Heat and work distributions for mixed Gauss-Cauchy process
NASA Astrophysics Data System (ADS)
Kuśmierz, Łukasz; Rubi, J. Miguel; Gudowska-Nowak, Ewa
2014-09-01
We analyze energetics of a non-Gaussian process described by a stochastic differential equation of the Langevin type. The process represents a paradigmatic model of a nonequilibrium system subject to thermal fluctuations and additional external noise, with both sources of perturbations considered as additive and statistically independent forcings. We define thermodynamic quantities for trajectories of the process and analyze contributions to mechanical work and heat. As a working example we consider a particle subjected to a drag force and two independent Levy white noises with stability indices $\\alpha=2$ and $\\alpha=1$. The fluctuations of dissipated energy (heat) and distribution of work performed by the force acting on the system are addressed by examining contributions of Cauchy fluctuations to either bath or external force acting on the system.
Jäntschi, Lorentz
2016-01-01
Multiple linear regression analysis is widely used to link an outcome with predictors for better understanding of the behaviour of the outcome of interest. Usually, under the assumption that the errors follow a normal distribution, the coefficients of the model are estimated by minimizing the sum of squared deviations. A new approach based on maximum likelihood estimation is proposed for finding the coefficients on linear models with two predictors without any constrictive assumptions on the distribution of the errors. The algorithm was developed, implemented, and tested as proof-of-concept using fourteen sets of compounds by investigating the link between activity/property (as outcome) and structural feature information incorporated by molecular descriptors (as predictors). The results on real data demonstrated that in all investigated cases the power of the error is significantly different by the convenient value of two when the Gauss-Laplace distribution was used to relax the constrictive assumption of the normal distribution of the error. Therefore, the Gauss-Laplace distribution of the error could not be rejected while the hypothesis that the power of the error from Gauss-Laplace distribution is normal distributed also failed to be rejected. PMID:28090215
Jäntschi, Lorentz; Bálint, Donatella; Bolboacă, Sorana D
2016-01-01
Multiple linear regression analysis is widely used to link an outcome with predictors for better understanding of the behaviour of the outcome of interest. Usually, under the assumption that the errors follow a normal distribution, the coefficients of the model are estimated by minimizing the sum of squared deviations. A new approach based on maximum likelihood estimation is proposed for finding the coefficients on linear models with two predictors without any constrictive assumptions on the distribution of the errors. The algorithm was developed, implemented, and tested as proof-of-concept using fourteen sets of compounds by investigating the link between activity/property (as outcome) and structural feature information incorporated by molecular descriptors (as predictors). The results on real data demonstrated that in all investigated cases the power of the error is significantly different by the convenient value of two when the Gauss-Laplace distribution was used to relax the constrictive assumption of the normal distribution of the error. Therefore, the Gauss-Laplace distribution of the error could not be rejected while the hypothesis that the power of the error from Gauss-Laplace distribution is normal distributed also failed to be rejected.
Hou, Chieh; Ateshian, Gerard A
2016-01-01
Fibrous biological tissues may be modeled using a continuous fiber distribution (CFD) to capture tension-compression nonlinearity, anisotropic fiber distributions, and load-induced anisotropy. The CFD framework requires spherical integration of weighted individual fiber responses, with fibers contributing to the stress response only when they are in tension. The common method for performing this integration employs the discretization of the unit sphere into a polyhedron with nearly uniform triangular faces (finite element integration or FEI scheme). Although FEI has proven to be more accurate and efficient than integration using spherical coordinates, it presents three major drawbacks: First, the number of elements on the unit sphere needed to achieve satisfactory accuracy becomes a significant computational cost in a finite element (FE) analysis. Second, fibers may not be in tension in some regions on the unit sphere, where the integration becomes a waste. Third, if tensed fiber bundles span a small region compared to the area of the elements on the sphere, a significant discretization error arises. This study presents an integration scheme specialized to the CFD framework, which significantly mitigates the first drawback of the FEI scheme, while eliminating the second and third completely. Here, integration is performed only over the regions of the unit sphere where fibers are in tension. Gauss-Kronrod quadrature is used across latitudes and the trapezoidal scheme across longitudes. Over a wide range of strain states, fiber material properties, and fiber angular distributions, results demonstrate that this new scheme always outperforms FEI, sometimes by orders of magnitude in the number of computational steps and relative accuracy of the stress calculation.
Noncoaxial Bessel-Gauss beams.
Huang, Chaohong; Zheng, Yishu; Li, Hanqing
2016-04-01
We proposed a new family of noncoaxial Gauss-truncated Bessel beams through multiplying conventional symmetrical Bessel beams by a noncoaxial Gauss function. These beams can also be regarded as the exponential-truncated version of Bessel-Gauss beams since they can be transformed into the product of Bessel-Gauss beams and an exponential window function along a certain Cartesian axis. The closed-form solutions of the angular spectra and paraxial propagation of these beams were derived. These beams have asymmetrical intensity distributions and carry the same orbit angular momentum per photon as the corresponding Bessel-Gauss beams. While propagating along the z axis, the mth (m≠0) noncoaxial Bessel-Gauss beams rotate their intensity distributions and the mth-order vortex at the beam center has a transverse shift along the direction perpendicular to the offset axis. Depending on the product of the transverse scalar factor of the Bessel beams and the offset between the Gaussian window function and the center of the Bessel beams, the noncoaxial Bessel-Gauss beams can produce unit vortices with opposite signs in pairs during propagation.
ERIC Educational Resources Information Center
Rice, Kathryn; Scott, Paul
2005-01-01
This article presents a brief biography of Johann Carl Friedrich Gauss. Gauss was born on April 30, 1777, in the German city of Braunschweig (Brunswick). He was the only child of Gebhard Dietrich Gauss and Dorothea Benze. Neither of Gauss's parents had much education, his father could read and write, but earned his living doing menial jobs such as…
Nonextensive entropies derived from Gauss' principle
NASA Astrophysics Data System (ADS)
Wada, Tatsuaki
2011-05-01
Gauss' principle in statistical mechanics is generalized for a q-exponential distribution in nonextensive statistical mechanics. It determines the associated stochastic and statistical nonextensive entropies which satisfy Greene-Callen principle concerning on the equivalence between microcanonical and canonical ensembles.
Vector Helmholtz-Gauss and vector Laplace-Gauss beams.
Bandres, Miguel A; Gutiérrez-Vega, Julio C
2005-08-15
We demonstrate the existence of vector Helmholtz-Gauss (vHzG) and vector Laplace-Gauss beams that constitute two general families of localized vector beam solutions of the Maxwell equations in the paraxial approximation. The electromagnetic components are determined starting from the scalar solutions of the two-dimensional Helmholtz and Laplace equations, respectively. Special cases of the vHzG beams are TE and TM Gaussian vector beams, nondiffracting vector Bessel beams, polarized Bessel-Gauss beams, modes in cylindrical waveguides and cavities, and scalar Helmholtz-Gauss beams. The general expression of the vHzG beams can be used straightforwardly to obtain vector Mathieu-Gauss and vector parabolic-Gauss beams, which to our knowledge have not yet been reported.
Asymmetric Bessel-Gauss beams.
Kotlyar, V V; Kovalev, A A; Skidanov, R V; Soifer, V A
2014-09-01
We propose a three-parameter family of asymmetric Bessel-Gauss (aBG) beams with integer and fractional orbital angular momentum (OAM). The aBG beams are described by the product of a Gaussian function by the nth-order Bessel function of the first kind of complex argument, having finite energy. The aBG beam's asymmetry degree depends on a real parameter c≥0: at c=0, the aBG beam is coincident with a conventional radially symmetric Bessel-Gauss (BG) beam; with increasing c, the aBG beam acquires a semicrescent shape, then becoming elongated along the y axis and shifting along the x axis for c≫1. In the initial plane, the intensity distribution of the aBG beams has a countable number of isolated optical nulls on the x axis, which result in optical vortices with unit topological charge and opposite signs on the different sides of the origin. As the aBG beam propagates, the vortex centers undergo a nonuniform rotation with the entire beam about the optical axis (c≫1), making a π/4 turn at the Rayleigh range and another π/4 turn after traveling the remaining distance. At different values of the c parameter, the optical nulls of the transverse intensity distribution change their position, thus changing the OAM that the beam carries. An isolated optical null on the optical axis generates an optical vortex with topological charge n. A vortex laser beam shaped as a rotating semicrescent has been generated using a spatial light modulator.
Nonzonal Expressions of GAUSS-KRÜGER Projection in Polar Regions
NASA Astrophysics Data System (ADS)
Li, Zhongmei; Bian, Shaofeng; Liu, Qiang; Li, Houpu; Chen, Cheng; Hu, Yanfeng
2016-06-01
With conformal colatitude introduced, based on the mathematical relationship between exponential and logarithmic functions by complex numbers, strict equation of complex conformal colatitude is derived, and then theoretically strict nonzonal expressions of Gauss projection in polar regions are carried out. By means of the computer algebra system, correctness of these expressions is verified, and sketches of Gauss-krüger projection without bandwidth restriction in polar regions are charted. In the Arctic or Antarctic region, graticule of nonzonal Gauss projection complies with people's reading habit and reflects real ground-object distribution. Achievements in this paper could perfect mathematical basis of Gauss projection and provide reference frame for polar surveying and photogrammetry.
Average intensity and spreading of a Lorentz-Gauss beam in turbulent atmosphere.
Zhou, Guoquan; Chu, Xiuxiang
2010-01-18
The propagation of a Lorentz-Gauss beam in turbulent atmosphere is investigated. Based on the extended Huygens-Fresnel integral and the Hermite-Gaussian expansion of a Lorentz function, analytical formulae for the average intensity and the effective beam size of a Lorentz-Gauss beam are derived in turbulent atmosphere. The average intensity distribution and the spreading properties of a Lorentz-Gauss beam in turbulent atmosphere are numerically demonstrated. The influences of the beam parameters and the structure constant of the atmospheric turbulence on the propagation of a Lorentz-Gauss beam in turbulent atmosphere are also discussed in detail.
Colon Cancer Risk Assessment - Gauss Program
An executable file (in GAUSS) that projects absolute colon cancer risk (with confidence intervals) according to NCI’s Colorectal Cancer Risk Assessment Tool (CCRAT) algorithm. GAUSS is not needed to run the program.
Doster, Timothy; Watnik, Abbie T
2016-12-20
As a means of increasing the channel capacity in free-space optical communication systems, two types of orbital angular momentum carrying beams, Bessel-Gauss and Laguerre-Gauss, are studied. In a series of numerical simulations, we show that Bessel-Gauss beams, pseudo-nondiffracting beams, outperform Laguerre-Gauss beams of various orders in channel efficiency and bit error rates.
Sampath, Rahul S; Sundar, Hari; Veerapaneni, Shravan
2010-01-01
We present fast adaptive parallel algorithms to compute the sum of N Gaussians at N points. Direct sequential computation of this sum would take O(N{sup 2}) time. The parallel time complexity estimates for our algorithms are O(N/n{sub p}) for uniform point distributions and O( (N/n{sub p}) log (N/n{sub p}) + n{sub p}log n{sub p}) for non-uniform distributions using n{sub p} CPUs. We incorporate a plane-wave representation of the Gaussian kernel which permits 'diagonal translation'. We use parallel octrees and a new scheme for translating the plane-waves to efficiently handle non-uniform distributions. Computing the transform to six-digit accuracy at 120 billion points took approximately 140 seconds using 4096 cores on the Jaguar supercomputer. Our implementation is 'kernel-independent' and can handle other 'Gaussian-type' kernels even when explicit analytic expression for the kernel is not known. These algorithms form a new class of core computational machinery for solving parabolic PDEs on massively parallel architectures.
Gauss-Bonnet gravitational baryogenesis
NASA Astrophysics Data System (ADS)
Odintsov, S. D.; Oikonomou, V. K.
2016-09-01
In this letter we study some variant forms of gravitational baryogenesis by using higher order terms containing the partial derivative of the Gauss-Bonnet scalar coupled to the baryonic current. This scenario extends the well known theory that uses a similar coupling between the Ricci scalar and the baryonic current. One appealing feature of the scenario we study is that the predicted baryon asymmetry during a radiation domination era is non-zero. We calculate the baryon to entropy ratio for the Gauss-Bonnet term and by using the observational constraints we investigate which are the allowed forms of the R + F (G) gravity controlling the evolution. Also we briefly discuss some alternative higher order terms that can generate a non-zero baryon asymmetry, even in the conformal invariance limit.
Crafting a Gauss Gun Demonstration
NASA Astrophysics Data System (ADS)
Blodgett, Matthew E.; Blodgett, E. D.
2006-12-01
A Gauss Gun launches a ferromagnetic projectile using a pulsed electromagnet. This demonstration provides a nice counterpoint to the popular Thompson's jumping ring demonstration, which launches a nonferromagnetic ring via repulsion of an induced current. The pulsed current must be short enough in duration so that the projectile is not retarded by lingering current in the launch solenoid, but also large enough to provide a suitably impressive velocity. This project involved an iterative design process, as we worked through balancing all the different design criteria. We recommend it as a very nice electronics design project which will produce a very portable and enjoyable demonstration. AAPT sponsor Earl Blodgett.
Laplace-Gauss and Helmholtz-Gauss paraxial modes in media with quadratic refraction index.
Kiselev, Aleksei P; Plachenov, Alexandr B
2016-04-01
The scalar theory of paraxial wave propagation in an axisymmetric medium where the refraction index quadratically depends on transverse variables is addressed. Exact solutions of the corresponding parabolic equation are presented, generalizing the Laplace-Gauss and Helmholtz-Gauss modes earlier known for homogeneous media. Also, a generalization of a zero-order asymmetric Bessel-Gauss beam is given.
Gauss Sum Factorization with Cold Atoms
Gilowski, M.; Wendrich, T.; Mueller, T.; Ertmer, W.; Rasel, E. M.; Jentsch, Ch.; Schleich, W. P.
2008-01-25
We report the first implementation of a Gauss sum factorization algorithm by an internal state Ramsey interferometer using cold atoms. A sequence of appropriately designed light pulses interacts with an ensemble of cold rubidium atoms. The final population in the involved atomic levels determines a Gauss sum. With this technique we factor the number N=263193.
The Tortured History of Gauss's Law
NASA Astrophysics Data System (ADS)
Spencer, Ross
2009-10-01
American physics textbooks contain the following equation, which is called Gauss's law: E .d S = qenclosed ɛ0 It is odd, however, that biographies of Karl Friedrich Gauss (1777-1855) contain no mention of this law. A brief history of this important result will be presented in which it will be shown that what we call Gauss's law today was originally guessed at by Joseph Priestly (1733-1804) after he read a letter from Benjamin Franklin (1706-1790), then was derived, forgotten, and re-derived several times in two different contexts by many of the luminaries of physics in the eighteenth and nineteenth centuries.
Complex source point theory of paraxial and nonparaxial cosine-Gauss and Bessel-Gauss beams.
Sheppard, Colin J R
2013-02-15
It shown how cosine-Gauss and Bessel-Gauss beams can be generated using the complex source point theory. Paraxial beams are treated first. An analytic expression is derived for the nonparaxial cosine-Gaussian beam, based on the complex source point approach, and numerical results are presented to illustrate its behavior. A way to generate nonparaxial Bessel-Gauss beams is also indicated.
Gauss-Lobatto to Bernstein polynomials transformation
NASA Astrophysics Data System (ADS)
Coluccio, Loredana; Eisinberg, Alfredo; Fedele, Giuseppe
2008-12-01
The aim of this paper is to transform a polynomial expressed as a weighted sum of discrete orthogonal polynomials on Gauss-Lobatto nodes into Bernstein form and vice versa. Explicit formulas and recursion expressions are derived. Moreover, an efficient algorithm for the transformation from Gauss-Lobatto to Bernstein is proposed. Finally, in order to show the robustness of the proposed algorithm, experimental results are reported.
Efficient modelling of gravity effects due to topographic masses using the Gauss-FFT method
NASA Astrophysics Data System (ADS)
Wu, Leyuan
2016-04-01
We present efficient Fourier-domain algorithms for modelling gravity effects due to topographic masses. The well-known Parker's formula originally based on the standard fast Fourier transform (FFT) algorithm is modified by applying the Gauss-FFT method instead. Numerical precision of the forward and inverse Fourier transforms embedded in Parker's formula and its extended forms are significantly improved by the Gauss-FFT method. The topographic model is composed of two major aspects, the geometry and the density. Versatile geometric representations, including the mass line model, the mass prism model, the polyhedron model and smoother topographic models interpolated from discrete data sets using high-order splines or pre-defined by analytical functions, in combination with density distributions that vary both laterally and vertically in rather arbitrary ways following exponential or general polynomial functions, now can be treated in a consistent framework by applying the Gauss-FFT method. The method presented has been numerically checked by space-domain analytical and hybrid analytical/numerical solutions already established in the literature. Synthetic and real model tests show that both the Gauss-FFT method and the standard FFT method run much faster than space-domain solutions, with the Gauss-FFT method being superior in numerical accuracy. When truncation errors are negligible, the Gauss-FFT method can provide forward results almost identical to space-domain analytical or semi-numerical solutions in much less time.
Anisotropic inflation in Gauss-Bonnet gravity
Lahiri, Sayantani
2016-09-19
We study anisotropic inflation with Gauss-Bonnet correction in presence of a massless vector field. In this scenario, exact anisotropic power-law inflation is realized when the inflaton potential, gauge coupling function and the Gauss-Bonnet coupling are exponential functions. We show that anisotropy becomes proportional to two slow-roll parameters of the theory and hence gets enhanced in presence of quadratic curvature corrections. The stability analysis reveals that anisotropic power-law solutions remain stable over a substantially large parameter region.
Galileo, Gauss, and the Green Monster
ERIC Educational Resources Information Center
Kalman, Dan; Teague, Daniel J.
2013-01-01
Galileo dropped cannonballs from the leaning tower of Pisa to demonstrate something about falling bodies. Gauss was a giant of mathematics and physics who made unparalleled contributions to both fields. More contemporary (and not a person), the Green Monster is the left-field wall at the home of the Boston Red Sox, Fenway Park. Measuring 37 feet…
On Gautschi's conjecture for generalized Gauss-Radau and Gauss-Lobatto formulae
NASA Astrophysics Data System (ADS)
Joulak, Hédi; Beckermann, Bernhard
2009-12-01
Recently, Gautschi introduced so-called generalized Gauss-Radau and Gauss-Lobatto formulae which are quadrature formulae of Gaussian type involving not only the values but also the derivatives of the function at the endpoints. In the present note we show the positivity of the corresponding weights; this positivity has been conjectured already by Gautschi. As a consequence, we establish several convergence theorems for these quadrature formulae.
Nonparaxial propagation of Lorentz-Gauss beams in uniaxial crystal orthogonal to the optical axis.
Wang, Xun; Liu, Zhirong; Zhao, Daomu
2014-04-01
Analytical expressions for the three components of nonparaxial propagation of a polarized Lorentz-Gauss beam in uniaxial crystal orthogonal to the optical axis are derived and used to investigate its propagation properties in uniaxial crystal. The influences of the initial beam parameters and the parameters of the uniaxial crystal on the evolution of the beam-intensity distribution in the uniaxial crystal are examined in detail. Results show that the statistical properties of a nonparaxial Lorentz-Gauss beam in a uniaxial crystal orthogonal to the optical axis are closely determined by the initial beam's parameters and the parameters of the crystal: the beam waist sizes-w(0), w(0x), and w(0y)-not only affect the size and shape of the beam profile in uniaxial crystal but also determine the nonparaxial effect of a Lorentz-Gauss beam; the beam profile of a Lorentz-Gauss beam in uniaxial crystal is elongated in the x or y direction, which is determined by the ratio of the extraordinary refractive index to the ordinary refractive index; with increasing deviation of the ratio from unity, the extension of the beam profile augments. The results indicate that uniaxial crystal provides an effective and convenient method for modulating the Lorentz-Gauss beams. Our results may be valuable in some fields, such as optical trapping and nonlinear optics, where a light beam with a special profile and polarization is required.
The Goos-Hanchen shift in Helmholtz-Gauss beams
NASA Astrophysics Data System (ADS)
Jezzini, Moises A.; Gutierrez-Vega, Julio C.
2006-08-01
We present a study of the total internal reflection of a Helmholtz-Gauss beam at a plane interface between two dielectric media. The derivation is based on the decomposition of the Helmholtz-Gauss beams in terms of its constituent plane waves components. We determine the shift predicted by the classical theory of the Goos- Hänchen shift and analyze the transverse intensity patterns of the reflected waves for a variety of Helmholtz-Gauss beam including Bessel-Gauss and Cosine-Gauss beams.
Entanglement temperature with Gauss-Bonnet term
NASA Astrophysics Data System (ADS)
Pal, Shesansu Sekhar; Panda, Sudhakar
2015-09-01
We compute the entanglement temperature using the first law-like of thermodynamics, ΔE =Tent ΔSEE, up to Gauss-Bonnet term in the Jacobson-Myers entropy functional in any arbitrary spacetime dimension. The computation is done when the entangling region is the geometry of a slab. We also show that such a Gauss-Bonnet term, which becomes a total derivative, when the co-dimension two hypersurface is four dimensional, does not contribute to the finite term in the entanglement entropy. We observe that the Weyl-squared term does not contribute to the entanglement entropy. It is important to note that the calculations are performed when the entangling region is very small and the energy is calculated using the normal Hamiltonian.
Phase anomalies in Bessel-Gauss beams.
Kim, Myun-Sik; Scharf, Toralf; Assafrao, Alberto da Costa; Rockstuhl, Carsten; Pereira, Silvania F; Urbach, H Paul; Herzig, Hans Peter
2012-12-17
Bessel-Gauss beams are known as non-diffracting beams. They can be obtained by focusing an annularly shaped collimated laser beam. Here, we report for the first time on the direct measurement of the phase evolution of such beams by relying on longitudinal-differential interferometry. We found that the characteristics of Bessel-Gauss beams cause a continuously increasing phase anomaly in the spatial domain where such beams do not diverge, i.e. there is a larger phase advance of the beam when compared to a referential plane wave. Simulations are in excellent agreement with measurements. We also provide an analytical treatment of the problem that matches both experimental and numerical results and provides an intuitive explanation.
Demystifying electric flux and Gauss's law
NASA Astrophysics Data System (ADS)
McManus, Jeff
2017-04-01
Many physics students have experienced the difficulty of internalizing concepts in electrostatics. After studying concrete, measurable details in mechanics, they are challenged by abstract ideas such as electric fields, flux, Gauss's law, and electric potential. There are a few well-known hands-on activities that help students get experience with these ideas. Perhaps the most popular are field-mapping activities in many forms ranging from metal electrodes in a shallow dish of water to metal pens and conductive paper. My experience of teaching with these activities in my AP Physics course left me disappointed and my students still mystified. Over the last several years, I have developed some hands-on activities that have helped my students better understand and apply these concepts. In this column, I will describe one such activity, a flux calculation that presents an opportunity to apply Gauss's law.
Vorticity, Stokes' Theorem and the Gauss's Theorem
NASA Astrophysics Data System (ADS)
Narayanan, M.
2004-12-01
Vorticity is a property of the flow of any fluid and moving fluids acquire properties that allow an engineer to describe that particular flow in greater detail. It is important to recognize that mere motion alone does not guarantee that the air or any fluid has vorticity. Vorticity is one of four important quantities that define the kinematic properties of any fluid flow. The Navier-Stokes equations are the foundation of fluid mechanics, and Stokes' theorem is used in nearly every branch of mechanics as well as electromagnetics. Stokes' Theorem also plays a vital role in many secondary theorems such as those pertaining to vorticity and circulation. However, the divergence theorem is a mathematical statement of the physical fact that, in the absence of the creation or destruction of matter, the density within a region of space can change only by having it flow into, or away from the region through its boundary. This is also known as Gauss's Theorem. It should also be noted that there are many useful extensions of Gauss's Theorem, including the extension to include surfaces of discontinuity in V. Mathematically expressed, Stokes' theorem can be expressed by considering a surface S having a bounding curve C. Here, V is any sufficiently smooth vector field defined on the surface and its bounding curve C. Integral (Surface) [(DEL X V)] . dS = Integral (Contour) [V . dx] In this paper, the author outlines and stresses the importance of studying and teaching these mathematical techniques while developing a course in Hydrology and Fluid Mechanics. References Arfken, G. "Gauss's Theorem." 1.11 in Mathematical Methods for Physicists, 3rd ed. Orlando, FL: Academic Press, pp. 57-61, 1985. Morse, P. M. and Feshbach, H. "Gauss's Theorem." In Methods of Theoretical Physics, Part I. New York: McGraw-Hill, pp. 37-38, 1953. Eric W. Weisstein. "Divergence Theorem." From MathWorld--A Wolfram Web Resource. http://mathworld.wolfram.com/DivergenceTheorem.html
Image segmentation using hidden Markov Gauss mixture models.
Pyun, Kyungsuk; Lim, Johan; Won, Chee Sun; Gray, Robert M
2007-07-01
Image segmentation is an important tool in image processing and can serve as an efficient front end to sophisticated algorithms and thereby simplify subsequent processing. We develop a multiclass image segmentation method using hidden Markov Gauss mixture models (HMGMMs) and provide examples of segmentation of aerial images and textures. HMGMMs incorporate supervised learning, fitting the observation probability distribution given each class by a Gauss mixture estimated using vector quantization with a minimum discrimination information (MDI) distortion. We formulate the image segmentation problem using a maximum a posteriori criteria and find the hidden states that maximize the posterior density given the observation. We estimate both the hidden Markov parameter and hidden states using a stochastic expectation-maximization algorithm. Our results demonstrate that HMGMM provides better classification in terms of Bayes risk and spatial homogeneity of the classified objects than do several popular methods, including classification and regression trees, learning vector quantization, causal hidden Markov models (HMMs), and multiresolution HMMs. The computational load of HMGMM is similar to that of the causal HMM.
Holographic isotropisation in Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Andrade, Tomás; Casalderrey-Solana, Jorge; Ficnar, Andrej
2017-02-01
We study holographic isotropisation of homogeneous, strongly coupled, non-Abelian plasmas in Gauss-Bonnet gravity with a negative cosmological constant. We focus on small values of the Gauss-Bonnet coupling parameter λ GB and linearise the equations of motion around a time-dependent background solution with λ GB = 0. We numerically solve the linearised equations and show that the entire time evolution of the pressure anisotropy can be well approximated by the linear in λ GB corrections to the quasinormal mode expansion, even in the cases of high anisotropy. We finally show that, quite generally, the time evolution of the pressure anisotropy with the Gauss-Bonnet term is approximately shifted with respect to the evolution without it, with the sign of the shift being directly related to the sign of the λ GB parameter. Combined with the observation that negative λ GB captures qualitative features of positive gauge coupling corrections, this suggests that the latter generically increase the isotropisation time of strongly coupled plasmas.
Scalar field evolution in Gauss-Bonnet black holes
Abdalla, E.; Konoplya, R.A.; Molina, C.
2005-10-15
It is presented a thorough analysis of scalar perturbations in the background of Gauss-Bonnet, Gauss-Bonnet-de Sitter and Gauss-Bonnet-anti-de Sitter black hole spacetimes. The perturbations are considered both in frequency and time domain. The dependence of the scalar field evolution on the values of the cosmological constant {lambda} and the Gauss-Bonnet coupling {alpha} is investigated. For Gauss-Bonnet and Gauss-Bonnet-de Sitter black holes, at asymptotically late times either power-law or exponential tails dominate, while for Gauss-Bonnet-anti-de Sitter black hole, the quasinormal modes govern the scalar field decay at all times. The power-law tails at asymptotically late times for odd-dimensional Gauss-Bonnet black holes does not depend on {alpha}, even though the black hole metric contains {alpha} as a new parameter. The corrections to quasinormal spectrum due to Gauss-Bonnet coupling is not small and should not be neglected. For the limit of near extremal value of the (positive) cosmological constant and pure de Sitter and anti-de Sitter modes in Gauss-Bonnet gravity we have found analytical expressions.
Efficient generation of Hermite-Gauss and Ince-Gauss beams through kinoform phase elements.
Aguirre-Olivas, Dilia; Mellado-Villaseñor, Gabriel; Sánchez-de-la-Llave, David; Arrizón, Victor
2015-10-01
We discuss the generation of Hermite-Gauss and Ince-Gauss beams employing phase elements whose transmittances coincide with the phase modulations of such beams. A scaled version of the desired field appears, distorted by marginal optical noise, at the element's Fourier domain. The motivation to perform this study is that, in the context of the proposed approach, the desired beams are generated with the maximum possible efficiency. A disadvantage of the method is the distortion of the desired beams by the influence of several nondesired beam modes generated by the phase elements. We evaluate such distortion employing the root mean square deviation as a figure of merit.
Normalization of optical Weber waves and Weber-Gauss beams.
Rodríguez-Lara, B M
2010-02-01
The normalization of energy divergent Weber waves and finite energy Weber-Gauss beams is reported. The well-known Bessel and Mathieu waves are used to derive the integral relations between circular, elliptic, and parabolic waves and to present the Bessel and Mathieu wave decomposition of the Weber waves. The efficiency to approximate a Weber-Gauss beam as a finite superposition of Bessel-Gauss beams is also given.
Graviton emission from a Gauss-Bonnet brane
Konya, Kenichiro
2007-05-15
We study the emission of gravitons by a homogeneous brane with the Gauss-Bonnet term into an anti-de Sitter five dimensional bulk spacetime. It is found that the graviton emission depends on the curvature scale and the Gauss-Bonnnet coupling and that the amount of emission generally decreases. Therefore nucleosynthesis constraints are easier to satisfy by including the Gauss-Bonnet term.
Fractional Fourier transform of Lorentz-Gauss beams.
Zhou, Guoquan
2009-02-01
Lorentz-Gauss beams are introduced to describe certain laser sources that produce highly divergent beams. The fractional Fourier transform (FRFT) is applied to treat the propagation of Lorentz-Gauss beams. Based on the definition of convolution and the convolution theorem of the Fourier transform, an analytical expression for a Lorentz-Gauss beam passing through an FRFT system has been derived. By using the derived expression, the properties of a Lorentz-Gauss beam in the FRFT plane are graphically illustrated with numerical examples.
Surface terms and the Gauss Bonnet Hamiltonian
NASA Astrophysics Data System (ADS)
Padilla, Antonio
2003-07-01
We derive the gravitational Hamiltonian starting from the Gauss Bonnet action, keeping track of all surface terms. This is done using the language of orthonormal frames and forms to keep things as tidy as possible. The surface terms in the Hamiltonian give a remarkably simple expression for the total energy of a spacetime. This expression is consistent with energy expressions found in Preprint hep-th/0212292. However, we can apply our results whatever the choice of background and whatever the symmetries of the spacetime.
Multivariate curve-fitting in GAUSS
Bunck, C.M.; Pendleton, G.W.
1988-01-01
Multivariate curve-fitting techniques for repeated measures have been developed and an interactive program has been written in GAUSS. The program implements not only the one-factor design described in Morrison (1967) but also includes pairwise comparisons of curves and rates, a two-factor design, and other options. Strategies for selecting the appropriate degree for the polynomial are provided. The methods and program are illustrated with data from studies of the effects of environmental contaminants on ducklings, nesting kestrels and quail.
Basic full-wave generalization of the real-argument Hermite-Gauss beam.
Seshadri, S R
2010-05-01
The linearly polarized real-argument Hermite-Gauss beam is investigated by the Fourier transform method. The complex power is obtained and the reactive power of the paraxial beam is found to be zero. The complex space source required for the full-wave generalization of the real-argument Hermite-Gauss beam is deduced. The resulting basic full real-argument Hermite-Gauss wave is determined. The real and the reactive powers of the full wave are evaluated. The reactive power of the basic full real-argument Hermite-Gauss wave is infinite, and the reasons for this singularity are described. The real power depends on kw(0), m, and n, where k is the wavenumber, w(0) is the e-folding distance of the Gaussian part of the input distribution, and m and n are the mode numbers. The variation in the real power with respect to changes in kw(0) for specified m and n as well as with respect to changes in m and n for a specified kw(0) is examined.
Reheating in Gauss-Bonnet-coupled inflation
NASA Astrophysics Data System (ADS)
van de Bruck, Carsten; Longden, Chris; Dimopoulos, Konstantinos
2016-07-01
We investigate the feasibility of models of inflation with a large Gauss-Bonnet coupling at late times, which have been shown to modify and prevent the end of inflation. Despite the potential of Gauss-Bonnet models in predicting favorable power spectra, capable of greatly lowering the tensor-to-scalar ratio compared to now-disfavored models of standard chaotic inflation, it is important to also understand in what context it is possible for postinflationary (p)reheating to proceed and hence recover an acceptable late-time cosmology. We argue that in the previously studied inverse power law coupling case, reheating cannot happen due to a lack of oscillatory solutions for the inflaton, and that neither instant preheating nor gravitational particle production would avoid this problem due to the persistence of the inflaton's energy density, even if it were to partially decay. Hence we proceed to define a minimal generalization of the model which can permit perturbative reheating and study the consequences of this, including heavily modified dynamics during reheating and predictions of the power spectra.
Scalar modified Bessel-Gauss beams and waves.
Seshadri, S R
2007-09-01
For modified Bessel-Gauss beams, the modulating function for the Gaussian, instead of a Bessel function of real argument, is a Bessel function of imaginary argument. The modified Bessel-Gauss beams and their full wave generalizations are treated with particular attention to the spreading properties on propagation for the azimuthal mode numbers m=0 and m=1. The spreading on propagation of the peak and the null in the radiation pattern obtained in the propagation direction for m=0 and m=1, respectively, is substantially less for the modified Bessel-Gauss waves than that for the corresponding Bessel-Gauss waves. The total power transported by the waves is determined and compared with that of the corresponding paraxial beam to assess the quality of the paraxial beam approximation for the wave. The powers in the Bessel-Gauss wave and the modified Bessel-Gauss wave are finite in contrast to that in the Bessel wave. With respect to both the spreading properties and the quality of the paraxial beam approximation, the modified Bessel-Gauss beam is an improvement over the Bessel-Gauss beam.
Holographic p-wave superconductors from Gauss-Bonnet gravity
Cai Ronggen; Nie Zhangyu; Zhang Haiqing
2010-09-15
We study the holographic p-wave superconductors in a five-dimensional Gauss-Bonnet gravity with an SU(2) Yang-Mills gauge field. In the probe approximation, we find that when the Gauss-Bonnet coefficient grows, the condensation of the vector field becomes harder, both the perpendicular and parallel components, with respect to the direction of the condensation, of the anisotropic conductivity decrease. We also study the mass of the quasiparticle excitations, the gap frequency and the DC conductivities of the p-wave superconductor. All of them depend on the Gauss-Bonnet coefficient. In addition, we observe a strange behavior for the condensation and the relation between the gap frequency and the mass of quasiparticles when the Gauss-Bonnet coefficient is larger than 9/100, which is the upper bound for the Gauss-Bonnet coefficient from the causality of the dual field theory.
Electromagnetic modified Bessel-Gauss beams and waves.
Seshadri, S R
2008-01-01
The transverse magnetic (TM) modified Bessel-Gauss beams and their full-wave generalizations are treated. Attention is paid to the spreading properties on propagation of the null in the radiation intensity pattern for the azimuthal mode numbers m=0 and 1. The rate of spreading of the null in the propagation direction is significantly less for the TM modified Bessel-Gauss waves than those for the corresponding TM Bessel-Gauss waves. The total power transported by the waves is determined and compared with that of the corresponding paraxial beam to estimate the quality of the paraxial beam approximation of the wave. The dependence of the quality of the paraxial beam approximation on the azimuthal mode number, the beam shape parameter, and the ratio of the beam waist to the wavelength has a regular pattern for the TM Bessel-Gauss wave and not for the TM modified Bessel-Gauss wave.
Optimization Experiments With A Double Gauss Lens
NASA Astrophysics Data System (ADS)
Brixner, Berlyn; Klein, Morris M.
1988-05-01
This paper describes how a lens can be generated by starting from plane surfaces. Three different experiments, using the Los Alamos National Laboratory optimization procedure, all converged on the same stable prescriptions in the optimum minimum region. The starts were made first from an already optimized lens appearing in the literature, then from a powerless plane-surfaces configuration, and finally from a crude Super Angulon configuration. In each case the result was a double Gauss lens, which suggests that this type of lens may be the best compact six-glass solution for one imaging problem: an f/2 aperture and a moderate field of view. The procedures and results are discussed in detail.
From entropy-maximization to equality-maximization: Gauss, Laplace, Pareto, and Subbotin
NASA Astrophysics Data System (ADS)
Eliazar, Iddo
2014-12-01
The entropy-maximization paradigm of statistical physics is well known to generate the omnipresent Gauss law. In this paper we establish an analogous socioeconomic model which maximizes social equality, rather than physical disorder, in the context of the distributions of income and wealth in human societies. We show that-on a logarithmic scale-the Laplace law is the socioeconomic equality-maximizing counterpart of the physical entropy-maximizing Gauss law, and that this law manifests an optimized balance between two opposing forces: (i) the rich and powerful, striving to amass ever more wealth, and thus to increase social inequality; and (ii) the masses, struggling to form more egalitarian societies, and thus to increase social equality. Our results lead from log-Gauss statistics to log-Laplace statistics, yield Paretian power-law tails of income and wealth distributions, and show how the emergence of a middle-class depends on the underlying levels of socioeconomic inequality and variability. Also, in the context of asset-prices with Laplace-distributed returns, our results imply that financial markets generate an optimized balance between risk and predictability.
Factorizing numbers with the Gauss sum technique: NMR implementations
Mahesh, T. S.; Rajendran, Nageswaran; Peng Xinhua; Suter, Dieter
2007-06-15
Several physics-based algorithms for factorizing large numbers were recently presented. A notable recent algorthm by Schleich et al. uses Gauss sums for distinguishing between factors and nonfactors. We demonstrate two NMR techniques that evaluate Gauss sums and thus implement their algorithm. The first one is based on differential excitation of a single spin magnetization by a cascade of rf pulses. The second method is based on spatial averaging and selective refocusing of magnetization for Gauss sums corresponding to factors. All factors of 16 637 and 52 882 363 are successfully obtained.0.
Slow-roll inflation with a Gauss-Bonnet correction
Guo Zongkuan; Schwarz, Dominik J.
2010-06-15
We consider slow-roll inflation for a single scalar field with an arbitrary potential and an arbitrary nonminimal coupling to the Gauss-Bonnet term. By introducing a combined hierarchy of Hubble and Gauss-Bonnet flow functions, we analytically derive the power spectra of scalar and tensor perturbations. The standard consistency relation between the tensor-to-scalar ratio and the spectral index of tensor perturbations is broken. We apply this formalism to a specific model with a monomial potential and an inverse monomial Gauss-Bonnet coupling and constrain it by the 7-year Wilkinson Microwave Anisotropy Probe data. The Gauss-Bonnet term with a positive (or negative) coupling may lead to a reduction (or enhancement) of the tensor-to-scalar ratio and hence may revive the quartic potential ruled out by recent cosmological data.
Composite Gauss-Legendre Quadrature with Error Control
ERIC Educational Resources Information Center
Prentice, J. S. C.
2011-01-01
We describe composite Gauss-Legendre quadrature for determining definite integrals, including a means of controlling the approximation error. We compare the form and performance of the algorithm with standard Newton-Cotes quadrature. (Contains 1 table.)
Strong gravitational lensing with Gauss-Bonnet correction
Sadeghi, J.; Vaez, H. E-mail: h.vaez@umz.ac.ir
2014-06-01
In this paper we investigate the strong gravitational lensing in a five dimensional background with Gauss-Bonnet gravity, so that in 4-dimensions the Gauss-Bonnet correction disappears. By considering the logarithmic term for deflection angle, we obtain the deflection angle α-circumflex and corresponding parameters ā and b-bar . Finally, we estimate some properties of relativistic images such as θ{sub ∞}, s and r{sub m}.
Domain walls in Einstein-Gauss-Bonnet bulk
Mazharimousavi, S. Habib; Halilsoy, M.
2010-10-15
We investigate the dynamics of a n-dimensional domain wall in a n+1-dimensional Einstein-Gauss-Bonnet bulk. Exact effective potential induced by the Gauss-Bonnet (GB) term on the wall is derived. In the absence of the GB term we recover the familiar gravitational and antiharmonic oscillator potentials. Inclusion of the GB correction gives rise to a minimum radius of bounce for the Friedmann-Robertson-Walker universe expanding with a negative pressure on the domain wall.
NASA Astrophysics Data System (ADS)
Gautschi, Walter
2009-06-01
The generation of generalized Gauss-Radau and Gauss-Lobatto quadrature formulae by methods developed by us earlier breaks down in the case of Jacobi and Laguerre measures when the order of the quadrature rules becomes very large. The reason for this is underflow resp. overflow of the respective monic orthogonal polynomials. By rescaling of the polynomials, and other corrective measures, the problem can be circumvented, and formulae can be generated of orders as high as 1,000.
Entanglement of Ince-Gauss Modes of Photons
NASA Astrophysics Data System (ADS)
Krenn, Mario; Fickler, Robert; Plick, William; Lapkiewicz, Radek; Ramelow, Sven; Zeilinger, Anton
2012-02-01
Ince-Gauss modes are solutions of the paraxial wave equation in elliptical coordinates [1]. They are natural generalizations both of Laguerre-Gauss and of Hermite-Gauss modes, which have been used extensively in quantum optics and quantum information processing over the last decade [2]. Ince-Gauss modes are described by one additional real parameter -- ellipticity. For each value of ellipticity, a discrete infinite-dimensional Hilbert space exists. This conceptually new degree of freedom could open up exciting possibilities for higher-dimensional quantum optical experiments. We present the first entanglement of non-trivial Ince-Gauss Modes. In our setup, we take advantage of a spontaneous parametric down-conversion process in a non-linear crystal to create entangled photon pairs. Spatial light modulators (SLMs) are used as analyzers. [1] Miguel A. Bandres and Julio C. Guti'errez-Vega ``Ince Gaussian beams", Optics Letters, Vol. 29, Issue 2, 144-146 (2004) [2] Adetunmise C. Dada, Jonathan Leach, Gerald S. Buller, Miles J. Padgett, and Erika Andersson, ``Experimental high-dimensional two-photon entanglement and violations of generalized Bell inequalities", Nature Physics 7, 677-680 (2011)
The AGS Ggamma Meter and Calibrating the Gauss Clock
Ahrens, Leif
2014-03-31
During AGS Polarized Proton acceleration periods, one output from the AGS Ggamma Meter, namely the energy (or Ggamma) calculated from the magnetic field in the AGS main magnets and the beam radius- both measured in particular instant, is used to figure out the times in the AGS magnet acceleration cycle when the beam passes through a particular set of depolarizing resonances. The resonance set occur whenever a particle’s Ggamma (energy*(G/m) becomes nearly equal to n*Qx (i.e. any integer multiplied by the horizontal betatron tune). This deliverable is why the machinery is referred to as the ''Ggamma Meter'' rather than the AGS energy meter. The Ggamma Meter takes as inputs a set of measurements of frequency (F(t)), radius (r(t)), and gauss clock counts (GCC(t)). The other energy (GgammaBr) assumes the field when the gauss clock starts counting is known. The change in field to time t is given by the measured accumulated gauss clock counts multiplied by the gauss clock calibration (gauss/GCC). In order to deal with experimental data, this calibration factor gets an added ad hoc complication, namely a correction dependent on the rate of change the counting rate. The Ggamma meter takes GCC(t) and together with the past history for this cycle calculates B(t).
Energy flux density and angular momentum density of Pearcey-Gauss vortex beams in the far field
NASA Astrophysics Data System (ADS)
Cheng, K.; Lu, G.; Zhong, X.
2017-02-01
The longitudinal and transverse energy flux density (EFD) and angular momentum density (AMD) of a Pearcey-Gauss vortex beam in the far field are studied using the vector angular spectrum representation and stationary phase method, where the influence of topological charge, noncanonical strength and off-axis distance of the embedded optical vortex on far-field vectorial structures of the corresponding beam is emphasized. For comparison, the EFD and AMD of the Pearcey-Gauss beam with non-vortex in the far field are also discussed. The results show that the longitudinal EFDs of the Pearcey-Gauss vortex beam exhibit parabolic patterns, and the number of parabolic dark zones equals the absolute value of topological charge of the embedded optical vortex in the input plane. While for the Pearcey-Gauss beam, the dark zones are not found owing to the non-vortex in the input plane. The motion of zero-intensity spot of whole beam appears by varying the off-axis distance. Noncanonical strength and off-axis distance both can adjust the magnitudes and directions of transverse EFD and control the spatial energy distributions of longitudinal EFD, but not change the net AMD.
Framed 4-graphs: Euler tours, Gauss circuits and rotating circuits
Il'yutko, Denis P
2011-09-30
We consider connected finite 4-valent graphs with the structure of opposite edges at each vertex (framed 4-graphs). For any of such graphs there exist Euler tours, in travelling along which at each vertex we turn from an edge to a nonopposite one (rotating circuits); and at the same time, it is not true that for any such graph there exists an Euler tour passing from an edge to the opposite one at each vertex (a Gauss circuit). The main result of the work is an explicit formula connecting the adjacency matrices of the Gauss circuit and an arbitrary Euler tour. This formula immediately gives us a criterion for the existence of a Gauss circuit on a given framed 4-graph. It turns out that the results are also valid for all symmetric matrices (not just for matrices realisable by a chord diagram). Bibliography: 24 titles.
Gauss-Bonnet chameleon mechanism of dark energy
Ito, Yusaku; Nojiri, Shin'ichi
2009-05-15
As a model of the current accelerated expansion of the Universe, we consider a model of the scalar-Einstein-Gauss-Bonnet gravity. This model includes the propagating scalar modes, which might give a large correction to the Newton law. In order to avoid this problem, we propose an extension of the chameleon mechanism where the scalar mode becomes massive due to the coupling with the Gauss-Bonnet term. Since the Gauss-Bonnet invariant does not vanish near the Earth or in the Solar System, even in the vacuum, the scalar mode is massive even in the vacuum and the correction to the Newton law could be small. We also discuss the possibility that the model could describe simultaneously the inflation in the early Universe, in addition to the current accelerated expansion.
Rotating black holes in dilatonic Einstein-Gauss-Bonnet theory.
Kleihaus, Burkhard; Kunz, Jutta; Radu, Eugen
2011-04-15
We construct generalizations of the Kerr black holes by including higher-curvature corrections in the form of the Gauss-Bonnet density coupled to the dilaton. We show that the domain of existence of these Einstein-Gauss-Bonnet-dilaton (EGBD) black holes is bounded by the Kerr black holes, the critical EGBD black holes, and the singular extremal EGBD solutions. The angular momentum of the EGBD black holes can exceed the Kerr bound. The EGBD black holes satisfy a generalized Smarr relation. We also compare their innermost stable circular orbits with those of the Kerr black holes and show the existence of differences which might be observable in astrophysical systems.
NASA Astrophysics Data System (ADS)
Wang, Dong; Tsui, Kwok-Leung; Zhou, Qiang
2016-05-01
Rolling element bearings are commonly used in machines to provide support for rotating shafts. Bearing failures may cause unexpected machine breakdowns and increase economic cost. To prevent machine breakdowns and reduce unnecessary economic loss, bearing faults should be detected as early as possible. Because wavelet transform can be used to highlight impulses caused by localized bearing faults, wavelet transform has been widely investigated and proven to be one of the most effective and efficient methods for bearing fault diagnosis. In this paper, a new Gauss-Hermite integration based Bayesian inference method is proposed to estimate the posterior distribution of wavelet parameters. The innovations of this paper are illustrated as follows. Firstly, a non-linear state space model of wavelet parameters is constructed to describe the relationship between wavelet parameters and hypothetical measurements. Secondly, the joint posterior probability density function of wavelet parameters and hypothetical measurements is assumed to follow a joint Gaussian distribution so as to generate Gaussian perturbations for the state space model. Thirdly, Gauss-Hermite integration is introduced to analytically predict and update moments of the joint Gaussian distribution, from which optimal wavelet parameters are derived. At last, an optimal wavelet filtering is conducted to extract bearing fault features and thus identify localized bearing faults. Two instances are investigated to illustrate how the proposed method works. Two comparisons with the fast kurtogram are used to demonstrate that the proposed method can achieve better visual inspection performances than the fast kurtogram.
Wormholes in dilatonic Einstein-Gauss-Bonnet theory.
Kanti, Panagiota; Kleihaus, Burkhard; Kunz, Jutta
2011-12-30
We construct traversable wormholes in dilatonic Einstein-Gauss-Bonnet theory in four spacetime dimensions, without needing any form of exotic matter. We determine their domain of existence, and show that these wormholes satisfy a generalized Smarr relation. We demonstrate linear stability with respect to radial perturbations for a subset of these wormholes.
Bounce universe from string-inspired Gauss-Bonnet gravity
Bamba, Kazuharu; Makarenko, Andrey N.; Myagky, Alexandr N.; Odintsov, Sergei D. E-mail: andre@tspu.edu.ru E-mail: odintsov@ieec.uab.es
2015-04-01
We explore cosmology with a bounce in Gauss-Bonnet gravity where the Gauss-Bonnet invariant couples to a dynamical scalar field. In particular, the potential and and Gauss-Bonnet coupling function of the scalar field are reconstructed so that the cosmological bounce can be realized in the case that the scale factor has hyperbolic and exponential forms. Furthermore, we examine the relation between the bounce in the string (Jordan) and Einstein frames by using the conformal transformation between these conformal frames. It is shown that in general, the property of the bounce point in the string frame changes after the frame is moved to the Einstein frame. Moreover, it is found that at the point in the Einstein frame corresponding to the point of the cosmological bounce in the string frame, the second derivative of the scale factor has an extreme value. In addition, it is demonstrated that at the time of the cosmological bounce in the Einstein frame, there is the Gauss-Bonnet coupling function of the scalar field, although it does not exist in the string frame.
Holographic vector superconductor in Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Lu, Jun-Wang; Wu, Ya-Bo; Cai, Tuo; Liu, Hai-Min; Ren, Yin-Shuan; Liu, Mo-Lin
2016-02-01
In the probe limit, we numerically study the holographic p-wave superconductor phase transitions in the higher curvature theory. Concretely, we study the influences of Gauss-Bonnet parameter α on the Maxwell complex vector model (MCV) in the five-dimensional Gauss-Bonnet-AdS black hole and soliton backgrounds, respectively. In the two backgrounds, the improving Gauss-Bonnet parameter α and dimension of the vector operator Δ inhibit the vector condensate. In the black hole, the condensate quickly saturates a stable value at lower temperature. Moreover, both the stable value of condensate and the ratio ωg /Tc increase with α. In the soliton, the location of the second pole of the imaginary part increases with α, which implies that the energy of the quasiparticle excitation increases with the improving higher curvature correction. In addition, the influences of the Gauss-Bonnet correction on the MCV model are similar to the ones on the SU(2) p-wave model, which confirms that the MCV model is a generalization of the SU(2) Yang-Mills model even without the applied magnetic field to some extent.
An Exodus II specification for handling gauss points.
Thompson, David C.; Jortner, Jeffrey N.; Pebay, Philippe Pierre
2007-11-01
This report specifies the way in which Gauss points shall be named and ordered when storing them in an EXODUS II file so that they may be properly interpreted by visualization tools. This naming convention covers hexahedra and tetrahedra. Future revisions of this document will cover quadrilaterals, triangles, and shell elements.
Gauss-Legendre Sky Pixelization (glesp) for CMB Maps
NASA Astrophysics Data System (ADS)
Doroshkevich, A. G.; Naselsky, P. D.; Verkhodanov, O. V.; Novikov, D. I.; Turchaninov, V. I.; Novikov, I. D.; Christensen, P. R.; Chiang, L.-Y.
A new scheme of sky pixelization is developed for CMB maps. The scheme is based on the Gauss-Legendre polynomials zeros and allows one to create strict orthogonal expansion of the map. A corresponding code has been implemented and comparison with other methods has been done.
Understanding Gauss's Law Using Spreadsheets
ERIC Educational Resources Information Center
Baird, William H.
2013-01-01
Some of the results from the electrostatics portion of introductory physics are particularly difficult for students to understand and/or believe. For students who have yet to take vector calculus, Gauss's law is far from obvious and may seem more difficult than Coulomb's. When these same students are told that the minimum potential…
Holographic superconductors with various condensates in Einstein-Gauss-Bonnet gravity
Pan Qiyuan; Wang Bin; Papantonopoulos, Eleftherios; Oliveira, Jeferson de; Pavan, A. B.
2010-05-15
We study holographic superconductors in Einstein-Gauss-Bonnet gravity. We consider two particular backgrounds: a d-dimensional Gauss-Bonnet-AdS black hole and a Gauss-Bonnet-AdS soliton. We discuss in detail the effects that the mass of the scalar field, the Gauss-Bonnet coupling and the dimensionality of the AdS space have on the condensation formation and conductivity. We also study the ratio {omega}{sub g}/T{sub c} for various masses of the scalar field and Gauss-Bonnet couplings.
Peng, Sun; Jin, Guo; Tingfeng, Wang
2013-07-01
Based on the generalized Huygens-Fresnel diffraction integral (Collins' formula), the propagation equation of Hermite-Gauss beams through a complex optical system with a limiting aperture is derived. The elements of the optical system may be all those characterized by an ABCD ray-transfer matrix, as well as any kind of apertures represented by complex transmittance functions. To obtain the analytical expression, we expand the aperture transmittance function into a finite sum of complex Gaussian functions. Thus the limiting aperture is expressed as a superposition of a series of Gaussian-shaped limiting apertures. The advantage of this treatment is that we can treat almost all kinds of apertures in theory. As application, we define the width of the beam and the focal plane using an encircled-energy criterion and calculate the intensity distribution of Hermite-Gauss beams at the actual focus of an aperture lens.
Holographic p-wave superfluid in Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Liu, Shancheng; Pan, Qiyuan; Jing, Jiliang
2017-02-01
We construct the holographic p-wave superfluid in Gauss-Bonnet gravity via a Maxwell complex vector field model and investigate the effect of the curvature correction on the superfluid phase transition in the probe limit. We obtain the rich phase structure and find that the higher curvature correction hinders the condensate of the vector field but makes it easier for the appearance of translating point from the second-order transition to the first-order one or for the emergence of the Cave of Winds. Moreover, for the supercurrents versus the superfluid velocity, we observe that our results near the critical temperature are independent of the Gauss-Bonnet parameter and agree well with the Ginzburg-Landau prediction.
Laguerre-Gauss beams versus Bessel beams showdown: peer comparison.
Mendoza-Hernández, Job; Arroyo-Carrasco, Maximino Luis; Iturbe-Castillo, Marcelo David; Chávez-Cerda, Sabino
2015-08-15
We present for the first time a comparison under similar circumstances between Laguerre-Gauss beams (LGBs) and Bessel beams (BB), and show that the former can be a better option for many applications in which BBs are currently used. By solving the Laguerre-Gauss differential equation in the asymptotic limit of a large radial index, we find the parameters to perform a peer comparison, showing that LGBs can propagate quasi-nondiffracting beams within the same region of space where the corresponding BBs do. We also demonstrate that LGBs, which have the property of self-healing, are more robust in the sense that they can propagate further than BBs under similar initial conditions.
Noether symmetries in Gauss-Bonnet-teleparallel cosmology
NASA Astrophysics Data System (ADS)
Capozziello, Salvatore; De Laurentis, Mariafelicia; Dialektopoulos, Konstantinos F.
2016-11-01
A generalized teleparallel cosmological model, f(T_{G},T), containing the torsion scalar T and the teleparallel counterpart of the Gauss-Bonnet topological invariant T_{{G}}, is studied in the framework of the Noether symmetry approach. As f({G}, R) gravity, where {G} is the Gauss-Bonnet topological invariant and R is the Ricci curvature scalar, exhausts all the curvature information that one can construct from the Riemann tensor, in the same way, f(T_{G},T) contains all the possible information directly related to the torsion tensor. In this paper, we discuss how the Noether symmetry approach allows one to fix the form of the function f(T_{G},T) and to derive exact cosmological solutions.
Debye screening versus Gauss law in electrostatics: Finite size effects
NASA Astrophysics Data System (ADS)
Dubey, Ritesh Kumar; Menon, V. J.; Mishra, M.; Tripathi, D. N.
2007-10-01
We revisit the well-known topics of self- and induced-screening in an otherwise isotropic neutral plasma/colloid. It is pointed out that the standard Debye-Hückel (DH) theory (ignoring finite size effects) suffers from many ambiguities related to net ionic numbers, total charge of the system, role of the electrostatic Gauss law, short-distance behaviour of the potential and incorrectly normalized pair correlation functions. We give a new formulation (incorporating finite size effects) such that ionic numbers are maintained, the total charge of the system has physically correct value, the Gauss law boundary conditions are rigorously obeyed, short-distance behaviour of the potential is guaranteed automatically, and correlation functions are correctly normalized. Numerical differences between the two approaches show up if the screening length μ-1 becomes comparable to the size R of the system.
Noether symmetries in Gauss-Bonnet-teleparallel cosmology.
Capozziello, Salvatore; De Laurentis, Mariafelicia; Dialektopoulos, Konstantinos F
2016-01-01
A generalized teleparallel cosmological model, [Formula: see text], containing the torsion scalar T and the teleparallel counterpart of the Gauss-Bonnet topological invariant [Formula: see text], is studied in the framework of the Noether symmetry approach. As [Formula: see text] gravity, where [Formula: see text] is the Gauss-Bonnet topological invariant and R is the Ricci curvature scalar, exhausts all the curvature information that one can construct from the Riemann tensor, in the same way, [Formula: see text] contains all the possible information directly related to the torsion tensor. In this paper, we discuss how the Noether symmetry approach allows one to fix the form of the function [Formula: see text] and to derive exact cosmological solutions.
Dark energy from Gauss-Bonnet and nonminimal couplings
NASA Astrophysics Data System (ADS)
Granda, L. N.; Jimenez, D. F.
2014-12-01
We consider a scalar-tensor model of dark energy with Gauss-Bonnet and nonminimal couplings. Exact cosmological solutions were found in the absence of potential that give equations of state of dark energy consistent with current observational constraints, but with different asymptotic behaviors depending on the couplings of the model. A detailed reconstruction procedure is given for the scalar potential and the Gauss-Bonnet coupling for any given cosmological scenario. In particular we consider conditions for the existence of a variety of cosmological solutions with accelerated expansion, including quintessence, phantom, de Sitter, and Little Rip. For the case of quintessence and phantom we have found a scalar potential of the Albrecht-Skordis type, where the potential is an exponential with a polynomial factor.
Bouncing loop quantum cosmology in Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Haro, J.; Makarenko, A. N.; Myagky, A. N.; Odintsov, S. D.; Oikonomou, V. K.
2015-12-01
We develop an effective Gauss-Bonnet extension of loop quantum cosmology, by introducing holonomy corrections in modified F (G ) theories of gravity. Within the context of our formalism, we provide a perturbative expansion in the critical density, a parameter characteristic of loop quantum gravity theories, and we result in having leading order corrections to the classical F (G ) theories of gravity. After extensively discussing the formalism, we present a reconstruction method that makes it possible to find the loop quantum cosmology corrected F (G ) theory that can realize various cosmological scenarios. We exemplify our theoretical constructions by using bouncing cosmologies, and we investigate which loop quantum cosmology corrected Gauss-Bonnet modified gravities can successfully realize such cosmologies.
Orbital angular momentum density of a general Lorentz-Gauss vortex beam
NASA Astrophysics Data System (ADS)
Zhou, Guoquan; Ji, Zhiyue; Ru, Guoyun
2016-07-01
Based on the vectorial Rayleigh-Sommerfeld integral formulae, the analytical expression of a general Lorentz-Gauss vortex beam with an arbitrary topological charge is derived in free space. By using the analytical expressions of the electromagnetic field beyond the paraxial approximation, the orbital angular momentum density of a general Lorentz-Gauss vortex beam can be calculated. The effects of the linearly polarized angle and the topological charge on the three components of the orbital angular momentum density are investigated in the reference plane. The two transversal components of the orbital angular momentum are composed of two lobes with the same areas and opposite signs. The longitudinal component of the orbital angular momentum density is composed of four lobes with the same areas. The sign of the orbital angular momentum density in a pair of lobes is positive, and that of the orbital angular momentum density in the other pair of lobes is negative. Moreover, the negative magnitude of the orbital angular momentum density is larger than the positive magnitude of the orbital angular momentum density. The linearly polarized angle affects not only the shape and the location of the lobes, but also the magnitude of the three components of the orbital angular momentum density. With increasing the topological charge, the distribution of the orbital angular momentum density expands, the magnitude of the orbital angular momentum density increases, and the shape of the lobe also slightly changes.
Accelerating the Gauss-Seidel Power Flow Solver on a High Performance Reconfigurable Computer
Byun, Jong-Ho; Ravindran, Arun; Mukherjee, Arindam; Joshi, Bharat; Chassin, David P.
2009-09-01
The computationally intensive power flow problem determines the voltage magnitude and phase angle at each bus in a power system for hundreds of thousands of buses under balanced three-phase steady-state conditions. We report an FPGA acceleration of the Gauss-Seidel based power flow solver employed in the transmission module of the GridLAB-D power distribution simulator and analysis tool. The prototype hardware is implemented on an SGI Altix-RASC system equipped with a Xilinx Virtex II 6000 FPGA. Due to capacity limitations of the FPGA, only the bus voltage calculations of the power network are implemented on hardware while the branch current calculations are implemented in software. For a 200,000 bus system, the bus voltage calculation on the FPGA achieves a 48x speed-up with PQ buses and a 62 times for PV over an equivalent sequential software implementation. The average overall speed up of the FPGA-CPU implementation with 100 iterations of the Gauss-Seidel power solver is 2.6x over a software implementation, with the branch calculations on the CPU accounting for 85% of the total execution time. The FPGA-CPU implementation also shows linear scaling with increase in the size of the input power network.
Long life of Gauss-Bonnet corrected black holes
Konoplya, R. A.; Zhidenko, A.
2010-10-15
Dictated by the string theory and various higher dimensional scenarios, black holes in D>4-dimensional space-times must have higher curvature corrections. The first and dominant term is quadratic in curvature, and called the Gauss-Bonnet (GB) term. We shall show that although the Gauss-Bonnet correction changes black hole's geometry only softly, the emission of gravitons is suppressed by many orders even at quite small values of the GB coupling. The huge suppression of the graviton emission is due to the multiplication of the two effects: the quick cooling of the black hole when one turns on the GB coupling and the exponential decreasing of the gray-body factor of the tensor type of gravitons at small and moderate energies. At higher D the tensor gravitons emission is dominant, so that the overall lifetime of black holes with Gauss-Bonnet corrections is many orders larger than was expected. This effect should be relevant for the future experiments at the Large Hadron Collider (LHC).
The LHCb Simulation Application, Gauss: Design, Evolution and Experience
NASA Astrophysics Data System (ADS)
Clemencic, M.; Corti, G.; Easo, S.; Jones, C. R.; Miglioranzi, S.; Pappagallo, M.; Robbe, P.; LHCb Collaboration
2011-12-01
The LHCb simulation application, Gauss, is based on the Gaudi framework and on experiment basic components such as the Event Model and Detector Description. Gauss also depends on external libraries for the generation of the primary events (PYTHIA 6, EvtGen, etc.) and on GEANT4 for particle transport in the experimental setup. The application supports the production of different types of events from minimum bias to B physics signals and particle guns. It is used for purely generator-level studies as well as full simulations. Gauss is used both directly by users and in massive central productions on the grid. The design and implementation of the application and its evolution due to evolving requirements will be described as in the case of the recently adopted Python-based configuration or the possibility of taking into account detectors conditions via a Simulation Conditions database. The challenge of supporting at the same time the flexibililty needed for the different tasks for which it is used, from evaluation of physics reach to background modeling, together with the stability and reliabilty of the code will also be described.
Spherical-earth gravity and magnetic anomaly modeling by Gauss-Legendre quadrature integration
NASA Technical Reports Server (NTRS)
Von Frese, R. R. B.; Hinze, W. J.; Braile, L. W.; Luca, A. J.
1981-01-01
Gauss-Legendre quadrature integration is used to calculate the anomalous potential of gravity and magnetic fields and their spatial derivatives on a spherical earth. The procedure involves representation of the anomalous source as a distribution of equivalent point gravity poles or point magnetic dipoles. The distribution of equivalent point sources is determined directly from the volume limits of the anomalous body. The variable limits of integration for an arbitrarily shaped body are obtained from interpolations performed on a set of body points which approximate the body's surface envelope. The versatility of the method is shown by its ability to treat physical property variations within the source volume as well as variable magnetic fields over the source and observation surface. Examples are provided which illustrate the capabilities of the technique, including a preliminary modeling of potential field signatures for the Mississippi embayment crustal structure at 450 km.
Durbin, Timothy J.
1983-01-01
The Gauss optimization technique can be used to identify the parameters of a model of a groundwater system for which the parameter identification problem is formulated as a least squares comparison between the response of the prototype and the response of the model. Unavoidable uncertainty in the true stress on the prototype and in the true response of the prototype to that stress will introduce errors into the parameter identification problem. A method for evaluating errors in the predictions of future water levels due to errors in recharge estimates was demonstrated. The method involves a Monte Carlo simulation of the parameter identification problem and of the prediction problem. The steps in the method are: (1) to prescribe the distribution of the recharge estimates; (2) to use this distribution to generate random sets of recharge estimates; (3) to use the Gauss optimization technique to identify the corresponding set of parameter estimates for each set of recharge estimates; (4) to make the corresponding set of hydraulic head predictions for each set of parameter estimates; and (5) to examine the distribution of hydraulic head predictions and to draw appropriate conclusions. Similarly, the method can be used independently or simultaneously to estimate the effect on hydraulic head predictions of errors in the measured water levels that are used in the parameter identification problem. The fit of the model to the data that are used to identify parameters is not a good indicator of these errors. A Monte Carlo simulation of the parameter identification problem can be used, however, to evaluate the effects on water level predictions of errors in the recharge (and pumpage) data used in the parameter identification problem. (Lantz-PTT)
Generalizing higher-order Bessel-Gauss beams: analytical description and demonstration.
Schimpf, Damian N; Schulte, Jan; Putnam, William P; Kärtner, Franz X
2012-11-19
We report on a novel class of higher-order Bessel-Gauss beams in which the well-known Bessel-Gauss beam is the fundamental mode and the azimuthally symmetric Laguerre-Gaussian beams are special cases. We find these higher-order Bessel-Gauss beams by superimposing decentered Hermite-Gaussian beams. We show analytically and experimentally that these higher-order Bessel-Gauss beams resemble higher-order eigenmodes of optical resonators consisting of aspheric mirrors. This work is relevant for the many applications of Bessel-Gauss beams in particular the more recently proposed high-intensity Bessel-Gauss enhancement cavities for strong-field physics applications.
Self-similar propagation of Hermite-Gauss water-wave pulses.
Fu, Shenhe; Tsur, Yuval; Zhou, Jianying; Shemer, Lev; Arie, Ady
2016-01-01
We demonstrate both theoretically and experimentally propagation dynamics of surface gravity water-wave pulses, having Hermite-Gauss envelopes. We show that these waves propagate self-similarly along an 18-m wave tank, preserving their general Hermite-Gauss envelopes in both the linear and the nonlinear regimes. The measured surface elevation wave groups enable observing the envelope phase evolution of both nonchirped and linearly frequency chirped Hermite-Gauss pulses, hence allowing us to measure Gouy phase shifts of high-order Hermite-Gauss pulses for the first time. Finally, when increasing pulse amplitude, nonlinearity becomes essential and the second harmonic of Hermite-Gauss waves was observed. We further show that these generated second harmonic bound waves still exhibit self-similar Hermite-Gauss shapes along the tank.
Application of Gauss's law space-charge limited emission model in iterative particle tracking method
NASA Astrophysics Data System (ADS)
Altsybeyev, V. V.; Ponomarev, V. A.
2016-11-01
The particle tracking method with a so-called gun iteration for modeling the space charge is discussed in the following paper. We suggest to apply the emission model based on the Gauss's law for the calculation of the space charge limited current density distribution using considered method. Based on the presented emission model we have developed a numerical algorithm for this calculations. This approach allows us to perform accurate and low time consumpting numerical simulations for different vacuum sources with the curved emitting surfaces and also in the presence of additional physical effects such as bipolar flows and backscattered electrons. The results of the simulations of the cylindrical diode and diode with elliptical emitter with the use of axysimmetric coordinates are presented. The high efficiency and accuracy of the suggested approach are confirmed by the obtained results and comparisons with the analytical solutions.
Fractional Hamiltonian monodromy from a Gauss-Manin monodromy
Sugny, D.; Jauslin, H. R.; Mardesic, P.; Pelletier, M.; Jebrane, A.
2008-04-15
Fractional Hamiltonian monodromy is a generalization of the notion of Hamiltonian monodromy, recently introduced by [Nekhoroshev, Sadovskii, and Zhilinskii, C. R. Acad. Sci. Paris, Ser. 1 335, 985 (2002); and Ann. Henri Poincare 7, 1099 (2006)] for energy-momentum maps whose image has a particular type of nonisolated singularities. In this paper, we analyze the notion of fractional Hamiltonian monodromy in terms of the Gauss-Manin monodromy of a Riemann surface constructed from the energy-momentum map and associated with a loop in complex space which bypasses the line of singularities. We also prove some propositions on fractional Hamiltonian monodromy for 1:-n and m:-n resonant systems.
Nonsingular Universes in Gauss-Bonnet Gravity’s Rainbow
NASA Astrophysics Data System (ADS)
Hendi, Seyed Hossein; Momennia, Mehrab; Eslam Panah, Behzad; Faizal, Mir
2016-08-01
In this paper, we study the rainbow deformation of Friedmann-Robertson-Walker (FRW) cosmology in both Einstein gravity and Gauss-Bonnet (GB) gravity. We demonstrate that the singularity in FRW cosmology can be removed because of the rainbow deformation of the FRW metric. We obtain the general constraints required for FRW cosmology to be free of singularities. We observe that the inclusion of GB gravity can significantly change the constraints required to obtain nonsingular universes. We use rainbow functions motivated by the hard spectra of gamma-ray bursts to deform FRW cosmology and explicitly demonstrate that such a deformation removes the singularity in FRW cosmology.
Nonlinear diffraction from high-order Hermite-Gauss beams.
Kalinowski, Ksawery; Shapira, Asia; Libster-Hershko, Ana; Arie, Ady
2015-01-01
We investigate experimentally and theoretically the nonlinearly diffracted second harmonic light from the first-order Hermite-Gauss beam. We investigate the cases of loosely and tightly focused beams in a periodically poled lithium niobate crystal in the temperature range near the birefringent phase matching. Unlike the case of fundamental Gaussian beam, the nonlinear diffracted beam is spatially structured. Its shape depends on the focusing conditions and on the crystal temperature. Furthermore, for the case of tight focusing, the diffracted beam structure depends on the beam's position with respect to the domain wall.
Gauss's law test of gravity at short range
NASA Technical Reports Server (NTRS)
Moody, M. V.; Paik, H. J.
1993-01-01
A null test of the gravitational inverse-square law can be performed by testing Gauss's law for the field. We have constructed a three-axis superconducting gravity gradiometer and carried out such a test. A lead pendulum weighing 1500 kg was used to produce a time-varying field. This experiment places a new (2-sigma) limit of alpha = (0.9 + or - 4.6) x 10 exp -4 at lambda of 1.5 m, where alpha and lambda are parameters for the generalized potential phi = -(GM/r)(l + alpha e exp -r/lambda).
Light trajectory in Bessel-Gauss vortex beams.
Xie, Chen; Giust, Remo; Jukna, Vytautas; Furfaro, Luca; Jacquot, Maxime; Lacourt, Pierre-Ambroise; Froehly, Luc; Dudley, John; Couairon, Arnaud; Courvoisier, Francois
2015-07-01
We investigate the early stage of propagation of Bessel-Gauss vortex beams where a transition regime shows a progressive lateral expansion of the main intensity ring before reaching a diffraction-free regime. The eikonal equation is used to characterize the beam structure. The beam is featured by a family of hyperboloids with variable waists, generating a tapered tubular caustic. Our analytical results are in excellent agreement with numerical and experimental results. We show the transition regime can be well eliminated by using hollow input beams.
Extension of Gauss' method for the solution of Kepler's equation
NASA Technical Reports Server (NTRS)
Battin, R. H.; Fill, T. J.
1978-01-01
Gauss' method for solving Kepler's equation is extended to arbitrary epochs and orbital eccentricities. Although originally developed for near parabolic orbits in the vicinity of pericenter, a generalization of the method leads to a highly efficient algorithm which compares favorably to other methods in current use. A key virtue of the technique is that convergence is obtained by a method of successive substitutions with an initial approximation that is independent of the orbital parameters. The equations of the algorithm are universal, i.e., independent of the nature of the orbit whether elliptic, hyperbolic, parabolic or rectilinear.
Gauss-Bonnet modified gravity models with bouncing behavior
NASA Astrophysics Data System (ADS)
Escofet, Anna; Elizalde, Emilio
2016-06-01
The following issue is addressed: How the addition of a Gauss-Bonnet term (generically coming from most fundamental theories, as string and M theories), to a viable model, can change the specific properties, and even the physical nature, of the corresponding cosmological solutions? Specifically, brand new original dark energy models are obtained in this way with quite interesting properties, which exhibit, in a unified fashion, the three distinguished possible cosmological phases corresponding to phantom matter, quintessence and ordinary matter, respectively. A model, in which the equation of state (EoS) parameter, w, is a function of time, is seen to lead either to a singularity of the Big Rip kind or to a bouncing solution which evolves into a de Sitter universe with w = -1. Moreover, new Gauss-Bonnet modified gravity models with bouncing behavior in the early stages of the universe evolution are obtained and tested for the validity and stability of the corresponding solutions. They allow for a remarkably natural, unified description of a bouncing behavior at early times and accelerated expansion at present.
Controllable light capsules employing modified Bessel-Gauss beams.
Gong, Lei; Liu, Weiwei; Zhao, Qian; Ren, Yuxuan; Qiu, Xingze; Zhong, Mincheng; Li, Yinmei
2016-07-08
We report, in theory and experiment, on a novel class of controlled light capsules with nearly perfect darkness, directly employing intrinsic properties of modified Bessel-Gauss beams. These beams are able to naturally create three-dimensional bottle-shaped region during propagation as long as the parameters are properly chosen. Remarkably, the optical bottle can be controlled to demonstrate various geometries through tuning the beam parameters, thereby leading to an adjustable light capsule. We provide a detailed insight into the theoretical origin and characteristics of the light capsule derived from modified Bessel-Gauss beams. Moreover, a binary digital micromirror device (DMD) based scheme is first employed to shape the bottle beams by precise amplitude and phase manipulation. Further, we demonstrate their ability for optical trapping of core-shell magnetic microparticles, which play a particular role in biomedical research, with holographic optical tweezers. Therefore, our observations provide a new route for generating and controlling bottle beams and will widen the potentials for micromanipulation of absorbing particles, aerosols or even individual atoms.
Driving corrugated donut rotors with Laguerre-Gauss beams.
Loke, Vincent L Y; Asavei, Theodor; Stilgoe, Alexander B; Nieminen, Timo A; Rubinsztein-Dunlop, Halina
2014-08-11
Tightly-focused laser beams that carry angular momentum have been used to trap and rotate microrotors. In particular, a Laguerre-Gauss mode laser beam can be used to transfer its orbital angular momentum to drive microrotors. We increase the torque efficiency by a factor of about 2 by designing the rotor such that its geometry is compatible with the driving beam, when driving the rotation with the optimum beam, rather than beams of higher or lower orbital angular momentum. Based on Floquet's theorem, the order of discrete rotational symmetry of the rotor can be made to couple with the azimuthal mode of the Laguerre-Gauss beam. We design corrugated donut rotors, that have a flat disc-like profile, with the help of the discrete dipole approximation and the T-matrix methods in parallel with experimental demonstrations of stable trapping and torque measurement. We produce and test such a rotor using two-photon photopolymerization. With a rotor that has 8-fold discrete rotational symmetry, an outer radius of 1.85 μm and a hollow core radius of 0.5 μm, we were able to transfer approximately 0.3 h̄ per photon of the orbital angular momentum from an LG04 beam.
Controllable light capsules employing modified Bessel-Gauss beams
Gong, Lei; Liu, Weiwei; Zhao, Qian; Ren, Yuxuan; Qiu, Xingze; Zhong, Mincheng; Li, Yinmei
2016-01-01
We report, in theory and experiment, on a novel class of controlled light capsules with nearly perfect darkness, directly employing intrinsic properties of modified Bessel-Gauss beams. These beams are able to naturally create three-dimensional bottle-shaped region during propagation as long as the parameters are properly chosen. Remarkably, the optical bottle can be controlled to demonstrate various geometries through tuning the beam parameters, thereby leading to an adjustable light capsule. We provide a detailed insight into the theoretical origin and characteristics of the light capsule derived from modified Bessel-Gauss beams. Moreover, a binary digital micromirror device (DMD) based scheme is first employed to shape the bottle beams by precise amplitude and phase manipulation. Further, we demonstrate their ability for optical trapping of core-shell magnetic microparticles, which play a particular role in biomedical research, with holographic optical tweezers. Therefore, our observations provide a new route for generating and controlling bottle beams and will widen the potentials for micromanipulation of absorbing particles, aerosols or even individual atoms. PMID:27388558
Unified solutions of extended Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Keskin, A. I.; Açıkgöz, I.
2016-12-01
We study some scale factor power-law solutions of the field equations of the extended Gauss Bonnet gravity in the spatial FRW (Friedmann-Robertson-Walker) universe. We consider the lagrangian density given by F ( R, G ) =f ( G ) + R + α R2 which exhibits a modification comparing with the modified Gauss Bonnet gravity. After constructing the Friedmann equations and finding the power-law solution we obtain the real valued of our model describing a mechanism that shows transitions among three stages of the universe (inflation, deceleration, acceleration) in an unified way. In particular, in this unified solution we obtained an inflation model without using any scalar field description when α>0, and also we verified our early time inflationary scenario using observational parameters, i.e. ns, r. Further, we research for the power-law solution of our model when the universe is in the phantom phase. Here, it is observed that the acceleration of the universe in phantom region is composed of two phases which congruent with the recent observations.
Gauss-Bonnet black holes with nonconstant curvature horizons
Maeda, Hideki
2010-06-15
We investigate static and dynamical n({>=}6)-dimensional black holes in Einstein-Gauss-Bonnet gravity of which horizons have the isometries of an (n-2)-dimensional Einstein space with a condition on its Weyl tensor originally given by Dotti and Gleiser. Defining a generalized Misner-Sharp quasilocal mass that satisfies the unified first law, we show that most of the properties of the quasilocal mass and the trapping horizon are shared with the case with horizons of constant curvature. It is shown that the Dotti-Gleiser solution is the unique vacuum solution if the warp factor on the (n-2)-dimensional Einstein space is nonconstant. The quasilocal mass becomes constant for the Dotti-Gleiser black hole and satisfies the first law of the black-hole thermodynamics with its Wald entropy. In the non-negative curvature case with positive Gauss-Bonnet constant and zero cosmological constant, it is shown that the Dotti-Gleiser black hole is thermodynamically unstable. Even if it becomes locally stable for the nonzero cosmological constant, it cannot be globally stable for the positive cosmological constant.
Application of linear gauss pseudospectral method in model predictive control
NASA Astrophysics Data System (ADS)
Yang, Liang; Zhou, Hao; Chen, Wanchun
2014-03-01
This paper presents a model predictive control(MPC) method aimed at solving the nonlinear optimal control problem with hard terminal constraints and quadratic performance index. The method combines the philosophies of the nonlinear approximation model predictive control, linear quadrature optimal control and Gauss Pseudospectral method. The current control is obtained by successively solving linear algebraic equations transferred from the original problem via linearization and the Gauss Pseudospectral method. It is not only of high computational efficiency since it does not need to solve nonlinear programming problem, but also of high accuracy though there are a few discrete points. Therefore, this method is suitable for on-board applications. A design of terminal impact with a specified direction is carried out to evaluate the performance of this method. Augmented PN guidance law in the three-dimensional coordinate system is applied to produce the initial guess. And various cases for target with straight-line movements are employed to demonstrate the applicability in different impact angles. Moreover, performance of the proposed method is also assessed by comparison with other guidance laws. Simulation results indicate that this method is not only of high computational efficiency and accuracy, but also applicable in the framework of guidance design.
Energy conditions in modified Gauss-Bonnet gravity
Garcia, Nadiezhda Montelongo; Harko, Tiberiu; Lobo, Francisco S. N.; Mimoso, Jose P.
2011-05-15
In considering alternative higher-order gravity theories, one is liable to be motivated in pursuing models consistent and inspired by several candidates of a fundamental theory of quantum gravity. Indeed, motivations from string/M theory predict that scalar field couplings with the Gauss-Bonnet invariant, G, are important in the appearance of nonsingular early time cosmologies. In this work, we discuss the viability of an interesting alternative gravitational theory, namely, modified Gauss-Bonnet gravity or f(G) gravity. We consider specific realistic forms of f(G) analyzed in the literature that account for the late-time cosmic acceleration and that have been found to cure the finite-time future singularities present in the dark energy models. We present the general inequalities imposed by the energy conditions and use the recent estimated values of the Hubble, deceleration, jerk and snap parameters to examine the viability of the above-mentioned forms of f(G) imposed by the weak energy condition.
Martínez-Herrero, R; Prado, F
2015-02-23
In the framework of the paraxial approximation, we derive the analytical expressions for describing the effect of the Gouy phase of Laguerre-Gauss beams on the polarization evolution of partially coherent vortex fields whose electric field vector at some transverse plane exhibits a radially polarized behavior. At each transverse plane, the polarization distribution across the beam profile is characterized by means of the percentage of irradiance associated with the radial or azimuthal components. The propagation laws for these percentages are also presented. As an illustrative example, we analyze a radially polarized partially coherent vortex beam.
Bessel-Gauss pulse as an appropriate mathematical model for optically realizable localized waves.
Reivelt, Kaido; Saari, Peeter
2004-06-01
We show that the field of the optically feasible luminal localized wave solutions of the scalar homogeneous wave equation can be modeled by means of Bessel-Gauss pulses. As the Bessel-Gauss pulses have a closed-form expression, this fact may be of great value in numerical simulations of various experimental situations.
A new sum analogous to Gauss sums and its fourth power mean.
Ru, Shaofeng; Zhang, Wenpeng
2014-01-01
The main purpose of this paper is to use the analytic methods and the properties of Gauss sums to study the computational problem of one kind of new sum analogous to Gauss sums and give an interesting fourth power mean and a sharp upper bound estimate for it.
Crossing of the phantom divide using tachyon-Gauss-Bonnet gravity
Sadeghi, J.; Banijamali, A.; Milani, F.; Setare, M. R.
2009-06-15
In this paper we consider two models. First, we study tachyon-Gauss-Bonnet gravity and obtain the condition of the equation of state crossing -1. Second, we discuss the modified Gauss-Bonnet gravity with the tachyon field and show the condition of {omega} crossing -1. Also, we plot figures for {omega} numerically in special potential and coupling function.
NASA Astrophysics Data System (ADS)
Muthuvalu, Mohana Sundaram
2016-06-01
In this paper, performance analysis of the preconditioned Gauss-Seidel iterative methods for solving dense linear system arise from Fredholm integral equations of the second kind is investigated. The formulation and implementation of the preconditioned Gauss-Seidel methods are presented. Numerical results are included in order to verify the performance of the methods.
Lascu, Dan
2014-01-01
We consider a family {τ m : m ≥ 2} of interval maps which are generalizations of the Gauss transformation. For the continued fraction expansion arising from τ m , we solve a Gauss-Kuzmin-type problem.
2014-01-01
We consider a family {τm : m ≥ 2} of interval maps which are generalizations of the Gauss transformation. For the continued fraction expansion arising from τm, we solve a Gauss-Kuzmin-type problem. PMID:24707226
Anisotopic inflation with a non-abelian gauge field in Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Lahiri, Sayantani
2017-01-01
In presence of Gauss-Bonnet corrections, we study anisotropic inflation aided by a massless SU(2) gauge field where both the gauge field and the Gauss-Bonnet term are non-minimally coupled to the inflaton. In this scenario, under slow-roll approximations, the anisotropic inflation is realized as an attractor solution with quadratic forms of inflaton potential and Gauss-Bonnet coupling function. We show that the degree of anisotropy is proportional to the additive combination of two slow-roll parameters of the theory. The anisotropy may become either positive or negative similar to the non-Gauss-Bonnet framework, a feature of the model for anisotropic inflation supported by a non-abelian gauge field but the effect of Gauss-Bonnet term further enhances or suppresses the generated anisotropy.
Gauss-Bonnet braneworld cosmological effect on relic density of dark matter
Okada, Nobuchika; Okada, Satomi
2009-05-15
In Gauss-Bonnet braneworld cosmology, the Friedmann equation of our four-dimensional Universe on 3-brane is modified in a high energy regime (Gauss-Bonnet regime), while the standard expansion law is reproduced in low energies (standard regime). We investigate the Gauss-Bonnet braneworld cosmological effect on the thermal relic density of cold dark matter when the freeze-out of the dark matter occurs in the Gauss-Bonnet regime. We find that the resultant relic density is considerably reduced when the transition temperature, which connects the Gauss-Bonnet regime with the standard regime, is low enough. This result is in sharp contrast with the result previously obtained in the Randall-Sundrum braneworld cosmology, where the relic density is enhanced.
Bessel-Gauss beam enhancement cavities for high-intensity applications.
Putnam, William P; Schimpf, Damian N; Abram, Gilberto; Kärtner, Franz X
2012-10-22
We introduce Bessel-Gauss beam enhancement cavities that may circumvent the major obstacles to more efficient cavity-enhanced high-field physics such as high-harmonic generation. The basic properties of Bessel-Gauss beams are reviewed and their transformation properties through simple optical systems (consisting of spherical and conical elements) are presented. A general Bessel-Gauss cavity design strategy is outlined, and a particular geometry, the confocal Bessel-Gauss cavity, is analyzed in detail. We numerically simulate the confocal Bessel-Gauss cavity and present an example cavity with 300 MHz repetition rate supporting an effective waist of 33 μm at the focus and an intensity ratio from the focus to the cavity mirror surfaces of 1.5 × 10(4).
Membrane paradigm for Einstein-Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Jacobson, Ted; Mohd, Arif; Sarkar, Sudipta
2017-03-01
We construct the membrane paradigm for black objects in Einstein-Gauss-Bonnet gravity in spacetime dimensions ≥5 . As in the case of general relativity, the horizon can be modeled as a membrane endowed with fluidlike properties. We derive the stress tensor for this membrane fluid and study the perturbation around static backgrounds with constant curvature horizon cross section, for which the stress tensor can be regularized with the usual redshift factor, and expressed in the form of a Newtonian viscous fluid with pressure, shear viscosity and bulk viscosity. We evaluate the transport coefficients for black holes with constant curvature horizons and negative or zero cosmological constant. For the black brane geometry our result for the ratio of shear viscosity to entropy density agrees with that obtained previously in different frameworks.
Fractional Hamiltonian monodromy from a Gauss-Manin monodromy
NASA Astrophysics Data System (ADS)
Sugny, D.; Mardešić, P.; Pelletier, M.; Jebrane, A.; Jauslin, H. R.
2008-04-01
Fractional Hamiltonian monodromy is a generalization of the notion of Hamiltonian monodromy, recently introduced by [Nekhoroshev, Sadovskií, and Zhilinskií, C. R. Acad. Sci. Paris, Ser. 1 335, 985 (2002); Nekhoroshev, Sadovskií, and Zhilinskií, Ann. Henri Poincare 7, 1099 (2006)] for energy-momentum maps whose image has a particular type of nonisolated singularities. In this paper, we analyze the notion of fractional Hamiltonian monodromy in terms of the Gauss-Manin monodromy of a Riemann surface constructed from the energy-momentum map and associated with a loop in complex space which bypasses the line of singularities. We also prove some propositions on fractional Hamiltonian monodromy for 1:-n and m :-n resonant systems.
Nonparaxial Bessel and Bessel-Gauss pincers light-sheets
NASA Astrophysics Data System (ADS)
Mitri, F. G.
2017-01-01
Nonparaxial optical Bessel and Bessel-Gauss pincers optical-sheets are introduced based upon the angular spectrum decomposition in plane waves. The angular spectrum function and the beam-shape coefficients are expressed by means of improper integrals computed numerically. The radiated component of the electric field is also evaluated, displaying unique features of the nonparaxial Bessel pincers light-sheets. This new type of auto-focusing light-sheets finds potential applications in the development of novel methods in optical light-sheet tweezers for particle manipulation in opto-fluidics, particle sizing and imaging. Numerical predictions for the scattering, radiation force and torque, and particle dynamics also benefit from the developed beam solution.
Near infrared reflectance analysis by Gauss-Jordan linear algebra
NASA Astrophysics Data System (ADS)
Honigs, D. E.; Freelin, J. M.; Hieftje, G. M.
1983-02-01
Near-infrared reflectance analysis (NIRA) is an analytical technique that uses the near-infrared diffuse reflectance of a sample at several discrete wavelengths to predict the concentration of one or more of the chemical species in that sample. However, because near-infrared bands from solid samples are both abundant and broad, the reflectance at a given wavelength usually contains contributions from several sample components, requiring extensive calculations on overlapped bands. In the present study, these calculations have been performed using an approach similar to that employed in multi-component spectrophotometry, but with Gauss-Jordan linear algebra serving as the computational vehicle. Using this approach, correlations for percent protein in wheat flour and percent benzene in hydrocarbons have been obtained and are evaluated. The advantages of a linear-algebra approach over the common one employing stepwise regression are explored.
Exponential fitted Gauss, Radau and Lobatto methods of low order
NASA Astrophysics Data System (ADS)
Martín-Vaquero, J.; Vigo-Aguiar, J.
2008-08-01
Several exponential fitting Runge-Kutta methods of collocation type are derived as a generalization of the Gauss, Radau and Lobatto traditional methods of two steps. The new methods are capable of the exact integration (with only round-off errors) of differential equations whose solutions are linear combinations of an exponential and ordinary polynomials. Theorems of the truncation error reveal the good behavior of the new methods for stiff problems. Plots of their absolute stability regions that include the whole of the negative real axis are provided. A different procedure to find the parameter of the method is proposed. The variable step Radau method of two stages is derived. Finally, numerical examples underscore the efficiency of the proposed codes, especially when they are integrating stiff problems.
Nonholonomic double-bracket equations and the Gauss thermostat.
Rojo, Alberto G; Bloch, Anthony M
2009-08-01
In this Rapid Communication we consider certain equations that arise from imposing a constant kinetic-energy constraint on a one-dimensional set of oscillators. This is a nonlinear nonholonomic constraint on these oscillators and the dynamics are consistent with Gauss's law of least constraint. Dynamics of this sort are of interest in nonequilibrium molecular dynamics. We show that under certain choices of external potential these equations give rise to a generalization of the so-called double-bracket equations which are of interest in studying gradient flows and integrable systems such as the Toda lattice. In the case of harmonic potentials the flow is described by a symmetric bracket and periodic solutions are obtained.
Black holes in the Einstein-Gauss-Bonnet theory and the geometry of their thermodynamics—II
NASA Astrophysics Data System (ADS)
Biswas, Ritabrata; Chakraborty, Subenoy
2010-03-01
In the present work we study (i) the charged black hole in Einstein-Gauss-Bonnet (EGB) theory, known as the Einstein-Maxwell-Gauss-Bonnet (EMGB) black hole and (ii) the black hole in EGB gravity with a Yang-Mills field. The thermodynamic geometry of these two black hole solutions has been investigated, using the modified entropy in Gauss-Bonnet theory.
Adaptive 6-DoF Haptic Contact Stiffness Using the Gauss Map.
Xu, Hongyi; Barbic, Jernej
2016-04-25
The penalty method is a popular approach to resolving contact in haptic rendering. In simulations involving complex distributed contact, there are, however, many simultaneous individual contacts. These contacts have normals pointing in several directions, many of which may be parallel, causing the stiffness effectively to add up in a temporally highly-varying and unpredictable way. Consequently, penalty-based simulation suffers from stability problems. Previous methods tackled this problem using implicit integration, or simply by scaling the stiffness down globally by the number of contacts. Although this provides some control over the net stiffness, it leads to large penetrations, as small contacts are effectively ignored when compared to larger contacts. We propose an adaptive stiffness method that employs the Gauss map of the normal distribution to ensure a spatially uniform and controllable stiffness in all the contact directions. Combined with virtual coupling saturation, the penetration can be kept shallow all the while haptic simulation remains stable, even for large-scale complex geometry with complex distributed 6-DoF contact scenarios. Our method is fast and can be applied to any penalty-based formulation between rigid objects. While used primarily for rigid objects, we also apply our method to reduced deformable objects. We demonstrate the effectiveness of our approach on several challenging 6-DoF haptic rendering scenarios, such as car engine and landing gear virtual assembly.
Error analysis in some Gauss-Turan-Radau and Gauss-Turan-Lobatto quadratures for analytic functions
NASA Astrophysics Data System (ADS)
Milovanovic, Gradimir V.; Spalevic, Miodrag M.
2004-03-01
We consider the generalized Gauss-Turan quadrature formulae of Radau and Lobatto type for approximating . The aim of this paper is to analyze the remainder term in the case when f is an analytic function in some region of the complex plane containing the interval [-1,1] in its interior. The remainder term is presented in the form of a contour integral over confocal ellipses (cf. SIAM J. Numer. Anal. 80 (1983) 1170). Sufficient conditions on the convergence for some of such quadratures, associated with the generalized Chebyshev weight functions, are found. Using some ideas from Hunter (BIT 35 (1995) 64) we obtain new estimates of the remainder term, which are very exact. Some numerical results and illustrations are shown.
Spherically symmetric brane in a bulk of f(R) and Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Chakraborty, Sumanta; SenGupta, Soumitra
2016-11-01
Effective gravitational field equations on a four-dimensional brane embedded in a five-dimensional bulk have been considered. Using the Einstein-Hilbert action along with the Gauss-Bonnet correction term, we have derived static spherically symmetric vacuum solution to the effective field equations, first order in the Gauss-Bonnet coupling parameter. The solution so obtained, has one part corresponding to general relativity with an additional correction term, proportional to the Gauss-Bonnet coupling parameter. The correction term modifies the spacetime structure, in particular, the location of the event horizon. Proceeding further, we have derived effective field equations for f(R) gravity with Gauss-Bonnet correction term and a static spherically symmetric solution has been obtained. In this case the Gauss-Bonnet term modifies both the event and cosmological horizon of the spacetime. There exists another way of obtaining the brane metric—expanding the bulk gravitational field equations in the ratio of bulk to brane curvature scale and assuming a separable bulk metric ansatz. It turns out that static, spherically symmetric solutions obtained from this perturbative method can be matched exactly, with the solutions derived earlier. This will hold for Einstein-Hilbert plus Gauss-Bonnet as well as for f(R) with the Gauss-Bonnet correction. Implications of these results are discussed.
Holographic superconductors in Gauss-Bonnet gravity with Born-Infeld electrodynamics
Jing Jiliang; Wang Liancheng; Pan Qiyuan; Chen Songbai
2011-03-15
We investigate the holographic superconductors in Gauss-Bonnet gravity with Born-Infeld electrodynamics. We find that the Gauss-Bonnet constant, the model parameters, and the Born-Infeld coupling parameter will affect the formation of the scalar hair, the transition point of the phase transition from the second order to the first order, and the relation connecting the gap frequency in conductivity with the critical temperature. The combination of Gauss-Bonnet gravity and the Born-Infeld electrodynamics provides richer physics in the phase transition and the condensation of the scalar hair.
The time delay in strong gravitational lensing with Gauss-Bonnet correction
Man, Jingyun; Cheng, Hongbo E-mail: hbcheng@ecust.edu.cn
2014-11-01
The time delay between two relativistic images in the strong gravitational lensing governed by Gauss-Bonnet gravity is studied. We make a complete analytical derivation of the expression of time delay in presence of Gauss-Bonnet coupling. With respect to Schwarzschild, the time delay decreases as a consequence of the shrinking of the photon sphere. As the coupling increases, the second term in the time delay expansion becomes more relevant. Thus time delay in strong limit encodes some new information about geometry in five-dimensional spacetime with Gauss-Bonnet correction.
Power spectra from an inflaton coupled to the Gauss-Bonnet term
Guo Zongkuan; Schwarz, Dominik J.
2009-09-15
We consider power-law inflation with a Gauss-Bonnet correction inspired by string theory. We analyze the stability of cosmological perturbations and obtain the allowed parameter space. We find that for Gauss-Bonnet-dominated inflation ultraviolet instabilities of either scalar or tensor perturbations show up on small scales. The Gauss-Bonnet correction with a positive (or negative) coupling may lead to a reduction (or enhancement) of the tensor-to-scalar ratio in the potential-dominated case. We place tight constraints on the model parameters by making use of the WMAP 5-year data.
On the remainder term of Gauss-Radau quadratures for analytic functions
NASA Astrophysics Data System (ADS)
Milovanovic, Gradimir V.; Spalevic, Miodrag M.; Pranic, Miroslav S.
2008-09-01
For analytic functions the remainder term of Gauss-Radau quadrature formulae can be represented as a contour integral with a complex kernel. We study the kernel on elliptic contours with foci at the points ±1 and a sum of semi-axes [varrho]>1 for the Chebyshev weight function of the second kind. Starting from explicit expressions of the corresponding kernels the location of their maximum modulus on ellipses is determined. The corresponding Gautschi's conjecture from [On the remainder term for analytic functions of Gauss-Lobatto and Gauss-Radau quadratures, Rocky Mountain J. Math. 21 (1991), 209-226] is proved.
Valuing option on the maximum of two assets using improving modified Gauss-Seidel method
NASA Astrophysics Data System (ADS)
Koh, Wei Sin; Muthuvalu, Mohana Sundaram; Aruchunan, Elayaraja; Sulaiman, Jumat
2014-07-01
This paper presents the numerical solution for the option on the maximum of two assets using Improving Modified Gauss-Seidel (IMGS) iterative method. Actually, this option can be governed by two-dimensional Black-Scholes partial differential equation (PDE). The Crank-Nicolson scheme is applied to discretize the Black-Scholes PDE in order to derive a linear system. Then, the IMGS iterative method is formulated to solve the linear system. Numerical experiments involving Gauss-Seidel (GS) and Modified Gauss-Seidel (MGS) iterative methods are implemented as control methods to test the computational efficiency of the IMGS iterative method.
Quasispherical gravitational collapse in 5D Einstein-Gauss-Bonnet gravity
Ghosh, Sushant G.; Jhingan, S.
2010-07-15
We obtain a general five-dimensional quasispherical collapsing solutions of irrotational dust in Einstein gravity with the Gauss-Bonnet combination of quadratic curvature terms. These solutions are a generalization, to Einstein-Gauss-Bonnet gravity, of the five-dimensional quasispherical Szkeres like collapsing solutions in general relativity. It is found that the collapse proceeds in the same way as in the analogous spherical collapse, i.e., there exists regular initial data such that the collapse proceed to form naked singularities violating cosmic censorship conjecture. The effect of Gauss-Bonnet quadratic curvature terms on the formation and locations of the apparent horizon is deduced.
Far-field properties of super-Lorentzian-Gauss mode beams
NASA Astrophysics Data System (ADS)
Zhou, Guoquan
2010-03-01
Far-field properties of super-Lorentzian-Gauss (SLG) SLG10 and SLG11 mode beams are investigated from the vectorial structure. Based on the vector angular spectrum representation and the method of stationary phase, the analytical TE and TM terms of the SLG10 and SLG11 mode beams in the far-field are presented. The energy flux distributions of the TE term, the TM term and the whole beam for the SLG10 and SLG11 mode beams are graphically demonstrated in the far-field reference plane. Far-field characteristics of the SLG10 and SLG11 mode beams are also evaluated by the power in the bucket (PIB). The energy flux distribution and its summands as well as PIBs of the SLG10 and SLG11 mode beams in the far-field are also compared with those of the corresponding Hermite-Gaussian (HG) HG10 and HG11 beams. The physical origin of the difference between the SLG10 and HG10 beams is also analyzed.
GaussFit - A system for least squares and robust estimation
NASA Technical Reports Server (NTRS)
Jefferys, W. H.; Fitzpatrick, M. J.; Mcarthur, B. E.
1988-01-01
GaussFit is a new computer program for solving least-squares and robust estimation problems. It has a number of unique features, including a complete programming language designed especially to formulate estimation problems, a built-in compiler and interpreter to support the programming language, and a built-in algebraic manipulator for calculating the required partial derivatives analytically. These features make GaussFit very easy to use, so that even complex problems can be set up and solved with minimal effort. GaussFit can correctly handle many cases of practical interest: nonlinear models, exact constraints, correlated observations, and models where the equations of condition contain more than one observed quantity. An experimental robust estimation capability is built into GaussFit so that data sets contaminated by outliers can be handled simply and efficiently.
Generation of pulsed Bessel-Gauss beams using passive axicon-theoretical and experimental studies.
Parsa, Shahrzad; Fallah, Hamid Reza; Ramezani, Mohsen; Soltanolkotabi, Mahmood
2012-10-20
We studied the conditions for generating passive Bessel-Gauss beams by using an axicon. We designed an appropriate Gaussian resonator and extracted a quasi-fundamental Gaussian mode from a pulsed Nd:YAG laser pumped by a Xenon flash lamp and measured its parameters, such as propagation factor, divergence angle, and Rayleigh range. Then we generated passive Bessel-Gauss beams using an axicon and investigated their propagation properties, theoretically and experimentally. For example, for the axicon of 1°, the output energy and the Rayleigh range of the generated Bessel-Gauss beams were measured to be 58 mJ and 229.3 mm, respectively. We compared these properties with our results of the Gaussian mode. Finally, by using axicons with different apex angles, and also by changing the beam spot size on the axicon, we generated Bessel-Gauss beams and studied their properties theoretically and experimentally.
Warm starting the projected Gauss-Seidel algorithm for granular matter simulation
NASA Astrophysics Data System (ADS)
Wang, Da; Servin, Martin; Berglund, Tomas
2016-03-01
The effect on the convergence of warm starting the projected Gauss-Seidel solver for nonsmooth discrete element simulation of granular matter are investigated. It is found that the computational performance can be increased by a factor 2-5.
GLESP 2.0: Gauss-Legendre Sky Pixelization for CMB Analysis
NASA Astrophysics Data System (ADS)
Doroshkevich, A. G.; Naselsky, P. D.; Verkhodanov, O. V.; Novikov, D. I.; Turchaninov, V. I.; Novikov, I. D.; Christensen, P. R.; Chiang, L.-Y.
2011-03-01
GLESP is a pixelization scheme for the cosmic microwave background (CMB) radiation maps. This scheme is based on the Gauss-Legendre polynomials zeros and allows one to create strict orthogonal expansion of the map.
Parallel full-waveform inversion in the frequency domain by the Gauss-Newton method
NASA Astrophysics Data System (ADS)
Zhang, Wensheng; Zhuang, Yuan
2016-06-01
In this paper, we investigate the full-waveform inversion in the frequency domain. We first test the inversion ability of three numerical optimization methods, i.e., the steepest-descent method, the Newton-CG method and the Gauss- Newton method, for a simple model. The results show that the Gauss-Newton method performs well and efficiently. Then numerical computations for a benchmark model named Marmousi model by the Gauss-Newton method are implemented. Parallel algorithm based on message passing interface (MPI) is applied as the inversion is a typical large-scale computational problem. Numerical computations show that the Gauss-Newton method has good ability to reconstruct the complex model.
Holographic Van der Waals-like phase transition in the Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
He, Song; Li, Li-Fang; Zeng, Xiao-Xiong
2017-02-01
The Van der Waals-like phase transition is observed in temperature-thermal entropy plane in spherically symmetric charged Gauss-Bonnet-AdS black hole background. In terms of AdS/CFT, the non-local observables such as holographic entanglement entropy, Wilson loop, and two point correlation function of very heavy operators in the field theory dual to spherically symmetric charged Gauss-Bonnet-AdS black hole have been investigated. All of them exhibit the Van der Waals-like phase transition for a fixed charge parameter or Gauss-Bonnet parameter in such gravity background. Further, with choosing various values of charge or Gauss-Bonnet parameter, the equal area law and the critical exponent of the heat capacity are found to be consistent with phase structures in temperature-thermal entropy plane.
The rich structure of Gauss-Bonnet holographic superconductors
NASA Astrophysics Data System (ADS)
Barclay, Luke
2011-10-01
We study fully backreacting, Gauss-Bonnet (GB) holographic superconductors in 5 bulk spacetime dimensions. We explore the system's dependence on the scalar mass for both positive and negative GB coupling, α. We find that when the mass approaches the Breitenlohner-Freedman (BF) bound and α → L 2 /4 the effect of backreaction is to increase the critical temperature, T c, of the system: the opposite of its effect in the rest of parameter space. We also find that reducing α below zero increases T c and that the effect of backreaction is diminished. We study the zero temperature limit, proving that this system does not permit regular solutions for a non-trivial, tachyonic scalar field and constrain possible solutions for fields with positive masses. We investigate singular, zero temperature solutions in the Einstein limit but find them to be incompatible with the concept of GB gravity being a perturbative expansion of Einstein gravity. We study the conductivity of the system, finding that the inclusion of backreaction hinders the development of poles in the conductivity that are associated with quasi-normal modes approaching the real axis from elsewhere in the complex plane.
Laguerre-Gauss basis functions in observer models
NASA Astrophysics Data System (ADS)
Burgess, Arthur E.
2003-05-01
Observer models based on linear classifiers with basis functions (channels) are useful for evaluation of detection performance with medical images. They allow spatial domain calculations with a covariance matrix of tractable size. The term "channelized Fisher-Hotelling observer" will be used here. It is also called the "channelized Hotelling observer" model. There are an infinite number of basis function (channel ) sets that could be employed. Examples of channel sets that have been used include: difference of Gaussian (DOG) filters, difference of Mesa (DOM) filters and Laguerre-Gauss (LG) basis functions. Another option, sums of LG functions (LGS), will also be presented here. This set has the advantage of having no DC response. The effect of the number of images used to estimate model observer performance will be described, for both filtered 1/f3 noise and GE digital mammogram backgrounds. Finite sample image sets introduce both bias and variance to the estimate. The results presented here agree with previous work on linear classifiers. The LGS basis set gives a small but statistically significant reduction in bias. However, this may not be of much practical benefit. Finally, the effect of varying the number of basis functions included in the set will be addressed. It was found that four LG bases or three LGS bases are adequate.
Charged black hole solutions in Gauss-Bonnet-massive gravity
NASA Astrophysics Data System (ADS)
Hendi, S. H.; Panahiyan, S.; Panah, B. Eslam
2016-01-01
Motivated by high interest in the close relation between string theory and black hole solutions, in this paper, we take into account the Einstein-Gauss-Bonnet Lagrangian in the context of massive gravity. We examine the possibility of black hole in this regard, and discuss the types of horizons. Next, we calculate conserved and thermodynamic quantities and check the validity of the first law of thermodynamics. In addition, we investigate the stability of these black holes in context of canonical ensemble. We show that number, type and place of phase transition points may be significantly affected by different parameters. Next, by considering cosmological constant as thermodynamical pressure, we will extend phase space and calculate critical values. Then, we construct thermodynamical spacetime by considering mass as thermodynamical potential. We study geometrical thermodynamics of these black holes in context of heat capacity and extended phase space. We show that studying heat capacity, geometrical thermodynamics and critical behavior in extended phase space lead to consistent results. Finally, we will employ a new method for obtaining critical values and show that the results of this method are consistent with those of other methods.
Design Improvement and Implementation of 3D Gauss-Markov Mobility Model
2013-02-19
AFFTC-PA-12430 Design Improvement and Implementation of 3D Gauss-Markov Mobility Model Mohammed Alenazi, Cenk Sahin , and James P.G. Sterbenz...0019 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Mohammed Alenazi, Cenk Sahin , and James P.G. Sterbenz 5d. PROJECT...Gauss-Markov Mobility Model Mohammed Alenazi and Cenk Sahin Faculty Advisor: James P.G. Sterbenz Department of Electrical Engineering & Computer Science
On the equivalence of Gaussian elimination and Gauss-Jordan reduction in solving linear equations
NASA Technical Reports Server (NTRS)
Tsao, Nai-Kuan
1989-01-01
A novel general approach to round-off error analysis using the error complexity concepts is described. This is applied to the analysis of the Gaussian Elimination and Gauss-Jordan scheme for solving linear equations. The results show that the two algorithms are equivalent in terms of our error complexity measures. Thus the inherently parallel Gauss-Jordan scheme can be implemented with confidence if parallel computers are available.
Short note on the mass matrix for Gauss-Lobatto grid points
NASA Astrophysics Data System (ADS)
Teukolsky, Saul A.
2015-02-01
The mass matrix for Gauss-Lobatto grid points is usually approximated by Gauss-Lobatto quadrature because this leads to a diagonal matrix that is easy to invert. The exact mass matrix and its inverse are full. We show that the exact mass matrix and its inverse differ from the approximate diagonal ones by a simple rank-1 update (outer product). They can thus be applied to an arbitrary vector in O (N) operations instead of O (N2).
Hawking radiation via tunneling from a d-dimensional black hole in Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Li, Gu-Qiang; Mo, Jie-Xiong
2017-04-01
We extend the Parikh-Wilczek method from Einstein gravity spacetime to Gauss-Bonnet modified gravity and study the tunneling radiation of particles across the event horizon of a d-dimensional Gauss-Bonnet Anti de-Sitter black hole. The emission rate of a particle is calculated. It is shown that the emission rate of massive particles takes the same functional form as that of massless particles although that their motion equations tunneling across the horizon are different. It is also shown that the emission spectrum deviates from the pure thermal spectrum but is consistent with an underlying unitary theory. In addition, significant but interesting phenomenon is demonstrated when Gauss-Bonnet term is present. The expression of the emission rate for a black hole in Gauss-Bonnet gravity differs from that for a black hole in Einstein gravity. After adopting the conventional tunneling rate, we obtain the expression of the entropy of the Gauss-Bonnet black hole, which is in accordance with the early results but does not obey the area law. So the research of tunneling radiation in this paper may serve as a new perspective of understanding the thermodynamics of black holes in Gauss-Bonnet gravity.
Constraining scalar-Gauss-Bonnet inflation by reheating, unitarity, and Planck data
NASA Astrophysics Data System (ADS)
Bhattacharjee, Srijit; Maity, Debaprasad; Mukherjee, Rupak
2017-01-01
We revisit the inflationary dynamics in detail for theories with Gauss-Bonnet gravity coupled to scalar functions, in light of the Planck data. Considering the chaotic inflationary scenario, we constrain the parameters of two models involving inflaton-Gauss-Bonnet coupling by current Planck data. For nonzero inflaton-Gauss-Bonnet coupling β , an inflationary analysis provides us a big cosmologically viable region in the space of (m , β ), where m is the mass of the inflaton. However, we study further on constraining β arising from reheating considerations and unitarity of tree-level amplitude involving 2-graviton →2 -graviton (h h →h h ) scattering. Our analysis, particularly on reheating significantly reduces the parameter space of (m , β ) for all models. The quadratic Gauss-Bonnet coupling parameter turns out to be more strongly constrained than that of the linear coupling. For the linear Gauss-Bonnet coupling function, we obtain β ≲1 03, with the condition β (m /MP)2≃10-4. However, the study of the Higgs inflation scenario in the presence of a Gauss-Bonnet term turns out to be completely disfavored.
Eliminating chromatic aberration in Gauss-type lens design using a novel genetic algorithm.
Fang, Yi-Chin; Tsai, Chen-Mu; Macdonald, John; Pai, Yang-Chieh
2007-05-01
Two different types of Gauss lens design, which effectively eliminate primary chromatic aberration, are presented using an efficient genetic algorithm (GA). The current GA has to deal with too many targets in optical global optimization so that the performance is not much improved. Generally speaking, achromatic aberrations have a great relationship with variable glass sets for all elements. For optics whose design is roughly convergent, glass sets for optics will play a significant role in axial and lateral color aberration. Therefore better results might be derived from the optimal process of eliminating achromatic aberration, which could be carried out by finding feasible glass sets in advance. As an alternative, we propose a new optimization process by using a GA and involving theories of geometrical optics in order to select the best optical glass combination. Two Gauss-type lens designs are employed in this research. First, a telephoto lens design is sensitive to axial aberration because of its long focal length, and second, a wide-angle Gauss design is complicated by lateral color aberration at the extreme corners because Gauss design is well known not to deal well with wide-angle problems. Without numbers of higher chief rays passing the element, it is difficult to correct lateral color aberration altogether for the Gauss design. The results and conclusions show that the attempts to eliminate primary chromatic aberrations were successful.
Features of warped geometry in presence of Gauss-Bonnet coupling
NASA Astrophysics Data System (ADS)
Choudhury, Sayantan; SenGupta, Soumitra
2013-02-01
We study the role of the Gauss-Bonnet corrections and two loop higher genus contribution to the gravity action on the Kaluza-Klien modes and their interactions for different bulk fields which enable one to study various phenomenological implications of string loop corrected Gauss-Bonnet modified warped geometry model in one canvas. We have explicitly derived a phenomenological bound on the Gauss-Bonnet parameter so that the required Planck to TeV scale hierarchy can be achieved through the warp factor in the light of recently discovered Higgs like boson at 125GeV. Moreover due to the presence of small perturbative Gauss-Bonnet as well as string loop corrections we have shown that the warping solution can be obtained for both de-Sitter and anti-de-Sitter bulk which is quite distinct from Randall-Sundrum scenario. Finally we have evaluated various interactions among these bulk fields and determined the coupling parameters and the Kaluza-Klien mode masses which is crucial to understand the phenomenology of a string two loop corrected Einstein-Gauss-Bonnet warp geometry.
Dark matter relic density in Gauss-Bonnet braneworld cosmology
Meehan, Michael T.; Whittingham, Ian B. E-mail: Ian.Whittingham@jcu.edu.au
2014-12-01
The relic density of symmetric and asymmetric dark matter in a Gauss-Bonnet (GB) modified Randall-Sundrum (RS) type II braneworld cosmology is investigated. The existing study of symmetric dark matter in a GB braneworld (Okada and Okada, 2009) found that the expansion rate was reduced compared to that in standard General Relativity (GR), thereby delaying particle freeze-out and resulting in relic abundances which are suppressed by up to O(10{sup −2}). This is in direct contrast to the behaviour observed in RS braneworlds where the expansion rate is enhanced and the final relic abundance boosted. However, this finding that relic abundances are suppressed in a GB braneworld is based upon a highly contrived situation in which the GB era evolves directly into a standard GR era, rather than passing through a RS era as is the general situation. This collapse of the RS era requires equating the mass scale m{sub α} of the GB modification and the mass scale m{sub σ} of the brane tension. However, if the GB contribution is to be considered as the lowest order correction from string theory to the RS action, we would expect m{sub α} > m{sub σ}. We investigate the effect upon the relic abundance of choosing more realistic values for the ratio R{sub m} ≡ m{sub α}/m{sub σ} and find that the relic abundance can be either enhanced or suppressed by more than two orders of magnitude. However, suppression only occurs for a small range of parameter choices and, overwhelmingly, the predominant situation is that of enhancement as we recover the usual Randall-Sundrum type behaviour in the limit R{sub m} >> 1. We use the latest observational bound Ω{sub DM}h{sup 2} = 0.1187 ± 0.0017 to constrain the various model parameters and briefly discuss the implications for direct/indirect dark matter detection experiments as well as dark matter particle models.
Gauss-bonnet black holes and possibilities for their experimental search
Alexeyev, S. O. Rannu, K. A.
2012-03-15
Corollaries of gravity models with second-order curvature corrections in the form of a Gauss-Bonnet term and possibilities (or impossibilities) for their experimental search or observations are discussed. The full version of the four-dimensional Schwarzschild-Gauss-Bonnet black hole solution and the constraint on the possible minimal black hole mass following from this model are considered. Using our solution as a model for the final stages of Hawking evaporation of black holes with a low initial mass (up to 10{sup 15} g) whose lifetime is comparable to that of our Universe, we have revealed differences in the patterns of evaporation: we have obtained high values of the emitted energy and showed the impossibility of an experimental search for primordial black holes by their evaporation products. Scenarios for the evaporation of Gauss-Bonnet black holes in multidimensional gravity models and possibilities for their experimental search are also discussed.
Magnetic-field effects on p-wave phase transition in Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Wu, Ya-Bo; Lu, Jun-Wang; Jin, Yong-Yi; Lu, Jian-Bo; Zhang, Xue; Wu, Si-Yu; Wang, Cui
2014-07-01
In the probe limit, we study the holographic p-wave phase transition in the Gauss-Bonnet gravity via numerical and analytical methods. Concretely, we study the influences of the external magnetic field on the Maxwell complex vector model in the five-dimensional Gauss-Bonnet-AdS black hole and soliton backgrounds, respectively. For the two backgrounds, the results show that the magnetic field enhances the superconductor phase transition in the case of the lowest Landau level, while the increasing Gauss-Bonnet parameter always hinders the vector condensate. Moreover, the Maxwell complex vector model is a generalization of the SU(2) Yang-Mills model all the time. In addition, the analytical results backup the numerical results. Furthermore, this model might provide a holographic realization for the QCD vacuum instability.
Static solutions with nontrivial boundaries for the Einstein-Gauss-Bonnet theory in vacuum
Dotti, Gustavo; Oliva, Julio; Troncoso, Ricardo
2010-07-15
The classification of a certain class of static solutions for the Einstein-Gauss-Bonnet theory in vacuum is performed in d{>=}5 dimensions. The class of metrics under consideration is such that the spacelike section is a warped product of the real line and an arbitrary base manifold. It is shown that for a generic value of the Gauss-Bonnet coupling, the base manifold must be necessarily Einstein, with an additional restriction on its Weyl tensor for d>5. The boundary admits a wider class of geometries only in the special case when the Gauss-Bonnet coupling is such that the theory admits a unique maximally symmetric solution. The additional freedom in the boundary metric enlarges the class of allowed geometries in the bulk, which are classified within three main branches, containing new black holes and wormholes in vacuum.
Holographic phase transitions of p-wave superconductors in Gauss-Bonnet gravity with backreaction
Cai Ronggen; Nie Zhangyu; Zhang Haiqing
2011-03-15
We investigate the phase transitions of holographic p-wave superconductors in (4+1)-dimensional Einstein-Yang-Mills-Gauss-Bonnet theories, in a grand canonical ensemble. Turning on the backreaction of the Yang-Mills field, it is found that the condensations of vector order parameter become harder if the Gauss-Bonnet coefficient grows up or the backreaction becomes stronger. In particular, the vector order parameter exhibits the features of first order and second order phase transitions, while only the second order phase transition is observed in the probe limit. We discuss the roles that the Gauss-Bonnet term and the backreaction play in changing the order of phase transition.
Inhomogeneous dust collapse in 5D Einstein-Gauss-Bonnet gravity
Jhingan, S.; Ghosh, Sushant G.
2010-01-15
We consider a Lemaitre-Tolman-Bondi type space-time in Einstein gravity with the Gauss-Bonnet combination of quadratic curvature terms, and present an exact solution in closed form. It turns out that the presence of the coupling constant of the Gauss-Bonnet terms {alpha}>0 completely changes the causal structure of the singularities from the analogous general relativistic case. The gravitational collapse of inhomogeneous dust in the five-dimensional Gauss-Bonnet extended Einstein equations leads to formation of a massive, but weak, timelike singularity which is forbidden in general relativity. Interestingly, this is a counterexample to three conjectures, viz., cosmic censorship conjecture, hoop conjecture, and Seifert's conjecture.
Dynamics of a Flat Multidimensional Anisotropic Universe in the Gauss-Bonnet Gravity
NASA Astrophysics Data System (ADS)
Toporensky, Alexey; Kirnos, Ilya; Pavluchenko, Sergyey
We consider a flat anisotropic metric in (4+1)- and (5+1)-dimensional space-time in Gauss-Bonnet gravity. In the present presentation we are interesting in the behavior mostly in the vicinity of the cosmological singularity, which allows us to take into account only corrections of the highest possible order. In our case it is the Gauss-Bonnet contribution, so we neglect Einstein terms. In the absence of matter sources this problem have been studied in Ref. 1,2, in the present presentation we take matter into account. The full Einstein - Gauss-Bonnet system shows a complicated behavior even in the vacuum case3,4 and we leave investigation of such system with matter for a future work.
Gauss-bonnet black holes and possibilities for their experimental search
NASA Astrophysics Data System (ADS)
Alexeyev, S. O.; Rannu, K. A.
2012-03-01
Corollaries of gravity models with second-order curvature corrections in the form of a Gauss-Bonnet term and possibilities (or impossibilities) for their experimental search or observations are discussed. The full version of the four-dimensional Schwarzschild-Gauss-Bonnet black hole solution and the constraint on the possible minimal black hole mass following from this model are considered. Using our solution as a model for the final stages of Hawking evaporation of black holes with a low initial mass (up to 1015 g) whose lifetime is comparable to that of our Universe, we have revealed differences in the patterns of evaporation: we have obtained high values of the emitted energy and showed the impossibility of an experimental search for primordial black holes by their evaporation products. Scenarios for the evaporation of Gauss-Bonnet black holes in multidimensional gravity models and possibilities for their experimental search are also discussed.
Warm-tachyon Gauss-Bonnet inflation in the light of Planck 2015 data
NASA Astrophysics Data System (ADS)
Motaharfar, Meysam; Sepangi, Hamid Reza
2016-11-01
We study a warm-tachyon inflationary model non-minimally coupled to a Gauss-Bonnet term. The general conditions required for reliability of the model are obtained by considerations of a combined hierarchy of Hubble and Gauss-Bonnet flow functions. The perturbed equations are comprehensively derived in the longitudinal gauge in the presence of slow-roll and quasi-stable conditions. General expressions for observable quantities of interest such as the tensor-to-scalar ratio, scalar spectral index and its running are found in the high dissipation regime. Finally, the model is solved using exponential and inverse power-law potentials, which satisfy the properties of a tachyon potential, with parameters of the model being constrained within the framework of the Planck 2015 data. We show that the Gauss-Bonnet coupling constant controls termination of inflation in such a way as to be in good agreement with the Planck 2015 data.
NASA Astrophysics Data System (ADS)
Glassmeier, K.-H.; Tsurutani, B. T.
2014-02-01
This is a translation of the Allgemeine Theorie des Erdmagnetismus published by Carl Friedrich Gauss in 1839 in the Resultate aus den Beobachtungen des Magnetischen Vereins im Jahre 1838. The current translation is based on an earlier translation by Elizabeth Juliana Sabine published in 1841. This earlier translation has been revised, corrected, and extended. Numerous biographical comments on the scientists named in the original text have been added as well as further information on the observational material used by Carl Friedrich Gauss. An attempt is made to provide a readable text to a wider scientific community, a text laying the foundation of today's understanding of planetary magnetic fields.
Tachyon Cosmology with Gauss-Bonnet and Non-Minimal Kinetic Couplings
NASA Astrophysics Data System (ADS)
Banijamali, A.
2016-05-01
We consider a tachyonic model of dark energy in which scalar field non-minimally coupled with curvature and kinetic part of its Lagrangian density. Additionally the model contains the Gauss-Bonnet coupling to the scalar field through an arbitrary function. The non-minimal Gauss-Bonnet coupling function and scalar field potential have been obtained for power-law solution and then for a dynamically varying equation of state. We have extracted the required condition for the so-called phantom divide line crossing in the model and represented such a crossing numerically.
Re-creating Gauss's method for non-electrical absolute measurements of magnetic fields and moments
NASA Astrophysics Data System (ADS)
Van Baak, D. A.
2013-10-01
In 1832, Gauss made the first absolute measurements of magnetic fields and of magnetic moments in experiments that are straightforward and instructive to replicate. We show, using rare-earth permanent magnets and a variation of Gauss's technique, that the horizontal component of the ambient geomagnetic field, as well as the size of the magnetic moments of such magnets, can be found. The method shows the connection between the SI and cgs emu unit systems for these quantities and permits an absolute realization of the Ampere with considerable precision.
Addendum to ''Thin-shell wormholes supported by ordinary matter in Einstein-Gauss-Bonnet gravity''
Simeone, Claudio
2011-04-15
Thin-shell wormholes are constructed starting from the exotic branch of the Wiltshire spherically symmetric solution of Einstein-Gauss-Bonnet gravity. The energy-momentum tensor of the shell is studied, and it is shown that configurations supported by matter satisfying the energy conditions exist for certain values of the parameters. Differing from the previous result associated with the normal branch of the Wiltshire solution, this is achieved for small positive values of the Gauss-Bonnet parameter and for vanishing charge.
Improving the full spectrum fitting method: accurate convolution with Gauss-Hermite functions
NASA Astrophysics Data System (ADS)
Cappellari, Michele
2017-04-01
I start by providing an updated summary of the penalized pixel-fitting (PPXF) method that is used to extract the stellar and gas kinematics, as well as the stellar population of galaxies, via full spectrum fitting. I then focus on the problem of extracting the kinematics when the velocity dispersion σ is smaller than the velocity sampling ΔV that is generally, by design, close to the instrumental dispersion σinst. The standard approach consists of convolving templates with a discretized kernel, while fitting for its parameters. This is obviously very inaccurate when σ ≲ ΔV/2, due to undersampling. Oversampling can prevent this, but it has drawbacks. Here I present a more accurate and efficient alternative. It avoids the evaluation of the undersampled kernel and instead directly computes its well-sampled analytic Fourier transform, for use with the convolution theorem. A simple analytic transform exists when the kernel is described by the popular Gauss-Hermite parametrization (which includes the Gaussian as special case) for the line-of-sight velocity distribution. I describe how this idea was implemented in a significant upgrade to the publicly available PPXF software. The key advantage of the new approach is that it provides accurate velocities regardless of σ. This is important e.g. for spectroscopic surveys targeting galaxies with σ ≪ σinst, for galaxy redshift determinations or for measuring line-of-sight velocities of individual stars. The proposed method could also be used to fix Gaussian convolution algorithms used in today's popular software packages.
The Generation of Higher-order Laguerre-Gauss Optical Beams for High-precision Interferometry
Carbone, Ludovico; Fulda, Paul; Bond, Charlotte; Brueckner, Frank; Brown, Daniel; Wang, Mengyao; Lodhia, Deepali; Palmer, Rebecca; Freise, Andreas
2013-01-01
Thermal noise in high-reflectivity mirrors is a major impediment for several types of high-precision interferometric experiments that aim to reach the standard quantum limit or to cool mechanical systems to their quantum ground state. This is for example the case of future gravitational wave observatories, whose sensitivity to gravitational wave signals is expected to be limited in the most sensitive frequency band, by atomic vibration of their mirror masses. One promising approach being pursued to overcome this limitation is to employ higher-order Laguerre-Gauss (LG) optical beams in place of the conventionally used fundamental mode. Owing to their more homogeneous light intensity distribution these beams average more effectively over the thermally driven fluctuations of the mirror surface, which in turn reduces the uncertainty in the mirror position sensed by the laser light. We demonstrate a promising method to generate higher-order LG beams by shaping a fundamental Gaussian beam with the help of diffractive optical elements. We show that with conventional sensing and control techniques that are known for stabilizing fundamental laser beams, higher-order LG modes can be purified and stabilized just as well at a comparably high level. A set of diagnostic tools allows us to control and tailor the properties of generated LG beams. This enabled us to produce an LG beam with the highest purity reported to date. The demonstrated compatibility of higher-order LG modes with standard interferometry techniques and with the use of standard spherical optics makes them an ideal candidate for application in a future generation of high-precision interferometry. PMID:23962813
The Gauss and Ampere Laws: Different Laws but Similar Difficulties for Student Learning
ERIC Educational Resources Information Center
Guisasola, Jenaro; Almudi, Jose M.; Salinas, Julia; Zuza, Kristina; Ceberio, Mikel
2008-01-01
This study aims to analyse university students' reasoning regarding two laws of electromagnetism: Gauss's law and Ampere's law. It has been supposed that the problems seen in understanding and applying both laws do not spring from students' misconceptions. Students habitually use reasoning known in the literature as 'common sense' methodology that…
An Alternative Method to Gauss-Jordan Elimination: Minimizing Fraction Arithmetic
ERIC Educational Resources Information Center
Smith, Luke; Powell, Joan
2011-01-01
When solving systems of equations by using matrices, many teachers present a Gauss-Jordan elimination approach to row reducing matrices that can involve painfully tedious operations with fractions (which I will call the traditional method). In this essay, I present an alternative method to row reduce matrices that does not introduce additional…
Thin-shell wormholes supported by ordinary matter in Einstein-Gauss-Bonnet gravity
Richarte, Martin G.; Simeone, Claudio
2007-10-15
The generalized Darmois-Israel formalism for Einstein-Gauss-Bonnet theory is applied to construct thin-shell Lorentzian wormholes with spherical symmetry. We calculate the energy localized on the shell, and we find that for certain values of the parameters wormholes could be supported by matter not violating the energy conditions.
Vallone, Giuseppe
2015-04-15
Circular beams were introduced as a very general solution to the paraxial wave equation carrying orbital angular momentum. Here, we study their properties by looking at their normalization and their expansion in terms of Laguerre-Gauss modes. We also study their far-field divergence and, for particular cases of the beam parameters, their possible experimental generation.
Beam propagation factors and kurtosis parameters of a Lorentz-Gauss vortex beam.
Zhou, Guoquan
2014-06-01
Based on the second-order and the higher-order moments, analytical expressions for the beam propagation factors of a Lorentz-Gauss vortex beam with l=1 have been derived, and analytical propagation expressions for the kurtosis parameters of a Lorentz-Gauss vortex beam with l=1 through a paraxial and real ABCD optical system have also been presented. The M² factor is determined by the parameters a and b and decreases with increasing the parameter a or b. The M² factor is validated to be larger than 2. The kurtosis parameters depend on the diffraction-free ranges of the Lorentz part, the parameters a and b, and the ratio A/B. The kurtosis parameters of a Lorentz-Gauss vortex beam propagating in free space are demonstrated in different reference planes. In the far field, the kurtosis parameter K decreases with increasing one of the parameters a and b. Upon propagation, the kurtosis parameter K first decreases, then increases, and finally tends to a saturated value. In any case, the kurtosis parameter K is larger than 2. This research is beneficial to optical trapping, guiding, and manipulation of microscopic particles and atoms using Lorentz-Gauss vortex beams.
A Modified Gauss-Jordan Procedure as an Alternative to Iterative Procedures in Multiple Regression.
ERIC Educational Resources Information Center
Roscoe, John T.; Kittleson, Howard M.
Correlation matrices involving linear dependencies are common in educational research. In such matrices, there is no unique solution for the multiple regression coefficients. Although computer programs using iterative techniques are used to overcome this problem, these techniques possess certain disadvantages. Accordingly, a modified Gauss-Jordan…
ERIC Educational Resources Information Center
Cudeck, Robert; And Others
1993-01-01
An implementation of the Gauss-Newton algorithm for the analysis of covariance structure that is specifically adapted for high-level computer languages is reviewed. This simple method for estimating structural equation models is useful for a variety of standard models, as is illustrated. (SLD)
Generation of J0-Bessel-Gauss beam by a heterogeneous refractive index map.
San-Roman-Alerigi, Damian P; Ng, Tien K; Zhang, Yaping; Ben Slimane, Ahmed; Alsunaidi, Mohammad; Ooi, Boon S
2012-07-01
In this paper, we present the theoretical studies of a refractive index map to implement a Gauss to a J(0)-Bessel-Gauss convertor. We theoretically demonstrate the viability of a device that could be fabricated on a Si/Si(1-y)O(y)/Si(1-x-y)Ge(x)C(y) platform or by photo-refractive media. The proposed device is 200 μm in length and 25 μm in width, and its refractive index varies in controllable steps across the light propagation and transversal directions. The computed conversion efficiency and loss are 90%, and -0.457 dB, respectively. The theoretical results, obtained from the beam conversion efficiency, self-regeneration, and propagation through an opaque obstruction, demonstrate that a two-dimensional (2D) graded index map of the refractive index can be used to transform a Gauss beam into a J(0)-Bessel-Gauss beam. To the best of our knowledge, this is the first demonstration of such beam transformation by means of a 2D index-mapping that is fully integrable in silicon photonics based planar lightwave circuits (PLCs). The concept device is significant for the eventual development of a new array of technologies, such as micro optical tweezers, optical traps, beam reshaping and nonlinear beam diode lasers.
Exact vs. Gauss-Seidel numerical solutions of the non-LTE radiation transfer problem
NASA Astrophysics Data System (ADS)
Quang, Carine; Paletou, Frédéric; Chevallier, Loïc
2004-12-01
Although published in 1995 (Trujillo Bueno & Fabiani Bendicho, ApJ 455, 646), the Gauss-Seidel method for solving the non-LTE radiative transfer problem has deserved too little attention in the astrophysical community yet. Further tests of the performances and of the accuracy of the numerical scheme are provided.
Goos-Hanchen and Imbert-Fedorov shifts for Hermite-Gauss beams.
Prajapati, Chandra; Ranganathan, D
2012-07-01
We study the lateral Goos-Hanchen and the transverse Imbert-Fedorov shift produced during the reflection of Hermite-Gauss beams H(m0) or H(0m) at a plane interface. The vector angular spectrum method for a light beam in terms of a two-form angular spectrum consisting of the two orthogonal polarized components was used. We have carried out a detailed numerical calculation of these shifts at different angles of incidence, over the whole range of incidence without making the usual approximations. The shift variation as a function of refractive index and order of the Hermite-Gauss beam is studied. We also compare the shift variations with the orientation of the lobes of the Hermite-Gauss beam. We observed that the shifts are nearly equal for the two cases H(m0) (lobe oriented in the plane of incidence) and H(0m) (lobe oriented perpendicular to plane of incidence). These are the first quantitative estimates of the shifts for Hermite-Gauss beams as per our knowledge and are relevant for all cases of slab geometry.
NASA Astrophysics Data System (ADS)
Xu, Luopeng; Dan, Youquan; Wang, Qingyuan
2015-10-01
The continuous wavelet transform (CWT) introduces an expandable spatial and frequency window which can overcome the inferiority of localization characteristic in Fourier transform and windowed Fourier transform. The CWT method is widely applied in the non-stationary signal analysis field including optical 3D shape reconstruction with remarkable performance. In optical 3D surface measurement, the performance of CWT for optical fringe pattern phase reconstruction usually depends on the choice of wavelet function. A large kind of wavelet functions of CWT, such as Mexican Hat wavelet, Morlet wavelet, DOG wavelet, Gabor wavelet and so on, can be generated from Gauss wavelet function. However, so far, application of the Gauss wavelet transform (GWT) method (i.e. CWT with Gauss wavelet function) in optical profilometry is few reported. In this paper, the method using GWT for optical fringe pattern phase reconstruction is presented first and the comparisons between real and complex GWT methods are discussed in detail. The examples of numerical simulations are also given and analyzed. The results show that both the real GWT method along with a Hilbert transform and the complex GWT method can realize three-dimensional surface reconstruction; and the performance of reconstruction generally depends on the frequency domain appearance of Gauss wavelet functions. For the case of optical fringe pattern of large phase variation with position, the performance of real GWT is better than that of complex one due to complex Gauss series wavelets existing frequency sidelobes. Finally, the experiments are carried out and the experimental results agree well with our theoretical analysis.
Analytical Limit Distributions from Random Power-Law Interactions
NASA Astrophysics Data System (ADS)
Zaid, Irwin; Mizuno, Daisuke
2016-07-01
Nature is full of power-law interactions, e.g., gravity, electrostatics, and hydrodynamics. When sources of such fields are randomly distributed in space, the superposed interaction, which is what we observe, is naively expected to follow a Gauss or Lévy distribution. Here, we present an analytic expression for the actual distributions that converge to novel limits that are in between these already-known limit distributions, depending on physical parameters, such as the concentration of field sources and the size of the probe used to measure the interactions. By comparing with numerical simulations, the origin of non-Gauss and non-Lévy distributions are theoretically articulated.
Dadhich, Naresh; Pons, Josep M
We study static black hole solutions in Einstein and Einstein-Gauss-Bonnet gravity with the topology of the product of two spheres, [Formula: see text], in higher dimensions. There is an unusual new feature of the Gauss-Bonnet black hole: the avoidance of a non-central naked singularity prescribes a mass range for the black hole in terms of [Formula: see text]. For an Einstein-Gauss-Bonnet black hole a limited window of negative values for [Formula: see text] is also permitted. This topology encompasses black strings, branes, and generalized Nariai metrics. We also give new solutions with the product of two spheres of constant curvature.
A new algorithm for computing multivariate Gauss-like quadrature points.
Taylor, Mark A.; Bos, Len P.; Wingate, Beth A.
2004-06-01
The diagonal-mass-matrix spectral element method has proven very successful in geophysical applications dominated by wave propagation. For these problems, the ability to run fully explicit time stepping schemes at relatively high order makes the method more competitive then finite element methods which require the inversion of a mass matrix. The method relies on Gauss-Lobatto points to be successful, since the grid points used are required to produce well conditioned polynomial interpolants, and be high quality 'Gauss-like' quadrature points that exactly integrate a space of polynomials of higher dimension than the number of quadrature points. These two requirements have traditionally limited the diagonal-mass-matrix spectral element method to use square or quadrilateral elements, where tensor products of Gauss-Lobatto points can be used. In non-tensor product domains such as the triangle, both optimal interpolation points and Gauss-like quadrature points are difficult to construct and there are few analytic results. To extend the diagonal-mass-matrix spectral element method to (for example) triangular elements, one must find appropriate points numerically. One successful approach has been to perform numerical searches for high quality interpolation points, as measured by the Lebesgue constant (Such as minimum energy electrostatic points and Fekete points). However, these points typically do not have any Gauss-like quadrature properties. In this work, we describe a new numerical method to look for Gauss-like quadrature points in the triangle, based on a previous algorithm for computing Fekete points. Performing a brute force search for such points is extremely difficult. A common strategy to increase the numerical efficiency of these searches is to reduce the number of unknowns by imposing symmetry conditions on the quadrature points. Motivated by spectral element methods, we propose a different way to reduce the number of unknowns: We look for quadrature formula
NASA Astrophysics Data System (ADS)
Cottrill, Gerald C.
A hybrid numerical algorithm combining the Gauss Pseudospectral Method (GPM) with a Generalized Polynomial Chaos (gPC) method to solve nonlinear stochastic optimal control problems with constraint uncertainties is presented. TheGPM and gPC have been shown to be spectrally accurate numerical methods for solving deterministic optimal control problems and stochastic differential equations, respectively. The gPC uses collocation nodes to sample the random space, which are then inserted into the differential equations and solved by applying standard differential equation methods. The resulting set of deterministic solutions is used to characterize the distribution of the solution by constructing a polynomial representation of the output as a function of uncertain parameters. Optimal control problems are especially challenging to solve since they often include path constraints, bounded controls, boundary conditions, and require solutions that minimize a cost functional. Adding random parameters can make these problems even more challenging. The hybrid algorithm presented in this dissertation is the first time the GPM and gPC algorithms have been combined to solve optimal control problems with random parameters. Using the GPM in the gPC construct provides minimum cost deterministic solutions used in stochastic computations that meet path, control, and boundary constraints, thus extending current gPC methods to be applicable to stochastic optimal control problems. The hybrid GPM-gPC algorithm was applied to two concept demonstration problems: a nonlinear optimal control problem with multiplicative uncertain elements and a trajectory optimization problem simulating an aircraft flying through a threat field where exact locations of the threats are unknown. The results show that the expected value, variance, and covariance statistics of the polynomial output function approximations of the state, control, cost, and terminal time variables agree with Monte-Carlo simulation
Complete gravity field of an ellipsoidal prism by Gauss-Legendre quadrature
NASA Astrophysics Data System (ADS)
Roussel, C.; Verdun, J.; Cali, J.; Masson, F.
2015-12-01
The increasing availability of geophysical models of the Earth's lithosphere and mantle has generated renewed interest in computation of theoretical gravity effects at global and regional scales. At the same time, the increasing availability of gravity gradient anomalies derived from satellite measurements, such as those provided by GOCE satellite, requires mathematical methods that directly model the gravity gradient anomalies in the same reference frame as GOCE gravity gradients. Our main purpose is to interpret these anomalies in terms of source and density distribution. Numerical integration methods for calculating gravity gradient values are generally based on a mass discretization obtained by decomposing the Earth's layers into a finite number of elementary solid bodies. In order to take into account the curvature of the Earth, spherical prisms or `tesseroids' have been established unequivocally as accurate computation tools for determining the gravitational effects of large-scale structures. The question which then arises from, is whether gravity calculation methods using spherical prisms remain valid when factoring in the ellipticity of the Earth. In the paper, we outline a comprehensive method to numerically compute the complete gravity field with the help of the Gauss-Legendre quadrature involving ellipsoidal shaped prisms. The assessment of this new method is conducted by comparison between the gravity gradient values of simple sources obtained by means of numerical and analytical calculations, respectively. A comparison of the gravity gradients obtained from PREM and LITHO1.0 models using spherical- and ellipsoidal-prism-based methods is also presented. Numerical results indicate that the error on gravity gradients, caused by the use of the spherical prism instead of its ellipsoidal counterpart to describe an ellipsoidally shaped Earth, is useful for a joint analysis with those deduced from GOCE satellite measurements. Provided that a suitable scaling
Higher-dimensional thin-shell wormholes in Einstein-Yang-Mills-Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Mazharimousavi, S. Habib; Halilsoy, M.; Amirabi, Z.
2011-01-01
We present thin-shell wormhole solutions in the Einstein-Yang-Mills-Gauss-Bonnet (EYMGB) theory in higher dimensions d >= 5. Exact black hole solutions are employed for this purpose where the radius of the thin shell lies outside the event horizon. For some reasons the cases d = 5 and d > 5 are treated separately. The surface energy-momentum of the thin shell creates surface pressures to resist against collapse and rendering stable wormholes possible. We test the stability of the wormholes against spherical perturbations through a linear energy-pressure relation and plot stability regions. Apart from this restricted stability we investigate the possibility of normal (i.e. non-exotic) matter which satisfies the energy conditions. For negative values of the Gauss-Bonnet (GB) parameter we obtain such physical wormholes.
BV weak solutions to Gauss-Codazzi system for isometric immersions
NASA Astrophysics Data System (ADS)
Christoforou, Cleopatra
The isometric immersion problem for surfaces embedded into R is studied via the fluid dynamic framework introduced in Chen et al. (2010) [6] as a system of balance laws of mixed-type. The techniques developed in the theory of weak solutions of bounded variation in continuum physics are employed to deal with the isometric immersions in the setting of differential geometry. The so-called BV framework is formed that establishes convergence of approximate solutions of bounded variation to the Gauss-Codazzi system and yields the C isometric realization of two-dimensional surfaces into R. Local and global existence results are established for weak solutions of small bounded variation to the Gauss-Codazzi system for negatively curved surfaces that admit equilibrium configurations. As an application, the case of catenoidal shell of revolution is provided.
Modified teleparallel theories of gravity: Gauss-Bonnet and trace extensions.
Bahamonde, Sebastian; Böhmer, Christian G
2016-01-01
We investigate modified theories of gravity in the context of teleparallel geometries with possible Gauss-Bonnet contributions. The possible coupling of gravity with the trace of the energy-momentum tensor is also taken into account. This is motivated by the various different theories formulated in the teleparallel approach and the metric approach without discussing the exact relationship between them. Our formulation clarifies the connections between different well-known theories. For instance, we are able to formulate the correct teleparallel equivalent of Gauss-Bonnet modified general relativity, amongst other results. Finally, we are able to identify modified gravity models which have not been studied in the past. These appear naturally within our setup and would make a interesting starting point for further studies.
Stability of anti-de sitter space in Einstein-Gauss-Bonnet gravity.
Deppe, Nils; Kolly, Allison; Frey, Andrew; Kunstatter, Gabor
2015-02-20
Recently it has been argued that in Einstein gravity anti-de Sitter spacetime is unstable against the formation of black holes for a large class of arbitrarily small perturbations. We examine the effects of including a Gauss-Bonnet term. In five dimensions, spherically symmetric Einstein-Gauss-Bonnet gravity has two key features: Choptuik scaling exhibits a radius gap, and the mass function goes to a finite value as the horizon radius vanishes. These suggest that black holes will not form dynamically if the total mass-energy content of the spacetime is too small, thereby restoring the stability of anti-de Sitter spacetime in this context. We support this claim with numerical simulations and uncover a rich structure in horizon radii and formation times as a function of perturbation amplitude.
Gauss-Bonnet black holes and holographic heat engines beyond large N
NASA Astrophysics Data System (ADS)
Johnson, Clifford V.
2016-11-01
Working in the extended black hole thermodynamics where a dynamical cosmological constant defines a thermodynamic pressure p, we study the efficiency of heat engines that perform mechanical work via the pdV terms now present in the First Law. Here the black hole itself is the working substance, and we focus on a judiciously chosen engine cycle. We work in Gauss-Bonnet-Einstein-Maxwell gravity with negative cosmological constant and, using a high temperature expansion, compare the results for these ‘holographic’ heat engines to that of previously studied cases with no Gauss-Bonnet sector. From the dual holographic large N field theory perspective, this amounts to studying the effects of a class of 1/N corrections to the efficiency of the cycle.
NASA Astrophysics Data System (ADS)
Rousseau, Guy; Gay, David; Piché, Michel
2006-09-01
A recent analysis [G. Rousseau, D. Gay and M. Piché, One-dimensional description of cylindrically symmetric laser beams: application to Bessel-type nondiffracting beams, J. Opt. Soc. Am. A, 22 (2005) 1274] has shown that any cylindrically symmetric laser beam can be synthesized from a single wave called a constituent wave. This representation allows the introduction of one-dimensional Cartesian root-mean-square (rms) parameters to describe the conical structure of cylindrically symmetric laser beams. In this paper, we compare the rms characterization of Bessel-Gauss beams in polar coordinates with that of their respective constituent waves in Cartesian coordinates. Numerical results reveal an asymptotic correspondence between polar and Cartesian rms parameters of Bessel-Gauss beams propagating in a nondiffracting regime. Such a correspondence eliminates misleading interpretations about the propagation factor and the Rayleigh range of nondiffracting Bessel-type beams characterized in terms of polar rms parameters.
Phase transition for black holes in dilatonic Einstein-Gauss-Bonnet theory of gravitation
NASA Astrophysics Data System (ADS)
Khimphun, Sunly; Lee, Bum-Hoon; Lee, Wonwoo
2016-11-01
We study the thermodynamic properties of a black hole and the Hawking-Page phase transition in the asymptotically anti-de Sitter spacetime in the dilatonic Einstein-Gauss-Bonnet theory of gravitation. We show how the higher-order curvature terms can influence both the thermodynamic properties and the phase transition. We evaluate both heat capacity and free energy difference to determine the local and global thermodynamic stabilities, respectively. We find that the phase transition occurs from the thermal anti-de Sitter to a small spherical black hole geometry and occurs to a hyperbolic black hole geometry in the (dilatonic) Einstein-Gauss-Bonnet theory of gravitation unlike those in Einstein's theory of gravitation.
Magnetic fields greater than 10 to the 20th power gauss. [in astrophysical systems
NASA Technical Reports Server (NTRS)
Lerche, I.; Schramm, D. N.
1977-01-01
Zaumen (1976) found that spontaneous pair production in a uniform magnetic field should be a feasible process for field strengths at least of the order of 10 to the 20th power gauss. This note points out that a magnetic field of this order of magnitude is most unlikely to occur in realistic astrophysical situations because of the large dynamical and quantum-mechanical effects such a field would produce. It is suggested that Zaumen's calculation would probably have little bearing on the suspected evolution of astrophysical systems since other processes (either dynamical or quantum-mechanical) apparently limit the field strength before such high magnetic fields would be reached. An upper limit of about 10 to the 16th power gauss is obtained by considering the isotropy of the 3-K blackbody radiation, the formation of collapsed objects in very high magnetic fields, and magnetic bremsstrahlung processes in quantum electrodynamics.
Application of Gauss-Seidel multilevel control to a single axis torsional model
NASA Technical Reports Server (NTRS)
Chichester, F. D.
1981-01-01
An approach to the application of multilevel control techniques for large space structures is presented. Gauss-Seidel second level controls and an extension of standard linear quadratic regulator techniques are applied to a model consisting of a flexible space vehicle comprising three rigid bodies rotating about a common axis. The method incorporates second order derivatives with respect to time, entailing the use of a two level hierarchy of subsystems. Gauss-Seidel second level control formulations were chosen to avoid the necessity of having as many controls as constraints or using gradient techniques in the choice of the Hamiltonian. The modular nature of the resulting control system allows applications for spacecraft with larger numbers of modules.
Hong-Ou-Mandel interference of entangled Hermite-Gauss modes
NASA Astrophysics Data System (ADS)
Zhang, Yingwen; Prabhakar, Shashi; Rosales-Guzmán, Carmelo; Roux, Filippus S.; Karimi, Ebrahim; Forbes, Andrew
2016-09-01
Hong-Ou-Mandel (HOM) interference is demonstrated experimentally for entangled photon pairs in the Hermite-Gauss (HG) basis. We use two Dove prisms in one of the paths of the photons to manipulate the entangled quantum state that enters the HOM interferometer. It is demonstrated that, when entangled photon pairs are in a symmetric Bell state in the Laguerre-Gauss (LG) basis, they will remain symmetric after decomposing them into the HG basis, thereby resulting in no coincidence events after the HOM interference. On the other hand, if the photon pairs are in an antisymmetric Bell state in the LG basis, then they will also be antisymmetric in the HG basis, thereby producing only coincidence events as a result of the HOM interference.
Area functional relation for 5D-Gauss-Bonnet-AdS black hole
NASA Astrophysics Data System (ADS)
Pradhan, Parthapratim
2016-08-01
We present area (or entropy) functional relation for multi-horizons five dimensional (5D) Einstein-Maxwell-Gauss-Bonnet-AdS black hole. It has been observed by exact and explicit calculation that some complicated function of two or three horizons area is mass-independent whereas the entropy product relation is not mass-independent. We also study the local thermodynamic stability of this black hole. The phase transition occurs at certain condition. Smarr mass formula and first law of thermodynamics have been derived. This mass-independent relation suggests they could turn out to be an universal quantity and further helps us to understanding the nature of black hole entropy (both interior and exterior) at the microscopic level. In the "Appendix", we have derived the thermodynamic products for 5D Einstein-Maxwell-Gauss-Bonnet black hole with vanishing cosmological constant.
ERIC Educational Resources Information Center
Smith, H. V.
2008-01-01
A method is derived for the numerical evaluation of the error term arising in some Gauss-type formulae modified so as to approximate Cauchy Principal Value integrals. The method uses Chebyshev polynomials of the first kind. (Contains 1 table.)
NASA Astrophysics Data System (ADS)
Ying, Teh Yuan; Yaacob, Nazeeruddin
2013-04-01
In this paper, a new implicit Runge-Kutta method which based on a 7-point Gauss-Kronrod-Lobatto quadrature formula is developed. The resulting implicit method is a 7-stage tenth order Gauss-Kronrod-Lobatto IIIA method, or in brief as GKLM(7,10)-IIIA. GKLM(7,10)-IIIA requires seven function of evaluations at each integration step and it gives accuracy of order ten. In addition, GKLM(7,10)-IIIA has stage order seven and being A-stable. Numerical experiments compare the accuracy between GKLM(7,10)-IIIA and the classical 5-stage tenth order Gauss-Legendre method in solving some test problems. Numerical results reveal that GKLM(7,10)-IIIA is more accurate than the 5-stage tenth order Gauss-Legendre method because GKLM(7,10)-IIIA has higher stage order.
Jiang, Chen; Liu, Xiaozhou; Liu, Jiehui; Mao, Yiwei; Marston, Philip L
2017-04-01
By means of series expansion theory, the incident quasi-Bessel-Gauss beam is expanded using spherical harmonic functions, and the beam coefficients of the quasi-Bessel-Gauss beam are calculated. According to the theory, the acoustic radiation force function, which is the radiation force per unit energy on a unit cross-sectional surface on a sphere made of diverse materials and immersed in an ideal fluid along the propagation axis of zero-order quasi-Bessel-Gauss progressive and standing beams, is investigated. The acoustic radiation force function is calculated as a function of the spherical radius parameter ka and the half-cone angle β with different beam widths in a progressive and standing zero-order Bessel-Gauss beam. Simulation results indicate that the acoustic radiation forces with different waist radii demonstrate remarkably different features from those found in previous studies. The results are expected to be useful in potential applications such as acoustic tweezers.
NASA Astrophysics Data System (ADS)
Ying, Teh Yuan; Yaacob, Nazeeruddin
2013-04-01
In this paper, a new implicit Runge-Kutta method which based on a 4-point Gauss-Kronrod-Radau II quadrature formula is developed. The resulting implicit method is a 4-stage sixth order Gauss-Kronrod-Radau IIA method, or in brief as GKRM(4,6)-IIA. GKRM(4,6)-IIA requires four function of evaluations at each integration step and it gives accuracy of order six. In addition, GKRM(4,6)-IIA has stage order four and being L-stable. Numerical experiments compare the accuracy between GKRM(4,6)-IIA and the classical 3-stage sixth order Gauss-Legendre method in solving some test problems. Numerical results reveal that GKRM(4,6)-IIA is more accurate than the 3-stage sixth order Gauss-Legendre method because GKRM(4,6)-IIA has higher stage order.
On the Chern-Gauss-Bonnet theorem for the noncommutative 4-sphere
NASA Astrophysics Data System (ADS)
Arnlind, Joakim; Wilson, Mitsuru
2017-01-01
We construct a differential calculus over the noncommutative 4-sphere in the framework of pseudo-Riemannian calculi, and show that for every metric in a conformal class of perturbations of the round metric, there exists a unique metric and torsion-free connection. Furthermore, we find a localization of the projective module corresponding to the space of vector fields, which allows us to formulate a Chern-Gauss-Bonnet type theorem for the noncommutative 4-sphere.
Rotation of large asymmetrical absorbing objects by Laguerre-Gauss beams.
Herne, Catherine M; Capuzzi, Kristina M; Sobel, Emily; Kropas, Ryan T
2015-09-01
In this Letter, we show the manipulation and rotation of opaque graphite through adhesion with optically trapped polystyrene spheres. The absorbing graphite is rotated by the orbital angular momentum transfer from a Laguerre-Gauss laser mode and is trapped due to the presence of refracting spheres. This technique is effective for trapping and rotating absorbing objects of all sizes, including those larger than the laser mode.
Geophex Airborne Unmanned Survey System (GAUSS). Topical report, October 1993--September 1996
1998-12-31
This document is a Final Technical Report that describes the results of the Geophex Airborne Unmanned Survey System (GAUSS) research project. The objectives were to construct a geophysical data acquisition system that uses a remotely operated unmanned aerial vehicle (UAV) and to evaluate its effectiveness for characterization of hazardous environmental sites. The GAUSS is a data acquisition system that mitigates the potential risk to personnel during geophysical characterization of hazardous or radioactive sites. The fundamental basis of the GAUSS is as follows: (1) an unmanned survey vehicle carries geophysical sensors into a hazardous location, (2) the pilot remains outside the hazardous site and operates the vehicle using radio control, (3) geophysical measurements and their spatial locations are processed by an automated data-acquisition system which displays data on an off-site monitor in real-time, and (4) the pilot uses the display to direct the survey vehicle for complete site coverage. The objective of our Phase I research was to develop a data acquisition and processing (DAP) subsystem and geophysical sensors suitable for UAV deployment. We integrated these two subsystems to produce an automated, hand-held geophysical surveying system. The objective of the Phase II effort was to modify the subsystems and integrate them into an airborne prototype. The completed GAUSS DAP system consists of a UAV platform, a laser tracking and ranging subsystem, a telemetry subsystem, light-weight geophysical sensors, a base-station computer (BC), and custom-written survey control software (SCS). We have utilized off-the-shelf commercial products, where possible, to reduce cost and design time.
NASA Astrophysics Data System (ADS)
Kirnos, I. V.; Makarenko, A. N.; Pavluchenko, S. A.; Toporensky, A. V.
2010-11-01
We investigate dynamics of (4 + 1) and (5 + 1) dimensional flat anisotropic Universe filled with a perfect fluid in the Gauss-Bonnet gravity. An analytical solutions valid for particular values of the equation of state parameter w = 1/3 have been found. For other values of w structure of cosmological singularity have been studied numerically. We found that for w > 1/3 the singularity is isotropic. Several important differences between (4 + 1) and (5 + 1) dimensional cases are discussed.
NASA Technical Reports Server (NTRS)
Chapman, G.; Kirk, D.
1974-01-01
The parameter identification scheme being used is a differential correction least squares procedure (Gauss-Newton method). The position, orientation, and derivatives of these quantities with respect to the parameters of interest (i.e., sensitivity coefficients) are determined by digital integration of the equations of motion and the parametric differential equations. The application of this technique to three vastly different sets of data is used to illustrate the versatility of the method and to indicate some of the problems that still remain.
Chen, Jinsong; Kemna, Andreas; Hubbard, Susan S.
2008-05-15
We develop a Bayesian model to invert spectral induced polarization (SIP) data for Cole-Cole parameters using Markov chain Monte Carlo (MCMC) sampling methods. We compare the performance of the MCMC based stochastic method with an iterative Gauss-Newton based deterministic method for Cole-Cole parameter estimation through inversion of synthetic and laboratory SIP data. The Gauss-Newton based method can provide an optimal solution for given objective functions under constraints, but the obtained optimal solution generally depends on the choice of initial values and the estimated uncertainty information is often inaccurate or insufficient. In contrast, the MCMC based inversion method provides extensive global information on unknown parameters, such as the marginal probability distribution functions, from which we can obtain better estimates and tighter uncertainty bounds of the parameters than with the deterministic method. Additionally, the results obtained with the MCMC method are independent of the choice of initial values. Because the MCMC based method does not explicitly offer single optimal solution for given objective functions, the deterministic and stochastic methods can complement each other. For example, the stochastic method can first be used to obtain the means of the unknown parameters by starting from an arbitrary set of initial values and the deterministic method can then be initiated using the means as starting values to obtain the optimal estimates of the Cole-Cole parameters.
Propagation Dynamics of Nonspreading Cosine-Gauss Water-Wave Pulses.
Fu, Shenhe; Tsur, Yuval; Zhou, Jianying; Shemer, Lev; Arie, Ady
2015-12-18
Linear gravity water waves are highly dispersive; therefore, the spreading of initially short wave trains characterizes water surface waves, and is a universal property of a dispersive medium. Only if there is sufficient nonlinearity does this envelope admit solitary solutions which do not spread and remain in fixed forms. Here, in contrast to the nonlinear localized wave packets, we present both theoretically and experimentally a new type of linearly nondispersive water wave, having a cosine-Gauss envelope, as well as its higher-order Hermite cosine-Gauss variations. We show that these waves preserve their width despite the inherent dispersion while propagating in an 18-m wave tank, accompanied by a slowly varying carrier-envelope phase. These wave packets exhibit self-healing; i.e., they are restored after bypassing an obstacle. We further demonstrate that these nondispersive waves are robust to weakly nonlinear perturbations. In the strong nonlinear regime, symmetry breaking of these waves is observed, but their cosine-Gauss shapes are still approximately preserved during propagation.
Slow-roll inflation with the Gauss-Bonnet and Chern-Simons corrections
Satoh, Masaki
2010-11-01
We study slow-roll inflation with the Gauss-Bonnet and Chern-Simons corrections. We obtain general formulas for the observables: spectral indices, tensor-to-scalar ratio and circular polarization of gravitational waves. The Gauss-Bonnet term violates the consistency relation r = −8n{sub T}. Particularly, blue spectrum n{sub T} > 0 and scale invariant spectrum |8n{sub T}|/r << 1 of tensor modes are possible. These cases require the Gauss-Bonnet coupling function of ξ{sub ,φ} ∼ 10{sup 8}/M{sub Pl}. We use examples to show new-inflation-type potential with 10M{sub Pl} symmetry breaking scale and potential with flat region in φ∼>10M{sub Pl} lead to observationally consistent blue and scale invariant spectra, respectively. Hence, these interesting cases can actually be realized. The Chern-Simons term produce circularly polarized tensor modes. We show an observation of these signals supports existence of the Chern-Simons coupling function of ω{sub ,φ} ∼ 10{sup 8}/M{sub Pl}. Thus, with future observations, we can fix or constrain the value of these coupling functions, at the CMB scale.
Steganalysis of content-adaptive JPEG steganography based on Gauss partial derivative filter bank
NASA Astrophysics Data System (ADS)
Zhang, Yi; Liu, Fenlin; Yang, Chunfang; Luo, Xiangyang; Song, Xiaofeng; Lu, Jicang
2017-01-01
A steganalysis feature extraction method based on Gauss partial derivative filter bank is proposed in this paper to improve the detection performance for content-adaptive JPEG steganography. Considering that the embedding changes of content-adaptive steganographic schemes are performed in the texture and edge regions, the proposed method generates filtered images comprising rich texture and edge information using Gauss partial derivative filter bank, and histograms of absolute values of filtered subimages are extracted as steganalysis features. Gauss partial derivative filter bank can represent texture and edge information in multiple orientations with less computation load than conventional methods and prevent redundancy in different filtered images. These two properties are beneficial in the extraction of low-complexity sensitive features. The results of experiments conducted on three selected modern JPEG steganographic schemes-uniform embedding distortion, JPEG universal wavelet relative distortion, and side-informed UNIWARD-indicate that the proposed feature set is superior to the prior art feature sets-discrete cosine transform residual, phase aware rich model, and Gabor filter residual.
Wake Numerical Simulation Based on the Park-Gauss Model and Considering Atmospheric Stability
NASA Astrophysics Data System (ADS)
Yang, Xiangsheng; Zhao, Ning; Tian, Linlin; Zhu, Jun
2016-06-01
In this paper, a new Park-Gauss model based on the assumption of the Park model and the Eddy-viscosity model is investigated to conduct the wake numerical simulation for solving a single wind turbine problem. The initial wake radius has been modified to improve the model’s numerical accuracy. Then the impact of the atmospheric stability based on the Park-Gauss model has been studied in the wake region. By the comparisons and the analyses of the test results, it turns out that the new Park-Gauss model could achieve better effects of the wind velocity simulation in the wake region. The wind velocity in the wake region recovers quickly under the unstable atmospheric condition provided the wind velocity is closest to the test result, and recovers slowly under stable atmospheric condition in case of the wind velocity is lower than the test result. Meanwhile, the wind velocity recovery falls in between the unstable and stable neutral atmospheric conditions.
Propagation Dynamics of Nonspreading Cosine-Gauss Water-Wave Pulses
NASA Astrophysics Data System (ADS)
Fu, Shenhe; Tsur, Yuval; Zhou, Jianying; Shemer, Lev; Arie, Ady
2015-12-01
Linear gravity water waves are highly dispersive; therefore, the spreading of initially short wave trains characterizes water surface waves, and is a universal property of a dispersive medium. Only if there is sufficient nonlinearity does this envelope admit solitary solutions which do not spread and remain in fixed forms. Here, in contrast to the nonlinear localized wave packets, we present both theoretically and experimentally a new type of linearly nondispersive water wave, having a cosine-Gauss envelope, as well as its higher-order Hermite cosine-Gauss variations. We show that these waves preserve their width despite the inherent dispersion while propagating in an 18-m wave tank, accompanied by a slowly varying carrier-envelope phase. These wave packets exhibit self-healing; i.e., they are restored after bypassing an obstacle. We further demonstrate that these nondispersive waves are robust to weakly nonlinear perturbations. In the strong nonlinear regime, symmetry breaking of these waves is observed, but their cosine-Gauss shapes are still approximately preserved during propagation.
Asymptotically (anti)-de Sitter solutions in Gauss-Bonnet gravity without a cosmological constant
Dehghani, M.H.
2004-09-15
In this paper I show that one can have asymptotically de Sitter, anti-de Sitter (AdS), and flat solutions in Gauss-Bonnet gravity without a cosmological constant term in field equations. First, I introduce static solutions whose three surfaces at fixed r and t have constant positive (k=1), negative (k=-1), or zero (k=0) curvature. I show that for k={+-}1 one can have asymptotically de Sitter, AdS, and flat spacetimes, while for the case of k=0, one has only asymptotically AdS solutions. Some of these solutions present naked singularities, while some others are black hole or topological black hole solutions. I also find that the geometrical mass of these five-dimensional spacetimes is m+2{alpha}|k|, which is different from the geometrical mass m of the solutions of Einstein gravity. This feature occurs only for the five-dimensional solutions, and is not repeated for the solutions of Gauss-Bonnet gravity in higher dimensions. Second, I add angular momentum to the static solutions with k=0, and introduce the asymptotically AdS charged rotating solutions of Gauss-Bonnet gravity. Finally, I introduce a class of solutions which yields an asymptotically AdS spacetime with a longitudinal magnetic field, which presents a naked singularity, and generalize it to the case of magnetic rotating solutions with two rotation parameters.
Development of a Double-Gauss Lens Based Setup for Optoacoustic Applications
Choi, Hojong; Ryu, Jae-Myung; Yeom, Jung-Yeol
2017-01-01
In optoacoustic (photoacoustic) systems, different echo signal intensities such as amplitudes, center frequencies, and bandwidths need to be compensated by utilizing variable gain or time-gain compensation amplifiers. However, such electronic components can increase system complexities and signal noise levels. In this paper, we introduce a double-Gauss lens to generate a large field of view with uniform light intensity due to the low chromatic aberrations of the lens, thus obtaining uniform echo signal intensities across the field of view of the optoacoustic system. In order to validate the uniformity of the echo signal intensities in the system, an in-house transducer was placed at various positions above a tissue sample and echo signals were measured and compared with each other. The custom designed double-Gauss lens demonstrated negligible light intensity variation (±1.5%) across the illumination field of view (~2 cm diameter). When the transducer was used to measure echo signal from an eye of a bigeye tuna within a range of ±1 cm, the peak-to-peak amplitude, center frequency, and their −6 dB bandwidth variations were less than 2 mV, 1 MHz, and 6%, respectively. The custom designed double-Gauss lens can provide uniform light beam across a wide area while generating insignificant echo signal variations, and thus can lower the burden of the receiving electronics or signal processing in the optoacoustic system. PMID:28273794
State space orderings for Gauss-Seidel in Markov chains revisited
Dayar, T.
1996-12-31
Symmetric state space orderings of a Markov chain may be used to reduce the magnitude of the subdominant eigenvalue of the (Gauss-Seidel) iteration matrix. Orderings that maximize the elemental mass or the number of nonzero elements in the dominant term of the Gauss-Seidel splitting (that is, the term approximating the coefficient matrix) do not necessarily converge faster. An ordering of a Markov chain that satisfies Property-R is semi-convergent. On the other hand, there are semi-convergent symmetric state space orderings that do not satisfy Property-R. For a given ordering, a simple approach for checking Property-R is shown. An algorithm that orders the states of a Markov chain so as to increase the likelihood of satisfying Property-R is presented. The computational complexity of the ordering algorithm is less than that of a single Gauss-Seidel iteration (for sparse matrices). In doing all this, the aim is to gain an insight for faster converging orderings. Results from a variety of applications improve the confidence in the algorithm.
NASA Astrophysics Data System (ADS)
Pavluchenko, Sergey A.
2016-07-01
In this paper we perform a systematic study of vacuum spatially flat anisotropic [(3 +D )+1 ]-dimensional Einstein-Gauss-Bonnet cosmological models. We consider models that topologically are the product of two flat isotropic submanifolds with different scale factors. One of these submanifolds is three dimensional and represents our 3D space and the other is D dimensional and represents extra dimensions. We consider no Ansatz on the scale factors, which makes our results quite general. With both Einstein-Hilbert and Gauss-Bonnet contributions in play and with the symmetry involved, the cases with D =1 , D =2 , D =3 , and D ≥4 have different dynamics due to the different structures of the equations of motion. We analytically analyze equations of motion in all cases and describe all possible regimes. It appears that the only regimes with nonsingular future asymptotes are the Kasner regime in general relativity and exponential regimes. As of the past asymptotes, for a smooth transition only the Kasner regime in Gauss-Bonnet is an option. With this at hand, we are down to only two viable regimes: the "pure" Kasner regime [transition from a high-energy (Gauss-Bonnet) to a low-energy (general relativity) Kasner regime] and a transition from a high-energy Kasner regime to an anisotropic exponential solution. It appears that these regimes take place for different signs of the Gauss-Bonnet coupling α : the "pure" Kasner regime occurs for α >0 at low D and α <0 for high D ; the anisotropic exponential regime is reached only for α >0 . So if we restrain ourselves with α >0 solutions (which would be the case, say, if we identify α with inverse string tension in heterotic string theory), the only late-time regimes are Kasner for D =1 , 2 and anisotropic exponential for D ≥2 . Also, low-energy Kasner regimes [a (t )∝tp] have expansion rates for (3 +1 )-dimensional subspace ("our Universe") ranging from p =0.5 (D =1 ) to p =1 /√{3 }≈0.577 (D →∞ ), which
The uselessness of the Fast Gauss Transform for summing Gaussian radial basis function series
NASA Astrophysics Data System (ADS)
Boyd, John P.
2010-02-01
The Fast Gauss Transform is an algorithm for summing a series of Gaussians which is sometimes much faster than direct summation. Gaussian series in d dimensions are of the form ∑j=1N λjexp(-[α/h]2 ‖x-xj‖2) where the xj are the centers, h is the average separation between centers and α is the relative inverse width parameter. We show that the speed-up of the Fast Gauss Transform is bounded by a factor Ω(α). When α≪1, Ω can be large. However, when applied to Gaussian radial basis function interpolation, it is difficult to apply the Gaussian basis in this parameter range because the interpolation matrix is exponentially ill-conditioned: the condition number κ˜(1/2)exp{π2}/{4α2} for a uniform, one-dimensional grid, and larger still in two dimensions or when the grid is irregular. Furthermore, the Gaussian RBF interpolant is ill-conditioned for most series in the sense that the interpolant is the small difference of terms with exponentially large coefficients. Fornberg and Piret developed a "QR-basis" that ameliorates this difficulty for approximations on the surface of a sphere, but because the recombined basis functions are perturbed spherical harmonics, not Gaussians, the Fast Gauss Transform is no longer applicable. The solution of the interpolation matrix system by a preconditioned iteration is less sensitive to condition numbers than direct methods because iterations are self-correcting and also because the preconditioning reduces the spread of the eigenvalues. However, each iteration requires a matrix-vector multiply which is fast only if this operation can be performed by some species of Fast Summation. When α˜O(1), alas, we show that Ω is not large and the Fast Gauss Transform is not accelerative. Gaussian RBFs are unusual among RBF species through the absence of long-range interactions due to the exponential decay of the Gaussians with distance from their centers; many other RBF species do have long-range interactions, and it is well
Measurements of the temporal onset of mega-Gauss magnetic fields in a laser-driven solenoid
NASA Astrophysics Data System (ADS)
Goyon, Clement; Polllock, B. B.; Turnbull, D. T.; Hazi, A.; Ross, J. S.; Mariscal, D. A.; Patankar, S.; Williams, G. J.; Farmer, W. A.; Moody, J. D.; Fujioka, S.; Law, K. F. F.
2016-10-01
We report on experimental results obtained at Omega EP showing a nearly linear increase of the B-field up to about 2 mega-Gauss in 0.75 ns in a 1 mm3 region. The field is generated using 1 TW of 351 nm laser power ( 8*1015 W/cm2) incident on a laser-driven solenoid target. The coil target converts about 1% of the laser energy into the B-field measured both inside and outside the coil using proton deflectometry with a grid and Faraday rotation of probe beam through SiO2 glass. Proton data indicates a current rise up to hundreds of kA with a spatial distribution in the Au solenoid conductor evolving in time. These results give insight into the generating mechanism of the current between the plates and the time behavior of the field. These experiments are motivated by recent efforts to understand and utilize High Energy Density (HED) plasmas in the presence of external magnetic fields in areas of research from Astrophysics to Inertial Confinement Fusion. We will describe the experimental results and scale them to a NIF hohlraum size. This work was performed under the auspices of the U.S. Department of Energy by LLNL under Contract DE-AC52-07NA27344.
ERIC Educational Resources Information Center
Bowers, Wayne A.
This monograph was written for the Conference of the New Instructional Materials in Physics, held at the University of Washington in summer, 1965. It is intended for students who have had an introductory college physics course. It seeks to provide an introduction to the idea of distributions in general, and to some aspects of the subject in…
Parallelization of Lower-Upper Symmetric Gauss-Seidel Method for Chemically Reacting Flow
NASA Technical Reports Server (NTRS)
Yoon, Seokkwan; Jost, Gabriele; Chang, Sherry
2005-01-01
Development of technologies for exploration of the solar system has revived an interest in computational simulation of chemically reacting flows since planetary probe vehicles exhibit non-equilibrium phenomena during the atmospheric entry of a planet or a moon as well as the reentry to the Earth. Stability in combustion is essential for new propulsion systems. Numerical solution of real-gas flows often increases computational work by an order-of-magnitude compared to perfect gas flow partly because of the increased complexity of equations to solve. Recently, as part of Project Columbia, NASA has integrated a cluster of interconnected SGI Altix systems to provide a ten-fold increase in current supercomputing capacity that includes an SGI Origin system. Both the new and existing machines are based on cache coherent non-uniform memory access architecture. Lower-Upper Symmetric Gauss-Seidel (LU-SGS) relaxation method has been implemented into both perfect and real gas flow codes including Real-Gas Aerodynamic Simulator (RGAS). However, the vectorized RGAS code runs inefficiently on cache-based shared-memory machines such as SGI system. Parallelization of a Gauss-Seidel method is nontrivial due to its sequential nature. The LU-SGS method has been vectorized on an oblique plane in INS3D-LU code that has been one of the base codes for NAS Parallel benchmarks. The oblique plane has been called a hyperplane by computer scientists. It is straightforward to parallelize a Gauss-Seidel method by partitioning the hyperplanes once they are formed. Another way of parallelization is to schedule processors like a pipeline using software. Both hyperplane and pipeline methods have been implemented using openMP directives. The present paper reports the performance of the parallelized RGAS code on SGI Origin and Altix systems.
Black hole initial data in Gauss-Bonnet gravity: Momentarily static case
Yoshino, Hirotaka
2011-05-15
We study the method for generating the initial data of black hole systems in Gauss-Bonnet gravity. The initial data are assumed to be momentarily static and conformally flat. Although the equation for the conformal factor is highly nonlinear, it is successfully solved by numerical relaxation for one-black-hole and two-black-hole systems. The common apparent horizon is studied in the two-black-hole initial data, and the result suggests that the Penrose inequalities are satisfied in this system. This is the first step for simulating black hole collisions in higher-curvature theories.
Energetics and optical properties of 6-dimensional rotating black hole in pure Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Abdujabbarov, Ahmadjon; Atamurotov, Farruh; Dadhich, Naresh; Ahmedov, Bobomurat; Stuchlík, Zdeněk
2015-08-01
We study physical processes around a rotating black hole in pure Gauss-Bonnet (GB) gravity. In pure GB gravity, the gravitational potential has a slower fall-off as compared to the corresponding Einstein potential in the same dimension. It is therefore expected that the energetics of a pure GB black hole would be weaker, and our analysis bears out that the efficiency of energy extraction by the Penroseprocess is increased to 25.8 % and the particle acceleration is increased to 55.28 %; the optical shadow of the black hole is decreased. These are in principle distinguishing observable features of a pure GB black hole.
Dataset for petroleum based stock markets and GAUSS codes for SAMEM.
Khalifa, Ahmed A A; Bertuccelli, Pietro; Otranto, Edoardo
2017-02-01
This article includes a unique data set of a balanced daily (Monday, Tuesday and Wednesday) for oil and natural gas volatility and the oil rich economies' stock markets for Saudi Arabia, Qatar, Kuwait, Abu Dhabi, Dubai, Bahrain and Oman, using daily data over the period spanning Oct. 18, 2006-July 30, 2015. Additionally, we have included unique GAUSS codes for estimating the spillover asymmetric multiplicative error model (SAMEM) with application to Petroleum-Based Stock Market. The data, the model and the codes have many applications in business and social science.
Small-displacement measurements using high-order Hermite-Gauss modes
Sun, Hengxin; Liu, Kui; Liu, Zunlong; Guo, Pengliang; Zhang, Junxiang; Gao, Jiangrui
2014-03-24
We present a scheme for small-displacement measurements using high-order Hermite-Gauss modes and balanced homodyne detection. We demonstrate its use with experimental results of displacement measurements using fundamental transverse mode TEM{sub 00} and first order transverse mode TEM{sub 10} as signal modes. The results show a factor of 1.41 improvement in measurement precision with the TEM{sub 10} mode compared with that with the TEM{sub 00} mode. This scheme has potential applications in precision metrology, atomic force microscopy, and optical imaging.
An incremental block-line-Gauss-Seidel method for the Navier-Stokes equations
NASA Technical Reports Server (NTRS)
Napolitano, M.; Walters, R. W.
1985-01-01
A block-line-Gauss-Seidel (LGS) method is developed for solving the incompressible and compressible Navier-Stokes equations in two dimensions. The method requires only one block-tridiagonal solution process per iteration and is consequently faster per step than the linearized block-ADI methods. Results are presented for both incompressible and compressible separated flows: in all cases the proposed block-LGS method is more efficient than the block-ADI methods. Furthermore, for high Reynolds number weakly separated incompressible flow in a channel, which proved to be an impossible task for a block-ADI method, solutions have been obtained very efficiently by the new scheme.
Herman, B M; Caudill, T R; Flittner, D E; Thome, K J; Ben-David, A
1995-07-20
Calculations that use the Gauss-Seidel method are presented of the diffusely scattered light in a spherical atmosphere with polarization fully included. Comparisons are made between this method and the Monte Carlo calculations of other researchers for spherical geometry in a pure Rayleigh atmosphere. Comparisons with plane-parallel atmospheres are also presented. Single-scatter intensity comparisons with spherical geometry show excellent agreement. When all orders of scattering are included, comparisons of polarization parameters I, Q and U as well as the plane of polarization show good agreement when allowances are made for the statistical variability inherent in the Monte Carlo method.
The solution of the Navier-Stokes equations using Gauss-Seidel line relaxation
NASA Technical Reports Server (NTRS)
Maccormack, Robert W.; Candler, Graham V.
1989-01-01
The Navier-Stokes equations in an implicit flux-split difference formulation are solved numerically using a Gauss-Seidel line-relaxation procedure. Particular attention is given to the selection of flux-vector splitting method and flux splitting in boundary layers. Results for sample problems involving (1) turbulent supersonic flow over a cone and (2) the viscous hypersonic flow of a chemically reacting gas in thermal nonequilibrium past a blunted cone are presented in extensive graphs and briefly characterized. The present flux-split procedures are shown to provide accurate shear-layer calculations.
A Stable Clock Error Model Using Coupled First and Second Order Gauss-Markov Processes
NASA Technical Reports Server (NTRS)
Carpenter, Russell; Lee, Taesul
2008-01-01
Long data outages may occur in applications of global navigation satellite system technology to orbit determination for missions that spend significant fractions of their orbits above the navigation satellite constellation(s). Current clock error models based on the random walk idealization may not be suitable in these circumstances, since the covariance of the clock errors may become large enough to overflow flight computer arithmetic. A model that is stable, but which approximates the existing models over short time horizons is desirable. A coupled first- and second-order Gauss-Markov process is such a model.
Observational limits on Gauss-Bonnet and Randall-Sundrum gravities
Alexeyev, S. O. Rannu, K. A.; Dyadina, P. I.; Latosh, B. N.; Turyshev, S. G.
2015-06-15
We discuss the possibilities of experimental search for the new physics predicted by the Gauss-Bonnet and the Randall-Sundrum theories of gravity. The effective four-dimensional spherically symmetrical solutions of these theories are analyzed. We consider these solutions in the weak-field limit and in the process of the primordial black hole evaporation. We show that the predictions of the discussed models are the same as of general relativity. Hence, current experiments are not applicable for such search, and therefore different methods of observation and higher accuracy are required.
Hydrodynamics with conserved current via AdS/CFT correspondence in the Maxwell-Gauss-Bonnet gravity
Hu Yapeng; Sun Peng; Zhang Jianhui
2011-06-15
Using the AdS/CFT correspondence, we study the hydrodynamics with conserved current from the dual Maxwell-Gauss-Bonnet gravity. After constructing the perturbative solution to the first order based on the boosted black brane solution in the bulk Maxwell-Gauss-Bonnet gravity, we extract the stress tensor and conserved current of the dual conformal fluid on its boundary, and also find the effect of the Gauss-Bonnet term on the dual conformal fluid. Our results show that the Gauss-Bonnet term can affect the parameters such as the shear viscosity {eta}, entropy density s, thermal conductivity {kappa} and electrical conductivity {sigma}. However, it does not affect the so-called Wiedemann-Franz law which relates {kappa} to {sigma}, while it affects the ratio {eta}/s. In addition, another interesting result is that {eta}/s can also be affected by the bulk Maxwell field in our case, which is consistent with some previous results predicted through the Kubo formula. Moreover, the anomalous magnetic and vortical effects by adding the Chern-Simons term are also considered in our case in the Maxwell-Gauss-Bonnet gravity.
Early-time cosmological solutions in Einstein-scalar-Gauss-Bonnet theory
NASA Astrophysics Data System (ADS)
Kanti, Panagiota; Gannouji, Radouane; Dadhich, Naresh
2015-10-01
In this work, we consider a generalized gravitational theory that contains the Einstein term, a scalar field, and the quadratic Gauss-Bonnet (GB) term. We focus on the early-universe dynamics, and demonstrate that a simple choice of the coupling function between the scalar field and the Gauss-Bonnet term and a simplifying assumption regarding the role of the Ricci scalar can lead to new, analytical, elegant solutions with interesting characteristics. We first argue, and demonstrate in the context of two different models, that the presence of the Ricci scalar in the theory at early times (when the curvature is strong) does not affect the actual cosmological solutions. By considering therefore a pure scalar-GB theory with a quadratic coupling function we derive a plethora of interesting, analytic solutions: for a negative coupling parameter, we obtain inflationary, de Sitter-type solutions or expanding solutions with a de Sitter phase in their past and a natural exit mechanism at later times; for a positive coupling function, we find instead singularity-free solutions with no big bang singularity. We show that the aforementioned solutions arise only for this particular choice of coupling function, a result that may hint at some fundamental role that this coupling function may hold in the context of an ultimate theory.
[MEG inverse solution using Gauss-Newton algorithm modified by Moore-Penrose inversion].
Li, J
2001-06-01
In magnetoencephalogram(MEG) basic studies, it is an important issue to estimate magnetic source parameters by inverse solution. It is known that the magnetic field equations are nonlinear, thus explicit solutions are difficult to obtain. However optimization methods are available to this parameter estimation. In many usually used nonlinear local optimization algorithms, Gauss-Newton's is of fast convergent speed. When this algorithm is used, the singularity of the Jacobien matrix about the minimum least square error must be considered carefully. If the matrix is singular, the equation for searching direction has no general solution. One way to overcome this problem is to use negative gradient as searching direction, but it may cause descent of convergent speed. Another way is known as Levenberg-Marquardt algorithm which makes the matrix non-singular by adding some improved factors to it. In this paper we utilize Moore-Penrose inversion for the solution of iterative searching direction equation. In appendix we demonstrate that the searching direction obtained by the proposed method is successful. Computer simulation also demonstrates that by reasonable selection of initial iterative values, the modified Gauss-Newton algorithm is effective for MEG inverse solution in the case with one or two source dipoles.
'Mass without mass' from thin shells in Gauss-Bonnet gravity
Gravanis, Elias; Willison, Steven
2007-04-15
Five tensor equations are obtained for a thin shell in Gauss-Bonnet gravity. There is the well-known junction condition for the singular part of the stress tensor intrinsic to the shell, which we also prove to be well defined. There are also equations relating the geometry of the shell (jump and average of the extrinsic curvature as well as the intrinsic curvature) to the nonsingular components of the bulk stress tensor on the sides of the thin shell. The equations are applied to spherically symmetric thin shells in the vacuum. The shells are part of the vacuum; they carry no energy tensor. We classify these solutions of 'thin shells of nothingness' in the pure Gauss-Bonnet theory. There are three types of solutions, with one, zero, or two asymptotic regions, respectively. The third kind of solutions are wormholes. Although vacuum solutions, they have the appearance of mass in the asymptotic regions. It is striking that in this theory, exotic matter is not needed in order for wormholes to exist--they can exist even with no matter.
Static and symmetric wormholes respecting energy conditions in Einstein-Gauss-Bonnet gravity
Maeda, Hideki; Nozawa, Masato
2008-07-15
Properties of n({>=}5)-dimensional static wormhole solutions are investigated in Einstein-Gauss-Bonnet gravity with or without a cosmological constant {lambda}. We assume that the spacetime has symmetries corresponding to the isometries of an (n-2)-dimensional maximally symmetric space with the sectional curvature k={+-}1, 0. It is also assumed that the metric is at least C{sup 2} and the (n-2)-dimensional maximally symmetric subspace is compact. Depending on the existence or absence of the general relativistic limit {alpha}{yields}0, solutions are classified into general relativistic (GR) and non-GR branches, respectively, where {alpha} is the Gauss-Bonnet coupling constant. We show that a wormhole throat respecting the dominant energy condition coincides with a branch surface in the GR branch, otherwise the null energy condition is violated there. In the non-GR branch, it is shown that there is no wormhole solution for k{alpha}{>=}0. For the matter field with zero tangential pressure, it is also shown in the non-GR branch with k{alpha}<0 and {lambda}{<=}0 that the dominant energy condition holds at the wormhole throat if the radius of the throat satisfies some inequality. In the vacuum case, a fine-tuning of the coupling constants is shown to be necessary and the radius of a wormhole throat is fixed. Explicit wormhole solutions respecting the energy conditions in the whole spacetime are obtained in the vacuum and dust cases with k=-1 and {alpha}>0.
Fabry-Pérot-Michelson interferometer using higher-order Laguerre-Gauss modes
NASA Astrophysics Data System (ADS)
Gatto, A.; Tacca, M.; Kéfélian, F.; Buy, C.; Barsuglia, M.
2014-12-01
One of the main noise sources for future interferometric gravitational wave detectors will be the thermal fluctuations of the mirrors used as test masses. To reduce the effect of this noise without changing the mirror material, size and temperature, the use of Laguerre-Gauss (LG) modes has been proposed. In this work we report the first experimental results obtained with a Fabry-Pérot Michelson interferometer operated with Laguerre-Gauss LG33 as input mode and developed as a table-top prototype to test alignment and matching procedures, possible control issues and optical performances of the LG33 . Among the results obtained, we have demonstrated the degradation of the interferometer contrast of the LG33 with respect to the Gaussian beam, predicted by several previous simulations works and due to the degeneracy of LG modes having the same order. In addition, the observed contrast degradation for the LG33 as well as the interferometer optical properties have been explained using a numerical simulation.
Imaging of trabecular meshwork using Bessel–Gauss light sheet with fluorescence
NASA Astrophysics Data System (ADS)
Jie Jeesmond Hong, Xun; Shinoj, V. K.; Murukeshan, V. M.; Baskaran, M.; Aung, Tin
2017-03-01
Ocular imaging technology that holds promise for both fundamental investigation and clinical detection of glaucoma is still a challenging research area. A direct view of the trabecular meshwork (TM) with high resolution is not generally possible because the iridocorneal angle region is obstructed by the sclera overlap. The best approach to observe the aqueous outflow system (AOS) is therefore to view from the opposite angle. In this research work, we developed two imaging systems for the high resolution ex vivo studies of the AOS inside porcine eye, based on a Gaussian illuminated and a digitally scanned Bessel–Gauss beam light sheet fluorescence configurations. The digitally scanned Bessel–Gauss beam is able to overcome the trade-off between the length and thickness of the Gaussian light sheet to give better imaging performance. It has adequate spatial resolution to resolve critical anatomical structures such as the TM, thereby enabling objective information about the AOS. This non-contact and non-invasive imaging methodology with excellent safety profile is expected to be well received by vision researchers and clinicians in the evaluation and management of glaucoma.
Recursive Gauss-Seidel median filter for CT lung image denoising
NASA Astrophysics Data System (ADS)
Dewi, Dyah Ekashanti Octorina; Faudzi, Ahmad Athif Mohd.; Mengko, Tati Latifah; Suzumori, Koichi
2017-02-01
Poisson and Gaussian noises have been known to affect Computed Tomography (CT) image quality during reconstruction. Standard median (SM) Filter has been widely used to reduce the unwanted impulsive noises. However, it cannot perform satisfactorily once the noise density is high. Recursive median (RM) filter has also been proposed to optimize the denoising. On the other hand, the image quality is degraded. In this paper, we propose a hybrid recursive median (RGSM) filtering technique by using Gauss-Seidel Relaxation to enhance denoising and preserve image quality in RM filter. First, the SM filtering was performed, followed by Gauss-Seidel, and combined to generate secondary approximation solution. This scheme was iteratively done by applying the secondary approximation solution to the successive iterations. Progressive noise reduction was accomplished in every iterative stage. The last stage generated the final solution. Experiments on CT lung images show that the proposed technique has higher noise reduction improvements compared to the conventional RM filtering. The results have also confirmed better anatomical quality preservation. The proposed technique may improve lung nodules segmentation and characterization performance.
Arrizón, Victor; Ruiz, Ulises; Aguirre-Olivas, Dilia; Sánchez-de-la-Llave, David; Ostrovsky, Andrey S
2014-03-01
We compare two phase optical elements that are employed to generate approximate Bessel-Gauss beams of arbitrary order. These elements are the helical axicon (HA) and the kinoform of the desired Bessel-Gauss beam. The HA generates a Bessel beam (BB) by free propagation, and the kinoform is employed in a Fourier spatial filtering optical setup. As the main result, it is obtained that the error in the BBs generated with the kinoform is smaller than the error in the beams obtained with the HA. On the other hand, it is obtained that the efficiencies of the methods are approximately 1.0 (HA) and 0.7 (kinoform).
Parsa, Shahrzad; Fallah, Hamid Reza; Ramezani, Mohsen; Soltanolkotabi, Mahmood
2012-11-01
Nondiffracting Bessel-Gauss beams are assumed as the superposition of infinite numbers of Gaussian beams whose wave vectors lie on a cone. Based on such a description, different methods are suggested to generate these fields. In this paper, we followed an active scheme to generate these beams. By introducing an axicon-based resonator, we designed the appropriate resonator, studied its resonance modes, and analyzed the beam propagation outside the resonator. Experimentally, we succeeded to obtain Bessel-Gauss beams of the first kind and zero order. We also investigated the changes in effective parameters on the output beam, both theoretically and experimentally.
Mazharimousavi, S. Habib; Halilsoy, M.; Amirabi, Z.
2010-05-15
Recently in [Phys. Rev. D 76, 087502 (2007) and Phys. Rev. D 77, 089903 (2008)] a thin-shell wormhole has been introduced in five-dimensional Einstein-Maxwell-Gauss-Bonnet gravity which was supported by normal matter. We wish to consider this solution and investigate its stability. Our analysis shows that for the Gauss-Bonnet parameter {alpha}<0, stability regions form for a narrow band of finely tuned mass and charge. For the case {alpha}>0, we iterate once more that no stable, normal matter thin-shell wormhole exists.
NASA Technical Reports Server (NTRS)
Yoon, Seokkwan; Kwak, Dochan
1991-01-01
A numerical method based on the pseudocompressibility concept is developed for solving the three-dimensional incompressible Navier-Stokes equations using the lower-upper symmetric-Gauss-Seidel implicit scheme. Very high efficiency is achieved in a new flow solver, INS3D-LU code, by accomplishing the complete vectorizability of the algorithm on oblique planes of sweep in three dimensions.
Is there a relation between the 2D Causal Set action and the Lorentzian Gauss-Bonnet theorem?
NASA Astrophysics Data System (ADS)
Benincasa, Dionigi M. T.
2011-07-01
We investigate the relation between the two dimensional Causal Set action, Script S, and the Lorentzian Gauss-Bonnet theorem (LGBT). We give compelling reasons why the answer to the title's question is no. In support of this point of view we calculate the causal set inspired action of causal intervals in some two dimensional spacetimes: Minkowski, the flat cylinder and the flat trousers.
GigaGauss solenoidal magnetic field inside bubbles excited in under-dense plasma
NASA Astrophysics Data System (ADS)
Lécz, Zs.; Konoplev, I. V.; Seryi, A.; Andreev, A.
2016-10-01
This paper proposes a novel and effective method for generating GigaGauss level, solenoidal quasi-static magnetic fields in under-dense plasma using screw-shaped high intensity laser pulses. This method produces large solenoidal fields that move with the driving laser pulse and are collinear with the accelerated electrons. This is in contrast with already known techniques which rely on interactions with over-dense or solid targets and generates radial or toroidal magnetic field localized at the stationary target. The solenoidal field is quasi-stationary in the reference frame of the laser pulse and can be used for guiding electron beams. It can also provide synchrotron radiation beam emittance cooling for laser-plasma accelerated electron and positron beams, opening up novel opportunities for designs of the light sources, free electron lasers, and high energy colliders based on laser plasma acceleration.
Critical behavior of charged black holes in Gauss-Bonnet gravity's rainbow
NASA Astrophysics Data System (ADS)
Hendi, Seyed Hossein; Panahiyan, Shahram; Eslam Panah, Behzad; Faizal, Mir; Momennia, Mehrab
2016-07-01
Following an earlier study regarding Gauss-Bonnet-Maxwell black holes in the presence of gravity's rainbow [S. H. Hendi and M. Faizal, Phys. Rev. D 92, 044027 (2015)], in this paper, we consider all constants as energy dependent ones. The geometrical and thermodynamical properties of this generalization is studied and the validation of the first law of thermodynamics is examined. Next, through the use of proportionality between the cosmological constant and the thermodynamical pressure, van der Waals-like behavior of these black holes in extended phase space is investigated. An interesting critical behavior for sets of rainbow functions in this case is reported. Also, the critical behavior of uncharged and charged solutions is analyzed and it is shown that the generalization to a charged case puts an energy dependent restriction on values of different parameters.
Border detection on Common Carotid Artery using Gauss-Markov Estimation
NASA Astrophysics Data System (ADS)
Koya, Yoshiharu; Mizoshiri, Isao
The arteriosclerosis is on the increase with an aging or change of our living environment. For that reason, diagnosis of the common carotid artery using echocardiogram is doing to take precautions carebropathy. The arteriosclerosis of the common carotid artery is diagnosed using Intima-Media Thickness (IMT) which is obtained from echocardiogram. In order to measure IMT from echocardiogram, it is required to detect a border which is a boundary between vessel tissue layers. The method of border detection requires reproducibility, high accuracy and high-speed. In this paper, we propose the high-accuracy and high-speed detection method by Gauss-Markov estimation. About high-accuracy, it realized by attaching importance to high reliable candidate point of border. And, about high-speed, it realized by calculating matrix only one time.
Gravitational bending angle of light for finite distance and the Gauss-Bonnet theorem
NASA Astrophysics Data System (ADS)
Ishihara, Asahi; Suzuki, Yusuke; Ono, Toshiaki; Kitamura, Takao; Asada, Hideki
2016-10-01
We discuss a possible extension of calculations of the bending angle of light in a static, spherically symmetric and asymptotically flat spacetime to a nonasymptotically flat case. We examine a relation between the bending angle of light and the Gauss-Bonnet theorem by using the optical metric. A correspondence between the deflection angle of light and the surface integral of the Gaussian curvature may allow us to take account of the finite distance from a lens object to a light source and a receiver. Using this relation, we propose a method for calculating the bending angle of light for such cases. Finally, this method is applied to two examples of the nonasymptotically flat spacetimes to suggest finite-distance corrections: the Kottler (Schwarzschild-de Sitter) solution to the Einstein equation and an exact solution in Weyl conformal gravity.
GigaGauss solenoidal magnetic field inside bubbles excited in under-dense plasma
Lécz, Zs.; Konoplev, I. V.; Seryi, A.; Andreev, A.
2016-01-01
This paper proposes a novel and effective method for generating GigaGauss level, solenoidal quasi-static magnetic fields in under-dense plasma using screw-shaped high intensity laser pulses. This method produces large solenoidal fields that move with the driving laser pulse and are collinear with the accelerated electrons. This is in contrast with already known techniques which rely on interactions with over-dense or solid targets and generates radial or toroidal magnetic field localized at the stationary target. The solenoidal field is quasi-stationary in the reference frame of the laser pulse and can be used for guiding electron beams. It can also provide synchrotron radiation beam emittance cooling for laser-plasma accelerated electron and positron beams, opening up novel opportunities for designs of the light sources, free electron lasers, and high energy colliders based on laser plasma acceleration. PMID:27796327
Extrinsic geometry of strings and the Gauss map of surfaces in R sup n
Parthasarathy, R.; Viswanathan, K.S. )
1992-03-30
This paper reports on a two-dimensional Euclidean string world sheet realized as a conformal immersion in R{sup n} which is mapped into the Grassmannian G{sub 2,n} through the generalized Gauss map. In order for the Grassmannian to represent tangent planes to a given surface, n {minus} 2 integrability conditions must be satisfied by the G{sub 2,n} fields. These conditions are explicitly derived for arbitrary n by realizing G{sub 2,n} as a quadric in CP{sup n{minus}1}. Both the intrinsic and the extrinsic geometrical properties of the string world sheet are expressed in terms of the Kahler {sigma} model fields.
Bessel-Gauss beams as rigorous solutions of the Helmholtz equation.
April, Alexandre
2011-10-01
The study of the nonparaxial propagation of optical beams has received considerable attention. In particular, the so-called complex-source/sink model can be used to describe strongly focused beams near the beam waist, but this method has not yet been applied to the Bessel-Gauss (BG) beam. In this paper, the complex-source/sink solution for the nonparaxial BG beam is expressed as a superposition of nonparaxial elegant Laguerre-Gaussian beams. This provides a direct way to write the explicit expression for a tightly focused BG beam that is an exact solution of the Helmholtz equation. It reduces correctly to the paraxial BG beam, the nonparaxial Gaussian beam, and the Bessel beam in the appropriate limits. The analytical expression can be used to calculate the field of a BG beam near its waist, and it may be useful in investigating the features of BG beams under tight focusing conditions.
Quantum dynamics of electronic transitions with Gauss-Hermite wave packets.
Borrelli, Raffaele; Peluso, Andrea
2016-03-21
A new methodology based on the superposition of time-dependent Gauss-Hermite wave packets is developed to describe the wave function of a system in which several interacting electronic states are coupled to a bath of harmonic oscillators. The equations of motion for the wave function parameters are obtained by employing the Dirac-Frenkel time-dependent variational principle. The methodology is applied to study the quantum dynamical behaviour of model systems with two interacting electronic states characterized by a relatively large reorganization energy and a range of energy biases. The favourable scaling properties make it a promising tool for the study of the dynamics of chemico-physical processes in molecular systems.
NASA Astrophysics Data System (ADS)
Shang, J. S.; Andrienko, D. A.; Huang, P. G.; Surzhikov, S. T.
2014-06-01
An efficient computational capability for nonequilibrium radiation simulation via the ray tracing technique has been accomplished. The radiative rate equation is iteratively coupled with the aerodynamic conservation laws including nonequilibrium chemical and chemical-physical kinetic models. The spectral properties along tracing rays are determined by a space partition algorithm of the nearest neighbor search process, and the numerical accuracy is further enhanced by a local resolution refinement using the Gauss-Lobatto polynomial. The interdisciplinary governing equations are solved by an implicit delta formulation through the diminishing residual approach. The axisymmetric radiating flow fields over the reentry RAM-CII probe have been simulated and verified with flight data and previous solutions by traditional methods. A computational efficiency gain nearly forty times is realized over that of the existing simulation procedures.
Near-infrared reflectance analysis by Gauss-Jordan linear algebra
Honigs, D.E.; Freelin, J.M.; Hieftje, G.M.; Hirschfeld, T.B.
1983-11-01
Near-infrared reflectance analysis is an analytical technique that uses the near-infrared diffuse reflectance of a sample at several discrete wavelengths to predict the concentration of one or more of the chemical species in that sample. However, because near-infrared bands from solid samples are both abundant and broad, the reflectance at a given wavelength usually contains contributions from several sample components, requiring extensive calculations on overlapped bands. In the present study, these calculations have been performed using an approach similar to that employed in multi-component spectrophotometry, but with Gauss-Jordan linear algebra serving as the computational vehicle. Using this approach, correlations for percent protein in wheat flour and percent benzene in hydrocarbons have been obtained and are evaluated. The advantages of a linear-algebra approach over the common one employing stepwise regression are explored.
NASA Astrophysics Data System (ADS)
Sun, Yuan; Xu, Hao; Zhao, Liu
2016-09-01
The holographic entanglement entropy is studied numerically in (4+1)-dimensional spherically symmetric Gauss-Bonnet AdS black hole spacetime with compact boundary. On the bulk side the black hole spacetime undergoes a van der Waals-like phase transition in the extended phase space, which is reviewed with emphasis on the behavior on the temperature-entropy plane. On the boundary, we calculated the regularized HEE of a disk region of different sizes. We find strong numerical evidence for the failure of equal area law for isobaric curves on the temperature-HEE plane and for the correctness of first law of entanglement entropy, and briefly give an explanation for why the latter may serve as a reason for the former, i.e. the failure of equal area law on the temperature-HEE plane.
NASA Astrophysics Data System (ADS)
Hendi, S. H.; Panahiyan, S.; Momennia, M.; Eslam Panah, B.
Taking into account the perturbative corrections of Einstein (EN)-Maxwell gravity, we study thermodynamical behavior of the black holes in the context of geometrical thermodynamics (GT). We consider a quadratic Maxwell invariant as a correction of Maxwell theory in electromagnetic viewpoint and Gauss-Bonnet (GB) gravity as a correction of EN theory in gravitational point of view. We study thermodynamical phase transition and show that employing Weinhold, Ruppeiner and Quevedo approaches fails to produce desirable results. Next, Hendi-Panahiyan-Eslam Panah-Momennia (HPEM) metric will be employed in order to study GT of the solutions. We show that this metric is capable of matching all the divergence points of its thermodynamical curvature scalar with phase transition and bound points. Moreover, the effects of the variation of different parameters on phase transition points will be investigated.
About the ellipticity of the Chebyshev-Gauss-Radau discrete Laplacian with Neumann condition
NASA Astrophysics Data System (ADS)
Trouette, B.; Delcarte, C.; Labrosse, G.
2010-09-01
The Chebyshev-Gauss-Radau discrete version of the polar-diffusion operator, {1}/{r}{∂}/{∂r}r{∂}/{∂r}-{k2}/{r2}, k being the azimuthal wave number, presents complex conjugate eigenvalues, with negative real parts, when it is associated with a Neumann boundary condition imposed at r = 1. It is shown that this ellipticity marginal violation of the original continuous problem is genuine and not due to some round-off error amplification. This situation, which does not lead per se to any particular computational difficulty, is taken here as an opportunity to numerically check the sensitivity of the quoted ellipticity to slight changes in the mesh. A particular mapping is chosen for that purpose. The impact of this option on the ellipticity and on the numerical accuracy of a computed flow is evaluated.
NASA Astrophysics Data System (ADS)
Wu, Yunhua; Cao, Xibin; Xing, Yanjun; Zheng, Pengfei; Zhang, Shijie
This paper addresses the problem of how to control spacecraft formation with coupled translational and rotational dynamics with optimized fuel usage using a single body fixed thruster and reaction wheels. The orientation of the thrust vector is constrained by the attitude and angular velocity. In particular, the star camera cannot point at the sun during formation maneuvering. The formation coupled control, which is a difficult problem with nonlinear and nonconvex attitude dynamics, is posed as a nonlinear optimal control problem and solved via direct transcription using the Gauss pseudospectral method. Examples demonstrate application of the proposed approach with simulated trajectory optimization of a dual-spacecraft formation initialization and a three-spacecraft reconfiguration problem.
A proximity algorithm accelerated by Gauss-Seidel iterations for L1/TV denoising models
NASA Astrophysics Data System (ADS)
Li, Qia; Micchelli, Charles A.; Shen, Lixin; Xu, Yuesheng
2012-09-01
Our goal in this paper is to improve the computational performance of the proximity algorithms for the L1/TV denoising model. This leads us to a new characterization of all solutions to the L1/TV model via fixed-point equations expressed in terms of the proximity operators. Based upon this observation we develop an algorithm for solving the model and establish its convergence. Furthermore, we demonstrate that the proposed algorithm can be accelerated through the use of the componentwise Gauss-Seidel iteration so that the CPU time consumed is significantly reduced. Numerical experiments using the proposed algorithm for impulsive noise removal are included, with a comparison to three recently developed algorithms. The numerical results show that while the proposed algorithm enjoys a high quality of the restored images, as the other three known algorithms do, it performs significantly better in terms of computational efficiency measured in the CPU time consumed.
Black hole solutions in string theory with Gauss-Bonnet curvature correction
Maeda, Kei-ichi; Ohta, Nobuyoshi; Sasagawa, Yukinori
2009-11-15
We present the black hole solutions and analyze their properties in the superstring effective field theory with the Gauss-Bonnet curvature correction terms. We find qualitative differences in our results from those obtained in the truncated model in the Einstein frame. The main difference in our model from the truncated one is that the existence of a turning point in the mass-area curve, the mass-entropy curve, and the mass-temperature curve in five and higher dimensions, where we expect a change of stability. We also find a mass gap in our model, where there is no black hole solution. In five dimensions, there exists a maximum black hole temperature and the temperature vanishes at the minimum mass, which is not found in the truncated model.
Black hole formation in AdS Einstein-Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Deppe, Nils; Kolly, Allison; Frey, Andrew R.; Kunstatter, Gabor
2016-10-01
AdS spacetime has been shown numerically to be unstable against a large class of arbitrarily small perturbations. In [1], the authors presented a preliminary study of the effects on stability of changing the local dynamics by adding a Gauss-Bonnet term to the Einstein action. Here we provide further details as well as new results with improved numerical methods. In particular, we elucidate new structure in Choptuik scaling plots. We also provide evidence of chaotic behavior at the transition between immediate horizon formation and horizon formation after the matter pulse reflects from the AdS conformal boundary. Finally, we present data suggesting the formation of naked singularities in spacetimes with ADM mass below the algebraic bound for black hole formation.
Coarse-to-fine markerless gait analysis based on PCA and Gauss-Laguerre decomposition
NASA Astrophysics Data System (ADS)
Goffredo, Michela; Schmid, Maurizio; Conforto, Silvia; Carli, Marco; Neri, Alessandro; D'Alessio, Tommaso
2005-04-01
Human movement analysis is generally performed through the utilization of marker-based systems, which allow reconstructing, with high levels of accuracy, the trajectories of markers allocated on specific points of the human body. Marker based systems, however, show some drawbacks that can be overcome by the use of video systems applying markerless techniques. In this paper, a specifically designed computer vision technique for the detection and tracking of relevant body points is presented. It is based on the Gauss-Laguerre Decomposition, and a Principal Component Analysis Technique (PCA) is used to circumscribe the region of interest. Results obtained on both synthetic and experimental tests provide significant reduction of the computational costs, with no significant reduction of the tracking accuracy.
NASA Astrophysics Data System (ADS)
Hendi, S. H.; Panahiyan, S.
2014-12-01
Motivated by the string corrections on the gravity and electrodynamics sides, we consider a quadratic Maxwell invariant term as a correction of the Maxwell Lagrangian to obtain exact solutions of higher dimensional topological black holes in Gauss-Bonnet gravity. We first investigate the asymptotically flat solutions and obtain conserved and thermodynamic quantities which satisfy the first law of thermodynamics. We also analyze thermodynamic stability of the solutions by calculating the heat capacity and the Hessian matrix. Then, we focus on horizon-flat solutions with an anti-de Sitter (AdS) asymptote and produce a rotating spacetime with a suitable transformation. In addition, we calculate the conserved and thermodynamic quantities for asymptotically AdS black branes which satisfy the first law of thermodynamics. Finally, we perform thermodynamic instability criterion to investigate the effects of nonlinear electrodynamics in canonical and grand canonical ensembles.
Geophex Airborne Unmanned Survey System (GAUSS). Topical report, October 1993--March 1995
1995-03-01
The objectives of the project are to construct a geophysical sensor system based on a remotely operated model helicopter (ROH) and to evaluate the efficacy of the system for characterization of hazardous environmental sites. Geophex Airborne Unmanned Survey System (GAUSS) is a geophysical survey system that uses a ROH as the survey vehicle. We have selected the ROH because of its advantages over fixed wing and ground based vehicles. Lower air speed and superior maneuverability of the ROH make it better suited for geophysical surveys than a fixed wing model aircraft. The ROH can fly close to the ground, allowing detection of weak or subtle anomalies. Unlike ground based vehicles, the ROH can traverse difficult terrain while providing a stable sensor platform. ROH does not touch the ground during the course of a survey and is capable of functioning over water and surf zones. The ROH has been successfully used in the motion picture industry and by geology companies for payload bearing applications. The only constraint to use of the airborne system is that the ROH must remain visible to the pilot. Obstructed areas within a site can be characterized by relocating the base station to alternate positions. GAUSS consists of a ROH with radio controller, a data acquisition and processing (DAP) system, and lightweight digital sensor systems. The objective of our Phase I research was to develop a DAP and sensors suitable for ROH operation. We have constructed these subsystems and integrated them to produce an automated, hand-held geophysical surveying system, referred to as the ``pre-prototype``. We have performed test surveys with the pre-prototype to determine the functionality of the and DAP and sensor subsystems and their suitability for airborne application. The objective of the Phase II effort will be to modify the existing subsystems and integrate them into an airborne prototype. Efficacy of the prototype for geophysical survey of hazardous sites will then be determined.
[A Hyperspectral Imagery Anomaly Detection Algorithm Based on Gauss-Markov Model].
Gao, Kun; Liu, Ying; Wang, Li-jing; Zhu, Zhen-yu; Cheng, Hao-bo
2015-10-01
With the development of spectral imaging technology, hyperspectral anomaly detection is getting more and more widely used in remote sensing imagery processing. The traditional RX anomaly detection algorithm neglects spatial correlation of images. Besides, it does not validly reduce the data dimension, which costs too much processing time and shows low validity on hyperspectral data. The hyperspectral images follow Gauss-Markov Random Field (GMRF) in space and spectral dimensions. The inverse matrix of covariance matrix is able to be directly calculated by building the Gauss-Markov parameters, which avoids the huge calculation of hyperspectral data. This paper proposes an improved RX anomaly detection algorithm based on three-dimensional GMRF. The hyperspectral imagery data is simulated with GMRF model, and the GMRF parameters are estimated with the Approximated Maximum Likelihood method. The detection operator is constructed with GMRF estimation parameters. The detecting pixel is considered as the centre in a local optimization window, which calls GMRF detecting window. The abnormal degree is calculated with mean vector and covariance inverse matrix, and the mean vector and covariance inverse matrix are calculated within the window. The image is detected pixel by pixel with the moving of GMRF window. The traditional RX detection algorithm, the regional hypothesis detection algorithm based on GMRF and the algorithm proposed in this paper are simulated with AVIRIS hyperspectral data. Simulation results show that the proposed anomaly detection method is able to improve the detection efficiency and reduce false alarm rate. We get the operation time statistics of the three algorithms in the same computer environment. The results show that the proposed algorithm improves the operation time by 45.2%, which shows good computing efficiency.
Electromagnetism, Local Covariance, the Aharonov-Bohm Effect and Gauss' Law
NASA Astrophysics Data System (ADS)
Sanders, Ko; Dappiaggi, Claudio; Hack, Thomas-Paul
2014-06-01
We quantise the massless vector potential A of electromagnetism in the presence of a classical electromagnetic (background) current, j, in a generally covariant way on arbitrary globally hyperbolic spacetimes M. By carefully following general principles and procedures we clarify a number of topological issues. First we combine the interpretation of A as a connection on a principal U(1)-bundle with the perspective of general covariance to deduce a physical gauge equivalence relation, which is intimately related to the Aharonov-Bohm effect. By Peierls' method we subsequently find a Poisson bracket on the space of local, affine observables of the theory. This Poisson bracket is in general degenerate, leading to a quantum theory with non-local behaviour. We show that this non-local behaviour can be fully explained in terms of Gauss' law. Thus our analysis establishes a relationship, via the Poisson bracket, between the Aharonov-Bohm effect and Gauss' law - a relationship which seems to have gone unnoticed so far. Furthermore, we find a formula for the space of electric monopole charges in terms of the topology of the underlying spacetime. Because it costs little extra effort, we emphasise the cohomological perspective and derive our results for general p-form fields A ( p < dim( M)), modulo exact fields, for the Lagrangian density . In conclusion we note that the theory is not locally covariant, in the sense of Brunetti-Fredenhagen-Verch. It is not possible to obtain such a theory by dividing out the centre of the algebras, nor is it physically desirable to do so. Instead we argue that electromagnetism forces us to weaken the axioms of the framework of local covariance, because the failure of locality is physically well-understood and should be accommodated.
A robust hidden Markov Gauss mixture vector quantizer for a noisy source.
Pyun, Kyungsuk Peter; Lim, Johan; Gray, Robert M
2009-07-01
Noise is ubiquitous in real life and changes image acquisition, communication, and processing characteristics in an uncontrolled manner. Gaussian noise and Salt and Pepper noise, in particular, are prevalent in noisy communication channels, camera and scanner sensors, and medical MRI images. It is not unusual for highly sophisticated image processing algorithms developed for clean images to malfunction when used on noisy images. For example, hidden Markov Gauss mixture models (HMGMM) have been shown to perform well in image segmentation applications, but they are quite sensitive to image noise. We propose a modified HMGMM procedure specifically designed to improve performance in the presence of noise. The key feature of the proposed procedure is the adjustment of covariance matrices in Gauss mixture vector quantizer codebooks to minimize an overall minimum discrimination information distortion (MDI). In adjusting covariance matrices, we expand or shrink their elements based on the noisy image. While most results reported in the literature assume a particular noise type, we propose a framework without assuming particular noise characteristics. Without denoising the corrupted source, we apply our method directly to the segmentation of noisy sources. We apply the proposed procedure to the segmentation of aerial images with Salt and Pepper noise and with independent Gaussian noise, and we compare our results with those of the median filter restoration method and the blind deconvolution-based method, respectively. We show that our procedure has better performance than image restoration-based techniques and closely matches to the performance of HMGMM for clean images in terms of both visual segmentation results and error rate.
Thermodynamics of Taub-NUT/bolt-AdS black holes in Einstein-Gauss-Bonnet gravity
Khodam-Mohammadi, A.; Monshizadeh, M.
2009-02-15
We give a review of the existence of Taub-NUT/bolt solutions in Einstein Gauss-Bonnet gravity with the parameter {alpha} in six dimensions. Although the spacetime with base space S{sup 2}xS{sup 2} has a curvature singularity at r=N, which does not admit NUT solutions, we may proceed with the same computations as in the CP{sup 2} case. The investigation of thermodynamics of NUT/bolt solutions in six dimensions is carried out. We compute the finite action, mass, entropy, and temperature of the black hole. Then the validity of the first law of thermodynamics is demonstrated. It is shown that in NUT solutions all thermodynamic quantities for both base spaces are related to each other by substituting {alpha}{sup CP{sup k}}=[(k+1)/k]{alpha}{sup S{sup 2}}{sup xS{sup 2}}{sup x...S{sub k}{sup 2}}. So, no further information is given by investigating NUT solutions in the S{sup 2}xS{sup 2} case. This relation is not true for bolt solutions. A generalization of the thermodynamics of black holes to arbitrary even dimensions is made using a new method based on the Gibbs-Duhem relation and Gibbs free energy for NUT solutions. According to this method, the finite action in Einstein Gauss-Bonnet is obtained by considering the generalized finite action in Einstein gravity with an additional term as a function of {alpha}. Stability analysis is done by investigating the heat capacity and entropy in the allowed range of {alpha}, {lambda}, and N. For NUT solutions in d dimensions, there exists a stable phase at a narrow range of {alpha}. In six-dimensional bolt solutions, the metric is completely stable for B=S{sup 2}xS{sup 2} and is completely unstable for the B=CP{sup 2} case.
Li, Yang; Zhang, Qingbin; Hong, Weiyi; Wang, Shaoyi; Wang, Zhe; Lu, Peixiang
2012-07-02
Single attosecond pulse generation with polarization gating Bessel-Gauss beam in relatively strongly-ionized media is investigated. The results show that Bessel-Gauss beam has the ability to suppress the spatial plasma dispersion effects caused by high density of free electrons, thus the laser field can maintain its spatial profile through highly-ionized medium. This indicates the use of Bessel-Gauss beam has advantages over Gaussian beam in high harmonic generation under high ionization conditions. In our scheme, significant improvement of spatiotemporal properties of harmonics is achieved and an isolated attosecond pulse with high beam quality is filtered out using polarization gating.
NASA Astrophysics Data System (ADS)
Nadgaran, H.; Fallah, R.
2015-08-01
Reshaping is the gradual adaptation of the pump profile toward the laser output profile. This work investigates the effects of pump reshaping on the generation of Bessel-Gauss (BG), Mathieu-Gauss (MG) and cosine-Gauss (CG) beams. The study uses our previous thermal model and compares the outcome of the model for three different cases, with and without pump reshaping. The results show that in a high power regime, inclusion of reshaping effects in any thermal model is necessary for comprehensive analysis of the thermal problem, whereas this effect can be safely neglected in models describing low power lasers.
NASA Astrophysics Data System (ADS)
Michel, N.; Stoitsov, M. V.
2008-04-01
The fast computation of the Gauss hypergeometric function F12 with all its parameters complex is a difficult task. Although the F12 function verifies numerous analytical properties involving power series expansions whose implementation is apparently immediate, their use is thwarted by instabilities induced by cancellations between very large terms. Furthermore, small areas of the complex plane, in the vicinity of z=e, are inaccessible using F12 power series linear transformations. In order to solve these problems, a generalization of R.C. Forrey's transformation theory has been developed. The latter has been successful in treating the F12 function with real parameters. As in real case transformation theory, the large canceling terms occurring in F12 analytical formulas are rigorously dealt with, but by way of a new method, directly applicable to the complex plane. Taylor series expansions are employed to enter complex areas outside the domain of validity of power series analytical formulas. The proposed algorithm, however, becomes unstable in general when |a|, |b|, |c| are moderate or large. As a physical application, the calculation of the wave functions of the analytical Pöschl-Teller-Ginocchio potential involving F12 evaluations is considered. Program summaryProgram title: hyp_2F1, PTG_wf Catalogue identifier: AEAE_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEAE_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 6839 No. of bytes in distributed program, including test data, etc.: 63 334 Distribution format: tar.gz Programming language: C++, Fortran 90 Computer: Intel i686 Operating system: Linux, Windows Word size: 64 bits Classification: 4.7 Nature of problem: The Gauss hypergeometric function F12, with all its parameters complex, is uniquely
NASA Astrophysics Data System (ADS)
Alkharji, Mohammed N.
Most fracture characterization methods provide a general description of the fracture parameters as part of the reservoirs parameters; the fracture interaction and geometry within the reservoir is given less attention. T-Matrix and Linear Slip effective medium fracture models are implemented to invert the elastic tensor for the parameters and geometries of the fractures within the reservoir. The fracture inverse problem has an ill-posed, overdetermined, underconstrained rank-deficit system of equations. Least-squares inverse methods are used to solve the problem. A good starting initial model for the parameters is a key factor in the reliability of the inversion. Most methods assume that the starting parameters are close to the solution to avoid inaccurate local minimum solutions. The prior knowledge of the fracture parameters and their geometry is not available. We develop a hybrid, enumerative and Gauss-Newton, method that estimates the fracture parameters and geometry from the elastic tensor with no prior knowledge of the initial parameter values. The fracture parameters are separated into two groups. The first group contains the fracture parameters with no prior information, and the second group contains the parameters with known prior information. Different models are generated from the first group parameters by sampling the solution space over a predefined range of possible solutions for each parameter. Each model generated by the first group is fixed and used as a starting model to invert for the second group of parameters using the Gauss-Newton method. The least-squares residual between the observed elastic tensor and the estimated elastic tensor is calculated for each model. The model parameters that yield the least-squares residual corresponds to the correct fracture reservoir parameters and geometry. Two synthetic examples of fractured reservoirs with oil and gas saturations were inverted with no prior information about the fracture properties. The
NASA Astrophysics Data System (ADS)
Bhrawy, A. H.; Baleanu, D.
2013-10-01
An efficient Legendre-Gauss-Lobatto collocation (L-GL-C) method is applied to solve the space-fractional advection diffusion equation with nonhomogeneous initial-boundary conditions. The Legendre-Gauss-Lobatto points are used as collocation nodes for spatial fractional derivatives as well as the Caputo fractional derivative. This approach is reducing the problem to the solution of a system of ordinary differential equations in time which can be solved by using any standard numerical techniques. The proposed numerical solutions when compared with the exact solutions reveal that the obtained solution produces highly accurate results. The results show that the proposed method has high accuracy and is efficient for solving the space-fractional advection diffusion equation.
Hudson, H M; Ma, J; Green, P
1994-01-01
Many algorithms for medical image reconstruction adopt versions of the expectation-maximization (EM) algorithm. In this approach, parameter estimates are obtained which maximize a complete data likelihood or penalized likelihood, in each iteration. Implicitly (and sometimes explicitly) penalized algorithms require smoothing of the current reconstruction in the image domain as part of their iteration scheme. In this paper, we discuss alternatives to EM which adapt Fisher's method of scoring (FS) and other methods for direct maximization of the incomplete data likelihood. Jacobi and Gauss-Seidel methods for non-linear optimization provide efficient algorithms applying FS in tomography. One approach uses smoothed projection data in its iterations. We investigate the convergence of Jacobi and Gauss-Seidel algorithms with clinical tomographic projection data.
(q,μ) and (p,q,ζ)-exponential functions: Rogers-Szego˝ polynomials and Fourier-Gauss transform
NASA Astrophysics Data System (ADS)
Hounkonnou, Mahouton Norbert; Nkouankam, Elvis Benzo Ngompe
2010-10-01
From the realization of q-oscillator algebra in terms of generalized derivative, we compute the matrix elements from deformed exponential functions and deduce generating functions associated with Rogers-Szegő polynomials as well as their relevant properties. We also compute the matrix elements associated with the (p,q)-oscillator algebra (a generalization of the q-one) and perform the Fourier-Gauss transform of a generalization of the deformed exponential functions.
NASA Astrophysics Data System (ADS)
Meng, K.; Li, J.
2016-10-01
We construct a new static black hole solution of Gauss-Bonnet massive gravity coupled to Maxwell and Yang-Mills fields in five dimensions. We calculate the thermodynamical quantities of the black hole and check the first law of black hole thermodynamics. Thermal stability of the black hole is explored in the context of both canonical and grand canonical ensembles. By identifying the cosmological constant as the pressure of the gravitational system, we study the phase transitions of the black hole.
Gauss-Newton inspired preconditioned optimization in large deformation diffeomorphic metric mapping
NASA Astrophysics Data System (ADS)
Hernandez, Monica
2014-10-01
In this work, we propose a novel preconditioned optimization method in the paradigm of Large Deformation Diffeomorphic Metric Mapping (LDDMM). The preconditioned update scheme is formulated for the non-stationary and the stationary parameterizations of diffeomorphisms, yielding three different LDDMM methods. The preconditioning matrices are inspired in the Hessian approximation used in Gauss-Newton method. The derivatives are computed using Frechet differentials. Thus, optimization is performed in a Sobolev space, in contrast to optimization in L2 commonly used in non-rigid registration literature. The proposed LDDMM methods have been evaluated and compared with their respective implementations of gradient descent optimization. Evaluation has been performed using real and simulated images from the Non-rigid Image Registration Evaluation Project (NIREP). The experiments conducted in this work reported that our preconditioned LDDMM methods achieved a performance similar or superior to well-established-in-literature gradient descent non-stationary LDDMM in the great majority of cases. Moreover, preconditioned optimization showed a substantial reduction in the execution time with an affordable increase of the memory usage per iteration. Additional experiments reported that optimization using Frechet differentials should be preferable to optimization using L2 differentials.
Subluminal group velocity and dispersion of Laguerre Gauss beams in free space
Bareza, Nestor D.; Hermosa, Nathaniel
2016-01-01
That the speed of light in free space c is constant has been a pillar of modern physics since the derivation of Maxwell and in Einstein’s postulate in special relativity. This has been a basic assumption in light’s various applications. However, a physical beam of light has a finite extent such that even in free space it is by nature dispersive. The field confinement changes its wavevector, hence, altering the light’s group velocity vg. Here, we report the subluminal vg and consequently the dispersion in free space of Laguerre-Gauss (LG) beam, a beam known to carry orbital angular momentum. The vg of LG beam, calculated in the paraxial regime, is observed to be inversely proportional to the beam’s divergence θ0, the orbital order ℓ and the radial order p. LG beams of higher orders travel relatively slower than that of lower orders. As a consequence, LG beams of different orders separate in the temporal domain along propagation. This is an added effect to the dispersion due to field confinement. Our results are useful for treating information embedded in LG beams from astronomical sources and/or data transmission in free space. PMID:27231195
Tong, Mei Song; Yang, Kuo; Sheng, Wei Tian; Zhu, Zhen Ying
2013-12-01
Reconstruction of unknown objects by microwave illumination requires efficient inversion for measured electromagnetic scattering data. In the integral equation approach for reconstructing dielectric objects based on the Born iterative method or its variations, the volume integral equations are involved because the imaging domain is fully inhomogeneous. When solving the forward scattering integral equation, the Nyström method is used because the traditional method of moments may be inconvenient due to the inhomogeneity of the imaging domain. The benefits of the Nyström method include the simple implementation without using any basis and testing functions and low requirement on geometrical discretization. When solving the inverse scattering integral equation, the Gauss-Newton minimization approach with a line search method (LSM) and multiplicative regularization method (MRM) is employed. The LSM can optimize the search of step size in each iteration, whereas the MRM may reduce the number of numerical experiments for choosing the regularization parameter. Numerical examples for reconstructing typical dielectric objects under limited observation angles are presented to illustrate the inversion approach.
NASA Astrophysics Data System (ADS)
Notaris, Sotirios
1995-03-01
Given a fixed n≥1, and a (monic) orthogonal polynomial πn(·)Dπn(·;dσ) relative to a positive measuredσ on the interval [a, b], one can define the nonnegative measure , to which correspond the (monic) orthogonal polynomials . The coefficients in the three-term recurrence relation for , whendσ is a Chebyshev measure of any of the four kinds, were obtained analytically in closed form by Gautschi and Li. Here, we give explicit formulae for the Stieltjes polynomials whendσ is any of the four Chebyshev measures. In addition, we show that the corresponding Gauss-Kronrod quadrature formulae for each of these , based on the zeros of and , have all the desirable properties of the interlacing of nodes, their inclusion in [-1, 1], and the positivity of all quadrature weights. Exceptions occur only for the Chebyshev measuredσ of the third or fourth kind andn even, in which case the inclusion property fails. The precise degree of exactness for each of these formulae is also determined.
Subluminal group velocity and dispersion of Laguerre Gauss beams in free space
NASA Astrophysics Data System (ADS)
Bareza, Nestor D.; Hermosa, Nathaniel
2016-05-01
That the speed of light in free space c is constant has been a pillar of modern physics since the derivation of Maxwell and in Einstein’s postulate in special relativity. This has been a basic assumption in light’s various applications. However, a physical beam of light has a finite extent such that even in free space it is by nature dispersive. The field confinement changes its wavevector, hence, altering the light’s group velocity vg. Here, we report the subluminal vg and consequently the dispersion in free space of Laguerre-Gauss (LG) beam, a beam known to carry orbital angular momentum. The vg of LG beam, calculated in the paraxial regime, is observed to be inversely proportional to the beam’s divergence θ0, the orbital order ℓ and the radial order p. LG beams of higher orders travel relatively slower than that of lower orders. As a consequence, LG beams of different orders separate in the temporal domain along propagation. This is an added effect to the dispersion due to field confinement. Our results are useful for treating information embedded in LG beams from astronomical sources and/or data transmission in free space.
Pulsed Bessel-Gauss beams: a depleted wave model for type II second-harmonic generation.
Sabaeian, Mohammad; Motazedian, Alireza; Mohammad Rezaee, Mostafa; Jalil-Abadi, Fatemeh Sedaghat
2014-11-10
In this work, a three-dimensional and time-dependent nonlinear wave model to describe the generation of pulsed Bessel-Gauss second-harmonic waves (SHWs) is presented. Three coupled equations, two for ordinary and extraordinary fundamental waves and one for extraordinary SHWs, describing type II second-harmonic generation (SHG) in a KTiOPO_{4} (KTP) crystal were solved by considering the depletion of fundamental waves (FWs). The results examined the validity of nondepleted wave approximation against the energy of pulses, beam spot size, and interaction length. It was shown that for pulses with spot sizes of ω_{f}=80 μm and energy of 0.8j, the nonlinear interaction was accomplished over a distance of ∼5 mm. Therefore, for KTP crystals with lengths longer than 5 mm, the nondepleted wave approximation can no longer be valid. To be valid, the crystal must be shorter than the interaction length, i.e., 5 mm.
Accurate computation of weights in classical Gauss-Christoffel quadrature rules
Yakimiw, E.
1996-12-01
For many classical Gauss-Christoffel quadrature rules there does not exist a method which guarantees a uniform level of accuracy for the Gaussian quadrature weights at all quadrature nodes unless the nodes are known exactly. More disturbing, some algebraic expressions for these weights exhibit an excessive sensitivity to even the smallest perturbations in the node location. This sensitivity rapidly increases with high order quadrature rules. Current uses of very high order quadratures are common with the advent of more powerful computers, and a loss of accuracy in the weights has become a problem and must be addressed. A simple but efficient and general method for improving the accuracy of the computation of the quadrature weights even though the nodes may carry a significant large error. In addition, a highly efficient root-finding iterative technique with superlinear converging rates for computing the nodes is developed. It uses solely the quadrature polynomials and their first derivatives. A comparison of this method with the eigenvalue method of Golub and Welsh implemented in most standard software libraries is made. The proposed method outperforms the latter from the point of view of both accuracy and efficiency. The Legendre, Lobatto, Radau, Hermite, and Laguerre quadrature rules are examined. 22 refs., 7 figs., 5 tabs.
Gauss-Newton inspired preconditioned optimization in large deformation diffeomorphic metric mapping.
Hernandez, Monica
2014-10-21
In this work, we propose a novel preconditioned optimization method in the paradigm of Large Deformation Diffeomorphic Metric Mapping (LDDMM). The preconditioned update scheme is formulated for the non-stationary and the stationary parameterizations of diffeomorphisms, yielding three different LDDMM methods. The preconditioning matrices are inspired in the Hessian approximation used in Gauss-Newton method. The derivatives are computed using Frechet differentials. Thus, optimization is performed in a Sobolev space, in contrast to optimization in L(2) commonly used in non-rigid registration literature. The proposed LDDMM methods have been evaluated and compared with their respective implementations of gradient descent optimization. Evaluation has been performed using real and simulated images from the Non-rigid Image Registration Evaluation Project (NIREP). The experiments conducted in this work reported that our preconditioned LDDMM methods achieved a performance similar or superior to well-established-in-literature gradient descent non-stationary LDDMM in the great majority of cases. Moreover, preconditioned optimization showed a substantial reduction in the execution time with an affordable increase of the memory usage per iteration. Additional experiments reported that optimization using Frechet differentials should be preferable to optimization using L(2) differentials.
Subluminal group velocity and dispersion of Laguerre Gauss beams in free space.
Bareza, Nestor D; Hermosa, Nathaniel
2016-05-27
That the speed of light in free space c is constant has been a pillar of modern physics since the derivation of Maxwell and in Einstein's postulate in special relativity. This has been a basic assumption in light's various applications. However, a physical beam of light has a finite extent such that even in free space it is by nature dispersive. The field confinement changes its wavevector, hence, altering the light's group velocity vg. Here, we report the subluminal vg and consequently the dispersion in free space of Laguerre-Gauss (LG) beam, a beam known to carry orbital angular momentum. The vg of LG beam, calculated in the paraxial regime, is observed to be inversely proportional to the beam's divergence θ0, the orbital order ℓ and the radial order p. LG beams of higher orders travel relatively slower than that of lower orders. As a consequence, LG beams of different orders separate in the temporal domain along propagation. This is an added effect to the dispersion due to field confinement. Our results are useful for treating information embedded in LG beams from astronomical sources and/or data transmission in free space.
A Gauss-Seidel Iteration Scheme for Reference-Free 3-D Histological Image Reconstruction
Daum, Volker; Steidl, Stefan; Maier, Andreas; Köstler, Harald; Hornegger, Joachim
2015-01-01
Three-dimensional (3-D) reconstruction of histological slice sequences offers great benefits in the investigation of different morphologies. It features very high-resolution which is still unmatched by in-vivo 3-D imaging modalities, and tissue staining further enhances visibility and contrast. One important step during reconstruction is the reversal of slice deformations introduced during histological slice preparation, a process also called image unwarping. Most methods use an external reference, or rely on conservative stopping criteria during the unwarping optimization to prevent straightening of naturally curved morphology. Our approach shows that the problem of unwarping is based on the superposition of low-frequency anatomy and high-frequency errors. We present an iterative scheme that transfers the ideas of the Gauss-Seidel method to image stacks to separate the anatomy from the deformation. In particular, the scheme is universally applicable without restriction to a specific unwarping method, and uses no external reference. The deformation artifacts are effectively reduced in the resulting histology volumes, while the natural curvature of the anatomy is preserved. The validity of our method is shown on synthetic data, simulated histology data using a CT data set and real histology data. In the case of the simulated histology where the ground truth was known, the mean Target Registration Error (TRE) between the unwarped and original volume could be reduced to less than 1 pixel on average after 6 iterations of our proposed method. PMID:25312918
A Gauss-Seidel iteration scheme for reference-free 3-D histological image reconstruction.
Gaffling, Simone; Daum, Volker; Steidl, Stefan; Maier, Andreas; Kostler, Harald; Hornegger, Joachim
2015-02-01
Three-dimensional (3-D) reconstruction of histological slice sequences offers great benefits in the investigation of different morphologies. It features very high-resolution which is still unmatched by in vivo 3-D imaging modalities, and tissue staining further enhances visibility and contrast. One important step during reconstruction is the reversal of slice deformations introduced during histological slice preparation, a process also called image unwarping. Most methods use an external reference, or rely on conservative stopping criteria during the unwarping optimization to prevent straightening of naturally curved morphology. Our approach shows that the problem of unwarping is based on the superposition of low-frequency anatomy and high-frequency errors. We present an iterative scheme that transfers the ideas of the Gauss-Seidel method to image stacks to separate the anatomy from the deformation. In particular, the scheme is universally applicable without restriction to a specific unwarping method, and uses no external reference. The deformation artifacts are effectively reduced in the resulting histology volumes, while the natural curvature of the anatomy is preserved. The validity of our method is shown on synthetic data, simulated histology data using a CT data set and real histology data. In the case of the simulated histology where the ground truth was known, the mean Target Registration Error (TRE) between the unwarped and original volume could be reduced to less than 1 pixel on average after six iterations of our proposed method.
Bright, Joanne N; Evans, Denis J; Searles, Debra J
2005-05-15
Deterministic thermostats are frequently employed in nonequilibrium molecular dynamics simulations in order to remove the heat produced irreversibly over the course of such simulations. The simplest thermostat is the Gaussian thermostat, which satisfies Gauss's principle of least constraint and fixes the peculiar kinetic energy. There are of course infinitely many ways to thermostat systems, e.g., by fixing sigma(i)/p(i)/mu+l. In the present paper we provide, for the first time, convincing arguments as to why the conventional Gaussian isokinetic thermostat (mu = 1) is unique in this class. We show that this thermostat minimizes the phase space compression and is the only thermostat for which the conjugate pairing rule holds. Moreover, it is shown that for finite sized systems in the absence of an applied dissipative field, all other thermostats (mu not = 1) perform work on the system in the same manner as a dissipative field while simultaneously removing the dissipative heat so generated. All other thermostats (mu not = 1) are thus autodissipative. Among all mu, thermostats, only the mu = 1 Gaussian thermostat permits an equilibrium state.
Late cosmic acceleration in a vector-Gauss-Bonnet gravity model
NASA Astrophysics Data System (ADS)
Oliveros, A.; Solis, Enzo L.; Acero, Mario A.
2016-12-01
In this work, we study a general vector-tensor model of dark energy (DE) with a Gauss-Bonnet term coupled to a vector field and without explicit potential terms. Considering a spatially flat Friedmann-Robertson-Walker (FRW) type universe and a vector field without spatial components, the cosmological evolution is analyzed from the field equations of this model considering two sets of parameters. In this context, we have shown that it is possible to obtain an accelerated expansion phase of the universe since the equation state parameter w satisfies the restriction - 1 < w < -1/3 (for suitable values of model parameters). Further, analytical expressions for the Hubble parameter H, equation state parameter w and the invariant scalar ϕ are obtained. We also find that the square of the speed of sound is negative for all values of redshift, therefore, the model presented here shows a sign of instability under small perturbations. We finally perform an analysis using H(z) observational data and we find that for the free parameter ξ in the interval (-23.9,-3.46) × 10-5, at 99.73% C.L. (and fixing η = -1 and ω = 1/4), the model has a good fit to the data.
AdS and Lifshitz scalar hairy black holes in Gauss-Bonnet gravity
NASA Astrophysics Data System (ADS)
Chen, Bin; Fan, Zhong-Ying; Zhu, Lu-Yao
2016-09-01
We consider Gauss-Bonnet (GB) gravity in general dimensions, which is nonminimally coupled to a scalar field. By choosing a scalar potential of the type V (ϕ )=2 Λ0+1/2 m2ϕ2+γ4ϕ4 , we first obtain large classes of scalar hairy black holes with spherical/hyperbolic/planar topologies that are asymptotic to locally anti- de Sitter (AdS) space-times. We derive the first law of black hole thermodynamics using Wald formalism. In particular, for one class of the solutions, the scalar hair forms a thermodynamic conjugate with the graviton and nontrivially contributes to the thermodynamical first law. We observe that except for one class of the planar black holes, all these solutions are constructed at the critical point of GB gravity where there exist unique AdS vacua. In fact, a Lifshitz vacuum is also allowed at the critical point. We then construct many new classes of neutral and charged Lifshitz black hole solutions for an either minimally or nonminimally coupled scalar and derive the thermodynamical first laws. We also obtain new classes of exact dynamical AdS and Lifshitz solutions which describe radiating white holes. The solutions eventually become AdS or Lifshitz vacua at late retarded times. However, for one class of the solutions, the final state is an AdS space-time with a globally naked singularity.
A convergence rates result for an iteratively regularized Gauss-Newton-Halley method in Banach space
NASA Astrophysics Data System (ADS)
Kaltenbacher, B.
2015-01-01
The use of second order information on the forward operator often comes at a very moderate additional computational price in the context of parameter identification problems for differential equation models. On the other hand the use of general (non-Hilbert) Banach spaces has recently found much interest due to its usefulness in many applications. This motivates us to extend the second order method from Kaltenbacher (2014 Numer. Math. at press), (see also Hettlich and Rundell 2000 SIAM J. Numer. Anal. 37 587620) to a Banach space setting and analyze its convergence. We here show rates results for a particular source condition and different exponents in the formulation of Tikhonov regularization in each step. This includes a complementary result on the (first order) iteratively regularized Gauss-Newton method in case of a one-homogeneous data misfit term, which corresponds to exact penalization. The results clearly show the possible advantages of using second order information, which get most pronounced in this exact penalization case. Numerical simulations for an inverse source problem for a nonlinear elliptic PDE illustrate the theoretical findings.
Rotating black holes in Einstein-dilaton-Gauss-Bonnet gravity with finite coupling
NASA Astrophysics Data System (ADS)
Maselli, Andrea; Pani, Paolo; Gualtieri, Leonardo; Ferrari, Valeria
2015-10-01
Among various strong-curvature extensions of general relativity, Einstein-dilaton-Gauss-Bonnet gravity stands out as the only nontrivial theory containing quadratic curvature corrections while being free from the Ostrogradsky instability to any order in the coupling parameter. We derive an approximate stationary and axisymmetric black hole solution of this gravitational theory in closed form, which is of fifth order in the black hole spin and of seventh order in the coupling parameter of the theory. This extends previous work that obtained the corrections to the metric only to second order in the spin and at the leading order in the coupling parameter, and allows us to consider values of the coupling parameter close to the maximum permitted by theoretical constraints. We compute some quantities which characterize this solution, such as the dilaton charge, the moment of inertia, and the quadrupole moment, and its geodesic structure, including the innermost stable circular orbit and the epicyclic frequencies for massive particles. The latter provides a valuable tool to test general relativity against strong-curvature corrections through observations of the electromagnetic spectrum of accreting black holes.
Improving the Gauss-Newton convergence of a certain position registration scheme
NASA Astrophysics Data System (ADS)
Toews, C.; Nelson, B.
2010-04-01
This paper explores practical and numerical facets of a position registration scheme first proposed in connection with cardiac surgery. The goal of the registration is to use voltage measurements to determine the shape of a bounded homogenous region embedded within an unknown and inhomogenous medium. We assume that a probe with one or more electrodes can access and be moved about within the region. At each of n discrete positions, each electrode records three voltages, one from each of three orthogonal fields that have been set up across the surrounding media. If the fields were linear, the position of the electrodes at each measurement could be read directly from the voltage data and the shape of the region inferred accordingly, but since the inhomogeneities in the surrounding media distort the fields, the problem becomes one of simultaneously calculating the electrode positions and the field distortions. In this paper we build on previous work by modeling the field distortions as having a low-order expansion in some known functional basis, and attempt to solve for both the expansion coefficients and the probe positions via a Gauss-Newton iteration. Our interest is focused on how well the reconstruction can be expected to succeed under variations in both the choice of orientation parameters and the shape of the probe. Our results, which are supported with numerical experiments on simulated data, suggest that proper attention to these factors can strongly influence the accuracy of the reconstruction.
Stability of Gauss-Bonnet black holes in anti-de Sitter space-time against scalar field condensation
Brihaye, Yves; Hartmann, Betti
2011-10-15
We study the stability of static, hyperbolic Gauss-Bonnet black holes in (4+1)-dimensional anti-de Sitter (AdS) space-time against the formation of scalar hair. Close to extremality the black holes possess a near-horizon topology of AdS{sub 2}xH{sup 3} such that within a certain range of the scalar field mass one would expect that they become unstable to the condensation of an uncharged scalar field. We confirm this numerically and observe that there exists a family of hairy black hole solutions labeled by the number of nodes of the scalar field function. We construct explicit examples of solutions with a scalar field that possesses zero nodes, one node, and two nodes, respectively, and show that the solutions with nodes persist in the limit of Einstein gravity, i.e. for vanishing Gauss-Bonnet coupling. We observe that the interval of the mass for which scalar field condensation appears decreases with increasing Gauss-Bonnet coupling and/or with increasing node number.
NASA Astrophysics Data System (ADS)
Anninos, Dionysios; Pastras, Georgios
2009-07-01
The local and global thermal phase structure for asymptotically anti-de Sitter black holes charged under an abelian gauge group, with both Gauss-Bonnet and quartic field strength corrections, is mapped out for all parameter space. We work in the grand canonical ensemble where the external electric potential is held fixed. The analysis is performed in an arbitrary number of dimensions, for all three possible horizon topologies — spherical, flat or hyperbolic. For spherical horizons, new metastable configurations are exhibited both for the pure Gauss-Bonnet theory as well as the pure higher derivative gauge theory and combinations thereof. In the pure Gauss-Bonnet theory with negative coefficient and five or more spatial dimensions, two locally thermally stable black hole solutions are found for a given temperature. Either one or both of them may be thermally favored over the anti-de Sitter vacuum — corresponding to a single or a double decay channel for the metastable black hole. Similar metastable configurations are uncovered for the theory with pure quartic field strength corrections, as well combinations of the two types of corrections, in three or more spatial dimensions. Finally, a secondary Hawking-Page transition between the smaller thermally favored black hole and thermal anti-de Sitter space is observed when both corrections are turned on and their couplings are both positive.
Crowther, Michael J; Look, Maxime P; Riley, Richard D
2014-09-28
Multilevel mixed effects survival models are used in the analysis of clustered survival data, such as repeated events, multicenter clinical trials, and individual participant data (IPD) meta-analyses, to investigate heterogeneity in baseline risk and covariate effects. In this paper, we extend parametric frailty models including the exponential, Weibull and Gompertz proportional hazards (PH) models and the log logistic, log normal, and generalized gamma accelerated failure time models to allow any number of normally distributed random effects. Furthermore, we extend the flexible parametric survival model of Royston and Parmar, modeled on the log-cumulative hazard scale using restricted cubic splines, to include random effects while also allowing for non-PH (time-dependent effects). Maximum likelihood is used to estimate the models utilizing adaptive or nonadaptive Gauss-Hermite quadrature. The methods are evaluated through simulation studies representing clinically plausible scenarios of a multicenter trial and IPD meta-analysis, showing good performance of the estimation method. The flexible parametric mixed effects model is illustrated using a dataset of patients with kidney disease and repeated times to infection and an IPD meta-analysis of prognostic factor studies in patients with breast cancer. User-friendly Stata software is provided to implement the methods.
The generation of arbitrary order, non-classical, Gauss-type quadrature for transport applications
Spence, Peter J.
2015-09-01
A method is presented, based upon the Stieltjes method (1884), for the determination of non-classical Gauss-type quadrature rules, and the associated sets of abscissae and weights. The method is then used to generate a number of quadrature sets, to arbitrary order, which are primarily aimed at deterministic transport calculations. The quadrature rules and sets detailed include arbitrary order reproductions of those presented by Abu-Shumays in [4,8] (known as the QR sets, but labelled QRA here), in addition to a number of new rules and associated sets; these are generated in a similar way, and we label them the QRS quadrature sets. The method presented here shifts the inherent difficulty (encountered by Abu-Shumays) associated with solving the non-linear moment equations, particular to the required quadrature rule, to one of the determination of non-classical weight functions and the subsequent calculation of various associated inner products. Once a quadrature rule has been written in a standard form, with an associated weight function having been identified, the calculation of the required inner products is achieved using specific variable transformations, in addition to the use of rapid, highly accurate quadrature suited to this purpose. The associated non-classical Gauss quadrature sets can then be determined, and this can be done to any order very rapidly. In this paper, instead of listing weights and abscissae for the different quadrature sets detailed (of which there are a number), the MATLAB code written to generate them is included as Appendix D. The accuracy and efficacy (in a transport setting) of the quadrature sets presented is not tested in this paper (although the accuracy of the QRA quadrature sets has been studied in [12,13]), but comparisons to tabulated results listed in [8] are made. When comparisons are made with one of the azimuthal QRA sets detailed in [8], the inherent difficulty in the method of generation, used there, becomes apparent
Gauss-Bonnet assisted braneworld inflation in light of BICEP2 and Planck data
NASA Astrophysics Data System (ADS)
Neupane, Ishwaree P.
2014-12-01
Motivated by the idea that quantum gravity corrections usually suppress the power of the scalar primordial spectrum (E-mode) more than the power of the tensor primordial spectrum (B-mode), in this paper we construct a concrete gravitational theory in five-dimensions for which V (ϕ )∝ϕn -type inflation (n ≥1 ) generates an appropriate tensor-to-scalar ratio that may be compatible with the BICEP2 and Planck data together. The true nature of gravity is five-dimensional and described by the action S =∫d5x √{|g | }M3(-6 λ M2+R +α M-2R2) where M is the five-dimensional Planck mass and R2=R2-4 Ra bRa b+Ra b c dRa b c d is the Gauss-Bonnet (GB) term. The five-dimensional "bulk" spacetime is anti-de Sitter (λ <0 ) for which inflation ends naturally. The effects of R2 term on the magnitudes of scalar and tensor fluctuations and spectral indices are shown to be important at the energy scale of inflation. For GB-assisted m2ϕ2-inflation, inflationary constraints from BICEP2 and Planck, such as, ns≃0.9603 (±0.0073 ), r =0.16 (+0.06 -0.05 ) and V*1 /4≳1.5 ×1 016 GeV are all satisfied for (-λ α )≃(3 -300 )×1 0-5.
NASA Astrophysics Data System (ADS)
Ivashchuk, V. D.; Ernazarov, K. K.
2017-01-01
A (n + 1)-dimensional gravitational model with cosmological constant and Gauss-Bonnet term is studied. The ansatz with diagonal cosmological metrics is adopted and solutions with exponential dependence of scale factors: ai ∼ exp (vit), i = 1, …, n, are considered. The stability analysis of the solutions with non-static volume factor is presented. We show that the solutions with v 1 = v 2 = v 3 = H > 0 and small enough variation of the effective gravitational constant G are stable if certain restriction on (vi ) is obeyed. New examples of stable exponential solutions with zero variation of G in dimensions D = 1 + m + 2 with m > 2 are presented.
NASA Astrophysics Data System (ADS)
Kajani, M. Tavassoli; Gholampoor, I.
2015-10-01
The purpose of this study is to present a new direct method for the approximate solution and approximate derivatives up to order k to the solution for kth-order Volterra integro-differential equations with a regular kernel. This method is based on the approximation by shifting the original problem into a sequence of subintervals. A Legendre-Gauss-Lobatto collocation method is proposed to solving the Volterra integro-differential equation. Numerical examples show that the approximate solutions have a good degree of accuracy.
Tze, Chia-Hsiung . Dept. of Physics)
1989-01-01
By way of the Gauss-Bonnet-Chern theorem, we present a higher dimensional extension of Polyakov's regularization of Wilson loops of point solitons. Spacetime paths of extended objects become hyper-ribbons with self-linking, twisting and writhing numbers. specifically we discuss the exotic spin and statistical phase entanglements of geometric n-membrane solitons of D-dimensional KP{sub 1} {sigma}-models with an added Hopf-Chern-Simons term where (n, D, K) = (0, 3, C), (2, 7, H), (6, 15, {Omega}). They are uniquely linked to the complex and quaternion and octonion division algebras. 22 refs.
Woods, M. P.; Plenio, M. B.
2016-02-15
Instances of discrete quantum systems coupled to a continuum of oscillators are ubiquitous in physics. Often the continua are approximated by a discrete set of modes. We derive error bounds on expectation values of system observables that have been time evolved under such discretised Hamiltonians. These bounds take on the form of a function of time and the number of discrete modes, where the discrete modes are chosen according to Gauss quadrature rules. The derivation makes use of tools from the field of Lieb-Robinson bounds and the theory of orthonormal polynomials.
NASA Astrophysics Data System (ADS)
Chu, Xiaoyu; Zhang, Jingrui; Lu, Shan; Zhang, Yao; Sun, Yue
2016-11-01
This paper presents a trajectory planning algorithm to optimise the collision avoidance of a chasing spacecraft operating in an ultra-close proximity to a failed satellite. The complex configuration and the tumbling motion of the failed satellite are considered. The two-spacecraft rendezvous dynamics are formulated based on the target body frame, and the collision avoidance constraints are detailed, particularly concerning the uncertainties. An optimisation solution of the approaching problem is generated using the Gauss pseudospectral method. A closed-loop control is used to track the optimised trajectory. Numerical results are provided to demonstrate the effectiveness of the proposed algorithms.
Alexandrescu, D; Fonea, M; Sava, N
1980-01-01
The authors made use of maps prepared in the projection system known as the "Universal Transverse Mercator" (Gauss-Kruger projection) for the study of an epidemiometric indicator in tuberculosis, namely the instantaneous prevalence of bacili carriers on December 31 1978 in the Ilfov District. The representation allows to evaluate the density of sources of infection, and as a consequence, of areas in which antiepidemic measured have to be intensified. The extension of the study to other districts could provide data for assessing the epidemiologic potential in various territories, as well as comparisons and the dynamics of the potential. The method could also be used in the study of other epidemiometric indicators.
Truncated Gauss-Newton Implementation for Multi-Parameter Full Waveform Inversion
NASA Astrophysics Data System (ADS)
Liu, Y.; Yang, J.; Dong, L.; Wang, Y.
2014-12-01
Full waveform inversion (FWI) is a numerical optimization method which aims at minimizing the difference between the synthetic and recorded seismic data to obtain high resolution subsurface images. A practical implementation for FWI is the adjoint-state method (AD), in which the data residuals at receiver locations are simultaneously back-propagated to form the gradient. Scattering-integral method (SI) is an alternative way which is based on the explicit building of the sensitivity kernel (Fréchet derivative matrix). Although it is more memory-consuming, SI is more efficient than AD when the number of the sources is larger than the number of the receivers. To improve the convergence of FWI, the information carried out by the inverse Hessian operator is crucial. Taking account accurately of the effect of this operator in FWI can correct illumination deficits, reserve the amplitude of the subsurface parameters, and remove artifacts generated by multiple reflections. In multi-parameter FWI, the off-diagonal blocks of the Hessian operator reflect the coupling between different parameter classes. Therefore, incorporating its inverse could help to mitigate the trade-off effects. In this study, we focus on the truncated Gauss-Newton implementation for multi-parameter FWI. The model update is computed through a matrix-free conjugate gradient solution of the Newton linear system. Both the gradient and the Hessian-vector product are calculated using the SI approach instead of the first- and second-order AD. However, the gradient expressed by kernel-vector product is calculated through the accumulation of the decomposed vector-scalar products. Thus, it's not necessary to store the huge sensitivity matrix beforehand. We call this method the matrix decomposition approach (MD). And the Hessian-vector product is replaced by two kernel-vector products which are then calculated by the above MD. By this way, we don't need to solve two additional wave propagation problems as in the
NASA Astrophysics Data System (ADS)
Mohd Fauzi, Norizyan Izzati; Sulaiman, Jumat
2013-04-01
The aim of this paper is to describe the application of Quarter-Sweep Gauss-Seidel (QSGS) iterative method using quadratic spline scheme for solving fourth order two-point linear boundary value problems. In the line to derive approximation equations, firstly the fourth order problems need to be reduced onto a system of second-order two-point boundary value problems. Then two linear systems have been constructed via discretization process by using the corresponding quarter-sweep quadratic spline approximation equations. The generated linear systems have been solved using the proposed QSGS iterative method to show the superiority over Full-Sweep Gauss-Seidel (FSGS) and Half-Sweep Gauss-Seidel (HSGS) methods. Computational results are provided to illustrate that the effectiveness of the proposed QSGS method is more superior in terms of computational time and number of iterations as compared to other tested methods.
NASA Astrophysics Data System (ADS)
Mišković, Olivera; Olea, Rodrigo
2011-01-01
Motivated by possible applications within the framework of anti-de Sitter gravity/conformal field theory correspondence, charged black holes with AdS asymptotics, which are solutions to Einstein-Gauss-Bonnet gravity in D dimensions, and whose electric field is described by nonlinear electrodynamics are studied. For a topological static black hole ansatz, the field equations are exactly solved in terms of the electromagnetic stress tensor for an arbitrary nonlinear electrodynamic Lagrangian in any dimension D and for arbitrary positive values of Gauss-Bonnet coupling. In particular, this procedure reproduces the black hole metric in Born-Infeld and conformally invariant electrodynamics previously found in the literature. Altogether, it extends to D>4 the four-dimensional solution obtained by Soleng in logarithmic electrodynamics, which comes from vacuum polarization effects. Falloff conditions for the electromagnetic field that ensure the finiteness of the electric charge are also discussed. The black hole mass and vacuum energy as conserved quantities associated to an asymptotic timelike Killing vector are computed using a background-independent regularization of the gravitational action based on the addition of counterterms which are a given polynomial in the intrinsic and extrinsic curvatures.
NASA Astrophysics Data System (ADS)
Doha, E. H.; Bhrawy, A. H.; Abdelkawy, M. A.; Van Gorder, Robert A.
2014-03-01
A Jacobi-Gauss-Lobatto collocation (J-GL-C) method, used in combination with the implicit Runge-Kutta method of fourth order, is proposed as a numerical algorithm for the approximation of solutions to nonlinear Schrödinger equations (NLSE) with initial-boundary data in 1+1 dimensions. Our procedure is implemented in two successive steps. In the first one, the J-GL-C is employed for approximating the functional dependence on the spatial variable, using (N-1) nodes of the Jacobi-Gauss-Lobatto interpolation which depends upon two general Jacobi parameters. The resulting equations together with the two-point boundary conditions induce a system of 2(N-1) first-order ordinary differential equations (ODEs) in time. In the second step, the implicit Runge-Kutta method of fourth order is applied to solve this temporal system. The proposed J-GL-C method, used in combination with the implicit Runge-Kutta method of fourth order, is employed to obtain highly accurate numerical approximations to four types of NLSE, including the attractive and repulsive NLSE and a Gross-Pitaevskii equation with space-periodic potential. The numerical results obtained by this algorithm have been compared with various exact solutions in order to demonstrate the accuracy and efficiency of the proposed method. Indeed, for relatively few nodes used, the absolute error in our numerical solutions is sufficiently small.
Küpper, H; Spiller, M; Küpper, F C
2000-11-15
Accurate quantification of pigments in mixtures is essential in all cases in which separation of pigments by chromatography is impracticable for one reason or another. An example is the analysis of in vivo formation of heavy metal-substituted chlorophylls in heavy metal-stressed plants. We describe here a novel, accurate UV/VIS spectrophotometric method for the quantification of individual chlorophyll derivatives in complex mixtures, which has the potential for universal applicability for mixtures difficult to separate. The method is based on the description of each pigment spectrum by a series of Gaussian peaks. A sample spectrum is then fitted by a linear combination of these "Gauss-peak spectra" including an automatic correction of wavelength inaccuracy and baseline instability of the spectrometer as well as a correction of the widening of absorbance peaks in more concentrated pigment solutions. The automatic correction of peak shifts can also partially correct shifts caused by processes like allomerization. In this paper, we present the Gauss-peak spectra for Mg-chlorophyll a, b, c, pheophytin a, b, c, Cu-chlorophyll a, b, c, and Zn-chlorophyll a in acetone; Mg-chlorophyll a, b, pheophytin a, b, Cu-chlorophyll a, b, allomerized Cu-chlorophyll a, b, and Zn-chlorophyll a, b in cyclohexane; Mg-chlorophyll a, b, pheophytin a, b, and Cu-chlorophyll a, b in diethyl ether.
Plasma Dispersion Function for the Kappa Distribution
NASA Technical Reports Server (NTRS)
Podesta, John J.
2004-01-01
The plasma dispersion function is computed for a homogeneous isotropic plasma in which the particle velocities are distributed according to a Kappa distribution. An ordinary differential equation is derived for the plasma dispersion function and it is shown that the solution can be written in terms of Gauss' hypergeometric function. Using the extensive theory of the hypergeometric function, various mathematical properties of the plasma dispersion function are derived including symmetry relations, series expansions, integral representations, and closed form expressions for integer and half-integer values of K.
NASA Astrophysics Data System (ADS)
Gurarii, G. Z.
2015-09-01
Extremely scarce data have been published on the structure of the geomagnetic field during the Gauss and early Matuyama chrons until recently. Only a few papers contain information about the characteristics of the field during the Gauss-Matuyama reversal, derived by studying the terrestrial sediments. This motivated us to revisit the paleomagnetism of the sedimentary rocks of Akchagyl age in the section of the Pirnuar Valley in West Kopet Dag, for the first time studied by us in the late 1960s-early 1970s. These rocks are the analog of the top Piacenzian-bottom Gelasian and span the mentioned time interval. The reanalysis was conducted with the use of the state-of-the-art paleomagnetic techniques and modern magnetostratigraphic timescale. We have studied a number of the characteristics which enabled us to distinguish the rocks whose remanence is most likely to have a depositional origin. Based on the paleomagnetic characteristics of these rocks, we reconstructed the structure of the paleomagnetic field for the studied interval (~270 ka) of the initial stage of the Gauss-Matuyama reversal and revealed the excursions at the final and initial stages of the Gauss and Matuyama chrons. This analysis has significantly updated the time constraints of the rock sedimentation in the studied section and supported the locations of the virtual geomagnetic pole during the reversal, obtained previously.
NASA Astrophysics Data System (ADS)
Doroshkevich, Andrei G.; Verkhodanov, Oleg V.; Naselsky, Pavel D.; Kim, Jaiseung; Novikov, Dmitry I.; Turchaninov, Viktor I.; Novikov, Igor D.; Chiang, Lung-Yih; Hansen, Martin
We present the development of the method for numerical analysis of polarization in the Gauss-Legendre sky pixelization (GLESP) scheme for CMB maps. This incorporation of the polarization transforms in the pixelization scheme GLESP completes the creation of our new method for numerical analysis of CMB maps. A comparison of GLESP and HEALPix calculations is done.
Coexistence of chaotic and non-chaotic states in the two-dimensional Gauss-Navier-Stokes dynamics
NASA Astrophysics Data System (ADS)
Giberti, C.; Rondoni, L.; Vernia, C.
2004-01-01
Recently, Gallavotti proposed an Equivalence Conjecture in hydrodynamics, which states that forced-damped fluids can be equally well represented by means of the Navier-Stokes equations (NS) and by means of time reversible modifications of NS called Gauss-Navier-Stokes equations (GNS). This Equivalence Conjecture received numerical support in several recent papers concerning two-dimensional fluid mechanics. The corresponding results rely on the fact that the NS and GNS systems only have one attracting set. Performing similar two-dimensional simulations, we find that there are conditions to be met by the GNS system for this to be the case. In particular, increasing the Reynolds number, while keeping fixed the number of Fourier modes, leads to the coexistence of different attractors. This makes difficult a test of the Equivalence Conjecture, but constitutes a spurious effect due to the insufficient spectral resolution. With sufficiently fine spectral resolution, the steady states are unique and the Equivalence Conjecture can be conveniently established.
Apostolopoulos, Pantelis S.; Brouzakis, Nikolaos; Tetradis, Nikolaos; Tzavara, Eleftheria
2007-10-15
We extend the covariant analysis of the brane cosmological evolution in order to take into account, apart from a general matter content and an induced-gravity term on the brane, a Gauss-Bonnet term in the bulk. The gravitational effect of the bulk matter on the brane evolution can be described in terms of the total bulk mass as measured by a bulk observer at the location of the brane. This mass appears in the effective Friedmann equation through a term characterized as generalized dark radiation that induces mirage effects in the evolution. We discuss the normal and self-accelerating branches of the combined system. We also derive the Raychaudhuri equation that can be used in order to determine if the cosmological evolution is accelerating.
Noack, Andreas; Bogan, Christina; Willke, Benno
2017-02-15
One of the limiting noise sources in the current generation of gravitational wave detectors, such as the advanced laser interferometer gravitational wave observatory (aLIGO), is the thermal noise in the interferometer's test mass coatings. One proposed method to reduce the coupling of this noise source to the gravitational wave readout is using a laser beam in the higher-order spatial LG_{33} mode within the interferometer. Here we show that the current four-mirror cavities of aLIGO are not compatible with Laguerre-Gauss modes due to astigmatism. A non-degeneracy of modes of the same order could be observed in experiment and simulation. We demonstrate that a non-planar cavity could be used instead as it compensates for the astigmatism and transmits the LG_{33} mode undisturbed.
Petrov, Nikolai I
2016-07-01
It is shown that the vector-vortex Laguerre-Gauss modes with polarization-orbital angular momentum (OAM) entanglement are the vector solutions of the Maxwell equations in a graded-index medium. Focusing of linearly and circularly polarized vortex light beams with nonzero azimuthal and radial indices in a cylindrical graded-index waveguide is investigated. The wave shape variation with distance taking into account the spin-orbit and nonparaxial effects is analyzed. The effect of long-term periodic revival of wave packets due to mode interference in a graded-index cylindrical optical waveguide is demonstrated. High efficiency transfer of a strongly focused spot through an optical waveguide over large distances takes place with a period of revival.
Preconditioning of the HiFi Code by Linear Discretization on the Gauss-Lobatto-Legendre Nodes
NASA Astrophysics Data System (ADS)
Glasser, A. H.; Lukin, V. S.
2013-10-01
The most challenging aspect of extended MHD simulation is the scaling of computational time as the problem size is scaled up. The use of high-order spectral elements, as in the HiFi code, is useful for handling multiple length scales and strong anisotropy, but detailed code profiling studies show that cpu time increases rapidly with increasing np, the polynomial degree of the spectral elements, due to the cost of Jacobian matrix formation and solution. We have implemented a method of matrix preconditioning based on linear discretization of the Jacobian matrix on the Gauss-Lobatto-Legendre interpolatory nodes. The resulting matrix has much fewer nonzero elements than the full Jacobian and shares the same vector format. The full solution is then obtained by matrix-free Newton-Krylov methods, which converges rapidly because the preconditioner provides an accurate approximation to the full problem. Scaling studies will be presented for a variety of applications.
NASA Technical Reports Server (NTRS)
Boltz, F. W.
1984-01-01
An algorithm is presented for efficient p-iterative solution of the Lambert/Gauss orbit-determination problem using second-order Newton iteration. The algorithm is based on a universal transformation of Kepler's time-of-flight equation and approximate inverse solutions of this equation for short-way and long-way flight paths. The approximate solutions provide both good starting values for iteration and simplified computation of the second-order term in the iteration formula. Numerical results are presented which indicate that in many cases of practical significance (except those having collinear position vectors) the algorithm produces at least eight significant digits of accuracy with just two or three steps of iteration.
Angelie, E; Sappey-Marinier, D; Mallet, J; Bonmartin, A; Sau, J
2000-06-01
Magnetic resonance spectroscopic imaging is limited by a low signal-to-noise ratio, so a compromise between spatial resolution and examination time is needed in clinical application. The reconstruction of truncated signal introduces a Point Spread Function that considerably affects the spatial resolution. In order to reduce spatial contamination, three methods, applied after Fourier transform image reconstruction, based on deconvolution or iterative techniques are tested to decrease Point Spread Function contamination. A Gauss-Seidel (GS) algorithm is used for iterative techniques with and without a non-negative constraint (GS+). Convergence and noise dependence studies of the GS algorithm have been done. The linear property of contamination was validated on a point sample phantom. A significant decrease of contamination without broadening the spatial resolution was obtained with GS+ method compared to a conventional apodization. This post-processing method can provide a contrast enhancement of clinical spectroscopic images without changes in acquisition time.
Graviton time delay and a speed limit for small black holes in Einstein-Gauss-Bonnet theory
NASA Astrophysics Data System (ADS)
Papallo, Giuseppe; Reall, Harvey S.
2015-11-01
Camanho, Edelstein, Maldacena and Zhiboedov have shown that gravitons can experience a negative Shapiro time delay, i.e. a time advance, in Einstein-Gauss-Bonnet theory. They studied gravitons propagating in singular "shock-wave" geometries. We study this effect for gravitons propagating in smooth black hole spacetimes. For a small enough black hole, we find that gravitons of appropriate polarisation, and small impact parameter, can experience time advance. Such gravitons can also exhibit a deflection angle less than π, characteristic of a repulsive short-distance gravitational interaction. We discuss problems with the suggestion that the time advance can be used to build a "time machine". In particular, we argue that a small black hole cannot be boosted to a speed arbitrarily close to the speed of light, as would be required in such a construction.
NASA Astrophysics Data System (ADS)
Maselli, Andrea; Gualtieri, Leonardo; Pani, Paolo; Stella, Luigi; Ferrari, Valeria
2015-03-01
Quasi-periodic oscillations (QPOs) observed in the X-ray flux emitted by accreting black holes are associated with phenomena occurring near the horizon. Future very large area X-ray instruments will be able to measure QPO frequencies with very high precision, thus probing this strong-field region. Using the relativistic precession model, we show the way in which QPO frequencies could be used to test general relativity (GR) against those alternative theories of gravity which predict deviations from the classical theory in the strong-field and high-curvature regimes. We consider one of the best-motivated high-curvature corrections to GR, namely, the Einstein-Dilaton-Gauss-Bonnet theory, and show that a detection of QPOs with the expected sensitivity of the proposed ESA M-class mission LOFT would set the most stringent constraints on the parameter space of this theory.
Dotti, Gustavo; Oliva, Julio; Troncoso, Ricardo
2007-09-15
An exhaustive classification of a certain class of static solutions for the five-dimensional Einstein-Gauss-Bonnet theory in vacuum is presented. The class of metrics under consideration is such that the spacelike section is a warped product of the real line with a nontrivial base manifold. It is shown that for generic values of the coupling constants the base manifold must be necessarily of constant curvature, and the solution reduces to the topological extension of the Boulware-Deser metric. It is also shown that the base manifold admits a wider class of geometries for the special case when the Gauss-Bonnet coupling is properly tuned in terms of the cosmological and Newton constants. This freedom in the metric at the boundary, which determines the base manifold, allows the existence of three main branches of geometries in the bulk. For the negative cosmological constant, if the boundary metric is such that the base manifold is arbitrary, but fixed, the solution describes black holes whose horizon geometry inherits the metric of the base manifold. If the base manifold possesses a negative constant Ricci scalar, two different kinds of wormholes in vacuum are obtained. For base manifolds with vanishing Ricci scalar, a different class of solutions appears resembling 'spacetime horns'. There is also a special case for which, if the base manifold is of constant curvature, due to a certain class of degeneration of the field equations, the metric admits an arbitrary redshift function. For wormholes and spacetime horns, there are regions for which the gravitational and centrifugal forces point towards the same direction. All of these solutions have finite Euclidean action, which reduces to the free energy in the case of black holes, and vanishes in the other cases. The mass is also obtained from a surface integral.
Spherical-earth Gravity and Magnetic Anomaly Modeling by Gauss-legendre Quadrature Integration
NASA Technical Reports Server (NTRS)
Vonfrese, R. R. B.; Hinze, W. J.; Braile, L. W.; Luca, A. J. (Principal Investigator)
1981-01-01
The anomalous potential of gravity and magnetic fields and their spatial derivatives on a spherical Earth for an arbitrary body represented by an equivalent point source distribution of gravity poles or magnetic dipoles were calculated. The distribution of equivalent point sources was determined directly from the coordinate limits of the source volume. Variable integration limits for an arbitrarily shaped body are derived from interpolation of points which approximate the body's surface envelope. The versatility of the method is enhanced by the ability to treat physical property variations within the source volume and to consider variable magnetic fields over the source and observation surface. A number of examples verify and illustrate the capabilities of the technique, including preliminary modeling of potential field signatures for Mississippi embayment crustal structure at satellite elevations.
D'Onofrio, Giuseppe; Pirozzi, Enrica
2016-09-26
We consider a stochastic differential equation in a strip, with coefficients suitably chosen to describe the acto-myosin interaction subject to time-varying forces. By simulating trajectories of the stochastic dynamics via an Euler discretization-based algorithm, we fit experimental data and determine the values of involved parameters. The steps of the myosin are represented by the exit events from the strip. Motivated by these results, we propose a specific stochastic model based on the corresponding time-inhomogeneous Gauss-Markov and diffusion process evolving between two absorbing boundaries. We specify the mean and covariance functions of the stochastic modeling process taking into account time-dependent forces including the effect of an external load. We accurately determine the probability density function (pdf) of the first exit time (FET) from the strip by solving a system of two non singular second-type Volterra integral equations via a numerical quadrature. We provide numerical estimations of the mean of FET as approximations of the dwell-time of the proteins dynamics. The percentage of backward steps is given in agreement to experimental data. Numerical and simulation results are compared and discussed.
Gao, Jie; Zhang, Yixin; Dan, Weiyi; Hu, Zhengda
2015-06-29
The turbulent effects of strong irradiance fluctuations on the probability densities and the normalized powers of the orbital angular momentum (OAM) modes are modeled for fractional Bessel Gauss beams in paraxial turbulence channel. We find that the probability density of signal OAM modes is a function of position deviation from the beam center, and the farther away from the beam center the detection position is, the smaller the probability density is. For fractional OAM quantum numbers, the average probability densities of signal/crosstalk modes oscillate along the beam radius except the half-integer. When the beam waist of source decreases or the irradiance fluctuation increases, the average probability density of the signal OAM mode drops. The peak of the average probability density of crosstalk modes shifts to outward of the beam center as beam waist gets larger. In the nearby region of beam center, the larger the quantum number deviation of OAM, the smaller the beam waist and the turbulence fluctuations are, the lower average probability densities of crosstalk OAM modes are. Especially, the increase of turbulence fluctuations can make the crosstalk stronger and more concentrated. Lower irradiance fluctuation can give rise to higher the normalized powers of the signal OAM modes, which is opposite to the crosstalk normalized powers.
Sainath, Kamalesh; Teixeira, Fernando L
2014-05-01
We discuss the application of complex-plane Gauss-Laguerre quadrature (CGLQ) to efficiently evaluate two-dimensional Fourier integrals arising as the solution to electromagnetic fields radiated by elementary dipole antennas embedded within planar-layered media exhibiting arbitrary material parameters. More specifically, we apply CGLQ to the long-standing problem of rapidly and efficiently evaluating the semi-infinite length "tails" of the Fourier integral path while simultaneously and robustly guaranteeing absolute, exponential convergence of the field solution despite diversity in the doubly anisotropic layer parameters, source type (i.e., electric or equivalent magnetic dipole), source orientation, observed field type (magnetic or electric), (nonzero) frequency, and (nonzero) source-observer separation geometry. The proposed algorithm exhibits robustness despite unique challenges arising for the fast evaluation of such two-dimensional integrals. Herein we develop the mathematical treatment to rigorously evaluate the tail integrals using CGLQ, as well as discuss and address the specific issues posed to the CGLQ method when anisotropic, layered media are present. To empirically demonstrate the CGLQ algorithm's computational efficiency, versatility, and accuracy, we perform a convergence analysis along with two case studies related to modeling of electromagnetic resistivity tools employed in geophysical prospection of layered, anisotropic Earth media and validating the ability of isoimpedance substrates to enhance the radiation performance of planar antennas placed in close proximity to metallic ground planes.
Parameter investigation with line-implicit lower-upper symmetric Gauss-Seidel on 3D stretched grids
NASA Astrophysics Data System (ADS)
Otero, Evelyn; Eliasson, Peter
2015-03-01
An implicit lower-upper symmetric Gauss-Seidel (LU-SGS) solver has been implemented as a multigrid smoother combined with a line-implicit method as an acceleration technique for Reynolds-averaged Navier-Stokes (RANS) simulation on stretched meshes. The computational fluid dynamics code concerned is Edge, an edge-based finite volume Navier-Stokes flow solver for structured and unstructured grids. The paper focuses on the investigation of the parameters related to our novel line-implicit LU-SGS solver for convergence acceleration on 3D RANS meshes. The LU-SGS parameters are defined as the Courant-Friedrichs-Lewy number, the left-hand side dissipation, and the convergence of iterative solution of the linear problem arising from the linearisation of the implicit scheme. The influence of these parameters on the overall convergence is presented and default values are defined for maximum convergence acceleration. The optimised settings are applied to 3D RANS computations for comparison with explicit and line-implicit Runge-Kutta smoothing. For most of the cases, a computing time acceleration of the order of 2 is found depending on the mesh type, namely the boundary layer and the magnitude of residual reduction.
NASA Astrophysics Data System (ADS)
Ohta, Nobuyoshi; Torii, Takashi
2013-09-01
We study charged black hole solutions in Einstein-Maxwell-Gauss-Bonnet theory with the dilaton field which is the low-energy effective theory of the heterotic string. The spacetime is D dimensional and assumed to be static and plane symmetric with the (D-2)-dimensional constant curvature space and asymptotically anti-de Sitter. By imposing the boundary conditions of the existence of the regular black hole horizon and proper behavior at infinity where the Breitenlohner-Freedman bound should be satisfied, we construct black hole solutions numerically. We give the relations among the physical quantities of the black holes such as the horizon radius, the mass, the temperature, and so on. The properties of the black holes do not depend on the dimensions qualitatively, which is different from the spherically symmetric and asymptotically flat case. There is nonzero lower limit for the radius of the event horizon below which no solution exists. The temperature of the black hole becomes smaller as the horizon radius is smaller but remains nonzero when the lower limit is attained.
NASA Astrophysics Data System (ADS)
Wie, Bong; Ahn, Jaemyung
2017-03-01
This paper is concerned with a classical yet still mystifying problem regarding multiple roots of the angles-only initial orbit determination (IOD) polynomial equations of Lagrange, Laplace, and Gauss of the form: f( x) = x 8+ a x 6+ b x 3+ c=0 where a, c<0. A possibility of multiple non-spurious roots of this 8th order polynomial equation with b>0 has been extensively treated in the celestial mechanics literature. However, the literature on applied astrodynamics has not treated this multiple-root issue in detail, and not many specific numerical examples with multiple roots are available in the literature. In this paper, a very simple method of determining the correct root from two or three non-spurious roots is presented, which doesn't utilize any a priori knowledge and/or additional observations of the object. The proposed method exploits a simple approximate polynomial equation of the form: g( x) = x 8+ a x 6=0. An approximate polynomial equation, either g( x) = x 8+ c=0 or g( x) = x 8+ a x 6= x 6( x 2+ a) = 0, can also be used for quickly estimating an initial guess of the correct root.
NASA Astrophysics Data System (ADS)
Wie, Bong; Ahn, Jaemyung
2016-09-01
This paper is concerned with a classical yet still mystifying problem regarding multiple roots of the angles-only initial orbit determination (IOD) polynomial equations of Lagrange, Laplace, and Gauss of the form: f(x) = x 8+a x 6+b x 3+c=0 where a,c<0. A possibility of multiple non-spurious roots of this 8th order polynomial equation with b>0 has been extensively treated in the celestial mechanics literature. However, the literature on applied astrodynamics has not treated this multiple-root issue in detail, and not many specific numerical examples with multiple roots are available in the literature. In this paper, a very simple method of determining the correct root from two or three non-spurious roots is presented, which doesn't utilize any a priori knowledge and/or additional observations of the object. The proposed method exploits a simple approximate polynomial equation of the form: g(x) = x 8+a x 6=0. An approximate polynomial equation, either g(x) = x 8+c=0 or g(x) = x 8+a x 6=x 6(x 2+a) = 0, can also be used for quickly estimating an initial guess of the correct root.
NASA Astrophysics Data System (ADS)
Blázquez-Salcedo, Jose Luis; Macedo, Caio F. B.; Cardoso, Vitor; Ferrari, Valeria; Gualtieri, Leonardo; Khoo, Fech Scen; Kunz, Jutta; Pani, Paolo
2016-11-01
Gravitational waves emitted by distorted black holes—such as those arising from the coalescence of two neutron stars or black holes—carry not only information about the corresponding spacetime but also about the underlying theory of gravity. Although general relativity remains the simplest, most elegant, and viable theory of gravitation, there are generic and robust arguments indicating that it is not the ultimate description of the gravitational universe. Here, we focus on a particularly appealing extension of general relativity, which corrects Einstein's theory through the addition of terms which are second order in curvature: the topological Gauss-Bonnet invariant coupled to a dilaton. We study gravitational-wave emission from black holes in this theory and (i) find strong evidence that black holes are linearly (mode) stable against both axial and polar perturbations, (ii) discuss how the quasinormal modes of black holes can be excited during collisions involving black holes, and finally (iii) show that future ringdown detections with a large signal-to-noise ratio would improve current constraints on the coupling parameter of the theory.
Downscaling of slip distribution for strong earthquakes
NASA Astrophysics Data System (ADS)
Yoshida, T.; Oya, S.; Kuzuha, Y.
2013-12-01
We intend to develop a downscaling model to enhance the earthquake slip distribution resolution. Slip distributions have been obtained by other researchers using various inversion methods. As a downscaling model, we are discussing fractal models that include mono-fractal models (fractional Brownian motion, fBm; fractional Lévy motion, fLm) and multi-fractal models as candidates. Log - log-linearity of k (wave number) versus E (k) (power spectrum) is the necessary condition for fractality: the slip distribution is expected to satisfy log - log-linearity described above if we can apply fractal model to a slip distribution as a downscaling model. Therefore, we conducted spectrum analyses using slip distributions of 11 earthquakes as explained below. 1) Spectrum analyses using one-dimensional slip distributions (strike direction) were conducted. 2) Averaging of some results of power spectrum (dip direction) was conducted. Results show that, from the viewpoint of log - log-linearity, applying a fractal model to slip distributions can be inferred as valid. We adopt the filtering method after Lavallée (2008) to generate fBm/ fLm. In that method, generated white noises (random numbers) are filtered using a power law type filter (log - log-linearity of the spectrum). Lavallée (2008) described that Lévy white noise that generates fLm is more appropriate than the Gaussian white noise which generates fBm. In addition, if the 'alpha' parameter of the Lévy law, which governs the degree of attenuation of tails of the probability distribution, is 2.0, then the Lévy distribution is equivalent to the Gauss distribution. We analyzed slip distributions of 11 earthquakes: the Tohoku earthquake (Wei et al., 2011), Haiti earthquake (Sladen, 2010), Simeulue earthquake (Sladen, 2008), eastern Sichuan earthquake (Sladen, 2008), Peru earthquake (Konca, 2007), Tocopilla earthquake (Sladen, 2007), Kuril earthquake (Sladen, 2007), Benkulu earthquake (Konca, 2007), and southern Java
NASA Astrophysics Data System (ADS)
Gorbachev, D. V.; Ivanov, V. I.
2015-08-01
Gauss and Markov quadrature formulae with nodes at zeros of eigenfunctions of a Sturm-Liouville problem, which are exact for entire functions of exponential type, are established. They generalize quadrature formulae involving zeros of Bessel functions, which were first designed by Frappier and Olivier. Bessel quadratures correspond to the Fourier-Hankel integral transform. Some other examples, connected with the Jacobi integral transform, Fourier series in Jacobi orthogonal polynomials and the general Sturm-Liouville problem with regular weight are also given. Bibliography: 39 titles.
Maeda, Hideki
2006-05-15
We give a model of the higher-dimensional spherically symmetric gravitational collapse of a dust cloud including the perturbative effects of quantum gravity. The n({>=}5)-dimensional action with the Gauss-Bonnet term for gravity is considered and a simple formulation of the basic equations is given for the spacetime M{approx_equal}M{sup 2}xK{sup n-2} with a perfect fluid and a cosmological constant. This is a generalization of the Misner-Sharp formalism of the four-dimensional spherically symmetric spacetime with a perfect fluid in general relativity. The whole picture and the final fate of the gravitational collapse of a dust cloud differ greatly between the cases with n=5 and n{>=}6. There are two families of solutions, which we call plus-branch and the minus-branch solutions. A plus-branch solution can be attached to the outside vacuum region which is asymptotically anti-de Sitter in spite of the absence of a cosmological constant. Bounce inevitably occurs in the plus-branch solution for n{>=}6, and consequently singularities cannot be formed. Since there is no trapped surface in the plus-branch solution, the singularity formed in the case of n=5 must be naked. On the other hand, a minus-branch solution can be attached to the outside asymptotically flat vacuum region. We show that naked singularities are massless for n{>=}6, while massive naked singularities are possible for n=5. In the homogeneous collapse represented by the flat Friedmann-Robertson-Walker solution, the singularity formed is spacelike for n{>=}6, while it is ingoing-null for n=5. In the inhomogeneous collapse with smooth initial data, the strong cosmic censorship hypothesis holds for n{>=}10 and for n=9 depending on the parameters in the initial data, while a naked singularity is always formed for 5{<=}n{<=}8. These naked singularities can be globally naked when the initial surface radius of the dust cloud is fine-tuned, and then the weak cosmic censorship hypothesis is violated.
NASA Astrophysics Data System (ADS)
Tian, David W.; Booth, Ivan
2014-07-01
This paper studies a generic fourth-order theory of gravity with Lagrangian density f(R,Rc2,Rm2,Lm), where Rc2 and Rm2 respectively denote the square of the Ricci and Riemann tensors. By considering explicit R2 dependence and imposing the "coherence condition" fR2=fRm2=-fRc2/4, the field equations of f(R,R2,Rc2,Rm2,Lm) gravity can be smoothly reduced to that of f(R,G,Lm) generalized Gauss-Bonnet gravity with G denoting the Gauss-Bonnet invariant. We use Noether's conservation law to study the f(R1,R2…,Rn,Lm) model with nonminimal coupling between Lm and Riemannian invariants Ri, and conjecture that the gradient of nonminimal gravitational coupling strength ∇μfLfLm is the only source for energy-momentum nonconservation. This conjecture is applied to the f(R,Rc2,Rm2,Lm) model, and the equations of continuity and nongeodesic motion of different matter contents are investigated. Finally, the field equation for Lagrangians including the traceless-Ricci square and traceless-Riemann (Weyl) square invariants is derived, the f(R,Rc2,Rm2,Lm) model is compared with the f(R,Rc2,Rm2,T)+2κLm model, and consequences of nonminimal coupling for black hole and wormhole physics are considered.
NASA Astrophysics Data System (ADS)
Jusufi, K.
2016-12-01
In the present paper we study the Hawking radiation as a quantum tunneling effect of spin-1 particles from a five-dimensional, spherically symmetric, Einstein-Yang-Mills-Gauss-Bonnet (5D EYMGB) black hole. We solve the Proca equation (PE) by applying the WKB approximation and separation of variables via Hamilton-Jacobi (HJ) equation which results in a set of five differential equations, and reproduces, in this way, the Hawking temperature. In the second part of this paper, we extend our results beyond the semiclassical approximation. In particular, we derive the logarithmic correction to the entropy of the EYMGB black hole and show that the quantum corrected specific heat indicates the possible existence of a remnant.
NASA Astrophysics Data System (ADS)
Campos-Enríquez, J. O.; Domínguez-Méndez, F.; Lozada-Zumaeta, M.; Morales-Rodríguez, H. F.; Andaverde-Arredondo, J. A.
2005-10-01
We explored applications (including limitations) of Gauss's theorem to the study of silicic calderas. First it enables us to determine the mass deficiency from calderas. Mass deficiency itself has also other potential applications. It enables to make qualitative comparisons between calderas. We can use the mass deficiency to test, in a quick way and as a preliminary step to a formal gravity inversion, for the feasibility of caldera types of simple geometry (i.e., piston subsidence and funnel models). This application can be done in a straightforward way, once the mass deficiency has been determined. For this purpose the mass deficiency is converted to the volume of material missing at the caldera. Subsequently, for example, this volume and the respective caldera diameter enable us to estimate the height of the cylinder fitting the piston subsidence model. If the obtained parameters are congruent with the known geology and geophysical information then the model may be considered further in the inversion of the gravity data for the detailed structure. Other simple models (i.e., the funnel model) can also be analyzed in this way. In particular, when working with a piston subsidence caldera type, the Gauss theorem enables us to estimate the caldera collapse (very difficult to obtain based on geologic information alone). These possible uses of Gauss's theorem are illustrated with the calderas of La Primavera, Los Azufres, and Los Humeros caldera (Mexico). The obtained mass deficiency from these calderas follow the linear mass deficiency-diameter trend observed for other calderas. In particular, because of their diameters and mass deficiencies, La Primavera and Krakatau calderas can be considered equiparable. This comparison is of the most importance considering that La Primavera is located in the neighbourhood of a metropolis (Guadalajara City). Since geophysical studies have already established a piston subsidence model for these calderas, we assessed Gauss's theorem
Bimodal Distribution of Magnetic Fields and Areas of Sunspots
NASA Astrophysics Data System (ADS)
Tlatov, Andrey G.; Pevtsov, Alexei A.
2014-04-01
We applied automatic identification of sunspot umbrae and penumbrae to daily observations from the Helioseismic Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to study their magnetic flux density ( B) and area ( A). The results confirm an already known logarithmic relationship between the area of sunspots and their maximum flux density. In addition, we find that the relation between average magnetic flux density () and sunspot area shows a bimodal distribution: for small sunspots and pores ( A≤20 millionth of solar hemisphere, MSH), (gauss), and for large sunspots ( A≥100 MSH), is about 600 G. For intermediate sunspots, average flux density linearly decreases from about 800 G to 600 G. A similar bimodal distribution was found in several other integral parameters of sunspots. We show that this bimodality can be related to different stages of sunspot penumbra formation and can be explained by the difference in average inclination of magnetic fields at the periphery of small and large sunspots.
Seghilani, Mohamed S.; Myara, Mikhael; Sellahi, Mohamed; Legratiet, Luc; Sagnes, Isabelle; Beaudoin, Grégoire; Lalanne, Philippe; Garnache, Arnaud
2016-01-01
The generation of a coherent state, supporting a large photon number, with controlled orbital-angular-momentum L = ħl (of charge l per photon) presents both fundamental and technological challenges: we demonstrate a surface-emitting laser, based on III-V semiconductor technology with an integrated metasurface, generating vortex-like coherent state in the Laguerre-Gauss basis. We use a first order phase perturbation to lift orbital degeneracy of wavefunctions, by introducing a weak anisotropy called here “orbital birefringence”, based on a dielectric metasurface. The azimuthal symmetry breakdown and non-linear laser dynamics create “orbital gain dichroism” allowing selecting vortex handedness. This coherent photonic device was characterized and studied, experimentally and theoretically. It exhibits a low divergence (<1°) diffraction limited beam, emitting 49 mW output power in the near-IR at λ ≃ 1 μm, a charge l = ±1, … ±4 (>50 dB vortex purity), and single frequency operation in a stable low noise regime (0.1% rms). Such high performance laser opens the path to widespread new photonic applications. PMID:27917885
NASA Astrophysics Data System (ADS)
Seghilani, Mohamed S.; Myara, Mikhael; Sellahi, Mohamed; Legratiet, Luc; Sagnes, Isabelle; Beaudoin, Grégoire; Lalanne, Philippe; Garnache, Arnaud
2016-12-01
The generation of a coherent state, supporting a large photon number, with controlled orbital-angular-momentum L = ħl (of charge l per photon) presents both fundamental and technological challenges: we demonstrate a surface-emitting laser, based on III-V semiconductor technology with an integrated metasurface, generating vortex-like coherent state in the Laguerre-Gauss basis. We use a first order phase perturbation to lift orbital degeneracy of wavefunctions, by introducing a weak anisotropy called here “orbital birefringence”, based on a dielectric metasurface. The azimuthal symmetry breakdown and non-linear laser dynamics create “orbital gain dichroism” allowing selecting vortex handedness. This coherent photonic device was characterized and studied, experimentally and theoretically. It exhibits a low divergence (<1°) diffraction limited beam, emitting 49 mW output power in the near-IR at λ ≃ 1 μm, a charge l = ±1, … ±4 (>50 dB vortex purity), and single frequency operation in a stable low noise regime (0.1% rms). Such high performance laser opens the path to widespread new photonic applications.
Visser, A.T.
1989-07-01
Most energy discharge power supplies obtain their bursts of power from the energy stored in charged capacitors when it is suddenly released into a load. This note describes the design of a similar small 800 Joules energy discharge type power supply and magnet. The magnet gap is 2 in.{times}2 in.{times}25-1/2 in. long and produces about 4.4 kGauss-meters at a rate of 12 pulses per minute. Each pulse is current regulated at the top for a duration of 6 msec. and varies less than 0.6% of set value. Current regulation at flattop is obtained by switching a resistor in and out of the discharge circuit with an IGBT at a rate of about 5 kHz. Most energy discharge systems produce half sine wave pulses, and current regulation is obtained by controlling the charge voltage at the energy storage capacitor, resulting only in a controlled peak current value of the half sine wave pulse. The current value at the top changes substantially during 6 msec. depending on the operating frequency.
Seghilani, Mohamed S; Myara, Mikhael; Sellahi, Mohamed; Legratiet, Luc; Sagnes, Isabelle; Beaudoin, Grégoire; Lalanne, Philippe; Garnache, Arnaud
2016-12-05
The generation of a coherent state, supporting a large photon number, with controlled orbital-angular-momentum L = ħl (of charge l per photon) presents both fundamental and technological challenges: we demonstrate a surface-emitting laser, based on III-V semiconductor technology with an integrated metasurface, generating vortex-like coherent state in the Laguerre-Gauss basis. We use a first order phase perturbation to lift orbital degeneracy of wavefunctions, by introducing a weak anisotropy called here "orbital birefringence", based on a dielectric metasurface. The azimuthal symmetry breakdown and non-linear laser dynamics create "orbital gain dichroism" allowing selecting vortex handedness. This coherent photonic device was characterized and studied, experimentally and theoretically. It exhibits a low divergence (<1°) diffraction limited beam, emitting 49 mW output power in the near-IR at λ ≃ 1 μm, a charge l = ±1, … ±4 (>50 dB vortex purity), and single frequency operation in a stable low noise regime (0.1% rms). Such high performance laser opens the path to widespread new photonic applications.
Kostakoglu, Lale; Goy, Andre; Martinelli, Giovanni; Caballero, Dolores; Crump, Michael; Gaidano, Gianluca; Baetz, Tara; Buckstein, Rena; Fine, Gregg; Fingerle-Rowson, Guenter; Berge, Claude; Sahin, Deniz; Press, Oliver; Sehn, Laurie
2017-02-01
An exploratory analysis of 75 follicular lymphoma patients treated with obinutuzumab or rituximab induction therapy (IT) for 4 weeks in the phase II GAUSS study aimed to determine whether positron emission tomography (PET) results could predict progression-free survival (PFS) and tumor response. The proportion of patients with a PFS event (progression or death) was higher in those who were PET-positive after IT (assessed using Deauville five-point scale criteria; 35/52, 67%) than PET-negative (5/20, 25%); the hazard ratio for progression or death was 0.25 (95%CI: 0.01-0.64; p = 0.0018). A significant association was also found when PET results were assessed using International Harmonization Project and European Organisation for Research and Treatment of Cancer criteria. Change between baseline and end of IT in values of standardized uptake value and other PET parameters were associated with PFS and response. Validation of these results in prospective studies of larger cohorts is warranted.
NASA Astrophysics Data System (ADS)
Kulikov, G. Yu.
2015-06-01
A technique for constructing nested implicit Runge-Kutta methods in the class of mono-implicit formulas of this type is studied. These formulas are highly efficient in practice, since the dimension of the original system of differential equations is preserved, which is not possible in the case of implicit multistage Runge-Kutta formulas of the general from. On the other hand, nested implicit Runge-Kutta methods inherit all major properties of general formulas of this form, such as A-stability, symmetry, and symplecticity in a certain sense. Moreover, they can have sufficiently high stage and classical orders and, without requiring high extra costs, can ensure dense output of integration results of the same accuracy as the order of the underlying method. Thus, nested methods are efficient when applied to the numerical integration of differential equations of various sorts, including stiff and nonstiff problems, Hamiltonian systems, and invertible equations. In this paper, previously proposed nested methods based on the Gauss quadrature formulas are generalized to Lobatto-type methods. Additionally, a unified technique for constructing all such methods is proposed. Its performance is demonstrated as applied to embedded examples of nested implicit formulas of various orders. All the methods constructed are supplied with tools for local error estimation and automatic variable-stepsize mesh generation based on an optimal stepsize selection. These numerical methods are verified by solving test problems with known solutions. Additionally, a comparative analysis of these methods with Matlab built-in solvers is presented.
NASA Astrophysics Data System (ADS)
Vicuña-Hernández, Verónica; Santiago, José T.; Jerónimo-Moreno, Yasser; Ramírez-Alarcón, Roberto; Cruz-Ramírez, Héctor; U'Ren, Alfred B.; Jáuregui-Renaud, Rocio
2016-12-01
We present an experimental and theoretical study of type I, frequency-degenerate spontaneous parametric down-conversion (SPDC) with a Bessel-Gauss pump in which we include both paraxial and nonparaxial pump beam configurations. We present measurements of the SPDC angular spectrum (AS), of the conditional angular spectrum (CAS) of signal-mode single photons as heralded by the detection of an idler photon, and of the transverse wave-vector signal-idler correlations (TWC). We show that as the pump is made increasingly nonparaxial, the AS acquires a nonconcentric double-cone structure, with the CAS shape depending on the azimuthal location of the heralding detector, while the signal-idler wave-vector correlation region splits into characteristic doublet stripes, representing as yet unexplored nontrivial, nonlocal quantum correlations between the signal and idler photons. Our work provides further understanding of SPDC with a particular class of structured pump beams, and we believe that the controlled presence of double wave-vector correlations represents an interesting resource for photon-pair quantum-state engineering.
Deremigio, Hilary; Kemper, Peter; Lamar, M Drew; Smith, Gregory D
2008-01-01
Mathematical models of calcium release sites derived from Markov chain models of intracellular calcium channels exhibit collective gating reminiscent of the experimentally observed phenomenon of stochastic calcium excitability (i.e., calcium puffs and sparks). We present a Kronecker structured representation for calcium release site models and perform benchmark stationary distribution calculations using numerical iterative solution techniques that leverage this structure. In this context we find multi-level methods and certain preconditioned projection methods superior to simple Gauss-Seidel type iterations. Response measures such as the number of channels in a particular state converge more quickly using these numerical iterative methods than occupation measures calculated via Monte Carlo simulation.
NASA Astrophysics Data System (ADS)
Lin, Fu-Jun; Chen, Zong-Hua; Li, Xiao-Qing; Liao, Jing-Jing; Zhu, Yun
2017-02-01
A GigaGauss quasi-steady magnetic field can be generated in astrophysical plasmas and laser-produced plasmas with high-frequency electromagnetic radiation through wave-wave and wave-particle interactions. A set of governing equations for this field are obtained in the plasma consisting of ultra-relativistic electrons following q-nonextensive distribution. The numerical results show that the initial field is unstable and can collapse to generate various spatially intermittent magnetic flux tubes. It can also be found that the behavior of the magnetic field is greatly dependent on the nonextensive index q, which may be helpful in understanding the magnetic turbulence.
NASA Astrophysics Data System (ADS)
Schuh, Wolf-Dieter; Brockmann, Jan Martin; Kargoll, Boris; Loth, Ina
2014-05-01
The modeling of satellite measurements series pose a special challenge because of the huge amount of data and the strong correlations between the measurements. In connection with the large number of parameters the rigorous computation of an appropriate stochastic model is a demanding task. This contribution discusses the large variety of possible strategies to treat correlated measurements with constant sampling rate. At first view the regularly structured covariance matrices suggest fast Toeplitz algorithms. But the equidistant measurement series can be also interpreted as a finite sequence of a time discrete covariance stationary stochastic processes with infinite extension. The stochastic process can be represented and analyzed in different quantities in the time domain as well as in the frequency domain. The signal itself and its autocovariance function in the time domain be accompanied by the periodogram and the spectral distribution/spectral density function in the frequency domain. These four quantities and their relations in between can be clearly represented in form of a "Magic Square", which gives a good basis to analyze the stochastic process, study truncation effects and model the behavior by parametric and non parametric approaches. The focus of this study considers the pro and cons of possible strategies to decorrelate finite sequences of measurements and is motivated by GOCE gradiometer measurements. The measurement series are characterized by large correlations over long time spans with a periodic behavior with respect to the orbital period and a fragmentation of the time series into parts, due to satellite maneuvers and calibration phases. The decorrelation process is crucial for the gravity field estimation. Therefore efficient strategies are necessary to get as much signal as possible also from the highly correlated, fragmented measurements series. Special attentions has to take place to avoid data loss during the warmup phase of recursive
2014-10-03
introduce distributed logics. Distributed logics lift the distribution structure of a distributed system directly into the logic, thereby parameterizing...the logic by the distribution structure itself. Each domain supports a “local modal logic.” The connections between domains are realized as...There are also multi- agent logic systems [12]. What distinguishes distributed logics from these are that the morphisms, i.e., the nbd maps, have
Rosa, Massimiliano; Warsa, James S; Perks, Michael
2010-12-14
We have implemented a cell-wise, block-Gauss-Seidel (bGS) iterative algorithm, for the solution of the S{sub n} transport equations on the Roadrunner hybrid, parallel computer architecture. A compute node of this massively parallel machine comprises AMD Opteron cores that are linked to a Cell Broadband Engine{trademark} (Cell/B.E.). LAPACK routines have been ported to the Cell/B.E. in order to make use of its parallel Synergistic Processing Elements (SPEs). The bGS algorithm is based on the LU factorization and solution of a linear system that couples the fluxes for all S{sub n} angles and energy groups on a mesh cell. For every cell of a mesh that has been parallel decomposed on the higher-level Opteron processors, a linear system is transferred to the Cell/B.E. and the parallel LAPACK routines are used to compute a solution, which is then transferred back to the Opteron, where the rest of the computations for the S{sub n} transport problem take place. Compared to standard parallel machines, a hundred-fold speedup of the bGS was observed on the hybrid Roadrunner architecture. Numerical experiments with strong and weak parallel scaling demonstrate the bGS method is viable and compares favorably to full parallel sweeps (FPS) on two-dimensional, unstructured meshes when it is applied to optically thick, multi-material problems. As expected, however, it is not as efficient as FPS in optically thin problems.
NASA Astrophysics Data System (ADS)
Loughman, R.; Flittner, D.; Nyaku, E.; Bhartia, P. K.
2014-07-01
The Gauss-Seidel Limb Scattering (GSLS) radiative transfer (RT) model simulates the transfer of solar radiation through the atmosphere, and is imbedded in the retrieval algorithm used to process data from the Ozone Mapping and Profiler Suite (OMPS) Limb Profiler (LP), which was launched on the Suomi NPP satellite in October 2011. A previous version of this model has been compared with several other limb scattering RT models in previous studies, including Siro, MCC++, CDIPI, LIMBTRAN, SASKTRAN, VECTOR, and McSCIA. To address deficiencies in the GSLS radiance calculations revealed in earlier comparisons, several recent changes have been added that improve the accuracy and flexibility of the GSLS model, including: 1. Improved treatment of the variation of the extinction coefficient with altitude, both within atmospheric layers and above the nominal top of the atmosphere (TOA). 2. Addition of multiple scattering source function calculations at multiple zeniths along the line of sight (LOS). 3. Re-introduction of the ability to simulate vector (polarized) radiances. 4. Introduction of variable surface properties along the limb LOS, with minimal effort required to add variable atmospheric properties along the LOS as well. 5. Addition of the ability to model multiple aerosol types within the model atmosphere. The model improvements numbered 1-3 above are verified by comparison to previously published results (using standard radiance tables whenever possible), demonstrating significant improvement in cases for which previous versions of the GSLS model performed poorly. The single-scattered radiance errors that were as high as 4% in earlier studies are now generally reduced to < 0.5%, while total radiance errors generally decline from > 10% to 1-2%. In all cases, the height dependence of the GSLS radiance error is greatly reduced.
NASA Astrophysics Data System (ADS)
Loughman, R.; Flittner, D.; Nyaku, E.; Bhartia, P. K.
2015-03-01
The Gauss-Seidel limb scattering (GSLS) radiative transfer (RT) model simulates the transfer of solar radiation through the atmosphere and is imbedded in the retrieval algorithm used to process data from the Ozone Mapping and Profiler Suite (OMPS) limb profiler (LP), which was launched on the Suomi NPP satellite in October 2011. A previous version of this model has been compared with several other limb scattering RT models in previous studies, including Siro, MCC++, CDIPI, LIMBTRAN, SASKTRAN, VECTOR, and McSCIA. To address deficiencies in the GSLS radiance calculations revealed in earlier comparisons, several recent changes have been added that improve the accuracy and flexibility of the GSLS model, including 1. improved treatment of the variation of the extinction coefficient with altitude, both within atmospheric layers and above the nominal top of the atmosphere; 2. addition of multiple-scattering source function calculations at multiple solar zenith angles along the line of sight (LOS); 3. introduction of variable surface properties along the limb LOS, with minimal effort required to add variable atmospheric properties along the LOS as well; 4. addition of the ability to model multiple aerosol types within the model atmosphere. The model improvements 1 and 2 are verified by comparison to previously published results (using standard radiance tables whenever possible), demonstrating significant improvement in cases for which previous versions of the GSLS model performed poorly. The single-scattered radiance errors that were as high as 4% in earlier studies are now generally reduced to 0.3%, while total radiance errors generally decline from 10% to 1-3%. In all cases, the tangent height dependence of the GSLS radiance error is greatly reduced.
Deino, A.L.; Kingston, J.D.; Glen, J.M.; Edgar, R.K.; Hill, A.
2006-01-01
The fluviolacustrine sedimentary sequence of the Chemeron Formation exposed in the Barsemoi River drainage, Tugen Hills, Kenya, contains a package of five successive diatomite/fluvial cycles that record the periodic development of freshwater lakes within the axial portion of the Central Kenya Rift. The overwhelming abundance in the diatomite of planktonic species of the genera Aulacoseira and Stephanodiscus, and the virtual absence of benthic littoral diatoms and detrital material indicate areally extensive, deep lake systems. A paleomagnetic reversal stratigraphy has been determined and chronostratigraphic tie points established by 40Ar/39Ar dating of intercalated tuffs. The sequence spans the interval 3.1-2.35??Ma and bears a detailed record of the Gauss/Matuyama paleomagnetic transition. The 40Ar/39Ar age for this boundary of 2.589 ?? 0.003??Ma can be adjusted to concordance with the Astronomical Polarity Time Scale (APTS) on the basis of an independent calibration to 2.610??Ma, 29??kyr older than the previous APTS age. The diatomites recur at an orbital precessional interval of 23??kyr and are centered on a 400-kyr eccentricity maximum. It is concluded that these diatomite/fluvial cycles reflect a narrow interval of orbitally forced wet/dry climatic conditions that may be expressed regionally across East Africa. The timing of the lacustrine pulses relative to predicted insolation models favors origination of moisture from the northern Africa monsoon, rather than local circulation driven by direct equatorial insolation. This moisture event at 2.7-2.55??Ma, and later East African episodes at 1.9-1.7 and 1.1-0.9??Ma, are approximately coincident with major global climatic and oceanographic events. ?? 2006 Elsevier B.V. All rights reserved.
Solar Intranetwork Magnetic Elements: Flux Distributions
NASA Astrophysics Data System (ADS)
Zhou, Guiping; Wang, Jingxiu; Jin, Chunlan
2013-04-01
The current study aims at quantifying the flux distributions of solar intranetwork (IN) magnetic field based on the data taken in four quiet and two enhanced network areas with the Narrow-band Filter Imager of the Solar Optical Telescope on board the Hinode satellite. More than 14000 IN elements and 3000 NT elements were visually identified. They exhibit a flux distribution function with a peak at 1 - 3×1016 Mx (maxwell) and 2 - 3×1017 Mx, respectively. We found that the IN elements contribute approximately to 52 % of the total flux and an average flux density of 12.4 gauss of the quiet region at any given time. By taking the lifetime of IN elements of about 3 min (Zhou et al., Solar Phys. 267, 63, 2010) into account, the IN fields are estimated to have total contributions to the solar magnetic flux up to 3.8×1026 Mx per day. No fundamental distinction can be identified in IN fields between the quiet and enhanced network areas.
NASA Astrophysics Data System (ADS)
Rexer, Moritz; Hirt, Christian
2015-11-01
In geodesy and geophysics, spherical harmonic techniques are popular for modelling topography and potential fields with ever-increasing spatial resolution. For ultra-high-degree spherical harmonic modelling, i.e. degree 10,000 or more, classical algorithms need to be extended to avoid under- or overflow problems associated with the computation of associated Legendre functions (ALFs). In this work, two quadrature algorithms—the Gauss-Legendre (GL) quadrature and the quadrature following Driscoll/Healy (DH)—and their implementation for the purpose of ultra-high (surface) spherical harmonic analysis of spheroid functions are reviewed and modified for application to ultra-high degree. We extend the implementation of the algorithms in the SHTOOLS software package (v2.8) by (1) the X-number (or Extended Range Arithmetic) method for accurate computation of ALFs and (2) OpenMP directives enabling parallel processing within the analysis. Our modifications are shown to achieve feasible computation times and a very high precision: a degree-21,600 band-limited (=frequency limited) spheroid topographic function may be harmonically analysed with a maximum space-domain error of 3 × 10^{-5} and 5 × 10^{-5} m in 6 and 17 h using 14 CPUs for the GL and for the DH quadrature, respectively. While not being inferior in terms of precision, the GL quadrature outperforms the DH algorithm in terms of computation time. In the second part of the paper, we apply the modified quadrature algorithm to represent for—the first time—gridded topography models for Earth, Moon and Mars as ultra-high-degree series expansions comprising more than 2 billion coefficients. For the Earth's topography, we achieve a resolution of harmonic degree 43,200 (equivalent to 500 m in the space domain), for the Moon of degree 46,080 (equivalent to 120 m) and Mars to degree 23,040 (equivalent to 460 m). For the quality of the representation of the topographic functions in spherical harmonics, we use the
NASA Astrophysics Data System (ADS)
Neighbors, C.; Cochran, E. S.; Ryan, K. J.; Kaiser, A. E.
2015-12-01
The seismic spectrum can be modeled by assuming a Brune spectrum and estimating the parameters of seismic moment (M0), corner frequency (fc), and the high frequency site attenuation (κ). Traditionally studies either hold fixed or use a predefined set of trial values for one of the parameters (e.g., fc) and then solve for the remaining parameters. Here, we use the Gauss-Newton nonlinear least-squares method to simultaneously determine the M0, fc, and high-frequency κ for each event-station pair. We use data collected during the Canterbury, New Zealand earthquake sequence. The seismic stations include the permanent GeoNet accelerometer network as well as a dense network of nearly 200 Quake-Catcher Network (QCN) MEMs accelerometers installed following the 3 September 2010 M 7.1 Darfield earthquake. We examine over 180 aftershocks ≥ Mw3.5 that occurred from 9 September 2010 to 31 July 2011 and are captured by both networks. We use Fourier-transformed S-wave windows that include 80% of the S-wave energy and fit the acceleration spectra between 0.5 and 20 Hz. We apply a path and site correction to the data as described in Oth and Kaiser (2014). Then, the records are smoothed using a Konno and Omachi (1998) filter and uniformly resampled in log space. Initial "best guesses" for M0 and fc are determined from GNS catalog magnitudes and by assuming a 100 bar (10 MPa) stress drop and an initial κ is determined from an automated high-frequency fit method. We use a parametric inversion technique that requires a single M0 and fc for each event, while κ is allowed to vary by station to reflect varying site conditions. Final solutions for M0, fc, and κ are iteratively calculated by minimizing the residual function. After Brune (1970, 1971), the stress drop is determined from the best-fit fc. Moment magnitudes determined agree well with the GNS catalog, with a median difference of 0.12 Mw and 0.20 Mw for GeoNet and QCN inversions, respectively. Stress drop results are within
NASA Astrophysics Data System (ADS)
Kordy, M. A.; Wannamaker, P. E.; Maris, V.; Cherkaev, E.; Hill, G. J.
2014-12-01
We have developed an algorithm for 3D simulation and inversion of magnetotelluric (MT) responses using deformable hexahedral finite elements that permits incorporation of topography. Direct solvers parallelized on symmetric multiprocessor (SMP), single-chassis workstations with large RAM are used for the forward solution, parameter jacobians, and model update. The forward simulator, jacobians calculations, as well as synthetic and real data inversion are presented. We use first-order edge elements to represent the secondary electric field (E), yielding accuracy O(h) for E and its curl (magnetic field). For very low frequency or small material admittivity, the E-field requires divergence correction. Using Hodge decomposition, correction may be applied after the forward solution is calculated. It allows accurate E-field solutions in dielectric air. The system matrix factorization is computed using the MUMPS library, which shows moderately good scalability through 12 processor cores but limited gains beyond that. The factored matrix is used to calculate the forward response as well as the jacobians of field and MT responses using the reciprocity theorem. Comparison with other codes demonstrates accuracy of our forward calculations. We consider a popular conductive/resistive double brick structure and several topographic models. In particular, the ability of finite elements to represent smooth topographic slopes permits accurate simulation of refraction of electromagnetic waves normal to the slopes at high frequencies. Run time tests indicate that for meshes as large as 150x150x60 elements, MT forward response and jacobians can be calculated in ~2.5 hours per frequency. For inversion, we implemented data space Gauss-Newton method, which offers reduction in memory requirement and a significant speedup of the parameter step versus model space approach. For dense matrix operations we use tiling approach of PLASMA library, which shows very good scalability. In synthetic
Zhang, Jixiang; Wei, Qinping; Liu, Kechang; Lu, Peiling
2003-06-01
On the basis of field observation and with the principles and methods of agricultural meteorology, the daily variations of the shadow width of jujube tree belts and the relative light intensity were analyzed in the jujube-wheat interplanting system, and the characteristics of vertical distribution of the light within the wheat canopy inside and outside the shadow were studied. The sunshine vertical distribution curves in the wheat canopy inside and outside the shadow were simulated by mathematical methods. The results showed that the shadow area of the south-north planting jujube tree belts was fairly wider, but the relative light illuminance was larger in early morning and late afternoon than at about noon. Although the sunshine vertical distribution in the wheat canopy inside and outside the shadow was obviously different, they both observed the decreasing law for Gauss Curve.
NASA Astrophysics Data System (ADS)
Jakšić, Nikola
2015-03-01
The optimality of the procedure of parameter identification is scrutinized in this paper. It was shown, with the relations between the mathematical theory of function approximation, three parameter probability distributions, which can adjust their shape, and the maximum-likelihood method, that the optimal expression of the distance between measured data and model fitting it can be established by using the three parameter probability distributions on the basis of iteration procedure, where the noise contained in the measured signal is extracted as well. The iterative method for optimal system/model parameter identification is presented and tested by the numerical experimentation. Four types of noise added to the simple single-degree-of-freedom system response are considered: Gauss, Cauchy, Laplace and Uniform. The method performs well for the noise types at relatively high noise content in the signal.
ERIC Educational Resources Information Center
Ryland, Jane N.
1988-01-01
The microcomputer revolution, in which small and large computers have gained tremendously in capability, has created a distributed computing environment. This circumstance presents administrators with the opportunities and the dilemmas of choosing appropriate computing resources for each situation. (Author/MSE)
NASA Technical Reports Server (NTRS)
Macready, William; Wolpert, David
2005-01-01
We demonstrate a new framework for analyzing and controlling distributed systems, by solving constrained optimization problems with an algorithm based on that framework. The framework is ar. information-theoretic extension of conventional full-rationality game theory to allow bounded rational agents. The associated optimization algorithm is a game in which agents control the variables of the optimization problem. They do this by jointly minimizing a Lagrangian of (the probability distribution of) their joint state. The updating of the Lagrange parameters in that Lagrangian is a form of automated annealing, one that focuses the multi-agent system on the optimal pure strategy. We present computer experiments for the k-sat constraint satisfaction problem and for unconstrained minimization of NK functions.
A New Linearization Method of Unbalanced Electrical Distribution Networks
Liu, Guodong; Xu, Yan; Ceylan, Oguzhan; Tomsovic, Kevin
2014-01-01
Abstract--- With increasing penetration of distributed generation in the distribution networks (DN), the secure and optimal operation of DN has become an important concern. As DN control and operation strategies are mostly based on the linearized sensitivity coefficients between controlled variables (e.g., node voltages, line currents, power loss) and control variables (e.g., power injections, transformer tap positions), efficient and precise calculation of these sensitivity coefficients, i.e. linearization of DN, is of fundamental importance. In this paper, the derivation of the node voltages and power loss as functions of the nodal power injections and transformers' tap-changers positions is presented, and then solved by a Gauss-Seidel method. Compared to other approaches presented in the literature, the proposed method takes into account different load characteristics (e.g., constant PQ, constant impedance, constant current and any combination of above) of a generic multi-phase unbalanced DN and improves the accuracy of linearization. Numerical simulations on both IEEE 13 and 34 nodes test feeders show the efficiency and accuracy of the proposed method.
NASA Technical Reports Server (NTRS)
Chung, Ming-Ying; Ciardo, Gianfranco; Siminiceanu, Radu I.
2007-01-01
The Saturation algorithm for symbolic state-space generation, has been a recent break-through in the exhaustive veri cation of complex systems, in particular globally-asyn- chronous/locally-synchronous systems. The algorithm uses a very compact Multiway Decision Diagram (MDD) encoding for states and the fastest symbolic exploration algo- rithm to date. The distributed version of Saturation uses the overall memory available on a network of workstations (NOW) to efficiently spread the memory load during the highly irregular exploration. A crucial factor in limiting the memory consumption during the symbolic state-space generation is the ability to perform garbage collection to free up the memory occupied by dead nodes. However, garbage collection over a NOW requires a nontrivial communication overhead. In addition, operation cache policies become critical while analyzing large-scale systems using the symbolic approach. In this technical report, we develop a garbage collection scheme and several operation cache policies to help on solving extremely complex systems. Experiments show that our schemes improve the performance of the original distributed implementation, SmArTNow, in terms of time and memory efficiency.
NASA Astrophysics Data System (ADS)
Siegel, J.; Siegel, Edward Carl-Ludwig
2011-03-01
Cook-Levin computational-"complexity"(C-C) algorithmic-equivalence reduction-theorem reducibility equivalence to renormalization-(semi)-group phase-transitions critical-phenomena statistical-physics universality-classes fixed-points, is exploited with Gauss modular/clock-arithmetic/model congruences = signal X noise PRODUCT reinterpretation. Siegel-Baez FUZZYICS=CATEGORYICS(SON of ``TRIZ''): Category-Semantics(C-S) tabular list-format truth-table matrix analytics predicts and implements "noise"-induced phase-transitions (NITs) to accelerate versus to decelerate Harel [Algorithmics(1987)]-Sipser[Intro. Theory Computation(1997) algorithmic C-C: "NIT-picking" to optimize optimization-problems optimally(OOPO). Versus iso-"noise" power-spectrum quantitative-only amplitude/magnitude-only variation stochastic-resonance, this "NIT-picking" is "noise" power-spectrum QUALitative-type variation via quantitative critical-exponents variation. Computer-"science" algorithmic C-C models: Turing-machine, finite-state-models/automata, are identified as early-days once-workable but NOW ONLY LIMITING CRUTCHES IMPEDING latter-days new-insights!!!
Nissen, Steven E; Dent-Acosta, Ricardo E; Rosenson, Robert S; Stroes, Erik; Sattar, Naveed; Preiss, David; Mancini, G B John; Ballantyne, Christie M; Catapano, Alberico; Gouni-Berthold, Ioanna; Stein, Evan A; Xue, Allen; Wasserman, Scott M; Scott, Rob; Thompson, Paul D
2016-03-01
Statins are the accepted standard for lowering low-density lipoprotein cholesterol (LDL-C). However, 5% to 10% of statin-treated patients report intolerance, mostly due to muscle-related adverse effects. Challenges exist to objective identification of statin-intolerant patients. Evolocumab is a monoclonal antibody that binds proprotein convertase subtilisin/kexin type 9 (PCSK9), resulting in marked LDL-C reduction. We report the design of Goal Achievement After Utilizing an Anti-PCSK9 Antibody in Statin-Intolerant Subjects 3 (GAUSS-3), a phase 3, multicenter, randomized, double-blind, ezetimibe-controlled study to compare effectiveness of 24 weeks of evolocumab 420 mg monthly vs ezetimibe 10 mg daily in hypercholesterolemic patients unable to tolerate an effective statin dose. The study incorporates a novel atorvastatin-controlled, double-blind, crossover phase to objectively identify statin intolerance. Eligible patients had LDL-C above the National Cholesterol Education Project Adult Treatment Panel III target level for the appropriate coronary heart disease risk category and were unable to tolerate ≥3 statins or 2 statins (one of which was atorvastatin ≤10 mg/d) or had a history of marked creatine kinase elevation accompanied by muscle symptoms while on 1 statin. This trial has 2 co-primary endpoints: mean percent change from baseline in LDL-C at weeks 22 and 24 and percent change from baseline in LDL-C at week 24. Key secondary efficacy endpoints include change from baseline in LDL-C, percent of patients attaining LDL-C <70 mg/dL (1.81 mmol/L), and percent change from baseline in total cholesterol, non-high-density lipoprotein cholesterol, and apolipoprotein B. Recruitment of 511 patients was completed on November 28, 2014.
NASA Astrophysics Data System (ADS)
Arai, Kohei; Liang, XingMing
2003-12-01
An estimation method for refractive index and size distribution of aerosols using measurements of direct and diffuse solar irradiance as well as the solar aureole by means of a modified simulated annealing is proposed. The proposed method is based on simulated annealing modified to acceralate a learning process by using a gradually decreasing oscillation function of temperature of annealing. By a using Gauss Seidel based atmospheric code, simulation data of direct and diffuse solar irradiance are generated together with estimated aureole measurements by means of an empirical method derived from experimental data. A comparison between the existing method proposed by P Romanov et.al. based on a linear inversion method and the proposed method is made. The results show double improvement of the estimation accuracy for both the aerosol size distribution and refractive index.
Product Distributions for Distributed Optimization. Chapter 1
NASA Technical Reports Server (NTRS)
Bieniawski, Stefan R.; Wolpert, David H.
2004-01-01
With connections to bounded rational game theory, information theory and statistical mechanics, Product Distribution (PD) theory provides a new framework for performing distributed optimization. Furthermore, PD theory extends and formalizes Collective Intelligence, thus connecting distributed optimization to distributed Reinforcement Learning (FU). This paper provides an overview of PD theory and details an algorithm for performing optimization derived from it. The approach is demonstrated on two unconstrained optimization problems, one with discrete variables and one with continuous variables. To highlight the connections between PD theory and distributed FU, the results are compared with those obtained using distributed reinforcement learning inspired optimization approaches. The inter-relationship of the techniques is discussed.
Distributive Education. Physical Distribution. Instructor's Curriculum.
ERIC Educational Resources Information Center
Missouri Univ., Columbia. Instructional Materials Lab.
This distributive education performance-based instructional unit is designed to help students understand the system of physical distribution and to act as an aid to guiding students in preparing for future careers in the transportation industry dealing with the retail, wholesale, and service occupations. (Physical distribution involves the moving…
High-Order Hyperbolic Residual-Distribution Schemes on Arbitrary Triangular Grids
NASA Technical Reports Server (NTRS)
Mazaheri, Alireza; Nishikawa, Hiroaki
2015-01-01
In this paper, we construct high-order hyperbolic residual-distribution schemes for general advection-diffusion problems on arbitrary triangular grids. We demonstrate that the second-order accuracy of the hyperbolic schemes can be greatly improved by requiring the scheme to preserve exact quadratic solutions. We also show that the improved second-order scheme can be easily extended to third-order by further requiring the exactness for cubic solutions. We construct these schemes based on the LDA and the SUPG methodology formulated in the framework of the residual-distribution method. For both second- and third-order-schemes, we construct a fully implicit solver by the exact residual Jacobian of the second-order scheme, and demonstrate rapid convergence of 10-15 iterations to reduce the residuals by 10 orders of magnitude. We demonstrate also that these schemes can be constructed based on a separate treatment of the advective and diffusive terms, which paves the way for the construction of hyperbolic residual-distribution schemes for the compressible Navier-Stokes equations. Numerical results show that these schemes produce exceptionally accurate and smooth solution gradients on highly skewed and anisotropic triangular grids, including curved boundary problems, using linear elements. We also present Fourier analysis performed on the constructed linear system and show that an under-relaxation parameter is needed for stabilization of Gauss-Seidel relaxation.
Enhancement display of veins distribution based on binocular vision and image fusion technology
NASA Astrophysics Data System (ADS)
Liu, Peng; Di, Si; Jin, Jian; Bai, Liping
2014-11-01
The capture and display of veins distribution is an important issue for some applications, such as medical diagnosis and identification. Therefore, it has become a popular topic in the field of biomedical imaging. Usually, people capture the veins distribution by infrared imaging, but the display result is similar with that of a gray picture and the color and details of skin cannot be remained. To some degree, it is unreal for doctors. In this paper, we develop a binocular vision system to carry out the enhancement display of veins under the condition of keeping actual skin color. The binocular system is consisted of two adjacent cameras. A visible band filter and an infrared band filter are placed in front of the two lenses, respectively. Therefore, the pictures of visible band and infrared band can be captured simultaneously. After that, a new fusion process is applied to the two pictures, which related to histogram mapping, principal component analysis (PCA) and modified bilateral filter fusion. The final results show that both the veins distribution and the actual skin color of the back of the hand can be clearly displayed. Besides, correlation coefficient, average gradient and average distortion are selected as the parameters to evaluate the image quality. By comparing the parameters, it is evident that our novel fusion method is prior to some popular fusion methods such as Gauss filter fusion, Intensity-hue-saturation (HIS) fusion and bilateral filter fusion.
NASA Astrophysics Data System (ADS)
Schäfer, Bernd; Flöter, Bernhard; Mann, Klaus; Keitel, Barbara; Plönjes, Elke; Tiedtke, Kai
2011-06-01
The wavefront as well as beam parameters of the free electron laser FLASH emitting in the EUV spectral range were determined from wavefront measurements using self supporting Hartmann sensors. The devices were applied for alignment of the ellipsoidal focusing mirror at Beamline 2 (BL2), reducing the rms wavefront aberrations by more than a factor of 3. Beam quality M² and other beam parameters were evaluated from wavefront and intensity data delivered by the Hartmann sensor. Furthermore, 100 two-dimensional single pulse intensity distributions were recorded at each of 32 axial positions, spaced app. +/-2 Rayleigh lengths around the waist of the optimized FEL beam with a magnifying EUV sensitized CCD camera. From these beam profile data the Wigner distribution function was reconstructed on two dimensional orthogonal subspaces. For separable beams this yields the complete Wigner distribution and gives comprehensive and high-resolution information on the propagation characteristics, including wavefront, mode content and spatial coherence. The wavefront of the optimized beam evaluated at waist position was in the order of λ?4 peak valley, whereas a significant contribution of uncorrelated higher order Hermite-Gauss modes and a global degree of coherence of 0.12 can be detected, leading to a substantial increase of the M² factor, which was determined to ~ 4.2 and ~ 3 in the horizontal and vertical direction, respectively. The obtained results are compared to the Hartmann experiments.
Likelihood Estimation for Generalized Mixed Exponential Distributions.
1984-07-01
specified beforehand. 23 S. . ... .- ~T§777 ~"~~ 7’.7 . -- ." F0 * 0 REFERENCES L. Armijo, "Minimization of Functions Having Lipschitz Continuous...and F. W. Fairman, Exponential Approximation via a Closed Form Gauss-Newton Method, IEEE Trans. Circuit Theory, CT-20 (1973), pp. 361-369. A. R...engineering disciplines of Chemical, Civil, Electrical , and Mechanical and Aerospace to newer, more specialized fields of Biomedical Engineering
A Semi-Automatic "Gauss" Program.
ERIC Educational Resources Information Center
Ehrlich, Amos
1988-01-01
The suggested program is designed for mathematics teachers. It concerns the solution of systems of linear equations, but it does not complete the job on its own. The user is the solver while the computer is merely a computing assistant. (MNS)
Gram-Schmidt Orthogonalization by Gauss Elimination.
ERIC Educational Resources Information Center
Pursell, Lyle; Trimble, S. Y.
1991-01-01
Described is the hand-calculation method for the orthogonalization of a given set of vectors through the integration of Gaussian elimination with existing algorithms. Although not numerically preferable, this method adds increased precision as well as organization to the solution process. (JJK)
2016-01-01
The Annual Coal Distribution Report (ACDR) provides detailed information on domestic coal distribution by origin state, destination state, consumer category, and method of transportation. Also provided is a summary of foreign coal distribution by coal-producing state. All data for the report year are final and this report supersedes all data in the quarterly distribution reports.
NASA Technical Reports Server (NTRS)
Soula, Serge; Chauzy, Serge
1991-01-01
During the Florida 89 experiment at Kennedy Space Center, a new system was used in order to obtain the vertical distribution of the electric field underneath thunderstorms. It consists of a standard shutter field mill at ground level and five other field sensors suspended from a cable fastened to a tethered balloon located at an altitude of about 1000 meters. It also includes a reception station for telemetered information transmitted by sensors, a processing system in order to store data, and real time display on a screen to show the simultaneous field variations at each level along with the instantaneous electric field profile. The first results obtained show the great importance of the electric field vertical distribution. The field detected at a height of 600m reaches 65 kV/m while that at the surface does not exceed 5 kV/m. The field intensity in altitude is a better criterion for determining the right moment to launch a rocket devoted to flash triggering. Using Gauss's law, the simultaneous field variations at several levels are used in order to evaluate charge densities. Average values close to 1nC.m(-3) are calculated in layers up to 600 m. The calculation of different average charge densities leads to the characterization of the layer between cloud and ground just before the leader propagation in the case of cloud to ground flash.
The effect of a dust size distribution on electrostatic sheaths in unmagnetized dusty plasmas
Benlemdjaldi, D.; Tahraoui, A.; Hugon, R.; Bougdira, J.
2013-04-15
In this work, the structure of plasma sheaths in presence of dust particles with different sizes is investigated numerically in a multifluid framework, where the dust size distribution is modeled by Gauss' law. For this, we have established a 1D, stationary, unmagnetized, and weakly collisional electronegative dusty plasma sheath model. The electrons and negative ions are considered in a local thermodynamic equilibrium, therefore, described by a Boltzmann distribution. On the other hand, positive ions and dust grains are described by fluid equations. The charging process is described by the orbit motion limited model. It is shown that taking into account dust grains with different sizes reduces considerably the sheath thickness. The behavior of dust surface potential is not affected, but the dust charge number is reduced, as well as the electrostatic force. It results in a decrease of layered structure. The presence of negative ions makes the structure of the electrostatic potential more oscillatory. The other physical parameters are also analyzed and discussed.
A Residuals Approach to Filtering, Smoothing and Identification for Static Distributed Systems
NASA Technical Reports Server (NTRS)
Rodriguez, G.
1985-01-01
An approach for state estimation and identification of spatially distributed parameters embedded in static distributed (elliptic) system models is advanced. The method of maximum likelihood is used to find parameter values that maximize a likelihood functional for the system model, or equivalently, that minimize the negative logarithm of this functional. To find the minimum, a Newton-Raphson search is conducted that from an initial estimate generates a convergent sequence of parameter estimates. For simplicity, a Gauss-Markov approach is used to approximate the Hessian in terms of products of first derivatives. The gradient and approximate Hessian are computed by first arranging the negative log likelihood functional into a form based on the square root factorization of the predicted covariance of the measurement process. The resulting data processing approach, referred to here by the new term of predicted data covariance square root filtering, makes the gradient and approximate Hessian calculations very simple. A closely related set of state estimates is also produced by the maximum likelihood method: smoothed estimates that are optimal in a conditional mean sense and filtered estimates that emerge from the predicted data covariance square root filter.
Fujii, K. Atsumi, S.; Watanabe, S.; Shikama, T.; Hasuo, M.; Goto, M.; Morita, S.
2014-02-15
We report development of a high dynamic range spectroscopic system comprising a spectrometer with 30% throughput and a camera with a low-noise fast-readout complementary metal-oxide semiconductor sensor. The system achieves a 10{sup 6} dynamic range (∼20 bit resolution) and an instrumental function approximated by a Voigt profile with Gauss and Lorentz widths of 31 and 0.31 pm, respectively, for 656 nm light. The application of the system for line profile observations of the Balmer-α emissions from high temperature plasmas generated in the Large Helical Device is also presented. In the observed line profiles, emissions are detected in far wings more than 1.0 nm away from the line center, equivalent to neutral hydrogen atom kinetic energies above 1 keV. We evaluate atom density distributions in the core plasma by analyzing the line profiles.
Exponentiated power Lindley distribution.
Ashour, Samir K; Eltehiwy, Mahmoud A
2015-11-01
A new generalization of the Lindley distribution is recently proposed by Ghitany et al. [1], called as the power Lindley distribution. Another generalization of the Lindley distribution was introduced by Nadarajah et al. [2], named as the generalized Lindley distribution. This paper proposes a more generalization of the Lindley distribution which generalizes the two. We refer to this new generalization as the exponentiated power Lindley distribution. The new distribution is important since it contains as special sub-models some widely well-known distributions in addition to the above two models, such as the Lindley distribution among many others. It also provides more flexibility to analyze complex real data sets. We study some statistical properties for the new distribution. We discuss maximum likelihood estimation of the distribution parameters. Least square estimation is used to evaluate the parameters. Three algorithms are proposed for generating random data from the proposed distribution. An application of the model to a real data set is analyzed using the new distribution, which shows that the exponentiated power Lindley distribution can be used quite effectively in analyzing real lifetime data.
Exponentiated power Lindley distribution
Ashour, Samir K.; Eltehiwy, Mahmoud A.
2014-01-01
A new generalization of the Lindley distribution is recently proposed by Ghitany et al. [1], called as the power Lindley distribution. Another generalization of the Lindley distribution was introduced by Nadarajah et al. [2], named as the generalized Lindley distribution. This paper proposes a more generalization of the Lindley distribution which generalizes the two. We refer to this new generalization as the exponentiated power Lindley distribution. The new distribution is important since it contains as special sub-models some widely well-known distributions in addition to the above two models, such as the Lindley distribution among many others. It also provides more flexibility to analyze complex real data sets. We study some statistical properties for the new distribution. We discuss maximum likelihood estimation of the distribution parameters. Least square estimation is used to evaluate the parameters. Three algorithms are proposed for generating random data from the proposed distribution. An application of the model to a real data set is analyzed using the new distribution, which shows that the exponentiated power Lindley distribution can be used quite effectively in analyzing real lifetime data. PMID:26644927
Cumulative Poisson Distribution Program
NASA Technical Reports Server (NTRS)
Bowerman, Paul N.; Scheuer, Ernest M.; Nolty, Robert
1990-01-01
Overflow and underflow in sums prevented. Cumulative Poisson Distribution Program, CUMPOIS, one of two computer programs that make calculations involving cumulative Poisson distributions. Both programs, CUMPOIS (NPO-17714) and NEWTPOIS (NPO-17715), used independently of one another. CUMPOIS determines cumulative Poisson distribution, used to evaluate cumulative distribution function (cdf) for gamma distributions with integer shape parameters and cdf for X (sup2) distributions with even degrees of freedom. Used by statisticians and others concerned with probabilities of independent events occurring over specific units of time, area, or volume. Written in C.
Drinking Water Distribution Systems
Learn about an overview of drinking water distribution systems, the factors that degrade water quality in the distribution system, assessments of risk, future research about these risks, and how to reduce cross-connection control risk.
Chapter on Distributed Computing
1989-02-01
MASSACHUSETTS LABORATORY FOR INSTITUTE OF COMPUTER SCIENCE TECHNOLOGY ("D / o O MIT/LCS/TM-384 CHAPTER ON DISTRIBUTED COMPUTING Leslie Lamport Nancy...22217 ELEMENT NO. NO. NO. ACCESSION NO. 11. TITLE (Miude Secuwity Ciaifiation) Chapter on Distributed Computing 12. PERSONAL AUTHOR(S) Lamport... distributed computing , distributed systems models, dis- tributed algorithms, message-passing, shared variables, 19. UBSTRACT (Continue on reverse if
A Truncated Cauchy Distribution
ERIC Educational Resources Information Center
Nadarajah, Saralees; Kotz, Samuel
2006-01-01
A truncated version of the Cauchy distribution is introduced. Unlike the Cauchy distribution, this possesses finite moments of all orders and could therefore be a better model for certain practical situations. One such situation in finance is discussed. Explicit expressions for the moments of the truncated distribution are also derived.
Distributed Learning Metadata Standards
ERIC Educational Resources Information Center
McClelland, Marilyn
2004-01-01
Significant economies can be achieved in distributed learning systems architected with a focus on interoperability and reuse. The key building blocks of an efficient distributed learning architecture are the use of standards and XML technologies. The goal of plug and play capability among various components of a distributed learning system…
Verification of LHS distributions.
Swiler, Laura Painton
2006-04-01
This document provides verification test results for normal, lognormal, and uniform distributions that are used in Sandia's Latin Hypercube Sampling (LHS) software. The purpose of this testing is to verify that the sample values being generated in LHS are distributed according to the desired distribution types. The testing of distribution correctness is done by examining summary statistics, graphical comparisons using quantile-quantile plots, and format statistical tests such as the Chisquare test, the Kolmogorov-Smirnov test, and the Anderson-Darling test. The overall results from the testing indicate that the generation of normal, lognormal, and uniform distributions in LHS is acceptable.
FRIB cryogenic distribution system
Ganni, Venkatarao; Dixon, Kelly D.; Laverdure, Nathaniel A.; Knudsen, Peter N.; Arenius, Dana M.; Barrios, Matthew N.; Jones, S.; Johnson, M.; Casagrande, Fabio
2014-01-01
The Michigan State University Facility for Rare Isotope Beams (MSU-FRIB) helium distribution system has been revised to include bayonet/warm valve type disconnects between each cryomodule and the transfer line distribution system, similar to the Thomas Jefferson National Accelerator Facility (JLab) and the Spallation Neutron Source (SNS) cryogenic distribution systems. The heat loads at various temperature levels and some of the features in the design of the distribution system are outlined. The present status, the plans for fabrication, and the procurement approach for the helium distribution system are also included.
Distributions in Spherical Coordinates with Applications to Classical Electrodynamics
ERIC Educational Resources Information Center
Gsponer, Andre
2007-01-01
A general and rigorous method to deal with singularities at the origin of a polar coordinate system is presented. Its power derives from a clear distinction between the radial distance and the radial coordinate variable, which makes that all delta functions and their derivatives are automatically generated, and ensures that the Gauss theorem is…
Geometry of escort distributions
NASA Astrophysics Data System (ADS)
Abe, Sumiyoshi
2003-09-01
Given an original distribution, its statistical and probabilistic attributes may be scanned using the associated escort distribution introduced by Beck and Schlögl and employed in the formulation of nonextensive statistical mechanics. Here, the geometric structure of the one-parameter family of the escort distributions is studied based on the Kullback-Leibler divergence and the relevant Fisher metric. It is shown that the Fisher metric is given in terms of the generalized bit variance, which measures fluctuations of the crowding index of a multifractal. The Cramér-Rao inequality leads to a fundamental limit for the precision of the statistical estimate of the order of the escort distribution. We also show quantitatively that it is inappropriate to use the original distribution instead of the escort distribution for calculating the expectation values of physical quantities in nonextensive statistical mechanics.
Bivariate extreme value distributions
NASA Technical Reports Server (NTRS)
Elshamy, M.
1992-01-01
In certain engineering applications, such as those occurring in the analyses of ascent structural loads for the Space Transportation System (STS), some of the load variables have a lower bound of zero. Thus, the need for practical models of bivariate extreme value probability distribution functions with lower limits was identified. We discuss the Gumbel models and present practical forms of bivariate extreme probability distributions of Weibull and Frechet types with two parameters. Bivariate extreme value probability distribution functions can be expressed in terms of the marginal extremel distributions and a 'dependence' function subject to certain analytical conditions. Properties of such bivariate extreme distributions, sums and differences of paired extremals, as well as the corresponding forms of conditional distributions, are discussed. Practical estimation techniques are also given.
Gas-liquid Phase Distribution and Void Fraction Measurements Using the MRI
NASA Technical Reports Server (NTRS)
Daidzic, N. E.; Schmidt, E.; Hasan, M. M.; Altobelli, S.
2004-01-01
We used a permanent-magnet MRI system to estimate the integral and spatially- and/or temporally-resolved void-fraction distributions and flow patterns in gas-liquid two-phase flows. Air was introduced at the bottom of the stagnant liquid column using an accurate and programmable syringe pump. Air flow rates were varied between 1 and 200 ml/min. The cylindrical non-conducting test tube in which two-phase flow was measured was placed in a 2.67 kGauss MRI with MRT spectrometer/imager. Roughly linear relationship has been obtained for the integral void-fraction, obtained by volume-averaging of the spatially-resolved signals, and the air flow rate in upward direction. The time-averaged spatially-resolved void fraction has also been obtained for the quasi-steady flow of air in a stagnant liquid column. No great accuracy is claimed as this was an exploratory proof-of-concept type of experiment. Preliminary results show that MRI a non-invasive and non-intrusive experimental technique can indeed provide a wealth of different qualitative and quantitative data and is especially well suited for averaged transport processes in adiabatic and diabatic multi-phase and/or multi-component flows.
Distributed Decision Making Environment.
1982-12-01
of a DDM Testbed 69 4.3.2 Design of Experiments on Distributed 71 Mission Planning 5. AUTOMATED DECISION MAKING TECHNIQUES 76 5.1 SEQUENTIAL...missile assignment scenario. A sequential assignment algorithm has been fully computer implemented and preliminary experiments with it have been run. An...implementation of a distributed version in which several humans can participate in experiments simultaneously. The distributed version will allow L1 us to
Distributed generation systems model
Barklund, C.R.
1994-12-31
A slide presentation is given on a distributed generation systems model developed at the Idaho National Engineering Laboratory, and its application to a situation within the Idaho Power Company`s service territory. The objectives of the work were to develop a screening model for distributed generation alternatives, to develop a better understanding of distributed generation as a utility resource, and to further INEL`s understanding of utility concerns in implementing technological change.
Cooling water distribution system
Orr, Richard
1994-01-01
A passive containment cooling system for a nuclear reactor containment vessel. Disclosed is a cooling water distribution system for introducing cooling water by gravity uniformly over the outer surface of a steel containment vessel using an interconnected series of radial guide elements, a plurality of circumferential collector elements and collector boxes to collect and feed the cooling water into distribution channels extending along the curved surface of the steel containment vessel. The cooling water is uniformly distributed over the curved surface by a plurality of weirs in the distribution channels.
Statistical distribution sampling
NASA Technical Reports Server (NTRS)
Johnson, E. S.
1975-01-01
Determining the distribution of statistics by sampling was investigated. Characteristic functions, the quadratic regression problem, and the differential equations for the characteristic functions are analyzed.
Advanced Distribution Management System
NASA Astrophysics Data System (ADS)
Avazov, Artur R.; Sobinova, Liubov A.
2016-02-01
This article describes the advisability of using advanced distribution management systems in the electricity distribution networks area and considers premises of implementing ADMS within the Smart Grid era. Also, it gives the big picture of ADMS and discusses the ADMS advantages and functionalities.
Distribution and Marketing Syllabus.
ERIC Educational Resources Information Center
New York State Education Dept., Albany. Bureau of Secondary Curriculum Development.
The distributive education program for grades 7 to 12 is organized around three career education phases: the career education phase (grades 7-10), the distributive phase (grade 11), and the competency cluster phase (grade 12). The grade 11 syllabus provides a six-page introduction which covers scheduling, cooperative work experience, the school…
Wigner distributions for qudits
Chaturvedi, S.
2006-11-15
Two new approaches to the problem of setting up Wigner distributions for finite level quantum systems are proposed. Both arise by looking at the structure of the familiar Wigner distribution for Cartesian quantum mechanics from different perspectives. The two approaches have one common feature--each involves a 'square root' operation though of very different kinds.
Metrics for Food Distribution.
ERIC Educational Resources Information Center
Cooper, Gloria S., Ed.; Magisos, Joel H., Ed.
Designed to meet the job-related metric measurement needs of students interested in food distribution, this instructional package is one of five for the marketing and distribution cluster, part of a set of 55 packages for metric instruction in different occupations. The package is intended for students who already know the occupational…
Groundwater and Distribution Workbook.
ERIC Educational Resources Information Center
Ekman, John E.
Presented is a student manual designed for the Wisconsin Vocational, Technical and Adult Education Groundwater and Distribution Training Course. This program introduces waterworks operators-in-training to basic skills and knowledge required for the operation of a groundwater distribution waterworks facility. Arranged according to the general order…
Parallel and Distributed Computing.
1986-12-12
program was devoted to parallel and distributed computing . Support for this part of the program was obtained from the present Army contract and a...Umesh Vazirani. A workshop on parallel and distributed computing was held from May 19 to May 23, 1986 and drew 141 participants. Keywords: Mathematical programming; Protocols; Randomized algorithms. (Author)
Jiang, Yazhou; Liu, Chen -Ching; Xu, Yin
2016-04-19
The increasing importance of system reliability and resilience is changing the way distribution systems are planned and operated. To achieve a distribution system self-healing against power outages, emerging technologies and devices, such as remote-controlled switches (RCSs) and smart meters, are being deployed. The higher level of automation is transforming traditional distribution systems into the smart distribution systems (SDSs) of the future. The availability of data and remote control capability in SDSs provides distribution operators with an opportunity to optimize system operation and control. In this paper, the development of SDSs and resulting benefits of enhanced system capabilities are discussed. A comprehensive survey is conducted on the state-of-the-art applications of RCSs and smart meters in SDSs. Specifically, a new method, called Temporal Causal Diagram (TCD), is used to incorporate outage notifications from smart meters for enhanced outage management. To fully utilize the fast operation of RCSs, the spanning tree search algorithm is used to develop service restoration strategies. Optimal placement of RCSs and the resulting enhancement of system reliability are discussed. Distribution system resilience with respect to extreme events is presented. Furthermore, test cases are used to demonstrate the benefit of SDSs. Active management of distributed generators (DGs) is introduced. Future research in a smart distribution environment is proposed.
Software distribution using xnetlib
Dongarra, J.J. |; Rowan, T.H.; Wade, R.C.
1993-06-01
Xnetlib is a new tool for software distribution. Whereas its predecessor netlib uses e-mail as the user interface to its large collection of public-domain mathematical software, xnetlib uses an X Window interface and socket-based communication. Xnetlib makes it easy to search through a large distributed collection of software and to retrieve requested software in seconds.
Univariate Probability Distributions
ERIC Educational Resources Information Center
Leemis, Lawrence M.; Luckett, Daniel J.; Powell, Austin G.; Vermeer, Peter E.
2012-01-01
We describe a web-based interactive graphic that can be used as a resource in introductory classes in mathematical statistics. This interactive graphic presents 76 common univariate distributions and gives details on (a) various features of the distribution such as the functional form of the probability density function and cumulative distribution…
Jiang, Yazhou; Liu, Chen -Ching; Xu, Yin
2016-04-19
The increasing importance of system reliability and resilience is changing the way distribution systems are planned and operated. To achieve a distribution system self-healing against power outages, emerging technologies and devices, such as remote-controlled switches (RCSs) and smart meters, are being deployed. The higher level of automation is transforming traditional distribution systems into the smart distribution systems (SDSs) of the future. The availability of data and remote control capability in SDSs provides distribution operators with an opportunity to optimize system operation and control. In this paper, the development of SDSs and resulting benefits of enhanced system capabilities are discussed. Amore » comprehensive survey is conducted on the state-of-the-art applications of RCSs and smart meters in SDSs. Specifically, a new method, called Temporal Causal Diagram (TCD), is used to incorporate outage notifications from smart meters for enhanced outage management. To fully utilize the fast operation of RCSs, the spanning tree search algorithm is used to develop service restoration strategies. Optimal placement of RCSs and the resulting enhancement of system reliability are discussed. Distribution system resilience with respect to extreme events is presented. Furthermore, test cases are used to demonstrate the benefit of SDSs. Active management of distributed generators (DGs) is introduced. Future research in a smart distribution environment is proposed.« less
The Distributed Criterion Design
ERIC Educational Resources Information Center
McDougall, Dennis
2006-01-01
This article describes and illustrates a novel form of the changing criterion design called the distributed criterion design, which represents perhaps the first advance in the changing criterion design in four decades. The distributed criterion design incorporates elements of the multiple baseline and A-B-A-B designs and is well suited to applied…
ERIC Educational Resources Information Center
Wild, Chris
2006-01-01
This paper is a personal exploration of where the ideas of "distribution" that we are trying to develop in students come from and are leading to, how they fit together, and where they are important and why. We need to have such considerations in the back of our minds when designing learning experiences. The notion of "distribution" as a lens…
A non-invasive Hall current distribution measurement system for Hall Effect thrusters
NASA Astrophysics Data System (ADS)
Mullins, Carl Raymond
A direct, accurate method to measure thrust produced by a Hall Effect thruster on orbit does not currently exist. The ability to calculate produced thrust will enable timely and precise maneuvering of spacecraft---a capability particularly important to satellite formation flying. The means to determine thrust directly is achievable by remotely measuring the magnetic field of the thruster and solving the inverse magnetostatic problem for the Hall current density distribution. For this thesis, the magnetic field was measured by employing an array of eight tunneling magnetoresistive (TMR) sensors capable of milligauss sensitivity when placed in a high background field. The array was positioned outside the channel of a 1.5 kW Colorado State University Hall thruster equipped with a center-mounted electride cathode. In this location, the static magnetic field is approximately 30 Gauss, which is within the linear operating range of the TMR sensors. Furthermore, the induced field at this distance is greater than tens of milligauss, which is within the sensitivity range of the TMR sensors. Due to the nature of the inverse problem, the induced-field measurements do not provide the Hall current density by a simple inversion; however, a Tikhonov regularization of the induced field along with a non-negativity constraint and a zero boundary condition provides current density distributions. Our system measures the sensor outputs at 2 MHz allowing the determination of the Hall current density distribution as a function of time. These data are shown in contour plots in sequential frames. The measured ratios between the average Hall current and the discharge current ranged from 0.1 to 10 over a range of operating conditions from 1.3 kW to 2.2 kW. The temporal inverse solution at 2.0 kW exhibited a breathing mode of 37 kHz, which was in agreement with temporal measurements of the discharge current.
NASA Technical Reports Server (NTRS)
Goswami, Kumar K.; Iyer, Ravishankar K.
1990-01-01
Discrete event-driven simulation makes it possible to model a computer system in detail. However, such simulation models can require a significant time to execute. This is especially true when modeling large parallel or distributed systems containing many processors and a complex communication network. One solution is to distribute the simulation over several processors. If enough parallelism is achieved, large simulation models can be efficiently executed. This study proposes a distributed simulator called DSIM which can run on various architectures. A simulated test environment is used to verify and characterize the performance of DSIM. The results of the experiments indicate that speedup is application-dependent and, in DSIM's case, is also dependent on how the simulation model is distributed among the processors. Furthermore, the experiments reveal that the communication overhead of ethernet-based distributed systems makes it difficult to achieve reasonable speedup unless the simulation model is computation bound.
Kuss, Oliver; Hoyer, Annika; Solms, Alexander
2014-01-15
There are still challenges when meta-analyzing data from studies on diagnostic accuracy. This is mainly due to the bivariate nature of the response where information on sensitivity and specificity must be summarized while accounting for their correlation within a single trial. In this paper, we propose a new statistical model for the meta-analysis for diagnostic accuracy studies. This model uses beta-binomial distributions for the marginal numbers of true positives and true negatives and links these margins by a bivariate copula distribution. The new model comes with all the features of the current standard model, a bivariate logistic regression model with random effects, but has the additional advantages of a closed likelihood function and a larger flexibility for the correlation structure of sensitivity and specificity. In a simulation study, which compares three copula models and two implementations of the standard model, the Plackett and the Gauss copula do rarely perform worse but frequently better than the standard model. We use an example from a meta-analysis to judge the diagnostic accuracy of telomerase (a urinary tumor marker) for the diagnosis of primary bladder cancer for illustration.
Distributed Propulsion Vehicles
NASA Technical Reports Server (NTRS)
Kim, Hyun Dae
2010-01-01
Since the introduction of large jet-powered transport aircraft, the majority of these vehicles have been designed by placing thrust-generating engines either under the wings or on the fuselage to minimize aerodynamic interactions on the vehicle operation. However, advances in computational and experimental tools along with new technologies in materials, structures, and aircraft controls, etc. are enabling a high degree of integration of the airframe and propulsion system in aircraft design. The National Aeronautics and Space Administration (NASA) has been investigating a number of revolutionary distributed propulsion vehicle concepts to increase aircraft performance. The concept of distributed propulsion is to fully integrate a propulsion system within an airframe such that the aircraft takes full synergistic benefits of coupling of airframe aerodynamics and the propulsion thrust stream by distributing thrust using many propulsors on the airframe. Some of the concepts are based on the use of distributed jet flaps, distributed small multiple engines, gas-driven multi-fans, mechanically driven multifans, cross-flow fans, and electric fans driven by turboelectric generators. This paper describes some early concepts of the distributed propulsion vehicles and the current turboelectric distributed propulsion (TeDP) vehicle concepts being studied under the NASA s Subsonic Fixed Wing (SFW) Project to drastically reduce aircraft-related fuel burn, emissions, and noise by the year 2030 to 2035.
Long distance entanglement distribution
NASA Astrophysics Data System (ADS)
Broadfoot, Stuart Graham
Developments in the interdisciplinary field of quantum information open up previously impossible abilities in the realms of information processing and communication. Quantum entanglement has emerged as one property of quantum systems that acts as a resource for quantum information processing and, in particular, enables teleportation and secure cryptography. Therefore, the creation of entangled resources is of key importance for the application of these technologies. Despite a great deal of research the efficient creation of entanglement over long distances is limited by inevitable noise. This problem can be overcome by creating entanglement between nodes in a network and then performing operations to distribute the entanglement over a long distance. This thesis contributes to the field of entanglement distribution within such quantum networks. Entanglement distribution has been extensively studied for one-dimensional networks resulting in "quantum repeater" protocols. However, little work has been done on higher dimensional networks. In these networks a fundamentally different scaling, called "long distance entanglement distribution", can appear between the resources and the distance separating the systems to be entangled. I reveal protocols that enable long distance entanglement distribution for quantum networks composed of mixed state and give a few limitations to the capabilities of entanglement distribution. To aid in the implementation of all entanglement distribution protocols I finish by introducing a new system, composed of an optical nanofibre coupled to a carbon nanotube, that may enable new forms of photo-detectors and quantum memories.
NASA Astrophysics Data System (ADS)
Decker, F.-J.
1995-05-01
The beam is often represented only by its position (mean) and the width (rms=root mean squared) of its distribution. To achieve these beam parameters in a noisy condition with high backgrounds, a Gaussian distribution with offset (4 parameters) is fitted to the measured beam distribution. This gives a very robust answer and is not very sensitive to background subtraction techniques. To get higher moments of the distribution, like skew or kurtosis, a fitting function with one or two more parameters is desired which would model the higher moments. In this paper we will concentrate on an Asymmetric Gaussian and a Super Gaussian function that will give something like the skew and the kurtosis of the distribution. This information is used to quantify special beam distribution. Some are unwanted like beam tails (skew) from transverse wakefields, higher order dispersive aberrations or potential well distortion in a damping ring. A negative kurtosis of a beam distribution describes a more rectangular, compact shape like with an over-compressed beam in z or a closed to double-horned energy distribution, while a positive kurtosis looks more like a ``Christmas tree'' and can quantify a beam mismatch after filamentation. Besides the advantages of the quantification, there are some distributions which need a further investigation like long flat tails which create background particles in a detector. In particle simulations on the other hand a simple rms number might grossly overestimate the effective size (e.g. for producing luminosity) due to a few particles which are far away from the core. This can reduce the practical gain of a big theoretical improvement in the beam size.
NASA Astrophysics Data System (ADS)
Decker, F. J.
1994-09-01
The beam is often represented only by its position (mean) and the width (rms = root mean squared) of its distribution. To achieve these beam parameters in a noisy condition with high backgrounds, a Gaussian distribution with offset (4 parameters) is fitted to the measured beam distribution. This gives a very robust answer and is not very sensitive to background subtraction techniques. To get higher moments of the distribution, like skew or kurtosis, a fitting function with one or two more parameters is desired which would model the higher moments. In this paper we will concentrate on an Asymmetric Gaussian and a Super Gaussian function that will give something like the skew and the kurtosis of the distribution. This information is used to quantify special beam distribution. Some are unwanted like beam tails (skew) from transverse wakefields, higher order dispersive aberrations or potential well distortion in a damping ring. A negative kurtosis of a beam distribution describes a more rectangular, compact shape like with an over-compressed beam in z or a closed to double-homed energy distribution, while a positive kurtosis looks more like a 'Christmas tree' and can quantify a beam mismatch after filamentation. Besides the advantages of the quantification, there are some distributions which need a further investigation like long flat tails which create background particles in a detector. In particle simulations on the other hand a simple rms number might grossly overestimate the effective size (e.g. for producing luminosity) due to a few particles which are far away from the core. This can reduce the practical gain of a big theoretical improvement in the beam size.
Decker, F.J.
1994-09-01
The beam is often represented only by its position (mean) and the width (rms = root mean squared) of its distribution. To achieve these beam parameters in a noisy condition with high backgrounds, a Gaussian distribution with offset (4 parmeters) is fitted to the measured beam distribution. This gives a very robust answer and is not very sensitive to background subtraction techniques. To get higher moments of the distribution, like skew or kurtosis, a fitting function with one or two more parameters is desired which would model the higher moments. In this paper we will concentrate on an Asymmetric Gaussian and a Super Gaussian function that will give something like the skew and the kurtosis of the distribution. This information is used to quantify special beam distribution. Some are unwanted like beam tails (skew) from transverse wakefields, higher order dispersive aberrations or potential well distortion in a damping ring. A negative kurtosis of a beam distribution describes a more rectangular, compact shape like with an over-compressed beam in z or a closed to double-homed energy distribution, while a positive kurtosis looks more like a ``Christmas tree`` and can quantify a beam mismatch after filamentation. Besides the advantages of the quantification, there are some distributions which need a further investigation like long flat tails which create background particles in a detector. In particle simulations on the other hand a simple rms number might grossly overestimate the effective size (e.g. for producing luminosity) due to a few particles which are far away from the core. This can reduce the practical gain of a big theoretical improvement in the beam size.
NASA Astrophysics Data System (ADS)
Williams, Mike; Egede, Ulrik; Paterson, Stuart; LHCb Collaboration
2011-12-01
The distributed analysis experience to date at LHCb has been positive: job success rates are high and wait times for high-priority jobs are low. LHCb users access the grid using the GANGA job-management package, while the LHCb virtual organization manages its resources using the DIRAC package. This clear division of labor has benefitted LHCb and its users greatly; it is a major reason why distributed analysis at LHCb has been so successful. The newly formed LHCb distributed analysis support team has also proved to be a success.
Technologies for Distributed Defense
Seiders, Barbara AB; Rybka, Anthony J.
2002-07-01
For Americans, the nature of warfare changed on September 11, 2001. Our national security henceforth will require distributed defense. One extreme of distributed defense is represented by fully deployed military troops responding to a threat from a hostile nation state. At the other extreme is a country of "citizen soldiers," with families and communities securing their common defense through heightened awareness, engagement as good neighbors, and local support of and cooperation with local law enforcement, emergency and health care providers. Technologies - for information exploitation, biological agent detection, health care surveillance, and security - will be critical to ensuring success in distributed defense.
Technologies for distributed defense
NASA Astrophysics Data System (ADS)
Seiders, Barbara; Rybka, Anthony
2002-07-01
For Americans, the nature of warfare changed on September 11, 2001. Our national security henceforth will require distributed defense. One extreme of distributed defense is represented by fully deployed military troops responding to a threat from a hostile nation state. At the other extreme is a country of 'citizen soldiers', with families and communities securing their common defense through heightened awareness, engagement as good neighbors, and local support of and cooperation with local law enforcement, emergency and health care providers. Technologies - for information exploitation, biological agent detection, health care surveillance, and security - will be critical to ensuring success in distributed defense.
DOLIB: Distributed object library
D`Azevedo, E.F.; Romine, C.H.
1995-12-01
DOLIB (Distributed Object Library) emulates global shared memory in distributed memory environments intended for scientific applications. Access to global arrays is through explicit calls to gather and scatter. Use of DOLIB does not rely on language extension, compiler or operating system supports. Shared memory provided by DOLIB was also used by DONIO (Distributed Network I/O Library) as large disk caches that gave improvements of 15 to 30 fold on the Intel Paragon. DOLIB shared memory simplifies the parallelization of the CHAMMP Semi-Lagrangian Transport (SLT) code that has particle tracking as the kernel computation.
NASA Astrophysics Data System (ADS)
Kepler, S. O.; Koester, D.; Romero, A. D.; Ourique, G.; Pelisoli, I.
2017-03-01
We present the mass distribution for all S/N ≥ 15 DA white dwarfs detected in the Sloan Digital Sky Survey up to Data Release 12 in 2015, fitted with Koester models for ML2/α=0.8 (Teff≥ 10000 K), and for DBs with S/N ≥ 10, fitted with ML2/α=1.25, for Teff >16 000 K. These mass distributions are for logg≥6.5 stars, i.e., excluding the Extremely Low Mass white dwarfs. We also present the mass distributions corrected by volume with the 1/Vmax approach, for stars brighter than g=19. Both distributions have a maximum at M=0.624 M ⊙ but very distinct shapes.
Estimating Bias Error Distributions
NASA Technical Reports Server (NTRS)
Liu, Tian-Shu; Finley, Tom D.
2001-01-01
This paper formulates the general methodology for estimating the bias error distribution of a device in a measuring domain from less accurate measurements when a minimal number of standard values (typically two values) are available. A new perspective is that the bias error distribution can be found as a solution of an intrinsic functional equation in a domain. Based on this theory, the scaling- and translation-based methods for determining the bias error distribution arc developed. These methods are virtually applicable to any device as long as the bias error distribution of the device can be sufficiently described by a power series (a polynomial) or a Fourier series in a domain. These methods have been validated through computational simulations and laboratory calibration experiments for a number of different devices.
Distribution System White Papers
EPA worked with stakeholders and developed a series of white papers on distribution system issues ranked of potentially significant public health concern (see list below) to serve as background material for EPA, expert and stakeholder discussions.
DOLIB: Distributed Object Library
D`Azevedo, E.F.; Romine, C.H.
1994-10-01
This report describes the use and implementation of DOLIB (Distributed Object Library), a library of routines that emulates global or virtual shared memory on Intel multiprocessor systems. Access to a distributed global array is through explicit calls to gather and scatter. Advantages of using DOLIB include: dynamic allocation and freeing of huge (gigabyte) distributed arrays, both C and FORTRAN callable interfaces, and the ability to mix shared-memory and message-passing programming models for ease of use and optimal performance. DOLIB is independent of language and compiler extensions and requires no special operating system support. DOLIB also supports automatic caching of read-only data for high performance. The virtual shared memory support provided in DOLIB is well suited for implementing Lagrangian particle tracking techniques. We have also used DOLIB to create DONIO (Distributed Object Network I/O Library), which obtains over a 10-fold improvement in disk I/O performance on the Intel Paragon.
NASA Technical Reports Server (NTRS)
Bahrami, K. A.; Kirkham, H.; Rahman, S.
1986-01-01
In a series of tests performed under the Department of Energy auspices, power line carrier propagation was observed to be anomalous under certain circumstances. To investigate the cause, a distribution system simulator was constructed. The simulator was a physical simulator that accurately represented the distribution system from below power frequency to above 50 kHz. Effects such as phase-to-phase coupling and skin effect were modeled. Construction details of the simulator, and experimental results from its use are presented.
NASA Technical Reports Server (NTRS)
Kanerva, Pentti
1988-01-01
Theoretical models of the human brain and proposed neural-network computers are developed analytically. Chapters are devoted to the mathematical foundations, background material from computer science, the theory of idealized neurons, neurons as address decoders, and the search of memory for the best match. Consideration is given to sparse memory, distributed storage, the storage and retrieval of sequences, the construction of distributed memory, and the organization of an autonomous learning system.
Polygamy of distributed entanglement
NASA Astrophysics Data System (ADS)
Buscemi, Francesco; Gour, Gilad; Kim, Jeong San
2009-07-01
While quantum entanglement is known to be monogamous (i.e., shared entanglement is restricted in multipartite settings), here we show that distributed entanglement (or the potential for entanglement) is by nature polygamous. By establishing the concept of one-way unlocalizable entanglement (UE) and investigating its properties, we provide a polygamy inequality of distributed entanglement in tripartite quantum systems of arbitrary dimension. We also provide a polygamy inequality in multiqubit systems and several trade-offs between UE and other correlation measures.
SUPERTHERMAL ELECTRON DISTRIBUTION
Kauffman, R
2007-12-20
This memo discusses the analysis of the high-energy x-ray distribution from a laser-induced plasma to determine the superthermal electron distribution. The methods of deconvolution outlined in I are similar to formulae derived in the literature not including and including effects due to electron stopping. In II the methods are applied to an x-ray spectrum from an Au disc irradiated by ARGUS.
Distributed computing in bioinformatics.
Jain, Eric
2002-01-01
This paper provides an overview of methods and current applications of distributed computing in bioinformatics. Distributed computing is a strategy of dividing a large workload among multiple computers to reduce processing time, or to make use of resources such as programs and databases that are not available on all computers. Participating computers may be connected either through a local high-speed network or through the Internet.
Population distribution policies.
Richardson, H W
1983-01-01
Population distribution policies have received increasing attention in recent years, especially in developing countries. One reason is that, especially in heavily primate developing countries, the spacial distribution of population (and economic activity) has generated conditions that conflict with important societal goals, such as interpersonal and interregional equity, national security, political stability, improvement in the quality of life, optimal resource exploitation, and long-term economic efficiency. Moreover, in many cases, the overall development strategy as reflected in macro and sectoral policies, has strong implicit spatial impacts that have, more often than not, reinforced an "unfavorable" population distribution, that is, one that conflicts with national goals and priorities. The only way to correct that is to modify the overall development strategy or to implement offsetting explicit population distribution policies. Many countries have adopted population distribution policies in recent years, but they have varied greatly in degree of implementation. Clear failures have been very common, and there have been almost no undiluted successes. This indifferent success should not be used as an argument against planned population distribution. The present article provides an overview of population distribution policies with special but not total reference to developing countries. Population goals are analyzed and the argument that rural-metropolitan migration is excessive is critically discussed. Policy instruments to influence the location of both households and firms are evaluated. It is argued that strategies to control primate city growth, to promote small towns and secondary cities and to implement rural-development programs are complementary rather than alternatives. Partial strategies, such as relocation of the national capital, countermagnets, new towns, border region policies and land colonization schemes, should be adopted only in rare cases
Sparse distributed memory overview
NASA Technical Reports Server (NTRS)
Raugh, Mike
1990-01-01
The Sparse Distributed Memory (SDM) project is investigating the theory and applications of massively parallel computing architecture, called sparse distributed memory, that will support the storage and retrieval of sensory and motor patterns characteristic of autonomous systems. The immediate objectives of the project are centered in studies of the memory itself and in the use of the memory to solve problems in speech, vision, and robotics. Investigation of methods for encoding sensory data is an important part of the research. Examples of NASA missions that may benefit from this work are Space Station, planetary rovers, and solar exploration. Sparse distributed memory offers promising technology for systems that must learn through experience and be capable of adapting to new circumstances, and for operating any large complex system requiring automatic monitoring and control. Sparse distributed memory is a massively parallel architecture motivated by efforts to understand how the human brain works. Sparse distributed memory is an associative memory, able to retrieve information from cues that only partially match patterns stored in the memory. It is able to store long temporal sequences derived from the behavior of a complex system, such as progressive records of the system's sensory data and correlated records of the system's motor controls.
Discrete Pearson distributions
Bowman, K.O.; Shenton, L.R.; Kastenbaum, M.A.
1991-11-01
These distributions are generated by a first order recursive scheme which equates the ratio of successive probabilities to the ratio of two corresponding quadratics. The use of a linearized form of this model will produce equations in the unknowns matched by an appropriate set of moments (assumed to exist). Given the moments we may find valid solutions. These are two cases; (1) distributions defined on the non-negative integers (finite or infinite) and (2) distributions defined on negative integers as well. For (1), given the first four moments, it is possible to set this up as equations of finite or infinite degree in the probability of a zero occurrence, the sth component being a product of s ratios of linear forms in this probability in general. For (2) the equation for the zero probability is purely linear but may involve slowly converging series; here a particular case is the discrete normal. Regions of validity are being studied. 11 refs.
Distributed Wind Market Applications
Forsyth, T.; Baring-Gould, I.
2007-11-01
Distributed wind energy systems provide clean, renewable power for on-site use and help relieve pressure on the power grid while providing jobs and contributing to energy security for homes, farms, schools, factories, private and public facilities, distribution utilities, and remote locations. America pioneered small wind technology in the 1920s, and it is the only renewable energy industry segment that the United States still dominates in technology, manufacturing, and world market share. The series of analyses covered by this report were conducted to assess some of the most likely ways that advanced wind turbines could be utilized apart from large, central station power systems. Each chapter represents a final report on specific market segments written by leading experts in this field. As such, this document does not speak with one voice but rather a compendium of different perspectives, which are documented from a variety of people in the U.S. distributed wind field.
Brown, Kenneth Dewayne; Dunson, David
2008-06-03
A distributed data transmitter (DTXR) which is an adaptive data communication microwave transmitter having a distributable architecture of modular components, and which incorporates both digital and microwave technology to provide substantial improvements in physical and operational flexibility. The DTXR has application in, for example, remote data acquisition involving the transmission of telemetry data across a wireless link, wherein the DTXR is integrated into and utilizes available space within a system (e.g., a flight vehicle). In a preferred embodiment, the DTXR broadly comprises a plurality of input interfaces; a data modulator; a power amplifier; and a power converter, all of which are modularly separate and distinct so as to be substantially independently physically distributable and positionable throughout the system wherever sufficient space is available.
Brown, Kenneth Dewayne; Dunson, David
2006-08-08
A distributed data transmitter (DTXR) which is an adaptive data communication microwave transmitter having a distributable architecture of modular components, and which incorporates both digital and microwave technology to provide substantial improvements in physical and operational flexibility. The DTXR has application in, for example, remote data acquisition involving the transmission of telemetry data across a wireless link, wherein the DTXR is integrated into and utilizes available space within a system (e.g., a flight vehicle). In a preferred embodiment, the DTXR broadly comprises a plurality of input interfaces; a data modulator; a power amplifier; and a power converter, all of which are modularly separate and distinct so as to be substantially independently physically distributable and positionable throughout the system wherever sufficient space is available.
Long, G.M.
1989-01-01
The purpose of this paper is to present a concise overview of the nature of a natural gas distribution utility. To this end, gas distribution'' is defined, then the functions performed while distributing natural gas are discussed. Topics presented include: franchise; planning (layouts, load estimation, sizing, system supply points, and storage considerations); design (codes/standards, materials, corrosion mitigation considerations, valves and fittings, vaults and stations, and main routing); construction (work force, sequencing, testing, purge and tie-in, and setting meters); operations (gas dispatching, customer service,and maintenance); continuity of supply; and sales and marketing. The paper concludes with discussion of converting an existing manufactured gas system over to natural gas. 4 refs., 6 figs.
Superpositions of probability distributions
NASA Astrophysics Data System (ADS)
Jizba, Petr; Kleinert, Hagen
2008-09-01
Probability distributions which can be obtained from superpositions of Gaussian distributions of different variances v=σ2 play a favored role in quantum theory and financial markets. Such superpositions need not necessarily obey the Chapman-Kolmogorov semigroup relation for Markovian processes because they may introduce memory effects. We derive the general form of the smearing distributions in v which do not destroy the semigroup property. The smearing technique has two immediate applications. It permits simplifying the system of Kramers-Moyal equations for smeared and unsmeared conditional probabilities, and can be conveniently implemented in the path integral calculus. In many cases, the superposition of path integrals can be evaluated much easier than the initial path integral. Three simple examples are presented, and it is shown how the technique is extended to quantum mechanics.
NASA Technical Reports Server (NTRS)
Wu, Sherman S. C.; Howington-Kraus, Annie E.; Ablin, Karyn K.
1991-01-01
A Digital Terrain Model (DTM) of Mars was derived with both Mercator and Sinusoidal Equal-Area projections from the global topographic map of Mars (scale 1:15 million, contour interval 1 km). Elevations on the map are referred to Mars' topographic datum that is defined by the gravity field at a 6.1-millibar pressure surface with respect to the center of mass of Mars. The DTM has a resolution at the equator of 1/59.226 degrees (exactly 1 km) per pixel. By using the DTM, the volumetric distribution of Mars topography above and below the datum has previously been calculated. Three types of elevation distributions of Mars' topography were calculated from the same DTM: (1) the frequency distribution of elevations at the pixel resolution; (2) average elevations in increments of 6 degrees in both longitude and latitude; and (3) average elevations in 36 separate blocks, each covering 30 degrees of latitude and 60 degrees of longitude.
Distributed circuit switching starnet
Chuan-lin Wu; Woei Lin; Min-chang Lin
1982-01-01
Starnet is a communication subnet which can cost-effectively connect hundreds or thousands of processors for distributed processing. It uses distributed control and circuit switching. Starnet's communication medium includes two major components: a multistage interconnection network and a set of interface units. The interconnection network uses a destination routing scheme with no central control. The interface unit provides handshaking between the computer/data node and the interconnection network under the control of a microprocessor. Detailed design of the communication medium is described. A model for comparing cost-effectiveness among starnet, crossbar and multiple buses is included. 7 references.
THERMAL DISTRIBUTION SYSTEM EXPERIMENT
KRAJEWSKI,R.F.; ANDREWS,J.W.; WEI,G.
1999-09-01
A laboratory experiment has been conducted which tests for the effects of distribution system purging on system Delivery Effectiveness (DE) as defined in ASHRAE 152P. The experiment is described in its configuration, instrumentation, and data acquisition system. Data gathered in the experiment is given and discussed. The results show that purging of the distribution system alone does not offer any improvement of the system DE. Additional supporting tests were conducted regarding experimental simulations of buffer zones and bare pipe and are also discussed.
76 FR 42768 - Capital Distribution
Federal Register 2010, 2011, 2012, 2013, 2014
2011-07-19
... Office of Thrift Supervision Capital Distribution AGENCY: Office of Thrift Supervision (OTS), Treasury... concerning the following information collection. Title of Proposal: Capital Distribution. OMB Number: 1550..., the information provides the OTS with a mechanism for monitoring capital distributions since...
Electronic software submittal/distribution
NASA Technical Reports Server (NTRS)
Clark, L. Scott
1991-01-01
Information on electronic software submittal and distribution is given in viewgraph form. A COSMIC program overview, and submittal/distribution issues of connectivity, software distribution, and solicitation of input/feedback are covered.
The Survivable Distributed Computing Environment
1994-06-01
an architecture for a survivable Distributed Computing Environment (SDCE). In essence, the SDCE will be a base upon which survivable distributed...and/or ISIS distributed Computing Environments to provide many of the SDCE requirements.
Distributed Continuous Registration.
ERIC Educational Resources Information Center
Myers, Donald L.
1981-01-01
The development, implementation, and features of Northern Colorado's continuous registration system are described. The system is an online distributed processing system, written in COBOL for an IBM Series I under the CPS operating system. Course selection, permit to enroll, and drop/add forms are provided. (Author/MLW)
1990-07-01
been reviewed and is approved for publication. APPROVED: RONALEq S. RA0SO Chief, C Systems Technology Division Directorate of Command and Control...metrics were then implemented using the Cronus Distributed Computing Environment. The results obtained for this implementation are presented. 4~- 14...Benchmarking Computational Throughput ................................................................... 9 3.2.1 The Proposed Model
Schooling and Income Distribution
ERIC Educational Resources Information Center
Marin, Alan; Psacharopoulos, George
1976-01-01
Analyzes the relationship between years of schooling and income distribution, based on human capital theory. (Available from North-Holland Publishing Company, P.O. Box 211, Amsterdam, the Netherlands; $13.50 annually, plus $4.00 postage and handling) (JG)
Age Distribution of Groundwater
NASA Astrophysics Data System (ADS)
Morgenstern, U.; Daughney, C. J.
2012-04-01
Groundwater at the discharge point comprises a mixture of water from different flow lines with different travel time and therefore has no discrete age but an age distribution. The age distribution can be assessed by measuring how a pulse shaped tracer moves through the groundwater system. Detection of the time delay and the dispersion of the peak in the groundwater compared to the tracer input reveals the mean residence time and the mixing parameter. Tritium from nuclear weapons testing in the early 1960s resulted in a peak-shaped tritium input to the whole hydrologic system on earth. Tritium is the ideal tracer for groundwater because it is an isotope of hydrogen and therefore is part of the water molecule. Tritium time series data that encompass the passage of the bomb tritium pulse through the groundwater system in all common hydrogeologic situations in New Zealand demonstrate a semi-systematic pattern between age distribution parameters and hydrologic situation. The data in general indicate high fraction of mixing, but in some cases also indicate high piston flow. We will show that still, 45 years after the peak of the bomb tritium, it is possible to assess accurately the parameters of age distributions by measuring the tail of the bomb tritium.
Distributed fuzzy system modeling
Pedrycz, W.; Chi Fung Lam, P.; Rocha, A.F.
1995-05-01
The paper introduces and studies an idea of distributed modeling treating it as a new paradigm of fuzzy system modeling and analysis. This form of modeling is oriented towards developing individual (local) fuzzy models for specific modeling landmarks (expressed as fuzzy sets) and determining the essential logical relationships between these local models. The models themselves are implemented in the form of logic processors being regarded as specialized fuzzy neural networks. The interaction between the processors is developed either in an inhibitory or excitatory way. In more descriptive way, the distributed model can be sought as a collection of fuzzy finite state machines with their individual local first or higher order memories. It is also clarified how the concept of distributed modeling narrows down a gap between purely numerical (quantitative) models and the qualitative ones originated within the realm of Artificial Intelligence. The overall architecture of distributed modeling is discussed along with the detailed learning schemes. The results of extensive simulation experiments are provided as well. 17 refs.
Aerosol distribution apparatus
Hanson, W.D.
An apparatus for uniformly distributing an aerosol to a plurality of filters mounted in a plenum, wherein the aerosol and air are forced through a manifold system by means of a jet pump and released into the plenum through orifices in the manifold. The apparatus allows for the simultaneous aerosol-testing of all the filters in the plenum.
Prototyping distributed simulation networks
NASA Technical Reports Server (NTRS)
Doubleday, Dennis L.
1990-01-01
Durra is a declarative language designed to support application-level programming. The use of Durra is illustrated to describe a simple distributed application: a simulation of a collection of networked vehicle simulators. It is shown how the language is used to describe the application, its components and structure, and how the runtime executive provides for the execution of the application.
Distributed Information Management.
ERIC Educational Resources Information Center
Pottenger, William M.; Callahan, Miranda R.; Padgett, Michael A.
2001-01-01
Reviews the scope and effects of distributed information management. Discusses cultural and social influences, including library and Internet culture, information and knowledge, electronic libraries, and social aspects of libraries; digital collections; indexing; permanent link systems; metadata; the Open Archives initiative; digital object…
Small School Distributive Education.
ERIC Educational Resources Information Center
Barnes, Bill
Information on an atypical 1966-67 Distributive Education pilot program in New Mexico was given. The program was unique since one instructor conducted this program in two schools which were in separate rural districts (Dexter and Hagerman). Since both communities were primarily agricultural, with small student populations, the cost of such a…
Planning for Distributed Systems.
ERIC Educational Resources Information Center
Chew, Robert L.
Reasons for distributed systems (DS) of planning and design for information services for colleges are discussed. The methodologies and approaches from industry and academe are contrasted to show how the process of DS can be effectively managed to meet a variety of institutional needs. DS represent a natural evolution of the historic development of…
Sorrells, M.A.
1990-01-01
This paper is a broad overview of industrial power distribution. Primary focus will be on selection of the various low voltage components to achieve the end product. Emphasis will be on the use of national standards to ensure a safe and well designed installation.
Distributed Treatment Systems.
Zgonc, David; Baideme, Matthew
2015-10-01
This section presents a review of the literature published in 2014 on topics relating to distributed treatment systems. This review is divided into the following sections with multiple subsections under each: constituent removal; treatment technologies; and planning and treatment system management.
NASA Astrophysics Data System (ADS)
Dewhurst, A.; Legger, F.
2015-12-01
The ATLAS experiment accumulated more than 140 PB of data during the first run of the Large Hadron Collider (LHC) at CERN. The analysis of such an amount of data is a challenging task for the distributed physics community. The Distributed Analysis (DA) system of the ATLAS experiment is an established and stable component of the ATLAS distributed computing operations. About half a million user jobs are running daily on DA resources, submitted by more than 1500 ATLAS physicists. The reliability of the DA system during the first run of the LHC and the following shutdown period has been high thanks to the continuous automatic validation of the distributed analysis sites and the user support provided by a dedicated team of expert shifters. During the LHC shutdown, the ATLAS computing model has undergone several changes to improve the analysis workflows, including the re-design of the production system, a new analysis data format and event model, and the development of common reduction and analysis frameworks. We report on the impact such changes have on the DA infrastructure, describe the new DA components, and include recent performance measurements.
NASA Astrophysics Data System (ADS)
Qin, Wei (Ivy); Cohen, Ira M.; Ayyaswamy, P. S.
2000-02-01
The low-current electric discharge from a fine wire anode to a planar cathode in atmospheric pressure air is numerically simulated from high-voltage prebreakdown through electron temperature growth, then ionization and consequent current growth to steady state, limited by a ballast resistor in the external circuit. Conservation of number (mass) for ions and electrons, Gauss' law for the self-consistent electric field, and energy conservation for electrons have been solved from breakdown to steady state in a body fitted coordinate system generated specifically for these two geometrically dissimilar electrodes. To facilitate the discussion of the results, the discharge has been categorized under (a) electron acceleration period, (b) charged particle generation period, (c) current increase and voltage drop period, and (d) current and voltage stabilization period. Results are given for transient electron, ion, and temperature distributions in the gap as well as current growth and voltage drop across the gap. Heat flux from the discharge to the wire is calculated. The numerical simulations were compared with experiments performed under the same conditions on a wire bonding machine with very close correspondence.
NASA Astrophysics Data System (ADS)
Romanyuk, O. N.; Pavlov, S. V.; Dovhaliuk, R. Yu.; Babyuk, N. P.; Obidnyk, M. D.; Kisala, P.; Suleimenov, B.
2013-01-01
A microfacet distribution function is presented. This function can be used to calculate the microfacet distribution term in BRDF models. The function differs from other well-known microfacet distribution functions like Blinn or Beckmann distributions in that it doesn`t use special functions like acos, tan, exp, pow and thus has lower computational complexity.
Properly Understanding the Impacts of Distributed Resources on Distribution Systems
Rizy, D Tom; Li, Fangxing; Li, Huijuan; Adhikari, Sarina; Kueck, John D
2010-01-01
The subject paper discusses important impacts of distributed resources on distribution networks and feeders. These include capacity, line losses, voltage regulation, and central system support (such as volt/var via central generators and substation) as the number, placement and penetration levels of distributed resources are varied. Typically, the impacts of distributed resources on the distribution system are studied by using steady-state rather than dynamic analysis tools. However, the response time and transient impacts of both system equipment (such as substation/feeder capacitors) and distributed resources needs to be taken into account and only dynamic analysis will provide the full impact results. ORNL is wrapping up a study of distributed resources interconnected to a large distribution system considering the above variables. A report of the study and its results will be condensed into a paper for this panel session. The impact of distributed resources will vary as the penetration level reaches the capacity of the distribution feeder/system. The question is how high of a penetration of distributed resource can be accommodated on the distribution feeder/system without any major changes to system operation, design and protection. The impacts most surely will vary depending upon load composition, distribution and level. Also, it is expected that various placement of distributed resources will impact the distribution system differently.
Bounding Species Distribution Models
NASA Technical Reports Server (NTRS)
Stohlgren, Thomas J.; Jarnevich, Cahterine S.; Morisette, Jeffrey T.; Esaias, Wayne E.
2011-01-01
Species distribution models are increasing in popularity for mapping suitable habitat for species of management concern. Many investigators now recognize that extrapolations of these models with geographic information systems (GIS) might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for "clamping" model extrapolations. We relied on two commonly used modeling approaches: classification and regression tree (CART) and maximum entropy (Maxent) models, and we tested a simple alteration of the model extrapolations, bounding extrapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suitable habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used [Current Zoology 57 (5): 642-647, 2011].
Distributed Visualization Project
NASA Technical Reports Server (NTRS)
Craig, Douglas; Conroy, Michael; Kickbusch, Tracey; Mazone, Rebecca
2016-01-01
Distributed Visualization allows anyone, anywhere to see any simulation at any time. Development focuses on algorithms, software, data formats, data systems and processes to enable sharing simulation-based information across temporal and spatial boundaries without requiring stakeholders to possess highly-specialized and very expensive display systems. It also introduces abstraction between the native and shared data, which allows teams to share results without giving away proprietary or sensitive data. The initial implementation of this capability is the Distributed Observer Network (DON) version 3.1. DON 3.1 is available for public release in the NASA Software Store (https://software.nasa.gov/software/KSC-13775) and works with version 3.0 of the Model Process Control specification (an XML Simulation Data Representation and Communication Language) to display complex graphical information and associated Meta-Data.
Triton's Temperature Distribution
NASA Astrophysics Data System (ADS)
Spencer, John; Stansberry, John; Vancleve, Jeff
2005-06-01
We propose to obtain a 25 - 40 micron spectrum of the thermal emission from Neptune's large and complex moon Triton. The spectrum will constrain surface temperature distributions (especially in the frost-free regions), surface/atmosphere interactions, and the time variability of its surface frost distribution and atmospheric pressure. This will be the first detection of Triton's thermal emission, apart from a marginal 47 micron observation by Voyager in 1989, filling a major gap in our understanding of this fascinating body. We will use a variety of strategies to reduce and characterize scattered and diffracted thermal radiation from Neptune, including observations with identical Neptune-relative pointing with and without Triton in the slit, and will also experiment with using the end of the slit to mask out Neptune.
``Just Another Distribution Channel?''
NASA Astrophysics Data System (ADS)
Lemstra, Wolter; de Leeuw, Gerd-Jan; van de Kar, Els; Brand, Paul
The telecommunications-centric business model of mobile operators is under attack due to technological convergence in the communication and content industries. This has resulted in a plethora of academic contributions on the design of new business models and service platform architectures. However, a discussion of the challenges that operators are facing in adopting these models is lacking. We assess these challenges by considering the mobile network as part of the value system of the content industry. We will argue that from the perspective of a content provider the mobile network is ‘just another’ distribution channel. Strategic options available for the mobile communication operators are to deliver an excellent distribution channel for content delivery or to move upwards in the value chain by becoming a content aggregator. To become a mobile content aggregator operators will have to develop or acquire complementary resources and capabilities. Whether this strategic option is sustainable remains open.
Distributed network scheduling
NASA Technical Reports Server (NTRS)
Clement, Bradley J.; Schaffer, Steven R.
2004-01-01
Distributed Network Scheduling is the scheduling of future communications of a network by nodes in the network. This report details software for doing this onboard spacecraft in a remote network. While prior work on distributed scheduling has been applied to remote spacecraft networks, the software reported here focuses on modeling communication activities in greater detail and including quality of service constraints. Our main results are based on a Mars network of spacecraft and include identifying a maximum opportunity of improving traverse exploration rate a factor of three; a simulation showing reduction in one-way delivery times from a rover to Earth from as much as 5 to 1.5 hours; simulated response to unexpected events averaging under an hour onboard; and ground schedule generation ranging from seconds to 50 minutes for 15 to 100 communication goals.
Towards heterogeneous distributed debugging
Damodaran-Kamal, S.K.
1995-04-01
Several years of research and development in parallel debugger design have given up several techniques, though implemented in a wide range of tools for an equally wide range of systems. This paper is an evaluation of these myriad techniques as applied to the design of a heterogeneous distributed debugger. The evaluation is based on what features users perceive as useful, as well as the ease of implementation of the features using the available technology. A preliminary architecture for such a heterogeneous tool is proposed. Our effort in this paper is significantly different from the other efforts at creating portable and heterogeneous distributed debuggers in that we concentrate on support for all the important issues in parallel debugging, instead of simply concentrating on portability and heterogeneity.
Distributed environmental control
NASA Technical Reports Server (NTRS)
Cleveland, Gary A.
1992-01-01
We present an architecture of distributed, independent control agents designed to work with the Computer Aided System Engineering and Analysis (CASE/A) simulation tool. CASE/A simulates behavior of Environmental Control and Life Support Systems (ECLSS). We describe a lattice of agents capable of distributed sensing and overcoming certain sensor and effector failures. We address how the architecture can achieve the coordinating functions of a hierarchical command structure while maintaining the robustness and flexibility of independent agents. These agents work between the time steps of the CASE/A simulation tool to arrive at command decisions based on the state variables maintained by CASE/A. Control is evaluated according to both effectiveness (e.g., how well temperature was maintained) and resource utilization (the amount of power and materials used).
Bounding species distribution models
Stohlgren, T.J.; Jarnevich, C.S.; Esaias, W.E.; Morisette, J.T.
2011-01-01
Species distribution models are increasing in popularity for mapping suitable habitat for species of management concern. Many investigators now recognize that extrapolations of these models with geographic information systems (GIS) might be sensitive to the environmental bounds of the data used in their development, yet there is no recommended best practice for "clamping" model extrapolations. We relied on two commonly used modeling approaches: classification and regression tree (CART) and maximum entropy (Maxent) models, and we tested a simple alteration of the model extrapolations, bounding extrapolations to the maximum and minimum values of primary environmental predictors, to provide a more realistic map of suitable habitat of hybridized Africanized honey bees in the southwestern United States. Findings suggest that multiple models of bounding, and the most conservative bounding of species distribution models, like those presented here, should probably replace the unbounded or loosely bounded techniques currently used. ?? 2011 Current Zoology.
2014-06-01
potential improvement in air defense for the armada, the SSC would be capable of plunging deeper into A2AD environments. In addition to the new ...Environment. http://www.brighton-webs.co.uk/distributions/triangular. British Broadcasting Company. 2014, May 08. BBC News Asia . http://www.bbc.com... news /world- asia -pacific-13748349. Cavas, Christopher P. 2014, January 19. Navy, Pentagon battle over LCS future. www.navytimes.com/article/20140109
2009-12-01
conduit to this significant source of processing power and John the Ripper is the key. BOINC is a distributed data processing system that...processed without changing significant portions of the structure. John the Ripper is a password cracking program that takes a password file and...strength of their password security policy. This thesis goes into detail on the inner workings of BOINC, John the Ripper , and the merger of the two
Symmetric generalized binomial distributions
Bergeron, H.; Curado, E. M. F.; Gazeau, J. P.; Rodrigues, Ligia M. C. S. E-mail: evaldo@cbpf.br E-mail: ligia@cbpf.br
2013-12-15
In two recent articles, we have examined a generalization of the binomial distribution associated with a sequence of positive numbers, involving asymmetric expressions of probabilities that break the symmetry win-loss. We present in this article another generalization (always associated with a sequence of positive numbers) that preserves the symmetry win-loss. This approach is also based on generating functions and presents constraints of non-negativeness, similar to those encountered in our previous articles.
New distributions in thermodynamics
NASA Astrophysics Data System (ADS)
Maslov, V. P.
2016-09-01
A model of the equation of state for classical gases consisting of nonpolar molecules is constructed under the assumption that the spinodal, critical isochore, and second virial coefficients of the gas have been set. The corresponding thermodynamic distributions are determined. It is shown that the isotherms constructed in the framework of the proposed model coincide with the isotherms of the van der Waals model obtained on a different basis.
Theoretical Delay Time Distributions
NASA Astrophysics Data System (ADS)
Nelemans, Gijs; Toonen, Silvia; Bours, Madelon
2013-01-01
We briefly discuss the method of population synthesis to calculate theoretical delay time distributions of Type Ia supernova progenitors. We also compare the results of different research groups and conclude that, although one of the main differences in the results for single degenerate progenitors is the retention efficiency with which accreted hydrogen is added to the white dwarf core, this alone cannot explain all the differences.
Program Facilitates Distributed Computing
NASA Technical Reports Server (NTRS)
Hui, Joseph
1993-01-01
KNET computer program facilitates distribution of computing between UNIX-compatible local host computer and remote host computer, which may or may not be UNIX-compatible. Capable of automatic remote log-in. User communicates interactively with remote host computer. Data output from remote host computer directed to local screen, to local file, and/or to local process. Conversely, data input from keyboard, local file, or local process directed to remote host computer. Written in ANSI standard C language.
Generalizing distributed sensing networks
Kuespert, J.; Kutscher, D.
1996-11-01
Recent research in airborne oil spill remote sensing [FBFG94] leads towards modular systems that consist of several distinct sensors to combine the capabilities of the different sensor classes. The Medusa project [GHW96] is an example of a distributed system. It exhibits a distributed architecture to provide a maximum of flexibility, concurrency and safety and must clearly be rated as a classical distributed application from a computer science point of view. This article describes the {open_quotes}sensor description system{close_quotes} (SDS). SDS allows the developer of sensing systems to minimize the effort of integrating his particular subsystem into an existing application. By applying formal methods to the integration process a developer is able to describe the abstract properties of his sensing system like parameter values, generated data format, applicable methods on the data etc. and can thus rely on the SDS tools to produce the required software backends automatically: A graphical user interface for parameter control, an online visualization, data transfer facilities to a database and finally the evaluation and interpretation facility. Ibis technique puts future sensing enterprises in a position where different classes of sensors can easily be combined almost off-the-shelf to build powerful systems in very short turnaround times. 10 refs., 7 figs.
NASA Technical Reports Server (NTRS)
Taft, Tucker, S.
1986-01-01
A distributed Ada program library is a key element in a distributed Ada Program Support Environment (APSE). To implement this successfully, the program library universe as defined by the Ada Reference Manual must be broken up into independently manageable pieces. This in turn requires the support of a distributed database system, as well as a mechanism for identifying compilation units, linkable subprograms, and Ada types in a decentralized way, to avoid falling victim to the bottlenecks of a global database and/or global unique-identifier manager. It was found that the ability to decentralize Ada program library activity is a major advantage in the management of large Ada programs. Currently, there are 18 resource-catalog revision sets, each in its own Host Interface (HIF) partition, plus 18 partitions for testing each of these, plus 11 partitions for the top-level compiler/linker/program library manager components. Compiling and other development work can proceed in parallel in each of these partitions, without suffering the performance bottlenecks of global locks or global unique-identifier generation.
Planning Systems for Distributed Operations
NASA Technical Reports Server (NTRS)
Maxwell, Theresa G.
2002-01-01
This viewgraph representation presents an overview of the mission planning process involving distributed operations (such as the International Space Station (ISS)) and the computer hardware and software systems needed to support such an effort. Topics considered include: evolution of distributed planning systems, ISS distributed planning, the Payload Planning System (PPS), future developments in distributed planning systems, Request Oriented Scheduling Engine (ROSE) and Next Generation distributed planning systems.
GASIFICATION FOR DISTRIBUTED GENERATION
Ronald C. Timpe; Michael D. Mann; Darren D. Schmidt
2000-05-01
A recent emphasis in gasification technology development has been directed toward reduced-scale gasifier systems for distributed generation at remote sites. The domestic distributed power generation market over the next decade is expected to be 5-6 gigawatts per year. The global increase is expected at 20 gigawatts over the next decade. The economics of gasification for distributed power generation are significantly improved when fuel transport is minimized. Until recently, gasification technology has been synonymous with coal conversion. Presently, however, interest centers on providing clean-burning fuel to remote sites that are not necessarily near coal supplies but have sufficient alternative carbonaceous material to feed a small gasifier. Gasifiers up to 50 MW are of current interest, with emphasis on those of 5-MW generating capacity. Internal combustion engines offer a more robust system for utilizing the fuel gas, while fuel cells and microturbines offer higher electric conversion efficiencies. The initial focus of this multiyear effort was on internal combustion engines and microturbines as more realistic near-term options for distributed generation. In this project, we studied emerging gasification technologies that can provide gas from regionally available feedstock as fuel to power generators under 30 MW in a distributed generation setting. Larger-scale gasification, primarily coal-fed, has been used commercially for more than 50 years to produce clean synthesis gas for the refining, chemical, and power industries. Commercial-scale gasification activities are under way at 113 sites in 22 countries in North and South America, Europe, Asia, Africa, and Australia, according to the Gasification Technologies Council. Gasification studies were carried out on alfalfa, black liquor (a high-sodium waste from the pulp industry), cow manure, and willow on the laboratory scale and on alfalfa, black liquor, and willow on the bench scale. Initial parametric tests
Performance and Application of Parallel OVERFLOW Codes on Distributed and Shared Memory Platforms
NASA Technical Reports Server (NTRS)
Djomehri, M. Jahed; Rizk, Yehia M.
1999-01-01
The presentation discusses recent studies on the performance of the two parallel versions of the aerodynamics CFD code, OVERFLOW_MPI and _MLP. Developed at NASA Ames, the serial version, OVERFLOW, is a multidimensional Navier-Stokes flow solver based on overset (Chimera) grid technology. The code has recently been parallelized in two ways. One is based on the explicit message-passing interface (MPI) across processors and uses the _MPI communication package. This approach is primarily suited for distributed memory systems and workstation clusters. The second, termed the multi-level parallel (MLP) method, is simple and uses shared memory for all communications. The _MLP code is suitable on distributed-shared memory systems. For both methods, the message passing takes place across the processors or processes at the advancement of each time step. This procedure is, in effect, the Chimera boundary conditions update, which is done in an explicit "Jacobi" style. In contrast, the update in the serial code is done in more of the "Gauss-Sidel" fashion. The programming efforts for the _MPI code is more complicated than for the _MLP code; the former requires modification of the outer and some inner shells of the serial code, whereas the latter focuses only on the outer shell of the code. The _MPI version offers a great deal of flexibility in distributing grid zones across a specified number of processors in order to achieve load balancing. The approach is capable of partitioning zones across multiple processors or sending each zone and/or cluster of several zones into a single processor. The message passing across the processors consists of Chimera boundary and/or an overlap of "halo" boundary points for each partitioned zone. The MLP version is a new coarse-grain parallel concept at the zonal and intra-zonal levels. A grouping strategy is used to distribute zones into several groups forming sub-processes which will run in parallel. The total volume of grid points in each
Palenstijn, Willem Jan; Bédorf, Jeroen; Sijbers, Jan; Batenburg, K Joost
2017-01-01
While iterative reconstruction algorithms for tomography have several advantages compared to standard backprojection methods, the adoption of such algorithms in large-scale imaging facilities is still limited, one of the key obstacles being their high computational load. Although GPU-enabled computing clusters are, in principle, powerful enough to carry out iterative reconstructions on large datasets in reasonable time, creating efficient distributed algorithms has so far remained a complex task, requiring low-level programming to deal with memory management and network communication. The ASTRA toolbox is a software toolbox that enables rapid development of GPU accelerated tomography algorithms. It contains GPU implementations of forward and backprojection operations for many scanning geometries, as well as a set of algorithms for iterative reconstruction. These algorithms are currently limited to using GPUs in a single workstation. In this paper, we present an extension of the ASTRA toolbox and its Python interface with implementations of forward projection, backprojection and the SIRT algorithm that can be distributed over multiple GPUs and multiple workstations, as well as the tools to write distributed versions of custom reconstruction algorithms, to make processing larger datasets with ASTRA feasible. As a result, algorithms that are implemented in a high-level conceptual script can run seamlessly on GPU-enabled computing clusters, up to 32 GPUs or more. Our approach is not limited to slice-based reconstruction, facilitating a direct portability of algorithms coded for parallel-beam synchrotron tomography to cone-beam laboratory tomography setups without making changes to the reconstruction algorithm.
Angular distributions in multifragmentation
Stoenner, R.W.; Klobuchar, R.L.; Haustein, P.E.; Virtes, G.J.; Cumming, J.B.; Loveland, W.
2006-04-15
Angular distributions are reported for {sup 37}Ar and {sup 127}Xe from 381-GeV {sup 28}Si+Au interactions and for products between {sup 24}Na and {sup 149}Gd from 28-GeV {sup 1}H+Au. Sideward peaking and forward deficits for multifragmentation products are significantly enhanced for heavy ions compared with protons. Projectile kinetic energy does not appear to be a satisfactory scaling variable. The data are discussed in terms of a kinetic-focusing model in which sideward peaking is due to transverse motion of the excited product from the initial projectile-target interaction.
Representation of orientation distributions
Wenk, H.R.; Kocks, U.F.
1985-01-01
This paper illustrates the principles presented with a particular experimental texture: from the surface layer of a copper polycrystal cold-rolled to 60% reduction in thickness. Four incomplete pole figures (200, 220, 222, and 113) were determined by x-ray diffraction in reflection geometry. The measured pole figures nearly exhibited orthorhombic symmetry (as expected), which was then strictly enforced by averaging the four quadrants of the pole figure. The orientation distribution function was obtained using the expansion in spherical harmonics (with only even-order coefficients up to l = 18).
Generic Distributed Systems Model
1989-03-01
networking of microcomputers or work- stations with a distributed system and a clear distinction between the two needs to be made. What is expected in a...INFORM.AT1ON PERTAI NING TO LOCATIONS AND POLICY CAN BE COMBINED WITH THE INITIAL DIAGRAM TO PRODUCE A PARTITIONED DFD. THE BOLD LINES REPRESENT SERVICES WHICH...PRA85] D.K. Pradhan, "Fault-tolerant. mIltiprocessor link and bus network Architectures," IEEE Trans. on Computers, Vol. 34, No. I, Jan. 1985, pp. 33
Distributed Optimization System
Hurtado, John E.; Dohrmann, Clark R.; Robinett, III, Rush D.
2004-11-30
A search system and method for controlling multiple agents to optimize an objective using distributed sensing and cooperative control. The search agent can be one or more physical agents, such as a robot, and can be software agents for searching cyberspace. The objective can be: chemical sources, temperature sources, radiation sources, light sources, evaders, trespassers, explosive sources, time dependent sources, time independent sources, function surfaces, maximization points, minimization points, and optimal control of a system such as a communication system, an economy, a crane, and a multi-processor computer.
Distributed aperture synthesis.
Rabb, David; Jameson, Douglas; Stokes, Andrew; Stafford, Jason
2010-05-10
Distributed aperture synthesis is an exciting technique for recovering high-resolution images from an array of small telescopes. Such a system requires optical field values measured at individual apertures to be phased together so that a single, high-resolution image can be synthesized. This paper describes the application of sharpness metrics to the process of phasing multiple coherent imaging systems into a single high-resolution system. Furthermore, this paper will discuss hardware and present the results of simulations and experiments which will illustrate how aperture synthesis is performed.
Distributed System Design Checklist
NASA Technical Reports Server (NTRS)
Hall, Brendan; Driscoll, Kevin
2014-01-01
This report describes a design checklist targeted to fault-tolerant distributed electronic systems. Many of the questions and discussions in this checklist may be generally applicable to the development of any safety-critical system. However, the primary focus of this report covers the issues relating to distributed electronic system design. The questions that comprise this design checklist were created with the intent to stimulate system designers' thought processes in a way that hopefully helps them to establish a broader perspective from which they can assess the system's dependability and fault-tolerance mechanisms. While best effort was expended to make this checklist as comprehensive as possible, it is not (and cannot be) complete. Instead, we expect that this list of questions and the associated rationale for the questions will continue to evolve as lessons are learned and further knowledge is established. In this regard, it is our intent to post the questions of this checklist on a suitable public web-forum, such as the NASA DASHLink AFCS repository. From there, we hope that it can be updated, extended, and maintained after our initial research has been completed.
NASA Astrophysics Data System (ADS)
Hughes, Richard
2004-05-01
Quantum key distribution (QKD) uses single-photon communications to generate the shared, secret random number sequences that are used to encrypt and decrypt secret communications. The unconditional security of QKD is based on the interplay between fundamental principles of quantum physics and information theory. An adversary can neither successfully tap the transmissions, nor evade detection (eavesdropping raises the key error rate above a threshold value). QKD could be particularly attractive for free-space optical communications, both ground-based and for satellites. I will describe a QKD experiment performed over multi-kilometer line-of-sight paths, which serves as a model for a satellite-to-ground key distribution system. The system uses single-photon polarization states, without active polarization switching, and for the first time implements the complete BB84 QKD protocol including, reconciliation, privacy amplification and the all-important authentication stage. It is capable of continuous operation throughout the day and night, achieving the self-sustaining production of error-free, shared, secret bits. I will also report on the results of satellite-to-ground QKD modeling.
Distributed Operations Planning
NASA Technical Reports Server (NTRS)
Fox, Jason; Norris, Jeffrey; Powell, Mark; Rabe, Kenneth; Shams, Khawaja
2007-01-01
Maestro software provides a secure and distributed mission planning system for long-term missions in general, and the Mars Exploration Rover Mission (MER) specifically. Maestro, the successor to the Science Activity Planner, has a heavy emphasis on portability and distributed operations, and requires no data replication or expensive hardware, instead relying on a set of services functioning on JPL institutional servers. Maestro works on most current computers with network connections, including laptops. When browsing down-link data from a spacecraft, Maestro functions similarly to being on a Web browser. After authenticating the user, it connects to a database server to query an index of data products. It then contacts a Web server to download and display the actual data products. The software also includes collaboration support based upon a highly reliable messaging system. Modifications made to targets in one instance are quickly and securely transmitted to other instances of Maestro. The back end that has been developed for Maestro could benefit many future missions by reducing the cost of centralized operations system architecture.
Distributed Active Archive Center
NASA Technical Reports Server (NTRS)
Bodden, Lee; Pease, Phil; Bedet, Jean-Jacques; Rosen, Wayne
1993-01-01
The Goddard Space Flight Center Version 0 Distributed Active Archive Center (GSFC V0 DAAC) is being developed to enhance and improve scientific research and productivity by consolidating access to remote sensor earth science data in the pre-EOS time frame. In cooperation with scientists from the science labs at GSFC, other NASA facilities, universities, and other government agencies, the DAAC will support data acquisition, validation, archive and distribution. The DAAC is being developed in response to EOSDIS Project Functional Requirements as well as from requirements originating from individual science projects such as SeaWiFS, Meteor3/TOMS2, AVHRR Pathfinder, TOVS Pathfinder, and UARS. The GSFC V0 DAAC has begun operational support for the AVHRR Pathfinder (as of April, 1993), TOVS Pathfinder (as of July, 1993) and the UARS (September, 1993) Projects, and is preparing to provide operational support for SeaWiFS (August, 1994) data. The GSFC V0 DAAC has also incorporated the existing data, services, and functionality of the DAAC/Climate, DAAC/Land, and the Coastal Zone Color Scanner (CZCS) Systems.
PULSE AMPLITUDE DISTRIBUTION RECORDER
Cowper, G.
1958-08-12
A device is described for automatica1ly recording pulse annplitude distribution received from a counter. The novelty of the device consists of the over-all arrangement of conventional circuit elements to provide an easy to read permanent record of the pulse amplitude distribution during a certain time period. In the device a pulse analyzer separates the pulses according to annplitude into several channels. A scaler in each channel counts the pulses and operates a pen marker positioned over a drivable recorder sheet. Since the scalers in each channel have the sanne capacity, the control circuitry permits counting of the incoming pulses until one scaler reaches capacity, whereupon the input is removed and an internal oscillator supplies the necessary pulses to fill up the other scalers. Movement of the chart sheet is initiated wben the first scaler reaches capacity to thereby give a series of marks at spacings proportional to the time required to fill the remaining scalers, and accessory equipment marks calibration points on the recorder sheet to facilitate direct reading of the number of external pulses supplied to each scaler.
Automated Gas Distribution System
NASA Astrophysics Data System (ADS)
Starke, Allen; Clark, Henry
2012-10-01
The cyclotron of Texas A&M University is one of the few and prized cyclotrons in the country. Behind the scenes of the cyclotron is a confusing, and dangerous setup of the ion sources that supplies the cyclotron with particles for acceleration. To use this machine there is a time consuming, and even wasteful step by step process of switching gases, purging, and other important features that must be done manually to keep the system functioning properly, while also trying to maintain the safety of the working environment. Developing a new gas distribution system to the ion source prevents many of the problems generated by the older manually setup process. This developed system can be controlled manually in an easier fashion than before, but like most of the technology and machines in the cyclotron now, is mainly operated based on software programming developed through graphical coding environment Labview. The automated gas distribution system provides multi-ports for a selection of different gases to decrease the amount of gas wasted through switching gases, and a port for the vacuum to decrease the amount of time spent purging the manifold. The Labview software makes the operation of the cyclotron and ion sources easier, and safer for anyone to use.
Distributed Semantic Overlay Networks
NASA Astrophysics Data System (ADS)
Doulkeridis, Christos; Vlachou, Akrivi; Nørvåg, Kjetil; Vazirgiannis, Michalis
Semantic Overlay Networks (SONs) have been recently proposed as a way to organize content in peer-to-peer (P2P) networks. The main objective is to discover peers with similar content and then form thematically focused peer groups. Efficient content retrieval can be performed by having queries selectively forwarded only to relevant groups of peers to the query. As a result, less peers need to be contacted, in order to answer a query. In this context, the challenge is to generate SONs in a decentralized and distributed manner, as the centralized assembly of global information is not feasible. Different approaches for exploiting the generated SONs for content retrieval have been proposed in the literature, which are examined in this chapter, with a particular focus on SON interconnections for efficient search. Several applications, such as P2P document and image retrieval, can be deployed over generated SONs, motivating the need for distributed and truly scalable SON creation. Therefore, recently several research papers focus on SONs as stated in our comprehensive overview of related work in the field of semantic overlay networks. A classification of existing algorithms according to a set of qualitative criteria is also provided. In spite of the rich existing work in the field of SONs, several challenges have not been efficiently addressed yet, therefore, future promising research directions are pointed out and discussed at the end of this chapter.
Vascular Distribution of Nanomaterials
Stapleton, Phoebe A.; Nurkiewicz, Timothy R.
2014-01-01
Once considered primarily occupational, novel nanotechnology innovation and application has led to widespread domestic use and intentional biomedical exposures. With these exciting advances, the breadth and depth of toxicological considerations must also be expanded. The vascular system interacts with every tissue in the body, striving to homeostasis. Engineered nanomaterials (ENM) have been reported to distribute in many different organs and tissues. However, these observations have tended to use approaches requiring tissue homogenization and/or gross organ analyses. These techniques, while effective in establishing presence, preclude an exact determination of where ENM are deposited within a tissue. It is necessary to identify this exact distribution and deposition of ENM throughout the cardiovascular system, with respect to vascular hemodynamics and in vivo/ in vitro ENM modifications taken into account if nanotechnology is to achieve its full potential. Distinct levels of the vasculature will first be described as individual compartments. Then the vasculature will be considered as a whole. These unique compartments and biophysical conditions will be discussed in terms of their propensity to favor ENM deposition. Understanding levels of the vasculature will also be discussed. Ultimately, future studies must verify the mechanisms speculated on and presented herein. PMID:24777845
Testing reveals proppant distribution
Crump, J.B. ); Ekstrand, B.B. ); Almond, S.W. )
1988-10-31
Sand distribution tests, undertaken to answer inquiries from a producing company, have shown that proppant placed during a hydraulic fracture treatment is evenly distributed into the perforated interval. Therefore, for planning purposes, a good assumption is that all perforations will pass essentially equal volumes of proppant, provided perforation quality is uniform, perforations are open, and bottom hole treating pressure is constant across the interval. Under simulated conditions, a fluid viscosity of 30 cp (511 sec/sup -1/) allowed 20/40 sand to ''turn to corner'' and pass through perforations with minimal stratification. This finding refutes the theory held by some that the bottom perforation is ''slugged'' with heavier concentration of sand than the upper perforations, and the theory's logical extension that after the bottom perforation is filled, it plugs and the perforation just above becomes the next bottom until the entire perforated interval is screened out. Tests described in this article were part of a program implemented to analyze causes of screen outs encountered in fracturing operations.
Differentially Private Distributed Sensing
Fink, Glenn A.
2016-12-11
The growth of the Internet of Things (IoT) creates the possibility of decentralized systems of sensing and actuation, potentially on a global scale. IoT devices connected to cloud networks can offer Sensing and Actuation as a Service (SAaaS) enabling networks of sensors to grow to a global scale. But extremely large sensor networks can violate privacy, especially in the case where IoT devices are mobile and connected directly to the behaviors of people. The thesis of this paper is that by adapting differential privacy (adding statistically appropriate noise to query results) to groups of geographically distributed sensors privacy could be maintained without ever sending all values up to a central curator and without compromising the overall accuracy of the data collected. This paper outlines such a scheme and performs an analysis of differential privacy techniques adapted to edge computing in a simulated sensor network where ground truth is known. The positive and negative outcomes of employing differential privacy in distributed networks of devices are discussed and a brief research agenda is presented.
Network aware distributed applications
Agarwal, Deborah; Tierney, Brian L.; Gunter, Dan; Lee, Jason; Johnston, William
2001-02-04
Most distributed applications today manage to utilize only a small percentage of the needed and available network bandwidth. Often application developers are not aware of the potential bandwidth of the network, and therefore do not know what to expect. Even when application developers are aware of the specifications of the machines and network links, they have few resources that can help determine why the expected performance was not achieved. What is needed is a ubiquitous and easy-to-use service that provides reliable, accurate, secure, and timely estimates of dynamic network properties. This service will help advise applications on how to make use of the network's increasing bandwidth and capabilities for traffic shaping and engineering. When fully implemented, this service will make building currently unrealizable levels of network awareness into distributed applications a relatively mundane task. For example, a remote data visualization application could choose between sending a wireframe, a pre-rendered image, or a 3-D representation, based on forecasts of CPU availability and power, compression options, and available bandwidth. The same service will provide on-demand performance information so that applications can compare predicted with actual results, and allow detailed queries about the end-to-end path for application and network tuning and debugging.
Coping with distributed computing
Cormell, L.
1992-09-01
The rapid increase in the availability of high performance, cost-effective RISC/UNIX workstations has been both a blessing and a curse. The blessing of having extremely powerful computing engines available on the desk top is well-known to many users. The user has tremendous freedom, flexibility, and control of his environment. That freedom can, however, become the curse of distributed computing. The user must become a system manager to some extent, he must worry about backups, maintenance, upgrades, etc. Traditionally these activities have been the responsibility of a central computing group. The central computing group, however, may find that it can no longer provide all of the traditional services. With the plethora of workstations now found on so many desktops throughout the entire campus or lab, the central computing group may be swamped by support requests. This talk will address several of these computer support and management issues by providing some examples of the approaches taken at various HEP institutions. In addition, a brief review of commercial directions or products for distributed computing and management will be given.
Distribution and moments of radial error. [Rayleigh distribution - random variables
NASA Technical Reports Server (NTRS)
White, R. G.
1975-01-01
An investigation of the moments and probability distribution of the resultant of two normally distributed random variables is presented. This is the so-called generalized Rayleigh distribution which has many applications in the study of wind shear, random noise, and radar. The most general formula was derived, and two special cases were considered for which tables of the moments and probability distribution functions are included as an appendix. One of the special cases was generalized to n-dimensions.
Distributed charging of electrical assets
Ghosh, Soumyadip; Phan, Dung; Sharma, Mayank; Wu, Chai Wah; Xiong, Jinjun
2016-02-16
The present disclosure relates generally to the field of distributed charging of electrical assets. In various examples, distributed charging of electrical assets may be implemented in the form of systems, methods and/or algorithms.
Distributed Wind Energy in Idaho
Gardner, John; Johnson, Kathryn; Haynes, Todd; Seifert, Gary
2009-01-31
This project is a research and development program aimed at furthering distributed wind technology. In particular, this project addresses some of the barriers to distributed wind energy utilization in Idaho.
Reliability evaluation of distribution systems containing renewable distributed generations
NASA Astrophysics Data System (ADS)
Alkuhayli, Abdulaziz Abddullah
Reliability evaluation of distribution networks, including islanded microgrid cases, is presented. The Monte Carlo simulation algorithm is applied to a test network. The network includes three types of distributed energy resources solar photovoltaic (PV), wind turbine (WT) and gas turbine (GT). These distributed generators contribute to supply part of the load during grid-connected mode, but supply the entire load during islanded microgrid operation. PV and WT stochastic models have been used to simulate the randomness of these resources. This study shows that the implementation of distributed generations can improve the reliability of the distribution networks.
DISTRIBUTED AMPLIFIER INCORPORATING FEEDBACK
Bell, P.R. Jr.
1958-10-21
An improved distributed amplifier system employing feedback for stabilization is presented. In accordance with the disclosed invention, a signal to be amplified is applled to one end of a suitable terminated grid transmission line. At intervals along the transmission line, the signal is fed to stable, resistance-capacitance coupled amplifiers incorporating feedback loops therein. The output current from each amplifier is passed through an additional tube to minimize the electrostatic capacitance between the tube elements of the last stage of the amplifier, and fed to appropriate points on an output transmission line, similar to the grid line, but terminated at the opposite (input) end. The output taken from the unterminated end of the plate transmission line is proportional to the input voltage impressed upon the grid line.
NASA Astrophysics Data System (ADS)
Norbeck, Edwin; Miller, Michael; Onel, Yasar
2010-11-01
For detector arrays that require 5 to 10 kV at a few microamps each for hundreds of detectors, using hundreds of HV power supplies is unreasonable. Bundles of hundreds of HV cables take up space that should be filled with detectors. A typical HV module can supply 1 ma, enough current for hundreds of detectors. It is better to use a single HV module and distribute the current as needed. We show a circuit that, for each detector, measures the current, cuts off the voltage if the current exceeds a set maximum, and allows the HV to be turned on or off from a control computer. The entire array requires a single HV cable and 2 or 3 control lines. This design provides the same voltage to all of the detectors, the voltage set by the single HV module. Some additional circuitry would allow a computer controlled voltage drop between the HV and each individual detector.
NASA Technical Reports Server (NTRS)
Ladany, I.; Andrews, J. T.; Evans, G. A.
1988-01-01
A ridge waveguide distributed feedback laser was developed in InGaAsP. These devices have demonstrated CW output powers over 7 mW with threshold currents as low as 60 mA at 25 C. Measurements of the frequency response of these devices show a 3 dB bandwidth of about 2 GHz, which may be limited by the mount. The best devices have a single mode spectra over the entire temperature range tested with a side mode suppression of about 20 dB in both CW and pulsed modes. The design of this device, including detailed modeling of the ridge guide structure, effective index calculations, and a discussion of the grating configuration are presented. Also, the fabrication of the devices is presented in some detail, especially the fabrication of and subsequent growth over the grating. In addition, a high frequency fiber pigtailed package was designed and tested, which is a suitable prototype for a commercial package.
Distributed road assessment system
Beer, N. Reginald; Paglieroni, David W
2014-03-25
A system that detects damage on or below the surface of a paved structure or pavement is provided. A distributed road assessment system includes road assessment pods and a road assessment server. Each road assessment pod includes a ground-penetrating radar antenna array and a detection system that detects road damage from the return signals as the vehicle on which the pod is mounted travels down a road. Each road assessment pod transmits to the road assessment server occurrence information describing each occurrence of road damage that is newly detected on a current scan of a road. The road assessment server maintains a road damage database of occurrence information describing the previously detected occurrences of road damage. After the road assessment server receives occurrence information for newly detected occurrences of road damage for a portion of a road, the road assessment server determines which newly detected occurrences correspond to which previously detected occurrences of road damage.
Protocols for distributive scheduling
NASA Technical Reports Server (NTRS)
Richards, Stephen F.; Fox, Barry
1993-01-01
The increasing complexity of space operations and the inclusion of interorganizational and international groups in the planning and control of space missions lead to requirements for greater communication, coordination, and cooperation among mission schedulers. These schedulers must jointly allocate scarce shared resources among the various operational and mission oriented activities while adhering to all constraints. This scheduling environment is complicated by such factors as the presence of varying perspectives and conflicting objectives among the schedulers, the need for different schedulers to work in parallel, and limited communication among schedulers. Smooth interaction among schedulers requires the use of protocols that govern such issues as resource sharing, authority to update the schedule, and communication of updates. This paper addresses the development and characteristics of such protocols and their use in a distributed scheduling environment that incorporates computer-aided scheduling tools. An example problem is drawn from the domain of space shuttle mission planning.
Overview of Aerosol Distribution
NASA Technical Reports Server (NTRS)
Kaufman, Yoram
2005-01-01
Our knowledge of atmospheric aerosols (smoke, pollution, dust or sea salt particles, small enough to be suspended in the air), their evolution, composition, variability in space and time and interaction with clouds and precipitation is still lacking despite decades of research. Understanding the global aerosol system is fundamental for progress in climate change and hydrological cycle research. While a single instrument was used to demonstrate 50 years ago that the global CO2 levels are rising, posing threat of global warming, we need an array of satellites and field measurements coupled with chemical transport models to understand the global aerosol system. This complexity of the aerosol problem results from their short lifetime (1 week) and variable chemical composition. A new generation of satellites provides exciting opportunities to measure the global distribution of aerosols, distinguishing natural from anthropogenic aerosol and measuring their interaction with clouds and climate. I shall discuss these topics and application of the data to air quality monitoring.
Process evaluation distributed system
NASA Technical Reports Server (NTRS)
Moffatt, Christopher L. (Inventor)
2006-01-01
The distributed system includes a database server, an administration module, a process evaluation module, and a data display module. The administration module is in communication with the database server for providing observation criteria information to the database server. The process evaluation module is in communication with the database server for obtaining the observation criteria information from the database server and collecting process data based on the observation criteria information. The process evaluation module utilizes a personal digital assistant (PDA). A data display module in communication with the database server, including a website for viewing collected process data in a desired metrics form, the data display module also for providing desired editing and modification of the collected process data. The connectivity established by the database server to the administration module, the process evaluation module, and the data display module, minimizes the requirement for manual input of the collected process data.
NASA Technical Reports Server (NTRS)
Denning, Peter J.
1989-01-01
Sparse distributed memory was proposed be Pentti Kanerva as a realizable architecture that could store large patterns and retrieve them based on partial matches with patterns representing current sensory inputs. This memory exhibits behaviors, both in theory and in experiment, that resemble those previously unapproached by machines - e.g., rapid recognition of faces or odors, discovery of new connections between seemingly unrelated ideas, continuation of a sequence of events when given a cue from the middle, knowing that one doesn't know, or getting stuck with an answer on the tip of one's tongue. These behaviors are now within reach of machines that can be incorporated into the computing systems of robots capable of seeing, talking, and manipulating. Kanerva's theory is a break with the Western rationalistic tradition, allowing a new interpretation of learning and cognition that respects biology and the mysteries of individual human beings.
Mediated semiquantum key distribution
NASA Astrophysics Data System (ADS)
Krawec, Walter O.
2015-03-01
In this work, we design a quantum key distribution protocol, allowing two limited semiquantum or "classical" users to establish a shared secret key with the help of a fully quantum server. A semiquantum user can prepare and measure qubits only in the computational basis and so must rely on this quantum server to produce qubits in alternative bases and also to perform alternative measurements. However, we assume that the server is untrusted and we prove the unconditional security of our protocol even in the worst case: when this quantum server is an all-powerful adversary. We also compute a lower bound of the key rate of our protocol, in the asymptotic scenario, as a function of the observed error rate in the channel, allowing us to compute the maximally tolerated error of our protocol. Our results show that a semiquantum protocol may hold similar security to a fully quantum one.
Nuclear Parton Distribution Functions
Schienbein, I.; Yu, J.-Y.; Keppel, Cynthia; Morfin, Jorge; Olness, F.; Owens, J.F.
2009-01-01
We study nuclear effects of charged current deep inelastic neutrino-iron scattering in the framework of a chi^2 analysis of parton distribution functions (PDFs). We extract a set of iron PDFs which are used to compute x_Bj-dependent and Q^2-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged-lepton--iron scattering. We find that, except for very high x_Bj, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.
Nuclear Parton Distribution Functions
I. Schienbein, J.Y. Yu, C. Keppel, J.G. Morfin, F. Olness, J.F. Owens
2009-06-01
We study nuclear effects of charged current deep inelastic neutrino-iron scattering in the framework of a {chi}{sup 2} analysis of parton distribution functions (PDFs). We extract a set of iron PDFs which are used to compute x{sub Bj}-dependent and Q{sup 2}-dependent nuclear correction factors for iron structure functions which are required in global analyses of free nucleon PDFs. We compare our results with nuclear correction factors from neutrino-nucleus scattering models and correction factors for charged-lepton--iron scattering. We find that, except for very high x{sub Bj}, our correction factors differ in both shape and magnitude from the correction factors of the models and charged-lepton scattering.
NASA Astrophysics Data System (ADS)
Aloisio, Giovanni; Fiore, Sandro; Negro, A.
2010-05-01
The CMCC Data Distribution Centre (DDC) is the primary entry point (web gateway) to the CMCC. It is a Data Grid Portal providing a ubiquitous and pervasive way to ease data publishing, climate metadata search, datasets discovery, metadata annotation, data access, data aggregation, sub-setting, etc. The grid portal security model includes the use of HTTPS protocol for secure communication with the client (based on X509v3 certificates that must be loaded into the browser) and secure cookies to establish and maintain user sessions. The CMCC DDC is now in a pre-production phase and it is currently used only by internal users (CMCC researchers and climate scientists). The most important component already available in the CMCC DDC is the Search Engine which allows users to perform, through web interfaces, distributed search and discovery activities by introducing one or more of the following search criteria: horizontal extent (which can be specified by interacting with a geographic map), vertical extent, temporal extent, keywords, topics, creation date, etc. By means of this page the user submits the first step of the query process on the metadata DB, then, she can choose one or more datasets retrieving and displaying the complete XML metadata description (from the browser). This way, the second step of the query process is carried out by accessing to a specific XML document of the metadata DB. Finally, through the web interface, the user can access to and download (partially or totally) the data stored on the storage device accessing to OPeNDAP servers and to other available grid storage interfaces. Requests concerning datasets stored in deep storage will be served asynchronously.
Efficient Methods for Stable Distributions
2007-11-02
are used, corresponding to the common values used in digital signal processing. Five new functions for discrete/quantized stable distributions were...written. • sgendiscrete generates discrete stable random variates. It works by generating continuous stable random variables using the Chambers- Mallows ...with stable distributions. It allows engineers and scientists to analyze data and work with stable distributions within the common matlab environment
Correction of Distributed Optical Aberrations
Baker, K; Olivier, S; Carrano, C; Phillion, D
2006-02-12
The objective of this project was to demonstrate the use of multiple distributed deformable mirrors (DMs) to improve the performance of optical systems with distributed aberrations. This concept is expected to provide dramatic improvement in the optical performance of systems in applications where the aberrations are distributed along the optical path or within the instrument itself. Our approach used multiple actuated DMs distributed to match the aberration distribution. The project developed the algorithms necessary to determine the required corrections and simulate the performance of these multiple DM systems.
Distributed Simulation for Space Exploration
NASA Technical Reports Server (NTRS)
Crues, Edwin Z.
2006-01-01
This viewgraph presentation reviews the use of simulation and modeling in preparation for the planned exploration initiatives. The Exploration Systems Mission Directorate (EMSD) Integrated Modeling and Simulation (IM&S) team strategy encompasses a wide spectrum of simulation and modeling policies and technologies. One prominent technology is distributed simulation. The DIstributed Simulation (DIS),a collaborative simulation project with international participation (US and Japan) is reviewed as an example of distributed simulation development. The Distributed Space Exploration Simulation (DSES) is another example of distributed simulation that is described
NASA Technical Reports Server (NTRS)
2008-01-01
NASA s advanced visual simulations are essential for analyses associated with life cycle planning, design, training, testing, operations, and evaluation. Kennedy Space Center, in particular, uses simulations for ground services and space exploration planning in an effort to reduce risk and costs while improving safety and performance. However, it has been difficult to circulate and share the results of simulation tools among the field centers, and distance and travel expenses have made timely collaboration even harder. In response, NASA joined with Valador Inc. to develop the Distributed Observer Network (DON), a collaborative environment that leverages game technology to bring 3-D simulations to conventional desktop and laptop computers. DON enables teams of engineers working on design and operations to view and collaborate on 3-D representations of data generated by authoritative tools. DON takes models and telemetry from these sources and, using commercial game engine technology, displays the simulation results in a 3-D visual environment. Multiple widely dispersed users, working individually or in groups, can view and analyze simulation results on desktop and laptop computers in real time.