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.     

THE EFFECT OF AEROBIC MESOPHILIC MICROFLORAL LEVELS ON THE ISOLATION OF INOCULATED LISTERIA MONOCYTOGENES STRAIN LM82 FROM SELECTED FOODS

The effect of aerobic mesophilic microfloral concentration on the isolation of Listeria monocytogenes LM82 was studied in 31 (18 cheeses and 7 noncheese) retail foods having standard plate counts of 10¹ to 10⁸ colony forming units (CFU)/g. Foods were spiked with L. monocytogenes and enriched at 30°C for 24 h in a selective enrichment broth used in a U.S. Food and Drug Administration method. Inoculum levels for isolation on modified McBride agar ranged from 0.1 to > 5 × 10³ with a geometric mean value of 5 inoculated CFU/g or 1.4 CFU/g. Pure Enterococcus (Streptococcus) faecalis ( 0 to 6 × 10⁶ inoculated CFU/mL ) in the absence of food matrix had no effect on the enrichment of L. monocytogenes. Ease of isolation of LM82 was independent of the food microflora concentration both generally and in the specific food type of 9 Brie cheeses. Competition, when it occurs, therefore, may be due to specific bacterial competitors rather than bacterial numbers .     

Comparison theorems for set stability of differential equations

Set stability and uniform set stability of differential equations involve known specific bounds on solutions of the differential equations under consideration. Comparison theorems are presented giving sufficient conditions for these forms of stability. The conditions include the existence of a Liapunov-Like function and the set stability of a scalar differential equation. Examples are given to demonstrate the method.