4,886 research outputs found
A study of course deviations during cross-country soaring
Several models are developed for studying the impact of deviations from course during cross country soaring flights. Analyses are performed at the microstrategy and macrostrategy levels. Two types of lift sources are considered: concentrated thermals and thermal streets. The sensitivity of the optimum speed solutions to various model, piloting and performance parameters is evaluated. Guides are presented to provide the pilot with criterions for making in-flight decisions. In general, course deviations are warranted during weak lift conditions, but are less justifiable with moderate to strong lift conditions
On the separable quotient problem for Banach spaces
While the classic separable quotient problem remains open, we survey general
results related to this problem and examine the existence of a particular
infinitedimensional separable quotient in some Banach spaces of vector-valued
functions, linear operators and vector measures. Most of the results presented
are consequence of known facts, some of them relative to the presence of
complemented copies of the classic sequence spaces c_0 and l_p, for 1 <= p <=
\infty. Also recent results of Argyros - Dodos - Kanellopoulos, and Sliwa are
provided. This makes our presentation supplementary to a previous survey (1997)
due to Mujica
A cross-correlation of WMAP and ROSAT
We cross-correlate the recent CMB WMAP 1 year data with the diffuse soft
X-ray background map of ROSAT. We look for common signatures due to galaxy
clusters (SZ effect in CMB, bremsstrahlung in X-rays) by cross-correlating the
two maps in real and in Fourier space. We do not find any significant
correlation and we explore the different reasons for this lack of correlation.
The most likely candidates are the possibility that we live in a low universe () and/or systematic effects in the data
especially in the diffuse X-ray maps which may suffer from significant cluster
signal subtraction during the point source removal process.Comment: To appear in New Astronomy Reviews, Proceedings of the CMBNET
Meeting, 20-21 February, 2003, Oxford, U
Cubic anisotropy in high homogeneity thin (Ga,Mn)As layers
Historically, comprehensive studies of dilute ferromagnetic semiconductors,
e.g., -type (Cd,Mn)Te and (Ga,Mn)As, paved the way for a quantitative
theoretical description of effects associated with spin-orbit interactions in
solids, such as crystalline magnetic anisotropy. In particular, the theory was
successful in explaining {\em uniaxial} magnetic anisotropies associated with
biaxial strain and non-random formation of magnetic dimers in epitaxial
(Ga,Mn)As layers. However, the situation appears much less settled in the case
of the {\em cubic} term: the theory predicts switchings of the easy axis
between in-plane and directions as a
function of the hole concentration, whereas only the
orientation has been found experimentally. Here, we report on the observation
of such switchings by magnetization and ferromagnetic resonance studies on a
series of high-crystalline quality (Ga,Mn)As films. We describe our findings by
the mean-field - Zener model augmented with three new ingredients. The
first one is a scattering broadening of the hole density of states, which
reduces significantly the amplitude of the alternating carrier-induced
contribution. This opens the way for the two other ingredients, namely the
so-far disregarded single-ion magnetic anisotropy and disorder-driven
non-uniformities of the carrier density, both favoring the
direction of the apparent easy axis. However, according to our results, when
the disorder gets reduced a switching to the orientation
is possible in a certain temperature and hole concentration range.Comment: 12 pages, 9 figure
The reconfigurable Josephson circulator/directional amplifier
Circulators and directional amplifiers are crucial non-reciprocal signal
routing and processing components involved in microwave readout chains for a
variety of applications. They are particularly important in the field of
superconducting quantum information, where the devices also need to have
minimal photon losses to preserve the quantum coherence of signals.
Conventional commercial implementations of each device suffer from losses and
are built from very different physical principles, which has led to separate
strategies for the construction of their quantum-limited versions. However, as
recently proposed theoretically, by establishing simultaneous pairwise
conversion and/or gain processes between three modes of a Josephson-junction
based superconducting microwave circuit, it is possible to endow the circuit
with the functions of either a phase-preserving directional amplifier or a
circulator. Here, we experimentally demonstrate these two modes of operation of
the same circuit. Furthermore, in the directional amplifier mode, we show that
the noise performance is comparable to standard non-directional superconducting
amplifiers, while in the circulator mode, we show that the sense of circulation
is fully reversible. Our device is far simpler in both modes of operation than
previous proposals and implementations, requiring only three microwave pumps.
It offers the advantage of flexibility, as it can dynamically switch between
modes of operation as its pump conditions are changed. Moreover, by
demonstrating that a single three-wave process yields non-reciprocal devices
with reconfigurable functions, our work breaks the ground for the development
of future, more-complex directional circuits, and has excellent prospects for
on-chip integration
CHARACTERISTIC OF BODY POSTURE OF THE PARTICIPANTS OF THE EUROPEAN JUNIOR VOLLEYBALL CHAMPIONSHIPS.
The lecture presents methods and results of study of volleyball players posture, age17-18 of different nationalities. The results show change curves in spine and biomechanical parameters under loading influence
Barriers and challenges for primary and secondary prevention of heart disease in sub-Saharan Africa
The diverse people of sub-Saharan Africa face a number of paradoxical challenges arising from economic development and urbanisation, including an increasing prevalence of noncommunicable forms of heart disease. Prevention programmes designed not only to detect those with established and often disabling forms of heart disease, but prevent disease progression and a premature death, are an obvious priority in this setting. This review article reflects on the barriers and challenges to effective primary and secondary prevention of heart disease in sub-Saharan Africa by (a) examining what residual issues challenge effective prevention in high-income countries? (b) what are the key ingredients to an integrated programme of primary and secondary prevention across the lifespan (from the population to individual)? and (c) considering the first two points, what are the barriers and challenges in sub-Saharan Africa to implementing cost-effective primary and secondary prevention using a systematic approach to “who, what and how”
Bounded resolutions for spaces Cp(X) and a characterization in terms of X
An internal characterization of the Arkhangel’ski˘ı-Calbrixmain theorem from [4] is obtained
by showing that the space Cp(X) of continuous real-valued functions on a Tychonoff space
X is K-analytic framed in RX if and only if X admits a nice framing. This applies to show
that a metrizable (or cosmic) space X is σ -compact if and only if X has a nice framing. We
analyse a few concepts which are useful while studying nice framings. For example, a class
of Tychonoff spaces X containing strictly Lindelöf Cˇ ech-complete spaces is introduced for
which a variant of Arkhangel’ski˘ı-Calbrix theorem for σ-boundedness of X is shown
Comparing and combining measurement-based and driven-dissipative entanglement stabilization
We demonstrate and contrast two approaches to the stabilization of qubit
entanglement by feedback. Our demonstration is built on a feedback platform
consisting of two superconducting qubits coupled to a cavity which are measured
by a nearly-quantum-limited measurement chain and controlled by high-speed
classical logic circuits. This platform is used to stabilize entanglement by
two nominally distinct schemes: a "passive" reservoir engineering method and an
"active" correction based on conditional parity measurements. In view of the
instrumental roles that these two feedback paradigms play in quantum
error-correction and quantum control, we directly compare them on the same
experimental setup. Further, we show that a second layer of feedback can be
added to each of these schemes, which heralds the presence of a high-fidelity
entangled state in realtime. This "nested" feedback brings about a marked
entanglement fidelity improvement without sacrificing success probability.Comment: 40 pages, 12 figure
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