Average Spread Research Articles

Verifying Ray Tracing Amplitude Methods for Global Magnetospheric Modeling

AbstractRay tracing is a commonly used method for modeling the propagation of electromagnetic waves in Earth's magnetosphere. To apply ray tracing results to global models of wave‐particle interaction such as energetic electron scattering, it is useful to map the discrete rays to a volume filling mesh. However, some methods have inherent losses of energy from the wave source, or do not account for the full range of wave properties within a sample volume. We have developed and tested a 3D magnetospheric ray tracing code “MESHRAY” which resolves these issues. MESHRAY uses the conservation of Poynting flux through ray triplets with finite volume to determine the local field amplitudes. Electromagnetic wave energy density from all ray data points is mapped to a mesh and verified against the wave source power for energy conservation varying time step length, number of rays, and total time steps. We find that the method is self‐consistent and numerically robust. We further investigate whether the neglect of phase information and superposition has a significant impact on the accuracy of mapping wave intensity to a mesh. We find excellent agreement between the analytic solution for waves emitted by a line source in a plane‐stratified medium and an equivalent ray tracing solution. When phase information is excluded, ray tracing reproduces an average amplitude spread over regions of coherent constructive and destructive interference. This may be an important consideration for interpolating ray tracing results of longer wavelength waves such as magnetosonic, electromagnetic ion cyclotron, or ULF waves.

Effect of solution heat treatment on the microstructure and crystallographic texture of IN939 fabricated by powder bed fusion-laser beam

The effect of various solution heat treatment temperatures (i.e., 1120, 1160, 1200 and 1240 °C) on the microstructure, grain morphology and crystallographic texture of IN939 fabricated by powder bed fusion-laser beam (PBF-LB) was investigated. Microstructural analyses showed that the high-temperature gradient and rapid solidification of the PBF-LB processing caused different resulting microstructures compared to conventionally produced counterparts. The melt pool morphologies and laser scanning paths were examined in the as-fabricated samples in the XZ- and XY-planes, respectively. After the application of solution heat treatment at 1120 °C, the as-fabricated PBF-LB initial microstructure was still apparent. For solution heat treatments of 1200 °C and above, the melt pool and scanning path morphologies disappeared and converted into a mixture of columnar grains in the XZ-plane and equiaxed grains in the XY-plane. On the other hand, large equiaxed grains were observed when the samples were solutionized at 1240 °C. Additionally, γ′ phase precipitated within the matrix after all solution heat treatment conditions, which led to increase in the microhardness values. According to electron backscatter diffraction (EBSD) analyses, both as-fabricated and solution heat-treated samples had intense texture with {001} plane normal parallel to the building direction. The first recrystallized grains began to appear when the samples were subjected to the solution heat treatment at 1160 °C and the fraction of the recrystallized grains increased with increasing temperature, as supported by kernel average misorientation (KAM) and grain spread orientation (GOS) analyses.

Middle Jurassic Paleolatitude of the Tethyan Himalaya: New Insights Into the Evolution of the Neo‐Tethys Ocean

AbstractThe paleogeography of the Tethyan Himalaya (TH) during the Mesozoic is vital to constrain the evolutionary history of the Neo‐Tethys Ocean, but reliable paleomagnetic data from Jurassic rocks in this area are scarce. Here, we report the first high‐quality paleomagnetic results from the Middle Jurassic (∼175–173 Ma) Lanongla Formation limestones in the Nyalam area of the TH. For most specimens, stepwise thermal or hybrid demagnetization reveals two well‐defined magnetization components. A low‐temperature component, which is isolated between natural remanent magnetization and 200–300°C, is consistent with the present geomagnetic field direction. A high‐temperature component, which is isolated between 300–350°C/10–25 mT and 500–580°C/60–120 mT, passes fold tests at the 95% and 99% confidence level, indicating a prefolding primary magnetization. The tilt‐corrected site‐mean direction for 28 paleomagnetic sites is Ds = 331.0° and Is = −49.9° with α95 = 2.7°, which provides a Fisherian site‐mean paleopole at 23.7°N, 292.9°E with A95 = 2.8° and a paleolatitude of 31.7 ± 2.8°S for the Nyalam study area (28.6°N, 86.1°E). A comparison between the reliable Middle Jurassic‐Early Cretaceous poles obtained from the TH and those observed from the Lhasa terrane reveals that the Neo‐Tethys Ocean for the reference point (29.1°N, 86.1°E) had a latitudinal width of 3,500 ± 1,000 km at ∼174 Ma, reached its greatest width of 7,000 ± 1,000 km at ∼137 Ma, and had an average latitudinal spreading rate of ∼10.4 cm/year during ∼174–137 Ma.

Incident Report and Analysis of the 2021 Cox’s Bazar Rohingya Refugee Camp Fire in Bangladesh

AbstractAccording to the UN Refugee Agency, roughly 980,000 people live in the Cox’s Bazar region in Bangladesh, making it the largest and most densely populated refugee camp in the world. The number of fires in this settlement rapidly increased in 2021. On 22 March, a large fire event occurred, where 15 fatalities and 560 injuries were reported, and more than 9500 homes were affected leaving 45,000 homeless. This work seeks to reconstruct this incident based on firefighters’ statements, information found in the media, and satellite imagery. The study shows that (a) the fire spread extremely fast, with linear spread rates between 79 and 310 m/h and an average areal spread rate of 92,850 m2/h estimated, (b) the firefighters performed two main operations, firefighting and the creation of fire barriers, (c) the residents self-evacuated, deciding when and where to evacuate, and (d) the residents’ actions were similar to what has been observed in residential fires, with several people mentioning looking for missing family members. Fire spread is analogous to wildland fires where conflagrations spread across large areas of combustible material. This work can be used in planning for future large-scale fire incidents in tented camps, and proactively seeking ways of mitigating their impact. This is the first detailed documentation of such a large-scale refugee camp incident in the academic literature.

Revised onset age of magnetochron M0r: Chronostratigraphic and geologic implications

Abstract The timing of the onset of magnetochron M0r and its duration are disputed, reflecting both a limited set of radioisotopic dates and uncertain magnetostratigraphic correlations. We present a chronostratigraphic framework for a reversed polarity interval based on two chronometers (40Ar/39Ar, U-Pb) and newly published paleomagnetic data from the Qingshan Group, Jiaolai Basin, China. Bayesian modeling of U-Pb zircon and 40Ar/39Ar sanidine dates suggests a minimum duration of 540 ± 37 k.y. (95% credible interval) for the reversed polarity interval. These findings are compatible with an astrochronologic age model for M-sequence seafloor magnetic anomalies, indicating that the reversely magnetized sediments correspond to magnetochron M0r rather than the shorter chron “M-1r.” Integration of U-Pb and 40Ar/39Ar ages constrains the onset of M0r to 120.29 ± 0.09 Ma, which is ~1 m.y. younger than that inferred in the current geologic time scale (GTS 2020). This finding also implies that the Cretaceous normal superchron (CNS) began at 119.70 ± 0.12 Ma and that the average seafloor spreading rate during the CNS was ~3.5% higher than that inferred from GTS 2020. It also suggests that oceanic anoxic event 1a began at 119.40 ± 0.12 Ma, thereby providing an updated chronologic basis for exploring the primary trigger of this carbon cycle perturbation.

Effect of geometrical dimensions on flame spread rate over U‐shaped polyurethane facade and theoretical analysis

AbstractPolyurethane is widely used in building facades as a good energy‐saving and environment‐friendly organic material, and the U‐shaped structure is a common facade form as it could improve indoor lighting and ventilation. Through numerical simulation and theoretical analysis, this study found the flame spread rate of polyurethane foam over a U‐shaped facade was affected by the structural dimensions due to three main factors: lateral air entrainment restriction, bottom air entrainment restriction, and flame fusion between the back wall flame and side wall flame. The average flame spread rate was negative linearly correlated with the back wall width and positive exponentially correlated with the side wall length. This was due to that the side walls caused lateral air entrainment restriction, reduced the heat loss, enhanced the thermal feedback, generated an upward induced airflow close to the back wall, elongated the flame, and also caused the flame fusion between side walls and the back wall, thus accelerated the flame spread process compared to the flat structures.

Free Float in the Polish Capital Market and Its Importance for Investors

Theoretical background: Free float (hereinafter referred to as FF) refers to the ratio of shares held by small investors (less than 5%) to all shares in a company. FF investors are generally unrelated to each other or to ma-jor shareholders and they constantly review the company’s current stock market valuation and thus improve the stock market efficiency. This means that the higher the FF, the potentially higher liquidity and better valuation of the company’s shares. A low FF recalls the institution of protecting the rights of minority shareholders, calls into question the sense of maintaining a public company status, and raises the potential risk of incorrect valuation. The literature generally lacks studies referring to all these issues as well as FF statistics in Poland. Purpose of the article: The purpose of the article is to sum up the term “free float”, analyze FF statistics on the Polish capital market, indicate the link between FF and market liquidity, identify potential risks associated with listed companies having low FF and to determine whether it makes sense for the strategic investor to maintain public company status with low FF. Research methods: Theoretical analysis (including analysis of capital market laws) and statistical analysis. Main findings: The research confirmed that the relationship between FF and stock market liquidity is positive, but only considering FF in nominal terms. On the Polish capital market, as the nominal level of FF increases, market capitalization and trading liquidity increase largely and the average market spread decreases slightly. The article also points out important risks associated with low FF conditioning low liquidity, such as the risk of stock manipulation and the risk of incorrect company valuation. Potential areas for changing the law on squeeze-out/sell out institutions due to the inadequacy of the FF percentage were also pointed out.

Did quantitative easing reduce the borrowing costs of firms? The risk‐taking channel

AbstractThis paper examines the effect of the Federal Reserve's quantitative easing (QE) on the cost of bank loans and documents large heterogeneous effects across different firms. In QE1, the average loan spread is 22.7 percent lower compared to the non‐QE period. This effect falls in QE2 and OT and then rises in QE3 and the tapering period. The rates of riskier loans are restrained more than less risky loans during QEs as banks take more risks by offering lower rates to attract risky borrowers. The Fed mortgage‐backed securities purchases have a larger impact in narrowing the borrowing cost difference between riskier and safer loans than the Fed Treasury purchases. Our results are robust to borrower, year‐quarter and bank fixed effects. Overall, our findings support that the risk‐taking channel of QE plays a significant role in the corporate bank loan market.

CONSTRUCTION OF URBAN WETLAND ECOLOGICAL LANDSCAPE PLANNING MODEL BASED ON MSPA ANALYSIS METHOD

The traditional method does not accurately select the ecological landscape pattern index of urban wetland, which leads to the problems of low accuracy and long planning time, in order to solve this problem, an urban wetland ecological landscape planning model based on MSPA analysis method is constructed. By analyzing the basic components of urban wetland ecological landscape, such as patch density, aggregation index, dispersion index, average fractal dimension, landscape segmentation, shape index, spread index and Shannon diversity index, MSPA analysis method is used to extract the core area, patch area and ring of urban wetland. According to the extraction results, the minimum function of cloud fusion transformation of three-dimensional wetland ecological landscape is calculated, and the function is used to calculate the three-dimensional translation transformation amount and rotation matrix of three-dimensional wetland ecological landscape model. The data in the three-dimensional model are used for wetland ecological landscape planning, so as to complete the construction of wetland ecological landscape planning model. The simulation results show that the urban wetland ecological landscape planning accuracy of the model is high and the planning time is short.

IMPACT OF COVID ON DURATION TIME OF TREATMENT IN CERVICAL CANCER

Duration Time of treatment (DTT) in cervical cancer is an essential prognostic factor. Longer treatment duration n is the most unfavorable prognostic factor for local control. [1]The main objective of this study is to investigate the impact of the pandemic on (DTT) in cervical cancer.Through a unicentric retrospective study carried out at the Radiotherapy department of the National Institute of Oncology, for 2 years, before and during the pandemic. Results: The number of patients followed before the pandemic was 138 and 157 during the pandemic. The average age before the pandemic was 54 and 53 during the pandemic. Squamous cell carcinoma accounted for 91% versus 9% adenocarcinoma. The average spread was 53 days before the pandemic, and 51 days during the pandemic. To facilitate patient care, a guesthouse has been made available to them. Moreover, a new system for programming and organizing brachytherapy was launched in July 2019, to control sprawl in these patients, and avoid its extension. Conclusion: Our study has made it possible to assess the impact of the pandemic on sprawling in our patients and the means to overcome the constraints of travel and organization for treatment within the optimal timeframe, in order to ensure a better local control.

Pricing climate change risk in corporate bonds

Using a firm’s geographic footprint to measure its exposure to sea level rise (SLR), I find that corporate bonds bear a climate risk premium upon issuance. A one standard deviation increase in firms’ SLR exposure is associated with a 7 basis point premium, representing a 3% increase in average yield spread. This effect is more pronounced for geographically concentrated firms, within industries vulnerable to extreme weather conditions, and after the Paris Agreement. I do not find evidence that credit rating agencies account for SLR exposure at bond issuance. Results are robust to placebo tests and inverse propensity weighting to address possible endogeneity.

Decoding the nuclear symmetry energy event-by-event in heavy-ion collisions with machine learning

Inferences of the nuclear symmetry energy from heavy-ion collisions are currently based on the comparison of measured observables and transport model simulations. Only the expectation values of observables over all considered events are used in these approaches, however, observables can be obtained event-by-event both in experiments and transport model simulations. By using the light gradient boosting machine (LightGBM), a modern machine-learning algorithm, we present a framework for inferring the density-dependent nuclear symmetry energy from observables in heavy-ion collisions on the event-by-event analysis. The ultrarelativistic quantum molecular dynamics (UrQMD) model simulations are used as training data. The symmetry energy slope parameter extracted with LightGBM event-by-event from test data also by UrQMD has an average spread of approximately 30 MeV from the truth, and is found to be robust against variations in model parameters. In addition, LightGBM can identify features that have the greatest effect on the physics of interest, thereby offering valuable insights. Our study suggests that the present framework can be a powerful tool and may offer a new paradigm to study the underlying physics in heavy-ion collisions.

Effects of flame retardants on extinction limits, spread rate, and smoke release in opposed-flow flame spread over thin cylindrical polyethylene samples in microgravity

Though flame retardants are considered for use in spacecraft, their performances in microgravity are still poorly understood. To assess their effects on flame extinction, opposed flame spread rate, and smoke emission in the absence of buoyant flows, thin cylindrical samples of Low Density Polyethylene (LDPE) loaded with intumescent flame retardants are ignited in parabolic flights. Two types of flame retardants characterized by different mechanisms of intumescence are considered, namely Expandable Graphite, (EG), and Ammonium polyphosphate / Pentaerythritol, (AP), for which thermal stress and chemical recombination drive physical expansion, respectively. Observations are then reported and contrasted with results obtained at normal gravity for different flame retardant loads, under varying oxygen content at given ambient pressure and flow velocity. Focusing on the flame leading edge, results related to flame spread and flame extinction are analyzed first. At normal gravity, increasing the flame retardant load improves fire safety through an increase in the flame extinction limit on the one hand, and a reduction in the average flame spread rate for all oxygen contents studied on the other hand. In contrast, results in microgravity show no modification in the extinction limit over the range of flame retardant loads studied, and the benefits in average flame spread rate reduction are less pronounced. Investigating then radiative quenching at the flame trailing edge, smoke emission is never evidenced at normal gravity. However, in microgravity, the addition of flame retardants increases the range of conditions leading to smoke emission, which is detrimental to fire safety. These observations are valid for both flame retardants, yet more pronounced for EG-loaded samples than AP-loaded samples. These ambivalent effects on fire safety of AP and EG addition in microgravity, which are not evidenced at normal gravity, call for a cautious integration of flame retardants in the scope of space exploration.

Gravity-driven coatings on curved substrates: a differential geometry approach

Drainage and spreading processes in thin liquid films have received considerable attention in the past decades. Yet, our understanding of three-dimensional cases remains sparse, with only a few studies focusing on flat and axisymmetric substrates. Here, we exploit differential geometry to understand the drainage and spreading of thin films on curved substrates, under the assumption of negligible surface tension and hydrostatic gravity effects. We develop a solution for the drainage on a local maximum of a generic substrate. We then investigate the role of geometry in defining the spatial thickness distribution via an asymptotic expansion in the vicinity of the maximum. Spheroids with a much larger (respectively smaller) height than the equatorial radius are characterized by an increasing (respectively decreasing) coating thickness when moving away from the pole. These thickness variations result from a competition between the variations of the substrate's slope and mean curvature. The coating of a torus presents larger thicknesses and a faster spreading on the inner region than on the outer region, owing to the different curvatures in these two regions. In the case of an ellipsoid with three different axes, spatial modulations in the drainage solution are observed as a consequence of a faster drainage along the short principal axis, faithfully reproduced by a three-dimensional asymptotic solution. Leveraging the conservation of mass, an analytical solution for the average spreading front is obtained. The solutions are in agreement with numerical simulations and experimental measurements obtained from the coating of a curing polymer on diverse substrates.

An experimental investigation of flames spread interaction over two parallel electrical wires of various separations

This paper investigated experimentally the interaction behaviors of flames spreading over two parallel adjacent electrical wires at various separation distances. Experiments were carried out with thin electrical wires of copper inner core and polyethylene (PE) insulation. The separation distances between the two parallel electrical wires (their core center distance) were ranged from 1 mm (flames merge) up to 20 mm (flames completely separate with behavior identical to that of one single electrical wire) to reveal the transition of the flame behaviors with increasing separation distance. The flame base width along the wire (Wf), flame height (Hf), average mass loss rate (AMLR, m˙) and flame spread rate (FSR, Vf) were measured to quantify this transition. Results showed that the flame height, the AMLR and the FSR all increased first and then decreased with increasing of separation distance. The FSR and AMLR were maximized at the same separation distance during the transition of flames separating from its base to complete separation with increasing separation distance. Five regimes were identified for the variation transition of flame spread rate with increasing separation distance, which can be interpreted physically by the change of convection and radiation feedback with separation distance. The maximum FSR of the wire-pair, which occurred at the separation of about 8∼10 times of the wire outer diameter, was around 12% ∼22% greater than that over one single wire. Such FSR increment was more remarkable if the wire size was larger. This experimental study provides fundamental knowledge, quantitative data and physical understanding of the phenomenon of flame spreading interactions over two parallel adjacent electrical wires.

Impact of Jatropha – Diesel Blend Drops on a Heated Surface

The impact of various Jatropha – diesel blend drops on a surface is presented by varying the surface temperature and the Weber number. Drop viscosity and density are observed to play critical roles. The maximum spread, average spreading velocity, and the recoiling intensity of a given drop are found to increase with surface temperature at a given Weber number and with Weber number at a given surface temperature. The spreading increases with the blend’s diesel content due to the decrease in viscosity and density. The viscosity and density of a given drop decline with the surface temperature, making the drop dissipate less energy and have higher inertia while spreading. The viscosity and surface energy reduction cause a drop to recede faster with the surface temperature. The maximum spread can be predicted well when the change in viscosity and density with surface temperature is incorporated in existing models used for lower surface temperatures.

Switchbacks in the Young Solar Wind: Electron Evolution Observed inside Switchbacks between 0.125 au and 0.25 au

Switchbacks are localized deviations from the nominal Parker spiral field in the solar wind. In this study, we investigate the electron distributions inside switchbacks, focusing primarily on the suprathermal (halo and strahl) populations. We explore electron parameters in relation to the angle of rotation of the magnetic field from radial to determine whether electron distributions observed within switchbacks have any differences from those outside of switchbacks. Our observations reveal several trends in the suprathermal electron populations inside switchbacks. We find that the sunward deficit in the electron velocity distribution function typically observed near the Sun is filled in at larger rotation angles. This results in the suprathermal electron density and heat flux in the antistrahl direction changing from a negative to a positive value. On many days, we also observe a positive correlation between the halo density and rotation angle, and this may suggest that the growth of the halo may fill in the sunward deficit. We also find that strahl distributions have an increased average angular spread at large magnetic field rotation angles. The increase in suprathermal electron flux in the antistrahl direction, and the increase in strahl width, together could suggest that enhanced scattering occurs inside switchbacks. Electron core beta values tend to increase with the magnetic field rotation angle, mainly due to a decrease in magnetic pressure. An increase in electron beta may favor the growth of instabilities inside switchbacks. The Parker Solar Probe observations therefore support an enhanced role for wave–particle interactions in switchbacks.

Machine learning neural-network identification for dynamic recrystallization grains during hot deformation of nickel-based superalloy

A novel multiscale dynamic standard for electron backscatter diffraction (EBSD) test has been constructed through the neural network to study the recrystallization behavior of Incoloy 925 superalloy during hot deformation. The average grain size distribution and grain orientation spread (GOS) distribution at different stages of dynamic recrystallization were analyzed. The recrystallized grains and deformed grains were described by grain size, length-diameter ratio, GOS, and GOS maximum value. The neural network can obtain the weight ratio of different influencing factors by learning the grain characteristics, which reveals excellent recognition accuracy for the different deformation states. • A novel multiscale dynamic standard was constructed through ANN for DRX recognition. • The “feature engineering” was quantified by grain size, length-diameter ratio, GOS, and GOS max value. • The ANN standard shows higher adaptability in different Ni-based superalloys.

Bending behavior of engineered cementitious composites (ECC) with different recycled and virgin polymer fibers

This study evaluated Engineered Cementitious Composites (ECC) with polyvinyl alcohol (PVA), polypropylene (PP) or recycled polyester (POL) fibers inserted in a matrix with elevated silica fume content. Several PP (2.2–2.6%) and POL (2.3–2.7%) contents were tested and compared to a compound containing 2.0% PVA. Flexural bending strength tests, the bending rupture modulus, number and width of cracks and deformation were measured at 5 different curing ages (7, 14, 28, 56 e 84 days). The test results also showed that in the fresh state, ECCPVA2.0 presented the best result with an average spread of 255 mm, followed by ECCPP2.4 and ECCPOL2.3. All Γ values obtained confirmed that all composites attained plastic consistency. In the hardened state, composites with POL fibers had tensile strength performance similar to PVA fibers with regards to deformation, deflection, rupture modulus, average crack width and number of cracks. In addition, ECCPOL2.7 demonstrated mechanical properties superior to ECCPVA2.0. So, the use of 2.7% POL content resulted in strengths higher than the reference PVA compound and demonstrated the potential of POL fibers in ECC development at ages over 28 days. The use of recycled POL fibers, at a content of 2.7%, resulted in an increase in the ductility of the composite, reaching the values of ECC-PVA at 28 and 84 days. On the other hand, PP composites did not present the expected behavior of an ECC. More specifically, the matrix had high tensile strength, modulus of elasticity and tenacity, which limited crack formation and overloaded the reinforcement fibers. Thus, PP fibers were deemed incompatible for ECCs with rich matrices.

The complex stellar system M 22: confirming abundance variations with high precision differential measurements

ABSTRACT M 22 (NGC 6656) is a chemically complex globular cluster-like system reported to harbour heavy element abundance variations. However, the extent of these variations and the origin of this cluster is still debated. In this work, we investigate the chemical in-homogeneity of M 22 using differential line-by-line analysis of high-quality (R = 110 000, S/N = 300 per pixel at 514 nm) VLT/UVES spectra of six carefully chosen red giant branch stars. By achieving abundance uncertainties as low as ∼0.01 dex (∼2 per cent), this high precision data validates the results of previous studies and reveals variations in Fe, Na, Si, Ca, Sc, Ti, Cr, Mn, Co, Ni, Zn, Y, Zr, La, Ce, Nd, Sm, and Eu. Additionally, we can confirm that the cluster hosts two stellar populations with a spread of at least 0.24 dex in [Fe/H] and an average s-process abundance spread of 0.65 dex. In addition to global variations across the cluster, we also find non-negligible variations within each of the two populations, with the more metal-poor population hosting larger spreads in elements heavier than Fe than the metal-rich. We address previous works that do not identify anomalous abundances and relate our findings to our current dynamical understanding of the cluster. Given our results, we suggest that M 22 is either a nuclear star cluster, the product of two merged clusters, or an original building block of the Milky Way.