2,213 research outputs found
Investigation of an anomalous flow condition of the Langley pilot model expansion tube
Free-stream flow velocity measurements were made in the Langley pilot model expansion tube during the test flow interval. During this interval, an anomalous dip in pitot pressure occurs for the expansion tube operating conditions employed. Within the test flow interval, the main conclusions reached from comparison of the measured flow velocity, pitot pressure, and tube wall pressure are: the variations which occur in velocity and wall pressure are small compared with the variations in pitot pressure; a corresponding dip in the derived flow density is associated with the dip in pitot pressure; and the value of the average density over the interval, which results from the expansion from the shocked intermediate chamber condition, is approximately one-half of the value that can result from only an isentropic process
Dynamic scaling of I-V data for the neutral 2D Coulomb gas
The value of the dynamic critical exponent z has been studied for
experimental two-dimensional superconducting and Josephson Junction array
systems in zero magnetic field via the Fisher-Fisher-Huse dynamic scaling
analysis. We found z~5.6, a relatively large value indicative of non-diffusive
dynamics. We extend this work here to simulational I-V curves that are also
found to be characterized by the same large value of z.Comment: 2 pages, 2 embedded figures, LT22 proceedings, Physica
Theory of the Stark Effect for P donors in Si
We develop a multi-valley effective mass theory for substitutional donors in
silicon in an inhomogeneous environment. Valley-orbit coupling is treated
perturbatively. We apply the theory to the Stark effect in Si:P. The method
becomes more accurate at high fields, and it is designed to give correct
experimental binding energies at zero field. Unexpectedly, the ground state
energy for the donor electron is found to increase with electric field as a
consequence of spectrum narrowing of the 1s manifold. Our results are of
particular importance for the Kane quantum computer.Comment: published versio
Neuronal Control of Swimming Behavior: Comparison of Vertebrate and Invertebrate Model Systems
Swimming movements in the leech and lamprey are highly analogous, and lack homology. Thus, similarities in mechanisms must arise from convergent evolution rather than from common ancestry. Despite over 40 years of parallel investigations into this annelid and primitive vertebrate, a close comparison of the approaches and results of this research is lacking. The present review evaluates the neural mechanisms underlying swimming in these two animals and describes the many similarities that provide intriguing examples of convergent evolution. Specifically, we discuss swim initiation, maintenance and termination, isolated nervous system preparations, neural-circuitry, central oscillators, intersegmental coupling, phase lags, cycle periods and sensory feedback. Comparative studies between species highlight mechanisms that optimize behavior and allow us a broader understanding of nervous system function
Spin Readout and Initialization in a Semiconductor Quantum Dot
Electron spin qubits in semiconductors are attractive from the viewpoint of
long coherence times. However, single spin measurement is challenging. Several
promising schemes incorporate ancillary tunnel couplings that may provide
unwanted channels for decoherence. Here, we propose a novel spin-charge
transduction scheme, converting spin information to orbital information within
a single quantum dot by microwave excitation. The same quantum dot can be used
for rapid initialization, gating, and readout. We present detailed modeling of
such a device in silicon to confirm its feasibility.Comment: Published versio
Some observations of heated gallium arsenide heteroface solar cells
GaAlAs/GaAs heteroface solar cells used in space offer advantages of higher operating temperatures and recovery from radiation damage using thermal annealing. Experiments were conducted to examine the effects on the room temperature photovoltaic properties of cells due to heating in a vacuum at temperatures encountered in radiation damage annealing. Some degradation of photovoltaic properties was observed for all the cells that were heated. The lifetime, due to heating, for a 20-percent degradation in output power was estimated for cells heated at 200 C and 400 C. The results for cells that were heated at 200 C for 1750 hours indicate a lifetime of at least 3 years. The results for cells that were heated at 400 C for 264 hours indicate that lifetimes in the range of 350 hours to 1400 hours may be expected. The results indicate that for cells that must be heated at 400 C the selection of fabrication techniques and materials is particularly important
Beyond the Three “Bs” How American Christians Approach Faith and Politics
While it is well known that religiosity measures inform modern political alignments and voting behavior, less is known about how people of various religious orthodoxies think about the role of religion in society. To learn more about this veritable “black box” with respect to whether and why people connect their spiritual life to the political world, we conducted several focus groups in randomly selected Christian congregations in a mid-sized Midwestern city. Our analysis offers confirmatory, amplifying, and challenging evidence with respect to the “Three Bs” (believing, behaving, and belonging) perspective on how religion affects politics. Specifically, we show that while contemporary measures of religious traditionalism accurately reflect individuals’ partisan, ideological, and issue preferences, attitudes regarding the broad intersection of faith and politics are perhaps best understood via the presence (or absence) of denominational guidance on questions of the role of religion in society. We conclude by offering suggestions for future survey research seeking to explain the relationship between religion and politics
STR-839: ADDRESSING THE ISSUES OF MODAL IDENTIFICATION USING TENSOR DECOMPOSITION
Modal identification has been an indispensable tool for condition assessment of critical civil infrastructure. Recently several signal processing techniques including time-frequency analysis have shown significant success in addressing wide range of challenges in modal identification of flexible structures. In a parallel development, tensor decomposition is explored as an attractive and versatile system identification tool that can use even a limited number of vibration sensors to estimate the modal parameters under ambient excitations. In this paper, the performance of tensor decomposition is evaluated for modal identification of a building model under a multitude of earthquake excitations
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