Mechanical Properties and Dislocation Structure Evolution in Ti6Al7Nb Alloy Processed by High Pressure Torsion

Ultrafine-grained biocompatible Ti-6Al-7Nb alloy was produced by high pressure torsion (HPT). Lattice defects—vacancies and dislocations—investigated by positron annihilation spectroscopy, observations by scanning electron microscopy, and microhardness evaluation are linked to the strain imposed by different numbers of HPT revolutions and to the distance from the specimen center. Positron annihilation spectroscopy showed significant increase of dislocation density and concentration of vacancy clusters after ½ of the HPT revolution. Microhardness increases by 20 pct with increasing strain, but it is heterogenous due to duplex microstructure. The heterogeneity of the microhardness increases with increasing strain, suggesting that a heavily deformed and fragmented α + β lamellar microstructure is more hardened than primary alpha grains. The defect structure is homogenous after ½ HPT revolution, while the microhardness becomes homogenous after 3 HPT revolutions only.     

Constructing control rules for a dynamic system: probabilistic qualitative models,lookahead and exaggeration

Dynamic systems have sometimes to be controlled in circumstances that are very inconvenient for classical control methods. In such cases, use of qualitative controllers seems to be a promising alternative, as they can be designed without having an exact mathematical model. A method for synthesizing control rules is presented, in which a probabilistic qualitative model is used together with a decision strategy that takes into account the results of qualitative simulation. As a case study, the problem of the inverted pendulum control is considered. By combining the model simulation lookahead and a decision criterion, an interesting phenomenon of ‘exaggerated simulation’ has emerged. Experimental results show that in certain cases, using an exaggerated force in the process of simulation considerably improves the performance of generated control rules. The exaggeration helps to detect some trends of the system's behaviour that would otherwise have remained hidden. Experiments and mathematical analysis show that the improvement due to the exaggeration is comparable to that achieved by a deeper lookahead in the state transition graph.     

Experimental design for parameter estimation of two time-scale model of photosynthesis and photoinhibition in microalgae

A method for parameter estimation of two time-scale model of photosynthesis and photoinhibition is presented.     

Artificial intelligence—morphological approach as a new technological forecasting technique

Technological forecasting is located in technological space for a certain engineering domain and is the first step in the research and development of a new technology. There are many techniques already developed for technological forecasting like extrapolation of trends, heuristics forecasting by expert e.g. Delphi method, etc. The morphological method (MM) is used to describe a technique for identifying, indexing, counting and parametrizing the collection of all possible devices to achieve a specified functional capability. This is not a forecasting per se, but it is a useful organizing tool, a source of insights, and a starting point for further analysis by other methods, Mila?i? (1976). In the paper we expand the capabilities of MM using artificial intelligence (Al) principles. The AI production system has a global data base, a set of production rules and a control system. Special attention is paid to control strategy-developing searching techniques in order to distinguish the explicit local knowledge about how to proceed toward a goal from any state from the implicit global knowledge of the complete solution. Some practical examples are also shown.     

Integrating resource production and construction using BIM

This paper presents the outcomes of a research and development project carried out at the University of Maribor, Construction IT Centre, with regard to the introduction of a building information model (BIM) and a model based construction process into the operational environment of a construction company. The initiative for the project came from the industry and was performed as a joined effort of the research organization and the construction company. Work was performed in the scope of an industrialized construction environment, with the main aim to integrate mass production prefabrication processes with construction site activities. BIM was used as a link between an enterprise resource planning (ERP) information system that supports manufacturing process and construction object related information, mainly handled by CAD tools. The benefits of this link are presented with regard to project progress monitoring and material flow management.     

Effect of annealing temperature on phase composition and tensile properties in isotactic poly(1‐butene)

The influence of annealing temperature on the kinetics of polymorphic changes and mechanical properties within the time in isotactic poly(1‐butene) (PB‐1) has been investigated by wide‐angle X‐ray scattering and tensile testing. Extruded tapes of PB‐1 have been exposed to several annealing temperatures: ?22, +5, +22, +40 and +60°C. The evolution of content of Phase I for various annealing temperatures upon time shows predominantly S‐shaped trend. Annealing temperature considerably affects the overall rate of transformation in PB‐1. On the other hand, the resulting mechanical properties are solely controlled by the polymorphic composition. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Describing the sorption characteristics of a ternary system of benzene (1) and alcohol (2) in a nonporous polymer membrane (3) by the Flory–Huggins model

The Flory–Huggins equation was used to describe results of total and preferential sorption measurements for the binary liquid mixture of benzene (1) and alcohol (2) in one of two nonporous polymer membranes (3), low‐density polyethylene (LDPE) and Nafion membrane. The concentration dependence of binary and ternary interaction parameters was determined. The interaction parameters for the benzene – methanol binary mixture were obtained from binary vapor‐liquid equilibrium data in the literature to decrease the number of adjusted parameters. The results show that use of a ternary interaction parameter is necessary. Data treatment was performed assuming either no crystallinity or an average crystallinity typical for the studied membranes. Subsequently, the limiting activity coefficients of solutes in LDPE were calculated from the values of the interaction parameters and their values compared to values of the limiting activity coefficients of benzene and methanol in hypothetical liquid alkane with the same density as LDPE obtained by the UNIFAC method. POLYM. ENG. SCI., 55:1187–1195, 2015. © 2014 Society of Plastics Engineers