24,726 research outputs found
Absolute profinite rigidity and hyperbolic geometry
We construct arithmetic Kleinian groups that are profinitely rigid in the
absolute sense: each is distinguished from all other finitely generated,
residually finite groups by its set of finite quotients. The Bianchi group
with is rigid in
this sense. Other examples include the non-uniform lattice of minimal co-volume
in and the fundamental group of the Weeks manifold
(the closed hyperbolic -manifold of minimal volume).Comment: v2: 35 pages. Final version. To appear in the Annals of Mathematics,
Vol. 192, no. 3, November 202
Science Leadership: Impact of the New Science Coordinators Academy
This article discusses the impact of the New Science Coordinators Academy (NSCA) on two cohorts of participants. The NSCA is one of four components of the Virginia Initiative for Science Teaching and Achievement (VISTA), a United States Department of Education (USED) science education reform grant. The NSCA is designed to support new school district science coordinators (with less than five years of experience) and to continue building the state science education infrastructure. Research in education leadership traditionally focuses on teacher leaders, principals, and district office personnel. Interestingly, research on district office personnel rarely distinguishes between the different roles of district personnel. This article seeks to inform the field by sharing the impact of an academy designed for new science coordinators on their learning, and to begin to understand their role and impact in their district. The five-day Academy engaged participants in a variety of experiences designed to facilitate the following: 1) build leadership skills; 2) build a common understanding and vision for hands-on science, inquiry, problem-based learning, and nature of science in the science classroom; 3) investigate data to improve student learning goals; 4) and, develop a science strategic plan. The data indicate that the NSCA was successful at meeting its goals to support the participants and to build a common language among these new coordinators. Initial data also support the variety of responsibilities of these participants and the positive impact of the Academy on their district work
Design and performance of a high-pressure-ratio, highly loaded axial-flow transonic compressor space
A 50-cm-diam. axial-flow transonic compressor stage with multiple-circular-arc blades was designed and tested. At design speed, a rotor peak efficiency of 0.85 occurred at an equivalent weight flow of 29.3 kg/sec. Stage peak efficiency was 0.79 at 28.6 kg/sec. Stage total pressure ratio at peak efficiency was 1.84. The stall margin at design speed was 5 percent. Rotor and stator losses were higher than predicted. The stator choked at design flow
Accurate measurement of telemetry performance
Performance of high rate telemetry stations used in the Deep Space Network is verified. Measurement techniques are discussed
A New Brown Dwarf Desert? A Scarcity of Wide Ultracool Binaries
We present the results of a deep-imaging search for wide companions to
low-mass stars and brown dwarfs using NSFCam on IRTF. We searched a sample of
132 M7-L8 dwarfs to magnitude limits of and ,
corresponding to secondary-primary mass ratios of . No companions
were found with separations between 2{\arcsec} to 31{\arcsec} (40 AU
to 1000 AU). This null result implies a wide companion frequency below
2.3% at the 95% confidence level within the sensitivity limits of the survey.
Preliminary modeling efforts indicate that we could have detected 85% of
companions more massive than and 50% above .Comment: 27 pages, 8 figures, 3 tables: accepted to the Astronomical Journa
Communicating the Value of Ergonomics to Management – Part 2: Ergonomics ROI Case Study Applications
More than ever, human factors engineers and ergonomists need to justify our practice’s value to management. How can we effectively communicate with management? How should we present a Return on Investment (ROI) that leadership will find useful that addresses company profits, cost savings, productivity, first time quality, and turnover? What else does management care about other than ROI? This second panel in a two panel series will specifically highlight case studies in which presenters give examples of situations in which ROI for ergonomics was investigated from a business value. The session will start with four case study lectures followed by a panel discussion led by the moderators. The audience will be encouraged to participate with their own questions and comments
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