title: Thai grade 10 and 11 students’ understanding of stoichiometry and related concepts

authors: Dahsah, Chanyah

subjects: alternative conceptions

abstract: The research reported in this case study explores the understanding of stoichiometry and related concepts of Thai science students in grades 10 and 11 after major national curriculum reforms. Students’ conceptions and alternative conceptions were investigated using a questionnaire - the Stoichiometry Concept Questionnaire (SCQ) (N = 97), which consists of 16 multiple-choice items, the choices for which respondents are required to provide reasons. The findings suggest that less than half of the students surveyed hold what is considered by a panel of experts to be a scientifically acceptable understanding for the conceptions investigated. The main student alternative conceptions are that one mole of all substances has a volume of 22.4 L at STP, that a solution that contains a greater mass of solute has the higher molar concentration, and that the limiting reagent is the reagent for which the lowest mass of reactant is present. Examination of students’ reasons suggests that they resort to the use of algorithms with little understanding of the underlying concepts. It thus seems the national educational reforms have not resulted in a sound understanding of some science concepts. It is recommended that curriculum developers should specify a need for conceptual understanding along with capability in numerical problem-solving in their learning objectives, and link this to assessment regimes that reward conceptual understanding. A need for on-going professional development seems essential if the intentions of the Thai curriculum reforms are to be realized.

text: Thai grade 10 and 11 students’ understanding of stoichiometry and related concepts The research reported in this case study explores the understanding of stoichiometry and related concepts of Thai science students in grades 10 and 11 after major national curriculum reforms. Students’ conceptions and alternative conceptions were investigated using a questionnaire - the Stoichiometry Concept Questionnaire (SCQ) (N = 97), which consists of 16 multiple-choice items, the choices for which respondents are required to provide reasons. The findings suggest that less than half of the students surveyed hold what is considered by a panel of experts to be a scientifically acceptable understanding for the conceptions investigated. The main student alternative conceptions are that one mole of all substances has a volume of 22.4 L at STP, that a solution that contains a greater mass of solute has the higher molar concentration, and that the limiting reagent is the reagent for which the lowest mass of reactant is present. Examination of students’ reasons suggests that they resort to the use of algorithms with little understanding of the underlying concepts. It thus seems the national educational reforms have not resulted in a sound understanding of some science concepts. It is recommended that curriculum developers should specify a need for conceptual understanding along with capability in numerical problem-solving in their learning objectives, and link this to assessment regimes that reward conceptual understanding. A need for on-going professional development seems essential if the intentions of the Thai curriculum reforms are to be realized.

year: 2008

title: Fractional modelling of rechargeable batteries

authors: Hasan, Rahat

subjects: Modelling

abstract: To develop a compact battery model, many authors begin by measuring the impedance of a battery over a frequency range of interest. Most of the models in the literature are either Thevenin-style or Randles’ model consisting of one or two RC networks and sometimes a Warburg element. These models are usually based on frequency range that stretches to only 1 mHz. This explains why they require several parameters to accurately reproduce the measured impedance data. In most applications, a battery goes through a charge/discharge cycle daily or even longer. Therefore, it seems logical to measure the impedance of the cell at frequencies reciprocal of period of charge. This corresponds to approximately 11.6 µHZ or lower. The impedance data at lower frequencies shows that any rechargeable battery can be simply modelled with a constant phase element in series with a resistor. Based on this observation, an equivalent circuit model and a mathematical model were proposed in this study. Similar to Randles’ model presented in 1947, the proposed models do not contain a source or any purely reactive element. The models were then fitted to the measured impedance data of both lithium-ion and nickel-metal hydride cells, the linear region of the charge-voltage curve, and the transient recovery tail that results from a step-change in load current.

text: Fractional modelling of rechargeable batteries To develop a compact battery model, many authors begin by measuring the impedance of a battery over a frequency range of interest. Most of the models in the literature are either Thevenin-style or Randles’ model consisting of one or two RC networks and sometimes a Warburg element. These models are usually based on frequency range that stretches to only 1 mHz. This explains why they require several parameters to accurately reproduce the measured impedance data. In most applications, a battery goes through a charge/discharge cycle daily or even longer. Therefore, it seems logical to measure the impedance of the cell at frequencies reciprocal of period of charge. This corresponds to approximately 11.6 µHZ or lower. The impedance data at lower frequencies shows that any rechargeable battery can be simply modelled with a constant phase element in series with a resistor. Based on this observation, an equivalent circuit model and a mathematical model were proposed in this study. Similar to Randles’ model presented in 1947, the proposed models do not contain a source or any purely reactive element. The models were then fitted to the measured impedance data of both lithium-ion and nickel-metal hydride cells, the linear region of the charge-voltage curve, and the transient recovery tail that results from a step-change in load current.

year: 2021

title: From mainstream to manaaki: Indigenising our approach to immigration

authors: Kukutai, Tahu

abstract: In recent years, discontent with migration and migrants in the wealthy global north has manifested in disturbing ways: cue Brexit, xenophobia, border paranoia, far-right nationalism and its bedfellow white supremacy. On the surface, Aotearoa New Zealand appears to have escaped the uglier aspects of this nativism. Despite the grumblings of the New Zealand First Party, no serious popular or political anti-immigration movement has appeared, and racially motivated attacks against migrants are relatively rare. This is despite the fact that Aotearoa has a much higher relative foreign-born population share than the United States or United Kingdom,1 and ‘superdiverse’ Auckland – which comprises at least 40 per cent migrants – now has the ignominious claim to being the fourthleast affordable city in the world, far outstripping London and New York.

text: From mainstream to manaaki: Indigenising our approach to immigration In recent years, discontent with migration and migrants in the wealthy global north has manifested in disturbing ways: cue Brexit, xenophobia, border paranoia, far-right nationalism and its bedfellow white supremacy. On the surface, Aotearoa New Zealand appears to have escaped the uglier aspects of this nativism. Despite the grumblings of the New Zealand First Party, no serious popular or political anti-immigration movement has appeared, and racially motivated attacks against migrants are relatively rare. This is despite the fact that Aotearoa has a much higher relative foreign-born population share than the United States or United Kingdom,1 and ‘superdiverse’ Auckland – which comprises at least 40 per cent migrants – now has the ignominious claim to being the fourthleast affordable city in the world, far outstripping London and New York.

year: 2017