4,249 research outputs found
Wind tunnel test results of a new leading edge flap design for highly swept wings, a vortex flap
A leading edge flap design for highly swept wings, called a vortex flap, was tested on an arrow wing model in a low speed wind tunnel. A vortex flap differs from a conventional plain flap in that it has a leading edge tab which is counterdeflected from the main portion of the flap. This results in intentional separation at the flap leading edge, causing a vortex to form and lie on the flap. By trapping this vortex, the vortex flap can result in significantly improved wing flow characteristics relative to conventional flaps at moderate to high angles of attack, as demonstrated by the flow visualization results of this tests
Quantified Uncertainty in Thermodynamic Modeling for Materials Design
Phase fractions, compositions and energies of the stable phases as a function
of macroscopic composition, temperature, and pressure (X-T-P) are the principle
correlations needed for the design of new materials and improvement of existing
materials. They are the outcomes of thermodynamic modeling based on the
CALculation of PHAse Diagrams (CALPHAD) approach. The accuracy of CALPHAD
predictions vary widely in X-T-P space due to experimental error, model
inadequacy and unequal data coverage. In response, researchers have developed
frameworks to quantify the uncertainty of thermodynamic property model
parameters and propagate it to phase diagram predictions. In previous studies,
uncertainty was represented as intervals on phase boundaries (with respect to
composition) or invariant reactions (with respect to temperature) and was
unable to represent the uncertainty in eutectoid reactions or in the stability
of phase regions. In this work, we propose a suite of tools that leverages
samples from the multivariate model parameter distribution to represent
uncertainty in forms that surpass previous limitations and are well suited to
materials design. These representations include the distribution of phase
diagrams and their features, as well as the dependence of phase stability and
the distributions of phase fraction, composition activity and Gibbs energy on
X-T-P location - irrespective of the total number of components. Most
critically, the new methodology allows the material designer to interrogate a
certain composition and temperature domain and get in return the probability of
different phases to be stable, which can positively impact materials design
A security proof of continuous-variable QKD using three coherent states
We introduce a ternary quantum key distribution (QKD) protocol and asymptotic
security proof based on three coherent states and homodyne detection. Previous
work had considered the binary case of two coherent states and here we
nontrivially extend this to three. Our motivation is to leverage the practical
benefits of both discrete and continuous (Gaussian) encoding schemes creating a
best-of-both-worlds approach; namely, the postprocessing of discrete encodings
and the hardware benefits of continuous ones. We present a thorough and
detailed security proof in the limit of infinite signal states which allows us
to lower bound the secret key rate. We calculate this is in the context of
collective eavesdropping attacks and reverse reconciliation postprocessing.
Finally, we compare the ternary coherent state protocol to other well-known QKD
schemes (and fundamental repeaterless limits) in terms of secret key rates and
loss.Comment: Close to the published versio
New Product Innovation with Multiple Features and Technology Constraints
We model a firm\u27s decisions about product innovation, focusing on the extent to which features should be improved or changed in the succession of models that comprise a life cycle. We show that the structure of the internal and external environment in which a firm operates suggests when to innovate to the technology frontier. The criterion is maximization of the expected present value of products during the life cycle. Computational studies complement the theoretical results and lead to insights about when to bundle innovations across features. The formalization was influenced by extensive interviews with managers in a high-technology firm that dominates its industry
Strategies for Reducing Moisture Content in Forest Residues at the Harvest Site
The moisture content (MC) of biomass derived from forest residues can pose a challenge to biomass utilization. It plays a significant role in determining the cost of transportation and subsequent market price. Additionally, emerging biomass conversion technologies, such as gasification, torrefaction, and briquetting, have very narrow specifications for the MC (e.g., \u3c15%) in their feedstocks. The goal of this study was to develop strategies for reducing moisture content by evaluating different arrangement patterns of forest residues and its effect on MC reduction at the harvest site. The study compared four different arrangement patterns including criss-cross, teepees, traditional piling (processor piled), and scattered residues in three different timber harvest units in northern California. Two of the arrangement patterns (criss-cross and processor piled) were also covered with a plastic cover. Samples were collected from each treatment using a transect method and were recorded for 12 months. There was an overall drop of MC from 52% (freshly cut) to 12% between all arrangements over the study period. The cost of construction per pile, averaged 41, and $48 for teepees, criss-cross, and processor piles, respectively. Even though, there was no significant difference in MC reduction between piles (except scattered), each pile arrangement of forest residues directly affected biomass feedstock operations, logistics, and costs
Methods for biological, chemical, and physical analyses in reservoirs
This manual contains detailed descriptions of biological, chemical and physical sampling and analytical procedures used at the Lake Mead Limnological Research Center. The manual was prepared in response to requests made by numerous individuals involved in the Las Vegas Valley Water Quality Program. This manual represents what we consider to be a reasonably complete compilation of methods useful in studying both general and specific limnological questions. While each section is sufficiently detailed to be of use to investigators with little experience in limnological methodology, the methods can be used on a wide variety of lakes and reservoirs, with relatively little modification
Low-mass companions to Hyades stars
It is now well established that a large fraction of the low-mass stars are
binaries or higher order multiples. Similarly a sizable fraction have giant
planets. In contrast to these, the situation for brown dwarf companions is
complicated: While close systems seem to be extremely rare, wide systems are
possibly more common. In this paper, we present new results on a survey for
low-mass companions in the Hyades. After measuring precisely the radial
velocity of 98 Hyades dwarf stars for 5 years, we have selected all stars that
show low-amplitude long-period trends. With AO-observations of these 14 stars
we found companion candidates around nine of them, where one star has two
companions. The two companions of HIP 16548 have masses between 0.07 to 0.08
Mo, and are thus either brown dwarfs or very low mass stars. In the case of HAN
172 we found a companion with a mass between 0.08 to 0.10 Mo, which is again
between a star and a brown dwarf. The other seven stars all have stellar
companions. In two additional cases, the RV-variations are presumably caused by
stellar activity, and in another case the companion could be a short-period
binary. The images of the remaining two stars are slightly elongated, which
might imply that even these are binaries. Because at least 12 of the 14 stars
showing low-amplitude RV trends turn out to have companions with a mass greater
than 70 MJupiter, or are just active, we finally estimate the number of
companions with masses between 10 MJupiter and 70 MJupiter within 8 AU of the
host stars in the Hyades as less equal 2%.Comment: 10 pages, 10 figure
Formalising Mathematics in Simple Type Theory
Despite the considerable interest in new dependent type theories, simple type
theory (which dates from 1940) is sufficient to formalise serious topics in
mathematics. This point is seen by examining formal proofs of a theorem about
stereographic projections. A formalisation using the HOL Light proof assistant
is contrasted with one using Isabelle/HOL. Harrison's technique for formalising
Euclidean spaces is contrasted with an approach using Isabelle/HOL's axiomatic
type classes. However, every formal system can be outgrown, and mathematics
should be formalised with a view that it will eventually migrate to a new
formalism
The Effects of Foam Rolling and Static Stretching on Flexibility and Acute Muscle Soreness
Please view abstract in the attached PDF file
Formal Verification of Nonlinear Inequalities with Taylor Interval Approximations
We present a formal tool for verification of multivariate nonlinear
inequalities. Our verification method is based on interval arithmetic with
Taylor approximations. Our tool is implemented in the HOL Light proof assistant
and it is capable to verify multivariate nonlinear polynomial and
non-polynomial inequalities on rectangular domains. One of the main features of
our work is an efficient implementation of the verification procedure which can
prove non-trivial high-dimensional inequalities in several seconds. We
developed the verification tool as a part of the Flyspeck project (a formal
proof of the Kepler conjecture). The Flyspeck project includes about 1000
nonlinear inequalities. We successfully tested our method on more than 100
Flyspeck inequalities and estimated that the formal verification procedure is
about 3000 times slower than an informal verification method implemented in
C++. We also describe future work and prospective optimizations for our method.Comment: 15 page
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