Teachers' Evaluations and the Definition of the Situation in the Classroom

The theoretical contribution of this paper is to regard teachers' evaluations with a prognostic claim about students' future academic ability as a result of a special social situation in the classroom. We assume that after teachers have framed the social situation, particular scripts of action will determine the criteria on which teachers ground their evaluations. In concrete terms, we propose a theoretical approach that integrates existing meritocratic and 'habitus' explanations in the comprehensive framework of frame selection theory with its important distinction between a more automatic and a more rational type of information processing. Our empirical contribution is to test the hypotheses that we deduced from our theoretical assumptions in a set of structural equation models. Using data from the Cologne High School Panel (CHiSP), we find that even when controlling for the path structure of the model, indicators for both kinds of concepts are statistically significant. However, regardless of the underlying type of information processing, the predictive power of indicators operationalizing the meritocratic explanation is comparatively higher.teachers' evaluations, inequality in educational opportunities, frame selection theory, structural equation modeling

Assessing the impact of changing electricity and CO2 prices on synthetic fuel production: Multi-criteria heat exchanger network synthesis

Facing the urgent need to reduce anthropogenic climate change, especially the emissions from the transport sector, climate-neutral fuels are gaining attention. Synthetic fuels serve as a long-term solution for aviation, maritime and heavy machinery. However, large-scale use requires cost-effectiveness, efficient production and resilience to price changes. We use mixed integer linear programming to simultaneously optimize the cell voltage of the solid oxide electrolysis cell, the heat exchanger network and the internal heat supply of a 1 MW PtL-plant. PtL-efficiency and production costs are used as objectives. Multiple Pareto fronts are calculated within reasonable price domains considering falling and rising electricity and CO2 prices. Deriving sensitivities on electricity and CO2 prices enables us to quantify the impact of price changes on operational and design parameters. The results show that sensitivity to price changes has different impacts on design and operating parameters, which can lead to unattractive solution domains in the Pareto front. Current electricity and CO2 prices result in production costs ranging from 1.83-2.36 EUR/kg. In the best case, fuels can be produced at 1.42-1.97 EUR/kg and at 3.88-4.28 EUR/kg in the worst case. This paper supports decision-makers in planning PtL-plants to ensure synthetic fuel availability on a global scale

Unlocking the Potential of Synthetic Fuel Production: Coupled Optimization of Heat Exchanger Network and Operating Parameters of a 1 MW Power-to-Liquid Plant

The use of synthetic fuels is a promising way to reduce emissions significantly. To accelerate cost-effective large-scale synthetic fuel deployment, we optimize a novel 1 MW PtL-plant in terms of PtL-efficiency and fuel production costs. For numerous plants, the available waste heat and temperature level depend on the operating point. Thus, to optimize efficiency and costs, the choice of the operating point is included in the heat exchanger network synthesis. All nonlinearities are approximated using piecewise linear models and transferred to MILP. Adapting the epsilon constraint method allows us to solve the multi-criteria problem with uniformly distributed solutions on the Pareto front. The results show that compared to the conventional design process, the production cost can be reduced to 1.83 EUR/kg and the PtL-efficiency can be increased to 61.30 %. By applying the presented method, climate-neutral synthetic fuels can be promoted and emissions can be reduced in the long term