1,895 research outputs found
A foldable 4.27 meter (14 foot) spacecraft antenna
The problems and solutions associated with the design, fabrication, and testing of a large, lightweight, radial-rib, folding, spacecraft antenna reflector are discussed. The antenna reflector was designed as a highly efficient communications system for outer-planet missions extending as far as approximately 59.839 x 10 to the 11th power meters (40 astronomical units) from the sun. The methods used to obtain a lightweight precision rib surface, the evaluation and fabrication of the metallic reflector mesh surface, and the surface-evaluation techniques used on the assembled antenna reflector are included
Initial test bed concentrator characterization
The operational characteristics and the mirror alignment technique of the test bed concentrator control system are highlighted. The final design of the TBC control system provided one axis of fast slew capability so that either the Sun acquisition or emergency off-Sun mode could be obtained in a minimum time. The procedure for getting on and off Sun is to run the elevation axis up to the approximate elevation of the Sun for the particular time of acquisition and then slew the concentrator on Sun in azimuth. The automatic Sun-acquisition system is controlled by two Sun sensors, one for each axis; each has a 2deg acquisition cone angle within which the concentrators are programmed to point. The mirror alignment technique chosen utilized a semi-distant incandescent light source which produced a reflected image on the focal point target. The concentrator was boresighted to the light by moving the concentrator while sighting along the cross hairs and through the apertures in the disks to the light source resulting in a maximum point error of 0.11 deg. Test plans to install a solar flux mapper to characterize the solar spot and to measure the size, shape, and intensity of the Sun's image are outlined
Space Telescope and Optical Reverberation Mapping Project. VI:Reverberating Disk Models for NGC 5548
We conduct a multiwavelength continuum variability study of the Seyfert 1 galaxy NGC 5548 to investigate the temperature structure of its accretion disk. The 19 overlapping continuum light curves (1158 Å to 9157 Å) combine simultaneous Hubble Space Telescope, Swift, and ground-based observations over a 180 day period from 2014 January to July. Light-curve variability is interpreted as the reverberation response of the accretion disk to irradiation by a central time-varying point source. Our model yields the disk inclination i =36 ̊± 10 ̊, temperature T1 = (44 ̊± 6) x 103 K at 1 light day from the black hole, and a temperature–radius slope (T ∝ r-a ) of ∝ = 0.99 ± 0.03. We also infer the driving light curve and find that it correlates poorly with both the hard and soft X-ray light curves, suggesting that the X-rays alone may not drive the ultraviolet and optical variability over the observing period. We also decompose the light curves into bright, faint, and mean accretion-disk spectra. These spectra lie below that expected for a standard blackbody accretion disk accreting at L/L Edd = 0.
A versatile high resolution objective for imaging quantum gases
We present a high resolution objective lens made entirely from catalog
singlets that has a numerical aperture of 0.36. It corrects for aberrations
introduced by a glass window and has a long working distance of 35mm, making it
suitable for imaging objects within a vacuum system. This offers simple high
resolution imaging for many in the quantum gas community. The objective
achieves a resolution of 1.3{\mu}m at the design wavelength of 780nm, and a
diffraction-limited field of view of 360{\mu}m when imaging through a 5mm
window. Images of a resolution target and a pinhole show quantitative agreement
with the simulated lens performance. The objective is suitable for
diffraction-limited imaging on the D2 line of all the alkalis by changing only
the aperture diameter, retaining numerical apertures above 0.32. The design
corrects for window thicknesses of up to 15mm if the singlet spacings are
modified
Reducing smoking in adolescents: cost-effectiveness results from the cluster randomized ASSIST (A Stop Smoking In Schools Trial)
Introduction: School-based smoking prevention programmes can be effective, but evidence on cost-effectiveness is lacking. We conducted a cost-effectiveness analysis of a school-based “peer-led” intervention.<p></p>
Methods: We evaluated the ASSIST (A Stop Smoking In Schools Trial) programme in a cluster randomized controlled trial. The ASSIST programme trained students to act as peer supporters during informal interactions to encourage their peers not to smoke. Fifty-nine secondary schools in England and Wales were randomized to receive the ASSIST programme or usual smoking education. Ten thousand seven hundred and thirty students aged 12–13 years attended participating schools. Previous work has demonstrated that the ASSIST programme achieved a 2.1% (95% CI = 0%–4.2%) reduction in smoking prevalence. We evaluated the public sector cost, prevalence of weekly smoking, and cost per additional student not smoking at 24 months.<p></p>
Results: The ASSIST programme cost of £32 (95% CI = £29.70–£33.80) per student. The incremental cost per student not smoking at 2 years was £1,500 (95% CI = £669–£9,947). Students in intervention schools were less likely to believe that they would be a smoker at age 16 years (odds ratio [OR] = 0.80; 95% CI = 0.66–0.96).<p></p>
Conclusions: A peer-led intervention reduced smoking among adolescents at a modest cost. The intervention is cost-effective under realistic assumptions regarding the extent to which reductions in adolescent smoking lead to lower smoking prevalence and/or earlier smoking cessation in adulthood. The annual cost of extending the intervention to Year 8 students in all U.K. schools would be in the region of £38 million and could result in 20,400 fewer adolescent smokers.<p></p>
Industry-University Cooperative Research Centers
This paper takes a first look at the effect of Industry-University Cooperative Research Centers (IUCRCs) on industrial R&D laboratories. IUCRCs are small academic centers designed to foster technology transfer between universities and firms. Since IUCRCs depend on industry support we expect them to further the research of member companies. Our findings suggest that IUCRCs promote industry-university technology transfer. We find strong associations between laboratory membership in IUCRCs and the importance of faculty consultants, co-authorship with faculty and hiring of graduate students to the laboratories. IUCRC membership contributes small increments, not always statistically significant, of 2% in laboratory patenting and research expenditures. Both estimates are larger for National Science Foundation IUCRCs, consistent with their quality and their sorting to larger laboratories. These results survive a simultaneous equation analysis of the joint decision to patent and join IUCRCs. Nevertheless more work is needed to separate the effect of the IUCRCs from the matching mechanism that assigns IUCRCs to R&D laboratories.
Myofibrillar Protein Turnover in Feed-Restricted and Realimented Beef Cattle
The objective of this study was to determine the effect of feed restriction and repletion on myofibrillar protein turnover in cattle. Crossbred steer calves (n = 12) about 310 d of age were assigned randomly to a diet of corn and silage that was 1) provided ad libitum for 146 d (ALC) or 2) restricted so steers gained .2 kg/d for 80 d but received ad libitum access to feed thereafter for 66 d (RFC). At 27, 55, 97, 118 and 146 d a 24-h urine sample and a blood sample were obtained. Urine was analyzed for Nτ-methylhistidine Nτ-MH), creatinine (C), urea nitrogen (UN) and total nitrogen (TN). Serum samples were analyzed for hydroxyproliine (HYF\u27), C and albumin (A). Body weights were lower (P \u3c .05) in RFC at 55, 97, 118 and 146 d. Excretion of Nτ-MH was lower (P \u3c .05) in the RFC at 27 and 55 d but higher at 118 d Urinary C excretion was higher in ALC at the last four sample times. Urinary UN and TN excretion were lower (P \u3c .05) in RFC at 55, 97 and 118 d; urinary UN also was lower (P \u3c .05) at d 146. Serum A was higher (P \u3c .05) in ALC at 55 and 118 d, respectively. Serum HYP was higher (P \u3c .05) in RFC at 27 and 55 d. Calculated myofibrillar protein breakdown rates (FBR) and fractional synthesis rates (FSR) were higher (P \u3c .05) in RFC at the last two sampling periods; FSR was lower for the RFC at the first sampling period. Realimentation after a period of feed restriction increased both synthesis and degradation of myofibrillar protein in beef cattle
Experiences in the Integration of Design Across the Mechanical Engineering Curriculum
The Faculty of the School of Mechanical Engineering at Purdue University have effected a major change in the Purdue Mechanical Engineering program by integrating design throughout the curriculum. In doing so, a significant level of faculty interaction has been achieved as well. The goals of the curriculum revision are: (1) to improve student skills in how to solve open-ended design problems, (2) to reduce the core of the curriculum to allow flexibility in course selection, and allow time for solving design problems, (3) to improve student skills in team work and communications, and (4) to improve student skills in using computers as tools for solving engineering problems. Reduction of the core allowed the addition of a sophomore cornerstone design course. This cornerstone course teaches students how to solve open-ended problems, bridging the gap between solution strategies that are effective for the science and mathematics courses, and those needed to solve open-ended engineering problems. The design fundamentals taught in the cornerstone course are applied in the core courses, such as heat transfer, thermodynamics, instrumentation, and machine design. The senior design experience comes primarily from a design elective and the capstone design course. This paper presents an overview of the curriculum revision process, and the changes which resulted from it. It also discusses the issues associated with infusing design projects into core courses which have traditionally focused on teaching engineering science fundamentals. Plans for the future evolution of the curriculum are also discussed
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