Toughening by Monoclinic Zirconia

The toughening induced by monoclinic ZrO₂ in the absence of microcracking was investigated, using ZnO as the host material. Toughness levels K_c in excess of the host toughness K_c^M were achieved, attaining a peak toughness K_c/K_c^M ∼1.7, at monoclinic ZrO₂ volume concentrations 0.2. This toughening is attributed to crack/particle interactions, associated with the deflection and bowing of the crack by the residual strain field around the monoclinic ZrO₂ particles.     

Phase Equilibria in the System Na2SiO3-Li2SiO3

Phase equilibria were studied for the system Na₂SiO_:rLi₂SiO₃. The 2 end-member metasilicates show limited mutual solid solubility with the (Na_2-χLi_χ)SiO₃ solid solutions being particularly extensive at solidus temperatures (0 x 1.06). Ordering of the latter solid solution occurs at the NaLiSiO_;) composition with a_supercellx= 6a_subcell During cooling of the solid solutions, metastable phase transformations occur; a twinned monoclinic metastable phase, low (Na, Li)₂SiO₃, has been characterized.     

Expert systems in production and operations management: research directions in assessing overall impact

The use and development of expert systems in public and private organizations continue to increase. Many of these systems are being developed for production and operations management. Unfortunately, the impacts that these systems are having in these environments have, for the most part, not been investigated. Most studies on expert systems to date centre either on the technical aspects or validation issues. No one has taken a systemic view that takes into account both the technical issues and the human issues that will have to be addressed in implementing these systems. This paper seeks to stimulate research into the overall impact of expert systems implementation in production. To this end, fourteen research propositions are developed and presented. In addition, the major variables associated with these propositions are combined into a causal model to show the relationships between them and to reveal an overall perspective of the impacts of expert systems implementation on the production process.     

Adaptive one-step-ahead control subject to an input-amplitude constraint

This paper investigates the adaptive control of a single-input/single-output process when there exists a constraint on the amplitude of the applied control signal. In particular, an adaptive control scheme is proposed and is shown to be globally convergent in the sense that the control asymptotically matches the amplitude-constrained one-step-ahead optimal control. Some simulation results are presented to demonstrate the performance of the scheme     

Gold Adsorption by Activated Carbon and Resin

Activated carbon and resins readily adsorb gold from cyanide leach solutions. The main advantages of carbon are its high selectivity towards gold, its ease of elution and its large particle size. On the other hand, resins do not suffer from the problems of pore blocking by fine particles in the slurry and show superior adsorption kinetics and higher loading capacity for gold. In addition, when resins are used in the form of fibre-reinforced sheets, many of the problems associated with beads are overcome. The experimental results are shown to fit the homogeneous surface diffusion model with certain modifications when pore blocking occurs. The Fritz and Schluender isotherm is used to describe the equilibrium behaviour of adsorbed species. This reduces to the well-known Freunlich isotherm when only one component (eg. Gold) need be considered.     

TOXICITY, MUTAGENICITY AND TERATOGENICITY OF BREVIANAMIDE, VIOMELLEIN AND XANTHOMEGNIN; SECONDARY METABOLITES OF PENICILLIUM VIRIDICATUM

The three major secondary metabolites of Penicillium viridicatum, brevianamide, xanthomegnin, and viomellein were tested for mutagenicity by the Salmonella/microsome test and for toxicity and teratogenicity by the chick embryo test. None were mutagenic. Viomellein was mildly toxic and teratogenic, xanthomegnin was the most toxic and was not a teratogen, and brevianamide was not toxic yet was the most teratogenic.     

ETHNICITY IN AN IMMIGRANT GATEWAY CITY: THE ASIAN CONDITION IN HOUSTON

The analysis explores the evolving condition of Houston's Chinese community into the early 21st century and its uncertain role within the local economy. Through a historical analysis, it examines Chinese immigration into Houston and the evolving and changing spatial settlements of Chinese immigrants in the city, showing the precarious nature of Houston Chinese neighborhoods. A quantitative analysis then examines whether disparities in economic prosperity are evident between Asian and White growth neighborhoods within Harris County between 1980 and 2000, when ethnic diversity was viewed as an important element of Houston's new economic development strategy. A principal components analysis (PCA) and a k‐means clustering technique are conducted on census tract data to identify neighborhood types and to analyze changes in neighborhood characteristics. The quantitative analysis reveals that the city's promotion and celebration of ethnic diversity, and the extensive investment by Houston's Asians into their neighborhoods, did not translate into improving economic prospects for Asian neighborhoods within Houston.     

Propositionally representing incomplete knowledge about existence

Abstract

This paper considers the problem of representing the knowledge state of an observed agent who has incomplete knowledge of existence. Agents in such knowledge states are said to have existential misconceptions. We describe preliminary work on representing the knowledge state of an agent who possesses existential misconceptions and how to detect when this occurs. The method is based on a simulation of the observed agent's processes of information acquisition. We describe an implementation of this system and study its operation in a simulated microworld. The agent's acquisition of existential misconceptions is correlated with the agent's inaccurate beliefs of equality. This makes it possible to characterize an agent's existential misconceptions by describing its inaccurate beliefs of equality.     

Development of a 5-Layer Passive Organic Dermal (POD) Sampler

A 5-layer passive organic dermal sampler was developed to allow the collection, retention, and recovery of a variety of organic compound classes simultaneously. The 5-layers, from outside in, consisted of polypropylene, polyurethane foam, C-18 solid-phase extraction disk, ethylene tetrafluoroethylene, and activated carbon cloth. The layers were enclosed in aluminum foil and placed in a muslin envelope that had a 40.0 mm diameter opening.

Ten samplers were spiked separately with three levels of diesel oil, a 50/50 diesel oil/asphalt mixture, and asphalt binder. For the diesel oil spikes, recoveries were 69.9, 71.3, 88.8, and 95.4% for 10, 10, 50, and 100 mg of diesel oil. For the 50/50 mixture, recoveries were 105.4, 92.8, and 92.0% for 10, 50, and 100 mg of the 50/50 mixture. For the asphalt binder spikes, recoveries were 104.7, 100.2, and 100.1% for 10, 50, and 100 mg of asphalt binder. For repeatability assessment, 7 samplers were spiked with 50 mg of the 50/50 mixture and recoveries averaged 92.6% (standard deviation 8.6). Samplers tested on asphalt paving workers proved functional, comfortable, flexible, and durable.     

Release of Single-Cell Protein by Induced Cell Lysis

A temperature sensitive lysis mutant of Saccharomyces cerevisiae JD 109, which grows normally at 27°C, stops growing and partially lyses at a nonpermissive temperature (37°C). In studies in a 14L fermentor with temperature shifted (from 27°C to 37°C) at 3.0 g/L cells, the effect of pH was investigated with the result that the rate of lysis is faster at pH 8 than at pH 5.6; the protein in the cells decreases from 45 to 35%. When both pH (from 5.6 to 8.0) and temperature are shifted, the culture showed a more noticeable inhibition of growth and lysis than when only pH was changed and the temperature was maintained at 27°C.