BRIAN (Brain image analysis): A toolkit for the analysis of multimodal brain datasets

The analysis of cognitive processes in man usually involves multiple examina­tion modalities which map different aspects of the brain. Among these proce­dures, at least one modality yielding anatomical information (i.e. MRI*) besidesone or more functional modalities (fMRI, PET, SPECT, EEG, MEG) are involved.Because these different examination methods yield complimentary informationabout the anatomical, metabolical and neurophysiological state of the brain, acombined data evaluation is highly desirable and will lead to results not achiev­able within one examination domain.Such studies are of importance in research (cognitive neuroscience) and ­ withan emphasis on pathological processes ­ in clinical disciplines like neurology,neurosurgery and psychiatry.We have developed a program package for the handling of image datasets(MRI, PET, SPECT, CCT) and signal datasets (EEG, MEG) which allows a com­bined analysis of these data sources in a four­dimensional coordinate space (x, y,z, and time)

Numerical analysis of wet separation of particles by density differences

Wet particle separation is widely used in mineral processing and plastic recycling to separate mixtures of particulate materials into further usable fractions due to density differences. This work presents efforts aiming to numerically analyze the wet separation of particles with different densities. In the current study the discrete element method (DEM) is used for the solid phase while the smoothed particle hydrodynamics (SPH) is used for modeling of the liquid phase. The two phases are coupled by the use of a volume averaging technique. In the current study, simulations of spherical particle separation were performed. In these simulations, a set of generated particles with two different densities is dropped into a rectangular container filled with liquid. The results of simulations with two different mixtures of particles demonstrated how separation depends on the densities of particles.Comment: This manuscript was accepted for the publication in the conference proceedings of ICNAAM 2016 conferenc

Extension of process models to predict batch screening results under the influence of moisture based on DEM simulations

Screening is a technical simple but still not fully understood process step, which can be used in a wide field of applications to separate bulk materials according to their particle sizes. A severe issue in screening technologies is that particles frequently prevail in moist conditions, due to effects related to the environment, the material or the process. This is often not preventable, although it is not preferred due to attractive forces altering the screening efficiency. For the design of dry screening processes, phenomenological models and detailed particle-based simulation approaches like the discrete element method (DEM) are available. The latter method has recently been extended and validated against experiments to calculate forces caused by liquid bridges formed out between particles or walls close to each other to meet the requirements to tackle real particle systems under moist conditions. In the investigation here, batch screening under the influence of moisture involving different sized glass spheres is investigated numerically with DEM simulations and by using process models. Therein, the related subprocesses stratification and passage as well as the influence of the operating parameters and the liquid amount on the fraction retained per size class are examined. Existing phenomenological process models, which can be applied efficiently for industrial applications due to their short calculation time, are extended to represent batch screening processes under moist conditions for the first time. Therefore, a benchmark is realized in which the fraction retained per size class over time for discontinuous screening under the influence of various amounts of liquid and different mechanical agitations obtained by DEM simulations and process models is compared. In this context, the process models are first adjusted to fit related simulation results and later used in a novel method to predict the outcome of screening with different operating parameters and liquid amounts. Thereby, process models, which consider the subprocesses stratification and passage, predict screening results for process parameters requiring interpolation or extrapolation in the investigated range very well. As a consequence, newly derived process models can function as prototypes to be applied in dynamic process simulation frameworks.DFG, SPP 1679, Dynamische Simulation vernetzter Feststoffprozess

The Words of Institution- An Exegetical Study

The words of institution for the Lord\u27s Supper can be taken absolutely literally. The only words which require any interpretation are “body” and “blood. These can be interpreted only in the light of the concept of communion.” On the basis of the text and in harmony with the Lutheran confessions this leads to three points, often called the Shibboleths of the doctrine

Effective mass overshoot in single degree of freedom mechanical systems with a particle damper

We study the response of a single degree of freedom mechanical system composed of a primary mass, M, a linear spring, a viscous damper and a particle damper. The particle damper consists in a prismatic enclosure of variable height that contains spherical grains (total mass m_p). Contrary to what it has been discussed in previous experimental and simulation studies, we show that, for small containers, the system does not approach the fully detuned mass limit in a monotonous way. Rather, the system increases its effective mass up and above M+m_p before reaching this expected limiting value (which is associated with the immobilization of the particles due to a very restrictive container). Moreover, we show that a similar effect appears in the tall container limit where the system reaches effective masses below the expected asymptotic value M. We present a discussion on the origin of these overshoot responses and the consequences for industrial applications.Comment: 16 pages, 6 figure

Cortical Surface Reconstruction from High-Resolution MR Brain Images

Reconstruction of the cerebral cortex from magnetic resonance (MR) images is an important step in quantitative analysis of the human brain structure, for example, in sulcal morphometry and in studies of cortical thickness. Existing cortical reconstruction approaches are typically optimized for standard resolution (~1 mm) data and are not directly applicable to higher resolution images. A new PDE-based method is presented for the automated cortical reconstruction that is computationally efficient and scales well with grid resolution, and thus is particularly suitable for high-resolution MR images with submillimeter voxel size. The method uses a mathematical model of a field in an inhomogeneous dielectric. This field mapping, similarly to a Laplacian mapping, has nice laminar properties in the cortical layer, and helps to identify the unresolved boundaries between cortical banks in narrow sulci. The pial cortical surface is reconstructed by advection along the field gradient as a geometric deformable model constrained by topology-preserving level set approach. The method's performance is illustrated on exvivo images with 0.25–0.35 mm isotropic voxels. The method is further evaluated by cross-comparison with results of the FreeSurfer software on standard resolution data sets from the OASIS database featuring pairs of repeated scans for 20 healthy young subjects

Thermal lattice boltzmann simulation of diffusion/ forced convection using a double mrt model

The Lattice-Boltzmann method (LBM) is an alternative and flexible approach for computational fluid dynamics (CFD). Unlike many other direct numerical simulation (DNS) techniques, LBM is not solving the Navier-Stokes equations but is based on the kinetic theory and the discrete Boltzmann equation. LBM utilizes a Cartesian mesh and hence does not require a complex mesh derivation or a re-meshing in case of moving boundaries. Thermal LBM (TLBM) which is capable of solving thermal convection/diffusion problems relies on a set of two distribution functions, the so called double distribution function (DDF) approach; one for the fluid density and one for the internal energy. For the carried out numerical investigations a 3D TLBM framework is derived involving a multiple-relaxation-time (MRT) collision operator for both, the fluid and the temperature field which is yet not applied widely. Hydrodynamic and thermal boundary conditions are represented by interpolated bounce back schemes. The derived TLBM framework is applied to diffusion and convection-diffusion problems (e.g. forced convection) for plane and curved boundaries and is validated against analytical solutions, when available or compared to established correlations. The thermal MRT operator is further compared against an existing LBM model based on a thermal Bhatnagar-Gross-Krook (BGK) operator regarding accuracy and numerical stability. Averaged and local heat transfer coefficients are presented. The findings indicate that the double MRT framework with interpolated boundary conditions offers a highly accurate and efficient approach for the analysis of heat transfer problems especially for particle/fluid systems under detailed resolved flow

DEM simulations of screening processes under the influence of moisture

In a wide field of applications, screening is required to separate bulk materials according to their particle sizes. Due to environmental, material or process related effects, particles frequently prevail in moist conditions, which is not preferred due to attractive forces altering the screening efficiency, but often not preventable. As for the design of dry screening processes detailed particle-based simulation approaches like the discrete element method (DEM) and phenomenological models are available, a step towards meeting the requirements for real particle systems under moist conditions is made. Therefore, batch screening under the influence of moisture is investigated experimentally and by using DEM simulations involving different sized polyoxymethylene and glass spheres. For this purpose, a DEM code is extended to calculate forces caused by liquid bridges, forming out between particles or walls close to each other under moist conditions. Thereby, the bridge formation and rupture and the liquid distribution are considered. First, the DEM framework is validated against experiments by monitoring the capillary and viscous force acting on two liquid bridge contact partners. Further extensive validations are performed by comparing the fraction retained over time and the final liquid distribution for discontinuous screening under the influence of various amounts of liquid for different mechanical agitations in experiments and simulations. Finally, the detailed liquid distribution over time in the DEM simulations is examined and general conclusions are drawn. The overall aim is to use the framework and the respective data, to extend phenomenological process models for screening under moist conditions in subsequent studies.DFG, SPP 1679, Dynamische Simulation vernetzter Feststoffprozess