arXiv subjects

Yan-Hui Han

Publications and source records attributed to Yan-Hui Han.

4 recordsLinked to original sources

arXiv2022

A Complete Graphical Solution for Undrained Cylindrical Cavity Expansion in K_0-Consolidated Mohr-Coulomb Soil

This paper develops a general and complete solution for the undrained cylindrical cavity expansion problem in non-associated Mohr-Coulomb soil under non-hydrostatic initial stress field (i.e., arbitrary K_0 values of the earth pressure coefficient), by expanding a unique and efficient graphical solution procedure recently proposed by Chen & Wang in 2022 for the special in situ stress case with K_0 = 1. The new generalized, graph-based theoretical framework contains two essential components: the geometrical analysis to track the stress path trajectory/evolution in different sectors of the deviatoric plane; and a full Lagrangian formulation of both the constitutive relationship and radial equilibrium equation to analytically determine the representative soil particle responses at the cavity surface. It is interesting to find that the cavity expansion deviatoric stress path is always composed of a series of piecewise straight lines, for all different case scenarios of K_0 being involved. The salient advantage/feature of the present general graphical approach lies in that it can deduce the cavity expansion responses in full closed form, nevertheless being free of the limitation of the intermediacy assumption for the vertical stress and of the difficulty existing in the traditional zoning method that involves cumbersome, sequential determination of distinct Mohr-Coulomb plastic regions. The analytical closed-form solutions developed herein can be regarded as a definitive one for the undrained cavity expansion problem in classical Mohr-Coulomb materials without the approximations and simplifications in previous solutions, and will be of great value for the interpretation of pressuremeter tests in cohesive-frictional soils.

physics.geo-ph↗

arXiv2017

A Monte Carlo approach to magnetar-powered transients: II. Broad-lined type Ic supernovae not associated with GRBs

Broad-lined type Ic supernovae (SNe Ic-BL) are a subclass of rare core collapse SNe whose energy source is debated in the literature. Recently a series of investigations on SNe Ic-BL with the magnetar (plus 56Ni) model were carried out. Evidence for magnetar formation was found for the well-observed SNe Ic-BL 1998bw and 2002ap. In this paper we systematically study a large sample of SNe Ic-BL not associated with gamma-ray bursts. We use photospheric velocity data determined in a homogeneous way. We find that the magnetar+56Ni model provides a good description of the light curves and velocity evolution of our sample of SNe Ic-BL, although some SNe (not all) can also be described by the pure-magnetar model or by the two-component pure-56Ni model (3 out of 12 are unlikely explained by two-component model). In the magnetar+56Ni model, the amount of 56Ni required to explain their luminosity is significantly reduced, and the derived initial explosion energy is, in general, in accordance with neutrino heating. Some correlations between different physical parameters are evaluated and their implications regarding magnetic field amplification and the total energy reservoir are discussed.

astro-ph.HE↗

arXiv2016

Solving the 56Ni puzzle of magnetar-powered broad-lined type Ic supernovae

Broad-lined type Ic supernovae (SNe Ic-BL) are of great importance because their association with long-duration gamma-ray bursts (LGRBs) holds the key to deciphering the central engine of LGRBs, which refrains from being unveiled despite decades of investigation. Among the two popularly hypothesized types of central engine, i.e., black holes and strongly magnetized neutron stars (magnetars), there is mounting evidence that the central engine of GRB-associated SNe (GRB-SNe) is rapidly rotating magnetars. Theoretical analysis also suggests that magnetars could be the central engine of SNe Ic-BL. What puzzled the researchers is the fact that light curve modeling indicates that as much as 0.2-0.5 solar mass of 56Ni was synthesized during the explosion of the SNe Ic-BL, which is unfortunately in direct conflict with current state-of-the-art understanding of magnetar-powered 56Ni synthesis. Here we propose a dynamic model of magnetar-powered SNe to take into account the acceleration of the ejecta by the magnetar, as well as the thermalization of the injected energy. Assuming that the SN kinetic energy comes exclusively from the magnetar acceleration, we find that although a major fraction of the rotational energy of the magnetar is to accelerate the SNe ejecta, a tiny fraction of this energy deposited as thermal energy of the ejecta is enough to reduce the needed 56Ni to 0.06 solar mass for both SN 1997ef and SN 2007ru. We therefore suggest that magnetars could power SNe Ic-BL both in aspects of energetics and of 56Ni synthesis.

astro-ph.HE↗

arXiv2016

Optical Transients Powered by Magnetars: Dynamics, Light Curves, and Transition to the Nebular Phase

Millisecond magnetars can be formed via several channels: core-collapse of massive stars, accretion-induced collapse of white dwarfs (WDs), double WD mergers, double neutron star (NS) mergers, and WD-NS mergers. Because the mass of ejecta from these channels could be quite different, their light curves are also expected to be diverse. We evaluate the dynamic evolution of optical transients powered by millisecond magnetars. We find that the magnetar with short spin-down timescale converts its rotational energy mostly into the kinetic energy of the transient, while the energy of a magnetar with long spin-down timescale goes into radiation of the transient. This leads us to speculate that hypernovae could be powered by magnetars with short spin-down timescales. At late times the optical transients will gradually evolve into a nebular phase because of the photospheric recession. We treat the photosphere and nebula separately because their radiation mechanisms are different. In some cases the ejecta could be light enough that the magnetar can accelerate it to a relativistic speed. It is well known that the peak luminosity of a supernova (SN) occurs when the luminosity is equal to the instantaneous energy input rate, as shown by Arnett (1979). We show that photospheric recession and relativistic motion can modify this law. The photospheric recession always leads to a delay of the peak time $t_{\mathrm{pk}}$ relative to the time $t_{\times }$ at which the SN luminosity equals the instantaneous energy input rate. Relativistic motion, however, may change this result significantly.

astro-ph.HE↗