162 research outputs found
Persistence of Lower Dimensional Tori of General Types in Hamiltonian Systems
2000 Mathematics Subject Classification. 37J40.The work is a generalization to [40] in which we study the persistence of lower dimensional tori of general type in Hamiltonian systems of general normal forms. By introducing a modified linear KAM iterative scheme to deal with small divisors, we shall prove a persistence result, under a Melnikov type of non-resonance condition, which particularly allows multiple and degenerate normal frequencies of the unperturbed lower dimensional tori.The first author was partially supported by NSFC grant 19971042, National 973 Project of
China: Nonlinearity, the outstanding young's project of Ministry of Education of China, and National outstanding young's award of China. The second author was partially supported by NSF grants DMS9803581 and DMS-0204119
Persistence of Invariant Tori on Submanifolds in Hamiltonian Systems
AMS (MOS). Mathematics Subject Classification. 58F05, 58F27, 58F30.Generalizing the degenerate KAM theorem under the Rüssmann non-degeneracy
and the isoenergetic KAM theorem, we employ a quasi-linear iterative scheme to study
the persistence and frequency preservation of invariant tori on a smooth sub-manifold
for a real analytic, nearly integrable Hamiltonian system. Under a nondegenerate
condition of Rüssmann type on the sub-manifold, we shall show the following: a) the majority of the unperturbed tori on the sub-manifold will persist; b) the perturbed toral frequencies can be partially preserved according to the maximal degeneracy of the Hessian of the unperturbed system and be fully preserved if the Hessian is nondegenerate; c) the Hamiltonian admits normal forms near the perturbed tori of arbitrarily prescribed high order. Under a sub-isoenergetic nondegenerate condition on an energy surface, we shall show that the majority of unperturbed tori give rise to invariant tori of the perturbed system of the same energy which preserve the ratio of certain components of the respective frequencies.The first author is partially supported by NSFC grant 19971042, National 973 key Project: Nonlinearity in China and
the outstanding youth project of Ministry of Education of China. The second author is partially supported by NSF grant DMS9803581.
This work is partially done when the second and third authors were visiting the National University of Singapore
Consent and Dissent: A Study of the Reaction of Chinese School Teachers in Guangzhou City Schools to Government Educational Reforms
This paper presents detailed qualitative evidence from a case study of teachers in five Chinese schools in one city. It explicitly seeks to show how developments in government policy towards education have altered the management of teacher labour inside schools as well as the teacher labour process as expressed by the teachers themselves in interviews and questionnaires. In this paper, we explore supervision, work intensification, and the erosion of professionalism. We conclude that some changes have taken place as predicted by the labour process model, but that the reaction of the teachers to more extensive controls has been variable. In particular senior school managers did have greater control with high levels of supervision, but that was generally welcomed as preferable to the previous system of outside control and neglect. While workload increased overall, the teachers were more likely to have to work outside of normal duties rather than experience any increase in formal contractual obligations
NPRF: A Neural Pseudo Relevance Feedback Framework for Ad-hoc Information Retrieval
Pseudo-relevance feedback (PRF) is commonly used to boost the performance of
traditional information retrieval (IR) models by using top-ranked documents to
identify and weight new query terms, thereby reducing the effect of
query-document vocabulary mismatches. While neural retrieval models have
recently demonstrated strong results for ad-hoc retrieval, combining them with
PRF is not straightforward due to incompatibilities between existing PRF
approaches and neural architectures. To bridge this gap, we propose an
end-to-end neural PRF framework that can be used with existing neural IR models
by embedding different neural models as building blocks. Extensive experiments
on two standard test collections confirm the effectiveness of the proposed NPRF
framework in improving the performance of two state-of-the-art neural IR
models.Comment: Full paper in EMNLP 201
A Knowledge Gradient Policy for Sequencing Experiments to Identify the Structure of RNA Molecules Using a Sparse Additive Belief Model
We present a sparse knowledge gradient (SpKG) algorithm for adaptively
selecting the targeted regions within a large RNA molecule to identify which
regions are most amenable to interactions with other molecules. Experimentally,
such regions can be inferred from fluorescence measurements obtained by binding
a complementary probe with fluorescence markers to the targeted regions. We use
a biophysical model which shows that the fluorescence ratio under the log scale
has a sparse linear relationship with the coefficients describing the
accessibility of each nucleotide, since not all sites are accessible (due to
the folding of the molecule). The SpKG algorithm uniquely combines the Bayesian
ranking and selection problem with the frequentist regularized
regression approach Lasso. We use this algorithm to identify the sparsity
pattern of the linear model as well as sequentially decide the best regions to
test before experimental budget is exhausted. Besides, we also develop two
other new algorithms: batch SpKG algorithm, which generates more suggestions
sequentially to run parallel experiments; and batch SpKG with a procedure which
we call length mutagenesis. It dynamically adds in new alternatives, in the
form of types of probes, are created by inserting, deleting or mutating
nucleotides within existing probes. In simulation, we demonstrate these
algorithms on the Group I intron (a mid-size RNA molecule), showing that they
efficiently learn the correct sparsity pattern, identify the most accessible
region, and outperform several other policies
Reliability Assurance for Deep Neural Network Architectures Against Numerical Defects
With the widespread deployment of deep neural networks (DNNs), ensuring the
reliability of DNN-based systems is of great importance. Serious reliability
issues such as system failures can be caused by numerical defects, one of the
most frequent defects in DNNs. To assure high reliability against numerical
defects, in this paper, we propose the RANUM approach including novel
techniques for three reliability assurance tasks: detection of potential
numerical defects, confirmation of potential-defect feasibility, and suggestion
of defect fixes. To the best of our knowledge, RANUM is the first approach that
confirms potential-defect feasibility with failure-exhibiting tests and
suggests fixes automatically. Extensive experiments on the benchmarks of 63
real-world DNN architectures show that RANUM outperforms state-of-the-art
approaches across the three reliability assurance tasks. In addition, when the
RANUM-generated fixes are compared with developers' fixes on open-source
projects, in 37 out of 40 cases, RANUM-generated fixes are equivalent to or
even better than human fixes.Comment: To appear at 45th International Conference on Software Engineering
(ICSE 2023), camera-ready versio
Special Libraries, November 1922
Volume 13, Issue 9https://scholarworks.sjsu.edu/sla_sl_1922/1008/thumbnail.jp
Transforming Programs between APIs with Many-to-Many Mappings
Transforming programs between two APIs or different versions of
the same API is a common software engineering task. However,
existing languages supporting for such transformation cannot
satisfactorily handle the cases when the relations between
elements in the old API and the new API are many-to-many
mappings: multiple invocations to the old API are supposed to be
replaced by multiple invocations to the new API. Since the
multiple invocations of the original APIs may not appear
consecutively and the variables in these calls may have different
names, writing a tool correctly to cover all such invocation
cases is not an easy task. In this paper we propose a novel
guided-normalization approach to address this problem. Our core
insight is that programs in different forms can be
semantics-equivalently normalized into a basic form guided by
transformation goals, and developers only need to write rules for
the basic form to address the transformation. Based on this
approach, we design a declarative program transformation
language, PATL, for adapting Java programs between different
APIs. PATL has simple syntax and basic semantics to handle
transformations only considering consecutive statements inside
basic blocks, while with guided-normalization, it can be extended
to handle complex forms of invocations. Furthermore, PATL ensures
that the user-written rules would not accidentally break def-use
relations in the program. We formalize the semantics of PATL on
Middleweight Java and prove the semantics-preserving property of
guided-normalization. We also evaluated our language with three
non-trivial case studies: i.e. updating Google Calendar API,
switching from JDom to Dom4j, and switching from Swing to
SWT. The result is encouraging; it shows that our language allows
successful transformations of real world programs with a small
number of rules and little manual resolution
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