Introduction: In Diffusion MRI, spherical functions are commonly employed to represent the diffusion information. The ODF is an intuitive spherical function since its maxima are aligned with the dominant fiber directions. Therefore, it is important to correctly determine these maximal directions, as they are the key to tracing fiber tracts. A tractography algorithm will suffer from cumulative e...

Recently, infeasibility issues in interior methods for nonconvex nonlinear programming have been studied. In particular, it has been shown how many line-search interior methods may converge to an infeasible point which is on the boundary of the feasible region with respect to the inequality constraints. The convergence is such that the search direction does not tend to zero, but the step length...

The purpose of this paper is to introduce a new instance of the Mesh Adaptive Direct Search (Mads) class of algorithms, which utilizes a more uniform distribution of poll directions than do other common instances, such as OrthoMads and LtMads. Our new implementation, called QrMads, bases its poll directions on an equal area partitioning of the n-dimensional unit sphere and the QR decomposition ...

We present the results of a search for small-scale anisotropy in the distribution of arrival directions of cosmic rays above 10 19 eV measured in stereo by the High Resolution Fly's Eye (HiRes) experiment. Performing an autocorrelation scan in energy and angular separation, we find that the strongest correlation signal in the HiRes stereo data set recorded between December 1999 and January 2004...

We search for alternatives to the trivial φ 4 field theory by including arbitrary powers of the self-coupling. Such theories are renormalizable when the natural cutoff dependencies of the coupling constants are taken into account. We find a continuum of fixed points, which includes the well-known Gaussian fixed point. The fixed point density has a maximum at a location corresponding to a theory...

In this short note we observe that results of Dennis and Audet extend naturally to a wide variety of deterministic sampling methods. For bound-constrained problems, we show that any method based on coordinate search which includes a sufficiently rich set of directions, for example random directions at each state of the sampling, will, when applied to Lipschitz continuous problems, have cluster ...

We develop a computationally eecient method to determine the interaction structure in a multidimensional binary sample. We use an interaction model based on orthogonal functions, and give a result on independence properties in this model. Using this result we develop an eecient approximation algorithm for estimating the parameters in a given undi-rected model. To nd the best model, we use a heu...

Two new nonlinear spectral conjugate gradient methods for solving unconstrained optimization problems are proposed. One is based on the Hestenes and Stiefel (HS) method and the spectral conjugate gradient method. The other is based on a mixed spectral HS-CD conjugate gradient method, which combines the advantages of the spectral conjugate gradient method, the HS method, and the CD method. The d...

In this paper, we present a three-view matching algorithm that takes into account surface foreshortening effects to match image feature points and provides surface normal directions at these points as a by-product. Compared to other existing, similar algorithms that consider surface foreshortening effects, our algorithm is more efficient since it decomposes a 2D surface orientation search into ...

We consider inflaton couplings to MSSM flat directions and the thermalization of the inflaton decay products, taking into account gauge symmetry breaking due to flat direction condensates. We then search for a suitable curvaton candidate among the flat directions, requiring an early thermally induced start for the flat direction oscillations to facilitate the necessary curvaton energy density d...