Incoherent Part Research Articles

Influence of the acceptance angle on the evaluation of reflectance data of randomly rough surfaces using scalar diffraction theory

Apart from coherent reflectance, which corresponds to specular reflection, the values obtained by real spectrophotometers also include contribution from incoherent reflectance, which represents light scattered by the samples and registered by the detector due to its finite acceptance angle. This work aims to investigate the influence of this second part on reflectance spectra measured for samples with randomly rough surfaces. Three silicon samples with roughened surfaces are investigated. The reflectance is measured using a commercial spectrophotometer with acceptance angles restricted by apertures placed in the incident and reflected beam. The proposed method is based on the simultaneous processing of spectral dependencies of reflectance measured with differently-sized apertures. The utilized theoretical approach is based on the scalar diffraction theory. Because the dependencies on both wavelength and acceptance angle are considered, a model providing correct predictions for these dependencies should also correctly describe how is the total reflectance separated into its coherent and incoherent parts. It is shown that the theoretical predictions for incoherent reflectance are consistent with the changes in the diameter of the apertures. It was possible to determine the RMS value of the heights as well as the estimate for the autocorrelation length and additional parameter controlling the course of the autocorrelation function. A short discussion comparing our results with those achieved using methods employed in earlier works is also provided.

Work extraction from quantum coherence in non-equilibrium environment

Ergotropy, which represents the maximum amount of work that can be extracted from a quantum system, has become a focal point of interest in the fields of quantum thermodynamics and information processing. In practical scenarios, the interaction of quantum systems with their surrounding environment is unavoidable. Recent studies have increasingly focused on analyzing open quantum systems affected by non-stationary environmental fluctuations due to their significant impact on various physical scenarios. While much research has concentrated on work extraction from these systems, it often assumes that the environmental degrees of freedom are substantial and that the environment is effectively in equilibrium. This has led us to explore work extraction from quantum systems under non-stationary environmental conditions. In this work, the dynamics of ergotropy will be investigated in a non-equilibrium environment for both Markovian and non-Markovian regime. In this study, both the coherent and incoherent parts of the ergotropy will be considered. It will be shown that for a non-equilibrium environment, the extraction of work is more efficient compared to when the environment is in equilibrium.

Pre-Detection and Pre-Registration Averaging of Full Wave Signals in Airborne LiDAR Bathymetry

A well-known technique to enhance the signal to noise ratio (SNR) of repetitive signals is to average them. The coherent parts of the signal add up constructively while the incoherent parts are averaged out. The prerequisite is that the signals are acquired under conditions of high repeatability, i.e., the signals must be sufficiently similar. In the present technical note, we describe an efficient method for maintaining signal similarity by ensuring spatial and temporal proximity of laser waveform signals obtained by a sensor operated from an airborne platform. The method makes use of a few auxiliary parameters such as laser pulse repetition rate, mirror rotation rate, platform altitude and flight speed. The method can be extended to be operated in real time.

Impact of pulse exposure on chimera state in ensemble of FitzHugh-Nagumo systems.

In this article, we consider the influence of a periodic sequence of Gaussian pulses on a chimera state in a ring of coupled FitzHugh-Nagumo systems. We found that on the way to complete spatial synchronization, one can observe a number of variations of chimera states that are not typical for the parameter range under consideration. For example, the following modes were found: breathing chimera, chimera with intermittency in the incoherent part, traveling chimera with strong intermittency, and others. For comparison, here we also consider the impact of a harmonic influence on the same chimera, and to preserve the generality of the conclusions, we compare the regimes caused by both a purely positive harmonic influence and a positive-negative one.

NOODLE: Joint Cross-View Discrepancy Discovery and High-Order Correlation Detection for Multi-View Subspace Clustering

Benefiting from the effective exploration of the valuable topological pair-wise relationship of data points across multiple views, multi-view subspace clustering (MVSC) has received increasing attention in recent years. However, we observe that existing MVSC approaches still suffer from two limitations that need to be further improved to enhance the clustering effectiveness. Firstly, previous MVSC approaches mainly prioritize extracting multi-view consistency, often neglecting the cross-view discrepancy that may arise from noise, outliers, and view-inherent properties. Secondly, existing techniques are constrained by their reliance on pair-wise sample correlation and pair-wise view correlation, failing to capture the high-order correlations that are enclosed within multiple views. To address these issues, we propose a novel MVSC framework via joi N t cr O ss-view discrepancy disc O very an D high-order corre L ation d E tection ( NOODLE ), seeking an informative target subspace representation compatible across multiple features to facilitate the downstream clustering task. Specifically, we first exploit the self-representation mechanism to learn multiple view-specific affinity matrices, which are further decomposed into cohesive factors and incongruous factors to fit the multi-view consistency and discrepancy, respectively. Additionally, an explicit cross-view sparse regularization is applied to incoherent parts, ensuring the consistency and discrepancy to be precisely separated from the initial subspace representations. Meanwhile, the multiple cohesive parts are stacked into a three-dimensional tensor associated with a tensor-Singular Value Decomposition (t-SVD) based weighted tensor nuclear norm constraint, enabling effective detection of the high-order correlations implicit in multi-view data. Our proposed method outperforms state-of-the-art methods for multi-view clustering on six benchmark datasets, demonstrating its effectiveness.

TAGGING EFFICIENCY ESTIMATION IN EXPERIMENTS WITH A COHERENT BREMSSTRAHLUNG BEAM

The angular dependences of the coherent and incoherent parts of the coherent bremsstrahlung (CB) are different, thus the CB beam tagging efficiency differs from that of the bremsstrahlung. It has energy dependence close to the CB beam spectrum and depends on the CB peak energy. Thus, in the course of the cross section measurements, the systematic, measurements of the tagging efficiency should be usually produced. The paper shows that tagging efficiency can be estimated computationally by taking into account the background contribution to the detectors of the tagging system. This allows one to get cross sections simultaneously with the cross section asymmetry measurements in the case when the systematic tagging efficiency measurements were not performed.

Localization effects in disordered quantum batteries.

We investigate the effect of localization on the local charging of quantum batteries (QBs) modeled by disordered spin systems. Two distinct schemes based on the transverse-field random Ising model are considered, with Ising couplings defined on a Chimera graph and on a linear chain with up to next-to-nearest-neighbor interactions. By adopting a low-energy demanding charging process driven by local fields only, we obtain that the maximum extractable energy by unitary processes (ergotropy) is highly enhanced in the ergodic phase in comparison with the many-body localization (MBL) scenario. As we turn off the next-to-nearest-neighbor interactions in the Ising chain, we have the onset of the Anderson localization phase. We then show that the Anderson phase exhibits a hybrid behavior, interpolating between large and small ergotropy as the disorder strength is increased. We also consider the splitting of total ergotropy into its coherent and incoherent contributions. This incoherent part implies in a residual ergotropy that is fully robust against dephasing, which is a typical process leading to the self-discharging of the battery in a real setup. Our results are experimentally feasible in scalable systems, such as in superconducting integrated circuits.

Resonance fluorescence in Λ, V and Ξ - type three-level configurations

We theoretically study the resonance fluorescence spectra of the lambda (Λ), vee (V) and cascade (Ξ) type three-level configurations. It is shown that each system with two detuning frequencies can be modelled using the SU(3) symmetry group to derive a generalized optical Bloch equation. For each configuration, this equation is solved to calculate the two-time correlation function by invoking the quantum regression theorem. The incoherent part of the power spectra gives the characteristic multi-peak fluorescence profiles which are different for different configurations. We also discuss how the dressed-state structure of such system can explain the origin of quintuplet profile of the fluorescent spectrum.

Heteroclinic switching between chimeras in a ring of six oscillator populations.

In a network of coupled oscillators, a symmetry-broken dynamical state characterized by the coexistence of coherent and incoherent parts can spontaneously form. It is known as a chimera state. We study chimera states in a network consisting of six populations of identical Kuramoto-Sakaguchi phase oscillators. The populations are arranged in a ring, and oscillators belonging to one population are uniformly coupled to all oscillators within the same population and to those in the two neighboring populations. This topology supports the existence of different configurations of coherent and incoherent populations along the ring, but all of them are linearly unstable in most of the parameter space. Yet, chimera dynamics is observed from random initial conditions in a wide parameter range, characterized by one incoherent and five synchronized populations. These observable states are connected to the formation of a heteroclinic cycle between symmetric variants of saddle chimeras, which gives rise to a switching dynamics. We analyze the dynamical and spectral properties of the chimeras in the thermodynamic limit using the Ott-Antonsen ansatz and in finite-sized systems employing Watanabe-Strogatz reduction. For a heterogeneous frequency distribution, a small heterogeneity renders a heteroclinic switching dynamics asymptotically attracting. However, for a large heterogeneity, the heteroclinic orbit does not survive; instead, it is replaced by a variety of attracting chimera states.

Wavelet analysis of supersonic shock-boundary-layer interaction

We present a wavelet analysis of supersonic shock-boundary-layer interaction. We have used direct numerical simulation data for supersonic flow over a compression ramp and performed orthogonal anisotropic wavelets. The wavelet-based method of extracting coherent structures is applied to the flow vorticity field, decomposed into coherent and incoherent contributions using thresholding of the wavelet coefficients. The statistics of the coherent part of vorticity are close to the statistics of the total field. The study aims to improve our understanding of the shock-boundary-layer interaction, the role of vorticity, and the relationship between the flow's coherent and incoherent vorticity components with the near-wall sound. Our analysis shows a substantial correlation between the incoherent part of vorticity components and wall-pressure fluctuations.

Coherent structure detection and the inverse cascade mechanism in two-dimensional Navier–Stokes turbulence

Coherent structures in two-dimensional Navier–Stokes turbulence are ubiquitously observed in nature, experiments and numerical simulations. The present study conducts a comparison between several structure detection schemes based on the Okubo–Weiss criterion, the vorticity magnitude and Lagrangian coherent structures (LCSs), focusing on the inverse cascade in two-dimensional hydrodynamic turbulence. A recently introduced vortex scaling phenomenology (Burgess & Scott, J. Fluid Mech., vol. 811, 2017, pp. 742–756) allows the quantification of the respective thresholds required by these methods based on physical properties of the flow. The resulting improved comparability allows us to identify characteristic relative differences in the detection sensitivity between the employed structure detection techniques. With respect to the inverse cascade of energy, coherent structures contribute, as expected, substantially less to the cross-scale flux than the residual incoherent parts of the flow although the energetically dominant coherent structures lead to an important large-scale deformation of the energy spectrum. This cascade inactivity can be understood by an increased misalignment of strain-rate and subgrid stress tensors within coherent structures. At the same time, the structures exhibit strong and localised nonlinear cross-scale interactions that appear to stabilise them. We quantify and interpret the resulting shape preservation of coherent structures in terms of a multi-scale gradient approach (Eyink, J. Fluid Mech., vol. 549, 2006, pp. 191–214) as the depletion of strain rotation and vorticity gradient stretching whereas the dynamics of the residual fluctuations are consistent with the vortex thinning picture.

Evolution of the spectral lineshape at the magnetic transition in Sr$$_2$$IrO$$_4$$ and Sr$$_3$$Ir$$_2$$O$$_7$$

Sr $$_2$$ IrO $$_4$$ and Sr $$_3$$ Ir $$_2$$ O $$_7$$ form two families of spin-orbit Mott insulators with quite different charge gaps and an antiferromagnetic (AF) ground state. This offers a unique opportunity to study the impact of long-range magnetic order in Mott insulators. It appears to play a different role in the two families, as there is almost no change of the resistivity at the magnetic transition $$T_N$$ in Sr $$_2$$ IrO $$_4$$ and a large one in Sr $$_3$$ Ir $$_2$$ O $$_7$$ . We use angle-resolved photoemission to study the evolution of the spectral lineshape through the magnetic transition. We use Ru and La substitutions to tune $$T_N$$ and discriminate changes due to temperature from those due to magnetic order. We evidence a shift and a transfer of spectral weight in the gap at $$T_N$$ in Sr $$_3$$ Ir $$_2$$ O $$_7$$ , which is absent in Sr $$_2$$ IrO $$_4$$ . We assign this behavior to a significantly larger coherent contribution to the spectral lineshape in Sr $$_3$$ Ir $$_2$$ O $$_7$$ , which evolves strongly at $$T_N$$ . On the contrary, the Sr $$_2$$ IrO $$_4$$ lineshape is dominated by the incoherent part, which is insensitive to $$T_N$$ . We compare these findings to theoretical expectations of the Slater vs Mott antiferromagnetism within dynamical mean field theory.

Quantum Optical Description of Radiation by a Two-Level System in Strong Laser Fields

We develop a quantum optical description of radiation from a two-level system (TLS) in strong laser fields, which provides a clear insight into the final states of the TLS and the harmonics field. It is shown that there are two emission channels: the Rayleigh-like channel and the Raman-like channel, which correspond to the TLS ending up in the ground state and excited state after the emission, respectively. The numerical result shows that the harmonics are mainly produced by the Rayleigh-like channel. In addition, according to the coherence of emission among the emitters, the radiation is divided into coherent parts that result from the semi-classical dipole oscillation and incoherent parts that result from the quantum fluctuations of the dipole moment. In the weak field limits, the Rayleigh-like channel corresponds to the coherent parts, and the Raman-like channel corresponds to the incoherent parts. However, in strong laser fields, both channels contribute to coherent and incoherent radiation, and how much they contribute depends on the final excitation. By manipulating the laser field, we can make the Rayleigh-like channel produce either coherent or incoherent radiation.

Propagation of 2-D SH waves in random media: Insights from ab initio numerical simulations and transport theory

Increasing the frequency range of physics-based predictions of earthquake ground motions requires to account for small-scale heterogeneities, which can only be described in a stochastic way. Although many studies have addressed the impact of random heterogeneities on ground motion intensity parameters obtained by numerical simulation, very few have verified the accuracy of their numerical solutions or controlled the scattering regime they were simulating. Here we present a comprehensive analysis ofSHwave propagation in 2D random media which covers a broad range of propagation regimes from ballistic to diffusive. The coherent and incoherent parts of the wavefield are examined independently. The random media consist in correlated density and velocity fluctuations described by a von Kármán autocorrelation function with a Hurst coefficient of 0.25 and a correlation lengtha= 500 m. The Birch correlation coefficient which relates density to velocity fluctuations takes 4 possible values between 0.5 and 1, and the standard deviation of the perturbations is either 5% or 10%. Spectral element simulations of SH wave propagation excited by a plane wave are performed for normalized wavenumbers (ka) up to 5. Analysis of the decay of the coherent wave amplitude, obtained through different averaging procedures, allows for a direct measure of the scattering attenuation, which we successfully compare with the predictions of the Dyson mean field theory. We also present the comparison between the energy envelopes measured from the synthetics and their theoretical counterpart provided by the radiative transfer theory and the diffusion approximation. Excellent agreement is found between numerical simulations and theoretical predictions of radiative transfer theory for the mean intensity. The numerical study highlights the difference of attenuation length between the mean field and the mean intensity. In the forward scattering regime, the peak intensity appears to decay exponentially over a length scale known as the transport mean free path. Furthermore, the fluctuations of intensity in the ballistic peak exhibit a transition from Log-normal to Exponential statistics. This transition occurs for a propagation distance of the order of the mean free path, which offers an alternative method of estimating this parameter.

Charging quantum batteries via Otto machines: Influence of monitoring

The charging of a quantum battery by a four-stroke quantum machine that works either as an engine or a refrigerator is investigated. The presented analysis provides the energetic behavior of the combined system in terms of the heat and workflows of the machine, the average, and variance of the battery's energy as well as the coherent and incoherent parts of its ergotropy. To monitor the battery state its energy is measured either after the completion of any cycle or after a prescribed number of cycles is carried out. The resulting battery performances greatly differ for those two cases. During the first charging epoch with an engine, the regular measurements speed up the charging, whereas the gain of ergotropy is more pronounced in the absence of measurements. In a later stage, the engine fails to work as such while it still continues charging the battery that eventually reaches the maximally charged state in the absence of intermediate measurements and a suboptimally charged state for a periodically measured battery. For a refrigerator, the charging of the measured battery also proceeds faster during the first epoch. Only during the second stage when the machine fails to extract heat from the cold bath the influence of the measurements become less pronounced leading to rather similar asymptotic states for the two measurement scenarios.

Juxtaposition as literary feature in Psalm 116

Identifying literary devices used in the (Hebrew) Old Testament serves as an aid to the understanding of a particular passage. In this contribution, juxtaposition as a literary device in Psalm 116 was investigated. A brief overview of the main problems in the research history of the Psalm is given, highlighting the date and composition, as well as the enigmatic verse 15. Drawing on other definitions of the term juxtaposition, the term was defined as a literary device used to imply comparison and especially contrast. In the rest of the article, juxtaposition as a literary device in this Psalm was investigated and eight different modes of juxtaposition were identified. It is argued that juxtaposition is the dominating and most prominent literary device that occurs in the Psalm. Finally, the contribution that the identification of juxtaposition as literary device makes to the understanding of this Psalm, was briefly discussed. Methodologically, the literary feature of juxtaposition was demonstrated through a careful reading of the text of Psalm 116. Once that was done, it became apparent that juxtaposition plays an important part in this psalm. The juxtaposition is of death versus life: it is an experience of the absence of YHWH in a Sheol-like situation in juxtapposition to the presence of YHWH in the temple; the temporal shift between present and past and the juxtaposition between the individual believer vis-à-vis the community of believers, all adds up to the conclusion that the Psalm displays a coherent unity, exactly because of the literary device of juxtaposition. Reading Scripture with a sensitivity to the literary devices that may be detected in passages of Scripture, is a rewarding exercise. It opens new possibilities to explore the meaning(s) these ancient texts have also for modern-day readers of the Bible.Contribution: Although juxtaposition as literary device has been pointed out in previous research publications on Psalm 116, the specific contribution of this article is to demonstrate that juxtaposition is the dominating literary device in the psalm. Psalm 116 has been seen in the past as a disunity made up of incoherent parts. The frequent occurrence of juxtaposition throughout the psalm adds to the unity of the psalm. Recognising juxtaposition as the dominating literary device adds new light on the theological meaning of the psalm and this fits in well with the focus of In die Skriflig to come to a better understanding of the Bible.

A New Low-Rank Structurally Incoherent Algorithm for Robust Image Feature Extraction

In order to solve the problem in which structurally incoherent low-rank non-negative matrix decomposition (SILR-NMF) algorithms only consider the non-negativity of the data and do not consider the manifold distribution of high-dimensional space data, a new structurally incoherent low rank two-dimensional local discriminant graph embedding (SILR-2DLDGE) is proposed in this paper. The algorithm consists of the following three parts. Firstly, it is vital to keep the intrinsic relationship between data points. By the token, we introduced the graph embedding (GE) framework to preserve locality information. Secondly, the algorithm alleviates the impact of noise and corruption uses the L1 norm as a constraint by low-rank learning. Finally, the algorithm improves the discriminant ability by encrypting the structurally incoherent parts of the data. In the meantime, we capture the theoretical basis of the algorithm and analyze the computational cost and convergence. The experimental results and discussions on several image databases show that the proposed algorithm is more effective than the SILR-NMF algorithm.

Separation of coherent and incoherent light by using optical vortex via spatial mode projection

We present a spatial light filter method which can distinguish light by its coherency. The unique orbital angular momentum and spiral phase front properties of the vortex beam generate a null intensity center area that can serve as a spatial window to filter out incoherent light. A spatial light modulator can be used to modulate the wavefront of the incident light beam. Thanks to diffraction, the spectra from the coherent and incoherent part are spatially separated at the backfocal plane of a lens. The coherent part forms a ring, and the incoherent part forms a spot in the null intensity center of the ring. This method offers a new perspective to enhance the signal-to-noise ratio in the field of applied optics, such as optical communication, and active remote sensing, such as light detection and ranging.

Patched patterns and emergence of chaotic interfaces in arrays of nonlocally coupled excitable systems.

We disclose a new class of patterns, called patched patterns, in arrays of non-locally coupled excitable units with attractive and repulsive interactions. The self-organization process involves the formation of two types of patches, majority and minority ones, characterized by uniform average spiking frequencies. Patched patterns may be temporally periodic, quasiperiodic, or chaotic, whereby chaotic patterns may further develop interfaces comprised of units with average frequencies in between those of majority and minority patches. Using chaos and bifurcation theory, we demonstrate that chaos typically emerges via a torus breakup and identify the secondary bifurcation that gives rise to chaotic interfaces. It is shown that the maximal Lyapunov exponent of chaotic patched patterns does not decay, but rather converges to a finite value with system size. Patched patterns with a smaller wavenumber may exhibit diffusive motion of chaotic interfaces, similar to that of the incoherent part of chimeras.

Development of a portable measuring system using ultrasound guided and surface waves to characterize concrete structures

A portable system was developed to be used in lab and on field. The system is composed of one emitter and 60 receivers. All of them are Dry Point Contact sensors, P-wave, S1803 from ACSYS, with a nominal frequency of 100kHz and a wide frequency range from 15kHz to 175kHz. The 60 receivers are equally spaced of 5mm which enables to make measurements over 30cm. The acquisition is made with a two-channels A1560 ACSYS device. We developed an electronic part to multiplex the acquisition of all the receiver signals. A Raspberry-Pi device is used to control four 16-channels analogic multiplexers. We designed and manufactured with a 3D-printer a holder for the DPC sensors and the electronic part. The A1560 device and the Raspberry-pi are controlled with a Python program on a digital tablet. For one acquisition, which lasts a few seconds, 60 a-scans are registered. Several acquisitions are repeated by moving the system of a few centimeters. The results are averaged to lower the incoherent part of the signals due to multi-scattering effects on concrete aggregates. The result is processed with a p-w Transform to get the dispersion diagram and to assess the dispersion curve. In the case of surface waves, when the structure thickness is larger than the smallest wavelength, the dispersion curve can be inversed with a tool like Dinver from Geopsy. The final result is the ultrasound speed profile with depth. In the case of Lamb waves, the dispersion curve is compared to A0 and S0 modes calculated with a tool like Disperse form Imperial College or CIVA frome CEA. This efficient tool is used to study different concrete structures: - thick structure with concrete cover affected by carbonation or leaching, - thin structure like 6cm-thickness and 60cm-diameter concrete/steel/concrete pipes used in the nuclear industry.