Guaiacol, a phenol derived compound produced by the thermal degradation of lignin, was selected as a model compound to study the catalytic hydrodeoxygenation (HDO) process for upgrading pyrolysis bio-oils. Guaiacol is among the major components of bio-oils; however, it is thermally unstable which leads to catalyst deactivation. In the present study, four noble metal catalysts (Pt, Pd, Rh, and Ru) supported on activated carbon were tested in a fixed-bed reactor at atmospheric pressure and their performance for the guaiacol HDO process was measured. Our results showed that, among the tested catalysts, Pt has higher deoxygenation activity and shows little deactivation for 5 h. Additionally, the operating temperature for the Pt catalyst was optimized and found to be 300 °C. Finally, results from catalyst characterization demonstrated that polyaromatic deposits, especially the condensed ring compounds, are the most likely cause for catalyst deactivation.

This paper describes a two-microphone, software-programmable noise-reduction device that was interfaced to the Nucleus Spectra 22 speech processor to act as a front-end noise-reduction preprocessor. The development for the portable processor and the noise-reduction algorithm, more formally known as beamforming, was originally motivated by complaints from individuals who use hearing aids. These individuals complain about a deterioration in performance with increasing levels of background noise. Since individuals who use cochlear implants have similar complaints, it was a natural extension to pose the question: "What benefit, if any, would the beamforming algorithm provide to individuals who use cochlear implants?" To arrive at an answer, the audio interface to the noise reduction device was modified (to make it compatible to the Nucleus Spectra 22 speech processor), and a set of precursory subject experiments were performed. 1 The precursory studies were specific to the Nucleus 22 Channel Cochlear Implant and the Spectra 22 speech processor, both manufactured by Cochlear Corporation and Cochlear Limited. The noisereduction device used in the precursory studies is known as the Alpha II and is developed by AudioLogic Inc.Eleven English-speaking subjects participated in a series of sessions during which they were tested with their own Spectra 22 speech processor and with the Alpha II beamforming algorithm acting to preprocess the input data to their device. The beamforming algorithm was configured for a beam width of ±15° (15° on either side of the listener). Five of the 11 subjects were tested with a no beam algorithm. The no beam program was used to demonstrate that any improvements measured with the Alpha II were caused by the beamforming algorithm and not by the addition of the second microphone.The subjects were tested at signal-tonoise ratios (SNRs) strong enough to degrade their Spectra alone scores in noise relative to their scores in quiet. The average noise score was 29.3% (SD:10.9) with the Spectra alone and 55.5% (SD:27.5) with the Spectra plus the Alpha II beam program. The average scores in noise for the five 1 This data is a subset of data originally submitted to and pending publication in Ear and Hearing. It is offered with the understanding that the manuscript is tutorial and not intended as a forum for results.

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A nonlinear frequency domain beamforming algorithm was evaluated as a noise reduction technique with eight cochlear implant patients, in a take-home trial. The subjects wore the prototype device coupled to the Nucleus processor for 5–8 weeks. The subjects were tested both before and after the take-home trial with a single noise source at 45 deg ipsilateral to the implant and with sentence type material. The results strongly favored the coupled device for noisy environments and indicated no additional benefits from a period of continued use. The subjective reports indicated that the two-microphone coupled device had a more robust sound quality and is preferred in noisy environments to the stand alone device. Currently the performance measures are being extended to cover sentence scores in a diffuse noise field (four speakers at different locations) and the results for both noise jammer arrangements will be reported.