Reflection Intensity Research Articles

Investigation of Changes in the Reflection Spectrum of Human Blood When Exposed to Laser Radiation With Wavelengths of 450 or 980 nm.

This study aimed to determine and explain changes in the reflectance spectrum of human blood in vitro when exposed to laser radiation at wavelengths of 450 or 980 nm. Reflectance spectra of venous blood samples were measured before and after exposure to a single pulse of 450 or 980 nm laser radiation. A numerical optical model based on the Monte Carlo method was applied. Laser irradiation at 450 and 980 nm caused the most significant changes in the reflectance spectrum around 600 nm, associated with alterations in blood oxygen saturation. The maximum efficiency of reducing oxygen saturation was 0.20%/W for 980 nm and 0.72%/W for 450 nm, likely due to differences in blood absorption at these wavelengths. The greatest change in intensity reflectance spectra and oxygen saturation of human venous blood occurs when exposed to laser radiation at 450 nm, not at 980 nm.

Vibrational, optical, electronic and electrocatalytic properties of SrCuSi4O10 ceramic

This research reports the synthesis of powdered SrCuSi4O10 ceramic powder, obtained through a solid-state chemical reaction methodology. The sample was characterized using X-ray powder diffraction (XRPD), Raman and Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), reflectance (R), electron paramagnetic resonance spectrum (EPR), lattice dynamic calculations, electronic and electrocatalytic properties analyses. The X-ray analysis showed that crystalline structure of SrCuSi4O10 compound belongs to a tetragonal system with the P4/ncc space group, containing four formulas per unit cell (Z = 4). The SEM micrographs present a morphology of layered microplates with some irregularity in size and shapes. UV–vis diffuse reflectance spectra show three intense reflection regions. Regarding the vibrational properties, the theoretical calculation was performed using a rigid ion model in order to assign the experimental Raman and IR modes. Additionally, electronic properties calculations were carried out using Density Functional Theory (DFT). Finally, the hydrogen evolution reaction (HER) performance of the SrCuSi4O10 electrocatalyst was evaluated.

Evaluation of Minimum-to-Severe Global and Macrovesicular Steatosis in Human Liver Specimens: A Portable Ambient Light-Compatible Spectroscopic Probe.

Hepatic steatosis (HS), particularly macrovesicular steatosis (MaS), influences transplant outcomes. Accurate assessment of MaS is crucial for graft selection. While traditional assessment methods have limitations, non-invasive spectroscopic techniques like Raman and reflectance spectroscopy offer promise. This study aimed to evaluate the efficacy of a portable ambient light-compatible spectroscopic system in assessing global HS and MaS in human liver specimens. A two-stage approach was employed on thawed snap-frozen human liver specimens under ambient room light: biochemical validation involving a comparison of fat content from Raman and reflectance intensities with triglyceride (TG) quantifications and histopathological validation, contrasting Raman-derived fat content with evaluations by an expert pathologist and a "Positive Pixel Count" algorithm. Raman and reflectance intensities were combined to discern significant (≥ 10%) discrepancies in global HS and MaS. The initial set of 16 specimens showed a positive correlation between Raman and reflectance-derived fat content and TG quantifications. The Raman system effectively differentiated minimum-to-severe global and macrovesicular steatosis in the subsequent 66 specimens. A dual-variable prediction algorithm was developed, effectively classifying significant discrepancies (> 10%) between algorithm-estimated global HS and pathologist-estimated MaS. Our study established the viability and reliability of a portable spectroscopic system for non-invasive HS and MaS assessment in human liver specimens. The compatibility with ambient light conditions and the ability to address limitations of previous methods marks a significant advancement in this field. By offering promising differentiation between global HS and MaS, our system introduces an innovative approach to real-time and quantitative donor HS assessments. The proposed method holds the promise of refining donor liver assessment during liver recovery and ultimately enhancingtransplantation outcomes.

Thermal cycles, structure and properties of welded joints in structural steels during welding in extreme cold conditions

The article summarizes research on the thermal cycles, structure, and properties of welded joints made from low-alloy and low-carbon steels during arc welding in sub-zero temperatures. This review aims to analyze previous research to create solid recommendations for welding steel bridge structures during winter conditions. The results of a comparison of experimental measurements of thermal cycles of welding samples with different sizes made at room and subzero ambient air temperatures (down to minus 50 °C) are considered. It is shown that in small plates with dimensions of 200 × 250 × 10 mm, due to more intense heat reflection from the edges of the specimen, the thermal cycles of welding at different temperatures do not differ significantly. In more massive samples (sized 450 × 250 × 10 mm), an increase in the cooling rate of the overheated welded joint area is observed compared to room temperature welding. The impact of hydrogen on the development of cold cracks in low-alloy steels during welding at temperatures below freezing is examined. Metallographic analysis has revealed that the structural changes that occur during the welding of various steel grades are notably different and are influenced by the steel’s chemical composition as well as the thermal cycle parameters of the welding process. Dilatometric studies indicate that variations in the levels of alloying elements within different grades significantly influence the kinetics of austenite transformation. Therefore, to identify the best welding techniques for subzero temperatures, it is essential to consider not just how heat disperses in these conditions, but also the kinetics of phase changes and their effects on the structure and properties of the products resulting from austenite decomposition.

In-situ observation of surface recrystallization of K-doped tungsten sheets using laser reflection

The microstructure of (doped) tungsten sheets is crucial for their mechanical behavior. Within this study, a new method, based on laser reflection, is proposed to in-situ determine the process of (secondary) recrystallization and the resulting grain size of (doped) tungsten sheets under ultra high vacuum conditions. The system introduced here allows to position the reflection setup at a reasonable distance from the sample to further observe the sample temperature via a pyrometer. The main signals of interest are the reflection intensity, the resulting distribution, and changes thereof. Furthermore, the proposed method can be carried out on polished and as rolled surfaces likewise. This novel method makes it possible to determine the secondary recrystallization temperature (TRx) in doped tungsten sheets within a single non-isothermal annealing procedure. The average surface grain size during isothermal annealing procedures can be evaluated as well. Even though the observations are generally restricted to the surface, in the case of tungsten sheets a sufficient determination of bulk recrystallization kinetics is possible as well. Furthermore, the obtained results show, that the recrystallization temperature can serve as a sufficient measure to describe the recrystallized microstructure. Even for different sample strains, TRx correctly predicts the average grain size resulting for various temperature increase rates. The proposed method provides a simple, coherent, and robust method to evaluate the recrystallization properties of (doped) tungsten sheets within a single measurement.

Influence of viscous shear boundary layers on the sound performance of acoustic metasurfaces

Acoustic metasurfaces are mostly designed in a static medium, ignoring the influence of flow characteristics. However, in actual aeroacoustic noise reduction, e.g., aircraft engine liner design, the background flow can have effects on the sound performance of acoustic metasurfaces, especially for a viscous shear flow. The effect of a viscous shear flow is often neglected in previous studies on the design and sound field prediction of acoustic metasurfaces. For considering the viscous and thermal dissipation effects, an analytical model is developed to predict the sound field of a periodic metasurface in a viscous shear boundary layer. In this model, the effective impedance based on the high-frequency limits is utilized to consider both the actual impedance of the acoustic metasurface and the effect of a finite-thickness viscous shear boundary layer. An acoustic metasurface designed in the static medium or even redesigned with only the effect of an inviscid shear flow is not suitable for wave manipulation when the Reynolds number (Re) changes significantly, since the viscosity is an important and non-negligible factor affecting the sound performance. For the cases in this work, the sound performance gradually deteriorates with the decrease in Re when Re≥5×106. When Re≤1×106, especially at Re=1×105, the existence of viscous shear flows could result in the destruction of expected anomalous reflection and significant intensity change of the reflected waves. This research provides a method for the design of acoustic metasurfaces under viscous shear flow conditions, which is significant for future aeroacoustic applications.

Robust and automatic beamstop shadow outlier rejection: combining crystallographic statistics with modern clustering under a semi-supervised learning strategy.

During the automatic processing of crystallographic diffraction experiments, beamstop shadows are often unaccounted for or only partially masked. As a result of this, outlier reflection intensities are integrated, which is a known issue. Traditional statistical diagnostics have only limited effectiveness in identifying these outliers, here termed Not-Excluded-unMasked-Outliers (NEMOs). The diagnostic tool AUSPEX allows visual inspection of NEMOs, where they form atypical pattern: clusters at the low-resolution end of the AUSPEX plots of intensities or amplitudes versus resolution. To automate NEMO detection, a new algorithm was developed by combining data statistics with a density-based clustering method. This approach demonstrates a promising performance in detecting NEMOs in merged data sets without disrupting existing data-reduction pipelines. Re-refinement results indicate that excluding the identified NEMOs can effectively enhance the quality of subsequent structure-determination steps. This method offers a prospective automated means to assess the efficacy of abeamstop mask, as well as highlighting the potential of modern pattern-recognition techniques for automating outlier exclusion during data processing, facilitating future adaptation to evolving experimental strategies.

Mitigation mechanism of porous media hood for the sonic boom emitted from maglev tunnel portals

The micro-pressure waves (MPW) released from maglev tunnel portals can generate audible sonic booms and cause structural resonance in surrounding buildings, posing challenges to developing high-speed maglev trains. This paper proposes a novel porous media hood (PMH) and investigates its mechanism for mitigating the sonic booms emitted from tunnels. The numerical model employs the improved delayed detached eddy simulation turbulence model and overset grid technology, validated against data from moving-model experiments. The influences of the PMH's inherent properties and geometric parameters on MPW, flow field evolution, and aerodynamic loads on the train body were comprehensively discussed. The research demonstrates that PMH effectively dampens the initial wavefront gradient at the entrance and reduces the MPW amplitude by intensifying radiation within its exit vicinity. The porosity of 0.2 facilitates a seamless transition for the streamlined head from the ventilated PMH to the airtight tunnel. Lengthening the PMH enhances its MPW mitigation effect, whereas the impact of PMH thickness is minor. The PMH effectively diminishes the reflection intensity of compression and expansion waves at the tunnel ends, leading to a reduction in the magnitude and changing rate of train aerodynamic loads. This underscores the PMH's potential to enhance passengers' auditory comfort and alleviate issues related to train sway.

Enhanced scattering from an almost-periodic optical temporal slab

We showcase the impact of almost-periodicity on the parametric amplification associated with the first-order momentum gap in photonic time-crystals with time-varying permittivity. Utilizing a vectorial coupled-wave theory approach, we rigorously analyze the scattering by a temporal slab of the considered medium. We pinpoint a critical regime wherein flaws in material tuning paradoxically enhance amplification due to the coupling of fewer, broader modes, resulting in a higher and broader pulselike amplification envelope. Additionally, we demonstrate that the intensity reflectances of time-reversed waves corresponding to secondary “Bragg” resonances achieve remarkably high levels of subharmonic parametric amplification, with the epsilon-near-zero regime serving as a preferred candidate for experimental implementation. Our counterintuitive findings highlight the potential of intentionally leveraging modulation desynchronization and impurities in the temporal unit cell of photonic time-crystals to enhance both the level and the bandwidth of amplification. Published by the American Physical Society 2024

Nanoscale Synergy: Unveiling Gas Sensing Paradigms Through First Principles Exploration of Vertical Hexagonal Boron Nitride/Graphene Heterostructures

Modern civilization relies on rapid and accurate gas molecule identification at low concentrations for environmental surveillance, civilian security, healthcare evaluation, and inside atmospheric control. Density functional theory simulations are used to study the adsorption of CH4, CO2, PH3, N2O, NH3, O3, and SO2 gas molecules on a vertical hexagonal boron nitride/graphene heterostructure using the CASTEP code. Negative adsorption energy is only detected for NH3, O3, and SO2 gases. Our adsorption energy measurements show that the heterostructure is sensitive to NH3, O3, and SO2 gas molecules but insensitive to other gas molecules, as shown by the positive results. Further electrical and optical properties are only performed on gas‐adsorbed structures. It is found that the pure heterostructure acts like a semiconductor and has a band gap of 1.742 eV, which changes when gas is absorbed. Each of the structures has high absorption coefficients in the UV region, making them promising candidates for optoelectronic devices. The determination of the adsorbed gas type can be achieved by measuring the peak intensity and peak position of reflection or absorption. Heterostructures exhibit superior sensing capabilities for NH3 compared to other gases because of their enhanced adsorption energy, distinctive electrical band gap, and notable optical characteristics.

Tactile sensation in relation to roughness and reflection of active initial lesions in primary (deciduous) and permanent dentition in vitro

ObjectivesThis study evaluated whether a relationship exist between tactile sensation, roughness and reflection intensity in active enamel lesions of primary (deciduous) and permanent dentition. MethodsFreshly extracted teeth of the primary (n=29) and permanent (n=60) dentition of patients who underwent serial extractions under general anesthesia due to multiple deep caries lesions showing active lesions (International Caries Detection and Assessment System scores of 2) were selected. The mean linear (Ra), area-related (Sa), volume-related (Vmc) roughness and vertical reflection intensity (VRI) of sound (S) and carious (C) areas were determined by using a 3D-laser-scanning-microscope and a multi-sensor microscope with two different chromatic-confocal optics. Furthermore, two blinded examiners evaluated the roughness by tactile examination using three different explorers (S23H,405CP11, S3C). ResultsMean differences (95%CI) between S and C for teeth of the primary dentition were: Ra:-1.9(-2.3;-0.4)µm, Sa:-31.8(-1.8;0.0)µm, Vmc:-1.8(-1.6;-0.0)ml/m2, VRI:29(20;43) and for teeth of the permanent dentition: Ra:-4.0(-2.5;-1.0)µm, Sa:-4.8(-3.0;-1.1)µm, Vmc:-4.6(-3.4;-0.5)ml/m2, VRI:34(19;44) differing significantly between S and C (p<0.05,Wilcoxon test). No significant difference was observed between 1st and 2nd dentition (p>0.05, Kruskal-Wallis test) as well as commercial and experimental optic (p>0.05). The highest positive predictive value (PPV) was achieved by examiner 1 with explorer S3C (1st dentition 67%;2nd dentition 100%;pooled dentition 88%)), while examiner 2 revealed the highest PPV with explorer S23H (89%;86%;88%). ConclusionDifferences in roughness and reflectance between sound and caries-active enamel surfaces could be evaluated in both primary and permanent dentition. These differences could also be reliably detected using three different explorers with good validity. However, the most predictive explorer seems to differ between examiners. Clinical SignificanceIn both primary (deciduous) and permanent dentition active caries lesions exhibit significantly higher roughness and lower vertical reflection intensity compared with sound enamel. These differences are detectable by blind tactile examination and objective methods such as 3D-laser-scanning or multi-sensor microscopy, highlighting their utility in caries diagnosis in both dentitions.

Novel multi-spectral short-wave infrared imaging for assessment of human burn wound depth.

Burn depth determination is critical for patient care but is currently lacking accuracy. Recent animal studies showed that Short Wave Infrared (SWIR) imaging can distinguish between superficial and deep burns. This is a first human study correlating reflectance of multiple SWIR bands using a SWIR assessment tool (SWAT) with burn depth classifications by surgeons and histology. Burns and adjacent normal skin in 11 patients with thermal injuries were imaged with visual and narrow bands centred at 1200, 1650, 1940 and 2250 nm and biopsies were taken from select areas. Reflectance intensities for each band in 273 regions of interest (ROI) were divided by the normal skin reflectance and combined into three Reflectance Indices (RIs). In addition, burns in ROIs and biopsies were classified by five surgeons and three pathologists, respectively, as superficial partial, deep partial, or full thickness. Results show that for burn depth increase classified by the surgeons, reflectance increased at 1200 and 2250, decreased at 1940, and didn't change at 1650 nm. In contrast, all three RIs increase with burn depth and predict the deep and full depths ROIs representing operable regions (Area Under Curve >0.6507, p < 0.0001). Pathologists' classification matched surgeons' classification of burn category only in eight of 21 biopsies (38.1%), but reflectance at all bands and one RI for all deep partial and full thickness biopsies were larger than in non-biopsy normal and superficial partial thickness ROIs (p < 0.0118). In conclusion, multi-spectral imaging with a new SWAT is a promising approach for evaluation of burn wound depth.

Numerical and experimental investigation on the operating characteristics of fan-shaped pulse detonation combustor

The internal flow channel of a turbine engine is typically annular. When circular pulse detonation combustors (PDCs) are installed in this channel, there is a problem with low section utilization rates. To solve this problem, a single-tube fan-shaped PDC test system was developed. The effects of ignition distance on the operating characteristics of the fan-shaped PDC using air and gasoline under different frequencies were studied through both experiment and 3-D numerical simulation. Numerical simulation was also used to investigate the formation and propagation characteristics of detonation waves. The results show that the fan-shaped PDC can operate stably at frequencies ranging from 5 to 25 Hz when the ignition distance is either 2.30 or 2.70 times the equivalent circle diameter from the thrust wall, and it is found to be better to ignite at a distance of 2.30 times the equivalent circle diameter. The blockage ratio of the lower arc surface is larger than that of the other surfaces. This results in more intense collision and reflection. A larger local high pressure area forms near the lower arc surface, which is conducive to the formation of detonation waves. However, the larger blockage ratio makes the flow loss larger, which weakens the intensity of the pressure waves near the lower arc surface. The detonation waves in the fan-shaped PDC travel closer to the upper arc surfaces.

A miniaturized microfluidic nanoplasmonic sensor with cavity reflection enhancement for ultrasensitive molecular interaction analysis

Molecular binding kinetics quantification is pivotal in the design of antibodies, small-molecule drugs, and early diagnosis of complex disease. This study presents a portable microfluidic system, featuring a nanoplasmonic sensor with cavity reflection enhancement (NSCRE), designed for the ultrasensitive detection and analysis of molecular interactions. This device comprises liquid flow paths, generic fiber spectrometers, a versatile NSCRE sensor chip, and a novel data analysis system. Furthermore, a neural network data processing system is developed based on a deep learning model to decrease significant data fluctuations caused by air segments. This “all-in-one” platform, integrating multifunctional, easy-to-use, and renewable NSCRE biosensors, boasts detection capabilities for both slow and rapid kinetics. It can automatically monitor interactions between molecules across a broad range of molecular weights (0.259–150 kDa), allowing for real-time, ultra-sensitive, and highly selective analysis. In addition, the platform with CRE effect facilitates a 7.2-fold increase in reflection intensity signals compared to that of a sensor without CRE. The immunoglobulin G detection with a limit of detection of 73 pM based on this device, showing a 50-fold increase in sensitivity compared to previously reported values. The miniaturized automatic detection system paves a new path for the use of molecular interaction analysis in life science research, drug discovery, early diagnosis, and other fields.

Compressed hyperspectral imaging based on image reflection intensity and differential fusion filtering

Existing spectral imaging technology based on compressed coding requires tens of minutes or even hours to obtain higher-quality spectral data. This limits their use in real dynamic scenarios and can only be discussed theoretically. Therefore, we propose a non-iterative algorithm model based on image reflection intensity-estimation aid (IRI-EA). The algorithm studies the approximate proportional relationship between the reflection strength of the RGB diagram and the corresponding spectrum image and reconstructs high-quality spectral data within about 20 s. By solving the difference map of the corresponding spectral scene, combining it with the spectral data of the IRI method, and introducing the total guidance (TG) filter, the reconstruction error can be significantly reduced, and the spectral reconstruction quality can be improved. Compared with other advanced methods, numerous experimental results indicate the advantages of this method in reconstruction quality and efficiency. Specifically, compared with the existing advanced methods, the average efficiency of our method has improved by at least 85%. Our reconstruction model opens up the possibility of processing real-time video and accelerating other methods.

Sequential Two-Mode Fusion Underwater Single-Photon Lidar Imaging Algorithm

Aiming at the demand for long-range and high-resolution imaging detection of small targets such as submerged submarine markers in shallow coastal waters, research on single-photon lidar imaging technology is carried out. This paper reports the sequential two-mode fusion imaging algorithm, which has a strong information extraction capability and can reconstruct scene target depth and reflection intensity images from complex signal photon counts. The algorithm consists of four steps: data preprocessing, extremely large group value estimation, noise sieving, and total variation smoothing constraints to image the target with high quality. Simulation and test results show that the imaging performance and imaging characteristics of the method are better than the current high-performance first-photon group imaging algorithm, indicating that the method has a great advantage in sparse photon counting imaging, and the method proposed in this paper constructs a clear depth and reflectance intensity image of the target scene, even in the 50,828 Lux ambient strong light and strong interference, the 0.1 Lux low-light environment, or the underwater high-attenuation environment.

In Situ Studies on the Influence of Surface Symmetry on the Growth of MoSe2 Monolayer on Sapphire Using Reflectance Anisotropy Spectroscopy and Differential Reflectance Spectroscopy

The surface symmetry of the substrate plays an important role in the epitaxial high-quality growth of 2D materials; however, in-depth and in situ studies on these materials during growth are still limited due to the lack of effective in situ monitoring approaches. In this work, taking the growth of MoSe2 as an example, the distinct growth processes on Al2O3 (112¯0) and Al2O3 (0001) are revealed by parallel monitoring using in situ reflectance anisotropy spectroscopy (RAS) and differential reflectance spectroscopy (DRS), respectively, highlighting the dominant role of the surface symmetry. In our previous study, we found that the RAS signal of MoSe2 grown on Al2O3 (112¯0) initially increased and decreased ultimately to the magnitude of bare Al2O3 (112¯0) when the first layer of MoSe2 was fully merged, which is herein verified by the complementary DRS measurement that is directly related to the film coverage. Consequently, the changing rate of reflectance anisotropy (RA) intensity at 2.5 eV is well matched with the dynamic changes in differential reflectance (DR) intensity. Moreover, the surface-dominated uniform orientation of MoSe2 islands at various stages determined by RAS was further investigated by low-energy electron diffraction (LEED) and atomic force microscopy (AFM). By contrast, the RAS signal of MoSe2 grown on Al2O3 (0001) remains at zero during the whole growth, implying that the discontinuous MoSe2 islands have no preferential orientations. This work demonstrates that the combination of in situ RAS and DRS can provide valuable insights into the growth of unidirectional aligned islands and help optimize the fabrication process for single-crystal transition metal dichalcogenide (TMDC) monolayers.

Potential of Raman-Reflectance Combination in Quantifying Liver Steatosis and Fat Droplet Size: Evidence From Monte Carlo Simulations and Phantom Studies.

This study explores a combined strategy of Raman and reflectance spectroscopy for quantifying liver fat content and fat droplet size, crucial in assessing donor livers. By using Monte Carlo simulations and experimental setups with oil-in-water phantoms, our findings indicate that Raman scattering can solely differentiate between varying fat contents. At the same time, reflectance intensity is influenced by both fat content and oil droplet size, with a more pronounced sensitivity to fat droplet size. This study demonstrates the efficacy of combined Raman and reflectance spectroscopy in assessing liver steatosis and fat droplet size, potentially aiding in assessing donor livers for transplantation.

One-Stage Synthesis of Microporous Carbon Adsorbents from Walnut Shells—Evolution of Porosity and Structure

One-stage synthesis technology for preparing carbon adsorbents with tailored porosity from agricultural waste is worthwhile due to their extensive application value. Thermal gravimetric analysis, low-temperature N2 adsorption, X-ray diffraction (XRD), small-angle X-ray scattering (SAXS), and Raman spectroscopy were used to record the structure transformations of carbon materials, namely pore development, proceeding in the course of the step-wise pyrolysis of renewable and low-cost raw materials such as walnut shells (WNSs), which was carried out within a temperature range of 240–950 °C in a CO2 flow. The minimum threshold carbonization temperature for preparing nanoporous carbon materials from WNSs, determined by the examination of the N2 adsorption data, was 500 °C. The maximum specific micropore volume and BET surface achieved in the process without holding a material at a specified temperature were only 0.19 cm3/g and 440 m2/g, respectively. The pyrolysis at 400–600 °C produced amorphous sp2 carbon. At a temperature as high as 750 °C, an increase in the X-ray reflection intensity indicated the ordering of graphite-like crystallites. At high burn-off degrees, the size of coherently scattering domains becomes smaller, and an increased background in X-ray patterns indicates the destruction of cellulose nanofibrils, the disordering of graphene stacks, and an increase in the amount of disordered carbon. At this stage, pores develop in the crystallites. They are tentatively assigned to crystallites with sizes of 15–20 nm and to micropores. According to the Raman spectra combined with the XRD and SAXS data, the structure of all the pyrolysis products is influenced by the complex structure of the walnut shell precursor, which comprises cellulose nanofibrils embedded in lignin. This structure was preserved in the initial stage of pyrolysis, and the graphitization of cellulose fibrils and lignin proceeds at different rates. Most of the pores accessible for gas molecules in the resulting carbon materials are associated with former cellulose fibrils.

LESA-Net: Semantic segmentation of multi-type road point clouds in complex agroforestry environment

Point-cloud semantic segmentation is a visual task essential for agricultural robots to comprehend natural agroforestry environments. However, owing to the extremely large amount of point-cloud data in agroforestry environments, learning effective features for semantic segmentation from large-scale point clouds is challenging. Therefore, to address this issue and achieve accurate semantic segmentation of different types of road-surface point clouds in large-scale agroforestry environments, this study proposes a point-cloud semantic segmentation network framework based on double-distance self-attention. First, a point-cloud local feature enhancement module is proposed. This module primarily extends the receptive field and enhances the generalizability of multidimensional features by incorporating reflection intensity information and a spatial feature-encoding block that is enhanced with contextual semantic information. Second, we introduce a dual-distance attention pooling (DDAPS) block based on the self-attention mechanism. This block initially learns the feature representation of the local neighborhood of each point through the self-attention mechanism. Then, it uses the DDAPS block to aggregate more discriminative local neighborhood point features. Finally, extensive experimental results on large-scale point-cloud datasets, SemanticKITTI and RELLIS-3D, demonstrate that our algorithm outperforms similar algorithms in large-scale agroforestry environments.