14,718 research outputs found
A flight-test evaluation of a go-around control system for a twin engine powered-lift STOL airplane
An automatic go-around control system was evaluated on the Augmentor Wing Jet Short Takeoff and Landing (STOL) Research Airplane (AWJSRA) as part of a study of an automatic landing system for a powered-lift STOL airplane. The results of the evaluation indicate that the go-around control system can successfully transition the airplane to a climb configuration from any initiation point during the glide-slope track or the flare maneuver prior to touchdown
Estimating spillovers using imprecisely measured networks
In many experimental contexts, whether and how network interactions impact
the outcome of interest for both treated and untreated individuals are key
concerns. Networks data is often assumed to perfectly represent these possible
interactions. This paper considers the problem of estimating treatment effects
when measured connections are, instead, a noisy representation of the true
spillover pathways. We show that existing methods, using the potential outcomes
framework, yield biased estimators in the presence of this mismeasurement. We
develop a new method, using a class of mixture models, that can account for
missing connections and discuss its estimation via the Expectation-Maximization
algorithm. We check our method's performance by simulating experiments on real
network data from 43 villages in India. Finally, we use data from a previously
published study to show that estimates using our method are more robust to the
choice of network measure
Spectra of phase point operators in odd prime dimensions and the extended Clifford group
We analyse the role of the Extended Clifford group in classifying the spectra
of phase point operators within the framework laid out by Gibbons et al for
setting up Wigner distributions on discrete phase spaces based on finite
fields. To do so we regard the set of all the discrete phase spaces as a
symplectic vector space over the finite field. Auxiliary results include a
derivation of the conjugacy classes of .Comment: Latex, 19page
Flight-test of the glide-slope track and flare-control laws for an automatic landing system for a powered-lift STOL airplane
An automatic landing system was developed for the Augmentor Wing Jet STOL Research Airplane to establish the feasibility and examine the operating characteristics of a powered-lift STOL transport flying a steep, microwave landing system (MLS) glide slope to automatically land on a STOL port. The flight test results address the longitudinal aspects of automatic powered lift STOL airplane operation including glide slope tracking on the backside of the power curve, flare, and touchdown. Three different autoland control laws were evaluated to demonstrate the tradeoff between control complexity and the resulting performance. The flight test and simulation methodology used in developing conventional jet transport systems was applied to the powered-lift STOL airplane. The results obtained suggest that an automatic landing system for a powered-lift STOL airplane operating into an MLS-equipped STOL port is feasible. However, the airplane must be provided with a means of rapidly regulation lift to satisfactorily provide the glide slope tracking and control of touchdown sink rate needed for automatic landings
Local cloning of entangled states
We investigate the conditions under which a set \SC of pure bipartite
quantum states on a system can be locally cloned deterministically
by separable operations, when at least one of the states is full Schmidt rank.
We allow for the possibility of cloning using a resource state that is less
than maximally entangled. Our results include that: (i) all states in \SC
must be full Schmidt rank and equally entangled under the -concurrence
measure, and (ii) the set \SC can be extended to a larger clonable set
generated by a finite group of order , the number of states in the
larger set. It is then shown that any local cloning apparatus is capable of
cloning a number of states that divides exactly. We provide a complete
solution for two central problems in local cloning, giving necessary and
sufficient conditions for (i) when a set of maximally entangled states can be
locally cloned, valid for all ; and (ii) local cloning of entangled qubit
states with non-vanishing entanglement. In both of these cases, a maximally
entangled resource is necessary and sufficient, and the states must be related
to each other by local unitary "shift" operations. These shifts are determined
by the group structure, so need not be simple cyclic permutations. Assuming
this shifted form and partially entangled states, then in D=3 we show that a
maximally entangled resource is again necessary and sufficient, while for
higher dimensional systems, we find that the resource state must be strictly
more entangled than the states in \SC. All of our necessary conditions for
separable operations are also necessary conditions for LOCC, since the latter
is a proper subset of the former. In fact, all our results hold for LOCC, as
our sufficient conditions are demonstrated for LOCC, directly.Comment: REVTEX 15 pages, 1 figure, minor modifications. Same as the published
version. Any comments are welcome
Quantum Mechanical Interaction-Free Measurements
A novel manifestation of nonlocality of quantum mechanics is presented. It is
shown that it is possible to ascertain the existence of an object in a given
region of space without interacting with it. The method might have practical
applications for delicate quantum experiments.Comment: (revised file with no need for macro), 12, TAUP 1865-91
A flight investigation of a terminal area navigation and guidance concept for STOL aircraft
A digital avionics system referred to as STOLAND has been test-flown in the NASA CV-340 to obtain performance data for time-controlled guidance in the manual flight director mode. The advanced system components installed in the cockpit included an electronic attitude director indicator and an electronic multifunction display. Navigation guidance and control computations were all performed in the digital computer. Approach paths were flown which included a narrow 180-deg turn and a 1-min, 5-deg straight-in approach to the 30-m altitude go-around point. Results are presented for 20 approaches: (1) blended radio/inertial navigation using TACAN and a microwave scanning beam landing guidance system (MODILS) permitted a smooth transition from area navigation (TACAN) to precision terminal navigation (MODILS), (2) guidance system (flight director) performance measured at an altitude of 30.5 m was within that prescribed for category II CTOL operations on a standard runway, and (3) time of arrival at a point about 2 mi from touchdown was about 4 sec plus or minus sec later than the computed nominal arrival time
A flight investigation of a terminal area navigation and guidance concept for STOL aircraft
A digital avionics system was installed in the CV-340 transport aircraft. Flight tests were made to obtain preliminary performance data in the manual flight director mode using time controlled guidance. These tests provide a basis for selection of terminal area guidance, navigation, and control system concepts for short haul aircraft and for investigating operational procedures
On the comparison of volumes of quantum states
This paper aims to study the \a-volume of \cK, an arbitrary subset of the
set of density matrices. The \a-volume is a generalization of the
Hilbert-Schmidt volume and the volume induced by partial trace. We obtain
two-side estimates for the \a-volume of \cK in terms of its Hilbert-Schmidt
volume. The analogous estimates between the Bures volume and the \a-volume
are also established. We employ our results to obtain bounds for the
\a-volume of the sets of separable quantum states and of states with positive
partial transpose (PPT). Hence, our asymptotic results provide answers for
questions listed on page 9 in \cite{K. Zyczkowski1998} for large in the
sense of \a-volume.
\vskip 3mm PACS numbers: 02.40.Ft, 03.65.Db, 03.65.Ud, 03.67.M
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