The photoelectrochemical behavior of TiO2 thin film electrodes, photocatalytically modified with Se islands, is described. The TiO2 thin films were electrodeposited on transparent conducting oxide glass substrates. The resultant electrode forms a n-TiO2/p-Se "photochemical diode" which, in turn, contacts an electrolyte phase. Both transient photocurrent profiles (in response to excitation light that is switched on or off) and steady-state current-potential curves in response to chopped irradiation are considered. We show that the relative dominance of the contributions from the TiO2 and Se components to the overall response of the photochemical diode/electrolyte junction crucially depends on the wavelength distribution of the excitation light source. A simple equivalent circuit representation of this junction is presented, comprised of a photodiode in parallel with two photodiodes connected in series back-to-back. Simulations of the transient and steady-state photoelectrochemical response of this system are presented, and are shown to be in good agreement with the corresponding experimental profiles.

No abstract

A simple and robust method to design a modified PID controller with good regulating and tracking characteristics is presented. Only two limit cycle measurements of the plant under relay control are required to design the modified PID controller. The design method has shown to work well in a number of simulations of industrial applications. One example is presented.

This report was preparedas an account of work sponsoredby an agency of the United States Government. Neither the United States Government or any agency thereof, nor any of their employees,makesany warranty,expressor implied,or assumesany legal liabilityor responsibility for the accuracy,completeness, or usefulnessof any information,apparatus,product,or process disclosed,or representsthat its use wouldnot infringeprivatelyowned rights.Reference hereinto any specificcommercial product, process, or serviceby trade name, trademark, manufacturer, or otherwise, does not necessarilyconstituteor implyits endorsement,recommendation, or favoring by the United States Government or any agency thereof. The views and opinionsof authors expressed herein do not necessadlystate or reflectthose of the UnitedStates Governmentor any agency thereof.