Phase Angle Approaches Research Articles

Light Scattering From High‐Porosity 3D Simulants of the Lunar Regolith at Small Phase Angles

AbstractLunar regolith consists of unconsolidated grains with high porosity, called the fairy castle structure. It is closely linked to the lunar opposition effect, which is the effect where brightness sharply increases as the phase angle approaches 0. However, owing to the Earth's gravity, it is difficult to reproduce the structure to study the physical characteristics of the lunar fairy castle structure in the laboratory. We designed a lunar fairy castle structure model for 3D printing. These models had high porosity and were simplified to tree‐like shapes. Various porous conditions of the surface were considered, represented by the number of trees, maximum trunk length, and maximum branch angle. In this study, a laboratory experiment was conducted to measure the reflectance of simulants with a fairy castle structure within a small phase angle range from 1.4 to 5.0. The result is analyzed for the sample porosity with the tangential slope of the reflectance S, which denotes the strength of the opposition effect. In addition, the results of this study were compared with lunar observation data. The porous samples exhibited a relatively large S value. The influence of branch length and attachment angle was very weak in this study. Samples with a porosity between 0.78 and 0.82 represent the similar S values to the lunar observation data, a mean porosity of lunar regolith. In conclusion, our findings suggest a potential correlation between porosity and the opposition effect in printed samples, proposing a new research approach for understanding the lunar opposition effect.

The Applicability of Limiting Phase Angle Temperatures for Specifying Asphalt Binder Low Temperature Performance

The paper discusses the applicability of using limiting phase angle temperatures, measured in the Dynamic Shear Rheometer, for low temperature ranking of performance, in comparison with limiting low temperature grades in accordance with AASHTO TP 122-16 extended Bending Beam Rheometer method. During this study, also other low-temperature test methods were compared to each other. For this purpose, 13 asphalt binders were sourced from around North-Eastern Europe, twelve of which are currently used throughout Estonia as well as the neighbouring countries. The thirteenth was a high-quality Laguna Venezuela binder that is no longer commercially available in the region but was deemed suitable for comparison. Samples were tested to measure their needle penetration, Superpave Grades, Fraass breaking points, AASHTO TP 122-16 limiting low temperature grades and limiting 30° phase angle temperatures. Additionally, a correlation found in previous work was applied to the set of samples studied in this paper. Of the binders tested, the low temperature behaviour of the Venezuelan binder stands out with better performance. The analysis suggests that the twelve commercially available binders are from a similar source which was observed through their tendency to undergo thermo-reversible aging. The study shows that the phase angle approach provides a reasonable surrogate for the AASHTO TP 122-16 limiting low temperature grade. However, the latter should currently remain the preferred approach.

Effects of thermal treatment on the mechanical and electromagnetic properties of 9Cr-1Mo steel

This paper presents the effects of thermal treatment conditions on the mechanical properties of 9Cr-1Mo steel. Each sample was normalized at 1,040 °C for 1 h prior to tempering at different temperatures for 2 hours. Three levels of tempering conditions, 600, 650, and 700 °C, were tested in this study. After treatment, the metallurgical structures of the samples were observed and characterized by optical microscope (OM), scanning electron microscope (SEM), energy dispersive X-ray spectrometer (EDS) and X-ray diffraction (XRD). Hardness and static tensile of the samples at room and elevated temperatures were also measured and analyzed. Non-destructive testing (NDT) associated with the eddy current method was employed to detect the microstructural changes of samples. The results revealed that the lath martensitic structure, lath boundaries, coarse precipitates, and prior austenite grain boundaries were found at grain boundaries and inside the matrix region. The average size of the particle and area fraction of carbide precipitates decreased with tempering temperature increases from 600 − 650 °C. The true yield stress and true ultimate tensile stress decreased while true strain increased when the tempering process was applied after the normalization. In addition, the use of the eddy current method at 100 kHz with proper conductivity could more accurately detect the microstructural changes of 9Cr-1Mo steel specimens than using the phase angle approach. The correlation coefficient of conductivity and true ultimate tensile strength was found to be 0.9459, indicating a high correlation between them.

Does investor sentiment differently affect stocks in different sectors? Evidence from China

PurposeThis paper aims to investigate the dynamic relationship between the investor sentiment and the return of various sectors in the Chinese stock market.Design/methodology/approachThe wavelet coherence and wavelet phase angle approaches are used to study the lead–lag associations between sentiment index and stock returns in a time–frequency way. The multiscale linear and nonlinear Granger causality tests are performed to explore whether there is a causality between them.FindingsThe empirical results show that during normal period, investor sentiment index has a stronger relationship with stock returns of industrials, consumer discretionary, health care, utilities, real estate and financial sectors. In crisis period, investor sentiment has a significant positive relationship with all industry sectors. In the short term, there is bidirectional causality between investor sentiment and stock returns of all sectors. In the medium and long run, almost all sector stock returns Granger-cause the investors' sentiment index but investor sentiment does not Granger-cause all sectors, which is in contrast to the developed markets.Practical implicationsThe interindustry impact of investment sentiment on the stock market can help construct arbitrage portfolio by investors who are interested in Chinese stock market.Originality/valueThis paper focuses on the industry sector differences of investor sentiment impact on the Chinese stock market. As far as the authors know, this is the first paper to explore the time–frequency relationship between sentiment index and industry stock returns in China using the time–frequency method based on wavelet coherence, which considers the heterogeneity of different types of investors' responses to various economic and financial events.

Model-based design of dynamic firing patterns for supervisory control of diesel engine vibration

Diesel engine cylinder deactivation (CDA) has been demonstrated to provide significant efficiency and aftertreatment thermal management benefits, enabling fuel-efficient emissions reduction from modern diesel engines at low load engine operation. Dynamic cylinder activation (DCA), a variant of CDA where the set of deactivated cylinders varies on a cycle-by-cycle basis, has been demonstrated to enable greater control over driveline torsional vibration while maintaining the fuel efficiency and thermal management benefits shown by fixed CDA via appropriate design of firing patterns. A model-based algorithmic approach to designing firing patterns during DCA – to control driveline torsional vibration in a user-defined frequency range, given firing density, engine speed, and maximum length of firing pattern – is described in this article. The described algorithm is generalizable to any engine configuration including different piston–cylinder layouts and number of cylinders. The algorithm is extended to design firing patterns for constrained DCA operation when CDA hardware is installed on a subset of cylinders of the engine. The resulting optimal firing patterns using the algorithm, for various combinations of inputs, are presented through an experimentally-validated simulation framework and discussed. It is demonstrated that the weighted phase-angle approach can accurately predict the frequencies and relative amplitudes of the vibration content, and, if theoretically possible, the proposed algorithm determines firing patterns that meet the specified requirements. The presented algorithm can be easily extended in future work for simultaneous selection of firing density and firing pattern during online, real-time implementation during both steady-state and transient operating conditions.

Grain Size Dependence of Brightness Phase Curves of the Lunar Surface

AbstractThe lunar opposition effect is the increase of brightness on the lunar surface when the phase angle approaches 0°, which is caused mainly by shadow‐hiding and coherent backscattering. However, the contribution of coherent backscattering is not yet well established. This study analyzes the contribution of coherent backscattering to the opposition effect using the correlation between the contribution of increased brightness of the theoretical coherent backscattering and the grain size of the reflecting surface. We analyze the correlation between the two using data from the Lunar Reconnaissance Orbiter Wide Angle Camera and median grain size d calculated by linear polarization observations. The size of effective scatterers of coherent backscattering is similar to the observation wavelength. In this case, the effective scatterer size for coherent backscattering is 0.6 μm. The results of our analyses show that there is no correlation between d and reflectance phase curve in the phase angle range from 0° to 6°. In addition, we analyze the distribution of grain size of lunar samples collected during the Apollo and Luna missions. We find an inversely proportional correlation between mean grain sizes and submicron grain content in the lunar samples. Therefore, d seems to indicate the content of effective scatterer. The strength of the coherent backscattering opposition effect seems to be affected by the content of the submicron grains. Thus, the lack of correlation between d and the opposition effect seems to imply minimal contribution of coherent backscattering to the lunar opposition effect.

Performance Evaluation of Crumb Rubber Asphalt Modified with Silicone‐Based Warm Mix Additives

This research was conducted to elucidate better understanding of the performance of crumb rubber asphalt modified with silicone‐based warm mix additives. Two different silicone‐based warm mix asphalt (WMA) additives (herein Tego XP and Addibit) were used to prepare crumb rubber modified (CRM) warm mix asphalt binders. The viscosity of these CRM binders was measured at different temperatures and shearing rates. Furthermore, softening point and penetration tests, Multiple Stress Creep Recovery (MSCR), Time Sweep (TS), Atomic Force Microscopy (AFM), Frequency sweep (FS), and Fourier Transform Infrared (FTIR) tests were also conducted on prepared samples. Based on these robust and rigorous laboratory experiments, it was established that viscosity of CRM binders was reduced by addition of Tego XP and Addibit WMA additives. However, WMA additives had different influence on rheological properties of the binder. CRM binder with Tego XP improved resistance to rutting of the binders but would degrade the fatigue performance. On the contrary, viscoelastic continuum damage (VECD) model results and those of phase angle approach revealed that the binder with Addibit improved resistance to fatigue cracking of the binders but had no adverse effects on high temperature rutting performance. FTIR test results established a presence of polydimethylsiloxane (PDMS) in CRM binders with Tego XP and Addibit. PDMS is a well‐known hydrophobic organic and inorganic polymer that is water repellent; therefore, binders containing these silicone‐based warm mix additives could be beneficial in resisting moisture damage in asphalt binders and mixtures. Morphology of CRM binders with and without WMA revealed good distribution of the rubber particles in asphalt binder matrix. Further addition of WMA increased surface roughness of the binder, which can be correlated to changes in microstructure properties of the binder. Therefore, the study concluded that addition of Tego XP and Addibit reduces viscosity and improves mechanical properties of the asphalt binder.

A Study on a Mechanism of Lateral Pedestrian-Footbridge Interaction

Based on the pedestrian lateral force hybrid Van der Pol/Rayleigh model, this study investigates the interaction dynamic model of a pedestrian-flexible footbridge lateral coupling system. A multi scale method is adopted to decouple the equation. The paper also studies the nonlinear dynamic response of the pedestrian-footbridge coupling system as well as the relationship between the lateral displacement of pedestrians and flexible footbridges, and the lateral interaction of the two variables. The results show that with the same frequency tuning parameters, when the mass ratio of pedestrians and footbridges is very small, the larger the mass ratio is, the larger the lateral response amplitude of pedestrians becomes. Conversely, when the mass ratio of pedestrians and footbridges is much larger, the larger the mass ratio is, the smaller the response amplitude becomes. When the natural frequency of a footbridge is larger, its Phase Angle becomes larger. As the lateral amplitude of pedestrians increases, the Phase Angle approaches zero. Moreover, regarding the variation of the Phase Angle between the interaction force and footbridge lateral vibration speed based on the lateral relative displacement of pedestrians, of which the variation range is (0, π ), as the pedestrians’ lateral amplitude increases, the Phase Angle approaches − π / 2 . The dynamic load coefficient varies linearly with the lateral amplitude of pedestrian vibrations.

Magnesium Perchlorate Mixed and Glutaraldehyde Crosslinked Potato Starch: An Economical and Flexible Electrolyte Membrane

AbstractEnvironment friendly polymer electrolyte systems are the most sought over option for cheap energy efficient storage devices. The present paper discusses the results of potato starch + Mg(ClO4)2 system which satisfy the technical and economical criteria to become a potential candidate for future electrolyte systems. The developed system has high ionic conductivity (≈2.01 × 10−2 S cm−1), low relaxation time (55 µs), and wide electrochemical stability window (≈3 V). The phase angle approaches −78˚ and maintains its value for 10 Hz to 1 kHz frequency range. The prepared electrolyte system, being free standing, flexible, and having the ability of being bended and twisted, is the suitable candidate for flexible electrochemical device fabrication. The equivalent series resistance is quite low (3.6 Ω) and high self‐resonance frequency ≈0.1 MHz, below which energy can be efficiently stored. Hence, the present study reports an economical, easy to handle, and environment friendly electrolyte system suitable for flexible electrochemical device fabrication.

AEMIP robust inversion using maximum phase angle Cole–Cole model re-parameterisation applied for HTEM survey over Lamego gold mine, Quadrilátero Ferrífero, MG, Brazil

ABSTRACTThis paper presents the results of airborne electromagnetic induced polarisation inversions using the Maximum Phase Angle (MPA) model for a helicopter time domain survey in the Quadrilátero Ferrífero area, Minas Gerais State (MG), Brazil. The inversions were conducted using a laterally constrained robust scheme, in order to decrease the difficulties to recover the multi-parametric model in a very ill-posed inverse problem, often found in induced polarisation studies. A set of six flight lines over the Lamego gold mine mineralised structure were inverted using the MPA re-parameterisation of the Cole–Cole model and also the classical resistivity-only parameterisation, in order to understand the implications of the induced polarisation effect in the data and, consequently, in the resistivity model. A synthetic study was also conducted, seeking to understand what to expect from the resistivity-only inversions in the real data. According to borehole lithological data and previous structural knowledge from the literature, the results from the Maximum Phase Angle approach indicate an important chargeable body that seems to be in good agreement with a sulfide enriched carbonaceous/graphite and altered mafic unities, which are important markers for the gold mineralisation.

Modifying potato starch by glutaraldehyde and MgCl2 for developing an economical and environment-friendly electrolyte system

AbstractBiodegradable polymer electrolyte systems are the most sought over option for cheap and energy efficient storage devices. Present paper discusses the results of potato starch + MgCl2system which satisfy the technical and economic criteria to become a potential candidate for future electrolyte systems. The developed system has high ionic conductivity (~3.43 × 10-2S/cm), low relaxation time (75 μs) and wide electrochemical stability window (ESW ~4.6 V). The phase angle approaches -79° and maintains its value for 10 Hz to 1 kHz frequency range. The prepared material is a free standing film which can be bended and twisted up to 90°, which makes it suitable for flexible electrochemical device fabrication. The equivalent series resistance (ESR) is quite low (3.41 Ω) and self-resonance frequency below which energy can be efficiently stored is approximately 0.1 MHz. Hence the present study reports an economical, easy to handle and environment friendly electrolyte suitable for electrochemical device fabrication.

Broad search for trajectories from Earth to Callisto–Ganymede–JOI double-satellite-aided capture at Jupiter from 2020 to 2060

Employing multiple gravity-assist flybys of Jupiter’s Galilean moons can save a substantial amount of \(\varDelta V\) when capturing into orbit about Jupiter. Using Callisto and Ganymede, the most massive and distant of the Galilean moons, as gravity-assist bodies reduces the Jupiter orbit insertion \(\varDelta V\) cost, while allowing the spacecraft to remain above the worst of Jupiter’s radiation belts. A phase-angle approach is used to find initial guesses for a Lambert targeter to find patched-conic Callisto–Ganymede transfers. A B-plane targeter using grid search methodology is used to backward target Earth to find launch conditions. Twenty-nine distinct patched-conic trajectories were found from Earth to Callisto–Ganymede–JOI capture throughout the search space from 2020–2060. Five promising trajectories were found that launch from Earth between July 11, 2023 and July 20, 2023, and arrive at Jupiter between February and September 2026. These trajectories were numerically integrated using GMAT and, in the author’s opinion, are excellent candidates for use on NASA’s planned Europa Clipper mission.

The opposition effect in Saturn’s main rings as seen by Cassini ISS: 2. Constraints on the ring particles and their regolith with analytical radiative transfer models

The opposition effect in Saturn’s main rings is characterized by a surge in ring brightness, when the phase angle approaches zero degree. This effect can be used to derive: physical properties of the ring particles and the ring layer, via the shadow hiding mechanism; and physical properties of the regolith grains that cover the ring particles, via the coherent backscattering mechanism. Since the exact origin of this effect is still a matter of debate, we try different combinations of the physical mechanisms cited above to derive constraints on the nature, the texture, and the disposition of the ring particles. In particular, we derive regolith grain sizes, particle sizes, differential power law indices, filling factors, and vertical thicknesses; and we compare them with independent works to validate or invalidate the assumptions of the opposition effect models used. Our coherent backscattering model provides grain sizes similar to the sizes estimated from water ice band depth modeling in the near infrared. Our shadow hiding model assuming a power law size distribution provides vertical thickness consistent with previous estimates from density waves measurements and N-body simulations. We show that the assumption of an homogeneous medium is a key parameter in the shadow hiding modeling. In the case of the B ring, we demonstrate that all previous photometric models assuming an homogeneous ring layer (i.e. uniform particle size distribution, random spacing of the particles and small filling factor) have led to a set of unconfirmed solutions. This result reinforces the idea that the Saturn’s main rings should be modeled as an heterogeneous medium.

Photometry of particulate surfaces at extremely small phase angles

We present results of goniometric photometry of different samples at extremely small phase angles using a new laboratory setup with a laser light source ( λ=0.63 μm). No opposition effect of carbon soot is found in the range 0.008–1.5°; whereas, MgO deposits and very disperse porous SiO 2 powder demonstrate a narrow brightness spike of significant amplitude. We find a strong dependence of phase curve slope in the range on albedo when studying mixtures of white chalk and carbon soot. These measurements as applied to interpretation of opposition effect observed for Kuiper belt objects suggest that the albedo of these objects cannot be small. Size particle separates of olivine reveal prominent opposition spikes independent of the particle size. Spherical particles with a diameter near 50 μm show significant differences in their scattering behavior depending on whether they form a monolayer or thick particulate surfaces. The latter show a sharp opposition surge unlike the monolayer. Except for the monolayer of spheres, no particulate surface in our measurements yet exhibits phase curve rounding as the phase angle approaches zero.

Mutators in space: the dynamics of high-mutability clones in a two-patch model.

Clones of bacteria possessing high-mutability rates (or mutators) are being observed in an increasing number of species. In a constant environment most mutations are deleterious, and hence the spontaneous mutation rate is generally low. However, mutators may play an important role in the adaptation of organisms to changing environments. To date, theoretical work has focused on temporal variability in the environment, implicitly assuming that environmental conditions are constant through space. Here, we develop a two-patch model to investigate how spatiotemporal environmental variability and dispersal might influence mutator dynamics. Environmental conditions in each patch fluctuate between two states; the rate of fluctuation varies in each patch at differing phase angles. We find that at low and intermediate rates of fluctuation, an increase in dispersal results in a decrease in the density of mutators. However, at high rates of environmental change, dispersal causes an increase in mutator density. For all frequencies of environmental fluctuation these trends are enhanced as the phase angle approaches 180 degrees. We argue that future work, both empirical and theoretical, is needed to improve our understanding of how spatiotemporal variability impacts on mutator densities and dynamics.

Coherent Backscatter Opposition Effect from Saturn Ring Particles and Their Regoliths

AbstractThe photometric phase curves of Saturn's A and B rings exhibit a sharp peak in reflectance when the phase angle approaches zero, commonly known as the opposition effect. Recent work has suggested that the width and amplitude of the opposition effect may be consistent with coherent backscattering from wavelength-sized grains which cover the surfaces of macroscopic ring particles.

A study on transmission error in a synchronous belt drive with eccentric pulley. Effect of eccentric phase angle of pulley and belt width.

The experiments with regard to the effect of an eccentric phase angle of the pulley were made for a transmission error in a synchronous belt drive with an eccentric pulley in the quasi-static condition under an initial tension, and these experimental results were compared with the computed results. The eccentric phase angle of the puley has a large effect on the transmission error. In order to maintain a small transmission error, the belt should be set up such that the eccentricities of the driving and driven pulleys cancel each other. When there is a meshing phase angle at the beginning of the meshing of the driven side, the transmission error having a period of one pitch of the pulley is decreased when this phase angle approaches zero, and the meshing phase angle exerts almost no influence on the transmission error having a period of one revolution of the driving pulley. Further, it was found that the amplitude of the transmission error having a period of one revolution of the driving pulley remains nearly constant regardless of the size of the belt width when the initial tension per unit width is the same.

Elimination of bilirubin interference in fluorimetric determination of fluorescein by phase-resolved fluorescence spectrometry

Phase-resolved fluorescence spectrometry is used to eliminate bilirubin interference in the fluorimetric quantitation of fluorescein, despite extensive excitation and emission spectral overlap of the two species. In this method, it is the difference in fluorescence lifetimes of the two species that provides the selectivity parameter. Results are given for a nulling approach and for a multiple phase-angle approach. In the nulling approach, intensity is measured at a detector phase angle at which the intensity for bilirubin is zero. In the multiple phase-angle approach, intensities at several phase angles are used to generate a matrix which is solved for the concentrations of fluorescein and bilirubin. Although a steady-state method yielded low results for fluorescein concentration in the presence of bilirubin concentration about 3 μM, the phase-resolved methods yielded correct values for fluorescein concentration with bilirubin concentration up to 10 μM.

Measurement of the nonlinear impedance of a satellite‐borne, electric dipole antenna

The nonlinear impedance of a satellite‐borne, electric dipole antenna was measured at ELF/VLF at drive voltages between 10 mv and 100 v peak‐to‐peak. The magnitude of the impedance is in general agreement with the predictions of theoretical models of plasma‐clad antennas. At low voltages the phase angle of the impedance is in agreement with linear sheath models, i.e., at low densities the current leads the voltage and as the density increases the phase angle approaches zero. However, at high drive voltages the current lags the voltage. Above 10 v p‐p the phase angle often exceeds +90 deg.

Small signal impedance of a solid core inductance

The design of a highly stabilized control system for a large electromagnet requires the knowledge of its small signal impedance as a function of frequency. The impedance of such an electromagnet was calculated, taking into account the effects of eddy currents but ignoring non-linearities in the magnetizing curve of the iron. It has been possible to use typical values for the relative incremental permeability and conductivity of iron to obtain a rather good estimate of its impedance over four decades above the lowest frequency for which reactive components of the impedance are significant. There is a change in slope in the curve of the magnitude of the impedance at a frequency corresponding to a skin depth equal to approximately three-quarters of the radius of cross section of the core. Above this frequency the magnitude of impedance rises at 3 dB per octave and the phase angle approaches 45°. At much higher frequencies the existence of stray capacities causes deviations from this predicted behaviour.