In this work, the characteristics of heterogeneous azeotropic distillation of isopropyl alcohol (IPA) + water (H2O) with cyclohexane (CyH) as an entrainer were investigated. Critical reflux, parametric sensitivity, and hysteresis were found by theoretical analysis and supported by experiment using a laboratory-scale sieve plate distillation column. At each given reflux rate, there are two branches of stable steady states as reboiler duty varies, one with desirable purity and another with almost no separation. The highest attainable purity is achieved at a specific reboiler duty. Beyond this duty there is a catastrophic loss in IPA purity. At higher refluxes, the temperature profiles of the column with highest attainable purity pass around the IPA + CyH azeotrope. A plateau at 69.3 °C characterizes this type of profile. There is little change of highest attainable IPA purity as reflux varies. When reflux is reduced below a critical value, the temperature profile of the column with highest attainable purity passes around the IPA + H2O azeotrope. The highest attainable IPA purity decreases substantially as reflux is reduced. The critical reflux represents an operating state that achieves high IPA purity with minimum energy consumption. Furthermore, at a given pair of reflux and reboiler duty, the steady-state temperature profile that achieves good separation is not unique. The exact position of the temperature front can be fixed at any position inside the column using a cyclic series of step changes in reboiler duty. This hysteresis phenomenon is attributable to changes in entrainer inventory inside the column.

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Comment on "Unraveling the conduction mechanism of Al-doped ZnO films by valence band soft x-ray photoemission spectroscopy" [Appl. Phys. Lett.86, 042104 (2005)] Appl.In this study, the interaction of undoped ZnO films with ͑NH 4 ͒ 2 S x treatment have been investigated by x-ray photoelectron spectroscopy, photoluminescence, optical transmittance, and four-point probe. According to the experimental results, we find that the formation of Zn-S bonds and the reduction of oxygen vacancies ͑i.e., the S occupation of oxygen vacancies͒ near the ZnO surface might lead to an increase in the upward band bending, resulting in an increase in the sheet resistance and work function of ZnO.

Zinc gallate (ZnGaO; ZGO) thin films were employed as the p-type transparent contact layer in deep-ultraviolet AlGaN-based light-emitting diodes (LEDs) to increase light output power. The transmittance of 200-nm-thick ZGO in deep-ultraviolet wavelength (280 nm) was as high as 92.3%. Two different ohmic contact structures, a dot-LED (D-LED; ZGO/dot-ITO/LED) and whole-LED (W-LED; ZGO/ITO/LED), exhibited improved light output power and current spreading compared to a conventional ITO-LED (C-LED). At an injection current of 20 mA, the D-LED and W-LED exhibited 33.7% and 12.3% enhancements in light output power, respectively, compared to the C-LED. The enhanced light output power of the D-LED can be attributed to an improvement in current spreading and enhanced light-extracting efficiency achieved by introducing ZGO/dot-ITO.