cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Constraint-Based Causal Discovery using Partial Ancestral Graphs in the presence of Cycles
Creators: name: Mooij, Joris M.
name: Claassen, Tom
Publisher: name: arXiv
Year: 2020
Subjects: subject: Statistics Theory (math.ST)
subject: Artificial Intelligence (cs.AI)
subject: Machine Learning (cs.LG)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences

description: While feedback loops are known to play important roles in many complex systems, their existence is ignored in a large part of the causal discovery literature, as systems are typically assumed to be acyclic from the outset. When applying causal discovery algorithms designed for the acyclic setting on data generated by a system that involves feedback, one would not expect to obtain correct results. In this work, we show that -- surprisingly -- the output of the Fast Causal Inference (FCI) algorithm is correct if it is applied to observational data generated by a system that involves feedback. More specifically, we prove that for observational data generated by a simple and $σ$-faithful Structural Causal Model (SCM), FCI is sound and complete, and can be used to consistently estimate (i) the presence and absence of causal relations, (ii) the presence and absence of direct causal relations, (iii) the absence of confounders, and (iv) the absence of specific cycles in the causal graph of the SCM. We extend these results to constraint-based causal discovery algorithms that exploit certain forms of background knowledge, including the causally sufficient setting (e.g., the PC algorithm) and the Joint Causal Inference setting (e.g., the FCI-JCI algorithm).
description: This version corrects some typos in the published version (Proceedings of the 36th Conference on Uncertainty in Artificial Intelligence (UAI), PMLR volume 124, 2020); it also provides proofs inline instead of in a supplement for improved readability
Low tension and wettability alteration EOR approaches for a high temperature high salinity carbonate reservoir
Creators: name: Tibrewala, Yash Vishal
name: 0000-0002-4410-1650
Publisher: name: The University of Texas at Austin
Year: 2021
Subjects: Ultra-low interfacial tension
Wettability alteration
Carbonate reservoir
Surfactant
Spontaneous imbibition
Core flood
Phase behavior

description: Carbonate reservoirs account for more than half of the world’s oil reserves. Many carbonate reservoirs have low oil recovery due to their heterogeneity and oil-wetness. This research work focuses on developing chemical enhanced oil recovery methods for a reservoir with high temperature (100°C), high salinity (35000 ppm) and light oil (40° API). The work tested deployment of both the ultra-low interfacial tension method and the wettability alteration method to increase the oil recovery. The ultra-low interfacial tension formulation was found to incorporate three surfactants at 0.5 wt% and one co-solvent at 0.75 wt%. It also used a polymer at 5000 ppm to control the mobility and increase the sweep efficiency. The solution was found by conducting phase behavior experiments on a range of surfactants and was tested in two sand packs made of the reservoir rock. The first flood (143mD) employed a salinity gradient and led to an oil recovery of 99.9%. The second flood (202mD) was conducted at constant salinity and led to an oil recovery of 98.1%. A single surfactant solution was found for the wettability alteration method. This process does not use any polymer. The solution was arrived at by conducting contact angle and spontaneous imbibition experiments. During the spontaneous imbibition experiment, the surfactant recovered 33% of total oil in place compared to only 10% recovered by the control sample (sea water). The surfactant was tested in a secondary core flood (0.17 mD) and led to an oil recovery of 54.3%. Additionally, it was tested in a tertiary core flood (2.87mD) and managed to increase the oil recovery from 51.9% during water flood to 69.2% after surfactant flood. Both methods have been successful in demonstrating an increase in oil recovery during a flood. The ultra-low interfacial tension approach could not be tested in reservoir core samples due to their low permeability and lack of polymer transport. While the wettability alteration approach has demonstrated a significantly less recovery than the ultra-low interfacial tension approach, it is expected to be much more cost effective due to the less amount of surfactant used and no use of polymers
Environmental effects with Frozen Density Embedding in Real-Time Time-Dependent Density Functional Theory using localized basis functions
Creators: name: De Santis, Matteo
name: Belpassi, Leonardo
name: Jacob, Christoph R.
name: Gomes, André Severo Pereira
name: Tarantelli, Francesco
name: Visscher, Lucas
name: Storchi, Loriano
Publisher: name: arXiv
Year: 2020
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: Frozen Density Embedding (FDE) represents a versatile embedding scheme to describe the environmental effect on the electron dynamics in molecular systems. The extension of the general theory of FDE to the real-time time-dependent Kohn-Sham method has previously been presented and implemented in plane-waves and periodic boundary conditions (Pavanello et al. J. Chem. Phys. 142, 154116, 2015). In the current paper, we extend our recent formulation of real-time time-dependent Kohn-Sham method based on localized basis set functions and developed within the Psi4NumPy framework (De Santis et al. J. Chem. Theory Comput. 2020, 16, 2410) to the FDE scheme. The latter has been implemented in its "uncoupled" flavor (in which the time evolution is only carried out for the active subsystem, while the environment subsystems remain at their ground state), using and adapting the FDE implementation already available in the PyEmbed module of the scripting framework PyADF. The implementation was facilitated by the fact that both Psi4NumPy and PyADF, being native Python API, provided an ideal framework of development using the Python advantages in terms of code readability and reusability. We demonstrate that the inclusion of the FDE potential does not introduce any numerical instability in time propagation of the density matrix of the active subsystem and in the limit of weak external field, the numerical results for low-lying transition energies are consistent with those obtained using the reference FDE calculations based on the linear response TDDFT. The method is found to give stable numerical results also in the presence of strong external field inducing non-linear effects.
Sharp Chandra View of ROSAT All-Sky Survey Bright Sources: I. Improvement of Positional Accuracy
Creators: name: Gao, Shuang
name: Wang, Song
name: Liu, Jifeng
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The ROSAT All-Sky Survey (RASS) represents one of the most complete and sensitive soft X-ray all-sky surveys to date. However, the deficient positional accuracy of the RASS Bright Source Catalog (BSC) and subsequent lack of firm optical identifications affect the multi-wavelength studies of X-ray sources. The widely used positional errors $σ_{pos}$ based on the Tycho Stars Catalog (Tycho-1) have previously been applied for identifying objects in the optical band. The considerably sharper Chandra view covers a fraction of RASS sources, whose $σ_{pos}$ could be improved by utilizing the sub-arcsec positional accuracy of Chandra observations. We cross-match X-ray objects between the BSC and \emph{Chandra} sources extracted from the Advanced CCD Imaging Spectrometer (ACIS) archival observations. A combined counterparts list (BSCxACIS) with \emph{Chandra} spatial positions weighted by the X-ray flux of multi-counterparts is employed to evaluate and improve the former identifications of BSC with the other surveys. Based on these identification evaluations, we suggest that the point-likeness of BSC sources and INS (isolated neutron stars) candidates should be carefully reconsidered.
description: 13 pages, 8 figures and 3 tables, accepted by RAA
Stability of 3D Optical Topologies and Reconstruction of Strongly Correlated Bi-photon States
Creators: name: Dehghan Manshadi, Seyedeh Fatemeh
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2023
Subjects: Optical Topologies
Quantum Optics

description: Structured light has shown great promises and impacts in various fields such as microscopy, optical trapping, sensing, classical communication, high dimensional quantum information, quantum key distribution (QKD) and quantum metrology. In this Thesis, we will be discussing two projects, in the context of structured light, one about the stability of 3D optical topologies and the other about the reconstruction of strongly correlated bi-photon states. In the introduction, we will be reviewing some of the basic concepts needed to follow the two projects. Starting from the spatial modes and their characteristics, we discuss about some interferometric approaches to reconstruct the phase and the amplitude of an electromagnetic field, either for a classical laser beam or for photons. Moreover, we briefly explain the spontaneous parametric down conversion (SPDC) process that is commonly used for generating entangled bi-photon states. In the second chapter, after giving an overview about singular optics and optical topologies, we explore the effect of different types of aberrations on three different 3D optical structures, Trefoil knot, Cinquefoil knot and Hopf Link. In this work we show that these structures are robust under aberrations with the highest strength if the defining aperture of the aberration is big enough. In addition, we discuss about how these aberrations will modify the structure if we decrease the size of the aperture and in which aperture the structures start to break and therefore, we investigate the impact of the strength under such apertures. In the third chapter, we return to the SPDC process, discuss the thin-crystal approximation, spatial mode correlations of an entangled bi-photon state, and coincidence imaging performed with time stamping cameras. We propose an approach to characterize an unknown two-photon state using interference between the unknown bi-photon state and a reference bi-photon state in addition to coincidence imaging. We show that this approach is faster, scalable and loss-free compared to projective measurements. Finally, in the conclusion, we put together the results of these two projects and discuss about the future work that can follow up on what is done so far.
Ultrashort laser pulses with chromatic astigmatism
Creators: name: Jolly, Spencer W.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: Ultrashort laser pulses are described having chromatic astigmatism, where the astigmatic phase varies linearly with the offset from the central frequency. Such a spatio-temporal coupling not only induces interesting space-frequency and space-time effects, but it removes cylindrical symmetry. We analyze the quantitative effects on the spatio-temporal pulse structure on the collimated beam and as it propagates through a focus, with both the fundamental Gaussian beam and Laguerre-Gaussian beams. Chromatic astigmatism is a new type of spatio-temporal coupling towards arbitrary higher complexity beams that still have a simple description, and may be applied to imaging, metrology, or ultrafast light-matter interaction.
description: 12 pages, 8 figures, submitted to Optics Express
Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars. V. Oxygen abundance in the metal-poor giant HD 122563 from OH UV lines
Creators: name: Prakapavičius, D.
name: Kučinskas, A.
name: Dobrovolskas, V.
name: Klevas, J.
name: Steffen, M.
name: Bonifacio, P.
name: Ludwig, H. -G.
name: Spite, M.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: Although oxygen is an important tracer of the early Galactic evolution, its abundance trends with metallicity are still relatively poorly known at [Fe/H] < -2.5. This is in part due to a lack of reliable oxygen abundance indicators in the metal-poor stars, in part due to shortcomings in 1D LTE abundance analyses. In this study we determined the oxygen abundance in the metal-poor halo giant HD 122563 using a 3D hydrodynamical CO5BOLD model atmosphere. Our main goal was to understand whether a 3D LTE analysis may help to improve the reliability of oxygen abundances determined from OH UV lines in comparison to those obtained using standard 1D LTE methodology. The oxygen abundance in HD 122563 was determined using 71 OH UV lines located in the wavelength range between 308-330 nm. The analysis was done using a high-resolution VLT UVES spectrum with a 1D LTE spectral line synthesis performed using the SYNTHE package and classical ATLAS9 model atmosphere. Subsequently, a 3D hydrodynamical CO5BOLD, and 1D hydrostatic LHD model atmospheres were used in order to compute 3D-1D abundance corrections. For this, the microturbulence velocity used with the 1D LHD model atmosphere was derived from the hydrodynamical CO5BOLD model atmosphere. As in previous studies, we found trends of the 1D LTE oxygen abundances determined from OH UV lines with line parameters, such as the line excitation potential and the line strength. These trends become significantly less pronounced in 3D LTE. Using OH UV lines we determined a 3D LTE oxygen abundance in HD 122563 of A(O) = 6.23 +/- 0.13. This is in fair agreement with the oxygen abundance obtained from OH IR lines, A(O) = 6.39 +/- 0.11, but it is noticeably lower than that determined using the forbidden [OI] line, A(O) = 6.53 +/- 0.15. While the exact cause for this discrepancy remains unclear, it is very likely that non-LTE effects may play a decisive role here.
description: 18 pages, 13 figures, 6 tables. Accepted for publication in A&A
Nonexistence of Invariant Tori Transverse to Foliations: An Application of Converse KAM Theory
Creators: name: Duignan, Nathan
name: Meiss, James D.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics
subject: 37J40, 34C14, 37J06, 65P10, 65P20

description: Invariant manifolds are of fundamental importance to the qualitative understanding of dynamical systems. In this work, we explore and extend MacKay's converse KAM condition to obtain a sufficient condition for the nonexistence of invariant surfaces that are transverse to a chosen 1D foliation. We show how useful foliations can be constructed from approximate integrals of the system. This theory is implemented numerically for two models, a particle in a two-wave potential and a Beltrami flow studied by Zaslavsky (Q-flows). These are both 3D volume-preserving flows, and they exemplify the dynamics seen in time-dependent Hamiltonian systems and incompressible fluids, respectively. Through both numerical and theoretical considerations, it is revealed how to choose foliations that capture the nonexistence of invariant tori with varying homologies.
description: 25 pages, 18 figures
Controlling the bursting size in the two-dimensional Rulkov model
Creators: name: López, Jennifer
name: Coccolo, Mattia
name: Capeáns, Rubén
name: 1
name: Sanjuán, Miguel A. F.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Adaptation and Self-Organizing Systems (nlin.AO)
subject: Chaotic Dynamics (nlin.CD)
subject: FOS: Physical sciences

description: We propose to control the orbits of the two-dimensional Rulkov model affected by bounded noise. For the correct parameter choice the phase space presents two chaotic regions separated by a transient chaotic region in between. One of the chaotic regions is the responsible to give birth to the neuronal bursting regime. Normally, an orbit in this chaotic region cannot pass through the transient chaotic one and reach the other chaotic region. As a consequence the burstings are short in time. Here, we propose a control technique to connect both chaotic regions and allow the neuron to exhibit very long burstings. This control method defines a region Q covering the transient chaotic region where it is possible to find an advantageous set $S \in Q$ through which the orbits can be driven with a minimal control. In addition we show how the set S changes depending on the noise intensity affecting the map, and how the set S can be used in different scenarios of control.
description: Controlled neruonal dynamics
A design theory for transparency of information privacy practices
Creators: name: Dehling, Tobias
name: Sunyaev, Ali
Publisher: name: arXiv
Year: 2023
Subjects: subject: Computers and Society (cs.CY)
subject: FOS: Computer and information sciences

description: The rising diffusion of information systems (IS) throughout society poses an increasingly serious threat to privacy as a social value. One approach to alleviating this threat is to establish transparency of information privacy practices (TIPP) so that consumers can better understand how their information is processed. However, the design of transparency artifacts (eg, privacy notices) has clearly not followed this approach, given the ever-increasing volume of information processing. Hence, consumers face a situation where they cannot see the 'forest for the trees' when aiming to ascertain whether information processing meets their privacy expectations. A key problem is that overly comprehensive information presentation results in information overload and is thus counterproductive for establishing TIPP. We depart from the extant design logic of transparency artifacts and develop a theoretical foundation (TIPP theory) for transparency artifact designs useful for establishing TIPP from the perspective of privacy as a social value. We present TIPP theory in two parts to capture the sociotechnical interplay. The first part translates abstract knowledge on the IS artifact and privacy into a description of social subsystems of transparency artifacts, and the second part conveys prescriptive design knowledge in form of a corresponding IS design theory. TIPP theory establishes a bridge from the complexity of the privacy concept to a metadesign for transparency artifacts that is useful to establish TIPP in any IS. In essence, transparency artifacts must accomplish more than offering comprehensive information; they must also be adaptive to the current information needs of consumers.
description: accepted author manuscript version
Super Cartan geometry and the super Ashtekar connection
Creators: name: Eder, Konstantin
Publisher: name: arXiv
Year: 2020
Subjects: subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: Differential Geometry (math.DG)
subject: FOS: Physical sciences
subject: FOS: Mathematics

description: This work is devoted to the geometric approach to supergravity. More precisely, we interpret $\mathcal{N}=1$, $D=4$ supergravity as a super Cartan geometry which provides a link between supergravity and Yang-Mills theory. To this end, we first review important aspects of the theory of supermanifolds and we establish a link between various different approaches. We then introduce super Cartan geometries using the concept of so-called enriched categories. This, among other things, will enable us to implement anticommutative fermionic fields. We will then also show that non-extended $D=4$ supergravity naturally arises in this framework. Finally, using this gauge-theoretic interpretation as well as the chiral structure of the underlying supersymmetry algebra, we will derive graded analoga of Ashtekar's self-dual variables and interpret them in terms of generalized super Cartan connections. This gives canonical chiral supergravity the structure of a Yang-Mills theory with gauge supergroup similar to the self-dual variables in ordinary first-order Einstein gravity which was first observed by Fülöp \cite{Fulop:1993wi}. We then construct the parallel transport map corresponding to the super connection in mathematical rigorous way using again enriched categories. This provides the possibility of quantizing gravity and matter degrees of freedom in loop quantum gravity in a unified way.
description: v2: equivalence proof extended in section 2.1, typos corrected, references added, 56 pages
Object Detection with Swin Vision Transformers from Raw ADC Radar Signals
Creators: name: Giroux, James
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2023
Subjects: vision transformer
radar
object detection

description: Object detection utilizing frequency modulated continuous wave radar is becoming increasingly popular in the field of autonomous vehicles. Radar does not possess the same drawbacks seen by other emission-based sensors such as LiDAR, primarily the degradation or loss of return signals due to weather conditions such as rain or snow. Thus, there is a necessity for fully autonomous systems to utilize radar sensing applications in downstream decision-making tasks, generally handled by deep learning algorithms. Commonly, three transformations have been used to form range-azimuth-Doppler cubes in which deep learning algorithms could perform object detection. This method has drawbacks, specifically the pre-processing costs associated with performing multiple Fourier Transforms and normalization. We develop a network utilizing raw radar analog-to-digital converter output capable of operating in near real-time given the removal of all pre-processing. We obtain inference time estimates one-fifth of the traditional range-Doppler pipeline, decreasing from $\SI{156}{\milli\second}$ to $\SI{30}{\milli\second}$, and similar decreases in comparison to the full range-azimuth-Doppler cube. Moreover, we introduce hierarchical Swin Vision transformers to the field of radar object detection and show their capability to operate on inputs varying in pre-processing, along with different radar configurations, \textit{i.e.}, relatively low and high numbers of transmitters and receivers. Our network increases both average recall, and mean intersection over union performance by $\sim 6-7\%$, obtaining state-of-the-art F1 scores as a result on high-definition radar. On low-definition radar, we note an increase in mean average precision of $\sim 2.5\%$ over state-of-the-art range-Doppler networks when raw analog-to-digital converter data is used, and a $\sim5\%$ increase over networks using the full range-azimuth-Doppler cube.
Measuring the integrated information of a quantum mechanism
Creators: name: Albantakis, Larissa
name: Prentner, Robert
name: Durham, Ian
Publisher: name: arXiv
Year: 2023
Subjects: subject: Quantum Physics (quant-ph)
subject: Neurons and Cognition (q-bio.NC)
subject: FOS: Physical sciences
subject: FOS: Biological sciences

description: Originally conceived as a theory of consciousness, integrated information theory (IIT) provides a theoretical framework intended to characterize the compositional causal information that a system, in its current state, specifies about itself. However, it remains to be determined whether IIT as a theory of consciousness is compatible with quantum mechanics as a theory of microphysics. Here, we present an extension of IIT's latest formalism to evaluate the mechanism integrated information ($φ$) of a system subset to finite-dimensional quantum systems (e.g., quantum logic gates). To that end, we translate a recently developed, unique measure of intrinsic information into a density matrix formulation, and extend the notion of conditional independence to accommodate quantum entanglement. The compositional nature of the IIT analysis might shed some light on the internal structure of composite quantum states and operators that cannot be obtained using standard information-theoretical analysis. Finally, our results should inform theoretical arguments about the link between consciousness, causation, and physics from the classical to the quantum.
description: 24 pages, 5 figures
Relativistic EOM-CCSD for core-excited and core-ionized state energies based on the 4-component Dirac-Coulomb(-Gaunt) Hamiltonian
Creators: name: Halbert, Loïc
name: Vidal, Marta Lopez
name: Shee, Avijit
name: Coriani, Sonia
name: Gomes, André Severo Pereira
Publisher: name: arXiv
Year: 2020
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: We report an implementation of the core-valence separation approach to the 4-component relativistic Hamiltonian based equation-of-motion coupled-cluster with singles and doubles theory (CVS-EOM-CCSD), for the calculation of relativistic core-ionization potentials and core-excitation energies. With this implementation, which is capable of exploiting double group symmetry, we investigate the effects of the different CVS-EOM-CCSD variants, and the use of different Hamiltonians based on the exact 2-component (X2C) framework, on the energies of different core ionized and excited states in halogen (CH$_3$I, HX and X$^-$, X = Cl-At) and xenon containing (Xe, XeF$_2$) species. Our results show that the X2C molecular mean-field approach [Sikkema et al., J. Chem. Phys. 2009, 131, 124116], based on 4-component Dirac-Coulomb mean-field calculations ($^2$DC$^M$) is capable of providing core excitations and ionization energies that are nearly indistinguishable from the reference 4-component energies for up to and including fifth-row elements. We observe that two-electron integrals over the small-component basis sets yield non-negligible contributions to core binding energies for the K and L edges for atoms such as iodine or astatine, and that the approach based on Dirac-Coulomb-Gaunt mean-field calculations ($^2$DCG$^M$) are significantly more accurate than X2C calculations for which screened two-electron spin-orbit interactions are included via atomic mean-field integrals.
description: 16 pages, 4 figures in main text, 7 figures in supplemental information
The Korean dairy food market : opportunities and implications for Australia : research project
Creators: name: Jeffery, A. C. .
Publisher: name: Monash University
Year: 2022

description: This thesis was scanned from the print manuscript for digital preservation and is copyright the author.
 Researchers can access this thesis by asking their local university, institution or public library to
 make a request on their behalf. Monash staff and postgraduate students can use the link in the References field.
Shape-based Feature Engineering for Solar Flare Prediction
Creators: name: Deshmukh, Varad
name: Berger, Thomas
name: Meiss, James
name: Bradley, Elizabeth
Publisher: name: arXiv
Year: 2020
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Machine Learning (cs.LG)
subject: FOS: Physical sciences
subject: FOS: Computer and information sciences

description: Solar flares are caused by magnetic eruptions in active regions (ARs) on the surface of the sun. These events can have significant impacts on human activity, many of which can be mitigated with enough advance warning from good forecasts. To date, machine learning-based flare-prediction methods have employed physics-based attributes of the AR images as features; more recently, there has been some work that uses features deduced automatically by deep learning methods (such as convolutional neural networks). We describe a suite of novel shape-based features extracted from magnetogram images of the Sun using the tools of computational topology and computational geometry. We evaluate these features in the context of a multi-layer perceptron (MLP) neural network and compare their performance against the traditional physics-based attributes. We show that these abstract shape-based features outperform the features chosen by the human experts, and that a combination of the two feature sets improves the forecasting capability even further.
description: To be published in Proceedings for Innovative Applications of Artificial Intelligence Conference 2021
Sturgeon River 2017 Aquatic Ecosystem Assessment
Creators: CPP Environmental
Publisher: name: University of Alberta Library
Year: 2019

This survey creates a baseline and status regarding the aquatic ecosystems (physical & chemical environment and living organisms) along the Sturgeon River. Twelve sampling stations were distributed throughout the length of the river, as well as along the main tributaries. At each sampling station on the Sturgeon River, physical habitat, water quality, vegetation, fish, and macroinvertebrate were surveyed. In the tributaries, only water quality was measured. (As cited on https://www.nswa.ab.ca/)
Minority-carrier dynamics in semiconductors probed by two-photon microscopy
Creators: name: Gaury, Benoit
name: Haney, Paul M.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Two-photon time-resolved photoluminescence has been recently applied to various semiconductor devices to determine carrier lifetime and surface recombination velocities. So far the theoretical modeling activity has been mainly limited to the commonly used one-photon counterpart of the technique. Here we provide the analytical solution to a 3D diffusion equation that describes two-photon microscopy in the low-injection regime. We focus on a system with a single buried interface with enhanced recombination, and analyze how transport, bulk and surface recombinations influence photoluminescence decays. We find that bulk measurements are dominated by diffusion at short times and by bulk recombination at long times. Surface recombination modifies bulk signals when the optical spot is less than a diffusion length away from the probed interface. In addition, the resolution is increased as the spot size is reduced, which however makes the signal more sensitive to diffusion.
description: 4 pages, 4 figures, IEEE PVSC 2016 proceeding paper
GIT: Detecting Uncertainty, Out-Of-Distribution and Adversarial Samples using Gradients and Invariance Transformations
Creators: name: Lust, Julia
name: Condurache, Alexandru P.
Publisher: name: arXiv
Year: 2023
Subjects: subject: Machine Learning (cs.LG)
subject: Computer Vision and Pattern Recognition (cs.CV)
subject: FOS: Computer and information sciences

description: Deep neural networks tend to make overconfident predictions and often require additional detectors for misclassifications, particularly for safety-critical applications. Existing detection methods usually only focus on adversarial attacks or out-of-distribution samples as reasons for false predictions. However, generalization errors occur due to diverse reasons often related to poorly learning relevant invariances. We therefore propose GIT, a holistic approach for the detection of generalization errors that combines the usage of gradient information and invariance transformations. The invariance transformations are designed to shift misclassified samples back into the generalization area of the neural network, while the gradient information measures the contradiction between the initial prediction and the corresponding inherent computations of the neural network using the transformed sample. Our experiments demonstrate the superior performance of GIT compared to the state-of-the-art on a variety of network architectures, problem setups and perturbation types.
description: Accepted at IJCNN 2023
Algorithmic asymptotic analysis: extending the arsenal of cancer immunology modeling
Creators: name: Patsatzis, Dimitrios G.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Dynamical Systems (math.DS)
subject: Tissues and Organs (q-bio.TO)
subject: FOS: Mathematics
subject: FOS: Biological sciences

description: The recent advances in cancer immunotherapy boosted the development of tumor-immune system models aiming to provide mechanistic understanding and indicate more efficient treatment regimes. However, the complexity of such models, their multi-scale dynamics and their overparameterized character renders them inaccessible for wide utilization. In this work, the dynamics of a fundamental model formulating the interactions of tumor cells with natural killer cells, CD8$^+$ T cells and circulating lymphocytes is examined. It is first shown that the long-term evolution of the system towards high-tumor or tumor-free equilibria is determined by the dynamics of an initial \emph{explosive stage} of tumor progression. Focusing on this stage, the algorithmic Computational Singular Perturbation methodology is employed to identify the underlying mechanisms confining the system's evolution towards the equilibrium and the governing slow dynamics along them. It is shown that these insights are preserved along different tumor-immune system and patient-dependent realizations. Utilizing the obtained mechanistic understanding, a novel reduced model is constructed in an algorithmic fashion, which accurately predicts the dynamics of the system during the explosive stage and includes half of the parameters of the detailed model. This present analysis demonstrates the potential of algorithmic asymptotic analysis to simplify the complex, overeparameterized and multi-scale nature of cancer immunology models and to indicate the interactions and cell types to target for more effective treatment development.
description: 22 pages, 6 figures + 3 supplemental figures
Dipole spin polarizabilities and gyrations of spin-1 particles in the Duffin-Kemmer-Petiau formalism
Creators: name: Maksimenko, N. V.
name: Vakulina, E. V.
name: Kuchin, S. M.
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences
subject: 81

description: In this paper relativistic-invariant phenomenological Lagrangians of interaction between spin-1 particles and electromagnetic field were obtained in the Duffin-Kemmer-Petiau formalism on the basis of the covariant model that takes into account both spin polarizabilities and gyrations of the above-mentioned particles. It was shown that in the suggested covariant model with regard to the crossing symmetry, spatial parity and gauge invariance conservation laws, definite spin polarizabilities and gyrations of spin-1 particles contribute to the expansion of Compton scattering amplitude, starting from the corresponding orders on energy of pfotons that is in the agreement with low-energy theorems for that process.
description: 14 pages
On-policy Object Goal Navigation with Exploration Bonuses
Creators: name: Maia, Eric
Publisher: name: Université d'Ottawa / University of Ottawa
Year: 2023
Subjects: Object Goal Navigation
Exploration Bonuses
Reinforcement Learning

description: Machine learning developments have contributed to overcome a wide range of issues, including robotic motion, autonomous navigation, and natural language processing. Of note are the advancements of reinforcement learning in the area of object goal navigation — the task of autonomously traveling to target objects with minimal a priori knowledge of the environment. Given the sparse placement of goals in unknown scenes, exploration is essential for reaching remote objects of interest that are not immediately visible to autonomous agents. Sparse rewards are a crucial problem in reinforcement learning that arises in object goal navigation, as positive rewards are only attained when targets are found at the end of an agent’s trajectory. As such, this work explores object goal navigation and the challenges it presents, along with the relevant reinforcement learning techniques applied to the task. An ablation study of the baseline approach for the RoboTHOR 2021 object goal navigation challenge is presented and used to guide the development of an on-policy agent that is computationally less expensive and obtains greater success in unseen environments. Then, original object goal navigation reward schemes that aggregate episodic and long-term novelty bonuses are proposed, and obtain success rates comparable to the respective object goal navigation benchmark at a fraction of training interactions with the environment.
Acoustically mediated long-range interaction among multiple spherical particles exposed to a plane standing wave
Creators: name: Zhang, Shenwei
name: Qiu, Chunyin
name: Wang, Mudi
name: Ke, Manzhu
name: Liu, Zhengyou
Publisher: name: arXiv
Year: 2016
Subjects: subject: Soft Condensed Matter (cond-mat.soft)
subject: FOS: Physical sciences

description: In this work, we study the acoustically mediated interaction forces among multiple well-separated spherical particles trapped in the same node or antinode plane of a standing wave. An analytical expression of the acoustic interaction force is derived, which is accurate even for the particles beyond the Rayleigh limit. Interestingly, the multi-particle system can be decomposed into a series of independent two-particle systems described by pairwise interactions. Each pairwise interaction is a long-range interaction, as characterized by a soft oscillatory attenuation (at the power exponent of n=-1 or -2). The vector additivity of the acoustic interaction force, which is not well expected considering the nonlinear nature of the acoustic radiation force, is greatly useful for exploring a system consisting of a large number of particles. The capability of self-organizing a big particle cluster can be anticipated through such acoustically controllable long-range interaction.
description: 7 figures & 20 pages
Implementation of relativistic coupled cluster theory for massively parallel GPU-accelerated computing architectures
Creators: name: Pototschnig, Johann V.
name: Papadopoulos, Anastasios
name: Lyakh, Dmitry I.
name: Repisky, Michal
name: Halbert, Loïc
name: Gomes, André Severo Pereira
name: Jensen, Hans Jørgen Aa.
name: Visscher, Lucas
Publisher: name: arXiv
Year: 2021
Subjects: subject: Chemical Physics (physics.chem-ph)
subject: FOS: Physical sciences

description: In this paper, we report a reimplementation of the core algorithms of relativistic coupled cluster theory aimed at modern heterogeneous high-performance computational infrastructures. The code is designed for efficient parallel execution on many compute nodes with optional GPU coprocessing, accomplished via the new ExaTENSOR back end. The resulting ExaCorr module is primarily intended for calculations of molecules with one or more heavy elements, as relativistic effects on electronic structure are included from the outset. In the current work, we thereby focus on exact 2-component methods and demonstrate the accuracy and performance of the software. The module can be used as a stand-alone program requiring a set of molecular orbital coefficients as starting point, but is also interfaced to the DIRAC program that can be used to generate these. We therefore also briefly discuss an improvement of the parallel computing aspects of the relativistic self-consistent field algorithm of the DIRAC program.
Counterexamples to a divergence lower bound for the covariant derivative of skew-symmetric 2-tensor fields
Creators: name: Borghini, Stefano
name: Mazzieri, Lorenzo
Publisher: name: arXiv
Year: 2023
Subjects: subject: Differential Geometry (math.DG)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Mathematics
subject: FOS: Physical sciences
subject: 53B20 (Primary) 53C21 (Secondary)

description: In arXiv:2103.15482 an estimate for suitable skew-symmetric 2-tensors was claimed. Soon after, this estimate has been exploited to claim powerful classification results: most notably, it has been employed to propose a proof of a Black Hole Uniqueness Theorem for vacuum static spacetimes with positive scalar curvature and in connection with the Besse Conjecture. In the present note we point out an issue in the argument proposed in arXiv:2103.15482 and we provide a counterexample to the estimate.
description: 8 pages
Mirror symmetry for extended affine Weyl groups
Creators: name: Brini, Andrea
name: van Gemst, Karoline
Publisher: name: arXiv
Year: 2021
Subjects: subject: Algebraic Geometry (math.AG)
subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: Exactly Solvable and Integrable Systems (nlin.SI)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: We give a uniform, Lie-theoretic mirror symmetry construction for the Frobenius manifolds defined by Dubrovin-Zhang in arXiv:hep-th/9611200 on the orbit spaces of extended affine Weyl groups, including exceptional Dynkin types. The B-model mirror is given by a one-dimensional Landau-Ginzburg superpotential constructed from a suitable degeneration of the family of spectral curves of the affine relativistic Toda chain for the corresponding affine Poisson--Lie group. As applications of our mirror theorem we give closed-form expressions for the flat coordinates of the Saito metric and the Frobenius prepotentials in all Dynkin types, compute the topological degree of the Lyashko-Looijenga mapping for certain higher genus Hurwitz space strata, and construct hydrodynamic bihamiltonian hierarchies (in both Lax-Sato and Hamiltonian form) that are root-theoretic generalisations of the long-wave limit of the extended Toda hierarchy.
description: 44 pages; v2: 54 pages, version accepted for publication on J. Ecol. Polytech (Math). A typo in Corollary 5.2 and Table 3 is fixed compared to the published version
Do dark matter halos explain lensing peaks?
Creators: name: Matilla, José Manuel Zorrilla
name: Haiman, Zoltán
name: Hsu, Daniel
name: Gupta, Arushi
name: Petri, Andrea
Publisher: name: arXiv
Year: 2016
Subjects: subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We have investigated a recently proposed halo-based model, Camelus, for predicting weak-lensing peak counts, and compared its results over a collection of 162 cosmologies with those from N-body simulations. While counts from both models agree for peaks with $\mathcal{S/N}>1$ (where $\mathcal{S/N}$ is the ratio of the peak height to the r.m.s. shape noise), we find $\approx 50\%$ fewer counts for peaks near $\mathcal{S/N}=0$ and significantly higher counts in the negative $\mathcal{S/N}$ tail. Adding shape noise reduces the differences to within $20\%$ for all cosmologies. We also found larger covariances that are more sensitive to cosmological parameters. As a result, credibility regions in the $\{Ω_m, σ_8\}$ are $\approx 30\%$ larger. Even though the credible contours are commensurate, each model draws its predictive power from different types of peaks. Low peaks, especially those with $23)$. Our results confirm the importance of using a cosmology-dependent covariance with at least a 14\% improvement in parameter constraints. We identified the covariance estimation as the main driver behind differences in inference, and suggest possible ways to make Camelus even more useful as a highly accurate peak count emulator.
The use of interpreters by Australian organisations in negotiations with the Japanese
Creators: name: Coulthard, Maxwell Ralph.
Publisher: name: Monash University
Year: 2022

description: This thesis was scanned from the print manuscript for digital preservation and is copyright the author.
 Researchers can access this thesis by asking their local university, institution or public library to
 make a request on their behalf. Monash staff and postgraduate students can use the link in the References field.
A Large Scale Commercial Farming and its Environmental impacts: The Case of Gambella Regional State
Creators: name: Wegari, Habtamu Temesgen
Publisher: name: Ethiopian Journals of Environment and Development
Year: 2019

description: The change in Ethiopia’s economic policy from small scale farming to large scale farming began with the global food and fuel crisis in 2007/8. This has led many countries including the Gulf States and several East Asian countries, to re-evaluate their strategies and secure land and water essentially to produce food and fuel. Consequently, in Ethiopia, more than four million hectares of land has been leased to investors for large-scale commercial farming out of which the total land area of 524,202.58 hectares has been distributed for both local and foreign investors in Gambella Regional State. Hence, the main purpose of the study was to assess the impacts of large-scale commercial farming on the sustainability of environment in Gambella regional state. To this end both primary and secondary data sources were utilized. The study found that, though the large-scale commercial farming is contributing to the economy both at national and regional level, it has adverse impacts on the environment. To mention a few, the unconstitutional procedure followed in land transfer, investors’ undue concern and care for natural resources, and the absence of guidelines and frameworks endanger the environment. In addition, the absence of synergy among actors contributed towards drastic environmental problems. Besides, the study found that the investment in the region is disconnecting the environment from its dependents (local people) and putting the sustainability of the environment in a query unless it is managed with immediate interventions by the concerned bodies.
description: Ethiopian Journals of Environment and Development, Vol 1 No 1 (2019): Large Scale Commercial Farming and its Environmental impacts: The Case of Gambella Regional State
SACHA: Soft Actor-Critic with Heuristic-Based Attention for Partially Observable Multi-Agent Path Finding
Creators: name: Lin, Qiushi
name: Ma, Hang
Publisher: name: arXiv
Year: 2023
Subjects: subject: Robotics (cs.RO)
subject: Artificial Intelligence (cs.AI)
subject: Multiagent Systems (cs.MA)
subject: FOS: Computer and information sciences

description: Multi-Agent Path Finding (MAPF) is a crucial component for many large-scale robotic systems, where agents must plan their collision-free paths to their given goal positions. Recently, multi-agent reinforcement learning has been introduced to solve the partially observable variant of MAPF by learning a decentralized single-agent policy in a centralized fashion based on each agent's partial observation. However, existing learning-based methods are ineffective in achieving complex multi-agent cooperation, especially in congested environments, due to the non-stationarity of this setting. To tackle this challenge, we propose a multi-agent actor-critic method called Soft Actor-Critic with Heuristic-Based Attention (SACHA), which employs novel heuristic-based attention mechanisms for both the actors and critics to encourage cooperation among agents. SACHA learns a neural network for each agent to selectively pay attention to the shortest path heuristic guidance from multiple agents within its field of view, thereby allowing for more scalable learning of cooperation. SACHA also extends the existing multi-agent actor-critic framework by introducing a novel critic centered on each agent to approximate $Q$-values. Compared to existing methods that use a fully observable critic, our agent-centered multi-agent actor-critic method results in more impartial credit assignment and better generalizability of the learned policy to MAPF instances with varying numbers of agents and types of environments. We also implement SACHA(C), which embeds a communication module in the agent's policy network to enable information exchange among agents. We evaluate both SACHA and SACHA(C) on a variety of MAPF instances and demonstrate decent improvements over several state-of-the-art learning-based MAPF methods with respect to success rate and solution quality.
description: Accepted to IEEE Robotics and Automation Letters (RA-L)
Assessment of Existing Water Supply and Demand Data for the Sturgeon River Basin
Creators: North Saskatchewan Watershed Alliance (NSWA)
Publisher: name: University of Alberta Library
Year: 2016

This report examines the hydroclimatic data, water use data and a water management model developed in 11 previous studies and makes recommendations on work required to update and/or improve the reliability of the data for future water quantity modeling. (As cited on https://www.nswa.ab.ca/)