PRINCIPAL COMPONENT ANALYSIS AND CLUSTER ANALYSIS IN MULTIVARIATE ASSESSMENT OF WATER QUALITY

This paper deals with the use of multivariate methods in drinking water analysis. During a five-year project, from 2008 to 2012, selected chemical parameters in 11 water supply networks of the Siedlce County were studied. Throughout that period drinking water was of satisfactory quality, with only iron and manganese ions exceeding the limits (21 times and 12 times, respectively). In accordance with the results of cluster analysis, all water networks were put into three groups of different water quality. A high concentration of chlorides, sulphates, and manganese and a low concentration of copper and sodium was found in the water of Group 1 supply networks. The water in Group 2 had a high concentration of copper and sodium, and a low concentration of iron and sulphates. The water from Group 3 had a low concentration of chlorides and manganese, but a high concentration of fluorides. Using principal component analysis and cluster analysis, multivariate correlation between the studied parameters was determined, helping to put water supply networks into groups according to similar water quality

Influence of Alkali Ions on Tribological Properties of Silicon Surface

Tribological properties of surfaces (friction, adhesion and wear) provide challenging limitations to the design of reliable machines on the micro- and nanometer scale as the surface to volume area increases and volume, mass and inertia of the mobile parts decrease. This study reports on the reduction in the friction force of silicon surfaces after the alkali metal ion exposure in the form of aqueous solutions. A scanning force microscope equipped with a liquid cell was used to investigate the friction force and the pull-off force of a flat silicon surface immersed in water and in different alkali metal chlorides solutions: LiCl, NaCl and CsCl. The concentration ranged from 0.1 up to 1000 µmol/l. The changes in the free surface energy of the initial surface and of the modified surfaces after drying were determined from contact angle measurements and from the acid–base adhesion theory. In both cases, in the liquid environment and after drying of the exposed silicon substrates in air, the friction force is reduced by approximately 50 %. Our results provide new, fundamental insight into the exchange of surface termination layers in particular for tribology. Also it is suggested to use the procedure as a low-cost alternative to improve the tribological properties of the silicon surface in particular in applications where lubricating fluids are not appropriate, e.g., in nanomachines and devices

The measurement of viscosity of ultrathin polymer films

Viscosity is a very important property of thin polymer films used in modern microelectronic technology i.e. in nanoimprint lithography.Hence, in this work we present a method for viscosity of ultrathin polymer films determination. The viscosity is evaluated from the response of the oscillating piezoelectric cantilever at the end of which an indentation probe is mounted (Fig. 1a). When a polymer film is indented, the resonant frequency of the oscillations is changed and the parameters of used model (i.e. Maxwell model) can be identified. The frequency of the oscillations is equal to tens of kilohertz therefore the influence of extremely high deformation velocities can be investigated by means of this method. It is also possible to conduct the experiments in elevated temperature (up to 150oC). The oscillations direction can be parallel as well as perpendicular to the film’s surface. The investigated films were made of PMMA. Their thickness ranges from a few nanometers up to 1 micrometer. The results were compared with other methods of the viscosity determination: the investigation of the creep response during nanoindentation, sinus mode nanoindentation and atomic force microscope based technique

Product differentiation in two-sided markets

Gegenstand dieser Arbeit ist die Differenzierung der Medien, insbesondere von online Medien. In der Arbeit wird ein Model entwickelt, welches das Hotelling Model auf zweiseitige Märkte erweitert. Aus diesem Model folgt, dass Mediendifferenzierung dann maximal ist, wenn Nutzer Werbung als sehr störend empfinden und Werbeauftraggeber eine bestimmte Gruppe von Nutzern besonders schätzen. Eine Analyse des polnischen Medienmarktes liefert eine vorläufige Bestätigung dieser Ergebnisse.The subject of this thesis is diversity in media markets, especially in the market of online news portals. In the thesis I develop a model which is an extension of the Hotelling model to two-sided markets. From this model it follows that the content of media platforms will be maximally differentiated if users strongly dislike advertising and if advertisers have a high valuation for users with given characteristics. An analysis of data from the polish online news portals market provides some confirmation of the model's finding

INFLUENCE OF PRECIPITATION AND THERMAL CONDITIONS ON STARCH CONTENT IN POTATO TUBERS FROM MEDIUM-EARLY CULTIVARS GROUP

The basis of this elaboration constituted data concerning mean starch content in nine medium-early cultivars of potato grown in six experimental stations belonging to COBORU (Research Centre for Cultivar Testing) in years 2010–2013. Using stepwise regression analysis the influence of thermal and precipitation conditions on starch content in potato cultivars was examined. Such analysis was performed for locations, years and particular cultivars. The analysis showed that starch content in tubers of medium-early potato cultivars depends more on precipitation than on thermal conditions. The relationship between starch content in tubers and precipitation and thermal conditions varied in different stations. In four stations (Karżniczka, Sulejów, Uhnin, Węgrzce) it depended on precipitation noted in August, in two (Uhnin and Słupia) – in July and in other two (Naroczyce and Słupia) – in June. Positive influence of temperature on starch content was noted only in August in Karżniczka. Starch content in tubers of Ametyst and Gawin cultivars depended on precipitation sum in August, Satina cultivar – in July, Oberon cultivar – in June and July, and Cekin, Finezja, Jurek, Stasia and Tajfun cultivars – on precipitation in July and August

Initial Penetration of an Elastic Axially Symmetric Indenter into a Rigid-Perfectly-Plastic Half-Space

This paper is concerned with the axially symmetric plastic flow of a rigid perfectly-plastic nonhardening halfspace. The initial penetration of the elastic indenter is studied based on Haar and von Karman hypothesis. The analytical distribution of contact stress and the approximate penetration depth of the indenter are obtained

BOX-PCR is an adequate tool for typing of clinical Pseudomonas aeruginosa isolates

In this study, the BOX-PCR fingerprinting technique was evaluated for the discrimination of clinical Pseudomonas aeruginosa isolates. All isolates were typeable and nearly half showed unique banding patterns. According to our results, BOX-PCR fingerprinting is applicable for typing of Pseudomonas aeruginosa isolates and can be considered a useful complementary tool for epidemiological studies of members of this genus. (Folia Histochemica et Cytobiologica 2011; Vol. 49, No. 4, pp. 734–738

Contact Displacements of Spatial Contact of a Rough Body and a Body with Coating

This paper is an example of the application of a structural nonlocal theory to the solution of the contact problem of a rough curvilinear body with plastic coating on another body. The main goal of these investigations is the creation of extrapolation methods of results of theoretical investigations from flat surfaces to any tribological system with curvilinear macro surfaces. This paper deals with the application of a phenomenological approach which is based on using the middle layer. It allows to represent a contact problem for real bodies as a superposition of two problems. The first one is the problem of penetration of rigid roughness in a plastic coating taking into account statistical characteristics of the surface. The second problem is the elastic deformation of smooth bodies with a circular area of interaction. The external load is supposed to be constant. The solution is obtained with the help of the contracting mapping principle and a simple iteration method. It is established that the first analytical approximation of solutions of the corresponding equations is useful for practical applications with sufficient accuracy. The paper deals with the case of plastic penetration of a surface asperity only when the macro contact stress is less than the yield stress of the coating, i.e. without macro plastic penetration of curvilinear bodies into this coating