Use of digital image analysis combined with fractal theory to determine particle morphology and surface texture of quartz sands

The particle morphology and surface texture play a major role in influencing mechanical and hydraulic behaviors of sandy soils. This paper presents the use of digital image analysis combined with fractal theory as a tool to quantify the particle morphology and surface texture of two types of quartz sands widely used in the region of Vitória, Espírito Santo, southeast of Brazil. The two investigated sands are sampled from different locations. The purpose of this paper is to present a simple, straightforward,reliable and reproducible methodology that can identify representative sandy soil texture parameters.The test results of the soil samples of the two sands separated by sieving into six size fractions are presented and discussed. The main advantages of the adopted methodology are its simplicity, reliability of the results, and relatively low cost. The results show that sands from the coastal spit(BS) have a greater degree of roundness and a smoother surface texture than river sands(RS). The values obtained in the test are statistically analyzed, and again it is confirmed that the BS sand has a slightly greater degree of sphericity than that of the RS sand. Moreover, the RS sand with rough surface texture has larger specific surface area values than the similar BS sand, which agree with the obtained roughness fractal dimensions. The consistent experimental results demonstrate that image analysis combined with fractal theory is an accurate and efficient method to quantify the differences in particle morphology and surface texture of quartz sands.

On the fluorescence enhancement mechanism of Er^(3+) in germanate glass containing silver particles

The spectral properties of trivalent erbium ions（Er^3＋） are systematically studied in a melt-quenched germanate glass（60 GeO2-20PbO-10BaO-10K2O-0.1Ag2O） containing silver（Ag） particles.Thermal treatment of the material leads to the precipitation of Ag particles as observed by transmission electron microscopy and confirmed by absorption spectrum for the obvious surface plasmon resonance peak of Ag particles.The fluorescence from Er^3＋ in the 10-min-annealed sample with Ag particles is found to be 4.2 times enhanced compared with the unannealed sample excited by 488-nm Ar＋ laser.A comparison is made between a spectral study performed on the unannealed Er^3＋-doped sample and the one annealed for 20 min.The data of absorption cross section and Judd-Ofelt intensity parameters show the agreement between the two samples no matter whether there are Ag particles,indicating that the introduction of Ag particles by post-heat treatment has no effect on the crystal field environment of Er^3＋ ions.The fluorescence enhancement is attributed to the surface plasmon oscillations of Ag particles in germanate glass.

Isotropic compression behavior of granular assembly with non-spherical particles by X-ray micro-computed tomography and discrete element modeling

The particle morphological properties,such as sphericity,concavity and convexity,of a granular assembly significantly affect its macroscopic and microscopic compressive behaviors under isotropic loading condition.However,limited studies on investigating the microscopic behavior of the granular assembly with real particle shapes under isotropic compression were reported.In this study,X-ray computed tomography(mCT)and discrete element modeling(DEM)were utilized to investigate isotropic compression behavior of the granular assembly with regard to the particle morphological properties,such as particle sphericity,concavity and interparticle frictions.The mCT was first used to extract the particle morphological parameters and then the DEM was utilized to numerically investigate the influences of the particle morphological properties on the isotropic compression behavior.The image reconstruction from mCT images indicated that the presented particle quantification algorithm was robust,and the presented microscopic analysis via the DEM simulation demonstrated that the particle surface concavity significantly affected the isotropic compression behavior.The observations of the particle connectivity and local void ratio distribution also provided insights into the granular assembly under isotropic compression.Results found that the particle concavity and interparticle friction influenced the most of the isotropic compression behavior of the granular assemblies.

Schrdinger Equation of a Particle on a Rotating Curved Surface

We derive the Schr6dinger equation of a particle constrained to move on a rotating curved surface S. Using the thin-layer quantization scheme to confine the particle on S, and with a proper choice of gauge transformation for the wave function, we obtain the well-known geometric potentiM Vg and an additive Coriolis-induced geometric potential in the co-rotationM curvilinear coordinates. This novel effective potential, which is included in the surface Schr6dinger equation and is coupled with the mean curvature of S, contains an imaginary part in the general case which gives rise to a non-Hermitian surface Hamiltonian. We find that the non-Hermitian term vanishes when S is a minimal surface or a revolution surface which is axially symmetric around the rolling axis.

Development and Evaluation of Stable Paracetamol Loaded Solid Dispersion with Enhanced Analgesic and Hepatoprotective Property

Paracetamol (PCM) is enlisted in the WHO model list as an essential medicine for pain and palliative care, but at overdose, it causes hepatic damage. This study was designed to assess the analgesic efficacy and hepatoprotective property of a solid dispersion (SD) loaded with PCM. A number of PCM loaded formulations (PSDs) were fabricated using silica alone or in combination with polyethylene glycol and/or Na-citrate followed by in-vitro dissolution profiling. Selected PSDs with improved dissolution profile were subjected to solid-state characterization (DSC, PXRD, FTIR, and SEM), stability study along with investigation of in-vivo analgesic efficacy and effect on hepatocytes. Among these, PSD10 showed a rapid and significantly higher in-vitro drug release than pure PCM. This improvement was distinct to other PSDs also. Solid-state characterization of PSD10 authenticated the conversion of crystalline PCM to amorphous form upon formulation. Subsequent oral administration of PSD10 in Swiss albino mice showed 1.44-fold greater analgesic efficacy than pure PCM at dose 30 mg/kg. Besides, at acute toxic dose, liver histology of PSD10 mice was comparable with NC mice indicating hepatic protection upon formulation, whereas the PCM mice showed extensive hepatic necrosis which was also endorsed by significantly higher values of SGPT, SGOT, and ALP than PSD10 mice. Finally, an accelerated stability study of PSD10 performed according to the guideline of ICH noticed no remarkable deviation in its dissolution performance as well as crystalline nature. Thus, this newly developed PSD10 may be a safe and promising alternative for pain management and palliative care.

Springback Prediction and Optimization of Variable Stretch Force Trajectory in Three-dimensional Stretch Bending Process

Most of the existing studies use constant force to reduce springback while researching stretch force. However, variable stretch force can reduce springback more efficiently. The current research on springback prediction in stretch bending forming mainly focuses on artificial neural networks combined with the finite element simulation. There is a lack of springback prediction by support vector regression（SVR）. In this paper, SVR is applied to predict springback in the three-dimensional stretch bending forming process, and variable stretch force trajectory is optimized. Six parameters of variable stretch force trajectory are chosen as the input parameters of the SVR model. Sixty experiments generated by design of experiments（DOE） are carried out to train and test the SVR model. The experimental results confirm that the accuracy of the SVR model is higher than that of artificial neural networks. Based on this model, an optimization algorithm of variable stretch force trajectory using particle swarm optimization（PSO） is proposed. The springback amount is used as the objective function. Changes of local thickness are applied as the criterion of forming constraints. The objection and constraints are formulated by response surface models. The precision of response surface models is examined. Six different stretch force trajectories are employed to certify springback reduction in the optimum stretch force trajectory, which can efficiently reduce springback. This research proposes a new method of springback prediction using SVR and optimizes variable stretch force trajectory to reduce springback.

Preparation and Thermoelectric Properties of SiO_2/β-Zn_4Sb_3 Nanocomposite Materials

A series of SiO2/β-Zn4Sb3 core-shell composite particles with 3, 6, 9, and 12 nm of SiO2 shell in thickness were prepared by coatingβ-Zn4Sb3 microparticles with SiO2 nanoparticles formed by hydrolyzing the tetraethoxysilane in alcohol-alkali-water solution. SiO2/β-Zn4Sb3 nanocomposite thermoelectric materials were fabricated with these core-shell composite particles by spark plasma sintering （SPS） method. Microstructure, phase composition, and thermoelectric properties of SiO2/β-Zn4Sb3 nanocomposite thermoelectric materials were systemically investigated. The results show thatβ-Zn4Sb3 microparticles are uniformly coated by SiO2 nanoparticles, and no any phase transformation reaction takes place during SPS process. The electrical and thermal conductivity gradually decreases, and the Seebeck coefficient increases compared to that ofβ-Zn4Sb3 bulk material, but the increment of Seebeck coefficient in high temperature range remarkably increases. The thermal conductivity of SiO2/β-Zn4Sb3 nanocomposite material with 12 nm of SiO2 shell is the lowest and only 0.56 W·m^-1·K^-1 at 460 K. As a result, the ZT value of the SiO2/β-Zn4Sb3 nanocomposite material reaches 0.87 at 700 K and increases by 30%.

Characteristics of phosphorus adsorption by sediment mineral matrices with different particle sizes

The particle size of sediment is one of the main factors that influence the phosphorus physical adsorption on sediment. In order to eliminate the effect of other components of sediment on the phosphorus physical adsorption, the sediment mineral matrices were obtained by removing inorganic matter, metal oxides, and organic matter from natural sediments, which were collected from the Nantong reach of the Yangtze River. The results show that an exponential relationship exists between the median particle size （Ds0） and specific surface area （Sg） of the sediment mineral matrices, and the fine sediment mineral matrix sample has a larger specific surface area and pore volume than the coarse sediment particles. The kinetic equations were used to describe the phosphorus adsorption process of the sediment mineral matrices, including the Elovich equation, quasi-first-order adsorption kinetic equation, and quasi-second-order adsorption kinetic equation. The results show that the quasi-second-order adsorption kinetic equation has the best fitting effect. Using the mass conservation and Langmuir adsorption kinetic equations, a formula was deduced to calculate the equilibrium adsorption capacity of the sediment mineral matrices. The results of this study show that the phosphorus adsorption capacity decreases with the increase of Ds0, indicating that the specific surface area and pore volume are the main factors in determining the phosphorus adsorption capacity of the sediment mineral matrices. This study will help understand the important role of sediment in the transformation of phosphorus in aquatic environments.

An experimental study on the influences of wind erosion on water erosion

In semi-arid regions, complex erosion resulted from a combination of wind and water actions has led to a massive soil loss and a comprehensive understanding of its mechanism is the first step toward prevention of the erosion. However, the mutual influences between wind erosion and water erosion have not been fully understood. This research used a wind tunnel and two rainfall simulators and simulated two rounds of alternations between wind erosion and water erosion（i.e., 1^（st） wind erosion–1^（st） water erosion and 2^（nd） wind erosion–2^（nd） water erosion） on three slopes（5°, 10°, and 15°） with six wind speeds（0, 9, 11, 13, 15, and 20 m/s） and five rainfall intensities（0, 30, 45, 60, and 75 mm/h）. The objective was to analyze the influences of wind erosion on succeeding water erosion. Results showed that the effects of wind erosion on water erosion were not the same in the two rounds of tests. In the 1^（st） round of tests, wind erosion first restrained and then intensified water erosion mostly because the blocking effect of wind-sculpted micro-topography on surface flow was weakened with the increase in slope. In the 2^（nd） round of tests, wind erosion intensified water erosion on beds with no rills at gentle slopes and low rainfall intensities or with large-size rills at steep slopes and high rainfall intensities. Wind erosion restrained water erosion on beds with small rills at moderate slopes and moderate rainfall intensities. The effects were mainly related to the fine grain layer, rills and slope of the original bed in the 2^（nd） round of tests. The findings can deepen our understanding of complex erosion resulted from a combination of wind and water actions and provide scientific references to regional soil and water conservation.

Experimental observation of surface phonon absorption in Zn fine particles coated with ZnO

FINE particles have attracted much attention in the past few years due to their unique physical and chemical properties. For gas-evaporated fine metallic particles, a thin oxide layer is usually formed on their surface. According to Ruppin’s prediction, a dielectric coating on metallic particles should have a series of surface modes between ωTO and ωLO, the long-wavelength transverse and longitudinal optical phonon frequencies of the dielectric. The frequency of

Experimental study on influence of blade angle and particle size on particle mechanics on a batch-operated single floor of a multiple hearth furnace

In industry,multiple hearth furnaces are used for the thermal treatment of particulate material.The current contribution concentrates on the experimental analysis of particle mechanics for a batch-operated single floor of a multiple hearth furnace.The particles are agitated on the circular floor by a single,rotating rabble arm equipped with three flat rabble blades of 10 mm thickness.The blade angle,defined as the angle,which the blade is inclined against the tangential direction,is varied from 0°to 90°.A single layer of spherical polyoxymethylene(POM)particles with three different diameters(5,10 and 20 mm)is placed on the floor.To analyze the results,two parameters have been extracted from image analysis when the bed of particles is agitated,first,the area not covered by particles and second,the frequency distribution of the mean distance among the particles.The particle free surface area increases with the inclination of the blades.The evolution of the particle free surface area differs for the different particle diameters.In general,the maximum particle free area for all blade angles is the largest for the 5 mm particles followed by the 20 mm particles.For the 10 mm particles,the particle free surface area starts for a blade angle of 0°at larger values than for the 20 mm particles but the values fall below the values for the 20 mm particles for larger blade angles.The reason for this behavior is discussed in detail.The mean distance among the particles is a parameter characterizing the length scales dominating the effects on the floor.The frequency distribution of the mean distance among particles provides infor-mation about the morphology of the particle bulk,for example,whether the free surface area is inter-spersed with particles.

Grinding behavior and surface appearance of(TiC_p+ TiB_w)/Ti-6Al-4V titanium matrix composites

（TiCp＋ TiBw）/Ti-6Al-4V titanium matrix composites（PTMCs） have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforcements, high strength and low thermal conductivity of Ti-6Al-4V alloy matrix. Grinding experiments with vitrified CBN wheels were conducted to analyze comparatively the grinding performance of PTMCs and Ti-6Al-4V alloy. Grinding force and force ratios, specific grinding energy, grinding temperature, surface roughness, ground surface appearance were discussed. The results show that the normal grinding force and the force ratios of PTMCs are much larger than that of Ti-6Al-4V alloy. Low depth of cut and high workpiece speed are generally beneficial to achieve the precision ground surface for PTMCs. The hard reinforcements of PTMCs are mainly removed in the ductile mode during grinding. However, the removal phenomenon of the reinforcements due to brittle fracture still exists, which contributes to the lower specific grinding energy and grinding temperature of PTMCs than Ti-6Al-4V alloy.

SURFACE MODIFICATION AND DISPERSION OF NANODIAMOND IN CLEAN OIL

The effect of different kinds of surfactants on the size distribution of nanodiamond particles in clean oil was studied. Results show that the dispersing stability of nanodiamond modified with surfactants YS-1 and SB-18 simulta-neously is much better than those modified with either of them because of synergism of the surfactants. And the particle size distribution in the system can be improved remarkably after the adoption of hyperdispersants such as SA-E and SA-F. Anchoring groups of those hyperdispersants can be bonded with the particle surface by chemical and/or hydrogen bonding and their soluble chains are well compatible with the dispersion media. As a result, the particles are uniformly distributed in the system owing to the steric stabilization. A very stable clean-oil based nanodiamond suspension with an average particle size of around 53.2 nm was prepared.

Unraveling the size distributions of surface properties for purple soil and yellow soil

Soils contain diverse colloidal particles whose properties are pertinent to ecological and human health, whereas few investigations systematically analyze the surface properties of these particles. The objective of this study was to elucidate the surface properties of particles within targeted size ranges（i.e. 〉 10, 1-10, 0.5-1, 0.2-0.5 and 〈 0.2 μm） for a purple soil（Entisol） and a yellow soil（Ultisol） using the combined determination method. The mineralogy of corresponding particle-size fractions was determined by X-ray diffraction.We found that up to 80% of the specific surface area and 85% of the surface charge of the entire soil came from colloidal-sized particles（〈 1 μm）, and almost half of the specific surface area and surface charge came from the smallest particles（〈 0.2 μm）. Vermiculite,illite, montmorillonite and mica dominated in the colloidal-sized particles, of which the smallest particles had the highest proportion of vermiculite and montmorillonite. For a given size fraction, the purple soil had a larger specific surface area, stronger electrostatic field, and higher surface charge than the yellow soil due to differences in mineralogy.Likewise, the differences in surface properties among the various particle-size fractions can also be ascribed to mineralogy. Our results indicated that soil surface properties were essentially determined by the colloidal-sized particles, and the 〈 0.2 μm nanoparticles made the largest contribution to soil properties. The composition of clay minerals within the diverse particle-size fractions could fully explain the size distributions of surface properties.

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.

Stochastic structural optimization using particle swarm optimization, surrogate models and Bayesian statistics

This paper focuses on a method to solve structural optimization problems using particle swarm optimization （PSO）, surrogate models and Bayesian statistics. PSO is a random/stochastic search algorithm designed to find the global optimum. However, PSO needs many evaluations compared to gradient-based optimization. This means PSO increases the analysis costs of structural optimization. One of the methods to reduce computing costs in stochastic optimization is to use approximation techniques. In this work, surrogate models are used, including the response surface method （RSM） and Kriging. When surrogate models are used, there are some errors between exact values and approximated values. These errors decrease the reliability of the optimum values and discard the realistic approximation of using surrogate models. In this paper, Bayesian statistics is used to obtain more reliable results. To verify and confirm the efficiency of the proposed method using surrogate models and Bayesian statistics for stochastic structural optimization, two numerical examples are optimized, and the optimization of a hub sleeve is demonstrated as a practical problem.