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A CATALOG OF LOW-MASS STAR-FORMING CORES OBSERVED WITH SHARC-II AT 350 <i>μ</i> m
摘要： We present a catalog of low-mass dense cores observed with the SHARC-II instrument at 350 μm. Our observations have an effective angular resolution of 10″, approximately 2.5 times higher than observations at the same wavelength obtained with the Herschel Space Observatory, albeit with lower sensitivity, especially to extended emission. The catalog includes 81 maps covering a total of 164 detected sources. For each detected source, we tabulate basic source properties including position, peak intensity, flux density in fixed apertures, and radius. We examine the uncertainties in the pointing model applied to all SHARC-II data and conservatively find that the model corrections are good to within ～3″, approximately 1/3 of the SHARC-II beam. We examine the differences between two array scan modes and find that the instrument calibration, beam size, and beam shape are similar between the two modes. We also show that the same flux densities are measured when sources are observed in the two different modes, indicating that there are no systematic effects introduced into our catalog by utilizing two different scan patterns during the course of taking observations. We find a detection rate of 95% for protostellar cores but only 45% for starless cores, and demonstrate the existence of a SHARC-II detection bias against all but the most massive and compact starless cores. Finally, we discuss the improvements in protostellar classification enabled by these 350 μm observations.
关键词： stars: formation,ISM: clouds,submillimeter: ISM,stars: low-mass
更新于2025-09-23 15:23:52
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Intelligent Indoor Mobile Robot Navigation Using Stereo Vision
摘要： Majority of the existing robot navigation systems, which facilitate the use of laser range finders, sonar sensors or artificial landmarks, has the ability to locate itself in an unknown environment and then build a map of the corresponding environment. Stereo vision,while still being a rapidly developing technique in the field of autonomous mobile robots, are currently less preferable due to its high implementation cost. This paper aims at describing an experimental approach for the building of a stereo vision system that helps the robots to avoid obstacles and navigate through indoor environments and at the same time remaining very much cost effective. This paper discusses the fusion techniques of stereo vision and ultrasound sensors which helps in the successful navigation through different types of complex environments. The data from the sensor enables the robot to create the two dimensional topological map of unknown environments and stereo vision systems models the three dimension model of the same environment.
关键词： Point clouds,Triangulation,SLAM,Arduino,Stereo vision system
更新于2025-09-23 15:23:52
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Leaf and wood classification framework for terrestrial LiDAR point clouds
摘要： 1. Leaf and wood separation is a key step to allow a new range of estimates from Terrestrial LiDAR data, such as quantifying above ground biomass, leaf and wood area, and their 3D spatial distributions. We present a new method to separate leaf and wood from single tree point clouds automatically. Our approach combines unsupervised classification of geometric features and shortest path analysis. 2. The automated separation algorithm and its intermediate steps are presented and validated. Validation consisted of using a testing framework with synthetic point clouds, simulated using ray-tracing and 3D tree models, and 10 field scanned tree point clouds. To evaluate results we calculated accuracy, kappa coefficient and F-score. 3. Validation using simulated data resulted in an overall accuracy of 0.83, ranging from 0.71 to 0.94. Per tree average accuracy from synthetic data ranged from 0.77 to 0.89. Field data results presented and overall average accuracy of 0.89. Analysis of each step showed accuracy ranging from 0.75 to 0.98. F-scores from both simulated and field data were similar, with scores from leaf usually higher than for wood. 4. Our separation method showed results similar to others in literature, albeit from a completely automated workflow. Analysis of each separation step suggests that the addition of path analysis improved the robustness of our algorithm. Accuracy can be improved with per tree parameter optimization. The library containing our separation script can be easily installed and applied to single tree point cloud. Average processing times are below 10 minutes for each tree.
关键词： field data,3D point clouds,simulated data,terrestrial LiDAR,material separation,LiDAR,testing framework
更新于2025-09-23 15:22:29
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Extinction and optical depth retrievals for CALIPSO's Version 4 data release
摘要： The Cloud–Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud–Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) satellite has been making near-global height-resolved measurements of cloud and aerosol layers since mid-June 2006. Version 4.10 (V4) of the CALIOP data products, released in November 2016, introduces extensive upgrades to the algorithms used to retrieve the spatial and optical properties of these layers, and thus there are both obvious and subtle differences between V4 and previous data releases. This paper describes the improvements made to the extinction retrieval algorithms and illustrates the impacts of these changes on the extinction and optical depth estimates reported in the CALIPSO lidar level 2 data products. The lidar ratios for both aerosols and ice clouds are generally higher than in previous data releases, resulting in generally higher extinction coefficients and optical depths in V4. A newly implemented algorithm for retrieving extinction coefficients in opaque layers is described and its impact examined. Precise lidar ratio estimates are also retrieved in these opaque layers. For semi-transparent cirrus clouds, comparisons between CALIOP V4 optical depths and the optical depths reported by MODIS collection 6 show substantial improvements relative to earlier comparisons between CALIOP version 3 and MODIS collection 5.
关键词： retrieval algorithms,clouds,CALIOP,lidar,optical depth,CALIPSO,aerosols,extinction,version 4
更新于2025-09-23 15:22:29
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CALIPSO lidar calibration at 1064&thinsp;nm: version 4 algorithm
摘要： Radiometric calibration of space-based elastic backscatter lidars is accomplished by comparing the measured backscatter signals to theoretically expected signals computed for some well-characterized calibration target. For any given system and wavelength, the choice of calibration target is dictated by several considerations, including signal-to-noise ratio (SNR) and target availability. This paper describes the newly implemented procedures used to calibrate the 1064 nm measurements acquired by CALIOP (i.e., the Cloud-Aerosol Lidar with Orthogonal Polarization), the two-wavelength (532 and 1064 nm) elastic backscatter lidar currently flying on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission. CALIOP’s 532 nm channel is accurately calibrated by normalizing the molecular backscatter from the uppermost aerosol-free altitudes of the CALIOP measurement region to molecular model data obtained from NASA’s Global Modeling and Assimilation Office. However, because CALIOP’s SNR for molecular backscatter measurements is prohibitively lower at 1064 nm than at 532 nm, the direct high-altitude molecular normalization method is not a viable option at 1064 nm. Instead, CALIOP’s 1064 nm channel is calibrated relative to the 532 nm channel using the backscatter from a carefully selected subset of cirrus cloud measurements. In this paper we deliver a full account of the revised 1064 nm calibration algorithms implemented for the version 4.1 (V4) release of the CALIPSO lidar data products, with particular emphases on the physical basis for the selection of “calibration quality” cirrus clouds and on the new averaging scheme required to characterize intra-orbit calibration variability. The V4 procedures introduce latitudinally varying changes in the 1064 nm calibration coefficients of 25 % or more, relative to previous data releases, and are shown to substantially improve the accuracy of the V4 1064 nm attenuated backscatter coefficients. By evaluating calibration coefficients derived using both water clouds and ocean surfaces as alternate calibration targets, and through comparisons to independent, collocated measurements made by airborne high spectral resolution lidar, we conclude that the CALIOP V4 1064 nm calibration coefficients are accurate to within 3 %.
关键词： calibration,lidar,CALIPSO,version 4 algorithm,cirrus clouds,1064 nm
更新于2025-09-23 15:22:29
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A radiative transfer module for calculating photolysis rates and solar heating in climate models: Solar-J v7.5
摘要： Solar-J is a comprehensive radiative transfer model for the solar spectrum that addresses the needs of both solar heating and photochemistry in Earth system models. Solar-J is a spectral extension of Cloud-J, a standard in many chemical models that calculates photolysis rates in the 0.18–0.8 μm region. The Cloud-J core consists of an eight-stream scattering, plane-parallel radiative transfer solver with corrections for sphericity. Cloud-J uses cloud quadrature to accurately average over correlated cloud layers. It uses the scattering phase function of aerosols and clouds expanded to eighth order and thus avoids isotropic-equivalent approximations prevalent in most solar heating codes. The spectral extension from 0.8 to 12 μm enables calculation of both scattered and absorbed sunlight and thus aerosol direct radiative effects and heating rates throughout the Earth’s atmosphere. The Solar-J extension adopts the correlated-k gas absorption bins, primarily water vapor, from the shortwave Rapid Radiative Transfer Model for general circulation model (GCM) applications (RRTMG-SW). Solar-J successfully matches RRTMG-SW’s tropospheric heating profile in a clear-sky, aerosol-free, tropical atmosphere. We compare both codes in cloudy atmospheres with a liquid-water stratus cloud and an ice-crystal cirrus cloud. For the stratus cloud, both models use the same physical properties, and we find a systematic low bias of about 3 % in planetary albedo across all solar zenith angles caused by RRTMG-SW’s two-stream scattering. Discrepancies with the cirrus cloud using any of RRTMG-SW’s three different parameterizations are as large as about 20–40 % depending on the solar zenith angles and occur throughout the atmosphere. Effectively, Solar-J has combined the best components of RRTMG-SW and Cloud-J to build a high-fidelity module for the scattering and absorption of sunlight in the Earth’s atmosphere, for which the three major components – wavelength integration, scattering, and averaging over cloud fields – all have comparably small errors. More accurate solutions with Solar-J come with increased computational costs, about 5 times that of RRTMG-SW for a single atmosphere. There are options for reduced costs or computational acceleration that would bring costs down while maintaining improved fidelity and balanced errors.
关键词： solar heating,clouds,Cloud-J,climate models,radiative transfer,photolysis rates,scattering,aerosols,RRTMG-SW,Solar-J
更新于2025-09-23 15:22:29
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[IEEE 2018 25th IEEE International Conference on Image Processing (ICIP) - Athens, Greece (2018.10.7-2018.10.10)] 2018 25th IEEE International Conference on Image Processing (ICIP) - Block-Based Motion Estimation Speedup for Dynamic Voxelized Point Clouds
摘要： Motion estimation is a key component in dynamic point cloud analysis and compression. We present a method for reducing motion estimation computation when processing block-based partitions of temporally adjacent point clouds. We propose the use of an occupancy map containing information regarding size or other higher-order local statistics of the partitions. By consulting the map, the estimator may significantly reduce its search space, avoiding expensive block-matching evaluations. To form the maps we use 3D moment descriptors efficiently computed with one-pass update formulas and stored as scalar-values for multiple, subsequent references. Results show that a speedup of 2 produces a maximum distortion dropoff of less than 2% for the adopted PSNR-based metrics, relative to distortion of predictions attained from full search. Speedups of 5 and 10 are achievable with small average distortion dropoffs, less than 3% and 5%, respectively, for the tested dataset.
关键词： 3D,motion estimation,Point clouds,volumetric media
更新于2025-09-23 15:22:29
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Distortion of Magnetic Fields in a Starless Core. V. Near-infrared and Submillimeter Polarization in FeSt 1-457
摘要： The relationship between submillimeter dust emission polarization and near-infrared (NIR) H-band polarization produced by dust dichroic extinction was studied for the cold starless dense core FeSt 1–457. The distributions of polarization angles (90°-rotated for the submillimeter) and degrees were found to be very different between submillimeter and NIR wavelengths. The mean polarization angles for FeSt 1-457 at submillimeter and NIR wavelengths are 132°. 1 ± 22°. 0 and 2°. 7 ± 16°. 2, respectively. The correlation between PH and AV was found to be linear from the outermost regions to the relatively dense lines of sight of AV ≈ 25 mag, indicating that NIR polarization reflects the overall polarization (magnetic field) structure of the core, at least in this density range. The flat PH/AV versus AV correlations were confirmed, and the polarization efficiency was found to be comparable to the observational upper limit. On the other hand, as reported by Alves et al. submillimeter polarization degrees show a clear linearly decreasing trend against AV from AV ≈ 20 mag to the densest center (AV ≈ 41 mag), appearing as a 'polarization hole' structure. The power-law index for the Psubmm versus AV relationship was obtained to be ≈?1, indicating that the alignment for the submillimeter-sensitive dust is lost. These very different polarization distributions at submillimeter and NIR wavelengths suggest either that (1) there are different radiation environments at these wavelengths or (2) submillimeter-sensitive dust is localized or (3) a combination of both.
关键词： polarization,dust, extinction,stars: magnetic field,ISM: clouds,stars: formation
更新于2025-09-23 15:22:29
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MIRIS observation of near-infrared diffuse Galactic light
摘要： We report near-infrared (IR) observations of high Galactic latitude clouds to investigate diffuse Galactic light (DGL), which is starlight scattered by interstellar dust grains. The observations were performed at 1.1 and 1.6 μm with a wide-field camera instrument, the Multi-purpose Infra-Red Imaging System (MIRIS) onboard the Korean satellite STSAT-3. The DGL brightness is measured by correlating the near-IR images with a far-IR 100 μm map of interstellar dust thermal emission. The wide-field observation of DGL provides the most accurate DGL measurement achieved to-date. We also find a linear correlation between optical and near-IR DGL in the MBM32 field. To study interstellar dust properties in MBM32, we adopt recent dust models with and without μm-sized very large grains and predict the DGL spectra, taking into account the reddening effect of the interstellar radiation field. The result shows that the observed color of the near-IR DGL is closer to the model spectra without very large grains. This may imply that dust growth in the observed MBM32 field is not active owing to the low density of its interstellar medium.
关键词： scattering,dust, extinction,ISM: clouds,infrared: ISM
更新于2025-09-23 15:22:29
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A new method to identify subclasses among AGB stars using <i>Gaia</i> and 2MASS photometry
摘要： Aims. We explore the wealth of high-quality photometric data provided by data release 2 (DR2) of the Gaia mission for long-period variables (LPVs) in the Large Magellanic Cloud (LMC). Our goal is to identify stars of various types and masses along the asymptotic giant branch. Methods. For this endeavour, we developed a new multi-band approach combining Wesenheit functions WRP,BP?RP and WKs,J?Ks in the Gaia BP, RP, and 2MASS J, Ks spectral ranges, respectively, and use a new diagram, (WRP,BP?RP ? WKs,J?Ks ) versus Ks, to distinguish between di?erent kinds of stars in our sample of LPVs. We used stellar population synthesis models to validate our approach. Results. We demonstrate the ability of the new diagram to discriminate between O- and C-rich objects, and to identify low-mass, intermediate-mass, and massive O-rich red giants, as well as extreme C-rich stars. Stellar evolution and population synthesis models guide the interpretation of the results, highlighting the diagnostic power of the new tool to discriminate between stellar initial masses, chemical properties, and evolutionary stages.
关键词： stars: evolution,Magellanic Clouds,stars: AGB and post-AGB,stars: variables: general
更新于2025-09-23 15:21:21