2,859 research outputs found
DMX Controlled Scenic Automation
SwiftScene DMX Control is a safe, simple, and low-cost solution to automated scenery marketed to educational level and low-income theaters. The module is an 18ā x 18ā electrical enclosure that attaches to the underside of a stage platform and is fully controlled wirelessly via a light board. This is a scaled down prototype meant as a proof of concept and product viability. It is capable of rotational motion and limited linear motion. This prototype meets expectations of traveling at 1 ft/s with acceleration and deceleration at 0.5 ft/s2, but speed and acceleration can be varied based on desired functionality. An actual product will be able to carry a higher load and perform closer to ideal specifications
Integration of a Stereo Vision System and GPS Data for Recording the Position of Feature Points in a Fixed World Coordinate System
This paper describes a laboratory system for recovering the global coordinates of feature points obtained from a moving camera. The prototype includes a stereo vision system combined with an overhead camera, which mimics a GPS receiver. The stereo vision system provides three dimensional feature point coordinates relative to the position of the cameras and the overhead camera provides three-dimensional coordinates of the camera in a āglobalā coordinate system. The fusion of these data provides three-dimensional feature point coordinates in a fixed origin global coordinate system
Bee-Friendly Beef: Developing Biodiverse Pastures to Increase Ecosystem Services
The capacity of grasslands to provide ecosystem services, such as pollinator resources, is often limited by lack of plant biodiversity. This is true of grasslands in the eastern US that are dominated by tall fescue (Festuca arundinacea) a non-native, cool-season grass that is typically toxic to cattle. This paper summarizes a research project in Virginia, USA exploring the idea that ecosystem services provided by tall fescue-dominated grasslands can be improved by increasing the plant biodiversity available to beef cattle and bees. Within three 6.5 ha tall fescue grasslands, we established 0.8 ha plots with a 17 species mix of native warm-season grasses (NWSGs) and wildflowers. Beginning in 2018, we measured grass and wildflower establishment, attractiveness of wildflowers to bees, abundance and diversity of bee communities in biodiverse pastures and adjacent tall fescue pastures. Many of the 18 species sown established well expect for NWSGs. Competition from wildflowers likely suppressed native grasses and limited forage availability for beef cattle. Cattle largely ignored the wildflowers. This finding suggests that cattle and pollinators can share this biodiverse grassland as their primary foods are mutually exclusive. The total number of bees was almost double in wildflower-enhanced grasslands compared with more typical tall fescue grasslands. We observed most bee landings on purple coneflower (Echinacea purpurea) and anise hyssop (Agastache foeniculum). Several weedy species such as milkweed (Asclepias syriaca) and musk thistle (Carduus nutans) were also attractive to bees. Preliminary analyses identified at least 28 bee morphospecies and a distinct bee community present in wildflower pastures. While these results were promising, more research is needed on ways to establish biodiverse grasslands so that a more optimal balance of grasses and wildflowers can be sustained to benefit both cattle production and pollinators
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
A Characterization of Visibility Graphs for Pseudo-Polygons
In this paper, we give a characterization of the visibility graphs of
pseudo-polygons. We first identify some key combinatorial properties of
pseudo-polygons, and we then give a set of five necessary conditions based off
our identified properties. We then prove that these necessary conditions are
also sufficient via a reduction to a characterization of vertex-edge visibility
graphs given by O'Rourke and Streinu
Simulation studies of a phenomenological model for elongated virus capsid formation
We study a phenomenological model in which the simulated packing of hard,
attractive spheres on a prolate spheroid surface with convexity constraints
produces structures identical to those of prolate virus capsid structures. Our
simulation approach combines the traditional Monte Carlo method with a modified
method of random sampling on an ellipsoidal surface and a convex hull searching
algorithm. Using this approach we identify the minimum physical requirements
for non-icosahedral, elongated virus capsids, such as two aberrant flock house
virus (FHV) particles and the prolate prohead of bacteriophage , and
discuss the implication of our simulation results in the context of recent
experimental findings. Our predicted structures may also be experimentally
realized by evaporation-driven assembly of colloidal spheres
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
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
A Novel Approach for Ellipsoidal Outer-Approximation of the Intersection Region of Ellipses in the Plane
In this paper, a novel technique for tight outer-approximation of the
intersection region of a finite number of ellipses in 2-dimensional (2D) space
is proposed. First, the vertices of a tight polygon that contains the convex
intersection of the ellipses are found in an efficient manner. To do so, the
intersection points of the ellipses that fall on the boundary of the
intersection region are determined, and a set of points is generated on the
elliptic arcs connecting every two neighbouring intersection points. By finding
the tangent lines to the ellipses at the extended set of points, a set of
half-planes is obtained, whose intersection forms a polygon. To find the
polygon more efficiently, the points are given an order and the intersection of
the half-planes corresponding to every two neighbouring points is calculated.
If the polygon is convex and bounded, these calculated points together with the
initially obtained intersection points will form its vertices. If the polygon
is non-convex or unbounded, we can detect this situation and then generate
additional discrete points only on the elliptical arc segment causing the
issue, and restart the algorithm to obtain a bounded and convex polygon.
Finally, the smallest area ellipse that contains the vertices of the polygon is
obtained by solving a convex optimization problem. Through numerical
experiments, it is illustrated that the proposed technique returns a tighter
outer-approximation of the intersection of multiple ellipses, compared to
conventional techniques, with only slightly higher computational cost
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