Gevoeligheidsanalyse berekening ammoniakemissie; Effect van variatie in penegratiegraden en emissiefactoren op de ammoniakemissie

Voor het monitoren van het ammoniakbeleid gericht op de landbouw is het van belang inzicht te hebben in de factoren die de hoogte van de ammoniakemissie beïnvloeden. Emissiefactoren en penetratie van emissiebeperkende technieken zijn voorbeelden van deze factoren. De vraag is wat het effect is van variatie rondom emissiefactoren en penetratiegraden op de hoogte van de ammoniakemissie. In het algemeen blijkt dat variatie rondom de emissiefactoren van meer invloed is op de hoogte van de ammoniakemissie dan de penetratiegraden van staltypen en mestaanwendingstechnieken. Deze conclusie geldt voor de monitoring van de ammoniakemissie op nationaal en provinciaal niveau. Op kleinere schaal kan de structuur van de landbouw sterk afwijken van het nationale c.q. provinciale beeld. Dit kan van invloed zijn op de prioriteitsstelling bij de verbetering van de monitoring van de ammoniakemissie

Promoting insight into algebraic formulas through graphing by hand

Student insight into algebraic formulas, including the ability to identify the structure of a formula and its components and to reason with and about formulas, is an issue in mathematics education. In this study, we investigated how 16- and 17-year-old pre-university students’ insight into algebraic formulas can be promoted through graphing formulas by hand. In an intervention of five 90-min lessons, 21 grade 11 students were taught to graph formulas by hand. The intervention’s design was based on experts’ strategies in graphing formulas, that is, using a combination of recognition and qualitative reasoning, and on principles of teaching complex skills. To assess the effect of this intervention, pre-, post-, and retention tests were administered, as well as a post-intervention questionnaire. Six students were asked to think aloud during the pre- and posttests. The results show that all students improved their abilities to graph formulas by hand. The think-aloud data suggest that the students improved both on recognition and reasoning, and give a detailed picture of how students used recognition and qualitative reasoning in combination. We conclude that graphing formulas by hand, based on the interplay of recognition and qualitative reasoning, might be a means to promote students’ insight into algebraic formulas