Towards a Conceptual Framework of an Educational Web Portal

Technology plays an important role in everyday life of K-6 students born in the digital age. In the past several decades, educational institutions have made substantial investments in technology infrastructure with the aim of enhancing student learning, increasing student achievement, and helping students acquire digital literacy skills early on in their education. However, to fully leverage web-based technologies for student learning and communication inside and outside of school, teachers must be prepared to effectively plan, develop, and integrate technology into the curriculum-based activities of their classrooms. Educational web portals with resources for teaching, learning and communicating, can help teachers create a “connected” classroom environment that extends student learning well beyond the school’s brick-and-mortar boundaries. This article delineates a framework of an educational web portal for an elementary school classroom. Three inter-related dimensions comprise the framework: 1) web portal structure, 2) web portal impacts, and 3) web portal development strategy. This framework is of value to educators and school administrators interested in integrating web portal technologies into the educational and social infrastructure of their schools

Analytical and numerical study of the ground-track resonances of Dawn orbiting Vesta

The aim of Dawn mission is the acquisition of data from orbits around two bodies, (4)Vesta and (1)Ceres, the two most massive asteroids. Due to the low thrust propulsion, Dawn will slowly cross and transit through ground-track resonances, where the perturbations on Dawn orbit may be significant. In this context, to safety go the Dawn mission from the approach orbit to the lowest science orbit, it is essential to know the properties of the crossed resonances. This paper analytically investigates the properties of the major ground-track resonances (1:1, 1:2, 2:3 and 3:2) appearing for Vesta orbiters: location of the equilibria, aperture of the resonances and period at the stable equilibria. We develop a general method using an averaged Hamiltonian formulation with a spherical harmonic approximation of the gravity field. If the values of the gravity field coefficient change, our method stays correct and applicable. We also discuss the effect of one uncertainty on the C20 and C22 coefficients on the properties of the 1:1 resonance. These results are checked by numerical tests. We determine that the increase of the eccentricity appearing in the 2:3 resonance is due to the C22 and S22 coefficients. Our method can be easily adapted to missions similar to Dawn because, contrarily to the numerical results, the analytical formalism stays the same and is valid for a wide range of physical parameters of the asteroid (namely the shape and the mass) as well as for different spacecraft orbits. Finally we numerically study the probability of the capture in resonance 1:1. Our paper reproduces, explains and supplements the results of Tricarico and Sykes (2010).Comment: 34 pages, 9 figures, 10 Table

Groupthink

How should a group with different opinions (but the same values) make decisions? In a Bayesian setting, the natural question is how to aggregate credences: how to use a single credence function to naturally represent a collection of different credence functions. An extension of the standard Dutch-book arguments that apply to individual decision-makers recommends that group credences should be updated by conditionalization. This imposes a constraint on what aggregation rules can be like. Taking conditionalization as a basic constraint, we gather lessons from the established work on credence aggregation, and extend this work with two new impossibility results. We then explore contrasting features of two kinds of rules that satisfy the constraints we articulate: one kind uses fixed prior credences, and the other uses geometric averaging, as opposed to arithmetic averaging. We also prove a new characterisation result for geometric averaging. Finally we consider applications to neighboring philosophical issues, including the epistemology of disagreement

Long-term perturbations due to a disturbing body in elliptic inclined orbit

In the current study, a double-averaged analytical model including the action of the perturbing body's inclination is developed to study third-body perturbations. The disturbing function is expanded in the form of Legendre polynomials truncated up to the second-order term, and then is averaged over the periods of the spacecraft and the perturbing body. The efficiency of the double-averaged algorithm is verified with the full elliptic restricted three-body model. Comparisons with the previous study for a lunar satellite perturbed by Earth are presented to measure the effect of the perturbing body's inclination, and illustrate that the lunar obliquity with the value 6.68\degree is important for the mean motion of a lunar satellite. The application to the Mars-Sun system is shown to prove the validity of the double-averaged model. It can be seen that the algorithm is effective to predict the long-term behavior of a high-altitude Martian spacecraft perturbed by Sun. The double-averaged model presented in this paper is also applicable to other celestial systems.Comment: 28 pages, 6 figure

Accelerating fluid-solid simulations (Lattice-Boltzmann & Immersed-Boundary) on heterogeneous architectures

We propose a numerical approach based on the Lattice-Boltzmann (LBM) and Immersed Boundary (IB) methods to tackle the problem of the interaction of solids with an incompressible fluid flow, and its implementation on heterogeneous platforms based on data-parallel accelerators such as NVIDIA GPUs and the Intel Xeon Phi. We explain in detail the parallelization of these methods and describe a number of optimizations, mainly focusing on improving memory management and reducing the cost of host-accelerator communication. As previous research has consistently shown, pure LBM simulations are able to achieve good performance results on heterogeneous systems thanks to the high parallel efficiency of this method. Unfortunately, when coupling LBM and IB methods, the overheads of IB degrade the overall performance. As an alternative, we have explored different hybrid implementations that effectively hide such overheads and allow us to exploit both the multi-core and the hardware accelerator in a cooperative way, with excellent performance results

Frequency tunability of solid-core photonic crystal fibers filled with nanoparticle-doped liquid crystals

We infiltrate liquid crystals doped with BaTiO3 nanoparticles in a photonic crystal fiber and compare the measured transmission spectrum with the one achieved without dopant. New interesting features, such as frequency modulation response of the device and a transmission spectrum with tunable attenuation on the short wavelength side of the widest bandgap, suggest a potential application of this device as a tunable all-in-fiber gain equalization filter with an adjustable slope. The tunability of the device is achieved by varying the amplitude and the frequency of the applied external electric field. The threshold voltage for doped and undoped liquid crystals in a silica capillary and in a glass cell are also measured as a function of the frequency of the external electric field and the achieved results are compared

Pressure Injuries in Nursing Homes: Investigating Racial/Ethnic Differences Using National Data

Context: In the United States, Black nursing home (NH) residents have higher rates of pressure injury (PI) than White residents. Although some studies ascribe this to a relatively high proportion of Black residents in NHs with poor outcomes and limited resources, the factors that associate with PIs and their consequences across and within NHs remain poorly understood. Also, little is known about PIs among residents of differing races and ethnicities. Objectives: Using four national datasets from 2016–2017, we evaluated U.S. NHs to characterize differences in PI-related outcomes among non-Hispanic Whites, non-Hispanic Blacks, Hispanics, Asians, American Indian or Alaska Natives, and Native Hawaiian or Other Pacific Islanders, and clarified the impact of resident-, facility-, and community-level characteristics on these outcomes. Methods: We calculated the annual incidence rate of PIs, the probability of PI healing, and the prevalence of PI-associated pain and analgesic prescription. We determined the bivariate associations between each of these outcomes and race/ethnicity, and between each outcome and multiple potential covariates. Multivariable analyses then evaluated the associations between each outcome and race/ethnicity while adjusting for covariates. Findings: In the bivariate analyses, the annual incidence rate of stage 2, 3, 4, and unstageable PIs for Whites was lower than Blacks and Hispanics, similar to American Indians or Alaska Natives, and higher than Asians and Native Hawaiians or Other Pacific Islanders. In the multivariable analyses, the PI incidence rate ratio was higher only among American Indians or Alaska Natives, and this difference was associated with a NH-level variable—the proportion of racial and ethnic minority residents. Other outcomes did not vary by race/ethnicity. An adjusted exploratory analysis was conducted to help explain the difference between the bivariate and multivariable analyses and revealed an important within-NH difference: Compared to Whites, the PI incidence rate ratios were higher in women who were Black, or American Indian or Alaska Native. Limitations: Our findings are correlational and may be impacted by unevaluated variables and the limitations of administrative data. Implications: In U.S. NHs, the annual incidence rate of PIs varies by race/ethnicity. Facility characteristics strongly influence this variation. Higher incidence rate ratios among racial and ethnic minority residents also are explained by differences within NHs and are striking among subgroups, including female residents who are Black, or American Indian or Alaska Native. Future research should evaluate the sexes separately and explore both across-NH and within-NH differences to determine whether there are structural inequities, bias, and disparate care