Simple Theory Research Articles

Effect of End Groups on the Cloud Point Temperature of Aqueous Solutions of Thermoresponsive Polymers: An Inside View by Flory-Huggins Theory.

In an effort to gain insight into the origin of the effects of end groups on the cloud point temperature (Tcp) as a function of the polymer molar mass of thermoresponsive polymers with lower critical solution behavior in dilute aqueous solutions, we use the Flory-Huggins (FH) theory amended for end groups. The theory was applied to available experimental data sets of poly(N-isopropylacrylamide) (PNIPAM), poly(4-vinylbenzyl methoxytris(oxyethylene) ether) (PTEGSt), and poly(α-hydro-ω-(4-vinylbenzyl)tetrakis(oxyethylene) ether) (PHTrEGSt). The theory relates the variations in TcpM,ϕcp for different end groups to the effective FH χ parameter of the end groups and explains the qualitative notion that the influence of the end groups is related to the hydrophobicity/hydrophilicity of the end groups relative to that of the so called intrinsic TcpM,ϕcp response of a polymer without end groups. The limits to the applicability of the FH theory are established, and a set of possible theoretical improvements is considered. The ultimate scrutiny of the simple FH theory and suggested improved theories must await the measurement of truly thermodynamic cloud points; the available cloud points are merely estimations of the thermodynamic cloud point, for which the deviation to the true cloud point cannot be established with sufficient accuracy.

A Simplified Radiation Characteristic Analysis Method for Defocus-Fed Parabolic Antennas in a W-Band Communication System

With increasing interest in the W-band, there is growing focus on parabolic reflector antennas that are known for efficiently inducing high-gain radiation characteristics. There is particular focus on parabolic antennas with diverse defocus-fed applications, including monopulse tracking, multi-beam formation using multiple feeds, and aperture-shared antennas for multi-band operation. Thus, a new simplified method is presented in this paper to analyze the radiation characteristics of defocus-fed parabolic antennas. The presented method is based on the discrete division of a parabolic reflector surface and considers only simplified wave propagation theory and the effect of the scalar function pattern from the feeder. Additionally, array theory is exclusively applied for the analysis of radiation characteristics. Therefore, the presented method uses a very simplified formula to calculate the radiation characteristics of a defocused parabolic reflector antenna. The performance of the presented method was evaluated by comparing the results with commercial EM tools. The results of the analysis confirm the applicability of the presented method for the analysis of defocus-fed parabolic antennas.

Towards a complete classification of 6D supergravities

The constraints arising from anomaly cancellation are particular strong for chiral theories in six dimensions. We make progress towards a complete classification of 6D supergravities with minimal supersymmetry and non-abelian gauge group. First, we generalize a previously known infinite class of anomaly-free theories which has \U0001d447 ≫ 9 to essentially any semi-simple gauge group and infinitely many choices for hypermultiplets. The construction relies on having many decoupled sectors all selected from a list of four simple theories which we identify. Second, we use ideas from graph theory to rephrase the task of finding anomaly-free theories as constructing cliques in a certain multigraph. A branch-and-bound type algorithm is described which can be used to explicitly construct, in a \U0001d447-independent way, anomaly-free theories with an arbitrary number of simple factors in the gauge group. We implement these ideas to generate an ensemble of O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(107) irreducible cliques from which anomaly-free theories may be easily built, and as a special case obtain a complete list of 19,847 consistent theories for \U0001d447 = 0, for which the maximal gauge group rank is 24. Modulo U(1), SU(2) and SU(3) simple factors and the new infinite families, we give a complete characterization of anomaly-free theories and show that the bound \U0001d447 ≤ 273 is sharp.

Examination of the high-frequency behavior of functionally graded porous nanobeams using nonlocal simple higher-order shear deformation theory

Examination of the high-frequency behavior of functionally graded porous nanobeams using nonlocal simple higher-order shear deformation theory

The Influence of the Flexibility of a Polymeric Adhesive Layer on the Mechanical Response of a Composite Reinforced Concrete Slab and a Reinforced Concrete Beam Girder.

This study addresses the challenges of modeling flexible connections in composite structures employing a polymeric adhesive layer. These types of connections provide a more uniform stress distribution compared to conventional rigid connectors. However, they lack standardized design rules and still require much research to sufficiently comprehend their properties. The novelty of this research lies in proposing an analytical solution to address these issues. Its aim is to investigate the influence of the stiffness of the polymer adhesive on the girder's deflection and on the maximum stresses in both the adhesive and concrete. The analyzed composite structure consists of a reinforced concrete (RC) slab and an RC beam connected with a layer of flexible polyurethane (FPU) adhesive. Analytical and numerical approaches for the description of the mechanical response of a composite bridge girder are presented. Another objective is to validate the analytical design formulas using 3D nonlinear numerical analysis, both in the case of uncracked and cracked concrete. Seven types of FPUs are tested in the uniaxial tension test, each examined at five strain rates. The obtained data is used to predict the mechanical response of the considered girder using finite element analysis (FEA) as well as with a simplified one-dimensional composite beam theory. Fair agreement is found between the FEA results and theoretical predictions. A comparison of the results obtained for these two models is performed, and the similarities and discrepancies are highlighted and discussed.

How 2D Nanoflakes Improve Transport in Mixed Matrix Membranes: Insights from a Simple Lattice Model and Dynamic Mean Field Theory.

Mixed matrix membranes (MMMs), incorporating graphene and graphene oxide structural fragments, have emerged as promising materials for challenging gas separation processes. What remains unclear is the actual molecular mechanism responsible for the enhanced permeability and perm-selectivity of these materials. With the fully atomistic models still unable to handle the required time and length scales, here, we employ a simple qualitative model based on the lattice representation of the physical system and dynamic mean field theory. We demonstrate that the performance enhancement results from the flux-regularization impact of the 2D nanoflakes and that this effect sensitively depends on the orientation of the nanoflakes and the properties of the interface between the nanoflakes and the polymer.

Research on eight machine learning algorithms applicability on different characteristics data sets in medical classification tasks.

With the vigorous development of data mining field, more and more algorithms have been proposed or improved. How to quickly select a data mining algorithm that is suitable for data sets in medical field is a challenge for some medical workers. The purpose of this paper is to study the comparative characteristics of the general medical data set and the general data sets in other fields, and find the applicability rules of the data mining algorithm suitable for the characteristics of the current research data set. The study quantified characteristics of the research data set with 26 indicators, including simple indicators, statistical indicators and information theory indicators. Eight machine learning algorithms with high maturity, low user involvement and strong family representation were selected as the base algorithms. The algorithm performances were evaluated by three aspects: prediction accuracy, running speed and memory consumption. By constructing decision tree and stepwise regression model to learn the above metadata, the algorithm applicability knowledge of medical data set is obtained. Through cross-verification, the accuracy of all the algorithm applicability prediction models is above 75%, which proves the validity and feasibility of the applicability knowledge.

Performance comparison of a standing-wave thermoacoustic engine with different resonator shapes with air working gas

The resonator is one of the key components of thermoacoustic machines and the choice of its geometry is of course of crucial importance, as it determines the way the machine operates. The resonator must be designed so that the quality factor of the resonance is as high as possible and must satisfy the technological production constraints related to the high pressurization of the working fluid and the presence of temperature non-uniformities. The shape of the resonator can be modified to reduce certain loss phenomena, particularly on the walls, and to limit the formation of harmonics in the high-level acoustic field. In this work, an acoustic power losses analysis and a numerical study of a standing-wave TAE with air working gas, considering changes in resonator shape, are performed to investigate the effect of resonator geometry on the thermoacoustic energy conversion. The acoustic power dissipation in the resonator is analyzed based on the simplified thermoacoustic theory and the numerical study is conducted based on a 2D numerical model based on a CFD analysis. Results show that the shape of the resonator significantly affects the frequency, the temperature along the stack, and the acoustic pressure produced on the TAE. In addition, it is shown that the resonator composed of two different diameters showed its ability to produce a high acoustic pressure amplitude (20.5% than the iso-diameter resonator) and minimize the viscous and thermal losses.

Molecular charmed baryons and pentaquarks from light-meson exchange saturation

The spectrum of the cqq baryons contains a few states whose nature is not clearly a three-quark composite and which might have a sizable baryon-meson component. Examples include the Σc(2800) or the Λc(2940). Here we explore the spectrum of two-body systems composed of a light, octet baryon and a charmed meson (or antimeson) within a simple contact-range theory in which the couplings are saturated by light-meson exchanges. This results in the prediction of a series of composite anticharmed pentaquarks (c¯qqqq) and singly charmed baryons (cq¯qqq). Among the latter we find J=12 ΞD and J=32 ΞD* bound states with masses matching those of the recently observed Ωc(3185) and Ωc(3327) baryons. Published by the American Physical Society 2024

Predicting Random Walks and a Data-Splitting Prediction Region

Perhaps the first nonparametric, asymptotically optimal prediction intervals are provided for univariate random walks, with applications to renewal processes. Perhaps the first nonparametric prediction regions are introduced for vector-valued random walks. This paper further derives nonparametric data-splitting prediction regions, which are underpinned by very simple theory. Some of the prediction regions can be used when the data distribution does not have first moments, and some can be used for high-dimensional data, where the number of predictors is larger than the sample size. The prediction regions can make use of many estimators of multivariate location and dispersion.

A unified theory for granular matter

Developing a unified theory to describe granular matter, which can behave like either solid or fluid, is one of the grand challenges in modern science. This is mainly because the current theories, rooted in different origins, interpret granular matter from disparate perspectives and are hard to merge. In this work, we demonstrate that it is possible to generate such a generic theory by bridging the elastoplastic theory of solids with the rheological law of granular flow. The proposed theory or mathematical model can well explain the avalanching behaviours occurring in solid-fluid phase transition, and other related concepts such as interparticle interlocking, dilatancy, hysteresis, scaling law, and flow regimes in describing granular matter. Its applicability is tested in a variety of granular systems where solid- and fluid-like states coexist. This work therefore offers a simple but general theory to describe granular matter in a unified way.

Voltage controlled iontronic switches: a computational method to predict electrowetting in hydrophobically gated nanopores

ABSTRACT Reliable and controllable switches are crucial in nanofluidics and iontronics. Ion channels found in nature serve as a rich source of inspiration due to their intricate mechanisms modulated by stimuli like pressure, temperature, chemical species, and voltage. The artificial replication of the properties of these channels is challenging due to their complex chemistry, limited stability range, and intricate moving parts, allosterically modulated. Nonetheless, we can harness some of the gating mechanisms of ion channels for nanofluidic and iontronic purposes. This theoretical and computational study explores the use of electrowetting in simple hydrophobic nanopores to control their conductance using an external applied voltage. We employ restrained molecular dynamics to calculate the free energy required for wetting a model nanopore under different voltages. Utilizing a simple theory, we generate free energy profiles across a wide voltage range. We also computed transition rates between conductive and non-conductive states, showing their voltage dependence and how this behavior can impair memory to the system, resembling the memristor behavior voltage-gated channels in the brain. The proposed framework provides a promising avenue for designing and controlling hydrophobic nanopores via electrowetting, enabling potential applications in neuromorphic iontronics.

Anisotropic run-and-tumble-turn dynamics.

Run-and-tumble processes successfully model several living systems. While studies have typically focused on particles with isotropic tumbles, recent examples exhibit "tumble-turns", in which particles undergo 90° tumbles and so possess explicitly anisotropic dynamics. We study the consequences of such tumble-turn anisotropicity at both short and long-time scales. We model run-and-tumble-turn particles as self-propelled particles subjected to an angular potential that favors directions of movement parallel to Cartesian axes. Using agent-based simulations, we study the effects of the interplay between rotational diffusion and an aligning potential on the particles' trajectories, which leads to the right-angled turns. We demonstrate that the long-time effect is to alter the tumble-turn time, which governs the long-time dynamics. In particular, when normalized by this timescale, trajectories become independent of the underlying details of the potential. As such, we develop a simplified continuum theory, which quantitatively agrees with agent-based simulations. We find that the purely diffusive hydrodynamic limit still exhibits anisotropic features at intermediate times and conclude that the transition to diffusive dynamics precedes the transition to isotropic dynamics. By considering short-range repulsive and alignment particle-particle interactions, we show how the anisotropic features of a single particle are inherited by the global order of the system. We hope this work will shed light on how active systems can extend local anisotropic properties to macroscopic scales, which might be important in biological processes occurring in anisotropic environments.

Relation between Mean-Field Theory and Atomic Structures in Chalcogenide Glasses

The authors conducted various of X-ray and neutron scattering experiments on typical chalcogenide glasses and clarified the relationship between the atomic structure and simple rigidity percolation theory.

Studying near-field propagation of generalized parabolic beams by virtual source method

Generalized parabolic beams have various optical morphologies. They can be used in different research fields, such as component design, aero-optics, and microwave wireless power transmission. Studying the near-field transmission characteristics of these beams is important for improving utilization efficiency. We develop a more accurate theoretical framework to precisely understand the propagation behaviors of complex light fields in the near-field range, especially to break through the limitations of conventional near-axis approximation. This framework fully reveals the propagation mechanism of parabolic beams and their energy transmission modes. Here, based on the principle of independent propagation and the virtual source method, a group of virtual sources are introduced to analyze generalized parabolic beams. These beams can be expanded into the superposition of infinite continuous integer Bessel beams. Then, by combining the Weber integral formula and the Fourier Bessel transform, we rigorously derive an integral expression for generalized parabolic beams during near-field propagation. This expression breaks through the limitation of the traditional paraxial approximation and contains all the key propagation parameters of the family of beams. Based on this integral expression, the intensity distribution and phase characteristics of the generalized parabolic beam along the optical axis are further calculated and analyzed to reveal its energy transfer mode and phase characteristics. By comparing the paraxial approximate solution with the nonparaxial corrected solution for generalized parabolic beams, the far-field propagation of generalized parabolic beams is found to be the same when the propagation distance is sufficiently long. Such simulation results indirectly confirm the correctness of the obtained theoretical solution. The simple paraxial approximation theory can be used conveniently to calculate the far-field propagation of generalized parabolic beams. However, large errors exist when paraxial theory is used to calculate the near-field distribution of generalized parabolic beams. Although calculating nonparaxial propagation is especially complex, the nonparaxial correction solution is necessary when generalized parabolic beams are used in near-field research. Such research results not only deepen the understanding of the propagation mechanism of generalized parabolic beams but also lay a theoretical foundation for studying the precise propagation behaviors of other complex light fields in near-field optics.

The problem-of-time and a quantum inferred discretization of space for a simple reparameterization invariant theory

The problem-of-time and a quantum inferred discretization of space for a simple reparameterization invariant theory

Control of Stability and Relative Humidity in the Radiative‐Convective Equilibrium Model Intercomparison Project

AbstractThe Radiative‐Convective Equilibrium Model Intercomparison Project (RCEMIP) exhibits a large spread in the simulated climate across models, including in profiles of buoyancy and relative humidity. Here we use simple theory to understand the control of stability, relative humidity, and their responses to warming. Across the RCEMIP ensemble, temperature profiles are systematically cooler than a moist adiabat, and convective available potential energy (CAPE) increases with warming at a rate greater than that expected from the Clausius‐Clapeyron relation. There is higher CAPE (greater instability) in models that are on average moister in the lower‐troposphere. To more explicitly evaluate the drivers of the intermodel spread, we use simple theory to estimate values of entrainment and precipitation efficiency (PE) given the simulated values of CAPE and lower‐tropospheric relative humidity. We then decompose the intermodel spread in CAPE and relative humidity (and their responses to warming) into contributions from variability in entrainment, PE, the temperature of the convecting top, and the inverse water vapor scale height. Model‐to‐model variation in entrainment is a dominant source of intermodel spread in CAPE and its changes with warming, while variation in PE is the dominant source of intermodel spread in relative humidity. We also decompose the magnitude of the CAPE increase with warming and find that atmospheric warming itself contributes most strongly to the CAPE increase, but the indirect effect of increases in the water vapor scale height with warming also contribute to increasing CAPE beyond that expected from Clausius‐Clapeyron.

Temperature dependence of the anisotropy of the infrared dielectric properties and phonon-plasmon coupling in n-doped 4H-SiC

Polarized infrared reflectivity spectroscopy is used to measure the temperature dependence of the anisotropy of the infrared dielectric properties and the coupling between phonon and plasmon modes in n-doped 4H-SiC. The advantage of polarized infrared spectroscopy over the commonly used Raman spectroscopy is that it enables dielectric, plasmonic, and transport properties to be probed along and perpendicular to the c-axis, which is impossible with Raman spectroscopy due to its selection rules. In addition, the infrared spectrum, comparatively rare for Raman spectroscopy, can be described at high temperatures with simple classical theory, providing more precise information on the properties of the material being measured. Analysis of the s- and p-polarized infrared reflectivity spectra of an n-doped 4H-SiC substrate shows that the strength and damping of the oscillators, the response of the bound electrons to an infrared excitation, the effective ion mass, and the transverse frequency and anharmonicity of the phonons of n-doped 4H-SiC are temperature-sensitive and strongly anisotropic. It also shows that the plasmonic properties of n-doped 4H-SiC, namely the relaxation time and the collective oscillation frequency of free electrons, are also highly anisotropic and, due to the long relaxation time of free electrons in the direction parallel to the c-axis, only the axial longitudinal phonon-plasmon modes split into low-frequency and high-frequency modes at temperatures above 700 K.

Effect of cross-sectional shape evolvement on the energy absorption performances of multicellular square tube

This study systematically investigated the effect of position evolvement of four ribs in multicellular square tube on its crashworthiness performance. Results show that the multicellular square tubes with the shape factors of k = 0.25 and k = 0.75 have better energy absorption performances than other multicellular square tubes under the same wall thickness or the same mass. The mean crush force is derived through the simplified super folding element theory. Moreover, multi-objective optimization of multicellular square tube is carried out and the optimal result is validated by the finite element model.

Deciphering the True FEC Reduction Mechanism and Its Implications to the Understanding of the SEI in Li-Ion Batteries

The main challenges in rechargeable batteries, especially when aiming for high energy density, arise from the limited electrochemical stability window of current state-of-the-art electrolytes. Negative electrode active materials, such as silicon, tin oxide and others, whose capacity is many times higher than that of graphite, often exhibit large volume expansion upon lithiation and therefore the SEI formed on their surface is unstable. The most popular strategy for improving their cycling stability is the use of electrolyte additives that are reduced at potentials more positive than the electrolyte solvents. Their decomposition products are incorporated in the SEI, leading to a more stable electrode/electrolyte interface.One of the most-investigated electrolyte additives is fluoroethylene carbonate (FEC), because it has been shown to lead to a significant performance enhancement of Si- and Sn-based anodes. Many reaction pathways have been proposed, however there is currently no agreement on the exact type of chemical compounds constituting the decomposition products, nor on the exact mechanism for FEC decomposition. To address these questions, we conducted a systematic study that tracked the morphological and chemical changes during electrochemical decomposition of FEC. We have found that despite FEC often being referred as a “film-forming” additive, the first stage of its decomposition leads instead to the formation of spherical particles, consisting mainly of lithium fluoride (see figure below);1 only later a carbonate-rich film covers the entire electrode, covering as well the LiF-rich spheres. This phenomenon has been overlooked before likely due to very simple reason, disclosed in our contribution.A detailed investigation using XPEEM—a surface-sensitive analytical technique with high lateral resolution—as a function of electrolyte composition shows that fluorine in the later-formed carbonate film comes from the electrolyte salt, while all fluorine from FEC decomposition resides in the spherical particles, formed upon FEC reduction. In addition, we have found that the size and amount of particles strongly depend on the cell medium, where electrolytes with higher dielectric constant lead to larger particle size, as does the presence of the high-capacity electroactive materials in the electrode, both contributing to the final properties of FEC-derived SEI. The results of this study provide a deeper understanding of how fluorine-containing additives work and enables tuning of the SEI properties to the desired morphological and chemical outcome by using the laws of simple crystal-growth theory by adjusting the inter-cell environment.This work demonstrates that, with the right analytical tools, the true nature of the even seemingly very-well studied compounds can be revealed and a full understanding of their decomposition mechanisms can be clarified. Acknowledgement This research was supported by InnoSuisse (Project number 18254.2) References Y. Surace, D. Leanza, M. Mirolo, Ł. Kondracki, C.A.F. Vaz, M. El Kazzi, P. Novák, S. Trabesinger, Energy Storage Materials 2022, 44, 156-167. Figure 1