Rigid Channel Research Articles

Accelerating Li-Ion Diffusion in LiFePO4 by Polyanion Lattice Engineering.

Despite the widespread commercialization of LiFePO4 as cathodes in lithium-ion batteries, the rigid 1D Li-ion diffusion channel along the [010] direction strongly limits its fast charge and discharge performance. Herein, lattice engineering is developed by the planar triangle BO3 3- substitution on tetrahedron PO4 3- to induce flexibility in the Li-ion diffusion channels, which are broadened simultaneously. The planar structure of BO3 3- may further provide additional paths between the channels. With these synergetic contributions, LiFe(PO4)0.98(BO3)0.02 shows the best performance, which delivers the high-rate capacity (66.8 mAhg-1 at 50 C) and long cycle stability (ultra-low capacity loss of 0.003% every cycle at 10 C) at 25°C. Furthermore, excellent rate performance (34.0 mAhg-1 at 40 C) and capacity retention (no capacity loss after 2500 cycles at 10 C) at -20°C are realized.

Investigation on flow field near confluence of two rigid channels at zero-degree

Investigation on flow field near confluence of two rigid channels at zero-degree

Study on the Coefficient of Apparent Shear Stress along Lines Dividing a Compound Cross-Section

A compound channel’s discharge capacity and boundary shear force can be predicted as a sum of the discharge capacity of different sub-regions once the apparent shear stress of the dividing line is reasonably quantified. The apparent shear stress was usually expressed as a coefficient multiplied by the difference between two squared velocities of two adjacent regions. This study investigated the range of the coefficient values and their influencing factors. Firstly, the optimal values of the coefficient were obtained based on experimental data. Then, comparisons between the optimal values and several parameters used in quantifying the apparent shear stress were conducted. The results show that the coefficient is mainly related to a morphological parameter of the floodplain and the ratio of resistance coefficients between the floodplain and the main channel. An empirical formula to calculate the coefficient was developed and introduced to calculate the flow discharge and boundary shear stress. Experimental data, including 142 sets of test data of symmetric-floodplain cases and 104 sets of one-floodplain cases, have been used to examine the prediction accuracy of discharges and boundary shear stress. For all these tests, the ranges of water depth of the main channel and the total width of the compound cross-section are about 0.05~0.30 m and 0.3~10 m, respectively; the Q range and the range of Froude numbers of the main channel flow are about 0.0033~1.11 m3/s and 0.3~2.3, respectively. Comparison with other methods and experimental data from both rigid and erodible compound channels indicated that the proposed method not only provided acceptable accuracy for the computation of discharge capacity and boundary shear stress of compound channels in labs but also gave insights for calculating discharge capacity in natural compound channels.

Effect of channel flexibility on confined water transport

Water transport through confined channels is a significant fundamental process in various scientific fields. However, the effect of channel flexibility, particularly on water transport through channels of a certain thickness common in experiments, has not been elucidated. Using non-equilibrium molecular dynamics, we found that flexible channels show lower entrance/exit resistances but higher interior resistances than rigid channels. Therefore, water transport through flexible non-atomically thick channels is slower than through rigid non-atomically thick counterparts, which is completely opposite to currently reported observations in atomically thick channels. Molecular analyses indicate that conical effects accelerate water transport through flexible atomically thick channel, but higher pore wall frictions inside channels hinder water transport through non-atomically thick channels. This work reveals the neglected effect of channel flexibility on water transport, which not only deepens the understanding of transport mechanisms, but also guides the experimental selection of rigid channels for water transport.

Yield–stress shear thinning and shear thickening fluid flows in deformable channels

Yield stress shear thinning/thickening fluids flow through flexible channels, tubes are widespread in the natural world with many technological applications. In this paper, analytical formulae for the velocity profiles and flow rate are derived using the Herschel–Bulkley rheological model in both rigid and deformable shallow channels, employing the lubrication approximation. To account for deformable walls, the approach outlined by Gervais et al (2006, Lab on a Chip 6 500-7) and Christov et al (2018 J. Fluid Mech. 841 267-86) is utilized, applying small displacement structural mechanics and perturbation theory, respectively. The newly derived formulae also enable the analysis of flow dynamics in Newtonian fluids, power-law fluids, and Bingham fluids as their limiting cases, all of which have been previously described in the literature and also serves as the validation cases. It is observed that deformability increases the effective channel height and the flow rate within the channel. Multiple scaling relationships for the flow rate are identified under different applied pressure regimes and deformability parameters. Additionally, it is noted that increasing the yield stress results in decreased velocity in both the plug flow and non-plug flow regions. Higher yield stress also corresponds to an increase in the yield surface height and the solid plug within the central region, leading to a reduction in the flow rate. Furthermore, the shear thinning/thickening index is found to have no impact on plug height, although an increase in this index causes a reduction in the flow rate due to the corresponding increase in shear thickening of the material.

Lq-norm multiple kernel fusion regression for self-cleansing sediment transport

Experimental and modeling studies have been conducted to develop an approach for self-cleansing rigid boundary open channel design such as drainage and sewer systems. Self-cleansing experiments in the literature are mostly performed on circular channel cross-section, while a few studies considered self-cleansing sediment transport in small rectangular channels. Experiments in this study were carried out in a rectangular channel with a length of 12.5 m, a width of 0.6 m, a depth of 0.7 m and having an automatic control system for regulating channel slope, discharge and sediment rate. Behind utilizing collected experimental data in this study, existing data in the literature for rectangular channels are used to develop self-cleansing models applicable for channel design. Through the modeling procedure, this study recommends Lq-norm multiple kernel fusion regression (LMKFR) techniques for self-cleansing sediment transport. The LMKFR is a regression technique based on the regularized kernel regression method which benefits from the combination of multiple information sources to improve the performance using the Lq-norm multiple kernel learning framework. The results obtained by LMKFR are compared to support vector regression benchmark and existing conventional regression self-cleansing sediment transport models in the literature for rectangular channels. The superiority of LMKFR is illustrated in an accurate modeling as compared with its alternatives in terms of various statistical error measurement criteria. The encouraging results of LMKFR can be linked to utilization of several kernels which are fused effectively using an Lq-norm prior that captures the intrinsic sparsity of the problem at hand. Promising performance of LMKFR technique in this study suggests it as an effective technique to be examined in similar environmental, hydrological and hydraulic problems.

Manipulation of Cationic Group Density in Covalent Organic Framework Membranes for Efficient Anion Transport.

Anion exchange membranes with high anion conductivity are highly desired for electrochemical applications. Increasing ion exchange capacity is a straightforward approach to enhancing anion conductivity but faces a challenge in dimensional stability. Herein, we report the design and preparation of three kinds of isoreticular covalent organic framework (COF) membranes bearing tunable quaternary ammonium group densities as anion conductors. Therein, the cationic groups are integrated into the backbones by flexible ether-bonded alkyl side chains. The highly quaternary ammonium-group-functionalized building units endow COF membranes with abundant cationic groups homogeneously distributed in the ordered channels. The flexible side chains alleviate electrostatic repulsion and steric hindrance caused by large cationic groups, ensuring a tight interlayer stacking and multiple interactions. As a result, our COF membranes achieve a high ion exchange capacity and exceptional dimensional stability simultaneously. Furthermore, the effect of the ionic group density on the ion conductivity in rigid COF channels is systematically explored. Experiments and simulations reveal that the ionic group concentration and side chain mobility jointly determine the ion transport behavior, resulting in the abnormal phenomenon that the anion conductivity is not positively correlated to the ionic group density. The optimal COF membrane achieves the ever-reported highest hydroxide ion conductivity over 300 mS cm-1 at 80 °C and 100% RH. This study offers insightful guidelines on the rational design and preparation of high-performance anion conductors.

Corrigendum: AQUA - Water Infrastructure, Ecosystems and Society 1 September 2023; 72 (9): 1748–1769. Turbulence modelling for depth-averaged velocity and boundary shear stress of a dense rigid grass bed open channel, Sarjati Sahoo, Jnana Ranjan Khuntia, Kamalini Devi, B. Sree Sai Prasad, Kishanjit Kumar Khatua, https://dx.doi.org/10.2166/aqua.2023.093

Corrigendum: <i>AQUA - Water Infrastructure, Ecosystems and Society</i> 1 September 2023; 72 (9): 1748–1769. Turbulence modelling for depth-averaged velocity and boundary shear stress of a dense rigid grass bed open channel, Sarjati Sahoo, Jnana Ranjan Khuntia, Kamalini Devi, B. Sree Sai Prasad, Kishanjit Kumar Khatua, https://dx.doi.org/10.2166/aqua.2023.093

Pyrrolidinium-functionalized Cardo (TPM) poly(arylene ether sulfone)s membranes for acid recovery: The effects of Cardo (TPM) microstructures

To explore the intrinsic correlation between the rigidity and distortion degree of polymer backbones and the diffusion dialysis (DD) performance of anion exchange membranes (AEMs), pyrrolidinium-functionalized poly(arylene ether sulfone)s containing different Cardo (TPM) moieties were prepared. The structures, properties and DD performance of above AEMs were systematically evaluated. As the Cardo (TPM) group angle increased, the d-spacing, fractional free volume, and membrane area resistance increased, and the microphase separation structures, hydrophilicity, and acid flux decreased, mainly because larger Cardo (TPM) group angles are unfavourable for the close packing of polymer chains in space. Both the Cardo-type and TPM-type AEMs exhibited universal ultrahigh H+/Fe2+ selectivity (S > 3819), which was mainly attributed to the synergistic influence of their rigid narrow ion transport channels, small pore diameter (0.48–0.62 nm) and narrow pore size distribution (0.24–0.68 Å). Additionally, due to the high-density amide groups of TPM units, which decreased the hydrophobicity of the polymer skeleton and induced the formation of an additional transport pathway for Fe2+ through hydrogen bonding interactions, the TPM-type AEMs showed both lower acid flux and selectivity, suggesting that the structure of hydrophilic auxiliary groups should be carefully designed when improving the DD performance of AEMs.

Adenine-based metal–organic framework with 1 D narrow channel for molecular-sieving separation of n-butane and isobutane

Molecular-sieving separation of isomeric C4 paraffins, n-butane (n-C4H10) and isobutane (iso-C4H10), is highly desired but challenging because of their very close molecular sizes and physical properties. However, most of the MOF adsorbents often undergo framework flexibility or ligand rotation or swing, leading to the variation of pore size and the loss of the molecular-sieving effect. In this work, an adenine-based MOF with a suitable window size and rigid narrow 1D channel, namely IPM-101, was selected for n-C4H10/iso-C4H10 separation. Adsorption experiments demonstrate that IPM-101 can sensitively adsorb n-C4H10 in the low-pressure region (0–0.05 bar) and reach a saturation state at 0.1 bar while iso-C4H10 is excluded by the size-exclusion effect. Owing to the high porosity, IPM-101 exhibits a high n-C4H10 adsorption capacity (51.6 cm3 g−1) at 1 bar and 298 K. Density functional theory (DFT) calculations clearly reveal the molecular-sieving mechanism that n-C4H10 molecule can diffuse into the pore channel of IPM-101 easily but the diffusion of iso-C4H10 in IPM-101 is kinetically forbidden for its high diffusion energy barrier. The breakthrough experiments show that n-C4H10 and iso-C4H10 can be efficiently separated and iso-C4H10 with a purity of up to 99.9 % can be directly collected. The regeneration experiments show that IPM-101 has good cycling stability for n-C4H10 adsorption and n-C4H10/iso-C4H10 separation. Therefore, the high separation efficiency, excellent regeneration ability, and low cost indicate that IPM-101 has great application potential for practical n-C4H10/ iso-C4H10 separation in industry.

Turbulence modelling for depth-averaged velocity and boundary shear stress of a dense rigid grass bed open channel

Abstract The present research focusses on a comparison of experimental and numerical approaches for flow over fixed artificial rigid grass bed channels. Various flow parameters like longitudinal velocity, depth-averaged velocity (DAV), boundary shear stress (BSS) and secondary current are analysed and compared with seven numerical models: standard, realizable and renormalization group (RNG) k–ε models and standard, shear stress transport (SST), generalized k–ω (GEKO) and Baseline (BSL) k–ω models. To evaluate the strength of the seven applied models, the error analysis has been performed. It is found that the RNG k–ε and SST k–ω models provided better results for both the DAV and BSS prediction, but the RNG k–ε model is found to be the most suitable for predicting the DAV and the SST k–ω model for BSS as compared to the other models. For the longitudinal velocity profiles, both the RNG k–ε and SST k–ω models are found to provide good agreement with experimental results at the centre of the channel, whereas the SST k–ω model is more accurate near the wall. Overall, the SST k–ω model has predicted the results with good accuracy for all the flow parameters considered in the present study.

Bilayer Zwitterionic Metal-Organic Framework for Selective All-Solid-State Superionic Conduction in Lithium Metal Batteries.

Solid-state batteries (SSBs) hold immense potential for improved energy density and safety compared to traditional batteries. However, existing solid-state electrolytes (SSEs) face challenges in meeting the complex operational requirements of SSBs. In this study, weintroduce a novel approach to address this issue by developing a metal-organic framework (MOF) with customized bilayer zwitterionic nano-channels (MOF-BZN) as high-performance SSEs. The bilayer zwitterionic nano-channels consist of a rigid anionic MOF channel with chemically grafted soft multi-cationic oligomers (MCOs) on the pore wall. This design enables selective superionic conduction, with MCOs restricting the movement of anions while coulombic interaction between MCOs and anionic framework promoting the dissociation of Li+ . MOF-BZN exhibits remarkable Li+ conductivity (8.76 × 10-4 S cm-1 ), high Li+ transference number (0.75), and a wide electrochemical window of up to 4.9V at 30°C. Ultimately, the SSB utilizing flame retarded MOF-BZN achieves an impressive specific energy of 419.6Wh kganode+cathode+electrolyte -1 under constrained conditions of high cathode loading (20.1mg cm-2 ) and limited lithium metal source. The constructed bilayer zwitterionic MOFs presents a pioneering strategy for developing advanced SSEs for highly efficient SSBs. This article is protected by copyright. All rights reserved.

Chirality induced spin selectivity: A classical spin-off.

We demonstrate that angular momentum selectivity of particles traversing chiral environments is not limited to the quantum regime and can be realized in classical scenarios also. In our classical variant, the electron spin, which is central to the quantum chirality induced spin selectivity (CISS) effect, is replaced by the self-rotation of a finite-volume body. The latter is coupled to the center of mass orbital motion of the body through a helical tube via wall friction that acts as a dissipative spin-orbit coupling term. As a specific example, we study C60 molecules that are initially spinning in opposite senses and investigate the effect of various external control parameters on their spatial separation when driven through a rigid helical channel. We highlight resemblances and inherent differences between the quantum CISS effect and its classical variant and discuss the potential of the latter to formulate a new paradigm for enantio-separation.

Snap-through instability during transmission of rotation by a flexible shaft with initial curvature

The geometric imperfection of a flexible shaft transmitting rotary motion along a curved path may result in a highly nonlinear relation between the rotation angles at the driving and driven ends. If the intrinsic curvature of the shaft surpasses a specific threshold, even snap-through instability becomes possible. Previously, the problem has been considered for the case when the shaft is confined in a rigid channel such that only the rotary motion is possible along its entire length. The present study focuses on the case of the freely deformable axis of the shaft. Just the locations and the tangential directions of its ends are fixed. We investigate the response of the shaft, in terms of rotation at the driven end, by combining analytical solutions using incremental equations from the theory of Kirchhoff rods and a finite element model that features a C1 continuous approximation of deflections and rotations. Comparison to the constrained case shows that the impact of the deformability of the axis grows both with the intrinsic curvature of the shaft and its angular length.

A new method for establishing operative channels in unilateral biportal endoscopic surgery: Technical notes and preliminary results.

The unilateral biportal endoscopic (UBE) technique has been widely used in spine surgery. At present, a traditional rigid working channel is available for the UBE system. A metal semicircular canal is located in the working channel. However, due to the metal material of the working channel, arthroscopy and instruments are constrained from moving in UBE surgery. Additionally, an assistant is needed during the procedure to hold the traditional working channel. For simplicity of operation and convenient movement of the arthroscopy and instrument, we describe a new method for establishing operative channels in UBE surgery. We retrospectively reviewed 50patients who underwent unilateral biportal endoscopic discectomy (UBED) from February 2020 to August 2020 via our new method. The Oswestry Disability Index (ODI) and visual analogue scale (VAS) score were measured preoperatively and 1month, 3months, 6months and 12months postoperatively. Statistical comparisons were made using analysis of covariance and paired t tests. The VAS scores for back pain at the five time points were 5.20 ± 2.57, 1.96 ± 0.95, 1.50 ± 0.84, 1.64 ± 1.08 and 1.18 ± 0.39. The leg pain VAS scores were 7.02 ± 2.25, 2.02 ± 1.27, 1.48 ± 0.89, 1.32 ± 0.79 and 0.88 ± 0.52. The ODI values were 51.08 ± 19.97, 19.62 ± 15.51, 8.26 ± 7.40, and 7.54 ± 6.42 to 3.24 ± 1.10. The postoperative ODIs and VAS scores of low back pain and leg pain were significantly lower than those before surgery, and differences were statistically significant (all p< 0.05). The pressure of the closed outflow was significantly higher than that of the open outflow (37.35 ± 13.11mm Hg vs. 24.55 ± 12.64mm Hg p= 0.003). After we tightened the infusion strap to open the outflow, the pressure decreased significantly (26.4 ± 14.08mm Hg vs. 37.35 ± 13.11mm Hg p= 0.015). There were 2cases of complications, including 1case of postoperative recurrence and 1case of dural tears. This study demonstrates the technical feasibility, safety, and efficacy of modified channel establishment in UBE surgery.

Passive tracer transport in peristaltic pumping of non-Newtonian blood flow: A mathematical model

The large time behavior of passive contaminant in non-Newtonian peristaltic blood flow in a two-dimensional (2D) channel (capillary) has been examined in this paper. The power-law model is employed in order to highlight the non-Newtonian blood characteristic. The study was conducted using the Reynolds decomposition technique, which converts a 2D transport problem into a 1D transport model in which species concentration can be decomposed into sectional average concentration and variation from its mean value. For flow velocity, the same decomposition method is used. This allows the derivation of the dispersion coefficient and convection coefficient. Using Fick’s law, the advection–diffusion equation is modified by replacing these coefficients by their corresponding average values and analytical solutions for the mean concentration are derived. In the absence of peristalsis effects ([Formula: see text]), i.e., for the straight rigid channel, the dispersion coefficient is invariant along the channel length. With increasing modulation (peristaltic wave) parameter, [Formula: see text], there is a strong elevation in advection coefficient in the initial half of the channel with a subsequent suppression in the second half of the channel, indicating that the location in the channel strongly influences advection characteristics. Advection coefficient is significantly elevated with increment in power-law rheological index (for shear-thinning fluids, [Formula: see text]) across the channel length and exhibits an oscillatory nature due to the peristaltic waves. In the shear-thickening range ([Formula: see text]), with progressive increase in n, an increment in peristaltic modulation parameter, [Formula: see text], induces a marked reduction in the axially average relative advection coefficient. Dispersion coefficient is initially boosted along the early section of the channel with increment in modulation parameter whereas further long the channel this trend is reversed. Increasing aspect ratio and Péclet number consistently boost dispersion coefficient along the entire channel length. The study provides a solid benchmark for further generalized simulations with computational fluid dynamics.

The onset of instability in a hydromagnetic channel flow of Casson fluid: the accurate solutions

We study the temporal stability of linear two-dimensional disturbances of plane Poiseuille flow of a Casson fluid in a rigid parallel channel under the influence of a uniform magnetic field. When the disturbance is taken in normal mode it transforms the perturbed equations to a fourth-order eigenvalue problem which is then solved by the spectral method. We first obtain sufficient conditions for the hydrodynamic stability in the channel by analyzing the nature of the growth rate and the Reynolds number. For the chosen set of parameters, the eigenspectra of the flow exhibit the familiar Y-shaped structure with three distinct modes depending on the phase speed approach. The eigenfunctions corresponding to the least stable and most unstable eigenmodes have the symmetric and antisymmetric modes. For a certain range of Casson parameter β and the magnetic number M, instability always appears on the wall mode for which the eigenfunction is antisymmetric about the channel center-line. The neutral stability curves that correspond to various values of β and M are found to be an extension of the continuation of the Tollmien-Schlichting instability that is noticed for a Newtonian channel flow. The regions of stability are enlarged for small β and large M.

Quasi-Orthogonal Configuration of Propylene within a Scalable Metal-Organic Framework Enables Its Purification from Quinary Propane Dehydrogenation Byproducts.

Propylene production via nonoxidative propane dehydrogenation (PDH) holds great promise in meeting growing global demand for propylene. Effective adsorptive purification of a low concentration of propylene from quinary PDH byproducts comprising methane (CH4), ethylene (C2H4), ethane (C2H6), propylene (C3H6), and propane (C3H8) has been an unsolved academic bottleneck. Herein, we now report an ultramicroporous zinc metal–organic framework (Zn-MOF, termed as 1) underlying a rigid one-dimensional channel, enabling trace C3H6 capture and effective separation from quinary PDH byproducts. Adsorption isotherms of 1 suggest a record-high C3H6 uptake of 34.0/92.4 cm3 cm–3 (0.01/0.1 bar) at 298 K. In situ spectroscopies, crystallographic experiments, and modeling have jointly elucidated that the outstanding propylene uptakes at lower pressure are dominated by multiple binding interactions and swift diffusion behavior, yielding quasi-orthogonal configuration of propylene in adaptive channels. Breakthrough tests demonstrate that 30.8 L of propylene with a serviceable purity of 95.0–99.4% can be accomplished from equimolar C3H6/C3H8 mixtures for 1 kg of activated 1. Such an excellent property is also validated by the breakthrough tests of quinary mixtures containing CH4/C2H4/C2H6/C3H6/C3H8 (3/5/6/42/44, v/v/v/v/v). Particularly, structurally stable 1 can be easily synthesized on the kilogram scale using cheap materials (only $167 for per kilogram of 1), which is important in industrial applications.

Defects modulating on MgAl-hydrotalcite nanosheet with improved performance in carbonyl sulfide elimination via a hydroxyl chemical looping route

Adsorption and dissociation of H2O along with the generated hydroxide ions (OH–) over catalyst plays key role in the carbonyl sulfur (COS) hydrolysis. Herein, we report a variety of magnesium aluminum layered double hydroxides nanosheet with abundant structural defects (MA-LDHs-SD-x) designed by a mechanochemistry method using white carbon black as the defects directing agent. The resulted MA-LDHs-SD-x possess abundant structural defects along with much enlarged BET surface area and pore volume (175 m2/g and 0.347 cm3/g vs 32 m2/g and 0.039 cm3/g), which provide enhanced amount of surface OH– base sites, tight and rigid diffusion channels for guest molecules. As expected, the MA-LDHs-SD-x were found to be rather active in catalyzing COS hydrolysis, nearly 100% conversion and selectivity can be achieved at only 30 °C without H2O in a span of 96 h through a hydroxyl chemical looping route, which showing potential application value in the industrial desulfuration.

Actin Turnover Required for Adhesion-Independent Bleb Migration

Cell migration is critical for many vital processes, such as wound healing, as well as harmful processes, such as cancer metastasis. Experiments have highlighted the diversity in migration strategies employed by cells in physiologically relevant environments. In 3D fibrous matrices and confinement between two surfaces, some cells migrate using round membrane protrusions, called blebs. In bleb-based migration, the role of substrate adhesion is thought to be minimal, and it remains unclear if a cell can migrate without any adhesion complexes. We present a 2D computational fluid-structure model of a cell using cycles of bleb expansion and retraction in a channel with several geometries. The cell model consists of a plasma membrane, an underlying actin cortex, and viscous cytoplasm. Cellular structures are immersed in viscous fluid which permeates them, and the fluid equations are solved using the method of regularized Stokeslets. Simulations show that the cell cannot effectively migrate when the actin cortex is modeled as a purely elastic material. We find that cells do migrate in rigid channels if actin turnover is included with a viscoelastic description for the cortex. Our study highlights the non-trivial relationship between cell rheology and its external environment during migration with cytoplasmic streaming.