633,225 research outputs found

    Turbulent skin-friction drag reduction by travelling waves induced by spanwise Lorentz force

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    The streamwise and spanwise travelling waves induced by spanwise Lorentz force are studied for skin-friction drag reduction in a turbulent channel. The streamwise travelling wave by spanwise Lorentz force on drag reduction is compared to the with the spanwise wall motion. The drag reduction map shows a drag reduction region and a drag increase region, depending on a time scale T=λ/(Ucω/κ)\mathscr{T}=\lambda/(\mathscr{U}_c-\omega/\kappa). For spanwise travelling wave, a large drag reduction appears at large oscillation frequencies and small spanwise wave numbers, while all stationary wave cases give a drag increase. When the wave travels at an oblique angle to the streamwise mean flow, the optimal drag reduction appears in backward travelling wave case. Generally, the backward streamwise travelling wave is found to be most efficient in drag reduction among all oblique travelling waves. Spanwise oscillation, forward streamwise travelling, spanwise travelling and backward streamwise travelling wave cases share a similar drag reduction mechanism: first, the spanwise motion directly breaks the near wall quasi-streamwise vortices structure array \cite{Jeong_etal1997}, which results in the shortening of streamwise streaks; second, the spanwise velocity layer maintains the asymmetry of the positive and negative quasi-streamwise vortices, which leads to a sustained drag reduction

    Conférence de M. Su-Min Ri

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    Ri Su-Min. Conférence de M. Su-Min Ri. In: École pratique des hautes études, Section des sciences religieuses. Annuaire. Tome 98, 1989-1990. 1989. pp. 340-342

    Su Ürünlerinin İnsanlara Olan Zararları

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    Su ürünleri, insanlarýn besin gereksinimi karþýlamasý-nýn yanýnda birçok saðlýk sorununun çözümü için de yararlandýklarý önemli kaynaklar arasýndadýr. Ancak su ürünleri bu yararlarýnýn yanýnda, bazý türlerinin saldýrýcý ve yýrtýcý, bazýlarýnýn elektriki organlara sahip ve diðer birgrup ise fanerotoksik (açýk zehirli) ya da kriptotoksik (gizli zehirli) o l u þ u y l a i n s a n s a ð l ý ð ý n ý n bozulmasýna ve hatta hayatýnýn s o n l a n m a s ý n a n e d e n olabilmektedirler. Bu çalýþma da insanlar için tehlikeli oluþturabilen su ürünleri tanýtýlarak, insanlara olan etkileri üzerinde durulmaktadýr

    Non-perturbative thermodynamics of SU (N) gauge theories

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    Engels J, Fingberg J, Karsch F, Miller D, Weber M. Non-perturbative thermodynamics of SU (N) gauge theories. Physics Letters, B. 1990;252(4):625-630.The pressure near the deconfinement transition as determined up to now in lattice gauge theories shows unphysical behaviour: it can become negative and may in SU (3) even have a gap at the transition. This has been attributed to the use of only perturbatively known derivatives of coupling constants. We propose a method to evaluate the pressure, which works without these derivatives, and is valid on large lattices. In SU (2) we study the finite-volume effects and show that for lattices with spatial extent N-sigma greater-than-or-similar-to 15 these effects are negligible. In SU (3) we then ontain a postive and continuous pressure. The influence of non-perturbative corrections to the beta-function on the energy density are investigated and found to be important, in particular for the latent heat

    Dr. Duane M. Jackson, Morehouse College, July 2011

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    This video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer

    "Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.

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    "Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states. By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement. To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
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