Interfacial Chemistry of an Aluminum-to-EPDM Rubber Bonding System

During recent assessment of aging in aluminum-to-rubber bonds on stored solid rocket motors, corrosion and minor insulator debonds were observed. A test was conducted to study the progressive effect of exposure to high humidity on the bondline; elevated temperature was used to accelerate the aging. In a parallel test, samples were held at elevated temperature in a dry atmosphere. The test results were compared with the analyses of corroded and noncorroded hardware samples. The predominant corrosion product detected at the bondlines was aluminum oxide/hydroxide. In general, there was a very good correlation between the Cl:Al atomic percent ratio calculated from X-ray photoelectron spectroscopy analysis of the ruptured bondline surfaces and the visual characterization of the extent of corrosion. The Cl:Al ratio, which represented the ratio of primer to corrosion product at the locus of failure, varied from 0.4 to 47. The implications for metal-to-rubber bond fabrication and storage are discussed.     

Who,what, why? An exploration of JoVE scientific video publications in tweets

This paper investigates how and why scientific video articles are communicated on Twitter. We use video articles published in the Journal of Visualized Experiments (JoVE) as our objects of study. We harvested tweets from October 2011 to November 2015 that contained one or more JoVE links. These tweets “citing” JoVE articles were analyzed both statistically and qualitatively. In this paper, we present the distribution of these tweets, with a closer look at the affordance use of Twitter including hashtags and mentions. In addition, we conducted a content analysis of the sampled Twitter accounts and tweets. We present the coding schemes and results of both Twitter user accounts and tweets text. In addition to the analysis of the coding results, we discuss the content of the tweets with particular attention to issues including the video/visual feature mentioned, the role of Twitter bots, and self-promotion of different stakeholders in the Twitter communication of JoVE video publications.     

Signal Propagation on Single Phase Power Distribution Lines at Power Line Carrier Frequencies

Two sets of propagation measurements were made on a 20,847 foot unenergized power distribution line in the frequency range 0 to 50 kHz. The line was configured with and without distribution transformers. From the first set of measurements a voltage transfer function was calculated for this line. In the second set of measurements the line was energized with a 25 kHz signal and the voltage, current and impedance were measured along the line. Various propagation characteristics such as attenuation, characteristic impedance, velocity of propagation, and standing wave ratios were determined from these measurements.     

Detection and classification of underwater acoustic transientsusing neural networks

Underwater acoustic transients can develop from a wide variety of sources. Accordingly, detection and classification of such transients by automated means can be exceedingly difficult. This paper describes a new approach to this problem based on adaptive pattern recognition employing neural networks and an alternative metric, the Hausdorff metric. The system uses self-organization to both generalize and provide rapid throughput while utilizing supervised learning for decision making, being based on a concept that temporally partitions acoustic transient signals, and as a result, studies their trajectories through power spectral density space. This method has exhibited encouraging results for a large set of simulated underwater transients contained in both quiet and noisy ocean environments, and requires from five to ten MFLOPS for the implementation described.     

Coupled electrooxidation and electrical conduction in a single gold nanowire

The resistance, R, of single gold nanowires was measured in situ during electrooxidation in aqueous 0.10 M sulfuric acid. Electrooxidation caused the formation of a gold oxide that is approximately 0.8 monolayers (ML) in thickness at +1.1 V vs saturated mercurous sulfate reference electrode (MSE) based upon coulometry and ex situ X-ray photoelectron spectroscopic analysis. As the gold nanowires were electrooxidized, R increased by an amount that depended on the wire thickness, ranging from Delta R/ R 0.10V = 14% for a 63 nm (h) x 200 nm (w) wire to 57% for an 18 nm (h) x 95 nm (w) wire at +1.1 V. These nanowires were millimeters in total length, but just 46 mum lengths were exposed to the electrolyte solution. The oxidation process and the accompanying increase in R were reversible: Reduction of the oxide at +0.10 V resulted in recovery of the reduced wire R except for a small resistance offset caused by the dissolution of approximately 0.4 ML of gold during each oxidation/reduction cycle. The measured increase in R during oxidation exceeds by a factor of 4 the predicted increases in R associated with the reduction in cross-sectional area of the nanowire and the expected decrease in the specular scattering parameter, p, at the gold-oxide interface at wire surfaces. We propose that this anomalous increase in R is caused by infiltration of the oxide into the nanowire at grain boundaries.     

Interpretation of CT studies: single-screen workstation versus film alternator

A prototype single-screen workstation with a 2,048 x 2,560-pixel high-brightness monitor, 0.11-second image display time, and simple ergonomic design was compared to a conventional horizontal film alternator in diagnostic interpretation of chest computed tomography (CT) studies. Four radiologists used either the workstation or film alternator in interpretation of studies obtained in 10 patients. A counterbalanced within-subject repeated measures experimental design was used. Response times were analyzed for both methods of interpretation. Grades of excellent, acceptable, and unacceptable were assigned by a blinded "grader" to reports of the radiologists. The average time needed for an interpretation at the workstation was 5.65 minutes. No interpretations were graded unacceptable. Retrospective power analysis showed that 16 observers rather than four would have been required to show that use of the workstation was faster than the alternator. With this 95% confidence interval, the workstation interpretation time is clinically equivalent to that with the alternator. These data show that this type of workstation has practical application in interpretation of CT, magnetic resonance imaging, and ultrasound studies.