Evaporation processes of water molecules from graphene edge: DFT and MD study

The evaporation processes of water molecules adsorbed in the edge region of graphene have been investigated by means of direct MO–MD method. A large system composed of 29 water molecules and a graphene sheet (C₉₆H₂₄) was used as a model system. The edge carbon atom of graphene was terminated by hydrogen atom. The geometry optimization showed that the water molecules interact with the hydrogen atoms in the edge region of graphene. At low temperature (300 K), the water molecules were dissociated as water clusters from the graphene. On the other hand, in addition to the dissociation of water clusters, the isolated water molecule was also found as dissociation product at high temperature (500 K). The mechanism of water evaporation was discussed on the basis of theoretical results.     

Stripping of surface water from particles in an injected bed

Mechanical water stripping has been observed in an injected bed; measurements have been made on the effects of the water content of the material, the bed depth, particle diameter, and injected gas speed on the stripping rate.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 30, No. 3, pp. 411–415, March, 1976.     

Re-entrainment of particles from powder structures: experimental investigations

The effectiveness of re-entrainment of particles from powder structures into air flowing through a powder aliquot placed in channel of rectangular cross-section was investigated experimentally. The shear stream of the gas causes breakage of the powder structure and particles or their clusters move to the air stream with an efficiency that depends on airflow rates and air humidity. At higher flow rates, large agglomerates are re-entrained, especially if the powder was conditioned at higher air humidity. The modifications of particles surfaces through adsorption of surfactants or electrostaticaly active substances cause the screening of the short-range cohesive forces between particles and particle processing make the re-entrainment more effective. Reduced size of particles clusters re-entrained into the air stream is also observed for modified surfaces of powder particles.     

An experimental study of the degradation of particles in complex plasma

Changes of melamine–formaldehyde resin (MF-R) particles occurring in complex dusty plasma have been investigated. Using a specially developed method, plasma-modified MF-R particles have been extracted from a dust trap after levitation for various periods of time and studied by electron microscopy techniques. Changes in the surface structure of MF-R particles are determined, and quantitative data on the variation in particle dimensions depending on the time of occurrence in plasma are obtained.     

Angular structure of radiation scattered by monolayers of particles: experimental study

An experimental study has been made of the angular structure of radiation scattered by monolayers of large nonabsorbing particles. We have investigated three media exhibiting different light-scattering properties: monodisperse polyvinyl toluene latex particles of 3.75-mum diameter suspended in water, polydisperse rice starch particles with a mean diameter of 6.4 mum suspended in water, and a mixture of ethyl and benzoic alcohols. It is shown that for large particles the structure of scattered radiation can be described in a single-scattering approximation. Analysis of the influence of polydispersity and the relative refractive index of particles on the intensity scattered by the monolayer has been performed.     

Theoretical and experimental study of multi-impact breakage of particles

An empirical relationship between compression tests and impact tests was established for three kinds of particles: NaCl, GNP (fertilizer granule based on phosphate) and potash (fertilizer granule). As a result, the theoretical fatigue model that was previously developed for single particle strength (crushing strength) for repeated compression loads (fatigue) could be used to describe the decrease in particle strength due to repeated impact loads. The predictions of the theoretical model were validated by impact experiments for the three tested materials. In order to compare the theoretical and experimental findings, the experimental results were analyzed by tracking a defined population of particles after each impact test. The comparison showed good agreement (deviation of up to 25% for an impact number of 10). The results show that as the number of impacts and the impact velocity increase, the crushing strength decreases.     

Modelling and experimental study on agglomeration of particles from coal combustion in multistage spouted fluidized tower

An experimental platform of spray agglomeration has been designed and built for removing small fly ash particles (PM₁₀) from coal combustion. Agglomerating model of fine particles during the spray process was developed by combining rapid coagulation theory and analysis of the interaction between droplets and particulates. Systematic experiments were conducted in multistage spouted tower using several kinds of agglomerant solutions. The influencing factors such as surfactant, pH value, flow rate of agglomerant solutions and inlet flue gas temperature were analyzed. SEM was used to analyze the microstructure of the aggregation. Based on this model, coagulation rate constant was calculated and the influences of original parameters were observed. The spray agglomeration mechanism of particles can be analyzed from both macroscopical and microcosmic aspects. Preliminary results are presented and discussed in this work. Final results indicate that the special shape of multistage spouted fluidized tower has significant influences on the effect of agglomeration. The findings from this work will be helpful to form the basis and provide guidance for further studies on the control of fine particles such as PM_2.5 or even smaller ones.     

Light scattering from nonspherical airborne particles: experimental and theoretical comparisons

A laser light-scattering instrument has been designed to permit an investigation of the spatial intensity distribution of light scattered by individual airborne particles constrained within a laminar flow, with a view to providing a means of classifying the particles in terms of their shape and size. Ultimately, a means of detecting small concentrations of potentially hazardous particles, such as asbestos fiber, is sought. The instrument captures data relating to the spatial distribution of light scattered from individual particles in flow. As part of an investigation to optimize orientation control over particles within the sample airstream, the instrument has been challenged with nonspherical particles of defined shape and size, and a simple theoretical treatment based on the Rayleigh-Gans formalism has been used to model the spatial intensity distribution of light scattered from these particle types and hence derive particle orientation data. Both experimental and theoretical scattering data arepresented, showing good agreement for all particle types examined.     

An experimental study of ash particles adhesion force in flue gas

In this study, experiments and analyses have been carried out to investigate the influences of denitrification and flue gas Waste Heat Recovery Systems (WHRS) on ash particles adhesion force. With use of a denitrification system, it is found that the ash particles adhesion force is strongly influenced by the mass ratio, R, of (NH₄)HSO₄ to ash. Three influencing zones are identified, i.e., little effect zone (R < 1:150), intermediate effect zone (1:150 < R < 1:60), and huge effect zone (R > 1:60). It is necessary to operate in the little effect zone in order to avoid ash deposition in the air preheater. With use of a WHRS, it is found that the ash adhesion force is strongly affected by the flue gas temperature in comparison with the Engineering Acid Dew Temperature (EADT). With decreasing temperature below the EADT, both the collected ash amount and ash adhesion force rise, and the detected particles size increases, indicating particle accumulation that improves ash collection efficiency.     

Possible binding sites for biotin stabilized water soluble Ag nanoparticles: an experimental and theoretical study

The evolution of Ag nanoparticles by photochemical reduction method and the effect of biotin on their UV-Visible absorption spectrum were studied. Surface modification studies were carried out on chemically reduced Ag nanoparticles. ATR-FTIR studies showed that the biotin molecules bind with the surface of Ag nanoparticles through the oxygen of the carboxylate group. Theoretical calculations were carried out on the structure of the biotin and the silver complex of biotin (biotin(-)-Ag+) by optimizing their structures using density functional calculations with the B3LYP method using the LANL2DZ basis set. Theoretical calculations and experimental evidence favors a preferential binding of biotin molecule to Ag nanoparticles through the carboxylate group.     

An experimental study on the influence of particles on grain boundary migration

The pinning effect of particles on grain boundary migration was studied in a Fe–20 mass% Cr alloy deoxidised with Ti and Zr. The different nitrogen contents (65, 248 and 490 ppm) were used to vary the number of precipitated inclusions. The specimens from equiaxed zones of metal samples with different particle densities were examined by in situ observations during a 60-min holding time at 1200 and 1400 °C in a Confocal Scanning Laser Microscope. The change of particles pinning effect on the grain growth was described by an average grain size, [`(D)]_\textA \bar{D}_{\text{A}} , and the ratio between the perimeter and area of grains, P _GB/A _G. It was found that the pinning effect of particles (mostly complex Ti–Zr oxynitrides) on grain growth decreased with a decreased nitrogen content in the metal. Furthermore, the effect of particles decreased with an increased temperature of treatment, due to the reduction of the number of particles on the grain boundaries.     

Evaporation of suspensions to form an incompressible cake and to fill filter pores with solid particles

Equations of filtration of suspensions to form an incompressible cake of particles on the surface of the filter with simultaneous passage of a certain share of the particles from the cake to the filter’s pore space and next to the region of a filtered liquid are derived from the principles of the mechanics of multiphase media. The influence of the travel of the particles in the region of the cake and the filter on the dynamics of growth of the cake bed is investigated. An analysis of the derived dynamic filtration equations shows that allowance for the factors of travel and accumulation of particles in the cake and the filter causes their total filtration resistance, in particular the resistance in the inertial component of the filtration law, to decrease.     

Self-organization of colloidal particles during drying of a droplet: Modeling and experimental study

Formation of structurized micro/nanoparticle aggregates in spray drying process is analyzed theoretically and experimentally. Colloids of mono- and bimodal particle size distribution are used as the precursors to demonstrate different patterns of particle self-organization inside the drying droplet. In case of monodisperse primary particles their self-organization in the final aggregate results in either a hollow or a full (packed) spherical structure. For primary particles with bimodal size distribution, either the layered structure of aggregates is formed (with smaller particles forming outer layer and the bigger particles captured inside) or the ordering of bigger particles on the aggregate surface is observed, depending on process parameters. Numerical investigations allow to predict and explain the conditions at which self-assembling of particles within powder aggregates takes place.     

Elastographic axial resolution criteria: an experimental study

In elastography, window size has been typically used synonymously with resolution. Strain is estimated by computing the gradient of the displacement estimates, which have a direct dependence on the window size. However, the resolution is also dependent on the separation between these windows. The intricate relationship between the window size, window shift, and resolution has not previously been explored. In this article, we perform a controlled simulation experiment to evaluate the relationship among elastographic axial resolution, window size, and window shift. We conclude that the axial resolution can be expressed as a bilinear function of window size and window shift, the latter having a much larger weight.     

Fracture of alumina: an experimental and numerical study

A numerical analysis of the fracture behaviour of alumina has been performed based on experimental crack growth studies. Single-edge notch bend and short-double cantilever beam specimens of diverse grain size alumina were tested under quasi-static growth conditions. Constitutive equations for the alumina were obtained from experimental results and used to carry out finite element analyses. The agreement between numerical and experimental results is very promising, e.g. the influence of grain size on fracture behaviour can be predicted accurately. The underlying toughening mechanisms are discussed.     

既有桥梁对相邻车-桥系统气动力的影响分析

为了研究既有桥梁对相邻车～桥系统气动力的影响,通过节段模型风洞试验,测试了考虑、不考虑既有桥梁干扰工况下相邻车-桥系统的气动力系数,数值模拟了作用在车-桥系统上的抖振力时程,并计算了抖振力极值.结果表明:既有桥梁对相邻车-桥系统气动力的影响显著,导致部分工况下列车、桥梁的气动力显著增大,结构设计中应充分考虑邻近桥梁的气...     

Damage and plasticity in adhesive layer: an experimental study

An experimental method is developed to identify a suitable model of in-elastic behaviour of an adhesive layer. Two prototype models are considered: an elastic-plastic model where the in-elasticity is considered due to permanent straining of the adhesive and an elastic-damage model where the in-elasticity is due to a reduction in elastic stiffness. Simulations show that the evaluated property is sensitive to the choice of model. In the experimental study of an engineering epoxy adhesive, the elastic-damage model fits the experiments. The study also reveals that plasticity and damage accumulated at the crack tip influences the evaluated fracture properties.     

Cracks and slits in compression and shear: an experimental study

Summary The behavior of the two main types of flows encountered in materials such as rocks, i.e., cracks and slits, under compressive and shear stresses has been examined. It was shown that the existence of a gap between the edges of a slit is allowing the inward movement, causing the development of a negativeK _I -SIF at its cornered extremities. On the other hand, for a slant ideal crack additional compressive stresses should develop because of the noncongruent deformation of its lips thus opposing the incompatible interpenetration of the crack flanks and causing an openingK _I -SIF. Finally, for an ideal crack normal to the global stresses in the plate the cracked body behaves as a continuum without any singularity.In order to verify the validity of the above arguments the method of caustics has been used. After developing the appropriate equations of the caustics a series of experiments were executed giving results which support the already developed theory.Notation A _i ,B _i ,S _i ,T _i coefficients of the solution of the cracked Brazilian disc - a semi-length of the crack - C constant dependent from the optical set-up and the optical and mechanical properties of the specimen - C _{r, f} rear and front face constant - c optical constant of the plate for reflections of the light rays from the rear face of the plate - d thickness of the specimen - D _(–) diameter of the caustic in compressive stress field - D ₁ ^max maximum diameter of caustic - D ₁ ^min minimum diameter of caustic - E modulus of elasticity - K _I,K _II stress intensity factors for the two modes of deformation - N _I,N _II dimensionless SIF's - P compressive load - r _{r, f} radii of the initial curves of the rear and front caustics - x, y cartesian coordinates on the specimen - x, y cartesian coordinates on the screen - Z ₀ distance between the specimen and the screen - angle between crack and main loading axis - angle between the effective position of the crack axis and its initial direction - _m is the magnification ratio of the optical set-up - stress at infinity - , normal and shear stresses in a direction parallel to the crack - tan coefficient of friction