Student difficulties in learning density: a distributed cognition perspective

Density has been reported as one of the most difficult concepts for secondary school students (e.g. Smith et al. 1997). Discussion about the difficulties of learning this concept has been largely focused on the complexity of the concept itself or student misconceptions. Few, if any, have investigated how the concept of density was constituted in classroom interactions, and what consequences these interactions have for individual students’ conceptual understanding. This paper reports a detailed analysis of two lessons on density in a 7th Grade Australian science classroom, employing the theory of Distributed Cognition (Hollan et al. 1999; Hutchins 1995). The analysis demonstrated that student understanding of density was shaped strongly by the public classroom discussion on the density of two metal blocks. It also revealed the ambiguities associated with the teacher demonstration and the student practical work. These ambiguities contributed to student difficulties with the concept of density identified in this classroom. The results of this study suggest that deliberate effort is needed to establish shared understanding not only about the purpose of the activities, but also about the meaning of scientific language and the utility of tools. It also suggests the importance of appropriate employment of instructional resources in order to facilitate student scientific understanding.

Spatial and temporal definition of Ochlerotatus camptorhynchus (Thomson) (Diptera: Culicidae) in the Gippsland Lakes system of eastern Victoria

The confirmed vector of Ross River virus, Ochlerotatus camptorhynchus (Thomson), is the dominant mosquito species inhabiting saline marshes in coastal Victoria. This paper re-examines previously published data on Oc. camptorhynchus, plus additional data collected since that time, and provides greater spatial and temporal definition of Oc. camptorhynchus numbers at seven sites across the Gippsland Lakes system of eastern Victoria. A total of 357 672 Oc. camptorhynchus was captured from 1188 trap-nights across the seven trap sites during trapping seasons from 1990 to 2001. The  dominance of Oc. camptorhynchus across the seven sites averaged 75%, with significant differences in mean abundance of Oc. camptorhynchus found between all trap sites. Significant differences in monthly abundance of Oc. camptorhynchus were observed for Wellington Shire. Increase in populations of Oc. camptorhynchus was associated with increases in rainfall at all trap sites, higher minimum temperatures at two of the seven trap sites, and wind speed at one trap site. Prioritisation of mosquito control may be applied based on spatial and temporal factors according to the findings of this study.

Is devaluation expansionary or contractionary? empirical evidence from Fiji

Devaluation has been traditionally promoted as an effective tool for increasing exports and improving the external position of the devaluing country if a nominal devaluation results in expenditure switching. In this article, our aim is to model the relationship between currency devaluations and output for Fiji. Following the approach in Bahmani et al. (2002), we extend the traditional model by incorporating other monetary and fiscal policy variables. We achieve our goal by using the recently developed bounds testing approach to cointegration and the autoregressive distributed lag model and find that devaluation is expansionary in the case of Fiji.

Estimating impacts of consumer prices on house prices

Real estate is widely considered as a reliable hedge of inflation rate and there have been many literatures examining the inflation-hedging characteristics of the real estate.  The study described in the paper focuses on testing the significances of impacts of consumer price on house price in eight Australia's capital cities.  The Autoregressive Distributed Lag model is introduced to obtain  the estimates of the coefficient.  The significances of the impacts are defined as the accept probability of t statistics of the coefficients.  Analyses and comparisons of these significances suggested that the impacts of consumer prices on house prices depend on the inherent characteristics of cities. 

Examining the relationship between trade balance and exchange rate : the case of China's trade with the USA

In this paper, we investigate the nexus between China's trade balance and the real exchange rate vis-à-vis the USA. Using the bounds testing approach to cointegration, we find evidence that China's trade balance and real exchange rate vis-à-vis the USA are cointegrated, and using the autoregressive distributed lag model we find that in both the short run and the long run a real devaluation of the Chinese RMB improves the trade balance; as a result, there is no evidence of a J-curve type adjustment.

Determinants of female fertility in Taiwan, 1966–2001 : empirical evidence from cointegration and variance decomposition analysis

This study investigates the determinants of the fertility rate in Taiwan over the period 1966–2001. Consistent with theory, the key explanatory variables in Taiwan's fertility model are real income, infant mortality rate, female education and female labor force participation rate. The test for cointegration is based on the recently developed bounds testing procedure while the long-run and short-run elasticities are based on the autoregressive distributed lag model. Among our key results, female education and female labor force participation rate are found to be the key determinants of fertility in Taiwan in the long run. The variance decom-position analysis indicates that in the long run approximately 45percent of the variation in fertility is explained by the combined impact of female labor force participation, mortality and income, implying that socioeconomic development played an important role in the fertility transition in Taiwan. This result is consistent with the traditional structural hypothesis.

Savings behaviour in Fiji : an empirical assessment using the ARDL approach to cointegration

Purpose – This paper aims to delineate the short- and long-run relationships between savings, real interest rate, income, current account deficits (CADs) and age dependency ratio in Fiji using cointegration and error correction models over the period 1968-2000.

Design/methodology/approach – The recently developed bounds testing approach to cointegration is used, which is applicable irrespective of whether the underlying variables are integrated of order one or order zero. Given the small sample size in this study, appropriate critical values were extracted from Narayan. To estimate the short- and long-run elasticities, the autoregressive distributed-lag model is used.

Findings – In the short- and long-run: a 1 per cent increase in growth rate increases savings by over 0.07 and 0.5 per cent, respectively; a 1 per cent increase in the CAD reduces savings rate by 0.01 and 0.02 per cent, respectively; and the negative coefficient on the real interest rate implies that the income effect dominates the substitution effect, while in the short-run the total effect of the real interest rate is positive, implying that the substitution effect dominates the income effect.

Originality/value – This paper makes the first attempt at estimating the savings function for the Fiji Islands. Given that Fiji's capital market is poorly developed, the empirical findings here have direct policy relevance.

Why do Australians, New Zealanders and Americans travel to Fiji? Evidence from cointegration, unit roots and parameter stability tests

The aim of this study was to estimate the demand for Fiji’s tourism from its three main source markets—Australia, New Zealand, and the US—using the bounds testing approach to cointegration. Our main finding was that visitor arrivals to Fiji and its key determinants are cointegrated over the 1970–2000 period. We then used the autoregressive distributed lag model to estimate short-run and long-run elasticities and found that income in origin countries, transport costs, and prices were significant determinants of Fiji’s tourism demand. We also found that coups negatively impact visitor arrivals from all markets. In testing for parameter stability, we established that the series were integrated of order one in the presence of a structural break. We then used the Hansen test for parameter stability and found that the parameters of our long-run model are stable over time.

An empirical analysis of Fiji’s import demand function

Purpose – This paper aims to estimate a disaggregated import demand model for Fiji using relative prices, total consumption, investment expenditure and export expenditure variables for the period 1970 to 2000.

Design/methodology/approach – The recently developed bounds testing approach to cointegration to test for a long run relationship is used, while the autoregressive distributed lag model is used to estimate short run and long run elasticities. These methodologies are shown to perform well in small sample sizes, particularly given that the bounds F-test critical values for small sample sizes generated by Narayan in 2004 and 2005 are used.

Findings – Amongst the key results it is found: a long run cointegration relationship among the variables when import demand is the dependent variable; and import demand to be inelastic and statistically significant at the 1 per cent level with respect to all the explanatory variables in both the long-run and the short-run.

Originality/value – The disaggregated import demand model estimated here provides a complete picture of the determinants of Fiji's imports. This model can be used by Fijian policy makers to draw pertinent policies and forecast import demand for Fiji.

Ecology and control of the southern saltmarsh mosquito, Ochlerotatus Camptorhynchus(Thomson), in Victoria

This study has revealed important ecological attributes of the southern saltmarsh mosquito in Victoria, resulting in an increased understanding of population peaks and their relation to Ross River virus disease and meteorological factors. Together with new information on its larval development, these results have further increased options for its control by local governments and public health authorities.

Can investors hedge residential price dynamics of Australia's capital cities?

The study described in this paper focuses on testing the short-run and
long-run relationships between house price and consumer price indices in Australia’s capital cities from 1998 to 2008. The autoregressive distributed lag model is adopted to obtain the estimates of the short-run relationships, while the error correction model is used to investigate the long-run relationships. The t-statistic is used to compute the significance of these relationships. The research results give no evidence that house price indices are correlated with consumer price indices in the short run. However, the long-run relationships between house and consumer price indices exist in most of the cities.

Chemical structure based prediction of PAN and oxidized PAN fiber density through a non-linear mathematical model

The production of carbon fiber, particularly the oxidation/stabilization step, is a complex process. In the present study, a non-linear mathematical model has been developed for the prediction of density of polyacrylonitrile (PAN) and oxidized PAN fiber (OPF), as a key physical property for various applications, such as energy and material optimization, modeling, and design of the stabilization process. The model is based on the available functional groups in PAN and OPF. Expected functional groups, including [Formula presented], [Formula presented], –CH2, [Formula presented], and [Formula presented], were identified and quantified through the full deconvolution analysis of Fourier transform infrared attenuated total reflectance (FT-IR ATR) spectra obtained from fibers. These functional groups form the basis of three stabilization rendering parameters, representing the cyclization, dehydrogenation and oxidation reactions that occur during PAN stabilization, and are used as the independent variables of the non-linear predictive model. The k-fold cross validation approach, with k = 10, has been employed to find the coefficients of the model. This model estimates the density of PAN and OPF independent of operational parameters and can be expanded to all operational parameters. Statistical analysis revealed good agreement between the governing model and experiments. The maximum relative error was less than 1% for the present model.

The J-curve : evidence from Fiji

This article provides new evidence on both long run and short-run determinants of trade balance for Fiji and investigates evidence of J-curve adjustment behaviour in the aftermath of a devaluation. We adopt a partial reduced form model that models the real trade balance directly as a function of the real exchange rate and real domestic and foreign incomes. Cointegration analysis is based on a recently developed autoregressive distributed lag approach—shown to provide robust results in finite samples. The long run elasticities are also estimated using a dynamic ordinary least squares approach and the Fully Modified Ordinary Least Squares (FM-OLS) approach. Amongst our key results we find that there is a long-run relationship between trade balance and its determinants. There is evidence of the J-curve pattern; growth in domestic income affects Fiji's trade balance adversely while foreign income improves it.

Estimating income and price elasticities of imports for Fiji in a cointegration framework

This paper estimates an import demand model for Fiji using the recently developed bounds testing approach to cointegration for the period 1972 to 1999. To estimate the long-run elasticities, we use three approaches: the autoregressive distributed lag (ARDL) model, the dynamic ordinary least squares (DOLS) approach and the fully modified ordinary least squares technique. Our results indicate a long-run cointegration relationship among the variables when import volume is the dependent variable. We find that the coefficient on income is elastic while the coefficient on relative prices (import price relative to domestic price) is unitary elastic in the long run. The error correction mechanism reveals that after any shock(s) to the determinants of import demand equilibrium is attained after 2 1/2 years.