Propellers of Minimum Induced Loss, and Water Tunnel Tests of Such a Propeller

The fundamental vortex theory for a single rotation propeller with a finite number of blades is reviewed. The theory leads to the specification of a radial distribution of bound circulation on each blade for minimum induced loss, analogous to the elliptic spanwise distribution of bound circulation on a wing for minimum induced drag. A propeller designed in accord with this theory has been tested in a water tunnel where it exhibited high efficiency in spite of localized cavitating flow. A knowledge of the flow field for an optimum propeller is of value to the airframe designer seeking to maximize the performance of the airplane-propeller combination

Preservation of wing leading edge suction at the plane of symmetry as a factor in wing-fuselage design

Most fuselage geometries cover a portion of the wing leading edge near the plane of symmetry, and it seems reasonable to expect that a large fraction of the leading edge suction which would be developed by the covered wing at high angles of attack is not developed on the fuselage. This is one of the reasons that the Oswald span efficiency factor for the wing body combination fails to approach the value predicted by lifting line theory for the isolated wing. Some traditional and recent literature on wing-body interference is discussed and high Reynolds number data on wing-body-nacelle drag are reviewed. An exposed central leading edge geometry has been developed for a sailplane configuration. Low Reynolds number tests have not validated the design concept

Design of Propellers for Motorsoarers

A method was developed for the design of propellers of minimum induced loss matched to an arbitrary operating point characterized by disc loading (thrust or power), air density, shaft speed, flight speed, and number of blades. A consistent procedure is outlined to predict the performance of these propellers under off design conditions, or to predict the performance of propellers of general geometry. The examples discussed include a man powered airplane, a hang glider with a 7.5 kW (10 hp) 8,000 rpm engine, and an airplane-like motorsoarer

Minimum Vertical Tail Drag

Tail size requirement calculations are presented for a vertical tail performing a coordinated turn reversal at corresponding load requirements with minimum tail drag

Role of Reconnection in AGN Jets

We discuss the possible role of reconnection in electro-magnetically dominated cores of relativistic AGN jets. We suggest that reconnection may proceed in a two-fold fashion: initial explosive collapse on the Alfven time-scale of a current-carrying jet (which is of the order of the light crossing time) and subsequent slow quasi-steady reconnection. Sites of explosive collapse are associated with bright knots, while steady-state reconnection re-energizes particles in the ``bridges'' between the knots. Ohmic dissipation in reconnection layers leads to particle acceleration either by inductive electric fields or by stochastic particle acceleration in the ensuing electro-magnetic turbulence.Comment: 4 pages, Proceedings of the conference "The Physics of Relativistic Jets in the CHANDRA and XMM Era", 23-27 September 2002, Bologn

Student Usage and Perceptions of Digital Devices in the Classroom and While Driving

The purpose of this study is to examine Central Washington University students’ use of electronic devices for non-class related purposes and while driving. For the purposes of the study, electronic devices are defined as cellphones, tablets, laptops, and any other devices that are non-essential to the classroom environment, and non-classroom purposes are defined as any non-course specific activities performed on an electronic device during lecture. The survey has two parts, the first focusing on electronic device usage in the classroom, and the second focusing on electronic device usage while operating a vehicle. The survey is administered online, and focuses on students over the age of eighteen. Psychology students represent the largest demographic, but the survey also draws from numerous other departments. Preliminary results are similar to those of studies regarding electronic device usage conducted at other universities, and indicate that the use of electronic devices is prominent in Central Washington University classrooms. These findings highlight how important it is for professors to understand students’ perceptions toward the use of electronic devices in the classroom for non-class related purposes

Regional agriculture surveys using ERTS-1 data

The Center for Remote Sensing Research has conducted studies designed to evaluate the potential application of ERTS data in performing agricultural inventories, and to develop efficient methods of data handling and analysis useful in the operational context for performing large area surveys. This work has resulted in the development of an integrated system utilizing both human and computer analysis of ground, aerial, and space imagery, which has been shown to be very efficient for regional crop acreage inventories. The technique involves: (1) the delineation of ERTS images into relatively homogeneous strata by human interpreters, (2) the point-by-point classification of the area within each strata on the basis of crop type using a human/machine interactive digital image processing system; and (3) a multistage sampling procedure for the collection of supporting aerial and ground data used in the adjustment and verification of the classification results

Electron heating and acceleration by magnetic reconnection in hot accretion flows

Both analytical and numerical works show that magnetic reconnection must occur in hot accretion flows. This process will effectively heat and accelerate electrons. In this paper we use the numerical hybrid simulation of magnetic reconnection plus test-electron method to investigate the electron acceleration and heating due to magnetic reconnection in hot accretion flows. We consider fiducial values of density, temperature, and magnetic parameter $\beta_e$ (defined as the ratio of the electron pressure to the magnetic pressure) of the accretion flow as $n_{0} \sim 10^{6} {\rm cm^{-3}}$, $T_{e}^0\sim 2\times 10^9 {\rm K}$, and $\beta_e=1$. We find that electrons are heated to a higher temperature $T_{e}=5\times 10^9$K, and a fraction $\eta\sim 8$ of electrons are accelerated into a broken power-law distribution, $dN(\gamma)\propto \gamma^{-p}$, with $p\approx 1.5$ and 4 below and above $\sim 1$ MeV, respectively. We also investigate the effect of varying $\beta$ and $n_0$. We find that when $\beta_e$ is smaller or $n_0$ is larger, i.e, the magnetic field is stronger, $T_e$, $\eta$, and $p$ all become larger.Comment: 6 pages, 6 figure; accepted by Ap

Barriers Encountered by Syringe Exchange Clients in Vermont

Introduction and Aims. Vermont CARES is a nonprofit HIV prevention and advocacy organization which provides a needle exchange program for intravenous drug users. Services are focused on education, prevention, testing, and harm reduction. The Syringe Support Program (SSP) offers clients clean syringes to reduce intravenous transmission of disease. Although SSP are proven avenues for harm reduction, barriers prevent users from utilizing services. Clients are limited by social, economic, and personal obstacles de- scribed in similar populations across the country. This project seeks to identify the barriers Vermont CARES clients face in accessing the SSP, determine needs, and evaluate interest in additional services. Methods. Our team and Vermont CARES staff held a focus group with St. Johnsbury clients to discuss services and barriers. A 39 question paper survey was distributed to three Vermont CARES sites during October, 2017 by Vermont CARES. Participation was voluntary and uncompensated. Sixty-three clients completed the survey. Results and Discussion. Of the 63 respondents, 61.9% stated that lack of ade- quate income contributed most to their inability to meet basic needs. These same clients faced the most barriers to access with economic hardship precipitated by sub- stance abuse, disability, and family commitments. In assessing additional services, clients sought food pantries, hygiene kits, and dental clinics. 56.4% of respondents would use safe injection facilities if provided. Those without income to meet basic needs expressed most interest in safe injection facilities (p=0.022). With barriers recognized, our future aim is to track efficacy of new services in impacting care and quality of life.https://scholarworks.uvm.edu/comphp_gallery/1268/thumbnail.jp