919 research outputs found
Temperature robust PCA based stress monitoring approach
In this paper, a guided wave temperature robust PCA-based stress monitoring
methodology is proposed. It is based on the analysis of the longitudinal guided wave propagating
along the path under stress. Slight changes in the wave are detected by means of PCA via statistical
T2 and Q indices. Experimental and numerical simulations of the guided wave propagating in
material under different temperatures have shown significant variations in the amplitude and the
velocity of the wave. This condition can jeopardize the discrimination of the different stress
scenarios detected by the PCA indices. Thus, it is proposed a methodology based on an extended
knowledge base, composed by a PCA statistical model for different discrete temperatures to
produce a robust classification of stress states under variable environmental conditions.
Experimental results have shown a good agreement between the predicted scenarios and the real
onesPostprint (author's final draft
Flow estimation in a steel pipe using guided waves
In this investigation, a flow rate estimation guided wave based scheme in pipes is
proposed. The effect of the fluid over the propagation of longitudinal waves has been
experimentally studied by using several laminar flows of water transported by a steel pipe. Results
have shown a decrease of the guided wave pattern repeatability and the signal energy as the flow
rate increase as a result of the energy leakage from the pipe to the fluid. A Matlab® script is used to
excite the PZT actuator via picoscope 2208 of Picotech®, the captured signal is acquired also by the
picoscope and the data is processed in Matlab. The test bench utilized is composed by a 1” sch 40
A-106 pipe, a needle valve and a centrifugal pump provides the flow energy. A couple of PZTs are
used in a picth-catch configuration to produce and capture the longitudinal waves along the cross
section of the pipe.Postprint (author's final draft
A robust one-step catalytic machine for high fidelity anti-cloning and W-state generation in a multi-qubit system
We propose a physically realizable machine which can either generate
multiparticle W-like states, or implement high fidelity () anti-cloning of an arbitrary qubit state, in a single step. Moreover
this universal machine acts as a catalyst in that it is unchanged after either
procedure, effectively resetting itself for its next operation. It also
possesses an inherent {\em immunity} to decoherence. Most importantly in terms
of practical multi-party quantum communication, the machine's robustness in the
presence of decoherence actually {\em increases} as the number of qubits
increases.Comment: 4 pages, 2 figure
Ultrafast deterministic generation of entanglement in a time-dependent asymmetric two-qubit-cavity system
We present an efficient scheme for the controlled generation of pure
two-qubit states possessing {\em any} desired degree of entanglement and a {\em
prescribed} symmetry in two cavity QED based systems, namely, cold trapped ions
and flying atoms. This is achieved via on-resonance ion/atom-cavity couplings
which are time-dependent and asymmetric, leading to a trapping vacuum state
condition which does not arise for identical couplings. A duality in the role
of the coupling ratio yields states with a given concurrence but opposing
symmetries. The experimental feasibility of the proposed scheme is also
discussed.Comment: 4 pages, 4 figure
Equivalent dynamical complexity in a many-body quantum and collective human system
Proponents of Complexity Science believe that the huge variety of emergent
phenomena observed throughout nature, are generated by relatively few
microscopic mechanisms. Skeptics however point to the lack of concrete examples
in which a single mechanistic model manages to capture relevant macroscopic and
microscopic properties for two or more distinct systems operating across
radically different length and time scales. Here we show how a single
complexity model built around cluster coalescence and fragmentation, can cross
the fundamental divide between many-body quantum physics and social science. It
simultaneously (i) explains a mysterious recent finding of Fratini et al.
concerning quantum many-body effects in cuprate superconductors (i.e. scale of
10^{-9} - 10^{-4} meters and 10^{-12} - 10^{-6} seconds), (ii) explains the
apparent universality of the casualty distributions in distinct human
insurgencies and terrorism (i.e. scale of 10^3 - 10^6 meters and 10^4 - 10^8
seconds), (iii) shows consistency with various established empirical facts for
financial markets, neurons and human gangs and (iv) makes microscopic sense for
each application. Our findings also suggest that a potentially productive shift
can be made in Complexity research toward the identification of equivalent
many-body dynamics in both classical and quantum regimes.Comment: 9 pages, 3 figures; version published in AIP Advance
Adapting agriculture to climate change
We evaluate the potential impacts and measure the potential limits of adaptation of agriculture to climate change. Pressures on land and water resources are expected to intensify existing risks in low latitude areas – e.g., South-East Asia deltas – and in regions with current water scarcity – e.g. Mediterranean, and create new opportunities in some northern temperate areas – e.g., Northern Russia, Northern Europe. The need to respond to these risks and opportunities is addressed by evaluating the costs and benefits of a number of technical and policy actions. The discussion aims to assist stakeholders facing the adaptation challenge and develop measures to reduce the vulnerability of the sector to climate change.Adaptation, climatic change, global production, mitigation, Agricultural and Food Policy, Crop Production/Industries, Land Economics/Use, Resource /Energy Economics and Policy, C51, C53, Q17, Q18,
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