Semi-transparent thin film solar cells by a solution process

Easily processed, low cost, and highly efficient solar cells are desirable for photovoltaic conversion of solar energy to electricity. We present the fabrication of precursor solution processed CuInGaS2 (CIGS) thin film solar cells on transparent indium tin oxide (ITO) substrates. The CIGS absorber film was prepared by a spin-coating method, followed by two successive heat treatment processes. The first annealing process was on a hot plate at 300 °C for 30 min in air to remove carbon impurities in the film; this was followed by a sulfurization process at 500 °C in an H₂S(1%)/Ar environment to form a polycrystalline CIGS film. The absorber film with an optical band-gap of 1.52 eV and a thickness of about 1.1 µm was successfully synthesized. Because of the usage of a transparent glass substrate, a bifacial CIGS thin film device could be achieved; its power conversion efficiency was measured to be 6.64% and 0.96% for front and rear illumination, respectively, under standard irradiation conditions.     

Modeling and analysis of rapid catalyst aging cycles

The primary mode of deactivation of automotive emission control catalysts is thermal aging, and it is well-known that high-temperature lean aging conditions are particularly detrimental. Since evaluating the long-term durability of automotive catalysts is costly and time-consuming, rapid catalyst aging cycles have been developed to mimic (in a reduced time) the catalyst deactivation under real-world driving conditions. One of the commonly used rapid catalyst aging tests is an exothermal aging cycle, which involves a combination of fuel-rich engine operation and supplemental air injection to generate high-temperature lean conditions within the catalyst bed. In this work, we use the previously developed transient three-way catalyst model to investigate the time evolution of the axial temperature profiles and exhaust air–fuel ratio (A/F) along the catalyst bed during the course of the exothermal rapid aging cycles. We find that the thermal front propagates downstream through the catalyst bed relatively slowly (compared to the concentration front) and this can limit the location within the catalyst bed and duration for high-temperature lean exposure. We also investigate how variations of some of the key system design and operating parameters can affect the extent and duration of high-temperature lean exposure. Finally, a simple analytical expression is developed which allows one to estimate the time it takes for the thermal front to travel through the catalyst bed. This time can be compared with the period of the lean A/F operation during the aging cycle to determine the location and duration of high-temperature lean exposure.     

Effect of silane functionalization of montmorillonite on epoxy/montmorillonite nanocomposite

Mechanical and dynamic mechanical properties of various montmorillonite (MMT)/epoxy nanocomposites were investigated. 3-aminopropyltriethoxysilane functionalized MMT was compared with commercial pristine MMT and ammonium salt substituted MMT. Qualitative evidence of silane functionalization was confirmed by FT-IR. XRD and TEM were used to characterize the degree of intercalation of MMT in epoxy nanocomposite. Tensile stress and elongation of MMT/epoxy nanocomposite were improved significantly by the silane functionalization of MMT. Dynamic mechanical analysis showed that silane functionalization of MMT resulted in active interactions between MMT and epoxy.     

The development of air-breathing proton exchange membrane fuel cell (PEMFC) with a cylindrical configuration

A small air-breathing proton exchange membrane fuel cell with a cylindrical configuration (Cy-PEMFC) and a helical flow-channel was developed to provide a uniform contact pressure to the membrane electrode assembly (MEA) with a thin cathode current collector. A comparison of the contact pressure and performance of the Cy-PEMFC and general planar PEMFC was performed to determine the effect of the cylindrical configuration. For the contact pressure comparison, numerical analysis was performed using commercial software. Numerical analysis showed that the Cy-PEMFC has its own structural advantage of changing the applied clamping pressure to a uniformly distributed contact pressure. The actual pressure measurements were carried out with pressure-sensitive film to support results of numerical analysis. These results also showed that the Cy-PEMFC had a uniformly distributed contact pressure, whereas the planar PEMFC did not. The polarization curves of both PEMFCs were measured to determine the performance variations caused by the uniform contact pressure and better mass transfer. The maximum power density of the Cy-PEMFC was 220 mW/cm², which was approximately 24% higher than the planar PEMFC.     

Vision-based global localization and mapping for mobile robots

We have previously developed a mobile robot system which uses scale-invariant visual landmarks to localize and simultaneously build three-dimensional (3-D) maps of unmodified environments. In this paper, we examine global localization, where the robot localizes itself globally, without any prior location estimate. This is achieved by matching distinctive visual landmarks in the current frame to a database map. A Hough transform approach and a RANSAC approach for global localization are compared, showing that RANSAC is much more efficient for matching specific features, but much worse for matching nonspecific features. Moreover, robust global localization can be achieved by matching a small submap of the local region built from multiple frames. This submap alignment algorithm for global localization can be applied to map building, which can be regarded as alignment of multiple 3-D submaps. A global minimization procedure is carried out using the loop closure constraint to avoid the effects of slippage and drift accumulation. Landmark uncertainty is taken into account in the submap alignment and the global minimization process. Experiments show that global localization can be achieved accurately using the scale-invariant landmarks. Our approach of pairwise submap alignment with backward correction in a consistent manner produces a better global 3-D map.     

Metal gate-HfO/sub 2/ MOS structures on GaAs substrate with and without Si interlayer

In this letter, we studied the effects of post-deposition anneal (PDA) time and Si interface control layer (ICL) on the electrical characteristics of the MOS capacitor with high-/spl kappa/ (HfO/sub 2/) material on GaAs. Thin equivalent oxide thickness (EOT<3 nm) with excellent capacitance-voltage (C-V) characteristics has been obtained. The thickness of the Si ICL and PDA time were correlated with C-V characteristics. It was found that high temperature Si ICL deposition and longer PDA time at 600/spl deg/C improved the C-V shape, leakage current, and especially frequency dispersion (<5%).     

Detection of zearalenone and related metabolites by fluorescence polarization immunoassay

Zearalenone is an estrogenic mycotoxin commonly found in grains throughout the world. A number of instrument- and antibody-based methods including enzyme-linked immunosorbent assays (ELISAs) have been developed to detect zearalenone (ZEN) and related toxins in commodities and foods. Although convenient, the commercial ELISAs for small molecules such as ZEN require a washing step to separate bound and unbound enzyme label before detection. In fluorescence polarization immunoassays, separation of bound and unbound label is not required, a property that reduces the time needed to perform the assays. We developed a fluorescence polarization immunoassay for ZEN in maize. When combined with a rapid extraction technique, the assay could be used to detect as little as 0.11 microg of ZEN g(-1) maize within 10 min. The assay showed cross-reactivity to the ZEN analogs zearalanone, alpha-zearalanol, alpha-zearalenol, beta-zearalenol, and beta-zearalanol of 195, 139, 102, 71, and 20%, respectively, relative to ZEN (100%). Recovery of ZEN from spiked maize over the range of 0.5 to 5 microg g(-1) averaged 100.2% (n = 12). The fluorescence polarization immunoassay results were comparable to those obtained with a liquid chromatographic method for the analysis of 60 naturally contaminated maize samples and maize samples amended with culture material. The fluorescence polarization immunoassay provides a rapid method for screening of maize for ZEN.