Graphite/InP and graphite/GaN Schottky barrier hydrogen sensors with electrophoretically deposited Pd or Pt nanoparticles

ABSTRACT: Large attention has been devoted worldwide to investigation of hydrogen sensors based on various Schottky diodes. We prepared graphite semimetal Schottky contacts on polished n-InP and on n-GaN wafers partly covered with nanoparticles of catalytic metals Pd or Pt by applying colloidal graphite. Metal nanoparticles were deposited electrophoretically from colloids prepared beforehand. Deposited nanoparticles were imaged by SEM, AFM and STM on the as-made and on the annealed-in-vacuum samples. Current-voltage characteristics of prepared Schottky diodes had very high rectification ratios, better than 1E7 at 1 V. It was shown that the barrier heights of these diodes was equal to the difference between the electron affinity of InP or GaP and the electron work function of the metal Pd or Pt (Schottky-Mott limit). That was a good precondition for high sensitivity of the diodes to hydrogen and indeed, high sensitivity to hydrogen, with the detection limit better than 1 ppm was proved.     

Wavelet analysis of experimental results for coupled structural–hydraulic behavior of the EURISOL target mock-up

During test runs of the The European Isotope Separation On-Line (EURISOL) target mock-up performed in December 2008, data were recorded for strain gages and for acceleration sensors. In this paper, the applicability of wavelet analysis for detecting the onset and the status of flow-induced cavitation is investigated for the first time. Even under noisy conditions, the detection of incipient cavitation was possible when combining measurements with data from structural and fluid dynamic simulations. The distribution of coefficients of suitably selected wavelets yields a quantitative measure for the extent of cavitation in the EURISOL target mock-up under representative flow conditions. Without cavitation, the distribution of the wavelet coefficients was Gaussian with a small standard deviation, whereas for developed cavitation the standard deviation was large and the probability density function (PDF) approached a uniform distribution.     

PageRank for bibliographic networks

In this paper, we present several modifications of the classical PageRank formula adapted for bibliographic networks. Our versions of PageRank take into account not only the citation but also the co-authorship graph. We verify the viability of our algorithms by applying them to the data from the DBLP digital library and by comparing the resulting ranks of the winners of the ACM E. F. Codd Innovations Award. Rankings based on both the citation and co-authorship information turn out to be “better” than the standard PageRank ranking.     

Antioxidant Characteristics of Hops and Hop Products

The method based on the reaction of stable DPPH radical proved to be the best for the determination of antioxidant characteristics of hops and hop products. Antioxidant activity is expressed as the rate of decline in absorbance of the reaction environment and assessed in relative percents. Differences in the values of antioxidant activity were determined in Czech and foreign hop varieties. The highest antioxidant activities in the scope of 70 to 80% rel. were measured in Saaz and Spalter Select. Antioxidant activity in most of the varieties moved in the scope of 40 to 60% rel. A part of antioxidant activity of hops is irreversibly lost in the course of drying. The loss does not usually exceed 5% of the original RA_DPPH value. Drying also resulted in a decrease of polyphenol compound contents. Drying in belt and chamber kilns is comparable from the point of view of preserving hop antioxidant properties. Results of determination of antioxidant activity in hot water extracts of raw hops and ground hops were comparable and statistically non‐significant. The same held true for pelletizing of ground hops. The antioxidant activity of raw hops declined in the course of long‐term storage in dependence on storage temperature. Storage temperature had no effect on the antioxidant activity of the hop pellets packed in a multi‐layer foil without air access.     

International harmonization of grid connection guidelines: adequate requirements for the prevention of unintentional islanding

Islanding is still one of the major controversial subjects in the international harmonization of grid connection requirements for distributed generation, and particularly photovoltaics. As long as islanding is not intended in order to back up a loss of mains, it should be avoided. The present study reviews the theory of unintentional islanding and assesses the probability of occurrence of the phenomenon, based on previous studies and theoretical considerations. While islanding is virtually impossible if only a small number of distributed generation units is connected to a distribution grid, with higher distributed generation densities, the possibility of islanding becomes realistic. The risk associated with unintentional islanding is estimated, and adequate requirements for functional safety of protection devices are determined in order to ensure the necessary additional degree of safety to be introduced by an islanding prevention device. Finally, a fundamental set of requirements with regard to islanding, to be included in an international grid connection guideline, is derived from the study. Copyright © 2003 John Wiley & Sons, Ltd.     

Biodiesel from rapeseed oil,methanol and KOH. 2. Composition of solution of KOH in methanol as reaction partner of oil

The composition of the solutions of solid KOH in methanol has been measured by means of determinating the content of water in the equilibrium mixture. The dependence of the equilibrium reaction extent ζ¹ and the concentration equilibrium constant Kc on the ratio of the initial amounts of methanol and KOH containing 0.164 and 16.27 wt‐% of water are determined and theoretically described. The concentration of CH₃O¯ ions can be calculated with these results. This value is very important for the course of the alkaline catalyzed methanolysis of rapeseed oil to biodiesel, because the methoxide ions are the true catalyst of such a transesterification.     

Active DLP hyperspectral illumination: a noninvasive, in vivo, system characterization visualizing tissue oxygenation at near video rates

We report use of a novel hyperspectral imaging system utilizing digital light processing (DLP) technology to noninvasively visualize in vivo tissue oxygenation during surgical procedures. The system's novelty resides in its method of illuminating tissue with precisely predetermined continuous complex spectra. The Texas Instruments digital micromirror device, DMD, chip consisting of 768 by 1024 mirrors, each 16 μm square, can be switched between two positions at 12.5 kHz. Switching the appropriate mirrors controls the intensity of light illuminating the tissue as a function of wavelength, active spectral illumination. Meaning, the tissue can be illuminated with a different spectrum of light within 80 μs. Precisely, predetermined spectral illumination penetrates into patient tissue, its chemical composition augments the spectral properties of the light, and its reflected spectra are detected and digitized at each pixel detector of a silicon charge-coupled device, CCD. Using complex spectral illumination, digital signal processing and chemometric methods produce chemically relevant images at near video rates. Specific to this work, tissue is illuminated spectrally with light spanning the visible electromagnetic spectrum (380 to 780 nm). Spectrophotometric images are detected and processed visualizing the percentage of oxyhemoglobin at each pixel detector and presented continuously, in real time, at 3 images per second. As a proof of principle application, kidneys of four live anesthetized pigs were imaged before, during, and after renal vascular occlusion. DLP Hyperspectral Imaging with active spectral illumination detected a 64.73 ± 1.5% drop in the oxygenation of hemoglobin within 30 s of renal arterial occlusion. Producing chemically encoded images at near video rate, time-resolved hyperspectral imaging facilitates monitoring renal blood flow during animal surgery and holds considerable promise for doing the same during human surgical interventions.     

A Review of Catalytic Membrane Layers for Gas/Liquid Reactions

This paper summarises the main ideas of how to use membranes with built-in catalytic function for performing catalysed gas/liquid reactions. Mass transfer effects on catalyst performance and other decisive factors for the design of industrial gas/liquid and gas/liquid/solid reactors are briefly reviewed. Various concepts for applying catalytic membrane layers in multiphase reactors are introduced and the motivation behind their use is explained. What follows is an assessment of the present achievements in using such concepts for gas/liquid reactions. The results available in literature are critically evaluated, focussing mainly on the field of liquid-phase hydrogenations and oxidations, which constitute the major areas where catalytic membranes have been applied to date to gas/liquid systems. The aim of such treatment is to point out the targets, to elaborate on how far the whole field has developed and what challenges remain, rather than to cover a multitude of specific aspects of the many different studies reported in literature.     

Iterative weighted finite transductions

We investigate 2-tape weighted finite automata called weighted finite transducers (WFT) and their applications to image processing. We show that probabilistic mutually recursive function systems (PMRFS) can be simulated by iterative weighted fimite transductions. We conjecture that iterative WFT are stronger than PMRFS and give examples of WFT that support this conjecture. We also show that the family of images defined by iterative WFT is closed under continuous invertible WFT relations which include invertible affine transformations as a special case. We give examples of iterative WFT which can compute mathematical functions given by a Taylor series with regular coefficients which cannot be computed by WFA. We discuss the implementation of an efficient image manipulation system which includes the implementation of efficient algorithms for the application of a WFT to an image in either pixel or WFA representation and for composition of WFT. The system also includes the Culik-Kari recursive WFA inference algorithm as a conversion from pixel representation to WFA representation.This work was supported by the National Science Foundation under Grant No. CCR-9202396. The work of the second author was partially supported by Grant of Slovak Academy of Sciences No. 88 and by EC Cooperative Action IC 1000 Algorithms for Future Technologies (Project ALTEC)