Damage from Particle Impact for Structural Ceramics

In this study, the relationship between the maximum impact force and velocity of partjcle has been derived on the basis of elastic theory and energy principle. Critical impact force and critical speed which cause initial damage is anaIVsed and its analytical expression is presented. The impact force for six dlfferent materials was measu red at the same condition to investigate the v8riation of impact pararneter with material properties. The authors provide a simple test method and experimental de vice to imitate the impact of moving particle, A series of experiments on ceramics and gIass were car ried out to study the dependence of residual strength on the impulse.

Element doping induced microstructural engineering enhancing the lithium storage performance of high-nickel layered cathodes

The high-nickel layered cathodes Li[Ni_(x)Co_(y)Mn_(1-x-y)]O_(2)(x≥0.8)with high specific capacity and long cycle life are considered as prospective cathodes for lithium-ion batteries.However,the microcrack formation and poor structural stability give rise to inferior rate performance and undesirable cycling life.Herein,we propose a dual modification strategy combining primary particle structure design and element doping to modify Li[Ni_(0.95)Co_(0.025)Mn_(0.025)]O_(2) cathode by tungsten and fluorine co-doped(W-F-NCM95).The doping of W can convert the microstructure of primary particles to the unique rod-like shape,which is beneficial to enhance the reversibility of phase transition and alleviate the generation of microcracks.F doping is conducive to alleviating the surface side reactions.Thus,due to the synergistic effect of W,F codoping,the obtained W-F-NCM95 cathodes deliver a high initial capacity of 236.1 mA h g^(-1) at 0.1 C and superior capacity retention of 88.7%over 100 cycles at 0.5 C.Moreover,the capacity still maintains73.8%after 500 cycles at 0.5 C and the texture of primary particle is intact.This work provides an available strategy by W and F co-doping to enhance the electrochemistry performance of high-nickel cathodes for practical application.

Literature overview of basic characteristics and flotation laws of flocs

Flocculation flotation is the most efficient method for recovering fine-grained minerals,and its essence lies in flotation and recovery of flocs.Fundamental physical characteristics of flocs are mainly determined by their apparent particle size and structure(density and morphology).Substantial researches have been conducted regarding the effect of floc characteristics on particle settling and water treatment.However,the influence of floc characteristics on flotation has not been widely studied.Based on the floc formation and flocculation flotation,this study reviews the fundamental physical characteristics of flocs from the perspectives of floc particle size and structure,summarizing the interaction between floc particle size and structure.Moreover,it thoroughly discusses the effect of floc particle size and structure on floc floatability,further revealing the influence of floc characteristics on bubble collision and adhesion and elucidating the mechanisms of interaction between flocs and bubbles.Thus,it is observed that floc particle size is not the only factor influencing flocculation flotation.Within the appropriate apparent particle size range,flocs with a compact structure exhibit higher efficiency in bubble collision and adhesion during flotation,thereby resulting in enhanced flotation performance.This study aims to provide a reference for flocculation flotation,targeting the development of more efficient and refined flocculation flotation processes in the future.

Preparation of Core-shell Structured Particles and Their Nucleation in Polyester:I. Preparation of Monodisperse SiO_2/PS Core-shell Composite Particles

To enhance the nucleation and crystallization properties of polyester (e.g., polyethylene terephthalate, PET), core-shell structured particles are used to improve these properties by controlling the inorganic dispersion properties in the polymers. In the paper, monodisperse particles of silica/polystyrene (PS) are prepared with both dispersion and emulsion polymerization techniques. The monodisperse silicon dioxide particles are first prepared with the seed growth method and modified by the coupling agents. Silica is properly modified with KH-570, and its size deviation is 3.0% or so. The modified silica then reacts with the mixture of ethanol, water medium, and monomer of styrene under dispersion polymerization. Results show that the dispersion polymerization technique is more suitable for monodisperse core-shell SiO2/PS particles than that of the emulsion. The morphology and molecular structure of the core-shell particles are investigated with the transmission electron microscope (TEM), and fourier transform infra-red spectroscopy (FTIR). The results show that the modified silica particles are successfully encapsulated with polystyrene. The average number of silica particles encapsulated into each polystyrene sphere decreases when the size of silica particles increases from 50 nm to 600 nm, and will approach one when the silica is greater than 380nm in size. The mass ratio for silica/PS particles in emulsion polymerization is 4.7/1, lower than that of 6.8/1 for dispersion polymerization, which is the first reported optimized data for preparing the similar monodisperse composite particles. Thus, the PS shell in the former is thinner than that in the latter.

Combustion Properties of Metal Particles as Components of Modified Double-Base Propellants

Metal particles such as aluminum（ Al）,magnesium（ Mg）,boron（ B） and nickel（ Ni）,as well as Mg/Al alloy（ Mg/Al = 3/4） are currently the most widely used ingredients in modified doublebase propellants. In this contribution,the combustion properties of the metal species are studied by means of the high-speed photography technique and the non-contact wavelet-based measurement of flame temperature distribution. The combustion process of the Al,Mg and Mg/Al samples shows both gas phase reaction and surface oxidation,which yield volatile and nonvolatile products,corresponding to the oxide and suboxide respectively. However,the combustion of B and Ni shows only gas phase reaction,due to their high melting point as well as high enthalpy of vaporization. In addition to the experiments,a hypothetical combustion model has been proposed to clarify the combustion characteristics of metal species in modified double-base propellants.

Climate Shifts and the Role of Nano Structured Particles in the Atmosphere

A global net sum equilibrium in heat exchange is a fact and thus a global climate change doesn’t exist, but climate shifts in climate cells, especially in the northern temperate cell, do. The global climate has been ever since homeostatic, and has recuperated far huger climate impacts in the past. Current climate models need a drastically revision on the focus of carbon dioxide as main driver. Carbon dioxide and other carbon gasses do influence albedo patterns, but provide globally a homeostatic effect with a commonly accepted increase impact of 0.3 degrees Celsius. Carbon dioxide does not trigger the climate shifts, but is an indicator of exhaust of combustion processes that emit very small particles which drive these climate shifts. They are the fine dust and nano structured particles that cause the shifts of the climate in cells, as demonstrated in this article and results i.e. in more thunder and lightning, extreme weather, distinct droughts and precipitation patterns. The causes underlying these shifts are nano structured particles in the upper troposphere and lower stratosphere, especially largely produced and remain in the temperate climate northern hemisphere cell and get dispersed by jet streams and low and high pressure areas. However, because of electrical charge, caused by friction or due to anthropogenic negatively charged nano structured particle, emissions will travel up to the lower stratosphere and become neutralized at the electro sphere level, and they do also have a tendency to move to the Arctic. The southern hemisphere climate faces limited anthropogenic emissions, because only 10 percent of the world population can contribute with less pollutant providing activities, and hasn’t changed, but that could well be because it is equally influenced and driven, like the northern hemisphere, by the variation of sun activity in diverse cycles. The present problem is that we produce huge amounts of air borne nano structured particles from combustion processes that never exist before. The only nano particles known in nature are those who are limited produced from volcano eruptions and natural forest fires. The natural feedback systems that moderate climate shifts and influence global climate are: convection by cumulonimbus clouds, sea currents and vegetation adaptation. A novel ultra-fine dust electric reduction device (UFDRS-System), created by the author, diminishs to a size of less than 10 nano particles in diameter and thus prevents major electrical drift of nano structured particulates in the upper troposphere and lower stratosphere and contributes largely in purifying the air and thus reduces the effects of climate shifts. Like solving the acid rain problems with sulphuric acid reduction and ozone depletion with CFCs proscription in the past, the present climate shifts can be mitigated via a reduction of the anthropogenic nano structured particulates in the atmosphere. The UFDRS-System together with the given nature’s solutions can re-balance our atmosphere in a period of two years or a little bit longer due to extension of the lifespan of a particle in the stratosphere.

Probing the effects of lithium doping on structures, properties, and stabilities of magnesium cluster anions

Bimetallic clusters have aroused tremendous interest because the property changes like structure,size,and composition have occurred.Herein,a structural search of the global minimum for anionic LiMg_(n)^(-)(n=2-11) clusters is performed using an efficient crystal structure analysis by particle swarm optimization(CALYPSO) structural searching program with subsequent density functional theory(DFT) calculations.A great variety of low energetic isomers are converged,and the most stable ones are confirmed by comparing their total energy of each size.It is found that the LiMg_(n)^(-)clusters are structurally consistent with corresponding Mg clusters anions except for LiMg_(5)^(-)and LiMg_(7)^(-).In all the doped clusters,the Li atom prefers to occupy the convex position.Simulated photoelectron spectra(PES),Infrared(IR),and Raman spectra of LiMg_(n)^(-)could be used as an essential evidence for identifying cluster structures experimentally in the future.Stability study reveals that a tower-like structure of LiMg_(9)^(-)has prominent stability and can be identified as a magic number cluster.The reason might be that there are both closed-shell 1S^(2)1P^(6)1D^(10)2S^(2) electronic configurations and stronger Li-Mg bonds caused by sp hybridization in the LiMg_(9)^(-)cluster.

Tomographic PIV investigation on coherent vortex structures over shark-skin-inspired drag-reducing riblets

Nature has shown us that the microstructure of the skin of fast-swimming sharks in the ocean can reduce the skin friction drag due to the well-known shark-skin effect.In the present study,the effect of shark-skin-inspired riblets on coherent vortex structures in a turbulent boundary layer（TBL） is investigated.This is done by means of tomographic particle image velocimetry（TPIV） measurements in channel fl ws over an acrylic plate of drag-reducing riblets at a friction Reynolds number of 190.The turbulent fl ws over drag-reducing riblets are verifie by a planar time-resolved particle image velocimetry（TRPIV） system initially,and then the TPIV measurements are performed.Two-dimensional（2D） experimental results with a dragreduction rate of around 4.81% are clearly visible over triangle riblets with a peak-to-peak spacing s＋of 14,indicating from the drag-reducing performance that the buffer layer within the TBL has thickened;the logarithmic law region has shifted upward and the Reynolds shear stress decreased.A comparison of the spatial topological distributions of the spanwise vorticity of coherent vortex structures extracted at different wall-normal heights through the improved quadrant splitting method shows that riblets weaken the amplitudesof the spanwise vorticity when ejection（Q2） and sweep（Q4） events occur at the near wall,having the greatest effect on Q4 events in particular.The so-called quadrupole statistical model for coherent structures in the whole TBL is verified Meanwhile,their spatial conditional-averaged topological shapes and the spatial scales of quadrupole coherent vortex structures as a whole in the overlying turbulent fl w over riblets are changed,suggesting that the riblets dampen the momentum and energy exchange between the regions of near-wall and outer portion of the TBL by depressing the bursting events（Q2 and Q4）,thereby reducing the skin friction drag.

A study on coherent structures and drag-reduction in the wall turbulence with polymer additives by TRPIV

An experimental measurement was performed us- ing time-resolved particle image velocimetry （TRPIV） to in- vestigate the spatial topological character of coherent struc- tures in wall-bounded turbulence of polymer additive solu- tion. The fully developed near-wall turbulent flow fields with and without polymer additives at the same Reynolds number were measured by TRPIV in a water channel. The compar- isons of turbulent statistics confirm that due to viscoelastic structure of long-chain polymers, the wall-normal velocity fluctuation and Reynolds shear stress in the near-wall region are suppressed significantly. Furthermore, it is noted that such a behavior of polymers is closely related to the decease of the motion of the second and forth quadrants, i.e., the ejection and sweep events, in the near-wall region. The spa- tial topological mode of coherent structures during bursts has been extracted by the new mu-level criteria based on locally averaged velocity structure function. Although the general shapes of coherent structures are unchanged by polymer additives, the fluctuating velocity, velocity gradient, velocity strain rate and vorticity of coherent structures during burst events are suppressed in the polymer additive solution com- pared with that in water. The results show that due to the polymer additives the occurrence and intensity of coherent structures are suppressed, leading to drag reduction.

A particle shape-based segmentation method to characterize spray dried materials by X-Ray microtomography

For accurate description of particle structure,single particle properties are required so that the properties of interest can be expressed as distributed parameters.X-Ray microtomography of the powder bed with subsequent particle separation can be used for this purpose.In this paper,a new algorithm for X-Ray microtomography images of spray dried particles was introduced since standard methods tend to fail if the particle size distribution is broad.The algorithm is based on 2D shape classification and subsequent 3D reconstitution of the particle using only a shape classifier as free parameter.The proposed algorithm was validated successfully.Using the algorithm,single particle porosities were obtained,which ranged from 0 to 70%.Prerequisites for the application of the algorithm are that a shape classifier can be set and that the 3D shape is regular.

In-Fiber Structured Particles and Filament Arrays from the Perspective of Fluid Instabilities

In-fiber structured particles and filament array have been recently emerging,providing unique advantages of feasible fabrication,diverse structures and sophisticated functionalities.This review will focus on the progress of this topic mainly from the perspective of fluid instabilities.By suppressing the capillary instability,the uniform layered structures down to nanometers are attained with the suitable materials selection.On the other hand,by utilizing capillary instability via post-drawing thermal treatment,the unprecedent structured particles can be designed with multimaterials for multifunctional fiber devices.Moreover,an interesting filamentation instability of a stretching viscous sheet has been identified during thermal drawing,resulting in an array of filaments.This review may inspire more future work to produce versatile devices for fiber electronics,either at a single fiber level or in large-scale fabrics and textiles,simply by manipulating and controlling fluid instabilities.

Crystalline phase of Y_2O_3 :Eu particles generated in a substrate-free flame process

In this study, factors affecting the crystal structure of flame-synthesized Y2O3 ：Eu particles were investigated, especially the particle size effect and its interaction with Eu doping concentration, Polydisperse Y2O3：Eu （size range 200 nm to 3μm） powder samples with Eu doping concentrations from 2,5 mol% to 25 mol% were generated in either H2/air or H2/O2 substrate-free flames. The crystal structure of the powder samples was determined by powder X-ray diffraction （XRD）, which was complemented by pho- toluminescence （PL） measurements. Single particle crystal structure was determined by single particle selected area electron diffraction （SAED）, and for the first time, by electron backscatter diffraction （EBSD）. H2/air flames resulted in cubic phase Y2O3：Eu particles with hollow morphology and irregular shapes, Particles from H2/O2 flames had dense and spherical morphology; samples with lower Eu doping concen- trations had mixed cubic/monoclinic phases; samples with the highest Eu doping concentrations were phase-pure monoclinic. For samples generated from H2/02 flames, a particle size effect and its interaction with Eu doping concentration were found： particles smaller than a critical diameter had the monoclinic phase, and this critical diameter increased with increasing Eu doping concentration, These findings suggest that the formation of monoclinic Y2O3：Eu is inevitable when extremely hot substrate-free flames are used, because typical flame-synthesized Y203 ：Eu particle sizes are well below the critical diameter, However, it may be possible to generate particles with dense, spherical morphology and the desired cubic structure by using a moderately high flame temperature that enables fast sintering without melting the particles.

Fabrication of virus-like particles with strip-pattern surface：A two-step self-assembly approach

Spherical nanostructures with striped patterns on the surfaces resembling the essential structures of natural virus particles were constructed through a two-step self-assembly approach of polystyrene-boligo（acrylic acid）（PS-b-oligo-AA） and poly（γ-benzyI L-glutamate）-b-poly（ethylene glycol）（PBLG-bPEG） copolymer mixtures in solution.On the basis of difference in hydrophilicity and self-assembly properties of the two copolymers,the two-step self-assembly process is realized.It was found that PS-boligo-AA copolymers formed spherical aggregates by adding a certain amount of water into polymer solutions in the first step.In the second step,two polymer solutions were mixed and water was further added,inducing the self-assembly of PBLG-b-PEG on the surfaces of PS-b-oligo-AA spheres to form striped patterns.In-depth study was conducted for the indispensable defects of striped patterns which are dislocations and ＋1/2 disclinations.The influencing factors such as the mixing ratio of two copolymers and the added water content in the first step on the morphology and defects of the striped patterns were investigated.This work not only presents an idea to interpret mechanism of the cooperative self-assembly behavior,but also provides an effective approach to construct virus-like particles and other complex structures with controllable morphology.

The Effect of Particle Shape on the Structure and Rheological Properties of Carbon-based Particle Suspensions

The structure and rheological properties of carbon-based particle suspensions, i.e., carbon black（CB）, multi-wall carbon nanotube（MWNT）, graphene and hollow carbon sphere（HCS） suspended in polydimethylsiloxane（PDMS）, are investigated. In order to study the effect of particle shape on the structure and rheological properties of suspensions, the content of surface oxygen-containing functional groups of carbon-based particles is controlled to be similar. Original spherical-like CB（fractal filler）, rod-like MWNT and sheet-like graphene form large agglomerates in PDMS, while spherical HCS particles disperse relatively well in PDMS. The dispersion state of carbon-based particles affects the critical concentration of forming a rheological percolation network. Under weak shear, negative normal stress differences（ΔN） are observed in CB, MWNT and graphene suspensions, while ΔN is nearly zero for HCS suspensions. It is concluded that the vorticity alignment of CB, MWNT and graphene agglomerates under shear results in the negative ΔN. However, no obvious structural change is observed in HCS suspension under weak shear, and accordingly, the ΔN is almost zero.

Effect of mixing structure on the hygroscopic behavior of ultrafine ammonium sulfate particles mixed with succinic acid and levoglucosan

Understanding the interactions between water and atmospheric aerosols is critical for estimating their impact on the radiation budget and cloud formation. The hygroscopic behavior of ultrafine （〈100nm） ammonium sulfate particles internally mixed with either succinic acid （slightly soluble） or levoglucosan （soluble） in different mixing structures （core-shell vs. well-mixed} were measured using a hygroscopicity tandem differential mobility analyzer （HTDMA）. During the hydration process （6-92% relative humidity （RH））, the size of core-shell particles （ammonium sulfate and succinic acid） remained unchanged until a slow increase in particle size occurred at 79Y~ RH; however, an abrupt increase in size （i.e., a clear deliquescence） was observed at ~72% RH for well-mixed particles with a similar volume fraction to the core-shell particles （80：20 by volume）. This increase might occur because the shell hindered the complete dissolution of the core-shell particles below 92% RH. The onset RH value was lower for the ammonium sulfate/levoglucosan core-shell particles than the ammonium sulfate/succinic acid core-shell particles due to levoglucosan＇s higher solubility relative to succinic acid. The growth factor （GF） of the core-shell particles was lower than that of the well-mixed particles, while the GF of the ammonium sulfate/levoglucosan particles was higher than that of ammonium sulfate/succinic acid particles with the same volume fractions. As the volume fraction of the organic species increased, the GF decreased. The data suggest that the mixing structure is also important when determining hygroscopic behavior of the mixed particles.

Time analysis of regional structure of large-scale particle using an interactive visual system

N-body numerical simulation is an important tool in astronomy.Scientists used this method to simulate the formation of structure of the universe,which is key to understanding how the universe formed.As research on this subject further develops,astronomers require a more precise method that enables expansion of the simulation and an increase in the number of simulation particles.However,retaining all temporal information is infeasible due to a lack of computer storage.In the circumstances,astronomers reserve temporal data at intervals,merging rough and baffling animations of universal evolution.In this study,we propose a deep-learning-assisted interpolation application to analyze the structure formation of the universe.First,we evaluate the feasibility of applying interpolation to generate an animation of the universal evolution through an experiment.Then,we demonstrate the superiority of deep convolutional neural network(DCNN)method by comparing its quality and performance with the actual results together with the results generated by other popular interpolation algorithms.In addition,we present PRSVis,an interactive visual analytics system that supports global volume rendering,local area magnification,and temporal animation generation.PRSVis allows users to visualize a global volume rendering,interactively select one cubic region from the rendering and intelligently produce a time-series animation of the high-resolution region using the deep-learning-assisted method.In summary,we propose an interactive visual system,integrated with the DCNN interpolation method that is validated through experiments,to help scientists easily understand the evolution of the particle region structure.

THE MICROPHYSICAL STRUCTURE OF SNOW CLOUDS AND THE GROWTH PROCESS OF SNOW PARTICLES IN WINTER IN XINJIANG

The microphysical structure of snow clouds and the growth process of snow crystals were observed by means of instrumented aircraft, weather radar, snow crystal observations etc. in Urumqi region during the winter of 1982. The analysis of three cases show that about 70% of snow mass growth is produced in the lower layer below 2000 m under the cold front, and that the concentration of ice crystals is as high as 60 L^(-1) and the supercooled water is absent in lower clouds. We may infer that the deposition of ice crystals and the aggregation of snow crystals are important processes for the snow development. The microphysical structure of the snow band near the front aloft and its characteristics as a seeder cloud are also described in this paper.

Experimental Study on Product Characteristics of Typical Pulverized Coal Preheated by a Self-Preheating Burner

As the major primary energy source in China,coal has been proved to be capable to improve its physical and chemical characteristics by the pretreatment of the self-preheating burner.In this study,the effects of altering operating conditions including preheating temperature(T_(p))and primary air equivalence ratio(λ_(p))on preheating characteristics of three typical pulverized coal were investigated on a bench-scale test rig.The high-temperature coal gas compositions along the axis of the riser and at the outlet of the self-preheating burner were measured,and the coal char and coal tar produced in the preheating process were collected and analyzed separately.The results indicated that with the significant release of volatile and the occurrence of chemical reactions,cracks and micropores emerged on the surface of the particles,making the pore structure on the surface more developed,and T_(p)had the most significant effect on the structure of coal particles.Additionally,there were evident differences in the corresponding operating conditions when the preheating characteristics of the three typical coal reached optimally.And preheating had the strongest influence on the degree of anthracite modification.With respect to coal tar,the increase of T_(p)andλ_(p)further promoted its secondary cracking and oxidation,resulting in a decrease in production yield.In this study,for bituminous coal and lignite,a large amount of coal tar were produced during preheating and the highest production yields could reach 5.74%and 6.15%,respectively.While for anthracite,the production yield was intensely low due to its own coal properties,all below 1.02%.

INVESTIGATIONS INTO THE DETACHMENT OF DIFFERENTLY STRUCTURED DUST LAYERS FROM SURFACES

A technique is presented for creating surface-adhering dust layers under defined conditions, and characterizing and stressing the layers created. The procedure described is shown to be suitable for the quantitative evaluation of the effects of different parameters such as particle size, porosity and surface roughness etc. on the stability of particle layers.

Spatiotemporal distribution of size-fractioned phytoplankton in the Yalu River Estuary,China

The grain size structure of phytoplankton has great influence on shellfish culture.The present study aimed to assess the spatial and temporal variation in the phytoplankton community structure in the Yalu River Estuary and to explore the relationship between the phytoplankton community structure and various environmental parameters in 2020.High-throughput sequencing was used in this study.The results showed that nanophytoplankton,especially Karlodinium veneficum,dominated the estuary throughout the year.The biomass ratio of picophytoplankton,nanophytoplankton,and microphytoplankton were 20:63:17 in spring,30:44:26 in summer,1:38:61 in autumn,and 2:45:53 in winter,respectively.Meanwhile,Dinophyta had the greatest biomass throughout the year,followed by Bacillariophyta.On the spatial dimension(Station average),COD,T,SST had a positive impact on total phytoplankton communities,and Dep had a negative impact.In the time dimension(Monthly average),the environmental factor that significantly controlled the phytoplankton community structure were NO2 and SST.