Nica-Toeplitz algebras associated with product systems over right LCM semigroups

We prove uniqueness of representations of Nica-Toeplitz algebras associated to product systems of $C^*$-correspondences over right LCM semigroups by applying our previous abstract uniqueness results developed for $C^*$-precategories. Our results provide an interpretation of conditions identified in work of Fowler and Fowler-Raeburn, and apply also to their crossed product twisted by a product system, in the new context of right LCM semigroups, as well as to a new, Doplicher-Roberts type $C^*$-algebra associated to the Nica-Toeplitz algebra. As a derived construction we develop Nica-Toeplitz crossed products by actions with completely positive maps. This provides a unified framework for Nica-Toeplitz semigroup crossed products by endomorphisms and by transfer operators. We illustrate these two classes of examples with semigroup $C^*$-algebras of right and left semidirect products.Comment: Title changed from "Nica-Toeplitz algebras associated with right tensor C*-precategories over right LCM semigroups: part II examples". The manuscript accepted in J. Math. Anal. App

Winter in a Svalbard Fiord Ecosystem

Data pertaining to the characteristics of an arctic fiord in winter were collected at the Polish Arctic Station situated in Hornsund at 77 degrees N, 15 degrees E on Svalbard. Winter in the fiord was defined in terms of climate (November-May), hydrology (January-March) and biology (November-March). The characteristic phenomena of winter in the fiord include a winter drop in the yearly biomass maximum to 0.1% for phytoplankton and 10% for zooplankton; a slowing of the growth rate among pelagic dominants such as Pseudocalanus elongatus and Calanus finmarchicus, as well as among the hyperbenthic dominants Onisimus littoralis and Mysis oculata; and heterotrophy or maintenance of metabolism among living phytoplankton cells found in the middle of the polar night in densities of 10-50 cells/L. Since the life cycles of invertebrates are highly seasonal, no winter breeders were observed and 90% of the examined species were breeding according to a K strategy. Migration takes place among all seabirds in the area, but about 1% of the eiders, fulmars and kittiwakes overwinter, feeding in the open water of polynyas and crevices in the fast ice.Key words: Arctic, winter ecology, fiord ecosystem, Svalbard, Hornsund fiordMots clés: Arctique, écologie de l’hiver, écosystème de fjord, Svalbard, fjord Hornsun

Studies on magnesium addition to copper produced in the continuous casting process and analysis of mechanical, electrical and structural properties of obtained casts

Article presents the effect of magnesium addition to copper in the range of 0,02 – 0,5 wt. %. on the mechanical, electrical and structural properties of obtained materials. All analysed alloys were produced by horizontal continuous casting set-up in the form of 9,5 mm rods. Obtained Cu-Mg alloys were next tested for their as-cast properties via Vickers hardness analysis, electrical conductivity measurements and macrostructure observations in both cross and longitudinal section. The aim of the research was to verify the influence of the magnesium content on the properties of selected Cu-Mg alloys, which are dedicated to use in overhead railway system for contact wires and catenaries

Research on Cu-Mg castings cold drawing process and analysis of mechanical and electrical properties of obtained wires

The aim of the conducted research works which are presented in the article was to determine the mechanical and electrical properties of Cu-Mg wires obtained in cold drawing process with total deformation at the level of 95 %. Base material for the research was obtained with the use of continuous casting process which allowed to produce CuMg0.02, CuMg0.05 and CuMg0.5 cylindrical rods with 9,5 mm diameter which were next cold drawn up to 1,97 mm diameter. After the cold drawing process Vickers hardness measurements along with static tensile test and electrical conductivity analysis were performed in order to determine the evolution of castings properties as a result of the applied cold deformation

Studies on magnesium addition to copper produced in the continuous casting process and analysis of mechanical, electrical and structural properties of obtained casts

Article presents the effect of magnesium addition to copper in the range of 0,02 – 0,5 wt. %. on the mechanical, electrical and structural properties of obtained materials. All analysed alloys were produced by horizontal continuous casting set-up in the form of 9,5 mm rods. Obtained Cu-Mg alloys were next tested for their as-cast properties via Vickers hardness analysis, electrical conductivity measurements and macrostructure observations in both cross and longitudinal section. The aim of the research was to verify the influence of the magnesium content on the properties of selected Cu-Mg alloys, which are dedicated to use in overhead railway system for contact wires and catenaries

Research on Cu-Mg castings cold drawing process and analysis of mechanical and electrical properties of obtained wires

The aim of the conducted research works which are presented in the article was to determine the mechanical and electrical properties of Cu-Mg wires obtained in cold drawing process with total deformation at the level of 95 %. Base material for the research was obtained with the use of continuous casting process which allowed to produce CuMg0.02, CuMg0.05 and CuMg0.5 cylindrical rods with 9,5 mm diameter which were next cold drawn up to 1,97 mm diameter. After the cold drawing process Vickers hardness measurements along with static tensile test and electrical conductivity analysis were performed in order to determine the evolution of castings properties as a result of the applied cold deformation

Graphite crystallizer and its surface quality as a factor affecting the copper continuous casting process

Pure copper is one of the best conducting metals among known materials, making it the first choice for wires and microwires. However, before subjecting to metal working, the material is being manufactured in the continuous casting lines. The experimental study conducted in laboratory conditions proved that the external surface quality, and thus the contact quality with the cooling system is being responsible for the worsening or improving of the heat transfer and therefore the temperature of the crystallizer itself. The conducted study might function as sort of a guideline for the industrial process

Optimalization of the metallurgical synthesis parameters of CuZn37 brass with nickel and silicon alloy additives

The modifying possibility of the commercial CuZn37 brass (M63) with nickel and silicon is being discussed throughout the article. The proposed alloy additives made it possible to improve the commercial brass properties by precipitation hardening, thus making it extremely competitive in comparison to base material. The study also discussed the conditions (temperature and time) of the metallurgical synthesis and its influence on the weight percentage of not only proposed alloy additives but also the amount of zinc loss from the commercial brass due to the evaporation during the metallurgical processes

Correlation between macrosegregation and mechanical properties in EN AW-6060 aluminium alloy billets obtained by continuous casting

Modern non-ferrous metal applications are faced to high requirements in terms of even distribution of the alloying elements. In general, the homogeneity of the chemical composition of the materials affect to their mechanical properties. As part of this paper the relationship between the local concentration of Mg and Si in 90 mm diameter billets from EN AW-6060 aluminium alloy and local variability of yield stress in experimental conditions which simulates technological conditions for hot metal forming processes. The phenomenon of macrosegregation remained specified for billets obtained in the technology of horizontal continuous casting, dedicated to extrusion or forging

Graphite crystallizer and its surface quality as a factor affecting the copper continuous casting process

Pure copper is one of the best conducting metals among known materials, making it the first choice for wires and microwires. However, before subjecting to metal working, the material is being manufactured in the continuous casting lines. The experimental study conducted in laboratory conditions proved that the external surface quality, and thus the contact quality with the cooling system is being responsible for the worsening or improving of the heat transfer and therefore the temperature of the crystallizer itself. The conducted study might function as sort of a guideline for the industrial process