Occurrence Of Collisions Research Articles

Subduction disruption, slab tears: ca. 1 Ma true collision of an ~30‐km‐thick oceanic plateau segment recorded by Yakutat slab nascent tear magmatism

AbstractDistinguishing the initiation of actual collision from flat‐slab subduction of oceanic buoyant highs along convergent margins is elusive because both can lead to inboard deformation and disrupt magmatic arcs. Volcanoes with nascent tear magmatic signatures provide a means to document both the occurrence and timing of actual oceanic buoyant high collision. There is a ~40‐year debate on when the true collision of the Yakutat plateau began in Alaska. Three newly identified ca. 1 Ma volcanoes with a north‐to‐south trench perpendicular orientation, nascent tear geochemical signatures, overlaying an imaged Yakutat slab tear, provide constraints on the timing of Yakutat collision and slab tearing. The ca. 1 Ma slab tear is coincident with Yakutat slab segmentation, northern continental Aleutian Arc rejuvenation, cessation of Wrangell Arc magmatism, increased collisional zone exhumation and eastern Yakutat trench abandonment. The documentation of nascent slab tear volcanoes may help resolve similar debates in other convergent margin settings.

Effect of Situation Kinematics on Drivers’ Rear-End Collision Avoidance Behaviour—A Combined Effect of Visual Looming, Speed, and Distance Analysis

Considering the large proportion of rear-end collisions occurring in our daily life and the severity it may lead to, the objective of this study was to investigate the effect of situation kinematics on drivers’ rear-end collision avoidance behaviour after brake onset. A wide range of lead vehicle deceleration scenarios were designed based on driving simulator experiments to collect drivers’ deceleration behaviour data. Different from measures (e.g., speed, the lead vehicle’s deceleration et al.) often adopted in previous studies, a visual looming-based measure at different time points was calculated combined with analysis of speed and distance to quantify situation kinematics in this study. The Spearman’s nonparametric rank correlation test was firstly conducted to examine the correlation between visual looming-based metrics and related deceleration behaviour. The mixed model was performed on drivers’ brake jerk and maximum deceleration rate, while the logistic model was then performed to predict the probability of the occurrence of rear-end collisions. Spearman’s nonparametric test showed that both deceleration ramp-up and drivers’ maximum deceleration rate increase significantly as the looming traces increase faster. Results of the logistic model indicated that the probability of occurrence of a potential collision might be higher if the situation at the brake onset is quite urgent and braking is moderate. It was demonstrated that both drivers’ deceleration ramp-up and maximum deceleration rate could be highly kinematic-dependent, and visual looming, driving speed, and distance can be useful information for drivers to take relative deceleration actions.

Ocean highways in the Western Mediterranean: Which are the areas with increased exposure to maritime traffic for loggerhead turtles?

Many marine megafauna taxa are tied to the sea surface for breathing which makes them vulnerable to vessel collisions. Sea turtles have developed efficient mechanisms to reduce surface time for breathing to a few seconds, but they can extend their surface periods to rest or to rewarm after diving into deep and colder waters. However, knowledge of collision occurrences is limited to data of turtles stranded along the coastline worldwide, whereas events occurring offshore go likely underestimated due to the sinking of carcasses. Here we performed a spatially explicit assessment to identify, for the first time, oceanic areas of higher exposure for sea turtles from maritime traffic in the Tyrrhenian Sea, Western Mediterranean. Satellite-tracking data were used to estimate utilization distributions of loggerhead turtles using Brownian bridge kernel density estimation. Maritime traffic density maps based on Automatic Identification System (AIS) data were extracted from open-access data layers, provided by the European Maritime Safety Agency, summarized, and used for the exposure analysis. Turtle occurrences were also investigated in response to vessel densities and seasonal patterns by fitting a generalized additive model to the data. Our results demonstrated that loggerhead turtles are potentially exposed to maritime traffic across the entire basin, especially in the easternmost part. The exposure varies among spring/summer and autumn/winter months. Highest turtle occurrences were found in regions primarily subjected to cargo, tanker, and passenger transportation. This study represents the first-ever effort to characterize the exposure of oceanic loggerhead turtles to maritime traffic and highlights oceanic areas of higher exposure where research and conservation efforts should be directed to understand the effective impact of this stressor on the species.

Quantifying Shear-induced Margination and Adhesion of Platelets in Microvascular Blood Flow

Platelet margination and adhesion are two critical and closely related steps in thrombus formation. Using dissipative particle dynamics (DPD) method that seamlessly models blood cells, blood plasma, and vessel walls with functionalized surfaces, we quantify the shear-induced margination and adhesion of platelets in microvascular blood flow. The results show that the occurrence of shear-induced RBC-platelet collisions has a remarkable influence on the degree of platelet margination. We characterize the lateral motion of individual platelets by a mean square displacement analysis of platelet trajectories, and find that the wall-induced lift force and the shear-induced displacement in wall-bounded flow cause the variation in near-wall platelet distribution. We then investigate the platelet adhesive dynamics under different flow conditions, by conducting DPD simulations of blood flow in a microtube with fibrinogen-coated wall surfaces. We find that the platelet adhesion is enhanced with the increase of fibrinogen concentration level but decreased with the increase of shear rate. These results are consistent with available experimental results. In addition, we demonstrate that the adherent platelets have a negative impact on the margination dynamics of the circulating platelets, which is mainly due to the climbing effect induced by the adherent ones. Taken together, these findings provide useful insights into the platelet margination and adhesion dynamics, which may facilitate the understanding of the predominant processes governing the initial stage of thrombus formation.

User-Centric Perspective in Random Access Cell-Free Aided by Spatial Separability

In a cell-free massive multiple-input–multiple-output (CF-mMIMO) network, multiple access points (APs) actively cooperate to serve users’ equipment (UEs). We consider how the random access (RA) problem can be addressed by such a network under the occurrence of pilot collisions. To find a solution, we embrace the user-centric perspective, which basically dictates that only a preferred set of APs needs to serve a UE. Due to the success of the strongest-user collision resolution (SUCRe) protocol for cellular (Ce) mMIMO, we extend it by considering the new setting. Besides, we establish that the user-centric perspective naturally equips a CF network with robust fundamentals for resolving collisions. We refer to this foundation as spatial separability, which enables multiple colliding UEs to access the network simultaneously. We then propose two novel RA protocols for CF-mMIMO: 1) the baseline cell-free (BCF) that resolves collisions with the concept of spatial separability alone and 2) the cell-free sucre (CF-SUCRe) that combines SUCRe and the spatial separability principle to resolve collisions. We evaluate our proposed RA protocols against the Ce-SUCRe. Respectively, the BCF and CF-SUCRe can support <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$7\times $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$4\times $ </tex-math></inline-formula> more UEs’ access on average compared to the Ce-SUCRe with an average energy efficiency gain based on the total power consumed (TPC) by the network per access attempt of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$52\times $ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$340\times $ </tex-math></inline-formula> . Among our procedures, even with a higher overhead, the CF-SUCRe is superior to BCF regarding TPC per access attempt. This is because the combination of methods for collision resolution allows many APs to be disconnected from the RA process without sacrificing much the performance. Finally, our numerical results can be reproduced using the code package available on: <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">github.com/victorcroisfelt/cf-ra-spatial-separability</i> .

Transfer Learning-Based Vehicle Collision Prediction

Traffic accident is an important problem in modern society. Vehicle collision prediction is one of the key technical points that must be broken through in the future driving system. However, due to the complexity of traffic environment and the difference of emergency ability of drivers, it is very difficult to predict vehicle collision. Although experts and scholars have tried to monitor and predict accidents in real time according to environmental conditions, overly agile warning or inaccurate prediction may cause serious consequences. Therefore, in order to more accurately predict the occurrence of vehicle collision, this paper analyses and models the driving mode of the vehicle based on transfer learning and using the previous performance data of the vehicle, so as to predict the future collision situation and even the collision time of the vehicle. Finally, using a real-world Internet of Vehicles data set, this paper implements a large number of experiments to verify the effectiveness of the proposed model.

Malunion deformity of the forearm: Three-dimensional length variation of interosseous membrane and bone collision.

It remains unclear to what extent the interosseous membrane (IOM) is affected through the whole range of motion (ROM) in posttraumatic deformities of the forearm. The purpose of this study is to describe the ligament- and bone-related factors involved in rotational deficit of the forearm. Through three-dimensional (3D) kinematic simulations on one cadaveric forearm, angular deformities of 5°in fourdirections (flexion, extension, valgus, varus) were produced at twolocations of the radius and the ulna (proximal and distal third). The occurrence of bone collision in pronation and the linear length variation of sixparts of the IOM through the whole ROM were compared between the 32 types of forearm deformities. Similar patterns could be observed among fourgroups: 12 types of deformity presented increased bone collision in pronation, 8presented an improvement of bone collision with an increase of the mean linear lengthening of the IOM in neutral rotation, 6had an increased linear lengthening of the IOM in supination with nearly unchanged bone collision in pronation and 6types presented nearly unchanged bone collision in pronation with a shortening of the mean linear length of IOM in supination or neutral rotation. This kinematic analysis provides a better understanding of the ligament- and bone-related factors expected to cause rotational deficit in forearm deformity and may help to refine the surgical indications of patient-specific corrective osteotomy.

Simulation of Urban Crash Occurrence Based on Real-World Crash Data

The intelligent application of simulation is of central importance for the successful development and testing of automated driving functions. Realistic virtual environments are required to assess and optimize both the efficiency and safety of automated driving functions in real-world traffic situations. While existing traffic flow simulation frameworks excel at evaluating traffic efficiency, the implementation of human failure models and traffic safety aspects is a current field of research. In this publication, the occurrence of human failures is inferred from real-world crash statistics and introduced into traffic simulation. A realistic traffic simulation setup of the city of Ingolstadt, Germany, is used as a basis for this simulation of crash occurrence. Focusing on intersections as the most important urban crash hot spots, the relation between human failures and the occurrence of collisions is estimated for each conflict point in the simulation network. From crash statistics, the distributions of crash quantities and types across the intersections in the simulation network are calculated. An Iterative Proportional Fitting algorithm is used to project crash counts available at the intersection level onto the “conflict level,” determined by intersecting traffic streams within intersections. Human failures are generated and applied to traffic participants in the simulation using a Monte Carlo selection. The results demonstrate the functionality of the method for calibrating models for realistic crash occurrence in traffic simulation. This methodology provides a basis for simultaneous evaluation of both traffic efficiency and traffic safety impacts of future developments in urban traffic networks.

Stellar collisions in globular clusters: Constraints on the initial mass function of the first generation of stars

Globular clusters display an anticorrelation between the fraction of the first generation of stars (N(G1)/N(tot)) and the slope of the present-day mass function of the clusters (αpd), which is particularly significant for massive clusters. In the framework of the binary-mediated collision scenario for the formation of the second-generation stars in globular clusters, we test the effect of a varying stellar initial mass function (IMF) of the G1 stars on the (N(G1)/N(tot)) − αpd anticorrelation. We use a simple collision model that has only two input parameters, the shape of the IMF of G1 stars and the fraction of G1 stars that coalesce to form second-generation stars. We show that a variable efficiency of the collision process is necessary in order to explain the (N(G1)/N(tot)) − αpd anticorrelation; however, the scatter in the anticorrelation can only be explained by variations in the IMF, and in particular by variations in the slope in the mass interval ≈(0.1–0.5) M⊙. Our results indicate that in order to explain the scatter in the (N(G1)/N(tot)) − αpd relation, it is necessary to invoke variations in the slope in this mass range between ≈ − 0.9 and ≈ − 1.9. Interpreted in terms of a Kroupa-like broken power law, this translates into variations in the mean mass of between ≈0.2 and 0.55 M⊙. This level of variation is consistent with what is observed for young stellar clusters in the Milky Way and may reflect variations in the physical conditions of the globular cluster progenitor clouds at the time the G1 population formed or may indicate the occurrence of collisions between protostellar embryos before stars settle on the main sequence.

Recognition Model and Simulation of Busy Waters in Fishing Area Based on Density Clustering

&lt;p&gt;In this paper, the characteristics of the potential behavior of ships contained in AIS information are con-sidered, in order to ensure the safety of navigation in merchant ships’ fishing areas and reduce the occur-rence of collisions between commercial fishing boats. Based on the DBSCAN density clustering algorithm, the identification model of busy water in fishing areas is developed and applied to Minnan fishery in the Taiwan Strait. In addition, a real ship simulation is performed based on real traffic flow data. The results demonstrate that the proposed model can accurately identify the spatial distribution and scale of busy fishing area, adjust the algorithm parameters according to the merchant ship scale, and generate the target-ed recommended route decision for the fishing area. Finally, the STELLAR EXPRESS is compared with the original route. The obtained results show that the recommended route provides a high safety in the fishing area, while retaining the ship operating costs. The model results can be used as a reference for maritime security departments in order to divide the fishing area warning water, and the identification method provides a novel approach for the safety supervision of maritime department. &lt;/p&gt; &lt;p&gt;&amp;nbsp;&lt;/p&gt;

Identification of contributing factors and hotspots of pedestrian-vehicle collisions in urban areas: An alternative hybrid method for small cities

Objective Traffic safety numbers in developing countries show a serious global problem that requires studies and actions to promote safety for the most vulnerable users, such as pedestrians, as a way of contributing to sustainable urban mobility. Therefore, this research proposes a hybrid method to identify contributing factors and critical points according to the profile of crashes involving pedestrians being run over by motor vehicles in small cities. Methods The proposed method uses multivariate data analysis, specifically Exploratory Factor Analysis (EFA) and Cluster Analysis (CA), combined with geospatial tools. The study scenario corresponds to pedestrian-vehicle collisions that occurred in the urban area of Cachoeira do Sul, a small city in Rio Grande do Sul, Brazil, recorded in police reports between 2015 and 2018. Additionally, Geographic Information Tools (GIS) were used to collect characteristics of the road environment. Results According to EFA, a set of attributes configured as contributing factors are discussed according to the components of the traffic system: user, road, vehicle, and environment. Subsequently, a CA was applied with the road-environmental factors, and three pedestrian-vehicle collision profiles were extracted, with clustering according to road segments with homogeneous characteristics. Moreover, a Kernel Density Estimate (KDE) was used to obtain heat maps of the pedestrian collisions profiles. The results allowed interventions to be proposed according to the contributing factors of each profile. Conclusions The multivariate statistical analysis supported the discussion of the factors contributing to the occurrence of pedestrian-vehicle collisions in small cities in developing countries. The spatial visualization of the results showed urban corridors with a high risk for pedestrians and the identification of hotspots in the city. In addition, the study demonstrated that the hybrid method tested is an alternative for the government of cities with few resources to promote safety mobility.

Cooperative control for multiple train systems: Self-adjusting zones, collision avoidance and constraints

In practical multiple train systems, the desired relative positions of adjacent trains are usually not fixed values but some certain zones which are called “self-adjusting zones” in this paper. However, most of the existing related works were concerned about the case of fixed values and few works focused on the more practical case when the desired relative positions are some certain zones. The aim of this paper is to investigate cooperative control for multiple train systems under moving block system by taking into account self-adjusting zones, collision avoidance and constraints simultaneously, where each train needs not to coordinate with other trains in its desired self-adjusting zones and can be self-adjusted freely. A distributed cooperative control algorithm is proposed to enable all trains to track the desired velocity and operate steadily in their self-adjusting zones by only utilizing the local information of neighbor trains, where a switching mechanism is introduced to ensure the trains to avoid collision. The analysis is performed mainly based on the properties of stochastic matrices and multiple model transformations. It is shown that the braking process can be equivalent to a special coordination process, and the braking process, the coordination process and the self-adjusting process can be unified as an integrated whole to be analyzed by using the properties of stochastic matrices. By addressing the state interactions of the train equivalent system under different scenarios, it is proved that all relative positions of adjacent trains converge into desired self-adjusting zones without the occurrence of collision, while all trains finally move in a desired velocity. Numerical examples are included to illustrate the obtained results.

Pandora's Box: A spatiotemporal assessment of elephant-train casualties in Assam, India.

Railways are an indispensable component of sustainable transportation systems, but also exact a toll on wildlife. Wild Asian elephants are often killed by trains in Assam, India, where we assess temporal variations in the occurrences of elephant-train collisions (ETCs) and casualties during 1990–2018. This study also assesses spatially varying relationships between elephant-train collision (ETC) rates and elephant and train densities in the adjoining 10 km2 grid cells of 11 prioritized railroad segments using ordinary least squares (OLS) and geographically weighted regression (GWR) models. The temporal analysis indicated that ETCs spiked at certain hours and months. The adult and calf elephant casualties on the railroads were found to be two to fivefold high during the post monsoon season compared to other seasons. During the operation period of meter gauge railroads (1990–1997), the proportions of ETCs and casualties were only 15.6% and 8.7% respectively. However, these increased substantially to 84.4% and 91.3% respectively during the operation of broad gauge railroads (1998–2018). The OLS model indicated that both elephant and train densities explained 37% of the variance of ETC rate, while GWR model showed 83% of the variance of ETC rate. The local coefficient values of GWR indicated that both the predictor variables interplayed significantly and positively to determine ETC rates in the Mariani-Nakachari and Khatkhati-Dimapur railroad segments. However, the relationship between ETC rate and elephant density is significantly negative in the Habaipur-Diphu railroad, implying that the elephant population along this railroad stretch is significantly affected by railways through large scale ETCs. Hence, there is an urgent need to address long-term mitigation strategies so that elephants can be conserved by providing safe passages and survival resources along railway lines.

Time-slotted LoRa MAC with variable payload support

LoRaWAN is an upcoming Low Power Wide Area Network (LPWAN) technology for Internet of Things implementations in various application domains. Despite its various advantages, LoRaWAN employs an Aloha-based MAC, which in terms of performance cannot guarantee high packet delivery ratio and low latency. To overcome this issue, we propose a time-slotted scheme, called TS-VP-LoRa, which supports multiple transmission times and packet sizes at the same time. In TS-VP-LoRa, scheduling is coordinated by the LoRa gateway, broadcasting beacon frames periodically for the synchronization of LoRa end-devices. A channel hopping mechanism is also proposed in order to minimize the occurrence of collisions and to evenly split the transmission load among all channels. TS-VP-LoRa is evaluated and compared to three other MAC-layer schemes in single gateway simulation scenarios with up to 500 nodes. The proposed scheme has proven to achieve low latency with high packet delivery ratios, significantly minimize collisions and maintain a relatively low energy consumption despite the scaling of the LoRa network.

A user study of directional tactile and auditory user interfaces for take-over requests in conditionally automated vehicles

General introduction of unconditionally and conditionally automated vehicles is expected to have a highly positive impact on the society, from increased accessibility to mobility and road traffic safety, to decreased environmental and economic negative impacts. However, there are several obstacles and risks slowing down the adoption of this technology, which are primarily related to the human–machine interaction (HMI) and exchange of control between the vehicle and the human driver. In this article, we present key takeaways for HMI design of take-over requests (TOR) that the vehicle issues to inform the driver to take over control of the vehicle. The key takeaways were developed based on the results of a user study, where directional tactile-ambient (visual) and auditory-ambient (visual) TOR user interfaces (UI) were evaluated with regards to commonly used take-over quality aspects (attention redirection, take-over time, correct interpretation of stimuli, off-road drive, brake application, lateral acceleration, minimal time-to-collision and occurrence of collision). 36 participants took part in the mixed design study, which was conducted in a driving simulator. The results showed that drivers’ attention was statistically significantly faster redirected with the auditory-ambient UI, however using the tactile-ambient UI resulted in less off-road driving and slightly less collisions. The results also revealed that drivers correctly interpreted the directional TOR stimuli more often than the non-directional one. Based on the study results, a list of key takeaways was developed and is presented in the conclusion of the paper. The results from this study are especially relevant to the TOR UI designers and the automotive industry, which tend to provide the most usable UI for ensuring safer end efficient human-vehicle interaction during the TOR task.

Activation and execution of the hepatic integrated stress response by dietary essential amino acid deprivation is amino acid specific.

Dietary removal of an essential amino acid (EAA) triggers the integrated stress response (ISR) in liver. Herein, we explored the mechanisms that activate the ISR and execute changes in transcription and translation according to the missing EAA. Wild‐type mice and mice lacking general control nonderepressible 2 (Gcn2) were fed an amino acid complete diet or a diet devoid of either leucine or sulfur amino acids (methionine and cysteine). Serum and liver leucine concentrations were significantly reduced within the first 6 h of feeding a diet lacking leucine, corresponding with modest, GCN2‐dependent increases in Atf4 mRNA translation and induction of selected ISR target genes (Fgf21, Slc7a5, Slc7a11). In contrast, dietary removal of the sulfur amino acids lowered serum methionine, but not intracellular methionine, and yet hepatic mRNA abundance of Atf4, Fgf21, Slc7a5, Slc7a11 substantially increased regardless of GCN2 status. Liver tRNA charging levels did not correlate with intracellular EAA concentrations or GCN2 status and remained similar to mice fed a complete diet. Furthermore, loss of Gcn2 increased the occurrence of ribosome collisions in liver and derepressed mechanistic target of rapamycin complex 1 signal transduction, but these changes did not influence execution of the ISR. We conclude that ISR activation is directed by intracellular EAA concentrations, but ISR execution is not. Furthermore, a diet devoid of sulfur amino acids does not require GCN2 for the ISR to execute changes to the transcriptome.

Environmental impacts on marine energy: collision risks for marine animals and priority species for monitoring in Brazil

ABSTRACT Brazil has great potential for the development of technologies for the conversion of marine energy from waves and tides, which raises the discussion about the possible environmental impacts of these projects. This article seeks to synthesize knowledge about the risks of collision of marine animals, such as mammals, fish and birds, with marine renewable energy (MRE) devices, as well as to identify priority species for environmental monitoring along the Brazilian coast. The risk of marine mammals colliding with MRE devices is influenced by regional and behavioral factors. The risk of collision in a fish community is influenced by the avoidance behavior, the distribution of fish in the MRE sites and the stages of the enterprise (installation, operation and maintenance). Seabird collision risk is influenced by species behavior (geographical distribution, seasonal habitat use, diving time and depth) and the location of MRE structures (surface and/or water column). The survey of priority species for monitoring the risk of collision with MRE devices in Brazil consisted of 5 species of marine mammals, 13 taxa of seabirds, 5 species of endangered sea turtles and 18 species or groups of species of fish of economic importance to the country. The research review did not record the occurrence of collisions with marine animals. However, this does not mean that they did not occur, but that they may not have been observed due to monitoring challenges. The study concluded that research on the interaction of marine animals with MRE devices should be encouraged, even in prototypes and non-commercial projects, in order to reduce knowledge gaps and support the development of MRE in an environmentally sound manner. Keywords: Marine renewable energy, Collision risk, Species, Marine animals.

Characteristics of Train-Pedestrian Collisions in Southwest China, 2011-2020.

Although train–pedestrian collisions are the primary source of railway casualties, the characteristics of this phenomenon have not been fully investigated in China. This study examined such collisions in the Greater Sichuan-Chongqing area of China by conducting a thorough descriptive analysis of 2090 incident records from 2011 to 2020. The results showed that such collisions have declined gradually over the past decade, but the fatality rate remains high. We found that such collisions were more likely to happen to men, senior citizens and people crossing the tracks and that they occurred more frequently in the morning. While collision rates dropped in February, collisions were more likely to occur in December. In contrast to the situation in Western countries, weekends were not related to increased occurrence. The absence of a protective fence led to a higher collision rate, but level crossings are no longer a concern since most such structures in China have been rebuilt as overpasses. Mild slopes and extreme curvatures were also found to increase the occurrence of such collisions. Freight trains were most likely to be involved in train–pedestrian collisions, and collisions caused by high-speed trains were rare both absolutely and relatively. However, when collisions did occur, higher train speeds were linked with higher fatality rates. The findings suggest that patterns of train–pedestrian collisions in China differ from those in the Western world. This difference might be caused by differences in culture, geography, weather and railway development policies. Future research directions and possible preventive measures are also discussed.

On the settling of spherical particles in power-law fluid at moderate Reynolds number

The present paper analyses the settling behavior of multiple spherical particles in a power-law fluid. The results were numerically solved by the lattice Boltzmann method for the fluid mass and momentum equations and the immersed boundary method for the particle dynamics. The transient particle position and velocity data were obtained for a constant Archimedes number of 1000 and density ratio of 2.25. The objects of the investigation were the solid volume fraction, between 0.2% and 3.3%, and the power-law index, from 0.6 to 1.25. The particles repel each other and avoid collision due to increased fluid viscosity in their gaps for the shear-thickening fluid. On the other hand, for shear-thinning fluids, a wake of low viscosity is formed behind the particles, which leads to a high occurrence of particle collisions. However, as the solid volume fraction increases, these effects become less noticeable, mainly because the settling transitions from viscous to collision-dominated. In all cases analyzed, the average terminal velocity was below the terminal velocity of a free particle.

An Energy Aware Multi Slot Scheduling with Two-Layer Hexagonal Based Integrated Aggregation Approach for Underwater Wireless Sensor Networks (UWSN)

In the present era, Underwater Wireless Sensor Network (UWSN) is an emerging technology that involves a huge amount of sensor nodes to collect and monitor information from the underwater environment. However, the data transmission process is constrained due to the collision and energy consumption which can adversely affect the performance. Hence, there is an essential need to develop a suitable mechanism that addresses these challenges using a data aggregation-based routing mechanism in UWSN. In this paper, a Multi-Slot Scheduling with a Two-Layer Hexagonal based Integrated Aggregation model (MSS-TLHIA) is proposed that offers a prolonged lifetime with less energy consumption and collision avoidance. In this model, data aggregation is performed using the aggregator node selection process. Initially, the entire network is partitioned into several hexagonal grids using the golden ratio. This partitioning offers an improved coverage area for every node which are participating in the network. Once the network is partitioned into coverage areas called clusters, a Cluster Head (CH) is selected using the ranking-based fuzzy mechanism. Then, an aggregator node is selected in common for both the layers of the hexagonal grids. In order to prevent the energy drain of the aggregator node completely and to prolong their lifetime, the aggregator node is re-selected for every time slot. Furthermore, the occurrence of collision is avoided by the multi-slot scheduling process. Experimental results demonstrate that the performance of the proposed model is compared with other existing protocols and achieves better results in terms of network lifetime, energy consumption, collision rate, packet dropped rate, packet delivery, and data forwarding measures.