2,622 research outputs found
Physical Mechanism of the d->d+is Transition
We discuss the basic physical mechanism of the d->d+is transition, which is
the currently accepted explanation for the results of tunneling experiments
into planes. Using the first-order perturbation theory, we show that the
zero-bias states drive the transition. We present various order-of-magnitude
estimates and consistency checks that support this picture.Comment: 7 pages, 2 figure
Graphical User Interface and Microprocessor Control Enhancement of a Pseudorandom Code Generator
Modern digital communication techniques often require the generation of pseudorandom numbers or sequences. The ability to quickly and easily produce various codes such as maximal length codes, Gold codes, Jet Propulsion Laboratory ranging codes, syncopated codes, and non-linear codes in a laboratory environment is essential. This thesis addresses the issue of providing automated computer control to previously built, manually controlled hardware incorporating the Stanford Telecom STEL-1032 Pseudo-Random Number (PRN) Coder. By incorporating a microcontroller into existing hardware, the STEL-1032 can now be conveniently controlled from a MATLAB Graphical User Interface (GUI). The user can quickly create, save, and recall various setups for the STEL-1032 in an easy to use GUI environment. In addition to having complete control of the STEL-1032\u27s internal actions, the microcontroller adds an extra measure of control possibilities by using various signals as possible interrupt sources. The microcontroller can sample the STEL-1032\u27s various outputs at a rate up to 320 kHz and the data can be imported directly into MATLAB for further analysis
2012 Census of California Water Transit Services ,MTI Report 12-02
The U.S. Bureau of Transportation Statistics conducts a nationwide census of ferry boat operators for the U.S. Department of Transportation and the collected information is used for statistical purposes. The Caltrans Division of Local Assistance has been asked by the Federal Highway Administration (FHWA) to gather data regarding ferry operations under MAP-21, the Moving Ahead for Progress in the 21st Century Act. MAP-21 includes a new formula program for ferry boats and ferry terminal facilities eligible under 23 USC 129(c) which authorizes federal participation in toll roads, bridges, tunnels, and ferries. FHWA has asked that Caltrans assure the ferry boat data is current for MAP-21. The Mineta Transportation Institute was contacted by Caltrans to conduct this research. The research team compiled a spreadsheet and accompanying maps that include ferry boats, routes, and operators along with a number of related characteristics including ownership (public or private), daily trip counts, regulation of fares, terminal locations (street address and coordinates), boarding statistics, and route segment lengths. The spreadsheet contains fields that will allow it to be linked in a Geographic Information System to Caltrans Earth software for further analysis. Additionally, where relevant, the report includes a brief description of expansion plans for certain ferry service providers
Different regimes of Forster energy transfer between an epitaxial quantum well and a proximal monolayer of semiconductor nanocrystals
We calculate the rate of non-radiative, Forster-type energy transfer (ET)
from an excited epitaxial quantum well (QW) to a proximal monolayer of
semiconductor nanocrystal quantum dots (QDs). Different electron-hole
configurations in the QW are considered as a function of temperature and
excited electron-hole density. A comparison of the theoretically determined ET
rate and QW radiative recombination rate shows that, depending on the specific
conditions, the ET rate is comparable to or even greater than the radiative
recombination rate. Such efficient Forster ET is promising for the
implementation of ET-pumped, nanocrystal QD-based light emitting devices.Comment: 14 pages, 4 figure
Positive and negative streamers in ambient air: measuring diameter, velocity and dissipated energy
Positive and negative streamers are studied in ambient air at 1 bar; they
emerge from a needle electrode placed 40 mm above a planar electrode. The
amplitudes of the applied voltage pulses range from 5 to 96 kV; most pulses
have rise times of 30 ns or shorter. Diameters, velocities and energies of the
streamers are measured. Two regimes are identified; a low voltage regime where
only positive streamers appear and a high voltage regime where both positive
and negative streamers exist. Below 5 kV, no streamers emerge. In the range
from 5 to 40 kV, positive streamers form, while the negative discharges only
form a glowing cloud at the electrode tip, but no streamers. For 5 to 20 kV,
diameters and velocities of the positive streamers have the minimal values of
d=0.2 mm and v \approx 10^5 m/s. For 20 to 40 kV, their diameters increase by a
factor 6 while the voltage increases only by a factor 2. Above the transition
value of 40 kV, streamers of both polarities form; they strongly resemble each
other, though the positive ones propagate further; their diameters continue to
increase with applied voltage. For 96 kV, positive streamers attain diameters
of 3 mm and velocities of 4*10^6 m/s, negative streamers are about 20 % slower
and thinner. An empirical fit formula for the relation between velocity v and
diameter d is v=0.5 d^2/(mm ns) for both polarities. Streamers of both
polarities dissipate energies of the order of several mJ per streamer while
crossing the gap.Comment: 20 pages, 9 figures, accepted for J. Phys.
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