413 research outputs found
Fast Attitude Maneuvers for the Lunar Reconnaissance Orbiter
This paper describes a new operational capability for fast attitude maneuvering that is being developed for the Lunar Reconnaissance Orbiter (LRO). The LRO hosts seven scientific instruments. For some instruments, it is necessary to per-form large off-nadir slews to collect scientific data. The accessibility of off-nadir science targets has been limited by slew rates and/or occultation, thermal and power constraints along the standard slew path. The new fast maneuver (FastMan) algorithm employs a slew path that autonomously avoids constraint violations while simultaneously minimizing the slew time. The FastMan algo-rithm will open regions of observation that were not previously feasible and improve the overall science return for LRO's extended mission. The design of an example fast maneuver for LRO's Lunar Orbiter Laser Altimeter that reduc-es the slew time by nearly 40% is presented. Pre-flight, ground-test, end-to-end tests are also presented to demonstrate the readiness of FastMan. This pioneer-ing work is extensible and has potential to improve the science data collection return of other NASA spacecraft, especially those observatories in extended mission phases where new applications are proposed to expand their utility
A Prograde, Low-Inclination Orbit for the Very Hot Jupiter WASP-3b
We present new spectroscopic and photometric observations of the transiting
exoplanetary system WASP-3. Spectra obtained during two separate transits
exhibit the Rossiter-McLaughlin (RM) effect and allow us to estimate the
sky-projected angle between the planetary orbital axis and the stellar rotation
axis, lambda = 3.3^{+2.5}_{-4.4} degrees. This alignment between the axes
suggests that WASP-3b has a low orbital inclination relative to the equatorial
plane of its parent star. During our first night of spectroscopic measurements,
we observed an unexpected redshift briefly exceeding the expected sum of the
orbital and RM velocities by 140 m/s. This anomaly could represent the
occultation of material erupting from the stellar photosphere, although it is
more likely to be an artifact caused by moonlight scattered into the
spectrograph.Comment: 23 pages, 4 figures, Accepted for publication in The Astrophysical
Journal, Replacement includes revised citation
Technology Facilitation in the Rural School: An Analysis of Options
A study examining technology support in rural schools surveyed 129 school technology coordinators in four upper plains states. Heavy pedagogical and technical demands were placed on rural technology coordinators. Rural technology coordinators should have teaching experience and advanced degree work in network administration, computer hardware characteristics, multimedia production, instructional design, and school leadership
Cost-Effectiveness and Impact Analysis of Adoption of Standard 90.1-2007 for New York State
This report is a subset of the commercial nationwide building energy code analysis. New York has cost criteria that must also be met, and this report includes those details. This report will be finalized when the nationwide analysis report is finalized in September
Waypoint Following Dynamics of a Quaternion Error Feedback Attitude Control System
Closed-loop attitude steering can be used to implement a non-standard
attitude maneuver by using a conventional attitude control system to track a
non-standard attitude profile. The idea has been employed to perform
zero-propellant maneuvers on the International Space Station and minimum time
maneuvers on NASA's TRACE space telescope. A challenge for operational
implementation of the idea is the finite capacity of a space vehicle's command
storage buffer. One approach to mitigate the problem is to downsample-and-hold
the attitude commands as a set of waypoints for the attitude control system to
follow. In this paper, we explore the waypoint following dynamics of a
quaternion error feedback control law for downsample-and-hold. It is shown that
downsample-and-hold induces a ripple between downsamples that causes the
satellite angular rate to significantly overshoot the desired limit. Analysis
in the -domain is carried out in order to understand the phenomenon. An
interpolating Chebyshev-type filter is proposed that allows attitude commands
to be encoded in terms of a set of filter coefficients. Using the interpolating
filter, commands can be issued at the ACS rate but with significantly reduced
memory requirements. The attitude control system of NASA's Lunar Reconnaissance
Orbiter is used as an example to illustrate the behavior of a practical
attitude control system.Comment: 24 pages; 11 figure
Control of hyperglycaemia in paediatric intensive care (CHiP): study protocol.
BACKGROUND: There is increasing evidence that tight blood glucose (BG) control improves outcomes in critically ill adults. Children show similar hyperglycaemic responses to surgery or critical illness. However it is not known whether tight control will benefit children given maturational differences and different disease spectrum. METHODS/DESIGN: The study is an randomised open trial with two parallel groups to assess whether, for children undergoing intensive care in the UK aged <or= 16 years who are ventilated, have an arterial line in-situ and are receiving vasoactive support following injury, major surgery or in association with critical illness in whom it is anticipated such treatment will be required to continue for at least 12 hours, tight control will increase the numbers of days alive and free of mechanical ventilation at 30 days, and lead to improvement in a range of complications associated with intensive care treatment and be cost effective. Children in the tight control group will receive insulin by intravenous infusion titrated to maintain BG between 4 and 7.0 mmol/l. Children in the control group will be treated according to a standard current approach to BG management. Children will be followed up to determine vital status and healthcare resources usage between discharge and 12 months post-randomisation. Information regarding overall health status, global neurological outcome, attention and behavioural status will be sought from a subgroup with traumatic brain injury (TBI). A difference of 2 days in the number of ventilator-free days within the first 30 days post-randomisation is considered clinically important. Conservatively assuming a standard deviation of a week across both trial arms, a type I error of 1% (2-sided test), and allowing for non-compliance, a total sample size of 1000 patients would have 90% power to detect this difference. To detect effect differences between cardiac and non-cardiac patients, a target sample size of 1500 is required. An economic evaluation will assess whether the costs of achieving tight BG control are justified by subsequent reductions in hospitalisation costs. DISCUSSION: The relevance of tight glycaemic control in this population needs to be assessed formally before being accepted into standard practice
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How Leaders Agree with Teachers in Schools on Measures of Leadership Practice: A Two-Level Latent Class Analysis of the Comprehensive Assessment of Leadership for Learning
Background: Across the recent research on school leadership, leadership for learning has emerged as a strong framework for integrating current theories, such as instructional, transformational, and distributed leadership as well as effective human resource practices, instructional evaluation, and resource allocation. Yet, questions remain as to how, and to what extent teachers and leaders practice the skills and tasks that are known to be associated with effective school leadership, and to what extent do teachers and leaders agree that these practices are taking place in their school. Purpose of the Study: We examine these issues through applying a congruency-typology model to the validation sample of the Comprehensive Assessment of Leadership for Learning (CALL), (117 schools across the US, including 3,367 teachers and their school leaders) to examine the extent to which there may be significantly different subgroups of teacher and leader responders to the survey, how these subgroups may cluster non-randomly in schools, and to what extent the subgroups of teachers and principals are aligned or not on their perception that the skills and practices of leadership for learning take place in their school. Research Design: We used multilevel latent class analysis (LCA) to identify significantly different types of teacher and leader responders to CALL, including a cross-level interaction to examine the extent to which there is a typology model of teacher responders across schools and the extent to which the teacher subgroup responses align with the leader of the school. Findings: We find that there are three statistically significant different subgroups of teacher responders to CALL, Low (31.4%), Moderate (43.3%), and High (25.4%). In addition, these subgroups cluster non-randomly across three different types of schools: schools with low leadership for learning (40.2%), moderate leadership for learning (47.0%), and the smallest subgroup, schools with high leadership for learning (12.8%). Conclusions: Our findings suggest that a congruency-typology model of leadership for learning is useful for understanding the context of practice, as schools may be on a continuum of practice in which there is strong alignment between teacher and leader responder types in the low and high schools – indicating problematic or beneficial contexts – but that leaders in the moderate type may be working to move their school towards instructional improvement through leadership for learning. As a quantitative phenomenology, this study provides a rich contextual analysis of the relationship between teachers and leaders on a multisource feedback survey of leadership for learning in schools. Keywords: School Leadership, Leadership for Learning, Leadership Styles, Instructional Leadership, Transformational Leadership, Latent Class Analysis, Mixture Modeling, Multivariate Methods, Multisource Feedback, Survey Research, Online Surveys, Teacher Leadership, Principal
Comparison of the Energy Efficiency Prescribed by ASHRAE/ANSI/IESNA Standard 90.1-1999 and ASHRAE/ANSI/IESNA Standard 90.1-2004
This document presents the qualitative comparison of DOE’s formal determination of energy savings of ANSI/ASHRAE/IESNA Standard 90.1-2004. The term “qualitative” is used in the sense of identifying whether or not changes have a positive, negative, or neutral impact on energy efficiency of the standard, with no attempt made to quantify that impact. A companion document will present the quantitative comparison of DOE’s determination. The quantitative comparison will be based on whole building simulation of selected building prototypes in selected climates. This document presents a comparison of the energy efficiency requirements in ANSI/ASHRAE/IESNA 90.1-1999 (herein referred to as Standard 90.1-1999) and ANSI/ASHRAE/IESNA 90.1-2004 (herein referred to as Standard 90.1-2004). The comparison was done through a thorough review of all addenda to Standard 90.1-1999 that were included in the published ANSI/ASHRAE/IESNA Standard 90.1-2001 (herein referred to as Standard 90.1-2001) and also all addenda to Standard 90.1-2001 that were included in the published Standard 90.1-2004. A summary table showing the impact of each addendum is provided. Each addendum to both Standards 90.1-1999 and 90.1-2001 was evaluated as to its impact on the energy efficiency requirements of the standard (greater efficiency, lesser efficiency) and as to significance. The final section of this document summarizes the impacts of the various addenda and proposes which addenda should be included in the companion quantitative portion of DOE’s determination. Addenda are referred to with the nomenclature addendum 90.1-xxz, where “xx” is either “99” for 1999 or “01” for 2001, and z is the ASHRAE letter designation for the addendum. Addenda names are shown in bold face in text. DOE has chosen not to prepare a separate evaluation of Standard 90.1-2001 as that standard does not appear to improve energy efficiency in commercial buildings. What this means for the determination of energy savings for Standard 90.1-2004 is that the baseline standard for comparison is Standard 90.1-1999 and all addenda to both Standards 90.1-1999 and 90.1-2001 must be considered to determine the overall change in efficiency between Standard 90.1-1999 and Standard 90.1-2004
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