This work describes the development of ZnO nanowire (NW) devices for ultraviolet detection and cost-effective gas
sensing. A dielectrophoresis (DEP) flow cell fabricated for the integration of NWs on different substrates is presented.
The system includes the possibility to set characteristic parameters such as alternating current (AC) frequency, amplitude
or flow speed in order to control NW trapping on specific sites defined by micro-gapped electrodes. The electrical
characteristics of the rectifying metal/NW contact fabricated by DEP are investigated in darkness and under direct
illumination of the metal-NW interface through the ZnO NW. A significant downshift of the turn-on voltage is observed
in the current-voltage characteristics during the illumination with photon energies higher than the ZnO bandgap. The
reduction is attributed to a barrier height lowering induced by interface charge emission. The effects of AC bias on the
thermal drift of the DC average current in NW devices are also discussed. Finally, the reaction kinetics of ethanol and
water vapors on the NW surface are compared through the analysis of the DC current under direct exposure to gas flows.
Device responses to more complex compound mixtures such as coffee or mint are also monitored over time, showing
different performance in both cases.
This paper describes an algorithm to regulate and control the acquisition of images of a computer vision system used to measure contact wire wear in railways. Real-time implementation of the algorithm is also shown. In this work it will be shown that is possible to base a control strategy on a simple measure derived from the image histogram. The system developed controls acquisition process varying the exposure time of CCD without the necessity to control other parameter of camera/digitiser combination as black and white reference levels of digitiser. In the control strategy proposed, histogram is used as exposure time indicator. A new architecture has been defined to implement the control system in real time. Implementation system has been divided in two processing .On the one hand, a hardware processing in which histogram values extraction is carried out by FPGAs (Field Programmable Gate Array).On the other hand, the calculation of new exposure time based on the histogram is carried out by a PC whose operating system is RTLinux.
The control system has been incorporated as a new module in the system used by RENFE (Spanish Railways Company) to measure the contact wire wear and measurement system precision has been increased considerably.
This paper is oriented to study techniques to improve the precision of the systems for wear measurement of contact wire in the railways. The problematic of wear measurement characterized by some important determining factors like rate of sampling and auscultation conditions is studied in detail. The different solutions to resolve the problematic successfully are examined. Issues related to image acquisition and image processing are discussed. Type of illumination and sensors employed, image processing hardware and image processing algorithms are some topics studied. Once analyzed each one factor which have influence on the precision of the measurement system, there are proposed an assembly of solutions that allow to optimize the conditions under which the inspection can be carried out. Part of the development exposed in this paper is the result of an investigation work in a project in collaboration with the Electronic Division of Engineering of the Escuela Técnica Superior de Ingenieros Industriales of the Universidad Politécnica de Madrid and the business RENFE (Spanish Railways Company) that has culminated in a system for measurement of contact wire (MEDES) which actually is been used on the laboratories coach of RENFE and the SNCF (France) The system is European patent.