Volume integral equations in non-linear 3-D magnetostatics

In this paper a discussion of volume integral formulations in three-dimensional non-linear magnetostatics is presented. Integral formulations are examined in connection with Whitney's elements in order to find new approaches. A numerical algorithm based on a formulation implying properly the continuity conditions of magnetic field strength H, i.e. an h-type formulation, is introduced. Results of demanding application problems are shown demonstrating the characteristics of this kind of volume integral approach. In addition, a discussion of the parallelized version of the numerical code based on the h-type approach is presented appended with numerical results illustrating the advantages of combining integral formulations with concurrent computing.     

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.     

Diffractive elements designed to suppress unwanted zeroth order due to surface depth error

Abstract

We consider a design approach to reduce unwanted zero-order intensity due to profile depth error in diffractive elements. Our method is based on addition of local bias phase to a binary element phase, leading to the introduction of a third phase level. We show theoretically and experimentally that gratings obtained with such modifications are more tolerant to profile depth error than conventionally designed binary or multilevel elements, thus reducing the appearance of unwanted zero order.     

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.     

Alternating copolymerization and terpolymerization of vinyl‐substituted phenolic antioxidants with propene and carbon monoxide by a palladium(II)‐based catalyst: polyketones containing intramolecular stabilizers

The copolymerization and terpolymerization reactions of the vinyl‐substituted phenolic stabilizers, 6‐tert‐butyl‐2‐(1,1‐dimethylhept‐6‐enyl)‐4‐methylphenol, o‐allylphenol, 4‐methylstyrene‐2,6‐di‐tert‐butylphenol and 2,6‐di‐tert‐butyl‐4‐allylphenol, with propene and carbon monoxide, by using the solvent‐stabilized palladium(II ) phosphine complex [Pd(dppp)(NCCH₃)₂](BF₄)₂ (dppp, 1,3‐bis(diphenylphosphino)propane) as a catalyst precursor and methanol as a co‐catalyst, is described. The influence of functional α‐olefins/CO units, distributed statistically along the propene/carbon monoxide (P/CO) copolymer backbone, on the molecular weight, glass transition temperature (T_g), elastic behavior and stability of the high‐molecular‐weight P/CO copolymer has been investigated. Loss of both elasticity and transparency were observed upon incorporating o‐allylphenol as a termonomer. The terpolymers, which contain phenolic stabilizers, were shown to be more stable when compared to the stabilizer‐free polyketones. In contrast to the propene/carbon monoxide copolymer, no degradation was observed for the 2,6‐di‐tert‐butyl‐4‐allylphenol/P/CO terpolymer; instead, the molar masses increased. Copyright © 2004 Society of Chemical Industry     

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.     

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.     

Behavioral profiles—a way to model and validate program behavior

Software architecture contains, in addition to its structural part, interaction patterns that can be regarded as part of the architectural solution of the system. The interaction patterns define architecturally significant behavior of the software system. In this paper we propose a visual modeling language, behavioral profiles, for specifying architecturally significant behavioral rules for an application. The language is built on the Unified Modeling Language (UML), which is a visual language widely used in software development. We show how behavioral profiles can be used to support software designers in creating behavioral models that conform to some predefined rules and for ensuring that an application behaves correctly with respect to the rules given in the profiles. A tool called Bebop was built to support software engineers in behavioral profile‐based design and analysis of program behavior. To evaluate the approach and the tools in different application domains, they are utilized in three cases. The size of the applications used in the cases varies from small to quite large software systems, and from academic to industrial ones. The examples demonstrate how the approach presented can be used in practice for different steps in a software engineering process. The examples cover specializing an application framework and monitoring the program execution in run‐time. In addition, they show how behavioral profiles can be used to support guided program comprehension and to validate program execution by analyzing execution traces. Copyright © 2010 John Wiley & Sons, Ltd.     

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.