Flux Angle Research Articles

Modeling the Emission and Polarization Properties of Pulsating Ultraluminous X‐Ray Sources

ABSTRACTPulsating Ultraluminous X‐ray Sources (PULXs) are a class of extragalactic sources with high X‐ray luminosity, in excess of erg , and showing pulsations that associate them with neutron stars accreting at a super‐Eddington rate. A simplified model is presented, which describes the thermal emission from an accreting, highly magnetized neutron star and includes the contributions from an accretion disk and an accretion envelope surrounding the star magnetosphere. Through numerical calculations, we determine the flux, pulsed fractions, polarization degree, and polarization angle considering various viewing geometries. The model is confronted with the XMM‐Newton spectra of M51 ULX‐7, and the best fitting viewing geometries are estimated. A measurement of the polarization observables, which will be available with future facilities, along with spectroscopic data obtained with XMM‐Newton, will provide considerable additional information on these sources.

A Residual Stator Flux Angle Based Interturn Short Circuit Fault Diagnosis Method alongside MPTC for Induction Motor Drives

A Residual Stator Flux Angle Based Interturn Short Circuit Fault Diagnosis Method alongside MPTC for Induction Motor Drives

Research on shear-thinning and surface properties of CaO–SiO2–CaF2–Al2O3-based mould flux

The main feature of high-efficiency continuous casting production is the increase in casting speed. This leads to an increased risk of slag entrapment in the liquid surface area of the mould and steel leakage due to the bonding of the casting billet. Both traditional mould flux and non-Newtonian fluid mould flux with only shear-thinning properties cannot effectively solve these problems. This study selected a practical high-casting speed thin slab mould flux from a steel plant as the original mould flux. Add 4.6–12.1% Al2O3 and 3.6–4.9% MnO and other additives to prepare a new type of mould flux with both shear thinning characteristics and high surface tension. The shear-thinning properties, interface properties and microstructure of the mould flux were detected and studied using methods such as the rotating cylinder method. The results showed that with the increase of Al2O3 content, the shear-thinning properties of the mould flux first enhanced and then weakened. The strongest effect was observed when the Al2O3 content was 8.7%. The contact angle, surface tension and interface tension of the mould flux were significantly improved and the degree of molecular polymerisation gradually increased. The shear-thinning properties of mould flux are mainly related to the Si–O–Al structure. The interaction force between Al3+ in the slag and the surface O2− of the mould flux increases, and the surface tension of the mould flux increases. When the Al2O3 content is more than 10.5%, a large amount of AlO2− will be repelled to the surface of the mould flux, and the change in surface tension is no longer significant.

Synchronous DTC for torque sub-harmonic reduction in low switching frequency induction motor drives

A direct torque control (DTC) algorithm with synchronous modulation for high-power induction motors is presented in this paper. While maintaining the dynamic response and robustness of a PI-based DTC operating in the stationary reference frame, the proposed scheme is able to keep an integer PWM modulation ratio, adjusting the stator flux angle and the switching period at each control step so that the synchronicity condition is always satisfied. In this way, it is possible to achieve an improvement of the very low-frequency harmonic spectrum of the torque, in particular by reducing torque sub-harmonics. These represent one of the main problems associated with low-frequency modulation typical of high-power drives and their reduction allows to avoid drawbacks such as resonance and mechanical stresses. The performance of the proposed algorithm is evaluated with experimental tests on a small-scale test bench.

A mathematical modelling for solar irradiance reduction of sunshades and some near-future albedo modification approaches for mitigation of global warming

To address the global warming problem, one of the space-based geoengineering solutions suggests the construction of an occluding disc that can work as a solar curtain to mitigate solar irradiation penetration to the earth atmosphere. A widely discussed concept needs the construction of a large-scale sunshade system near the Sun–Earth L1 equilibrium point in order to control the average global temperature. However, to improve the accuracy of theoretical estimations, more consistent modeling of the Sun-Curtain-Earth system and solar irradiance reduction rate are required. This study revisits the mathematical modeling of the solar irradiance reduction system and considers the fundamentals of shading physics. Simplified mathematical modeling of solar irradiance reduction rate is derived based on the solar flux density. For the climate control, controllability of the reduction rate by using some physical parameters (e.g., flux reflection rate and angle of the curtain) is discussed. Based on the results of this model, the technical challenges and feasibility of constructing a sunshade system at L1 Lagrange point are evaluated. Some technologically feasible, near-future options for the warming problem are discussed briefly.

Variability of energetic proton flux and pitch angle distributions in the Earth's radiation belt modulated by geomagnetic storms

Energetic protons trapped in the radiation belt, as a vital component of the ring current system, are observationally and theoretically modulated by geomagnetic disturbances. Utilizing Van Allen Probe observations, we statistically analyzed their temporal variations at 55–489 keV as well as their pitch angle distributions (PADs) index n (fitted by sinn∂, where ∂ is the pitch angle) in response to geomagnetic storms. It shows that protons at low energies are more easily accelerated during storms. The threshold of accelerations becomes greater for high-energy protons, while a large value of n can persist for a few days to months. Further investigations suggest that one-quarter of the storms increase the proton flux at all energy channels (55–489 keV) both inside and outside the plasmapause location (Lpp). Specifically, more than half of the storms enhance the flux for protons at Ek > 400 keV inside and close to the Lpp as well as protons at Ek < 100 keV deep inside the Lpp. Comparably, protons at larger pitch angles (near 90°) are more easily lost outside the Lpp, which results in more pronounced pancake PADs with larger n. The index n preferentially decreases at L > 5 during 75% of the storms on the dayside, while it decreases at L = ∼4 during 50% of the storms on the nightside, showing significant day–night asymmetry. Further detailed investigations revealed that source and loss processes, including radial diffusion, magnetopause shadowing, and wave–particle interactions, account for the statistical results. The present study provides quantitative information on the overall characteristics of energetic proton fluxes, which can enhance the comprehension of the radiation belts.

Microstructures, electrical and mechanical properties of the magnetron sputter deposited metal thin films at variable angles

In this work, we investigate the microstructures, mechanical and electrical properties of the Cr, Fe, Ni, Cu, and Al thin films that were grown by using magnetron sputtering at various angles. The relationships among the electrical and mechanical properties (resistivity, nanoindentation hardness, and modulus), structural parameters (domain size, thickness, column angle), and sputter deposition conditions (flux angle, deposition rate) were investigated through the Pearson correlation analysis. Electrical resistivity was found to be significantly affected by both the domain size and the deposition rate. A strong correlation between hardness and domain size was observed. However, Young's moduli did not exhibit a correlation within the investigated parameter space.

Ultra‐Inclined Nanocolumnar ZnO Films Sputtered Using a Novel Masking Configuration Providing Controlled and Restricted Oblique Angle Deposition for Enhanced Sensing Platforms

AbstractOblique angle deposition (OAD) of inclined thin films is mainly performed using electron beam evaporation due to its accurate point source control over the incoming evaporated flux angle α, leading to thin films with a nanocolumnar inclination angle β. However, the utilization of magnetron sputtering (MS) with an extended source for OAD is not extensively studied and reported. This work presents a thorough analysis of ZnO inclined thin films deposited by a novel restricted DC‐reactive MS‐OAD technique. OAD‐inclined films are deposited at α ranged 60°‐88°, where incoming flux is restricted using a patented masking configuration enabling tunable control of deposited nanocolumn angular range. The described technique provides accurate control over the resulting β (99.5% reproducibility), allowing demonstrated βmax of 47.3°, close to theoretical limits predicted for ZnO. The approach discussed here probes enhanced control of β comparable to that observed in evaporation, however using an extended source, resulting in high‐quality reproducible nanocolumnar‐inclined films. The mentioned improvements result from the exploration of operational parameters such as magnetron power, working pressure, and chamber temperature, as well as the design of the restricting configuration and substrate holders and their influence on the resulting inclined thin film crystallinity, and morphology.

Robust flux angle control of induction motors to improve efficiency at light loads

AbstractVector control of induction motors has provided us with both good performance and acceptable efficiency at rated loads. Using this method at light loads reduces the efficiency due to the adjustment of motor flux at the rated value. Electric motors are normally used even at lower loads than the rated ones and often selected oversized. Enhancing the efficiency of induction motors at light loads will significantly reduce electric energy consumption. A novel method called Flux Angle Control (FAC) of the induction motor is presented to improve efficiency in the steady state at light loads. To increase the accuracy of the induction motor model we consider iron losses. This method controls the angle between the stator flux (stator current) and the d‐axis (rotor flux direction). The primary aim of the flux angle control method is to reduce the flux level and increase the flux angle at light loads. The optimal flux angle is sensitive to some induction motor parameters. The proposed method offers several advantages compared to similar methods, including high efficiency, minimal sensitivity of the optimal flux angle to changes in motor parameters, a reduced number of calculations, and easy implementation. The validity of this method is examined through experiments.

Design and Implementation of VSI for Solar Water Pump Control

The hardware design, implementation, and digital control method for three-phase AC induction motors based on Field-Oriented Control is discussed in this work Solar-powered water pumping systems have become an practical option for remote irrigation and water supply as renewable energy sources obtain importance. This research enhances such systems performance and dependability by employing a Voltage Source Inverter. In order to optimize the energy transfer to the water pump, the recommended approach uses the Voltage Source Inverter capabilities to transform the variable DC output of the solar panels into a controlled AC supply. The research looks at the choice of power components, control algorithms, and modulation strategies while designing the Voltage Source Inverter. The most suitable modulation strategy is determined after an in-depth review of several different approaches to ensure greater pump performance. This research clarifies on how solar energy conversion and pump control work together to provide sustainable water management in off-grid areas. The research paper "Design and implementation of VSI for Solar Water Pump Control" demonstrates how solar water pumping systems can be optimized using power electronics and control. The project addresses efficiency difficulties and operational differences to create efficient and reliable solar-powered water delivery systems, which support environmental sustainability and rural development. Based on the power of the PV panel, the P&O MPPT method calculates the submersible pump speed. The sensorless speed control method eliminates the requirement for location or speed sensors. The Black Electro-Motives Force calculates speed by estimating the flux angle in the absence of mechanical speed sensors. This method reduces costs and simplifies the system simply by eliminating the requirement for expensive and complicated speed sensors. In order to determine steady-state and dynamic performance in varying insolation conditions, a prototype 5.5 KW inverter was constructed. In conclusion up, the research provided a thorough summary of the hardware and control aspects required for Field-Oriented Control in irrigation systems. The practical outcomes of this study have the potential to spur advancements in irrigation technology and the incorporation of renewable energy, resulting in substantial gains for agricultural productivity and environmental conservation.

Augmented speed control scheme of dual induction motors with mutual flux angle control loop

Augmented speed control scheme of dual induction motors with mutual flux angle control loop

Tunable properties of SnOx sputter-deposited by RGPP and GLAD techniques: A potential candidate for photosensing and all-oxide solar cells

In this work, optical and electrical properties of tin-oxide (SnOx) thin-films were investigated for broadband photosensing and photovoltaic applications. The GLancing Angle Deposition (GLAD) and Reactive Gas Pulsing Process (RGPP) techniques were used to study the effects of the oxygen ratio variation and deposition angle on the film optoelectronic and photovoltaic properties. The deposition angle of the particle flux was kept at 80° and the injected oxygen gas concentration was tuned by changing the oxygen pulsing time from 0 to 20 s. It is found that the material band gap increases from 0.9 eV to 3.56 eV when the oxygen content increases. The deposited SnOx films exhibited improved and tuned optoelectronic properties, demonstrating their potential applications for developing alternative broadband photosensing layers and eco-friendly all-oxide solar cells. In this regard, SnOx-based photosensor and all-oxide SnOx solar cell structures were developed using the deposited thin-films. It is revealed that the prepared SnOx photosensor shows the highest responsivity of 32.7 mA/W and improved ION/IOFF ratio of 48 dB. Moreover, the optimized all-oxide SnOx solar cell demonstrates a high efficiency of 3.41 %, a short-circuit current of 14.53 mA/cm2 and an open circuit voltage of 0.49 V. These interesting results make the proposed elaboration process based on combined RGPP and GLAD techniques highly suitable for the development of high-performance optoelectronic and photovoltaic devices based on cost-effective metal oxide materials.

A PARAMETRIC STUDY ON THE THERMAL HOMOGENEITY OF VAPOR CHAMBER IN A BATTERY COOLING SYSTEM

For the battery cooling system, the large temperature difference of the coolant between the inlet and outlet leads to a decrease in the thermal homogeneity of batteries. To improve the thermal homogeneity, a designed composite liquid cooling system was analyzed combined with a grooved vapor chamber and a cooling plate. The parametric study on the thermal homogeneity was conducted including the height, width, length of grooved wick, filling ratio, flow rate of coolant, heat flux, and inclination angle. The results show that a preferable thermal homogeneity can be obtained at 20% filling ratio as the height and width of the channel increase, especially under the positive inclination angle of 20°. The heat source surface can be kept uniform within the temperature difference of 5°C in spite of the temperature rise of coolant up to 11.5°C under the flowing rate of 8.32 × 10<sup>-4</sup> kg/s. An empirical correlation of the "suppression ratio," containing the structural and operating parameters, is summarized to evaluate the suppressing function of the vapor chamber on the temperature difference of coolant. This research is aimed to provide a scientific basis for predicting the thermal homogeneity of the vapor chamber in a battery liquid cooling system.

Model Predictive Current Control of an Induction Motor Considering Iron Core Losses and Saturation

The paper considers the model predictive current control (MPCC) of an induction motor (IM) drive and evaluates five IM models of different complexities—from conventional to magnetic saturation, iron losses, and stray-load losses—for the MPCC design. The validity of each considered IM model and the corresponding MPCC algorithm is evaluated by comparison of the following performance metrics: the total harmonic distortion of the stator current, the average switching frequency, the rotor flux magnitude error, the rotor flux angle error, and the product of the first two metrics. The metrics’ values are determined in wide ranges of the rotor speed (0.1–1 p.u.) and load torque (0–1 p.u.) through simulations performed in the MATLAB Simulink environment. The obtained results allow us to identify the IM model that offers the best tradeoff between the practicability and accuracy. Furthermore, a control effort penalization (CEP) is suggested to reduce the average switching frequency and, hence, the power converter losses. This involves constraining the simultaneous switching to a maximum of two branches of the three-phase power converter, as well as inclusion of the weighted switching penalization term in the cost function. Finally, the performance—both steady-state and dynamic—of the proposed MPCC system with CEP is compared with that of the analogous field-oriented controlled (FOC) IM drive. The inverter switching frequency is reduced more than twice by including the frequency-dependent iron-loss resistance in the MPCC. It is additionally reduced by implementing the proposed CEP strategy without sacrificing many other performance metrics, thus achieving a performance comparable to the FOC IM drive.

Heat transfer performance of the L-shaped flat gravity heat pipe used for zero-carbon heating houses

The L-shaped flat gravity heat pipe (LFGHP) is applied to the building envelope to effectively improve solar heat gain and achieve zero-carbon heating due to its ultrahigh equivalent thermal conductivity (ke) and thermal diode effect. In this paper, the forward and reverse heat transfer models of LFGHP are developed and experimentally verified. An experimental platform is built to experimentally study the thermal start-up time and the key factors on forward heat transfer, including the working fluid and filling ratio, the bending angle, the inclination angle, the length ratio of the condenser to the evaporator, the cooling temperature, and the heat flux. The ke of an LFGHP in practical use during a whole day is obtained. The results show that: (1) The heat transfer model of LFGHP can be regarded as three series thermal resistances in forward heat transfer and three parallel thermal resistances in reverse heat transfer, and the thermal diode effect is experimentally verified, with a rectification ratio over 170. (2) The acetone heat pipe with a volume filling ratio of 10% is of the highest ke and is the optimum combination of working fluid and filling ratio. (3) The ke in forward heat transfer increases with the decrease of bending angle and inclination angle, and increases with the increase of heat flux, cooling temperature, and length ratio of the condenser to the evaporator. (4) The thermal start-up time shortens with the increase of heat flux and inclination angle and can be neglected in applications. This study is helpful for the selection and design of the LFGHP used in solar houses and has guiding significance for the improvement and optimization of the practical applications of zero-carbon heating houses.

Kimberlite eruptions driven by slab flux and subduction angle

Kimberlites are sourced from thermochemical upwellings which can transport diamonds to the surface of the crust. The majority of kimberlites preserved at the Earth’s surface erupted between 250 and 50 million years ago, and have been attributed to changes in plate velocity or mantle plumes. However, these mechanisms fail to explain the presence of strong subduction signatures observed in some Cretaceous kimberlites. This raises the question whether there is a subduction process that unifies our understanding of the timing of kimberlite eruptions. We develop a novel formulation for calculating subduction angle based on trench migration, convergence rate, slab thickness and density to connect the influx of slab material into the mantle with the timing of kimberlite eruptions. We find that subduction angles combined with peaks in slab flux predict pulses of kimberlite eruptions. High rates of subducting slab material trigger mantle return flow that stimulates fertile reservoirs in the mantle. These convective instabilities transport slab-influenced melt to the surface at a distance inbound from the trench corresponding to the subduction angle. Our deep-time slab dip formulation has numerous potential applications including modelling the deep carbon and water cycles, and an improved understanding of subduction-related mineral deposits.

Validation of Foreground Emission Model using GALEX Medium Observations

The study of diffuse ultraviolet (UV) background radiation is vital in the investigation of stellar and galactic evolution. Space-based UV observations are comprised of both foreground and background radiations. The foreground emission in an observation is a result of solar contamination in the direction of observation. In our previous work, we modeled airglow (one of the major constituents of the foreground emission) as a function of 10.7 cm Solar Flux and Sun Angle with great accuracy using GALEX deep observations. We adopt a similar methodology to validate the obtained model and run equivalent experiments here using far-UV (FUV) and near-UV (NUV) GALEX medium imaging surveys (MIS) with a total exposure time greater than 3300 s. We obtained a predictive model having excellent compatibility with the earlier model. Our analysis shows that the total foreground emission varies between 59 and 295 photon units in FUV whereas in NUV, it varies between 671 and 1195 photon units depending upon the date and time of observation. We also noticed a strong correlation between the background emission and optical depth both in FUV and NUV, especially in the low density regions. This clearly indicates that the major contributor in diffuse background radiation is the starlight scattered by interstellar dust grains.

Investigation of free convection flow around near horizontal surfaces using particle image velocimetry

In this work, an analysis of free convection fluid flow characteristics around a flat heated surface, slightly inclined to the horizontal, has been carried out with the help of particle image velocimetry technique. Experiments were performed on a plate immersed in water and subjected to a uniform heat flux. The influence of different inclinations of the plate and heat fluxes on the flow characteristics has been analyzed. Based on the flow characteristics, different regimes—attached, transition, and buoyant plume regime—have been identified. It is observed that the onset of transition increases with the inclination angle and decreases with the heat flux. On the other hand, the length of the transition regime increases with an increase in the inclination angle and heat flux. The plume width or plume regime is found to first decrease due to necking and then increase in the vertical direction due to horizontal diffusion. Also, an increase in heat flux and inclination angle causes an increase in plume width at a particular height from the plate. It is observed that the inner velocity boundary layer thickness decreases in the laminar regime and increases in the transition regime along the length of the plate.

Effect of geometric variation and solar flux distribution on performance enhancement of absorber tube thermal characteristics for compound parabolic collectors

A compound parabolic collector (CPC) is a concentrated solar thermal technology widely used for thermal energy storage and electricity generation. Usage of proficient absorber tube configuration improves its thermal efficiency and the present study is an attempt to numerically evaluate the feasibility of employing elliptical absorber tube design in CPCs. Initially, the thermal characteristics of the conventional circular and proposed elliptical absorber tube configurations were evaluated for an ideal condition, taking into account the solar radiation effect from Monte-Carlo ray-tracing analysis. The effect of governing factors that include fluid flow rate (0.015–0.05 kg/min), heat flux (1175–1200 W/m2), and inclination angle (3°) were analyzed for optimum condition identification delivering maximum efficiency. Further analysis was focused on evaluating the thermal loss influence with face-split and top-wall insulation conditions. Results indicated that the elliptical configuration outperformed the circular tube with an increment in the maximum temperature rise by 42.2%, 33.4%, and 27.7% for simple, face-split, and face-split top-wall insulated conditions along with better stability over the local hydrodynamic changes. Face-split analysis contributed to better realistic results over constant heat flux and it was inferred that the inclined face-split elliptical configuration exhibited maximum thermal efficiency with higher temperature rise and nominal pressure drop characteristics.

트랙션용 다자유도 구형 전동기의 구동을 위한 간접 벡터 제어 연구

The multi-degree-of-freedom spherical motor for traction has characteristics of rotation and steering. Although it is base on the rotation principle of an induction motor, only a spherical motor control method is required for rotation and steering. In order to estimate the speed command of the rotor, the mechanical angular velocity of the rotor is measured using an optical sensor, and the slip angular velocity is calculated with the current command of the d-q axis stator of the synchronous coordinate system. The rotor magnetic flux angle can be obtained in the above two ways, and through this, the vector control of the spherical motor is achieved. The desired magnetic flux component current and torque component current are distributed to operate the spherical motor. As such, the indirect vector control method has advantages in that it is simple to implement because it does not use the magnetic flux linkage of the rotor and that it is easy to operate from low speed to rated speed.