Coarse Bifurcation Studies of Bubble Flow Microscopic Simulations

The parametric behavior of regular periodic arrays of rising bubbles is investigated with the aid of 2-dimensional BGK Lattice-Boltzmann (LB) simulators. The Recursive Projection Method is implemented and coupled to the LB simulators, accelerating their convergence towards what we term coarse steady states. Efficient stability/bifurcation analysis is performed by computing the leading eigenvalues/eigenvectors of the coarse time stepper. Our approach constitutes the basis for system-level analysis of processes modeled through microscopic simulations.Comment: 4 pages, 3 figure

Video Compressive Sensing for Dynamic MRI

We present a video compressive sensing framework, termed kt-CSLDS, to accelerate the image acquisition process of dynamic magnetic resonance imaging (MRI). We are inspired by a state-of-the-art model for video compressive sensing that utilizes a linear dynamical system (LDS) to model the motion manifold. Given compressive measurements, the state sequence of an LDS can be first estimated using system identification techniques. We then reconstruct the observation matrix using a joint structured sparsity assumption. In particular, we minimize an objective function with a mixture of wavelet sparsity and joint sparsity within the observation matrix. We derive an efficient convex optimization algorithm through alternating direction method of multipliers (ADMM), and provide a theoretical guarantee for global convergence. We demonstrate the performance of our approach for video compressive sensing, in terms of reconstruction accuracy. We also investigate the impact of various sampling strategies. We apply this framework to accelerate the acquisition process of dynamic MRI and show it achieves the best reconstruction accuracy with the least computational time compared with existing algorithms in the literature.Comment: 30 pages, 9 figure

Vere-Jones' Self-Similar Branching Model

Motivated by its potential application to earthquake statistics, we study the exactly self-similar branching process introduced recently by Vere-Jones, which extends the ETAS class of conditional branching point-processes of triggered seismicity. One of the main ingredient of Vere-Jones' model is that the power law distribution of magnitudes m' of daughters of first-generation of a mother of magnitude m has two branches m'm with exponent beta+d, where beta and d are two positive parameters. We predict that the distribution of magnitudes of events triggered by a mother of magnitude $m$ over all generations has also two branches m'm with exponent beta+h, with h= d \sqrt{1-s}, where s is the fraction of triggered events. This corresponds to a renormalization of the exponent d into h by the hierarchy of successive generations of triggered events. The empirical absence of such two-branched distributions implies, if this model is seriously considered, that the earth is close to criticality (s close to 1) so that beta - h \approx \beta + h \approx \beta. We also find that, for a significant part of the parameter space, the distribution of magnitudes over a full catalog summed over an average steady flow of spontaneous sources (immigrants) reproduces the distribution of the spontaneous sources and is blind to the exponents beta, d of the distribution of triggered events.Comment: 13 page + 3 eps figure

Satisfação do cliente em relação aos serviços hoteleiros: uma revisão sistemática e uma agenda de pesquisa

In the highly competitive world, the hotel industry's success depends on the quality of services they provide, which gives wow feelings and high customer satisfaction. Many researchers have tried to assess customer satisfaction towards hotel services by proposing different models. Hence, the present study attempts to identify the influencing factors for determining customer satisfaction towards hotel services by conducting a systematic literature review. During the search process, 457 articles were obtained from the Web of Science database, and after filtration, 91 articles were used for further analysis. The result revealed that the top six influential factors affecting customer satisfaction towards hotel services are empathy, assurance, reliability, responsiveness, tangibility, and green practices. If customers are satisfied, they will be motivated to revisit, spread positive word of mouth, and build loyalty. Moreover, the results identified that the USA, Malaysia, and China are the leading countries in this field. This study provides an extensive literature review, which otherwise is an unexplored area so far, which offers valuable insight for the hotel service providers to improve their services and also to the researchers and academicians to develop and propose new theories.En un mundo altamente competitivo, el éxito de la industria hotelera depende de la calidad de los servicios que brinda, lo que genera sensaciones asombrosas y una alta satisfacción del cliente. Muchos investigadores han intentado evaluar la satisfacción del cliente hacia los servicios hoteleros proponiendo diferentes modelos. Por lo tanto, el presente estudio intenta identificar los factores que influyen en la determinación de la satisfacción del cliente hacia los servicios hoteleros mediante la realización de una revisión sistemática de la literatura. Durante el proceso de búsqueda, se obtuvieron 457 artículos en la base de datos Web of Science y, después de la filtración, se utilizaron 91 artículos para un análisis posterior. El resultado reveló que los seis factores principales que influyen en la satisfacción del cliente hacia los servicios hoteleros son la empatía, la garantía, la confiabilidad, la capacidad de respuesta, la tangibilidad y las prácticas sostenibles. Si los clientes están satisfechos, se motivarán a revisitar, difundir recomendaciones positivas y construir lealtad. Además, los resultados identificaron que Estados Unidos, Malasia y China son los países líderes en este campo. Este estudio proporciona una revisión integral de la literatura, un área hasta ahora poco explorada, ofreciendo ideas valiosas para que los proveedores de servicios hoteleros mejoren sus servicios, así como para que los investigadores y académicos desarrollen y propongan nuevas teorías.Num mundo altamente competitivo, o sucesso da indústria hoteleira depende da qualidade dos serviços que presta, o que proporciona sensações surpreendentes e elevada satisfação do cliente. Muitos pesquisadores têm tentado avaliar a satisfação do cliente em relação aos serviços hoteleiros propondo diferentes modelos. Assim, o presente estudo tenta identificar os fatores que influenciam a determinação da satisfação do cliente em relação aos serviços hoteleiros, através da realização de uma revisão sistemática da literatura. Durante o processo de busca, foram obtidos 457 artigos na base de dados Web of Science e, após filtragem, 91 artigos foram utilizados para posterior análise. O resultado revelou que os seis principais fatores que influenciam a satisfação do cliente em relação aos serviços hoteleiros são empatia, garantia, confiabilidade, capacidade de resposta, tangibilidade e práticas sustentáveis. Se os clientes estiverem satisfeitos, serão motivados a revisitar, propagar recomendações positivas e construir lealdade. Além disso, os resultados identificaram que os Estados Unidos, Malásia e China são os países líderes nesse campo. Este estudo fornece uma revisão abrangente da literatura, uma área até então pouco explorada, oferecendo insights valiosos para os provedores de serviços hoteleiros melhorarem seus serviços, bem como para pesquisadores e acadêmicos desenvolverem e propor novas teorias

Hyperfine interaction and electronic spin fluctuation study on Sr2−x_{2-x}Lax_xFeCoO6_6 (x = 0, 1, 2) by high-resolution back-scattering neutron spectroscopy

The study of hyperfine interaction by high-resolution inelastic neutron scattering is not very well known compared to the other competing techniques viz. NMR, M\"ossbauer, PACS etc. Also the study is limited mostly to magnetically ordered systems. Here we report such study on Sr$_{2-x}$La$_x$FeCoO$_6$ (x = 0, 1, 2) of which first (Sr$_2$FeCoO$_6$ with x = 0) has a canonical spin spin glass, the second (SrLaFeCoO$_6$ with x = 1) has a so-called magnetic glass and the third (La$_2$FeCoO$_6$ with x = 2) has a magnetically ordered ground state. Our present study revealed clear inelastic signal for SrLaFeCoO$_6$, possibly also inelastic signal for Sr$_2$FeCoO$_6$ below the spin freezing temperatures $T_{sf}$ but no inelastic signal at all for for the magnetically ordered La$_2$FeCoO$_6$ in the neutron scattering spectra. The broadened inelastic signals observed suggest hyperfine field distribution in the two disordered magnetic glassy systems and no signal for the third compound suggests no or very small hyperfine field at the Co nucleus due to Co electronic moment. For the two magnetic glassy system apart from the hyperfine signal due only to Co, we also observed electronic spin fluctuations probably from both Fe and Co electronic moments. \end{abstract

Anomalous Power Law Distribution of Total Lifetimes of Branching Processes Relevant to Earthquakes

We consider a branching model of triggered seismicity, the ETAS (epidemic-type aftershock sequence) model which assumes that each earthquake can trigger other earthquakes (``aftershocks''). An aftershock sequence results in this model from the cascade of aftershocks of each past earthquake. Due to the large fluctuations of the number of aftershocks triggered directly by any earthquake (``productivity'' or ``fertility''), there is a large variability of the total number of aftershocks from one sequence to another, for the same mainshock magnitude. We study the regime where the distribution of fertilities $\mu$ is characterized by a power law $\sim 1/\mu^{1+\gamma}$ and the bare Omori law for the memory of previous triggering mothers decays slowly as $\sim 1/t^{1+\theta}$, with $0 < \theta <1$ relevant for earthquakes. Using the tool of generating probability functions and a quasistatic approximation which is shown to be exact asymptotically for large durations, we show that the density distribution of total aftershock lifetimes scales as $\sim 1/t^{1+\theta/\gamma}$ when the average branching ratio is critical ($n=1$). The coefficient $1<\gamma = b/\alpha<2$ quantifies the interplay between the exponent $b \approx 1$ of the Gutenberg-Richter magnitude distribution $\sim 10^{-bm}$ and the increase $\sim 10^{\alpha m}$ of the number of aftershocks with the mainshock magnitude $m$ (productivity) with $\alpha \approx 0.8$. More generally, our results apply to any stochastic branching process with a power-law distribution of offsprings per mother and a long memory.Comment: 16 pages + 4 figure

Effectiveness, safety and acceptability of ‘see and treat' with cryotherapy by nurses in a cervical screening study in India

We evaluated a ‘see and treat' procedure involving screening, colposcopy, biopsy and cryotherapy by trained nurses in one-visit in field clinics in a cervical screening study in South India for its acceptability, safety and effectiveness in curing cervical intraepithelial neoplasia (CIN). Women positive on visual inspection with acetic acid (VIA) were advised colposcopy, directed biopsies and cryotherapy if they had colposcopic impression of CIN in one visit by nurses in field clinics supervised by a doctor. Side effects and complications were assessed and cure rates were evaluated with VIA, colposcopy and biopsy if colposcopic abnormalities were suspected. Cure was defined as no clinical or histological evidence of CIN at ⩾6 months from treatment. Of the 2513 women offered ‘see and treat' procedure, 1879 (74.8%) accepted. Of the 1397 women with histologically proved CIN treated with cryotherapy, 1026 reported for follow-up evaluation. Cure rates were 81.4% (752 out of 924) for women with CIN 1; 71.4% (55 out of 77) for CIN 2 and 68.0% (17 out of 25) for CIN 3. Minor side effects and complications were documented in less than 3% of women. ‘See and treat' with cryotherapy by nurses under medical supervision is acceptable, safe and effective for cervical cancer prevention in low-resource settings