29,069 research outputs found
Voices from the diaspora: changing hierarchies and dynamics of Chinese multilingualism
The so-called Chinese diasporas, i.e. Chinese communities outside Greater China (China, Hong Kong, Macau, and Taiwan), have traditionally been dialect dominant; that is, the vast majority of Chinese immigrants are speakers of (especially Southern) dialects. Cantonese and Hokkien are two of the most prominent dialects. With globalization and the rise of China as a world politico-economic power, the national, standardized variety, Putonghua, is gaining particular prestige amongst the Chinese diasporas. For example, all the Cantonese schools for British Chinese children in the UK now also teach Putonghua, but none of the Putonghua schools teach Cantonese. Using ethnographic interviews with and participant observation of Chinese people of different generations in various diasporic communities, this paper examines the changing hierarchies of varieties of Chinese, the implications of such changes for the education and identity development of the young, and the constitution of a (speech) community in the post-modern era. It focuses on language attitude and linguistic practices (including literacy practices). It also investigates the tensions between the competing ideologies and discourses on national and ethnic identities, nationalism, community relations and cultural values
On Weak Topology for Optimal Control of Switched Nonlinear Systems
Optimal control of switched systems is challenging due to the discrete nature
of the switching control input. The embedding-based approach addresses this
challenge by solving a corresponding relaxed optimal control problem with only
continuous inputs, and then projecting the relaxed solution back to obtain the
optimal switching solution of the original problem. This paper presents a novel
idea that views the embedding-based approach as a change of topology over the
optimization space, resulting in a general procedure to construct a switched
optimal control algorithm with guaranteed convergence to a local optimizer. Our
result provides a unified topology based framework for the analysis and design
of various embedding-based algorithms in solving the switched optimal control
problem and includes many existing methods as special cases
Preen Gland-Secreted Alkanols Enhance Male Attractiveness in Parrots
The skin glands are widely used in pheromone production throughout the vertebrate worlds. Growing evidences show that birds also have chemical communication, but the uropygial (also called preen or oil) glands, serving as only specialized skin glands of birds, have no sex pheromones characterized. Here, by combining GC-MS analysis and bioassay, we show with the budgerigar, Melopsittacus undulatus, that birds can used the preen gland-secreted volatiles (a blend of octadecanol, nonadecanol and eicosanol for male budgerigars) spread over body plumage when preening to convey sex information. Here, we first report the avian pheromones derived from the uropyginal gland and suggests that the gland has broader implications than previously known (e.g. plumage waterproofing and reflectance in sexual behaviour of birds
Hyper-accreting black hole as GRB central engine. I: Baryon loading in GRB jets
A hyper-accreting stellar-mass black hole has been long speculated as the
best candidate of central engine of gamma-ray bursts (GRBs). Recent rich
observations of GRBs by space missions such as Swift and Fermi pose new
constraints on GRB central engine models. In this paper, we study the baryon
loading processes of a GRB jet launched from a black hole central engine. We
consider a relativistic jet powered by -annihilation or by the
Blandford-Znajek (BZ) mechanism. We consider baryon loading from a
neutrino-driven wind from a neutrino-cooling-dominated accretion flow. For a
magnetically dominated BZ jet, we consider neutron-drifting from the magnetic
wall surrounding the jet and subsequent positron capture and proton-neutron
inelastic collisions. The minumim baryon loads in both types of jet are
calculated. We find that in both cases, a more luminous jet tends to be more
baryon poor. A neutrino-driven "fireball" is typically "dirtier" than a
magnetically dominated jet, while a magnetically dominated jet can be much
cleaner. Both models have the right scaling to interpret the empirical
relation discovered recently. Since some neutrino-driven
jets have too much baryon loading as compared with the data, we suggest that at
least a good fraction of GRBs should have a magnetically dominated central
engine.Comment: 9 pages, 2 figures; Accepted for publication in Ap
Multi-View Active Learning in the Non-Realizable Case
The sample complexity of active learning under the realizability assumption
has been well-studied. The realizability assumption, however, rarely holds in
practice. In this paper, we theoretically characterize the sample complexity of
active learning in the non-realizable case under multi-view setting. We prove
that, with unbounded Tsybakov noise, the sample complexity of multi-view active
learning can be , contrasting to
single-view setting where the polynomial improvement is the best possible
achievement. We also prove that in general multi-view setting the sample
complexity of active learning with unbounded Tsybakov noise is
, where the order of is
independent of the parameter in Tsybakov noise, contrasting to previous
polynomial bounds where the order of is related to the parameter
in Tsybakov noise.Comment: 22 pages, 1 figur
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