Evaluation of Nonuniformity of Elastic Properties of Sheets Made from Closed-Сell Polyolefin Foams by Acoustic Method

The widespread use of polyolefin foams in strategically important industries is due to their high thermal, sound and vibration insulation properties. The aim of the work was to evaluate the non-uniformity of elastic properties over the area of sheets of polyolefin foams of various types using the acoustic non-contact shadow amplitude method of testing and confirmation by the structural analysis method.The article presents the developed installation and a new method of non-contact acoustic testing of sheets made of closed-cell polyolefin foams based on recording the amplitude of the pulse that passed through the sheet and allowing to assess to the unevenness of its elastic properties during scanning. Studies of uneven elastic properties were carried out on sheets of closed-cell polyolefin foams of the ISOLON 500 and ISOLON 300 brands which differ in material and manufacturing technology (technique of cross-linking, method and multiplicity of foaming).It is shown that the absolute amplitude of the signal and its spread relative to the average value is affected by the structure of the foam polyolefin material and its heterogeneity over the area of the studied sheet determined by the production technology which is confirmed visually using microscopy.Studies have shown the effect on the indications unevenness of the method of obtaining and the apparent density of the material. It is shown that the most uneven elastic properties and structure belong to sheets of polyolefin foam obtained by chemical cross-linking technology (the unevenness of Δ was 6.5 %). Among the physically cross-linked sheets of polyolefin foam the most uniform in structure and elastic properties are samples made of ethylene vinyl acetate with Δ = 3.8 %, as well as sheets with a high foaming rate (Δ = 3.9 %). The unevenness of structure of the studied sheets of polyolefin foams was confirmed by optical microscopy of sections in two mutually perpendicular directions.

A New Measurement Method for High Voltages Applied to an Ion Trap Generated by an RF Resonator

A new method is proposed to measure unknown amplitudes of radio frequency (RF) voltages applied to ion traps, using a pre-calibrated voltage divider with RF shielding. In contrast to previous approaches that estimate the applied voltage by comparing the measured secular frequencies with a numerical simulation, we propose using a pre-calibrated voltage divider to determine the absolute amplitude of large RF voltages amplified by a helical resonator. The proposed method does not require measurement of secular frequencies and completely removes uncertainty caused by limitations of numerical simulations. To experimentally demonstrate our method, we first obtained a functional relation between measured secular frequencies and large amplitudes of RF voltages using the calibrated voltage divider. A comparison of measured relations and simulation results without any fitting parameters confirmed the validity of the proposed method. Our method can be applied to most ion trap experiments. In particular, it will be an essential tool for surface ion traps which are extremely vulnerable to unknown large RF voltages and for improving the accuracy of numerical simulations for ion trap experiments.

Análisis acústico-estadístico de las consonantes fricativas labiodentales e interdentales sonoras y áfonas del mapudungun hablado en Alto Biobío

This study presents the results of an acoustic and statistical analysis of labiodental and interdental fricative consonants, voiced and voiceless, from a variety of Mapudungun spoken in Alto Biobío. The present study aims to determine whether spectral, durational and amplitude parameters are able to differentiate these sounds by place of articulation and voicing. Results showed that spectral moments, duration, absolute amplitude and normalized amplitude were able to distinguish between voiced and voiceless fricatives, whilst variance, duration and normalized amplitude were able to separate labiodental from interdental consonants. However, the capability that variance and duration absolute had at distinguishing between voiced and voiceless consonants is restricted to labiodental consonants when the interaction between voicing, place of articulation and participant’s sex was considered. These results are discussed in the light of literature on the usefulness of these acoustic measurements at capturing contrasts of manner of articulation, place and voicing, and in view of previous studies on the properties of the phonetic and phonemic systems in this variety of Mapudungun.

Quasi-6-day wave effects in ionospheric E and F region during the recent solar maximum 2014–2015

We show the statistical characteristics of quasi-6-day wave (Q6DW) absolute amplitude in foE and foF2 during 2014–2015 by using six ionosondes at different latitudes. The results show that foE perturbations maximized at mid-latitudes during equinoxes, and the maximum amplitude of Q6DW in foF2 occurred near the northern crest of equatorial ionospheric anomaly (EIA). In addition, the absolute amplitude of Q6DW in foF2 increased with increasing solar activity. Our observations suggest that the dissipative Q6DW-like oscillations in the lower thermosphere may cause variations in the thermospheric neutral density via mixing effect and further result in foE disturbances in Q6DW events. Furthermore, the E region wind dynamo could also be modulated by the 6-day wave, thus leading to the disturbances in vertical plasma velocity via E × B drifts and F region electron density. Our observational investigation provides evidence of thermosphere–ionosphere coupling in the mid- and low-latitude region.

A speech envelope landmark for syllable encoding in human superior temporal gyrus

The most salient acoustic features in speech are the modulations in its intensity, captured by the amplitude envelope. Perceptually, the envelope is necessary for speech comprehension. Yet, the neural computations that represent the envelope and their linguistic implications are heavily debated. We used high-density intracranial recordings, while participants listened to speech, to determine how the envelope is represented in human speech cortical areas on the superior temporal gyrus (STG). We found that a well-defined zone in middle STG detects acoustic onset edges (local maxima in the envelope rate of change). Acoustic analyses demonstrated that timing of acoustic onset edges cues syllabic nucleus onsets, while their slope cues syllabic stress. Synthesized amplitude-modulated tone stimuli showed that steeper slopes elicited greater responses, confirming cortical encoding of amplitude change, not absolute amplitude. Overall, STG encoding of the timing and magnitude of acoustic onset edges underlies the perception of speech temporal structure.

Does rehearsal matter? Left anterior temporal alpha and theta band changes correlate with the beneficial effects of rehearsal on working memory

Rehearsal during working memory (WM) maintenance facilitates retrieval. Less is known about how rehearsal modulates WM delay activity. In the present study, 44 participants completed a Sternberg Task with either intact novel scenes or phase-scrambled scenes, which had similar color and spatial frequency but lacked semantic content. During each condition participants generated a descriptive label and covertly rehearsed or suppressed (repeated “the”) during the delay. This was easy in the former but more difficult in the later condition where scenes lacked semantic content. Behavioral performance and EEG delay activity was analyzed as a function of maintenance strategy. Performance during WM revealed a benefit of rehearsal for phase-scrambled but not intact scenes. Examination of the absolute amplitude revealed three underlying sources of activity for rehearsal, including the left anterior temporal (TAL), left and midline parietal regions. Increases in alpha and theta activity in TAL were correlated with improvement in performance on WM with rehearsal only when labeling was not automatic (i.e. phase-scrambled scenes), which may reflect differences in labeling and rehearsal (i.e. semantic associations vs. shallow labels). We conclude that rehearsal only benefits memory for visual stimuli that lack semantic information, and that this is correlated with changes in alpha and theta rhythms.

A speech envelope landmark for syllable encoding in human superior temporal gyrus

Listeners use the slow amplitude modulations of speech, known as the envelope, to segment continuous speech into syllables. However, the underlying neural computations are heavily debated. We used high-density intracranial cortical recordings while participants listened to natural and synthesized control speech stimuli to determine how the envelope is represented in the human superior temporal gyrus (STG), a critical auditory brain area for speech processing. We found that the STG does not encode the instantaneous, moment-by-moment amplitude envelope of speech. Rather, a zone of the middle STG detects discrete acoustic onset edges, defined by local maxima in the rate-of-change of the envelope. Acoustic analysis demonstrated that acoustic onset edges reliably cue the information-rich transition between the consonant-onset and vowel-nucleus of syllables. Furthermore, the steepness of the acoustic edge cued whether a syllable was stressed. Synthesized amplitude-modulated tone stimuli showed that steeper edges elicited monotonically greater cortical responses, confirming the encoding of relative but not absolute amplitude. Overall, encoding of the timing and magnitude of acoustic onset edges in STG underlies our perception of the syllabic rhythm of speech.

GEOLOGICAL SETTINGS AND SEISMIC ATTRIBUTES IN ALBIAN CARBONATES RESERVOIRS – SOUTHWEST OF CAMPOS BASIN (RJ – BRAZIL)

ABSTRACT. The importance of carbonates reservoirs in the global oil stage justifies studies aimed to determine the distribution of their physical properties. Moreover, as these reservoirs are considered complex in a geophysical context, it is necessary to reduce the geological uncertainty related to the main reservoir facies distribution. Based on this previous issue, this work outlines a method of obtaining pseudo-physical properties such as porosity (φ) and density (ρ) of two carbonate reservoirs using quantitative analysis of seismic attribute maps. These intervals were delimited by a structural-stratigraphic trap (faults and lateral variation of carbonate facies) at the Albian level from the Southwest of Campos Basin, where an oil producer field is located in a structural high. The reservoirs are of good quality, with an average porosity of 20%, directly calculated from well logs (mainly NPhi). This property features a high variation throughout the field, justified by the heterogeneity of the carbonate rock. Qualitatively, the reservoir distribution was obtained from the integration of structural, isoproperties and seismic attribute maps, which were applied above each reservoir surface maps; among them, the Maximum Negative Amplitude, Maximum Absolute Amplitude and Minimum Amplitude showed a linear relation at the correlation crossplot of density and porosity (R2>0.74). So, such process showed to be successful in characterization of the mentioned properties. Keywords: porosity, seismic interpretation, carbonates physical properties, well correlation. RESUMO. A importância dos reservatórios carbonáticos no cenário petrolífero mundial justifica estudos que objetivam determinar a distribuição de suas propriedades físicas. Além disso, como estes reservatórios são considerados complexos de serem caracterizados no âmbito geofísico, é necessário diminuir a incerteza geológica associada à distribuição das principais fácies reservatórios. Com base neste contexto, este trabalho apresenta um método de obtenção de pseudopropriedade, como porosidade (φ) e densidade (ρ), de dois reservatórios carbonáticos com base em análise quantitativa de mapas de atributos sísmicos. Estes intervalos foram delimitados por uma trapa estrutural-estratigráfica (falhas e variação lateral de fácies carbonáticas) no nível Albiano do sudoeste da Bacia de Campos, onde um campo produtor de hidrocarbonetos está situado sobre um alto estrutural. Nesta região, os reservatórios são de boa qualidade com porosidade média de 20%, calculada diretamente de perfis de poços (NPhi). Esta propriedade apresenta alta variação ao longo do campo, justificada pela heterogeneidade da rocha carbonática. Qualitativamente, a distribuição do reservatório foi obtida pela integração de mapas estruturais, de isopropriedades e de atributos sísmicos, os quais foram calculados nos mapas de cada reservatório; entre eles, Máxima Amplitude Negativa, Máxima Amplitude Absoluta e Mínima Amplitude apresentaram uma relação linear nos gráficos de correlação com a densidade e porosidade (coeficiente R2>0.74). Assim, esse processo se mostrou eficaz na caracterização das propriedades mencionadas. Palavras-chave: porosidade, interpretação sísmica, propriedades físicas dos carbonatos, correlação de poços.

Full-waveform inversion of triplicated data using a normalized-correlation-coefficient-based misfit function

Summary In seismic full-waveform inversion (FWI), the choice of misfit function determines what information in data is used and ultimately affects the resolution of the inverted images of the Earth's structure. Misfit functions based on traveltime have been successfully applied in global and regional tomographic studies. However, wave propagation through the upper mantle results in multiple phases arriving at a given receiver in a narrow time interval resulting in complicated waveforms that evolve with distance. To extract waveform information as well as traveltime, we use a misfit function based on the normalized correlation coefficient (CC). This misfit function is able to capture the waveform complexities in both phase and relative amplitude within the measurement window. It is also insensitive to absolute amplitude differences between modeled and recorded data, which avoids problems due to uncertainties in source magnitude, radiation pattern, receiver site effects or even miscalibrated instruments. These features make the misfit function based on normalized CC a good candidate to achieve high-resolution images of complex geological structures when interfering phases coexist in the measurement window, such as triplication waveforms. From synthetic tests, we show the advantages of this misfit function over the cross-correlation traveltime misfit function. Preliminary inversion of data from an earthquake in Northeast China images a sharper and stronger amplitude slab stagnant in the middle of the transition zone than FWI of cross-correlation traveltime.