Effects of planform geometry on hover performance of a 2-meter-diameter model of a four-bladed rotor

Hover tests were conducted on three small scale rotors to evaluate the effects of blade planform taper on rotor hover performance. Tests were conducted on a rectangular swept-tip configuration, on a configuration with a 3 to 1 taper over the outboard 20 percent of the span, and on a configuration with a 5 to 1 taper over the outboard 20 percent of the blade span. The investigation covered a range of thrust coefficients from 0 to 0.0075 and a range of tip speeds from 300 to 600 ft/sec. The tests showed that both tapered configurations had better hover performance than the swept-tip rectangular configuration and that the 3 to 1 taper configuration was better than the 5 to 1 taper configuration. The test results were compared with predictions made with a prescribed wake analysis, a momentum analysis, and a simplified free wake analysis

Gyrotron experiments employing a field emission array cathode

The design and operation of a field emission array (FEA) cathode and the subsequent demonstration of the first FEA gyrotron are presented. Up to 10 mA from 30 000 tips was achieved reproducibly from each of ten chips in a gyrotron environment, namely, a vacuum 1 x 10(-8) mbar, -50 kV potential with multiple chip operation, The design parameters of the FEA gun were similar to those of a magnetron injection gun with an achievable electron beam current of 50-100 mA and measured power 720 W cw. Coherent microwave radiation was detected in both TE(02) at 30.1 GHz and TE(03) at 43.6 GHz, with a starting current of 1 mA

Free-flight investigation of the stability and control characteristics of a STOL model with an externally blown jet flap

The stability and control characteristics of a four-engine turbofan STOL transport model having an externally blown jet flap have been investigated by means of the flying-model technique in the Langley full-scale tunnel. The flight characteristics of the model were investigated under conditions of symmetric and asymmetric (one engine inoperative) thrust at lift coefficients up to 9.5 and 5.5, respectively. Static characteristics were studied by conventional power-on force tests over the flight-test angle-of-attack range including the stall. In addition to these tests, dynamic longitudinal and lateral stability calculations were performed for comparison with the flight-test results and for use in correlating the model results with STOL handling-qualities criteria

On the structure of non-full-rank perfect codes

The Krotov combining construction of perfect 1-error-correcting binary codes from 2000 and a theorem of Heden saying that every non-full-rank perfect 1-error-correcting binary code can be constructed by this combining construction is generalized to the $q$-ary case. Simply, every non-full-rank perfect code $C$ is the union of a well-defined family of $\mu$-components $K_\mu$, where $\mu$ belongs to an "outer" perfect code $C^*$, and these components are at distance three from each other. Components from distinct codes can thus freely be combined to obtain new perfect codes. The Phelps general product construction of perfect binary code from 1984 is generalized to obtain $\mu$-components, and new lower bounds on the number of perfect 1-error-correcting $q$-ary codes are presented.Comment: 8 page

Numerical simulation of unconstrained cyclotron resonant maser emission

When a mainly rectilinear electron beam is subject to significant magnetic compression, conservation of magnetic moment results in the formation of a horseshoe shaped velocity distribution. It has been shown that such a distribution is unstable to cyclotron emission and may be responsible for the generation of Auroral Kilometric Radiation (AKR) an intense rf emission sourced at high altitudes in the terrestrial auroral magnetosphere. PiC code simulations have been undertaken to investigate the dynamics of the cyclotron emission process in the absence of cavity boundaries with particular consideration of the spatial growth rate, spectral output and rf conversion efficiency. Computations reveal that a well-defined cyclotron emission process occurs albeit with a low spatial growth rate compared to waveguide bounded simulations. The rf output is near perpendicular to the electron beam with a slight backward-wave character reflected in the spectral output with a well defined peak at 2.68GHz, just below the relativistic electron cyclotron frequency. The corresponding rf conversion efficiency of 1.1% is comparable to waveguide bounded simulations and consistent with the predictions of kinetic theory that suggest efficient, spectrally well defined radiation emission can be obtained from an electron horseshoe distribution in the absence of radiation boundaries.Publisher PD

Some Student Perceptions of Grades Received on Speeches

Frequent evaluation of student work is standard practice in basic courses. Frequent evaluation assumes a relationship between the evaluation and improved performance. In higher education, evaluations are often expressed as grades. This study examines the relationship between twelve grades students receive on their speeches, and the affective and motivational effects those grades might have. Generally, the study found that students prefer higher grades but are motivated by lower grades. Specifically, the study indicates disparity between instructor intention in using pluses and minuses with grades and student reaction to the pluses and minuses

Seeding rates for precision seeded canola

Non-Peer Reviewe

Growth-Quality Evaluation of Black Walnut Wood. Part II-Color Analyses of Veneer Produced on Different Sites

Heartwood color is an important wood quality parameter in the grading of black walnut veneer. One of the primary factors that causes a reduction in veneer grade is variability in heartwood color. This variability may be in the form of streaked heartwood or in coloration not of a uniform light chocolate brown nature. Black walnut trees from four distinctly different sites were selected to describe wood color of commercially prepared veneer sheets, using standard color measurement techniques, so that within-tree, between-tree, and between-site variations could be determined. Selected logs were sliced into veneer by a commercial process and the veneer was graded according to industrial standards. Reflectance data were obtained from selected veneer samples and these data were transformed into standard color parameters. Wide ranges in luminance and purity parameters were obtained. However, only the differences in luminance were detectable upon visual examination. This suggests that variability in luminance (i.e., darkness or lightness) is the primary cause of heartwood color variability. These analyses revealed statistically significant within-site differences in heartwood luminance, but within-tree differences were also observed. Between-site differences were considered less important than within-site differences

Web-based Media Literacy to Prevent Tobacco Use among High School Students

Facilitator-led smoking media literacy (SML) programs have improved media literacy and reduced intention to smoke. However, these programs face limitations including high costs and barriers to standardization. We examined the efficacy of a Web-based media literacy program in improving smoking media literacy skills among adolescents. Sixty-six 9th grade students participated in a Web-based SML tobacco education program based on health behavior theory. Pre- and post-test assessments demonstrated statistically significant changes in the primary outcome of total SML as well as each of the individual SML items. However, there were inconsistent changes in other theory-based outcomes including attitudes and normative beliefs