Perfect Reflection Research Articles

All-Angle Scanning Perfect Anomalous Reflection by Using Passive Aperiodic Gratings

All-Angle Scanning Perfect Anomalous Reflection by Using Passive Aperiodic Gratings

ИСПОЛЬЗОВАНИЕ ИНФОРМАЦИОННЫХ РЕСУРСОВ СИСТЕМЫ ВНУТРЕННЕГО КОНТРОЛЯ ПРИ НАЛОГОВОМ МОНИТОРИНГЕ КОМПАНИИ

The main instrument for regulating the company’s activities is financial control. In the current market realities, companies are increasingly showing interest in internal control as the main means of regulation. Proper implementation of the internal monitoring system is the key to the effectiveness of companies. Its analysis is aimed at acquiring a set of tasks that help expand the company’s control features and increase the effectiveness of its further work. The key purpose of using the internal control system in this case is to ensure the most perfect and reliable reflection of information about activities in the financial statements. In this paper, the basic concepts of the internal control and monitoring system of this system are studied. However, the emphasis is on a more detailed coverage of the concept of tax monitoring and consideration of the aspect of methodological recommendations for collecting evidence in tax monitoring.

Extremely Thin Perfect Absorber by Generalized Multipole Bianisotropic Effect

AbstractSymmetry breaking plays a crucial role in understanding the fundamental physics underlying numerous physical phenomena, including the electromagnetic response in resonators, giving rise to intriguing effects such as directional light scattering, supercavity lasing, and topologically protected states. This work demonstrates that adding a small fraction of lossy metal (as low as 1 × 10−6 in volume) to a lossless dielectric resonator breaks inversion symmetry (IS), thereby lifting its degeneracy, leading to a strong bianisotropic response. In the case of the metasurface composed of such resonators, this effect leads to unidirectional perfect absorption while maintaining nearly perfect reflection from the opposite direction. It has developed more general Onsager‐Casimir relations for the polarizabilities of particle arrays, taking into account the contributions of quadrupoles, which shows that bianisotropy is not solely due to dipoles, but also involves high‐order multipoles. The experimental validation demonstrates an extremely thin terahertz‐perfect absorber with a wavelength‐to‐thickness ratio of up to 25,000, where the material thickness is only 2% of the theoretical minimum thickness dictated by the fundamental limit. The findings can pave a new route to design devices for applications involving optical‐to‐heat conversion processes.

Efficient waste heat recovery from molten carbonate fuel cells through graphene-collector thermionic generators

The waste heat released by molten carbonate fuel cells (MCFCs) contains considerable energy that can be captured for electric power generation. Nonetheless, the current high-grade heat harvesting devices for the MCFC cogeneration of electrical power are still constrained by low power output or energy conversion. To address this challenge, we present a novel hybrid system that combines an MCFC and a graphene-collector thermionic generator (GCTG), in which the GCTG can efficiently harness the exhaust heat released from the MCFC and generate additional electricity. The results show that the hybrid system’s maximum power density reaches 0.298 W/cm2, which is 1.6 times that of the sole MCFC at 923 K, demonstrating that the hybrid system delivers a significant boost in output performance. Furthermore, finite-time thermodynamics estimates the hybrid system’s optimal operating regions and key parameter designs. The optimal performance of the hybrid system can be further improved by selecting the optimal area ratio, raising the MCFC operating temperature, strengthening the heat transfer coefficient, lowering the thermal emissivity of the thermionic emitter, and manufacturing the perfect optical reflector. The MCFC-GCTG outperforms other MCFC-based hybrid systems regarding output performance, demonstrating that GCTG can more effectively exploit the waste heat released from MCFCs than other heat recovery devices. This study offers valuable theoretical guidance for the strategic optimization of the MCFC-GCTG hybrid system, thereby paving a constructive strategy towards realizing advanced, high-performance MCFC cogeneration systems.

Perfect Absorption and Reflection Modulation Based on Asymmetric Slot-Assisted Gratings without Mirrors.

As a perfect graphene absorber without any external mirrors, we proposed asymmetric slot-assisted grating structures supporting two degenerate resonant modes of the guided-mode resonances (GMR) and the quasi-bound states in the continuum (quasi-BIC). The GMR mode functions as an internal mirror in conjunction with the background scattering, while the quasi-BIC, which is responsible for perfect graphene absorption, stems from the horizontal symmetry breaking by an asymmetric slot. By properly shifting the slot center from the grating center, the leakage rate of quasi-BIC can be controlled in such a way as to satisfy the critical coupling condition. We provide a comprehensive study on the coupling mechanism of two degenerate resonant modes for a one-port system mimicking the resonance. We also numerically demonstrated that our proposed grating structures show an excellent reflection-type modulation performance at optical wavelength ranges when doped double-layer graphene is applied. Due to the perfect absorption at the OFF state, a high modulation depth of ~50 dB can be achieved via a small Fermi level variation of ~0.05 eV. To obtain the lower insertion loss at the ON state, the higher Fermi level is required to decrease the graphene absorption coefficient.

Electromagnetic characterization of a metasurface composed of thin circular dielectric disk under normal incidence

Electromagnetic characterization of a metasurface composed of circular dielectric disks under normal incidence is presented. A dielectric disk is assumed to be infinitesimally thin with moderate values of the relative permittivity so that it can be modeled as an electric dipole. Thus, for the considered infinitesimally thin metasurface, normal electric surface polarization current is negligible. An analytic expression of electric polarizability of a thin circular dielectric disk has been derived for completeness. For most of the presented results, it is assumed that dielectric disk is made of realistic materials. Some interesting applications of realistic metasurfaces as a transparent sheet and a perfect reflector have also been discussed.

Subverting the Civilising Mission in Conrad’s Heart of Darkness

Conrad's Heart of Darkness (1899) is often presented as one of the harshest indictments of the colonial entreprise in Africa. Yet, a large number of critics consider that it perpetuates the colonial discourse in several ways. The aim of this paper is to critically look at the colonial discourse in Conrad’s novella from a postcolonial and Marxist standpoint. To be specific, we demonstrate the limitations and contradictions of the theory of the civilising mission, which portrays Africa as the “heart of darkness” and Africans as uncivilised individuals who need to be enlightened by Europeans. The analysis concludes that, above their moral corruption, the colonists, through the atrocity of their actions and their greed, are a perfect reflection of a Western civilisation corrupted by the capitalist spirit that underpins it. In this sense, they are proof that the theory of the civilising mission is a fallacy. The real savages are those who think that they bear the light of civilisation. Black people are savages only in the Western imagination. In reality, they are the victims of the savagery, the darkness inherent in Western materialistic culture.

Omnidirectional broadband phase modulation by total internal reflection.

Phase modulation plays a crucial role in shaping optical fields and physical optics. However, traditional phase modulation techniques are highly dependent on angles and wavelengths, limiting their applicability in smart optical systems. Here, we propose a first-principle theory for achieving constant phase modulation independent of incident angle and wavelength. By utilizing a hyperbolic metamaterial and engineering-specific optical parameters, different reflective phase jumps are achieved and tailored for both transverse electric (TE) and transverse magnetic (TM) waves. The aimed reflection phase difference between TE and TM waves can be thus achieved omnidirectionally and achromatically. As an example, we propose a perfect omnidirectional broadband reflection quarter wave plate. This work provides fundamental insights into manipulating optical phases through optical parameter engineering.

Honing in on a topological zero-bias conductance peak

A popular signature of Majorana bound states in topological superconductors is the quantized zero-energy conductance peak. However, a similar zero energy conductance peak can also arise due to non-topological reasons. Here we show that these trivial and topological zero energy conductance peaks can be distinguished via the zero energy local density of states (LDOSs) and local magnetization density of states (LMDOSs). We find that the zero-energy LDOSs and the LMDOSs exhibit periodic oscillations for a trivial zero-bias conductance peak (ZBCP). In contrast, these oscillations disappear for the topological ZBCP because of perfect Andreev reflection at zero energy in topological superconductor junctions. Our results suggest that the zero-energy LDOSs and the LMDOSs can be used as an experimental probe to distinguish a trivial zero-energy conductance peak from a topological zero-energy conductance peak.

Optimization of the Geometrical Design for an All-Dielectric Metasurface Sensor with a High Refractive-Index Response

This study aims to develop a refractive-index sensor operating in the visible region using an all-dielectric metasurface, which was chosen for its advantages of low optical loss and narrow spectral bandwidth, compared to those of conventional metallic metasurfaces. COMSOL software was utilized as a calculation tool to simulate the resonant properties of an all-dielectric metasurface composed of a circular nanohole-structured titanium oxide (TiO2) thin film, with the aim of enhancing the sensitivity of the refractive index for sensing targets. The simulation focused on finding the best geometrical conditions for the all-dielectric metasurface to achieve high sensitivity. Two resonance modes observed in this metasurface were considered: the quasi-bound-state-in-the-continuum (qBIC) mode and the perfect-reflection (PR) mode. The simulated results demonstrated that high sensitivities of 257 nm/RIU at the PR mode and 94 nm/RIU at the qBIC mode in the visible spectral range could be obtained by periodically constructing the metasurface with a unit cell having a lattice constant of 350 nm, a nanohole radius of 160 nm, and a nanohole depth of 250 nm. Furthermore, the study showed that the resonance mode that enabled high sensitivity was the PR mode, with a sensitivity nearly three times larger than that of the qBIC mode and the ability to reach the highest reflectance at the resonance wavelength. The optimized feature had the highest reflectance at a resonant wavelength of 570.19 nm, and although the quality factor was 25.50, these designed parameters were considered sufficient for developing a refractive index biosensor with high sensitivity and optical efficiency when operating in the visible spectral range.

Clutter Effect Investigation on Co-Polarized Chipless RFID Tags and Mitigation Using Cross-Polarized Tags, Analytical Model, Simulation, and Measurement.

Chipless radio frequency identification (RFID) technology is expected to replace barcode technology due to its ability to read in non-line-of-sight (NLOS) situations, long reading range, and low cost. Currently, there is extensive research being conducted on frequency-coded (FC) co-polarized radar cross-section (RCS)-based tags, which are widely used. However, detecting co-polarized chipless RFID tags in cluttered environments is still a challenge, as confirmed by measuring two co-polarized tags in front of a perfect metal reflector (30.5cm×22.5cm). To address this challenge, a realistic mathematical model for a chipless RFID system has been developed that takes into account the characteristics of the reader and the tag, as well as reflections from cluttered objects. This extensive mathematical model developed for linear chipless RFID systems in clutter scenarios holds the potential to greatly assist researchers in their exploration of RCS-based tags. By relying solely on simulations, this model provides a tool to effectively analyze and understand RCS-based tags, ultimately simplifying the process of generating more authentic tag designs. This model has been simulated and verified with measurement results by placing a single flat metal reflector behind two co-polarized one-bit designs: a dipole array tag and a square patch tag. The results showed that the interfering signal completely overlaps the ID of the co-polarized tag, severely limiting its detectability. To solve this issue, the proposed solution involves reading the tag in cross-polarization mode by etching a diagonal slot in the square patch tag. This proposed tag provides high immunity to the environment and can be detected in front of both dielectric and metallic objects.

Ultrasound multifrequency strategy to estimate the lung surface roughness, in silico and in vitro results

Lung ultrasound (LUS) is an important imaging modality to assess the state of the lung surface. Nevertheless, LUS is limited to the visual evaluation of imaging artifacts, especially the vertical ones. These artifacts are observed in pathologies characterized by a reduction of dimensions of air-spaces (alveoli). In contrast, there exist pathologies, such as chronic obstructive pulmonary disease (COPD), in which an enlargement of air-spaces can occur, which causes the lung surface to behave essentially as a perfect reflector, thus not allowing ultrasound penetration. This characteristic high reflectivity could be exploited to characterize the lung surface. Specifically, air-spaces of different sizes could cause the lung surface to have a different roughness, whose estimation could provide a way to assess the state of the lung surface. In this study, we present a quantitative multifrequency approach aiming at estimating the lung surface’s roughness by measuring image intensity variations along the lung surface as a function of frequency. This approach was tested both in silico and in vitro, and it showed promising results. For the in vitro experiments, radiofrequency (RF) data were acquired from a novel experimental model. The results showed consistency between in silico and in vitro experiments.

A functionality switchable meta-device: from perfect reflection to perfect absorption

Tunable meta-devices trigger immense interest in many applications like biosensing, thermal camouflage, radiative cooling, thermal emitting, infrared imaging, and energy harvesting. This paper presents a polarization-independent broadband tunable absorbing and reflecting meta-device using a phase change material Germanium-Antimony-Tellurium (GST). The proposed design manifests high absorptivity >80% over a broadband range of wavelength spanning the mid-IR regime. Furthermore, by changing the phase of GST material from crystalline to amorphous with the help of external stimuli, the absorbance of the device was reduced to almost zero in the range from 4 μm to 12 μm. To previse the angular constancy of the meta-absorber, the absorptivity was scrutinized under different incidence angles in both transverse magnetic (TM) and transverse electric (TE) polarizations which manifested the robustness of the proposed meta-absorber. As a result, the proposed absorber has tunable broadband absorbance and angular stability, which proclaim great potential in applications such as thermal camouflage, radiation detection, thermal emitter, and stealth technology, etc.

Wide-Passband Reconfigurable Frequency Selective Rasorber Design Based on Fluidity of EGaIn

In this letter, we propose a wide-passband reconfigurable frequency selective rasorber (FSR) design based on the fluidity of liquid metal. To achieve wide-passband reconfigurability, a new type of reconfigurable frequency selective surface with wide-passband elliptic filter response is introduced for the first time, whose bandpass state can be switched to a perfect reflection state by controlling the injection and the extraction of liquid metal in microchannels. Furthermore, a new resistive film loop with a minimum insertion loss of 0.23 dB is presented by loading four circular spiral resonators. Finally, the FSR can realize the reconstruction of the absorption-transmission-absorption (ATA) and absorption-reflection-absorption (ARA) modes. The simulation results show that in ATA mode, the design exhibits a wide passband with a fractional 3 dB bandwidth reaching up to 42.8%, and a passband minimum insertion loss of 0.86 dB at 13 GHz. In ARA mode, the bandwidth for return loss less than 3 dB is 12.8%. Prototypes were fabricated and measured. Compared with previous FSRs, our proposed FSR has advantages such as reconfigurable characteristics, a wide transmission band, and high-frequency selectivity.

Nonlinear optical switch based on coherent perfect absorption.

Coherent perfect absorption (CPA) or reflection (CPR) are methods to realize the extreme manipulation on an optical field. We propose a scheme to operate a bistable switch with convertible CPA and/or CPR. Generally, CPA and CPR occur with different input-field phases. For example, CPA is realized when two input probe beams are in phase; instead, CPR is achieved when they are out of phase. In this scheme, a CPA state can be converted to a CPR state by an incoherent field although two input fields are in phase. When we use the incoherent field as a switching field, the CPA (CPR) state is treated as the closed (open) state. As a result, the switching efficiency can theoretically reach a maximum value, i.e., η = 1. In addition, the switch can be operated in the linear regime with a weak input field, and in the nonlinear or bistable regime with a strong input field. Moreover, the efficiency of the bistable switch is sensitively dependent on the input-field intensity. It provides a potential application of this work on sensitive optical detecting.

Efficient asymmetrical transmission through a metagrating for underwater acoustic waves

Acoustic asymmetrical transmission is a theoretical and engineering challenge because of the reciprocity of the linear acoustic wave equation. It can be achieved by systems breaking reciprocity or by reciprocal systems relying solely on spatial symmetry breaking. Metagratings are planar structures relying on Bragg's diffraction to reroute wave energy toward a desired direction and are eventually able to achieve asymmetrical transmission when build from an asymmetrical pattern of multiple basic elements. The challenge for water-like media is to combine the geometrical complexity of the structure with good acoustic impedance contrast and practical feasibility. In this work, we build a reciprocal metagrating from brass cylinders arranged according to a numerically optimized pattern and obtain highly efficient asymmetrical transmission for underwater acoustic waves. Around 200 kHz, the structure transmits nearly all incident energy toward a 45° angle when insonified from one side, but act as a near perfect reflector when insonified from the other. The effect relies entirely on the simple phenomena of linear wave diffraction and interference. The generality and efficiency of this device could be of interest for applications in underwater acoustics or medical ultrasounds.

Graphene-Based Refractive Index Sensor With a 1-D Topological Photonic System

A terahertz refractive index sensor, which relies on utilizing the Tamm plasmon polariton and localized topological edge state, is proposed in a one-dimensional photonic crystal based on graphene. The proposed sensor structure is an active photonic device due to graphene’s tunable Fermi energy and optical properties. High sensitivity and a high figure of merit (FOM) are the results of the topological protection that allows a perfect zero reflection. Furthermore, the study investigates the sensing performance with various structural and material parameters. This refractive index sensor has the potential to be modified for use in industrial and diagnostic applications.

Unidirectional Perfect Reflection and Radiation in Double-Lattice Photonic Crystals

Unidirectional Perfect Reflection and Radiation in Double-Lattice Photonic Crystals

Efficient Anomalous Reflector Design Using Array Antenna Scattering Synthesis

A perfect anomalous reflector is designed by employing the receiving and scattering array antenna theory to optimize the scattering characteristics of a planar reflecting surface. For periodic reflectors with a supercell consisting of a relatively few reactively loaded radiating elements, reflection amplitudes into propagating Floquet modes are controlled in an algebraic optimization of the load reactances, avoiding brute-force optimization via electromagnetic simulations. Wide-angle reflectors are numerically designed and compared with the conventional reflectarray designs, showing that the proposed design approach achieves reflection efficiencies higher than the linear reflection phase gradient method in a computationally efficient manner.

Thermodynamic analysis and parameter optimization of a hybrid system based on SOFC and graphene-collector thermionic energy converter

The exhaust heat released from SOFCs (solid oxide fuel cells) possesses tremendous energy that can be recovered for energy cascade utilization. Nevertheless, low conversion efficiency or power density limits the SOFC’s high-grade waste heat recovery capabilities for the cogeneration of electric power. To address this challenge, a novel hybrid system coupling a SOFC with a GTEC (graphene-collector thermionic energy converter) is proposed, where the GTEC harvests the high-grade exhaust heat produced by the SOFC and generates extra electricity. It is found that the maximum power density of the hybrid system can reach 0.774 W/cm2 at 1073 K, which is 1.20 times higher than that of the sole SOFC, indicating that the hybrid system offers a considerable improvement in output performance. Additionally, the optimal operating conditions and major parameter designs of the hybrid system are determined from the perspective of finite-time thermodynamics. Choosing the optimal area ratio, increasing the SOFC operating temperature, enhancing the heat transfer coefficient, decreasing the thermal emissivity, and fabricating the perfect optical reflector can further improve the optimal performance of the hybrid system. Compared with other SOFC-based hybrid systems, the SOFC-GTEC provides better output performance, proving that the GTEC can more efficiently utilize the exhaust heat produced by SOFC than other energy harvesting devices. This work provides crucial theoretical guidance on the optimal designs and parametric analysis of SOFC-GTEC hybrid systems, thus paving the way towards developing high-performance SOFC cogeneration systems.