46,640 research outputs found
Handling qualities requirements for control configured vehicles
The potential effects of fly by wire and control configured vehicle concepts on flying qualities are considered. Failure mode probabilities and consequences, controllability, and dynamics of highly augmented aircraft are among the factors discussed in terms of design criteria
The Evolution of the Mexican-Born Workforce in the United States
This paper examines the evolution of the Mexican-born workforce in the United States using data drawn from the decennial U.S. Census throughout the entire 20th century. It is well known that there has been a rapid rise in Mexican immigration to the United States in recent years. Interestingly, the share of Mexican immigrants in the U.S. workforce declined steadily beginning in the 1920s before beginning to rise in the 1960s. It was not until 1980 that the relative number of Mexican immigrants in the U.S. workforce was at the 1920 level. The paper examines the trends in the relative skills and economic performance of Mexican immigrants, and contrasts this evolution with that experienced by other immigrants arriving in the United States during the period. The paper also examines the costs and benefits of this influx by examining how the Mexican influx has altered economic opportunities in the most affected labor markets and by discussing how the relative prices of goods and services produced by Mexican immigrants may have changed over time.
Design study of large area 8 cm x 8 cm wrapthrough cells for space station
The design of large area silicon solar cells for the projected NASA space station is discussed. It is based on the NASA specification for the cells which calls for an 8 cm by 8 cm cell of wrapthrough type with gridded back contacts. The beginning of life (BOL) power must be 1.039 watts per cell or larger and maximum end of life (EOL) after 10 years in the prescribed orbit under an equivalent 1MeV electron radiation damage fluence of 5 times 10 to the 13th power e/square cm. On orbit efficiency is to be optimized by a low thermal absorptance goal (thermal alpha) of .63
Medical Malpractice Litigation Under National Health Insurance: Essential or Expendable?
Identification of time-continuous models from sampled data is a long standing topic of discussion, and many approaches have been suggested. The Maximum Likelihood method is asymptotically and theoretically superior to other methods. However, it may suffer from numerical inaccuracies at fast sampling and it also requires reliable initial parameter values. A number of efficient and useful alternatives to the maximum-likelihood method have been developed over the years. The most important of these are State-Variable filters, combined with Instrumental Variable methods, including the simplified refined IV method. In this contribution we perform unpretentious numerical experiments to comment on these methods, and their mutual benefits.CADIC
ASCA observations of type-2 Seyfert galaxies: II. The Importance of X-ray Scattering and Reflection
We discuss the importance of X-ray scattering and Compton reflection in
type-2 Seyfert galaxies, based upon the analysis of ASCA observations of 25
such sources. Consideration of the iron Kalpha, [O III] line and X-ray
variability suggest that NGC 1068, NGC 4945, NGC 2992, Mrk 3, Mrk 463E and Mrk
273 are dominated by reprocessed X-rays. We examine the properties of these
sources in more detail.
We find that the iron Kalpha complex contains significant contributions from
neutral and high-ionization species of iron. Compton reflection, hot gas and
starburst emission all appear to make significant contributions to the observed
X-ray spectra.
Mrk 3 is the only source in this subsample which does not have a significant
starburst contamination. The ASCA spectrum below 3 keV is dominated by hot
scattering gas with U_X ~ 5, N_H ~ 4 x 10^23 cm^-2. This material is more
highly ionized than the zone of material comprising the warm absorber seen in
Seyfert~1 galaxies, but may contain a contribution from shock-heated gas
associated with the jet. Estimates of the X-ray scattering fraction cover 0.25
- 5%. The spectrum above 3 keV appears to be dominated by a Compton reflection
component although there is evidence that the primary continuum component
becomes visible close to 10 keV.Comment: 27 pages, 6 figures. LaTeX with encapsulated postscript. To appear in
the Astrophysical Journal. Also available via
http://lheawww.gsfc.nasa.gov/~george/papers/gnt_s2p2/abstract.htm
The Sorting Index and Permutation Codes
In the combinatorial study of the coefficients of a bivariate polynomial that
generalizes both the length and the reflection length generating functions for
finite Coxeter groups, Petersen introduced a new Mahonian statistic ,
called the sorting index. Petersen proved that the pairs of statistics
and have the same joint distribution over
the symmetric group, and asked for a combinatorial proof of this fact. In
answer to the question of Petersen, we observe a connection between the sorting
index and the B-code of a permutation defined by Foata and Han, and we show
that the bijection of Foata and Han serves the purpose of mapping
to . We also give a type analogue of the
Foata-Han bijection, and we derive the quidistribution of and over signed
permutations. So we get a combinatorial interpretation of Petersen's
equidistribution of and . Moreover, we show that
the six pairs of set-valued statistics ,
, , ,
and are equidistributed over signed
permutations. For Coxeter groups of type , Petersen showed that the two
statistics and are equidistributed. We introduce two statistics
and for elements of and we prove that the two
pairs of statistics and are
equidistributed.Comment: 25 page
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