Single Ribbon Research Articles

Angle-controlled strong and weak coupling in photon molecules

Strong light-matter coupling occurs when the rate of energy exchange between the electromagnetic mode and the molecular ensemble exceeds the competitive dissipation process. Coupled photon molecules with near-field light-matter interactions may produce new hybridized states when they reach the strong coupling region. Tunable Terahertz (THz) meta materials can be used to design sensors, optical modulators, etc., to improve imaging sensitivity and resolution. In this work, we use the scattering-type scanning near-field microscopy (s-SNOM) to demonstrate an angle-controlled coupling strength in a tunable photon molecules system. The system consists of a base waveguide layer and a single ribbon structure. By changing the in-plane angle between ribbon and incidence, the coupling strength between ribbon resonance and waveguide mode ranges from 0.03 to 0.08 THz, leading to the system’s transformation from weak to strong coupling. This work offers a new platform for actively controlling strong light-matter interaction and further applications in strong coupling.

Single Crystalline GeSe Van Der Waals Ribbons With Uniform Layer Stacking, High Carrier Mobility, and Adjustable Edge Morphology.

Performance of the group IV monochalcogenide GeSe in solar cells, electronic, and optoelectronic devices is expected to improve when high-quality single crystalline material is used rather than polycrystalline films. Crystalline flakes represent an attractive alternative to bulk single crystals as their synthesis may be developed to be scalable, faster, and with higher overall yield. However, large - and especially large and thin - single crystal flakes are notoriously hard to synthesize. Here it is demonstrated that vapor-liquid-solid growth combined with direct lateral vapor-solid incorporation produces high-quality single crystalline GeSe ribbons with tens of micrometers size and controllable thickness. Electron microscopy shows that the ribbons exhibit perfect equilibrium (AB) van der Waals stacking order without extended defects across the entire thickness, in contrast to the conventional case of substrate-supported flakes where material is added via layer-by-layer nucleation and growth on the basal plane. Electrical measurements show anisotropic transport and a high Hall mobility of 85 cm2V-1s-1, on par with the best single crystals to date. Growth from mixed GeSe and SnSe vapors, finally, yields ribbons with unchanged structure and composition but with jagged edges, promising for applications that rely on ample chemically active edge sites, such as catalysis or photocatalysis.

Development of new correlation for the prediction of power number for closed clearance impellers using machine learning methods trained on literature data

AbstractThe accurate estimation of the power number for closed clearance impellers holds significant importance in industries such as chemical, biochemical, paper and pulp, as well as paints, pigments, and polymers. Existing state‐of‐the‐art correlations for predicting power numbers, however, are inaccurate for impeller Reynolds number . In this study, we compiled a dataset of 1470 data points from 15 research articles in the open literature, covering five types of impellers: (i) anchor; (ii) gate; (iii) single helical ribbon; (iv) double helical ribbon; and (v) helical ribbon with screw. Six machine learning models, namely artificial neural networks (ANN), CatBoost regressor, extra tree regressor, support vector regressor, random forest, and XGBoost regressor, were developed and compared. The results revealed that ANN emerged as the most efficient model, demonstrating the highest testing R2 value of 0.99 and the lowest testing MAPE of 7.3%. Further, we used the ANN model to develop a novel set of process correlations to estimate impeller power numbers for the industrially important anchor and double helical ribbon impellers: which significantly outperform the existing state‐of‐the‐art correlations available in literature.

Retinal Structure of Poecilia sphenops: Photoreceptor Mosaics, Synaptic Ribbon Patterns, and Glial Cell Expressions.

The specific arrangement and distribution of photoreceptors in the retina can vary among different fish species, with each species exhibiting adaptations related to its habitat, behavior, and visual requirements. Poecilia sphenops, a diurnal fish, was the focus of this study. The retinas of a total of eighteen Molly fish were investigated utilizing light and electron microscopy. The retina exhibited a square mosaic pattern of the inner segments of cones. This pattern comprised double cones positioned along the sides of a square, with two types of single cones situated at the center and corners of the square arrangement across the entire retina. The corner cones were slightly shorter than the central ones. Additionally, the outer plexiform layer contained both cone pedicles and rod spherules. The rod spherule consisted of a single synaptic ribbon arranged in a triad or quadrat junctional arrangement within the invaginating free ends of the horizontal and bipolar cell processes. On the other hand, cone pedicles have more than one synaptic ribbon in their junctional complex. The inner nuclear layer consisted of the amacrine, bipolar, Müller, and horizontal cell bodies. Müller cell processes, expressing GFAP, extended across all retinal layers, segmenting the deeper retina into alternating fascicles of optic axons and ganglion cells. The outer and inner plexiform layers showed many astrocyte cell processes expressing GFAP. In conclusion, the current study is the first record of the retinal structures of Molly fish. This study illustrated the mosaic arrangement of photoreceptors and GFAP expression patterns of astrocytes and Müller cells. The presence of three cone types, coupled with a sufficient number of rods, likely facilitates motion awareness for tasks like finding food and performing elaborate mating ceremonies.

Light and electron microscopic observations on retinal neurons of red-tail shark (Epalzeorhynchos bicolor H. M. Smith, 1931).

The structure of photoreceptors (PR) and the arrangement of neurons in the retina of red-tail shark were investigated using light and electron microscopy. The PR showed a mosaic arrangement and included double cones, single cones (SC), and single rods. Most cones occur as SC. The ratio between the number of cones and rods was 3:1.39 (±0.29). The rods were tall that reached the pigmented epithelium. The outer plexiform layer (OPL) showed a complex synaptic connection between the horizontal and photoreceptor terminals that were surrounded by Müller cell processes. Electron microscopy showed that the OPL possessed both cone pedicles and rod spherules. Each rod spherule consisted of a single synaptic ribbon within the invaginating terminal endings of the horizontal cell (hc) processes. In contrast, the cone pedicles possessed many synaptic ribbons within their junctional complexes. The inner nuclear layer consisted of bipolar, amacrine, Müller cells, and hc. Müller cells possessed intermediate filaments and cell processes that can reach the outer limiting membrane and form connections with each other by desmosomes. The ganglion cells were large multipolar cells with a spherical nucleus and Nissl' bodies in their cytoplasm. The presence of different types of cones arranged in a mosaic pattern in the retina of this species favors the spatial resolution of visual objects. RESEARCH HIGHLIGHTS: This is the first study demonstrating the structure and arrangement of retinal neurons of red-tail shark using light and electron microscopy. The current study showed the presence of different types of cones arranged in a mosaic pattern that may favor the spatial resolution of visual objects in this species. The bipolar, amacrine, Müller, and horizontal cells could be demonstrated.

Crystallographic models of ribbons and ribbon-based J-aggregate nanotubes from the geometry of tube ends.

Self-assembly into tubular structures typically proceeds by helical winding of ribbon intermediates, however, only the central parts of the tubes, that retain no information on the ribbon geometry, have received attention so far. We propose the procedure of establishing the crystal structure of ribbons and ribbon-based tubes on the basis of crystallographic analysis of the tube-end geometry, where the terminal parts of the ribbons fold and form characteristic mono/bilayer polygonal shapes. The terminal parts of flattened J-aggregate nanotubes of trimethine cyanine dye were clearly resolved in electron microscopy and atomic force microscopy images, and the original parallelogram shape of ribbons was reconstructed and interpreted as a two-dimensional [1-10]/[010] facetted crystal with inclined molecular π-stacks parallel to the long ribbon side. The back-reconstructed molecular orientations in a tube wall tend to be close to the tube normal. A two-stage "nucleation and growth" type model of the ribbon to tube transition is proposed that takes into account the established ribbon mechanical asymmetry. The model includes closure of the single ribbon loop as a nucleation event and explains, mostly observed in experiments, nearly rectangular shapes of tubes by the transition kinetics. Due to its universal character, the suggested approach can be applied to any ribbon-based tubes, regardless of their chemical composition.

Fluid-structure Interaction Study on Drag Characteristics of Flexible Ribbon

The flexible ribbon can be used as a projectile stabilizing device to provide a stable moment for the projectile, and the research on its drag characteristics is of great significance. This paper uses the arbitrary Lagrange-Euler (ALE) method to simulate the fluid-structure interaction process of the ribbon swinging in the airflow. The numerical method is validated by comparing it with wind tunnel experimental results from previous literature. This study utilized numerical simulation to investigate the impact of inflow velocity, ribbon material properties, and ribbon shape on drag characteristics. The research concluded that for a single ribbon, the drag value increases as the incoming flow velocity, ribbon material density, elastic modulus, and length-width ratio increase. In addition, the drag value of the annular ribbon is greater than that of the double ribbon. The drag values of the double ribbon and the annular ribbon are averaged to one side, the unilateral drag of the annular ribbon is greater than that of the single ribbon, and the unilateral drag of the double ribbon is smaller than that of the single ribbon. The conclusions can provide a reference for studying flexible ribbon stabilized projectiles.

Electrical Characteristics of Single Layer Graphene Ribbons in a Wide Temperature Range

This paper provides electrical characterization of single layer graphene ribbon devices defined as back-gated graphene transistors. The two-terminal back-gated graphene ribbon devices were fabricated on a conventional Si substrate covered by a 90 nm-thick thermal SiO2. The chemical vapor deposition process was used for the graphene layer deposition and its quality was checked with optical microscopy, scanning electron microscopy and Raman spectroscopy. For the device fabrication, optical lithography was used for electrode patterns through a mask, and Ti/Au (10 nm/100 nm) metallic contacts were deposited by thermal evaporation. We report low and high field electrical measurements of several devices, under a controlled environment over a wide temperature range, from 77 to 300 K. At 77 K, the drain current decreases, i.e. the resistance of the graphene increases, and the nonlinearity is still present. The maximum influence of the temperature is reached at the charges neutrality point, and we observe that the temperature could influence the position of the charge neutrality point. This indicates that the carriers are thermally activated, which yields a least pronounced current with the increase of the back gate voltage.

Roles of solidification rate and Co substitution for Cr on single phase ordered Fe2CrSi alloy formation

A comprehensive experimental and theoretical study on the structural, electronic, and magnetic properties of bulk Co-substituted Fe2CrSi Heusler alloys has been carried out. The impact of rapid solidification on the formation of phase pure Fe2CrSi alloy has also been explored. Bulk Fe2Cr1-xCoxSi (where x = 0, 0.1, 0.2, 0.3, and 0.5) alloy samples were prepared using arc melting, and melt-spinning was employed to prepare Fe2CrSi ribbons at two different wheel velocities (20 and 30 ms−1). Our investigation revealed that the Fe2CrSi Heusler alloys with a Co substitution in the range of 0.2 ≤ x ≤ 0.5 exhibited a single L21 phase structure. However, for x = 0 and 0.1, there were 27 % and 11 % A15 impurity phases, respectively, coexisting with the L21 phase. On the other hand, the sample melt-spun at 20 ms−1 contained only 7 % impurity phase, while the one melt-spun at 30 ms−1 was free of any impurity phase. First principles calculations using the GGA + U approach showed that the single phase ribbon sample exhibited 12.5 % DO3 type disorder, indicating a change in site preference resulting from a high solidification rate. All the experimental and calculated magnetic moments of the alloys were in agreement with the Slater-Pauling rule. Our results suggest that the Fe2Cr0.75Co0.25Si alloy is a promising candidate for spintronic device applications due to its half-metallic nature.

Three-Dimensional Ultrastructure of the Normal Rod Photoreceptor Synapse and Degenerative Changes Induced by Retinal Detachment.

The rod photoreceptor synapse is the first synapse of dim-light vision and one of the most complex in the mammalian CNS. The components of its unique structure, a presynaptic ribbon and a single synaptic invagination enclosing several postsynaptic processes, have been identified, but disagreements about their organization remain. Here, we have used EM tomography to generate high-resolution images of 3-D volumes of the rod synapse from the female domestic cat. We have resolved the synaptic ribbon as a single structure, with a single arciform density, indicating the presence of one long site of transmitter release. The organization of the postsynaptic processes, which has been difficult to resolve with past methods, appears as a tetrad arrangement of two horizontal cell and two rod bipolar cell processes. Retinal detachment severely disrupts this organization. After 7 d, EM tomography reveals withdrawal of rod bipolar dendrites from most spherules; fragmentation of synaptic ribbons, which lose their tight association with the presynaptic membrane; and loss of the highly branched telodendria of the horizontal cell axon terminals. After detachment, the hilus, the opening through which postsynaptic processes enter the invagination, enlarges, exposing the normally sequestered environment within the invagination to the extracellular space of the outer plexiform layer. Our use of EM tomography provides the most accurate description to date of the complex rod synapse and details changes it undergoes during outer segment degeneration. These changes would be expected to disrupt the flow of information in the rod pathway.SIGNIFICANCE STATEMENT Ribbon-type synapses transmit the first electrical signals of vision and hearing. Despite their crucial role in sensory physiology, the three-dimensional ultrastructure of these synapses, especially the complex organization of the rod photoreceptor synapse, is not well understood. We used EM tomography to obtain 3-D imaging at nanoscale resolution to help resolve the organization of rod synapses in normal and detached retinas. This approach has enabled us to show that in the normal retina a single ribbon and arciform density oppose a tetrad of postsynaptic processes. In addition, it enabled us to provide a 3-D perspective of the ultrastructural changes that occur in response to retinal detachment.

Mixing effects on the gas flow and mass transfer in a vertical single helical ribbon agitated reactor for propylene polymerization

The gas–solid vertical single helical ribbon agitated reactor is widely used in the polypropylene industry. The gas flow and mass transfer determine the heat transfer capacity and product quality. In this work, the pressure drop was measured below and above minimum fluidization velocity (umf). Then, the axial and radial dispersion coefficients (DL and DR) were estimated below umf by measuring the step residence time distribution and the stationary radial tracer profiles, respectively. Pressure analysis show the agitation significantly reduces the bed pressure drop, changing the fixed bed below umf and bubbling bed above umf to an agitated bed with a periodic voidage. The DL was proportional to the gas velocity, with little influences of the stirring speed. The radial tracer profiles show the bed is divided by the inner diameter of the helical ribbon into the peripheral ascending region and the central descending region, without gas exchange between them. Furthermore. the tracer profiles in the descending region are classified into two types. For type I, the DR, calculated by the plug flow model with radial dispersion, is proportional to the gas velocity, with little effects of stirring speed. Type II shows uniform profiles due to the deflection of the gas flow toward the low pressure area at the inner diameter of helical ribbon. The causes of the two types are explained by the relative size of particle circulation and gas flux. These two flow regimes are quantitatively clarified with an empirical correlation of Re and Fr as flow regime transition boundary, namely dispersed plug flow and perfect mixing flow. With lower Re and higher Fr, it changes from dispersed plug flow to perfect mixing flow.

Strength distributions of laminated FeNi-based metal amorphous nanocomposite ribbons

Metal Amorphous Nanocomposite (MANC) materials offer low losses at high magnetic switching frequency, enabling high power density motors with increased rotational speed. While MANCs have high strength, they are brittle. The use of motor components such as a rotor consisting of brittle material presents a reliability concern. Here, a promising MANC alloy is subjected to tensile tests and failure is observed with high-speed photography. A method is developed to prepare tensile specimens of laminated MANC and epoxy layers, simulating the stacking of an epoxy-impregnated tape-wound core. Tensile tests are conducted for single layer ribbon and for five- and ten-layer stacks of laminated material with thin layers of thermosetting epoxy. Failure distributions are shown to have increasing Weibull modulus with increasing layer count. The composite MANC material system is modeled using chain-of-bundles models. Using a k-failure model, we show that single ribbon strength distribution data can be used to predict well the failure distribution of laminated stacks. The agreement occurs when the assumed ineffective length, over which load is recovered in a failed layer, is comparable to the observed interlaminar separation length.

Ribbon Synapses and Retinal Disease: Review.

Synaptic ribbons are presynaptic protein complexes that are believed to be important for the transmission of sensory information in the visual system. Ribbons are selectively associated with those synapses where graded changes in membrane potential drive continuous neurotransmitter release. Defective synaptic transmission can arise as a result of the mutagenesis of a single ribbon component. Visual diseases that stem from malfunctions in the presynaptic molecular machinery of ribbon synapses in the retina are rare. In this review, we provide an overview of synaptopathies that give rise to retinal malfunction and our present understanding of the mechanisms that underlie their pathogenesis and discuss muscular dystrophies that exhibit ribbon synapse involvement in the pathology.

Analysis on affecting factors of the ribbon fluctuation in Array-MRF

Large aperture planar optical elements are required in high power laser systems, and the mid-spatial frequency error of the surface of the high-power laser component will affect the normal operation of the high-power laser system. In recent years, there are many new MRF devices, but these devices only improve the removal efficiency of polishing materials and ignore the stability of MRF tools. As we all know, the fluctuation of the MRF polishing ribbon will affect the stability of the removal function, which will make the surface of the processed component produce the mid-spatial frequency error. Therefore, based on the array magnetorheological pole structure newly developed in our laboratory, this paper tests its magnetic field distribution and studies the influencing factors of array magnetorheological ribbon fluctuation. Based on the magnetic field force, the effects of magnetorheological fluid flow, polishing wheel speed, and magnetic pole structure on ribbon fluctuation are analyzed. Finally, by using the improved array magnetorheological device to obtain a stable removal function, the volume removal efficiency of fused silica reaches 0.022mm3/min, which verifies the feasibility of the improved device and doubles the removal efficiency of magnetorheological finishing of a single ribbon. Therefore, we use controlled magnetorheological processing flow and speed to control ribbon fluctuations and designing the magnetic pole structure, to control the stability of magnetorheological processing.

LIBS Protocol for the Assessment of Depth Profile, Homogeneity, and Quantification of Fe/Co - based Bilayer Ribbon

The present work explores the applicability of a single spectroscopic technique, Laser-induced breakdown spectroscopy (LIBS), for the rapid quality assessment and quantification of individual layers of an amorphous bilayer ribbon (thickness ~ 35 μm). This kind of materials (ribbon) offer a convolution of the two sets of unique properties of individual layer, in a single ribbon, in contrast to the layered systems prepared by thin film technologies, and are useful and applicable for sensing and actuating in different experimental conditions. The sample was prepared by rapid quenching using the modified double-nozzle technique. One side of the ribbon is a layer of iron (Fe) - silicon (Si) - boron (B) and other side of the ribbon consists of cobalt (Co) - silicon (Si) - boron (B). Owing to its versatility and advantages, LIBS has been used for assessing the elemental distribution on the surface of the investigated matrices and across the layer interface. After optimizing the experimental parameters, the LIBS measurements have been performed using a Q-switched Nd:YAG laser working at its second harmonic wavelength (532 nm) with the 30 mJ/pulse energy under ambient air and atmospheric pressure conditions. Following the LIBS spectral analysis, a chemometric approach, principal component analysis (PCA), has been used for the visualization of the spectra from the two layers and to observe dominant spectral lines responsible for the discrimination of both layers. The depth profile analysis of the layers has been carried out using LIBS and the number of pulses corresponding to the individual layers have been correlated with the depth of the ablation craters obtained using the 3D-optical profilometry in order to estimate the thickness of the individual layers and the ablation rates. Furthermore, the homogeneity of the sample has been examined by measuring the intensity of selected spectral lines corresponding to the composition of the sample. Calibration-free (CF) - LIBS analysis has been performed for the compositional quantification of both layers of the sample and found in a good agreement with the production ratio. This work paves the way towards the investigation and control of the properties of such intelligent materials.

Silica Particle-Mediated Growth of Single Crystal Graphene Ribbons on Cu(111) Foil.

The authors report the growth of micrometer-long single-crystal graphene ribbons (GRs) (tapered when grown above 900°C, but uniform width when grown in the range 850°C to 900°C) using silica particle seeds on single crystal Cu(111) foil. Tapered graphene ribbons grow strictly along the Cu<101> direction on Cu(111) and polycrystalline copper (Cu) foils. Silica particles on both Cu foils form (semi-)molten Cu-Si-O droplets at growth temperatures, then catalyze nucleation and drive the longitudinal growth of graphene ribbons. Longitudinal growth is likely by a vapor-liquid-solid (VLS) mechanism but edge growth (above 900°C) is due to catalytic activation of ethylene (C2 H4 ) and attachment of C atoms or species ("vapor solid" or VS growth) at the edges. It is found, based on the taper angle of the graphene ribbon, that the taper angle is determined by the growth temperature and the growth rates are independent of the particle size. The activation enthalpy (1.73± 0.03eV) for longitudinal ribbon growth on Cu(111) from ethylene is lower than that for VS growth at the edges of the GRs (2.78 ±0.15eV) and for graphene island growth (2.85± 0.07eV) that occurs concurrently.

Structure modeling hints at a granular organization of the Golgi ribbon

BackgroundIn vertebrate cells, the Golgi functional subunits, mini-stacks, are linked into a tri-dimensional network. How this “ribbon” architecture relates to Golgi functions remains unclear. Are all connections between mini-stacks equal? Is the local structure of the ribbon of functional importance? These are difficult questions to address, without a quantifiable readout of the output of ribbon-embedded mini-stacks. Endothelial cells produce secretory granules, the Weibel-Palade bodies (WPB), whose von Willebrand Factor (VWF) cargo is central to hemostasis. The Golgi apparatus controls WPB size at both mini-stack and ribbon levels. Mini-stack dimensions delimit the size of VWF "boluses” whilst the ribbon architecture allows their linear co-packaging, thereby generating WPBs of different lengths. This Golgi/WPB size relationship suits mathematical analysis.ResultsWPB lengths were quantized as multiples of the bolus size and mathematical modeling simulated the effects of different Golgi ribbon organizations on WPB size, to be compared with the ground truth of experimental data. An initial simple model, with the Golgi as a single long ribbon composed of linearly interlinked mini-stacks, was refined to a collection of mini-ribbons and then to a mixture of mini-stack dimers plus long ribbon segments. Complementing these models with cell culture experiments led to novel findings. Firstly, one-bolus sized WPBs are secreted faster than larger secretory granules. Secondly, microtubule depolymerization unlinks the Golgi into equal proportions of mini-stack monomers and dimers. Kinetics of binding/unbinding of mini-stack monomers underpinning the presence of stable dimers was then simulated. Assuming that stable mini-stack dimers and monomers persist within the ribbon resulted in a final model that predicts a “breathing” arrangement of the Golgi, where monomer and dimer mini-stacks within longer structures undergo continuous linking/unlinking, consistent with experimentally observed WPB size distributions.ConclusionsHypothetical Golgi organizations were validated against a quantifiable secretory output. The best-fitting Golgi model, accounting for stable mini-stack dimers, is consistent with a highly dynamic ribbon structure, capable of rapid rearrangement. Our modeling exercise therefore predicts that at the fine-grained level the Golgi ribbon is more complex than generally thought. Future experiments will confirm whether such a ribbon organization is endothelial-specific or a general feature of vertebrate cells.

Pulling thin single crystal silicon wafers from a melt: The new leading-edge solar substrate

The Floating Silicon Method (FSM) has been established as a viable, stable method for growing single crystal ribbons directly from a silicon melt. With intense helium jet cooling to drive the linear progress of a [111] facet, pulled in the 〈110〉 direction, ribbons in the 0.6 – 3.0 mm thickness range can be grown at linear growth rates from 0.3 mm/s to >6 mm/s as reported in the literature. We report on recent progress towards growing (100) oriented ribbons with a net thickness of <200 µm and a ribbon width up to 18 cm using a stable, continuous process in the Leading Edge prototype furnace. The 3D details of the single crystal growth are explained using the mechanics of the Limit Cycle Theory, with novel Internal Side Effect morphology described by a proposed Facet Flow Theory. Grown-in crystalline defect distributions are described as well as values of critical impurities like oxygen, carbon, dopants, and metals that are relevant for use as wafers for solar cells.

Nanoelectrode Ensembles Consisting of Carbon Nanotubes

Incorporating the nanoscale properties of carbon nanotubes (CNTs) and their assemblies into macroscopic materials is at the forefront of scientific innovation. The electrical conductivity, chemical inertness, and large aspect ratios of these cylindrical structures make them ideal electrode materials for electrochemical studies. The ability to assemble CNTs into nano-, micro-, and macroscale materials broadens their field of applications. Here, we report the fabrication of random arrays of CNT cross-sections and their performance as nanoelectrode ensembles (NEEs). Single ribbons of drawable CNTs were employed to create the CNT-NEEs that allows easier fabrication of nanoscale electrodes for general electrochemical applications. Surface analysis of the prepared NEEs using scanning electron microscopy showed a random distribution of CNTs within the encapsulating polymer. Electrochemical testing via cyclic voltammetry and scanning electrochemical cell microscopy revealed voltametric differences from the typical macroelectrode response with the steady-state nature of NEEs. Finally, when the NEE was employed for Pb2+ detection using square-wave anodic stripping voltammetry, a limit of detection of 0.57 ppb with a linear range of 10–35 ppb was achieved.

Particle movement characteristics in a gas–solid vertical single helical ribbon agitated reactor

The gas–solid vertical single helical ribbon agitated reactor (G-S-VSAR) is a gas–solid dense-phase agitated reactor, in which the interaction between the agitator and the dense granules dominates the flow field and transfer behavior. The particle movement characteristics are essential for determining the reactor space–time yield and product quality. In this work, the particle residence time distribution (RTD) was measured through magnetic-particles pulse experiment to investigate the overall movement and mixing characteristics of a G-S-VSAR, with the effects of rotation speed and gas velocity studied. The RTD curves were featured by time lag, bypass peak and exponential tail, and thus a model of ‘PFR + double parallel CSTRs’ was established. Results showed that the increase in rotation speed could eliminate the bypass, but only reduce the lag time. The lag time adversely influenced the mixing. Photography was applied to characterize the local particle movements near the reactor wall. It was found that the particles spiraled upwardly along the wall in laminar-like flow and the fully mixed state reached after one circulation. During the spiraled process, the undulating displacement in the vertical direction was induced by agitation in the ribbon-wall gap, which inhibited the radial mixing. Therefore, a narrow gap was recommended for reducing such undulating movements and promoting radial mixing.