Effect of a realistic three-body force on the spectra of medium-mass hypernuclei

We adopt the Hartree-Fock (HF) method in the proton-neutron-$\Lambda$ (p-n-$\Lambda$) formalism and the nucleon-$\Lambda$ Tamm-Dancoff Approximation (N$\Lambda$ TDA) to study the energy spectra of medium-mass hypernuclei. The formalism is developed for a potential derived from effective field theories which includes explicitly the 3-body $NNN$ forces plus the $YN$ LO potential. The energy spectra of selected medium-mass hypernuclei are presented and their properties discussed. The present calculation is the first step of a project devoted to {\it ab initio} studies of hypernuclei in medium and heavy mass regions. This may provide a guide for a better understanding of the $YN$ interactions at momentum scales not accessible in few-body hypernuclei.Comment: 7 pages, 9 figures, accepted in Physica Script

Descriptive analysis of reports on autonomous vehicle collisions in California: January 2021–June 2022

Pokorny, P., & Høye, A. (2022). Descriptive analysis of reports on autonomous vehicle collisions in California: January 2021–June 2022. Traffic Safety Research, 2, 000011.The characteristics of autonomous vehicles’ collisions from 2021 and the first half of 2022 in California confirm trends reported in previous years. Driving in autonomous mode was associated with fewer instances in which the AV was deemed to be at fault in a collision. Most collisions in autonomous mode were rear-end collisions at intersections. Single vehicle collisions occurred mostly in manual mode. Collisions with vulnerable road users occurred mostly while the autonomous vehicle was in manual mode, often right after disengagement from autonomous mode. In collisions with other vehicles that occurred after disengagement, the other vehicles were frequently deemed to be at fault. Compared to 2021, the collision reports from the first half of 2022 indicate higher shares of collisions in autonomous mode, rear-end collisions, and collisions with vulnerable road users.publishedVersio

Finite Element Analysis of Building Collapse during Demolition

A computational strategy that employs a multi-level approach to model the physical phenomena that occur during a structural collapse is used to simulate demolition of a multi-story precast concrete building. The building is modeled by means of beam elements, whose rigidity relations have been derived from a fracture mechanics-based model of cracked RC panels and joints. The motion and deformation of the collapsing building are solved as a transient dynamic problem in the finite displacements/ rotations range. The presented approach appears as an efficient way to verify whether a proposed demolition method leads to the desired mechanism of building collapse. By simulating various blasting scenarios, the most suitable demolition procedure is identified

Dynamics of Dust Particles Released from Oort Cloud Comets and Their Contribution to Radar Meteors

The Oort Cloud Comets (OCCs), exemplified by the Great Comet of 1997 (Hale-Bopp), are occasional visitors from the heatless periphery of the solar system. Previous works hypothesized that a great majority of OCCs must physically disrupt after one or two passages through the inner solar system, where strong thermal gradients can cause phase transitions or volatile pressure buildup. Here we study the fate of small debris particles produced by OCC disruptions to determine whether the imprints of a hypothetical population of OCC meteoroids can be found in the existing meteor radar data. We find that OCC particles with diameters D<10 um are blown out from the solar system by radiation pressure, while those with D>1 um have a very low Earth-impact probability. The intermediate particle sizes, D=100 um, represent a sweet spot. About 1% of these particles orbitally evolve by Poynting-Robertson drag to reach orbits with semimajor axis a=1 AU. They are expected to produce meteors with radiants near the apex of the Earth's orbital motion. We find that the model distributions of their impact speeds and orbits provide a good match to radar observations of apex meteors, except for the eccentricity distribution, which is more skewed toward e=1 in our model. Finally, we propose an explanation for the long-standing problem in meteor science related to the relative strength of apex and helion/antihelion sources. As we show in detail, the observed trend, with the apex meteors being more prominent in observations of highly sensitive radars, can be related to orbital dynamics of particles released on the long-period orbits

Measuring exposure for cyclists and micro-mobility users

Data about bicycle usage is an important input parameter for several purposes. They are used to describe changes towards more sustainable transport, and partly to say something about changes towards more active transport as opposed to passive modes oftransport. Importantly such data are used as the denominator when calculating crash risk: for cyclists. In Norway, as in most countries, these data are captured in several ways today. This is partly done by using data from the national travel behavior survey, partly using figures from stationazy or mobile bicycle counters, and partly using other methods such as manual counts, etc. The technological development has provided several new opportunities to register such travel, in the form of more advanced stationary counters, advanced algorithms that interprets signal data, video recording solutions and app-based measurement systems. At the sam.e time, we see that development in the transport sector also creates new challenges. In just a few years, electric scooters have radically changed the traffic picture in cities and towns in Norway. There is therefore a need for more knowledge about different forms of ways to measure bicycle and micro-mobility use, their strengths and weaknesses, and what kind of strategies the authorities should have to be equipped to meet future changes in the transport field, as exemplified by the recent intlux of e-scooters. The current paper aims to respond to these challenges by answering the following research questions: • What are the relative strengths and weaknesses of different data sources for measuring cycling and micromobility use? • How weil do the different sources function to capture micromobility and to differentiate between traditional cycling and micromobility? • How can the different data sources be used as input for calculating crash risk for various forms of soft mobility (i.e. cycling and micromobility)

Dry Separation of Brown Coal Fly Ash, Determination of Properties of Separated Parts, and Their Application in High Volume Cementitious Pastes

The dry separation of brown coal fly ash of density 2.21 g/cm3, specific surface area 5112 cm2/g, having d50 and d97 of 60 and 231 µm was carried out in this research using ultrafine air classifier. Classifiers wheel speed was increased from 2000 to 10000 rpm to obtain fine and coarse products. Median diameter of 5.62 µm was obtained for fine products at a speed of 10000 rpm with nearly 90% decrease in median particle size as compared raw fly ash. Particle morphology was observed on optical, electron microscopes which showed that at 10000 rpm classifiers wheel speed, average fine particles morphology changed from angular and rounded slaggy particles to spherical particles. Cement – 60% fine products samples showed an increase of 26% of compressive strength at 90 days as compared to raw fly ash and linear relationship was developed between median diameter of fines and compressive strength

Precision measurements of radar transverse scattering speeds from meteor phase characteristics

We describe an improved technique for using the backscattered phase from meteor radar echo measurements just prior to the specular point ($t_{0}$) to calculate meteor speeds and their uncertainty. Our method, which builds on earlier work of Cervera et al (1997), scans possible speeds in the Fresnel distance - time domain with a dynamic, sliding window and derives a best-speed estimate from the resultant speed distribution. We test the performance of our method, called pre-$t_{0}$ speeds by sliding-slopes technique (PSSST), on transverse scattered meteor echoes observed by the Middle Atmosphere Alomar Radar System (MAARSY) and the Canadian Meteor Orbit Radar (CMOR), and compare the results to time-of-flight and Fresnel transform speed estimates. Our novel technique is shown to produce good results when compared to both model and speed measurements using other techniques. We show that our speed precision is $\pm$5$\%$ at speeds less than 40 km/s and we find that more than 90$\%$ of all CMOR multi-station echoes have PSSST solutions. For CMOR data, PSSST is robust against the selection of critical phase value and poor phase unwrapping. Pick errors of up to $\pm$6 pulses for meteor speeds less than about 50 km/s produce errors of less than $\pm$5$\%$ of the meteoroid speed. In addition, the width of the PSSST speed Kernel density estimate (KDE) is used as a natural measure of uncertainty that captures both noise and $t_0$ pick uncertainties.Comment: Accepted for publication to Radio Science on 2020-06-2