Artificial Polarization Research Articles

Target Surface pBRDF Model Optimization and Polarization Characteristics Analysis

In this paper, the scattering characteristics of polarized light are studied based on the microsurface element theory, and the Polarization Bi-directional Reflection Distribution Function (pBRDF) model applicable to rough surfaces is established according to the three-component model, and the expression of polarization of reflected light from the target surface is derived based on the model, and the accuracy of the model is verified by comparing the model with the conventional model. The modeling is also carried out from the scattering perspective, and the relationship between different artificial target particle diameters and polarization characteristics is analyzed. The results show that the Degree Of Polarization (DOP) is strongly related to the detection zenith angle. The DOP of the target is largest in the direction of the mirror reflection of the source. The polarization characteristics of different materials are different, and the relative error of the established model is significantly smaller than that of the conventional model. And the scattering model can make preliminary classification of different man-made targets according to different particle diameters, which can provide theoretical support for the analysis of the polarization characteristics of the target surface.

Space-variant polarization conversion with artificial birefringent metallic elements

We present an artificial birefringent space-variant polarization converter for the near infrared, λ = 1550 nm. Each hollow waveguide has a rectangular shape with lateral dimensions of 1550 nm in the x-direction and 1034 nm as the largest length in the y-direction. The whole device consists of approximately 2000 × 2500 hollow waveguides realized in a 2-µm-thick gold structure. They are separated by sidewalls with a width of less than 500 nm. By proper choice of the lateral widths of the individual holes, a pixel-wise polarization conversion of an incoming wave field is possible. By suitable choice of the fabrication parameters, a birefringent phase shift up to 2π can be achieved. Hence, the structure is able to fully convert the state of polarization, e.g., from linear to circular. For fabrication of the device, femtosecond 3D direct laser writing was combined with electroplating. Here, we describe the operation of our device as a space-variant polarization converter by measuring the angle-dependent transmitted power and by calculating the ellipticity and the phase delay dependent on position as well as the azimuth angle from the experimentally determined powers.

Digital tribalism, between fury and farce: let's burst the bubble of artificial polarization on the Internet

En los últimos años ha crecido la preocupación en la opinión pública sobre la polarización política. Algunos autores señalan internet y las redes sociales como una causa de esa polarización. En ese contexto, este artículo aborda los diferentes usos que los sujetos hacen de internet y que dan lugar a distintas formas de polarización. El artículo parte de la revisión bibliográfica sobre las bases neuropsicológicas del comportamiento político y la naturaleza de la polarización política. Sobre este fundamento, el artículo presenta las formas en que tiene lugar la polarización en internet, así como los supuestos morales y epistémicos de la polarización política. Frente a estas formas de polarización, el artículo desarolla el concepto de polarización artificial . Este concepto pretende explicar cómo los usos expresivos de la red generan una percepción errónea de polarización entre los usuarios. Ejemplos de polarización artificial son los discursos incendiarios, los linchamientos virtuales o el exhibicionismo moral. Como resultado, el artículo presenta algunas indicaciones para desactivar los procesos de polarización artificial y construir un ambiente más sosegado en la red.

Determination of Major Axis of Elliptically Polarized Wave Generated by Artificial Anisotropic Polarizers

The major axis of the elliptically polarized wave generated by a linearly polarized (LP) radiating source and an artificial anisotropic polarizer has been analyzed in this communication. Both theoretical and experimental results show that the major axis of the elliptically polarized wave generated by such a combination has an angle of 0° or 90° to the E-plane of the LP radiator. The angle between the major axis and the E-plane depends on the phase difference of the two orthogonal electric components after propagating through the polarizer. Measurement has been conducted for verification which covered the entire V-band (50–75 GHz). The result in this communication provides instructions for the usage of artificial anisotropic polarizers in detection and measurement, such as the calculation of the polarization efficiency during transmission.

Повышение психологической устойчивости молодежи к манипуляционному воздействию в сети Интернет

Increasing psychological resistance to manipulative influence and preventing the involvement of minors in illegal activities with the help of information and communication technologies (ICTs) are important tasks of the State. The article analyzes some psychological mechanisms that contribute to manipulation on the Internet, including the effects of normative influence, conformity, perceived interpersonal similarity, cascades of available information, emotional contagion, hemophilicity, false memories, and multiple sources. The authors analyze the main strategies for promoting false and misleading information: artificial polarization, managing false accounts on behalf of public opinion leaders, creating emotional messages, using conspiracy theories, trolling aimed at provoking harassment of users on the network, defaming and delegitimizing opponents. Attention is also drawn to ways to counteract destructive information and psychological impact, which include not only ways to improve the legislative apparatus and the use of software and technical solutions, but also to increase the level of psychological stability of citizens, conducting preventive and preventive measures aimed at forming ideas about information threats, their types, methods of identification and protection, group norms and values. The author points out the need to develop and implement special psychological trainings and games created in the form of computer programs, mobile applications and online simulators in the socio-cultural and educational environment.

Acoustic Willis meta-atom beyond the bounds of passivity and reciprocity

Willis metamaterial enables exotic manipulations of acoustic waves with a precise combination of bulk modulus, mass density, and Willis parameters. While the realization of unrestricted and completely decoupled constitutive parameters would extend the horizon of future applications, the restriction of passivity and reciprocity dictate a hard bound in the values of achievable polarizabilities and correlations between them. Here, we break the bound of passivity and reciprocity by instituting a basis and independent kernel for each constitutive polarization in a virtualized metamaterial platform, active metamaterials realizing artificial polarization with the digital convolution. We demonstrate decoupled control of all four constitutive parameters in a nonreciprocal regime, at the same time achieving values of polarizabilities beyond the passivity limit. Broadband, flat-response nonreciprocal Willis coupling is also demonstrated with analytically designed causal frequency dispersion. Our approach will be useful for nonreciprocal wave manipulation and communication for broadband operation.

«Богословие ковида», или «Знаменательная буря» коронавирусной пандемии

The article examines various theological aspects of the perception of the coronavirus pandemic in the global Orthodoxy in general and the Russian Orthodox Church in particular. Among other aspects, it touches upon issues pertinent to the practices of celebration and distribution of the Eucharist under the conditions of hygienic restrictions. It also explores Christological arguments in support of each practice. The article proposes some particular interpretations of both phenomenology and etiology of the so‑called Covid dissidence. It argues that artificial polarization on the ideological grounds between the so‑called “liberals” and “conservatives” is one of the reasons why many bishops, priests, and lay people in the Russian Orthodox Church mistrust the quarantine measures.

Ultrathin tri-band reflective cross-polarization artificial electromagnetic metasurface

A high-efficiency tri-band artificial electromagnetic (EM) polarization manipulating metasurface is proposed, which is employing two metal rectangle rings composed of a single-layer reflectance surface. There are three frequency bands generated by the artificial EM polarization manipulating metasurfaces, with 3-dB bandwidth at 9.10–12.40, 15.55–23.80 and 24.71–30.00 GHz, and the relative bandwidth is 30.7%, 41.9% and 19.4%, respectively. The polarization converter ratio of the polarization manipulating metasurfaces is great than 90% at 9.8–12.2, 19–22.6, and 24.9–29.5 GHz, respectively. There are five resonance frequencies at 10.5, 11.8, 20.9, 25.7 and 28.3 GHz, where the polarization converter ratio is almost reached 100%. Equivalent circuit and surface current distributions reveal that the coupling results from the strong electric and magnetic resonances between the top surface and bottom ground. Experimental results of the prototype are basically consistent with the simulation results, which clearly show that the metasurfaces have multiband characteristics and higher efficiency.

Updated Design of the CMB Polarization Experiment Satellite LiteBIRD

Recent developments of transition-edge sensors (TESs), based on extensive experience in ground-based experiments, have been making the sensor techniques mature enough for their application on future satellite cosmic microwave background (CMB) polarization experiments. LiteBIRD is in the most advanced phase among such future satellites, targeting its launch in Japanese Fiscal Year 2027 (2027FY) with JAXA’s H3 rocket. It will accommodate more than 4000 TESs in focal planes of reflective low-frequency and refractive medium-and-high-frequency telescopes in order to detect a signature imprinted on the CMB by the primordial gravitational waves predicted in cosmic inflation. The total wide frequency coverage between 34 and 448 GHz enables us to extract such weak spiral polarization patterns through the precise subtraction of our Galaxy’s foreground emission by using spectral differences among CMB and foreground signals. Telescopes are cooled down to 5 K for suppressing thermal noise and contain polarization modulators with transmissive half-wave plates at individual apertures for separating sky polarization signals from artificial polarization and for mitigating from instrumental 1/f noise. Passive cooling by using V-grooves supports active cooling with mechanical coolers as well as adiabatic demagnetization refrigerators. Sky observations from the second Sun–Earth Lagrangian point, L2, are planned for 3 years. An international collaboration between Japan, the USA, Canada, and Europe is sharing various roles. In May 2019, the Institute of Space and Astronautical Science, JAXA, selected LiteBIRD as the strategic large mission No. 2.

Broadband Terahertz Polarization Converter and Asymmetric Transmission Based on Coupled Dielectric‐Metal Grating

AbstractCoupled dielectric‐metal gratings are investigated for broadband terahertz (THz) wave polarization conversion and asymmetric transmission by the experiments and numerical simulations, which are composed of the subwavelength Si grating and metallic wire grating layers. The dielectric grating layer with a large artificial birefringence and low dispersion is employed as a phase engineered waveplate, and the metal wire grating arranged with a 45° angle to the dielectric grating is utilized as a high‐efficiency polarizer. Due to the subwavelength integration, this coupled grating presents a local resonance coupling mechanism between dielectric and metal gratings, which greatly enhances the polarization rotation and expands the bandwidth, not a simple combination with dielectric and metallic gratings. The results demonstrate that a broadband asymmetric transmission with an extinction ratio of 30dB from 0.2 to 1.2 THz is achieved and the highest transmission of 90% can be obtained. It provides a simple way towards practical applications for THz artificial dispersion materials, polarization control and asymmetric transmission.

Consistency and bicharacteristic analysis of integral porosity shallow water models. Explaining model oversensitivity to mesh design

The Integral Porosity and Dual Integral Porosity two-dimensional shallow water models have been proposed recently as efficient upscaled models for urban floods. Very little is known so far about their consistency and wave propagation properties. Simple numerical experiments show that both models are unusually sensitive to the computational grid. In the present paper, a two-dimensional consistency and characteristic analysis is carried out for these two models. The following results are obtained: (i) the models are almost insensitive to grid design when the porosity is isotropic, (ii) anisotropic porosity fields induce an artificial polarization of the mass/momentum fluxes along preferential directions when triangular meshes are used and (iii) extra first-order derivatives appear in the governing equations when regular, quadrangular cells are used. The hyperbolic system is thus mesh-dependent, and with it the wave propagation properties of the model solutions. Criteria are derived to make the solution less mesh-dependent, but it is not certain that these criteria can be satisfied at all computational points when real-world situations are dealt with.

A Low-RCS and High-Gain Circularly Polarized Antenna With a Low Profile

A low-radar-cross-section and high-gain broadband circularly polarized (CP) antenna with a low profile was specially designed using metasurface concepts. A polarization conversion metasurface is designed and used as the radiator of the proposed CP antenna. It is shown that a good axial ratio and high gain can be obtained over a broad band. Three kinds of artificial magnetic conductors are arranged around the polarization conversion metasurface. By making the discrepancies of the reflection phases among the artificial magnetic conductors and polarization conversion metasurface to be 90° in turn, the monostatic radar cross section of the proposed antenna is reduced in a wide frequency band covering the operation frequency band of the CP antenna. Good agreement between the experimental and simulation results is obtained.

Development of a Precise Polarization Modulator for UV Spectropolarimetry

We developed a polarization modulation unit (PMU) to rotate a waveplate continuously in order to observe solar magnetic fields by spectropolarimetry. The non-uniformity of the PMU rotation may cause errors in the measurement of the degree of linear polarization (scale error) and its angle (crosstalk between Stokes-Q and -U), although it does not cause an artificial linear polarization signal (spurious polarization). We rotated a waveplate with the PMU to obtain a polarization modulation curve and estimated the scale error and crosstalk caused by the rotation non-uniformity. The estimated scale error and crosstalk were <0.01 % for both. This PMU will be used as a waveplate motor for the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP) rocket experiment. We confirmed that the PMU has the sufficient performance and function for CLASP.

Ideal and Nonideal Theory: Untangling the Debate

In reviewing some of the literature, ideal and non-ideal theories are presented as opposing or at least competing theories, in the same manner as are liberal and progressive theories of education. Some scholars suggest that ideal theory ought to precede non-ideal theory, while others suggest just the opposite. This is referred to in the literature as ‘the priority objection.’ Some suggest we don’t need ideal theory at all and should exclusively use non-ideal theory. Others focus on how this scholar misses the point, that scholar leaves something out, or this scholar has it right and here’s why. My objective in this paper is to argue that aside from important and scholarly discussions, ideal theory and non-ideal theory are artificially polarized. Further, and more radically, characterizing ideal and non-ideal theories as two separate enterprises and as ‘theories’ are category mistakes. Not surprisingly, because of the artificial polarization and category mistakes, the debate is rather confused and stuck. This paper attempts to untangle the confusion and open up the dialogue.

Appropriators not Position Takers: The Distorting Effects of Electoral Incentives on Congressional Representation

Congressional districts create two levels of representation. Studies of representation focus on a disaggregated level: the electoral connection between representatives and constituents. But there is a collective level of representation—the result of aggregating across representatives. This article uses new measures of home styles to demonstrate that responsiveness to constituents can have negative consequences for collective representation. The electoral connection causes marginal representatives—legislators with districts composed of the other party's partisans—to emphasize appropriations in their home styles. But it causes aligned representatives—those with districts filled with copartisans—to build their home styles around position taking. Aggregated across representatives, this results in an artificial polarization in stated party positions: aligned representatives, who tend to be ideologically extreme, dominate policy debates. The logic and evidence in this article provide an explanation for the apparent rise in vitriolic debate, and the new measures facilitate a literature on home styles.

Designing Synthetic Regulatory Networks Capable of Self-Organizing Cell Polarization

How cells form global, self-organized structures using genetically encoded molecular rules remains elusive. Here, we take a synthetic biology approach to investigate the design principles governing cell polarization. First, using a coarse-grained computational model, we searched for all possible simple networks that can achieve polarization. All solutions contained one of three minimal motifs: positive feedback, mutual inhibition, or inhibitor with positive feedback. These minimal motifs alone could achieve polarization under limited conditions; circuits that combined two or more of these motifs were significantly more robust. With these design principles as a blueprint, we experimentally constructed artificial polarization networks in yeast, using a toolkit of chimeric signaling proteins that spatially direct the synthesis and degradation of phosphatidylinositol (3,4,5)-trisphosphate (PIP(3)). Circuits with combinatorial motifs yielded clear foci of synthetic PIP(3) that can persist for nearly an hour. Thus, by harnessing localization-regulated signaling molecules, we can engineer simple molecular circuits that reliably execute spatial self-organized programs.

Polarization switching and patterning in self-assembled peptide tubular structures

Self-assembled peptide nanotubes are unique nanoscale objects that have great potential for a multitude of applications, including biosensors, nanotemplates, tissue engineering, biosurfactants, etc. The discovery of strong piezoactivity and polar properties in aromatic dipeptides [A. Kholkin, N. Amdursky, I. Bdikin, E. Gazit, and G. Rosenman, ACS Nano 4, 610 (2010)] opened up a new perspective for their use as biocompatible nanoactuators, nanomotors, and molecular machines. Another, as yet unexplored functional property is the ability to switch polarization and create artificial polarization patterns useful in various electronic and optical applications. In this work, we demonstrate that diphenylalanine peptide nanotubes are indeed electrically switchable if annealed at a temperature of about 150 °C. The new orthorhombic antipolar structure that appears after annealing allows for the existence of a radial polarization component, which is directly probed by piezoresponse force microscopy (PFM) measurements. Observation of the relatively stable polarization patterns and hysteresis loops via PFM testifies to the local reorientation of molecular dipoles in the radial direction. The experimental results are complemented with rigorous molecular calculations and create a solid background of electric-field induced deformation of aromatic rings and corresponding polarization switching in this emergent material.

Adsorption and spin state properties of Cr, Ni, Mo, and Pt deposited on Li+ and Na+ monovalent cation impurities of MgO (001) surface: DFT calculations

We have analyzed, by means of density functional theory calculations and the embedded cluster model, the adsorption and spin-state properties of Cr, Ni, Mo, and Pt deposited on a MgO crystal. We considered deposition at the Mg(2+) site of a defect-free surface and at Li(+) and Na(+) sites of impurity-containing surfaces. To avoid artificial polarization effects, clusters of moderate sizes with no border anions were embedded in simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. The interaction between a transition metal atom and a surface results from a competition between Hund's rule for the adsorbed atom and the formation of a chemical bond at the interface. We found that the adsorption energies of the metal atoms are significantly enhanced by the cation impurities, and the adsorption energies of the low-spin states of spin-quenched complexes are always more favorable than those of the high-spin states. Spin polarization effects tend to preserve the spin states of the adsorbed atoms relative to those of the isolated atoms. The metal-support interactions stabilize the low-spin states of the adsorbed metals with respect to the isolated metals, but the effect is not always enough to quench the spin. Spin quenching occurs for Cr and Mo complexes at the Mg(2+) site of the pure surface and at Li(+) and Na(+) sites of the impurity-containing surfaces. Variations of the spin-state properties of free metals and of the adsorption and spin-state properties of metal complexes are correlated with the energies of the frontier orbitals. The electrostatic potential energy curves provide further understanding of the nature of the examined properties.

Magnetic and binding properties of metal-divacancy complexes at MgO (0 0 1) surface: DFT calculations

We have analyzed the magnetic and binding properties of Ni, Cr, Mo, and Pt metals deposited on the defect free and defect containing surfaces of MgO by means of density functional theory calculations and embedded cluster model. Clusters of moderate sizes with no border anions, to avoid artificial polarization effects, were embedded in the simulated Coulomb fields that closely approximate the Madelung fields of the host surfaces. Spin quenching occurs for Cr and Mo complexes at the defect free (terrace) surface, and Cr, Mo, and Pt complexes at the defect containing “pit” divacancy surface. The binding energies of the metals are significantly enhanced on the cationic vacancy end of the divacancy. The adsorption energies of the low spin states of spin quenched complexes are always greater than those of the high spin states. The metal–support interactions stabilize the low spin states of the adsorbed metals with respect to the isolated metals, but the effect is not always enough to quench the spin. The encountered variations in magnetic properties of free metals and of metal complexes are correlated with the energy gaps of the frontier orbitals. Spin contamination affect the adsorbate–substrate distances, Mulliken charges, Mulliken spin densities, natural charge, natural orbital population, and provide rationalization for the reported magnetic and binding properties. The electrostatic potential energy curves provide clearer understanding of the nature of magnetic and binding interactions. The magnetic and binding properties of a single metal atom adsorbed on a particular surface result from a competition between Hund's rule for the adsorbed metal, and the formation of a chemical bond at the interface.

White-throated sparrows calibrate their magnetic compass by polarized light cues during both autumn and spring migration

The interaction and hierarchy of celestial and magnetic compass cues used by migratory songbirds for orientation has long been the topic of an intense debate. We have previously shown that migratory Savannah sparrows, Passerculus sandwichensis, use polarized light cues near the horizon at sunrise and sunset to recalibrate their magnetic compass. Birds exposed to a +/-90 deg. shifted artificial polarization pattern at sunrise or sunset recalibrated their magnetic compass, but only when given full access to celestial cues, including polarized light cues near the horizon. In the current study, we carried out cue conflict experiments with white-throated sparrows, Zonotrichia albicollis, during both spring and autumn migration in a transition zone between the species' breeding and wintering areas on the south shore of Lake Ontario. We show that white-throated sparrows also recalibrate their magnetic compass by polarized light cues at sunrise and sunset. Sunrise exposure to an artificial polarization pattern shifted relative to the natural magnetic field or exposure to a shift of the magnetic field relative to the natural sky both led to recalibration of the magnetic compass, demonstrating that artificial polarizing filters do not create an anomalous, unnatural orientation response. Our results further indicate that there is no evidence for a difference in compass hierarchy between different phases of migration, confirming previous work showing that polarized light cues near the horizon at sunrise and sunset provide the primary calibration reference both in the beginning and at the end of migration.