Herbert De Gersem, Olaf Henze, Thomas Weiland and Andreas Binder
The purpose of this paper is to offer a simulation method for predicting the impedance of machine windings at higher frequencies.
Abstract
Purpose
The purpose of this paper is to offer a simulation method for predicting the impedance of machine windings at higher frequencies.
Design/methodology/approach
A transmission‐line model (TLM) is developed based on parameters calculated on the basis of electroquasistatic and magnetoquasistatic finite‐element (FE) model of the winding cross‐section.
Findings
The FE formulations for the low‐ and high‐frequency limits give acceptable results for the respective frequency ranges. An eddy‐current formulation is only accurate on a broader region when the FE mesh is sufficiently fine to resolve the skin depth.
Research limitations/implications
The paper is restricted to frequency‐domain simulations.
Practical implications
The results of the paper improve the understanding of higher‐frequency parasitic effects in electrical drives with long windings.
Originality/value
The paper shows the limitations of the FE methods used for determining the parameters of the TLMs and remedies to avoid these.
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Studies the spinel pigments containing Zn, Ca, and Mg cations from the point of view of reactivity with corrosive substances of acidic nature, which diffuse through the coating at…
Abstract
Studies the spinel pigments containing Zn, Ca, and Mg cations from the point of view of reactivity with corrosive substances of acidic nature, which diffuse through the coating at activated corrosion. Proposes the mechanisms of anticorrosive activities of these pigments in an epoxy resin based binder, showing a high chemical stability. A microscopy method was used for following the diffusion of corrosive acidic substances through the film.
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Cara Greta Kolb, Maja Lehmann, Johannes Kriegler, Jana-Lorena Lindemann, Andreas Bachmann and Michael Friedrich Zaeh
This paper aims to present a requirements analysis for the processing of water-based electrode dispersions in inkjet printing.
Abstract
Purpose
This paper aims to present a requirements analysis for the processing of water-based electrode dispersions in inkjet printing.
Design/methodology/approach
A detailed examination of the components and the associated properties of the electrode dispersions has been carried out. The requirements of the printing process and the resulting performance characteristics of the electrode dispersions were analyzed in a top–down approach. The product and process side were compared, and the target specifications of the dispersion components were derived.
Findings
Target ranges have been identified for the main component properties, balancing the partly conflicting goals between the product and the process requirements.
Practical implications
The findings are expected to assist with the formulation of electrode dispersions as printing inks.
Originality/value
Little knowledge is available regarding the particular requirements arising from the systematic qualification of aqueous electrode dispersions for inkjet printing. This paper addresses these requirements, covering both product and process specifications.
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Andrea Nana Ofori-Boadu, Richard Yeboah Abrokwah, Spero Gbewonyo and Elham Fini
The purpose of this paper is to investigate the effect of an admixture, Swine-waste Bio-char (SB), on the water absorption characteristics of cement pastes.
Abstract
Purpose
The purpose of this paper is to investigate the effect of an admixture, Swine-waste Bio-char (SB), on the water absorption characteristics of cement pastes.
Design/methodology/approach
The effect of SB percentages, heat treatment temperatures, water/binder ratios, and age on the water absorption percentages (WAPs) of SB modified cement pastes were investigated using scanning electron microscopy-energy dispersive spectra, FTIR, Brunauer-Emmett-Teller, and laboratory experiments.
Findings
The WAPs of cement pastes with SBs produced at the low treatment temperature (LTT) of 340°C and 400°C were significantly lower (p<0.01) than pastes with SBs produced at the high treatment temperature (HTT) of 600°C and 800°C. This was attributed primarily to the more dominant presence of hydrophobic alkyl surface groups from non-volatilized matter in LTT-SBs. This had also resulted in lower surface areas and pore volumes in LTT-SBs. As a result of the volatilization of these labile hydrophobic groups at HTT, HTT-SBs were more hydrophilic and had higher surface areas and pore volumes. Consequently, HTT-SB pastes had higher WAPs and no significant differences (p<0.05) existed between HTT-SB pastes and control pastes. Also, low water/binder ratios and aging reduced water absorption of SB modified cement pastes.
Practical implications
LTT-SBs reduce water absorption and could reduce concrete deterioration; and as such, associated building repair, maintenance, and adaptation costs. Notably, reductions in concrete water absorption will extend the service life of concrete buildings and infrastructures, particularly in unfavorable environmental conditions. The observed benefits are tempered by the current lack of information on the effects of SB on compression strength, workability, and other durability properties.
Social implications
SB utilization in concrete buildings will enhance swine-waste disposal and reduce negative environmental impacts on swine farming communities; consequently, improving their quality of life.
Originality/value
Current bio-char research is focused on plant-derived bio-char toward soil remediation and contaminant removal, with very limited applications in concrete. This research advances knowledge for developing livestock-derived bio-char, as a PCRM, toward more sustainable and durable concrete structures.
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Christoph Endenich, Andreas Hoffjan, Anne Krutoff and Rouven Trapp
This paper aims to study the internationalisation of management accounting research in the German-speaking countries and to analyse whether researchers from these countries rely…
Abstract
Purpose
This paper aims to study the internationalisation of management accounting research in the German-speaking countries and to analyse whether researchers from these countries rely on their intellectual heritage or adapt to the conventions prevailing in the international community.
Design/methodology/approach
This paper provides a research taxonomy of 273 papers published by management accounting researchers from the German-speaking countries between 2005 and 2018 in domestic and international journals with regard to topics, settings, methods, data origins and theories of these papers. The study also systematically compares these publications with the publications by international scholars as synthesised in selected prior bibliometric studies.
Findings
The findings suggest that German-speaking researchers increasingly adapt to the conventions prevailing in the international management accounting literature. Indicative of this development is the crowding out of traditional core areas of German-speaking management accounting such as cost accounting by management control topics. The study also finds that German-speaking researchers increasingly rely on the research methods and theories prevailing internationally.
Research limitations/implications
The paper documents considerable changes in the publications of management accounting researchers from the German-speaking countries. These changes raise the question how other national research communities internationalise and whether these processes lead to a greater homogenisation of international management accounting research, which might impair the advancement of management accounting knowledge.
Originality/value
This paper provides first empirical evidence on how management accounting research conducted in the German-speaking countries has changed in the course of the internationalisation of the research community and builds an important basis for future research in other geographic settings.
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Studies the effects of non‐isometric pigments on the anticorrosion properties of coating films. The optimum concentrations for using iron mica, muscovite, and graphite have been…
Abstract
Studies the effects of non‐isometric pigments on the anticorrosion properties of coating films. The optimum concentrations for using iron mica, muscovite, and graphite have been determined. The results obtained on using the natural iron mica are compared to those obtained with a synthetic product. As binders for the coatings epoxy resin, polyurethane and alkyd resins were used. The results allow the conclusion that on the pigmentation with iron mica the protection function of top coatings against the corrosive media can be considerably increased.
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Petr Benda and Andréa Kalendová
The aim of the work is to develop an anticorrosion pigment based on an oxide mixture with lamellar particles. The pigments are prepared from lamellar zinc, zinc oxide and…
Abstract
Purpose
The aim of the work is to develop an anticorrosion pigment based on an oxide mixture with lamellar particles. The pigments are prepared from lamellar zinc, zinc oxide and magnetite by calcination. An alkaline earth carbonate is added when embedding a third cation in the lattice of the ferrite that forms the envelope of the lamellar zinc. The properties of the pigments are tested both in the powdered state and when embedded in an epoxy-ester system using different pigment volume concentrations (PVC).
Design/methodology/approach
The properties of paints containing synthesised oxide mixture-based pigments at various volume concentrations and with the Q factor – Q = PVC/CPVC = 0.65 – were examined (where CPVC is critical pigment volume concentration). A series of isometric ferrite pigments were also synthesised for a comparison. Paints of both types with PVC = 10, 15 and 20 per cent were formulated. Steel panels coated with the paints were subjected to corrosion and mechanical tests.
Findings
The oxide mixtures with lamellar particles were subjected to particle size analysis and found to make up a broad distribution curve. Electron microscopy photographs confirmed that the oxide mixture pigments contained lamellar particles with a surface layer. A high anticorrosion effect was achieved owing to the combination of different oxide types.
Research limitations/implications
The properties of the oxide mixtures with lamellar particles are described. Their particle distribution curves can be obtained by particle size analysis methods with a view to obtaining additional information on the status and properties of the pigment particles that may be useful in the development of better paints/coating materials.
Practical implications
Oxide mixtures with lamellar particles can be used in paints protecting construction steel.
Originality/value
The composition of the prepared oxide mixture-based pigments is novel. Each oxide acts by its own anticorrosion mechanism and the final beneficial effect is due to their concerted action.
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Andrea Kalendova and Tereza Hájková
– This paper aims to synthesize anticorrosion pigments containing tungsten for paints intended for corrosion protection of metals.
Abstract
Purpose
This paper aims to synthesize anticorrosion pigments containing tungsten for paints intended for corrosion protection of metals.
Design/methodology/approach
The anticorrosion pigments were prepared by high-temperature, solid-state synthesis from the respective oxides, carbonates and calcium metasilicate. Stoichiometric tungstates and core-shell tungstates with a nonisometric particle shape containing Ca, Sr, Zn, Mg and Fe were synthesized. The pigments were examined by X-ray diffraction analysis and by scanning electron microscopy. Paints based on an epoxy resin and containing the substances at a pigment volume concentration (PVC) = 10 volume per cent were prepared. The paints were subjected to physico-mechanical tests and to tests in corrosion atmospheres. The corrosion test results were compared to those of the paint with a commercial pigment, which is used in many industrial applications.
Findings
The tungstate structure of each pigment was elucidated. The core-shell tungstates exhibit a nonisometric particle shape. The pigments prepared were found to impart a very good anticorrosion efficiency to the paints. A high efficiency was demonstrated for the stoichiometric tungstates containing Fe and Zn and for core-shell tungstates containing Mg and Zn.
Practical implications
The pigments can be used with advantage for the formulation of paints intended for corrosion protection of metals. The pigments also improve the paints’ physical properties.
Originality/value
The use of the pigments in anticorrosion paints for the protection of metals is new. The benefits include the use and the procedure of synthesis of anticorrosion pigments which are free from heavy metals and are acceptable from the environmental protection point of view. Moreover, the core-shell tungstates, whose high efficiency is comparable to that of the stoichiometric tungstates, have lower tungsten content.
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Andrea Nana Ofori-Boadu, DeAndria Bryant, Christian Bock-Hyeng, Zerihun Assefa, Frederick Aryeetey, Samira Munkaila and Elham Fini
The purpose of this study is to explore the feasibility of utilizing agricultural (almond shell, rice husk and wood) waste biochars for partial cement replacement by evaluating…
Abstract
Purpose
The purpose of this study is to explore the feasibility of utilizing agricultural (almond shell, rice husk and wood) waste biochars for partial cement replacement by evaluating the relationships between the physiochemical properties of biochars and the early-age characteristics of cement pastes.
Design/methodology/approach
Biochars are prepared through the thermal decomposition of biomass in an inert atmosphere. Using varying percentages, biochars are used to replace ordinary Portland cement (OPC) in cement pastes at a water/binder ratio of 0.35. Characterization methods include XPS, FTIR, SEM, TGA, BET, Raman, loss-on-ignition, setting, compression and water absorption tests.
Findings
Accelerated setting in biochar-modified cement pastes is attributed to chemical interactions between surface functional groups of biochars and calcium cations from OPC, leading to the early development of metal carboxylate and alkyne salts, alongside the typical calcium-silicate-hydrate (C-S-H). Also, metal chlorides such as calcium chlorides in biochars contribute to the accelerate setting in pastes. Lower compression strength and higher water absorption result from weakened microstructure due to poor C-S-H development as the high carbon content in biochars reduces water available for optimum C-S-H hydration. Amorphous silica contributes to strength development in pastes through pozzolanic interactions. With its optimal physiochemical properties, rice-husk biochars are best suited for cement replacement.
Research limitations/implications
While biochar parent material properties have an impact on biochar properties, these are not investigated in this study. Additional investigations will be conducted in the future.
Practical implications
Carbon/silicon ratio, oxygen/carbon ratio, alkali and alkaline metal content, chlorine content, carboxylic and alkyne surface functional groups and surface areas of biochars may be used to estimate biochar suitability for cement replacement. Biochars with chlorides and reactive functional groups such as C=C and COOH demonstrate potential for concrete accelerator applications. Such applications will speed up the construction of concrete structures and reduce overall construction time and related costs.
Social implications
Reductions in OPC production and agricultural waste deterioration will slow down the progression of negative environmental and human health impacts. Also, agricultural, manufacturing and construction employment opportunities will improve the quality of life in agricultural communities.
Originality/value
Empirical findings advance research and practice toward optimum utilization of biomass in cement-based materials.
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If a weather‐beaten structural steelwork, protected by a full system of anticorrosive coatings, will show a lifetime of over 20 years without any maintenance during this time, we…
Abstract
If a weather‐beaten structural steelwork, protected by a full system of anticorrosive coatings, will show a lifetime of over 20 years without any maintenance during this time, we will speak of a ‘longterm Corrosion Protection.’ These 20 years often seem to be too long, but many case‐histories of structural steelworks over the whole of Europe, such as bridges, tankfarms, cranes etc. will prove it. By the way, the German Railway Administration foresees a major repainting of their objects only every 20 years, the Swiss Federal Railway Administration only after 25–30 years. The most parts of these protective coatings are pigmented with Micaceous Iron Oxide (MIO), a pigment with the highest life expectance.