Pull-out and fragmentation in model fibre composites

An experimental study has been carried out of debonding and fibre rupture in model composites. A single glass rod or fibre was embedded in the centre of a long transparent silicone rubber block. Strains in the rubber in close proximity to the rod or fibre were measured as the specimen was slowly stretched. Pull-out forces, strain distributions, and debonded lengths are compared with the predictions of a simple theory based on a fracture energy criterion for debonding, and taking into account friction at the debonded interface. Experiments were carried out with rods of different diameter, rubber blocks of varied cross-section, and with two levels of adhesion. By extrapolating the debonded length to zero, values of the debonding force in the absence of friction were obtained. They were in accord with fracture energies of about 50 J/m² for weak bonding and about 200 J/m² for strong bonding. Fibre fragmentation lengths were measured also. They were in reasonable agreement with the inferred fracture energies and the measured frictional properties of silicone rubber sliding on glass. In a separate study, it was found that the frictional stress between cast silicone rubber and glass was approximately constant, about 0.1 MPa, rather than proportional to pressure, for pressures exceeding about 0.02 MPa. This feature is attributed to a particularly smooth interface between the two materials.     

High spatial order finite element method to solve Maxwell's equations in time domain

This paper presents a finite element method with high spatial order for solving the Maxwell equations in the time domain. In the first part, we provide the mathematical background of the method. Then, we discuss the advantages of the new scheme compared to a classical finite-difference time-domain (FDTD) method. Several examples show the advantages of using the new method for different kinds of problems. Comparisons in terms of accuracy and CPU time between this method, the FDTD and the finite-volume time-domain methods are given as well.     

On the design of multiple key hashing files for concurrent orthogonal range retrieval between two disks

This paper concerns the following problem: given a set of multi-attribute records, a fixed number of buckets and a two-disk system, arrange the records into the buckets and then store the buckets between the disks in such a way that, over all possible orthogonal range queries (ORQs), the disk access concurrency is maximized. We shall adopt the multiple key hashing (MKH) method for arranging records into buckets and use the disk modulo (DM) allocation method for storing buckets onto disks. Since the DM allocation method has been shown to be superior to any other allocation methods for allocating an MKH file onto a two-disk system for answering ORQs, the real issue is knowing how to determine an optimal way for organizing the records into buckets based upon the MKH concept.

A performance formula that can be used to evaluate the average response time, over all possible ORQs, of an MKH file in a two-disk system using the DM allocation method is first presented. Based upon this formula, it is shown that our design problem is related to a notoriously difficult problem, namely the Prime Number Problem. Then a performance lower bound and an efficient algorithm for designing optimal MKH files in certain cases are presented. It is pointed out that in some cases the optimal MKH file for ORQs in a two-disk system using the DM allocation method is identical to the optimal MKH file for ORQs in a single-disk system and the optimal average response time in a two-disk system is slightly greater than one half of that in a single-disk system.     

Hydrological simulations in the Rhine basin.

Simulations with regional climate models (RCMs), carried out for the Rhine basin, have been analyzed in the context of implications of the possible future discharge of the Rhine river. In a first analysis, the runoff generated by the RCMs is compared to observations, in order to detect the way the RCMs treat anomalies in precipitation in their land surface component. A second analysis is devoted to the frequency distribution of area averaged precipitation, and the impact of selection of various driving global climate models.     

ESD phenomena in GMR heads in the manufacturing process of HDD and GMR heads

It is well known that giant magnetoresistive (GMR) heads used for hard disk drives (HDD) are very sensitive to electrostatic discharge (ESD). In this paper, we describe a method of categorizing ESD damage modes from a standpoint of magnetic influences on the heads as observed by quasi-static test (QST) characteristics as well as electromagnetic characteristics like off-track profiles. In addition, we report an example of GMR stack interlayer diffusion which is one type of hard ESD damage. We also present an example of ESD damage that happened in an actual production process and its preventive measures as guidelines.