1,153 research outputs found
Engine panel seals for hypersonic engine applications: High temperature leakage assessments and flow modelling
A critical mechanical system in advanced hypersonic engines is the panel-edge seal system that seals gaps between the articulating horizontal engine panels and the adjacent engine splitter walls. Significant advancements in seal technology are required to meet the extreme demands placed on the seals, including the simultaneous requirements of low leakage, conformable, high temperature, high pressure, sliding operation. In this investigation, the seal concept design and development of two new seal classes that show promise of meeting these demands will be presented. These seals include the ceramic wafer seal and the braided ceramic rope seal. Presented are key elements of leakage flow models for each of these seal types. Flow models such as these help designers to predict performance-robbing parasitic losses past the seals, and estimate purge coolant flow rates. Comparisons are made between measured and predicted leakage rates over a wide range of engine simulated temperatures and pressures, showing good agreement
Collapses and revivals of exciton emission in a semiconductor microcavity: detuning and phase-space filling effects
We investigate exciton emission of quantum well embedded in a semiconductor
microcavity. The analytical expressions of the light intensity for the cases of
excitonic number state and coherent state are presented by using secular
approximation. Our results show that the effective exciton-exciton interaction
leads to the appearance of collapse and revival of the light intensity. The
revival time is twice compared the coherent state case with that of the number
state. The dissipation of the exciton-polariton lowers the revival amplitude
but does not alter the revival time. The influences of the detuning and the
phase-space filling are studied. We find that the effect of the higher-order
exciton-photon interaction may be removed by adjusting the detuning.Comment: 7 pages, 3 figure
Experimental Decoy Quantum Key Distribution Up To 130KM Fiber
Decoy State Quantum Key Distribution (QKD), being capable of beating PNS
attack and uncon- ditionally secure, have become an attractive one recently.
But, in many QKD systems, disturbances of transmission channel make quantum bit
error rate (QBER) increase which limits both security distance and key bit rate
of real-life decoy state QKD systems. We demonstrate the two-intensity decoy
QKD with one-way Faraday-Michelson phase modulation system, which is free of
channel dis- turbance and keeps interference fringe visibility (99%) long
period, near 130KM single mode optical fiber in telecom (1550 nm) wavelength.
This is longest distance fiber decoy state QKD system based on two intensity
protocol.Comment: 4 pages, 2figure
Gravitational Anomaly and Hawking Radiation of Brane World Black Holes
We apply Wilczek and his collaborators' anomaly cancellation approach to the
3-dimensional Schwarzschild- and BTZ-like brane world black holes induced by
the generalized C metrics in the Randall-Sundrum scenario. Based on the fact
that the horizon of brane world black hole will extend into the bulk spacetime,
we do the calculation from the bulk generalized C metrics side and show that
this approach also reproduces the correct Hawking radiation for these brane
world black holes. Besides, since this approach does not involve the dynamical
equation, it also shows that the Hawking radiation is only a kinematic effect.Comment: 11 pages. v2: minor changes and references adde
From the Complete Yang Model to Snyder's Model, de Sitter Special Relativity and Their Duality
By means of Dirac procedure, we re-examine Yang's quantized space-time model,
its relation to Snyder's model, the de Sitter special relativity and their
UV-IR duality. Starting from a dimensionless dS_5-space in a 5+1-d Mink-space a
complete Yang model at both classical and quantum level can be presented and
there really exist Snyder's model, the dS special relativity and the duality.Comment: 7 papge
Three Kinds of Special Relativity via Inverse Wick Rotation
Since the special relativity can be viewed as the physics in an inverse Wick
rotation of 4-d Euclid space, which is at almost equal footing with the 4-d
Riemann/Lobachevski space, there should be important physics in the inverse
Wick rotation of 4-d Riemann/Lobachevski space. Thus, there are three kinds of
special relativity in de Sitter/Minkowski/anti-de Sitter space at almost equal
footing, respectively. There is an instanton tunnelling scenario in the
Riemann-de Sitter case that may explain why \La be positive and link with the
multiverse.Comment: 3 pages, no figures, to appear in Chin. Phys. Let
Bosonization and phase Diagram of the one-dimensional t-J model
We present an analytic study of the phase diagram of the one-dimensional t-J
model and a couple of its cousins. To deal with the interactions induced by the
no double occupancy constraints, we introduce a deformation of the Hubbard
operators. When the deformation parameter is small, the induced
interactions are softened, accessible by perturbation theory. We combine
bososnization with renormalization group techniques to map out the phase
diagram of the system. We argue that when , there is no essential
change in the phase diagram. Comparison with the existing results in the
literature obtained by other methods justifies our deformation approach.Comment: 24 pages, 1 Figur
Global Synchronization of Neutral-Type Stochastic Delayed Complex Networks
This paper is concerned with the delay-dependent synchronization criterion for neutral-type stochastic delayed complex networks. Firstly, expectations of stochastic crossterms containing the ItĂ´ integral are investigated. In fact, for stochastic delay systems, if we want to obtain the delay-dependent condition with less conservatism, how to deal with expectations of stochastic cross terms properly is of vital importance, and many existing results did not deal with expectations of these stochastic cross terms correctly. Then, based on this, this paper establishes a novel delay-dependent synchronization criterion for neutral-type stochastic delayed complex networks. In the derivation process, the mathematical development avoids bounding stochastic cross terms. Thus, this method shows less conservatism. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed approach
Effect of non-phytate phosphorus levels and phytase sources on the growth performance, serum biochemical and tibial parameters of broiler chickens
A 3Ă—3 fattorial arrangement with dietary non-phytate phosphorus (NPP) levels and phytase sources (3- and 6-phytase) was conducted to evaluate the effects of NPP levels, phytase sources and their possible interactions on growth performance, serum biochemical and tibia parameters of broiler chickens from hatch to 42 days of age. A total of 540 1-day-old Arbor Acres male broiler chicks were randomly allocated into nine dietary treatments, each containing 5 replicates pens with 12 birds per pen. Interaction was statistically significant in the performance till day 21 of trial, supplementation of low NPP diet decreased body weight (BW) (P<0.001), depressed average daily gain (ADG) (P<0.001) and deteriorated average daily feed intake (ADFI) (P<0.001) over day 42. During the 8-to-21-day period, even if interaction between NPP levels and phytase sources was significant (P<0.01), BW, ADG and ADFI always increased due to dietary supplementation of phytase, with source not differing. Dietary high NPP enhanced serum calcium and P concentrations on day 21 and 42 (linear contrast, P<0.01), while decreased alkaline phosphatase (AKP) activity on day 42 (linear contrast, P<0.001), and interaction was not significant. Both dietary sources of phytase decreased serum AKP activities on day 42 (P<0.001), and urea nitrogen content on day 21 (P<0.01) and 42 (P<0.001). Both phytase improved ash percentage on day 21 and P content in tibia at 21 and 42 days of age (P<0.001). The results confirmed that dietary supplementation of phytase may enhance P availability during the 8-to-21-day period. Nevertheless, no difference between the two phytase sources was observed
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