Height Of Deposit Research Articles

DEM modelling of the influence of initial stress state on the discharge rate of spherical particles from a model silo

Formulation of a proper physical law describing the dynamics of discharge of granular solids has been undertaken by researchers for decades. A frequently expressed opinion is the existence of the free-fall arch region and independence of the discharge rate on pressure. The objective of this study was to explore the impact of dynamic particle–particle contact interactions in the vicinity of the orifice on the discharge flow rate from a model silo by means of DEM simulations with special attention paid to the impact of the bedding height and bottom pressure. The DEM simulations were performed with an assembly of spherical particles poured on a flat bottom of the cylindrical model silo with a height-to-diameter ratio of 1.14. The bottom pressure was changed by changing the height of the bedding deposit and depositing an additional layer of very dense particles on the top of the bedding of primary particles. The results indicate that the discharge rate was affected by both the orifice diameter and mean bottom pressure during storage. The correction coefficient derived from the integral of the dimensionless acceleration of particles along the dimensionless movement path allowed obtaining very good approximation of the discharge rate using the well known Beverloo equation in the entire range of change of the orifice size and bottom pressure.

Predictors of visual outcome in post-fever retinitis: a retrospective analysis.

To identify the predictors of final visual outcome in cases with post-fever retinitis (PFR). This is a retrospective study of cases with diagnosis of post-fever retinitis. Colour fundus photograph and optical coherence tomography (OCT) parameters at presentation and final visit were analysed. Various factors at presentation [age, systemic illness, best-corrected visual acuity (BCVA), area of retinitis and hard exudates, OCT parameters], at final visit (OCT parameters) and the treatment modalities used were correlated with BCVA at final visit. Twenty-four eyes of 16 patients with PFR were included in the study. Median BCVA at presentation was 6/60 and at final visit was 6/9. By multiple linear regression after adjusting for other variables, for every 1 unit increase in height of subretinal fluid (SRF) at fovea at presentation, the value of final BCVA decreased by 0.001 unit. For every 1 unit increase in extent of ellipsoid zone (EZ) loss and subfoveal deposit height, the value of final BCVA decreased by 0.0001 unit and 0.004 unit, respectively. The baseline OCT parameters that had negative correlation with final BCVA included central macular thickness (r: - 0.5182, p: 0.02), maximum SRF height (r: - 0.5539, p < 0.01) and SRF height at fovea (r: - 0.582, p < 0.01). The OCT parameters at final visit which had a negative correlation with final BCVA included disorganisation of retinal inner layers (DRIL) within 1000 microns from centre of fovea (r: - 0.6494, p < 0.01), height of subfoveal deposit (r: - 0.7627, p < 0.01), horizontal extent of subfoveal deposit (r: - 0.6695, p < 0.01) and extent of EZ loss (r: - 0.8216, p < 0.01). Height of SRF at presentation, extent of EZ loss and subfoveal deposit height at final visit were associated with poor final BCVA in PFR.

The impact of provider-specific factors on the profitability of contract for difference traders

This paper uses statistics about profitability of the provider's clients to examine whether the providers have an impact on the profitability of retail CFD traders. Using OLS method and estimated nonparametric confidence intervals, the influence of three provider-specific factors were tested: height of minimum deposit, height of transaction costs, and ability of the provider to trade on its own account. The model was estimated both using pre-COVID-19 pandemic data and data gathered during the pandemic. Statistically significant influence of the transaction costs was observed in both periods. The influence of height of minimum deposit was significant only before the pandemic.

A study on the additive manufacturing of a high chromium Nickel-based superalloy by extreme high-speed laser metal deposition

Nickel-based superalloys have been widely used in manufacturing turbine blades, vanes, and discs of aircrafts and power generators that serve in challenging environment. In order to meet the requirements for rapid manufacturing of these large-scale and high-performance components, the extreme high-speed laser metal deposition (EHLMD) technology have attracted great attention in recent years. The EHLMD technology can significantly improve the efficiency compared with conventional laser metal deposition (LMD). Meanwhile, the solidification condition and the resultant microstructures and mechanical properties can also be dramatically changed. In this study, a high chromium superalloy (K648) has been additively manufacturing by using EHLMD for the first time. The key process parameters and the resulted microstructure and mechanical properties are investigated. The results have shown that the most important factors affecting the height, width, and depth of the single-track deposit of EHLMD K648 superalloy are powder feeding rate, laser power, and scanning speed, respectively. The height and the width of the deposits are the largest when the laser power, scanning speed, and the powder feeding rate are 1400 W, 25 m/min, and 30 g/min. There exist some incomplete fusions in the interlayer region and some pores in the interior region of the multi-track-multi-layer deposits. Columnar grains grow in the build direction within each layer, while equiaxed grains tend to form in the interlayer region. The average value of microhardness of EHLMD K648 superalloy is about 298.1 HV. The ultimate strength of EHLMD K648 superalloy is slightly lower than that of the forging GH648 superalloy but higher than that of the conventional LMD K648 superalloy.

Deposition of Colloidal Particles during the Evaporation of Sessile Drops: Dilute Colloidal Dispersions

The deposition of colloidal silica particles during the evaporation of sessile drops on a smooth substrate has been modeled by the simultaneous solution of the Navier–Stokes equations, the convective-diffusive equation for particles, and the diffusion equation for evaporated vapor in the gas phase. Isothermal conditions were assumed. A mapping was created to show the conditions for various deposition patterns for very dilute suspensions. Based on values of the Peclet (Pe) number and Damkholer numbers (Da and Da−1), the effects of adsorption and desorption were discussed according to the map. Simulations were also done for suspensions with a high particle concentration to form a solid phase during the evaporation by using a packing criterion. The simulations predicted the height and width of the ring deposit near the contact line, and the results compared favorably to experimental particle deposition patterns.

Integrated Experimental Approach for Alloying of Surface Layer Ti6Al4V+B4C Metal Matrix Composites using Laser Treatment

Surface engineering applications have brought the titanium and its alloys into the limelight in the manufacturing industries such as the aerospace, automobile, marine, chemical processing industry, nuclear power and biomedical. Despite the growths experienced in the use of this material, it is plagued with poor wear behaviour, especially when in contact with other materials during application. In this research work, the reinforcement of titanium alloy (Ti6Al4V) and boron carbide (B4C) ceramic powders was employed to form the Ti6Al4V+B4C composites. The effect of laser power on the micrograph, microhardness, surface roughness and wear has been investigated. The micrographic evaluation, the geometrical analyses and the effect of laser power on the width and height of deposit, aspect ratio and dilution rate were also evaluated. The highest aspect ratio of 5.31 and dilution rate of 63.81 % was observed in sample MB5 deposited with a laser power of 2400 W. The dry sliding friction and wear conducted using a 10 mm diameter tungsten carbide ball and a normal load of 25 N revealed that sample MB2 produced at a laser power of 1800 W has the lowest wear depth and wear width of 74.6 µm and 1080.77 µm. From the lowest COF attributed by sample MB5, it can be inferred that coefficient of friction does not determine the wear loss due to the sticking of some wear debris to the wear track during sliding action. Thus, other wearing factors are also considered for the wear loss evaluation. However, this composite can be used for the repair of the worm part of a rotating shaft and turbine blades.

Amino acid racemisation and uranium-series dating of a last interglacial raised beach, Kingscote, Kangaroo Island, southern Australia

ABSTRACTThe extent to which scleractinian coral inhabited southern Australia during the warm intervals of the Quaternary is poorly understood because identifiable corals from interglacial sedimentary records are scarce. Here we document the presence of a sub-tropical coral, Goniopora lobata, recovered together with warm water mollusc species from a raised cobble and boulder beach conglomerate at Kingscote, Kangaroo Island, dated by uranium-series and amino acid racemisation methods respectively to the last interglacial (MIS 5e). The presence of this assemblage preserved within the Glanville Formation at Kingscote suggests a 2–3° C higher than present last interglacial coastal water temperature for northern Kangaroo Island. The height of the last interglacial shoreline deposit was measured by theodolite, and points to a mean last interglacial sea level 3.1 ± 0.4 m higher than present.

Thermal histories and microstructures in Direct Energy Deposition of a High Speed Steel thick deposit

The results of 2D Finite Element thermal simulations of Direct Energy Deposition of a High Speed Steel thick deposit explain the observed microstructural heterogeneities over the whole height of a 36-layer deposit. The Finite Element model is validated by the recorded substrate temperature and the melt pool depth of the last clad layer experimentally measured. The correlation between the computed thermal fields and the microstructures of three points of interest located at different depths within the deposit is carried out. The effect of both the melt superheating temperature and the thermal cyclic history on the carbides type, shape and size is discussed.

POSTFIRE CONDITION AND RENEWAL OF FOREST PHYTOCENOSES ON THE TERRITORY OF THE REPUBLIC OF BELARUS

Results of long-term stationary research on influence of the pyrogenic factor on the efficiency and the postfire condition of forest phytocenoses of Belarus are presented. It has been found out that the size of the postfire falling off of trees and their radial gain in plantations of the main forest forming breeds are determined by the type and intensity of a fire, the forest and taxation characteristics of forest stands as well as biological features of tree species. Dependence of the size of the postfire falling off by the quantity of trees and a stock in pine, spruce, birch and black alder plantations on their average diameter and average height of deposit on trunks are revealed at the ground fires, depths of burn-out of organic horizons of the soil and damage rate of root systems of trees – at the soil fires. The description of scales for identification of damage rate in plantations of the main forest forming breeds from fires and their fire resistance is given. The reforestation methods in the burnt-out places in various forest vegetation conditions which provide formation of biologically steady and highly productive plantations of economic valuable tree species are presented. There is a card of forest fire division into districts of the territory of Belarus on the basis of which types and volumes of actions for fire-prevention arrangement of the forest fund of the legal entities which conduct forestry for the purpose of minimization of the area of wildfires and their consequences are differentiated.

CHANGES OF RADIAL GROWTH IN PINE STAND DAMAGED BY FIRE IN WEST POLISSYA

The authors have estimated the consequences of surface fire in 2012 on 50-year-old pure pine stand in Polissya by dendrochronological methods. In the course of study we have detected depression of pine radial growth that was intensified by droughts and worsening of sanitary tree state after damaging stand by forest fire. Criterias of anomality of weather conditions were calculated on basis of deviation temperature and precipitation from long-term average series of temperature and precipitation (1945-2015).Some features of formation of tree rings in damaged by fire stand including dependence on categories of sanitary state of trees and Kraft classes. Decrease of radial growth was heightened with worsening of tree state. Decrease of width tree rings was revealed at comparison period after fire with period before one: for broken trees by 44 %, very broken trees by 49 % and for dying trees by 75 %. Radial growth didn't recover till state before fire and saved clearly hierarchy tendency: dominant trees had the biggest radial growth and sub-dominant trees had less growth. In damaged stand after fire decrease of width of late (by 68 %) and early wood (by 47 %) we detected at comparison the period after fire and the period before fire. In control stand appropriate values were 8 % and 11 %. Regression model regarding dependence of index radial growth from height of deposit on stems was built.

From Nanowires to Nanopores: A Versatile Method for Electroless Deposition of Nanostructures on Micropatterned Organic Substrates.

We demonstrate a fast, flexible, parallel, and highly controllable method by which to synthesize a variety of nanoscale and mesoscale structures. This method addresses one of the most significant challenges in nanoscience: the in situ parallel placement and synthesis of nano-objects over the mesoscale. The method is based on electroless nanowire deposition on micropatterned substrates (ENDOM). In ENDOM nanostructures are produced at the boundary between two unlike materials if two conditions are met: (a) deposition is kinetically preferred on one of the materials while (b) transport of reactants is favored on the other. In this study, copper structures were deposited on patterned -OH/-CH3-terminated alkanethiolate self-assembled monolayers (SAMs) by exploiting the different reaction rates of electroless deposition on these using the reducing agent dimethylamine borane (DMAB). We demonstrate production of nanowires (width < 100 nm), mesowires (100 nm < width < ∼3000 nm), nanorings, nanopores, and nanochannels. We show that a variety of experimental conditions can be employed, making this method compatible with many substrates. We have also studied the nucleation and growth kinetics of the ENDOM process. The width of the deposit grows exponentially with deposition time and can be modeled using classical nucleation theory. Although the deposit width increases, the height and grain size of the copper deposit is constant (to within experimental uncertainty) with deposition time. These observations indicate that the minimum deposit width is controlled by the nanoparticle dimensions and so can be controlled using the reaction conditions.

Dynamic of Radially Growth Trees Damaged by Fire in Pine Stands Steppe Zone of Kharkiv Region

Purpose. The study of pre- and after the fire of pine forest stands forest steppe Harkivschyny. Methods. Dendrochronological. Results. Dynamics of results of dendroclimatic and dendroindication researches of pine stands on three permanent research plots damaged by fires in 2011. Trees that have good sanitary state and dominant trees restore the tree radial growth in 2 -3 years, at the same time trees in most damaged stand where height of deposit on tree stems are 3.87, didn’t revive the radial growth still. Significant relationships between defoliation and the radial growth for 2013 for second research plot (height of deposit on tree stem is 1,87 м) When the radial growth start to revive. This regression model was described by curves of third degree. Conclusions. It was found that less fire damaged trees that have the best sanitary conditions and are predominant, restored radial growth for 2 - 3 years.

Influence of particle shape and sample width on uniaxial compression of assembly of prolate spheroids examined by discrete element method

We use numerical simulations based on the discrete element method (DEM) to study the response of a cuboidal assembly of spherical (diameter d) or spheroidal particles to uniaxial compression. This study examines the influences of slight deviations from the spherical shape of particles or of the thickness of cuboidal samples on the packing and mechanical characteristics of the assembly. The spheroidal particles were fabricated by the multisphere method. Eight different particle shapes were considered, each with the same volume and with aspect ratios α from 1.0 to 2.5. The final vertical height and larger horizontal depth of the cuboidal deposit were 15d, whereas the thickness ranged from 1.025d to 10d. Upon increasing the assembly thickness or deviating from a spherical shape, numerical examinations by the DEM revealed clear differences in the packing structure and uniaxial compression of assemblies of spheroidal particles. The departure from a spherical shape results in intense changes in contact network, which is manifested as changes in the volume fraction, mean number of contacts per particle, and ordering of the deposits. For the more elongated particles, the pressure ratio as a function of spheroid aspect ratio reached nearly constant values regardless of the sample thickness.

Effects of processing parameters on crystal growth and microstructure formation in laser powder deposition of single-crystal superalloy

A self-consistent three-dimensional (3D) mathematical model was developed to predict the crystal growth and microstructure formation in the laser powder deposition (LPD) of single-crystal (SX) superalloy. The effects of the governing processing parameters of LPD, i.e. laser power, scanning speed, powder feeding rate on the crystal growth and microstructure formation were studied systemically through the mathematical modeling and experimental approaches. Experiments with SX nickel-based superalloy Rene N5 were conducted to verify the computational results. The results indicate that the processing parameters have a profound influence on the molten pool shape and in turn the resulted epitaxial crystal growth patterns in the deposited bead. The height ratio (height of epitaxial columnar dendrite to total height of deposit) of the epitaxial columnar dendrite along the [001]/〈100〉 crystallographic orientation increases up to 52% with the increase of the scanning speed, but decreases down to 42% with the increase of laser power. The simulation results and experimental results of the epitaxial height ratio agree reasonably well. With the optimized processing parameters, the laser deposited multi-layer SX sample with continuous growth columnar dendrite microstructure is demonstrated.

Analysis of Products at Reaction Sites by Fluorescence Microspectroscopy Using the f-NSOM Technique

Reaction products at inclusion sites on Al 2024 have been analyzed in the early stage of pitting by fluorescence microspectroscopy via functional near-field scanning optical microscopy (f-NSOM). From the invariant peak position on the f-NSOM fluorescence spectra at various reaction sites, it appears that the Al oxyhydroxide matrix surrounding the fluorescein dye species is uniform in composition and structure, independent of location. Furthermore, changes in the peak intensity at these sites were proportional to the height of the product deposit. This means that the fluorescein is bound at sites in the product that are uniformly distributed. In addition, the number of binding sites is proportional to the thickness of the product. The chemical analysis of energy dispersive X-ray spectroscopy for the inclusion at each ring core revealed that both the height and intensity of the product rings around Mg-enriched Al-Cu-Mg inclusions were greater in value than that around Mg-deficient inclusions and simultaneously enhanced with increasing width. This originates from the spontaneous Al oxyhydroxide precipitation triggered by vigorous dealloying Mg ions from the large-sized inclusion with high initial content of Mg. © 2005 The Electrochemical Society. All rights reserved.

Sphere‐Cap Mercury Microelectrodes for Scanning Electrochemical Microscopy Above an Insulating Substrate

AbstractSphere‐cap mercury microelectrodes, fabricated onto platinum microdisks 1 and 10 μm radius, were employed as tips in scanning electrochemical microscopy (SECM). Experimental current vs distance curves were acquired above an insulating substrate with a series of sphere caps whose aspect ratio h/a (h is the height of mercury deposit, a is the disk basal radius) varied between 0.28 and 2.14. It was found that the hindered diffusion effect of the insulating surface was the less pronounced the higher was the h/a parameter of the sphere cap. Comparison of experimental and theoretical approach curves displayed a fairly good agreement for subhemisphere caps (h&lt;a), and a less satisfactory agreement for hemispherical (h=a) and superhemispherical (h&gt;a) caps. Preliminary coupled anodic stripping voltammetry and SECM measurements were also performed for the investigation on local chemical equilibria involving heavy metals at sediment/water interfaces.

Effects of Crack Starter Bead Preparation in Drop-Weight Test on Nil-Ductility Transition Temperature

The procedure for making crack starter weld deposit on drop-weight test (DWT) specimens was altered from two passes to one pass in about 1990. The effects of some parameters of crack starter weld process on drop-weight test results were studied. Results of this study indicated that length of overlap of the second pass and height of crack starter beads were most effective on nil-ductility temperature (TNDT). When overlap length and bead height of two-pass deposit were small enough, TNDT obtained by two-pass deposit became lower than one-pass TNDT, the discrepancy being by as much as 25°C. TNDT values for 24 Japanese steels were determined using two different DWT methods, one-pass deposit and two-pass deposit having small overlap length and bead height. The difference of TNDT depending on DWT method could be seen only for high-toughness low-alloy steel base metals. For other materials (i.e., low-to-medium-toughness low-alloy steel base metals, weld metals, and high-toughness carbon steels), TNDTS by two-pass and one-pass deposits were essentially the same. For lower-toughness steels, TNDT was frequently lower than the temperature of vTcv − 33°C), and thus, the reference nil-ductility temperature RTNDT was determined from Charpy impact test results. These results can be taken as a way of interpreting the past toughness evaluations made for operating plants using the two-pass TNDT.

The influence of the height of powdery food deposit on the growth of the drug-store beetle, Stegobium paniceum L.

The influence of the height of powdery food deposit on the growth of the drug-store beetle, <i>Stegobium paniceum</i> L.

PARAMETER INTERACTIONS IN STENCIL PRINTING OF SOLDER PASTE

The stencil printing of solder paste is affected by a large number of factors, including printer settings, stencil aperture geometry, and environmental conditions. A fractional factorial experiment was designed to determine the effects and interactions of some of these parameters. A two-level design on eleven factors was used, with all main effects, two-way interactions and most three-way interactions estimable. The height of the solder paste deposit was measured at certain points on each of sixty-four boards. These measurements were analyzed using ANOVA and ANCOVA, and the most significant factors and interactions identified.The screening experiment presented here is part of a more detailed ongoing investigation of the factors controlling solder paste printing, funded by EPSRC.

Scaling of rough surfaces with nonlinear diffusion.

Surface properties of a random-deposition model that includes the effects of surface diffusion with nonlinear diffusivity are studied in 1+1 dimensions. The nonlinear diffusivity D(h) obeys a power law ${\mathit{h}}^{\mathit{k}}$. For a sufficiently large deposit, the variation of the surface thickness with the height of deposit shows anomalous behavior for the power k. It is found that the exponent \ensuremath{\beta}, describing how the surface thickness grows with the height, is given by \ensuremath{\beta}=(1-k)/40 (for kg1), \ensuremath{\beta}=0 (for k=1), \ensuremath{\beta}=(1-k)/4g0 (for 1gkg0), \ensuremath{\beta}=1/4 (for k=0; linear diffusion), and \ensuremath{\beta}=1/2 (for k0). The case of k=1 is a marginal state, and the surface thickness approaches a constant value with increasing height.