Time Spread Research Articles

Leather Solid Waste–Derived Collagen Polypeptide Based Foam for the Sustainable and Clean Production of Foam‐Based Extinguishing Agents

AbstractHerein, a novel leather solid waste–derived collagen polypeptide (CP)–based foam (CF) is developed with good chemical stability, good degradability, considerably poor metal corrosive properties, and high‐efficiency fire‐extinguishing properties. The developed CP is used as a raw material to obtain CF via free‐radical emulsion polymerization using maleic anhydride and oleic acrylic resins. Thereafter, a foam‐based extinguishing agent (FP) with ideal flame retardant properties is synthesized by blending the obtained CF with common and fluorine‐containing (sodium perfluoro nonyloxybenzenesulfonate) surfactants. The prepared materials are characterized using Fourier‐transform infrared spectroscopy, X‐ray diffraction, fire‐extinguishing effect, and other analytical techniques. Results show that the synthesized FP exhibited good thermal and chemical stabilities as well as considerably low cytotoxicity and biotoxicity. A spreading test and preliminary fire‐extinguishing test on an oil surface indicated that the FP has a relatively high spreading speed and good air‐insulation performance. In particular, compared with that of a traditional extinguishing agent, the full spreading time of 7‐FP is 40% lower, with the total extinguishing time being 28 s. Overall, the results suggested that the prepared CP materials are effective extinguishing agents and may have notable value in various fireproofing applications.

The radial spreading of volcanic umbrella clouds deduced from satellite measurements

Analysis of thermal infrared satellite measurements of umbrella clouds generated by volcanic eruptions suggests that asymptotic gravity current models of the temporal (t) radial (r) spreading (r ~tf, f < 1) of the umbrella-shaped intrusion do not adequately explain the observations. Umbrella clouds from 13 volcanic eruptions are studied using satellite data that have spatial resolutions of ~4–25 km2 and temporal resolutions of 1–60 minutes. The umbrella cloud morphology is evaluated using digital image processing tools in a Lagrangian frame of reference. At the onset of neutral buoyancy, the radial spreading is better explained by a stronger dependence on time of r ~ t, rather than t2/3, t3/4, or t2/9. This flow regime exists on the order of minutes and has not been observed previously in satellite data. This may be of significance as it provides a means to rapidly (within the first 2–3 observations) determine the volumetric eruption rate. A hyperbolic tangent model, r ~ tanh(t) is presented that matches the entire radial spreading time history and has a conserved torus-shaped volume in which the intrusion depth is proportional to sech(t). This model also predicts the observed radial velocities. The data and the model estimates of the volumetric flow rate for the 15 January 2022 Hunga eruption are found to be 3.6–5 × 1011 m3s−1, the largest ever measured.

Sparse Code Multiple Access With Time Spreading and Repetitive Transmissions

ABSTRACTFor the next‐generation communication systems, to improve spectral efficiency and increase the data rate, new multiple access techniques have been investigated. Orthogonal multiple access techniques are widely used in traditional communication systems while nonorthogonal multiple access (NOMA), proposed in 5G, has been a promising technology for satisfying the demand for future wireless communication networks. Sparse code multiple access (SCMA) is a code‐domain NOMA method that provides diversity gain with signal constellation coding. However, to increase the performance of SCMA, there are only limited works provided in the literature in terms of codebook design and receiver design. In this paper, a new multiple‐access model is proposed by applying various diversity techniques for downlink SCMA. The performance of the proposed model is evaluated with both computer simulations and theoretical analysis. Results show that the proposed model provides a 1.6 dB gain in terms of the bit error rate (BER) under the Rayleigh fading channel.

Insights on film and TV series analysis in sociology in times of digital media spread

This article aims to combine research agendas on Digital Sociology and the Sociology of cinema, explicitly considering the spread of Serial TV Shows on streaming platforms such as Netflix and HBO-Max. Since the early 2000s, with Web 2.0 allowing a shift in the traffic and consumption of multimedia–music, photos, videos, and animation– on the Internet, the presence of audiovisual content in everyday life has become more intensified than before with cinema and broadcast television. It is argued in this paper that this technological shift changes how societies and individuals relate to electronically mediated images and constitute symbolic and valuation references through social life. However, much of the cultural and imagistic references set in motion in present digital media were established by cinema and television currently in the 20th century, being seen in a naturalized way, although historically produced. This paper reviews Pierre Sorlín’s sociological approach to films as ideological productions, contributing to form historical and social shared ways of conceiving reality, and Sorlin’s methodological guidelines for analyzing films. However, the differences between cinema and television series are considered, according to Esquenazi’s approach to TV series. Nevertheless, this paper highlights how technical and cultural specificities of today’s digital media, paired with a deep individualization process, set new analytical challenges. So, it is presented an analytical reflection that places together connectivity and cinematic culture in order to comprehend how today’s ideologies are partly influenced by specific recurrent imagistic constructions diffused by streaming platforms by using cinema and television languages.

Bias in mobility datasets drives divergence in modeled outbreak dynamics

BackgroundDigital data sources such as mobile phone call detail records (CDRs) are increasingly being used to estimate population mobility fluxes and to predict the spatiotemporal dynamics of infectious disease outbreaks. Differences in mobile phone operators’ geographic coverage, however, may result in biased mobility estimates.MethodsWe leverage a unique dataset consisting of CDRs from three mobile phone operators in Bangladesh and digital trace data from Meta’s Data for Good program to compare mobility patterns across these sources. We use a metapopulation model to compare the sources’ effects on simulated outbreak trajectories, and compare results with a benchmark model with data from all three operators, representing around 100 million subscribers across the country.ResultsWe show that mobility sources can vary significantly in their coverage of travel routes and geographic mobility patterns. Differences in projected outbreak dynamics are more pronounced at finer spatial scales, especially if the outbreak is seeded in smaller and/or geographically isolated regions. In some instances, a simple diffusion (gravity) model was better able to capture the timing and spatial spread of the outbreak compared to the sparser mobility sources.ConclusionsOur results highlight the potential biases in predicted outbreak dynamics from a metapopulation model parameterized with non-population representative data, and the limits to the generalizability of models built on these types of novel human behavioral data.

Radiation and Scattering of Massive Photons

With the aid of a modified Planck’s law for massive photons, it is shown that the ratio of the mean value of the photon mass equivalent to its rest (invariant) mass tends to be one with a decrease in temperature. A modified Stefan - Boltzmann law is obtained at different temperature regimes, as well as the Wien’s displacement law. At high temperatures the modified Planck’ s law approaches the standard Planck’ s law. It is also shown that the cross-section of the Thomson scattering slightly increases opacity of the scattering medium. The Compton shift in frequency for a massive photon appears to be frequency-dependent and slightly less than its value for a massless photon, except in the case of forward scattering when no change in frequency takes place. Astrophysical aspects of the massive photon hypothesis are discussed with regard to standard stellar models, early stages of the Universe, and the Breit-Weeler process, as well as active galactic nuclei. Estimates of the spreading time of the wave packet of the massive photon show that for frequencies ν ≥ 4.052 × 109Hz(λ ≤ 7.4) it exceeds the age of the Universe.

Enhancing reliability with MIMO aided dual iterations for mobile video transmission system

AbstractFuturistic requirements of mobile communication systems ask for discovering new possibilities and dimensions to enable ultrafast and reliable communication. This work relates to the advancements in jointly decoded iterative multimedia communication systems for the H.264 source standard. The beneficial technique of Over-Complete Mapping (OCM) is utilized for introducing redundancy in the highly compressed source encoded video streams. Differential Space–Time Spreading (DSTS) is invoked along with Rate-3/4 Recursive Systematic Convolutional (RSC) as intermediate encoder in the proposed three-stage setup. More specifically, the RSC encoder is beneficial in attaining the iterative gain as it divides the decoder into two parts. The DSTS is invoked with the Sphere Packing (SP) modulation which is highly desirable for the non-coherent detection schemes without requiring any information from the channel. The proposed system comprises of three main components, namely OCM, Rate-3/4 RSC and SP modules, thus we call this as three-stage system. The iterative decoding enhances the Bit-Error Rate (BER) and Peak Signal-to-Noise Ratio (PSNR) performances of the joint source-channel systems. Furthermore, to expeditiously predict the convergence pattern of the proposed three-stage iteratively decoded systems, EXtrinsic Information Transfer (EXIT) chart analysis is performed. Moreover, the effect of variations in the minimum Hamming distance ($${d}_{H,min}$$ d H , m i n ) is observed for the proposed three-stage system. The $${{DSTS}-{SP}-{RSC}-{OCM}}_{[5 15]}$$ DSTS - SP - RSC - OCM [ 515 ] having $${d}_{H,min}=6$$ d H , m i n = 6 exhibits a gain of 20 dB against the benchmarker $${{DSTS}-{SP}-{RSC}-{OCM}}_{[2 6]}^{*}$$ DSTS - SP - RSC - OCM [ 26 ] ∗ with $${d}_{H,min}=1$$ d H , m i n = 1 at the PSNR degradation point of 1 dB over a correlated Rayleigh fading channel.

Optimal Timing for Safe Bivalving of Fiberglass Casts Is Before the Exothermic Peak.

Cast saw injury is a notable source of medicolegal risk. Previous work with plaster casts demonstrated that cast saw injury was minimized by waiting 12 minutes before removal. In this study, we evaluate the safety parameters of fiberglass casting materials. Eight-ply plaster and fiberglass casts were applied to a pediatric forearm model at variable dip-water temperatures, and the mean time to reach their exothermic peak was determined. Fiberglass casts were then maintained at the manufacturer's recommended dip-water temperature and removed at intervals of 2 (before exothermic peak), 6 (approximately fiberglass's exothermic peak), or 12 (after exothermic peak) minutes. All casts were removed by a pediatric orthopaedic surgeon blinded to the cast set time. Cast/blade temperature, saw force, blade-to-skin contact, bivalve time, cast spreading force, and cut completeness were assessed individually and as short (<6-minutes) or long (≥6-minutes) set times. Fiberglass casts exothermically peaked markedly earlier (5.2 [IQR = 5-5.4] minutes) than plaster (14.8 [IQR=13.7-15.3] minutes), P < 0.0001, at maximum temperatures, which did not markedly differ. Downward force applied during fiberglass cast removal was markedly lower in the short versus long set time groups [average forces of 8.3 (IQR=6.4-10.4) versus 12.9 (IQR=11.1-14.5) Newtons, P < 0.0001, as were maximum forces: 23.2 (IQR=18.9-26.6) versus 43.8 (IQR=38.6-48.5) Newtons, P < 0.0001]. Bivalve time and maximum cast spreading force were decreased in short set times with 40.5 (IQR=39.2-44.7) versus 44.4 (IQR=40.6-47.3) seconds (P = 0.06) and 15.5 (IQR=14-18.5) versus 21.5 (IQR=18-26.5) N (P = 0.07), respectively. Maximum saw blade temperature was markedly lower in the short (99.6°C [IQR=98.2-105.6°C]) versus long (130.6°C [IQR=121.9-141°C]) set times (P = 0.04). No notable differences in blade-to-skin touches or touch duration were detected. Unlike plaster, fiberglass casts cut before exothermically peaking were associated with less downward force, faster bivalve times, and decreased spread force without increased blade temperature or skin contacts. This suggests that fiberglass casts can be bivalved markedly earlier without increased risk of injury.

Paleoindian, East Asian and Siberian components of the Eskimo oral traditions

The possibility to use analytical units extracted from traditional narratives for the study of prehistoric migrations and contacts follows from the works of Franz Boas published bet­ween 1895 and 1915. In the 1920s, the priorities of American anthropology changed, so the folklore studies missed the opportunity to become a tool of historic research. Here we try to advance a project abandoned a hundred years ago. Our database consists of more than 80,000 abstracts of texts from all over the world and helps to determine the approximate time of spread of narrative episodes and mythological ideas. The study analyzes the parallels between the narrative motives of the Eskimo and motives collected outside of the Arctic. Since the Paleo-Eskimo are associated with the Denbigh flint complex, which appeared in Alaska about 3000 BC and, which is usually believed to descend from the Eas­tern Siberian Belkachi culture, it can be assumed that Siberian links must prevail in the narratives of the Eskimo. Instead, parallels for those episodes and images that typical for the Arctic are found mostly in South America. Apparently, these motives appeared in the New World during its initial peopling around 15,000 cal. BC. The narrative analogies between the Arctic and the East Asia are less numerous and some of them are also found in South American traditions. The American parallels in Siberia are widespread among the Indians but not among the Eskimo. To date, only one episode of Eskimo tales with definite Siberian roots, namely “The Blind Hunter”, has been identified. Though possibly related to the Belkachi tradition, this motif is also typical for the Indians of the North American Northwest, one case recorded in South America. The Eskimo version is slightly different from the main one. It probably split from it in Alaska and was brought to Canada and Greenland by the Paleo-Eskimo or by the Inuit. The Eskimo oral traditions emerged in Alaska and in major part go back not to the Siberian language ancestors of the Eskimo and Aleuts but to the local substratum.

The influence of microgrooves on the dynamics of drop spreading on textured surfaces

In years of intensive development of electronic and microelectronic equipment, the problem of ensuring the scheduled thermal mode of both individual elements of such equipment and large-sized products, such as data storage databases, has become increasingly acute. Therefore, researchers from many countries are currently making active attempts to develop new systems for ensuring scheduled operating modes of electronic computer elements. One of the options for solving this problem is the drop cooling of surfaces of electronic and microelectronic equipment heated to high temperatures. This technology involves the formation of a cluster on the heat-removal surface of highly loaded computer elements. This allows extreme heat fluxes to be removed through phase change. However, despite a fairly large volume of research on this topic, there are still many unsolved problems in this area of knowledge. For example, the parameters (deposition height, drop feed rate, etc.) of water drop deposition on the surface of substrates used for cooling have not been determined yet. Moreover, the efficiency of drop cooling increases if the surface from which heat is removed is modified (roughness is formed). However, the patterns of spreading and evaporation of coolant drops on rough surfaces have not been sufficiently studied yet. Therefore, the aim of the work was to establish, based on the results of the experiments, the scale of the influence of the fall height of water drops on the characteristics and conditions of their spreading on a textured and polished surface. The paper presents the experimental results of the process of water drop impact on a textured surface. The main characteristics of a liquid drop spreading over a textured surface have been investigated. To establish the characteristics and conditions of spreading (drop spreading speed and time, drop shape stabilization time), typical shapes (in the midsection) of a drop spreading over the surface have been established. It is shown that the characteristic time of formation of the equilibrium state of the “water drop – substrate” system is no more than 0.1 s. This is significantly less than the drop evaporation time, even on high-temperature surfaces. The effect of surface anisotropy on the characteristics and conditions of spreading has been analyzed. It is shown that when water moves across the grooves, drop spreading is higher than along the grooves. A hypothesis has been developed to describe this effect.

Constraining of homogenized information on online spreading

The spread of homogenized information on social networks can create certain positive promotional effects. However, if it is excessively spread, it may lead to constraining effects and even cause negative impacts. In this paper, a spreading model called C-SIRI is proposed, which conducts an in-depth study on the constraining mechanism in the process of information spreading, as well as the rules and characteristics affecting its impact. Taking the COVID-19 epidemic information spreading on Sina Weibo social network from March 2020 to May 2022 as an example, the reliability of this model is verified. The results show that content homogeneity, participation degree and false proportion have a significant influence on the constraining mechanism of social network information spreading, and the threshold of information spreading constraining is closely related to the spreading times. This research helps to understand the role of constraining mechanism in information spreading and promote the application of social networks in information spreading prediction and control.

Impact of spreading time on flavor quality in Duyun Maojian summer green tea

Duyun Maojian (DYMJ) is a prestigious green tea in China. The summer tea has higher tea polyphenols contents than spring tea, which reduces the green tea flavor quality and limits utilization of summer tea. Spreading is an important technology for optimizing tea quality, but its effect on DYMJ summer green tea is still unclear. In this study, we employed transcriptomics and volatile metabolomics to investigate the effect of spreading times (0, 1, 2, 3, 4, 5, 6, 7 h) on the flavor quality of DYMJ summer green tea. Sensory evaluation showed that the best taste was obtained at 4 h of spreading time. All indexes of main taste compounds reached peaking within 3–5 h (except for catechin). At 3–5 h of spreading time, important aromatic compounds with distinct floral and fruity flavors (such as phenylethanol, geraniol and cis-jasmone) were highest. Correlation analysis showed that there was a significant relationship between the main taste components and the tea aroma. In addition, transcriptomic analysis suggests that pathways related to hormone signaling and flavonoid biosynthesis in tea plants may play a key role in tea spreading. This study provides a theoretical framework for the processing of DYMJ summer green tea.

Research on the Dynamic Spreading and Wettability Characteristics of Droplets on Coal Dust.

The dynamics of droplets spreading on surfaces have been extensively studied across various influencing factors, necessitating an exploration of their effect on wettability. Herein, the specific composition, size distribution, and contact angle of the coal dust preparation were characterized by a series of experiments to determine the conditions for the simulation. Meanwhile, the multiphase volume of the fluid method was implemented in the simulations, predicated on appropriate boundary conditions, and verified by a mesh independence test. The findings confirmed that the numerical approach for contact angle validation had a minor deviation, making it suitable for multiphase interface tracking. Besides, the typical wetting pattern of droplets was hereby identified into three stages, including the moving stage (stage I), the periodic wetting stage (stage II), and the balancing stage (stage III). The initial diameter could effectively increase the coverage area and spreading time for stage II. Obviously, the first amplitude of first maximum spreading diameter (D max-1) significantly increased with higher impact velocities, corresponding to an increase in kinetic energy. Despite the significant spreading effect of the falling height mainly on D max-1 and contact time, the increased trend of wetting efficiency was not obvious. However, the spreading factor and wetting efficiency decreased with increased roughness height. Finally, the difference in spreading wettability was illustrated based on the spreading wetting mechanism. The wetting efficiency of droplets on coal dust was remarkably influenced by the dynamic spreading behaviors of droplets. Overall, the findings from this study offer insights into the extent of spreading wetting that occurs before a droplet reaches an equilibrium state.

Modeling the interaction between wildfires and windthrows: A pilot case study for Italian Alps

Wildland fires and windthrows represent relevant disturbances for forest ecosystems worldwide. In this context, especially for Italian catchments, the interaction between windthrows and changes in wildfire behaviour starting from ALS data processing is scarcely investigated. Therefore, this research aims to compute a multi-temporal analysis of the interaction between windthrows and wildfire behaviour in a forested area (Veneto region, northern Italy), recently affected by the renamed Vaia windstorm. The semi-empirical FlamMap model was applied, starting from ALS data processing implemented in R for mapping the spatial distribution of forest attributes and fuels within the catchment. The role of windthrows in altering wildfire behaviour was investigated considering ALS point clouds acquired before and after the occurrence of the storm Vaia. Digital Terrain Models (DTMs), Canopy Height Models (CHMs), topographic data and metrics describing forest structure were extracted from ALS data for both scenarios at 5 m resolution, to compare changes in wildfire behaviour over time. Differences in Rate of Spread (RoS), flame length (FL), midflame windspeed (WS) and arrival time (AT) were assessed, and their correlation with windstorm damages was investigated at the catchment detail. , An increase of RoS, FL, and WS greater than 30 m/min, 3 m and 1.1 m/s were respectively estimated in windthrown areas, as well as a decrease of AT greater than 30 min, attesting the key role of windthrows in altering wildfire behaviour over time. The correlation between windthrows and changes in wildfire attributes was finally modeled by computing regression analysis, with R2 of 0.86, 0.93, 0.62, and 0.91 resulted for RoS, FL, WS and AT. This research represents a pilot case study for better detecting changes in wildfires behaviour due to windthrows occurrence, therefore proposing and carrying out effective planning and management strategies for disturbed forest stands over time.

Position-independent product increase rate in a shaker mill revealed by position-resolved in situ synchrotron powder X-ray diffraction

We investigated the position and time dependence of a mechanochemical reaction induced by ball milling using in situ synchrotron powder X-ray diffraction with changing X-ray irradiation position. The mechanochemical reduction of AgCl with Cu was monitored in situ with the X-rays incident at two different vertical positions on the jar. Our previously developed multi-distance Rietveld method was applied to analyze the in situ diffraction data with a 1 min resolution. Both the vertical and the horizontal sample positions were determined using the sample-to-detector distances from the in situ data. Position dependence was found in the powder spreading and induction time. We reveal that the increase rate of the product is independent of the sample position when measured with a 1 min time resolution, confirming the validity of in situ monitoring of part of the space in a milling jar for a gradual mechanochemical reaction.

New insights into impact-induced removal of the deposited droplet

This paper presents a comprehensive investigation into the collision dynamics of equal and unequal-sized nanodroplets on a flat surface using molecular dynamics simulations, revealing new insights into scaling laws and energy dissipation mechanisms. The simulations, conducted with the Large-Scale Atomic/Molecular Massively Parallel Simulator software, involved an initially stationary droplet on the surface and a suspended droplet with varying diameter ratios (λ) and impact velocities. The results show that at low Weber numbers (We &amp;lt; 24.15), the droplets tend to deposit after impact, while at higher Weber numbers (We ≥ 24.15), they undergo spreading and retraction, ultimately rebounding. The study reveals that the dimensionless contact time (t*) and maximum spreading factor (βmax*) in collisions between droplets of different sizes do not follow the same scaling relationship observed in single nanodroplet impacts. By redefining the Weber and Reynolds numbers (Re), the new scaling relationships t* ∼ We2/3Re−1/3λ−1/3 and βmax* ∼ We2/3Re−1/3λ−1/3 are proposed and validated. This work represents a further in-depth study of previous research on single nanodroplet impact, introducing for the first time the diameter ratio in unequal droplet impacts into the variation patterns of contact time and maximum spreading diameter. Moreover, these findings highlight the importance of revisiting and potentially revising classical theories to accommodate the unique physical phenomena that emerge at smaller scales.

Binary collision dynamics of immiscible Newtonian and non-Newtonian fluid droplets

This experimental and theoretical study is devoted to the investigation of head-on collisions of two immiscible Newtonian and non-Newtonian droplets. The density of the two droplets is similar, and the viscosity of 0.3% carboxymethyl cellulose droplet is slightly larger than 10 cSt silicone oil. The sizes and relative velocity of the colliding droplets close to the point of impact are measured by means of image processing. The deformed states after the impact and their evolution with time are studied by experimental visualization and the energy evolution with time are discussed by numerical results. The accuracy of the two-dimensional axisymmetric three-phase flow computational model is validated. We study the effects of collisions of non-Newtonian droplets with Newtonian droplets and the subsequent retraction kinetics. Droplet “cannibalization” is commonly observed: after collision and spreading, the droplet retracts rapidly, resulting in a Newtonian droplet wrapping around a non-Newtonian droplet. We show the whole process of droplet collision captured by a high-speed camera and obtain the cloud and velocity vector maps of the droplets by numerical simulation. The droplet wrapping phenomenon is produced by different three-phase interfacial tensions and viscosities. We delineate the different phases of the collision process and discuss the dominant forces in each phase. We calculate the energy evolution of the spreading phase and use it to derive a predictive model for the dimensionless maximum spreading diameter and spreading time.

Probing the contact time of droplet impacts: From the Hertz collision to oscillation regimes.

Droplet rebound on nonwetting surfaces is a common phenomenon. However, the underlying physics regulating the contact time remains unclear. In this work, we investigate droplet impacts on superamphiphobic surfaces through experiments and theoretical analyses. By analyzing the spreading and retraction of droplet impinging processes over a wide range of Weber numbers (We), it is revealed that droplet impacts experience three regimes as We is varied, which are denoted as the Hertz collision (We<1), transition (1<We<10), and oscillation (We>10) regimes. In the Hertz collision regime, the droplet impinging process is temporally symmetric, i.e., the spreading time, t_{S}, and the retraction time, t_{R}, are almost the same. Furthermore, t_{S} and t_{R} decrease with increasing We and follow a power-law dependence, which is different from previous theories. In the transition regime, t_{S} remains dominated by the Hertz collision, while t_{R} is governed by droplet oscillation. In the oscillation regime, t_{S}, t_{R}, and the total contact time, t_{C}, become independent of We. These three regimes are valid for both monophase and compound droplets. The findings in this work advance the understanding and offer a clear picture of droplet impact dynamics.

Experimental Investigation of the Combustion Characteristics and Thermal Hazards of Methylsilyl-Modified Silica Aerogels.

The thermal safety of hydrophobic silica aerogels (SAs) is essential to thermal insulation applications. Herein, trimethylchlorosilane (TMCS), dimethyldichlorosilane (DMDCS), and methyltrichlorosilane (MTCS) were employed as surface modifiers to prepare three different methylsilyl-modified SAs (i.e., TSA, DSA, and MSA) and their combustion characteristics and thermal hazards were experimentally studied in detail. The cone calorimeter test found that the three SAs have similar combustion processes and the variations in ignition time and fire spread rate with the heat flux obey simple logarithmic and linear relationships, respectively. It further found that TSA has the most methylsilyl groups on silica skeletons and thus has the largest heat release, followed by DSA and MSA in turn, implying that TSA has the greatest fire hazard among the three SAs. These results further demonstrate that the type and quantity of methylsilyl groups on the skeletons of SAs significantly affect the thermal hazard of methylsilyl-modified SAs. In addition, the combustion mechanism of the methylsilyl-modified SAs is discussed. In total, this work experimentally studies the combustion characteristics of methylsilyl-modified SAs and compares their thermal hazards, clarifying the potential fire risk of methylsilyl-modified SAs in practical thermal insulation applications.

Ultrafast Charge and Exciton Diffusion in Monolayer Films of 9-Armchair Graphene Nanoribbons.

Determining the electronic transport properties of graphene nanoribbons is crucial for assessing their suitability for applications. So far, this has been highly challenging both through experimental and theoretical approaches. This is particularly the case for graphene nanoribbons that are prepared by chemical vapor deposition, which is a scalable and industry-compatible bottom-up growth method that results in closely packed arrays of ribbons with relatively short lengths of a few tens of nanometers. In this study, the experimental technique of spatiotemporal microscopy is applied to study monolayer films of 9-armchair graphene nanoribbons prepared using this growth method, and combined with linear-scaling quantum transport calculations of arrays of thousands of nanoribbons. Both approaches directly resolve electronic spreading in space and time through diffusion and give an initial diffusivity approaching 200 cm2 s-1 during the first picosecond after photoexcitation. This corresponds to a mobility up to 550 cm2 V-1 s-1. The quasi-free carriers then form excitons, which spread with a diffusivity of tens of cm2 s-1. The results indicate that this relatively large charge carrier mobility is the result of electronic transport not being hindered by defects nor inter-ribbon hopping. This confirms their suitability for applications that require efficient electronictransport.