Multiple Internal Reflections Research Articles

Research on Dry Chemical Detection TechnologyBased on Reflectance Photometry

In response to the issues of insufficient stability and accuracy in dry chemical detection using reflectance photometry, caused by the divergence and multiple internal reflections of the reflected light signal from the sample and the multilayer dry film test strip, a dry chemical reflectance photometry detection system based on an integrating sphere is designed. Firstly, an integrating sphere device is incorporated to reduce signal divergence and loss, ensuring even detection of the sample's reflected light signal and improving detection stability. Secondly, Light Tools optical simulation analysis is performed, and an integrating sphere detection model is established. Thirdly, the Williams-Clapper equation is employed to correct the error in reflectance density caused by multiple internal reflections, enhancing detection accuracy. Experimental validation demonstrates that the developed integrating sphere-based dry chemical reflectance photometry detection system improves the stability and accuracy of the detection system.

Design and development of speckle-free high-power laser-driven phosphor converted compact automotive headlamp module

The applicability of diode-lasers in automobile headlights is an advanced innovation for the automobile illumination industry due to the extraordinary properties of laser light over conventional light sources, such as high brightness, wide colour gamut, high directionality, low energy consumptions and long lifetime. Lasers are highly coherent in nature, so they encounter the problem of unwanted speckles and spurious fringes and always require a high level of opto-thermal engineering along with speckle reduction mechanisms for high lumen laser applications. Targeting such challenges, in this paper, we report an innovative design and development scheme for a high lumen laser-based automotive headlamp module. The headlamp prototype comprises a set of four cylindrical diffusers which distribute the high energy laser radiation via scattering along the length of the diffusers within a metallic mirro-based pyramidal cavity reflector. The scattered laser light from cylindrical diffusers interacts with a remote phosphor layer that prevents phosphor–resin burning. The pyramidal cavity reflector plays an important role in making the laser light uniform and speckle-free, via spatial and angular diversity, as light exits from the cavity after multiple internal reflections. This reflector redirects the highly concentrated white light over a long range without using any projection lens. The design and performance of the headlight system was studied using TracePro simulation software and tested experimentally in a photometric laboratory. The International Commission on Illumination (CIE) coordinates of the light generated by the headlamp was (0.3947, 0.4908) and the correlated colour temperature was 4240 K, which represents warm white light illumination.

Revealing the Loss Mechanism of Chemically-Induced Hot Electron Transport.

Hot electrons are crucial for unraveling the intrinsic relationship between chemical reactions and charge transfer in heterogeneous catalysis. Significant research focused on real-time detection of reaction-driven hot electron flow (chemicurrent) to elucidate the energy conversion mechanisms, but it remains elusive because carrier generation contributes to only part of the entire process. Here, a theoretical model for quantifying the chemicurrent yield is presented by clarifying the contributions of hot carrier losses from the internal emission and multiple reflections. The experimental chemicurrent yield verifies our model with a reliable mean free path of hot electrons, emphasizing the importance of comprehensive consideration of the transport process besides hot electron generation. Moreover, Pt nanoparticles (NPs)-decorated Au/TiO2 is examined, showing the role of NPs-induced carrier losses in the performance of catalytic nanodiodes. These findings are expected to contribute to understanding the hot electron detection efficiency and designing nanodiodes with enhanced hot carrier flow and catalytic activity.

Multilayered silver nanowires and graphene fluoride-based aramid nanofibers for excellent thermoconductive electromagnetic interference shielding materials with low-reflection

Multilayered films composed of alternating layers of graphene fluoride (GF) and silver nanowires (AgNWs) in an aramid nanofiber (ANF) matrix were fabricated. The films were prepared by sequential vacuum filtration of GF@ANF and AgNWs@ANF suspensions to obtain multilayered composite architectures. The multilayered GF@ANF/AgNWs@ANF films exhibited exceptional mechanical flexibility and strength, with tensile strength up to 130 MPa and 5000 bending cycles with negligible performance deterioration. The films displayed remarkably high electromagnetic interference (EMI) shielding effectiveness up to 54 dB in X-band frequencies, attributed to the multiple internal reflections in the multilayered structure. EMI shielding was dominated by absorption rather than reflection, enabling attenuation of incident microwaves without secondary pollution. The multilayered films also exhibited ultrahigh in-plane thermal conductivity of up to 45 W/mK, owing to the thermally conductive GF and AgNWs networks. The EMI shielding effectiveness and thermal conductivity were retained after temperature and bending cycling. The composite films also demonstrated excellent flame retardancy. This study provides an effective route toward concurrent enhancement of multi-functional properties through architectural engineering at the nanoscale. The combination of robust EMI shielding, mechanical flexibility, thermal management, and fire safety highlights the potential of rationally designed multilayered composites for practical applications in 5 G wearable electronics devices, communications systems, and radar technologies.

Experimental Investigations on the Ferromagnetic Resonance and Absorbing Properties of a Ferrofluid in the Microwave Range

Measurements of complex magnetic permeability, μ(f,H) = μ′(f,H) − iμ″(f,H) and dielectric permittivity ε(f,H) = ε′(f,H) − iε″(f,H), in the frequency range, f of (0.4–7) GHz, and polarizing field, H of (0–135) kA/m, were performed, for a kerosene-based ferrofluid with magnetite nanoparticles. Based on these measurements, the phenomenon of ferromagnetic resonance was highlighted and some microwave propagation parameters of the ferrofluid were determined: the attenuation constant, α(f,H), and the reflection coefficient, R(f,H), at the air-material interface, at the normal incidence. Knowing these parameters we proposed a theoretical model establishing for the first time an equation that allows the calculation of the overall reflection coefficient, Rw(f,H), at the normal incidence of the wave, for a ferrofluid of thickness d, deposited on a totally reflective support, following multiple internal reflections of the electromagnetic wave in the material. The results show that by increasing both, H, and d, the parameter, Rw(f,H) presents a minimum that decreases from 0.90 (for d = 2 mm) to 0.64 (for d = 10 mm), at frequency f = 5 GHz, which indicates an increase in the absorption of the electromagnetic wave by the ferrofluid. The obtained results are useful in the study of some materials that could be used as electromagnetic absorbers in the microwave range, by the determination of the overall reflection coefficient, Rw(f,H), controlled both by the thickness, d, of the absorber and by the external applied field, H.

Synthesis of core-shell NiO/BFO nanocomposites for microwave absorbing applications

Magnetic core-shell nanostructures are often employed in high-performance microwave-absorbing applications due to their strong concurrent magnetic-dielectric losses. However, microwave absorbers designed using a single core-shell nanostructure may not attain the desired bandwidth of absorption. Herein, we introduce core-shell nanocomposites of (100-x)NiO/(x)BiFeO3 (x = 0, 25, 50, 75, & 100), prepared by a facile two-step sol-gel wet-chemical method for high-efficiency absorbing applications. Measurements of microwave absorption performance show that the core-shell 50NiO/50BiFeO3 (x = 50) nanocomposite exhibits a remarkable reflection loss of up to −27.3 dB at a matching thickness of 1.9 mm, and the corresponding −10 dB reflection loss bandwidth extends to 6.8 GHz (in X- and Ku-bands). The study suggests that the fabricated core-shell nanocomposite has the potential to be a promising candidate for lightweight microwave absorbing applications. This is evidenced by its showcased improved efficiency, attributed to the synergistic effects of magnetic-dielectric losses, multiple internal reflections, superior impedance matching, and enhanced interfacial polarization at NiO/BiFeO3 interfaces.

Microwave-assisted ZnO-decorated carbon urchin resembling 'shish-kebab' morphology with self-healing and enhanced electromagnetic shielding properties.

Herein, inspired by Acacia auriculiformis fruit, the shish-kebab-like growth of ZnO on carbon urchin (ZnO@CU) was designed using microwave radiation, thus leading to a hierarchal 3D structure that can promote multiple internal reflections through polarization centers. This hierarchal structure was then dispersed in a designer polyetherimide (PEI) matrix containing dynamic covalent bonds that can undergo metathesis, triggered by temperature, to harness self-healing properties in the composite. Such key attributes are required for their potential use in EMI shielding applications where frequent repairs are indispensable. Morphological investigation revealed that the ZnO flower was periodically nucleated like 'shish-kebab' structures on CU surfaces. CU was designed from short carbon fibers using a facile modified method. The EMI shielding performance of the resulting composites was investigated in the X-band, illustrating a shielding effectiveness of -40.6 dB for 2 wt% of ZnO@CU loading, and the composite can be preserved after the self-healing procedure. The ZnO 'kebabs' on 'CU shish' facilitated multiple scattering and numerous polarization centers to improve the EMI shielding performances at extremely low filler contents. In addition, the mechanical and thermal properties of the composite showed improved structural integrity and superior resistance to extreme temperatures, respectively. Overall, the proposed ZnO@CU/PEI composite has great potential to fulfill the increasing demands for lightweight EMI shielding materials in many fields.

DLP–printable hyperbranched polyborosilazane for microwave absorbing SiBCN(O) ceramic metastructure

This work introduces a novel digital light processing (DLP) printable SiBCN(O) ceramic precursor (UV-hPBSZ), derived through a straightforward aminolysis approach. The unique hyperbranched molecular structure of UV-hPBSZ leads to remarkable UV curing efficiency, excellent printability, satisfied ceramic yield, and consistent shrinkage ratio. UV-hPBSZ also exhibits superior resistance against cracking and collapse during the polymer-to-ceramic process, thus enabling the fabrication of intricate SiBCN(O) ceramic structures. Upon pyrolysis at 1200 °C, the resulting SiBCN(O) ceramic demonstrates outstanding electromagnetic wave (EMW) absorption performance, achieving full coverage in the X band (RLmin = -36.68 dB). To showcase the design flexibility, a distinctive metastructure is proposed and successfully fabricated using DLP printing technique. This SiBCN(O) metastructure absorber enables impressive EMW absorption in the Ku band (94.6 % coverage), attributed to surface resonance effects and multiple internal reflections. Moreover, SiBCN(O) ceramics exhibit excellent high-temperature stability, with less than a 1.63 % total mass change from room temperature to 1400 °C. UV-hPBSZ offers a simple but versatile way to control dielectric properties, which opens up new possibilities for multifunctional integrated EMW absorbers suitable for both ambient and high-temperature conditions.

An application of internal multiple prediction and primary reflection retrieval to salt structures

Irregular salt bodies complicate the seismic wavefield propagation and cause multipathing, leading to intricate internal multiples that cannot be easily suppressed during data processing. To investigate the performance of internal multiple removal in salt bodies, we compare two types of Marchenko-based internal multiple removal strategies. One focuses on internal multiple prediction (IMP) based on Marchenko redatuming and seismic interferometry. With the retrieved upgoing and downgoing Green’s functions, internal multiples can be reconstructed using convolutional interferometry. The second method emphasizes primary reflection retrieval (PRR) by capturing primary reflections without adaptive subtraction. It is derived from a modified method based on the Gel’fand-Levitan-Marchenko equation. Testing with the Pluto salt model, we find that for the IMP the critical point is obtaining the purely scattering components of the upgoing and downgoing Green’s functions from the complicated wavefield. Our complex salt model indicates that the predicted internal multiples’ adaptive subtraction also introduces an extra challenge for attenuation quality. We develop a layer-by-layer adaptive subtraction scheme for the IMP to obtain primary reflections. The constant-time truncation operator in the time domain makes the PRR independent of additional model information, which can exclude internal multiples from the primary reflections. However, selecting an appropriate smoothing window for truncation requires further investigation. We evaluate the weaknesses of these methods and enhance each method individually. Our numerical results indicate that these improved schemes can correctly handle internal multiples in salt structure scenarios. In the addition, we study the robustness of the IMP when an erroneous background velocity model is used to estimate the direct arrival and the effects of sampling on the virtual receiver/source lines in IMP.

DETECTING MOISTURE IN BAUXITE USING MICROWAVES

AbstractMathematical modelling of microwaves travelling through bauxite ore provides a way to compute moisture content in the free space transmission method given data on signal attenuation, phase shift and variable bauxite depth. We extend a recently developed four-layer model that uses coupled ordinary differential wave equations for the electric field together with continuity boundary conditions at interfaces between ore, air and antenna to find a solution that incorporates multiple internal reflections in ore and air. The model provides good fits to data, depending on ore permittivity and conductivity.Our extensions are to use effective medium models to obtain electromagnetic properties of the ore mixture from moisture content and to incorporate the damping effects of scattering from the ore surface. Our model leads to a formula for the received signal showing how signal strengths SS and phase shifts depend on the moisture content of the bauxite ore, through the effects of moisture on permittivity and conductivity. We show that SS may be noninvertible, indicating that attenuation data alone cannot be used to infer moisture content. Combining with phase data typically corrects the noninvertibility. Reducing the operating frequency dramatically improves the usefulness of signal strength data for inferring moisture content.

Hyperelastic, Robust, Fire‐Safe Multifunctional MXene Aerogels with Unprecedented Electromagnetic Interference Shielding Efficiency

AbstractMXene aerogels have shown great potential for many important functional applications, in particular electromagnetic interference (EMI) shielding. However, it has been a grand challenge to create mechanically hyperelastic, air‐stable, and durable MXene aerogels for enabling effective EMI protection at low concentrations due to the difficulties in achieving tailorable porous structures, excellent mechanical elasticity, and desired antioxidation capabilities of MXene in air. Here, a facile strategy for fabricating MXene composite aerogels by co‐assembling MXene and cellulose nanofibers during freeze‐drying followed by surface encapsulation with fire‐retardant thermoplastic polyurethane (TPU) is reported. Because of the maximum utilization of pore structures of MXene, and conductive loss enhanced by multiple internal reflections, as‐prepared aerogel with 3.14 wt% of MXene exhibits an exceptionally high EMI shielding effectiveness of 93.5 dB, and an ultra‐high MXene utilization efficiency of 2977.71 dB g g−1, tripling the values in previous works. Owing to the presence of multiple hydrogen bonding and the TPU elastomer, the aerogel exhibits a hyperelastic feature with additional strength, excellent stability, superior durability, and high fire safety. This study provides a facile strategy for creating multifunctional aerogels with great potential for applications in EMI protection, wearable devices, thermal management, pressure sensing, and intelligent fire monitoring.

Synthesis of Elements in Compact Stars in Pycnonuclear Reactions with Carbon Isotopes: Quasibound States vs. States of Zero-Points Vibrations

(1) Purpose: Conditions of formation of compound nuclear systems needed for synthesis of heavy nuclei in pycnonuclear reactions in compact stars are studied on a quantum mechanical basis. (2) Methods: The method of multiple internal reflections is applied for pycnonuclear reactions in compact stars with new calculations of quasibound spectra and spectra of zero-point vibrations. (3) Results: Peculiarities of the method are analyzed for reaction with isotopes of Carbon. The developed method takes into account continuity and conservation of quantum flux (describing pycnonuclear reaction) inside the full spacial region of reaction, including the nuclear region. This gives the appearance of new states (called quasibound states) in which compound nuclear systems of Magnesium are formed with the largest probability. These states have not been studied yet in synthesis of elements in stars. Energy spectra of zero-point vibrations and spectra of quasibound states are estimated with high precision for reactions with isotopes of Carbon. For the first time, the influence of plasma screening on quasibound states and states of zero-point vibrations in pycnonuclear reactions has been studied. (4) Conclusions: The probability of formation of a compound nucleus in quasibound states in pycnonuclear reaction is essentially larger than the probability of formation of this system in states of zero-point vibrations studied by Zel’dovich and followers. Therefore, synthesis of Magnesium from isotopes of Carbon is more probable through the quasibound states than through the states of zero-point vibrations in compact stars. Energy spectra of zero-point vibrations are changed essentially after taking plasma screening into account. Analysis shows that from all studied isotopes of Magnesium, only 24Mg is stable after synthesis at an energy of relative motion of 4.881 MeV of the incident nuclei 12C.

Propagator and transfer matrices, Marchenko focusing functions and their mutual relations

SUMMARY Many seismic imaging methods use wavefield extrapolation operators to redatum sources and receivers from the surface into the subsurface. We discuss wavefield extrapolation operators that account for internal multiple reflections, in particular propagator matrices, transfer matrices and Marchenko focusing functions. A propagator matrix is a square matrix that ‘propagates’ a wavefield vector from one depth level to another. It accounts for primaries and multiples and holds for propagating and evanescent waves. A Marchenko focusing function is a wavefield that focuses at a designated point in space at zero time. Marchenko focusing functions are useful for retrieving the wavefield inside a heterogeneous medium from the reflection response at its surface. By expressing these focusing functions in terms of the propagator matrix, the usual approximations (such as ignoring evanescent waves) are avoided. While a propagator matrix acts on the full wavefield vector, a transfer matrix (according to the definition used in this paper) ‘transfers’ a decomposed wavefield vector (containing downgoing and upgoing waves) from one depth level to another. It can be expressed in terms of decomposed Marchenko focusing functions. We present propagator matrices, transfer matrices and Marchenko focusing functions in a consistent way and discuss their mutual relations. In the main text we consider the acoustic situation and in the appendices we discuss other wave phenomena. Understanding these mutual connections may lead to new developments of Marchenko theory and its applications in wavefield focusing, Green’s function retrieval and imaging.

A Functionalized Monte Carlo 3D Radiative Transfer Model: Radiative Effects of Clouds Over Reflecting Surfaces

AbstractIn the Earth Sciences, the 3D radiative transfer equation is often solved for by Monte Carlo (MC) methods. They can, however, be computationally taxing, and that can narrow their range of application and limit their use in explorations of model parameter spaces. A novel family of MC algorithms is investigated here in which single simulations provide estimates of both radiative quantities A for a set of parameters , as usual, as well as the overarching functional (x) that can be evaluated, extremely efficiently, at any x. One such algorithm is developed and demonstrated for horizontally averaged broadband solar radiative fluxes as functions of surface albedo for uniform Lambertian surfaces beneath inhomogeneous cloudy atmospheres. Simulations for a high‐resolution synthetic cloud field, at various solar zenith angles, illustrate the potential of the method to gain insights into the nature of 3D radiative effects for complicated atmosphere‐surface conditions using information specially derived from the MC simulation. For simulations performed with a single surface albedo it is found that as surface albedo increases, 3D radiative effects increase, too, with maxima occurring at middling to large values, and then decrease. By utilizing the derived coefficients that describe it was established that these 3D effects stem from differences in fractions of radiation entrapped at successive orders of internal multiple reflections for 1D and 3D transfer.

Carbon composite foams from the wasted banana leaf for EMI shielding and thermal insulation

Low-density fire-resistant materials with high EMI shielding effectiveness and low thermal conductivity are extremely important in aerospace and defence applications. Utilization of agricultural residues for achieving this reduces CO2 emission as well as produces wealth for the farmers. Herein, a fibre extracted from the wasted matured banana leaf by a simple chopping and grinding using a mixture-grinder is used for the preparation of carbon composite foams. The banana leaf fibres dispersed in sucrose solution are consolidated by filter-pressing followed by freeze drying to produce banana leaf fibre-sucrose composites. The carbon produced from sucrose during carbonization binds the carbonized banana leaf fibre to produce the carbon composite foams. The XRD pattern and Raman analysis indicated the turbostratic nature of the carbon, and XPS analysis shows the presence of oxygen-containing functional groups. The textural property measurement and TEM analysis indicated the presence of micro and meso pores in the carbon composite foams. The foam density (0.14–0.28 g cm−3), compressive strength (0.14–0.88 MPa), electrical conductivity (3.7–8.7 S m−1), and thermal conductivity (0.095–0.144 W m-1 K−1) of the carbon composite foams increases with an increase in sucrose solution concentration (300–700 g L−1). The carbon composite foams exhibit a reflection-dominated EMI shielding with high total shielding effectiveness in the range of 48.3–77.5 dB. The multiple internal reflections within a range of macropores available in the carbon composite foams, leading to enhanced absorption, are responsible for the excellent EMI shielding characteristics.

Квантові ефекти пікноядерних реакцій у компактних зорях: Нові квазізв’язані стани та спектроскопія

Quantum effects in pycnonuclear reactions in compact stars at zero temperatures are studied with high precision. The reaction 16O + 16O was analyzed using the method of multiple internal reflections. The study of such reactions requires full consideration of quantum fluxes in the internal nuclear region. This reduces the rate and number of pycnonuclear reactions up to 1.8 times. This leads to the appearance of new states (which we call quasibound states) where the compound nuclear system is formed with maximal probability. As shown, the minimal energy of such a state is slightly higher than the energy of zero-mode oscillations in the lattice nodes in the pycnonuclear reaction, however, the probability of the formation of a compound system in a quasibound state is significantly greater than the corresponding probability in a state of zero-mode oscillations. It is reasonable to say that the frequency of reactions in quasi-bound states is more likely than in states of zero-mode oscillations. This can lead to significant changes in estimates of reaction rates in stars.

Formation of Silver Layer with a Multiporous Structure from Silver Nanoparticles for Highly Efficient Electromagnetic Interference Shielding Materials

In this work, we describe a simple and effective strategy for the fabrication of a thin silver (Ag) layer with a multiporous structure, showing a high electromagnetic interference shielding effectiveness (EMI SE). The Ag layer with a multiporous structure was produced by a simple spray coating of conductive ink containing porous Ag nanoparticles synthesized using a simple chemical reduction method in a wet medium, followed by a low-energy sintering process to develop the Ag layer with an interconnected multiporous structure and average thickness of ∼5.5 μm. The produced Ag layer possessed a remarkable multiporous structure, which was composed of pores in Ag NPs and additional pores generated by coalescence of Ag NPs during the sintering process. Even the thin Ag layer exhibited a high EMI SE (62.3 dB, 99.9% shielding) owing to the multiporous structure, which was comparable to that of Ag foil with much lower Ag loading. This multiporous structure helped to increase the internal multiple reflections of electromagnetic waves. The substantial shielding effectiveness of the obtained multiporous Ag layer was demonstrated by measuring the EMI SE of the Ag layer coated PCB antenna. Our approach is a suitable and alternative EMI shielding method to replace present package-level EMI shielding materials such as Ag foil for a wide range of applications.

Low-cost photoreactors for highly photon/energy-efficient solar-driven synthesis

Low-cost photoreactors for highly photon/energy-efficient solar-driven synthesis

Methodology for computing Fourier-transform infrared spectroscopy interferograms.

With the utilization of Fourier-transform infrared (FTIR) spectroscopy for a multitude of commercial applications, a robust methodology for designing, implementing, and servicing these systems in commercial settings is becoming increasingly paramount. Here we present a method allowing for the numerical evaluation of the interferogram signal in a FTIR spectroscopy system, in which the incident electric field can exhibit any arbitrary spectral content. The developed model assesses multiple internal reflections occurring within a beam splitter (BS) and compensating plate (CP), allows for the presence or absence of the CP, and obtains the interferogram in absolute units. The interferogram is evaluated for the representative scenarios of an incident electric field having a blackbody spectral distribution (interacting with a BS and CP composed of S i O 2) and a randomly chosen spectral distribution (interacting with a BS composed of ZnSe and no CP).

A laboratory study of the phase ratio imagery method

As a new planetary remote sensing tool, the phase ratio imagery calculates the ratio of images taken at different phase angles and may suppress surface albedo variations and enhance surface texture features. This technique has been used in the study of surface structure of airless bodies such as the Moon and Mercury. To understand the effectiveness of the method, we carried out laboratory phase ratio measurements on eight planetary analog materials including four pure minerals olivine, orthopyroxene, labradorite, ilmenite and four mixtures, the lunar regolith simulant JSC-1A, the lunar highland simulant, the Martian soil simulant, and the CI asteroid simulant, all in two size distributions, 0–45 μm and 90–105 μm. For each sample, the phase ratio A(α1)/A(α2) is obtained by measuring the reflectance at two phase angles α1 and α2 with α1<α2 at two radiation wavelengths, 633 nm and 905 nm. The results show that: (1) The particle size distributions can be differentiated by measuring the phase ratio A(α1)/A(α2), and in order to increase the discriminative power of the particle size distribution, the value of (α1-α2) should be as large as possible. (2) For pure minerals, larger grains have smaller phase ratio values, because larger grains of pure minerals are more forward scattering, leading to larger A(α2) and thus smaller phase ratio. For mixtures with simulated agglutinates that hold minerals together as composite particles, larger grains have higher phase ratios because they are less forward scattering due to multiple internal reflections and hence more absorptions. Since real planetary regoliths are likely dominated by composite particles with agglutinates, it is expected that larger grains would have larger phase ratio values.