Plasma Magnetosphere Formation Around Oscillating Magnetized Neutron Stars

The notion of death line of rotating pulsars is applied to model of oscillating neutron stars. It is shown that the magnetosphere of typical non-rotating oscillating stars may not contain secondary plasma to support the generation of radio emission in the region of open field lines of plasma magnetosphere.Comment: Accepted for publication in Astrophysics & Space Scienc

The Mars Hopper: Development, Simulation and Experimental Validation of a Radioisotope Exploration Probe for the Martian Surface

An advanced exploration probe has been proposed by the Center for Space Nuclear Research (CSNR) to acquire detailed data from the Martian surface and subsurface, ‘hop’ large distances to multiple sites in short periods of time and perform this task repeatedly. Although several similar flying vehicles have been proposed utilizing various power sources and complex designs, e.g. solar-electric and chemical-based, the CSNR’s Mars Hopper is based on a radioisotope thermal rocket (RTR) concept. The Mars Hopper’s design relies on the high specific energies [J/kg] of radioisotopes and enhances their low specific power [W/kg] through the use of a thermal capacitance material to store thermal energy over time. During operation, the RTR transfers the stored thermal energy to a flowing gas, which is then expanded through a converging-diverging nozzle, producing thrust. Between flights, the platform will have ample time to perform in-depth science at each location while the propellant tanks and thermal capacitor recharge. Recharging the propellant tanks is accomplished by sublimation freezing of the ambient CO2 atmosphere with a cryocooler, followed by heating and pressurization to yield a liquid storage state. The proposed Mars Hopper will undergo a ballistic flight, consuming the propellant in both ascent and descent, and by using multiple hopper platforms, information can be gathered on a global scale, enabling better resource resolution and providing valuable information for a possible Mars sample-return mission. The CSNR, collaborating with the Idaho National Laboratory (INL) and three universities (University of Idaho, Utah State University and Oregon State University), has identified key components and sub-systems necessary for the proposed hopper. Current project activities include the development of a lab-scale prototypic Mars Hopper and test facility, along with computational fluid dynamics (CFD)/thermal-hydraulic models to yield a better understanding of the heat transfer process and complex nature of turbulent CO2 flow. Laboratory experimentation will aid design iterations and the development of both tethered and free-flying terrestrial hoppers that utilize an electrically heated core. The knowledge base acquired from these activities will refine the Mars Hopper’s future performance and optimize the RTR core components prior to constructing the final design

Causes and Dynamics of User Frustration in an Academic Library

published or submitted for publicatio

Social information access for the rest of us : an exploration of social YouTube

Adaptive Hypermedia and Adaptive Web-Based Systems (AH '08), Hannover, Germany, July 29 – August 1, 2008The motivation behind many Information Retrieval systems is to identify and present relevant information to people given their current goals and needs. Learning about user preferences and access patterns recent technologies make it possible to model user information needs and adapt services to meet these needs. In previous work we have presented ASSIST, a general-purpose platform which incorporates various types of social support into existing information access systems and reported on our deployment experience in a highly goal driven environment (ACM Digital Library). In this work we present our experiences in applying ASSIST to a domain where goals are less focused and where casual exploration is more dominant; YouTube. We present a general study of YouTube access patterns and detail how the ASSIST architecture affected the access patterns of users in this domain.Science Foundation IrelandConference detailshttp://www.ah2008.org