Diameter Glass Beads Research Articles

Demonstration of nonlinear tuning curve vibration response using a homemade analog sweep spectrum analyzer

A super-heterodyne sweep spectrum analyzer has been designed (using analog circuitry), built and tested to cover the 5 to 1000 Hz range. The analyzer employs a linear ramp voltage versus time, driving a voltage-controlled oscillator VCO that generates a sweep from 32.768 kHz to 33.768 kHz in 70 s. An analog AD734 multiplies the VCO signal by a sinusoidal signal (generated by a watch crystal 32.768 kHz oscillator). The “mixer” signal is low-pass filtered and amplified to generate a 5-1000 Hz swept tone using a 2-in. speaker. The accelerometer (mounted on a thin circular clamped acrylic plate) vibration response involves multiplying this signal by the VCO, then filtering this “mixer” signal using a 4-stage watch crystal ladder filter with a 1 Hz bandwidth. This signal is squared and low-pass filtered to generate the time (converted to frequency) vs. mean-squared voltage response on an oscilloscope. In the demonstration, 300 g of 6 mm diameter glass beads are supported by the 11.4 cm diam, 3.2 mm thick plate and upper rigid cylindrical wall column. The nonlinear tuning curve vibration response is recorded for various incremental drive amplitudes to demonstrate that the tuning curve resonant frequency significantly decreases with increasing drive amplitude.

A steady-state kinetic interface-sensitive tracer (KIS-SST) method to measure capillary associated interfacial area in a simultaneous co-flow condition

We propose a novel method to measure the specific capillary-associated interfacial area (awn) between non-wetting and wetting fluids by applying kinetic interface-sensitive (KIS) tracers under steady-state two-phase co-flow conditions. Seven column experiments were conducted with a column filled with glass beads (diameter d50 = 170 μm), serving as the solid grain network of a porous granular material. The experiments were performed for two flow scenarios, i.e., five experiments were performed for drainage conditions (increasing non-wetting saturation) and two experiments for imbibition conditions (increasing wetting saturation). To obtain different saturation levels in the column and, consequently, different capillarity-induced interfacial areas between the fluids, the experiments were performed for different fractional flow ratios (i.e., the ratio between injection rate of the wetting phase and total injection rate). The concentrations of the KIS tracer reaction by-product were recorded at each saturation level and the corresponding interfacial area was calculated. As a result of the fractional flow condition a wide range of wetting phase saturation is created (0.3 < Sw < 0.8). The measured awn increases with decreasing wetting phase saturation for the range 0.55 < Sw < 0.8, and then is followed by a drop in wetting phase saturation of 0.3 < Sw < 0.55. A good fit for our calculated awn is obtained (RMSE <0.16) using a polynomial model. Additionally, the results of the proposed method are compared to published experimental data and the method's main advantages and limitations are discussed.

Investigation of ultrasound propagation through dense glass bead packings immersed in water

Conventional ultrasound imaging generally relies on a single scattering assumption and a constant sound hypothesis. However, in dense granular sediments where the glass beads diameter is comparable to the wavelength (typically 500 μm), both hypothesizes are no longer valid, resulting in a loss of resolution and contrast, up to the situation where a target to image could totally vanish in the fog. To better characterize this strongly scattering medium, we have conducted several ultrasonic experiments in reflection and in transmission, either on the diffused wave or on the coherent one. Both the transport and scattering mean free paths are estimated in the imaging bandwidth (1–5 MHz), alongside with the phase velocity and extinction length of the coherent wave. These results are compared with an analytical model, i.e. Generalized Coherent Potential Approximation*, which considers a coated sphere buried in an effective medium. Finally, we show a dispersive beamformer which takes into account the measured phase and group velocity. This allows us to obtain a more resolved and contrasted image in such a scattering medium. * Jing X, Sheng P, Zhou M. Phys Rev Lett. 1991

Glass beads increase the formation kinetics of beta-lactoglobulin amyloid fibrils

In this study beta-lactoglobulin solutions were processed with glass beads in an orbital shaker at high temperatures and low pH value to identify the effect of mechanical stressing and surfaces on amyloid aggregation kinetics. The information will provide a better understanding on how specific mechanical factors provide a nucleation supporting effect on the assembling of building blocks for a more efficient production of functional amyloid aggregates. Because aggregate morphologies vary at pH 2 (semiflexible) or pH 3.5 (worm-like), examination at both pH values gives information about their specific formation and stability characteristics. Different diameters of glass beads (20–1000 μm), and different shaking frequencies (0 - 280 min−1) were used to vary mechanical stress energy, which was quantified by CFD-DEM simulations. To investigate surface effects, the hydrophobicity and surface roughness of glass beads was altered by modification with stearic acid. Amyloid aggregates and bead surfaces were analysed by ThT-assay, AFM and ATR-FTIR.Hydrophobic beads with high surface roughness affected the aggregation negatively. The use of non-hydrophobic beads increased the formation kinetics of fibrils but not of worm-like aggregates, although, both morphologies had a reduced mean length.

An investigation towards the optimum design of retro-reflective materials as building envelopes for the enhancement of optical performance

Retro-reflective (RR) materials may represent an advanced solution for building envelopes, as they could contribute to Urban Heat Island mitigation. This study could bring novelty to the current state of the art on this topic, as it proposes to investigate the optimum design of glass beads RR materials for building application. To this aim, the impact of glass beads superficial density and diameter on the optical performance of RR materials has been further explored. In particular, 15 RR glass beads samples were developed, using a highly reflective paint as substrate and varying both glass beads superficial density and diameter. Also a diffusive sample, without RR glass beads, was made for comparison. Three different glass beads superficial density ranges and five diameter ranges were investigated. Samples were tested through spectrophotometric and angular reflection distribution analysis. All RR samples exhibited an overall lower solar reflectance compared to the diffusive sample, whereas RR samples with 200 ÷ 300 µm diameter exhibited the highest RR capability. By reducing glass beads superficial density, generally a reduction of RR performance was observed.

Adsorption Dynamics of Surface-Modified Silica Nanoparticles at Solid-Liquid Interfaces.

Understanding the adsorption dynamics of nanoparticles at solid-liquid interfaces is of paramount importance to engineer nanoparticles for a variety of applications. The nanoparticle surface chemistry is significant for controlling the adsorption dynamics. This study aimed to experimentally examine the adsorption of surface-modified round-shaped silica nanoparticles (with an average diameter of 12 nm), grafted with hydrophobic (propyl chains) and/or hydrophilic (polyethylene glycol chains) agents, at an aqueous solution-silica interface with spherical soda-lime glass beads (diameter of 3 mm) being used as adsorbents. While no measurable adsorption was observed for solely hydrophobic or hydrophilic nanoparticles, a considerable level of adsorption was detected for nanoparticles comprising both hydrophobic and hydrophilic agents. Various kinetic models were employed to model the adsorption dynamics of the responsive nanoparticles. The results demonstrated that the mixed diffusion-kinetics models could predict the dynamics better than the adsorption diffusion models, indicating that the dynamics is controlled by a combination of liquid film diffusion, intra-particle diffusion, and mass action. Additionally, the adsorption of the surface-modified silica nanoparticles onto a mineral silica surface was examined using molecular dynamics simulations. The interaction energy for nanoparticles comprising both hydrophobic and hydrophilic agents was evaluated to be more favorable than that of solely hydrophobic or hydrophilic nanoparticles.

Triaxial test on glass beads simulating coarse-grained soil

It is feasible to study the mechanical characteristics of coarse-grained soil by simulated granular materials such as glass beads. In this paper, 3 mm diameter glass beads are used to conduct drained and undrained triaxial tests under different confining pressures to explore their strength, deformation and critical state characteristics. Specifically, the influence of drainage and confining pressure on the stick-slip phenomenon of glass beads is reported. The experimental findings from triaxial tests show that the stress-strain relationship of glass beads softens when the confining pressure is high. Under the undrained condition, the initial modulus increases with the increase in the confining pressure. In contrast, it is not significantly affected by the confining pressure in the drained condition. It is quite evident that the glass beads hardly contract during the shearing process, and their stress path is approximately a segmented straight line. The slope of the critical state line under the undrained condition is greater than that under the drained condition, and the friction angle of the glass beads under the undrained and drained conditions is calculated to be 28.1° and 29.5°, respectively. The phenomenon of stick-slip has been depicted for the different test conditions, and the stick-slip amplitude linearly increases with the confining pressure, especially in the undrained condition. It is also found that the maximum energy released from the phenomenon of stick-slip increases linearly with the confining pressure.

Impact of different light curing modes on the cuspal deflection of maxillary premolars restored with nanohybrid resin restoration

INTRODUCTION: The influence of various light-curing modes may lead to polymerization shrinkage resulting in contraction stresses in composite resin. These stresses leads to linear movement of the cusp tips of the tooth as a result of interactions between polymerization shrinkage stress of the composite and adherence of the cavity wall of the tooth. That may lead to restoration failure. AIM: Comparative evaluation of the effect of different light-curing modes on the cuspal deflection of class II Mesio-occlusal-distal cavity restored with Nano-hybrid composite resin restorative material. METHOD: Thirty-six standardized MOD preparations were prepared on maxillary first premolars. Three groups(n=12) were divided according to different light-curing modes of Blue phase LED curing light- Group 1: soft-start curing mode; Group 2: pulse curing mode; Group 3: continuous curing mode. 1mm diameter glass beads were fixed to each cusp tip as a reference point for intercuspal distance to measure initial cuspal deflection for each group. MOD Preparations were etched and bonded with adhesive resin to provide micromechanical attachment and restored with Nano-hybrid composite restoration using the incremental technique. The cuspal deflection was then measured with the Digital micrometer gauge and the mean difference was measured for each group.

Nonlinear distortion correction for posterior eye segment optical coherence tomography with application to tree shrews.

We propose an empirical distortion correction approach for optical coherence tomography (OCT) devices that use a fan-scanning pattern to image the posterior eye segment. Two types of reference markers were used to empirically estimate the distortion correction approach in tree shrew eyes: retinal curvature from MRI images and implanted glass beads of known diameter. Performance was tested by correcting distorted images of the optic nerve head. In small animal eyes, our purposed method effectively reduced nonlinear distortions compared to a linear scaling method. No commercial posterior segment OCT provides anatomically correct images, which may bias the 3D interpretation of these scans. Our method can effectively reduce such bias.

Quantification of sonochemical and sonophysical effects in a 20 kHz probe-type sonoreactor: Enhancing sonophysical effects in heterogeneous systems with milli-sized particles

Even though acoustic cavitation has been widely investigated, only few researchers focused on the relationship between sonochemical and sonophysical activities and on the enhancement of sonophysical activity. In this study, sonochemical and sonophysical activities were investigated in a heterogeneous system to understand the relationship between these two activities and to suggest optimal conditions for ultrasonic desorption/extraction processes comprising milli-sized glass beads. The sonochemical activity was quantitatively analyzed using potassium iodide dosimetry in homogeneous and heterogeneous systems. Sonophysical activity was quantitatively and qualitatively analyzed using paint-coated bead desorption tests and aluminum foil erosion tests under three probe positions of “T” (1 cm below the liquid surface), “B” (1 cm above the vessel bottom), and “M” (midpoint between “T” and “B”). Three different sizes of glass beads (diameter: 0.2, 1.0, and 4.0 mm) were used in this study. The highest sonochemical activity was obtained at “B” in both homogeneous and heterogeneous systems. However, three times lower sonochemical activity was observed in the heterogeneous system than in the homogeneous system because significant attenuation and unstable reflection of ultrasound occurred in the bead layer and suspension. Higher sonophysical activity was observed, when the bead size decreased and the probe approached the bottom. However, no significant sonophysical activity was detected when the beads were attached to the bottom. Therefore, the sonophysically active region was the zone around the probe body, opposite to the ultrasound irradiation tip, and only suspended beads could undergo severe cavitational actions. This was confirmed via aluminum foil tests. Several erosion marks on the foil were observed in the area around the probe body, whereas no severe damage was observed at the bottom. Moreover, the degree of sonophysical activity did not change for various saturating gases. This might be due to the different thresholds of sonochemical and sonophysical activities.

A first-order physical model for the prediction of shear-induced particle migration and lubricating layer formation during concrete pumping

For the first time, a first-order physical correlation between pumping parameters (pressure and flow rate), granular skeleton properties (particle diameter and packing properties) and LL properties (thickness and viscosity) is proposed. This correlation is derived from the analysis of the equations driving shear-induced particle migration in dense suspensions. The model predictions in terms of lubricating layer apparent viscosity are compared to experimental measurements in the case of model concretes prepared with glass beads of various diameters, conventional-vibrated concretes and self-compacting concretes. This comparison is carried out for two flow typologies, namely the Sliper, known for its ability to mimic concrete pumping, and a co-axial tribometer. In all cases, the proposed model is shown to be able to capture qualitatively the observed main features and their evolutions despite the absence of any fitting parameters.

Sonochemical activity in ultrasonic reactors under heterogeneous conditions

Due to its physical and chemical effects, ultrasound is widely used for industrial purposes, especially in heterogeneous medium. Nevertheless, this heterogeneity can influence the ultrasonic activity. In this study, the effect of the addition of inert glass beads on the sonochemical activity inside an ultrasonic reactor is investigated by monitoring the formation rate of triiodide, and the ultrasonic power is measured by calorimetry and by acoustic radiation. It was found that the sonochemical activity strongly depends on the surface area of the glass beads in the medium: it decreases above a critical area value (around 10−2 m2), partly due to wave scattering and attenuation. This result is confirmed for a large range of frequencies (from 20 to 1135 kHz) and glass beads diameters (from 8-12 µm to 6 mm). It was also demonstrated that above a given threshold of the surface area, only part of the supplied ultrasonic power is devoted to chemical effects of ultrasound. Finally, the acoustic radiation power appears to describe the influence of solids on sonochemical activity, contrary to the calorimetric power.

Phase speed in water-saturated sand and glass beads at MHz frequencies.

Measurements of the phase velocity of compressional sound waves in water-saturated granular materials are reported for the 1.0-2.0 MHz frequency range. The sound speed estimates are based on travel times through granular layer thicknesses ranging from 8 to 17 mm. Three types of granular media were used: 336 μm median diameter glass beads and two natural sands with median diameters of 219 and 406 μm. These grain sizes and frequency range correspond to 0.5<ka<1.2, where k is the wavenumber and a the grain radius. To remove trapped air, the samples were boiled under pressure before transfer to the measurement tank. The results are compared to previously reported experimental results and to the Schwartz and Plona [J. Appl. Phys. 55(11), 3971-3977 (1984)] multiple scattering prediction, confirming negative dispersion for ka > 0.5. Scaling the data by a factor depending on porosity and grain density reduces the spread among the available phase speed estimates by nearly a factor of 2, from 12.5% to 6.9%.

Isolated buoyant convection in a two-layered porous medium with an inclined permeability jump

Abstract

Effect of horizontal vibrations on mass flow rate and segregation during hopper discharge: discrete element method approach

Vibration is often utilized as a means of initiating and/or controlling flow from hopper in industries dealing with powder/granular materials such as packing, conveying, etc. The effect of horizontal vibration on gravity flow of granular material from conical hopper is modeled using the discrete element method. Material considered in this study includes glass beads of diameter ranging between 0.7 mm and 2.0 mm. The flow dynamics and segregation of material are analyzed for different mixtures characterized based on mass percentage of smaller particles (fines) and multi-component mixtures (binary and ternary) at different vibration parameters. The study includes the influence of vibration frequency, acceleration amplitude, fines percentage, diameter ratio and mixture components on segregation and mass flow rate during vibratory hopper discharge. The extent of segregation is calculated by means of mass fraction of fines inside hopper for different operating conditions. The numerical results indicate that the increase in vibration acceleration at a fixed frequency results into increased mass flow rate and there exists acceleration amplitude beyond which segregation is predominant. Mixture components play significant role in segregation behaviour and binary mixture suffers more segregation as compared to ternary mixture. The spatial distribution of the velocity profile indicates that different mixtures behave differently at a particular vibration conditions. The phenomena like sieving or percolation are also observed based on the analysis of top view simulation snap shots.

Effect of porosity on thermal conductivity of porous materials

The basic idea of porous materials has been used in different applications of engineering science especially regards to thermal insulation. In this study the effect of porosity on thermal conductivity has been investigated experimentally by using Cylindrical thermal probe (TP02® Hukseflux). During transmission the heat power in the probe, the temperature is variation as a function of the natural logarithm. The slope of the graph is representing the proportion inverse to the thermal conductivity. Different materials in terms of porosity have been selected to identify influence of porosity on thermal conductivity. At first fluid material (glycerol) with no porosity, and after that glass beads of different diameters to introduce the porosity and different types of glass wool as an example of insulation materials. Comsol Multiphysics® axisymmetric module 2-D has been used to validate the experimental results.

In-situ observation for natural gas hydrate in porous medium: Water performance and formation characteristic

Extensive efforts have been made regarding gas hydrate sample reconstruction in the laboratory for a better understanding and development of natural gas resources. Magnetic resonance imaging (MRI) is a useful method for directly observing the reconstruction of methane hydrate, yet relevant studies remain limited. In this study, a 9.4-T 400-MHz MRI instrument was employed to investigate CH4 hydrate formation in porous media involving various initial water saturation levels and sand diameters. Pressure histories and MRI signal variations were monitored to discuss the process of CH4 hydrate growth, and the three main formation stages of induction, rapid growth, and slow formation were determined. Furthermore, the liquid water performance in MRI micro-images was analyzed to predict the characteristics of CH4 hydrate formation. The results indicated that CH4 hydrate formed in a spatially and temporally random manner and that pore plugging occurred owing to the residual water encased in grown hydrate. Additionally, phase saturations, water conversion percentages, and formation rates were defined to evaluate the effect of sand diameter and initial water saturation on CH4 hydrate formation. With the reduction in the diameter of quartz glass beads from 400 μm to 100 μm, the average hydrate formation rate increased from 0.0010 min−1 to 0.0034 min−1, respectively. When the initial water saturation decreased to the optimized value (0.22 in this study), the water conversion percentage and hydrate saturation increased.

Effects of Glass Beads Packing on SF6 Abatement by Packed Bed Plasma

This article investigated the effects of SF6 degradation by packed bed DBD (PBDBD) with packing material of glass beads (diameter of 4 mm). The results show that the packing materials effectively increased the discharge voltage and discharge current amplitudes and promote the generation of filamentary discharges. In addition, the packing materials promoted the charge transfer process between the reactor electrodes and shortened the charge time in one DBD discharge cycle. SF6 degraded more thoroughly in the packed bed reactor (PBR). The energy yield of the SF6 abatement in PBR reached up to 17.1 g/kWh with a degradation rate of 88.6%. The degradation by-products of SF6 were mainly SO2F2, SOF2, SO2, OF2, SOF4 and SiF4. After NaOH solution scrubbing, the residual gas contained SO2F2 and SOF4 which need further treatment. The experimental results show that PBDBD with glass beads as packing materials has a potential for the application of SF6 waste gas treatment.

Mixing and regime transition analysis of liquid-solid conical fluidized bed through RPT technique

The current work focuses on the hydrodynamic study of liquid-solid mono and binary conical fluidized bed using the radioactive particle tracking technique. Two different sizes 0.6 and 1 mm diameter glass beads were used for the experiment. Two different bed compositions, mono dispersed (100 wt% of each solid) and 50 wt% mixture of the solids, were studied. A rich data base, including instantaneous velocities, mean and RMS velocities, granular temperature, etc., were calculated by suitable post-processing. Further, Hurst exponent, autocorrelation function, segregation index, Kolmogorov entropy, and correlation dimension were calculated using time series data to understand the mixing and chaotic nature of the fluidized bed for each set of data. Good degree of mixing was observed even at a low velocity of 0.07 m/s. Kolmogorov entropy and correlation dimension indicate regime change at liquid inlet velocity of 0.1 m/s for both mono and 50 wt% binary bed.

Investigation on the effect of temperature on evaporative characteristic length of a porous medium

Evaporation from a porous medium goes through three different stages; the physics of drying is completely different in each stage. In the first stage, liquid films maintain high hydraulic conductivity leading to high evaporation rates; it mainly depends on the atmospheric demand. Duration of stage 1 is given in terms of a suitable length scale, Lcap, which originates from the competition between the capillary, gravitational, and viscous forces. It is known that Lcap depends strongly on the particle size and distribution of the pore sizes in a porous medium. We report experiments of evaporation from an initially saturated homogeneous porous medium consisting of nearly mono-disperse (0.70–0.85 mm diameter) glass beads, while heating from above using IR radiation. We found significant changes in Lcap values depending on the incident heat load. We discuss these results based on changes in the fluid properties, such as surface tension and sub-surface temperature gradient. It is expected that such a study would be beneficial not only to the drying industries but also in the agricultural sector and cooling devices.