Fractoemission from Lead Zirconate-Titanate

We present measurements of the electron, positive ion, and photon emission accompanying the fracture in vacuum of poly-crystalline 95/5 lead zirconate-titanate. The intensities of the charged-particle components of this fractoemission are shown to depend strongly on the direction (relative to the direction of fracture) and magnitude of polarization. The most intense emission is observed when the fracture surfaces are perpendicular to the polarization direction. The emission intensity increases monotonically with polarization. These results are interpreted in terms of a model involving charge separation on the fracture surfaces leading to a microdischarge during fracture. Implications to the interpretation of triboluminesence effects are discussed.     

Phase Studies Concerning Sintering in Aluminas Doped with Ti4+

Previous solid state analyses of sintering in Ti⁴⁺-doped-commercial alumina are shown to be in error because a liquid phase exists in the appropriate region of the Al₂O₃−TiO₃−Na₂Ophase diagram at least by 1350^°C, a temperature lower than that at which "solid state" studies were conducted. It is suggested that liquid-phase sintering is a much more common occurrence than was realized formerly.     

Physical and chemical characteristics of butterfat fractions obtained by crystallization from molten fat

Both summer and winter butterfats were fractionated using a laboratory procedure which was designed to simulate a commercial fractionation process. The process is based on a slow, controlled cooling of the melted fat, a short stabilization time at the fractionation temperature, and separation of the crystals from the liquid oil by vacuum filtration using a stainless steel perforated disc. Fractionation temperatures of 29, 26, 23 and 19 C for winter butterfat and 29 and 19 C for summer butterfat were used to obtain solid and liquid fractions at each temperature. Three replications at each temperature showed good reproducibility of results. The fractions were characterized by their fatty acid and triglyceride compositions, melting and crystallization behavior, iodine value, peroxide value and melting point. Presented at the AOCS meeting in Philadelphia in May 1985.     

The function of bleaching earths in the processing of palm,palm kernel and coconut oils

The results presented in the literature, which attempt to elucidate the mechanisms by which triglyceride oils are bleached by earths, are reviewed. The impact of this work and how the mechanistic proposals affect changes in oil properties are considered, with particular emphasis on the needs of the palm oil processor. Important properties include color, metals and phosphorus content and oxidative stability of the oil. Investigations made in our own laboratories have been aimed at elucidating the effect of varying physical and chemical properties of the bleaching earth on the quality of bleached and deodorized oils. Techniques used in this work are pore-size distribution, surface area, scanning and transmission electron microscopy and a variety of chemical and X-ray analysis methods. The ability to vary such parameters in montmorillonite clays by alteration of process conditions to give materials with specific performance characteristics is demonstrated. Comparisons are made between acid-activated montmorillonites and other clay types.     

Rare earth oxides as carbon oxidation catalysts

The behavior of a number of rare earth oxides as catalysts for the oxidation of graphite in air has been investigated by the methods of thermal analysis. Of the oxides studied, only CeO₂ showed significant activity in accelerating the gasification of graphite by oxygen between 500 and 1000°C. Cerium salts, which decompose to a finely dispersed oxide phase at low temperatures, e.g. Ce (III) nitrate and ammonium Ce (IV) nitrate, were found to be very active catalysts. The catalytic effect may be due to a redox process involving the cyclic conversion of the oxide from the Ce (IV) to the Ce (III) oxidation state, or the oxide particles may provide sites for the dissociative chemisorption of oxygen.     

Optical networks for local loop applications

Some of the options for optical technology within the local loop environment are examined. In particular, passive shared access networks have been considered in some detail. These networks show great promise for delivering existing telephone services to small to medium business customers (4-30 lines) economically by the early 1990s. Extending fiber to the home will also be possible by virtue of a similar passive network infrastructure for customers requiring new broadband services beyond the single telephone line. For one-line plain old telephone service (POTS) customers, an intermediate approach of terminating the fiber network at the final network distribution point, with copper retained for the final leg, may be used prior to the provision of broadband services. A key feature of the passive optical network architecture is the use of wavelength-division multiplexing (WDM) as an upgrade strategy, allowing graceful upgrading from telephone services to multichannel high-definition television (HDTV) on gigabit/second bearers and full two-way switched broadband services employing wavelength routing across the network     

Long-term transients in a reactor under forced concentration cycling

In the approach to a cycle-invariant state in the forced feed concentration cycling of the CO oxidation over a NiO catalyst, a very long transient has been observed lasting 80 ks or more. This transient appears to be associated only with CO pretreatment of the catalyst and is not a general phenomenon. The slow convergence to the cycle-invariant state reported in certain modelling calculations in the literature appears to have a different cause.     

Comparing word fragment completion and cued recall with letter cues.

Cued recall with word stems as cues and fragment completion rely on different types of letter cues and also differ in the explicit–implicit nature of the retrieval orientation. Despite these differences, variables effective in one task may be effective in the other because both rely on letter cues. Two variables known to affect cued recall were manipulated: Lexical set size (number of words that fit the letter cue) and meaning set size (number of associates generated to the studied words). Across four experiments, subjects in each task were less likely to recover targets from larger lexical sets. However, meaning set size affected cued recall but not fragment completion. These results indicate that fragment completion and letter-cued recall are based on lexical search but that cued recall also involves a semantic search component. Furthermore, type of retrieval cue had a greater effect than type of retrieval orientation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low-cost, high-efficiency quasi-planar array of waveguide-fed circularly polarized microstrip antennas

A low-cost quasiplanar Ku-band array of circularly polarized microstrip antennas benefiting from a low-loss waveguide feed network is demonstrated (patent pending). The 32 elements of the array which are arranged in a 2-by-16 configuration are subdivided into four two-by-four subarrays. To maintain feed losses and thus the overall noise temperature at a minimum, the subarrays are excited using a one-by-four corporate feed network of hollow metallic waveguides. This network is composed of E-plane components such as Tee-junctions and bends and is manufactured out of only two metallic pieces that accommodate the feed network in the form of milled grooves. Because of insensitivity of the exploited E-plane components to air gaps or slight misalignments, the pieces are secured together with only four screws without welding, braising, or conducting adhesives. Owing to a low-loss foam substrate, the array elements show high circular polarization gain of 9 dBic and wide relative bandwidth of 4%. To achieve circular polarization, use is made of circular patches with two nearly perpendicular perturbations. Using sequential rotation of the elements along with quadrature phase shifting, the axial ratio of the array is reduced to 1 dB over 4% of bandwidth. The measured circular polarization gain of the array amounts to 23 dBic with an aperture efficiency of 63% in the Ku-band of frequencies. The achieved efficiency, which is higher than the reported efficiency for comparable planar arrays with microstrip feed networks, can be credited to the low losses of only 0.2 dB in its waveguide corporate feed. The paper also presents measurement results for an arrangement of two inclined single arrays mounted in parallel. This configuration which has a measured circular polarization gain of 25.7 dBic with an axial ratio of 1 dB is desirable for mobile low-profile antenna systems.