High efficiency of seaplanes

A table is presented which includes data for calculating the index of efficiency. The author uses this data to conclude that seaplanes cannot be considered inferior to terrestrial airplanes

Thermal Analysis and Modeling of Steady-State Rod Growth During Gas-Phase Solid Freeform Fabrication

An analysis ofthe steady-state growth ofrods during gas-phase solidfreeform fabrication is presented. It is demonstrated that heat transfer controls the evolution ofshape during laser-induced pyrolysis of slender 3-D structures. Insulating and conductive deposit materials were studied, using both simple analytic and numerical simulations to demonstrate how steady-state rod growth is achieved.Mechanical Engineerin

The effect of negative and positive contact on prejudice reduction in portuguese adolescents in the school context

Drawing from the contact hypothesis, the present research examines the effect of positive and negative contact on intergroup attitudes of white and black secondary school adolescents in Portugal (N = 85). Both majority and minority groups are examined in a longitudinal design. Cross-lagged regression analyses shows that the "from contact to less prejudice" path is confirmed only for majority group students, for whom positive contact was effective in intergroup bias reduction. Negative contact predicts negative intergroup attitudes for both groups, with a strongest effect for the minority group member. In comparison, emerged that for majority group students, positive contact is more influential on bias reduction. For minority group students, negative contact is more powerful in increasing negative intergroup attitudes more than the positive contact is to its reduction, and the opposite path was found too, as intergroup bias was a predictor of negative contact. These results underline the importance of analysing both positive and negative intergroup contact effects on ethnic prejudice, considering that the potential of negative contact in the increase of prejudice was largely neglected in the area of intergroup relations

Some Ideas on Racing Seaplanes

This report presents the author's designs and construction of various seaplanes to raced in the Schneider Cup. The results of tests are presented as well as discussions of various structures like floats and wings

Cost-performance analysis of silicon carbide fibers

Side-by-side studies of tensile strength and high-temperature exposures were conducted for High-Nicalon Type S, Sylramic, and Laser-Printed Silicon Carbide fibers. This battery of tests supports the well-known superior properties of CVD-derived Silicon Carbide, such as Specialty Materials’ SCS Ultra. SCS Ultra, however, is derived from CVD onto a continuous core filament substrate, hence it can only be produced in large diameter continuous filaments (90-140 µm). In contrast, laser-printing of SiC fibers relies on self-seeded Laser-Induced Chemical Vapor Deposition, which does away with the core filament substrate requirement, achieving much smaller diameters (adjustable between 14 and 50 µm) and growth rates, while replicating SCS Ultra’s superior properties. This paper also discusses economic projections for laser-printed SiC fiber production. Each laser beam produces one continuous filament. Lasers are currently at $100/beam with the cost expected to continue to fall to$50/beam in the next 5 years. Current fiber laser printers are at 384 beams per unit. This means 120 laser printers are needed per metric ton of 25 µm SiC fiber per year. This places capital equipment costs at a fraction of current polymer-derived SiC fibers production, with specific energetic requirements (kW-h/Ton) and raw material exploitation (kg out / kg in) improvements by one order of magnitude or greater. Long-term projections for mass-produced laser-printed fibers present a realistic pathway to $1000/lb CVD-quality SiC fibers