Time Spread Research Articles

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 < 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.

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.

Dynamic characteristics of droplet impact on a cold cylindrical surface

The freezing phenomenon often leads to economic and safety losses in various industries. Studying the processes of droplets impact on cold surfaces is beneficial in preventing potential harm. In this study, the processes of droplet impact on a cold cylindrical surface are investigated by high-speed photography. How the dynamic characteristics are affected by Weber number and surface temperature are studied. The results indicate that when the surface temperature is between −25 to −5 °C, an increase in Weber number results in higher initial kinetic energy and greater viscous dissipation. During the spreading process, the initial kinetic energy predominates, leading to an increase in the maximum spreading ratio. However, the rise in viscous dissipation contributes to an increase in the stable ratio. As Weber number increases, both the maximum spreading time and stable time decrease. Over the same range of surface temperatures, a decrease in surface temperature results in increased viscous dissipation, which leads to a reduction in the maximum spreading ratio. The maximum spreading time and stable time, however, are not significantly affected by surface temperature. Moreover, the relationships of the maximum spreading ratios and stable ratios between axial and circumferential directions are constructed respectively. These relationships exhibit similar linear characteristics, which are not affected by the Weber number and surface temperature.

Spread efficiency of energy demand in the industrial chain: a perspective from economic distance

This paper investigates the spread efficiency of energy demand in the industrial chain based on the input-output method. The concept of intersectoral economic distance and spread efficiency was introduced to formulate the energy demand spread functions. Then, an empirical study was conducted based on China's 2017 input-output data and nearly 3,500 companies were listed in the Chinese A-share market. The results show that the sectoral average spread time is 32.75 days. Manufacturing plays a central role in the spread of energy demand. In the short term, the logistics sector has the greatest pulling effect on energy demand, while the electric power sector has the greatest impact on energy demand in the long term. Energy demand caused by exports is greater than consumption and investment. Finally, sectoral economic distances and actual spread functions for 9 main energy sources are provided to help us better predict energy demand.

Shorten spreading duration enhance the quality of summer Meitan Cuiya tea

Meitan Cuiya (MTCY), a representative green tea from Guizhou, China, may exhibit lower quality in summer due to increased bitterness and astringency. Spreading is a common method to enhance tea quality, but its impact on summer MTCY remains unclear. This study combined transcriptomics and volatile metabolomics to investigate the effects of spreading duration on quality of summer fresh tea leaves and MTCY. Results showed that spreading time shortened to 4 h improved the taste of MTCY, due to lower catechins and higher theanine levels. This duration also yielded woody floral scent in MTCY, marked by high levels of trans-Cubebol, linalool, (Z)-linalool oxide. Transcriptomic analysis linked the 4-h spreading to proteasome activities. Aroma formation was related to diterpenoid and flavonoid biosynthesis. Additionally, gibberellins and auxin were associated with quality formation in fresh tea leaves. This research lays a foundation for improving quality of fresh tea leaves and MTCY in summer.

Effect of Cr, Al and Mo additives on the wetting characteristics of molten Ni on (Ti, Zr, Hf, Nb, Ta)C high entropy ceramics

For the first time, the wetting behavior of the (Ti, Zr, Hf, Nb, Ta)C) high entropy carbide ceramics by molten Ni-based alloys was investigated using a sessile drop technique in a vacuum environment. Adding 10wt% of Cr, Mo, or Al into Ni resulted in final contact angles of 14°, 10°, and 14° on the (Ti, Zr, Hf, Nb, Ta)C substrate, respectively. The interaction mechanism between (Ti, Zr, Hf, Nb, Ta)C and Ni-based alloys occurs in two stages: the dissolution and interaction of the elements Ti, Zr, Hf with the alloys and the dissolution of NbC and TaC at the grain boundaries. SEM observations revealed that Cr and Al additives do not interact with carbides, while Mo was dissolved in carbides. Due to the low contact angle, minimal interaction region between alloy and ceramic, and short time of drop spreading, NiAl alloy is proven to be a promising binder for the HEC-based composites.

A novel quaternary ammonium triethanolamine modified polyester polyether for rapid wetting and penetration pretreatment for digital inkjet dyeing of polyester fabric

Green environmental protection and digitisation are vital for the future development of the textile printing and dyeing industry. Dispersed dye digital inkjet dyeing, as a new technology, enables on-demand low-liquor dyeing and controllable segment dyeing of polyester fabric. This facilitates the transformation, upgrading and sustainable development of the printing and dyeing industry. Due to its inherent hydrophobicity, polyester fabric poses challenges in terms of quick wetting and penetration of ink droplets. To enhance its moisture absorption and rapid wettability, a novel pre-treatment agent, i.e. cationic polyester polyether (CPP), was synthesised via the triethanolamine quaternisation modification of polyester polyether. The wetting and penetration behaviours of ink droplets on the CPP-pre-treated fabric were studied, and the colour performance of CPP-pre-treated dyed fabric was investigated. Results showed that the optimal conditions for CPP synthesis were a DMT to PEG molar ratio of 3:1, a molecular weight of PEG 2000 and a PEG to NAB molar ratio of 1:0.2. At a CPP concentration of 0.3 %o.w.f., the CPP-pre-treated fabric exhibited excellent moisture absorption and rapid wetting with water spreading time of 4 s, wicking height of 9.5 cm/5 min and ink droplet spreading time of 960 ms. Compared with the original inkjet-dyed fabric, the front K/S value of CPP-pre-treated dyed fabric decreased to 17.1 and the back K/S value increased to 16.0. The colour penetration was 93.3 %, which was 13 % higher than that of the original fabric. Thus, CPP pre-treatment of polyester fabric can facilitate complete dyeing of the fabric even within the interior of yarns.

Dilute Polymer Droplets Show Generalized Wetting Dynamics via an Average Viscosity.

Despite the prevalence of non-Newtonian fluids in various practical applications, comprehensive dynamic wetting models are lacking. Existing models often oversimplify complex rheological behavior, limiting our ability to predict wetting dynamics. This work introduces and experimentally validates a generalized model for the dynamic wetting of non-Newtonian shear-thinning fluids (dilute polymer solutions) on solid substrates. We experimentally analyzed 12 different shear-thinning fluids using both a power-law model and Carreau-Yasuda model. The data clearly show that the dynamic contact angle can be generalized using an average viscosity to capture rheological changes during droplet spreading. The average viscosity was defined using the fluid's constitutive model over shear rates relevant to the spreading process. Using a small droplet approximation, we propose and validate a semianalytical spreading model to predict the basal radius of non-Newtonian droplets. The model agrees well with the experimental data. Additionally, the average viscosity was used to define a spreading time scale, which is capable of collapsing the spreading of different non-Newtonian fluids onto a master spreading curve. This work offers significant potential for predicting the dynamic shape and spreading of non-Newtonian fluids with complex rheologies in a range of applications and industrial processes.

Computational Modelling of 2004 Off West Coast of Sumatra Earthquake-Tsunami Wave Propagation Using Two-Dimensional Cellular Automata in the Eastern Indian Coast

ABSTRACT The ability to detect destructive tsunamis and spare lives from serious harm has made the computation of tsunami wave dynamics increasingly important. The tremendous loss of life and property brought on by the 26th of December, 2004 tsunami has raised the demand for accurate and timely propagation of tsunami wave simulations. These days, a variety of early warning technologies and models are utilized to predict tsunami waves. The propagation phase of a tsunami wave is simulated using two-dimensional cellular automata of rectangular lattices in eight directions from this research. Modelling of the Sumatra-Andaman earthquake in 2004 to simulate the propagation of tsunami waves to strike the northern coasts of India. The earliest tsunami arrival time, travel time, and wave spread rate are determined from this study, and the results are verified using historical data.

Operators of quantum theory of Dirac's free field

Abstract The quantum theory of free Dirac's massive fermions is reconstructed around the new conserved spin operator and its corresponding position one proposed initially by Pryce long time ago and re-defined recently with the help of a new spin symmetry and suitable spectral representations. [I. I. Cot\u aescu, Eur. Phys. J. C (2022) 82:1073]. This approach is generalized here associating to any integral operator in configuration representation a pair of integral operators acting directly on particle and antiparticle wave spinors in momentum representation without affecting the mode spinors. This framework allows an effective quantization procedure giving a large set of one-particle operators with physical meaning as the spin and orbital parts of the isometry generators, the Pauli-Lubanski and position operators or other spin-type operators proposed so far. A special attention is paid to the operators which mix the particle and antiparticle sectors whose off-diagonal associated operators have oscillating terms producing Zitterbevegung. The principal operators of this type including the usual coordinate operator are derived here for the first time. As an application, it is shown that an apparatus measuring these new observables may prepare and detect one-particle wave-packets moving uniformly without Zitterbewegung or spin dynamics, spreading in time normally as any other relativistic even non-relativistic wave-packet. Content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Article funded by SCOAP3 and published under licence by Chinese Physical Society and the Institute of High Energy Physics of the Chinese Academy of Science and the Institute of Modern Physics of the Chinese Academy of Sciences and IOP Publishing Ltd.

Nanoscale particle-droplet coalescence-induced jumping on superhydrophobic surfaces: Insights from molecular dynamics simulations

The removal of solid particles from superhydrophobic surfaces via coalescence-induced droplet jumping has gained increasing attention. However, the underlying mechanisms, especially the nanoscale dynamics of particle-droplet coalescence, remain largely underexplored. In our research, we employ molecular dynamics simulations to investigate the influences of the radius, wettability, and arrangement of solid particles on the particle-droplet jumping velocity and energy conversion efficiency. We observe notable rotational motions during the jumping events. Our findings reveal that the arc length of the wetted area on spherical particles and the spreading time of droplets exhibit a power-law relationship. As the particle-to-droplet radius ratio increases, the jumping velocity and energy conversion efficiency initially increase but subsequently decrease. Moreover, enhanced particle wettability leads to an increase in jumping velocity while a slight decrease in translational energy conversion efficiency. The velocities of coalescence-induced particle-droplet jumping at the nanoscale are consistent with predictions from the momentum model. Significantly, our results show that the rotationally symmetric multi-particle arrangements can effectively enhance the jumping velocity and energy conversion efficiency, thus improving particle removal efficiency. Our study not only deepens the understanding of coalescence-induced particle-droplet jumping behaviors, but also provides a foundation for developing more effective particle removal strategies on superhydrophobic surfaces.

Closing the Net on Transient Sources of Ultrahigh-energy Cosmic Rays

The arrival directions of ultrahigh-energy cosmic rays (UHECRs) observed above 4 × 1019 eV provide evidence of localized excesses that are key to identifying their sources. We leverage the 3D matter distribution from optical and infrared surveys as a density model of UHECR sources, which are considered to be transient. Agreement of the sky model with UHECR data imposes constraints on both the emission rate per unit matter and the time spread induced by encountered turbulent magnetic fields. Based on radio measurements of cosmic magnetism, we identify the Local Sheet as the magnetized structure responsible for the kiloyear duration of UHECR bursts for an observer on Earth and find that the turbulence amplitude must be within 0.5–20 nG for a coherence length of 10 kpc. At the same time, the burst-rate density must be above 50 Gpc−3 yr−1 for Local Sheet galaxies to reproduce the UHECR excesses and below 5000 Gpc−3 yr−1 (30,000 Gpc−3 yr−1) for the Milky Way (Local Group galaxies) not to outshine other galaxies. For the transient emissions of protons and nuclei to match the energy spectra of UHECRs, the kinetic energy of the outflows responsible for UHECR acceleration must be below 4 × 1054 erg and above 5 × 1050 erg (2 × 1049 erg) if we consider the Milky Way (or not). The only stellar-sized transients that satisfy both Hillas’ and our criteria are long-duration gamma-ray bursts.

A Platform for Ultra-Fast Proton Probing of Matter in Extreme Conditions.

Recent developments in ultrashort and intense laser systems have enabled the generation of short and brilliant proton sources, which are valuable for studying plasmas under extreme conditions in high-energy-density physics. However, developing sensors for the energy selection, focusing, transport, and detection of these sources remains challenging. This work presents a novel and simple design for an isochronous magnetic selector capable of angular and energy selection of proton sources, significantly reducing temporal spread compared to the current state of the art. The isochronous selector separates the beam based on ion energy, making it a potential component in new energy spectrum sensors for ions. Analytical estimations and Monte Carlo simulations validate the proposed configuration. Due to its low temporal spread, this selector is also useful for studying extreme states of matter, such as proton stopping power in warm dense matter, where short plasma stagnation time (<100 ps) is a critical factor. The proposed selector can also be employed at higher proton energies, achieving final time spreads of a few picoseconds. This has important implications for sensing technologies in the study of coherent energy deposition in biology and medical physics.

Morphological Seed Traits Predict Early Performance of Native Species to Pelletized Seed Enhancement Technologies.

Native seeds are a finite resource, and their inclusion in revegetation is vital for supporting restoration outcomes that are both effective and scalable. Pelletized seed enhancement technologies (SETs) offer a promising solution to improve seed use efficiency in ecological restoration. Yet, knowledge of how diverse suites of native species perform when pelletized is required to optimize the application of SETs to the many species and ecosystems where restoration is required. Using a greenhouse trial of 64 Australian plant species, we assessed species performance to pelleting by evaluating (1) overall species amenability to pelleting based on total emergence and survival and (2) how pelleting modifies the rate of emergence based on average time to emergence, emergence rate index, and time spread of emergence. We investigated the potential for using morphological seed traits (seed endosperm:seed ratio, seed length, seed area, and seed coat thickness) to predict performance outcomes, by identifying traits that may aid in the prediction of species amenability to pelleting and emergence speed when pelletized. We found that some species demonstrate high amenability to pelleting and that pelleting can modify the emergence rates for many species. This work advances our understanding of the applicability of SETs for diverse native species, demonstrating the application of such technologies for meeting ecological restoration goals.

Aqueous-Deficient Dry Eye Increases Lipid Layer Thickness Measured by Dynamic Tear Interferometry.

To investigate the impact of aqueous deficiency on lipid layer thickness (LLT) measurement in dry eye disease before and after treatment of aqueous-deficient dry eye (ADDE) using dynamic tear interferometry. This prospective comparative study included 230 eyes from 230 patients with ADDE. The treatment group with punctal plug insertion was compared with the control group. The average LLT (LLTave) was measured with a LipiView II tear interferometer at baseline and after 1 month. Correlation analyses were performed with the indices of the dynamics of the tear film lipid layer (TFLL). Baseline LLTave values were 116.1 ± 26.7 and 112.3 ± 27.6 nm in the treatment group (n = 121) and the control group (n = 109), respectively. At 1 month, LLTave significantly decreased in the treatment group (difference -41.8 [95% confidence interval (CI) -47.2 to -36.3], P = 0.003). The values of tear meniscus height (TMH) at baseline and 1-month follow-up were negatively correlated with LLTave (both P < 0.001). Spreading time of TFLL to equilibrium and the deviation of TFLL were positively correlated with LLTave (all P < 0.001) and negatively correlated with TMH (P < 0.001 and 0.009). In multivariate analysis (adjusted R2 = 0.411, P < 0.001), LLTave was associated with TMH (B = -1.068; P < 0.001), adjusting for age, sex, and meibomian gland expressibility. In ADDE, the TFLL was measured to be thicker than the normal range of 60 to 99 nm and became thinner with treatment. LLT was affected by not only meibum secretion but also aqueous status due to changes in the dynamics of TFLL.

Quantitative analysis of the high speed and high precision waveform digital system for Jinping Neutrino Experiment

The Jinping Neutrino Experiment (JNE) aims to construct a 500-ton liquid scintillator detector for detecting and studying neutrinos. In JNE data analysis, particle energy and position reconstruction are crucial, with result accuracy closely related to the performance of the waveform digitization system. This study developed a quantitative model to explore correlations between sampling characteristics (effective number of bits and sampling rate) and detector system performance (single photoelectron charge spectrum resolution and transfer time spread). Additionally, three ADCs (Tsinghua ADC13B1G, ADI AD9695, TI ADS54J60) and MCP-PMTs were utilized to validate the model accuracy. The experimental results for the system charge spectrum resolution are in alignment with the theoretical predictions. When the ENOB of the ADC exceeds 10.66-bit and the sampling rate exceeds 1 GSPS, the system charge spectrum resolution is better than 45%, approaching the PMT inherent resolution of 44%. The transfer time spread within the system demonstrates minimal impact from the ADC sampling characteristics. These results serve as a reference for upgrading the JNE 60-channel and 4000-channel readout electronic systems. Additionally, this study can assist developers in maximizing the performance of physics experiment readout electronics systems within constrained budgets.

Experimental study on the dynamics of a liquid nitrogen droplet impacting a surface under Leidenfrost conditions

Liquid nitrogen droplet impacting a superheated surface is a fundamental phenomenon of liquid nitrogen spray cooling, whereas the mechanisms behind which are still unclear. We designed and developed a visual experimental system to investigate the dynamics of a liquid nitrogen droplet impacting a superheated surface under cryogenic conditions. The impact dynamics of the liquid nitrogen droplet at the Leidenfrost state are captured, and the effects of Weber number (We) and surface temperature on the spreading and rebound characteristics of the droplet are analyzed. The findings show that the droplet exhibits spreading, retraction and rebound at a low We. Droplet spreading and rebound characteristics are mainly affected by We while insensitive to surface temperature. The maximum spreading coefficient exhibits a power-law increase with We, while the maximum rebound coefficient shows an upward and then downward trend with We. The dimensionless maximum spreading time, dimensionless residence time, and dimensionless maximum rebound time show power-law increase with We. Corresponding fitting correlations for these factors for liquid nitrogen droplets are also proposed. This study contributes to an in-depth understanding of the impact dynamics of cryogenic liquid droplet under cryogenic conditions.

THE EFFECT OF VARIOUS MOLOTOV COCKTAILS ON DIFFERENT SURFACES AND EVALUATION OF FIRE CHANGES

Objective:Molotov cocktails are a classic homemade weapon used over the past 80 years; also known as gasoline bombs. However, there is not enough research in the literature. Molotov cocktail is classified as a mildly explosive substance. But a Molotov cocktail is not an explosive. This is a handmade lighter. It is used to set fire to targets in terrorist attacks. Methods:In our study, classic homemade Molotov cocktails were used. Oil, diluent, sugar, cologne, epoxy resin, paraffin, egg white, liquid and solid detergent, bleach, wood glue were added to the mixture. Parameters such as burning temperature, burning time, glass and nail spreading diameter, and residues of the Molotov cocktail were investigated. The prepared molotov cocktails were broken on 5 different floors, and the effect of changing the floor on the parameters was investigated. Results:In our study, 51 (59.3%) of 86 molotov cocktails were broken. Most of the destruction occurred in the wall. According to the results we obtained, a relationship was found between the content of the Molotov cocktail, the burning temperature and the time. It was found that the damage was increased with the addition of substances to the mixture. Conclusion: In addition, in our study, it was noticed that the Molotov cocktail did not explode by itself and did not cause damage to the environment by throwing nails.

Amphiphilic Superspreading Polymer Membranes Prepared by Capillary Force-Driven Self-Assembly.

To overcome the two main obstacles of large-scale application of superspreading material, self assembly is used to prepare superspreading polymer membrane (SPPM) in this work. An amphiphilic SPPM is prepared by capillary force-driven self assembly using PP melt-blown nonwovens and polyvinyl alcohol (PVA). The prepared SPPM has low preparation cost and stable performance since self assembly needs low energy consumption, and the production is thermodynamically stable. By using cryo-electron microscopy, transmission electron microscopy, X-ray photoelectron spectrum and scanning electron microscope with energy dispersive X-ray spectroscopy. It is proved that PVA is successfully assembled on the fiber surface of PP melt-blown nonwovens. The prepared SPPM has excellent spreading performance, the "spreading times" of both water and oil are less than 0.5 s. They showed much superior performance compared to traditional materials when applied in oil-water separation, seawater desalination, and ion separation. This work will definitely promote the development of self assembly, superspreading materials, and related sciences.