7,498 research outputs found
Computer program to assess impact of fatigue and fracture criteria on weight and cost of transport aircraft
A preliminary design analysis tool for rapidly performing trade-off studies involving fatigue, fracture, static strength, weight, and cost is presented. Analysis subprograms were developed for fatigue life, crack growth life, and residual strength; and linked to a structural synthesis module which in turn was integrated into a computer program. The part definition module of a cost and weight analysis program was expanded to be compatible with the upgraded structural synthesis capability. The resultant vehicle design and evaluation program is named VDEP-2. It is an accurate and useful tool for estimating purposes at the preliminary design stage of airframe development. A sample case along with an explanation of program applications and input preparation is presented
The 1960s and their Aftermath: From Peaceful Protest to Guerilla Warfare
In many esential respects the 1960s differed markedly from previous ages of social protest and agitation. It was a period of economic prosperity, not decline and depression. The agents of rebellion were youthful, finding their own path and ignoring the past. The rebellion was world wide, but from out of its incubation in the United States the manifestations were first, strongest, and most lasting. Here, in a selection of material from the University of Michigan's Labadie Collection, are the paper witnesses to that era.http://deepblue.lib.umich.edu/bitstream/2027.42/120284/1/the_1960s_93.pd
Bulk Fermi surface and electronic properties of CuBiSe
The electronic properties of CuBiSe have been
investigated using Shubnikov-de Haas and optical reflectance measurements.
Quantum oscillations reveal a bulk, three-dimensional Fermi surface with
anisotropy 2 and a modest increase in
free-carrier concentration and in scattering rate with respect to the undoped
BiSe, also confirmed by reflectivity data. The effective mass is
almost identical to that of BiSe. Optical conductivity reveals a
strong enhancement of the bound impurity bands with Cu addition, suggesting
that a significant number of Cu atoms enter the interstitial sites between Bi
and Se layers or may even substitute for Bi. This conclusion is also supported
by X-ray diffraction measurements, where a significant increase of microstrain
was found in CuBiSe, compared to BiSe.Comment: Accepted to Phys. Rev B (R
Readout of solid-state charge qubits using a single-electron pump
A major difficulty in realizing a solid-state quantum computer is the
reliable measurement of the states of the quantum registers. In this paper, we
propose an efficient readout scheme making use of the resonant tunneling of a
ballistic electron produced by a single electron pump. We treat the measurement
interaction in detail by modeling the full spatial configuration, and show that
for pumped electrons with suitably chosen energy the transmission coefficient
is very sensitive to the qubit state. We further show that by using a short
sequence of pumping events, coupled with a simple feedback control procedure,
the qubit can be measured with high accuracy.Comment: 5 pages, revtex4, 4 eps figures. v2: published versio
In-situ measurements of the optical absorption of dioxythiophene-based conjugated polymers
Conjugated polymers can be reversibly doped by electrochemical means. This
doping introduces new sub-bandgap optical absorption bands in the polymer while
decreasing the bandgap absorption. To study this behavior, we have prepared an
electrochemical cell allowing measurements of the optical properties of the
polymer. The cell consists of a thin polymer film deposited on gold-coated
Mylar behind which is another polymer that serves as a counterelectrode. An
infrared transparent window protects the upper polymer from ambient air. By
adding a gel electrolyte and making electrical connections to the
polymer-on-gold films, one may study electrochromism in a wide spectral range.
As the cell voltage (the potential difference between the two electrodes)
changes, the doping level of the conjugated polymer films is changed
reversibly. Our experiments address electrochromism in
poly(3,4-ethylene-dioxy-thiophene) (PEDOT) and
poly(3,4-dimethyl-propylene-dioxy-thiophene) (PProDOT-Me). This closed
electrochemical cell allows the study of the doping induced sub-bandgap
features (polaronic and bipolaronic modes) in these easily oxidized and highly
redox switchable polymers. We also study the changes in cell spectra as a
function of polymer thickness and investigate strategies to obtain cleaner
spectra, minimizing the contributions of water and gel electrolyte features
Scaling laws for the photo-ionisation cross section of two-electron atoms
The cross sections for single-electron photo-ionisation in two-electron atoms
show fluctuations which decrease in amplitude when approaching the
double-ionisation threshold. Based on semiclassical closed orbit theory, we
show that the algebraic decay of the fluctuations can be characterised in terms
of a threshold law as with exponent
obtained as a combination of stability exponents of the triple-collision
singularity. It differs from Wannier's exponent dominating double ionisation
processes. The details of the fluctuations are linked to a set of infinitely
unstable classical orbits starting and ending in the non-regularisable triple
collision. The findings are compared with quantum calculations for a model
system, namely collinear helium.Comment: 4 pages, 1 figur
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