Characteristics of wake vortex generated by a Boeing 727 jet transport during two-segment and normal ILS approach flight paths

A series of flight tests was conducted to evaluate the vortex wake characteristics of a Boeing 727 (B727-200) aircraft during conventional and two-segment ILS approaches. Twelve flights of the B727, which was equipped with smoke generators for vortex marking, were flown and its vortex wake was intentionally encountered by a Lear Jet model 23 (LR-23) and a Piper Twin Comanche (PA-30). Location of the B727 vortex during landing approach was measured using a system of photo-theodolites. The tests showed that at a given separation distance there were no readily apparent differences in the upsets resulting from deliberate vortex encounters during the two types of approaches. Timed mappings of the position of the landing configuration vortices showed that they tended to descend approximately 91 m(300 ft) below the flight path of the B727. The flaps of the B727 have a dominant effect on the character of the trailed wake vortex. The clean wing produces a strong, concentrated vortex but as the flaps are lowered, the vortex system becomes more diffuse. Pilot opinion and roll acceleration data indicate that 4.5 n.mi. would be a minimum separation distance at which roll control of light aircraft (less than 5,670 kg (12,500 lb) could be maintained during parallel encounters of the B727's landing configuration wake. This minimum separation distance is generally in scale with results determined from previous tests of other aircraft using the small roll control criteria

Design, fabrication, and structural testing of a lightweight shadow shield for deep-space application

Two full-scale, lightweight, double-sheeted shadow shields were developed as the primary element of a deep-space thermal protection system for liquid-hydrogen propellant tankage. The thermal and mechanical considerations used in s, the method of fabrication, and the environmental testing results on a prototype shield are discussed. Testing consisted of a transient cooldown period, a prolonged cold soak, and a transient warmup. The mechanical and thermal analyses used in the shield design are sufficient to produce a lightweight rugged shadow shield assembly that is structurally adequate for its intended application

Mechanisms for Stable Sonoluminescence

A gas bubble trapped in water by an oscillating acoustic field is expected to either shrink or grow on a diffusive timescale, depending on the forcing strength and the bubble size. At high ambient gas concentration this has long been observed in experiments. However, recent sonoluminescence experiments show that in certain circumstances when the ambient gas concentration is low the bubble can be stable for days. This paper presents mechanisms leading to stability which predict parameter dependences in agreement with the sonoluminescence experiments.Comment: 4 pages, 3 figures on request (2 as .ps files

Bubble Shape Oscillations and the Onset of Sonoluminescence

An air bubble trapped in water by an oscillating acoustic field undergoes either radial or nonspherical pulsations depending on the strength of the forcing pressure. Two different instability mechanisms (the Rayleigh--Taylor instability and parametric instability) cause deviations from sphericity. Distinguishing these mechanisms allows explanation of many features of recent experiments on sonoluminescence, and suggests methods for finding sonoluminescence in different parameter regimes.Comment: Phys. Rev. Lett., in pres

University student perceptions of the current and future role of non-carbon emitting energy sources in the world

This article documents university student perceptions of the role and viability of non-carbon emitting energy sources in the short term (1 to 3 years) and medium term (10 to 30 years) for Earth. Consequently, the perceptions of 7,980 students at the University of Idaho (Moscow, ID, USA) about the future of geothermal energy (G), hydropower energy (H), nuclear power (NP), ocean thermal energy conversion (OTEC), solar energy (S) and wind energy (W) were measured between 1993 and 2016. All students were enrolled in the introductory environmental science class. Two survey instruments were used to gather this data. The first survey instrument evaluated six energy sources in 1994, 1998, 2002, 2006, 2010 and 2014. The second instrument focused on questions about nuclear energy. In the first survey a significant portion of the students considered solar, wind and nuclear power to be viable nonemitting carbon energy sources in the medium-term (10 to 30 years) future. Also, students taking the survey in later years (2006, 2010, 2014) were much more likely to consider non-carbon energy sources viable in the near and mid-term than students taking the survey in 1994, 1998 and 2002. In general, 46.7% of students considered nuclear power a serious problem at the beginning of the course; however, at the end of the term less than 36% of students still held their initial negative opinion. In addition, a significant majority of the students changed from indicating that fossil fuels were preferable to nuclear energy, an opinion they held at the beginning of the course, to favoring or at least saying that nuclear power was no worse than fossil fuels at the conclusion of the term. The significant findings of this study were: (1) students considered both solar and wind energy viable alternatives that have the potential to be significant on a world-wide basis within 30 years; (2) students saw only a limited expansion of hydropower and geothermal energy in the next 30 years; and (3) once students were educated in an unbiased way – including both the pros and cons of using nuclear energy – they were more receptive to view the nuclear power option favorably

Universal transport in 2D granular superconductors

The transport properties of quench condensed granular superconductors are presented and analyzed. These systems exhibit transitions from insulating to superconducting behavior as a function of inter-grain spacing. Superconductivity is characterized by broad transitions in which the resistance drops exponentially with reducing temperature. The slope of the log R versus T curves turns out to be universaly dependent on the normal state film resistance for all measured granular systems. It does not depend on the material, critical temperature, geometry, or experimental set-up. We discuss possible physical scenarios to explain these findings.Comment: 4 pages, 3 figure

The challenge of the chiral Potts model

The chiral Potts model continues to pose particular challenges in statistical mechanics: it is ``exactly solvable'' in the sense that it satisfies the Yang-Baxter relation, but actually obtaining the solution is not easy. Its free energy was calculated in 1988 and the order parameter was conjectured in full generality a year later. However, a derivation of that conjecture had to wait until 2005. Here we discuss that derivation.Comment: 22 pages, 3 figures, 29 reference

An Independent and External Validation of the ACC NCDR Bleeding Risk Score among a National Multi-Site Community Hospital Registry of Cardiac Interventions

Background: An accurate tool with good discrimination for bleeding would be useful to clinicians for improved management of all their patients. Bleeding risk models have been published but not externally validated in independent clinical dataset. We chose the NCDR PCI score to validate within a large, multi-site community datasets. The aim of the study was to determine the diagnostic utility of this bleeding risk score tool. Methods: This is a large-scale retrospective analysis utilizing American College of Cardiology data from a 37-hospital health system. The central repository of PCI procedures between 6-1-2009 and 6-30-2012 was utilized to validate the NCDR PCI bleeding risk score (BRS) among 4693 patients. The primary endpoint was major bleeding. Discriminant analysis calculating the receiver operating characteristic curve was performed. Results: There were 143 (3.0%) major bleeds. Mean bleeding risk score was 14.7 (range 3 - 42). Incidence of bleeding by risk category: low (0.5%), intermediate (1.7%), and high risk (7.6%). Patients given heparin had 113 (3.7%) major bleeds and those given bivalirudin had 30 (2.1%) major bleeds. Tool accuracy was poor to fair (AUC 0.78 heparin, 0.65 bivalirudin). Overall accuracy was 0.71 (CI: 0.66-0.76). Accuracy did not improve when confined to just the intermediate risk group (AUC 0.58; CI: 0.55-0.67). Conclusion: Bleeding risk tools have low predictive value. Adjustment for anticoagulation use resulted in poor discrimination because bivalirudin differentially biases outcomes toward no bleeding. The current state of bleeding risk tools provides little support for diagnostic utility in regards to major bleeding and therefore have limited clinical applicability

Social interaction contexts bias the perceived expressions of interactants

The present study sought to determine whether contextual information available when viewing social interactions from third-person perspectives, may influence observers’ perception of the interactants’ facial emotion. Observers judged whether the expression of a target face was happy or fearful, in the presence of a happy, aggressive or neutral interactant. In two experiments, the same target expressions were judged to be happier when presented in the context of a happy interactant, than when interacting with a neutral or aggressive partner. We failed to show that the target expression was judged as more fearful when interacting with an aggressive partner. Importantly, observers’ perception of the target expression was not modulated by the emotion of the context interactant when the interactants were presented back-to-back, suggesting that the bias depends on the presence of an intact interaction arrangement. These results provide valuable insight into how social contextual effects shape our perception of facial emotion