Preliminary study of a wing-tip vortex using laser velocimetry

Measurements have been made in the wake of a semi-span NACA 0015 airfoil with emphasis on the region of the wing tip vortex. The spanwise and streamwise velocity components were measured using a two-component laser Doppler velocimeter. The purpose of the study was to initiate the operation of a laser velocimeter system and to perform preliminary wake measurements in preparation for a more extensive study of the structure and near field development of a tip vortex

NACA 0015 wing pressure and trailing vortex measurements

A NACA 0015 semispan wing was placed in a low-speed wind tunnel, and measurements were made of the pressure on the upper and lower surface of the wing and of velocity across the vortex trailing downstream from the tip of the wing. Pressure data were obtained for both 2-D and 3-D configurations. These data feature a detailed comparison between wing tips with square and round lateral edges. A two-component laser velocimeter was used to measure velocity profiles across the vortex at numerous stations behind the wing and for various combinations of conditions. These conditions include three aspect ratios, three chord lengths, a square- and a round lateral-tip, presence or absence of a boundary-layer trip, and three image plane positions located opposite the wing tip. Both pressure and velocity measurements were made for the angles of attack 4 deg less than or equal to alpha less than or equal to 12 deg and for Reynolds numbers 1 x 10(exp 6) less than or equal to Re less than or equal to 3 x 10(exp 6)

Fluorine gas as a cleaning agent for Apollo bulk-sample containers

A technique has been developed for cleaning Apollo bulk sample containers using fluorine gas as the cleaning agent

The free inverse semigroup on two commuting generators

AbstractIn this paper we utilize the zig-zag representations to characterize the free inverse semigroup on two commuting generators

Ordered groupoids and the holomorph of an inverse semigroup

We present a construction for the holomorph of an inverse semigroup, derived from the cartesian closed structure of the category of ordered groupoids. We compare the holomorph with the monoid of mappings that preserve the ternary heap operation on an inverse semigroup: for groups these two constructions coincide. We present detailed calculations for semilattices of groups and for the polycyclic monoids.Comment: 16 page

Dietary calcium intake does not meet the nutritional requirements of children with chronic kidney disease and on dialysis

Background: Adequate calcium (Ca) intake is required for bone mineralization in children. We assessed Ca intake from diet and medications in children with CKD stages 4–5 and on dialysis (CKD4–5D) and age-matched controls, comparing with the UK Reference Nutrient Intake (RNI) and international recommendations. Methods: Three-day prospective diet diaries were recorded in 23 children with CKD4–5, 23 with CKD5D, and 27 controls. Doses of phosphate (P) binders and Ca supplements were recorded. Results: Median dietary Ca intake in CKD4–5D was 480 (interquartile range (IQR) 300–621) vs 724 (IQR 575–852) mg/day in controls (p = 0.00002), providing 81% vs 108% RNI (p = 0.002). Seventy-six percent of patients received  200% RNI. Three children (6%) exceeded the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) upper limit of 2500 mg/day. None with a total Ca intake  2 × RNI was hypercalcemic. Conclusions: Seventy-six percent of children with CKD4–5D had a dietary Ca intake < 100% RNI. Restriction of dairy foods as part of a P-controlled diet limits Ca intake. Additional Ca from medications is required to meet the KDOQI guideline of 100–200% normal recommended Ca intake

Radial Structure in the TW Hya Circumstellar Disk

We present new near-infrared interferometric data from the CHARA array and the Keck Interferometer on the circumstellar disk of the young star, TW Hya, a proposed "transition disk." We use these data, as well as previously published, spatially resolved data at 10 μm and 7 mm, to constrain disk models based on a standard flared disk structure. We find that we can match the interferometry data sets and the overall spectral energy distribution with a three-component model, which combines elements at spatial scales proposed by previous studies: optically thin, emission nearest the star, an inner optically thick ring of emission at roughly 0.5 AU followed by an opacity gap and, finally, an outer optically thick disk starting at ~4 AU. The model demonstrates that the constraints imposed by the spatially resolved data can be met with a physically plausible disk but this requires a disk containing not only an inner gap in the optically thick disk as previously suggested, but also a gap between the inner and outer optically thick disks. Our model is consistent with the suggestion by Calvet et al. of a planet with an orbital radius of a few AU. We discuss the implications of an opacity gap within the optically thick disk

PHASES Differential Astrometry and the Mutual Inclination of the V819 Herculis Triple Star System

V819 Herculis is a well-studied triple star system consisting of a ``wide'' pair with 5.5 year period, one component of which is a 2.2-day period eclipsing single-line spectroscopic binary. Differential astrometry measurements from the Palomar High-precision Astrometric Search for Exoplanet Systems (PHASES) are presented and used to determine a relative inclination between the short- and long-period orbits of 23.6 +- 4.9 degrees. This represents only the sixth unambiguous determination of the mutual inclination of orbits in a hierarchical triple system. This result is combined with those for the other five systems for analysis of the observed distribution of mutual inclinations in nearby triple systems. It is found that this distribution is different than that which one would expect from random orientations with statistical significance at the 94% level; implications for studying the spatial distribution of angular momentum in star forming regions is discussed.Comment: Accepted for publication in Astronomy and Astrophysics; changed direction of axis for figure 2

Evaluation of the ET2000 Guardrail End Treatment

The objectives of this study were to monitor and report the performance of the ET2000 guardrail end treatment design in traffic accidents. Data for a total of 34 collisions involving the ET2000 were identified. In most cases, an accident report was obtained and the damaged guardrail was inspected. The involved vehicle was inspected when available. Proper or improper performance of end treatments in the collisions were judged based on whether it performed as designed. Field performance of the ET2000, as documented in traffic accidents, shows that, considering all the impacts, this end treatment has performed properly. In several instances the end treatment bent, rather than being pushed straight back, during the collision. This could typically be related to the angle at which impact occurred. Results warrant continued use of this end treatment. However, its cost would not justify a widespread use on all types of highways