Epsilon-Near-Zero Metamaterials

This Element introduces the exotic wave phenomena arising from the extremely small optical refractive index, and sheds light on the underlying mechanisms, with a primary focus on the basic concepts and fundamental wave physics. The authors reveal the exciting applications of ENZ metamaterials, which have profound impacts over a wide range of fields of science and technology. The sections are organized as follows: in Section 2, the authors demonstrate the extraordinary wave properties in ENZ metamaterials, analyzing the unique wave dynamics and the resulting effects. Section 3 is dedicated to introducing various realization methods of the ENZ metamaterials with periodic and non-periodic styles. The applications of ENZ metamaterials are discussed in Sections 4 and 5, from the perspectives of microwave engineering, optics, and quantum physics. The authors close in Section 6 by presenting an outlook on the development of ENZ metamaterials and discussing the key challenges addressed in future works.

Wave Number and Input Impedance of a VLF Insulated Linear Antenna in an Anisotropic Ionosphere

We report a method to obtain the wave number and input impedance of a very low frequency (VLF) insulated linear antenna in an anisotropic ionosphere. Due to the anisotropy, electromagnetic fields in the ionosphere are decomposed into the ordinary wave and extraordinary wave. Wave equations for the layered structure are applied to access the wave number of the insulated antenna in the ionosphere via the derivation of the eigenvalue equation by using boundary conditions. The expression for the wave number is given based on some approximation formulas. Then, King’s antenna theory is further employed to solve the input impedance and current distribution of the antenna in the anisotropic medium. After the validation of the method is performed, near-field characteristics for an insulated antenna with different medium parameters in the anisotropic ionosphere are discussed. Effects of the electric density and geomagnetic field of the time-and space-varying anisotropic ionosphere on the distribution of normalized current are analyzed. This finding provides a promising avenue for getting electromagnetic characteristics of space-borne antennas.

Extraordinary and upper-hybrid waves in spin quantum magnetoplasmas with vacuum polarization effect

The propagation of extraordinary and upper-hybrid waves in spin quantum magnetoplasmas with vacuum polarization effect is investigated. Based on the quantum magnetohydrodynamics model including Bohm potential, arbitrary relativistic degeneracy pressure and spin force, and Maxwell's equations modified by the spin current and vacuum polarization current, the dispersion relations of extraordinary and upper-hybrid waves are derived. The analytical and numerical results show that quantum effects (Bohm potential, degeneracy pressure and spin magnetization energy) and the vacuum polarization effect modify the propagation of the extraordinary wave. Under the action of a strong magnetic field, the plasma frequency is obviously increased by the vacuum polarization effect.

Pure and Linear Frequency Converter Temporal Metasurface

Metasurfaces are ultrathin structures which are constituted by an array of subwavelength scatterers with designable scattering responses. They have opened up unprecedented exciting opportunities for extraordinary wave engineering processes. On the other hand, frequency converters have drawn wide attention due to their vital applications in telecommunication systems, health care devices, radio astronomy, military radars and biological sensing systems. Here, we show that a spurious-free and linear frequency converter metasurface can be realized by leveraging unique properties of engineered transmissive temporal supercells. Such a metasurface is formed by time-modulated supercells; themselves are composed of temporal and static patch resonators and phase shifters. This represents the first frequency converter metasurface possessing large frequency conversion ratio with controllable frequency bands and transmission magnitude. In contrast to conventional nonlinear mixers, the proposed temporal frequency converter offers a linear response. In addition, by taking advantage of the proposed surface-interconnector-phaser-surface (SIPS) architecture, a spurious-free and linear frequency conversion is achievable, where all undesired mixing products are strongly suppressed. The proposed metasurface may be digitally controlled and programmed through a field programmable gate array. This makes the spurious-free and linear frequency converter metasurface a prominent solution for wireless and satellite telecommunication systems, as well as invisibility cloaks and radars. This study opens a way to realize more complicated and enhanced-efficiency spectrum-changing metasurface.

Numerical simulation of a slow extraordinary wave in magnetoactive plasma

Численно и аналитически исследовано влияние внешнего магнитного поля на плоские нерелятивистские нелинейные плазменные колебания. Для инициализации медленной необыкновенной волны в магнитоактивной плазме предложен способ построения недостающих начальных условий на основе решения линейной задачи методом Фурье. С целью численного моделирования нелинейной волны построена схема метода конечных разностей второго порядка точности типа МакКормака на основе эйлеровых переменных. Показано, что при учете внешнего магнитного поля ленгмюровские колебания трансформируются в медленную необыкновенную волну, энергия которой вибрирует при перемещении от начала координат. При этом скорость волны увеличивается с ростом внешнего постоянного поля, что способствует выносу энергии из первоначальной области локализации колебаний. The effect of an external magnetic field on plane non-relativistic nonlinear plasma oscillations is studied numerically and analytically. A method for the initialization a slow extraordinary wave in a magnetoactive plasma is proposed for constructing the missing initial conditions based on solving a linear problem using the Fourier method. For the purpose of numerical simulation of a nonlinear wave, a scheme of the second-order accuracy finite difference method of the MacCormack type based on Euler variables is constructed. It is shown that, when the external magnetic field is taken into account, the Langmuir oscillations are transformed into a slow extraordinary wave whose energy vibrates when moving from the origin. In this case, the wave velocity increases with the growth of the external constant field, which contributes to the removal of energy from the initial region of localization of oscillations.

The populist challenge to the European Court of Human Rights

This article analyzes the European Court of Human Rights (ECtHR) from the perspective of the recent extraordinary wave of populism in Europe. It argues that populism poses a serious and distinctive challenge to the ECtHR since supranational judicial review is at odds with the populist ideology. What makes the populist challenge distinctive is the combination of the ideological basis of populism, its wide appeal and capacity to reach ordinary people, and populists’ tendency to remove limitations on their power. With respect to the last point, the article introduces a categorization of anti-court techniques and takes stock of the ECtHR’s institutional setting. It concludes that although the situation is not perfect—the budget and judicial selection are especially problematic—the ECtHR is rather well insulated from eventual attacks targeting its structural features or the judicial personnel. However, including the ECtHR in the “narrative of blame,” populism is very strong in another anti-court strategy—achieving gradual erosion of a court through delegitimization. That is particularly threatening for the ECtHR due to its vulnerability to legitimacy challenges manifested in the past decade. As a result, the populist challenge will likely require careful management of the ECtHR’s social legitimacy.

Modeling Covid-19 Pandemic Responses in Malaysia for the First 145 Days Duration (Jan. 25 – June 17, 2020)

Background At 145 days from Jan. 25, the Covid-19 recovery rate was 92.5% of the total cumulative cases of 8,515 with 1.4% fatalities were recorded in Malaysia. On top of the provided medical services and facilities, the recoveries could be mainly resulted from the Movement Control Order (MCO) enforcements in six phases for mitigating the pandemic nationwide. To understand the Covid-19 pandemic trend and dynamic mathematically to the MCO phases, the applicability of the proposed models ( tri-logistic growth model) on covid-19 related responses was studied by using the ‘matured’ 145-day data duration. The study also aimed at, (1) identifying information/parameters obtained through modeling technique that could be used in explaining the pattern of dynamic subjected to MCO enforcements, and (2) forecasting the quantitative information for postdate days beyond the used data duration. Methods Each serial layered-logistic growth of cumulative cases, recoveries, fatalities, and active cases were linked among them via the asymptotic cumulative cases and the nature of the recovery-fatality complementarity. The used data of Jan. 25 – Jun. 17, 2020 were quite ‘matured’ trend as observed in the ‘plateauing’ of cumulative cases. The appropriate R2 was used for model fitness analysis. The innovative SAS program writing of SAS9.4 version was used for the analysis. Conclusion Predicted cumulative cases, recoveries, fatalities, and active cases vs. days were significantly fitted to the observed values (R2 > 99 %), indicating the validity of the tri-logistic growth proposed model. Via the derivative of cumulative cases function, the daily cases or dynamic model was significant (R2=70%) with the fluctuating daily cases moved around the predicted curve. The authority has been classified the pandemic as of two waves (Jan. 25 – Feb. 26, 2020, and Feb. 27, 2020 onwards), and these were regrouped as wave 1 (primary wave) in this study. Within this one wave, the study shows that covid-19 in Malaysia has three cycles: cycle 1(1o cycle) [Jan. 25 – Apr.27], cycle 2 [Apr. 28 – May 14] and cycle 3 [May 15 and onwards] with the aggressiveness order of wave 1 > wave 3 > wave 2 (wave 3 had mainly caused by local foreigners). The observed cumulative cases were slightly higher than the predicted (by 0.07% -0.49%) during Jun 13 – 17 suggesting small room of resources still available for covid-19 infection, thus, maintaining the current MCO is crucial. Beyond Jun.17, the forecasts of cumulative cases, recoveries, fatalities, and active cases at June 30 would be 8500, 8168, 128, and 202 cases, respectively, with daily cases of 1 case day-1 . If no any further odd-extraordinary wave occurrence, the country would probably be enjoying a non-significant covid or ‘covid-free’ pandemic by the July end or mid-August, 2020. The model had validated the correctness and appropriateness of the MCO phases’ enforcements. The active cases model was the resultant of linkages of all models via asymptotic cumulative cases. Based on above resultant and the logistic growth function applicability in various fields, the modeling approach involving serial tri-logistic functions could probably be used in analyzing covid or covid-related epidemic elsewhere and in the future.