1,448 research outputs found
Sharp-crested weirs
No full textPresented at SCADA and related technologies for irrigation district modernization: a USCID water management conference on October 26-29, 2005 in Vancouver, Washington.Real-time flow measurement and monitoring are important components of modern irrigation SCADA systems. Many projects have existing sharp-crested weir structures that have not been incorporated into SCADA systems because they are partially contracted, and thus do not have a simple rating equation relationship. The Kindsvater-Carter procedure for calibrating partially contracted sharp-crested weirs is accurate and straightforward, but also somewhat tedious. Existing computer programs simplify the process but can presently be applied only to individual measurements. This paper presents a Microsoft® Excel spreadsheet model that can compute complete rating tables for sharp-crested weirs with full or partial flow contraction, using the Kindsvater-Carter procedure. Furthermore, through regression analysis, the spreadsheet determines a simplified rating equation that can easily be incorporated into remote terminal units (RTUs) and SCADA systems. The spreadsheet can be applied to fully contracted V-notch weirs with included angles of 25° to 100°, partially or fully contracted 90° V-notch weirs, partially or fully contracted rectangular weirs (including suppressed rectangular weirs), and fully contracted Cipoletti weirs
Sharp tridiagonal pairs
No full textAbstractLet K denote a field and let V denote a vector space over K with finite positive dimension. We consider a pair of K-linear transformations A:V→V and A∗:V→V that satisfies the following conditions: (i) each of A,A∗ is diagonalizable; (ii) there exists an ordering {Vi}i=0d of the eigenspaces of A such that A∗Vi⊆Vi-1+Vi+Vi+1 for 0⩽i⩽d, where V-1=0 and Vd+1=0; (iii) there exists an ordering {Vi∗}i=0δ of the eigenspaces of A∗ such that AVi∗⊆Vi-1∗+Vi∗+Vi+1∗ for 0⩽i⩽δ, where V-1∗=0 and Vδ+1∗=0; (iv) there is no subspace W of V such that AW⊆W, A∗W⊆W, W≠0, W≠V. We call such a pair a tridiagonal pair on V. It is known that d=δ and for 0⩽i⩽d the dimensions of Vi,Vd-i,Vi∗,Vd-i∗ coincide. We say the pair A,A∗ is sharp whenever dimV0=1. A conjecture of Tatsuro Ito and the second author states that if K is algebraically closed then A,A∗ is sharp. In order to better understand and eventually prove the conjecture, in this paper we begin a systematic study of the sharp tridiagonal pairs. Our results are summarized as follows. Assuming A,A∗ is sharp and using the data Φ=(A;{Vi}i=0d;A∗;{Vi∗}i=0d) we define a finite sequence of scalars called the parameter array. We display some equations that show the geometric significance of the parameter array. We show how the parameter array is affected if Φ is replaced by (A∗;{Vi∗}i=0d;A;{Vi}i=0d) or (A;{Vd-i}i=0d;A∗;{Vi∗}i=0d)or (A;{Vi}i=0d;A∗;{Vd-i∗}i=0d). We prove that if the isomorphism class of Φ is determined by the parameter array then there exists a nondegenerate symmetric bilinear form 〈,〉 on V such that 〈Au,v〉=〈u,Av〉 and 〈A∗u,v〉=〈u,A∗v〉 for all u,v∈V
On the base pressure of 3D turbulent bluff body wakes with sharp separation
No full textParticle Image Velocimetry (PIV) and pressure measurements are used to study the turbulent wake of Ahmed bluff body. A cavity on the base is created to control the base pressure and modify the recirculating bubble and its equilibrium
Sharp-interface limit of the Allen-Cahn action functional in one space dimension
No full textWe analyze the sharp-interface limit of the action minimization problem for the stochastically perturbed Allen-Cahn equation in one space dimension. The action is a deterministic functional which is linked to the behavior of the stochastic process in the small noise limit. Previously, heuristic arguments and numerical results have suggested that the limiting action should “count” two competing costs: the cost to nucleate interfaces and the cost to propagate them. In addition, constructions have been used to derive an upper bound for the minimal action which was proved optimal on the level of scaling. In this paper, we prove that for d = 1, the upper bound achieved by the constructions is in fact sharp. Furthermore, we derive a lower bound for the functional itself, which is in agreement with the heuristic picture. To do so, we characterize the sharp-interface limit of the space-time energy measures. The proof relies on an extension of earlier results for the related elliptic problem
Oncometabolite induced primary cilia loss in pheochromocytoma
No full textBarts and the London Charity Clinical Research Training Fellowships to Samuel M. O’Toole [grant number MRD0191]; Medical Research Council (MRC) [grant number MR/L002876/1].
UK Biotechnology and Biological Sciences Research Council (BBSRC) [grant
503 number BB/M0020611] and MRC [grant number MR/N009185/1] to Dr Tyson V. Shar
Sharp Estimates in Smoothing Theorems for Schrödinger Semigroups
No full textAbstractThe smoothing properties of Schrödinger semigroups, e−tH, H=−12Δ+V, on the scale of Bessel potential spaces Lp, α are studied. We strengthen the (Lp−Lp, α)-smoothing theorem due to M. A. Kon and the author. The new version of this theorem contains a sharp time-estimate for the norm of the semigroup e−tH. We also get an estimate for the constants arising in the form-boundedness inequality for the Kato class potentials
Random matrices and random boxes
No full textThis thesis concerns two questions on random structures: the semi-circular law for adjacency matrix of regular random graph and the piercing number for random boxes. Random matrices: We proved in full generality the semi-circular law for random d-regular graph model in the case d tends to infinity as n does. Our result complements the McKay law [19], which applied for the case d is an absolute constant. Random boxes. Take n random boxes with axis-parallel edges inside the unit cube [0; 1][superscript]d, the piercing number is the minimum number of points needed to pierce all boxes. Using hypergraph setting, we was able to prove a near sharp estimation for the piercing number. This thesis is based on two papers by the author [31] and [30] (joint work with Van Vu and Ke Wang).Ph.D.Includes bibliographical referencesIncludes vitaby Linh V. Tra
A subaltern critical geopolitics of the war on terror: postcolonial security in Tanzania
No full textCurrently, hegemonic geographical imaginations are dominated by the affective geopolitics of the War on Terror, and related security practice is universalised into what has been called ‘‘globalized fear’’ (Pain, 2009). Critical approaches to geopolitics have been attentive to the Westerncentric nature of this imaginary, however, studies of non-Western perceptions of current geopolitics and the nature of fear will help to further displace dominant geopolitical imaginations. Africa, for example, is a continent that is often captured in Western geopolitics – as a site of failed states, the coming anarchy, passive recipient of aid, and so on – but geopolitical representations originating in Africa rarely make much of an impact on political theory.
This paper aims to add to critical work on the so-called War on Terror from a perspective emerging from the margins of the dominant geopolitical imagination. It considers the geopolitical imagination of the War on Terror from a non-Western source, newspapers in Tanzania
Sharp bound on the truncated metric dimension of trees
No full textA k-truncated resolving set of a graph is a subset S⊆V of its vertex set such that the vector (dk(s,v))s∈S is distinct for each vertex v∈V where dk(x,y)=min{d(x,y),k+1} is the graph distance truncated at k+1. We think of elements of a k-truncated resolving set as sensors that can measure up to distance k. The k-truncated metric dimension (Tmdk) of a graph G is the minimum cardinality of a k-truncated resolving set of G. We give a sharp lower bound on Tmdk for any tree T in terms of its number of vertices |T| and the measuring radius k. Our result is that Tmdk(T)≥|T|⋅3/(k2+4k+3+1{k≡1(mod3)})+ck, disproving earlier conjectures by Frongillo et al. that suspected |T|/(⌊k2/4⌋+2k)+ck′ as general lower bound, where ck, ck′ are k-dependent constants. We provide a construction for trees with the largest number of vertices with a given Tmdk value. The proof that our optimal construction cannot be improved relies on edge-rewiring procedures of arbitrary (suboptimal) trees with arbitrary resolving sets, which reveal the structure of how small subsets of sensors measure and resolve certain areas in the tree that we call the attraction of those sensors. The notion of ‘attraction of sensors’ might be useful in other contexts beyond trees to solve related problems. We also provide an improved lower bound on Tmdk of arbitrary trees that takes into account the structural properties of the tree, in particular, the number and length of simple paths of degree-two vertices terminating in leaf vertices. This bound complements the result of the above-mentioned work of Frongillo et al., where only trees without degree-two vertices were considered, except the simple case of a single path.</p
Direct numerical simulation of turbulent Taylor-Couette flow with grooved walls
No full textWe present direct numerical simulations of Taylor-Couette flow with grooved walls up to inner cylinder Reynolds number of , corresponding to Taylor number of . The simulations are performed at a fixed radius ratio . The grooves are axisymmetric V-shaped obstacles attached to the wall with a tip angle of . Results are compared with the smooth wall case in order to investigate the effects of the grooved walls. In particular, we focus on the effective scaling laws for torque, boundary layers and flow structures. With increasing , the boundary layer thickness finally becomes smaller than the groove height. When this happens, the plumes are ejected from tips of the grooves and a secondary circulation between the grooves is formed. This is associated with a sharp increase of the torque and thus the effective scaling law for the torque becomes much steeper. Further increasing does not result in an additional slope increases. Instead, the effective scaling law saturates to the same ``ultimate'' regime effective exponents seen for smooth walls
- …
