Asymptotic theory of two-dimensional trailing-edge flows

Problems of laminar and turbulent viscous interaction near trailing edges of streamlined bodies are considered. Asymptotic expansions of the Navier-Stokes equations in the limit of large Reynolds numbers are used to describe the local solution near the trailing edge of cusped or nearly cusped airfoils at small angles of attack in compressible flow. A complicated inverse iterative procedure, involving finite-difference solutions of the triple-deck equations coupled with asymptotic solutions of the boundary values, is used to accurately solve the viscous interaction problem. Results are given for the correction to the boundary-layer solution for drag of a finite flat plate at zero angle of attack and for the viscous correction to the lift of an airfoil at incidence. A rational asymptotic theory is developed for treating turbulent interactions near trailing edges and is shown to lead to a multilayer structure of turbulent boundary layers. The flow over most of the boundary layer is described by a Lighthill model of inviscid rotational flow. The main features of the model are discussed and a sample solution for the skin friction is obtained and compared with the data of Schubauer and Klebanoff for a turbulent flow in a moderately large adverse pressure gradient

Large NcN_c Universality of The Baryon Isgur--Wise Form Factor: The Group Theoretical Approach

In a previous article, it has been proved under the framework of chiral soliton model that the same Isgur--Wise form factor describes the semileptonic $\Lambda_b\to\Lambda_c$ and $\Sigma^{(*)}_b\to\Sigma^{(*)}_c$ decays in the large $N_c$ limit. It is shown here that this result is in fact independent of the chiral soliton model and is solely the consequence of the spin-flavor SU(4) symmetry which arises in the baryon sector in the large $N_c$ limit.Comment: 10 pages in REVTeX, no figure

Finite Element Solution of Axisymmetrical Dynamic Problems of Shells of Revolution

Finite element solution for natural frequencies and mode shapes of free axisymmetrical vibrations and dynamic response of arbitrary rotationally symmetric shell

Local transient rheological behavior of concentrated suspensions

This paper reports experiments on the shear transient response of concentrated non-Brownian suspensions. The shear viscosity of the suspensions is measured using a wide-gap Couette rheometer equipped with a Particle Image Velocimetry (PIV) device that allows measuring the velocity field. The suspensions made of PMMA particles (31$\mu$m in diameter) suspended in a Newtonian index- and density-matched liquid are transparent enough to allow an accurate measurement of the local velocity for particle concentrations as high as 50%. In the wide-gap Couette cell, the shear induced particle migration is evidenced by the measurement of the time evolution of the flow profile. A peculiar radial zone in the gap is identified where the viscosity remains constant. At this special location, the local particle volume fraction is taken to be the mean particle concentration. The local shear transient response of the suspensions when the shear flow is reversed is measured at this point where the particle volume fraction is well defined. The local rheological measurements presented here confirm the macroscopic measurements of Gadala-Maria and Acrivos (1980). After shear reversal, the viscosity undergoes a step-like reduction, decreases slower and passes through a minimum before increasing again to reach a plateau. Upon varying the particle concentration, we have been able to show that the minimum and the plateau viscosities do not obey the same scaling law with respect to the particle volume fraction. These experimental results are consistent with the scaling predicted by Mills and Snabre (2009) and with the results of numerical simulation performed on random suspensions [Sierou and Brady (2001)]. The minimum seems to be associated with the viscosity of an isotropic suspension, or at least of a suspension whose particles do not interact through non-hydrodynamic forces, while the plateau value would correspond to the viscosity of a suspension structured by the shear where the non-hydrodynamic forces play a crucial role

Automated Big Text Security Classification

In recent years, traditional cybersecurity safeguards have proven ineffective against insider threats. Famous cases of sensitive information leaks caused by insiders, including the WikiLeaks release of diplomatic cables and the Edward Snowden incident, have greatly harmed the U.S. government's relationship with other governments and with its own citizens. Data Leak Prevention (DLP) is a solution for detecting and preventing information leaks from within an organization's network. However, state-of-art DLP detection models are only able to detect very limited types of sensitive information, and research in the field has been hindered due to the lack of available sensitive texts. Many researchers have focused on document-based detection with artificially labeled "confidential documents" for which security labels are assigned to the entire document, when in reality only a portion of the document is sensitive. This type of whole-document based security labeling increases the chances of preventing authorized users from accessing non-sensitive information within sensitive documents. In this paper, we introduce Automated Classification Enabled by Security Similarity (ACESS), a new and innovative detection model that penetrates the complexity of big text security classification/detection. To analyze the ACESS system, we constructed a novel dataset, containing formerly classified paragraphs from diplomatic cables made public by the WikiLeaks organization. To our knowledge this paper is the first to analyze a dataset that contains actual formerly sensitive information annotated at paragraph granularity.Comment: Pre-print of Best Paper Award IEEE Intelligence and Security Informatics (ISI) 2016 Manuscrip

Linear and nonlinear optical properties of carbon nanotube-coated single-mode optical fiber gratings

This paper was published in OPTICS LETTERS and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OL.36.002104. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law[EN] Single-wall carbon nanotube deposition on the cladding of optical fibers has been carried out to fabricate an all-fiber nonlinear device. Two different nanotube deposition techniques were studied. The first consisted of repeatedly immersing the optical fiber into a nanotube supension, increasing the thickness of the coating in each step. The second deposition involved wrapping a thin film of nanotubes around the optical fiber. For both cases, interaction of transmitted light through the fiber core with the external coating was assisted by the cladding mode resonances of a tilted fiber Bragg grating. Ultrafast nonlinear effects of the nanotube-coated fiber were measured by means of a pump-probe pulses experiment. © 2011 Optical Society of America.This work was financially supported by the European Commission under the FP7 EURO-FOS Network of Excellence (ICT-2007-2-224402), the Ministerio de Educación y Ciencia SINADEC project (TEC2008-06333), and the Natural Sciences and Engineering Research Council of Canada (NSERC). The work of G. E. Villanueva was supported by the Ministerio de Educación y Ciencia Formación de Profesorado Universitario programs. The work of P. Pérez-Millán was supported by the Juan de la Cierva program, JCI-2009-05805.Villanueva Ibáñez, GE.; Jakubinek, M.; Simard, B.; Oton Nieto, CJ.; Matres Abril, J.; Shao, L.; Pérez Millán, P.... (2011). Linear and nonlinear optical properties of carbon nanotube-coated single-mode optical fiber gratings. Optics Letters. 36(11):2104-2106. https://doi.org/10.1364/OL.36.002104S210421063611Sakakibara, Y., Rozhin, A. G., Kataura, H., Achiba, Y., & Tokumoto, M. (2005). Carbon Nanotube-Poly(vinylalcohol) Nanocomposite Film Devices: Applications for Femtosecond Fiber Laser Mode Lockers and Optical Amplifier Noise Suppressors. Japanese Journal of Applied Physics, 44(4A), 1621-1625. doi:10.1143/jjap.44.1621Chow, K. K., Yamashita, S., & Song, Y. W. (2009). A widely tunable wavelength converter based on nonlinear polarization rotation in a carbon-nanotube-deposited D-shaped fiber. Optics Express, 17(9), 7664. doi:10.1364/oe.17.007664Set, S. Y., Yaguchi, H., Tanaka, Y., & Jablonski, M. (2004). Ultrafast Fiber Pulsed Lasers Incorporating Carbon Nanotubes. IEEE Journal of Selected Topics in Quantum Electronics, 10(1), 137-146. doi:10.1109/jstqe.2003.822912Chow, K. K., Tsuji, M., & Yamashita, S. (2010). Single-walled carbon-nanotube-deposited tapered fiber for four-wave mixing based wavelength conversion. Applied Physics Letters, 96(6), 061104. doi:10.1063/1.3304789Chow, K. K., & Yamashita, S. (2009). Four-wave mixing in a single-walled carbon-nanotube-deposited D-shaped fiber and its application in tunable wavelength conversion. Optics Express, 17(18), 15608. doi:10.1364/oe.17.015608Choi, S. Y., Rotermund, F., Jung, H., Oh, K., & Yeom, D.-I. (2009). Femtosecond mode-locked fiber laser employing a hollow optical fiber filled with carbon nanotube dispersion as saturable absorber. Optics Express, 17(24), 21788. doi:10.1364/oe.17.021788Chan, C.-F., Chen, C., Jafari, A., Laronche, A., Thomson, D. J., & Albert, J. (2007). Optical fiber refractometer using narrowband cladding-mode resonance shifts. Applied Optics, 46(7), 1142. doi:10.1364/ao.46.001142Kingston, C. T., Jakubek, Z. J., Dénommée, S., & Simard, B. (2004). Efficient laser synthesis of single-walled carbon nanotubes through laser heating of the condensing vaporization plume. Carbon, 42(8-9), 1657-1664. doi:10.1016/j.carbon.2004.02.020Jakubinek, M. B., Johnson, M. B., White, M. A., Guan, J., & Simard, B. (2010). Novel Method to Produce Single-Walled Carbon Nanotube Films and Their Thermal and Electrical Properties. Journal of Nanoscience and Nanotechnology, 10(12), 8151-8157. doi:10.1166/jnn.2010.3014Vallaitis, T., Koos, C., Bonk, R., Freude, W., Laemmlin, M., Meuer, C., … Leuthold, J. (2008). Slow and fast dynamics of gain and phase in a quantum dot semiconductor optical amplifier. Optics Express, 16(1), 170. doi:10.1364/oe.16.00017

Theory of emission from an active photonic lattice

The emission from a radiating source embedded in a photonic lattice is calculated. The analysis considers the photonic lattice and free space as a combined system. Furthermore, the radiating source and electromagnetic field are quantized. Results show the deviation of the photonic lattice spectrum from the blackbody distribution, with intracavity emission suppressed at certain frequencies and enhanced at others. In the presence of rapid population relaxation, where the photonic lattice and blackbody populations are described by the same equilibrium distribution, it is found that the enhancement does not result in output intensity exceeding that of the blackbody at the same frequency. However, for slow population relaxation, the photonic lattice population has a greater tendency to deviate from thermal equilibrium, resulting in output intensities exceeding those of the blackbody, even for identically pumped structures.Comment: 19 pages, 11 figure