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We have observed that Variational Mode Decomposition (VMD) exhibits instability in the denoising and separation of noisy multitone signals. Specifically, minor changes in factors such as signal-to-noise ratio, frequency spacing, sampling rate, and probability distribution can significantly impact the decomposition results. To address this issue, we have developed the Dual-VMD-correlation algorithm. This algorithm effectively mitigates the impact of beat effects when harmonics of closely spaced frequencies are superimposed, enabling stable denoising of noisy multitone signals and the separation of each individual tone signal. The algorithm holds promise for applications in frequency-modulated continuous wave laser detection. It can address challenges related to denoising laser echo signals interfered with by aerosols and the difficulty in separating backscatter interference from the target reflected signal spectrum. [ABSTRACT FROM AUTHOR]

We report a two-layer Mueller matrix model of polarized light propagation through layered human skin. Our model is based on single scattering approximation and the fact that the main scatterers in the top layer are various types of cells and the scatterers beneath it consist of fibers. By modeling the first layer mainly with spherical particles inducing the characteristics represented by Mueller matrices of depolarization and diattenuation, the second layer mainly with cylindrical scatterers inducing the retardance caused by scattering and birefringence, and considering the effects of the first layer to the second one, and the equal weight of contributions from both layers to a scatterer, it is possible to separate polarization properties of the medium induced by light propagation and scattering processes. One advantage of our model is that its extension to multi-layer tissues is straightforward. Polarization effects of human nail fold are identified. [ABSTRACT FROM AUTHOR]

Surface water plays a vital role in the spread of infectious diseases. Information on the spatial and temporal dynamics of surface water availability is thus critical to understanding, monitoring and forecasting disease outbreaks. Before the launch of Sentinel-1 Synthetic Aperture Radar (SAR) missions, surface water availability has been captured at various spatial scales through approaches based on optical remote sensing data. A critical drawback of the latter is data loss due to cloud cover, however few studies have quantified this. This study evaluated data loss due to clouds in three Western Ghats (India) districts. These forest-agricultural mosaic landscapes, where water-related diseases are prevalent, experience the Indian monsoon. We compared surface water areas mapped by thresholding 10m Sentinel-1A SAR data with the optical 30m Landsat-derived Joint Research Centre (JRC) Global Surface Water product, currently the only globally available long-term monthly surface water data product. Backscatter thresholds were identified manually, and our Bayesian algorithm found these thresholds were very likely (>97%). While the Sentinel-1 SAR-based and JRC's optical-based approach mapped surface water extent with high overall accuracy (> 98%) when the cloud cover was low, the unmapped surface water area was substantial in the JRC product during the monsoon months. Across the districts, the average cloud cover in the July-August period was 92% or 90% for 2017 and 2018 respectively, resulting in 25% or 23% of the surface water area being unmapped. Also, the more detailed 10m resolution of Sentinel-1A SAR helped detect the many small water features missed by 30m JRC. Thus, for predicting water-related disease risks linked to small water features or monsoon rainfall, Sentinel-1A SAR is more effective. Finally, automatic backscatter thresholding for unvegetated surface water mapping can be effective if threshold values are adapted to regional-specific backscatter spatial and temporal variations. [ABSTRACT FROM AUTHOR]

Introduction: Remotely-sensed acoustic backscatter is an indispensable tool for seabed mapping, among other disciplines. Almost a decade after the GeoHab Backscatter Working Group published its guidelines and recommendations report, new technologies, new challenges and new questions have emerged. Given the range of potential backscatter research avenues, it can be difficult to align research programs with the priorities of the community of practice. Prioritization of backscatter research topics is thus necessary to establish a roadmap for acoustic backscatter research efforts. Methods: We asked the international community working with acoustic backscatter to submit their priority research questions over a 5- to 10-year horizon. We analyzed and curated a total of 177 research questions from 73 contributors, and the resulting 104 questions were grouped into eight broad recurring themes: "Technologies", "Calibration", "Data acquisition and ground-truthing", "Data processing", "Post-processing, quality control, data handling, and curation", "Data analysis", "Data interpretation", and "Applications and end uses". A follow-up survey based on the final list of questions was distributed to characterize the community working with backscatter and to identify key research priorities. Results: A total of 120 responses originating from 23 countries were used for the analyses. Most respondents were researchers (68%), while others were technicians (25%) or department or program managers (11%), among other roles. Affiliations of respondents included academia (43%), governmental agencies (37%), and industry/private sector (18%). After scaling the responses, the most commonly selected theme was "Post-processing, quality control, data handling, and curation", followed by "Calibration" and "Data analysis". Respondents consistently ranked several research questions as priorities. The two questions that were identified as priorities by over 25% of respondents were "How can we move towards absolute calibration of different systems to allow interregional comparisons?", and "How can we quantify seafloor backscatter quality and develop standards similar to what exists with bathymetry?". Discussion: All eight themes are represented in the top 10 priority questions, underscoring the need for contributions to backscatter research from multiple perspectives to advance the field. The ranking of priority questions encourages collaboration within the community and will serve as a roadmap for backscatter research programs over the next decade. [ABSTRACT FROM AUTHOR]

Realistic representation of microwave backscattering from vegetated surfaces is important for developing accurate soil moisture retrieval algorithms that use synthetic aperture radar (SAR) imagery. Many studies have reported considerable discrepancies between the simulated and observed backscatter. However, there has been limited effort to identify the sources of errors and contributions quantitatively using process-based backscatter simulation in comparison with extensive ground observations. This study examined the influence of input uncertainties on simulated backscatter from a first-order radiative transfer model, named the Wheat Canopy Scattering Model (WCSM), using ground-based and airborne data collected during the SMAPVEX12 campaign. Input uncertainties to WCSM were simulated using error statistics for two crop growth stages. The Sobol' method was adopted to analyze the uncertainty in WCSM-simulated backscatters originating from different inputs before and after the wheat ear emergence. The results show that despite the presence of wheat ears, uncertainty in root mean square (RMS) height of 0.2 cm significantly influences simulated co-polarized backscatter uncertainty. After ear emergence, uncertainty in ears dominates simulated cross-polarized backscatter uncertainty. In contrast, uncertainty in RMS height before ear emergence dominates the accuracy of simulated cross-polarized backscatter. These findings suggest that considering wheat ears in the model structure and precise representation of surface roughness is essential to accurately simulate backscatter from a wheat field. Since the discrepancy between the simulated and observed backscatter coefficients is due to both model and observation uncertainty, the uncertainty of the UAVSAR data was estimated by analyzing the scatter between multiple backscatter coefficients obtained from the same targets near-simultaneously, assuming the scatter represents the observation uncertainty. Observation uncertainty of UAVSAR backscatter for HH, VV, and HV polarizations are 0.8 dB, 0.87 dB, and 0.86 dB, respectively. Discrepancies between WCSM-simulated backscatter and UAVSAR observations are discussed in terms of simulation and observation uncertainty. [ABSTRACT FROM AUTHOR]

Millimeter-wave (MMW) radar is capable of providing high temporal–spatial measurements of the ocean surface. Some topics, such as the characterization of the radar echo, have attracted widespread attention from researchers. However, most existing research studies focus on the backscatter of the ocean surface at low microwave bands, while the sea surface backscattering mechanism in the 77 GHz frequency band remains not well interpreted. To address this issue, in this paper, the investigation of the scattering mechanism is carried out for the 77 GHz frequency band ocean surface at small incidence angles. The backscattering coefficient is first simulated by applying the quasi-specular scattering model and the corrected scattering model of geometric optics (GO4), using two different ocean wave spectrum models (the Hwang spectrum and the Kudryavtsev spectrum). Then, the dependence of the sea surface normalized radar cross section (NRCS) on incidence angles, azimuth angles, and sea states are investigated. Finally, by comparison between model simulations and the radar-measured data, the 77 GHz frequency band scattering characterization of sea surfaces at the near-nadir incidence is verified. In addition, experimental results from the wave tank are shown, and the difference in the scattering mechanism is further discussed between water surfaces and oceans. The obtained results seem promising for a better understanding of the ocean surface backscattering mechanism in the MMW frequency band. It provides a new method for fostering the usage of radar technologies for real-time ocean observations. [ABSTRACT FROM AUTHOR]

Precisely predicting vegetation backscatter involves various challenges, such as complex vegetation structure, soil–vegetation interaction, and data availability. Deep learning (DL) works as a powerful tool to analyze complex data and approximate the nonlinear relationship between variables, thus exhibiting potential applications in microwave scattering problems. However, few DL-based approaches have been developed to reproduce vegetation backscatters owing to the lack of acquiring a large amount of training data. Motivated by a relatively accurate single-scattering radiative transfer model (SS-RTM) and radar measurements, we, for the first time to our knowledge, introduce a transfer learning (TL)-based approach to estimate the radar backscatter of vegetation canopy in the case of soybean fields. The proposed approach consists of two steps. In the first step, a simulated dataset was generated by the SS-RTM. Then, we pre-trained two baseline networks, namely, a deep neural network (DNN) and long short-term memory network (LSTM), using the simulated dataset. In the second step, limited measured data were utilized to fine-tune the previously pre-trained networks on the basis of TL strategy. Extensive experiments, conducted on both simulated data and in situ measurements, revealed that the proposed two-step TL-based approach yields a significantly better and more robust performance than SS-RTM and other DL schemes, indicating the feasibility of such an approach in estimating vegetation backscatters. All these outcomes provide a new path for addressing complex microwave scattering problems. [ABSTRACT FROM AUTHOR]

In the last decade, substantial progress has been made to improve the performance of optical gyroscopes for inertial navigation applications in terms of critical parameters such as bias stability, scale factor stability, and angular random walk (ARW). Specifically, resonant fiber optic gyroscopes (RFOGs) have emerged as a viable alternative to widely popular interferometric fiber optic gyroscopes (IFOGs). In a conventional RFOG, a single-wavelength laser source is used to generate counter-propagating waves in a ring resonator, for which the phase difference is measured in terms of the resonant frequency shift to obtain the rotation rate. However, the primary limitation of RFOG performance is the bias drift, which can be attributed to nonreciprocal effects such as Rayleigh backscattering, back-reflections, polarization instabilities, Kerr nonlinearity, and environmental fluctuations. In this paper, we review the challenges and opportunities of achieving performance enhancement in RFOGs. [ABSTRACT FROM AUTHOR]

The rapid deployment and enhanced communication capabilities of unmanned aerial vehicles (UAVs) have enabled numerous real-time sensing applications. These scenarios often necessitate task offloading and execution under stringent transmission delay constraints, particularly for time-critical applications such as disaster rescue and environmental monitoring. This paper investigates the improvement of MEC-based task offloading services in energy-constrained UAV networks using backscatter communication (BackCom) with non-orthogonal multiple access (BAC-NOMA). The proposed BAC-NOMA protocol allows uplink UAVs to utilize downlink signals for backscattering tasks instead of transmitting through uplink NOMA. A resource allocation problem is formulated, aimed at minimizing offloading delays for uplink users. By converting the initially non-convex problem into a convex one, an iterative algorithm is developed to solve it. Simulation results demonstrate that the proposed protocol significantly reduces offloading delays relative to existing benchmarks. [ABSTRACT FROM AUTHOR]

Corneal densitometry (CD) uses the biological properties of the cornea to visualize the morphology of the cornea and determine the degree of corneal transparency. At present, it is an emerging metric that has shown promise in various clinical diagnosis and evaluation of eye diseases and surgeries. We introduce the different methodologies used to measure CD. Furthermore, we systematically categorize the diagnostic value of CD into high, medium, and low levels based on its clinical significance. By analyzing a wide range of conditions, including keratoconus, postrefractive surgery changes, and other corneal pathologies, we assess the utility of CD in each context. We also discuss the potential implications of these classifications for disease monitoring and prognosis evaluation. Our review underscores the importance of integrating CD assessments into routine clinical practice to enhance the accuracy and effectiveness of diagnostic processes for corneal disorders. [ABSTRACT FROM AUTHOR]

A three‐dimensional (3D) microstructural volume is reconstructed from a stack of two‐dimensional sections which was obtained by serial sectioning coupled with electron back scattering diffraction (EBSD) mapping of a 316L austenitic stainless steel. A new alignment algorithm named linear translation by minimising the indicator (LTMI) is proposed to reduce the translational misalignments between adjacent sections by referencing to coherent twin boundaries which are flat and lying on {111} planes. The angular difference between the measured orientation of a flat twin boundary and that of the {111} plane is used as an indicator of the accuracy of the alignment operations. This indicator is minimised through linear translations of the centroids of triangular facets, which constitute grain boundaries at a distance not restricted by the in‐plane step size of the EBSD maps. And hence the systematic trend in the translational misalignments can be effectively reduced. The LTMI alignment procedure proposed herein effectively corrects the misalignments remained by other methods on a 3D‐EBSD data prepared using serial sectioning methods. The accuracy in distinguishing between coherent and incoherent twin boundaries is significantly improved. LAY DESCRIPTION: Accurately reconstructing the three‐dimensional (3D) microscopic structure of metal materials is crucial for exploring the relationship between the structure and properties of materials. Researchers utilise electron backscatter diffraction (EBSD) technique to sequentially acquire two‐dimensional (2D) images layer by layer, which are then stacked to reconstruct the three‐dimensional (3D) microstructure of the material. However, misalignments during this stacking process can result in an incorrect alignment between the layers, leading to distortion of the entire 3D volume. Previous methods aligned layers by making adjacent layers as similar as possible, but this could introduce cumulative errors. This work has proposed a new alignment method, 'Linear translation by minimising the indicator' (LTMI), which utilises coherent twin boundaries as additional references to guide the stacking process and accurately find the correct position between layers. Coherent twin boundaries serve as references because of their characteristics: these boundaries are special structures within the material, having a flat morphology and lying on specific crystal planes. Layers are shifted repeatedly until all the coherent twin boundaries in the sample display these characteristics, signifying that the layers are properly aligned. The LTMI method offers a way to significantly enhance the accuracy of 3D microstructural analysis, which is essential for designing materials that are strong and durable, with profound implications for the materials field. [ABSTRACT FROM AUTHOR]

Indonesia is an archipelago country which has more sea than land area that become a maritime trade route, so it is necessary to improve the safety of ship navigation, such as with ship detection for ship monitoring. As technology develops, remote sensing can be utilized in the maritime field using SAR data for ship detection. With the current advanced technology of computer vision, object detection can be progressively done using deep learning. The capture of these objects especially in the sea can be provided by SAR space-borne images. This research focuses on ship detection using variety of YOLO with 3 different datasets, such as model 1 using Sentinel-1 image with RGB composite which Sigma Nought VV polarization for red, Sigma Nought VH polarization for green, and Sigma Nought VV/VH polarization for blue. While Official-SSDD was used in model 2, and a combination of Sentinel-1 using Sigma Nought VH polarization and Official-SSDD was used in model 3. Then, ship detection model evaluated and validated using AIS (Automatic Identification System) data. The result shows Model 3 on YOLOv9 is the best model for ship detection in Surabaya area with mAP 43.90%, while for Banjarmasin area Model 1 on YOLOv4 is the best model with mAP 26.78%. YOLOv4 is the best algorithm with mAP 26.78% based on every model performance. Model 3 and 1 are the most suitable data for ship detecting in Surabaya and Banjarmasin area because this data contains Surabaya and Banjarmasin scene as YOLOv9 and YOLOv4 also improve model performance due to architectural improvement. [ABSTRACT FROM AUTHOR]

In this article, we propose to synthesize realistic underwater images with a novel image formation model, considering both downwelling depth and line of sight (LOS) distance as cue and call it as Realistic Synthetic Underwater Image Generation Model, RSUIGM. The light interaction in the ocean is a complex process and demands specific modeling of direct and backscattering phenomenon to capture the degradations. Most of the image formation models rely on complex radiative transfer models and in-situ measurements for synthesizing and restoration of underwater images. Typical image formation models consider only LOS distance z and ignore downwelling depth d in the estimation of effect of direct light scattering. We derive the dependencies of downwelling irradiance in direct light estimation for generation of synthetic underwater images unlike state-of-the-art image formation models. We propose to incorporate the derived downwelling irradiance in estimation of direct light scattering for modeling the image formation process and generate realistic synthetic underwater images with the proposed RSUIGM, and name it as RSUIGM dataset. We demonstrate the effectiveness of the proposed RSUIGM by using RSUIGM dataset in training deep learning based restoration methods. We compare the quality of restored images with state-of-the-art methods using benchmark real underwater image datasets and achieve improved results. In addition, we validate the distribution of realistic synthetic underwater images versus real underwater images both qualitatively and quantitatively. The proposed RSUIGM dataset is available here.1 [ABSTRACT FROM AUTHOR]

Snow is considered contaminated when any foreign materials are deposited/mixed with it, which can accelerate melting and significantly impact the snow cover's radiative balance. Such an enhanced melting rate results in a reduction in freshwater sources at the catchment level. In optical remote sensing, snow contamination is widely studied using a normalizing difference index called the snow contamination index. This is based on the finding that the impact of snow contamination diminishes with wavelength and is most noticeable in the visible spectrum (0.3—0.7 μm). However, the study of snow contamination using optical remote sensing is hindered in the Himalayan terrain due to enduring cloud cover in the region. Synthetic Aperture Radar (SAR) data such as Sentinel-1 can be used to ensure all-weather monitoring of such areas. This study focuses on the SAR backscattering behavior at the C-band of clear and contaminated snow for March 2022 in a part of the Eastern Himalayas of Arunachal Pradesh, India. An attempt has been made to utilize Landsat-9 and Sentinel-1 to study the snow contamination. The SAR backscattering for snow conditions (clear/contaminated) is studied using thresholds obtained from the Landsat-9 snow cover map. The SCI and SAR backscattering statistical analysis shows a negative correlation (R2 > 0.6) at a 95% confidence level. It is observed that in the microwave region of the C-band, contaminated snow has a comparatively higher backscattering value than clear snow. However, in the visible wavelength, the contaminated snow has a lower reflectance value than clean snow. Such behavior of the snowpack in the microwave region of the C-band is explained using the physical properties of the snowpack and the dominant scattering mechanism over the surface. The key findings of this study suggest that SAR backscattering is affected by snow contamination due to changes in the local incidence angle, snow wetness, and surface roughness. This research provides critical insight into snow contamination using microwave remote sensing, which can be the first step toward developing an index for radar observations. [ABSTRACT FROM AUTHOR]

Objective: Peripheral nerves remain a challenging target for medical imaging, given their size, anatomical complexity, and structural heterogeneity. Quantitative ultrasound (QUS) applies a set of techniques to estimate tissue acoustic parameters independent of the imaging platform. Many useful medical and laboratory applications for QUS have been reported, but challenges remain for deployment in vivo, especially for heterogeneous tissues. Several phenomena introduce variability in attenuation estimates, which may influence the estimation of other QUS parameters. For example, estimating the backscatter coefficient (BSC) requires compensation for the attenuation of overlying tissues between the transducer and the underlying tissue of interest. The purpose of this study is to extend prior studies by investigating the efficacy of several analytical methods of estimating attenuation compensation on QUS outcomes in the human median nerve. Methods: Median nerves were imaged at the volar wrist in vivo and beam‐formed radiofrequency (RF) data were acquired. Six analytical approaches for attenuation compensation were compared: 1–2) attenuation estimated by applying spectral difference method (SDM) and spectral log difference method (SLDM) independently to regions of interest (ROIs) overlying the nerve and to the nerve ROI itself; 3–4) attenuation estimation by applying SDM and SLDM to ROIs overlying the nerve, and transferring these properties to the nerve ROI; and 5–6) methods that apply previously published values of tissue attenuation to the measured thickness of each overlying tissue. Mean between‐subject estimates of BSC‐related outcomes as well as within‐subject variability of these outcomes were compared among the 6 methods. Results: Compensating for attenuation using SLDM and values from the literature reduced variability in BSC‐based outcomes, compared to SDM. Variability in attenuation coefficients contributes substantially to variability in backscatter measurements. Conclusion: This work has implications for the application of QUS to in vivo diagnostic assessments in peripheral nerves and possibly other heterogeneous tissues. [ABSTRACT FROM AUTHOR]

The Fe–Mn–Cr–N steel was subjected to cold compression at room temperature, followed by annealing at medium temperature of 750 °C, 850 °C, and 950 °C for different time lengths. The microstructure evolution and static recrystallization (SRX) behavior of deformed Fe–Mn–Cr–N steel were investigated by optical microscope (OM) and electron back scatter diffraction (EBSD). The Johnson–Mehl–Avrami–Kolmogorov (JMAK) kinetic model of static recrystallization was established. By comparing the annealing temperature, it can be found that annealing at 750 °C is not sufficient to stimulate significant static recrystallization in Fe–Mn–Cr–N steel with different strain, and the microstructure consists of a small number of recrystallized grains and a large number of deformed substructures. When annealing at 950 °C, the holding time of 15 minutes has led to grain coarsening, while the annealing at 850 °C can achieve fine-grained control under appropriate strain and holding time. In the annealing process, the formation of equiaxed new grains is accompanied by the nucleation of a large number of twins, which is dominated by the recrystallization of twinning mechanism. The induction of Σ3 twin clusters and the interaction of Σ3–Σ9–Σ27 grain boundaries accelerate the recrystallization process, resulting in grain refinement. However, the number of twins is more sensitive to strain. When the Fe–Mn–Cr–N steel is deformed 70 to 80 pct and annealed at 850 °C for 5 minutes, relatively sufficient recrystallized microstructure (VSRX = 88.3 pct) with average grain size of ~ 7.9 μm can be obtained. Furthermore, the grain boundary fraction of Σ3 twins reaches 36.0 pct. In other words, a short period of annealing at about 850 °C after large strain can achieve grain refinement and control the number of Σ3 twins. Based on grain boundary engineering (GBE), high performance Fe–Mn–Cr–N steel can be obtained by rolling and annealing process using this method. [ABSTRACT FROM AUTHOR]

ABSTRACT Solar geoengineering (SG) is an interim solution to combat global warming, which involves scattering back a tiny fraction of the incoming sunlight. Hence, SG and its potential impacts are important to study for the identification of changing weather patterns over regions of climate vulnerable South Asia. This study explores the projected spatio‐temporal patterns of two meteorological parameters, temperature and precipitation, under SG numerical experiment (stratospheric aerosol injection), relative to projected climate change. Furthermore, future projections of same meteorological parameters without SG under a representative concentration pathway (RCP 4.5) will also be studied for comparative analysis. Offsetting climate parameters are associated with multiple risk factors. Thus, both SG and non‐SG scenarios will be studied for the future time period. The results indicate that the temperature reduces by −0.62°C under the SG G4 scenario and spatial distribution patterns of temperature also depicts an overall cooling effects during the G4 implementation (2020–2029) and continuation (2030–2069) phase. Moreover, on a regional scale, a cold bias (less severe) is projected as compared to projected climate under RCP 4.5. Our findings show that, precipitation is also projected to be decreased by −0.02 mm day−1. Dry bias pattern is projected during implementation phase only. The G4 based SG continuation and termination (2070–2090) phases depict no drastic change in precipitation over South Asia. [ABSTRACT FROM AUTHOR]

The Atmospheric Laser Doppler Instrument (ALADIN) aboard Aeolus was the first spaceborne high-resolution lidar and measured vertical profiles of aerosol optical properties at 355 nm at an incidence angle of ∼ 35°. Although Aeolus was primarily developed to provide vertical profiles of wind speed, aerosols and cloud products, its lidar surface returns (LSRs) have been shown to contain useful information about ultraviolet (UV) surface reflectivity and have agreed well with passive remote sensing reflectance. With a focus on the process to incorporate the LSR algorithm into the Aeolus Level-2A product, we describe the methodology and evaluate the results of the adopted LSR retrieval. The algorithm combines attenuated backscattering parameters (Level-2 Aeolus Profile Processor Algorithm, L2 AEL-PRO, data) with information on the surface bin detection (Level-1 data) to produce attenuated LSR estimates (e.g., surface-integrated attenuated backscatter) for all bins where the ground was detected. The correction for producing final LSR estimates at the original Aeolus resolution is performed using the Aeolus L2 retrievals, namely, the aerosol optical depth (AOD) and Rayleigh optical depth, to ensure that LSRs are free of the effects of atmospheric attenuating features, such as optically thick clouds and thick aerosol conditions (AOD > 1.0). The evaluation shows that Aeolus LSR estimates produced using this approach agree well with the UV Lambertian-equivalent reflectivity (LER) from the Global Ozone Monitoring Experiment-2 (GOME-2; LERG) and TROPOspheric Monitoring Instrument (TROPOMI; LERT) climatologies at all spatial scales. For four reference orbits (10 September 2018, 30 November 2018, 11 January 2019 and 1 May 2019), all cloud and aerosol-free LSR estimates agree well with both LER references, with correlation coefficient (r) values varying from 0.55 to 0.71. For monthly scales, the agreement was moderate to high for the LSR–LERT comparison (r = 0.61–0.77 depending on the month) and weak to moderate for the LSR–LERG comparison (r = 0.44–0.64). Globally, the averaged 2.5° × 2.5° LSR estimates exhibit very high agreement with both the LERG (0.90) and LERT (0.92) references. With respect to reproducing the regional monthly dynamics, LSR and LER agree very well in snow- or ice-covered regions (r > 0.90), semiarid regions (r > 0.90), arid regions (r > 0.70), and some regions with mixed vegetation (like Australia; r = 0.94), whereas no agreement was found for ocean regions due to the Aeolus optical setup, which is favorable for the ocean subsurface but not for direct surface backscatter probing. We unveiled four reflectivity clusters of LSRs at the 2.5° × 2.5° grid scale, manifesting a transition from white to darker surfaces in descending LSR magnitude order: (1) ice, (2) snow, (3) surface without snow and (4) water. Regionally, the LSR–LER agreement can vary and yields the highest correlation values in regions where snow is present in winter, indicating the excellent sensitivity of Aeolus LSRs to white surfaces such as snow. This finding is corroborated by the very good agreement of LSRs with modeled snow cover that we demonstrated (r = 0.62–0.74 between these parameters in such regions), while the sensitivity to purely vegetation-driven changes in the surface is lower, as indicated by the comparison between LSRs and the normalized difference vegetation index (NDVI) without snow (r < 0.30 in the regional analysis). By demonstrating the usability of LSRs for scientific applications at non-nadir angles, our work deepens the knowledge about LSRs, which has mostly been based on nadir-looking Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) studies in the past. Using experiences from both the nadir-looking CALIPSO and the highly non-nadir Aeolus mission, a framework for the effective LSR utilization using future lidar missions such as EarthCARE and Aeolus-2 can be effectively designed. [ABSTRACT FROM AUTHOR]

The demand for wearable monitoring devices in contemporary medicine has significantly increased, especially in dynamic environments where traditional bulky equipment is impractical. Conventional flexible wearable devices or systems suffer from limited air and moisture permeability, lack of stretchability, and high power consumption, which restrict their long‐term usage and comfort. Herein, a stretchable and breathable backscattered monitoring system (SBBMS) is introduced, integrated with a fabric substrate. To address the challenges associated with fabric substrate system fabrication and encapsulation, a printing‐cutting‐transfer technology is proposed. This method enables the creation of unique, low‐cost, high‐precision, and robust circuit routing and electronic devices on fabric, maintaining high compatibility with commercial surface mounting technology while minimizing sacrifices in breathability. Additionally, a backscatter communication mechanism is designed and implemented to achieve wireless data transmission, which significantly reduces power consumption. Combined with energy management technology and hydrogel batteries, the SBBMS receives safe, multi‐source, and eco‐friendly energy support. Furthermore, through meticulous design, all modules—including the antenna, circuit, and battery—are made stretchable, providing the system with excellent strain‐resistive performance. The approach paves the way for the development of breathable, high‐performance, and highly integrated fabric‐based wearable systems, catering to specific user groups such as athletes, soldiers, and pilots. [ABSTRACT FROM AUTHOR]

In recent decades, the value and utility of multibeam bathymetry and backscatter data has been increasingly recognized within the field of seascape ecology (the ocean-centric equivalent of landscape ecology) to map the bio- and geodiversity of the ocean floor. More recently, multispectral multibeam backscatter has emerged as a promising endeavor in seabed classification, and its acoustic response across multiple frequencies has been studied in a range of substrates. Coral reef systems are an under-represented seabed type within this research, as these shallow water ecosystems are more commonly mapped with optical remote sensing techniques. Further investigation is necessary to determine the extent to which backscatter data can contribute to the characterization of these habitats–especially for reef systems that are beyond the reach of optical remote sensing approaches. This study investigates the multifrequency acoustic response of coral reefs in two study areas on the Abrolhos Shelf, Brazil. Backscatter mosaics and angular response curves (ARC) are investigated to explore the potential applications of these data for enhanced reef seascape characterization. In both survey areas, the acoustic mapping revealed extensive reef features, and the assessment of acoustic response was influenced by reef surface roughness and biological attributes (algal cover). Results contribute significantly to the understanding of multi-frequency signatures in reef seascapes and highlight the potential of backscatter for mapping and monitoring the health of these ecosystems. Herein, the higher frequencies were found to be fundamental for detection of subtle variations in texture in the inter-reef region of both study areas; this underscores the value of employing these frequencies in a multispectral framework for discerning heterogeneities in coarse substrate types. Furthermore, the lower frequencies were indispensable for more precise delineation of reef characteristics in the Abrolhos Channel area, whereas the higher frequencies were the most effective in identifying reefs with epibiotic cover (those characterized by flatter ARC associated with lower backscatter values) in the Forgotten Reefs region. [ABSTRACT FROM AUTHOR]

Water distribution in the structure of vein quartz formed as a result of successive plastic deformations associated with dislocation slip and subsequent recrystallization was estimated using infrared microspectroscopic (μFTIR) mapping. Water contained in quartz demonstrates a broad absorption band in the IR range at 2800–3750 cm−1, which indicates its molecular state and suggests the presence of water bearing water inclusions. In addition to water, the presence of an absorption band located at 2341 cm−1 seems to be due to the presence of carbon dioxide in a molecular state. A necessary step before assessing the distribution of volatile components in the quartz structure was to calibrate the boundaries obtained by calculating the intensity ratios of the peaks at 1118 and 1160 cm−1 in the reflectance spectrum and using electron back scatter diffraction (EBSD). A variety of fluid distributions in different elements of the structure was observed. At medium temperatures and medium strain rates, dislocation mass transfer is effective during dislocation slip. At low strain rates and elevated temperatures, the contribution of diffusion creep gradually increases, which facilitates the interaction of volatile components with migrating boundaries. It was found that in the process of successive rearrangements, migration of fluid components occurs within the main elements of the structure due to the redistribution of dislocations between defects of different scale levels. Redistribution of fluid from fluid inclusions as a result of plastic deformations in the quartz structure is one of the ways of relaxing intracrystalline stresses during strengthening of the structure. [ABSTRACT FROM AUTHOR]

Synthetic Aperture Radar (SAR) Coherent Change Detection allows for the detection of very small scene changes. This is particularly useful for Intelligence, Surveillance and Reconnaissance as small changes such as vehicle tracks can be identified. Rapidly collecting repeat pass SAR imagery is important in these applications. For space‐borne platforms, such repeat passes may however have significant differences, or baselines. Coherent Change Detection products are reliant on high coherence for good interpretability. This work investigates the sources and levels of incoherence associated with bistatic SAR imagery for a variety of baselines using simulations and measured laboratory data for two ground types. Additionally, spatially variant incoherence trimming is implemented. The paper shows the importance of angle‐dependant backscatter on the coherence of sub‐resolution cell scatterers. [ABSTRACT FROM AUTHOR]

Since 2017, Antarctic sea ice coverage has shown significant reductions, and therefore observations of its surface melting behavior are of utmost importance. Here we study the capability of the Ku-band Chinese-French Oceanography Satellite Scatterometer (CFOSCAT) launched in 2018 to detect surface melting and compare it with more established observations of the C-band Advanced Scatterometer (ASCAT) in orbit since 2007. Both CFOSCAT and ASCAT observations show increases in radar backscatter of more than 2 dB over perennial ice once the ice surface warms and destructive snow metamorphism commences, defined as pre-melt onset (PMO). Backscatter increases by more than 3 dB once prominent thaw–freeze cycles commence, defined as snowmelt onset (SMO). Scatterometer data are compared with drifting buoy and ERA5 reanalysis air temperature data to support the interpretation of melt-related snow processes. Between 2019 and 2022, the average CFOSCAT pre-melt and snowmelt onset dates for 12 perennial ice study regions are 9 November (±23 d) and 1 December (±22 d), earlier than those of ASCAT on 21 November (±22 d) and 11 December (±25 d), respectively. Sensitivity tests show that results depend slightly on chosen backscatter thresholds but little on sea ice concentration. The derived SMOs are in good agreement with previous studies, but the SMO difference between dual-frequency radar observations is smaller than that reported by previous studies due to the sensor differences and different spatiotemporal resolutions. SMO differences between dual-frequency radar observations were also found to be potentially related to regional differences in snow metamorphism. With regard to the long-term changes in SMO, there are strong interannual and regional variabilities in SMO changes, and no consistent changes could be detected among different sub-regions with the beginning of Antarctic sea ice decline after 2015. Dual-frequency CFOSCAT and ASCAT observations hold strong promise for a better understanding of snowmelt processes on Antarctic sea ice, and it is necessary to extend the observation of Antarctic snowmelt based on dual-frequency scatterometers. [ABSTRACT FROM AUTHOR]

Fish scale microchemistry can be used to make life‐history inferences, although ecological studies examining scale composition are relatively rare. Salmon scales have an external layer of calcium phosphate hydroxyl apatite (HAP). The structure, hardness, and calcium content of this layer have been shown to vary within and between species. This variation may lead to misinterpretation of trace element profiles. This study uses backscatter scanning electron microscopy with electron dispersive spectrometry to compare scales from salmon populations and to present a more detailed analysis of scale HAP than was previously available. Our findings extend the range of salmon populations for which HAP Ca is available and confirm previous findings that the HAP Ca is relatively invariable within this species. [ABSTRACT FROM AUTHOR]

Laser direct writing (LDW) is versatile in structuring fibers with micro‐sized functional elements such as fiber Bragg grating (FBG) and backscattering centers by finely manipulating back and side scattering from laser‐induced refractive index modified (RIM) points. However, the side‐scattering is a lesser‐explored property in laser‐structured fibers. In this work, a concise physical model is established to understand the side‐scattering as a combined effect of microstructure and geometry of RIM points. Based on a single‐pulsed LDW method, the parametric decoupling between scattering loss (α) and coupling strength (κ) coefficients of FBGs is reported, whose cross‐section is customized to have a flattened ellipse with thoroughly positive RIM, enabling controllable reflectivity from −21.33 dB to −0.0018 dB while maintaining narrow bandwidth and low loss. Exemplarily, a designed FBG realizes ultra‐low loss of 0.008 dB with a resonance attenuation of 10.81 dB, exhibiting a record‐breaking κ/α of 2083. Using this FBG as the high‐reflective mirror of a home‐made bismuth‐doped fiber laser, narrow‐band lasing with a high optical signal‐to‐noise ratio of ≈43 dB is achieved, demonstrating flexibilities of the proposed approach in customizing both back‐ and side‐scattering in fibers and opening up wide opportunities for combining multifunctional components into optical fibers and realizing all‐fiber networks. [ABSTRACT FROM AUTHOR]

As an important shoreline vegetation and highly productive ecosystem, mangroves play an essential role in the protection of coastlines and ecological diversity. Accurate mapping of the spatial distribution of mangroves is crucial for the protection and restoration of mangrove ecosystems. Supervised classification methods rely on large sample sets and complex classifiers and traditional thresholding methods that require empirical thresholds, given the problems that limit the feasibility and stability of existing mangrove identification and mapping methods on large scales. Thus, this paper develops a novel mangrove index (spectral and SAR mangrove index, SSMI) and Gaussian mixture model (GMM) mangrove mapping method, which does not require training samples and can automatically and accurately map mangrove boundaries by utilizing only single-scene Sentinel-1 and single-scene Sentinel-2 images from the same time period. The SSMI capitalizes on the fact that mangroves are differentiated from other land cover types in terms of optical characteristics (greenness and moisture) and backscattering coefficients of SAR images and ultimately highlights mangrove forest information through the product of three expressions (f (S) = red egde/SWIR1, f (B) = 1/(1 + e-VH), f (W)=(NIR-SWIR1)/(NIR+SWIR1)). The proposed SSMI was tested in six typical mangrove distribution areas in China where climatic conditions and mangrove species vary widely. The results indicated that the SSMI was more capable of mapping mangrove forests than the other mangrove indices (CMRI, NDMI, MVI, and MI), with overall accuracys (OA) higher than 0.90 and F1 scores as high as 0.93 for the other five areas except for the Maowei Gulf (S5). Moreover, the mangrove maps generated by the SSMI were highly consistent with the reference maps (HGMF_2020、LASAC_2018 and IMMA). In addition, the SSMI achieves stable performance, as shown by the mapping results of the other two classification methods (K-means and Otsu's algorithm). Mangrove mapping in six typical mangrove distribution areas in China for five consecutive years (2019–2023) and experiments in three Southeast Asian countries with major mangrove distributions (Thailand, Vietnam, and Indonesia) demonstrated that the SSMIs constructed in this paper are highly stable across time and space. The SSMI proposed in this paper does not require reference samples or predefined parameters; thus, it has great flexibility and applicability in mapping mangroves on a large scale, especially in cloudy areas. [ABSTRACT FROM AUTHOR]

Acoustic surveys are important for fish stock assessments, but fish responses to survey vessels can bias acoustic estimates. We leveraged quiet uncrewed surface vessels (USVs) to characterize potential bias in acoustic surveys. Five conventional motorized ships overtook USVs from astern over 2 km transects at night in Lake Superior in 2022. We examined the difference in acoustic backscatter, average target depth, and average target strength (TS) between USV and motorized vessels. Although sound level measurements from the motorized vessels sometimes exceeded recommendations for scientific vessels, we did not detect differences in acoustic measures among survey vessels. However, the USVs recorded 2 dB higher acoustic backscatter and TS than motorized vessels, leading to ∼15% higher fish densities with drones when using in situ TS and echo integration. Differences in fish density would increase to 30%–60% if a standard TS value was applied. Target depth did not differ between USVs and motorized ships. These results are consistent with a change in orientation but not depth of insonified fish and limited horizontal avoidance of motorized survey vessels. [ABSTRACT FROM AUTHOR]

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Copyright of Remote Sensing for Natural Resources is the property of Remote Sensing for Natural Resources Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

High-resolution mapping of deep-sea polymetallic nodules is needed (a) to understand the reasons behind their patchy distribution, (b) to associate nodule coverage with benthic fauna occurrences, and (c) to enable an accurate resource estimation and mining path planning. This study used an autonomous underwater vehicle to map 37 km2 of a geomorphologically complex site in the Eastern Clarion–Clipperton Fracture Zone. A multibeam echosounder system (MBES) at 400 kHz and a side scan sonar at 230 kHz were used to investigate the nodule backscatter response. More than 30,000 seafloor images were analyzed to obtain the nodule coverage and train five machine learning (ML) algorithms: generalized linear models, generalized additive models, support vector machines, random forests (RFs) and neural networks (NNs). All models ML yielded similar maps of nodule coverage with differences occurring in the range of predicted values, particularly at parts with irregular topography. RFs had the best fit and NNs had the worst spatial transferability. Attention was given to the interpretability of model outputs using variable importance ranking across all models, partial dependence plots and domain knowledge. The nodule coverage is higher on relatively flat seafloor (< 3°) with eastward-facing slopes. The most important predictor was the MBES backscatter, particularly from incident angles between 25 and 55°. Bathymetry, slope, and slope orientation were important geomorphological predictors. For the first time, at a water depth of 4500 m, orthophoto-mosaics and image-derived digital elevation models with 2-mm and 5-mm spatial resolutions supported the geomorphological analysis, interpretation of polymetallic nodules occurrences, and backscatter response. [ABSTRACT FROM AUTHOR]

The hot deformation behavior and microstructure evolution of electron beam-melted Mo-42Re alloy were studied by hot compression tests at 1200 ~ 1500 °C and 0.001 ~ 1 s−1. Based on the experimental results, a constitutive model was developed to predict the flow stress and the average absolute relative error, and the Pearson correlation coefficient of the model was 3.75% and 0.98, respectively. The microstructure after deformation was characterized using electron back scatter diffraction (EBSD) and transmission electron microscope (TEM) techniques. The microstructural analysis results showed that dynamic recovery (DRV) was the dominant mechanism during hot deformation in the selected temperature range, with only partial dynamic recrystallization (DRX) occurring. The temperature for complete DRX should be above 1500 °C. At low temperature (1200 °C) and high strain rate (1 s−1), the sub-grain nucleation was identified as the dominant mechanism for DRX. At elevated temperature (1500 °C) and low strain rates (0.001 s−1), grain boundary bulging was observed to be the primary nucleation mechanism. Recrystallized grains were more likely to form at deformed grain boundaries. During deformation at high temperatures or low strain rates, the larger strain accumulation at grain boundaries was more readily released, facilitating the formation of recrystallized grains. [ABSTRACT FROM AUTHOR]

We show that analyzing archived and future multibeam backscatter and bathymetry data, in tandem with regional environmental parameters, can help to identify polymetallic nodule fields in the world's oceans. Extensive archived multibeam transit data through remote areas of the world's oceans are available for data mining. New multibeam data will be made available through the Seabed 2030 Project. Uniformity of along- and across-track backscatter, backscatter intensity, angular response, water depth, nearby ground-truth data, local slope, sedimentation rate, and seafloor age provide thresholds for discriminating areas that are permissive to nodule presence. A case study of this methodology is presented, using archived multibeam data from a remote section of the South Pacific along the Foundation Seamounts between the Selkirk paleomicroplate and East Pacific Rise, that were collected during the 1997 Foundation–Hotline expedition on R/V Atalante. The 12 kHz Simrad EM12D multibeam data and the other forementioned data strongly suggest that a previously unknown nodule occurrence exists along the expedition transit. We also compare the utility of three different backscatter products to demonstrate that scans of printed backscatter maps can be a useful substitute for digital backscatter mosaics calculated using primary multibeam data files. We show that this expeditious analysis of legacy multibeam data could characterize benthic habitat types efficiently in remote deep-ocean areas, prior to more time-consuming and expensive video and sample acquisition surveys. Additionally, utilizing software other than specialty sonar processing programs during this research allows an exploration of how multibeam data products could be interrogated by a broader range of scientists and data users. Future mapping, video, and sampling cruises in this area would test our prediction and investigate how far it might extend to the north and south. [ABSTRACT FROM AUTHOR]

Augmented reality (AR) mirrors are novel displays that have great potential for commercial applications such as virtual apparel try-on. Typically the camera is placed beside the display, leading to distorted perspectives during user interaction. In this paper, we present a novel approach to address this problem by placing the camera behind a transparent display, thereby providing users with a perspective-aligned experience. Simply placing the camera behind the display can compromise image quality due to optical effects. We meticulously analyze the image formation process, and present an image restoration algorithm that benefits from physics-based data synthesis and network design. Our method significantly improves image quality and outperforms existing methods especially on the underexplored wire and backscatter artifacts. We then carefully design a full AR mirror system including display and camera selection, real-time processing pipeline, and mechanical design. Our user study demonstrates that the system is exceptionally well-received by users, highlighting its advantages over existing camera configurations not only as an AR mirror, but also for video conferencing. Our work represents a step forward in the development of AR mirrors, with potential applications in retail, cosmetics, fashion, etc. The image restoration dataset and code are available at https://perspective-armirror.github.io/. [ABSTRACT FROM AUTHOR]

Non-orthogonal multiple access (NOMA) enables the parallel offloading of multiuser tasks, effectively enhancing throughput and reducing latency. Backscatter communication, which passively reflects radio frequency (RF) signals, improves energy efficiency and extends the operational lifespan of terminal devices. Both technologies are pivotal for the next generation of wireless networks. However, there is little research focusing on optimizing the transmit power in backscatter-assisted NOMA-MEC systems from a green IoT perspective. In this paper, we aim to minimize the transmit energy consumption of a Hybrid Access Point (HAP) while ensuring task deadlines are met. We consider the integration of Backscatter Communication (BackCom) and Active Transmission (AT), and leverage NOMA technology and user cooperation to mitigate the double near–far effect. Specifically, we formulate a transmit energy consumption minimization problem, accounting for task deadline constraints, task offloading decisions, transmit power allocation, and energy constraints. To tackle the non-convex optimization problem, we employ variable substitution and convex optimization theory to transform the original non-convex problem into a convex one, which is then efficiently solved. We deduce the semi-closed form expression of the optimal solution and propose an energy-efficient algorithm to minimize the transmit power of the entire wireless powered MEC. The extensive simulation results demonstrate that our proposed scheme significantly reduces the HAP transmit power by around 8% compared to existing schemes, validating the effectiveness of our approach. This study provides valuable insights for the design of green IoT systems by optimizing the transmit power in NOMA-MEC networks. [ABSTRACT FROM AUTHOR]

The C-band Synthetic Aperture Radar (SAR) on board of the Sentinel-1 satellites have a strong potential to retrieve Surface Soil Moisture (SSM). Using a change detection model to Sentinel-1 backscatter, an SSM product at a kilometre scale resolution over Europe could be established in the Copernicus Global Land Service (CGLS). Over areas with dense vegetation and high biomass. The geometry and water content influence the seasonality of the backscatter dynamics and hamper the SSM retrieval quality from Sentinel-1. This study demonstrates the effect of woody vegetation on SSM retrievals and proposes a masking method at the native resolution of Sentinel-1's Interferometric Wide (IW) swath mode. At a continental 20 m grid, four dense vegetation masks are implemented over Europe in the resampling of the backscatter to a kilometre scale. The resulting backscatter is then used as input for the TUWien (TUW) change detection model and compared to both in-situ and modelled SSM. This paper highlights the potential of high-resolution vegetation datasets to mask for non-soil moisture-sensitive pixels at a sub-kilometre resolution. Results show that both correlation and seasonality of the retrieved SSM are improved by masking the dense vegetation at a 20 m resolution. HIGHLIGHTS: Dense vegetation reduces the ability to retrieve surface soil moisture at a kilometre scale from Sentinel-1 backscatter which is currently available on the Copernicus Global Land Service portal. Applying selective masking for vegetation during the resampling phase improves Sentinel-1 sensitivity to soil moisture. A novel vegetation-corrected Sentinel-1 surface soil moisture product is processed over Europe for the period 2016–2022 included. The Sentinel-1 forest mask improves the Sentinel-1 SSM product correlation and seasonality compared to both modelled and in-situ datasets. [ABSTRACT FROM AUTHOR]

To implement, examine the feasibility of, and evaluate the performance of quantitative ultrasound (QUS) with a handheld point-of-care US (POCUS) device for assessing liver fat in adults. This prospective IRB-approved, HIPAA-compliant pilot study enrolled adults with overweight or obesity. Participants underwent chemical-shift-encoded magnetic resonance imaging to estimate proton density fat fraction (PDFF) and, within 1 mo, QUS with a POCUS device by expert sonographers and novice operators (no prior US scanning experience). Radiofrequency data from the liver collected with the POCUS device were analyzed offline using probe-specific calibrations to estimate two QUS parameters: attenuation coefficient (AC) and backscatter coefficient (BSC). Area under the receiver operating characteristic curve (AUC) of each parameter was estimated for classifying presence/absence of hepatic steatosis (defined as PDFF ≥ 5%). Spearman rank correlation between each parameter and PDFF was estimated and its significance assessed. Of 18 participants (mean age, 43 y ± 14; 17 women), 8 had hepatic steatosis (PDFF ≥ 5%). Both AC and BSC classified hepatic steatosis accurately with AUCs of 0.96–0.97 for expert and 0.88–0.89 for novice operators (p < 0.01 for all) and correlated significantly with PDFF with rho's of 0.65–0.69 for expert and 0.58–0.65 for novice operators (p < 0.02 for all). QUS can be implemented on a POCUS device and can be performed by expert or novice operators after limited training in adults with overweight or obesity with promising initial results. [ABSTRACT FROM AUTHOR]

Chirality-induced spin selectivity has been reported in many experiments, but a generally accepted theoretical explanation has not yet been proposed. Here, we introduce a simple model system of a straight cylindrical free-electron wire containing a helical string of atomic scattering centers with spin–orbit interaction. The advantage of this simple model is that it allows deriving analytical expressions for the spin scattering rates, such that the origin of the effect can be easily followed. We find that spin-selective scattering can be viewed as resulting from the constructive interference of partial waves scattered by the spin–orbit terms. We demonstrate that forward scattering rates are independent of spin, while back scattering is spin dependent over wide windows of energy. Although the model does not represent the full details of electron transmission through chiral molecules, it clearly reveals a mechanism that could operate in chiral systems. [ABSTRACT FROM AUTHOR]

Shelves surrounding reefless volcanic islands usually host sediment that is considered to result mostly from erosion of pre‐existing volcanic rocks, with minor contributions from active volcanism and biogenic production. However, due to the scarcity of studies on volcanic islands, the way in which sediment is produced and deposited in these settings is still relatively poorly understood. In this study, a source‐to‐sink approach is used to understand how sediments on the southern shelf of the inactive volcanic island of Porto Santo (Madeira Archipelago) have formed. To achieve this aim, sediment texture, composition (carbon content) and morphoscopic characterization are integrated with acoustic information from the shelf (multibeam bathymetry, backscatter imagery and sediment thickness). Seafloor sediments are mostly moderately sorted sands with carbonate skeletal particles representing around 80% of the grains and minor volcaniclasts and aeolianite particles from inland subaerial erosion. Multibeam and seismic data allow recognizing some elongated erosive–depositional features that give insights into present‐day and past currents on the shelf. Additionally, an assessment of the subaerial sediment contribution to the shelf has been compared to the overall sediment volume present there. The findings indicate that the current sediment volume significantly exceeds the terrigenous supply, suggesting a significant primary biogenic carbonate production on the shelf. The sediment microscopic characterization supports this hypothesis, which leads to the conclusion that on low‐relief inactive volcanic islands, like Porto Santo, the contribution of carbonate factories to shelf sediment has a bigger role than previously considered. [ABSTRACT FROM AUTHOR]

In this paper, the effect of heat input on the temperature of bobbin tool friction stir welding (BT-FSW) joint in 16-mm-thickness 6061-T6 aluminum alloy plate is investigated by means of COMSOL Multiphysics 5.6 multi-physics field simulation software and K-sheathed thermocouple. Furthermore, the effect of heat input on the microstructure and mechanical properties of the joint is explored through the use of confocal laser scanning microscope (CLSM), electron back scatter diffraction (EBSD), and hardness and tensile measurements. The thermal impact factor (f) is regarded as a representation of heat input, and the experimental results show that when the f-value increases from 1.5 to 2.5, the simulated peak temperature increases from 426.85 to 467.85 °C, and the simulated temperature is higher about 10℃ than the measured temperature. Hole-type defects are observed at the junction of advancing side (AS) thermal-mechanically affected zone (TMAZ) and stirred zone (SZ) of the joint when f-value is 2, and the size of the defect increases when f-value is 2.5. The average grain size and the degree of recrystallization of SZ increase, but the dislocation density decreases as the f-value increases. Comparing the microhardness curves of the three groups of joints, it is found that the microhardness of each region decreases with the increase of f-value, with the microhardness of SZ decreasing from 88 to 72 HV. The tensile strength of the joints decreases from 225 to 199 MPa, the elongation increases from 8.33 to 10.32%, and the fracture morphology changes from equiaxial dimple to parabolic dimple. [ABSTRACT FROM AUTHOR]

Satellite radar altimeters like CryoSat‐2 estimate sea ice thickness by measuring the return‐time of transmitted radar pulses, reflected from the sea ice and ocean surface, to measure the radar freeboard. Converting freeboard to thickness requires an assumption regarding the fractional depth of the snowpack from which the radar waves backscatter (α) $(\alpha)$. We derive sea ice thickness from CryoSat‐2 radar freeboard data with incremental values for α $\alpha $, for the 2010–2021 winter periods. By comparing these to sea ice thickness estimates derived from upward‐looking sonar moorings, we find that α $\alpha $ values between 35%–80% result in the best representation of interannual variability observed over first‐year ice, reduced to < ${< } $55% over multi‐year ice. The underestimating bias in retrievals caused by optimizing this metric can be removed by reducing the waveform retracking threshold to 20%–50%. Our results pave the way for a new generation of 'partial penetration' sea ice thickness products from radar altimeters. Plain Language Summary: Satellite altimeters like CryoSat‐2 can be used to estimate sea ice thickness by estimating how far sea ice floes stick out above the waterline. This is done by measuring the time taken for radar waves to travel to the surface of the ice floe and back to the altimeter. All current winter sea ice thickness estimates assume that the radar waves return entirely from the sea ice surface, and not from the overlying snow cover. A growing body of research suggests this may not be the case, with weather and snow conditions affecting the fraction of the detected radar power that comes from the ice surface. We consider how well CryoSat‐2 estimates capture whether the ice is thicker or thinner than usual at a given time of year. We find that its skill is highest when we assume that 35%–80% of the radar power comes from the sea ice surface, and 20%–65% comes from the snow surface. However, improving this aspect of skill makes the sea ice thickness estimates too low. To address this, we show that a simple change in the waveform processing method can counter this bias. Key Points: CryoSat‐2 retrievals of sea ice thickness have historically been tuned to minimize bias rather than to capture interannual variabilityWe use upward‐looking sonar moorings to tune the treatment of both waveform retracking and snowpack penetration by radar wavesTuning to optimize interannual variability indicates partial penetration for all retracking thresholds [ABSTRACT FROM AUTHOR]

This study aims to explore the forest aboveground biomass relationship to C-band backscatter. A one-hectare area in Wytham Woods, located west of Oxford, was selected for this research. The area has a total of 525 trees of seven different tree species. The Michigan Microwave Canopy Scattering Model (MIMICS), a two-layer radiative transfer model, was applied to simulate canopy backscatter responses in this deciduous UK forest. Model parameters related to forest structure were derived from previously published terrestrial laser (LiDAR) data. Simulated backscatter was performed for co-polarized and cross-polarized modes at a C-band frequency range and incidence angles (20° to 45° at 5° increments). The research includes five objectives: i) backscatter sensitivity analysis from the variation of different model parameters; ii) backscatter seasonal effect under spring–summer (leaf-on) and autumn–winter (leaf-off) periods; iii) backscatter comparison between species as well as between simulated and satellite observations in a spatial pattern; iv) relationship between simulated backscatter and aboveground biomass; and v) relationship between MIMICS forest structure parameters and simulated backscatter. Sensitivity analysis results showed significant differences in backscatter from changes in leaf distribution, leaf thickness and water content (leaf, trunk and soil) for both polarization modes in leaf-on scenarios. Leaf-off scenarios presented significant differences from changes in branch distribution but only for the co-polarized mode. Seasonal variations presented significant backscatter differences between spring–summer and autumn–winter scenarios; additionally, backscatter differences among species for each seasonality in the co-polarized mode were observed. The computation of the grid resolution (20 m × 20 m) showed a range of backscatter values depending on the grid and incidence angle. Higher backscatter values were observed for the satellite data than for the simulated data. Finally, the aboveground biomass and the MIMICS input parameters presented high random variability and little systematic co-variation with the total backscatter on both simulated seasons, suggesting that more robust allometric equations for biomass estimation are required. [ABSTRACT FROM AUTHOR]

Backscatter and derived parameters from Synthetic Aperture Radar (SAR) may vary across the swath as the incident angle increases from the near to the far range, especially in the ScanSAR mode. Previous studies characterize this angular variation in the form of linear regression for commonly used ice types, namely first-year (FYI) and multi-year (MYI). The present study took advantage of the appearance of three grounded multi-year ice floes, viewed at different radar incidence angles, in a series of 22 RADARSAT-2 fully-polarimetric images, acquired over the Resolute Passage in the Canadian Arctic, during the period from 21 October to 28 December 2017. The ice properties remained invariant during the observation period; hence, variation of radar parameters of MYI can be attributed to change of incidence angle only. Quantification of angular variation of the selected SAR parameters was performed. They include conventional orthogonal backscatter coefficients, derived parameters from the incoherent decomposition of Cloude-Pottier, Yamaguchi, and Touzi, as well as a set of parameters from the compact polarimetry mode. Results specify the parameters that reveal variation with incidence angle and present the linear regressions equations. The explanation for the behaviour of each parameter, in terms of showing or not showing an angular trend, is offered. Results will be useful when using the polarimetric parameters in the sea ice classification scheme. [ABSTRACT FROM AUTHOR]

The LuTan-1 (LT-1) satellite, launched in 2022, is China's first L-band full-polarimetric Synthetic Aperture Radar (SAR) constellation, boasting interferometry capabilities. However, given its limited use in subsidence monitoring to date, a comprehensive evaluation of LT-1's interferometric quality and capabilities is necessary. In this study, we utilized the Differential Interferometric Synthetic Aperture Radar (DInSAR) technique to analyze mining-induced subsidence results near Shenmu City (China) with LT-1 data, revealing nine subsidence areas with a maximum subsidence of −19.6 mm within 32 days. Furthermore, a comparative analysis between LT-1 and Sentinel-1 data was conducted focusing on the aspects of subsidence results, interferometric phase, scattering intensity, and interferometric coherence. Notably, LT-1 detected some subsidence areas larger than those identified by Sentinel-1, attributed to LT-1's high resolution, which significantly enhances the detectability of deformation gradients. Additionally, the coherence of LT-1 data exceeded that of Sentinel-1 due to LT-1's L-band long wavelength compared to Sentinel-1's C-band. This higher coherence facilitated more accurate capturing of differential interferometric phases, particularly in areas with large-gradient subsidence. Moreover, the quality of LT-1's monitoring results surpassed that of Sentinel-1 in root mean square error (RMSE), standard deviation (SD), and signal-to-noise ratio (SNR). In conclusion, these findings provide valuable insights for future subsidence-monitoring tasks utilizing LT-1 data. Ultimately, the systematic differences between LT-1 and Sentinel-1 satellites confirm that LT-1 is well-suited for detailed and accurate subsidence monitoring in complex environments. [ABSTRACT FROM AUTHOR]

This paper introduces the Ocean Derived Column Optical Depth (ODCOD) algorithm. ODCOD is now being used to retrieve full-column optical depths from the 532 nm measurements acquired by the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud-Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) spacecraft. ODCOD uses the lidar integrated attenuated backscatter from the ocean surface, together with collocated wind speed estimates from Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), to estimate the full-column optical depths of particulates (i.e., clouds and aerosols) in the Earth's atmosphere. Unlike CALIOP's standard retrievals, which estimate optical depths only when particulate layers are detected, ODCOD retrievals deliver a comprehensive estimate that accounts for attenuation by all particulates present within the lidar profiles. This paper describes the ODCOD algorithm, develops random uncertainty estimates, and characterizes the systematic differences between ODCOD optical depths and those reported by previously validated data sets. This paper presents performance assessments of ODCOD cloud-free profiles to compare the ODCOD aerosol optical depth (AOD) retrievals to collocated measurements made by the airborne High Spectral Resolution Lidar (HSRL) instruments flown by NASA Langley Research Center (LaRC), to daytime estimates derived from the Moderate Resolution Imaging Spectroradiometer (MODIS), and to daytime and nighttime retrievals using the Synergized Optical Depth of Aerosols (SODA) algorithm. ODCOD AODs are biased high relative to LaRC HSRL AODs by 0.009 ± 0.043 (median ± median absolute deviation), with a correlation coefficient of 0.724, and biased low relative to MODIS by 0.009 ± 0.041, with a correlation coefficient of 0.834. Relative to SODA, which derives AOD from a combination of CALIOP and CloudSat ocean surface measurements, ODCOD is biased high in the daytime by 0.004 ± 0.035 and higher at night by 0.027 ± 0.034, with correlation coefficients of 0.887 and 0.891, respectively. Because ODCOD estimates are independent from the standard CALIOP optical depth retrievals, they offer potential for future advances in the CALIPSO data record, both in validating CALIOP's standard estimates and as a potential total column constraint to improve extinction coefficient retrievals. [ABSTRACT FROM AUTHOR]

The objective of this work is to address the need for versatile and effective tissue characterization in abdominal ultrasound diagnosis using a simpler system. We evaluated the backscattering coefficient (BSC) of several tissue-mimicking phantoms utilizing three different ultrasonic probes: a single-element transducer, a linear array probe for clinical use, and a laboratory-made annular array probe. The single-element transducer, commonly used in developing fundamental BSC evaluation methods, served as a benchmark. The linear array probe provided a clinical comparison, while the annular array probe was tested for its potential in high-frequency and high-resolution ultrasonic observations. Our findings demonstrate that the annular array probe meets clinical demands by providing accurate BSC measurements, showcasing its capability for high-frequency and high-resolution imaging with a simpler, more versatile system. [ABSTRACT FROM AUTHOR]

Objectives: Examine the histomorphometric bone composition, following alveolar ridge preservation techniques and unassisted socket healing. Materials and Methods: Forty‐two patients (42) requiring a single rooted tooth extraction were randomly allocated into three groups (n = 14 per group): Group 1: Guided Bone Regeneration (GBR) using deproteinised bovine bone mineral (DBBM) and a porcine collagen membrane; Group 2: Socket Seal (SS) technique using DBBM and a porcine collagen matrix; Group 3: Unassisted socket healing (Control). Trephined bone biopsies were harvested following a 4‐month healing period. Forty‐two samples underwent Back‐Scattered Electrons ‐Scanning Electron Microscopy (BSE‐SEM) imaging, with 15 samples examined using Xray Micro‐Tomography (XMT) (n = 6 for each GBR/SS and n = 3 Control). Images were analysed to determine the percentage (%) of connective tissue, new bone formation, residual DBBM particles and direct bone to DBBM particle contact (osseointegration). Results: BSE‐SEM analysis demonstrated that new bone formation was higher in the Control (45.89% ± 11.48) compared to both GBR (22.12% ± 12.7/p <.004) and SS (27.62% ± 17.76/p <.005) groups. The connective tissue percentage in GBR (49.72% ± 9), SS (47.81% ± 12.57) and Control (47.81% ± 12.57) groups was similar. GBR (28.17% ± 16.64) and SS (24.37% ± 18.61) groups had similar levels of residual DBBM particles. XMT volumetric analysis indicated a lower level of bone and DBBM particles in all test groups, when matched to the BSE‐SEM area measurements. Osseointegration levels (DBBM graft and bone) were recorded at 35.66% (± 9.8) for GBR and 31.18% (± 19.38) for SS. Conclusion: GBR and SS ARP techniques presented with less bone formation when compared to unassisted healing. GBR had more direct contact/osseointegration between the DBBM particles and newly formed bone. [ABSTRACT FROM AUTHOR]

This paper proposes an innovative multi-scale method for determining gas pressure parameters of superplastic forming, which is based on the quantitative relationship between the grain growth mechanism and fracture mechanism of Tie6Ale4V alloy. The high-temperature tensile tests were conducted on the material at temperatures ranging from 700, 800, 840, 890, 920, and 950 °C, strain rates were selected as 10-2~10-4/s. The grain size measurements were observed using electron back-scatter diffraction (EBSD). Particularly, the relation between grain size changes and fracture behaviour is specifically discovered using a physically-based dynamic material model (DMM), and the grain size thresholds for each forming limit are proposed. The physical fracture mechanism is named the "Grain growth based fracture (GGBF)" mechanism. Furthermore, an innovative method based on the GGBF mechanism is proposed to design the superplastic forming loading, and practical four-layer hollow structures experiments are applied to validate the fracture mechanism in superplastic forming. In total, A superplastic forming GGBF mechanism has been verified, and it is expected to be helpful for shape and property control in the forming process of complex structures. [ABSTRACT FROM AUTHOR]

Rapid acquisition of millimeter‐resolution subterranean images can significantly improve the efficiency of archaeological excavation and facilitate the preservation of artifacts. For excavation sites with limited space, small and portable imaging equipment is necessary. Compton backscatter imaging (CBI) is a single‐sided non‐destructive testing technique, which typically requires a short scan time to obtain high‐resolution images. It has great potential in archaeological excavation, supporting archaeologists to make quick judgments. This research utilized a compact, easy‐to‐carry handheld backscatter system, making it particularly suitable and beneficial for on‐site archaeological excavation. Tests were performed in the framework of the excavation of a chariot pit at Dajuan Han Tomb in Xi'an (Shaanxi Province, China) to validate the applicability of this technique in imaging soil structure changes and detecting cultural artifacts. The experimental results show that CBI can clearly image bronze artifacts buried underground, which means practical value in archaeological excavation. [ABSTRACT FROM AUTHOR]