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A novel sensing approach combining sol-gel technology and standard graded index telecommunications fibre is presented. The tip of telecommunication fibre is etched using hydrofluoric acid resulting in a parabolic shaped cavity characteristic of the refractive index profile of the fibre. This cavity is then filled with sol-gel-derived silica doped with an analyte-sensitive dye. This configuration is evaluated using both fluorescence and absorption-based indicators for sensing chemical species such as oxygen and ammonia. The compatibility of the immobilisation system on telecommunications fibre with semiconductor laser diode excitation makes this approach particularly suited to quasidistributed sensing. Preliminary results for multi-point pH sensing incorporating an 850nm Optical Time Domain Reflectometer and a near-infra-red dye are presented. The characterisation of a new family of materials known as organically modified silicates (Ormosils) is also carried out. Film thickness and temporal stability are monitored as a function of organic : inorganic precursor ratio while film microstructure is examined using FTIR spectroscopy.

A novel sensing approach combining sol-gel technology and standard graded index telecommunications fibre is presented. The tip of telecommunication fibre is etched using hydrofluoric acid resulting in a parabolic shaped cavity characteristic of the refractive index profile of the fibre. This cavity is then filled with sol-gel-derived silica doped with an analyte-sensitive dye. This configuration is evaluated using both fluorescence and absorption-based indicators for sensing chemical species such as oxygen and ammonia. The compatibility of the immobilisation system on telecommunications fibre with semiconductor laser diode excitation makes this approach particularly suited to quasidistributed sensing. Preliminary results for multi-point pH sensing incorporating an 850nm Optical Time Domain Reflectometer and a near-infra-red dye are presented. The characterisation of a new family of materials known as organically modified silicates (Ormosils) is also carried out. Film thickness and temporal stability are monitored as a function of organic : inorganic precursor ratio while film microstructure is examined using FTIR spectroscopy.

A novel sensing approach combining sol-gel technology and standard graded index telecommunications fibre is presented. The tip of telecommunication fibre is etched using hydrofluoric acid resulting in a parabolic shaped cavity characteristic of the refractive index profile of the fibre. This cavity is then filled with sol-gel-derived silica doped with an analyte-sensitive dye. This configuration is evaluated using both fluorescence and absorption-based indicators for sensing chemical species such as oxygen and ammonia. The compatibility of the immobilisation system on telecommunications fibre with semiconductor laser diode excitation makes this approach particularly suited to quasidistributed sensing. Preliminary results for multi-point pH sensing incorporating an 850nm Optical Time Domain Reflectometer and a near-infra-red dye are presented. The characterisation of a new family of materials known as organically modified silicates (Ormosils) is also carried out. Film thickness and temporal stability are monitored as a function of organic : inorganic precursor ratio while film microstructure is examined using FTIR spectroscopy.

In support of soil classification objectives related to an on going study of non-linear soil response, tomographic techniques were developed and tested using seismic data. The data were collected at three locations at Landfill 4, Hill AFB, Utah. The site is a land-fill waste site which had been isolated from the prevailing ground-water flow by a slurry trench. The objective of this study was to identify the effectiveness of geophysical techniques for seismic velocity measurements and tomographic/imaging analyses. Seismic data were collected between pairs of 50 ft. deep boreholes on either side of the slurry trench. First break picks were analyzed using an iterative back-projection tomographic technique utilizing curved rays. Initial processing revealed that smearing of velocity anomalies between the boreholes occurred because of non-optimum placement of shots and receivers. Adding reasonable constraints to the inversion, however, showed a low-velocity region, terminating between 35 and 40 ft., at the trench location. Diffraction arrivals travelling around the base of the low-velocity region further constrained its depth. Other minor low-velocity zones, possibly indicating layers with increased silt content, were also indicated by the inversion model. This study showed that cross-borehole tomography can be a useful tool in delineating velocity anomalies roughly perpendicular to paths between the boreholes, but that velocity anomalies parallel to the boreholes will be smeared unless additional constraints are imposed. A modification to the data acquisition technique to help overcome this problem would be to use additional high-energy shot-points on the surface between the boreholes.

The polymerization of ethylene over a supported chromium oxide catalyst was studied first in the complete absence of oxygen and then with controlled amounts of oxygen (60 to 600 micro mole/g catalyst) present. The catalyst was prepared by impregnating a microspheroidal silica-alumina (87 - 13 wt. %) with a dilute solution of chromic acid. This raw compound was then activated by heating it in vacuo at 550C. The data indicated that the inhibitory effect of oxygen involved the chemisorption of some oxygen containing species which could in time be displaced by an excess of ethylene. A comparison of the molecular weight distributions of the products with the rates of polymerization at shutdown suggested that higher rates of reaction cause local heating within the reactor, thereby increasing local rates of chain transfer and broadening the distribution. (Author)

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Originally published by: New York (State). Bureau of Municipal Accounts

Originally published by: New York (State). Bureau of Municipal Accounts

Originally published by: New York (State). Bureau of Municipal Accounts

Originally published by: New York (State). Bureau of Municipal Accounts