1,293 research outputs found
Large-time behavior of the weak solution to 3D Navier-Stokes equations
No full textThe weak solution to the Navier–Stokes equations in a bounded domain D ⊂ R[superscript 3] with a smooth boundary is proved to be unique provided that it satisfies an additional requirement. This solution exists for all t ≥ 0. In a bounded domain D the solution decays exponentially
fast as t → ∞if the force term decays at a suitable rat
James Earl Ray, convicted for the assassination of Reverend Dr. Martin Luther King Jr., testifies before the House Select Committee on Assassinations, day two
No full textJames Earl Ray, convicted for the assassination of Reverend Dr. Martin Luther King Jr., testifies before the House Select Committee on Assassinations on the second of three days of hearings. Mark Lane, Ray's attorney, accuses the committee of switching documents. G. Robert Blakey comments on the delivery of paperwork to Mark Lane on the previous day. Louis Stokes (D-OH), Chairman of the Committee, questions Ray about the second rifle Ray purchased. Ray discusses his various aliases and says he knew almost nothing about King and that he was unaware King was staying in Camden. Stokes questions Ray on his location at the time of King's murder. Stokes reads from Memphis newspapers telling of King's intended itinerary and Ray claims to have been unaware of the papers' contents. Ray answers questions from Floyd Fithian (D-IN), about Ray's escape from the Missouri prison and his flight to Canada. Technical interruption of the broadcast signal at 4:34:38 until 4:35:14
Optical-phonon resonances with saddle-point excitons in twisted-bilayer graphene
No full textTwisted-bilayer graphene (tBLG) exhibits van Hove singularities in the density of states that can be tuned by changing the twisting angle θ. A θ-defined tBLG has been produced and characterized with optical reflectivity and resonance Raman scattering. The θ-engineered optical response is shown to be consistent with persistent saddle-point excitons. Separate resonances with Stokes and anti-Stokes Raman scattering components can be achieved due to the sharpness of the two-dimensional saddle-point excitons, similar to what has been previously observed for one-dimensional carbon nanotubes. The excitation power dependence for the Stokes and anti-Stokes emissions indicate that the two processes are correlated and that they share the same phonon
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
On the adaptive selection of the parameter in stabilized finite element approximations
No full textA systematic approach is developed for the selection of the stabilization parameter for stabilized finite element approximation of the Stokes problem, whereby the parameter is chosen to minimize a computable upper bound for the error in the approximation. The approach is applied in the context of both a single fixed mesh and an adaptive mesh refinement procedure. The optimization is carried out by a derivative-free optimization algorithm and is based on minimizing a new fully computable error estimator. Numerical results are presented illustrating the theory and the performance of the estimator, together with the optimization algorith
Aberrant functional connectivity in dissociable hippocampal networks is associated with deficits in memory.
No full textIn the healthy human brain, evidence for dissociable memory networks along the anterior-posterior axis of the hippocampus suggests that this structure may not function as a unitary entity. Failure to consider these functional divisions may explain diverging results among studies of memory adaptation in disease. Using task-based and resting functional MRI, we show that chronic seizures disrupting the anterior medial temporal lobe (MTL) preserve anterior and posterior hippocampal-cortical dissociations, but alter signaling between these and other key brain regions. During performance of a memory encoding task, we found reduced neural activity in human patients with unilateral temporal lobe epilepsy relative to age-matched healthy controls, but no upregulation of fMRI signal in unaffected hippocampal subregions. Instead, patients showed aberrant resting fMRI connectivity within anterior and posterior hippocampal-cortical networks, which was associated with memory decline, distinguishing memory-intact from memory-impaired patients. Our results highlight a critical role for intact hippocampo-cortical functional communication in memory and provide evidence that chronic injury-induced functional reorganization in the diseased MTL is behavioral inefficient
On the role of the helicity in the energy transfer in three-dimensional turbulence
No full textBehavior of the turbulent flows could be changed by changing the nature of the external force or the confining geometry which essentially results in breaking some of the symmetries of the ideal homogeneous and isotropic flows. In a numerical simulation, however, it is possible to selectively break symmetries of the Navier-Stokes equations with other constraints like helicity. In a recent [1] simulation of a decimated version of the incompressible three dimensional Navier-Stokes equations, where helicity was maintained sign-definite using a helical projection, a reversal of energy cascade similar to two-dimensional Navier-Stokes equations was observed. The sign- definite helicity breaks the parity symmetry of the flow. It is one of the important symmetries of the flow that contributes to the forward energy cascade in three dimensional Navier-Stokes equations. In our study we measure the degree to which the parity symmetry controls the direction of the cascade. We introduce a mechanism in which the parity is broken stochastically but in a time frozen manner with helical constraints. We keep triadic interactions in Fourier space involving modes with definite sign of helicity and decimate the triads of other modes with opposite sign of helicity with a fixed probability. We studied the cascade of energy in three dimensional turbulence by changing the relative weight between positive and negative helicity modes. We present the results from our recent simulations
Strong solutions for the Navier–Stokes–Voigt equations with non-negative density
No full textThe aim of this work is to study the Navier–Stokes–Voigt equations that govern flows with non-negative density of incompressible fluids with elastic properties. For the associated nonlinear initial-and boundary-value problem, we prove the global-in-time existence of strong solutions (velocity, density and pressure). We also establish some other regularity properties of these solutions and find the conditions that guarantee the uniqueness of velocity and density. The main novelty of this work is the hypothesis that, in some subdomain of space, there may be a vacuum at the initial moment, that is, the possibility of the initial density vanishing in some part of the space domain.All authors were supported by the Grant No. AP19676624 Ministry of Science and Higher Education of the Republic of Kazakhstan
(Kazakhstan). The first author was also partially supported by CIDMA under the Portuguese Foundation for Science and Technology MultiAnnual Financing Program for R & D Units (FCT, https://ror.org/00snfqn58).publishe
A lattice model for the Eulerian secription of heavy particles suspensions in one and two dimensions
No full textModeling of heavy particles motion in turbulent flows still represents a challenge in engineering applications at high Reynolds number. Various techniques have arisen for describing such mono-dispersed solid phases with statistical methods. Some of those techniques relies on the assumption of using a velocity field to describe the particles motion, which is valid at small Stokes number, others using large-eddy simulations, or using one and two-points probability density functions in Gaussian flows. Here we present another method based on a lattice discretization of the phase space in one and two dimensions for a synthetic flow in one dimension and a turbulent flow in two dimensions for the description of a dilute solid phase in the case of a Stokes coupling between the particles and the fluid and a brownian diffusion. This method is suited for any Stokes numbers in the limit of numerical stability and shows a good agreement with the Lagrangian particles statistics like radial distribution functions and collision rates
- …
