1,564 research outputs found
Embedding Schemes for Interconnection Networks.
Graph embeddings play an important role in interconnection network and VLSI design. Designing efficient embedding strategies for simulating one network by another and determining the number of layers required to build a VLSI chip are just two of the many areas in which graph embeddings are used. In the area of network simulation we develop efficient, small dilation embeddings of a butterfly network into a different size and/or type of butterfly network. The genus of a graph gives an indication of how many layers are required to build a circuit. We have determined the exact genus for the permutation network called the star graph, and have given a lower bound for the genus of the permutation network called the pancake graph. The star graph has been proposed as an alternative to the binary hypercube and, therefore, we compare the genus of the star graph with that of the binary hypercube. Another type of embedding that is helpful in determining the number of layers is a book embedding. We develop upper and lower bounds on the pagenumber of a book embedding of the k-ary hypercube along with an upper bound on the cumulative pagewidth
A powerful heuristic for telephone gossiping
A refined heuristic for computing schedules for gossiping in the telephone model is presented. The heuristic is fast: for a network with n nodes and m edges, requiring R rounds for gossiping, the running time is O(R n log(n) m) for all tested classes of graphs. This moderate time consumption allows to compute gossiping schedules for networks with more than 10,000 PUs and 100,000 connections. The heuristic is good: in practice the computed schedules never exceed the optimum by more than a few rounds. The heuristic is versatile: it can also be used for broadcasting and more general information dispersion patterns. It can handle both the unit-cost and the linear-cost model. Actually, the heuristic is so good, that for CCC, shuffle-exchange, butterfly de Bruijn, star and pancake networks the constructed gossiping schedules are better than the best theoretically derived ones. For example, for gossiping on a shuffle-exchange network with 2^{13} PUs, the former upper bound was 49 rounds, while our heuristic finds a schedule requiring 31 rounds. Also for broadcasting the heuristic improves on many formerly known results. A second heuristic, works even better for CCC, butterfly, star and pancake networks. For example, with this heuristic we found that gossiping on a pancake network with 7! PUs can be performed in 15 rounds, 2 fewer than achieved by the best theoretical construction. This second heuristic is less versatile than the first, but by refined search techniques it can tackle even larger problems, the main limitation being the storage capacity. Another advantage is that the constructed schedules can be represented concisely
Manipulating models and grasping the ideas they represent
This article notes the convergence of recent thinking in neuroscience and grounded cognition regarding the way we understand mental representation and recollection: ideas are dynamic and multi-modal, actively created at the point of recall. Also, neurophysiologically, re-entrant signalling among cortical circuits allows non-conscious processing to support our deliberative thoughts and actions. The qualitative research we describe examines the exchanges occurring during semi-structured interviews with 360 children age 3â13, including 294 from New Zealand (158 boys, 136 girls) and 66 from China (34 boys, 32 girls) concerning their understanding of the shape and motion of the Earth, Sun and Moon (ESM). We look closely at the relationships between what is revealed as children manipulate their own play-dough models and their apparent understandings of ESM concepts. In particular, we focus on the switching taking place between what is said, what is drawn and what is modelled. The evidence is supportive of Edelmanâs view that memory is non-representational and that concepts are the outcome of perceptual mappings, a view which is also in accord with Barsalouâs notion that concepts are simulators or skills which operate consistently across several modalities. Quantitative data indicate that the dynamic structure of memory/concept creation is similar in both genders and common to the cultures/ethnicities compared (New Zealand European and MÄori; Chinese Han) and that repeated interviews in this longitudinal research lead to more advanced modelling skills and/or more advanced shape and motion concepts, the results supporting hypotheses (KolmogorovâSmirnov alpha levels.05; rs: p < .001)
Recursive Linear Bounds for the Vertex Chromatic Number of the Pancake Graph
The pancake graph has been the subject of research. While studies on the various aspects of the graph are abundant, results on the chromatic properties may be further enhanced. Revolving around such context, the paper advances an alternative method to produce novel linear bounds for the vertex chromatic number of the pancake graph. The accompanying demonstration takes advantage of symmetries inherent to the graph, capturing the prefix reversal of subsequences through a homomorphism. Contained within the argument is the incorporation of known vertex chromatic numbers for certain orders of pancake graphs, rendering tighter bounds possible upon the release of new findings. In closing, a comparison with existing bounds is done to establish the relative advantage of the proposed technique
The physics of dipolar bosonic quantum gases
This article reviews the recent theoretical and experimental advances in the
study of ultracold gases made of bosonic particles interacting via the
long-range, anisotropic dipole-dipole interaction, in addition to the
short-range and isotropic contact interaction usually at work in ultracold
gases. The specific properties emerging from the dipolar interaction are
emphasized, from the mean-field regime valid for dilute Bose-Einstein
condensates, to the strongly correlated regimes reached for dipolar bosons in
optical lattices.Comment: Review article, 71 pages, 35 figures, 350 references. Submitted to
Reports on Progress in Physic
Sentiment analysis in restaurants on social media reviews: the case of Giethoorn restaurants
Social media has become a main platform for users to express their opinions and feelings and a vast number of available and valuable data in form of text has been created for researchers and operators to hear the usersâ voice in different industries. As a consequence, text mining and sentiment analysis have gained big attention and the supporting business intelligence tools to analyze the unstructured data and interpret it into useful and readable information also have been developed rapidly. The Lexalytics, a text mining artificial intelligence tool, is applied to support to present a research method using data mining in order to suggest how to improve the performance of Zwaantje, a restaurant in a touristic Dutch village, through analyzing the reviews of all the restaurants in the village from the most frequently used social media platforms under the four restaurant quality factors namely food and beverage, service, atmosphere and value. Finding of the research is presented by the key themes extracted by Lexalytics with comparison of the customersâ review sentiment between Zwaantje and the benchmark restaurants set by a specific approach under the abovementioned quality dimensions, in which the F&B and service are most commented by the customers. The outcomes demonstrate that text mining can generate insights from different aspects in the restaurant industry and the proposed approach are valuable to the restaurant management.A internet e as redes sociais tornaram-se a principal plataforma para os utilizadores expressarem as suas opiniĂ”es e âsentimentosâ. Um elevado nĂșmero de dados encontra-se disponĂvel para pesquisadores e operadores conhecerem as ideais dos usuĂĄrios sobre diferentes sectores. Como consequĂȘncia, o data mining e a anĂĄlise de âsentimentosâ atingiram um elevado protagonismo, assim como as ferramentas de suporte para analisar os dados nĂŁo estruturados e interpretĂĄ-los em informaçÔes Ășteis e legĂveis. O Lexalytics, uma ferramenta de inteligĂȘncia artificial de data mining, Ă© aplicado como suporte para apresentar um mĂ©todo de pesquisa para sugerir como melhorar o desempenho do âZwaantjeâ, um restaurante situado numa vila turĂstica holandesa, por meio da anĂĄlise das avaliaçÔes de todos os restaurantes da vila presentes na internet, tendo como base os quatro factores de qualidade do restaurante, ou seja, comida e bebida, serviço, ambiente e valor. O resultado da pesquisa Ă© apresentado pelos principais temas extraĂdos pelo Lexalytics,
tendo como base a avaliação dos clientes apresentada para o âZwaantjeâ face aos restaurantes
de referĂȘncia, consubstanciada numa abordagem especĂfica sob as dimensĂ”es de qualidade
acima mencionadas, em que a comida, bebida e serviço, são as variåveis mais comentadas pelos
clientes. Os resultados demonstram que o data mining pode gerar percepçÔes sobre diferentes aspectos do sector da restauração e a abordagem proposta é valiosa para a gestão dos restaurantes
GIZMO: A New Class of Accurate, Mesh-Free Hydrodynamic Simulation Methods
We present two new Lagrangian methods for hydrodynamics, in a systematic
comparison with moving-mesh, SPH, and stationary (non-moving) grid methods. The
new methods are designed to simultaneously capture advantages of both
smoothed-particle hydrodynamics (SPH) and grid-based/adaptive mesh refinement
(AMR) schemes. They are based on a kernel discretization of the volume coupled
to a high-order matrix gradient estimator and a Riemann solver acting over the
volume 'overlap.' We implement and test a parallel, second-order version of the
method with self-gravity & cosmological integration, in the code GIZMO: this
maintains exact mass, energy and momentum conservation; exhibits superior
angular momentum conservation compared to all other methods we study; does not
require 'artificial diffusion' terms; and allows the fluid elements to move
with the flow so resolution is automatically adaptive. We consider a large
suite of test problems, and find that on all problems the new methods appear
competitive with moving-mesh schemes, with some advantages (particularly in
angular momentum conservation), at the cost of enhanced noise. The new methods
have many advantages vs. SPH: proper convergence, good capturing of
fluid-mixing instabilities, dramatically reduced 'particle noise' & numerical
viscosity, more accurate sub-sonic flow evolution, & sharp shock-capturing.
Advantages vs. non-moving meshes include: automatic adaptivity, dramatically
reduced advection errors & numerical overmixing, velocity-independent errors,
accurate coupling to gravity, good angular momentum conservation and
elimination of 'grid alignment' effects. We can, for example, follow hundreds
of orbits of gaseous disks, while AMR and SPH methods break down in a few
orbits. However, fixed meshes minimize 'grid noise.' These differences are
important for a range of astrophysical problems.Comment: 57 pages, 33 figures. MNRAS. A public version of the GIZMO code,
user's guide, test problem setups, and movies are available at
http://www.tapir.caltech.edu/~phopkins/Site/GIZMO.htm
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