2,897 research outputs found
Trade, Technology and the Great Divergence
This paper develops a model that captures the key features of the Industrial Revolution and the Great Divergence between the industrializing \North" and the lagging \South." In particular, a convincing story is needed for why North-South divergence occurred so dramatically during the late 19th Century, a good hundred years after the beginnings of the Industrial Revolution. To this end we construct a trade/growth model that includes both endogenous biased technologies and intercontinental trade. The Industrial Revolution began as a sequence of unskilled-labor intensive innovations which initially incited fertil- ity increases and limited human capital formation in both the North and the South. The subsequent co-evolution of trade and technological growth however fostered an inevitable di- vergence in living standards - the South increasingly specialized in production that worsened their terms of trade and spurred even greater fertility increases and educational declines. Biased technological changes in both regions only reinforced this pattern. The model high- lights how pronounced divergence ultimately arose from interactions between specialization from trade and technological forces.
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
Ear-clipping Based Algorithms of Generating High-quality Polygon Triangulation
A basic and an improved ear clipping based algorithm for triangulating simple
polygons and polygons with holes are presented. In the basic version, the ear
with smallest interior angle is always selected to be cut in order to create
fewer sliver triangles. To reduce sliver triangles in further, a bound of angle
is set to determine whether a newly formed triangle has sharp angles, and edge
swapping is accepted when the triangle is sharp. To apply the two algorithms on
polygons with holes, "Bridge" edges are created to transform a polygon with
holes to a degenerate polygon which can be triangulated by the two algorithms.
Applications show that the basic algorithm can avoid creating sliver triangles
and obtain better triangulations than the traditional ear clipping algorithm,
and the improved algorithm can in further reduce sliver triangles effectively.
Both of the algorithms run in O(n2) time and O(n) space.Comment: Proceedings of the 2012 International Conference on Information
Technology and Software Engineering Lecture Notes in Electrical Engineering
Volume 212, 2013, pp 979-98
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
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
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
Work Attitudes of Students who are Deaf and Their Potential Employers
This study examined the attitudes held by high school students who are deaf and their potential employers regarding employees who are deaf. The subjects of this study were 30 employers from a large metropolitan area in the southeast and 30 high school students who are deaf. Subjects responded to a Likert scale that focused on how each group perceived the others\u27 opinions of work-related issues and attitudes. Results indicated three individual areas of significance (i.e., writing, intelligence, and inability to use a telephone) and one significant aggregate group (i.e., communication). The authors discuss these results from the perspective of providing information to professionals preparing high school students who are deaf for the world of work
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
Casting Light Upon The Great Endarkenment
While the Enlightenment promoted thinking for oneself independent of religious authority, the āEndarkenmentā (Millgram 2015) concerns deference to a new authority: the specialist, a hyperspecializer. Non-specialists need to defer to such authorities as they are unable to understand their reasoning. Millgram describes how humans are capable of being serial hyperspecializers, able to move from one specialism to another. We support the basic thrust of Millgramās position, and seek to articulate how the core idea is deployed in very different ways in relation to extremely different philosophical areas. We attend to the issue of the degree of isolation of different specialists and we urge greater emphasis on parallel hyperspecialization, which describes how different specialisms can be embodied in one person at one time
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