Application of Calorimetric Low Temperature Detectors (CLTD’s) for Precise Stopping Power Measurements of Heavy Ions in Matter

Calorimetric low temperature detectors (CLTD’s) have been included in a B-ToF setup, that has already been used several times to perform energy loss measurements at the accelerator laboratory of the University of Jyväskylä. The new experimental setup enabled a precise determination of stopping power data for 0.05–1 MeV/u (^{131}) Xe ions in carbon, nickel and gold. The results are presented and compared to data from literature and theoretical predictions. As a by-product, due to the excellent energy resolution of CLTD’s for heavy ions at low energies, an observation of channeling effects in very thin polycrystalline targets and a determination of the channeling energy loss for 0.1–0.5 MeV/u (^{131}) Xe-ions in Ni- and Au-absorbers was possible.     

FATIGUE OF POLYCRYSTALLINE COPPER AT CONSTANT AND VARIABLE PLASTIC STRAIN AMPLITUDES

Fatigue behavior of polycrystalline copper of two different grain sizes was studied using constant and randomly varying plastic strain amplitude tests. The different regimes in the ess-curves of large-grained samples (d? 2.0 mm) were found to be reflected also in the measured fatigue lives in both test modes. The variable amplitude fatigue lives of the small-grained samples (d? 0.03 mm) seemed to follow the Coffin–Manson linear law. The damage accumulation rate in variable amplitude tests was found to be lower than in the corresponding constant amplitude tests, e.g. when expressed as cumulative plastic strains to failure. The fatigue life predictions based on the Palmgren–Miner rule, rain-flow analysis and the constant amplitude life data measured in this work were also conservative.     

Parallel computation of three-dimensional nonlinear magnetostatic problems

We describe a general-purpose parallel code for computing accurate solutions to large computationally demanding, 3D, nonlinear magnetostatic problems. The code, CORAL, is based on a volume integral equation formulation. Using an IBM SP parallel computer and iterative solution methods, we successfully solved the dense linear systems inherent in such formulations. A key component of our work was the use of the PETSc library, which provides parallel portability and access to the latest linear algebra solution technology. Copyright © 1999 John Wiley & Sons, Ltd.     

Tetrahedral mesh generation in convex primitives

This paper presents a method for generating tetrahedral meshes in three-dimensional primitives. Given a set of closed and convex polyhedra having non-zero volume and some mesh controlling parameters, the polyhedra are automatically split to tetrahedra satisfying the criteria of standard finite element meshes. The algorithm tries to generate elements close to regular tetrahedra by maximizing locally the minimum solid angles associated to a set of a few neighbouring tetrahedra. The input parameters define the size of the tetrahedra and they can be used to increase or decrease the discretization locally. All the new nodes, which are not needed to describe the geometry, are generated automatically.     

Hydrophobic nanocellulose aerogels as floating, sustainable, reusable, and recyclable oil absorbents

Highly porous nanocellulose aerogels can be prepared by vacuum freeze-drying from microfibrillated cellulose hydrogels. Here we show that by functionalizing the native cellulose nanofibrils of the aerogel with a hydrophobic but oleophilic coating, such as titanium dioxide, a selectively oil-absorbing material capable of floating on water is achieved. Because of the low density and the ability to absorb nonpolar liquids and oils up to nearly all of its initial volume, the surface modified aerogels allow to collect organic contaminants from the water surface. The materials can be reused after washing, recycled, or incinerated with the absorbed oil. The cellulose is renewable and titanium dioxide is not environmentally hazardous, thus promoting potential in environmental applications.