Bulletin of the Polish Academy of Sciences Technical Sciences

A short overview of the developments of functional materials featuring miniaturisation and integration is illustrated by examples taken from the ?eld of ceramic functional materials. To obtain new materials new methods are required. Most of them are microfabrication processes developed by the "top-down" approach.

Biocompatible coatings produced on the basis of the chemically extracted natural hydroxyapatite (HAp) from the animal bones were deposited using multiplex method comprising glow discharge nitriding (GDN) of the titanium alloy substrate and pulsed laser deposition (PLD) of HAp on the formerly fabricated titanium nitride layer (TiN). The TiN interlayer plays an important role improving adhesion of HAp to substrate and preserves the direct contact of the tissue with metallic substrate in the case of possible cracking of HAp coating. Surface morphology of deposited layers, crystallographic texture and residual stress were studied in relation to the type of laser applied to ablation (Nd:YAG or ArF excimer), laser repetition, temperature of substrate and atmosphere in the reactive chamber.

In this work studies ofM OVPE growth of InAlGaAs/AlGaAs/GaAs heterostructures are presented. The HRXRD and SIMS measurements indicate the high structural and optical properties as well as high uniformity oft hickness and composition ofI nAlGaAs quantum wells. This work is the .rst step towards elaboration oft he technology oft he strained InAlGaAs/GaAs heterostructures for advanced optoelectronic devices working in the visible part oft he spectrum. The investigations ofSi (n-type), Zn (p-type) .-doped GaAs epilayers and centre Si-.-doped InxGa1-xAs single quantum well (SQW) are presented. The .-doping layer was formed by SiH4 or DEZn introduction during the growth interruption. The electrical and optical properties oft he obtained structures were examined using C-V measurement, EC-V electrochemical pro.ler, Raman spectroscopy (RS), photore.ectance (PR) and photocurrent (PC) spectroscopies. Technology oft hick GaN layers grown on sapphire by HVPE is very promising as a part off reestanding GaN substrates manufacturing. Further works will be focused on the optimisation of growth, separating layers from substrates and surface polishing. The in.uence oft he growth parameters on the properties of( Ga, Al)N/Al2O3 and Mg dopant incorporation was studied.

This paper presents the results obtained from the structural re.nement of selected metals and alloys produced by severe plasticdeformation processes. Large levels of deformations were produced using four methods, which di.ered in the character and dynamics of the loading, as well as in the intensity and homogeneity oft he plastic strain .eld. Qualitative and quantitative studies of the re.ned microstructure were carried out using stereological and computer image analytical methods. Microhardness and selected mechanical properties, such as strength and yield point, were also determined.

Pulse electrochemical machining (PECM) provides an economical and e.ective method for machining high strength, heat-resistantmaterials into complex shapes such as turbine blades, die, molds and micro cavities. Pulse Electrochemical Machining involves the application of a voltage pulse at high current density in the anodic dissolution process. Small interelectrode gap, low electrolyte .ow rate, gap state recovery during the pulse o.-times lead to improved machining accuracy and surface .nish when compared with ECM using continuous current. This paper presents a mathematical model for PECM and employs this model in a computer simulation of the PECM process for determination of the thermal limitation and energy consumption in PECM. The experimental results and discussion of the characteristics PECM are presented.

There is a growing need for a more accurate assessment of the load carrying capacity of highway bridges. The traditional approach is based on consideration of individual components rather than structures. Consequently, the acceptance criteria are formulated in terms of the allowable stress, or ultimate moment, in a component. However, it has been observed that the load carrying capacity of the whole structure (system) is often much larger than what is determined by the design of components. The difference can be attributed to the system behaviour. Quantification of this difference is the subject of the system reliability. There is a need to take advantage of the available system reliability methods and advanced structural analysis methods and apply them in the design of bridges and evaluation of existing structures. The current advanced analytical procedures allow for a numerically accurate but deterministic analysis of strain/stress in a bridge. Mathematical procedures exist for the calculation of reliability for various idealized systems: parallel, series, and combinations. There are also new developments in materials, technology, and field testing which can be used to improve bridge design and evaluation. This paper deals with calculation of the reliability of the whole bridge structure, taking into account realistic boundary conditions, and site-specific load and resistance parameters.

This paper presents revised and extended version of theory proposed in the late 1970-ties by A. ˇCyras and his co-workers. This theory, based upon the notion of duality in mathematical programming, allows us to generate variational principles and to investigate existence and uniqueness of solutions for the broad class of problems of elasticity and plasticity. The paper covers analysis of solids made of linear elastic, elastic-strain hardening, elastic-perfectly plastic and rigid-perfectly plastic material. The novelty with respect to ˇCyras’s theory lies in taking into account loads dispersed over the volume and displacements enforced on the part of surface. A new interpretation of optimum load for a rigid-perfectly plastic body is also given.

The second part of the paper presents finite-dimensional models of linear elastic, elastic-strain hardening, elastic-perfectly plastic

and rigid-perfectly plastic structures. These models can be seen as a result of discretisation procedure applied to the models of solids derived in the Part I. The implications of sub-dividing degrees of freedom into those with prescribed external forces and those with given displacements are discussed. It is pointed out that the dual energy principles given in this part of the paper can serve as a direct basis for numerical computations.

The notion of the normal transfer matrix and the notion of the structure decomposition of normal transfer matrix for 2D general model are introduced. Necessary and sufficient conditions for the existence of the structure decomposition of normal transfer matrix are established. A procedure for computation of the structure decomposition is proposed and illustrated by the numerical example. It is shown that the impulse response matrix of the normal model is independent of the polynomial part of its structure decomposition.

One of the main problems of electrical power quality is to ensure a constant power ?ux from the supply system to the receiver, keeping in the same time the undisturbed wave form of the current and voltage signals. Distortion of signals are caused by nonlinear or time varying receivers, voltage changes or power losses in a supply system. The wave-form of the voltage of the source may also be deformed. This study seeks the optimal current and voltage wave-form by means of an optimization criteria. The optimization problem is de?ned in Hilbert space and the special functionals are minimized. The source inner impedance operator is linear and time-varying. Some examples of calculations are presented.