المؤلفون: Larsen, Bjorn, Mingarelli, Chiara M. F., Hazboun, Jeffrey S., Chalumeau, Aurelien, Good, Deborah C., Simon, Joseph, Agazie, Gabriella, Anumarlapudi, Akash, Archibald, Anne M., Arzoumanian, Zaven, Baker, Paul T., Brook, Paul R., Cromartie, H. Thankful, Crowter, Kathryn, DeCesar, Megan E., Demorest, Paul B., Dolch, Timothy, Ferrara, Elizabeth C., Fiore, William, Fonseca, Emmanuel, Freedman, Gabriel E., Garver-Daniels, Nate, Gentile, Peter A., Glaser, Joseph, Jennings, Ross J., Jones, Megan L., Kaplan, David L., Kerr, Matthew, Lam, Michael T., Lorimer, Duncan R., Luo, Jing, Lynch, Ryan S., McEwen, Alexander, McLaughlin, Maura A., McMann, Natasha, Meyers, Bradley W., Ng, Cherry, Nice, David J., Pennucci, Timothy T., Perera, Benetge B. P., Pol, Nihan S., Radovan, Henri A., Ransom, Scott M., Ray, Paul S., Schmiedekamp, Ann, Schmiedekamp, Carl, Shapiro-Albert, Brent J., Stairs, Ingrid H., Stovall, Kevin, Susobhanan, Abhimanyu, Swiggum, Joseph K., Wahl, Haley M., Champion, David J., Cognard, Ismael, Guillemot, Lucas, Hu, Huanchen, Keith, Michael J., Liu, Kuo, McKee, James W., Parthasarathy, Aditya, Perrodin, Delphine, Possenti, Andrea, Shaifullah, Golam M., Theureau, Gilles

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Astrophysics of Galaxies, Astrophysics - Instrumentation and Methods for Astrophysics

الوصف: Pulsar timing arrays (PTAs) are designed to detect low-frequency gravitational waves (GWs). GWs induce achromatic signals in PTA data, meaning that the timing delays do not depend on radio-frequency. However, pulse arrival times are also affected by radio-frequency dependent "chromatic" noise from sources such as dispersion measure (DM) and scattering delay variations. Furthermore, the characterization of GW signals may be influenced by the choice of chromatic noise model for each pulsar. To better understand this effect, we assess if and how different chromatic noise models affect achromatic noise properties in each pulsar. The models we compare include existing DM models used by NANOGrav and noise models used for the European PTA Data Release 2 (EPTA DR2). We perform this comparison using a subsample of six pulsars from the NANOGrav 15 yr data set, selecting the same six pulsars as from the EPTA DR2 six-pulsar dataset. We find that the choice of chromatic noise model noticeably affects the achromatic noise properties of several pulsars. This is most dramatic for PSR J1713+0747, where the amplitude of its achromatic red noise lowers from $\log_{10}A_{\text{RN}} = -14.1^{+0.1}_{-0.1}$ to $-14.7^{+0.3}_{-0.5}$, and the spectral index broadens from $\gamma_{\text{RN}} = 2.6^{+0.5}_{-0.4}$ to $\gamma_{\text{RN}} = 3.5^{+1.2}_{-0.9}$. We also compare each pulsar's noise properties with those inferred from the EPTA DR2, using the same models. From the discrepancies, we identify potential areas where the noise models could be improved. These results highlight the potential for custom chromatic noise models to improve PTA sensitivity to GWs.

الوصول الحر: http://arxiv.org/abs/2405.14941Test

المؤلفون: Oscar H. Salcedo (ORCID 0000-0002-7231-9219), David J. Carrejo (ORCID 0000-0001-6951-7217), Sergio Luna (ORCID 0000-0003-3058-410X)

المصدر: International Journal of Education in Mathematics, Science and Technology. 2024 12(1):20-39.

تمت مراجعته من قبل الزملاء: Y

Page Count: 21

الواصفات: STEM Education, Curriculum Development, Instructional Improvement, 21st Century Skills, Undergraduate Study, Engineering Education, Educational Change, Student Experience, Praxis, Instructional Design, Evaluation, Systems Approach

مستخلص: This paper discusses engineering praxis ethos (EPE), a proposed framework for constructing a STEM learning environment embedding interrelated components of learner experience and design activity, which can support curriculum and instructional design and evaluation in STEM education. The authors propose that STEM is a meta-discipline that relies on the design life cycle, the intellectual root of engineering disciplinary knowledge. The nature of design and design activity calls attention to domain-specific needs of STEM teachers and focuses discussions and critiques about the epistemological adequacy of integrated STEM content knowledge. Given the urgent need for learners to develop 21st century skills in STEM, the authors argue for the feasibility of incorporating both mathematical and simulation models using new technologies when designing experiences for learners. An example of teaching and learning systems thinking in undergraduate engineering education highlights how EPE can be a viable theory of action for STEM educators.

Abstractor: As Provided

المؤلفون: Sabour, Sara, Goli, Lily, Kopanas, George, Matthews, Mark, Lagun, Dmitry, Guibas, Leonidas, Jacobson, Alec, Fleet, David J., Tagliasacchi, Andrea

مصطلحات موضوعية: Computer Science - Computer Vision and Pattern Recognition, Computer Science - Machine Learning

الوصف: 3D Gaussian Splatting (3DGS) is a promising technique for 3D reconstruction, offering efficient training and rendering speeds, making it suitable for real-time applications.However, current methods require highly controlled environments (no moving people or wind-blown elements, and consistent lighting) to meet the inter-view consistency assumption of 3DGS. This makes reconstruction of real-world captures problematic. We present SpotlessSplats, an approach that leverages pre-trained and general-purpose features coupled with robust optimization to effectively ignore transient distractors. Our method achieves state-of-the-art reconstruction quality both visually and quantitatively, on casual captures.

الوصول الحر: http://arxiv.org/abs/2406.20055Test

المؤلفون: Warne, David J., Crossman, Kerryn, Heron, Grace E. M., Sharp, Jesse A., Jin, Wang, Wu, Paul Pao-Yen, Simpson, Matthew J., Mengersen, Kerrie, Ortiz, Juan-Carlos

مصطلحات موضوعية: Statistics - Applications, Quantitative Biology - Populations and Evolution, 62P12 (Primary)

الوصف: Coral reefs are increasingly subjected to major disturbances threatening the health of marine ecosystems. Substantial research underway to develop intervention strategies that assist reefs in recovery from, and resistance to, inevitable future climate and weather extremes. To assess potential benefits of interventions, mechanistic understanding of coral reef recovery and resistance patterns is essential. Recent evidence suggests that more than half of the reefs surveyed across the Great Barrier Reef (GBR) exhibit deviations from standard recovery modelling assumptions when the initial coral cover is low ($\leq 10$\%). New modelling is necessary to account for these observed patterns to better inform management strategies. We consider a new model for reef recovery at the coral cover scale that accounts for biphasic recovery patterns. The model is based on a multispecies Richards' growth model that includes a change point in the recovery patterns. Bayesian inference is applied for uncertainty quantification of key parameters for assessing reef health and recovery patterns. This analysis is applied to benthic survey data from the Australian Institute of Marine Sciences (AIMS). We demonstrate agreement between model predictions and data across every recorded recovery trajectory with at least two years of observations following disturbance events occurring between 1992--2020. This new approach will enable new insights into the biological, ecological and environmental factors that contribute to the duration and severity of biphasic coral recovery patterns across the GBR. These new insights will help to inform managements and monitoring practice to mitigate the impacts of climate change on coral reefs.

الوصول الحر: http://arxiv.org/abs/2406.19591Test

المؤلفون: Rani, Raffaele, Li, Jia-Lun, Moore, Toby J. T., Eden, David J., Rigby, Andrew J., Park, Geumsook, Lee, Yueh-Ning

مصطلحات موضوعية: Astrophysics - Astrophysics of Galaxies

الوصف: Stars form in the densest regions of molecular clouds, however, there is no universal understanding of the factors that regulate cloud dynamics and their influence on the gas-to-stars conversion. This study considers the impact of Galactic shear on the rotation of giant molecular clouds (GMCs) and its relation to the solenoidal modes of turbulence. We estimate the direction of rotation for a large sample of clouds in the \ce{^{13}CO}/\ce{C^{18}O} (3-2) Heterodyne Inner Milky Way Plane Survey (CHIMPS) and their corresponding sources in a new segmentation of the \ce{^{12}CO}(3-2) High-Resolution Survey (COHRS). To quantify the strength of shear, we introduce a parameter that describes the shear's ability to disrupt growing density perturbations within the cloud. Although we find no correlation between the direction of cloud rotation, the shear parameter, and the magnitude of the velocity gradient, the solenoidal fraction of the turbulence in the CHIMPS sample is positively correlated with the shear parameter and behaves similarly when plotted over Galactocentric distance. GMCs may thus not be large or long-lived enough to be affected by shear to the point of showing rotational alignment. In theory, Galactic shear can facilitate the rise of solenoidal turbulence and thus contribute to suppressing star formation. These results also suggest that the rotation of clouds is not strictly related to the overall rotation of the disc, but is more likely to be the imprint of Kelvin-Helmholtz instabilities in the colliding flows that formed the clouds.
Comment: Accepted, MNRAS

الوصول الحر: http://arxiv.org/abs/2406.19637Test

المؤلفون: Xie, Le, Majumder, Subir, Huang, Tong, Zhang, Qian, Chang, Ping, Hill, David J., Shahidehpour, Mohammad

مصطلحات موضوعية: Electrical Engineering and Systems Science - Systems and Control

الوصف: Addressing the urgency of climate change necessitates a coordinated and inclusive effort from all relevant stakeholders. Critical to this effort is the modeling, analysis, control, and integration of technological innovations within the electric energy system, which plays a crucial role in scaling up climate change solutions. This perspective article presents a set of research challenges and opportunities in the area of electric power systems that would be crucial in accelerating Gigaton-level decarbonization. Furthermore, it highlights institutional challenges associated with developing market mechanisms and regulatory architectures, ensuring that incentives are aligned for stakeholders to effectively implement the technological solutions on a large scale.
Comment: 17 pages, 2 figures

الوصول الحر: http://arxiv.org/abs/2406.17976Test

المؤلفون: Liu, Yihan, Warne, David J, Simpson, Matthew J

مصطلحات موضوعية: Physics - Applied Physics, Nonlinear Sciences - Cellular Automata and Lattice Gases, Quantitative Biology - Quantitative Methods, 92B99, 82M99, 62M99

الوصف: In vitro cell biology experiments are routinely used to characterize cell migration properties under various experimental conditions. These experiments can be interpreted using lattice-based random walk models to provide insight into underlying biological mechanisms, and continuum limit partial differential equation (PDE) descriptions of the stochastic models can be used to efficiently explore model properties instead of relying on repeated stochastic simulations. Working with efficient PDE models is of high interest for parameter estimation algorithms that typically require a large number of forward model simulations. Quantitative data from cell biology experiments usually involves non-negative cell counts in different regions of the experimental images, and it is not obvious how to relate finite, noisy count data to the solutions of continuous PDE models that correspond to noise-free density profiles. In this work we illustrate how to develop and implement likelihood-based methods for parameter estimation, parameter identifiability and model prediction for lattice-based models describing collective migration with an arbitrary number of interacting subpopulations. We implement a standard additive Gaussian measurement error model as well as a new physically-motivated multinomial measurement error model that relates noisy count data with the solution of continuous PDE models. Both measurement error models lead to similar outcomes for parameter estimation and parameter identifiability, whereas the standard additive Gaussian measurement error model leads to non-physical prediction outcomes. In contrast, the new multinomial measurement error model involves a lower computational overhead for parameter estimation and identifiability analysis, as well as leading to physically meaningful model predictions.
Comment: 34 pages, 7 figures

الوصول الحر: http://arxiv.org/abs/2406.16296Test

المؤلفون: Dey, Lankeswar, McLaughlin, Maura A., Wahl, Haley M., Demorest, Paul B., Arzoumanian, Zaven, Blumer, Harsha, Brook, Paul R., Burke-Spolaor, Sarah, Cromartie, H. Thankful, DeCesar, Megan E., Dolch, Timothy, Ellis, Justin A., Ferdman, Robert D., Ferrara, Elizabeth C., Fiore, William, Fonseca, Emmanuel, Garver-Daniels, Nate, Gentile, Peter A., Glaser, Joseph, Good, Deborah C., Jennings, Ross J., Jones, Megan L., Lam, Michael T., Lorimer, Duncan R., Luo, Jing, Lynch, Ryan S., Ng, Cherry, Nice, David J., Pennucci, Timothy T., Pol, Nihan S., Ransom, Scott M., Spiewak, Renée, Stairs, Ingrid H., Stovall, Kevin, Swiggum, Joseph K.

مصطلحات موضوعية: Astrophysics - High Energy Astrophysical Phenomena, Astrophysics - Instrumentation and Methods for Astrophysics

الوصف: Pulsar timing array experiments have recently uncovered evidence for a nanohertz gravitational wave background by precisely timing an ensemble of millisecond pulsars. The next significant milestones for these experiments include characterizing the detected background with greater precision, identifying its source(s), and detecting continuous gravitational waves from individual supermassive black hole binaries. To achieve these objectives, generating accurate and precise times of arrival of pulses from pulsar observations is crucial. Incorrect polarization calibration of the observed pulsar profiles may introduce errors in the measured times of arrival. Further, previous studies (e.g., van Straten 2013; Manchester et al. 2013) have demonstrated that robust polarization calibration of pulsar profiles can reduce noise in the pulsar timing data and improve timing solutions. In this paper, we investigate and compare the impact of different polarization calibration methods on pulsar timing precision using three distinct calibration techniques: the Ideal Feed Assumption (IFA), Measurement Equation Modeling (MEM), and Measurement Equation Template Matching (METM). Three NANOGrav pulsars-PSRs J1643$-$1224, J1744$-$1134, and J1909$-$3744-observed with the 800 MHz and 1.5 GHz receivers at the Green Bank Telescope (GBT) are utilized for our analysis. Our findings reveal that all three calibration methods enhance timing precision compared to scenarios where no polarization calibration is performed. Additionally, among the three calibration methods, the IFA approach generally provides the best results for timing analysis of pulsars observed with the GBT receiver system. We attribute the comparatively poorer performance of the MEM and METM methods to potential instabilities in the reference noise diode coupled to the receiver and temporal variations in the profile of the reference pulsar, respectively.
Comment: 21 pages, 6 figures, 1 table, submitted to Astrophysical Journal

الوصول الحر: http://arxiv.org/abs/2406.13463Test

المؤلفون: Chan, Ya-Chu, Liu, Lee R., Scheck, Andrew, Nesbitt, David J., Ye, Jun, Rosenberg, Dina

مصطلحات موضوعية: Physics - Atomic Physics, Physics - Chemical Physics, Quantum Physics

الوصف: The quantum mechanical nature of spherical top molecules is particularly evident at low angular momentum quantum number J. Using infrared spectroscopy on the 8.4$\mu$m rovibrational band of buffer gas cooled $^{12}$C$_{60}$, we observe the hitherto unseen R(J = 0 - 29) rotational progression, including the complete disappearance of certain transitions due to the molecule's perfect icosahedral symmetry and identical bosonic nuclei. The observation of extremely weak C$_{60}$ absorption is facilitated by a laser desorption C$_{60}$ vapor source, which transfers 1000-fold less heat to the cryogenic buffer gas cell than a traditional oven source. This technique paves the way to cooling C$_{60}$ and other large gas phase molecules to much lower temperatures, providing continued advances for spectral resolution and sensitivity.

الوصول الحر: http://arxiv.org/abs/2406.13907Test

المؤلفون: Cheng, Yuxuan, Lonial, Benjamin F., Sista, Shivnag, Meer, David J., Hofert, Anisa, Weeks, Eric R., Shattuck, Mark D., O'Hern, Corey S.

مصطلحات موضوعية: Physics - Computational Physics, Physics - Fluid Dynamics

الوصف: Capillary droplets form due to surface tension when two immiscible fluids are mixed. We describe the motion of gravity-driven capillary droplets flowing through narrow constrictions and obstacle arrays in both simulations and experiments. Our new capillary deformable particle model recapitulates the shape and velocity of single oil droplets in water as they pass through narrow constrictions in microfluidic chambers. Using this experimentally validated model, we simulate the flow and clogging of single capillary droplets in narrow channels and obstacle arrays and find several important results. First, the capillary droplet speed profile is nonmonotonic as the droplet exits the narrow orifice, and we can tune the droplet properties so that the speed overshoots the terminal speed far from the constriction. Second, in obstacle arrays, we find that extremely deformable droplets can wrap around obstacles, which leads to decreased average droplet speed in the continuous flow regime and increased probability for clogging in the regime where permanent clogs form. Third, the wrapping mechanism causes the clogging probability in obstacle arrays to become nonmonotonic with surface tension $\Gamma$. At large $\Gamma$, the droplets are nearly rigid and the clogging probability is large since the droplets can not squeeze through the gaps between obstacles. With decreasing $\Gamma$, the clogging probability decreases as the droplets become more deformable. However, in the small-$\Gamma$ limit the clogging probability increases, since the droplets are extremely deformable and cause clogs as they wrap around the obstacles. The results from these studies are important for developing a predictive understanding of capillary droplet flows through complex and confined geometries.

الوصول الحر: http://arxiv.org/abs/2406.13776Test