Sometimes mathematics is different - studies on mathematical practices in electrical engineering

The six studies collected in this thesis deal with praxeological analyses of mathematical practices in a Signal Transmission module of an electrical engineering study programme. The research framework is the Anthropological Theory of the Didactic (ATD). Our analyses concern the introduction of the Dirac delta impulse in textbooks on signals and systems, the lecturer’s sample solution to an exercise on the envelope demodulator, and the lecturer’s sample solution and the students’ solutions to an exercise on amplitude modulation. Three research foci are developed in the collected studies. The first focus is The subject-specific reconstruction of mathematical practices (Hochmuth & Peters, 2021; Peters & Hochmuth, 2021). We analyse two exercises and the corresponding sample solutions given by the lecturer and students’ solutions. Based on methodological developments we were able to reconstruct aspects of two different mathematical discourses as well as how they interact within the analysed practices. We also propose a graphical representation of the results of our analyses. The second focus is The epistemological and philosophical relationship between mathematics and electrical engineering (Hochmuth & Peters, 2020, 2022). Our aim is to gain a better understanding of the mathematical practices involved in the introduction of the Dirac delta impulse in a textbook on signals and systems. We realised that certain mathematical steps could be better understood from an engineering point of view if historical-philosophical studies of the relationship between physics and mathematics were also taken into account. Here, we are not referring to the philosophical positions of students or lecturers. We are referring to philosophical studies that focus on the societal aspects that play a role in the historical concrete formation of practices. The case of the Dirac impulse is well suited to illustrate the fruitfulness of such studies for subject-specific analyses. Finally, the third focus is Revisiting the relationship between mathematics and electrical engineering, on how ideas for the development of teaching can be derived from the other two perspectives (Peters, 2022; Peters & Hochmuth, 2022). Looking back at our previous studies, we show how our research findings allow for a conceptualisation of the relationship between mathematics and engineering that differs from the standard application and modelling approaches. We also focus on the phenomenon of disconnectedness of the mathematical practices in mathematics service courses and engineering courses.Based on our analyses of engineering mathematical practices, we develop the idea of modifying exercises from a mathematics service course. The key feature of this approach is that it is an alternative to the usual approaches that propose the use of engineering application examples or the use of modelling tasks

Engineering mathematics - Reflections on the dialectics of in and for

Poster presented at the conference

Self-Efficacy of Beginning Counselors to Counsel Clients in Crisis

Crisis situations are becoming more and more prevalent in our society today, and as a result, counselors should be aware of the overarching effects of various crisis situations and how they can affect their clients. The purpose of this study was to examine the effect of preparedness on beginning counselors’ levels of self-efficacy and their perceived abilities to handle crisis interventions. A purposeful sample of master’s-level counseling students, enrolled in a Crises Intervention Preparation course for Mental Health Responders, were administered the Counselor’s Self-Efficacy Scale to assess their levels of self-efficacy. Findings indicated that counseling students who studied theoretical strategies for approaching various crises, assessed the realities associated with their prospective client base, and tentatively planned flexible intervention models felt confident in their abilities to make effective decisions for supporting clients during crisis situations

Self-Efficacy of Beginning Counselors to Counsel Clients in Crisis

Crisis situations are becoming more and more prevalent in our society today, and as a result, counselors should be aware of the overarching effects of various crisis situations and how they can affect their clients. The purpose of this study was to examine the effect of preparedness on beginning counselors’ levels of self-efficacy and their perceived abilities to handle crisis interventions. A purposeful sample of master’s-level counseling students, enrolled in a Crises Intervention Preparation course for Mental Health Responders, were administered the Counselor’s Self-Efficacy Scale to assess their levels of self-efficacy. Findings indicated that counseling students who studied theoretical strategies for approaching various crises, assessed the realities associated with their prospective client base, and tentatively planned flexible intervention models felt confident in their abilities to make effective decisions for supporting clients during crisis situations

Hydrogenolysis of lignin in ZnCl₂ and KCl as an inorganic molten salt medium

Lignin can be converted into monomeric products with the aid of molten salt media. Molten zinc chloride (ZnCl₂)/potassium chloride (KCl) mixtures are suitable for this purpose. The application of an eutectic mixture with low melting points leads to similar main products as are obtained by pyrolysis. The hydrogenolysis of an organosolv lignin in molten salts of ZnCl₂/KCl was investigated as a function of reaction temperature, residence time, and lignin concentration, and the composition of liquid products and monophenols was analyzed by gas chromatography-mass spectrometry (GC-MS). The yields can be optimized by the proper selection of the reaction temperature. A longer residence time and higher lignin concentrations lead to increased formation of solid residues and gaseous products. The liquid products mainly consist of substituted phenols derived from lignins. Polymeric products are the result of condensation reactions (i.e., the formation of new C-C linkages in the course of secondary reactions)

Life cycle assessment (LCA) of a battery home storage system based on primary data

While the market for battery home storage systems (HSS) is growing rapidly, there are still few well-modelled life cycle assessment (LCA) studies available for quantifying their potential environmental benefits and impacts. Existing studies mainly rely on data for electric vehicles and often lack a thorough modelling approach, especially regarding the peripheral components. This paper presents a full cradle to grave LCA of a Lithium iron phosphate (LFP) battery HSS based on primary data obtained by part-to-part dismantling of an existing commercial system with a focus on the impact of the peripheral components. Additionally, alternative battery chemistries (Sodium ion battery (SIB) and two lithium nickel manganese cobalt oxides, (NMC811, and NMC622) are investigated under the consideration of the same periphery. This approach allows a comprehensive com parison between present and emerging cell chemistries that can be potentially considered for an HSS. The total greenhouse gas emissions of the HSS are 84 g CO2eq/KWh of electricity delivered over its lifetime in a residential PV application, or 31 g CO2eq/KWh over lifetime when excluding the use-phase impact. The peripheral components contribute between 37% and 85% to the total gross manufacturing impacts of the HSS, depending on the considered cell chemistry and the impact category. Especially the inverter plays an important role, and its impacts are significantly higher than those obtained when using the standard ecoinvent dataset, indicating that the contribution of power electronics might often be underestimated when using this dataset. In terms of cell chemistries, the considered SIB turns out to be not yet competitive with LIB chemistries due to its lower energy density and lifetime, but might become so when reaching similar lifetimes

Beurteilung unterschiedlicher Energiefruchtfolgen hinsichtlich ihrer Nachhaltigkeit und Rentabilität bei der Rohstoffversorgung von Biogasanlagen für die Region Mecklenburg – Vorpommern

Ziel ist es, einen nachhaltigen, umweltverträglichen Energiepflanzenanbau für die Region Mecklenburg-Vorpommern zu schaffen, unter dem Fokus der Ackerflächenkonkurrenz zwischen Energiepflanzen- und Lebensmittelanbau. Geprüft werden dafür 8 unterschiedliche Energiefruchtfolgen auf Ertrag, Methangasausbeute, Nährstoffkreisläufe, Humus- und Energiebilanz und ökonomische Gesichtspunkte. Gleichzeitig sollen Bewertungsschwachstellen von Analyseverfahren aufgezeigt werden und Denkanstöße für eine Neuentwicklung von Charakterisierungsmethoden ökologischer und ökonomischer Natur geben

Life cycle assessment (LCA) of a battery home storage system based on primary data

While the market for battery home storage systems (HSS) is growing rapidly, there are still few well-modelled life cycle assessment (LCA) studies available for quantifying their potential environmental benefits and impacts. Existing studies mainly rely on data for electric vehicles and often lack a thorough modelling approach, especially regarding the peripheral components. This paper presents a full cradle to grave LCA of a Lithium iron phosphate (LFP) battery HSS based on primary data obtained by part-to-part dismantling of an existing commercial system with a focus on the impact of the peripheral components. Additionally, alternative battery chemistries (Sodium ion battery (SIB) and two lithium nickel manganese cobalt oxides, (NMC811,and NMC622) are investigated under the consideration of the same periphery. This approach allows a comprehensive comparison between present and emerging cell chemistries that can be potentially considered for an HSS. The total greenhouse gas emissions of the HSS are 84 g CO2eq/KWh of electricity delivered over its lifetime in a residential PV application, or 31 g CO2eq/KWh over lifetime when excluding the use-phase impact. The peripheral components contribute between 37% and 85% to the total gross manufacturing impacts of the HSS, depending on the considered cell chemistry and the impact category. Especially the inverter plays an important role, and its impacts are significantly higher than those obtained when using the standard ecoinvent dataset, indicating that the contribution of power electronics might often be underestimated when using this dataset. In terms of cell chemistries, the considered SIB turns out to be not yet competitive with LIB chemistries due to its lower energy density and lifetime, but might become so when reaching similar lifetimes

Effect of natural aging on the chemical composition of norway spruce, fir, and european oak wood.

The chemical composition of a number of naturally aged construction wood samples of spruce, fir and oak was investigated. The content of lignin, polysaccharide, and extractives was determined using wet chemical and chromatographic methods. Differences to non-aged wood samples were found particularly found on oak wood samples with regard to lignin and polysaccharide content as well as to cellulose crystallinity. The composition of wood extractives of aged and non-aged wood samples revealed degradation processes due to oxidation and slight hydrolysis. The investigation showed that the relative content of the structural wood constituents depends on the sample age as well as the conditions they were aged under. The different degradation rates of those structural components may lead to contradictory results regarding their contents at certain degrees of aging. Cellulose crystallinity values are affected by extractives content