Revisit Behavior in Social Media: The Phoenix-R Model and Discoveries

How many listens will an artist receive on a online radio? How about plays on a YouTube video? How many of these visits are new or returning users? Modeling and mining popularity dynamics of social activity has important implications for researchers, content creators and providers. We here investigate the effect of revisits (successive visits from a single user) on content popularity. Using four datasets of social activity, with up to tens of millions media objects (e.g., YouTube videos, Twitter hashtags or LastFM artists), we show the effect of revisits in the popularity evolution of such objects. Secondly, we propose the Phoenix-R model which captures the popularity dynamics of individual objects. Phoenix-R has the desired properties of being: (1) parsimonious, being based on the minimum description length principle, and achieving lower root mean squared error than state-of-the-art baselines; (2) applicable, the model is effective for predicting future popularity values of objects.Comment: To appear on European Conference on Machine Learning and Principles and Practice of Knowledge Discovery in Databases 201

Group theory for structural analysis and lattice vibrations in phosphorene systems

Group theory analysis for two-dimensional elemental systems related to phosphorene is presented, including (i) graphene, silicene, germanene and stanene, (ii) dependence on the number of layers and (iii) two stacking arrangements. Departing from the most symmetric $D_{6h}^{1}$ graphene space group, the structures are found to have a group-subgroup relation, and analysis of the irreducible representations of their lattice vibrations makes it possible to distinguish between the different allotropes. The analysis can be used to study the effect of strain, to understand structural phase transitions, to characterize the number of layers, crystallographic orientation and nonlinear phenomena.Comment: 24 pages, 3 figure

Theoretical investigation of moir\'e patterns in quantum images

Moir\'e patterns are produced when two periodic structures with different spatial frequencies are superposed. The transmission of the resulting structure gives rise to spatial beatings which are called moir\'e fringes. In classical optics, the interest in moir\'e fringes comes from the fact that the spatial beating given by the frequency difference gives information about details(high spatial frequency) of a given spatial structure. We show that moir\'e fringes can also arise in the spatial distribution of the coincidence count rate of twin photons from the parametric down-conversion, when spatial structures with different frequencies are placed in the path of each one of the twin beams. In other words,we demonstrate how moir\'e fringes can arise from quantum images

Analysis of trends in seasonal electrical energy consumption via non-negative tensor factorization

This paper looks at the extraction of trends of household electrical seasonal consumption via load disaggregation. With the proviso that data for several home devices can be embedded in a tensor, non-negative multi-way array factorization is performed in order to extract the most relevant components. In the initial decomposition step the decomposed signals are incorporated in the test signal consisting of the whole-home measured consumption. After this the disaggregated data corresponding to each electrical device is obtained by factorizing the associated matrix through the learned model. Finally, we evaluate the performance of load disaggregation by the supervised method, and study the trends along several years and across seasons. Towards this end, computational experiments were yielded using real-world data from household electrical consumption measurements along several years. While breaking down the whole house energy consumption into appliance level gives less accurate estimates in the late years, we empirically show the adequacy of this method for handling the earlier years and the estimates of the underlying seasonal trend-cycle.info:eu-repo/semantics/acceptedVersio

Museu de Arte do Rio – MAR: uma abordagem do valor patrimonial

Há décadas, a região portuária da cidade do Rio de Janeiro tem sido alvo de estudos e projetos de revitalização. A instituição, em 2009, por lei municipal, da Operação Urbana Consorciada da Área de Especial Interesse Urbanístico da Região Portuária do Rio de Janeiro foi feita no intuito de garantir a implementação do projeto de requalificação urbana intitulado Porto Maravilha. Com relação à preservação do patrimônio cultural, o Porto Maravilha apresenta ações voltadas para o resgate da memória local, tendo o Museu de Arte do Rio (MAR) como âncora do projeto. Instalado na Praça Mauá, o MAR teve como desafio unir construções de características arquitetônicas distintas e com diferentes níveis de proteção. Ao analisar as intervenções realizadas para a adaptação do edifício do antigo Palácio Dom João VI ao uso de museu, pode-se verificar que algumas de suas características são sacrificadas em favor da nova função. Questiona-se, a partir deste exemplo, a relação entre a intenção da intervenção e os resultados obtidos pelo projeto adotado, no que se refere à preservação dos valores que o edifício representa para a sociedade e que motivaram sua proteção. Este artigo se propõe a analisar como as escolhas de projeto de adaptação ao uso de Museu impactaram nos valores atribuídos aos edifícios constituintes do MAR