619 research outputs found
Thermal barrier coating life prediction model development
The objectives are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, and then to develop and verify life prediction models accounting for these degradation modes. Two possible predominant failure mechanisms being evaluated are bond coat oxidation and bond coat creep
Implementation of quantum maps by programmable quantum processors
A quantum processor is a device with a data register and a program register.
The input to the program register determines the operation, which is a
completely positive linear map, that will be performed on the state in the data
register. We develop a mathematical description for these devices, and apply it
to several different examples of processors. The problem of finding a processor
that will be able to implement a given set of mappings is also examined, and it
is shown that while it is possible to design a finite processor to realize the
phase-damping channel, it is not possible to do so for the amplitude-damping
channel.Comment: 10 revtex pages, no figure
Thermal barrier coating life prediction model
This is the first report of the first phase of a 3-year program. Its objectives are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, then to develop and verify life prediction models accounting for these degradation modes. The first task (Task I) is to determine the major failure mechanisms. Presently, bond coat oxidation and bond coat creep are being evaluated as potential TBC failure mechanisms. The baseline TBC system consists of an air plasma sprayed ZrO2-Y2O3 top coat, a low pressure plasma sprayed NiCrAlY bond coat, and a Rene'80 substrate. Pre-exposures in air and argon combined with thermal cycle tests in air and argon are being utilized to evaluate bond coat oxidation as a failure mechanism. Unexpectedly, the specimens pre-exposed in argon failed before the specimens pre-exposed in air in subsequent thermal cycles testing in air. Four bond coats with different creep strengths are being utilized to evaluate the effect of bond coat creep on TBC degradation. These bond coats received an aluminide overcoat prior to application of the top coat to reduce the differences in bond coat oxidation behavior. Thermal cycle testing has been initiated. Methods have been selected for measuring tensile strength, Poisson's ratio, dynamic modulus and coefficient of thermal expansion both of the bond coat and top coat layers
Time dependent nonclassical properties of even and odd nonlinear coherent states
We construct even and odd nonlinear coherent states of a parametric
oscillator and examine their nonclassical properties.It has been shown that
these superpositions exhibit squeezing and photon antibunching which change
with time.Comment: 3 eps figure
Thermal barrier coating life prediction model development
This report describes work performed to determine the predominat modes of degradation of a plasma sprayed thermal barrier coating system and to develop and verify life prediction models accounting for these degradation modes. The primary TBC system consisted of a low pressure plasma sprayed NiCrAlY bond coat, an air plasma sprayed ZrO2-Y2O3 top coat, and a Rene' 80 substrate. The work was divided into 3 technical tasks. The primary failure mode to be addressed was loss of the zirconia layer through spalling. Experiments showed that oxidation of the bond coat is a significant contributor to coating failure. It was evident from the test results that the species of oxide scale initially formed on the bond coat plays a role in coating degradation and failure. It was also shown that elevated temperature creep of the bond coat plays a role in coating failure. An empirical model was developed for predicting the test life of specimens with selected coating, specimen, and test condition variations. In the second task, a coating life prediction model was developed based on the data from Task 1 experiments, results from thermomechanical experiments performed as part of Task 2, and finite element analyses of the TBC system during thermal cycles. The third and final task attempted to verify the validity of the model developed in Task 2. This was done by using the model to predict the test lives of several coating variations and specimen geometries, then comparing these predicted lives to experimentally determined test lives. It was found that the model correctly predicts trends, but that additional refinement is needed to accurately predict coating life
Quantum Copying: Beyond the No-Cloning Theorem
We analyze to what extent it is possible to copy arbitrary states of a
two-level quantum system. We show that there exists a "universal quantum
copying machine", which approximately copies quantum mechanical states in such
a way that the quality of its output does not depend on the input. We also
examine a machine which combines a unitary transformation with a selective
measurement to produce good copies of states in a neighborhood of a particular
state. We discuss the problem of measurement of the output states.Comment: RevTex, 26 pages, to appear in Physical Review
Thermal barrier coating life prediction model
The objectives of this program are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, and then to develop and verify life prediction models accounting for these degradation modes. The program is divided into two phases, each consisting of several tasks. The work in Phase 1 is aimed at identifying the relative importance of the various failure modes, and developing and verifying life prediction model(s) for the predominant model for a thermal barrier coating system. Two possible predominant failure mechanisms being evaluated are bond coat oxidation and bond coat creep. The work in Phase 2 will develop design-capable, causal, life prediction models for thermomechanical and thermochemical failure modes, and for the exceptional conditions of foreign object damage and erosion
Purification and correlated measurements of bipartite mixed states
We prove that all purifications of a non-factorable state (i.e., the state
which cannot be expressed in a form ) are
entangled. We also show that for any bipartite state there exists a pair of
measurements which are correlated on this state if and only if the state is
non-factorable.Comment: 4 revtex pages, to appear in Phys. Rev.
Entanglement of coherent states and decoherence
A possibility to produce entangled superpositions of strong coherent states
is discussed. A recent proposal by Howell and Yazell [Phys. Rev. A 62, 012102
(2000)] of a device which entangles two strong coherent coherent states is
critically examined. A serious flaw in their design is found. New modified
scheme is proposed and it is shown that it really can generate non-classical
states that can violate Bell inequality. Moreover, a profound analysis of the
effect of losses and decoherence on the degree of entanglement is accomplished.
It reveals the high sensitivity of the device to any disturbances and the
fragility of generated states
Noise-free scattering of the quantized electromagnetic field from a dispersive linear dielectric
We study the scattering of the quantized electromagnetic field from a linear,
dispersive dielectric using the scattering formalism for quantum fields. The
medium is modeled as a collection of harmonic oscillators with a number of
distinct resonance frequencies. This model corresponds to the Sellmeir
expansion, which is widely used to describe experimental data for real
dispersive media. The integral equation for the interpolating field in terms of
the in field is solved and the solution used to find the out field. The
relation between the in and out creation and annihilation operators is found
which allows one to calculate the S-matrix for this system. In this model, we
find that there are absorption bands, but the input-output relations are
completely unitary. No additional quantum noise terms are required.Comment: Revtex, submitted to Physical Review
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