Spreading Process Research Articles

Role of gravity magnitude on flowability and powder spreading in the powder bed fusion additive manufacturing process: Towards additive manufacturing in space

Understanding powder spreading under low gravity conditions is essential for optimizing final products using additive manufacturing in space. In this study, we investigated the role of gravity on flowability and spreading mechanisms through combined experimental and discrete element method (DEM) studies. Three powders with different theoretical densities were used to reenact low compressive conditions resembling those in a low-gravity environment. The influence of low compressive conditions on flowability and spreading behavior was examined using the Hall flowmeter, rotating drum, and spreading experiments. In the experimental result, the static flowability was primarily affected by the presence of elongated particles rather than the compressive conditions. The dynamic AoR of TD_4 powder increased compared to that of TD_8 powder, despite the presence of spherical particles with a smooth surface finish. A DEM simulation study was conducted using TD_8 powder to investigate the impact of different gravity levels on dynamic flowability. The DEM studies revealed that the dynamic flowability under rotation was decreased under low gravity owing to the promoted cohesive interactions. The powder spreading experiment was performed using the three powders with different theoretical densities. The in-situ observation with particle image velocimetry analysis revealed that kinetic energy dissipation in the spreading process was accelerated in the TD_8 powder pile, despite its high interparticle friction and cohesive force. The powder spreading simulation was conducted using TD_8 powder to clarify the effect of low gravity on the powder spreading process. In TD_8 powder under 1 G, particle supply was facilitated by a synergistic effect of free-falling and deposited particles. However, increased cohesive interactions under 0.5 G and 0.16 G restricted particle supply via free-falling, consequently reducing the powder bed density by about 2 % and 6.2 %, respectively. These findings prove that the cohesive force predominantly controls dynamic flowability and powder bed quality in the spreading process under low gravity conditions.

Impact and spread dynamics of a viscoelastic droplet on an inclined hydrophilic surface

In this work, the impact of a three-dimensional viscoelastic droplet on an inclined hydrophilic surface is investigated by means of direct numerical simulations. The volume-of-fluid method is adopted to capture the interface, and the Oldroyd-B model is used to describe the rheological behavior of the viscoelastic droplet. The effects of the Weissenberg number (Wi) and the Weber number (We) on the impacting and spreading processes are studied, including the viscoelastic droplet shape, velocity, energy transformation, and stress distribution. Our results are in good agreement with the experimental data in the literature. In particular, the elastic force markedly influences droplet deformation at intermediate Wi values, although this trend diminishes at higher or lower Wi values. With increasing We, the impacting viscoelastic droplet reaches its maximum deformation more rapidly, while the nonmonotonic peak of kinetic energy indicates that the droplet elasticity plays significant role at moderate We. Additionally, the inclination of the surface has a pronounced effect on the droplet spreading process, and the elongated viscoelastic droplet at larger inclination angle is likely to experience a stronger oscillation. According to further analyses, We exerts a modest influence on the change rates of the droplet potential energy and spreading length in the flow direction. However, a larger inclination angle reduces stress concentration and accelerates the change rates. Due to the oscillation dynamics, Wi exhibits a non-monotonic effect on the spreading process and induces a monotonous increase in potential energy of viscoelastic droplets. The above analyses provide insights into the impact mechanism of droplets on an inclined hydrophilic wall and, therefore, will guide the applications in the future.

Численное моделирование миграции фильтрационных вод от объектов размещения твердых коммунальных отходов через грунтовые защитные сооружения

The paper studies numerically he processes of pollutant migration from the municipal solid waste (MSW) landfill and discusses the obtained results. Pollution of the natural environment with residues of substances and products resulting from the human household and industrial activities is one of the most urgent problems both in Russia and all over the world. In economically developed countries, in which waste management strategies are implemented to minimize garbage accumulation, priority is given to neutralization and recycling technologies, The beneficial effect of such strategy is a significant reduction of the waste volume. In Russia, despite the positive dynamics in the use of new waste management technologies, the main method of their treatment is disposal at MSW landfills. On the territory of Russia, along with the MSW landfills operated and built in accordance with environmental requirements, there are a large number of unauthorized landfills, which are of serious hazard to the environment. This raises the question of assessing the impact of such facilities on the environment. To study the characteristics of the pollutant distribution and determine the waste migration parameters, the archival data from a set of field and laboratory studies in the area of the existing MSW disposal site were used. A numerical model was constructed to describe the hydrodynamics of the migration of substances in the soil and soil layer forming the base of a solid waste disposal facility. The process of pollutant spreading is described in terms of dry residue. The model takes into account such factors as convective transport, diffusion and geological composition of the base of the waste disposal site, which have a significant impact on the pollutant migration.

“KOREAN WAVE” AS A MASSIVE POPULAR CULTURAL PHENOMENON OF THE MODERN TIME

Nowadays, young people from all over the world are fascinated by the mass popular culture of South Korea. This process of spread of Korean culture in the world came to be called “Korean current” or “Korean wave”, which became a kind of “Korean cultural boom”. The spread of the “Korean wave” has been compared to a viral disease that first spread throughout East Asia, then Southeast Asia, and eventually engulfed the entire world. Despite the fact that the phenomenon of the “Korean wave” had a sufficient public resonance, due to its novelty and unexpected emergence, it remains an understudied subject of scientific study, especially in the West and in particular in Ukraine. That is why the topic of this study is relevant nowadays. The aim of the article to investigate the mass cultural phenomenon “Korean wave”, to analyze its sources and dynamics of development, to characterize its inherent features, to determine the aspects of its spread and popularization, to investigate its influence on world society and culture, as well as to find out the peculiarities of its influence on the consciousness of the masses. The research methodology is based on a philosophical and cultural analysis of such a mass phenomenon of modern artistic culture as the “Korean wave”. When writing the work, we tried to adhere to the principles of objectivism, systematicity, comprehensiveness and multifactoriality. To comply with these principles, we used a number of general scientific and special methods in the research: comparative-historical, axiological, phenomenological, logical, retrospective, analytical-synthetic, socio-critical, systemic, structural-functional, generalizing and statistical. Adherence to these principles and methods made it possible to avoid bias and tendencies in judgments. Results. Such a mass cultural phenomenon as the “Korean wave” is a kind of entanglement of opposite principles: modern Western (progressive-innovative) and traditional Eastern (Confucian) cultural values. It manifests itself in the spread of fashion to everything Korean (or to be more precise, South Korean): not only K-pop, dramas, toys, clothes and other types of South Korean entertainment industry, but also Korean cuisine, household items, etc. In the past, despite the geographical proximity and cultural connectivity, for political reasons the countries of Asia largely suppressed cultural exchanges among themselves. China, Korea and Japan began to develop cultural ties between themselves relatively recently. It should also be noted that South Korea is a country that was previously considered a cultural periphery in international exchanges, now it plays an important role in the regionalization of mass culture as a whole in East and Southeast Asia and the product produced by it is considered a center of mass culture and one of the ways of cultural exchange throughout Asia. Conclusions. To sum up, we can say that the great popularity of the “Korean wave” is a kind of leap in the modern culture of South Korea. This phenomenon is represented not only by the synthesis of modern Western (European-American) culture and traditional Eastern (Korean), but also by the fact that in our time it has turned into a powerful locomotive of the entire South Korean economy, a kind of “dragon’s head”. The phenomenon of the “Korean wave” helps to raise the level of the image of South Korea as a prosperous country, and also visually demonstrates the modern South Korean culture to the world. The “Korean Wave” demonstrates to other countries in Asia and to the whole world in general that South Korea is not a periphery in our time, it is no longer a third world country, and it is as modern an urbanized country as most of the developed countries of the West, which has not only modernized its culture, but also spread it, and even managed to influence other countries and their cultures.

Creating, publishing, and spreading processes of health-related contents in internet news sites: evaluation of the opinions of actors in health communication.

The accuracy and reliability of health information disseminated through news is crucial, as it directly impacts both individual and societal health outcomes. This study aims to analyze the publication process of health content in Türkiye and its implications for public health. By examining the perspectives of various health communication stakeholders, the study seeks to identify existing issues and propose potential solutions. The research uses a mixed-methods approach, including baseline content analysis of 846 news by 133 criteria, quantitative research with 78 participants encompassing bureaucrats, academics, journalists, and health association members, and 15 in-depth interviews for comprehensive insights. The content analysis indicated that 23.2% of the analyzed news articles lacked credible sources, while 63% did not mention the author's name. A striking 96.2% of respondents stated that inaccurate health news poses a risk to public health, emphasizing the urgent need for standardized reporting practices. The majority (90.9%) pinpointed the media as the primary catalysts for infodemic spread, with 93.5% citing gatekeepers as barriers to accurate information. Eroding trust in media, fueled by unethical practices, harms both media credibility and effective public health interventions. The study underscores the necessity for a collaborative approach among public institutions, academia, and media, focusing on responsibility, regulation, and sanctions against the infodemic. The research advocates for a balanced approach that prioritizes health rights and press freedom within a stakeholder-driven framework, highlighting that legislation alone cannot fully enhance the digital information ecosystem.

Full-scale experimental and numerical study of smoke spread and temperature distribution in a room-corridor structure building

This paper aims to study the smoke spread and temperature distribution inside a full-scale room-corridor structure building. A series of experiments and simulations with different fuel properties and fuel configurations (crib and pool fires) were carried out. There was a barrier at the top of the left end of the corridor, and the end wall was on the right side. The fire source was located in the room. The evolution of the smoke spread process, pressure distribution, and temperature distribution in rooms and corridors were obtained and analyzed. The results indicate that the barrier and the end wall hinder the smoke spread and make it to accumulate below the corridor ceiling. This causes the smoke layer height of the corridor to be lower than the top of the door, which changes the pressure distribution inside and outside the room and also affects the temperature distribution. Based on the changes of pressure distribution, some correction formulas for the gas flow rate and mass flux at the opening are proposed. Under the effect of the barrier and the end wall, the smoke temperature in the room and the corridor increases. A smoke temperature decaying model along the corridor direction is proposed. Some methods are used and compared to calculate the smoke layer height based on the vertical temperature distribution. The smoke layer height determined by the buoyancy frequency method is most consistent with the experimental observation values.

Measuring the fire growth potential of combustible solids using a cone calorimeter

The fire growth rate of interior linings, furnishings, and construction materials is measured in full-scale fire tests such as the ASTM E84 Steiner Tunnel, the ISO 9705 room fire, and a passenger aircraft fuselage as the flame-spread rate, time-to-flashover, or time to incapacitation, respectively. The results are used to indicate the level of passive fire protection afforded by the combustible material or product in the test without providing any insight into the burning process. These large-scale tests require many square meters of product, are very expensive to conduct, and can exhibit poor repeatability–making them unsuitable for product development, quality control, product surveillance, or regulatory compliance. For this reason, smaller (0.01 m2) samples are tested in bench-scale fire calorimeters under controlled conditions, and these one-dimensional burning histories are correlated with the results of the two- and three-dimensional burning histories in full-scale fire tests by a variety of empirical and semi-empirical fire propagation indices, as well as analytic and computer models specific to the full-scale fire test. The approach described here defines the potential of a material to grow a fire in terms of cone calorimeter data obtained under standard conditions. The fire growth potential, λ (m2/J), is the coupled process of surface flame spread and in-depth burning that is defined as the product of ignitability (1/ E ign) and combustibility (Δ Q/Δ E) obtained from a combustion energy diagram measured in a cone calorimeter at an external radiant energy flux [Formula: see text] (W/m2) above the critical flux for burning, [Formula: see text]. However, the potential for fire growth, λ≡ (1/ Ei gn)(Δ Q/Δ E) is only realized as a hazard when the heat of combustion of the product per unit surface area, Hc (J/m2), is sufficient to grow the fire. The dimensionless fire hazard of a combustible product of thickness b is therefore, Π = λ Hc, while the fire hazard of the component materials is an average over the product thickness, π = Π/ b. The measurement of λ, Π, and π from combustion energy diagrams of heat release Q (J/m2) versus incident energy E (J/m2) is described, as well as a physical basis for a fire growth potential that provides simple analytic forms for λ in terms of the parameters reported in cone calorimeter tests. Experimental data from the literature show that rapid fire growth in full-scale fire tests of combustible materials occurs above a value of Π determined by the severity of the fire test.

Probabilistic Discrete‐Time Models for Spreading Processes in Complex Networks: A Review

AbstractResearch into network dynamics of spreading processes typically employs both discrete and continuous time methodologies. Although each approach offers distinct insights, integrating them can be challenging, particularly when maintaining coherence across different time scales. This review focuses on the Microscopic Markov Chain Approach (MMCA), a probabilistic f ramework originally designed for epidemic modeling. MMCA uses discrete dynamics to compute the probabilities of individuals transitioning between epidemiological states. By treating each time step—usually a day—as a discrete event, the approach captures multiple concurrent changes within this time frame. The approach allows to estimate the likelihood of individuals or populations being in specific states, which correspond to distinct epidemiological compartments. This review synthesizes key findings from the application of this approach, providing a comprehensive overview of its utility in understanding epidemic spread.

Characteristics of concurrent flame spread over convex charring materials

In real forest fire scenarios, there are a large number of convex and concave terrains at the junction of flat land and slopes. In this paper, a typical charring material, kraft paper, is selected as the experimental sample, and the variation law of key characteristic parameters of flame spread over convex solid surface are investigated. The experimental results show that all the flame spread processes have obvious deceleration behaviors, and the influence mechanism of flame tangent angle on the flame spread deceleration of convex surfaces is revealed. The characteristic length of the pyrolysis zone shows a tendency of increasing and then decreasing with time. The variation curves of radiant heat flux present two peaks. Combining with the characteristic length, the reason for the occurrence of two peaks is explained. The exponential relationship between the instantaneous mass loss rate and the characteristic length of the pyrolysis zone is obtained. Based on the range of power exponents, the heat transfer controlling mechanism in the pyrolysis zone is classified into three categories for all the working conditions. Moreover, a piecewise power-law relationship between the dimensionless maximum flame height and the dimensionless heat release rate is established. The results of this study will fill the research gap of flame spread of solid materials with curved surfaces, and will be of great academic value for the improvement and development of theories on building and forest fire safety.

Process optimization of continuous aramid fiber reinforced PA12 filaments and printed composites

AbstractA multi‐stage fiber spreading process for the preparation of high‐performance continuous aramid fiber reinforced nylon 12 (CAF/PA12) composites was proposed in this paper. The effects of spreading rod crown radius, spreading rod axis height and traction speed on fiber impregnation effect and filaments properties were investigated. The fiber volume fraction of the prepared filament was approximately 30%. And the maximum tensile strength and modulus of the filaments were 839.89 MPa and 41.35 GPa, which were 34.36% and 34.30% higher than unspreading filaments, respectively. The influences of printing process parameters such as printing temperature, the combination of layer thickness and printing spacing on the transverse tensile properties of the specimens were studied. Printed specimens reached a transverse tensile strength and tensile modulus of 13.988 MPa and 1.293 GPa, respectively. The influences on low velocity impact properties of the specimens were also investigated in terms of impact energy and printing stacking sequences. Results revealed that the impact threshold energy of orthotropic ([0/90/0/90]2) specimens was 50 J. Quasi‐isotropic ([0/45/90/−45]2) specimens exhibited the superior impact resistance with an impact load of 4.939 kN. Macro‐ and micro‐matrix crack, surface buckling, fiber fracture and delamination were the main failure modes of the specimens.Highlights A novel thermoplastic composite filament forming process was proposed, and the filament forming equipment was designed and manufactured. Continuous aramid fiber‐reinforced PA12 filaments with about 30% fiber content were prepared by orthogonal tests under different forming process conditions, which showed maximum tensile properties of 839.89 MPa and 41.35 GPa, respectively. Spreading multiplication was positively related to filament tensile properties, which was major affected by the axial height of the spreading rod. Transverse tensile strength (13.988 MPa tensile strength and 1.293 GPa tensile modulus) of printed specimens was investigated under different printing parameters. Fiber orientation had a significant effect on the low‐velocity impact properties. Micro‐ and macro‐matrix crack, surface buckling, fiber fracture and delamination were the main failure modes of the low‐velocity impact specimens.

EVALUASI TEKNIS KONSEP PADA DESAIN ALAT PENEBAR PUPUK BUTIRAN

The technique of spreading fertilizer on rice plants is an important part of equalizing land fertility. In general, farmers use their hands to spread granular fertilizer. The spreading process results in an irregular distribution of fertilizer and also takes a relatively long time. The aim of this research is to design a granular fertilizer spreader based on a technical evaluation of the concept. The Pahl and Beitz design method became a theoretical reference in finalizing the design of the granular fertilizer spreader form. Working drawings are prepared based on ISO standards using Solidwork 2018 software. Based on the results of the technical evaluation of the concept, the design of the granular fertilizer spreader is composed of thirty-three constituent components.

Premixed calcium silicate-based ceramic sealers promote osteogenic/cementogenic differentiation of human periodontal ligament stem cells: A microscopy study.

To evaluate the effects of premixed calcium silicate based ceramic sealers on the viability and osteogenic/cementogenic differentiation of human periodontal ligament stem cells (hPDLSCs). The materials evaluated were TotalFill BC Sealer (TFbc), AH Plus Bioceramic Sealer (AHPbc), and Neosealer Flo (Neo). Standardized discs and 1:1, 1:2, and 1:4 eluates of the tested materials were prepared. The following in vitro experiments were carried out: ion release, cell metabolic activity 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cell migration, immunofluorescence experiment, cell attachment, gene expression, and mineralization assay. Statistical analyses were performed using one-way ANOVA followed by Tukey's post hoc test (p < .05). Increased Ca2+ release was detected in TFbc compared to AHPbc and Neo (*p < .05). Biological assays showed a discrete cell metabolic activity and cell migration in Neo-treated cell, whereas scanning electronic microscopy assay exhibited that TFbc group had a better cell adhesion process of substrate attachment, spreading, and cytoskeleton development on the niche-like structures of the cement than AHPbc and Neo. The sealers tested were able to induce overexpression of the CEMP-1, ALP, and COL1A1 genes in the first days of exposure, particularly in the case of TFbc (***p < .001). All materials tested significantly increased the mineralization of hPDLSCs when compared to the negative control, although more pronounced calcium deposition was observed in the TFbc-treated cells (***p < .001). Our results suggested that TFbc promotes cell differentiation, both by increasing the expression of key osteo/odontogenic genes and by promoting mineralization of the extracellular matrix, whereas this phenomenon was less evident in Neo and AHPbc. RESEARCH HIGHLIGHTS: TFbc group had a better cell adhesion process of substrate attachment, spreading, and cytoskeleton development on the niche-like structures of the cement than AHPbc and Neo. The sealers tested were able to induce overexpression of the CEMP-1, ALP, and COL1A1 genes in the first days of exposure, particularly in the case of TFbc. All materials tested significantly increased the mineralization of hPDLSCs when compared to the negative control, although more pronounced calcium deposition was observed in the TFbc-treated cells.

Numerical simulation of solidification of molten slag impacting inclined wall in boiler based on smoothed particle hydrodynamics method

In order to study the process of high temperature liquid slag impinging on the wall, the slagging phase change is produced by combustion of high alkali coal in a boiler chamber. In this paper, based on the smoothed particle hydrodynamics (SPH) method, the flow spreading and solidification model of slag particles hitting the inclined wall are established, and the dynamic process of flow spreading and the phase change of slag particles hitting the wall are analyzed by simulating the deposition process of the phase change of slag particles hitting the wall. The effects of different inclination angles of the wall on its deformation and solidification heat transfer are further discussed. It is shown that the change of inclination angle during the impact of single slag on the wall has a greater influence on the spreading flow process. During the impact of single/double slag on the wall with different inclination angles, the time taken by the double slag to reach the final spreading length and complete phase transition is nearly five times longer than that of the single slag. The direction of slag impact also has an effect on the spreading and phase transition. This SPH method provides a novel numerical simulation idea to study the kinetic behavior of molten slag hitting the wall and the problems related to phase change deposition in boilers.

Multilevel Visual Analysis of Aggregate Geo-Networks.

Numerous patterns found in urban phenomena, such as air pollution and human mobility, can be characterized as many directed geospatial networks (geo-networks) that represent spreading processes in urban space. These geo-networks can be analyzed from multiple levels, ranging from the macro-level of summarizing all geo-networks, meso-level of comparing or summarizing parts of geo-networks, and micro-level of inspecting individual geo-networks. Most of the existing visualizations cannot support multilevel analysis well. These techniques work by: 1) showing geo-networks separately with multiple maps leads to heavy context switching costs between different maps; 2) summarizing all geo-networks into a single network can lead to the loss of individual information; 3) drawing all geo-networks onto one map might suffer from the visual scalability issue in distinguishing individual geo-networks. In this study, we propose GeoNetverse, a novel visualization technique for analyzing aggregate geo-networks from multiple levels. Inspired by metro maps, GeoNetverse balances the overview and details of the geo-networks by placing the edges shared between geo-networks in a stacked manner. To enhance the visual scalability, GeoNetverse incorporates a level-of-detail rendering, a progressive crossing minimization, and a coloring technique. A set of evaluations was conducted to evaluate GeoNetverse from multiple perspectives.

Time series modeling and forecasting of epidemic spreading processes using deep transfer learning

Traditional data-driven methods for modeling and predicting epidemic spreading typically operate in an independent and identically distributed setting. However, epidemic spreading on complex networks exhibits significant heterogeneity across different phases, regions, and viruses, indicating that epidemic time series may not be independent and identically distributed due to temporal and spatial variations. In this article, a novel deep transfer learning method integrating convolutional neural networks (CNNs) and bi-directional long short-term memory (BiLSTM) networks is proposed to model and forecast epidemics with heterogeneous data. The proposed method combines a CNN-based layer for local feature extraction, a BiLSTM-based layer for temporal analysis, and a fully connected layer for prediction, and employs transfer learning to enhance the generalization ability of the CNN-BiLSTM model. To improve prediction performance, hyperparameter tuning is conducted using particle swarm optimization during model training. Finally, we adopt the proposed approach to characterize the spatio-temporal spreading dynamics of COVID-19 and infer the pathological heterogeneity among epidemics of severe acute respiratory syndrome (SARS), influenza A (H1N1), and COVID-19. The comprehensive results demonstrate the effectiveness of the proposed approach in exploring the spatiotemporal variations in the spread of epidemics and characterizing the epidemiological features of different viruses. Moreover, the proposed method can significantly reduce modeling and predicting errors in epidemic spread to some extent.

Characterizing pedestrian contact interaction trajectories to understand spreading risk in human crowds

A spreading process can be observed when particular information, substances, or diseases spread through a population over time in social and biological systems. It is widely believed that contact interactions among individual entities play an essential role in the spreading process. Although contact interactions are often influenced by geometrical conditions, little attention has been paid to understand their effects, especially on contact duration among pedestrians. To examine how the pedestrian flow setups affect contact duration distribution, we have analyzed trajectories of pedestrians in contact interactions collected from pedestrian flow experiments of uni-, bi- and multi-directional setups. Based on turning angle entropy and efficiency, we have classified the type of motion observed in the contact interactions. We have found that the majority of contact interactions in the unidirectional flow setup can be categorized as confined motion, hinting at the possibility of long-lived contact duration. However, ballistic motion is more frequently observed in the other flow conditions, yielding frequent, brief contact interactions. Our results demonstrate that observing more confined motions is likely associated with the increase of parallel contact interactions regardless of pedestrian flow setups. This study highlights that the confined motions tend to yield longer contact duration, suggesting that the infectious disease transmission risk would be considerable even for low transmissibility. These results have important implications for crowd management in the context of minimizing spreading risk.This work is an extended version of Kwak et al. (2023) presented at the 2023 International Conference on Computational Science (ICCS).

Effect of the paste spreadability on ultrasonic transducer fabricated by pressureless sintering of nano-Ag

Paste spreadability is critical to paste spread layer and thus the quality of final product in pressureless sintering of nano-Ag, but the metrics and the underlying mechanics have not yet been well acknowledged. In this work, various ultrasonic transducers are fabricated by pressureless sintering of various nano-Ag pastes. Particle dynamics mechanism during the paste spreading process and the relationship between paste viscosity and spreadability are clarified. The influences of paste spreadability on dynamic performances of transducer are analysed, and the underlying mechanisms are also investigated. The results show that the normalized mass of Ag NPs is basically positively correlated with the flatness of the coupling layer, and the flatness of the coupling layer is also positively correlated with the peak-to-peak voltage and SNR of the transducer. The attenuation in the far-field scattering process mainly depends on the porosity of the coupling layer.

Infection patterns in simple and complex contagion processes on networks.

Contagion processes, representing the spread of infectious diseases, information, or social behaviors, are often schematized as taking place on networks, which encode for instance the interactions between individuals. The impact of the network structure on spreading process has been widely investigated, but not the reverse question: do different processes unfolding on a given network lead to different infection patterns? How do the infection patterns depend on a model's parameters or on the nature of the contagion processes? Here we address this issue by investigating the infection patterns for a variety of models. In simple contagion processes, where contagion events involve one connection at a time, we find that the infection patterns are extremely robust across models and parameters. In complex contagion models instead, in which multiple interactions are needed for a contagion event, non-trivial dependencies on models parameters emerge, as the infection pattern depends on the interplay between pairwise and group contagions. In models involving threshold mechanisms moreover, slight parameter changes can significantly impact the spreading paths. Our results show that it is possible to study crucial features of a spread from schematized models, and inform us on the variations between spreading patterns in processes of different nature.

Ring-shaped colloidal patterns on saline water films

HypothesisElectrostatically stabilised colloidal particles destabilise when brought into contact with cations causing the particles to aggregate in clusters. When a drop with stabilised colloidal partices is deposited on a liquid film containing cations the delicate balance between the fluid-mechanical and physicochemical properties of the system governs the spreading dynamics and formation of colloidal particle clusters. ExperimentsHigh-speed imaging and digital holographic microscopy were used to characterise the spreading process. FindingsWe reveal that a spreading colloidal drop evolves into a ring-shaped pattern after it is deposited on a thin saline water film. Clustered colloidal particles aggregate into larger trapezoidally-shaped ‘supraclusters’. Using a simple model we show that the trapezoidal shape of the supraclusters is determined by the transition from inertial spreading dynamics to Marangoni flow. These results may be of interest to applications such as wet-on-wet inkjet printing, where particle destabilisation and hydrodynamic flow coexist.

Geochemical constraints on ridge-plume interaction in the West Philippine Basin

The West Philippine Basin is not only a back-arc basin resulting from the subduction of the paleo-plates, but it has also undergone modification due to intraplate processes. However, the interaction between intraplate processes and back-arc spreading processes remains unclear. In this study, we present geochemical compositions of basaltic lavas from various tectonic sites in the West Philippine Basin. Lavas from the Benham Rise and its adjacent seamount, as well as basement crust samples from the West Philippine Basin, are similar to oceanic island basalts and mid-oceanic ridge basalts, respectively. The lavas from the Central Basin Fault lie between the two aforementioned types. Based on the mixing modeling of geochemical data, morphological structure of the West Philippine Basin, and age data for lavas, we developed a conceptual model for the three-stage tectonic evolution, with the simultaneous influence of back-arc spreading and mantle plume processes.