7,592 research outputs found
When voters decide: Causes, correlates and effects of the time-of-voting-decision
Why do individuals make their vote decisions at the point in time at which they do, and what impact does the time-of-voting-decision (TOVD) have upon other important political variables? Through a series of integrated articles, this dissertation explores the causes, correlates and effects of TOVD in Canada. The first two articles explore the relationships between TOVD and political attitudes, employing TOVD as both an independent and dependent variable. The first examines the impact that consistency, intensity and direction of summary political attitudes have on TOVD, and introduces a new measure of attitudinal ambivalence. The second article employs cognitive dissonance theory to argue that TOVD can influence attitudes towards parties, after an election occurs. The third and fourth articles respectively consider the relationships between TOVD and vote sincerity, and an individual’s ability to vote for the party that best reflects his or her own policy preferences. Insincere voters are found to have a relatively late TOVD, which the third article attributes to the fact that these individuals are able to use the campaign period to update their expectations about the competitive prospects of candidates and parties. The fourth and final article uses TOVD as a mediating variable to evaluate the impact of the campaign period on correct voting rates. It finds that late deciders, who are able to use the campaign period to collect information to inform their vote decisions, are actually less likely to vote correctly than are early deciders. The dissertation also includes a research note which outlines a new method of identifying invalid TOVD responses, and illustrates the importance of removing such cases. As a whole, this dissertation adds significantly to our knowledge of TOVD, a variable which, until now, has received relatively little scholarly attention
On one-sided primitivity of Banach algebras
Let be the semigroup with identity, generated by and , subject to
being invertible and . We study two Banach algebra completions of
the semigroup algebra . Both completions are shown to be
left-primitive and have separating families of irreducible infinite-dimensional
right modules. As an appendix, we offer an alternative proof that
is left-primitive but not right-primitive. We show further that, in contrast to
the completions, every irreducible right module for is finite
dimensional and hence that has a separating family of such
modules.Comment: 14 pages. To appear, with minor changes, in the Proceedings of the
Edinburgh Mathematical Societ
Sublinear Estimation of Weighted Matchings in Dynamic Data Streams
This paper presents an algorithm for estimating the weight of a maximum
weighted matching by augmenting any estimation routine for the size of an
unweighted matching. The algorithm is implementable in any streaming model
including dynamic graph streams. We also give the first constant estimation for
the maximum matching size in a dynamic graph stream for planar graphs (or any
graph with bounded arboricity) using space which also
extends to weighted matching. Using previous results by Kapralov, Khanna, and
Sudan (2014) we obtain a approximation for general graphs
using space in random order streams, respectively. In
addition, we give a space lower bound of for any
randomized algorithm estimating the size of a maximum matching up to a
factor for adversarial streams
Maximum Matching in Turnstile Streams
We consider the unweighted bipartite maximum matching problem in the one-pass
turnstile streaming model where the input stream consists of edge insertions
and deletions. In the insertion-only model, a one-pass -approximation
streaming algorithm can be easily obtained with space , where
denotes the number of vertices of the input graph. We show that no such result
is possible if edge deletions are allowed, even if space is
granted, for every . Specifically, for every , we show that in the one-pass turnstile streaming model, in order to compute
a -approximation, space is
required for constant error randomized algorithms, and, up to logarithmic
factors, space is sufficient. Our lower bound result is
proved in the simultaneous message model of communication and may be of
independent interest
The role of Zn in the sustainable one-pot synthesis of dimethyl carbonate from carbon dioxide, methanol and propylene oxide
Dimethyl carbonate (DMC) can be applied as a greener alternative to more hazardous materials, e.g. phosgene or dimethyl sulfate. Herein, one-pot synthesis of DMC from propylene oxide, methanol and CO2 using alkali halide catalysts under mild conditions was studied. Addition of Zn powder to the K2CO3-NaBr-ZnO catalyst system was seen to increase DMC selectivity from 19.8% (TOF = 39.0 h-1) to 40.2% (TOF = 78.1 h-1) at 20 bar and 160 °C for 5 h. Catalyst characterisation showed that Zn powder increases the stability of the catalyst, preventing the active ingredients on the catalyst surface from leaching. An increase in propylene oxide conversion to DMC is attributed to the increase of Zn2+ ions in the reaction solution. Elevated pressure was not found to be a necessary reaction condition for transesterification. This study shows that increased selectivity to DMC can be achieved at mild conditions with the addition of Zn powder
The role of Zn in the sustainable one-pot synthesis of dimethyl carbonate from carbon dioxide, methanol and propylene oxide
Dimethyl carbonate (DMC) can be applied as a greener alternative to more hazardous materials, e.g. phosgene or dimethyl sulfate. Herein, one-pot synthesis of DMC from propylene oxide, methanol and CO2 using alkali halide catalysts under mild conditions was studied. Addition of Zn powder to the K2CO3-NaBr-ZnO catalyst system was seen to increase DMC selectivity from 19.8% (TOF = 39.0 h-1) to 40.2% (TOF = 78.1 h-1) at 20 bar and 160 °C for 5 h. Catalyst characterisation showed that Zn powder increases the stability of the catalyst, preventing the active ingredients on the catalyst surface from leaching. An increase in propylene oxide conversion to DMC is attributed to the increase of Zn2+ ions in the reaction solution. Elevated pressure was not found to be a necessary reaction condition for transesterification. This study shows that increased selectivity to DMC can be achieved at mild conditions with the addition of Zn powder
Temperature-dependent Hall scattering factor and drift mobility in remotely doped Si:B/SiGe/Si heterostructures
Hall-and-Strip measurements on modulation-doped SiGe heterostructures and combined Hall and capacitance–voltage measurements on metal-oxide-semiconductor (MOS)-gated enhancement mode structures have been used to deduce Hall scattering factors, rH, in the Si1 – xGex two-dimensional hole gas. At 300 K, rH was found to be equal to 0.4 for x = 0.2 and x = 0.3. Knowing rH, it is possible to calculate the 300 K drift mobilities in the modulation-doped structures which are found to be 400 cm2 V – 1 s – 1 at a carrier density of 3.3 × 1011 cm – 2 for x = 0.2 and 300 cm2 V – 1 s – 1 at 6.3 × 1011 cm – 2 for x = 0.3, factors of between 1.5 and 2.0 greater than a Si pMOS control
Submodular Maximization Meets Streaming: Matchings, Matroids, and More
We study the problem of finding a maximum matching in a graph given by an
input stream listing its edges in some arbitrary order, where the quantity to
be maximized is given by a monotone submodular function on subsets of edges.
This problem, which we call maximum submodular-function matching (MSM), is a
natural generalization of maximum weight matching (MWM), which is in turn a
generalization of maximum cardinality matching (MCM). We give two incomparable
algorithms for this problem with space usage falling in the semi-streaming
range---they store only edges, using working memory---that
achieve approximation ratios of in a single pass and in
passes respectively. The operations of these algorithms
mimic those of Zelke's and McGregor's respective algorithms for MWM; the
novelty lies in the analysis for the MSM setting. In fact we identify a general
framework for MWM algorithms that allows this kind of adaptation to the broader
setting of MSM.
In the sequel, we give generalizations of these results where the
maximization is over "independent sets" in a very general sense. This
generalization captures hypermatchings in hypergraphs as well as independence
in the intersection of multiple matroids.Comment: 18 page
- …