3,404 research outputs found
Intrinsic limits governing MBE growth of Ga-assisted GaAs nanowires on Si(111)
Diffusion-enhanced and desorption-limited growth regimes of Ga-assisted GaAs
nanowires were identified. In the latter regime, the number of vertical NWs
with a narrow length distribution was increased by raising the growth
temperature. The maximum axial growth rate; which can be quantified by the
supplied rate of As atoms, is achieved when a dynamical equilibrium state is
maintained in Ga droplets i.e. the number of impinging As atoms on the droplet
surface is equivalent to that of direct deposited Ga atoms combining with the
diffusing ones. The contribution of Ga diffusion to the wire growth was
evidenced by the diameter-dependent NW axial growth rate
The institutional context influencing rural-urban migration choices and strategies for young married women and men in Vietnam
This report draws together secondary data and informed opinion relating to the wider context in which young married rural-urban migrants must craft strategies for managing their reproductive and family lives. In contrast to long standing patterns of male migration, the increasing numbers of migrants and the emergence of new forms of migration mean that young married women are increasingly moving for work too. The report outlines the wider situation in which these dynamics are occurring: the growing inequalities in the context of doi moi, the declining barrier that household registration poses to mobility, and the changing opportunities for work in the city. It also reviews changing gender relations in Vietnam with particular attention to changes in marriage and marital relations, in sexuality and fertility and in parenting. Finally it explores how changes in social entitlements in Vietnam may affect these migrants with special attention to maternal health, child health and children’s education. The report concludes that migrants with young families and new marriages face a plethora of barriers and opportunities that they must negotiate and that the strategies they formulate are dynamic and involve complex trade-offs
Discretely exact derivatives for hyperbolic PDE-constrained optimization problems discretized by the discontinuous Galerkin method
This paper discusses the computation of derivatives for optimization problems
governed by linear hyperbolic systems of partial differential equations (PDEs)
that are discretized by the discontinuous Galerkin (dG) method. An efficient
and accurate computation of these derivatives is important, for instance, in
inverse problems and optimal control problems. This computation is usually
based on an adjoint PDE system, and the question addressed in this paper is how
the discretization of this adjoint system should relate to the dG
discretization of the hyperbolic state equation. Adjoint-based derivatives can
either be computed before or after discretization; these two options are often
referred to as the optimize-then-discretize and discretize-then-optimize
approaches. We discuss the relation between these two options for dG
discretizations in space and Runge-Kutta time integration. Discretely exact
discretizations for several hyperbolic optimization problems are derived,
including the advection equation, Maxwell's equations and the coupled
elastic-acoustic wave equation. We find that the discrete adjoint equation
inherits a natural dG discretization from the discretization of the state
equation and that the expressions for the discretely exact gradient often have
to take into account contributions from element faces. For the coupled
elastic-acoustic wave equation, the correctness and accuracy of our derivative
expressions are illustrated by comparisons with finite difference gradients.
The results show that a straightforward discretization of the continuous
gradient differs from the discretely exact gradient, and thus is not consistent
with the discretized objective. This inconsistency may cause difficulties in
the convergence of gradient based algorithms for solving optimization problems
Policy implications of the family strategies of low-income rural-urban labour migrants in their peak child-bearing years in Vietnam
Effects of thermal and quantum fluctuations on the phase diagram of a spin-1 87Rb Bose-Einstein condensate
We investigate effects of thermal and quantum fluctuations on the phase
diagram of a spin-1 87Rb Bose-Einstein condensate (BEC) under a quadratic
Zeeman effect. Due to the large ratio of spinindependent to spin-dependent
interactions of 87Rb atoms, the effect of noncondensed atoms on the condensate
is much more significant than that in scalar BECs. We find that the condensate
and spontaneous magnetization emerge at different temperatures when the ground
state is in the brokenaxisymmetry phase. In this phase, a magnetized condensate
induces spin coherence of noncondensed atoms in different magnetic sublevels,
resulting in temperature-dependent magnetization of the noncondensate. We also
examine the effect of quantum fluctuations on the order parameter at absolute
zero, and find that the ground-state phase diagram is significantly altered by
quantum depletion.Comment: Comment: 21 pages, 7 figures Comment: 20 pages, 7 figures, paper
reconstructed, nomenclature changed, references added, grammatical errors
correcte
Spectral-spatial classification of hyperspectral images: three tricks and a new supervised learning setting
Spectral-spatial classification of hyperspectral images has been the subject
of many studies in recent years. In the presence of only very few labeled
pixels, this task becomes challenging. In this paper we address the following
two research questions: 1) Can a simple neural network with just a single
hidden layer achieve state of the art performance in the presence of few
labeled pixels? 2) How is the performance of hyperspectral image classification
methods affected when using disjoint train and test sets? We give a positive
answer to the first question by using three tricks within a very basic shallow
Convolutional Neural Network (CNN) architecture: a tailored loss function, and
smooth- and label-based data augmentation. The tailored loss function enforces
that neighborhood wavelengths have similar contributions to the features
generated during training. A new label-based technique here proposed favors
selection of pixels in smaller classes, which is beneficial in the presence of
very few labeled pixels and skewed class distributions. To address the second
question, we introduce a new sampling procedure to generate disjoint train and
test set. Then the train set is used to obtain the CNN model, which is then
applied to pixels in the test set to estimate their labels. We assess the
efficacy of the simple neural network method on five publicly available
hyperspectral images. On these images our method significantly outperforms
considered baselines. Notably, with just 1% of labeled pixels per class, on
these datasets our method achieves an accuracy that goes from 86.42%
(challenging dataset) to 99.52% (easy dataset). Furthermore we show that the
simple neural network method improves over other baselines in the new
challenging supervised setting. Our analysis substantiates the highly
beneficial effect of using the entire image (so train and test data) for
constructing a model.Comment: Remote Sensing 201
Greening hotels: does motivating hotel employees promote in-role green performance? The role of culture
In the new global economy, environmentally friendly policies have become a central issue for firms. The increasing attention given to the benefits of those policies has prompted research on the development of environmental management systems that encourage employees to engage in environmental activities. However, there is limited evidence concerning the relationship between employee motivation and employees’ in-role green performance, in addition to the potential impact of culture and organizational citizenship behavior for the environment. Through a quantitative study of 301 managerial and non-managerial employees working in three- to five-star hotels, this study makes a major contribution by demonstrating that practices aimed at motivating hotel employees (e.g. green reward and performance management) are significantly linked with employees’ in-role green performance and organizational citizenship behavior for the environment. The findings also indicate that the influence of green rewards on employees’ in-role green performance and organizational citizenship behaviors for the environment is stronger when hotels are managed by Western corporations. Conversely, the study showed that the effect of green performance management on these two dependent variables is not moderated by culture. This article supports efforts to widen national cultural perspectives in the development and application of green human resource management
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