NASA Astrophysics Data System (ADS)
Rad, Jamal Amani; Parand, Kourosh; Abbasbandy, Saeid
2015-05-01
For the first time in mathematical finance field, we propose the local weak form meshless methods for option pricing; especially in this paper we select and analysis two schemes of them named local boundary integral equation method (LBIE) based on moving least squares approximation (MLS) and local radial point interpolation (LRPI) based on Wu's compactly supported radial basis functions (WCS-RBFs). LBIE and LRPI schemes are the truly meshless methods, because, a traditional non-overlapping, continuous mesh is not required, either for the construction of the shape functions, or for the integration of the local sub-domains. In this work, the American option which is a free boundary problem, is reduced to a problem with fixed boundary using a Richardson extrapolation technique. Then the θ -weighted scheme is employed for the time derivative. Stability analysis of the methods is analyzed and performed by the matrix method. In fact, based on an analysis carried out in the present paper, the methods are unconditionally stable for implicit Euler (θ = 0) and Crank-Nicolson (θ = 0.5) schemes. It should be noted that LBIE and LRPI schemes lead to banded and sparse system matrices. Therefore, we use a powerful iterative algorithm named the Bi-conjugate gradient stabilized method (BCGSTAB) to get rid of this system. Numerical experiments are presented showing that the LBIE and LRPI approaches are extremely accurate and fast.
NASA Astrophysics Data System (ADS)
Rahimian, Abtin; Veerapaneni, Shravan Kumar; Biros, George
2010-09-01
We consider numerical algorithms for the simulation of hydrodynamics of two-dimensional vesicles suspended in a viscous Stokesian fluid. The motion of vesicles is governed by the interplay between hydrodynamic and elastic forces. Continuum models of vesicles use a two-phase fluid system with interfacial forces that include tension (to maintain local "surface" inextensibility) and bending. Vesicle flows are challenging to simulate. On the one hand, explicit time-stepping schemes suffer from a severe stability constraint due to the stiffness related to high-order spatial derivatives in the bending term. On the other hand, implicit time-stepping schemes can be expensive because they require the solution of a set of nonlinear equations at each time step. Our method is an extension of the work of Veerapaneni et al. [S.K. Veerapaneni, D. Gueyffier, D. Zorin, G. Biros, A boundary integral method for simulating the dynamics of inextensible vesicles suspended in a viscous fluid in 2D, Journal of Computational Physics 228(7) (2009) 2334-2353], in which a semi-implicit time-marching scheme based on a boundary integral formulation of the Stokes problem for vesicles in an unbounded medium was proposed. In this paper, we consider two important generalizations: (i) confined flows within arbitrary-shaped stationary/moving geometries; and (ii) flows in which the interior (to the vesicle) and exterior fluids have different viscosity. In the rest of the paper, we will refer to this as the " viscosity contrast". These two problems require solving additional integral equations and cause nontrivial modifications to the previous numerical scheme. Our method does not have severe time-step stability constraints and its computational cost-per-time-step is comparable to that of an explicit scheme. The discretization is pseudo-spectral in space, and multistep BDF in time. We conduct numerical experiments to investigate the stability, accuracy and the computational cost of the algorithm
Boundary Preserving Dense Local Regions.
Kim, Jaechul; Grauman, Kristen
2015-05-01
We propose a dense local region detector to extract features suitable for image matching and object recognition tasks. Whereas traditional local interest operators rely on repeatable structures that often cross object boundaries (e.g., corners, scale-space blobs), our sampling strategy is driven by segmentation, and thus preserves object boundaries and shape. At the same time, whereas existing region-based representations are sensitive to segmentation parameters and object deformations, our novel approach to robustly sample dense sites and determine their connectivity offers better repeatability. In extensive experiments, we find that the proposed region detector provides significantly better repeatability and localization accuracy for object matching compared to an array of existing feature detectors. In addition, we show our regions lead to excellent results on two benchmark tasks that require good feature matching: weakly supervised foreground discovery and nearest neighbor-based object recognition.
Nonequilibrium chemistry boundary layer integral matrix procedure
NASA Technical Reports Server (NTRS)
Tong, H.; Buckingham, A. C.; Morse, H. L.
1973-01-01
The development of an analytic procedure for the calculation of nonequilibrium boundary layer flows over surfaces of arbitrary catalycities is described. An existing equilibrium boundary layer integral matrix code was extended to include nonequilibrium chemistry while retaining all of the general boundary condition features built into the original code. For particular application to the pitch-plane of shuttle type vehicles, an approximate procedure was developed to estimate the nonequilibrium and nonisentropic state at the edge of the boundary layer.
Local Electrostatic Moments and Periodic Boundary Conditition
Schultz, P.A.
1998-12-04
Electronic structure calculations frequently invoke periodic boundary conditions to solve for electrostatic potentials. For systems that are electronically charged, or contain dipole (or higher) moments, this artifice introduces spurious potentials due to the interactions between the system and multipole moments of its periodic images in aperiodic directions. I describe a method to properly handle the multipole moments of the electron density in electronic structure calculations using periodic boundary conditions. The density for which an electrostatic potential is to be evaluated is divided into two pieces. A local density is constructed that matches the desired moments of the full density, and its potential computed treating this density as isolated. With the density of this local moment countercharge removed from the full density, the remainder density lacks the troublesome moments and its electrostatic potential can be evaluated accurately using periodic boundary conditions.
Path Integrals on Manifolds with Boundary
NASA Astrophysics Data System (ADS)
Ludewig, Matthias
2017-09-01
We give time-slicing path integral formulas for solutions to the heat equation corresponding to a self-adjoint Laplace type operator acting on sections of a vector bundle over a compact Riemannian manifold with boundary. More specifically, we show that such a solution can be approximated by integrals over finite-dimensional path spaces of piecewise geodesics subordinated to increasingly fine partitions of the time interval. We consider a subclass of mixed boundary conditions which includes standard Dirichlet and Neumann boundary conditions.
Integrated Laboratories: Crossing Traditional Boundaries
ERIC Educational Resources Information Center
Dillner, Debra K.; Ferrante, Robert F.; Fitzgerald, Jeffrey P.; Heuer, William B.; Schroeder, Maria J.
2007-01-01
A new, integrated laboratory curriculum was recently developed at the U.S. Naval Academy in response to the 1999 ACS Committee on Professional Training guidelines that required inclusion of biochemistry and a stronger emphasis on student research. To meet these ACS requirements and to introduce more student choice in the major, we embarked on a…
Integrated Laboratories: Crossing Traditional Boundaries
ERIC Educational Resources Information Center
Dillner, Debra K.; Ferrante, Robert F.; Fitzgerald, Jeffrey P.; Heuer, William B.; Schroeder, Maria J.
2007-01-01
A new, integrated laboratory curriculum was recently developed at the U.S. Naval Academy in response to the 1999 ACS Committee on Professional Training guidelines that required inclusion of biochemistry and a stronger emphasis on student research. To meet these ACS requirements and to introduce more student choice in the major, we embarked on a…
Integrated watershed planning across jurisdictional boundaries
NASA Astrophysics Data System (ADS)
Watts, A. W.; Roseen, R.; Stacey, P.; Bourdeau, R.
2014-12-01
We will present the foundation for an Coastal Watershed Integrated Plan for three communities in southern New Hampshire. Small communities are often challenged by complex regulatory requirements and limited resources, but are wary of perceived risks in engaging in collaborative projects with other communities. Potential concerns include loss of control, lack of resources to engage in collaboration, technical complexity, and unclear benefits. This project explores a multi-town subwatershed application of integrated planning across jurisdictional boundaries that addresses some of today's highest priority water quality issues: wastewater treatment plant upgrades for nutrient removal; green infrastructure stormwater management for developing and re-developing areas; and regional monitoring of ecosystem indicators in support of adaptive management to achieve nutrient reduction and other water quality goals in local and downstream waters. The project outcome is a collaboratively-developed inter-municipal integrated plan, and a monitoring framework to support cross jurisdictional planning and assess attainment of water quality management goals. This research project has several primary components: 1) assessment of initial conditions, including both the pollutant load inputs and the political, economic and regulatory status within each community, 2) a pollutant load model for point and non-point sources, 3) multi-criteria evaluation of load reduction alternatives 4) a watershed management plan optimized for each community, and for Subwatersheds combining multiple communities. The final plan will quantify the financial and other benefits/drawbacks to each community for both inter municipal and individual pollution control approaches. We will discuss both the technical and collaborative aspects of the work, with lessons learned regarding science to action, incorporation of social, economic and water quality assessment parameters, and stakeholder/researcher interaction.
Boundary Value Problems With Integral Conditions
NASA Astrophysics Data System (ADS)
Karandzhulov, L. I.; Sirakova, N. D.
2011-12-01
The weakly perturbed nonlinear boundary value problems (BVP) for almost linear systems of ordinary differential equations (ODE) are considered. We assume that the nonlinear part contain an additional function, which defines the perturbation as singular. Then the Poincare method is not applicable. The problem of existence, uniqueness and construction of a solution of the posed BVP with integral condition is studied.
Detecting natural occlusion boundaries using local cues
DiMattina, Christopher; Fox, Sean A.; Lewicki, Michael S.
2012-01-01
Occlusion boundaries and junctions provide important cues for inferring three-dimensional scene organization from two-dimensional images. Although several investigators in machine vision have developed algorithms for detecting occlusions and other edges in natural images, relatively few psychophysics or neurophysiology studies have investigated what features are used by the visual system to detect natural occlusions. In this study, we addressed this question using a psychophysical experiment where subjects discriminated image patches containing occlusions from patches containing surfaces. Image patches were drawn from a novel occlusion database containing labeled occlusion boundaries and textured surfaces in a variety of natural scenes. Consistent with related previous work, we found that relatively large image patches were needed to attain reliable performance, suggesting that human subjects integrate complex information over a large spatial region to detect natural occlusions. By defining machine observers using a set of previously studied features measured from natural occlusions and surfaces, we demonstrate that simple features defined at the spatial scale of the image patch are insufficient to account for human performance in the task. To define machine observers using a more biologically plausible multiscale feature set, we trained standard linear and neural network classifiers on the rectified outputs of a Gabor filter bank applied to the image patches. We found that simple linear classifiers could not match human performance, while a neural network classifier combining filter information across location and spatial scale compared well. These results demonstrate the importance of combining a variety of cues defined at multiple spatial scales for detecting natural occlusions. PMID:23255731
Integrating Local Governmental Topics.
ERIC Educational Resources Information Center
Centner, Terence J.
1994-01-01
Students who pursue business and professional careers in natural resources and life science (NRLS) will have a decided need for a basic understanding of local government topics that shape public policy. Suggests that a responsible curriculum in NRLS should provide students with opportunities to explore these issues, and discusses methods for…
Theoretical Foundations of Incorporating Local Boundary Conditions into Nonlocal Problems
NASA Astrophysics Data System (ADS)
Aksoylu, Burak; Beyer, Horst Reinhard; Celiker, Fatih
2017-08-01
We study nonlocal equations from the area of peridynamics on bounded domains. We present four main results. In our recent paper, we have discovered that, on R, the governing operator in peridynamics, which involves a convolution, is a bounded function of the classical (local) governing operator. Building on this, as main result 1, we construct an abstract convolution operator on bounded domains which is a generalization of the standard convolution based on integrals. The abstract convolution operator is a function of the classical operator, defined by a Hilbert basis available due to the purely discrete spectrum of the latter. As governing operator of the nonlocal equation we use a function of the classical operator, this allows us to incorporate local boundary conditions into nonlocal theories. As main result 2, we prove that the solution operator can be uniquely decomposed into a Hilbert-Schmidt operator and a multiple of the identity operator. As main result 3, we prove that Hilbert-Schmidt operators provide a smoothing of the input data in the sense a square integrable function is mapped into a function that is smooth up to boundary of the domain. As main result 4, for the homogeneous nonlocal wave equation, we prove that continuity is preserved by time evolution. Namely, the solution is discontinuous if and only if the initial data is discontinuous. As a consequence, discontinuities remain stationary.
Boundary Integral Corrected Particle In Cell
NASA Astrophysics Data System (ADS)
Andrew, Christlieb; Keith, Cartwright
2007-11-01
Numerical heating is a serous problem in PIC modeling of cross field Diffusion. Recent work by the author has shown that for, electrostatic problems, the Boundary Integral Treecode (BIT) has far less numerical heating than traditional PIC and that numerical heating can be nearly eliminated if regularization is added to the BIT field solver. In this work we consider the application of BIT as a sub-cell method within each PIC cell, where the boundary conditions on BIT come from the fields computed on the PIC mesh. The goal is to minimize numerical heating in PIC while allowing for mesh spacing in PIC to be much greater than a Debye length. Our overall objective is to inherit the parallel capability of legacy PIC codes while providing high accuracy.
Grain-boundary free energy via thermodynamic integration
NASA Astrophysics Data System (ADS)
Lusk, Mark T.; Fellinger, Michael R.; Beale, Paul D.
2006-02-01
In a previous publication by Lusk and Beale [Phys. Rev. E 69, 026117 (2004)], fluctuating cell (FC) theory was used to estimate the free energy of symmetric tilt grain boundaries in an assembly of nearly hard disks. The FC method is much faster than the more traditional thermodynamic integration, but the accuracy of the algorithm has not been assessed in association with persistent defect structures. This motivated the present work wherein the FC free energies are compared directly with the data obtained via thermodynamic integration from an Einstein crystal to an assembly of hard disks. This comparison is made over the range of possible misorientations for symmetric tilt boundaries and indicates that the FC method gives quantitatively accurate estimates for grain-boundary free energy. We also demsonstrate that the FC approximation is quantitatively accurate at determining the free-energy contribution of each particle whether in the bulk or the grain boundary. The FC calculation is about two orders of magnitude faster than a full thermodynamic integration. This approach may offer a numerically efficient means of estimating the free energy of persistent defect structures to greater accuracy than is afforded by the quasiharmonic and local harmonic approximations.
Wafer-scale boundary value integrated circuit architecture
Delgado-Frias, J.G.
1986-01-01
Wafer scale integration (WSI) technology offers the potential for improving speed and reliability of a large integrated circuit system. An architecture is presented for a boundary value integrated circuit engine which lends itself to implementation in WSI. The philosophy underpinning this architecture includes local communication, cell regularity, and fault tolerance. The research described here proposes, investigates, and simulates this computer architecture and its flaw avoidance schemes for a WSI implementation. Boundary value differential equation computations are utilized in a number of scientific and engineering applications. A boundary value machine is ideally suited for solutions of finite difference and finite element problems with specified boundary values. The architecture is a 2-D array of computational cells. Each basic cell has four bit serial processing elements (PEs) and a local memory. Most communications is limited to transfer between adjacent PEs to reduce complexity, avoid long delays, and localize the effects of silicon flaws. Memory access time is kept short by restricting memory service to PEs in the same cell. I/O operation is performed by means of a row multiple single line I/O bus, which allows fast, reliable and independent data transference. WSI yield losses are due to gross defects and random defects. Gross defects which affect large portions of the wafer are usually fatal for any WSI implementation. Overcoming random defects which cover either a small area or points is achieved by defect avoidance schemes that are developed for this architecture. Those schemes are provided at array, cell, and communication level. Capabilities and limitations of the proposed WSI architecture can be observed through the simulations. Speed degradation of the array and the PE due to silicon defects is observed by means of simulation. Also, module and bus utilization are computed and presented.
Boundary-Layer Receptivity and Integrated Transition Prediction
NASA Technical Reports Server (NTRS)
Chang, Chau-Lyan; Choudhari, Meelan
2005-01-01
The adjoint parabold stability equations (PSE) formulation is used to calculate the boundary layer receptivity to localized surface roughness and suction for compressible boundary layers. Receptivity efficiency functions predicted by the adjoint PSE approach agree well with results based on other nonparallel methods including linearized Navier-Stokes equations for both Tollmien-Schlichting waves and crossflow instability in swept wing boundary layers. The receptivity efficiency function can be regarded as the Green's function to the disturbance amplitude evolution in a nonparallel (growing) boundary layer. Given the Fourier transformed geometry factor distribution along the chordwise direction, the linear disturbance amplitude evolution for a finite size, distributed nonuniformity can be computed by evaluating the integral effects of both disturbance generation and linear amplification. The synergistic approach via the linear adjoint PSE for receptivity and nonlinear PSE for disturbance evolution downstream of the leading edge forms the basis for an integrated transition prediction tool. Eventually, such physics-based, high fidelity prediction methods could simulate the transition process from the disturbance generation through the nonlinear breakdown in a holistic manner.
NASA Astrophysics Data System (ADS)
Xie, Guizhong; Zhang, Dehai; Zhang, Jianming; Meng, Fannian; Du, Wenliao; Wen, Xiaoyu
2016-12-01
As a widely used numerical method, boundary element method (BEM) is efficient for computer aided engineering (CAE). However, boundary integrals with near singularity need to be calculated accurately and efficiently to implement BEM for CAE analysis on thin bodies successfully. In this paper, the distance in the denominator of the fundamental solution is first designed as an equivalent form using approximate expansion and the original sinh method can be revised into a new form considering the minimum distance and the approximate expansion. Second, the acquisition of the projection point by Newton-Raphson method is introduced. We acquire the nearest point between the source point and element edge by solving a cubic equation if the location of the projection point is outside the element, where boundary integrals with near singularity appear. Finally, the subtriangles of the local coordinate space are mapped into the integration space and the sinh method is applied in the integration space. The revised sinh method can be directly performed in the integration element. Averification test of our method is proposed. Results demonstrate that our method is effective for regularizing the boundary integrals with near singularity.
Anelastic Relaxations Associated with Local Disordering in Grain Boundaries
1993-04-02
AD-A263 101 FAif i1 . .. FOREIGN AEROSPACE SCIENCE AND TECHNOLOGY CENTER ANELASTIC RELAYAtIONS ASSOCIATED) WI TH I-OCAL DISORDERING IN GRAIN...ID(RS)T-0308-92 2 April 1993 MICROFICHE NR: C3 C, oo 4 1 ANELASTIC RELAXATIONS ASSOCIATED WITH iLOCAL DISORDERING IN GRAIN BOUNDARIES By: Cheng Bolin...tra.,slation were extracted from the best quality copy avail.ible. Anelastic relaxations associated with local disordering in grain boundaries Cheng
Boundary dual of bulk local operators
NASA Astrophysics Data System (ADS)
Sanches, Fabio; Weinberg, Sean J.
2017-07-01
We provide a procedure to determine if a given nonlocal operator in a large-N holographic CFT is dual to a local bulk operator on the geometry associated with a particular code subspace of the CFT. This procedure does not presuppose knowledge of the bulk geometry. We are able to pick out local operators in a large region of the bulk, called the "localizable region," that can extend beyond event horizons in certain cases. The method relies heavily on the quantum error correcting structure of AdS /CFT and, in particular, on entanglement wedge reconstruction. As a byproduct of this machinery, we are able to reconstruct the metric in the localizable region up to a conformal factor. This suggests a connection between our program and the recent light-cone cut approach to bulk reconstruction.
A non-local computational boundary condition for duct acoustics
NASA Technical Reports Server (NTRS)
Zorumski, William E.; Watson, Willie R.; Hodge, Steve L.
1994-01-01
A non-local boundary condition is formulated for acoustic waves in ducts without flow. The ducts are two dimensional with constant area, but with variable impedance wall lining. Extension of the formulation to three dimensional and variable area ducts is straightforward in principle, but requires significantly more computation. The boundary condition simulates a nonreflecting wave field in an infinite duct. It is implemented by a constant matrix operator which is applied at the boundary of the computational domain. An efficient computational solution scheme is developed which allows calculations for high frequencies and long duct lengths. This computational solution utilizes the boundary condition to limit the computational space while preserving the radiation boundary condition. The boundary condition is tested for several sources. It is demonstrated that the boundary condition can be applied close to the sound sources, rendering the computational domain small. Computational solutions with the new non-local boundary condition are shown to be consistent with the known solutions for nonreflecting wavefields in an infinite uniform duct.
Boundary-integral methods in elasticity and plasticity. [solutions of boundary value problems
NASA Technical Reports Server (NTRS)
Mendelson, A.
1973-01-01
Recently developed methods that use boundary-integral equations applied to elastic and elastoplastic boundary value problems are reviewed. Direct, indirect, and semidirect methods using potential functions, stress functions, and displacement functions are described. Examples of the use of these methods for torsion problems, plane problems, and three-dimensional problems are given. It is concluded that the boundary-integral methods represent a powerful tool for the solution of elastic and elastoplastic problems.
Solution of elastoplastic torsion problem by boundary integral method
NASA Technical Reports Server (NTRS)
Mendelson, A.
1975-01-01
The boundary integral method was applied to the elastoplastic analysis of the torsion of prismatic bars, and the results are compared with those obtained by the finite difference method. Although fewer unknowns were used, very good accuracy was obtained with the boundary integral method. Both simply and multiply connected bodies can be handled with equal ease.
Anelastic relaxations associated with local disordering in grain boundaries
NASA Astrophysics Data System (ADS)
Cheng, Bolin; Ge, Tingsui
1993-04-01
Internal friction and micro-creep measurements were performed with high-purity Al bamboo-crystal specimens. The relaxation strength was found to decrease with the decrease of the temperature of measurement and became zero at about 0.4 T sub m, (T sub m being melting temperature). This reflects the occurrence of local disordering in the bamboo boundary region at this temperature. This result conforms to the picture of grain boundary disordering constructed by atomic simulation studies.
Instability of a Supersonic Boundary-Layer with Localized Roughness
NASA Technical Reports Server (NTRS)
Marxen, Olaf; Iaccarino, Gianluca; Shaqfeh, Eric S. G.
2010-01-01
A localized 3-D roughness causes boundary-layer separation and (weak) shocks. Most importantly, streamwise vortices occur which induce streamwise (low U, high T) streaks. Immersed boundary method (volume force) suitable to represent roughness element in DNS. Favorable comparison between bi-global stability theory and DNS for a "y-mode" Outlook: Understand the flow physics (investigate "z-modes" in DNS through sinuous spanwise forcing, study origin of the beat in DNS).
Local and social facets of planetary boundaries: right to nutrients
NASA Astrophysics Data System (ADS)
Kahiluoto, Helena; Kuisma, Miia; Kuokkanen, Anna; Mikkilä, Mirja; Linnanen, Lassi
2015-10-01
Anthropogenic nutrient flows exceed the planetary boundaries. The boundaries and the current excesses vary spatially. Such variations have both an ecological and a social facet. We explored the spatial variation using a bottom-up approach. The local critical boundaries were determined through the current or accumulated flow of the preceding five years before the planetary boundary criteria were met. Finland and Ethiopia served as cases with contrasting ecology and wealth. The variation in excess depends on historical global inequities in the access to nutrients. Globally, the accumulated use per capita is 2300 kg reactive nitrogen (Nr) and 200 kg phosphorus (P). For Finland, the accumulated use per capita is 3400 kg Nr and 690 kg P, whereas for Ethiopia, it is 26 kg Nr and 12 kg P. The critical N boundary in Finland is currently exceeded by 40 kg cap-1 a-1 and the accumulated excess is 65 kg cap-1 a-1, while the global current excess is 24 kg cap-1 a-1 and there is space in Ethiopia to increase even the accumulated flow. The critical P boundary is exceeded in Finland and (although less so) in Ethiopia, but for contrary reasons: (1) the excessive past inflow to the agrifood system in Finland and (2) the excessive outflow from the agrifood system triggered by deficits in inflow and waste management in Ethiopia. The critical boundaries set by Finnish marine systems are lower and those set by freshwaters are higher than the planetary boundaries downscaled per capita. The shift to dominance of internal loading in watercourses represents a tipping point. We conclude that food security within the safe boundaries requires global redistribution of nutrients in residues, soils and sediments and of rights to use nutrients. Bottom-up assessments reveal local dynamics that shed new light on the relevant boundary criteria and on estimates and remedies.
Integrable Boundary for Quad-Graph Systems: Three-Dimensional Boundary Consistency
NASA Astrophysics Data System (ADS)
Caudrelier, Vincent; Crampé, Nicolas; Zhang, Qi Cheng
2014-02-01
We propose the notion of integrable boundary in the context of discrete integrable systems on quad-graphs. The equation characterizing the boundary must satisfy a compatibility equation with the one characterizing the bulk that we called the three-dimensional (3D) boundary consistency. In comparison to the usual 3D consistency condition which is linked to a cube, our 3D boundary consistency condition lives on a half of a rhombic dodecahedron. The We provide a list of integrable boundaries associated to each quad-graph equation of the classification obtained by Adler, Bobenko and Suris. Then, the use of the term ''integrable boundary'' is justified by the facts that there are Bäcklund transformations and a zero curvature representation for systems with boundary satisfying our condition. We discuss the three-leg form of boundary equations, obtain associated discrete Toda-type models with boundary and recover previous results as particular cases. Finally, the connection between the 3D boundary consistency and the set-theoretical reflection equation is established.
Treatment of domain integrals in boundary element methods
Nintcheu Fata, Sylvain
2012-01-01
A systematic and rigorous technique to calculate domain integrals without a volume-fitted mesh has been developed and validated in the context of a boundary element approximation. In the proposed approach, a domain integral involving a continuous or weakly-singular integrand is first converted into a surface integral by means of straight-path integrals that intersect the underlying domain. Then, the resulting surface integral is carried out either via analytic integration over boundary elements or by use of standard quadrature rules. This domain-to-boundary integral transformation is derived from an extension of the fundamental theorem of calculus to higher dimension, and the divergence theorem. In establishing the method, it is shown that the higher-dimensional version of the first fundamental theorem of calculus corresponds to the well-known Poincare lemma. The proposed technique can be employed to evaluate integrals defined over simply- or multiply-connected domains with Lipschitz boundaries which are embedded in an Euclidean space of arbitrary but finite dimension. Combined with the singular treatment of surface integrals that is widely available in the literature, this approach can also be utilized to effectively deal with boundary-value problems involving non-homogeneous source terms by way of a collocation or a Galerkin boundary integral equation method using only the prescribed surface discretization. Sample problems associated with the three-dimensional Poisson equation and featuring the Newton potential are successfully solved by a constant element collocation method to validate this study.
Isogeometric Analysis of Boundary Integral Equations
2015-04-21
lower) halves. For the cube , the Neumann boundary conditions are prescribed on the top and bottom faces , and the Dirichlet boundary conditions on ...standard parametrizations based on 16 (torus), 8 (sphere), and 6 ( cube ) NURBS patches. For each shape, the patches were used to generate five meshes via...the iteration count and the spectral condition number show a logarithmic dependence on h. For the cube , the mathematical foundations are not well
Magnetization due to localized states on graphene grain boundary
Dutta, Sudipta; Wakabayashi, Katsunori
2015-01-01
Magnetism in graphene has been found to originate from various defects, e.g., vacancy, edge formation, add-atoms etc. Here, we discuss about an alternate route of achieving magnetism in graphene via grain boundary. During chemical vapor deposition of graphene, several graphene nucleation centers grow independently and face themselves with unusual bonding environment, giving rise to the formation of grain boundaries. We investigate the origin of magnetism in such grain boundaries within first-principles calculations, by letting two nucleation centers interact with each other at their interface. We observe formation of unprecedented point defect, consisting of fused three-membered and larger carbon rings, which induces net magnetization to graphene quantum dots. In case of periodic lattices, the appearance of array of point defects leads to the formation of magnetic grain boundaries. The net magnetization on these defects arises due to the deviation from bipartite characteristics of pristine graphene. We observe magnetic grain boundary induced dispersion less flat bands near Fermi energy, showing higher localization of electrons. These flat bands can be accessed via small doping, leading to enhanced magnetism. Moreover, the grain boundaries can induce asymmetric spin conduction behavior along the cross boundary direction. These properties can be exploited for sensor and spin-filtering applications. PMID:26145161
Instability of a Local Downflow in a Turbulent Boundary Layer
NASA Astrophysics Data System (ADS)
Lundgren, Thomas
2006-11-01
In the laminar Hiemenz stagnation point flow a downflow produces a straining flow along the boundary. This flow is unstable (Hammerlin,1955) with neutral eigensolution consisting of alternating sign vortex cells of uniform strength along the flow direction. Low-speed and high-speed streaks at the cell boundaries increase in amplitude in the flow direction. In the turbulent problem a local downflow is envisioned to be caused by large scale structures in the outer part of the boundary layer. The Reynolds-averaged equations were employed with an eddy viscosity which depens only on the distance from the wall. The resulting equations are unstable to longitudinal vortices with a structure similar to the Hiemenz neutral egensolutin, with a continuous spectrum of the spanwise wavenumber. It is found that the wavenumber must be smaller than a critical value which depends on the local strainrate. In general when the downflow is weaker the critical wavenuber is smaller (streak spacing larger).
40 CFR 255.21 - Local consultation on boundaries.
Code of Federal Regulations, 2013 CFR
2013-07-01
... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Local consultation on boundaries. 255.21 Section 255.21 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES IDENTIFICATION OF REGIONS AND AGENCIES FOR SOLID WASTE MANAGEMENT Procedures for Identifying Regions and...
40 CFR 255.21 - Local consultation on boundaries.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Local consultation on boundaries. 255.21 Section 255.21 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES IDENTIFICATION OF REGIONS AND AGENCIES FOR SOLID WASTE MANAGEMENT Procedures for Identifying Regions and...
40 CFR 255.21 - Local consultation on boundaries.
Code of Federal Regulations, 2014 CFR
2014-07-01
... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Local consultation on boundaries. 255.21 Section 255.21 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES IDENTIFICATION OF REGIONS AND AGENCIES FOR SOLID WASTE MANAGEMENT Procedures for Identifying Regions and...
40 CFR 255.21 - Local consultation on boundaries.
Code of Federal Regulations, 2011 CFR
2011-07-01
... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Local consultation on boundaries. 255.21 Section 255.21 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES IDENTIFICATION OF REGIONS AND AGENCIES FOR SOLID WASTE MANAGEMENT Procedures for Identifying Regions and...
40 CFR 255.21 - Local consultation on boundaries.
Code of Federal Regulations, 2012 CFR
2012-07-01
... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Local consultation on boundaries. 255.21 Section 255.21 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES IDENTIFICATION OF REGIONS AND AGENCIES FOR SOLID WASTE MANAGEMENT Procedures for Identifying Regions and...
Integrable boundary-value problems and nonlinear Fourier harmonics
Bikbaev, R.F.
1995-11-10
For the nonlinear Schrodinger equation, the integrable boundary-value problem on a segment is considered. The concept of nonlinear {theta}-harmonics similar to the ordinary Fourier harmonics in the linear case is suggested. A solution of the initial boundary-value problem on the semi-axis is constructed by means of reduction to the Cauchy problem on the whole axis.
Breaking integrability at the boundary: the sine-Gordon model with Robin boundary conditions
NASA Astrophysics Data System (ADS)
Arthur, Robert; Dorey, Patrick; Parini, Robert
2016-04-01
We explore boundary scattering in the sine-Gordon model with a non-integrable family of Robin boundary conditions. The soliton content of the field after collision is analysed using a numerical implementation of the direct scattering problem associated with the inverse scattering method. We find that an antikink may be reflected into various combinations of an antikink, a kink, and one or more breathers, depending on the values of the initial antikink velocity and a parameter associated with the boundary condition. In addition we observe regions with an intricate resonance structure arising from the creation of an intermediate breather whose recollision with the boundary is highly dependent on the breather phase.
On the Implementation of 3D Galerkin Boundary Integral Equations
Nintcheu Fata, Sylvain; Gray, Leonard J
2010-01-01
In this article, a reverse contribution technique is proposed to accelerate the construction of the dense influence matrices associated with a Galerkin approximation of singular and hypersingular boundary integral equations of mixed-type in potential theory. In addition, a general-purpose sparse preconditioner for boundary element methods has also been developed to successfully deal with ill-conditioned linear systems arising from the discretization of mixed boundary-value problems on non-smooth surfaces. The proposed preconditioner, which originates from the precorrected-FFT method, is sparse, easy to generate and apply in a Krylov subspace iterative solution of discretized boundary integral equations. Moreover, an approximate inverse of the preconditioner is implicitly built by employing an incomplete LU factorization. Numerical experiments involving mixed boundary-value problems for the Laplace equation are included to illustrate the performance and validity of the proposed techniques.
An(1) affine Toda field theories with integrable boundary conditions revisited
NASA Astrophysics Data System (ADS)
Doikou, Anastasia
2008-05-01
Generic classically integrable boundary conditions for the An(1) affine Toda field theories (ATFT) are investigated. The present analysis rests primarily on the underlying algebra, defined by the classical version of the reflection equation. We use as a prototype example the first non-trivial model of the hierarchy i.e. the A2(1) ATFT, however our results may be generalized for any An(1) (n > 1). We assume here two distinct types of boundary conditions called some times soliton preserving (SP), and soliton non-preserving (SNP) associated to two distinct algebras, i.e. the reflection algebra and the (q) twisted Yangian respectively. The boundary local integrals of motion are then systematically extracted from the asymptotic expansion of the associated transfer matrix. In the case of SNP boundary conditions we recover previously known results. The other type of boundary conditions (SP), associated to the reflection algebra, are novel in this context and lead to a different set of conserved quantities that depend on free boundary parameters. It also turns out that the number of local integrals of motion for SP boundary conditions is `double' compared to those of the SNP case.
Single frequency sound propagation in flat waveguides with locally reactive impedance boundaries.
Min, Hequn; Chen, Weisong; Qiu, Xiaojun
2011-08-01
A coherent image source method is presented for evaluating single frequency sound propagation from a point source in a flat waveguide with two infinite and parallel locally reactive boundaries. The method starts from formulating reflections of the spherical sound radiation into integrals of plane wave expansion, and the analytical evaluation of the integrals is simplified by introducing a physically plausible assumption that wave front shapes remain the same before and after each reflection on a reflective boundary. The proposed model can determine coherently the sound fields at arbitrary receiver locations in a flat waveguide, even when one boundary is highly sound absorptive. Being compared with the classical wave theory and the existing coherent ray-based methods, it is shown that the proposed method provides considerable accuracy and advantages to predict sound propagation in flat waveguides with a sound absorptive ceiling and a reflective floor over a broad frequency range, particularly at large distances from the source where the existing methods are problematic.
Crossing Boundaries: Explorations in Integrative Curriculum.
ERIC Educational Resources Information Center
Braunger, Jane; Hart-Landsberg, Sylvia
Curriculum in the United States is largely a fragmented set of subjects and teachers to present them. Many Pacific Northwestern educators are looking for innovative ways to organize curriculum that over comes the traditional structure. As knowledge of the learning process increases, integrative curriculum is being employed more frequently. Several…
On integrable boundaries in the 2 dimensional O(N) σ-models
NASA Astrophysics Data System (ADS)
Aniceto, Inês; Bajnok, Zoltán; Gombor, Tamás; Kim, Minkyoo; Palla, László
2017-09-01
We make an attempt to map the integrable boundary conditions for 2 dimensional non-linear O(N) σ-models. We do it at various levels: classically, by demanding the existence of infinitely many conserved local charges and also by constructing the double row transfer matrix from the Lax connection, which leads to the spectral curve formulation of the problem; at the quantum level, we describe the solutions of the boundary Yang-Baxter equation and derive the Bethe-Yang equations. We then show how to connect the thermodynamic limit of the boundary Bethe-Yang equations to the spectral curve.
Optimal control problem for impulsive systems with integral boundary conditions
NASA Astrophysics Data System (ADS)
Ashyralyev, Allaberen; Sharifov, Y. A.
2012-08-01
In the present work the optimal control problem is considered, when the state of the system is described by the impulsive differential equations with integral boundary conditions. Applying the Banach contraction principle the existence and uniqueness of solution is proved for the corresponding boundary problem by the fixed admissible control. The first and second variation of the functional is calculated. Various necessary conditions of optimality of the first and second order are obtained by the help of the variation of the controls.
Localized temporal change of the Earth's inner core boundary.
Wen, Lianxing
2006-11-10
Compressional waves of an earthquake doublet (two events occurring in the South Sandwich Islands on 1 December 1993 and 6 September 2003), recorded at three seismic stations in Russia and Kyrgyzstan and reflected off Earth's inner core boundary, arrived at least from 39 to 70 milliseconds earlier in the 2003 event than in the 1993 event. Such changes indicate that Earth's inner core radius enlarged locally beneath middle Africa by 0.98 to 1.75 kilometers between the times of these two events. Changes of the inner core radius may be explained by either a differential motion of the inner core, assuming that irregularities are present at the inner core boundary and fixed to the inner core, or a rapid growth of the inner core by this amount.
Shao, Yeqin; Gao, Yaozong; Wang, Qian; Yang, Xin; Shen, Dinggang
2015-01-01
Automatic and accurate segmentation of the prostate and rectum in planning CT images is a challenging task due to low image contrast, unpredictable organ (relative) position, and uncertain existence of bowel gas across different patients. Recently, regression forest was adopted for organ deformable segmentation on 2D medical images by training one landmark detector for each point on the shape model. However, it seems impractical for regression forest to guide 3D deformable segmentation as a landmark detector, due to large number of vertices in the 3D shape model as well as the difficulty in building accurate 3D vertex correspondence for each landmark detector. In this paper, we propose a novel boundary detection method by exploiting the power of regression forest for prostate and rectum segmentation. The contributions of this paper are as follows: 1) we introduce regression forest as a local boundary regressor to vote the entire boundary of a target organ, which avoids training a large number of landmark detectors and building an accurate 3D vertex correspondence for each landmark detector; 2) an auto-context model is integrated with regression forest to improve the accuracy of the boundary regression; 3) we further combine a deformable segmentation method with the proposed local boundary regressor for the final organ segmentation by integrating organ shape priors. Our method is evaluated on a planning CT image dataset with 70 images from 70 different patients. The experimental results show that our proposed boundary regression method outperforms the conventional boundary classification method in guiding the deformable model for prostate and rectum segmentations. Compared with other state-of-the-art methods, our method also shows a competitive performance. PMID:26439938
Shao, Yeqin; Gao, Yaozong; Wang, Qian; Yang, Xin; Shen, Dinggang
2015-12-01
Automatic and accurate segmentation of the prostate and rectum in planning CT images is a challenging task due to low image contrast, unpredictable organ (relative) position, and uncertain existence of bowel gas across different patients. Recently, regression forest was adopted for organ deformable segmentation on 2D medical images by training one landmark detector for each point on the shape model. However, it seems impractical for regression forest to guide 3D deformable segmentation as a landmark detector, due to large number of vertices in the 3D shape model as well as the difficulty in building accurate 3D vertex correspondence for each landmark detector. In this paper, we propose a novel boundary detection method by exploiting the power of regression forest for prostate and rectum segmentation. The contributions of this paper are as follows: (1) we introduce regression forest as a local boundary regressor to vote the entire boundary of a target organ, which avoids training a large number of landmark detectors and building an accurate 3D vertex correspondence for each landmark detector; (2) an auto-context model is integrated with regression forest to improve the accuracy of the boundary regression; (3) we further combine a deformable segmentation method with the proposed local boundary regressor for the final organ segmentation by integrating organ shape priors. Our method is evaluated on a planning CT image dataset with 70 images from 70 different patients. The experimental results show that our proposed boundary regression method outperforms the conventional boundary classification method in guiding the deformable model for prostate and rectum segmentations. Compared with other state-of-the-art methods, our method also shows a competitive performance.
Galerkin Boundary Integral Analysis for the 3D Helmholtz Equation
Swager, Melissa; Gray, Leonard J; Nintcheu Fata, Sylvain
2010-01-01
A linear element Galerkin boundary integral analysis for the three-dimensional Helmholtz equation is presented. The emphasis is on solving acoustic scattering by an open (crack) surface, and to this end both a dual equation formulation and a symmetric hypersingular formulation have been developed. All singular integrals are defined and evaluated via a boundary limit process, facilitating the evaluation of the (finite) hypersingular Galerkin integral. This limit process is also the basis for the algorithm for post-processing of the surface gradient. The analytic integrations required by the limit process are carried out by employing a Taylor series expansion for the exponential factor in the Helmholtz fundamental solutions. For the open surface, the implementations are validated by comparing the numerical results obtained by using the two different methods.
Cross Stream Differencing for Integral Boundary Layer Equations.
1987-11-01
smaller artificial viscosity. R6sum6 Un sch6ma de differentiation transversale de premier ordre explicite, stable et efficace, avec une faible erreur de...DIFFERENCING FOR INTEGRAL BOUNDARY LAYER EQUATIONS 4 AU-HORS (Last name, first name, middle initial, If military, show rank, e.g. Doe, Mal John EJ Hally
Application of boundary integral equations to elastoplastic problems
NASA Technical Reports Server (NTRS)
Mendelson, A.; Albers, L. U.
1975-01-01
The application of boundary integral equations to elastoplastic problems is reviewed. Details of the analysis as applied to torsion problems and to plane problems is discussed. Results are presented for the elastoplastic torsion of a square cross section bar and for the plane problem of notched beams. A comparison of different formulations as well as comparisons with experimental results are presented.
Integrating Science with Local Experiences
ERIC Educational Resources Information Center
Black, Kathie
2004-01-01
Science exists in many forms, but an appreciation of science as an integral part of every day does not occur in the vacuum of laboratory experience or through classroom activities. Throughout the communities, a plethora of places exist to see science at work, from the usually recommended museums and parks to the less thought of factories and…
Integrating Science with Local Experiences
ERIC Educational Resources Information Center
Black, Kathie
2004-01-01
Science exists in many forms, but an appreciation of science as an integral part of every day does not occur in the vacuum of laboratory experience or through classroom activities. Throughout the communities, a plethora of places exist to see science at work, from the usually recommended museums and parks to the less thought of factories and…
Numerical solution of boundary-integral equations for molecular electrostatics.
Bardhan, J.; Mathematics and Computer Science; Rush Univ.
2009-03-07
Numerous molecular processes, such as ion permeation through channel proteins, are governed by relatively small changes in energetics. As a result, theoretical investigations of these processes require accurate numerical methods. In the present paper, we evaluate the accuracy of two approaches to simulating boundary-integral equations for continuum models of the electrostatics of solvation. The analysis emphasizes boundary-element method simulations of the integral-equation formulation known as the apparent-surface-charge (ASC) method or polarizable-continuum model (PCM). In many numerical implementations of the ASC/PCM model, one forces the integral equation to be satisfied exactly at a set of discrete points on the boundary. We demonstrate in this paper that this approach to discretization, known as point collocation, is significantly less accurate than an alternative approach known as qualocation. Furthermore, the qualocation method offers this improvement in accuracy without increasing simulation time. Numerical examples demonstrate that electrostatic part of the solvation free energy, when calculated using the collocation and qualocation methods, can differ significantly; for a polypeptide, the answers can differ by as much as 10 kcal/mol (approximately 4% of the total electrostatic contribution to solvation). The applicability of the qualocation discretization to other integral-equation formulations is also discussed, and two equivalences between integral-equation methods are derived.
A Kernel-free Boundary Integral Method for Elliptic Boundary Value Problems.
Ying, Wenjun; Henriquez, Craig S
2007-12-10
This paper presents a class of kernel-free boundary integral (KFBI) methods for general elliptic boundary value problems (BVPs). The boundary integral equations reformulated from the BVPs are solved iteratively with the GMRES method. During the iteration, the boundary and volume integrals involving Green's functions are approximated by structured grid-based numerical solutions, which avoids the need to know the analytical expressions of Green's functions. The KFBI method assumes that the larger regular domain, which embeds the original complex domain, can be easily partitioned into a hierarchy of structured grids so that fast elliptic solvers such as the fast Fourier transform (FFT) based Poisson/Helmholtz solvers or those based on geometric multigrid iterations are applicable. The structured grid-based solutions are obtained with standard finite difference method (FDM) or finite element method (FEM), where the right hand side of the resulting linear system is appropriately modified at irregular grid nodes to recover the formal accuracy of the underlying numerical scheme. Numerical results demonstrating the efficiency and accuracy of the KFBI methods are presented. It is observed that the number of GM-RES iterations used by the method for solving isotropic and moderately anisotropic BVPs is independent of the sizes of the grids that are employed to approximate the boundary and volume integrals. With the standard second-order FEMs and FDMs, the KFBI method shows a second-order convergence rate in accuracy for all of the tested Dirichlet/Neumann BVPs when the anisotropy of the diffusion tensor is not too strong.
A Kernel-free Boundary Integral Method for Elliptic Boundary Value Problems ⋆
Ying, Wenjun; Henriquez, Craig S.
2013-01-01
This paper presents a class of kernel-free boundary integral (KFBI) methods for general elliptic boundary value problems (BVPs). The boundary integral equations reformulated from the BVPs are solved iteratively with the GMRES method. During the iteration, the boundary and volume integrals involving Green's functions are approximated by structured grid-based numerical solutions, which avoids the need to know the analytical expressions of Green's functions. The KFBI method assumes that the larger regular domain, which embeds the original complex domain, can be easily partitioned into a hierarchy of structured grids so that fast elliptic solvers such as the fast Fourier transform (FFT) based Poisson/Helmholtz solvers or those based on geometric multigrid iterations are applicable. The structured grid-based solutions are obtained with standard finite difference method (FDM) or finite element method (FEM), where the right hand side of the resulting linear system is appropriately modified at irregular grid nodes to recover the formal accuracy of the underlying numerical scheme. Numerical results demonstrating the efficiency and accuracy of the KFBI methods are presented. It is observed that the number of GM-RES iterations used by the method for solving isotropic and moderately anisotropic BVPs is independent of the sizes of the grids that are employed to approximate the boundary and volume integrals. With the standard second-order FEMs and FDMs, the KFBI method shows a second-order convergence rate in accuracy for all of the tested Dirichlet/Neumann BVPs when the anisotropy of the diffusion tensor is not too strong. PMID:23519600
Local-time representation of path integrals.
Jizba, Petr; Zatloukal, Václav
2015-12-01
We derive a local-time path-integral representation for a generic one-dimensional time-independent system. In particular, we show how to rephrase the matrix elements of the Bloch density matrix as a path integral over x-dependent local-time profiles. The latter quantify the time that the sample paths x(t) in the Feynman path integral spend in the vicinity of an arbitrary point x. Generalization of the local-time representation that includes arbitrary functionals of the local time is also provided. We argue that the results obtained represent a powerful alternative to the traditional Feynman-Kac formula, particularly in the high- and low-temperature regimes. To illustrate this point, we apply our local-time representation to analyze the asymptotic behavior of the Bloch density matrix at low temperatures. Further salient issues, such as connections with the Sturm-Liouville theory and the Rayleigh-Ritz variational principle, are also discussed.
Local Data Integration in East Central Florida
NASA Technical Reports Server (NTRS)
Case, Jonathan L.; Manobianco, John T.
1999-01-01
The Applied Meteorology Unit has configured a Local Data Integration System (LDIS) for east central Florida which assimilates in-situ and remotely-sensed observational data into a series of high-resolution gridded analyses. The ultimate goal for running LDIS is to generate products that may enhance weather nowcasts and short-range (less than 6 h) forecasts issued in support of the 45th Weather Squadron (45 WS), Spaceflight Meteorology Group (SMG), and the Melbourne National Weather Service (NWS MLB) operational requirements. LDIS has the potential to provide added value for nowcasts and short-ten-n forecasts for two reasons. First, it incorporates all data operationally available in east central Florida. Second, it is run at finer spatial and temporal resolutions than current national-scale operational models such as the Rapid Update Cycle and Eta models. LDIS combines all available data to produce grid analyses of primary variables (wind, temperature, etc.) at specified temporal and spatial resolutions. These analyses of primary variables can be used to compute diagnostic quantities such as vorticity and divergence. This paper demonstrates the utility of LDIS over east central Florida for a warm season case study. The evolution of a significant thunderstorm outflow boundary is depicted through horizontal and vertical cross section plots of wind speed, divergence, and circulation. In combination with a suitable visualization too], LDIS may provide users with a more complete and comprehensive understanding of evolving mesoscale weather than could be developed by individually examining the disparate data sets over the same area and time.
Integrated care in the daily work: coordination beyond organisational boundaries.
Petrakou, Alexandra
2009-07-09
In this paper, integrated care in an inter-organisational cooperative setting of in-home elderly care is studied. The aim is to explore how home care workers coordinate their daily work, identify coordination issues in situ and discuss possible actions for supporting seamless and integrated elderly care at home. The empirical findings are drawn from an ethnographic workplace study of the cooperation and coordination taking place between home care workers in a Swedish county. Data were collected through observational studies, interviews and group discussions. The paper identifies a need to support two core issues. Firstly, it must be made clear how the care interventions that are currently defined as 'self-treatment' by the home health care should be divided. Secondly, the distributed and asynchronous coordination between all care workers involved, regardless of organisational belonging must be better supported. Integrated care needs to be developed between organisations as well as within each organisation. As a matter of fact, integrated care needs to be built up beyond organisational boundaries. Organisational boundaries affect the planning of the division of care interventions, but not the coordination during the home care process. During the home care process, the main challenge is the coordination difficulties that arise from the fact that workers are distributed in time and/or space, regardless of organisational belonging. A core subject for future practice and research is to develop IT tools that reach beyond formal organisational boundaries and processes while remaining adaptable in view of future structure changes.
Many-body-localization transition: sensitivity to twisted boundary conditions
NASA Astrophysics Data System (ADS)
Monthus, Cécile
2017-03-01
For disordered interacting quantum systems, the sensitivity of the spectrum to twisted boundary conditions depending on an infinitesimal angle ϕ can be used to analyze the many-body-localization transition. The sensitivity of the energy levels {{E}n}(φ ) is measured by the level curvature {{K}n}=En\\prime \\prime(0) , or more precisely by the Thouless dimensionless curvature {{k}n}={{K}n}/{{ Δ }n} , where {{ Δ }n} is the level spacing that decays exponentially with the size L of the system. For instance {{ Δ }n}\\propto {{2}-L} in the middle of the spectrum of quantum spin chains of L spins, while the Drude weight {{D}n}=L{{K}n} studied recently by Filippone et al (arxiv:1606.07291v1) involves a different rescaling. The sensitivity of the eigenstates |{{\\psi}n}(φ )> is characterized by the susceptibility {χn}=-Fn\\prime \\prime(0) of the fidelity {{F}n}= |<{{\\psi}n}(0)|{{\\psi}n}(φ )>| . Both observables are distributed with probability distributions displaying power-law tails {{P}β}(k)≃ {{A}β}|k{{|}-(2+β )} and Q(χ )≃ {{B}β}{χ-\\frac{3+β{2}}} , where β is the level repulsion index taking the values {β\\text{GOE}}=1 in the ergodic phase and {β\\text{loc}}=0 in the localized phase. The amplitudes {{A}β} and {{B}β} of these two heavy tails are given by some moments of the off-diagonal matrix element of the local current operator between two nearby energy levels, whose probability distribution has been proposed as a criterion for the many-body-localization transition by Serbyn et al (2015 Phys. Rev. X 5 041047).
Defining a boundary in goal localization: Infinite number of points or extended surfaces.
Mou, Weimin; Zhou, Ruojing
2013-07-01
Four experiments examined the roles of extended surfaces and the number of points in the boundary superiority effect in goal localization. Participants learned the locations of 4 objects in the presence of a boundary, landmarks, or both in an immersive virtual environment by reproducing the locations with feedback. Participants then localized the objects in the presence of either the boundary or the landmarks during testing without feedback. The results showed that when both 1 landmark and a circular boundary were presented during learning, localization error during testing increased significantly when only the landmark was presented during testing, whereas localization error did not increase when only the boundary was presented during testing, thus demonstrating a boundary superiority effect. This boundary superiority effect was not observed when 36 landmarks forming a circle and a circular boundary were presented during learning. The landmark superiority effect was observed when 36 landmarks, forming a circular shape, and 1/36th part of the circular boundary were presented during learning. Furthermore, when a varied number of landmarks were presented with a circular boundary during learning, the localization error when the boundary was removed during testing was negatively correlated with the number of the landmarks. These results indicate that the superiority of a circular boundary to a landmark might be due to the larger number of points in the circular boundary but not due to the extended surface of the circular boundary.
Multistep and Multistage Boundary Integral Methods for the Wave Equation
NASA Astrophysics Data System (ADS)
Banjai, Lehel
2009-09-01
We describe how time-discretized wave equation in a homogeneous medium can be solved by boundary integral methods. The time discretization can be a multistep, Runge-Kutta, or a more general multistep-multistage method. The resulting convolutional system of boundary integral equations falls in the family of convolution quadratures of Ch. Lubich. In this work our aim is to discuss a new technique for efficiently solving the discrete convolutional system and to present large scale 3D numerical experiments with a wide range of time-discretizations that have up to now not appeared in print. One of the conclusions is that Runge-Kutta methods are often the method of choice even at low accuracy; yet, in connection with hyperbolic problems BDF (backward difference formulas) have been predominant in the literature on convolution quadrature.
Integral analysis of boundary layer flows with pressure gradient
NASA Astrophysics Data System (ADS)
Wei, Tie; Maciel, Yvan; Klewicki, Joseph
2017-09-01
This Rapid Communication investigates boundary layer flows with a pressure gradient using a similarity/integral analysis of the continuity equation and momentum equation in the streamwise direction. The analysis yields useful analytical relations for Ve, the mean wall-normal velocity at the edge of the boundary layer, and for the skin friction coefficient Cf in terms of the boundary layer parameters and in particular βRC, the Rotta-Clauser pressure gradient parameter. The analytical results are compared with experimental and numerical data and are found to be valid. One of the main findings is that for large positive βRC (an important effect of an adverse pressure gradient), the friction coefficient is closely related to βRC as Cf∝1 /βRC , because δ /δ1,δ1/δ2=H , and d δ /d x become approximately constant. Here, δ is the boundary layer thickness, δ1 is the displacement thickness, δ2 is the momentum thickness, and H is the shape factor. Another finding is that the mean wall-normal velocity at the edge of the boundary layer is related to other flow variables as UeVe/uτ2=H +(1 +δ /δ1+H ) βRC , where Ue is the streamwise velocity at the edge of the boundary layer. At zero pressure gradient, this relation reduces to U∞V∞/uτ2=H , as recently derived by Wei and Klewicki [Phys. Rev. Fluids 1, 082401 (2016), 10.1103/PhysRevFluids.1.082401].
Discretization of the Induced-Charge Boundary Integral Equation
Bardhan, Jaydeep P.; Eisenberg, Robert S.; Gillespie, Dirk
2013-01-01
Boundary-element methods (BEM) for solving integral equations numerically have been used in many fields to compute the induced charges at dielectric boundaries. In this paper, we consider a more accurate implementation of BEM in the context of ions in aqueous solution near proteins, but our results are applicable more generally. The ions that modulate protein function are often within a few Angstroms of the protein, which leads to the significant accumulation of polarization charge at the protein/solvent interface. Computing the induced charge accurately and quickly poses a numerical challenge in solving a popular integral equation using BEM. In particular, the accuracy of simulations can depend strongly on seemingly minor details of how the entries of the BEM matrix are calculated. We demonstrate that when the dielectric interface is discretized into flat tiles, the qualocation method of Tausch, Wang, and White (IEEE. Trans. Comput.-Aided Des. 20:1398, 2001) to compute the BEM matrix elements is always more accurate than the traditional centroid collocation method. Qualocation is no more expensive to implement than collocation and can save significant computional time by reducing the number of boundary elements needed to discretize the dielectric interfaces. PMID:19658728
Discretization of the induced-charge boundary integral equation.
Bardhan, J. P.; Eisenberg, R. S.; Gillespie, D.; Rush Univ. Medical Center
2009-07-01
Boundary-element methods (BEMs) for solving integral equations numerically have been used in many fields to compute the induced charges at dielectric boundaries. In this paper, we consider a more accurate implementation of BEM in the context of ions in aqueous solution near proteins, but our results are applicable more generally. The ions that modulate protein function are often within a few angstroms of the protein, which leads to the significant accumulation of polarization charge at the protein-solvent interface. Computing the induced charge accurately and quickly poses a numerical challenge in solving a popular integral equation using BEM. In particular, the accuracy of simulations can depend strongly on seemingly minor details of how the entries of the BEM matrix are calculated. We demonstrate that when the dielectric interface is discretized into flat tiles, the qualocation method of Tausch et al. [IEEE Trans Comput.-Comput.-Aided Des. 20, 1398 (2001)] to compute the BEM matrix elements is always more accurate than the traditional centroid-collocation method. Qualocation is not more expensive to implement than collocation and can save significant computational time by reducing the number of boundary elements needed to discretize the dielectric interfaces.
Application of the boundary integral method to immiscible displacement problems
Masukawa, J.; Horne, R.N.
1988-08-01
This paper presents an application of the boundary integral method (BIM) to fluid displacement problems to demonstrate its usefulness in reservoir simulation. A method for solving two-dimensional (2D), piston-like displacement for incompressible fluids with good accuracy has been developed. Several typical example problems with repeated five-spot patterns were solved for various mobility ratios. The solutions were compared with the analytical solutions to demonstrate accuracy. Singularity programming was found to be a major advantage in handling flow in the vicinity of wells. The BIM was found to be an excellent way to solve immiscible displacement problems. Unlike analytic methods, it can accommodate complex boundary shapes and does not suffer from numerical dispersion at the front.
Boundary layer integral matrix procedure code modifications and verifications
NASA Technical Reports Server (NTRS)
Evans, R. M.; Morse, H. L.
1974-01-01
A summary of modifications to Aerotherm's Boundary Layer Integral Matrix Procedure (BLIMP) code is presented. These modifications represent a preliminary effort to make BLIMP compatible with other JANNAF codes and to adjust the code for specific application to rocket nozzle flows. Results of the initial verification of the code for prediction of rocket nozzle type flows are discussed. For those cases in which measured free stream flow conditions were used as input to the code, the boundary layer predictions and measurements are in excellent agreement. In two cases, with free stream flow conditions calculated by another JANNAF code (TDK) for use as input to BLIMP, the predictions and the data were in fair agreement for one case and in poor agreement for the other case. The poor agreement is believed to result from failure of the turbulent model in BLIMP to account for laminarization of a turbulent flow. Recommendations for further code modifications and improvements are also presented.
Galerkin boundary integral equation method for spontaneous rupture propagation problems
NASA Astrophysics Data System (ADS)
Goto, H.; Bielak, J.
2007-12-01
We develop a Galerkin finite element boundary integral equation method (GaBIEM) for spontaneous rupture propagation problems for a planar fault embedded in a homogeneous full 2D space. A simple 2D anti plane rupture propagation problem, with a slip-weakening friction law, is simulated by the GaBIEM. This method allows one to separate explicitly the kernel into singular static and time-dependent parts, and a nonsingular dynamic component. The simulated results throw light into the performance of the GaBIEM and highlight differences with respect to that of the traditional, collocation, boundary integral equation method (BIEM). The rate of convergence of the GaBIEM, as measured from a root mean square (RMS) analysis of the difference of approximate solutions corresponding to increasingly finer element sizes is of a higher order than that of the BIEM. There is no restriction on the CFL stability number since an implicit, unconditionally stable method is used for the time integration. The error of the approximation increases with the time step, as expected, and it can remain below that of the BIEM.
Application of boundary integral equations to elastoplastic problems
NASA Technical Reports Server (NTRS)
Mendelson, A.; Albers, L. U.
1975-01-01
The application of the boundary integral equation method (BIE) to the elastoplastic torsion problem is considered. It is found that the BIE is very suitable for the elastoplastic analysis of the torsion of prismatic bars. A comparison of the BIE with the finite difference method shows savings for the BIE concerning the number of unknowns which have to be determined and also a much faster convergence rate. Attention is given to the problem of an edge-notched beam in pure bending, taking into account a biharmonic formulation and a displacement formulation.
A boundary integral formalism for stochastic ray tracing in billiards
Chappell, David J.; Tanner, Gregor
2014-12-15
Determining the flow of rays or non-interacting particles driven by a force or velocity field is fundamental to modelling many physical processes. These include particle flows arising in fluid mechanics and ray flows arising in the geometrical optics limit of linear wave equations. In many practical applications, the driving field is not known exactly and the dynamics are determined only up to a degree of uncertainty. This paper presents a boundary integral framework for propagating flows including uncertainties, which is shown to systematically interpolate between a deterministic and a completely random description of the trajectory propagation. A simple but efficient discretisation approach is applied to model uncertain billiard dynamics in an integrable rectangular domain.
On a problem for wave equation with local data on the whole boundary
NASA Astrophysics Data System (ADS)
Yessirkegenov, Nurgisa
2016-12-01
In the current paper we propose a new formulation of a local boundary value problem for a one-dimensional wave equation in a rectangular domain in which boundary conditions are given on the whole boundary. We prove the well-posedness of the boundary value problem in the classical and generalized senses. The proof of the well-posedness of the formulated problem is reduced to question of the existence and uniqueness of solutions of the corresponding functional equations.
Boundary integral equation method for electromagnetic and elastic waves
NASA Astrophysics Data System (ADS)
Chen, Kun
In this thesis, the boundary integral equation method (BIEM) is studied and applied to electromagnetic and elastic wave problems. First of all, a spectral domain BIEM called the spectral domain approach is employed for full wave analysis of metal strip grating on grounded dielectric slab (MSG-GDS) and microstrips shielded with either perfect electric conductor (PEC) or perfect magnetic conductor (PMC) walls. The modal relations between these structures are revealed by exploring their symmetries. It is derived analytically and validated numerically that all the even and odd modes of the latter two (when they are mirror symmetric) find their correspondence in the modes of metal strip grating on grounded dielectric slab when the phase shift between adjacent two unit cells is 0 or pi. Extension to non-symmetric case is also made. Several factors, including frequency, grating period, slab thickness and strip width, are further investigated for their impacts on the effective permittivity of the dominant mode of PEC/PMC shielded microstrips. It is found that the PMC shielded microstrip generally has a larger wave number than the PEC shielded microstrip. Secondly, computational aspects of the layered medim doubly periodic Green's function (LMDPGF) in matrix-friendly formulation (MFF) are investigated. The MFF for doubly periodic structures in layered medium is derived, and the singularity of the periodic Green's function when the transverse wave number equals zero in this formulation is analytically extracted. A novel approach is proposed to calculate the LMDPGF, which makes delicate use of several techniques including factorization of the Green's function, generalized pencil of function (GPOF) method and high order Taylor expansion to derive the high order asymptotic expressions, which are then evaluated by newly derived fast convergent series. This approach exhibits robustness, high accuracy and fast and high order convergence; it also allows fast frequency sweep for
Defining a Boundary in Goal Localization: Infinite Number of Points or Extended Surfaces
ERIC Educational Resources Information Center
Mou, Weimin; Zhou, Ruojing
2013-01-01
Four experiments examined the roles of extended surfaces and the number of points in the boundary superiority effect in goal localization. Participants learned the locations of 4 objects in the presence of a boundary, landmarks, or both in an immersive virtual environment by reproducing the locations with feedback. Participants then localized the…
A spectral boundary integral method for flowing blood cells
NASA Astrophysics Data System (ADS)
Zhao, Hong; Isfahani, Amir H. G.; Olson, Luke N.; Freund, Jonathan B.
2010-05-01
A spectral boundary integral method for simulating large numbers of blood cells flowing in complex geometries is developed and demonstrated. The blood cells are modeled as finite-deformation elastic membranes containing a higher viscosity fluid than the surrounding plasma, but the solver itself is independent of the particular constitutive model employed for the cell membranes. The surface integrals developed for solving the viscous flow, and thereby the motion of the massless membrane, are evaluated using an O(NlogN) particle-mesh Ewald (PME) approach. The cell shapes, which can become highly distorted under physiologic conditions, are discretized with spherical harmonics. The resolution of these global basis functions is, of course, excellent, but more importantly they facilitate an approximate de-aliasing procedure that stabilizes the simulations without adding any numerical dissipation or further restricting the permissible numerical time step. Complex geometry no-slip boundaries are included using a constraint method that is coupled into an implicit system that is solved as part of the time advancement routine. The implementation is verified against solutions for axisymmetric flows reported in the literature, and its accuracy is demonstrated by comparison against exact solutions for relaxing surface deformations. It is also used to simulate flow of blood cells at 30% volume fraction in tubes between 4.9 and 16.9 μm in diameter. For these, it is shown to reproduce the well-known non-monotonic dependence of the effective viscosity on the tube diameter.
The Boundary/Pedestal Integrated Science Application for FSP
Rognlien, T. D.; Snyder, P. B.
2011-06-17
This Integrated Science Application (ISA) represents a combination of the former Integrated Boundary and Pedestal Science Drivers carried out over the last year as part of the Fusion Simulation Program’s planning phase. Those Science Driver plans, as well as four others, can be viewed on the website (http://fspscidri.web.lehigh.edu/index.php/Main_Page). The Boundary Science Driver report is also available as LLNL document LLNL-TR-471260. The plans described in those documents assumed ample resources would be available. This document represents a plan of vital importance for developing powerful simulation tools for magnetic fusion energy devices, but is of substantially less scope than the original Science Drivers because of budget limitations and the fact that here two Science Drivers are merged owing to the close proximity of the two regions that they model: (1) the warm plasma region known as the scrapeoff layer (SOL) where magnetic field lines directly contact material structures together with the associate plasma-wall interactions and (2) the adjacent hotter plasma region know as the pedestal, which is the beginning of the confining closed magnetic field line core.
Integrated program designed for local governments.
1993-01-01
Local Philippine governments are required under the 1991 Local Government Code to plan and manage their own health and nutrition programs. In response to their requests, the Municipal Integrated Nutrition Program (MINP) is being developed. This program will integrate the local efforts of the following national nutrition programs: the Teacher-Child-Parent Approach of the Department of Education, Culture, and Sports; the Community-Based Planning and Management of Nutrition Programs of the Department of Health; the Early Childhood Enrichment Program of the Department of Social welfare and Development; and the Bio-Intensive Gardening for Home/Community Food Security of the Department of Agriculture. The Nutrition Center of the Philippines (NCP) has assisted in the development, testing, and evaluation of the MINP. In 1993, MINP models will begin in 1 or 2 barangays in Carmen, Cebu; Hilongos, Leyte; and Dapitan City in Zamboanga del Norte. NCP will provide program materials and technical assistance. Modeling activities will include advocating to local government units; designing and installing nutrition planning capability via planning workshops; packaging of program requirements and costs; designing a strategy to mobilize resources; facilitating purchase, delivery, and payment of program requirements; facilitating and coordinating training; designing and installing a monitoring and evaluation system; and documenting and disseminating. Local government officials, technical government agencies, nongovernment organizations, and private entities will work together.
Shen, Hui-min; Lee, Kok-Meng; Hu, Liang; Foong, Shaohui; Fu, Xin
2016-01-01
Localization of active neural source (ANS) from measurements on head surface is vital in magnetoencephalography. As neuron-generated magnetic fields are extremely weak, significant uncertainties caused by stochastic measurement interference complicate its localization. This paper presents a novel computational method based on reconstructed magnetic field from sparse noisy measurements for enhanced ANS localization by suppressing effects of unrelated noise. In this approach, the magnetic flux density (MFD) in the nearby current-free space outside the head is reconstructed from measurements through formulating the infinite series solution of the Laplace's equation, where boundary condition (BC) integrals over the entire measurements provide "smooth" reconstructed MFD with the decrease in unrelated noise. Using a gradient-based method, reconstructed MFDs with good fidelity are selected for enhanced ANS localization. The reconstruction model, spatial interpolation of BC, parametric equivalent current dipole-based inverse estimation algorithm using reconstruction, and gradient-based selection are detailed and validated. The influences of various source depths and measurement signal-to-noise ratio levels on the estimated ANS location are analyzed numerically and compared with a traditional method (where measurements are directly used), and it was demonstrated that gradient-selected high-fidelity reconstructed data can effectively improve the accuracy of ANS localization.
de Munck, J C
1992-09-01
A method is presented to compute the potential distribution on the surface of a homogeneous isolated conductor of arbitrary shape. The method is based on an approximation of a boundary integral equation as a set linear algebraic equations. The potential is described as a piecewise linear or quadratic function. The matrix elements of the discretized equation are expressed as analytical formulas.
The Application of a Boundary Integral Equation Method to the Prediction of Ducted Fan Engine Noise
NASA Technical Reports Server (NTRS)
Dunn, M. H.; Tweed, J.; Farassat, F.
1999-01-01
The prediction of ducted fan engine noise using a boundary integral equation method (BIEM) is considered. Governing equations for the BIEM are based on linearized acoustics and describe the scattering of incident sound by a thin, finite-length cylindrical duct in the presence of a uniform axial inflow. A classical boundary value problem (BVP) is derived that includes an axisymmetric, locally reacting liner on the duct interior. Using potential theory, the BVP is recast as a system of hypersingular boundary integral equations with subsidiary conditions. We describe the integral equation derivation and solution procedure in detail. The development of the computationally efficient ducted fan noise prediction program TBIEM3D, which implements the BIEM, and its utility in conducting parametric noise reduction studies are discussed. Unlike prediction methods based on spinning mode eigenfunction expansions, the BIEM does not require the decomposition of the interior acoustic field into its radial and axial components which, for the liner case, avoids the solution of a difficult complex eigenvalue problem. Numerical spectral studies are presented to illustrate the nexus between the eigenfunction expansion representation and BIEM results. We demonstrate BIEM liner capability by examining radiation patterns for several cases of practical interest.
Inclusion of Separation in Integral Boundary Layer Methods
NASA Astrophysics Data System (ADS)
Wallace, Brodie; O'Neill, Charles
2016-11-01
An integral boundary layer (IBL) method coupled with a potential flow solver quickly allows simulating aerodynamic flows, allowing for aircraft geometries to be rapidly designed and optimized. However, most current IBL methods lack the ability to accurately model three-dimensional separated flows. Various IBL equations and closure relations were investigated in an effort to develop an IBL capable of modeling separation. Solution techniques, including a Newton's method and the inverse matrix solving program GMRES, as well as methods for coupling an IBL with a potential flow solver were also investigated. Results for two-dimensional attached flow as well as methods for expanding an IBL to model three-dimensional separation are presented. Funding from NSF REU site Grant EEC 1358991 is greatly appreciated.
Thermal Momentum Distribution from Path Integrals with Shifted Boundary Conditions
NASA Astrophysics Data System (ADS)
Giusti, Leonardo; Meyer, Harvey B.
2011-04-01
For a thermal field theory formulated in the grand canonical ensemble, the distribution of the total momentum is an observable characterizing the thermal state. We show that its cumulants are related to thermodynamic potentials. In a relativistic system, for instance, the thermal variance of the total momentum is a direct measure of the enthalpy. We relate the generating function of the cumulants to the ratio of (a) a partition function expressed as a Matsubara path integral with shifted boundary conditions in the compact direction and (b) the ordinary partition function. In this form the generating function is well suited for Monte Carlo evaluation, and the cumulants can be extracted straightforwardly. We test the method in the SU(3) Yang-Mills theory and obtain the entropy density at three different temperatures.
A Fast Spectral Galerkin Method for Hypersingular Boundary Integral Equations in Potential Theory
Nintcheu Fata, Sylvain; Gray, Leonard J
2009-01-01
This research is focused on the development of a fast spectral method to accelerate the solution of three-dimensional hypersingular boundary integral equations of potential theory. Based on a Galerkin approximation, the Fast Fourier Transform and local interpolation operators, the proposed method is a generalization of the Precorrected-FFT technique to deal with double-layer potential kernels, hypersingular kernels and higher-order basis functions. Numerical examples utilizing piecewise linear shape functions are included to illustrate the performance of the method.
NASA Astrophysics Data System (ADS)
Belov, A. A.; Igumnov, L. A.; Litvinchuk, S. Yu.; Metrikin, V. S.
2016-11-01
Two approaches (classical and nonclassical) of the boundary integral equation method for solving three-dimensional dynamical boundary value problems of elasticity, viscoelasticity, and poroelasticity are considered. The boundary integral equation model is used for porous materials. The Kelvin-Voigt model and the weakly singular hereditary Abel kernel are used to describe the viscoelastic properties. Both approaches permit solving the dynamic problems exactly not only in the isotropic but also in the anisotropic case. The boundary integral equation solution scheme is constructed on the basis of the boundary element technique. The numerical results obtained by the classical and nonclassical approaches are compared.
Maintaining a Cognitive Map in Darkness: The Need to Fuse Boundary Knowledge with Path Integration
Cheung, Allen; Ball, David; Milford, Michael; Wyeth, Gordon; Wiles, Janet
2012-01-01
Spatial navigation requires the processing of complex, disparate and often ambiguous sensory data. The neurocomputations underpinning this vital ability remain poorly understood. Controversy remains as to whether multimodal sensory information must be combined into a unified representation, consistent with Tolman's “cognitive map”, or whether differential activation of independent navigation modules suffice to explain observed navigation behaviour. Here we demonstrate that key neural correlates of spatial navigation in darkness cannot be explained if the path integration system acted independently of boundary (landmark) information. In vivo recordings demonstrate that the rodent head direction (HD) system becomes unstable within three minutes without vision. In contrast, rodents maintain stable place fields and grid fields for over half an hour without vision. Using a simple HD error model, we show analytically that idiothetic path integration (iPI) alone cannot be used to maintain any stable place representation beyond two to three minutes. We then use a measure of place stability based on information theoretic principles to prove that featureless boundaries alone cannot be used to improve localization above chance level. Having shown that neither iPI nor boundaries alone are sufficient, we then address the question of whether their combination is sufficient and – we conjecture – necessary to maintain place stability for prolonged periods without vision. We addressed this question in simulations and robot experiments using a navigation model comprising of a particle filter and boundary map. The model replicates published experimental results on place field and grid field stability without vision, and makes testable predictions including place field splitting and grid field rescaling if the true arena geometry differs from the acquired boundary map. We discuss our findings in light of current theories of animal navigation and neuronal computation, and
Maintaining a cognitive map in darkness: the need to fuse boundary knowledge with path integration.
Cheung, Allen; Ball, David; Milford, Michael; Wyeth, Gordon; Wiles, Janet
2012-01-01
Spatial navigation requires the processing of complex, disparate and often ambiguous sensory data. The neurocomputations underpinning this vital ability remain poorly understood. Controversy remains as to whether multimodal sensory information must be combined into a unified representation, consistent with Tolman's "cognitive map", or whether differential activation of independent navigation modules suffice to explain observed navigation behaviour. Here we demonstrate that key neural correlates of spatial navigation in darkness cannot be explained if the path integration system acted independently of boundary (landmark) information. In vivo recordings demonstrate that the rodent head direction (HD) system becomes unstable within three minutes without vision. In contrast, rodents maintain stable place fields and grid fields for over half an hour without vision. Using a simple HD error model, we show analytically that idiothetic path integration (iPI) alone cannot be used to maintain any stable place representation beyond two to three minutes. We then use a measure of place stability based on information theoretic principles to prove that featureless boundaries alone cannot be used to improve localization above chance level. Having shown that neither iPI nor boundaries alone are sufficient, we then address the question of whether their combination is sufficient and--we conjecture--necessary to maintain place stability for prolonged periods without vision. We addressed this question in simulations and robot experiments using a navigation model comprising of a particle filter and boundary map. The model replicates published experimental results on place field and grid field stability without vision, and makes testable predictions including place field splitting and grid field rescaling if the true arena geometry differs from the acquired boundary map. We discuss our findings in light of current theories of animal navigation and neuronal computation, and elaborate on
Control of a shock wave-boundary layer interaction using localized arc filament plasma actuators
NASA Astrophysics Data System (ADS)
Webb, Nathan Joseph
Supersonic flight is currently possible, but expensive. Inexpensive supersonic travel will require increased efficiency of high-speed air entrainment, an integral part of air-breathing propulsion systems. Although mixed compression inlet geometry can significantly improve entrainment efficiency, numerous Shock Wave-Boundary Layer Interactions (SWBLIs) are generated in this configuration. The boundary layer must therefore develop through multiple regions of adverse pressure gradient, causing it to thicken, and, in severe cases, separate. The associated increase in unsteadiness can have adverse effects on downstream engine hardware. The most severe consequence of these interactions is the increased aerodynamic blockage generated by the thickened boundary layer. If the increase is sufficient, it can choke the flow, causing inlet unstart, and resulting in a loss of thrust and high transient forces on the engine, airframe, and aircraft occupants. The potentially severe consequences associated with SWBLIs require flow control to ensure proper operation. Traditionally, boundary layer bleed has been used to control the interaction. Although this method is effective, it has inherent efficiency penalties. Localized Arc Filament Plasma Actuators (LAFPAs) are designed to generate perturbations for flow control. Natural flow instabilities act to amplify certain perturbations, allowing the LAFPAs to control the flow with minimal power input. LAFPAs also have the flexibility to maintain control over a variety of operating conditions. This work seeks to examine the effectiveness of LAFPAs as a separation control method for an oblique, impinging SWBLI. The low frequency unsteadiness in the reflected shock was thought to be the natural manifestation of a Kelvin-Helmholtz instability in the shear layer above the separation region. The LAFPAs were therefore placed upstream of the interaction to allow their perturbations to convect to the receptivity region (near the shear layer origin
Erlikhman, Gennady; Kellman, Philip J.
2016-01-01
Spatiotemporal boundary formation (SBF) is the perception of illusory boundaries, global form, and global motion from spatially and temporally sparse transformations of texture elements (Shipley and Kellman, 1993a, 1994; Erlikhman and Kellman, 2015). It has been theorized that the visual system uses positions and times of element transformations to extract local oriented edge fragments, which then connect by known interpolation processes to produce larger contours and shapes in SBF. To test this theory, we created a novel display consisting of a sawtooth arrangement of elements that disappeared and reappeared sequentially. Although apparent motion along the sawtooth would be expected, with appropriate spacing and timing, the resulting percept was of a larger, moving, illusory bar. This display approximates the minimal conditions for visual perception of an oriented edge fragment from spatiotemporal information and confirms that such events may be initiating conditions in SBF. Using converging objective and subjective methods, experiments showed that edge formation in these displays was subject to a temporal integration constraint of ~80 ms between element disappearances. The experiments provide clear support for models of SBF that begin with extraction of local edge fragments, and they identify minimal conditions required for this process. We conjecture that these results reveal a link between spatiotemporal object perception and basic visual filtering. Motion energy filters have usually been studied with orientation given spatially by luminance contrast. When orientation is not given in static frames, these same motion energy filters serve as spatiotemporal edge filters, yielding local orientation from discrete element transformations over time. As numerous filters of different characteristic orientations and scales may respond to any simple SBF stimulus, we discuss the aperture and ambiguity problems that accompany this conjecture and how they might be resolved
Numerical algorithm for the third-order partial differential equation with local boundary conditions
NASA Astrophysics Data System (ADS)
Ashyralyev, Allaberen; Belakroum, Kheireddine; Guezane-Lakoud, Assia
2017-09-01
Three-step difference schemes generated by Taylor's decomposition on four points for the approximate solution of the local boundary-value problems for a third order partial differential equation are presented. Results of numerical experiments are provided.
Boundary Ambiguity in Parents with Chronically Ill Children: Integrating Theory and Research
ERIC Educational Resources Information Center
Berge, Jerica M.; Holm, Kristen E.
2007-01-01
This article integrates theory and research related to boundary ambiguity in parents of children with a chronic health condition. We propose that boundary ambiguity is a risk factor for psychological distress in these parents. Clinical applications and a case example highlight how boundary ambiguity can be assessed and managed in clinical settings…
Boundary diffraction wave integrals for diffraction modeling of external occulters.
Cady, Eric
2012-07-02
An occulter is a large diffracting screen which may be flown in conjunction with a telescope to image extrasolar planets. The edge is shaped to minimize the diffracted light in a region beyond the occulter, and a telescope may be placed in this dark shadow to view an extrasolar system with the starlight removed. Errors in position, orientation, and shape of the occulter will diffract additional light into this region, and a challenge of modeling an occulter system is to accurately and quickly model these effects. We present a fast method for the calculation of electric fields following an occulter, based on the concept of the boundary diffraction wave: the 2D structure of the occulter is reduced to a 1D edge integral which directly incorporates the occulter shape, and which can be easily adjusted to include changes in occulter position and shape, as well as the effects of sources-such as exoplanets-which arrive off-axis to the occulter. The structure of a typical implementation of the algorithm is included.
A time-domain finite element boundary integral approach for elastic wave scattering
NASA Astrophysics Data System (ADS)
Shi, F.; Lowe, M. J. S.; Skelton, E. A.; Craster, R. V.
2017-08-01
The response of complex scatterers, such as rough or branched cracks, to incident elastic waves is required in many areas of industrial importance such as those in non-destructive evaluation and related fields; we develop an approach to generate accurate and rapid simulations. To achieve this we develop, in the time domain, an implementation to efficiently couple the finite element (FE) method within a small local region, and the boundary integral (BI) globally. The FE explicit scheme is run in a local box to compute the surface displacement of the scatterer, by giving forcing signals to excitation nodes, which can lie on the scatterer itself. The required input forces on the excitation nodes are obtained with a reformulated FE equation, according to the incident displacement field. The surface displacements computed by the local FE are then projected, through time-domain BI formulae, to calculate the scattering signals with different modes. This new method yields huge improvements in the efficiency of FE simulations for scattering from complex scatterers. We present results using different shapes and boundary conditions, all simulated using this approach in both 2D and 3D, and then compare with full FE models and theoretical solutions to demonstrate the efficiency and accuracy of this numerical approach.
Integrable boundary value problems for elliptic type Toda lattice in a disk
Guerses, Metin; Habibullin, Ismagil; Zheltukhin, Kostyantyn
2007-10-15
The concept of integrable boundary value problems for soliton equations on R and R{sub +} is extended to regions enclosed by smooth curves. Classes of integrable boundary conditions in a disk for the Toda lattice and its reductions are found.
Boundary integral approach for propagating interfaces in a binary non-isothermal mixture
NASA Astrophysics Data System (ADS)
Alexandrov, D. V.; Galenko, P. K.
2017-03-01
A method based on boundary integral approach to the propagation of curved phase interface in a binary non-isothermal mixture is developed. Previously known equations and solutions for thermally controlled growth and needle-like dendrites follow from the obtained boundary integral equations as limiting cases.
Application of boundary integral method to elastic analysis of V-notched beams
NASA Technical Reports Server (NTRS)
Rzasnicki, W.; Mendelson, A.; Albers, L. U.
1973-01-01
A semidirect boundary integral method, using Airy's stress function and its derivatives in Green's boundary integral formula, is used to obtain an accurate numerical solution for elastic stress and strain fields in V-notched beams in pure bending. The proper choice of nodal spacing on the boundary is shown to be necessary to achieve an accurate stress field in the vicinity of the tip of the notch. Excellent agreement is obtained with the results of the collocation method of solution.
Piloting and Path Integration within and across Boundaries
ERIC Educational Resources Information Center
Mou, Weimin; Wang, Lin
2015-01-01
Three experiments investigated whether navigation is less efficient across boundaries than within boundaries. In an immersive virtual environment, participants learned objects' locations in a large room or a small room. Participants then pointed to the objects' original locations after physically walking a circuitous path without vision.…
Piloting and Path Integration within and across Boundaries
ERIC Educational Resources Information Center
Mou, Weimin; Wang, Lin
2015-01-01
Three experiments investigated whether navigation is less efficient across boundaries than within boundaries. In an immersive virtual environment, participants learned objects' locations in a large room or a small room. Participants then pointed to the objects' original locations after physically walking a circuitous path without vision.…
NASA Astrophysics Data System (ADS)
Ginzburg, Irina; Roux, Laetitia; Silva, Goncalo
2015-10-01
This work demonstrates that in advection-diffusion Lattice Boltzmann schemes, the local mass-conserving boundary rules, such as bounce-back and local specular reflection, may modify the transport coefficients predicted by the Chapman-Enskog expansion when they enforce to zero not only the normal, but also the tangential boundary flux. In order to accommodate it to the bulk solution, the system develops a Knudsen-layer correction to the non-equilibrium part of the population solution. Two principal secondary effects-(i) decrease in the diffusion coefficient, and (ii) retardation of the average advection velocity, obtained in a closed analytical form, are proportional, respectively, to freely assigned diagonal weights for equilibrium mass and velocity terms. In addition, due to their transverse velocity gradients, the boundary layers affect the longitudinal diffusion coefficient similarly to Taylor dispersion, as they grow as the square of the Péclet number. These numerical artifacts can be eliminated or reduced by a proper space distribution of the free-tunable collision eigenvalue in two-relaxation-time schemes.
Seismological evidence for a localized mushy zone at the Earth's inner core boundary.
Tian, Dongdong; Wen, Lianxing
2017-08-01
Although existence of a mushy zone in the Earth's inner core has been hypothesized several decades ago, no seismic evidence has ever been reported. Based on waveform modeling of seismic compressional waves that are reflected off the Earth's inner core boundary, here we present seismic evidence for a localized 4-8 km thick zone across the inner core boundary beneath southwest Okhotsk Sea with seismic properties intermediate between those of the inner and outer core and of a mushy zone. Such a localized mushy zone is found to be surrounded by a sharp inner core boundary nearby. These seismic results suggest that, in the current thermo-compositional state of the Earth's core, the outer core composition is close to eutectic in most regions resulting in a sharp inner core boundary, but deviation from the eutectic composition exists in some localized regions resulting in a mushy zone with a thickness of 4-8 km.The existence of a mushy zone in the Earth's inner core has been suggested, but has remained unproven. Here, the authors have discovered a 4-8 km thick mushy zone at the inner core boundary beneath the Okhotsk Sea, indicating that there may be more localized mushy zones at the inner core boundary.
NASA Technical Reports Server (NTRS)
Evans, R. M.
1975-01-01
Accurate predictions of the thrust loss due to boundary layer effects and of the wall heat flux are very important to the design and performance evaluation of rocket nozzles. A method used in analytical procedures for liquid fuel rocket engine performance prediction and evaluation is presented. A computer program is examined that is a fast and accurate procedure for solving the set of boundary layer equation (momentum, energy, and species) for laminar or turbulent, chemically reacting flows with a wide variety of boundary conditions. Results of comparison of the various turbulent models are presented. A summary of the modifications and additions to the program is examined.
A non-local free boundary problem arising in a theory of financial bubbles
Berestycki, Henri; Monneau, Regis; Scheinkman, José A.
2014-01-01
We consider an evolution non-local free boundary problem that arises in the modelling of speculative bubbles. The solution of the model is the speculative component in the price of an asset. In the framework of viscosity solutions, we show the existence and uniqueness of the solution. We also show that the solution is convex in space, and establish several monotonicity properties of the solution and of the free boundary with respect to parameters of the problem. To study the free boundary, we use, in particular, the fact that the odd part of the solution solves a more standard obstacle problem. We show that the free boundary is and describe the asymptotics of the free boundary as c, the cost of transacting the asset, goes to zero. PMID:25288815
NASA Astrophysics Data System (ADS)
Biglar, M.; Stachowicz, F.; Trzepiecinski, T.; Gromada, M.
2017-02-01
Recent experiments on polycrystalline materials show that microcrystalline materials have a strong dependency ona grain size. In this study, mechanical and electrical properties of polycrystalline materials in micro level were studied by using averaging theorems. To completely understand the size-dependency of polycrystalline materials, an integral non-local approach that can predict the stress-strain relations for these materials was presented. In microcrystalline materials, crystalline and grain-boundary were considered as two separate phases. Mechanical properties of the crystalline phase were modelled using crystalline brittle material and is composed of randomly distributed and orientated single crystal anisotropic elastic grains. For microcrystalline materials, the surface-to-volume ratio of the grain boundaries is low enough to ignore its contribution to the elastic deformation. Therefore, the grain boundary phase was not considered in microcrystalline materials and mechanical properties of the crystalline phase were modelled using appropriate integral non-local approach. Finally, the constitutive equations for polycrystalline materials were implemented into a boundary integral equation and the results and some examples are provided for piezoelectric ceramic.
Observation of spin-charge separation and boundary bound states via the local density of states
NASA Astrophysics Data System (ADS)
Schoenauer, Benedikt; Schmitteckert, Peter; Schuricht, Dirk
2017-05-01
We numerically calculate the local density of states (LDOS) of a one-dimensional Mott insulator with open boundaries, which is modelled microscopically by a (extended) Hubbard chain at half filling. In the Fourier transform of the LDOS we identify several dispersing features corresponding to propagating charge and spin degrees of freedom, thus providing a visualization of the spin-charge separation in the system. We also consider the effect of an additional boundary potential, which, if sufficiently strong, leads to the formation of a boundary bound state which is clearly visible in the LDOS as a nondispersing feature inside the Mott gap.
High order local absorbing boundary conditions for acoustic waves in terms of farfield expansions
NASA Astrophysics Data System (ADS)
Villamizar, Vianey; Acosta, Sebastian; Dastrup, Blake
2017-03-01
We devise a new high order local absorbing boundary condition (ABC) for radiating problems and scattering of time-harmonic acoustic waves from obstacles of arbitrary shape. By introducing an artificial boundary S enclosing the scatterer, the original unbounded domain Ω is decomposed into a bounded computational domain Ω- and an exterior unbounded domain Ω+. Then, we define interface conditions at the artificial boundary S, from truncated versions of the well-known Wilcox and Karp farfield expansion representations of the exact solution in the exterior region Ω+. As a result, we obtain a new local absorbing boundary condition (ABC) for a bounded problem on Ω-, which effectively accounts for the outgoing behavior of the scattered field. Contrary to the low order absorbing conditions previously defined, the error at the artificial boundary induced by this novel ABC can be easily reduced to reach any accuracy within the limits of the computational resources. We accomplish this by simply adding as many terms as needed to the truncated farfield expansions of Wilcox or Karp. The convergence of these expansions guarantees that the order of approximation of the new ABC can be increased arbitrarily without having to enlarge the radius of the artificial boundary. We include numerical results in two and three dimensions which demonstrate the improved accuracy and simplicity of this new formulation when compared to other absorbing boundary conditions.
Fast Integration of One-Dimensional Boundary Value Problems
NASA Astrophysics Data System (ADS)
Campos, Rafael G.; Ruiz, Rafael García
2013-11-01
Two-point nonlinear boundary value problems (BVPs) in both unbounded and bounded domains are solved in this paper using fast numerical antiderivatives and derivatives of functions of L2(-∞, ∞). This differintegral scheme uses a new algorithm to compute the Fourier transform. As examples we solve a fourth-order two-point boundary value problem (BVP) and compute the shape of the soliton solutions of a one-dimensional generalized Korteweg-de Vries (KdV) equation.
NASA Astrophysics Data System (ADS)
Geng, Weihua
2013-05-01
In this paper, we present a parallel higher-order boundary integral method to solve the linear Poisson-Boltzmann (PB) equation. In our method, a well-posed boundary integral formulation is used to ensure the fast convergence of Krylov subspace linear solver such as GMRES. The molecular surfaces are first discretized with flat triangles and then converted to curved triangles with the assistance of normal information at vertices. To maintain the desired accuracy, four-point Gauss-Radau quadratures are used on regular triangles and sixteen-point Gauss-Legendre quadratures together with regularization transformations are applied on singular triangles. To speed up our method, we take advantage of the embarrassingly parallel feature of boundary integral formulation, and parallelize the schemes with the message passing interface (MPI) implementation. Numerical tests show significantly improved accuracy and convergence of the proposed higher-order boundary integral Poisson-Boltzmann (HOBI-PB) solver compared with boundary integral PB solver using often-seen centroid collocation on flat triangles. The higher-order accuracy results achieved by present method are important to sensitive solvation analysis of biomolecules, particularly when accurate electrostatic surface potentials are critical in the molecular simulation. In addition, the higher-order boundary integral schemes presented here and their associated parallelization potentially can be applied to solving boundary integral equations in a general sense.
Inviscid/Boundary-Layer Aeroheating Approach for Integrated Vehicle Design
NASA Technical Reports Server (NTRS)
Lee, Esther; Wurster, Kathryn E.
2017-01-01
A typical entry vehicle design depends on the synthesis of many essential subsystems, including thermal protection system (TPS), structures, payload, avionics, and propulsion, among others. The ability to incorporate aerothermodynamic considerations and TPS design into the early design phase is crucial, as both are closely coupled to the vehicle's aerodynamics, shape and mass. In the preliminary design stage, reasonably accurate results with rapid turn-representative entry envelope was explored. Initial results suggest that for Mach numbers ranging from 9-20, a few inviscid solutions could reasonably sup- port surface heating predictions at Mach numbers variation of +/-2, altitudes variation of +/-10 to 20 kft, and angle-of-attack variation of +/- 5. Agreement with Navier-Stokes solutions was generally found to be within 10-15% for Mach number and altitude, and 20% for angle of attack. A smaller angle-of-attack increment than the 5 deg around times for parametric studies and quickly evolving configurations are necessary to steer design decisions. This investigation considers the use of an unstructured 3D inviscid code in conjunction with an integral boundary-layer method; the former providing the flow field solution and the latter the surface heating. Sensitivity studies for Mach number, angle of attack, and altitude, examine the feasibility of using this approach to populate a representative entry flight envelope based on a limited set of inviscid solutions. Each inviscid solution is used to generate surface heating over the nearby trajectory space. A subset of a considered in this study is recommended. Results of the angle-of-attack sensitivity studies show that smaller increments may be needed for better heating predictions. The approach is well suited for application to conceptual multidisciplinary design and analysis studies where transient aeroheating environments are critical for vehicle TPS and thermal design. Concurrent prediction of aeroheating
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
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.
Applications of boundary theory to the concept of service integration in the human services.
Halley, A A
1997-01-01
Service integration (SI) is an aspect of theorizing about organizations and governance. To discover questions for future practice and theory-building, the analysis here reframes the SI concept in the human services from the typical starting point of fragmentation-integration to the imperatives of boundary theory. Extant SI discourse is a confused array of descriptive, normative, and explanatory theory. An action-reflection interplay with conflicting and missing values is revealed. Boundary spanning and boundarylessness, defined in five metaphors, illustrate boundary theory. Selected literature on SI in the human services is translated into boundary theory (e.g., types of SI boundaries, SI boundary values and roles) and a research agenda is posed.
Shear flow beneath oceanic plates - Local nonsimilarity boundary layers for olivine rheology
NASA Technical Reports Server (NTRS)
Yuen, D. A.; Tovish, A.; Schubert, G.
1978-01-01
The principle of local similarity, which has been used to model the two-dimensional boundary layers in the oceanic upper mantle, permits calculation of the temperature, velocity, and stress fields with essentially analytic techniques. Finite difference numerical methods are hard pressed to resolve the detail required by the large variation of viscosity between the lithosphere and the asthenosphere. In this paper the local similarity approximation has been justified by quantitatively evaluating the effect of nonsimilarity due to viscous heating, nonlinear temperature- and pressure-dependent rheology, buoyancy, adiabatic cooling, etc. Nonsimilar effects produce only small modifications of the locally similar boundary layers; important geophysical observables such as surface heat flux and ocean floor topography are given to better than 10 percent by the locally similar solution. A posteriori evaluations of the terms neglected in the boundary layer simplification of the complete equations have been conducted on the locally similar temperature and velocity profiles close to the spreading ridge. The boundary layer models are valid to depths of 100 km at 3 m.y. and 10 km at 0.3 m.y.
Shear flow beneath oceanic plates - Local nonsimilarity boundary layers for olivine rheology
NASA Technical Reports Server (NTRS)
Yuen, D. A.; Tovish, A.; Schubert, G.
1978-01-01
The principle of local similarity, which has been used to model the two-dimensional boundary layers in the oceanic upper mantle, permits calculation of the temperature, velocity, and stress fields with essentially analytic techniques. Finite difference numerical methods are hard pressed to resolve the detail required by the large variation of viscosity between the lithosphere and the asthenosphere. In this paper the local similarity approximation has been justified by quantitatively evaluating the effect of nonsimilarity due to viscous heating, nonlinear temperature- and pressure-dependent rheology, buoyancy, adiabatic cooling, etc. Nonsimilar effects produce only small modifications of the locally similar boundary layers; important geophysical observables such as surface heat flux and ocean floor topography are given to better than 10 percent by the locally similar solution. A posteriori evaluations of the terms neglected in the boundary layer simplification of the complete equations have been conducted on the locally similar temperature and velocity profiles close to the spreading ridge. The boundary layer models are valid to depths of 100 km at 3 m.y. and 10 km at 0.3 m.y.
NASA Astrophysics Data System (ADS)
Bhattacharya, Amitabh
2013-11-01
An efficient algorithm for simulating Stokes flow around particles is presented here, in which a second order Finite Difference method (FDM) is coupled to a Boundary Integral method (BIM). This method utilizes the strong points of FDM (i.e. localized stencil) and BIM (i.e. accurate representation of particle surface). Specifically, in each iteration, the flow field away from the particles is solved on a Cartesian FDM grid, while the traction on the particle surface (given the the velocity of the particle) is solved using BIM. The two schemes are coupled by matching the solution in an intermediate region between the particle and surrounding fluid. We validate this method by solving for flow around an array of cylinders, and find good agreement with Hasimoto's (J. Fluid Mech. 1959) analytical results.
Local homeoprotein diffusion can stabilize boundaries generated by graded positional cues
Quiñinao, Cristóbal; Prochiantz, Alain; Touboul, Jonathan
2016-01-01
Boundary formation in the developing neuroepithelium decides on the position and size of compartments in the adult nervous system. In this study, we start from the French Flag model proposed by Lewis Wolpert, in which boundaries are formed through the combination of morphogen diffusion and of thresholds in cell responses. In contemporary terms, a response is characterized by the expression of cell-autonomous transcription factors, very often of the homeoprotein family. Theoretical studies suggest that this sole mechanism results in the formation of boundaries of imprecise shapes and positions. Alan Turing, on the other hand, proposed a model whereby two morphogens that exhibit self-activation and reciprocal inhibition, and are uniformly distributed and diffuse at different rates lead to the formation of territories of unpredictable shapes and positions but with sharp boundaries (the ‘leopard spots’). Here, we have combined the two models and compared the stability of boundaries when the hypothesis of local homeoprotein intercellular diffusion is, or is not, introduced in the equations. We find that the addition of homeoprotein local diffusion leads to a dramatic stabilization of the positioning of the boundary, even when other parameters are significantly modified. This novel Turing/Wolpert combined model has thus important theoretical consequences for our understanding of the role of the intercellular diffusion of homeoproteins in the developmental robustness of and the changes that take place in the course of evolution. PMID:25968317
The stabilization of a hypersonic boundary layer using local sections of porous coating
NASA Astrophysics Data System (ADS)
Wang, Xiaowen; Zhong, Xiaolin
2012-03-01
The stabilization effect of porous coating on the hypersonic boundary layers over flat plates and cones has been studied by theoretical analyses, experiments, and numerical simulations. It was found that porous coating slightly destabilizes Mack's first mode whereas it significantly stabilizes Mack's second mode. In previous studies, porous coating covers either the entire flat plate or the surface around half the cone circumference. The effect of porous coating location on boundary-layer stabilization has not been considered. Furthermore, the destabilization of Mack's first mode has not been studied in detail. In this paper, the stabilization of a Mach 5.92 flat-plate boundary layer using local sections of porous coating is studied with the emphasis on the effect of porous coating location and the first-mode destabilization. Artificial disturbances corresponding to a single boundary-layer wave are introduced near the leading edge. A series of stability simulations are carried out by locally putting felt-metal porous coatings along the flat plate. It is found that disturbances are destabilized or stabilized when porous coating is located upstream or downstream of the synchronization point. For felt-metal porous coating, the destabilization of Mack's first mode is significant. The results suggest that an efficient way to stabilize hypersonic boundary-layer flows is to put porous coating downstream of the synchronization point. Finally, porous coating is used to stabilize the boundary layer disturbed by one blowing-suction actuator.
Direct numerical simulation of bedload transport using a local, dynamic boundary condition
Schmeeckle, M.W.; Nelson, J.M.
2003-01-01
Temporally and spatially averaged models of bedload transport are inadequate to describe the highly variable nature of particle motion at low transport stages. The primary sources of this variability are the resisting forces to downstream motion resulting from the geometrical relation (pocket friction angle) of a bed grain to the grains that it rests upon, variability of the near-bed turbulent velocity field and the local modification of this velocity field by upstream, protruding grains. A model of bedload transport is presented that captures these sources of variability by directly integrating the equations of motion of each particle of a simulated mixed grain-size sediment bed. Experimental data from the velocity field downstream and below the tops of upstream, protruding grains are presented. From these data, an empirical relation for the velocity modification resulting from upstream grains is provided to the bedload model. The temporal variability of near-bed turbulence is provided by a measured near-bed time series of velocity over a gravel bed. The distribution of pocket friction angles results as a consequence of directly calculating the initiation and cessation of motion of each particle as a result of the combination of fluid forcing and interaction with other particles. Calculations of bedload flux in a uniform boundary and simulated pocket friction angles agree favourably with previous studies.
Boundary uniqueness theorems for functions whose integrals over hyperbolic discs vanish
Ochakovskaya, Oksana A
2013-02-28
Sharp conditions are found describing the admissible rate of decrease of a nontrivial function whose integrals over all hyperbolic discs with fixed radius vanish. For the first time, the boundary behaviour of the function is investigated in a neighbourhood of a single point on the boundary of the domain of definition. Bibliography: 17 titles.
Non-local sub-characteristic zones of influence in unsteady interactive boundary-layers
NASA Technical Reports Server (NTRS)
Rothmayer, A. P.
1992-01-01
The properties of incompressible, unsteady, interactive, boundary layers are examined for a model hypersonic boundary layer and internal flow past humps or, equivalently, external flow past short-scaled humps. Using a linear high frequency analysis, it is shown that the domains of dependence within the viscous sublayer may be a strong function of position within the sublayer and may be strongly influenced by the pressure displacement interaction, or the prescribed displacement condition. Detailed calculations are presented for the hypersonic boundary layer. This effect is found to carry over directly to the fully viscous problem as well as the nonlinear problem. In the fully viscous problem, the non-local character of the domains of dependence manifests itself in the sub-characteristics. Potential implications of the domain of dependence structure on finite difference computations of unsteady boundary layers are briefly discussed.
Multiple integral representation for the trigonometric SOS model with domain wall boundaries
NASA Astrophysics Data System (ADS)
Galleas, W.
2012-05-01
Using the dynamical Yang-Baxter algebra we derive a functional equation for the partition function of the trigonometric SOS model with domain wall boundary conditions. The solution of the equation is given in terms of a multiple contour integral.
NASA Astrophysics Data System (ADS)
Zempo, Keiichi; Mizutani, Koichi; Wakatsuki, Naoto
2013-07-01
Compassing the spatial shape is sometimes performed to develop a surround speaker system or enhance a signal. Although the spatial shape is reconstituted from the boundary position, conventional methods offer arrays consisting of a large number of elements (microphones and loudspeakers). In this research, we developed a method of localizing the acoustic reflective boundary based on the direction-of-arrival (DOA) of direct and reflected sounds using a pair of microphones. This method offers the DOA values of direct and reflected arbitrary sound sources. Although the estimation involves some estimation errors caused by approximations in the calculation, the correction function was obtained from several conditions numerically. Results indicate that it is possible to localize the reflective boundary almost accurately (the average error ratio from the true value is below 10%) through the presented method.
Local inhomogeneities in a Robertson-Walker background. II - Flux conditions at boundary surfaces
NASA Astrophysics Data System (ADS)
Lake, K.
1980-12-01
Energy flux conditions imposed on spherical boundary surfaces are examined. The zero-flux restriction, which is the hallmark of the standard Swiss cheese type construction, is relaxed. A class of locally inhomogeneous exact solutions to the Einstein equations which admit an effectively Newtonian accretion model is discussed.
A Boundary Integral Approach for Three-Dimensional Underwater Explosion Bubble Dynamics
1992-06-01
AD-A252 412 TECHNICAL REPORT BRL-TR-3365 BRL A BOUNDARY INTEGRAL APPROACH FOR THREE-DIMENSIONAL UNDERWATER EXPLOSION BUBBLE DYNAMICS STEPHEN...Dimensional Underwater Explosion Bubble Dynamics______________________________________________ 1I162618BAH80 6. AUTHOR(S) Stephen Wikerson 7...ABSTRACT (Maximum 200 words) The development of a numerical solution for three-dimensional underwater explosion bubble dynamics using the Boundary Integral
NASA Astrophysics Data System (ADS)
Bermúdez, María.; Neal, Jeffrey C.; Bates, Paul D.; Coxon, Gemma; Freer, Jim E.; Cea, Luis; Puertas, Jeronimo
2017-04-01
Inflow discharge and outflow stage estimates for hydraulic flood models are generally derived from river gauge data. Uncertainties in the measured inflow data and the neglect of rainfall-runoff contributions to the modeled domain downstream of the gauging locations can have a significant impact on these estimated "whole reach" inflows and consequently on flood predictions. In this study, a method to incorporate rating curve uncertainty and local rainfall-runoff dynamics into the predictions of a reach-scale flood model is proposed. The methodology is applied to the July 2007 floods of the River Severn in UK. Discharge uncertainty bounds are generated applying a nonparametric local weighted regression approach to stage-discharge measurements for two gauging stations. Measured rainfall downstream from these locations is used as input to a series of subcatchment regional hydrological model to quantify additional local inflows along the main channel. A regional simplified-physics hydraulic model is then applied to combine these contributions and generate an ensemble of discharge and water elevation time series at the boundaries of a local-scale high complexity hydraulic model. Finally, the effect of these rainfall dynamics and uncertain boundary conditions are evaluated on the local-scale model. Accurate prediction of the flood peak was obtained with the proposed method, which was only possible by resolving the additional complexity of the extreme rainfall contributions over the modeled area. The findings highlight the importance of estimating boundary condition uncertainty and local rainfall contributions for accurate prediction of river flows and inundation at regional scales.
NASA Astrophysics Data System (ADS)
De La Rosa Gomez, Alejandro; MacKay, Niall; Regelskis, Vidas
2017-04-01
We present a general method of folding an integrable spin chain, defined on a line, to obtain an integrable open spin chain, defined on a half-line. We illustrate our method through two fundamental models with sl2 Lie algebra symmetry: the Heisenberg XXX and the Inozemtsev hyperbolic spin chains. We obtain new long-range boundary Hamiltonians and demonstrate that they exhibit Yangian symmetries, thus ensuring integrability of the models we obtain. The method presented provides a ;bottom-up; approach for constructing integrable boundaries and can be applied to any spin chain model.
Application of boundary integral method to elastoplastic analysis of V-notched beams
NASA Technical Reports Server (NTRS)
Rzasnicki, W.; Mendelson, A.
1975-01-01
The boundary integral equation method was applied in the solution of the plane elastoplastic problems. The use of this method was illustrated by obtaining stress and strain distributions for a number of specimens with a single edge notch and subjected to pure bending. The boundary integral equation method reduced the nonhomogeneous biharmonic equation to two coupled Fredholm-type integral equations. These integral equations were replaced by a system of simultaneous algebraic equations and solved numerically in conjunction with the method of successive elastic solutions.
Application of boundary integral method to elastoplastic analysis of V-notched beams
NASA Technical Reports Server (NTRS)
Rzasnicki, W.; Mendelson, A.; Albers, L. U.; Raftopoulos, D. D.
1974-01-01
The boundary integral equation method was applied in the solution of the plane elastoplastic problem. The use of this method was illustrated by obtaining stress and strain distributions for a number of specimens with a single-edge notch and subjected to pure bending. The boundary integral equation method reduced the inhomogeneous biharmonic equation to two coupled Fredholm-type integral equations. These integral equations were replaced by a system of simultaneous algebraic equations and solved numerically in conjunction with a method of successive elastic solutions.
Application of boundary integral method to elastoplastic analysis of v-notched beams
NASA Technical Reports Server (NTRS)
Rzasnicki, W.; Mendelson, A.
1974-01-01
The boundary integral equation method was applied in the solution of the plane elastoplastic problems. The use of this method was illustrated by obtaining stress and strain distributions for a number of specimens with a single edge notch and subjected to pure bending. The boundary integral equation method reduced the non-homogeneous biharmonic equation to two coupled Fredholm-type integral equations. These integral equations were replaced by a system of simultaneous algebraic equations and solved numerically in conjunction with the method of successive elastic solutions.
Comments on localized and integral localized approximations in spherical coordinates
NASA Astrophysics Data System (ADS)
Gouesbet, Gérard; Lock, James A.
2016-08-01
Localized approximation procedures are efficient ways to evaluate beam shape coefficients of laser beams, and are particularly useful when other methods are ineffective or inefficient. Comments on these procedures are, however, required in order to help researchers make correct decisions concerning their use. This paper has the flavor of a short review and takes the opportunity to attract the attention of the readers to a required refinement of terminology.
Si segregation at Fe grain boundaries analyzed by ab initio local energy and local stress.
Bhattacharya, Somesh Kr; Kohyama, Masanori; Tanaka, Shingo; Shiihara, Yoshinori
2014-09-03
Using density-functional theory calculations combined with recent local-energy and local-stress schemes, we studied the effects of Si segregation on the structural, mechanical and magnetic properties of the Σ3(1 1 1) and Σ11(3 3 2) Fe GBs formed by rotation around the [1 1 0] axis. The segregation mechanism was analyzed by the local-energy decomposition of the segregation energy, where the segregation energy is expressed as a sum of the following four terms: the local-energy change of Si atoms from the isolated state in bulk Fe to the GB segregated state, the stabilization of replaced Fe atoms from the GB to the bulk, the local-energy change of neighboring Fe atoms from the pure GB to the segregated GB and the local-energy change of neighboring Fe atoms from the system of an isolated Si atom in the bulk Fe to the pure bulk Fe. The segregation energy and value of each term greatly depends on the segregation site and Si concentration. The segregation at interface Fe sites with higher local energies in the original GB configurations naturally leads to higher segregation-energy gains, while interface sites with lower local energies can lead to larger energy gains if stronger Si-Fe interactions occur locally in the final segregated configurations. The high Si concentration reduces the segregation-energy gain per Si atom due to the local-energy increases of Si atoms neighboring to each other or through the reduction in the number of stabilized Fe atoms per Si atom as observed in a Si dimer in bulk Fe. In the Si-segregated GBs, Si-Fe bonds enhance local Young's moduli and tend to suppress the interface weakening, while the GB adhesion is slightly reduced. And Fe atoms contacting Si atoms have reduced magnetic moments, due to Si-Fe sp-d hybridization interactions.
Integrating Observations of the Boundary Current Flow around Sri Lanka
2014-09-30
around Sri Lanka 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT...Boundary Current Flow around Sri Lanka Uwe Send and Matthias Lankhorst Scripps Institution of Oceanography 9500 Gilman Drive, Mail Code 0230...time at two sites near Sri Lanka . OBJECTIVES Deploy and operate two seafloor instruments called PIES (pressure-sensing inverted echo sounders) in
Topology and boundary shape optimization as an integrated design tool
NASA Technical Reports Server (NTRS)
Bendsoe, Martin Philip; Rodrigues, Helder Carrico
1990-01-01
The optimal topology of a two dimensional linear elastic body can be computed by regarding the body as a domain of the plane with a high density of material. Such an optimal topology can then be used as the basis for a shape optimization method that computes the optimal form of the boundary curves of the body. This results in an efficient and reliable design tool, which can be implemented via common FEM mesh generator and CAD type input-output facilities.
Three-dimensional analysis of chevron-notched specimens by boundary integral method
NASA Technical Reports Server (NTRS)
Mendelson, A.; Ghosn, L.
1983-01-01
The chevron-notched short bar and short rod specimens was analyzed by the boundary integral equations method. This method makes use of boundary surface elements in obtaining the solution. The boundary integral models were composed of linear triangular and rectangular surface segments. Results were obtained for two specimens with width to thickness ratios of 1.45 and 2.00 and for different crack length to width ratios ranging from 0.4 to 0.7. Crack opening displacement and stress intensity factors determined from displacement calculations along the crack front and compliance calculations were compared with experimental values and with finite element analysis.
Local patches of turbulent boundary layer behaviour in classical-state vertical natural convection
NASA Astrophysics Data System (ADS)
Ng, Chong Shen; Ooi, Andrew; Lohse, Detlef; Chung, Daniel
2016-11-01
We present evidence of local patches in vertical natural convection that are reminiscent of Prandtl-von Kármán turbulent boundary layers, for Rayleigh numbers 105-109 and Prandtl number 0.709. These local patches exist in the classical state, where boundary layers exhibit a laminar-like Prandtl-Blasius-Polhausen scaling at the global level, and are distinguished by regions dominated by high shear and low buoyancy flux. Within these patches, the locally averaged mean temperature profiles appear to obey a log-law with the universal constants of Yaglom (1979). We find that the local Nusselt number versus Rayleigh number scaling relation agrees with the logarithmically corrected power-law scaling predicted in the ultimate state of thermal convection, with an exponent consistent with Rayleigh-Bénard convection and Taylor-Couette flows. The local patches grow in size with increasing Rayleigh number, suggesting that the transition from the classical state to the ultimate state is characterised by increasingly larger patches of the turbulent boundary layers.
A boundary integral algorithm for the Laplace Dirichlet-Neumann mixed eigenvalue problem
NASA Astrophysics Data System (ADS)
Akhmetgaliyev, Eldar; Bruno, Oscar P.; Nigam, Nilima
2015-10-01
We present a novel integral-equation algorithm for evaluation of Zaremba eigenvalues and eigenfunctions, that is, eigenvalues and eigenfunctions of the Laplace operator with mixed Dirichlet-Neumann boundary conditions; of course, (slight modifications of) our algorithms are also applicable to the pure Dirichlet and Neumann eigenproblems. Expressing the eigenfunctions by means of an ansatz based on the single layer boundary operator, the Zaremba eigenproblem is transformed into a nonlinear equation for the eigenvalue μ. For smooth domains the singular structure at Dirichlet-Neumann junctions is incorporated as part of our corresponding numerical algorithm-which otherwise relies on use of the cosine change of variables, trigonometric polynomials and, to avoid the Gibbs phenomenon that would arise from the solution singularities, the Fourier Continuation method (FC). The resulting numerical algorithm converges with high order accuracy without recourse to use of meshes finer than those resulting from the cosine transformation. For non-smooth (Lipschitz) domains, in turn, an alternative algorithm is presented which achieves high-order accuracy on the basis of graded meshes. In either case, smooth or Lipschitz boundary, eigenvalues are evaluated by searching for zero minimal singular values of a suitably stabilized discrete version of the single layer operator mentioned above. (The stabilization technique is used to enable robust non-local zero searches.) The resulting methods, which are fast and highly accurate for high- and low-frequencies alike, can solve extremely challenging two-dimensional Dirichlet, Neumann and Zaremba eigenproblems with high accuracies in short computing times-enabling, in particular, evaluation of thousands of eigenvalues and corresponding eigenfunctions for a given smooth or non-smooth geometry with nearly full double-precision accuracy.
D'Elia, Marta; Perego, Mauro; Bochev, Pavel B.; Littlewood, David John
2015-12-21
We develop and analyze an optimization-based method for the coupling of nonlocal and local diffusion problems with mixed volume constraints and boundary conditions. The approach formulates the coupling as a control problem where the states are the solutions of the nonlocal and local equations, the objective is to minimize their mismatch on the overlap of the nonlocal and local domains, and the controls are virtual volume constraints and boundary conditions. When some assumptions on the kernel functions hold, we prove that the resulting optimization problem is well-posed and discuss its implementation using Sandia’s agile software components toolkit. As a result, the latter provides the groundwork for the development of engineering analysis tools, while numerical results for nonlocal diffusion in three-dimensions illustrate key properties of the optimization-based coupling method.
D'Elia, Marta; Perego, Mauro; Bochev, Pavel B.; ...
2015-12-21
We develop and analyze an optimization-based method for the coupling of nonlocal and local diffusion problems with mixed volume constraints and boundary conditions. The approach formulates the coupling as a control problem where the states are the solutions of the nonlocal and local equations, the objective is to minimize their mismatch on the overlap of the nonlocal and local domains, and the controls are virtual volume constraints and boundary conditions. When some assumptions on the kernel functions hold, we prove that the resulting optimization problem is well-posed and discuss its implementation using Sandia’s agile software components toolkit. As a result,more » the latter provides the groundwork for the development of engineering analysis tools, while numerical results for nonlocal diffusion in three-dimensions illustrate key properties of the optimization-based coupling method.« less
Feischl, Michael; Gantner, Gregor; Praetorius, Dirk
2015-01-01
We consider the Galerkin boundary element method (BEM) for weakly-singular integral equations of the first-kind in 2D. We analyze some residual-type a posteriori error estimator which provides a lower as well as an upper bound for the unknown Galerkin BEM error. The required assumptions are weak and allow for piecewise smooth parametrizations of the boundary, local mesh-refinement, and related standard piecewise polynomials as well as NURBS. In particular, our analysis gives a first contribution to adaptive BEM in the frame of isogeometric analysis (IGABEM), for which we formulate an adaptive algorithm which steers the local mesh-refinement and the multiplicity of the knots. Numerical experiments underline the theoretical findings and show that the proposed adaptive strategy leads to optimal convergence. PMID:26085698
NASA Astrophysics Data System (ADS)
Feischl, Michael; Gantner, Gregor; Praetorius, Dirk
2015-06-01
We consider the Galerkin boundary element method (BEM) for weakly-singular integral equations of the first-kind in 2D. We analyze some residual-type a posteriori error estimator which provides a lower as well as an upper bound for the unknown Galerkin BEM error. The required assumptions are weak and allow for piecewise smooth parametrizations of the boundary, local mesh-refinement, and related standard piecewise polynomials as well as NURBS. In particular, our analysis gives a first contribution to adaptive BEM in the frame of isogeometric analysis (IGABEM), for which we formulate an adaptive algorithm which steers the local mesh-refinement and the multiplicity of the knots. Numerical experiments underline the theoretical findings and show that the proposed adaptive strategy leads to optimal convergence.
Moore, Kara A.; Stanton, Maureen L.
2014-01-01
Adaptation to novel conditions beyond current range boundaries requires the presence of suitable sites within dispersal range, but may be impeded when emigrants encounter poor habitat and sharply different selection pressures. We investigated fine-scale spatial heterogeneity in ecological dynamics and selection at a local population boundary of the annual plant Gilia tricolor. In two years, we planted G. tricolor seeds in core habitat, margin habitat at the edge of the local range, and exterior habitat in order to measure spatial and temporal variation in habitat quality, opportunity for selection, and selection on phenotypic traits. We found a striking decline in average habitat quality with distance from the population core, yet some migrant seeds were successful in suitable, unoccupied microsites at and beyond the range boundary. Total and direct selection on four out of five measured phenotypic traits varied across habitat zones, as well as between years. Moreover, the margin habitat often exerted unique selection pressures that were not intermediate between core and exterior habitats. This study reveals that a combination of ecological and evolutionary forces, including propagule limitation, variation in habitat quality and spatial heterogeneity in phenotypic selection may reduce opportunities for adaptive range expansion, even across a very local population boundary. PMID:24717472
Moore, Kara A; Stanton, Maureen L
2014-01-01
Adaptation to novel conditions beyond current range boundaries requires the presence of suitable sites within dispersal range, but may be impeded when emigrants encounter poor habitat and sharply different selection pressures. We investigated fine-scale spatial heterogeneity in ecological dynamics and selection at a local population boundary of the annual plant Gilia tricolor. In two years, we planted G. tricolor seeds in core habitat, margin habitat at the edge of the local range, and exterior habitat in order to measure spatial and temporal variation in habitat quality, opportunity for selection, and selection on phenotypic traits. We found a striking decline in average habitat quality with distance from the population core, yet some migrant seeds were successful in suitable, unoccupied microsites at and beyond the range boundary. Total and direct selection on four out of five measured phenotypic traits varied across habitat zones, as well as between years. Moreover, the margin habitat often exerted unique selection pressures that were not intermediate between core and exterior habitats. This study reveals that a combination of ecological and evolutionary forces, including propagule limitation, variation in habitat quality and spatial heterogeneity in phenotypic selection may reduce opportunities for adaptive range expansion, even across a very local population boundary.
NASA Astrophysics Data System (ADS)
Gudi, Thirupathi; Nataraj, Neela; Pani, Amiya K.
2008-06-01
In this paper, an hp -local discontinuous Galerkin method is applied to a class of quasilinear elliptic boundary value problems which are of nonmonotone type. On hp -quasiuniform meshes, using the Brouwer fixed point theorem, it is shown that the discrete problem has a solution, and then using Lipschitz continuity of the discrete solution map, uniqueness is also proved. A priori error estimates in broken H^1 norm and L^2 norm which are optimal in h , suboptimal in p are derived. These results are exactly the same as in the case of linear elliptic boundary value problems. Numerical experiments are provided to illustrate the theoretical results.
Integral Method of Boundary Characteristics in Solving the Stefan Problem: Dirichlet Condition
NASA Astrophysics Data System (ADS)
Kot, V. A.
2016-09-01
The integral method of boundary characteristics is considered as applied to the solution of the Stefan problem with a Dirichlet condition. On the basis of the multiple integration of the heat-conduction equation, a sequence of identical equalities with boundary characteristics in the form of n-fold integrals of the surface temperature has been obtained. It is shown that, in the case where the temperature profile is defined by an exponential polynomial and the Stefan condition is not fulfilled at a moving interphase boundary, the accuracy of solving the Stefan problem with a Dirichlet condition by the integral method of boundary characteristics is higher by several orders of magnitude than the accuracy of solving this problem by other known approximate methods and that the solutions of the indicated problem with the use of the fourth-sixth degree polynomials on the basis of the integral method of boundary characteristics are exact in essence. This method surpasses the known numerical methods by many orders of magnitude in the accuracy of calculating the position of the interphase boundary and is approximately equal to them in the accuracy of calculating the temperature profile.
NASA Astrophysics Data System (ADS)
Ivanyshyn Yaman, Olha; Le Louër, Frédérique
2016-09-01
This paper deals with the material derivative analysis of the boundary integral operators arising from the scattering theory of time-harmonic electromagnetic waves and its application to inverse problems. We present new results using the Piola transform of the boundary parametrisation to transport the integral operators on a fixed reference boundary. The transported integral operators are infinitely differentiable with respect to the parametrisations and simplified expressions of the material derivatives are obtained. Using these results, we extend a nonlinear integral equations approach developed for solving acoustic inverse obstacle scattering problems to electromagnetism. The inverse problem is formulated as a pair of nonlinear and ill-posed integral equations for the unknown boundary representing the boundary condition and the measurements, for which the iteratively regularized Gauss-Newton method can be applied. The algorithm has the interesting feature that it avoids the numerous numerical solution of boundary value problems at each iteration step. Numerical experiments are presented in the special case of star-shaped obstacles.
INTEGRATING A LINEAR INTERPOLATION FUNCTION ACROSS TRIANGULAR CELL BOUNDARIES
J. R. WISEMAN; J. S. BROCK
2000-04-01
Computational models of particle dynamics often exchange solution data with discretized continuum-fields using interpolation functions. These particle methods require a series expansion of the interpolation function for two purposes: numerical analysis used to establish the model's consistency and accuracy, and logical-coordinate evaluation used to locate particles within a grid. This report presents discrete-expansions for a linear interpolation function commonly used within triangular cell geometries. Discrete-expansions, unlike a Taylor's series, account for interpolation discontinuities across cell boundaries and, therefore, are valid throughout a discretized domain. Verification of linear discrete-expansions is demonstrated on a simple test problem.
Shape integral method for magnetospheric shapes. [boundary layer calculations
NASA Technical Reports Server (NTRS)
Michel, F. C.
1979-01-01
A method is developed for calculating the shape of any magnetopause to arbitrarily high precision. The method uses an integral equation which is evaluated for a trial shape. The resulting values of the integral equation as a function of auxiliary variables indicate how close one is to the desired solution. A variational method can then be used to improve the trial shape. Some potential applications are briefly mentioned.
Integrating Observations of the Boundary Current Flow around Sri Lanka
2015-09-30
of Bengal. For this, the flow around Sri Lanka is critical since it exchanges salt and freshwater between the Bay of Bengal and the Arabian Sea...content and an integral of sound slowness (which depends on integrated heat and salt ) of the water column. Pairing such measurements at the end...including the role they play in transporting salt /fresh water and heat. These transports are an important component of the climate system in the Indian
NASA Astrophysics Data System (ADS)
Li, Yuan; Dang, HuaYang; Xu, GuangTao; Fan, CuiYing; Zhao, MingHao
2016-08-01
The extended displacement discontinuity boundary integral equation (EDDBIE) and boundary element method is developed for the analysis of planar cracks of arbitrary shape in the isotropic plane of three-dimensional (3D) transversely isotropic thermo-magneto-electro-elastic (TMEE) media. The extended displacement discontinuities (EDDs) include conventional displacement discontinuity, electric potential discontinuity, magnetic potential discontinuity, as well as temperature discontinuity across crack faces; correspondingly, the extended stresses represent conventional stress, electric displacement, magnetic induction and heat flux. Employing a Hankel transformation, the fundamental solutions for unit point EDDs in 3D transversely isotropic TMEE media are derived. The EDDBIEs for a planar crack of arbitrary shape in the isotropic plane of a 3D transversely isotropic TMEE medium are then established. Using the boundary integral equation method, the singularities of near-crack border fields are obtained and the extended stress field intensity factors are expressed in terms of the EDDs on crack faces. According to the analogy between the EDDBIEs for an isotropic thermoelastic material and TMEE medium, an analogical solution method for crack problems of a TMEE medium is proposed for coupled multi-field loadings. Employing constant triangular elements, the EDDBIEs are discretized and numerically solved. As an application, the problems of an elliptical crack subjected to combined mechanical-electric-magnetic-thermal loadings are investigated.
Fermionic path integrals and local anomalies
NASA Astrophysics Data System (ADS)
Roepstorff, G.
2003-05-01
No doubt, the subject of path integrals proved to be an immensely fruitful human, i.e. Feynman's idea. No wonder it is more timely than ever. Some even claim that it is the most daring, innovative and revolutionary idea since the days of Heisenberg and Bohr. It is thus likely to generate enthusiasm, if not addiction among physicists who seek simplicity together with perfection. Professor Devreese's long-lasting interest in, if not passion on the subject stems from his firm conviction that, beyond being the tool of choice, path integration provides the key to all quantum phenomena, be it in solid state, atomic, molecular or particle physics as evidenced by the impressive list of publications at the address http://lib.ua.ac.be/AB/a867.html. In this note, I review a pitfall of fermionic path integrals and a way to get around it in situations relevant to the Standard Model of particle physics.
NASA Technical Reports Server (NTRS)
Choudhari, Meelan; Street, Craig L.
1991-01-01
Previous theoretical work on the boundary layer receptivity problem has utilized large Reynolds number asymptotic theories, thus being limited to a narrow part of the frequency - Reynolds number domain. An alternative approach is presented for the prediction of localized instability generation which has a general applicability, and also accounts for finite Reynolds number effects. This approach is illustrated for the case of Tollmien-Schlichting wave generation in a Blasius boundary layer due to the interaction of a free stream acoustic wave with a region of short scale variation in the surface boundary condition. The specific types of wall inhomogeneities studied are: regions of short scale variations in wall suction, wall admittance, and wall geometry (roughness). Extensive comparison is made between the results of the finite Reynolds number approach and previous asymptotic predictions, which also suggests an alternative way of using the latter at Reynolds numbers of interest in practice.
Development of an integrated BEM (Boundary Element Mesh) for hot fluid-structure interaction
NASA Technical Reports Server (NTRS)
Dargush, G. F.; Banerjee, P. K.
1987-01-01
A boundary integral representation for a coupled approach to fluid flow and solid deformation problems associated with the design of hot-section components such as those in the Space Shuttle Main Engine is discussed. The formulation is based on the fundamental analytical solution of the Navier-Stokes equation for fluid velocity in an infinite domain. This fundamental solution was obtained by decomposing a Navier-Stokes equation into vorticity and dilation transport equations. A boundary integral involving convolutions in time was then constructed in which the convective terms appear in the volume integral.
NASA Astrophysics Data System (ADS)
Bermúdez, María; Neal, Jeffrey C.; Bates, Paul D.; Coxon, Gemma; Freer, Jim E.; Cea, Luis; Puertas, Jerónimo
2016-04-01
Flood inundation models require appropriate boundary conditions to be specified at the limits of the domain, which commonly consist of upstream flow rate and downstream water level. These data are usually acquired from gauging stations on the river network where measured water levels are converted to discharge via a rating curve. Derived streamflow estimates are therefore subject to uncertainties in this rating curve, including extrapolating beyond the maximum observed ratings magnitude. In addition, the limited number of gauges in reach-scale studies often requires flow to be routed from the nearest upstream gauge to the boundary of the model domain. This introduces additional uncertainty, derived not only from the flow routing method used, but also from the additional lateral rainfall-runoff contributions downstream of the gauging point. Although generally assumed to have a minor impact on discharge in fluvial flood modeling, this local hydrological input may become important in a sparse gauge network or in events with significant local rainfall. In this study, a method to incorporate rating curve uncertainty and the local rainfall-runoff dynamics into the predictions of a reach-scale flood inundation model is proposed. Discharge uncertainty bounds are generated by applying a non-parametric local weighted regression approach to stage-discharge measurements for two gauging stations, while measured rainfall downstream from these locations is cascaded into a hydrological model to quantify additional inflows along the main channel. A regional simplified-physics hydraulic model is then applied to combine these inputs and generate an ensemble of discharge and water elevation time series at the boundaries of a local-scale high complexity hydraulic model. Finally, the effect of these rainfall dynamics and uncertain boundary conditions are evaluated on the local-scale model. Improvements in model performance when incorporating these processes are quantified using observed
On the determination of phase boundaries via thermodynamic integration across coexistence regions
Abramo, Maria Concetta Caccamo, Carlo Costa, Dino Giaquinta, Paolo V. Malescio, Gianpietro Munaò, Gianmarco; Prestipino, Santi
2015-06-07
Specialized Monte Carlo methods are nowadays routinely employed, in combination with thermodynamic integration (TI), to locate phase boundaries of classical many-particle systems. This is especially useful for the fluid-solid transition, where a critical point does not exist and both phases may notoriously go deeply metastable. Using the Lennard-Jones model for demonstration, we hereby investigate on the alternate possibility of tracing reasonably accurate transition lines directly by integrating the pressure equation of state computed in a canonical-ensemble simulation with local moves. The recourse to this method would become a necessity when the stable crystal structure is not known. We show that, rather counterintuitively, metastability problems can be alleviated by reducing (rather than increasing) the size of the system. In particular, the location of liquid-vapor coexistence can exactly be predicted by just TI. On the contrary, TI badly fails in the solid-liquid region, where a better assessment (to within 10% accuracy) of the coexistence pressure can be made by following the expansion, until melting, of the defective solid which has previously emerged from the decay of the metastable liquid.
Engaging Students: Integrated Learning and Research across Disciplinary Boundaries
ERIC Educational Resources Information Center
Gilbert, Lucia Albino; Schuilt, Paige E.; Ekland-Olson, Sheldon
2005-01-01
As campuses across the country explore ways to strengthen interdisciplinary studies and involve undergraduates in research, questions emerge about how best to integrate existing course offerings and majors, develop curricular rigor and agility, and strengthen administrative coordination. This article discusses two successful initiatives to…
Weaver, P. M.
2016-01-01
The safe design of primary load-bearing structures requires accurate prediction of stresses, especially in the vicinity of geometric discontinuities where deleterious three-dimensional stress fields can be induced. Even for thin-walled structures significant through-thickness stresses arise at edges and boundaries, and this is especially precarious for laminates of advanced fibre-reinforced composites because through-thickness stresses are the predominant drivers in delamination failure. Here, we use a higher-order equivalent single-layer model derived from the Hellinger–Reissner mixed variational principle to examine boundary layer effects in laminated plates comprising constant-stiffness and variable-stiffness laminae and deforming statically in cylindrical bending. The results show that zigzag deformations, which arise due to layerwise differences in the transverse shear moduli, drive boundary layers towards clamped edges and are therefore critically important in quantifying localized stress gradients. The relative significance of the boundary layer scales with the degree of layerwise anisotropy and the thickness to characteristic length ratio. Finally, we demonstrate that the phenomenon of alternating positive and negative transverse shearing deformation through the thickness of composite laminates, previously only observed at clamped boundaries, can also occur at other locations as a result of smoothly varying the material properties over the in-plane dimensions of the laminate. PMID:27843401
Huang, Kuo-Feng; Liao, Jung-Wei; Hsieh, Cheng-Yu; Wang, Liang-Wei; Huang, Yen-Chun; Wen, Wei-Chih; Chang, Mu-Tung; Lo, Shen-Chuan; Yuan, Jun; Lin, Hsiu-Hau; Lai, Chih-Huang
2015-01-01
Magnetic patterning, with designed spatial profile of the desired magnetic properties, has been a rising challenge for developing magnetic devices at nanoscale. Most existing methods rely on locally modifying magnetic anisotropy energy or saturation magnetization, and thus post stringent constraints on the adaptability in diverse applications. We propose an alternative route for magnetic patterning: by manipulating the local intergranular exchange coupling to tune lateral magnetic properties. As demonstration, the grain boundary structure of Co/Pt multilayers is engineered by thermal treatment, where the stress state of the multilayers and thus the intergranular exchange coupling can be modified. With Ag passivation layers on top of the Co/Pt multilayers, we can hinder the stress relaxation and grain boundary modification. Combining the pre-patterned Ag passivation layer with thermal treatment, we can design spatial variations of the magnetic properties by tuning the intergranular exchange coupling, which diversifies the magnetic patterning process and extends its feasibility for varieties of new devices. PMID:26156786
Localized oxidation near cracks and lamellar boundaries in a gamma titanium aluminide alloy
Kameda, J.; Gold, C.R.; Lee, E.S.; Bloomer, T.E.; Yamaguchi, M.
1995-07-01
Small punch (SP) tests on single grained titanium aluminide (Ti-48 at. % Al) specimens with 12{degree} and 80{degree} lamellar orientations with respect to the tensile stress axis were conducted at 1,123 K in air. Brittle cracks readily extended through the thickness in the 80{degree} lamellar structure. In a SP specimen with the 12{degree} lamellar structure load-interrupted at the strain of 0.43%, surface cracks with the depth of 15--25 {mu}m were formed along lamellar boundaries. Local oxidation behavior on partly sputtered surfaces in the load-interrupted 12{degree} lamellar specimen was examined using scanning Auger microprobe (SAM). Oxygen enriched regions were observed near cracks and some lamellar layers. The mechanisms of high temperature oxygen-induced cracking are discussed in terms of the local oxidation near cracks and lamellar boundaries.
Integrals of motion for one-dimensional Anderson localized systems
NASA Astrophysics Data System (ADS)
Modak, Ranjan; Mukerjee, Subroto; Yuzbashyan, Emil A.; Shastry, B. Sriram
2016-03-01
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, so as to enhance the analogy with quantum integrable systems. We answer this in the affirmative in the present work. We construct a set of nontrivial integrals of motion for Anderson localized models, in terms of the original creation and annihilation operators. These are found as a power series in the hopping parameter. The recently found Type-1 Hamiltonians, which are known to be quantum integrable in a precise sense, motivate our construction. We note that these models can be viewed as disordered electron models with infinite-range hopping, where a similar series truncates at the linear order. We show that despite the infinite range hopping, all states but one are localized. We also study the conservation laws for the disorder free Aubry-Andre model, where the states are either localized or extended, depending on the strength of a coupling constant. We formulate a specific procedure for averaging over disorder, in order to examine the convergence of the power series. Using this procedure in the Aubry-Andre model, we show that integrals of motion given by our construction are well-defined in localized phase, but not so in the extended phase. Finally, we also obtain the integrals of motion for a model with interactions to lowest order in the interaction.
Integrals of motion for one-dimensional Anderson localized systems
Modak, Ranjan; Mukerjee, Subroto; Yuzbashyan, Emil A.; Shastry, B. Sriram
2016-03-02
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, so as to enhance the analogy with quantum integrable systems. Weanswer this in the affirmative in the present work. We construct a set of nontrivial integrals of motion for Anderson localized models, in terms of the original creation and annihilation operators. These are found as a power series in the hopping parameter. The recently found Type-1 Hamiltonians, which are known to be quantum integrable in a precise sense, motivate our construction.Wenote that these models can be viewed as disordered electron models with infinite-range hopping, where a similar series truncates at the linear order.Weshow that despite the infinite range hopping, all states but one are localized.Wealso study the conservation laws for the disorder free Aubry–Andre model, where the states are either localized or extended, depending on the strength of a coupling constant.Weformulate a specific procedure for averaging over disorder, in order to examine the convergence of the power series. Using this procedure in the Aubry–Andre model, we show that integrals of motion given by our construction are well-defined in localized phase, but not so in the extended phase. Lastly, we also obtain the integrals of motion for a model with interactions to lowest order in the interaction.
Open-ocean boundary conditions from interior data: Local and remote forcing of Massachusetts Bay
Bogden, P.S.; Malanotte-Rizzoli, P.; Signell, R.
1996-01-01
Massachusetts and Cape Cod Bays form a semienclosed coastal basin that opens onto the much larger Gulf of Maine. Subtidal circulation in the bay is driven by local winds and remotely driven flows from the gulf. The local-wind forced flow is estimated with a regional shallow water model driven by wind measurements. The model uses a gravity wave radiation condition along the open-ocean boundary. Results compare reasonably well with observed currents near the coast. In some offshore regions however, modeled flows are an order of magnitude less energetic than the data. Strong flows are observed even during periods of weak local wind forcing. Poor model-data comparisons are attributable, at least in part, to open-ocean boundary conditions that neglect the effects of remote forcing. Velocity measurements from within Massachusetts Bay are used to estimate the remotely forced component of the flow. The data are combined with shallow water dynamics in an inverse-model formulation that follows the theory of Bennett and McIntosh [1982], who considered tides. We extend their analysis to consider the subtidal response to transient forcing. The inverse model adjusts the a priori open-ocean boundary condition, thereby minimizing a combined measure of model-data misfit and boundary condition adjustment. A "consistency criterion" determines the optimal trade-off between the two. The criterion is based on a measure of plausibility for the inverse solution. The "consistent" inverse solution reproduces 56% of the average squared variation in the data. The local-wind-driven flow alone accounts for half of the model skill. The other half is attributable to remotely forced flows from the Gulf of Maine. The unexplained 44% comes from measurement errors and model errors that are not accounted for in the analysis.
Mixed direct-iterative methods for boundary integral formulations of dielectric solvation models.
Corcelli, S A; Kress, J D; Pratt, L R; Tawa, G J
1996-01-01
This paper describes a mixed direct-iterative method for boundary integral formulations of dielectric solvation models. We give an example for which a direct solution at thermal accuracy is nontrivial and for which Gauss-Seidel iteration diverges in rare but reproducible cases. This difficulty is analyzed by obtaining the eigenvalues and the spectral radius of the iteration matrix. This establishes that the nonconvergence is due to inaccuracies of the asymptotic approximations for the matrix elements for accidentally close boundary element pairs on different spheres. This difficulty is cured by checking for boundary element pairs closer than the typical spatial extent of the boundary elements and for those pairs performing an 'in-line' Monte Carlo integration to evaluate the required matrix elements. This difficulty are not expected and have not been observed when only a direct solution is sought. Finally, we give an example application of these methods to deprotonation of monosilicic acid in water.
Non-local Second Order Closure Scheme for Boundary Layer Turbulence and Convection
NASA Astrophysics Data System (ADS)
Meyer, Bettina; Schneider, Tapio
2017-04-01
There has been scientific consensus that the uncertainty in the cloud feedback remains the largest source of uncertainty in the prediction of climate parameters like climate sensitivity. To narrow down this uncertainty, not only a better physical understanding of cloud and boundary layer processes is required, but specifically the representation of boundary layer processes in models has to be improved. General climate models use separate parameterisation schemes to model the different boundary layer processes like small-scale turbulence, shallow and deep convection. Small scale turbulence is usually modelled by local diffusive parameterisation schemes, which truncate the hierarchy of moment equations at first order and use second-order equations only to estimate closure parameters. In contrast, the representation of convection requires higher order statistical moments to capture their more complex structure, such as narrow updrafts in a quasi-steady environment. Truncations of moment equations at second order may lead to more accurate parameterizations. At the same time, they offer an opportunity to take spatially correlated structures (e.g., plumes) into account, which are known to be important for convective dynamics. In this project, we study the potential and limits of local and non-local second order closure schemes. A truncation of the momentum equations at second order represents the same dynamics as a quasi-linear version of the equations of motion. We study the three-dimensional quasi-linear dynamics in dry and moist convection by implementing it in a LES model (PyCLES) and compare it to a fully non-linear LES. In the quasi-linear LES, interactions among turbulent eddies are suppressed but nonlinear eddy—mean flow interactions are retained, as they are in the second order closure. In physical terms, suppressing eddy—eddy interactions amounts to suppressing, e.g., interactions among convective plumes, while retaining interactions between plumes and the
NASA Technical Reports Server (NTRS)
Tetervin, Neal; Lin, Chia Chiao
1951-01-01
A general integral form of the boundary-layer equation, valid for either laminar or turbulent incompressible boundary-layer flow, is derived. By using the experimental finding that all velocity profiles of the turbulent boundary layer form essentially a single-parameter family, the general equation is changed to an equation for the space rate of change of the velocity-profile shape parameter. The lack of precise knowledge concerning the surface shear and the distribution of the shearing stress across turbulent boundary layers prevented the attainment of a reliable method for calculating the behavior of turbulent boundary layers.
Behavior of boundary string field theory associated with integrable massless flow.
Fujii, A; Itoyama, H
2001-06-04
We put forward an idea that the boundary entropy associated with integrable massless flow of thermodynamic Bethe ansatz (TBA) is identified with tachyon action of boundary string field theory. We show that the temperature parametrizing a massless flow in the TBA formalism can be identified with tachyon energy for the classical action at least near the ultraviolet fixed point, i.e., the open string vacuum.
NASA Astrophysics Data System (ADS)
Zieniuk, Eugeniusz; Kapturczak, Marta
2017-07-01
In recent studies of parametric integral equations system (PIES), the input data, necessary to define the shape of boundary, was defined in precise way. However, it is just assumption for further calculations. In practice even the most accurate measurement instruments generate errors. Therefore, in this paper we decide to propose the method for modelling and solving the boundary value problems with uncertainly defined shape of boundary. In view of advantages in precisely defined problems, we decide to generalize PIES method. To define the uncertainty of the input data we propose the modification of directed interval arithmetic.
Singularity Preserving Numerical Methods for Boundary Integral Equations
NASA Technical Reports Server (NTRS)
Kaneko, Hideaki (Principal Investigator)
1996-01-01
In the past twelve months (May 8, 1995 - May 8, 1996), under the cooperative agreement with Division of Multidisciplinary Optimization at NASA Langley, we have accomplished the following five projects: a note on the finite element method with singular basis functions; numerical quadrature for weakly singular integrals; superconvergence of degenerate kernel method; superconvergence of the iterated collocation method for Hammersteion equations; and singularity preserving Galerkin method for Hammerstein equations with logarithmic kernel. This final report consists of five papers describing these projects. Each project is preceeded by a brief abstract.
A finite element-boundary integral method for cavities in a circular cylinder
NASA Technical Reports Server (NTRS)
Kempel, Leo C.; Volakis, John L.
1992-01-01
Conformal antenna arrays offer many cost and weight advantages over conventional antenna systems. However, due to a lack of rigorous mathematical models for conformal antenna arrays, antenna designers resort to measurement and planar antenna concepts for designing non-planar conformal antennas. Recently, we have found the finite element-boundary integral method to be very successful in modeling large planar arrays of arbitrary composition in a metallic plane. We extend this formulation to conformal arrays on large metallic cylinders. In this report, we develop the mathematical formulation. In particular, we discuss the shape functions, the resulting finite elements and the boundary integral equations, and the solution of the conformal finite element-boundary integral system. Some validation results are presented and we further show how this formulation can be applied with minimal computational and memory resources.
Analyzing diffraction gratings by a boundary integral equation Neumann-to-Dirichlet map method.
Wu, Yumao; Lu, Ya Yan
2009-11-01
For analyzing diffraction gratings, a new method is developed based on dividing one period of the grating into homogeneous subdomains and computing the Neumann-to-Dirichlet (NtD) maps for these subdomains by boundary integral equations. For a subdomain, the NtD operator maps the normal derivative of the wave field to the wave field on its boundary. The integral operators used in this method are simple to approximate, since they involve only the standard Green's function of the Helmholtz equation in homogeneous media. The method retains the advantages of existing boundary integral equation methods for diffraction gratings but avoids the quasi-periodic Green's functions that are expensive to evaluate.
NASA Astrophysics Data System (ADS)
Gu, Boliang; Nihei, Kurt T.; Myer, Larry R.
1996-07-01
This paper describes a boundary integral equation method for simulating two-dimensional elastic wave propagation in a rock mass with nonwelded discontinuities, such as fractures, joints, and faults. The numerical formulation is based on the three-dimensional boundary integral equations that are reduced to two dimensions by numerical integration along the axis orthogonal to the plane of interest. The numerical technique requires the assembly and solution of the coefficient matrix only for the first time step, resulting in a significant reduction in computational time. Nonwelded discontinuities are each treated as an elastic contact between blocks of a fractured rock mass. Across such an elastic contact, seismic stresses are continuous and particle displacements are discontinuous by an amount which is proportional to the stress on the discontinuity and inversely to the specific stiffness of the discontinuity. Simulations demonstrate that such formulated boundary element method successfully models elastic wave propagation along and across a single fracture generated by a line source.
Boundary integral method for stationary states of two-dimensional quantum systems
Kosztin, I.; Schulten, K.
1997-04-01
The boundary integral method for calculating the stationary states of a quantum particle in nano-devices and quantum billiards is presented in detail at an elementary level. According to the method, wave functions inside the domain of the device or billiard are expressed in terms of line integrals of the wavefunction and its normal derivative along the domain`s boundary; the respective energy eigenvalues are obtained as the roots of Fredholm determinants. Numerical implementations of the method are described and applied to determine the energy level statistics of billiards with circular and stadium shapes and demonstrate the quantum mechanical characteristics of chaotic motion. The treatment of other examples as well as the advantages and limitations of the boundary integral method are discussed.
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.
Sugisaka, Jun-ichiro; Yasui, Takashi; Hirayama, Koichi
2015-05-01
We expand the difference-field boundary element method (DFBEM) to calculate wave scattering from a variety of local periodic structure defects. The DFBEM is a numerical method for simulating the diffraction caused by a periodic surface-relief structure with a defect. Although it is more efficient than conventional techniques such as the finite-difference time-domain (FDTD) method, the original DFBEM is limited to projection defects. Here, we derive the integral equations and expressions for crack and buried-pillar defects, and also demonstrate some numerical analyses, validating the results by comparison with results from the FDTD method and the dielectric interface boundary conditions.
[Boundaries and integrity in the "Social Contract for Spanish Science", 1907-1939].
Gómez, Amparo
2014-01-01
This article analyzes the relationship between science and politics in Spain in the early 20th century from the perspective of the Social Contract for Science. The article shows that a genuine social contract for science was instituted in Spain during this period, although some boundary and integrity problems emerged. These problems are analyzed, showing that the boundary problems were a product of the conservative viewpoint on the relationship between science and politics, while the integrity problems involved the activation of networks of influence in the awarding of scholarships to study abroad. Finally, the analysis reveals that these problems did not invalidate the Spanish social contract for science.
Magnetic local time variation and scaling of poleward auroral boundary dynamics
NASA Astrophysics Data System (ADS)
Longden, N.; Chisham, G.; Freeman, M. P.
2014-12-01
The balance of dayside and nightside reconnection processes within the Earth's magnetosphere and its effect on the amount of open magnetic flux threading the ionosphere is well understood in terms of the expanding-contracting polar cap model. However, the nature and character of the consequential fluctuations in the polar cap boundary are poorly understood. By using the poleward auroral luminosity boundary (PALB), as measured by the FUV instrument of the IMAGE spacecraft, as a proxy for the polar cap boundary, we have studied the motion of this boundary for more than 2 years across the complete range of magnetic local time. Our results show that the dayside PALB dynamics are broadly self-similar on timescales of 12 min to 6 h and appear to be monofractal. Similarity with the characteristics of solar wind and interplanetary magnetic field variability suggests that this dayside monofractal behavior is predominantly inherited from the solar wind via the reconnection process. The nightside PALB dynamics exhibit scale-free behavior at intermediate time scales (12-90 min) and appear to be multifractal. We propose that this character is a result of the intermittent multifractal structure of magnetotail reconnection.
Dynamical many-body localization in an integrable model
NASA Astrophysics Data System (ADS)
Keser, Aydin Cem; Ganeshan, Sriram; Refael, Gil; Galitski, Victor
2016-08-01
We investigate dynamical many-body localization and delocalization in an integrable system of periodically-kicked, interacting linear rotors. The linear-in-momentum Hamiltonian makes the Floquet evolution operator analytically tractable for arbitrary interactions. One of the hallmarks of this model is that depending on certain parameters, it manifests both localization and delocalization in momentum space. We present a set of "emergent" integrals of motion, which can serve as a fundamental diagnostic of dynamical localization in the interacting case. We also propose an experimental scheme, involving voltage-biased Josephson junctions, to realize such many-body kicked models.
Blow-up problems for the heat equation with a local nonlinear Neumann boundary condition
NASA Astrophysics Data System (ADS)
Yang, Xin; Zhou, Zhengfang
2016-09-01
This paper estimates the blow-up time for the heat equation ut = Δu with a local nonlinear Neumann boundary condition: The normal derivative ∂ u / ∂ n =uq on Γ1, one piece of the boundary, while on the rest part of the boundary, ∂ u / ∂ n = 0. The motivation of the study is the partial damage to the insulation on the surface of space shuttles caused by high speed flying subjects. We show the finite time blow-up of the solution and estimate both upper and lower bounds of the blow-up time in terms of the area of Γ1. In many other work, they need the convexity of the domain Ω and only consider the problem with Γ1 = ∂ Ω. In this paper, we remove the convexity condition and only require ∂Ω to be C2. In addition, we deal with the local nonlinearity, namely Γ1 can be just part of ∂Ω.
Yi, Chucai; Tian, Yingli
2012-09-01
In this paper, we propose a novel framework to extract text regions from scene images with complex backgrounds and multiple text appearances. This framework consists of three main steps: boundary clustering (BC), stroke segmentation, and string fragment classification. In BC, we propose a new bigram-color-uniformity-based method to model both text and attachment surface, and cluster edge pixels based on color pairs and spatial positions into boundary layers. Then, stroke segmentation is performed at each boundary layer by color assignment to extract character candidates. We propose two algorithms to combine the structural analysis of text stroke with color assignment and filter out background interferences. Further, we design a robust string fragment classification based on Gabor-based text features. The features are obtained from feature maps of gradient, stroke distribution, and stroke width. The proposed framework of text localization is evaluated on scene images, born-digital images, broadcast video images, and images of handheld objects captured by blind persons. Experimental results on respective datasets demonstrate that the framework outperforms state-of-the-art localization algorithms.
Salient object detection based on discriminative boundary and multiple cues integration
NASA Astrophysics Data System (ADS)
Jiang, Qingzhu; Wu, Zemin; Tian, Chang; Liu, Tao; Zeng, Mingyong; Hu, Lei
2016-01-01
In recent years, many saliency models have achieved good performance by taking the image boundary as the background prior. However, if all boundaries of an image are equally and artificially selected as background, misjudgment may happen when the object touches the boundary. We propose an algorithm called weighted contrast optimization based on discriminative boundary (wCODB). First, a background estimation model is reliably constructed through discriminating each boundary via Hausdorff distance. Second, the background-only weighted contrast is improved by fore-background weighted contrast, which is optimized through weight-adjustable optimization framework. Then to objectively estimate the quality of a saliency map, a simple but effective metric called spatial distribution of saliency map and mean saliency in covered window ratio (MSR) is designed. Finally, in order to further promote the detection result using MSR as the weight, we propose a saliency fusion framework to integrate three other cues-uniqueness, distribution, and coherence from three representative methods into our wCODB model. Extensive experiments on six public datasets demonstrate that our wCODB performs favorably against most of the methods based on boundary, and the integrated result outperforms all state-of-the-art methods.
Cortical systems for local and global integration in discourse comprehension.
Egidi, Giovanna; Caramazza, Alfonso
2013-05-01
To understand language, we integrate what we hear or read with prior context. This research investigates the neural systems underlying this integration process, in particular the integration of incoming linguistic information with local, proximal context and with global, distal context. The experiments used stories whose endings were locally consistent or locally inconsistent. In addition, the stories' global context was either relevant or irrelevant for the integration of the endings. In Experiment 1, reading latencies showed that the perceived consistency of an ending depended on its fit with the local context, but the availability of a relevant global context attenuated this effect. Experiment 2 used BOLD fMRI to study whether different neural systems are sensitive to the local consistency of the endings and the relevance of the global context. A first analysis evaluated BOLD responses during the comprehension of story endings. It identified three networks: one sensitive to consistency with local context, one sensitive to the relevance of the global context, and one sensitive to both factors. These findings suggest that some regions respond to the holistic relation of local and global contexts while others track only the global or the local contexts. A second analysis examined correlations between BOLD activity during listening of the story endings and subsequent memory for those endings. It revealed two distinct networks: Positive correlations in areas usually involved in semantic processing and memory for language, and negative correlations in sensory, motor, and visual areas, indicating that weaker activity in the latter regions is conducive to better memory for linguistic content. More widespread memory correlates were found when global context was relevant for understanding a story ending. We conclude that integration at the discourse level involves the cooperation of different networks each sensitive to separate aspects of the task, and that integration is
A Formulation of Asymptotic and Exact Boundary Conditions Using Local Operators
NASA Technical Reports Server (NTRS)
Hagstrom, T.; Hariharan, S. I.
1998-01-01
In this paper we describe a systematic approach for constructing asymptotic boundary conditions for isotropic wave-like equations using local operators. The conditions take a recursive form with increasing order of accuracy. In three dimensions the recursion terminates and the resulting conditions are exact for solutions which are described by finite combinations of angular spherical harmonics. First, we develop the expansion for the two-dimensional wave equation and construct a sequence of easily implementable boundary conditions. We show that in three dimensions and analogous conditions are again easily implementable in addition to being exact. Also, we provide extensions of these ideas to hyperbolic systems. Namely, Maxwell's equations for TM waves are used to demonstrate the construction. Finally, we provide numerical examples to demonstrate the effectiveness of these conditions for a model problem governed by the wave equation.
Wu, Han-Chun; Chaika, Alexander N.; Hsu, Ming-Chien; Huang, Tsung-Wei; Abid, Mourad; Abid, Mohamed; Aristov, Victor Yu; Molodtsova, Olga V.; Babenkov, Sergey V.; Niu, Yuran; Murphy, Barry E.; Krasnikov, Sergey A.; Lübben, Olaf; Liu, Huajun; Chun, Byong Sun; Janabi, Yahya T.; Molotkov, Sergei N.; Shvets, Igor V.; Lichtenstein, Alexander I.; Katsnelson, Mikhail I.; Chang, Ching-Ray
2017-01-01
Graphene supports long spin lifetimes and long diffusion lengths at room temperature, making it highly promising for spintronics. However, making graphene magnetic remains a principal challenge despite the many proposed solutions. Among these, graphene with zig-zag edges and ripples are the most promising candidates, as zig-zag edges are predicted to host spin-polarized electronic states, and spin–orbit coupling can be induced by ripples. Here we investigate the magnetoresistance of graphene grown on technologically relevant SiC/Si(001) wafers, where inherent nanodomain boundaries sandwich zig-zag structures between adjacent ripples of large curvature. Localized states at the nanodomain boundaries result in an unprecedented positive in-plane magnetoresistance with a strong temperature dependence. Our work may offer a tantalizing way to add the spin degree of freedom to graphene. PMID:28198379
NASA Astrophysics Data System (ADS)
Wu, Han-Chun; Chaika, Alexander N.; Hsu, Ming-Chien; Huang, Tsung-Wei; Abid, Mourad; Abid, Mohamed; Aristov, Victor Yu; Molodtsova, Olga V.; Babenkov, Sergey V.; Niu, Yuran; Murphy, Barry E.; Krasnikov, Sergey A.; Lübben, Olaf; Liu, Huajun; Chun, Byong Sun; Janabi, Yahya T.; Molotkov, Sergei N.; Shvets, Igor V.; Lichtenstein, Alexander I.; Katsnelson, Mikhail I.; Chang, Ching-Ray
2017-02-01
Graphene supports long spin lifetimes and long diffusion lengths at room temperature, making it highly promising for spintronics. However, making graphene magnetic remains a principal challenge despite the many proposed solutions. Among these, graphene with zig-zag edges and ripples are the most promising candidates, as zig-zag edges are predicted to host spin-polarized electronic states, and spin-orbit coupling can be induced by ripples. Here we investigate the magnetoresistance of graphene grown on technologically relevant SiC/Si(001) wafers, where inherent nanodomain boundaries sandwich zig-zag structures between adjacent ripples of large curvature. Localized states at the nanodomain boundaries result in an unprecedented positive in-plane magnetoresistance with a strong temperature dependence. Our work may offer a tantalizing way to add the spin degree of freedom to graphene.
Integrating Sustainability into the Curriculum: Crossing Disciplinary Boundaries
NASA Astrophysics Data System (ADS)
Pushnik, J.
2012-12-01
The next generation will confront an increased number of global issues that interface the complexities of socioeconomic perspectives, environmental stability, poverty and development. Recently California State University Chico undertook a general education reform, providing a unique opportunity to craft a general education pathway to prepare students for these challenges by focusing a curriculum on sustainability. The Sustainability Pathway emphasizes a system thinking approach to help students understand and be able to address a set of problems involving the biosphere processes, human institutions and the economic vitality. The curriculum intentionally integrates courses from across the disciplines of natural sciences, social sciences, agriculture, engineering, economics, arts and humanities into a central focused theme of sustainability. The diverse backgrounds and academic focus of the participating faculty has necessitate the development of a common language and a cohesion within the curriculum. To address these needs a faculty learning community (FLC) was established to build on a common set of case studies. Three regional environmental water related issues were selected that had demonstrable socioeconomic, equity/ethical dimensions and environmental consequences. These case studies are Klamath River basin in northern California, the Bay-Delta project in the central part of the state and the Sultan Sea in southern California. Members of the FLC has contributed a perspective from their academic discipline which includes proposed reading lists, web based resources and PowerPoint presentations which are housed in common web- based resource repository. The pedagogical rational is to create linkages and cohesion among the courses in the curriculum by iteratively examining these case studies as basis for development of a multidisciplinary perspective as students progress through their general education.
NASA Astrophysics Data System (ADS)
Gorev, V. N.; Katasonov, M. M.; Kozlov, V. V.
In recent years the longitudinal localized vortex disturbances, so called “streaky structures”, or “puffs” appearing in boundary layers under the effect of external flow turbulence are of much interest. Once these disturbances are generated, they amplify downstream, turn into the incipient spots, and finally, result in laminar-turbulent transition “1, 2”. In the present work wave packets (forerunners) occurring in the regions preceding a drastic change of flow velocity inside the boundary layer at the localized disturbances fronts are in focus. Their characteristics and dynamics have been studied experimentally in straight wing boundary layer. The investigations were carried out in the subsonic low-turbulent wind tunnel T-324, ITAM SB RAS. Free stream velocity was in the range 4 < U∞ < 8 m/s. Free stream turbulence level was in the range 0.04%U∞ < Tu < 0.79%U∞. The high level of free stream turbulence was generated from grid located at the beginning of the wing tunnel test section. One model of a straight wing was 1000 mm span with the chord of 450 mm, an other model was 200 mm span and 290 mm chord. The models were set vertically at positive (5°) and zero angle of attack. The localized disturbances (streaks) were generated via blowing (suction) through a thin slot arranged in the surface parallel to the leading edge. In the present experiments the high-frequency perturbations, i.e. forerunners, at the leading and back fronts of the localized disturbances evolving in the boundary layer have been found. Their characteristics affected by the external-flow pressure gradient, free stream turbulence level (Tu), the way of the longitudinal structures generation, and velocity gradients induced by the latter were investigated. In particular, it was observed that the forerunners are strongly amplified in the adverse pressure gradient flow being much influenced by local velocity gradients. The results of the study make reason to consider the forerunners as
Effects of local and global mechanical distortions to hypervelocity boundary layers
NASA Astrophysics Data System (ADS)
Flaherty, William P.
The response of hypervelocity boundary layers to global mechanical distortions due to concave surface curvature is examined. Surface heat transfer, visual boundary layer thickness, and pressure sensitive paint (PSP) data are obtained for a suite of models with different concave surface geometries. Results are compared to predictions using existing approximate methods. Near the leading edge, good agreement is observed, but at larger pressure gradients, predictions diverge significantly from the experimental data. Up to a factor of five underprediction is reported in regions with greatest distortion. Curve fits to the experimental data are compared with surface equations. It is demonstrated that reasonable estimates of the laminar heat flux augmentation may be obtained as a function of the local turning angle for all model geometries, even at the conditions of greatest distortion. As a means of introducing additional local distortions, vortex generators are used to impose streamwise structures into the boundary layer. The response of the large scale vortical structures to an adverse pressure gradient is investigated. For a flat plate baseline case, heat transfer augmentation at similar levels to turbulent flow is measured. For the concave geometries, increases in heat transfer by factors up to 2.6 are measured over the laminar values, though for higher turning angle cases, a relaxation to below undisturbed values is reported at turning angles between 10 and 15 degrees. The scaling of heat transfer with turning angle that is identified for the laminar boundary layer response is found to be robust even in the presence of the imposed vortex structures. PSP measurements indicated that natural streaks form over concave models even when imposed vorticity is present. Correlations found between the heat transfer and natural streak formation are discussed and indicate possible vortex interactions.
Bardhan, J. P.; Mathematics and Computer Science
2008-10-14
The importance of molecular electrostatic interactions in aqueous solution has motivated extensive research into physical models and numerical methods for their estimation. The computational costs associated with simulations that include many explicit water molecules have driven the development of implicit-solvent models, with generalized-Born (GB) models among the most popular of these. In this paper, we analyze a boundary-integral equation interpretation for the Coulomb-field approximation (CFA), which plays a central role in most GB models. This interpretation offers new insights into the nature of the CFA, which traditionally has been assessed using only a single point charge in the solute. The boundary-integral interpretation of the CFA allows the use of multiple point charges, or even continuous charge distributions, leading naturally to methods that eliminate the interpolation inaccuracies associated with the Still equation. This approach, which we call boundary-integral-based electrostatic estimation by the CFA (BIBEE/CFA), is most accurate when the molecular charge distribution generates a smooth normal displacement field at the solute-solvent boundary, and CFA-based GB methods perform similarly. Conversely, both methods are least accurate for charge distributions that give rise to rapidly varying or highly localized normal displacement fields. Supporting this analysis are comparisons of the reaction-potential matrices calculated using GB methods and boundary-element-method (BEM) simulations. An approximation similar to BIBEE/CFA exhibits complementary behavior, with superior accuracy for charge distributions that generate rapidly varying normal fields and poorer accuracy for distributions that produce smooth fields. This approximation, BIBEE by preconditioning (BIBEE/P), essentially generates initial guesses for preconditioned Krylov-subspace iterative BEMs. Thus, iterative refinement of the BIBEE/P results recovers the BEM solution; excellent agreement
NASA Astrophysics Data System (ADS)
Bardhan, Jaydeep P.
2008-10-01
The importance of molecular electrostatic interactions in aqueous solution has motivated extensive research into physical models and numerical methods for their estimation. The computational costs associated with simulations that include many explicit water molecules have driven the development of implicit-solvent models, with generalized-Born (GB) models among the most popular of these. In this paper, we analyze a boundary-integral equation interpretation for the Coulomb-field approximation (CFA), which plays a central role in most GB models. This interpretation offers new insights into the nature of the CFA, which traditionally has been assessed using only a single point charge in the solute. The boundary-integral interpretation of the CFA allows the use of multiple point charges, or even continuous charge distributions, leading naturally to methods that eliminate the interpolation inaccuracies associated with the Still equation. This approach, which we call boundary-integral-based electrostatic estimation by the CFA (BIBEE/CFA), is most accurate when the molecular charge distribution generates a smooth normal displacement field at the solute-solvent boundary, and CFA-based GB methods perform similarly. Conversely, both methods are least accurate for charge distributions that give rise to rapidly varying or highly localized normal displacement fields. Supporting this analysis are comparisons of the reaction-potential matrices calculated using GB methods and boundary-element-method (BEM) simulations. An approximation similar to BIBEE/CFA exhibits complementary behavior, with superior accuracy for charge distributions that generate rapidly varying normal fields and poorer accuracy for distributions that produce smooth fields. This approximation, BIBEE by preconditioning (BIBEE/P), essentially generates initial guesses for preconditioned Krylov-subspace iterative BEMs. Thus, iterative refinement of the BIBEE/P results recovers the BEM solution; excellent agreement
NASA Technical Reports Server (NTRS)
Patel, D. K.; Czarnecki, K. R.
1977-01-01
An investigation was made to determine the feasibility of using a boundary layer integral method to study the separation of a turbulent boundary layer on a two dimensional ramp at supersonic speeds. The numerical calculations were made for a free stream Mach number of 3, a Reynolds number of 10 million, and over a ramp angle range from 0 deg to 30 deg. For ramp angles where no flow separation was indicated, theoretical calculations were in reasonable agreement with experimental data except for a somewhat belated rise in pressure. For larger ramp angles, where separation was present, the investigation produced results that were not in agreement with experiment or with results calculated by time dependent Navier-Stokes methods. This apparently was true because no provision had been made for a proper shock boundary layer interaction where strong normal pressure gradients are induced within the boundary layer under the shock independent of surface curvature effects.
Brown, Phil
2013-06-01
This article reviews the personal and professional processes of developing an interdisciplinary approach to understanding the complex issues of environmental health in their community, political-economic, social science, and scientific contexts. This interdisciplinary approach includes a synthesis of research, policy work, and advocacy. To examine multiple forms of interdisciplinarity, I examine pathways of integrating medical and environmental sociology via three challenges to the boundaries of traditional research: (1) crossing the boundaries of medical and environmental sociology, (2) linking social science and environmental health science, and (3) crossing the boundary of research and advocacy. These boundary crossings are discussed in light of conceptual and theoretical developments of popular epidemiology, contested illnesses, and health social movements. This interdisciplinary work offers a more comprehensive sociological lens for understanding complex problems and a practical ability to join with scientists, activists, and officials to meet public health needs for amelioration and prevention of environmental health threats.
Fiebelkorn, Ian C; Foxe, John J; Schwartz, Theodore H; Molholm, Sophie
2010-05-01
The brain processes multisensory features of an object (e.g., its sound and shape) in separate cortical regions. A key question is how representations of these features bind together to form a coherent percept (the 'binding problem'). Here we tested the hypothesis that the determination of an object's visuospatial boundaries is paramount to the linking of its multisensory features (i.e., that the refinement of attended space through the formation of visual boundaries establishes the boundaries for multisensory feature integration). We recorded both scalp and intracranial electrophysiological data in response to Kanizsa-type illusory contour stimuli (in which pacman-like elements give the impression of a single object), their non-illusory counterparts, and auditory stimuli. Participants performed a visual task and ignored sounds. Enhanced processing of task-irrelevant sounds when paired with attended visual stimuli served as our metric for multisensory feature integration [e.g., Busse et al. (2005) Proc. Natl Acad. Sci. USA 102: 18751-18756]. According to our hypothesis, task-irrelevant sounds paired with Kanizsa-type illusory contour stimuli (which have well-defined boundaries) should receive enhanced processing relative to task-irrelevant sounds paired with non-illusory contour stimuli (which have ambiguous boundaries). The scalp data clearly support this prediction and, combined with the intracranial data, advocate for an important extension of models for multisensory feature integration. We propose a model in which (i) the visual boundaries of an object are established through processing in occipitotemporal cortex, and (ii) attention then spreads to cortical regions that process features that fall within the object's established visual boundaries, including its task-irrelevant multisensory features.
Boucher, Yan; Cordero, Otto X.; Takemura, Alison; Hunt, Dana E.; Schliep, Klaus; Bapteste, Eric; Lopez, Philippe; Tarr, Cheryl L.; Polz, Martin F.
2011-01-01
Vibrio cholerae represents both an environmental pathogen and a widely distributed microbial species comprised of closely related strains occurring in the tropical to temperate coastal ocean across the globe (Colwell RR, Science 274:2025–2031, 1996; Griffith DC, Kelly-Hope LA, Miller MA, Am. J. Trop. Med. Hyg. 75:973–977, 2006; Reidl J, Klose KE, FEMS Microbiol. Rev. 26:125–139, 2002). However, although this implies dispersal and growth across diverse environmental conditions, how locally successful populations assemble from a possibly global gene pool, relatively unhindered by geographic boundaries, remains poorly understood. Here, we show that environmental Vibrio cholerae possesses two, largely distinct gene pools: one is vertically inherited and globally well mixed, and the other is local and rapidly transferred across species boundaries to generate an endemic population structure. While phylogeographic analysis of isolates collected from Bangladesh and the U.S. east coast suggested strong panmixis for protein-coding genes, there was geographic structure in integrons, which are the only genomic islands present in all strains of V. cholerae (Chun J, et al., Proc. Natl. Acad. Sci. U. S. A. 106:15442–15447, 2009) and are capable of acquiring and expressing mobile gene cassettes. Geographic differentiation in integrons arises from high gene turnover, with acquisition from a locally cooccurring sister species being up to twice as likely as exchange with conspecific but geographically distant V. cholerae populations. PMID:21486909
NASA Astrophysics Data System (ADS)
Petit, R.; Hugonin, J. P.
1984-12-01
In 1977, we published two papers on the diffraction of electromagnetic waves at a locally deformed flat boundary surface and at a locally deformed plane wave-guide. Since this time, an important theoretical and numerical study of locally deformed stratified media has been carried out in our lab. This study has been summarized three years ago in the J.O.S.A. and it has been presented last year as a thesis dissertation. But both the J.O.S.A. paper and the thesis are difficult to read for non specialists because the involved mathematics are rather subtle and, at least, tedious for experimenters. In other words, an important work has been done, which seems to be unknown to most of "practical people". We thought that a SPIE meeting is a good opportunity to cure this regrettable situation. A computer program is now available which probably might be very useful for those working on rough dielectric surfaces and on guided wave devices with corrugated boundaries. We would like to present to engineers the possibilities and the limits of this big computer code called hereafter Program (P)
Integrals of motion for one-dimensional Anderson localized systems
Modak, Ranjan; Mukerjee, Subroto; Yuzbashyan, Emil A.; ...
2016-03-02
Anderson localization is known to be inevitable in one-dimension for generic disordered models. Since localization leads to Poissonian energy level statistics, we ask if localized systems possess ‘additional’ integrals of motion as well, so as to enhance the analogy with quantum integrable systems. Weanswer this in the affirmative in the present work. We construct a set of nontrivial integrals of motion for Anderson localized models, in terms of the original creation and annihilation operators. These are found as a power series in the hopping parameter. The recently found Type-1 Hamiltonians, which are known to be quantum integrable in a precisemore » sense, motivate our construction.Wenote that these models can be viewed as disordered electron models with infinite-range hopping, where a similar series truncates at the linear order.Weshow that despite the infinite range hopping, all states but one are localized.Wealso study the conservation laws for the disorder free Aubry–Andre model, where the states are either localized or extended, depending on the strength of a coupling constant.Weformulate a specific procedure for averaging over disorder, in order to examine the convergence of the power series. Using this procedure in the Aubry–Andre model, we show that integrals of motion given by our construction are well-defined in localized phase, but not so in the extended phase. Lastly, we also obtain the integrals of motion for a model with interactions to lowest order in the interaction.« less
Event-Related Potential Indicators of Text Integration across Sentence Boundaries
ERIC Educational Resources Information Center
Yang, Chin Lung; Perfetti, Charles A.; Schmalhofer, Franz
2007-01-01
An event-related potentials (ERPs) study examined word-to-text integration processes across sentence boundaries. In a two-sentence passage, the accessibility of a referent for the first content word of the second sentence (the target word) was varied by the wording of the first sentence in one of the following ways: lexically (explicitly using…
Chen, Ke
1996-12-31
We study various preconditioning techniques for the iterative solution of boundary integral equations, and aim to provide a theory for a class of sparse preconditioners. Two related ideas are explored here: singularity separation and inverse approximation. Our preliminary conclusion is that singularity separation based preconditioners perform better than approximate inverse based while it is desirable to have both features.
ERIC Educational Resources Information Center
Kao, Gloria Yi-Ming; Lin, Sunny S. J.; Sun, Chuen-Tsai
2008-01-01
The authors address the role of computer support for building conceptual self-awareness--that is, enabling students to think outside of concept boundaries in hope of enhancing creative potential. Based on meta-cognition theory, we developed an integrated concept mapping system (ICMSys) to improve users' conceptual self-awareness in addition to…
Quantum Integrals for a Semi-Infinite q-Boson System with Boundary Interactions
NASA Astrophysics Data System (ADS)
van Diejen, Jan Felipe; Emsiz, Erdal
2015-05-01
We provide explicit formulas for the quantum integrals of a semi-infinite q-boson system with boundary interactions. These operators and their commutativity are deduced from the Pieri formulas for a qto 0 Hall-Littlewood type degeneration of the Macdonald-Koornwinder polynomials.
ERIC Educational Resources Information Center
Kao, Gloria Yi-Ming; Lin, Sunny S. J.; Sun, Chuen-Tsai
2008-01-01
The authors address the role of computer support for building conceptual self-awareness--that is, enabling students to think outside of concept boundaries in hope of enhancing creative potential. Based on meta-cognition theory, we developed an integrated concept mapping system (ICMSys) to improve users' conceptual self-awareness in addition to…
Su, Yong R.; He, Zijiang J.; Ooi, Teng Leng
2010-01-01
A monocular boundary contour (MBC) rivalry stimulus has two half-images, a homogeneous grating and the same homogeneous grating with an additional disc region. The outline/frame of the MBC disc is created by relative phase-shift, or orientation difference. We found the increment contrast threshold and reaction time to detect a monocular Gabor probe elevated on the homogeneous half-image pedestal. The interocular suppression begins as early as 80 msec upon stimulus onset. Moreover, the suppression magnitude is larger when the MBC disc is defined by orientation difference rather than phase-shift, revealing the suppression caused by competing local features in addition to MBC. PMID:20624411
Tarasov, Yu.V. Shostenko, L.D.
2015-05-15
A unified theory for the conductance of an infinitely long multimode quantum wire whose finite segment has randomly rough lateral boundaries is developed. It enables one to rigorously take account of all feasible mechanisms of wave scattering, both related to boundary roughness and to contacts between the wire rough section and the perfect leads within the same technical frameworks. The rough part of the conducting wire is shown to act as a mode-specific randomly modulated effective potential barrier whose height is governed essentially by the asperity slope. The mean height of the barrier, which is proportional to the average slope squared, specifies the number of conducting channels. Under relatively small asperity amplitude this number can take on arbitrary small, up to zero, values if the asperities are sufficiently sharp. The consecutive channel cut-off that arises when the asperity sharpness increases can be regarded as a kind of localization, which is not related to the disorder per se but rather is of entropic or (equivalently) geometric origin. The fluctuating part of the effective barrier results in two fundamentally different types of guided wave scattering, viz., inter- and intramode scattering. The intermode scattering is shown to be for the most part very strong except in the cases of (a) extremely smooth asperities, (b) excessively small length of the corrugated segment, and (c) the asperities sharp enough for only one conducting channel to remain in the wire. Under strong intermode scattering, a new set of conducting channels develops in the corrugated waveguide, which have the form of asymptotically decoupled extended modes subject to individual solely intramode random potentials. In view of this fact, two transport regimes only are realizable in randomly corrugated multimode waveguides, specifically, the ballistic and the localized regime, the latter characteristic of one-dimensional random systems. Two kinds of localization are thus shown to
Impact of local atomic stress on oxygen segregation at tilt boundaries in silicon
NASA Astrophysics Data System (ADS)
Ohno, Yutaka; Inoue, Kaihei; Fujiwara, Kozo; Kutsukake, Kentaro; Deura, Momoko; Yonenaga, Ichiro; Ebisawa, Naoki; Shimizu, Yasuo; Inoue, Koji; Nagai, Yasuyoshi; Yoshida, Hideto; Takeda, Seiji; Tanaka, Shingo; Kohyama, Masanori
2017-02-01
Using the atom probe tomography, transmission electron microscopy, and ab initio calculations, we investigate the three-dimensional distributions of oxygen atoms segregating at the typical large-angle grain boundaries (GBs) ( Σ 3 { 111 } , Σ 9 { 221 } , Σ 9 { 114 } , Σ 9 { 111 } / { 115 } , and Σ 27 { 552 } ) in Czochralski-grown silicon ingots. Oxygen atoms with a covalent radius that is larger than half of the silicon's radius would segregate at bond-centered positions under tensile stresses above about 2 GPa, so as to attain a more stable bonding network by reducing the local stresses. The number of oxygen atoms segregating in a unit GB area N GB (in atoms/nm2) is hypothesized to be proportional to both the number of the tensilely-stressed positions in a unit boundary area n bc and the average concentration of oxygen atoms around the boundary [ O i ] (in at. %) with N GB ˜ 50 n bc [ O i ] . This indicates that the probability of oxygen atoms at the segregation positions would be, on average, fifty times larger than in bond-centered positions in defect-free regions.
Study of flow control by localized volume heating in hypersonic boundary layers
NASA Astrophysics Data System (ADS)
Keller, M. A.; Kloker, M. J.; Kirilovskiy, S. V.; Polivanov, P. A.; Sidorenko, A. A.; Maslov, A. A.
2014-12-01
Boundary-layer flow control is a prerequisite for a safe and efficient operation of future hypersonic transport systems. Here, the influence of an electric discharge—modeled by a heat-source term in the energy equation—on laminar boundary-layer flows over a flat plate with zero pressure gradient at Mach 3, 5, and 7 is investigated numerically. The aim was to appraise the potential of electro-gasdynamic devices for an application as turbulence generators in the super- and hypersonic flow regime. The results with localized heat-source elements in boundary layers are compared to cases with roughness elements serving as classical passive trips. The numerical simulations are performed using the commercial code ANSYS FLUENT (by ITAM) and the high-order finite-difference DNS code NS3D (by IAG), the latter allowing for the detailed analysis of laminar flow instability. For the investigated setups with steady heating, transition to turbulence is not observed, due to the Reynolds-number lowering effect of heating.
N{sup ±}-integrals and boundary values of Cauchy-type integrals of finite measures
Aliev, R. A. E-mail: alievrashid@box.az
2014-07-31
Let Γ be a simple closed Lyapunov contour with finite complex measure ν, and let G{sup +} be the bounded and G{sup −} the unbounded domains with boundary Γ. Using new notions (so-called N-integration and N{sup +}- and N{sup −}-integrals), we prove that the Cauchy-type integrals F{sup +}(z), z∈G{sup +}, and F{sup −}(z), z∈G{sup −}, of ν are Cauchy N{sup +}- and N{sup −}-integrals, respectively. In the proof of the corresponding results, the additivity property and the validity of the change-of-variable formula for the N{sup +}- and N{sup −}-integrals play an essential role. Bibliography: 21 titles. (paper)
NASA Astrophysics Data System (ADS)
Rogowitz, Anna; Grasemann, Bernhard; Clancy White, Joseph
2015-04-01
Strain localization in monomineralic rocks is often associated with brittle precursors, resulting in stress and strain concentration, followed by grain size reduction and activation of grain-size-sensitive deformation mechanisms such as diffusion creep, grain boundary sliding and cataclastic flow. The aforementioned mechanisms typically tend to produce a random crystallographic orientation or a decrease in intensity of a pre-existing texture. However, reports of fine grained polycrystalline materials showing a preferred crystallographic orientation indicate a need for subsequent grain re-organization by either static annealing or the activation of additional deformation mechanisms in conjunction with grain boundary sliding. We present observations from an almost pure calcite marble layer from Syros Island (Cyclades, Greece) deformed in lower greenschist facies conditions. The presence of a crack (i.e. cross-cutting element) that rotated during shear resulted in the formation of a flanking structure. At the location of maximum displacement (120 cm) along the cross-cutting element, the marble is extremely fine grained (3 µm) leading to anticipation of deformation by grain-size-sensitive mechanisms. Detailed microstructural analysis of the highly strained (80 < gamma < 1000) calcite ultramylonite by optical microscopy, electron backscatter diffraction and scanning transmission electron microscopy show that recrystallization by bulging results in small, strain-free grains. The change in grain size appears to be concomitant with increased activity of independent grain boundary sliding as indicated by a random misorientation angle distribution. At the same time, dislocation multiplication through Frank-Read sources produces high mean dislocation density (~ 5x10^13 m^-2) as well as a weak primary CPO; the latter all argue that grain boundary sliding was accommodated by dislocation activity. Theoretical and experimental determined relationships (paleowattmeter
Dynamical many-body localization in an integrable model
NASA Astrophysics Data System (ADS)
Keser, Ayin C.; Ganeshan, Sriram; Refael, Gil; Galitski, Victor
We investigate dynamical many-body localization and delocalization in an integrable system of periodically-kicked, interacting linear rotors. The linear-in-momentum Hamiltonian makes the Floquet evolution operator analytically tractable for arbitrary interactions. One of the hallmarks of this model is that depending on certain parameters, it manifest both localization and delocalization in momentum space. We explicitly show that, for this model, the energy being bounded at long times is neither a necessary nor a sufficient condition for dynamical localization. We present a set of integrals of motion, which can serve as a fundamental diagnostic of dynamical localization. We also propose an experimental scheme, involving voltage-biased Josephson junctions, to realize such many-body kicked models.
Local isotropy in distorted turbulent boundary layers at high Reynolds number
NASA Technical Reports Server (NTRS)
Saddoughi, Seyed G.
1993-01-01
This is a report on the continuation of our experimental investigations of the hypothesis of local isotropy in shear flows. This hypothesis, which states that at sufficiently high Reynolds numbers the small-scale structures of turbulent motions are independent of large-scale structures and mean deformations, has been used in theoretical studies of turbulence and computational methods such as large-eddy simulation. Since Kolmogorov proposed his theory, there have been many experiments, conducted in wakes, jets, mixing layers, a tidal channel, and atmospheric and laboratory boundary layers, in which attempts have been made to verify - or refute - the local-isotropy hypothesis. However, a review of the literature over the last five decades indicated that, despite all these experiments in shear flows, there was no consensus in the scientific community regarding this hypothesis, and, therefore, it seemed worthwhile to undertake a fresh experimental investigation into this question.
Daeva, S.G.; Setukha, A.V.
2015-03-10
A numerical method for solving a problem of diffraction of acoustic waves by system of solid and thin objects based on the reduction the problem to a boundary integral equation in which the integral is understood in the sense of finite Hadamard value is proposed. To solve this equation we applied piecewise constant approximations and collocation methods numerical scheme. The difference between the constructed scheme and earlier known is in obtaining approximate analytical expressions to appearing system of linear equations coefficients by separating the main part of the kernel integral operator. The proposed numerical scheme is tested on the solution of the model problem of diffraction of an acoustic wave by inelastic sphere.
The turbulent bottom boundary layer and its influence on local dynamics over the continental shelf
NASA Astrophysics Data System (ADS)
Dewey, Richard D.; Leblond, Paul H.; Crawford, William R.
1988-11-01
We report on measurements of the structure of the bottom boundary layer on the continental shelf off Vancouver Island. A time series of vertical profiles obtained with the microstructure profiler FLY II revealed large temporal variations in the dissipation rate and in the density structure. The near-bottom current structure was simultaneously measured at fixed heights with conventional current meters. The data reveal the association between the predominantly diurnal tide and the variations in the structure of the bottom boundary layer. A clear distinction appears between the turbulent bottom boundary layer (8-40 m deep in a total water depth of 138 m) and the well-mixed layer (20-40 m deep). The two layers vary independently, with horizontal advection dominating the fluctuations in the thickness of the well-mixed layer while local dissipation is more closely related to the thickness of the turbulent layer. Variations in the density structure of the bottom layer are related to the strength and direction of the vertical shear and to the regional distribution of isopycnals. Current veering is commonly concentrated above the well-mixed layer. The evolution of the characteristics of the bottom layers is followed through a tidal cycle and related to local dissipation and other variables. Microstructure measurements from six locations over the southern portion of the Vancouver Island continental shelf are used to estimate the influence of turbulent energy dissipation on regional-scale flows. That fraction of the dissipation taking place in the bottom boundary layer is attributed to barotropic tidal flows, while that occurring above it is associated with nearly geostrophic baroclinic flows. Results give a lower limit of ˜ 1070 km for the length scale of shelf wave decay, in good agreement with current models; the estimates of tidal friction based on our dissipation measurements are however much lower than required by astronomical observations. An estimate of 230 h is
Local interstellar magnetic field determined from the interstellar boundary explorer ribbon
Zirnstein, E. J.; Heerikhuisen, J.; Funsten, H. O.; Livadiotis, G.; McComas, D. J.; Pogorelov, N. V.
2016-02-08
The solar wind emanating from the Sun interacts with the local interstellar medium (LISM), forming the heliosphere. Hydrogen energetic neutral atoms (ENAs) produced by the solar-interstellar interaction carry important information about plasma properties from the boundaries of the heliosphere, and are currently being measured by NASA's Interstellar Boundary Explorer (IBEX). IBEX observations show the existence of a “ribbon” of intense ENA emission projecting a circle on the celestial sphere that is centered near the local interstellar magnetic field (ISMF) vector. Here we show that the source of the IBEX ribbon as a function of ENA energy outside the heliosphere, uniquely coupled to the draping of the ISMF around the heliopause, can be used to precisely determine the magnitude (2.93 ± 0.08 μG) and direction (227.°28 ± 0.°69, 34.°62 ± 0.°45 in ecliptic longitude and latitude) of the pristine ISMF far (~1000 AU) from the Sun. We find that the ISMF vector is offset from the ribbon center by ~8.°3 toward the direction of motion of the heliosphere through the LISM, and their vectors form a plane that is consistent with the direction of deflected interstellar neutral hydrogen, thought to be controlled by the ISMF. Lastly, our results yield draped ISMF properties close to that observed by Voyager 1, the only spacecraft to directly measure the ISMF close to the heliosphere, and give predictions of the pristine ISMF that Voyager 1 has yet to sample.
Charged hadrons in local finite-volume QED+QCD with C⋆ boundary conditions
NASA Astrophysics Data System (ADS)
Lucini, B.; Patella, A.; Ramos, A.; Tantalo, N.
2016-02-01
In order to calculate QED corrections to hadronic physical quantities by means of lattice simulations, a coherent description of electrically-charged states in finite volume is needed. In the usual periodic setup, Gauss's law and large gauge transformations forbid the propagation of electrically-charged states. A possible solution to this problem, which does not violate the axioms of local quantum field theory, has been proposed by Wiese and Polley, and is based on the use of C⋆ boundary conditions. We present a thorough analysis of the properties and symmetries of QED in isolation and QED coupled to QCD, with C⋆ boundary conditions. In particular we learn that a certain class of electrically-charged states can be constructed in a fully consistent fashion without relying on gauge fixing and without peculiar complications. This class includes single particle states of most stable hadrons. We also calculate finite-volume corrections to the mass of stable charged particles and show that these are much smaller than in non-local formulations of QED.
NASA Astrophysics Data System (ADS)
Mácha, Václav; Tichý, Jakub
2014-10-01
We prove an L q theory result for generalized Stokes system in a {{C}^{2,1}} domain complemented with the perfect slip boundary conditions and under Φ-growth conditions. Since the interior regularity was obtained in Diening and Kaplický (Manu Math 141:336-361, 2013), a regularity up to the boundary is an aim of this paper. In order to get the main result, we use Calderón-Zygmund theory and the method developed in Caffarelli and Peral (Ann Math 130:189-213, 1989). We obtain higher integrability of the first gradient of a solution.
Simple non-integrable models for anharmonic localization
NASA Astrophysics Data System (ADS)
Houle, Paul A.
1997-03-01
Computer simulation reveals vibrational excitations can be localized in a perfect nonlinear lattice without defects in 1, 2 and 3 dimensions. I study simple models in detail to seek the essential physics and to investigate the possibility of finding localized excitations in real lattices. Starting with an five-atom circular chain with a quadratic plus quartic potential and imposing reflection symmetry on the initial conditions, I derive a non-integrable system with two degrees of freedom. This truncated system has a continuous family of periodic orbits of varying energy which remain localized for thousands of periods when transplanted onto an initially static 20-atom chain. I observe chaos, mode locking, and periodic orbits corresponding to standing waves with 5-atom spatial periodicity. In the truncated problem, localized trajectories lie on nested KAM tori; displacements from a central periodic orbit correspond to phonon-like modes superimposed on the localized mode. I investigate the stability matrix of the localized periodic orbits and semiclassically quantize the localized mode as a single degree of freedom which gains additional zero point energy from the quasi-phonons; semiclassical analysis may offer insight into the existence, production and detection of localized excitations. Additional information and Java simulations can be found at localization/> http://www.msc.cornell.edu/h~oule/localization/.
Boundary element model for simulating sound propagation and source localization within the lungs.
Ozer, M B; Acikgoz, S; Royston, T J; Mansy, H A; Sandler, R H
2007-07-01
An acoustic boundary element (BE) model is used to simulate sound propagation in the lung parenchyma. It is computationally validated and then compared with experimental studies on lung phantom models. Parametric studies quantify the effect of different model parameters on the resulting acoustic field within the lung phantoms. The BE model is then coupled with a source localization algorithm to predict the position of an acoustic source within the phantom. Experimental studies validate the BE-based source localization algorithm and show that the same algorithm does not perform as well if the BE simulation is replaced with a free field assumption that neglects reflections and standing wave patterns created within the finite-size lung phantom. The BE model and source localization procedure are then applied to actual lung geometry taken from the National Library of Medicine's Visible Human Project. These numerical studies are in agreement with the studies on simpler geometry in that use of a BE model in place of the free field assumption alters the predicted acoustic field and source localization results. This work is relevant to the development of advanced auscultatory techniques that utilize multiple noninvasive sensors to construct acoustic images of sound generation and transmission to identify pathologies.
Lee, Yong Woo; Lee, Duck Joo
2014-12-01
Kirchhoff's formula for the convective wave equation is derived using the generalized function theory. The generalized convective wave equation for a stationary surface is obtained, and the integral formulation, the convective Kirchhoff's formula, is derived. The formula has a similar form to the classical Kirchhoff's formula, but an additional term appears due to a moving medium effect. For convenience, the additional term is manipulated to a final form as the classical Kirchhoff's formula. The frequency domain boundary integral can be obtained from the current time domain boundary integral form. The derived formula is verified by comparison with the analytic solution of source in the uniform flow. The formula is also utilized as a boundary integral equation. Time domain boundary element method (BEM) analysis using the boundary integral equation is conducted, and the results show good agreement with the analytical solution. The formula derived here can be useful for sound radiation and scattering by arbitrary bodies in a moving medium in the time domain.
Living Authors, Living Stories: Integrating Local Authors into Our Curriculum
ERIC Educational Resources Information Center
Newman, Beatrice Mendez
2009-01-01
Keeping literature classrooms vibrant, energized, and current can require supreme pedagogical effort, especially in light of students' sometimes pointed disinterest in traditional and/or canonical texts. Integrating local authors into a standard curriculum can be an effective strategy for invigorating students' interest in literature and helping…
NASA Astrophysics Data System (ADS)
López-Martínez, Rafael; Barragán, Ricardo; Bernal, Juan Pablo; Reháková, Daniela; Gómez-Tuena, Arturo; Martini, Michelangelo; Ortega, Carlos
2017-04-01
The integration of calpionellid biostratigraphy, microfacies analysis, Usbnd Pb geochronology, and strontium chemostratigraphy improves the definition of the Berriasian-Valanginian boundary in the Tlatlauquitepec area and validates the age of calpionellid zones from eastern Mexico in this interval. An age of 139.85 Ma derived from 87Sr/86Sr ratio within the base of Calpionellites Zone defines the Berriasian-Valanginian boundary. Additionally, the 134.0 ± 0.5 Ma Usbnd Pb age returned by zircon grains from a tuff level exposed at the top of the succession confirms the Valanginian age of the whole analyzed section. Microfacies analysis reveals sea level variations that can be coincident with the KVa1-KVa4 eustatic cycles. These new data suggest that calpionellid biostratigraphy represents the most useful tool for the definition of the Berriasian-Valanginian time boundary in central Mexico and its correlation with the rest of the Tethyan domain.
Modeling photonic crystals by boundary integral equations and Dirichlet-to-Neumann maps
Yuan Jianhua; Lu Yayan Antoine, Xavier
2008-04-20
Efficient numerical methods for analyzing photonic crystals (PhCs) can be developed using the Dirichlet-to-Neumann (DtN) maps of the unit cells. The DtN map is an operator that takes the wave field on the boundary of a unit cell to its normal derivative. In frequency domain calculations for band structures and transmission spectra of finite PhCs, the DtN maps allow us to reduce the computation to the boundaries of the unit cells. For two-dimensional (2D) PhCs with unit cells containing circular cylinders, the DtN maps can be constructed from analytic solutions (the cylindrical waves). In this paper, we develop a boundary integral equation method for computing DtN maps of general unit cells containing cylinders with arbitrary cross sections. The DtN map method is used to analyze band structures for 2D PhCs with elliptic and other cylinders.
Mendoza-Arenas, J J; Clark, S R; Jaksch, D
2015-04-01
In this work we analyze the simultaneous emergence of diffusive energy transport and local thermalization in a nonequilibrium one-dimensional quantum system, as a result of integrability breaking. Specifically, we discuss the local properties of the steady state induced by thermal boundary driving in a XXZ spin chain with staggered magnetic field. By means of efficient large-scale matrix product simulations of the equation of motion of the system, we calculate its steady state in the long-time limit. We start by discussing the energy transport supported by the system, finding it to be ballistic in the integrable limit and diffusive when the staggered field is finite. Subsequently, we examine the reduced density operators of neighboring sites and find that for large systems they are well approximated by local thermal states of the underlying Hamiltonian in the nonintegrable regime, even for weak staggered fields. In the integrable limit, on the other hand, this behavior is lost, and the identification of local temperatures is no longer possible. Our results agree with the intuitive connection between energy diffusion and thermalization.
The Prediction of Ducted Fan Engine Noise Via a Boundary Integral Equation Method
NASA Technical Reports Server (NTRS)
Farassat, F.; Dunn, M. H.; Tweed, J.
1996-01-01
A computationally efficient Boundary Integral Equation Method (BIEM) for the prediction of ducted fan engine noise is presented. The key features of the BIEM are its versatility and the ability to compute rapidly any portion of the sound field without the need to compute the entire field. Governing equations for the BIEM are based on the assumptions that all acoustic processes are linear, generate spinning modes, and occur in a uniform flow field. An exterior boundary value problem (BVP) is defined that describes the scattering of incident sound by an engine duct with arbitrary profile. Boundary conditions on the duct walls are derived that allow for passive noise control treatment. The BVP is recast as a system of hypersingular boundary integral equations for the unknown duct surface quantities. BIEM solution methodology is demonstrated for the scattering of incident sound by a thin cylindrical duct with hard walls. Numerical studies are conducted for various engine parameters and continuous portions of the total pressure field are computed. Radiation and duct propagation results obtained are in agreement with the classical results of spinning mode theory for infinite ducts.
Localization of ductile deformation in lithosphere and rocks: the role of grain boundary sliding
NASA Astrophysics Data System (ADS)
Dimanov, Alexandre; Rahanel, Jean; Bornert, Michel; Bourcier, Mathieu; Gaye, Ag; Heripre, Eva; Ludwig, Wolfgang
2017-04-01
Ductile strain of the lithosphere localizes in multi-scale shear zones, ranging from km to mm scales. The resulting mylonites/ultramylonites present microstructural signatures of several concomitant deformation mechanisms. Besides cataclastic features, crystal plasticity dominates in volume, but grain boundary sliding and diffusive/solution mass transport act along interfaces. Considering solely the inherited natural microstructures does not make clear the chronology of appearance and the interactions between these mechanisms. Therefore, inference of the overall mylonitic rheology seems illusory. We have therefore realized over the last decade a systematic rheological characterization of the high temperature flow of various synthetic anorthite - diopside mixtures. The data clearly suggest Newtonian type of rheology as best adapted to the materials representative of the lower crust mylonites. However, the post mortem microstructures undoubtedly evidenced the coexistence of both crystal plasticity and grain boundary sliding processes. Yet, the specific roles of each mechanism in the localization process remained unclear. In order to clarify these aspects we realized a multi-scale micromechanical in situ investigation of the ductile deformation of synthetic rock-salt. The mechanical tests were combined with in-situ optical microscopy, scanning electron microscopy and X-ray tomography (MCT). Digital image correlation (DIC) techniques allowed for measurements and characterization of the multi-scale organization of 2D and 3D full strain fields. Macroscopic and mesoscopic shear bands appear at the sample and microstructure scales, respectively. DIC evidenced the development of discrete slip bands within individual grains, and hence of dominant crystal plasticity. Combination of DIC and EBSD allowed for identification of active slip systems. Conversely, DIC allowed for the identification and the precise quantification of minor activity (< 5% contribution) of grain boundary
RCS of waveguide cavities - A hybrid boundary-integral/modal approach
NASA Astrophysics Data System (ADS)
Ling, Hao
1990-09-01
A hybrid technique combining the flexibility of the boundary-integral method and the efficiency of the modal approach is presented. The technique is used for analyzing the electromagnetic scattering from open waveguide cavities. The generalized scattering matrices of the arbitrary waveguide discontinuity regions are determined using a boundary-integral equation formulation. The scattering matrix of the composite structure is found by cascading the scattering matrices of individual sections. The radar cross section of the open cavity is then calculated by a reciprocity formulation in conjunction with the Kirchhoff approximation. Excellent agreements with the standard method of moments solution and with experimental data for offset bend structures are found. Examples of cavities with arbitrarily shaped and absorber-coated terminations are also presented.
A finite element-boundary integral method for conformal antenna arrays on a circular cylinder
NASA Technical Reports Server (NTRS)
Kempel, Leo C.; Volakis, John L.; Woo, Alex C.; Yu, C. Long
1992-01-01
Conformal antenna arrays offer many cost and weight advantages over conventional antenna systems. In the past, antenna designers have had to resort to expensive measurements in order to develop a conformal array design. This is due to the lack of rigorous mathematical models for conformal antenna arrays, and as a result the design of conformal arrays is primarily based on planar antenna design concepts. Recently, we have found the finite element-boundary integral method to be very successful in modeling large planar arrays of arbitrary composition in a metallic plane. Herewith we shall extend this formulation for conformal arrays on large metallic cylinders. In this we develop the mathematical formulation. In particular we discuss the finite element equations, the shape elements, and the boundary integral evaluation, and it is shown how this formulation can be applied with minimal computation and memory requirements. The implementation shall be discussed in a later report.
A finite element-boundary integral method for conformal antenna arrays on a circular cylinder
NASA Technical Reports Server (NTRS)
Kempel, Leo C.; Volakis, John L.
1992-01-01
Conformal antenna arrays offer many cost and weight advantages over conventional antenna systems. In the past, antenna designers have had to resort to expensive measurements in order to develop a conformal array design. This was due to the lack of rigorous mathematical models for conformal antenna arrays. As a result, the design of conformal arrays was primarily based on planar antenna design concepts. Recently, we have found the finite element-boundary integral method to be very successful in modeling large planar arrays of arbitrary composition in a metallic plane. We are extending this formulation to conformal arrays on large metallic cylinders. In doing so, we will develop a mathematical formulation. In particular, we discuss the finite element equations, the shape elements, and the boundary integral evaluation. It is shown how this formulation can be applied with minimal computation and memory requirements.
Navigating the boundary of science for decision making at the state and local level
NASA Astrophysics Data System (ADS)
Gonzales, L. M.; Wood, C.; Boland, M. A.; Rose, C. A.
2015-12-01
Scientific information should play a vital role in many decision making processes, yet issues incorporating geoscience information often arise due to inherent differences between how scientists and decision makers operate. Decision makers and scientists have different priorities, produce work at different rates, and often lack an understanding of each others' institutional constraints. Boundary organizations, entities that facilitate collaboration and information flow across traditional boundaries such as that between scientists and decision makers, are in a unique position to improve the dialogue between disparate groups. The American Geosciences Institute (AGI), a nonprofit federation of 50 geoscience societies and organizations, is linking the geoscience and decision-making communities through its Critical Issues Program. AGI's Critical Issues program has first-hand experience in improving the transfer of information across the science-decision making boundary, particularly in areas pertaining to water resources and hazards. This presentation will focus on how, by collaborating with organizations representing the decision making and geoscience communities to inform our program development, we have created our three main content types - website, webinar series, and research database - to better meet the needs of the decision-making process. The program presents existing geoscience information in a way that makes the interconnected nature of geoscience topics more easily understood, encourages discussion between the scientific and decision-making communities, and has established a trusted source of impartial geoscience information. These efforts have focused on state and local decision makers—groups that increasingly influence climate and risk-related decisions, yet often lack the resources to access and understand geoscience information.
Local atomic structure of Pb(Zr-Ti)O3 near the morphotropic phase boundary.
NASA Astrophysics Data System (ADS)
Dmowski, Wojciech; Egami, Takeshi; Farber, Leon; Davies, Peter K.
2001-03-01
We have studied the local atomic structure of PbZrO_3-PbTiO3 solid solution (PZT) near the morphotropic phase boundary (MPB) using pulsed neutron scattering. The PZT phase diagram is characterized by the almost vertical MPB at 48-52rich rhombohedral phase from the tetragonal Ti rich phase. In our study, in addition to Rietveld analysis, we used the pair distribution function (PDF) method. Since the PDF is obtained by the Fourier transformation of both the Bragg peaks and diffuse scattering the inter-atomic distances are obtained without the assumption of the unit cell symmetry. While the crystal structure changes substantially through the MPB, we found that the local atomic structure does not show dramatic changes. The actual change is more of a statistical nature in the population of Pb displacements. Crystallographically the Pb displacement is in [100] in the tetragonal phase and [111] in the rhombohedral phase, with the rotation from one to the other in the intermediate monoclinic phase. Locally, however, pure [111] Pb displacements are not observed even in the Zr-rich rhombohedral phase. The [100] displacements are majority in the tetragonal phase, while they are gradually replaced by the [110] displacements through the MPB. These observations suggest that the "polarization rotation" is driven by the gradual change in the partition of the Pb displacement patterns, and the crystal structure reflects the change in the average structure.
DROPOUTS IN SOLAR ENERGETIC PARTICLES: ASSOCIATED WITH LOCAL TRAPPING BOUNDARIES OR CURRENT SHEETS?
Seripienlert, A.; Ruffolo, D.; Matthaeus, W. H.; Chuychai, P. E-mail: scdjr@mahidol.ac.t E-mail: piyanate@gmail.co
2010-03-10
In recent observations by the Advanced Composition Explorer, the intensity of solar energetic particles exhibits sudden, large changes known as dropouts. These have been explained in terms of turbulence or a flux tube structure in the solar wind. Dropouts are believed to indicate filamentary magnetic connection to a localized particle source near the solar surface, and computer simulations of a random-phase model of magnetic turbulence have indicated a spatial association between dropout features and local trapping boundaries (LTBs) defined for a two-dimensional (2D) + slab model of turbulence. Previous observations have shown that dropout features are not well associated with sharp magnetic field changes, as might be expected in the flux tube model. Random-phase turbulence models do not properly treat sharp changes in the magnetic field, such as current sheets, and thus cannot be tested in this way. Here, we explore the properties of a more realistic magnetohydrodynamic (MHD) turbulence model (2D MHD), in which current sheets develop and the current and magnetic field have characteristic non-Gaussian statistical properties. For this model, computer simulations that trace field lines to determine magnetic connection from a localized particle source indicate that sharp particle gradients should frequently be associated with LTBs, sometimes with strong 2D magnetic fluctuations, and infrequently with current sheets. Thus, the 2D MHD + slab model of turbulent fluctuations includes some realistic features of the flux tube view and is consistent with the lack of an observed association between dropouts and intense magnetic fields or currents.
Local structure of the convective boundary layer measured by a volume-imaging radar
NASA Astrophysics Data System (ADS)
Pollard, Brian David
For over 30 years, radars have examined the structure of the convective boundary layer (CBL). Those studies have consisted either of the three dimensional structure of km-scale features, or of the vertical structure of local, 1 to 100 m-scale features. A new instrument, the Turbulent Eddy Profiler (TEP), images the local, three dimensional character of the CBL with the 10 m-scale resolution of current vertically profiling systems. This thesis presents TEP CBL measurements, including /tilde Cn2, the local refractive index structure-function parameter, and w, the vertical velocity. Qualitative horizontal and vertical images are shown. The scales of the measured structures are then quantified through calculation of the correlation distance. To examine larger scale features, effective volumes are constructed from TEP time series data through Taylor's hypothesis. Within those volumes, the statistical properties of /tilde Cn2 and w and calculated. These measurements highlight some of the capabilities of the TEP system, and give a unique picture of the morphology and evolution of /tilde Cn2 and w in the CBL. Many of the TEP measurements are compared to appropriately scaled large-eddy simulation (LES) predictions. The LES qualitative CBL structure agrees well with the measurements, while the statistical values of /tilde Cn2 agree well for only some of the measured data. Those /tilde Cn2 comparisons are the first of their kind, however, and suggest that LES may become a useful tool in CBL propagation studies.
Localized electronic states at grain boundaries on the surface of graphene and graphite
NASA Astrophysics Data System (ADS)
Luican-Mayer, Adina; Barrios-Vargas, Jose E.; Toft Falkenberg, Jesper; Autès, Gabriel; Cummings, Aron W.; Soriano, David; Li, Guohong; Brandbyge, Mads; Yazyev, Oleg V.; Roche, Stephan; Andrei, Eva Y.
2016-09-01
Recent advances in large-scale synthesis of graphene and other 2D materials have underscored the importance of local defects such as dislocations and grain boundaries (GBs), and especially their tendency to alter the electronic properties of the material. Understanding how the polycrystalline morphology affects the electronic properties is crucial for the development of applications such as flexible electronics, energy harvesting devices or sensors. We here report on atomic scale characterization of several GBs and on the structural-dependence of the localized electronic states in their vicinity. Using low temperature scanning tunneling microscopy and spectroscopy, together with tight binding and ab initio numerical simulations we explore GBs on the surface of graphite and elucidate the interconnection between the local density of states and their atomic structure. We show that the electronic fingerprints of these GBs consist of pronounced resonances which, depending on the relative orientation of the adjacent crystallites, appear either on the electron side of the spectrum or as an electron-hole symmetric doublet close to the charge neutrality point. These two types of spectral features will impact very differently the transport properties allowing, in the asymmetric case to introduce transport anisotropy which could be utilized to design novel growth and fabrication strategies to control device performance.
A boundary integral method for an inverse problem in thermal imaging
NASA Technical Reports Server (NTRS)
Bryan, Kurt
1992-01-01
An inverse problem in thermal imaging involving the recovery of a void in a material from its surface temperature response to external heating is examined. Uniqueness and continuous dependence results for the inverse problem are demonstrated, and a numerical method for its solution is developed. This method is based on an optimization approach, coupled with a boundary integral equation formulation of the forward heat conduction problem. Some convergence results for the method are proved, and several examples are presented using computationally generated data.
NASA Technical Reports Server (NTRS)
Edwards, S.; Reuther, J.; Chattot, J. J.
1997-01-01
The objective of this paper is to present a control theory approach for the design of airfoils in the presence of viscous compressible flows. A coupled system of the integral boundary layer and the Euler equations is solved to provide rapid flow simulations. An adjunct approach consistent with the complete coupled state equations is employed to obtain the sensitivities needed to drive a numerical optimization algorithm. Design to target pressure distribution is demonstrated on an RAE 2822 airfoil at transonic speed.
Implicit Boundary Integral Methods for the Helmholtz Equation in Exterior Domains
2016-06-01
differential equations on surfaces. SIAM J. Sci. Comput., 31(6):4330–4350, 2009. [13] A.-W. Maue. Zur Formulierung eines allgemeinen Beugungsproblems...Implicit boundary integral methods for the Helmholtz equation in exterior domains Chieh Chen and Richard Tsai∗ Abstract We propose a new algorithm...for solving Helmholtz equations in the exterior domain. The algorithm not only combines the advantages of implicit surface representation and the
The Reduction of Ducted Fan Engine Noise Via a Boundary Integral Equation Method
NASA Technical Reports Server (NTRS)
Tweed, John
2000-01-01
Engineering studies for reducing ducted fan engine noise were conducted using the noise prediction code TBIEM3D. To conduct parametric noise reduction calculations, it was necessary to advance certain theoretical and computational aspects of the boundary integral equation method (BIEM) described in and implemented in TBIEM3D. Also, enhancements and upgrades to TBIEM3D were made for facilitating the code's use in this research and by the aeroacoustics engineering community.
Canonical formulation and path integral for local vacuum energy sequestering
NASA Astrophysics Data System (ADS)
Bufalo, R.; KlusoÅ, J.; Oksanen, M.
2016-08-01
We establish the Hamiltonian analysis and the canonical path integral for a local formulation of vacuum energy sequestering. In particular, by considering the state of the Universe as a superposition of vacuum states corresponding to different values of the cosmological and gravitational constants, the path integral is extended to include integrations over the cosmological and gravitational constants. The result is an extension of the Ng-van Dam form of the path integral of unimodular gravity. It is argued to imply a relation between the fraction of the most likely values of the gravitational and cosmological constants and the average values of the energy density and pressure of matter over spacetime. Finally, we construct and analyze a Becchi-Rouet-Stora-Tyutin-exact formulation of the theory, which can be considered as a topological field theory.
Computations of Turbulent Boundary Layers Subjected to Various Localized Pressure Gradients
NASA Astrophysics Data System (ADS)
Vinuesa Motilva, Ricardo; Nagib, Hassan
2009-11-01
Four different localized pressure gradient configurations were computed using a commercially available code by means of four RANS turbulence models (SA, k-ɛ, SST and RSM), and compared with experimental measurements of the mean flow quantities and the wall shear stress. The pressure gradients were imposed on high Reynolds number, 2-D turbulent boundary layer developing on a flat plate by changing the ceiling geometry. Two converging humps (at x=2m and x=5.5m from the leading edge of the plate) and two diverging humps at the same locations were considered. The SST model produced the best agreement with experiments. A complimentary study about how the models deal with numerical transition was done by solving a zero pressure gradient (ZPG) configuration. We find that the major differences between the results from the models when predicting mean flow quantities are essentially produced by the numerical transition process. This process does not belong to the models themselves, and it is a procedure by which the software transforms the simple laminar boundary conditions at the inlet into inflow conditions which characterize the turbulent flow when turbulence has already been developed. Therefore, models requiring the simplest inflow conditions lead to better results and consequently models such as the RSM suffer the most and ultimately lead to inferior results.
BOTDA road-embedded strain sensing system for landslide boundary localization
NASA Astrophysics Data System (ADS)
Iten, Michael; Puzrin, Alexander M.
2009-03-01
The determination and monitoring of landslide boundaries is essential for analysis of creeping landslides. A novel landslide boundary localization technique has been recently proposed and tested on two large creeping landslides in an urban area. The technique uses asphalt road-embedded distributed fiber optic sensors. This paper deals with the issue of interpretation of the monitoring records. It has been shown that an improved protection of the cable increases the measurement strain range, but leads to non-linear strain-frequency response. Two methods of strain data interpretation have been analyzed: the truncated average method (TAM) and the convolution product (CP). Advantage of the TAM is in its simplicity; disadvantage is that the amount of the valid sampling points is significantly reduced, especially when the fixed strain section lengths are close to the spatial resolution. The alternative CP method uses all sampling points in the vicinity of the fixation point, but is rather complex, especially considering that a proper interpretation of the measured data can be only achieved using a weighting function with parameters dependent on the strain step at the fixation point. Further signal processing and data interpretation models should be encouraged to improve system accuracy.
A boundary integral approach to analyze the viscous scattering of a pressure wave by a rigid body
Homentcovschi, Dorel; Miles, Ronald N.
2008-01-01
The paper provides boundary integral equations for solving the problem of viscous scattering of a pressure wave by a rigid body. By using this mathematical tool uniqueness and existence theorems are proved. Since the boundary conditions are written in terms of velocities, vector boundary integral equations are obtained for solving the problem. The paper introduces single-layer viscous potentials and also a stress tensor. Correspondingly, a viscous double-layer potential is defined. The properties of all these potentials are investigated. By representing the scattered field as a combination of a single-layer viscous potential and a double-layer viscous potential the problem is reduced to the solution of a singular vectorial integral equation of Fredholm type of the second kind. In the case where the stress vector on the boundary is the main quantity of interest the corresponding boundary singular integral equation is proved to have a unique solution. PMID:18709178
NASA Technical Reports Server (NTRS)
Robertson, J. S.; Siegman, W. L.; Jacobson, M. J.
1989-01-01
There is substantial interest in the analytical and numerical modeling of low-frequency, long-range atmospheric acoustic propagation. Ray-based models, because of frequency limitations, do not always give an adequate prediction of quantities such as sound pressure or intensity levels. However, the parabolic approximation method, widely used in ocean acoustics, and often more accurate than ray models for lower frequencies of interest, can be applied to acoustic propagation in the atmosphere. Modifications of an existing implicit finite-difference implementation for computing solutions to the parabolic approximation are discussed. A locally-reacting boundary is used together with a one-parameter impedance model. Intensity calculations are performed for a number of flow resistivity values in both quiescent and windy atmospheres. Variations in the value of this parameter are shown to have substantial effects on the spatial variation of the acoustic signal.
Localized and distributed boundary-layer receptivity to convected unsteady wake in free stream
NASA Technical Reports Server (NTRS)
Choudhari, Meelan
1994-01-01
Receptivity to a model convected disturbance in the presence of localized and distributed variations in wall geometry and wall-suction velocity is examined. The model free-stream disturbance corresponds to the time-harmonic wake of a vibrating ribbon that is placed at a suitable distance above the surface of a thin airfoil. The advantages of using this disturbance for experiments on receptivity to convected disturbances are outlined. A brief parametric study is presented for a flat-plate boundary layer. The study quantifies the effect of wake position as well as wake width; in addition, it should be helpful in the choice of an optimal setting for a controlled experiment of the above type, which the above parametric study shows as feasible.
Resistive switching in hafnium dioxide layers: Local phenomenon at grain boundaries
NASA Astrophysics Data System (ADS)
Lanza, M.; Bersuker, G.; Porti, M.; Miranda, E.; Nafría, M.; Aymerich, X.
2012-11-01
Overcoming challenges associated with implementation of resistive random access memory technology for non-volatile information storage requires identifying the material characteristics responsible for resistive switching. In order to connect the switching phenomenon to the nano-scale morphological features of the dielectrics employed in memory cells, we applied the enhanced conductive atomic force microscopy technique for in situ analysis of the simultaneously collected electrical and topographical data on HfO2 stacks of various degrees of crystallinity. We demonstrate that the resistive switching is a local phenomenon associated with the formation of a conductive filament with a sufficiently small cross-section, which is determined by the maximum passing current. Switchable filament is found to be formed at the dielectric sites where the forming voltages were sufficiently small, which, in the case of the stoichiometric HfO2, is observed exclusively at the grain boundary regions representing low resistant conductive paths through the dielectric film.
The Spectral Flow for Dirac Operators on Compact Planar Domains with Local Boundary Conditions
NASA Astrophysics Data System (ADS)
Prokhorova, Marina
2013-09-01
Let Dt, {0≤slantt≤slant1} be a 1-parameter family of Dirac type operators on a two-dimensional disk with m - 1 holes. Suppose that all operators Dt have the same symbol, and that D1 is conjugate to D0 by a scalar gauge transformation. Suppose that all operators Dt are considered with the same elliptic local boundary condition. Our main result is a computation of the spectral flow for such a family of operators. The answer is obtained up to multiplication by an integer constant depending only on the number of holes in the disk. This constant is calculated explicitly for the case of the annulus (m = 2).
An Adaptive Fast Direct Solver for Boundary Integral Equations in Two Dimensions
2009-08-21
described in Sections 5 and 6. In each of the experiments, we apply Nystrom discretization to one of the following boundary integral 19 I I I equations...7.5) via the Nystrom method with piecewise Gaussian quadrature displays high rates of convergence, so long as the kernel K(x,y) and the layer density...Analysis, Ann. of Math. Stud., 112 (1986), pp. 131-183. [17] R. KRESS, Integral Equations, Springer-Verlag, New York, 1999. [18] R. KRESS, A Nystrom method
Kreienkamp, Amelia B.; Liu, Lucy Y.; Minkara, Mona S.; Knepley, Matthew G.; Bardhan, Jaydeep P.; Radhakrishnan, Mala L.
2013-01-01
We analyze and suggest improvements to a recently developed approximate continuum-electrostatic model for proteins. The model, called BIBEE/I (boundary-integral based electrostatics estimation with interpolation), was able to estimate electrostatic solvation free energies to within a mean unsigned error of 4% on a test set of more than 600 proteins—a significant improvement over previous BIBEE models. In this work, we tested the BIBEE/I model for its capability to predict residue-by-residue interactions in protein–protein binding, using the widely studied model system of trypsin and bovine pancreatic trypsin inhibitor (BPTI). Finding that the BIBEE/I model performs surprisingly less well in this task than simpler BIBEE models, we seek to explain this behavior in terms of the models’ differing spectral approximations of the exact boundary-integral operator. Calculations of analytically solvable systems (spheres and tri-axial ellipsoids) suggest two possibilities for improvement. The first is a modified BIBEE/I approach that captures the asymptotic eigenvalue limit correctly, and the second involves the dipole and quadrupole modes for ellipsoidal approximations of protein geometries. Our analysis suggests that fast, rigorous approximate models derived from reduced-basis approximation of boundary-integral equations might reach unprecedented accuracy, if the dipole and quadrupole modes can be captured quickly for general shapes. PMID:24466561
NASA Astrophysics Data System (ADS)
He, Han; Wang, Huaning
2008-05-01
The boundary integral equation (BIE) method was first proposed by Yan and Sakurai (2000) and used to extrapolate the nonlinear force-free magnetic field in the solar atmosphere. Recently, Yan and Li (2006) improved the BIE method and proposed the direct boundary integral equation (DBIE) formulation, which represents the nonlinear force-free magnetic field by direct integration of the magnetic field on the bottom boundary surface. On the basis of this new method, we devised a practical calculation scheme for the nonlinear force-free field extrapolation above solar active regions. The code of the scheme was tested by the analytical solutions of Low and Lou (1990) and was applied to the observed vector magnetogram of solar active region NOAA 9077. The results of the calculations show that the improvement of the new computational scheme to the scheme of Yan and Li (2006) is significant, and the force-free and divergence-free constraints are well satisfied in the extrapolated fields. The calculated field lines for NOAA 9077 present the X-shaped structure and can be helpful for understanding the magnetic configuration of the filament channel as well as the magnetic reconnection process during the Bastille Day flare on 14 July 2000.
NASA Technical Reports Server (NTRS)
Hu, Fang Q.
1994-01-01
It is known that the exact analytic solutions of wave scattering by a circular cylinder, when they exist, are not in a closed form but in infinite series which converges slowly for high frequency waves. In this paper, we present a fast number solution for the scattering problem in which the boundary integral equations, reformulated from the Helmholtz equation, are solved using a Fourier spectral method. It is shown that the special geometry considered here allows the implementation of the spectral method to be simple and very efficient. The present method differs from previous approaches in that the singularities of the integral kernels are removed and dealt with accurately. The proposed method preserves the spectral accuracy and is shown to have an exponential rate of convergence. Aspects of efficient implementation using FFT are discussed. Moreover, the boundary integral equations of combined single and double-layer representation are used in the present paper. This ensures the uniqueness of the numerical solution for the scattering problem at all frequencies. Although a strongly singular kernel is encountered for the Neumann boundary conditions, we show that the hypersingularity can be handled easily in the spectral method. Numerical examples that demonstrate the validity of the method are also presented.
LOCAL INTERSTELLAR MAGNETIC FIELD DETERMINED FROM THE INTERSTELLAR BOUNDARY EXPLORER RIBBON
Zirnstein, E. J.; Livadiotis, G.; McComas, D. J.; Heerikhuisen, J.; Pogorelov, N. V.; Funsten, H. O.
2016-02-10
The solar wind emanating from the Sun interacts with the local interstellar medium (LISM), forming the heliosphere. Hydrogen energetic neutral atoms (ENAs) produced by the solar-interstellar interaction carry important information about plasma properties from the boundaries of the heliosphere, and are currently being measured by NASA's Interstellar Boundary Explorer (IBEX). IBEX observations show the existence of a “ribbon” of intense ENA emission projecting a circle on the celestial sphere that is centered near the local interstellar magnetic field (ISMF) vector. Here we show that the source of the IBEX ribbon as a function of ENA energy outside the heliosphere, uniquely coupled to the draping of the ISMF around the heliopause, can be used to precisely determine the magnitude (2.93 ± 0.08 μG) and direction (227.°28 ± 0.°69, 34.°62 ± 0.°45 in ecliptic longitude and latitude) of the pristine ISMF far (∼1000 AU) from the Sun. We find that the ISMF vector is offset from the ribbon center by ∼8.°3 toward the direction of motion of the heliosphere through the LISM, and their vectors form a plane that is consistent with the direction of deflected interstellar neutral hydrogen, thought to be controlled by the ISMF. Our results yield draped ISMF properties close to that observed by Voyager 1, the only spacecraft to directly measure the ISMF close to the heliosphere, and give predictions of the pristine ISMF that Voyager 1 has yet to sample.
Local interstellar magnetic field determined from the interstellar boundary explorer ribbon
Zirnstein, E. J.; Heerikhuisen, J.; Funsten, H. O.; ...
2016-02-08
The solar wind emanating from the Sun interacts with the local interstellar medium (LISM), forming the heliosphere. Hydrogen energetic neutral atoms (ENAs) produced by the solar-interstellar interaction carry important information about plasma properties from the boundaries of the heliosphere, and are currently being measured by NASA's Interstellar Boundary Explorer (IBEX). IBEX observations show the existence of a “ribbon” of intense ENA emission projecting a circle on the celestial sphere that is centered near the local interstellar magnetic field (ISMF) vector. Here we show that the source of the IBEX ribbon as a function of ENA energy outside the heliosphere, uniquelymore » coupled to the draping of the ISMF around the heliopause, can be used to precisely determine the magnitude (2.93 ± 0.08 μG) and direction (227.°28 ± 0.°69, 34.°62 ± 0.°45 in ecliptic longitude and latitude) of the pristine ISMF far (~1000 AU) from the Sun. We find that the ISMF vector is offset from the ribbon center by ~8.°3 toward the direction of motion of the heliosphere through the LISM, and their vectors form a plane that is consistent with the direction of deflected interstellar neutral hydrogen, thought to be controlled by the ISMF. Lastly, our results yield draped ISMF properties close to that observed by Voyager 1, the only spacecraft to directly measure the ISMF close to the heliosphere, and give predictions of the pristine ISMF that Voyager 1 has yet to sample.« less
Strong Local-Nonlocal Coupling for Integrated Fracture Modeling
Littlewood, David John; Silling, Stewart A.; Mitchell, John A.; Seleson, Pablo D.; Bond, Stephen D.; Parks, Michael L.; Turner, Daniel Z.; Burnett, Damon J.; Ostien, Jakob; Gunzburger, Max
2015-09-01
Peridynamics, a nonlocal extension of continuum mechanics, is unique in its ability to capture pervasive material failure. Its use in the majority of system-level analyses carried out at Sandia, however, is severely limited, due in large part to computational expense and the challenge posed by the imposition of nonlocal boundary conditions. Combined analyses in which peridynamics is em- ployed only in regions susceptible to material failure are therefore highly desirable, yet available coupling strategies have remained severely limited. This report is a summary of the Laboratory Directed Research and Development (LDRD) project "Strong Local-Nonlocal Coupling for Inte- grated Fracture Modeling," completed within the Computing and Information Sciences (CIS) In- vestment Area at Sandia National Laboratories. A number of challenges inherent to coupling local and nonlocal models are addressed. A primary result is the extension of peridynamics to facilitate a variable nonlocal length scale. This approach, termed the peridynamic partial stress, can greatly reduce the mathematical incompatibility between local and nonlocal equations through reduction of the peridynamic horizon in the vicinity of a model interface. A second result is the formulation of a blending-based coupling approach that may be applied either as the primary coupling strategy, or in combination with the peridynamic partial stress. This blending-based approach is distinct from general blending methods, such as the Arlequin approach, in that it is specific to the coupling of peridynamics and classical continuum mechanics. Facilitating the coupling of peridynamics and classical continuum mechanics has also required innovations aimed directly at peridynamic models. Specifically, the properties of peridynamic constitutive models near domain boundaries and shortcomings in available discretization strategies have been addressed. The results are a class of position-aware peridynamic constitutive laws for
Path-integral formula for local thermal equilibrium
NASA Astrophysics Data System (ADS)
Hongo, Masaru
2017-08-01
We develop a complete path-integral formulation of relativistic quantum fields in local thermal equilibrium, which brings about the emergence of thermally induced curved spacetime. The resulting action is shown to have full diffeomorphism invariance and gauge invariance in thermal spacetime with imaginary-time independent backgrounds. This leads to the notable symmetry properties of emergent thermal spacetime: Kaluza-Klein gauge symmetry, spatial diffeomorphism symmetry, and gauge symmetry. A thermodynamic potential in local thermal equilibrium, or the so-called Massieu-Planck functional, is identified as a generating functional for conserved currents such as the energy-momentum tensor and the electric current.
Upper limit of applicability of the local similarity theory in the stable atmospheric boundary layer
NASA Astrophysics Data System (ADS)
Grachev, A. A.; Andreas, E. L.; Fairall, C. W.; Guest, P. S.; Persson, P. O. G.
2012-04-01
The applicability of the classical Monin-Obukhov similarity theory (1954) has been limited by constant flux assumption, which is valid in a narrow range z/L < 0.1 in the stable boundary layer (SBL). Nieuwstadt (1984) extended the range of applicability of the original theory using the local scaling (height-dependent) in place of the surface scaling, but the limits of applicability of the local similarity theory in the SBL have been blurred. Measurements of atmospheric turbulence made over the Arctic pack ice during the Surface Heat Budget of the Arctic Ocean experiment (SHEBA) are used to clarify this issue. Based on spectral analysis of wind velocity and temperature fluctuations, it is shown that when both gradient Richardson number, Ri, and flux Richardson number, Rf, exceed a "critical value" about 0.2-0.25, inertial subrange associated with a Kolmogorov cascade dies out and vertical turbulent fluxes become small. Some small-scale turbulence survives even in the supercritical regime but this is non-Kolmogorov turbulence and it decays rapidly with further increasing stability. The similarity theory is based on the turbulent fluxes in the high frequency part of the spectra associated with energy-containing/flux-carrying eddies. Spectral densities in this high-frequency band collapse along with the Kolmogorov energy cascade. Therefore, applicability of the local Monin-Obukhov similarity theory in the SBL is limited by inequalities Ri < Ri_cr and Rf < Rf_cr (however, Rf_cr = 0.2-0.25 is a primary threshold). Application of this prerequisite shows that both the flux-profile and flux-variances relationships follow to the classical Monin-Obukhov local z-less predictions after the irrelevant cases have been filtered out.
NASA Technical Reports Server (NTRS)
Mendelson, A.
1977-01-01
Two advances in the numerical techniques of utilizing the BIE method are presented. The boundary unknowns are represented by parabolas over each interval which are integrated in closed form. These integrals are listed for easy use. For problems involving crack tip singularities, these singularities are included in the boundary integrals so that the stress intensity factor becomes just one more unknown in the set of boundary unknowns thus avoiding the uncertainties of plotting and extrapolating techniques. The method is applied to the problems of a notched beam in tension and bending, with excellent results.
Local conservation laws in spin-\\frac{1}{2} XY chains with open boundary conditions
NASA Astrophysics Data System (ADS)
Fagotti, Maurizio
2016-06-01
We revisit the conserved quantities of the spin-\\frac{1}{2} XY model with open boundary conditions. In the absence of a transverse field, we find new families of local charges and show that half of the seeming conservation laws are conserved only if the number of sites is odd. In even chains the set of noninteracting charges is abelian, like in the periodic case when the number of sites is odd. In odd chains the set is doubled and becomes non-abelian, like in even periodic chains. The dependence of the charges on the parity of the chain’s size undermines the common belief that the thermodynamic limit of diagonal ensembles exists. We consider also the transverse-field Ising chain, where the situation is more ordinary. The generalization to the XY model in a transverse field is not straightforward and we propose a general framework to carry out similar calculations. We conjecture the form of the bulk part of the local charges and discuss the emergence of quasilocal conserved quantities. We provide evidence that in a region of the parameter space there is a reduction of the number of quasilocal conservation laws invariant under chain inversion. As a by-product, we study a class of block-Toeplitz-plus-Hankel operators and identify the conditions that their symbols satisfy in order to commute with a given block-Toeplitz.
Evaluation of nonlocal and local planetary boundary layer schemes in the WRF model
NASA Astrophysics Data System (ADS)
Xie, Bo; Fung, Jimmy C. H.; Chan, Allen; Lau, Alexis
2012-06-01
A realistic reproduction of planetary boundary layer (PBL) structure and its evolution is critical to numerical simulation of regional meteorology and air quality. Conversely, insufficient realism in the simulated physical properties often leads to degraded meteorological and air quality prognostic skills. This study employed the Weather Research and Forecasting model (WRF) to evaluate model performance and to quantify meteorological prediction differences produced by four widely used PBL schemes. Evaluated were two nonlocal PBL schemes, YSU and ACM2, and two local PBL schemes, MYJ and Boulac. The model grid comprised four nested domains at horizontal resolutions of 27 km, 9 km, 3 km and 1 km respectively. Simulated surface variables 2 m temperature and 10 m wind at 1 km resolution were compared to measurements collected in Hong Kong. A detailed analysis of land-atmosphere energy balance explicates heat flux and temperature variability among the PBL schemes. Differences in vertical profiles of horizontal velocity, potential temperature, bulk Richardson number and water vapor mixing ratio were examined. Diagnosed PBL heights, estimated by scheme specific formulations, exhibited the large intrascheme variance. To eliminate formulation dependence in PBL height estimation, lidar measurements and a unified diagnosis were jointly used to reanalyze PBL heights. The diagnosis showed that local PBL schemes produced shallower PBL heights than those of nonlocal PBL schemes. It is reasonable to infer that WRF, coupled with the ACM2 PBL physics option can be a viable producer of meteorological forcing to regional air quality modeling in the Pearl River Delta (PRD) Region.
Improving of local ozone forecasting by integrated models.
Gradišar, Dejan; Grašič, Boštjan; Božnar, Marija Zlata; Mlakar, Primož; Kocijan, Juš
2016-09-01
This paper discuss the problem of forecasting the maximum ozone concentrations in urban microlocations, where reliable alerting of the local population when thresholds have been surpassed is necessary. To improve the forecast, the methodology of integrated models is proposed. The model is based on multilayer perceptron neural networks that use as inputs all available information from QualeAria air-quality model, WRF numerical weather prediction model and onsite measurements of meteorology and air pollution. While air-quality and meteorological models cover large geographical 3-dimensional space, their local resolution is often not satisfactory. On the other hand, empirical methods have the advantage of good local forecasts. In this paper, integrated models are used for improved 1-day-ahead forecasting of the maximum hourly value of ozone within each day for representative locations in Slovenia. The WRF meteorological model is used for forecasting meteorological variables and the QualeAria air-quality model for gas concentrations. Their predictions, together with measurements from ground stations, are used as inputs to a neural network. The model validation results show that integrated models noticeably improve ozone forecasts and provide better alert systems.
Galerkin boundary integral equation method for spontaneous rupture propagation problems: SH-case
NASA Astrophysics Data System (ADS)
Goto, Hiroyuki; Bielak, Jacobo
2008-03-01
We develop a Galerkin finite element boundary integral equation method (GaBIEM) for spontaneous rupture propagation problems for a planar fault embedded in a homogeneous full 2-D space. A 2-D antiplane rupture propagation problem, with a slip-weakening friction law, is simulated by the GaBIEM. This method allows one to eliminate the strong singularities from the integral representation of the traction, and to separate explicitly the expression for the traction into an instantaneous component; static and time-dependent components with weakly (logarithmic) singular kernels; and a dynamic component and a quasi-static component, with continuous, bounded, kernels. Simulated results throw light into the performance of the GaBIEM and highlight differences with respect to that of the traditional, collocation, boundary integral equation method (BIEM). Both methods converge with a power law with respect to grid size, with different exponents. There is no restriction on the CFL stability number for the GaBIEM since an implicit, unconditionally stable method is used for the time integration. The error of the approximation increases with the time step, as expected, and it can remain below that of the BIEM.
Active flow control insight gained from a modified integral boundary layer equation
NASA Astrophysics Data System (ADS)
Seifert, Avraham
2016-11-01
Active Flow Control (AFC) can alter the development of boundary layers with applications (e.g., reducing drag by separation delay or separating the boundary layers and enhancing vortex shedding to increase drag). Historically, significant effects of steady AFC methods were observed. Unsteady actuation is significantly more efficient than steady. Full-scale AFC tests were conducted with varying levels of success. While clearly relevant to industry, AFC implementation relies on expert knowledge with proven intuition and or costly and lengthy computational efforts. This situation hinders the use of AFC while simple, quick and reliable design method is absent. An updated form of the unsteady integral boundary layer (UIBL) equations, that include AFC terms (unsteady wall transpiration and body forces) can be used to assist in AFC analysis and design. With these equations and given a family of suitable velocity profiles, the momentum thickness can be calculated and matched with an outer, potential flow solution in 2D and 3D manner to create an AFC design tool, parallel to proven tools for airfoil design. Limiting cases of the UIBL equation can be used to analyze candidate AFC concepts in terms of their capability to modify the boundary layers development and system performance.
Local Boundedness for Minimizers of Some Polyconvex Integrals
NASA Astrophysics Data System (ADS)
Cupini, Giovanni; Leonetti, Francesco; Mascolo, Elvira
2017-04-01
We give a regularity result for local minimizers {u}:{Ω subset R^3 to R^3} of a special class of polyconvex functionals. Under some structure assumptions on the energy density, we prove that local minimizers u are locally bounded. For each component {u^{α}} of u, we first prove a Caccioppoli's inequality and then apply De Giorgi's iteration method to get the boundedness of {u^{α}}. Our result can be applied to the polyconvex integral int_Ω ( sumlimits_{α = 1}3 |D u^α|p + |operatorname{adj}_2 Du|^q + |operatorname{det} Du|r) dx with suitable {p,q,r > 1}.
Integrity of the reactor coolant boundary of the European pressurized water reactor (EPR)
Goetsch, D.; Bieniussa, K.; Schulz, H.; Jalouneix, J.
1997-04-01
This paper is an abstract of the work performed in the frame of the development of the IPSN/GRS approach in view of the EPR conceptual safety features. EPR is a pressurized water reactor which will be based on the experience gained by utilities and designers in France and in Germany. The reactor coolant boundary of a PWR includes the reactor pressure vessel (RPV), those parts of the steam generators (SGs) which contain primary coolant, the pressurizer (PSR), the reactor coolant pumps (RCPs), the main coolant lines (MCLs) with their branches as well as the other connecting pipes and all branching pipes including the second isolation valves. The present work covering the integrity of the reactor coolant boundary is mainly restricted to the integrity of the main coolant lines (MCLs) and reflects the design requirements for the main components of the reactor coolant boundary. In the following the conceptual aspects, i.e. design, manufacture, construction and operation, will be assessed. A main aspect is the definition of break postulates regarding overall safety implications.
The Reduction of Ducted Fan Engine Noise Via A Boundary Integral Equation Method
NASA Technical Reports Server (NTRS)
Tweed, J.; Dunn, M.
1997-01-01
The development of a Boundary Integral Equation Method (BIEM) for the prediction of ducted fan engine noise is discussed. The method is motivated by the need for an efficient and versatile computational tool to assist in parametric noise reduction studies. In this research, the work in reference 1 was extended to include passive noise control treatment on the duct interior. The BEM considers the scattering of incident sound generated by spinning point thrust dipoles in a uniform flow field by a thin cylindrical duct. The acoustic field is written as a superposition of spinning modes. Modal coefficients of acoustic pressure are calculated term by term. The BEM theoretical framework is based on Helmholtz potential theory. A boundary value problem is converted to a boundary integral equation formulation with unknown single and double layer densities on the duct wall. After solving for the unknown densities, the acoustic field is easily calculated. The main feature of the BIEM is the ability to compute any portion of the sound field without the need to compute the entire field. Other noise prediction methods such as CFD and Finite Element methods lack this property. Additional BIEM attributes include versatility, ease of use, rapid noise predictions, coupling of propagation and radiation both forward and aft, implementable on midrange personal computers, and valid over a wide range of frequencies.
Integrated local correlation: a new measure of local coherence in fMRI data.
Deshpande, Gopikrishna; LaConte, Stephen; Peltier, Scott; Hu, Xiaoping
2009-01-01
This article introduces the measure of integrated local correlation (ILC) for assessing local coherence in the brain using functional magnetic resonance imaging (fMRI) data and characterizes the measure in terms of reproducibility, the effect of physiological noise, and the dependence on image resolution. The coupling of local neuronal processes influences coherence in a voxel's neighborhood. ILC is defined, for each voxel, as the integration of its spatial correlation function. This integrated measure does not require the specification of a neighborhood and, as demonstrated by experimental data, is effectively independent of image resolution. Respiratory and cardiac fluctuations do not considerably alter the ILC value except in isolated areas in and surrounding large vessels. With resting-state fMRI data, ILC was demonstrated to be tissue-specific, higher in gray matter than white matter, and reproducible across consecutive runs in healthy individuals. Within the gray matter, ILC was found to be higher in the default mode network, particularly the posterior and anterior cingulate cortices. Comparing ILC maps obtained from resting state and continuous motor task data, we observed reduced local coherence in the default mode network during the task. Finally, we compared ILC and regional homogeneity by examining their ability to discriminate between gray and white matters in resting state data and found ILC to be more sensitive.
Integrated modeling and characterization of local crack chemistry
Savchik, J.A.; Burke, M.S.
1995-12-31
The MULTEQ computer program has become an industry wide tool which can be used to calculate the chemical composition in a flow occluded region as the solution within concentrates due to a local boiling process. These results can be used to assess corrosion concerns in plant equipment such as steam generators. Corrosion modeling attempts to quantify corrosion assessments by accounting for the mass transport processes involved in the corrosion mechanism. MULTEQ has played an ever increasing role in defining the local chemistry for such corrosion models. This paper will outline how the integration of corrosion modeling with the analysis of corrosion films and deposits can lead to the development of a useful modeling tool, wherein MULTEQ is interactively linked to a diffusion and migration transport process. This would provide a capability to make detailed inferences of the local crack chemistry based on the analyses of the local corrosion films and deposits inside a crack and thus provide guidance for chemical fixes to avoid cracking. This methodology is demonstrated for a simple example of a cracked tube. This application points out the utility of coupling MULTEQ with a mass transport process and the feasibility of an option in a future version of MULTEQ that would permit relating film and deposit analyses to the local chemical environment. This would increase the amount of information obtained from removed tube analyses and laboratory testing that can contribute to an overall program for mitigating tubing and crevice corrosion.
Solving the hypersingular boundary integral equation for the Burton and Miller formulation.
Langrenne, Christophe; Garcia, Alexandre; Bonnet, Marc
2015-11-01
This paper presents an easy numerical implementation of the Burton and Miller (BM) formulation, where the hypersingular Helmholtz integral is regularized by identities from the associated Laplace equation and thus needing only the evaluation of weakly singular integrals. The Helmholtz equation and its normal derivative are combined directly with combinations at edge or corner collocation nodes not used when the surface is not smooth. The hypersingular operators arising in this process are regularized and then evaluated by an indirect procedure based on discretized versions of the Calderón identities linking the integral operators for associated Laplace problems. The method is valid for acoustic radiation and scattering problems involving arbitrarily shaped three-dimensional bodies. Unlike other approaches using direct evaluation of hypersingular integrals, collocation points still coincide with mesh nodes, as is usual when using conforming elements. Using higher-order shape functions (with the boundary element method model size kept fixed) reduces the overall numerical integration effort while increasing the solution accuracy. To reduce the condition number of the resulting BM formulation at low frequencies, a regularized version α = ik/(k(2 )+ λ) of the classical BM coupling factor α = i/k is proposed. Comparisons with the combined Helmholtz integral equation Formulation method of Schenck are made for four example configurations, two of them featuring non-smooth surfaces.
NASA Astrophysics Data System (ADS)
Luo, Qiang
2016-11-01
In this paper, we revisit the lattice vibration of a one-dimensional monatomic linear chain under open and periodic boundary conditions, and give the exact conditions for the emergence of the local vibration mode when one of the atoms is replaced by an impurity. Our motivation is twofold. Firstly, in deriving the dispersion relation of the atoms, the periodic boundary condition is overwhelmingly utilized while the open boundary condition is seldom used. Therefore we manage to obtain the dispersion relation under both boundary conditions simultaneously by the Molinari formula. Secondly, in the presence of an impurity, the local vibration mode can emerge as long as the mass of the impurity m\\prime is smaller than the mass of the perfect atom m to a certain degree, which can be measured by the mass ratio δ =\\tfrac{m-m\\prime }{m}. At the periodic boundary condition, the critical mass ratio is 0 or \\tfrac{1}{N}, depending on whether the length N of the chain is even or odd. At the open boundary condition, the critical mass ratio is \\tfrac{N}{2N-1} if the impurity locates at the end of the chain, while it is \\tfrac{N}{(2{N}{{l}}+1)(2{N}{{r}}+1)} with N l and N r the number of atoms at the left- and right-hand sides of the impurity if the impurity locates at the middle.
NASA Technical Reports Server (NTRS)
Hu, Fang Q.; Pizzo, Michelle E.; Nark, Douglas M.
2016-01-01
Based on the time domain boundary integral equation formulation of the linear convective wave equation, a computational tool dubbed Time Domain Fast Acoustic Scattering Toolkit (TD-FAST) has recently been under development. The time domain approach has a distinct advantage that the solutions at all frequencies are obtained in a single computation. In this paper, the formulation of the integral equation, as well as its stabilization by the Burton-Miller type reformulation, is extended to cases of a constant mean flow in an arbitrary direction. In addition, a "Source Surface" is also introduced in the formulation that can be employed to encapsulate regions of noise sources and to facilitate coupling with CFD simulations. This is particularly useful for applications where the noise sources are not easily described by analytical source terms. Numerical examples are presented to assess the accuracy of the formulation, including a computation of noise shielding by a thin barrier motivated by recent Historical Baseline F31A31 open rotor noise shielding experiments. Furthermore, spatial resolution requirements of the time domain boundary element method are also assessed using point per wavelength metrics. It is found that, using only constant basis functions and high-order quadrature for surface integration, relative errors of less than 2% may be obtained when the surface spatial resolution is 5 points-per-wavelength (PPW) or 25 points-per-wavelength squared (PPW2).
Graphical construction of a local perspective on differentiation and integration
NASA Astrophysics Data System (ADS)
Hong, Ye Yoon; Thomas, Michael O. J.
2015-06-01
Recent studies of the transition from school to university mathematics have identified a number of epistemological gaps, including the need to change from an emphasis on equality to that of inequality. Another crucial epistemological change during this transition involves the movement from the pointwise and global perspectives of functions usually established through the school curriculum to a view of function that includes a local, or interval, perspective. This is necessary for study of concepts such as continuity and limit that underpin calculus and analysis at university. In this study, a first-year university calculus course in Korea was constructed that integrated use of digital technology and considered the epistemic value of the associated techniques. The aim was to encourage versatile thinking about functions, especially in relation to properties arising from a graphical investigation of differentiation and integration. In this paper, the results of this approach for the learning of derivative and antiderivative, based on integrated technology use, are presented. They show the persistence of what Tall ( Mathematics Education Research Journal, 20(2), 5-24, 2008) describes as symbolic world algebraic thinking on the part of a significant minority of students, who feel the need to introduce algebraic methods, in spite of its disadvantages, even when no explicit algebra is provided. However, the results also demonstrate the ability of many of the students to use technology mediation to build local or interval conceptual thinking about derivative and antiderivative functions.
NASA Astrophysics Data System (ADS)
Ashbach, Jason A.
Periodic metallodielectric frequency selective surface (FSS) designs have historically seen widespread use in the microwave and radio frequency spectra. By scaling the dimensions of an FSS unit cell for use in a nano-fabrication process, these concepts have recently been adapted for use in optical applications as well. While early optical designs have been limited to wellunderstood geometries or optimized pixelated screens, nano-fabrication, lithographic and interconnect technology has progressed to a point where it is possible to fabricate metallic screens of arbitrary geometries featuring curvilinear or even three-dimensional characteristics that are only tens of nanometers wide. In order to design an FSS featuring such characteristics, it is important to have a robust numerical solver that features triangular elements in purely two-dimensional geometries and prismatic or tetrahedral elements in three-dimensional geometries. In this dissertation, a periodic finite element method code has been developed which features prismatic elements whose top and bottom boundaries are truncated by numerical integration of the boundary integral as opposed to an approximate representation found in a perfectly matched layer. However, since no exact solution exists for the calculation of triangular elements in a boundary integral, this process can be time consuming. To address this, these calculations were optimized for parallelization such that they may be done on a graphics processor, which provides a large increase in computational speed. Additionally, a simple geometrical representation using a Bezier surface is presented which provides generality with few variables. With a fast numerical solver coupled with a lowvariable geometric representation, a heuristic optimization algorithm has been used to develop several optical designs such as an absorber, a circular polarization filter, a transparent conductive surface and an enhanced, optical modulator.
Nichols, D.J.; Brown, J.L.; Attrep, M.; Orth, C.J.
1992-01-01
A newly discovered Cretaceous-Tertiary (K-T) boundary locality in the western Powder River basin, Wyoming, is characterized by a palynologically defined extinction horizon, a fern-spore abundance anomaly, a strong iridium anomaly, and shock-metamorphosed quartz grains. Detailed microstratigraphic analyses show that about one third of the palynoflora (mostly angiosperm pollen) disappeared abruptly, placing the K-T boundary within a distinctive, 1- to 2-cm-thick claystone layer. Shocked quartz grains are concentrated at the top of this layer, and although fern-spore and iridium concentrations are high in this layer, they reach their maximum concentrations in a 2-cm-thick carbonaceous claystone that overlies the boundary claystone layer. The evidence supports the theory that the K-T boundary event was associated with the impact of an extraterrestrial body or bodies. Palynological analyses of samples from the K-T boundary interval document extensive changes in the flora that resulted from the boundary event. The palynologically and geochemically defined K-T boundary provides a unique time-line of use in regional basin analysis. ?? 1992.
NASA Technical Reports Server (NTRS)
Collins, J. D.; Volakis, John L.
1992-01-01
A method that combines the finite element and boundary integral techniques for the numerical solution of electromagnetic scattering problems is presented. The finite element method is well known for requiring a low order storage and for its capability to model inhomogeneous structures. Of particular emphasis in this work is the reduction of the storage requirement by terminating the finite element mesh on a boundary in a fashion which renders the boundary integrals in convolutional form. The fast Fourier transform is then used to evaluate these integrals in a conjugate gradient solver, without a need to generate the actual matrix. This method has a marked advantage over traditional integral equation approaches with respect to the storage requirement of highly inhomogeneous structures. Rectangular, circular, and ogival mesh termination boundaries are examined for two-dimensional scattering. In the case of axially symmetric structures, the boundary integral matrix storage is reduced by exploiting matrix symmetries and solving the resulting system via the conjugate gradient method. In each case several results are presented for various scatterers aimed at validating the method and providing an assessment of its capabilities. Important in methods incorporating boundary integral equations is the issue of internal resonance. A method is implemented for their removal, and is shown to be effective in the two-dimensional and three-dimensional applications.
NASA Technical Reports Server (NTRS)
Gong, J.; Volakis, J. L.; Chatterjee, A.; Jin, J. M.
1992-01-01
A hybrid finite element boundary integral formulation is developed using tetrahedral and/or triangular elements for discretizing the cavity and/or aperture of microstrip antenna arrays. The tetrahedral elements with edge based linear expansion functions are chosen for modeling the volume region and triangular elements are used for discretizing the aperture. The edge based expansion functions are divergenceless thus removing the requirement to introduce a penalty term and the tetrahedral elements permit greater geometrical adaptability than the rectangular bricks. The underlying theory and resulting expressions are discussed in detail together with some numerical scattering examples for comparison and demonstration.
Analysis of Well-Clear Boundary Models for the Integration of UAS in the NAS
NASA Technical Reports Server (NTRS)
Upchurch, Jason M.; Munoz, Cesar A.; Narkawicz, Anthony J.; Chamberlain, James P.; Consiglio, Maria C.
2014-01-01
The FAA-sponsored Sense and Avoid Workshop for Unmanned Aircraft Systems (UAS) defnes the concept of sense and avoid for remote pilots as "the capability of a UAS to remain well clear from and avoid collisions with other airborne traffic." Hence, a rigorous definition of well clear is fundamental to any separation assurance concept for the integration of UAS into civil airspace. This paper presents a family of well-clear boundary models based on the TCAS II Resolution Advisory logic. Analytical techniques are used to study the properties and relationships satisfied by the models. Some of these properties are numerically quantifed using statistical methods.
Extending the diffusion approximation to the boundary using an integrated diffusion model
Chen, Chen; Du, Zhidong; Pan, Liang
2015-06-15
The widely used diffusion approximation is inaccurate to describe the transport behaviors near surfaces and interfaces. To solve such stochastic processes, an integro-differential equation, such as the Boltzmann transport equation (BTE), is typically required. In this work, we show that it is possible to keep the simplicity of the diffusion approximation by introducing a nonlocal source term and a spatially varying diffusion coefficient. We apply the proposed integrated diffusion model (IDM) to a benchmark problem of heat conduction across a thin film to demonstrate its feasibility. We also validate the model when boundary reflections and uniform internal heat generation are present.
Combining the boundary shift integral and tensor-based morphometry for brain atrophy estimation
NASA Astrophysics Data System (ADS)
Michalkiewicz, Mateusz; Pai, Akshay; Leung, Kelvin K.; Sommer, Stefan; Darkner, Sune; Sørensen, Lauge; Sporring, Jon; Nielsen, Mads
2016-03-01
Brain atrophy from structural magnetic resonance images (MRIs) is widely used as an imaging surrogate marker for Alzheimers disease. Their utility has been limited due to the large degree of variance and subsequently high sample size estimates. The only consistent and reasonably powerful atrophy estimation methods has been the boundary shift integral (BSI). In this paper, we first propose a tensor-based morphometry (TBM) method to measure voxel-wise atrophy that we combine with BSI. The combined model decreases the sample size estimates significantly when compared to BSI and TBM alone.
Griffith, Boyce E.; Peskin, Charles S.
2010-01-01
We describe an immersed boundary method for problems of fluid-solute-structure interaction. The numerical scheme employs linearly implicit timestepping, allowing for the stable use of timesteps that are substantially larger than those permitted by an explicit method, and local mesh refinement, making it feasible to resolve the steep gradients associated with the space charge layers as well as the chemical potential, which is used in our formulation to control the permeability of the membrane to the (possibly charged) solute. Low Reynolds number fluid dynamics are described by the time-dependent incompressible Stokes equations, which are solved by a cell-centered approximate projection method. The dynamics of the chemical species are governed by the advection-electrodiffusion equations, and our semi-implicit treatment of these equations results in a linear system which we solve by GMRES preconditioned via a fast adaptive composite-grid (FAC) solver. Numerical examples demonstrate the capabilities of this methodology, as well as its convergence properties. PMID:20454540
A locally stabilized immersed boundary method for the compressible Navier-Stokes equations
NASA Astrophysics Data System (ADS)
Brehm, C.; Hader, C.; Fasel, H. F.
2015-08-01
A higher-order immersed boundary method for solving the compressible Navier-Stokes equations is presented. The distinguishing feature of this new immersed boundary method is that the coefficients of the irregular finite-difference stencils in the vicinity of the immersed boundary are optimized to obtain improved numerical stability. This basic idea was introduced in a previous publication by the authors for the advection step in the projection method used to solve the incompressible Navier-Stokes equations. This paper extends the original approach to the compressible Navier-Stokes equations considering flux vector splitting schemes and viscous wall boundary conditions at the immersed geometry. In addition to the stencil optimization procedure for the convective terms, this paper discusses other key aspects of the method, such as imposing flux boundary conditions at the immersed boundary and the discretization of the viscous flux in the vicinity of the boundary. Extensive linear stability investigations of the immersed scheme confirm that a linearly stable method is obtained. The method of manufactured solutions is used to validate the expected higher-order accuracy and to study the error convergence properties of this new method. Steady and unsteady, 2D and 3D canonical test cases are used for validation of the immersed boundary approach. Finally, the method is employed to simulate the laminar to turbulent transition process of a hypersonic Mach 6 boundary layer flow over a porous wall and subsonic boundary layer flow over a three-dimensional spherical roughness element.
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.
Integration of local motion is normal in amblyopia
NASA Astrophysics Data System (ADS)
Hess, Robert F.; Mansouri, Behzad; Dakin, Steven C.; Allen, Harriet A.
2006-05-01
We investigate the global integration of local motion direction signals in amblyopia, in a task where performance is equated between normal and amblyopic eyes at the single element level. We use an equivalent noise model to derive the parameters of internal noise and number of samples, both of which we show are normal in amblyopia for this task. This result is in apparent conflict with a previous study in amblyopes showing that global motion processing is defective in global coherence tasks [Vision Res. 43, 729 (2003)]. A similar discrepancy between the normalcy of signal integration [Vision Res. 44, 2955 (2004)] and anomalous global coherence form processing has also been reported [Vision Res. 45, 449 (2005)]. We suggest that these discrepancies for form and motion processing in amblyopia point to a selective problem in separating signal from noise in the typical global coherence task.
Integration of Image Data for Refining Building Boundaries Derived from Point Clouds
NASA Astrophysics Data System (ADS)
Perera, S. N.; Hetti Arachchige, N.; Schneider, D.
2014-08-01
Geometrically and topologically correct 3D building models are required to satisfy with new demands such as 3D cadastre, map updating, and decision making. More attention on building reconstruction has been paid using Airborne Laser Scanning (ALS) point cloud data. The planimetric accuracy of roof outlines, including step-edges is questionable in building models derived from only point clouds. This paper presents a new approach for the detection of accurate building boundaries by merging point clouds acquired by ALS and aerial photographs. It comprises two major parts: reconstruction of initial roof models from point clouds only, and refinement of their boundaries. A shortest closed circle (graph) analysis method is employed to generate building models in the first step. Having the advantages of high reliability, this method provides reconstruction without prior knowledge of primitive building types even when complex height jumps and various types of building roof are available. The accurate position of boundaries of the initial models is determined by the integration of the edges extracted from aerial photographs. In this process, scene constraints defined based on the initial roof models are introduced as the initial roof models are representing explicit unambiguous geometries about the scene. Experiments were conducted using the ISPRS benchmark test data. Based on test results, we show that the proposed approach can reconstruct 3D building models with higher geometrical (planimetry and vertical) and topological accuracy.
An overview of boundary integral formulations for potential flows in fluid-fluid systems
NASA Astrophysics Data System (ADS)
Canot, E.; Achard, J.-L.
Three-dimensional flow problems involving a system of two incompressible constant-density fluids separated by a moving interface are investigated, comparing the theoretical foundations and numerical implementation of two classes of boundary-integral methods based on the irrotational-flow approximation (Baker et al., 1982; Roberts, 1983). Although the strength of the singularity induced at the interface obeys a general Fredholm integral equation of the second kind in each case, the method of Roberts is found to be simpler to apply in practice. Numerical results for vibration in a spherical globule and for the axisymmetric Rayleigh-Taylor instability in an unbounded fluid-fluid system are presented in graphs and discussed in detail: good general agreement with experimental data is observed.
Analysis of mixed-mode crack propagation using the boundary integral method
NASA Technical Reports Server (NTRS)
Mendelson, A.; Ghosn, L. J.
1986-01-01
Crack propagation in a rotating inner raceway of a high speed roller bearing is analyzed using the boundary integral equation method. The method consists of an edge crack in a plate under tension, upon which varying Hertzian stress fields are superimposed. A computer program for the boundary integral equation method was written using quadratic elements to determine the stress and displacement fields for discrete roller positions. Mode I and Mode II stress intensity factors and crack extension forces G sub 00 (energy release rate due to tensile opening mode) and G sub r0 (energy release rate due to shear displacement mode) were computed. These calculations permit determination of that crack growth angle for which the change in the crack extension forces is maximum. The crack driving force was found to be the alternating mixed-mode loading that occurs with each passage of the most heavily loaded roller. The crack is predicted to propagate in a step-like fashion alternating between radial and inclined segments, and this pattern was observed experimentally. The maximum changes DeltaG sub 00 and DeltaG sub r0 of the crack extension forces are found to be good measures of the crack propagation rate and direction.
Bardhan, Jaydeep P.; Knepley, Matthew G.; Brune, Peter
2015-01-01
In this paper, we present an exact, infinite-series solution to Lorentz nonlocal continuum electrostatics for an arbitrary charge distribution in a spherical solute. Our approach relies on two key steps: (1) re-formulating the PDE problem using boundary-integral equations, and (2) diagonalizing the boundary-integral operators using the fact that their eigenfunctions are the surface spherical harmonics. To introduce this uncommon approach for calculations in separable geometries, we first re-derive Kirkwood’s classic results for a protein surrounded concentrically by a pure-water ion-exclusion (Stern) layer and then a dilute electrolyte, which is modeled with the linearized Poisson–Boltzmann equation. The eigenfunction-expansion approach provides a computationally efficient way to test some implications of nonlocal models, including estimating the reasonable range of the nonlocal length-scale parameter λ. Our results suggest that nonlocal solvent response may help to reduce the need for very high dielectric constants in calculating pH-dependent protein behavior, though more sophisticated nonlocal models are needed to resolve this question in full. An open-source MATLAB implementation of our approach is freely available online. PMID:26273581
Shojaaee, Zahra; Roux, Jean-Noël; Chevoir, François; Wolf, Dietrich E
2012-07-01
We report on a numerical study of the shear flow of a simple two-dimensional model of a granular material under controlled normal stress between two parallel smooth frictional walls moving with opposite velocities ± V. Discrete simulations, which are carried out with the contact dynamics method in dense assemblies of disks, reveal that, unlike rough walls made of strands of particles, smooth ones can lead to shear strain localization in the boundary layer. Specifically, we observe, for decreasing V, first a fluidlike regime (A), in which the whole granular layer is sheared, with a homogeneous strain rate except near the walls, then (B) a symmetric velocity profile with a solid block in the middle and strain localized near the walls, and finally (C) a state with broken symmetry in which the shear rate is confined to one boundary layer, while the bulk of the material moves together with the opposite wall. Both transitions are independent of system size and occur for specific values of V. Transient times are discussed. We show that the first transition, between regimes A and B, can be deduced from constitutive laws identified for the bulk material and the boundary layer, while the second one could be associated with an instability in the behavior of the boundary layer. The boundary zone constitutive law, however, is observed to depend on the state of the bulk material nearby.
NASA Astrophysics Data System (ADS)
Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata
2016-01-01
In this paper, based on piezoforce measurements, we show the presence of opposite polarization at grains and grain boundaries of Al-doped ZnO (AZO). The polarization can be flipped by 180° in phase by switching the polarity of the applied electric field, revealing the existence of nanoscale pseudoferroelectricity in AZO grown on Pt/TiO2/SiO2/Si substrate. We also demonstrate an experimental evidence on local band bending at grain boundaries of AZO films using conductive atomic force microscopy and Kelvin probe force microscopy. The presence of an opposite polarization at grains and grain boundaries gives rise to a polarization-driven barrier formation at grain boundaries. With the help of conductive atomic force microscopy, we show that the polarization-driven barrier along with the defect-induced electrostatic potential barrier account for the measured local band bending at grain boundaries. The present study opens a new avenue to understand the charge transport in light of both polarization and electrostatic effects.
Kumar, Mohit; Basu, Tanmoy; Som, Tapobrata
2016-01-07
In this paper, based on piezoforce measurements, we show the presence of opposite polarization at grains and grain boundaries of Al-doped ZnO (AZO). The polarization can be flipped by 180° in phase by switching the polarity of the applied electric field, revealing the existence of nanoscale pseudoferroelectricity in AZO grown on Pt/TiO{sub 2}/SiO{sub 2}/Si substrate. We also demonstrate an experimental evidence on local band bending at grain boundaries of AZO films using conductive atomic force microscopy and Kelvin probe force microscopy. The presence of an opposite polarization at grains and grain boundaries gives rise to a polarization-driven barrier formation at grain boundaries. With the help of conductive atomic force microscopy, we show that the polarization-driven barrier along with the defect-induced electrostatic potential barrier account for the measured local band bending at grain boundaries. The present study opens a new avenue to understand the charge transport in light of both polarization and electrostatic effects.
Solution of Poisson's Equation with Global, Local and Nonlocal Boundary Conditions
ERIC Educational Resources Information Center
Aliev, Nihan; Jahanshahi, Mohammad
2002-01-01
Boundary value problems (BVPs) for partial differential equations are common in mathematical physics. The differential equation is often considered in simple and symmetric regions, such as a circle, cube, cylinder, etc., with global and separable boundary conditions. In this paper and other works of the authors, a general method is used for the…
Solution of Poisson's Equation with Global, Local and Nonlocal Boundary Conditions
ERIC Educational Resources Information Center
Aliev, Nihan; Jahanshahi, Mohammad
2002-01-01
Boundary value problems (BVPs) for partial differential equations are common in mathematical physics. The differential equation is often considered in simple and symmetric regions, such as a circle, cube, cylinder, etc., with global and separable boundary conditions. In this paper and other works of the authors, a general method is used for the…
NASA Astrophysics Data System (ADS)
Elliott, David; Johnston, Peter R.
2007-06-01
In the two-dimensional boundary element method, one often needs to evaluate numerically integrals of the form where j2 is a quadratic, g is a polynomial and f is a rational, logarithmic or algebraic function with a singularity at zero. The constants a and b are such that -1[less-than-or-equals, slant]a[less-than-or-equals, slant]1 and 0integration. In this case the direct application of Gauss-Legendre quadrature can give large truncation errors. By making the transformation x=a+bsinh([mu]u-[eta]), where the constants [mu] and [eta] are chosen so that the interval of integration is again [-1,1], it is found that the truncation errors arising, when the same Gauss-Legendre quadrature is applied to the transformed integral, are much reduced. The asymptotic error analysis for Gauss-Legendre quadrature, as given by Donaldson and Elliott [A unified approach to quadrature rules with asymptotic estimates of their remainders, SIAM J. Numer. Anal. 9 (1972) 573-602], is then used to explain this phenomenon and justify the transformation.
NASA Technical Reports Server (NTRS)
Schowalter, D. G.; DeCroix, D. S.; Lin, Y. L.; Arya, S. P.; Kaplan, M. L.
1996-01-01
It was found that the homogeneity of the surface drag coefficient plays an important role in the large scale structure of turbulence in large-eddy simulation of the convective atmospheric boundary layer. Particularly when a ground surface temperature was specified, large horizontal anisotropies occurred when the drag coefficient depended upon local velocities and heat fluxes. This was due to the formation of streamwise roll structures in the boundary layer. In reality, these structures have been found to form when shear is approximately balanced by buoyancy. The present cases, however, were highly convective. The formation was caused by particularly low values of the drag coefficient at the entrance to thermal plume structures.
Stability of high-speed boundary layer on a sharp cone with localized wall heating or cooling
NASA Astrophysics Data System (ADS)
Soudakov, V. G.; Fedorov, A. V.; Egorov, I. V.
2015-06-01
A localized heating or cooling effect on stability and transition of the boundary layer flow on a sharp cone is analyzed at the Mach number 6. The mean flows are calculated using axisymmetric Navier-Stokes equations. The spatial linear stability analysis is performed for twodimensional (2D) disturbances related to the Mack second mode. The transition onset points are estimated using the eN method. In this framework, the heater or cooler may cause earlier or later transition depending on the choice of critical N-factor. Direct numerical simulations (DNS) of 2D wave propagating in the boundary layer are compared with stability results.
NASA Technical Reports Server (NTRS)
Mager, Arthur
1952-01-01
The Navier-Stokes equations of motion and the equation of continuity are transformed so as to apply to an orthogonal curvilinear coordinate system rotating with a uniform angular velocity about an arbitrary axis in space. A usual simplification of these equations as consistent with the accepted boundary-layer theory and an integration of these equations through the boundary layer result in boundary-layer momentum-integral equations for three-dimensional flows that are applicable to either rotating or nonrotating fluid boundaries. These equations are simplified and an approximate solution in closed integral form is obtained for a generalized boundary-layer momentum-loss thickness and flow deflection at the wall in the turbulent case. A numerical evaluation of this solution carried out for data obtained in a curving nonrotating duct shows a fair quantitative agreement with the measures values. The form in which the equations are presented is readily adaptable to cases of steady, three-dimensional, incompressible boundary-layer flow like that over curved ducts or yawed wings; and it also may be used to describe the boundary-layer flow over various rotating surfaces, thus applying to turbomachinery, propellers, and helicopter blades.
[Integration and boundaries between health and social care. 2008 SESPAS Report].
Zunzunegui Pastor, María Victoria; Lázaro Y de Mercado, Pablo
2008-04-01
We examine the opportunities to establish integrated services in Spain. The new law on services for disabled people approved by the Spanish Parliament in December 2006 and the Mental Health Plan of the Spanish Ministry of Health are used to illustrate policies that will require a high degree of integration among organizational, financial and clinical levels. In this context, some of the following questions arise: what do we know about the effectiveness of the integration of health and social services? Who should be the targets of integration and what are the structures needed for patient-centered services? Who should be responsible for and manage these services? An outline of Leutz's five criteria for integration is reviewed and the results from international experiences are discussed. We conclude that Spain is at a crossroads for the integration of services for disabled people and people with mental health problems. We recommend that a system of integrated services be organized for people with moderate or severe disability. This system should be decentralized at the levels of local health and social services, with a single budget estimated on a capitation basis. Clinical and financial responsibility should be shared between the interdisciplinary team and the case manager (nursing or social work professionals).
Haider, M A; Guilak, F
2000-06-01
The micropipette aspiration test has been used extensively in recent years as a means of quantifying cellular mechanics and molecular interactions at the microscopic scale. However, previous studies have generally modeled the cell as an infinite half-space in order to develop an analytical solution for a viscoelastic solid cell. In this study, an axisymmetric boundary integral formulation of the governing equations of incompressible linear viscoelasticity is presented and used to simulate the micropipette aspiration contact problem. The cell is idealized as a homogeneous and isotropic continuum with constitutive equation given by three-parameter (E, tau 1, tau 2) standard linear viscoelasticity. The formulation is used to develop a computational model via a "correspondence principle" in which the solution is written as the sum of a homogeneous (elastic) part and a nonhomogeneous part, which depends only on past values of the solution. Via a time-marching scheme, the solution of the viscoelastic problem is obtained by employing an elastic boundary element method with modified boundary conditions. The accuracy and convergence of the time-marching scheme are verified using an analytical solution. An incremental reformulation of the scheme is presented to facilitate the simulation of micropipette aspiration, a nonlinear contact problem. In contrast to the halfspace model (Sato et al., 1990), this computational model accounts for nonlinearities in the cell response that result from a consideration of geometric factors including the finite cell dimension (radius R), curvature of the cell boundary, evolution of the cell-micropipette contact region, and curvature of the edges of the micropipette (inner radius a, edge curvature radius epsilon). Using 60 quadratic boundary elements, a micropipette aspiration creep test with ramp time t* = 0.1 s and ramp pressure p*/E = 0.8 is simulated for the cases a/R = 0.3, 0.4, 0.5 using mean parameter values for primary chondrocytes
Bhattacharya, Amitabh; Kesarkar, Tejas
2016-10-01
A combination of finite difference (FD) and boundary integral (BI) methods is used to formulate an efficient solver for simulating unsteady Stokes flow around particles. The two-dimensional (2D) unsteady Stokes equation is being solved on a Cartesian grid using a second order FD method, while the 2D steady Stokes equation is being solved near the particle using BI method. The two methods are coupled within the viscous boundary layer, a few FD grid cells away from the particle, where solutions from both FD and BI methods are valid. We demonstrate that this hybrid method can be used to accurately solve for the flow around particles with irregular shapes, even though radius of curvature of the particle surface is not resolved by the FD grid. For dilute particle concentrations, we construct a virtual envelope around each particle and solve the BI problem for the flow field located between the envelope and the particle. The BI solver provides velocity boundary condition to the FD solver at "boundary" nodes located on the FD grid, adjacent to the particles, while the FD solver provides the velocity boundary condition to the BI solver at points located on the envelope. The coupling between FD method and BI method is implicit at every time step. This method allows us to formulate an O(N) scheme for dilute suspensions, where N is the number of particles. For semidilute suspensions, where particles may cluster, an envelope formation method has been formulated and implemented, which enables solving the BI problem for each individual particle cluster, allowing efficient simulation of hydrodynamic interaction between particles even when they are in close proximity. The method has been validated against analytical results for flow around a periodic array of cylinders and for Jeffrey orbit of a moving ellipse in shear flow. Simulation of multiple force-free irregular shaped particles in the presence of shear in a 2D slit flow has been conducted to demonstrate the robustness of
NASA Astrophysics Data System (ADS)
Bhattacharya, Amitabh; Kesarkar, Tejas
2016-10-01
A combination of finite difference (FD) and boundary integral (BI) methods is used to formulate an efficient solver for simulating unsteady Stokes flow around particles. The two-dimensional (2D) unsteady Stokes equation is being solved on a Cartesian grid using a second order FD method, while the 2D steady Stokes equation is being solved near the particle using BI method. The two methods are coupled within the viscous boundary layer, a few FD grid cells away from the particle, where solutions from both FD and BI methods are valid. We demonstrate that this hybrid method can be used to accurately solve for the flow around particles with irregular shapes, even though radius of curvature of the particle surface is not resolved by the FD grid. For dilute particle concentrations, we construct a virtual envelope around each particle and solve the BI problem for the flow field located between the envelope and the particle. The BI solver provides velocity boundary condition to the FD solver at "boundary" nodes located on the FD grid, adjacent to the particles, while the FD solver provides the velocity boundary condition to the BI solver at points located on the envelope. The coupling between FD method and BI method is implicit at every time step. This method allows us to formulate an O (N ) scheme for dilute suspensions, where N is the number of particles. For semidilute suspensions, where particles may cluster, an envelope formation method has been formulated and implemented, which enables solving the BI problem for each individual particle cluster, allowing efficient simulation of hydrodynamic interaction between particles even when they are in close proximity. The method has been validated against analytical results for flow around a periodic array of cylinders and for Jeffrey orbit of a moving ellipse in shear flow. Simulation of multiple force-free irregular shaped particles in the presence of shear in a 2D slit flow has been conducted to demonstrate the robustness of
NASA Astrophysics Data System (ADS)
Gorev, V. N.; Katasonov, M. M.; Kozlov, V. V.; Motyrev, P. A.
2009-12-01
Turbulence production processes in boundary layer at a high level of free-stream turbulence have been studied. The tests were carried out in the MT-324 subsonic wind tunnel of ITAM, SB RAS, on models of straight and 45° swept wings at Reynolds numbers Rec1 = 97000 and Rec2 = 137000, and also at low ( Tu = 0.18 % U ∞) and high ( Tu = 0.79 and 2.31 % U ∞) levels of free-stream turbulence. The longitudinal localized disturbances developing in the boundary layer under the action of free-stream turbulence were artificially modeled using local air suction through a slot on the model surface. Wave packets, or forerunners, produced in the boundary layer, in the region preceding the abrupt local change of flow velocity near the localized-disturbance fronts, were examined. The high level of free-stream turbulence was found to accelerate the downstream evolution of the wave packets and their transformation into turbulent spots.
NASA Technical Reports Server (NTRS)
Choudhari, Meelan; Streett, Craig L.
1992-01-01
Previous theoretical work on the boundary layer receptivity problem has utilized large Reynolds number asymptotic theories, thus being limited to a narrow part of the frequency-Reynolds number domain. An alternative approach is presented for the prediction of localized instability generation which has a general applicability, and also accounts for finite Reynolds number effects. This approach is illustrated for the case of Tollmien-Schlichting wave generation in a Blasius boundary layer due to the interaction of a free stream acoustic wave with a region of short scale variation in the surface boundary condition. The specific types of wall inhomogeneities studied are: regions of short scale variations in wall suction, wall admittance, and wall geometry (roughness). Extensive comparison is made between the results of the finite Reynolds number approach and previous asymptotic predictions, which also suggests an alternative way of using the latter at Reynolds numbers of interest in practice.
NASA Technical Reports Server (NTRS)
Choudhari, Meelan; Streett, Craig L.
1992-01-01
Previous theoretical work on the boundary layer receptivity problem has utilized large Reynolds number asymptotic theories, thus being limited to a narrow part of the frequency-Reynolds number domain. An alternative approach is presented for the prediction of localized instability generation which has a general applicability, and also accounts for finite Reynolds number effects. This approach is illustrated for the case of Tollmien-Schlichting wave generation in a Blasius boundary layer due to the interaction of a free stream acoustic wave with a region of short scale variation in the surface boundary condition. The specific types of wall inhomogeneities studied are: regions of short scale variations in wall suction, wall admittance, and wall geometry (roughness). Extensive comparison is made between the results of the finite Reynolds number approach and previous asymptotic predictions, which also suggests an alternative way of using the latter at Reynolds numbers of interest in practice.
NASA Technical Reports Server (NTRS)
Jin, Jian-Ming; Volakis, John L.; Collins, Jeffery D.
1991-01-01
A review of a hybrid finite element-boundary integral formulation for scattering and radiation by two- and three-dimensional composite structures is presented. In contrast to other hybrid techniques involving the finite element method, the proposed one is in principle exact and can be implemented using a low O(N) storage. This is of particular importance for large scale applications and is a characteristic of the boundary chosen to terminate the finite element mesh, usually as close to the structure as possible. A certain class of these boundaries lead to convolutional boundary integrals which can be evaluated via the fast Fourier transform (FFT) without a need to generate a matrix; thus, retaining the O(N) storage requirement. The paper begins with a general description of the method. A number of two- and three-dimensional applications are then given, including numerical computations which demonstrate the method's accuracy, efficiency, and capability.
Local and Global Illumination in the Volume Rendering Integral
Max, N; Chen, M
2005-10-21
This article is intended as an update of the major survey by Max [1] on optical models for direct volume rendering. It provides a brief overview of the subject scope covered by [1], and brings recent developments, such as new shadow algorithms and refraction rendering, into the perspective. In particular, we examine three fundamentals aspects of direct volume rendering, namely the volume rendering integral, local illumination models and global illumination models, in a wavelength-independent manner. We review the developments on spectral volume rendering, in which visible light are considered as a form of electromagnetic radiation, optical models are implemented in conjunction with representations of spectral power distribution. This survey can provide a basis for, and encourage, new efforts for developing and using complex illumination models to achieve better realism and perception through optical correctness.
Mardanov, M. J.; Mahmudov, N. I.; Sharifov, Y. A.
2014-01-01
We study a boundary value problem for the system of nonlinear impulsive fractional differential equations of order α (0 < α ≤ 1) involving the two-point and integral boundary conditions. Some new results on existence and uniqueness of a solution are established by using fixed point theorems. Some illustrative examples are also presented. We extend previous results even in the integer case α = 1. PMID:24782675
Mardanov, M J; Mahmudov, N I; Sharifov, Y A
2014-01-01
We study a boundary value problem for the system of nonlinear impulsive fractional differential equations of order α (0 < α ≤ 1) involving the two-point and integral boundary conditions. Some new results on existence and uniqueness of a solution are established by using fixed point theorems. Some illustrative examples are also presented. We extend previous results even in the integer case α = 1.
Integrating remote sensing and GIS data for the Natural Systems Boundary (NSB) model
Leary, T.J.; Flamm, R.O.; Haddad, K.D.
1997-06-01
Significant alterations in hydrology, water quality, and land use have put the entire south Florida ecosystem on the brink of collapse. Considerable federal, state, and local efforts have focused on this region to develop and implement management options for environmental and economic restoration and sustainability. The Governor`s Commission for a Sustainable South Florida was created to represent a broad array of interests in the region and is charged with setting the state is vision, direction, and management options for an environmentally and economically sustainable south Florida ecosystem. The Commission`s Science Research Advisory Committee (SRAC) was given the responsibility of delineating and evaluating alternative natural system boundaries. To meet the Commission`s recommendations, the SRAC empowered the Florida Marine Research Institute (FMR1) to develop a GIS-based modeling application. The resulting ARCVIEW application allows managers and scientists to delineate alternative Natural Systems Boundaries (NSBs) by varying the selection and weight (relative importance) of management criteria such as hydrology, habitat, wildlife, and water quality. Repetitive model runs with modifications to the user-defined inputs afford managers the opportunity to better understand the complexity of the data and their relationship to management objectives.
Furukawa, Hideaki; Miyazawa, Takaya; Wada, Naoya; Harai, Hiroaki
2014-01-13
Optical packet and circuit integrated (OPCI) networks provide both optical packet switching (OPS) and optical circuit switching (OCS) links on the same physical infrastructure using a wavelength multiplexing technique in order to deal with best-effort services and quality-guaranteed services. To immediately respond to changes in user demand for OPS and OCS links, OPCI networks should dynamically adjust the amount of wavelength resources for each link. We propose a resource-adjustable hybrid optical packet/circuit switch and transponder. We also verify that distributed control of resource adjustments can be applied to the OPCI ring network testbed we developed. In cooperation with the resource adjustment mechanism and the hybrid switch and transponder, we demonstrate that automatically allocating a shared resource and moving the wavelength resource boundary between OPS and OCS links can be successfully executed, depending on the number of optical paths in use.
A Family of Well-Clear Boundary Models for the Integration of UAS in the NAS
NASA Technical Reports Server (NTRS)
Munoz, Cesar A.; Narkawicz, Anthony; Chamberlain, James; Consiglio, Maria; Upchurch, Jason
2014-01-01
The FAA-sponsored Sense and Avoid Workshop for Unmanned Aircraft Systems (UAS) defines the concept of sense and avoid for remote pilots as "the capability of a UAS to remain well clear from and avoid collisions with other airborne traffic." Hence, a rigorous definition of well clear is fundamental to any separation assurance concept for the integration of UAS into civil airspace. This paper presents a family of well-clear boundary models based on the TCAS II Resolution Advisory logic. For these models, algorithms that predict well-clear violations along aircraft current trajectories are provided. These algorithms are analogous to conflict detection algorithms but instead of predicting loss of separation, they predict whether well-clear violations will occur during a given lookahead time interval. Analytical techniques are used to study the properties and relationships satisfied by the models.
Connectivity as an alternative to boundary integral equations: Construction of bases
Herrera, Ismael; Sabina, Federico J.
1978-01-01
In previous papers Herrera developed a theory of connectivity that is applicable to the problem of connecting solutions defined in different regions, which occurs when solving partial differential equations and many problems of mechanics. In this paper we explain how complete connectivity conditions can be used to replace boundary integral equations in many situations. We show that completeness is satisfied not only in steady-state problems such as potential, reduced wave equation and static and quasi-static elasticity, but also in time-dependent problems such as heat and wave equations and dynamical elasticity. A method to obtain bases of connectivity conditions, which are independent of the regions considered, is also presented. PMID:16592522
Learning to cross boundaries: the integration of a health network to deliver seamless care.
van Wijngaarden, Jeroen D H; de Bont, Antoinette A; Huijsman, Robbert
2006-12-01
We analysed the development of an integrated network from a learning perspective to see how care givers from different organisations were able to cross the professional and organisational boundaries that existed between them to make sure patients receive the right care, at the right moment, in the right place. We show how through a process of collective learning social contacts between health professionals increased and improved. These professionals learned to speak each other's language, learned how other professionals and organisations work and learned to look at the care process from a network perspective instead of only from a professional or organisational perspective. Through this learning process, they also experienced the limitations of standardizing knowledge in criteria, protocols and rules, and the value of direct contact for sharing information and knowledge, to ensure continuity in care.
NASA Astrophysics Data System (ADS)
Dieudonné, E.; Ravetta, F.; Pelon, J.; Goutail, F.; Pommereau, J.-P.
2013-03-01
A statistical linear relationship between NO2 surface concentration and its integrated content in the atmospheric boundary layer (ABL) is established in urban conditions, using ABL depth as an ancillary parameter. This relationship relies on a unique data set including 20 months of observations from a ground-based UV-visible light spectrometer and from an aerosol lidar, both located in Paris inner city center. Measurements show that in all seasons, large vertical gradients of NO2 concentration exist in Paris developed ABL, explaining why the average concentration retrieved is only about 25% of NO2 surface concentration. This result shows that the commonly used hypothesis of constant mixing ratio in the ABL is not valid over urban areas, where large NOx emissions occur. Moreover, the relationship obtained is robust, and the studied area lacks of any particular orographic features, so that our results should be more widely applicable to pollution survey from space-borne observations.
Coastal Hazards and Integration of Impacts in Local Adaptation Planning
NASA Astrophysics Data System (ADS)
Knudsen, P.; Sorensen, C.; Molgaard, M. R.; Broge, N. H.; Andersen, O. B.
2016-12-01
Data on sea and groundwater levels, precipitation, land subsidence, geology, and geotechnical soil properties are combined with information on flood and erosion protection measures to analyze water-related impacts from climate change at an exposed coastal location. Future sea extremes will have a large impact but several coupled effects in the hydrological system need to be considered as well to provide for optimal protection and mitigation efforts. For instance, the investment and maintenance costs of securing functional water and wastewater pipes are significantly reduced by incorporating knowledge about climate change. The translation of regional sea level rise evidence and projections to concrete impact measures should take into account the potentially affected stakeholders who must collaborate on common and shared adaptation solutions. Here, knowledge integration across levels of governance and between research, private and public institutions, and the local communities provides: understanding of the immediate and potential future challenges; appreciation of different stakeholder motives, business agendas, legislative constraints etc., and a common focus on how to cost-efficiently adapt to and manage impacts of climate change. By construction of a common working platform that is updated with additional data and knowledge, e.g. from future regional models or extreme events, advances in sea level research can more readily be translated into concrete and local impact measures in a way that handles uncertainties in the future climate and urban development as well as suiting the varying stakeholder needs.
Toward structurally integrated locally resonant metamaterials for vibration attenuation
NASA Astrophysics Data System (ADS)
Schmied, Jascha U.; Sugino, Christopher; Bergamini, Andrea; Ermanni, Paolo; Ruzzene, Massimo; Erturk, Alper
2017-04-01
In this contribution, we explore the use of locally resonant metamaterials for multi-functional structural load- bearing concepts using analytical, numerical, and experimental techniques. Locally resonant metamaterials exhibit bandgaps at wavelengths much larger than the lattice dimension. This is a promising feature for low- frequency vibration attenuation. The presented work aims to investigate highly integrated structural concepts and experimentally validated prototypes for vibration reduction in load-bearing applications. The goal is to explore and extend the design space of lightweight structural systems, by designing multi-functional periodic structural elements, preserving structural stiffness while concurrently enabling sufficiently wideband damping performance over a target frequency range of interest. Following a generalized theoretical modeling framework for bandgap design and analysis in finite structures, the focus is placed on the design, fabrication, and analysis of a load-carrying frame development with internally resonant components. Finite-element modeling is employed to design and analyze the frequency response of the frame and simplified analytical solution is compared with this numerical solution. Experimental validations are presented for a 3D-printed prototype. The effects of various parameters are reported both based on numerical and experimental findings.
NASA Technical Reports Server (NTRS)
Goldman, L. J.; Augler, R. E.
1980-01-01
A generalized analysis to predict the two-dimensional aerodynamic losses of film-cooled vanes by using integral boundary-layer parameters is presented. Heat-transfer and trailing-edge injection effects are included in the method. An approximate solution of the generalized equations is also included to show more clearly the effect of the different boundary-layer and cooling parameters on the losses. The analytical predictions agree well with the experimental results, indicating that available boundary-layer calculations for cooled vanes are of sufficient accuracy to use in the prediction method.
NASA Astrophysics Data System (ADS)
Hudson, S. R.; Monticello, D. A.; Reiman, A. H.; Strickler, D. J.; Hirshman, S. P.
2003-06-01
For the (non-axisymmetric) stellarator class of plasma confinement devices to be feasible candidates for fusion power stations it is essential that, to a good approximation, the magnetic field lines lie on nested flux surfaces; however, the inherent lack of a continuous symmetry implies that magnetic islands are guaranteed to exist. Magnetic islands break the smooth topology of nested flux surfaces and chaotic field lines result when magnetic islands overlap. An analogous case occurs with 11/2-dimension Hamiltonian systems where resonant perturbations cause singularities in the transformation to action-angle coordinates and destroy integrability. The suppression of magnetic islands is a critical issue for stellarator design, particularly for small aspect ratio devices. Techniques for `healing' vacuum fields and fixed-boundary plasma equilibria have been developed, but what is ultimately required is a procedure for designing stellarators such that the self-consistent plasma equilibrium currents and the coil currents combine to produce an integrable magnetic field, and such a procedure is presented here for the first time. Magnetic islands in free-boundary full-pressure full-current stellarator magnetohydrodynamic equilibria are suppressed using a procedure based on the Princeton Iterative Equilibrium Solver [A.H.Reiman & H.S.Greenside, Comp. Phys. Comm., 43:157, 1986.] which iterates the equilibrium equations to obtain the plasma equilibrium. At each iteration, changes to a Fourier representation of the coil geometry are made to cancel resonant fields produced by the plasma. As the iterations continue, the coil geometry and the plasma simultaneously converge to an equilibrium in which the island content is negligible. The method is applied to a candidate plasma and coil design for the National Compact Stellarator eXperiment [G.H.Neilson et.al., Phys. Plas., 7:1911, 2000.].
Direct localization of poles of a meromorphic function from measurements on an incomplete boundary
NASA Astrophysics Data System (ADS)
Nara, Takaaki; Ando, Shigeru
2010-01-01
This paper proposes an algebraic method to reconstruct the positions of multiple poles in a meromorphic function field from measurements on an arbitrary simple arc in it. A novel issue is the exactness of the algorithm depending on whether the arc is open or closed, and whether it encloses or does not enclose the poles. We first obtain a differential equation that can equivalently determine the meromorphic function field. From it, we derive linear equations that relate the elementary symmetric polynomials of the pole positions to weighted integrals of the field along the simple arc and end-point terms of the arc when it is an open one. Eliminating the end-point terms based on an appropriate choice of weighting functions and a combination of the linear equations, we obtain a simple system of linear equations for solving the elementary symmetric polynomials. We also show that our algorithm can be applied to a 2D electric impedance tomography problem. The effects of the proximity of the poles, the number of measurements and noise on the localization accuracy are numerically examined.
NASA Astrophysics Data System (ADS)
Barucq, H.; Bendali, A.; Fares, M.; Mattesi, V.; Tordeux, S.
2017-02-01
A general symmetric Trefftz Discontinuous Galerkin method is built for solving the Helmholtz equation with piecewise constant coefficients. The construction of the corresponding local solutions to the Helmholtz equation is based on a boundary element method. A series of numerical experiments displays an excellent stability of the method relatively to the penalty parameters, and more importantly its outstanding ability to reduce the instabilities known as the "pollution effect" in the literature on numerical simulations of long-range wave propagation.
NASA Astrophysics Data System (ADS)
Gu, Yan; Gao, Hongwei; Chen, Wen; Wang, Huijuan; Zhang, Chuanzeng
2017-05-01
One of the typical and most significant issues of almost all boundary element analyses is the accurate evaluation of nearly singular boundary element integrals. In this study, we review some numerical techniques used currently to calculate nearly singular integrals and propose an improved algorithm to calculate integrals with nearly strong (and beyond) singularities. This new method has full generally and can be easily included in any existing computer code. The method is tested in general three-dimensional boundary element analysis. Comparison of this method with some of the existing methods is also presented. It is shown that several orders of magnitude improvement in relative errors can be obtained using the proposed method when compared to a straightforward implementation of Gaussian quadrature.
Andrews, D.J.
1985-01-01
A numerical boundary integral method, relating slip and traction on a plane in an elastic medium by convolution with a discretized Green function, can be linked to a slip-dependent friction law on the fault plane. Such a method is developed here in two-dimensional plane-strain geometry. Spontaneous plane-strain shear ruptures can make a transition from sub-Rayleigh to near-P propagation velocity. Results from the boundary integral method agree with earlier results from a finite difference method on the location of this transition in parameter space. The methods differ in their prediction of rupture velocity following the transition. The trailing edge of the cohesive zone propagates at the P-wave velocity after the transition in the boundary integral calculations. Refs.
NASA Astrophysics Data System (ADS)
Bajars, Janis; Chappell, David
2017-06-01
A boundary integral framework for stochastic ray tracing in billiards was recently proposed in [1]. In particular, a phase-space boundary integral model for propagating uncertain ray or particle flows was described and shown to interpolate between deterministic and random models of the flow propagation. In this work we describe a discretisation scheme for this class of boundary transfer operators using piecewise constant collocation in the spatial variable and the Nyström method in the momentum variable. The simplicity of the spatial basis functions means that the corresponding spatial integration can be performed analytically. A range of quadrature rules are compared for the Nyström method and numerical results with relevance to high-frequency vibro-acoustic wave problems are presented.
Argani, L. P.; Bigoni, D.; Capuani, D.; Movchan, N. V.
2014-01-01
The infinite-body three-dimensional Green's function set (for incremental displacement and mean stress) is derived for the incremental deformation of a uniformly strained incompressible, nonlinear elastic body. Particular cases of the developed formulation are the Mooney–Rivlin elasticity and the J2-deformation theory of plasticity. These Green's functions are used to develop a boundary integral equation framework, by introducing an ad hoc potential, which paves the way for a boundary element formulation of three-dimensional problems of incremental elasticity. Results are used to investigate the behaviour of a material deformed near the limit of ellipticity and to reveal patterns of shear failure. In fact, within the investigated three-dimensional framework, localized deformations emanating from a perturbation are shown to be organized in conical geometries rather than in planar bands, so that failure is predicted to develop through curved and thin surfaces of intense shearing, as can for instance be observed in the cup–cone rupture of ductile metal bars. PMID:25197258
Argani, L P; Bigoni, D; Capuani, D; Movchan, N V
2014-09-08
The infinite-body three-dimensional Green's function set (for incremental displacement and mean stress) is derived for the incremental deformation of a uniformly strained incompressible, nonlinear elastic body. Particular cases of the developed formulation are the Mooney-Rivlin elasticity and the J2-deformation theory of plasticity. These Green's functions are used to develop a boundary integral equation framework, by introducing an ad hoc potential, which paves the way for a boundary element formulation of three-dimensional problems of incremental elasticity. Results are used to investigate the behaviour of a material deformed near the limit of ellipticity and to reveal patterns of shear failure. In fact, within the investigated three-dimensional framework, localized deformations emanating from a perturbation are shown to be organized in conical geometries rather than in planar bands, so that failure is predicted to develop through curved and thin surfaces of intense shearing, as can for instance be observed in the cup-cone rupture of ductile metal bars.
Carrington, David Bradley; Monayem, A. K. M.; Mazumder, H.; Heinrich, Juan C.
2015-03-05
A three-dimensional finite element method for the numerical simulations of fluid flow in domains containing moving rigid objects or boundaries is developed. The method falls into the general category of Arbitrary Lagrangian Eulerian methods; it is based on a fixed mesh that is locally adapted in the immediate vicinity of the moving interfaces and reverts to its original shape once the moving interfaces go past the elements. The moving interfaces are defined by separate sets of marker points so that the global mesh is independent of interface movement and the possibility of mesh entanglement is eliminated. The results is a fully robust formulation capable of calculating on domains of complex geometry with moving boundaries or devises that can also have a complex geometry without danger of the mesh becoming unsuitable due to its continuous deformation thus eliminating the need for repeated re-meshing and interpolation. Moreover, the boundary conditions on the interfaces are imposed exactly. This work is intended to support the internal combustion engines simulator KIVA developed at Los Alamos National Laboratories. The model's capabilities are illustrated through application to incompressible flows in different geometrical settings that show the robustness and flexibility of the technique to perform simulations involving moving boundaries in a three-dimensional domain.
NASA Astrophysics Data System (ADS)
Zhang, Hui; Cesnik, Carlos E. S.
2016-04-01
Local interaction simulation approach (LISA) is a highly parallelizable numerical scheme for guided wave simulation in structural health monitoring (SHM). This paper addresses the issue of simulating wave propagation in unbounded domain through the implementation of non-reflective boundary (NRB) in LISA. In this study, two different categories of NRB, i.e., the non-reflective boundary condition (NRBC) and the absorbing boundary layer (ABL), have been investigated in the parallelized LISA scheme. For the implementation of NRBC, a set of general LISA equations considering the effect from boundary stress is obtained first. As a simple example, the Lysmer and Kuhlemeyer (L-K) model is applied here to demonstrate the easiness of NRBC implementation in LISA. As a representative of ABL implementation, the LISA scheme incorporating the absorbing layers with increasing damping (ALID) is also proposed, based on elasto-dynamic equations considering damping effect. Finally, an effective hybrid model combining L-K and ALID methods in LISA is developed, and guidelines for implementing the hybrid model is presented. Case studies on a three-dimensional plate model compares the performance of hybrid method to that of L-K and ALID acting independently. The simulation results demonstrate that best absorbing efficiency is achieved with the hybrid method.
Rudolf, Katrin; Umetsu, Daiki; Aliee, Maryam; Sui, Liyuan; Jülicher, Frank; Dahmann, Christian
2015-11-15
Tissue organization requires the interplay between biochemical signaling and cellular force generation. The formation of straight boundaries separating cells with different fates into compartments is important for growth and patterning during tissue development. In the developing Drosophila wing disc, maintenance of the straight anteroposterior (AP) compartment boundary involves a local increase in mechanical tension at cell bonds along the boundary. The biochemical signals that regulate mechanical tension along the AP boundary, however, remain unknown. Here, we show that a local difference in Hedgehog signal transduction activity between anterior and posterior cells is necessary and sufficient to increase mechanical tension along the AP boundary. This difference in Hedgehog signal transduction is also required to bias cell rearrangements during cell intercalations to keep the characteristic straight shape of the AP boundary. Moreover, severing cell bonds along the AP boundary does not reduce tension at neighboring bonds, implying that active mechanical tension is upregulated, cell bond by cell bond. Finally, differences in the expression of the homeodomain-containing protein Engrailed also contribute to the straight shape of the AP boundary, independently of Hedgehog signal transduction and without modulating cell bond tension. Our data reveal a novel link between local differences in Hedgehog signal transduction and a local increase in active mechanical tension of cell bonds that biases junctional rearrangements. The large-scale shape of the AP boundary thus emerges from biochemical signals inducing patterns of active tension on cell bonds. © 2015. Published by The Company of Biologists Ltd.
Local Melatoninergic System as the Protector of Skin Integrity
Slominski, Andrzej T.; Kleszczyński, Konrad; Semak, Igor; Janjetovic, Zorica; Żmijewski, Michał A.; Kim, Tae-Kang; Slominski, Radomir M.; Reiter, Russel J.; Fischer, Tobias W.
2014-01-01
The human skin is not only a target for the protective actions of melatonin, but also a site of melatonin synthesis and metabolism, suggesting an important role for a local melatoninergic system in protection against ultraviolet radiation (UVR) induced damages. While melatonin exerts many effects on cell physiology and tissue homeostasis via membrane bound melatonin receptors, the strong protective effects of melatonin against the UVR-induced skin damage including DNA repair/protection seen at its high (pharmocological) concentrations indicate that these are mainly mediated through receptor-independent mechanisms or perhaps through activation of putative melatonin nuclear receptors. The destructive effects of the UVR are significantly counteracted or modulated by melatonin in the context of a complex intracutaneous melatoninergic anti-oxidative system with UVR-enhanced or UVR-independent melatonin metabolites. Therefore, endogenous intracutaneous melatonin production, together with topically-applied exogenous melatonin or metabolites would be expected to represent one of the most potent anti-oxidative defense systems against the UV-induced damage to the skin. In summary, we propose that melatonin can be exploited therapeutically as a protective agent or as a survival factor with anti-genotoxic properties or as a “guardian” of the genome and cellular integrity with clinical applications in UVR-induced pathology that includes carcinogenesis and skin aging. PMID:25272227
Local melatoninergic system as the protector of skin integrity.
Slominski, Andrzej T; Kleszczyński, Konrad; Semak, Igor; Janjetovic, Zorica; Zmijewski, Michał A; Kim, Tae-Kang; Slominski, Radomir M; Reiter, Russel J; Fischer, Tobias W
2014-09-30
The human skin is not only a target for the protective actions of melatonin, but also a site of melatonin synthesis and metabolism, suggesting an important role for a local melatoninergic system in protection against ultraviolet radiation (UVR) induced damages. While melatonin exerts many effects on cell physiology and tissue homeostasis via membrane bound melatonin receptors, the strong protective effects of melatonin against the UVR-induced skin damage including DNA repair/protection seen at its high (pharmocological) concentrations indicate that these are mainly mediated through receptor-independent mechanisms or perhaps through activation of putative melatonin nuclear receptors. The destructive effects of the UVR are significantly counteracted or modulated by melatonin in the context of a complex intracutaneous melatoninergic anti-oxidative system with UVR-enhanced or UVR-independent melatonin metabolites. Therefore, endogenous intracutaneous melatonin production, together with topically-applied exogenous melatonin or metabolites would be expected to represent one of the most potent anti-oxidative defense systems against the UV-induced damage to the skin. In summary, we propose that melatonin can be exploited therapeutically as a protective agent or as a survival factor with anti-genotoxic properties or as a "guardian" of the genome and cellular integrity with clinical applications in UVR-induced pathology that includes carcinogenesis and skin aging.
Holographic QCD integrated back to hidden local symmetry
Harada, Masayasu; Matsuzaki, Shinya; Yamawaki, Koichi
2010-10-01
We develop a previously proposed gauge-invariant method to integrate out an infinite tower of Kaluza-Klein (KK) modes of vector and axial-vector mesons in a class of models of holographic QCD (HQCD). The HQCD is reduced by our method to chiral perturbation theory with hidden local symmetry (HLS), having only the lowest KK mode identified as the HLS gauge boson. We take the Sakai-Sugimoto model as a concrete HQCD, and completely determine the O(p{sup 4}) terms as well as the O(p{sup 2}) terms from the Dirac-Born-Infeld part and the anomaly-related (intrinsic-parity odd) gauge-invariant terms from the Chern-Simons part. Effects of higher KK modes are fully included in these terms. To demonstrate the power of our method, we compute momentum dependences of several form factors, such as the pion electromagnetic form factors, and the {pi}{sup 0}-{gamma} and {omega}-{pi}{sup 0} transition form factors, compared with experiment, which was not achieved before due to the complication of handling infinite sums. We also study other anomaly-related quantities like {gamma}{sup *}-{pi}{sup 0}-{pi}{sup +}-{pi}{sup -} and {omega}-{pi}{sup 0}-{pi}{sup +}-{pi}{sup -} vertex functions.
Integrating federal health care resources at the local level.
Simmons, J
1989-01-01
Hospitals throughout the country are increasingly sharing health services, jointly purchasing supplies, and merging. The Veterans Administration (VA)-Department of Defense (DoD) Health Resources Sharing Law of 1982 (PL 97-174) has encouraged much closer relationships between hospitals of these agencies than had existed previously. All VA hospitals within 50 miles of a military treatment facility now have multiservice agreements. Before passage of the law, only a handful of facilities were involved in limited sharing. Closer relationships have led to expanded care for federal beneficiaries at considerable cost savings. In Albuquerque, New Mexico, for example, the VA Medical Center houses the VA and Air Force hospital operations, obviating the need for a separate freestanding hospital. The lack of VA authority to receive reimbursement from the Civilian Health and Medical Program for the Uniformed Services and a lack of a reimbursement incentive for military hospitals to share are identified as factors preventing greater coordination. Even greater local integration of services is likely to occur in the future.
Locally Contractive Dynamics in Generalized Integrate-and-Fire Neurons.
Jimenez, Nicolas D; Mihalas, Stefan; Brown, Richard; Niebur, Ernst; Rubin, Jonathan
2013-09-10
Integrate-and-fire models of biological neurons combine differential equations with discrete spike events. In the simplest case, the reset of the neuronal voltage to its resting value is the only spike event. The response of such a model to constant input injection is limited to tonic spiking. We here study a generalized model in which two simple spike-induced currents are added. We show that this neuron exhibits not only tonic spiking at various frequencies but also the commonly observed neuronal bursting. Using analytical and numerical approaches, we show that this model can be reduced to a one-dimensional map of the adaptation variable and that this map is locally contractive over a broad set of parameter values. We derive a sufficient analytical condition on the parameters for the map to be globally contractive, in which case all orbits tend to a tonic spiking state determined by the fixed point of the return map. We then show that bursting is caused by a discontinuity in the return map, in which case the map is piecewise contractive. We perform a detailed analysis of a class of piecewise contractive maps that we call bursting maps and show that they robustly generate stable bursting behavior. To the best of our knowledge, this work is the first to point out the intimate connection between bursting dynamics and piecewise contractive maps. Finally, we discuss bifurcations in this return map, which cause transitions between spiking patterns.
Abd-Elhameed, Waleed M.; Doha, Eid H.; Bassuony, Mahmoud A.
2014-01-01
Two numerical algorithms based on dual-Petrov-Galerkin method are developed for solving the integrated forms of high odd-order boundary value problems (BVPs) governed by homogeneous and nonhomogeneous boundary conditions. Two different choices of trial functions and test functions which satisfy the underlying boundary conditions of the differential equations and the dual boundary conditions are used for this purpose. These choices lead to linear systems with specially structured matrices that can be efficiently inverted, hence greatly reducing the cost. The various matrix systems resulting from these discretizations are carefully investigated, especially their complexities and their condition numbers. Numerical results are given to illustrate the efficiency of the proposed algorithms, and some comparisons with some other methods are made. PMID:24616620
NASA Technical Reports Server (NTRS)
Kojima, Fumio
1989-01-01
The geometrical structure of the boundary shape for a two-dimensional boundary value problem is identified. The output least square identification method is considered for estimating partially unknown boundary shapes. A numerical parameter estimation technique using the spline collocation method is proposed.
NASA Technical Reports Server (NTRS)
Collins, Jeffery D.; Volakis, John L.
1989-01-01
A new technique is presented for computing the scattering by 2-D structures of arbitrary composition. The proposed solution approach combines the usual finite element method with the boundary integral equation to formulate a discrete system. This is subsequently solved via the conjugate gradient (CG) algorithm. A particular characteristic of the method is the use of rectangular boundaries to enclose the scatterer. Several of the resulting boundary integrals are therefore convolutions and may be evaluated via the fast Fourier transform (FFT) in the implementation of the CG algorithm. The solution approach offers the principle advantage of having O(N) memory demand and employs a 1-D FFT versus a 2-D FFT as required with a traditional implementation of the CGFFT algorithm. The speed of the proposed solution method is compared with that of the traditional CGFFT algorithm, and results for rectangular bodies are given and shown to be in excellent agreement with the moment method.
Farooq, M U; Villaurrutia, R; MacLaren, I; Kungl, H; Hoffmann, M J; Fundenberger, J-J; Bouzy, E
2008-06-01
Reliable EBSD mapping of 90 degree domains in a tetragonal ferroelectric perovskite has been achieved for the first time, together with reliable automated orientation determination from TEM-Kikuchi patterns. This has been used to determine misorientation angles at 90 degree domain boundaries and thus local c/a ratios. The sources of orientation noise/error and their effects on the misorientation angle data have been thoroughly analyzed and it is found that this gives a cosine distribution of misorientation angles about the mean with a characteristic width related to the width of the orientation noise distribution. In most cases, a good agreement is found between local c/a ratios and global measurements by X-ray diffraction, but some clear discrepancies have also been found suggesting that real local variations are present, perhaps as a consequence of compositional inhomogeneities.
NASA Astrophysics Data System (ADS)
Jarvis, Ian
2014-05-01
The Cenomanian-Turonian boundary (CTB) interval ~ 94 Ma represented a period of major global palaeoenvironmental change. Increasingly detailed multidisciplinary studies integrating sedimentological, palaeontological and geochemical data from multiple basins, are enabling the development of refined but complex models that aid understanding of the mechanisms driving changes in ocean productivity and climate. This paper reviews some of the exciting new developments in this field. Facies change characterizes the CTB interval in most areas. In the Chalk seas of northern Europe, a widespead hiatus was followed by the deposition of clay-rich organic-lean beds of the Plenus Marl and its equivalents, and then nodular chalks. In the North Sea basin and its onshore extension in eastern England and northern Germany, black shales of the Black Band (Blodøks Formation, Hasseltal Formation) occur. Similarly, in northern Tethys, a brief interval of black shale accumulation within a predominantly carbonate succession, is exemplified by the Niveau Thomel in the Vocontian Basin (SE France), and the Livello Bonarelli in Italy. Widespread deposition of organic-rich marine sediments during CTB times led to 12C depletion in surface carbon reservoirs (oceans, atmosphere, biosphere), and a large positive global δ13C excursion preserved in marine carbonates and both marine and terrestrial organic matter (Oceanic Anoxic Event 2). Significant biotic turnover characterises the boundary interval, and inter-regional correlation may be achieved at high resolution using integrated biostratigraphy employing macrofossils (ammonites, inoceramid bivalves), microfossils (planktonic foraminifera, dinoflagellate cysts) and calcareous nannofossils. Correlations can be tested against those based on comparison of δ13C profiles - carbon isotope chemostratigraphy, supplemented by oxygen isotope and elemental data. Interpretation of paired carbonate - organic matter δ13C data from multiple CTB sections
NASA Astrophysics Data System (ADS)
Gao, Y.; Balaram, P.; Islam, S.
2009-12-01
Water issues and problems have bewildered humankind for a long time yet a systematic approach for understanding such issues remain elusive. This is partly because many water-related problems are framed from a contested terrain in which many actors (individuals, communities, businesses, NGOs, states, and countries) compete to protect their own and often conflicting interests. We argue that origin of many water problems may be understood as a dynamic consequence of competition, interconnections, and feedback among variables in the Natural and Societal Systems (NSSs). Within the natural system, we recognize that triple constraints on water- water quantity (Q), water quality (P), and ecosystem (E)- and their interdependencies and feedback may lead to conflicts. Such inherent and multifaceted constraints of the natural water system are exacerbated often at the societal boundaries. Within the societal system, interdependencies and feedback among values and norms (V), economy (C), and governance (G) interact in various ways to create intractable contextual differences. The observation that natural and societal systems are linked is not novel. Our argument here, however, is that rigid disciplinary boundaries between these two domains will not produce solutions to the water problems we are facing today. The knowledge needed to address water problems need to go beyond scientific assessment in which societal variables (C, G, and V) are treated as exogenous or largely ignored, and policy research that does not consider the impact of natural variables (E, P, and Q) and that coupling among them. Consequently, traditional quantitative methods alone are not appropriate to address the dynamics of water conflicts, because we cannot quantify the societal variables and the exact mathematical relationships among the variables are not fully known. On the other hand, conventional qualitative study in societal domain has mainly been in the form of individual case studies and therefore
NASA Astrophysics Data System (ADS)
Friedrich, Johannes; Fetzer, Ingo; Cornell, Sarah
2016-04-01
The planetary boundaries framework is an approach to global sustainability that emphasises non-linear threshold behavior in anthropogenically perturbed Earth system processes. However, knowledge about the characteristics and positions of thresholds, and the scope for management of the boundaries is not well established. Global integrated models can help to improve this understanding, by reflecting the complex feedbacks between human and environmental systems. This study analyses the current state of integrated models with regard to the main processes identified as 'critical Earth system processes' in the planetary boundaries framework, and identifies gaps and suggests priorities for future improvements. Our approach involves creating a common ontology of model descriptions, and performing a network analysis on the state of system integration in models. The distinct clusters of specific biophysical and social-economic systems obviously has enabled progress in those specific areas of global change, but it now constrains analysis of important human-driven Earth system dynamics. The modeling process therefore has to be improved through technical integration, scientific gap-filling, and also changes in scientific institutional dynamics. Combined, this can advance model potentials that may help us to find sustainable pathways within planetary boundaries.
Sorokin, Sergey V
2011-03-01
Helical springs serve as vibration isolators in virtually any suspension system. Various exact and approximate methods may be employed to determine the eigenfrequencies of vibrations of these structural elements and their dynamic transfer functions. The method of boundary integral equations is a meaningful alternative to obtain exact solutions of problems of the time-harmonic dynamics of elastic springs in the framework of Bernoulli-Euler beam theory. In this paper, the derivations of the Green's matrix, of the Somigliana's identities, and of the boundary integral equations are presented. The vibrational power transmission in an infinitely long spring is analyzed by means of the Green's matrix. The eigenfrequencies and the dynamic transfer functions are found by solving the boundary integral equations. In the course of analysis, the essential features and advantages of the method of boundary integral equations are highlighted. The reported analytical results may be used to study the time-harmonic motion in any wave guide governed by a system of linear differential equations in a single spatial coordinate along its axis.
NASA Astrophysics Data System (ADS)
Ashyralyev, Allaberen; Sharifov, Y. A.
2012-08-01
The system of nonlinear impulsive differential equations with two-point and integral boundary conditions are investigated. Theorems on existence and uniqueness of a solution are established under some sufficient conditions on nonlinear terms. A simple example of application of the main result of this paper is presented.
NASA Technical Reports Server (NTRS)
Gokoglu, Suleyman A.
1988-01-01
This paper investigates the role played by vapor-phase chemical reactions on CVD rates by comparing the results of two extreme theories developed to predict CVD mass transport rates in the absence of interfacial kinetic barrier: one based on chemically frozen boundary layer and the other based on local thermochemical equilibrium. Both theories consider laminar convective-diffusion boundary layers at high Reynolds numbers and include thermal (Soret) diffusion and variable property effects. As an example, Na2SO4 deposition was studied. It was found that gas phase reactions have no important role on Na2SO4 deposition rates and on the predictions of the theories. The implications of the predictions of the two theories to other CVD systems are discussed.
NASA Technical Reports Server (NTRS)
Gokoglu, Suleyman A.
1988-01-01
This paper investigates the role played by vapor-phase chemical reactions on CVD rates by comparing the results of two extreme theories developed to predict CVD mass transport rates in the absence of interfacial kinetic barrier: one based on chemically frozen boundary layer and the other based on local thermochemical equilibrium. Both theories consider laminar convective-diffusion boundary layers at high Reynolds numbers and include thermal (Soret) diffusion and variable property effects. As an example, Na2SO4 deposition was studied. It was found that gas phase reactions have no important role on Na2SO4 deposition rates and on the predictions of the theories. The implications of the predictions of the two theories to other CVD systems are discussed.
NASA Astrophysics Data System (ADS)
Karakasidis, Theodoros E.
2002-08-01
Using molecular dynamics and a rigid ion potential we studied the vibrational properties of a Σ5(3 1 0)[0 0 1] tilt grain boundary in NiO. We calculated the local density of states and the mean square displacement (MSD) of the cation and ion sublattice for a wide temperature range. We examined their behaviour in the directions parallel and normal to the boundary as a function from the grain boundary plane. We found that the local phonon density of states of the sites of the boundary are altered with comparison to the bulk presenting in general a shift towards lower frequencies in the direction normal to the boundary and toward higher frequencies in the direction parallel to the grain boundary. This anisotropy, which is conformed by the results of the MSDs, is maintained up to high temperatures. We have also observed that the increase of temperature leads to the gradual loosening of the binding of atoms.
Some free boundary problems involving non-local diffusion and aggregation
Carrillo, José Antonio; Vázquez, Juan Luis
2015-01-01
We report on recent progress in the study of evolution processes involving degenerate parabolic equations which may exhibit free boundaries. The equations we have selected follow two recent trends in diffusion theory: considering anomalous diffusion with long-range effects, which leads to fractional operators or other operators involving kernels with large tails; and the combination of diffusion and aggregation effects, leading to delicate long-term equilibria whose description is still incipient. PMID:26261360
NASA Astrophysics Data System (ADS)
La Nave, Gabriele; Phillips, Philip W.
2016-12-01
We show explicitly that the full structure of IIB string theory is needed to remove the nonlocalities that arise in boundary conformal theories that border hyperbolic spaces on AdS5 . Specifically, using the Caffarelli/Silvestri [1], Graham/Zworski [2], and Chang/Gonzalez [3] extension theorems, we prove that the boundary operator conjugate to bulk p-forms with negative mass in geodesically complete metrics is inherently a nonlocal operator, specifically the fractional conformal Laplacian. The nonlocality, which arises even in compact spaces, applies to any degree p-form such as a gauge field. We show that the boundary theory contains fractional derivatives of the longitudinal components of the gauge field if the gauge field in the bulk along the holographic direction acquires a mass via the Higgs mechanism. The nonlocality is shown to vanish once the metric becomes incomplete, for example, either (1) asymptotically by adding N transversely stacked Dd-branes or (2) exactly by giving the boundary a brane structure and including a single transverse Dd-brane in the bulk. The original Maldacena conjecture within IIB string theory corresponds to the former. In either of these proposals, the location of the Dd-branes places an upper bound on the entanglement entropy because the minimal bulk surface in the AdS reduction is ill-defined at a brane interface. Since the brane singularities can be circumvented in the full 10-dimensional spacetime, we conjecture that the true entanglement entropy must be computed from the minimal surface in 10-dimensions, which is of course not minimal in the AdS5 reduction.
Impact of boundary-layer separation on local exhaust design and worker exposure
George, D.K.; Flynn, M.R.; Goodman, R.
1990-01-01
Flow visualization and tracer gas studies were conducted in a wind tunnel with a mannequin, to examine the phenomenon of boundary layer separation as it relates to a worker's breathing zone concentration. A simple conceptual model was used which was based on mass transport by vortex shedding. The model provided a reasonable estimate of the mannequin breathing zone concentration. An empirical model was developed which then related the measured concentration to the distance from the source to the breathing zone for conditions where the contaminant was released downstream in a uniform flow. The results of the mannequin experiments suggested that boundary layer separation plays a significant part in determining the concentration of contaminant in the breathing zone. The interaction of the separated boundary layer with a contaminant source downstream of a person in uniform flow can pull contaminant back into the breathing zone of the person. The amount of contaminant observed in the breathing zone was much less when the mannequin was positioned such that the air could flow from the side. The turbulent mixing zone was formed more to the side of the mannequin and thus has less opportunity to interact with the contaminant source. These results suggested that in situations such as paint booths where a worker is immersed in a uniform flow, a higher level of control may be achieved by standing to the side of the workpiece.
Fernandez, Ana; Gillespie, James A; Smith-Merry, Jennifer; Feng, Xiaoqi; Astell-Burt, Thomas; Maas, Cailin; Salvador-Carulla, Luis
2016-03-24
Objective Australian mental health care remains hospital centric and fragmented; it is riddled with gaps and does little to promote recovery. Reform must be built on better knowledge of the shape of existing services. Mental health atlases are an essential part of this knowledge base, enabling comparison with other regions and jurisdictions, but must be based on a rigorous classification of services. The main aim of this study is to create an integrated mental health atlas of the Western Sydney LHD in order to help decision makers to better plan informed by local evidence.Methods The standard classification system, namely the Description and Evaluation of Services and Directories in Europe for Long-term Care model, was used to describe and classify adult mental health services in the Western Sydney Local Health District (LHD). This information provided the foundation for accessibility maps and the analysis of the provision of care for people with a lived experience of mental illness in Western Sydney LHD. All this data was used to create the Integrated Mental Health Atlas of Western Sydney LHD.Results The atlas identified four major gaps in mental health care in Western Sydney LHD: (1) a lack of acute and sub-acute community residential care; (2) an absence of services providing acute day care and non-acute day care; (3) low availability of specific employment services for people with a lived experience of mental ill-health; and (4) a lack of comprehensive data on the availability of supported housing.Conclusions The integrated mental health atlas of the Western Sydney LHD provides a tool for evidence-informed planning and critical analysis of the pattern of adult mental health care.What is known about the topic? Several reports have highlighted that the Australian mental health system is hospital based and fragmented. However, this knowledge has had little effect on actually changing the system.What does this paper add? This paper provides a critical analysis of
Prototype Local Data Integration System and Central Florida Data Deficiency
NASA Technical Reports Server (NTRS)
Manobianco, John; Case, Jonathan
1998-01-01
This report describes the Applied Meteorology Unit's (AMU) task on the Local Data Integration System (LDIS) and central Florida data deficiency. The objectives of the task are to identify all existing meteorological data sources within 250 km of the Kennedy Space Center (KSC) and the Eastern Range at Cape Canaveral Air Station (CCAS), identify and configure an appropriate LDIS to integrate these data, and implement a working prototype to be used for limited case studies and data non-incorporation (DNI) experiments. The ultimate goal for running LDIS is to generate products that may enhance weather nowcasts and short-range (less than 6 h) forecasts issued in support of the 45th Weather Squadron (45 WS), Spaceflight Meteorology Group (SMG), and the Melbourne National Weather Service (NWS MLB) operational requirements. The LDIS has the potential to provide added value for nowcasts and short term forecasts for two reasons. First, it incorporates all data operationally available in east central Florida. Second, it is run at finer spatial and temporal resolutions than current national-scale operational models. In combination with a suitable visualization tool, LDIS may provide users with a more complete and comprehensive understanding of evolving fine-scale weather features than could be developed by individually examining the disparate data sets over the same area and time. The utility of LDIS depends largely on the reliability and availability of observational data. Therefore, it is important to document all existing meteorological data sources around central Florida that can be incorporated by it. Several factors contribute to the data density and coverage over east central Florida including the level in the atmosphere, distance from KSC/CCAS, time, and prevailing weather. The central Florida mesonet consists of existing surface meteorological and hydrological data available from the Tampa NWS and data servers at Miami and Jacksonville. However the utility of these
Strategies to Integrate America’s Local Police Agencies into Domestic Counterterrorism
2007-11-02
USAWC STRATEGY RESEARCH PROJECT STRATEGIES TO INTEGRATE AMERICA’S LOCAL POLICE AGENCIES INTO DOMESTIC COUNTERTERRORISM by Colonel Blair C. Alexander...Strategies to Integrate America’s Local Police Agencies into Domestic 5b. GRANT NUMBER Counterterrorism 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d...Z39-18 ABSTRACT AUTHOR: Colonel Blair C. Alexander TITLE: Strategies to Integrate America’s Local Police Agencies into Domestic Counterterrorism FORMAT
NASA Astrophysics Data System (ADS)
Yuan, Zhengwen; Xiao, Hong; Xie, Hongbiao
2014-02-01
Precise strip-shape control theory is significant to improve rolled strip quality, and roll flattening theory is a primary part of the strip-shape theory. To improve the accuracy of roll flattening calculation based on semi-infinite body model, a new and more accurate roll flattening model is proposed in this paper, which is derived based on boundary integral equation method. The displacement fields of the finite length semi-infinite body on left and right sides are simulated by using finite element method (FEM) and displacement decay functions on left and right sides are established. Based on the new roll flattening model, a new 4Hi mill deformation model is established and verified by FEM. The new model is compared with Foppl formula and semi-infinite body model in different strip width, roll shifting value and bending force. The results show that the pressure and flattening between rolls calculated by the new model are more precise than other two models, especially near the two roll barrel edges.
Off-shell amplitudes as boundary integrals of analytically continued Wilson line slope
NASA Astrophysics Data System (ADS)
Kotko, P.; Serino, M.; Stasto, A. M.
2016-08-01
One of the methods to calculate tree-level multi-gluon scattering amplitudes is to use the Berends-Giele recursion relation involving off-shell currents or off-shell amplitudes, if working in the light cone gauge. As shown in recent works using the light-front perturbation theory, solutions to these recursions naturally collapse into gauge invariant and gauge-dependent components, at least for some helicity configurations. In this work, we show that such structure is helicity independent and emerges from analytic properties of matrix elements of Wilson line operators, where the slope of the straight gauge path is shifted in a certain complex direction. This is similar to the procedure leading to the Britto-Cachazo-Feng-Witten (BCFW) recursion, however we apply a complex shift to the Wilson line slope instead of the external momenta. While in the original BCFW procedure the boundary integrals over the complex shift vanish for certain deformations, here they are non-zero and are equal to the off-shell amplitudes. The main result can thus be summarized as follows: we derive a decomposition of a helicity-fixed off-shell current into gauge invariant component given by a matrix element of a straight Wilson line plus a reminder given by a sum of products of gauge invariant and gauge dependent quantities. We give several examples realizing this relation, including the five-point next-to-MHV helicity configuration.
Boundary integral simulations of dissolving drops in segmented two-phase flows
NASA Astrophysics Data System (ADS)
Ramchandran, Arun; Leary, Thomas
2015-11-01
Recent years have seen an upsurge in the literature reporting the microfluidic measurement of the kinetics of `fast' gas-liquid reactions by recording the shrinkage of bubbles in segmented flows of these gas-liquid combinations in microfluidic channels. A critical aspect of the data analysis in these experiments is the knowledge of how dissolution influences the velocity field in the liquid slug, and hence, the mass transport characteristics. Unfortunately, there is no literature on this connection for dissolving bubbles. Our research addresses this gap using boundary integral simulations. The effects of the dissolution rate on the film thickness and the inter-drop separation are examined as a function of the capillary number and the viscosity ratio. The results demonstrate that dissolution can enhance the degree of mixing appreciably from one slug to the next. A curious result is that the film thickness and the droplet separation distance can change significantly beyond a critical capillary number, producing flow patterns completely different from those known for the undissolving bubble case. These results will guide the selection of operating regimes that enable convenient interpretation of data from experiments to deduce kinetic constants.
T.F. Eibert; J.L. Volakis; Y.E. Erdemli
2002-03-03
Hybrid finite element (FE)--boundary integral (BI) analysis of infinite periodic arrays is extended to include planar multilayered Green's functions. In this manner, a portion of the volumetric dielectric region can be modeled via the finite element method whereas uniform multilayered regions can be modeled using a multilayered Green's function. As such, thick uniform substrates can be modeled without loss of efficiency and accuracy. The multilayered Green's function is analytically computed in the spectral domain and the resulting BI matrix-vector products are evaluated via the fast spectral domain algorithm (FSDA). As a result, the computational cost of the matrix-vector products is kept at O(N). Furthermore, the number of Floquet modes in the expansion are kept very few by placing the BI surfaces within the computational unit cell. Examples of frequency selective surface (FSS) arrays are analyzed with this method to demonstrate the accuracy and capability of the approach. One example involves complicated multilayered substrates above and below an inhomogeneous filter element and the other is an optical ring-slot array on a substrate several hundred wavelengths in thickness. Comparisons with measurements are included.
Arcioni, P.; Bressan, M.; Perregrini, L.
1995-08-01
Computer codes for the electromagnetic analysis of arbitrarily shaped cavities are very important for many applications, in particular for the design of interaction structures for particle accelerators. The design of accelerating cavities results in complicated shapes, that are obtained carrying on repeated analyses to optimize a number of parameters, such as Q-factors, beam coupling impedances, higher-order-mode spectrum, and so on. The interest in the calculation of many normalized modes derives also from the important role they play in the eigenvector expansion of the electromagnetic field in a closed region. The authors present an efficient algorithm to determine the resonant frequencies and the normalized modal fields of arbitrarily shaped cavity resonators filled with a lossless, isotropic, and homogeneous medium. The algorithm is based on the boundary integral method (BIM). The unknown current flowing on the cavity wall is considered inside a spherical resonator, rather than in free-space, as it is usual in the standard BIM. The electric field is expressed using the Green`s function of the spherical resonator, approximated by a real rational function of the frequency. Consequently, the discretized problem can be cast into the form of a real matrix linear eigenvalue problem, whose eigenvalues and eigenvectors yield the resonant frequencies and the associated modal currents. Since the algorithm does not require any frequency-by-frequency recalculation of the system matrices, computing time is much shorter than in the standard BIM, especially when many resonances must be found.
NASA Astrophysics Data System (ADS)
Calvisi, Michael; Manmi, Kawa; Wang, Qianxi
2014-11-01
Ultrasound contrast agents (UCAs) are microbubbles stabilized with a shell typically of lipid, polymer, or protein and are emerging as a unique tool for noninvasive therapies ranging from gene delivery to tumor ablation. The nonspherical dynamics of contrast agents are thought to play an important role in both diagnostic and therapeutic applications, for example, causing the emission of subharmonic frequency components and enhancing the uptake of therapeutic agents across cell membranes and tissue interfaces. A three-dimensional model for nonspherical contrast agent dynamics based on the boundary integral method is presented. The effects of the encapsulating shell are approximated by adapting Hoff's model for thin-shell, spherical contrast agents to the nonspherical case. A high-quality mesh of the bubble surface is maintained by implementing a hybrid approach of the Lagrangian method and elastic mesh technique. Numerical analyses for the dynamics of UCAs in an infinite liquid and near a rigid wall are performed in parameter regimes of clinical relevance. The results show that the presence of a coating significantly reduces the oscillation amplitude and period, increases the ultrasound pressure amplitude required to incite jetting, and reduces the jet width and velocity.
Community Integration, Local Media Use, and Democratic Processes.
ERIC Educational Resources Information Center
McLeod, Jack M.; And Others
1996-01-01
Explicates the concept of community integration and its dimensions. Specifies structural and media antecedents and political consequences of these dimensions. Uses 15 indicators to test the hypothesis that integration is a multidimensional concept. Reveals that community integration has at least five dimensions: psychological attachment,…
NASA Astrophysics Data System (ADS)
Ghosh, Subhajit; Bose, Santanu; Mandal, Nibir
2016-04-01
The southward tapering Himalayan tectonic wedge is sliding over the upper boundary of the subducting Indian crust that act as the basal low angle detachment fault, known as the Main Himalayan Thrust (MHT). It is now established that at least four crustal-scale south verging thrust faults, such as Main Central Thrust (MCT), Daling Thrust (~ Ramgarh Thrust ~ Shumar Thrust) (DT), Main Boundary Thrust (MBT) and Main Frontal Thrust (MFT), have emerged from the MHT, striking the entire length of Himalayan mountain belts. These structures accommodated hundreds of kilometers of crustal shortening since India-Asia collision and eventually, juxtaposed different tectono-metamorphic rocks in their hanging wall. Field investigations reveal increased number of thrust faults towards the frontal Himalayan mountain belts and their spacing between the successive thrusts are relatively small in contrast to the hinterland part of the mountain belt. For example, in the Eastern Himalayan belt the MBT zone in the Lesser Himalayan Sequence is marked by several such closely spaced thrusts. The present work is aimed to delineate factors that likely to have influenced for the development of such high frequency thrusting. Employing the model of Coulomb Wedge Theory (CWT), several researchers have shown that spacing between two consecutive thrusts is a function of basal friction and pore fluid pressure ratio. However, this model does not explain the cause of closely spaced thrust localization towards the frontal mountain belts during the wedge growth. Our present study using field relations and physical modeling shows that relative strength difference between the basal low angle detachment fault and the interface-strength of the varying lithology of the cover rocks has a major role for such thrust localization with narrow thrust spacing. Moreover, our findings may become useful for structural interpretation for the localization of Main Boundary Thrust zone in the frontal Himalayan mountain
Singh, Ajay V.; Gollner, Michael J.
2016-01-01
Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex interactions occurring at the interface between gas-phase flames and condensed-phase fuels. The current research provides a technique to explore the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar boundary layers. Experiments have previously been conducted in both forced and free convective environments over both solid and liquid fuels. A unique methodology, based on the Reynolds Analogy, was used to estimate local mass burning rates and flame heat fluxes for these laminar boundary layer diffusion flames utilizing local temperature gradients at the fuel surface. Local mass burning rates and convective and radiative heat feedback from the flames were measured in both the pyrolysis and plume regions by using temperature gradients mapped near the wall by a two-axis traverse system. These experiments are time-consuming and can be challenging to design as the condensed fuel surface burns steadily for only a limited period of time following ignition. The temperature profiles near the fuel surface need to be mapped during steady burning of a condensed fuel surface at a very high spatial resolution in order to capture reasonable estimates of local temperature gradients. Careful corrections for radiative heat losses from the thermocouples are also essential for accurate measurements. For these reasons, the whole experimental setup needs to be automated with a computer-controlled traverse mechanism, eliminating most errors due to positioning of a micro-thermocouple. An outline of steps to reproducibly capture near-wall temperature gradients and use them to assess local burning rates and heat fluxes is provided. PMID:27285827
Singh, Ajay V; Gollner, Michael J
2016-06-01
Modeling the realistic burning behavior of condensed-phase fuels has remained out of reach, in part because of an inability to resolve the complex interactions occurring at the interface between gas-phase flames and condensed-phase fuels. The current research provides a technique to explore the dynamic relationship between a combustible condensed fuel surface and gas-phase flames in laminar boundary layers. Experiments have previously been conducted in both forced and free convective environments over both solid and liquid fuels. A unique methodology, based on the Reynolds Analogy, was used to estimate local mass burning rates and flame heat fluxes for these laminar boundary layer diffusion flames utilizing local temperature gradients at the fuel surface. Local mass burning rates and convective and radiative heat feedback from the flames were measured in both the pyrolysis and plume regions by using temperature gradients mapped near the wall by a two-axis traverse system. These experiments are time-consuming and can be challenging to design as the condensed fuel surface burns steadily for only a limited period of time following ignition. The temperature profiles near the fuel surface need to be mapped during steady burning of a condensed fuel surface at a very high spatial resolution in order to capture reasonable estimates of local temperature gradients. Careful corrections for radiative heat losses from the thermocouples are also essential for accurate measurements. For these reasons, the whole experimental setup needs to be automated with a computer-controlled traverse mechanism, eliminating most errors due to positioning of a micro-thermocouple. An outline of steps to reproducibly capture near-wall temperature gradients and use them to assess local burning rates and heat fluxes is provided.
NASA Astrophysics Data System (ADS)
Yang, Zhichun; Zhou, Jian; Gu, Yingsong
2014-10-01
A flow field modified local piston theory, which is applied to the integrated analysis on static/dynamic aeroelastic behaviors of curved panels, is proposed in this paper. The local flow field parameters used in the modification are obtained by CFD technique which has the advantage to simulate the steady flow field accurately. This flow field modified local piston theory for aerodynamic loading is applied to the analysis of static aeroelastic deformation and flutter stabilities of curved panels in hypersonic flow. In addition, comparisons are made between results obtained by using the present method and curvature modified method. It shows that when the curvature of the curved panel is relatively small, the static aeroelastic deformations and flutter stability boundaries obtained by these two methods have little difference, while for curved panels with larger curvatures, the static aeroelastic deformation obtained by the present method is larger and the flutter stability boundary is smaller compared with those obtained by the curvature modified method, and the discrepancy increases with the increasing of curvature of panels. Therefore, the existing curvature modified method is non-conservative compared to the proposed flow field modified method based on the consideration of hypersonic flight vehicle safety, and the proposed flow field modified local piston theory for curved panels enlarges the application range of piston theory.
Foster, Michele; Burridge, Letitia; Donald, Maria; Zhang, Jianzhen; Jackson, Claire
2016-01-14
Service delivery innovation is at the heart of efforts to combat the growing burden of chronic disease and escalating healthcare expenditure. Small-scale, locally-led service delivery innovation is a valuable source of learning about the complexities of change and the actions of local change agents. This exploratory qualitative study captures the perspectives of clinicians and managers involved in a general practitioner-led integrated diabetes care innovation. Data on these change agents' perspectives on the local innovation and how it works in the local context were collected through focus groups and semi-structured interviews at two primary health care sites. Transcribed data were analysed thematically. Normalization Process Theory provided a framework to explore perspectives on the individual and collective work involved in putting the innovation into practice in local service delivery contexts. Twelve primary health care clinicians, hospital-based medical specialists and practice managers participated in the study, which represented the majority involved in the innovation at the two sites. The thematic analysis highlighted three main themes of local innovation work: 1) trusting and embedding new professional relationships; 2) synchronizing services and resources; and 3) reconciling realities of innovation work. As a whole, the findings show that while locally-led service delivery innovation is designed to respond to local problems, convincing others to trust change and managing the boundary tensions is core to local work, particularly when it challenges taken-for-granted practices and relationships. Despite this, the findings also show that local innovators can and do act in both discretionary and creative ways to progress the innovation. The use of Normalization Process Theory uncovered some critical professional, organizational and structural factors early in the progression of the innovation. The key to local service delivery innovation lies in building
NASA Astrophysics Data System (ADS)
Bellassoued, M.; Jellali, D.; Yamamoto, M.
2008-07-01
In this paper we consider the stability of the inverse problem of determining a function q(x) in a wave equation in a bounded smooth domain in from boundary observations. This information is enclosed in the hyperbolic (dynamic) Dirichlet-to-Neumann map associated to the solutions to the wave equation. We prove in the case of n[greater-or-equal, slanted]2 that q(x) is uniquely determined by the range restricted to a subboundary of the Dirichlet-to-Neumann map whose stability is a type of double logarithm.
Integration of Satellite and Surface Data Using a Radiative-Convective Oceanic Boundary-Layer Model.
NASA Astrophysics Data System (ADS)
Betts, Alan K.; Minnis, Patrick; Ridgway, W.; Young, David F.
1992-04-01
A mixing-line boundary-layer model is used to retrieve cloud-top height from satellite-derived cloud-top temperature using 700-hPa National Meteorological Center (NMC) analyses and the Comprehensive Ocean and Atmosphere Data Set (COADS) surface data as supporting datasets. Results are compared with the fixed-lapse-rate method of retrieving boundary-layer depth from sea surface temperatures (SST) and cloud-top temperatures. A radiative-convective equilibrium boundary-layer model is used to retrieve boundary-layer structure given SST and surface wind, satellite cloud-top temperatures and cloud fraction, and the 700-hPa NMC thermodynamic analyses. Good agreement is found between the COADS data and the model solutions for low-level temperature and moisture. This suggests that equilibrium boundary-layer models may be of use over remote oceans in the retrieval of boundary-layer structure.
NASA Technical Reports Server (NTRS)
Abarbanel, Saul; Gottlieb, David; Carpenter, Mark H.
1994-01-01
It has been previously shown that the temporal integration of hyperbolic partial differential equations (PDE's) may, because of boundary conditions, lead to deterioration of accuracy of the solution. A procedure for removal of this error in the linear case has been established previously. In the present paper we consider hyperbolic (PDE's) (linear and non-linear) whose boundary treatment is done via the SAT-procedure. A methodology is present for recovery of the full order of accuracy, and has been applied to the case of a 4th order explicit finite difference scheme.
NASA Astrophysics Data System (ADS)
Hess, G. D.; Garratt, J. R.
Data for the cross-isobaric angle 0, the geostrophic drag coefficient Cg, and the functions A and B of Rossby number similarity theory, obtained from meteorological field experiments, are used to evaluate a range of models of the neutral, barotropic planetary boundary layer. The data give well-defined relationships for 0, Cg, and the integrated dissipation rate over the boundary layer, as a function of the surface Rossby number. Lettau's first-order closure mixing-length model gives an excellent fit to the data; other simple models give reasonable agreement. However more sophisticated models, e.g., higher-order closure, large-eddy simulation, direct numerical simulation and laboratory models, give poor fits to the data. The simplemodels have (at least) one free parameter in their turbulence closure that is matched toatmospheric observations; the more sophisticated models either base their closure onmore general flows or have no free closure parameters. It is suggested that all of theatmospheric experiments that we could locate violate the strict simplifying assumptionsof steady, homogeneous, neutral, barotropic flow required by the sophisticated models.The angle 0 is more sensitive to violations of the assumptions than is Cg.
Singular integrals related to the Radon transform and boundary value problems.
Phong, D H; Stein, E M
1983-12-01
Two classes of integral operators are introduced that combine features of Calderón-Zygmund singular integrals, the Hilbert integral, and the Radon transform. Examples and applications arising from integral geometry and several complex variables are discussed.
Singular integrals related to the Radon transform and boundary value problems
Phong, D. H.; Stein, E. M.
1983-01-01
Two classes of integral operators are introduced that combine features of Calderón—Zygmund singular integrals, the Hilbert integral, and the Radon transform. Examples and applications arising from integral geometry and several complex variables are discussed. PMID:16593402
Ergodicity and Energy Distributions for Some Boundary Driven Integrable Hamiltonian Chains
NASA Astrophysics Data System (ADS)
Balint, Peter; Lin, Kevin K.; Young, Lai-Sang
2010-02-01
We consider systems of moving particles in 1-dimensional space interacting through energy storage sites. The ends of the systems are coupled to heat baths, and resulting steady states are studied. When the two heat baths are equal, an explicit formula for the (unique) equilibrium distribution is given. The bulk of the paper concerns nonequilibrium steady states, i.e., when the chain is coupled to two unequal heat baths. Rigorous results including ergodicity are proved. Numerical studies are carried out for two types of bath distributions. For chains driven by exponential baths, our main finding is that the system does not approach local thermodynamic equilibrium as system size tends to infinity. For bath distributions that are sharply peaked Gaussians, in spite of the near-integrable dynamics, transport properties are found to be more normal than expected.
NASA Astrophysics Data System (ADS)
Wang, Hao; Kohyama, Masanori; Tanaka, Shingo; Shiihara, Yoshinori
2017-01-01
Tensile deformation and failure of Σ9 tilt grain boundaries (GBs) in Al and Cu have been examined by first-principles tensile tests (FPTTs). Local-energy and local-stress schemes were applied to clarify the variations of local energies and local hydrostatic stresses for all atoms during the deformation process. The GBs in Al and Cu exhibited quite different tensile behaviours in the FPTTs, despite their similar initial configurations. For the Al GB, there are two stages of deformation before failure. In the first stage, the back bonds of the interfacial bonds are mainly stretched, due to special high strength of the interfacial reconstructed bonds. In the second stage, the interfacial bonds begin to be significantly stretched due to high concentrated stresses, while stretching of the back bonds is suppressed. The atoms at the interfacial, back and bulk bonds have very different variations of local energies and local stresses during each stage, because the behaviour of each atom is significantly dependent on each local structural change due to the high sensitivity of sp electrons to the local environment in Al. The Cu GB has much higher tensile strength, and a natural introduction of stacking faults (SFs) occurs via the {111}< 112> shear slip in the bulk regions between the interfaces before the maximum stress is reached. This is caused by the smaller SF energy and lower ideal shear strength of Cu than Al, and is triggered by highly accumulated local energies and stress at the interface atoms. The local-energy distribution around the SF is consistent with the previous theoretical estimation. After the introduction of the SF, the local energies and stresses of all the atoms in the Cu GB supercell tend to become similar to each other during the tensile process, in contrast to the inhomogeneity in the Al GB. The origins of the different tensile behaviours observed for Al and Cu GBs are discussed with respect to the different bonding natures of Al and Cu, which are
Two Examples of Integrated Aquifer Characterization at Local and Regional Scales
NASA Astrophysics Data System (ADS)
Lefebvre, R.; Gloaguen, E.; Rivard, C.; Parent, M.; Morin, R. H.; Pugin, A.; Pullan, S.; Crow, H.; Paradis, D.; Tremblay, L.; Blouin, M.; Laurencelle, M.
2012-12-01
An integrated aquifer characterization approach was developed with the aim of efficiently providing detailed data that could be used to develop conceptual hydrogeological models and quantitatively describe the spatial continuity and heterogeneity of unconsolidated sediments. The approach involves the integration of geological, hydraulic, geophysical and geochemical data. The emphasis of the approach is placed on the acquisition of detailed and continuous indirect data and selective soil sampling and direct measurements of hydraulic properties covering the full range of materials present in the system. Direct data are used to establish relations between indirect hydrogeophysical measurements and hydrofacies (HF), which are material types with distinct hydraulic conductivity (K). Surface geophysical surveys are used to provide 1D or 2D definitions of sediment structures and material types. Hydraulic tests are used to define HF and estimate their ranges of K. Groundwater (GW) geochemistry (major, minor, isotopes, GW age) is used to support the definition of conceptual models and to provide constraints on numerical models of GW flow and transport (mass and GW age). The approach relies on the geostatistical integration of multi-source data to define aquifer boundaries, on the recognition of HF and estimation of K from CPT/SMR data using fuzzy clustering and relevant vector machines for HF classification and K regression, on the geostatistical simulation of HF and K to provide the spatial distribution of hydraulic parameters in GW flow and transport models, and on the validation of these models using geochemical data. The integrated characterization approach was first developed and tested at local scale for the study of a shallow granular aquifer within a 12 km2 sub-watershed where a former unlined landfill is located. Results are being applied to the assessment of the efficiency of natural attenuation as a site management approach. The integrated characterization
NASA Astrophysics Data System (ADS)
Rogowitz, A.; White, J. C.; Grasemann, B.
2016-03-01
Extreme strain localization occurred in the centre of the cross-cutting element of a flanking structure in almost pure calcite marbles from Syros, Greece. At the maximum displacement of 120 cm along the cross-cutting element, evidence of grain size sensitive deformation mechanisms can be found in the ultramylonitic marbles, which are characterized by (1) an extremely small grain size ( ˜ 3 µm), (2) grain boundary triple junctions with nearly 120° angles, (3) a weak crystallographic preferred orientation with very low texture index (J = 1.4), (4) a random misorientation angle distribution curve and (5) the presence of small cavities. Using transmission electron microscopy, a deformation sequence is observed comprising recrystallization dominantly by bulging, resulting in the development of the fine-grained ultramylonite followed by the development of a high dislocation density ( ˜ 1013 m-2) with ongoing deformation of the fine-grained ultramylonite. The arrangement of dislocations in the extremely fine-grain-sized calcite differs from microstructures created by classical dislocation creep mediated by combined glide and thermally activated climb. Instead, it exhibits extensive glide and dislocation networks characteristic of recovery accommodated by cross-slip and network-assisted dislocation movement without formation of idealized subgrain walls. The enabling of grain boundary sliding to dislocation activity is deemed central to initiating and sustaining strain softening and is argued to be an important strain localization process in calcite rocks, even at a high strain rate ( ˜ 10-9 s-1) and low temperature (300 °C).
NASA Astrophysics Data System (ADS)
Rogowitz, A.; White, J. C.; Grasemann, B.
2015-09-01
Extreme strain localization occurred in the center of the cross-cutting element of a flanking structure in almost pure calcite marbles from Syros, Greece. At the maximum displacement of 120 cm along the cross-cutting element evidence of grain size sensitive deformation mechanisms can be found in the ultramylonitic marbles, which are characterized by (1) an extremely small grain size (∼3 μm), (2) grain boundary triple junctions with nearly 120° angles, (3) a weak crystallographic preferred orientation with very low texture index (J=1.4), (4) a random misorientation angle distribution curve and (5) the presence of small cavities. Using transmission electron microscopy a deformation sequence is observed comprising, first recrystallization by bulging resulting in the development of the fine-grained ultramylonite followed by the evolution of a high dislocation density (∼1013 m-2) with ongoing deformation of the fine-grained ultramylonite. The arrangement of dislocations in the extremely fine grain sized calcite differs from microstructures created by classical dislocation creep mediated by combined glide and thermally activated climb. Instead, it exhibits extensive glide and dislocation networks characteristic of recovery accommodated by cross-slip and network-assisted dislocation movement without formation of idealized subgrain walls. The enabling of grain boundary sliding to dislocation activity is deemed central to initiating and sustaining strain softening and is argued to be an important strain localization process in calcite rocks, even at high strain rate (10-9 s-1) and low temperature (300 °C).
NASA Astrophysics Data System (ADS)
Castro-Orgaz, Oscar; Dey, Subhasish
2011-10-01
Geophysical flows of practical interest encompass turbulent boundary layer flows. The velocity profile in turbulent flows is generally described by a log- or a power-law applicable to certain zones of the boundary layer, or by wall-wake law for the entire zone of the boundary layer. In this study, a novel theory is proposed from which the power-law velocity profile is obtained for the turbulent boundary layer flow. The new power-law profile is based on the conservation of mass and the skin friction within the boundary layer. From the proposed theory, analytical expressions for the power-law velocity profile are presented, and their Reynolds-number dependency is highlighted. The velocity profile, skin friction coefficient and boundary layer thickness obtained from the proposed theory are validated by the reliable experimental data for zero-pressure gradient turbulent boundary layers. The expressions for Reynolds shear stress and eddy viscosity distributions across the boundary layer are also obtained and validated by the experimental data.
Localized temporal variation of Earth's inner-core boundary from high-quality waveform doublets
NASA Astrophysics Data System (ADS)
Xin, Danhua
2016-04-01
The accurate determination of the topography of an Earth's internal boundary is difficult because of the possible trade-off with the velocity of the media above it. Here we use waveform-doublet method to map the ICB topography. A waveform doublet is a pair of earthquakes occurring at essentially the same spatial position and received by the same station with high similarity in their waveforms (Poupinet et al. 1984), which make the exact detection of the ICB topography possible. In this study, we used this method to detect temporal change of the ICB using doublets from the Western Pacific (WP) area to increase global coverage of the ICB. Compared with previous study using doublets from South Sandwich Islands (SSI) (Song and Dai, 2008), the new samples showed negligible temporal change of the ICB.
Bresme, F.; Armstrong, J.
2014-01-07
We report non-equilibrium molecular dynamics simulations of heat transport in models of molecular fluids. We show that the “local” thermal conductivities obtained from non-equilibrium molecular dynamics simulations agree within numerical accuracy with equilibrium Green-Kubo computations. Our results support the local equilibrium hypothesis for transport properties. We show how to use the local dependence of the thermal gradients to quantify the thermal conductivity of molecular fluids for a wide range of thermodynamic states using a single simulation.
NASA Astrophysics Data System (ADS)
Kiselev, Yu. N.; Orlov, M. V.; Orlov, S. M.
2015-11-01
An infinite-horizon two-sector economy model with a Cobb-Douglas production function and a utility function that is an integral functional with discounting and a logarithmic integrand is investigated. The application of Pontryagin's maximum principle yields a boundary value problem with special conditions at infinity. The search for the solution of the maximum-principle boundary value problem is complicated by singular modes in its optimal solution. In the construction of the solution to the problem, they are described in analytical form. Additionally, a special version of the sweep method in continuous form is proposed, which is of interest from theoretical and computational points of view. An important result is the proof of the optimality of the extremal solution obtained by applying the maximum-principle boundary value problem.
Moore, Benjamin L; Aitken, Stuart; Semple, Colin A
2015-05-27
Interphase chromosomes adopt a hierarchical structure, and recent data have characterized their chromatin organization at very different scales, from sub-genic regions associated with DNA-binding proteins at the order of tens or hundreds of bases, through larger regions with active or repressed chromatin states, up to multi-megabase-scale domains associated with nuclear positioning, replication timing and other qualities. However, we have lacked detailed, quantitative models to understand the interactions between these different strata. Here we collate large collections of matched locus-level chromatin features and Hi-C interaction data, representing higher-order organization, across three human cell types. We use quantitative modeling approaches to assess whether locus-level features are sufficient to explain higher-order structure, and identify the most influential underlying features. We identify structurally variable domains between cell types and examine the underlying features to discover a general association with cell-type-specific enhancer activity. We also identify the most prominent features marking the boundaries of two types of higher-order domains at different scales: topologically associating domains and nuclear compartments. We find parallel enrichments of particular chromatin features for both types, including features associated with active promoters and the architectural proteins CTCF and YY1. We show that integrative modeling of large chromatin dataset collections using random forests can generate useful insights into chromosome structure. The models produced recapitulate known biological features of the cell types involved, allow exploration of the antecedents of higher-order structures and generate testable hypotheses for further experimental studies.
Improving IMES Localization Accuracy by Integrating Dead Reckoning Information
Fujii, Kenjiro; Arie, Hiroaki; Wang, Wei; Kaneko, Yuto; Sakamoto, Yoshihiro; Schmitz, Alexander; Sugano, Shigeki
2016-01-01
Indoor positioning remains an open problem, because it is difficult to achieve satisfactory accuracy within an indoor environment using current radio-based localization technology. In this study, we investigate the use of Indoor Messaging System (IMES) radio for high-accuracy indoor positioning. A hybrid positioning method combining IMES radio strength information and pedestrian dead reckoning information is proposed in order to improve IMES localization accuracy. For understanding the carrier noise ratio versus distance relation for IMES radio, the signal propagation of IMES radio is modeled and identified. Then, trilateration and extended Kalman filtering methods using the radio propagation model are developed for position estimation. These methods are evaluated through robot localization and pedestrian localization experiments. The experimental results show that the proposed hybrid positioning method achieved average estimation errors of 217 and 1846 mm in robot localization and pedestrian localization, respectively. In addition, in order to examine the reason for the positioning accuracy of pedestrian localization being much lower than that of robot localization, the influence of the human body on the radio propagation is experimentally evaluated. The result suggests that the influence of the human body can be modeled. PMID:26828492
LOCI: Fast Outlier Detection Using the Local Correlation Integral
2002-11-01
Density-based approach. This was proposed by M. Breunig , et al. [BKNS00]. It relies on the local outlier factor (LOF) of each object, which depends...VLDB, pages 299–310, 1995. [BKNS00] M.M. Breunig , H.P. Kriegel, R.T. Ng, and J. Sander. Lof: Identifying density-based local outliers. In Proc
33 CFR 230.20 - Integration with State and local procedures.
Code of Federal Regulations, 2010 CFR
2010-07-01
... 33 Navigation and Navigable Waters 3 2010-07-01 2010-07-01 false Integration with State and local procedures. 230.20 Section 230.20 Navigation and Navigable Waters CORPS OF ENGINEERS, DEPARTMENT OF THE ARMY, DEPARTMENT OF DEFENSE PROCEDURES FOR IMPLEMENTING NEPA § 230.20 Integration with State and local...
Studying the active deformation of distributed plate boundaries by integration of GNSS networks
NASA Astrophysics Data System (ADS)
D'Agostino, Nicola; Avallone, Antonio; Cecere, Gianpaolo; D'Anastasio, Elisabetta
2013-04-01
In the last decade GNSS networks installed for different purposes have proliferated in Italy and now provide a large amount of data available to geophysical studies. In addition to the existing regional and nation-wide scientific GNSS networks developed by ASI (http://geodaf.mt.asi.it), INGV (http://ring.gm.ingv.it) and OGS (http://crs.inogs.it/frednet), a large number (> 400) of continuously-operating GPS stations have been installed in the framework of regional and national networks, both publicly-operated and commercial, developed to provide real-time positioning capability to surveyors. Although the quality of the data and metadata associated to these stations is generally lower with respect to the "scientific" CGPS stations, the increased density and redundancy in crustal motion information, resulting in more than 500 stations with more than 2.5 years of observations, significantly increase the knowledge of the active deformation of the Italian territory and provides a unique image of the crustal deformation field. The obtained GPS velocity field is analysed and various features ranging from the definition of strain distribution and microplate kinematics within the plate boundary, to the evaluation of tectonic strain accumulation on active faults are presented in this work. Undeforming, aseismic regions (Sardinia, Southern Apulia) provide test sites to evaluate the lower bound on the accuracy achievable to measure tectonic deformation. Integration of GNSS networks significantly improves the resolution of the strain rate field in Central Italy showing that active deformation is concentrated in a narrow belt along the crest of the Apennines, consistently with the distribution of the largest historical and recent earthquakes. Products derived from dense GPS velocity and strain rate fields include map of earthquake potential developed under the assumption that the rate of seismic moment accumulation measured from geodesy distributes into earthquake sizes that
Khan, AZ; Pitsinis, V; Mudan, SS
2007-01-01
Pancreatic cancer is an aggressive malignancy, relatively resistant to chemotherapy and radiotherapy, which usually presents late. Disease specific mortality approaches unity despite advances in adjuvant therapy. We present the first reported case of complete pathological response following neoadjuvant therapy in a locally advanced pancreatic adenocarcinoma. PMID:18081235
Exploring the Global/Local Boundary in Education in Developing Countries: The Case of the Caribbean
ERIC Educational Resources Information Center
George, June; Lewis, Theodore
2011-01-01
This article focuses on education in developing countries in the context of globalization and with specific reference to the Caribbean. It examines the concept of globalization and related concepts and positions developing countries within this context. It explores the possibility of the creation of a third space where the local and the global can…
Silva, Silvio Fernandes da; Souza, Nathan Mendes; Barreto, Jorge Otávio Maia
2014-11-01
The scope of this article was to identify the boundaries of the autonomy of local administration in the context of the federal pact in the Brazilian Unified Health System and the importance and potential for promoting innovation, creativity and evidence-based decision-making by local governments. The methodology used was to ask questions that favored dialogue with the specific literature to identify the influence of centrally-formulated policies in spaces of local autonomy and then to identify strategies to foster innovation, creativity and the systematic use of evidence-based research in health policy implementation. A gradual reduction in municipal decision-making autonomy was detected due to increased financial commitment of the municipalities resulting from responsibilities assumed, albeit with the possibility of reverting this trend in the more recent context. Some determinants and challenges for the dissemination of innovative practices were analyzed and some relevant national and international experiences in this respect were presented. The conclusion drawn is that it is possible to make local decision-making more effective provided that initiatives are consolidated to promote this culture and the formulation and implementation of evidence-based health policies.
Hsieh, Kimberly; Kochat, Vidya; Zhang, Xiang; Gong, Yongji; Tiwary, Chandra Sekhar; Ajayan, Pulickel M; Ghosh, Arindam
2017-09-13
Despite its importance in the large-scale synthesis of transition metal dichalcogenides (TMDC) molecular layers, the generic quantum effects on electrical transport across individual grain boundaries (GBs) in TMDC monolayers remain unclear. Here we demonstrate that strong carrier localization due to the increased density of defects determines both temperature dependence of electrical transport and low-frequency noise at the GBs of chemical vapor deposition (CVD)-grown MoS2 layers. Using field effect devices designed to explore transport across individual GBs, we show that the localization length of electrons in the GB region is ∼30-70% lower than that within the grain, even though the room temperature conductance across the GB, oriented perpendicular to the overall flow of current, may be lower or higher than the intragrain region. Remarkably, we find that the stronger localization is accompanied by nearly 5 orders of magnitude enhancement in the low-frequency noise at the GB region, which increases exponentially when the temperature is reduced. The microscopic framework of electrical transport and noise developed in this paper may be readily extended to other strongly localized two-dimensional systems, including other members of the TMDC family.
NASA Astrophysics Data System (ADS)
Macdonald, David; Flecker, Rachel
2017-04-01
The plate boundary system between the Eurasian and North American plates (EUR-NAM) is multi-stranded and mostly aseismic, except in its southernmost 1,000 km, which runs north-south through the island of Sakhalin, on the west side of the Sea of Okhotsk. This dextral transform system has several inactive and two active strands, which have slip rates of 0.86 mm a-1and 1.09 mm a-1 over the past 3.6 Ma. The island is in a state of transpression and recent seismic activity includes the 7.6 magnitude Neftegorsk earthquake (1995). In the Mesozoic, Sakhalin was part of the Eurasian plate and formed the forearc to the Sikhote Al'in arc (K2-Pg), the latest of three Mesozoic arcs accreted to east Asia. Subduction of Pacific crust under Sakhalin shut down by southward migration of an arc-arc cusp from a position north of Sakhalin in the latest Cretaceous to its present position in Hokkaido, leaving Sakhalin isolated in a retro-arc position. Over this interval, the old forearc of Sakhalin was covered by a thick sedimentary cover of locally sourced terrestrial conglomerates and sandstones, marine mudrocks and diatomites, and clean, well-sorted sands deposited in the giant palaeo-Amur delta. Timing of initiation of the NAM-EUR plate boundary in east Asia is debated but is generally thought to be Miocene, coincident with formation of the Kuril Arc. It is also suggested that the Sakhalin portion of the plate boundary system propagated northwards from Hokkaido though the Neogene. However, in this paper we present new evidence to suggest that the present plate configuration dates from the Oligocene and that the whole length of the Sakhalin segment of the plate boundary came into existence at the same time. We show that tectonism in Sakhalin focused on three discontinuities in the former forearc: (a) the arc-forearc boundary; (b) the axis of the forearc basin (west Sakhalin); and (c) the boundary between forearc basin and accretionary complex (east Sakhalin). The Neogene succession is
Wi-Fi/MARG Integration for Indoor Pedestrian Localization
Tian, Zengshan; Jin, Yue; Zhou, Mu; Wu, Zipeng; Li, Ze
2016-01-01
With the wide deployment of Wi-Fi networks, Wi-Fi based indoor localization systems that are deployed without any special hardware have caught significant attention and have become a currently practical technology. At the same time, the Magnetic, Angular Rate, and Gravity (MARG) sensors installed in commercial mobile devices can achieve highly-accurate localization in short time. Based on this, we design a novel indoor localization system by using built-in MARG sensors and a Wi-Fi module. The innovative contributions of this paper include the enhanced Pedestrian Dead Reckoning (PDR) and Wi-Fi localization approaches, and an Extended Kalman Particle Filter (EKPF) based fusion algorithm. A new Wi-Fi/MARG indoor localization system, including an Android based mobile client, a Web page for remote control, and a location server, is developed for real-time indoor pedestrian localization. The extensive experimental results show that the proposed system is featured with better localization performance, with the average error 0.85 m, than the one achieved by using the Wi-Fi module or MARG sensors solely. PMID:27973412
Wi-Fi/MARG Integration for Indoor Pedestrian Localization.
Tian, Zengshan; Jin, Yue; Zhou, Mu; Wu, Zipeng; Li, Ze
2016-12-10
With the wide deployment of Wi-Fi networks, Wi-Fi based indoor localization systems that are deployed without any special hardware have caught significant attention and have become a currently practical technology. At the same time, the Magnetic, Angular Rate, and Gravity (MARG) sensors installed in commercial mobile devices can achieve highly-accurate localization in short time. Based on this, we design a novel indoor localization system by using built-in MARG sensors and a Wi-Fi module. The innovative contributions of this paper include the enhanced Pedestrian Dead Reckoning (PDR) and Wi-Fi localization approaches, and an Extended Kalman Particle Filter (EKPF) based fusion algorithm. A new Wi-Fi/MARG indoor localization system, including an Android based mobile client, a Web page for remote control, and a location server, is developed for real-time indoor pedestrian localization. The extensive experimental results show that the proposed system is featured with better localization performance, with the average error 0.85 m, than the one achieved by using the Wi-Fi module or MARG sensors solely.
Stenroos, Matti
2016-11-21
Boundary element methods (BEM) are used for forward computation of bioelectromagnetic fields in multi-compartment volume conductor models. Most BEM approaches assume that each compartment is in contact with at most one external compartment. In this work, I present a general surface integral equation and BEM discretization that remove this limitation and allow BEM modeling of general piecewise-homogeneous medium. The new integral equation allows positioning of field points at junctioned boundary of more than two compartments, enabling the use of linear collocation BEM in such a complex geometry. A modular BEM implementation is presented for linear collocation and Galerkin approaches, starting from the standard formulation. The approach and resulting solver are verified in four ways, including comparisons of volume and surface potentials to those obtained using the finite element method (FEM), and the effect of a hole in skull on electroencephalographic scalp potentials is demonstrated.
NASA Technical Reports Server (NTRS)
Jin, Jian-Ming; Volakis, John L.
1990-01-01
A numerical technique is proposed for the electromagnetic characterization of the scattering by a three-dimensional cavity-backed aperture in an infinite ground plane. The technique combines the finite element and boundary integral methods to formulate a system of equations for the solution of the aperture fields and those inside the cavity. Specifically, the finite element method is employed to formulate the fields in the cavity region and the boundary integral approach is used in conjunction with the equivalence principle to represent the fields above the ground plane. Unlike traditional approaches, the proposed technique does not require knowledge of the cavity's Green's function and is, therefore, applicable to arbitrary shape depressions and material fillings. Furthermore, the proposed formulation leads to a system having a partly full and partly sparse as well as symmetric and banded matrix which can be solved efficiently using special algorithms.
NASA Astrophysics Data System (ADS)
Stenroos, Matti
2016-11-01
Boundary element methods (BEM) are used for forward computation of bioelectromagnetic fields in multi-compartment volume conductor models. Most BEM approaches assume that each compartment is in contact with at most one external compartment. In this work, I present a general surface integral equation and BEM discretization that remove this limitation and allow BEM modeling of general piecewise-homogeneous medium. The new integral equation allows positioning of field points at junctioned boundary of more than two compartments, enabling the use of linear collocation BEM in such a complex geometry. A modular BEM implementation is presented for linear collocation and Galerkin approaches, starting from the standard formulation. The approach and resulting solver are verified in four ways, including comparisons of volume and surface potentials to those obtained using the finite element method (FEM), and the effect of a hole in skull on electroencephalographic scalp potentials is demonstrated.
NASA Technical Reports Server (NTRS)
Ghosn, L. J.
1988-01-01
Crack propagation in a rotating inner raceway of a high-speed roller bearing is analyzed using the boundary integral method. The model consists of an edge plate under plane strain condition upon which varying Hertzian stress fields are superimposed. A multidomain boundary integral equation using quadratic elements was written to determine the stress intensity factors KI and KII at the crack tip for various roller positions. The multidomain formulation allows the two faces of the crack to be modeled in two different subregions, making it possible to analyze crack closure when the roller is positioned on or close to the crack line. KI and KII stress intensity factors along any direction were computed. These calculations permit determination of crack growth direction along which the average KI times the alternating KI is maximum.
NASA Technical Reports Server (NTRS)
Ghosn, L. J.
1988-01-01
Crack propagation in a rotating inner raceway of a high-speed roller bearing is analyzed using the boundary integral method. The model consists of an edge plate under plane strain condition upon which varying Hertzian stress fields are superimposed. A multidomain boundary integral equation using quadratic elements was written to determine the stress intensity factors KI and KII at the crack tip for various roller positions. The multidomain formulation allows the two faces of the crack to be modeled in two different subregions, making it possible to analyze crack closure when the roller is positioned on or close to the crack line. KI and KII stress intensity factors along any direction were computed. These calculations permit determination of crack growth direction along which the average KI times the alternating KI is maximum.
Integral method for the calculation of three-dimensional, laminar and turbulent boundary layers
NASA Technical Reports Server (NTRS)
Stock, H. W.
1978-01-01
The method for turbulent flows is a further development of an existing method; profile families with two parameters and a lag entrainment method replace the simple entrainment method and power profiles with one parameter. The method for laminar flows is a new development. Moment of momentum equations were used for the solution of the problem, the profile families were derived from similar solutions of boundary layer equations. Laminar and turbulent flows at the wings were calculated. The influence of wing tapering on the boundary layer development was shown. The turbulent boundary layer for a revolution ellipsoid is calculated for 0 deg and 10 deg incidence angles.
Local Structure of Sb in Cretaceous-Tertiary Boundary Clays from Stevns Klint By the XAFS Method
NASA Astrophysics Data System (ADS)
Hongu, H.; Yoshiasa, A.; Tobase, T.; Hiratoko, T.; Isobe, H.; Arima, H.; Sugiyama, K.; Okube, M.
2014-12-01
The Cretaceous-Tertiary (K-T) mass extinctions has been thought to be due to the asteroid impact since Ir anomalies was found by Alvarez et al. (1980) . The boundary clay is also enriched in Cr, Co, Ni, Cu, Zn, As and Sb. Especially concentrations of Sb and As are unusually large. However, the origins and concentration processes of Sb are unknown. In this study, local structure around antimony atoms in K-T boundary clay from Stevns Klint, Denmark, was determined by Sb K-edge XAFS spectroscopy. The XAFS analyses give the information about the chemical state and coordination environment around Sb atoms and help identify of the concentration phase, and also may provide various kinds of information about the asteroid impact and mass extinction. The XAFS measurements were performed at the BL-NW10A beamline at the Photon Factory in KEK, Tsukuba, Japan. The XANES spectra and radial structure function (RSF) showed that Sb in K-T boundary clays is high oxidation state Sb5+ and occupies a SbO6 octahedral site. The Sb-O interatomic distance in K-T clay sample is 2.08(1) A. It is known that Sb5+ is stable form in soil and soil water under an equilibrium situation within the Earth's surface environment. Antimony belongs to group 15 in the periodic table below arsenic, and the chemical behavior of Sb5+ is similar to that of As5+. Because there is a close correlation on co-precipitation between As and Fe (Ebihara and Miura, 1996; Sakai et al., 2007) , it is considered that Sb also correlates closely with Fe compounds (e.g., ferric hydroxides). Abundant ferric hydroxides occur in K-T boundary clays. It is considered that one of the reasons of abnormal high concentrations of Sb and As in K-T boundary clays is a lot of dust from impact ejecta falls with iron ions and deposits on surface of the Earth for a short period of time after the asteroid impact. ReferencesL. W. Alvarez, Science, 208, 1095-1108 (1980) M. Ebihara and T. Miura, Geochimica et Cosmochimica Acta, 60, 5133
Auditory Localization Performance with Gamma Integrated Eye and Ear Protection
2016-12-01
Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person...front-back confusions). 15. SUBJECT TERMS auditory localization, TCAPS, hearing protection, eye protection, auditory situation awareness 16. SECURITY...documented effects have led to the inclusion of auditory localization ability as a measure of auditory “situation awareness ” for TCAPS, and it has been
Klaseboer, Evert; Sepehrirahnama, Shahrokh; Chan, Derek Y C
2017-08-01
The general space-time evolution of the scattering of an incident acoustic plane wave pulse by an arbitrary configuration of targets is treated by employing a recently developed non-singular boundary integral method to solve the Helmholtz equation in the frequency domain from which the space-time solution of the wave equation is obtained using the fast Fourier transform. The non-singular boundary integral solution can enforce the radiation boundary condition at infinity exactly and can account for multiple scattering effects at all spacings between scatterers without adverse effects on the numerical precision. More generally, the absence of singular kernels in the non-singular integral equation confers high numerical stability and precision for smaller numbers of degrees of freedom. The use of fast Fourier transform to obtain the time dependence is not constrained to discrete time steps and is particularly efficient for studying the response to different incident pulses by the same configuration of scatterers. The precision that can be attained using a smaller number of Fourier components is also quantified.
Homentcovschi, Dorel
2008-01-01
This paper gives a regular vector boundary integral equation for solving the problem of viscous scattering of a pressure wave by a rigid body. Firstly, single-layer viscous potentials and a generalized stress tensor are introduced. Correspondingly, generalized viscous double-layer potentials are defined. By representing the scattered field as a combination of a single-layer viscous potential and a generalized viscous double-layer potential, the problem is reduced to the solution of a vectorial Fredholm integral equation of the second kind. Generally, the vector integral equation is singular. However, there is a particular stress tensor, called pseudostress, which yields a regular integral equation. In this case, the Fredholm alternative applies and permits a direct proof of the existence and uniqueness of the solution. The results presented here provide the foundation for a numerical solution procedure. PMID:19865494
NASA Astrophysics Data System (ADS)
Walls, C.; Blume, F.; Meertens, C.; Arnitz, E.; Lawrence, S.; Miller, S.; Bradley, W.; Jackson, M.; Feaux, K.
2007-12-01
equipment includes CDMA Proxicast modems, Hughes Vsat, Intuicom 900 MHz Ethernet bridge radios and several "real-time" sites use 2.4 GHz Wilan radios. Ultimately, 125 of the existing former-SCIGN GPS stations will be integrated into the So Cal region of PBO, of which 25 have real-time data streams. At the time of this publication the total combined Southern California region has over 40 stations streaming real-time data using both radios and CDMA modems. The real-time GPS sites provide specific benefits beyond the standard GPS station: they can provide a live correction for local surveyors and can be used to trigger an alarm if large displacements are recorded. The cross fault spatial distribution of these 336 GPS stations in the seismically active southern California region has the grand potential of augmenting a strong motion earthquake early warning system.
Coulter, R. L.; Gao, W.; Lesht, B. M.
2000-04-04
Measurements at the central facility of the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) are intended to verify, improve, and develop parameterizations in radiative flux models that are subsequently used in General Circulation Models (GCMs). The reliability of this approach depends upon the representativeness of the local measurements at the central facility for the site as a whole or on how these measurements can be interpreted so as to accurately represent increasingly large scales. The variation of surface energy budget terms over the SGP CART site is extremely large. Surface layer measurements of the sensible heat flux (H) often vary by a factor of 2 or more at the CART site (Coulter et al. 1996). The Planetary Boundary Layer (PBL) effectively integrates the local inputs across large scales; because the mixed layer height (h) is principally driven by H, it can, in principal, be used for estimates of surface heat flux over scales on the order of tens of kilometers. By combining measurements of h from radiosondes or radar wind profiles with a one-dimensional model of mixed layer height, they are investigating the ability of diagnosing large-scale heat fluxes. The authors have developed a procedure using the model described by Boers et al. (1984) to investigate the effect of changes in surface sensible heat flux on the mixed layer height. The objective of the study is to invert the sense of the model.
NASA Astrophysics Data System (ADS)
Grachev, Andrey A.; Andreas, Edgar L.; Fairall, Christopher W.; Guest, Peter S.; Persson, P. Ola G.
2013-04-01
Measurements of atmospheric turbulence made over the Arctic pack ice during the Surface Heat Budget of the Arctic Ocean experiment (SHEBA) are used to determine the limits of applicability of Monin-Obukhov similarity theory (in the local scaling formulation) in the stable atmospheric boundary layer. Based on the spectral analysis of wind velocity and air temperature fluctuations, it is shown that, when both the gradient Richardson number, Ri, and the flux Richardson number, Rf, exceed a `critical value' of about 0.20-0.25, the inertial subrange associated with the Richardson-Kolmogorov cascade dies out and vertical turbulent fluxes become small. Some small-scale turbulence survives even in this supercritical regime, but this is non-Kolmogorov turbulence, and it decays rapidly with further increasing stability. Similarity theory is based on the turbulent fluxes in the high-frequency part of the spectra that are associated with energy-containing/flux-carrying eddies. Spectral densities in this high-frequency band diminish as the Richardson-Kolmogorov energy cascade weakens; therefore, the applicability of local Monin-Obukhov similarity theory in stable conditions is limited by the inequalities Ri < Ri cr and Rf < Rf cr. However, it is found that Rf cr = 0.20-0.25 is a primary threshold for applicability. Applying this prerequisite shows that the data follow classical Monin-Obukhov local z-less predictions after the irrelevant cases (turbulence without the Richardson-Kolmogorov cascade) have been filtered out.
NASA Astrophysics Data System (ADS)
Guo, H.; Huang, Q. M.; Liu, P. Q.; Feng, T.
2015-08-01
The effects of localized unsteady ejection by synthetic jet with slot-type exit on a turbulent boundary layer at zero pressure gradient conditions were investigated downstream of the slot using hot-wire anemometry. This work is to investigate the influence of unsteady disturbance on turbulent structures at small scales, i.e., in the isotropy recovery range (IRR) and the shear-dominated range (SDR). In the near-slot region, our results show that IRR is extended and SDR is shortened for the perturbed flow in the near-wall region, which contributes to the decrease in anisotropy and intermittency. For the perturbed flow, only one scaling behavior of the longitudinal structure functions similar to the classical Kolmogorov-like scaling is observed in IRR.
NASA Astrophysics Data System (ADS)
Su, Ying; Zou, Xingfu
2014-01-01
In this paper, we study the spatial-temporal patterns of the solutions to the diffusive non-local Nicholson's blowflies equations with time delay (maturation time) subject to the no flux boundary condition. We establish the existence of both spatially homogeneous periodic solutions and various spatially inhomogeneous periodic solutions by investigating the Hopf bifurcations at the spatially homogeneous steady state. We also compute the normal form on the centre manifold, by which the bifurcation direction and stability of the bifurcated periodic solutions can be determined. The results show that the bifurcated homogeneous periodic solutions are stable, while the bifurcated inhomogeneous periodic solutions can only be stable on the corresponding centre manifold, implying that generically the model can only allow transient oscillatory patterns. Finally, we present some numerical simulations to demonstrate the theoretic results. For these transient patterns, we derive approximation formulas which are confirmed by numerical simulations.
NASA Astrophysics Data System (ADS)
Marxen, Olaf; Iaccarino, Gianluca; Shaqfeh, Eric
2007-11-01
Knowledge of heat load on the surface of vehicles (re-)entering a planetary atmosphere is important for heat-shield design. Prediction of laminar-turbulent transition is a key factor for the design. We carry out numerical simulations of a flat-plate boundary layer with and without localized roughness element (small hump). The compressible Navier-Stokes equations are solved for a calorically perfect gas. Small perturbations at a fixed frequency are triggered at the wall. Their downstream convective amplification is compared between flat-plate and hump case. The roughness element leads to increased disturbance amplification. Peak amplitude levels are reached in the vicinity of the hump. The effect of the roughness element seems similar to the effect of a shock impinging on a wall. The present study shall be extended to include high-temperature gas effects as well as three-dimensional disturbances (oblique waves).
Time-dependent behavior of a localized electron at a heterojunction boundary of graphene
Jang, Min S.; Kim, Hyungjun; Atwater, Harry A.; Goddard, William A.
2010-01-01
We develop a finite-difference time-domain(FDTD) method for simulating the dynamics of graphene electrons, denoted GraFDTD. We then use GraFDTD to study the temporal behavior of a single localized electron wave packet, showing that it exhibits optical-like dynamics including the Goos–Hänchen effect [F. Goos and H. Hänchen, Ann. Phys.436, 333 (1947)] at a heterojunction, but the behavior is quantitatively different than for electromagnetic waves. This suggests issues that must be addressed in designing graphene-based electronic devices analogous to optical devices. GraFDTD should be useful for studying such complex time-dependent behavior of a quasiparticle in graphene.
Integrating Local Green Assets into Brownfields Redevelopment: Tools and Examples
EnviroAtlas is a free, online public mapping tool that characterizes green infrastructure and its connection to human health and wellness. The high resolution data contained in this tool can be used to incorporate local green infrastructure into Brownfields redevelopment to benef...
Integrating Local Green Assets into Brownfields Redevelopment: Tools and Examples
EnviroAtlas is a free, online public mapping tool that characterizes green infrastructure and its connection to human health and wellness. The high resolution data contained in this tool can be used to incorporate local green infrastructure into Brownfields redevelopment to benef...
NASA Astrophysics Data System (ADS)
Lanzoni, S.; Bogoni, M.; Nittrouer, J. A.; Cantelli, A.
2016-12-01
Modeling of long-term evolution of meander planforms is usually applied to river reaches characterized by a uniform flow perturbed by the effects of the curvature and width distributions. However, in nature meandering rivers may be characterized by localized variations due to external conditions, e.g. changes in floodplain slope (geologic variation), confluence of a tributary into the main river (hydrologic variation), or backwater effects (hydrodynamic variation). As a consequence, the hypothesis of a sufficiently long reach having constant forcing characteristic could limit the reliability of the numerical simulations. We developed a mathematical extension of a well-known fully coupled two-dimensional morphodynamic model (i.e., the ZS model) able to manage an internally localized boundary condition which affects the characteristic of the main flow. The resulting modular model computes the flow field in the two meandering sub-reaches determined by the presence of a section entailing prescribed changes in external conditions, and simulates the long-term lateral migration above the floodplain surface due to erosion and deposition processes at the banks, and the possible occurrence of neck cutoffs. Calibration runs and simulations based on real test cases show that internal variations in the parameters controlling the flow field might strongly affect the morphodynamic behavior of the migrating planforms. Future research shall provide an extension of this approach in order to manage multiple internal boundary conditions within the investigated river reach. The aim is to relax the common hypothesis of a unique formative uniform flow, exploiting the less restrictive assumption of a sequence of uniform flows to describe the flow field that establishes in the river and controls its morphodynamic behaviour.
RF performances of inductors integrated on localized p+-type porous silicon regions
NASA Astrophysics Data System (ADS)
Capelle, Marie; Billoué, Jérôme; Poveda, Patrick; Gautier, Gaël
2012-09-01
To study the influence of localized porous silicon regions on radiofrequency performances of passive devices, inductors were integrated on localized porous silicon regions, full porous silicon sheet, bulk silicon and glass substrates. In this work, a novel strong, resistant fluoropolymer mask is introduced to localize the porous silicon on the silicon wafer. Then, the quality factors and resonant frequencies obtained with the different substrates are presented. A first comparison is done between the performances of inductors integrated on same-thickness localized and full porous silicon sheet layers. The effect of the silicon regions in the decrease of performances of localized porous silicon is discussed. Then, the study shows that the localized porous silicon substrate significantly reduces losses in comparison with high-resistivity silicon or highly doped silicon bulks. These results are promising for the integration of both passive and active devices on the same silicon/porous silicon hybrid substrate.
In Vivo Evidence of Reduced Integrity of the Gray-White Matter Boundary in Autism Spectrum Disorder.
Andrews, Derek Sayre; Avino, Thomas A; Gudbrandsen, Maria; Daly, Eileen; Marquand, Andre; Murphy, Clodagh M; Lai, Meng-Chuan; Lombardo, Michael V; Ruigrok, Amber N V; Williams, Steven C; Bullmore, Edward T; The Mrc Aims Consortium; Suckling, John; Baron-Cohen, Simon; Craig, Michael C; Murphy, Declan G M; Ecker, Christine
2017-02-01
Atypical cortical organization and reduced integrity of the gray-white matter boundary have been reported by postmortem studies in individuals with autism spectrum disorder (ASD). However, there are no in vivo studies that examine these particular features of cortical organization in ASD. Hence, we used structural magnetic resonance imaging to examine differences in tissue contrast between gray and white matter in 98 adults with ASD and 98 typically developing controls, to test the hypothesis that individuals with ASD have significantly reduced tissue contrast. More specifically, we examined contrast as a percentage between gray and white matter tissue signal intensities (GWPC) sampled at the gray-white matter boundary, and across different cortical layers. We found that individuals with ASD had significantly reduced GWPC in several clusters throughout the cortex (cluster, P < 0.05). As expected, these reductions were greatest when tissue intensities were sampled close to gray-white matter interface, which indicates a less distinct gray-white matter boundary in ASD. Our in vivo findings of reduced GWPC in ASD are therefore consistent with prior postmortem findings of a less well-defined gray-white matter boundary in ASD. Taken together, these results indicate that GWPC might be utilized as an in vivo proxy measure of atypical cortical microstructural organization in future studies. © The Author 2017. Published by Oxford University Press.
Integrating Local Public Health Agencies into the Homeland Security Community
2007-03-01
public health needs that require attention (such as poor prenatal health, teen pregnancy , and sexually transmitted diseases) it is not difficult to...such as maternal and child health care or family planning education. One primary educational responsibility best accomplished with state and local...transformation in law enforcement is the concept of community policing. Community policing broadens the nature of police functions and makes better use
On a boundary-localized Higgs boson in 5D theories.
Barceló, Roberto; Mitra, Subhadip; Moreau, Grégory
In the context of a simple five-dimensional (5D) model with bulk matter coupled to a brane-localized Higgs boson, we point out a non-commutativity in the 4D calculation of the mass spectrum for excited fermion towers: the obtained expression depends on the choice in ordering the limits, [Formula: see text] (infinite Kaluza-Klein tower) and [Formula: see text] ([Formula: see text] being the parameter introduced for regularizing the Higgs Dirac peak). This introduces the question of which one is the correct order; we then show that the two possible orders of regularization (called I and II) are experimentally equivalent, as both can typically reproduce the measured observables, but that the one with less degrees of freedom (I) could be uniquely excluded by future experimental constraints. This conclusion is based on the exact matching between the 4D and 5D analytical calculations of the mass spectrum - via regularizations of type I and II. Beyond a deeper insight into the Higgs peak regularizations, this matching brings another confirmation of the validity of the 5D mixed formalism. All the conclusions, deduced from regularizing the Higgs peak through a brane shift or a smoothed square profile, are expected to remain similar in realistic models with a warped extra-dimension. The complementary result of the study is that the non-commutativity disappears, both in the 4D and the 5D calculations, in the presence of higher order derivative operators. For clarity, the 4D and 5D analytical calculations, matching with each other, are presented in the first part of the paper, while the second part is devoted to the interpretation of the results.
NASA Astrophysics Data System (ADS)
Volkoff, Tyler; Kwon, Yongkyung; Whaley, K. Birgitta
2016-10-01
We present a path integral Monte Carlo study of the global superfluid fraction and local superfluid density in cylindrically symmetric reservoirs of liquid 4He separated by nanoaperture arrays. The superfluid response to both translations along the axis of symmetry (longitudinal response) and rotations about the cylinder axis (transverse response) are computed, together with radial and axial density distributions that reveal the microscopic inhomogeneity arising from the combined effects of the confining external potential and the 4He-4He interatomic potentials. We make a microscopic determination of the length scale of decay of superfluidity at the radial boundaries of the system by analyzing the local superfluid density distribution to extract a displacement length that quantifies the superfluid mass displacement away from the boundary. We find that the longitudinal superfluid response is reduced in reservoirs separated by a septum containing sufficiently small apertures compared to a cylinder with no intervening aperture array, for all temperatures below Tλ. For a single aperture in the septum, a significant drop in the longitudinal superfluid response is seen when the aperture diameter is made smaller than twice the empirical temperature-dependent 4He healing length, consistent with the formation of a weak link between the reservoirs. Increasing the diameter of a single aperture or the number of apertures in the array results in an increase of the superfluid density toward the expected bulk value.
Sumets, P. P.; Cater, J. E.; Long, D. S.; Clarke, R. J.
2015-01-01
We describe a new boundary-integral representation for biphasic mixture theory, which allows us to efficiently solve certain elastohydrodynamic–mobility problems using boundary element methods. We apply this formulation to model the motion of a rigid particle through a microtube which has non-uniform wall shape, is filled with a viscous Newtonian fluid, and is lined with a thin poroelastic layer. This is relevant to scenarios such as the transport of small rigid cells (such as neutrophils) through microvessels that are lined with an endothelial glycocalyx layer (EGL). In this context, we examine the impact of geometry upon some recently reported phenomena, including the creation of viscous eddies, fluid flux into the EGL, as well as the role of the EGL in transmitting mechanical signals to the underlying endothelial cells. PMID:26345494
NASA Astrophysics Data System (ADS)
Kitanine, N.; Maillet, J. M.; Niccoli, G.
2014-05-01
We solve the longstanding problem of defining a functional characterization of the spectrum of the transfer matrix associated with the most general spin-1/2 representations of the six-vertex reflection algebra for general inhomogeneous chains. The corresponding homogeneous limit reproduces the spectrum of the Hamiltonian of the spin-1/2 open XXZ and XXX quantum chains with the most general integrable boundaries. The spectrum is characterized by a second order finite difference functional equation of Baxter type with an inhomogeneous term which vanishes only for some special but yet interesting non-diagonal boundary conditions. This functional equation is shown to be equivalent to the known separation of variables (SOV) representation, hence proving that it defines a complete characterization of the transfer matrix spectrum. The polynomial form of the Q-function allows us to show that a finite system of generalized Bethe equations can also be used to describe the complete transfer matrix spectrum.
Thomas B. Lynch; Jeffrey H. Gove
2014-01-01
The typical "double counting" application of the mirage method of boundary correction cannot be applied to sampling systems such as critical height sampling (CHS) that are based on a Monte Carlo sample of a tree (or debris) attribute because the critical height (or other random attribute) sampled from a mirage point is generally not equal to the critical...
Interim user's manual for boundary layer integral matrix procedure, version J
NASA Technical Reports Server (NTRS)
Evans, R. M.; Morse, H. L.
1974-01-01
A computer program for analyzing two dimensional and axisymmetric nozzle performance with a variety of wall boundary conditions is described. The program has been developed for application to rocket nozzle problems. Several aids to usage of the program and two auxiliary subroutines are provided. Some features of the output are described and three sample cases are included.
A Stokes Flow Boundary Integral Measurement of Tubular Structure Cross Sections in Two Dimensions
2003-01-01
computer graphics and image processing, notably for image inpainting /reconstruction [3]. Examples for using the boundary element approach in com...IEEE, 2001, vol. 1, pp. 87–92. [3] M. Bertalmio, A. L. Bertozzi, and G. Sapiro, “Navier-Stokes, Fluid Dynamics, and Image and Video Inpainting ,” in
Modification site localization scoring integrated into a search engine.
Baker, Peter R; Trinidad, Jonathan C; Chalkley, Robert J
2011-07-01
Large proteomic data sets identifying hundreds or thousands of modified peptides are becoming increasingly common in the literature. Several methods for assessing the reliability of peptide identifications both at the individual peptide or data set level have become established. However, tools for measuring the confidence of modification site assignments are sparse and are not often employed. A few tools for estimating phosphorylation site assignment reliabilities have been developed, but these are not integral to a search engine, so require a particular search engine output for a second step of processing. They may also require use of a particular fragmentation method and are mostly only applicable for phosphorylation analysis, rather than post-translational modifications analysis in general. In this study, we present the performance of site assignment scoring that is directly integrated into the search engine Protein Prospector, which allows site assignment reliability to be automatically reported for all modifications present in an identified peptide. It clearly indicates when a site assignment is ambiguous (and if so, between which residues), and reports an assignment score that can be translated into a reliability measure for individual site assignments.
Integration of cloud, grid and local cluster resources with DIRAC
NASA Astrophysics Data System (ADS)
Fifield, Tom; Carmona, Ana; Casajús, Adrián; Graciani, Ricardo; Sevior, Martin
2011-12-01
Grid computing was developed to provide users with uniform access to large-scale distributed resources. This has worked well, however there are significant resources available to the scientific community that do not follow this paradigm - those on cloud infrastructure providers, HPC supercomputers or local clusters. DIRAC (Distributed Infrastructure with Remote Agent Control) was originally designed to support direct submission to the Local Resource Management Systems (LRMS) of such clusters for LHCb, matured to support grid workflows and has recently been updated to support Amazon's Elastic Compute Cloud. This raises a number of new possibilities - by opening avenues to new resources, virtual organisations can change their resources with usage patterns and use these dedicated facilities for a given time. For example, user communities such as High Energy Physics experiments, have computing tasks with a wide variety of requirements in terms of CPU, data access or memory consumption, and their usage profile is never constant throughout the year. Having the possibility to transparently absorb peaks on the demand for these kinds of tasks using Cloud resources could allow a reduction in the overall cost of the system. This paper investigates interoperability by following a recent large-scale production excercise utilising resources from these three different paradigms, during the 2010 Belle Monte Carlo run. Through this, it discusses the challenges and opportunities of such a model.
Integrating Self-Localization, Proprioception, Pain, and Performance.
Bellan, Valeria; Wallwork, Sarah B; Gallace, Alberto; Spence, Charles; Moseley, G Lorimer
2017-03-01
The ability to know where our own body and body parts are in space is often taken for granted, yet it is of fundamental importance for the majority of our everyday activities, let alone high performance activities such as dancing. This review focuses on the concept of self-localization, the monitoring of the space surrounding one's body, and the disruptions that occur in the presence of pain. A conceptual model is presented of the cortical body matrix with which to consider self-localization; also provided are its historical context, underlying assumptions, and current limitations. Issues described include the neurophysiological and behavioral background to the cortical body matrix model, its application to pain and performance, and the rapidly growing use of bodily illusions to investigate how it is that we know where we are, that we exist in a given location, and that we can interact with the space that surrounds us. Recent insights are drawn on from behavioral, clinical, neuroimaging, and physiological research. Spatial performance is discussed in people with and without pain and its relevance for prevention of injuries, the role of pain during performance, and pain education for dancers and their teachers.
NASA Astrophysics Data System (ADS)
Cho, Kyoungmi; Jin, Emilia Kyung
2013-04-01
This is a sensitivity study about stability function which decides the K-profile of the local scheme in boundary layer scheme of NWP(Numerical Weather Prediction) models. Stability function is a factor to decide to K-Profile which consists of mixing length and vertical wind gradient. We conduct sensitivity experiments using the SCM(Single Column Model) and the global model. We apply the revised Louis-Tiedke-Geleyn(Viterbo et al., 1999) method(EXP2) stability function instead of the SHARP(Beare et al., 2004) and Long Tail(Beare et al., 2004) method(CTL) for stability conditions. For unstable conditions, the Troen-Mahrt (Troen and Mahrt 1986) method(EXP1) stability function is applied instead of Holtslag-Boville(Holtslag and Boville 1993) method(CTL). As a result of SCM experiments, EXP1 and EXP2 overestimate surface heat fluxes and underestimate temperature and specific humidity at 1.5m compared to CTL. In vertical temperature and specific humidity analysis results, the temperature is higher than CTL and the humidity is lower than CTL below the 850hPa. On the other hand, the temperature is lower and the humidity is higher than CTL over the 850hPa. In short, sensitivity tests indicate that air condition is drier at low layer and moister at upper layer than CTL case. We analyze time series about variety boundary layer variables such as surface fluxes, temperature at 1.5m and wind stress for global model experiments. As a result, while sensitivity tests are similar to CTL during initial 5days among total prediction time and the variables have a difference compared to CTL case after initial 5 days. In vertical structure analysis about variables, vertical velocity have an effect temperature and humidity at low levels as vertical velocity of EXP1 and EXP2 is stronger than CTL at the low levels after initial 5 days. Sensitivity tests show that variables such as temperature, specific humidity and vertical velocity overestimate at low levels including boundary layer. As a
Olowoporoku, Dotun; Hayes, Enda; Longhurst, James; Parkhurst, Graham
2012-06-30
Regardless of its intent and purposes, the first decade of the Local Air Quality Management (LAQM) framework had little or no effect in reducing traffic-related air pollution in the UK. Apart from the impact of increased traffic volumes, the major factor attributed to this failure is that of policy disconnect between the process of diagnosing air pollution and its management, thereby limiting the capability of local authorities to control traffic-related sources of air pollution. Integrating air quality management into the Local Transport Plan (LTP) process therefore presents opportunities for enabling political will, funding and joined-up policy approach to reduce this limitation. However, despite the increased access to resources for air quality measures within the LTP process, there are local institutional, political and funding constraints which reduce the impact of these policy interventions on air quality management. This paper illustrate the policy implementation gaps between central government policy intentions and the local government process by providing evidence of the deprioritisation of air quality management compared to the other shared priorities in the LTP process. We draw conclusions on the policy and practice of integrating air quality management into transport planning. The evidence thereby indicate the need for a policy shift from a solely localised hotspot management approach, in which the LAQM framework operates, to a more holistic management of vehicular emissions within wider spatial administrative areas. Copyright © 2012 Elsevier Ltd. All rights reserved.
2009-01-01
robust sequential organization performance in environments with considerable reverberation. Index Terms – Sequential organization, binaural sound ... Binaural Cue Extraction Two primary binaural cues used by humans for localization of sound sources are interaural time difference (ITD) and...Sequential Organization of Speech in Reverberant Environments by Integrating Monaural Grouping and Binaural Localization John Woodruff Department of
Integrating Local Databases with Remote Files, Print Materials and Reference Services.
ERIC Educational Resources Information Center
Pope, Nolan F.
1982-01-01
Discusses the impact of local online databases on library reference services, including their integration with remote files such as Dialog, Orbit, and the Information Bank. Online catalog databases, multiple local databases (analytics for journal articles, indexes), and batch processing of data are noted. Six references are cited. (EJS)
ARN Integrated Retail Module (IRM) System at Ft. Bliss - Central Issue Facility (CIF) Local Tariff
2008-03-14
Number SP0103-02-D-0018 / Delivery Order 0014 ARN Integrated Retail Module (IRM) System at Ft. Bliss Prepared for: Defense Logistics Agency March...February 2007 4. TITLE AND SUBTITLE ARN Integrated Retail Module (IRM) System at Ft. Bliss - Central Issue Facility (CIF) Local Tariff 5. FUNDING...Visibility System (AAVS) and other databases over the Internet, and AdvanTech established ARN Integrated Retail Module (IRM) at Ft. Bliss, TX Page
Knierim, James J; Neunuebel, Joshua P; Deshmukh, Sachin S
2014-02-05
The hippocampus receives its major cortical input from the medial entorhinal cortex (MEC) and the lateral entorhinal cortex (LEC). It is commonly believed that the MEC provides spatial input to the hippocampus, whereas the LEC provides non-spatial input. We review new data which suggest that this simple dichotomy between 'where' versus 'what' needs revision. We propose a refinement of this model, which is more complex than the simple spatial-non-spatial dichotomy. MEC is proposed to be involved in path integration computations based on a global frame of reference, primarily using internally generated, self-motion cues and external input about environmental boundaries and scenes; it provides the hippocampus with a coordinate system that underlies the spatial context of an experience. LEC is proposed to process information about individual items and locations based on a local frame of reference, primarily using external sensory input; it provides the hippocampus with information about the content of an experience.
NASA Astrophysics Data System (ADS)
Bozkaya, C.; Tezer-Sezgin, M.
2006-06-01
A numerical scheme which is a combination of the dual reciprocity boundary element method (DRBEM) and the differential quadrature method (DQM), is proposed for the solution of unsteady magnetohydrodynamic (MHD) flow problem in a rectangular duct with insulating walls. The coupled MHD equations in velocity and induced magnetic field are transformed first into the decoupled time-dependent convection-diffusion-type equations. These equations are solved by using DRBEM which treats the time and the space derivatives as nonhomogeneity and then by using DQM for the resulting system of initial value problems. The resulting linear system of equations is overdetermined due to the imposition of both boundary and initial conditions. Employing the least square method to this system the solution is obtained directly at any time level without the need of step-by-step computation with respect to time. Computations have been carried out for moderate values of Hartmann number (M50) at transient and the steady-state levels. As M increases boundary layers are formed for both the velocity and the induced magnetic field and the velocity becomes uniform at the centre of the duct. Also, the higher the value of M is the smaller the value of time for reaching steady-state solution.
Local, integrated control of blood flow: Professor Tudor Griffith Memorial.
Edwards, David H
2013-11-01
Professor Tudor Griffith was one of the founding members of the European Study Group on Cardiovascular Oscillations, and hosted the 1st ESGCO Conference in Cardiff, Wales in 2000. Tudor was a passionate scientist, who managed to combine his enthusiasm for vascular biology with his background in physics, to make key and insightful advances to our knowledge and understanding of the integrated vascular control mechanisms that co-ordinate blood flow in tissue perfusion. He had a particular interest in the endothelium, the monolayer of cells that lines the entire cardiovascular system and which is in prime position to sense a wide variety of modulatory stimuli, both chemical and mechanical. Over the last 20 years Tudor produced a series of research papers in which he used chaos theory to analyse the behaviour of arteries that underpins vasomotion. The research led to the development of mathematical models that were able to predict calcium oscillations in vascular smooth muscle with a view to predicting events in a complete virtual artery. This article will review the field in which he worked, with an obvious emphasis on his contribution. Copyright © 2013 Elsevier B.V. All rights reserved.
RECQL4 LOCALIZES TO MITOCHONDRIA AND PRESERVES MITOCHONDRIAL DNA INTEGRITY
Croteau, Deborah L.; Rossi, Marie L.; Canugovi, Chandrika; Tian, Jane; Sykora, Peter; Ramamoorthy, Mahesh; Wang, ZhengMing; Singh, Dharmendra Kumar; Akbari, Mansour; Kasiviswanathan, Rajesh; Copeland, William C.; Bohr, Vilhelm A.
2012-01-01
SUMMARY RECQL4 is associated with Rothmund-Thomson Syndrome (RTS), a rare autosomal recessive disorder characterized by premature aging, genomic instability and cancer predisposition. RECQL4 is a member of the RecQ-helicase family, and has many similarities to WRN protein, which is also implicated in premature aging. There is no information about whether any of the RecQ helicases play roles in mitochondrial biogenesis, which is strongly implicated in the aging process. Here, we used microscopy to visualize RECQL4 in mitochondria. Fractionation of human and mouse cells also showed that RECQL4 was present in mitochondria. Q-PCR amplification of mitochondrial DNA demonstrated that mtDNA damage accumulated in RECQL4-deficient cells. Microarray analysis suggested that mitochondrial bioenergetic pathways might be affected in RTS. Measurements of mitochondrial bioenergetics showed a reduction in the mitochondrial reserve capacity after lentiviral knockdown of RECQL4 in two different primary cell lines. Additionally, biochemical assays with RECQL4, mitochondrial transcription factor A and mitochondrial DNA polymerase γ showed that the polymerase inhibited RECQL4’s helicase activity. RECQL4 is the first 3′ to 5′ RecQ helicase to be found in both human and mouse mitochondria and the loss of RECQL4 alters mitochondrial integrity. PMID:22296597
NASA Astrophysics Data System (ADS)
Petrizzo, Maria Rose
2014-05-01
Planktonic foraminifera are marine protozoans characterized by an excellent geological record and by high morphological diversification and speciation rates. For these reasons, they have been widely used in biostratigraphy and strongly contributed to the multi-disciplinary efforts to improve Cretaceous chronostratigraphy in pelagic settings. A critical time is the Albian to Santonian interval for which a high-resolution multiple bio-, geochemical and physical integrated stratigraphy framework exportable worldwide is still needed. This is partially because a consistent correlation of the planktonic foraminifera bioevents and calibration against other stratigraphic tools often lacks in accuracy, resolution and reproducibility of the data. At present the GSSPs for the base of the Cenomanian (Mt Risou, SE France), the base of the Turonian (Pueblo, Colorado) and the base of the Santonian (Olazagutia, N Spain) stages have been established and ratified by IUGS. Planktonic foraminifera bioevents are primary defining criteria for the Albian/Cenomanian boundary (appearance level of Thalmanninella globotruncanoides), and secondary defining criteria for the Cenomanian/Turonian (appearance level of Helvetoglobotruncana helvetica) and Coniacian/Santonian (appearance level of Globotruncana linneiana) boundaries. However, the identifications of the foraminiferal index species across those boundaries have been reported to be sometimes difficult or unreliable from a number of localities worldwide either because of their rarity or uncertainty in the taxonomic identifications. Reasons rely on many factors, such as poor sampling resolution, incomplete exposure, facies differences, fossil preservation quality, diachronous taxa occurrences, and regional/provincial distribution of the index species. Often, discrepancies pertain to taxonomic inconsistencies, species misidentifications and different species concepts that accumulate over time in the literature. Nevertheless, biostratigraphy
Heinen, M; Kull, H-J
2009-05-01
Exact radiation boundary conditions on the surface of a sphere are presented for the single-particle time-dependent Schrödinger equation with a localized interaction. With these boundary conditions, numerical computations of spatially unbounded outgoing wave solutions can be restricted to the finite volume of a sphere. The boundary conditions are expressed in terms of the free-particle Green's function for the outside region. The Green's function is analytically calculated by an expansion in spherical harmonics and by the method of Laplace transformation. For each harmonic number a discrete boundary condition between the function values at adjacent radial grid points is obtained. The numerical method is applied to quantum tunneling through a spherically symmetric potential barrier with different angular-momentum quantum numbers l . Calculations for l=0 are compared to exact theoretical results.
NASA Astrophysics Data System (ADS)
Darabant, András; Rai, Prem Bahadur; Staudhammer, Christina Lynn; Dorji, Tshewang
2016-08-01
Dendrocalamus hamiltonii, a large, clump-forming bamboo, has great potential to contribute towards poverty alleviation efforts across its distributional range. Harvesting methods that maximize yield while they fulfill local objectives and ensure sustainability are a research priority. Documenting local ecological knowledge on the species and identifying local users' goals for its production, we defined three harvesting treatments (selective cut, horseshoe cut, clear cut) and experimentally compared them with a no-intervention control treatment in an action research framework. We implemented harvesting over three seasons and monitored annually and two years post-treatment. Even though the total number of culms positively influenced the number of shoots regenerated, a much stronger relationship was detected between the number of culms harvested and the number of shoots regenerated, indicating compensatory growth mechanisms to guide shoot regeneration. Shoot recruitment declined over time in all treatments as well as the control; however, there was no difference among harvest treatments. Culm recruitment declined with an increase in harvesting intensity. When univariately assessing the number of harvested culms and shoots, there were no differences among treatments. However, multivariate analyses simultaneously considering both variables showed that harvested output of shoots and culms was higher with clear cut and horseshoe cut as compared to selective cut. Given the ease of implementation and issues of work safety, users preferred the horseshoe cut, but the lack of sustainability of shoot production calls for investigating longer cutting cycles.
Darabant, András; Rai, Prem Bahadur; Staudhammer, Christina Lynn; Dorji, Tshewang
2016-08-01
Dendrocalamus hamiltonii, a large, clump-forming bamboo, has great potential to contribute towards poverty alleviation efforts across its distributional range. Harvesting methods that maximize yield while they fulfill local objectives and ensure sustainability are a research priority. Documenting local ecological knowledge on the species and identifying local users' goals for its production, we defined three harvesting treatments (selective cut, horseshoe cut, clear cut) and experimentally compared them with a no-intervention control treatment in an action research framework. We implemented harvesting over three seasons and monitored annually and two years post-treatment. Even though the total number of culms positively influenced the number of shoots regenerated, a much stronger relationship was detected between the number of culms harvested and the number of shoots regenerated, indicating compensatory growth mechanisms to guide shoot regeneration. Shoot recruitment declined over time in all treatments as well as the control; however, there was no difference among harvest treatments. Culm recruitment declined with an increase in harvesting intensity. When univariately assessing the number of harvested culms and shoots, there were no differences among treatments. However, multivariate analyses simultaneously considering both variables showed that harvested output of shoots and culms was higher with clear cut and horseshoe cut as compared to selective cut. Given the ease of implementation and issues of work safety, users preferred the horseshoe cut, but the lack of sustainability of shoot production calls for investigating longer cutting cycles.
Boriskina, Svetlana V; Sewell, Phillip; Benson, Trevor M; Nosich, Alexander I
2004-03-01
A fast and accurate method is developed to compute the natural frequencies and scattering characteristics of arbitrary-shape two-dimensional dielectric resonators. The problem is formulated in terms of a uniquely solvable set of second-kind boundary integral equations and discretized by the Galerkin method with angular exponents as global test and trial functions. The log-singular term is extracted from one of the kernels, and closed-form expressions are derived for the main parts of all the integral operators. The resulting discrete scheme has a very high convergence rate. The method is used in the simulation of several optical microcavities for modern dense wavelength-division-multiplexed systems.
NASA Technical Reports Server (NTRS)
Santanello, Joseph A., Jr.; Peters-Lidard, Christa D.; Kumar, Sujay V.
2011-01-01
The inherent coupled nature of earth s energy and water cycles places significant importance on the proper representation and diagnosis of land atmosphere (LA) interactions in hydrometeorological prediction models. However, the precise nature of the soil moisture precipitation relationship at the local scale is largely determined by a series of nonlinear processes and feedbacks that are difficult to quantify. To quantify the strength of the local LA coupling (LoCo), this process chain must be considered both in full and as individual components through their relationships and sensitivities. To address this, recent modeling and diagnostic studies have been extended to 1) quantify the processes governing LoCo utilizing the thermodynamic properties of mixing diagrams, and 2) diagnose the sensitivity of coupled systems, including clouds and moist processes, to perturbations in soil moisture. This work employs NASA s Land Information System (LIS) coupled to the Weather Research and Forecasting (WRF) mesoscale model and simulations performed over the U.S. Southern Great Plains. The behavior of different planetary boundary layers (PBL) and land surface scheme couplings in LIS WRF are examined in the context of the evolution of thermodynamic quantities that link the surface soil moisture condition to the PBL regime, clouds, and precipitation. Specifically, the tendency toward saturation in the PBL is quantified by the lifting condensation level (LCL) deficit and addressed as a function of time and space. The sensitivity of the LCL deficit to the soil moisture condition is indicative of the strength of LoCo, where both positive and negative feedbacks can be identified. Overall, this methodology can be applied to any model or observations and is a crucial step toward improved evaluation and quantification of LoCo within models, particularly given the advent of next-generation satellite measurements of PBL and land surface properties along with advances in data assimilation
NASA Technical Reports Server (NTRS)
Santanello, Joseph A., Jr.; Peters-Lidard, Christa D.; Kumar, Sujay V.
2011-01-01
The inherent coupled nature of earth s energy and water cycles places significant importance on the proper representation and diagnosis of land atmosphere (LA) interactions in hydrometeorological prediction models. However, the precise nature of the soil moisture precipitation relationship at the local scale is largely determined by a series of nonlinear processes and feedbacks that are difficult to quantify. To quantify the strength of the local LA coupling (LoCo), this process chain must be considered both in full and as individual components through their relationships and sensitivities. To address this, recent modeling and diagnostic studies have been extended to 1) quantify the processes governing LoCo utilizing the thermodynamic properties of mixing diagrams, and 2) diagnose the sensitivity of coupled systems, including clouds and moist processes, to perturbations in soil moisture. This work employs NASA s Land Information System (LIS) coupled to the Weather Research and Forecasting (WRF) mesoscale model and simulations performed over the U.S. Southern Great Plains. The behavior of different planetary boundary layers (PBL) and land surface scheme couplings in LIS WRF are examined in the context of the evolution of thermodynamic quantities that link the surface soil moisture condition to the PBL regime, clouds, and precipitation. Specifically, the tendency toward saturation in the PBL is quantified by the lifting condensation level (LCL) deficit and addressed as a function of time and space. The sensitivity of the LCL deficit to the soil moisture condition is indicative of the strength of LoCo, where both positive and negative feedbacks can be identified. Overall, this methodology can be applied to any model or observations and is a crucial step toward improved evaluation and quantification of LoCo within models, particularly given the advent of next-generation satellite measurements of PBL and land surface properties along with advances in data assimilation
Michel, Marcus; Aliee, Maryam; Rudolf, Katrin; Bialas, Lisa; Jülicher, Frank; Dahmann, Christian
2016-01-01
The separation of cells with distinct fates and functions is important for tissue and organ formation during animal development. Regions of different fates within tissues are often separated from another along straight boundaries. These compartment boundaries play a crucial role in tissue patterning and growth by stably positioning organizers. In Drosophila, the wing imaginal disc is subdivided into a dorsal and a ventral compartment. Cells of the dorsal, but not ventral, compartment express the selector gene apterous. Apterous expression sets in motion a gene regulatory cascade that leads to the activation of Notch signaling in a few cell rows on either side of the dorsoventral compartment boundary. Both Notch and apterous mutant clones disturb the separation of dorsal and ventral cells. Maintenance of the straight shape of the dorsoventral boundary involves a local increase in mechanical tension at cell bonds along the boundary. The mechanisms by which cell bond tension is locally increased however remain unknown. Here we use a combination of laser ablation of cell bonds, quantitative image analysis, and genetic mutants to show that Notch and Apterous are required to increase cell bond tension along the dorsoventral compartment boundary. Moreover, clonal expression of the Apterous target gene capricious results in cell separation and increased cell bond tension at the clone borders. Finally, using a vertex model to simulate tissue growth, we find that an increase in cell bond tension at the borders of cell clones, but not throughout the cell clone, can lead to cell separation. We conclude that Apterous and Notch maintain the characteristic straight shape of the dorsoventral compartment boundary by locally increasing cell bond tension. PMID:27552097
NASA Astrophysics Data System (ADS)
Wang, Qianxi; Manmi, Kawa; Calvisi, Michael L.
2015-02-01
Ultrasound contrast agents (UCAs) are microbubbles stabilized with a shell typically of lipid, polymer, or protein and are emerging as a unique tool for noninvasive therapies ranging from gene delivery to tumor ablation. While various models have been developed to describe the spherical oscillations of contrast agents, the treatment of nonspherical behavior has received less attention. However, the nonspherical dynamics of contrast agents are thought to play an important role in therapeutic applications, for example, enhancing the uptake of therapeutic agents across cell membranes and tissue interfaces, and causing tissue ablation. In this paper, a model for nonspherical contrast agent dynamics based on the boundary integral method is described. The effects of the encapsulating shell are approximated by adapting Hoff's model for thin-shell, spherical contrast agents. A high-quality mesh of the bubble surface is maintained by implementing a hybrid approach of the Lagrangian method and elastic mesh technique. The numerical model agrees well with a modified Rayleigh-Plesset equation for encapsulated spherical bubbles. Numerical analyses of the dynamics of UCAs in an infinite liquid and near a rigid wall are performed in parameter regimes of clinical relevance. The oscillation amplitude and period decrease significantly due to the coating. A bubble jet forms when the amplitude of ultrasound is sufficiently large, as occurs for bubbles without a coating; however, the threshold amplitude required to incite jetting increases due to the coating. When a UCA is near a rigid boundary subject to acoustic forcing, the jet is directed towards the wall if the acoustic wave propagates perpendicular to the boundary. When the acoustic wave propagates parallel to the rigid boundary, the jet direction has components both along the wave direction and towards the boundary that depend mainly on the dimensionless standoff distance of the bubble from the boundary. In all cases, the jet
NASA Astrophysics Data System (ADS)
Tamura, Tomoyuki; Karasuyama, Masayuki; Kobayashi, Ryo; Arakawa, Ryuichi; Shiihara, Yoshinori; Takeuchi, Ichiro
2017-10-01
We propose a new scheme based on machine learning for the efficient screening in grain-boundary (GB) engineering. A set of results obtained from first-principles calculations based on density functional theory (DFT) for a small number of GB systems is used as a training data set. In our scheme, by partitioning the total energy into atomic energies using a local-energy analysis scheme, we can increase the training data set significantly. We use atomic radial distribution functions and additional structural features as atom descriptors to predict atomic energies and GB energies simultaneously using the least absolute shrinkage and selection operator, which is a recent standard regression technique in statistical machine learning. In the test study with fcc-Al [110] symmetric tilt GBs, we could achieve enough predictive accuracy to understand energy changes at and near GBs at a glance, even if we collected training data from only 10 GB systems. The present scheme can emulate time-consuming DFT calculations for large GB systems with negligible computational costs, and thus enable the fast screening of possible alternative GB systems.
NASA Technical Reports Server (NTRS)
Kaufman, A. J.; Knoll, A. H.; Semikhatov, M. A.; Grotzinger, J. P.; Jacobsen, S. B.; Adams, W.
1996-01-01
Carbonate-rich sedimentary rocks of the western Anabar region, northern Siberia, preserve an exceptional record of evolutionary and biogeochemical events near the Proterozoic/Cambrian boundary. Sedimentologically, the boundary succession can be divided into three sequences representing successive episodes of late transgressive to early highstand deposition; four parasequences are recognized in the sequence corresponding lithostratigraphically to the Manykal Formation. Small shelly fossils are abundant and include many taxa that also occur in standard sections of southeastern Siberia. Despite this coincidence of faunal elements, biostratigraphic correlations between the two regions have been controversial because numerous species that first appear at or immediately above the basal Tommotian boundary in southeastern sections have first appearances scattered through more than thirty metres of section in the western Anabar. Carbon- and Sr-isotopic data on petrographically and geochemically screened samples collected at one- to two-metre intervals in a section along the Kotuikan River, favour correlation of the Staraya Reckha Formation and most of the overlying Manykai Formation with sub-Tommotian carbonates in southeastern Siberia. In contrast, isotopic data suggest that the uppermost Manykai Formation and the basal 26 m of the unconformably overlying Medvezhya Formation may have no equivalent in the southeast; they appear to provide a sedimentary and palaeontological record of an evolutionarily significant time interval represented in southeastern Siberia only by the sub-Tommotian unconformity. Correlations with radiometrically dated horizons in the Olenek and Kharaulakh regions of northern Siberia suggest that this interval lasted approximately three to six million years, during which essentially all 'basal Tommotian' small shelly fossils evolved.
NASA Technical Reports Server (NTRS)
Kaufman, A. J.; Knoll, A. H.; Semikhatov, M. A.; Grotzinger, J. P.; Jacobsen, S. B.; Adams, W.
1996-01-01
Carbonate-rich sedimentary rocks of the western Anabar region, northern Siberia, preserve an exceptional record of evolutionary and biogeochemical events near the Proterozoic/Cambrian boundary. Sedimentologically, the boundary succession can be divided into three sequences representing successive episodes of late transgressive to early highstand deposition; four parasequences are recognized in the sequence corresponding lithostratigraphically to the Manykal Formation. Small shelly fossils are abundant and include many taxa that also occur in standard sections of southeastern Siberia. Despite this coincidence of faunal elements, biostratigraphic correlations between the two regions have been controversial because numerous species that first appear at or immediately above the basal Tommotian boundary in southeastern sections have first appearances scattered through more than thirty metres of section in the western Anabar. Carbon- and Sr-isotopic data on petrographically and geochemically screened samples collected at one- to two-metre intervals in a section along the Kotuikan River, favour correlation of the Staraya Reckha Formation and most of the overlying Manykai Formation with sub-Tommotian carbonates in southeastern Siberia. In contrast, isotopic data suggest that the uppermost Manykai Formation and the basal 26 m of the unconformably overlying Medvezhya Formation may have no equivalent in the southeast; they appear to provide a sedimentary and palaeontological record of an evolutionarily significant time interval represented in southeastern Siberia only by the sub-Tommotian unconformity. Correlations with radiometrically dated horizons in the Olenek and Kharaulakh regions of northern Siberia suggest that this interval lasted approximately three to six million years, during which essentially all 'basal Tommotian' small shelly fossils evolved.
NASA Astrophysics Data System (ADS)
Ander Arrillaga, Jon; Bosveld, Fred; Jiménez, Pedro A.; Baltink, Henk K.; Yagüe, Carlos; Hensen, Arjan; van Dinther, Danielle; Frumau, Arnoud; Dudhia, Jimy; Zhao, Wanjun; Vilà-Guerau de Arellano, Jordi
2017-04-01
The diurnal evolution of the Atmospheric Boundary Layer (ABL) in Cabauw (Netherlands) is investigated by considering the role of local and non-local forcings. By local, we understand, the surface fluxes that drive the growing of the ABL in addition to the non-local entrained fluxes. We study potential disruptions occurring in spring and particularly in summer driven by the formation of sea-breeze flows in the form of density currents, due to the proximity of both The North Sea and the Ijsselmeer closed sea. Moreover, this interactive system of surface, boundary layer and mesoscale may play a role in the transport of carbon dioxide and its diurnal variability. Our method is based on the analysis of a comprehensive 10-yr observational database (2001-2010), which gives the opportunity to understand the ABL dynamics from a robust perspective. To support the analysis, modelling results obtained from the WRF mesoscale model are available during the entire 10-year period. The model is run every 48 h to maintain it close to the synoptic conditions calculated by the ERA-Interim state. A fine horizontal resolution of 2 km is used, and the vertical levels are set to match the observational ones (2, 10, 20, 40, 80, 140 and 200 m). In order to identify the sea-breeze arrival, we apply a sea-breeze criteria selection algorithm. It is developed and adapted after a sea-breeze observational study in the Cantabrian Coast (Spain) to filter the sea-breeze events occurring in Cabauw, and consequently analyse their impact in the ABL and the surface fluxes. Preliminary results show that this criteria is able to distinguish between the two main wind directions related to the sea breeze in Cabauw. Our finding shows that the sea-breeze days are characterized by a sharp increment of the wind speed and a noticeable increase of the specific humidity at around 16-17 UTC.
Path-integral Monte Carlo method for the local Z2 Berry phase.
Motoyama, Yuichi; Todo, Synge
2013-02-01
We present a loop cluster algorithm Monte Carlo method for calculating the local Z(2) Berry phase of the quantum spin models. The Berry connection, which is given as the inner product of two ground states with different local twist angles, is expressed as a Monte Carlo average on the worldlines with fixed spin configurations at the imaginary-time boundaries. The "complex weight problem" caused by the local twist is solved by adopting the meron cluster algorithm. We present the results of simulation on the antiferromagnetic Heisenberg model on an out-of-phase bond-alternating ladder to demonstrate that our method successfully detects the change in the valence bond pattern at the quantum phase transition point. We also propose that the gauge-fixed local Berry connection can be an effective tool to estimate precisely the quantum critical point.
Integrated approach to improving local CD uniformity in EUV patterning
NASA Astrophysics Data System (ADS)
Liang, Andrew; Hermans, Jan; Tran, Timothy; Viatkina, Katja; Liang, Chen-Wei; Ward, Brandon; Chuang, Steven; Yu, Jengyi; Harm, Greg; Vandereyken, Jelle; Rio, David; Kubis, Michael; Tan, Samantha; Dusa, Mircea; Singhal, Akhil; van Schravendijk, Bart; Dixit, Girish; Shamma, Nader
2017-03-01
Extreme ultraviolet (EUV) lithography is crucial to enabling technology scaling in pitch and critical dimension (CD). Currently, one of the key challenges of introducing EUV lithography to high volume manufacturing (HVM) is throughput, which requires high source power and high sensitivity chemically amplified photoresists. Important limiters of high sensitivity chemically amplified resists (CAR) are the effects of photon shot noise and resist blur on the number of photons received and of photoacids generated per feature, especially at the pitches required for 7 nm and 5 nm advanced technology nodes. These stochastic effects are reflected in via structures as hole-to-hole CD variation or local CD uniformity (LCDU). Here, we demonstrate a synergy of film stack deposition, EUV lithography, and plasma etch techniques to improve LCDU, which allows the use of high sensitivity resists required for the introduction of EUV HVM. Thus, to improve LCDU to a level required by 5 nm node and beyond, film stack deposition, EUV lithography, and plasma etch processes were combined and co-optimized to enhance LCDU reduction from synergies. Test wafers were created by depositing a pattern transfer stack on a substrate representative of a 5 nm node target layer. The pattern transfer stack consisted of an atomically smooth adhesion layer and two hardmasks and was deposited using the Lam VECTOR PECVD product family. These layers were designed to mitigate hole roughness, absorb out-of-band radiation, and provide additional outlets for etch to improve LCDU and control hole CD. These wafers were then exposed through an ASML NXE3350B EUV scanner using a variety of advanced positive tone EUV CAR. They were finally etched to the target substrate using Lam Flex dielectric etch and Kiyo conductor etch systems. Metrology methodologies to assess dimensional metrics as well as chip performance and defectivity were investigated to enable repeatable patterning process development. Illumination
NASA Technical Reports Server (NTRS)
Henry, Donald P., Jr.; Banerjee, Prasanta K.
1988-01-01
New two- and three-dimensional BEM formulations are developed for steady-state and transient uncoupled thermoelasticity. These new procedures differ from previous work in that additional surface of volume integration is not required to incorporate thermal loads in the analysis. Instead, thermal body forces are introduced in the BEM system via particular integrals. The present formulation is implemented in a general-purpose multiregion system, and examples are presented to demonstrate the accuracy and versatility of the method.
NASA Technical Reports Server (NTRS)
Henry, Donald P., Jr.; Banerjee, Prasanta K.
1988-01-01
New two- and three-dimensional BEM formulations are developed for steady-state and transient uncoupled thermoelasticity. These new procedures differ from previous work in that additional surface of volume integration is not required to incorporate thermal loads in the analysis. Instead, thermal body forces are introduced in the BEM system via particular integrals. The present formulation is implemented in a general-purpose multiregion system, and examples are presented to demonstrate the accuracy and versatility of the method.
Yan, Zai You; Hung, Kin Chew; Zheng, Hui
2003-05-01
Regularization of the hypersingular integral in the normal derivative of the conventional Helmholtz integral equation through a double surface integral method or regularization relationship has been studied. By introducing the new concept of discretized operator matrix, evaluation of the double surface integrals is reduced to calculate the product of two discretized operator matrices. Such a treatment greatly improves the computational efficiency. As the number of frequencies to be computed increases, the computational cost of solving the composite Helmholtz integral equation is comparable to that of solving the conventional Helmholtz integral equation. In this paper, the detailed formulation of the proposed regularization method is presented. The computational efficiency and accuracy of the regularization method are demonstrated for a general class of acoustic radiation and scattering problems. The radiation of a pulsating sphere, an oscillating sphere, and a rigid sphere insonified by a plane acoustic wave are solved using the new method with curvilinear quadrilateral isoparametric elements. It is found that the numerical results rapidly converge to the corresponding analytical solutions as finer meshes are applied.
Local integrals of motion in the two-site Anderson-Hubbard model
NASA Astrophysics Data System (ADS)
Wortis, R.; Kennett, Malcolm P.
2017-10-01
It has been proposed that the states of fully many-body localized systems can be described in terms of conserved local pseudospins. Due to the multitude of ways to define these, the explicit identification of the optimally local pseudospins in specific systems is non-trivial. Given continuing intense interest in the role of disorder in strongly correlated systems, we consider the disordered Hubbard model. By studying a small system we provide concrete examples of the form of local integrals of motion in the Anderson-Hubbard model. Moreover, we are able not only to identify the most local choice but also to explore the nature of the distribution of possible choices. We track the evolution of the optimally localized pseudospins as hopping and interactions are varied to move the system away from the trivially localized atomic limit.
Mur-Veeman, Ingrid; Hardy, Brian; Steenbergen, Marijke; Wistow, Gerald
2003-09-01
This paper addresses the impact of the public-private mix in the Dutch and English health and social care systems on the development and delivery of integrated care. Integrated care is conceived of as an organisational process of coordination which seeks to achieve seamless and continuous care, tailored to the patients' needs and based on a holistic view of the patient. We describe both systems' structures and characteristics from a historical perspective, which means that developments and processes within the systems are put in the spotlight. We demonstrate that the dividing- or fault-lines, such as the financial split between short-term and long-term care in the Netherlands and the divisions between health and social care as well as between the public, private and voluntary sectors in England have hindered integrated care development and delivery in both countries. Contradictory interests, differences in professional and organisational cultures, power relations, and mistrust between and within these sectors have had a clear impact on integrated care development and delivery within networks of public authorities and public and/or private providers. We explain these phenomena in terms of network theory as a basis for drawing lessons for policy makers and those developing integrated care networks.
Wave breaking over sloping beaches using a coupled boundary integral-level set method
Garzon, M.; Adalsteinsson, D.; Gray, L.; Sethian, J.A.
2003-12-08
We present a numerical method for tracking breaking waves over sloping beaches. We use a fully non-linear potential model for in-compressible, irrotational and inviscid flow, and consider the effects of beach topography on breaking waves. The algorithm uses a Boundary Element Method (BEM) to compute the velocity at the interface, coupled to a Narrow Band Level Set Method to track the evolving air/water interface, and an associated extension equation to update the velocity potential both on and off the interface. The formulation of the algorithm is applicable to two and three dimensional breaking waves; in this paper, we concentrate on two-dimensional results showing wave breaking and rollup, and perform numerical convergence studies and comparison with previous techniques.
Thinking outside Discipline Boundaries to Integrate Indian Education for All across the Curriculum
ERIC Educational Resources Information Center
Carjuzaa, Jioanna; Hunts, Holly
2013-01-01
The Montana Indian Education for All (IEFA) Act is an unprecedented reform effort 40 years in the making. In this paper we summarize the IEFA professional development opportunities provided to faculty at a land grant university in the western United States while highlighting a faculty member's personal efforts to integrate IEFA in a culturally…
Tello-Leal, Edgar; Chiotti, Omar; Villarreal, Pablo David
2012-12-01
The paper presents a methodology that follows a top-down approach based on a Model-Driven Architecture for integrating and coordinating healthcare services through cross-organizational processes to enable organizations providing high quality healthcare services and continuous process improvements. The methodology provides a modeling language that enables organizations conceptualizing an integration agreement, and identifying and designing cross-organizational process models. These models are used for the automatic generation of: the private view of processes each organization should perform to fulfill its role in cross-organizational processes, and Colored Petri Net specifications to implement these processes. A multi-agent system platform provides agents able to interpret Colored Petri-Nets to enable the communication between the Healthcare Information Systems for executing the cross-organizational processes. Clinical documents are defined using the HL7 Clinical Document Architecture. This methodology guarantees that important requirements for healthcare services integration and coordination are fulfilled: interoperability between heterogeneous Healthcare Information Systems; ability to cope with changes in cross-organizational processes; guarantee of alignment between the integrated healthcare service solution defined at the organizational level and the solution defined at technological level; and the distributed execution of cross-organizational processes keeping the organizations autonomy.
Is health systems integration being advanced through Local Health District planning?
Saunders, Carla; Carter, David J
2016-04-21
Objective Delivering genuine integrated health care is one of three strategic directions in the New South Wales (NSW) Government State Health Plan: Towards 2021. This study investigated the current key health service plan of each NSW Local Health District (LHD) to evaluate the extent and nature of health systems integration strategies that are currently planned.Methods A scoping review was conducted to identify common key principles and practices for successful health systems integration to enable the development of an appraisal tool to content assess LHD strategic health service plans.Results The strategies that are planned for health systems integration across LHDs focus most often on improvements in coordination, health care access and care delivery for complex at-risk patients across the care continuum by both state- and commonwealth-funded systems, providers and agencies. The most common reasons given for integrated activities were to reduce avoidable hospitalisation, avoid inappropriate emergency department attendance and improve patient care.Conclusions Despite the importance of health systems integration and finding that all NSW LHDs have made some commitment towards integration in their current strategic health plans, this analysis suggests that health systems integration is in relatively early development across NSW.What is known about the topic? Effective approaches to managing complex chronic diseases have been found to involve health systems integration, which necessitates sound communication and connection between healthcare providers across community and hospital settings. Planning based on current health systems integration knowledge to ensure the efficient use of scarce resources is a responsibility of all health systems.What does this paper add? Appropriate planning and implementation of health systems integration is becoming an increasingly important expectation and requirement of effective health systems. The present study is the first of its
Local CRH signaling promotes synaptogenesis and circuit integration of adult-born neurons
Garcia, Isabella; Quast, Kathleen B.; Huang, Longwen; Herman, Alexander M.; Selever, Jennifer; Deussing, Jan M.; Justice, Nicholas J.; Arenkiel, Benjamin R.
2014-01-01
Summary Neural activity either enhances or impairs de novo synaptogenesis and circuit integration of neurons, but how this activity is mechanistically relayed in the adult brain is largely unknown. Neuropeptide-expressing interneurons are widespread throughout the brain and are key candidates for conveying neural activity downstream via neuromodulatory pathways that are distinct from classical neurotransmission. With the goal of identifying signaling mechanisms that underlie neuronal circuit integration in the adult brain, we have virally traced local Corticotropin-releasing hormone (CRH)-expressing inhibitory interneurons with extensive presynaptic inputs onto new neurons that are continuously integrated into the adult rodent olfactory bulb. Local CRH signaling onto adult-born neurons promotes and/or stabilizes chemical synapses in the olfactory bulb, revealing a neuromodulatory mechanism for continued circuit plasticity, synapse formation, and integration of new neurons in the adult brain. PMID:25199688
Nonequilibrium quantum dynamics and transport: from integrability to many-body localization
NASA Astrophysics Data System (ADS)
Vasseur, Romain; Moore, Joel E.
2016-06-01
We review the non-equilibrium dynamics of many-body quantum systems after a quantum quench with spatial inhomogeneities, either in the Hamiltonian or in the initial state. We focus on integrable and many-body localized systems that fail to self-thermalize in isolation and for which the standard hydrodynamical picture breaks down. The emphasis is on universal dynamics, non-equilibrium steady states and new dynamical phases of matter, and on phase transitions far from thermal equilibrium. We describe how the infinite number of conservation laws of integrable and many-body localized systems lead to complex non-equilibrium states beyond the traditional dogma of statistical mechanics.
NASA Astrophysics Data System (ADS)
Jackson, M.; Eriksson, S.; Barbour, K.; Venator, S.; Mencin, D.; Prescott, W.
2006-12-01
EarthScope is an NSF-funded, national science initiative to explore the structure and evolution of the North American continent and to understand the physical processes controlling earthquakes and volcanoes. This large-scale experiment provides locally based opportunities for education and outreach which engage students at various levels and the public. UNAVCO is responsible for the Plate Boundary Observatory (PBO) component of EarthScope. PBO includes the installation and operations and maintenance of large networks of Global Positioning Satellite (GPS), strainmeter, seismometer, and tiltmeter instruments and the acquisition of satellite radar imagery, all of which will be used to measure and map the smallest movements across faults, the magma movement inside active volcanoes and the very wide areas of deformation associated with plate tectonic motion. UNAVCO, through its own education and outreach activities and in collaboration with the EarthScope E&O Program, uses the PBO construction activities to increase the understanding and public appreciation of geodynamics, earth deformation processes, and their relevance to society. These include programs for public outreach via various media, events associated with local installations, a program to employ students in the construction of PBO, and development of curricular materials by use in local schools associated with the EarthScope geographic areas of focus. PBO provides information to the media to serve the needs of various groups and localities, including interpretive centers at national parks and forests, such as Mt. St. Helens. UNAVCO staff contributed to a television special with the Spanish language network Univision Aquí y Ahora program focused on the San Andreas Fault and volcanoes in Alaska. PBO participated in an Education Day at the Pathfinder Ranch Science and Outdoor Education School in Mountain Center, California. Pathfinder Ranch hosts two of the eight EarthScope borehole strainmeters in the Anza
Gurkan, Umut Atakan; Tasoglu, Savas; Akkaynak, Derya; Avci, Oguzhan; Unluisler, Sebnem; Canikyan, Serli; Maccallum, Noah; Demirci, Utkan
2012-09-01
Stimuli responsive, smart interface materials are integrated with microfluidic technologies creating new functions for a broad range of biological and clinical applications by controlling the material and cell interactions. Local capture and on-demand local release of cells are demonstrated with spatial and temporal control in a microfluidic system. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
NASA Astrophysics Data System (ADS)
Dineva, Petia; Rangelov, Tsviatko
2016-12-01
Elastic wave scattering by cracks at macro- and nano-scale in anisotropic plane under conditions of plane strain is studied in this work. Furthermore, time-harmonic loads due to incident plane longitudinal P- or shear SV- wave are assumed to hold. In a subsequent step, the elastodynamic fundamental solution for general anisotropic continua derived in closed-form via the Radon transform is implemented in a numerical scheme based on the traction boundary integral equation method (BIEM). The surface elasticity effect in the case of nano-crack is taken into consideration via non-classical boundary condition along the crack surface proposed by Gurtin and Murdoch [1]. The numerical results obtained herein reveal substantial differences between anisotropic materials containing a macro- and a nano-crack in terms of their dynamic stress response, where the latter case demonstrates clearly the strong influence of the size-effects. Finally, these types of examples serve to illustrate the present approach and to show its potential for evaluating the stress concentration fields (SCF) inside cracked nanocomposites. The obtained results concern the reliability and safety of the advancing nanomaterials.
NASA Technical Reports Server (NTRS)
Lua, Yuan J.; Liu, Wing K.; Belytschko, Ted
1993-01-01
In this paper, the mixed boundary integral equation method is developed to study the elastic interactions of a fatigue crack and a micro-defect such as a void, a rigid inclusion or a transformation inclusion. The method of pseudo-tractions is employed to study the effect of a transformation inclusion. An enriched element which incorporates the mixed-mode stress intensity factors is applied to characterize the singularity at a moving crack tip. In order to evaluate the accuracy of the numerical procedure, the analysis of a crack emanating from a circular hole in a finite plate is performed and the results are compared with the available numerical solution. The effects of various micro-defects on the crack path and fatigue life are investigated. The results agree with the experimental observations.
NASA Technical Reports Server (NTRS)
Hu, Fang; Pizzo, Michelle E.; Nark, Douglas M.
2017-01-01
It has been well-known that under the assumption of a constant uniform mean flow, the acoustic wave propagation equation can be formulated as a boundary integral equation, in both the time domain and the frequency domain. Compared with solving partial differential equations, numerical methods based on the boundary integral equation have the advantage of a reduced spatial dimension and, hence, requiring only a surface mesh. However, the constant uniform mean flow assumption, while convenient for formulating the integral equation, does not satisfy the solid wall boundary condition wherever the body surface is not aligned with the uniform mean flow. In this paper, we argue that the proper boundary condition for the acoustic wave should not have its normal velocity be zero everywhere on the solid surfaces, as has been applied in the literature. A careful study of the acoustic energy conservation equation is presented that shows such a boundary condition in fact leads to erroneous source or sink points on solid surfaces not aligned with the mean flow. A new solid wall boundary condition is proposed that conserves the acoustic energy and a new time domain boundary integral equation is derived. In addition to conserving the acoustic energy, another significant advantage of the new equation is that it is considerably simpler than previous formulations. In particular, tangential derivatives of the solution on the solid surfaces are no longer needed in the new formulation, which greatly simplifies numerical implementation. Furthermore, stabilization of the new integral equation by Burton-Miller type reformulation is presented. The stability of the new formulation is studied theoretically as well as numerically by an eigenvalue analysis. Numerical solutions are also presented that demonstrate the stability of the new formulation.
Integrating local and CRI online documentation using SGML and DynaWeb
Shuler, V.; Girill, T.R.
1997-04-01
This paper tells how Lawrence Livermore National Laboratory enriched CRI`s online documentation set by publishing local manuals using the same SGML DTD used by CRI and delivered using (a more sophisticated version of) the same World Wide Web server (DynaWeb3.0). This approach supports flexible local content and styles, yet integrates local and CRI manuals through one access mechanism and user interface. We explain the basic strategy involved, compare the benefits of this approach with three alternatives, and discuss the problems to which it gives rise.
Local time of Lévy random walks: A path integral approach
NASA Astrophysics Data System (ADS)
Zatloukal, Václav
2017-05-01
The local time of a stochastic process quantifies the amount of time that sample trajectories x (τ ) spend in the vicinity of an arbitrary point x . For a generic Hamiltonian, we employ the phase-space path-integral representation of random walk transition probabilities in order to quantify the properties of the local time. For time-independent systems, the resolvent of the Hamiltonian operator proves to be a central tool for this purpose. In particular, we focus on the local times of Lévy random walks (Lévy flights), which correspond to fractional diffusion equations.
NASA Astrophysics Data System (ADS)
Sezen-Barrie, Asli; Moore, Joel; Roig, Cara E.
2015-08-01
Drawn from the norms and rules of their fields, scientists use variety of practices, such as asking questions and arguing based on evidence, to engage in research that will contribute to our understanding of Earth and beyond. In this study, we explore how preservice teachers' learn to teach scientific practices while teaching plate tectonic theory. In particular, our aim is to observe which scientific practices preservice teachers use while teaching an earth science unit, how do they integrate these practices into their lessons, and what challenges do they face during their first time teaching of an earth science content area integrated with scientific practices. The study is designed as a qualitative, exploratory case study of seven preservice teachers while they were learning to teach plate tectonic theory to a group of middle school students. The data were driven from the video records and artifacts of the preservice teachers' learning and teaching processes as well as written reflections on the teaching. Intertextual discourse analysis was used to understand what scientific practices preservice teachers choose to integrate into their teaching experience. Our results showed that preservice teachers chose to focus on four aspects of scientific practices: (1) employing historical understanding of how the theory emerged, (2) encouraging the use of evidence to build up a theory, (3) observation and interpretation of data maps, and (4) collaborative practices in making up the theory. For each of these practices, we also looked at the common challenges faced by preservice teachers by using constant comparative analysis. We observed the practices that preservice teachers decided to use and the challenges they faced, which were determined by what might have come as in their personal history as learners. Therefore, in order to strengthen preservice teachers' background, college courses should be arranged to teach important scientific ideas through scientific practices
NASA Astrophysics Data System (ADS)
Søe-Knudsen, A.; Sorokin, S. V.
2010-09-01
The combined methodology of boundary integral equations and finite elements is formulated and applied to study the wave propagation phenomena in compound piping systems consisting of straight and curved pipe segments with compact elastic supports. This methodology replicates the concept of hierarchical boundary integral equations method proposed by L. I. Slepyan to model the time-harmonic wave propagation in wave guides, which have components of different dimensions. However, the formulation presented in this article is tuned to match the finite element format, and therefore, it employs the dynamical stiffness matrix to describe wave guide properties of all components of the assembled structure. This matrix may readily be derived from the boundary integral equations, and such a derivation is superior over the conventional derivation from the transfer matrix. The proposed methodology is verified in several examples and applied for analysis of periodicity effects in compound piping systems of several alternative layouts.
NASA Astrophysics Data System (ADS)
Howe, M.; Moulik, P.; Seeber, L.; Kim, W.; Steckler, M. S.
2012-12-01
The Himalayan and the Burma Arcs converge onto the Indian plate from opposite sides near their syntaxial juncture and have reduced it to a sliver. Both geology and seismicity point to recent internal deformation and high seismogenic potential within this sliver. Large historical earthquakes, including the Great Indian earthquake of 1897 (Mw ~8.1), along with the recent seismicity, suggest that the cratonic blocks in the region are bounded by active faults. The most prominent is the E-W trending Dauki Fault, a deeply-rooted, north-dipping thrust fault, situated between the Shillong massif to the north and the Sylhet Basin to the south. Along the Burma Arc, the subducted seismogenic slab of the Indian plate is continuous north to the syntaxis. Yet the Naga and Tripura segments of the accretionary fold belt, respectively north and south of the easterly extrapolation of the Dauki fault, are distinct. Accretion has advanced far westward into the foredeep of the Dauki structure along the front of the Tripura segment, while it has remained stunted facing the uplifted Shillong massif along the Naga segment. Moreover, the Dauki topographic front can be traced eastwards across the Burma Arc separating the two segments. Recent earthquakes support the hypothesis that the Dauki convergence structure continues below the Burma accretionary belt. Using teleseismic and regional data from the deployment of a local network, we explore the interaction of the Dauki thrust fault with the Burma Arc subduction zone. Preliminary observations include: While seismicity is concentrated in the slab at the eastward extrapolation of the Dauki fault, shallow seismicity is diffuse and does not illuminate the Dauki fault itself. P-axes in moment-tensor solutions of earthquakes within the Indian plate tend to be directed N-S and are locally parallel to the India-Burma boundary, particularly in the slab. T-axes tend to be oriented E-W with a strong tendency to follow the slab down dip. This pattern
Bernhard, Stefan; Möhlenkamp, Stefan; Tilgner, Andreas
2006-01-01
Background The pressure drop – flow relations in myocardial bridges and the assessment of vascular heart disease via fractional flow reserve (FFR) have motivated many researchers the last decades. The aim of this study is to simulate several clinical conditions present in myocardial bridges to determine the flow reserve and consequently the clinical relevance of the disease. From a fluid mechanical point of view the pathophysiological situation in myocardial bridges involves fluid flow in a time dependent flow geometry, caused by contracting cardiac muscles overlying an intramural segment of the coronary artery. These flows mostly involve flow separation and secondary motions, which are difficult to calculate and analyse. Methods Because a three dimensional simulation of the haemodynamic conditions in myocardial bridges in a network of coronary arteries is time-consuming, we present a boundary layer model for the calculation of the pressure drop and flow separation. The approach is based on the assumption that the flow can be sufficiently well described by the interaction of an inviscid core and a viscous boundary layer. Under the assumption that the idealised flow through a constriction is given by near-equilibrium velocity profiles of the Falkner-Skan-Cooke (FSC) family, the evolution of the boundary layer is obtained by the simultaneous solution of the Falkner-Skan equation and the transient von-Kármán integral momentum equation. Results The model was used to investigate the relative importance of several physical parameters present in myocardial bridges. Results have been obtained for steady and unsteady flow through vessels with 0 – 85% diameter stenosis. We compare two clinical relevant cases of a myocardial bridge in the middle segment of the left anterior descending coronary artery (LAD). The pressure derived FFR of fixed and dynamic lesions has shown that the flow is less affected in the dynamic case, because the distal pressure partially recovers
Bernhard, Stefan; Möhlenkamp, Stefan; Tilgner, Andreas
2006-06-21
The pressure drop-flow relations in myocardial bridges and the assessment of vascular heart disease via fractional flow reserve (FFR) have motivated many researchers the last decades. The aim of this study is to simulate several clinical conditions present in myocardial bridges to determine the flow reserve and consequently the clinical relevance of the disease. From a fluid mechanical point of view the pathophysiological situation in myocardial bridges involves fluid flow in a time dependent flow geometry, caused by contracting cardiac muscles overlying an intramural segment of the coronary artery. These flows mostly involve flow separation and secondary motions, which are difficult to calculate and analyse. Because a three dimensional simulation of the haemodynamic conditions in myocardial bridges in a network of coronary arteries is time-consuming, we present a boundary layer model for the calculation of the pressure drop and flow separation. The approach is based on the assumption that the flow can be sufficiently well described by the interaction of an inviscid core and a viscous boundary layer. Under the assumption that the idealised flow through a constriction is given by near-equilibrium velocity profiles of the Falkner-Skan-Cooke (FSC) family, the evolution of the boundary layer is obtained by the simultaneous solution of the Falkner-Skan equation and the transient von-Kármán integral momentum equation. The model was used to investigate the relative importance of several physical parameters present in myocardial bridges. Results have been obtained for steady and unsteady flow through vessels with 0 - 85% diameter stenosis. We compare two clinical relevant cases of a myocardial bridge in the middle segment of the left anterior descending coronary artery (LAD). The pressure derived FFR of fixed and dynamic lesions has shown that the flow is less affected in the dynamic case, because the distal pressure partially recovers during re-opening of the vessel in
S.R. Hudson; D.A. Monticello; A.H. Reiman; D.J. Strickler; S.P. Hirshman; L-P. Ku; E. Lazarus; A. Brooks; M.C. Zarnstorff; A.H. Boozer; G-Y. Fu; and G.H. Neilson
2003-09-15
For the (non-axisymmetric) stellarator class of plasma confinement devices to be feasible candidates for fusion power stations it is essential that, to a good approximation, the magnetic field lines lie on nested flux surfaces; however, the inherent lack of a continuous symmetry implies that magnetic islands responsible for breaking the smooth topology of the flux surfaces are guaranteed to exist. Thus, the suppression of magnetic islands is a critical issue for stellarator design, particularly for small aspect ratio devices. Pfirsch-Schluter currents, diamagnetic currents, and resonant coil fields contribute to the formation of magnetic islands, and the challenge is to design the plasma and coils such that these effects cancel. Magnetic islands in free-boundary high-pressure full-current stellarator magnetohydrodynamic equilibria are suppressed using a procedure based on the Princeton Iterative Equilibrium Solver [Reiman and Greenside, Comp. Phys. Comm. 43 (1986) 157] which iterate s the equilibrium equations to obtain the plasma equilibrium. At each iteration, changes to a Fourier representation of the coil geometry are made to cancel resonant fields produced by the plasma. The changes are constrained to preserve certain measures of engineering acceptability and to preserve the stability of ideal kink modes. As the iterations continue, the coil geometry and the plasma simultaneously converge to an equilibrium in which the island content is negligible, the plasma is stable to ideal kink modes, and the coils satisfy engineering constraints. The method is applied to a candidate plasma and coil design for the National Compact Stellarator Experiment [Reiman, et al., Phys. Plasmas 8 (May 2001) 2083].
Local fracture properties and dissimilar weld integrity in nuclear power plants
NASA Astrophysics Data System (ADS)
Wang, Guozhen; Wang, Haitao; Xuan, Fuzhen; Tu, Shantung; Liu, Changjun
2013-09-01
In this paper, the local fracture properties in a Alloy52M dissimilar metal welded joint (DMWJ) between A508 ferritic steel and 316 L stainless steel in nuclear power plants were investigated by using the single-edge notched bend (SENB) specimens, and their use in integrity assessment of DMWJ structures was analyzed. The results show that the local fracture resistance in the DMWJ is determined by local fracture mechanism, and which is mainly related to the microstructures and local strength mismatches of materials at the crack locations. The initial cracks always grow towards the materials with lower strength, and the crack path deviation is mainly controlled by the local strength mismatch. If the local fracture properties could not be used for cracks in the heat affected zones (HAZs), interface and near interface zones, the use of the fracture properties ( J-resistance curves) of base metals or weld metals following present codes will unavoidably produce non-conservative (unsafe) or excessive conservative assessment results. In most cases, the assessment results will be potentially unsafe. Therefore, it is recommended to obtain and use local mechanical and fracture properties in the integrity assessment of DMWJs.
NASA Astrophysics Data System (ADS)
Chuvil'deev, V. N.; Kopylov, V. I.; Nokhrin, A. V.; Bakhmet'ev, A. M.; Sandler, N. G.; Tryaev, P. V.; Kozlova, N. A.; Tabachkova, N. Yu.; Mikhailov, A. S.; Chegurov, M. K.; Smirnova, E. S.
2017-01-01
The influence of the structural-phase state of grain boundaries in a Ti4Al2V (commercial PT3V grade) pseudo-alpha-titanium alloy on its susceptibility to hot-salt intergranular corrosion (IGC) has been studied. It is established that IGC-tested alloy samples exhibit corrosion-induced defects of two types. More extended defects of the first type occur at the V-rich boundaries of coarse grains, while short defects of the second type reside at the grain boundaries with composition close to that of the grain body. The existence of the two types of IGC defects is explained by the classical theory of galvanic microcouples (microcells), according to which the IGC intensity is proportional to the difference of corrosion-active impurity concentrations between the grain boundary and body.
An Integrated Online Library System as a Node in a Local Area Network: The Mitre Experience.
ERIC Educational Resources Information Center
Kidwell, Mary Coyle
1987-01-01
Discusses the Mitre Corporation's implementation of OCLC's LS/2000 integrated library system using a local area network (LAN). LAN issues--requirements, equipment, reliability, growth, security, and traffic--are covered in general and as they relate to Mitre. Installation of the LAN/system interface and benefits and drawbacks of using a LAN for…
An Integrated Program Structure and System of Account Codes for PPBS in Local School Districts.
ERIC Educational Resources Information Center
Miller, Donald R.
This monograph presents a comprehensive but tentative matrix program structure and system of account codes that have been integrated to facilitate the implementation of PPB systems in local school districts. It is based on the results of an extensive analysis of K-12 public school district programs and management practices. In its entirety, the…
NASA Technical Reports Server (NTRS)
Sloss, J. M.; Kranzler, S. K.
1972-01-01
The equivalence of a considered integral equation form with an infinite system of linear equations is proved, and the localization of the eigenvalues of the infinite system is expressed. Error estimates are derived, and the problems of finding upper bounds and lower bounds for the eigenvalues are solved simultaneously.
A Tough-Love Pedagogy in Rehabilitation: Integration of Rehabilitation Ideology with Local Cultures
ERIC Educational Resources Information Center
Chang, Ling-Hui; Wang, Jye
2009-01-01
This study problematizes a unique therapeutic relationship in rehabilitation and how the interaction reflects the integration of rehabilitation ideology with local cultures. The data drew from a larger ethnographic study of a rehabilitation unit in Taiwan. Participants included 21 patient-caregiver pairs and their rehabilitation professionals.…
ERIC Educational Resources Information Center
Bodzin, Alec M.
2008-01-01
The author describes an after-school science club program for urban 4th-grade students that integrated instructional technologies to investigate a pond ecosystem in the local schoolyard. The author conducted a design-based evaluation study to examine the effectiveness of the program in promoting environmental attitudes and understandings of the…
ERIC Educational Resources Information Center
Bodzin, Alec M.
2008-01-01
The author describes an after-school science club program for urban 4th-grade students that integrated instructional technologies to investigate a pond ecosystem in the local schoolyard. The author conducted a design-based evaluation study to examine the effectiveness of the program in promoting environmental attitudes and understandings of the…
ERIC Educational Resources Information Center
Carter, Erik W.; Blustein, Carly L.; Bumble, Jennifer L.; Harvey, Sarah; Henderson, Lynnette M.; McMillan, Elise D.
2016-01-01
Amidst decades of attention directed toward improving employment outcomes for people with intellectual and developmental disabilities (IDD), few efforts have been made to engage communities in identifying local solutions for expanding integrated employment opportunities. We examined the implementation and outcomes of "community…
The integration of local chromatic motion signals is sensitive to contrast polarity.
Wuerger, Sophie M; Ruppertsberg, Alexa; Malek, Stephanie; Bertamini, Marco; Martinovic, Jasna
2011-05-01
Global motion integration mechanisms can utilize signals defined by purely chromatic information. Is global motion integration sensitive to the polarity of such color signals? To answer this question, we employed isoluminant random dot kinematograms (RDKs) that contain a single chromatic contrast polarity or two different polarities. Single-polarity RDKs consisted of local motion signals with either a positive or a negative S or L-M component, while in the different-polarity RDKs, half the dots had a positive S or L-M component, and the other half had a negative S or L-M component. In all RDKs, the polarity and the motion direction of the local signals were uncorrelated. Observers discriminated between 50% coherent motion and random motion, and contrast thresholds were obtained for 81% correct responses. Contrast thresholds were obtained for three different dot densities (50, 100, and 200 dots). We report two main findings: (1) dependence on dot density is similar for both contrast polarities (+S vs. -S, +LM vs. -LM) but slightly steeper for S in comparison to LM and (2) thresholds for different-polarity RDKs are significantly higher than for single-polarity RDKs, which is inconsistent with a polarity-blind integration mechanism. We conclude that early motion integration mechanisms are sensitive to the polarity of the local motion signals and do not automatically integrate information across different polarities.
NASA Astrophysics Data System (ADS)
Warner, Thomas T.; Sheu, Rong-Shyang
2000-05-01
Four 6-day simulations of the atmospheric conditions over the Arabian Desert during the time of the 1991 detonation and release of toxic material at the Khamisiyah, Iraq, weapons depot were performed using a mesoscale model run in a data-assimilation mode. These atmospheric simulations are being employed in a forensic analysis of the potential contribution of the toxic material to so-called Gulf War illness. The transport and concentration of such surface-released contaminants are related strongly to the planetary boundary layer (PBL) depth and the horizontal wind speed in the PBL. The product of the PBL depth and the mean wind speed within it is referred to as the ventilation and is used as a metric of the horizontal transport within the PBL. Thus, a corollary study to the larger forensic analysis involves employing the model solutions and available data in an analysis of the multiscale spatial variability of the daytime desert PBL depth and ventilation as they are affected by surface forcing from terrain elevation variations, coastal circulations, and contrasts in surface physical properties.The coarsest computational grid spanned the entire northern Arabian Desert and surrounding areas of the Middle East, and represented the large-scale PBL modulation by the orography. The PBL depths were greatest over the high elevations of the western Arabian Peninsula and over the Zagros Mountains in western Iran and were shallowest over water bodies and the lower elevations in the Tigris-Euphrates Valley. Higher-resolution grids in the nest (the smallest grid increment was 3.3 km) showed that the PBL depth minimum in the Tigris-Euphrates Valley was likely a consequence of compensating subsidence associated with the thermally forced daytime upward motion over the Zagros Mountains to the east in Iran, with possible contributions from an elevated mixed layer. Further local modulation of the daytime desert PBL occurred as a result of the inland penetration of the coastal sea
Li, Lu; Peng, Hu; Chen, Xun; Cheng, Juan; Gao, Dayong
2016-04-01
Transfer function design is a key issue in direct volume rendering. Many sophisticated transfer functions have been proposed to visualize boundaries in volumetric data sets such as computed tomography and magnetic resonance imaging. However, it is still conventionally challenging to reliably detect boundaries. Meanwhile, the interactive strategy is complicated for new users or even experts. In this paper, we first propose the human-centric boundary extraction criteria and our boundary model. Based on the model we present a boundary visualization method through a what material you pick is what boundary you see approach. Users can pick out the material of interest to directly convey semantics. In addition, the 3-D canny edge detection is utilized to ensure the good localization of boundaries. Furthermore, we establish a point-to-material distance measure to guarantee the accuracy and integrity of boundaries. The proposed boundary visualization is intuitive and flexible for the exploration of volumetric data.
NASA Technical Reports Server (NTRS)
Yates, E. Carson, Jr.; Desmarais, Robert N.
1990-01-01
The technique of implicit differentiation has been used in combination with linearized lifting-surface theory to derive analytical expressions for aerodynamic sensitivities (i.e., rates of change of lifting pressures with respect to general changes in aircraft geometry, including planform variations) for steady or oscillating planar or nonplanar lifting surfaces in subsonic, sonic, or supersonic flow. The geometric perturbation is defined in terms of a single variable, and the user need only provide simple expressions or similar means for defining the continuous or discontinuous global or local perturbation of interest. Example expressions are given for perturbations of the sweep, taper, and aspect ratio of a wing with trapezoidal semispan planform. The present process appears to be readily adaptable to more general surface-panel methods.
The Local Integrity Approach for Urban Contexts: Definition and Vehicular Experimental Assessment.
Margaria, Davide; Falletti, Emanuela
2016-01-26
A novel cooperative integrity monitoring concept, called "local integrity", suitable to automotive applications in urban scenarios, is discussed in this paper. The idea is to take advantage of a collaborative Vehicular Ad hoc NETwork (VANET) architecture in order to perform a spatial/temporal characterization of possible degradations of Global Navigation Satellite System (GNSS) signals. Such characterization enables the computation of the so-called "Local Protection Levels", taking into account local impairments to the received signals. Starting from theoretical concepts, this paper describes the experimental validation by means of a measurement campaign and the real-time implementation of the algorithm on a vehicular prototype. A live demonstration in a real scenario has been successfully carried out, highlighting effectiveness and performance of the proposed approach.
NASA Technical Reports Server (NTRS)
Cahan, B. D.; Scherson, Daniel; Reid, Margaret A.
1988-01-01
A new algorithm for an iterative computation of solutions of Laplace's or Poisson's equations in two dimensions, using Green's second identity, is presented. This algorithm converges strongly and geometrically and can be applied to curved, irregular, or moving boundaries with nonlinear and/or discontinuous boundary conditions. It has been implemented in Pascal on a number of micro- and minicomputers and applied to several geometries. Cases with known analytic solutions have been tested. Convergence to within 0.1 percent to 0.01 percent of the theoretical values are obtained in a few minutes on a microcomputer.
NASA Technical Reports Server (NTRS)
Cahan, B. D.; Scherson, Daniel; Reid, Margaret A.
1988-01-01
A new algorithm for an iterative computation of solutions of Laplace's or Poisson's equations in two dimensions, using Green's second identity, is presented. This algorithm converges strongly and geometrically and can be applied to curved, irregular, or moving boundaries with nonlinear and/or discontinuous boundary conditions. It has been implemented in Pascal on a number of micro- and minicomputers and applied to several geometries. Cases with known analytic solutions have been tested. Convergence to within 0.1 percent to 0.01 percent of the theoretical values are obtained in a few minutes on a microcomputer.
NASA Astrophysics Data System (ADS)
Barnett, Alex H.; Nelson, Bradley J.; Mahoney, J. Matthew
2015-09-01
We apply boundary integral equations for the first time to the two-dimensional scattering of time-harmonic waves from a smooth obstacle embedded in a continuously-graded unbounded medium. In the case we solve, the square of the wavenumber (refractive index) varies linearly in one coordinate, i.e. (Δ + E +x2) u (x1 ,x2) = 0 where E is a constant; this models quantum particles of fixed energy in a uniform gravitational field, and has broader applications to stratified media in acoustics, optics and seismology. We evaluate the fundamental solution efficiently with exponential accuracy via numerical saddle-point integration, using the truncated trapezoid rule with typically 102 nodes, with an effort that is independent of the frequency parameter E. By combining with a high-order Nyström quadrature, we are able to solve the scattering from obstacles 50 wavelengths across to 11 digits of accuracy in under a minute on a desktop or laptop.
NASA Astrophysics Data System (ADS)
Sakaeta, Kuniyuki; Nonaka, Kenichiro; Sekiguchi, Kazuma
2016-09-01
Localization is an important function for the robots to complete various tasks. For localization, both internal and external sensors are used generally. The odometry is widely used as the method based on the internal sensors, but it suffers from cumulative errors. In the method using the laser range sensor (LRS) which is a kind of external sensor, the estimation accuracy is affected by the number of available measurement data. In our previous study, we applied moving horizon estimation (MHE) to the vehicle localization for integrating the LRS measurement data and the odometry information where the weightings of them are balanced relatively adapting to the number of the available LRS measurement data. In this paper, the effectiveness of the proposed localization method is verified through both numerical simulations and experiments using a 1/10 scale vehicle. The verification is conducted in the situations where the vehicle position cannot be localized uniquely on a certain direction using the LRS measurement data only. We achieve accurate localization even in such a situation by integrating the odometry and LRS based on MHE. We also show the superiority of the method through comparisons with a method using extended Kalman filter (EKF).
Monitoring the northern Chile megathrust with the Integrated Plate boundary Observatory Chile (IPOC)
NASA Astrophysics Data System (ADS)
Schurr, Bernd; Asch, Günter; Cailleau, Beatrice; Diaz, Guillermo Chong; Barrientos, Sergio; Vilotte, Jean-Pierre; Oncken, Onno
2010-05-01
thousand aftershocks during the following week using waveform cross-correlation and the double-difference algorithm. Aftershocks reveal that rupture during this earthquake was confined to the deeper part (35 - 55 km depth) of the seismogenic coupling zone, except near the Mejillones peninsula that marks rupture termination in the south. Here earthquake activity reaches to depths of 20 km and even shallower, possibly indicating upper plate activation. The sequence also features an M 6.8 earthquake that broke the oceanic slab on an almost vertical plane at the down-dip end of the megathrust rupture. Confrontation with the aftershock distribution of the 1995 M 8.0 Antofagasta earthquake on the adjoining southern segment reveals an intriguing mirror symmetry with an axis crossing the Mejillones peninsula, emphasizing the penisula's significance as a segment boundary. Since then activity inside the remaining seismic gap to the north picked up with three earthquakes exceeding magnitude 6, maybe heralding the next great rupture.
NASA Astrophysics Data System (ADS)
Kahnert, Michael
2006-09-01
Explicit symmetry relations for the Green's function subject to homogeneous boundary conditions are derived for arbitrary linear differential or integral equation problems in which the boundary surface has a set of symmetry elements. For corresponding homogeneous problems subject to inhomogeneous boundary conditions implicit symmetry relations involving the Green's function are obtained. The usefulness of these symmetry relations is illustrated by means of a recently developed self-consistent Green's function formalism of electromagnetic and acoustic scattering problems applied to the exterior scattering problem. One obtains explicit symmetry relations for the volume Green's function, the surface Green's function, and the interaction operator, and the respective symmetry relations are shown to be equivalent. This allows us to treat boundary symmetries of volume-integral equation methods, boundary-integral equation methods, and the T matrix formulation of acoustic and electromagnetic scattering under a common theoretical framework. By specifying a specific expansion basis the coordinate-free symmetry relations of, e.g., the surface Green's function can be brought into the form of explicit symmetry relations of its expansion coefficient matrix. For the specific choice of radiating spherical wave functions the approach is illustrated by deriving unitary reducible representations of non-cubic finite point groups in this basis, and by deriving the corresponding explicit symmetry relations of the coefficient matrix. The reducible representations can be reduced by group-theoretical techniques, thus bringing the coefficient matrix into block-diagonal form, which can greatly reduce ill-conditioning problems in numerical applications.
NASA Astrophysics Data System (ADS)
Caffrey, Peter F.; Hoppel, William A.; Shi, Jainn J.
2006-12-01
The dynamics of aerosols in the marine boundary layer are simulated with a one-dimensional, multicomponent, sectional aerosol model using vertical profiles of turbulence, relative humidity, temperature, vertical velocity, cloud cover, and precipitation provided by 3-D mesoscale meteorological model output. The Naval Research Laboratory's (NRL) sectional aerosol model MARBLES (Fitzgerald et al., 1998a) was adapted to use hourly meteorological input taken from NRL's Coupled Ocean-Atmosphere Prediction System (COAMPS). COAMPS-generated turbulent mixing coefficients and large-scale vertical velocities determine vertical exchange within the marine boundary layer and exchange with the free troposphere. Air mass back trajectories were used to define the air column history along which the meteorology was retrieved for use with the aerosol model. Details on the integration of these models are described here, as well as a description of improvements made to the aerosol model, including transport by large-scale vertical motions (such as subsidence and lifting), a revised sea-salt aerosol source function, and separate tracking of sulfate mass from each of the five sources (free tropospheric, nucleated, condensed from gas phase oxidation products, cloud-processed, and produced from heterogeneous oxidation of S(IV) on sea-salt aerosol). Results from modeling air masses arriving at Oahu, Hawaii, are presented, and the relative contribution of free-tropospheric sulfate particles versus sea-salt aerosol from the surface to CCN concentrations is discussed. Limitations and benefits of the method are presented, as are sensitivity analyses of the effect of large-scale vertical motions versus turbulent mixing.
Pollonini, Luca; Re, Rebecca; Simpson, Richard J; Dacso, Clifford C
2012-01-01
Current methods for monitoring exercise exertion rely upon heart rate monitors, which represent a crude and lagging indicator of conditioning. The rationale for the present study is that both systemic and local metabolic mechanisms are responsible for physical performance, and therefore they should be simultaneously quantified to achieve an objective assessment of human conditioning. We propose a compact, wearable near-infrared spectroscopy (NIRS) device integrated with electrocardiography (ECG) and photoplethysmography (PPG) to simultaneously assess the cardiovascular and local response to exercise. The system was tested on subjects performing a graded maximal exercise by comparing our readings with metabolic variables measured with respiratory gas analysis. We found strong correlations between local deoxyhemoglobin concentration [HHb], heart rate and oxygen uptake, as well as between oxyhemoglobin concentration [HbO(2)] and stroke volume. This study shows that combined NIRS, ECG and PPG measurements yield useful information to understand the interplay between systemic and local muscular responses to exercise.
NASA Astrophysics Data System (ADS)
Korotaev, Valery V.; Denisov, Victor M.; Rodrigues, Joel J. P. C.; Serikova, Mariya G.; Timofeev, Andrey V.
2015-05-01
The paper deals with the creation of integrated monitoring systems. They combine fiber-optic classifiers and local sensor networks. These systems allow for the monitoring of complex industrial objects. Together with adjacent natural objects, they form the so-called geotechnical systems. An integrated monitoring system may include one or more spatially continuous fiber-optic classifiers based on optic fiber and one or more arrays of discrete measurement sensors, which are usually combined in sensor networks. Fiber-optic classifiers are already widely used for the control of hazardous extended objects (oil and gas pipelines, railways, high-rise buildings, etc.). To monitor local objects, discrete measurement sensors are generally used (temperature, pressure, inclinometers, strain gauges, accelerometers, sensors measuring the composition of impurities in the air, and many others). However, monitoring complex geotechnical systems require a simultaneous use of continuous spatially distributed sensors based on fiber-optic cable and connected local discrete sensors networks. In fact, we are talking about integration of the two monitoring methods. This combination provides an additional way to create intelligent monitoring systems. Modes of operation of intelligent systems can automatically adapt to changing environmental conditions. For this purpose, context data received from one sensor (e.g., optical channel) may be used to change modes of work of other sensors within the same monitoring system. This work also presents experimental results of the prototype of the integrated monitoring system.
NASA Astrophysics Data System (ADS)
Yong, Liu; Qichao, Hong; Lihua, Liang
1999-05-01
This paper presents an elasto-viscoplastic consistent tangent operator (CTO) based boundary element formulation, and application for calculation of path-domain independent J integrals (extension of the classical J integrals) in nonlinear crack analysis. When viscoplastic deformation happens, the effective stresses around the crack tip in the nonlinear region is allowed to exceed the loading surface, and the pure plastic theory is not suitable for this situation. The concept of consistency employed in the solution of increment viscoplastic problem, plays a crucial role in preserving the quadratic rate asymptotic convergence of iteractive schemes based on Newton's method. Therefore, this paper investigates the viscoplastic crack problem, and presents an implicit viscoplastic algorithm using the CTO concept in a boundary element framework for path-domain independent J integrals. Applications are presented with two numerical examples for viscoplastic crack problems and J integrals.
Case study of the integration of a local health department and a community health center.
Lambrew, J M; Ricketts, T C; Morrissey, J P
1993-01-01
As rural communities struggle to sustain health services locally, innovative alternatives to traditional programs are being developed. A significant adaptation is the rural health network or alliance that links local health departments and community health centers. The authors describe how a rural local health department and community health center, the core organizations in publicly sponsored primary care, came to share a building and administrative and service activities. Both the details of this alliance and its development are examined. The case history reveals that circumstance and State involvement were the catalysts for service integration, more so than the need for or the benefits of the arrangement. The closure of a county-owned hospital created a situation in which State officials were able to broker a cooperative agreement between the two agencies. This case study suggests two hypotheses: that need for integrated services alone may not be sufficient to catalyze the development of primary care alliances and that strong policy support may override any local and internal resistance to integration.
Fagerholm, Nora; Käyhkö, Niina; Van Eetvelde, Veerle
2013-09-01
In many developing countries, political documentation acknowledges the crucial elements of participation and spatiality for effective land use planning. However, operative approaches to spatial data inclusion and representation in participatory land management are often lacking. In this paper, we apply and develop an integrated landscape characterization approach to enhance spatial knowledge generation about the complex human-nature interactions in landscapes in the context of Zanzibar, Tanzania. We apply an integrated landscape conceptualization as a theoretical framework where the expert and local knowledge can meet in spatial context. The characterization is based on combining multiple data sources in GIS, and involves local communities and their local spatial knowledge since the beginning into the process. Focusing on the expected information needs for community forest management, our characterization integrates physical landscape features and retrospective landscape change data with place-specific community knowledge collected through participatory GIS techniques. The characterization is established in a map form consisting of four themes and their synthesis. The characterization maps are designed to support intuitive interpretation, express the inherently uncertain nature of the data, and accompanied by photographs to enhance communication. Visual interpretation of the characterization mediates information about the character of areas and places in the studied local landscape, depicting the role of forest resources as part of the landscape entity. We conclude that landscape characterization applied in GIS is a highly potential tool for participatory land and resource management, where spatial argumentation, stakeholder communication, and empowerment are critical issues.
NASA Astrophysics Data System (ADS)
Fagerholm, Nora; Käyhkö, Niina; Van Eetvelde, Veerle
2013-09-01
In many developing countries, political documentation acknowledges the crucial elements of participation and spatiality for effective land use planning. However, operative approaches to spatial data inclusion and representation in participatory land management are often lacking. In this paper, we apply and develop an integrated landscape characterization approach to enhance spatial knowledge generation about the complex human-nature interactions in landscapes in the context of Zanzibar, Tanzania. We apply an integrated landscape conceptualization as a theoretical framework where the expert and local knowledge can meet in spatial context. The characterization is based on combining multiple data sources in GIS, and involves local communities and their local spatial knowledge since the beginning into the process. Focusing on the expected information needs for community forest management, our characterization integrates physical landscape features and retrospective landscape change data with place-specific community knowledge collected through participatory GIS techniques. The characterization is established in a map form consisting of four themes and their synthesis. The characterization maps are designed to support intuitive interpretation, express the inherently uncertain nature of the data, and accompanied by photographs to enhance communication. Visual interpretation of the characterization mediates information about the character of areas and places in the studied local landscape, depicting the role of forest resources as part of the landscape entity. We conclude that landscape characterization applied in GIS is a highly potential tool for participatory land and resource management, where spatial argumentation, stakeholder communication, and empowerment are critical issues.
Schilling, Sabine; Willecke, Maria; Aegerter-Wilmsen, Tinri; Cirpka, Olaf A; Basler, Konrad; von Mering, Christian
2011-04-01
Non-intermingling, adjacent populations of cells define compartment boundaries; such boundaries are often essential for the positioning and the maintenance of tissue-organizers during growth. In the developing wing primordium of Drosophila melanogaster, signaling by the secreted protein Hedgehog (Hh) is required for compartment boundary maintenance. However, the precise mechanism of Hh input remains poorly understood. Here, we combine experimental observations of perturbed Hh signaling with computer simulations of cellular behavior, and connect physical properties of cells to their Hh signaling status. We find that experimental disruption of Hh signaling has observable effects on cell sorting surprisingly far from the compartment boundary, which is in contrast to a previous model that confines Hh influence to the compartment boundary itself. We have recapitulated our experimental observations by simulations of Hh diffusion and transduction coupled to mechanical tension along cell-to-cell contact surfaces. Intriguingly, the best results were obtained under the assumption that Hh signaling cannot alter the overall tension force of the cell, but will merely re-distribute it locally inside the cell, relative to the signaling status of neighboring cells. Our results suggest a scenario in which homotypic interactions of a putative Hh target molecule at the cell surface are converted into a mechanical force. Such a scenario could explain why the mechanical output of Hh signaling appears to be confined to the compartment boundary, despite the longer range of the Hh molecule itself. Our study is the first to couple a cellular vertex model describing mechanical properties of cells in a growing tissue, to an explicit model of an entire signaling pathway, including a freely diffusible component. We discuss potential applications and challenges of such an approach.
NASA Astrophysics Data System (ADS)
Zieniuk, Eugeniusz; Kapturczak, Marta; Sawicki, Dominik
2016-06-01
In solving of boundary value problems the shapes of the boundary can be modelled by the curves widely used in computer graphics. In parametric integral equations system (PIES) such curves are directly included into the mathematical formalism. Its simplify the way of definition and modification of the shape of the boundary. Until now in PIES the B-spline, Bézier and Hermite curves were used. Recent developments in the computer graphics paid our attention, therefore we implemented in PIES possibility of defining the shape of boundary using the NURBS curves. The curves will allow us to modeling different shapes more precisely. In this paper we will compare PIES solutions (with applied NURBS) with the solutions existing in the literature.
NASA Astrophysics Data System (ADS)
Shapkalijevski, Metodija M.; Ouwersloot, Huug G.; Moene, Arnold F.; Vilà-Guerau de Arrellano, Jordi
2017-02-01
By characterizing the dynamics of a convective boundary layer above a relatively sparse and uniform orchard canopy, we investigated the impact of the roughness-sublayer (RSL) representation on the predicted diurnal variability of surface fluxes and state variables. Our approach combined numerical experiments, using an atmospheric mixed-layer model including a land-surface-vegetation representation, and measurements from the Canopy Horizontal Array Turbulence Study (CHATS) field experiment near Dixon, California. The RSL is parameterized using an additional factor in the standard Monin-Obukhov similarity theory flux-profile relationships that takes into account the canopy influence on the atmospheric flow. We selected a representative case characterized by southerly wind conditions to ensure well-developed RSL over the orchard canopy. We then investigated the sensitivity of the diurnal variability of the boundary-layer dynamics to the changes in the RSL key scales, the canopy adjustment length scale, Lc, and the β = u*/|U| ratio at the top of the canopy due to their stability and dependence on canopy structure. We found that the inclusion of the RSL parameterization resulted in improved prediction of the diurnal evolution of the near-surface mean quantities (e.g. up to 50 % for the wind velocity) and transfer (drag) coefficients. We found relatively insignificant effects on the modelled surface fluxes (e.g. up to 5 % for the friction velocity, while 3 % for the sensible and latent heat), which is due to the compensating effect between the mean gradients and the drag coefficients, both of which are largely affected by the RSL parameterization. When varying Lc (from 10 to 20 m) and β (from 0.25 to 0.4 m), based on observational evidence, the predicted friction velocity is found to vary by up to 25 % and the modelled surface-energy fluxes (sensible heat, SH, and latent heat of evaporation, LE) vary up to 2 and 9 %. Consequently, the boundary-layer height varies up to
Integrating communication theory and practice: Successes and challenges in boundary-spanning work
NASA Astrophysics Data System (ADS)
Weiss, M.; Fallon Lambert, K.
2014-12-01
The Science Policy Exchange (SPE) is a consortium of leaders in ecosystem research united to facilitate science from innovation to impact. In our unique model, we catalyze actionable science on pressing environmental issues such as climate change, and undertake comprehensive stakeholder engagement, public communication, and policy outreach. Built on more than 10 years of experience creating programs at the interface of science and policy at Hubbard Brook, Harvard Forest, and other LTER sites, we apply science communication research to practice in various ways depending on the context and problem being addressed. In keeping with the research on co-production and the importance of establishing credibility, salience, and legitimacy, we engage stakeholders from the outset of each project. Stakeholders and scientists collaborate to define the scope of the project, frame questions relevant to society, and define communication products to meet their needs. To promote broader distribution and uptake, we combine message development, storytelling, and media training to craft and deliver relatable stories that tap into news values and human values. Three recent SPE successes include: (1) Wildlands and Woodlands: A regional forest conservation report released in 2010 that generated 137 media stories and influenced land conservation policy, (2) Changes to the Land: A suite of communication products developed in 2013 for a landscape scenarios project in Massachusetts that saturated the state's media markets and have been widely cited by policymakers, and (3) Co-benefits of Carbon Standards: A national air quality report released in 2014 that was cited in 76 media stories and helped reframe the national debate on carbon dioxide emissions standards in terms of their potential local health and environmental benefits. We will describe our successful applications of science communication research and discuss several critical disconnections between research and practice. These include
Integration of local pattern elements into a global shape in human vision
Saarinen, Jukka; Levi, Dennis M.; Shen, Bridgitte
1997-01-01
The spatial extent of the cortical filters selective for different spatial frequencies and orientations is limited. We studied psychophysically how information from the local filters is integrated into global pattern shapes, i.e., whether performance in the identification of a global pattern consisting of small, locally oriented Gabor elements depends on the orientations of those elements. The observer was presented with an E-like stimulus pattern shape comprised of oriented Gabor patches on a blank background, and the performance measure was the threshold contrast for identifying the orientation of the E pattern (four possible rotated orientations). The results showed that contrast thresholds were significantly lower when the local elements all shared the same orientation (e.g., all horizontal) compared with the condition in which the elements had mixed orientations (both horizontal and vertical). The enhancement effect due to uniform local orientations can be explained by two factors: One is local facilitatory interactions between the orientation selective filters, and the other is second-order information integration across the filters. PMID:9223350
NASA Technical Reports Server (NTRS)
Zimmerle, D.; Bernhard, R. J.
1985-01-01
An alternative method for performing singular boundary element integrals for applications in linear acoustics is discussed. The method separates the integral of the characteristic solution into a singular and nonsingular part. The singular portion is integrated with a combination of analytic and numerical techniques while the nonsingular portion is integrated with standard Gaussian quadrature. The method may be generalized to many types of subparametric elements. The integrals over elements containing the root node are considered, and the characteristic solution for linear acoustic problems are examined. The method may be generalized to most characteristic solutions.
MacLaren, I.; Sala, B.; Andersson, S. M. L.; ...
2015-10-17
Here, the atomic structure and chemistry of thin films of Bi(Fe,Mn)O3 (BFMO) films with a target composition of Bi2FeMnO6 on SrTiO3 are studied using scanning transmission electron microscopy imaging and electron energy loss spectroscopy. It is shown that Mn4+-rich antiphase boundaries are locally nucleated right at the film substrate and then form stepped structures that are approximately pyramidal in three dimensions. These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å. Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is muchmore » closer to bulk values for BFMO. This suggests that to improve the crystallographic perfection of the films whilst retaining the strain state through as much of the film as possible, ways need to be found to prevent nucleation of the antiphase boundaries. Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions.« less
MacLaren, I; Sala, B; Andersson, S M L; Pennycook, T J; Xiong, J; Jia, Q X; Choi, E-M; MacManus-Driscoll, J L
2015-12-01
The atomic structure and chemistry of thin films of Bi(Fe,Mn)O3 (BFMO) films with a target composition of Bi2FeMnO6 on SrTiO3 are studied using scanning transmission electron microscopy imaging and electron energy loss spectroscopy. It is shown that Mn(4+)-rich antiphase boundaries are locally nucleated right at the film substrate and then form stepped structures that are approximately pyramidal in three dimensions. These have the effect of confining the material below the pyramids in a highly strained state with an out-of-plane lattice parameter close to 4.1 Å. Outside the area enclosed by the antiphase boundaries, the out-of-plane lattice parameter is much closer to bulk values for BFMO. This suggests that to improve the crystallographic perfection of the films whilst retaining the strain state through as much of the film as possible, ways need to be found to prevent nucleation of the antiphase boundaries. Since the antiphase boundaries seem to form from the interaction of Mn with the Ti in the substrate, one route to perform this would be to grow a thin buffer layer of pure BiFeO3 on the SrTiO3 substrate to minimise any Mn-Ti interactions.
NASA Astrophysics Data System (ADS)
Bassetti, M.; Miller, K. G.; Monteverde, D.; Mountain, G.; Proust, J.; Scienceparty, E.
2010-12-01
, respectively. There were 11 cases where there was a minimal lithologic expression of the seismic sequence boundary; many of these occur in a position basinward of the clinoform inflection point and correlate to the juxtaposition of relatively deep-water facies above and below the sequence boundary. Surfaces recognized in the core and on seismic profiles as maximum flooding surfaces and sequence boundaries are also associated with peaks of gamma ray values. Oligocene sequences were only sampled at Site M27, but have minimal sedimentological and seismic expression due to basinal locations and sequence boundaries must be picked by chronostratigraphic gaps. Limited core recovery prevented firm evaluation of uppermost middle to upper Miocene sequences. Excellent recovery of lower to lower middle Miocene sequences allows core-seismic integration that confirms the hypothesis that sequence bounding unconformities and their correlative conformities are major impedance contrasts.
NASA Technical Reports Server (NTRS)
Meredith, B. D.
1984-01-01
The evolutionary growth of the Space Station and the diverse activities onboard are expected to require a hierarchy of integrated,local area networks capable of supporting data, voice and video communications. In addition, fault tolerant network operation is necessary to protect communications between critical systems attached to the net and to relieve the valuable human resources onboard Space Station of day-to-day data system repair tasks. An experimental, local area network is being developed which will serve as a testbed for investigating candidate algorithms and technologies for a fault tolerant, integrated network. The establishment of a set of rules or protocols which govern communications on the net is essential to obtain orderly and reliable operation. A hierarchy of protocols for the experimental network is presented and procedures for data and control communications are described.
Local integration accounts for weak selectivity of mouse neocortical parvalbumin interneurons
Scholl, Benjamin; Pattadkal, Jagruti J.; Dilly, Geoffrey A.; Priebe, Nicholas J.; Zemelman, Boris V.
2015-01-01
SUMMARY Dissecting the functional roles of excitatory and inhibitory neurons in cortical circuits is a fundamental goal in neuroscience. Of particular interest are their roles in emergent cortical computations such as binocular integration in primary visual cortex (V1). We measured the binocular response selectivity of genetically-defined subpopulations of excitatory and inhibitory neurons. Parvalbumin (PV+) interneurons received strong inputs from both eyes, but lacked selectivity for binocular disparity. Because broad selectivity could result from heterogeneous synaptic input from neighboring neurons, we examined how individual PV+ interneuron selectivity compared to that of the local neuronal network, which is primarily composed of excitatory neurons. PV+ neurons showed functional similarity to neighboring neuronal populations over spatial distances resembling measurements of synaptic connectivity. On the other hand, excitatory neurons expressing CaMKIIα displayed no such functional similarity with the neighboring population. Our findings suggest that broad selectivity of PV+ interneurons results from nonspecific integration within local networks. PMID:26182423
Local Integration Accounts for Weak Selectivity of Mouse Neocortical Parvalbumin Interneurons.
Scholl, Benjamin; Pattadkal, Jagruti J; Dilly, Geoffrey A; Priebe, Nicholas J; Zemelman, Boris V
2015-07-15
Dissecting the functional roles of excitatory and inhibitory neurons in cortical circuits is a fundamental goal in neuroscience. Of particular interest are their roles in emergent cortical computations such as binocular integration in primary visual cortex (V1). We measured the binocular response selectivity of genetically defined subpopulations of excitatory and inhibitory neurons. Parvalbumin (PV+) interneurons received strong inputs from both eyes but lacked selectivity for binocular disparity. Because broad selectivity could result from heterogeneous synaptic input from neighboring neurons, we examined how individual PV+ interneuron selectivity compared to that of the local neuronal network, which is primarily composed of excitatory neurons. PV+ neurons showed functional similarity to neighboring neuronal populations over spatial distances resembling measurements of synaptic connectivity. On the other hand, excitatory neurons expressing CaMKIIα displayed no such functional similarity with the neighboring population. Our findings suggest that broad selectivity of PV+ interneurons results from nonspecific integration within local networks. VIDEO ABSTRACT.
2016-03-21
In-Situ Cladding Annealing for Post-Fabrication Trimming of Silicon Photonic Integrated Circuits Steven Spector1, Jeffrey M. Knecht, and Paul W...alone. In this work, we report the use of localized annealing via in situ heaters to induce a permanent change in the refractive index of the...resonant wavelength of a ring resonator was adjusted by as much as 3.0 nm, when annealing the entire substrate. Adjusting the resonant wavelength
Planar analytic systems having locally analytic first integrals at an isolated singular point
NASA Astrophysics Data System (ADS)
Zhang, Xiang
2004-05-01
The aim of this paper is to answer the open problem 3 posed by Chavarriga et al (1999 J. Diff. Eqns 157 163-82). The problem is to characterize analytic systems having an isolated singular point formed by hyperbolic sectors which are Cohgr locally integrable at this singular point. This project is partially supported by the National Natural Science Foundation of China grant number 10231020, and Shuguang plan of Shanghai.