NIFTy 3 – Numerical Information Field Theory: A Python Framework for Multicomponent Signal Inference on HPC Clusters

NIFTy , “Numerical Information Field Theory,” is a software framework designed to ease the development and implementation of field inference algorithms. Field equations are formulated independently of the underlying spatial geometry allowing the user to focus on the algorithmic design. Under the hood, NIFTy ensures that the discretization of the implemented equations is consistent. This enables the user to prototype an algorithm rapidly in 1D and then apply it to high‐dimensional real‐world problems. This paper introduces NIFTy  3, a major upgrade to the original NIFTy  framework. NIFTy  3 allows the user to run inference algorithms on massively parallel high performance computing clusters without changing the implementation of the field equations. It supports n‐dimensional Cartesian spaces, spherical spaces, power spaces, and product spaces as well as transforms to their harmonic counterparts. Furthermore, NIFTy  3 is able to handle non‐scalar fields, such as vector or tensor fields. The functionality and performance of the software package is demonstrated with example code, which implements a mock inference inspired by a real‐world algorithm from the realm of information field theory. NIFTy  3 is open‐source software available under the GNU General Public License v3 (GPL‐3) at https://gitlab.mpcdf.mpg.de/ift/NIFTy/tree/NIFTy_3 .     

Kinetics of ionization-recombination processes in nonideal hydrogen plasmas

The time evolution of the relative populations of excited atomic levels in a reacting dense H-plasma is studied on the basis of rate equations. Many-particle effects are taken into account via energy level shifts. It is found that the occupation of the bound state levels is essentially smaller than for the ideal case. It is shown that the mechanism of the relaxation to the thermal equilibrium depends on the density. Inversions of the level populations can be observed.     

Dipole Chains in Zeolite Pores: The Effects of Symmetry Breaking

Abstract

Dipole molecules become arranged in a highly ordered manner within zeolite pores. They are oriented nearly parallel to the straight channels and aligned collectively into one specific direction. They form arrangements different from the crystallization in the free bulk as well as different from arrangements in amorphous hosts. This polar arrangement results in (i) a lowering of the symmetry of the guest-host system compared to the host, (ii) nonlinear optical effects of second order such as second harmonic generation, (iii) a macroscopic polarization giving rise to pyroelectric effects and (iv) special phase transition phenomena in these one-dimensional systems.     

Geometric Variational Inference

Efficiently accessing the information contained in non-linear and high dimensional probability distributions remains a core challenge in modern statistics. Traditionally, estimators that go beyond point estimates are either categorized as Variational Inference (VI) or Markov-Chain Monte-Carlo (MCMC) techniques. While MCMC methods that utilize the geometric properties of continuous probability distributions to increase their efficiency have been proposed, VI methods rarely use the geometry. This work aims to fill this gap and proposes geometric Variational Inference (geoVI), a method based on Riemannian geometry and the Fisher information metric. It is used to construct a coordinate transformation that relates the Riemannian manifold associated with the metric to Euclidean space. The distribution, expressed in the coordinate system induced by the transformation, takes a particularly simple form that allows for an accurate variational approximation by a normal distribution. Furthermore, the algorithmic structure allows for an efficient implementation of geoVI which is demonstrated on multiple examples, ranging from low-dimensional illustrative ones to non-linear, hierarchical Bayesian inverse problems in thousands of dimensions.     

Adhesion of microcapsules

The adhesion of microcapsules to an attractive contact potential is studied theoretically. The axisymmetric shape equations are solved numerically. Beyond a universal threshold strength of the potential, the contact radius increases in proportion to the square root of the strength. Scaling functions for the corresponding amplitudes are derived as a function of the elastic parameters.     

A model establishment and numerical simulation of dynamic coupled hydraulic–mechanical–electric–structural system for hydropower station

Nonlinear Dynamics - A nonlinear dynamic coupled model for hydropower station system, which contains the model of water-carriage system, water turbine system, speed governor system,...     

Messung derL-Auger-, Fluoreszenz- und Coster-Kronig-Ausbeuten von Gold

An apparatus is described, with which, for the first time, the spectra of Augere-lectrons and of X-rays, produced by the impact of electrons, were measured simultaneously. The electron spectrometer was a magnetic 180°-spectrometer with a half-width of 0·5%. The X-ray spectrometer was a NaJ-crystal with a photomultiplier. The electron- and the X-rays were produced in metallic foils of a thickness of 50 Å by the impact of 55-keV-electrons. The knownK-fluorescence-yields of copper and selenium were used to determine the various yields for theL-shells of gold. TheL-fluorescence-yields areω _L1 =0·08±0·01;ω _L2 =0·26±0·03;ω _L3 =0·24±0·02.     

光学表面光散射特性分析

通过对光学表面光散射特性的研究,结果表明:光散射强度随入射光波长的增加而减小,随表面粗糙度增加而增加.     

Über die Zersetzlichkeit komplexer Metallcyanide bei der Cyanidbestimmung in Abwasser

Serial studies on the behaviour of simple and complex cyanides against the attack of dilute sulphuric acid within the determination of “total cyanide” in waste water resulted in the cyanide complexes of zinc, cadmium, copper, nickel, iron(II) and iron(III) being decomposed quite rapidly by dilute sulphuric acid in the concentration range of ≦ 100 mg CN-/l. Consequently, in such cases the total amount of cyanide can be determined in the first 25 ml of the distillate.