1,161 research outputs found
Genesis of d'Alembert's paradox and analytical elaboration of the drag problem
We show that the issue of the drag exerted by an incompressible fluid on a
body in uniform motion has played a major role in the early development of
fluid dynamics. In 1745 Euler came close, technically, to proving the vanishing
of the drag for a body of arbitrary shape; for this he exploited and
significantly extended existing ideas on decomposing the flow into thin
fillets; he did not however have a correct picture of the global structure of
the flow around a body. Borda in 1766 showed that the principle of live forces
implied the vanishing of the drag and should thus be inapplicable to the
problem. After having at first refused the possibility of a vanishing drag,
d'Alembert in 1768 established the paradox, but only for bodies with a
head-tail symmetry. A full understanding of the paradox, as due to the neglect
of viscous forces, had to wait until the work of Saint-Venant in 1846.Comment: 10 pages, 4 figures, Physica D, in pres
Virtual lines, a deadlock-free and real-time routing mechanism for ATM networks
In this paper, we present a routing mechanism and buffer allocation mechanism for an ATM switching fabric. Since the fabric will be used to transfer multimedia traffic, it should provide a guaranteed throughput and a bounded latency. We focus on the design of a suitable routing mechanism that is capable of fulfilling these requirements and is free of deadlocks. We will describe two basic concepts that can be used to implement deadlock-free routing. Routing of messages is closely related to buffering. We have organized the buffers into parallel FIFO's, each representing a virtual line. In this way, we not only have solved the problem of head of line blocking, but we can also give real-time guarantees. We will show that for local high-speed networks, it is more advantageous to have a proper flow control than to have large buffers. Although the virtual line concept can have a low buffer utilization, the transfer efficiency can be higher. The virtual line concept allows adaptive routing. The total throughput of the network can be improved by using alternative routes. Adaptive routing is attractive in networks where alternative routes are not much longer than the initial route(s). The network of the switching fabric is built up from switching elements interconnected in a Kautz topology
Virtual lines, a deadlock free and real-time routing mechanism for ATM networks
In this paper we present a routing mechanism and buffer allocation mechanism for an ATM switching fabric. Since the fabric will be used to transfer multimedia traffic it should provide a guaranteed throughput and a bounded latency. We focus on the design of a suitable routing mechanism that is capable to fulfil these requirements and is free of deadlocks. We will describe two basic concepts that can be used to implement deadlock free routing. Routing of messages is closely related to buffering. We have organized the buffers into parallel fifos, each representing a virtual line. In this way we not only have solved the problem of Head Of Line blocking, but we can also give real-time guarantees. We will show that for local high-speed networks it is more advantageous to have a proper flow control than to have large buffers. Although the virtual line concept can have a low buffer utilization, the transfer efficiency can be higher. The virtual lines concept allows adaptive routing. The total throughput of the network can be improved by using alternative routes. Adaptive routing is attractive in networks where alternative routes are not much longer than the initial route(s). The network of the switching fabric is built up from switching elements interconnected in a Kautz topology
Unwinding relaxation dynamics of polymers
The relaxation dynamics of a polymer wound around a fixed obstacle
constitutes a fundamental instance of polymer with twist and torque and it is
of relevance also for DNA denaturation dynamics. We investigate it by
simulations and Langevin equation analysis. The latter predicts a relaxation
time scaling as a power of the polymer length times a logarithmic correction
related to the equilibrium fluctuations of the winding angle. The numerical
data support this result and show that at short times the winding angle
decreases as a power-law. This is also in agreement with the Langevin equation
provided a winding-dependent friction is used, suggesting that such reduced
description of the system captures the basic features of the problem.Comment: 4 pages, 5 figures. Accepted for publication in Phys. Rev. Let
Carbohydrate and nitrogen reserves in the hard red winter wheat (Triticum aestivum L.) variety 'Newton'
Photocopy of typescript
A study of nineteen children placed for adoption by the North Shore Children's Friend Society between January 1, 1950 and December 31, 1954.
Thesis (M.S.)--Boston Universit
An experimental investigation of bacitracin-penicillin synergism on the early growth of turkeys
Not available.Walter E. GerardNot ListedNot ListedMaster of ScienceDepartment Not ListedCunningham Memorial Library, Terre Haute, Indiana State University.isua-thesis-1953-gerardMastersTitle from document title page. Document formatted into pages: contains 64p. : ill. Includes appendix and bibliography
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