66 research outputs found

    Degradation of Toxic Indigo Carmine Dye by Electrosynthesized Ferrate (VI)

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    Response surface methodology was applied for optimizing indigo carmine (IC) dye removal by electrochemically produced ferrate (VI). Box-Behnken design was employed in this study, and design parameters were pH, Fe (VI) dose and initial dye concentration (Co). R2 and adjusted R2 values were very high that indicated very good accuracy for the employed model. Optimum operational conditions were: 4.08-7.69 for pH, 24-118.83 mg/L for Fe (VI) dose and 60.68-99.13 mg/L for complete removal of IC. Produced by electrochemical method Ferrate (VI) provides high effectiveness for IC dye-containing synthetic wastewater

    Frequency versus time domain parameter estimation: Application to a slot milling operation

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    The time domain recursive least squares estimation of parameters in the presence of additive output noise of harmonic form leads to biased estimates. However, frequency domain least squares parameter estimation, where the frequency range contaminated by the noise is eliminated, can be used to obtain good parameter estimates. Both the time domain and frequency domain methods are described, and applied to the example of a slot milling operation. A model of the resultant force response to feedrate changes in slot milling, based on previously reported experimental studies, is presented. The force measurement is corrupted by harmonic noise arising from runout on the milling cutter. Simulation studies are performed, using a flat band width multi-frequency test signal to persistently excite the system. The time domain approach leads to poor estimates as expected, while the frequency domain approach gives good parameter estimates. The advantages and disadvantages of both methods are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27244/1/0000251.pd

    Study of thin film poly-crystalline CdTe solar cells presenting high acceptor concentrations achieved by in-situ arsenic doping

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    Doping of CdTe using Group-V elements (As, P, and Sb) has gained interest in pursuit of increasing the cell voltage of CdTe thin film solar devices. Studies on bulk CdTe crystals have shown that much higher acceptor concentration than the traditional copper treatment is possible with As, P or Sb, enabled by high process temperature and/or rapid thermal quenching under Cd overpressure. We report a comprehensive study on in-situ As doping of poly-crystalline CdTe solar cells by MOCVD, whereby high acceptor densities, approaching 3 × 1016 cm−3 were achieved at low growth temperature of 390 °C. No As segregation could be detected at grain boundaries, even for 1019 As cm−3. A shallow acceptor level (+0.1 eV) due to AsTe substitutional doping and deep-level defects were observed at elevated As concentrations. Devices with variable As doping were analysed. Narrowing of the depletion layer, enhancement of bulk recombination, and reduction in device current and red response, albeit a small near infrared gain due to optical gap reduction, were observed at high concentrations. Device modelling indicated that the properties of the n-type window layer and associated interfacial recombination velocity are highly critical when the absorber doping is relatively high, demonstrating a route for obtaining high cell voltage
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