Enhanced densification of white cast iron powders by cyclic phase transformations under stress

It is shown that densification of white cast iron powders under stress can be enhanced by multiple phase transformations through thermal cycling. This enhancement occurs by accelerated creep flow during phase changes (transformation superplasticity). The approximate stress range where transformation-assisted densification can occur is shown to be between 1.7 MPa (250 psi) and 34.5 MPa (5000 psi). Below 1.7 MPa insufficient strain occurs during phase transformation to cause significant densification even after many transformation cycles. Above 34.5 MPa, densification occurs principally by normal slip creep. Transformation warm pressing of white cast iron powders leads to dense compacts at low pressures and short times. In addition, because the transformation temperature is low, the ultrafine structures existing in the original powders are retained in the densified compacts. formerly with the Department of Materials Science and Engineering, Stanford University,     

A systematic approach for fine-tuning of fuzzy controllers applied to WWTPs

A systematic approach for fine-tuning fuzzy controllers has been developed and evaluated for an aeration control system implemented in a WWTP. The challenge with the application of fuzzy controllers to WWTPs is simply that they contain many parameters, which need to be adjusted for different WWTP applications. To this end, a methodology based on model simulations is used that employs three statistical methods: (i) Monte-Carlo procedure: to find proper initial conditions, (ii) Identifiability analysis: to find an identifiable parameter subset of the fuzzy controller and (iii) minimization algorithm: to fine-tune the identifiable parameter subset of the controller. Indeed, the initial location found by Monte-Carlo simulations provided better results than using trial and error approach when identifying parameters of the fuzzy controller. The identifiable subset was reduced to 4 parameters from a total of 33, which improved the quality of the optimization of the control system by a minimization algorithm. Overall the systematic approach considerably improved the performance of the control system as measured by the Integral Absolute Error (deviation between the set-point and the controlled variable) of the controllers. Moreover, the methodology overcomes the dependency of the initial parameter space issue typical of local identifiability analysis. All in all this systematic approach is expected to facilitate the design and application of fuzzy controllers in particular to WWTPs compared to the time-consuming and tedious trial and error approach currently used in practice.     

Development of a temperature control model used in HVAC systems in school spaces in Mediterranean climate

In this paper a temperature control model used in heating, Ventilating and air-conditioning (HVAC) systems in school spaces, in Mediterranean climate, is developed. This empirical model considers the indoor preferred environmental temperature, the outdoor environmental temperature and the adaptation to the seasons of the year and to the spaces.     

Fault Tolerance Analysis of Communication System Interleavers: the 802.11a Case Study

The study of Multiple Soft errors on memory modules caused by radiation effects represents an interesting field of current research. The fault tolerance of these devices in radiation environments is traditionally analyzed and increased by means of soft error protection mechanisms as EDAC codes or physical interleaving. As Communication System interleavers are mainly implemented using memories, a similar protection against soft errors to the one used for memory devices could be performed, as a conventional solution, when they are used in critical missions. In this paper, the knowledge of the system is used to apply the communication interleaving pattern as physical interleaving employing the inherent redundancy (added by previous modules of the Communication System) of the data processed by the interleaver as an error correction mechanism. Therefore a similar protection to the conventional solutions is obtained but with a reduced cost.

Damage tolerance assessment by bend and shear tests of two multilayer composites: Glass fibre reinforced metal laminate and aluminium roll-bonded laminate

The damage tolerance of an aluminium roll-bonded laminate (ALH19) and a glass fibre reinforced laminate (GLARE) (both based on Al 2024-T3) has been studied. The composite laminates have been tested under 3-point bend and shear tests on the interfaces to analyze their fracture behaviour. During the bend tests different fracture mechanisms were activated for both laminates, which depend on the constituent materials and their interfaces. The high intrinsic toughness of the pure Al 1050 layers present in the aluminium roll-bonded laminate (ALH19), together with extrinsic toughening mechanisms such as crack bridging and interface delamination were responsible for the enhanced toughness of this composite laminate. On the other hand, crack deflection by debonding between the glass fibres and the plastic resin in GLARE was the main extrinsic toughening mechanism present in this composite laminate.     

Standard formulas of parenteral nutrition. A study of their use in a general hospital

The goal of the study was to evaluate the use of parenteral nutrition formulas with standardized g. of nitrogen, carbohydrates and lipids, and to analyze whether the nutritional requirements of the patients treated in our hospital were covered by said formulas or whether it was necessary to change and/or standardize a new formula. To do so, a review was made of 5.646 parental nutrition mixtures prepared in the Pharmacy Service and patterned by the Nutrition Service from April, 1991, to May, 1992, for 308 adult patients. The distribution of the mixtures by services, diagnoses and the frequency of the different standard formulas were studied, comparing standard formula frequency with that of non-standard formulas. Findings showed that 41.9% of nutrition mixtures were patterned in surgery, and the most common diagnosis, cancer, appeared in 24%. Of the mixtures, 67.6% were preestablished formulas, and 32.4% were non-standard formulas. The order of frequency among standard formulas was: basic standard formulas, stress formulas, initial formulas, peripheral formulas, hemodialysis formulas and low-volume formulas. All covered the nutritional needs of a large share of the patients for the different pathologies in which they were indicated. Nevertheless the question of designing a new formula to cover a greater number of situations was raised. Protocolization should take place rationally, to meet the hospital's most frequent pathologies, and effectiveness should be evaluated after tracking and checking each patient.     

Processing and superplastic properties of fine-grained iron carbide

Fine-grained iron carbide material (80 vol pct iron carbide and 20 vol pct of an iron-base second phase) was prepared using two different powder metallurgy procedures: (1) hot isostatic pressing followed by uniaxial pressing and (2) hot extrusion followed by uniaxial pressing. Both procedures yield materials that are superplastic at elevated temperature with low values of the stress exponent (n = 2 to 1) and tensile elongations as high as 600 pct. The strain rate in then = 2 region is inversely proportional to approximately the cube of the grain size with an activation energy for superplastic flow between 200 and 240 kJ/mol. It is postulated that superplastic flow in the iron carbide material, in then = 2 region, is grain-boundary sliding accommodated by slip controlled by iron diffusion along iron carbide grain boundaries. The flow stress in compression is about 2 times higher than in tension in the region where grain-boundary sliding is the rate-controlling process. It is believed that the difference in flow stress is a result of the greater ease of grain-boundary sliding in tension than in compression. Tensile elongations were observed to increase with a decrease in stress and a decrease in grain size. These effects are quantitatively explained by a fracture mechanics model that has been developed to predict the tensile ductility of superplastic ceramics.     

Development of ferrous laminated composites with unique microstructures by control of carbon diffusion

A novel method is described for preparing ferrous laminated composites, containing ultrahigh carbon steel as one of the components, which results in hard and soft layers bounded by sharp and discrete interfaces. The method is based on increasing the activity of carbon in iron by silicon addition; in this manner, the carbon is made to segregate into specific layers by heat treatment at low temperatures (∼770 °C). The results are ferrous laminated composites with discrete and sharp interfaces that consist of hard layers containing spherical carbide particles embedded in a matrix of ultrafine martensite or ferrite adjoining soft layers of a coarse grained iron alloy. In addition, the high activity of carbon is shown to result in total depletion of carbon in a silicon containing UHC steel ribbon bonded to mild steel. D. W. KUM, formerly Postdoctoral Fellow with the Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305,     

The influence of olive oil on human health: not a question of fat alone

Olive oil is the most representative food in the traditional Mediterranean diet and its most important source of MUFA. The healthy benefits of MUFA-rich diets on plasma cholesterol levels, were the first to generate interest in this dietary model. In addition to the benefits conferred by its lipids, olive oil has other biological effects, some of them also related to MUFA. However, most recent studies have shown that there are a number of properties that depend on, or are potentiated by, the consumption of olive oil, such as virgin olive oil, that is rich in microcomponents. This foodstuff, thanks to its double set of benefits, thus tends to produce a better lipid profile and a less prothrombotic environment, promoting antioxidant and anti-inflammatory effects, with a greater endothelial protective capacity. In view of these effects, it would appear that when olive oil is the basic source of dietary alimentary fat it has a major antiatherogenic capacity, which is not shared to the same extent by other oils that are rich in oleic acid but lack its characteristic micronutrients.     

Assessing anthropogenic pressures on estuarine fish nurseries along the Portuguese coast: a multi-metric index and conceptual approach

Estuaries are among the most productive ecosystems and simultaneously among the most threatened by conflicting human activities which damage their ecological functions, namely their nursery role for many fish species. A thorough assessment of the anthropogenic pressures in Portuguese estuarine systems (Douro, Ria de Aveiro, Mondego, Tejo, Sado, Mira, Ria Formosa and Guadiana) was made applying an aggregating multi-metric index, which quantitatively evaluates influences from key components: dams, population and industry, port activities and resource exploitation. Estuaries were ranked from most (Tejo) to least pressured (Mira), and the most influential types of pressure identified. In most estuaries overall pressure was generated by a dominant group of pressure components, with several systems being afflicted by similar problematic sources. An evaluation of the influence of anthropogenic pressures on the most important sparidae, soleidae, pleuronectidae, moronidae and clupeidae species that use these estuaries as nurseries was also performed. To consolidate information and promote management an ecological conceptual model was built to identify potential problems for the nursery function played by these estuaries, identifying pressure agents, ecological impacts and endpoints for the anthropogenic sources quantified in the assessment. This will be important baseline information to safeguard these vital areas, articulating information and forecasting the potential efficacy of future management options.