1,586 research outputs found
Standards of Practice in Postsecondary Special Needs Programming: Student and Administrator Opinion
Standards of practice for postsecondary special needs programmes are an important element to determining programme effectiveness and programme successes. A number of groups have now suggested practice standards for postsecondary special needs programmes. We amalgamated these suggested practices and queried Ontario students and administrators regarding their opinion of these practice standards. Overall, strong support for most suggested practices was found among students and administrators. However, administrators less strongly supported practices that required enhanced funding, staffing and resources. In addition, students less strongly supported practices that could reduce individualized programming and increase time commitments. Administrators pointed out barriers to achieving practice standards. Time commitments, workload, funding, unclear working definitions (i.e., standards for transition, disabilities) and institutional policy constraints were barriers to achieving suggested practice standards.Les normes qui reĢgissent les pratiques des programmes adapteĢs du niveau postsecondaire repreĢsentent un eĢleĢment important dans la deĢtermination de l'efficaciteĢ de ceux-ci et de leur succeĢs. Un certain nombre de groupes ont suggeĢreĢ des normes de pratique pour ces programmes eĢducatifs speĢciaux. Nous avons regroupeĢ ces pratiques suggeĢreĢes et avons interrogeĢ des eĢtudiants en Ontario ainsi que des administrateurs afin d'obtenir leur opinion sur ces nonnes de pratique. En geĢneĢral, un soutien important aĢ l'eĢgard de la plupart des pratiques suggeĢreĢes a eĢteĢ noteĢ parmi les eĢtudiants et les membres de l'administration. Toutefois, les administrateurs ont reĢserveĢ un accueil moins enthousiaste aux pratiques qui neĢcessitent une augmentation du financement, du personnel et des ressources. De plus, les eĢtudiants ont moins bien accueilli les pratiques qui seraient susceptibles de reĢduire les programmes personnaliseĢs et qui augmenteraient leur investissement en terme de temps. Les administrateurs ont preĢciseĢ les obstacles aĢ la reĢalisation de ces pratiques; les barrieĢres identifieĢes pour leur mise en place furent : l'investissement en terme de temps, la charge de travail, le financement, des conditions de travail mal deĢfinies (c'est-aĢ-dire les normes de transition, d'incapaciteĢs) et les contraintes des politiques institutionnelles
Simulations of slow positron production using a low energy electron accelerator
Monte Carlo simulations of slow positron production via energetic electron
interaction with a solid target have been performed. The aim of the simulations
was to determine the expected slow positron beam intensity from a low energy,
high current electron accelerator. By simulating (a) the fast positron
production from a tantalum electron-positron converter and (b) the positron
depth deposition profile in a tungsten moderator, the slow positron production
probability per incident electron was estimated. Normalizing the calculated
result to the measured slow positron yield at the present AIST LINAC the
expected slow positron yield as a function of energy was determined. For an
electron beam energy of 5 MeV (10 MeV) and current 240 A (30 A)
production of a slow positron beam of intensity 5 10 s is
predicted. The simulation also calculates the average energy deposited in the
converter per electron, allowing an estimate of the beam heating at a given
electron energy and current. For low energy, high-current operation the maximum
obtainable positron beam intensity will be limited by this beam heating.Comment: 11 pages, 15 figures, submitted to Review of Scientific Instrument
Facets for Art Gallery Problems
The Art Gallery Problem (AGP) asks for placing a minimum number of stationary
guards in a polygonal region P, such that all points in P are guarded. The
problem is known to be NP-hard, and its inherent continuous structure (with
both the set of points that need to be guarded and the set of points that can
be used for guarding being uncountably infinite) makes it difficult to apply a
straightforward formulation as an Integer Linear Program. We use an iterative
primal-dual relaxation approach for solving AGP instances to optimality. At
each stage, a pair of LP relaxations for a finite candidate subset of primal
covering and dual packing constraints and variables is considered; these
correspond to possible guard positions and points that are to be guarded.
Particularly useful are cutting planes for eliminating fractional solutions.
We identify two classes of facets, based on Edge Cover and Set Cover (SC)
inequalities. Solving the separation problem for the latter is NP-complete, but
exploiting the underlying geometric structure, we show that large subclasses of
fractional SC solutions cannot occur for the AGP. This allows us to separate
the relevant subset of facets in polynomial time. We also characterize all
facets for finite AGP relaxations with coefficients in {0, 1, 2}.
Finally, we demonstrate the practical usefulness of our approach. Our cutting
plane technique yields a significant improvement in terms of speed and solution
quality due to considerably reduced integrality gaps as compared to the
approach by Kr\"oller et al.Comment: 29 pages, 18 figures, 1 tabl
Rates of convergence for empirical spectral measures: a soft approach
Understanding the limiting behavior of eigenvalues of random matrices is the
central problem of random matrix theory. Classical limit results are known for
many models, and there has been significant recent progress in obtaining more
quantitative, non-asymptotic results. In this paper, we describe a systematic
approach to bounding rates of convergence and proving tail inequalities for the
empirical spectral measures of a wide variety of random matrix ensembles. We
illustrate the approach by proving asymptotically almost sure rates of
convergence of the empirical spectral measure in the following ensembles:
Wigner matrices, Wishart matrices, Haar-distributed matrices from the compact
classical groups, powers of Haar matrices, randomized sums and random
compressions of Hermitian matrices, a random matrix model for the Hamiltonians
of quantum spin glasses, and finally the complex Ginibre ensemble. Many of the
results appeared previously and are being collected and described here as
illustrations of the general method; however, some details (particularly in the
Wigner and Wishart cases) are new.
Our approach makes use of techniques from probability in Banach spaces, in
particular concentration of measure and bounds for suprema of stochastic
processes, in combination with more classical tools from matrix analysis,
approximation theory, and Fourier analysis. It is highly flexible, as evidenced
by the broad list of examples. It is moreover based largely on "soft" methods,
and involves little hard analysis
Engineering Art Galleries
The Art Gallery Problem is one of the most well-known problems in
Computational Geometry, with a rich history in the study of algorithms,
complexity, and variants. Recently there has been a surge in experimental work
on the problem. In this survey, we describe this work, show the chronology of
developments, and compare current algorithms, including two unpublished
versions, in an exhaustive experiment. Furthermore, we show what core
algorithmic ingredients have led to recent successes
Universal microscopic correlation functions for products of independent Ginibre matrices
We consider the product of n complex non-Hermitian, independent random
matrices, each of size NxN with independent identically distributed Gaussian
entries (Ginibre matrices). The joint probability distribution of the complex
eigenvalues of the product matrix is found to be given by a determinantal point
process as in the case of a single Ginibre matrix, but with a more complicated
weight given by a Meijer G-function depending on n. Using the method of
orthogonal polynomials we compute all eigenvalue density correlation functions
exactly for finite N and fixed n. They are given by the determinant of the
corresponding kernel which we construct explicitly. In the large-N limit at
fixed n we first determine the microscopic correlation functions in the bulk
and at the edge of the spectrum. After unfolding they are identical to that of
the Ginibre ensemble with n=1 and thus universal. In contrast the microscopic
correlations we find at the origin differ for each n>1 and generalise the known
Bessel-law in the complex plane for n=2 to a new hypergeometric kernel 0_F_n-1.Comment: 20 pages, v2 published version: typos corrected and references adde
Wavelet Based Fractal Analysis of Airborne Pollen
The most abundant biological particles in the atmosphere are pollen grains
and spores. Self protection of pollen allergy is possible through the
information of future pollen contents in the air. In spite of the importance of
airborne pol len concentration forecasting, it has not been possible to predict
the pollen concentrations with great accuracy, and about 25% of the daily
pollen forecasts have resulted in failures. Previous analysis of the dynamic
characteristics of atmospheric pollen time series indicate that the system can
be described by a low dimensional chaotic map. We apply the wavelet transform
to study the multifractal characteristics of an a irborne pollen time series.
We find the persistence behaviour associated to low pollen concentration values
and to the most rare events of highest pollen co ncentration values. The
information and the correlation dimensions correspond to a chaotic system
showing loss of information with time evolution.Comment: 11 pages, 7 figure
Risk factors for inpatient violence and self-harm in forensic psychiatry:The role of head injury, schizophrenia and substance misuse
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