arXiv subjects

W. Y. Zhang

Publications and source records attributed to W. Y. Zhang.

10 recordsLinked to original sources

arXiv2022

The Effects of Space Weather on Flight Delays

Although the sun is really far away from us, some solar activities could still influence the performance and reliability of space-borne and ground-based technological systems on Earth. Those time-varying conditions in space caused by the sun are also called space weather, as the atmospheric conditions that can affect weather on the ground. It is known that aviation activities can be affected during space weather events, but the exact effects of space weather on aviation are still unclear. Especially how the flight delays, the top topic concerned by most people, will be affected by space weather has never been thoroughly researched. By analyzing huge amount of flight data (~5X106 records), for the first time, we demonstrate that space weather events could have systematically modulating effects on flight delays. The average arrival delay time and 30-minute delay rate during space weather events are significantly increased by 81.34% and 21.45% respectively compared to those during quiet periods. The evident negative correlation between the yearly flight regularity rate and the yearly mean total sunspot number during 22 years also confirms such delay effects. Further studies indicate that the interference in communication and navigation caused by geomagnetic field fluctuations and ionospheric disturbances associated with the space weather events will increase the flight delay time and delay rate. These results expand the traditional field of space weather research and could also provide us with brand new views for improving the flight delay predications.

astro-ph.SR↗

arXiv2022

Characteristics of Flight Delays during Solar Flares

Solar flare is one of the severest solar activities on the sun, and it has many important impacts on the near-earth space. It has been found that flight arrival delays will increase during solar flare. However, the detailed intrinsic mechanism of how solar flares influence the delays is still unknown. Based on 5-years huge amount of flight data, here we comprehensively analyze the flight departure delays during 57 solar flares. It is found that the averaged flight departure delay time during solar flares increased by 20.68% (7.67 min) compared to those during quiet periods. It is also shown that solar flare related flight delays reveal apparent time and latitude dependencies. Flight delays during dayside solar flares are more serious than those during nightside flares, and the longer (shorter) delays tend to occur in the lower (higher) latitude airport. Further analyses suggest that flight delay time and delay rate would be directly modulated by the solar intensity (soft X-ray flux) and the Solar Zenith Angle. For the first time, these results indicate that the communication interferences caused by solar flares will directly affect flight departure delay time and delay rate. This work also expands our conventional understandings to the impacts of solar flares on human society, and it could also provide us with brand new views to help prevent or cope with flight delays.

astro-ph.SR↗

arXiv2022

Analyses of Flight Time During Solar Proton Events and Solar Flares

Analyzing the effects of space weather on aviation is a new and developing topic. It has been commonly accepted that the flight time of the polar flights may increase during solar proton events because the flights have to change their route to avoid the high-energy particles. However, apart from such phenomenon, researches related to the flight time during space weather events is very rare. Based on the analyses of 39 representative international air routes around westerlies, it is found that 97.44% (94.87%) of the commercial airplanes on the westbound (eastbound) air routes reveal shorter (longer) flight time during solar proton events compared to those during quiet periods, and the averaged magnitude of change in flight time is ~10 min or 0.21%-4.17% of the total flight durations. Comparative investigations reassure the certainty of such phenomenon that the directional differences in flight time are still incontrovertible regardless of over-land routes (China-Europe) or over-sea routes (China-Western America). Further analyses suggest that the solar proton events associated atmospheric heating will change the flight durations by weakening certain atmospheric circulations, such as the polar jet stream. While the polar jet stream will not be obviously altered during solar flares so that the directional differences in flight time are not found. Besides the conventional space weather effects already known, this paper is the first report that indicates a distinct new scenario of how the solar proton events affect flight time. These analyses are also important for aviation since our discoveries could help the airways optimize the air routes to save passenger time costs, reduce fuel costs and even contribute to the global warming issues.

astro-ph.SR↗

arXiv2015

The cross-correlation analysis in Z source GX 349+2

Using all the observations from Rossi X-ray Timing Explorer for Z source GX 349+2, we systematically carry out cross-correlation analysis between its soft and hard X-ray light curves. During the observations from January 9 to January 29, 1998, GX 349+2 traced out the most extensive Z track on its hardness-intensity diagram, making a comprehensive study of cross-correlation on the track. The positive correlations and positively correlated time lags are detected throughout the Z track. Outside the Z track, anti-correlations and anti-correlated time lags are found, but the anti-correlated time lags are much longer than the positively correlated time lags, which might indicate different mechanisms for producing the two types of time lags. We argue that neither the short-term time lag models nor the truncated accretion disk model can account for the long-term time lags in neutron star low mass X-ray binaries (NS-LMXBs). We suggest that the extended accretion disk corona model could be an alternative model to explain the long-term time lags detected in NS-LMXBs.

astro-ph.HE↗

arXiv2013

A new ignition scheme using hybrid indirect-direct drive for inertial confinement fusion

A new hybrid indirect-direct-drive ignition scheme is proposed for inertial confinement fusion: a cryogenic capsule encased in a hohlraum is first compressed symmetrically by indirect-drive x-rays, and then accelerated and ignited by both direct-drive lasers and x-rays. A steady high-density plateau newly formed between the radiation and electron ablation fronts suppresses the rarefaction at the radiation ablation front and greatly enhances the drive pressure. Meanwhile, multiple shock reflections at the fuel/hot-spot interface are prevented during capsule deceleration. Thus rapid ignition and burn are realized. In comparison with the conventional indirect drive, the hybrid drive implodes the capsule with a higher velocity ($\sim4.3\times10^7$ cm/s) and a much lower convergence ratio ($\sim$25), and the growth of hydrodynamic instabilities is significantly reduced, especially at the fuel/hot-spot interface.

physics.plasm-ph↗

arXiv2013

Structural and magnetic properties of Pr-alloyed MnBi nanostructures

The structural and magnetic properties of Pr-alloyed MnBi (short MnBi-Pr) nanostructures with a range of Pr concentrations have been investigated. The nanostructures include thin films having Pr concentrations 0, 2, 3, 5 and 9 atomic percent and melt-spun ribbons having Pr concentrations 0, 2, 4 and 6 percent respectively. Addition of Pr into the MnBi lattice has produced a significant change in the magnetic properties of these nanostructures including an increase in coercivity and structural phase transition temperature, and a decrease in saturation magnetization and anisotropy energy. The highest value of coercivity measured in the films is 23 kOe and in the ribbons is 5.6 kOe. The observed magnetic properties are explained as the consequences of competing ferromagnetic and antiferromagnetic interactions.

cond-mat.mtrl-sci↗

arXiv2011

Nonlinear evolution of the ablative Rayleigh-Taylor instability with preheating

Evolution of the single-mode ablative Rayleigh-Taylor instability in the presence of preheating is investigated numerically. It is found that the instability evolution depends strongly on the preheating length $L$ in front of the ablation-front interface. For weak preheating ($L/L_{\rm SH}\leq f_0$, where $L_{\rm SH}$ is the Spitzer-Harm length and $f_0\sim 20$ is a critical value), the linear growth rate has a sharp maximum and a secondary spike-bubble structure is generated. Interaction of this growing structure with the master spike-bubble leads to rupture of the latter. However, for strong preheating ($L/L_{\rm SH}>20$), the linear growth rate has no sharp maximum and no secondary spike-bubble is generated. Instead, the master spike-bubble evolves into an elongated jet. These results are interpreted in terms of the evolution and interaction of the instability-generated harmonic modes.

physics.plasm-ph↗

arXiv2005

Effect of Ti doping on the electrical transport and magnetic properties of layered compound Na0.8CoO2

Effect of Ti doping on the electrical transport and magnetic properties of layered Na0.8Co1-xTixO2 compounds has been investigated. The lattice parameters a and c increase with x. A minor amount of Ti doping results in a metal-insulator transition at low temperatures. For samples with x > 0.03, the variable-range hopping process dominates the transport behavior above a certain temperature. The temperature dependence of magnetization of all the samples is found to obey the Curie-Weiss law. The mechanism of the doping effect is discussed.

cond-mat.str-el↗

arXiv2004

Particle acceleration through the resonance of high magnetic field and high frequency electromagnetic wave

We propose a new particle acceleration mechanism. Electron can be accelerated to relativistic energy within a few electromagnetic wave cycles through the mechanism which is named electromagnetic and magnetic field resonance acceleration (EMRA). We find that the electron acceleration depends not only on the electromagnetic wave intensity, but also on the ratio between electron Larmor frequency and electromagnetic wave frequency. As the ratio approaches to unity, a clear resonance peak is observed, corresponding to the EMRA. Near the resonance regime, the strong magnetic fields still affect the electron acceleration dramatically. We derive an approximate analytical solution of the relativistic electron energy in adiabatic limit, which provides a full understanding of this phenomenon. In typical parameters of pulsar magnetospheres, the mechanism allows particles to increase their energies through the resonance of high magnetic field and high frequency electromagnetic wave in each electromagnetic wave period. The energy spectra of the accelerated particles exhibit the synchrotron radiation behavior. These can help to understand the remaining emission of high energy electron from radio pulsar within supernova remnant. The other potential application of our theory in fast ignition scheme of inertial confinement fusion is also discussed.

physics.plasm-ph↗

arXiv2003

Effects of Mn-substitution for Co on the structure and physical properties of NayCoO2

Structure, transport and magnetic properties have been investigated for layered NaCo1-xMnxO2 materials. With the increase of Mn-doping amount, measurements of x-ray diffraction indicate that the in-plane lattice parameter a decreases progressively, and, conversely, the lattice parameter c increases rapidly. Small amount of Mn doping (i.e. 3% Mn in our work) could result in a metal-insulator transition. Electron energy loss spectroscopy (EELS) measurement shows that the Co valence is about 3.3 and remains unchanged with doping. In contrast, the valence of Mn increases rapidly with doping and reaches 3.7 for the sample with x=0.5. The temperature dependence of magnetization of the samples is found to obey the Curie-Weiss law. Some relevant results have been discussed in terms of the disorder effect induced by doping of magnetic ions.

cond-mat.str-el↗