Individual Collisions Research Articles

A closer look at individual collisions of dust aggregates: material mixing and exchange on microscopic scales

ABSTRACT Collisions between aggregates with different histories and compositions are expected to be commonplace in dynamically active protoplanetary discs. None the less, relatively little is known about how collisions themselves may contribute to the resulting mixing of material. Here, we use state-of-the-art granular dynamics simulations to investigate mixing between target/projectile material in a variety of individual aggregate-aggregate collisions, and use the results to discuss the efficiency of collisional mixing in protoplanetary environments. We consider sticking collisions (up to 10–20 m s–1 for our set-up) and disruptive collisions (40 m s–1) of ballistic particle–cluster aggregation (BPCA) and ballistic cluster–cluster aggregation (BCCA) clusters, and quantify mixing in the resulting fragments on both individual fragment and sub-aggregate levels. We find that the mass fraction of material that can be considered to be ‘well-mixed’ (i.e. locally made up of a mix of target and projectile material) to be limited, typically between 3 and 6 per cent for compact BPCA precursors, and increasing to 20–30 per cent for more porous BCCA clusters. The larger fragments produced in disruptive collisions are equally heterogeneous, suggesting aggregate–aggregate collisions are a relatively inefficient way of mixing material with different origins on small scales.

Design and optimisation of rotary vibrating screening process in silicon photovoltaic panel recycling: A particle-scale model study

The efficient separation of crushed solar panel particles is a critical step in photovoltaics (PV) recycling. In this paper, a DEM-based computer model is used to investigate the separation of crushed solar panel particles in a variety of shapes (including rod-like glass particles and chip-like solar cell particles and small broken residue) at the particle scale in a lab-scale rotary vibrating screen. The screening process of individual particles, including looseness, stratification, collision and penetration, can be well captured by the DEM simulations. Then the effects of several key vibration parameters on screening efficiency are studied, including circular displacements and oscillatory amplitude and frequency, and their underlying mechanism is explored at the particle scale. The simulation results show that with the increase of circular displacements from 1 to 3 mm, the screening efficiency increases from 89.5% to 91.8%. With the rise of oscillatory amplitude from 0.1° to 0.6°, the screening efficiency decreases significantly from 92.0% to 87.3%. With the increase of oscillatory frequency from 10 Hz to 25 Hz, the screening efficiency decreases slightly from 92.1% to 91.2%. The optimal screening condition is identified, i.e., >3 mm circular displacement, <0.1° oscillatory amplitude, and < 10 Hz oscillatory frequency, significantly enhancing screening efficiency. This study is helpful for rotary vibrating screen device scale-up and process optimisation in the PV recycling industry.

Dylematy interpretacyjne stosowania sygnałów drogowych ze szczególnym uwzględnieniem sygnalizatora S-2 w „bezpiecznym” zarządzaniu ruchem drogowym. Część II/III

Interpretative dilemmas of the use of road signals with particular emphasis on the S-2 signal in “safe” traffic management. Part II/III In this part of the article, the authors focus their attention on the formal and legal issues related to the design of traffic signals on roads and intersections in Poland. A synthesis of the characteristics of the necessary content of the design of traffic organization with traffic lights, approved by the competent authority managing traffic on the road is given. A historical outline of the guidelines for the implementation of the signal allowing turning in the direction indicated by the green arrow is provided. The most important aspect of this part of the article is a commentary on the current legal provisions regarding the permissibility and inadmissibility of allowing simultaneous movement of individual collision streams – with particular emphasis on vehicle streams controlled by the S-2 traffic signal. The commentary includes separate references to the legal status from the original version of the requirements made in 2004 and from the 2008 and 2015 amendments to the regulations. In the authors’ opinion, these descriptions provide key points explaining the complexity of the problem for designers, reviewers, and approvers of signals controlled traffic organization. An effort has been made to explain comprehensively all possible situations since there is currently a non-uniform application of signal phases at intersections and different opinions on the questions of interpreting the correct application of the "green arrow" signal. The results of the study in this regard are included in part III of the article.

A MODEL FOR SURFACE NANORELIEF FORMATION UNDER GAS CLUSTER ION IRRADIATION

A model for the evolution of surface nanorelief under irradiation with gas cluster ions is proposed. The model is based on consideration of individual collisions of clusters with a surface. The amount of substance sputtered from the collision area and the e ciency of its redeposition onto other surface elements are determined. The performance of the model is shown when compared with experimental data. The stages of smoothing of a harmonic relief are studied. A new measure of the e ectiveness of surface smoothing is proposed.

Coordinated multi-stage and multi-objective optimization approach for ship collision avoidance decision-making

Appropriate decision-making is essential to prevent ship collisions and further ensure navigational safety at sea. Current research on collision avoidance decision-making (CADM) primarily aims to find limited feasible solutions based on a designated safe distance under the strong assumption that ships take no or little maneuvering actions. To overcome such limitations, a multi-stage and multi-objective CADM optimization approach is proposed to satisfy the requirements of safety and economy, while considering the ship path uncertainties and risk preferences of ship officers. First, a comprehensive collision risk estimation method is formulated by quantifying degree of domain violation and probability of domain violation (PDV) in dynamic and uncertain situations. Then, the CADM for each individual ship is treated as a multi-objective optimization problem, and a three-stage optimization approach outlines the process to find optimal collision avoidance path. Preliminary non-dominated solutions are obtained and filtered to enhance the robustness by an accepted threshold of the PDV. Optimal solutions are selected for ship officers with different risk preferences. Finally, the coordinated collision avoidance path for multi-ship encounter is determined based on the exchange of individual collision avoidance path through several rounds of coordination. The effectiveness of CADM method is validated through extensive case studies. The results show that it can provide feasible solutions for multi-objectives and adaptively determine the most appropriate scheme for ship officers with different risk preferences to make coordinated decisions.

Air pollution and motor vehicle collisions in New York city

Road traffic accidents are a pervasive feature of everyday life, killing 36,500 people, injuring 4.5 million and, overall, generating costs to the American society of $340 billion in 2019. Understanding the underlying factors can improve the design of prevention strategies. We use all road traffic collisions in New York City between 2013 and 2021 (N = 1,269,600) and match each individual collision to the nearest weather and air pollution station. Our study uses highly disaggregated data using an hourly frequency of collisions at a fine spatial level incorporating various air pollutants and weather factors. We employ an instrumental variable approach using temperature inversions to provide exogenous variation in air pollution addressing endogeneity and measurement error concerns. We find that higher concentrations of carbon monoxide (CO) and sulfur dioxide (SO2) increase the number of collisions but leave the severity (persons injured or killed) unaffected. Part of this can be explained by the effect of air pollutants on aggressive behavior: CO (p < .05) and SO2 (p < .01) increase the number of collisions caused by aggressive driving. Interestingly, this channel is only present in male drivers. Our results provide additional evidence that air pollution not only adversely affects health, but also has “non-health” related effects which are costly for the society.

Business Case for Transit Bus Automated Collision Avoidance Systems

Although the National Transportation Safety Board has strongly recommended the application of collision avoidance warning systems and automated emergency braking (CAWS/AEB), the transit industry has lagged behind autos and trucks. CAWS/AEB for buses is more complex than for cars and trucks and represents a niche market. If bus manufacturers and suppliers are to invest in developing this technology, they will need to be convinced there is a market for it. Transit agencies also will need to be convinced that the technology works and is affordable. For both vendors and purchasers, a business case could be made that some or all of the expense of procuring and deploying the technology can be recovered through savings from reduced insurance premiums and claims payouts by preventing or mitigating collisions. This paper describes two methods for estimating the business case for equipping transit buses with CAWS/AEB. First, industrywide data on the numbers of collisions and casualty and liability expenses incurred by transit agencies were examined, and statistical relationships were modeled to determine whether reducing the numbers of collisions would reduce casualty and liability expenses. Second, individual collision claims records for specific transit agencies were examined to determine whether the collisions could have been prevented by CAWS/AEB, and the potential savings.

Experimental investigation of particle aggregation in a humid and turbulent environment

Aggregation of wetted particles in a turbulent flow is experimentally investigated. The particles settle through nearly isotropic turbulence inside a humid air chamber. The particles are pre-chilled so that wetting occurred even at sub-saturated humidity levels. Aggregates that fall out of the turbulent flow are physically sampled and their size distributions quantified to infer bulk sticking efficiencies at various humidity levels. Optical particle tracking techniques are used to detect individual time-resolved collision events, forming an independent measure of the sticking efficiency parameterized by a collision Stokes number. The two methods are contrasted and the limitations of each are discussed. The data are used to develop a new version of the early Costa sticking model, which is utilized by various volcanic ash transport codes. The key outcome of this work is a generalized Costa sticking model which incorporates the effect of the water film thickness coating the particles.

A Glycosidic‐Bond‐Based Mass‐Spectrometry‐Cleavable Cross‐linker Enables In Vivo Cross‐linking for Protein Complex Analysis

AbstractChemical cross‐linking mass spectrometry (CXMS) has emerged as a powerful technology to analyze protein complexes. However, the progress of in vivo CXMS studies has been limited by cross‐linking biocompatibility and data analysis. Herein, a glycosidic bond‐based MS‐cleavable cross‐linker of trehalose disuccinimidyl ester (TDS) was designed and synthesized, which was fragmented in MS under CID/HCD to simplify the cross‐linked peptides into conventional single peptides via selective cleavage between glycosidic and peptide bonds under individual MS collision energy. Consequently, the cross‐linking identification accuracy and throughput were significantly enhanced, and the popular MS mode of stepped HCD was allowed. In addition, TDS showed proper cell‐penetrating properties while being highly water‐soluble, making it non‐DMSO dependent during solubilization. Collectively, TDS provides a promising toolkit for CXMS characterization of living systems with high biocompatibility and accuracy.

A Glycosidic-Bond-Based Mass-Spectrometry-Cleavable Cross-linker Enables In Vivo Cross-linking for Protein Complex Analysis.

Chemical cross-linking mass spectrometry (CXMS) has emerged as a powerful technology to analyze protein complexes. However, the progress of in vivo CXMS studies has been limited by cross-linking biocompatibility and data analysis. Herein, a glycosidic bond-based MS-cleavable cross-linker of trehalose disuccinimidyl ester (TDS) was designed and synthesized, which was fragmented in MS under CID/HCD to simplify the cross-linked peptides into conventional single peptides via selective cleavage between glycosidic and peptide bonds under individual MS collision energy. Consequently, the cross-linking identification accuracy and throughput were significantly enhanced, and the popular MS mode of stepped HCD was allowed. In addition, TDS showed proper cell-penetrating properties while being highly water-soluble, making it non-DMSO dependent during solubilization. Collectively, TDS provides a promising toolkit for CXMS characterization of living systems with high biocompatibility and accuracy.

A deterministic collision avoidance decision-making system for multi-MASS encounter situation

Efficient identification of multi-ship encounter situation concerning action priority analysis is of vital significance for making effective and practical collision avoidance manoeuvres. However, action priority analysis is strongly involved in conflict urgency quantification, collision candidates relevance analysis as well as the contribution analysis within the encountering ships. In this paper, considering Maritime Autonomous Surface Ship, a deterministic collision avoidance decision-making system is established to estimate multi-MASS encounter situation. To this end, the approach index and asymmetrical Gaussian fitting method are deployed to assess collision risk, while the encountering ships are analytically distinguished into different clusters based on the Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm. By virtue of the improved Sharpley value method, the collision avoidance action priority is elaboratively sorted for different clusters. Accordingly, each individual collision avoidance manoeuvres are collaboratively generated by the modified velocity obstacle algorithm with certain time delay. Eventually, the proposed decision-making system is synthesized by functional modules including data-processing, conflict assessment detection, relevance analysis, action priority analysis, path planning and performance monitor. Simulation results demonstrate that this proposed decision-making system can perform significant superiority in various maritime environment in line with the practice of coordination and navigation.

Integral measurements of plural and multiple scattering of electrons with energies between 10 and 100 keV for [formula omitted]: I. Thin and intermediate-thickness targets

Angle-integrated plural- and multiple-scattering distributions have been measured for electrons impinging with kinetic energies from 10 to 100 keV on targets with atomic numbers between those of C and Bi and mass thicknesses ranging from ≈5 to 300 μg/cm2. The thinnest targets, ≈5 to 20 μg/cm2, are not self-supporting and have been deposited on C backings with areal densities around 10 μg/cm2. The intermediate-thickness ones are made of a single element and have mass thicknesses of ≈100 to 300 μg/cm2. The electrons scattered at frontal angles are collected with a Faraday cup covering the polar angles below 12.0°. In addition, to supplement this information, an aluminium ring spanning a polar angle interval of 9.1° has been installed around the entrance of the Faraday cup and the charge deposited on it has also been recorded. The electrical current in the scattering chamber is measured as well so as to provide an accurate normalisation. Corrections for the fraction of impinging electrons backscattered by both the Faraday cup and the ring are applied to the data. The measurements are compared with the predictions of a Monte Carlo code that simulates each individual elastic collision. For targets made of a single element, the analytical Goudsmit–Saunderson and Lewis theories are tested as well. In all cases, the single-scattering angular differential cross sections, obtained by partial-wave solution of the Dirac equation in a self-consistent central potential, are taken from the ICRU Report 77. Good agreement is found within the uncertainties of the data. An analytical formula for the angular integration of the Goudsmit–Saunderson distribution is presented in an Appendix.

Coagulation rate coefficients for fractal-like agglomerates in the diffusive and ballistic limits

Predicting agglomeration dynamics in aerosol or colloidal systems requires accurate models for the agglomerate collision rate. In the present work, numerical simulations cover the ballistic and the diffusive collision regimes as limiting cases and are used to derive coagulation rate coefficients for a large number of agglomerate sizes and morphologies. The simulations account for both the translational and rotational motion of agglomerates and allow for the monitoring of individual collision events. The results suggest that the power law suffices to characterize the clusters’ morphologies and that representative collision radii of agglomerates are mainly controlled by two parameters: (i) the radius of gyration, Rg, and (ii) the morphology characterized by the fractal dimension Df. Collision radii for the diffusive regime are up to 10% above the corresponding ballistic results and cluster rotation also increases the effective collision radius. The latter effect can lead to differences of up to 16% in the diffusive regime. In contrast, interpenetration effects, i.e. a small cluster passing through a larger cluster without collision, are less pronounced in the diffusive limit. The results provide strong correlations between collision radii and key parameters for both regimes such that improved analytical expressions for the coagulation rate coefficients can be suggested. Compared to existing models for the ballistic and diffusive regimes, the proposed correlations offer reduced complexity across an extended range of the relevant parameter space.

Modeling approaches for atmospheric ion–dipole collisions: all-atom trajectory simulations and central field methods

Abstract. Ion–dipole collisions can facilitate the formation of atmospheric aerosol particles and play an important role in their detection in chemical ionization mass spectrometers. Conventionally, analytical models, or simple parametrizations, have been used to calculate the rate coefficients of ion–dipole collisions in the gas phase. Such models, however, neglect the atomistic structure and charge distribution of the collision partners. To determine the accuracy and applicability of these approaches under atmospheric conditions, we calculated collision cross sections and rate coefficients from all-atom molecular dynamics collision trajectories, sampling the relevant range of impact parameters and relative velocities, and from a central field model using an effective attractive interaction fitted to the long-range potential of mean force between the collision partners. We considered collisions between various atmospherically relevant molecular ions and dipoles and charged and neutral dipolar clusters. Based on the good agreement between collision cross sections and rate coefficients obtained from molecular dynamics trajectories and a generalized central field model, we conclude that the effective interactions between the collision partners are isotropic to a high degree, and the model is able to capture the relevant physicochemical properties of the systems. In addition, when the potential of mean force is recalculated at the respective temperatures, the central field model exhibits the correct temperature dependence of the collision process. The classical parametrization by Su and Chesnavich (1982), which combines a central field model with simplified trajectory simulations, is able to predict the collision rate coefficients and their temperature dependence quite well for molecular systems, but the agreement worsens for systems containing clusters. Based on our results, we propose the combination of potential of mean force calculation and a central field model as a viable and elegant alternative to the brute force sampling of individual collision trajectories over a large range of impact parameters and relative velocities.

Exploring Influential Factors Affecting the Severity of Urban Expressway Collisions: A Study Based on Collision Data.

When traffic collisions occur on urban expressways, the consequences, including injuries, the loss of lives, and damage to properties, are more serious. However, the existing research on the severity of expressway traffic collisions has not been deeply explored. The purpose of this research was to investigate how various factors affect the severity of urban expressway collisions. The severity of urban expressway collisions was set as the dependent variable, which could be divided into three categories: slight collisions, severe collisions, and fatal collisions. Ten variables, including individual characteristics, collision characteristics, and road environment conditions, were selected as independent factors. Based on 975 valid urban expressway collisions, an ordered logistic regression model was established to evaluate the impacts of influence factors on the severity of these crashes. The results show that gender, collision modality, road pavement conditions, road surface conditions, and visibility are significant factors that affect the severity of urban expressway collisions. Females were more likely to be involved in more severe urban expressway collisions than males. For collisions involving pedestrians and non-motorized vehicles, the risk of more severe injury was 7.508 times higher than that associated with vehicle–vehicle collisions. The probability of more severe collisions on urban expressways with poor pavement conditions and wet surface conditions is greater than that on urban expressways with good pavement conditions and dry surface conditions. In addition, as visibility increases, the probability of more severe collisions on urban expressways gradually decreases. These results provide more effective strategies to reduce casualties as a result of urban expressway collisions.

(Digital Presentation) Stochastic Impact Electrochemistry in a Lateral-Flow Sensor Architecture

During the recent SARS-CoV-2 pandemic, lateral flow assays (LFAs) have written an indescribable story of success, as they provide means for decentralized, low-cost, and easy-to-use testing. However, LFAs in their most common form support only qualitative results and their sensitivity and limit of detection is significantly limited by the colorimetric readout method. In contrast, single-impact electrochemistry offers the possibility to quantify species beyond picomolar concentrations by recording individual species collisions with a biased microelectrode. Within this work, we investigate the integration of stochastic sensing into a LFA-architecture by combining a wax-patterned microchannel with a microelectrode array in order to detect silver nanoparticles by their oxidative dissolution. Here, we demonstrate the possibility to resolve individual nanoparticle collisions in a paper-based microchannel using a simplified reference-on-chip setup. Furthermore, we simulated a lateral-flow sensor, by flushing previously dried silver nanoparticles towards the electrode array, where the particles are subsequently detected. This proof-of-principle illustrates that single-impact electrochemistry might be a promising technique to extend the capability of LFAs. Especially, the integration of functionalized nanoparticle labels could enable the rapid and on-site detection of very dilute species with exceptional sensitivity.

Granular cooling of ellipsoidal particles in microgravity

A three-dimensional granular gas of ellipsoids is established by exposing the system to the microgravity environment of the International Space Station. We use two methods to measure the dynamics of the constituent particles and report the long-time development of the granular temperature until no further particle movement is detectable. The resulting cooling behavior can be well described by Haff’s cooling law with time scale τ. Different analysis methods show evidence of particle clustering towards the end of the experiment. By using the kinetic theory for ellipsoids we compare the translational energy dissipation of individual collision events with the overall cooling time scale τ. The difference from this comparison indicates how energy is distributed in different degrees of freedom including both translation and rotation during the cooling.

Single-Impact Electrochemistry in Paper-Based Microfluidics.

Microfluidic paper-based analytical devices (μPADs) have experienced an unprecedented story of success. In particular, as of today, most people have likely come into contact with one of their two most famous examples─the pregnancy or the SARS-CoV-2 antigen test. However, their sensing performance is constrained by the optical readout of nanoparticle agglomeration, which typically allows only qualitative measurements. In contrast, single-impact electrochemistry offers the possibility to quantify species concentrations beyond the pM range by resolving collisions of individual species on a microelectrode. Within this work, we investigate the integration of stochastic sensing into a μPAD design by combining a wax-patterned microchannel with a microelectrode array to detect silver nanoparticles (AgNPs) by their oxidative dissolution. In doing so, we demonstrate the possibility to resolve individual nanoparticle collisions in a reference-on-chip configuration. To simulate a lateral flow architecture, we flush previously dried AgNPs along a microchannel toward the electrode array, where we are able to record nanoparticle impacts. Consequently, single-impact electrochemistry poses a promising candidate to extend the limits of lateral flow-based sensors beyond current applications toward a fast and reliable detection of very dilute species on site.

Enriching Roadside Safety Assessments Using LiDAR Technology: Disaggregate Collision-Level Data Fusion and Analysis

Fatalities and serious injuries still represent a significant portion of run-off-the-road (ROR) collisions on highways in North America. In order to address this issue and design safer and more forgiving roadside areas, more empirical evidence is required to understand the association between roadside elements and safety. The inability to gather that evidence has been attributed in many cases to limitations in data collection and data fusion capabilities. To help overcome such issues, this paper proposes using LiDAR datasets to extract the information required to analyze factors contributing to the severity of ROR collisions on a localized collision level. Specifically, the paper proposes a new method for extracting pole-like objects and tree canopies. Information about other roadside assets, including signposts, alignment attributes, and side slopes is also extracted from the LiDAR scans in a fully automated manner. The extracted information is then attached to individual collisions to perform a localized assessment. Logistic regression is then used to explore links between the extracted features and the severity of fixed-object collisions. The analysis is conducted on 80 km of roads from 10 different highways in Alberta, Canada. The results show that roadside attributes vary significantly for the different collisions along the 80 km analyzed, indicating the importance of utilizing LiDAR to extract such features on a disaggregate collision level. The regression results show that the steepness of side slopes and the offset of roadside objects had the most significant impacts on the severity of fixed-object collisions.

Enhanced Electrochemistry of Single Plasmonic Nanoparticles.

The structure-function relationship of plasmon-enhanced electrochemistry (PEEC) is of great importance for the design of efficient PEEC catalysts, but is rarely investigated at single nanoparticle level for the lack of an efficient nanoscale methodology. Herein, we report the utilization of nanoparticle impact electrochemistry to allow single nanoparticle PEEC, where the effect of incident light on the plasmonic Ag/Au nanoparticles for accelerating cobalt metal-organic framework nanosheets (Co-MOFNs) catalyzed hydrogen evolution reaction (HER) is systematically explored. It is found that the plasmon-excited hot carrier injection can lower the reaction activation energy, resulting in a much promoted reaction probability and the integral charge generated from individual collisions. Besides, a plasmonic nanoparticle filtering method is established to effectively distinguish different plasmonic nanoparticles. This work provides a unique view in understanding the intrinsic physicochemical properties for PEEC at the nano-confined domains.