Flux Density Variations Research Articles

Magnetic Railway Sleeper Detector

In an ever expanding railway network all around the world, the need for track maintenance grows steadily. Traditionally, one major part of track maintenance is ramming large vibrating steel picks into the gravel between and under railway sleepers to compress the gravel and generate a safe substructure. Even today, maintenance personnel still have to manually locate the sleepers if they cannot be detected by computer vision systems or visually by the operator. Here we developed a first of its kind magnetic sleeper detector, even able to find sleepers, buried in gravel, undetectable by vision based systems. Our approach of magnetic detection is based on a DC magnetic field excitation and a detector moving with respect to the rail system, including the sleepers and fasteners for mounting the rails. Due to railway application constraints a large air gap between the sensor and the sleeper structure is required, which significantly complicates the magnetic sensing task for robust sleeper detection. The design and optimization of the magnetic circuit was based on extensive 3D simulation studies to ensure highest possible variation in magnetic flux density at the sensor locations for absence and presence of a sleeper. Furthermore, a low noise and high sensitivity electronic circuit has been realized to cope with sensor signal offsets from unknown or changing sensor orientations with respect to the earth’s magnetic field, or magnetic interferences from other trains potentially passing by during active measurements. Since we only want to detect sleepers in close vicinity of the moving sensor system, digital signal processing of the acquired signals can easily compensate for disturbing slowly changing or static field components within real world application scenarios. We demonstrate that magnetic detection of even buried sleepers on railway tracks is possible for distances of up to 172 mm between the sensor and the sleeper. This enables an even higher level of railway maintenance automation previously impossible in certain scenarios.

A review of approaches to assessment of potential radon hazard of land plots

According to Rosstat statistics, in recent years there has been a tendency in the Russian Federation to increase the intensity of construction, while both the number of buildings put into operation and their total area are increasing. The assessment of the potential radon hazard of land plots for construction provides the possibility of timely inclusion of the necessary protective (preventive) measures against radon in the design of buildings. This is a legal requirement in cases where the density of radon flux from the ground surface within the building area exceeds the established hygienic standards (action levels). The paper presents a review of Russian and foreign approaches to assessing the potential radon hazard of land plots conducted within the framework of engineering and environmental surveys. The current regulatory requirements to radiation safety indicators of land plots for construction of residential, public and industrial buildings and facilities in the Russian Federation are analyzed. The main drawbacks of the algorithm for determining the potential radon hazard of land plots, used in the current guidelines MU 2.6.1.2398-08 approved at the federal level more than 15 years ago, are described. Critical remarks (the unsuitability of the value of density of radon flux from the ground surface for designing radon protective and mitigation (remedial) measures, lack of consideration of seasonal variations of radon flux density, etc.) accumulated over the years as a result of practical application of these guidelines are presented. Benefits and drawbacks of foreign approaches to assessing the potential radon hazard of the territory based on the results of measurements of radon concentration in soil gas, as well as the very possibility of a transition in Russian regulations from the density of radon flux from the ground surface to the radon concentration in soil gas, are analyzed. Some rational proposals of various Russian research teams on improving the algorithm for determining the potential radon hazard of land plots are considered.

A Pressure Sensor Based on the Interaction between a Hard Magnet Magnetorheological Elastomer and a Hall Effect Structure

In this article, we report a novel pressure sensing method based on the Hall effect and a hard magnet magnetorheological elastomer (hmMRE). The elastic property of the MRE under pressure was used to generate spatial variation in the magnetic flux density around the MRE, and the variation was detected by the Hall effect device underneath. As the first development in this kind of pressure sensing mechanism, we conducted research for the following three purposes: (1) to verify the Hall effect on the output signal, (2) to understand the sensor output variations under different modes of operation, and (3) to utilize the mechanism as a pressure sensor. We characterized the sensor with its operation parameters, such as signal polarity switching depending on wiring directions, signal amplitude, and offset shift depending on the input voltage. Based on the analyses, we concluded that the Hall voltage represents the pressure applied on the hmMRE, and the new pressure sensing mechanism was devised successfully.

Impact of Fine Water Mist Curtains on Fire Safety in Historic Buildings: A Case Study of Foshan Historical and Cultural District, Guangdong Province, China

ABSTRACT To address inadequate fire separation distances in historical buildings leading to extensive fire spread, practical research employing Fire Dynamics Simulator (FDS) was conducted. The study involved simulating a historical and cultural block in Foshan City to analyze variations in heat flux density and temperatures within a 5-meter radius of windows under fire powers of 1.5 MW, 6 MW, and 10 MW, with window openings at 10%, 25%, and 50%, respectively. The aim was to preserve the original architectural integrity without modifying existing fire separations. Augmentation of fire protection through the implementation of a fine water mist water curtain between buildings was proposed, and its efficacy in smoke and heat insulation was evaluated. Results indicate that, at 1.5 MW fire power, adjacent structures remain relatively secure with current fire separations. However, at 6 MW and 10 MW, fire spread to neighboring buildings was significant regardless of window opening area. Implementation of the water curtain with a nozzle flow coefficient (K) of 80, typical for standard coverage area sprinkler nozzles, and a spacing of 0.8 m, proved effective in enhancing smoke and heat insulation while also offering cost efficiencies. Optimal results were achieved with an average droplet size of 200 µm and nozzle pressure set at 6.0 MPa, corresponding to a nozzle flow rate of 615 L/min. These findings provide valuable insights for drafting specifications for the adaptive reuse of historical buildings and deploying fine water mist water curtains in confined spaces.

General relativistic effects and the near-infrared variability of Sgr A*

A systematic study, based on the third-moment structure function, of Sgr A*’s variability finds an exponential rise time, τ1,obs = 14.8−1.5+0.4 minutes, and decay time, τ2,obs = 13.1−1.4+1.3 minutes. This symmetry of the flux-density variability is consistent with earlier work, and we interpret it as being caused by the dominance of Doppler boosting, as opposed to gravitational lensing, in Sgr A*’s light curve. A relativistic, semi-physical model of Sgr A* confirms an inclination angle of i ≲ 45°. The model also shows that the emission of the intrinsic radiative process can have some asymmetry even though the observed emission does not. The third-moment structure function, which is a measure of the skewness of the light-curve increments, may be a useful summary statistic in other contexts of astronomy because it senses only temporal asymmetry; that is, it averages to zero for any temporally symmetric signal.

A comprehensive study on electromagnetic torque and rotor UMP based on an improved 3D static air-gap eccentricity model

Static air-gap eccentricity (SAGE) is a common fault in generators. Current researches primarily focus on the parallel SAGE types, while the inclined static air-gap eccentricity (ISAGE) has been rarely investigated. This paper proposes an improved air-gap eccentricity model and presents a study on the electromagnetic-mechanical properties in synchronous generators under typical ISAGE running conditions. Such electromagnetic-mechanical properties include not only the magnetic flux density (MFD) variations, but also the mechanical responses of the electromagnetic torque (EMT) and rotor unbalanced magnetic pulls (UMP). The typical ISAGE factors include: 1) a varied rotor inclined angle θ, and 2) different values of axial inclined distance z (indicates the offset combination case of the two rotor ends). This work is based on the MFD analysis calculation. Theoretical analysis, finite element analysis, and experimental study are carried out, respectively, by taking a 5 kVA two-pole prototype generator as the study object. It is shown that the electromagnetic-mechanical properties of the generator will change when the inclined eccentricity occurs. The EMT, and the rotor UMP as well as the vibrations will increase as the rotor inclined θ and z increase. Specifically, the 2nd harmonic has the most significant variation.

Long-term Variation of the Solar Polar Magnetic Fields at Different Latitudes

The polar magnetic fields of the Sun play an important role in governing solar activity and powering fast solar wind. However, because our view of the Sun is limited in the ecliptic plane, the polar regions remain largely uncharted. Using the high spatial resolution and polarimetric precision vector magnetograms observed by Hinode from 2012 to 2021, we investigate the long-term variation of the magnetic fields in polar caps at different latitudes. The Hinode magnetic measurements show that the polarity reversal processes in the north and south polar caps are non-simultaneous. The variation of the averaged radial magnetic flux density reveals that, in each polar cap, the polarity reversal is completed successively from the 70° latitude to the pole, reflecting a poleward magnetic flux migration therein. These results clarify the polar magnetic polarity reversal process at different latitudes.

Effects of La-Co Co-Substitution and Magnetic Field Pressing on the Structural and Magnetic Properties of SrM Hexaferrites

We carefully investigated the effects of La-Co co-substitution and magnetic field pressing (MFP) on the structural and magnetic properties of SrM hexaferrites. Samples composed of Sr1−xLaxFe12−xCoxO19 were sintered at 1230 °C for 2 h in air with sintering additives composed of 0.7 wt% CaCO3 and 0.7 wt% SiO2. A single M-type phase was confirmed to exist up to x = 0.3. Rietveld refinement revealed a slight decrease in lattice parameter a and the unit cell volume (Vcell) with an increasing x, while parameter c showed a significant decrease. The saturation magnetization (Ms) values increased from 70.90 to 72.40 emu/g with an increasing x from 0.0 to 0.15 and then decreased to 71.38 emu/g with further increasing of x to 0.3, while the anisotropy field (Ha) increased from 17.7 to 25.9 kOe, leading to a continuous increase in the intrinsic coercivity (Hci), from 3.52 to 5.00 kOe, respectively. Using the MFP process, the c-axis of M-type hexaferrite grains could be effectively aligned to the applied field direction, which significantly affected the microstructures and, thus, magnetic properties of samples. Unlike non-MFP samples, exhibiting a significant increase in the average grain size (davg) but almost unaltered average thickness (tavg) with an increasing x from 0.0 to 0.3, MFP-processed samples exhibited almost unaltered davg values but a continuous decrease in tavg. Consequently, the variation in remanent flux density (Br) versus x followed that of Ms versus x and thus exhibited the highest Br of 4.05 kG for x = 0.15, leading to the highest maximum energy product {(BH)max} of 3.62 MGOe. With an increasing x from 0.0 to 0.3, the Hci values continuously increased from 3.14 to 3.84 kOe mainly due to a continuous increase in Ha, although they were significantly lowered in comparison with those of non-MFP samples because of a large increase in Br for a given composition x. A higher Mr/Ms ratio always resulted in a larger (BH)max in our samples regardless of x. A careful comparison of the microstructures and magnetic properties between MFP and non-MFP samples provided valuable insights into a broad area of permanent magnet optimization.

Wideband polarization and spectral properties of 18 high Galactic latitude pulsars

The broad-spectrum polarization and spectral characteristics of pulsars contain crucial information about the origin of their radio emission. These properties, together with pulsar flux density variations, can also be used to guide future surveys of radio pulsars and probe the Galactic interstellar medium. In this paper, we present studies of 18 pulsars at high Galactic latitudes using the Ultra-Wideband Low (UWL) receiver of the Parkes radio telescope. For these pulsars, we measured their wideband flux densities, spectral indices, and polarization fractions. We obtain seven new rotation measures (RMs) and refine the RMs of another ten pulsars. In this sample of pulsars, we observed significant variations in their flux densities, suggesting that previous shallow surveys were likely to miss a population of pulsars at high galactic latitude. In addition, we identified a previously reported isolated pulsar (PSR J1947−18) as a potential binary system.

Influence of choosing materials on 6/4 switched reluctance motor performance

The Switched Reluctance Motor (SRM) is used in many industrial applications that require high torque due to its ability to achieve high and efficient performance, simplicity, low material costs and ease of design. This motor functions on the principle of generating motion by attracting and repulsing magnetic cores. The SRM is characterized by the efficient use of energy in applications that require rapid changes in speed and has a higher resistance to shocks and vibrations. Among the essential factors that affect the performance of the SRM motors are the embrace of poles stator and rotor, dimensions, the size of the motor, the shapes of rotor geometry and the number of stator and rotor poles. This paper aims to study the effect of material selection on improving the SRM performance. First, we created a basic design of the SRM with appropriate characteristics to obtain the best operation conditions of high speed and torque. Then, we applied different materials and compared the obtained results using the ANSYS RMxprt tool. We focused on studying the effect of selecting materials in the rotor and stator parts on the SRM 6/4 performance through the efficiency, total losses, speed and rated torque. After comparing and analyzing the basic results, a two-dimensional model of the SRM was created using the ANSYS Maxwell 2D tool to evaluate the motor’s performance. The analysis includes the curves of torque, speed, current, flux linkages and voltage, in addition to the variation of flux lines and magnetic flux density. The results were analyzed using the finite element method (FEM), which is characterized by speed and accuracy in electromagnetic analysis and various data.

Modelling of sap flux density of oak in a humid region in China

AbstractTranspiration plays a vital role in determining the watershed water cycle. However, we still have little knowledge of the characteristics of tree transpiration in the Hanjiang River Basin, which is the water source for the middle route of South‐to‐North water diversion project. Here, we measured sap flux density of oak trees (Quercus, the dominant species here) at the 10‐min resolution for 2 years and explored its response to the environmental conditions. The incoming short‐wave radiation and vapour pressure deficit well explained the variation of daytime sap flux density, and a statistical model was then proposed to calculate the daytime sap flux density correspondingly; then a nighttime sap flux density module was proposed based on the daytime sap flux density calculation. Sap flux density showed clear counter‐clockwise hysteresis response to incoming short‐wave radiation, and clockwise hysteresis response to vapour pressure deficit. Our sap flux density model can well reproduce the corresponding hysteresis response to incoming short‐wave radiation and vapour pressure deficit. This study unravelled the environmental controls of sap flux density of the oak trees in the Hanjiang River Basin, proposed an efficient model for the sap flux density simulation, provided important knowledge for understanding the corresponding forests' water use, which is of critical significance in determining the water availability for the middle route of the South‐to‐North water diversion project.

Impact of 3D air gap eccentricity on winding insulation temperature characteristic in PMSG

The static air gap eccentricity is one of the prevalent faults in permanent magnet synchronous generators. In previous studies, the variation of magnetic flux density, stator current and vibration have been studied mostly. However, the temperature characteristic of winding insulation under 3D static air gap eccentricity fault is rarely investigated. As a supplement, this paper comprehensively analyzes the influence of radial static air gap eccentricity, axial static air gap eccentricity and the combined static air gap eccentricity (radial static air gap eccentricity and axial static air gap eccentricity) fault on the winding insulation thermal response. The whole work is based on not only the loss of core and windings but also the temperature rise of the winding insulation, which is carried out through theoretical analysis, finite element calculation, and experiment verification. It is shown that radial static air gap eccentricity will increase the winding insulation temperature whatever in singe radial static air gap eccentricity or combined static air gap eccentricity, while axial static air gap eccentricity has the opposite effect. Specifically, the winding insulation temperature in radial static air gap eccentricity 0.1 mm, 0.2 mm and 0.3 mm cases are 57.18℃, 59.10℃ and 61.04℃, respectively, which is 3.29℃, 5.21℃ and 7.15℃ higher than that under normal condition. However, under axial static air gap eccentricity, winding insulation temperature will decrease by 1.84℃, 4.11℃ and 5.9℃, respectively. When axial static air gap eccentricity is unchanged and radial static air gap eccentricity is increased, the winding insulation temperature will increase by 1.5℃ and 3.23℃, respectively. On the contrary, when radial static air gap eccentricity is unchanged and axial static air gap eccentricity increases, the winding insulation temperature decreases by 2.54℃ and 5.66℃, respectively. The end part and the join between the end and line parts of the winding insulation are the most dangerous positions to suffer from static thermal wear.

Photosystem II efficiency in response to diurnal and seasonal variations in photon flux density and air temperature for green, yellow-green, and purple-leaved cultivars of sweet potato [Ipomoea batatas (L.) Lam

Photosystem II efficiency in response to diurnal and seasonal variations in photon flux density and air temperature for green, yellow-green, and purple-leaved cultivars of sweet potato [Ipomoea batatas (L.) Lam

MODELING OF SPATIAL-TEMPORAL VARIATIONS OF PHYSICAL PROCESS PARAMETERS IN THE IONOSPHERIC PLASMA OVER UKRAINE DURING THE MAXIMUM PHASE OF THE 24-TH SOLAR ACTIVITY CYCLE (2012—2015)

The object of research is physical processes occurring in the ionospheric plasma. The subject of research: spatial-temporal variations of the main parameters of the ionospheric plasma, which were obtained using incoherent scatter radar. Research methods include the ground-based radiophysical method of incoherent scatter of radio waves, statistical analysis of observation results, and semi-empirical modeling of parameters of dynamic and thermal processes. Modeling and analysis of spatial-temporal variations of the dynamic and thermal processes parameters in the ionosphere during the maximum phase of the 24th solar activity cycle (2012—2015) have been performed using experimental data obtained by the Kharkiv incoherent scatter radar. For the periods of the equinoxes and solstices, diurnal dependences of process parameters in the ionospheric plasma at altitudes from 210 to 450 km were constructed. The values of plasma transfer velocity due to ambipolar diffusion, the density of the full plasma flux, and the flux of charged particles due to ambipolar diffusion were determined. The values of the energy supplied to the electron gas, the density of the heat flux transferred by electrons from the plasmasphere to the ionosphere, as well as the velocity of the equivalent neutral wind and the meridional component of the neutral wind velocity, were calculated. It was established that for the considered periods, the effects of space weather variations and geomagnetic activity were significantly manifested in variations of the plasma flux density due to ambipolar diffusion, the density of the full plasma flux, as well as the energy supplied to electrons per unit time. Quantitative and qualitative characteristics of these parameters were typical but changed significantly (by 2…3 times) in some cases, even with a slight increase in geomagnetic activity.

Radio Properties of the Quasar J1718+4239, the Proposed Source of the Neutrino Event IceCube-201221A

NVSS J171822+423948 was recently identified as the most probable counterpart of the neutrino event IC-201221A. Based on the highly variable γ-ray, optical, and mid-infrared emission, the dates of the flaring events, and optical spectroscopy in the field of interest, this object was classified as a neutrino-emitting blazar candidate. Since its radio properties were not discussed in detail, we present archival observations. High-amplitude total radio flux density variability supports the connection between the flares at higher energies and the neutrino event.

Large-scale Effect of an Accretion Burst in the High-Mass Young Stellar Object G358.93-0.03-MM1

The high-mass young stellar object G358.93-0.03-MM1 underwent a rapid accretion burst event from 2019 January to June, resulting in flares observed in most class II methanol maser transitions starting in mid-January. In contrast, the 22.235 GHz water maser flare started in mid-April. To investigate the physical origin of this significant difference, we made the Karl G. Jansky Very Large Array observations toward the G358.93-0.03 region on 2019 March 23 and April 4 and obtained the intensity and spatial distribution images of the water maser as well as the continuum emissions at Ku and K bands on the epoch close to the water maser flare. A comparative analysis, incorporating previously reported detections in February (pre-water maser flare) and June (post-water maser flare), reveals the time lag between the accretion burst and water maser flare. These observations confirm the variations of the propagation speed of a heatwave induced by the accretion burst in different directions: the heatwave is decelerated in dense regions (e.g., the disk and jet), whereas in directions from G358-MM1 to water maser components, the heatwave speed is supposed to be close to the speed of light. Variations in flux density and spatial positions were detected for water masers and continuum emissions, indicating that the accretion burst event originating from G358-MM1 affects not only the immediate environment within a dense structure of 0.″2 (1400 au at a source distance of 6.75 kpc) around MM1 itself, but also exerts influence on broader-scale regions extending up to approximately 3″ (21,000 au).

The W-tube energy pile heat transfer model with variable heat flow considering heat exchange between pile and circulating water

In order to provide a more comprehensive depiction of the actual heat transfer process in energy piles, this research paper presents an approximate solution for a finite line heat source model operating under variable heat flow conditions. This solution is established by integrating the finite line heat source model and the superposition principle. Furthermore, the W-tube heat exchanger is divided into many segments, and a segmented superposition approach is used based on the thermal response. Consequently, a heat transfer model for a single-pile heat source is formulated, taking into consideration the heat exchange between the circulating water and the energy pile. Notably, the soil temperature predicted by this proposed model closely aligns with the results obtained from the FLUENT numerical model, thereby substantiating the accuracy of the proposed approach. Simultaneously, the heat transfer model is employed to analyze variations in temperature and heat flux density within the heat exchanger and to investigate the influence of parameters such as mass-flow rate, pile-soil heat transfer coefficient, pile-soil density, and pile-soil specific heat capacity on the heat transfer characteristics of energy piles. This model enables the determination of time-varying heat flux and precise outlet temperature, thereby facilitating a rapid assessment of the heat transfer efficiency of energy piles.

A Novel Combined Method for Measuring the Three-Dimensional Rotational Angle of a Spherical Joint.

To improve the measurement accuracy of the three-dimensional rotation angle of a spherical joint, a novel approach is proposed in this study, which combines magnetic detection by a Hall sensor and surface feature identification by an eddy current sensor. Firstly, a permanent magnet is embedded in the ball head of a spherical joint, and Hall sensors are set and distributed in the ball socket to measure the variation in the magnetic flux density when the spherical joint rotates, which are related to the 3D rotation angle. In order to further improve the measurement accuracy and robustness, we also set grooves on the ball head and use eddy current sensors to synchronously identify the rotation angle of the ball head. After the combination of two signals is performed, a measurement model is established using the RBF neural network by training, and the real-time measurement of the 3D rotation angle of the spherical joint is realized. The feasibility and superiority of this method are validated through experiments. The experimental results indicate that the measurement accuracy is substantially promoted compared to the preliminary measurement scheme based on spherical coding; the average measurement error of the single axis is reduced by 9'9″. The root mean square errors for the measurements of the 3D rotation angles in this proposed method are as follows: pitch angle α has an error of 1'8″, yaw angle β has an error of 2'15″, and roll angle γ has an error of 29'6″.

A Comprehensive Observational Study of the FRB 121102 Persistent Radio Source

FRB 121102 is the first fast radio burst to be spatially associated with a persistent radio source (QRS 121102), the nature of which remains unknown. We constrain the physical size of QRS 121102 by measuring its flux-density variability with the VLA from 12 to 26 GHz. Any such variability would likely be due to Galactic refractive scintillation and would require the source radius to be ≲1017 cm at the host-galaxy redshift. We found the radio variability to be lower than the scintillation theory predictions for such a small source, leaving open the possibility for non-AGN models for QRS 121102. In addition, we roughly estimated the mass of any potential supermassive black hole (BH) associated with QRS 121102 from the line width of the host-galaxy Hα emission using a new optical spectrum from the Keck Observatory. The line width indicates a supermassive BH mass of ≲104∼5 M ⊙, too low for the observed radio luminosity and X-ray luminosity constraints, if QRS 121102 were an AGN. Finally, some dwarf galaxies that host supermassive BHs may be the stripped cores of massive galaxies during tidal interactions with companion systems. We find no nearby galaxy at the same redshift as the QRS 121102 host from low-resolution Keck spectra or the PanSTARRS catalog. In conclusion, we find no evidence supporting the hypothesis that QRS 121102 is an AGN. We instead argue that the inferred size and flat radio spectrum favor a plerion interpretation. We urge continued broadband radio monitoring of QRS 121102 to search for long-term evolution.

Irradiation device development with changing neutron spectrum

This paper presents a sketch drawing of the developed design of an irradiating device, which allows to regulate the neutron energy spectrum in it, as well as the results of neutron-physical calculations with predicted values of the range of neutron flux density variation in different energy groups. It is shown that the fraction of thermal and over-thermal neutrons in the dry irradiation channel increases with increasing beryllium filling packing fraction. While the fraction of fast neutrons (> 1.15 MeV) decreases. In the wet irradiation channel, the dependence of thermal and over-thermal neutrons is similar to that in the dry channel, but the effect is much smaller.