Experimental investigations of thin walled, squared cross – section composite tubes applied to static compression.

This paper deals with the experimental investigations of thin-walled, squared crosssection composite tubes subjected to a static compression. The main purpose of this paper is to present and discuss different methods of data analysis while investigating stability of thin-walled structures. Performed experiments were conducted by employing Zwick/Roel universal test stand; non-contact, geometrical - optical principled system Aramis produced by GOM company and strain-gauge technique. Different methods of determining buckling loads were employed, discussed and compared. Moreover all problems, occurring during experiments and data analysis were emphasized in order to show what kind of difficulties could appear during processing the results of measurements. As an example, comparing non-dimensional strain-gauges data with dimensional non-contact system Aramis results of measurements can quoted

Influence of roughness on ZDDP tribofilm formation in boundary lubricated fretting

Influence of initial surface topography on tribofilm formation in ZDDP lubricated contact was analysed. A small displacement fretting tests with sinusoidal motion were carried out in classical sphere/plane configuration. A range of surfaces with different initial roughness were prepared by milling and grinding processes. Tests were carried out using variable displacement method where amplitude of imposed displacement was gradually increased after every 1000 cycles from 2 to 30 µm. The surfaces after tribological tests were measured by interferometric profiler. Main findings confirm that initial roughness has a significant influence on antiwear tribofilm formation in boundary lubricated contact. Tribofilm form faster and require less energy to activate in case of rough surface obtained by milling process than in case of smooth grinded surface. However, in contact lubricated by ZDDP additive a significant transfer of material occurred from plane to sphere specimen

Insertion of a measurable function

Some theorems on the existence of continuous real-valued functions on a topological space (for example, insertion, extension, and separation theorems) can be proved without involving uncountable unions of open sets. In particular, it is shown that well-known characterizations of normality (for example the Katětov-Tong insertion theorem, the Tietze extension theorem, Urysohn's lemma) are characterizations of normal σ-rings. Likewise, similar theorems about extremally disconnected spaces are true for σ-rings of a certain type. This σ-ring approach leads to general results on the existence of functions of class α

Effect of freezer storage on quality of M. longissimus lumborum from fallow deer (Dama dama L.)

The aim of this study was to analyse changes in the quality of meat (M. longissimus lumborum) from 11 fallow deer (Dama dama L.) bucks, which had been deep-frozen (-26 °C) for 10 months. The proximate chemical composition, physico-chemical properties and sensory properties of the meat were analysed. Fallow deer aged 17–18 months were hunter-harvested in north-eastern Poland in November and December of the same hunting season. The results revealed that freezer storage did not influence the proximate chemical composition of meat (protein, fat, ash) or the content of water-soluble nitrogen compounds. An analysis of the physico-chemical properties of meat revealed that long-term freezer-stored meat was characterized by higher pH, lower contribution of redness (a*) and yellowness (b*), lower chroma (C*), greater natural drip loss, lower ability to bind added water, and greater cooking loss. Freezer storage improved meat tenderness but reduced meat juiciness. The results of the study also indicated that long-term freezer storage (-26 °C) of vacuum-packaged meat allowed it to maintain its good quality, which indicates that this storage method could help meet consumer demand for fallow deer meat between hunting seasons.Keywords: Freezing, game meat, meat quality, vacuum packagin

Elemental boron doping behavior in silicon molecular beam epitaxy

Boron-doped Si epilayers were grown by molecular beam epitaxy (MBE) using an elemental boron source, at levels up to 2×1020 cm−3, to elucidate profile control and electrical activation over the growth temperature range 450–900 °C. Precipitation and surface segregation effects were observed at doping levels of 2×1020 cm−3 for growth temperatures above 600 °C. At growth temperatures below 600 °C, excellent profile control was achieved with complete electrical activation at concentrations of 2×1020 cm−3, corresponding to the optimal MBE growth conditions for a range of Si/SixGe1−x heterostructures

Probing the interfacial and sub-surface structure of Si/Si1 – xGex multilayers

The ability to determine structural and compositional information from the sub-surface region of a semiconductor material has been demonstrated using a new time-of-flight medium energy ion scattering spectroscopy (ToF-MEISS) system. A series of silicon–silicon/germanium (Si/Si1 – xGex) heterostructure and multilayer samples, grown using both solid source molecular beam epitaxy (MBE) and gas source chemical vapor deposition (CVD) on Si(100) substrates, have been investigated. These data indicate that each individual layer of Si1 – xGex (x ~ 0.22) in both two- and three-period samples, can be uniquely identified with a resolution of approximately 3 nm. A comparison of MBE and CVD grown samples has also been made using layers with similar structures and composition. The total Ge content of each sample was confirmed using conventional Rutherford backscattering spectrometry