Coherent Component Research Articles

Experimental Investigation of Coherent Ergotropy in a Single Spin System.

Ergotropy is defined as the maximum amount of work that can be extracted through a unitary cyclic evolution. It plays a crucial role in assessing the work capacity of a quantum system. Recently, the significance of quantum coherence in work extraction has been theoretically identified, revealing that quantum states with more coherence possess more ergotropy compared to their dephased counterparts. However, an experimental study of the coherent ergotropy remains absent. Here, we report an experimental investigation of the coherent ergotropy in a single spin system. Based on the method of measuring ergotropy with an ancilla qubit, both the coherent and incoherent components of the ergotropy for the nonequilibrium state were successfully extracted. The increase in ergotropy induced by the increase in the coherence of the system was observed by varying the coherence of the state. Our work reveals the interplay between quantum thermodynamics and quantum information theory, future investigations could further explore the role other quantum attributes play in thermodynamic protocols.

Collisions Between Dark Matter Confined High Velocity Clouds and Magnetized Galactic Disks: The Smith Cloud. II.

We present high-resolution simulations of high velocity clouds (HVCs) colliding with the outer part of the Galactic disk. All of the simulations include a 3 × 108 M ⊙ dark matter subhalo. Three simulations model a dark matter subhalo without a gaseous component, while eight simulations model a dark matter subhalo accompanied by a gaseous cloud of mass 2–8 × 106 M ⊙. Half of the simulations include the coherent component of the Galaxy's magnetic field. Each simulation spans ∼40 million years before the collision and ∼40 million years after the collision. The collisions between the gas cloud and disk splash gas into the halo, punch half-kiloparsec-size holes in the disk, and form long-lived, multi-kiloparsec-size shells. Each shell encloses a bubble of relatively cool gas. Holes and shells of these scales would be observable, and some have been observed in the past. We determine the fate of the HVC gas, temperature, composition, and ionization state of the bubble and shell gas, size and longevity of the holes, and effects of cloud density. Simulations show that the clouds do not survive the chaos of passage through the disk, but instead become part of the splash, bubble, and shell. Some dark matter clouds may appear to carry material with them long after the collision, but this material is shell gas that was captured by the dark matter subhalo. These results have ramifications for the Smith Cloud and other clouds hypothesized to have hit the Galactic disk.

Analysis of Wind Power Fluctuation in Wind Turbine Wakes Using Scale-Adaptive Large Eddy Simulation

In large wind farms, the interaction of atmospheric turbulence and wind turbine wakes leads to complex vortex dynamics and energy dissipation, resulting in reduced wind velocity and subsequent loss of wind power. This study investigates the influence of vortex stretching on wind power fluctuations within wind turbine wakes using scale-adaptive large eddy simulation. The proper orthogonal decomposition method was employed to extract the most energetic contributions to the wind power spectra. Vertical profiles of mean wind speed, Reynolds stresses, and dispersive stresses were analyzed to assess energy dissipation rates. Our simulation results showed excellent agreement when compared with wind tunnel data and more advanced numerical models, such as the actuator line model and the actuator line model with hub and tower effects. This highlights the important role of coherent and energetic flow components in the spectral behavior of wind farms. The findings indicate a persistent energy cascading length scale in the wake of wind turbines, emphasizing the vertical transport of energy to turbine blades. These results complement existing literature and provide new insights into the dynamics of wind turbine wakes and their impact on wind farm performance.

Transport of non-equilibrium quasiparticle excitations in superconducting aluminum

The electron transport of non-equilibrium quasiparticles injected into superconducting aluminum from a normal metal has been experimentally studied at ultralow temperatures. We studied hybrid nanostructures in the form of a T-shaped normal metal electrode (copper) – a dielectric tunnel layer (aluminum oxide) – a superconducting fork (aluminum), which can be considered as a solid-state analogues of a two-beam optical interferometer. At fixed bias voltages larger than the superconducting gap, a non-monotonic dependence of the tunnel current on perpendicular magnetic field is observed. The effect is interpreted as the presence of a coherent component of the quasiparticle current.

Scatterer spacing based on Gabor atoms matched from harmonic ultrasound echoes to improve assessment of microwave‐induced thermal lesions

AbstractBackgroundMicrowave ablation (MWA) is a minimally invasive alternative for the treatment of unresectable liver tumors. To verify the effectiveness and safety of MWA, it is critical to measure the temperature variation and assess the regions of the microwave‐induced thermal lesions.PurposeRecent studies have indicated that the locations of optimally matched Gabor atoms (LOMGA) from ultrasound radiofrequency (RF) echo signals allow accurate and stable scatterer spacing estimation. Herein, a harmonic‐based LOMGA method is proposed to estimate the scatterer spacing for improving the assessment of microwave‐induced thermal lesions.MethodsThe mean scatterer spacing (MSS) is estimated via the LOMGA method incorporating the selection of concise atoms from separated second‐harmonic RF echo signals with the pulse‐inversion algorithm for thermal lesion evaluation. In vitro experiments, 10 fresh porcine liver samples were ablated at different time nodes during the ablation period, and 200 sets of second‐harmonic and fundamental RF echo signals were randomly selected from the regions of interest in the coagulated liver samples for MSS estimation. The means and standard deviations of the MSSs, as well as the linear regression for the mean MSSs, were calculated from fundamental and second‐harmonic signals for comparison and evaluation, the receiver operating characteristic (ROC) curves for the 200 sets of fundamental‐based and harmonic‐based MSS estimates from the 10 liver samples at five pairs of adjacent time nodes were calculated, and one‐way analysis of variance (ANOVA) tests were performed for the five pairs of adjacent time nodes. The fundamental and harmonic‐based p‐values in the ANOVA tests and the areas under the ROC curves (AUCs) were calculated to statistically analyze the differences in the MSSs between adjacent time nodes.ResultsThe harmonic‐based increments in the intensity variation and coherent components were larger than the fundamental‐based increments with the increasing ablation time. The harmonic‐based MSSs from the 10 liver samples at five pairs of adjacent time nodes were found to be highly statistically significant (p < 0.01). Thus, the harmonic‐based MSSs had greater variations. Compared with the fundamental‐based results, for the five preset ST values, the average increment in the harmonic‐based mean slopes was 69.22% and the average decrement in the mean standard deviations was 11.67% for the linear‐fitting MSS results, and the results were statistically significant (p < 0.05).ConclusionHarmonic‐based MSSs are more sensitive and robust to variations in coagulated tissues, which is advantageous for the assessment of microwave‐induced thermal lesions.

The mean scatterer spacing estimation with the Gabor atoms selected based on the Nakagami distribution

Abstract Mean scatterer spacing (MSS) is a quantitative signature for disease diagnosis and tissue characterization. However, it is difficult to objectively extract the coherent components from the ultrasound RF echo signals to improve the accuracy performance of the MSS estimation. In the present study, a novel MSS estimation method with the matched Gabor atoms selected based on Nakagami parameters is proposed. Firstly, the ultrasound signals are decomposed into a series of Gabor atoms, and the envelopes of the residual signals are fitted with the Nakagami distribution. Then, the second order difference (SOD) of the shape parameters in Nakagami distribution is calculated to select the optimal atoms to match the coherent components. Finally, the locations of the selected Gabor atoms are used to estimate the MSS. In order to evaluate the performance of the proposed method, the simulated RF echo signals are modelled based on four regular degrees of the scatterer distributions, and then the optimally matched atoms are selected to estimate MSSs. The results based on simulated signals demonstrate that the propose method can provide accurate MSS estimation, which are advantageous for improving quantitative diagnosis of diseases and tissue characterization

Distributed Acoustic Sensing Signal Model Under Static Fiber Conditions

This paper presents a statistical model for distributed acoustic sensor interrogation units that utilizes laser pulses transmitted into fiber optics. Interactions within the fiber lead to localized acoustic energy, resulting in backscatter, which is a reflection of the light. Explicit equations were used to calculate the amplitudes and phases of backscattered signals. The proposed model accurately predicts the amplitude signal spectrum and autocorrelation, aligning well with experimental observations. This study also explores the phase signal characteristics relevant to optical time-domain reflectometry (OTDR) system sensing applications, demonstrating consistency with the experimental results. The experiments were conducted using Python coding, enabling the analysis of the individual components of the Distributed Acoustic Sensing (DAS) system. The assumptions of the model include the static condition of the fiber, implying the absence of external forces or vibrations. Consequently, no external acoustic disturbances were considered. The backscattered signal comprises a random noise component resulting from intrinsic fiber imperfections, and a coherent component arising from the interplay between the laser pulse and the fiber. Keywords: distributed acoustic sensing, fiber optics, optical time-domain reflectometry, Rayleigh scattering.

Subband Independent Component Analysis for Coherence Enhancement.

Cortico-muscular coherence (CMC) is becoming a common technique for detection and characterization of functional coupling between the motor cortex and muscle activity. It is typically evaluated between surface electromyogram (sEMG) and electroencephalogram (EEG) signals collected synchronously during controlled movement tasks. However, the presence of noise and activities unrelated to observed motor tasks in sEMG and EEG results in low CMC levels, which often makes functional coupling difficult to detect. In this paper, we introduce Coherent Subband Independent Component Analysis (CoSICA) to enhance synchronous cortico-muscular components in mixtures captured by sEMG and EEG. The methodology relies on filter bank processing to decompose sEMG and EEG signals into frequency bands. Then, it applies independent component analysis along with a component selection algorithm for re-synthesis of sEMG and EEG designed to maximize CMC levels. We demonstrate the effectiveness of the proposed method in increasing CMC levels across different signal-to-noise ratios first using simulated data. Using neurophysiological data, we then illustrate that CoSICA processing achieves a pronounced enhancement of original CMC. Our findings suggest that the proposed technique provides an effective framework for improving coherence detection. The proposed methodologies will eventually contribute to understanding of movement control and has high potential for translation into clinical practice.

Analysis X-ray diffractograms from near-surface layers of monocrystals: development of models, algorithms and software

An algorithm for analyzing double-crystal rocking curves from the near-surface layers of monocrystals has been proposed, and corresponding software has been developed. It is taken into account that to obtain correct results, both coherent and diffuse components of X-ray scattering need to be considered. The possibility of simultaneous analysis of rocking curves from several reflections is provided. To approximate experimental rocking curves with theoretical ones, an approach that simultaneously uses three different approximation methods has been utilized. The effectiveness of the proposed approach is confirmed by verifying the uniqueness of the obtained results.

Electron Cyclotron Maser Emission and the Brightest Solar Radio Bursts

This paper investigates the incidence of coherent emission in solar radio bursts, using a revised catalog of 3800 solar radio bursts observed by the Nobeyama Radio Polarimeters from 1988 to 2023. We focus on the 1.0 and 2.0 GHz data, where radio fluxes of order 1010 Jy have been observed. Previous work has suggested that these bursts are due to electron cyclotron maser (ECM) emission. In at least one well-studied case, the bright emission at 1 GHz consists of narrowband spikes of millisecond duration. Coherent emission at 1 GHz can be distinguished from traditional incoherent gyrosynchrotron flare emission based on the radio spectrum: Gyrosynchrotron emission at 1 GHz usually has a spectrum rising with frequency, so bursts in which 1 GHz is stronger than higher-frequency measurements are unlikely to be incoherent gyrosynchrotron. Based on this criterion, it is found that for bursts exceeding 100 sfu, three-quarters of all bursts at 1 GHz and half of all 2 GHz bursts have a dominant coherent emission component, assumed to be ECM. The majority of the very bright bursts at 1 GHz are highly circularly polarized, consistent with a coherent emission mechanism, but not always 100% polarized. The frequency range from 1 to 2 GHz is heavily utilized for terrestrial applications, and these results are relevant for understanding the extreme flux levels that may impact such applications. Further, they provide a reference for comparison with the study of ECM emission from other stars and potentially exoplanets.

Time sequence variation of incoherent and coherent random laser based on positive replica of abalone shell

Besides the scattering structures, the energy transfer (ET) process in the gain medium plays a significant role in the competition between coherent (comprising strongly coherent components) and incoherent (consisting of weakly coherent or “hidden” coherent components) modes of random lasers. In this study, bichromatic emission random lasers were successfully created using polydimethylsiloxane (PDMS) replicas with grooved structures that imitate the inner surface of abalone shells as scattering substrates. The influence mechanism of the ET process from the monomer to dimer in the Rhodamine 640 dye on the competition of random laser modes was thoroughly investigated from both spectral and temporal dimensions. It was confirmed that the ET process can reduce the gain of monomers while amplifying the gain of dimers. By considering the dominant high-efficiency ET processes, an energy transfer factor associated with the pump energy density was determined. Notably, for the first time, it was validated that the statistical distribution characteristics of the time sequence variations in the coherent random laser generated by dimers closely resemble a normal distribution. This finding demonstrates the feasibility of producing high-quality random number sequences.

Feature based bipolar plate forming

By the end of the 1990s, the global peak of energy supply from oil and gas deposits had already been reached. Since then, there has been a clear trend towards the development of new, more sustainable ways of supplying energy. To realize this reduction, a holistic and rapid restructuring of the energy supply towards CO2-free and renewable energy production, storage and processing across all areas of life is necessary. The development and implementation of a functioning hydrogen economy can be crucial with respect to the goal of climate neutrality. The scale-up and commercialization of technologies for the cost-effective production and use of hydrogen carry significant importance. Accordingly, innovative production technologies and process chains must be developed to be able to manufacture fuel cells reliably in high volumes and at optimized costs. In this context, BPPs in the PEM-FC are responsible for about 80 % of the total weight, just over 50 % of the system volume, and up to 40 % of the total cost. Current research approaches in the field of BPP forming focus mainly on the optimization of a pre-selected production technology. Thereby, the possibility of combining different forming technologies to represent a holistic process chain is mostly disregarded. This research gap is to be closed by the developments within the scope of this work. The bipolar plate is not to be regarded as a coherent component, but as a composition of different geometric features.

Constraints on UHECR Sources and Extragalactic Magnetic Fields from Directional Anisotropies

A dipole anisotropy in ultra–high-energy cosmic ray (UHECR) arrival directions, of extragalactic origin, is now firmly established at energies E > 8 EeV. Furthermore, the UHECR angular power spectrum shows no power at smaller angular scales than the dipole, apart from hints of possible individual hot or warm spots for energy thresholds ≳40 EeV. Here we exploit the magnitude of the dipole and the limits on smaller-scale anisotropies to place constraints on two quantities: the extragalactic magnetic field (EGMF) and the number density of UHECR sources or the volumetric event rate if UHECR sources are transient. We also vary the bias between the extragalactic matter and the UHECR source densities, reflecting whether UHECR sources are preferentially found in over- or underdense regions, and find that little or no bias is favored. We follow Ding et al. (2021) in using the CosmicFlows-2 density distribution of the local universe as our baseline distribution of UHECR sources, but we improve and extend that work by employing an accurate and self-consistent treatment of interactions and energy losses during propagation. Deflections in the Galactic magnetic field are treated using either the full JF12 magnetic field model, with both random and coherent components, or just the coherent part, to bracket the impact of the GMF on the dipole anisotropy. This large-scale structure model gives good agreement with both the direction and magnitude of the measured dipole anisotropy and forms the basis for simulations of discrete sources and the inclusion of EGMF effects.

Accelerating the convergence of free electron laser simulations by retrieving a spatially coherent component of microbunching

A simple method to reduce the numerical cost in free electron laser (FEL) simulations is presented, which is based on retrieving a spatially coherent component of microbunching to suppress artifact effects that can potentially overestimate the FEL gain; this significantly reduces the number of macroparticle to reach the numerical convergence and enables the computation of amplified radiation with semianalytical formulas. Examples of FEL simulations performed to demonstrate the proposed method show that the computation time to get a reliable result is reduced by 1–2 orders of magnitude depending on the simulation condition. Published by the American Physical Society 2024

Analytical examination of dynamic elements in modern architectural facades for advanced structural aesthetics

Introduction: The visual appeal and distinctiveness of a building’s external appearance can be enhanced by incorporating aesthetically pleasing and structurally coherent components, such as diagrids and external bracings. These components not only contribute to the building’s visual appeal but also communicate its structural logic. The aim of this research is to investigate how architectural surfaces can contribute to a building’s urban identity by integrating visually appealing and structurally sound structural systems.Methods: The research focuses on analyzing and understanding the formal structure, generating diverse patterns, and assessing their impact on stability. The goal is to develop architectural surface components that are both aesthetically pleasing and proficient in their application. The study involves analyzing architectural projects that address surfaces in alignment with structural connections and various connecting and modulating mechanisms. Significant architectural achievements from different historical periods were examined to construct a comprehensive knowledge framework.Results: The research conducted a detailed analytical and descriptive investigation into the intricate mechanisms of form surfaces within Modernity and Deconstruction architecture and their impact on structural relationships. The study revealed that by integrating structural connections and modulating mechanisms, it is possible to create architectural surface components that enhance a building’s visual appeal, artistic expression, and urban identity while maintaining structural stability and balance.Conclusion: The research concludes that integrating structural connections and modulating mechanisms into architectural surface components can significantly enhance a building’s visual appeal, artistic expression, and urban identity. By developing aesthetically pleasing and structurally sound elements, such as diagrids and external bracings, architects can create buildings that not only communicate their structural logic but also contribute to the overall urban fabric. This study provides valuable insights for architects and designers seeking to enhance the visual and structural qualities of their buildings.

Switchable multi-wavelength coherent polarization manipulation component based on single-layered hollowed S-shaped metasurface

High-performance metasurface polarization manipulation components have important applications in the fields of polarization imaging, polarization detection, and communication. Single-layered metasurface components have attracted a great deal of interest, but it is still a challenge to realize high-efficiency and dynamic polarization manipulation. Combined with coherent control techniques, we propose a single-layered hollowed S-shaped metasurface design that may accomplish multi-wavelength polarization switching in the optical to near-infrared band. The single-layered metasurface enables a real-time switchable effect between dual-wavelength and single-wavelength polarization properties by controlling the phase difference between two coherent counter-propagating lights. The physical mechanism of switchable multi-wavelength coherent polarization manipulation is elucidated based on the electric field distribution of the hollowed S-shaped structure. The effect of metal layer thickness on the switchable coherent polarization properties is investigated in detail. The proposed hollowed S-shaped metasurface significantly improves the polarization performance of the single-layered structure, which is expected to facilitate the development of switchable and compact polarization components.

Harmonic Turbulent Stress Budgets in Forced Transonic Flow over a Bump

The transonic flow over a bump is studied using implicit large-eddy simulations. To replicate rotor/stator interactions occurring in turbomachinery, harmonic forcing of the backpressure is imposed at the outlet. Various perturbation frequencies are prescribed and encompass different regimes, from a fully locked configuration to a decoupling between the unperturbed and forced flows. The mean solution is, however, found to be independent of the perturbation. In a triple-decomposition framework, the coherent component of the flow is extracted by phase averaging. Organized structures of streamwise velocity and turbulence kinetic energy are highlighted. Whereas these structures are of similar shapes beneath the shock system, their extent in the downstream boundary layer is controlled by the frequency of the perturbation. The mean and harmonic turbulent stress budgets are presented. A typical three-peak distribution of mean turbulent diffusion is reported, which is also found to appear for coherent turbulent diffusion. Harmonic production arises mainly from the mean shear and its modulation.

Adaptive beamforming for maximum SINR in the presence of correlated interferences

The conventional steering vector (SV) based beamformers such as the minimum variance distortionless response (MVDR) can suffer from severe performance degradation due to the signal cancellation in the presence of correlated interferences. A partially correlated interference can be decomposed into two components, the coherent component and the other uncorrelated with the desired signal. The SVs of the desired signal and the coherent interference components compose the composite steering vector (CSV). In this paper, a beamforming method is presented that can achieve the maximum signal-to-interference-plus-noise ratio (SINR) via the use of the CSV and the interference covariance matrix (ICM) formed by the uncorrelated interference components only. The estimates of the CSV and the ICM are extracted from the sample matrix through oblique projections. In the estimation process, neither the interference powers nor the desired signal power is estimated, though the direction estimation is carried out using the multiple signal classification (MUSIC). We make theoretical performance analysis, which shows that the CSV based method is more effective as the correlation between the desired signal and the interferences increases and as the desired signal power becomes small. Simulation results demonstrate that it not only converges very quickly to the maximum SINR but also is robust to pointing errors.

Joint analysis and segmentation of time-varying data with outliers

Principal-Component Analysis (PCA) is a fundamental tool in data science and machine learning, used for compressing, analyzing, visualizing, and processing large datasets. At the same time, temporal segmentation is important for coherent component analysis of big data collections generated by time-varying distributions. However, both segmentation and PCA can be critically affected and misled by corrupted points that often exist in big data collections. To address these issues, we propose a novel and robust method for joint segmentation and principal-component analysis of time-varying data, based on L1-norm formulations. Our proposed method estimates robust L1-norm principal components (L1-PCs) over different temporal horizons and combines them to perform outlier detection, data segmentation, and subspace estimation. Numerical studies on real-world data, including videos and smartphone-sensed human body motion measurements, corroborate the merits of the proposed method in terms of segmentation, PCA, and outlier detection/removal.

Long-period directivity pulses of strong ground motion during the 2023 Mw7.8 Kahramanmaraş earthquake

Damages due to large earthquakes are influenced by broadband source effects that remain enigmatic. Here we develop a broadband (0–10 Hz) source model of the disastrous 2023 Mw7.8 Kahramanmaraş, Türkiye, earthquake by modeling recordings of 100 stations. The model combines coherent and incoherent rupture propagation at low and high frequencies, respectively. We adopt a planar 300 km long kinked fault geometry from geology and pre-constrain the slip model from seismic and geodetic data. We demonstrate that the southwestward rupture propagation was delayed by ~15 s and that the observed strong waveform pulses can be explained by the directivity effect due to a specific combination of the coherent and incoherent components. We show that even a rough estimate of major rupture parameters makes the ground motion simulations of such large events possible, and may thus improve the efficiency of rapid, physics-based, shaking estimation for emergency response and seismic hazard assessment.