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At least 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
NASA NTRS2020

Modelling climate change impacts on maize yields under low nitrogen input conditions in sub‐Saharan Africa

Smallholder farmers in sub‐Saharan Africa (SSA) currently grow rainfed maize with limited inputs including fertilizer. Climate change may exacerbate current production constraints. Crop models can help quantify the potential impact of climate change on maize yields, but a comprehensive multimodel assessment of simulation accuracy and uncertainty in these low‐input systems is currently lacking. We evaluated the impact of varying [CO2], temperature and rainfall conditions on maize yield, for different nitrogen (N) inputs (0, 80, 160 kg N/ha) for five environments in SSA, including cool subhumid Ethiopia, cool semi‐arid Rwanda, hot subhumid Ghana and hot semi‐arid Mali and Benin using an ensemble of 25 maize models. Models were calibrated with measured grain yield, plant biomass, plant N, leaf area index, harvest index and in‐season soil water content from 2‐year experiments in each country to assess their ability to simulate observed yield. Simulated responses to climate change factors were explored and compared between models. Calibrated models reproduced measured grain yield variations well with average relative root mean square error of 26%, although uncertainty in model prediction was substantial (CV = 28%). Model ensembles gave greater accuracy than any model taken at random. Nitrogen fertilization controlled the response to variations in [CO2], temperature and rainfall. Without N fertilizer input, maize (i) benefited less from an increase in atmospheric [CO2], (ii) was less affected by higher temperature or decreasing rainfall and (iii) was more affected by increased rainfall because N leaching was more critical. The model inter-comparison revealed that simulation of daily soil N supply and N leaching plays a crucial role in simulating climate change impacts for low-input systems. Climate change and N input interactions have strong implications for the design of robust adaptation practices across SSA, because the impact of climate change will be modified if farmers intensify maize production with more mineral fertilizer.

Crop simulation model↗
NASA NTRSDate not supplied

Advocacy and Allyship by Men for Women in Engineering-Related Fields at the College Level

Diversity enables better and more creative problem solving, with greater financial impact on organizations, according to multiple studies in the past 10 years. One long-standing limitation on diversity in technology fields is the persistently-low representation of females. This is often seen in the collegiate environment more than in the professional world, and greater efforts need to be made in college classrooms and labs to address it. Most succinctly, more men need to directly involve themselves as advocates for and allies of women. This panel engages with professionals of both binary gender identities who currently ally and advocate for women in engineering, computing, and technology fields. The goals of the panel are to identify common reasons why men should advocate for women, create support around the simple actions that can be taken in advocacy, and encourage greater allyship for women in the academic world and beyond. The panelists include both men and women from across multiple intersectional identities. The questions include (1) for what reasons are you an ally or advocate for women in engineering-related fields, (2) what experiences have you had in which you have had to take immediate action as an advocate or ally, (3) what do you recommend for easy-to-implement actions to advocate, and (4) how can advocates and allies help implement change at their own institutions. For the paper, each panelist would be asked these questions and their answers would be provided unedited, followed by a summary discussion of actionable items. For the panel presentation session, each panelist will have the opportunity to highlight aspects of their answers bring life to their thoughts to each question and together with other members of the panel can build for an in-depth discussion.

Brian Kirkmeyer↗
NASA NTRS2022

Above-Aircraft Cirrus Cloud and Aerosol Optical Depth From Hyperspectral Irradiances Measured By a Total-Diffuse Radiometer

This study develops the use of spectral total and diffuse irradiance measurements, made from a prototype hyperspectral total-diffuse sunshine pyranometer (SPN-S), to retrieve layer fine-mode aerosol (τ aer ) and total optical depths from airborne platforms. Additionally, we use spectral analysis in an attempt to partition the total optical depth into its τ aer and cirrus cloud optical depth (τ cld ) components in the absence of coarse-mode aerosols. Two retrieval methods are developed: one leveraging information in the diffuse irradiance and the other using spectral characteristics of the transmitted direct beam, with each approach best suited for specific cloud and aerosol conditions. The SPN-S has advantages over traditional sun photometer systems, including no moving parts and a low cost. However, a significant drawback of the instrument is that it is unable to measure the direct-beam irradiance as accurately as sun photometers. To compensate for the greater measurement uncertainty in the radiometric irradiances, these retrieval techniques employ ratioed inputs or spectral information to reduce output uncertainty. This analysis uses irradiance measurements from the SPN-S and the solar spectral flux radiometer (SSFR) aboard the National Aeronautics and Space Administration’s (NASA) P-3 aircraft during the 2018 deployment of the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign and the 2019 Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP 2 Ex) mission to quantify above-aircraft cirrus τ cld and derive vertical profiles of layer τ aer . Validation of the τ aer retrieval is accomplished by comparison with co-located measurements of direct solar irradiance made by the Sky-Scanning Sun-Tracking Atmospheric Research (4STAR) and in situ measurements of aerosol optical depth. For the aggregated 2018 ORACLES results, regression between the SPN-S-based method and sun photometer τ aer values yields a slope of 0.96 with an R 2 of 0.96, while the root mean square error (RMSE) is 3.0 x 10 -2 . When comparing the retrieved τ aer to profiles of integrated in situ measurements of optical extinction, the slope, R 2 , and RMSE values for ORACLES are 0.90, 0.96, and 3.4 x 10 -2 , and for CAMP 2 Ex they are 0.94, 0.97, and 3.4 x 10 -2 , respectively. This paper is a demonstration of methods for deriving cloud and aerosol optical properties in environments where both atmospheric constituents may be present. With improvements to the low-cost SPN-S radiometer instrument, it may be possible to extend these methods to a broader set of sampling applications, such as ground-based settings.

spectral instrument (SPN-S)↗
NASA NTRS2022

Low-Speed Performance Enhancement using Localized Active Flow Control: Simulations, Scaling and Design of Localized Active Flow Control on the Common Research Model (4/4)

This report is dedicated to the application of localized AFC on the NASA CRM-HL wind tunnel model, with focus on the aileron application discussed in the CFD study (final report document #2). The experience developed for the Reference Aircraft guided the implementation on the CRM model. CFD evaluations are performed on a representative high-lift configuration, for a set of aileron deflections, and at relevant flow conditions. Alternative flow control actuator layouts are proposed and design consideration for practical integration into the existing CRM-HL model are set forth. The CFD simulations indicate that the aerodynamic performance improvements due to AFC obtained for the CRM-HL are consistent with those achieved for the Reference Aircraft. The observed changes in L/D are smaller than for the Reference Aircraft because the CRM has a higher leading edge sweep angle and a different relative aileron size. Conceptual design studies confirmed that the integration of an AFC equipped aileron into the existing wind tunnel model is feasible.

AFC↗
NASA NTRS2022

Combined UV and IR Ozone Profile Retrieval from TROPOMI and CrIS Measurements

Vertical ozone profiles from combined spectral measurements in the ultraviolet and infrared spectral range were retrieved by using data from the TROPOspheric Monitoring Instrument on the Sentinel-5 Precursor (TROPOMI/S5P) and the Cross-track Infrared Sounder on the Suomi National Polar-orbiting Partnership (CrIS/Suomi-NPP), which are flying in loose formation 3 min apart in the same orbit. A previous study of ozone profiles retrieved exclusively from TROPOMI UV spectra showed that the vertical resolution in the troposphere is clearly limited (Mettig et al., 2021). The vertical resolution and the vertical extent of the ozone profiles is improved by combining both wavelength ranges compared to retrievals limited to UV or IR spectral data only. The combined retrieval particularly improves the accuracy of the retrieved tropospheric ozone and to a lesser degree stratospheric ozone up to 30 km. An increase in the degrees of freedom (DOF) by 1 DOF was found in the UV + IR retrieval compared to the UV-only retrieval. Compared to previous publications, which investigated combinations of UV and IR observations from the Ozone Monitoring Instrument and Tropospheric Emission Spectrometer (OMI and TES) and Global Ozone Monitoring Experiment version 2 and Infrared Atmospheric Sounding Interferometer (GOME-2 and IASI) pairs, the degree of freedom is lower, which is attributed to the reduced spectral resolution of CrIS compared to TES or IASI. Tropospheric lidar and ozonesondes were used to validate the ozone profiles and tropospheric ozone content (TOC). In their comparison with tropospheric lidars, both ozone profiles and TOCs show smaller biases for the retrieved data from the combined UV + IR observation than from the UV observations alone. For the ozone profiles below 10 km, the mean differences are around ±10 % and the mean TOC varies around ±3 DU. We show that TOCs from the combined retrieval agree better with ozonesonde results at northern latitudes than the UV-only and IR-only retrievals and also have lower scatter. In the tropics, the IR-only retrieval shows the best agrement with TOCs derived from ozonesondes. While in general the TOCs show good agreement with ozonesonde data, the profiles have a positive bias of around 30 % between 10 and 15 km. The reason is probably a positive stratospheric bias from the IR retrieval. The comparison of the UV + IR and UV ozone profiles up to 30 km with the Microwave Limb Sounder (MLS) demonstrates the improvement of the UV + IR profile in the stratosphere above 18 km. In comparison to the UV-only approach the retrieval shows improvements of up to 10 % depending on latitude but can also show worse results in some regions and latitudes.

Ozone↗
NASA NTRSDate not supplied

Intracranial Effects of Intermittent Lower Body Negative Pressure with Head Down Tilt Bed Rest: Comparison to Upright Posture

INTRODUCTION Spaceflight-associated neuro-ocular syndrome (SANS) affects a majority of astronauts during long-duration spaceflight. SANS is hypothesized to result from an unrelenting headward fluid shift that occurs in the microgravity environment. Altered intracranial structure and physiology documented in spaceflight and head-down tilt (HDT) experiments(1, 2) are also theorized to be related to chronic headward fluid shift and thereby can provide an independent quantitative assessment related to this mechanism. As a potential countermeasure, lower body negative pressure (LBNP) applied in the supine posture has shown efficacy in reducing headward fluid shift(3). However, it remains unknown if intermittent LBNP simulating daily upright posture fluid redistribution can mitigate SANS and intracranial changes associated with long-duration spaceflight. The goal of this study was to quantify the effects of daily application of LBNP or daily exposure to the upright posture on intracranial structure and physiology during long-term HDT in order to evaluate the potential efficacy of LBNP as a countermeasure to SANS. METHODS 22 healthy volunteers (11 men; 11 women; mean age = 35 years (SD=9.2)(age range = 24 to 52 years); mean BMI = 24.0 kg/m2 (SD=2.8)) completed an MRI study performed at the German Aerospace Facility in Cologne, Germany. Strict six-degree head-down tilt (HDT) bedrest was used as a spaceflight analog to induce a continuous headward fluid shift for 30 days. The subjects were divided equally into two groups of interventions: 1) LBNP for 3-hour sessions twice daily and 2) seated position for 3-hour sessions twice daily. Interventions were divided into morning and afternoon sessions for both groups. The LBNP intervention was maintained at 25 mmHg  2 mmHg. Pulse-gated MRI phase-contrast flow imaging was used to quantify cerebral artery stroke volume (CASV) and peak-to-peak cerebral spinal fluid (CSF) velocity (CSFVp-p) within the cerebral aqueduct. A 3D T1-MPRAGE sequence was used to quantify volumetric changes of the brain and intracranial CSF spaces using MRI Cloud software. MRI acquisitions were obtained at baseline (BDC, supine posture), 15 days into HDT (HDT15), 29 days into HDT (HDT29), and 12 days after recovery (R12, supine posture). The data were analyzed by a mixed model, which included intervention, time (four nominal levels BDC, HDT15, HDT29, R12), and intervention-time interaction as the fixed effects and included subject as a random effect. RESULTS Compared to BDC there was no statistically significant difference in CASV and CSFVp-p during HDT except for CASV at HDT29 (seated group) where there was a 1.7 mL (12%) decrease (P<0.01). Compared to BDC there was a statistically significant increase in intracranial volume (ICV; ICV = white matter + gray matter + CSF) for both interventions at HDT15 (Δ13 mL, 0.9 % (LBNP group); Δ15 mL, 1.0%, (seated group)) and HDT29 (Δ19 mL, 1.2%, (LBNP group); Δ23 mL, 1.5%) (seated group)) (All Ps<.001). Compared to baseline, lateral ventricular volume increased at HDT15 (Δ0.9 mL, 5.5%) and HDT29 (Δ1.8 mL, 10%)) for LBNP only (P=.001 for each). During HDT, white matter volume remained stable compared to baseline for both interventions. There were no significant intervention effects in the overall response to HDT (All Ps >.2). CONCLUSION LBNP had a similar response to the seated posture during 29 days of HDT. Although there was an increase in ICV and lateral ventricular volume with HDT there was no change in intracranial physiological parameters with LBNP suggesting an overall diminished response to the long-term effects of HDT. The lack of any significant increase in white matter volume during HDT with LBNP suggests maintenance of cerebral interstitial fluid transport. Final conclusions are pending the data collection for the control group (no intervention) which will be completed in 2023.

Larry A Kramer↗
NASA NTRS2024

Xplo-SA9T: Optimization of Sorbent Technology With Existing and New Amine Variants for Carbon Dioxide Removal and Humidity Control

Scrubbing of the spacesuit air stream to control humidity and regulate carbon dioxide (CO 2 ) relies on amine-loaded resins, colloquially known as sorbents. The efficacy of Rapid Cycle Amine technology relies on the propensity of nitrogens toward adsorption of CO 2 while simultaneously offering regenerative properties under vacuum or positive pressure. The commonly utilized sorbent, SA9T, was recreated and evaluated further to increase stability and serve as a benchmark comparison for newly synthesized amine sorbent technologies. Ongoing storage studies with eight different environments will allow the development of applicable storage protocols and provide insight into possible ammonia generation pathways. Attempts to alleviate the known issues with SA9T included the alteration of the primary amine (tetraethylenepentamine), the choice of resin, and the particle size distribution. In-house CO 2 breakthrough experiments were conducted using a specialized apparatus that can simulate spacesuit conditions, offering high-quality triplicate capacity analysis affording direct comparison to known adsorbents in the literature. Thermo-Desorption Gas Chromatography Mass Spectrometry studies on the synthesized materials revealed any reagent or solvent offgassing while Nuclear Magnetic Resonance spectroscopy tracked the stability of the bound amine. Scanning Electron Microscope images of sieved materials provided a more accurate size interpretation facilitating synthetic design and pressure drop elimination. All efficient sorbents were synthesized to a commercial batch scale subsequent to evaluation including Xplo-SA9T.

John R Tidwell↗
DOE OSTI2023

Measurement of the muon anomalous precession frequency in runs 2 \& 3 of the Muon $g-2$ Experiment at Fermilab

This dissertation presents a measurement of the muon anomalous precession frequency for the Runs 2 \& 3 data of the E989 Muon $g-2$ Experiment at Fermilab. The muon anomalous precession frequency is one of two key inputs, the other being the magnetic field, used to precisely determine the muon magnetic anomaly, $a_{\mu}$. In April 2021, the E989 collaboration reported its first measurement of $a_{\mu}$ to an unprecedented precision of 460 parts-per-billion (ppb). This result is in agreement with the previous measurement performed by the E821 collaboration at Brookhaven National Laboratory, and the combined experimental value is in tension with the Standard Model prediction at 4.2$\sigma$, a possible hint of new physics. The first result from E989 was based on the Run-1 data, which was collected in 2018 and comprises 6\% of the experiment’s target statistics; the Run-1 result was statistics-limited. The Runs 2 \& 3 data were collected in 2019-2020 and constitute a four-fold increase i n statistics compared to Run-1 and consequently, a factor of two reduction in the measurement’s statistical uncertainty. This reduced statistical uncertainty, as well as continued understanding of systematic effects, will result in an even more precise measurement of $a_{\mu}$ and will help clarify the observed tension between theory and experiment. The precession frequency analysis presented in this dissertation includes a number of improvements compared to Boston University's Run-1 analysis: the implementation of a more robust pileup-subtraction procedure, the implementation of a kernel ratio method, the adoption of the statistically optimal asymmetry-weighted method, and investigations that led to an improved understanding of an outstanding residual slow effect. This dissertation motivates a measurement of the muon magnetic anomaly, describes the experimental principle, gives an overview of the E989 experiment, and presents a precession frequency analysis with full systematic unc ertainty evaluation for the Runs 2 \& 3 data. The combined precession frequency measurement, using the ratio asymmetry-weighted method, has a statistical uncertainty of 201 ppb and a systematic uncertainty of 25 ppb, constituting the most precise determination of the muon anomalous precision frequency to date.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

Superconducting penetration depth through a Van Hove singularity: Sr 2 ⁢RuO 4 under uniaxial stress

A plethora of experiments in Sr 2 RuO 4 have reached conflicting conclusions about the symmetry of the superconducting gap. To probe the gap’s structure in k-space, we use strain to continuously tune the band structure through a Van Hove singularity (VHS) while imaging the superconductivity with scanning SQUID microscopy. We find that the superfluid density peaks at the VHS and that the temperature dependence of the penetration depth is T 2 -quadratic over the entire measured range of strain ε. These results are consistent with a gap structure that has vertical line nodes, experimentally confirming that non-local effects in the Meissner screening can lead to T 2 behavior and clarifying the nature of the low-energy excitations in Sr 2 RuO 4 .

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1992

Plasma observations near Neptune - Results from Voyager 2

Results from observations made by the Plasma Science experiment on Voyager 2 at Neptune are reviewed. The magnetosphere of Neptune is filled with a tenuous plasma, which consists of at least two components: a light ion, probably H(+) and a heavy ion, probably N(+). Triton's atmosphere or ionosphere is thought to be the source of both heavy and light ions. Much of the low energy plasma in the inner magnetosphere is concentrated near the magnetic equator and near closest approach to the planet. The large tilt of the magnetic dipole axis from the rotation axis produces a dynamic magnetosphere which goes from an earthlike configuration to a pole-on configuration and back every 16 hours. The polar cusp regions change location and size as the planet rotates; at the time of the inbound magnetopause crossing, the phase of Neptune's rotation was such that the spacecraft entered the magnetosphere through the southern polar cusp region. Outbound from Neptune observations made in the magnetosheath show a possible signature of diurnal oscillation of the plasma mantle that grows, shrinks, and rocks, in a diurnal cycle. After the encounter with Neptune's magnetosphere, an upstream wave event was observed when the interplanetary magnetic field connected to the bow shock. The low frequency waves observed appear to be a mixture of Alfvenic and/or fast mode waves propagating away from the planet.

Zhang, Ming↗
NASA NTRS1985

Proceedings of the First National Workshop on the Global Weather Experiment: Current Achievements and Future Directions, volume 2, part 2

An assessment of the status of research using Global Weather Experiment (GWE) data and of the progress in meeting the objectives of the GWE, i.e., better knowledge and understanding of the atmosphere in order to provide more useful weather prediction services. Volume Two consists of a compilation of the papers presented during the workshop. These cover studies that addressed GWE research objectives and utilized GWE information. The titles in Part 2 of this volume include General Circulation Planetary Waves, Interhemispheric, Cross-Equatorial Exchange, Global Aspects of Monsoons, Midlatitude-Tropical Interactions During Monsoons, Stratosphere, Southern Hemisphere, Parameterization, Design of Observations, Oceanography, Future Possibilities, Research Gaps, with an Appendix.

Source record↗
DOE OSTI2022

On the Correspondence Between Atmosphere-Only and Coupled Simulations for Radiative Feedbacks and Forcing From CO 2

Atmosphere-only experiments are widely used to investigate climate feedbacks simulated in more computationally expensive fully coupled global climate model simulations. We confirm that this remains a valid approach by comparing the radiative feedbacks and forcing between coupled and atmosphere-only simulations for the latest models taking part in the 6th phase of the Coupled Model Intercomparison Project (CMIP6). For global-mean cloud feedbacks, we find a better than previously known correspondence between these experiments, which applies even to the response of individual cloud properties (amount, altitude, and optical depth) and holds even when considering atmosphere-only simulations of only 1 yr duration. For regional cloud feedbacks, the correspondence between the two experiments is generally present at every geographic location except for the tropical Pacific but takes longer experiments to reveal. For the lapse rate and surface albedo feedbacks, the correspondence between the two experiments is weaker due to the non-uniform warming pattern and loss of sea ice in the coupled experiment. For the across-model relationship between 4xCO 2 effective radiative forcing and feedback, we find a different behavior across experiments in CMIP6 than in CMIP5, casting doubt on the physical significance of previous results that highlighted an anti-correlation between the two quantities. Overall, these results confirm the utility of atmosphere-only experiments particularly to study cloud feedbacks, which are the dominant source of inter-model spread in climate sensitivity.

58 GEOSCIENCES↗
NASA NTRS1994

Effects of Hypergravity on Statocyst Development in Embryonic Aplysia californica

Aplysia californica is a marine gastropod mollusc with bilaterally paired statocysts as gravity-reccptor organs. Data from three experiments in which embryonic Aplysia californica were exposed to 2 x g arc discussed. The experimental groups were exposed to excess gravity until hatching (9-12 day), whereas control groups were maintained at normal gravity. Body diameter was measured before exposure to 2 x g. Statocyst, statolith and body diameter were each determined for samples of 20 embryos from each group on successive days. Exposure to excess gravity led to an increase in body size. Statocyst size was not affected by exposure to 2 x g. Statolith size decreased with treatment as indicated by smaller statolith-to-body ratios observed in the 2 x g group in all three experiments. Mean statolith diameter was significantly smaller for the 2 x g group in Experiment 1 but not in Experiments 2 and 3. Defective statocysts, characterized by very small or no statoliths, were found in the 2 x g group in Experiments 1 and 2.

Pedrozo, Hugo A.↗
DOE OSTI2020

Associative nitrogen fixation linked with three perennial bioenergy grasses in field and greenhouse experiments

Abstract Associative nitrogen (N 2 )‐fixation (ANF) by bacteria in the root‐zone of perennial bioenergy grasses has the potential to replace or supplement N fertilizer and support sustainable production of biomass, but its application in marginal ecosystems requires further evaluation. In this study, we first combined both greenhouse and field experiments, to explore the N 2 fixation effects of three temperate feedstocks Miscanthus × giganteus (giant miscanthus, Freedom), Panicum virgatum (switchgrass, Alamo), and Saccharum sp. (energycane, Ho 02‐147). In field studies across three growing seasons, plant and soil pools of candidate feedstocks were partially composed of N derived from the atmosphere (Ndfa). Energycane, giant miscanthus, and switchgrass were estimated to derive >30%, %Ndfa. Greenhouse studies were also performed to trace isotopically labeled 15 N 2 into plant biomass and soil pools. Evidence for Ndfa was detected in all three feedstock grasses (using reference 15 N of soil, chicory, and sorghum, δ 15 N~+7.0). Isotopically labeled 15 N 2 was traced into biomass (during grass elongation stage) and soil pools. Extrapolation of rates during the 24 hr labeling period to 50 days estimated 30%–55% of plant Ndfa, with the greatest Ndfa for energycane. The findings of the field natural abundance and greenhouse 15 N 2 feeding experiments provided complementary evidence that perennial bioenergy grasses have the potential to support relatively high rates of ANF, and accumulate diazotroph‐derived N into biomass when grown on non‐fertilized soil.

09 BIOMASS FUELS↗
DOE OSTI2022

Beam and Spin Optics Simulation Tutorials, Using Zgoubi Exercises and Solutions 2 - RHIC Run 22 Spin Transparency Experiment

High electron and ion polarizations are paramount design requirements for the future Electron Ion Collider (EIC) at BNL. A “spin transparency” mode of operation, inherited from the “figure-8” ring design [1], allows preservation and control of electron and ion spin polarization in a collider or storage ring [2, 3]. It makes the ring lattice “invisible” to the spin and allows for polarization control by small quasi-static magnetic fields with practically no effect on beam orbital parameters. Beam polarization can then be fully controlled by small adjustments of snake axis orientation (a few degrees) and snake strengths (a few percent); polarization orientation at IPs can be controlled without spin rotators, spins can be adiabatically flipped without the need of ac magnets. The transparent spin mode has been demonstrated in simulations [2] for the purpose of being tested experimentally during RHIC Run 22. This experiment was aimed at providing data to validate the principles. Yellow RHIC ring (Fig. 1.1) was configured in the transparent spin mode by aligning the axes of its two helical snakes (located respectively in the 3 o’clock and 9 o’clock sextants) parallel to the longitudinal axis. Experiment goals and expected results, ad hoc procedures and hardware requirements, are addressed in Refs. [2, 3].

43 PARTICLE ACCELERATORS↗
NASA NTRS2002

Repetition blindness has a perceptual locus: evidence from online processing of targets in RSVP streams

Four experiments tested whether repetition blindness (RB; reduced accuracy reporting repetitions of briefly displayed items) is a perceptual or a memory-recall phenomenon. RB was measured in rapid serial visual presentation (RSVP) streams, with the task altered to reduce memory demands. In Experiment 1 only the number of targets (1 vs. 2) was reported, eliminating the need to remember target identities. Experiment 2 segregated repeated and nonrepeated targets into separate blocks to reduce bias against repeated targets. Experiments 3 and 4 required immediate "online" buttonpress responses to targets as they occurred. All 4 experiments showed very strong RB. Furthermore, the online response data showed clearly that the 2nd of the repeated targets is the one missed. The present results show that in the RSVP paradigm, RB occurs online during initial stimulus encoding and decision making. The authors argue that RB is indeed a perceptual phenomenon.

Form Perception↗
DOE OSTI2022

Using dorsal surface for individual identification of dairy calves through 3D deep learning algorithms

Advances in machine learning techniques have allowed the development of computer vision systems (CVS) that can accurately predict several phenotypes of interest for livestock operations. In this context, 3D images taken from a top-down view are particularly useful for estimating body condition score, growth development, and body biometrics in cattle. Frequently, such CVS rely on identification (ID) systems, such as electronic tags, as a way to match animal ID and the predicted phenotype. However, the same 3D images used to predict body weight and other animal biometrics could be adopted for animal recognition as well. Such alternative would optimize CVS to recognize animal ID and monitor growth development simultaneously while leveraging the same hardware infrastructure. Furthermore, this strategy could be used to recognize animals with similar color patterns. Nonetheless, growing animals are continuously changing body shape, which could limit its use as an invariant feature for pattern recognition. Thus, the objectives of this study were: (1) to compare algorithms for different 3D object representations to identify individual animals; and (2) to evaluate how short-term changes in body shape due to animal growth affect the predictive performance of these algorithms. For objective 1, the algorithms were trained (n = 4,558) and tested (n = 1,139) using images from 38 Holstein calves. For objective 2, we designed three different experiments using images (n = 2,347) from five Holstein calves taken over six weeks during their growing period, always training and testing on different weeks. Each experiment evaluated how changing a different parameter of the image capturing procedure affected the predictive ability of the trained algorithms. In the first experiment, we varied the total number of images per animal in the training set; in the second experiment, we varied the number of weeks while keeping a fixed number of images in the training set; and in the third experiment, we skipped weeks between images in the training and test sets. The F 1 score for objective (1) was up to 0.804 when testing with the last frames of each video, and up to 0.959 when using random frames for testing. For objective (2), the F 1 score was up to 0.947 for the first experiment when using 130 images per animal; up to 0.979 for the second experiment when using all five weeks; and up to 0.917 when not skipping weeks between training and testing. In conclusion, these results show that deep learning algorithms can be used to identify individual animals through their dorsal area 3D surfaces, and, from our experiments using calves in their growing period, that they are robust enough to account for changes in body shape and size, making them a promising tool for animal recognition during growth.

3D neural networks↗