Radiation Modes Research Articles

Analyzing porous cold storage unit in presence of hybrid nano-powders considering Galerkin method

The article presents a comprehensive simulation study on cold storage porous containers, employing the Galerkin method to analyze their thermal behavior. A key focus of the investigation is the incorporation of both radiation and conduction modes within the mathematical model, acknowledging their significant roles in the freezing process. To enhance the freezing rate, hybrid nanoparticles are introduced into H2O, aiming to speed up the solidification. Notably, the study integrates adaptive grid techniques to achieve higher modeling accuracy, with verification processes confirming a high level of agreement between simulation results and experimental data. This research also underscores the potential for improved energy efficiency in cold storage systems, contributing to the sustainability of natural resources by reducing energy consumption and enhancing the overall efficiency of thermal storage systems. Through meticulous examination, the study explores the impacts of various factors on freezing, including the fraction of hybrid nano-powders (ϕ), porosity (γ), and the radiation factor (Rd). Remarkably, the introduction of porous media causes to a substantial increment in the freezing rate, resulting in an improvement of approximately 91.19 %. Moreover, the inclusion of the radiation term in the model significantly reduces the completion time by approximately 30.85 %, underscoring the importance of considering radiation effects in such systems. Additionally, dispersing hybrid nano-powders into the water, results in a decrement in the freezing time around 7.21 %. This approach highlights the significant potential for optimizing energy use in thermal storage applications, thereby promoting the conservation and sustainable management of natural resources.

Impact of Higher Harmonics of Gravitational Radiation on the Population Inference of Binary Black Holes

Templates modeling just the dominant mode of gravitational radiation are generally sufficient for the unbiased parameter inference of near-equal-mass compact binary mergers. However, neglecting the subdominant modes can bias the inference if the binary is significantly asymmetric, very massive, or has misaligned spins. In this work, we explore if neglecting these subdominant modes in the parameter estimation of nonspinning binary black hole mergers can bias the inference of their population-level properties such as mass and merger redshift distributions. Assuming the design sensitivity of the advanced LIGO-Virgo detector network, we find that neglecting subdominant modes will not cause a significant bias in the population inference, although including them will provide more precise estimates. This is primarily because asymmetric binaries are expected to be rarer in our detected sample, due to their intrinsic rareness and the observational selection effects. The increased precision in the measurement of the maximum black hole mass can help in better constraining the upper mass gap in the mass spectrum.

A low-profile frequency- and pattern-reconfigurable metantenna for UAV joint RadCom systems

To address the specific requirements of antennas in Unmanned Aerial Vehicle (UAV) joint radar-communication (RadCom) systems, a novel low-profile reconfigurable metantenna with the capability of frequency and pattern reconfiguration is proposed in this paper. The proposed antenna consists of a metasurface layer with 3 × 3 square unit cells and a simple feeding network with two pairs of PIN diodes. Specifically, the designed metantenna has a low profile of 0.064 λ0 (λ0 is the free space wavelength at 5.5 GHz). And measured results show that, for the broadside radiation mode, the −10 dB operating bandwidth is about 12.1 %, ranging from 5.05 to 5.7 GHz with a maximum gain of 8.9 dBi. For the conical radiation mode, the −10 dB operating bandwidth is about 21.9 %, ranging from 5.88 to 7.33 GHz with a maximum gain of 6.83 dBi. Given its excellent radiation performance, the metantenna designed for UAV joint RadCom systems holds significant research significance and value in the field of multifunctional reconfigurable antennas.

Hadronization and decay of excited heavy hadrons in Herwig 7

We revisit the hadronization and decay of excited heavy mesons and heavy baryons in Herwig 7 general-purpose event-generator, following four distinct steps: (i) Passing through the polarisation of heavy hadrons at the end of parton shower through the application of heavy quark effective theory (HQET), where the emergence of a spin-flavour symmetry allows for the determination of the polarisations of the excited heavy mesons and heavy baryons from the helicity states of the light and heavy quarks. (ii) Improving the strong and radiative decay modes of the excited heavy mesons, where in the absence of conclusive experimental data on many of the decays, one needs to rely on HQET symmetries to determine the favoured decay modes, widths and branching ratios. (iii) Re-examination of the production rates of heavy hadrons using all available experimental data sources and (iv) performing a general tune for Herwig’s free parameters to reflect the implemented changes. We compare our predictions against existing experimental data in the presence/absence of the newly implemented updates. These improvements will be available with Herwig-7.3.0 public release.

Power counting to saturation

We present a description of saturation in small x deep inelastic scattering from power counting in a top-down effective theory derived from quantum chromodynamics (QCD). A factorization formula isolates the universal physics of the nucleus at leading power in x. The onset of saturation is then understood as a breakdown in the expansion in an emergent power counting parameter, which is defined by the matrix element of a gauge invariant operator. We identify a new radiation mode, which enables us to extend previous literature by distinguishing the appearance of the saturation scale from the transition to nonlinear evolution. Published by the American Physical Society 2024

Spin-Polarization Control of Photoelectrons Using Poincaré Fields.

Efficient helicity transfer from Poincaré fields to electrons of hydrogenic ions is revealed for the first time by four-dimensional relativistic simulations. The magnetic multipole class of Poincaré fields is chosen due to its fundamental role in light-matter spin coupling, and the calculation is demonstrated for Ne^{9+} ion irradiated by single and multimode x-ray pulses. Photoelectrons of both helicities emerge synchronously from the ion ensemble, and their directionality is controllable through the radiation mode numbers. The helicity density distributions display novel structures composed of jets, spirals, and rings, among others, that are unique to the combination of atomic and field parameters. Our approach to generate spin-polarized leptons using Poincaré fields may provide a new platform for helicity characterization based on advanced numerical capabilities.

Functionality Expansion of Guided Mode Radiation via On-Chip Metasurfaces.

On-chip metasurfaces play a crucial role in bridging the guided mode and free-space light, enabling full control over the wavefront of scattered free-space light in an optimally compact manner. Recently, researchers have introduced various methods and on-chip metasurfaces to engineer the radiation of guided modes, but the total functions that a single metasurface can achieve are still relatively limited. In this work, we propose a novel on-chip metasurface design that can multiplex up to four distinct functions. We can efficiently control the polarization state, phase, angular momentum, and beam profile of the radiated waves by tailoring the geometry of V-shaped nanoantennas integrated on a slab waveguide. We demonstrate several innovative on-chip metasurfaces for switchable focusing/defocusing and for multifunctional generators of orbital angular momentum beams. Our on-chip metasurface design is expected to advance modern integrated photonics, offering applications in optical data storage, optical interconnection, augmented reality, and virtual reality.

Metric perturbations of Kerr spacetime in Lorenz gauge: circular equatorial orbits

We construct the metric perturbation in Lorenz gauge for a compact body on a circular equatorial orbit of a rotating black hole (Kerr) spacetime, using a newly-developed method of separation of variables. The metric perturbation is formed from a linear sum of differential operators acting on Teukolsky mode functions, and certain auxiliary scalars, which are solutions to ordinary differential equations in the frequency domain. For radiative modes, the solution is uniquely determined by the s=±2 Weyl scalars, the s = 0 trace, and s=0,1 gauge scalars whose amplitudes are determined by imposing continuity conditions on the metric perturbation at the orbital radius. The static (zero-frequency) part of the metric perturbation, which is handled separately, also includes mass and angular momentum completion pieces. The metric perturbation is validated against the independent results of a 2+1D time domain code, and we demonstrate agreement at the expected level in all components, and the absence of gauge discontinuities. In principle, the new method can be used to determine the Lorenz-gauge metric perturbation at a sufficiently high precision to enable accurate second-order self-force calculations on Kerr spacetime in future. We conclude with a discussion of extensions of the method to eccentric and non-equatorial orbits.

A hardware/firmware-based switching gate multiplexing method for pulse mode radiation detectors

We present a hardware/firmware-based switching gate multiplexing method for pulse mode radiation detectors that can combine many detector signals into two readout channels. One readout channel passes the signal of the multiplexed detector that “fired” first, and the other channel provides a variable-width logic pulse, i.e., a pulse width modulation (PWM) signal, that identifies the active detector. The multiplexed output pulse is produced by passing the first active detector’s signal to a fan-in circuit by gating on the corresponding channel for a fixed duration while blocking all other detector signals. It does this using individual analog switches for all the detector signals. Each switch is controlled by a fixed width logic pulse that is triggered by the arrival of the first active detector pulse. Both the fixed width logic pulse and the PWM signal are generated using a field-programmable gate array (FPGA). To demonstrate the proposed multiplexing method, a prototype four-channel multiplexer was developed for use with four NaI(Tl) detectors. The performance of the multiplexer was evaluated in terms of its ability to retain energy resolution, timing resolution, and original pulse shape. The proposed multiplexing method showed very little degradation in energy resolution and timing resolution or alteration of pulse shape. The switching gate feature of the proposed method enables the multiplexer output to have very low noise contribution from the inactive channels. This multiplexing technique also has the unique capability of isolating and recovering the first active detector’s output pulse in cases where there is overlap between pulses from different detectors in a single digitized record. These features make the proposed hardware/firmware-based switching gate multiplexing method very promising for application to large radiation detector networks.

Time‐Space‐Coding Radiation‐Stealth Metasurface with Amplitude‐Phase Co‐Modulation

AbstractThe integrated design of radiation and stealth holds significant importance for radar communication and camouflage. Currently, radar systems primarily rely on radomes for off‐band stealth. However, achieving in‐band stealth by radomes and absorbing materials is challenging. Even more challenging is the dynamic control of both in‐band radiation and stealth. Therefore, a novel space‐time‐coding metasurface is proposed for radiation and stealth modes regulation. By adjusting the two PIN diodes loaded on the meta‐atom, switching between radiation and scattering modes can be achieved. A 1‐bit reflection phase can be achieved in the scattering mode. The stealth is achieved by controlling the scattering properties of the metasurface. In the radiation mode, 2‐bit phase modulation is achieved by separately controlling the PIN diodes on the meta‐atom and the 3 dB coupler. Additionally, by varying the size of the meta‐atom in the y‐polarization direction, a 1‐bit reflection phase also can be achieved. To validate the proposed radiation‐stealth metasurface characteristics, a 12 × 12 prototype is fabricated. This prototype demonstrates important functionalities, including dual‐mode radiation, amplitude‐phase co‐modulation space‐time‐coding stealth, and space‐coding stealth.

The Role of Active Galactic Nucleus Winds in Galaxy Formation: Connecting AGN Outflows at Low Redshifts to the Formation/Evolution of Their Host Galaxies

Using Sloan Digital Sky Survey (SDSS) spectra, we applied an automatic method to search for outflows (OFs) in three large samples of narrow-line active galactic nuclei (AGN) at low redshifts (z < 0.4), separated into three spectral activity classes: radio-loud galaxies (RGs), 15,793; radio-quiet Seyfert 2 AGN (Sy2), 18,585; and LINERs, 25,656. In general, the probability of detecting an OF decreases along the sequence Sy1→Sy2→LINER/RG and independently of the AGN class, the wind velocity, traced by W80, increases with the AGN luminosity. Moreover W80 is systematically higher in RGs or any of the other AGN classes when detected in radio. These results support the idea that there are two main modes of production of OF, the radiative mode dominant in radio-quiet AGN and the jet mode dominant in RGs, although both modes could also happen simultaneously at different levels. From the spectra and SDSS photometry, the characteristics of the AGN host galaxies and their supermassive black holes (SMBHs) were also retrieved using the stellar population synthesis code STARLIGHT. This revealed that, independently of the AGN spectral class, (1) galaxy hosts with OFs have systematically later morphological types and higher star formation rates (SFRs) than their counterparts without OF, (2) the AGN occupy different positions in the specific diagnostic diagram (specific black hole accretion rate (sBHAR) versus specific SFR), which suggests they follow different evolutionary paths congruent with the morphology of their galaxy hosts, and (3) they show no evidence of AGN quenching or triggering of star formation. These results are consistent with a scenario explaining the different AGN classes as consequences of different formation processes of galaxies: early-type galaxies (LINERs and RGs) formed bigger bulges and more massive SMBHs, exhausting their reservoir of gas more rapidly than late-type galaxies (Sy2 and Sy1), and thereby quenching their star formation and starving their SMBHs.

Legume: A free implementation of the guided-mode expansion method for photonic crystal slabs

We describe legume, a free electromagnetic solver that implements the guided-mode expansion method for patterned multilayer waveguides, or photonic crystal slabs. legume has a built-in tool for automatic differentiation, which makes it suitable for the inverse design of photonic crystal structures with desired physical properties. Compared to a previous version of the method (M. Minkov et al., 2020 [12]), here we introduce several new features of the code, we discuss additional technical aspects of the method and its numerical implementation. The novel features that are treated in this paper include: (i) the separation of modes according to their mirror symmetry with respect to a vertical symmetry plane of the photonic structure, (ii) the problem of polarization mixing in coupling to far-field radiation modes, and (iii) the description of active two-dimensional layers through a suitably formulated radiation-matter coupling Hamiltonian, allowing to describe the physics of both weakly and strongly coupled exciton-photon modes, the latter leading to photonic crystal polariton eigenmodes. Detailed and direct comparisons with rigorous coupled-wave analysis simulations are used to test the accuracy of the method and the numerical efficiency of the code. These newly added features of the legume code significantly increase the prospective applications of guided-mode expansion, making it a very practical and versatile tool enabling the design of advanced photonic structures and the description of radiation-matter interaction. Program summaryProgram Title:legumeCPC Library link to program files:https://doi.org/10.17632/kf3cwknx4d.1Developer's repository link:https://github.com/fancompute/legumeLicensing provisions: MITProgramming language: PythonNature of problem: Dispersion and radiative losses of photonic eigenmodes in patterned multilayer waveguides/photonic crystal slabs/periodic metasurfaces. Interaction of photonic modes with exciton resonances leading to exciton-polaritons. Inverse design by optimization of the parameters.Solution method: Finite-basis expansion using a basis of guided modes of an effective homogeneous waveguide, perturbation theory to describe coupling with far-field radiation. Quantum theory of excitons, photons and their interaction to describe the occurrence of exciton-polaritons. Automatic differentiation via Autograd to implement inverse design. In this upgraded version of the legume code we implement symmetrization with respect to a vertical mirror plane and light-matter interaction for exciton-polaritons. Inverse design has been described previously, here we focus on the new features and applications of the code.

X-ray-driven multi-bit quantum random number generator

Random numbers are vital in cryptography, simulation modeling, and gambling. This study presents a scheme for a multi-bit quantum random number generator utilizing X-ray radiation. Using a homemade multi-pixel single-photon detector array, we extract randomness from three modes of X-ray radiation: arrival time, spatial position, and polarization direction. We employ the Toeplitz Matrix Hashing extractor for randomness distillation, resulting in the extraction of 40.4 million random bits at a rate of 33.7 bits per photon. The generated random numbers pass all test criteria in the National Institute of Standards and Technology statistical test suite. Our work paves what we believe to be a novel method for generating multi-bit quantum random numbers, promising enhanced security and reliability in various technological applications.

Recent Progress in Light Polarization Control Schemes for Silicon Integrated Photonics

AbstractLight polarization control is a target in photonics, and this paper provides a comprehensive review of research from various groups on the silicon‐on‐insulator (SOI) platform. It draws comparisons between devices such as polarization splitters (PS), polarizers, and polarization splitters/rotators (PSR). These devices are fabricated using various technologies, including silicon nanowires, ridge waveguides, hybrid plasmonic waveguides, and subwavelength grating (SWG) waveguides. A detailed review of polarizers used as cleanup filters in splitters is initiated. Subsequently, various polarization splitters utilizing asymmetric directional couplers (ADCs), which typically exhibiting low extinction ratios (ERs), are delved. To enhance ERs, a detailed comparison of methods outlined in the literature is provided. One notable method includes integrating on‐chip polarizers at both ports to eliminate unwanted light fractions and achieve exceptionally high ERs. Furthermore, SWG‐based polarizers and splitters commonly face issues with Bragg reflections that can affect other photonic devices and lasers and ways to minimize unwanted polarization back reflections in SWG‐designed polarization control devices are examined. Finally, emerging applications in mid‐infrared (MIR) sensing are explored, highlighting the necessity of polarization rotators for on‐chip transverse electric (TE) operation, since quantum cascade lasers, the primary sources in this range, emitting radiation in the (TM) mode.

Jaynes-Cummings interaction with a traveling light pulse

The Jaynes-Cummings model provides a simple and accurate description of the interaction between a two-level quantum emitter and a single mode of quantum radiation. Due to the multimode continuum of eigenmodes in free space and in waveguides, the Jaynes-Cummings model should not be expected to properly describe the interaction between an emitter and a traveling pulse of quantum radiation. In this article, we review a cascaded quantum system approach that accurately describes the interaction of a quantum system with an incident quantum pulse of radiation. When applied to the two-level system, different iterations of this approach lead to master equations with different Jaynes-Cummings-like Hamiltonians and damping terms.

Monitoring of Curing Process of Epoxy Resin by Long-Period Fiber Gratings.

The curing of epoxy resin is a complex thermo-chemical process that is difficult to monitor using existing sensing systems. We monitored the curing process of an epoxy resin by using long-period fiber gratings. The refractive index of the epoxy resin increases during the curing process and can be measured to determine the degree of curing. We employed long-period fiber gratings that are sensitive to the refractive index of an external medium for the measurement of refractive index changes in the resin. We observed that the resonances of long-period fiber gratings increased their depth with the increased refractive index of the resin, which was well described by our simulation taking the coupling to radiation modes into account. We demonstrated that the degree of cure can be estimated from the depth of the grating resonances using a phenomenological model. At the same time, long-period fiber gratings are sensitive to temperature variations and internal strains that are induced during curing. These factors may affect the measurements of curing degree and should also be addressed.

Acoustic resolvent analysis of turbulent jets

Abstract We perform a resolvent analysis of a compressible turbulent jet, where the optimisation domain of the response modes is located in the acoustic field, excluding the hydrodynamic region, in order to promote acoustically efficient modes. We examine the properties of the acoustic resolvent and assess its potential for jet-noise modelling, focusing on the subsonic regime. Resolvent forcing modes, consistent with previous studies, are found to contain supersonic waves associated with Mach wave radiation in the response modes. This differs from the standard resolvent in which hydrodynamic instabilities dominate. We compare resolvent modes with SPOD modes educed from LES data. Acoustic resolvent response modes generally have better alignment with acoustic SPOD modes than standard resolvent response modes. For the optimal mode, the angle of the acoustic beam is close to that found in SPOD modes for moderate frequencies. However, there is no significant separation between the singular values of the leading and sub-optimal modes. Some suboptimal modes are furthermore shown to contain irrelevant structure for jet noise. Thus, even though it contains essential acoustic features absent from the standard resolvent approach, the SVD of the acoustic resolvent alone is insufficient to educe a low-rank model for jet noise. But because it identifies the prevailing mechanisms of jet noise, it provides valuable guidelines in the search of a forcing model (Karban et al. in J Fluid Mech 965:18, 2023). Graphical abstract

Comparative analysis of electrochemical behaviors of lithium-ion batteries using the dual potential MSMD battery models: case studies on various thermal conditions

The high energy density and long cycle life of lithium-ion batteries make them a preferred option for electric vehicles. The efficiency and life span of lithium-ion batteries are particularly sensitive to temperature; thus, it becomes essential to maintain an ideal temperature range. In this context, we concentrated on two widely used electro-chemistry (Equivalent Circuit Model and NTGK) models of a single cell of a dual potential MSMD Lithium-ion Battery while taking into account two significant methods of heat transfer under varying C-rates (0.25C, 1C, 2C, and 5C). We investigated the highest temperatures that two e-chemistry models could reach in varying ambient temperatures (typical summer, winter, and room temperature). The maximum temperature-raising tendency in the ECM due to natural convection is greater than the maximum temperature-raising tendency due to radiation regardless of the environmental temperatures and various C rates (0.25C, 1C, and 2C). However, the trend line of the maximum temperature rise is different in the NTGK model, where the maximum temperature rise due to radiation is greater than the maximum temperature rise due to convection for 0.25C, 1C, and 2C rates in -5°C and 40°C environmental temperatures. In the NTGK model, at 0.25C, 1C, and 2C rates for winter and summer temperatures, the maximum temperature rise owing to radiation is larger than that due to convection. The NTGK model, however, produced somewhat superior findings for the radiation mode of heat transfer at ambient temperature. Therefore, it can be said that convection is a better thermal condition than natural convection in the NTGK model.

Scalar radiation with a quartic Galileon

The class of Galileon scalar fields theories encapsulate the Vainshtein screening mechanism, which is characteristic of a large range of infrared modified theories of gravity. Such theories can lead to testable departures from general relativity through fifth forces and new scalar modes of gravitational radiation. However, the inherent nonlinearity of the Vainshtein mechanism has limited analytic attempts to describe Galileon theories with both cubic and quartic interactions. To improve on this, we perform direct numerical simulations of the quartic Galileon model for a rotating binary source and infer the power spectrum of given multipoles. To tame numerical instabilities we utilize a low-pass filter, extending previous work on the cubic Galileon. Our findings show that the multipole expansion is well defined and under control. Moreover, our results confirm that despite being a nonlinear scalar, the dominant Galileon radiation is quadrupole, and we find a new scaling behavior deep inside the Vainshtein region. Published by the American Physical Society 2024

Ozone Monitoring Spectrometer-Limb observation (OMSL) on-orbit polarization correction for atmospheric radiation measurements

OMSL is a passive, space-based spectrometer designed to obtain the vertical profiles of trace gases such as ozone, by measuring atmospheric radiation in limb-viewing mode. Due to the presence of internal components such as gratings and dichroic mirror, OMSL is sensitive to polarization of incident light, which can lead to errors in the radiometric measurements, especially when the incident light is fully polarized. To eliminate the errors, an on-orbit polarization correction method is applied to OMSL. The key to this method is to calculate the polarization correction factor by combining the on-orbit polarization measurement and the pre-flight polarization calibration. In this paper, the on-orbit polarization correction method is introduced in detail. Furthermore, the first results of the on-orbit correction are analyzed and compared with simulation of the SCIATRAN.