Spectral Pairs Research Articles

Statistical Investigation of Wave Propagation in the Quiet-Sun Using IRIS Spectroscopic Observations

In this analysis, we use spectroscopic observations of the quiet Sun made by the IRIS instrument and investigate wave propagation. We analyze various spectral lines formed in different atmospheric layers, such as the photosphere, chromosphere, and transition region. We examine the Doppler velocity time series at various locations in the quiet Sun to determine the dominant oscillation periods. Our results executing statistical analysis resemble those of the classical physical scenario, indicating that the photosphere is mainly characterized by the dominant 5 minute period, while the chromosphere is primarily associated with the 3 minute oscillation period. In the transition region, we observe a variety of oscillation periods, with dominant periods of 3, 8, and 12 minutes. We estimate the cutoff frequency by deducing the phase difference between two Doppler velocity time series obtained from spectral line pairs in different atmospheric layers formed at different temperatures. This reveals a significant correlation between 3 minute periods in the transition region and photospheric oscillations, suggesting that these oscillations in the transition region might propagate from the photosphere. Additionally, we analyze the phase difference between chromospheric oscillations and photospheric oscillations, demonstrating that only the 3 minute oscillations propagate upward. Based on the statistical analyses, we suggest the presence of magnetoacoustic waves in the solar atmosphere, some of which are propagating from the lower solar atmosphere upward, while some others are propagating downward. The transition region carries both long-period oscillations generated in situ and some photospheric oscillations that are also able to reach there from below.

Precise Spectral Overlap-Based Donor-Acceptor Pair for a Sensitive Traffic Light-Typed Bimodal Multiplexed Lateral Flow Immunoassay.

Bimodal-type multiplexed immunoassays with complementary mode-based correlation analysis are gaining increasing attention for enhancing the practicability of the lateral flow immunoassay (LFIA). Nonetheless, the restriction in visually indistinguishable multitargets induced by a single fluorescent color and difficulty in single acceptor ineffectual fluorescence quenching due to the various spectra of multiple different donors impede the further execution of colorimetric-fluorescence bimodal-type multiplexed LFIAs. Herein, the precise spectral overlap-based donor-acceptor pair construction strategy is proposed by regulating the size of the nanocore, coating it with an appropriate nanoshell, and selecting a suitable fluorescence donor with distinct colors. By in situ coating Prussian blue nanoparticles (PBNPs) on AuNPs with a tunable size and absorption spectrum, the resultant APNPs demonstrate efficient fluorescence quenching ability, higher colloidal stability, remarkable colorimetric intensity, and an enhanced antibody coupling efficiency, all of which facilitate highly sensitive bimodal-type LFIA analysis. Following integration with competitive-type immunoreaction, this precise spectral overlap-supported spatial separation traffic light-typed colorimetric-fluorescence dual-response assay (coined as the STCFD assay) with the limits of detection of 0.013 and 0.152 ng mL-1 for ractopamine and clenbuterol, respectively, was proposed. This work illustrates the superiority of the rational design of a precise spectral overlap-based donor-acceptor pair, hinting at the enormous potential of the STCFD assay in the point-of-care field.

Hamiltonian Monodromy via spectral Lax pairs

Hamiltonian Monodromy is the simplest topological obstruction to the existence of global action-angle coordinates in a completely integrable system. We show that this property can be studied in a neighborhood of a focus-focus singularity by a spectral Lax pair approach. From the Lax pair, we derive a Riemann surface which allows us to compute in a straightforward way the corresponding Monodromy matrix. The general results are applied to the Jaynes–Cummings model and the spherical pendulum.

Enhancement of Stopping Power Ratio (SPR) Estimation Accuracy through Image-Domain Dual-Energy Computer Tomography for Pencil Beam Scanning System: A Simulation Study.

Our study aims to quantify the impact of spectral separation on achieved theoretical prediction accuracy of proton-stopping power when the volume discrepancy between calibration phantom and scanned object is observed. Such discrepancy can be commonly seen in our CSI pediatric patients. One of the representative image-domain DECT models is employed on a virtual phantom to derive electron density and effective atomic number for a total of 34 ICRU standard human tissues. The spectral pairs used in this study are 90 kVp/140 kVp, without and with 0.1 mm to 0.5 mm additional tin filter. The two DECT images are reconstructed via a conventional filtered back projection algorithm (FBP) on simulated noiseless projection data. The best-predicted accuracy occurs at a spectral pair of 90 kVp/140 kVp with a 0.3 mm tin filter, and the root-mean-squared average error is 0.12% for tissue substitutes. The results reveal that the selected image-domain model is sensitive to spectral pair deviation when there is a discrepancy between calibration and scanning conditions. This study suggests that an optimization process may be needed for clinically available DECT scanners to yield the best proton-stopping power estimation.

Oxygen bounty for Earth-like exoplanets: spectra of Earth through the Phanerozoic

ABSTRACT In the search for life in the Universe, Earth provides a template of evolution for the one habitable planet we know. Earth’s atmospheric composition has changed significantly throughout its history. The last 500 Myr – the Phanerozoic Eon, which includes the origins of animals, dinosaurs, and land plants – saw oxygen rise from ≤10 per cent to 35 per cent. But the resulting transmission spectra are a crucial missing piece in our search for signs of life in exoplanet atmospheres. Here, we simulate the atmosphere and transmission spectra of the Phanerozoic, using estimates from established climate models, and present the first high-resolution transmission spectra for Phanerozoic Earth. We demonstrate that the spectral biosignature pairs O2 + CH4 and O3 + CH4 in the atmosphere of a transiting Earth-like planet would indicate a biosphere, with O2 and O3 features potentially stronger than for modern Earth. The full model and high-resolution transmission spectra, covering 0.4–20 µm, are available online and provides a tool to plan and optimize observations, train retrieval methods, and interpret upcoming observations with ground- and space-based telescopes.

Vector-valued nonuniform multiresolution analysis associated with linear canonical transform domain

A generalization of Mallat?s classical multiresolution analysis, based on the theory of spectral pairs, was considered in two articles by Gabardo and Nashed. In this setting, the associated translation set is no longer a discrete subgroup of R but a spectrum associated with a certain one-dimensional spectral pair and the associated dilation is an even positive integer related to the given spectral pair. In this paper, we continue the study based on this nonstandard setting and introduce vector-valued nonuniform multiresolution analysis associated with linear canonical transform (LCT-VNUMRA) where the associated subspace V?0 of the function space L2 (R,CM) has an orthonormal basis of the form {?(x ? ?)e? ??A B (t2??2)} ??? where ? = {0, r/N} + 2Z,N ? 1 is an integer and r is an odd integer such that r and N are relatively prime. We establish a necessary and sufficient condition for the existence of associated wavelets and derive an algorithm for the construction of vector-valued nonuniform multiresolution analysis starting from a vector refinement mask with appropriate conditions

Simultaneous Measurement of Multiparameter of Diesel Engine Exhaust Based on Mid-Infrared Laser Absorption Spectroscopy

Exhaust parameters of an engine carry vital information that can help to understand its transient duty cycles. We developed a mid-infrared wavelength modulation spectroscopic sensor for simultaneous measurement of exhaust temperature, pressure, and NO and NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentrations by using two quantum cascade lasers (QCLs) for the first time. The dual-channel signals were demodulated and normalized respectively with a specially designed digital lock-in amplifier, achieving calibration-free measurements to adapt to the harsh and variable working conditions of diesel engines. Two-line thermometry was performed using a newly selected spectral line pair of NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (1629.85 and 1630.33 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ). Simultaneous measurement of the quadruple parameter of diesel exhaust, i.e. temperature, pressure, and NO and NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentrations, was first achieved using only three spectral lines and a developed multi-parameter inversion algorithm. The feasibility of the sensor was demonstrated in field tests in an in-service vehicle. Exhaust temperature, pressure, and NO and NO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentrations were obtained continuously with 0.1 s time intervals, which clearly show these parameters in the transition and steady stages of the engine, respectively. The method and results can be used to evaluate the engine operation performance and combustion diagnostics.

Generalized inequalities for nonuniform wavelet frames in linear canonical transform domain

A constructive algorithm based on the theory of spectral pairs for constructing nonuniform wavelet basis in L2(R) was considered by Gabardo and Nashed. In this setting, the associated translation set is a spectrum ? which is not necessarily a group nor a uniform discrete set, given ? = {0, r/N} + 2Z, where N ? 1 (an integer) and r is an odd integer with 1 ? r ? 2N?1 such that r and N are relatively prime and Z is the set of all integers. In this article, we continue this study based on non-standard setting and obtain some inequalities for the nonuniform wavelet system {f?j,?(x) = (2N)j/2f((2N)jx??)e???A/B (t2??2), j ? Z, ? ? ?}to be a frame associated with linear canonical transform in L2(R). We use the concept of linear canonical transform so that our results generalise and sharpen some well-known wavelet inequalities.

Deep learning-based method for automatic resolution of gas chromatography-mass spectrometry data from complex samples

Modern gas chromatography-mass spectrometry (GC-MS) is the workhorse for the high-throughput profiling of volatile compounds in complex samples. It can produce a considerable amount of two-dimensional data, and automatic methods are required to distill chemical information from raw GC-MS data efficiently. In this study, we proposed an Automatic Resolution method (AutoRes) based on pseudo-Siamese convolutional neural networks (pSCNN) to extract the meaningful features swamped by the noises, baseline drifts, retention time shifts, and overlapped peaks. Two pSCNN models were trained with 400,000 augmented spectral pairs, respectively. They can predict the selective region (pSCNN1) and elution region (pSCNN2) of compounds in an untargeted manner. The accuracies of the pSCNN1 model and the pSCNN2 model on their test sets are 99.9% and 92.6%, respectively. Then, the chromatographic profile of each component was automatically resolved by full rank resolution (FRR) based on the predicted regions by these models. The performance of AutoRes was evaluated on the simulated and plant essential oil datasets. Compared to AMDIS and MZmine, AutoRes resolves more reasonable mass spectra, chromatograms, and peak areas to identify and quantify compounds. The average match scores of AutoRes (925 and 936) outperformed AMDIS (909 and 925) and MZmine (888 and 916) when resolving mass spectra from overlapped peaks on the Set Ⅰ and Set Ⅱ of plant essential oil dataset and matching them against the NIST17 library. It extracted peak areas and mass spectra automatically from 10 GC-MS files of plant essential oils, and the entire process was completed in 8 min without any prior information or manual intervention. It is implemented in Python and is available as an open-source package at https://github.com/dyjfan/AutoRes.

Enhancing UAV images to improve the observation of submerged whales using a water column correction method

Enhancing <scp>UAV</scp> images to improve the observation of submerged whales using a water column correction method

Establishing an isoelectronic line ratio temperature diagnostic for soft X-ray absorption spectroscopy

For diagnosing temperatures of high-energy-density plasmas, relying on the ratio of a pair of isoelectronic spectral lines provides the alternative of “matched charge-state transits in different elements” to the more conventional, “unmatched charge-state transits in the same-element” spectral-line-ratio technique. In contrast to a novel previous establishment of isoelectronic emission-line ratio determination of plasma temperature, this report determines plasma temperature from the ratio of isoelectronic absorption spectral line pairs. The feasibility of this technique is assessed from experimentally acquired transmission spectra, spanning the 7–15 Å range, through a 0.4μm MgO-NaF foil, tamped with CH, x-ray-radiation heated by a z-pinch dynamic hohlraum (ZPDH), and backlit by the brief X-ray burst upon imploding-wire stagnation on the Z pulsed-power facility at Sandia National Laboratories. As expected from the slight difference between interstage and isoelectronic absorption processes, a quantitative comparison between the value of isoelectronic-absorption-derived temperature and the value of inter-stage-absorption-derived temperature is shown to yield a well correlated, slight difference in inferred values of plasma temperature associated with local thermodynamic equilibrium.

Three-dimensional reconstruction of flame temperature and H2O concentration using water vapor integrated spectral band emission

Efficient and accurate reconstruction of flame temperature and species concentration is very useful for combustion monitoring. In this work, the integrated spectral band ratio (ISBR) method, which uses the ratio of two integrated spectral radiative intensities to infer temperature, is applied to reconstruct three-dimensional flame temperature and H2O concentration distributions. First, the ratio of two integrated spectral radiative intensities is justified by gas radiation theory to only depend on gas temperature, and the influence of gas concentration and pressure on the ratio is negligible. Then, a spectral band pair is carefully selected for the measurement with an atmospheric path between the detector and the flame. In the selected spectral bands, CO2 and CO emissions are negligible compared to H2O emission, and atmospheric absorption can be ignored. Meanwhile, gas temperature is monotonically related to the ratio of integrated spectral radiative intensities. When the uncertainty of the ratio is 2%, the error of reconstructed temperature is less than 38K with gas temperature close to 3000K, and the error decreases as the gas temperature goes down. Finally, numerical experiments on reconstruction of axisymmetric and non-axisymmetric flames are carried out. Results show that three-dimensional distributions of flame temperature and H2O concentration can be reconstructed with high accuracy.

Discrete vector-valued nonuniform Gabor frames

Gabor frames have interested many mathematicians and physicists due to their potential applications in time-frequency analysis, in particular, signal processing. A Gabor system is a collection of vectors which is obtained by applying modulation and shift operators to non-zero functions in signal spaces. In many applications, for example, signal processing related to Gabor systems, the corresponding shifts may not be uniform. That is, the set associated with shifts may not be a group under usual addition. We analyze discrete vector-valued nonuniform Gabor frames (DVNUG frames, in short) in discrete vector-valued nonuniform signal spaces, where the indexing set associated with shifts may not be a subgroup of real numbers under usual addition, but a spectrum which is based on the theory of spectral pairs. First, we give necessary and sufficient conditions for the existence of DVNUG Bessel sequences in discrete vector-valued nonuniform signal spaces in terms of Fourier transformations of the modulated window sequences. We provide a characterization of DVNUG frames in discrete vector-valued nonuniform signal spaces. It is shown that DVNUG frames are stable under small perturbation of window sequences associated with given discrete vector-valued nonuniform Gabor systems. We observed that the arithmetic mean sequences associated with window sequences of a given DVNUG frame collectively constitute a discrete nonuniform Gabor frame. Finally, we discuss an interplay between window sequences of DVNUG systems and their corresponding coordinates.

On the Riemann-Hilbert problem for the integrable three-coupled Hirota system with a [formula omitted] matrix Lax pair

In this work, we will investigate a complete integrable variable coefficient three-coupled Hirota system, which possesses a generalization of fourth-order matrix spectral problem AKNS type Lax pair. With the help of the unified transform method, the initial-boundary value problems (IBVPs) of the three-coupled Hirota equation on the half-line will be discussed. In other words, one can obtain the solutions of the three-coupled Hirota equation by solving a fourth-order matrix Riemann-Hilbert problem in the complex ξ-plane. Furthermore, we will show that three spectral functions φ(ξ),ϕ(ξ) and ψ(ξ) are not independent but meet a key relationship, i.e. the so-called global relation.

Fractional vector-valued nonuniform MRA and associated wavelet packets on $$L^2\big ({\mathbb {R}},{\mathbb {C}}^M\big )$$

A generalization of Mallat’s classical multiresolution analysis, based on the theory of spectral pairs, was considered in two articles by Gabardo and Nashed. In this setting, the associated translation set is no longer a discrete subgroup of \({\mathbb {R}}\) but a spectrum associated with a certain one-dimensional spectral pair and the associated dilation is an even positive integer related to the given spectral pair. In this paper, we continue the study based on this nonstandard setting and introduce fractional vector-valued nonuniform multiresolution analysis (Fr-VNUMRA) where the associated subspace of the function space has an orthonormal basis. We establish a necessary and sufficient condition for the existence of associated wavelets and derive an algorithm for the construction of fractional vector-valued nonuniform multiresolution analysis starting from a vector refinement mask with appropriate conditions. Nevertheless, to extend the scope of the present study, we worked to construct the associated wavelet packets for such an MRA and investigate their properties by means of fractional Fourier transform.

On a quadratic form associated with a surface automorphism and its applications to Singularity Theory

We study the nilpotent part N′ of a pseudo-periodic automorphism h of a real oriented surface with boundary Σ. We associate a quadratic form Q defined on the first homology group (relative to the boundary) of the surface Σ. Using the twist formula and techniques from mapping class group theory, we prove that the form Q̃ obtained after killing kerN is positive definite if all the screw numbers associated with certain orbits of annuli are positive. We also prove that the restriction of Q̃ to the absolute homology group of Σ is even whenever the quotient of the Nielsen–Thurston graph under the action of the automorphism is a tree. The case of monodromy automorphisms of Milnor fibers Σ=F of germs of curves on normal surface singularities is discussed in detail, and the aforementioned results are specialized to such situation. This form Q is determined by the Seifert form but can be much more easily computed. Moreover, the form Q̃ is computable in terms of the dual resolution or semistable reduction graph, as illustrated with several examples. Numerical invariants associated with Q̃ are able to distinguish plane curve singularities with different topological types but same spectral pairs. Finally, we discuss a generic linear germ defined on a superisolated surface. In this case the plumbing graph is not a tree and the restriction of Q̃ to the absolute monodromy of Σ=F is not even.

Contributed Session III: Disentangling object color from illuminant color: The role of color shifts

Research has shown that disentangling surface and illuminant colors was possible based on various scene statistics. This study investigates the statistical cues induced by the chromatic effects of interreflections. We present a numerical analysis of ambiguous spectral pairs, in which the spectral power distribution of the illuminant in one scene matched the surface reflectance function in the other scene and vice versa. If the scenes are flat or convex and perfectly matte (Lambertian), the reflected light spectra of both cases are identical. However, the incident light undergoes interreflections for concave scenes. The spectral power of interreflections will be absorbed spectrally in an exponential way, dependent on the number of interreflections. We found that this causes systematic shifts towards the spectral reflectance peaks, resulting in brightness, saturation and hue shifts. Those paired cases' color differences (CIEDE2000) are so large that humans would be able to observe them if viewed simultaneously. In addition, we find that the color shifts cause qualitatively different gradients for chromatic materials and achromatic light and vice versa. Further psychophysical testing is necessary to see whether the different color shifts for the two cases can be recognized in isolation due to material or light properties. Moreover, the light densities and light vectors are spectrally different for these cases, creating different appearances of 3D objects in non-empty rooms.

High capacity speech steganography for the G723.1 coder based on quantised line spectral pairs interpolation and CNN auto-encoding

High capacity speech steganography for the G723.1 coder based on quantised line spectral pairs interpolation and CNN auto-encoding

Joint Disparity Estimation and Pseudo NIR Generation From Cross Spectral Image Pairs

Cross spectral stereo matching is a challenging task due to different spectral properties causing unreliable results in correspondence estimation. In this paper, we propose joint disparity estimation and pseudo near infrared (NIR) generation from cross spectral image pairs. To bridge the spectral gap between paired images, we adopt differential map operations and non-local blocks to improve the local attention and global attention of the network. The proposed network is based on unsupervised learning that consists of one encoder and two decoders, which performs both spectral translation and disparity estimation. For cooperative learning, we use difference map operation to connect two decoders, thus improving the inference ability of the decoder in regions even with large spectral differences. Experimental results show that the proposed network achieves good performance in cross spectral stereo matching for unreliable regions such as shadows and glasses. Moreover, the proposed network generates pseudo NIR images nearly the same as the ground truth even in the regions with large spectral difference. Besides, we achieve real-time speed of 27 FPS for <inline-formula> <tex-math notation="LaTeX">$582\times 429$ </tex-math></inline-formula> image pairs on RTX 2060 6G GPU due to the low computational complexity.

Water column compensation workflow for hyperspectral imaging data

Our article describes a data processing workflow for hyperspectral imaging data to compensate for the water column in shallow, clear to moderate optical water types. We provide a MATLAB script that can be readily used to implement the described workflow. We break down each code segment of this script so that it is more approachable for use and modification by end users and data providers. The workflow initially implements the method for water column compensation described in Lyzenga (1978) and Lyzenga (1981), generating depth invariant indices from spectral band pairs. Given the high dimensionality of hyperspectral imaging data, an overwhelming number of depth invariant indices are generated in the workflow. As such, a correlation based feature selection methodology is applied to remove redundant depth invariant indices. In a post-processing step, a principal component transformation is applied, extracting features that account for a substantial amount of the variance from the non-redundant depth invariant indices while reducing dimensionality. To fully showcase the developed methodology and its potential for extracting bottom type information, we provide an example output of the water column compensation workflow using hyperspectral imaging data collected over the coast of Philpott's Island in Long Sault Parkway provincial park, Ontario, Canada.•Workflow calculates depth invariant indices for hyperspectral imaging data to compensate for the water column in shallow, clear to moderate optical water types.•The applied principal component transformation generates features that account for a substantial amount of the variance from the depth invariant indices while reducing dimensionality.•The output (both depth invariant index image and principal component image) allows for the analysis of bottom type in shallow, clear to moderate optical water types.