Explanation of the embedding strength of particle board

By the earlier derived theory of the embedding strength, based on the equilibrium method of plasticity, it is possible to fully explain the empirical relations and test results of an investigation of the embedding strength of particle boards leading to a new insight for the right design rules.     

MT-compatible laser-ablated interconnections for optical printed circuit boards

Integration of optical interconnections on a printed circuit board (PCB) is very challenging, since compatibility should be maintained with standard PCB manufacturing technology. This paper describes the use of laser ablation, a technique already used in PCB manufacturing for drilling microvias, as a suitable technique for the fabrication of multimode polymer waveguides, micromirrors, alignment features, and microlenses. A frequency-tripled Nd-YAG laser and a KrF excimer laser are used, both mounted on the same stage, resulting in very high alignment accuracies. This paper demonstrates a parallel optical link over approximately 5-cm-long PCB integrated waveguides, fully connected using a standard MT-based connector. This proves that laser ablation can be a key technology in optical board manufacturing to reach the stringent coupling tolerances.     

Gradient profile prediction in functionally graded materials processed by electrophoretic deposition

Electrophoretic deposition (EPD) allows the formation of plate-shaped binary functionally graded materials (FGM) by depositing from a powder suspension to which a second suspension is continuously added during the process. The deposition yield is described as a function of time and starting composition of both suspensions, resulting in a model of the EPD process that allows predicting the composition gradient in the green deposit as well as in the sintered material. The model presented enables calculation of the composition gradient in the FGM material from the starting composition of the suspensions, the EPD operating parameters and the powder-specific EPD characteristics. The powder-specific parameters, i.e. the effective charge, the electrophoretic mobility, the specific conductivity of the intermicellar liquid and the specific resistance of the deposit, incorporated in the model were experimentally determined from EPD of the individual homogeneous powder suspensions. The model was verified for the ZrO₂-Al₂O₃ system by the actual preparation and analysis of two different FGM materials. Because of the excellent correlation between the predicted and the measured concentration profiles, the described model allows to precisely engineer and design the composition profile in FGM materials produced by EPD.     

Sensitivity and selectivity of intraneural stimulation using a silicon electrode array

Artificial electrical stimulation of peripheral nerves needs the development of multielectrode devices which stimulate individual fibers or small groups in a selective and sensitive way. To this end, a multielectrode array in silicon technology has been developed, as well as experimental paradigms and model calculations for sensitivity and selectivity measures. The array consists of twelve platinum electrode sites (10 x 50 microns at 50 microns interdistance) on a 45 microns thick tip-shaped silicon substrate and a Si3N4 insulating glass cover layer. The tip is inserted in the peroneal nerve of the rat during acute experiments to stimulate alpha motor fibers of the extensor digitorum longus muscle. Sensitivity calculations and experiments show a cubic dependence of the number of stimulated motor units on current amplitude of the stimulatory pulse (recruitment curves), starting at single motor level. Selectivity was tested by a method based on the refractory properties of neurons. At the lowest stimulus levels (for one motor unit) selectivity is maximal when two electrodes are separated by 200-250 microns, which was estimated also on theoretical grounds. The study provides clues for future designs of two- and three-dimensional devices.     

Theoretical and experimental study of nematic liquid crystaldisplay cells using the in-plane-switching mode

In this paper a two-dimensional (2-D) dynamic model, based on a tensor formulation and solved numerically by combining finite elements and finite differences, is proposed and used for analyzing nematic liquid crystal (LC) test cells with interdigital electrodes. We compare theoretical and experimental results concerning the switching behavior, response mechanism, and viewing angle characteristics of nematic LC pixel structures which use the in-plane-switching (IPS) mode. The good agreement observed between theory and experiment in terms of electro-optical properties validates our modeling and demonstrates its potential for design optimization. We show that the proposed LC test cells, using the in-plane-switching mode, ensure switching-ON and -OFF response times of 22 and 28 ms, respectively, and excellent viewing angle characteristics     

High-energy neutrons effect on strained and non-strained SOI MuGFETs and planar MOSFETs

A comparative investigation of high-energy neutrons effect on strained and non-strained devices with different geometries is presented. Both single-gate planar and multiple-gate (MuG) silicon-on-insulator (SOI) devices are considered. Device response to the neutron irradiation is assessed through the variations of threshold voltage and transconductance maximum. The difference between strained and non-strained device response to the high-energy neutrons exposure is clearly evidenced. The reasons for such a difference are discussed. Analysis of the experimental results allows for suggesting that strain relaxation is one of the probable causes.     

Beneficial Effect of Pt and of Pre-Oxidation on the Oxidation Behaviour of an NiCoCrAlYTa Bond-Coating for Thermal Barrier Coating Systems

The oxidation behaviour of a thermal barrier coating (TBC) system is a major concern as the growth of the thermally grown oxide (TGO) layer on the bond-coating creates stresses that greatly favour the thermal barrier spallation. To delay the loss of the thermal protection provided, research has focused on the bond-coating composition and microstructure as well as on the parameters required for a suitable pre-oxidation treatment before the deposition of the ceramic top coat. Platinum is known to enhance the oxidation/corrosion resistance of MCrAlY coatings. The effect of Pt on the oxidation behaviour of a NiCoCrAlYTa coating was assessed in this study. In addition, pre-oxidation treatments were conducted to determine if the oxidation behaviour of the modified NiCoCrAlYTa coating could be further improved.