10,501 research outputs found
Automatic assessment of sequence diagrams
In previous work we showed how student-produced entity-relationship diagrams (ERDs) could be automatically marked with good accuracy when compared with human markers. In this paper we report how effective the same techniques are when applied to syntactically similar UML sequence diagrams and discuss some issues that arise which did not occur with ERDs. We have found that, on a corpus of 100 student-drawn sequence diagrams, the automatic marking technique is more reliable that human markers. In addition, an analysis of this corpus revealed significant syntax errors in student-drawn sequence diagrams. We used the information obtained from the analysis to build a tool that not only detects syntax errors but also provides feedback in diagrammatic form. The tool has been extended to incorporate the automatic marker to provide a revision tool for learning how to model with sequence diagrams
On the Quantum Resolution of Cosmological Singularities using AdS/CFT
The AdS/CFT correspondence allows us to map a dynamical cosmology to a dual
quantum field theory living on the boundary of spacetime. Specifically, we
study a five-dimensional model cosmology in type IIB supergravity, where the
dual theory is an unstable deformation of supersymmetric SU(N) gauge
theory on \Rbar\times S^3. A one-loop computation shows that the coupling
governing the instability is asymptotically free, so quantum corrections cannot
turn the potential around. The big crunch singularity in the bulk occurs when a
boundary scalar field runs to infinity, in finite time. Consistent quantum
evolution requires that we impose boundary conditions at infinite scalar field,
i.e. a self-adjoint extension of the system. We find that quantum spreading of
the homogeneous mode of the boundary scalar leads to a natural UV cutoff in
particle production as the wavefunction for the homogeneous mode bounces back
from infinity. However a perturbative calculation indicates that despite this,
the logarithmic running of the boundary coupling governing the instability
generally leads to significant particle production across the bounce. This
prevents the wave packet of the homogeneous boundary scalar to return close to
its initial form. Translating back to the bulk theory, we conclude that a
quantum transition from a big crunch to a big bang is an improbable outcome of
cosmological evolution in this class of five-dimensional models.Comment: 91 pages, 24 figures; v2: minor reorganization of introduction,
clarifying comments throughout; 77 pages, 22 figures;v5: error corrected
which significantly changes conclusio
Toward the automated assessment of entity-relationship diagrams
The need to interpret imprecise diagrams (those with malformed, missing or extraneous features) occurs in the automated assessment of diagrams. We outline our proposal for an architecture to enable the interpretation of imprecise diagrams. We discuss our preliminary work on an assessment tool, developed within this architecture, for automatically grading answers to a computer architecture examination question. Early indications are that performance is similar to that of human markers. We will be using Entity-Relationship Diagrams (ERDs) as the primary application area for our investigation of automated assessment. This paper will detail our reasons for choosing this area and outline the work ahead
Excluded minors in cubic graphs
Let G be a cubic graph, with girth at least five, such that for every
partition X,Y of its vertex set with |X|,|Y|>6 there are at least six edges
between X and Y. We prove that if there is no homeomorphic embedding of the
Petersen graph in G, and G is not one particular 20-vertex graph, then either
G\v is planar for some vertex v, or G can be drawn with crossings in the plane,
but with only two crossings, both on the infinite region. We also prove several
other theorems of the same kind.Comment: 62 pages, 17 figure
Financial Benefits of Florida Generic Orange Juice Marketing
The benefits to Florida orange growers of generic orange juice advertising are assessed using additive, nonlinear, regional econometric models, measuring the impact of category and brand marketing efforts on category demand while controlling for pricing and various other factors. The study shows that generic marketing efforts increased orange juice category demand by 8.3 percent, resulting in increased orange prices and a benefit-to-cost ratio to Florida growers of 3.5 to 1. Branded promotional activity was found to primarily fuel brand switching and pantry-loading, with only modest impacts on overall category demand.marketing mix, marketing spend optimization, checkoff program, orange juice, benefit to cost ratio, Marketing,
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