Analytical models of a fault-tolerant multiple module microprocessor system

Imperial Users onl

Airfoil noise reductions through leading edge serrations

This paper provides an experimental investigation into the use of leading edge (LE) serrations as a means of reducing the broadband noise generated due to the interaction between the aerofoil's LE and impinging turbulence. Experiments are performed on a flat plate in an open jet wind tunnel. Grids are used to generate isotropic homogeneous turbulence. The leading edge serrations are in the form of sinusoidal profiles of wavelengths, λ, and amplitudes, 2h. The frequency and amplitude characteristics are studied in detail in order to understand the effect of LE serrations on noise reduction characteristics and are compared with straight edge baseline flat plates. Noise reductions are found to be insignificant at low frequencies but significant in the mid frequency range (500 Hz-8 kHz) for all the cases studied. The flat plate results are also compared to the noise reductions obtained on a serrated NACA-65 aerofoil with the same serration profile. Noise reductions are found to be significantly higher for the flat plates with a maximum noise reduction of around 9 dB compared with about 7 dB for the aerofoil. In general, it is observed that the sound power reduction level (ΔPWL) is sensitive to the amplitude, 2h of the LE serrations but less sensitive to the serration wavelength, λ. Thus, this paper sufficiently demonstrates that the LE amplitude acts as a key parameter for enhancing the noise reduction levels in flat plates and aerofoils

Temperature Dependence of Gluon and Ghost Propagators in Landau-Gauge Yang-Mills Theory below the Phase Transition

The Dyson-Schwinger equations of Landau-gauge Yang-Mills theory for the gluon and ghost propagators are investigated. Numerical results are obtained within a truncation scheme which has proven to be successful at vanishing temperature. For temperatures up to 250 MeV we find only minor quantitative changes in the infrared behaviour of the gluon and ghost propagators. The effective action calculated from these propagators is temperature-independent within the numerical uncertainty.Comment: 9 pages, 14 figures, submitted to EPJ C, typos corrected, reference and 2 minor clarifications added, in v3: one paragraph extended, some references added, version to appear in EPJ

Experimental and Numerical Simulation of the Microcrack Coalescence Mechanism in Rock-Like Material

Скальные породы и скалоподобные материалы часто разрушаются при сжатии вследствие инициирования, распространения и слияния ранее возникших микротрещин. Выполнены экспериментальные и численные исследования механизма процесса слияния микротрещин в материалах типа скальных пород. Экспериментальные исследования включают в себя испытания на одноосное сжатие образцов, изготовленных из смеси цемента марки портланд пуццолан, слюды и воды..Скельні породи і скелеподібні матеріали часто руйнуються при стисненні внаслідок ініціювання, поширення і злиття мікротріщин, що з’явилися раніше. Виконано експериментальні і числові дослідження механізму процесу злиття мікротріщин у матеріалах типу скельних порід. Експериментальні дослідження включають випробування на одновісний стиск зразків, виготовлених із суміші цементу марки портланд пуцолан, слюди і води

Determining lymphocyte radiosensitivity of healthy individuals and prostate cancer patients using premature chromosome condensation

Background and purpose: Cytogenetic tests are used to assess the individual�s radiosensitivity and the potential to develop cancerous diseases. Our aim was to assess the radiosensitivity of patients with prostate cancer and healthy individuals based on Premature Chromosome Condensation (PCC). Materials and methods: 3.5 ml blood was collected from peripheral veins of 10 healthy individuals and 10 patients with prostate cancer and put into 7 sterile microtubes. All samples, except the controls, were irradiated to 6MV beams of a Siemens LINAC at different doses (0.25, 0.5, 1, 2, 4 and 6 Gy). Chemical PCC test was performed on each sample and the prepared slides were scored. The Kruskal-Wallis non-parametric ANOVA and Mann-Whitney statistical tests were used to compare the chromosomal aberrations resulted from different dose levels in each group (healthy/cancerous), and identical doses resulted from the two groups, respectively. Results: There was a significant correlation between irradiation dose (for doses �0.5 Gy) and the rings in both of the healthy and prostate cancer patients indicating an increase in the number of rings with dose escalation (P<0.05). Comparing healthy individuals and cancerous patients revealed no significant difference in their ring number at the same level of radiation doses (P= 0.784). Conclusion: In theory, PCC test should be capable of determining more chromosomal aberrations than dicentric test, so, if the FISH test is used simultaneously, we might be able to score dicentrics and other fragments. By these, it may also be possible to better differentiate the radiosensitivity of healthy individuals and prostate cancer patients. © 2016, Mazandaran University of Medical Sciences. All rights reserved

Gauge covariance and the fermion-photon vertex in three- and four- dimensional, massless quantum electrodynamics

In the quenched approximation, the gauge covariance properties of three vertex Ans\"{a}tze in the Schwinger-Dyson equation for the fermion self energy are analysed in three- and four- dimensional quantum electrodynamics. Based on the Cornwall-Jackiw-Tomboulis effective action, it is inferred that the spectral representation used for the vertex in the gauge technique cannot support dynamical chiral symmetry breaking. A criterion for establishing whether a given Ansatz can confer gauge covariance upon the Schwinger-Dyson equation is presented and the Curtis and Pennington Ansatz is shown to satisfy this constraint. We obtain an analytic solution of the Schwinger-Dyson equation for quenched, massless three-dimensional quantum electrodynamics for arbitrary values of the gauge parameter in the absence of dynamical chiral symmetry breaking.Comment: 17 pages, PHY-7143-TH-93, REVTE

Window on Higgs Boson: Fourth Generation b′b^\prime Decays Revisited

Direct and indirect searches of the Higgs boson suggest that 113 GeV $\lesssim m_H \lesssim$ 170 GeV is likely. With the LEP era over and the Tevatron Run II search via $p\bar p \to WH+X$ arduous, we revisit a case where $WH$ or $ZH +$ jets could arise via strong $b^\prime\bar b^\prime$ pair production. In contrast to 10 years ago, the tight electroweak constraint on $t^\prime$--$b^\prime$ (hence $t^\prime$--$t$) splitting reduces FCNC $b^\prime\to bZ$, $bH$ rates, making $b^\prime\to cW$ naturally competitive. Such a "cocktail solution" is precisely the mix that could evade the CDF search for $b^\prime\to bZ$, and the $b^\prime$ may well be lurking below the top. In light of the Higgs program, this two-in-one strategy should be pursued.Comment: 4 pages, RevTex, 4 eps figures, One more figure, version to be published in Phys. Rev.