9,853 research outputs found
Learning Discourse-level Diversity for Neural Dialog Models using Conditional Variational Autoencoders
While recent neural encoder-decoder models have shown great promise in
modeling open-domain conversations, they often generate dull and generic
responses. Unlike past work that has focused on diversifying the output of the
decoder at word-level to alleviate this problem, we present a novel framework
based on conditional variational autoencoders that captures the discourse-level
diversity in the encoder. Our model uses latent variables to learn a
distribution over potential conversational intents and generates diverse
responses using only greedy decoders. We have further developed a novel variant
that is integrated with linguistic prior knowledge for better performance.
Finally, the training procedure is improved by introducing a bag-of-word loss.
Our proposed models have been validated to generate significantly more diverse
responses than baseline approaches and exhibit competence in discourse-level
decision-making.Comment: Appeared in ACL2017 proceedings as a long paper. Correct a
calculation mistake in Table 1 E-bow & A-bow and results into higher score
Superradiant instability of the charged scalar field in stringy black hole mirror system
It has been shown that the mass of the scalar field in the charged stringy
black hole is never able to generate a potential well outside the event horizon
to trap the superradiant modes. This is to say that the charged stringy black
hole is stable against the massive charged scalar perturbation. In this paper
we will study the superradiant instability of the massless scalar field in the
background of charged stringy black hole due to a mirror-like boundary
condition. The analytical expression of the unstable superradiant modes is
derived by using the asymptotic matching method. It is also pointed out that
the black hole mirror system becomes extremely unstable for a large charge
of scalar field and the small mirror radius .Comment: 5 pages, no figure, published versio
Time evolutions of scalar field perturbations in -dimensional Reissner-Nordstr\"om Anti-de Sitter black holes
Reissner-Nordstr\"om Anti-de Sitter (RNAdS) black holes are unstable against
the charged scalar field perturbations due to the well-known superradiance
phenomenon. We present the time domain analysis of charged scalar field
perturbations in the RNAdS black hole background in general dimensions. We show
that the instabilities of charged scalar field can be explicitly illustrated
from the time profiles of evolving scalar field. By using the Prony method to
fit the time evolution data, we confirm the mode that dominates the long time
behavior of scalar field is in accordance with the quasinormal mode from the
frequency domain analysis. The superradiance origin of the instability can also
be demonstrated by comparing the real part of the dominant mode with the
superradiant condition of charged scalar field. It is shown that all the
unstable modes are superradiant, which is consistent with the analytical result
in the frequency domain analysis. Furthermore, we also confirm there exists the
rapid exponential growing modes in the RNAdS case, which makes the RNAdS black
hole a good test ground to investigate the nonlinear evolution of superradiant
instability.Comment: 15 pages, 7 figure
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ORIGINS AND SEASONAL VARIATION OF DISINFECTION BYPRODUCT PRECURSORS
Disinfection byproducts (DBPs) are formed from the disinfectant (e.g., chlorine) reacting with components of natural organic matter (NOM) in water drawn from surface water supplies, and are considered as the cause of potential serious human health problems. DBP precursors originate in large reservoirs from at least three types of sources: (1) watershed or allochthonous, (2) algal or autochthonous, and (3) bottom sediments or benthic. The properties of the NOM and the DBP precursor content of that NOM are unique to each source.
The first objective of this dissertation was to use temporal and spatial water quality data from a drinking water reservoir to shed light on autochthonous and benthic sources of NOM and DBP precursors.
The second objective of this dissertation was to identify the seasonal variation and spatial fate of DBP precursors in a drinking water system located in a temperate environment where seasonal variations of surface water quality and water temperature are considerable.
Organic matter released from plants is quite likely the most important fraction as potential DBP precursors, especially in heavily forested catchments. However, very few studies have been conducted on plant leachate as DBP precursors.
The third objective of this dissertation was to characterize the organic matter that is released by plants, and examine their potentials to form DBPs under light, dark, and dark-with-biocide conditions.
The final objective of this dissertation was to determine the comparative significance of DBP (i.e., trihalomethanes, dihaloacetic acids, and trihaloacetic acids) precursors released from profundal sediments of a water supply impoundment under aerobic, hypoxic, and anaerobic conditions
Time domain analysis of superradiant instability for the charged stringy black hole-mirror system
It has been proved that the charged stringy black holes are stable under the
perturbations of massive charged scalar fields. However, superradiant
instability can be generated by adding the mirror-like boundary condition to
the composed system of charged stringy black hole and scalar field. The
unstable boxed quasinormal modes have been calculated by using both analytical
and numerical method. In this paper, we further provide a time domain analysis
by performing a long time evolution of charged scalar field configuration in
the background of the charged stringy black hole with the mirror-like boundary
condition imposed. We have used the ingoing Eddington-Finkelstein coordinates
to derive the evolution equation, and adopted Pseudo-spectral method and the
forth-order Runge-Kutta method to evolve the scalar field with the initial
Gaussian wave packet. It is shown by our numerical scheme that Fourier
transforming the evolution data coincides well with the unstable modes computed
from frequency domain analysis. The existence of the rapid growth mode makes
the charged stringy black hole a good test ground to study the nonlinear
development of superradiant instability.Comment: 7 pages, 6 figures, and 5 tables. References adde
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