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Technical Reports | 2016

Technology Overview

Strasser C. Technology Overview. New York State Wood Heat Report: An Energy, Environmental, and Market Assessment - Final Report. April 2016. Chapter 8; 141-206.

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Peer Reviewed Scientific Journals | 2016

The influence of oxygen availability on off-gassing rates of emissions from stored wood pellets

Meier F, Sedlmayer I, Emhofer W, Wopienka E, Schmidl C, Haslinger W, Hofbauer H. The influence of oxygen availability on off-gassing rates of emissions from stored wood pellets. Energy & Fuels. 18 February 2016;30(2): 1006-1012.

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The phenomenon of off-gassing from wood pellets during storage has been the cause of several, in some cases fatal, accidents due to toxic atmospheres in storages. To optimize safety measures the nature of the responsible processes needs to be clarified. In this study the impact of O2 availability, which is a decisive factor for the presumed oxidation of fatty acids, is pointed out. Off-gassing rates of CO, CO2, VOC, and CH4 of pellets at relatively constant O2 levels of approximately 35%, 20%, and <1% over a period of 20 d at approximately 295 K were investigated. For this purpose 7 kg of spruce pellets was stored under simulated ventilation of the atmosphere in a 31 L tank. Gas concentrations were determined every 24 h by GC-FID/TCD. Compared to the mean emission rates at 35% O2 of CO (0.22 mg kg–1pelletsd.b. in 24 h) and CO2 (0.76 mg kg–1pelletsd.b. in 24 h) the lowest O2 concentration of <1% resulted in a significant reduction of off-gassing rates of 40% for both gases. In contrast the release rates of VOCs and also CH4 decreased with the higher O2 concentration (0.035 to 0.025 mg kg–1pelletsd.b. in 24 h; 0.0085 to 0.0061 mg kg–1pelletsd.b. in 24 h), presumably, because of increased onward reactions to CO and CO2. Since off-gassing was not prevented by the lack of O2 (<1% O2-trial) it is assumed that the O2 required for the reactions originated from the biomass itself. During the storage of pellets at 20% O2, emission rates of CO (0.18 mg kg–1pelletsd.b. in 24 h) and CO2 (0.79 mg kg–1pelletsd.b. in 24 h) at the start decreased by more than 20% and those for VOCs (0.032 mg kg–1pelletsd.b. in 24 h) by almost 30% after 3 weeks. It can be assumed that in ventilated storages the reactivity and thus a potential risk from off-gases from wood pellets decreases considerably in only a few weeks. The effects of aging, in terms of declining reactivity at relatively constant tank conditions, on off-gassing rates could be clarified for the first time. A realistic development of the decline of reactivity of the material itself could be determined.


Peer Reviewed Scientific Journals | 2016

The interplay of self-reflection, social interaction and random events in the dynamics of opinion flow in two-party democracies

Lichtenegger K, Hadzibeganovic T. The interplay of self-reflection, social interaction and random events in the dynamics of opinion flow in two-party democracies. International Journal of Modern Physics C. 1 May 2016;27(5).

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We propose a continuous process opinion formation model to study the dynamics of a multi-level relationship between voters, political parties, and facts in two-party democratic elections. In our model, opinions can take any real value between two extremes and an unaligned, moderate opinion state without a preference. Starting with a random opinion configuration, individual voter opinions evolve and change over time due to self-reflection, inter-personal communication, external media influence, and noise. Parties are influenced by their own ideologies, facts, and voters’ opinions. Elections are held periodically and the party that is closer in opinion to the majority of voters forms the new government. The government policy is then expected to be in proximity to the voter opinions and the policies of the currently ruling political party. We analyze the tension of opinions as a measure of how dramatically opinions can disagree within a given sample of voters and the success of the government and parties as the degree of coincidence between the policies and facts. Our model generates realistic quasi-periodic alternations between incumbents and challengers that are typical for two-party systems. Moreover, our model shows that relative to other voters’ strategies, conscious voting can lead to more successful governments of not only fact-oriented but also pragmatic and balanced political parties, irrespective of the strategies of the competing opposition parties. In addition, our simulations uncover several interesting features including less victories for strictly ideological or fact-oriented parties unless they include some aspects of populism or pragmatism. In this sense, our model can also describe situations where election outcomes are not necessarily based on votes for the current programs of competing parties and their placement on relevant issues, but instead result from voters’ dissatisfaction with the previous government and the votes against it.


Read More: http://www.worldscientific.com/doi/abs/10.1142/S0129183116500650

Peer Reviewed Scientific Journals | 2016

The Virtual Biomass Grate Furnace - An Overall CFD Model for Biomass Combustion Plants

Ali Shiehnejadhesar, Ramin Mehrabian, Robert Scharler, Christoph Hochenauer. The Virtual Biomass Grate Furnace - An Overall CFD Model for Biomass Combustion Plants. 24rd European Biomass Conference & Exhibition (poster).

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This paper presents the virtual biomass grate furnace, which comprises of comprehensive CFD models of all relevant processes for the simulation of biomass grate furnaces. The models consist of a 3D packed bed model, a gas phase combustion model for laminar to highly turbulent flows and a model to account for the influence of the flue gas streaks arising from the fuel bed in the freeboard. The simulation results of a 20 kW underfeed stoker furnace show that the overall CFD model is able to provide valuable insight on the processes occurring in the packed bed and freeboard and their interactions.


Contributions to trade journals | 2016

The wood pellet market in Austria: A structural market model analysis

Christa Kristöfel, Christoph Strasser, Erwin Schmid, Ulrich B. Morawetz, The wood pellet market in Austria: A structural market model analysis, Energy Policy, Volume 88, January 2016, Pages 402-412,

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Peer Reviewed Scientific Journals | 2016

Thermal Stability of Bed Particle Layers on Naturally Occurring Minerals from Dual Fluid Bed Gasification of Woody Biomass

Kuba M, He H, Kirnbauer F, Skoglund N, Boström D, Öhman M, Hofbauer H. Thermal Stability of Bed Particle Layers on Naturally Occurring Minerals from Dual Fluid Bed Gasification of Woody Biomass. Energy & Fuels. 20 October 2016;30(10): 8277-8285.

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The use of biomass as feedstock for gasification is a promising way of producing not only electricity and heat but also fuels for transportation and synthetic chemicals. Dual fluid bed steam gasification has proven to be suitable for this purpose. Olivine is currently the most commonly used bed material in this process due to its good agglomeration performance and its catalytic effectiveness in the reduction of biomass tars. However as olivine contains heavy metals such as nickel and chromium no further usage of the nutrient-rich ash is possible and additional operational costs arise due to necessary disposal of the ash fractions. This paper investigates possible alternative bed materials and their suitability for dual fluid bed gasification systems focusing on the behavior of the naturally occurring minerals olivine, quartz and K-feldspar in terms of agglomeration and fractionation at typical temperatures. To this end samples of bed materials with layer formation on their particles were collected at the industrial biomass combined heat and power (CHP) plant in Senden, Germany, which uses olivine as the bed material and woody biomass as feedstock. The low cost logging residue feedstock contains mineral impurities such as quartz and K-feldspar which become mixed into the fluidized bed during operation. Using experimental analysis and thermochemical it was found that the layers on olivine and K-feldspar showed a significantly lower agglomeration tendency than quartz. Significant fractionation of particles or their layers could be detected for olivine and quartz, whereas K-feldspar layers were characterized by a higher stability. High catalytic activity is predicted for all three minerals once Ca-rich particle layers are fully developed. However quartz may be less active during the build-up of the layers due to lower amounts of Ca in the initial layer formation.
 


Conference Papers | 2016

Thermochemische Behandlung eines niederkalorischen Reststoffes zur Gewinnung von Sekundärrohstoffen

Meirhofer M, Dißauer C, Strasser C, Kranner R, Wartha C. Thermochemische Behandlung eines niederkalorischen Reststoffes zur Gewinnung von Sekundärrohstoffen. e-nova 2016 (oral presentation). November 2016, Pinkafeld, Austria.

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Reviewed Conference Papers | 2016

Toxicological characterization of particulate emissions from straw, Miscanthus, and poplar pellet combustion in residential boilers

Kasurinen S, Jalava PI, Uski O, Happo MS, Brunner T, Mäki-Paakkanen J, Jokiniemi J, Obernberger I, Hirvonen MR. Toxicological characterization of particulate emissions from straw, Miscanthus, and poplar pellet combustion in residential boilers. Aerosol Science and Technology. 2 January 2016;50(1): 41-51.

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Wood pellets have been used in domestic heating appliances for three decades. However, because the share of renewable energy for heating will likely rise over the next several years, alternative biomass fuels, such as short-rotation coppice or energy crops, will be utilized. We tested particulate emissions from the combustion of standard softwood pellets and three alternative pellets (poplar, Miscanthus sp., and wheat straw) for their ability to induce inflammatory, cytotoxic, and genotoxic responses in a mouse macrophage cell line. Our results showed clear differences in the chemical composition of the emissions, which was reflected in the toxicological effects. Standard softwood and straw pellet combustion resulted in the lowest PM1 mass emissions. Miscanthus sp. and poplar combustion emissions were approximately three times higher. Emissions from the herbaceous biomass pellets contained higher amounts of chloride and organic carbon than the emissions from standard softwood pellet combustion. Additionally, the emissions of the poplar pellet combustion contained the highest concentration of metals. The emissions from the biomass alternatives caused significantly higher genotoxicity than the emissions from the standard softwood pellets. Moreover, straw pellet emissions caused higher inflammation than the other samples. Regarding cytotoxicity, the differences between the samples were smaller. Relative toxicity was generally highest for the poplar and Miscanthus sp. samples, as their emission factors were much higher. Thus, in addition to possible technical problems, alternative pellet materials may cause higher emissions and toxicity. The long-term use of alternative fuels in residential-scale appliances will require technological developments in both burners and filtration.


Peer Reviewed Scientific Journals | 2016

Two-stage cultivation of N-rich and N–deprived Acutodesmus obliquus biomass: Influence of cultivation and dewatering methods on microalgal biomass used in anaerobic digestion

Gruber M, Nussbaumer M, Jerney J, Ludwig I, Zohar E, Lang I, Bochmann G, Schagerl M, Obbard JP, Fuchs W, Drosg B. Two-stage cultivation of N-rich and N–deprived Acutodesmus obliquus biomass: Influence of cultivation and dewatering methods on microalgal biomass used in anaerobic digestion. Algal Research. July 2016;17: 105-112.

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Conference contributions | 2015

"Investigations on the catalytic activity of bed material coating regarding the water-gas-shift reaction and the steam reforming of model compounds for lighter and heavier hydrocarbons"

Kuba M, Havlik F, Kirnbauer F, Hofbauer H. Investigations on the catalytic activity of bed material coating regarding the water-gas-shift reaction and the steam reforming of model compounds for lighter and heavier hydrocarbons, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (oral presentation)

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Peer Reviewed Scientific Journals | 2015

Acutodesmus obliquus as a benchmark strain for evaluating methane production from microalgae: Influence of different storage and pretreatment methods on biogas yield

Gruber-Brunhumer MR, Jerney J, Zohar E, Nussbaumer M, Hieger C, Bochmann G, Schagerl M, Obbard JP, Fuchs W, Drosg B. Acutodesmus obliquus as a benchmark strain for evaluating methane production from microalgae: Influence of different storage and pretreatment methods on biogas yield. Algal Research. 01 November 2015;12:230-238.

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Peer Reviewed Scientific Journals | 2015

Air staging to reduce emissions from energy crop combustion in small scale applications

Carroll JP, Finnan JM, Biedermann F, Brunner T, Obernberger I. Air staging to reduce emissions from energy crop combustion in small scale applications. Fuel. 2015;155:37-43.

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The results of experimental work to investigate the effects of air staging on emissions from energy crop combustion in small scale applications are presented. Five different biomass fuels (wood, willow, miscanthus, tall fescue and cocksfoot) were combusted in a small scale (35 kW) biomass boiler and three different tests looking at the effects of (1) air ratio in the primary combustion chamber (primary air ratio), (2) temperature in the primary combustion chamber, and (3) overall excess air ratio, on NOx and particulate emissions were conducted. It was shown that by varying the primary air ratio, NOx emission reductions of between 15% (wood) and 30% (Miscanthus) and PM1 reductions of between 16% (cocksfoot) and 26% (wood) were possible. For all fuels, both NOx and particulate emissions were minimised at a primary air ratio of 0.8. Particulate emissions from miscanthus increased with increasing temperature in the primary combustion chamber, NOx emissions from Miscanthus and from willow also increased with temperature. Overall excess air ratio has no effect on emissions as no significant differences were found for any of the fuels. Emissions of particulates and oxides of nitrogen from a wide range of biomass feedstocks can be minimised by optimising the primary air ratio and by maintaining a temperature in the primary combustion chamber of approximately 900 °C.


Peer Reviewed Scientific Journals | 2015

Anaerobic digestion of thermal pretreated brewers' spent grains

Bochmann G, Drosg B, Fuchs W. Anaerobic digestion of thermal pretreated brewers' spent grains. Environmental Progress and Sustainable Energy. 2015;34(4):1092-6.

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Anaerobic digestion offers a good opportunity to degrade residues from breweries to biogas. To improve the anaerobic degradation process thermal pretreatment of brewers' spent grains (BSG) offers the opportunity to increase degradation rate and biogas yield. Aim of the work is to show the influence of the thermal pretreatment of BSG to anaerobic digestion. BSG were pretreated at different temperature levels from 100 to 200°C. The biogas production of thermally pretreated BSG lies between 30 and 40% higher than for untreated reference. The temperature of the pretreatment process has a significant influence on the degradation rate or gas yield, respectively. Up to a temperature of 160°C, the biogas yield rises. Temperatures over 160°C result in a slower degradation and decreasing biogas yield. Substrate with and without pretreatment gave a daily biogas yield of 430 and 389 Nm3 × kg-1 VS, respectively. Batch analysis of the biochemical methane potential gives a total methane yield of 409.8 Nm3 CH4 × kg-1 VS of untreated brewers' spent grains and 467.6 Nm3 CH4 × kg-1 VS of the pretreated samples. For pretreatment energy balance estimation has been carried out. Without any heat recovery demand is higher than the energy surplus resulting from pretreatment of BSG. With energy recovery by heat exchanger the net energy yield could be increased to 38.87 kWh × kg-1 FM or 8.81%. © 2015 American Institute of Chemical Engineers Environ Prog.


Peer Reviewed Scientific Journals | 2015

Application of an empirical model in CFD simulations to predict the local high temperature corrosion potential in biomass fired boilers.

Gruber T, Scharler R, Obernberger I. Application of an empirical model in CFD simulations to predict the local high temperature corrosion potential in biomass fired boilers. Biomass and Bioenergy. Volume 79, August 2015, Pages 145-154.

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To gain reliable data for the development of an empirical model for the prediction of the local high temperature corrosion potential in biomass fired boilers, online corrosion probe measurements have been carried out. The measurements have been performed in a specially designed fixed bed/drop tube reactor in order to simulate a superheater boiler tube under well-controlled conditions. The investigated boiler steel 13CrMo4-5 is commonly used as steel for superheater tube bundles in biomass fired boilers. Within the test runs the flue gas temperature at the corrosion probe has been varied between 625 °C and 880 °C, while the steel temperature has been varied between 450 °C and 550 °C to simulate typical current and future live steam temperatures of biomass fired steam boilers. To investigate the dependence on the flue gas velocity, variations from 2 m·s−1 to 8 m·s−1 have been considered. The empirical model developed fits the measured data sufficiently well. Therefore, the model has been applied within a Computational Fluid Dynamics (CFD) simulation of flue gas flow and heat transfer to estimate the local corrosion potential of a wood chips fired 38 MW steam boiler. Additionally to the actual state analysis two further simulations have been carried out to investigate the influence of enhanced steam temperatures and a change of the flow direction of the final superheater tube bundle from parallel to counter-flow on the local corrosion potential.


Conference contributions | 2015

Application of numerical modelling to biomass grate furnaces

Mehrabian R, Shiehnejadhesar A., Scharler R. Application of numerical modelling to biomass grate furnaces. Internation conference on advances in mechanical engineering, Istanbul 2015.

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The direct combustion of the biomass is the most advanced and mature technology in the field of energetic biomass utilisation. The legislations on the amount of emitted pollutants and the plant efficiency of biomass combustion systems are continually being restricted. Therefore constant improvement of the plant efficiency and emission reduction is required Numerical modelling is gaining increasing importance for the development of biomass combustion technologies. In this paper an overview about the numerical modelling efforts deal with the most relevant phenomena in biomass grate firing systems is given. The numerical modelling results in a deeper understanding of the underlying processes in biomass combustion plants. Therefore, it leads to a faster and safer procedure of development of a new technology.


Conference contributions | 2015

AshMelT Project Background – Why this work was necessary

Schwabl M, Wopienka E. AshMelT Workshop “AshMelT Project Background – Why this work was necessary” (held during de World Sustainable Energy Days 2015), 25th-27th of February, Wels, Austria, 2015.

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Other Presentations | 2015

Aspects of microalgal biomass as feedstock in biogas plants

Gruber M, Zohar E, Jerney J, Ludwig I, Bochmann G, Nussbaumer L, Montgomery L, Fuchs W, Drosg B, Schöpp T, Obbard JP. Aspects of microalgal biomass as feedstock in biogas plants, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (visual presentation)

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Conference contributions | 2015

Ausbrandregelung durch zusätzliche Messung des Kohlenmonoxidgehalts im Rauchgas

Bischof J, Gölles M, Obernberger I, Baumbach G. Ausbrandregelung durch zusätzliche Messung des Kohlenmonoxidgehalts im Rauchgas. 27. Deutscher Flammentag. September 2015, Clausthal, Germany.

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Conference contributions | 2015

Benz(a)pyrene emission measurements in flue gas from residential biomass combustion appliances

Meier F, Schwabl M, Sedlmayer I, Kleinhappl M, Schmidl C, Haslinger W. Benz(a)pyrene emission measurements in flue gas from residential biomass combustion appliances, 23rd European Biomass Conference 2015, 1st-4th of June 2015, Vienna, Austria. (visual presentation)

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Peer Reviewed Scientific Journals | 2015

Bioavailability of essential trace elements and their impact on anaerobic digestion of slaughterhouse waste

Ortner M, Rameder M, Rachbauer L, Bochmann G, Fuchs W. Bioavailability of essential trace elements and their impact on anaerobic digestion of slaughterhouse waste. Biochemical Engineering Journal. 15 July 2015;99:107-113.

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Conference contributions | 2015

Biomasse der Zukunft – Bioenergie der Zukunft?

Wopienka E. Biomasse der Zukunft – Bioenergie der Zukunft? Internationale Konferenz auf Schloss Weinzierl 2015, 29th of Januar 2015, Wieselburg, Austria.

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Conference Papers | 2015

Challenges toward model-based control for hybrid biomass-based heating systems

Unterberger V, Gölles M. Challenges toward model-based control for hybrid biomass-based heating systems. e-nova 2015. November 2015, Pinkafeld, Austria. Unterberger V, Gölles M. Challenges toward model-based control for hybrid biomass-based heating systems. Nachhaltige Gebäude, Graz. Leykam. 2015;10:393-404.

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Biomass boilers used for residential heating and hot water supply are typically combined with a buffer storage and solar collectors. However, the annual utilization rates typically achieved with such systems are far below those theoretically possible, which is mainly because of the often poor quality of both the individual control of the components as well as the high-level control of the entire system. The control strategies typically applied consist of simple decou-pled control circuits with linear controllers, which cannot deal with the mostly nonlinear and coupled behaviour of the components and thus do not ensure their reasonable interaction. The most appropriate approach to address these challenges is the application of model-based control techniques. Within the paper an overview of mathematical models suitable for control purposes, a simple to implement load forecasting method as well as control strate-gies for both the individual components and the entire system are presented. Future chal-lenges for a practical implementation of this novel approach are discussed in the outlook sec-tion.


Peer Reviewed Scientific Journals | 2015

Closing the Nutrient Cycle in Two-Stage Anaerobic Digestion of Industrial Waste Streams

Rachbauer L, Gabauer W, Scheidl S, Ortner M, Fuchs W, Bochmann G. Closing the Nutrient Cycle in Two-Stage Anaerobic Digestion of Industrial Waste Streams. Energy Fuels 2015;29(7):4052-4057.

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Industrial waste streams from brewing industries and distilleries provide a valuable but largely unused alternative substrate for biogas production by anaerobic digestion. High sulfur loads in the feed caused by acidic pretreatment to enhance bioavailability are responsible for H2S formation during anaerobic digestion. Microbiological oxidation of H2S provides an elegant technique to remove this toxic gas compound. Moreover, it allows for recovery of sulfuric acid, the final product of aerobic sulfide oxidation, as demonstrated in this study. Two-stage anaerobic digestion of brewer’s spent grains, the major byproduct in the brewing industry, allows for the release of up to 78% of total H2S formed in the first pre-acidification stage. Desulfurization of such pre-acidification gas in continuous acidic biofiltration with immobilized sulfur-oxidizing bacteria resulted in a maximum H2S elimination capacity of 473 g m–3 h–1 at an empty bed retention time of 91 s. Complete H2S removal was achieved at inlet concentrations of up to 6363 ppm. The process was shown to be very robust, and even after an interruption of H2S feeding for 10 days, excellent removal efficiency was immediately restored. A maximum sulfate production rate of 0.14 g L–1 h–1 was achieved, and a peak concentration of 4.18 g/L sulfuric acid was reached. Further experiments addressed the reduction of fresh water and chemicals to minimize process expenses. It was proven that up to 50% of mineral medium that is required in large amounts during microbiological desulfurization can be replaced by the liquid fraction of the digestate. The conducted study demonstrates the viability of microbial sulfur recovery with theoretical recovery rates of up to 44%.


Peer Reviewed Scientific Journals | 2015

Combustion related characterisation of Miscanthus peat blends applying novel fuel characterisation tools

Sommersacher P, Brunner T, Obernberger I, Kienzl N, Kanzian W. Combustion related characterisation of Miscanthus peat blends applying novel fuel characterisation tools. Fuel 2015;158:253-262.

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Conference contributions | 2015

Control of a Biomass-Furnace Based on Input-Output-Linearization

Schörghuber C, Reichhartinger M, Horn M, Gölles M, Seeber R. Control of a Biomass-Furnace Based on Input-Output-Linearization, European Control Conference 2015, 15th-17th of July 2015, Linz, Austria. p 3513-3518.

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