7,256 research outputs found
Chemical synthesis of monomeric self-sealant type esters Status report
Synthesis of alkyl esters of alpha-cyanosorbic acid for self-sealing polymerizatio
Hospital Quality Oversight by the Joint Commission on the Accreditation of Healthcare Organizations
Measurement of vortex velocities over a wide range of vortex age, downstream distance and free stream velocity
A wind tunnel test was conducted to obtain vortex velocity signatures over a wide parameter range encompassing the data conditions of several previous researchers while maintaining a common instrumentation and test facility. The generating wing panel was configured with both a revolved airfoil tip shape and a square tip shape and had a semispan aspect of 4.05/1.0 with a 121.9 cm span. Free stream velocity was varied from 6.1 m/sec to 76.2 m/sec and the vortex core velocities were measured at locations 3, 6, 12, 24 and 48 chordlengths downstream of the wing trailing edge, yielding vortex ages up to 2.0 seconds. Wing pitch angles of 6, 8, 9 and 12 deg were investigated. Detailed surface pressure distributions and wing force measurements were obtained for each wing tip configuration. Correlation with vortex velocity data taken in previous experiments is good. During the rollup process, vortex core parameters appear to be dependent primarily on vortex age. Trending in the plateau and decay regions is more complex and the machanisms appear to be more unstable
Recommended from our members
Nonperiodic Optical Flickering In Hz Herculis
NASA NGR 44-012-209NSF GP-25901, GP-41796Astronom
Governance and Performance: Theory-Based Evidence from US Coast Guard Inspections
Given three stylized facts about the US Coast Guard (USCG), namely, soft penalties for safety violations, low incidence of penalties relative to the number of violations, and substantial resources devoted to inspections of vessels, this paper seeks (i) a theoretical lens to view USCG activities and (ii) an empirical assessment of whether those activities improve performance. Harrington’s (1988) model is motivated by these stylized facts about US regulation in general, and provides a solution via targeting of good and poor performers. The model generates hypotheses about optimal regulation in the context of pollution prevention activities of the USCG. An organization-level panel data set consisting of thousands of US flag tank barges is constructed to test those hypotheses. A count model that controls for vessel heterogeneity yields mixed evidence. If USCG inspections are considered exogenous variables (as the theory presumes), they appear to prevent pollution spills. But if inspections are endogenous and respond to previous spills then correcting for endogeneity reverses the earlier result. In addition, violations are found to be good predictors of pollution occurrences, suggesting that inspections are not as effective as they could be. Targeting as in Harrington’s model therefore appears to be incomplete, and the findings suggest that more complete targeting could increase performance. An interesting finding is that stronger penalties could increase performance.Harrington model; Inspections; Penalties; Oil Spills; USCG;
Phase Lags in the Optical-Infrared Light Curves of AGB Stars
To search for phase lags in the optical-infrared light curves of asymptotic
giant branch stars, we have compared infrared data from the COBE DIRBE
satellite with optical light curves from the AAVSO and other sources. We found
17 examples of phase lags in the time of maximum in the infrared vs. that in
the optical, and 4 stars with no observed lags. There is a clear difference
between the Mira variables and the semi-regulars in the sample, with the
maximum in the optical preceding that in the near-infrared in the Miras, while
in most of the semi-regulars no lags are observed. Comparison to published
theoretical models indicates that the phase lags in the Miras are due to strong
titanium oxide absorption in the visual at stellar maximum, and suggests that
Miras pulsate in the fundamental mode, while at least some semi-regulars are
first overtone pulsators. There is a clear optical-near-infrared phase lag in
the carbon-rich Mira V CrB; this is likely due to C2 and CN absorption
variations in the optical.Comment: AJ, in pres
- …