Experimental measurements of the laminar separation bubble on an Eppler 387 airfoil at low Reynolds numbers

An experimental investigation was conducted to measure the flow velocity in the boundary layer of an Eppler 387 airfoil. In particular, the laminar separation bubble that this airfoil exhibits at low Reynolds numbers was the focus. Single component laser Doppler velocimetry data were obtained at a Reynolds number of 100,000 at an angle of attack of 2.0 degree. Static Pressure and flow visualization data for the Eppler 387 airfoil were also obtained. The difficulty in obtaining accurate experimental measurements at low Reynolds numbers is addressed. Laser Doppler velocimetry boundary layer data for the NACA 663-018 airfoil at a Reynolds number of 160,000 and angle of attack of 12 degree is also presented

Breaking time-reversal symmetry with a superconducting flux capacitor

We present the design of a passive, on-chip microwave circulator based on a ring of superconducting tunnel junctions. We investigate two distinct physical realisations, based on either Josephson junctions (JJ) or quantum phase slip elements (QPS), with microwave ports coupled either capacitively (JJ) or inductively (QPS) to the ring structure. A constant bias applied to the center of the ring provides the symmetry breaking (effective) magnetic field, and no microwave or rf bias is required. We find that this design offers high isolation even when taking into account fabrication imperfections and environmentally induced bias perturbations and find a bandwidth in excess of 500 MHz for realistic device parameters.Comment: 10 pages, 11 figures, including supplementary material - published as "Passive on-chip, superconducting circulator using rings of tunnel junctions

Elliptic Reciprocity

The paper introduces the notions of an elliptic pair, an elliptic cycle and an elliptic list over a square free positive integer d. These concepts are related to the notions of amicable pairs of primes and aliquot cycles that were introduced by Silverman and Stange. Settling a matter left open by Silverman and Stange it is shown that for d=3 there are elliptic cycles of length 6. For d not equal to 3 the question of the existence of proper elliptic lists of length n over d is reduced to the the theory of prime producing quadratic polynomials. For d=163 a proper elliptic list of length 40 is exhibited. It is shown that for each d there is an upper bound on the length of a proper elliptic list over d. The final section of the paper contains heuristic arguments supporting conjectured asymptotics for the number of elliptic pairs below integer X. Finally, for d congruent to 3 modulo 8 the existence of infinitely many anomalous prime numbers is derived from Bunyakowski's Conjecture for quadratic polynomials.Comment: 17 pages, including one figure and two table

Algebraic properties of generalized Rijndael-like ciphers

We provide conditions under which the set of Rijndael functions considered as permutations of the state space and based on operations of the finite field \GF (p^k) ($p\geq 2$ a prime number) is not closed under functional composition. These conditions justify using a sequential multiple encryption to strengthen the AES (Rijndael block cipher with specific block sizes) in case AES became practically insecure. In Sparr and Wernsdorf (2008), R. Sparr and R. Wernsdorf provided conditions under which the group generated by the Rijndael-like round functions based on operations of the finite field \GF (2^k) is equal to the alternating group on the state space. In this paper we provide conditions under which the group generated by the Rijndael-like round functions based on operations of the finite field \GF (p^k) ($p\geq 2$) is equal to the symmetric group or the alternating group on the state space.Comment: 22 pages; Prelim0

BRINGING HYPERSONIC MISSILE CAPABILITY TO THE FLEET

Hypersonic glide body weapons represent a revolutionary change in offensive capabilities for militaries around the world. The U.S. Navy is developing a hypersonic glide body capability with the Conventional Prompt Strike Program, which has a scheduled initial operational capability of 2025. This capstone project has developed candidate systems that describe how the Army's Long Range Hypersonic Weapon (LRHW) system could be integrated onto various vessels to deliver a hypersonic glide body capability to the Navy before the Conventional Prompt Strike Program is operational. Research indicates that the LRHW is the most mature hypersonic glide body system developed by the United States, and integrating its use aboard Navy ships is the most likely path to success. This capstone describes the user concerns, system requirements, and concepts of operation through the development of systems engineering products that describe each of the candidate systems.Civilian, Department of the NavyCivilian, Department of the ArmyCivilian, Department of the ArmyCivilian, Northrop GrummanApproved for public release. Distribution is unlimited

Electrochemical Monitoring Of Electrogalvanizing Solutions

The corrosion resistance of steel is vastly improved when a zinc cathodic protective layer is applied. In recent years there has been renewed interest in producing this galvanized coating electrolytically. As with many deposition processes, the control of the operating parameters is very important in order to produce good quality zinc coatings. The homogeneity, ductility and smoothness of the zinc layer are critical. These factors are usually influenced by the electrochemical nature of the solution and organic additives are often used to assist in control. Studies on the polarization behavior of solutions for electro galvanizing electrolytes were made. Cyclic voltammetry techniques were used to develop methods which might be applicable in monitoring the active organic content of liquor ice in solution. The morphologies and orientations of the zinc were studied using SEM and X-ray diffraction techniques. © 1986 Chapman and Hall Ltd

Minimal Steiner Trees for 2k×2kSquare Lattices

AbstractWe prove a conjecture of Chung, Graham, and Gardner (Math. Mag.62(1989), 83–96), giving the form of the minimal Steiner trees for the set of points comprising the vertices of a 2k×2ksquare lattice. Each full component of these minimal trees is the minimal Steiner tree for the four vertices of a square

Analysis of Precipitate Redistribution in Inconel 617 Using Integrated Electron Backscatter Diffraction and Energy Dispersive Spectroscopy

Inconel 617 (IN617), a candidate alloy for applications in the Next Generation Nuclear Plant, derives its oxidation resistance and strength at temperatures above 900°C from both solid solution strengthening and the precipitation of carbides [1]. Cr-rich carbides (usually M23C6) reside primarily on grain boundaries, while Mo-rich carbides (usually M6C) tend to be within grains [1-4]. Both intragranular and intergranular carbides play an important role in the creep behavior of the alloy [1]. During creep, intragranular carbides can dissolve and re-precipitate at grain boundaries, especially on boundaries in tension [1]. While the precipitate distribution before and after creep deformation has been investigated, the role of grain boundary character has not been included in the analysis