Polarization Combinations Research Articles

Theoretical Studies on the Evolution of Solar Filaments in Response to New Emerging Flux

Abstract New emerging flux (NEF) has long been considered a mechanism for solar eruptions, but the detailed process remains an open question. In this work, we explore how NEF drives a coronal magnetic configuration to erupt. This configuration is created by two magnetic sources of strengths M and S embedded in the photosphere, one electric-current-carrying flux rope (FR) floating in the corona, and an electric current induced on the photospheric surface by the FR. The source M is fixed, accounting for the initial background field, and S changes, playing the role of NEF. We introduce the channel function C to forecast the overall evolutionary behavior of the configuration. The location, polarity, and strength of NEF govern the evolutionary behavior of the FR before eruption. In the case of ∣S/M∣ < 1, with reconnection occurring between new and old fields, the configuration in equilibrium evolves to the critical state, invoking the catastrophe. In this case, if the polarities of the new and old fields are opposite, reconnection occurs as NEF is close to the FR, and if the polarities are the same, reconnection happens as NEF appears far from the FR. With different combinations of the relative polarity and the location, the evolutionary behavior of the system gets complex, and the catastrophe may not occur. If ∣S/M∣ > 1 and the two fields have opposite polarity, the catastrophe always takes place, but if the polarities are the same, the catastrophe occurs only as NEF is located far from the FR; otherwise, the evolution ends up either with a failed eruption or without a catastrophe at all.

Population Genetics and Gene Flow in Cyphotilapia frontosa and Cyphotilapia gibberosa Along the East Coast of Lake Tanganyika

The radiation of cichlid species in the East African Great Lakes is remarkable and rapid. The population genetics of two deep-water Cyphotilapia species along the east coast of Lake Tanganyika from Burundi to southern Tanzania was determined using ddRAD-seq. A combination of ADMIXTURE, PCA, genome polarization, and 2D site frequency spectrum analyses confirmed the presence of two species, C. frontosa in the north and C. gibberosa in the south, as documented in other studies. We also found evidence of a potential hybrid zone connecting the two species at a sharp genetic cline centered in the middle of the lake and apparent introgression in both directions, but predominantly from ‘gibberosa’ into ‘frontosa’. The highest proportion of introgressed ‘gibberosa’ ancestry was present in the southernmost populations of C. frontosa collected near Karilani Island and Cape Kabogo. At the intra-specific level, there was support for between 1 and 3 populations of C. frontosa, whereas the results indicated only a single homogeneous population of C. gibberosa. The presence of different morphs in the lake despite the low levels of heterozygosity suggests that a small number of loci may be involved in the morphological variation and/or that there is a more complex interplay between genetics and the environment in different locations.

Tracking dendrites and solid electrolyte interphase formation with dynamic nuclear polarization-NMR spectroscopy.

Polymer-ceramic composite electrolytes enable safe implementation of Li metal batteries with potentially transformative energy density. Nevertheless, the formation of Li-dendrites and its complex interplay with the Li-metal solid electrolyte interphase (SEI) remain a substantial obstacle which is poorly understood. Here we tackle this issue by a combination of solid-state NMR spectroscopy and Overhauser dynamic nuclear polarization (DNP) which boosts NMR interfacial sensitivity through polarization transfer from the metal conduction electrons. We achieve detailed molecular-level insight into dendrites formation and propagation within the composites and determine the composition and properties of their SEI. We find that the dendrite's quantity and growth path depend on the ceramic content and correlated with battery's lifetime. We show that the enhancement of Li resonances in the SEI occurs through Li/Li+ charge transfer in Overhauser DNP, allowing us to correlate DNP enhancements and Li transport and directly determine the SEI lithium permeability. These findings have promising implications for SEI design and dendrites management which are essential for the realization of Li metal batteries.

Flood inundation mapping in SAR images based on nonlocal polarization combination features

Accurately and promptly monitoring of flood inundation is crucial for disaster relief and loss assessment. Although some advancements have been achieved in flood mapping based on synthetic aperture radar (SAR) data, the current research usually extracts flood information at a level such as a single temporal image, single polarization or local neighborhood features. In addition, these methods often rely on learning samples, geographic features, or priori hypotheses (e.g. the histogram of the image has bimodal characteristics), which limits their practicality in large-scale rapid automated mapping. Therefore, we propose an automated flood inundation mapping method for multi-temporal SAR images by using a nonlocal polarization combination feature (NPCF). In this study, we first construct multiple polarization combination features of Sentinel-1 data, and then select the optimal combination feature suitable for flood mapping. On this basis, the different information, before and after the flood disaster, is extracted based on NPCF. Finally, the flood inundation area is obtained through an optimal automated threshold method. Experimental results show that: 1) (VV + VH)2 performs better than the other dual-polarization combination features and the single polarization (VV or VH) feature in flood inundation mapping; 2) NPCF performs better than 10 other advanced flood inundation mapping methods. Additionally, NPCF was further used for rapid mapping of two flood events, and the results showed that Kappa was greater than 0.85. Overall, NPCF achieves automated mapping of flood inundation areas, and can provide timely and reliable disaster information for disaster relief in flood events with high timeliness requirements.

Giant Modulation of Second-Harmonic Generation in CuInP2S6 by Interfacing with MoS2 Atomic Layers.

Probing and manipulating the intriguing nonlinear optical responses in van der Waals (vdW) ferroelectrics offer opportunities for their applications in nanophotonics. Here, we report the observation of giant and tunable second-harmonic generation (SHG) in ferroelectric CuInP2S6 (CIPS) and CIPS/MoS2 heterostructures. The results show that CIPS, ranging from multilayer to bulk-like samples, all exhibit strong SHG with giant anisotropy. The SHG anisotropy is attributed to the local strain along the a-axis that naturally exists in CIPS, as evidenced by piezoresponse force microscopy measurement. We further realized the strong modulation of SHG in CIPS by interfacing with monolayer MoS2. A combination of polarization, temperature, and thickness-dependent SHG and photoluminescence analyses shows that the nonlinear optical signal control in CIPS/MoS2 heterostructures is unrelated to the polar symmetry of CIPS and MoS2 but is driven by light absorption-mediated interfacial coupling. Our study provides a material platform based on vdW ferroelectric heterostructures for achieving dynamic control of nonlinear optical responses, which shows great potential applications in modern nanophotonics.

Interfacial dynamic impermeable crack analysis in dissimilar piezoelectric materials by a new interaction integral

Dynamic intensity factors (IFs) provide an important parameter for assessing the failure risk of an interfacial crack for piezoelectric composites exposed to electromechanical impact loadings. In the present research, a new dynamic interaction integral (I-integral) is built for computing the dynamic stress IFs (SIFs) and electric displacement IF (EDIF) of an interfacial crack located in dissimilar inhomogeneous piezoelectric media. Through proper selection of auxiliary variables, the domain expression of I-integral for the inhomogeneous piezoelectric bi-materials does not need to take into account any derivative term for any piezoelectric material property. Further, after rigorous theoretical derivation, the resulting I-integral is still valid for complex models where the integration domain contains other multiple interfaces, regardless of whether the extra materials are straight or curved. Incorporating the modified extended finite element method, the accuracy is confirmed by checking the dynamic IFs extracted from the I-integral with referenced results. The domain-independence is tested by varying ranges of integration domains for inhomogeneous piezoelectric bi-materials and multi-interface piezoelectric composites. Finally, typical examples are employed to discuss the influences of the direction and magnitude of electric impact loading, combination of polarizations, inhomogeneous degree of piezoelectric bi-materials and complex distribution of diverse material properties on the dynamic IFs.

Holographic multiplexing recording with an orthogonal polarized array.

This study combines tensor polarization holography theory and multichannel recording techniques and proposes a novel polarization encoding method, the orthogonal polarized array (OPA). This method can efficiently and independently reconstruct polarization holograms using accurate OPA waves in the reference-based multiplexing technique when the reference waves in the reading process have the same polarization state as those in the recording process. The novelty is that the multiplexing dimensions of the OPA can reach any number without limitations. Based on theoretical analyses of polarization hologram superposition characteristics and material characteristics, a polarization multiplexing holographic memory with an orthogonal linearly polarized array recording configuration was designed. The experimental results were verified, demonstrating the independent reconstruction of three and five holograms under array waves with different polarization combinations. In addition to high-density optical data storage, this study provides a new paradigm for high-capacity optical displays and information encryption applications.

Using SAR imagery to extract flash flood sediment deposition area in the northern Loess Plateau

The lack of hydrology data brings challenges to the accurate simulation of the inundation range of flash floods using hydrodynamic models. In addition, the water bodies of flash floods often disappear quickly, which makes it difficult for remote sensing satellites to extract flash flood inundated areas without standing water. There is currently no research using flood sediment deposition areas to characterize flash floods in areas without water accumulation. To address this research gap, we developed a method based on Google Earth Engine (GEE) that uses Sentinel-1 SAR imagery to automatically extract flash flood sediment deposition areas. This method, termed Power Operation of Different Polarization Combination (PODPC), differs from other feature extraction methods in that it utilizes not only the original Vertical-Vertical (VV) and Vertical-Horizontal (VH) polarizations and their simple combinations but also employs power operations and threshold techniques to extrac t sediment deposition areas. We explored the advanced features of PODPC in terms of extraction accuracy, threshold segmentation effect, and sediment deposition area distribution. The results demonstrate that the histograms generated by PODPC exhibit clearer bimodal characteristics, facilitating better threshold selection. VV3, (VV + VH)6, and (VV × VH)3 produced fewer false deposition areas, achieving an overall accuracy of 92 % ∼ 93 %. Compared to commonly used methods such as VV, VH, and VV + VH, PODPC increased the overall accuracy by an average of 23 %. (VV-VH)n and (VV/VH)n are are considered unsuitable for the extraction of sediment deposition areas. The extracted sediment deposition area can serve as indicator of flash flood severity and as validation and input data for flash flood models, enhancing the scientific assessment of flash flood disasters.

Lasting effects of transcranial direct current stimulation on the inducibility of synaptic plasticity by paired-associative stimulation in humans

BackgroundTranscranial direct current stimulation (tDCS) is capable of eliciting changes in cortical neuroplasticity. Increasing duration or repetition of tDCS during the after-effects of a first stimulation has been hypothesized to enhance efficacy. Computational models suggest sequential stimulation patterns with changing polarities to further enhance effects. Lasting tDCS effects on neural plasticity are of great importance for clinical applications.ObjectiveThe study systematically examined the influence of different tDCS paradigms on long term potentiation (LTP)-like plasticity in humans, focusing on stimulation duration, repetition frequency and sequential combinations of changing polarities as the underlying characteristics.MethodsAmplitude changes of motor evoked potentials (MEP) were measured in response to paired associative stimulation (PAS) 6 h after application of different tDCS protocols. In total, 36 healthy participants completed the study, randomised into three groups with different stimulation protocols (N = 12 each).ResultstDCS was able to display lasting modulatory effects on the inducibility of LTP-like plasticity in the human motor cortex 6 h after stimulation. TDCS with the anode on primary motor cortex significantly increased MEP amplitudes following PAS induction. Further analyses highlighted single stimulation block duration to be of higher importance than repetitive protocols for efficacy of effects.ConclusionstDCS is capable of inducing lasting changes in the brain’s capability to interact with future stimuli. Especially, effects on the inducibility of LTP-like plasticity might only be detectable with specific tests such as PAS and might otherwise be overlooked. Refined tDCS protocols should focus on higher current and duration of single stimulations instead of implementing complex repetitive schedules.

Magnetostratigraphy and rock magnetic studies on the Cretaceous‐Paleogene transition strata along the Um Sohryngkew River, Therriaghat, Meghalaya, India

A combination of magnetic polarity and rock magnetic analysis on the well‐documented section of the Um Sohryngkew River (USR) in the south Shillong Plateau, NE India, produced a sharp reversal marking the C29r‐C29n geomagnetic polarity transition at approximately 65.688 Ma. The rock magnetic studies indicate ferrimagnetic dominant mineralogy with abundance of SSD grains, with an anomalous peak in susceptibility coinciding with Ir‐rich limonitic layer. The magnetic reversal occurs precisely 61 m above the Ir‐rich distinct in situ limonitic layer, indicating that the C29r‐C29n geomagnetic reversal post‐dates the widely accepted Ir‐anomaly based K‐Pg boundary by approximately 355 Ka. Furthermore, the rock magnetic studies indicate its frequency dependence coinciding with the Ir‐rich limonitic layer suggesting a possible dust/aerosol source, while akaganéite is reported from the interval approximately 1 m below peak susceptibility, indicating signature of Deccan volcanism. This study infers the completeness of the USR section with a high rate of sedimentation of approximately 17 cm/ka among the marine K‐Pg boundary sections in the world.

Weighted Variable Optimization-Based Method for Estimating Soil Salinity Using Multi-Source Remote Sensing Data: A Case Study in the Weiku Oasis, Xinjiang, China

Soil salinization is a significant global threat to sustainable agricultural development, with soil salinity serving as a crucial indicator for evaluating soil salinization. Remote sensing technology enables large-scale inversion of soil salinity, facilitating the monitoring and assessment of soil salinization levels, thus supporting the prevention and management of soil salinization. This study employs multi-source remote sensing data, selecting 8 radar polarization combinations, 10 spectral indices, and 3 topographic factors to form a feature variable dataset. By applying a normalized weighted variable optimization method, highly important feature variables are identified. AdaBoost, LightGBM, and CatBoost machine learning methods are then used to develop soil salinity inversion models and evaluate their performance. The results indicate the following: (1) There is generally a strong correlation between radar polarization combinations and vegetation indices, and a very high correlation between various vegetation indices and the salinity index S3. (2) The top five feature variables, in order of importance, are Aspect, VH2, Normalized Difference Moisture Index (NDMI), VH, and Vegetation Moisture Index (VMI). (3) The method of normalized weighted importance scoring effectively screens important variables, reducing the number of input feature variables while enhancing the model’s inversion accuracy. (4) Among the three machine learning models, CatBoost performs best overall in soil salt content (SSC) prediction. Combined with the top five feature variables, CatBoost achieves the highest prediction accuracy (R2 = 0.831, RMSE = 2.653, MAE = 1.034) in the prediction phase. This study provides insights for the further development and application of methods for collaborative inversion of soil salinity using multi-source remote sensing data.

Bulk photovoltaic effect in ferroelectric nematic liquid crystals.

The bulk photovoltaic (BPV) effect in ferroelectric liquid crystals is of increasing scientific interest owing to its great potential for light-energy conversion. The ferroelectric nematic phase exhibits a huge spontaneous polarization that can be aligned to a preferred direction. In this Letter, we investigate the tensorial properties of the BPV effect in the planarly aligned ferroelectric nematic phase of the liquid crystalline material RM734. A steady-state short-circuit photocurrent of ~160 pA and an open-circuit photovoltage of ~50 mV were observed in a cell with a thickness of 5.5 µm under the illumination of ultraviolet light without any bias voltage. Based on the photocurrent measurements in different electrode configurations, the non-zero elements of the BPV tensor were obtained. The BPV effect is attributed to the combination of the spontaneous polarization and the asymmetric distribution of photoinduced charge carriers. This study not only provides an understanding of the bulk PV mechanism in soft ferroelectrics but also promises a wide range of unprecedented, to the best of our knowledge, benefits for light harvesting to engineer marketable photovoltaic devices.

Online Raman spectroscopy for quantitative detection and characterization of aerosolized soot.

Ex-situ Raman spectroscopy is a well-established method for the structural characterization of soot but necessitates a sampling step before analysis is made. This work studied the potential to perform Raman spectroscopic measurements of soot directly in the combustion exhaust gases, i.e., online Raman measurements. Two types of soot were produced from a Mini-CAST soot generator, one immature with high organic content and one mature with low organic content. Also, two different measurement configurations were used, a 90-degree and a backscattering configuration, as well as different polarization combinations of the laser radiation and the detected photons. Spectrally resolved Raman signals were successfully recorded and analyzed for the two soot types showing differences between the characteristic D and G peaks as well as the photoluminescence signal. Additionally, the Raman cross section was determined for both soot types and found to be higher for the immature soot. It was also found that a horizontally polarized laser excitation and a 90-degree collection angle had the best potential to reduce the interference from ambient gases. This study can be seen as a first step towards remote sensing of soot.

"Spatio-temporal symmetries of electronic chirality flips in oriented RbCs induced by two coincident laser pulses with circular ++,+-,-+,-- polarizations".

Recently it has been shown that two coincident well designed laser pulses with two different combinations of circular polarizations ( ++ or -+ ) can create chiral electronic densities in an oriented heteronuclear diatomic molecule. Subsequently, the chirality flips from the electronic Ra to Sa to Ra to Sa etc. enantiomers, with periods in the femtosecond (fs) and attosecond (as) time domains. The results were obtained by means of quantum dynamics simulations for oriented NaK. Here we investigate the electronic chirality flips in oriented RbCs induced by all possible ( ++ , -+ , +- , -- ) combinations of circular polarizations of two coincident well-designed laser pulses. Accordingly, the ++ and -- as well as the +- and -+ combinations generate opposite electronic enantiomers, e. g. Ra versus Sa, followed by opposite periodic chirality flips, e.g. form Ra to Sa to Ra to Sa etc. versus form Sa to Ra to Sa to Ra etc, with periods in the fs and as time domains, respectively. The laser induced spatio-temporal symmetries are derived from first principles and illustrated by quantum dynamics simulations.

Full‐Phase Parameter Modulation with Arbitrary Polarization Combination via Bidirectional Asymmetric Transmission Meta‐Devices

AbstractThe bidirectional asymmetric transmission (BAT) meta‐devices have attracted widespread attention as an emerging display, encryption, and information storage platform. Generally, the multiplexing capability of BAT meta‐devices determines the upper limit of the loading capacity of multi‐task integrated systems. However, existing BAT meta‐devices still depend on structural properties and the arrangement of meta‐atoms, limiting the number of manipulated channels, operating frequency, and polarization combinations. Herein, a universal BAT meta‐device, enabling bidirectional eight‐phase‐channel asymmetric transmission, composed of bilayer spatially cascaded birefringent metasurfaces (BMs) is proposed to allow for arbitrary polarization combination via the inverse design method and validated in the microwave region. In addition, the polarization multiplexing capabilities of BAT meta‐devices are further extended via a Lego‐like physical mechanism. The proposed design strategy may facilitate BAT meta‐devices functional innovation and advanced application deployment in holographic images, duplex communication, and secret‐key‐sharing data encryption.

Political Drivers of State Fiscal Cyclicality

This study examines political factors influencing US state fiscal policy cyclicality. US states largely pursue procyclical fiscal policy, despite the federal government operating countercyclically. Institutional factors, such as balanced-budget rules, have been examined as influences on state cyclicality, with little prior focus on political factors. This article examines the impacts of electoral competitiveness, political polarization, and legislative turnover on state cyclicality. The combination of polarization and turnover is associated with procyclical policy, while the effect of competition on cyclicality is conditional on year from election. Both effects vary during economic upturns compared to downturns. State institutional design implications are considered.

Simultaneous polarization and wavelength merging for efficient fiber coupling system using a designed one-mirror prism

The difference in beam quality between the fast-axis and slow-axis directions of semiconductor lasers limits its wide application. Conventional development methods for solving this problem require a large number of optical components. A one-mirror prism shaping scheme based on wavelength combination and polarization combination techniques is proposed to simultaneously halve the optical width in the slow-axis direction and fill in the dark region in the fast-axis direction to improve and equalize the beam quality. Compared with the traditional beam shaping scheme, the design does not use the cutting-translation-rearrangement of prism technology to avoid uneven spot distribution at the same time, the use of the design of a single prism can achieve several functions to improve the efficiency of prism utilization, to avoid the use of prism stacks, the whole system is simple and compact, easy to implement The design couples two laser stacks, both consisting of 10 cm-bars, into the target fiber with a fiber characteristic of 400 μm, 0.22. An output power of 1415.8 W is obtained from the output end of the fiber, and the coupling efficiency is calculated to be 88.5%.

A MWCMLAI-Net method for LAI inversion in maize and rice using GF-3 and Lutan radar data

ABSTRACT This study aimed at alleviating the problems of unsatisfactory inversion accuracy and weak model stability in LAI remote sensing quantitative inversion. The properties and complex scattering mechanism of SAR data specify the polarization combinations and frequencies. This paper proposes an improved water cloud model combined with a deep neural network (MWCMLAI-Net) for high-precision inversion. The polarized GF-3 (C-band) and Lutan (L-band) were used to investigate the potential of SAR images to estimate LAI, a strong indicator of crop productivity. The study selected xiangfu district in the eastern part of Kaifeng City, Henan Province, as the test area and investigated the LAI of maize and rice. The RV I Freeman Model, backward scattering coefficient extracted by the modified cloud and water model (MWCM), and LAI obtained by the inversion of the MWCM were used as the inputs, and the MWCMLAI-Net inversion of the LAI was constructed. The results showed that the model’s inverted LAI fitting accuracies of maize and rice for the three fertility periods were better than the other models, with R 2 above 0.8516 and RMSE below 0.3999 m2/m2. The addition of noise did not affect the results.

Polarised cross sections for vector boson production with Sherpa

Measurements of vector boson polarisation in vector boson production processes offer a powerful probe of the electroweak symmetry breaking mechanism, scrutinising the Standard Model and new physics scenarios alike. Since massive vector bosons can only be observed as intermediate particles, polarised cross section templates from simulation are necessary to extract their polarisation from measurable unpolarised distributions. In this work we present an extension of the Sherpa Monte-Carlo event generator allowing the simulation of polarised cross sections for vector boson production processes. Based on the narrow-width approximation, polarised cross sections of all possible polarisation combinations for an arbitrary number of intermediate vector bosons can be simulated in a single simulation run. In addition, it is possible to directly predict the interference between different intermediate polarisation states, and various differing polarisation definitions can be studied simultaneously. Besides the simulation of polarised cross sections at fixed LO and LO+PS accuracy as well as in multijet-merged calculations, we also present parton-shower-matched polarised cross sections with approximate NLO QCD corrections in the vector boson production processes. We demonstrate that the differences of this approximation to full NLO QCD predictions are small and it thus opens up the possibility for fully-simulated calculations at the hadron level including polarisation information and higher-order QCD effects for the first time.

Performance analysis of SAR filtering techniques using SVM and Wishart Classifier

The main objective of this work is to analyze the performance of different filtering techniques used to remove speckle noise from PolSAR images. The proposed work shall also provide an insight on the use of various filters on PolSAR images with regards to preservation of edges, point target detection and image classification. Quad-Pol, fully polarimetric SAR Data acquired form the ALOS PalSAR 1 Satellite of the San Francisco Region, USA is used in the study. The SAR data which is in the form of a scattering Matrix (S-Matrix) is first converted to a Coherence Matrix (T-Matrix). The T-Matrix has been used since it is the most suitable matrix representation of scattering and includes consideration of the phase of various polarization combinations. Different filters are applied on the T-Matrix. The filters used are Box Car Filter, Gaussian Filter, IDAN Filter, Lee Refined Filter, Lee Sigma Filter, Lopez Filter, Non-Local Means Filter, and Scattering Model Based Filter. The performance of the different filtering techniques is evaluated using the most used Support Vector Machines (SVM) with Radial Basis function as the kernel with cross validations and Wishart classifiers. The SVM and Wishart classifiers are considered in this study since they give highest accuracies and require the least time for training. A short comparative study is also presented by comparing SVM classifier with seven others to justify the use of SVM Classifier. Three different classes, namely Water, Forest and settlements are considered. Scores like individual class accuracies, Overall Accuracy (OA), Kappa Score, Precision, & Recall are used to determine the classification performance after each filtering technique. Box car filter has the highest overall accuracy of 99.5% after applying SVM Classifier. IDAN filter has the highest overall accuracy of 97.68% after applying Wishart Classifier on it. However, classification carried out on the Boxcar filtered image not only gives high overall accuracy but also maintains edges and point targets.