22,929 research outputs found
Polytopes of Minimum Positive Semidefinite Rank
The positive semidefinite (psd) rank of a polytope is the smallest for
which the cone of real symmetric psd matrices admits an affine
slice that projects onto the polytope. In this paper we show that the psd rank
of a polytope is at least the dimension of the polytope plus one, and we
characterize those polytopes whose psd rank equals this lower bound. We give
several classes of polytopes that achieve the minimum possible psd rank
including a complete characterization in dimensions two and three
A Key to Container-Breeding Mosquitoes of Michigan (Diptera: Cllllcidae), With Notes on Their Biology
An illustrated key to larvae and notes on the biology of container-breeding mosquitoes of Michigan are presented. Two species included in the key. Aedes aegypti and Aedes albopictus. are not endemic in Michigan, but occasional introductions could occur with commercial shipments of scrap tires or other containers
The Functions and Practices of a Television Network
An Iterative Learning Control disturbance rejection approach is considered and it is shown that iteration variant learning filters can asymptotically give the controlled variable zero error and zero variance. Convergence is achieved with the assumption that the relative model error is less than one. The transient response of the suggested ILC algorithm is also discussed using a simulation example
Solar dynamic power for space station freedom
The Space Station Freedom Program is presently planned to consist of two phases. At the completion of Phase 1, Freedom's manned base will consist of a transverse boom with attached manned modules and 75 kW of available electric power supplied by photovoltaic (PV) power sources. In Phase 2, electric power available to the manned base will be increased to 125 kW by the addition of two solar dynamic (SD) power modules, one at each end of the transverse boom. Power for manned base growth beyond Phase 2 will be supplied by additional SD modules. Studies show that SD power for the growth eras will result in life cycle cost savings of 4 billion when compared to PV-supplied power. In the SD power modules for Space Station Freedom, an offset parabolic concentrator collects and focuses solar energy into a heat receiver. To allow full power operation over the entire orbit, the receiver includes integral thermal energy storage by means of the heat of fusion of a salt mixture. Thermal energy is removed from the receiver and converted to electrical energy by a power conversion unit (PCU) which includes a closed brayton cycle (CBC) heat engine and an alternator. The receiver/PCU/radiator combination will be completely assembled and charged with gas and cooling fluid on Earth before launch to orbit. The concentrator subassemblies will be pre-aligned and stowed in the orbiter bay before launch. On orbit, the receiver/PCU/radiator assembly will be installed as a unit. The pre-aligned concentrator panels will then be latched together and the total concentrator attached to the receiver/PCU/radiator by the astronauts. After final electric connections are made and checkout is complete, the SD power module will be ready for operation
Close-Range Photogrammetric Measurement of Static Deflections for an Aeroelastic Supercritical Wing
Close range photogrammetric measurements were made for the lower wing surface of a full span aspect ratio 10.3 aeroelastic supercritical research wing. The measurements were made during wind tunnel tests for quasi-steady pressure distributions on the wing. The tests were conducted in the NASA Langley Transonic Dynamics Tunnel at Mach numbers up to 0.90 and dynamic pressures up to 300 pounds per square foot. Deflection data were obtained for 57 locations on the wing lower surface using dual non-metric cameras. Representative data are presented as graphical overview to show variations and trends of spar deflection with test variables. Comparative data are presented for photogrammetric and cathetometric results of measurements for the wing tip deflections. A tabulation of the basic measurements is presented in a supplement to this report
Use of Urinary Pregnanediol 3-glucuronide to Confirm Ovulation
Objective Urinary hormonal markers may assist in increasing the efficacy of Fertility Awareness Based Methods (FABM). This study uses urinary pregnanediol-3a-glucuronide (PDG) testing to more accurately identify the infertile phase of the menstrual cycle in the setting of FABM. Methods Secondary analysis of an observational and simulation study, multicentre, European study. The study includes 107 women and tracks daily first morning urine (FMU), observed the changes in cervical mucus discharge, and ultrasonography to identify the day of ovulation over 326 menstrual cycles. The following three scenarios were tested: (A) use of the daily pregnandiol-3a-glucuronide (PDG) test alone; (B) use of the PDG test after the first positive urine luteinizing hormone (LH) kit result; (C) use of the PDG test after the disappearance of fertile type mucus. Two models were used: (1) one day of PDG positivity; or (2) waiting for three days of PDG positivity before declaring infertility. Results After the first positivity of a LH test or the end of fertile mucus, three consecutive days of PDG testing over a threshold of 5 μg/mL resulted in a 100% specificity for ovulation confirmation. They were respectively associated an identification of an average of 6.1 and 7.6 recognized infertile days. Conclusions The results demonstrate a clinical scenario with 100% specificity for ovulation confirmation and provide the theoretical background for a future development of a competitive lateral flow assay for the detection of PDG in the urine
SE and I system testability: The key to space system FDIR and verification testing
The key to implementing self-diagnosing design is a systems engineering task focused on design for testability concurrent with design for functionality. The design for testability process described here is the product of several years of DOD study and experience. Its application to the space station has begun on Work Package II under NASA and McDonnell direction. Other work package teams are being briefed by Harris Corporation with the hope of convincing them to embrace the process. For the purpose of this discussion the term testability is used to describe the systems engineering process by which designers can assure themselves and their reviewers that their designs are TESTABLE, that is they will support the downstream process of determining their functionality. Due to the complexity and density of present-day state-of-the-art designs, such as pipeline processors and high-speed integrated circuit technology, testability feature design is a critical requirement of the functional design process. A systematic approach to Space systems test and checkout as well as fault detection fault isolation reconfiguration (FDFIR) will minimize operational costs and maximize operational efficiency. An effective design for the testability program must be implemented by all contractors to insure meeting this objective. The process is well understood and technology is here to support it
New Records of Michigan Cicadidae (Homoptera), With Notes on the Use of Songs to Monitor Range Changes
We present records of Diceroprocta vitripennis, Tibicen chloromera, and Tibicen pruinosa (new state record) in Michigan. Monitoring geographic range changes and population size differences by song suggests several population situations for cicadas: (1) sizable populations in most areas of apparently good habitat; (2) widely separated single individuals or small populations on the edges of populated regions, representing range extensions that may be of limited duration; (3) one or a few individuals present only once, probably transferred in soil on roots, and ultimately unsuccessful. Species- specific calling songs allow sensitive measurement of species\u27 range changes
A study of the elements copper through uranium in Sirius A: Contributions from STIS and ground-based spectra
We determine abundances or upper limits for all of the 55 stable elements
from copper to uranium for the A1 Vm star Sirius. The purpose of the study is
to assemble the most complete picture of elemental abundances with the hope of
revealing the chemical history of the brightest star in the sky, apart from the
Sun. We also explore the relationship of this hot metallic-line (Am) star to
its cooler congeners, as well as the hotter, weakly- or non-magnetic
mercury-manganese (HgMn) stars. Our primary observational material consists of
{\em Hubble Space Telescope} () spectra taken with the Space Telescope
Imaging Spectrograph (STIS) in the ASTRAL project. We have also used archival
material from the %\citep/{ayr10}. satellite, and from the
Goddard High-Resolution Spectrograph (GHRS), as well as ground-based spectra
from Furenlid, Westin, Kurucz, Wahlgren, and their coworkers, ESO spectra from
the UVESPOP project, and NARVAL spectra retrieved from PolarBase. Our analysis
has been primarily by spectral synthesis, and in this work we have had the
great advantage of extensive atomic data unavailable to earlier workers. We
find most abundances as well as upper limits range from 10 to 100 times above
solar values. We see no indication of the huge abundance excesses of 1000 or
more that occur among many chemically peculiar (CP) stars of the upper main
sequence. The picture of Sirius as a hot Am star is reinforced.Comment: With 6 Figures and 4 Tables; accepted for publication in Ap
Ecology of Juvenile Walleye Pollock, Theragra chalcogramma: Papers from the workshop "The Importance of Prerecruit Walleye Pollock to the Bering Sea and North Pacific Ecosystems" Seattle, Washington, 28-30 October 1993
The Alaska Fisheries Science Center (AFSC), National
Marine Fisheries Service (NMFS), hosted an international
workshop, 'The Importance of Prerecruit Walleye Pollock to the Bering Sea and North Pacific Ecosystems," from 28 to 30 October 1993. This workshop was held in conjunction with the annual International North Pacific Marine Science Organization (PICES) meeting held in Seattle. Nearly 100 representatives from government agencies, universities, and the fishing industry in Canada, Japan, the People's Republic of China, Russia, and the United States took part in the workshop to review and discuss current knowledge on juvenile pollock from the postlarval period to the time they recruit to the fisheries. In addition to its importance to humans as a major commercial species, pollock also serves as a major forage species for many marine fishes, birds, and mammals in the North Pacific region.
(PDF file contains 236 pages.
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