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See detailOn the capability to derive mass estimates from high-low satellite-to-satellite tracking data
Weigelt, Matthias UL; van Dam, Tonie UL; Tourian, M. J. et al

Poster (2013, December)

Recently it has been shown that it is possible to derive time-variable gravity signals from high-low satellite-to-satellite tracking (hl-SST) missions (Weigelt et al. 2013, JGR:Solid Earth, doi:10.1002 ... [more ▼]

Recently it has been shown that it is possible to derive time-variable gravity signals from high-low satellite-to-satellite tracking (hl-SST) missions (Weigelt et al. 2013, JGR:Solid Earth, doi:10.1002/jgrb.50283). Based on the GPS information only, we will present results derived from the dedicated gravity field missions CHAMP, GRACE and GOCE which allow us to determine mass estimates for various applications. Hydrologically induced mass changes on land cause the strongest mass variations in the gravity field and can be easily identified in the hl-SST data, especially in areas with strong signals such as the Amazon basin. Ice melt in Greenland can be derived from the data and mass estimates compare well to corresponding GRACE estimates. Also, loading time series based on these gravity field solutions agree well with GPS observations for various stations around the globe. We also discuss the limitations of the data, e.g. in detecting signals related to glacial isostatic adjustment or earthquake-induced gravity field changes. Overall, we will demonstrate that the quality of the GPS data is sufficient nowadays and with a proper processing strategy it is possible to derive reasonable mass estimates. As such, this type of observations may allow to bridge a possible gap between GRACE and its successor GRACE Follow-On scheduled for launch in 2017. [less ▲]

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See detailOn the Capacity of Variable Density Cellular Systems under Multicell Decoding
Chatzinotas, Symeon UL; Imran, Muhammad Ali; Tzaras, Costas

in IEEE Communications Letters (2008), 12(7), 496-498

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See detailOn the cardinality index of fuzzy measures and the signatures of coherent systems
Mathonet, Pierre UL; Marichal, Jean-Luc UL

in Mesiar, Radko; Pap, Endre; Klement, Erich Peter (Eds.) 34th Linz Seminar on Fuzzy Set Theory (LINZ 2013) - Non-Classical Measures and Integrals (2013)

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See detailOn the category of Lie n-algebroids
Bonavolontà, Giuseppe UL; Poncin, Norbert UL

in Journal of Geometry & Physics (2013), 73

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See detailOn the change in helix handedness at transitions between the sm-c* and sm-ca* phases in chiral smectic liquid crystals
Lagerwall, Jan UL; Giesselmann, Frank; Osipov, Mikhail A.

in Liquid Crystals (2006), 33(6), 625-633

Using a discrete model for the synclinic SmC* and the anticlinic SmC􏰀a phases we give a theoretical explanation for the fact that the helix twisting sense reverses at a transition between these phases ... [more ▼]

Using a discrete model for the synclinic SmC* and the anticlinic SmC􏰀a phases we give a theoretical explanation for the fact that the helix twisting sense reverses at a transition between these phases (direct transition or via the so-called chiral smectic C ‘subphases’) and we derive an explicit expression for the helical pitch in the SmC􏰀a phase. As the theory shows and as we also demonstrate experimentally, the reversal is of a different nature from helix inversions within a single phase, where the inversion is always coupled to a pitch divergence. At a clinicity change the common behaviour is instead pitch-shortening on approaching the phase transition and the associated helix twisting sense reversal. The phenomenon may be put to use in smart mixing in order to control the helix pitch, either for achieving long pitch for surface-stabilized ferroelectric and antiferroelectric liquid crystal displays; or a very short pitch, in the case of devices utilizing the deformed helix mode. [less ▲]

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See detailOn the characterization of generalized Dhombres equations having non constant local analytic or formal solutions
Reich, Ludwig; Tomaschek, Jörg UL

in Annales Universitatis Scientiarium Budapestinensis de Rolando Eötvös Nominatae Sectio Computatorica (2013), 41

We discuss solvability conditions of the generalized Dhombres functional equation in the complex domain. Our focus lies on the so-called 'infinity' case, but also the $z_0$--case is investigated. That ... [more ▼]

We discuss solvability conditions of the generalized Dhombres functional equation in the complex domain. Our focus lies on the so-called 'infinity' case, but also the $z_0$--case is investigated. That means that we consider solutions of a generalized Dhombres equation with initial value $f(\infty)=w_0$, $w_0 \neq 0$, or $f(\infty)=\infty$, or $f(z_0)=1$ for $z_0 \neq 0, \infty$. For both situations we give a characterization of the generalized Dhombres equations which are solvable. [less ▲]

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See detailOn the characterization of generalized Dhombres functional equations
Tomaschek, Jörg UL

Scientific Conference (2013, May 23)

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See detailOn the choice of a phase interchange strategy for a multiscale DEM-VOF Method
Pozzetti, Gabriele UL; Peters, Bernhard UL

in AIP Conference Proceedings (2017), 1863

In this work a novel Multiscale DEM-VOF method is adopted to study three phase flows. It consists in solving the fluid momentum, mass conservation and the phase advection at a different scale with respect ... [more ▼]

In this work a novel Multiscale DEM-VOF method is adopted to study three phase flows. It consists in solving the fluid momentum, mass conservation and the phase advection at a different scale with respect to the fluid-particle coupling problem. This allows the VOF scheme to resolve smaller fluid structures than a classic DEM-VOF method, and opens the possibility of adopting different volume interchange techniques. Two different volume interchange techniques are here described and compared with reference to high and low particle concentration scenarios. Considerations about the respective computational costs are also proposed. [less ▲]

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See detailOn the choice of parameters in the phase field method for simulating crack initiation with experimental validation
Nguyen, Thanh Tung UL; Yvonnet, J.; Bornert, M. et al

in International Journal of Fracture (2016), 197(2), 213--226

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See detailOn the classical solution to the linear-constrained minimum energy problem
Schiltz, Jang UL; Boissaux, Marc UL

in International Journal of Control (2012), 1

Minimum energy problems involving linear systems with quadratic performance criteria are classical in optimal control theory. The case where controls are constrained is discussed in Athans and Falb (1966 ... [more ▼]

Minimum energy problems involving linear systems with quadratic performance criteria are classical in optimal control theory. The case where controls are constrained is discussed in Athans and Falb (1966) [Athans, M. and Falb, P.L. (1966), Optimal Control: An Introduction to the Theory and Its Applications, New York: McGraw-Hill Book Co.] who obtain a componentwise optimal control expression involving a saturation function expression. We show why the given expression is not generally optimal in the case where the dimension of the control is greater than one and provide a numerical counterexample. [less ▲]

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See detailOn the coexistence of SmC* and SmCa* phases in binary chiral-dopant antiferroelectric mixtures
Lagerwall, Jan UL; Parghi, D. D.; Heppke, Gerd et al

in Ferroelectrics (2000), 244

We present the results from investigations on a series of binary chiral- dopant liquid-crystalline mixtures. The racemic host materials possess tilted smectic phases with varying strengths of synclinic ... [more ▼]

We present the results from investigations on a series of binary chiral- dopant liquid-crystalline mixtures. The racemic host materials possess tilted smectic phases with varying strengths of synclinic and anticlinic ordering (SmC and SmCalt phases respectively). The dopants used were either a strongly synclinic-favouring non liquid-crystalline chiral material (commonly used in FLC chiral-dopant mixtures) or a strongly anticlinic (antiferroelectric) material ((S)-MHPOBC). The electrooptic and dielectric properties of the mixtures were investigated in test cells of different thickness and the influence of each mixture component on the observed physical properties is discussed. [less ▲]

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See detailOn the Cohomological Crepant Resolution Conjecture for the complexified Bianchi orbifolds
Perroni, Fabio; Rahm, Alexander UL

in Algebraic and Geometric Topology (in press)

We give formulae for the Chen--Ruan orbifold cohomology for the orbifolds given by a Bianchi group acting on complex hyperbolic 3-space. The Bianchi groups are the arithmetic groups PSL_2(A), where A is ... [more ▼]

We give formulae for the Chen--Ruan orbifold cohomology for the orbifolds given by a Bianchi group acting on complex hyperbolic 3-space. The Bianchi groups are the arithmetic groups PSL_2(A), where A is the ring of integers in an imaginary quadratic number field. The underlying real orbifolds which help us in our study, given by the action of a Bianchi group on real hyperbolic 3-space (which is a model for its classifying space for proper actions), have applications in physics. We then prove that, for any such orbifold, its Chen-Ruan orbifold cohomology ring is isomorphic to the usual cohomology ring of any crepant resolution of its coarse moduli space. By vanishing of the quantum corrections, we show that this result fits in with Ruan's Cohomological Crepant Resolution Conjecture. [less ▲]

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See detailOn the cohomology of the Nijenhuis-Richardson graded Lie algebra of the space of functions of a manifold
Poncin, Norbert UL

in Journal of Algebra (2001), 243(1), 16-40

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See detailOn the collaborative work between psychiatry and social work in developing transcultural capability in mental health care.
Lurbe-Puerto, Katia UL; Baumann, Michèle UL

in Effets psychosociaux de la mondialisation sur la santé mentale. (2011)

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See detailOn the combined effect of periodic signals and colored noise on velocity uncertainties
Klos, Anna; Olivares Pulido, German UL; Teferle, Felix Norman UL et al

in GPS Solutions (2017)

The velocity estimates and their uncertainties derived from position time series of Global Navigation Satellite System stations are affected by seasonal signals and their harmonics, and the statistical ... [more ▼]

The velocity estimates and their uncertainties derived from position time series of Global Navigation Satellite System stations are affected by seasonal signals and their harmonics, and the statistical properties, i.e., the stochastic noise, contained in the series. If the deterministic model in the form of linear trend and periodic terms is not accurate enough to describe the time series, it will alter the stochastic model, and the resulting effect on the velocity uncertainties can be perceived as a result of a misfit of the deterministic model. The effects of insufficiently modeled seasonal signals will propagate into the stochastic model and falsify the results of the noise analysis, in addition to velocity estimates and their uncertainties. We provide the general dilution of precision (GDP) of velocity uncertainties as the ratio of uncertainties of velocities determined from to two different deterministic models while accounting for stochastic noise at the same time. In this newly defined GDP, the first deterministic model includes a linear trend, while the second one includes a linear trend and seasonal signals. These two are tested with the assumption of white noise only as well as the combinations of power-law and white noise in the data. The more seasonal terms are added to the series, the more biased the velocity uncertainties become. With increasing time span of observations, the assumption of seasonal signals becomes less important, and the power-law character of the residuals starts to play a crucial role in the determined velocity uncertainties. With reference frame and sea level applications in mind, we argue that 7 and 9 years of continuous observations is the threshold for white and flicker noise, respectively, while 17 years are required for random-walk to decrease GDP below 5% and to omit periodic oscillations in the GNSS-derived time series taking only the noise model into consideration. [less ▲]

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See detailOn the Comparison of Radial Base Functions and Single Layer Density Representations in Local Gravity Field Modelling from Simulated Satellite Observations
Weigelt, Matthias UL; Keller, W.; Antoni, M.

in Sneeuw, Nico; Novák, Pavel; Crespi, Mattia (Eds.) et al VII Hotine-Marussi Symposium on Mathematical Geodesy (2012, January)

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See detailOn the Comparison of Radial Base Functions and Single Layer Density Representations in Local Gravity Field Modelling from Simulated Satellite Observations
Weigelt, Matthias UL; Keller, Wolfgang; Antoni, Markus

Scientific Conference (2009, June)

The recovery of local (time-variable) gravity features from satellite-to-satellite tracking missions is one of the current challenges in Geodesy. Often, a global spherical harmonic analysis is used and ... [more ▼]

The recovery of local (time-variable) gravity features from satellite-to-satellite tracking missions is one of the current challenges in Geodesy. Often, a global spherical harmonic analysis is used and the area of interest is selected later on. However, this approach has deficiencies since leakage and incomplete recovery of signal are common side effects. In order to make better use of the signal content, a gravity recovery using localizing base functions can be employed. In this paper, two different techniques are compared in a case study using simulated potential observations at satellite level – namely position-optimized radial base functions and a single layer representation using a piecewise continuous density. The first one is the more common approach. Several variants exist which mainly differ in the choice of the position of the base function and the regularization method. Here, the position of each base is subject to an adjustment process. On the other hand, the chosen radial base functions are developed as a series of Legendre functions which still have a global support although they decay rapidly. The more rigorous approach is to use base functions with a strictly finite support. One possible choice is a single layer representation whereas the density is discretized by basic shapes like triangles, rectangles, or higher order elements. Each type of shape has its own number of nodes. The higher the number of nodes of a particular element, the more complicated becomes the solution strategy but at the same time the regularity of the solution increases. Here, triangles are used for the comparison. As a result, the radial base functions in the employed variant allow a modeling with a minimum number of parameters but do not achieve the same level of approximation as the discretized single layer representation. The latter do so at the cost of a higher number of parameters and regularization. This case study offers an interesting comparison of a near localizing with a strictly localizing base function. However, results can currently not be generalized as other variants of the radial base functions might perform better. Also, the extension to a GRACE-type observable is desirable. [less ▲]

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See detailOn the complexity of input/output logic
Sun, Xin UL; Ambrossio, Diego Agustin UL

in Proceedings of the Fifth International Conference on Logic, Rationality and Interaction (2015)

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See detailOn the Complexity of Input/Output Logic
Robaldo, Livio UL; Sun, Xin

in Journal of Applied Logic (2017)

Detailed reference viewed: 74 (4 UL)