Magnetic suspension options for spacecraft inertia-wheel applications

Design criteria for spacecraft inertia-wheel suspensions are listed. The advantages of magnetic suspensions over other suspension types for spacecraft inertia-wheel applications are cited along with the functions performed by magnetic suspension. The common designs for magnetic suspensions are enumerated. Materials selection of permanent magnets and core materials is considered

The Elementary Persuasive Letter: Two Cases Of Situated Competence, Strategy, And Agency

Research on persuasive writing by elementary children posits primarily a developmental perspective, claiming that elementary-age children can effectively argue through talk but not through writing. While this view is commonly held, this article presents counterevidence. Drawing on two cases of third and fourth grade children writing persuasive letters gathered during six-month naturalistic studies of literacy practices and social identities in contrastive communities (one urban, one suburban), these data challenge the developmental generalization by showing that children in these settings can write persuasively. Further, this work complicates understandings of children\u27s persuasive writing by showing how assignments and local cultures shape children\u27s writing. Evidence is developed through rich description of the case study settings and instructional tasks, a typology of the children\u27s persuasive strategies, and a critical discourse analysis of the children\u27s persuasive letters. This study suggests that children in both communities are capable of persuasive writing, although they enact different patterns of response, drawing on locally learned discourses. The settings, the hybridity of the persuasive letter as both argument and letter, and the children\u27s habitus may account for some of the differences in how the children address the tasks through ranges of centeredness and agentive strategies. Differing patterns of response suggest new frames for viewing and fostering children\u27s argumentative competence in a range of settings, including understandings of agency. The author encourages a research agenda that accounts for socially situated classroom and community practices, and argues for ongoing research and critique of the power and place of persuasive writing for children in a range of schools

Casting And Recasting Gender: Children Constituting Social Identities Through Literacy Practices

Considers how gender, identity and literacy are entangled and mutually constitutive. Concludes that social experience, desire, proximate others, and the ways in which children can draw upon these in the classroom are aspects of the situated condition that deserve more prominence in literacy and identity research

Students And Service Staff Learning And Researching Together On A College Campus

Describes the preliminary study of a service learning program at Swarthmore College that paired students and college service staff in learning partnerships and as researchers of the program. Three primary questions were answered: How does service within a college campus count as service learning? How was the program community-shaping as well as personally enriching for students and staff? What place does participatory research have in service learning projects

Two-Color Terawatt Laser System For High-Intensity Laser-Plasma Experiments

We report a two-color terawatt laser system for use in controlling laser-plasma instabilities. The system includes a commercial 45 TW Ti:Sapphire laser system at 800 nm, temporally synchronized with a 1 TW CPA Raman-Ti:Sapphire hybrid laser centered at 873nm that we designed and built to complement the 800 nm system. The two-color system will be used to seed, enhance, suppress, or otherwise control a variety of instabilities which arise in laser-plasma interactions.Physic

LWFA With Low Energy Raman Seeded Pulses

Analytical and numerical calculations of plasma wakefield excitation and particle acceleration by Raman seeded laser pulse in self-modulation regime are presented. We derive energy threshold for self-modulation of diffraction-limited pulses. The parameter range where the Raman seeded amplitude plays an important role is investigated. We show that the seeded amplitude provides a coherent control mechanism for the phase of the wakefield wave. We show that with the use of Raman seed self-modulated wakefield acceleration is achievable for the pulses of intensities much lower than those typically used in the experiments. In particular, our 2D particle-in-cell simulations show that 30 mJ pulse combined with Raman seeded pulse, which is 1% in intensity of the main pulse is capable of generating similar to1 nC of relativistic electrons.Physic

A superconducting large-angle magnetic suspension

The component technologies were developed required for an advanced control moment gyro (CMG) type of slewing actuator for large payloads. The key component of the CMG is a large-angle magnetic suspension (LAMS). The LAMS combines the functions of the gimbal structure, torque motors, and rotor bearings of a CMG. The LAMS uses a single superconducting source coil and an array of cryoresistive control coils to produce a specific output torque more than an order of magnitude greater than conventional devices. The designed and tested LAMS system is based around an available superconducting solenoid, an array of twelve room-temperature normal control coils, and a multi-input, multi-output control system. The control laws were demonstrated for stabilizing and controlling the LAMS system