In-process grinding monitoring through acoustic emission

This work aims to investigate the efficiency of digital signal processing tools of acoustic emission signals in order to detect thermal damages in grinding processes. To accomplish such a goal, an experimental work was carried out for 15 runs in a surface grinding machine operating with an aluminum oxide grinding wheel and ABNT 1045 Steel as work material. The acoustic emission signals were acquired from a fixed sensor placed on the workpiece holder. A high sampling rate data acquisition system working at 2.5 MHz was used to collect the raw acoustic emission instead of the root mean square value usually employed. Many statistical analyses have shown to be effective to detect burn, such as the root mean square (RMS), correlation of the AE, constant false alarm rate (CFAR), ratio of power (ROP) and mean-value deviance (MVD). However, the CFAR, ROP, Kurtosis and correlation of the AE have been presented more sensitive than the RMS. Copyright © 2006 by ABCM.

Calling sites and acoustic partitioning in species of the Hyla nana and rubicundula groups (Anura, Hylidae)

We analysed spatial and acoustic partitioning among four species of Hyla belonging to two species-groups: nana (H. nana and H. sanborni) and rubicundula (H. elianeae and H. jimi). Field activities were conducted at three permanent ponds, from 1998 through 2001. Four attributes of the calling sites were analysed: perch height, distance of the perch from the edge of the pond, type of perch (vegetation) and the individual's position on the perch. There was extensive overlap in the four calling-site variables analysed. However, we found spatial segregation did occur in calling site height and the distance of perches from pond edges. Bioacoustic analyses revealed behavioural differences among species in calling activity, both time of onset and peak calling in chorus. There was acoustic partitioning among species the fundamental frequency of the advertisement calls, principally as a function of the temporal structure (e.g. note duration, rate of note repetition, duration and rate of repetition of the calling pulses). We propose that differences in physical attributes of calling site and in characteristics of calls allow these species to exist in sympatry.

PTCa/PEEK composite acoustic emission sensors

Composites made of Calcium-modified lead titanate (PTCa) and poly (ether-etherketone) (PEEK) high performance polymer matrix were prepared in the film form using a hot press. The ceramic volume fraction reaches up to 60 percent providing a composite with 0-3 and 1-3 mixed connectivities due to the high ceramic content and the resulting materials could be considered PEEK-bonded PTCa particulate composite. The composites were characterized using piezoelectric spectroscopy and ultrasonic immersion techniques. Values up to 38.5 pC/N were obtained for the longitudinal d33 piezoelectric coefficient. The composite was surface-mounted on a carbon fiber plate-like specimen and the ability of the PTCa/PEEK composite to detect acoustic emission (AE) is reported. © 2006 IEEE.

Visual and acoustic signaling in three species of Brazilian nocturnal tree frogs (anura, hylidae)

Visual communication seems to be widespread among nocturnal anurans, however, reports of these behaviors in many Neotropical species are lacking. Therefore, we gathered information collected during several sporadic field expeditions in central and southern Brazil with three nocturnal tree frogs: Aplastodiscus perviridis, Hypsiboas albopunctatus and H. bischoffi. These species displayed various aggressive behaviors, both visual and acoustic, towards other males. For A. perviridis we described arm lifting and leg kicking; for H. albopunctatus we described the advertisement and territorial calls, visual signalizations, including a previously unreported behavior (short leg kicking), and male-male combat; and for H. bischoffi we described the advertisement and fighting calls, toes and fingers trembling, leg lifting, and leg kicking. We speculate about the evolution of some behaviors and concluded that the use of visual signals among Neotropical anurans may be much more common than suggested by the current knowledge. © 2007 Departamento de Ciências Biológicas.

Direct and indirect connections between cochlear root neurons and facial motor neurons: Pathways underlying the acoustic pinna reflex in the albino rat

Cochlear root neurons (CRNs) are involved in the acoustic startle reflex, which is widely used in behavioral models of sensorimotor integration. A short-latency component of this reflex, the auricular reflex, promotes pinna movements in response to unexpected loud sounds. However, the pathway involved in the auricular component of the startle reflex is not well understood. We hypothesized that the auricular reflex is mediated by direct and indirect inputs from CRNs to the motoneurons responsible for pinna movement, which are located in the medial subnucleus of the facial motor nucleus (Mot7). To assess whether there is a direct connection between CRNs and auricular motoneurons in the rat, two neuronal tracers were used in conjunction: biotinylated dextran amine, which was injected into the cochlear nerve root, and Fluoro-Gold, which was injected into the levator auris longus muscle. Under light microscopy, close appositions were observed between axon terminals of CRNs and auricular motoneurons. The presence of direct synaptic contact was confirmed at the ultrastructural level. To confirm the indirect connection, biotinylated dextran amine was injected into the auditory-responsive portion of the caudal pontine reticular nucleus, which receives direct input from CRNs. The results confirm that the caudal pontine reticular nucleus also targets the Mot7 and that its terminals are concentrated in the medial subnucleus. Therefore, it is likely that CRNs innervate auricular motoneurons both directly and indirectly, suggesting that these connections participate in the rapid auricular reflex that accompanies the acoustic startle reflex. © 2008 Wiley-Liss, Inc.

Habitat heterogeneity and use of physical and acoustic space in anuran communities in Southeastern Brazil

Habitat heterogeneity and use of physical and acoustic space in anuran communities in Southeastern Brazil. We intended to verify if structural and physiognomical characteristics of water bodies influence on the degree of overlap among calling sites of 23 anurans species, if anuran species use different calling sites in different water bodies, and if there is some relationship between the degree of advertisement call (based on seven call features) and calling site differentiation. Then, we determined calling sites (based in four variables) and recorded the advertisement call for anuran species that occurred in 10 water bodies of northwestern São Paulo State. We also determined the environmental heterogeneity (based in four environmental descriptors) for each water body. Males of most species used similar calling sites in each water body, probably because of the high uniformity of the environment, as a consequence of agricultural impacts on edge vegetation of the studied ponds. Most species (18 out of 19 species) called from different sites in the ponds where they occurred, which can be associated with differences in horizontal and vertical distribution of vegetation in the studied ponds. From the 19 species analyzed, only males of Pseudopaludicola aff. saltica called in sites with the same characteristics in different ponds. Advertisement call of Hylidae species was more similar to each other than were Leiuperidae and Leptodactylidae among themselves. The aquatic/terrestrial anurans (Bufonidae, Leiuperidae, Leptodactylidae and Microhylidae) occupied similar calling sites but presented quite distinct advertisement calls, while Hylidae species presented an inverse pattern: a high similarity on advertisement call features but used different calling sites, which indicates a niche complementarity between physical (calling site use) and acoustic (advertisement call) space use. © 2008 Departamento de Ciências Biológicas.

Piezoelectric composite film for acoustic emission detection

The continuous technological advances require materials with properties that conventional material cannot display. Material property combinations are being the focus to the development of composite materials, which are considered a multiphase material that exhibits properties of the constituent phases. One interesting material to be studied as sensing material is the composite made of ferroelectric ceramic and polymeric matrix as a two-phases composite material. In that case, the combinations properties intended are the high piezo and pyroelectric activities of the dense ceramic with the impact resistance, flexibility, formability and low densities of the polymer. Using the piezoelectric property of the composite film, it can be used to detect acoustic emission (AE), which is a transient elastic wave generated by sudden deformation in materials under stress. AE can be applied for evaluating the health of structures in a nondestructive way and without any lapse of time. The preliminary result indicates that the composite Pz34/PEEK can be used as sensing material for nondestructive evaluation. ©2009 IEEE.

Impedance spectroscopy study of solid-state dye-sensitized solar cells with varying Spiro-OMeTAD concentration

This work reports on the changes of performance of solid-state cells dye-sensitized solar cells with the variation of concentration of spiro-OMeTAD between 5% and 25% in the fabrication of the cell. Variations of charge recombination and capacitance correlate with the improvement of current-potential characteristics at increasing spiro-OMeTAD content, which is explained by reduction of transport resistance for hole transport, the increase of charge separation in the dye molecules, and importantly, with the increase of the β-factor in the recombination resistance, that causes a reduction of the diode ideality factor. © 2010 Materials Research Society.

Versatile and easy-to-assemble measurement system for impedance-based structural health monitoring

In this paper we present a versatile and easy-to-assemble measurement system for structural health monitoring (SHM) based on the electromechanical impedance (EMI) technique. The hardware of the proposed system consists only of a common data acquisition (DAQ) device with external resistors and allows real-time data acquisition from multiple sensors. Besides the low-cost compared to conventional impedance analyzers, the hardware and the software are simple and easier to implement than other measurement systems that have been recently proposed.

Real-time estimation of transmission line impedance based on modal analysis theory

The objective of this paper is to show a methodology to estimate the longitudinal parameters of transmission lines. The method is based on the modal analysis theory and developed from the currents and voltages measured at the sending and receiving ends of the line. Another proposal is to estimate the line impedance in function of the real-time load apparent power and power factor. The procedure is applied for a non-transposed 440 kV three-phase line. © 2011 IEEE.

Using the electrochemical impedance spectroscopy to characterize carbon steel in biodiesel medium

Electrochemical impedance spectroscopy measurements using two carbon steel electrodes in soybean biodiesel medium, produced by methylic route, were performed in an electrochemical cell that allows positioning the two electrodes face-to-face. To retain the biodiesel between the electrodes and prevent its leakage a porous membrane soaked in biodiesel was used. The amplitude of the AC potential and the area of the electrodes were varied. The linearity between disturbance and response signals was observed for tests when the amplitude of the AC potential was lower than 1500 mV (rms). The electrical resistance of biodiesel dominates the global response and carbon steel presents low corrosion, which is observed only at low frequency, and was confirmed by chemical tests performed in the membrane. In conclusion the electrical resistance of biodiesel can be estimated using electrochemical impedance spectroscopy with two electrodes set up. ©The Electrochemical Society.

Components of the acoustic swallowing signal: Preliminary study

Purpose: To analyze the components of the acoustic signal of swallowing using a specific software. Methods: Fourteen healthy subjects ranging in age from 20 to 50 years (mean age 31±10 years), were evaluated. Data collection consisted on the simultaneous capture of the swallowing audio with a microphone and of the swallowing videofluoroscopic image. The bursts of the swallowing acoustic signal were identified and their duration and the interval between them were later analyzed using a specific software, which allowed the simultaneous analyses between the acoustic wave and the videofluoroscopic image. Results: Three burst components were identified in most of the swallows evaluated. The first burst presented mean time of 87.3 milliseconds (ms) for water and 78.2 for the substance. The second burst presented mean time of 112.9 ms for water and 85.5 for the pasty substance. The mean interval between first and second burst was 82.1 ms for water and 95.3 ms for the pasty consistency, and between second and third burst was 339.8 ms for water and 322.0 ms for the pasty consistency. Conclusion: The software allowed the visualization of three bursts during the swallowing of healthy individuals, and showed that the swallowing signal in normal subjects is highly variable.

Associations between bioelectrical impedance parameters and cardiovascular events in chronic dialysis patients

Purpose: Malnutrition and fluid overload contribute to the poor cardiovascular prognosis of dialysis patients. Since bioelectrical impedance analysis is an option for the evaluation of body composition and for the monitoring of hydration state, it may assist in the identification of subjects at high cardiovascular risk. The objective of this study was to evaluate the association between bioelectrical impedance parameters and cardiovascular events. Methods: The association between bioelectrical impedance parameters and fatal and non-fatal cardiovascular outcome was evaluated in 145 dialysis patients. Results: The mean age of the population studied was 54.9 ± 15.4 years, 49.7 % were males, and 35.9 % had diabetes. Forty (27.6 %) patients developed cardiovascular events during the 16 months (8; 32) of follow-up. Comparison of patients with and without cardiovascular events revealed higher extracellular mass/body cell mass (ECM/BCM) and extracellular water/total body water ratios and higher C-reactive protein levels in the former. Survival analysis showed that an ECM/BCM ratio >1.2 and a phase angle <6° were associated with poor cardiovascular prognosis. Among nondiabetic patients, these parameters and capacitance were independently associated with cardiovascular events, suggesting that poor nutritional status and fluid overload are associated with the occurrence of these events. Conclusions: Phase angle, capacitance and ECM/BCM ratio are valuable parameters for the evaluation of cardiovascular prognosis, supporting the use of bioelectrical impedance for the clinical assessment of dialysis patients. © 2012 Springer Science+Business Media Dordrecht.

A new microcontrolled structural health monitoring system based on the electromechanical impedance principle

This article presents a new method to detect damage in structures based on the electromechanical impedance principle. The system follows the variations in the output voltage of piezoelectric transducers and does not compute the impedance itself. The proposed system is portable, autonomous, versatile, and could efficiently replace commercial instruments in different structural health monitoring applications. The identification of damage is performed by simply comparing the variations of root mean square voltage from response signals of piezoelectric transducers, such as lead zirconate titanate patches bonded to the structure, obtained for different frequencies of the excitation signal. The proposed system is not limited by the sampling rate of analog-to-digital converters, dispenses Fourier transform algorithms, and does not require a computer for processing, operating autonomously. A low-cost prototype based on microcontroller and digital synthesizer was built, and experiments were carried out on an aluminum structure and excellent results have been obtained. © The Author(s) 2012.

From widespread to microendemic: Molecular and acoustic analyses show that Ischnocnema guentheri (Amphibia: Brachycephalidae) is endemic to Rio de Janeiro, Brazil

Many species of tropical amphibians are restricted to very small ranges, and this microendemism coupled with ongoing habitat loss and susceptibility to emerging pathogens imperils the long-term persistence of these species. Incomplete taxonomic and distributional knowledge may obscure conservation assessment, particularly in putatively widespread species that are typically considered to be of Least Concern in Red List assessments, but that in fact may constitute complexes of partly microendemic species. Such is the case in the Steindachner's Robber Frog, Ischnocnema guentheri which, together with the recently recognized Ischnocnema henselii, is thought to occupy most of the Brazilian Atlantic Forest. To test whether these taxa may constitute a species complex of range-restricted and thus potentially threatened species, we analyzed 160 samples of I. guentheri and/or I. henselii for two molecular markers, 16S rRNA (16S) and recombination activation gene 1 (RAG1). To verify the monophyly of the complex, closely related species were also included in the 16S analysis. Congruent evidence from the molecular data and from analyses of advertisement calls support the existence of six distinct species within the complex: I. guentheri and I. henselii as well as four candidate new species. The lineages are distributed as a mosaic in the Atlantic Forest and are sympatric at some localities without indication of admixture. Their phylogeographical pattern partially agrees with paleo-models for the Atlantic Forest, but also suggests the existence of micro-refugia in less stable areas. I. guentheri, previously considered to be widespread, was found only in its type locality, a reserve within the urban area of Rio de Janeiro city. Although none of the species studied appears highly threatened with extinction, we recommend their IUCN threat status to be re-evaluated carefully for the next comprehensive update of the Red List of Brazil's amphibians. © 2013 Springer Science+Business Media Dordrecht.