Pumping Mechanism Research Articles

Feedback-controlled flux modulation for high-temperature superconducting magnets in persistent current mode

High-temperature superconducting (HTS) magnets have found wide applications in high-field settings owing to their high current capabilities. Typically, these magnets are powered by high-current power supplies via current leads, which can complicate insulation between cryogenic and room temperature environments. However, new developments in flux pumps for HTS magnets have enabled charging of kA levels of current without power supplies. By combining flux pumps with HTS persistent current operation, it is possible to achieve accurate flux modulation and eliminate the need for power supplies and current leads. In this study, we report on a novel feedback-controlled flux modulation for HTS magnets in persistent current operations. This flux modulation is based on a flux pump mechanism that generates a DC voltage across the charging superconductor by applying a current higher than its critical current. With closed-loop feedback control, our flux modulation can achieve precise injection and reduction of HTS magnet current in increments of 0.5 A. This technology can lead to stable magnetic fields in HTS magnet designs. We anticipate that this work will enable future magnets to operate in a stable persistent current mode within a closed cryogenic chamber, significantly reducing the footprint and power demand of HTS magnets and opening up new opportunities for their applications.

Eco-morphodynamic carbon pumping by the largest rivers in the Neotropics

The eco-morphodynamic activity of large tropical rivers in South and Central America is analyzed to quantify the carbon flux from riparian vegetation to inland waters. We carried out a multi-temporal analysis of satellite data for all the largest rivers in the Neotropics (i.e, width > 200 m) in the period 2000–2019, at 30 m spatial resolution. We developed a quantification of a highly efficient Carbon Pump mechanism. River morphodynamics is shown to drive carbon export from the riparian zone and to promote net primary production by an integrated process through floodplain rejuvenation and colonization. This pumping mechanism alone is shown to account for 8.9 million tons/year of carbon mobilization in these tropical rivers. We identify signatures of the fluvial eco-morphological activity that provide proxies for the carbon mobilization capability associated with river activity. We discuss river migration—carbon mobilization nexus and effects on the carbon intensity of planned hydroelectric dams in the Neotropics. We recommend that future carbon-oriented water policies on these rivers include a similar analysis.

A Computer-Aided Intelligent Fault Diagnosis Method for Axial Hydraulic Piston Pump

<p>Axial hydraulic piston pump is widely used in industrial production due to its high pressure resistance and large displacement characteristics, but high pressure and large displacement are also the main causes of piston pump failure. Starting from the fault mechanism of the axial hydraulic piston pump, this paper analyzes and studies the signal characteristics of the fault, and establishes the fault signal acquisition and analysis model. Finally, it discusses the construction of the diagnosis system from both hardware and software, so that the processed typical fault signals can be sent into the intelligent diagnosis system to determine the fault type. Finally, the method in this paper is verified by experiments, which proves the reliability and effectiveness of the diagnosis system.</p> <p> </p>

Biomimetic micropump: Leveraging a novel propagative rhythmic membrane function

We discuss bioinspired pumping mechanism in a microfluidic configuration, consistent with the newly formulated propagative rhythmic contraction–expansion of a membrane attached to the channel wall. We aptly demonstrate the kinematics of the proposed membrane function and describe the wall profile developed due to the propagative expansion–contraction phases of the actuation cycle. The transport equations governing the flow dynamics are solved analytically in the purview of the lubrication theory. An analysis of the proposed model establishes that the fluidic functionality of a channel equipped with a single elastic membrane that operates following the propagation expansion-contraction modes can produce a unidirectional flow, and acts as a micropump in the process. By depicting the flow velocity, velocity contours, and streamlines patterns in the flow pathway, we discuss and demonstrate the eventual consequence of these flow parameters to the net throughput during both the compression and expansion phases of the process. We establish the efficacy of the novel membrane function by demonstrating augmented net throughput obtained from the proposed configuration. The membrane function developed in this endeavor will provide greater flexibility to the researchers to carry out further research in the field and will make the underlying analysis even easier in systems that utilize electromagnetic fields in the flow system.

Unsteady Simulation and Analysis of Energy Loss Mechanism of a Vertical Volute Pump Under Stall Conditions

AbstractThis study comprehensively investigates the flow features and energy loss mechanisms under stall conditions based on computational fluid dynamics (CFD) and hydraulic loss visualization techniques. The three-dimensional unsteady Reynolds-averaged Navier– Stokes (URANS) equations were solved using the shear stress transport (SST) k–ω turbulence model. Furthermore, the entire flow domain of the vertical volute pump was considered to capture the boundary flow behavior accurately. The results illustrate that the critical stall condition occurs at 0.7Qd, where the H–Q curve exhibits a positive slope, and the deep stall condition occurs at 0.65Qd. The growth rate of energy loss from critical stall to deep stall is 182.2%. In the stall condition, a secondary vortex appears at the impeller inlet. A high energy loss occurs at the suction side and trailing edge in the impeller caused by the reduction in the effective inflow area. The energy loss in the blade suction side guide vane is primarily due to the friction loss under the critical stall condition. By contrast, under the deep stall condition, the energy loss in the outlet of the guide vane is mainly the impact loss from the volute of the rear gunner. The impact effect can result in high energy losses near the volute tongue. The entropy production analysis demonstrates that the hydraulic losses in the diffuser are literately greater than that in the impeller and inlet pipe. Hence, optimization of such components can be taken into consideration in future works for performance improvement.

Characterization of a Sub‐Atmospheric Pressure‐Inducing Micropump Based on Flow Rate and Gauge Pressure Measurements

AbstractThe pumping mechanism in multi‐inlet microfluidic channels usually requires multiple micropumps to be separately attached to each inlet. Unfortunately, this may create fluid leakage resulting from a considerably high internal pressure. To address this, a passive sub‐atmospheric pressure‐inducing micropump is proposed and its performance is characterized as a function of the flow rate and the gauge pressure. With this pump, a sufficiently high flow rate is generated, comparable to some active‐piezoelectric micropumps. The gauge pressure is exponentially descending with time and can be crudely classified into three regions of high, moderate, and slow pressure‐release times. Overall, the stabilized pressure is identified within 70 s < t ≤ 300 s for slow rate mixing while rapid mixing is applicable at t ≤ 70 s.

Pump Excited-State Absorption at 442 ± 1 nm for Efficient Visible Fluoride Fiber Lasers

In the well-known excited-state absorption (ESA) process, population inversion of the laser transition can be achieved by a strong pump ESA involving a lower laser level. The exploitation of pump ESA has expanded from the visible to the near-infrared spectral range, based on various laser sources. Extending the operating wavelength of the pump ESA is greatly significant for the development of rare-earth-doped fluoride fiber lasers. Herein, we report, presumably, the shortest operating wavelength of pump ESA at 442 ± 1 nm for an efficient continuous-wave visible fluoride fiber laser. A novel scheme for direct blue diode pumping was proposed and demonstrated in an Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fluoride fiber. Utilizing a 442 ± 1 nm blue laser diode, single-wavelength ground-state absorption (GSA) and ESA pumping mechanism were investigated not only for double populating of the upper laser level by GSA and ESA, but also to depopulate the lower laser level by ESA. We report a slope efficiency of 50.3% with respect to the launched pump power of 442 ± 1 nm and an output power of up to 327 mW for a 750 nm fiber laser. This result is an order of magnitude higher than that previously reported for a directly blue-diode-pumped deep-red Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fluoride fiber laser. Moreover, the numerical modeling results were in good agreement with the experimental results. Our approach represents a significant advancement for blue pump ESA in visible fluoride fiber lasers, which opens new capabilities for blue-diode pumping for a wide range of future applications.

Vacuum chamber conditioning and saturation simulation tool (VacuumCOST): Enabling time-dependent simulations of pressure and NEG sticking in UHV chambers

Modern particle accelerators, synchrotrons, and other machines requiring UHV frequently make use of NEG coatings to achieve low pressures and resulting high beam stability and lifetime. It is the nature of NEG pumps and coatings, that a limited amount of gas can be pumped before saturation is reached, at which point the NEG must be re-activated to pump efficiently again. While the pumping mechanism and absorption limits are well understood and software packages exist for simulating the steady-state vacuum systems, there is a need for simulating the temporal evolution of the pumping capability of NEG coatings in regions of high outgassing rates such as near crotch absorbers. This paper presents a simple framework, written in Python, for running time-dependent simulations of NEG-coated vacuum systems in molecular flow, by making use of the command-line interface of the already widely used MolFlow simulation software. It also compares simulation results with accelerator pressure measurements.

Modeling virus transport and dynamics in viscous flow medium

ABSTRACT In this paper, we developed a mathematical model to simulate virus transport through a viscous background flow driven by the natural pumping mechanism. Two types of respiratory pathogens viruses (SARS-Cov-2 and Influenza-A) are considered in this model. The Eulerian–Lagrangian approach is adopted to examine the virus spread in axial and transverse directions. The Basset–Boussinesq–Oseen equation is considered to study the effects of gravity, virtual mass, Basset force, and drag forces on the viruses transport velocity. The results indicate that forces acting on the spherical and non-spherical particles during the motion play a significant role in the transmission process of the viruses. It is observed that high viscosity is responsible for slowing the virus transport dynamics. Small sizes of viruses are found to be highly dangerous and propagate rapidly through the blood vessels. Furthermore, the present mathematical model can help to better understand the viruses spread dynamics in a blood flow.

Mechanism of charge injection-based electrohydrodynamic pump with interdigitated electrodes

The mechanisms of a charge injection-induced electrohydrodynamic pump using the lattice Boltzmann method are numerically investigated in this paper. The pump is composed of a dielectric liquid layer and two substrate layers with embedded electrodes. There are three possible flow modes found, which are associated with the generation of local convective rolls for different electrode arrangements, namely, modes associated with one and two vortices and an irrotational mode. For different flow modes, results are presented for both the transient development of the flow field and the steady-state total flow rate and pressure. A distinct four-state transition can be observed in the temporal record of the velocity field. Regarding pumping ability, it is found that the irrotational mode can lead to optimal performance, while the single-vortex flow mode gives the worst performance.

Surgery assistance system for continuous resection of brain tumors-proposal of continuous tumor resection forceps, tumor cell separation, dehydration, and isolation mechanism

The tumor resection ratio must be improved due the increased possibility of recurrence or malignancy. The purpose of this study was to develop a system that includes forceps with a continuous suction function and flow cytometry to diagnose the malignancy of the tumor for safe, accurate, and effective surgery. A newly developed continuous tumor resection forceps consists of a triple pipe structure, which enables continuous suction of the tumor by integrating the reflux water and suction system. The forceps includes tip opening/closure detection switch to control the adsorption and suction strength when tip is opened and closed. To perform accurate tumor diagnosis using flow cytometry, a filtering mechanism was developed for dehydrating reflux water from continuous suction forceps. In addition, a cell isolation mechanism comprising a roller pump and shear force loading mechanism was also newly developed. By using a triple pipe structure, a significantly larger tumor collection ratio was observed compared to the previous double-pipe structure. By performing suction pressure control with the opening/closure detection switch, inaccurate suction can be prevented. By widening the filter area of dehydration mechanism, it was possible to improve the reflux water dehydration ratio. The most appropriate filter area was 85 mm2. By using a newly developed cell isolation mechanism, the processing time can be reduced to less than 1/10 of the original time, keeping the same cell isolation ratio, when compared to the existing pipetting method. Neurosurgery assistance system with continuous tumor resection forceps and a cell separation, dehydration and isolation mechanism was developed. An effective and safe tumor resection, accurate and fast diagnosis of malignancy can be achieved by using the current system.

A Study of a Bistable Reciprocating Piston Pump Driven by Shape Memory Alloys and Recuperative Springs

This paper presents and examines a new design concept for a bistable reciprocating piston pump. The bistable pump mechanism belongs to the bistable mechanisms, which have two stable positions at the end of the suction and discharge strokes. The transition between the stable positions is achieved by using triggering force at each beginning of suction and discharge and subsequent movement using a recuperative spring. In this mechanism, the triggering forces are created by two Shape Memory Alloy (SMA) wires. Geometric and force expressions for the pump suction and discharge strokes are derived. Additional equations are obtained for the balance of moments for the two stable equilibrium positions and the unstable position in the middle of the stroke. Numerical studies have been conducted for the suction and discharge strokes, considering the force exerted by the gas on the piston, which is modelled by an indicator diagram assuming a polytropic process. It was found that the load on the mechanism has significant non-uniformity. The diagrams illustrating the distribution of total moments showed that the cold SMA wire shifted the point of instability. The numerical example shows how to choose the right spring stiffness to obtain energy recovery. In this way, the triggering SMA forces act only at the beginning of the two strokes and, after that, the recuperative forces substitute the action of the SMA forces. The theoretical relationships and methods presented here are suitable for synthesizing new pumps or analyzing similar mechanisms.

CFD Simulation of Centrifugal Pump with Different Impeller Blade Trailing Edges

The centrifugal pump is one of the most widely used types of power machinery in the field of ship and ocean engineering, and the shape of the impeller blade trailing edge has an important influence on their performance. To reveal the mechanism of the effect of different trailing edges on external performance, the internal flow of 16 types of impeller blade trailing edges of a centrifugal pump, consisting of Bezier trailing edges, rounding on the pressure side, cutting on the suction side, and the original trailing edge is studied by numerical simulation. The reverse flow, shaft power, and energy loss distribution in the impeller and diffuser along the streamwise direction are analyzed by calculating them on each micro control body sliced from the fluid domain. The entropy production theory and Ω-vortex identification method are used to display the magnitude and location of energy loss and the vortex structure. Finally, a static structural analysis of the impeller with different trailing edges is performed. The results show that different impeller trailing edges can clearly affect the efficiency of the pump, i.e., the thinner the trailing edge, the higher the efficiency, with the thickest model reducing efficiency by 5.71% and the thinnest model increasing efficiency by 0.59% compared to the original one. Changing the shape of the impeller trailing edge has a great influence on the reverse flow, shaft power, and energy loss near the impeller trailing edge and diffuser inlet but has little influence on the leading part of the impeller. The distribution of local entropy production rate, energy loss, and reverse flow along the streamwise direction shows similar rules, with a local maximum near the leading edge of the impeller due to the impact effect, and a global maximum near the impeller trailing edge resulting from strong flow separation and high vortex strength due to the jet-wake flow. Thinning the impeller trailing edge and smoothing its connection with the blade can reduce the vortex strength and entropy production near the impeller trailing edge and diffuser inlet, improve the flow pattern, and reduce energy loss, thus improving the pump efficiency. In all models, the maximum equivalent stress is less than 6.5 MPa and the maximum total deformation is less than 0.065mm. The results are helpful for a deeper understanding of the complex flow mechanism of the centrifugal pump with different blade trailing edges.

Distribution Mechanism of Asymmetric Axial Piston Pump

Pump-controlled single-rod hydraulic cylinders are energy-saving and efficient, which is the development direction of hydraulic systems in the future. However, the flow imbalance caused by the unequal effective areas of the two chambers of single-rod hydraulic cylinders has always restricted the development and application of pump-controlled single-rod hydraulic cylinders. The flow rate of the inlet and outlet ports of the ordinary axial piston pump is equal and the flow rate of the large and small chambers of the single rod hydraulic cylinder does not match. In order to solve this problem, the ordinary axial piston pump is improved into an asymmetric axial piston pump, on this basis, the flow distribution mechanism of the asymmetric axial piston pump is explored, and the design theory of the asymmetric axial piston pump is improved. Theoretical analysis of the relationship between the angle of the distribution window of the asymmetrical axial piston pump and the area ratio of the single-rod hydraulic cylinder is carried out, and its mathematical model is derived. Design of valve plates for asymmetrical axial piston pumps to match single rod hydraulic cylinders with different area ratios. The physical model of the asymmetrical axial piston pump and the asymmetrical axial piston pump controlled single-rod hydraulic cylinder system was established in the computer simulation software AMESim. The simulation analysis of the inlet and outlet flow of the asymmetric axial piston pump under different working conditions and the matching of the asymmetric axial piston pump and the single-rod hydraulic cylinder with different area ratios. The simulation results show that the use of an asymmetrical axial piston pump can compensate the flow imbalance caused by the unequal effective areas of the two chambers of the single-rod hydraulic cylinder, so that the flow of the asymmetrical axial piston pump and the single-rod hydraulic cylinder can completely match.

Identification of a Functionally Efficient and Thermally Stable Outward Sodium-Pumping Rhodopsin (BeNaR) from a Thermophilic Bacterium.

Rhodopsins are transmembrane proteins with retinal chromophores that are involved in photo-energy conversion and photo-signal transduction in diverse organisms. In this study, we newly identified and characterized a rhodopsin from a thermophilic bacterium, Bellilinea sp. Recombinant Escherichia coli cells expressing the rhodopsin showed light-induced alkalization of the medium only in the presence of sodium ions (Na+), and the alkalization signal was enhanced by addition of a protonophore, indicating an outward Na+ pump function across the cellular membrane. Thus, we named the protein Bellilinea Na+-pumping rhodopsin, BeNaR. Of note, its Na+-pumping activity is significantly greater than that of the known Na+-pumping rhodopsin, KR2. We further characterized its photochemical properties as follows: (i) Visible spectroscopy and HPLC revealed that BeNaR has an absorption maximum at 524 nm with predominantly (>96%) the all-trans retinal conformer. (ii) Time-dependent thermal denaturation experiments revealed that BeNaR showed high thermal stability. (iii) The time-resolved flash-photolysis in the nanosecond to millisecond time domains revealed the presence of four kinetically distinctive photointermediates, K, L, M and O. (iv) Mutational analysis revealed that Asp101, which acts as a counterion, and Asp230 around the retinal were essential for the Na+-pumping activity. From the results, we propose a model for the outward Na+-pumping mechanism of BeNaR. The efficient Na+-pumping activity of BeNaR and its high stability make it a useful model both for ion transporters and optogenetics tools.

Detection of mexB Multidrug Efflux Gene in Some Local Isolates of Pseudomonas aeruginosa

According to the prevalence of multidrug resistance bacteria, especially Pseudomonas aeruginosa, in which the essential mechanism of drug resistance is the ability to possess an efflux pump by which extrusion of antimicrobial agents usually occurs, this study aims to detect the presence of mexB multidrug efflux gene in some local isolates of this bacteria that show resistance towards three antibiotics, out of five. Sensitivity test to antibiotics was performed on all isolates by using meropenem (10µg/disc), imipenem (10µg/disc), amikacin (30 μg/disc), ciprofloxacin (5µg/disc) and ceftazidime (30 µg/disc). Conventional PCR results showed the presence of mexB gene (244bp) in four isolates out of ten (40%). In addition,25, 50μg/ml of curcumin was used to detect its efficacy with the antibiotics that the bacteria showed resistance towards. Results showed the highest resistance for ciprofloxacin (80%), while all of them were sensitive to imipenem. In addition, the present results show that both concentrations of curcumin (25, 50μg/ml) were effective in increasing the zone of inhibition from zero to 10 mm for isolates towards amikacin. Same result was obtained towards ciprofloxacin, except for an increase of inhibition zone from zero to 7 mm to one isolate (38T) when treated with 50 μg/ml, and finally an increase in sensitivity to ceftazidime was found and inhibition zone was increased from 8 to 11 for the second isolate (42E), which revealed that curcumin potentiates antibiotics activity by inhibition of efflux pump mechanisms that can be related to the synergetic activity between antibiotics and curcumin.

Carbonyl Cyanide 3-Chloro Phenyl Hydrazone (CCCP) Restores the Colistin Sensitivity in Brucella intermedia.

Brucella intermedia (formerly Ochrobactrum intermedium), a non-fermentative bacterium, has been isolated from animals and human clinical specimens. It is naturally resistant to polymyxins, including colistin (CO), and may cause opportunistic infections in humans. We isolated six Brucella intermedia strains from Senegalese monkey stool. In order to determine whether an efflux pump mechanism was involved in CO resistance in B. intermedia, we evaluated the effects of verapamil (VRP), reserpine (RSP), phe-arg β-naphthylamide dihydrochloride (PAβN) and carbonyl cyanide 3-chloro phenyl hydrazone (CCCP), four efflux pump inhibitors, on these colistin-resistant strains. Using the broth microdilution method, a CO and CCCP combination of 2 µg/mL and 10 µg/mL, respectively, significantly reduced the CO minimal inhibitory concentration (MIC) of B. intermedia, supporting an efflux pump mechanism. In contrast, VRP, PAβN and RSP did not restore CO susceptibility. A time kill assay showed a bactericidal effect of the CO-CCCP combination. Genomic analysis revealed a potential implication in the CO resistance mechanism of some conserved efflux pumps, such as YejABEF, NorM and EmrAB, as previously reported in other bacteria. An inhibitory effect of the CO-CCCP combination was observed on biofilm formation using the crystal violet method. These results suggest that the intrinsic CO resistance in Brucella intermedia is linked to an efflux pump mechanism and that the synergistic effect of CO-CCCP may open a new field to identify new treatments to restore antibiotic efficacy in humans.

Effects of injection directions and boundary exchange times on adaptive pumping in heterogeneous porous media: Pore-scale simulation

Adaptive pumping, changing pumping rates or exchanging injection and extraction wells, is an enhancement of traditional Pump-and-Treat (P&T) technology. Since most previous studies on adaptive pumping are conducted through field-scale simulations, the mechanism behind it is not fully understood. An in-depth investigation of the pore-scale remediation mechanism of adaptive pumping is undoubtedly helpful in combining it with other decontamination methods to further enhance the remediation efficiency. In this study, coupling the Cahn–Hilliard phase field method and the Navier-Stokes equations, the dynamic displacement process in a heterogeneous porous medium is obtained. The effects of initial injection direction, boundary exchange times, and displacement regimes on the interface evolution and the remediation efficiency are systematically investigated. The results present that a significant increase in phase interface area is the most critical remediation mechanism for adaptive pumping. The effects of injection directions and boundary exchange times on remediation performance are mainly determined by the differences in pore connectivity and flow parameters. Higher pore connectivity under high and low viscosity ratios inhibits and promotes remediation performance, respectively. At high viscosity ratios, the residual oil morphology in the matrix after adaptive pumping is similar to that obtained by positive pumping with the opposite initial injection direction. The improvement in remediation performance of adaptive pumping is more significant under low viscosity ratio conditions. These results provide new pore-scale insights into the remediation mechanism of adaptive pumping, which contribute to the design and application of innovative remediation methods.

Watt-Level High-Efficiency Deep-Red Ho3+:ZBLAN Fiber Laser

To date, Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fluoride fibers have been investigated as a viable route for deep-red fiber lasers. However, high output performance deep-red fiber lasers around 750 nm have been proven challenging to achieve due to limitations in both the excitation source and pumping mechanism. In this study, we use a home-made 640 nm pump source to develop a deep-red laser with a high pumping rate, and obtain a compact watt-level high efficiency deep-red laser output. Population inversion is achieved by strong excited state absorption in a Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped ZBLAN fiber. We realize a maximum 1.46 W deep-red fiber laser operating at 752.6 nm, and its slope efficiency is as high as 53%. The improved rate equations are used to describe the quasi-four-level system, and the experimental results agree well with the simulations. Moreover, with the development of blazed grating, we demonstrate a tunable deep-red fiber laser with a tuning range of 13.7 nm, from 746.5 to 760.2 nm, which is the widest tuning range of Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fiber laser at deep-red wavelengths.

A low-cost and portable centrifugal microfluidic platform for continuous processing of large sample volumes

Centrifugal microfluidic platforms are becoming increasing popular in many research and diagnostic applications. A major challenge in centrifugal microfluidics is continuous handling of large sample volumes. Keeping the flow rate constant during sample inflow is difficult without a pump. We report an affordable (&amp;lt;USD 40) and portable platform that can handle sample volumes of up to 50 ml without a pump. We use a Mariotte bottle for sample inflow into the disk at a constant flow rate and with a throughput of 1 ml/s. Our pumping mechanism allows basic operations, such as volume metering, flow switching, and mixing. Our platform fulfills the need for portable and affordable instrumentation in developing countries.