Educação matemática pela arte
Gusmão, Lucimar Donizete
2013-08-28
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24,714 records were found.
One of the major problems in frequent pattern mining is the explosion of
the number of results, making it difficult to identify the interesting frequent
patterns. In a recent paper [14] we have shown that an MDL-based approach
gives a dramatic reduction of the number of frequent item sets to consider.
Here we show that MDL gives similarly good reductions for frequent patterns
on other types of data, viz., on sequences and trees. Reductions of two
to three orders of magnitude are easily attained on data sets from the webmining
field.
We describe and compare two algorithms for making data sets monotone with
as few label changes as possible. These algorithms are useful for preparing data sets
for the analysis with data mining algorithms that require monotone data. Also, the
relabeled data set can be viewed as the monotone classifier with minimum error rate
on the training data. The first algorithm is a greedy algorithm that runs in O(LN3)
time, where L is the number of distinct class labels, and N is the number of observations,
but it is not guaranteed to perform the minimum number of label changes
required. The second algorithm is an exact algorithm based on a translation of the
problem to finding a maximum weight independent set in the so-called monotonicity
violation graph. This problem, in turn, is solved by solving a minimum flow problem
in a transportation netw...
Metals halides with the fluorite structure attain conductivity values typical of ionic melts far below their melting points, and also go through a second-order transition. Conductivity data for the fluorites are reviewed, and it is shown that the anion vacancies have a large and unique mobility value at the transition temperatures Tc. At Tc only small concentrations of defects are present, which strongly contradicts the concept of anion-sublattice melting. The conductivity mechanism above Tc is discussed in relation with the enhanced ionic motion model developed for concentrated anion-excess solid solutions based upon flourites. As a consequences of unusually large defect mobilities at Tc it is noted that retard ionic motion occurs above Tc.
Web Cube is a server side programming model for building interactive web applications. Compared
to typical server side approaches used nowadays, Web Cube offers better abstraction
mechanism and built-in safety. It imposes a more logical organization of its components. As a
direct result of this applications become inherently secure and development is less error prone.
Web Cube is based on Seuss, a framework for modelling distributed systems. Seuss is rather
light weight, but is abstract enough to allow convenient programming. It comes with a simple
but powerful logic that allows safety and other temporal properties of a Web Cube application
to be specified and verified.
A delay-line position readout system connected to the proportional counter of a gas-filled heavy-ion detector was constructed and tested in a magnetic spectrograph. The measured position resolution was less than 0.3 mm (fwhm) which is 0.1% of the full detector length (250 mm). The differential nonlinearity of the readout system was found to be less than 1.0 mm.
Type error messages that are reported for incorrect functional programs
can be difficult to understand. The reason for this is that most type inference
algorithms proceed in a mechanical, syntax-directed way, and are unaware
of inference techniques used by experts to explain type inconsistencies. We formulate
type inference as a constraint problem, and analyze the collected constraints
to improve the error messages (and, as a result, programming efficiency).
A special data structure, the type graph, is used to detect global properties of
a program, and furthermore enables us to uniformly describe a large collection
of heuristics which embed expert knowledge in explaining type errors. Some of
these also suggest corrections to the programmer. Our work has been fully implemented
and is used in practical situations, showing that it scales ...
While quantitative probabilistic networks (QPNs) allow experts to state influences
between nodes in the network as influence signs, rather than conditional probabilities,
inference in these networks often leads to ambiguous results due to unresolved trade-offs
in the network. Various enhancements have been proposed that incorporate a notion
of strength of the influence, such as enhanced and rich enhanced operators. Although
inference in standard (i.e., not enhanced) QPNs can be done in time polynomial to the
length of the input, the computational complexity of inference in these enhanced networks
has not been determined yet. In this paper, we introduce relaxation schemes to relate
these enhancements to the more general case where continuous influence intervals are
used. We show that inference in networks with continuous influence inter...
This paper addresses the problem of maneuvering an object by pushing it through an
environment with obstacles. Instead of only pushing the object through open areas, we
also allow it to use compliance, e.g. allowing it to slide along obstacle boundaries. Using
compliance has a number of advantages: it extends the number of situations in which a
push plan can be found, it allows for simpler (i.e. less complicated) paths in many cases
and it often helps solving narrow passage problems. Here, we present an approach based
on the Rapidly-exploring Random Tree (RRT). Our approach yields paths through the
open space, but also exploits the power of compliance.
