300 research outputs found
Quantitative Assessment of Flame Stability Through Image Processing and Spectral Analysis
This paper experimentally investigates two generalized methods, i.e., a simple universal index and oscillation frequency, for the quantitative assessment of flame stability at fossil-fuel-fired furnaces. The index is proposed to assess the stability of flame in terms of its color, geometry, and luminance. It is designed by combining up to seven characteristic parameters extracted from flame images. The oscillation frequency is derived from the spectral analysis of flame radiation signals. The measurements involved in these two methods do not require prior knowledge about fuel property, burner type, and other operation conditions. They can therefore be easily applied to flame stability assessment without costly and complex adaption. Experiments were carried out on a 9-MW heavy-oil-fired combustion test rig over a wide range of combustion conditions including variations in swirl vane position of the tertiary air, swirl vane position of the secondary air, and the ratio of the primary air to the total air. The impact of these burner parameters on the stability of heavy oil flames is investigated by using the index and oscillation frequency proposed. The experimental results obtained demonstrate the effectiveness of the methods and the importance of maintaining a stable flame for reduced NOx emissions. It is envisaged that such methods can be easily transferred to existing flame closed-circuit television systems and flame failure detectors in power stations for flame stability monitoring
Minimal sets determining universal and phase-covariant quantum cloning
We study the minimal input sets which can determine completely the universal
and the phase-covariant quantum cloning machines. We find that the universal
quantum cloning machine, which can copy arbitrary input qubit equally well,
however can be determined completely by only four input states located at the
four vertices of a tetrahedron. The phase-covariant quantum cloning machine,
which can copy all qubits located on the equator of the Bloch sphere, can be
determined by three equatorial qubits with equal angular distance. These
results sharpen further the well-known results that BB84 states and six-states
used in quantum cryptography can determine completely the phase-covariant and
universal quantum cloning machines. This concludes the study of the power of
universal and phase-covariant quantum cloning, i.e., from minimal input sets
necessarily to full input sets by definition. This can simplify dramatically
the testing of whether the quantum clone machines are successful or not, we
only need to check that the minimal input sets can be cloned optimally.Comment: 7 pages, 4 figure
Quantum Cloning Machines and the Applications
No-cloning theorem is fundamental for quantum mechanics and for quantum
information science that states an unknown quantum state cannot be cloned
perfectly. However, we can try to clone a quantum state approximately with the
optimal fidelity, or instead, we can try to clone it perfectly with the largest
probability. Thus various quantum cloning machines have been designed for
different quantum information protocols. Specifically, quantum cloning machines
can be designed to analyze the security of quantum key distribution protocols
such as BB84 protocol, six-state protocol, B92 protocol and their
generalizations. Some well-known quantum cloning machines include universal
quantum cloning machine, phase-covariant cloning machine, the asymmetric
quantum cloning machine and the probabilistic quantum cloning machine etc. In
the past years, much progress has been made in studying quantum cloning
machines and their applications and implementations, both theoretically and
experimentally. In this review, we will give a complete description of those
important developments about quantum cloning and some related topics. On the
other hand, this review is self-consistent, and in particular, we try to
present some detailed formulations so that further study can be taken based on
those results.Comment: 98 pages, 12 figures, 400+ references. Physics Reports (published
online
Unified Universal Quantum Cloning Machine and Fidelities
We present a unified universal quantum cloning machine, which combines
several different existing universal cloning machines together including the
asymmetric case. In this unified framework, the identical pure states are
projected equally into each copy initially constituted by input and one half of
the maximally entangled states. We show explicitly that the output states of
those universal cloning machines are the same. One importance of this unified
cloning machine is that the cloning procession is always the symmetric
projection which reduces dramatically the difficulties for implementation. Also
it is found that this unified cloning machine can be directly modified to the
general asymmetric case. Besides the global fidelity and the single-copy
fidelity, we also present all possible arbitrary-copy fidelities.Comment: 4 pages, 2 figure
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