the radio propagation area, there is a research effort to characterize the outdoor urban channel. The developed model described here uses a 2.5 D ray-tracing algorithm based on geometrical optics and uniform theory of diffraction concepts in outdoor environments. The model implements several techniques that could be considered by a future standard of fifth-generation mobile communications for the transmission of ultrawideband signals through line-of-sight (LOS) and non-LOS channels with a high density of scatterers, such as trees, poles, and diffuse scattering by rough building walls. In addition, simulations and comparisons are performed in environments where measurement campaigns were carried out, considering the following metrics: received power, mean delay, root mean square delay spread, and cross-polar discrimination. The comparison between simulation and experimental results shows a good agreement. Possible model impairments are also discussed.

Se out of control

Within the framework of a uniform theory of the so-called se constructions in Spanish, I propose to explain a control ban that has received almost no attention in the previous bibliography. Specifically, as long as a subject control sentence has an impersonal SE as controller, the subordinate infinitive clause cannot contain any other instance of the clitic SE, other than the so-called spurious SE. The source of this restriction follows, as I will argue, from a legibility problem at LF produced, specifically, by a failed attempt to apply Agree between PRO and the embedded SE, which, as we shall see, acts as a probe for A-movement. If the explanation that I offer is correct, it also follows a series of theoretical conclusions that directly affect the way in which we must conceive of the design of Agree in the syntax and its effect at the LF interface. In particular, the system tolerates certain Agree failures (Preminger 2014) as long as it does not affect legibility in the semantics. Indeed, the theory of SE constructions that I assume here derives the distinction between paradigmatic and non-paradigmatic SE as the result of successful or unsuccessful Agree applications, respectively. The limit of this tolerance to failed applications of Agree must be found in the type of semantic object that can be deduced at LF. This limit is illustrated with the aforementioned restriction in control and impersonal SE contexts that motivates the present study.

A hybrid numerical model for long-range electromagnetic wave propagation

A hybrid numerical model is presented for solving long range electromagnetic wave propagation problems involving objects on or above the ground surface by hybridizing the two-way split-step parabolic equation (2W-SSPE) method with the method of moments (MoM). The advantages of the proposed model are twofold: (i) It reduces the staircasing error in irregular terrain modeling, which usually occurs when the standard SSPE method is used alone. This is achieved by employing the MoM to more accurately obtain the scattered fields from slanted/curved surfaces. (ii) It enables the SSPE method to handle the problems involving objects above the Earth's surface, which cannot be easily modeled by the standard SSPE method due to difficulty in imposing boundary conditions. The accuracy of the hybrid method is numerically verified by comparing the numerical results with those of the 2W-SSPE and the GO+UTD (geometric optic + uniform theory of diffraction) methods in some representative propagation problems.

Data Reconstruction Method for CD Basis Weight Analysis of Paper by using Compressed Sensing Technology

The control of the cross-directional (CD) basis weight of paper is very challenging. The actuator of the system needs to control the properties of the entire sheet according to a set of restricted data measured by a scanning sensor. The scanning sensor measures the sheet in the cross direction of the paper. For the moving sheet, CD variations were those along an axis perpendicular to the motion of the sheet, while MD (machine direction) variations were those along the axis of motion. One of the problems that make the CD control difficult is data sampling, which is obtained by continuously measuring the CD basis weight of paper through multiple scanning sensors. As the paper moves vertically, the scanning sensor can only measure the “Z” shape area on the paper. When the scanning frequency was not at least twice the maximum frequency of the paper variation, it was difficult to estimate the sheet profile. According to the sparse characteristics of paper signal, a novel approach to accurately reconstruct the sheet properties by a random sampling protocol was proposed by using compressed sensing technology. Compared with the simple bandwidth based uniform sampling theory, it could accurately reconstruct the real process variations from less measurement data. Based on the reconstructed data and actual industrial process data, the CD response model was identified and the reconstruction effect was verified. The CD and MD basis weight data were separated by the predictive separation algorithm, which ensured the basis for CD control. The approach of the compressed sensing technology was found to be effective.

Long-time behaviour for a non-autonomous Klein-Gordon-Zakharov system

The aim of this paper is to study the long-time dynamics of solutions of the evolution system{utt−Δu+u+η(−Δ)12ut+aϵ(t)(−Δ)12vt=f(u),(x,t)∈Ω×(τ,∞),vtt−Δv+η(−Δ)12vt−aϵ(t)(−Δ)12ut=0,(x,t)∈Ω×(τ,∞), subject to boundary conditionsu=v=0,(x,t)∈∂Ω×(τ,∞), where Ω is a bounded smooth domain in Rn, n≥3, with the boundary ∂Ω assumed to be regular enough, η>0 is constant, aϵ is a Hölder continuous function and f is a dissipative nonlinearity. This problem is a non-autonomous version of the well known Klein-Gordon-Zakharov system. Using the uniform sectorial operators theory, we will show the local and global well-posedness of this problem in H01(Ω)×L2(Ω)×H01(Ω)×L2(Ω). Additionally, we prove existence, regularity and upper semicontinuity of pullback attractors.

Radiation From a Monopole Antenna Array on an Electrically Large Conducting Convex Surface

Asymptotic solutions based on the uniform geometrical theory of diffraction (UTD) are well developed and efficient for analyzing radiation, mutual coupling, and scattering associated with electrically large conducting convex surfaces. Relevant UTD solutions are available mostly for infinitesimal sources on or far away from the surface. Hence, UTD solutions have been extensively used to analyze radiation from conformal antennas and antenna arrays on an electrically large convex surface. In this letter, it is proposed to predict far and near field radiations from a monopole antenna array on an electrically large conducting convex surface as a nonconformal array. A UTD solution that allows sources to be on or slightly off the surface is employed after identifying ray paths. UTD results are validated with those of the multilevel fast multipole method.

Research on Fault Location of Distribution Lines Based on the Standing Wave Principle

Aiming at the fast and accurate location of a single-phase ground fault in the distribution network, a single terminal injection signal location method, based on the standing wave principle, is proposed. Firstly, the double conductor standing wave principle formation, based on uniform transmission line theory, is analyzed, and the mathematical model of the fault distance algorithm is established. Secondly, a fault detection circuit is built by simulation, and the distribution trend of the standing wave and its relationship with unit capacitance and unit inductance are studied. By setting the source signal frequency and detection point interval and other parameters, the fault location of this method under direct grounding fault and through grounding resistance fault is simulated and studied. Finally, the fault distance is calculated and located by an experiment. The results show that the positioning accuracy is high, which verifies the effectiveness of the standing wave positioning method.

Diffraction of waves by a planar junction of impedance and perfect electromagnetic conductor half-planes

In this study, diffraction of waves by a planar junction between impedance and perfect electromagnetic conductor half-planes is investigated. The method of transition boundary is used for the solution of the problem. The diffracted wave expressions are expressed in terms of the Fresnel functions by using the uniform theory of diffraction method. Thus, finite magnitudes are obtained at the transition regions and the results are analyzed numerically for different set of parameters.

Theory of uniformity applied to elastic dielectric materials and piezoelectricity

Building on the celebrated works by Toupin (1963) on non-linear elastic dielectric materials and by Noll (1967) on the theory of material uniformity, we use the method of linear perturbations to obtain a generalised form of the equations of piezoelectricity in the linear regime, i.e., below the ferroelectric threshold. More specifically, in their most general form, the piezoelectric constitutive equations that we obtain include an anelastic strain and an anelastic polarisation, both arising from the intrinsic inhomogeneity of the body and according to the theory of material uniformity. These are distinct from the irreversible strain and polarisation that occur at values of stress and electric field above the ferroelectric threshold. Some of the known standard forms of the piezoelectricity equations are retrieved as particular cases.

Experimental Evaluation of Over-the-rooftop Propagation Loss Prediction Model for the Spectrum Sharing at 26 GHz Band

Due to the scarcity of the frequency spectrum for 5G, the incumbent systems are expected to share the spectrum with 5G systems especially for those operating within the band assigned by Radio Regulations of International Telecommunication Union. For the spectrum sharing between fixed wireless access and 5G at 26 GHz band, the authors have proposed a simple prediction method of the propagation loss, which considers only the over-the-rooftop path and uniform theory of diffraction for multiple edges covering the transition zone. This paper presents the evaluation of the error of the proposed prediction model by comparing with the results of measurement campaign in the urban area.

Application of heuristic UTD formulation for describing scattering by a thin and multilayer anisotropic slab

The previously developed heuristic uniform theory of diffraction (UTD) corner and wedge diffraction coefficients for a thin lossless anisotropic slab are generalized and applied for predicting electromagnetic scattering by a thin and multilayer anisotropic slab with complex permittivity and permeability tensors. The effective reflection and transmission coefficients of a thin and multilayer slab are used in the heuristic formulation to determine the scattered fields. Numerical results are provided for various scattering problems that demonstrate the application of the heuristic formulations for a thin and multilayer structure.

Fast diffraction pathfinding for dynamic sound propagation

In the context of geometric acoustic simulation, one of the more perceptually important yet difficult to simulate acoustic effects is diffraction, a phenomenon that allows sound to propagate around obstructions and corners. A significant bottleneck in real-time simulation of diffraction is the enumeration of high-order diffraction propagation paths in scenes with complex geometry (e.g. highly tessellated surfaces). To this end, we present a dynamic geometric diffraction approach that consists of an extensive mesh preprocessing pipeline and complementary runtime algorithm. The preprocessing module identifies a small subset of edges that are important for diffraction using a novel silhouette edge detection heuristic. It also extends these edges with planar diffraction geometry and precomputes a graph data structure encoding the visibility between the edges. The runtime module uses bidirectional path tracing against the diffraction geometry to probabilistically explore potential paths between sources and listeners, then evaluates the intensities for these paths using the Uniform Theory of Diffraction. It uses the edge visibility graph and the A* pathfinding algorithm to robustly and efficiently find additional high-order diffraction paths. We demonstrate how this technique can simulate 10th-order diffraction up to 568 times faster than the previous state of the art, and can efficiently handle large scenes with both high geometric complexity and high numbers of sources.

On the Use of UTD-Based Models for RF Path Loss Prediction Due to Diffraction on a Forest-Covered Ridge

Irregular terrains covered with forest vegetation represent a challenging scenario for radio planning. A case of particular interest is the one where a forest-covered high hill or mountain is interposed to the link, for which typical diffraction loss models usually apply as good approximations, even disregarding the vegetation influence. Pragmatic approaches to incorporate the forest contribution, such as adding a clutter height, usually improve accuracy a little further. In this scope, this paper assesses the performance of some models based on the Uniform Theory of Diffraction (UTD) for RF path loss prediction in such ridges. Special attention goes to a hybrid model in which the forest is a uniform layer over a wedge that represents the ridge, and its influence is incorporated into the diffraction coefficient. The path loss predictions are compared with measurements from a mountainous region of the USA, and the statistical adherence of the models to the measured data is discussed. Overall, the slightly better performance of the models which incorporate the vegetation influence was confirmed, the hybrid model performing the best for frequencies below 910 MHz.

A Highly Inclusive Theory of Q-Switched Lasers

A highly inclusive theory of Q-switched lasers is presented which applies to both actively and passively Q-switched lasers. The theory expands on the author’s previous publications on energy optimization to include: (1) saturable absorbers exhibiting excited state absorption and therefore a finite Figure of Merit (FOM); (2) unequal beam areas in the gain and absorbing media; and (3) both pulsed and CW pumping. Design curves for optimizing the output energy for pulse pumped lasers and CW pumped lasers at a desired pulse rate are provided. As in the author’s previous work, the optimization equation is obtained utilizing Lagrange Multipliers and yields the value of the parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\rho = ln(n_{i}/n_{f})$ </tex-math></inline-formula> which maximizes the single pulse energy, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n_{i}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n_{f}$ </tex-math></inline-formula> are the laser inversion population densities before and after Q-switching. Using this initial result, the associated optimum absorber transmission and mirror reflectivity, pulse energy, peak power, and pulse width can be computed sequentially via simple formulas. The aforementioned parameters can all be expressed as functions of two variables, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$z_{eff}$ </tex-math></inline-formula> , which are slight modifications of the variables <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> and z previously introduced by the author for passively Q-switched lasers having infinite FOM and equal beam areas The term “plane wave theory” has sometimes been used by this and other authors in prior publications to describe a uniform pump profile in the laser medium, but we will refer to this special case more accurately as the “uniform pump theory”. The theory is extended here in the final section to include non-uniform pumping. The common case of a Q-switched laser end-pumped by a quasi-Gaussian CW laser is considered in detail and the theoretical results are found to agree well with experimental data.

Active control of building structures under seismic load using a new uniform deformation-based control algorithm

There are several algorithms for determining control forces of active devices in civil engineering structures. Uniform distribution of deformations theory is a structural concept which mainly focuses on equalizing deformations in order to promote the utilization of ductility capacity of structural elements thereby mitigating damages to a structure. In common active control algorithms, deformation uniformity and reducing damages are barely noted. In this research, a new active control algorithm regarding uniform deformation theory will be proposed. Uniform distribution of Deformation Control (UDC) algorithm consists of a massless optimized Virtual Added linear structure with Pinned connections (VAP) which is added to a desired original structure. This VAP can be treated as an added stiffness matrix. Once the parameters of the VAP were optimized in a manner that the desired responses were obtained from the new integrated structure, then, the new integrated structure is developed and analyzed in each time step. Finally, the VAP beams axial forces are extracted and applied to the original structure as control forces via active control devices such as active tendons.This proposed control algorithm is simple and effective in reducing responses especially drifts, making more uniform thereby reducing structural damages as well as decreasing the required capacity of actuators and the power consumption eventually. High potential and promising performance of the proposed UDC algorithm will be represented through numerical investigation in an office building example. The results are compared with Nonlinear Instantaneous Optimal Control (NIOC) algorithm as a very common active control algorithm for linear and nonlinear structures.

Limit Theory for Stationary Autoregression with Heavy-Tailed Augmented GARCH Innovations

This paper considers stationary autoregressive (AR) models with heavy-tailed, general GARCH (G-GARCH) or augmented GARCH noises. Limit theory for the least squares estimator (LSE) of autoregression coefficient ρ=ρn is derived uniformly over stationary values in [0,1), focusing on ρn→1 as sample size n tends to infinity. For tail index α∈(0,4) of G-GARCH innovations, asymptotic distributions of the LSEs are established, which are involved with the stable distribution. The convergence rate of the LSE depends on 1−ρn2, but no condition on the rate of ρn is required. It is shown that, for the tail index α∈(0,2), the LSE is inconsistent, for α=2, logn/(1−ρn2)-consistent, and for α∈(2,4), n1−2/α/(1−ρn2)-consistent. Proofs are based on the point process and the asymptotic properties in AR models with G-GARCH errors. However, this present work provides a bridge between pure stationary and unit-root processes. This paper extends the existing uniform limit theory with three issues: the errors have conditional heteroscedastic variance; the errors are heavy-tailed with tail index α∈(0,4); and no restriction on the rate of ρn is necessary.