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Item type:Publication, Access status: without files , New CAP Reduction Mechanisms for IEEE 802.15.4 DSME to Support Fluctuating Traffic in IoT SystemsIn 2015, the IEEE 802.15.4 standard was expanded by the Deterministic and Synchronous Multi-Channel Extension (DSME) to increase reliability, scalability and energy-efficiency in industrial applications. The extension offers a TDMA/FDMA-based channel access, where time is divided into two alternating phases, a contention access period (CAP) and a contention free period (CFP). During the CAP, transmission slots can be allocated offering an exclusive access to the shared medium during the CFP. The fraction of CFP’s time slots in a dataframe is a critical value, because it directly influences agility and throughput. A high throughput demands that the CFP is much longer than the CAP, i.e., a high value of tau, because application data is only sent during the CFP. High agility is given if the expected waiting time to send a CAP message is short and that the length of the CAPs are long enough to accommodate necessary GTS negotiations, i.e., a low value of tau. Once DSME is configured according to the needs of an application, tau can only assume one of two values and cannot be changed at run-time. In this paper, we propose two extensions of DSME that allow to adopt tau to the current traffic pattern. We show theoretically and through simulations that the proposed extensions provide a high degree of responsiveness to traffic fluctuations while keeping the throughput high.Publicationtype: Conference Paper71 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Antioxidant activity of deodorizer distillate fractions in rapeseed oilFractions of rapeseed oil deodorizer distillate containing vinylsyringol and its dimer, which are degradation products of sinapic acid, and other phenolic compounds were investigated for their potential use as antioxidants in refined rapeseed oil. Vinylsysringol, vinylsyringol dimer (VSD), and sinapic acid could effectively inhibit the formation of hydroperoxides, propanal, and hexanal in rapeseed oil triglycerides during storage at 40°C in the dark and at 25°C under light. In the presence of tocopherol, the addition of VSD increased the oxidative stability considerably at low tocopherol concentrations (25 μM) and if the VSD concentration was 10–20 times as high as the tocopherol concentration. The addition of polyphenolic rich fractions of the deodorizer distillate to commercial rapeseed oil resulted in slightly accelerated lipid oxidation in the dark at 40°C but did not influence the formation of hydroperoxides under light at 25°C. Practical applications: This study does not give any implications to change the process conditions during refining in a way that VSD would be removed from the oil. On the other hand, the fractions could be added for their positive health effects or as flavouring in savory products without jeopardizing the storage stability of the oil. Fractions of rapeseed oil deodorizer distillate rich in phenolic compounds were investigated for their potential use as antioxidants in rapeseed oil. The isolated compounds effectively inhibited lipid oxidation in the dark and under light. In the presence of tocopherol, the addition of the dimer increased the oxidative stability considerably at low tocopherol and high vinly syringol dimer concentrations. The addition of polyphenolic rich fractions of the deodorizer distillate to commercial rapeseed oil resulted in slightly accelerated lipid oxidation in the dark at 40°C but did not influence the formation of hydroperoxides under light at 25°C.Publicationtype: Journal Article231 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Advances in mathematical modeling of supercritical extraction processes(Nova Science Publishers, Incorporated, 2014-04-01); ; ; A new trend in mathematical modeling of supercritical extraction process from plant material is presented.The most of the previously published models considered properties of the fixed bed of plant material during the extraction to be constant. This assumption might be quite true in the case of plant materials with relatively low quantity of extractables. However, the fixed bed property change may occur in the case of extraction from material with high quantities of extractables. Recently, mathematical model which took into account particle density, bed porosity and particle diameter as variables was derived. In this chapter, the model is further improved by introducing variable solubility of the extract in supercritical fluid. On the basis of new experimental results on the binary equilibrium of the system supercritical fluid - extract present in solid, a relationship between solubility in supercritical fluid and oil content in solid was established. The new model was derived which took into account particle density, bed porosity, particle diameter and solubility in supercritical fluid as variables. The model was verified on results from experiments in which the kintecis of supercritical extraction from rapseed was analyzed. Parameters of the model showed expected behaviour with respect to the change of particle size. Further analysis, shown in this chapter, showed that, if the dependency of solubility from the concentration in the solid phase is not accounted for, the model tends to overestimate the yield of the extraction.The new model is so far, the most realistic model and one of the most demanding models regarding experimental work and mathematical tools for the description of mass transfer in fixed beds.Publicationtype: Book Part827 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Influence of different pre-treatment methods on isolation of extracts with strong antibacterial activity from lichen Usnea barbata using carbon dioxide as a solvent(Elsevier, 2013-01-24); ; ; ; Multiplication and spreading of multiresistant pathogenic bacteria that cause fatal infections in humans and animals have boosted research on implementation of newer technologies for producing natural substances with strong antibacterial activities. In this study, SFE from lichen Usnea barbata was investigated for different pre-treatment methods with respect to extracts' yield, usnic acid recovery and antibacterial activity against more than thirty methicillin resistant staphylococci strains. Extraction of U. barbata with subcritical carbon dioxide was studied as well. Extraction yield, usnic acid content and antibacterial activity of the extracts were strongly affected by the pre-treatment method. Intensive pre-treatment methods such as flaking and cutting + grinding caused a considerable comminution of the lichen thallus and enabled high extraction yields. On the other hand, mild pre-treatment of the lichen such as impact + shearing enabled isolation of extracts with lower MIC values. Experimental results indicated that extraction with liquid carbon dioxide at 30 MPa and 25 °C was the most favorable condition at which a satisfactory high extraction yield was obtained (2.08%). Extract isolated with liquid carbon dioxide had a high usnic acid content in the extract (632 g/kg) and a very strong antibacterial activity (average MIC of 19.11 μg/mL). Antibacterial activity of all the extracts against tested strains was comparable to the pure usnic acid or even stronger. This study indicated a potential use of the supercritical extracts of U. barbata in pharmaceutical formulations for treatment of infections caused by staphylococci. © 2013 Elsevier B.V.Publicationtype: Journal Article108 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Application of short path distillation for recovery of polyphenols from deodorizer distillate(Wiley-VCH, 2011-07); ; ; ; During physical refining of oil derived from 'high temperature short time' (HTST) pretreated rapeseeds, polyphenols are separated from the oil during deodorization and accumulate together with other high-value minor compounds in the so-called deodorizer distillate. For recovery of these compounds single-stage and multistage short path distillations were carried out in a laboratory scale apparatus at evaporation temperatures between 110 and 170°C and pressures between 0.006 and 0.01mbar. In addition, the removal of traces of pesticides from rapeseed deodorizer distillate was investigated. It was observed that these compounds can be separated from deodorizer distillate by means of short path distillation very effectively. On the basis of these experiments, a recovery process for polyphenols was proposed involving short path distillation, acid catalyzed esterification with methanol, solvent crystallization and solvent extraction processes. The final product was a polyphenol enriched extract containing about 14% of polyphenols. A polyphenol recovery of 50% is considered to be reachable and fractions rich in tocopherols and sterols may be obtained as by-products. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Publicationtype: Journal Article37 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Dissolving carbon dioxide in high viscous substrates to accelerate biocatalytic reactionsSolvent free biotransformation of polyglycerol-3 and lauric acid yields polyglycerol-3-laurate and water. This conversion can be catalyzed by Novozym 435. However, the performance is limited by the viscosity of polyglycerol as well as of polyglycerol-3-laurate. A decrease of viscosity by increasing reaction temperature is only possible in a certain temperature range because of the limited stability of the applied enzyme. By dissolving high dense carbon dioxide into the reaction system the viscosity could be reduced, keeping the temperature at an acceptable level at the same time. Thus the reaction rate was increased by a factor of 4 while working at a pressure of 280 bar and 60°C. © 2011 Wiley Periodicals, Inc.Publicationtype: Journal ArticleScopus© Citations 4 21