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(2003)Journal ArticleThe commonly used value of the intrinsic carrier density of crystalline silicon at 300 K is ni = 1.00×1010 cm–3. It was experimentally determined by Sproul and Green, J. Appl. Phys. 70, 846 (1991), using specially designed solar cells. In this article, we demonstrate that the Sproul and Green experiment was influenced by band-gap narrowing, even though the dopant density of their samples was low (1014 to 1016 cm–3). We reinterpret their measurements by numerical simulations with a random-phase approximation model for band-gap narrowing, thereby obtaining ni = 9.65×109 cm–3 at 300 K. This value is consistent with results obtained by Misiakos and Tsamakis, J. Appl. Phys. 74, 3293 (1993), using capacitance measurements. In this way, long-prevailing inconsistencies between independent measurement techniques for the determination of ni are resolved.
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(2003)Conference PaperAssessing whether an organisation is achieving sustainability can be difficult. Different audiences require different types of information to understand ecological sustainability and in order to understand the combined impacts, overall performance needs to be reported in an aggregated way. Sydney Water uses several complementary tools to assess and communicate progress towards sustainability. The methodology used to assess combined impacts must be scientifically robust, easily communicated and allow benchmarking of performance in order to reflect any transition towards sustainability. Sydney Water has over two years calculated its ecological footprint (EF), in an innovative approach based on input-output analysis and land disturbance. Integrating scenarios into these pilot studies has allowed Sydney Water to effectively communicate some aspects of its impacts in its public reporting. Ecological footprint is an excellent education and communications tool and may have potential as a decision support tool in the future. At present EF can highlight areas for consideration by the Corporation but is not directly used in decision making and planning. Further research is needed to incorporate downstream impacts into EF, such as the impacts on receiving waters. Further, as it is based on financial and economic data, the EF methodology is not equipped to deliver the detailed assessment required for assessment of specific planning options. The use of EF by a water service provider must take place in a wider context of sustainability reporting and planning, building on the strengths of a tool kit of different methodologies. Sydney Water has a range of other sustainability tools, including life cycle assessment (LCA) which are used to develop the Corporation’s long-term plans and strategies. The organisation has used life cycle assessment (LCA) to provide predictive, comparative sustainability assessments of alternative options as part of its strategic planning process. These assessments include upstream and downstream effects but are not suitable for all audiences
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(2003)Conference PaperA number of studies have questioned the criterion validity of peer assessed oral presentations. Claims have been made that students are likely to employ a different perspective from teachers when assessing overall presentation quality, even when both are guided by a common checklist of relevant skill components.To date, no empirical investigations have been undertaken to determine how students differ from staff in the criteria they apply. this paper analyses peer and teacher assessment data from thesis presentations made by engineering students in a fourth year communications subject. The data consists of peer and teacher ratings on eight skill components listed on a checklist (used for feedback only), together with a global mark for the presentation (the summative assessment).The scores on the eight items were then subject to multiple regression analysis using the global mark as the criterion. Substantial differences were found between the two multiple regression equations. Discussion focuses on how these differences affect the validity of peer assessments, and the level of agreement between teacher and student assessment.