Spreading Behavior Research Articles

Effects of confined distance and wire spacing on flame spread over double electrical wires for the layout design in buildings

In this study, the flame merging and flame spread behaviors over two identical parallel electrical wires (the ratios of copper core diameter to entire wire diameter are: 6mm/10 mm and 8mm/12 mm for typeⅠand typeⅡ, respectively) were experimentally investigated under different wire spacings (3∼18 mm) and confined distances(10∼30 mm). The results show that the smaller confined distance D will promote the merging, making the wire spacing s increase for the fully merging. With the increase of D, the flame width and flame spread rate Vf will increase.While the flame height will be stretched at smaller D. And Vf is larger than that of single wire at the same D for different wire spacings.The interesting finding is that a pool fire is formed at the middle of the wire spacing when s and D are small, which will enhance the flame spread.The heat flux feedback of components including of the conductive heat flux q˙c″, the first single flame heat flux q˙f1″, the second flame heat flux q˙f2″, the pool fire heat flux q˙pf″ and the gypsum board heat flux q˙g″ are quantitatively analyzed. At the intermittent and non merging stages, the convective and radiative heat fluxes q˙vf2″ and q˙rf2″ will decrease largely due to the interaction weakened greatly. Based on the heat transfer analysis, a flame spread model is established, which can well predict the flame spread rate.These findings can give the useful suggestions on the layout design of electrical wires in confined space in buildings.

Dynamics of SIR Model on Random Networks

we focus on studying the dynamics of infectious disease spreading SIR model on random networks. We investigate how various parameters of the network influence the behavior of spreading and analyze the occurrence of phase transitions within this networkframework. Our analysis reveals the critical role of network connectivity in shaping the dynamics of disease transmission and highlights the presence of mean-field phase transitions.Additionally, we employ both analytical techniques and simulation methods to extract critical thresholds for the model and compare them for validation. By delving into the intricate dynamics of disease spreading on random networks, this work offers valuableinsights into the mechanisms driving epidemic propagation and provides a theoretical foundation for studying disease control strategies and public health interventions.

Experimental Investigation and Theoretical Analysis of Flame Spread Dynamics over Discrete Thermally Thin Fuels with Various Inclination Angles and Gap Sizes

Flame spread over discrete fuels is a typical phenomenon in fire scenes. Experimental and theoretical research on flame spread over discrete thermally thin fuels separated by air gaps with different inclination angles was conducted in the present study. Experiments with six inclination angles ranging from 0° to 85° and various fuel coverage rates from 0.421 to 1 were designed. The flame spread behavior, the characteristic flame size, and the flame spread rate were analyzed. The results show that the flow pattern, stability, and flame size exhibit different characteristics with different inclination angles and gap sizes. As the inclination angle increases, particularly with smaller gaps, turbulent and oscillating flames are observed, while larger gap sizes promote flame stability. The mechanism of flame propagation across the gap depends on the interplay between the flame jump effect and heat transfer, which evolves with gap size. Average flame height, average flame width, and flame spread rate initially increase and then decline with the increase in fuel coverage, peaking at fuel coverage rates between 0.93 and 0.571 for different inclination angles. A theoretical model is proposed to predict the flame spread rate and the variation in the flame spread rate with inclination angle and fuel coverage. Furthermore, the map determined by inclination angle and fuel coverage is partitioned into distinct regions, comprising the accelerated flame spread region, the flame spread weakening region, and the failed flame spread region. These findings provide valuable insights into flame spread dynamics over discrete thermally thin fuels under diverse conditions.

Precise Asymptotic Spreading Behavior for an Epidemic Model with Nonlocal Dispersal

Precise Asymptotic Spreading Behavior for an Epidemic Model with Nonlocal Dispersal

Flame-retardant wire burning behavior by jet flame heating: Ignition, charring, and secondary flame spread

This research presents an in-depth examination of the combustion characteristics of flame-retardant electrical wires, contrasting behavior with non-flame-retardant counterparts under jet flame heating. The study systematically investigates the pyrolysis process, ignition patterns, charring behavior, and the development of secondary flames in wires with different core diameters and insulation materials. Findings indicate the heightened susceptibility of thinner wires to rapid heating, pyrolysis and charring, leading to faster ignition and more intense secondary flame development. This insight is crucial for tailoring flame-retardant formulations to specific wire dimensions. The research also delves into the thermal dynamics within the wires, highlighting how the core diameter influences axial heat conduction and, consequently, the overall flame spread behavior and pyrolysis rate. A critical discovery is the relationship between heating duration and flame sustainability, establishing a specific range of heating times for sustaining secondary flames in flame-retardant wires. Theoretical models used in the study explained the critical heat flux heating time for wire ignition, offering insights into improved fire prevention strategies, particularly in prolonged heat exposure scenarios. These findings not only advance our understanding of flame-retardant wire behavior under fire conditions but also provide guidance for selecting and using electrical wires, thereby optimizing fire safety in diverse applications.

Study on the flame radiative heat transfer and near-field radiation heat flux predictive model of vehicle fires in a tunnel

As a major form of heat transfer, flame thermal radiation has an important effect on the ignition of adjacent energy, fire spread and environmental damage. Forecasting the flame radiation heat flux can provide theoretical basis for fire hazard assessment, fire extinguishing and salvation. Meanwhile, the distinctive structure of the arc tunnel can result in significant variations in the local heat and mass transfer processes during tunnel fires compared to those in rectangular tunnels, leading to different fire characteristics parameters. In this study, experiments and theoretical analyses were conducted to investigate the flame length scale and near-field radiation heat flux on the lower surface of an arc-shaped ceiling induced by vehicle fires in a tunnel. The findings reveal that the flame length scale in the transverse direction beneath the arc-shaped ceiling decreases with an increasing burner aspect ratio and increases with the increasing heat release rate. A dimensionless model of the flame length scale under the arced ceiling with various burner aspect ratios was proposed based on the amount of remaining unburned fuel after flame impingement and the buoyancy component along the arc-shaped ceiling. Simultaneously, radiative heat fluxes on the lower surface also increase with rising heat release rate. The flame geometry beneath the arc-shaped ceiling is assumed to be a combination of a cuboid and an arc plate model based on the actual flame length scale. Subsequently, the view factor, radiative fraction, and flame surface area are analyzed to predict the radiative heat fluxes on the lower surface. The predictions of the cuboid and arc plate flame model show good agreement with the current experimental data. This work presents a dimensionless correlation of the flame length scale and calculates the view factor between the target and the arc plate to predict the near-field radiative heat flux more accurately. This approach also facilitates the understanding of flame spreading behavior and thermal hazards impacted by arced ceiling.

A Bayesian latent variable model for the optimal identification of disease incidence rates given information constraints

Abstract We present an original approach for measuring infections as a latent variable and making use of serological and expert surveys to provide ground truth identification during the early pandemic period. Compared to existing approaches, our model relies more on empirical information than strong structural forms, permitting inference with relatively few assumptions of cumulative infections. We also incorporate a range of political, economic, and social covariates to richly parameterize the relationship between epidemic spread and human behaviour. To show the utility of the model, we provide robust estimates of total infections that account for biases in COVID-19 cases and tests counts in the U.S. from March to July of 2020, a period of time when accurate data about the nature of the SARS-CoV-2 virus was of limited availability. In addition, we can show how sociopolitical factors like the Black Lives Matter protests and support for President Donald Trump are associated with the spread of the virus via changes in fear of the virus and cell phone mobility. A reproducible version of this article is available as an Rmarkdown file at https://github.com/CoronaNetDataScience/covid_model.

Interplay of virtual and physical channels in propagating green behaviour: A study integrating motivation-opportunity-ability and theory of planned behaviour

Traditional communication channels and new “human-computer interaction” spread channels are intertwined, facilitating the promote of the concept of “green for all”. This paper integrates the influence of virtual channel and physical channel attributes into the Motivation-Opportunity-Ability theory (MOA) and Theory of Planned Behavior (TPB) to explore the spread process of public green behaviors. The results show that: (1) In the composite effect, environmental responsibility (ER) and external objective factors (EOF) have no significant impact on the propagation of green behavior among the public. Both virtual channel attributes (VCA) and physical channel attributes (PCA) can accelerate the spread process of public green behavior, with PCA having the greatest impact on the propagation of public green behavior. (2) ER, VCA, PCA, EOF, and external subjective factors (ESF) can all promote the spread of public green behavior through the intermediary chain of spread motivation and spread intention. Among them, channel attributes more directly influence the spread of green behavior, and the chain mediating effect of ER through the chain was the most significant. At the same time, ESF plays a significant moderating role between the intention to spread and propagation behavior (PB), effectively bridging the gap between behavior and intention. (3) Further heterogeneity analysis shows that, compared with males, PCA has a greater promoting effect on the green behavior propagation of females, while VCA has a more significant positive effect on the green behavior propagation of the more educated public. Finally, this article examines the presence of intermediary and regulatory mechanisms among various income groups. Research has found that promoting the creation of conducive conditions for comprehensive green behavior propagation and developing targeted and mass-oriented green behavior propagation strategies by all societal stakeholders are crucial for enhancing public engagement in green practices.

An Investigation of the Behaviors and Characteristics of the Interfacial Bonding Capacity between Cement Emulsified Asphalt Composite Binder and Reclaimed Asphalt Pavement

The interfacial bonding capacity between cement emulsified asphalt composite binder (CEACB) and reclaimed asphalt pavement (RAP) plays a critical role in improving the pavement performance of cold recycled asphalt emulsion mixtures (CRAEMs). This study aims to investigate the formation and development of the interfacial bonding capacity between CEACB and RAP. First, the dynamic wettability and the spreading behaviors of CEACB on RAP surfaces were explored according to the surface free energy theory. Second, digital image processing (DIP) technology was employed to recognize interfacial failure patterns. Lastly, the influence of internal and external factors on the interfacial bonding capacity between CEACB and RAP during the curing process was analyzed via grey relational analysis (GRA). The results indicate that a moderate cement content with a mass ratio of asphalt to cement equivalent to 1.0 can significantly enhance the wettability of CEACB on RAP surfaces. By appropriately prolonging the curing time and controlling the curing temperature, it is possible to increase the bonding strength between CEACB and RAP. Additionally, a strong correlation exists between initial wettability and ultimate bonding capacity during the bonding strength curing process. The good wettability that developed in the initial stage of interfacial strength formation relates to the decreased spalling rate of CEACB on the RAP surface. This study is not only devoted to understanding the mechanisms that can enhance CRAEM performance but also provides important guidance for practical engineering applications of cold recycled asphalt pavements.

Spreading Behavior of Non-Spherical Particles with Reconstructed Shapes Using Discrete Element Method in Additive Manufacturing.

The spreading behavior of particles has a significant impact on the processing quality of additive manufacturing. Compared with spherical metal material, polymer particles are usually non-spherical in shape. However, the effects of particle shape and underlying mechanisms remain unclear. Here, the spreading process of particles with reconstructed shapes (non-spherical particles decomposed into several spherical shapes by stereo-lithography models) are simulated by integrating spherical particles with the discrete element method. The results show that more cavities form in the spreading beds of particles with reconstructed shapes than those of spheres with blade spreading. Correspondingly, particles with reconstructed shapes have lower packing densities, leading to more uniform packing patterns. Slow propagation speeds of velocity and angular velocity lead to "right-upwards" turning boundaries for particles with reconstructed shapes and "right-downwards" turning boundaries for spherical particles. Moreover, as the blade velocity increases, the packing density decreases. Our calculation results verify each other and are in good agreement with the experiment, providing more details of the behavior of non-spherical particles before additive manufacturing. The comprehensive comparison between polymer non-spherical particles and spherical particles helps develop a reasonable map for the appropriate choice of operating parameters in real processes.

A Reaction-diffusion System Modeling the Transmission of Typhoid Fever in a Periodic Environment

Typhoid fever is a life-threatening infection caused by the bacterium Salmonella Typhi, and it is still an important issue in developing countries. There are two infection routes of Typhoid fever, namely, the human-to-human transmission and the environment-to-human transmission. It is evident that people living near rivers may have a higher rate of typhoid infection, and temperature changes also have significant impacts on Typhoid transmission dynamics. In the model, the population of human will be divided into susceptible individuals, infected individuals, carrier individuals, individuals under treatment, and recovered individuals. Then a periodic dispersion-reaction system is used to describe the transport and the interactions between human and bacteria in the environment. The solution maps of the proposed periodic dispersion-reaction system lack the compactness since the population under treatment has no diffusion term, which makes analysis more difficult. After the feasible domain is chosen carefully, the eventually boundedness of the solutions can be established, and the loss of compactness is overcome if the initial data is chosen from the feasible domain. In order to introduce the reproduction number <I>R<sub>0</sub></I>, the linearized system around the disease-free state is constructed, and the basic reproduction number is defined as the spectral radius of the next generation operator. Then the comparison principle and persistence theory can be utilized to establish that the index <I>R<sub>0</sub></I> completely determines the threshold behavior of the typhoid spread. Brief mathematical and biological interpretations are also presented.

Copper Quantum Dot/Polyacrylamide Composite Nanospheres: Spreading on Quartz Flake Surfaces and Displacing Crude Oil in Microchannel Chips.

Polyacrylamide, silica, and other nanoparticles have all been realized in the field of enhanced oil recovery. Researchers often explore the mechanisms of spreading behavior and simulated displacement to develop more efficient types of nanoparticles. In this study, copper quantum dots were introduced into a acrylamide copolymerization system to obtain composite nanospheres and its structure, topographic, and application performance were characterized. The results show that the composite nanospheres have a particle size of around 25 nm, are uniformly loaded with copper particles, and have good temperature resistance. The spreading ability on the quartz flake surfaces and displacement effect in microchannels of composite nanospheres, acrylamide copolymer nanospheres, and copper quantum dots were compared by nanofluid spreading experiments and microchannel chip oil displacement experiments. The results indicate that the composite nanospheres can effectively reduce the water contact angle, promote the spreading of aqueous phase, and accelerate the oil droplet removal process; the accelerating effect is stronger than other samples. Its oil displacement effect is also the strongest, and it is minimized by the influence of channel size, temperature, and dispersing medium, with better stratigraphic adaptability. This work supports the practical application of copper quantum dot/polyacrylamide composite nanospheres in the oilfield.

On the spreading behavior of a droplet on a circular cylinder using the lattice Boltzmann method

On the spreading behavior of a droplet on a circular cylinder using the lattice Boltzmann method

Effects of one-side confinement and current on heat transfer mechanisms over single electrical wire flame spread behaviors

The electrical wire fire often occurs in the confined space, making the flame spread behavior complex and the risk increase. In this paper, experimental and theoretical study on the flame spread over three types of polyethylene (PE) electrical wires under different side-confined distances (0∼40 mm) and currents (0∼60 A) was carried out.The ratios of copper diameter to entire wire diameter were 6mm/10 mm, 8mm/12 mm, and 6mm/12 mm for type I, type II and type III, respectively. The results show that, with the increase of s, the flame width and height, and flame spread rate will firstly increase to the maximum peaks at the position of s = 5 mm with attachment wall effect, and then gradually decrease to the values of the unconfined conditions. And with the increase of current, these parameters will gradually increase to the largest at I = 40 A and then decrease for I = 60 A, as the current effect changes from preheating to dripping acceleration.The firm correlation between preheating length δph and pressure difference ΔP is built, which demonstrates the smallest preheating length is at s = 5 mm with the maximum promotion of heat transfer by gypsum board. On the other hand, the generated Joule heat by the current will enhance the length of preheating, making it proportional to current. Meanwhile, it is found that, the dripping frequency influenced by the dripping mass rate, will increase with the current. The heat transfer components including of the solid conduction heat flux (q˙joule″ and q˙c″), flame heat flux (q˙νf″ and q˙rf″) and gypsum board heat flux (q˙rg″ and q˙νg″) are quantitatively analyzed. Correspondingly, a heat transfer model over flame spread is established, which can well predict the flame spread rate.As the diameter of the wire is relatively small, the controlling heat transfer is the flame convective heat flux q˙νf″ in this research. In addition, it is illustrated that, the heat flux of gypsum board q˙νg″+q˙rg″ will decrease with the increase of copper core diameter from type I of 6 mm to type II of 8 mm.While the solid conduction heat flux of copper q˙c″+q˙joule″ will decrease with the increase of thickness of PE from type I of 2 mm to type III of 3 mm. These findings can well give the understanding of heat transfer of flame spread over electrical wires with the effects of sidewall and current.

Research on information spreading of SISIOIN model in social networks

This paper focuses on the internal law of online public opinion spreading under the conditions of different types of spreaders by constructing the model of public opinion spreading by subtypes of spreaders. The new [Formula: see text] model is constructed by abstracting factors such as netizens’ interests, emotions and views on hot events in the Internet into propensity indices. The simulation results show that the spread of public opinion after categorizing netizens is more in line with the spread of public opinion in reality. Moreover, netizens tend to show different spreading behaviors in different public opinion cases, and the degree of change in netizens’ propensity varies greatly. All the data used in the simulation experiments are real data and analyzed with real events. The research results are helpful for what kind of control strategies are adopted after the occurrence of hotspot events.

Nonlinear spreading behavior across multi-platform social media universe.

Understanding how harmful content (mis/disinformation, hate, etc.) manages to spread among online communities within and across social media platforms represents an urgent societal challenge. We develop a non-linear dynamical model for such viral spreading, which accounts for the fact that online communities dynamically interconnect across multiple social media platforms. Our mean-field theory (Effective Medium Theory) compares well to detailed numerical simulations and provides a specific analytic condition for the onset of outbreaks (i.e., system-wide spreading). Even if the infection rate is significantly lower than the recovery rate, it predicts system-wide spreading if online communities create links between them at high rates and the loss of such links (e.g., due to moderator pressure) is low. Policymakers should, therefore, account for these multi-community dynamics when shaping policies against system-wide spreading.

Unit Maxwell-Boltzmann Distribution and Its Application to Concentrations Pollutant Data

In the vast statistical literature, there are numerous probability distribution models that can model data from real-world phenomena. New probability models, nevertheless, are still required in order to represent data with various spread behaviors. It is a known fact that there is a great need for new models with limited support. In this study, a flexible probability model called the unit Maxwell-Boltzmann distribution, which can model data values in the unit interval, is derived by selecting the Maxwell-Boltzmann distribution as a base-line model. The important characteristics of the derived distribution in terms of statistics and mathematics are investigated in detail in this study. Furthermore, the inference problem for the mentioned distribution is addressed from the perspectives of maximum likelihood, method of moments, least squares, and maximum product space, and different estimators are obtained for the unknown parameter of the distribution. The derived distribution outperforms competitive models according to different fit tests and information criteria in the applications performed on four actual air pollutant concentration data sets, indicating that it is an effective model for modeling air pollutant concentration data.

Investigation on the spreading behaviour of sand powder used in binder jet 3D printing

Investigation on the spreading behaviour of sand powder used in binder jet 3D printing

Kinetics-based wetting properties of microdroplets impacting respirable coal dust particles

The removal of respirable coal dust particles has been the focus of domestic and foreign research, and the spray dust suppression technology has been adopted for the prevention and control process; it is based on the mechanism whereby liquid droplets impact dust particles. To further study the wetting properties of microdroplets impacting respirable coal dust particles based on kinetics, this study focused on the droplet morphology, and mathematical and physical models of a microdroplet impacting a respirable coal dust particle were established to explore the variation laws of the droplet spreading and wetting under central and non-central impacts, for which the CLSVOF numerical simulation approach was adopted. The results showed the occurrence of gas retention at the phase interface, which affected the droplet wetting characteristics on the coal dust surface, after the contact between the liquid and dust particles. The influence of the impact velocity, particle size ratio, contact angle, and offset distance on the droplet spreading behavior was investigated by comparative analysis of 12 working conditions with different parameters. The droplets can completely wrap the coal dust particles under only one working condition parameter (V = 5m/s,Φ = 2,θ = 90°,L = 0 μm). The microdroplets are extremely difficult to wet respirable coal dust particles and the spreading behavior of the final droplet could be divided into three states: static adsorption, complete encapsulation and permanent escape. Our results can help better understand the wetting relationship between microdroplets and respirable coal dust particles, serving as a basis for dust prevention and control.

Spreading speeds for time heterogeneous prey-predator systems with nonlocal diffusion on a lattice

We investigate the spreading behaviour for the solutions of a non-autonomous prey-predator system on a discrete lattice. These time variations are assumed to enjoy an averaging property. This includes periodicity, almost periodicity and unique ergodicity as special cases. The spatial motion of individuals from one site to another is modelled by a discrete convolution operator. In order to take into account external fluctuations such as seasonality, daily variations and so on, the convolution kernels and reaction terms may vary with time. Our analysis of the spreading speeds of invasion of the species is based on the careful and detailed study of the hair-trigger effect and spreading speed for a non-autonomous scalar Fisher-KPP equation on a lattice. Then, we are able to compare the solutions of the prey-predator system with those of a suitable scalar Fisher-KPP equation and derive the invasion speeds of the prey and of the predator.