Active exterior cloaking for the 2D Laplace and Helmholtz equations.
Vasquez, Fernando Guevara; Milton, Graeme W; Onofrei, Daniel
2009-08-14
A new cloaking method is presented for 2D quasistatics and the 2D Helmholtz equation that we speculate extends to other linear wave equations. For 2D quasistatics it is proven how a single active exterior cloaking device can be used to shield an object from surrounding fields, yet produce very small scattered fields. The problem is reduced to finding a polynomial which is close to 1 in a disk and close to 0 in another disk, and such a polynomial is constructed. For the 2D Helmholtz equation it is numerically shown that three exterior cloaking devices placed around the object suffice to hide it. PMID:19792644
Preconditioning the Helmholtz Equation for Rigid Ducts
NASA Technical Reports Server (NTRS)
Baumeister, Kenneth J.; Kreider, Kevin L.
1998-01-01
An innovative hyperbolic preconditioning technique is developed for the numerical solution of the Helmholtz equation which governs acoustic propagation in ducts. Two pseudo-time parameters are used to produce an explicit iterative finite difference scheme. This scheme eliminates the large matrix storage requirements normally associated with numerical solutions to the Helmholtz equation. The solution procedure is very fast when compared to other transient and steady methods. Optimization and an error analysis of the preconditioning factors are present. For validation, the method is applied to sound propagation in a 2D semi-infinite hard wall duct.
Monopoles, instantons, and the Helmholtz equation
NASA Astrophysics Data System (ADS)
Franchetti, Guido; Maldonado, Rafael
2016-07-01
In this work we study the dimensional reduction of smooth circle invariant Yang-Mills instantons defined on 4-manifolds which asymptotically become circle fibrations over hyperbolic 3-space. A suitable choice of the 4-manifold metric within a specific conformal class gives rise to singular and smooth hyperbolic monopoles. A large class of monopoles is obtained if the conformal factor satisfies the Helmholtz equation on hyperbolic 3-space. We describe simple configurations and relate our results to the Jackiw-Nohl-Rebbi construction, for which we provide a geometric interpretation.
Boundary regularized integral equation formulation of the Helmholtz equation in acoustics.
Sun, Qiang; Klaseboer, Evert; Khoo, Boo-Cheong; Chan, Derek Y C
2015-01-01
A boundary integral formulation for the solution of the Helmholtz equation is developed in which all traditional singular behaviour in the boundary integrals is removed analytically. The numerical precision of this approach is illustrated with calculation of the pressure field owing to radiating bodies in acoustic wave problems. This method facilitates the use of higher order surface elements to represent boundaries, resulting in a significant reduction in the problem size with improved precision. Problems with extreme geometric aspect ratios can also be handled without diminished precision. When combined with the CHIEF method, uniqueness of the solution of the exterior acoustic problem is assured without the need to solve hypersingular integrals. PMID:26064591
Iterative solution of the Helmholtz equation
Larsson, E.; Otto, K.
1996-12-31
We have shown that the numerical solution of the two-dimensional Helmholtz equation can be obtained in a very efficient way by using a preconditioned iterative method. We discretize the equation with second-order accurate finite difference operators and take special care to obtain non-reflecting boundary conditions. We solve the large, sparse system of equations that arises with the preconditioned restarted GMRES iteration. The preconditioner is of {open_quotes}fast Poisson type{close_quotes}, and is derived as a direct solver for a modified PDE problem.The arithmetic complexity for the preconditioner is O(n log{sub 2} n), where n is the number of grid points. As a test problem we use the propagation of sound waves in water in a duct with curved bottom. Numerical experiments show that the preconditioned iterative method is very efficient for this type of problem. The convergence rate does not decrease dramatically when the frequency increases. Compared to banded Gaussian elimination, which is a standard solution method for this type of problems, the iterative method shows significant gain in both storage requirement and arithmetic complexity. Furthermore, the relative gain increases when the frequency increases.
NASA Astrophysics Data System (ADS)
Kashirin, A. A.; Smagin, S. I.; Taltykina, M. Yu.
2016-04-01
Interior and exterior three-dimensional Dirichlet problems for the Helmholtz equation are solved numerically. They are formulated as equivalent boundary Fredholm integral equations of the first kind and are approximated by systems of linear algebraic equations, which are then solved numerically by applying an iteration method. The mosaic-skeleton method is used to speed up the solution procedure.
Multigrid and cyclic reduction applied to the Helmholtz equation
NASA Technical Reports Server (NTRS)
Brackenridge, Kenneth
1993-01-01
We consider the Helmholtz equation with a discontinuous complex parameter and inhomogeneous Dirichlet boundary conditions in a rectangular domain. A variant of the direct method of cyclic reduction (CR) is employed to facilitate the design of improved multigrid (MG) components, resulting in the method of CR-MG. We demonstrate the improved convergence properties of this method.
Mahillo-Isla, R; Gonźalez-Morales, M J; Dehesa-Martínez, C
2011-06-01
The slowly varying envelope approximation is applied to the radiation problems of the Helmholtz equation with a planar single-layer and dipolar sources. The analyses of such problems provide procedures to recover solutions of the Helmholtz equation based on the evaluation of solutions of the parabolic wave equation at a given plane. Furthermore, the conditions that must be fulfilled to apply each procedure are also discussed. The relations to previous work are given as well. PMID:21643384
Volume integrals of ellipsoids associated with the inhomogeneous Helmholtz equation
NASA Technical Reports Server (NTRS)
Fu, L. S.; Mura, T.
1982-01-01
Problems of wave phenomena in the fields of acoustics, electromagnetics and elasticity are often reduced to an integration of the inhomogeneous Helmholtz equation. Results are presented for volume integrals associated with the inhomogeneous Helmholtz equation, for an ellipsoidal region. By using appropriate Taylor series expansions and the multinomial theorem, these volume integrals are obtained in series form for regions r greater than r-prime and r less than r-prime, where r and r-prime are the distances from the origin to the point of observation and the source. Derivatives of these integrals are easily evaluated. When the wavenumber approaches zero the results reduce directly to the potentials of ellipsoids of variable densities.
Precise evaluation of the Helmholtz equation for optical propagation.
Pond, John E; Sutton, George W
2015-01-01
A precise computational integration of the Helmholtz equation was performed for laser propagation of an electromagnetic wave with no approximations or linearization. This computation integration was performed using 64-bit processors. This is illustrated for a uniform monochromatic beam from a circular aperture that has a uniform intensity. It predicts many Arago spots and near-field intensity fluctuations for a large ratio of aperture size to wavelength and converges to the usual Airy pattern in the far field. PMID:25531618
On the vector Helmholtz equation in toroidal waveguides
Biro, Thomas
2005-02-15
A wave splitting method is proposed to solve the problem of propagation of microwaves in a circular waveguide bend of circular cross section. The splitting method, applied to the vector Helmholtz equation, gives a stable solution in terms of waves propagating to the right and to the left in the bend. The formulation is particularly transparent for analyzing the scattering properties of toroidal bends. The basis for the transparency of the method is that the wave splitting is formally exact as the exponential of the square root of a differential operator. The modal functions of the straight cylindrical waveguide are chosen as basis functions in the transverse quasi-toroidal variables.
A double-sweeping preconditioner for the Helmholtz equation
NASA Astrophysics Data System (ADS)
Eslaminia, Mehran; Guddati, Murthy N.
2016-06-01
A new preconditioner is developed to increase the efficiency of iterative solution of the Helmholtz equation. The key idea of the proposed preconditioner is to split the domain of interest into smaller subdomains and sequentially approximate the forward and backward components of the solution. The sequential solution is facilitated by approximate interface conditions that ignore the effect of multiple reflections. The efficiency of the proposed method is tested using various 2-D heterogeneous media. We observe that the proposed preconditioner results in good convergence, with number of iterations growing very slowly with increasing frequency. We also note that the mesh size and number of subdomains do not affect the convergence rate. Finally, we find that the overall computational time is much smaller than that of the sweeping preconditioner.
Reck, Kasper; Thomsen, Erik V; Hansen, Ole
2011-01-31
The scalar wave equation, or Helmholtz equation, describes within a certain approximation the electromagnetic field distribution in a given system. In this paper we show how to solve the Helmholtz equation in complex geometries using conformal mapping and the homotopy perturbation method. The solution of the mapped Helmholtz equation is found by solving an infinite series of Poisson equations using two dimensional Fourier series. The solution is entirely based on analytical expressions and is not mesh dependent. The analytical results are compared to a numerical (finite element method) solution. PMID:21368995
First-order system least-squares for the Helmholtz equation
Lee, B.; Manteuffel, T.; McCormick, S.; Ruge, J.
1996-12-31
We apply the FOSLS methodology to the exterior Helmholtz equation {Delta}p + k{sup 2}p = 0. Several least-squares functionals, some of which include both H{sup -1}({Omega}) and L{sup 2}({Omega}) terms, are examined. We show that in a special subspace of [H(div; {Omega}) {intersection} H(curl; {Omega})] x H{sup 1}({Omega}), each of these functionals are equivalent independent of k to a scaled H{sup 1}({Omega}) norm of p and u = {del}p. This special subspace does not include the oscillatory near-nullspace components ce{sup ik}({sup {alpha}x+{beta}y)}, where c is a complex vector and where {alpha}{sub 2} + {beta}{sup 2} = 1. These components are eliminated by applying a non-standard coarsening scheme. We achieve this scheme by introducing {open_quotes}ray{close_quotes} basis functions which depend on the parameter pair ({alpha}, {beta}), and which approximate ce{sup ik}({sup {alpha}x+{beta}y)} well on the coarser levels where bilinears cannot. We use several pairs of these parameters on each of these coarser levels so that several coarse grid problems are spun off from the finer levels. Some extensions of this theory to the transverse electric wave solution for Maxwell`s equations will also be presented.
Numerical solution of the nonlinear Helmholtz equation using nonorthogonal expansions
Fibich, G. . E-mail: fibich@math.tau.ac.il; Tsynkov, S. . E-mail: tsynkov@math.ncsu.edu
2005-11-20
In [J. Comput. Phys. 171 (2001) 632-677] we developed a fourth-order numerical method for solving the nonlinear Helmholtz equation which governs the propagation of time-harmonic laser beams in media with a Kerr-type nonlinearity. A key element of the algorithm was a new nonlocal two-way artificial boundary condition (ABC), set in the direction of beam propagation. This two-way ABC provided for reflectionless propagation of the outgoing waves while also fully transmitting the given incoming beam at the boundaries of the computational domain. Altogether, the algorithm of [J. Comput. Phys. 171 (2001) 632-677] has allowed for a direct simulation of nonlinear self-focusing without neglecting nonparaxial effects and backscattering. To the best of our knowledge, this capacity has never been achieved previously in nonlinear optics. In the current paper, we propose an improved version of the algorithm. The principal innovation is that instead of using the Dirichlet boundary conditions in the direction orthogonal to that of the laser beam propagation, we now introduce Sommerfeld-type local radiation boundary conditions, which are constructed directly in the discrete framework. Numerically, implementation of the Sommerfeld conditions requires evaluation of eigenvalues and eigenvectors for a non-Hermitian matrix. Subsequently, the separation of variables, which is a key building block of the aforementioned nonlocal ABC, is implemented through an expansion with respect to the nonorthogonal basis of the eigenvectors. Numerical simulations show that the new algorithm offers a considerable improvement in its numerical performance, as well as in the range of physical phenomena that it is capable of simulating.
A spectral boundary integral equation method for the 2-D Helmholtz equation
NASA Technical Reports Server (NTRS)
Hu, Fang Q.
1994-01-01
In this paper, we present a new numerical formulation of solving the boundary integral equations reformulated from the Helmholtz equation. The boundaries of the problems are assumed to be smooth closed contours. The solution on the boundary is treated as a periodic function, which is in turn approximated by a truncated Fourier series. A Fourier collocation method is followed in which the boundary integral equation is transformed into a system of algebraic equations. It is shown that in order to achieve spectral accuracy for the numerical formulation, the nonsmoothness of the integral kernels, associated with the Helmholtz equation, must be carefully removed. The emphasis of the paper is on investigating the essential elements of removing the nonsmoothness of the integral kernels in the spectral implementation. The present method is robust for a general boundary contour. Aspects of efficient implementation of the method using FFT are also discussed. A numerical example of wave scattering is given in which the exponential accuracy of the present numerical method is demonstrated.
SOME NEW FINITE DIFFERENCE METHODS FOR HELMHOLTZ EQUATIONS ON IRREGULAR DOMAINS OR WITH INTERFACES.
Wan, Xiaohai; Li, Zhilin
2012-06-01
Solving a Helmholtz equation Δu + λu = f efficiently is a challenge for many applications. For example, the core part of many efficient solvers for the incompressible Navier-Stokes equations is to solve one or several Helmholtz equations. In this paper, two new finite difference methods are proposed for solving Helmholtz equations on irregular domains, or with interfaces. For Helmholtz equations on irregular domains, the accuracy of the numerical solution obtained using the existing augmented immersed interface method (AIIM) may deteriorate when the magnitude of λ is large. In our new method, we use a level set function to extend the source term and the PDE to a larger domain before we apply the AIIM. For Helmholtz equations with interfaces, a new maximum principle preserving finite difference method is developed. The new method still uses the standard five-point stencil with modifications of the finite difference scheme at irregular grid points. The resulting coefficient matrix of the linear system of finite difference equations satisfies the sign property of the discrete maximum principle and can be solved efficiently using a multigrid solver. The finite difference method is also extended to handle temporal discretized equations where the solution coefficient λ is inversely proportional to the mesh size. PMID:22701346
Li,Jing; Tu, Xuemin
2008-12-10
A variant of balancing domain decomposition method by constraints (BDDC) is proposed for solving a class of indefinite system of linear equations, which arises from the finite element discretization of the Helmholtz equation of time-harmonic wave propagation in a bounded interior domain. The proposed BDDC algorithm is closely related to the dual-primal finite element tearing and interconnecting algorithm for solving Helmholtz equations (FETI-DPH). Under the condition that the diameters of the subdomains are small enough, the rate of convergence is established which depends polylogarithmically on the dimension of the individual subdomain problems and which improves with the decrease of the subdomain diameters. These results are supported by numerical experiments of solving a Helmholtz equation on a two-dimensional square domain.
NASA Astrophysics Data System (ADS)
Khalilov, E. H.
2016-07-01
The surface integral equation for a spatial mixed boundary value problem for the Helmholtz equation is considered. At a set of chosen points, the equation is replaced with a system of algebraic equations, and the existence and uniqueness of the solution of this system is established. The convergence of the solutions of this system to the exact solution of the integral equation is proven, and the convergence rate of the method is determined.
Volume integrals associated with the inhomogeneous Helmholtz equation. Part 1: Ellipsoidal region
NASA Technical Reports Server (NTRS)
Fu, L. S.; Mura, T.
1983-01-01
Problems of wave phenomena in fields of acoustics, electromagnetics and elasticity are often reduced to an integration of the inhomogeneous Helmholtz equation. Results are presented for volume integrals associated with the Helmholtz operator, nabla(2) to alpha(2), for the case of an ellipsoidal region. By using appropriate Taylor series expansions and multinomial theorem, these volume integrals are obtained in series form for regions r 4' and r r', where r and r' are distances from the origin to the point of observation and source, respectively. Derivatives of these integrals are easily evaluated. When the wave number approaches zero, the results reduce directly to the potentials of variable densities.
On the solution of the Helmholtz equation on regions with corners.
Serkh, Kirill; Rokhlin, Vladimir
2016-08-16
In this paper we solve several boundary value problems for the Helmholtz equation on polygonal domains. We observe that when the problems are formulated as the boundary integral equations of potential theory, the solutions are representable by series of appropriately chosen Bessel functions. In addition to being analytically perspicuous, the resulting expressions lend themselves to the construction of accurate and efficient numerical algorithms. The results are illustrated by a number of numerical examples. PMID:27482110
The Two Dimensional Euler Equations on Singular Exterior Domains
NASA Astrophysics Data System (ADS)
Gérard-Varet, David; Lacave, Christophe
2015-12-01
This paper is a follow-up of Gérard-Varet and Lacave (Arch Ration Mech Anal 209(1):131-170, 2013), on the existence of global weak solutions to the two dimensional Euler equations in singular domains. In Gérard-Varet and Lacave (Arch Ration Mech Anal 209(1):131-170, 2013), we have established the existence of weak solutions for a large class of bounded domains, with initial vorticity in L p ( p > 1). For unbounded domains, we have proved a similar result only when the initial vorticity is in {Lpc} ( p > 2) and when the domain is the exterior of a single obstacle. The goal here is to retrieve these two restrictions: we consider general initial vorticity in {L1 {\\cap} Lp} ( p > 1), outside an arbitrary number of obstacles (not reduced to points).
A High-Order Direct Solver for Helmholtz Equations with Neumann Boundary Conditions
NASA Technical Reports Server (NTRS)
Sun, Xian-He; Zhuang, Yu
1997-01-01
In this study, a compact finite-difference discretization is first developed for Helmholtz equations on rectangular domains. Special treatments are then introduced for Neumann and Neumann-Dirichlet boundary conditions to achieve accuracy and separability. Finally, a Fast Fourier Transform (FFT) based technique is used to yield a fast direct solver. Analytical and experimental results show this newly proposed solver is comparable to the conventional second-order elliptic solver when accuracy is not a primary concern, and is significantly faster than that of the conventional solver if a highly accurate solution is required. In addition, this newly proposed fourth order Helmholtz solver is parallel in nature. It is readily available for parallel and distributed computers. The compact scheme introduced in this study is likely extendible for sixth-order accurate algorithms and for more general elliptic equations.
Chang, Zheng; Zhou, Xiaoming; Hu, Jin; Hu, Gengkai
2010-02-15
In a recent paper, Chen et al. [Opt. Express 17, 3581 (2009)] develop an approach to design invisible cloaks with controllable constitutive parameters by adjusting the constant k in the Helmholtz's equation. In this comment, we discuss the limitation of the free parameter k in designing cloaks. It is found that the real constant k can be chosen only as limited values in order to avoid the singular material parameters. PMID:20389403
Fathi, S. M. Saberi
2010-12-15
In this paper we first show in the framework of quaternion analysis how the fundamental solutions of the Dirac operators with vector potential can be obtained. Then, we use the obtained results to present a derivation of the exact analytic Green function for the Helmholtz equation, i.e., ({Delta}+|a(x)|{sup 2})G{sub 0}(x)={delta}(x), for the case a(x) is a monogenic (analytic) vector potential.
Chen, Xi; Fu, Yunqi; Yuan, Naichang
2009-03-01
An approach to design an invisible cloak with controlled constitutive parameters and arbitrary shaped boundaries is presented. Helmholtz's equation is adopted to establish a mapping between original and transformed coordinates inside the cloak. Then the constitutive parameters are obtained by the established mapping. The analytical solution of a regular cloak and the numerical solution of an irregular cloak both verify that that our method will guide electromagnetic wave efficiently and control the constitutive parameters of the cloak conveniently. It has great significance in realizing a cloak practically. PMID:19259197
Petrov-Galerkin's method hybrid with finite element into the Helmholtz equation solution. Part II
NASA Astrophysics Data System (ADS)
Rabadan Malda, Itzala; Salazar Cordero, Emigdio; Ortega Herrera, Jose Angel
2002-11-01
This work proposes a hybridization between Petrov-Galerkins numeric method and finite element method (FEM) to resolve Helmholtz equation when dominion is an open or semiopen tube-shaped configuration and with determinate number of holes over cylindrical surface. It's pretended to solve these kind of cavities, thereby it allows us to obtain very important design parameters like: cavity length, quantity, size and distance between toneholes, form and size of mouthpiece or outlet. These parameters are design basis into acoustic and musical instrumentation: baffles outlet pipes, diffusers, silencers, flutes, oboes, saxophones, trumpets, quenas, and many more. In this way it's expected to determine advantages of this numeric method above another using actually.
Solution of the three-dimensional Helmholtz equation with nonlocal boundary conditions
NASA Technical Reports Server (NTRS)
Hodge, Steve L.; Zorumski, William E.; Watson, Willie R.
1995-01-01
The Helmholtz equation is solved within a three-dimensional rectangular duct with a nonlocal radiation boundary condition at the duct exit plane. This condition accurately models the acoustic admittance at an arbitrarily-located computational boundary plane. A linear system of equations is constructed with second-order central differences for the Helmholtz operator and second-order backward differences for both local admittance conditions and the gradient term in the nonlocal radiation boundary condition. The resulting matrix equation is large, sparse, and non-Hermitian. The size and structure of the matrix makes direct solution techniques impractical; as a result, a nonstationary iterative technique is used for its solution. The theory behind the nonstationary technique is reviewed, and numerical results are presented for radiation from both a point source and a planar acoustic source. The solutions with the nonlocal boundary conditions are invariant to the location of the computational boundary, and the same nonlocal conditions are valid for all solutions. The nonlocal conditions thus provide a means of minimizing the size of three-dimensional computational domains.
Vortex lattices generated by the Kelvin-Helmholtz instability in the Gross-Pitaevskii equation
Ohta, A.; Kashiwa, R.; Sakaguchi, H.
2010-11-15
Vortex streets are formed from sheared initial conditions in classical fluids even without viscosity, which is called the Kelvin-Helmholtz instability. We demonstrate that similar vortex streets are generated from sheared initial conditions by the direct numerical simulation of the Gross-Pitaevskii (GP) equation which describes the dynamics of the Bose-Einstein condensates. Furthermore, we show the vortex-lattice formation from sheared initial conditions analogous to the rigid-body rotation in the GP equation under a rotating harmonic potential. The vortex-lattice formation by the dynamical instability in the system without energy dissipation differs from the vortex-lattice formation process by the imaginary time evolution of the GP equation where the lowest energy state is obtained.
A dispersion minimizing scheme for the 3-D Helmholtz equation based on ray theory
NASA Astrophysics Data System (ADS)
Stolk, Christiaan C.
2016-06-01
We develop a new dispersion minimizing compact finite difference scheme for the Helmholtz equation in 2 and 3 dimensions. The scheme is based on a newly developed ray theory for difference equations. A discrete Helmholtz operator and a discrete operator to be applied to the source and the wavefields are constructed. Their coefficients are piecewise polynomial functions of hk, chosen such that phase and amplitude errors are minimal. The phase errors of the scheme are very small, approximately as small as those of the 2-D quasi-stabilized FEM method and substantially smaller than those of alternatives in 3-D, assuming the same number of gridpoints per wavelength is used. In numerical experiments, accurate solutions are obtained in constant and smoothly varying media using meshes with only five to six points per wavelength and wave propagation over hundreds of wavelengths. When used as a coarse level discretization in a multigrid method the scheme can even be used with down to three points per wavelength. Tests on 3-D examples with up to 108 degrees of freedom show that with a recently developed hybrid solver, the use of coarser meshes can lead to corresponding savings in computation time, resulting in good simulation times compared to the literature.
A general approach for high order absorbing boundary conditions for the Helmholtz equation
NASA Astrophysics Data System (ADS)
Zarmi, Asaf; Turkel, Eli
2013-06-01
When solving a scattering problem in an unbounded space, one needs to implement the Sommerfeld condition as a boundary condition at infinity, to ensure no energy penetrates the system. In practice, solving a scattering problem involves truncating the region and implementing a boundary condition on an artificial outer boundary. Bayliss, Gunzburger and Turkel (BGT) suggested an Absorbing Boundary Condition (ABC) as a sequence of operators aimed at annihilating elements from the solution's series representation. Their method was practical only up to a second order condition. Later, Hagstrom and Hariharan (HH) suggested a method which used auxiliary functions and enabled implementation of higher order conditions. We compare various absorbing boundary conditions (ABCs) and introduce a new method to construct high order ABCs, generalizing the HH method. We then derive from this general method ABCs based on different series representations of the solution to the Helmholtz equation - in polar, elliptical and spherical coordinates. Some of these ABCs are generalizations of previously constructed ABCs and some are new. These new ABCs produce accurate solutions to the Helmholtz equation, which are much less dependent on the various parameters of the problem, such as the value of k, or the eccentricity of the ellipse. In addition to constructing new ABCs, our general method sheds light on the connection between various ABCs. Computations are presented to verify the high accuracy of these new ABCs.
Gumerov, Nail A; Duraiswami, Ramani
2009-01-01
The development of a fast multipole method (FMM) accelerated iterative solution of the boundary element method (BEM) for the Helmholtz equations in three dimensions is described. The FMM for the Helmholtz equation is significantly different for problems with low and high kD (where k is the wavenumber and D the domain size), and for large problems the method must be switched between levels of the hierarchy. The BEM requires several approximate computations (numerical quadrature, approximations of the boundary shapes using elements), and these errors must be balanced against approximations introduced by the FMM and the convergence criterion for iterative solution. These different errors must all be chosen in a way that, on the one hand, excess work is not done and, on the other, that the error achieved by the overall computation is acceptable. Details of translation operators for low and high kD, choice of representations, and BEM quadrature schemes, all consistent with these approximations, are described. A novel preconditioner using a low accuracy FMM accelerated solver as a right preconditioner is also described. Results of the developed solvers for large boundary value problems with 0.0001 less, similarkD less, similar500 are presented and shown to perform close to theoretical expectations. PMID:19173406
High-order numerical solution of the nonlinear Helmholtz equation with axial symmetry
NASA Astrophysics Data System (ADS)
Baruch, G.; Fibich, G.; Tsynkov, S.
2007-07-01
The nonlinear Helmholtz (NLH) equation models the propagation of intense laser beams in a Kerr medium. The NLH takes into account the effects of nonparaxiality and backward scattering that are neglected in the more common nonlinear Schrodinger model. In [G. Fibich, S. Tsynkov, High-order two-way artificial boundary conditions for nonlinear wave propagation with backscattering, J. Comput. Phys., 171 (2001) 632-677] and [G. Fibich, S. Tsynkov, Numerical solution of the nonlinear Helmholtz equation using nonorthogonal expansions, J. Comput. Phys., 210 (2005) 183-224], a novel high-order numerical method for solving the NLH was introduced and implemented in the case of a two-dimensional Cartesian geometry. The NLH was solved iteratively, using the separation of variables and a special nonlocal two-way artificial boundary condition applied to the resulting decoupled linear systems. In the current paper, we propose a major improvement to the previous method. Instead of using LU decomposition after the separation of variables, we employ an efficient summation rule that evaluates convolution with the discrete Green's function. We also extend the method to a three-dimensional setting with cylindrical symmetry, under both Dirichlet and Sommerfeld-type transverse boundary conditions.
Compressed Liquid Densities and Helmholtz Energy Equation of State for Fluoroethane (R161)
NASA Astrophysics Data System (ADS)
Qi, Haiyan; Fang, Dan; Gao, Kehui; Meng, Xianyang; Wu, Jiangtao
2016-06-01
In this study, compressed liquid densities of Fluoroethane (R161, CAS No. 353-36-6) were measured using a high-pressure vibrating-tube densimeter over the temperature range from (283 to 363) K with pressures up to 100 MPa. A Helmholtz energy equation of state for R161 was developed from these density measurements and other experimental thermodynamic property data from the literature. The formulation is valid for temperatures from the triple point temperature of 130 K to 420 K with pressures up to 100 MPa. The approximate uncertainties of properties calculated with the new equation of state are estimated to be 0.25 % in density, 0.2 % in saturated liquid density between 230 K and 320 K, and 0.2 % in vapor pressure below 350 K. Deviations in the critical region are higher for all properties. The extrapolation behavior of the new formulation at high temperatures and high pressures is reasonable.
NASA Astrophysics Data System (ADS)
Luo, Songting; Qian, Jianliang; Burridge, Robert
2014-08-01
In some applications, it is reasonable to assume that geodesics (rays) have a consistent orientation so that the Helmholtz equation may be viewed as an evolution equation in one of the spatial directions. With such applications in mind, we propose a new Eulerian computational geometrical-optics method, dubbed the fast Huygens sweeping method, for computing Green functions of Helmholtz equations in inhomogeneous media in the high-frequency regime and in the presence of caustics. The first novelty of the new method is that the Huygens-Kirchhoff secondary source principle is used to integrate many locally valid asymptotic solutions to yield a globally valid asymptotic solution so that caustics associated with the usual geometrical-optics ansatz can be treated automatically. The second novelty is that a butterfly algorithm is adapted to carry out the matrix-vector products induced by the Huygens-Kirchhoff integration in O(Nlog N) operations, where N is the total number of mesh points, and the proportionality constant depends on the desired accuracy and is independent of the frequency parameter. To reduce the storage of the resulting traveltime and amplitude tables, we compress each table into a linear combination of tensor-product based multivariate Chebyshev polynomials so that the information of each table is encoded into a small number of Chebyshev coefficients. The new method enjoys the following desired features: (1) it precomputes a set of local traveltime and amplitude tables; (2) it automatically takes care of caustics; (3) it constructs Green functions of the Helmholtz equation for arbitrary frequencies and for many point sources; (4) for a specified number of points per wavelength it constructs each Green function in nearly optimal complexity in terms of the total number of mesh points, where the prefactor of the complexity only depends on the specified accuracy and is independent of the frequency parameter. Both two-dimensional (2-D) and three-dimensional (3
On solutions of the mixed Dirichlet-Navier problem for the polyharmonic equation in exterior domains
NASA Astrophysics Data System (ADS)
Matevosyan, O. A.
2016-01-01
We study the unique solvability of the mixed Dirichlet-Navier problem for the polyharmonic equation in exterior domains under the assumption that a generalized solution of this problem has a bounded Dirichlet integral with weight | x| a . Depending on the value of the parameter a, we prove a uniqueness theorem or present exact formulas for the dimension of the solution space of the mixed Dirichlet-Navier problem in the exterior of a compact set.
NASA Astrophysics Data System (ADS)
Lu, Wangtao; Qian, Jianliang; Burridge, Robert
2016-05-01
In some applications, it is reasonable to assume that geodesics (rays) have a consistent orientation so that the Helmholtz equation can be viewed as an evolution equation in one of the spatial directions. With such applications in mind, starting from Babich's expansion, we develop a new high-order asymptotic method, which we dub the fast Huygens sweeping method, for solving point-source Helmholtz equations in inhomogeneous media in the high-frequency regime and in the presence of caustics. The first novelty of this method is that we develop a new Eulerian approach to compute the asymptotics, i.e. the traveltime function and amplitude coefficients that arise in Babich's expansion, yielding a locally valid solution, which is accurate close enough to the source. The second novelty is that we utilize the Huygens-Kirchhoff integral to integrate many locally valid wavefields to construct globally valid wavefields. This automatically treats caustics and yields uniformly accurate solutions both near the source and remote from it. The third novelty is that the butterfly algorithm is adapted to accelerate the Huygens-Kirchhoff summation, achieving nearly optimal complexity O (Nlog N), where N is the number of mesh points; the complexity prefactor depends on the desired accuracy and is independent of the frequency. To reduce the storage of the resulting tables of asymptotics in Babich's expansion, we use the multivariable Chebyshev series expansion to compress each table by encoding the information into a small number of coefficients. The new method enjoys the following desired features. First, it precomputes the asymptotics in Babich's expansion, such as traveltime and amplitudes. Second, it takes care of caustics automatically. Third, it can compute the point-source Helmholtz solution for many different sources at many frequencies simultaneously. Fourth, for a specified number of points per wavelength, it can construct the wavefield in nearly optimal complexity in terms
NASA Technical Reports Server (NTRS)
Bayliss, A.; Goldstein, C. I.; Turkel, E.
1984-01-01
The Helmholtz Equation (-delta-K(2)n(2))u=0 with a variable index of refraction, n, and a suitable radiation condition at infinity serves as a model for a wide variety of wave propagation problems. A numerical algorithm was developed and a computer code implemented that can effectively solve this equation in the intermediate frequency range. The equation is discretized using the finite element method, thus allowing for the modeling of complicated geometrices (including interfaces) and complicated boundary conditions. A global radiation boundary condition is imposed at the far field boundary that is exact for an arbitrary number of propagating modes. The resulting large, non-selfadjoint system of linear equations with indefinite symmetric part is solved using the preconditioned conjugate gradient method applied to the normal equations. A new preconditioner is developed based on the multigrid method. This preconditioner is vectorizable and is extremely effective over a wide range of frequencies provided the number of grid levels is reduced for large frequencies. A heuristic argument is given that indicates the superior convergence properties of this preconditioner.
Effect of triangular element orientation on finite element solutions of the Helmholtz equation
NASA Technical Reports Server (NTRS)
Baumeister, K. J.
1986-01-01
The Galerkin finite element solutions for the scalar homogeneous Helmholtz equation are presented for no reflection, hard wall, and potential relief exit terminations with a variety of triangular element orientations. For this group of problems, the correlation between the accuracy of the solution and the orientation of the linear triangle is examined. Nonsymmetric element patterns are found to give generally poor results in the model problems investigated, particularly for cases where standing waves exist. For a fixed number of vertical elements, the results showed that symmetric element patterns give much better agreement with corresponding exact analytical results. In laminated wave guide application, the symmetric pyramid pattern is convenient to use and is shown to give excellent results.
Absence of Critical Points of Solutions to the Helmholtz Equation in 3D
NASA Astrophysics Data System (ADS)
Alberti, Giovanni S.
2016-05-01
The focus of this paper is to show the absence of critical points for the solutions to the Helmholtz equation in a bounded domain {Ωsubset{R}3} , given by div(a nabla u_{ω}g)-ω qu_{ω}g=0&quad {in Ω,} u_{ω}g=g&quad{on partialΩ.} We prove that for an admissible g there exists a finite set of frequencies K in a given interval and an open cover {overline{Ω}=\\cup_{ωin K} Ω_{ω}} such that {|nabla u_{ω}g(x)| > 0} for every {ωin K} and {xinΩ_{ω}} . The set K is explicitly constructed. If the spectrum of this problem is simple, which is true for a generic domain {Ω} , the admissibility condition on g is a generic property.
Wave Gradiometry and Helmholtz Equation Solutions Applied to USArray across the Contiguous U.S.
NASA Astrophysics Data System (ADS)
Liu, Y.; Holt, W. E.
2015-12-01
Wave gradiometry is an array processing technique utilizing the shape of seismic wavefields captured by USArray TA stations to determine fundamental wave propagation characteristics. We first explore a compatibility relation that links spatial gradients of the wavefield with the displacements and the time derivatives of displacements through two unknown coefficients Aand B, which are solved through iterative, damped least-square inversion, to provide estimates of phase velocity, back-azimuth, radiation pattern and geometrical spreading. We show that the A-coefficient corresponds to the gradient of logarithmic amplitude and the B-coefficient corresponds approximately to the local dynamic phase velocity. These vector fields are interpolated to explore a second compatibility relation through solutions to the Helmholtz equation. For most wavefields passing through the eastern U.S., we show that the A-coefficients are generally orthogonal to the B-coefficients. Where they are not completely orthogonal, there is a strong positive correlation between the gradients of B-coefficients and changes in geometrical spreading, which can be further linked with areas of strong energy focusing and defocusing. We then obtain isotropic phase velocity maps across the contiguous United States for 20 - 150 s Rayleigh wave by stacking results from 700 earthquakes. The strong velocity variations in the western U.S. correlate well with known geological features and the am- plitude correction terms from Helmholtz equation solutions generally improve the resolution of small-scale structures for all periods analyzed. We also observe a velocity change along the approximate boundary of the early Paleozoic continental margin in the eastern U.S and two significant low velocity anomalies within the central Appalachians, one centered where Eocene basaltic volcanism has occurred, and the other within the northeastern U.S., possibly associated with the Great Meteor Hotspot track.
NASA Astrophysics Data System (ADS)
Nguyen, N. C.; Peraire, J.; Reitich, F.; Cockburn, B.
2015-06-01
We introduce a new hybridizable discontinuous Galerkin (HDG) method for the numerical solution of the Helmholtz equation over a wide range of wave frequencies. Our approach combines the HDG methodology with geometrical optics in a fashion that allows us to take advantage of the strengths of these two methodologies. The phase-based HDG method is devised as follows. First, we enrich the local approximation spaces with precomputed phases which are solutions of the eikonal equation in geometrical optics. Second, we propose a novel scheme that combines the HDG method with ray tracing to compute multivalued solution of the eikonal equation. Third, we utilize the proper orthogonal decomposition to remove redundant modes and obtain locally orthogonal basis functions which are then used to construct the global approximation spaces of the phase-based HDG method. And fourth, we propose an appropriate choice of the stabilization parameter to guarantee stability and accuracy for the proposed method. Numerical experiments presented show that optimal orders of convergence are achieved, that the number of degrees of freedom to achieve a given accuracy is independent of the wave number, and that the number of unknowns required to achieve a given accuracy with the proposed method is orders of magnitude smaller than that with the standard finite element method.
Helmholtz and parabolic equation solutions to a benchmark problem in ocean acoustics.
Larsson, Elisabeth; Abrahamsson, Leif
2003-05-01
The Helmholtz equation (HE) describes wave propagation in applications such as acoustics and electromagnetics. For realistic problems, solving the HE is often too expensive. Instead, approximations like the parabolic wave equation (PE) are used. For low-frequency shallow-water environments, one persistent problem is to assess the accuracy of the PE model. In this work, a recently developed HE solver that can handle a smoothly varying bathymetry, variable material properties, and layered materials, is used for an investigation of the errors in PE solutions. In the HE solver, a preconditioned Krylov subspace method is applied to the discretized equations. The preconditioner combines domain decomposition and fast transform techniques. A benchmark problem with upslope-downslope propagation over a penetrable lossy seamount is solved. The numerical experiments show that, for the same bathymetry, a soft and slow bottom gives very similar HE and PE solutions, whereas the PE model is far from accurate for a hard and fast bottom. A first attempt to estimate the error is made by computing the relative deviation from the energy balance for the PE solution. This measure gives an indication of the magnitude of the error, but cannot be used as a strict error bound. PMID:12765364
NASA Technical Reports Server (NTRS)
Tam, Christopher K. W.; Webb, Jay C.
1994-01-01
In this paper finite-difference solutions of the Helmholtz equation in an open domain are considered. By using a second-order central difference scheme and the Bayliss-Turkel radiation boundary condition, reasonably accurate solutions can be obtained when the number of grid points per acoustic wavelength used is large. However, when a smaller number of grid points per wavelength is used excessive reflections occur which tend to overwhelm the computed solutions. Excessive reflections are due to the incompability between the governing finite difference equation and the Bayliss-Turkel radiation boundary condition. The Bayliss-Turkel radiation boundary condition was developed from the asymptotic solution of the partial differential equation. To obtain compatibility, the radiation boundary condition should be constructed from the asymptotic solution of the finite difference equation instead. Examples are provided using the improved radiation boundary condition based on the asymptotic solution of the governing finite difference equation. The computed results are free of reflections even when only five grid points per wavelength are used. The improved radiation boundary condition has also been tested for problems with complex acoustic sources and sources embedded in a uniform mean flow. The present method of developing a radiation boundary condition is also applicable to higher order finite difference schemes. In all these cases no reflected waves could be detected. The use of finite difference approximation inevita bly introduces anisotropy into the governing field equation. The effect of anisotropy is to distort the directional distribution of the amplitude and phase of the computed solution. It can be quite large when the number of grid points per wavelength used in the computation is small. A way to correct this effect is proposed. The correction factor developed from the asymptotic solutions is source independent and, hence, can be determined once and for all. The
NASA Astrophysics Data System (ADS)
Mohamed, Mamdouh S.; Hirani, Anil N.; Samtaney, Ravi
2016-05-01
A conservative discretization of incompressible Navier-Stokes equations is developed based on discrete exterior calculus (DEC). A distinguishing feature of our method is the use of an algebraic discretization of the interior product operator and a combinatorial discretization of the wedge product. The governing equations are first rewritten using the exterior calculus notation, replacing vector calculus differential operators by the exterior derivative, Hodge star and wedge product operators. The discretization is then carried out by substituting with the corresponding discrete operators based on the DEC framework. Numerical experiments for flows over surfaces reveal a second order accuracy for the developed scheme when using structured-triangular meshes, and first order accuracy for otherwise unstructured meshes. By construction, the method is conservative in that both mass and vorticity are conserved up to machine precision. The relative error in kinetic energy for inviscid flow test cases converges in a second order fashion with both the mesh size and the time step.
High-Order Accurate Solutions to the Helmholtz Equation in the Presence of Boundary Singularities
NASA Astrophysics Data System (ADS)
Britt, Darrell Steven, Jr.
Problems of time-harmonic wave propagation arise in important fields of study such as geological surveying, radar detection/evasion, and aircraft design. These often involve highfrequency waves, which demand high-order methods to mitigate the dispersion error. We propose a high-order method for computing solutions to the variable-coefficient inhomogeneous Helmholtz equation in two dimensions on domains bounded by piecewise smooth curves of arbitrary shape with a finite number of boundary singularities at known locations. We utilize compact finite difference (FD) schemes on regular structured grids to achieve highorder accuracy due to their efficiency and simplicity, as well as the capability to approximate variable-coefficient differential operators. In this work, a 4th-order compact FD scheme for the variable-coefficient Helmholtz equation on a Cartesian grid in 2D is derived and tested. The well known limitation of finite differences is that they lose accuracy when the boundary curve does not coincide with the discretization grid, which is a severe restriction on the geometry of the computational domain. Therefore, the algorithm presented in this work combines high-order FD schemes with the method of difference potentials (DP), which retains the efficiency of FD while allowing for boundary shapes that are not aligned with the grid without sacrificing the accuracy of the FD scheme. Additionally, the theory of DP allows for the universal treatment of the boundary conditions. One of the significant contributions of this work is the development of an implementation that accommodates general boundary conditions (BCs). In particular, Robin BCs with discontinuous coefficients are studied, for which we introduce a piecewise parameterization of the boundary curve. Problems with discontinuities in the boundary data itself are also studied. We observe that the design convergence rate suffers whenever the solution loses regularity due to the boundary conditions. This is
Scattering mean free path in continuous complex media: beyond the Helmholtz equation.
Baydoun, Ibrahim; Baresch, Diego; Pierrat, Romain; Derode, Arnaud
2015-09-01
We present theoretical calculations of the ensemble-averaged (or effective or coherent) wave field propagating in a heterogeneous medium considered as one realization of a random process. In the literature, it is usually assumed that heterogeneity can be accounted for by a random scalar function of the space coordinates, termed the potential. Physically, this amounts to replacing the constant wave speed in Helmholtz' equation by a space-dependent speed. In the case of acoustic waves, we show that this approach leads to incorrect results for the scattering mean free path, no matter how weak the fluctuations. The detailed calculation of the coherent wave field must take into account both a scalar and an operator part in the random potential. When both terms have identical amplitudes, the correct value for the scattering mean free paths is shown to be more than 4 times smaller (13/3, precisely) in the low-frequency limit, whatever the shape of the correlation function. Based on the diagrammatic approach of multiple scattering, theoretical results are obtained for the self-energy and mean free path within Bourret's and on-shell approximations. They are confirmed by numerical experiments. PMID:26465578
The method of polarized traces for the 2D Helmholtz equation
NASA Astrophysics Data System (ADS)
Zepeda-Núñez, Leonardo; Demanet, Laurent
2016-03-01
We present a solver for the 2D high-frequency Helmholtz equation in heterogeneous acoustic media, with online parallel complexity that scales optimally as O (N/L), where N is the number of volume unknowns, and L is the number of processors, as long as L grows at most like a small fractional power of N. The solver decomposes the domain into layers, and uses transmission conditions in boundary integral form to explicitly define "polarized traces", i.e., up- and down-going waves sampled at interfaces. Local direct solvers are used in each layer to precompute traces of local Green's functions in an embarrassingly parallel way (the offline part), and incomplete Green's formulas are used to propagate interface data in a sweeping fashion, as a preconditioner inside a GMRES loop (the online part). Adaptive low-rank partitioning of the integral kernels is used to speed up their application to interface data. The method uses second-order finite differences. The complexity scalings are empirical but motivated by an analysis of ranks of off-diagonal blocks of oscillatory integrals. They continue to hold in the context of standard geophysical community models such as BP and Marmousi 2, where convergence occurs in 5 to 10 GMRES iterations. While the parallelism in this paper stems from decomposing the domain, we do not explore the alternative of parallelizing the systems solves with distributed linear algebra routines.
A study of domain decomposition methods applied to the discretized Helmholtz equation
NASA Astrophysics Data System (ADS)
Tramel, Robert Wallace
2001-09-01
In this work a domain decomposition based preconditioner of the additive Schwarz type is developed and tested on the linear systems which arise out of the application of the Green's Function/Wave Expansion Discretization. (GFD/WED) method to Helmholtz's equation. In order to develop the additive Schwarz preconditioner, use is made of a class of one-sided Artificial Radiation Boundary Conditions (ARBC) developed during the course of this work. These ARBCs are computationally shown to be quite accurate for use on their own. The ARBC's are used to radiatively couple the various sub-domains which are naturally part of domain decomposition based methods in such a manner as to ensure that the system matrix, when restricted to the sub-domains, is non-singular. In addition, the inter-domain ARBC is constructed such that the solution to the global linear system is unaffected by the presence of the artificial boundaries. The efficacy and efficiency of the method is demonstrated on one, two, and three-dimensional test cases.
Lu, Huancai; Wu, Sean F
2009-03-01
The vibroacoustic responses of a highly nonspherical vibrating object are reconstructed using Helmholtz equation least-squares (HELS) method. The objectives of this study are to examine the accuracy of reconstruction and the impacts of various parameters involved in reconstruction using HELS. The test object is a simply supported and baffled thin plate. The reason for selecting this object is that it represents a class of structures that cannot be exactly described by the spherical Hankel functions and spherical harmonics, which are taken as the basis functions in the HELS formulation, yet the analytic solutions to vibroacoustic responses of a baffled plate are readily available so the accuracy of reconstruction can be checked accurately. The input field acoustic pressures for reconstruction are generated by the Rayleigh integral. The reconstructed normal surface velocities are validated against the benchmark values, and the out-of-plane vibration patterns at several natural frequencies are compared with the natural modes of a simply supported plate. The impacts of various parameters such as number of measurement points, measurement distance, location of the origin of the coordinate system, microphone spacing, and ratio of measurement aperture size to the area of source surface of reconstruction on the resultant accuracy of reconstruction are examined. PMID:19275312
NASA Astrophysics Data System (ADS)
Li, Jingzhi; Liu, Hongyu; Rondi, Luca; Uhlmann, Gunther
2015-04-01
We develop a very general theory on the regularized approximate invisibility cloaking for the wave scattering governed by the Helmholtz equation in any space dimensions via the approach of transformation optics. There are four major ingredients in our proposed theory: (1) The non-singular cloaking medium is obtained by the push-forwarding construction through a transformation that blows up a subset in the virtual space, where is an asymptotic regularization parameter. will degenerate to K 0 as , and in our theory K 0 could be any convex compact set in , or any set whose boundary consists of Lipschitz hypersurfaces, or a finite combination of those sets. (2) A general lossy layer with the material parameters satisfying certain compatibility integral conditions is employed right between the cloaked and cloaking regions. (3) The contents being cloaked could also be extremely general, possibly including, at the same time, generic mediums and, sound-soft, sound-hard and impedance-type obstacles, as well as some sources or sinks. (4) In order to achieve a cloaking device of compact size, particularly for the case when is not "uniformly small", an assembly-by-components, the (ABC) geometry is developed for both the virtual and physical spaces and the blow-up construction is based on concatenating different components. Within the proposed framework, we show that the scattered wave field corresponding to a cloaking problem will converge to u 0 as , with u 0 being the scattered wave field corresponding to a sound-hard K 0. The convergence result is used to theoretically justify the approximate full and partial invisibility cloaks, depending on the geometry of K 0. On the other hand, the convergence results are conducted in a much more general setting than what is needed for the invisibility cloaking, so they are of significant mathematical interest for their own sake. As for applications, we construct three types of full and partial cloaks. Some numerical experiments are
NASA Astrophysics Data System (ADS)
Wu, Haijun; Jiang, Weikang; Zhang, Haibin
2016-07-01
In the procedure of the near-field acoustic holography (NAH) based on the fundamental solutions for Helmholtz equation (FS), the number of FS and the measurement setup to obtain their coefficients are two crucial issues to the successful reconstruction. The current work is motivated to develop a framework for the NAH which supplies a guideline to the determination of the number of FS as well as an optimized measurement setup. A mapping relationship between modes on surfaces of boundary and hologram is analytically derived by adopting the modes as FS in spherical coordinates. Thus, reconstruction is converted to obtain the coefficients of participant modes on holograms. In addition, an integral identity is firstly to be derived for the modes on convex surfaces, which is useful in determining the inefficient or evanescent modes for acoustic radiation in free space. To determine the number of FS adopted in the mapping relationship based NAH (MRS-based NAH), two approaches are proposed to supply reasonable estimations with criteria of point-wise pressure and energy, respectively. A technique to approximate a specific degree of mode on patches by a set of locally orthogonal patterns is explored for three widely used holograms, such as planar, cylindrical and spherical holograms, which results in an automatic determinations of the number and position of experimental setup for a given tolerance. Numerical examples are set up to validate the theory and techniques in the MRS-based NAH. Reconstructions of a cubic model demonstrate the potential of the proposed method for regular models even with corners and shapers. Worse results for the elongated cylinder with two spherical caps reveal the deficiency of the MRS-based NAH for irregular models which is largely due to the adopted modes are FS in spherical coordinates. The NAH framework pursued in the current work provides a new insight to the reconstruction procedure based on the FS in spherical coordinates.
NASA Astrophysics Data System (ADS)
Samtaney, Ravi; Mohamed, Mamdouh; Hirani, Anil
2015-11-01
We present examples of numerical solutions of incompressible flow on 2D curved domains. The Navier-Stokes equations are first rewritten using the exterior calculus notation, replacing vector calculus differential operators by the exterior derivative, Hodge star and wedge product operators. A conservative discretization of Navier-Stokes equations on simplicial meshes is developed based on discrete exterior calculus (DEC). The discretization is then carried out by substituting the corresponding discrete operators based on the DEC framework. By construction, the method is conservative in that both the discrete divergence and circulation are conserved up to machine precision. The relative error in kinetic energy for inviscid flow test cases converges in a second order fashion with both the mesh size and the time step. Numerical examples include Taylor vortices on a sphere, Stuart vortices on a sphere, and flow past a cylinder on domains with varying curvature. Supported by the KAUST Office of Competitive Research Funds under Award No. URF/1/1401-01.
NASA Astrophysics Data System (ADS)
Natarajan, Logesh Kumar
This dissertation presents a structure-borne noise analysis technology that is focused on providing a cost-effective noise reduction strategy. Structure-borne sound is generated or transmitted through structural vibration; however, only a small portion of the vibration can effectively produce sound and radiate it to the far-field. Therefore, cost-effective noise reduction is reliant on identifying and suppressing the critical vibration components that are directly responsible for an undesired sound. However, current technologies cannot successfully identify these critical vibration components from the point of view of direct contribution to sound radiation and hence cannot guarantee the best cost-effective noise reduction. The technology developed here provides a strategy towards identifying the critical vibration components and methodically suppressing them to achieve a cost-effective noise reduction. The core of this technology is Helmholtz equation least squares (HELS) based nearfield acoustic holography method. In this study, the HELS formulations derived in spherical co-ordinates using spherical wave expansion functions utilize the input data of acoustic pressures measured in the nearfield of a vibrating object to reconstruct the vibro-acoustic responses on the source surface and acoustic quantities in the far field. Using these formulations, three steps were taken to achieve the goal. First, hybrid regularization techniques were developed to improve the reconstruction accuracy of normal surface velocity of the original HELS method. Second, correlations between the surface vibro-acoustic responses and acoustic radiation were factorized using singular value decomposition to obtain orthogonal basis known here as the forced vibro-acoustic components (F-VACs). The F-VACs enables one to identify the critical vibration components for sound radiation in a similar manner that modal decomposition identifies the critical natural modes in a structural vibration. Finally
Ciraolo, Giulio Gargano, Francesco Sciacca, Vincenzo
2013-08-01
We study a new approach to the problem of transparent boundary conditions for the Helmholtz equation in unbounded domains. Our approach is based on the minimization of an integral functional arising from a volume integral formulation of the radiation condition. The index of refraction does not need to be constant at infinity and may have some angular dependency as well as perturbations. We prove analytical results on the convergence of the approximate solution. Numerical examples for different shapes of the artificial boundary and for non-constant indexes of refraction will be presented.
A parallel multigrid-based preconditioner for the 3D heterogeneous high-frequency Helmholtz equation
Riyanti, C.D. . E-mail: C.D.Riyanti@tudelft.nl; Kononov, A.; Erlangga, Y.A.; Vuik, C.; Oosterlee, C.W.; Plessix, R.-E.; Mulder, W.A.
2007-05-20
We investigate the parallel performance of an iterative solver for 3D heterogeneous Helmholtz problems related to applications in seismic wave propagation. For large 3D problems, the computation is no longer feasible on a single processor, and the memory requirements increase rapidly. Therefore, parallelization of the solver is needed. We employ a complex shifted-Laplace preconditioner combined with the Bi-CGSTAB iterative method and use a multigrid method to approximate the inverse of the resulting preconditioning operator. A 3D multigrid method with 2D semi-coarsening is employed. We show numerical results for large problems arising in geophysical applications.
NASA Technical Reports Server (NTRS)
Zhong, W. F.; Fu, L. S.
1983-01-01
Results are presented for volume integrals associated with the Helmholtz operator, nabla(2) + alpha(2), for the cases of a finite cylindrical region and a region of rectangular parallelepiped. By using appropriate Taylor series expansions and multinomial theorem, these volume integrals are obtained in series form for regions r r' and r 4', where r and r' are distances from the origin to the point of observation and source, respectively. When the wave number approaches zero, the results reduce directly to the potentials of variable densities.
The Dirichlet problem for the two-dimensional Helmholtz equation for an open boundary
NASA Technical Reports Server (NTRS)
Hayashi, Y.
1973-01-01
Development of a complete theory of the two-dimensional Dirichlet problem for an open boundary. It is shown that the solution of the Dirichlet problem for an open boundary requires the solution of a Fredholm integral equation of the first kind. Although a Fredholm integral equation of the first kind usually has no solution if the kernel is continuous, owing to the logarithmic singularity of the kernel, the equation in this case is converted to a singular integral equation with a Cauchy kernel. It is proven that the homogeneous adjoint equation of the singular integral equation has no nonzero solution. By virtue of this result, and with the aid of an existence theorem known in the theory of singular integral equations, the existence of solutions of the singular integral equation, and then of the unique solution of the Fredholm integral equation of the first kind is proved.
NASA Technical Reports Server (NTRS)
Grosse, Ralf
1990-01-01
Propagation of sound through the turbulent atmosphere is a statistical problem. The randomness of the refractive index field causes sound pressure fluctuations. Although no general theory to predict sound pressure statistics from given refractive index statistics exists, there are several approximate solutions to the problem. The most common approximation is the parabolic equation method. Results obtained by this method are restricted to small refractive index fluctuations and to small wave lengths. While the first condition is generally met in the atmosphere, it is desirable to overcome the second. A generalization of the parabolic equation method with respect to the small wave length restriction is presented.
NASA Astrophysics Data System (ADS)
Chapman, Alexander Lloyd
Recently, a sound source identification technique called CRAFT was developed as an advance in the state of the art in inverse noise problems. It addressed some limitations associated with nearfield acoustic holography and a few of the issues with inverse boundary element method. This work centers on two critical issues associated with the CRAFT algorithm. Although CRAFT employs the complete general solution associated with the Helmholtz equation, the approach taken to derive those equations results in computational inefficiency when implemented numerically. In this work, a mathematical approach to derivation of the basis equations results in a doubling in efficiency. This formulation of CRAFT is termed general Helmholtz equation, least-squares method (GEN-HELS). Additionally, the numerous singular points present in the gradient of the basis functions are shown here to resolve to finite limits. As a realistic test case, a diesel engine surface pressure and velocity are reconstructed to show the increase in efficiency from CRAFT to GEN-HELS. Keywords: Inverse Numerical Acoustics, Acoustic Holography, Helmholtz Equation, HELS Method, CRAFT Algorithm.
NASA Technical Reports Server (NTRS)
Young, D. P.; Woo, A. C.; Bussoletti, J. E.; Johnson, F. T.
1986-01-01
A general method is developed combining fast direct methods and boundary integral equation methods to solve Poisson's equation on irregular exterior regions. The method requires O(N log N) operations where N is the number of grid points. Error estimates are given that hold for regions with corners and other boundary irregularities. Computational results are given in the context of computational aerodynamics for a two-dimensional lifting airfoil. Solutions of boundary integral equations for lifting and nonlifting aerodynamic configurations using preconditioned conjugate gradient are examined for varying degrees of thinness.
NASA Astrophysics Data System (ADS)
Nakao, Mitsuhiro
We prove the existence of global decaying solutions to the exterior problem for the Klein-Gordon equation with a nonlinear localized dissipation and a derivative nonlinearity. To derive the required estimates of solutions we employ a 'loan' method.
Inverse scattering for an exterior Dirichlet program
NASA Technical Reports Server (NTRS)
Hariharan, S. I.
1981-01-01
Scattering due to a metallic cylinder which is in the field of a wire carrying a periodic current is considered. The location and shape of the cylinder is obtained with a far field measurement in between the wire and the cylinder. The same analysis is applicable in acoustics in the situation that the cylinder is a soft wall body and the wire is a line source. The associated direct problem in this situation is an exterior Dirichlet problem for the Helmholtz equation in two dimensions. An improved low frequency estimate for the solution of this problem using integral equation methods is presented. The far field measurements are related to the solutions of boundary integral equations in the low frequency situation. These solutions are expressed in terms of mapping function which maps the exterior of the unknown curve onto the exterior of a unit disk. The coefficients of the Laurent expansion of the conformal transformations are related to the far field coefficients. The first far field coefficient leads to the calculation of the distance between the source and the cylinder.
NASA Astrophysics Data System (ADS)
Chatterjee, Kausik
2016-06-01
The objective of this paper is the extension and application of a newly-developed Green's function Monte Carlo (GFMC) algorithm to the estimation of the derivative of the solution of the one-dimensional (1D) Helmholtz equation subject to Neumann and mixed boundary conditions problems. The traditional GFMC approach for the solution of partial differential equations subject to these boundary conditions involves "reflecting boundaries" resulting in relatively large computational times. My work, inspired by the work of K.K. Sabelfeld is philosophically different in that there is no requirement for reflection at these boundaries. The underlying feature of this algorithm is the elimination of the use of reflecting boundaries through the use of novel Green's functions that mimic the boundary conditions of the problem of interest. My past work has involved the application of this algorithm to the estimation of the solution of the 1D Laplace equation, the Helmholtz equation and the modified Helmholtz equation. In this work, this algorithm has been adapted to the estimation of the derivative of the solution which is a very important development. In the traditional approach involving reflection, to estimate the derivative at a certain number of points, one has to a priori estimate the solution at a larger number of points. In the case of a one-dimensional problem for instance, to obtain the derivative of the solution at a point, one has to obtain the solution at two points, one on each side of the point of interest. These points have to be close enough so that the validity of the first-order approximation for the derivative operator is justified and at the same time, the actual difference between the solutions at these two points has to be at least an order of magnitude higher than the statistical error in the estimation of the solution, thus requiring a significantly larger number of random-walks than that required for the estimation of the solution. In this new approach
NASA Astrophysics Data System (ADS)
Chevalier, Paul; Bouchon, Patrick; Haïdar, Riad; Pardo, Fabrice
2014-08-01
Helmholtz resonators are widely used acoustic components able to select a single frequency. Here, based on an analogy between acoustics and electromagnetism wave equations, we present an electromagnetic 2D Helmholtz resonator made of a metallic slit-box structure. At the resonance, the light is funneled in the λ/800 apertures, and is subsequently absorbed in the cavity. As in acoustics, there is no higher order of resonance, which is an appealing feature for applications such as photodetection or thermal emission. Eventually, we demonstrate that the slit is of capacitive nature while the box behaves inductively. We derive an analytical formula for the resonance wavelength, which does not rely on wave propagation and therefore does not depend on the permittivity of the material filling the box. Besides, in contrast with half-wavelength resonators, the resonance wavelength can be engineered by both the slit aspect ratio and the box area.
NASA Astrophysics Data System (ADS)
Amore, Paolo; Boyd, John P.; Fernández, Francisco M.; Rösler, Boris
2016-05-01
We apply second order finite differences to calculate the lowest eigenvalues of the Helmholtz equation, for complicated non-tensor domains in the plane, using different grids which sample exactly the border of the domain. We show that the results obtained applying Richardson and Padé-Richardson extrapolations to a set of finite difference eigenvalues corresponding to different grids allow us to obtain extremely precise values. When possible we have assessed the precision of our extrapolations comparing them with the highly precise results obtained using the method of particular solutions. Our empirical findings suggest an asymptotic nature of the FD series. In all the cases studied, we are able to report numerical results which are more precise than those available in the literature.
NASA Astrophysics Data System (ADS)
Kolybasova, V. V.; Krutitskii, P. A.
2010-09-01
We consider a skew derivative problem for a function which is harmonic in the exterior of open arcs in a plane. This problem models electric current in a semiconductor film from electrodes of arbitrary shapes in the presence of a magnetic field. A numerical method for solving the problem is proposed. The method is based on the boundary integral equation approach. The proposed numerical method is tested for different values of parameters and different shapes of the electrodes.
Dahms, Rainer N.
2014-12-31
The fidelity of Gradient Theory simulations depends on the accuracy of saturation properties and influence parameters, and require equations of state (EoS) which exhibit a fundamentally consistent behavior in the two-phase regime. Widely applied multi-parameter EoS, however, are generally invalid inside this region. Hence, they may not be fully suitable for application in concert with Gradient Theory despite their ability to accurately predict saturation properties. The commonly assumed temperature-dependence of pure component influence parameters usually restricts their validity to subcritical temperature regimes. This may distort predictions for general multi-component interfaces where temperatures often exceed the critical temperature of vapor phase components. Then, the calculation of influence parameters is not well defined. In this paper, one of the first studies is presented in which Gradient Theory is combined with a next-generation Helmholtz energy EoS which facilitates fundamentally consistent calculations over the entire two-phase regime. Illustrated on pentafluoroethane as an example, reference simulations using this method are performed. They demonstrate the significance of such high-accuracy and fundamentally consistent calculations for the computation of interfacial properties. These reference simulations are compared to corresponding results from cubic PR EoS, widely-applied in combination with Gradient Theory, and mBWR EoS. The analysis reveals that neither of those two methods succeeds to consistently capture the qualitative distribution of obtained key thermodynamic properties in Gradient Theory. Furthermore, a generalized expression of the pure component influence parameter is presented. This development is informed by its fundamental definition based on the direct correlation function of the homogeneous fluid and by presented high-fidelity simulations of interfacial density profiles. As a result, the new model preserves the accuracy of previous
Dahms, Rainer N.
2014-12-31
The fidelity of Gradient Theory simulations depends on the accuracy of saturation properties and influence parameters, and require equations of state (EoS) which exhibit a fundamentally consistent behavior in the two-phase regime. Widely applied multi-parameter EoS, however, are generally invalid inside this region. Hence, they may not be fully suitable for application in concert with Gradient Theory despite their ability to accurately predict saturation properties. The commonly assumed temperature-dependence of pure component influence parameters usually restricts their validity to subcritical temperature regimes. This may distort predictions for general multi-component interfaces where temperatures often exceed the critical temperature of vapor phasemore » components. Then, the calculation of influence parameters is not well defined. In this paper, one of the first studies is presented in which Gradient Theory is combined with a next-generation Helmholtz energy EoS which facilitates fundamentally consistent calculations over the entire two-phase regime. Illustrated on pentafluoroethane as an example, reference simulations using this method are performed. They demonstrate the significance of such high-accuracy and fundamentally consistent calculations for the computation of interfacial properties. These reference simulations are compared to corresponding results from cubic PR EoS, widely-applied in combination with Gradient Theory, and mBWR EoS. The analysis reveals that neither of those two methods succeeds to consistently capture the qualitative distribution of obtained key thermodynamic properties in Gradient Theory. Furthermore, a generalized expression of the pure component influence parameter is presented. This development is informed by its fundamental definition based on the direct correlation function of the homogeneous fluid and by presented high-fidelity simulations of interfacial density profiles. As a result, the new model preserves the accuracy of
Northeastern Exterior, Northwestern Exterior, & Southwestern Exterior Elevations, Northeastern Interior, Southeastern Interior, & Southwestern Interior Elevations, Floor Plan, and Eastern Corner Detail - Manatoc Reservation, Vale Edge Adirondack, 1075 Truxell Road, Peninsula, Summit County, OH
2013 Problem 12: Helmholtz Carousel
NASA Astrophysics Data System (ADS)
Qi, Jia'an; Qin, Zhihang; Wang, Sihui; Zhou, Huijun
2015-10-01
In our solution, we try to investigate the origin of the force that propels the Helmholtz Carousel. We build a theoretical model from the fundamental hydrodynamics. As the propelling force is in fact a nonlinear effect, we examine the nonlinear terms with care. The nonlinear terms in our equation corresponding to two origins of the force: one origins from the nonlinearity of the impedance, the other origins from nonlinear "restoring force". We will prove that the true origin of the force effect is the nonlinear impedance, which resembles the recoil force of a balloon that breathes air in and out unsymmetrically in a period of motion. Modification to linear impedance is also made which is important in giving a correct resonant frequency. Finally, we optimize the Helmholtz carousel according to the predictions of our model. Among the parameters we investigated, specific frequency, neck length, neck radius values exist to optimize the Helmholtz carousel, while larger resonator volume produces larger driving force. Predictions based on our model are supported by experimental results.
Visualizing interior and exterior jet aircraft noise
NASA Astrophysics Data System (ADS)
Moondra, Manmohan S.
In today's competitive aerospace industry, the quest for quiet has drawn significant attention to both the interior and exterior design of an airplane. Understanding the noise generation mechanisms of a jet aircraft is a crucial first step toward developing the most cost-effective noise and vibrations abatement methods. In this investigation, the Helmholtz Equation Least Squares (HELS) based nearfield acoustic holography will be used to understand noise transmission caused by jet engine and turbulence into the fuselage of a jet aircraft cruising at 30,000 ft. Modern propulsive jet engines produce exterior noise sources with a high amplitude noise field and complicated characteristics, which makes them very difficult to characterize. In particular, there are turbulent eddies that are moving through the jet at high speeds along the jet boundary. These turbulent eddies in the shear layer produce a directional and frequency dependent noise. The original HELS approach assumes a spherical source at the origin and computes the acoustic field based on spherical emission from this source. This assumption of one source at the origin is not sufficient to characterize a complex source like a jet. As such, a modified HELS approach is introduced that will help improve the source characterization as it is not dependent on a single source at the origin but a number of virtual sources throughout the space. Custom microphones are created to take acoustic pressure measurements around the jet engine. These measured acoustic pressures are then taken as input to the modified HELS algorithm to visualize the noise pattern of a subsonic jet engine.
Inverse scattering for an exterior Dirichlet problem. [due to metallic cylinder
NASA Technical Reports Server (NTRS)
Hariharan, S. I.
1982-01-01
Scattering caused by a metallic cylinder in the field of a wire carrying a periodic current is studied, with a view to determining the location and shape of the cylinder in light of far field measurements between the cylinder and the wire. The associated direct problem is the exterior Dirichlet problem for the Helmholtz equation in two dimensions, and an improved low frequency estimate for its solution by integral equation methods is shown by inverse scattering calculations to be accurate to this estimate. The far field measurements are related to low frequency boundary integral equations whose solutions may be expressed in terms of a mapping function for the exterior of the unknown curve onto the exterior of a unit disk. The conformal transformation's Laurent expansion coefficients can be related to those of the far field, the first of which leads to the calculation of the distance between the source and the cylinder, while the other coefficients are determined by placing the source in a different location.
Solution of Exterior Acoustic Problems by the Boundary Element Method.
NASA Astrophysics Data System (ADS)
Kirkup, Stephen Martin
Available from UMI in association with The British Library. The boundary element method is described and investigated, especially in respect of its application to exterior two -dimensional Laplace problems. Both empirical and algebraic analyses (including the effects of approximation of the boundary and boundary functions and the precision of the evaluation of the discrete forms) are developed. Methods for the automatic evaluation of the discrete forms of the Laplace and Helmholtz integral operators are reviewed and extended. Boundary element methods for the solution of exterior Helmholtz problems with general (but most importantly Neumann) boundary conditions are reviewed and some are explicitly stated using a new notation. Boundary element methods based on the boundary integral equations introduced by Brakhage & Werner/ Leis/ Panich/ Kussmaul (indirect) and Burton & Miller (direct) are given prime consideration and implemented for three -dimensional problems. The influence of the choice of weighting parameter on the performance of the methods is explored and further guidance is given. The application of boundary element methods and methods based on the Rayleigh integral to acoustic radiation problems are considered. Methods for speeding up their solution via the boundary element method are developed. Library subroutines for the solution of acoustic radiation problems are described and demonstrated. Computational techniques for the problem of predicting the noise produced by a running engine are reviewed and appraised. The application of the boundary element method to low-noise engine design and in the design of noise shields is considered. The boundary element method is applied to the Ricardo crankcase simulation rig, which is an engine -like structure. A comparison of predicted and measured sound power spectra is given.
Solution of exterior acoustic problems by the boundary element method
NASA Astrophysics Data System (ADS)
Kirkup, Stephen Martin
The boundary element method is described and investigated, especially in respect of its application to exterior two-dimensional Laplace problems. Both empirical and algebraic analyses (including the effects of approximation of the boundary and boundary functions and the precision of the evaluation of the discrete forms) are developed. Methods for the automatic evaluation of the discrete forms of the Laplace and Helmholtz integral operators are reviewed and extended. Boundary element methods for the solution of exterior Helmholtz problems with general (but most importantly Neumann) boundary conditions are reviewed and some are explicitly stated using a new notation. Boundary element methods based on the boundary integral equations introduced by Brakhage and Werner/Leis/Panich/Kussmaul (indirect) and Burton and Miller (direct) are given prime consideration and implemented for three-dimensional problems. The influence of the choice of weighting parameter on the performance of the methods is explored and further guidance is given. The application of boundary element methods and methods based on the Rayleigh integral to acoustic radiation problems are considered. Methods for speeding up their solution via the boundary element method are developed. Library subroutines for the solution of acoustic radiation problems are described and demonstrated. Computational techniques for the problem of predicting the noise produced by a running engine are reviewed and appraised. The application of the boundary element method to low-noise engine design and in the design of noise shields is considered. The boundary element method is applied to the Ricardo crankcase simulation rig, which is an engine-like structure. A comparison of predicted and measured sound power spectra is given.
NASA Technical Reports Server (NTRS)
Hagstrom, Thomas; Hariharan, S. I.; Maccamy, R. C.
1993-01-01
We consider the solution of scattering problems for the wave equation using approximate boundary conditions at artificial boundaries. These conditions are explicitly viewed as approximations to an exact boundary condition satisfied by the solution on the unbounded domain. We study the short and long term behavior of the error. It is provided that, in two space dimensions, no local in time, constant coefficient boundary operator can lead to accurate results uniformly in time for the class of problems we consider. A variable coefficient operator is developed which attains better accuracy (uniformly in time) than is possible with constant coefficient approximations. The theory is illustrated by numerical examples. We also analyze the proposed boundary conditions using energy methods, leading to asymptotically correct error bounds.
Nonlinearity of Helmholtz resonators
NASA Technical Reports Server (NTRS)
Sirignano, W. A.
1972-01-01
Consideration of the nonlinear damping of pressure oscillations by means of acoustic liners consisting of a perforated plate communicating with a volume or of individual Helmholtz resonators. A nonlinear analysis leads to a modified first-order theory; in particular, some second-order damping effects (due to the formation of jets through the orifices) are considered, while other less important damping effects (of second order) are neglected. The effect of the vena contracta in the orifice flow is also taken into account, and the conditions of maximum damping are discussed. A determination is made of the orifice velocity, the cavity pressure, the admittance coefficient, the resistance, and the reactance, and good agreement is found between the theoretically determined resistance and orifice velocity and the pertinent experimental data.
Generalized Helmholtz Conditions for Non-Conservative Lagrangian Systems
NASA Astrophysics Data System (ADS)
Bucataru, Ioan; Constantinescu, Oana
2015-12-01
In this paper we provide generalized Helmholtz conditions, in terms of a semi-basic 1-form, which characterize when a given system of second order ordinary differential equations is equivalent to the Lagrange equations, for some given arbitrary non-conservative forces. For the particular cases of dissipative or gyroscopic forces, these conditions, when expressed in terms of a multiplier matrix, reduce to those obtained in Mestdag et al. (Differential Geom. Appl. 29(1), 55-72, 2011). When the involved geometric structures are homogeneous with respect to the fibre coordinates, we show how one can further simplify the generalized Helmholtz conditions. We provide examples where the proposed generalized Helmholtz conditions, expressed in terms of a semi-basic 1-form, can be integrated and the corresponding Lagrangian and Lagrange equations can be found.
Shim3d Helmholtz Solution Package
Energy Science and Technology Software Center (ESTSC)
2009-01-29
This suite of codes solves the Helmholtz Equation for the steady-state propagation of single-frequency electromagnetic radiation in an arbitrary 2D or 3D dielectric medium. Materials can be either transparent or absorptive (including metals) and are described entirely by their shape and complex dielectric constant. Dielectric boundaries are assumed to always fall on grid boundaries and the material within a single grid cell is considered to be uniform. Input to the problem is in the formmore » of a Dirichlet boundary condition on a single boundary, and may be either analytic (Gaussian) in shape, or a mode shape computed using a separate code (such as the included eigenmode solver vwave20), and written to a file. Solution is via the finite difference method using Jacobi iteration for 3D problems or direct matrix inversion for 2D problems. Note that 3D problems that include metals will require different iteration parameters than described in the above reference. For structures with curved boundaries not easily modeled on a rectangular grid, the auxillary codes helmholtz11(2D), helm3d (semivectoral), and helmv3d (full vectoral) are provided. For these codes the finite difference equations are specified on a topological regular triangular grid and solved using Jacobi iteration or direct matrix inversion as before. An automatic grid generator is supplied.« less
The Helmholtz Hierarchy: phase space statistics of cold dark matter
Tassev, Svetlin V.
2011-10-01
We present a new formalism to study large-scale structure in the universe. The result is a hierarchy (which we call the ''Helmholtz Hierarchy'') of equations describing the phase space statistics of cold dark matter (CDM). The hierarchy features a physical ordering parameter which interpolates between the Zel'dovich approximation and fully-fledged gravitational interactions. The results incorporate the effects of stream crossing. We show that the Helmholtz hierarchy is self-consistent and obeys causality to all orders. We present an interpretation of the hierarchy in terms of effective particle trajectories.
Evaluation of the applicability of Helmholtz resonators for low frequency acoustic liners
NASA Astrophysics Data System (ADS)
Vanderwal, J. M. M.
1988-09-01
A literature study was performed on the acoustic behavior of those Helmholtz resonator type liners which are most promising for low frequency sound absorption in aero-engine applications. The equations for the acoustic impedance of various types of Helmholtz resonators were analyzed as well as the conditions for the validity of these equations. An experimental program is defined for a further analysis of various types of resonators.
Zhou Qi-huang
1988-12-01
Starting with the general expression of a static state axisymmetric metric and using the principle of equivalence and the Maccullagh formula, the Einstein--Maxwell equations of a charged axisymmetric celestial body are obtained. Next, using the method of undetermined coefficients these equations are solved up to fourth-order approximate. These sets of solutions are generally appropriate for all kinds of charged axisymmetric celestial bodies.
28. EXTERIOR CAN CONVEYOR Exterior section of empty can ...
28. EXTERIOR - CAN CONVEYOR Exterior section of empty can conveyor which transported cans from the third floor of the main warehouse (right) to the canning area. - Hovden Cannery, 886 Cannery Row, Monterey, Monterey County, CA
Helmholtz solitons at nonlinear interfaces.
Sánchez-Curto, J; Chamorro-Posada, P; McDonald, G S
2007-05-01
Reflection and refraction of spatial solitons at dielectric interfaces, accommodating arbitrarily angles of incidence, is studied. Analysis is based on Helmholtz soliton theory, which eliminates the angular restriction associated with the paraxial approximation. A novel generalization of Snell's law is discovered that is valid for collimated light beams and the entire angular domain. Our new theoretical predictions are shown to be in excellent agreement with full numerical simulations. New qualitative features of soliton refraction and limitations of previous paraxial analyses are highlighted. PMID:17410257
Fluid mechanical model of the Helmholtz resonator
NASA Technical Reports Server (NTRS)
Hersh, A. S.; Walker, B.
1977-01-01
A semi-empirical fluid mechanical model of the acoustic behavior of Helmholtz resonators is presented which predicts impedance as a function of the amplitude and frequency of the incident sound pressure field and resonator geometry. The model assumes that the particle velocity approaches the orifice in a spherical manner. The incident and cavity sound fields are connected by solving the governing oscillating mass and momentum conservation equations. The model is in agreement with the Rayleigh slug-mass model at low values of incident sound pressure level. At high values, resistance is predicted to be independent of frequency, proportional to the square root of the amplitude of the incident sound pressure field, and virtually independent of resonator geometry. Reactance is predicted to depend in a very complicated way upon resonator geometry, incident sound pressure level, and frequency. Nondimensional parameters are defined that divide resonator impedance into three categories corresponding to low, moderately low, and intense incident sound pressure amplitudes. The two-microphone method was used to measure the impedance of a variety of resonators. The data were used to refine and verify the model.
A tunable electromechanical Helmholtz resonator
NASA Astrophysics Data System (ADS)
Liu, Fei
Acoustic liners are used in turbofan engine nacelles for the suppression of engine noise. For a given engine, there are different optimum impedance distributions associated with take-off, cut-back, and approach flight conditions. The impedance of conventional acoustic liners is fixed for a given geometry, and conventional active liner approaches are impractical. This project addresses the need for a tunable impedance through the development of an electromechanical Helmholtz resonator (EMHR). The device consists of a Helmholtz resonator with the standard rigid backplate replaced by a compliant piezoelectric composite. Analytical models (i.e., a lumped element model (LEM) and a transfer matrix (TM) representation of the EMHR) are developed to predict the acoustic behavior of the EMHR. The EMHR is experimentally investigated using the standard two-microphone method (TMM). The measurement results validate both the LEM and the TM of the EMHR. Good agreement between predicted and measured impedance is obtained. Short- and open-circuit loads define the limits of the tuning range using resistive and capacitive loads. There is approximately a 9% tuning limit under these conditions for the non-optimized resonator configuration studied. Inductive shunt loads result in a 3 degree-of-freedom (DOF) system and an enhanced tuning range of over 47% that is not restricted by the short- and open-circuit limits. Damping coefficient measurements for a piezoelectric backplate in a vacuum chamber are performed and indicate that the damping is dominated by structural damping losses. A Pareto optimization design based on models of the EMHR is performed with non-inductive loads. The EMHR with non-inductive loads has 2DOF and two resonant frequencies. The tuning ranges of the two resonant frequencies of the EMHR with non-inductive loads cannot be optimized simultaneously, so a trade-off (Pareto solution) must be reached. The Pareto solution shows how design trade-offs can be used to satisfy
De Kock, Liesbet
2016-04-01
In this analysis, the classical problem of Hermann von Helmholtz's (1821-1894) Kantianism is explored from a particular vantage point, that to my knowledge, has not received the attention it deserves notwithstanding its possible key role in disentangling Helmholtz's relation to Kant's critical project. More particularly, we will focus on Helmholtz's critical engagement with Kant's concept of intuition [Anschauung] and (the related issue of) his dissatisfaction with Kant's doctrinal dualism. In doing so, it soon becomes clear that both (i) crucially mediated Helmholtz's idiosyncratic appropriation and criticism of (certain aspects of) Kant's critical project, and (ii) can be considered as a common denominator in a variety of issues that are usually addressed separately under the general header of (the problem of) Helmholtz's Kantianism. The perspective offered in this analysis can not only shed interesting new light on some interpretive issues that have become commonplace in discussions on Helmholtz's Kantianism, but also offers a particular way of connecting seemingly unrelated dimensions of Helmholtz's engagement with Kant's critical project (e.g. Helmholtz's views on causality and space). Furthermore, it amounts to the rather surprising conclusion that Helmholtz's most drastic revision of Kant's project pertains to his assumption of free will as a formal condition of experience and knowledge. PMID:27083081
A transverse Kelvin-Helmholtz instability in a magnetized plasma
NASA Technical Reports Server (NTRS)
Kintner, P.; Dangelo, N.
1977-01-01
An analysis is conducted of the transverse Kelvin-Helmholtz instability in a magnetized plasma for unstable flute modes. The analysis makes use of a two-fluid model. Details regarding the instability calculation are discussed, taking into account the ion continuity and momentum equations, the solution of a zero-order and a first-order component, and the properties of the solution. It is expected that the linear calculation conducted will apply to situations in which the plasma has experienced no more than a few growth periods.
Parametric design of tri-axial nested Helmholtz coils
Abbott, Jake J.
2015-05-15
This paper provides an optimal parametric design for tri-axial nested Helmholtz coils, which are used to generate a uniform magnetic field with controllable magnitude and direction. Circular and square coils, both with square cross section, are considered. Practical considerations such as wire selection, wire-wrapping efficiency, wire bending radius, choice of power supply, and inductance and time response are included. Using the equations provided, a designer can quickly create an optimal set of custom coils to generate a specified field magnitude in the uniform-field region while maintaining specified accessibility to the central workspace. An example case study is included.
Sunshade for building exteriors
Braunstein, Richard; McKenna, Gregory B.; Hewitt, David W.; Harper, Randolph S.
2002-01-01
A sunshade for shading window exteriors includes at least one connecting bracket for attachment to a window mullion, a blade support strut attached to the connecting bracket at a first joint, and a plurality of louvered blades supported by the blade support strut at a second joint. The pivot angle at the first joint may be varied to extend the louvered blades a desired distance from the window mullion. The louvered blades are positioned at a preselected fixed profile angle on the second joint in order to optimize shading at the latitude where the sunshade is installed. In a preferred embodiment, the louvered blades have top walls supporting photovoltaic cells and the sunshade includes electric cables for connecting the photovoltaic cells to an electric circuit.
Kelvin-Helmholtz instabilities with Godunov smoothed particle hydrodynamics
NASA Astrophysics Data System (ADS)
Cha, Seung-Hoon; Inutsuka, Shu-Ichiro; Nayakshin, Sergei
2010-04-01
Numerical simulations for the non-linear development of Kelvin-Helmholtz instability in two different density layers have been performed with the particle-based method (Godunov SPH) developed by Inutsuka. The Godunov SPH can describe the Kelvin-Helmholtz instability even with a high-density contrast, while the standard SPH shows the absence of the instability across a density gradient. The interaction of a dense blob with a hot ambient medium has been performed also. The Godunov SPH describes the formation and evolution of the fingers due to the combinations of Rayleigh-Taylor, Richtmyer-Meshkov and Kelvin-Helmholtz instabilities. The blob test result coincides well with the results of the grid-based codes. An inaccurate handling of a density gradient in the standard SPH has been pointed out as the direct reason of the absence of the instabilities. An unphysical force happens at the density gradient even in a pressure equilibrium, and repulses particles from the initial density discontinuity. Therefore, the initial perturbation damps, and a gap form at the discontinuity. The unphysical force has been studied in terms of the consistency of a numerical scheme. Contrary to the standard SPH, the momentum equation of the Godunov SPH does not use the particle approximation, and has been derived from the kernel convolution or a new Lagrangian function. The new Lagrangian function used in the Godunov SPH is more analogous to the real Lagrangian function for continuum. The momentum equation of the Godunov SPH has much better linear consistency, so the unphysical force is greatly reduced compared to the standard SPH in a high density contrast.
Extraordinary acoustic transmission mediated by Helmholtz resonators
Koju, Vijay; Rowe, Ebony; Robertson, William M.
2014-07-15
We demonstrate perfect transmission of sound through a rigid barrier embedded with Helmholtz resonators. The resonators are confined within a waveguide and they are oriented such that one neck protrudes onto each side of the barrier. Perfect sound transmission occurs even though the open area of the necks is less than 3% of the barrier area. Maximum transmission occurs at the resonant frequency of the Helmholtz resonator. Because the dimensions of the Helmholtz resonators are much smaller than the resonant wavelength, the transmission is independent of the direction of sound on the barrier and of the relative placement of the necks. Further, we show that the transmitted sound experiences a continuous phase transition of π radians as a function of frequency through resonance. In simulations of adjacent resonators with slightly offset resonance frequencies, the phase difference leads to destructive interference. By expanding the simulation to a linear array of tuned Helmholtz resonators we show that it is possible to create an acoustic lens. The ability of Helmholtz resonator arrays to manipulate the phase of a plane acoustic wave enables a new class of sonic beam-forming devices analogous to diffractive optics.
Laplace-Gauss and Helmholtz-Gauss paraxial modes in media with quadratic refraction index.
Kiselev, Aleksei P; Plachenov, Alexandr B
2016-04-01
The scalar theory of paraxial wave propagation in an axisymmetric medium where the refraction index quadratically depends on transverse variables is addressed. Exact solutions of the corresponding parabolic equation are presented, generalizing the Laplace-Gauss and Helmholtz-Gauss modes earlier known for homogeneous media. Also, a generalization of a zero-order asymmetric Bessel-Gauss beam is given. PMID:27140777
Exterior dimension of fat fractals
NASA Technical Reports Server (NTRS)
Grebogi, C.; Mcdonald, S. W.; Ott, E.; Yorke, J. A.
1985-01-01
Geometric scaling properties of fat fractal sets (fractals with finite volume) are discussed and characterized via the introduction of a new dimension-like quantity which is called the exterior dimension. In addition, it is shown that the exterior dimension is related to the 'uncertainty exponent' previously used in studies of fractal basin boundaries, and it is shown how this connection can be exploited to determine the exterior dimension. Three illustrative applications are described, two in nonlinear dynamics and one dealing with blood flow in the body. Possible relevance to porous materials and ballistic driven aggregation is also noted.
Theory of a generalized Helmholtz resonator.
NASA Technical Reports Server (NTRS)
Tang, P. K.; Sirignano, W. A.
1973-01-01
Based on the jet-flow model which is manifested in the nonlinearity of the orifice flow upon the passage of a high intensity wave, the theory of a generalized Helmholtz resonator has been developed. The results for some special devices, such as the conventional Helmholtz resonator and the quarter-wave tube, can be obtained through this general approach. The performance of the acoustic damper is characterized by a quantity known as the real part of the admittance coefficient. It is known that the conventional Helmholtz resonator has the lowest peak performance but the response is quite flat over a certain frequency range. On the other hand, a quarter-wave tube offers the largest peak in energy absorption with rather poor off-resonance behavior. Once the orifice length goes beyond the quarter-wave tube configuration, the performance of the so-called long damping device is even less attractive away from resonance.
Helmholtz and the psychophysiology of time.
Debru, C
2001-09-01
After having measured the velocity of the nervous impulse in the 1850s, Helmholtz began doing research on the temporal dimensions of visual perception. Experiments dealing with the velocity of propagation in nerves (as well as with aspects of perception) were carried out occasionally for some fifteen years until their final publication in 1871. Although the temporal dimension of perception seems to have interested Helmholtz less than problems of geometry and space, his experiments on the time of perception were technically rather subtle and seminal, especially compared with experiments performed by his contemporaries, such as Sigmund Exner, William James, Rudolf Hermann Lotze, Ernst Mach, Wilhelm Volkmann, and Wilhelm Wundt. Helmholtz's conception of the temporal aspects of perception reflects the continuity that holds between psychophysiological research and the Kantian philosophical background. PMID:12068897
Large Eddy Simulations of Kelvin-Helmholtz Instabilities in Stratified Ocean Flows
NASA Astrophysics Data System (ADS)
Brown, Dana; Goodman, Louis; Raessi, Mehdi
2012-11-01
Numerical simulations of turbulence in the ocean environment are used to supplement and enhance understanding of observational data. Here, using the NGA framework (Dejardins et al., JCP 2008), direct numerical simulations (DNS) and large eddy simulations (LES) of Kelvin-Helmholtz instabilities are employed to study turbulence in presence of density stratification. Kelvin-Helmholtz instabilities have been shown to be a common source of turbulence in the ocean. Past DNS studies of Kelvin Helmholtz instabilities have compared favorably with observational data, but were limited to moderate Reynolds numbers. Here, LES is used to solve the filtered incompressible NS equations at a higher Reynolds number, Re = 10,000. The effect of increased Reynolds number on the turbulence behavior is examined in terms of velocity spectra and energy budgets.
Non-static vacuum strings: exterior and interior solutions
Stein-Schabes, J.A.
1986-01-01
New non-static cylindrically symmetric solutions of Einsteins's equations are presented. Some of these solutions represent string-like objects. An exterior vacuum solution is matched to a non-vacuum interior solution for different forms of the energy-momentum tensor. They generalize the standard static string. 12 refs.
De Kock, Liesbet
2014-12-01
This paper aims at contributing to the ongoing efforts to get a firmer grasp of the systematic significance of the entanglement of idealism and empiricism in Helmholtz's work. Contrary to existing analyses, however, the focal point of the present exposition is Helmholtz's attempt to articulate a psychological account of objectification. Helmholtz's motive, as well as his solution to the problem of the object are outlined, and interpreted against the background of his scientific practice on the one hand, and that of empiricist and (transcendental) idealist analyses of experience on the other. The specifically psychological angle taken, not only prompts us to consider figures who have hitherto been treated as having only minor import for Helmholtz interpretation (most importantly J.S. Mill and J.G. Fichte), it furthermore sheds new light on some central tenets of the latter's psychological stance that have hitherto remained underappreciated. For one thing, this analysis reveals an explicit voluntarist tendency in Helmholtz's psychological theory. In conclusion, it is argued that the systematic significance of Helmholtz's empirico-transcendentalism with respect to questions of the mind is best understood as an attempt to found his empirical theory of perception in a second order, normative account of epistemic subjectivity. PMID:25549449
Pressure Calculation in a Compressor Cylinder by a Modified New Helmholtz Modelling
NASA Astrophysics Data System (ADS)
MA, Y.-C.; MIN, O.-K.
2001-06-01
Pressure pulsation has a critical importance in the design of refrigerant compressor since it affects the performance by increasing over-compression loss, and it acts as a noise and vibration source. For the numerical analysis of pressure pulsation, quasi-steady flow equation has been used because of its easy manipulation derived from the pressure difference. By considering the dynamic effects of fluid, a new Helmholtz resonator model was also proposed on the basis of the continuity and the momentum equations, which consists of necks and cavities in flow manifolds.In this paper, a modified new Helmholtz resonator is introduced to include the gas inertia effect due to the volume decrease in the cavity. Comparisons between this modified new Helmholtz calculations and experimental results show that it is necessary to include the gas inertia effect in predicting pressure over-shooting phenomena at an instant of valve opening state and this modified new Helmholtz model can describe the over-compression phenomena in the compressor cylinder, a phenomenon which hinders a noise source identification of compressor.
Hermann von Helmholtz and his students
NASA Astrophysics Data System (ADS)
Mulligan, Joseph F.
1989-01-01
During the years 1871-1888, when Hermann von Helmholtz was professor of physics at the University of Berlin, physicists from all over the world flocked to Berlin to study and do research with him. Among these were the German physicists Max Planck, Heinrich Kayser, Eugen Goldstein, Wilhelm Wien, and Heinrich Hertz, and Americans Henry Rowland, A. A. Michelson, and Michael Pupin. Examples of Helmholtz's scientific and personal interactions with these students and research associates show why he is justly considered the outstanding physics mentor of the 19th century. Both his ideas and his students played a major role in the development of physics in the late 19th and early 20th centuries.
Kelvin Helmholtz Instability in Planetary Magnetospheres
NASA Astrophysics Data System (ADS)
Johnson, Jay R.; Wing, Simon; Delamere, Peter A.
2014-11-01
Kelvin-Helmholtz instability plays a particularly important role in plasma transport at magnetospheric boundaries because it can control the development of a turbulent boundary layer, which governs the transport of mass, momentum, and energy across the boundary. Waves generated at the interface can also couple into body modes in the plasma sheet and inner magnetosphere where they can play an important role in plasma sheet transport and particle energization in the inner magnetosphere. Kinetic and electron-scale effects are important for the development of K-H instability, leading to secondary instabilities and plasma mixing. The development of vortices that entwine magnetosheath field lines with magnetospheric field lines also allows reconnection and the interchange of plasma blobs from open to closed field lines. Dawn-dusk asymmetries in Kelvin-Helmholtz development at planetary boundary layers may result from several effects including plasma corotation, kinetic effects, magnetic geometry, or asymmetric distribution of plasma. Examples are provided throughout the solar system illustrating the pervasive effects of the Kelvin-Helmholtz instability on plasma transport.
Cladding Attachment Over Thick Exterior Insulating Sheathing
Baker, P.; Eng, P.; Lepage, R.
2014-01-01
The addition of insulation to the exterior of buildings is an effective means of increasing the thermal resistance of both wood framed walls as well as mass masonry wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use of wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location (Straube and Smegal 2009, Pettit 2009, Joyce 2009, Ueno 2010). The research presented in this report is intended to help develop a better understanding of the system mechanics involved and the potential for environmental exposure induced movement between the furring strip and the framing. BSC sought to address the following research questions: 1. What are the relative roles of the mechanisms and the magnitudes of the force that influence the vertical displacement resistance of the system? 2. Can the capacity at a specified deflection be reliably calculated using mechanics based equations? 3. What are the impacts of environmental exposure on the vertical displacement of furring strips attached directly through insulation back to a wood structure?
Cladding Attachment Over Thick Exterior Insulating Sheathing
Baker, P.; Eng, P.; Lepage, R.
2014-01-01
The addition of insulation to the exterior of buildings is an effective means of increasing the thermal resistance of both wood framed walls as well as mass masonry wall assemblies. For thick layers of exterior insulation (levels greater than 1.5 inches), the use of wood furring strips attached through the insulation back to the structure has been used by many contractors and designers as a means to provide a convenient cladding attachment location (Straube and Smegal 2009, Pettit 2009, Joyce 2009, Ueno 2010). The research presented in this report is intended to help develop a better understanding of the system mechanics involved and the potential for environmental exposure induced movement between the furring strip and the framing. BSC sought to address the following research questions: 1.What are the relative roles of the mechanisms and the magnitudes of the force that influence the vertical displacement resistance of the system? 2.Can the capacity at a specified deflection be reliably calculated using mechanics based equations? 3.What are the impacts of environmental exposure on the vertical displacement of furring strips attached directly through insulation back to a wood structure?
Divergence Boundary Conditions for Vector Helmholtz Equations with Divergence Constraints
NASA Technical Reports Server (NTRS)
Kangro, Urve; Nicolaides, Roy
1997-01-01
The idea of replacing a divergence constraint by a divergence boundary condition is investigated. The connections between the formulations are considered in detail. It is shown that the most common methods of using divergence boundary conditions do not always work properly. Necessary and sufficient conditions for the equivalence of the formulations are given.
Numerical Method for Darcy Flow Derived Using Discrete Exterior Calculus
NASA Astrophysics Data System (ADS)
Hirani, A. N.; Nakshatrala, K. B.; Chaudhry, J. H.
2015-05-01
We derive a numerical method for Darcy flow, and also for Poisson's equation in mixed (first order) form, based on discrete exterior calculus (DEC). Exterior calculus is a generalization of vector calculus to smooth manifolds and DEC is one of its discretizations on simplicial complexes such as triangle and tetrahedral meshes. DEC is a coordinate invariant discretization, in that it does not depend on the embedding of the simplices or the whole mesh. We start by rewriting the governing equations of Darcy flow using the language of exterior calculus. This yields a formulation in terms of flux differential form and pressure. The numerical method is then derived by using the framework provided by DEC for discretizing differential forms and operators that act on forms. We also develop a discretization for a spatially dependent Hodge star that varies with the permeability of the medium. This also allows us to address discontinuous permeability. The matrix representation for our discrete non-homogeneous Hodge star is diagonal, with positive diagonal entries. The resulting linear system of equations for flux and pressure are saddle type, with a diagonal matrix as the top left block. The performance of the proposed numerical method is illustrated on many standard test problems. These include patch tests in two and three dimensions, comparison with analytically known solutions in two dimensions, layered medium with alternating permeability values, and a test with a change in permeability along the flow direction. We also show numerical evidence of convergence of the flux and the pressure. A convergence experiment is included for Darcy flow on a surface. A short introduction to the relevant parts of smooth and discrete exterior calculus is included in this article. We also include a discussion of the boundary condition in terms of exterior calculus.
The Kelvin–Helmholtz instability at Venus: What is the unstable boundary?
Möstl, Ute V.; Erkaev, Nikolay V.; Zellinger, Michael; Lammer, Helmut; Gröller, Hannes; Biernat, Helfried K.; Korovinskiy, Daniil
2011-01-01
The Kelvin–Helmholtz instability gained scientific attention after observations at Venus by the spacecraft Pioneer Venus Orbiter gave rise to speculations that the instability contributes to the loss of planetary ions through the formation of plasma clouds. Since then, a handful of studies were devoted to the Kelvin–Helmholtz instability at the ionopause and its implications for Venus. The aim of this study is to investigate the stability of the two instability-relevant boundary layers around Venus: the induced magnetopause and the ionopause. We solve the 2D magnetohydrodynamic equations with the total variation diminishing Lax–Friedrichs algorithm and perform simulation runs with different initial conditions representing the situation at the boundary layers around Venus. Our results show that the Kelvin–Helmholtz instability does not seem to be able to reach its nonlinear vortex phase at the ionopause due to the very effective stabilizing effect of a large density jump across this boundary layer. This seems also to be true for the induced magnetopause for low solar activity. During high solar activity, however, there could occur conditions at the induced magnetopause which are in favour of the nonlinear evolution of the instability. For this situation, we estimated roughly a growth rate for planetary oxygen ions of about 7.6 × 1025 s−1, which should be regarded as an upper limit for loss due to the Kelvin–Helmholtz instability. PMID:22347723
Accurate boundary conditions for exterior problems in gas dynamics
NASA Technical Reports Server (NTRS)
Hagstrom, Thomas; Hariharan, S. I.
1988-01-01
The numerical solution of exterior problems is typically accomplished by introducing an artificial, far field boundary and solving the equations on a truncated domain. For hyperbolic systems, boundary conditions at this boundary are often derived by imposing a principle of no reflection. However, waves with spherical symmetry in gas dynamics satisfy equations where incoming and outgoing Riemann variables are coupled. This suggests that natural reflections may be important. A reflecting boundary condition is proposed based on an asymptotic solution of the far field equations. Nonlinear energy estimates are obtained for the truncated problem and numerical experiments presented to validate the theory.
Accurate boundary conditions for exterior problems in gas dynamics
NASA Technical Reports Server (NTRS)
Hagstrom, Thomas; Hariharan, S. I.
1988-01-01
The numerical solution of exterior problems is typically accomplished by introducing an artificial, far-field boundary and solving the equations on a truncated domain. For hyperbolic systems, boundary conditions at this boundary are often derived by imposing a principle of no reflection. However, waves with spherical symmetry in gas dynamics satisfy equations where incoming and outgoing Riemann variables are coupled. This suggests that natural reflections may be important. A reflecting boundary condition is proposed based on an asymptotic solution of the far-field equations. Nonlinear energy estimates are obtained for the truncated problem and numerical experiments presented to validate the theory.
Helmholtz's early empiricism and the Erhaltung der Kraft.
Jurkowitz, Edward
2010-01-01
Hermann Helmholtz has often been understood to have started research under the influence of Kant, and then to have made a transition to a later mature empiricist phase. Without claiming that in 1847 Helmholtz held the same positions that he later espoused, I suggest that already in his 1847 'Uber die Erhaltung der Kraft' one may find important aspects of his later empiricism. I highlight the ways in which, from early on, Helmholtz turned Kant to use in developing an empirical program of inquiry into possible basic natural causes. To that end, I indicate how, throughout his arguments, Helmholtz employed, sometimes explicitly, but often tacitly, an empiricist logic, one that ran contrary to any form of transcendental deduction, and even to all a priori knowledge. Instead of deriving aspects about the ultimate constituents of nature, Helmholtz aimed to define the proper project for physical natural science. The first part of the paper describes the context of discussion in which Helmholtz entered. The bulk of the paper then analyzes Helmholtz's arguments in order to make space between (1) Kantian, and other, deductions of characteristics that must be true of nature and (2) Helmholtz's delineation of empirically determinable characteristics of presumed ultimate elements of nature, ones that he meant to be specified and delimited through future experimental research. The paper highlights that throughout his discussion Helmholtz meant to define the proper project for physical natural science, a project rife with empiricist aspects. PMID:20503777
Measuring the acoustic response of Helmholtz resonators
NASA Astrophysics Data System (ADS)
Monteiro, Martín; Marti, Arturo C.; Vogt, Patrik; Kasper, Lutz; Quarthal, Dominik
2015-04-01
Many experiments have been proposed to investigate acoustic phenomena in college and early undergraduate levels, in particular the speed of sound,1-9 by means of different methods, such as time of flight, transit time, or resonance in tubes. In this paper we propose to measure the acoustic response curves of a glass beaker filled with different gases, used as an acoustic resonator. We show that these curves expose many interesting peaks and features, one of which matches the resonance peak predicted for a Helmholtz resonator fairly well, and gives a decent estimate for the speed of sound in some cases. The measures are obtained thanks to the capabilities of smartphones.
Applications of the electromagnetic Helmholtz resonator*
NASA Astrophysics Data System (ADS)
Stoneback, Russell Alan
An electromagnetic Helmholtz resonator comprised of a capacitor with an aperture is investigated theoretically and experimentally. It is proposed that this resonance may be described using effective impedances describing the capacitor and aperture, similar to lumped element descriptions of the acoustic Helmholtz resonator. The dipole impedance of an electromagnetic aperture is derived and verified using the finite element method. Incorporating standard network relations, the aperture impedance can be used to calculate radiated power. Measurements of a capacitor demonstrates that the transmitted voltage through the capacitor is modified by induced charges. An induced voltage is introduced, and predictions agree with observations. Measurements of a capacitor with an aperture in the grounded plate indicate that induced currents cancel the imaginary impedance of the aperture, and double the real impedance. The observed impedance is close to predictions using the derived aperture impedance, confirming the utility of the aperture impedance in describing the system. The numerically obtained aperture electromagnetic fields are similar to the Birkeland current distribution and the cross polar cap potential in the Earth's polar ionosphere, motivating a model where the polar ionosphere is treated as an effective aperture. It is proposed that this effective aperture interacts with the capacitor formed between the Earth and ionosphere, creating an electromagnetic Helmholtz resonator. Predictions made with this model agree with measurements of transmitted power and phase velocity by FAST during a geomagnetic substorm, measurements of the Ionospheric Alfven Resonator, and oscillations recorded by ground based magnetometers. The same effective aperture behavior is expected in sunspots and polar coronal holes. A peak is predicted in Alfven wave power across the transition region for waves with a 5 min. period that delivers an average power over 100 W/m2 to the corona, sufficient to
Magnetic reconnection in the two-dimensional Kelvin-Helmholtz instability.
Knoll, D A; Chacón, L
2002-05-27
Magnetic reconnection in the two-dimensional Kelvin-Helmholtz instability is studied. The flow is modeled by the reduced MHD equations with constant resistivity and viscosity. For super-Alfvénic flow, localized transient reconnection is observed on the Kelvin-Helmholtz time scale (this is not new). We study this transient reconnection and consider the peak reconnection rate which occurs with the initial vortex formation. Over the range of resistivities considered, it is shown that this peak reconnection rate is not a function of resistivity, and is a function of the initial flow shear. Additionally, it is demonstrated that there is a fundamental difference between the evolution of a problem at S = 200 and S = 10,000. PMID:12059480
Measuring Earth's Local Magnetic Field Using a Helmholtz Coil
NASA Astrophysics Data System (ADS)
Williams, Jonathan E.
2014-04-01
In this paper, I present a low-cost interactive experiment for measuring the strength of Earth's local magnetic field. This activity can be done in most high schools or two-year physics laboratories with limited resources, yet will have a tremendous learning impact. This experiment solidifies the three-dimensional nature of Earth's magnetic field vector and helps reinforce the aspect of the vertical component of Earth's magnetic field. Students should realize that Earth's magnetic field is not fully horizontal (except at the magnetic equator) and that a compass simply indicates the direction of the horizontal component of Earth's magnetic field. A magnetic dip needle compass can be used to determine the angle (known as the "dip angle" or "inclination angle") measured from the direction in which Earth's magnetic field vector points to the horizontal. In this activity, students will be able to determine the horizontal component of the field using a Helmholtz coil and, knowing the dip angle, the Earth's magnetic field strength can be determined.
Kelvin-Helmholtz instability at the magnetopause boundary
NASA Technical Reports Server (NTRS)
Wu, C. C.
1986-01-01
An MHD model is defined for the convective Kelvin-Helmholtz instability (CKHI) which satellite data indicates produces vortices in the near-earth region of the plasma sheet through turbulence caused by shear flow. The MHD equations are solved as an initial value problem, which reveals that the CKHI growth rate is the same as that of the periodic KHI (PKHI). However, the CKHI is not as limited in the range of amplitude as is the PKHI, which experiences stability in nonlinear growth because of the periodic characteristics of the growth. A perpendicularly moving CKHI can produce a large vortex flow and shocks off the vortex boundary. The satellite data indicate that the vortices are in the size range of 10-20 earth radii. Additional effects can include the expulsion of magnetic flux and the formation of the boundary layer. The success of the model up to the point of formation of the boundary layer is taken as an incentive for further model development using more realistic magnetospheric data.
Helmholtz decomposition coupling rotational to irrotational flow of a viscous fluid.
Joseph, Daniel D
2006-09-26
In this work, I present the form of the Navier-Stokes equations implied by the Helmholtz decomposition in which the relation of the irrotational and rotational velocity fields is made explicit. The idea of self-equilibration of irrotational viscous stresses is introduced. The decomposition is constructed by first selecting the irrotational flow compatible with the flow boundaries and other prescribed conditions. The rotational component of velocity is then the difference between the solution of the Navier-Stokes equations and the selected irrotational flow. To satisfy the boundary conditions, the irrotational field is required, and it depends on the viscosity. Five unknown fields are determined by the decomposed form of the Navier-Stokes equations for an incompressible fluid: the rotational component of velocity, the pressure, and the harmonic potential. These five fields may be readily identified in analytic solutions available in the literature. It is clear from these exact solutions that potential flow of a viscous fluid is required to satisfy prescribed conditions, like the no-slip condition at the boundary of a solid or continuity conditions across a two-fluid boundary. It can be said that equations governing the Helmholtz decomposition describe the modification of irrotational flow due to vorticity, but the analysis shows the two fields are coupled and cannot be completely determined independently. PMID:16983077
For a statistical interpretation of Helmholtz' thermal displacement
NASA Astrophysics Data System (ADS)
Podio-Guidugli, Paolo
2016-05-01
On moving from the classic papers by Einstein and Langevin on Brownian motion, two consistent statistical interpretations are given for the thermal displacement, a scalar field formally introduced by Helmholtz, whose time derivative is by definition the absolute temperature.
Experimental realization of extraordinary acoustic transmission using Helmholtz resonators
Crow, Brian C.; Cullen, Jordan M.; McKenzie, William W.; Koju, Vijay; Robertson, William M.
2015-02-15
The phenomenon of extraordinary acoustic transmission through a solid barrier with an embedded Helmholtz resonator (HR) is demonstrated. The Helmholtz resonator consists of an embedded cavity and two necks that protrude, one on each side of the barrier. Extraordinary transmission occurs for a narrow spectral range encompassing the resonant frequency of the Helmholtz resonator. We show that an amplitude transmission of 97.5% is achieved through a resonator whose neck creates an open area of 6.25% of the total barrier area. In addition to the enhanced transmission, we show that there is a smooth, continuous phase transition in the transmitted sound as a function of frequency. The frequency dependent phase transition is used to experimentally realize slow wave propagation for a narrow-band Gaussian wave packet centered at the maximum transmission frequency. The use of parallel pairs of Helmholtz resonators tuned to different resonant frequencies is experimentally explored as a means of increasing the transmission bandwidth. These experiments show that because of the phase transition, there is always a frequency between the two Helmholtz resonant frequencies at which destructive interference occurs whether the resonances are close or far apart. Finally, we explain how the phase transition associated with Helmholtz-resonator-mediated extraordinary acoustic transmission can be exploited to produce diffractive acoustic components including sub-wavelength thickness acoustic lenses.
Two-dimensional, phase modulated lattice sums with application to the Helmholtz Green’s function
Linton, C. M.
2015-01-15
A class of two-dimensional phase modulated lattice sums in which the denominator is an indefinite quadratic polynomial Q is expressed in terms of a single, exponentially convergent series of elementary functions. This expression provides an extremely efficient method for the computation of the quasi-periodic Green’s function for the Helmholtz equation that arises in a number of physical contexts when studying wave propagation through a doubly periodic medium. For a class of sums in which Q is positive definite, our new result can be used to generate representations in terms of θ-functions which are significant generalisations of known results.
Feasibilty of exterior vascular laser irradiation therapy
NASA Astrophysics Data System (ADS)
Chen, Rong; Xie, Shusen; Li, Hui; Li, Buhong; Chen, Yanjiao; Zhang, Xiaodong; Chen, Huifang; Xia, Xiangnan; Lin, Aizhen
1998-08-01
In order to study the exterior vascular laser irradiation therapy for replacing the intravascular laser irradiation therapy, we measure the distribution of radiant fluence rate in exterior vascular laser irradiation in vivo and imitative intravascular laser irradiation. The result shows that the average radiant fluence rate of exterior vascular and intravascular is 1.11 and 10.81 respectively, which is ten times between them. In order to get the radiant fluence rate corresponding to the intravascular laser irradiation, we suggest that about 20 mW HeNe laser could be used in exterior vascular laser irradiation therapy, and the laser must irradiate on the vascular perpendicularly. The suitable patient with exposed vascular must be chosen, and the diameter of the irradiated vascular is about 6 mm. Our experiment result, especially the data measured in vivo, will be useful for the research of light transport in human tissue.
7 CFR 1980.315 - Escrow accounts for exterior development.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 7 Agriculture 14 2011-01-01 2011-01-01 false Escrow accounts for exterior development. 1980.315... Escrow accounts for exterior development. When proposed exterior development work cannot be completed... escrow account for exterior development only may be established by the originating lender if...
7 CFR 1980.315 - Escrow accounts for exterior development.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 7 Agriculture 14 2010-01-01 2009-01-01 true Escrow accounts for exterior development. 1980.315... Escrow accounts for exterior development. When proposed exterior development work cannot be completed... escrow account for exterior development only may be established by the originating lender if...
24 CFR 3280.105 - Exit facilities; exterior doors.
Code of Federal Regulations, 2013 CFR
2013-04-01
... 24 Housing and Urban Development 5 2013-04-01 2013-04-01 false Exit facilities; exterior doors... § 3280.105 Exit facilities; exterior doors. (a) Number and location of exterior doors. Manufactured homes shall have a minimum of two exterior doors located remote from each other. (1) Required egress...
24 CFR 3280.105 - Exit facilities; exterior doors.
Code of Federal Regulations, 2010 CFR
2010-04-01
... 24 Housing and Urban Development 5 2010-04-01 2010-04-01 false Exit facilities; exterior doors... § 3280.105 Exit facilities; exterior doors. (a) Number and location of exterior doors. Manufactured homes shall have a minimum of two exterior doors located remote from each other. (1) Required egress...
24 CFR 3280.105 - Exit facilities; exterior doors.
Code of Federal Regulations, 2011 CFR
2011-04-01
... 24 Housing and Urban Development 5 2011-04-01 2011-04-01 false Exit facilities; exterior doors... § 3280.105 Exit facilities; exterior doors. (a) Number and location of exterior doors. Manufactured homes shall have a minimum of two exterior doors located remote from each other. (1) Required egress...
NASA Astrophysics Data System (ADS)
Wang, S.; De Hoop, M. V.; Xia, J.; Li, X.
2011-12-01
We consider the modeling of elastic seismic wave propagation on a rectangular domain via the discretization and solution of the inhomogeneous coupled Helmholtz equation in 3D, by exploiting a parallel multifrontal sparse direct solver equipped with Hierarchically Semi-Separable (HSS) structure to reduce the computational complexity and storage. In particular, we are concerned with solving this equation on a large domain, for a large number of different forcing terms in the context of seismic problems in general, and modeling in particular. We resort to a parsimonious mixed grid finite differences scheme for discretizing the Helmholtz operator and Perfect Matched Layer boundaries, resulting in a non-Hermitian matrix. We make use of a nested dissection based domain decomposition, and introduce an approximate direct solver by developing a parallel HSS matrix compression, factorization, and solution approach. We cast our massive parallelization in the framework of the multifrontal method. The assembly tree is partitioned into local trees and a global tree. The local trees are eliminated independently in each processor, while the global tree is eliminated through massive communication. The solver for the inhomogeneous equation is a parallel hybrid between multifrontal and HSS structure. The computational complexity associated with the factorization is almost linear with the size of the Helmholtz matrix. Our numerical approach can be compared with the spectral element method in 3D seismic applications.
[Hermann von Helmholtz and Carl Stumpf on consonance and dissonance].
Kursell, Julia
2008-06-01
The article juxtaposes Hermann von Helmholtz's work in the experimental physiology of hearing and Carl Stumpf's tone psychology, focusing on the problem of consonance and dissonance in music. It argues that the experimental set-up plays a major role in the approaches to hearing of both Helmholtz and Stumpf, shaping their redefinition of the musical concepts of consonance and dissonance. Helmholtz, however, explains dissonance as resulting from the beats that are heard when sound waves interfere, while Stumpf explains consonance from the fusion (Verschmelzung) of sounds, noting that two tones, depending on their distance cannot always be recognized as two but are heard as one single tone. Helmholtz's definition of dissonance eventually threatens his own theory of hearing, which is based on the mechanical principle of resonance and considers sound to be composed of sinusoidal waves. Both the physical and the mathematical tools he uses cannot easily be brought into accordance with his experimental findings on beats, which ask for a discrimination of fast changes in intensity. Dissonance thus becomes "unrecomendable" for Helmholtz, because it overstrains the ear. Stumpf's research, in contrast, has its point of departure in the historically given set of intervals and tries to find a principle that would explain this choice. His tests with experimental subjects who have no conscious knowledge of musical harmony and prove incapable to follow or reproduce music reveals to him a difference between the unity and multiplicity of tones. PMID:19048722
Federal Register 2010, 2011, 2012, 2013, 2014
2010-06-16
... Assistance on March 18, 2010, applicable to workers of Plastic Omnium Automotive Exteriors, LLC, Anderson, South Carolina. The notice was published in the Federal Register April 23, 2010 (75 FR 21356). The... Employment and Training Administration Plastic Omnium Automotive Exteriors, LLC, Anderson, SC; Plastic...
NASA Astrophysics Data System (ADS)
Gómez, Daniel O.; Bejarano, Cecilia; Mininni, Pablo D.
2014-06-01
We study the stability of shear flows in a fully ionized plasma. Kelvin-Helmholtz is a well known, macroscopic and ideal shear-driven instability. In sufficiently low density plasmas, also the microscopic Hall magneto-shear instability can take place. We performed three-dimensional simulations of the Hall-MHD equations where these two instabilities are present, and carried out a comparative study. We find that when the shear flow is so intense that its vorticity surpasses the ion-cyclotron frequency of the plasma, the Hall magneto-shear instability is not only non-negligible, but it actually displays growth rates larger than those of the Kelvin-Helmholtz instability.
Self-Similar Wave Produced by Local Perturbation of the Kelvin-Helmholtz Shear-Layer Instability
NASA Astrophysics Data System (ADS)
Hoepffner, Jérôme; Blumenthal, Ralf; Zaleski, Stéphane
2011-03-01
We show that the Kelvin-Helmholtz instability excited by a localized perturbation yields a self-similar wave. The instability of the mixing layer was first conceived by Helmholtz as the inevitable growth of any localized irregularity into a spiral, but the search and uncovering of the resulting self-similar evolution was hindered by the technical success of Kelvin’s wavelike perturbation theory. The identification of a self-similar solution is useful since its specific structure is witness of a subtle nonlinear equilibrium among the forces involved. By simulating numerically the Navier-Stokes equations, we analyze the properties of the wave: growth rate, propagation speed and the dependency of its shape upon the density ratio of the two phases of the mixing layer.
Piecewise lexsegment ideals in exterior algebras
NASA Astrophysics Data System (ADS)
Shakin, D. A.
2005-02-01
The problem of describing the Hilbert functions of homogeneous ideals of an exterior algebra over a field containing a fixed monomial ideal I is considered. For this purpose the notion of a piecewise lexsegment ideal in an exterior algebra is introduced generalizing the notion of a lexsegment ideal. It is proved that if I is a piecewise lexsegment ideal, then it is possible to describe the Hilbert functions of the homogeneous ideals containing I in a way similar to that suggested by Kruskal and Katona for the situation I=0. Moreover, a generalization of the extremal properties of lexsegment ideals is obtained (the inequality for the Betti numbers).
Design for a High Energy Density Kelvin-Helmholtz Experiment
Hurricane, O A
2007-10-29
While many high energy density physics (HEDP) Rayleigh-Taylor and Richtmyer-Meshkov instability experiments have been fielded as part of basic HEDP and astrophysics studies, not one HEDP Kelvin-Helmholtz (KH) experiment has been successfully performed. Herein, a design for a novel HEDP x-ray driven KH experiment is presented along with supporting radiation-hydrodynamic simulation and theory.
Directional organization and shape formation: new illusions and Helmholtz's Square
Pinna, Baingio
2015-01-01
According to Helmholtz's Square illusion, a square appears wider when it is filled with vertical lines and higher when filled with horizontal lines (Helmholtz von, 1866). Recently, Pinna (2010a) demonstrated that the grouping of small squares on the basis of the similarity principle influences also perception of their shape and of the whole emerging shapes. The direction imparted by grouping is the main attribute that influences the shape by polarizing it in the same direction both globally and locally. The rectangle illusion is opposite to what expected on the basis of Helmholtz's Square illusion. Aim of this work is to solve the antinomy between the two sets of illusions and to demonstrate a common explanation based on the interaction between different sources of directional organization. This was accomplished by introducing some new phenomena and through phenomenological experiments proving the role played by the directional shape organization in shape formation. According to our results, Helmholtz's square illusion shows at least two synergistic sources of directional organization: the direction of the grouping of the lines due to their similarity of the luminance contrast and the direction of the grouping of the lines due to the good continuation. PMID:25784870
Nonlocal stability analysis of the MHD Kelvin-Helmholtz instability in a compressible plasma
Miura, A.; Pritchett, P.L.
1982-09-01
A general stability analysis is performed for the Kelvin-Helmholtz instability in sheared magnetohydrodynamic flow of finite thickness in a compressible plasma. The analysis allows for arbitrary orientation of the magnetic field B/sub 0/, velocity flow v/sub 0/, and wave vector k in the plane perpendicular to the velocity gradient, and no restrictions are imposed on the sound or Alfven Mach numbers. The stability problem is reduced to the solution of a single-order differential equation, which includes a gravitational term to represent coupling between the Kelvin-Helmholtz mode and the interchange mode. In the incompressible limit it is shown that the Kelvin-Helmholtz mode is completely stabilized for any velocity profile as long as the condition V/sub 0/<2v/sub A/ (kxB/sub 0/)/(kxv/sub 0/) is satisfied, where V/sub 0/ is the total velocity jump across the shear layer. Numerical results are obtained for a hyperbolic tangent velocity profile for the transverse (B/sub 0/perpendicularv/sub 0/) and parallel (B/sub 0/parallelv/sub 0/) flow configurations. Only modes with k..delta..<2 are unstable, where ..delta.. is the scale length of the shear layer. The fastest growing modes occur for k..delta..approx.0.5--1.0. Compressibility and a magnetic field component parallel to the flow are found to be stabilizing effects. For the transverse case, only the fast magnetosonic mode is destabilized, but if the kxB/sub 0/not =0, the instability contains Alfven-mode and slow-mode components as well. The Alfven component gives rise to a field-aligned current inside the shear layer. In the parallel case, both Alfven and slow magnetosonic components are present, with the Alfven mode confined inside the shear layer. The results of the analysis are used to discuss the stability of sheared plasma flow at the magnetopause boundary and in the solar wind. At the magnetopause boundary, the fastest growing Kelvin-Helmholtz mode has a frequency of 0 (V/sub 0//2..delta..), which overlaps with
Results of a supersonic, single-mode, shockwave-driven Kelvin-Helmholtz instability experiment
NASA Astrophysics Data System (ADS)
Wan, W. C.; Malamud, G.; di Stefano, C. A.; Trantham, M. R.; Klein, S. R.; Shimony, A.; Shvarts, D.; Kuranz, C. C.; Drake, R. P.
2014-10-01
The Kelvin-Helmholtz instability is a hydrodynamic process that causes mixing at an interface with shear flow. It is prevalent in many high-energy-density systems such as fusion research, core-collapse supernovae, and protoplanetary disks. Although it is common to simplify the Euler equations by assuming incompressibility, this assumption does not account for the inhibited growth rate found in supersonic flows. Here, we present the first laboratory observations of single-mode, compressible Kelvin-Helmholtz instability growth. This experiment was performed at the OMEGA-EP facility using three beams stitched into a 28 ns square pulse to sustain a shockwave in low-density foam. The shockwave generated shear along the interface between the foam and a high-density plastic, seeded with a precisely machined single-mode sinusoidal perturbation. The system was diagnosed using radiography with a spherically bent crystal. This work is funded by the U.S. Department of Energy, through the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, Grant Number DE-NA0001840, the National Laser User Facility Program, Grant Number DE-NA0000850, and the Laboratory for Laser Energetics, University of Rochester by the NNSA/OICF under Cooperative Agreement No. DE-FC52-08NA28302.
Quantitative Reappraisal of the Helmholtz-Guyton Resonance Theory of Frequency Tuning in the Cochlea
Babbs, Charles F.
2011-01-01
To explore the fundamental biomechanics of sound frequency transduction in the cochlea, a two-dimensional analytical model of the basilar membrane was constructed from first principles. Quantitative analysis showed that axial forces along the membrane are negligible, condensing the problem to a set of ordered one-dimensional models in the radial dimension, for which all parameters can be specified from experimental data. Solutions of the radial models for asymmetrical boundary conditions produce realistic deformation patterns. The resulting second-order differential equations, based on the original concepts of Helmholtz and Guyton, and including viscoelastic restoring forces, predict a frequency map and amplitudes of deflections that are consistent with classical observations. They also predict the effects of an observation hole drilled in the surrounding bone, the effects of curvature of the cochlear spiral, as well as apparent traveling waves under a variety of experimental conditions. A quantitative rendition of the classical Helmholtz-Guyton model captures the essence of cochlear mechanics and unifies the competing resonance and traveling wave theories. PMID:22028708
A WELL-POSED KELVIN-HELMHOLTZ INSTABILITY TEST AND COMPARISON
McNally, Colin P.; Lyra, Wladimir; Passy, Jean-Claude E-mail: wlyra@jpl.nasa.gov
2012-08-01
Recently, there has been a significant level of discussion of the correct treatment of Kelvin-Helmholtz instability (KHI) in the astrophysical community. This discussion relies largely on how the KHI test is posed and analyzed. We pose a stringent test of the initial growth of the instability. The goal is to provide a rigorous methodology for verifying a code on two-dimensional KHI. We ran the problem in the Pencil Code, Athena, Enzo, NDSPMHD, and Phurbas. A strict comparison, judgment, or ranking, between codes is beyond the scope of this work, though this work provides the mathematical framework needed for such a study. Nonetheless, how the test is posed circumvents the issues raised by tests starting from a sharp contact discontinuity yet it still shows the poor performance of smoothed particle hydrodynamics (SPH). We then comment on the connection between this behavior to the underlying lack of zeroth-order consistency in SPH interpolation. We comment on the tendency of some methods, particularly those with very low numerical diffusion, to produce secondary Kelvin-Helmholtz billows on similar tests. Though the lack of a fixed, physical diffusive scale in the Euler equations lies at the root of the issue, we suggest that in some methods an extra diffusion operator should be used to damp the growth of instabilities arising from grid noise. This statement applies particularly to moving-mesh tessellation codes, but also to fixed-grid Godunov schemes.
Electron-Atom Ionization Calculations using Propagating Exterior Complex Scaling
NASA Astrophysics Data System (ADS)
Bartlett, Philip
2007-10-01
The exterior complex scaling method (Science 286 (1999) 2474), pioneered by Rescigno, McCurdy and coworkers, provided highly accurate ab initio solutions for electron-hydrogen collisions by directly solving the time-independent Schr"odinger equation in coordinate space. An extension of this method, propagating exterior complex scaling (PECS), was developed by Bartlett and Stelbovics (J. Phys. B 37 (2004) L69, J. Phys. B 39 (2006) R379) and has been demonstrated to provide computationally efficient and accurate calculations of ionization and scattering cross sections over a large range of energies below, above and near the ionization threshold. An overview of the PECS method for three-body collisions and the computational advantages of its propagation and iterative coupling techniques will be presented along with results of: (1) near-threshold ionization of electron-hydrogen collisions and the Wannier threshold laws, (2) scattering cross section resonances below the ionization threshold, and (3) total and differential cross sections for electron collisions with excited targets and hydrogenic ions from low through to high energies. Recently, the PECS method has been extended to solve four-body collisions using time-independent methods in coordinate space and has initially been applied to the s-wave model for electron-helium collisions. A description of the extensions made to the PECS method to facilitate these significantly more computationally demanding calculations will be given, and results will be presented for elastic, single-excitation, double-excitation, single-ionization and double-ionization collisions.
Evaluation of commercially available exterior digital VMDs
Ringler, C.E.; Hoover, C.E.
1995-06-01
This report discusses the testing and evaluation of thirteen commercially available exterior digital video motion detection (VMD) systems. The systems were evaluated for use in a specific outdoor application. The report focuses primarily on the testing parameters, each system`s advertised features, and the nuisance alarm and detection test results.
EXTERIOR, A view looking east at the west elevation of ...
EXTERIOR, A view looking east at the west elevation of the building, including an exterior staircase that leads to the roof - Department of Energy, Mound Facility, Hydrolysis House Building (HH Building), One Mound Road, Miamisburg, Montgomery County, OH
EXTERIOR, A view looking south toward the northwest corner of ...
EXTERIOR, A view looking south toward the northwest corner of the building including an exterior staircase that leads to the roof - Department of Energy, Mound Facility, B Building, One Mound Road, Miamisburg, Montgomery County, OH
Exterior view of north and east exterior walls of LongTerm ...
Exterior view of north and east exterior walls of Long-Term Oxidizer Silo (T-28B), looking south. Silo was designed to assess long-term environmental impacts on storage of the Titan II's oxidizer (nitrogen tetroxide). The shorter Oxidizer Conditioning Structure (T-28D) is located behind and to the immediate left of T-28B - Air Force Plant PJKS, Systems Integration Laboratory, Long-Term Oxidizer Silo, Waterton Canyon Road & Colorado Highway 121, Lakewood, Jefferson County, CO
46 CFR 154.1105 - Exterior water spray system: General.
Code of Federal Regulations, 2011 CFR
2011-10-01
... 46 Shipping 5 2011-10-01 2011-10-01 false Exterior water spray system: General. 154.1105 Section... Equipment Firefighting § 154.1105 Exterior water spray system: General. Each liquefied flammable gas vessel and each liquefied toxic gas vessel must have an exterior water spray system that meets §§...
7 CFR 1980.315 - Escrow accounts for exterior development.
Code of Federal Regulations, 2014 CFR
2014-01-01
... Escrow accounts for exterior development. When proposed exterior development work cannot be completed... development work. (b) The contract for development work must provide for completion within 120 days. (c) The... 7 Agriculture 14 2014-01-01 2014-01-01 false Escrow accounts for exterior development....
7 CFR 1980.315 - Escrow accounts for exterior development.
Code of Federal Regulations, 2013 CFR
2013-01-01
... Escrow accounts for exterior development. When proposed exterior development work cannot be completed... development work. (b) The contract for development work must provide for completion within 120 days. (c) The... 7 Agriculture 14 2013-01-01 2013-01-01 false Escrow accounts for exterior development....
7 CFR 1980.315 - Escrow accounts for exterior development.
Code of Federal Regulations, 2012 CFR
2012-01-01
... Escrow accounts for exterior development. When proposed exterior development work cannot be completed... development work. (b) The contract for development work must provide for completion within 120 days. (c) The... 7 Agriculture 14 2012-01-01 2012-01-01 false Escrow accounts for exterior development....
24 CFR 3280.105 - Exit facilities; exterior doors.
Code of Federal Regulations, 2014 CFR
2014-04-01
... 24 Housing and Urban Development 5 2014-04-01 2014-04-01 false Exit facilities; exterior doors... § 3280.105 Exit facilities; exterior doors. Link to an amendment published at 78 FR 73981, Dec. 9, 2013. (a) Number and location of exterior doors. Manufactured homes shall have a minimum of two...
Two-dimensional sonic crystals with Helmholtz resonators.
Hu, Xinhua; Chan, C T; Zi, Jian
2005-05-01
We present a type of sonic crystal composed with an array of two-dimensional Helmholtz resonators, which in the long-wave regime have both a high relative acoustic refractive index n and at the same time, a small acoustic impedance Z mismatch with air for airborne sound. We analyze the n and Z of such sonic crystals by finite-difference time-domain simulations, and by mapping our results to a corresponding electromagnetic (EM) model, and we find that our Helmholtz resonant sonic crystal has a bigger effective magnetic permeability mu than the conventional rigid-cylinder sonic crystal in its EM counterpart. As a result, a thin convergent lens with very good focusing effect is demonstrated based on our crystal. PMID:16089593
Acoustic superlens using Helmholtz-resonator-based metamaterials
Yang, Xishan; Yin, Jing; Yu, Gaokun Peng, Linhui; Wang, Ning
2015-11-09
Acoustic superlens provides a way to overcome the diffraction limit with respect to the wavelength of the bulk wave in air. However, the operating frequency range of subwavelength imaging is quite narrow. Here, an acoustic superlens is designed using Helmholtz-resonator-based metamaterials to broaden the bandwidth of super-resolution. An experiment is carried out to verify subwavelength imaging of double slits, the imaging of which can be well resolved in the frequency range from 570 to 650 Hz. Different from previous works based on the Fabry-Pérot resonance, the corresponding mechanism of subwavelength imaging is the Fano resonance, and the strong coupling between the neighbouring Helmholtz resonators separated at the subwavelength interval leads to the enhanced sound transmission over a relatively wide frequency range.
Voluntarism in early psychology: the case of Hermann von Helmholtz.
De Kock, Liesbet
2014-05-01
The failure to recognize the programmatic similarity between (post-)Kantian German philosophy and early psychology has impoverished psychology's historical self-understanding to a great extent. This article aims to contribute to recent efforts to overcome the gaps in the historiography of contemporary psychology, which are the result of an empiricist bias. To this end, we present an analysis of the way in which Hermann von Helmholtz's theory of perception resonates with Johann Gottlieb Fichte's Ego-doctrine. It will be argued that this indebtedness is particularly clear when focusing on the foundation of the differential awareness of subject and object in perception. In doing so, the widespread reception of Helmholtz's work as proto-positivist or strictly empiricist is challenged, in favor of the claim that important elements of his theorizing can only be understood properly against the background of Fichte's Ego-doctrine. PMID:24818740
Dense magnetospheric plasma and Kelvin-Helmholtz waves
NASA Astrophysics Data System (ADS)
Walsh, B.
2015-12-01
The coupling of energy between the solar wind and a planetary magnetosphere is a function of the plasma parameters on both sides of the planet's magnetopause. Scientists routinely monitor the changing conditions in the solar wind in efforts to predict the dynamics at the magnetopause, but there can also be significant changes within the magnetosphere that play a role. On the magnetospheric side, the plasma density can change by several orders of magnitude (0.1cm-3 to 50cm-3). The current study investigates the role of dense magnetospheric plasma in the formation of Kelvin-Helmholtz waves at the magnetopause boundary. Spacecraft observations and SuperDARN radar measurements are presented showing the occurrence of Kelvin-Helmholtz waves on the dayside magnetopause under relatively low shear flows in the presence of a dense plasmaspheric plume.
Maxwell Equations and the Redundant Gauge Degree of Freedom
ERIC Educational Resources Information Center
Wong, Chun Wa
2009-01-01
On transformation to the Fourier space (k,[omega]), the partial differential Maxwell equations simplify to algebraic equations, and the Helmholtz theorem of vector calculus reduces to vector algebraic projections. Maxwell equations and their solutions can then be separated readily into longitudinal and transverse components relative to the…
Numerical simulations of magnetic Kelvin-Helmholtz instability at a twisted solar flux tube
NASA Astrophysics Data System (ADS)
Murawski, K.; Chmielewski, P.; Zaqarashvili, T. V.; Khomenko, E.
2016-04-01
The paper aims to study the response of a solar small-scale and weak magnetic flux tube to photospheric twisting motions. We numerically solve three-dimensional ideal magnetohydrodynamic equations to describe the evolution of the perturbation within the initially static flux tube, excited by twists in the azimuthal component of the velocity. These twists produce rotation of the magnetic field lines. Perturbation of magnetic field lines propagates upwardly, driving vertical and azimuthal flow as well as plasma compressions and rarefactions in the form of eddies. We conclude that these eddies result from the sheared azimuthal flow which seeds Kelvin-Helmholtz instability (KHI) between the flux tube and the ambient medium. Numerically obtained properties of the KHI confirm the analytical predictions for the occurrence of the instability.
Chemical potential, Helmholtz free energy and entropy of argon with kinetic Monte Carlo simulation
NASA Astrophysics Data System (ADS)
Fan, C.; Do, D. D.; Nicholson, D.; Ustinov, E.
2014-01-01
We present a method based on kinetic Monte Carlo (kMC) to determine the chemical potential, Helmholtz free energy and entropy of a fluid within the course of a simulation. The procedure requires no recourse to auxiliary methods to determine the chemical potential, such as the implementation of a Widom scheme in Metropolis Monte Carlo simulations, as it is determined within the course of the simulation. The equation for chemical potential is proved, for the first time in the literature, to have a direct connection with inverse Widom potential theory in using real molecules rather than ghost molecules. We illustrate this new procedure by several examples, including fluid argon and adsorption of argon as a non-uniform fluid on a graphite surface and in slit pores.
Numerical simulation of the excitation of a Helmholtz resonator by a grazing flow.
Mallick, S; Shock, R; Yakhot, V
2003-10-01
The process of noise generation in a flow-excited Helmholtz resonator involves strong interaction between a time-dependent fluid flow and acoustic resonance. Quantitative prediction of this effect, requiring accurate prediction of time-dependent features of a flow over complex three-dimensional bodies, turbulence modeling, compressibility and Mach number effects, is one of the major challenges to computational fluid dynamics. In this paper a numerical procedure based on the lattice kinetic equation, combined with the RNG turbulence model, is applied to describe a well-controlled experiment on acoustic resonance excitation by a grazing flow [Nelson et al., J. Sound Vib. 78, 15-27 (1981)]. The achieved agreement between numerical and physical experiments is very good. The simulations reveal a universality transformation enabling comparison of the data for different inlet conditions. PMID:14587584
Evolution of the magnetic field generated by the Kelvin-Helmholtz instability
Modestov, M.; Bychkov, V.; Brodin, G.; Marklund, M.; Brandenburg, A.
2014-07-15
The Kelvin-Helmholtz instability in an ionized plasma is studied with a focus on the magnetic field generation via the Biermann battery (baroclinic) mechanism. The problem is solved by using direct numerical simulations of two counter-directed flows in 2D geometry. The simulations demonstrate the formation of eddies and their further interaction and merging resulting in a large single vortex. In contrast to general belief, it is found that the instability generated magnetic field may exhibit significantly different structures from the vorticity field, despite the mathematically identical equations controlling the magnetic field and vorticity evolution. At later stages of the nonlinear instability development, the magnetic field may keep growing even after the hydrodynamic vortex strength has reached its maximum and started decaying due to dissipation.
Numerical simulations of magnetic Kelvin-Helmholtz instability at a twisted solar flux tube
NASA Astrophysics Data System (ADS)
Murawski, K.; Chmielewski, P.; Zaqarashvili, T. V.; Khomenko, E.
2016-07-01
The paper aims to study the response of a solar small-scale and weak magnetic flux tube to photospheric twisting motions. We numerically solve three-dimensional ideal magnetohydrodynamic equations to describe the evolution of the perturbation within the initially static flux tube, excited by twists in the azimuthal component of the velocity. These twists produce rotation of the magnetic field lines. Perturbation of magnetic field lines propagates upwardly, driving vertical and azimuthal flow as well as plasma compressions and rarefactions in the form of eddies. We conclude that these eddies result from the sheared azimuthal flow which seeds Kelvin-Helmholtz instability (KHI) between the flux tube and the ambient medium. Numerically obtained properties of the KHI confirm the analytical predictions for the occurrence of the instability.
Kelvin-Helmholtz wave generation beneath hovercraft skirts
NASA Astrophysics Data System (ADS)
Sullivan, P. A.; Walsh, C.; Hinchey, M. J.
1993-05-01
When a hovercraft is hovering over water, the air flow beneath its skirts can interact with the water surface and generate waves. These, in turn, can cause the hovercraft to undergo violent self-excited heave motions. This note shows that the wave generation is due to the classical Kelvin-Helmholtz mechanism where, beyond a certain air flow rate, small waves at the air water interface extract energy from the air stream and grow.
Acoustic control in enclosures using optimally designed Helmholtz resonators
NASA Astrophysics Data System (ADS)
Driesch, Patricia Lynne
A virtual design methodology is developed to minimize the noise in enclosures with optimally designed, passive, acoustic absorbers (Helmholtz resonators). A series expansion of eigen functions is used to represent the acoustic absorbers as external volume velocities, eliminating the need for a solution of large matrix eigen value problems. A determination of this type (efficient model/reevaluation approach) significantly increases the design possibilities when optimization techniques are implemented. As a benchmarking exercise, this novel methodology was experimentally validated for a narrowband acoustic assessment of two optimally designed Helmholtz resonators coupled to a 2D enclosure. The resonators were tuned to the two lowest resonance frequencies of a 30.5 by 40.6 by 2.5 cm (12 x 16 x 1 inch) cavity with the resonator volume occupying only 2% of the enclosure volume. A maximum potential energy reduction of 12.4 dB was obtained at the second resonance of the cavity. As a full-scale demonstration of the efficacy of the proposed design method, the acoustic response from 90--190 Hz of a John Deere 7000 Ten series tractor cabin was investigated. The lowest cabin mode, referred to as a "boom" mode, proposes a significant challenge to a noise control engineer since its anti-node is located near the head of the operator and often generates unacceptable sound pressure levels. Exploiting the low frequency capability of Helmholtz resonators, lumped parameter models of these resonators were coupled to the enclosure via an experimentally determined acoustic model of the tractor cabin. The virtual design methodology uses gradient optimization techniques as a post processor for the modeling and analysis of the unmodified acoustic interior to determine optimal resonator characteristics. Using two optimally designed Helmholtz resonators; potential energy was experimentally reduced by 3.4 and 10.3 dB at 117 and 167 Hz, respectively.
Excavationless Exterior Foundation Insulation Exploratory Study
Mosimann, Garrett; Wagner, Rachel; Schirber, Tom
2013-02-01
The key objective of this exploratory study was to investigate the feasibility of the development or adoption of technologies that would enable a large percentage of existing homes in cold climates to apply a combination 'excavationless' soil removal process with appropriate insulation and water management on the exterior of existing foundations at a low cost. Our approach was to explore existing excavation and material technologies and systems to discover whether potential successful combinations existed.
Excavationless Exterior Foundation Insulation Field Study
Schirber, T.; Mosiman, G.; Ojczyk, C.
2014-10-01
Building science research supports installing exterior (soil side) foundation insulation as the optimal method to enhance the hygrothermal performance of new homes. With exterior foundation insulation, water management strategies are maximized while insulating the basement space and ensuring a more even temperature at the foundation wall. However, such an approach can be very costly and disruptive when applied to an existing home, requiring deep excavation around the entire house. The NorthernSTAR Building America Partnership team implemented an innovative, minimally invasive foundation insulation upgrade technique on an existing home. The approach consisted of using hydrovac excavation technology combined with a liquid insulating foam. The team was able to excavate a continuous 4" wide by 4' to 5' deep trench around the entire house, 128 linear feet, except for one small part under the stoop that was obstructed with concrete debris. The combination pressure washer and vacuum extraction technology also enabled the elimination of large trenches and soil stockpiles normally produced by backhoe excavation. The resulting trench was filled with liquid insulating foam, which also served as a water-control layer of the assembly. The insulation was brought above grade using a liquid foam/rigid foam hybrid system and terminated at the top of the rim joist. Cost savings over the traditional excavation process ranged from 23% to 50%. The excavationless process could result in even greater savings since replacement of building structures, exterior features, utility meters, and landscaping would be minimal or non-existent in an excavationless process.
Excavationless Exterior Foundation Insulation Field Study
Schirber, T.; Mosiman, G.; Ojczyk, C.
2014-09-01
Building science research supports installing exterior (soil side) foundation insulation as the optimal method to enhance the hygrothermal performance of new homes. With exterior foundation insulation, water management strategies are maximized while insulating the basement space and ensuring a more even temperature at the foundation wall. However, such an approach can be very costly and disruptive when applied to an existing home, requiring deep excavation around the entire house. The NorthernSTAR Building America Partnership team implemented an innovative, minimally invasive foundation insulation upgrade technique on an existing home. The approach consisted of using hydrovac excavation technology combined with liquid insulating foam. The team was able to excavate a continuous 4 inches wide by 4 feet to 5 feet deep trench around the entire house, 128 linear feet, except for one small part under the stoop that was obstructed with concrete debris. The combination pressure washer and vacuum extraction technology also enabled the elimination of large trenches and soil stockpiles normally produced by backhoe excavation. The resulting trench was filled with liquid insulating foam, which also served as a water-control layer of the assembly. The insulation was brought above grade using a liquid foam/rigid foam hybrid system and terminated at the top of the rim joist. Cost savings over the traditional excavation process ranged from 23% to 50%. The excavationless process could result in even greater savings since replacement of building structures, exterior features, utility meters, and landscaping would be minimal or non-existent in an excavationless process.
NASA Astrophysics Data System (ADS)
Xie, Zheng; Ye, Zheng; Ma, Yu-Jie
2009-12-01
Numerical simulation of antennae is a topic in computational electromagnetism, which is concerned with the numerical study of Maxwell equations. By discrete exterior calculus and the lattice gauge theory with coefficient R, we obtain the Bianchi identity on prism lattice. By defining an inner product of discrete differential forms, we derive the source equation and continuity equation. Those equations compose the discrete Maxwell equations in vacuum case on discrete manifold, which are implemented on Java development platform to simulate the Gaussian pulse radiation on antennaes.
A comparison of high-order polynomial and wave-based methods for Helmholtz problems
NASA Astrophysics Data System (ADS)
Lieu, Alice; Gabard, Gwénaël; Bériot, Hadrien
2016-09-01
The application of computational modelling to wave propagation problems is hindered by the dispersion error introduced by the discretisation. Two common strategies to address this issue are to use high-order polynomial shape functions (e.g. hp-FEM), or to use physics-based, or Trefftz, methods where the shape functions are local solutions of the problem (typically plane waves). Both strategies have been actively developed over the past decades and both have demonstrated their benefits compared to conventional finite-element methods, but they have yet to be compared. In this paper a high-order polynomial method (p-FEM with Lobatto polynomials) and the wave-based discontinuous Galerkin method are compared for two-dimensional Helmholtz problems. A number of different benchmark problems are used to perform a detailed and systematic assessment of the relative merits of these two methods in terms of interpolation properties, performance and conditioning. It is generally assumed that a wave-based method naturally provides better accuracy compared to polynomial methods since the plane waves or Bessel functions used in these methods are exact solutions of the Helmholtz equation. Results indicate that this expectation does not necessarily translate into a clear benefit, and that the differences in performance, accuracy and conditioning are more nuanced than generally assumed. The high-order polynomial method can in fact deliver comparable, and in some cases superior, performance compared to the wave-based DGM. In addition to benchmarking the intrinsic computational performance of these methods, a number of practical issues associated with realistic applications are also discussed.
Black and gray Helmholtz-Kerr soliton refraction
Sanchez-Curto, Julio; Chamorro-Posada, Pedro; McDonald, Graham S.
2011-01-15
Refraction of black and gray solitons at boundaries separating different defocusing Kerr media is analyzed within a Helmholtz framework. A universal nonlinear Snell's law is derived that describes gray soliton refraction, in addition to capturing the behavior of bright and black Kerr solitons at interfaces. Key regimes, defined by beam and interface characteristics, are identified, and predictions are verified by full numerical simulations. The existence of a unique total nonrefraction angle for gray solitons is reported; both internal and external refraction at a single interface is shown possible (dependent only on incidence angle). This, in turn, leads to the proposal of positive or negative lensing operations on soliton arrays at planar boundaries.
Design of an autonomous exterior security robot
NASA Technical Reports Server (NTRS)
Myers, Scott D.
1994-01-01
This paper discusses the requirements and preliminary design of robotic vehicle designed for performing autonomous exterior perimeter security patrols around warehouse areas, ammunition supply depots, and industrial parks for the U.S. Department of Defense. The preliminary design allows for the operation of up to eight vehicles in a six kilometer by six kilometer zone with autonomous navigation and obstacle avoidance. In addition to detection of crawling intruders at 100 meters, the system must perform real-time inventory checking and database comparisons using a microwave tags system.
Automated visual inspection of an airplane exterior
NASA Astrophysics Data System (ADS)
Jovančević, Igor; Orteu, Jean-José; Sentenac, Thierry; Gilblas, Rémi
2015-04-01
This paper deals with the inspection of an airplane using a Pan-Tilt-Zoom camera mounted on a mobile robot moving around the airplane. We present image processing methods for detection and inspection of four different types of items on the airplane exterior. Our detection approach is focused on the regular shapes such as rounded corner rectangles and ellipses, while inspection relies on clues such as uniformity of isolated image regions, convexity of segmented shapes and periodicity of the image intensity signal. The initial results are promising and demonstrate the feasibility of the envisioned robotic system.
View of exterior circumferential path at northeast side of building ...
View of exterior circumferential path at northeast side of building beneath trellis, looking southeast - National Zoological Park, Bird House, 3001 Connecticut Avenue NW, Washington, District of Columbia, DC
11. Exterior detail view of northeast corner, showing stucco finish ...
11. Exterior detail view of northeast corner, showing stucco finish and woodwork details - American Railway Express Company Freight Building, 1060 Northeast Division Street, Bend, Deschutes County, OR
Marguerite Arnet Residence, exterior window detail, looking north. Adam ...
Marguerite Arnet Residence, exterior window detail, looking north. - Adam & Bessie Arnet Homestead, Marguerite Arnet Residence, 560 feet northeast of Adam & Bessie Arnet Residence, Model, Las Animas County, CO
Marguerite Arnet Residence, exterior door detail, looking north. Adam ...
Marguerite Arnet Residence, exterior door detail, looking north. - Adam & Bessie Arnet Homestead, Marguerite Arnet Residence, 560 feet northeast of Adam & Bessie Arnet Residence, Model, Las Animas County, CO
1. EXTERIOR OF ADMINISTRATION BUILDING 202, LOOKING NORTHNORTHWEST. Mill ...
1. EXTERIOR OF ADMINISTRATION BUILDING 202, LOOKING NORTH-NORTHWEST. - Mill Valley Air Force Station, Administration Building, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
2. EXTERIOR EAST ELEVATION VIEW OF ADMINISTRATION BUILDING 202, LOOKING ...
2. EXTERIOR EAST ELEVATION VIEW OF ADMINISTRATION BUILDING 202, LOOKING SOUTH. - Mill Valley Air Force Station, Administration Building, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
EXTERIOR VIEW, LOOKING WEST, WITH CENTER SPAN EXTENDING ACROSS WARRIOR ...
EXTERIOR VIEW, LOOKING WEST, WITH CENTER SPAN EXTENDING ACROSS WARRIOR RIVER. - Gulf, Mobile & Ohio Railroad Bridge, Spans Black Warrior River between Northport & Tuscaloosa, Tuscaloosa, Tuscaloosa County, AL
EXTERIOR VIEW, LOOKING TOWARDS TUSCALOOSA, WITH CONCRETE PIERS AND CENTER ...
EXTERIOR VIEW, LOOKING TOWARDS TUSCALOOSA, WITH CONCRETE PIERS AND CENTER SPAN. - Gulf, Mobile & Ohio Railroad Bridge, Spans Black Warrior River between Northport & Tuscaloosa, Tuscaloosa, Tuscaloosa County, AL
EXTERIOR VIEW, LOOKING TOWARDS TUSCALOOSA, WITH APPROACH, CONCRETE PIERS AND ...
EXTERIOR VIEW, LOOKING TOWARDS TUSCALOOSA, WITH APPROACH, CONCRETE PIERS AND CENTER SPAN. - Gulf, Mobile & Ohio Railroad Bridge, Spans Black Warrior River between Northport & Tuscaloosa, Tuscaloosa, Tuscaloosa County, AL
1. EXTERIOR OF BUILDING 402, CIVIL ENGINEERING STORAGE, LOOKING SOUTH. ...
1. EXTERIOR OF BUILDING 402, CIVIL ENGINEERING STORAGE, LOOKING SOUTH. - Mill Valley Air Force Station, Civil Engineering Storage, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
1. EXTERIOR OF CENTRAL HEATING STATION, BUILDING 102, LOOKING NORTH. ...
1. EXTERIOR OF CENTRAL HEATING STATION, BUILDING 102, LOOKING NORTH. - Mill Valley Air Force Station, Central Heating Station, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
1. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING FRONT FACADE OF ...
1. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING FRONT FACADE OF ADMINISTRATION BUILDING. - Bonneville Project, Administration Building, South side of main entrance, Bonneville Project, Bonneville, Multnomah County, OR
5. GENERAL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING EAST FACADE OF ...
5. GENERAL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING EAST FACADE OF ADMINISTRATION BUILDING. - Bonneville Project, Administration Building, South side of main entrance, Bonneville Project, Bonneville, Multnomah County, OR
1. GENERAL EXTERIOR VIEW LOOKING SOUTHEAST AT DOWNSTREAM FACE OF ...
1. GENERAL EXTERIOR VIEW LOOKING SOUTHEAST AT DOWNSTREAM FACE OF DAM/SPILLWAY. VIEW TAKEN FROM WASHINGTON SHORELINE. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
4. GENERAL EXTERIOR VIEW LOOKING WEST, SHOWING REAR WING OF ...
4. GENERAL EXTERIOR VIEW LOOKING WEST, SHOWING REAR WING OF ADMINISTRATION BUILDING. - Bonneville Project, Administration Building, South side of main entrance, Bonneville Project, Bonneville, Multnomah County, OR
1. EXTERIOR, SIDE OF PICKLE BARREL RESTAURANT AND ADJOINING STORE ...
1. EXTERIOR, SIDE OF PICKLE BARREL RESTAURANT AND ADJOINING STORE - Silverton Historic District, East Thirteenth & Green Streets (Commercial Building), East Thirteenh & Green Streets, Silverton, San Juan County, CO
10. Southeast view interior, typical exterior office, room 27 ...
10. Southeast view interior, typical exterior office, room 27 - Selfridge Field, Building No. 1050, Northwest corner of Doolittle Avenue & D Street; Harrison Township, Mount Clemens, Macomb County, MI
A multiple degree of freedom electromechanical Helmholtz resonator.
Liu, Fei; Horowitz, Stephen; Nishida, Toshikazu; Cattafesta, Louis; Sheplak, Mark
2007-07-01
The development of a tunable, multiple degree of freedom (MDOF) electromechanical Helmholtz resonator (EMHR) is presented. An EMHR consists of an orifice, backing cavity, and a compliant piezoelectric composite diaphragm. Electromechanical tuning of the acoustic impedance is achieved via passive electrical networks shunted across the piezoceramic. For resistive and capacitive loads, the EMHR is a 2DOF system possessing one acoustic and one mechanical DOF. When inductive ladder networks are employed, multiple electrical DOF are added. The dynamics of the multi-energy domain system are modeled using lumped elements and are represented in an equivalent electrical circuit, which is used to analyze the tunable acoustic input impedance of the EMHR. The two-microphone method is used to measure the acoustic impedance of two EMHR designs with a variety of resistive, capacitive, and inductive shunts. For the first design, the data demonstrate that the tuning range of the second resonant frequency for an EMHR with non-inductive shunts is limited by short- and open-circuit conditions, while an inductive shunt results in a 3DOF system possessing an enhanced tuning range. The second design achieves stronger coupling between the Helmholtz resonator and the piezoelectric backplate, and both resonant frequencies can be tuned with different non-inductive loads. PMID:17614489
Helmholtz Resonator for Lead Zirconate Titanate Acoustic Energy Harvester
NASA Astrophysics Data System (ADS)
Matsuda, Tomohiro; Tomii, Kazuki; Hagiwara, Saori; Miyake, Shuntaro; Hasegawa, Yuichi; Sato, Takamitsu; Kaneko, Yuta; Nishioka, Yasushiro
2013-12-01
Acoustic energy harvesters that function in environments where sound pressure is extremely high (~150 dB), such as in engine rooms of aircrafts, are expected to be capable of powering wireless health monitoring systems. This paper presents the power generation performances of a lead-zirconate-titanate (PZT) acoustic energy harvester with a vibrating PZT diaphragm. The diaphragm had a diameter of 2 mm, consisting of Al(0.1 μm)/PZT(1 μm)/Pt(0.1 μm)/Ti(0.1 μm)/SiO2(1.5 μm). The harvester generated a power of 1.7×10-13 W under a sound pressure level of 110 dB at the first resonance frequency of 6.28 kHz. It was found that the generated power was increased to 6.8×10-13 W using a sound-collecting Helmholtz resonator cone with the height of 60 mm. The cone provided a Helmholtz resonance at 5.8 kHz, and the generated power increased from 3.4×10-14 W to 1.4×10-13 W at this frequency. The cone was also effective in increasing the bandwidth of the energy harvester.
Helmholtz and Goethe -- controversies at the birth of modern neuroscience.
Kesselring, Jürg
2013-01-01
Hermann von Helmholtz (1821-1894), a great German scientist and philosopher, made his mark during the exciting twilight period from the Enlightenment and Romanticism to the beginnings of modern neuroscience and offered new perspectives through his work. His early inclination was for physics, which he found more attractive than purely geometric and algebraic studies, but his father was not able to make it possible for him to study physics, and so he studied medicine in order to earn a living. His lecture before the Physical Society in Berlin on July 23, 1847, 'about the conservation of the force' marked an epochal turn, even though his intention had been to deliver 'merely, some critical investigations and arrangement of facts in favor of the physiologists' as well as good arguments for the refusal of the theory of 'vitality'. Even though these new concepts were at first dismissed as fantastic speculation by some of the authorities in physics and philosophy of the day, they were enthusiastically welcomed by younger students of philosophy and the older men soon had to allow themselves to be persuaded that the effectiveness of vitality, though great and beautiful, is actually always dependent on some source of energy. Helmholtz critically assessed Goethe as a physical scientist but he did not dispute his great importance as a poet. PMID:23257785
Another Look at Helmholtz's Model for the Gravitational Contraction of the Sun
ERIC Educational Resources Information Center
Tort, A. C.; Nogarol, F.
2011-01-01
We take another look at the Helmholtz model for the gravitational contraction of the Sun. We show that there are two other pedagogically useful ways of rederiving Helmholtz's main results that make use of Gauss's law, the concept of gravitational field energy and the work-kinetic energy theorem. An account of the energy balance involved in the…
NASA Technical Reports Server (NTRS)
Pierce, Allan D.
1989-01-01
Transient sound propagation in an inhomogeneous moving medium is considered. For circumstances in which the medium is slowly varying over distances of a wavelength but possibly varying substantially over the propagation distance, a derivation is given of a new wave equation, which implicitly allows for diffraction and scattering and which also is consistent with earlier geometrical acoustics formulations. This wave equation is used as a starting point to derive a version of the Helmholtz-Kirchhoff integral relation that applies to inhomogeneous moving medium. It is suggested that a good approximation to the Green's function that appears in this relation is that derived from geometrical acoustics, the approximation becoming progressively better the shorter the distance between surfaces in the computation. It should also be at least as good as conventional ray acoustics, but can account for diffraction effects, such as at caustics.
17. DETAIL OF INTERIOR AND EXTERIOR WALL CONSTRUCTION, VIEW TOWARD ...
17. DETAIL OF INTERIOR AND EXTERIOR WALL CONSTRUCTION, VIEW TOWARD NORTHEAST CORNER, THIRD BAY Showing insulated exterior wall at right; asphalt felt on interior separation wall at left; sill beam, stud, and concrete foundation detailing of interior wall. - U.S. Military Academy, Ice House, Mills Road at Howze Place, West Point, Orange County, NY
18. DETAIL OF EXTERIOR WALL CONSTRUCTION, VIEW TOWARD EAST, THIRD ...
18. DETAIL OF EXTERIOR WALL CONSTRUCTION, VIEW TOWARD EAST, THIRD BAY Showing furring strips, kraft faced cellulose fiber insulation, and asphalt felt applied to interior of exterior wall studs. - U.S. Military Academy, Ice House, Mills Road at Howze Place, West Point, Orange County, NY
5. EXTERIOR OF WEST (REAR) SIDE OF BUILDING 103 SHOWING ...
5. EXTERIOR OF WEST (REAR) SIDE OF BUILDING 103 SHOWING TALL RUSTIC STYLE CHIMNEY WITH GABLE FRAME, AND CONCRETE STEPS TO SIDE ENTRY DOOR AT PHOTO RIGHT. CHANGE IN EXTERIOR WALL DELINEATING 1946 BEDROOM ADDITION AND REMODELED WINDOW TO BATHROOM ARE VISIBLE AT PHOTO LEFT. VIEW TO NORTHEAST. - Rush Creek Hydroelectric System, Worker Cottage, Rush Creek, June Lake, Mono County, CA
46 CFR 154.1105 - Exterior water spray system: General.
Code of Federal Regulations, 2014 CFR
2014-10-01
... 46 Shipping 5 2014-10-01 2014-10-01 false Exterior water spray system: General. 154.1105 Section 154.1105 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Firefighting § 154.1105 Exterior water spray system: General. Each liquefied flammable gas...
46 CFR 154.1105 - Exterior water spray system: General.
Code of Federal Regulations, 2013 CFR
2013-10-01
... 46 Shipping 5 2013-10-01 2013-10-01 false Exterior water spray system: General. 154.1105 Section 154.1105 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS... Equipment Firefighting § 154.1105 Exterior water spray system: General. Each liquefied flammable gas...
Experimental study of liquid level gauge for liquid hydrogen using Helmholtz resonance technique
NASA Astrophysics Data System (ADS)
Nakano, Akihiro; Nishizu, Takahisa
2016-07-01
The Helmholtz resonance technique was applied to a liquid level gauge for liquid hydrogen to confirm the applicability of the technique in the cryogenic industrial field. A specially designed liquid level gauge that has a Helmholtz resonator with a small loudspeaker was installed in a glass cryostat. A swept frequency signal was supplied to the loudspeaker, and the acoustic response was detected by measuring the electrical impedance of the loudspeaker's voice coil. The penetration depth obtained from the Helmholtz resonance frequency was compared with the true value, which was read from a scale. In principle, the Helmholtz resonance technique is available for use with liquid hydrogen, however there are certain problems as regards practical applications. The applicability of the Helmholtz resonance technique to liquid hydrogen is discussed in this study.
Exterior differentiation in the Regge calculus
Brewin, L.
1986-01-01
Regge manifolds are piecewise continuous manifolds constructed from a finite number of basic building blocks. On such manifolds piecewise continuous forms can be defined in a way similar to differential forms on a differentiable manifold. Regge manifolds are used extensively in the construction of space-times in numerical general relativity. In this paper a definition of exterior differentiation suitable for use on piecewise continuous forms on a Regge manifold is presented. It is shown that this definition leads to a version of Stokes' theorem and also to the usual result that d/sup 2/ = 0. This is preceded by a discussion of certain geometrical properties of the Regge manifolds. It is shown that the version of Stokes' theorem presented here coincides with the usual definition when the Regge manifold is refined, by increasing the number of cells while keeping the total volume constant, to a smooth manifold.
Acoustic solitons in waveguides with Helmholtz resonators: transmission line approach.
Achilleos, V; Richoux, O; Theocharis, G; Frantzeskakis, D J
2015-02-01
We report experimental results and study theoretically soliton formation and propagation in an air-filled acoustic waveguide side loaded with Helmholtz resonators. We propose a theoretical modeling of the system, which relies on a transmission-line approach, leading to a nonlinear dynamical lattice model. The latter allows for an analytical description of the various soliton solutions for the pressure, which are found by means of dynamical systems and multiscale expansion techniques. These solutions include Boussinesq-like and Korteweg-de Vries pulse-shaped solitons that are observed in the experiment, as well as nonlinear Schrödinger envelope solitons, that are predicted theoretically. The analytical predictions are in excellent agreement with direct numerical simulations and in qualitative agreement with the experimental observations. PMID:25768623
Magnetic effects on the coalescence of Kelvin-Helmholtz vortices.
Nakamura, T K M; Fujimoto, M
2008-10-17
We simulate the coalescence process of MHD-scale Kelvin-Helmholtz vortices with the electron inertial effects taken into account. Reconnection of highly stretched magnetic field lines within a rolled-up vortex destroys the vortex itself and the coalescence process, which is well known in ordinary fluid dynamics, is seen to be inhibited. When the magnetic field is initially antiparallel across the shear layer, on the other hand, multiple vortices are seen to coalesce continuously because another type of magnetic reconnection prevents the vortex decay. This type of reconnection at the hyperbolic point also changes the field line connectivity and thus leads to large-scale plasma mixing across the shear layer. PMID:18999678
Magnetic Effects on the Coalescence of Kelvin-Helmholtz Vortices
Nakamura, T. K. M.; Fujimoto, M.
2008-10-17
We simulate the coalescence process of MHD-scale Kelvin-Helmholtz vortices with the electron inertial effects taken into account. Reconnection of highly stretched magnetic field lines within a rolled-up vortex destroys the vortex itself and the coalescence process, which is well known in ordinary fluid dynamics, is seen to be inhibited. When the magnetic field is initially antiparallel across the shear layer, on the other hand, multiple vortices are seen to coalesce continuously because another type of magnetic reconnection prevents the vortex decay. This type of reconnection at the hyperbolic point also changes the field line connectivity and thus leads to large-scale plasma mixing across the shear layer.
Measuring the off axis magnetic field within a Helmholtz Coil
NASA Astrophysics Data System (ADS)
Pluhar, Edward; Martell, Eric
2013-03-01
Helmholtz coils are used because they produce nearly uniform magnetic fields on-axis. Prior research, namely Graf's thin coil experiment [The Physics Teacher, pp. 360 (2012)], has accurately measured the axial magnetic field produced by a thin coil; however, the magnetic field off-axis is known to be significantly more complicated and cannot be calculated analytically. In this research, I have numerically determined the magnetic field off-axis in the region between the two coils and compared those calculations with measured values. I then determined the effect the deviation from uniformity has on the behavior of a charged particle moving through this region, such as in the well-known electron charge-to-mass ratio experiment.
Ubiquity of Kelvin–Helmholtz waves at Earth's magnetopause
Kavosi, Shiva; Raeder, Joachim
2015-01-01
Magnetic reconnection is believed to be the dominant process by which solar wind plasma enters the magnetosphere. However, for periods of northward interplanetary magnetic field (IMF) reconnection is less likely at the dayside magnetopause, and Kelvin–Helmholtz waves (KHWs) may be important agents for plasma entry and for the excitation of ultra-low-frequency (ULF) waves. The relative importance of KHWs is controversial because no statistical data on their occurrence frequency exist. Here we survey 7 years of in situ data from the NASA THEMIS (Time History of Events and Macro scale Interactions during Substorms) mission and find that KHWs occur at the magnetopause ∼19% of the time. The rate increases with solar wind speed, Alfven Mach number and number density, but is mostly independent of IMF magnitude. KHWs may thus be more important for plasma transport across the magnetopause than previously thought, and frequently drive magnetospheric ULF waves. PMID:25960122
Ubiquity of Kelvin-Helmholtz waves at Earth's magnetopause.
Kavosi, Shiva; Raeder, Joachim
2015-01-01
Magnetic reconnection is believed to be the dominant process by which solar wind plasma enters the magnetosphere. However, for periods of northward interplanetary magnetic field (IMF) reconnection is less likely at the dayside magnetopause, and Kelvin-Helmholtz waves (KHWs) may be important agents for plasma entry and for the excitation of ultra-low-frequency (ULF) waves. The relative importance of KHWs is controversial because no statistical data on their occurrence frequency exist. Here we survey 7 years of in situ data from the NASA THEMIS (Time History of Events and Macro scale Interactions during Substorms) mission and find that KHWs occur at the magnetopause ∼19% of the time. The rate increases with solar wind speed, Alfven Mach number and number density, but is mostly independent of IMF magnitude. KHWs may thus be more important for plasma transport across the magnetopause than previously thought, and frequently drive magnetospheric ULF waves. PMID:25960122
Evaluating gyro-viscosity in the Kelvin-Helmholtz instability by kinetic simulations
NASA Astrophysics Data System (ADS)
Umeda, Takayuki; Yamauchi, Natsuki; Wada, Yasutaka; Ueno, Satoshi
2016-04-01
In the present paper, the gyro-viscous term [W. B. Thompson, Pep. Prog. Phys. 24, 363-424 (1961)] is evaluated by using a full kinetic Vlasov simulation result of the Kelvin-Helmholtz instability (KHI). The average velocity (velocity field) and the pressure tensor are calculated from a high-resolution data of the velocity distribution functions obtained by the Vlasov simulation, which used to approximate the gyro-viscous term according to Thompson (1961). The direct comparison between the pressure tensor and the gyro-viscous term shows a good agreement. It is also shown that the off-diagonal pressure gradient enhanced the linear growth of the KHI when the inner product between the vorticity of the primary velocity shear layer and the magnetic field is negative, which is consistent with the previous Finite-Larmor-Radius(FLR)-MHD simulation result, but not with the previous kinetic simulation results. This result suggest that it is not enough for reproducing the kinetic simulation result to include the gyro-viscous term only in the equation of motion in fluid simulations.
Evaluating gyro-viscosity in the Kelvin-Helmholtz instability by kinetic simulations
NASA Astrophysics Data System (ADS)
Umeda, Takayuki; Yamauchi, Natsuki; Wada, Yasutaka; Ueno, Satoshi
2016-05-01
In the present paper, the finite-Larmor-radius (gyro-viscous) term [K. V. Roberts and J. B. Taylor, Phys. Rev. Lett. 8, 197-198 (1962)] is evaluated by using a full kinetic Vlasov simulation result of the Kelvin-Helmholtz instability (KHI). The velocity field and the pressure tensor are calculated from the high-resolution data of the velocity distribution functions obtained by the Vlasov simulation, which are used to approximate the Finite-Larmor-Radius (FLR) term according to Roberts and Taylor [Phys. Rev. Lett. 8, 197-198 (1962)]. The direct comparison between the pressure tensor and the FLR term shows an agreement. It is also shown that the anisotropic pressure gradient enhanced the linear growth of the KHI when the inner product between the vorticity of the primary velocity shear layer and the magnetic field is negative, which is consistent with the previous FLR-magnetohydrodynamic simulation result. This result suggests that it is not sufficient for reproducing the kinetic simulation result by fluid simulations to include the FLR term (or the pressure tensor) only in the equation of motion for fluid.
Accurate methods for computing inviscid and viscous Kelvin-Helmholtz instability
NASA Astrophysics Data System (ADS)
Chen, Michael J.; Forbes, Lawrence K.
2011-02-01
The Kelvin-Helmholtz instability is modelled for inviscid and viscous fluids. Here, two bounded fluid layers flow parallel to each other with the interface between them growing in an unstable fashion when subjected to a small perturbation. In the various configurations of this problem, and the related problem of the vortex sheet, there are several phenomena associated with the evolution of the interface; notably the formation of a finite time curvature singularity and the ‘roll-up' of the interface. Two contrasting computational schemes will be presented. A spectral method is used to follow the evolution of the interface in the inviscid version of the problem. This allows the interface shape to be computed up to the time that a curvature singularity forms, with several computational difficulties overcome to reach that point. A weakly compressible viscous version of the problem is studied using finite difference techniques and a vorticity-streamfunction formulation. The two versions have comparable, but not identical, initial conditions and so the results exhibit some differences in timing. By including a small amount of viscosity the interface may be followed to the point that it rolls up into a classic ‘cat's-eye' shape. Particular attention was given to computing a consistent initial condition and solving the continuity equation both accurately and efficiently.
Helmholtz resonance in a piezoelectric-hydraulic pump-based hybrid actuator
NASA Astrophysics Data System (ADS)
Kim, Gi-Woo; Wang, K. W.
2011-01-01
This paper demonstrates that a hydraulically acting Helmholtz resonator can exist in a piezoelectric-hydraulic pump (PHP) based hybrid actuator, which in turn affects the volumetric efficiency of the PHP. The simulation and experimental results illustrate the effect of Helmholtz resonance on the flow rate performance of the PHP. The study also shows how to shift the Helmholtz resonant frequency to a higher value through changing parameters such as the cylinder diameter and the effective bulk modulus of the working fluid, which will improve the volumetric efficiency and broaden the operating frequency range of the PHP actuator.
Autonomous navigation for structured exterior environments
Pletta, J B
1993-12-01
The Telemanaged Mobile Security Station (TMSS) was developed at Sandia National Laboratories to investigate the role of mobile robotics in exterior perimeter security systems. A major feature of the system is its capability to perform autonomous patrols of the security site`s network of roads. Perimeter security sites are well known, structured environments; the locations of the roads, buildings, and fences are relatively static. A security robot has the advantage of being able to learn its new environment prior to autonomous travel. The TMSS robot combines information from a microwave beacon system and on-board dead reckoning sensors to determine its location within the site. The operator is required to teleoperate the robot in a teach mode over all desired paths before autonomous operations can commence. During this teach phase, TMSS stores points from its position location system at two meter intervals. This map data base is used for planning paths and for reference during path following. Details of the position location and path following systems will be described along with system performance and recommendations for future enhancements.
Infinite-range exterior complex scaling as a perfect absorber in time-dependent problems
Scrinzi, Armin
2010-05-15
We introduce infinite range exterior complex scaling (irECS) which provides for complete absorption of outgoing flux in numerical solutions of the time-dependent Schroedinger equation with strong infrared fields. This is demonstrated by computing high harmonic spectra and wave-function overlaps with the exact solution for a one-dimensional model system and by three-dimensional calculations for the H atom and an Ne atom model. We lay out the key ingredients for correct implementation and identify criteria for efficient discretization.
13. CO'S STATEROOM (CABIN'S QUARTERS), PORT EXTERIOR. NOTE PORTHOLE AND ...
13. CO'S STATEROOM (CABIN'S QUARTERS), PORT EXTERIOR. NOTE PORTHOLE AND WOODEN FRAME WINDOWS. - U.S. Coast Guard Cutter WHITE LUPINE, U.S. Coast Guard Station Rockland, east end of Tillson Avenue, Rockland, Knox County, ME
Exterior view to the southeast of the west camera bunker ...
Exterior view to the southeast of the west camera bunker outside the fenced facility area - Nevada Test Site, Test Cell C Facility, West Camera Bunker, Area 25, Jackass Flats, Road J, Mercury, Nye County, NV
122. HISTORIC AMERICAN BUILDINGS SURVEY TEAM MEASURING EXTERIOR OF INDEPENDENCE ...
122. HISTORIC AMERICAN BUILDINGS SURVEY TEAM MEASURING EXTERIOR OF INDEPENDENCE HALL (LEE NELSON ON CORNER LEANING OVER) - Independence Hall Complex, Independence Hall, 500 Chestnut Street, Philadelphia, Philadelphia County, PA
10. Historic exterior view of Building 100. August 22, 1957. ...
10. Historic exterior view of Building 100. August 22, 1957. On file at NASA Plumbrook Research Center, Sandusky, Ohio. NASA photo number C-45766. - Rocket Engine Testing Facility, GRC Building No. 100, NASA Glenn Research Center, Cleveland, Cuyahoga County, OH
16. GENERAL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING TRANSMISSION TOWERS ON ...
16. GENERAL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING TRANSMISSION TOWERS ON WEST END OF BRADFORD ISLAND; BRADFORD SLOUGH DOWNSTREAM FROM POWERHOUSE #1 IS IN FOREGROUND. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
7. EXTERIOR VIEW TO THE SOUTHWEST OF THE NORTH AND ...
7. EXTERIOR VIEW TO THE SOUTHWEST OF THE NORTH AND EAST ELEVATIONS. - Nevada Test Site, Reactor Maintenance Assembly & Dissassembly Facility, Area 25, Jackass Flats, Junction of Roads F & G, Mercury, Nye County, NV
6. EXTERIOR VIEW TO THE SOUTH OF THE NORTH ELEVATION ...
6. EXTERIOR VIEW TO THE SOUTH OF THE NORTH ELEVATION OF THE HOT DISASSEMBLY AREA. - Nevada Test Site, Reactor Maintenance Assembly & Dissassembly Facility, Area 25, Jackass Flats, Junction of Roads F & G, Mercury, Nye County, NV
9. EXTERIOR VIEW TO THE NORTHWEST OF THE SOUTH AND ...
9. EXTERIOR VIEW TO THE NORTHWEST OF THE SOUTH AND EAST ELEVATIONS. - Nevada Test Site, Reactor Maintenance Assembly & Dissassembly Facility, Area 25, Jackass Flats, Junction of Roads F & G, Mercury, Nye County, NV
8. EXTERIOR VIEW TO THE WEST OF THE EAST ELEVATION ...
8. EXTERIOR VIEW TO THE WEST OF THE EAST ELEVATION OF THE HOT DISASSEMBLY AREA. - Nevada Test Site, Reactor Maintenance Assembly & Dissassembly Facility, Area 25, Jackass Flats, Junction of Roads F & G, Mercury, Nye County, NV
2. EXTERIOR VIEW TO THE NORTH OF THE SOUTH ELEVATION ...
2. EXTERIOR VIEW TO THE NORTH OF THE SOUTH ELEVATION OF THE HOT DISASSEMBLY AREA. - Nevada Test Site, Reactor Maintenance Assembly & Dissassembly Facility, Area 25, Jackass Flats, Junction of Roads F & G, Mercury, Nye County, NV
4. EXTERIOR VIEW TO THE EAST OF THE WEST ELEVATION ...
4. EXTERIOR VIEW TO THE EAST OF THE WEST ELEVATION OF THE COLD ASSEMBLY AREA. - Nevada Test Site, Reactor Maintenance Assembly & Dissassembly Facility, Area 25, Jackass Flats, Junction of Roads F & G, Mercury, Nye County, NV
Transverse electromagnetic horn antenna with resistively-loaded exterior surfaces
Aurand, John F.
1999-01-01
An improved transverse electromagnetic (TEM) horn antenna comprises a resistive loading material on the exterior surfaces of the antenna plates. The resistive loading material attenuates or inhibits currents on the exterior surfaces of the TEM horn antenna. The exterior electromagnetic fields are of opposite polarity in comparison to the primary and desired interior electromagnetic field, thus inherently cause partial cancellation of the interior wave upon radiation or upon reception. Reducing the exterior fields increases the radiation efficiency of the antenna by reducing the cancellation of the primary interior field (supported by the interior surface currents). This increases the transmit gain and receive sensitivity of the TEM horn antenna, as well as improving the transient (time-domain) response.
1. EXTERIOR, NORTH & WEST ELEVATIONS, LOOKING SOUTHEAST (Hans Muesig ...
1. EXTERIOR, NORTH & WEST ELEVATIONS, LOOKING SOUTHEAST (Hans Muesig & Robert Ryan, Photographers, March 1979) - Methodist Episcopal Church of Montour, East side of South Walnut Street, Montour, Gem County, ID
EXTERIOR VIEW, LOOKING EAST, FRONT FACADE AND ENTRANCE TO COMPANY ...
EXTERIOR VIEW, LOOKING EAST, FRONT FACADE AND ENTRANCE TO COMPANY SCHOOL FOR CHILDREN OF BLACK TCI-US STEEL RED ORE MINE WORKERS - Company School for Blacks, 413 Morgan Road, Bessemer, Jefferson County, AL
Facility No. 175, exterior oblique view of northeast and northwest ...
Facility No. 175, exterior oblique view of northeast and northwest sides, corner of Facility No. 176 is in background - U.S. Naval Base, Pearl Harbor, Landplane Hangar Type, Wasp Boulevard and Gambier Bay Street, Pearl City, Honolulu County, HI
52. DETAIL VIEW OF FRONT DOOR (EXTERIOR), FLUTED BUTTRESSES, AND ...
52. DETAIL VIEW OF FRONT DOOR (EXTERIOR), FLUTED BUTTRESSES, AND PARAPETED GABLE, NORTHWEST SIDE OF CAPTAIN'S GALLEY, LOOKING EAST - Huntington Beach Municipal Pier, Pacific Coast Highway at Main Street, Huntington Beach, Orange County, CA
7. NORTH EXTERIOR SIDE SHOWING TRIANGULAR KNEE BRACE SUPPORTS AND ...
7. NORTH EXTERIOR SIDE SHOWING TRIANGULAR KNEE BRACE SUPPORTS AND ENCLOSED PORCH SCREENED WINDOWS. VIEW TO SOUTH. - Big Creek Hydroelectric System, Powerhouse 8, Operator Cottage, Big Creek, Big Creek, Fresno County, CA
2. EXTERIOR OBLIQUE VIEW OF BUILDING 746 FROM EAST K ...
2. EXTERIOR OBLIQUE VIEW OF BUILDING 746 FROM EAST K STREET, LOOKING SOUTHEAST. - Oakland Naval Supply Center, Gymnasium-Cafeteria-Theater, East K Street between Eleventh & Twelfth Streets, Oakland, Alameda County, CA
22. FANTAIL DECK, SHOWING DETAIL OF DECK EXTENSION AND EXTERIOR ...
22. FANTAIL DECK, SHOWING DETAIL OF DECK EXTENSION AND EXTERIOR LOCKING MECHANISM ON HATCH DOOR TO CREW'S BERTHING. - U.S. Coast Guard Cutter WHITE HEATH, USGS Integrated Support Command Boston, 427 Commercial Street, Boston, Suffolk County, MA
EXTERIOR, A close up view, looking southeast at the dock ...
EXTERIOR, A close up view, looking southeast at the dock and overhead piping - Department of Energy, Mound Facility, Hydrolysis House Building (HH Building), One Mound Road, Miamisburg, Montgomery County, OH
EXTERIOR, A view looking southeast toward the north elevation of ...
EXTERIOR, A view looking southeast toward the north elevation of the building including the dock and overhead piping and stacks - Department of Energy, Mound Facility, Hydrolysis House Building (HH Building), One Mound Road, Miamisburg, Montgomery County, OH
EXTERIOR, A view looking northeast toward the south elevation and ...
EXTERIOR, A view looking northeast toward the south elevation and stacks of HH Building - Department of Energy, Mound Facility, Hydrolysis House Building (HH Building), One Mound Road, Miamisburg, Montgomery County, OH
EXTERIOR, A view looking northwest from far hill toward the ...
EXTERIOR, A view looking northwest from far hill toward the Mounds complex and the HH Building - Department of Energy, Mound Facility, Hydrolysis House Building (HH Building), One Mound Road, Miamisburg, Montgomery County, OH
EXTERIOR, A view looking northeast at the south and west ...
EXTERIOR, A view looking northeast at the south and west facades of the building and staircase - Department of Energy, Mound Facility, Hydrolysis House Building (HH Building), One Mound Road, Miamisburg, Montgomery County, OH
EXTERIOR, A view looking west that captures the east elevation ...
EXTERIOR, A view looking west that captures the east elevation of the building with parking lot to the right - Department of Energy, Mound Facility, Hydrolysis House Building (HH Building), One Mound Road, Miamisburg, Montgomery County, OH
44. EXTERIOR VIEW, GREEN SWITCH TOWER, COS COB, SHOWING BARS ...
44. EXTERIOR VIEW, GREEN SWITCH TOWER, COS COB, SHOWING BARS LINKING SWITCH LEVERS AND PIPES LEADING TO SWITCHES - New York, New Haven & Hartford Railroad, Automatic Signalization System, Long Island Sound shoreline between Stamford & New Haven, Stamford, Fairfield County, CT
5. EXTERIOR VIEW OF ELECTROSTATIC PRECIPITATORS FOR OPEN HEARTH NO. ...
5. EXTERIOR VIEW OF ELECTROSTATIC PRECIPITATORS FOR OPEN HEARTH NO. 5 (Martin Stupich) - U.S. Steel Homestead Works, Open Hearth Steelmaking Plant, Along Monongahela River, Homestead, Allegheny County, PA
3. EXTERIOR VIEW INTO PART OF OPEN HEARTH NO. 5 ...
3. EXTERIOR VIEW INTO PART OF OPEN HEARTH NO. 5 WITH RAILROAD TRESTLE IN FOREGROUND. (Jet Lowe) - U.S. Steel Homestead Works, Open Hearth Steelmaking Plant, Along Monongahela River, Homestead, Allegheny County, PA
4. EXTERIOR VIEW OF ELECTROSTATIC PRECIPITATORS FOR OPEN HEARTH NO. ...
4. EXTERIOR VIEW OF ELECTROSTATIC PRECIPITATORS FOR OPEN HEARTH NO. 5 (Martin Stupich) - U.S. Steel Homestead Works, Open Hearth Steelmaking Plant, Along Monongahela River, Homestead, Allegheny County, PA
9. VIEW EAST; EXTERIOR DETAIL OF WEST ELEVATION INCLUDING COLUMBUS ...
9. VIEW EAST; EXTERIOR DETAIL OF WEST ELEVATION INCLUDING COLUMBUS HALL. - Naval Undersea Warfare Center, Bowditch Hall, 600 feet east of Smith Street & 350 feet south of Columbia Cove, West bank of Thames River, New London, New London County, CT
CAR MACHINE SHOP, SECOND FLOOR, PAINT SPRAY ROOM EXTERIOR AND ...
CAR MACHINE SHOP, SECOND FLOOR, PAINT SPRAY ROOM EXTERIOR AND ATTIC FLOOR SUPPORT COLUMNS AND BEAMS, LOOKING WEST. - Southern Pacific, Sacramento Shops, Car Machine Shop, 111 I Street, Sacramento, Sacramento County, CA
Detail; Street Car Waiting House, support for exterior light fixture ...
Detail; Street Car Waiting House, support for exterior light fixture - North Philadelphia Station, Street Car Waiting House, 2900 North Broad Street, on northwest corner of Broad Street & Glenwood Avenue, Philadelphia, Philadelphia County, PA
Exterior doorway detail south side of building (first floor) east ...
Exterior doorway detail south side of building (first floor) east inset porch; interior staircase visible in background - Fitzsimons General Hospital, Open Air Tuberculosis Ward, West Pennington Avenue & North Hickey Street Southwest Corner, Aurora, Adams County, CO
View of exterior circumferential path at northwest side of building, ...
View of exterior circumferential path at northwest side of building, looking east toward building entrance - National Zoological Park, Bird House, 3001 Connecticut Avenue NW, Washington, District of Columbia, DC
2. GENERAL EXTERIOR VIEW LOOKING WEST, SHOWING CHANNEL DOWNSTREAM FROM ...
2. GENERAL EXTERIOR VIEW LOOKING WEST, SHOWING CHANNEL DOWNSTREAM FROM NAVIGATION LOCK #1; MOVABLE BRIDGE IS VISIBLE IN LEFT FOREGROUND. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
12. DETAIL EXTERIOR VIEW OF FISH PASSAGE BETWEEN THE SOUTH ...
12. DETAIL EXTERIOR VIEW OF FISH PASSAGE BETWEEN THE SOUTH END OF POWERHOUSE #1 AND NAVIGATION LOCK #1. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
9. DETAIL EXTERIOR VIEW LOOKING SOUTHEAST, SHOWING DOWNSTREAM MITER GATES ...
9. DETAIL EXTERIOR VIEW LOOKING SOUTHEAST, SHOWING DOWNSTREAM MITER GATES FOR NAVIGATION LOCK #1. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
12. Exterior detail view of roof structure at eave, showing ...
12. Exterior detail view of roof structure at eave, showing exposed rafter tails, skip sheathing and gutter - American Railway Express Company Freight Building, 1060 Northeast Division Street, Bend, Deschutes County, OR
Low-cost exterior insulation process and structure
Vohra, A.
1999-03-02
A low-cost exterior insulation process of stacking bags of insulating material against a wall and covering them with wire mesh and stucco provides a durable structure with good insulating value. 2 figs.
EXTERIOR VIEW, BEE HIVE COKE OVEN DOOR. Pratt Coal ...
EXTERIOR VIEW, BEE HIVE COKE OVEN DOOR. - Pratt Coal & Coke Company, Pratt Mines, Coke Ovens & Railroad, Bounded by First Street, Avenue G, Third Place, Birmingham Southern Railroad, Birmingham, Jefferson County, AL
2. EXTERIOR SITE VIEW OF STRUCTURE 408 AND RADOME 409 ...
2. EXTERIOR SITE VIEW OF STRUCTURE 408 AND RADOME 409 ON RIGHT, LOOKING NORTHEAST. - Mill Valley Air Force Station, Radar Domes, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
1. GENERAL EXTERIOR VIEW OF THE ELECTRIC FURNACE STEELMAKING PLANT ...
1. GENERAL EXTERIOR VIEW OF THE ELECTRIC FURNACE STEELMAKING PLANT LOOKING NORTHEAST. - U.S. Steel Duquesne Works, Electric Furnace Steelmaking Plant, Along Monongahela River, Duquesne, Allegheny County, PA
EXTERIOR VIEW, BLAST FURNACE NO. 3 (JANE FURNACE) CENTER, NO. ...
EXTERIOR VIEW, BLAST FURNACE NO. 3 (JANE FURNACE) CENTER, NO. 3 CAST HOUSE TO THE LEFT, WEST ORE BRIDGE TO THE RIGHT. - Pittsburgh Steel Company, Monessen Works, Blast Furnace No. 3, Donner Avenue, Monessen, Westmoreland County, PA
2. EXTERIOR VIEW LOOKING SOUTHEAST AT ELECTRIC FURNACE BUILDING AND ...
2. EXTERIOR VIEW LOOKING SOUTHEAST AT ELECTRIC FURNACE BUILDING AND ELECTRIC FURNACE OFFICE & CHEMICAL LABORATORY BUILDING. INGOT MOLDS IN RIGHT FOREGROUND. - U.S. Steel Duquesne Works, Electric Furnace Steelmaking Plant, Along Monongahela River, Duquesne, Allegheny County, PA
Exterior oblique view of the east end and the south ...
Exterior oblique view of the east end and the south side. Showing the Dust Collector on the right. View facing northwest - U.S. Naval Base, Pearl Harbor, Sawmill, Seventh Street near Avenue E, Pearl City, Honolulu County, HI
Looking Southwest to Dry and Wet Exterior Scrubbers at Rear ...
Looking Southwest to Dry and Wet Exterior Scrubbers at Rear of Oxide Building - Hematite Fuel Fabrication Facility, Oxide Building & Oxide Loading Dock, 3300 State Road P, Festus, Jefferson County, MO
Marguerite Arnet Residence, exterior roof structure detail, looking northwest. ...
Marguerite Arnet Residence, exterior roof structure detail, looking northwest. - Adam & Bessie Arnet Homestead, Marguerite Arnet Residence, 560 feet northeast of Adam & Bessie Arnet Residence, Model, Las Animas County, CO
1. Mill exterior, high grade chute partially restored on the ...
1. Mill exterior, high grade chute partially restored on the outside of mill building center of picture. Looking northeast from below bridge. - Kennecott Copper Corporation, Concentration Mill, On Copper River & Northwestern Railroad, Kennicott, Valdez-Cordova Census Area, AK
General exterior view to northeast (Building 203 in background right) ...
General exterior view to northeast (Building 203 in background right) - Charlestown Navy Yard, Oxygen Plant, Midway along northern boundary of Charlestown Navy Yard, on Little Mystic Channel, near junction of Eighteenth Street & Fourth Avenue, Boston, Suffolk County, MA
22. EXTERIOR DETAIL VIEW OF SOUTHEAST CORNER OF BRIDGE, 1932 ...
22. EXTERIOR DETAIL VIEW OF SOUTHEAST CORNER OF BRIDGE, 1932 SECTION, SOUTH BANK, LOOKING NORTHEAST TO SOUTHWEST - Rowdy Creek Bridge, Spanning Rowdy Creek at Fred Haight Drive, Smith River, Del Norte County, CA
EXTERIOR VIEW, POWELL AVENUE (SOUTH) ELEVATION, PEDESTRIAN PASSAGEWAY AT LEFT ...
EXTERIOR VIEW, POWELL AVENUE (SOUTH) ELEVATION, PEDESTRIAN PASSAGEWAY AT LEFT SIDE OF UNDERPASS - Twentieth Street Underpass, At Railroad Reservation, Twentieth Street at the Tracks between Morris & Powell Avenues, Birmingham, Jefferson County, AL
Exterior view of southern half of east porch, showing entrance ...
Exterior view of southern half of east porch, showing entrance to second story of la casa, view towards the west - Pou Coffee Processing Structure, Casa No. 2, Highway 139, Kilometer 12, Maraguez, Ponce Municipio, PR
4. DETAIL VIEW OF CROSS SECTION OF STRUCTURE, SHOWING EXTERIOR ...
4. DETAIL VIEW OF CROSS SECTION OF STRUCTURE, SHOWING EXTERIOR FACINGS LINED WITH RUBBLE BACKING AND EARTH INFILL, LOOKING EAST - Rock Wall, North side of Battle Creek Canyon, Shingletown, Shasta County, CA
EXTERIOR VIEW OF THE FRONT AND NORTHWEST SIDE OF BUILDING ...
EXTERIOR VIEW OF THE FRONT AND NORTHWEST SIDE OF BUILDING 471 FACING SOUTH - U.S. Naval Base, Pearl Harbor, Waterfront Transit Shed, Corner of Northampton Avenue & Simms Street, Pearl City, Honolulu County, HI
EXTERIOR VIEW OF THE FRONT AND SOUTH SIDE OF BUILDING ...
EXTERIOR VIEW OF THE FRONT AND SOUTH SIDE OF BUILDING 447 FACING NORTHWEST - U.S. Naval Base, Pearl Harbor, Waterfront Transit Shed, Between Northampton Avenue & Wharf K3, Pearl City, Honolulu County, HI
EXTERIOR VIEW OF THE REAR AND SOUTH SIDE OF BUILDING ...
EXTERIOR VIEW OF THE REAR AND SOUTH SIDE OF BUILDING 477 FACING NORTH - U.S. Naval Base, Pearl Harbor, Waterfront Transit Shed, Corner of Astoria Avenue & Gaffney Street, Pearl City, Honolulu County, HI
EXTERIOR VIEW OF THE REAR AND SOUTHEAST SIDE OF BUILDING ...
EXTERIOR VIEW OF THE REAR AND SOUTHEAST SIDE OF BUILDING 471 FACING NORTHEAST - U.S. Naval Base, Pearl Harbor, Waterfront Transit Shed, Corner of Northampton Avenue & Simms Street, Pearl City, Honolulu County, HI
EXTERIOR VIEW OF THE FRONT AND NORTH SIDE OF BUILDING ...
EXTERIOR VIEW OF THE FRONT AND NORTH SIDE OF BUILDING 477 FACING SOUTH - U.S. Naval Base, Pearl Harbor, Waterfront Transit Shed, Corner of Astoria Avenue & Gaffney Street, Pearl City, Honolulu County, HI
EXTERIOR VIEW OF THE FRONT AND NORTH SIDE OF BUILDING ...
EXTERIOR VIEW OF THE FRONT AND NORTH SIDE OF BUILDING 447 FACING SOUTHWEST - U.S. Naval Base, Pearl Harbor, Waterfront Transit Shed, Between Northampton Avenue & Wharf K3, Pearl City, Honolulu County, HI
4. Exterior, detail south elevation, showing jointing of logs on ...
4. Exterior, detail south elevation, showing jointing of logs on later extension. Sept. 12, 1940. Mixon. - Upper Swedish Log Cabin, Darby Creek vicinity, Clifton Heights (Upper Darby Township), Darby, Delaware County, PA
2. Exterior, general view of rear and end, from west. ...
2. Exterior, general view of rear and end, from west. Sept. 12, 1940. Photo by Stanly P. Mixon. - Upper Swedish Log Cabin, Darby Creek vicinity, Clifton Heights (Upper Darby Township), Darby, Delaware County, PA
3. Exterior, detail view of north elevation, from northeast, showing ...
3. Exterior, detail view of north elevation, from northeast, showing joint of addition. Sept. 12, 1940. Mixon. - Upper Swedish Log Cabin, Darby Creek vicinity, Clifton Heights (Upper Darby Township), Darby, Delaware County, PA
Photographic copy of reproduced photograph dated 1942. Exterior view, west ...
Photographic copy of reproduced photograph dated 1942. Exterior view, west elevation. Building camouflaged during World War II. - Grand Central Air Terminal, 1310 Air Way, Glendale, Los Angeles County, CA
7. EXTERIOR, SIDE VIEW FROM GARDEN SHOWING GRAPE ARBOR undated ...
7. EXTERIOR, SIDE VIEW FROM GARDEN SHOWING GRAPE ARBOR undated - Jean Baptiste Valle House, 99 South Main Street (Northwest corner of Main & Market Streets), Sainte Genevieve, Ste. Genevieve County, MO
Exterior oblique view of southeast and northeast side. View facing ...
Exterior oblique view of southeast and northeast side. View facing west-southwest - U.S. Naval Base, Pearl Harbor, Forge Shop & Galvanizing Shop, Sixth Street between Avenues D & E, Pearl City, Honolulu County, HI
32. Credit JTL. Exterior transformer bank; note lightning arrestors removed ...
32. Credit JTL. Exterior transformer bank; note lightning arrestors removed from pad and smaller arrestors installed on transformers and in area near air switches. - Dam No. 4 Hydroelectric Plant, Potomac River, Martinsburg, Berkeley County, WV
1. EXTERIOR VIEW, OBLIQUE PERSPECTIVE, LOOKING NORTHEAST, WITH SIDE AND ...
1. EXTERIOR VIEW, OBLIQUE PERSPECTIVE, LOOKING NORTHEAST, WITH SIDE AND FRONT ELEVATIONS OF THE CHURCH AND THE GAZEBO BAND STAND (LEFT) - St. Mark's Catholic Church, 1040 Tenth Avenue West, Thomas, Jefferson County, AL
1. EXTERIOR VIEW SHOWING THE SOUTHWEST & SOUTHEAST SIDES OF ...
1. EXTERIOR VIEW SHOWING THE SOUTHWEST & SOUTHEAST SIDES OF THE AUDITORIUM, LOOKING NORTHEAST - Fort McCoy, Building No. T-1056, Southwest of intersection of South Tenth Avenue & South "X" Street, Block 10, Sparta, Monroe County, WI
2. EXTERIOR OBLIQUE VIEW OF BUILDING 218 WITH DOMES TO ...
2. EXTERIOR OBLIQUE VIEW OF BUILDING 218 WITH DOMES TO THE RIGHT, LOOKING NORTHWEST. - Mill Valley Air Force Station, Consolidated Open Mess, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
EXTERIOR ELEVATION, LOOKING SOUTH, ALSO SHOWING THE NORFOLK SOUTHERN STEAM ...
EXTERIOR ELEVATION, LOOKING SOUTH, ALSO SHOWING THE NORFOLK SOUTHERN STEAM RESTORATION FLOOR INTERIOR WITH A DRILL PRESS (LEFT) AND BORING MILL (RIGHT). - Norfolk & Southern Steam Locomotive No. 1218, Norris Yards, East of Ruffner Road, Irondale, Jefferson County, AL
6. EXTERIOR ELEVATION OF SOUTH END OF EAST FACADE OF ...
6. EXTERIOR ELEVATION OF SOUTH END OF EAST FACADE OF STEAM PLANT, BUILDING 740, LOOKING WEST. - Oakland Naval Supply Center, Steam Plant, Sixth Street south of East K Street, Oakland, Alameda County, CA
5. EXTERIOR ELEVATION OF NORTH END OF EAST FACADE OF ...
5. EXTERIOR ELEVATION OF NORTH END OF EAST FACADE OF STEAM PLANT, BUILDING 740, LOOKING WEST. - Oakland Naval Supply Center, Steam Plant, Sixth Street south of East K Street, Oakland, Alameda County, CA
3. EXTERIOR OF SOUTH SIDE SHOWING DOOR TO ENCLOSED FRONT ...
3. EXTERIOR OF SOUTH SIDE SHOWING DOOR TO ENCLOSED FRONT PORCH ON PHOTO RIGHT AND DOOR TO KITCHEN AT PHOTO LEFT. VIEW TO NORTH. - Bishop Creek Hydroelectric System, Control Station, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA
1. EXTERIOR CONTEXT VIEW OF BUILDING 620, THE SEWAGE EJECTOR, ...
1. EXTERIOR CONTEXT VIEW OF BUILDING 620, THE SEWAGE EJECTOR, LOOKING NORTHEAST. - Mill Valley Air Force Station, Sewage Ejector, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
9. EXTERIOR PERSPECTIVE OF POWER PLANT BUILDING LOOKING NORTHEAST. DRY ...
9. EXTERIOR PERSPECTIVE OF POWER PLANT BUILDING LOOKING NORTHEAST. DRY CANAL BED IN FOREGROUND. - Potomac Power Plant, On West Virginia Shore of Potomac River, about 1 mile upriver from confluence with Shenandoah River, Harpers Ferry, Jefferson County, WV
7. EXTERIOR OF POWER PLANT BUILDING LOOKING NORTHWEST. DETAIL OF ...
7. EXTERIOR OF POWER PLANT BUILDING LOOKING NORTHWEST. DETAIL OF TRASH RACK IN FOREGROUND. - Potomac Power Plant, On West Virginia Shore of Potomac River, about 1 mile upriver from confluence with Shenandoah River, Harpers Ferry, Jefferson County, WV
EXTERIOR VIEW WITH HEART OF DIXIE MUSEUM'S HISTORIC LOCOMOTIVE IN ...
EXTERIOR VIEW WITH HEART OF DIXIE MUSEUM'S HISTORIC LOCOMOTIVE IN MUSEUM'S POWELL AVENUE YARD (BOTTOM) AND SOUTHERN RAILWAY BOXCAR ON ACTIVE TRACKAGE (ABOVE). - Heart of Dixie Railroad, Rolling Stock, 1800 Block Powell Avenue, Birmingham, Jefferson County, AL
1. EXTERIOR VIEW OF THE EXPLOSIVE STORAGE SHED, BUILDING 306, ...
1. EXTERIOR VIEW OF THE EXPLOSIVE STORAGE SHED, BUILDING 306, LOOKING NORTHWEST. - Mill Valley Air Force Station, Explosive Storage, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
INTERIOR VIEW OF HALL. SHOWING THE THREELIGHT EXTERIOR DOOR TO ...
INTERIOR VIEW OF HALL. SHOWING THE THREE-LIGHT EXTERIOR DOOR TO THE COVERED PATIO AREA AND THE TELEPHONE NICHE. VIEW FACING SOUTHWEST. - Hickam Field, Officers' Housing Type G, 205 Seventh Street, Honolulu, Honolulu County, HI
14. EAST ELEVATION, COTTAGE. EXTERIOR NEARLY RESTORED. INTERIOR UNDERGOING RESTORATION. ...
14. EAST ELEVATION, COTTAGE. EXTERIOR NEARLY RESTORED. INTERIOR UNDERGOING RESTORATION. EUCALYPTUS TREE PLANTED BY GERTRUDE KEIL PLANNED FOR REMOVAL. - Gold Ridge Farm, 7777 Bodega Avenue, Sebastopol, Sonoma County, CA
46. Exterior view at the corner of Seventh Avenue and ...
46. Exterior view at the corner of Seventh Avenue and Olive Way, looking NE. Opening night film, 'The Broadway Melody,' displayed on the canopy marquee. - Fox Theater, Seventh Avenue & Olive Way, Seattle, King County, WA
5. EXTERIOR OF NORTH SIDE SHOWING ENCLOSED FRONT PORCH AREA, ...
5. EXTERIOR OF NORTH SIDE SHOWING ENCLOSED FRONT PORCH AREA, ALUMINUM SLIDING GLASS WINDOW GLAZING REPLACEMENTS, AND RAILING FOR STAIRS TO BASEMENT. VIEW TO SOUTHWEST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA
21. Southeast corner of switch house addition, including exterior transformers ...
21. Southeast corner of switch house addition, including exterior transformers and start of power transmission line. Employee House No. 1 is in the background. - Rock Creek Hydroelectric Project, Rock Creek, Baker County, OR
1. EXTERIOR VIEW TO THE NORTHWEST OF ANCILLARY STRUCTURES ASSOCIATED ...
1. EXTERIOR VIEW TO THE NORTHWEST OF ANCILLARY STRUCTURES ASSOCIATED WITH AND SURROUNDING BUILDING 3210. - Nevada Test Site, Test Cell C Facility, Elevated Water Tower, Area 25, Jackass Flats, Road J, Mercury, Nye County, NV
8. Interior view of administrator's office, showing exterior windows; near ...
8. Interior view of administrator's office, showing exterior windows; near northwest corner of west wing; view to south. - Ellsworth Air Force Base, Administration Office, 2704 George Drive, Blackhawk, Meade County, SD
2. REAR VIEW SHOWING SPLIT SHAKE EXTERIOR AND HEXAHEDRAL PLAN ...
2. REAR VIEW SHOWING SPLIT SHAKE EXTERIOR AND HEXAHEDRAL PLAN AND DENSE LANDSCAPE - Camp Cleawox, Adirondack Sleeping Shelter, Oregon Dunes National Recreation Area, Siuslaw National Forest, Florence, Lane County, OR
1. VIEW OF BUILDING 883 EXTERIOR, LOOKING SOUTHEAST. VENTILATION EQUIPMENT ...
1. VIEW OF BUILDING 883 EXTERIOR, LOOKING SOUTHEAST. VENTILATION EQUIPMENT IS VISIBLE. (11/27/56) - Rocky Flats Plant, Uranium Rolling & Forming Operations, Southeast section of plant, southeast quadrant of intersection of Central Avenue & Eighth Street, Golden, Jefferson County, CO
3. Readiness Crew Building exterior, south and east sides, overall ...
3. Readiness Crew Building exterior, south and east sides, overall view, looking northwest. Thalheimer - Whiteman Air Force Base, Bomber Alert Facility S-6, 1300 Alert Road, Knob Noster, Johnson County, MO
4. Readiness Crew Building exterior, three tunnels on the south ...
4. Readiness Crew Building exterior, three tunnels on the south side, looking west-northwest. Thalheimer - Whiteman Air Force Base, Bomber Alert Facility S-6, 1300 Alert Road, Knob Noster, Johnson County, MO
4. EXTERIOR CONTEXT OF BUILDING 220 WITH FOUNDATION OF 224 ...
4. EXTERIOR CONTEXT OF BUILDING 220 WITH FOUNDATION OF 224 IN THE FOREGROUND, LOOKING NORTH. - Mill Valley Air Force Station, Mess Hall, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
1. EXTERIOR VIEW, LOOKING EAST, WITH ENTRANCES AND SIDE ELEVATIONS ...
1. EXTERIOR VIEW, LOOKING EAST, WITH ENTRANCES AND SIDE ELEVATIONS ALONG THE OLD BANKHEAD HIGHWAY (NOW 20TH STREET) AND ELLIOTT BOULEVARD - G. W. Posey Store, Twentieth Street & Elliot Boulevard, Jasper, Walker County, AL
29. EXTERIOR CAN CONVEYOR One of three external can ...
29. EXTERIOR - CAN CONVEYOR One of three external can conveyor systems which criss-crossed the multi-leveled confusion of roof structures of the cannery complex. - Hovden Cannery, 886 Cannery Row, Monterey, Monterey County, CA
1. EXTERIOR OF ENGINE ROOM, CONTAINING UNITEDTOD TWINTANDEM ENGINE, FOR ...
1. EXTERIOR OF ENGINE ROOM, CONTAINING UNITED-TOD TWIN-TANDEM ENGINE, FOR 40" BLOOMING MILL - Republic Iron & Steel Company, Youngstown Works, Blooming Mill & Blooming Mill Engines, North of Poland Avenue, Youngstown, Mahoning County, OH
2. EXTERIOR OF ENGINE ROOM, CONTAINING MESTACORLISS CROSSCOMPOUND ENGINE, FOR ...
2. EXTERIOR OF ENGINE ROOM, CONTAINING MESTA-CORLISS CROSS-COMPOUND ENGINE, FOR 40" BLOOMING MILL - Republic Iron & Steel Company, Youngstown Works, Blooming Mill & Blooming Mill Engines, North of Poland Avenue, Youngstown, Mahoning County, OH
5. EAGLE CREEK RECREATION AREA, EXTERIOR VIEW OF PORTION OF ...
5. EAGLE CREEK RECREATION AREA, EXTERIOR VIEW OF PORTION OF EAGLE CREEK OVERLOOK. - Historic Columbia River Highway, Eagle Creek Recreation Area, Historic Columbia River Highway at Eagle Creek, Troutdale, Multnomah County, OR
Electrical cable connector-clamp has smooth exterior surface
NASA Technical Reports Server (NTRS)
1965-01-01
Electrical cable connector-clamp fitted with a collet has a smooth exterior surface that can be easily gripped. The collet clamps a portion of the cable and provides for connecting it to a standard electrical connector.
19. INTERIOR, VIEW THROUGH TRIANGULARARCHED DOORWAY TO EXTERIOR Moravian ...
19. INTERIOR, VIEW THROUGH TRIANGULAR-ARCHED DOORWAY TO EXTERIOR - Moravian Pottery & Tile Works, Southwest side of State Route 313 (Swamp Road), Northwest of East Court Street, Doylestown, Bucks County, PA
Detail, exterior side of doubleplanked north end, Burton Park Club ...
Detail, exterior side of double-planked north end, Burton Park Club House, view to south-southwest (135mm lens). - Burton Park, Club House & Amphitheater, Adjacent ot south end of Chestnut Avenue, San Carlos, San Mateo County, CA
55. Exterior view of marine railway #4. BBW work Tug ...
55. Exterior view of marine railway #4. BBW work Tug Sam on the ways seen from Port Bow. This was first railway built by BBW on site (Ca.1936). - Barbour Boat Works, Tryon Palace Drive, New Bern, Craven County, NC
40. Exterior view of dockage, marine railway #4, and assembly ...
40. Exterior view of dockage, marine railway #4, and assembly building. Note BBW Tug Sam on railway and BBW-Built Stardust (#1) at end of dock. - Barbour Boat Works, Tryon Palace Drive, New Bern, Craven County, NC
57. Exterior view of marine railway #4. BBW work Tun ...
57. Exterior view of marine railway #4. BBW work Tun Sam on the ways seen from Starboard Bow. Note rail/roller type (steel railway/steel wheels). - Barbour Boat Works, Tryon Palace Drive, New Bern, Craven County, NC
4. EXTERIOR OBLIQUE VIEW OF THE ADMINISTRATION BUILDING, LOOKING EASTNORTHEAST. ...
4. EXTERIOR OBLIQUE VIEW OF THE ADMINISTRATION BUILDING, LOOKING EAST-NORTHEAST. - Mill Valley Air Force Station, Administration Building, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
3. EXTERIOR SOUTH ELEVATION VIEW OF THE ADMINISTRATION BUILDING 202, ...
3. EXTERIOR SOUTH ELEVATION VIEW OF THE ADMINISTRATION BUILDING 202, LOOKING WEST-NORTHWEST. - Mill Valley Air Force Station, Administration Building, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
6. Historic American Buildings Survey EXTERIOR SUMMERGARDEN, SHOWING EAST ELEVATION ...
6. Historic American Buildings Survey EXTERIOR SUMMERGARDEN, SHOWING EAST ELEVATION OF 1893-94 PORTION OF BUILDING, PHOTOCOPY c. 1898 - Das Deutsche Haus, 401 East Michigan Street, Indianapolis, Marion County, IN
8. EXTERIOR DETAIL OF FRONT ENTRY PORCH SHOWING ORIGINAL ARTS ...
8. EXTERIOR DETAIL OF FRONT ENTRY PORCH SHOWING ORIGINAL ARTS AND CRAFTS STYLE ELECTRICAL LANTERN. VIEW TO SOUTH. - Rush Creek Hydroelectric System, Clubhouse Cottage, Rush Creek, June Lake, Mono County, CA
EXTERIOR NORTH VIEW, WITH BUILDING 91 (ORIGINALLY THE WRIGHT FIELD ...
EXTERIOR NORTH VIEW, WITH BUILDING 91 (ORIGINALLY THE WRIGHT FIELD LAUNDRY) IN THE FOREGROUND - Wright-Patterson Air Force Base, Area B, Building 67, Emergency Power Plant, North side of Third Street between D & E Streets, Dayton, Montgomery County, OH
EXTERIOR CLOSEUP VIEW OF SINGLE BAY ON WEST FACADE ...
EXTERIOR CLOSEUP VIEW OF SINGLE BAY ON WEST FACADE - Wright-Patterson Air Force Base, Area B, Building 56, Wright Field Warehouse, block bounded by E & F, Third & Fifth Streets, Dayton, Montgomery County, OH
Exterior view of hipped roof with coffee processing structure in ...
Exterior view of hipped roof with coffee processing structure in background, view towards the southwest - Pou Coffee Processing Structure, Casa No. 2, Highway 139, Kilometer 12, Maraguez, Ponce Municipio, PR
1. Photocopy of photograph (Original source unknown, date unknown) EXTERIOR, ...
1. Photocopy of photograph (Original source unknown, date unknown) EXTERIOR, SOUTH FRONT OF ADOBE INCLUDING ENVIRONS - Gaspar Orena House, East de la Guerra Street, Santa Barbara, Santa Barbara County, CA
5. DETAIL EXTERIOR VIEW OF CUPOLA AND WEATHER VANE ON ...
5. DETAIL EXTERIOR VIEW OF CUPOLA AND WEATHER VANE ON TOP OF THE FISH HATCHERY BUILDING. - Bonneville Project, Fish Hatchery, On Columbia River bordered on South by Union Pacific, Bonneville, Multnomah County, OR
EXTERIOR VIEW, LOOKING NORTHEAST, WITH SLAB YARD. AT RIGHT IS ...
EXTERIOR VIEW, LOOKING NORTHEAST, WITH SLAB YARD. AT RIGHT IS HOT STRIP MILL BUILDING AND FURNACE. VIEW AT LEFT IS TOWARD CUT TO LENGTH BUILDING. - Central Iron Foundry Site, 1700 Holt Road, Holt, Tuscaloosa County, AL
2. VAL CONTROL STATION, VIEW OF INTERIOR SHOWING EXTERIOR DOOR, ...
2. VAL CONTROL STATION, VIEW OF INTERIOR SHOWING EXTERIOR DOOR, WINDOWS AND CONTROL PANELS, LOOKING SOUTHEAST. - Variable Angle Launcher Complex, Control Station, CA State Highway 39 at Morris Reservior, Azusa, Los Angeles County, CA
Exterior overall oblique view of the northeast and southeast sides ...
Exterior overall oblique view of the northeast and southeast sides - U.S. Naval Base, Pearl Harbor, Scrap Metal Packaging Facility, Seventh Street between Facility Nos. 6 & 247, Pearl City, Honolulu County, HI
Exterior view of the southwest side, taken from Facility No. ...
Exterior view of the southwest side, taken from Facility No. 247 with Facility No. 6 beyond - U.S. Naval Base, Pearl Harbor, Scrap Metal Packaging Facility, Seventh Street between Facility Nos. 6 & 247, Pearl City, Honolulu County, HI
EXTERIOR VIEW, LOOKING WEST, WITH CENTER SPAN EXTENDING ACROSS WARRIOR ...
EXTERIOR VIEW, LOOKING WEST, WITH CENTER SPAN EXTENDING ACROSS WARRIOR RIVER AND COAL BARGES (LEFT). - Gulf, Mobile & Ohio Railroad Bridge, Spans Black Warrior River between Northport & Tuscaloosa, Tuscaloosa, Tuscaloosa County, AL
DETAIL ELEVATION VIEW OF EXTERIOR STAIRS ON THE EAST END ...
DETAIL ELEVATION VIEW OF EXTERIOR STAIRS ON THE EAST END OF BUILDING 63, FACING SOUTH. - Naval Computer & Telecommunications Area Station, Enlisted Men's Barracks, West corner of Central Street & Midway Drive, Wahiawa, Honolulu County, HI
Exterior view of boiler house looking southwest with steam exhaust ...
Exterior view of boiler house looking southwest with steam exhaust vents in foreground. Engine house is on left. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV
Exterior view looking northwest with construction facilities of "new" pumping ...
Exterior view looking northwest with construction facilities of "new" pumping station in foreground. Doug Hine is man in picture. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV
Detail exterior view looking southwest of gas cooling system. Engine ...
Detail exterior view looking southwest of gas cooling system. Engine house is shown in right background. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV
Detail exterior view looking north showing piping system adjacent to ...
Detail exterior view looking north showing piping system adjacent to engine house. Gas cooling system is on far right. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV
Detail exterior view looking northwest showing field gas cleaner in ...
Detail exterior view looking northwest showing field gas cleaner in the center. - Burnsville Natural Gas Pumping Station, Saratoga Avenue between Little Kanawha River & C&O Railroad line, Burnsville, Braxton County, WV
1. EXTERIOR VIEW OF BUILDING THAT HOUSES THE HOT ROLL ...
1. EXTERIOR VIEW OF BUILDING THAT HOUSES THE HOT ROLL MILL, ALSO KNOWN AS THE NO. 31 HOT ROLL MILL; LOOKING SOUTHWEST - American Brass Company, Kenosha Works, Hot Roll Mill, Kenosha, Kenosha County, WI
1. BLOWER (EXTERIOR CONFIGURATION). Hot Springs National Park Bathhouse ...
1. BLOWER (EXTERIOR CONFIGURATION). - Hot Springs National Park Bathhouse Row, Maurice Bathhouse: Mechanical & Piping Systems, State Highway 7, 1 mile north of U.S. Highway 70, Hot Springs, Garland County, AR
5. Detail of bin wall, showing the thinner exterior wall ...
5. Detail of bin wall, showing the thinner exterior wall next to the inner wall with its alternating courses of channel tile and hollow tile. - Saint Anthony Elevator No. 3, 620 Malcom Avenue, Southeast, Minneapolis, Hennepin County, MN
View of exterior detail; bay on north side of front ...
View of exterior detail; bay on north side of front gable element. - Mare Island Naval Shipyard, Quarters P, Walnut Avenue, northwest corner of Walnut Avenue & Fifth Street, Vallejo, Solano County, CA
1. EXTERIORS OF PAINT LOCKER, BUILDING 101, ON RIGHT, AND ...
1. EXTERIORS OF PAINT LOCKER, BUILDING 101, ON RIGHT, AND CIVIL ENGINEERING STORAGE, BUILDING 105 ON LEFT, LOOKING NORTH. - Mill Valley Air Force Station, Storage Building Types, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
Exterior, looking west Beale Air Force Base, Perimeter Acquisition ...
Exterior, looking west - Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Civil Engineering Storage Building, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA
1. EXTERIOR OF CIVIL ENGINEERING MAINTENANCE SHOP, BUILDING 103, LOOKING ...
1. EXTERIOR OF CIVIL ENGINEERING MAINTENANCE SHOP, BUILDING 103, LOOKING NORTH. - Mill Valley Air Force Station, Civil Engineering Maintenance Shop, East Ridgecrest Boulevard, Mount Tamalpais, Mill Valley, Marin County, CA
4. EXTERIOR VIEW LOOKING EAST. WATER IN THE AQUEDUCT CAN ...
4. EXTERIOR VIEW LOOKING EAST. WATER IN THE AQUEDUCT CAN CAN BE DIVERTED AT THE WASTE WEIR TO BE DISCHARGED INTO THE CULVERT IN FOREGROUND. - Old Croton Aqueduct, Northern Waste Weir, Snowden Avenue & Van Wick Street, Ossining, Westchester County, NY
3. EXTERIOR VIEW, LOOKING EAST, SHOWING QUENCH TOWER, WITH QUENCH ...
3. EXTERIOR VIEW, LOOKING EAST, SHOWING QUENCH TOWER, WITH QUENCH IN PROGRESS, WILPUTTE BATTERY, COAL PRE-HEATING UNIT, INCLINE CONVEYOR AND BATHHOUSE. - Alabama By-Products Company, Coke Plant, Highway 79 (Pinson Valley Parkway), Tarrant City, Jefferson County, AL
10. Exterior view of NE corner showing crenellated parapet. ...
10. Exterior view of NE corner showing crenellated parapet. - Central of Georgia Railway, Savannah Repair Shops & Terminal Facilities, Engine Boiler & Pattern Building, Bounded by West Broad, Jones, West Boundary & Hull Streets, Savannah, Chatham County, GA
1. EXTERIOR VIEW TO THE NORTHEAST OF A BROCK HOUSE ...
1. EXTERIOR VIEW TO THE NORTHEAST OF A BROCK HOUSE USED FOR THE WATER FILTERING SYSTEM. - Nevada Test Site, Pluto Facility, Water Filtering System Brock House, Area 26, Wahmonie Flats, Cane Spring Road, Mercury, Nye County, NV
2. EXTERIOR VIEW TO THE NORTH OF WATER FILTERING EQUIPMENT ...
2. EXTERIOR VIEW TO THE NORTH OF WATER FILTERING EQUIPMENT AND BROCK HOUSES ALONG THE EAST SIDE OF THE COMPOUND. - Nevada Test Site, Pluto Facility, Area 26, Wahmonie Flats, Cane Spring Road, Mercury, Nye County, NV
4. EXTERIOR VIEW TO THE NORTH OF THE WATER TOWER ...
4. EXTERIOR VIEW TO THE NORTH OF THE WATER TOWER AND MISCELLANEOUS EQUIPMENT ALONG THE EAST SIDE OF THE COMPOUND. - Nevada Test Site, Pluto Facility, Area 26, Wahmonie Flats, Cane Spring Road, Mercury, Nye County, NV
3. EXTERIOR VIEW TO THE NORTHEAST OF A RAILROAD CAR ...
3. EXTERIOR VIEW TO THE NORTHEAST OF A RAILROAD CAR ON THE TRACKS AND THE PARTS OF AN ENGINE STAND. - Nevada Test Site, Pluto Facility, Area 26, Wahmonie Flats, Cane Spring Road, Mercury, Nye County, NV
VIEW OF LAMP FIXTURE (EXTERIOR) ADJACENT TO ENTRANCE AT SOUTHWEST ...
VIEW OF LAMP FIXTURE (EXTERIOR) ADJACENT TO ENTRANCE AT SOUTHWEST CORNER OF BUILDING 23, FACING NORTH - Roosevelt Base, Auditorium-Gymnasium, West Virginia Street between Richardson & Reeves Avenues, Long Beach, Los Angeles County, CA
3. DETAIL EXTERIOR VIEW LOOKING SOUTHEAST SHOWING CENTER GABLE SECTION ...
3. DETAIL EXTERIOR VIEW LOOKING SOUTHEAST SHOWING CENTER GABLE SECTION OF THE FISH HATCHERY BUILDING. - Bonneville Project, Fish Hatchery, On Columbia River bordered on South by Union Pacific, Bonneville, Multnomah County, OR
24. DETAIL EXTERIOR VIEW LOOKING EAST, SHOWING FISH LADDER AT ...
24. DETAIL EXTERIOR VIEW LOOKING EAST, SHOWING FISH LADDER AT NORTH END OF DAM/SPILLWAY; WATER FLOWING THROUGH FISH LADDER IS VISIBLE AT BOTTOM. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
2. GENERAL EXTERIOR VIEW OF FISH HATCHERY BUILDING LOOKING NORTH; ...
2. GENERAL EXTERIOR VIEW OF FISH HATCHERY BUILDING LOOKING NORTH; REINFORCED CONCRETE FISH PONDS IN FOREGROUND. - Bonneville Project, Fish Hatchery, On Columbia River bordered on South by Union Pacific, Bonneville, Multnomah County, OR
6. DETAIL EXTERIOR VIEW OF WINDOW SHUTTERS ON OUTSIDE OF ...
6. DETAIL EXTERIOR VIEW OF WINDOW SHUTTERS ON OUTSIDE OF FISH HATCHERY BUILDING. - Bonneville Project, Fish Hatchery, On Columbia River bordered on South by Union Pacific, Bonneville, Multnomah County, OR
1. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING FACADE OF FISH ...
1. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING FACADE OF FISH HATCHERY BUILDING. - Bonneville Project, Fish Hatchery, On Columbia River bordered on South by Union Pacific, Bonneville, Multnomah County, OR
22. DETAIL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING FISH LADDER AT ...
22. DETAIL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING FISH LADDER AT NORTH END OF DAM/SPILLWAY; VIEW SHOWS SECTION OF FISH LADDER NEAR WHERE IT ENTERS THE COLUMBIA RIVER. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
9. GENERAL EXTERIOR VIEW LOOKING NORTH, SHOWING FORMER FISH HATCHERY ...
9. GENERAL EXTERIOR VIEW LOOKING NORTH, SHOWING FORMER FISH HATCHERY OFFICE BUILDING (PRESENTLY USED AS GARDENER'S OFFICE). - Bonneville Project, Fish Hatchery, On Columbia River bordered on South by Union Pacific, Bonneville, Multnomah County, OR
4. DETAIL EXTERIOR VIEW OF FISH HATCHERY BUILDING'S CENTRAL GABLE; ...
4. DETAIL EXTERIOR VIEW OF FISH HATCHERY BUILDING'S CENTRAL GABLE; MASONRY WALL AND FLOWERBED IN FOREGROUND. - Bonneville Project, Fish Hatchery, On Columbia River bordered on South by Union Pacific, Bonneville, Multnomah County, OR
OBLIQUE VIEW. NOTE THE ROUGHSURFACED EXTERIOR OF THE CONCRETE WALLS. ...
OBLIQUE VIEW. NOTE THE ROUGH-SURFACED EXTERIOR OF THE CONCRETE WALLS. VIEW FACING NORTHEAST - U.S. Naval Base, Pearl Harbor, Ford Island 5-Inch Antiaircraft Battery, Battery Command Center, Ford Island, Pearl City, Honolulu County, HI
17. GENERAL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING FISH LADDER ON ...
17. GENERAL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING FISH LADDER ON BRADFORD ISLAND; VIEW IS TAKEN FROM ROOF OF POWERHOUSE #1; THE DAM/SPILLWAY IS IN RIGHT BACKGROUND. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
25. GENERAL EXTERIOR VIEW LOOKING WEST, SHOWING FISH LADDER DOWNSTREAM ...
25. GENERAL EXTERIOR VIEW LOOKING WEST, SHOWING FISH LADDER DOWNSTREAM FROM THE DAM/SPILLWAY ON THE WASHINGTON SHORE. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
2. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING DOWNSTREAM FACE OF ...
2. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING DOWNSTREAM FACE OF DAM/SPILLWAY; PARKING LOT/WORK AREA ON WASHINGTON SHORE IS VISIBLE IN FOREGROUND. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
6. GENERAL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING UPSTREAM FACE OF ...
6. GENERAL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING UPSTREAM FACE OF DAM/SPILLWAY; FOLIAGE IN FOREGROUND IS ON WASHINGTON SHORELINE. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
3. GENERAL EXTERIOR VIEW LOOKING NORTH, SHOWING REAR FACADE OF ...
3. GENERAL EXTERIOR VIEW LOOKING NORTH, SHOWING REAR FACADE OF ADMINISTRATION BUILDING'S WEST WING. - Bonneville Project, Administration Building, South side of main entrance, Bonneville Project, Bonneville, Multnomah County, OR
8. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING UPSTREAM FACE OF ...
8. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING UPSTREAM FACE OF DAM/SPILLWAY; THE VIEW HIGHLIGHTS THE UPSTREAM APPEARANCE OF THE PIERS SUPPORTING THE MOVABLE STONEY GATES. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
10. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING UPSTREAM FACE OF ...
10. GENERAL EXTERIOR VIEW LOOKING SOUTH, SHOWING UPSTREAM FACE OF DAM/SPILLWAY; ELECTRICALLY-OPERATED GATE MECHANISMS ARE ON RIGHT; GANTRY CRANES ARE VISIBLE IN CENTER/LEFT. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
13. DETAIL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING CONTROL TOWER AT ...
13. DETAIL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING CONTROL TOWER AT UPSTREAM FACE OF DAM/SPILLWAY ON BRADFORD ISLAND. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
1. GENERAL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING FRONT FACADE OF ...
1. GENERAL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING FRONT FACADE OF AUDITORIUM; ENTRANCE ROAD TO BONNEVILLE PROJECT IS IN FOREGROUND; FLAGPOLE IS IN CENTER. - Bonneville Project, Auditorium, Columbia River, 1 mile Northeast of Exit 40, Interstate 84, Bonneville, Multnomah County, OR
2. GENERAL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING LANDSCAPING AROUND ENTRANCE ...
2. GENERAL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING LANDSCAPING AROUND ENTRANCE ROAD TO BONNEVILLE PROJECT; THE AUDITORIUM IS PARTIALLY VISIBLE IN CENTER BACKGROUND. - Bonneville Project, Columbia River, 1 mile Northeast of Exit 40, off Interstate 84, Bonneville, Multnomah County, OR
2. GENERAL EXTERIOR VIEW LOOKING EAST, SHOWING FRONT AND WEST ...
2. GENERAL EXTERIOR VIEW LOOKING EAST, SHOWING FRONT AND WEST FACADE OF ADMINISTRATION BUILDING. - Bonneville Project, Administration Building, South side of main entrance, Bonneville Project, Bonneville, Multnomah County, OR
12. DETAIL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING CONTROL TOWER AT ...
12. DETAIL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING CONTROL TOWER AT SOUTH END OF DAM/SPILLWAY; ENTRANCE TO BRADFORD ISLAND FISH LADDER IS VISIBLE IN FOREGROUND. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
18. GENERAL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING FISH LADDER ON ...
18. GENERAL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING FISH LADDER ON BRADFORD ISLAND; DAM/SPILLWAY IS VISIBLE IN CENTER BACKGROUND. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
4. GENERAL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING ENTRANCE ROAD TO ...
4. GENERAL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING ENTRANCE ROAD TO BONNEVILLE PROJECT. - Bonneville Project, Columbia River, 1 mile Northeast of Exit 40, off Interstate 84, Bonneville, Multnomah County, OR
4. DETAIL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING PIERS AND MOVABLE ...
4. DETAIL EXTERIOR VIEW LOOKING NORTHEAST, SHOWING PIERS AND MOVABLE STONEY GATES ON DOWNSTREAM FACE OF DAM/SPILLWAY. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR
EXTERIOR OF LOCKER ROOM PROJECTION, FACING SOUTHEAST Cape Canaveral ...
EXTERIOR OF LOCKER ROOM PROJECTION, FACING SOUTHEAST - Cape Canaveral Air Force Station, Launch Complex 34, Operations Support Building, Freedom Road, Southwest of Launch Stand CX-34, Cape Canaveral, Brevard County, FL
EXTERIOR DOOR DETAIL, CORRIDOR 137, FACING EAST Cape Canaveral ...
EXTERIOR DOOR DETAIL, CORRIDOR 137, FACING EAST - Cape Canaveral Air Force Station, Launch Complex 34, Operations Support Building, Freedom Road, Southwest of Launch Stand CX-34, Cape Canaveral, Brevard County, FL
EXTERIOR VIEW OF FORTYTHIRD STREET STREETSCAPE WITH BUNGALOWS, SIDEWALKS AND ...
EXTERIOR VIEW OF FORTY-THIRD STREET STREETSCAPE WITH BUNGALOWS, SIDEWALKS AND STREET TREES ORIGINAL TO THE JEMISON AND COMPANY DEVELOPMENT OF THE 'MODEL' INDUSTRIAL TOWN. - City of Fairfield, Fairfield, Jefferson County, AL
6. Neg. No. F52, Apr 13, 1930, EXTERIOR EAST ...
6. Neg. No. F-52, Apr 13, 1930, EXTERIOR - EAST SIDE OF WAREHOUSE AND LOADING DOCK, SHOWING CRANE, LOOKING NORTH - Ford Motor Company Long Beach Assembly Plant, Crane, 700 Henry Ford Avenue, Long Beach, Los Angeles County, CA
9. TROJAN MILL, EXTERIOR FROM NORTHWEST, c. 191828. WINTER SNOW ...
9. TROJAN MILL, EXTERIOR FROM NORTHWEST, c. 1918-28. WINTER SNOW SHOWS LINE OF CRUDE ORE BIN STAIR. CREDIT JW. - Bald Mountain Gold Mill, Nevada Gulch at head of False Bottom Creek, Lead, Lawrence County, SD
25. Photocopy of photograph (Source unknown, c. 19231925) EXTERIOR, CLOSEUP ...
25. Photocopy of photograph (Source unknown, c. 1923-1925) EXTERIOR, CLOSE-UP OF SOUTH FRONT OF MISSION AFTER RESTORATION, C. 1923-1925 - Mission San Francisco Solano de Sonoma, First & Spain Streets, Sonoma, Sonoma County, CA
EXTERIOR, A view looking west between the south side of ...
EXTERIOR, A view looking west between the south side of the building and a stack which is located in the courtyard - Department of Energy, Mound Facility, B Building, One Mound Road, Miamisburg, Montgomery County, OH
EXTERIOR, A view looking northeast toward the south side of ...
EXTERIOR, A view looking northeast toward the south side of the building including the diesel fuel tank and bottom portion of a stack - Department of Energy, Mound Facility, B Building, One Mound Road, Miamisburg, Montgomery County, OH
EXTERIOR, A view looking east that captures the southwest corner ...
EXTERIOR, A view looking east that captures the southwest corner of the building with surveyor's rod to indicate scale - Department of Energy, Mound Facility, B Building, One Mound Road, Miamisburg, Montgomery County, OH
EXTERIOR, A view from above looking southwest toward the roof ...
EXTERIOR, A view from above looking southwest toward the roof and stacks of B Building with I Building in the background - Department of Energy, Mound Facility, B Building, One Mound Road, Miamisburg, Montgomery County, OH
1. EXTERIOR VIEW LOOKING NORTHWEST AT BATCH FURNACE BUILDING, 22' ...
1. EXTERIOR VIEW LOOKING NORTHWEST AT BATCH FURNACE BUILDING, 22' BAR MILL BUILDING, AND 22 BAR MILL MOTOR ROOM. - U.S. Steel Duquesne Works, 22-Inch Bar Mill, Along Monongahela River, Duquesne, Allegheny County, PA
1. EXTERIOR VIEW, FRONT (EAST) FACADE WITH FIVE POINTS FOUNTAIN ...
1. EXTERIOR VIEW, FRONT (EAST) FACADE WITH FIVE POINTS FOUNTAIN (CENTER), DULION APARTMENTS AND ELEVENTH AVENUE SOUTH (RIGHT). VIEW TAKEN JUST AFTER BIRMINGHAM BLIZZARD OF 1993. - Highlands United Methodist Church, 1045 Twentieth Street South, Birmingham, Jefferson County, AL
6. EXTERIOR OF REAR (EAST END) AND NORTH SIDE SHOWING ...
6. EXTERIOR OF REAR (EAST END) AND NORTH SIDE SHOWING ASBESTOS SIDING, BACKYARD LAWN, AND CLOTHESLINE. VIEW TO SOUTHWEST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA
5. VIEW OF EXTERIOR FACINGS, SOUTH ELEVATION, ILLUSTRATING RANDOM COURSING ...
5. VIEW OF EXTERIOR FACINGS, SOUTH ELEVATION, ILLUSTRATING RANDOM COURSING THAT USES UNSQUARED, IRREGULAR BASALT STONE WITH SMALLER FRAGMENTS SNECKED INTO THE JOINTING, LOOKING NORTH - Rock Wall, North side of Battle Creek Canyon, Shingletown, Shasta County, CA
41. AUXILIARY CHAMBER, CONCRETE ENCLOSURE CHAMBER AIR LOCK (EXTERIOR), LOOKING ...
41. AUXILIARY CHAMBER, CONCRETE ENCLOSURE CHAMBER AIR LOCK (EXTERIOR), LOOKING NORTHEAST FROM SOUTHWEST CORNER (LOCATION AAA) - Shippingport Atomic Power Station, On Ohio River, 25 miles Northwest of Pittsburgh, Shippingport, Beaver County, PA
4. DETAIL ALONG WEST SIDE, SHOWING EXTERIOR STAIRWAY, BUILDING NO. ...
4. DETAIL ALONG WEST SIDE, SHOWING EXTERIOR STAIRWAY, BUILDING NO. 1 IN THE CENTER DISTANCE, AND ONE OF THE BENDING SHOPS AT RIGHT. - United Engineering Company Shipyard, Engineering Building, 2900 Main Street, Alameda, Alameda County, CA
3. EXTERIOR NORTHEAST CORNER VIEW, FACING SOUTHWEST. BUILDING NO 42 ...
3. EXTERIOR NORTHEAST CORNER VIEW, FACING SOUTHWEST. BUILDING NO 42 GARAGE & TRANSPORTATION MAINTENANCE FACILITY - NASA Industrial Plant, Garage & Transportation Maintenance Facility, 12214 Lakewood Boulevard, Downey, Los Angeles County, CA
4. EXTERIOR NORTHWEST CORNER VIEW, FACING SOUTHEAST. BUILDING NO 42 ...
4. EXTERIOR NORTHWEST CORNER VIEW, FACING SOUTHEAST. BUILDING NO 42 GARAGE & TRANSPORTATION MAINTENANCE FACILITY - NASA Industrial Plant, Garage & Transportation Maintenance Facility, 12214 Lakewood Boulevard, Downey, Los Angeles County, CA
2. EXTERIOR SOUTHEAST CORNER VIEW, FACING NORTHWEST. BUILDING NO 42 ...
2. EXTERIOR SOUTHEAST CORNER VIEW, FACING NORTHWEST. BUILDING NO 42 GARAGE & TRANSPORTATION MAINTENANCE FACILITY - NASA Industrial Plant, Garage & Transportation Maintenance Facility, 12214 Lakewood Boulevard, Downey, Los Angeles County, CA
1. EXTERIOR SOUTHWEST CORNER VIEW, FACING NORTHEAST. BUILDING NO. 42 ...
1. EXTERIOR SOUTHWEST CORNER VIEW, FACING NORTHEAST. BUILDING NO. 42 GARAGE & TRANSPORTATION MAINTENANCE FACILITY - NASA Industrial Plant, Garage & Transportation Maintenance Facility, 12214 Lakewood Boulevard, Downey, Los Angeles County, CA
3. BUILDING 901, EXTERIOR DETAILING ON NORTH SIDE SHOWING CONCRETE ...
3. BUILDING 901, EXTERIOR DETAILING ON NORTH SIDE SHOWING CONCRETE FOUNDATION AND METAL TERMITE SHIELD. - Presidio of San Francisco, Warehouse, West End of Crissy Field, Livingston Street, San Francisco, San Francisco County, CA
The point-source method for 3D reconstructions for the Helmholtz and Maxwell equations
NASA Astrophysics Data System (ADS)
Ben Hassen, M. F.; Erhard, K.; Potthast, R.
2006-02-01
We use the point-source method (PSM) to reconstruct a scattered field from its associated far field pattern. The reconstruction scheme is described and numerical results are presented for three-dimensional acoustic and electromagnetic scattering problems. We give new proofs of the algorithms, based on the Green and Stratton-Chu formulae, which are more general than with the former use of the reciprocity relation. This allows us to handle the case of limited aperture data and arbitrary incident fields. Both for 3D acoustics and electromagnetics, numerical reconstructions of the field for different settings and with noisy data are shown. For shape reconstruction in acoustics, we develop an appropriate strategy to identify areas with good reconstruction quality and combine different such regions into one joint function. Then, we show how shapes of unknown sound-soft scatterers are found as level curves of the total reconstructed field.
Effect of Helmholtz Oscillation on Auto-shroud for APS Tungsten Carbide Coating
NASA Astrophysics Data System (ADS)
Jin, Younggil; Choi, Sooseok; Yang, Seung Jae; Park, Chong Rae; Kim, Gon-Ho
2013-06-01
The atmospheric-pressure plasma spray (APS) of tungsten coating was performed using tungsten carbide (WC) powder by means of DC plasma torch equipped with a stepped anode nozzle as a potential method of W coating on graphite plasma-facing component of fusion reactors. This nozzle configuration allows Helmholtz oscillation mode dominating in APS arc fluctuation, and the variation of auto-shroud effect with Helmholtz oscillation characteristics can be investigated. Tungsten coating made from WC powder has lower porosity and higher tungsten purity than that made from pure tungsten powder. The porosity and chemical composition of coatings were investigated by mercury intrusion porosimetry and x-ray photoelectron spectroscopy, respectively. The purity of tungsten coating layer is increased with the increasing frequency of Helmholtz oscillation and the increasing arc current. The modulation of Helmholtz oscillation frequency and magnitude may enhance the decarburization of WC to deposit tungsten coating without W-C and W-O bond from WC powder.
Reconstruction of Propagating Kelvin-Helmholtz Vortices at Mercury's Magnetopause
NASA Technical Reports Server (NTRS)
Sundberg, Torbjoern; Boardsen, Scott A.; Slavin, James A.; Blomberg, Lars G.; Cumnock, Judy A.; Solomon, Sean C.; Anderson, Brian J.; Korth, Haje
2011-01-01
A series of quasi-periodic magnetopause crossings were recorded by the MESSENGER spacecraft during its third flyby of Mercury on 29 September 2009, likely caused by a train of propagating Kelvin-Helmholtz (KH) vortices. We here revisit the observations to study the internal structure of the waves. Exploiting MESSENGER s rapid traversal of the magnetopause, we show that the observations permit a reconstruction of the structure of a rolled-up KH vortex directly from the spacecraft s magnetic field measurements. The derived geometry is consistent with all large-scale fluctuations in the magnetic field data, establishes the non-linear nature of the waves, and shows their vortex-like structure. In several of the wave passages, a reduction in magnetic field strength is observed in the middle of the wave, which is characteristic of rolled-up vortices and is related to the increase in magnetic pressure required to balance the centrifugal force on the plasma in the outer regions of a vortex, previously reported in computer simulations. As the KH wave starts to roll up, the reconstructed geometry suggests that the vortices develop two gradual transition regions in the magnetic field, possibly related to the mixing of magnetosheath and magnetospheric plasma, situated at the leading edges from the perspectives of both the magnetosphere and the magnetosheath.
MAGNETIC KELVIN-HELMHOLTZ INSTABILITY AT THE SUN
Foullon, Claire; Verwichte, Erwin; Nakariakov, Valery M.; Nykyri, Katariina; Farrugia, Charles J.
2011-03-01
Flows and instabilities play a major role in the dynamics of magnetized plasmas including the solar corona, magnetospheric and heliospheric boundaries, cometary tails, and astrophysical jets. The nonlinear effects, multi-scale and microphysical interactions inherent to the flow-driven instabilities, are believed to play a role, e.g., in plasma entry across a discontinuity, generation of turbulence, and enhanced drag. However, in order to clarify the efficiency of macroscopic instabilities in these processes, we lack proper knowledge of their overall morphological features. Here we show the first observations of the temporally and spatially resolved evolution of the magnetic Kelvin-Helmholtz instability in the solar corona. Unprecedented high-resolution imaging observations of vortices developing at the surface of a fast coronal mass ejecta are taken by the new Solar Dynamics Observatory, validating theories of the nonlinear dynamics involved. The new findings are a cornerstone for developing a unifying theory on flow-driven instabilities in rarefied magnetized plasmas, which is important for understanding the fundamental processes at work in key regions of the Sun-Earth system.
MESSENGER observations of multiscale Kelvin-Helmholtz vortices at Mercury
NASA Astrophysics Data System (ADS)
Gershman, Daniel J.; Raines, Jim M.; Slavin, James A.; Zurbuchen, Thomas H.; Sundberg, Torbjörn; Boardsen, Scott A.; Anderson, Brian J.; Korth, Haje; Solomon, Sean C.
2015-06-01
Observations by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft in Mercury's magnetotail demonstrate for the first time that Na+ ions exert a dynamic influence on Mercury's magnetospheric system. Na+ ions are shown to contribute up to ~30% of the ion thermal pressure required to achieve pressure balance in the premidnight plasma sheet. High concentrations of planetary ions should lead to Na+ dominance of the plasma mass density in these regions. On orbits with northward-oriented interplanetary magnetic field and high (i.e., >1 cm-3) Na+ concentrations, MESSENGER has often recorded magnetic field fluctuations near the Na+ gyrofrequency associated with the Kelvin-Helmholtz (K-H) instability. These nightside K-H vortices are characteristically different from those observed on Mercury's dayside that have a nearly constant wave frequency of ~0.025 Hz. Collectively, these observations suggest that large spatial gradients in the hot planetary ion population at Mercury may result in a transition from a fluid description to a kinetic description of vortex formation across the dusk terminator, providing the first set of truly multiscale observations of the K-H instability at any of the diverse magnetospheric environments explored in the solar system.
Monolithically integrated Helmholtz coils by 3-dimensional printing
Li, Longguang; Abedini-Nassab, Roozbeh; Yellen, Benjamin B.
2014-06-23
3D printing technology is of great interest for the monolithic fabrication of integrated systems; however, it is a challenge to introduce metallic components into 3D printed molds to enable broader device functionality. Here, we develop a technique for constructing a multi-axial Helmholtz coil by injecting a eutectic liquid metal Gallium Indium alloy (EGaIn) into helically shaped orthogonal cavities constructed in a 3D printed block. The tri-axial solenoids each carry up to 3.6 A of electrical current and produce magnetic field up to 70 G. Within the central section of the coil, the field variation is less than 1% and is in agreement with theory. The flow rates and critical pressures required to fill the 3D cavities with liquid metal also agree with theoretical predictions and provide scaling trends for filling the 3D printed parts. These monolithically integrated solenoids may find future applications in electronic cell culture platforms, atomic traps, and miniaturized chemical analysis systems based on nuclear magnetic resonance.
Parallel Helmholtz resonators for a planar acoustic notch filter
NASA Astrophysics Data System (ADS)
Isozaki, Akihiro; Takahashi, Hidetoshi; Tamura, Hiroto; Takahata, Tomoyuki; Matsumoto, Kiyoshi; Shimoyama, Isao
2014-12-01
This paper reports on an acoustic planar notch filter with a sub-wavelength thickness at the notch frequency. The developed notch filter consists of a number of spherical Helmholtz resonators (HRs) connected to a hole created in a plate. The HRs were placed at the in-plane vertices of a regular polygon. A simulated pressure distribution revealed that this uniform arrangement of HRs improves the silencing effect because the uniform applied waves emitted from the HRs act as canceling waves to the cross-section of the short hole (in this case, the length of the hole is sub-wavelength). The total pressure emitted from the HRs is equal regardless of the number of HRs connected to the hole. Therefore, the arrangement of HRs is essential for realizing a planar notch filter. Simulated transmittance spectra showed that the depth of the dip in the transmittance increased with the number of uniformly arranged HRs. We confirmed that the experimental transmittance spectra of fabricated notch filters, which consisted of between one and six HRs, agreed with the simulated transmittance spectra. The design of the acoustic filter presented in this study and the corresponding analysis should motivate further development of thin acoustic filters.
A fiber-optic hydrophone with a cylindrical Helmholtz resonator
NASA Astrophysics Data System (ADS)
Wang, Zefeng; Hu, Yongming; Ni, Ming; Meng, Zhou; Luo, Hong
2007-11-01
A passive homodyne Michelson interferometric fiber-optic hydrophone with a single-hole cylindrical Helmholtz resonator has been manufactured. To validate the theoretical results that the fluid coefficient of viscosity has great influence on the maximum sensitivity at the resonant frequency, the acoustic sensitivity frequency response of the fiber-optic hydrophone has been measured in a standing-wave tank filled with castor oil. The viscosity coefficient of castor oil will change with the variation of the temperature. Experimental Results show that the fiber-optic hydrophone frequency responses of different temperature have identical form except that the maximum sensitivities are different. The acoustic sensitivities of low frequency are about -159dB re 1rad/μPa. While the maximum sensitivities near the measured resonant frequency of 800Hz go down with the fall of the temperature, i.e. with the increase of the viscosity coefficient, which is agree with the theoretical conclusions. This fiber-optic hydrophone is a prototype device for a class of sensors that used to eliminate aliasing in the future sonar systems.
Heavy Ion Effects on Kelvin-Helmholtz Instability: Hybrid Study
NASA Astrophysics Data System (ADS)
Burgess, D.; Lin, D.
2015-12-01
Kelvin-Helmholtz instability (KHI) is a candidate mechanism for solar wind tansportation into the magnetosphere. The statistical study of Bouhram et al. 2005 has shown that heavy ions could dominate the magnetopause for as much as 30% of the time on the dusk side. Thus the influence of heavy ions in solar wind-magnetosphere coupling should not be neglected. However, the magnetohydrodynamic (MHD) linear theory for KHI does not include any ion effects, and people working on the heavy ion effects have not come to an agreement either. Whether the heavy ions promote or inhibit the KHI still remains not well addressed. With a two-dimensional hybrid model, we investigated the effects of ion mass number on the KHI growth rate, starting from the simplest case of uniform density and uniform magnetic field perpendicular to the shear flow. It is shown that the growth rate of the KHI is lower with a heavier mass number. We try to to derive the linear theory for the kinetic KHI and compare it with the hybrid simulation results. The linear theory with ion effects considered is going to be further verified with varying heavy ion fractions and finite magnetic shear. More implications for the dawn-dusk asymmetry of KHI on planetary magnetopause are desirable when comparing the results of opposite magnetic field directions relative to the flow vorticity.
Vortex convection in the flow-excited Helmholtz resonator
NASA Astrophysics Data System (ADS)
Dai, Xiwen
2016-05-01
Vorticity convection as well as its excitation to a Helmholtz resonator is studied numerically. Convection velocities of both the concentrated vortical structure and the total distributed vorticity in the orifice region are calculated. Results indicate that the vortex convection velocity is the more useful one in controlling the oscillation frequency. The excitation pressure from the vortical flow is found almost in phase with the fluctuation of the total circulation in the orifice region. This helps us to deduce that vorticity accumulation in the opening region and its relatively simultaneous efflux, due to the shear layer rolling-up into a vortex, are responsible for the pressure fluctuation that excites the acoustic mode of the cavity. It is found that the frequency characteristics can be significantly varied by the system damping. Increasing the damping leads to a reduction in the range of the Strouhal number of oscillation, which is associated with the disappearing lock-in effect in frequency. The dependence of the vortex convection velocity and the critical Strouhal number for the maximum oscillation on damping is also shown.
Helmholtz, Riemann, and the Sirens: Sound, Color, and the "Problem of Space"
NASA Astrophysics Data System (ADS)
Pesic, Peter
2013-09-01
Emerging from music and the visual arts, questions about hearing and seeing deeply affected Hermann Helmholtz's and Bernhard Riemann's contributions to what became called the "problem of space [ Raumproblem]," which in turn influenced Albert Einstein's approach to general relativity. Helmholtz's physiological investigations measured the time dependence of nerve conduction and mapped the three-dimensional manifold of color sensation. His concurrent studies on hearing illuminated musical evidence through experiments with mechanical sirens that connect audible with visible phenomena, especially how the concept of frequency unifies motion, velocity, and pitch. Riemann's critique of Helmholtz's work on hearing led Helmholtz to respond and study Riemann's then-unpublished lecture on the foundations of geometry. During 1862-1870, Helmholtz applied his findings on the manifolds of hearing and seeing to the Raumproblem by supporting the quadratic distance relation Riemann had assumed as his fundamental hypothesis about geometrical space. Helmholtz also drew a "close analogy … in all essential relations between the musical scale and space." These intersecting studies of hearing and seeing thus led to reconsideration and generalization of the very concept of "space," which Einstein shaped into the general manifold of relativistic space-time.
The research and analysis of the uniformity of the magnetic field of the square Helmholtz coil
NASA Astrophysics Data System (ADS)
Pan, Xin; Liu, Jun; Wu, Chen; Lu, Jun
2015-10-01
A three-dimensional magnetic field generator has been constructed taking advantage of three groups of square Helmholtz coils in order to do research on the magnetic susceptibility of optical sensors. Whether the uniformity in the center of the magnetic field is standard has to be analyzed to ensure the accuracy of test data from the optical sensor. Regarding square Helmholtz coil as four current-carrying conductor, three-dimensional space magnetic intensity and its uniformity of square Helmholtz coil were analyzed, and the result of simulating data were given. Due to that two coils may partly produce magnetic-field component possibly cancelling each other out, Bx, By, which can have an effect on the uniformity of the magnetic field, so that we need to evaluate the effects. First, we build a mathematical model of the magnetic field intensity of the square Helmholtz coil in the three-dimensional space. Then, some related analysis data and structural models of the three-dimensional uniform magnetic field of the square Helmholtz coil are given by Using the computer software MATLAB and LABVIEW. Finally, that square Helmholtz coils can be applied to study the magnetic susceptibility of optical sensors is proven to be feasible with the standardized testing environments of the magnetic susceptibility and evaluation methods proposed.
Design and fabrication of a high Tc BSCCO based square helmholtz coil
NASA Astrophysics Data System (ADS)
Pramoda K, Nayak; U, Prasad; A, Amardas; D, Patel; S, Pradhan
2010-02-01
A square Helmholtz coil has been designed and fabricated using commercial grade HTS BSCCO tape with double pancake configuration. The present work is aimed at generating uniform magnetic field with a square Helmholtz coil pair useful in laboratory applications. It has an advantages over the circular Helmholtz coil which had been fabricated and validated by us earlier in terms of field uniformity. This coil is intended to be used as a background field/magnet for circular Helmholtz coil and possible characterization of High T c tapes. Design parameters details, magnetic field generated and the fabrication techniques of this square Helmholtz coil have been described in this paper. Measured current voltage (I-V) characteristics following 1.0 μV/cm criteria and magnetic field profiles of the square Helmholtz coil have been presented in this report in greater detail. From the I-V characteristics, the critical current based on self field dependent of HTS co il is found to be 84 A. The maximum magnetic field is found to be 0.05 T from the magnetic field characteristics.
NASA Astrophysics Data System (ADS)
Li, X.; Li, S. W.
2012-07-01
In this paper, an efficient global optimization algorithm in the field of artificial intelligence, named Particle Swarm Optimization (PSO), is introduced into close range photogrammetric data processing. PSO can be applied to obtain the approximate values of exterior orientation elements under the condition that multi-intersection photography and a small portable plane control frame are used. PSO, put forward by an American social psychologist J. Kennedy and an electrical engineer R.C. Eberhart, is a stochastic global optimization method based on swarm intelligence, which was inspired by social behavior of bird flocking or fish schooling. The strategy of obtaining the approximate values of exterior orientation elements using PSO is as follows: in terms of image coordinate observed values and space coordinates of few control points, the equations of calculating the image coordinate residual errors can be given. The sum of absolute value of each image coordinate is minimized to be the objective function. The difference between image coordinate observed value and the image coordinate computed through collinear condition equation is defined as the image coordinate residual error. Firstly a gross area of exterior orientation elements is given, and then the adjustment of other parameters is made to get the particles fly in the gross area. After iterative computation for certain times, the satisfied approximate values of exterior orientation elements are obtained. By doing so, the procedures like positioning and measuring space control points in close range photogrammetry can be avoided. Obviously, this method can improve the surveying efficiency greatly and at the same time can decrease the surveying cost. And during such a process, only one small portable control frame with a couple of control points is employed, and there are no strict requirements for the space distribution of control points. In order to verify the effectiveness of this algorithm, two experiments are
Improved beam propagation method equations.
Nichelatti, E; Pozzi, G
1998-01-01
Improved beam propagation method (BPM) equations are derived for the general case of arbitrary refractive-index spatial distributions. It is shown that in the paraxial approximation the discrete equations admit an analytical solution for the propagation of a paraxial spherical wave, which converges to the analytical solution of the paraxial Helmholtz equation. The generalized Kirchhoff-Fresnel diffraction integral between the object and the image planes can be derived, with its coefficients expressed in terms of the standard ABCD matrix. This result allows the substitution, in the case of an unaberrated system, of the many numerical steps with a single analytical step. We compared the predictions of the standard and improved BPM equations by considering the cases of a Maxwell fish-eye and of a Luneburg lens. PMID:18268554
Incompressible spectral-element method: Derivation of equations
NASA Technical Reports Server (NTRS)
Deanna, Russell G.
1993-01-01
A fractional-step splitting scheme breaks the full Navier-Stokes equations into explicit and implicit portions amenable to the calculus of variations. Beginning with the functional forms of the Poisson and Helmholtz equations, we substitute finite expansion series for the dependent variables and derive the matrix equations for the unknown expansion coefficients. This method employs a new splitting scheme which differs from conventional three-step (nonlinear, pressure, viscous) schemes. The nonlinear step appears in the conventional, explicit manner, the difference occurs in the pressure step. Instead of solving for the pressure gradient using the nonlinear velocity, we add the viscous portion of the Navier-Stokes equation from the previous time step to the velocity before solving for the pressure gradient. By combining this 'predicted' pressure gradient with the nonlinear velocity in an explicit term, and the Crank-Nicholson method for the viscous terms, we develop a Helmholtz equation for the final velocity.
Multi-Scale Kelvin-Helmholtz Vortices Along Mercury's Magnetopause
NASA Astrophysics Data System (ADS)
Gershman, D. J.; Raines, J. M.; Slavin, J. A.; Zurbuchen, T.; Sundberg, T.; Boardsen, S. A.; Anderson, B. J.; Korth, H.; Solomon, S. C.
2014-12-01
Data from the Fast Imaging Plasma Spectrometer (FIPS) and Magnetometer (MAG) sensors on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft have revealed stark differences in the Kelvin-Helmholtz (K-H) instability at Mercury compared with that at Earth. Although K-H vortices have been documented in planetary magnetospheres at the interface of magnetosheath and magnetospheric plasmas, such features at Mercury have been observed exclusively on the dusk side. From a survey of 58 K-H events, we find that these vortices have two distinct sets of behavior separated by the dusk terminator. On the dayside, the wave frequencies measured by MAG are nearly constant at ~0.025 Hz (~40 s period) under a variety of magnetosheath conditions, whereas the wave frequency measured on the nightside is correlated with the strength of the magnetic field near the magnetopause and matches the local Na+ gyrofrequency. The polarization of these waves inside the magnetosphere is distinctly right-handed, consistent with non-linear roll-up of K-H vortices as opposed to the left-handed ion-cyclotron wave mode. During these events, measurements from FIPS reveal strong (~30%) concentrations of Na+ in the nightside plasma sheet adjacent to the magnetopause. The keV energies of these planetary ions provide them with gyroradii that are ~500-1000 km, a scale at which a kinetic description of the K-H instability may be appropriate at Mercury. These data suggest a transition from fluid-scale to kinetic scale K-H vortices from day to night along Mercury's duskside magnetopause.
Remote Sensing and Earth System Dynamics: The Helmholtz Alliance
NASA Astrophysics Data System (ADS)
Hajnsek, I.; Eineder, M.; Walter, T. R.; Friedrich, A. M.; Bieber, P.; Huth, A.; Papathanassiou, K.; Montzka, C.; Wollschläger, U.; Thies, B.; Humbert, A.; Braun, M.; Krieger, G.; Moreira, A.
2014-12-01
The main objective of the five year funded German Helmholtz Alliance "Remote Sensing and Earth System Dynamics" is the development and evaluation of novel bio/geo-physical information products derived from data acquired by a new generation of remote sensing satellites; and their integration in Earth system models for improving understanding and modelling the ability of global environmental processes and ecosystem change. The Alliance is organized in 4 research topics, each one dedicated to a specific Earth sphere with a specific scientific goal: Biosphere: Global forest structure and biomass dynamics are evaluated for forest and biodiversity monitoring and the quantification of the global carbon cycle; Geosphere: The ability to measure topographic variations with millimeter accuracy is explored for improving the understanding of earthquake and volcano activities; Hydrosphere: The quantification of soil moisture and its variations at high spatial resolution is assessed with respect to hydrological models and the global water cycle; Cryosphere: The estimation of melting processes in snow, ice and permafrost regions is addressed in terms of global climate change. The Alliance has been founded in June 2012 and comprises around 120 scientists with a financial support for 50 PhDs and Postdocs having different backgrounds and nationalities. 18 national research centers and universities are participating which represent a unique opportunity to exploit and widen the expertise of all participating centers and to maximize their role and contribution in the international environmental change science. In this talk the objectives of the Alliance and research highlights will be presented which were obtained in the first 2.5 years of its research activities.
An extended Dirac equation in noncommutative spacetime
NASA Astrophysics Data System (ADS)
Mendes, R. Vilela
2016-05-01
Stabilizing, by deformation, the algebra of relativistic quantum mechanics a noncommutative spacetime geometry is obtained. The exterior algebra of this geometry leads to an extended massless Dirac equation which has both a massless and a large mass solution. The nature of the solutions is discussed as well as the effects of coupling the two solutions.
Kansa, E.; Shumlak, U.; Tsynkov, S.
2013-02-01
Confining dense plasma in a field reversed configuration (FRC) is considered a promising approach to fusion. Numerical simulation of this process requires setting artificial boundary conditions (ABCs) for the magnetic field because whereas the plasma itself occupies a bounded region (within the FRC coils), the field extends from this region all the way to infinity. If the plasma is modeled using single fluid magnetohydrodynamics (MHD), then the exterior magnetic field can be considered quasi-static. This field has a scalar potential governed by the Laplace equation. The quasi-static ABC for the magnetic field is obtained using the method of difference potentials, in the form of a discrete Calderon boundary equation with projection on the artificial boundary shaped as a parallelepiped. The Calderon projection itself is computed by convolution with the discrete fundamental solution on the three-dimensional Cartesian grid.
Plasmoid and Kelvin-Helmholtz instabilities in Sweet-Parker current sheets
NASA Astrophysics Data System (ADS)
Loureiro, N. F.; Schekochihin, A. A.; Uzdensky, D. A.
2013-01-01
A two-dimensional (2D) linear theory of the instability of Sweet-Parker (SP) current sheets is developed in the framework of reduced magnetohydrodynamics. A local analysis is performed taking into account the dependence of a generic equilibrium profile on the outflow coordinate. The plasmoid instability [Loureiro , Phys. Plasmas 14, 100703 (2007)] is recovered, i.e., current sheets are unstable to the formation of a large-wave-number chain of plasmoids (kmaxLCS˜S3/8, where kmax is the wave number of fastest growing mode, S=LCSVA/η is the Lundquist number, LCS is the length of the sheet, VA is the Alfvén speed, and η is the plasma resistivity), which grows super Alfvénically fast (γmaxτA˜S1/4, where γmax is the maximum growth rate, and τA=LCS/VA). For typical background profiles, the growth rate and the wave number are found to increase in the outflow direction. This is due to the presence of another mode, the Kelvin-Helmholtz (KH) instability, which is triggered at the periphery of the layer, where the outflow velocity exceeds the Alfvén speed associated with the upstream magnetic field. The KH instability grows even faster than the plasmoid instability γmaxτA˜kmaxLCS˜S1/2. The effect of viscosity (ν) on the plasmoid instability is also addressed. In the limit of large magnetic Prandtl numbers Pm=ν/η, it is found that γmax˜S1/4Pm-5/8 and kmaxLCS˜S3/8Pm-3/16, leading to the prediction that the critical Lundquist number for plasmoid instability in the Pm≫1 regime is Scrit˜104Pm1/2. These results are verified via direct numerical simulation of the linearized equations, using an analytical 2D SP equilibrium solution.
From Helmholtz to Schlick: The evolution of the sign-theory of perception.
Oberdan, Thomas
2015-08-01
Efforts to trace the influence of fin de siècle neo-Kantianism on early 20th Century philosophy of science have led scholars to recognize the powerful influence on Moritz Schlick of Hermann von Helmholtz, the doyen of 19th Century physics and a leader of the zurȕck zu Kant movement. But Michael Friedman thinks that Schlick misunderstood Helmholtz' signature philosophical doctrine, the sign-theory of perception. Indeed, Friedman has argued that Schlick transformed Helmholtz' Kantian view of spatial intuition into an empiricist version of the causal theory of perception. However, it will be argued that, despite the key role the sign-theory played in his epistemology, Schlick thought the Kantianism in Helmholtz' thought was deeply flawed, rendered obsolete by philosophical insights which emerged from recent scientific developments. So even though Schlick embraced the sign-theory, he rejected Helmholtz' ideas about spatial intuition. In fact, like his teacher, Max Planck, Schlick generalized the sign-theory into a form of structural realism. At the same time, Schlick borrowed the method of concept-formation developed by the formalist mathematicians, Moritz Pasch and David Hilbert, and combined it with the conventionalism of Henri Poincaré. Then, to link formally defined concepts with experience, Schlick's introduced his 'method of coincidences', similar to the 'point-coincidences' featured in Einstein's physics. The result was an original scientific philosophy, which owed much to contemporary scientific thinkers, but little to Kant or Kantianism. PMID:26193786
Gyroresonance of Kelvin-Helmholtz vortices with Na+ in Mercury's magnetotail
NASA Astrophysics Data System (ADS)
Gingell, Peter; Sundberg, Torbjorn; Burgess, David
2015-04-01
Observations of Mercury's plasma environment by the MESSENGER spacecraft have revealed that the planet hosts a strongly asymmetric magnetosphere as a result of an off-axis internal magnetic field, and significant finite Larmor radius effects at the boundary layer between magnetospheric and solar wind plasma environments. Linear analysis and global hybrid simulations suggest asymmetric growth of the Kelvin-Helmholtz instability between the dusk and dawn flanks of the magnetopause, and indeed Kelvin-Helmholtz waves have been observed almost exclusively at the dusk flank during northward IMF. A previous study has shown that Kelvin-Helmholtz waves at the dusk flank are observed predominantly at scales associated with the gyration of hot sodium ions - a population originating at the dayside exosphere, and distributed preferentially at the dusk flank. This suggests that a resonance may occur between sodium ion gyration and Kelvin-Helmholtz vortex growth. Using two- and three-dimensional local hybrid simulations of dusk and dawn boundaries, with varying magnetospheric sodium ion density, we have reproduced the main observational features: we see a strong peak in the Kelvin-Helmholtz wave spectra at sodium gyro scales at the dusk boundaries, and suppression of the growth of vortices at the dawn boundaries. We examine the mechanism of the resonant interaction between counter-gyrating sodium ions and K-H vortices using test particle simulations. Finally, we discuss the effect of the sodium ion population on cross-boundary particle transport.
Equation of State for the Lennard-Jones Fluid
NASA Astrophysics Data System (ADS)
Thol, Monika; Rutkai, Gabor; Köster, Andreas; Lustig, Rolf; Span, Roland; Vrabec, Jadran
2016-06-01
An empirical equation of state correlation is proposed for the Lennard-Jones model fluid. The equation in terms of the Helmholtz energy is based on a large molecular simulation data set and thermal virial coefficients. The underlying data set consists of directly simulated residual Helmholtz energy derivatives with respect to temperature and density in the canonical ensemble. Using these data introduces a new methodology for developing equations of state from molecular simulation. The correlation is valid for temperatures 0.5 < T/Tc < 7 and pressures up to p/pc = 500. Extensive comparisons to simulation data from the literature are made. The accuracy and extrapolation behavior are better than for existing equations of state.
Numerical conformal mapping methods for exterior and doubly connected regions
DeLillo, T.K.; Pfaltzgraff, J.A.
1996-12-31
Methods are presented and analyzed for approximating the conformal map from the exterior of the disk to the exterior a smooth, simple closed curve and from an annulus to a bounded, doubly connected region with smooth boundaries. The methods are Newton-like methods for computing the boundary correspondences and conformal moduli similar to Fornberg`s method for the interior of the disk. We show that the linear systems are discretizations of the identity plus a compact operator and, hence, that the conjugate gradient method converges superlinearly.
Klosterhaus, Susan; McKee, Lester J; Yee, Donald; Kass, Jamie M; Wong, Adam
2014-05-01
Extensive evidence of the adverse impacts of polychlorinated biphenyls (PCBs) to wildlife, domestic animals, and humans has now been documented for over 40 years. Despite the ban on production and new use of PCBs in the United States in 1979, a number of fish consumption advisories remain in effect, and there remains considerable uncertainty regarding ongoing environmental sources and management alternatives. Using a blind sampling approach, 25 caulk samples were collected from the exterior of ten buildings in the San Francisco Bay Area and analyzed for PCBs using congener-specific gas chromatography-mass spectrometry (GC-MS) and chlorine using portable X-ray fluorescence (XRF). PCBs were detected in 88% of the caulk samples collected from the study area buildings, with 40% exceeding 50 ppm. Detectable PCB concentrations ranged from 1 to 220,000 ppm. These data are consistent with previous studies in other cities that have identified relatively high concentrations of PCBs in concrete and masonry buildings built between 1950 and 1980. Portable XRF was not a good predictor of the PCB content in caulk and the results indicate that portable XRF analysis may only be useful for identifying caulk that contains low concentrations of Cl (≤ 10,000 ppm) and by extension low or no PCBs. A geographic information system-based approach was used to estimate that 10,500 kg of PCBs remain in interior and exterior caulk in buildings located in the study area, which equates to an average of 4.7 kg PCBs per building. The presence of high concentrations in the exterior caulk of currently standing buildings suggests that building caulk may be an ongoing source of PCBs to the San Francisco Bay Area environment. Further studies to expand the currently small international dataset on PCBs in caulking materials in buildings of countries that produced or imported PCBs appear justified in the context of both human health and possible ongoing environmental release. PMID:24518434
Number and measure: Hermann von Helmholtz at the crossroads of mathematics, physics, and psychology.
Darrigol, Olivier
2003-09-01
In 1887 Helmholtz discussed the foundations of measurement in science as a last contribution to his philosophy of knowledge. This essay borrowed from earlier debates on the foundations of mathematics (Grassmann/Du Bois), on the possibility of quantitative psychology (Fechner/Kries, Wundt/Zeller), and on the meaning of temperature measurement (Maxwell,Mach.). Late nineteenth-century scrutinisers of the foundations of mathematics (Dedekind, Cantor, Frege, Russell) made little of Helmholtz's essay. Yet it inspired two mathematicians with an eye on physics (Poincaré and Hölder), and a few philosopher-physicists (Mach, Duhem,Campbell). The aim of the present paper is to situate Helmholtz's contribution in this complex array of nineteenth-century philosophies of number, quantity, and measurement. PMID:14560724
A validated non-linear Kelvin-Helmholtz benchmark for numerical hydrodynamics
NASA Astrophysics Data System (ADS)
Lecoanet, D.; McCourt, M.; Quataert, E.; Burns, K. J.; Vasil, G. M.; Oishi, J. S.; Brown, B. P.; Stone, J. M.; O'Leary, R. M.
2016-02-01
The non-linear evolution of the Kelvin-Helmholtz instability is a popular test for code verification. To date, most Kelvin-Helmholtz problems discussed in the literature are ill-posed: they do not converge to any single solution with increasing resolution. This precludes comparisons among different codes and severely limits the utility of the Kelvin-Helmholtz instability as a test problem. The lack of a reference solution has led various authors to assert the accuracy of their simulations based on ad hoc proxies, e.g. the existence of small-scale structures. This paper proposes well-posed two-dimensional Kelvin-Helmholtz problems with smooth initial conditions and explicit diffusion. We show that in many cases numerical errors/noise can seed spurious small-scale structure in Kelvin-Helmholtz problems. We demonstrate convergence to a reference solution using both ATHENA, a Godunov code, and DEDALUS, a pseudo-spectral code. Problems with constant initial density throughout the domain are relatively straightforward for both codes. However, problems with an initial density jump (which are the norm in astrophysical systems) exhibit rich behaviour and are more computationally challenging. In the latter case, ATHENA simulations are prone to an instability of the inner rolled-up vortex; this instability is seeded by grid-scale errors introduced by the algorithm, and disappears as resolution increases. Both ATHENA and DEDALUS exhibit late-time chaos. Inviscid simulations are riddled with extremely vigorous secondary instabilities which induce more mixing than simulations with explicit diffusion. Our results highlight the importance of running well-posed test problems with demonstrated convergence to a reference solution. To facilitate future comparisons, we include as supplementary material the resolved, converged solutions to the Kelvin-Helmholtz problems in this paper in machine-readable form.
NASA Astrophysics Data System (ADS)
Hamlin, Nathaniel D.; Newman, William I.
2013-04-01
We explore, via analytical and numerical methods, the Kelvin-Helmholtz (KH) instability in relativistic magnetized plasmas, with applications to astrophysical jets. We solve the single-fluid relativistic magnetohydrodynamic (RMHD) equations in conservative form using a scheme which is fourth order in space and time. To recover the primitive RMHD variables, we use a highly accurate, rapidly convergent algorithm which improves upon such schemes as the Newton-Raphson method. Although the exact RMHD equations are marginally stable, numerical discretization renders them unstable. We include numerical viscosity to restore numerical stability. In relativistic flows, diffusion can lead to a mathematical anomaly associated with frame transformations. However, in our KH studies, we remain in the rest frame of the system, and therefore do not encounter this anomaly. We use a two-dimensional slab geometry with periodic boundary conditions in both directions. The initial unperturbed velocity peaks along the central axis and vanishes asymptotically at the transverse boundaries. Remaining unperturbed quantities are uniform, with a flow-aligned unperturbed magnetic field. The early evolution in the nonlinear regime corresponds to the formation of counter-rotating vortices, connected by filaments, which persist in the absence of a magnetic field. A magnetic field inhibits the vortices through a series of stages, namely, field amplification, vortex disruption, turbulent breakdown, and an approach to a flow-aligned equilibrium configuration. Similar stages have been discussed in MHD literature. We examine how and to what extent these stages manifest in RMHD for a set of representative field strengths. To characterize field strength, we define a relativistic extension of the Alfvénic Mach number MA. We observe close complementarity between flow and magnetic field behavior. Weaker fields exhibit more vortex rotation, magnetic reconnection, jet broadening, and intermediate turbulence
Enhanced acoustoelectric coupling in acoustic energy harvester using dual Helmholtz resonators.
Peng, Xiao; Wen, Yumei; Li, Ping; Yang, Aichao; Bai, Xiaoling
2013-10-01
In this paper, enhanced acoustoelectric transduction in an acoustic energy harvester using dual Helmholtz resonators has been reported. The harvester uses a pair of cavities mechanically coupled with a compliant perforated plate to enhance the acoustic coupling between the cavity and the plate. The experimental results show that the volume optimization of the second cavity can significantly increase the generated electric voltage up to 400% and raise the output power to 16 times as large as that of a harvester using a single Helmholtz resonator at resonant frequencies primarily related to the plate. PMID:24081260
NASA Astrophysics Data System (ADS)
Zeninari, Virginie; Vallon, Raphaël; Risser, Christophe; Parvitte, Bertrand
2016-01-01
We report on the use of a photoacoustic Helmholtz sensor for the detection of large concentrations of methane. In this case, methane is in concentration where the photoacoustic signal is no more linear with concentration. Moreover the resonance frequency of the Helmholtz resonant cell is modified, as the concentration of methane cannot be neglected. This situation is simulated using a finite element method with the software Comsol Multiphysics. Simulation is compared with experimental results from 0.1 % up to 8 % of methane concentration in air.
The influence of Hermann von Helmholtz on Heinrich Hertz's contributions to physics
NASA Astrophysics Data System (ADS)
Mulligan, Joseph F.
1987-08-01
Heinrich Hertz, the discoverer of radio-frequency electromagnetic radiation, also made important contributions to our knowledge of the photoelectric effect, cathode rays, electromagnetic theory, classical mechanics, and meteorology. In 1878 Hertz enrolled at the University of Berlin to study physics under Professor Hermann von Helmholtz. For the rest of his life he maintained a very close personal and scientific relationship with his mentor. The influence of Helmholtz on Hertz's choice of research topics and on the kind of physicist Hertz became is documented from the writings of these two famous physicists.
Realistic exact solution for the exterior field of a rotating neutron star
Pachon, Leonardo A.; Rueda, Jorge A.; Sanabria-Gomez, Jose D.
2006-05-15
A new six-parametric, axisymmetric, and asymptotically flat exact solution of Einstein-Maxwell field equations having reflection symmetry is presented. It has arbitrary physical parameters of mass, angular momentum, mass-quadrupole moment, current octupole moment, electric charge, and magnetic dipole, so it can represent the exterior field of a rotating, deformed, magnetized, and charged object; some properties of the closed-form analytic solution such as its multipolar structure, electromagnetic fields, and singularities are also presented. In the vacuum case, this analytic solution is matched to some numerical interior solutions representing neutron stars, calculated by Berti and Stergioulas [E. Berti and N. Stergioulas, Mon. Not. R. Astron. Soc. 350, 1416 (2004)], imposing that the multipole moments be the same. As an independent test of accuracy of the solution to describe exterior fields of neutron stars, we present an extensive comparison of the radii of innermost stable circular orbits (ISCOs) obtained from the Berti and Stergioulas numerical solutions, the Kerr solution [R. P. Kerr, Phys. Rev. Lett. 11, 237 (1963)], the Hartle and Thorne solution [J. B. Hartle and K. S. Thorne, Astrophys. J. 153, 807 (1968)], an analytic series expansion derived by Shibata and Sasaki [M. Shibata and M. Sasaki, Phys. Rev. D 58, 104011 (1998)], and our exact solution. We found that radii of ISCOs from our solution fits better than others with realistic numerical interior solutions.
14. DETAIL EXTERIOR VIEW LOOKING WEST, SHOWING TRANSFORMER UNITS ON ...
14. DETAIL EXTERIOR VIEW LOOKING WEST, SHOWING TRANSFORMER UNITS ON THE UPSTREAM SIDE OF POWERHOUSE #1; THE THREE TRANSFORMERS SHOWN WORK IN CONCERT WITH ONE ANOTHER TO RAISE THE VOLTAGE OF THREE-PHASE ALTERNATING CURRENT PRODUCED BY THE GENERATORS. - Bonneville Project, Powerhouse No.1, Spanning Bradford Slough, from Bradford Island, Bonneville, Multnomah County, OR
Exterior oblique view of northeast and southeast sides with heavy ...
Exterior oblique view of northeast and southeast sides with heavy weight sliding doors, louvered entry door, view facing west - U.S. Naval Base, Pearl Harbor, Industrial X-Ray Building, Off Sixth Street, adjacent to and south of Facility No. 11, Pearl City, Honolulu County, HI
View of north side from exterior stairs of adjacent building, ...
View of north side from exterior stairs of adjacent building, bottom cut off by fringed buildings, view facing south-southwest - U.S. Naval Base, Pearl Harbor, Industrial X-Ray Building, Off Sixth Street, adjacent to and south of Facility No. 11, Pearl City, Honolulu County, HI
EXTERIOR VIEW OF COVERED OPEN WALKWAY, LOOKING SOUTHWEST AT BUILDING ...
EXTERIOR VIEW OF COVERED OPEN WALKWAY, LOOKING SOUTHWEST AT BUILDING T-10125 (LEFT) & BUILDING T-10124 (RIGHT) - Fort McCoy, Building No. T-10602, South & North Sides of South Eighth Avenue, Connecting Buildings T-10124, T-10125, T-10126; & Northeast Side of Building T-10106, Block 10, Sparta, Monroe County, WI
42. Historic photo of exterior of Building 202 test cell, ...
42. Historic photo of exterior of Building 202 test cell, January 26, 1960. On file at NASA Plumbrook Research Center, Sandusky, Ohio. NASA photo number C-52534. - Rocket Engine Testing Facility, GRC Building No. 202, NASA Glenn Research Center, Cleveland, Cuyahoga County, OH
39. Historic photo of Building 202 test cell exterior, showing ...
39. Historic photo of Building 202 test cell exterior, showing fiberglass cladding blown out by hydrogen fire during rocket engine testing, April 27, 1959. On file at NASA Plumbrook Research Center, Sandusky, Ohio. NASA photo number C-50472. - Rocket Engine Testing Facility, GRC Building No. 202, NASA Glenn Research Center, Cleveland, Cuyahoga County, OH
Exterior view along the west side, showing the alternating wood ...
Exterior view along the west side, showing the alternating wood and steel ceiling beams and metal sash windows, view facing northeast - U.S. Marine Corps Base Hawaii, Kaneohe Bay, Warehouse 250, Aviation Storehouse, C Street between Fifth & Sixth Streets, Kaneohe, Honolulu County, HI
5. EXTERIOR VIEW TO THE SOUTHEAST OF THE NORTH AND ...
5. EXTERIOR VIEW TO THE SOUTHEAST OF THE NORTH AND WEST ELEVATIONS, WITH THE COLD ASSEMBLY AREA TO THE RIGHT AND THE HOT DISASSEMBLY AREA TO THE LEFT. - Nevada Test Site, Reactor Maintenance Assembly & Dissassembly Facility, Area 25, Jackass Flats, Junction of Roads F & G, Mercury, Nye County, NV
1. EXTERIOR VIEW TO THE NORTH OF THE SOUTH ELEVATIONS ...
1. EXTERIOR VIEW TO THE NORTH OF THE SOUTH ELEVATIONS OF THE R-MAD FACILITY WITH THE COLD ASSEMBLY AREA ON THE LEFT AND THE HOT DISASSEMBLY AREA TO THE RIGHT. - Nevada Test Site, Reactor Maintenance Assembly & Dissassembly Facility, Area 25, Jackass Flats, Junction of Roads F & G, Mercury, Nye County, NV
3. EXTERIOR VIEW TO THE NORTH OF THE SOUTH ELEVATION ...
3. EXTERIOR VIEW TO THE NORTH OF THE SOUTH ELEVATION OF THE ADMINISTRATION AREA IN THE COLD ASSEMBLY AREA, WITH THE MAIN ENTRANCE 'KENNEDY DOORS' IN THE MIDDLE. - Nevada Test Site, Reactor Maintenance Assembly & Dissassembly Facility, Area 25, Jackass Flats, Junction of Roads F & G, Mercury, Nye County, NV
8. VIEW OF STUDDING, EXTERIOR WALL FURRING AND LINTELS FOR ...
8. VIEW OF STUDDING, EXTERIOR WALL FURRING AND LINTELS FOR NEW WINDOW OPENINGS. NORTH WING, FIRST FLOOR DURING REHABILITATION OF HOSPITAL BUILDING, 1938. PLEASE CREDIT: BUREAU OF YARDS AND DOCKS, NATIONAL ARCHIVES - U. S. Naval Asylum, Laning Hall, Gray's Ferry Avenue, Philadelphia, Philadelphia County, PA
EXTERIOR VIEW, LOOKING NORTH, OF THE 'OLD PIT' WITH EXTRACTION ...
EXTERIOR VIEW, LOOKING NORTH, OF THE 'OLD PIT' WITH EXTRACTION OF LIMESTONE IN PROCESS. AN ELEVEN-HOLE SHOT IS DISLODGING APPROXIMATELY 25,000 TONS OF LIMESTONE FOR USE IN ROAD CONSTRUCTION. - Vulcan Material Company, Calera Quarry, 1614 Highway 84, Calera, Shelby County, AL
9. EXTERIOR OF ENCLOSED PORTION OF SECOND FLOOR WEST SIDE ...
9. EXTERIOR OF ENCLOSED PORTION OF SECOND FLOOR WEST SIDE APARTMENT ENTRYWAY SHOWING STAIR LANDING AND OPEN FRONT DOOR FLANKED BY PAIRED 4-LIGHT OVER 4-LIGHT DOUBLE-HUNG, WOOD-FRAME WINDOWS. VIEW TO NORTHEAST. - Lee Vining Creek Hydroelectric System, Triplex Cottage, Lee Vining Creek, Lee Vining, Mono County, CA
7. Interior view of unoccupied space; showing machinery, exterior windows ...
7. Interior view of unoccupied space; showing machinery, exterior windows and double doors, enclosed hinged double doors; northeast corner of building; view to southwest - Ellsworth Air Force Base, Transmitter Standby Building, 200 yards east of County Road, Blackhawk, Meade County, SD
6. SOUTH EXTERIOR SIDE SHOWING TRIANGULAR KNEE BRACE SUPPORTS AND ...
6. SOUTH EXTERIOR SIDE SHOWING TRIANGULAR KNEE BRACE SUPPORTS AND ENCLOSED PORCH SCREENED WINDOWS. ON BASIC FLOOR-PLAN FOR THE SIX-ROOM HOUSE THIS END WAS THE FRONT ENTRANCE. VIEW TO NORTH. - Big Creek Hydroelectric System, Powerhouse 8, Operator Cottage, Big Creek, Big Creek, Fresno County, CA
The Conversion of Exterior Wall Facings for Climbing Activities.
ERIC Educational Resources Information Center
March, Bill; Toft, Murray
1979-01-01
The conversion of existing exterior walls to provide facilities for outdoor rock climbing activities is described with particular emphasis on design to provide practice in basic movement skills such as correct use of holds, balance, controlled change of position, traversing, and moving up and down. (JMF)
4. EXTERIOR OF EAST SIDE SHOWING STAIRS TO CATWALK AND ...
4. EXTERIOR OF EAST SIDE SHOWING STAIRS TO CATWALK AND OPEN UTILITY ROOM DOOR. OPEN DOOR AT BOTTOM OF STAIRS LEADS TO BASEMENT. VIEW TO SOUTHWEST. - Big Creek Hydroelectric System, Powerhouse 8, Operator Cottage, Big Creek, Big Creek, Fresno County, CA
Exterior oblique view of the west end and the south ...
Exterior oblique view of the west end and the south side, Facility No. 6 is behind - U.S. Naval Base, Pearl Harbor, Flask Storage, West side of Seventh Street between Facility Nos. 1107 & S1115, Pearl City, Honolulu County, HI
46 CFR 154.1105 - Exterior water spray system: General.
Code of Federal Regulations, 2012 CFR
2012-10-01
... 46 Shipping 5 2012-10-01 2012-10-01 false Exterior water spray system: General. 154.1105 Section 154.1105 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) CERTAIN BULK DANGEROUS CARGOES SAFETY STANDARDS FOR SELF-PROPELLED VESSELS CARRYING BULK LIQUEFIED GASES Design, Construction and Equipment Firefighting § 154.1105...
EXTERIOR VIEW, FRONT (NORTH) ELEVATION. THIS THREESTORY BRICK BUILDING WITH ...
EXTERIOR VIEW, FRONT (NORTH) ELEVATION. THIS THREE-STORY BRICK BUILDING WITH DEEPLY-BRACKETED AND OVERHANGING EAVES INCLUDES MULTIPLE BAYS CONSTRUCTED BEGINNING IN 1913 TO SERVE AS A 'CIVIC CENTER' FOR ACIPCO EMPLOYEES AND THEIR FAMILIES. THE BUILDING CURRENTLY INCLUDES THE TIME OFFICE, CAFETERIA, AND AUDITORIUM. - American Cast Iron Pipe Company, Service Building, 1501 Thirty-first Avenue North, Birmingham, Jefferson County, AL
10. DETAIL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING REAR SIDE OF ...
10. DETAIL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING REAR SIDE OF REINFORCED CONCRETE GUIDEWALL BUILT ON THE SOUTH SIDE OF THE CHANNEL DOWNSTREAM FROM NAVIGATION LOCK #1. MASONRY RIPRAP ON NORTH SIDE OF CHANNEL IS VISIBLE IN THE CENTER/RIGHT BACKGROUND. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
5. GENERAL EXTERIOR VIEW LOOKING EAST, SHOWING EMPTY NAVIGATION LOCK ...
5. GENERAL EXTERIOR VIEW LOOKING EAST, SHOWING EMPTY NAVIGATION LOCK #1 WITH DOWNSTREAM MITER GATES OPEN; PHOTO TAKEN FROM MIDDLE OF SWING BRIDGE DOWNSTREAM FROM LOCK. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
7. GENERAL EXTERIOR VIEW LOOKING EAST, SHOWING NAVIGATION LOCK #1 ...
7. GENERAL EXTERIOR VIEW LOOKING EAST, SHOWING NAVIGATION LOCK #1 FILLED WITH WATER AND CONTAINING A SHIPMENT OF FLOATING LOGS; THE LOCK WILL SOON BE EMPTIED SO THE LOGS CAN CONTINUE THEIR JOURNEY DOWNSTREAM - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
6. GENERAL EXTERIOR VIEW LOOKING SOUTHEAST, SHOWING NAVIGATION LOCK #1 ...
6. GENERAL EXTERIOR VIEW LOOKING SOUTHEAST, SHOWING NAVIGATION LOCK #1 FILLED WITH WATER; PHOTO IS TAKEN FROM TOP OF MITER GATES AT DOWNSTREAM END OF LOCK. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
14. DETAIL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING CONTROL HOUSE AT ...
14. DETAIL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING CONTROL HOUSE AT UPSTREAM END OF NAVIGATION LOCK #1; POWERHOUSE #1 IS PARTIALLY VISIBLE IN BACKGROUND. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
13. DETAIL EXTERIOR VIEW LOOKING NORTH, SHOWING TOP OF MITER ...
13. DETAIL EXTERIOR VIEW LOOKING NORTH, SHOWING TOP OF MITER GATES AT DOWNSTREAM END OF NAVIGATION LOCK #1; POWERHOUSE #1 IS VISIBLE IN BACKGROUND. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
11. DETAIL EXTERIOR VIEW OF EQUIPMENT AND FISH LIFTS BETWEEN ...
11. DETAIL EXTERIOR VIEW OF EQUIPMENT AND FISH LIFTS BETWEEN POWERHOUSE #1 AND NAVIGATION LOCK #1; VIEW IS TAKEN FROM ROOF OF POWERHOUSE #1. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
1. GENERAL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING DOWNSTREAM END OF ...
1. GENERAL EXTERIOR VIEW LOOKING SOUTHWEST, SHOWING DOWNSTREAM END OF NAVIGATION LOCK #1 WITH CHAMBER FILLED; THE CONTROL HOUSE IS ON RIGHT; VIEW IS TAKEN FROM ROOF OF POWERHOUSE #1. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
8. GENERAL EXTERIOR VIEW LOOKING NORTHWEST TOWARD UPSTREAM END OF ...
8. GENERAL EXTERIOR VIEW LOOKING NORTHWEST TOWARD UPSTREAM END OF NAVIGATION LOCK #1; SOUTH END OF POWERHOUSE #1 IS VISIBLE ON RIGHT; BRADFORD SLOUGH IS VISIBLE IN FOREGROUND. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
3. GENERAL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING BARGE AFTER EXITING ...
3. GENERAL EXTERIOR VIEW LOOKING NORTHWEST, SHOWING BARGE AFTER EXITING FROM DOWNSTREAM END OF NAVIGATION LOCK #1; SWING BRIDGE IS IN PROCESS OF CLOSING. - Bonneville Project, Navigation Lock No. 1, Oregon shore of Columbia River near first Powerhouse, Bonneville, Multnomah County, OR
29. EXTERIOR VIEW OF FOREBAY SIDE. NOTE COMPLETION OF WOODEN ...
29. EXTERIOR VIEW OF FOREBAY SIDE. NOTE COMPLETION OF WOODEN SOUTH WALL WHICH FACILITATED EASY GENERATOR MOVEMENT IN AND OUT OF BUILDING. ALSO NOTE ELECTRIC TURBINE PIT GATE HOISTING MACHINE, c. 1918. - Dam No. 5 Hydroelectric Plant, On Potomac River, Hedgesville, Berkeley County, WV
6. CONSTRUCTION PROGRESS VIEW (EXTERIOR) OF TANK, CABLE CHASE, AND ...
6. CONSTRUCTION PROGRESS VIEW (EXTERIOR) OF TANK, CABLE CHASE, AND MOUNDED BUNKER. CONSTRUCTION WAS 99 PERCENT COMPLETE. CAMERA IS FACING WEST. INEL PHOTO NUMBER 65-5435, TAKEN OCTOBER 20, 1965. - Idaho National Engineering Laboratory, Advanced Reentry Vehicle Fusing System, Scoville, Butte County, ID
1. Photocopy: CA. 1880 LITHOGRAPH SHOWING EXTERIOR VIEW OF CHURCH, ...
1. Photocopy: CA. 1880 LITHOGRAPH SHOWING EXTERIOR VIEW OF CHURCH, from the collection of American Catholic Historical Society. Please use the following credit line: American Catholic Historical Society Ryan Memorial Library Historical Collections St. Charles Seminary Overbrook, Philadelphia, Pa. 19151 - Church of the Immaculate Conception, 1020 North Front Street, Philadelphia, Philadelphia County, PA
3. Photocopy: CA. 1880 LITHOGRAPH SHOWING EXTERIOR VIEW OF CHURCH, ...
3. Photocopy: CA. 1880 LITHOGRAPH SHOWING EXTERIOR VIEW OF CHURCH, from the collection of American Catholic Historical Society. Please use the following credit line: American Catholic Historic Society Ryan Memorial Library Historical Collections St. Charles Seminary Overbrook Philadelphia, Pa. 19151 - Church of St. Philip de Neri (Roman Catholic), 220-228 Queen Street, Philadelphia, Philadelphia County, PA
Exterior oblique view of south (front) side, eight doors open, ...
Exterior oblique view of south (front) side, eight doors open, "Supply Dept. SS-19", "27" on left edge, view facing east - U.S. Naval Base, Pearl Harbor, Paint & Oil Storehouse, Avenue D near Seventh Street intersection, Pearl City, Honolulu County, HI
81. EXTERIOR VIEW, EAST SIDE, SHOWING ENTRANCE TO BOILER ROOM ...
81. EXTERIOR VIEW, EAST SIDE, SHOWING ENTRANCE TO BOILER ROOM ON LEFT, ENTRANCE TO STABLES AT CENTER, AND ENTRANCE TO ENGINE ROOM ON RIGHT. - Gruber Wagon Works, Pennsylvania Route 183 & State Hill Road at Red Bridge Park, Bernville, Berks County, PA
EXTERIOR VIEW, LOOKING WEST, AT FORMER TCIUS STEEL COMPANY BEE ...
EXTERIOR VIEW, LOOKING WEST, AT FORMER TCI-US STEEL COMPANY BEE HIVE OVEN RUINS WITH FORESTED OVERGROWTH. - Pratt Coal & Coke Company, Pratt Mines, Coke Ovens & Railroad, Bounded by First Street, Avenue G, Third Place, Birmingham Southern Railroad, Birmingham, Jefferson County, AL
1. EXTERIOR VIEW, LOOKING WEST, OF CAST IRON FENCE AND ...
1. EXTERIOR VIEW, LOOKING WEST, OF CAST IRON FENCE AND MARBLE MONUMENTS IN THIS GRAVE PLOT IN THE COLUMBIANA CEMETERY WHICH DATE TO 1864. IRON WORK MANUFACTURED AT SHELBY IRONWORKS FOR IRONMASTER'S FIRST WIFE AND DAUGHTER'S GRAVES. - Ware Cemetery Plot, Shelby County Road 25, Columbiana, Shelby County, AL
EXTERIOR VIEW, LOOKING WEST, WITH SWITCHING ENGINE TRANSPORTING TORPEDO LADLE ...
EXTERIOR VIEW, LOOKING WEST, WITH SWITCHING ENGINE TRANSPORTING TORPEDO LADLE FILLED WITH MOLTEN IRON TO THE Q-BOP FURNACES. VERTICAL CONVEYOR TRANSPORTS ALL PROCESS MATERIAL INCLUDING COKE AND PELLETS TO FURNACE. - U.S. Steel, Fairfield Works, Blast Furnace No. 8, North of Valley Road, West of Ensley-Pleasant Grove Road, Fairfield, Jefferson County, AL
EXTERIOR VIEW, NO. 3 CAST HOUSE CENTER AND BLAST FURNACE ...
EXTERIOR VIEW, NO. 3 CAST HOUSE CENTER AND BLAST FURNACE NO. 3 (JANE FURNACE)/ORE BRIDGE TO THE RIGHT, WITH SINTERING PLANT CONVEYORS & TRANSFER HOUSE IN FOREGROUND. - Pittsburgh Steel Company, Monessen Works, Blast Furnace No. 3, Donner Avenue, Monessen, Westmoreland County, PA
126. EXTERIOR VIEW, LOOKING NORTH, SHOWING CAST SHED NO. 2, ...
126. EXTERIOR VIEW, LOOKING NORTH, SHOWING CAST SHED NO. 2, FURNACE NO. 2, STOVES, POWER HOUSE, STACKS, FURNACE NO. 1 CAST SHED. FURNACE NO. 2 IS IN PROCESS OF RESTORATION. - Sloss-Sheffield Steel & Iron, First Avenue North Viaduct at Thirty-second Street, Birmingham, Jefferson County, AL
2. EXTERIOR OVERVIEW LOOKING DOWN MAIN RESIDENTIAL STREET SHOWING FRONT ...
2. EXTERIOR OVERVIEW LOOKING DOWN MAIN RESIDENTIAL STREET SHOWING FRONT (EAST) END AND SOUTH SIDE OF BUILDING 105. GLACIAL MORAINE FORMING WESTERN BACKDROP TO PLANT 4 SETTING IN BACKGROUND. VIEW TO NORTH. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA
21. FANTAIL DECK, SHOWING DETAIL OF DECK EXTENSION AND EXTERIOR ...
21. FANTAIL DECK, SHOWING DETAIL OF DECK EXTENSION AND EXTERIOR LOCKING MECHANISM ON HATCH DOOR TO CREW'S BERTHING. - U.S. Coast Guard Cutter WHITE LUPINE, U.S. Coast Guard Station Rockland, east end of Tillson Avenue, Rockland, Knox County, ME
5. EXTERIOR OF SOUTH SIDE SHOWING ELECTRICAL JUNCTION BOX NEXT ...
5. EXTERIOR OF SOUTH SIDE SHOWING ELECTRICAL JUNCTION BOX NEXT TO SOUTH SIDE DOOR AND CHAIN-LINK FENCE AROUND GARDEN AREA AT REAR OF HOUSE. VIEW TO NORTHWEST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA
Exterior oblique view of trash chute, balconies, and unit entrances ...
Exterior oblique view of trash chute, balconies, and unit entrances on west side of Building 10, from courtyard, looking southeast - North Beach Place, 501 Bay Street, 600 Francisco Street, 501 Bay Street, 600 Francisco Street, San Francisco, San Francisco County, CA
Exterior direct detail view of revised entry handicap ramp at ...
Exterior direct detail view of revised entry handicap ramp at east side of Building 7 (including 3-story trash dump tower), looking north - North Beach Place, 431 Bay Street, 530 Francisco Street, 431 Bay Street, 530 Francisco Street, San Francisco, San Francisco County, CA
Exterior direct view of north side of stair no. 3 ...
Exterior direct view of north side of stair no. 3 (showing half-round 3-story trash dump tower) from balcony of Building 3, looking east - North Beach Place, Bounded by Bay Street, Mason Street, Francisco Street, & Columbus Avenue, San Francisco, San Francisco County, CA
General exterior view showing remnants of loading dock at three ...
General exterior view showing remnants of loading dock at three main doors, view to north - Charlestown Navy Yard, Oxygen Plant, Midway along northern boundary of Charlestown Navy Yard, on Little Mystic Channel, near junction of Eighteenth Street & Fourth Avenue, Boston, Suffolk County, MA
Exterior direct view of (nonoriginal), solar heating panels, and top ...
Exterior direct view of (non-original), solar heating panels, and top of typical rectangular trash-dump tower at roof of Building 6, looking north - North Beach Place, 401 Bay Street, 500 Francisco Street, 401 Bay Street, 500 Francisco Street, San Francisco, San Francisco County, CA
5. Photocopy of old exterior photo showing Western Saving Fund ...
5. Photocopy of old exterior photo showing Western Saving Fund Society before the addition of ca. 1910 building. Original photo, late 19th century, is at the Philadelphia Free Library, Philadelphia Collection, Print and Picture Department. - Western Saving Fund Society of Philadelphia, 1000-1008 Walnut Street, Philadelphia, Philadelphia County, PA
2. EXTERIOR VIEW OF DOWNSTREAM SIDE OF COTTAGE 191 TAKEN ...
2. EXTERIOR VIEW OF DOWNSTREAM SIDE OF COTTAGE 191 TAKEN FROM ROOF OF GARAGE 393. CAMERA FACING SOUTHEAST. COTTAGE 181 AND CHILDREN'S PLAY AREA VISIBLE ON EITHER SIDE OF ROOF. GRAPE ARBOR IN FOREGROUND. - Swan Falls Village, Cottage 191, Snake River, Kuna, Ada County, ID
4. EXTERIOR OF SOUTH END OF BUILDING 108 SHOWING STORM ...
4. EXTERIOR OF SOUTH END OF BUILDING 108 SHOWING STORM PORCH ADDITION AND WINDOWS ALONG BACK (WEST SIDE) OF HOUSE. NOTE ORIGNAL SHORT CHIMNEY AT CREST OF ROOF. VIEW TO NORTH. - Rush Creek Hydroelectric System, Clubhouse Cottage, Rush Creek, June Lake, Mono County, CA
5. EXTERIOR OF SOUTH END OF HOUSE SHOWING OPEN DOOR ...
5. EXTERIOR OF SOUTH END OF HOUSE SHOWING OPEN DOOR TO BASEMENT BELOW KITCHEN, ORIGINAL PAIRED WOODFRAMED SLIDING-GLASS WINDOWS ON KITCHEN WALL AND 1LIGHT OVER 1-LIGHT DOUBLE-HUNG WINDOW ON STORM PORCH ADDITION. VIEW TO WEST. - Rush Creek Hydroelectric System, Clubhouse Cottage, Rush Creek, June Lake, Mono County, CA
1. EXTERIOR OF BUILDING 125 FROM MAIN PLANT 4 RESIDENTIAL ...
1. EXTERIOR OF BUILDING 125 FROM MAIN PLANT 4 RESIDENTIAL STREET SHOWING BUILDING AT PHOTO RIGHT CENTER (WITH WHITE JEEP PARKED IN FRONT) BETWEEN WORKER COTTAGE (BUILDING 115) AT PHOTO LEFT AND RECREATION HALL (BUILDING 109) AT PHOTO RIGHT. VIEW TO SOUTH. - Bishop Creek Hydroelectric System, Plant 4, Lightning Arrestor Vault, Bishop Creek, Bishop, Inyo County, CA
22. EXTERIOR, VIEW OF THE PORTECOCHERE FROM THE NORTH WITH ...
22. EXTERIOR, VIEW OF THE PORTE-COCHERE FROM THE NORTH WITH THE MARK TWAIN CARRIAGE HOUSE (HABS No. CT-365-A) IN THE BACKGROUND - Mark Twain House, 351 Farmington Avenue (corrected from original address of 531 Farmington Avenue), Hartford, Hartford County, CT
VIEW OF STATION LEARY FACING NORTH SHOWING EXPOSED EXTERIOR FRONT ...
VIEW OF STATION LEARY FACING NORTH SHOWING EXPOSED EXTERIOR FRONT OF THE CONCRETE CONCEALMENT INCLUDING POST 1920 DOORWAY ALTERATIONS, SANDSTONE FLANK-WALLS ARE VISIBLE AT REAR SIDES - White's Point Reservation, Base End Stations, B"3, Bounded by Voyager Circle & Mariner Drive, San Pedro, Los Angeles County, CA
VIEW OF STATION LEARY FACING NORTHWEST, SHOWING EXPOSED EXTERIOR FRONT ...
VIEW OF STATION LEARY FACING NORTHWEST, SHOWING EXPOSED EXTERIOR FRONT AND LEFT SIDE OF THE CONCRETE CONCEALMENT, SANDSTONE FLANKWALL IS VISIBLE AT LEFT REAR - White's Point Reservation, Base End Stations, B"3, Bounded by Voyager Circle & Mariner Drive, San Pedro, Los Angeles County, CA
2. VIEW OF STATION FARLEY FACING NORTH SHOWING EXPOSED EXTERIOR ...
2. VIEW OF STATION FARLEY FACING NORTH SHOWING EXPOSED EXTERIOR FRONT OF THE CONCRETE CONCEALMENT, SANDSTONE FLANK-WALLS ARE VISIBLE AT REAR SIDES. - White's Point Reservation, Base End Stations, B"6, Bounded by Voyager Circle & Mariner Drive, San Pedro, Los Angeles County, CA
VIEW OF STATION BARLOW FACING NORTH SHOWING EXPOSED EXTERIOR FRONT ...
VIEW OF STATION BARLOW FACING NORTH SHOWING EXPOSED EXTERIOR FRONT OF THE CONCRETE CONCEALMENT, SANDSTONE FLANK-WALL FRAGMENT VISIBLE AT LEFT REAR - White's Point Reservation, Base End Stations, B"1, Bounded by Voyager Circle & Mariner Drive, San Pedro, Los Angeles County, CA
3. VIEW OF STATION PARLEY FACING NORTHWEST, SHOWING EXPOSED EXTERIOR ...
3. VIEW OF STATION PARLEY FACING NORTHWEST, SHOWING EXPOSED EXTERIOR FRONT AND LEFT SIDE OF THE CONCRETE CONCEALMENT, SANDSTONE FLANKWALL IS VISIBLE AT LEFT REAR. - White's Point Reservation, Base End Stations, B"6, Bounded by Voyager Circle & Mariner Drive, San Pedro, Los Angeles County, CA
VIEW OF STATION SAXTON FACING NORTH SHOWING EXPOSED EXTERIOR FRONT ...
VIEW OF STATION SAXTON FACING NORTH SHOWING EXPOSED EXTERIOR FRONT OF THE CONCRETE CONCEALMENT, SANDSTONE FLANK-WALLS ARE VISIBLE AT REAR SIDES - White's Point Reservation, Base End Stations, B"2, Bounded by Voyager Circle & Mariner Drive, San Pedro, Los Angeles County, CA
VIEW OF STATION BARLOW SHOWING EXPOSED EXTERIOR FRONT AND LEFT ...
VIEW OF STATION BARLOW SHOWING EXPOSED EXTERIOR FRONT AND LEFT SIDE OF THE CONCRETE CONCEALMENT WITH SANDSTONE FLANK-WALL FRAGMENT, FACING NORTHWEST - White's Point Reservation, Base End Stations, B"1, Bounded by Voyager Circle & Mariner Drive, San Pedro, Los Angeles County, CA
16. EXTERIOR NORTH END OF TULE RIVER POWERHOUSE SHOWING POWERHOUSE ...
16. EXTERIOR NORTH END OF TULE RIVER POWERHOUSE SHOWING POWERHOUSE AT PHOTO CENTER, SUBSTATION AT PHOTO RIGHT FOREGROUND, OFFICE BEHIND SUBSTATION AT RIGHT OF POWERHOUSE, AND MACHINE SHOP AT LEFT OF POWERHOUSE. THIS PHOTOGRAPH DUPLICATES HISTORIC VIEW SHOWN IN PHOTO CA-216-17. VIEW TO SOUTHEAST. - Tule River Hydroelectric Project, Water Conveyance System, Middle Fork Tule River, Springville, Tulare County, CA
1. EXTERIOR OVERVIEW SHOWING BISHOP CREEK PLANT 4 RESIDENTIAL COMPLEX. ...
1. EXTERIOR OVERVIEW SHOWING BISHOP CREEK PLANT 4 RESIDENTIAL COMPLEX. BUILDING 113 IS VISIBLE AT RIGHT PHOTO CENTER. PLANT 5 INTAKE DAM AT PHOTO LEFT. VIEW TO WEST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA
1. EXTERIOR OVERVIEW SHOWING BISHOP CREEK PLANT 4 RESIDENTIAL COMPLEX. ...
1. EXTERIOR OVERVIEW SHOWING BISHOP CREEK PLANT 4 RESIDENTIAL COMPLEX. ROOF OF BUILDING 105 IS VISIBLE IN UPPER PHOTO CENTER. PLANT 5 INTAKE DAM AT PHOTO LEFT. VIEW TO WEST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA
1. EXTERIOR OVERVIEW OF NORTH END OF RUSH CREEK POWERHOUSE ...
1. EXTERIOR OVERVIEW OF NORTH END OF RUSH CREEK POWERHOUSE RESIDENTIAL COMPLEX SHOWING BUILDING 108 AT PHOTO RIGHT AND BUILDING 105 AT PHOTO CENTER BEHIND SWITCHRACKS AND TREE. POWERHOUSE IS AT EXTREME PHOTO LEFT. VIEW TO WEST. - Rush Creek Hydroelectric System, Worker Cottage, Rush Creek, June Lake, Mono County, CA
1. EXTERIOR OVERVIEW SHOWING BISHOP CREEK PLANT 4 RESIDENTIAL COMPLEX. ...
1. EXTERIOR OVERVIEW SHOWING BISHOP CREEK PLANT 4 RESIDENTIAL COMPLEX. BUILDING 122 IS VISIBLE AT PHOTO CENTER. PLANT 5 INTAKE DAM AT PHOTO LEFT. VIEW TO WEST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA
2. EXTERIOR NORTH CORNER OF BUILDING 106 FROM MAIN RESIDENTIAL ...
2. EXTERIOR NORTH CORNER OF BUILDING 106 FROM MAIN RESIDENTIAL STREET. CONCRETE WALKWAY FROM STREET TO FRONT SCREENED-IN PORCH IS VISIBLE AT PHOTO CENTER. BUILDING 115 IS AT PHOTO RIGHT BACKGROUND. VIEW TO SOUTHEAST. - Bishop Creek Hydroelectric System, Plant 4, Worker Cottage, Bishop Creek, Bishop, Inyo County, CA
1. EXTERIOR OVERVIEW OF NORTH END OF RUSH CREEK POWERHOUSE ...
1. EXTERIOR OVERVIEW OF NORTH END OF RUSH CREEK POWERHOUSE RESIDENTIAL COMPLEX SHOWING BUILDING 108 AT PHOTO RIGHT AND BUILDING 105 AT PHOTO CENTER BEHIND TREE. RUSH CREEK POWERHOUSE IS PARTIALLY VISIBLE AT EXTREME PHOTO LEFT). VIEW TO WEST. - Rush Creek Hydroelectric System, Clubhouse Cottage, Rush Creek, June Lake, Mono County, CA
1. EXTERIOR OVERVIEW OF SOUTH END OF RUSH CREEK POWERHOUSE ...
1. EXTERIOR OVERVIEW OF SOUTH END OF RUSH CREEK POWERHOUSE RESIDENTIAL COMPLEX SHOWING THE RUSH CREEK POWERHOUSE AT PHOTO RIGHT (TAILRACE IN FOREGROUND), BUILDING 106 NEXT TO THE POWERHOUSE AT PHOTO LEFT CENTER, AND BUILDING 103 AT UPPER PHOTO LEFT ABOVE AND BEHIND BUILDING 106. VIEW TO SOUTH. - Rush Creek Hydroelectric System, Worker Cottage, Rush Creek, June Lake, Mono County, CA
42. EXTERIOR, DETAIL VIEW OF SLATE SHINGLES ON ROOF AND ...
42. EXTERIOR, DETAIL VIEW OF SLATE SHINGLES ON ROOF AND JIG-SAWED FRET WORK SKIRTING FROM THE INSIDE OF THE TEXAS DECK (PORCH) - Mark Twain House, 351 Farmington Avenue (corrected from original address of 531 Farmington Avenue), Hartford, Hartford County, CT
3. Historic American Buildings Survey UNDATED EXTERIOR SHOWING NORTH AND ...
3. Historic American Buildings Survey UNDATED EXTERIOR SHOWING NORTH AND EAST FACADES (View B) This view shows clapboards on gable end and therefore, predates View A which shows shingles in upper gable From the collection of Mrs. L. T. Hazall, descendent of Rev. Woodward - Reverend John Woodward House, 409 Forbes Avenue, New Haven, New Haven County, CT
EXTERIOR PERSPECTIVE OF HOUSE AND MILKROOM LOOKING SOUTHEAST FROM GARAGE ...
EXTERIOR PERSPECTIVE OF HOUSE AND MILKROOM LOOKING SOUTHEAST FROM GARAGE (This image shows the gable-roofed punch out entrance into the kitchen that was added in the mid-1980s when the kitchen was remodeled. Penn Cove can be seen in the distance) - Arnold Farm, House, 1948 Arnold Road, Coupeville, Island County, WA
Exterior view looking down through the approximate centerline of the ...
Exterior view looking down through the approximate centerline of the upper hatch and docking ring on the external airlock on the Orbiter Discovery. This photograph was take in the Orbiter Processing Facility at the Kennedy Space Center. - Space Transportation System, Orbiter Discovery (OV-103), Lyndon B. Johnson Space Center, 2101 NASA Parkway, Houston, Harris County, TX
30. EXTERIOR VIEW LOOKING INTO THE THIRD TAILRACE (COUNTING FROM ...
30. EXTERIOR VIEW LOOKING INTO THE THIRD TAILRACE (COUNTING FROM THE DOWNSTREAM END TO THE UPSTREAM END SOUTHEAST TO NORTHWEST). NOTE THE STEEL BULKHEAD OF THE FLUME AND THE DRAFT TUBE EXTENDING BENEATH THE SILT DEPOSITS AND WATER LINE. - Potomac Power Plant, On West Virginia Shore of Potomac River, about 1 mile upriver from confluence with Shenandoah River, Harpers Ferry, Jefferson County, WV
28. EXTERIOR VIEW LOOKING INTO THE SECOND TAILRACE (COUNTING FROM ...
28. EXTERIOR VIEW LOOKING INTO THE SECOND TAILRACE (COUNTING FROM THE DOWNSTREAM END TO THE UPSTREAM END SOUTHEAST TO NORTHWEST). NOTE THE STEEL BULKHEAD OF THE FLUME AND THE DRAFT TUBE EXTENDING BENEATH THE SILT DEPOSITS. - Potomac Power Plant, On West Virginia Shore of Potomac River, about 1 mile upriver from confluence with Shenandoah River, Harpers Ferry, Jefferson County, WV
27. EXTERIOR VIEW LOOKING INTO THE FIRST TAILRACE (COUNTING FROM ...
27. EXTERIOR VIEW LOOKING INTO THE FIRST TAILRACE (COUNTING FROM THE DOWNSTREAM END TO THE UPSTREAM END SOUTHEAST TO NORTHWEST). - Potomac Power Plant, On West Virginia Shore of Potomac River, about 1 mile upriver from confluence with Shenandoah River, Harpers Ferry, Jefferson County, WV
9. EXTERIOR VIEW OF FRONT ENTRANCE TO BUNKER. CAMERA FACING ...
9. EXTERIOR VIEW OF FRONT ENTRANCE TO BUNKER. CAMERA FACING EAST. TANK COVER AND FRAME TO THE REAR OF VIEW. INEL PHOTO NUMBER 65-6170, TAKEN NOVEMBER 10, 1965. - Idaho National Engineering Laboratory, Advanced Reentry Vehicle Fusing System, Scoville, Butte County, ID