The BKZ as an alternative to the Wagner model for fitting shear and elongational flow data of an LDPE melt

For the low density polyethylene Melt I, which is the melt for which the most complete set of shear and elongational data exists, the semi-empirical single integral Wagner model gives an excellent data-fit, but suffers the drawback of having no entropic constitutive equation, that is a relationship between strain history and elastic free energy from which viscous heating and cohesive failure can be predicted. We show here that the BKZ model, which does possess an entropic constitutive equation, gives as good a fit as does the Wagner model to both the shear and elongational data.     

Computer simulation of a carbon-deposition plasma in CH4

A transport and reaction model of a low-pressure, high-frequency (13.56 MHz) CH₄ plasma used for diamondlike carbon (a-C:H) deposition was developed. The model includes reactions among four molecular species (CH₄, C₂ H₆, C₂H₄, and H₂), five radicals and atom (CH₃, CH₂, CH, C₂H₅, and H), and four ions (CH₄⁺ , CH₃⁺, CH₅⁺, and C ₂H₅⁺). It also accounts for the influence of the sticking coefficient of species at the walls. Calculated values of the dissociation degree for several flow rates are in good agreement with experimental measurements made by quadrupole mass spectroscopy. A simple surface-model based on the hydrogen coverage of surface and ion flux and energy at the substrate surface was established. This model permitted the calculation of the deposition rate on the powered electrode as a function of the power applied to this electrode. Good agreement between experimental and calculated growth rates was obtained when CH₃, C₂H₅, and CH₂ were assumed to participate in film formation, and when hydrogen removal by ion bombardment with variable energy as a function of the power was included in the model     

Measurement and analysis of the ν2 and ν4 infrared bands of 13CD4

A Fourier transform infrared spectrum of 91% ¹³CD₄ has been recorded between 885 and 1193 cm^?1 with a resolution of 0.04 cm^?1. The frequencies of 600 lines were measured with an accuracy of ±0.003 cm^?1. Of these, approximately 368 are assigned as allowed transitions in ν₄, 95 are forbidden ν₄ transitions, and 137 belong to ν₂; maximum upper state J values are 20 for ν₄ and 19 for ν₂. The ground state tensor constants D_t, H_4t, and H_6t were obtained by fitting them to four rotational transitions observed by Kreiner and Opferkuch in the infrared-microwave double-resonance spectrum. An interacting-band analysis of the $\text{ν}{}_2\text{ν}{}_4$ diad then yields 22 spectroscopic constants for these Coriolis-coupled fundamentals and fits the experimental frequencies with an rms deviation of 0.0055 cm^?1 for 432 unblended lines that were assigned unit weight. A ν₄P⁺(12) transition at 943.3812 cm^?1, nearly coincident with the 10P(22) emission of the ¹²C¹⁶O₂ laser, has been investigated by heterodyne spectroscopy and its detuning (?64 MHz) and absorption coefficient have been determined. Such coincidences may lead to the development of laser analytical techniques for ¹³CD₄, which is a useful nonradioactive atmospheric tracer. ¹³CD₄ transitions that are within 300 MHz of isotopic CO₂ laser lines are tabulated for this purpose and for use in double-resonance experiments.     

A technique for simulating the amplifier-to-eardrum transfer function of an in situ hearing aid

There are numerous articles wherein mathematical models of various parts of an in situ hearing aid have been reported. Such parts include, for example, the microphone, receiver, cylindrical tubes carrying sound to the eardrum and out through the earmold vent, and the external path from the vent back to the microphone. This article extends these earlier works to include the hearing-aid amplifier. In particular, a mathematical technique for characterizing the amplifier in combination with the receiver is reported. Cascade parameters of a two-port model of one particular amplifier/receiver combination are obtained by this method. The cascade-parameter data and the method of obtaining this data are verified by two different experimental procedures. One procedure involves both computing and measuring the input driving-point impedance of the amplifier/receiver combination. In the second procedure, the amplifier-to-eardrum transfer function of a hearing aid incorporating this same amplifier/receiver combination and mounted on an artificial ear is both computed and measured. Experimental and computed values of this transfer function for three different earmold geometries are in reasonably close agreement. The amplifier/receiver model reported herein will be used in future studies of acoustic feedback in hearing aids.     

Voice responses to changes in pitch of voice or tone auditory feedback

The present study was undertaken to examine if a subject's voice F0 responded not only to perturbations in pitch of voice feedback but also to changes in pitch of a side tone presented congruent with voice feedback. Small magnitude brief duration perturbations in pitch of voice or tone auditory feedback were randomly introduced during sustained vowel phonations. Results demonstrated a higher rate and larger magnitude of voice F0 responses to changes in pitch of the voice compared with a triangular-shaped tone (experiment 1) or a pure tone (experiment 2). However, response latencies did not differ across voice or tone conditions. Data suggest that subjects responded to the change in F0 rather than harmonic frequencies of auditory feedback because voice F0 response prevalence, magnitude, or latency did not statistically differ across triangular-shaped tone or pure-tone feedback. Results indicate the audio-vocal system is sensitive to the change in pitch of a variety of sounds, which may represent a flexible system capable of adapting to changes in the subject's voice. However, lower prevalence and smaller responses to tone pitch-shifted signals suggest that the audio-vocal system may resist changes to the pitch of other environmental sounds when voice feedback is present.     

Insight into 3D micro‐CT data: exploring segmentation algorithms through performance metrics

Three‐dimensional (3D) micro‐tomography (µ‐CT) has proven to be an important imaging modality in industry and scientific domains. Understanding the properties of material structure and behavior has produced many scientific advances. An important component of the 3D µ‐CT pipeline is image partitioning (or image segmentation), a step that is used to separate various phases or components in an image. Image partitioning schemes require specific rules for different scientific fields, but a common strategy consists of devising metrics to quantify performance and accuracy. The present article proposes a set of protocols to systematically analyze and compare the results of unsupervised classification methods used for segmentation of synchrotron‐based data. The proposed dataflow for Materials Segmentation and Metrics (MSM) provides 3D micro‐tomography image segmentation algorithms, such as statistical region merging (SRM), k‐means algorithm and parallel Markov random field (PMRF), while offering different metrics to evaluate segmentation quality, confidence and conformity with standards. Both experimental and synthetic data are assessed, illustrating quantitative results through the MSM dashboard, which can return sample information such as media porosity and permeability. The main contributions of this work are: (i) to deliver tools to improve material design and quality control; (ii) to provide datasets for benchmarking and reproducibility; (iii) to yield good practices in the absence of standards or ground‐truth for ceramic composite analysis.