Effects of changes in MOLB-type SOFC cell geometry on temperature distribution and heat transfer rate in interconnects

A numerical simulation tool for modeling MOLB-type solid oxide fuel cells was described. A mathematical model was developed and simulations were carried out to study the effect of cell geometry on the temperature distribution and heat transfer rate in interconnects. The simulations took into account the impact of co-flow and counter-flow patterns on the distribution of temperature. The results show that in counter-flow conditions there are lower temperature gradients and more uniform temperature distribution, which significantly affects conductive and corrosion properties and durability of the interconnect.     

Double Bond Stereochemistry Influences the Susceptibility of Short-Chain Isoprenoids and Polyprenols to Decomposition by Thermo-Oxidation

Isoprenoid alcohols are common constituents of living cells. They are usually assigned a role in the adaptation of the cell to environmental stimuli, and this process might give rise to their oxidation by reactive oxygen species. Moreover, cellular isoprenoids may also undergo various chemical modifications resulting from the physico‐chemical treatment of the tissues, e.g., heating during food processing. Susceptibility of isoprenoid alcohols to heat treatment has not been studied in detail so far. In this study, isoprenoid alcohols differing in the number of isoprene units and geometry of the double bonds, β‐citronellol, geraniol, nerol, farnesol, solanesol and Pren‐9, were subjected to thermo‐oxidation at 80 °C. Thermo‐oxidation resulted in the decomposition of the tested short‐chain isoprenoids as well as medium‐chain polyprenols with simultaneous formation of oxidized derivatives, such as hydroperoxides, monoepoxides, diepoxides and aldehydes, and possible formation of oligomeric derivatives. Oxidation products were monitored by GC‐FID, GC‐MS, ESI‐MS and spectrophotometric methods. Interestingly, nerol, a short‐chain isoprenoid with a double bond in the cis (Z) configuration, was more oxidatively stable than its trans (E) isomer, geraniol. However, the opposite effect was observed for medium‐chain polyprenols, since Pren‐9 (di‐trans‐poly‐cis‐prenol) was more susceptible to thermo‐oxidation than its all‐trans isomer, solanesol. Taken together, these results experimentally confirm that both short‐ and long‐chain polyisoprenoid alcohols are prone to thermo‐oxidation.     

Investigations on rheological strains of compressed concrete elements strengthened with external composite reinforcement CFRP

The results of experimental studies on rheological strains of compressed concrete elements strengthened with surface CFRP materials are presented in this paper. The objective of the investigations was to estimate the influence of long-term load on strains and load-bearing capacity of compressed elements strengthened with CFRP materials. The studies were performed on specimens with various types of reinforcement. The specimens were strengthened with external composite reinforcement – longitudinal segments of CFRP strips and transverse confinement executed with CFRP sheets. The experimental studies were divided into two stages, in which specimens were subjected to long-term axial compression. The objects of the investigations were cylindrical specimens with a diameter of 113 mm and height of 350 mm. The plain concrete specimens were loaded with the level of about 1/3f_cm,cyl (mean cylinder compressive strength of the concrete). After the period of initial loading the specimens were strengthened and the level of effort was increased to about 2/3f_cm,cyl. The tests were conducted in constant thermal and moisture conditions. In the paper, the dependences of long-term strains increase in time are presented for the experimental elements. Additionally, theoretical studies connected with rheological model identification were performed.     

Determination of the adulteration of butter

The adulteration of butter is a serious problem due to economic advantages taken by replacing expensive milk fat with cheaper oil without informing the customers. The authentication of milk fat methods include analysis of bulk components, especially triacylglycerols, fatty acids, sterols and tocopherols. Fatty acid and sterol composition was analysed by using GC‐MS. TAG and tocopherol profiles were examined by HPLC with diode array (DAD) and fluorescence detectors (FLDs). In addition, identification of selected TAG of butter fat was conducted by LC‐atmospheric pressure chemical ionisation (APCI)/MS technique. The lipid composition of 16 different butters available on Polish market were investigated. The cholesterol content in butter fat ranged from 176.8 to 264.8 mg/100 g of fat and in two samples of milk fat β‐sitosterol was found. The total saturated fatty acid (SFA) content in milk fat was 67.1–73.5%, monounsaturated fatty acid 24.5–30.5% and polyunsaturated fatty acid was 1.2–2.0%. Abnormalities in fatty acid profiles, e.g. high concentration of linoleic fatty acid, were found in two butters. These abnormalities were also determined in TAG profiles. The examination of tocopherols in butter fat confirmed that two products were adulterated by the addition of plant oils because they contained δ‐tocopherol which is typical for plant origin foodstuffs. The methods described are useful for investigating milk fat adulterations, and the most efficient are analysis of sterols and tocopherols composition. Practical applications: The described methods are useful for investigating adulteration of milk fat. Traditional strategies rely on examination of fatty acids methyl esters and TAG; these methods have some disadvantages. Due to the variability of fatty acid composition of milk fat and because TAG analysis is complex and time consuming, FA analysis is not an efficient approach for butter authentication. The most efficient method for butter authentication is qualitative and quantitative analysis of sterols and tocopherols. This analysis will determine if components of plant origin were used for butter production.     

XPS study of reductively and non-reductively modified coals

Two demineralised coals: Mequinenza and Illinois No. 6 have been subjected to reduction and reductive methylation in the potassium/liquid ammonia system and to non-reductive methylation by the Liotta method. The initial coals and the products obtained have been analysed by classical chemical methods and by the X-ray photoelectron spectroscopy (XPS) method. The coal surface has been found susceptible to oxidation by atmospheric oxygen, but the differences in the elemental composition between the surface and the bulk sample proved small. Deconvolution of the XPS spectrum has shown that the dominant form of oxygen in all samples is ether and hydroxyl oxygen and the dominant form of nitrogen is pyrrolic nitrogen. It has also been shown that the main sulphur species in the initial Mequinenza coal is sulphidic sulphur, while Illinois No. 6 is richer in thiophenic systems. The results have confirmed an earlier finding that modification of coals in the potassium/liquid ammonia system leads to elimination of sulphur from some thiophene compounds.     

Parallel hybrid metaheuristics for the flexible job shop problem

A parallel approach to flexible job shop scheduling problem is presented in this paper. We propose two double-level parallel metaheuristic algorithms based on the new method of the neighborhood determination. Algorithms proposed here include two major modules: the machine selection module refer to executed sequentially, and the operation scheduling module executed in parallel. On each level a metaheuristic algorithm is used, therefore we call this method meta²heuristics. We carry out a computational experiment using Graphics Processing Units (GPU). It was possible to obtain the new best known solutions for the benchmark instances from the literature.     

Activated Carbon Modified with Different Chemical Agents as a Catalyst in the Dehydration and Dehydrogenation of Isopropanol

Activated carbons modified with different chemical agents such as HNO₃, H₂SO₄, peroxyacetic acid (PAA), air, NH₃ and Cl₂ have been tested as catalysts in decomposition (dehydration and dehydrogenation) of isopropanol. The majority of the samples obtained have been characterised by well-developed microporous surface with a small contribution of mesopores (8–18%). The influence of the surface area of the samples on their catalytic performance has been insignificant. The carbon oxidation with oxidants in the liquid or gas phase leads to an increased catalytic activity and the dominant process is dehydration of the alcohol studied. Carbon modification by contact with gas ammonia or chlorine results in a decrease in the catalytic activity and a significant increase in the contribution of dehydrogenation of isopropanol. It has been shown that such behaviour of the catalysts has been a consequence of changes in the acid-base character of the carbons induced by their modification.     

Decomposition of methane in the presence of ethanol over activated carbon catalyst

The interest in hydrogen as a potential fuel of the future has stimulated development of new technologies of its production. The main method of hydrogen production is based on the process of steam reforming of methane, but recently increasing attention has been paid to the catalytic decomposition of methane (CDM) whose advantage is its pro-ecological character. This reaction, besides hydrogen, produces also catalytically low-active carbonaceous deposit which settles on the surface of the catalyst and leads to its deactivation. The study reported is an attempt at suppressing the catalyst deactivation by developing a method leading to formation of carbonaceous deposit potentially active in CDM process. For this purpose, it was proposed that the reaction system would contain methane and ethanol. Simultaneous decomposition of these two substances was performed in parallel at three temperatures of 750, 850 or 950 °C. The catalyst was activated carbon obtained from the hazelnut shells. The addition of ethanol was found to have a positive effect on the course of CDM, leading to an increase in the amount of hydrogen produced and to stabilisation of the catalyst activity at a high level.     

Influence of ethylene on carbon-catalysed decomposition of methane

Catalytic decomposition of methane is a much promising pro-ecological method of hydrogen production. However, the drawback of this method is fast deactivation of the catalyst by deposition of a low-active methane-originated carbon on its surface. In this study an attempt has been made to reduce the process of catalyst deactivation by adding admixture of ethylene to methane directed to the reactor. The study has been performed on the activated carbon obtained by Na₂CO₃ activation of pine wood and two commercial types of activated carbons. All the carbon types have been subjected to ultimate analysis, determination of the surface area and pore structure. It has been shown that ethylene also forms a carbonaceous deposit but in contrast to the methane-originated deposit the ethylene-originated one shows good catalytic properties in the reaction of methane decomposition. The addition of 20% ethylene seems to be optimum for ensuring high yield of hydrogen for a long time. The ethylene admixture addition is the more effective the higher the temperature of the process.