Mössbauer investigation of the transformations of the iron minerals in oil shale during retorting

Iron phases in raw and retorted shales have been studied from the TOSCO II, Paraho, and Lawrence Livermore Laboratory (LLL) 125 kg retorting processes by Mössbauer effect spectroscopy. Using the Mössbauer effect, changes in the iron mineralogy during retorting were monitored. Results show that the pyrite fraction in the TOSCO II, and LLL hydrogen run S-9 samples underwent changes during retorting whereas the iron-containing carbonates did not. As in other pyrolysis processes, FeS₂ breakdown is affected by the presence of organic matter. Hydrogen released by the indigenous kerogen acts to reduce pyrite to the magnetic sulphide pyrrhotite. In all of the retorts containing oxygen, carbonate breakdown was observed prior to pyrite oxidation. Free oxygen is introduced to several retorts. The iron minerals within these systems eventually become a mixture of the oxides hematite and magnetite. This study demonstrates that alteration of specific iron minerals during retorting may be controlled by varying the internal retorting conditions.     

Anion exchange resins prepared from polystyrene crosslinked via a Friedel–Crafts reaction

The preparation of anion exchange resins from polystyrene crosslinked via a Friedel–Crafts reaction is investigated. Chloromethylation of a highly swollen styrene–hexahydrotriacrylolyl-s-triazine copolymer with a mixture of chlorosulfonic acid and methylal is accompanied by the crosslinking of the initially flexible copolymer. The crosslinking efficiency is dependent on the conditions (temperature, nature of solvent) of chloromethylation and can be explained by cationic postpolymerization of polystyrene or poly(benzylchloride), which takes place concurrently with the chloromethylation.     

Low-loss polarization-insensitive InP-InGaAsP optical space switches for fiber optical communication

High-performance InP-InGaAsP optical space switches are reported, which in monolithic four switch arrangements reach fiber-to-fiber losses as low as 5 dB. Polarization insensitivity is within /spl plusmn/0.5 dB. On-off ratios throughout the 1.53-1.56 /spl mu/m wavelength range exceed 15 dB. Switch rearrangement times are below 200 ps.     

Beryllium bombardment for In0.53Gao0.47As and InP photoconductors with picosecond response times

High-speed photoconductors, based on epitaxial In_0.53Ga_0.47As layers and semi-insulating InP, were integrated into broadband coplanar 50 Ω microwave structures for applications like optoelectronic sampling. To shorten the response times from the nanosecond to the low picosecond range the devices were bombarded with beryllium ions. Implantation doses and profiles were optimized with the help of the TRIM85 Monte Carlo program. With doses of 10¹⁴ cm⁻², response times as short as 2 and 3 ps were achieved for the In_0.53Ga_0.47As and InP photoconductors respectively. Electric properties of bombardment-related defects are deduced experimentally and compared to models for In_0.53Ga_0.47As explaining the observed time-response characteristics.     

Measurement of true specific heats of bituminous coals of different rank,and of a high-temperature coke,in the temperature range 30–350 °C

The true specific heats of four bituminous coals from the Ruhr district with volatile matter ranging between 9 and 37 wt% and of a high-temperature coke were measured with an adiabatic metal calorimeter. The precision of the equipment was checked by measurements on pure nickel, with the result that the experimental values were found to differ by <1% from the adequately accurate average values given in the literature. The results of this study and the scrutiny of all obtainable systematic specific heat measurements of bituminous coals lead to the conclusion that, contrary to the opinion given in the literature, the specific heats do not increase rectilinearly with the volatile matter. The relation of the specific heats of the coals investigated to volatile matter and temperature can be explained by the chemical composition and structure of the coals. The specific heats calculated from the distribution of the elements carbon, hydrogen and oxygen in the structural groups of bituminous coals correspond well to the experimental values. The procedure is more promising than that using only the results of immediate analysis without taking into account chemical composition and structure. In the initial stage of pyrolysis, variations from a monotonic increase are observed and semiquantitative considerations on this are given. The effect of temperature on the specific heats of coals is compared with that on other physical quantities and explained.     

IR pyrometry in diamond anvil cell above 400 K

Temperature measurements in a laser heated diamond anvil cell (DAC) are currently limited to temperatures above 1000 K using optics and detectors in the visible range. We have built a pyrometer in the IR range and expanded the lower limit of temperature detection to 400 K. The pyrometer is designed for very low thermal radiation intensities, measured sequentially through a set of bandpass filters in the range of 1.2-3.4 microm using very efficient IR photodetectors. The thermal radiation from the center of the cw Nd:YAG laser heated spot is least square fitted to a Planck curve, using a gray body approximation. Melting is detected by changes in the light scattering picture of an auxiliary He-Ne laser from the surface of the hot spot, and by a change in slope in the plot of hot spot temperature versus laser power. In this work we demonstrate measurement of the melting curve of zinc up to 25 GPa. The melting curve is in very good agreement with previous results which were taken up to 6 GPa in a large volume press.     

Hyperanalytic denoising.

A new threshold rule for the estimation of a deterministic image immersed in noise is proposed. The full estimation procedure is based on a separable wavelet decomposition of the observed image, and the estimation is improved by introducing the new threshold to estimate the decomposition coefficients. The observed wavelet coefficients are thresholded, using the magnitudes of wavelet transforms of a small number of "replicates" of the image. The "replicates" are calculated by extending the image into a vector-valued hyperanalytic signal. More than one hyperanalytic signal may be chosen, and either the hypercomplex or Riesz transforms are used, to calculate this object. The deterministic and stochastic properties of the observed wavelet coefficients of the hyperanalytic signal, at a fixed scale and position index, are determined. A "universal" threshold is calculated for the proposed procedure. An expression for the risk of an individual coefficient is derived. The risk is calculated explicitly when the "universal" threshold is used and is shown to be less than the risk of "universal" hard thresholding, under certain conditions. The proposed method is implemented and the derived theoretical risk reductions substantiated.     

A Bayesian model for the joint optimization of quality and maintenance decisions

We develop a model for the economic design of a Bayesian control chart for monitoring a process mean. The process may randomly suffer failures that result in a non‐operating state, and thus call for an immediate corrective maintenance action, as well as assignable causes that shift the process mean to an undesirable level. Quality shifts, apart from poorer quality outcome and higher operational cost, also result in higher failure rate. Consequently, their removal, besides improving the outcome quality and reducing the quality‐related cost, is also a preventive maintenance action since it reduces the probability of a failure. The proposed Bayesian model allows the determination of the design parameters that minimize the total expected quality and maintenance cost per time unit. The effectiveness of the proposed model is evaluated through the comparison of its expected cost against the optimum expected cost of the simpler variable‐parameter Shewhart chart. Copyright © 2010 John Wiley & Sons, Ltd.     

Risk factors in oil and gas industry returns: International evidence

The recent boom in oil prices has attracted many investors to oil companies in search of both returns and diversification benefits. This analysis of the risk factors of investing in the oil and gas industry in 34 countries finds evidence that oil price is a globally priced factor for the oil industry. The oil and gas sector in developed countries responds more strongly to oil price changes than in emerging markets. Oil and gas industry returns also respond asymmetrically to changes in oil prices; oil price rises have a greater impact than oil price drops. There is no parallel to the asymmetry of oil price changes in other industries related to commodities. If there is any asymmetry, it is in the opposite direction from oil. Negative commodity price changes have a greater impact than positive ones. The results seem to indicate that the oil and gas industry is distinguished by a pass-through effect.