Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application. Phase 1 summary report: Shear web design development

An advanced composite shear web design concept was developed for the Space Shuttle orbiter main engine thrust beam structure. Various web concepts were synthesized by a computer-aided adaptive random search procedure. A practical concept is identified having a titanium-clad + or - 45 deg boron/epoxy web plate with vertical boron/epoxy reinforced aluminum stiffeners. The boron-epoxy laminate contributes to the strength and stiffness efficiency of the basic web section. The titanium-cladding functions to protect the polymeric laminate parts from damaging environments and is chem-milled to provide reinforcement in selected areas. Detailed design drawings are presented for both boron/epoxy reinforced and all-metal shear webs. The weight saving offered is 24% relative to all-metal construction at an attractive cost per pound of weight saved, based on the detailed designs. Small scale element tests substantiate the boron/epoxy reinforced design details in critical areas. The results show that the titanium-cladding reliably reinforces the web laminate in critical edge load transfer and stiffener fastener hole areas

Physics of Proximity Josephson Sensor

We study the proximity Josephson sensor (PJS) in both bolometric and calorimetric operation and optimize it for different temperature ranges between 25 mK and a few Kelvin. We investigate how the radiation power is absorbed in the sensor and find that the irradiated sensor is typically in a weak nonequilibrium state. We show in detail how the proximity of the superconductors affects the device response: for example via changes in electron-phonon coupling and out-of-equilibrium noise. In addition, we estimate the applicability of graphene as the absorber material.Comment: 13 pages, 11 figures, submitted to Journal of Applied Physics, v2: Addition of a new section discussing the radiation coupling to the device, several minor change

Theory of temperature fluctuation statistics in superconductor-normal metal tunnel structures

We describe the statistics of temperature fluctuations in a SINIS structure, where a normal metal island (N) is coupled by tunnel junctions (I) to two superconducting leads (S). We specify conditions under which this structure exhibits manifestly non-Gaussian fluctuations of temperature. We consider both the Gaussian and non-Gaussian regimes of these fluctuations, and the current fluctuations that are caused by the fluctuating temperature. We also describe a measurement setup that could be used to observe the temperature fluctuations.Comment: 10 pages, 9 figures, final versio

Evaluation of a metal shear web selectively reinforced with filamentary composites for space shuttle application

A final program summary is reported for test and evaluation activities that were conducted for space shuttle web selection. Large scale advanced composite shear web components were tested and analyzed to evaluate application of advanced composite shear web construction to a space shuttle orbiter thrust structure. The shear web design concept consisted of a titanium-clad + or - 45 deg boron/epoxy web laminate stiffened with vertical boron-epoxy reinforced aluminum stiffeners and logitudinal aluminum stiffening. The design concept was evaluated to be efficient and practical for the application that was studied. Because of the effects of buckling deflections, a requirement is identified for shear buckling resistant design to maximize the efficiency of highly-loaded advanced composite shear webs

Field location and player roles as constraints on emergent 1-vs-1 interpersonal patterns of play in football

This study examined effects of player roles on interpersonal patterns of coordination that sustain decision-making in 1-vs-1 sub-phases of football in different field locations near the goal (left-, middle- and right zone). Participants were fifteen U-16 yrs players from a local competitive amateur team. To measure interpersonal patterns of coordination in the 1-vs-1 dyads we recorded: (i) the relative distance value between each attacker and defender to the centre of the goal, and (ii), the relative angle between the centre of the goal, each defender and attacker. Results revealed how variations in field locations near the goal (left-, middle- and right-zones) constrained the relative distance and relative angle values that emerged between them and the goal. It reveals that relative position of the goal is a key informational variable that sustained participants’ behaviours for dribbling and shooting. Higher values of relative distance and angle were observed in the middle zone, compared to other zones. Players’ roles also constitute a constraint on the interpersonal coordination for dribbling and shooting. Additionally, it seems that players’ foot preference constrains the dynamics of interpersonal patterns of coordination between participants, especially in left and right zones. The findings suggest that to increase participants’ opportunities for action, coaches should account with field positions, players’ roles and preference foot

On the optimality of gluing over scales

We show that for every $\alpha > 0$, there exist $n$-point metric spaces (X,d) where every "scale" admits a Euclidean embedding with distortion at most $\alpha$, but the whole space requires distortion at least $\Omega(\sqrt{\alpha \log n})$. This shows that the scale-gluing lemma [Lee, SODA 2005] is tight, and disproves a conjecture stated there. This matching upper bound was known to be tight at both endpoints, i.e. when $\alpha = \Theta(1)$ and $\alpha = \Theta(\log n)$, but nowhere in between. More specifically, we exhibit $n$-point spaces with doubling constant $\lambda$ requiring Euclidean distortion $\Omega(\sqrt{\log \lambda \log n})$, which also shows that the technique of "measured descent" [Krauthgamer, et. al., Geometric and Functional Analysis] is optimal. We extend this to obtain a similar tight result for $L_p$ spaces with $p > 1$.Comment: minor revision

The use of laptop computers in programming lectures

This research explores the effect of the use of laptop computers on students&rsquo; learning experiences during lectures. Our methodology involves embedding laptops with visualization software as a learning aid during lectures. We then employ a framework of seven principles of good practice in higher education to evaluate the impact of the use of laptop computers on the learning experience of computer programming students. Overall, we found that students were highly motivated and supportive of this innovative use of laptop computers with lectures.<br /

Electrons and holes in Si quantum well: a room-temperature transport and drag resistance study

We investigate carrier transport in a single 22 nm-thick double-gated Si quantum well device, which has independent contacts to electrons and holes. Conductance, Hall density and Hall mobility are mapped in a broad double-gate voltage window. When the gate voltage asymmetry is not too large only either electrons or holes occupy the Si well and the Hall mobility shows the fingerprints of volume inversion/accumulation. At strongly asymmetric double-gate voltage an electric field induced electron-hole (EH) bi-layer is formed inside the well. The EH drag resistance R_{he} is explored at balanced carrier densities: R_{he} decreases monotonically from 860 to 37 Ohms when the electron and hole density is varied between ~0.4-1.7x10^{16} m^{-2}