title: A computerized Langmuir probe system

authors: Pilling, L.S.

subjects: Langmuir probes

abstract: For low pressure plasmas it is important to record entire single or double Langmuir probe characteristics accurately. For plasmas with a depleted high energy tail, the accuracy of the recorded ion current plays a critical role in determining the electron temperature. Even for high density Maxwellian distributions, it is necessary to accurately model the ion current to obtain the correct electron density. Since the electron and ion current saturation values are, at best, orders of magnitude apart, a single current sensing resistor cannot provide the required resolution to accurately record these values. We present an automated, personal computer based data acquisition system for the determination of fundamental plasma properties in low pressure plasmas. The system is designed for single and double Langmuir probes, whose characteristics can be recorded over a bias voltage range of ±70 V with 12 bit resolution. The current flowing through the probes can be recorded within the range of 5 nA–100 mA. The use of a transimpedance amplifier for current sensing eliminates the requirement for traditional current sensing resistors and hence the need to correct the raw data. The large current recording range is realized through the use of a real time gain switching system in the negative feedback loop of the transimpedance amplifier.

text: A computerized Langmuir probe system For low pressure plasmas it is important to record entire single or double Langmuir probe characteristics accurately. For plasmas with a depleted high energy tail, the accuracy of the recorded ion current plays a critical role in determining the electron temperature. Even for high density Maxwellian distributions, it is necessary to accurately model the ion current to obtain the correct electron density. Since the electron and ion current saturation values are, at best, orders of magnitude apart, a single current sensing resistor cannot provide the required resolution to accurately record these values. We present an automated, personal computer based data acquisition system for the determination of fundamental plasma properties in low pressure plasmas. The system is designed for single and double Langmuir probes, whose characteristics can be recorded over a bias voltage range of ±70 V with 12 bit resolution. The current flowing through the probes can be recorded within the range of 5 nA–100 mA. The use of a transimpedance amplifier for current sensing eliminates the requirement for traditional current sensing resistors and hence the need to correct the raw data. The large current recording range is realized through the use of a real time gain switching system in the negative feedback loop of the transimpedance amplifier.

year: 2003-07

title: Food miles or carbon emissions? Exploring labelling preference for food transport footprint with a stated choice study

authors: Caputo, Vincenzina

abstract: The ecological footprint of food transport can be communicated using carbon dioxide emissions (CO₂ label) or by providing information about both the length of time and the mileage travelled (food miles label). We use stated choice data to estimate conventional unobserved taste heterogeneity models and extend them to a specification that also addresses attribute nonattendance. The implied posterior distributions of the marginal willingness to pay values are compared graphically and are used in validation regressions. We find strong bimodality of taste distribution as the emerging feature, with different groups of subjects having low and high valuations for these labels. The best fitting model shows that CO₂ and food miles valuations are much correlated. CO₂ valuations can be high even for those respondents expressing low valuations for food miles. However, the reverse is not true. Taken together, the results suggest that consumers tend to value the CO₂ label at least as much and sometimes more than the food miles label.

text: Food miles or carbon emissions? Exploring labelling preference for food transport footprint with a stated choice study The ecological footprint of food transport can be communicated using carbon dioxide emissions (CO₂ label) or by providing information about both the length of time and the mileage travelled (food miles label). We use stated choice data to estimate conventional unobserved taste heterogeneity models and extend them to a specification that also addresses attribute nonattendance. The implied posterior distributions of the marginal willingness to pay values are compared graphically and are used in validation regressions. We find strong bimodality of taste distribution as the emerging feature, with different groups of subjects having low and high valuations for these labels. The best fitting model shows that CO₂ and food miles valuations are much correlated. CO₂ valuations can be high even for those respondents expressing low valuations for food miles. However, the reverse is not true. Taken together, the results suggest that consumers tend to value the CO₂ label at least as much and sometimes more than the food miles label.

year: 2013

title: Reflections on relationship-building between tangata whenua and local government: Notes from research and practice

authors: Neill, Beth

subjects: New Zealand

abstract: In this paper, the author takes a reflective look at two areas: the preliminary discussions and fieldwork they undertook to set up a collaborative doctoral research project exploring relationship-building between
tangata whenua and local government (regional and district councils); and their
practice as a community psychologist within local government, advising on social
research and community participation in a number of environmental management
projects.

text: Reflections on relationship-building between tangata whenua and local government: Notes from research and practice In this paper, the author takes a reflective look at two areas: the preliminary discussions and fieldwork they undertook to set up a collaborative doctoral research project exploring relationship-building between
tangata whenua and local government (regional and district councils); and their
practice as a community psychologist within local government, advising on social
research and community participation in a number of environmental management
projects.

year: 2003-06