Size Structure Research Articles

Laser interaction with undercritical foams of different spatial structures

The interaction of high-power laser pulses with undercritical foams produced by different techniques but with the same average density is studied at the PALS laser facility. The spatial–temporal evolution of X-ray emission is observed using an X-ray streak camera, electron and ion temperatures are measured by X-ray spectroscopy, and hot-electron production is characterized by monochromatic X-ray imaging. Transmission of a femtosecond laser probe pulse through foams is observed in the near and far fields. In spite of large differences in pore size and foam structure, the velocity of ionization front propagation is quite similar for all the foams studied and is slower than that in a homogeneous material of the same average density. The ion temperature in the plasma behind the ionization front is a few times higher than the electron temperature. Hot-electron production in plastic foams with small pores is strongly suppressed compared with that in solid targets, whereas in foams produced by additive manufacturing, it is significantly increased to the level observed in bare copper foil targets.

Effect of Froth on the Interaction Between Coal Particles and Cake Structures in the Dewatering Process of Clean Coal

Effective coal slurry water solid–liquid separation is indispensable for the recycling and sustainable development of coal resources. The interaction between bubble and coal particles plays a critical role in the process of dewatering for clean coal. In this study, we firstly conducted a comprehensive investigation of the impact of froth on the interactions between coal particles by rheological measurement and particle aggregation behavior. Furthermore, the macroscopic dewatering performance of coal slurry in the presence of froth and its microscopic cake structure were investigated using the filtration test and X-ray microtomography (CT). It was found that the interaction between coal particles in the presence of froth was enhanced as a result of the dynamic shear value, combined with the large floc size and compact structure, which led to a higher cake moisture and higher filtration velocity. The CT results indicated that the enhanced interaction of particles in the presence of froth also led to a dense microstructure of the filter cake. The porosity of the filter cake decreased to 2.05% when the aeration time increased from 0 s to 90 s, the throat radius in the filter cake was reduced to 1.32 μm, and the number of throat passages was reduced to one third. Multiple blind pores and low coordination numbers led to a poor connectivity of the pore network and high moisture content.

Self-similarity of communities of the ABCD model

The Artificial Benchmark for Community Detection (ABCD) graph is a random graph model with community structure and power-law distribution for both degrees and community sizes. The model generates graphs similar to the well-known LFR model but it is faster and can be investigated analytically. In this paper, we show that the ABCD model exhibits some interesting self-similar behaviour, namely, the degree distribution of ground-truth communities is asymptotically the same as the degree distribution of the whole graph (appropriately normalized based on their sizes). As a result, we can not only estimate the number of edges induced by each community but also the number of self-loops and multi-edges generated during the process. Understanding these quantities is important as (a) rewiring self-loops and multi-edges to keep the graph simple is an expensive part of the algorithm, and (b) every rewiring causes the underlying configuration models to deviate slightly from uniform simple graphs on their corresponding degree sequences.

Alloying Strategy Regulating Size and Electronic Structure of Mo0.25Nb0.75Se2 to Achieve High‐Performance Lithium–Sulfur Batteries

The utilization of catalysts in lithium−sulfur batteries has proven to be an efficacious avenue for enhancing the kinetics of polysulfide conversion. Specially, the size and electronic structure of catalysts play a pivotal role in harnessing the active sites and intrinsic catalysis activity. Outstanding MoSe2 and NbSe2 are selected from 16 universal transition metal selenides based on the proposed binary descriptor. Then, an alloying strategy is devised to prepare Mo0.25Nb0.75Se2 flakelets for further improvement of the intrinsic catalysis. The integration of density functional theory calculations and electrochemical analysis demonstrates that alloying Mo with Nb can regulate the surface energy and indexes of band match and lattice mismatch, thereby enabling Mo0.25Nb0.75Se2 to possess a small size, suitable adsorption energy and low reaction energy barrier. This optimization enhances the catalysis of sulfur reduction/evolution reaction and the reversible deposition/stripping of lithium. Consequently, an assembled Ah‐level pouch cell is realized with dramatic cycle stability. With the electrolyte/sulfur ratio of 2.36 μL mg S–1, the cell can deliver a high energy density of up to 505.4 Wh kgtotal−1. This work pioneers a universal strategy for sculpting the geometric configurations and electronic structures of catalysts, to achieve enhanced catalytic activity and precise interpretation of structure−activity relationships.

Overcomplete intermediate representation of two-particle Green's functions and its relation to partial spectral functions

Two-particle response functions are a centerpiece of both experimental and theoretical quantum many-body physics. Yet, due to their size and discontinuity structure, they are challenging to handle numerically. Recently, two advances were made to tackle this problem: first, the overcomplete intermediate representation (OIR), which provides a highly efficient compression of Green's functions in imaginary frequency, and second, partial spectral functions (PSFs), which allow for an efficient evaluation in real frequency. We show that there is a two-to-one correspondence between PSFs and OIR coefficients and exploit this fact to construct the OIR for three-or-more-particle propagators. We then use OIR to fit and compress imaginary-frequency data obtained from the numerical renormalization group (NRG), reaching a compression ratio of more than 400. Finally, we attempt to match the OIR data to partial Green's functions from NRG. Due to the overcompleteness, we achieve only qualitative agreement. Published by the American Physical Society 2024

Preparation of Expandable Polymer Plugging Agent and Its Application in Water‐Based Drilling Fluid

ABSTRACTIn order to reduce the economic loss caused by well leakage and the lag of drilling progress, it is very important to use plugging materials reasonably and effectively. Expandable polymer materials can better fill cracks and holes of different sizes by absorbing water expansion and deforming. In this article, an expandable polymer plugging agent (PSMAN) was prepared by soap‐free emulsion polymerization using methyl methacrylate (MMA), styrene (St), 2‐acrylamide‐2‐methylpropanesulfonic acid (AMPS) as reaction monomers, N‐hydroxymethyl acrylamide (NMA) as a cross‐linking agent, and ammonium persulfate (APS) as initiator. The optimal synthesis conditions were determined by designing the orthogonal experiments, and the various properties of the materials were tested and evaluated. The experimental results show that PSMAN has good high temperature resistance, spherical structure, and median particle size of 15.099 μm, and the water absorption rate of room temperature at 24 h reaches 37.8 g/g, and pressure bearing capacity can reach 5 MPa. The addition of polymer to water‐based drilling fluid can increase the viscosity of drilling fluid and improve the rheological properties of drilling fluid by a small amount. Under normal temperature and medium pressure, the polymer can form a dense film on the surface of the mud cake, thereby reducing the filtration of drilling fluid and effectively improving the stability of the wellbore.

Modeling ground vibration excited by a high-speed train running along a viaduct railway using a new structure-soil interaction method

Ground vibrations generated by high-speed trains running along railways either at grade or on viaduct bridges, are greatly concerned by the railway industry. Considering the train-track-bridge-abutment-pile-soil interactions involved, modeling the problem in an analytical manner is almost impossible, while conventional numerical methods struggle to accurately simulate the dynamic properties of infinitely large soils. Therefore, this study introduces a new substructure methodology for train-track-bridge-abutment-pile-soil interactions that leverages an ingenious combination of the 2.5-dimensional finite element-boundary element method (2.5D FE-BE) for dynamics of infinitely long periodic structures, and a local 3-dimensional finite element model for pile-soil interaction. This innovative method allows for the consideration of detailed pile-soil coupling using a local finite element model, all while retaining the ability to account for the infinite size of the soil structure using the 2.5-dimensional finite element-boundary elements. After a comparison between model prediction and field measurement, the model is employed to explore the environmental vibration characteristics of on-viaduct high-speed railways and analyze the vibration reduction effects of various measures, including rail fasteners, track slab pads, and bridge bearings.

Experimental optimization for synthesis of cerium-doped titanium dioxide nanoparticles by modified sol-gel process

A systematic experimental optimization procedure was developed for the synthesis of cerium-doped titanium dioxide nanoparticles (CeTNPs) based on modified sol-gel process. The nanocomposite was prepared using titanium tetraisopropoxide (TTIP) as a catalyst precursor, while utilizing the non-ionic surfactant Triton X-114 in cyclohexane as a stabilizing agent. The synthesis process was optimized by identifying the main experimental factors that affect the properties of the nanoparticles, primarily the structural phase and particle size. The synthesized samples were characterized by X-ray diffraction (XRD) for phase and size, field emission scanning electron microscope (FE-SEM) for morphology, particle size analyzer (PSA) for size distribution, and Brunaur, Emmett, and Teller (BET) for surface area and pores characteristics. The photocatalytic activity of the optimized sample was tested for the removal of methyl orange (MO) and lead (II) from aqueous solutions, and the results indicate superior performance as the catalyst uptakes were 14.8 mg/l and 11.4 mg/l for methyl orange and lead (II), respectively.The main highlights of the proposed procedure are as follows:•Identification of the key variables impacting the structural and morphological properties.•Establishing the levels of each factor based on experimental findings.•Generation of all possible combinations of factors based on ANOVA, then characterization of the synthesized material from every possible combination.

Mechanism, microstructure and performance of novel electron beam freeform fabrication compared with conventional method

This paper proposes a new method: the pre-melting electron beam freeform fabrication method. This new method aims to mitigate the excessive heat input associated with directly forming a molten pool on the deposit and the poor formation caused by severe agitation of the molten pool. Consequently, it seeks to refine the internal microstructure of the part and enhance its mechanical properties. Using TC4 alloy as the research subject, this study performs a comparative analysis between the EBF and PEBF methods in terms of structural composition, deposit formation, cross-sectional morphology, microstructure, tensile strength, fracture path, and grain size. The research findings indicate that the PEBF method, due to its significantly lower heat input, results in the maximum α phase width being reduced to 1/4 to 1/5 of that observed with the EBF method. This reduction in α phase width leads to an increase in the tensile strength of the deposit from 784 to 840 MPa and an enhancement in the fracture strain from 0.22 to 0.34, which is close to the strength difference (68 MPa) calculated for the two methods using the Hall-Petch equation. The comparative results underscore the superiority of the PEBF method, demonstrating its potential to improve mechanical properties.

Highly dispersive nickel vanadium oxide nanoparticles anchored on nickel cobalt phosphate micron-sheets as cathodes for high-energy hybrid supercapacitor devices

The effective strategies of customizing suitable orientation and rationalizing structures are significant for developing high-performance energy storage materials applied in supercapacitors, which are regarded as promising clean energy storage devices. To obtain highly efficient MOF (metal-organic framework)-derived phosphate electrode, it is necessary to combine it with highly conductive materials for a synergistical effect. So, in this work, the Ni-Co DH (double hydroxide) is used as sacrificial template to prepare MOF through a reverse strategy, which makes a foundation for shaping anisotropic orientation to impede structural stack. The Ni3V2O8 nanoparticles are dispersedly anchored on NiCo-P micron-sheet through a conversion from nanostructured MOF/Ni3V2O8. The evolution in structural size avoids agglomeration of Ni3V2O8 nanoparticles, which also leads to shaggy and intact NiCo-P micron-sheets, thereby improving fully contact with electrolyte. As a result, the obtained NiCo-P/Ni3V2O8 with abundant electroactive sites and valences displays extraordinary specific capacitance of 2520 F g−1 (1134 mA h g−1) at 1 A g−1 with capacitance retention of 89.05 % even when the current density increases to 10 A g−1. The NiCo-P/Ni3V2O8 and AC as cathode and anode, respectively, are assembled into a hybrid supercapacitor (HSC) device to fulfil requirement for high-performance supercapacitor devices. As-made NiCo-P/Ni3V2O8//AC HSC delivers preeminent specific energy density (SE) of 65 Wh Kg−1 at specific power density (SP) of 750 W Kg−1.

Size Structure and Growth of Snail Terebralia palustris in Mangrove Ecosystem on Pannikiang Island

Terebralia palustris is a snail that lives in the mangrove ecosystem. This needs to be done considering that the condition factor (Ponderal Index) and size structure can be a reference for snail management later. Research on the condition factor (Ponderal Index) has never been studied. This research was conducted from August 2018 to July 2019 on Pannikiang Island. Sampling in December 2018 and January 2019 was not performed for weather reasons. The research stations were A and B. Sampling used one large plot measuring 100 m2, and inside, it contained four small plots measuring 0.25 m2 (0.5 m x 0.5 m), which were placed randomly. Data analysis used regression. The condition factor was calculated based on the growth pattern of the total length and weight of the snail's body. The measurement results obtained ten size groups in males and 11 in females. The length (SL) and weight (W) in female snails were more significant than in males. The test results showed that each month of observation showed negative allometry. The snail condition factor fluctuated.

Laminar jet flow at the microscale: The characteristic sizes and the wave development

Laminar jet flow is an underlying phenomenon used to generate droplets efficiently. However, its hydrodynamics at the microscale remains unknown. This work focuses on the scale effect. We innovatively propose the difference between the jet at the microscale and that at the regular scale is not in the wave development but in the regime of flow pattern, and it’s much more stable at the microscale. The characteristic effect at the microscale due to the intensified gas/liquid/solid–liquid interaction is first reported. The variations of characteristic sizes and hydrodynamics with the kinetic energy, physical property, and structural size at the microscale are analyzed by introducing two key parameters − wave velocity and wave numbers, which are first proposed. The result shows that the kinetic energy determines the hydrodynamics. Viscosity and interfacial tension significantly affect the microscale laminar jet. Using wave numbers, Tyler’s equation is modified, guiding the design of effective microdroplet-generation devices.

INVESTIGATING LARGE-SCALE STRUCTURES IN TURBULENT MIXING LAYERS USING TWO-POINT CORRELATION

The formation and development of large-scale structures are primary research subjects in the study of turbulent mixing layers. Visualizing these structures based on published experimental data enhances the understanding of complex flow behaviors, which is the main objective of this article. The authors employed a two-point statistical correlation method to evaluate the size of large vortex structures along the interaction region. Additionally, the article provides a guide for analyzing the turbulent energy spectrum at selected fixed points. The calculations were performed using MATLAB software. The results indicate that at the beginning of the mixing layer, the vortices are small and highly anisotropic, with large-scale structures stretching in irregular directions. Further downstream, the vortices increase in size in all directions, and the degree of anisotropy decreases. In the self-similar region, isotropic states are almost achieved. The energy spectrum analysis findings align with Kolmogorov's theory of energy cascade in turbulent flow. The two-point statistical correlation method proves to be highly effective for analyzing structures within turbulent flows.

Construction of superhydrophobic PDMS@PS-SiO2 films with self-cleaning properties via a simple template approach for efficient water harvesting

Superhydrophobic materials have a wide range of applications in the fields of anticorrosion, anti-dust, anti-ice and anti-fouling due to their self-cleaning, anti-wetting and anti-bacterial properties. However, there are problems in the preparation process, such as cumbersome processes, inconsistent properties of the prepared hydrophobic surfaces, and environmental pollution by fluoropolymers. Therefore, it is especially critical to develop a simple method to prepare green and efficient superhydrophobic surfaces. Here, a simple template method is used to prepare superhydrophobic surfaces. The Polystyrene (PS) honeycomb patterned film was used as a template, and the microstructure inside the pores of the PS film was changed by filling silica particles inside the template. Reproduction of the surface microstructure of PS films using polydimethylsiloxane (PDMS). The shape and size of the template structure are adjusted to regulate the surface microstructure, which in turn achieves the control of the overall hydrophobicity. The transition from PDMS hydrophobicity to superhydrophobicity was achieved by changing the structure of the PS film surface. The PDMS@PS-SiO2 film achieved a water contact angle of 153°, an increase of 48° compared to the original film. Tested at different temperatures and pH, PDMS@PS-SiO2 film has good stability performance. Immersing the film in pollutants still maintains its own cleaning properties and is not easily contaminated for long-term use. The morphology of the film surface was observed using electron microscopy to demonstrate the successful preparation of the film as well as to explore the reason for the variation of the hydrophobic performance. In addition, using PDMS@PS-SiO2 film as the substrate of the hydrophobic film, the bionic water-collecting film was prepared with a water-collecting performance of 20.12 ± 0.15 mg min−1 cm−2. The reuse of mist was achieved. This method provides a new idea for the preparation of superhydrophobic surfaces and solving the problem of water shortage.

Preparation, Characterization and Immune Activity of ViolaPhilippicaPolysaccharide PLGA Nanoparticles.

Recent pharmacological studies have demonstrated that Viola philippicapolysaccharide (VPP) exhibits a modulating effect on immune activity. However, its utilization has been hampered by its large particle size and complex spatial structure. Poly-lactic-co-glycolic acid copolymer (PLGA) is recognized as an effective drug delivery carrier, exhibiting excellent biochemical properties. In this experiment, VPP was encapsulated with PLGA to form Viola philippica polysaccharide PLGA nanoparticles (VPP-PLGA NPs). The morphological structure and immunomodulatory effects of VPP-PLGA NPs were evaluated. The particle size of VPP-PLGA NPs was reduced compared to VPP, and the optimal preparation conditions were as follows: the ratio of the organic phase to the internal aqueous phase was 8:1, the ratio of the external aqueous phase to the primary emulsion was 7:1, and the concentration of PLGA was 20 mg/mL. Additionally, VPP-PLGA NPs significantly increased the NO content, IL-4, and IFN-γ levels in RAW264.7 cells, as well as enhanced their phagocytic activity. Furthermore, VPP-PLGA NPs were found to increase NO content and IFN-γ secretion in bone marrow-derived dendritic cells (BMDCs). These findings suggest that VPP-PLGA NPs could enhance the immune activity and may be utilized as a VPP delivery system for inducing strong immune responses.

The Microstructural Evolution and Mechanical Properties of Boron-Doped Ti35Zr30V10Nb25 Refractory High-Entropy Alloy

The addition of oxygen or nitrogen in refractory high-entropy alloys (HEAs) has been widely reported, but studies on boron-doped HEAs have mainly focused on the segregation of boron elements at grain boundaries. The changes in the microstructure and mechanical properties in TiZrNb-based HEAs remain enigmatic. In this work, boron-doped Ti35Zr30V10Nb25 (Ti35-xB) refractory HEAs were designed to elucidate their microstructural evolution and mechanical properties. Unlike oxygen and nitrogen, trace amounts of boron addition result in the formation of borides, and boron exhibits a strong repulsion towards Zr, leading to Zr-depleted borides. Borides distributed along the grain boundaries refine the grain size and dendritic structure. The borides and structural refinement effect enhance the strain-hardening capacity and uniform elongation, resulting in an over 15% uniform elongation for Ti35-0.25B.

Can omnivory explain variation in size-density relationships? The case of Leptonema in a neotropical stream

Community size structure potentially depicts the constant amount of small abundant organisms sustaining larger, rarer ones. Strong size structuring is expected under a constant predator-prey mass ratio yet omnivory, as defined by organisms feeding at multiple trophic levels, can disrupt this pattern. Here, we investigated the size structure of macroinvertebrate communities in two tropical streams before and after a heavy rain event. We found that one taxon, Leptonema (a net-spinning caddisfly), was overabundant at all sites, strongly deviating from the allometric expectation given their body size. By analyzing their gut-content, we found evidence of true omnivory with inclusion of animal prey with increasing body size. As omnivory is a key factor in ecosystem stability, the presence of overabundant species could be an important element to consider when implementing conservation and restoration policies.

Marine protection and environmental forcing influence fish‐derived nutrient cycling in kelp forests

Abstract Animal consumers excrete dissolved inorganic nitrogen, an essential nutrient for regulating primary production and macroalgal growth in the ocean. Often overlooked in attempts to explain kelp forest productivity, relatively little is known about the role of consumers in nutrient cycling in temperate systems, such as the magnitude of nutrients excreted and the factors that influence spatial and temporal variability in consumer‐derived nutrients. To investigate the supply of ammonium (NH4+) excreted by the dominant members of the nearshore rocky reef fish community, we combined empirically‐measured relationships between excretion rate and body mass with data on fish density and size structure from visual SCUBA surveys conducted from 2005 to 2018 in the northern Channel Islands, California, USA. The fish community excreted a substantial amount of ammonium to the kelp forest (mean: 95.5–131.3 μmol·m−2·h−1), however excretion varied substantially among sites and over time (range: 23.1–247.9 μmol·m−2·h−1). The ammonium supply was influenced by the establishment of marine protected areas (MPAs) that restricted fishing activities and environmental characteristics that influenced geographic and temporal shifts in the overarching fish community structure. Fish‐derived ammonium excretion rates were 50%–80% greater inside MPAs compared to areas open to fishing, while environmental and habitat characteristics (e.g. habitat vertical relief, kelp biomass, wave exposure, chlorophyll a) explained 85% of the spatial variation in community excretion rates. In contrast, large‐scale oceanographic phenomena (e.g. North Pacific Gyre Oscillation index) and past patterns of fish recruitment explained 57% of the temporal variation in nutrient excretion over the 14‐year time series. Results suggest that fish‐derived ammonium may provide an important and underappreciated nutrient source to kelp beds, particularly during low‐nutrient periods (e.g. seasonal reductions in upwelling or El Niño‐Southern Oscillation events), and that fishing disrupts these nutrient cycling pathways. Fishes likely play a critical role in supporting the resiliency of kelp forest ecosystems by supplying a relatively constant source of reduced nitrogen that can be utilized by giant kelp and other macroalgae to fuel primary production of biogenic habitat. Read the free Plain Language Summary for this article on the Journal blog.

Population characteristics, seasonal distribution, and suppression potential of introduced Northern Pike in a Great Plains stream

AbstractObjectiveThe objectives of this study were to describe the population dynamics, reproductive characteristics, and movement of Northern Pike Esox lucius in the Niobrara River drainage of Wyoming. This information was used to estimate the necessary level of suppression to meaningfully reduce their abundance and thereby facilitate persistence of native nongame fishes.MethodsIn 2019 and 2020, Northern Pike were sampled to describe population size structure, age structure, growth, and mortality. An additional 42 gravid female Northern Pike were collected across 2020–2023 to determine a length–fecundity relationship. Vulnerability to recruitment overfishing was modeled with a static spawning potential ratio model. Finally, 15 mature fish were implanted with radio transmitters in 2021 and 2022 and tracked for 1 year to determine seasonal dispersal and spawning locations.ResultSampled Niobrara River drainage Northern Pike (n = 213) varied from 127 to 749 mm total length. Estimated ages of fish were between 0 and 8 years, and total annual mortality was estimated at 42% (95% confidence interval = 36–48%) in the presumed absence of fishing mortality. Recruitment was extremely stable, and growth was relatively fast through age 2. Some females matured at age 1, and all females were mature by age 2 and spawned annually. Estimated total fecundity for females between 297 and 914 mm total length varied from 3573 to 154,877 eggs. Most telemetered fish moved little throughout the year, but movements as large as 5.9 river kilometers were observed. Modeling suggests that exploitation of age‐1 and older Northern Pike should exceed 42% and exploitation of age‐2 and older fish should exceed 85% to meaningfully reduce the population's reproductive potential.ConclusionNorthern Pike growth and reproductive potential at older ages may be more limited in small prairie streams than within their native range. Observed annual home range was small, and spawning occurred annually in consistent locations. The necessary intensity of mechanical removal to achieve meaningful suppression in this system will likely require an intensive and ongoing interstate effort.

Decisive role of organic fluorophore and surface defect state in the photoluminescence of carbon quantum dots

Carbon quantum dots (CQDs) hold significant promise for applications in biological imaging, sensing, and optoelectronic devices owing to their superior photostability and low toxicity. Nevertheless, the elucidation of their photoluminescence mechanism remains an open question, necessitating further comprehensive investigation. In this Letter, CQDs exhibiting ultraviolet (UV) and white fluorescence were isolated through silica gel column chromatography separation of the crude product obtained from a one-step solvothermal synthesis. CQDs with different luminescent properties exhibit the same crystal structure and similar particle size distributions. Both CQDs exhibit orthorhombic structure where C60/C70 molecules are located at lattice points, having average particle sizes of 2.71 and 2.98 nm, respectively. Consequently, the luminescent properties of the synthesized CQDs are predominantly governed by their surface structure. The results of microstructure characterization and spectroscopic analysis demonstrate that the UV emission originates from the C(=O)OH and C–O–C related luminescent moieties within organic fluorophores, and the blue emission band is attributed to defect states related to surface group C–O–C, while the green/yellow emission arises from C(=O)O related surface defect levels. These observations have gained a profound understanding of the luminescent genesis of CQDs, broadened the luminescence coverage wavelength range of CQDs, and enriched the family of CQDs materials.