1,324 research outputs found
TopSig: Topology Preserving Document Signatures
Performance comparisons between File Signatures and Inverted Files for text
retrieval have previously shown several significant shortcomings of file
signatures relative to inverted files. The inverted file approach underpins
most state-of-the-art search engine algorithms, such as Language and
Probabilistic models. It has been widely accepted that traditional file
signatures are inferior alternatives to inverted files. This paper describes
TopSig, a new approach to the construction of file signatures. Many advances in
semantic hashing and dimensionality reduction have been made in recent times,
but these were not so far linked to general purpose, signature file based,
search engines. This paper introduces a different signature file approach that
builds upon and extends these recent advances. We are able to demonstrate
significant improvements in the performance of signature file based indexing
and retrieval, performance that is comparable to that of state of the art
inverted file based systems, including Language models and BM25. These findings
suggest that file signatures offer a viable alternative to inverted files in
suitable settings and from the theoretical perspective it positions the file
signatures model in the class of Vector Space retrieval models.Comment: 12 pages, 8 figures, CIKM 201
Document Clustering with K-tree
This paper describes the approach taken to the XML Mining track at INEX 2008
by a group at the Queensland University of Technology. We introduce the K-tree
clustering algorithm in an Information Retrieval context by adapting it for
document clustering. Many large scale problems exist in document clustering.
K-tree scales well with large inputs due to its low complexity. It offers
promising results both in terms of efficiency and quality. Document
classification was completed using Support Vector Machines.Comment: 12 pages, INEX 200
K-tree: Large Scale Document Clustering
We introduce K-tree in an information retrieval context. It is an efficient
approximation of the k-means clustering algorithm. Unlike k-means it forms a
hierarchy of clusters. It has been extended to address issues with sparse
representations. We compare performance and quality to CLUTO using document
collections. The K-tree has a low time complexity that is suitable for large
document collections. This tree structure allows for efficient disk based
implementations where space requirements exceed that of main memory.Comment: 2 pages, SIGIR 200
Random Indexing K-tree
Random Indexing (RI) K-tree is the combination of two algorithms for
clustering. Many large scale problems exist in document clustering. RI K-tree
scales well with large inputs due to its low complexity. It also exhibits
features that are useful for managing a changing collection. Furthermore, it
solves previous issues with sparse document vectors when using K-tree. The
algorithms and data structures are defined, explained and motivated. Specific
modifications to K-tree are made for use with RI. Experiments have been
executed to measure quality. The results indicate that RI K-tree improves
document cluster quality over the original K-tree algorithm.Comment: 8 pages, ADCS 2009; Hyperref and cleveref LaTeX packages conflicted.
Removed clevere
Improving the Efficiency of an Ideal Heat Engine: The Quantum Afterburner
By using a laser and maser in tandem, it is possible to obtain laser action
in the hot exhaust gases involved in heat engine operation. Such a "quantum
afterburner" involves the internal quantum states of working gas atoms or
molecules as well as the techniques of cavity quantum electrodynamics and is
therefore in the domain of quantum thermodynamics. As an example, it is shown
that Otto cycle engine performance can be improved beyond that of the "ideal"
Otto heat engine.Comment: 5 pages, 3 figure
A quantum-mechanical Maxwell's demon
A Maxwell's demon is a device that gets information and trades it in for
thermodynamic advantage, in apparent (but not actual) contradiction to the
second law of thermodynamics. Quantum-mechanical versions of Maxwell's demon
exhibit features that classical versions do not: in particular, a device that
gets information about a quantum system disturbs it in the process. In
addition, the information produced by quantum measurement acts as an additional
source of thermodynamic inefficiency. This paper investigates the properties of
quantum-mechanical Maxwell's demons, and proposes experimentally realizable
models of such devices.Comment: 13 pages, Te
What Should Congress Members Do? Using Survey Embedded Experiments to Study Citizensâ Clientelistic Expectations in Mexico
How do citizens view the work of their legislators? Do they think representatives should legislate and oversee the executive, or do they believe representatives should deliver resources to their community and help individuals with problems? Do they expect both? In Latin America surveys typically show that popular evaluations of the national congress are overwhelmingly negative but are not able to explain why. Are congresses held in low esteem because people think that congress is not legislating well or efficiently overseeing the executive, or because citizens do not know what legislators are supposed to do and want them to deliver pork for their district and personalistic benefits for themselves? Since clientelism targets the poor and plays an important role in elections in developing democ- racies, it is important to know if poor citizens truly have different views than wealthier citizens about what a member of congress should do once elected. We use quasi-experimental procedures in a public opinion survey administered in Mexico City to begin to address these questions. Our findings indicate that poorer citizens, people with no or very little education, have greater expectations of clientelism than wealthier citizens but that their view of a legislatorâs job is more subtle, and more democratic than would be predicted by clientelism theory.How do citizens view the work of their legislators? Do they think representatives should legislate and oversee the executive, or do they believe representatives should deliver resources to their community and help individuals with problems? Do they expect both? In Latin America surveys typically show that popular evaluations of the national congress are overwhelmingly negative but are not able to explain why. Are congresses held in low esteem because people think that congress is not legislating well or efficiently overseeing the executive, or because citizens do not know what legislators are supposed to do and want them to deliver pork for their district and personalistic benefits for themselves? Since clientelism targets the poor and plays an important role in elections in developing democ- racies, it is important to know if poor citizens truly have different views than wealthier citizens about what a member of congress should do once elected. We use quasi-experimental procedures in a public opinion survey administered in Mexico City to begin to address these questions. Our findings indicate that poorer citizens, people with no or very little education, have greater expectations of clientelism than wealthier citizens but that their view of a legislatorâs job is more subtle, and more democratic than would be predicted by clientelism theory
L\'evy Distribution of Single Molecule Line Shape Cumulants in Low Temperature Glass
We investigate the distribution of single molecule line shape cumulants,
, in low temperature glasses based on the sudden jump,
standard tunneling model. We find that the cumulants are described by L\'evy
stable laws, thus generalized central limit theorem is applicable for this
problem.Comment: 5 pages, 3 figure
Performance of discrete heat engines and heat pumps in finite time
The performance in finite time of a discrete heat engine with internal
friction is analyzed. The working fluid of the engine is composed of an
ensemble of noninteracting two level systems. External work is applied by
changing the external field and thus the internal energy levels. The friction
induces a minimal cycle time. The power output of the engine is optimized with
respect to time allocation between the contact time with the hot and cold baths
as well as the adiabats. The engine's performance is also optimized with
respect to the external fields. By reversing the cycle of operation a heat pump
is constructed. The performance of the engine as a heat pump is also optimized.
By varying the time allocation between the adiabats and the contact time with
the reservoir a universal behavior can be identified. The optimal performance
of the engine when the cold bath is approaching absolute zero is studied. It is
found that the optimal cooling rate converges linearly to zero when the
temperature approaches absolute zero.Comment: 45 pages LaTeX, 25 eps figure
From XML Retrieval to Semantic Search and Beyond:The INEX, SBS, and MC2 Labs of CLEF 2012-2018
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