Effectiveness of Surface Treatment Techniques for Composite Bonding with Different Contamination Levels

Various surface treatment techniques have been developed to promote adhesive bond performance for composite structural components in aerospace applications. The condition of the pre-bond surface is critical to achieving desirable bond quality. Contamination on bonding surfaces is well recognized as a major threat to ultimate bond performance. Variation in contamination level has brought additional challenges into manufacturing process control. High fidelity surface treatment techniques are required for effective removal of contaminants over a wide range of contamination levels. In this study, a common contaminant, i.e. silicone mold release, was introduced to pre-bond composite surfaces with different concentrations. Plasma and laser surface treatment techniques were performed and their effectiveness in restoring and enhancing desirable bond quality was investigated. Surface characterization techniques, including water contact angle goniometry, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, were conducted to assess the condition of contaminated surfaces and the improvement induced by plasma and laser surface treatments. Failure modes from a customized double cantilever beam test were investigated before and after surface treatments. Fundamental mechanisms of plasma and laser surface treatments on the composite bonding surfaces were also investigated

Development and implementation of plasma sprayed nanostructured ceramic coatings

Abstract A broad overview of the science and technology leading to the development and implementation of the first plasma sprayed nanostructured coating is described in this paper. Nanostructured alumina and titania powders were blended and reconstituted to a sprayable size. Thermal spray process diagnostics, modeling and Taguchi design of experiments were used to define the optimum plasma spray conditions to produce nanostructured alumina-titania coatings. It was found that the microstructure and properties of these coatings could be related to a critical process spray parameter (CPSP), defined as the gun power divided by the primary gas flow rate. Optimum properties were determined at intermediate values of CPSP. These conditions produce limited melting of the powder and retained nanostructure in the coatings. A broad range of mechanical properties of the nanostructured alumina-titania coatings was evaluated and compared to the Metco 130 commercial baseline. It was found that the nanostructured alumina-titania coatings exhibited superior wear resistance, adhesion, toughness and spallation resistance. The technology for plasma spraying these nanostructured coatings was transferred to the US Navy and one of their approved coating suppliers. They confirmed the superior properties of the nanostructured alumina-titania coatings and qualified them for use in a number of shipboard and submarine applications.

Nonlinear adiabatic response of interacting quantum dots

We develop a generic method in Liouville space to describe the dissipative dynamics of coherent interacting quantum dots with adiabatic time dependence beyond linear response. We show how the adiabatic response can be related to effective quantities known from real-time renormalization group methods for stationary quantities. We propose the study of a generalized $RC$-time as a characteristic time scale. We apply the method to the interacting resonant level model and calculate the nonlinear adiabatic charge response to time-dependent gate voltages, tunneling barriers and Coulomb interaction. The generalized $RC$-time is found to acquire a unique form in all cases, in contrast to the capacitance and the charge relaxation resistance. We discuss the observability of the effects in molecular systems and cold atom setups.Comment: 6 page

Does voice amplification increase intelligibility in people with Parkinson's disease

Background/Aims: Patients with speech intelligibility difficulties associated with a quiet voice are often prescribed a voice amplifier. This study examined whether artificial voice amplification improved intelligibility in people with Parkinson's disease and whether there was an optimum increase that brought about best improvement. Methods: Twelve people diagnosed with Parkinson's disease (mild=4, moderate intelligibility difficulties=8) and five age-matched controls read low predictability sentences in their habitual voice. Audio recordings were digitally manipulated to create samples at +2.3 dB, +5 dB and +10 dB amplification. Listeners transcribed the recorded sentences. The percentage of words correctly identified was compared across levels of amplification and groups. Results: Participants with moderate Parkinson's disease were significantly less intelligible than controls in all conditions. Moderately, but not mildly affected participants with Parkinson's disease showed higher intelligibility in the amplified conditions, though statistically significantly only at +2.3 dB. No other significant effects of intensity or interactions with groups were found. At an individual level, some participants showed clear advantages of amplification. Conclusion: Based on results from the current participants, potential benefits of amplification cannot be promised to all people with Parkinson's disease. Nevertheless, several provisos regarding methods employed suggest the question can gainfully be pursued using broader measures to assess effects of amplification with more varied groups of people with Parkinson's disease and with other aetiologies where voice production can be an issue

Impairment of Vowel Articulation as a Possible Marker of Disease Progression in Parkinson's Disease

Purpose: The aim of the current study was to survey if vowel articulation in speakers with Parkinson’s disease (PD) shows specific changes in the course of the disease. Method: 67 patients with PD (42 male) and 40 healthy speakers (20 male) were tested and retested after an average time interval of 34 months. Participants had to read a given text as source for subsequent calculation of the triangular vowel space area (tVSA) and vowel articulation index (VAI). Measurement of tVSA and VAI were based upon analysis of the first and second formant of the vowels /a/, /i/and /u / extracted from defined words within the text. Results: At first visit, VAI values were reduced in male and female PD patients as compared to the control group, and showed a further decrease at the second visit. Only in female Parkinsonian speakers, VAI was correlated to overall speech impairment based upon perceptual impression. VAI and tVSA were correlated to gait impairment, but no correlations were seen between VAI and global motor impairment or overall disease duration. tVSA showed a similar reduction in the PD as compared to the control group and was also found to further decline between first and second examination in female, but not in male speakers with PD. Conclusions: Measurement of VAI seems to be superior to tVSA in the description of impaired vowel articulation and its further decline in the course of the disease in PD. Since impairment of vowel articulation was found to be independent fro

Valence states of nanocrystalline Ceria under combined effects of hydrogen reduction and particle size

10.1063/1.3371687Applied Physics Letters9612-APPL