Dynamic interactions between hypersonic vehicle aerodynamics and propulsion system performance

Described here is the development of a flexible simulation model for scramjet hypersonic propulsion systems. The primary goal is determination of sensitivity of the thrust vector and other system parameters to angle of attack changes of the vehicle. Such information is crucial in design and analysis of control system performance for hypersonic vehicles. The code is also intended to be a key element in carrying out dynamic interaction studies involving the influence of vehicle vibrations on propulsion system/control system coupling and flight stability. Simple models are employed to represent the various processes comprising the propulsion system. A method of characteristics (MOC) approach is used to solve the forebody and external nozzle flow fields. This results in a very fast computational algorithm capable of carrying out the vast number of simulation computations needed in guidance, stability, and control studies. The three-dimensional fore- and aft body (nozzle) geometry is characterized by the centerline profiles as represented by a series of coordinate points and body cross-section curvature. The engine module geometry is represented by an adjustable vertical grid to accommodate variations of the field parameters throughout the inlet and combustor. The scramjet inlet is modeled as a two-dimensional supersonic flow containing adjustable sidewall wedges and multiple fuel injection struts. The inlet geometry including the sidewall wedge angles, the number of injection struts, their sweepback relative to the vehicle reference line, and strut cross-section are user selectable. Combustion is currently represented by a Rayleigh line calculation including corrections for variable gas properties; improved models are being developed for this important element of the propulsion flow field. The program generates (1) variation of thrust magnitude and direction with angle of attack, (2) pitching moment and line of action of the thrust vector, (3) pressure and temperature distributions throughout the system, and (4) performance parameters such as thrust coefficient, specific impulse, mass flow rates, and equivalence ratio. Preliminary results are in good agreement with available performance data for systems resembling the NASP vehicle configuration

Interview with Arnold Roach by Mike Hastings

Biographical NoteGeorge “Arnold” Roach was born in Rockland, Maine, on July 28th, 1929, to Nora Nelson Roach and Herbert Ezio Roach. He grew up in Houlton and summered in Rockland. His father, Herbert Roach, was a potato farmer, buyer, and machinery dealer. Arnold attended the University of Maine and in 1951 joined the National Guard. While farming potatoes in Aroostook County, he served on the National Potato Promotion Board as board president and acted as an adviser to Mitchell on Maine’s agricultural issues. He was a part of the Clinton-Gore transition team for the Department of Agriculture and worked for the Clinton administration for eight years. At the time of this interview, he was retired and living in southern Aroostook County. SummaryInterview includes discussion of: background in potato politics; working on the Clinton-Gore transition team; involvement with the Department of Agriculture; the National Guard Army Reserve program; Mitchell\u27s campaign for governor 1974; interactions with Mitchell, photographs; topics in potato politics; potato farming and the organic food movement; Mitchell\u27s potato advisors and involvement in the trade; Roach\u27s daughter Elizabeth\u27s position as the director of the U.S Senate Page Program; and general thoughts about Mitchell

BY NEED AND BY NAME: SCHOOL LEADERS FOSTERING ENVIRONMENTS FOR GRANDPARENTS RAISING GRANDCHILDREN

Children raised by their grandparents are a steadily growing demographic in schools throughout the United States. When parents are unable to care for their children, grandparents sometimes assume the role of primary caregiver. This is especially true when they are faced with the threat of placing their grandchildren in the foster care system. More often than not, these grandparents are not adequately prepared for the challenges of raising children who have lost their parent through death, drug abuse or incarceration and few resources exist to guide elementary school principals to engage this demographic. Regardless of the growing numbers of caregiving grandparents there exists a dearth of research and literature to guide school leaders in effectively engaging these grandparents in school involvement. The purpose of this study was to understand principals’ experiences with grandparents raising grandchildren (GRG), to discover grandparent’s experiences and perspectives on their own experiences in their grandchildren’s schools, and finally, construct theory on how elementary principals create and nurture positive and productive relationships with grandparents raising grandchildren. Analysis of date contributed to the development of propositions that reflect study findings. These propositions contributed to the development of a framework toward theory: Although principals were cognizant of the challenges GRG face, this knowledge did not influence their leadership. As a result, their leadership practices created school environments in which GRGs were effectively engaged in two-way communication but limited decision-making. Furthermore, the schools did not provide a bridge to resources to meet many of the challenges GRG and their families faced

Nano-scale superhydrophobicity: suppression of protein adsorption and promotion of flow-induced detachment

Wall adsorption is a common problem in microfluidic devices, particularly when proteins are used. Here we show how superhydrophobic surfaces can be used to reduce protein adsorption and to promote desorption. Hydrophobic surfaces, both smooth and having high surface roughness of varying length scales (to generate superhydrophobicity), were incubated in protein solution. The samples were then exposed to flow shear in a device designed to simulate a microfluidic environment. Results show that a similar amount of protein adsorbed onto smooth and nanometer-scale rough surfaces, although a greater amount was found to adsorb onto superhydrophobic surfaces with micrometer scale roughness. Exposure to flow shear removed a considerably larger proportion of adsorbed protein from the superhydrophobic surfaces than from the smooth ones, with almost all of the protein being removed from some nanoscale surfaces. This type of surface may therefore be useful in environments, such as microfluidics, where protein sticking is a problem and fluid flow is present. Possible mechanisms that explain the behaviour are discussed, including decreased contact between protein and surface and greater shear stress due to interfacial slip between the superhydrophobic surface and the liquid

Scanning Electron Microscopy of Early Atherosclerosis in Rabbits Using Aortic Casts

Our research involves measuring the size and location of atherosclerotic lesions on the intimal surface of arteries. To this end we have developed a new method in which scanning electron micrographs of vascular casts with impressions of these lesions on their surface are used. This method is compared with light microscopy and scanning electron microscopy of tissue with lesions. All three methods are found to detect lesions equally well. We also examine the cellular elements in the lesion to determine how the images are formed

Turbulent transport in tokamak plasmas with rotational shear

Nonlinear gyrokinetic simulations have been conducted to investigate turbulent transport in tokamak plasmas with rotational shear. At sufficiently large flow shears, linear instabilities are suppressed, but transiently growing modes drive subcritical turbulence whose amplitude increases with flow shear. This leads to a local minimum in the heat flux, indicating an optimal E x B shear value for plasma confinement. Local maxima in the momentum fluxes are also observed, allowing for the possibility of bifurcations in the E x B shear. The sensitive dependence of heat flux on temperature gradient is relaxed for large flow shear values, with the critical temperature gradient increasing at lower flow shear values. The turbulent Prandtl number is found to be largely independent of temperature and flow gradients, with a value close to unity.Comment: 4 pages, 5 figures, submitted to PR

Microstability analysis of pellet fuelled discharges in MAST

Reactor grade plasmas are likely to be fuelled by pellet injection. This technique transiently perturbs the profiles, driving the density profile hollow and flattening the edge temperature profile. After the pellet perturbation, the density and temperature profiles relax towards their quasi-steady-state shape. Microinstabilities influence plasma confinement and will play a role in determining the evolution of the profiles in pellet fuelled plasmas. In this paper we present the microstability analysis of pellet fuelled H-mode MAST plasmas. Taking advantage of the unique capabilities of the MAST Thomson scattering system and the possibility of synchronizing the eight lasers with the pellet injection, we were able to measure the evolution of the post-pellet electron density and temperature profiles with high temporal and spatial resolution. These profiles, together with ion temperature profiles measured using a charge exchange diagnostic, were used to produce equilibria suitable for microstability analysis of the equilibrium changes induced by pellet injection. This analysis, carried out using the local gyrokinetic code GS2, reveals that the microstability properties are extremely sensitive to the rapid and large transient excursions of the density and temperature profiles, which also change collisionality and beta e significantly in the region most strongly affected by the pellet ablation.Comment: 21 pages, 10 figures. This is an author-created, un-copyedited version of an article submitted for publication in Plasma Physics and Controlled Fusion. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from i