Artificial three-body equilibria for hybrid low-thrust propulsion

This paper proposes a new concept of creating artificial equilibrium points in the circular restricted three body problem, where the third body uses a hybrid of solar sail and solar electric propulsion. The work aims to investigate the use of a hybrid sail for artificial equilibrium points that are technologically di±cult with either of these propulsion systems alone. The hybrid sail has freedom in specifying the sail lightness number, then minimizing the required thrust acceleration from the solar electric propulsion thruster while satisfying the equilibrium condition. The stability analysis of such artificial equilibrium points by a linear method results in a linear time varying (mass) system. The freezing time method then provides unstable and marginally stable regions for hybrid solar sail artificial equilibria. We compare these propulsion systems with a given payload mass and mission life for a polar observation mission. For a near term sail assembly loading we find for the hybrid sail a substantially lower propellant mass compared to solar electric propulsion and lower sail length with respect to a solar sail, and a lower initial spacecraft mass

Local spatial analysis and dynamic simulation of childhood obesity and neighbourhood walkability in a major Canadian city

Body weight is an important indicator of current and future health and it is even more critical in children, who are tomorrow’s adults. This paper analyzes the relationship between childhood obesity and neighbourhood walkability in Calgary, Canada. A multivariate analytical framework recognizes that childhood obesity is also associated with many factors, including socioeconomic status, foodscapes, and environmental factors, as well as less measurable factors, such as individual preferences, that could not be included in this analysis. In contrast with more conventional global analysis, this research employs localized analysis and assesses need-based interventions. The <i>one-size-fit-all </i>strategy may not effectively control obesity rates, since each neighbourhood has unique characteristics that need to be addressed individually. This paper presents an innovative framework combining local analysis with simulation modeling to analyze childhood obesity. Spatial models generally do not deal with simulation over time, making it cumbersome for health planners and policy makers to effectively design and implement interventions and to quantify their impact over time. This research fills this gap by integrating geographically weighted regression (GWR), which identifies vulnerable neighbourhoods and critical factors for childhood obesity, with simulation modeling, which evaluates the impact of the suggested interventions on the targeted neighbourhoods. Neighbourhood walkability was chosen as a potential target for localized interventions, owing to the crucial role of walking in developing a healthy lifestyle, as well as because increasing walkability is relatively more feasible and less expensive then modifying other factors, such as income. Simulation results suggest that local walkability interventions can achieve measurable declines in childhood obesity rates. The results are encouraging, as improvements are likely to compound over time. The results demonstrate that the integration of GWR and simulation modeling is effective, and the proposed framework can assist in designing local interventions to control and prevent childhood obesity

Doubly perturbed S3S_3 neutrinos and the s13s_{13} mixing parameter

We further study a predictive model for the masses and mixing matrix of three Majorana neutrinos. At zeroth order the model yielded degenerate neutrinos and a generalized ``tribimaximal" mixing matrix. At first order the mass splitting was incorporated and the tribimaximal mixing matrix emerged with very small corrections but with a zero value for the parameter $s_{13}$. In the present paper a different, assumed weaker, perturbation is included which gives a non zero value for $s_{13}$ and further corrections to other quantities. These corrections are worked out and their consequences discussed under the simplifying assumption that the conventional CP violation phase vanishes. It is shown that the existing measurements of the parameter $s_{23}$ provide strong bounds on $s_{13}$ in this model.Comment: 8 page

Light levitated geostationary cylindrical orbits are feasible

This paper discusses a new family of non-Keplerian orbits for solar sail spacecraft displaced above or below the Earth's equatorial plane. The work aims to prove the assertion in the literature that displaced geostationary orbits exist, possibly to increase the number of available slots for geostationary communications satellites. The existence of displaced non-Keplerian periodic orbits is ¯rst shown analytically by linearization of the solar sail dynamics around a geostationary point. The full displaced periodic solution of the non-linear equations of motion is then obtained using a Hermite-Simpson collocation method with inequality path constraints. The initial guess to the collocation method is given by the linearized solution and the inequality path constraints are enforced as a box around the linearized solution. The linear and nonlinear displaced periodic orbits are also obtained for the worst-case Sun-sail orientation at the solstices. Near-term and high-performance sails can be displaced between 10 km and 25 km above the Earth's equatorial plane during the summer solstice, while a perforated sail can be displaced above the usual station-keeping box (75 £ 75 km) of nominal geostationary satellites. Light-levitated orbit applications to Space Solar Power are also considered

DO GLASS IONOMER CEMENTS MATURE APPRECIABLY? A CRITICAL REVIEW

Introduction: The earliest glass ionomer cement (GIC) had low strength when tested after 24 hours. However, after long periods, strength increased. This was initially thought to be a property of all GICs, but some later materials either did not increase or got weaker. Objectives: This review aims at determining whether changes in the chemical composition of the glass component of GICs do result in different strength changes or whether other formulation changes are also responsible. In addition, it aims at evaluating changes in other non-mechanical properties, such as abrasion and erosion. Materials and methods: Search engines were used to find relevant references included in Ovid SP, Pubmed and Index Copernicus.Results and discussion: In experimental GICs strength, changes have an inverse correlation with initial (24 hours) strength. For commercial GICs, no such relationship is found. High phosphorus contents result in large increases in strength from initial low strength values. Other properties also show maturation changes. In particular, both resistance to abrasion and erosion increase in the relatively few GICs tested, including some which do not show strength increases. Conclusions: GICs have the potential to improve their properties when matured for periods longer than 24 hours, however this property is dependent on glass composition

Severe Anaphylaxis to Volplex, a Colloid Solution during Cesarean Section: A Case Report and Review

Anaphylaxis is a life-threatening event that can occur anytime during pregnancy. It has been reported following administration of various substances with adverse maternal and neonatal consequences. It should be considered in the differential diagnosis of intrapartum collapse. We encountered a case of severe anaphylactic reaction following a routine cesarean section. It is very important that all members of the perinatal team are aware of early recognition and management of anaphylactic reaction. We think that it is important to highlight this as a further case report of severe anaphylactic reaction to a colloid solution and discuss the pathophysiology and management

Design and Development of a Multi-Sided Tabletop Augmented Reality 3D Display Coupled with Remote 3D Imaging Module

This paper proposes a tabletop augmented reality (AR) 3D display paired with a remote 3D image capture setup that can provide three-dimensional AR visualization of remote objects or persons in real-time. The front-side view is presented in stereo-3D format, while the left-side and right-side views are visualized in 2D format. Transparent glass surfaces are used to demonstrate the volumetric 3D augmentation of the captured object. The developed AR display prototype mainly consists of four 40 × 30 cm2 LCD panels, 54% partially reflective glass, an in-house developed housing assembly, and a processing unit. The capture setup consists of four 720p cameras to capture the front-side stereo view and both the left- and right-side views. The real-time remote operation is demonstrated by connecting the display and imaging units through the Internet. Various system characteristics, such as range of viewing angle, stereo crosstalk, polarization perseverance, frame rate, and amount of reflected and transmitted light through partially reflective glass, were examined. The demonstrated system provided 35% optical transparency and less than 4% stereo crosstalk within a viewing angle of ±20 degrees. An average frame rate of 7.5 frames per second was achieved when the resolution per view was 240 × 240 pixels