The surface layer of friction plastics

The tribological problems of plastics used for friction brakes with particular emphasis on the design problems of materials with optimal characteristics for the working conditions of shoe brakes for underground railways were investigated. The phenomena associated with the friction and wear of these materials were identified by examining the surface layers of samples using the following techniques: optical and scanning electron microscopy, X-ray microanalysis and thermogravimetric analysis at temperatures up to 1270 K. A model of the structure of the surface layer of friction materials was developed. It consists of five layers which differ in composition, structure and properties. This model is important in the development of new friction materials with specified tribological characteristics.     

Effect of temperature and PH value on the stability of bioactive compounds and antioxidative activity of juice from colour-fleshed potatoes

The colour-fleshed potatoes represent a good raw material for the extraction of juices with a high content of biologically active compounds and a high antioxidant activity. The blue-fleshed potatoes turned out to be a rich source of total polyphenols, as they had approximately 3.5 times higher content of identified anthocyanidins. Regardless of anthocyanin composition, all juices made of colour-fleshed potatoes were highly stable. Both, high temperature, exposure time to these temperatures, and medium pH had no significant effect on changes in total polyphenols content of potato juices. The juices examined, especially these made of blue-fleshed potatoes, demonstrated a higher ABTS+ stability during their heating than during pH changes. In addition, a higher antioxidant activity of juices was determined at neutral and alkaline than at acidic pH value of the medium.     

Doomed program points

Any programming error that can be revealed before compiling a program saves precious time for the programmer. While integrated development environments already do a good job by detecting, e.g., data-flow abnormalities, current static analysis tools suffer from false positives (“noise”) or require strong user interaction. We propose to avoid this deficiency by defining a new class of errors. A program fragment is doomed if its execution will inevitably fail, regardless of which state it is started in. We use a formal verification method to identify such errors fully automatically and, most significantly, without producing noise. We report on experiments with a prototype tool.     

Influence of Cr doping on the phase composition of Cr,Ca:YAG ceramics by solid state reaction sintering

In the present work, the influence of Cr and Ca co-additives on the phase formation under conditions emulated the real sintering process of Cr⁴⁺:YAG ceramics is studied. The XRD analysis of the treated samples revealed the difference in formation rates of intermediate phases between the samples with and without the Cr₂O₃ additive. The formation of intermediate phases in the solid-state reaction between Y₂O₃ and Al₂O₃ is observed to shift toward higher temperatures (ie, toward the stage of fast shrinkage) if the mixture of Cr₂O₃ and CaO is added. The reason for such shift is the appearance of new intermediate, which contains Cr⁴⁺ ions in perovskite structure, as has been established by optical absorption and luminescent investigations. It is found that the Cr,Ca:YAG ceramics prepared by vacuum solid state reaction sintering at 1750°C, 10 hours possesses better optical transparency than Ca:YAG ceramics prepared under the same conditions.     

Resistance to Coking Determination by Temperature Programmed Reaction of n-Butane with Steam

Resistance to coking is one of the most important characteristics of nickel catalysts used for steam reforming of hydrocarbons, CO₂ reforming or methanation of carbon oxides. Microbalance reactors have for a long time played an important role in catalyst deactivation studies, providing coking and coke gasification rates. However, conventional thermogravimetric microbalances have a number of limitations. The aim of this paper is to compare initial temperatures of coking of Ni and Ni-Mo catalysts (with different resistance to coking) obtained in the temperature-programmed reaction of _n-butane with steam with the results of coking rates obtained by the traditional thermogravimetric method. The investigations showed great agreement of the results.     

DEVELOPMENT OF A KNOWLEDGE-BASED ECONOMY IN POLAND

ABSTRACT

In order to maintain the high level of growth in a knowledge-based economy, it is essential to create the special atmosphere in a social environment that supports its development.

The development of a knowledge-based economy requires human capital, the appropriate development of an information infrastructure, and national innovation systems to be interlinked.

The main actions for creating the knowledge-based economy in European-Union–accessing countries are as follows:

1. building institution for research and development and a system of economical incentives.

2. developing an educational system that enables the creation of intellectual capital.

3. building the national information infrastructure, focusing on providing easy access to teleinformation technologies and its promotion and application in central organs of public administration and local governance in the public and private sector, as well as building the basis of a civil society.

     

Vibrations of beams with constructional friction

The objects of analysis are vibrations of beams taking account of hysteresis loop in selected nodes (GAPs). The occurrence of the hysteresis phenomenon may result from Coulomb friction. The beams have been modelled by finite elements. The method is provided with algorithm and computer program which was used in the preparation of example.     

Insolvency modeling in the cellular telecommunication industry

In this article, we test several models (decision tress and neural networks) to predict customer insolvency at one of the cellular telecommunication operator in Poland. In comparison to previous studies on customer insolvency, our research presents novelty in the following areas. First of all, we deal with cellular telecommunication customers who use services without paying dues (the literature show the studies that dealt mainly with fixed line operators or banking industry). Secondly, we have a large dataset with 205 explanatory variables derived from the database (previous studies dealt with smaller datasets). Thirdly, we test the quality of the models three months after the estimation with lift and ROC curves to assess the models performance over the time.The main findings from the research are twofold: (1) artificial neural networks perform well when modeling the customer’s insolvency and the best model can capture significant amount of money owed by insolvent customers; (2) decision trees get old quickly and their performance decrease over the time in the top percentiles of the score.