Centrifugal Mixing Research Articles

Submesoscale Dynamics of a Gulf Stream Frontal Eddy in the South Atlantic Bight

AbstractFrontal eddies are commonly observed and understood as the product of an instability of the Gulf Stream along the southeastern U.S. seaboard. Here, the authors study the dynamics of a simulated Gulf Stream frontal eddy in the South Atlantic Bight, including its structure, propagation, and emergent submesoscale interior and neighboring substructure, at very high resolution (dx = 150 m). A rich submesoscale structure is revealed inside the frontal eddy. Meander-induced frontogenesis sharpens the gradients and forms very sharp fronts between the eddy and the adjacent Gulf Stream. The strong straining increases the velocity shear and suppresses the development of barotropic instability on the upstream face of the meander trough. Barotropic instability of the sheared flow develops from small-amplitude perturbations when the straining weakens at the trough. Small-scale meandering perturbations evolve into rolled-up submesoscale vortices that are advected back into the interior of the frontal eddy. The deep fronts mix the tracer properties and enhance vertical exchanges of tracers between the mixed layer and the interior, as diagnosed by virtual Lagrangian particles. The frontal eddy also locally creates a strong southward flow against the shelf leading to topographic generation of submesoscale centrifugal instability and mixing. In eddy-resolving models that do not resolve these submesoscale processes, there is a significant weakening of the intensity of the upwelling in the core of the frontal eddies, and their decay is generally too fast.

Magnetic and electrically conductive epoxy/graphene/carbonyl iron nanocomposites for efficient electromagnetic interference shielding

Abstract Magnetic and electrically conductive epoxy nanocomposites are fabricated by compounding thermally reduced graphene oxide (TGO) and magnetic carbonyl iron (CI) using a solvent-free and efficient centrifugal mixing method. The addition of TGO sheets not only forms an interconnected conducting network within the epoxy matrix, but also prevents the aggregation of heavy CI components. The incorporation of CI components leads to obvious increases in permeability, magnetic loss, and electromagnetic interference (EMI) shielding properties. Among different shapes of CI components, spherical CI particles result in the best EMI shielding performance. The ternary nanocomposites exhibit excellent shielding effectiveness (>36 dB within 9.5–12 GHz) and a maximum value of ∼40 dB at 11.7 GHz, much higher than that (∼20 dB) of epoxy/TGO nanocomposite with the same content of TGO. Wave absorption loss is confirmed to be the main EMI shielding mechanism for the epoxy nanocomposites. The high EMI shielding performance makes the epoxy nanocomposites promising for EMI shielding applications.

Centrifugal Instability and Mixing in the California Undercurrent

AbstractA regional numerical study of the California Current System near Monterey Bay, California, is conducted using both hydrostatic and nonhydrostatic models. Frequent sighting of strong anticyclones (Cuddies) have occurred in the area, and previous studies have identified Monterey Bay as an apparent region of strong unbalanced flow generation. Here, by means of a downscaling exercise, a domain just downstream of Point Sur is analyzed and argued to be a preferred site of diapycnal mixing. The scenario suggested by the simulations involves the generation of negative relative vorticity in a bottom boundary layer of the California Undercurrent on the continental shelf break. At Point Sur, the current separates from the coast and moves into deep waters where it rapidly develops finite-amplitude instabilities. These manifest as isopycnal overturnings, but in contrast to the normal Kelvin–Helmholtz paradigm for mixing, this study argues that the instability is primarily centrifugal. The evidence for this comes from comparisons of the model with linear results for ageostrophic instabilities. Mixing increases background potential energy. The authors argue the regional potential energy generation near Point Sur in the upper few hundred meters is comparable to that found in open-ocean regions of strong diapycnal mixing, either by abyssal tides and lee waves near topography. This study computes diapycnal fluxes and estimates turbulent diffusivities to argue mixing by centrifugal instability is characterized by diffusivities O(10−4) m2 s−1, although the potential for contamination by explicit diffusivities exists.

Versatile sample environments and automation for biological solution X-ray scattering experiments at the P12 beamline (PETRA III, DESY).

A high-brilliance synchrotron P12 beamline of the EMBL located at the PETRA III storage ring (DESY, Hamburg) is dedicated to biological small-angle X-ray scattering (SAXS) and has been designed and optimized for scattering experiments on macromolecular solutions. Scatterless slits reduce the parasitic scattering, a custom-designed miniature active beamstop ensures accurate data normalization and the photon-counting PILATUS 2M detector enables the background-free detection of weak scattering signals. The high flux and small beam size allow for rapid experiments with exposure time down to 30-50 ms covering the resolution range from about 300 to 0.5 nm. P12 possesses a versatile and flexible sample environment system that caters for the diverse experimental needs required to study macromolecular solutions. These include an in-vacuum capillary mode for standard batch sample analyses with robotic sample delivery and for continuous-flow in-line sample purification and characterization, as well as an in-air capillary time-resolved stopped-flow setup. A novel microfluidic centrifugal mixing device (SAXS disc) is developed for a high-throughput screening mode using sub-microlitre sample volumes. Automation is a key feature of P12; it is controlled by a beamline meta server, which coordinates and schedules experiments from either standard or nonstandard operational setups. The integrated SASFLOW pipeline automatically checks for consistency, and processes and analyses the data, providing near real-time assessments of overall parameters and the generation of low-resolution models within minutes of data collection. These advances, combined with a remote access option, allow for rapid high-throughput analysis, as well as time-resolved and screening experiments for novice and expert biological SAXS users.

Centrifugal multiplexing fixed-volume dispenser on a plastic lab-on-a-disk for parallel biochemical single-end-point assays

In this study, a multiple sample dispenser for precisely metered fixed volumes was successfully designed, fabricated, and fully characterized on a plastic centrifugal lab-on-a-disk (LOD) for parallel biochemical single-end-point assays. The dispenser, namely, a centrifugal multiplexing fixed-volume dispenser (C-MUFID) was designed with microfluidic structures based on the theoretical modeling about a centrifugal circumferential filling flow. The designed LODs were fabricated with a polystyrene substrate through micromachining and they were thermally bonded with a flat substrate. Furthermore, six parallel metering and dispensing assays were conducted at the same fixed-volume (1.27 μl) with a relative variation of ±0.02 μl. Moreover, the samples were metered and dispensed at different sub-volumes. To visualize the metering and dispensing performances, the C-MUFID was integrated with a serpentine micromixer during parallel centrifugal mixing tests. Parallel biochemical single-end-point assays were successfully conducted on the developed LOD using a standard serum with albumin, glucose, and total protein reagents. The developed LOD could be widely applied to various biochemical single-end-point assays which require different volume ratios of the sample and reagent by controlling the design of the C-MUFID. The proposed LOD is feasible for point-of-care diagnostics because of its mass-producible structures, reliable metering/dispensing performance, and parallel biochemical single-end-point assays, which can identify numerous biochemical.

1602 円柱に孔を有する遠心撹拌体の基礎特性

1602 円柱に孔を有する遠心撹拌体の基礎特性

Verification of energy efficiency of a low-thrust liquid-propellant engine with the deflector-centrifugal injecting pattern

The article gives information about developed in Design Bureau Chemical Machinery behalf A.M. Isaev deflector centrifugal pattern mixing of propellants nitrogen tetroxide and unsymmetrical dimethylhydrazine, in which established liquid rocket engines (LREST) in a wide range of rods from 25 to 400 N. Design Bureau Chemical Machinery behalf A.M. Isaev on the basis of joint with KUAI (now SSAU named after Korolev, Samara) and studies on the characterization of the primary oxidant film on the deflector, the parameters of the secondary oxidant film on the inner wall of the combustion chamber, the parameters of the film cone spray nozzle centrifugal fuel in a venue with a secondary film oxidant parameters of the layer of liquid-phase mixing the oxidizer and fuel components on the inner wall of the combustion chamber was established mathematical model calculations of liquid-phase mixing of the components in the mixing element LREST with centrifugal deflection circuit mixing the components on the wall of the combustion chamber. Based on this Design Bureau Chemical Machinery behalf A.M. Isaev developed technique of calculations and design of LREST with centrifugal deflection circuit mixing fuel. Using this method in Design Bureau Chemical Machinery behalf A.M. Isaev designed iPart LREST 25, 50, 100, 200, 400N, with deflector centrifugal mixing scheme. Parametric studies were conducted LREST of 25, 50, 100, 200, 400 N to determine the degree of influence of various design and operational parameters of the element, such as the angle of leakage jets on the deflector angle leakage of primary films on the wall of the combustion chamber, the mean free path of the secondary oxidant film the wall of the chamber performance-liquid phase mixing of the fuel components. The results of experimental studies have confirmed the increased energy efficiency of small thrust jet engine thrust of 25, 50, 100, 200, 400 N with deflection centrifugal mixing scheme, expressed in a high specific impulse of more than 3000 m / s at the same time a large margin the temperature of engine components. Maximum temperature of the wall of the combustion chamber is at 1200 С that is provided by a large margin 600 С (permissible material temperature chamber - niobium alloy with molybdenum coating bi-silicified MoSi2 1800 С).

Разработка математических моделей новых конструкций смесительных агрегатов центробежного типа при получении сухих комбинированных продуктов

Разработка математических моделей новых конструкций смесительных агрегатов центробежного типа при получении сухих комбинированных продуктов

Influence of Nanoclay Dispersion Methods on the Mechanical Behavior of E-Glass/Epoxy Nanocomposites.

Common dispersion methods such as ultrasonic sonication, planetary centrifugal mixing and magnetic dispersion have been used extensively to achieve moderate exfoliation of nanoparticles in polymer matrix. In this study, the effect of adding three roll milling to these three dispersion methods for nanoclay dispersion into epoxy matrix was investigated. A combination of each of these mixing methods with three roll milling showed varying results relative to the unmodified polymer laminate. A significant exfoliation of the nanoparticles in the polymer structure was obtained by dispersing the nanoclay combining three roll milling to magnetic and planetary centrifugal mixing methods. This exfoliation promoted a stronger interfacial bond between the matrix and the fiber, which increased the final properties of the E-glass/epoxy nanocomposite. However, a combination of ultrasound sonication and three roll milling on the other hand, resulted in poor clay exfoliation; the sonication process degraded the polymer network, which adversely affected the nanocomposite final properties relative to the unmodified E-glass/epoxy polymer.

Preparation of SiO<sub>2</sub>/PEG Shear Thickening System by Centrifugal Dispersion

The nano-SiO2/polyethylene glycol (PEG) dispersion system was prepared by centrifugal mixing, and its rheological properties were investigated. The results showed the revolution and rotation speed during the centrifugal mixing have a significant effect on the rheological properties of SiO2/PEG system. When the revolution speed of the centrifugal mixer was fixed at a high speed of 1200rpm, the shear thickening effect of SiO2/PEG was gradually increased with the decrease of rotation speed, and the maximum viscosity (η) of 12340 mPa•s appeared at the rotation speed of 200 rpm. At the low revolution speed of 700 rpm, the increase of the rotation speed significantly enhanced the shear thickening effect. When the rotation speed was 700rpm, the maximum viscosity was up to 86130mPa s. In steady state experiments, the systems show a shear-thinning property under low shear rate. When the shear rate exceeded a critical value (γ= 24.92 s-1), the viscosity first increased, and then decreased sharply. In the dynamic experiments, with the increase of angular frequency (ω), the loss modulus (G″) also increased and the systems behaved as a shear-thickening fluid.

Effect of air staging on a coaxial swirled natural gas flame

In the framework of a research program to investigate air staging applied to swirling flames, an experimental investigation aimed at studying pollutant emissions is reported. Staged combustion is accepted as an effective way to reduce nitrogen oxides in gas turbine combustors and, in the present study, is applied to a swirled flame fueled by natural gas, to analyze the potential for further reducing nitrogen oxides emissions in a coaxial, non-premixed combustor under overall lean conditions. The results indicate that the full benefits of air staged combustion in swirling flames depend mainly on the method of fuel injection. The most common method of axial injection of a premixed jet into a co-axial swirling airflow does not realize the required fast mixing. By radial injection of the premixed first stage in the secondary co-axial airflow, more efficient and faster centrifugal mixing is achieved, and hence shorter residence time and higher combustion intensity. This fuel injection strategy results in a more stable flame and dramatic reduction of NOx emissions when the first stage equivalence ratio is approaching the stoichiometric value. Still photographs of the flame and isothermal flow patterns are also reported to help correlate flame morphology and mixing features with nitrogen oxides emission.

Processing and properties of syntactic foams reinforced with carbon nanotubes

AbstractThis article presents synthesis and mechanical characterization of carbon nanotube (CNT)‐reinforced syntactic foams. Following a dispersion approach (comprising ultrasonic, calendering, and vacuum centrifugal mixing), single‐ and multi‐walled functionalized CNTs (FCNTs) were incorporated into two foam composites containing various commercially available microballoon grades (S38HS, S60HS, and H50 from 3M). The FCNT‐reinforced composites were tested for compressive strength and apparent shear strength before and after hot/wet conditioning. The results showed that the FCNT‐reinforced composites' mechanical properties depended on the vacuum pressure used during processing. Compared with pristine and commercially available syntactic foam (EC‐3500 from 3M), the FCNT‐reinforced composites processed at high vacuum (0.2 kPa) showed significant increase in compressive strength and apparent shear strength before and after hot/wet conditioning. Dynamic mechanical analysis showed an increase of about 22°C in glass transition temperature for composites processed at high vacuum with 0.5 wt % FCNT and 45 wt % S38HS–5 wt % S60HS microballoons. Thermogravimetric analysis indicated water absorption and lower decomposition temperature for the FCNT‐reinforced composite mixed at atmospheric pressure, whereas no significant change was observed for the compound processed at high vacuum. Fracture analysis showed matrix failure for the composite processed at high vacuum and microballoon crushing for the composite mixed at atmospheric pressure. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Thermo-mechanical properties of a highly filled polymeric composites for Fused Deposition Modeling

This paper presents an investigation on thermal and mechanical properties of new metal-particle filled Acrylonitrile Butadiene Styrene (ABS) composites for applications in Fused Deposition Modeling rapid prototyping process. Test samples of Iron/ABS and Copper/ABS composites involving metal content up to 40% by volume have been made by controlled centrifugal mixing, thermally compounded through a single-screw extruder and compression moulding. Dynamic Mechanical Analysis (DMA) techniques were used in order to characterize viscoelastic properties of these newly developed composites materials for use in Fused Deposition Modeling process. It has been shown that significant improvements of ABS thermal and mechanical properties due to incorporation of metallic fillers can potentially promote processing of high performance and functional prototypes on the existing FDM platform for a wide range of applications. Sample prototypes from the new composite materials have been successfully made and tested.

Rheological Properties of a Particulate-Filled Polymeric Composite through Fused Deposition Process

This paper presents an investigation on rheological properties of a new ABS (acrylonitrile-butadiene-styrene)-Iron composite for application in Fused Deposition Modelling rapid prototyping process. Test samples of ABS-Iron composites have been made by controlled centrifugal mixing and thermal compounding through a single-screw extruder and compression moulding. Rheological characterization was conducted using a capillary rheometer by measuring pressure drop at the die while varying the extrusion speed. Apparent shear rate and shear stress as well as viscosity of the melts were calculated. Modulated differential-scanning calorimetry (MDSC) techniques were used in order to characterize viscoelastic properties of these newly developed composites materials. Non-Newtonian behaviour of the composite melt has shown to follow a cross model of shear thinning characteristics.

Radiopaque dental adhesives: Dispersion of flame-made Ta 2O 5/SiO 2 nanoparticles in methacrylic matrices

Objectives Radiopaque dental adhesive (DA) of low viscosity were made by forming stable suspensions of weakly agglomerated Ta 2O 5/SiO 2 nanoparticles with primary particle size of about 10 nm. Methods The particles were prepared by one-step flame-spray pyrolysis. Particles were functionalized with γ-methacryloxypropyltrimethoxysilane (MPS) and dispersed in a methacrylic monomer matrix by centrifugal mixing and ultrasonication. Particle size distributions were analyzed by X-ray disc centrifugation of suspensions and TEM analysis of cured sample composites, while average primary particle size was obtained by N 2 adsorption and X-ray diffraction. Results The dispersion method affected the aggregate size distribution of both untreated and surface functionalized particles in these suspensions. The influence of particle content on suspension viscosity, aggregate size distribution and that of Ta 2O 5 content on radiopacity was investigated. The shear bond strength of such radiopaque particle-containing adhesives on enamel and dentin was comparable to that of the particle-free reference adhesive. Conclusions Flame-made Ta 2O 5/SiO 2 nanoparticles can be introduced readily into dental adhesives as they form quite stable suspensions. Viscosity stayed low even after adding radiopaque particles up to 20 wt.%. The resulting composites had radiopacity comparable to that of enamel facilitating their distinction from marginal gaps. Bond strength was not significantly influenced by the presence of particles in the adhesive.

Structure of Human Eg5 in Complex with a New Monastrol-based Inhibitor Bound in the R Configuration

Drugs that target mitotic spindle proteins have been proven useful for tackling tumor growth. Eg5, a kinesin-5 family member, represents a potential target, since its inhibition leads to prolonged mitotic arrest through the activation of the mitotic checkpoint and apoptotic cell death. Monastrol, a specific dihydropyrimidine inhibitor of Eg5, shows stereo-specificity, since predominantly the (S)-, but not the (R)-, enantiomer has been shown to be the biologically active compound in vitro and in cell-based assays. Here, we solved the crystal structure (2.7A) of the complex between human Eg5 and a new keto derivative of monastrol (named mon-97), a potent antimitotic inhibitor. Surprisingly, we identified the (R)-enantiomer bound in the active site, and not, as for monastrol, the (S)-enantiomer. The absolute configuration of this more active (R)-enantiomer has been unambiguously determined via chemical correlation and x-ray analysis. Unexpectedly, both the R- and the S-forms inhibit Eg5 ATPase activity with IC(50) values of 110 and 520 nM (basal assays) and 150 nm and 650 nm (microtubule-stimulated assays), respectively. However, the difference was large enough for the protein to select the (R)- over the (S)-enantiomer. Taken together, these results show that in this new monastrol family, both (R)- and (S)-enantiomers can be active as Eg5 inhibitors. This considerably broadens the alternatives for rational drug design.

The development and application of centrifugal flotation systems in wastewater treatment

Flotation as a wastewater treatment technique is designed to remove all particles generally encountered as very fine emulsions, suspended solids, and colloids from wastewater. Historically, Dissolved Air Flotation (DAF) has been used to achieve this removal. More recently, other flotation techniques such as induced air, electro, cavitational, and Centrifugal Flotation Systems (CFS) have been applied in wastewater treatment. CFS use centrifugal force to enhance mixing of particles and bubbles with treatment chemicals and accelerate solid/liquid separation. In the most recent design, centrifugal hydrocyclone mixing was combined with small dissolved-air flotation bubbles leading to the development of the hybrid, dissolved-air centrifugal flotation.

The distortion dipole rotational spectrum of [formula omitted]: A low temperature far-infrared study

The perturbation-allowed distortion moment spectrum of CH 4 has been studied between 20 and 100 cm - 1 with a Fourier transform spectrometer at a temperature of 113.5 K similar to that in the atmospheres of Saturn and Titan. Data were obtained at a resolution of 0.06 cm - 1 and of 0.24 cm - 1 with a sample gas pressure of 794 Torr using an absorption path length of 60.0 m . For each ( J + 1 ← J ) , the tetrahedral fine structure was blended together into a single R ( J ) envelope. Six such envelopes for J = 3 – 8 were measured, the strongest having a signal-to-noise ratio ∼ 80 . From an intensity analysis of R ( 5 ) , R ( 6 ) , and R ( 7 ) , the distortion dipole moment μ D of methane was determined to be 23.82 ( 0.88 ) and 23.94 ( 1.20 ) μ D from the low- and high-resolution spectra, respectively, in excellent agreement with earlier less precise intensity measurements at room temperature and the value of 24.06 ( 0.45 ) μ D obtained from the Stark effect by Ozier [Ground-state electric dipole moment of methane. Phys Rev Lett 1971;27: 1329–32]. Based on these results, it is recommended that the intensities for these transitions in the HITRAN/GEISA data bases be scaled upward by a factor of 1.154 . This line spectrum arising from centrifugal distortion mixing was superimposed on a broad continuum due to collision-induced translation-rotation transitions. This continuum was measured from 20 – 180 cm - 1 (with a gap between 100 and 120 cm - 1 ), and is compared with the theoretical model of Borysow and Frommhold [Collision-induced rototranslational absorption spectra of CH 4–CH 4 pairs at temperatures from 50 to 300 K. Ap J 1987;318:940–3] at a lower temperature and with higher absolute accuracy than previously possible. Two features near 125.6 and 157.3 cm - 1 , each ∼ 5 cm - 1 wide, are seen to arise from rotational transitions in CH 4 – CH 4 dimers. The study of the distortion dipole spectrum has direct application to the measurement of the CH 4 : H 2 ratio and the temperature structure in the atmospheres of the Giant Planets and Titan.

NEW DEVELOPMENTS IN MIXING, FLOCCULATION AND FLOTATION FOR INDUSTRIAL WASTEWATER PRETREATMENT AND MUNICIPAL WASTEWATER TREATMENT

NEW DEVELOPMENTS IN MIXING, FLOCCULATION AND FLOTATION FOR INDUSTRIAL WASTEWATER PRETREATMENT AND MUNICIPAL WASTEWATER TREATMENTSolid/liquid separations are commonly the first step in any wastewater treatment. Such technologies are mature and new developments are rare. However, in the last decade some significant improvements in separation techniques for industrial wastewater pretreatment have been implemented. Advances in the technology include more efficient, faster centrifugal mixing of treatment chemicals and...Author(s)Miroslav ColicDwain MorseWade MorseJan D. MillerSourceProceedings of the Water Environment FederationSubjectSession 29: Industrial Issues & Treatment Technology: Novel Physical Chemical ProcessesDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2005ISSN1938-6478SICI1938-6478(20050101)2005:14L.2380;1-DOI10.2175/193864705783867026Volume / Issue2005 / 14Content sourceWEFTECFirst / last page(s)2380 - 2407Copyright2005Word count257

A Rapid, High Throughput Micro Sugar‐Snap Cookie Quality Test Procedure Using Asymmetrical Centrifugal Mixing

ABSTRACTA modified AACC 45‐g flour cookie procedure using asymmetrical centrifuge mixing as a replacement for conventional mixing has been developed. Ingredients are added to a pin cup in the same proportion as in the Approved Method 10‐50D (AACC 2000) sugar‐snap cookie test and mixed in a single step for 15 sec at 2,500 rpm. The dough is then processed and the resulting cookies are scored according to the AACC Approved Method 10–52 40‐g flour micro cookie test method. Cookies produced from a control cookie flour and four commercial soft wheat flours with the new mixing method did not show the characteristic surface cracking patterns normally obtained with conventional three‐stage mixing. However, with the exception of one spread value, no significant differences in spread, thickness, or the ratio of spread to thickness were evident when results were compared with those obtained with the AACC Approved Method 10‐50D 225‐g flour test method using a Hobart mixer equipped with a paddle. Cookies produced from two sets of advanced soft white spring wheat breeder lines, including control cultivars, using the asymmetrical centrifuge mixing procedure were also very comparable in spread, thickness, and ratio compared with those produced using 225 g of flour in the AACC Approved Method. Reproducibility of test results for all cookie parameters for both commercial and advanced plant breeder samples were comparable to the AACC Approved Method 10‐50D 225‐g flour test method. The very short mixing time and the ability to quickly clean or use multiple pin cups should allow very high throughput of flour samples relative to the use of conventional mixers for cookie testing.