Flux Characteristics Research Articles

Experimental Procedure for Determining the Remanent Magnetic Flux Value Using the Nominal AC Energization

The laboratory setup and corresponding experimental procedure for determining the remanent magnetic flux in the magnetic core of a single-phase transformer are presented in this paper. Using the proposed method, the remanent flux can be determined without prior knowledge of any parameter or past states of the transformer which is a significant advantage compared to previously known methods. Furthermore, reliable information about the remanent flux could be obtained using less equipment than other methods. Only electrical measurements are needed, without any physical intervention in the core or some other parts of the transformer. However, the major drawback is that some new unknown value of the remanent flux is set after the measuring procedure. Various initial conditions of the remanent flux and the closing voltage angle are set before each energization of the transformer to prove the validity of the proposed method, which can be used to obtain some characteristics of the remanent flux, such as stability over time or its dependence on some external factors.

Variation of the performance of YBa[formula omitted]Cu[formula omitted]O[formula omitted] radio frequency superconducting quantum interference device with bicrystal grain boundary angle

High transition temperature (high-Tc) superconducting quantum interference devices (SQUIDs) based on bicrystal grain boundary junctions have been utilized in a wide range of applications. To explore the effect of the bicrystal grain boundary angle on the property of the high-Tc SQUID, we fabricated and characterized YBa2Cu3O7−δ (YBCO) radio frequency (rf) SQUIDs using [001]-tilt grain boundary junctions on SrTiO3 (STO) bicrystal substrates with three different misorientation angles of θ=18∘, 24°, and 30°. Unlike the device of θ=18∘ showing only the triangular waveform of the voltage–flux (V−Φ) characteristics, for device of θ=24∘ and 30°, the shape of the V−Φ curve can be tuned from approximately triangular into nearly rectangular by adjusting the working point of the device. It suggests that, as θ increases from 18° to 30°, the operation of the device may change from the hysteretic mode into the nonhysteretic mode. This is backed by electrical transport measurements of YBCO bicrystal junctions on separate STO substrates, which help to reveal that lying behind the indicated changeover of the SQUID operation mode is the exponential decrease of the junction critical current density Jc as θ increases. The white noise of the device, which decreases with increasing flux-to-voltage transfer coefficient ∂V/∂Φ, shows a large drop as θ increases to 24°. For both 24° and 30° devices, the white field noise at 77 K is about 90 fT/Hz1/2 at respective optimum working points. For device of 30° with nearly rectangular V−Φ characteristics showing the largest ∂V/∂Φ among the fabricated samples, the white noise region extends below 10 Hz and a field noise of 145 fT/Hz1/2 at 1 Hz is shown, demonstrating the potential of obtaining high-performance bicrystal YBCO rf SQUIDs with this grain boundary angle.

Study on the wear resistance and mechanism of AlCrCuFe2NiTix high-entropy surfacing alloys

The revolutionary design concept of high-entropy alloys has brought new opportunities and challenges to the development of advanced metal materials. In this work, the design idea of a high-entropy alloy is combined with the characteristics of flux cored wire, and AlCrCuFe2NiTix high-entropy flux cored wires were prepared. AlCrCuFe2NiTix high-entropy surfacing alloys were prepared using gas metal arc welding technology. The wear properties of AlCrCuFe2NiTix high-entropy surfacing alloys were analysed using an MFT-4000 reciprocating friction and wear tester. The phase composition and microstructure of AlCrCuFe2NiTix high-entropy surfacing alloys were analysed using XRD, SEM, EBSD, and TEM, and the strengthening mechanism and wear mechanism of the alloy were discussed. The results show that AlCrCuFe2NiTix high-entropy surfacing alloys are composed of the BCC/B2 + FCC phase. With increasing Ti content, the Laves phase begins to precipitate and exists stably. The microstructure of the alloy presents a typical dendritic structure, and the DR region is rich in Fe, Cr, Al and Ni. The BCC and B2 phases are coherently distributed in the dendrites with a spinodal decomposition network structure. The ID region is rich in Cu and Ti, and the Cu-rich FCC phase is segregated in the form of nanoparticles in the ID region, while the lamellar Laves phase precipitates in the ID region. With increasing Ti content, the microhardness of AlCrCuFe2NiTix high-entropy surfacing alloys shows an increasing trend, while their wear loss, friction coefficient, specific wear rate and other indicators show a trend of first decreasing and then increasing. The maximum microhardness is 597 HV, and the minimum specific wear rate is 9.1606 × 10−8 mm3/N mm. This is mainly because the precipitation of the B2 coherent phase and Laves phase hinders the movement of dislocations, resulting in an improvement in the strength and microhardness of the alloy. However, excessive Ti addition causes the Laves phase to increase sharply and segregate in the ID region, which is extremely prone to stress concentration during dislocation movement, thus inducing crack initiation. The fractured Laves phase exacerbates the grain-abrasion of the alloy and reduces its wear resistance.

Multi-scale spectral characteristics of latent heat flux over flooded rice and winter wheat rotation system

Multi-scale spectral characteristics of latent heat flux over flooded rice and winter wheat rotation system

Wall heat flux in supersonic turbulent expansion flow with shock impingement

We perform direct numerical simulations to investigate the characteristics of wall heat flux (WHF) in the interaction of an oblique shock wave at an angle of 33.2° and free-stream Mach number M ∞ = 2.25 impinging on supersonic turbulent expansion corners with deflection angles of 0o (flat plate), 6o and 12o. The effect of the expansion on the WHF characteristics is analysed by comparing it to the interaction with the flat plate under the same flow conditions and a fixed shock impingement point. In the post-expansion region, the decreased mean WHF is found to collapse onto the flat plate case when scaled with the mean wall pressure. The statistical properties of the WHF fluctuations, including probability density function, frequency spectra, and space–time correlations, are comparatively analysed. The expansion causes an increase in the occurrence probability of negative extreme events, an enhancement of high-frequency energy, and an inhibition of intermediate-frequency energy. The increased expansion angle also results in a faster recovery of characteristic spanwise length scales and an increase in convection velocity. We use the mean WHF decomposition method in conjunction with bidimensional empirical mode decomposition to quantitatively analyse the impact of expansion on scale contributions. It is demonstrated that the presence of the expansion corner has no significant impact on the decomposed results, but it significantly reduces the contribution associated with outer large-scale structures.

Highly Permeable Sulfonated Polydopamine Integrated MXene Membranes for Efficient Surfactant-Stabilized Oil-in-Water Separation.

MXene is an incredibly promising two-dimensional material with immense potential to serve as a high-performing separating or barrier layer to develop advanced membranes. Despite the significant progress made in MXene membranes, two major challenges still exist: (i) effectively stacking MXene nanosheets into defect-free membranes and (ii) the high fouling tendency of MXene-based membranes. To address these issues, we employed sulfonated polydopamine (SPD), which simultaneously serves as a binding agent to promote the compact assembling of Ti3C2Tx MXenes (MX) nanosheets and improves the antifouling properties of the resulting sulfonated polydopamine-functionalized MX (SPDMX) membranes. The SPDMX membrane was tested for challenging surfactant-stabilized oil-in-water separation with an impressive efficiency of 98%. Moreover, an ultrahigh permeability of 1620 LMH/bar was also achieved. The sulfonation of PD helps in improving the antifouling characteristics of SPDMX by developing a strong hydration layer and enhancing the oleophobicity of the membrane. The underwater SPDMX membrane appeared superoleophobic with an oil contact angle of 153°, whereas the ceramic membrane exhibited an oil contact angle of 137°. The SPDMX membranes showed an improved flux recovery (31%) compared to the nonsulfonated counterpart. This work highlights the appropriate functionalization of MXene as a promising approach to developing MXene membranes with high permeation flux and better antifouling characteristics for oily wastewater treatment.

Maximum torque per ampere control of a PMa-SynRM based on a signal injection method considering the flux characteristics

Maximum torque per ampere control of a PMa-SynRM based on a signal injection method considering the flux characteristics

Seasonal variations and driving mechanisms of CO2 fluxes over a winter-wheat and summer-maize rotation cropland in the North China plain

Characterization of crop CO2 fluxes in different growing periods and their corresponding responses to abiotic and biotic factors is essential for the adaption of cropland ecosystem carbon balance to future climate change and management practices. In this study, based on long-term (2003–2018) monitoring of CO2 fluxes, meteorological data and leaf area index (LAI) of a winter wheat-summer maize rotation cropland in the North China Plain, the relationship between CO2 fluxes of different growing periods and the driving factors (i.e., abiotic and biotic factors) was explored to identify the important affecting factors. The Random Forest (RF) algorithm revealed that LAI was the most important driving factor of CO2 fluxes in the wheat season, except for WGPW (from sowing to maturity). Net ecosystem productivity (NEP) had significant positive relationships with LAI, photosynthetically active radiation (PAR) and soil water content (SWC) in four different growing periods. Air temperature (Ta) was positively correlated with ecosystem respiration (ER), and LAI and PAR were positively correlated with gross primary productivity (GPP). In the maize season, the RF algorithm revealed that LAI, PAR and SWC were important drivers of CO2 fluxes. NEP and GPP had significant negative relationships with precipitation (PPT) in RGPM (from tasseling to maturity) and WGPM (from sowing to maturity). Ta was positively correlated with ER, and SWC was positively correlated with NEP and GPP except for VGP2M (from jointing to tasseling). For annual fluxes, the interannual variability (IAV) of NEP, ER and GPP were mainly attributed to IAV of the maximum daily NEP (NEPmax), maximum daily ER (ERmax) and maximum daily GPP (GPPmax), respectively. Our findings provide deep insight into CO2 flux characteristics of wheat-maize rotation systems in different growing periods and their influencing mechanisms, which are crucial for predicting the carbon cycle of cropland ecosystems under climate change.

Thermal neutron detection and track recognition method in reference and out-of-field radiotherapy FLASH electron fields using Timepix3 detectors.

Objective.This work presents a method for enhanced detection, imaging, and measurement of the thermal neutron flux.Approach. Measurements were performed in a water tank, while the detector is positioned out-of-field of a 20 MeV ultra-high pulse dose rate electron beam. A semiconductor pixel detector Timepix3 with a silicon sensor partially covered by a6LiF neutron converter was used to measure the flux, spatial, and time characteristics of the neutron field. To provide absolute measurements of thermal neutron flux, the detection efficiency calibration of the detectors was performed in a reference thermal neutron field. Neutron signals are recognized and discriminated against other particles such as gamma rays and x-rays. This is achieved by the resolving power of the pixel detector using machine learning algorithms and high-resolution pattern recognition analysis of the high-energy tracks created by thermal neutron interactions in the converter.Main results. The resulting thermal neutrons equivalent dose was obtained using conversion factor (2.13(10) pSv·cm2) from thermal neutron fluence to thermal neutron equivalent dose obtained by Monte Carlo simulations. The calibrated detectors were used to characterize scattered radiation created by electron beams. The results at 12.0 cm depth in the beam axis inside of the water for a delivered dose per pulse of 1.85 Gy (pulse length of 2.4μs) at the reference depth, showed a contribution of flux of 4.07(8) × 103particles·cm-2·s-1and equivalent dose of 1.73(3) nSv per pulse, which is lower by ∼9 orders of magnitude than the delivered dose.Significance. The presented methodology for in-water measurements and identification of characteristic thermal neutrons tracks serves for the selective quantification of equivalent dose made by thermal neutrons in out-of-field particle therapy.

Biological carbon pump responses to multiscale physical processes: a review of sediment trap studies in the South China Sea

Accurately assessing the capacity of the modern ocean to photosynthetically fix and sequester atmospheric CO2, termed the biological carbon pump (BCP), is a key component in studies on the marine carbon cycle and the global climate system. Particulate organic carbon (POC) flux into the ocean interior is an important indicator of the BCP strength, and it can be directly measured by sediment traps on time scales from days to years. This study has been conducted in the South China Sea (SCS) for over three decades. The SCS is one of the largest tropical marginal seas, located in the Asian monsoon region with frequent occurrence of dynamic physical processes and anthropogenic perturbations. It hosts an ideal natural laboratory to investigate the response of the BCP to multiscale physical processes. In this mini review, we briefly introduce the study history of mooring sediment traps in the SCS, synthesize the processes that regulate the temporal variability in mesopelagic POC flux, and how it is sensitive to climate changes. The time-series characteristics of the POC flux are clearly linked to primary production, as well as the key physical processes in the upper layer. The seasonal East Asian monsoon, intraseasonal eddies, aerosol deposition and interannual El Niño Southern Oscillation (ENSO) events are the main controlling factors over weekly to yearly timescales. Together, they suggest that the multiscale physical forcing in the upper layer regulates the mesopelagic POC export flux by controlling nutrient supplementation and subsequent POC production.

Modeling and simulation of extra high voltage magnetically controlled shunt reactor based on PSCAD

For the two typical topologies of the extra high voltage magnetically controlled shunt reactor (MCSR), this study introduces its specific wiring methods and working principles. It conducts an analysis of the change characteristics and response characteristics of the core magnetic flux under different wiring modes of the controlled shunt reactor body. Based on PSCAD, two typical structures are used to model the body of the first 500 kV MCSR put into operation in a provincial power grid and perform steady-state and dynamic simulations. The results of field experiments are compared and analyzed. The winding connection mode of the device’s body electromagnetic transient model is determined, which lays a foundation for the follow-up research.

Design and Analysis of Wide Speed Regulation of Variable Leakage Flux Reverse Salient-Pole Motor

In this article, a new variable leakage flux reverse salient-pole motor (VLF-RSPM) is raised to widen the speed range. The innovation is to realize both reverse salient-pole characteristics and variable leakage flux characteristics by using a method of adding magnetic bridges and magnetic barriers. Firstly, the evolution of the topological structure and working principle of the motor are introduced. Secondly, based on 2D Finite Element Analysis (FEA), the electromagnetic properties and noise of the motor are analyzed in detail, and the electromagnetic properties are contrasted with that of the conventional V-type synchronous motor (CVTSM). The results show that VLF-RSPM has the advantages of small torque ripple, strong magnetic weakening ability, low noise, high efficiency, and low risk of permanent magnet demagnetization under different conditions. In addition, it is verified that the proposed motor extends the speed range.

Spatiotemporal Variation Characteristics of Main Pollutant Fluxes in the Yangtze River Basin from 2017 to 2020

Based on the monitoring data of various pollutants at important water system points in the Yangtze River Basin from 2017 to 2020, research on the flux change law of the main and tributary water systems in the Yangtze River Basin was carried out at the spatiotemporal scale, and the spatial change response, interannual change trend, and flux correlation analysis were analyzed from the aspects of water quantity, quality, and flux so as to reveal the spatial-temporal contribution characteristics of pollutant flux in the upper, middle, and lower reaches of the Yangtze River Basin. The results showed that over the past four years, the concentration of major pollutants in the Yangtze River Basin showed an overall downward trend. The concentration of total phosphorus (TP) and ammonia (NH+4-N) decreased significantly. The concentration of total nitrogen (TN) and total phosphorus (TP) in the main stream gradually increased from west to east. The annual concentration of permanganate index in the upper, middle, and lower reaches decreased by 18.5%, 16.0%, and 14.0%, respectively, from 2017 to 2020, with the highest decline in the upper reaches. The four-year average value of the spatial distribution of runoff significantly increased from 466×108 m3 to 9923×108 m3. The two lake basins in the tributary river lake water system had the largest contribution to the water volume. The fluxes of permanganate index, total phosphorus (TP), and total nitrogen (TN) among the main pollutants showed an annual increase and then decrease trend. The pollutant fluxes in the Minjiang River, Tuojiang River, Jialing River, and the middle reaches of the two lakes contributed greatly to the river inflow. There were differences in fluxes in different regional water environments. The results of correlation and hierarchical cluster analysis showed that the permanganate index and TP fluxes were highly significantly correlated with water volume, and there was a significant correlation between biochemical oxygen demand (BOD5) and total nitrogen (TN), total phosphorus (TP), and chemical oxygen demand (COD). The main pollutants showed strong differences in the flood and non-flood periods and had a significant response in the flood season from July to September. The research results can provide scientific basis and theoretical support for the integrated management and precise prevention and control of the aquatic environment in the Yangtze River Basin.

Protein valorisation from acid whey – Screening of various micro- and ultrafiltration membranes concerning the filtration performance

Cross-flow filtration allows a product-preserving and energy-saving unit operation for the production of whey protein concentrates (WPC) from acid whey. In micro- and ultrafiltration applications, size-exclusion is the governing separation mechanism. Flux and retention characteristics of 12 organic membranes of pore sizes between 5 and 450 nm were compared. Screening on a laboratory filtration plant revealed large differences regarding hydraulic resistance of the membrane and resistance of the deposit layer that forms on the membrane surface during filtration. As a result, notable variations in the permeate flux were observed between membranes. In contrast, the differences in protein retention were less pronounced. The protein transmission for all ultrafiltration membranes was below 5% whereas microfiltration membranes showed a deposit layer-dependent transmission behaviour. Compared with the conventional WPC35 production, the overall filtration efficiency with regard to the process duration for a comparable membrane area was 3-fold enhanced by a more appropriate membrane selection.

Heat flux characteristics of a single droplet splashing on the liquid film obtained with a thermal lattice Boltzmann method

The double-distribution-function thermal lattice Boltzmann method is employed to investigate the heat flux characteristics of single droplet impact on a liquid film above a heated wall. The effects of impact velocity, liquid film thickness, droplet radius, and viscosity coefficient on the average and instant heat flux distribution are analyzed. The droplet impact first breaks the steady-state thermal boundary layer in the impact region, causing the heat flux in the wall impact region to increase. This is because the temperature gradient between the liquid film and the wall increases as the droplet dives downward and expands. The velocity discontinuity at the liquid jet sheet prevents the transfer of the transverse velocity in the liquid film to the static region, yielding a transition region. Convective heat transfer is dominant in the impact and transition regions, while conductive heat transfer is dominant in the static region. Moreover, a large impact velocity promotes the synergy between the temperature and flow velocity fields, enhancing the heat transfer efficiency. The kinetic energy consumption of the droplet increases with the liquid film thickness, which causes the heat flux to decrease. The effect of droplet radius on the heat flux at the wall is minimal. Furthermore, an increased liquid viscosity is not beneficial for wall heat dissipation.

The g-C3N4-TiO2 nanocomposite for non-volatile memory and artificial synaptic device applications

Recently, 2D layered materials like graphitic carbon nitride (g-C3N4) are gaining significant attention due to their excellent structural and electronic properties. Metal oxide and g-C3N4 composite can enhance chemical and electronic properties which can ultimately enhance device performance. Given this, we report the synthesis of g-C3N4–TiO2 nanocomposite by the ex-situ (solid state reaction) method for resistive switching (RS) applications. Initially, the TiO2 nanoparticles (NPs) were optimized by using annealing them at different temperatures and composited with the g-C3N4. The devices fabricated using g-C3N4–TiO2 nanocomposite shows good RS properties at very low SET and RESET voltages (< 0.5 V), similar to the biological voltage scale. The distribution of switching voltages of all devices was studied using the cumulative probability and Weibull distribution techniques. Moreover, switching voltages were modeled and predicted using the statistical time series analysis method. All fabricated devices demonstrated the double-valued charge flux characteristics, suggesting the presence of a non-ideal memristor effect. The optimized g-C3N4-TiO2 (TiO2 NPs annealed at 450 °C) device shows good endurance and retention memory properties. Moreover, the optimized g-C3N4-TiO2 device can mimic the various bio-synaptic properties such as potentiation-depression, excitatory postsynaptic current, and paired-pulse facilitation. The charge transport results reveal that Ohmic and Child's square law dominated the conduction of the device. Based on electrical and charge transport results, a plausible filamentary RS effect is presented. This study suggested that the g-C3N4-TiO2 is beneficial for both memory and neuromorphic computing applications.

Low-cost ceramic membranes manufacture using INKJET technology for active layer deposition and validation on membrane bioreactors

The fabrication of eco-friendly ceramic membranes based on low-cost raw materials, using digital INKJET printing techniques for active layer deposition and its validation in a membrane bioreactor (MBR) has been studied. The raw materials used in the manufacture of the support layer were UA50/2 clay, chamotte, calcium carbonate and potato starch. A MBR laboratory plant was operated to treat municipal wastewater with three ceramic membranes with different grammages in the selective layer deposition. The membrane performance at laboratory scale was evaluated in terms of transmembrane pressure (TMP) evolution for a constant permeate flux, permeate quality and mixed liquor characteristics. From these experiments, it was selected the membrane which obtained the lowest TMP profile maintaining appropriate water quality parameters (chemical oxygen demand (COD) removal percentage around 90% and turbidity around 0.06 NTU). This membrane was also operated at pilot plant scale in order to validate it at higher scale. Results indicated that TMP values were in the range of 0.06 and 0.1 bar, COD removal percentage was around 98% and microbiology analysis demonstrated that the quality of the effluent, according to European regulation 2020/741, can be classified as Class A and it can be reused for non-potable purposes.

Extended 2-D Magnetic Field Modeling of Linear Motor to Investigate the Magnetic Force Parameters of High-Speed Superconducting Maglev

A 2D numerical finite element model of a linear synchronous motor (LSM) is extended based on the magnetic field and moving mesh properties to investigate the magnetic flux and magnetic force characteristics of the high-speed EML Maglev system, by using HTS coils rather than lower current carrying copper coils on the onboard unit and PMs on the ground. In this 2D LSM model, the transient, time dependent solver is used to obtain the magnetic flux densities. Both the propulsion and levitation forces increased with increasing supercurrent J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c0</sub> values indicating the advantage of using the superconducting windings in PM-LSM of Maglev vehicles as compared to the copper wires. It was also determined that although the propulsion force is obtained on a comparable level with the studies in literature, the lower levitation force issue than the EDS, despite the better propulsion to levitation force ratio, can be overcame by using the high flux trapping capacity bulk HTSs in the onboard unit together with the superconducting coils. The determined higher propulsion force in this PM-LSM Maglev model indicates that the Maglev vehicle can reach higher velocities in a short-distance and thus this vehicle can be effectively used in short-distance travels in addition to the long-distance transportation. On the other hand, since the EDS system to be accelerated in a certain time interval via conventional wheels to achieve sufficient levitation, PM-LSM system can be integrated into the EDS Maglev system to ensure higher acceleration in a short time interval in addition to the higher levitation and propulsion force performances.

An Optimized Flow Cytometric Method to Demonstrate the Differentiation Stage-Dependent Ca2+ Flux Responses of Peripheral Human B Cells.

Calcium (Ca2+) flux acts as a central signaling pathway in B cells, and its alterations are associated with autoimmune dysregulation and B-cell malignancies. We standardized a flow-cytometry-based method using various stimuli to investigate the Ca2+ flux characteristics of circulating human B lymphocytes from healthy individuals. We found that different activating agents trigger distinct Ca2+ flux responses and that B-cell subsets show specific developmental-stage dependent Ca2+ flux response patterns. Naive B cells responded with a more substantial Ca2+ flux to B cell receptor (BCR) stimulation than memory B cells. Non-switched memory cells responded to anti-IgD stimulation with a naive-like Ca2+ flux pattern, whereas their anti-IgM response was memory-like. Peripheral antibody-secreting cells retained their IgG responsivity but showed reduced Ca2+ responses upon activation, indicating their loss of dependence on Ca2+ signaling. Ca2+ flux is a relevant functional test for B cells, and its alterations could provide insight into pathological B-cell activation development.

Experimental Analysis of Local Condensation Heat Transfer Characteristics of CF3I Inside a Plate Heat Exchanger

Due to its low global warming potential (GWP) and good environmental properties, CF3I can be a suitable component of refrigerant mixtures in the field of refrigeration and air conditioning. In this work, the local condensation heat transfer characteristics of CF3I were experimentally investigated in a plate heat exchanger (PHE). The condensation heat transfer experiments were carried out under conditions of vapor qualities from 1.0 to 0.0, at saturation temperatures of 25–30 °C, mass fluxes of 20–50 kg/m2s, and heat fluxes of 10.4–13.7 kW/m2. Local heat transfer coefficients were found to vary in both the horizontal and vertical directions of the plate heat exchanger showing similar trends in all mass fluxes. In addition, the characteristics of local heat flux and wall temperature distribution as a function of distance from the inlet to the outlet of the refrigerant channel were explored in detail. The comparison of the experimental data of CF3I with that of R1234yf in the same test facility showed that the heat transfer coefficients of CF3I were comparable to R1234yf at a low vapor quality and a mass flux of 20 kg/m2s. However, R1234yf exhibited a transfer coefficient about 1.5 times higher at all vapor qualities and a mass flux of 50 kg/m2s. The newly developed correlation predicts well the experimentally obtained data for both CF3I and R1234yf within ±30%.