Direct Observation of Tetragonal Distortion in Epitaxial Structures through Secondary Peak Split in a Synchrotron Radiation Renninger Scan

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

GREEN MACHINING ORIENTED TO DIMINISH DENSITY GRADIENT FOR MINIMIZATION of DISTORTION IN ADVANCED CERAMICS

After sintering advanced ceramics, there are invariably distortions, caused in large part by the heterogeneous distribution of density gradients along the compacted piece. To correct distortions, machining is generally used to manufacture pieces within dimensional and geometric tolerances. Hence, narrow material removal limit conditions are applied, which minimize the generation of damage. Another alternative is machining the compacted piece before sintering, called the green ceramic stage, which allows machining without damage to mechanical strength. Since the greatest concentration of density gradients is located in the outer-most layers of the compacted piece, this study investigated the removal of different allowance values by means of green machining. The output variables are distortion after sintering, tool wear, cutting force, and the surface roughness of the green ceramics and the sintered ones. The following results have been noted: less distortion is verified in the sintered piece after 1mm allowance removal; and the higher the tool wear the worse the surface roughness of both green and sintered pieces.

Comparative Analysis of Objective Distortion Measures for Speech Signals Degraded by Noise

Speech signals degraded by additive noise can affects different applications in telecommunication. The noise may degrades the intelligibility of the speech signals and its waveforms as well. In some applications such as speech coding, both intelligibility and waveform quality are important but only intelligibility has been focused lastly. So, modern speech quality measurement techniques such as PESQ (Perceptual Evaluation of Speech Quality) have been used and classical distortion measurement techniques such as Cepstral Distance are becoming unused. In this paper it is shown that some classical distortion measures are still important in applications where speech corrupted by additive noise has to be evaluated.

A comment on a nonideal centrifugal vibrator machine behavior with soft and hard springs

This paper concerns a type of rotating machine (centrifugal vibrator), which is supported on a nonlinear spring. This is a nonideal kind of mechanical system. The goal of the present work is to show the striking differences between the cases where we take into account soft and hard spring types. For soft spring, we prove the existence of homoclinic chaos. By using the Melnikov's Method, we show the existence of an interval with the following property: if a certain parameter belongs to this interval, then we have chaotic behavior; otherwise, this does not happen. Furthermore, if we use an appropriate damping coefficient, the chaotic behavior can be avoided. For hard spring, we prove the existence of Hopf's Bifurcation, by using reduction to Center Manifolds and the Bezout Theorem (a classical result about algebraic plane curves).

Presence of excited electronic state in CaWO4 crystals provoked by a tetrahedral distortion: An experimental and theoretical investigation

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Contribution of distributed generators to the harmonic distortion in low voltage power network

In the last 20 years immense efforts have been made to utilize renewable energy sources for electric power generation. This paper investigates some aspects of integration of the distributed generators into the low voltage distribution network. An assessment of impact of the distributed generators on the voltage and current harmonic distortion in the low voltage network is performed. Results obtained from a case study, using real-life low voltage network, are presented and discussed.

Effect of green machining on distortion and surface finishing in advanced ceramic

An alternative for grinding of sintered ceramic is the machining on the green state of the ceramic, which presents easy cutting without the introduction of harmful defects to its mechanical resistance. However, after sintering there are invariably distortions caused by the heterogeneous distribution of density gradients, which are located in the most outlying portions of the compacted workpiece. In order to minimize these density gradients, this study examined the influence of different allowance values and their corresponding influence in distortion after sintering alumina specimens with 99.8 % purity by turning operation using cemented carbide tool. Besides distortion, other output variables were analyzed, such as tool wear, cutting force and surface roughness of green and sintered ceramics. Results showed a distortion reduction up to 81.4%. Green machining is beneficial for reducing surface roughness in both green and sintered states. Cutting tool wear has a direct influence on surface roughness and cutting force.

THE RETINAL TARGETS OF CENTRIFUGAL NEURONS AND THE RETINAL NEURONS PROJECTING TO THE ACCESSORY OPTIC-SYSTEM

In birds, neurons of the isthmo-optic nucleus (ION), as well as ''ectopic'' neurons, send axons to the retina, where they synapse on cells in the inner nuclear layer (INL). Previous work has shown that centrifugal axons can be divided into two anatomically distinct types depending on their mode of termination: either ''convergent'' or ''divergent'' (Ramon y Cajal, 1889; Maturana and Frenk, 1965). We show that cytochrome-oxidase histochemistry specifically labels ''convergent'' centrifugal axons and target neurons which appear to be amacrine cells, as well as three ''types'' of ganglion cells: two types found in the INL (displaced ganglion cells) and one in the ganglion cell layer. Labeled target amacrine cells have distinct darkly labeled ''nests'' of boutons enveloping the somas, are associated with labeled centrifugal fibers, and are confined to central retina. Lesions of the isthmo-optic tract abolish the cytochrome-oxidase labeling in the centrifugal axons and in the target amacrine cells but not in the ganglion cells. Cytochromeoxidase-labeled ganglion cells in the INL are large; one type is oval and similar to the classical displaced ganglion cells of Dogiel, which have been reported to receive centrifugal input; the other type is rounder. Rhodamine beads injected into the accessory optic system results in retrograde label in both types of cells, showing that two distinct types of displaced ganglion cells project to the accessory optic system in chickens. The ganglion cells in the ganglion cell layer that label for cytochrome oxidase also project to the accessory optic system. These have proximal dendrites that ramify in the outer inner plexiform layer. Neither the target amacrine cells nor either of the displaced ganglion cells are immunoreactive for the inhibitory transmitter gamma aminobutyric acid. At least some of the target amacrine cells may, however, be cholinoceptive: we found that the antibody to the alpha-7 subunit of the nicotinic ACh receptor labels a population of cells in the INL that are similar in location, size, and the presence of labeled bouton-like structures to those we find labeled with cytochrome oxidase. This antibody also labels neurons in the ION proper but not ectopic cells. In conclusion, it appears that cytochrome oxidase may be a marker for ''convergent'' centrifugal axons and at least one of their target cells in the INL.

Transient evoked and distortion product otoacoustic emissions in a group of neonates

Introduction The most commonly used method in neonatal hearing screening programs is transient evoked otoacoustic emissions in the first stage of the process. There are few studies comparing transient evoked otoacoustic emissions with distortion product, but some authors have investigated the issue. Objective To correlate the results of transient evoked and distortion product otoacoustic emissions in a Brazilian maternity hospital. Methods This is a cross-sectional, comparative, and prospective study. The study included 579 newborns, ranging from 6 to 54 days of age, born in a low-risk maternity hospital and assessed for hearing loss. All neonates underwent hearing screening by transient evoked and distortion product otoacoustic emissions. The results were analyzed using the Spearman correlation test to relate the two procedures. Results The pass index on transient evoked otoacoustic emissions was 95% and on distortion product otoacoustic emissions was 91%. The comparison of the two procedures showed that 91% of neonates passed on both procedures, 4.5% passed only on transient evoked otoacoustic emissions, 0.5% passed only on distortion product otoacoustic emissions, and 4% failed on both procedures. The inferential analysis showed a significant strong positive relationship between the two procedures. Conclusion The failure rate was higher in distortion product otoacoustic emissions when compared with transient evoked; however, there was correlation between the results of the procedures.