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Using the Spreadsheet as a Tool for Teaching the Fundamentals of Engineering
This paper will demonstrate how the electronic spreadsheet has been used in a freshman level Fundamentals of Engineering course to prepare students for maximizing their analytical skills with the most ubiquitous analytical tool available today.Cockrell School of Engineerin
A comparison of measured and theoretical predictions for STS ascent and entry sonic booms
Sonic boom measurements have been obtained during the flights of STS-1 through 5. During STS-1, 2, and 4, entry sonic boom measurements were obtained and ascent measurements were made on STS-5. The objectives of this measurement program were (1) to define the sonic boom characteristics of the Space Transportation System (STS), (2) provide a realistic assessment of the validity of xisting theoretical prediction techniques, and (3) establish a level of confidence for predicting future STS configuration sonic boom environments. Detail evaluation and reporting of the results of this program are in progress. This paper will address only the significant results, mainly those data obtained during the entry of STS-1 at Edwards Air Force Base (EAFB), and the ascent of STS-5 from Kennedy Space Center (KSC). The theoretical prediction technique employed in this analysis is the so called Thomas Program. This prediction technique is a semi-empirical method that required definition of the near field signatures, detailed trajectory characteristics, and the prevailing meteorological characteristics as an input. This analytical procedure then extrapolates the near field signatures from the flight altitude to an altitude consistent with each measurement location
Control optimization of a lifting body entry problem by an improved and a modified method of perturbation function
A study of the solution problem of a complex entry optimization was studied. The problem was transformed into a two-point boundary value problem by using classical calculus of variation methods. Two perturbation methods were devised. These methods attempted to desensitize the contingency of the solution of this type of problem on the required initial co-state estimates. Also numerical results are presented for the optimal solution resulting from a number of different initial co-states estimates. The perturbation methods were compared. It is found that they are an improvement over existing methods
Correlation of predicted and measured sonic boom characteristics from the reentry of STS-1 orbiter
Characteristics from sonic boom pressure signatures recorded at 11 locations during reentry of the Space Shuttle Orbiter Columbia are correlated with characteristics of wind tunnel signatures extrapolated from flight altitudes for Mach numbers ranging from 1.23 to 5.87. The flight pressure signature were recorded by microphones positioned at two levels near the descent groundtrack along the California corridor. The wind tunnel signatures used in theoretical predictions were measured using a 0.0041-scale model Orbiter. The mean difference between all measured and predicted overpressures is 12 percent from measured levels. With one exception, the flight signatures are very similar to theoretical n-waves
A general analytical method for artificial- satellite lifetime determination
Analytical method artificial satellite lifetime determinatio
Optical Monitoring of Quasars: I. Variability
We present an analysis of quasar variability from data collected during a
photometric monitoring of 50 objects carried out at CNPq/Laboratorio Nacional
de Astrofisica, Brazil, between March 1993 and July 1996. A distinctive feature
of this survey is its photometric accuracy, ~ 0.02 V mag, achieved through
differential photometry with CCD detectors, what allows the detection of faint
levels of variability. We find that the relative variability, delta = sigma /
L, observed in the V band is anti-correlated with both luminosity and redshift,
although we have no means of discovering the dominant relation, given the
strong coupling between luminosity and redshift for the objects in our
sample.We introduce a model for the dependence of quasar variability on
frequency that is consistent with multi-wavelength observations of the nuclear
variability of the Seyfert galaxy NGC 4151. We show that correcting the
observed variability for this effect slightly increases the significance of the
trends of variability with luminosity and redshift. Assuming that variability
depends only on the luminosity, we show that the corrected variability is
anti-correlated with luminosity and is in good agreement with predictions of a
simple Poissonian model. The energy derived for the hypothetical pulses, ~
10^50 erg, agrees well with those obtained in other studies. We also find that
the radio-loud objects in our sample tend to be more variable than the
radio-quiet ones, for all luminosities and redshifts.Comment: 17 pages, 12 figures, accepted for publication in MNRAS (uses MNRAS
style
Preliminary sonic boom correlation of predicted and measured levels for STS-1 entry
A preliminary analysis correlating peaks from sonic boom pressure signatures recorded during the descent trajectory of the Orbiter Columbia, which landed in the dry lake bed at Edwards Air Force Base (EAFB), California, with measured wind tunnel signatures extrapolated from flight altitudes to the ground has been made for Mach numbers ranging from 1.3 to 6. The flight pressure signatures were recorded by microphones positioned at ground level near the groundtrack, whereas the wind tunnel signatures were measured during a test of a 0.0041-scale model Orbiter. The agreement between overpressure estimates based on wind tunnel data using preliminary flight trajectory data and oscillograph traces from ground measurements appears reasonable at this time for the range of Mach numbers considered. More detailed studies using final flight trajectory data and digitized ground measured data will be performed
Weak ergodicity breaking of receptor motion in living cells stemming from random diffusivity
Molecular transport in living systems regulates numerous processes underlying
biological function. Although many cellular components exhibit anomalous
diffusion, only recently has the subdiffusive motion been associated with
nonergodic behavior. These findings have stimulated new questions for their
implications in statistical mechanics and cell biology. Is nonergodicity a
common strategy shared by living systems? Which physical mechanisms generate
it? What are its implications for biological function? Here, we use single
particle tracking to demonstrate that the motion of DC-SIGN, a receptor with
unique pathogen recognition capabilities, reveals nonergodic subdiffusion on
living cell membranes. In contrast to previous studies, this behavior is
incompatible with transient immobilization and therefore it can not be
interpreted according to continuous time random walk theory. We show that the
receptor undergoes changes of diffusivity, consistent with the current view of
the cell membrane as a highly dynamic and diverse environment. Simulations
based on a model of ordinary random walk in complex media quantitatively
reproduce all our observations, pointing toward diffusion heterogeneity as the
cause of DC-SIGN behavior. By studying different receptor mutants, we further
correlate receptor motion to its molecular structure, thus establishing a
strong link between nonergodicity and biological function. These results
underscore the role of disorder in cell membranes and its connection with
function regulation. Due to its generality, our approach offers a framework to
interpret anomalous transport in other complex media where dynamic
heterogeneity might play a major role, such as those found, e.g., in soft
condensed matter, geology and ecology.Comment: 27 pages, 5 figure
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