Flux Maps Research Articles

Open-Phase Faulty Five-Phase Permanent Magnet Assisted Synchronous Reluctance Motor Model With Stepped Skew

Commonly, healthy five-phase permanent magnet assisted synchronous reluctance machines (PMaSynRMs) are modeled in harmonic fixed rotating ( dq1dq ) reference frames. Such approaches feature several levels of detail, namely, constant parameters or saturation in four axes, i.e., 4-D saturation or cross-saturation effects in conjunction with space harmonics in 5-D models. In this article, a 6-D model is proposed that comprises all aforementioned nonlinearities not just in faultless but also in open-phase fault conditions. Moreover, magnetic axial asymmetry introduced by discrete skew is taken into account and included in the investigated modeling. The proposed 6-D model is based on flux maps obtained from static Finite-Element program posteriori modified to comprise the skewing effect. Very close to finite-element precision is guaranteed and experimental validations have been performed to confirm the authenticity and contrast the effectiveness of the open-phase model with skew.

Downscaling Building Energy Consumption Carbon Emissions by Machine Learning

The rapid rate of urbanization is causing increasing annual urban energy usage, drastic energy shortages, and pollution. Building operational energy consumption carbon emissions (BECCE) account for a substantial proportion of greenhouse gas emissions, crucially influencing global warming and the sustainability of urban socioeconomic development. As a foundation of building energy conservation, determination of refined statistics of BECCE is attracting increasing attention. However, reliable and accurate representation of BECCE remains lacking. This study proposed an innovative downscaling method to generate a gridded BECCE intensity benchmark dataset with 1 km2 spatial resolution. First, we calculated BECCE at the provincial level by energy balance table application. Second, on the basis of building climate demarcation, partial least squares regression models were used to establish the BECCE behavior equations for three climate regions. Third, Cubist regression models were built, retrieving down scale at the prefecture level to 1 km2 BECCE, which well-captured the complex relationships between BECCE and multisource covariates (i.e., gross domestic product, population, ground surface temperature, heating degree days, and cooling degree days). The downscaled product was verified using anthropogenic heat flux mapping at the same resolution. In comparison with other published pixel-based datasets of building energy usage, the gridded BECCE intensity map produced in this study showed good agreement and high spatial heterogeneity. This new BECCE intensity dataset could serve as a fundamental database for studies on building energy conservation and forecast carbon emissions, and could support decision makers in developing strategies for realizing the CO2 emission peak and carbon neutralization.

Experimental analysis of the optical loss of a dusty Fresnel lens with a novel solar flux test system

The effect of dust deposition on a point-focus Fresnel lens is experimentally analyzed using a novel outdoor solar flux test system. The solar flux maps of the concentration region of the Fresnel lens are obtained. A detailed mathematical heat transfer model of the thermocouple is developed to calculate the solar flux density at a given spot temperature. The solar flux intensity and shape, spot temperature, dust deposition density, and imaging distance are analyzed. The flux spot exhibits an ellipsoidal Gaussian distribution. As the dust density increases from 0 g/m2 to 5 g/m2, the peak flux exhibits a decrease of 57.4%, and the spot temperature decreases from 307 °C to 98.1 °C. An average optical loss of 16.69% is obtained for each 1 g/m2 increase in the dust density. Error sources and estimates of the system are analyzed. The experimental measurements are in good agreement with the theoretical values. The deviation is within 8.33%, and the maximum deviation is 18.39 kW/m2.

Leveraging the ALMA Atacama Compact Array for Cometary Science: An Interferometric Survey of Comet C/2015 ER61 (PanSTARRS) and Evidence for a Distributed Source of Carbon Monosulfide

Abstract We report the first survey of molecular emission from cometary volatiles using standalone Atacama Compact Array (ACA) observations from the Atacama Large Millimeter/Submillimeter Array (ALMA) toward comet C/2015 ER61 (PanSTARRS) carried out on UT 2017 April 11 and 15, shortly after its April 4 outburst. These measurements of HCN, CS, CH3OH, H2CO, and HNC (along with continuum emission from dust) probed the inner coma of C/2015 ER61, revealing asymmetric outgassing and discerning parent from daughter/distributed source species. This work presents spectrally integrated flux maps, autocorrelation spectra, production rates, and parent scale lengths for each molecule and a stringent upper limit for CO. HCN is consistent with direct nucleus release in C/2015 ER61, whereas CS, H2CO, HNC, and potentially CH3OH are associated with distributed sources in the coma. Adopting a Haser model, parent scale lengths determined for H2CO (L p ∼ 2200 km) and HNC (L p ∼ 3300 km) are consistent with previous work in comets, whereas significant extended source production (L p ∼ 2000 km) is indicated for CS, suggesting production from an unknown parent in the coma. The continuum presents a point-source distribution with a flux density implying an excessively large nucleus, inconsistent with other estimates of the nucleus size. It is best explained by the thermal emission of slowly moving outburst ejectas, with total mass 5–8 × 1010 kg. These results demonstrate the power of the ACA for revealing the abundances, spatial distributions, and locations of molecular production for volatiles in moderately bright comets such as C/2015 ER61.

Optical characterization of a fixed focus Scheffler reflector for pressurized solar receiver testing

In this work, a method of focal region flux characterization of Scheffler fixed focus concentrator is presented. Being a fixed focus concentrator, Scheffler dish serves as an ideal focusing unit for on-Sun testing of scaled down high pressure receiver designs under actual boundary conditions. Flux characterization is performed numerically by tracing the ray trajectories from their inception till the focal region and experimentally using point-based heat flux sensors. A circular plate is mounted at the focal region with five water cooled heat flux sensors attached. Four of these sensors are positioned around a diameter of size corresponding to an existing cavity receiver aperture diameter and one sensor is located at the plate centre. These sensors help to obtain the point based flux measurements in the region. Since the dish is not parabolic, a non-Gaussian flux profile is obtained, and spatial averaging of the flux data is performed analytically to obtain an averaged heat flux value. This averaged flux density is then matched with the spatially resolved flux map average value obtained from the numerical analysis. Average thermal power intercepted on the target surface is also measured, which serves as a useful procedure for estimating the radiative power incident on the receiver aperture. Further, as a demonstration exercise of the present fixed focus dish characterization method, a receiver testing methodology with an existing hybrid cavity and tubular design using compressed air is presented.

MDBA: An accurate and efficient method for aiming heliostats

In a solar power tower plant, the role of the heliostat aiming strategy is to control the radiative flux distribution at the receiver surface to avoid thermally induced damage, while minimising spillage losses and maximising the receiver thermal efficiency. Flux limitations arise from factors including the heat transfer fluid stability limits, and thermo-mechanical stress limits in receiver pipes. Maximised flux, as close as possible to local flux limits, facilitates an overall smaller receiver with lower thermal losses. Methods exist to sequentially optimise aiming points of single heliostats, using fast convolution-based optical simulations to evaluate individual flux maps. However, to accurately determine receiver flux distributions, ray-tracing is preferred. Ray-tracing is computationally expensive and determination of the aim-points for every heliostat independently potentially leads to impractical simulation times. In this study, a new parameterisation of heliostat aim-point locations is introduced that significantly simplifies the aiming problem. The new aiming model, named Modified Deviation-Based Aiming (MDBA), enables efficient use of ray-tracing to optimise the aiming strategy and, together with receiver thermal and mechanical models, is able to closely match the flux distribution to local values of allowable flux on the receiver. This new parameterisation enables accurate aiming strategy interpolation, used to dynamically predict full field aim-points at different sun positions and values of direct normal irradiance (DNI). A reference case with a surround field and a cylindrical external receiver compatible with the Gen3 Liquid Pathway project is presented to test the capability of the method developed in this study.

Generation of Low‐Latitude Seamount‐Trapped Waves: A Case Study of the Seychelles Plateau

AbstractBaroclinic seamount‐trapped waves are thought to influence their surrounding ecosystem; however, trapped waves are not well‐studied in near‐equatorial settings, where stratification is strong and Burger numbers are large. Motivated by observations, we use daily output (2005–2009) from the global Parallel Ocean Program Model (POP) to examine topographically trapped baroclinic waves around the Seychelles Plateau () in the tropical Indian Ocean. These trapped waves are associated with velocity and temperature oscillations at periods of 15–16 days, similar to the dominant period of some equatorial Yanai waves. Energy flux maps using POP output suggest that quasi‐biweekly equatorial Yanai waves excite trapped waves on the western and south‐western flanks of the Seychelles Plateau, near the surface. The anticyclonic energy flux associated with the trapped wave extends vertically throughout the water column and around most of the plateau circumference, diminishing on the eastern flank of the plateau. This work highlights the role that equatorial planetary waves and trapped waves play in facilitating energy redistribution, dissipation, and mixing in the tropical ocean.

The First Global Carbon Dioxide Flux Map Derived from TanSat Measurements

Space-borne measurements of atmospheric greenhouse gas concentrations provide global observation constraints for top-down estimates of surface carbon flux. Here, the first estimates of the global distribution of carbon surface fluxes inferred from dry-air CO2 column (XCO2) measurements by the Chinese Global Carbon Dioxide Monitoring Scientific Experimental Satellite (TanSat) are presented. An ensemble transform Kalman filter (ETKF) data assimilation system coupled with the GEOS-Chem global chemistry transport model is used to optimally fit model simulations with the TanSat XCO2 observations, which were retrieved using the Institute of Atmospheric Physics Carbon dioxide retrieval Algorithm for Satellite remote sensing (IAPCAS). High posterior error reduction (30%–50%) compared with a priori fluxes indicates that assimilating satellite XCO2 measurements provides highly effective constraints on global carbon flux estimation. Their impacts are also highlighted by significant spatiotemporal shifts in flux patterns over regions critical to the global carbon budget, such as tropical South America and China. An integrated global land carbon net flux of 6.71 ± 0.76 Gt C yr−1 over 12 months (May 2017–April 2018) is estimated from the TanSat XCO2 data, which is generally consistent with other inversions based on satellite data, such as the JAXA GOSAT and NASA OCO-2 XCO2 retrievals. However, discrepancies were found in some regional flux estimates, particularly over the Southern Hemisphere, where there may still be uncorrected bias between satellite measurements due to the lack of independent reference observations. The results of this study provide the groundwork for further studies using current or future TanSat XCO2 data together with other surface-based and space-borne measurements to quantify biosphere-atmosphere carbon exchange.

Magnetic skew interface in five-phase ferrite assisted synchronous reluctance motor model

Permanent Magnet Assisted Five-Phase Synchronous Machine is analytically modeled in the rotating (dq1dq3) reference frames. The cross saturation and space harmonics are captured in the magnetic flux maps obtained from static 2D finite element (FE) analysis. In this paper, a method to incorporate the skewing effect in the flux map distribution for the first and third harmonic is presented. The original flux for one motor segment is used to calculate fluxes of the first and third planes in the consecutive skewing segments. Respective rotator operators allow to sum the contribution from axial slice and shift the resulting map to the desired zero reference position. Eventually, a dynamic model is established on the new corrected flux maps. FE and experimental validations have been performed to confirm the authenticity of the proposed technique.

Characterizing the plasma-induced thermal loads on a 200 kW light-ion helicon plasma source via infra-red thermography

The light-ion helicon plasma source of the Proto-MPEX linear plasma device has been recently upgraded to enable pulsed (0.5–1 s) operation up to 200 kW. The main objective of this work is to report on the plasma-induced surface heat fluxes incident on the helicon window during high power operation (60–150 kW net power) for the purpose of the design of the upcoming material plasma exposure eXperiment (MPEX). The IR imaging system and associated physics models for the extraction of surface heat fluxes are presented. Experimental results demonstrate that the control of the plasma strike point via magnetic flux mapping and the use of dedicated limiters is effective at reducing the heat loads on the dielectric window. Moreover, it is found that the flux mapping must create a gap between the plasma and the dielectric window of at least the plasma radial decay length. Extrapolated to 200 kW net RF power, this mode of operation can reduce the power lost to the dielectric window by 33%. The results presented have direct application to the design of high-powered helicon plasma sources that operate in a steady state. Examples include linear divertor simulators such as MPEX, electric thrusters, negative ion sources for NBI and linear plasma–material interaction test stands.

A modified indirect flux mapping system for high-flux solar simulators

To further make a compromise among the accuracy, convenience, safety, and measuring power range of the flux mapping in the high-flux solar simulator, a modified indirect flux mapping system that combines a water-cooled Lambertian target and a gray spot superposition method was firstly designed. Then, measuring errors of the modified system were analyzed, which were found to be acceptable. Then, a comparison between the modified system and a reference indirect system was conducted, indicating that the modified system is reliable. Then, based on the modified system, the flux distributions of a 30 kWe high-flux solar simulator were measured, finding the modified system can exceed the upper limit of the reference indirect system which burned a target under a relatively small power value. In addition, more analysis pointed out that the modified system can reduce the system complexity and improve the mapping accuracy compared with the direct or traditional indirect flux mapping systems. Results from current study indicated the modified system is reliable and suitable for wide-range flux mapping of the solar simulator.

A Kalman filtering of the Self-Powered Neutron Detector current to determine excess reactivity

Self-powered neutron detectors are common sensory devices for flux mapping purposes in nuclear reactors. A Kalman filtering strategy has been explored in this work to overcome the inherent delay in certain designs thereof enabling their application for the online monitoring and control activities. Determination of the core excess reactivity by way of the current reading in a Rhodium detector has thus been attempted as a generalization to the well-known reactor inverse kinetics problem. Efficient reactivity estimation is reported. Further analysis carried out for a Cobalt SPND excludes the need for additional current compensation as this detector predominantly enjoys a fairly rapid γinduced electric current.

Influence of matrix-filler thermal conductivity on micro heat transfer in two-component composites

The maps of local heat fluxes in the composite matrix with randomly located heat-insulating and heat-conducting inclusions have been calculated in this work. It was shown that with a significant difference in the thermal conductivity of inclusions and matrix, the main heat transfer occurs through the induced heat-conducting channels. It was found that the weighted average angles of local heat fluxes deviation from the direction of the temperature difference between the sample faces depend on the concentration of heat-insulating and heat-conducting inclusions of various sizes. A sublinear decrease or super linear increase in the effective thermal conductivity of the composite with an increase in the concentration of heat-insulating or heat-conducting inclusions, respectively, was associated with a change in the path length of local heat fluxes due to the flow at an angle to the direction of the temperature difference. An approximation formula for the dependence of the composite effective thermal conductivity on the filler concentration has been proposed, which makes it possible to take into account the presence of both heat-conducting and heat-insulating inclusions.

A comprehensive review on optical analysis of parabolic trough solar collector

The optical analysis is one of the most important parameters to investigate the performance of the parabolic trough solar collector (PTSC). The output of the optical analysis is used as an input for the thermal analysis. The journey of the flux distribution studies started back in 1950 for the PTSC with a flat receiver. Since then, various methods and procedures were developed by the researchers to analyze the flux distribution on the receiver surface. Majorly the techniques can be divided into three categories: analytical approach, measurement techniques such as photogrammetry, flux mapping and flux scanning, and flux distribution using modeling software. The most widely used raytracing technique is Monte Carlo ray tracing. It has been extensively used to provide coupled optical and thermal performance of the PTSC. This study critically summarizes the various raytracing techniques along with the effect of various parameters such as sun shape, rim angle, aperture, geometrical concentration ratio, receiver shape, optical errors, secondary reflector, incidence angle, on the flux distribution of PTSC. Finally, the numerical studies are proposed for future work related to this domain.

Aspherical lens design for real light-emitting diode with flux compensation through angular flux mapping

A design scheme for an aspherical lens including two step processes is proposed and demonstrated to direct appropriate flux to the expected target illumination. The first-step design is based on a point source and the surface geometry is determined. The flux deviation between the design and target illumination becomes the factor in the optimization process, and the angular flux compensation is done to adjust the light pattern. Finally, the experimental result shows that high similarity between the target and the measurement is observed and full width at half maximum angle error is within 3%, which are both better than those in the aspherical lens design based a point source and a real light-emitting diode without optimization by flux compensation.

Tokamak free-boundary plasma equilibrium computation using finite elements of class [formula omitted] and [formula omitted] within a mortar element approach

The numerical simulation of the equilibrium of the plasma in a tokamak as well as its self-consistent coupling with resistive diffusion should benefit from higher regularity of the approximation of the magnetic flux map. In this work, we propose a finite element approach on a triangular mesh of the poloidal section, that couples piece-wise linear finite elements in a region that does not contain the plasma and reduced Hsieh-Clough-Tocher finite elements elsewhere. This approach gives the flexibility to achieve easily and at low cost higher order regularity for the approximation of the flux function in the domain covered by the plasma, while preserving accurate meshing of the geometric details in the rest of the computational domain. The continuity of the numerical solution at the coupling interface is weakly enforced by mortar projection. A new technique for the computation of the geometrical coefficients is also presented.

The Relationship Between Large Scale Thermospheric Density Enhancements and the Spatial Distribution of Poynting Flux

AbstractLarge thermospheric neutral density enhancements in the cusp region have been examined for many years. The Challenging Minisatellite Payload (CHAMP) satellite for example has enabled many observations of the perturbation, showing that it is mesoscale in size and exists statistically over solar cycle timescales. Further studies examining the relationship with magnetospheric energy input have shown that fine‐scale Poynting fluxes are associated with the density perturbations on a case‐by‐case basis, whilst others have found that mesoscale downward fluxes also exist in the cusp region statistically. In this study, we use nearly 8 years of the overlapping Super Dual Auroral Radar Network and Active Magnetosphere and Planetary Electrodynamics Response Experiment datasets to generate global‐scale patterns of the high‐latitude and height‐integrated Poynting flux into the ionosphere, with a time resolution of 2 min. From these, average patterns are generated based on the interplanetary magnetic field orientation. We show the cusp is indeed an important feature in the Poynting flux maps, but the magnitude does not correlate well with statistical neutral mass density perturbations observed by the CHAMP satellite on similar spatial scales. Importantly, the lack of correlation between mesoscale height‐integrated Poynting fluxes and the cusp neutral mass density enhancement gives possible insight into other processes that may account for the discrepancy, such as energy deposition at finer scale sizes or at higher altitudes than captured.

An X-ray and radio study of the Hubble Frontier Field cluster Abell S1063

ABSTRACT We present results from Chandra X-ray observations and 325 MHz Giant Metrewave Radio Telescope (GMRT) observations of the massive and X-ray luminous cluster of galaxies Abell S1063. We report the detection of large-scale ‘excess brightness’ in the residual Chandra X-ray surface brightness map that extends at least 2.7 Mpc towards the north-east from the centre of the cluster. We also present a high fidelity X-ray flux and temperature map using Chandra archival data of 122 ks that shows the disturbed morphology in the cluster. The residual flux map shows the first observational confirmation of the merging axis proposed in earlier simulations. The average temperature within R500 is 11.7 ± 0.56 keV that makes AS1063 one of the hottest clusters in the nearby Universe. The integrated radio flux density at 325 MHz is found to be 62.0 ± 6.3 mJy. The integrated spectrum of the radio halo follows a power law with a spectral index α = −1.43 ± 0.13. The radio halo is found to be significantly under-luminous that favored for both the hadronic as well as the turbulent re-acceleration mechanism for its origin.

Investigating the neutronic, thermal-hydraulic, and solid mechanics analysis for AP-1000 nuclear reactor

ABSTRACT This study investigates the neutronic, thermal-hydraulic, and solid mechanics analyses for one of the central fuel assemblies with 2.35% U235 enrichment in the AP-1000 Reactor. MCNPX 2.7 computer code, which depends on a Monte Carlo algorithm, was applied to perform the neutronic calculations. Both COMSOL-Multiphysics, based on the numerical solution for the centered rod sub-channel model, and MATLAB, based on the analytical solution for the same model, were applied to perform the thermal-hydraulic analysis. COMSOL-Multiphysics was used to perform the solid mechanics analysis. The neutronic, thermal hydraulics, and solid mechanics analyses play an essential role in the control, design, and safety of nuclear reactors. The calculations of criticality, reactivity, fuel burn-up, neutron flux, and power mapping were performed.‎ From the power mapping, the hot channel was determined and its maximum PPF. Upon getting the maximum PPF, which occurred in channel number 30 and equals 1.357, the thermal-hydraulic calculations using both COMSOL-Multiphysics and MATLAB were applied to determine the temperature distribution of the fuel, clad, and coolant. The departure from nucleate boiling ratio (DNBR) distribution was calculated to determine the minimum departure from ‎nucleate boiling ratio (MDNBR). The MDNBR results were 2.154 based on the analytical approach and 2.20 based on ‎the numerical approach. These values are higher than the limiting value of 1.75, which assure that no nucleate boiling ‎problems will occur. The solid mechanics calculations were investigated by coupling three kinds of physics using COMSOL-Multiphysics (the heat transfer in solid physics to perform the thermal load, turbulence flow RANS K-OMEGA to perform the pressure load, and solid mechanics physics). This coupling was used to determine the von-Mises stress, volumetric strain, and the total displacement for both the fuel and the clad material. The total fuel outer surface displacement was calculated to assure that no surface contact would happen between the ‎fuel and clad material to avoid chemical interactions between them. The displacement was calculated to be 0.007 mm, which is less than the He-gap ‎thickness, 0.008 mm. The coupling between different physics is one of the most well-developed techniques used for simulating the exact situation inside nuclear reactors. This coupling was done using the computational fluid dynamics (CFD) approach. All the calculations for the benchmark problem (a single fuel Assembly (G-9), near Beginning of Life, hot Full Power, equilibrium Xenon, and unrodded Core) were conducted. The obtained results were within the safety limits outlined in the design control document (DCD). Eventually, the results were in line with earlier efforts that utilized different codes for simulating neutronic analysis.

Influence of Europa’s Time‐Varying Electromagnetic Environment on Magnetospheric Ion Precipitation and Surface Weathering

AbstractWe combine the electromagnetic fields from a hybrid model with a particle‐tracing code to calculate the time‐varying spatial distribution of magnetospheric ion flux onto the surface of Jupiter’s moon Europa. The electromagnetic fields at Europa are perturbed by the sub‐alfvénic interaction of the moon’s ionosphere and induced dipole with the magnetospheric plasma. These perturbations substantially modify magnetospheric ion trajectories at all energies. We calculate spatially resolved surface flux maps of thermal and energetic ions for various distances between Europa and the center of Jupiter’s magnetospheric plasma sheet. The upstream ion distributions are constrained through in‐situ particle data from the Galileo and Juno spacecraft. These maps are then combined to obtain the average distribution of magnetospheric ion surface flux over a full synodic rotation. Our results show that the draping and pileup of the magnetic field reduce ion flux onto Europa’s trailing hemisphere by several orders of magnitude, while a significant number of the incident ions are deflected onto the leading hemisphere. Taking into account the deflection of energetic ions in the draped electromagnetic fields shifts the region of minimum energetic ion surface flux from Europa’s wakeside equator to its ramside equator. This generates an “inverted bullseye” pattern of energetic ion flux centered at the trailing apex. Despite drastic changes to the morphology of the ion surface flux when the alfvénic plasma interaction is included, we still find a strong correlation between variations of sulfuric acid concentration observed across Europa’s surface by Galileo and our modeled sulfur influx pattern.