Learning conversions in science: The case of vocational students in the UK

The paper describes two aspects of a research project that focused on vocational science students. The paper begins with a general description of vocational science in the UK, to put the work in context. It then outlines an analysis of the ways in which these students approach problems involving converting between units of measurement. Finally the development and evaluation of computer‐based activities designed to support students in learning about unit conversion are described

A study of the use of abstract types for the representation of engineering units in integration and test applications

Physical quantities using various units of measurement can be well represented in Ada by the use of abstract types. Computation involving these quantities (electric potential, mass, volume) can also automatically invoke the computation and checking of some of the implicitly associable attributes of measurements. Quantities can be held internally in SI units, transparently to the user, with automatic conversion. Through dimensional analysis, the type of the derived quantity resulting from a computation is known, thereby allowing dynamic checks of the equations used. The impact of the possible implementation of these techniques in integration and test applications is discussed. The overhead of computing and transporting measurement attributes is weighed against the advantages gained by their use. The construction of a run time interpreter using physical quantities in equations can be aided by the dynamic equation checks provided by dimensional analysis. The effects of high levels of abstraction on the generation and maintenance of software used in integration and test applications are also discussed

Prices, unit values and local measurement units in rural surveys: an econometric approach with an application to poverty measurement in Ethiopia

For many research problems in developing countries, some information on prices faced by households is required for the analysis, for example if subsistence consumption is a substantial part of consumption. These prices are not readily available from household surveys, nor is it straightforward to observe them. Furthermore, quantities consumed and produced are often in local units presenting further problems for the analysis. We provide an econometric approach to estimate prices and quantity conversion factors from household expenditure data. We use panel data from rural Ethiopia to illustrate the approach and to investigate the potential exogenous quality bias in the estimation of the prices. In an application, we show that the conclusions about poverty changes over time are significantly affected by using less appropriate strategies to convert local units and to value subsistence consumption. We find that mean unit values result in the overestimation of prices due to outliers and other sources of measurement error. Exogenous consumer price sources, often collected at larger markets outside the village, tend to be slightly lower than our estimates.household surveys, unit values, subsistence consumption, local measurement units, poverty

Databook for human factors engineers. Volume 2 - Common formulas, metrics, definitions

Human factors engineering manual including mathematical formulas, nomographs, conversion tables, units of measurement, and nomenclature

Prices, Unit Values and Local Measurement Units in Rural Surveys: an Econometric Approach with an Application to Poverty Measurement in Ethiopia

For many research problems in developing countries, some information on prices faced by households is required, for example if subsistence consumption is a substantial part of consumption. These prices are not readily available from household surveys, and at times they are not easily observed, for example if markets are thin and systematic price information can only be observed from markets some distance away from communities. Furthermore, quantities consumed and produced are often in local units presenting further problems for the analysis. We provide an econometric approach to estimate prices and quantity conversion factors from household expenditure data, using data from rural Ethiopia to illustrate the approach. In an application, we show that the conclusions about poverty changes over time are significantly affected by using alternative strategies to convert local units and to value subsistence consumption. We find in our case that mean unit values result in the overestimation of prices due to outliers and other sources of measurement error. Exogenous consumer price sources, often collected at larger markets outside the village, tend to give slightly lower values than our estimates.household surveys, unit values, subsistence consumption, local measurement units, poverty

Prices, local measurement units and subsistence consumption in rural surveys: An econometric approach with an application to Ethiopia

For many research problems in developing countries, some information on prices faced by households is required for the analysis, but these prices are not readily available from household surveys, nor is it straightforward to observe them, especially if subsistence consumption is a substantial part of consumption. Furthermore, quantities consumed and produced are often in local units presenting further problems for the analysis. Building on Deaton’s (1987) seminal work, we provide an econometric approach to estimate prices and quantity conversion factors from household expenditure data.. We use panel data from rural Ethiopia to illustrate the approach and to investigate the potential quality bias in the estimation of the prices. In an application we show that the conclusions about poverty changes over time are significantly affected by using less appropriate strategies to convert local units and to value subsistence consumption.household surveys, unit values, subsistence consumption, local measurement units

Fundamentals of Measurement: Giovanni Giorgi and the International System of Units

Electrical engineers and technicians face today many professional challenges, but the problem of the choice of the measurement units and their conversion is not one of those. Our colleagues working in mechanics or thermal engineering have to deal with inches and metres, gallons and litres, calories, BTUs and joules. In electricity, everything is smoother: the voltage is always measured in volt, the resistance in ohm; one volt times one ohm gives one watt, and so on. No ambiguities occur, no calculations with weird conversion factors are needed

The fundamental constants of physics and the International System of Units

Air Canada managed to have a passenger aircraft run out of fuel in mid-air due to confusion about metric units (Stephenson in Mars climate orbiter mishap investigation board phase I report, NASA, 1999), and NASA lost an entire spacecraft due to a misunderstanding amongst engineers about the units used in the propulsion system design (Witkin in Jet's fuel ran out after metric conversion errors, The New York Times, 1983). Measurements only make sense if the units are correct and well-defined. A unit of measurement is a definite magnitude of a quantity, defined by convention or law. Any other quantity of that kind can then be expressed as a multiple or submultiple of the unit of measurement. The Egyptians used the Farao as definite magnitude, while many years later, the french revolutionists introduced the earth as a reference and laid the foundations for the modern decimal system. Since recently, we have a truly universal and stable system that uses physics's natural constants and laws to define the base units of measurement. This paper explains how this new concept works and how it is implemented in practice

Mind the gap – development of conversion models between accelerometer- and IMU-based measurements of arm and trunk postures and movements in warehouse work

Sensor type (accelerometers only versus inertial measurement units, IMUs) and angular velocity computational method (inclination versus generalized velocity) have been shown to affect the measurements of arm and trunk movements. This study developed models for conversions between accelerometer and IMU measurements of arm and trunk inclination and between accelerometer and IMU measurements of inclination and generalized (arm) velocities. Full-workday recordings from accelerometers and IMUs of arm and trunk postures and movements from 38 warehouse workers were used to develop 4 angular (posture) and 24 angular velocity (movement) conversion models for the distributions of the data. A power function with one coefficient and one exponent was used, and it correlated well (r2 > 0.999) in all cases to the average curves comparing one measurement with another. These conversion models facilitate the comparison and merging of measurements of arm and trunk movements collected using the two sensor types and the two computational methods