Linear Components Research Articles

Optimal Model Averaging Estimation for the Varying-Coefficient Partially Linear Models with Missing Responses

In this paper, we propose a model averaging estimation for the varying-coefficient partially linear models with missing responses. Within this context, we construct a HRCp weight choice criterion that exhibits asymptotic optimality under certain assumptions. Our model averaging procedure can simultaneously address the uncertainty on which covariates to include and the uncertainty on whether a covariate should enter the linear or nonlinear component of the model. The simulation results in comparison with some related strategies strongly favor our proposal. A real dataset is analyzed to illustrate the practical application as well.

SIMULATION OF INTERMEDIATE VISCOELASTIC SUPPORT UNDER NON-STATIONARY VIBRATIONS OF TIMOSHENKO BEAMS

When modeling mechanical objects and their systems, mathematical models developed for an elastic domain are most often used, which in some cases can lead to significant inaccuracies in calculations. The use of mathematical models that take into account visco-elastic properties or energy dissipation allows to obtain more realistic models, which will make it possible to obtain more accurate calculation results. In the paper non-stationary loading of a mechanical system, consisting of a beam hinged at the edges, and an additional support installed in the span of the beam is considered. We use a beam deformation model, which is based on the hypotheses of S. P. Timoshenko and takes into account the inertia of rotation and shear. The system of partial differential equations describing the deformation of the beam is solved by expanding the desired functions into the corresponding Fourier series and subsequent using the integral Laplace transform. The additional support is assumed to be realistic rather than absolutely rigid, having linear elastic and viscous components. It is assumed that at the point of attachment of the additional support to the beam their displacements coincide. The reaction between the beam and the additional support is replaced by an external unknown concentrated force applied to the beam, which changes with time. The law of change in time of this unknown reaction is determined from the solution of the Volterra integral equation. A method for obtaining an integral equation for an unknown reaction is described. Analytical relations and calculation results for specific numerical parameters are given. The influence of stiffness and viscosity on the determined reaction of the additional support, as well as on the deflections of the beam at various points, is investigated. The results obtained can also be used for damping forced vibrations of mechanical systems.

Associations between source-apportioned PM2.5 and 30-day readmissions in heart failure patients

BackgroundAir pollution exposure is a significant risk factor for morbidity and mortality, especially for those with pre-existing chronic disease. Previous studies highlighted the risks that long-term particulate matter exposure has for readmissions. However, few studies have evaluated source and component specific associations particularly among vulnerable patient populations. ObjectivesUse electronic health records from 5556 heart failure (HF) patients diagnosed between July 5, 2004 and December 31, 2010 that were part of the EPA CARES resource in conjunction with modeled source-specific fine particulate matter (PM2.5) to estimate the association between exposure to source and component apportioned PM2.5 at the time of HF diagnosis and 30-day readmissions. MethodsWe used zero-inflated mixed effects Poisson models with a random intercept for zip code to model associations while adjusting for age at diagnosis, year of diagnosis, race, sex, smoking status, and neighborhood socioeconomic status. We undertook several sensitivity analyses to explore the impact of geocoding precision and other factors on associations and expressed associations per interquartile range increase in exposures. ResultsWe observed associations between 30-day readmissions and an interquartile range increase in gasoline- (16.9% increase; 95% confidence interval = 4.8%, 30.4%) and diesel-derived PM2.5 (9.9% increase; 95% confidence interval = 1.7%, 18.7%), and the secondary organic carbon component of PM2.5 (SOC; 20.4% increase; 95% confidence interval = 8.3%, 33.9%). Associations were stable in sensitivity analyses, and most consistently observed among Black study participants, those in lower income areas, and those diagnosed with HF at an earlier age. Concentration-response curves indicated a linear association for diesel and SOC. While there was some non-linearity in the gasoline concentration-response curve, only the linear component was associated with 30-day readmissions. DiscussionThere appear to be source specific associations between PM2.5 and 30-day readmissions particularly for traffic-related sources, potentially indicating unique toxicity of some sources for readmission risks that should be further explored.

An Integrated Grasshopper Optimization Algorithm with Artificial Neural Network for Trusted Nodes Classification Problem

Wireless Body Area Network (WBAN) is a tool that improves real-time patient health observation in hospitals, asylums, especially at home. WBAN has grown popularity in recent years due to its critical role and vast range of medical applications. Due to the sensitive nature of the patient information being transmitted through the WBAN network, security is of paramount importance. To guarantee the safe movement of data between sensor nodes and various WBAN networks, a high level of security is required in a WBAN network. This research introduces a novel technique named Integrated Grasshopper Optimization Algorithm with Artificial Neural Network (IGO-ANN) for distinguishing between trusted nodes in WBAN networks by means of a classification approach, hence strengthening the safety of such networks. Feature extraction process is done by using Linear Regression-Based Principal Component Analysis (LR-PCA). The test results demonstrated that the proposed IGO-ANN method attains the greatest performance in terms of accuracy, end to end delay and packet delivery ratio regarding trusted WBAN nodes classification than certain existing methods.

High-Efficiency Diagnosis of Antenna Radiation Characteristics Based on Scanning Optic-Induced Plasma Scattering Technology

This article presents an innovative quasi-real-time antenna near-field diagnosis method, by scanning a laser-induced plasma on a silicon wafer and imaging the field with the synchronously produced scattered signals. Several approaches have been devised to adapt to the antenna diagnosis scenarios. By using the multilayer matching approach, the issue of multiple reflection disturbance between the aperture and silicon wafer is avoided, especially for large aperture antennae at high frequencies. The accuracy of near-field distribution is improved, and far-field patterns can be transformed directly. The experimental results of a Ka-band 20 dB standard antenna agree well with the simulation results. Diagnosis of radiation states in the reactive near-field region is demonstrated, and the resonate modes of a 2.4 GHz Wi-Fi patch antenna at different frequencies are clearly observed. The experiments of a TM01 mode antenna verify the full polarization diagnosis ability of the method, and the linear polarization component is measured with the help of a polarization grid. The demonstrated diagnosis method has the advantages of high efficiency, ultraclose measurement distance, and superresolution and provides a highly promising and widely available method for antenna diagnosis.

Matrix approach to solve polynomial equations

Polynomials are widely employed to represent numbers derived from mathematical operations in nearly all areas of mathematics. The ability to factor polynomials entirely into linear components allows for a wide range of problem simplifications. This paper presents and demonstrates a novel straightforward approach to solving polynomial problems by converting them to matrix equations. Each polynomial of degree n can be decomposed into a sum of degree ⌈n2⌉ polynomials squared, i.e., ∑i=0naixi=∑i=1⌈n2⌉+1∑j=0j=⌈n2⌉bi,jxj2. It follows that the complexity of factorizing a polynomial of degree 2n is equivalent to that of factorizing polynomial of degree 2n−1. The proposed method for solving fourth-degree polynomials will be a valuable contribution to linear algebra due to its simplicity compared to the current method. This work presents a unique approach to solving polynomials of four or fewer degrees and presents new possibilities for tackling larger degrees. Additionally, our methodology can also be used for educational purposes.

New discussion on the existence and controllability of fractional evolution inclusion of order 1 < r < 2 without compactness

In this article, we investigate the existence and controllability results for fractional evolution inclusions in Banach spaces. By eliminating compactness hypotheses on the semigroup produced by the linear component and any requirements on the multivalued nonlinearity defined in terms of measures of noncompactness, we apply a new method to arrive at the existence of mild solutions and controllability results. In fact, to satisfy the existence and controllability requirements, we propose a fixed‐point strategy for weakly sequentially closed maps. Finally, a concrete example is provided to highlight our theoretical findings.

Determination of optimum planting density of very small potato minitubers and appropriate pot size for maximizing seed tuber production in screenhouse conditions

AbstractTissue culture, aeroponics, and hydroponics have improved the production of first‐generation potato (Solanum tuberosum L.) minitubers in Ethiopia. However, some minitubers may be very small (<5 g) and would probably fail to survive in open‐field conditions. Thus, they are usually replanted in screenhouses in pots as single tubers/hills. The impact of pot size and number of minitubers that can be feasibly planted per pot to obtain optimal yield with little impact on progeny tuber size require investigation to optimize indoor seed potato production. Consequently, a screenhouse experiment was conducted at Adet Agricultural Research Center, Amhara, Ethiopia, between 2020 and 2021 to investigate the effect of seed density and different pot sizes on a number of tubers harvested per pot, per planted minituber, and average tuber weight (g). Experimental treatment factors were potato variety at two levels, pot size at three levels, and seed density at five levels. Five replications per treatment combination, each with four pots, were used. Analysis of variance, with seed density up to cubic component as single‐degree polynomial contrast, showed that the assessed variables were not significantly (P ≤ 0.05) affected by potato variety. All two‐ and three‐way factor interactions except pot size by seed density for the number of tubers harvested per planted minituber were not significant (P ≤ 0.05). Pot size significantly (P ≤ 0.05) affected the number of tubers harvested per pot and per planted minituber but not the average tuber weight. All the assessed variables were significantly (P ≤ 0.05) affected by seed density. The number of tubers harvested per pot increased significantly (P ≤ 0.05) with increasing pot size and seed density. Polynomial regression showed that linear and quadratic components of seed density as a predictor of the assessed variables were significant (P ≤ 0.05); however, its polynomial components did not significantly (P ≤ 0.05) interact with main treatment factors. The estimated optimum seed density from the derivatives of the polynomial functions was five tubers per pot. The predicted minimum average tuber weight was 18.5 g, which is appreciably high for good open‐field minituber survival. Meanwhile, the 10‐L pot produced significantly (P ≤ 0.05) more minitubers than other pot sizes; however, it had the lowest production efficiency per unit area of screenhouse and per kilogram of culture substrate. Thus, 2‐ and 6‐L pots, each planted with five minitubers, irrespective of the potato variety are recommended to maximize productivity of minitubers and screenhouse space with little or no impact on progeny tuber size.

Interaction of physico-chemical parameters with Shannon-Weaver Diversity Index based on phytoplankton diversity in coastal water of Diu, India

Phytoplankton acts as carbon sinks due to photosynthetic efficacy and their diversity is expressed by SWDI (Shannon-Weaver Diversity Index), which depends on water quality parameters. The coastal water of Diu was studied for three seasons, and the relationship between different parameters and SWDI was established. Subsequently, an attempt was made to build up a prediction model of SWDI based on multilayer perceptron Artificial neural network (ANN) using the R programme. Analysis shows interrelationship between the water quality parameters and phytoplankton diversity is same in linear principal component analysis (PCA) and neural network model. Variations of different parameters depend on seasonal changes. The ANN model shows that ammonia and phosphate are key parameters that influence the SWDI of phytoplankton. Seasonal variation in SWDI is related to variation in water quality parameters, as explained by both ANN and PCA. Hence, the ANN model can be an important tool for coastal environmental interaction study.

Observation of terahertz-induced dynamical spin canting in orthoferrite magnon by magnetorefractive probing

Intense terahertz pulses offer unique pathway to resonantly drive the correlated spin systems up to the nonlinear regime. However, detection of such nonlinear spin dynamics often suffers from the small signal amplitude that can be easily hindered by the linear background components. In order to efficiently extract the nonlinear signals, here we demonstrate that magnetooptical effect can be utilized. We excite spin precession in orthoferrite YFeO3 by the magnetic field of intense terahertz pulse and probe its dynamics by transient transmissivity change in the near infrared. The observed waveforms contain quasi-ferromagnetic-mode magnon oscillation and its second harmonics with a comparably strong amplitude. The result can be explained by dielectric function derived from magnetorefractive Hamiltonian. We reveal that the strong second harmonic signal microscopically originates from the dynamics of the quasi-ferromagnetic mode magnon at nonlinear regime, wherein spin canting angle periodically oscillates.

Acoustic frequency multiplication and pure second-harmonic generation of phonons by magnetic transducers

We predict frequency multiplication of surface acoustic waves in dielectric substrates via the ferromagnetic resonance of adjacent magnetic transducers when driven by microwaves. We find pure second-harmonic generation (SHG) without any linear and third-harmonic components by a magnetic nanowire. The SHG and linear phonon pumping are switched by varying the saturated magnetization direction of the wire, or resolved directionally when pumped by a magnetic nanodisk. We address the high efficiency of SHG with comparable magnitude to that of the linear response, as well as a unique nonreciprocal phonon transport that is remarkably distinct in different phonon harmonics. Such an acoustic frequency comb driven by microwaves should bring exceptional tunability for miniaturized phononic and spintronic devices.

Wiener predistorter for nonlinear satellite downlinks

SummaryThe nonlinear power amplifier and the analogue output channel filter with nonconstant group delay add nonlinear and linear distortions to the satellite transmitted signal, respectively. Recently, there has been growing interest in using Wiener predistorters, consisting of separate nonlinear and linear components, to compensate for these distortions in the satellite downlinks. The Wiener predistorter has been shown to effectively deal with signal distortions and has lower complexity compared to other state‐of‐the‐art methods. In this paper, we argue that fully compensating the nonconstant group‐delay distortion degrades the overall performance of the Wiener predistortion systems. This is primarily due to the increased peak‐to‐average power ratio of the signal at the output of the linear predistorter. We show that the overall performance of the Wiener predistorter can be improved by undercompensating the group‐delay distortion. We propose two optimizations to address the PAPR growth problem and show using simulations that our approach leads to significant improvement in predistortion performance. Using our Wiener predistorter, the total degradation gap to the ideal limiter channel can be reduced to merely 0.34 dB for 64‐APSK modulated signals.

Bilinear Planar Hall Effect in Topological Insulators Due to Spin‐Momentum Locking Inhomogeneity

Herein, the effect of spin‐momentum locking inhomogeneity on the planar Hall effect in topological insulators (TIs) is studied. Using the minimal model describing surface states of 3D TIs and semiclassical Boltzmann formalism, the planar Hall conductivity (PHC) within the generalized relaxation time approximation is derived. Herein, it is found that the total PHC consists of linear and nonlinear (in electric field) components. The linear term is a conventional PHC which scales quadratically with an external magnetic field, whereas the nonlinear term reveals bilinear behavior, that is, changes its sign when either charge current density or in‐plane magnetic‐field orientation is reversed. It is shown that the emergent nonlinear planar Hall effect is a consequence of spin‐momentum locking inhomogeneity in the TIs with isotropic energy dispersion, and dominates over the conventional planar Hall effect.

Beyond linear neural envelope tracking: a mutual information approach

Objective. The human brain tracks the temporal envelope of speech, which contains essential cues for speech understanding. Linear models are the most common tool to study neural envelope tracking. However, information on how speech is processed can be lost since nonlinear relations are precluded. Analysis based on mutual information (MI), on the other hand, can detect both linear and nonlinear relations and is gradually becoming more popular in the field of neural envelope tracking. Yet, several different approaches to calculating MI are applied with no consensus on which approach to use. Furthermore, the added value of nonlinear techniques remains a subject of debate in the field. The present paper aims to resolve these open questions. Approach. We analyzed electroencephalography (EEG) data of participants listening to continuous speech and applied MI analyses and linear models. Main results. Comparing the different MI approaches, we conclude that results are most reliable and robust using the Gaussian copula approach, which first transforms the data to standard Gaussians. With this approach, the MI analysis is a valid technique for studying neural envelope tracking. Like linear models, it allows spatial and temporal interpretations of speech processing, peak latency analyses, and applications to multiple EEG channels combined. In a final analysis, we tested whether nonlinear components were present in the neural response to the envelope by first removing all linear components in the data. We robustly detected nonlinear components on the single-subject level using the MI analysis. Significance. We demonstrate that the human brain processes speech in a nonlinear way. Unlike linear models, the MI analysis detects such nonlinear relations, proving its added value to neural envelope tracking. In addition, the MI analysis retains spatial and temporal characteristics of speech processing, an advantage lost when using more complex (nonlinear) deep neural networks.

Deep learning-enabled broadband full-Stokes polarimeter with a portable fiber optical spectrometer.

Portable fiber optical spectrometers (PFOSs) have been widely used in the contemporary industrial and agricultural production and life due its low cost and small volume. PFOSs mainly combine one fiber to guide light and one optical spectrometer to detect spectra. In this work, we demonstrate that PFOSs can work as a broadband full-Stokes polarimeter through slightly bending the fiber several times and establishing the mapping relationship between the Stokes parameters S^ and the bending-dependent light intensities I^, i.e., S^=f(I^). The different bending geometries bring different birefringence effects and reflection effects that change the polarization state of the out-going light. In the meanwhile, the grating owns a polarization-depended diffraction efficiency especially for the asymmetric illumination geometry that introduces an extrinsic chiroptical effect, which is sensitive to both the linear and spin components of light. The minimum mean squared error (MSE) can reach to smaller than 1% for S1, S2, and S3 at 810 nm, and the averaged MSE in the wave band from 440 nm to 840 nm is smaller than 2.5%, where the working wavelength can be easily extended to arbitrary wave band by applying PFOSs with proper parameters. Our findings provide a convenient and practical method for detecting full-Stokes parameters.

New Wine Old Bottles: Feistel Structure Revised

This paper mainly investigates the iterative structures whose decryption is similar to the encryption. Firstly, we unify many well-known structures which share similar procedures between the decryption and the encryption, and give a sufficient and necessary condition for this structure to be bijective, which reveals many new insights into the Feistel structure as well as the Lai-Massey structure. Secondly, we analyze the security of the unified structure against the known cryptanalysis. By extending the dual structure from a Feistel structure to the unified structure, we prove that a differential of the unified structure is impossible if and only if it is a zero-correlation linear hull of its dual structure, which presents a generalized link between the impossible differential and zero-correlation linear cryptanalysis shown in CRYPTO 2015. Significantly, several constraints on the linear components of the cipher and the permutation on the branches of the cipher are specified to make the structure resilient to differential and linear cryptanalysis. Furthermore, in the case that the order of the permutation equals the number of the branches <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$n$ </tex-math></inline-formula> , we prove that there always exist a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(3n-1)$ </tex-math></inline-formula> -round impossible differential and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$(3n-1)$ </tex-math></inline-formula> -round zero-correlation linear hull of the structure, and also present an algorithm to construct these distinguishers. Finally, we propose some novel structures which might be used in future block cipher designs.

Sensitivity Analysis of Ship Manoeuvring Mathematical Models

Sensitivity analysis is applied to ship manoeuvring mathematical models as a means of dealing with model uncertainties, and often leads to model simplifications. A rather standard 3DOF manoeuvring model was tuned with the available results of full-scale trials of a naval combatant and was further used as the reference model for sensitivity analysis. The present research was based on multiple perturbed simulations of the turning, zigzag and spiral manoeuvres. A salient feature of the present study is that the perturbations were applied to the total hydrodynamic forces and moments as well as separately to their characteristic parts, i.e., to the linear and nonlinear single-variable and coupled components. Another special feature is that the deviations of the perturbated responses were estimated not only considering the standard manoeuvring performance indices, but also through application of the Euclidean metric directly to the time histories and to the spiral curve. The performed analysis permitted the sensitivity of the model to be traced to various parameters and groups thereof. It was established that the highest sensitivity of the model was to linear and some nonlinear multivariable parameters, and the Euclidean metric permitted a more detailed analysis than that based only on standard discrete manoeuvring indices. The obtained results are expected to be useful in the application of system identification methods to typical inherently stable fast surface-displacement ships.

Dependence of ocean surface filaments on wind speed: An observational study of North Atlantic right whale habitat

Coherent filaments at the ocean surface often appear to be transient watermass boundaries, where currents converge, surfactants accumulate, and frontal structure at depth can possibly delineate enhanced biological activity in the upper water column. Spaceborne synthetic aperture radar (SAR) permits filaments to be observed at O[1-km] resolution, but extensive coherent structures are more apparent in weaker winds. A wind speed adjustment is proposed for filaments (i.e., contiguous SAR contrasts) of at least 10 km in length. Measures of dependence (distance correlation and the linear and nonlinear components of Pearson correlation) are examined to identify a broad peak in the relationship between filament contrast and weak or moderate values of surface wind speed, where a variable wind speed exponent is employed to maximize these measures.Three locations of recent North Atlantic right whale (Eubalaena glacialis) sightings in the Gulf of St. Lawrence are sampled between 2008 and 2020 by 324 Radarsat-2 SAR scenes and 10-m wind speed from the ERA5 reanalysis. The inverse relationship between SAR contrast magnitude and wind speed is quantified, and a reduced correlation is obtained for all three domains when SAR contrast is weighted by wind speed to the power of 0.8. A more uniform emphasis on ocean surface structure within a SAR scene, or across multiple scenes, can thus be considered in the search for prey aggregations of the North Atlantic right whale.

GNSS_Vel_95CI.py: A Python Module for Calculating the Uncertainty of GNSS-Derived Site Velocity

GNSS_Vel_95CI.py is an open-source Python-3 module for calculating the 95% confidence interval (95% CI) for the site velocity derived from global navigation satellite systems (GNSS) daily positions, which are often affected by time-correlated noises. The detailed methodology for calculating the 95% CI is documented in a recent article (Wang 2022) and initially programmed in Fortran. However, few young researchers (e.g., graduate students) are familiar with Fortran now. In an effort to support a broader user community, we have realized the method in the Python programming language, which has been commonly taught in current college curriculums. Through the use of this module, researchers and engineers can focus on the applications of GNSS time series, rather than on coding and data processing. In particular, the module has the option to output the autocorrelation function (ACF) and the GNSS time-series decomposition results: the linear, nonlinear, seasonal, and residual components, which allow students and researchers having little coding experience to conduct advanced GNSS time-series analysis. The module is versatile, easy to install through the pip installer and GitHub, and simple to use. An example Python program is provided to illustrate the use of this module.

ОПИСАНИЕ ЛИНЕЙНОЙ И НЕЛИНЕЙНОЙ ТЕРМОПОЛЗУЧЕСТИ БЕТОНА НА ОСНОВЕ РЕОЛОГИЧЕСКОЙ МОДЕЛИ И ЭНЕРГЕТИЧЕСКОЙ ТЕОРИИ НЕЛИНЕЙНОЙ ПОЛЗУЧЕСТИ

This article discusses the isolation of linear and nonlinear components of thermal creep deformations on the basis of the energy theory of nonlinear creep and prolonged strength proposed by V.D. Harlab. For the theoretical description of the thermal creep of concrete, a rheo-logical model with a variable number of elastic and viscous bonds (V.D. Kharlab, I.A. Kupriyanov) was used. Analysis of numerical calculations confirmed the assumption that the nonlinear component of creep is independent of temperature. The results are recommended for use in the design of concrete structures operating in conditions of temperature changes.