Large Channel Research Articles

Effects of Jet-to-Target Surface Spacing and Pin-Fin Height on Jet Impingement Heat Transfer in a Rectangular Channel

Abstract An experimental study was completed to quantify heat transfer enhancement, pressure loss, and crossflow effect within a channel of inline impinging jets. The jet diameter is 5.08 mm; the jet-to-jet spacings in the streamwise and spanwise directions are fixed at x/d = 11.1 and y/d = 5.9, respectively. The effect of jet-to-target surface spacing was considered with z/d = 3 and 6. For both jet-to-target surface spacings, smooth, short pin-finned, and long pin-finned target surfaces were investigated. Both roughened surfaces have a staggered array of 120 copper pin-fins. The pin-to-jet diameter ratio is fixed at D/d = 0.94. The pin height-to-jet diameter ratio for the short and long pins are H1/d = 1.5 and H2/d = 2.75, respectively. Regionally averaged heat transfer coefficient distributions were measured on the target surface, and these distributions were coupled with pressure measurements through the array. The heat transfer augmentation and pressure penalty were investigated over a range of jet Reynolds numbers (10k–70k). The results show high discharge coefficients for all the cases. The channels with the small jet-to-target surface spacing experience double the crossflow effect of the large spacing channels. The addition of surface roughness showed a negligible effect on the crossflow. The best heat transfer performance was observed in the narrow impingement channel with the long pins.

Low-cost zeolite-based sorbents prepared from industrial perlite by-product material for Zn2+ and Ni2+ removal from aqueous solutions: synthesis, properties and sorption efficiency

The conversion of waste/by-product materials into efficient sorbents is at the forefront of innovative remediation techniques. In the present study, the relationships among the synthesis conditions, physicochemical properties of synthesized sorbents and Zn2+ and Ni2+ removal efficiencies were studied in detail. Zeolite X, zeolite P, phillipsite, analcime, sodalite and cancrinite were synthesized from industrial perlite by-product material. The zeolite content in the synthesized sorbents and zeolite framework topology (dimensions, numbers and spatial configuration of channels) were the key factors affecting the removal of Zn2+ and Ni2+ from aqueous solutions. Zeolite X-based sorbent exhibited the best sorption performance mainly due to the large zeolite channel dimensions, low Si/Al ratio, high cation exchange capacity and high specific surface area. Nevertheless, the efficiency and stability of this sorbent need to be tested under field conditions prior to its application for remediation technologies.

Discharge prediction in partly vegetated channel flows: Adaptation of IDCM method with a curved interface and large-scale roughness elements

This study provides new insight into how to predict flow discharges of partly vegetated channels with emergent vegetation. By adapting for the first time the Interacting Divided Channel Method (IDCM), applied with a curved interface approach and with the presence of large-scale roughness elements (not considered in previous studies), the total and zonal discharges of partly vegetated channels were predicted based on a series of experimental results in this study together with collected data from previous studies. Consideration of transverse momentum transfer in terms of apparent shear stress at curved interface plane showed better performance with IDCM than the Divided Channel Method (DCM) with both curved and classic vertical/diagonal divisions. In this study, we also proposed a series of expressions, easily applicable, to predict the zonal discharges of a partly vegetated channel.Many experiments were carried out in a physical model of a very large rectangular channel with the presence of rows of vertical, rigid, circular, and rough steel cylinders, representing emergent rigid vegetation. The rows of cylinders were partially mounted on the bottom of the channel, leaving lateral areas of free circulation near the walls. The three-dimensional components of the flow velocity were measured using a 3D Acoustic Doppler Velocimeter (ADV)-Vectrino.

Dual template using P123-gelatin for synthesized large mesoporous silica for enhanced adsorption of dyes

Mesoporous Silica with a large mesopore channel was synthesized using the sol-gel method for dye adsorption. A dual template consisting of P123 and gelatin at different ratios was employed in the sol-gel synthesis to enhance surface area and mesopore diameter. Gelatin is a green pore directing agent that strengthens P123 thermal stability during the calcination of silicate gel. Optimization of P123:gelatin ratio to 1:0.02 increased the surface area of mesoporous silica to 561.9 m2/g and expanded the pore diameter to 10 nm. The large pore diameter and surface area enhanced methylene blue adsorption capacity to 363.63 mg/g. The adsorption of methylene blue on mesoporous silica follows the pseudo second-order kinetic and the Langmuir model. Regeneration studies using thermal and chemical treatments exhibited the potential of mesoporous silica as an adsorbent for multiple adsorption-desorption of dyes.

Anisotropic dense collagen hydrogels with two ranges of porosity to mimic the skeletal muscle extracellular matrix

Despite the crucial role of the extracellular matrix (ECM) in the organotypic organization and function of skeletal muscles, most 3D models do not mimic its specific characteristics, namely its biochemical composition, stiffness, anisotropy, and porosity. Here, a novel 3D in vitro model of muscle ECM was developed reproducing these four crucial characteristics of the native ECM. An anisotropic hydrogel mimicking the muscle fascia was obtained thanks to unidirectional 3D printing of dense collagen with aligned collagen fibrils. The space between the different layers was tuned to generate an intrinsic network of pores (100 μm) suitable for nutrient and oxygen diffusion. By modulating the gelling conditions, the mechanical properties of the construct reached those measured in the physiological muscle ECM. This artificial matrix was thus evaluated for myoblast differentiation. The addition of large channels (600 μm) by molding permitted to create a second range of porosity suitable for cell colonization without altering the physical properties of the hydrogel. Skeletal myoblasts embedded in Matrigel®, seeded within the channels, organized in 3D, and differentiated into multinucleated myotubes. These results show that porous and anisotropic dense collagen hydrogels are promising biomaterials to model skeletal muscle ECM.

Surface wettability regulation on the miniaturized V-shaped channels fabricated by hot-embossing

The combination of functional microstructure and surface wettability regulation is an advanced strategy to achieve greatly enhanced functions such as heat transfer, drag reduction and corrosion resistance, and has broad application prospects in aerospace, microelectronics, biomedical and other fields. This study proposes a cost-effective and environmental-friendly method to fabricate miniaturized V-shaped channels, and the surface wettability and droplet behavior of fabricated channels are investigated. Miniaturized V-shaped channels are fabricated by hot-embossing, and the wetting transitions to the Cassie state as the scale of the embossed channels increases. After subsequent modification with ultrafast laser and fluorine-free stearic acid, V-shaped channels with superhydrophilic and hydrophobic properties are obtained. Rough nanotextures are formed on channels after laser scanning, and the inherent anisotropic wetting could be alleviated by combining with stearic acid modification. The droplet spreading captured by the high-speed camera shows that the droplet can completely spread on the superhydrophilic channels fabricated by the ultrafast laser, and the larger the dimension of the channels, the stronger the spreading anisotropy and the smaller the spreading ratio. By contrast, the droplet on the hydrophobic channels spreads first and then shrinks, and the anisotropy of droplet spreading or shrinking decreases. Interestingly, the hydrophobic channel dimension is found to have a significant effect on the droplet behaviors. The droplet could full bouncing or form satellite droplet when it impacts the hydrophobic channels with smaller dimension, whereas the droplet on the larger channels tends to be pinned or breakup. The relationship between miniaturized channel dimension and droplet wetting should be appreciated in practical engineering applications, which will facilitate the development of novel functionally enhanced surfaces.

Mechanochemistry-guided reticular assembly for stabilizing enzymes with covalent organic frameworks

Structural stabilization of enzymes by porous frameworks is an emerging strategy in biotechnology that may accelerate large-scale industrial application of biocatalysts. Herein, we stabilize an enzyme by wrapping it with covalent organic frameworks in situ using a mild mechanochemistry-guided assembly. This mechanochemical strategy circumvents the harsh conditions often necessary for covalent organic frameworks’ crystallization, and hence avoids enzyme denaturation during the de novo encapsulation. The covalent-linked topology and tailorable large pore channels of the covalent organic framework host not only stabilize enzymes, but also outperform the well-explored enzyme-zeolite imidazole framework counterparts in terms of catalytic efficiency, functional diversity, and structural stability. This work offers a greener and convenient mechanochemistry-guided assembly strategy, enabling template-free enzyme encapsulation across multiple enzyme and covalent organic framework pore structures. • A mechanochemical strategy for engineering enzyme-COFs biohybrids is reported • The mechanochemical method is demonstrated across multiple enzymes and COFs • The enzyme-encapsulated COFs are structurally stable and catalytically active Immobilization of enzymes without disrupting their function is an important component of biocatalysis. Here, Gao et al. report a mechanochemistry-guided assembly strategy for bottom-up construction of enzyme-encapsulated covalent organic framework biocomposites.

Single-crystalline Mn2V2O7 anodes with high rate and ultra-stable capability for sodium-ion batteries

The abundant sodium resources provide a great potential for the practical application of sodium ion batteries (SIBs). However, the development of feasible anode materials with high-rate capability to solve the slow diffusion kinetics of Na+ has always been a major challenge for high performance SIBs. Herein, a layer-structured metal vanadate Mn2V2O7 (MnVO) with large open channel within its crystal structure frame is for the first time identified as a promising candidate for high-rate SIB anodes, which ensures a large pseudocapacitance contribution. Moreover, the prepared micron size single crystal structure of MnVO effectively shortens the diffusion and transmission paths of Na+ ions and electrons, thus accomplishing high capacity (a reversible capacity of 250 mA h g−1 at 0.2 A g−1), excellent cycling stability (125 mA h g−1 at 10 A g−1 after 3500 cycles with 98% capacity retention) and fast charge and discharge rates (120 mA h g−1 at 20 A g−1 after 5000 cycles). This work explores transition metal vanadates as SIB anodes with excellent rate performance.

Comparative study of unilateral biportal endoscopy and coaxial large channel endoscopy for lumbar spinal stenosis

Objective: To compare the efficacy of unilateral biportal endoscopy (UBE) and coaxial large channel endoscopy for lumbar spinal stenosis. Methods: A total of 176 patients with lumbar spinal stenosis treated in Tianjin Hospital from March 2015 to October 2021 were included in this study. Of the patients, 110 cases were treated with UBE, including 52 males and 58 females, with a mean age of (75.1±10.4) years; while 66 cases were treated with coaxial large channel endoscopy, including 31 males and 35 females, with an average age of (77.2±13.1) years. The visual analogue scale (VAS) score of pain and Oswestry disability index (ODI) were compared before and after surgery between the two groups, with the improvement rate calculated. The operation time, intraoperative blood loss, perioperative conditions and complications were compared. The operation efficacy was evaluated according to MacNab scale and was compared between the two groups. Results: There was no significant differences in age, gender, disease course, VAS of pain, ODI and index levels between the two groups before operation (all P>0.05). The operation time and postoperative drainage in UBE group and coaxial large channel endoscopy group were comparable [(60.1±12.4)min, (62.5±13.2)min and (103.8±20.7)ml, (98.5±22.1)ml, respectively, both P>0.05]. After the operation, the VAS score of low back pain, VAS score of leg pain and ODI of the two groups were all lower than those before operation, and decreased continuously during follow-up; and under the repeated measures analysis of variance, significant differences were found between different time points (all P<0.05), no significant difference was found between the two groups (all P>0.05), nor interaction between groups and time points was detected (all P>0.05). The patients were followed-up for (18.0±4.2) months (6 to 30 months). There was no significant difference in VAS and ODI improvement rates and excellent rate of efficacy between the two groups at the last follow-up (all P>0.05). Conclusions: Both UBE and coaxial large channel endoscopy can provide excellent results for lumbar spinal stenosis. UBE has sufficient decompression and is convenient to explore and remove the herniated disc.

High-fidelity multiplexing meta-hologram for information display, storage and encryption

Holography has been continuously spurring tremendous interest of researchers attributed to its unparalleled capability of photographically reconstructing the desired images. Based on the metasurfaces with multiple degrees of freedom, multiplexing meta-holograms are experiencing the research upsurge because of enormous application potential. However, existing multiplexing meta-holograms cannot tailor the amplitude information, and possess limited imaging channels and high channel crosstalk, which hinder the improvement of information capacity and imaging quality of multiplexing meta-holograms. Herein, an innovative multiplexing meta-hologram based on the helicity-assisted meta-atoms is proposed, which can perfectly reconstruct four independent images by altering the working frequency, polarization state and propagation direction of incident waves, and theoretically realize the holography in sixteen different channels by easily rotating, mirroring, and arranging the structures of meta-atoms. Numerous simulations and experiments collectively corroborate the feasibility of our methodology, and the quantitative analyses verify the high fidelity of the reconstructed images, which results from the low crosstalk between the amplitude modulation and phase modulation in different imaging channels. This inspiring strategy of multiplexing meta-hologram with large channel capacity and high imaging quality will have promising application prospects in information display, storage and encryption, and provide an alternative path for the design of multifunctional microwave devices.

Construction and Test of an Instrumented 2D Channel with Rainfall and Insolation Control

This paper presents the construction and testing of a large instrumented 2D channel for the simulation of the performance of compacted barriers under controlled conditions of insolation and rainfall. Details of the main apparatus devices and capabilities and the results of a long-term test performed on a capillary barrier (CB) are presented. The performed test aimed to simulate the behavior of the CB over 1 year in typical semi-arid conditions. The channel behavior was considered very promising. Boundary conditions in terms of rainfall and insolation were adequately properly imposed and suction values, moisture content, runoff and bottom drainage were measured throughout the test. As for the CB performance, the upper clayey layer of soil presented undesirable shrinkage cracks that impacted the CB performance, mainly at the end of the period of evaluation. The obtained results point to the need to use of thicker layers than used in the experiments in order to preserve the integrity of the clayey soil near the interface with the bottom coarse soil layer.

Self-regulated immobilization behavior of multiple heavy metals via zeolitization towards a novel hydrothermal technology for soil remediation

More efficient soil remediation technologies are highly anticipated to treat large quantities of heavy metal-polluted urban sites nowadays. Herein, a novel hydrothermal technology of converting heavy metal-polluted soils into zeolites for in-situ immobilizing heavy metals was proposed. The zeolites (analcime and cancrinite) could be synthesized hydrothermally with certain Na/Si and Al/Si ratios. The formed zeolites could manage to change their species and structure during zeolitization to accommodate different heavy metals in soil according to their size and charge. Since smaller-size Cu2+ was introduced, analcime and some cancrinite possessing small cages could be formed adaptively to immobilize the Cu2+ by replacing Na+ and forming Cu2+-OH and Cu2+-O. Whereas, cancrinite with large channels managed to form to immobilize the larger-size Cd2+ by forming Cd2+-O. Interplanar spacing variation of zeolites also corresponded to their structural change for accommodating different heavy metals. Leaching results showed the amounts of Cu and Cd leached from the synthesized zeolites were reduced to 0.005% and 0.05% respectively, reflecting a more stable immobilization of smaller heavy metals by small cages, in agreement with the results of distribution coefficient (Kd). Negligible effect of pH environment on the leaching rates further confirmed the stable structural immobilization of heavy metals by zeolites.

Bio-inspired salt-fouling resistant graphene evaporators for solar desalination of hypersaline brines

Solar seawater desalination may provide an economical and environmentally friendly means to address the global freshwater crisis. However, salt crystals can precipitate and accumulate on evaporator surfaces during solar seawater desalination, leading to significant deterioration of the performance. Current anti-salt fouling strategies generally suffer from low evaporation rates particularly during the desalination of hypersaline brines. In this paper, we propose bio-inspired graphene evaporators with well-aligned tubular channels to achieve effective solar desalination of hypersaline brines with simultaneously enhanced evaporation rate and long-term anti-salt fouling performance. The unique hierarchical large and small channels inside the evaporators not only increase evaporating surface area, but also provide low-tortuosity pathways for fast salt ion diffusion from the evaporation surfaces to bulk brine. Consequently, the proposed device achieves a high evaporation rate of 2.60 kg m−2 h−1 during a 24-h continuous evaporation test in a hypersaline brine (20 wt% NaCl solution) under one-sun irradiation, among the best values reported in previous studies. Meanwhile, salt precipitation is observed to preferentially occur at the edges of the top surface, leaving the main evaporation area clean during the desalination process. The bio-inspired graphene evaporators with well-aligned tubular channels exhibit great potential for practical solar seawater desalination applications.

Thermoacoustic Soret separation.

In a fluid mixture in a channel with an axial time-averaged temperature gradient, high-amplitude oscillating flow can greatly increase the axial flux of thermal diffusion (Soret) separation of the components of the mixture. The enhancement occurs when the oscillating lateral temperature gradient greatly exceeds the axial gradient, causing a large oscillating concentration that can be favorably time-phased with the oscillating flow. This process can occur even with a negligible pressure oscillation or with a negligible temperature response to pressure, as is the case in most liquid solutions. The thermal boundary condition imposed by realistic solids on thermoacoustic liquids is imperfect, adding mathematical complications that are absent for typical gases, for which the solid surface is temporally isothermal. Compared with gas mixtures, the high Lewis number in typical liquid solutions reduces the separation flux associated with the time-averaged temperature gradient, but it also reduces the remixing associated with the time-averaged mole-fraction gradient. For large enough channels, the second-law separation efficiency is only slightly reduced from that of steady liquid Soret separation.

A Partial Reciprocity-Based Channel Prediction Framework for FDD Massive MIMO With High Mobility

Massive multiple-input multiple-output (MIMO) is believed to deliver unrepresented spectral efficiency gains for 5G and beyond. However, a practical challenge arises during its commercial deployment, which is known as the “curse of mobility”. The performance of massive MIMO drops alarmingly when the velocity level of user increases. In this paper, we tackle the problem in frequency division duplex (FDD) massive MIMO with a novel Channel State Information (CSI) acquisition framework. A joint angle-delay-Doppler (JADD) wideband precoder is proposed for channel training. Our idea consists in the exploitation of the partial channel reciprocity of FDD and the angle-delay-Doppler channel structure. More precisely, the base station (BS) estimates the angle-delay-Doppler information of the UL channel based on UL pilots using Matrix Pencil (MP) method. It then computes the wideband JADD precoders according to the extracted parameters. Afterwards, the user estimates and feeds back some scalar coefficients for the BS to reconstruct the predicted DL channel. Asymptotic analysis shows that the CSI prediction error converges to zero when the number of BS antennas and the bandwidth increases. Numerical results with industrial channel model demonstrate that our framework can well adapt to high speed (350 km/h), large CSI delay (10 ms) and channel sample noise.

Comparison of the short-term effects of lumbar endoscopic and microscopic tubular unilateral laminotomy with bilateral decompression in the treatment of elderly patients with lumbar spinal stenosis

ObjectiveTo compare the clinical efficacy of lumbar endoscopic Delta large channel and microscopic tubular Quadrant channel unilateral laminotomy with bilateral decompression in the treatment of elderly patients with lumbar spinal stenosis.MethodsA total of 40 patients aged above 75 years with lumbar spinal stenosis admitted from June 2019 to August 2021 were reviewed, in which the observation group was treated with the Delta large channel technique and the control group was treated with Quadrant channel open decompression. The general data, duration of illness, operation time, intraoperative bleeding, VAS score preoperatively, 3 days postoperatively, 3 months postoperatively and 6 months postoperatively, and ODI index of the two groups were recorded in the two groups.ResultsThe observation group had significantly shorter operation time (59.93 ± 10.46 min vs 77.66 ± 12.44 min, P < 0.001) and less intraoperative bleeding (21.06 ± 4.59 mL vs 51.00 ± 10.02 mL, P < 0.001) than the control group. There were no significant differences between the two groups in the duration of illness (11.85 ± 5.08 years vs 13.80 ± 7.40 years, P = 0.337), VAS score preoperatively (6.05 ± 1.19 vs 6.40 ± 1.47, P = 0.412), 3 days postoperatively (1.90 ± 0.85 vs 2.00 ± 1.08, P = 0.746), 3 months postoperatively (1.10 ± 0.31 vs 1.20 ± 0.41, P = 0.389) and 6 months postoperatively (1.25 ± 0.44 vs 1.30 ± 0.57, P = 0.759), and ODI index preoperatively (0.78 ± 0.07 vs 0.74 ± 0.07, P = 0.09), 3 months postoperatively (0.28 ± 0.06 vs 0.30 ± 0.05, P = 0.189) and 6 months postoperatively (0.21 ± 0.07 vs 0.22 ± 0.04, P = 0.444) (P > 0.05). The ODI index 3 days postoperatively in the observation group was significantly lower than that in the control group (0.33 ± 0.06 vs 0.37 ± 0.05, P = 0.022).ConclusionBoth surgical methods had good clinical outcomes for the treatment of lumbar spinal stenosis. However, Delta large channel endoscopy had a clearer vision, less trauma and lower incidence of early postoperative back pain than that of Quadrant channel open decompression.

Endoscopic Transluminal Stent Placement for Malignant Afferent Loop Obstruction

Malignant afferent loop obstruction (ALO) is rare condition and is difficult to manage. Endoscopic transluminal treatment has become easier with the advent of balloon-assisted enteroscopes with a large working channels and self-expandable metal stent (SEMS) with a 9 Fr delivery system. From July 2016 to March 2022, 22 patients with symptomatic malignant ALO who underwent endoscopic transluminal treatment (Initial cohort), of which 18 patients received endoscopic transluminal SEMS placement (SEMS cohort), were retrospectively evaluated. We evaluated outcomes of endoscopic transluminal treatment and long-term outcomes of SEMS placement for malignant ALO. In the Initial cohort, technical and clinical success rates were both 95.5%. The median procedural time was 28.0 min. One case of guidewire-induced micro-perforation occurred as an early complication (4.5%). In the SEMS cohort, and no early complication was observed. Recurrent obstruction occurred in two cases (11.1%) during the follow-up period (median: 102 days). One was managed by additional SEMS placement and the other was treated conservatively. High technical and clinical success was achieved by endoscopic transluminal treatment with short procedural time for malignant ALO. Endoscopic SEMS placement also appears to be safe and effective, and additional SEMS placement can be considered in cases of re-obstruction.

Performance evaluation of PDM-256-QAM inter-satellite optical wireless system (IsOWC) using DSP and different wavelength windows

Abstract For communication in space, information transmission lines are critical for reaching the whole world. A long delay and a poor data transfer rates have been observed in radio frequency (RF) communication and therefore inter-satellite communication has become more common in recent years and optical wireless communication has advanced dramatically. Owing to its multiple advantages, including large channel bandwidth, high-speed connectivity and economical operations, IsOWC technology is becoming popular among researchers. Uniphase modulations such as NRZ modulation does not have efficient spectrum for high speed inter-satellite communication. PDM-256-QAM at 160 Gbps over IsOWC channel is demonstrated in this work using matched filter and DSP. Proposed system is investigated for PDM-256-QAM at 850 and 1550 nm wavelength and results analyzed in terms of Q factor, log symbol error rate (SER) and error vector magnitude (EVM).

Artificial Water Channels—Progress Innovations and Prospects

Artificial Water Channels—Progress Innovations and Prospects

Reaction within the coulomb-cage; science in retrospect

The Coulomb-cage is defined as the space where the electrostatic interaction between two bodies is more intensive than the thermal energy (kBT). For small molecule, the Coulomb-cage is a small sphere, extending only few water molecules towards the bulk and its radius is sensitive to the ionic strength of the solution. For charged proteins or membranal structures, the Coulomb-cage can engulf large fraction of the surface and provides a preferred pathway for ion propagation along the surface. Similarly, electrostatic potential at the inner space of a channel can form preferential trajectories passage for ions. The dynamics of ions inside the Coulomb-cage of ions was formulated by the studies of proton-anion recombination of excited photoacids. In the present article, we recount the study of intra- Coulomb-cage reaction taking place on the surface of macro-molecular bodies like micelles, membranes, proteins and intra-protein cavities. The study progressed stepwise, tracing the dynamics of a proton ejected from a photo-acid molecule located at defined sites (on membrane, inter-membrane space, active site of enzyme, inside Large Pore Channels etc.). Accumulation of experimental observations encouraged us to study of the reaction mechanism by molecular dynamics simulations of ions within the Coulomb-cage of proteins surface or inside large pores. The intra-Coulomb-cage proton transfer events follows closely the fine structure of the electrostatic field inside the cage and reflects the shape of nearby dielectric boundaries, the temporal ordering of the solvent molecules and the structural fluctuations of the charged side chains. The article sums some 40 years of research, which in retrospect clarifies the intra-Coulomb-cage reaction mechanism.