Wyniki wyszukiwania - BazTech

1

Plomba urbanistyczna jako wypełnienie struktury funkcjonalno-przestrzennej na przykładzie terenu zajezdni autobusowej na warszawskim Mokot

Duda Magdalena, Trębacz Paweł

PUA Przestrzeń Urbanistyka Architektura

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2023

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Vol. 1

50--76

PL

Obecnie w Polsce w kontekście realizowania osiedli mieszkaniowych brakuje form regulacji ze strony wspólnoty samorządowej na poziomie projektu zagospodarowania. Określałyby one nowo tworzony układ miejskiej przestrzeni publicznej dla powstającego zespołu zabudowy na podstawie struktury urbanistycznej większej jednostki urbanistycznej. Na studialnych opracowaniach zaprezentowano wyniki poszukiwań zmian funkcjonalnych i przestrzennych urbanistycznej plomby na wytypowanym terenie przekształceń – miejskiej zajezdni autobusowej w warszawskiej dzielnicy Mokotów.

EN

Currently, in Poland, in the context of the implementation of housing estates, there are no forms of regulation on the part of the local government community at the level of the development project defining the newly created layout of urban public space for the emerging development complex, based on the urban structure of the larger urban unit. The study presents the results of the search for functional and spatial changes in the urban infill (titled seal) in the selected area of transformation – the Municipal Bus Depot in Warsaw’s Mokotów district.

2

Structure and thermal expansion of liquid bismuth

Mudry S., Shtablavyi I., Liudkevych U., Winczewski S.

Materials Science Poland

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2015

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Vol. 33, No. 4

767--773

EN

Experimental structural data for liquid Bi were used for estimation of the main structure parameters as well as the thermal expansion coefficient both in super cooled and superheated temperature ranges. It was shown that the equilibrium melt had a positive thermal expansion coefficient within a temperature range upon melting and a negative one at higher temperatures. The former was related to structure changes upon melting, whereas the latter with topologic disordering upon further heating. It was found that the superheated melt had a negative thermal expansion coefficient. The results obtained from structural data were compared with the thermal expansion coefficient calculated from the data of density for liquid Bi.

3

Thermodynamic pattern selection in the stripes generated periodically during the (Zn) - single crystal growth

Wołczyński W.

Archives of Metallurgy and Materials

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2013

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Vol. 58, iss. 2

309--313

EN

The (Zn) - hexagonal single crystal growth was performed by the Bridgman system. Some eutectic stripes were generated periodically in the single crystal. The stripes consisted of the strengthening inter-metallic compound, Zn16Ti and (Zn) - solid solution. Two morphology transitions were recorded. At the first threshold growth rate, L-shape irregular rods transformed into regular lamellar structure. The transition was accompanied by the irregular into regular morphology alteration. The regular lamella into regular rods transition occurred at the second threshold growth rate. The new, proposed thermodynamic pattern selection criterion (PSC) of the lower minimum entropy production was applied to describe the structural transitions. The solid/liquid interface perturbation of the (Zn) - phase was referred to the marginal stability.

PL

Heksagonalny monokryształ roztworu stałego (Zn) został wyprodukowany w układzie Bridgmana. Prążki eutektyczne zostały wygenerowane periodycznie w monokrysztale. Prążki składały się z umacniającego związku międzymetalicznego Zn16Ti oraz roztworu stałego (Zn). Zarejestrowano dwa przejścia morfologiczne. Przy pierwszej prędkości progowej nieregularne włókna o przekroju L doznały transformacji w regularne płytki. Temu przejściu towarzyszyła przemiana morfologii nieregularnej w regularna. Regularne płytki dokonały transformacji w regularne włókna przy drugiej prędkości progowej. Niższe minimum produkcji entropii to proponowane, nowe kryterium termodynamiczne dla selekcji struktur, jakie zastosowano by opisać przejścia strukturalne. Perturbacja frontu krystalizacji fazy (Zn) została odniesiona do stanu stabilności marginalnej.

4

Nitrogen hardening of creep-resistant G-NiCr28W alloy

Pirowski Z., Wodnicki J., Gwiżdż A.

Archives of Foundry Engineering

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2010

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Vol. 10, iss. 3

79--84

EN

In the group of creep-resistant materials, most important are heat-resistant nickel-based alloys. The G-NiCr28W alloy subject to detailed examinations was observed to have two different austenite-like phases. In the interdendritic spaces of alloy matrix, the presence of another phase, also characterised by paramagnetic properties, was detected. Inside this interdendritic phase, local areas of a lamellar structure, composed of both of the above mentioned phases, were present. Nitrogen treatment was observed to raise the microhardness of both these phases. The presence of nitrogen made the regions of a lamellar structure disappear completely. Their place was occupied by precipitates dispersed in the matrix, and occasionally forming large clusters. It has been observed that cold work can harden the G-NiCr28W alloy to a very small degree only, in spite of the fact that hardness is increasing systematically with the increasing degree of cold work. The said alloy, when enriched with nitrogen added as an alloying element, is characterised by hardness higher than the hardness of its nitrogen-free counterpart. The value of hardness is increasing even more under the effect of low-degree cold work, although increasing further the degree of cold work seems to have no effect on hardness increase. The problem faced in nickel-based materials is the possibility of making defect-free castings from alloys with high nitrogen content. Alloys investigated in the present study were remelted, cast and subject to solidification under high nitrogen pressure in the furnace chamber. However, melting carried out under these conditions could not prevent the occurrence of non-metallic inclusions which, while being unable to pass to a riser, formed local clusters or even thin films, resulting in numerous microcracks or discontinuities encompassing large regions of the casting. This problem seems to be of major concern and is the first one to require prompt solution in the currently executed large research project.

5

Casting structure change caused by magnetic field

Szajnar J.

Journal of Achievements in Materials and Manufacturing Engineering

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2007

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Vol. 24, nr 1

297-306

EN

Purpose: In this work problems of crystallization process for pure metal and alloy castings solidifying under forced convection resulting from use of rotational or rotational reversing magnetic field are presented. Design/methodology/approach: Influence of changes caused by forced convection in solidification conditions on columnar crystals zone and its limitation was studied. Obtained results show that magnetic field changes thermal and concentration conditions. Both conditions are connected with magnetic field induction B, that is with liquid metal velocity Vcm ahead of crystallization front. Examples of magnetic field application for casting structure change are shown. Findings: Model of columnar to equiaxed structure transition was based on modified concentration stability criterion of crystallization front, in which measurements of alloy addition concentration along ingot radius were incorporated. Gradient-kinetic conditions were evaluated with use of computer simulation of solidification process. Crystallization conditions at the interface enabled tracking of solidification process for actual casting from its surface to its axis. It was then possible to analyze relation between thermal and concentration conditions in time of solidification and to determine position of crystallization front stability loss, which after some simplifications can be considered as the columnar crystals zone width. Research limitations/implications: Experimental results confirmed justness of introduced model. In analysis also simulation results were used describing liquid metal flow ahead of crystallization front for different types of the interface showing qualitative relations between crystallization front geometry and structure changes. Practical implications: Relations are proposed, which can be used for columnar crystals zone width taking into account nominal concentration of alloy addition Co, forced by magnetic field liquid metal velocity Vcm and thermal conditions represented by pouring temperature Tzal, thermal gradient at the crystallization front at the moment of forced convection termination GT or difference in temperature on casting cross section delta T. Originality/value: This paper is a result of several studies conducted in Foundry Department since many years and connected of physical factors (ultrasonic vibrations, electromagnetic field) influence on crystallization process of static and continuous castings.

6

Warunki transformacji struktury w odlewach krzepnących przy wymuszonej konwekcji

Szajnar J.

Krzepnięcie Metali i Stopów

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2000

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R. 2, nr 42

33--41

PL

W pracy dokonano analizy warunków utraty trwałości frontu krystalizacji w odlewach krzepnących pod działaniem wirującego pola magnetycznego. Badania przeprowadzono na wlewkach walcowych ze stopu ZnAl0,2. Analizę przeprowadzono w oparciu o metodę perturbacyjną Mullinsa i Sekerki [1] oraz kryterium stabilności marginalnej Langera i Mullera-Krumbhaara [2]. Stwierdzono, że szybka utrata stabilności frontu krystalizacji tworzy warunki do szybkiego przejścia z krzepnięcia kierunkowego do krzepnięcia objętościowego. Określając miejsce utraty trwałości frontu można z pewnym przybliżeniem wyznaczyć lub prognozować szerokości strefy kryształów kolumnowych.