Galvanomagnetic Phenomena in Layered Organic Conductors

The dependence of the resistance and the Hall field in organic metals with the quasi-two-dimensional electron energy spectrum on the magnetic field strength and orientation is analyzed in the strong field limit. The inter-plane resistance is shown to be strongly dependent on the of magnetic field orientation. When the angle between the field and the highly conducting plane is zero, the resistance increases linearly in a relatively wide field range. The angle dependence of magnetoresistance at small is nonmonotonic: it exhibits a local minimum and then a sharp peak around = 0. The Hall constant in strong magnetic field does not depend on the field orientation.     

Mechanical testing of plasma-sprayed coatings of ceramics

Mechanical tests have been performed on two types of plasma-sprayed ceramic coatings: magnesium zirconate (ZM) on aluminium alloy and chromium oxide (CO) on cast iron. Tensile strength, shear strength, energy relaxation rate and crack velocity have been determined. Results obtained with double-torsion tests show good agreement with those of double-cantilever-beam tests. Fracture always occurred in the ceramic for the ZM coating and at the interface for the CO one. Finally, acoustic emission monitoring carried out during bending tests was used to point out different types of emission, and to correlate them with micrographic examinations in order to identify some damaging processes.[/p]     

Tight complexity bounds for the two-dimensional real knapsack problem

We study the complexity of the 2-dimensional knapsack problem , where . The problem is defined in terms of real numbers and we study it where an integral solution is sought under a real number model of computation. We obtain a tight complexity bound , where . Received: November 1998 / Accepted: December 1998     

Fracture mechanics models applied to delayed failure of LVL beams

Several theories for modelling fracture and slow growth of a crack in wood have been developed. The various models may be differentiated by the specifically regarded stress levels, failure mechanisms and averaging procedures. This paper deals with the application of viscoelastic fracture mechanics models to predict delayed failure of a timber element in bending. Simulations are compared to experimental results of bending tests carried out on LVL (Laminated Veneer Lumber) notched beams. This analysis emphasizes the influence of the geometry and of the size of the beam as well as of the damage area on the delayed failure.     

Rapid Screening of Lectins for Multivalency Effects with a Glycodendrimer Microarray

Multivalency is an important phenomenon in protein–carbohydrate interactions. In order to evaluate glycodendrimers as multivalent inhibitors of carbohydrate binding proteins, we displayed them on a microarray surface. Valencies were varied from 1 to 8, and corrections were made for the valencies so that all surfaces contained the same amount of the sugar ligand. Five different carbohydrates were attached to the dendrimers. A series of fluorescent lectins was evaluated, and for each of them a binding profile was obtained from a single experiment showing both the specificity of the lectin for a certain sugar and whether it prefers multivalent ligands or not. Very distinct binding patterns were seen for the various lectins. The results were rationalized with respect to the interbinding distances of the lectins.     

Influence of Ultrasonic Oscillation on Static and Sliding Friction

Vibrations of varying frequency and amplitude are used in many technological areas to control and reduce friction. In this study we report the results of systematic high-precision measurements of the static and sliding friction under the influence of ultrasonic oscillations. We investigate the effect of ultrasonic oscillations for in-plane and out-of-plane oscillations in the completely relevant interval of oscillation amplitudes and sliding velocities and for various material pairings. The experimental results are interpreted on the basis of both macroscopic and microscopic models. There are two main effects which are of interest for tribological applications. Firstly, the frictional force typically decreases with increasing oscillation amplitude, with an oscillation amplitude of about 0.1???m typically being sufficient for a significant decrease of frictional force. Secondly, the decrease of force is larger at smaller sliding velocities; therefore, at sufficiently large oscillation amplitudes, the frictional force always increases with sliding velocity. This effect can be used to suppress frictionally induced vibrations.     

A conductimetric method for the study of mixing phenomena in liquids

A new conductimetric microprobe and conductimeter have been designed to study mixing phenomena in fluids of non-uniform composition in turbulent flow. For the case of a parallelepipedic cell with two parallel jets at different salt tracer concentrations, the spatial distribution and the mean and variance of the fluctuation of the tracer are obtained experimentally and used to characterise the state of local mixing.A theoretical expression for the mean concentration is obtained by solving the convective diffusion equation. Comparison of experimental and theoretical results is satisfactory and proves to be a sufficiently good test of the reliability of the apparatus used.     

A novel approach to piecewise analytic agricultural machinery path reconstruction

Before analysing machinery operation in fields, it has to be coped with the problem that the GPS signals of GPS receivers located on the machines contain measurement noise, are time-discrete, and the underlying physical system describing the positions, axial and absolute velocities, angular rates and angular orientation of the operating machines during the whole working time are unknown. This research work presents a new three-dimensional mathematical approach using kinematic relations based on control variables as Euler angular velocities and angles and a discrete target control problem, such that the state control function is given by the sum of squared residuals involving the state and control variables to get such a physical system, which yields a noise-free and piecewise analytic representation of the positions, velocities, angular rates and angular orientation. It can be used for a further detailed study and analysis of the problem of why agricultural vehicles operate in practice as they do.