122,116 research outputs found
Refractory inclusions in the Ornans C30 chondrite
Several types of metedorites contain unusual objects 10 micrometers to 2 centimeters across that are enriched in refractory elements such as calcium, aluminum and titanium. These objects, commonly known as refractory inclusions, are most abundant in the meteorites known as carbonaceous chondrites. The refractory inclusions that have been found in the Ornans metedorite, a member of a little-studied group of carbonaceous chondrites are described. Some refractory inclusions in Ornans resemble those found in other meteorites, while others are unlike any seen before. The unusual inclusions in Ornans contain minerals with extraordinary enrichments in highly refractory elements
Investigating jet and jet-like artefacts from Prehistoric Scotland: the National Museums Scotland project
Explicit solution of an inverse first-passage time problem for L\'{e}vy processes and counterparty credit risk
For a given Markov process and survival function on
, the inverse first-passage time problem (IFPT) is to find a
barrier function such that the survival
function of the first-passage time is given
by . In this paper, we consider a version of the IFPT problem
where the barrier is fixed at zero and the problem is to find an initial
distribution and a time-change such that for the time-changed process
the IFPT problem is solved by a constant barrier at the level zero.
For any L\'{e}vy process satisfying an exponential moment condition, we
derive the solution of this problem in terms of -invariant
distributions of the process killed at the epoch of first entrance into the
negative half-axis. We provide an explicit characterization of such
distributions, which is a result of independent interest. For a given
multi-variate survival function of generalized frailty type, we
construct subsequently an explicit solution to the corresponding IFPT with the
barrier level fixed at zero. We apply these results to the valuation of
financial contracts that are subject to counterparty credit risk.Comment: Published at http://dx.doi.org/10.1214/14-AAP1051 in the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Constraints to the Growth of Native American Gaming
Since the Indian Gaming Regulatory Act was passed in 1988, high-stakes bingo halls and casino operations have spread to reservations across the country and generated millions of dollars in revenues for their respective tribes. While some tribes have been able to exploit their sovereign status and establish high-stakes bingo parlors and casinos on reservations across the country, this study describes how external and internal constraints limit the adoption of gaming ventures by other tribes. Constraints include the location of the reservations, increasing competition, disagreements among tribal members, and opposition from the private and public sectors
Analysis of potential helicopter vibration reduction concepts
Results of analytical investigations to develop, understand, and evaluate potential helicopter vibration reduction concepts are presented in the following areas: identification of the fundamental sources of vibratory loads, blade design for low vibration, application of design optimization techniques, active higher harmonic control, blade appended aeromechanical devices, and the prediction of vibratory airloads. Primary sources of vibration are identified for a selected four-bladed articulated rotor operating in high speed level flight. The application of analytical design procedures and optimization techniques are shown to have the potential for establishing reduced vibration blade designs through variations in blade mass and stiffness distributions, and chordwise center-of-gravity location
Calibration of Hewlett-Packard network analyzers: A precision viewpoint
Alternative calibration procedures are examined for Hewlett-Packard vector network analyzers which lead to an improved open-circuit capacitance model, and hence, higher measurement accuracy
Heavy cosmic strings
We argue that cosmic strings with high winding numbers generally form in
first-order gauge symmetry breaking phase transitions, and we demonstrate this
using computer simulations. These strings are heavier than single-winding
strings and therefore more easily observable. Their cosmological evolution may
also be very different.Comment: 4 pages, updated to match the published versio
Queen Conch ranching and educational outreach as part of the Seaflower Biosphere Reserve, Colombia
Development of a surface isolation estimation technique suitable for application of polar orbiting satellite data
A technique is developed for the estimation of total daily insolation on the basis of data derivable from operational polar-orbiting satellites. Although surface insolation and meteorological observations are used in the development, the algorithm is constrained in application by the infrequent daytime polar-orbiter coverage
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