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1
Content available Investigation on Reactions at Corners of Cast Part during Investment Casting of Reactive AZ91 Magnesium Alloy
Vyas Akash V., Sutaria Mayur .
Archives of Foundry Engineering
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2020
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Vol. 20, iss. 4
139--144
EN
The magnesium alloy investment castings have greater potential for automobile and air-craft applications due to the higher strength to weight ratio of magnesium alloys and capability of the investment casting process to produce near net shape complex castings. The interfacial-mould metal reactions during investment casting of magnesium alloy inhibit successful production of quality castings. This paper presents the investigation done on the reactions at corners of AZ91 magnesium alloy cast part produced through investment casting. The stepped shape geometry of casting was selected to study the reactions at convex and concave corners of the cast part. The reacted surfaces were characterised using the SEM-EDX and XRD. The formation of oxides was observed on cast surface from characterisation. The temperature profile recorded at corners were helpful to understand the heat dissipation during the solidification of metal at corners. It was observed that the reactions occurred at the concave corner were more as compared to the convex corner of the cast part.
2
Content available remote Reakcje o narastającej szybkości
Głowiński J., Hałat A., Hoffmann J., Popławski D., Klakočar-Ciepacz M.
Przemysł Chemiczny
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2017
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T. 96, nr 1
213--216
PL
Szybkość tworzenia produktu w reakcji wyróżniającej się ciągłym wzrostem lub wzrostem asymptotycznie osiągającym maksimum szybkości opisano równaniem potęgowym r = Aαa(1 - α)b(1 - β)c, w którym zmiennymi niezależnymi są stopnie przereagowania substratów α i β.
EN
In the reaction where the rate of reaction constantly increases or asymptotically attains a max. value, the rate of product formation was described as a power-law equation. The conversions of substrates were used as the independent variables.
3
Content available Laccases – enzymes with an unlimited potential
Kaczmarek M. B., Kwiatos N., Szczęsna-Antczak M., Bielecki S.
Biotechnology and Food Science
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2017
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Vol. 81, nr 1
41--70
EN
Laccases (EC 1.10.3.2) are among the few enzymes, the history of which dates back to the 19th century. These oxidoreductases are present in almost all known fungi, some species of higher plants and insects. Moreover, in recent years, these enzymes have also been found in some bacterial organisms. Due to their significant properties and structure of the catalytic centre, laccases have been classified as the multicopper oxidases (MCOs). These enzymes are able to catalyse the oxidation of phenolic and non-phenolic compounds, with the aid of small molecules referred to as mediators. Thanks to their diverse nature, laccases have gained attention of both scientists and entrepreneurs from all over the world. Their significance is reflected in countless scientific and industrial applications, wherein laccases have become inseparable from chemical syntheses, the food industry, textile industry, biosensor design and the environmental protection. This paper gathers the most important information and the latest scientific discoveries relating to this desirable biocatalyst.
4
Content available From biomass towards syngas
Kardaś D.
Transactions of the Institute of Fluid-Flow Machinery
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2015
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nr 127
63--89
EN
The article presents and overview of selected physical and chemical issues relating to biomass gasification. It also includes the history of the development of thermal wood treatment technology, with particular attention paid to Polish threads. Basic physical and chemical properties of biomass are discussed, using wood and straw as representative examples. Main types of gravitational gasifying reactors are presented, along with the analysis of basic mechanisms of homogeneous and heterogeneous chemical reactions in the reactor bed. The equation of motion of bed particles is derived based on particle volume changes caused by pyrolysis and surface reactions.
5
Content available Test Reactions To Study Efficiency Of Mixing
Jasińska M.
Chemical and Process Engineering
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2015
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Vol. 36, nr 2
171--208
EN
Effects of mixing on the course of fast chemical reactions are relatively well understood, especially in homogeneous systems. This enables to design and operate chemical reactors with the goal to achieve a high yield of a desired product and use systems of complex reactions as a chemical probe (chemical test reactions) to identify progress of mixing and quality of mixture. Recently, a number of studies have focused on the application of chemical test reactions to identify energy efficiency of mixing, being a convenient way of comparing mixers and reactors in terms of their mixing efficiency. This review offers a presentation of chemical test reactions available in the literature and methods of applications of test reactions to identify the energy efficiency of mixing. Also methods to assess the extent of micromixing by measuring product distribution or segregation index, and to determine the time constant for mixing are presented for single phase homogeneous systems and two-phase liquid-liquid systems.
6
Content available Polynitrobenzenes Containing Alkoxy and Alkylenedioxy groups: Potential HEMs and Precursors of New Energetic Materials
Šarlauskas J.
Central European Journal of Energetic Materials
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2010
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Vol. 7, nr 4
313-324
EN
Several di-, tri- and tetranitroderivatives of alkoxy-, dialkoxy-, trialkoxy- and cyclic alkylenedioxybenzene derivatives were synthesized by nitration of starting compounds under different conditions and their properties were compared to the already known 2,4,6-trinitroanisole and TNT. Synthesized trinitro- and tetranitrocompounds of alkoxy-/alkylenedioxybenzene (especially cyclic derivatives) may serve as useful precursors for the synthesis of numerous energetic derivatives. The highest melting point (286 C) and calculated density (1.907 g/cm3) is marked for 5,6,7,8-tetranitro-2,3-dihydro-1,4-benzodioxine (TNBD). Promising properties of the latter compound allow further exploration of this material as a potential thermostable HEM.
7
Content available Zastosowanie komputerowego rachunku symbolicznego do zagadnień zginania belek
Hałat W.
Górnictwo i Geoinżynieria
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2007
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R. 31, z. 3
171-182
PL
Systemy obliczeniowe zwane CAS (ang. Computer Algebra System) zajmują szczególne miejsce wśród pakietów programów wspomagających prace naukowo-techniczne. Mają one szerokie możliwości rozwiązywania zaawansowanych zadań z różnych dziedzin inżynierskich, w tym także problemów związanych z geotechniką i budownictwem. Za pomocą rachunku symbolicznego przedstawiono wpływ podparcia na wartości: sił reakcji, momentów zginających, sił tnących, kątów ugięcia i linii ugięcia w zginanych belkach. Otrzymane rozwiązania, w postaci symbolicznych wzorów matematycznych, zostały zobrazowane wykresami. Wykresy z konieczności narysowane zostały na wartościach liczbowych, a nie symbolicznych.
EN
CAS Calculations methods (Computer Algebra System) take a special position in supporting software packages for technical scientific research works. They can be used for a wide range of advanced applications in various engineering solutions including constructions and geotechnics. With the symbolic calculations method it has been presented the role of support onto: reaction forces, bending moments, transversal forces, bending angles and profile lines in the beams under bending process. The results in the form of symbolic mathematical formulas are illustrated with diagrams that have been plotted obviously based on number values but not symbols.
8
Content available In-situ observations of devolatilisation of coal
Strezov V., Lucas J. A., Osborn S. R., Strezov L.
Polish Geological Institute Special Papers
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2002
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Vol. 7
253-258
EN
Coal devolatilisation phenomena were observed in-situ during heating. A single particle of coal of approximately 1 mm diameter was placed on a stainless steel strip heated by an alternative current source. The behaviour of the coal particle was recorded at 100 times magnification through an arrangement of a long focal distance microscope attached to a CCD camera. The two different coal types examined (thermal and coking coal) exhibited significant differences during heating. At about 460oC, during the plastic stage, the coking coal showed rapid swelling and formation of bubbles within the liquid. Unlike the coking coal, the thermal coal showed very little swelling, although devolatilisation (predominantly tars for both coals) was taking place. The volatiles were diffusing to the surface of the particle through the pores in the char, without any significant swelling. At temperatures above 600oC, significant shrinking was observed with the coking coal, while in both samples, evolution of hydrogen was monitored. These observations were compared to the measured specific heats for these coals. The specific heats showed significant differences between the samples associated with a very complex behaviour following the onset of softening. While the coking coal exhibited predominantly exothermic reactions coinciding with the observed swelling phenomena, the thermal coal showed a sequence of endothermic and exothermic reactions. The changes in the specific heats also correlated well with the observed evolution of hydrogen (and shrinking for the coking coal) at higher temperatures.
9
Content available remote Reakcje związków metalo- i metaloidoorganicznych w wysokiej temperaturze
Starowieyski K. B.
Przemysł Chemiczny
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1999
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T. 78, nr 4
132-134
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