cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Online learning design in higher education: a holistic investigation of people, processes and pedagogy
Creators: name: Papageorgiou, Vasiliki
Publisher: name: Imperial College London
Year: 2022

description: The design and provision of online learning by universities has gained traction globally as a strategic move towards flexible education maximising students’ learning opportunities. A promising approach for designing high-quality online learning is collaborative design where educators work with interdisciplinary digital learning professionals. However, to date, studies that have taken a holistic approach to examine the nature and outcomes of the design work between these key university actors in a single project are lacking. This thesis addresses this gap by investigating the decision-making processes of educators and digital learning professionals during online learning design, the factors influencing their decisions, and the rationale behind their pedagogic choices. Cultural-historical activity theory was adopted as the theoretical framework to enable a thorough investigation of educators’ and digital learning professionals’ online learning design work within their broader sociocultural context. A multiple case study was employed as the overarching methodology with data collected from seven design teams (‘cases’) across six UK-based universities involved in ongoing online learning design cycles. One-to-one interviews in two stages (before and after the design of online modules) and non-participant observation of design meetings were conducted to capture participants’ insights. Relevant documents were also analysed as secondary evidence sources. Findings revealed participants’ decisions were made through framing, sharing insider knowledge and expertise, forward-looking, and breadth-first design processes. Their decisions were influenced by four levels of interacting and interdependent factors: individual, team, community and network, and institutional. The pedagogic rationale behind participants’ decisions indicates their practice re-culturation and has been conceptualised in this research as holistic, multivoiced, and connected. Collaborative design also proved to support educators’ professional development in (co-)design, pedagogy, and learning technology. These findings contribute to a multifaceted and contemporary understanding of online learning design and highlight practical implications for educators, digital learning professionals, university leadership, industry partners, and researchers.
Axial resonances a1(1260), b1(1235) and their decays from the lattice
Creators: name: Lang, C. B.
name: Leskovec, Luka
name: Mohler, Daniel
name: Prelovsek, Sasa
Publisher: name: arXiv
Year: 2014
Subjects: subject: High Energy Physics - Lattice (hep-lat)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: The light axial-vector resonances $a_1(1260)$ and $b_1(1235)$ are explored in Nf=2 lattice QCD by simulating the corresponding scattering channels $ρπ$ and $ωπ$. Interpolating fields $\bar{q} q$ and $ρπ$ or $ωπ$ are used to extract the s-wave phase shifts for the first time. The $ρ$ and $ω$ are treated as stable and we argue that this is justified in the considered energy range and for our parameters $m_π\simeq 266~$MeV and $L\simeq 2~$fm. We neglect other channels that would be open when using physical masses in continuum. Assuming a resonance interpretation a Breit-Wigner fit to the phase shift gives the $a_1(1260)$ resonance mass $m_{a1}^{res}=1.435(53)(^{+0}_{-109})$ GeV compared to $m_{a1}^{exp}=1.230(40)$ GeV. The $a_1$ width $Γ_{a1}(s)=g^2 p/s$ is parametrized in terms of the coupling and we obtain $g_{a_1ρπ}=1.71(39)$ GeV compared to $g_{a_1ρπ}^{exp}=1.35(30)$ GeV derived from $Γ_{a1}^{exp}=425(175)$ MeV. In the $b_1$ channel, we find energy levels related to $π(0)ω(0)$ and $b_1(1235)$, and the lowest level is found at $E_1 \gtrsim m_ω+m_π$ but is within uncertainty also compatible with an attractive interaction. Assuming the coupling $g_{b_1ωπ}$ extracted from the experimental width we estimate $m_{b_1}^{res}=1.414(36)(^{+0}_{-83})$.
description: 15 pages, 4 figures, updated to match published version
Two problems in arithmetic geometry inspired by homotopy theory: enriched curve counting for the Yau-Zaslow formula, and a homotopic approach to the valuative section conjecture
Creators: name: Pajwani, Jesse
Publisher: name: Imperial College London
Year: 2023

description: This thesis comprises work the author has done on two separate problems in arithmetic geometry whose origins lie in homotopy theory. The work in these problems are separate, but linked by the underlying techniques and philosophies. The first part of this thesis is based around an enriched version of the Yau–Zaslow formula for counting rational curves on K3 surfaces, and is joint work with Ambrus P´al. In order to produce this arithmetic enrichment, we first need an invariant that allows us to count. We first construct this invariant, then relate this invariant to more classical invariants. We then prove some basic properties about this invariant, such as its compatibility with transfer maps and Galois twists. We then focus on the question of whether this invariant is compatible with natural power structures, and answer the question affirmitively in dimension 0. Following this, we discuss a “Fubini theorem” for this invariant proving a version of a Fubini theorem, as well as showing that the na¨ıve version of the Fubini theorem does not hold in this context. Finally, we pull this all together to provide an arithmetic refinement of the Yau–Zaslow formula, closely following Beauville’s original strategy. The second part of this thesis is based around a variation of a result of Pop and Stix, relating the section conjecture to valuations on our variety. We first show that we can rephrase this result in terms of ´etale homotopy types and Berkovich spaces. We then show that we can relate the ´etale homotopy type of a variety to its Berkovich space, before using this to give an alternative proof of this theorem. Our alternative proof extends the result to hold over more general fields, and we can use this flexibility to extend the theorem to a larger class of varieties as well.
Vortices evolution in the solar atmosphere: A dynamical equation for the swirling strength
Creators: name: Cuissa, J. R. Canivete
name: Steiner, O.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: We study vortex dynamics in the solar atmosphere by employing and deriving the analytical evolution equations of two vortex identification criteria. The two criteria used are vorticity and the swirling strength. Vorticity can be biased in the presence of shear flows, but its dynamical equation is well known; the swirling strength is a more precise criterion for the identification of vortical flows, but its evolution equation is not known yet. Therefore, we explore the possibility of deriving a dynamical equation for the swirling strength. We then apply the two equations to analyze radiative MHD simulations of the solar atmosphere produced with the CO5BOLD code. We present a detailed review of the swirling strength criterion and the mathematical derivation of its evolution equation. This equation did not exist in the literature before and it constitutes a novel tool that is suitable for the analysis of a wide range of problems in (magneto-)hydrodynamics. By applying this equation to numerical models, we find that hydrodynamical and magnetic baroclinicities are the driving physical processes responsible for vortex generation in the convection zone and the photosphere. Higher up in the chromosphere, the magnetic terms alone dominate. Moreover, we find that the swirling strength is produced at small scales in a chaotic fashion, especially inside magnetic flux concentrations. The swirling strength represents an appropriate criterion for the identification of vortices in turbulent flows, such as those in the solar atmosphere. Moreover, its evolution equation, which is derived in this paper, is pivotal for obtaining precise information about the dynamics of these vortices and the physical mechanisms responsible for their production and evolution. Since this equation is available, the swirling strength is now the ideal quantity to study the dynamics of vortices in (magneto-)hydrodynamics.
description: 12 pages, to be published in A&A
Growing Cosine Unit: A Novel Oscillatory Activation Function That Can Speedup Training and Reduce Parameters in Convolutional Neural Networks
Creators: name: Noel, Mathew Mithra
name: L, Arunkumar
name: Trivedi, Advait
name: Dutta, Praneet
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: Computer Vision and Pattern Recognition (cs.CV)
subject: Neural and Evolutionary Computing (cs.NE)
subject: FOS: Computer and information sciences
subject: I.5

description: Convolutional neural networks have been successful in solving many socially important and economically significant problems. This ability to learn complex high-dimensional functions hierarchically can be attributed to the use of nonlinear activation functions. A key discovery that made training deep networks feasible was the adoption of the Rectified Linear Unit (ReLU) activation function to alleviate the vanishing gradient problem caused by using saturating activation functions. Since then, many improved variants of the ReLU activation have been proposed. However, a majority of activation functions used today are non-oscillatory and monotonically increasing due to their biological plausibility. This paper demonstrates that oscillatory activation functions can improve gradient flow and reduce network size. Two theorems on limits of non-oscillatory activation functions are presented. A new oscillatory activation function called Growing Cosine Unit(GCU) defined as $C(z) = z\cos z$ that outperforms Sigmoids, Swish, Mish and ReLU on a variety of architectures and benchmarks is presented. The GCU activation has multiple zeros enabling single GCU neurons to have multiple hyperplanes in the decision boundary. This allows single GCU neurons to learn the XOR function without feature engineering. Experimental results indicate that replacing the activation function in the convolution layers with the GCU activation function significantly improves performance on CIFAR-10, CIFAR-100 and Imagenette.
description: 20 Pages
Quasilinear elliptic equations with sub-natural growth terms in bounded domains
Creators: name: Hara, Takanobu
Publisher: name: arXiv
Year: 2020
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 35J92, 35J20, 42B37

description: We consider the existence of positive solutions to weighted quasilinear elliptic differential equations of the type \[ \begin{cases} - Δ_{p, w} u = σu^{q} & \text{in $Ω$}, \\ u = 0 & \text{on $\partial Ω$} \end{cases} \] in the sub-natural growth case $0 < q < p - 1$, where $Ω$ is a bounded domain in $\mathbb{R}^{n}$, $Δ_{p, w}$ is a weighted $p$-Laplacian, and $σ$ is a nonnegative (locally finite) Radon measure on $Ω$. We give criteria for the existence problem. For the proof, we investigate various properties of $p$-superharmonic functions, especially the solvability of Dirichlet problems with infinite measure data.
von Neumann's inequality for row contractive matrix tuples
Creators: name: Hartz, Michael
name: Richter, Stefan
name: Shalit, Orr
Publisher: name: arXiv
Year: 2021
Subjects: subject: Functional Analysis (math.FA)
subject: Complex Variables (math.CV)
subject: Operator Algebras (math.OA)
subject: FOS: Mathematics
subject: 47A13, 46E22, 47L55

description: We prove that for all $n\in \mathbb{N}$, there exists a constant $C_{n}$ such that for all $d \in \mathbb{N}$, for every row contraction $T$ consisting of $d$ commuting $n \times n$ matrices and every polynomial $p$, the following inequality holds: \[
 \|p(T)\| \le C_{n} \sup_{z \in \mathbb{B}_d} |p(z)| . \] We apply this result and the considerations involved in the proof to several open problems from the pertinent literature. First, we show that Gleason's problem cannot be solved contractively in $H^\infty(\mathbb{B}_d)$ for $d \ge 2$. Second, we prove that the multiplier algebra $\operatorname{Mult}(\mathcal{D}_a(\mathbb{B}_d))$ of the weighted Dirichlet space $\mathcal{D}_a(\mathbb{B}_d)$ on the ball is not topologically subhomogeneous when $d \ge 2$ and $a \in (0,d)$. In fact, we determine all the bounded finite dimensional representations of the norm closed subalgebra $A(\mathcal{D}_a(\mathbb{B}_d))$ of $\operatorname{Mult}(\mathcal{D}_a(\mathbb{B}_d))$ generated by polynomials. Lastly, we also show that there exists a uniformly bounded nc holomorphic function on the free commutative ball $\mathfrak{C}\mathfrak{B}_d$ that is levelwise uniformly continuous but not globally uniformly continuous.
description: 20 pages. v2: the constants C_{d,n} are shown to be uniformly bounded in d for fixed n. v3: small changes
Monte-Carlo simulation of ELT scale multi-object adaptive optics deformable mirror requirements and tolerances
Creators: name: Basden, A. G.
name: Bharmal, N. A.
name: Myers, R. M.
name: Morris, S. L.
name: Morris, T. J.
Publisher: name: arXiv
Year: 2013
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: Instrumentation and Detectors (physics.ins-det)
subject: FOS: Physical sciences

description: Multi-object adaptive optics (MOAO) has been demonstrated by the CANARY instrument on the William Herschel Telescope. However, for proposed MOAO systems on the next generation Extremely Large Telescopes, such as EAGLE, many challenges remain. Here we investigate requirements that MOAO operation places on deformable mirrors (DMs) using a full end-to-end Monte-Carlo AO simulation code. By taking into consideration a prior global ground-layer (GL) correction, we show that actuator density for the MOAO DMs can be reduced with little performance loss. We note that this reduction is only possible with the addition of a GL DM, whose order is greater than or equal to that of the original MOAO mirrors. The addition of a GL DM of lesser order does not affect system performance (if tip/tilt star sharpening is ignored). We also quantify the maximum mechanical DM stroke requirements (3.5 $μ$m desired) and provide tolerances for the DM alignment accuracy, both lateral (to within an eighth of a sub-aperture) and rotational (to within 0.2$^\circ$). By presenting results over a range of laser guide star asterism diameters, we ensure that these results are equally applicable for laser tomographic AO systems. We provide the opportunity for significant cost savings to be made in the implementation of MOAO systems, resulting from the lower requirement for DM actuator density.
description: Accepted for publication in MNRAS
Planetary migration in wind-fed non-stationary accretion disks in binary systems
Creators: name: Nekrasov, Alexey D.
name: Zhuravlev, Viacheslav V.
name: Popov, Sergei B.
Publisher: name: arXiv
Year: 2024
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: An accretion disk can be formed around a secondary star in a binary system when the primary companion leaves the Main sequence and starts to lose mass at an enhanced rate. We study the accretion disk evolution and planetary migration in wide binaries. We use a numerical model of a non-stationary alpha-disk with a variable mass inflow. We take into account that the low-mass disk has an extended region that is optically thin along the rotation axis. We consider irradiation by both the host star and the donor. The migration path of a planet in such a disk is determined by the migration rate varying during the disk evolution. Giant planets may open/close the gap several times over the disk lifetime. We identify the new type of migration specific to parts of the growing disk with a considerable radial gradient of an aspect ratio. Its rate is enclosed between the type 2 and the fast type 1 migration rates being determined by the ratio of time and radial derivatives of the disk aspect ratio. Rapid growth of the wind rate just before the envelope loss by the donor leads to the formation of a zone of decretion, which may lead to substantial outward migration. In binaries with an initial separation $a\lesssim 100$\,AU migration becomes most efficient for planets with 60--80 Earth masses. This results in approaching a short distance from the host star where tidal forces become non-negligible. Less massive Neptune-like planets at the initial orbits $r_\mathrm{p} \lesssim 2$\,AU can reach these internal parts in binaries with $a \lesssim 30$\,AU. In binaries, mass loss by the primary component at late evolutionary stages can significantly modify the structure of a planetary system around the secondary component resulting in mergers of relatively massive planets with a host star.
description: 28 pages, 14 figures, 5 tables, accepted to be published in A&A
Performance of the Segment Anything Model in Various RFI/Events Detection in Radio Astronomy
Creators: name: Yang, Yanbin
name: Zhao, Feiyu
name: Liang, Ruxi
name: Guo, Quan
name: Gu, Junhua
name: Huang, Yan
name: Yu, Yun
Publisher: name: arXiv
Year: 2024
Subjects: subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences

description: The emerging era of big data in radio astronomy demands more efficient and higher-quality processing of observational data. While deep learning methods have been applied to tasks such as automatic radio frequency interference (RFI) detection, these methods often face limitations, including dependence on training data and poor generalization, which are also common issues in other deep learning applications within astronomy. In this study, we investigate the use of the open-source image recognition and segmentation model, Segment Anything Model (SAM), and its optimized version, HQ-SAM, due to their impressive generalization capabilities. We evaluate these models across various tasks, including RFI detection and solar radio burst (SRB) identification. For RFI detection, HQ-SAM (SAM) shows performance that is comparable to or even superior to the SumThreshold method, especially with large-area broadband RFI data. In the search for SRBs, HQ-SAM demonstrates strong recognition abilities for Type II and Type III bursts. Overall, with its impressive generalization capability, SAM (HQ-SAM) can be a promising candidate for further optimization and application in RFI and event detection tasks in radio astronomy.
description: 19 pages, 18 figures, 7 tables. Accepted for publication in PASA
CubiXMusashi: Fusion of Wire-Driven CubiX and Musculoskeletal Humanoid Musashi toward Unlimited Performance
Creators: name: Inoue, Shintaro
name: Kawaharazuka, Kento
name: Suzuki, Temma
name: Yuzaki, Sota
name: Ribayashi, Yoshimoto
name: Sahara, Yuta
name: Okada, Kei
Publisher: name: arXiv
Year: 2024
Subjects: subject: Robotics (cs.RO)
subject: FOS: Computer and information sciences

description: Humanoids exhibit a wide variety in terms of joint configuration, actuators, and degrees of freedom, resulting in different achievable movements and tasks for each type. Particularly, musculoskeletal humanoids are developed to closely emulate human body structure and movement functions, consisting of a skeletal framework driven by numerous muscle actuators. The redundant arrangement of muscles relative to the skeletal degrees of freedom has been used to represent the flexible and complex body movements observed in humans. However, due to this flexible body and high degrees of freedom, modeling, simulation, and control become extremely challenging, limiting the feasible movements and tasks. In this study, we integrate the musculoskeletal humanoid Musashi with the wire-driven robot CubiX, capable of connecting to the environment, to form CubiXMusashi. This combination addresses the shortcomings of traditional musculoskeletal humanoids and enables movements beyond the capabilities of other humanoids. CubiXMusashi connects to the environment with wires and drives by winding them, successfully achieving movements such as pull-up, rising from a lying pose, and mid-air kicking, which are difficult for Musashi alone. This concept demonstrates that various humanoids, not limited to musculoskeletal humanoids, can mitigate their physical constraints and acquire new abilities by connecting to the environment and driving through wires.
description: Accepted Humanoids2024, website - https://shin0805.github.io/cubixmusashi/, YouTube - https://youtu.be/IvzP98-r_mo
Study of non-neutral electron plasma lenses for focusing laser-driven ion beams
Creators: name: Dascalu, Titus-Stefan
Publisher: name: Imperial College London
Year: 2023

description: As the need for scale-up in the provision of radiotherapy (RT) is clear, developing cost-effective and robust technologies for RT is ever more crucial. Novel proton- and ion-acceleration techniques based on high-power lasers can provide beams with unique characteristics. To make full use of a number of these techniques, the particles need to be converted efficiently into a beam. This thesis describes work on the development of space-charge plasma lenses for capturing and focusing laser-driven protons and ions. A non-neutral electron plasma, which is confined by external electric and magnetic fields, generates transverse focusing. The work is undertaken as part of the LhARA project. As a starting point, an existing prototype Gabor lens is modelled with particle-in-cell (PIC) simulations. It is found that an unstable plasma can lead to deleterious focusing effects comparable to those recorded previously in beam tests. A number of plasma instabilities is linked to the initial production of non-uniform electron clouds within the lens. Validation of the PIC code used to model confined plasmas is carried out using the results from experiments with low-density, magnetically-trapped electron clouds. The capabilities of the particle trap used throughout the experiments are characterised by measurements of the density, size, and evolution in time of the confined electron clouds. This thesis also includes a first design of a normal-conducting solenoid suitable for LhARA. The magnet requires moderate to large power consumption due to Joule losses, in addition to a complex cooling system. These requirements are found to be particularly sensitive to the bore diameter and a strategy to reduce them with a transversely-graded coil is described. Finally, the performance of plasma lenses and solenoids is evaluated by tracking a realistic laser-driven proton beam through the LhARA Stage~1 beam-line. Two models of the space-charge field produced by plasma lenses are presented.
MULTI-ELECTRON REDOX CHEMISTRY WITH THORIUM AND CERIUM IMINOQUINONE COMPLEXES TO FORM RARE MULTIPLE BONDS
Creators: name: Mudiyanselage, Ramitha Y.P.R. Dissanayake
Publisher: name: Purdue University Graduate School
Year: 2022
Subjects: Crystallography
F-block chemistry
Organometallic chemistry

description: Thorium complexes primarily exist in the thermodynamically stable (IV) oxidation state with only a few low-valent thorium(III) and thorium(II) complexes having been isolated. As a result, redox chemistry with thorium at the metal center is synthetically challenging without carefully selected ligand systems. This redox-restricted nature of thorium(IV) makes redox-active ligands (RALs) an attractive option to facilitate multi-electron redox chemistry with thorium. In this work, first, a series of thorium(IV) complexes featuring the redox-active iminoquinone ligand and its derivatives, including the iminosemiquinone and amidophenolate species, were synthesized and characterized. Rare thorium oxygen multiple bonds were then accessed by exploiting the RALs on the thorium center and using dioxygen in dry air. Other oxidation chemistry was attempted with the thorium amidophenolate complexes as well. Second, armed with the knowledge of synthesizing multiple bonds with thorium(IV) complexes, similar chemistry was explored with cerium as it is in the same group as thorium. A series of cerium(III) and cerium(IV) complexes featuring the redox-active iminoquinone ligand and its derivatives were synthesized. Oxidation chemistry was explored with the cerium amidophenolate complexes and a rare cerium oxo was isolated. Finally, with interest in expanding and addressing a gap in the literature related to the synthesis, characterization, and utility of thorium alkyls, several tetrabenzylthorium complexes were synthesized, characterized, and some reactivity was explored. A highlight of this work involved the isolation of the first crystal structure of ligand and solvent free tetrabenzylthorium since its first synthesis in 1974. Full spectroscopic and structural characterization of the complexes was performed via 1H NMR spectroscopy, X-ray crystallography, EPR spectroscopy, electronic absorption spectroscopy, and SQUID magnetometry, which all confirmed the identity and electronic structure of these complexes.
Various facets of phases in gravitational wave physics
Creators: name: Margalit, Aoibheann
Publisher: name: Imperial College London
Year: 2023

description: This thesis contains two main results related to low-frequency gravitational waves. The first is a prescription for causality within low energy effective field theories (EFTs), specialised to gravitational theories. An EFT is a framework for parametrising macroscopic physics while remaining agnostic about the microscopic degrees of freedom. It turns out that the most generic naïvely local and covariant EFT action is not necessarily consistent with a physical UV theory, and thus imposing the causal propagation of waves can place non-trivial constraints on the EFT. Our criteria for “infrared causality” is that scattered waves do not experience a resolvable time advance relative to the geometry of the background. We apply this condition to the Gauss–Bonnet operator on black hole and pp-wave spacetimes and show that, within the EFT’s regime of validity, causality is respected. The second result relates to gravitational wave backgrounds (GWBs) within the standard cosmological model. We show that scalar perturbations to the background metric ruin any phase coherence in the GWB which may have been present at emission. The main consequence is that phase-coherent mapping methods have no foreseeable application to GWBs.
Tight Bounds for Connectivity of Random K-out Graphs
Creators: name: Sood, Mansi
name: Yagan, Osman
Publisher: name: arXiv
Year: 2020
Subjects: subject: Information Theory (cs.IT)
subject: Combinatorics (math.CO)
subject: Probability (math.PR)
subject: FOS: Computer and information sciences
subject: FOS: Mathematics

description: Random K-out graphs are used in several applications including modeling by sensor networks secured by the random pairwise key predistribution scheme, and payment channel networks. The random K-out graph with $n$ nodes is constructed as follows. Each node draws an edge towards $K$ distinct nodes selected uniformly at random. The orientation of the edges is then ignored, yielding an undirected graph. An interesting property of random K-out graphs is that they are connected almost surely in the limit of large $n$ for any $K \geq2$. This means that they attain the property of being connected very easily, i.e., with far fewer edges ($O(n)$) as compared to classical random graph models including Erdős-Rényi graphs ($O(n \log n)$). This work aims to reveal to what extent the asymptotic behavior of random K-out graphs being connected easily extends to cases where the number $n$ of nodes is small. We establish upper and lower bounds on the probability of connectivity when $n$ is finite. Our lower bounds improve significantly upon the existing results, and indicate that random K-out graphs can attain a given probability of connectivity at much smaller network sizes than previously known. We also show that the established upper and lower bounds match order-wise; i.e., further improvement on the order of $n$ in the lower bound is not possible. In particular, we prove that the probability of connectivity is $1-Θ({1}/{n^{K^2-1}})$ for all $K \geq 2$. Through numerical simulations, we show that our bounds closely mirror the empirically observed probability of connectivity.
Multi-axis and multi-material additive manufacturing of electrical traces
Creators: name: Hong, Freddie Taewoo
Publisher: name: Imperial College London
Year: 2023

description: Design and manufacture of next generation intelligent and connected devices is an interdisciplinary research that incorporates a range of research areas, including additive manufacturing (AM), design, human-to-computer interaction (HCI), electrical engineering and materials science. The subject’s diversity of influence requires the cross-pollination of knowledge and research ideas to develop and expand its applications. Contributions to building the next generation of intelligent and connected devices will involve enhanced automation in design and production, mass-customised manufacturing for bespoke applications, and increased accessibility of affordable and precise fabrication tools, all of which will be key contributors to new changes in production and delivery chain of future connected devices. A practical strategy toward next generation device design and manufacture lies in increasing hardware and software innovations for constructing various freeform 3D printed parts with functionalities that can be utilised as an end use product. Such innovations could include the following: i) Expanded multi-functionality, multi-axis and multi-material of the AM, wherein 3D printed parts can conduct electricity, combine various materials seamlessly and be constructed in conformal layers that the printed parts have uniform structural properties on all surfaces formed by continuous material extrusion. A multi-axis machine could also perform assemblies such as pick and place to fully automate the manufacturing process of electronic objects ii) Increased availability of parametric and automated approaches to design and computation. Multi-axis 3D printing requires complex process to generate toolpaths for controlling the printer. New developments of the design software for structural electronics and multi- axis toolpaths generator dedicated for AM will ease the workflow and reduce the labour intensity involved in the chain process of design to manufacturing.
Surviving in the Neptune desert. The ultra-short period Neptune LTT 9779 b survived thanks to an unusually X-ray faint host star
Creators: name: Fernández Fernández, Jorge
name: Wheatley, Peter J.
name: King, George W.
Publisher: name: Zenodo
Year: 2023

description: I present XMM-Newton observations of the sun-like star LTT 9779 together with a study of the X-ray evaporation of its transiting planet, LTT 9779 b, the first ultra-hot Neptune in the Neptune desert. Its presence so close to its star is puzzling, as the intense XUV flux it receives from its star should have stripped it of its H/He-rich atmosphere. I find that only an X-ray faint host star is able to explain both our observations as well as the survival of the planet’s atmosphere under photoevaporation. LTT 9779 b is a super-Neptune (4.7 Earth radii) with a gaseous envelope that constitutes 8% of its mass. The planet, with an age of 2 Gyr, orbits its host star every 19 hours. This planet is one of the few that populate the Neptune desert, a region of parameter space at very short periods thought to be cleared out by stellar X-ray and extreme ultraviolet radiation (together, XUV), which drives substantial evaporation and can completely strip planets of their gaseous envelopes down to their rocky core. LTT 9779 b, however, is the only known ultra-short period planet in the Neptune desert that maintains a significant atmosphere. In order to find feasible evaporation pasts that can explain its current state, I simulated the star’s XUV emission history by modelling its spin period evolution, as faster rotation produces higher XUV fluxes. I confirm that the XUV history expected for a solar-mass star should have already stripped LTT 9779 b of its envelope, ruling out this scenario. Moreover, I find that the planet’s atmosphere is only able to survive a faint stellar XUV history that matches the measured upper limits for both its spin period and its X-ray luminosity, which I estimated using XMM-Newton measurements.
A central limit theorem for Latin hypercube sampling with dependence and application to exotic basket option pricing
Creators: name: Aistleitner, Christoph
name: Hofer, Markus
name: Tichy, Robert
Publisher: name: arXiv
Year: 2013
Subjects: subject: Computational Finance (q-fin.CP)
subject: FOS: Economics and business
subject: 62H20 (62G05 62G20 62K15 62P05 91B82)

description: We consider the problem of estimating $\mathbb{E} [f(U^1, \ldots, U^d)]$, where $(U^1, \ldots, U^d)$ denotes a random vector with uniformly distributed marginals. In general, Latin hypercube sampling (LHS) is a powerful tool for solving this kind of high-dimensional numerical integration problem. In the case of dependent components of the random vector $(U^1, \ldots, U^d)$ one can achieve more accurate results by using Latin hypercube sampling with dependence (LHSD). We state a central limit theorem for the $d$-dimensional LHSD estimator, by this means generalising a result of Packham and Schmidt. Furthermore we give conditions on the function $f$ and the distribution of $(U^1, \ldots, U^d)$ under which a reduction of variance can be achieved. Finally we compare the effectiveness of Monte Carlo and LHSD estimators numerically in exotic basket option pricing problems.
Reshetikhin-Turaev TQFTs close under generalised orbifolds
Creators: name: Carqueville, Nils
name: Mulevicius, Vincentas
name: Runkel, Ingo
name: Schaumann, Gregor
name: Scherl, Daniel
Publisher: name: arXiv
Year: 2021
Subjects: subject: Quantum Algebra (math.QA)
subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: We specialise the construction of orbifold graph TQFTs introduced in Carqueville et al., arXiv:2101.02482 to Reshetikhin-Turaev defect TQFTs. We explain that the modular fusion category ${\mathcal{C}}_{\mathcal{A}}$ constructed in Mulevičius-Runkel, arXiv:2002.00663 from an orbifold datum $\mathcal{A}$ in a given modular fusion category $\mathcal{C}$ is a special case of the Wilson line ribbon categories introduced as part of the general theory of orbifold graph TQFTs. Using this, we prove that the Reshetikhin-Turaev TQFT obtained from ${\mathcal{C}}_{\mathcal{A}}$ is equivalent to the orbifold of the TQFT for $\mathcal{C}$ with respect to the orbifold datum $\mathcal{A}$.
description: 56 pages
Stability in simple heteroclinic networks in $\mathbb{R}^4$
Creators: name: Castro, Sofia B. S. D.
name: Lohse, Alexander
Publisher: name: arXiv
Year: 2014
Subjects: subject: Dynamical Systems (math.DS)
subject: FOS: Mathematics
subject: 34C37, 37C80, 37C75

description: We describe all heteroclinic networks in $\mathbb{R}^4$ made of simple heteroclinic cycles of types $B$ or $C$, with at least one common connecting trajectory. For networks made of cycles of type $B$, we study the stability of the cycles that make up the network as well as the stability of the network. We show that even when none of the cycles has strong stability properties the network as a whole may be quite stable. We prove, and provide illustrative examples of, the fact that the stability of the network does not depend {\em a priori} uniquely on the stability of the individual cycles.
10 Controle em Foco, ONUS DA PROVA INTEGRIDADE E CONTROLE CONCOMITANTE NAS PRESTACOES DE CONTAS DAS OSS.
Creators: name: Ministério Publico de Contas do Estado de Minas Gerais
Publisher: name: Zenodo
Year: 2021

description: O presente artigo tem como objetivo analisar o dever de as entidades do terceiro setor prestarem contas da sua atuação complementar no âmbito do SUS, por meio da distribuição compartilhada do ônus da prova quanto ao manejo regular dos recursos públicos, à luz do art. 70, parágrafo único da Constituição Federal. Neste trabalho, será discutido o alcance do regime de integridade das entidades beneficiárias de repasses na área da saúde (referido no art. 7º, VIII da Lei 12.846/2013), para que haja, a cada liquidação de despesa, controle dos riscos de burla e fuga ao regime jurídico administrativo. Serão abordadas as possíveis medidas a serem adotadas pelos gestores públicos responsáveis e pelas entidades do terceiro setor, no intuito de mitigar a fragilidade gerencial de avaliação dos custos e resultados verificados em tais parcerias na consecução da política pública da saúde. Dado esse panorama, busca-se um ciclo dinâmico, plurilateral e tempestivo de cruzamento de dados e análise de riscos, a cada ato formal de liquidação de despesa, para que a execução terceirizada das ações e serviços públicos de saúde seja consonante com as necessidades de saúde da população em uma equação de custo-efetividade. Conclui-se, assim, pela possibilidade de atuação preventiva e concomitante de todas as instâncias de controle e, em especial, do Ministério Público de Contas no que se refere ao controle da aplicação terceirizada dos recursos do SUS, em prol da eficácia concreta do direito fundamental à saúde.
Equivalence and congruence of matrices under the action of standard parabolic subgroups
Creators: name: Szechtman, Fernando
Publisher: name: arXiv
Year: 2013
Subjects: subject: Rings and Algebras (math.RA)
subject: FOS: Mathematics
subject: 15A21

description: We find necessary and sufficient conditions for $P$-equivalence of arbitrary matrices and $P$-congruence of symmetric and alternating matrices, where $P$ is standard parabolic subgroup of $GL_n(F)$ and $F$ is an arbitrary field.
A new control- and management architecture for SDN-enabled quantum key distribution networks
Creators: name: Horoschenkoff, Peter
name: Rödiger, Jasper
name: Wilske, Martin
Publisher: name: arXiv
Year: 2024
Subjects: subject: Networking and Internet Architecture (cs.NI)
subject: FOS: Computer and information sciences

description: This paper aims to address the challenge of designing secure and high performance Quantum Key Distribution Networks (QKDN), which are essential for encrypted communication in the era of quantum computing. Focusing on the control and management (CM) layer essential for monitoring and routing, the study emphasizes centrally managed software defined networks (SDN). We begin by analyzing QKDN routing characteristics needed for evaluating two existed architectures and the proposed, new CM layer implementation. Following the theoretical analysis, we conduct a discrete-event based simulation in which the proposed architecture is compared to an existent serving as performance-baseline. The results provide recommendations based on use cases for which different architectures show superiority and offer valuable insights into the development and evaluation of CM architectures for QKDNs.
description: This project has received funding from the German research ministry "Bundesministerium fuer Bildung, Wissenschaft, Forschung und Technologie" (BMBF) as part of the DemoQuanDT research and innovation programm under grand agreement No. 16KISQ074
Vanishing discount problem and the additive eigenvalues on changing domains
Creators: name: Tu, Son N. T.
Publisher: name: arXiv
Year: 2020
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics

description: We study the asymptotic behavior, as $λ\rightarrow 0^+$, of the state-constraint Hamilton--Jacobi equation $ϕ(λ) u_λ(x) + H(x,Du_λ(x)) = 0$ in $(1+r(λ))Ω$ and the corresponding additive eigenvalues, or ergodic constant $H(x,Dv(x)) = c(λ)$ in $(1+r(λ))Ω$ with state-constraint. Here, $Ω$ is a bounded domain of $ \mathbb{R}^n$, $ϕ(λ), r(λ):(0,\infty)\rightarrow \mathbb{R}$ are continuous functions such that $ϕ$ is nonnegative and $\lim_{λ\rightarrow 0^+} ϕ(λ) = \lim_{λ\rightarrow 0^+} r(λ) = 0$. We obtain both convergence and non-convergence results in the convex setting. Moreover, we provide a very first result on the asymptotic expansion of the additive eigenvalue $c(λ)$ as $λ\rightarrow 0^+$. The main tool we use is a duality representation of solution with viscosity Mather measures.
description: 34 pages, 3 figures. AMSart style, revision version
Reduced Atmospheres of Post-Impact Worlds: Hiding Reducing Power in the Planet Core
Creators: name: Itcovitz, Jonathan P.
name: Rae, Auriol S.P.
name: Davison, Thomas M.
name: Collins, Gareth S.
name: Shorttle, Oliver
Publisher: name: Zenodo
Year: 2023
Subjects: Planetary Science
Impacts Phenomenena
Planetary Atmospheres
Prebiotic Chemistry

description: Reduced surface environments are required for many prebiotic chemical pathways. Large impacts onto Hadean Earth have been suggested as scenarios able to generate such environments on a global scale. Physical and chemical processes that occur shortly after impact can, however, limit the reducing power that is available at planet surface. Here, we present impact simulations and chemical calculations that demonstrate the efficient loss of reducing power from the post-impact planetary surface. This loss occurs via the dynamic escape of impactor core material, or the sinking of this material to the planet core, during impact, and through interactions between the atmosphere and the impact-generated melt phase. We suggest that post-impact surface environments are sufficiently reduced that species important to prebiotic chemistry can form (e.g., HCN, HCCCN). Additionally, the formation of a reduced impact-generated melt phase allows for reducing power to be stored in the planet mantle, where it can degas to the surface on geologic timescales.
description: {"references": ["W\u00fcnnemann, K., Collins, G. S., & Osinski, G. R. (2008). Numerical modelling of impact melt production in porous rocks. Earth and Planetary Science Letters, 269(3-4), 530-539.", "Bottke, W. F., Walker, R. J., Day, J. M., Nesvorny, D., & Elkins-Tanton, L. (2010). Stochastic late accretion to Earth, the Moon, and Mars. science, 330(6010), 1527-1530.", "Day, J. M., Brandon, A. D., & Walker, R. J. (2016). Highly siderophile elements in Earth, Mars, the Moon, and asteroids. Reviews in Mineralogy and Geochemistry, 81(1), 161-238.", "Genda, H., Brasser, R., & Mojzsis, S. J. (2017). The terrestrial late veneer from core disruption of a lunar-sized impactor. Earth and Planetary Science Letters, 480, 25-32.", "Marchi, S., Canup, R. M., & Walker, R. J. (2018). Heterogeneous delivery of silicate and metal to the Earth by large planetesimals. Nature geoscience, 11(1), 77-81.", "Benner, S. A., Bell, E. A., Biondi, E., Brasser, R., Carell, T., Kim, H. J., ... & Trail, D. (2020). When did life likely emerge on Earth in an RNA\u2010first process?. ChemSystemsChem, 2(2), e1900035.", "Zahnle, K. J., Lupu, R., Catling, D. C., & Wogan, N. (2020). Creation and evolution of impact-generated reduced atmospheres of early Earth. The Planetary Science Journal, 1(1), 11.", "Citron, R. I., & Stewart, S. T. (2022). Large impacts onto the early Earth: planetary sterilization and iron delivery. The Planetary Science Journal, 3(5), 116.", "Itcovitz, J. P., Rae, A. S., Citron, R. I., Stewart, S. T., Sinclair, C. A., Rimmer, P. B., & Shorttle, O. (2022). Reduced atmospheres of post-impact worlds: The early Earth. The Planetary Science Journal, 3(5), 115."]}
Josephson effect and odd-frequency pairing in superconducting junctions with unconventional magnets
Creators: name: Fukaya, Yuri
name: Maeda, Kazuki
name: Yada, Keiji
name: Cayao, Jorge
name: Tanaka, Yukio
name: Lu, Bo
Publisher: name: arXiv
Year: 2024
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: FOS: Physical sciences

description: We consider Josephson junctions formed by coupling two conventional superconductors via an unconventional magnet and investigate the formation of Andreev bound states, their impact on the Josephson effect, and the emergent superconducting correlations. We focus on unconventional magnets known as $d$-wave altermagnets and $p$-wave magnets. We find that the Andreev bound states in $d$-wave altermagnet and $p_y$-wave magnet Josephson junctions strongly depend on the transverse momentum, with a spin splitting and low-energy minima as a function of the superconducting phase difference $φ$. In contrast, the Andreev bound states for $p_{x}$-wave magnets are insensitive to the transverse momentum. We show that the Andreev bound states can be probed by the local density of states in the middle of the junction, which also reveals that $d_{x^{2}-y^{2}}$- and $p$-wave magnet junctions are prone to host zero energy peaks. While the zero-energy peak in $d_{x^{2}-y^{2}}$-wave altermagnet junctions tends to oscillate with the magnetic order, it remains robust in $p$-wave magnet junctions. We also demonstrate that the critical currents in $d$-wave altermagnet Josephson junctions exhibit an oscillatory decay with the increase of the magnetic order, while the oscillations are absent in $p$-wave magnet junctions albeit the currents exhibit a slow decay. Furthermore, we also demonstrate that the interplay of the Josephson effect and unconventional magnetic order of $d$-wave altermagnets and $p$-wave magnets originates from odd-frequency spin-triplet $s$-wave superconducting correlations that are otherwise absent. Our results can serve as a guide to pursue the new functionality of Josephson junctions based on unconventional magnets.
description: 17 pages, 8 figures
Tri-meson state $\boldsymbol{\bar{B}\bar{B}^*\bar{B}^*}$
Creators: name: Deng, Cheng-Rong
name: An, Chun-Sheng
Publisher: name: arXiv
Year: 2024
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We systematically explore the trimeson states $\bar{B}\bar{B}^*\bar{B}^*$ with various isospin-spin configurations in the quark model by solving exactly the six-body Schrödinger equations with the Gaussian expansion method. The configuration $\left[[\bar{B} \bar{B}^*]^1_0\bar{B}^*\right]^0_{\frac{1}{2}}$ is not only approximately 10.2 MeV lower than the threshold of its constituent particles but also about 0.2 MeV below that of the compact tetraquark state $[\bar{B}\bar{B}^*]^1_0$ and $\bar{B}^*$. This configuration manifests a loose two-body bound state composed of $[\bar{B}\bar{B}^*]^1_0$ and $\bar{B}^* $, with a size of around 4.75 fm. In contrast, the configurations $\left[[\bar{B}\bar{B}^*]^1_1\bar{B}^*\right]^0_{\frac{1}{2}}$, $\left[\bar{B}[\bar{B}^*\bar{B}^*]^0_1\right]^0_{\frac{1}{2}}$, and $\left[[\bar{B}\bar{B}^*]^1_1\bar{B}^*\right]^1_{\frac{1}{2}}$ exhibit binding energies of less than 1 MeV relative to their constituent particles, establishing a loose three-meson bound state. After coupling three configurations with $\frac{1}{2}0^-$, the trimeson state with $\frac{1}{2}0^-$ remains a loosely two-body bound state with a binding energy around 1.5 MeV and a huge size of 2.20 fm, in which the configuration $\left[[\bar{B}\bar{B}^*]^1_0\bar{B}^*\right]^0_{\frac{1}{2}}$ is dominant, contributing $80\%$ to the overall probability. Among the four bound configurations, the $σ$-meson exchange plays a decisive role. The meson pair $[\bar{B}\bar{B}^*]^1_0$, resembling the short-range strong correlated $p$-$n$ pair in nuclear physics, prevails over other types of meson pairs. The meson pair $[\bar{B}\bar{B}^*]^1_0$ not only contributes to the binding mechanisms but also influences the spatial structures of those stable trimeson configurations.
description: 10 pages, 3 figures, 3 tables