Impurity in a granular gas under nonlinear Couette flow

We study in this work the transport properties of an impurity immersed in a granular gas under stationary nonlinear Couette flow. The starting point is a kinetic model for low-density granular mixtures recently proposed by the authors [Vega Reyes F et al. 2007 Phys. Rev. E 75 061306]. Two routes have been considered. First, a hydrodynamic or normal solution is found by exploiting a formal mapping between the kinetic equations for the gas particles and for the impurity. We show that the transport properties of the impurity are characterized by the ratio between the temperatures of the impurity and gas particles and by five generalized transport coefficients: three related to the momentum flux (a nonlinear shear viscosity and two normal stress differences) and two related to the heat flux (a nonlinear thermal conductivity and a cross coefficient measuring a component of the heat flux orthogonal to the thermal gradient). Second, by means of a Monte Carlo simulation method we numerically solve the kinetic equations and show that our hydrodynamic solution is valid in the bulk of the fluid when realistic boundary conditions are used. Furthermore, the hydrodynamic solution applies to arbitrarily (inside the continuum regime) large values of the shear rate, of the inelasticity, and of the rest of parameters of the system. Preliminary simulation results of the true Boltzmann description show the reliability of the nonlinear hydrodynamic solution of the kinetic model. This shows again the validity of a hydrodynamic description for granular flows, even under extreme conditions, beyond the Navier-Stokes domain.Comment: 23 pages, 11 figures; v2: Preliminary DSMC results from the Boltzmann equation included, Fig. 11 is ne

An exact solution of the inelastic Boltzmann equation for the Couette flow with uniform heat flux

In the steady Couette flow of a granular gas the sign of the heat flux gradient is governed by the competition between viscous heating and inelastic cooling. We show from the Boltzmann equation for inelastic Maxwell particles that a special class of states exists where the viscous heating and the inelastic cooling exactly compensate each other at every point, resulting in a uniform heat flux. In this state the (reduced) shear rate is enslaved to the coefficient of restitution $\alpha$, so that the only free parameter is the (reduced) thermal gradient $\epsilon$. It turns out that the reduced moments of order $k$ are polynomials of degree $k-2$ in $\epsilon$, with coefficients that are nonlinear functions of $\alpha$. In particular, the rheological properties ($k=2$) are independent of $\epsilon$ and coincide exactly with those of the simple shear flow. The heat flux ($k=3$) is linear in the thermal gradient (generalized Fourier's law), but with an effective thermal conductivity differing from the Navier--Stokes one. In addition, a heat flux component parallel to the flow velocity and normal to the thermal gradient exists. The theoretical predictions are validated by comparison with direct Monte Carlo simulations for the same model.Comment: 16 pages, 4 figures,1 table; v2: minor change

Mass gap for gravity localized on Weyl thick branes

We study the properties of a previously found family of thick brane configurations in a pure geometric Weyl integrable 5D space time, a non-Riemannian generalization of Kaluza-Klein (KK) theory involving a geometric scalar field. Thus the 5D theory describes gravity coupled to a self-interacting scalar field which gives rise to the structure of the thick branes. Analyzing the graviton spectrum for this class of models, we find that a particularly interesting situation arises for a special case in which the 4D graviton is separated from the KK gravitons by a mass gap. The corresponding effective Schroedinger equation has a modified Poeschl-Teller potential and can be solved exactly. Apart from the massless 4D graviton, it contains one massive KK bound state, and the continuum spectrum of delocalized KK modes. We discuss the mass hierarchy problem, and explicitly compute the corrections to Newton's law in the thin brane limit.Comment: 6 pages in Revtex, no figures, journal version, significately revised and extende

Analyzing the alignment between the Green Lean and Circular strategies: Towards a Circular Lean approach

Green Lean tools are aligned with the Circular Economy strategy as they aim at reducing waste, however, they miss the creation of value through waste. Therefore, this paper investigates whether the current implementation of the Green Lean strategy promotes the introduction of the Circular philosophy to achieve sustainable management production processes. It analyses how the resources were managed by implementing the different strategies and tools presented in Green Lean case studies under the lens of Circular Economy, and highlights future research paths on the Circular Lean integration. An analysis of the implementation of Green Lean case studies, selected through a Systematic Literature Review, from the manufacturing sector is conducted.The majority of Green Lean implementations were aimed at minimizing waste, which is aligned with the narrowing strategy of Circular Economy and only a few cases studies aimed at closing the production cycles. Even though the main results indicate that being eco-efficient is a good starting point to move towards sustainability, from a Circular Economy point of view, this approach could remain limited. Therefore, the current contribution of Green Lean to the implementation of circular practices is limited. It can be concluded that introducing the circular philosophy in the Green Lean methodology can be achieved through redirecting Green Lean from waste reduction towards a value creation focus. The originality of this paper is that it provides a critical review of the literature on the topic of Green Lean integration and Circular Economy

Evaluation of a portable image overlay projector for the visualisation of surgical navigation data: phantom studies

Introduction: Presenting visual feedback for image-guided surgery on a monitor requires the surgeon to perform time-consuming comparisons and diversion of sight and attention away from the patient. Deficiencies in previously developed augmented reality systems for image-guided surgery have, however, prevented the general acceptance of any one technique as a viable alternative to monitor displays. This work presents an evaluation of the feasibility and versatility of a novel augmented reality approach for the visualisation of surgical planning and navigation data. The approach, which utilises a portable image overlay device, was evaluated during integration into existing surgical navigation systems and during application within simulated navigated surgery scenarios. Methods: A range of anatomical models, surgical planning data and guidance information taken from liver surgery, cranio-maxillofacial surgery, orthopaedic surgery and biopsy were displayed on patient-specific phantoms, directly on to the patient's skin and on to cadaver tissue. The feasibility of employing the proposed augmented reality visualisation approach in each of the four tested clinical applications was qualitatively assessed for usability, visibility, workspace, line of sight and obtrusiveness. Results: The visualisation approach was found to assist in spatial understanding and reduced the need for sight diversion throughout the simulated surgical procedures. The approach enabled structures to be identified and targeted quickly and intuitively. All validated augmented reality scenes were easily visible and were implemented with minimal overhead. The device showed sufficient workspace for each of the presented applications, and the approach was minimally intrusiveness to the surgical scene. Conclusion: The presented visualisation approach proved to be versatile and applicable to a range of image-guided surgery applications, overcoming many of the deficiencies of previously described AR approaches. The approach presents an initial step towards a widely accepted alternative to monitor displays for the visualisation of surgical navigation dat

Propiedades psicométricas de la Escala de Motivación Académica de los Adolescentes (EMAA) en una muestra representativa de estudiantes de instituto de la República Dominicana

Within the growing body of research that has focused on academic success, academic motivation has gathered considerable attention. The aim of this this research is to present the first validation of the Adolescents’ Academic Motivation Scale (AAMS). Total sample was composed by 1712 students of secondary education from two districts in the Dominican Republic. The main measurement outcome was the AAMS. Results from the CFA were satisfactory: χ2(5) = 57.73, p < .001; CFI = .970; RMSEA = .079 [.061, .097], and SRMR = .024. IRT analyses favored the two-parameter logistic model, indicating that items were not equally discriminant. Structural Equation Model with latent variables in which academic motivation was a significant predictor of grades resulted in excellent fit: χ2(53) = 182.76, p < .001; CFI = .980; RMSEA = .038 90% CI [.032, .044], and SRMR = .025. In sum, this work presents an exhaustive psychometric analysis of the AAMS in a representative sample of high school Dominican students.Entre el creciente cuerpo de investigación que se ha centrado en el éxito académico, la motivación académica ha captado considerable atención. El objetivo de esta investigación es presentar la primera validación de la Escala de Motivación Académica de los Adolescentes (EMAA). La muestra total estuvo compuesta por 1712 estudiantes de secundaria de dos distritos de la República Dominicana. La medida principal fue la EMAA. Los resultados del AFC fueron satisfactorios: χ2(5) = 57.73, p < .001; CFI = .970; RMSEA = .079, 90% CI [.061, .097], y SRMR = .024. Los análisis de TRI favorecieron al modelo logístico de dos parámetros, indicando que los ítems no fueron igualmente discriminativos. El Modelo de Ecuaciones Estructurales en el que la motivación académica predecía de forma estadísticamente significativa las calificaciones obtuvo un ajuste excelente: χ2(53) = 182.76, p < .001; CFI = .980; RMSEA = .038 [.032, .044], and SRMR = .025. En resumen, este trabajo presenta un exhaustivo análisis psicométrico de la EMAA en una muestra representativa de estudiantes dominicanos de instituto

Epidemiological characteristics of skin disorders in cetaceans from South American waters

We document the macroscopic phenotypic characteristics (relative size, location, pattern, colour, extension), prevalence and evolution of five types of skin disorders of unknown aetiology, including ‘green-brown plaques’ (GBP), ‘orange patches’ (OPA), ‘cutaneous nodules’ (NOD), ‘pale dermatitis’ (PAD) and ‘expansive annular lesions’ (EAL) in five odontocete species (n = 559 individuals) from the Southeast Pacific (n = 230) and Southwest Atlantic (n = 329) oceans. GBP affected two likely-adult Sotalia guianensis traveling side-by-side in a freshwater area of the Cananéia Estuary in August 2009. Low salinity is suggested as predisposing factor. OPA were distinguished in three of 209 (1.4%) free-ranging S. guianensis in Sepetiba Bay, Brazil, during winter months of 2005-2008. Epibiont diatoms are suspected aetiological agents. NOD were chronically present in one male adult Orcinus orca observed off the coast of southern Brazil in 2007-2010. PAD was seen in free-ranging individuals and carcasses of Tursiops truncatus, S. guianensis and Pseudorca crassidens from both the Atlantic and Pacific Oceans in 1992 and in 2004-2009. Prevalence was 1% in 103 S. guianensis from Paranaguá Estuary (Brazil), 2.3% in 222 S. guianensis from Sepetiba Bay and 6.9% in 87 inshore T. truncatus from Paracas Bay, Peru. Although in some cases the lesions covered up to 35-40% of the visible body surface and ulcers may occur there was no evidence of mortality and, in time-series of six individuals, PAD eventually healed. In six T. truncatus and five S. guianensis acutely affected, PAD was associated with minor cutaneous injuries and scars, including tooth rakes, suggesting infection routes for opportunistic pathogens. EAL were noted in a Cephalorhynchus eutropia calf from Palena province, Chile, in 2003 and in a P. crassidens calf washed ashore dead in southern Brazil in 2009. The C. eutropia calf disappeared, and probably died, two weeks after first observation. Prevalence of EAL was 6.7% in 15 C. eutropia in 2002-2004. These data suggest that EAL are potentially lethal in calves. PAD and EAL were primarily seen in cetaceans inhabiting biologically or chemically contaminated nearshore waters. In view of their emergence and occasional severity these disorders should be the subject of systematic monitoring

Three Experimental Phases of Cornstarch-Based Biodegradable Plastic

Three Experimental Phases of Cornstarch-Based Biodegradable Plastic is the focus of this current study whose purpose was to create a bio-plastic from eco-friendly materials as a platform for an alternative commercial plastic. This study used a pre-experimental research design where three bio-plastic experiments were monitored to identify which among them was likely to produce the most efficient bio-plastic. At the end of the study, it was concluded that in terms of elasticity, tear resistance, appearance, texture, and odor, Experimental Two with four tablespoons of cornstarch, one cup of water, two tablespoons of vinegar, and two tablespoons of glycerin, is the most reliable among the three experiments.                 Hence, this study recommends to the biologists and scientists that may use this study to help them find ways to lessen biological problems caused by non-biodegradable plastics; to the producers that the study may help them to create and manufacture bio-plastics and to improve the study using other materials for the product to last longer indoors; to the consumers that the study may let them know the reliability and liability of the plastic they use in their everyday life; and to the future researchers who will want to conduct a further study about bio-plastics, this study may serve as a related study and think of an intervention to improve the results from the problem