2,670 research outputs found
Algorithms to measure diversity and clustering in social networks through dot product graphs.
Social networks are often analyzed through a graph model of the network. The dot product model assumes that two individuals are connected in the social network if their attributes or opinions are similar. In the model, a d-dimensional vector a v represents the extent to which individual v has each of a set of d attributes or opinions. Then two individuals u and v are assumed to be friends, that is, they are connected in the graph model, if and only if a u · a v  ≥ t, for some fixed, positive threshold t. The resulting graph is called a d-dot product graph..
We consider two measures for diversity and clustering in social networks by using a d-dot product graph model for the network. Diversity is measured through the size of the largest independent set of the graph, and clustering is measured through the size of the largest clique. We obtain a tight result for the diversity problem, namely that it is polynomial-time solvable for d = 2, but NP-complete for d ≥ 3. We show that the clustering problem is polynomial-time solvable for d = 2. To our knowledge, these results are also the first on the computational complexity of combinatorial optimization problems on dot product graphs.
We also consider the situation when two individuals are connected if their preferences are not opposite. This leads to a variant of the standard dot product graph model by taking the threshold t to be zero. We prove in this case that the diversity problem is polynomial-time solvable for any fixed d
Nature of the Missing Near-side Amplitude in Calculations of Intermediate Energy (d,p) and (p,d) Reactions
This research was sponsored by the National Science Foundation Grant NSF PHY 87-1440
What graphs are 2-dot product graphs?
From a set of d-dimensional vectors for some integer d ≥ 1, we obtain a d-dot product graph by letting each vector au correspond to a vertex u and by adding an edge between two vertices u and v if and only if their dot product au · av ≥ t, for some fixed, positive threshold t. Dot product graphs can be used to model social networks. To understand the position of d-dot product graphs in the landscape of graph classes, we consider the case d = 2, and investigate how 2-dot product graphs relate to a number of other known graph classes
Fewer Pulls Required When Using a Powered Bone Marrow Biopsy System to Obtain Core Samples in the Multiple Myeloma Patients Population
Evaluation of new and existing desiccants in lentil
Non-Peer ReviewedGlobally, herbicide resistance has become a major challenge for many producers. In western Canada, many lentil (Lens culinaris L.) producers have great difficulty controlling Group 2 resistant biotypes. Two of these problematic weeds, wild mustard (Sinapis arvensis L.) and kochia (Kochia scoparia), are particularly challenging for lentil growers and can cause extensive yield loss when not adequately controlled. Desiccation is primarily used to dry down lentil for harvest ease and efficiency but can also be used as a late season control for actively growing weeds. The objective of this project is to evaluate the response of wild mustard and kochia to different herbicides, tank mixed with two different rates of glyphosate (450 g a.e. ha-1 and 900 g a.e. ha-1) at Saskatoon and Scott, Saskatchewan over a 2 year period. Desiccation occurred when the lentil seed moisture content was approximately 30%. Preliminary results are under investigation. Evaluation of seed and plant moisture of the treated plots is ongoing, along with an evaluation of the effects of the treatments on viability and vigour of affected weed seeds
Children's working understanding of knowledge sources : confidence in knowledge gained from testimony
In three experiments children aged between 3 and 5 years (N = 38; 52; 94; mean ages 3;7 to 5;2) indicated their confidence in their knowledge of the identity of a hidden toy. With the exception of some 3-year-olds, children revealed working understanding of their knowledge source by showing high confidence when they had seen or felt the toy, and lower confidence when they had been told its identity by an apparently well-informed speaker, especially when the speaker subsequently doubted the adequacy of his access to the toy. After a 2-minute delay, 3-to 4- year olds, unlike
4- to 5-year-olds, failed to see the implications of the speaker’s doubt about his access
Random forests with random projections of the output space for high dimensional multi-label classification
We adapt the idea of random projections applied to the output space, so as to
enhance tree-based ensemble methods in the context of multi-label
classification. We show how learning time complexity can be reduced without
affecting computational complexity and accuracy of predictions. We also show
that random output space projections may be used in order to reach different
bias-variance tradeoffs, over a broad panel of benchmark problems, and that
this may lead to improved accuracy while reducing significantly the
computational burden of the learning stage
A Reference Section for the Otavi Group (Damara Supergroup) in Eastern Kaoko Zone near Ongongo, Namibia
A reference section for the Otavi Group (Damara Supergroup) in the East Kaoko Zone near Ongongo is proposed and described. The section is easily accessible, well exposed, suitable for field excursions, and well documented in terms of carbonate lithofacies, depositional sequences and stableisotope chemostratigraphy. The late Tonian Ombombo Subgroup is 355 m thick above the basal Beesvlakte Formation, which is not included in the section due to poor outcrop and complex structure. The earlymiddle Cryogenian Abenab Subgroup is 636 m thick and the early Ediacaran Tsumeb Subgroup is 1020 m thick. While the section is complete in terms of formations represented, the Ombombo and lower Abenab subgroups have defined gaps due to intermittent uplift of the northward-sloping Makalani rift shoulder. The upper Abenab and Tsumeb subgroups are relatively thin due to erosion of a broad shallow trough during late Cryogenian glaciation and flexural arching during post-rift thermal subsidence of the carbonate platform
Annulus Amplitudes in the Minimal Superstring
We study the annulus amplitudes in the (2,4) minimal superstring theory using
the continuum worldsheet approach. Our results reproduce the semiclassical
behavior of the wavefunctions of FZZT-branes recently studied in hep-th/0412315
using the dual matrix model. We also study the multi-point functions of neutral
FZZT-branes and find the agreement between their semiclassical limit and the
worldsheet annulus calculation.Comment: 15 pages, lanlma
Cosmic D--term Strings as Wrapped D3 Branes
We describe cosmic D--term strings as D3 branes wrapped on a resolved
conifold. The matter content that gives rise to D--term strings is shown to
describe the world--volume theory of a space--filling D3 brane transverse to
the conifold which itself is a wrapped D5 brane. We show that, in this brane
theory, the tension of the wrapped D3 brane mathces that of the D--term string.
We argue that there is a new type of cosmic string which arises from fractional
D1 branes on the world--volume of a fractional D3 brane.Comment: 13 pages in phyzzx.tex; eq. (17) corrected, other minor corrections;
v3: more minor correction
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