Glass Spheres Research Articles

Effects of Solid-to-Fluid Conductivity Ratio on Thermal Convection in Fluid-Saturated Porous Media at Low Darcy Number

Abstract This study presents experimental data on the effects of the solid-to-fluid thermal conductivity ratio on natural convective heat transfer in a fluid-saturated porous medium heated from below. Argon is used as the saturating fluid, while a bed of glass, steel, or aluminum spheres constitutes the solid porous matrix. Emphasis is placed on attaining high Rayleigh numbers while maintaining low Darcy numbers (5.68 × 10−8 ≤Da≤5.22 × 10−7). At low modified Rayleigh numbers (Ra*) corresponding to the Darcy regime, the Nusselt number is independent of the medium conductivity. As Ra* increases and the system transitions into Forchheimer regime, the data diverge, with Nusselt numbers decreasing with increased thermal conductivity ratio at a fixed Ra*. This non-intuitive result is shown to be the result of the traditional choice of Ra* and Da as the controlling parameters since the heat transfer coefficient appears independent of the conductivity ratio. Scaling arguments are used to identify transition points between the regimes, which yield the transition criterion Ra* ~ Prp, where Prp is the modified Prandtl number. When the data are expressed by scaling with Prp, it is shown that the data for multiple parameter combinations collapse onto a single curve, which also agrees well with theoretical predictions. In light of this finding, the data from available literature are assessed, and it is proposed that deviations from theory are likely the result of the strong porous medium condition (low Da) not being satisfied.

Detection and quantification of small and low-uptake lesions for differentiated thyroid carcinoma using non-time-of-flight iodine-124 PET/MRI.

124-iodine (124I) is used for positron emission tomography (PET) diagnostics and therapy planning in patients with differentiated thyroid cancer (DTC). Small lesion sizes(<10mm) and low 124I uptake are challenging conditions for the detection of DTC lymph node lesions. The aim of this study was to systematically investigate the lesion detectability and quantification performance under clinically challenging imaging conditions using non-time-of-flight (TOF) PET/magnetic resonance imaging (MRI) in the clinical context of radionuclide therapy planning of DTC patients. PET/MR measurements were performed on the Siemens Biograph mMR using a small lesion NEMA-like phantom (six glass spheres, diameters 3.7-9.7mm). 60 min list-mode data were acquired for nine activity concentrations (AC) ranging from 25kBq/mL to 0.25kBq/mL using a sphere-to-background ratio of 20:1. PET list-mode data were divided into five timeframes (60, 30, 16, 8, and 4min) and reconstructed using either ordered-subsets expectation maximization (OSEM) or OSEM+ point spread function (PSF) algorithm. For all reconstructions, the smallest detectable sphere size was investigated in a human observer study. Partial volume effect (PVE) corrected PET images (contour and oversize-based approach) were analyzed considering a±30% deviation range between imaged and true AC as acceptable. Clinical data of eight DTC patients with small lymph node lesions were evaluated to assess agreement between the PVE correction approaches. Longer PET acquisition times, higher ACs, and PSF reconstructions resulted in improved PET image quality and overall improved lesion detectability. The smallest 3.7mm sphere was only visible under the best imaging conditions. Using a typical clinical 124I whole-body PET/MRI protocol with an acquisition time of 8 min using OSEM reconstructions, all lesions of ≥6.5mm in diameter could be detected and the quantification provided reliable results approximately above 5.0kBq/mL. An accurate quantification of ACs in the 4.8mm sphere was not feasible in this study. In the clinical evaluation of 10 lesions, a good agreement between oversize- and contour-based PVE corrections was observed(<15% deviation). The results showed that a reliable quantification of 124I uptake with PET/MRI is feasible and, therefore, could be used to perform radioiodine pre-therapy lesion dosimetry and individualized therapy planning in DTC patients.

Capillary rise in a packing of glass spheres

A series of experiments are performed to give insight into the mechanisms of liquid rise in a 3D dense random packing of glass spheres. A sharp knee in the log-log plot of water height h versus time t curve is observed, with an attendant change in h(t) characteristic from h∝t0.5 to h∝t0.05. This behaviour is observed for 5 choices of diameter distribution of spheres, such that the mean diameter is in the range of 0.22 mm to 1.20 mm, and the ratio of standard deviation to mean diameter lies between 0.014 and 0.157. Immediate arrest in water rise occurs when the water reservoir is removed from the bottom of the column, in support of the conclusion that water rise is by capillary action. In the post-knee regime of the h(t) response, water rise occurs in a jerky manner by a series of jumps, involving transverse jumps and more occasional vertical jumps in water ingress; each jump is by an increment of sphere diameter. The incubation time for each vertical jump is sensitive to height of meniscus and dictates the overall rate of water rise. Pendular-rings at the junctions between glass spheres are not observed above the meniscus; this casts doubt upon the notion that the jerky motion of the meniscus is due to the incubation time for a vapour-fed pendular-ring to grow and coalesce with the meniscus. Possible sources of the height-dependent incubation time for each vertical jump are discussed, including a time-dependent increase in surface tension. Additional insight is obtained by observing water rise, and glycerol rise in (i) a monolayer of glass spheres, (ii) in a capillary tube of diameter slightly greater than that of the glass beads and filled with a single column of glass spheres and (iii) an empty capillary tube. Continued liquid rise beyond the knee in the h(t) curve is noted in all cases except for that of an empty capillary tube.

Probing marginal stability in the spherical p = 2 model

Abstract In this paper, we investigate the marginally stable nature of the low-temperature trivial spin-glass phase in spherical p = 2 spin glass by perturbing the system with three different kinds of non-linear interactions. In particular, we compare the effect of three additional dense four-body interactions, namely ferromagnetic couplings, purely disordered couplings and couplings with competing disordered and ferromagnetic interactions. Our study, characterized by the effort to present in a clear and pedagogical way the derivation of all the results, shows that the marginal stability property of the spherical spin glass depends in fact on which kind of perturbation is applied to the system. In general, a certain degree of frustration is needed in the additional terms in order to induce a transition from a trivial to a non-trivial spin-glass phase. On the other hand, the addition of generic non-frustrated interactions does not destabilize the trivial spin-glass phase.

Investigation of cutting forces of glass sphere reinforced polymer composites

AbstractIn this study, the effects of reinforcement ratio, drill bit material, and drilling process parameters on the cutting forces generated during the drilling of glass sphere‐reinforced polypropylene composites were investigated experimentally. Test specimens were produced by conventional injection‐moulding of glass sphere reinforced polypropylene composite materials at 5 %, 10 % and 20 % wt. ratios. High speed steel, titanium‐coated high‐speed steel, and carbide drill bits with 4 mm diameter were preferred for drilling. In addition, the drilling process was carried out on a 3‐axis computer numeric control milling machine. Three different feed rates of 0.05 mm/rev, 0.10 mm/rev, and 0.15 mm/rev and cutting speeds of 12 m⋅min−1, 16 m⋅min−1, and 20 m⋅min−1 were determined for the drilling process. In addition, Taguchi experimental optimization method, analysis of variance and scanning electron microscopy were used to investigate the morphology of the drilled surface and the wear mechanisms occurring on the drill bit due to the drilling process. The test findings showed that the maximum torque value was 54.64 N⋅mm and the maximum thrust force was 100.43 N. The optimum test parameter for cutting forces was observed as C1D3FR1CS3. Drill parameter had an effect of 40.96 % on thrust force and 36.11 % on torque.

The Objective Response and Disease Control Rates in Patients with Liver Metastastic Breast Cancer Receiving Transarterial Radioembolization: A Meta-Analysis.

To meta-analyze the utility of transarterial radioembolization (TARE) in patients with liver metastatic breast cancer (BC), based on the objective response rate (ORR) and disease control rate (DCR). A literature search was performed retrieving studies with (1) at least 10 patients with liver metastatic BC treated with TARE and (2) adequate information to derive ORR and DCR. The ORR is the ratio between patients with liver lesions showing complete response (CR) or partial response (PR) over the total number of patients treated with TARE; the DCR is the ratio between patients with CR, PR, or stable disease (SD) over the total number of patients treated with TARE. Eighteen studies (650 patients) were eligible; the ORR of TARE resulted 50.71% (95% C.I.: 40.04-61.36) and the DCR resulted 88.37% (95% C.I.: 81.89-93.57). Taking into account resin spheres (395 patients), the ORR was 60.35% (95% C.I.: 46.55-73.36) and the DCR was 92.73% (95% C.I.: 87.17-96.80%). Considering glass spheres (144 patients), the ORR was 32.38% (95% C.I.: 18.43-48.16) and the DCR was 82.69% (95% C.I.: 59.29-97.26). This meta-analysis favors the use of TARE in patients with liver metastatic BC either with resin or glass spheres.

A multi-approach study on CO2 absorption in packed beds: Theoretical, experimental, and CFD perspectives on gas phase pulsation

This work seeks to improve CO2 absorption efficiency in packed bed columns by substituting amine-based solvents with sodium hydroxide and implementing gas phase pulsation to enhance mass transfer coefficients. Experimental analysis and computational fluid dynamics modeling were employed to investigate the impact of pulsation on absorption efficiency under various conditions. Essential parameters comprised superficial liquid velocity (1.2–4.6 cm/s), pulsation frequency (0–10 Hz), amplitude (0–20 mm), and NaOH concentration (0.25 N to 2 N), while maintaining a constant superficial gas velocity of 120 cm/s and a solute gas concentration of 13 %. Three packing materials—glass spheres, ceramic Raschig rings, and ceramic Pall rings—were evaluated. The results demonstrated that ceramic Pall rings exhibited the greatest efficiency. Pulsation, namely at 9.06 Hz and 20 mm amplitude, enhanced the volumetric mass transfer coefficient by as much as 4.53 times for Pall rings. Increased column diameters (from 7.00 cm to 11.5 cm) enhanced performance. The findings show advancement of more efficient CO2 absorption (by switching from chemical absorption using amine based solvents to classical chemical absorption using aqueous NaOH solution) for industrial applications, aiding climate change mitigation initiatives.

Hybrid Geopolymer Composites Based on Fly Ash Reinforced with Glass and Flax Fibers

This article’s aim is to analyze physical, mechanical, and fracture properties as well as the thermal investigation of geopolymer composites reinforced with flax, glass fiber, and also the hybrid combination of fibers. Two types of matrices were considered as composites matrices. The first composition was based on fly ash and river sand. The second matrix composition contained fly ash and glass spheres. The content of reinforcement was 1% by mass. Compressive strength and three-point bending fracture tests were performed. The values of fracture toughness and fracture energy were determined. The resonance method was used to verify the dynamic characteristics, such as the dynamic modulus of elasticity and the dynamic Poisson ratio. The results show that single-type fibers in composites based on fly ash and glass spheres did not affect compressive strength. However, introducing hybrid reinforcement increased compressive strength by about 10% compared to the reference specimens. Flax fibers and hybrid reinforcement ensured higher fracture toughness and energy. The results also revealed great potential for glass sphere application to geopolymer materials in terms of fracture mechanics and thermal properties. Despite the lower strength properties in relation to geopolymers based on sand aggregate, applying reinforced fibers into the composite with glass spheres enhanced the compressive strength compared to other materials. Materials modified with glass spheres have a thermal conductivity twice as low as that of materials containing river sand.

Dynamic failures at the metal-glass interface under impact loading

To investigate dynamic fracture behavior in the metal, three metal spheres (e.g., steel sphere, high purity tungsten sphere, and high purity lead sphere) are accelerated by the gas gun devices to impact glass spheres under the critical speed range (i.e., from 70 m/s to 210 m/s). The velocity interferometer system for any reflector (VISAR) devices are employed to measure the particle velocities at the back surface of glass sphere, and high-speed photographs are utilized to capture the failure process at the metal-glass interface. Due to the asynchronous evolutions of stress fields and strain fields in the violent failure process, the results illustrate quite different failure mechanisms from those by the Split Hopkinson Pressure Bar (SHPB) impacting. Fragmentations of the glass sphere are caused mainly by the radial cracks and the lateral cracks around the metal-glass interface and the edges of the sphere with increasing impact velocity. Dynamic failures in the three metal impactors exhibit different modes, e.g., tensile fracture in the steel impactor, shear fracture in the tungsten impactor, and compressed yielding in the lead impactor. The transferring of strain energy releasing is introduced to describe the failure behavior at the metal-glass interface, and a relaxation-diffusion equation of strain energy releasing is then established based on the experimental results and the numeric results by the discrete element method (DEM). The evolutions of failures at the metal-glass interface are discussed. Further investigation is conducted to describe the dynamic fractures in tungsten impactors and steel impactors based on the dimensional analyses, and the quantitative expressions of these strain rate dependent fracture strains and crack width in the metal impactors are obtained. The results are helpful for the profound understanding of the dynamic fracture in the metal structures and the dynamic fragmentations in the brittle material when subjected to impact loading.

Synergetic effect of hybrid surface treatment on the mechanical properties of adhesively bonded AA2024-T3 joints

ABSTRACT Improving the surface properties of AA2024-T3 aluminium alloys is crucial for achieving durable and sustainable joints. For this purpose, AA2024-T3 alloys were first sandblasted at 4, 5 and 6 bar pressures using aluminium oxide and glass sphere abrasives. Then, the sandblasted samples were subjected to the chemical surface treatment resulting in a hybrid surface process. The surface properties of sandblasted and hybrid surface-treated AA2024-T3 alloys were characterised by 3D image analysis, contact angle and roughness measurement. Additionally, single-lap joints were fabricated using adhesives with low and high viscosity. The effect of changes in the viscosity of adhesives and the surface properties of the AA2024-T3 on the mechanical properties of the joints has been analysed in detail. It was found that both sandblasting and hybrid surface treatments applied to AA2024-T3 alloys caused significant improvement in the mechanical properties of the joints. AA2024-T3 alloys, which were chemically surface treated after being sandblasted with glass spheres at 6 bar pressure, were joined using low and high viscosity adhesives, and the failure load of these joints increased by approximately 110% and 68%, respectively, compared to untreated samples. In the case of aluminium oxide usage, the increase rates were determined to be 93% and 43%.

The use of ensembles trees machine learning method in estimating damping of granular materials

Granular Materials (GM) employed within the mechanism of particle dampers attenuate the vibration energy due to their interparticle and particle-wall interactions. Estimating their damping effect using the analytical equivalent single mass approach overlooked the particles' individual losses that are built into the total damping. Alternatively, the numerical techniques (e.g., Discrete Element) are time-inefficient and computationally demanding. Therefore, this study explores the implementation of Machine learning (ML) algorithms to estimate the damping effect of GM. The ML model in this study will rely on a Data-Driven Modeling approach (DDM) incorporating the ensemble tress nonlinear regressor method. The models' training and testing data were obtained from an experimental setup of an acrylic beam internally integrated with Stainless Steel (SS) and glass spheres undergoing low excitation amplitude (RMS &lt;1N). The main aim was to map between seven input features (e.g. filling ratio) and one targeted output: the beam's damped frequency response. Three ensemble trees' algorithms were used to create the DDM; Decision Tree, Random Forest, and XGBoost. The hyperparameter combination based on the Gridsearch CV function increases the prediction accuracy of each model. The developed ML models provided high accuracy (86-93%) in predicting the damping effect of the granular materials spheres.

Experimental study into the sedimentation process of solids of different origin

Sedimentation refers to the first stage of wastewater treatment from mechanical impurities. Its rate depends on the density and particle size of impurities, as well as the density and viscosity of dispersion medium. In industrial sedimentation tanks, particle settling can occur in laminar, transient or turbulent modes. Aim. To establish the criterion equations and their coefficients for sedimentation processes of sand, glass and polyamide granules. Sedimentation of sand particles of 0.001– 0.003 m, spherical glass particles with the diameter of 0.0025–0.004 m and polyamide granules with the volume-surface mean diameter of 0.0022–0.003 m was carried out in a measured glass cylinder filled with distilled water. Each solid particle was measured, then, it came into contact with the water surface by means of tweezers, and released, starting to settle to the bottom of the cylinder under the action of gravity. A stopwatch was used to time the particle passaging between the marks of the measured cylinder. Calculations were performed using dimensional analysis. According to the test results, the dependences of the Reynolds number on the Archimedes number were established for the sedimentation of sand particles and polyamide granules in the transient mode, while spherical glass particles in the turbulent mode. In addition, the criterion equations of the solid particles sedimentation in the liquid were derived. The coefficients for these equations were experimentally determined. The equations and coefficients obtained in the study can be used in the design of settling tanks for mechanical treatment of wastewater to remove sand, glass and polymer particles.

A universal drag model for liquid-solid fluidization: Experiment, data-driven modeling, CFD modeling and simulation

Various industrial applications are performed in liquid-solid fluidized beds where drag force plays a significant role in affecting the expansion characteristics of granular-bed, and then determines the mass/heat transfer performance. This study employs dimensionless learning data-driven modeling method, which is derived from the principle of dimensional invariance, to automatically discover the relationship between the drag coefficient and hydraulic dimensionless numbers from the liquid-solid fluidization data. It is found that the Fr number (=ul2/gds) also plays important role in improving the prediction accuracy of drag model except for Re number (=dsulρl/μl). The proposed data-driven modeling method has desired robustness, and the yielded drag model can be applicable to other liquid-solid systems, such as water-polystyrene spheres and water-coal particles, although it is derived from the fluidization of spherical glass beads in rising tap-water. The proposed drag model can also provide good CFD simulation results that agree very well with the experiment data with the relative error less than 5 %.

Enhanced EMI Shielding Efficiency of Graphene Nanoplatelets and Glass Sphere Composite‐Loaded Ultralight Weight Flexible Polyurethane Foam

ABSTRACTGraphene nanoplatelets and glass sphere (GNP@GS) composite is prepared using a simple mixing process and is loaded in flexible polyurethane foam to produce ultralight weight, high‐performance, electromagnetic interference (EMI) shielding material. The presence of a glass sphere enhances the mobility of graphene nanoplatelets in a polymer matrix forming a continuous conductive network thereby achieving better electrical conductivity and enhanced EMI shielding efficiency. The electrical conductivity of the synthesized GNP@GS/PU foam composites was achieved between 5.69 × 10−8 and 13.25 × 10−4 S/cm at varying filler loading. The maximum shielding effectiveness (i.e., −24.43 dB) was found at 12 wt% GNP@GS‐loaded samples. The shielding results show that the composites have the potential to be employed as ultralight weight, flexible EM shielding materials. These materials are essential in many applications because they are good shield materials that prevent electronic equipment from electromagnetic‐interference, better heat dissipation from the device, and also flexible to support fall protection.

Phase‐Transition Variations in Granular Materials Under Multi‐Period Vibrations: Implications for Triggering Landslides After Multiple Earthquakes

AbstractEarthquake‐triggered landslides are widely recognized. Despite extensive research on the seismic responses of landslides triggered by single earthquakes, there is a lack of understanding of the seismic responses of landslides due to earthquake sequences and multiple earthquakes, and the mechanisms of dynamic weakening under multiple earthquakes still lack support from experimental results. To explore their seismic response characteristics and triggering mechanism, a series of multi‐period vibrations ring shear tests and dynamic triaxial‐bender tests were conducted with glass spheres. The experimental results show that the co‐vibration slip occurred during the vibration process, and as the vibration periods increased, the sample gradually slipped after vibration, eventually leading to accelerated instability. The sample exhibited a transition from a solid‐semi‐solid state to a liquid state due to the increase in vibration periods. Further results show that the shear modulus progressively weakened with successive vibration periods. The weakening of the shear strength of the sample caused by multi‐periods vibration was affected by the amplitude, the vibration time, and the interval time between two periods of vibration. Our study provided insights into how multiple earthquakes of seismic sequence and seismically active area trigger landslides.

Shear Mechanism and Optimal Estimation of the Fractal Dimension of Glass Bead-Simulated Sand

Spherical glass beads weaken the influences of particle morphology, surface properties, and microscopic fabric on shear strength, which is significant for revealing the relationship between macroscopic particle friction mechanisms and the particle size distribution of sand. This paper explores the shear mechanical properties of glass beads with different particle size ratios under different confining pressures. It obtains the particle size ratio and fractal dimension D through an optimal mechanical response. Simultaneously, we explore the range of the fractal dimension D under well-graded conditions. The test results show that the strain-softening degree of Rs is more obvious under a highly effective confining pressure, and the strain-softening degree of Rs can reach 0.669 when the average particle size d¯ is 0.5 mm. The changes in the normalized modulus ratio Eu/Eu50 indicate that the particle ratio and arrangement are the fundamental reasons for the different macroscopic shear behaviors of particles. The range of the peak effective internal friction angle φ is 23 °~35 °, and it first increases and then decreases with the increase in the effective confining pressure. As the average particle size increases, the peak stress ratio MFL and the peak effective internal friction angle φ first increase and then decrease, and both can be expressed using the Gaussian function. The range of the fractal dimension D for well-graded particles is 1.873 to 2.612, and the corresponding average particle size d¯ ranges from 0.433 to 0.598. Under the optimal mechanical properties of glass beads, the particle size ratio of 0.25 mm to 0.75 mm is 23:27, and the fractal dimension D is 2.368. The study results provide a reference for exploring friction mechanics mechanisms and the optimal particle size distributions of isotropic sand.

Contamination of consumer composts by metals, microplastics and other microscopic debris.

Very little information exists on the particle and chemical contamination of consumer (horticultural) composts. In this study, anthropogenic microcellulosics (AMCs), microplastics (MPs) and other microscopic debris, along with anthropogenically impacted metals (Cu, Zn, Pb), have been determined in 12 composts (seven garden composts and five growbags) purchased at outlets in the UK. AMCs and MPs, determined microscopically, were present in all samples at up to about 1100kg-1 dw. AMCs were more abundant and were dominated by fibres constructed of rayon and cotton, while petroleum-based MPs exhibited a greater diversity in shape and polymeric construction (including polyolefins, polyethylene terephthalate, polyvinyl chloride, resins, paints and rubbers). Other microdebris, present in much smaller concentrations in the composts, consisted of fragments of glass, metal and machined wood and spherical glass beads. Concentrations of the anthropogenically impacted metals, Cu, Pb and Zn, determined directly by energy-dispersive X-ray fluorescence spectrometry, were heterogeneously distributed and averaged 52.4, 192 and 51.6mgkg-1 dw, respectively. Although concentrations of anthropogenic particles were not related to cost or type of compost, physico-chemical properties or metal concentrations, a significant relationship between Pb content and particle diversity (number of polymers and debris types) was established. This relationship might result from the general contamination of the environment by both Pb and anthropogenic particulates, or the association of the metal with various types of material (e.g. paints, polyvinyl chloride, glass). Despite the ubiquity and diversity of MPs and microdebris in consumer composts, an understanding of their impacts on plant growth, either directly or indirectly (e.g. by interacting with metals), is unknown.

Investigating supercritical flow characteristics and movement of sediment particles in a narrow channel bend using PTV and video footage

This experimental study investigates the cause of nonuniform invert abrasion observed at sediment bypass tunnel (SBT) bends by examining the variations in velocity distributions, turbulence properties, bed shear stress, and bulk sediment movements under three supercritical bend flow conditions, detailed investigation of such flow is scarce. Using a laboratory-scaled model (1:22) of the downstream bend at Solis SBT, Switzerland, the research utilized particle tracking velocimetry and high-speed cameras with spherical sandstones and glass spheres representing sediments. The results indicate that as the secondary currents develop in the flow direction, the flow properties and sediments redistribute across the channel: the high-momentum fluids are directed toward the outer wall, the bed shear stress increases toward the outer wall, and the sediments are pushed toward the inner wall, which then follow this path downstream, even in straight sections, despite lower bed shear stress. This distribution of sediments, driven by secondary currents, leads to deeper invert abrasions toward the inner wall at SBT bends and downstream sections. Thus, these abrasions are primarily influenced by sediment movement rather than the bed shear stress alone. The study's findings are also valuable for validating future numerical simulations.

Chemical strengthening of glass powder particles

It is well known that chemical strengthening of glass brings the benefit of increased fracture strength. Despite extensive research on processing and mechanics at the macroscale, the effectiveness of chemical strengthening on glass elements with all three dimensions in the micrometer regime remains largely unexplored. Here, we develop a novel process for chemical strengthening of micrometer-sized spherical glass powder particles and study the fracture behavior of these particles with in-situ particle compression tests inside a scanning electron microscope. Cross-sectional microscopy and energy dispersive spectroscopy measurements confirm ion exchange and show an increase in diffusion depth with an increase in processing time and temperature. We report a higher fracture strength for chemically strengthened powder particles compared with the as-received ones. We show that the increase in fracture strength is associated to the compressive residual stress resulting from ion exchange during chemical strengthening.

Experimental investigation of erosion and transport of binary sediment in sewer pipes

ABSTRACT Understanding sediment transport in storm sewer systems is essential to prevent pipe blockages, associated flooding, and maintenance. In this research, a laboratory study was conducted in a pipe to investigate the erosion and transport process of a binary sediment, i.e., a material with two different particle sizes. The sediment used in this study was a mixture of two sizes of spherical glass beads (0.8 and 4 mm) and two sizes of natural soil (sand and gravel), with different amounts of small size particles. The results show that the critical velocities for the initiation of sediment transport increase linearly with a decrease in the fine particle content of the mixture. A method to predict the critical velocity of a binary mixture is proposed based on the fine content and the critical velocity of single-size large particle and single-size small particle sediments. The transport rate of the mixture lies between that of the single-size large sediment and single-size small sediment. The transport rate is increased with an increase in the fine content, which means that mixing small particles with large particles can significantly increase the transport rate of large particles and the total transport rate.