360 research outputs found
Modelling shadow banking system and housing market in China
Given the lessons learned from the financial crisis and housing crash in Japan and the
US, as well as the strong connection between the shadow banking sector and property
market in the second-largest economy, China, it is essential to understand the
mechanism of a model that contains both shadow banking activities and the housing
market. Therefore, the first objective of this thesis is to model the Chinese banking
and housing sector and understand the underlying mechanism. The second objective
is related to a methodological issue. In recent years, many researchers, especially in
mainland China, have been exploring the Chinese shadow banking system. Most
researchers either only calibrate or use Bayesian estimation to estimate their model.
However, none of the approaches test the model against real data. Different models
can tell different stories and potentially provide different policy implications. However,
if the model is rejected by the actual data, all the results and policy suggestions might
become insignificant. Therefore, in my research, I adopt two different estimation
approaches, Bayesian estimation and Indirect Inference approach, to first provide
some understanding about Chinese shadow banking system, and second, to discover
whether my model can or cannot be rejected by the actual data
From Shortcuts to Triggers: Backdoor Defense with Denoised PoE
Language models are often at risk of diverse backdoor attacks, especially
data poisoning. Thus, it is important to investigate defense solutions for
addressing them. Existing backdoor defense methods mainly focus on backdoor
attacks with explicit triggers, leaving a universal defense against various
backdoor attacks with diverse triggers largely unexplored. In this paper, we
propose an end-to-end ensemble-based backdoor defense framework, DPoE (Denoised
Product-of-Experts), which is inspired by the shortcut nature of backdoor
attacks, to defend various backdoor attacks. DPoE consists of two models: a
shallow model that captures the backdoor shortcuts and a main model that is
prevented from learning the backdoor shortcuts. To address the label flip
caused by backdoor attackers, DPoE incorporates a denoising design. Experiments
on SST-2 dataset show that DPoE significantly improves the defense performance
against various types of backdoor triggers including word-level,
sentence-level, and syntactic triggers. Furthermore, DPoE is also effective
under a more challenging but practical setting that mixes multiple types of
trigger.Comment: Work in Progres
Three-dimensional Magnetic Restructuring in Two Homologous Solar Flares in the Seismically Active NOAA AR 11283
We carry out a comprehensive investigation comparing the three-dimensional
magnetic field restructuring, flare energy release, and the helioseismic
response, of two homologous flares, the 2011 September 6 X2.1 (FL1) and
September 7 X1.8 (FL2) flares in NOAA AR 11283. In our analysis, (1) a twisted
flux rope (FR) collapses onto the surface at a speed of 1.5 km/s after a
partial eruption in FL1. The FR then gradually grows to reach a higher altitude
and collapses again at 3 km/s after a fuller eruption in FL2. Also, FL2 shows a
larger decrease of the flux-weighted centroid separation of opposite magnetic
polarities and a greater change of the horizontal field on the surface. These
imply a more violent coronal implosion with corresponding more intense surface
signatures in FL2. (2) The FR is inclined northward, and together with the
ambient fields, it undergoes a southward turning after both events. This agrees
with the asymmetric decay of the penumbra observed in the peripheral regions.
(3) The amounts of free magnetic energy and nonthermal electron energy released
during FL1 are comparable to those of FL2 within the uncertainties of the
measurements. (4) No sunquake was detected in FL1; in contrast, FL2 produced
two seismic emission sources S1 and S2 both lying in the penumbral regions.
Interestingly, S1 and S2 are connected by magnetic loops, and the stronger
source S2 has weaker vertical magnetic field. We discuss these results in
relation to the implosion process in the low corona and the sunquake
generation.Comment: 12 pages, 9 figures, accepted to the Astrophysical Journa
- …