Absorption Principle Research Articles

Dual-band all-optical logic gate based on coherent control principles

In this paper, we present a dual-band all-optical logic gate based on a coherent perfect absorption metasurface. By utilizing the principle of coherent perfect absorption, we can manipulate the interference between two input signals by adjusting their relative phase difference. This allows us to implement logic functions such as AND, OR, and XOR in the second (1310 nm) and third (1550 nm) windows of the communication band. Moreover, we present the concept of "contrast" as a quantitative metric to assess the performance of each logic gate. The simulation results show that the contrast between the AND gate and the XOR gate can reach 6.4 dB and 17.8 dB at 1310 nm, as well as 6.1 dB and 18.9 dB at 1550 nm, rendering it highly advantageous for practical applications. The realization of ultrafast operation and low power consumption in coherent perfect absorption metasurfaces would significantly contribute to advancing the progress of optical data processing.

Layered heterogeneous structures integrated device for multiplication, division arithmetic unit and multiple-physical sensing

A layered heterogeneous structure (LHS), consisting of silver, liquid crystal, and nonlinear dielectric layers, is proposed to realize functions of computing and sensing. By leveraging the optical Tamm state, the intrinsic absorption principle of liquid crystal, and nonlinear effects, the design of an integrated device capable of passive multiplication and division operations, along with high-performance multi-physical quantity sensing functionalities, is achieved. The given LHS exhibits Janus properties, with different physical functions manifested depending on the direction of electromagnetic wave (EW) propagation. During forward propagation of EWs, the LHS displays high and sharp absorptivity peaks at 774.8 and 1517.6 nm. The relationship between the two peaks approximates a frequency multiplication factor of 1.960, enabling signal multiplication. Furthermore, the two absorptivity peaks at different wavelengths facilitate the sensing of serum creatinine solution concentration and external pressure, with sensitivity (S), quality factors (Q), and figure of merit (FOM) of 266.76 μmol L−1/nm and 213.33 GPa/nm, as well as 248.76 and 348.22, 84.1 L (μmol)−1 and 49.06 GPa−1, respectively. During backward propagation of EWs, absorptivity peaks with distinct resolutions are observed at 1423 and 2809 nm, with a multiple relationship between them of 1.974, enabling frequency doubling for signal division. Additionally, the absorptivity curve facilitates temperature sensing over a wide range from 257 to 347 K. Owing to the unique temperature S of liquid crystal, different sensitivities and resolutions are observed at 257 to 297 K and 307 to 347 K, with S of 1.015 and 0.686 K/nm, and corresponding Q and FOM of 21.57 and 12.576, 0.076 K−1 and 0.003 04 K−1, respectively.

Exploring the Dynamics of Charge Transfer in Photocatalysis: Applications of Femtosecond Transient Absorption Spectroscopy.

Artificial photocatalytic energy conversion is a very interesting strategy to solve energy crises and environmental problems by directly collecting solar energy, but low photocatalytic conversion efficiency is a bottleneck that restricts the practical application of photocatalytic reactions. The key issue is that the photo-generated charge separation process spans a huge spatio-temporal scale from femtoseconds to seconds, and involves complex physical processes from microscopic atoms to macroscopic materials. Femtosecond transient absorption (fs-TA) spectroscopy is a powerful tool for studying electron transfer paths in photogenerated carrier dynamics of photocatalysts. By extracting the attenuation characteristics of the spectra, the quenching path and lifetimes of carriers can be simulated on femtosecond and picosecond time scales. This paper introduces the principle of transient absorption, typical dynamic processes and the application of femtosecond transient absorption spectroscopy in photocatalysis, and summarizes the bottlenecks faced by ultrafast spectroscopy in photocatalytic applications, as well as future research directions and solutions. This will provide inspiration for understanding the charge transfer mechanism of photocatalytic processes.

Mourre theory and spectral analysis of energy-momentum operators in relativistic quantum field theory

A central task of theoretical physics is to analyse spectral properties of quantum mechanical observables. In this endeavour, Mourre’s conjugate operator method emerged as an effective tool in the spectral theory of Schrödinger operators. This paper introduces a novel class of examples from relativistic quantum field theory that are amenable to Mourre’s method. By assuming Lorentz covariance and the spectrum condition, we derive a limiting absorption principle for the energy-momentum operators and provide new proofs of the absolute continuity of the energy-momentum spectra. Moreover, under the assumption of dilation covariance, we show that the spectrum of the relativistic mass operator is purely absolutely continuous in (0,∞)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$(0,\\infty )$$\\end{document}.

The doctrine of ancillary restrictions as a delimitation tool and an absorption principle: twin notions but not identical twins

Abstract Contrary to the general view, ‘ancillary restrictions’ designate two separate conceptions, which should be treated as separate doctrines. As a ‘delimitation tool’, ancillarity separates ‘naked’ and ‘ancillary’ restrictions based on ‘reasonable necessity’. As an ‘absorption principle’, ancillarity is a rule of thumb that screens out certain lawful agreements based on the idea that a lawful main transaction (or the legality of the main transaction) absorbs all objectively necessary (indispensable) restrictions.

A non-contact solid particle moisture sensor based on near-infrared spectroscopy technology

The detection of moisture content in solid particles has important applications in fields such as biological research, coal mine production, and medicine. This article develops a non-contact solid particle moisture sensor (NcSPMS). NcSPMS uses the multi-light source detection method based on the principle of diffuse reflection absorption to detect the moisture content of solid particles with different particle sizes, distributions and colors. Firstly, the stacked LED light source structure (SLED-LSS) was designed to achieve illumination of LED light source for measurement (M-LED) and the LED light source for reference (R-LED) at the same position and exit angle, eliminating the influence of irregular particle size and distribution on diffuse reflected light intensity. Secondly, the stacked LED array light source structure (SLEDA-LSS) was designed to improve the detection light intensity and enable NcSPMS to detect the moisture content of solid particles of different colors. Thirdly, modulated light technology is used for the transmission of moisture content information. Two modulation frequencies were set to modulate the measurement light source and reference light source, and different intensities of square wave currents were determined to drive the M-LED and R-LED to improve detection accuracy. Fourthly, the FFT-KF data processing method was designed to effectively extract the information of diffuse reflection measurement light intensity. Finally, the function expression of moisture content was obtained through cubic fitting, and the detection of moisture content by NcSPMS was achieved. In order to verify the effectiveness of NcSPMS, the NcSPMS control system was designed. The experimental results show that compared with SLED-LSS, SLEDA-LSS improves measurement accuracy; the different current pairs driving M-LED and R-LED affect the measurement accuracy of NcSPMS; NcSPMS can detect the moisture content of white, yellow, green, red, and black sand particles, with the detection range of 0.10–11.00 %. The relative uncertainty obtained by applying NcSPMS to the detection of nickel ore particles is 4.37 %.

Limiting absorption principle and radiation conditions for Schrödinger operators with long-range potentials

We show Rellich's theorem, the limiting absorption principle, and a Sommerfeld uniqueness result for a wide class of one-body Schrödinger operators with long-range potentials, extending and refining previously known results. Our general method is based on elementary commutator estimates, largely following the scheme developed recently by Ito and Skibsted.

Analysis of influence of deep processing of metallic mineral materials on electromagnetic wave absorption performance

In this paper, the effects of deep processing of metallic mineral materials on electromagnetic wave absorption properties were studied. Firstly, the background and significance of the research are introduced, and the importance of metallic mineral materials in the field of electromagnetic wave absorption is expounded. Then the basic principle of electromagnetic wave absorption and the characteristics and influencing factors of metal mineral materials are discussed. In the section of deep processing technology, different processing methods and their applications are listed. Through experimental design and method, the electromagnetic wave absorption properties of metal mineral materials after deep processing are tested and analyzed. The experimental results are obtained and discussed. Finally, the application prospect of metallic mineral materials in electromagnetic wave absorption field is prospected, and the technical improvement and future development direction are put forward. This study provides an important reference for deepening the understanding of electromagnetic wave absorption properties of metallic mineral materials, and provides a reference for further research in related fields.

Direct Absorption Solar Collector: An Experimental Investigation of Al2O3-H2O Nanofluid over the Flat Plate at Different Tilt Angles, and Mass-Flow Rates

The escalating demand for solar thermal energy, coupled with the current inefficiencies in existing systems, underscores the critical need for innovative advancements in thermal storage solar collectors. The efficiency of solar collectors relies not solely on design effectiveness but also on the thermophysical properties, such as heat capacity and thermal conductivity, inherent in the working fluid. This study investigates a novel solar collector with a gross area of 0.36 m2, operating on the principle of direct absorption. Experimental investigations were done at various tilt angles (15°, 20°, and 30°) with respect to the horizontal, considering different flow rates and nanofluid settlement within the base fluids. The use of Al2O3 nanoparticles into the base fluid as water, exhibits significant positive effects on the thermophysical properties of the nanofluids, with a volume concentration of 0.003%. The efficiency of the solar collector was calculated across three mass flow rates (0.5, 1, and 1.33 L/min) at each tilt angle. Notably, the study reveals that the efficiency peaks at a 15° tilt due to an optimal flow configuration for maximum energy harvest across all three mass flow rates. Increasing the mass flow rate yields efficiency increments for all tilt angles (15°, 20°, and 30°), with 1 L/min emerging as the optimal mass-flow rate in most cases. This research not only addresses the immediate need for improved solar thermal technologies but also aligns with global sustainability goals, contributing to the IEA Net Zero Emissions initiative and supporting UN Sustainable Development Goals 7, 9, and 11. The paper also includes a critical literature review on the use of nanofluids in solar thermal collectors to improve thermo-physical properties and enhance solar efficiency. Additionally, the key findings regarding the influence and tilt angle on solar efficiency are discussed.

On spectral and scattering theory for one-body quantum systems in crossed constant electric and magnetic fields

In this paper, we study the spectral and scattering theory on the Hamiltonians which govern one-body quantum systems in crossed constant electric and magnetic fields. As one of the spectral features of the Hamiltonians, we show the absence of bound states of theirs under some appropriate conditions on the potentials. Moreover, by using the limiting absorption principle for the Hamiltonians, we give a simplified proof of the asymptotic completeness in short-range scattering.

Signal Processing from the Radiation Detector of the Radiometric Density Meter Using the Low-Pass Infinite Impulse Response Filter in the Measurement Path in the Coal Enrichment Process Control System

One of the most common coal preparations is enrichment in a jig using a float regulation system. The latest solutions propose to compensate for significant measurement errors of the float by introducing a radiometric density meter operating on the principle of gamma radiation absorption into the bottom product discharge zone of the jig. The signal from the radiometric density meter detector is in the form of a sequence of pulses with a Poisson time distribution, which are counted by a counter, as a form of digital low-pass filter. The requirement to maintain accuracy at an appropriate level forces the measurement time to be extended, which worsens the dynamic properties. Changes in the density of the coal–water medium have an unsteady, cyclical course, resulting from the principle of operation of the jig. The research goal was to develop an algorithm for processing the signal from the radiation detector using an IIR filter in the measurement path in a way that ensures optimization of the dynamic properties of the radiometric density meter operating in the control system of the coal enrichment process in the jig. For this purpose, a low-pass IIR filter was introduced into the measurement path to process the signal from the pulse counter. The identified course of the medium density for one cycle (the first) served as a reference signal. A first-order IIR filter was proposed, with a constant parameter selected on the basis of the reference signal and a parameter depending on the time derivative of the identified density of the medium. The mean squared error MSE was adopted as an indicator for assessing the dynamic properties of the radiometric density meter. The results of simulation tests showed that introducing an IIR filter into the measurement path gives better results in terms of the adopted criterion than using a counter with a constant measurement time. The best results (MSE = 2.05 × 10−4) were obtained using an IIR filter with a parameter that is a linear function of the derivative of the medium density over time, determined for one air pulsation cycle and applied in four subsequent cycles. These results were obtained for an adaptive first-order filter with a variable parameter a from the designated range from 0.833 to 0.999, for a measurement time of 2 ms.

INVESTIGATION OF THE SOLUTION OF THE SOLUTION OF THE MIXED PROBLEM FOR THE WAVE EQUATION INCLUDING THE TIME DERIVATIVE BOUNDARY CONDITION IN A MULTIDIMENSIONAL STRIP WHEN t →+∞

Abstract. In mechanics and physics, the propagation of waves over long distances leads to boundary problems for the wave equation in a strip. An example of this is the propagation of sound in the sea and radio waves in the atmosphere. The principle of limit absorption for these problems in a two-dimensional band is studied in the monograph of L. M. Brekhovskikh.

DYNAMIC CONTACT PROBLEMS FOR COMPOSITE MEDIA WITH ANISOTROPIC STRUCTURE

The paper for the first time develops a method for solving dynamic contact problems on the effect of a rigid die in the form of a strip of finite width on a layered anisotropic composite. By applying Mandelstam's principle of marginal absorption, the initial boundary value problem is reduced to a boundary value problem with absorption having a single solution. The symbol of the integral equation has no singularities on the real axis. The contact problem is reduced to solving a two-dimensional integral equation with a difference kernel. The application of the Fourier transform along the coordinate along the strip reduces the integral equation to a one-dimensional one containing a free real parameter of the Fourier transform. Integral equations with an exact solution are introduced, with symbols majoring above and below the symbol of the integral equation. Using the factorization method, the initial integral equation is reduced to two integral equations of the second type, the operator of which turns out to be compressive with a sufficiently large bandwidth. By applying the Newton–Kantorovich method to this integral equation, an exact solution of the integral equation is constructed in an operator form. The presence of the majorant symbol of the integral equation allows us to obtain an upper and lower estimate of the constructed exact solution of the integral equation containing the parameter of the Maldenstam limit absorption principle. After that, in the constructed solution, this parameter rushes to zero from above. The solution of the integral equation is obtained in an analytical form and allows us to identify all its singular features. The result is important when searching for harbingers of an increase in seismicity in mountainous areas. The method is applicable in all cases when it is possible to construct a Green function for a non-mixed boundary value problem in a layered anisotropic composite.

Temperature-tunable terahertz metamaterial device based on VO2 phase transition principle.

Terahertz devices play an irreplaceable role in the development of terahertz technology. However, at present, it is difficult for most natural materials to respond in the terahertz band, making the devices made of them perform poorly. In order to realize the diversity and tunability of device functions, we designed a terahertz metamaterial device composed of the thermally-induced phase change material VO2. The device structure is composed of a Au bottom layer, a SiO2 dielectric layer and a VO2 top layer. Through software simulation, we found that when T = 313 K, the device has complete reflection ability in the whole terahertz band. When T = 342 K, the average absorptivity is above 95% in the ultra-wide band range of 4.71-9.41 THz, and the absorptivity reaches an amazing 0.99999 at 6.31 THz. Thus, the maximum thermal modulation range of the device is 0.001-0.99999. The Bruggeman effective medium theory clarifies the phase transition characteristics of vanadium dioxide. The Drude model establishes the functional relationship between the conductivity of vanadium dioxide and temperature. The basic principle of high absorption was described using the impedance matching theory. We also drew the electric field intensity diagram during the temperature rise of the device to further confirm the reason for the change in the device performance. In addition, the influence of the absence of different structural layers on the absorptivity was simulated, which reflected the role of each layer structure more intuitively. We also explored the influence of the geometric size of the device on the absorptivity, which provided a certain reference value for practical application. In short, we have designed a tunable terahertz device with simple structure, high absorptivity, and wide absorption bandwidth, which can be used in the fields of energy collection, electromagnetic stealth, and modulation.

Research Progress of Ceramic-based Absorbing Composite Materials

Absorbing materials can convert electromagnetic energy into other forms of energy. In recent years, ceramic-based absorbing composite materials have received widespread attention from researchers in many fields, such as mobile communications and military technology due to their excellent performance in corrosion resistance and stability, and have extremely broad application prospects. This article first briefly describes the structure and absorption principle of ceramic matrix composite absorbing materials. Then the research progress of ceramic-based absorbing materials in recent years was reviewed, including the preparation processes and advantages and disadvantages of various ceramic substrates. Finally, we review the practical application scenarios of this material and discuss future research directions and urgent problems to be solved.

PLANE PROBLEMS ABOUT THE ACTION OF OSCILLATING LOAD ON THE BOUNDARY OF AN ELASTIC ISOTROPIC LAYER IN THE PRESENCE OF SURFACE STRESSES

In this paper, symmetric and antisymmetric plane problems about the action of oscillating load on the boundary of an elastic isotropic nanothin layer are considered. The nanoscale layer thickness is considered by introducing surface stresses in accordance with the Gurtin-Murdoch theory. According to this theory, it is assumed that, in addition to external loads, surface stresses act on the layer boundaries, which are described by Hooke's “surface” law. As a result, the properties of the elastic material of the layer with nanoscale thickness become different from the properties of the material of a regular-sized body, which is typical for nanomechanics problems. A standard technique was used for the solution of formulated problems, including the application of limiting absorption principle, the Fourier transform over infinitely extended coordinate and the theory of residues for finding the inverse Fourier transform. It is shown how it is possible to obtain solutions in the form of series in natural waves, in which the wave numbers are defined as the roots of the corresponding dispersion equations. For a specific example, dispersion relations were studied and graphs of the first dispersion curves were plotted. The behavior of barrier frequencies, changes in wave numbers and zones of existence of backward waves at different nanoscale layer thicknesses are analyzed. The results of the analysis showed that for an ultrathin layer, surface effects have a significant impact on the dispersion relations, and the trends in the dispersion curves can differ significantly for different modes and layer thicknesses.

Multi‐Field Coupled Motion Induces Electromagnetic Wave Absorbing Property Regeneration of Elastomer in Marine Environment

AbstractThe mechanical‐electromagnetic dual healing system equips warships with the same reproducibility as biological skin, enabling rapid restoration of electromagnetic stealth and overcoming disturbances in the marine environment. However, the principle of electromagnetic wave absorption (EWA) property regeneration and co‐healing model are still largely unknown. Herein, a bio‐inspired intelligent elastomer is created that combines 2D EWA mediums with an underwater self‐healing fluoropolymer framework, realizing multifunctional integration. It demonstrates excellent broadband EWA characteristics (8.68 GHz, 2.16 mm) and promising underwater self‐healing (23.73%, 3 h). Notably, the dynamic interweaving motion between chemical and physical fields (i.e., dielectric and magnetic fields) facilitates positive chain effects of mechanical healing on electromagnetic function. Consequently, this interdependence drives efficient EWA property regeneration (94.1%, 3 h), including but not limited to underwater and air. Furthermore, the system boasts excellent hydrophobicity and chemical stability for seawater and strong alkali. Overall, this work is the first to present an effective strategy for quickly restoring electromagnetic stealth in marine environments, which expands the feasibility boundary of the interdisciplinarity.

A limiting absorption principle for high-order Schrödinger operators in critical spaces

A limiting absorption principle for high-order Schrödinger operators in critical spaces

Doğada Bulunan Darbe Sönümleme Sisteminin Yapısal Analoji Yoluyla Geri Tepme Mekanizmasına Entegre Edilmesi

Bu çalışmada ateşli silahlarda gerçekleşen geri tepmenin kullanıcı tarafından deneyimlenen etkisini azaltabilecek nitelikte biyomimetik tabanlı bir çözüm önerisi geliştirilmiştir. Bu bağlamda, ağaçkakanların kafa yapısında bulunan darbe sönümleme sisteminin ana bileşenleri yapısal analoji yöntemi ile Remington 870 model ateşli silahın kabza tasarımında kullanılmıştır. Halihazırda kullanılan orijinal kabza modeli ile biyomimetik yaklaşım kullanılarak tasarlanan modeller karşılaştırılıp, eksenel ve toplam deformasyon, reaksiyon kuvveti ve gerilme değerleri birlikte değerlendirilmiş ve silahlarda geri tepmenin en aza indirilebilmesi için kabza tasarımı ile ilgili bazı öneriler getirilmiştir.

Scattering theory with both regular and singular perturbations

We provide an asymptotic completeness criterion and a representation formula for the scattering matrix of the scattering couple (A_{\mathsf B},A) , where both A and A_{\mathsf B} are self-adjoint operator and A_{\mathsf B} formally corresponds to adding to A two terms, one regular and the other singular. In particular, our abstract results apply to the couple (\Delta_{\mathsf B},\Delta) , where \Delta is the free self-adjoint Laplacian in L^{2}(\mathbb{R}^{3}) and \Delta_{\mathsf B} is a self-adjoint operator in a class of Laplacians with both a regular perturbation, given by a short-range potential, and a singular one describing boundary conditions (like Dirichlet, Neumann and semi-transparent \delta and \delta' ones) at the boundary of an open, bounded Lipschitz domain. The results hinge upon a limiting absorption principle for A_{\mathsf B} and a Kreĭn-like formula for the resolvent difference (-A_{\mathsf B}+z)^{-1}-(-A+z)^{-1} which puts on an equal footing the regular (here, in the case of the Laplacian, a Kato–Rellich potential suffices) and the singular perturbations.