Constant Space Research Articles

Quantum pseudo-harmonic oscillator potential in non-Euclidean space: application to diatomic molecules

Abstract The present work analyzes a physical system with a quantum pseudo-harmonic oscillator in three-dimensional constant curvature spaces within the framework of non-relativistic theory. We present expressions for the energy equation and radial wavefunctions that depend on the curvature parameter k, using the functional analysis approach and the asymptotic iteration method. Additionally, we calculate the energy eigenvalues for diatomic molecules N2, H2, and ScH as a function of the constant curvature k. Using the Hellmann-Feynmann theorem, we derive expressions for the curvature-dependent expectation values of r-2 and p2, which we detail for the diatomic molecule system in this work. Furthermore, we perform a comparative analysis of the results for non-Euclidean space (spherical and hyperbolic spaces with constant curvature) and Euclidean space.

Dynamic nonlinear control strategies for resilient heterogeneous vehicle platooning and handling Byzantine attacks in communication networks.

This paper addresses the challenges of maintaining stability in heterogeneous vehicle platooning under the influence of communication disruptions caused by Byzantine attacks within a leader-follower framework. To enhance resilience, we propose a nonlinear control strategy tailored for a third-order heterogeneous dynamic model, integrating leader-follower interconnections with adaptable control gains. Utilizing a constant time headway spacing policy with gap adjustments, we derive control gains that secure internal platoon stability. A Lyapunov-based stability approach is employed to mitigate the destabilizing effects of Byzantine attacks, ensuring robust performance even in adverse conditions. Numerical simulations validate the controller's effectiveness, showing rapid convergence to stable platoon behavior within 10 seconds and maintaining a tracking error below 10 percent, despite simulated attacks. These results demonstrate the practical feasibility of the proposed controller in ensuring stability and resilience in real-world platooning scenarios where communication integrity is compromised.

All-optical mapping of Ca2+ transport and homeostasis in dendrites

Calcium mediates many important signals in dendrites. However, the basic transport properties of calcium in dendrites have been difficult to measure: how far and how fast does a local influx of calcium propagate? We developed an all-optical system for simultaneous targeted Ca2+ import and Ca2+ concentration mapping. We co-expressed a blue light-activated calcium selective channelrhodopsin, CapChR2, with a far-red calcium sensor, FR-GECO1c, in cultured rat hippocampal neurons, and used patterned optogenetic stimulation to introduce calcium into cells with user-defined patterns of space and time. We determined a mean steady-state length constant for Ca2+ transport ϕ ∼ 5.8 μm, a half-life for return to baseline t1/2 ∼ 1.7 s, and an effective diffusion coefficient D ∼ 20 μm2/s, though there were substantial differences in Ca2+ dynamics between proximal and distal dendrites. At high Ca2+ concentration, distal dendrites showed nonlinear activation of Ca2+ efflux, which we pharmacologically ascribed to the NCX1 antiporter. Genetically encoded tools for all-optical mapping of Ca2+ transport and handling provide a powerful capability for studying this important messenger.

String Stable Bidirectional Platooning Control for Heterogeneous Connected Automated Vehicles

Article String Stable Bidirectional Platooning Control for Heterogeneous Connected Automated Vehicles Dengfeng Pan * School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Melbourne, VIC 3122, Australia * Correspondence: E-mail: dengfengpan@swin.edu.au Received: 8 August 2024 Accepted: 18 September 2024 Published: 27 December 2024 Abstract: In vehicular platoons, disturbances can be amplified significantly downstream in the platoon if not adequately addressed, potentially leading to traffic jams or collisions. This paper tackles the challenge in maintaining string stability of heterogeneous vehicular platoons under a bidirectional communication topology and a refined constant time headway spacing policy. First, unlike the commonly used constant spacing policy and constant time headway policy, a refined constant time headway policy that combines the benefits of constant spacing and constant time headway policies is presented to enhance platooning safety while maintaining traffic efficiency. Second, a distributed adaptive estimator is designed such that each follower ensures its real-time estimation on the inaccessible leader's full states. The proposed estimators also well accommodate the heterogeneity among vehicles, allowing distinct inertial lag parameters of the vehicle longitudinal dynamics. Third, leveraging a bidirectional communication topology, a distributed scalable platoon controller is developed to guarantee the desired individual stability and string stability requirements of the vehicle platoon without the need of any global information of the communication topology. Formal sufficient conditions are provided on the existence of the desired estimator and controller gains. Finally, numerical simulations are conducted to verify the efficacy of the derived theoretical results. The simulations highlight the string stability and superiority of the proposed spacing policy, demonstrating the effectiveness of the proposed platooning control method.

DC allowable electric field strength for naphthenic‐based and paraffin‐based transformer oils

AbstractCurrently, the design of transformers insulation predominantly depends on the allowable alternating current (AC) field values for insulating oil established by Weidmann in the 1980s, lacking the research under direct current (DC) voltage for converter transformers. This study selects naphthenic oils and paraffin‐based oil transformer oil as research subjects, establishing a practical measurement platform to ascertain the oil breakdown characteristics under DC voltage. Furthermore, it statistically analyses the allowable DC field values of the oil. The findings elucidate that (1) the three‐parameter Weibull distribution is more suitable to conduct a statistical analysis for oil breakdown probability, yielding a fitting degree up to 99.95%. (2) for a constant electrode spacing, a 14.81% voltage increment escalates the breakdown probability of the oil gap from 3.33% to 73.33%. Concurrently, an increase in electrode spacing leads to a substantial decrement in the breakdown field strength of transformer oil, with KI25X experiencing a 54.51% reduction as electrode spacing extends from 5 to 25 mm. (3) the constant terms of the allowable DC field strength for S4, KI50X, and KI25X are found to be 19.728, 17.221, and 19.281, respectively. (4) a thorough analysis for differences in physicochemical properties and electrical parameters elucidates the variations in insulation properties across different transformer oils. The findings presented in this study offer essential theoretical and technical foundations for the design, evaluation, and enhancement of insulation structures in converter transformers.

Correlated physics, charge and magnetic orders in moiré kagomé systems

Abstract Moiré systems have emerged as an ideal platform for exploring the interaction effects and correlated states. However, most of the experimental systems were based on either the triangular or honeycomb lattice. In this study, based on the self-consistent Hartree-Fock calculation, we investigate the phase diagram of the Kagomé lattice in a recently discovered system with two degenerate Γ valley orbitals and strong spin-orbit coupling. By focusing on the filling factors of 1/2, 1/3 and 2/3, we identified various symmetry-breaking states by adjusting the screening length and dielectric constant. At the half filling, we discovered that the spin-orbit coupling induced Dzyaloshinskii-Moriya interaction stabilized a classical magnetic sate with 120° ordering. Additionally, we observed a transition to a ferromagnetic state with out-of-plane ordering. In the case of 1/3 filling, the system is ferromagnetically ordered due to the lattice frustration. Furthermore, for 2/3 filling, the system exhibits a pinned droplet state and a 120° magnetic ordered state at weak and immediate coupling strengths, respectively. For strong coupling case, when dealing with non-integer filling, the system is always charged ordered with sublattice polarization. Our study serves as a starting point for exploring the effects of correlation in moiré Kagomé system.

Seamless scale‐up of tube‐in‐tube millireactors by annular structure and feed method design: Micromixing, residence time distribution and heat transfer

AbstractFlow chemistry is widely valued for its enhanced transport properties and safety, but scaling up while maintaining the advantages of the microenvironment in small‐scale systems remains challenging. We addressed this by developing a novel tube‐in‐tube millireactor with a multi‐hole jet inlet and deflectors, designed to maintain consistent flow regimes and optimize micromixing, residence time distribution (RTD), and heat transfer at various scales. The reactor increases flux by enlarging tube diameters and incorporating micro‐holes and deflectors, all while maintaining a constant annular space. This design, validated through both CFD modeling and experimental results, maintains consistent fluid flow and excellent transfer properties, achieving micromixing time below 2 ms at Reh > 2000, a plug‐flow‐like RTD profile, and a heat transfer capacity up to 12.4 times greater than conventional designs. This study presents a simple, scalable approach to millireactor design, combining “number‐up” and “size‐up” strategies, offering a cost‐effective solution for industrial applications.

The equivalence of smooth and synthetic notions of timelike sectional curvature bounds

Timelike sectional curvature bounds play an important role in spacetime geometry, both for the understanding of classical smooth spacetimes and for the study of Lorentzian (pre-)length spaces introduced by Kunzinger and Sämann [Ann. Global Anal. Geom. 54 (2018), pp. 399-447]. In the smooth setting, a bound on the sectional curvature of timelike planes can be formulated via the Riemann curvature tensor. In the synthetic setting, bounds are formulated by comparing various geometric configurations to the corresponding ones in constant curvature spaces. The first link between these notions in the Lorentzian context was established by Harris [Indiana Univ. Math. J. 31 (1982), pp. 289–308], which was instrumental in the proof of powerful results in spacetime geometry (see Beem et al. [Toponogov splitting theorem for Lorentzian manifolds, Springer, Berlin, 1985; J. Differential Geom. 22 (1985), pp. 29–42]; Galloway and Ling [Gen. Relativity Gravitation 50 (2018), p. 7]). For general semi-Riemannian manifolds, the equivalence between sectional curvature bounds and synthetic bounds was established by Alexander and Bishop [Comm. Anal. Geom. 16 (2008), pp. 251–282]; however in this approach the sectional curvatures of both timelike and spacelike planes have to be considered. In this article, we fill a gap in the literature by proving the full equivalence between sectional curvature bounds on timelike planes and synthetic timelike bounds on strongly causal spacetimes. As an essential tool, we establish Hessian comparison for the time separation and signed distance functions.

A modiolar-pillar gradient in auditory-nerve dendritic length: A novel post-synaptic contribution to dynamic range?

Auditory-nerve fibers (ANFs) from a given cochlear region can vary in threshold sensitivity by up to 60 dB, corresponding to a 1000-fold difference in stimulus level, although each fiber innervates a single inner hair cell (IHC) via a single synapse. ANFs with high-thresholds also have low spontaneous rates (SRs) and synapse on the side of the IHC closer to the modiolus, whereas the low-threshold, high-SR fibers synapse on the side closer to the pillar cells. Prior biophysical work has identified modiolar-pillar differences in both pre- and post-synaptic properties, but a comprehensive explanation for the wide range of sensitivities remains elusive. Here, in guinea pigs, we used immunostaining for several neuronal markers, including Caspr, a key protein in nodes of Ranvier, to reveal a novel modiolar-pillar gradient in the location of the first ANF heminodes, presumed to be the site of the spike generator, just outside the sensory epithelium. Along the cochlea, from apex to base, the unmyelinated terminal dendrites of modiolar ANFs were 2-4 times longer than those of pillar ANFs. This modiolar-pillar gradient in dendritic length, coupled with the 2-4 fold smaller caliber of modiolar dendrites seen in prior single-fiber labeling studies, suggests there could be a large difference in the number of length constants between the synapse and the spike initiation zone for low- vs high-SR fibers. The resultant differences in attenuation of post-synaptic potentials propagating along these unmyelinated dendrites could be a key contributor to the observed range of threshold sensitivities among ANFs.

(Invited) Mechanical Suppression of Electron Transfer in Subnanometer Confinement between MXene Layers

Ion adsorption and electron transfer are the primary charge storage mechanisms in porous electrodes. Desolvation/solvation of ions in subnanometer confinement may alter the balance between those two processes. For 2D materials like MXenes, there is a continuous change in interlayer spacing as ions are transported and stored between the layers. However, little is known about the effect of the mechanical constraint (pressure) on electrochemistry in confinement. In this work, the ion transportation process in between mechanically constrained MXene layers is monitored by combining in-situ UV-vis spectroscopy, in-situ optical spectroscopy, and in-situ XRD characterization. Compared with spray-coated Ti3C2Tx films, physically constrained Ti3C2Tx film with a constant interlayer spacing exhibited exceptional capabilities in suppressing redox reactions. Notably, this property of faradaic suppression under mechanical strain led to the application of MXene-based electrochemical cells as high-pressure electrochemical sensors.

Compressive performance of three-dimensional multilevel sandwich composite structures

This study reports a two-dimensional bi-directional E-glass woven fabric preform structure is converted into a three-dimensional sandwich composite structure with the help of wooden molds and matrix material. One to three levels of sandwich composite are prepared with a rectangular core configuration by keeping the specimen’s constant dimensions. A second multilevel sandwich composite sample set is developed with hexagonal, square, and triangular core configurations, maintaining length, width, height, and weight constant. The developed composite samples are characterized by their compressive properties. For single, double, and triple-level sandwich composites with rectangular cores, it is found that increasing the number of levels led to an increase in compressive load capacity, with triple-level structures exhibiting the highest strength. However, an increase in the number of levels resulted in a decrease in specific compressive load. Additionally, the energy absorption capacity increases as the number of levels increases. In the case of multilevel sandwich composites with triangular, square, and hexagonal core, the triangular core demonstrated the highest compressive strength and energy absorption capacity compared to square and hexagonal configurations. The failure modes of the sandwich composite structure have also been discussed. The results indicate that the sandwich composite’s compressive, energy absorption properties, and failure modes depend on many parameters, such as the number of levels, core structure, free wall length, face sheet length, and loading direction. The findings of this study will provide valuable insights into potential applications and performance of these advanced sandwich structures, enabling improved design and optimization for specific engineering applications across diverse industries.

A comprehensive analysis of the structural, phonon, electronic, mechanical, optical, and thermophysical properties of cubic Ca3SbX3 (X = Cl, Br): DFT - GGA and mBJ studies

The current investigation employed first-principles calculation to assess the structural, phonon, mechanical, electronic, optical, thermodynamic, and thermoelectric properties of lead-free cubic Ca3SbX3 (X = Cl, Br). The dynamic stability of both compounds is assessed by analyzing the phonon dispersion spectrum. The distance between atoms is significantly reduced, leading to a large drop in the bond length, cell volume, and lattice constant of Ca3SbX3 (X = Cl, Br) compounds upon applying pressure. Ca3SbCl3 and Ca3SbBr3 compounds have direct bandgaps (Γ-Γ) of 2.57 and 2.27 eV via mBJ functional and 1.82 and 1.34 eV via GGA functional at 0 GPa pressure. Additionally, the bandgaps of Ca3SbCl3 and Ca3SbBr3 decrease to 1.65 eV and 1.45 eV, respectively, when accounting for the quantum effects of spin-orbit coupling (SOC). As the level of pressure rises to 30 GPa, Ca3SbCl3 and Ca3SbBr3 compound's band gaps reduce to 0.89 and 0.65 eV via mBJ functional and 0.27 and 0.12 via GGA functional. Increasing pressure is shown to reduce the effective mass, thereby enhancing the conductivity of both types of charge carriers. The reduced recombination rate signifies both compounds' greater absorption capabilities, making them more suitable for solar absorbers. The analysis of the mechanical properties indicates that as pressure increases, the elastic moduli rise, and the material transitions from being brittle to becoming more ductile. Additionally, both materials show a redshift of absorption and optical conductivity with improved dielectric constants at high pressure owing to the alteration in the bandgap, which is more appropriate for surgical instruments and solar absorbers. Thermodynamic properties show their temperature tolerance and appropriateness for high temperatures. Lastly, their thermoelectric property evaluation indicates high PF and near unity ZT, suggesting their use in thermoelectric devices.

Divertor Tokamak Test: Impact of NBI shine-through and beam-plasma interaction on Divertor Tokamak Test facility

IntroductionIn this work, we aim to explore numerically the behavior of beam energetic particles in the Divertor Tokamak Test (DTT), a superconductive device equipped with a Neutral Beam Injection (NBI) system capable of injecting neutrals up to 510 keV.MethodWe explore beam ionization and beam slowing down for different DTT plasma scenarios. Numerical simulations are performed using the ASCOT suite of codes, including a wide-range scan of plasma density and beam injection energy. For different plasma conditions, we estimate shine-through losses, including the heat fluxes on the first wall thanks to dedicated particle tracing simulations. Orbits of newly-born fast ions are characterized by means of the constant of motion phase space, showing how trapped energetic particles’ population and prompt losses change with plasma density and NBI energy.Results and discussionSlowing down simulations show that NBI injection at 510 keV is well coupled to DTT plasmas. DTT NBI will be one of the sources of auxiliary ion heating, with an absorbed power ratio of up to ∼50% depending on plasma and beam parameters. At low plasma densities, energetic particle confinement is less efficient, and NBI power and/or energy reduction is expected.

A Space-Efficient One-Pass Online SVM Algorithm

In this paper we consider the problem of training a Support Vector Machine (SVM) online using a stream of data in random order. We provide a fast online training algorithm for general SVM on very large datasets. Based on the geometric interpretation of SVM known as the polytope distance, our algorithm uses a gradient descent procedure to solve the problem. With high probability our algorithm outputs an [Formula: see text]-approximation result in constant time and space, which is independent of the size of the dataset, where [Formula: see text]-approximation means that the separating margin of the classifier is almost optimal (with error [Formula: see text]), and the number of misclassified training points is very small (with error [Formula: see text]). Experimental results show that our algorithm outperforms most of existing online algorithms, especially in the space requirement aspect, while maintaining high accuracy.

A modiolar-pillar gradient in auditory-nerve dendritic length: a novel post-synaptic contribution to dynamic range?

Auditory-nerve fibers (ANFs) from a given cochlear region can vary in threshold sensitivity by up to 60 dB, corresponding to a 1000-fold difference in stimulus level, although each fiber innervates a single inner hair cell (IHC) via a single synapse. ANFs with high-thresholds also have low spontaneous rates (SRs) and synapse on the side of the IHC closer to the modiolus, whereas the low-threshold, high-SR fibers synapse on the side closer to the pillar cells. Prior biophysical work has identified modiolar-pillar differences in both pre- and post-synaptic properties, but a comprehensive explanation for the wide range of sensitivities remains elusive. Here, in guinea pigs, we used immunostaining for several neuronal markers, including Caspr, a key protein in nodes of Ranvier, to reveal a novel modiolar-pillar gradient in the location of the first ANF heminodes, presumed to be the site of the spike generator, just outside the sensory epithelium. Along the cochlea, from apex to base, the unmyelinated terminal dendrites of modiolar ANFs were 2 - 4 times longer than those of pillar ANFs. This modiolar-pillar gradient in dendritic length, coupled with the 2 - 4 fold smaller caliber of modiolar dendrites seen in prior single-fiber labeling studies, suggests there could be a large difference in the number of length constants between the synapse and the spike initiation zone for low- vs high-SR fibers. The resultant differences in attenuation of post-synaptic potentials propagating along these unmyelinated dendrites could be a key contributor to the observed range of threshold sensitivities among ANFs.

The VST ATLAS Quasar Survey – III. Halo mass function via quasar clustering and quasar-CMB lensing cross-clustering

ABSTRACT We exploit the VST ATLAS quasar (QSO) catalogue to perform three measurements of the quasar halo mass profile. First, we make a new estimate of the angular autocorrelation function of ≈230 000 ATLAS quasars with $z_{\rm photo}\lesssim 2.5$ and $17 < g < 22$. By comparing with the $\Lambda$CDM mass clustering correlation function, we measure the quasar bias to be $b_{\rm Q}\approx 2.1$, implying a quasar halo mass of $M_{\rm halo} \approx 8.5\times 10^{11}\,h^{-1}\,{\rm M}_\odot$. Second, we cross-correlate these $z\approx 1.7$ ATLAS quasars with the Planck cosmic microwave background (CMB) lensing maps, detecting a somewhat stronger signal at $4\,{\rm arcmin} < \theta < 60\,{\rm arcmin}$ than previous authors. Scaling these authors’ model fit to our data, we estimate a quasar host halo mass of $M_{\rm halo}\approx 8.3\times 10^{11}\,h^{-1}\,{\rm M}_\odot$. Third, we fit halo occupation sistribution (HOD) model parameters to our quasar autocorrelation function and from the derived halo mass function, we estimate a quasar halo mass of $M_{\rm halo}\approx 2.5\times 10^{12}\,h^{-1}\,{\rm M}_\odot$. We then compare our HOD model prediction to our quasar-CMB lensing result, confirming their consistency. We find that most (≈2/3) QSOs have halo masses within a factor of ≈3 of this average mass. An analysis based on the probability of X-ray detections of AGN in galaxies and the galaxy stellar mass function gives a similarly small mass range. Finally, we compare the quasar halo mass and luminosity functions and suggest that gravitational growth may produce the constant space density with redshift seen in the quasar luminosity function.

Response study of impact of slot area variation in miniature antenna for Kurtz-Above band applications in 5G/6G wireless communication

Modern fifth-generation/sixth generation (5G/6G) wireless demand for efficient miniature antenna. To fulfill these demands here efforts have been made using high frequency structure simulator software (HFSS) to design a compact microstrip patch antenna (MPA). The design of the antenna consisted of two slots- one located near the feed line and the other one at the opposite side of the feed line. The volumetric dimension of the proposed antenna was 13.2 mm x 11.4 mm x 1.6 mm, designed at resonant frequency 33 GHz, employing 1.6 mm thick Rogers RT Duroid 5880 substrate having dielectric constant 2.2 and loss tangent 0.0013. A transmission line having a length of 5.7 mm and a width of 2 mm was used to excite the antenna for electromagnetic radiation fields. Antenna parameters simulation results were obtained for different slot areas, keeping other design parameters like dimensions of ground, patch, substrate, and feed port fixed. Different slot areas were selected by changing slot width, keeping its length constant. A gain of 7.7 dB with voltage standing wave ratio (VSWR) of 1.9 and return loss (S11) -19.23 dB was obtained for slot width 3 mm and area 1.5 mm2. The directivity of the antenna was reported as 5.7dB, with a very good surface current density of 104.94 Amp/m, considered sufficient in the fringing fields breaking situation. Bandwidth was found to be inversely proportional to slot width. VSWR, S11, and 3D gain showed inverse dependence on slot area. Gain and S11 change in direct proportion to feed width whereas VSWR changes inversely with feed length. The proposed MPA is suitable for satellites, mobile phones, wireless communication systems, and remote sensing applications.

Three-dimensional Anderson localization of light in materials with fluctuating electric and magnetic properties.

Anderson localization of electromagnetic waves, caused by the disorder-induced arrest of wave diffusion, has been experimentally observed in systems with spatially fluctuating permeability, but only in lower dimensions, not in three dimensions. This paper introduces what we believe to be a novel theoretical approach to the Maxwell equations considering both electric and magnetic disorder. It demonstrates that when both the dielectric constant and magnetic permeability fluctuate in space, the spectral range for three-dimensional Anderson localization significantly increases.

Performing the changing landscape

This exposition refers to arts-based research on simultaneous performative walking and singing practice in a changing environment. The act of walking is put in the context of landscape and singing representing two aspects of relation to the environment – inner and outer landscape. The object of research is traditional and authorial songs and their bodily and sensual interconnection with the process of experiencing landscape. This experience is gained with a group of artists and environmentalists who have over the course of more than a year repetitively walked through the landscape of the natural park Prokop Valley in Prague and its adjacent urban areas. Qualitative research is taken within the project “Walking as a liquid constant in urban space and landscape”. The method of data collection uses mental maps, inspired by the concept of Kevin Lynch, as a means of documentation. The exposition has three parts 1) the opening video essay, 2) Opus caementicium, autoethnographic reflection of the site, where the project takes place, and 3) Fugue of the vanishing world – an essay on the musical aspect of the project. Chapter titles are inspired by musical terminology that has content connotations in the text or mirrors the structuring of text and musical compositions.

Synthesis of dynamic modelling framework and optimal control strategy for virtually coupled train sets with guaranteed safety

Virtual coupling represents a novel railway operational mechanism, wherein several trains share state information and adjust their behaviours based on control objectives, which include safety (collision avoidance) assurance and stability (uniform velocity and constant spacing between trains) maintenance. However, the conflict between safety and stability requirements becomes more apparent, as the closer spacing between trains. Moreover, the hybrid nature of the train platoon operation, which involves both discrete events and continuous dynamics, also poses a significant barrier to the control strategy synthesis. This paper presents the Virtually Coupled Train Sets (VCTS) dynamic modelling framework and strategy synthesis approach to address these problems. A Hybrid Markov Decision Process (HMDP) is adopted for relative longitudinal dynamics modelling of trains, considering the influence of the uncertainty dynamic of trains ahead. A Stackelberg game-based strategy synthesis algorithm is applied for the safe guarantee by overcoming the uncertainty, and a Q-learning method is used for stability strategy selection from the safe strategy. The results showed a 17.95% expansion in the safe state space when compared to the general relative braking scheme (which assumes maximal acceleration during the delay horizon). In a four-train tracking operation scenario, compared with Q-learning without safe constraints, our approach gives similar stability performance; compared with Q-learning with general relative braking safe constraints, our approach not only assurance safety but has a better stability performance.