Angle Distribution Research Articles

Geometric Fidelity Requirements for Meshes in Automotive Lidar Simulation

The perception of vegetation is a critical aspect of off-road autonomous navigation, and consequentially a critical aspect of the simulation of autonomous ground vehicles (AGVs). Representing vegetation with triangular meshes requires detailed geometric modeling that captures the intricacies of small branches and leaves. In this work, we propose to answer the question, “What degree of geometric fidelity is required to realistically simulate lidar in AGV simulations?” To answer this question, in this work we present an analysis that determines the required geometric fidelity of digital scenes and assets used in the simulation of AGVs. Focusing on vegetation, we use a comparison of the real and simulated perceived distribution of leaf orientation angles in lidar point clouds to determine the number of triangles required to reliably reproduce realistic results. By comparing real lidar scans of vegetation to simulated lidar scans of vegetation with a variety of geometric fidelities, we find that digital tree models (meshes) need to have a minimum triangle density of >1600 triangles per cubic meter in order to accurately reproduce the geometric properties of lidar scans of real vegetation, with a recommended triangle density of 11,000 triangles per cubic meter for best performance. Furthermore, by comparing these experiments to past work investigating the same question for cameras, we develop a general “rule-of-thumb” for vegetation mesh fidelity in AGV sensor simulation.

“Two-dimensional distribution reconstruction and emittance diagnostics of proton beam phase space using tomography”

A two-dimensional distribution of a proton beam in phase space was reconstructed using beam profile data and a tomography technique in this study. These beam profile data were acquired by a wire scanner under various beam optics conditions, employing an experimental procedure identical, in principle, to the quadrupole magnet (QM) scan method to diagnose beam parameters. According to beam optics, beam profile data measured while changing the QM current is the same as that measured while rotating the beam distribution in the phase space. Thus, the set of the beam profile data can be converted into a sinogram, serving as source data for tomography. A filtered-back-projection (FBP) method is applied to reconstruct the beam distribution from this sinogram. However, if the range and distribution of the rotation angle are not sufficient, the reconstructed distribution data will be inaccurate, which will negatively affect beam parameter evaluation. To solve this limitation, a simulator incorporating the beam optics theory with the tomography was developed to derive an efficient experimental condition. The beam distribution in the phase space was successfully reconstructed, and the beam parameters evaluated from this were also confirmed to match well with the values obtained from the QM scan.

Constraining Possible γ-Ray Burst Emission from GW230529 Using Swift-BAT and Fermi-GBM

GW230529 is the first compact binary coalescence detected by the LIGO–Virgo–KAGRA collaboration with at least one component mass confidently in the lower mass gap, corresponding to the range 3–5 M ⊙. If interpreted as a neutron star–black hole merger, this event has the most symmetric mass ratio detected so far and therefore has a relatively high probability of producing electromagnetic (EM) emission. However, no EM counterpart has been reported. At the merger time t 0, Swift-BAT and Fermi-GBM together covered 100% of the sky. Performing a targeted search in a time window [t 0 − 20 s, t 0 + 20 s], we report no detection by the Swift-BAT and Fermi-GBM instruments. Combining the position-dependent γ-ray flux upper limits and the gravitational-wave posterior distribution of luminosity distance, sky localization, and inclination angle of the binary, we derive constraints on the characteristic luminosity and structure of the jet possibly launched during the merger. Assuming a top-hat jet structure, we exclude at 90% credibility the presence of a jet that has at the same time an on-axis isotropic luminosity ≳1048 erg s−1 in the bolometric band 1 keV–10 MeV and a jet opening angle ≳15°. Similar constraints are derived by testing other assumptions about the jet structure profile. Excluding GRB 170817A, the luminosity upper limits derived here are below the luminosity of any GRB observed so far.

Surgical management of severe planovalgus foot deformity in children with generalised joint hypermobility

BackgroundThis study aimed to evaluate the outcomes of calcaneal lengthening osteotomy (CLO) and double arthrodesis of the talonavicular and calcaneocuboid joints (DA) for correcting planovalgus foot deformity exclusively in patients with generalised joint hypermobility. MethodsWe retrospectively reviewed 29 feet in 17 consecutive patients who underwent either CLO or DA. The mean age at surgery was 11.3 ± 2.3 years, and the mean follow-up duration was 7.7 ± 3.2 years. Preoperative and final follow-up radiographs and dynamic foot-pressure measurements were analysed. ResultsBoth operations significantly improved the radiographic parameters, except for the lateral talocalcaneal angle in the CLO group. Pedobarographic study demonstrated an elevation of the medial longitudinal arch and an improved foot-pressure distribution after both surgeries. The plantar pressure in the lateral forefoot significantly increased only in the DA group, while the pressures exerted on the medial forefoot and hindfoot and the arch index improved only in the CLO group. ConclusionsBoth CLO and DA effectively improve the foot alignments of the deformity in patients with generalised joint hypermobility. However, differences were observed in the changes in the lateral talocalcaneal angle and plantar pressure distribution between the two procedures. Level of evidenceTherapeutic Level III.

Competing Influences of Earthward Convection and Azimuthal Drift Loss on the Pitch Angle Distribution of Energetic Electrons

Competing Influences of Earthward Convection and Azimuthal Drift Loss on the Pitch Angle Distribution of Energetic Electrons

Quantifying the Role of EMIC Wave Scattering During the 27 February 2014 Storm by RAM‐SCB Simulations

AbstractElectromagnetic Ion Cyclotron (EMIC) wave scattering has been proved to be responsible for the fast loss of both radiation belt (RB) electrons and ring current (RC) protons. However, its role in the concurrent dropout of these two co‐located populations remains to be quantified. In this work, we study the effect of EMIC wave scattering on both populations during the 27 February 2014 storm by employing the global physics‐based RAM‐SCB model. Throughout this storm event, MeV RB electrons and 100s keV RC protons experienced simultaneous dropout following the occurrence of intense EMIC waves. By implementing data‐driven initial and boundary conditions, we perform simulations for both populations through the interplay with EMIC waves and compare them against Van Allen Probes observations. The results indicate that by including EMIC wave scattering loss, especially by the He‐band EMIC waves, the model aligns closely with data for both populations. Additionally, we investigate the simulated pitch angle distributions (PADs) for both populations. Including EMIC wave scattering in our model predicts a 90° peaked PAD for electrons with stronger losses at lower pitch angles, while protons exhibit an isotropic PAD with enhanced losses at pitch angles above 40°. Furthermore, our model predicts considerable precipitation of both particle populations, predominantly confined to the afternoon to midnight sector (12 hr < MLT < 24 hr) during the storm's main phase, corresponding closely with the presence of EMIC waves.

Generation and Impacts of Whistler‐Mode Waves During Energetic Electron Injections in Jupiter's Outer Radiation Belt

AbstractEnergetic particle injections are commonly observed in Jupiter's magnetosphere and have important impacts on the radiation belts. We evaluate the roles of electron injections in the dynamics of whistler‐mode waves and relativistic electrons using Juno measurements and wave‐particle interaction modeling. The Juno spacecraft observed injected electron flux bursts at energies up to 300 keV at M shell ∼11 near the magnetic equator during perijove‐31. The electron injections are related to chorus wave bursts at 0.05–0.5 fce frequencies, where fce is the electron gyrofrequency. The electron pitch angle distributions are anisotropic, peaking near 90° pitch angle, and the fluxes are high during injections. We calculate the whistler‐mode wave growth rates using the observed electron distributions and linear theory. The frequency spectrum of the wave growth rate is consistent with that of the observed chorus magnetic intensity, suggesting that the observed electron injections provide free energy to generate whistler‐mode chorus waves. We further use quasilinear theory to model the impacts of chorus waves on 0.1–10 MeV electrons. Our modeling shows that the chorus waves could cause the pitch angle scattering loss of electrons at <1 MeV energies and accelerate relativistic electrons at multiple MeV energies in Jupiter's outer radiation belt. The electron injections also provide an important seed population at several hundred keV energies to support the acceleration to higher energies. Our wave‐particle interaction modeling demonstrates the energy flow from the electron injections to the relativistic electron population through the medium of whistler‐mode waves in Jupiter's outer radiation belt.

Radio Emission from the Magnetically Active M Dwarf UV Ceti from 1 to 105 GHz

BL and UV Ceti are a nearby (2.7 pc) binary system with similar masses, spectral types, and rapid rotation rates, but very different magnetic activity. UV Ceti’s much stronger large-scale magnetic field may cause this difference, highlighting key unanswered questions about dynamo processes in fully convective objects. Here, we present multiepoch characterization of the radio spectrum of UV Ceti spanning 1–105 GHz, exhibiting flared emission similar to coronal activity, auroral-like emission analogous to planetary magnetospheres, and slowly varying persistent emission. Radio observations are a powerful means to probe the role that the large-scale magnetic field of UV Ceti has in nonthermal particle acceleration because radio-frequency phenomena result from both the activity of small-scale field features as well as large-scale auroral current systems. We find temporal variability at all bands observed, and a hint of rotational modulation in the degree of circular polarization up to 40 GHz. The persistent component of the emission is fairly constant from 1 to 105 GHz, making optically thick emission or optically thin gyrosynchrotron from electrons with an isotropic pitch angle distribution unlikely. We discuss the possibility of emission mechanisms analogous to Jupiter’s radiation belts.

Long-term phase angle muscle imaging under electrical muscle stimulation (EMS) by phase angle electrical impedance tomography

Objectives. Phase angle muscle imaging has been proposed by phase angle electrical impedance tomography (ΦEIT) under electrical muscle stimulation (EMS) for long-term monitoring of muscle quality improvement, especially focusing on calf muscles. Approach. In the experiments, twenty-four subjects are randomly assigned either to three groups: control group (CG, n = 8), low voltage intensity of EMS training group (LG, n = 8), and optimal voltage intensity of EMS training group (OG, n = 8). Main results. From the experimental results, phase angle distribution images Ф are cleared reconstructed by ФEIT as four muscle compartments over five weeks experiments, which are called the M 1 muscle compartments composed of gastrocnemius muscle, M 2 muscle compartments composed of soleus muscle, M 3 muscle compartments composed of tibialis-posterior muscle, flexor digitorum longus muscle, and flexor pollicis longus muscle, and M 4 muscle compartment composed of the tibialis anterior muscle, extensor digitorum longus muscle, and peroneus longus muscle. Ф is inversely correlated with age, namely the Ф decreases with increasing age. A paired samples t-test was conducted to elucidate the statistical significance of spatial-mean phase angle in all domain <Ф>Ω and in each muscle compartment <Ф> M with reference to the conventional phase angle Ф by bioelectrical impedance analysis, muscle grey-scale G muscle by ultrasound, and maximal dynamic strength S Max by one-repetition maximum test. Significance. From the t-test results, <Ф>Ω have good correlation with Ф and S Max. In the OG, <Ф W5>Ω, Ф W5, and (S Max)W5 were significantly higher than in the first week (n = 8, p < 0.05). A significant increase in the phase angle of both M 1 and M 4 muscle compartments is observed after five weeks in LG and OG groups. Only the OG group shows a significant increase in the phase angle of M 2 muscle compartment after five weeks. However, no significant changes in the spatial-mean phase angle of M 3 compartment are observed in each group. In conclusion, ФEIT satisfactorily monitors the response of each compartment in calf muscle to long-term EMS training.

Anchorage force transfer mechanism and bearing capacity theoretical of pawl bolt anchored in plain concrete

In this paper, the anchorage mechanism and bearing capacity of the special type of pawl bolt anchored in concrete under uplift load were studied. Static tests were carried out on two typical pawl bolts, namely 135° and 180° pawl bolts, and the effects of anchorage depth and pawl type on their failure modes were studied. The experimental results show that the uplift bearing capacity of pawl bolt is improved more effectively than that of smooth bolt. The two typical failure modes of pawl bolts under uplift load are concrete breakout failure and bolt yield failure. The concrete breakout failure exclusively occurs with anchorage depth of 5d, while the failure mode could change from concrete breakout failure to bolt yield failure with the increase of anchorage depth. The finite element model was established to elucidate the failure mechanism of anchorage bolt and concrete. The crack propagation and diffusion angle distribution of anchorage concrete can be directly judged by concrete tensile damage and stress vector in simulation analysis. Additionally, a calculation method to accurately predict the uplift bearing capacity of pawl bolt was proposed, which considered the effect of diffusion angle θi on the uplift bearing capacity and further discusses the change law of cone diffusion angle θi and concrete crack propagation. The calculated results exhibited a concordance with the experimental and numerical results, which shows that the formula presented in this paper can be considered reliable and can guide the practical engineering design.

X-ray scattering based scanning tomography for imaging and structural characterization of cellulose in plants.

X-ray and neutron scattering have long been used for structural characterization of cellulose in plants. Due to averaging over the illuminated sample volume, these measurements traditionally overlooked the compositional and morphological heterogeneity within the sample. Here, a scanning tomographic imaging method is described, using contrast derived from the X-ray scattering intensity, for virtually sectioning the sample to reveal its internal structure at a resolution of a few micrometres. This method provides a means for retrieving the local scattering signal that corresponds to any voxel within the virtual section, enabling characterization of the local structure using traditional data-analysis methods. This is accomplished through tomographic reconstruction of the spatial distribution of a handful of mathematical components identified by non-negative matrix factorization from the large dataset of X-ray scattering intensity. Joint analysis of multiple datasets, to find similarity between voxels by clustering of the decomposed data, could help elucidate systematic differences between samples, such as those expected from genetic modifications, chemical treatments or fungal decay. The spatial distribution of the microfibril angle can also be analyzed, based on the tomographically reconstructed scattering intensity as a function of the azimuthal angle.

Effect of basicity on the structure and viscosity properties of HIsmelt slag: A molecular dynamics simulation

ABSTRACT HIsmelt is an emerging and potentially promising non-blast furnace ironmaking process, and the characteristics of its slag are crucial to the smelting process. Currently, there is no atomic-scale research on the slag of the HIsmelt process. In this work, molecular dynamics simulations were employed to investigate the effect of basicity on the structure and viscosity properties of the HIsmelt CaO-SiO2-Al2O3-FeO slag system at 1773 K. The slag structure was characterised by calculating structural parameters, including radial distribution function, coordination number, oxygen type, and bond angle distribution. Furthermore, the viscosity of the slag system was estimated by using the self-diffusion coefficient and compared with mathematical models. The results indicate that basicity has a negligible impact on the short-range ordering of aluminosilicates in the HIsmelt slag system. As slag basicity increases from 0.4 to 1.8, the concentration of bridging oxygen decreases, non-bridging oxygen increases, and the [SiO4]4+ and [AlO4]5+ network structures undergo depolymerisation in the system. Additionally, the self-diffusion coefficient of atoms increases, and the slag viscosity exhibits a declining trend with increasing basicity. In the basicity range of 0.8 −1.8, the current MD simulations align with the results of the previous models.

On the question whether surface roughness can explain the absence of a prominent single-collision peak in keV heavy-ion scattering off a polycrystalline Ru surface

In a joint experimental and modeling effort, we have studied 15 keV Ar2+, Kr2+, and Xe2+ projectiles scattering off a polycrystalline Ru surface to assess the possible role of surface roughness in the apparent near-absence of the single-collision (SC) peak for Xe, the heaviest of the ions. The surface roughness of the Ru sample was determined by atomic force microscopy (AFM). The AFM image is used as input to simulations by means of the ray tracing code SPRAY. The observed spectra display a significant SC peak in the energy distributions of reflected Ar and Kr ions, which is not the case for Xe. The energy spectrum produced by the reflection of Xe and recoiled Ru ions closely corresponds to the results obtained from our SPRAY simulations. It is evident that surface roughness plays a crucial role in the visibility of the SC peak. From simulations for different target roughnesses, it is clear that a concentrated distribution of inclination angles centered around 2° effectively reduces the intensity of the single-collision peak for Xe ion scattering. The presence of a distinct SC peak for Ar and Kr ions, unlike Xe ions, supports the notion that the absence of a prominent SC peak in Xe ion scattering is not primarily due to geometric blocking of trajectories by surface roughness. This suggests that for slow, heavy ions like Xe, scattering effects arising from the nearest neighbors to the binary collision partner are significant and should be carefully examined.

Parsimonious Topology Based on Frank-Kasper Polyhedra in Metal-Organic Frameworks.

A new topology previously unknown in metal-organic frameworks (MOFs) provides an important clue to uncovering a new series of polyhedral MOFs. We report a novel MOF crystallized in a parsimonious mep topology based on Frank-Kasper (FK) polyhedra. The distribution of angles in a tetrahedral arrangement (T-O-T) is crucial for the formation of FK polyhedra in mep topology. This finding led us to investigate the T-O-T angle distribution in related zeolites and zeolitic imidazolate frameworks (ZIFs). Unlike zeolites, it is extremely difficult to achieve high T-O-T angles in ZIFs, which prevents the formation of some FK topologies. Density functional theory (DFT) total energy calculations support a correlation between T-O-T angles and the feasibility of new tetrahedron-based FK frameworks. This result may lead to innovative ways of accessing new cellular topologies by simple chemical tweaking of T-O-T angles.

Distribution of angles to lattice points seen from a fast moving observer

Distribution of angles to lattice points seen from a fast moving observer

Field theory of active chiral hard disks: a first-principles approach to steric interactions

A first-principles approach for active chiral hard disks is presented, that explicitly accounts for steric interactions on the two-body level. We derive an effective one-body equation for the joint probability distribution of positions and angles of the particles. By projecting onto the angular modes, we write a hierarchy for the lowest hydrodynamic modes, i.e. particle density, polarisation, and nematic tensor. Introducing dimensionless variables in the equations, we highlight the assumptions, which—though inherent—are often included implicit in typical closure schemes of the hierarchy. By considering different regimes of the Péclet number, the well-known models in active matter can be obtained through our consideration. Explicitly, we derive an effective diffusive description and by going to higher orders in the closure scheme, we show that this first-principles approach results in the recently introduced Active Model B +, a natural extension of the Model B for active processes. Remarkably, here we find that chirality can change the sign of the phenomenological activity parameters.

Nonresonant central exclusive production of charged-hadron pairs in proton-proton collisions at s=13 TeV

The central exclusive production of charged-hadron pairs in pp collisions at a center-of-mass energy of 13 TeV is examined, based on data collected in a special high-β* run of the LHC. The nonresonant continuum processes are studied with the invariant mass of the centrally produced two-pion system in the resonance-free region, mπ+π−&lt;0.7 or mπ+π−&gt;1.8 GeV. Differential cross sections as functions of the azimuthal angle between the surviving protons, squared exchanged four-momenta, and mπ+π− are measured in a wide region of scattered proton transverse momenta, between 0.2 and 0.8 GeV, and for pion rapidities |y|&lt;2. A rich structure of interactions related to double-pomeron exchange is observed. A parabolic minimum in the distribution of the two-proton azimuthal angle is observed for the first time. It can be interpreted as an effect of additional pomeron exchanges between the protons from the interference between the bare and the rescattered amplitudes. After model tuning, various physical quantities are determined that are related to the pomeron cross section, proton-pomeron and meson-pomeron form factors, pomeron trajectory and intercept, and coefficients of diffractive eigenstates of the proton. © 2024 CERN, for the CMS and TOTEMs Collaboration 2024 CERN

Distinct Sub- to Superdiffuse Insulin Granule Transport Behaviors in β-Cells Are Strongly Affected by Granule Age.

Intracellular transport is a complex process that is difficult to describe by a single general model for motion. Here, we study the transport of insulin containing vesicles, termed granules, in live MIN6 cells. We characterize how the observed heterogeneity is affected by different intracellular factors by constructing a MIN6 cell line by CRISPR-CAS9 that constitutively expresses mCherry fused to insulin and is thus packaged in granules. Confocal microscopy imaging and single particle tracking of the granule transport provide long trajectories of thousands of single granule trajectories for statistical analysis. Mean squared displacement (MSD), angle correlation distribution, and step size distribution analysis allowed identifying five distinct granule transport subpopulations, from nearly immobile and subdiffusive to run-pause and superdiffusive. The subdiffusive subpopulation recapitulates the subordinated random walk we reported earlier (Tabei, 2013; ref 18). We show that the transport characteristics of the five subpopulations have a strong dependence on the age of insulin granules. The five subpopulations also reflect the effect of local microtubule and actin networks on transport in different cellular regions. Our results provide robust metrics to clarify the heterogeneity of granule transport and demonstrate the roles of microtubule versus actin networks with granule age since initial packaging in the Golgi.

Long-chain alkyl groups enhance the water-repellent properties of short-chain perfluoroalkyl compounds: An experimental and computer simulation study

The polymers composed of long-chain stearyl acrylate (SA) and short-chain (perfluorohexyl) ethyl methacrylate (FA) were synthesized using the emulsion polymerization technique. Cotton fabric was then coated with these polymers to act as a water-repellent agent. Surface wetting properties of the coated cotton fabric were tested. In a peculiar manner, the water repellency of the coatings did not improve with the increase of the perfluorohexyl group. Therefore, the polymer's crystallization behaviors and melting temperature were assessed through differential scanning calorimetry (DSC) and computer simulation. A computer simulation was employed to analyze the density, surface energy, element distribution, chain arrangement, bond order parameter, and surface images of the polymer film. The results suggest that water repellency is not directly related to the film's surface energy but rather depends on the element proportion, bond angle distribution, and dihedral angle torsion energy. The key points will serve as invaluable indicators for the development of a highly efficient water-repellent coating with a low proportion of fluorine and provide a more sustainable solution for water-repellent applications.

Design and fabrication of a porous prism film for display backlight applications

This study demonstrates a fabrication method of a porous brightness enhancement film (pBEF) that offers brightness enhancement, light diffusion, color shift reduction, and improved thermal stability. During the ultraviolet imprinting and solvent evaporation processes, the nano/submicron-sized air pores are generated within the polymer prism structure, and micropatterns spontaneously form on the prism surface. The inner pores ranging from 30 to 450 nm can effectively scatter light to mitigate color shift, which is caused by multiple internal reflections within the prism structure. The micropatterns have multiple rings formed one around another with 5–15-µm diameter on the prism surface improve visual quality. Moreover, the obtained functions are achieved in a single film solution, obviating the need for using multiple materials, and the fabrication process is relatively simple and fast as it is conducted under ambient conditions. When the pBEF is integrated into a liquid-crystal display backlight, it provides the brightness enhancement performance and comparable viewing angle distribution of a regular BEF combined with an additional diffuser (two films) and increases brightness by ∼8% compared to a bead prism (particle-based BEF). Additionally, it reduces the redshift (Δxy) from 0.1605 to 0.1415. Furthermore, the pBEF exhibits a lower coefficient of thermal expansion than the regular BEF.