Finite state automata: Dynamic task environments in problem solving research.

This paper presents a new research paradigm for analysing human learning in dynamic task environments based on the theory of finite-state automata. Some of the advantages of the approach are outlined. (1) It is possible to design classes of formally well-described dynamic task environments instead of idiosyncratic microworlds that are difficult if not impossible to compare. (2) The approach suggests assumptions about the mental representation of a discrete dynamic system. (3) The finite-state automata formalism suggests systematic and appropriate diagnostic procedures. (4) Using finite-state automata to design dynamic task environments, one does not have to give up the "ecological validity" appeal of computer-simulated scenarios. An experiment on the utility of an external memory support system with system complexity and type of memory support as independent variables is reported to illustrate the application of the formal framework. Systematically derived dependent variables reflect both system knowledge and control performance. The results suggest that the benefits due to the availability of the external aid vary as a function of the complexity of the task. Also, using reaction time measurements, priming phenomena have been found that point to the importance of sequentiality in the representation of discrete systems. It is concluded that the approach, although not entirely new in experimental psychology, awaits further exploration in research on human learning in dynamic task environments and promises to be a stimulating paradigm for both basic and applied research

Diskrete dynamische Systeme: Der Einfluß perzeptueller Merkmale auf Komposition und Transfer von Bediensequenzen

Es werden zwei Experimente berichtet, in denen der Einfluß der Gruppierung von Bedienelementen auf die Organisation und Nutzung von Bedienwissen untersucht wird. In Experiment 1 wurde zunächst geprüft, in welchem Ausmaß verschiedene Arten perzeptueller Strukturierungen der Bedienoberfläche eines abstrakten Automaten bei der Reproduktion von Bediensequenzen zur Induktion von Chunks führen. Der Einfluß der Strukturierung war nicht eindeutig und hing für verschiedene Modalitäten davon ab, ob die Sequenzen vorgeführt wurden oder durch Probieren selbst herausgefunden werden mußten. In Experiment 2 wurde untersucht, inwieweit Transferleistungen bei unterschiedlichen Bedingungen der Transferierbarkeit von Bedienwissen durch die perzeptuelle Strukturierung der Bedienelemente beeinflußt werden. In der Erwerbsphase wurde die Gelegenheit zur Komposition von Wissenselementen über zwei verschiedene Lernkriterien variiert. In der anschließenden Transferphase konnten entweder (1) die gesamte Teilsequenz innerhalb eines Bereichs, (2) zwei aufeinanderfolgende Teilsequenzen benachbarter Bereiche oder (3) einzelne Komponenten übertragen werden. Für den Transfer erwiesen sich sowohl die Bereichszugehörigkeit als auch das unmittelbare Aufeinanderfolgen von Komponenten als bedeutsam. Die Ergebnisse implizieren, daß nicht die Strukturierung der Bedienoberfläche per se, sondern die sich in der Zeit daraus ergebende Abfolge der Strukturierungsbereiche für Organisation und Nutzung von Wissen über entsprechende Sequenzen entscheidend ist

Influence of reactor type on production cost of fast pyrolysis bio-oil

The design of a fast pyrolysis reactor to convert biomass has a decisive influence on quality and yield of fast pyrolysis bio-oil (FPBO). Quality requirements are comparably low for the application of FPBO as gasifier fuel for subsequent conversion to synthesis gas, e.g. in the case of the bioliq® concept to convert (ash-rich) agricultural residues to drop-in, 2nd generation biofuels. Within this concept, one optimization parameter of fast pyrolysis is to maximize carbon yield in the liquid product while keeping product requirements that allow feeding into a high-pressurized entrained flow gasifier. This optimization space allows for a more flexible choice of reactor design. The aim of this study is to investigate the influence of reactor type on production cost of FPBO within above outlined framework, i.e. as feedstock for a downstream gasifier. The investigation will be based on two different type of reactors. First, a twin-screw mixing reactor (TSMR) is being considered, which resembles the actual realization of the 500 kg h-1 fast pyrolysis pilot unit that is being operated as part of the bioliq® project. Second, a fluidized bed reactor (FBR) will be compared to that, which represents state of the art technology of industrial fast pyrolysis units. One important difference between the two reactors is the necessity of a fluidizing agent in case of the FBR, which in turn influences process design and equipment size, specifically in the product recovery section. This additional (inert gas) volume flow is not required in the case of a mechanical mixing, as is the case in the chosen TSMR. At the same time it is obvious that there will be a significant difference in mixing conditions of biomass and heat carrier particles in the two types of reactors, which will translate to a difference in heating rate of the biomass particles. This in turn might affect FPBO quality and yield. Experiments have been conducted to compare FPBO yields from process development units that feature a TSMR and an FBR, respectively. No significant differences in FPBO yield have been observed. On the one hand this leads to the conclusion that the high heat transfer required to achieve one of the fast pyrolysis conditions (i.e. high temperature of primary pyrolysis inside the biomass particle) is comparable in both types of reactors. This could be explained by the high bulk density achieved during mechanical agitation as compared to that of a fluidized bed, which is capable of making up the lower mixing intensity if a proper ratio of biomass to heat carrier particles is kept. On the other hand, wheat straw (which is the ‘model’ feedstock for the bioliq® project) was used as feedstock in these experiments This choice might also lead to not observing differences between the two reactor types. Wheat straw is characterized by high ash content (around 8%) which increases the significance of secondary cracking reactions and thus lowers any effects of reactor type. Wheat straw also exhibits high heterogeneity which translates to increased standard deviation of the results (confirmed by multiple test runs) and an increased difficulty to detect differences in FPBO yield. Based on the experimental results, the effect of process design on FPBO production cost are reduced to investment and operation cost. Existing production cost calculations for the bioliq® concept have been reviewed and updated due to the currentness of the underlying data. Additionally, relevant process design changes and equipment cost will be implemented for consideration of an FBR instead of the TSMR. Finally, a sensitivity analysis is conducted to reflect changes in product yield based on available literature data for fast pyrolysis of wheat straw in order to account for the previously discussed uncertainty of the obtained experimental results

State of the art auger reactor design and scale up for biomass fast pyrolysis

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Modeling fast pyrolysis of waste biomass: Improving predictive capability

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Thermodynamic-based Solvent Selection for the Separation of Lignin- derived Molecules

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Overcoming challenges in fast pyrolysis of lignin: Strategies and experiments

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Challenges in Kinetic Parameter Determination for Wheat Straw Pyrolysis

Wheat straw is a renewable agricultural by-product that is currently underutilized in the production of bioenergy and bioproducts due to its high ash content, as well as high transport costs due to its low volumetric energy density. The thermogravimetric analysis of this material produces derivative curves with a single broad peak, making it difficult to identify the three conventional pseudo-components (cellulose, hemicellulose, and lignin), which is resolved using the second derivative to determine inflection points. Model-fitting methods and isoconversional methods were applied to determine the degradation kinetics of wheat straw at two different particle sizes, as well as that of a reference feedstock (beech wood), and the obtained values were used to divide the degradation curves to be compared to the experimental data. Seven different pyrolysis reaction networks from the literature were given a similar treatment to determine which provides the best estimation of the actual pyrolysis process for the case of the feedstocks under study. The impact of the potassium content in the feedstock was considered by comparing the original pathway with a modification dependent on the experimental potassium content and an estimated optimum value