Mathematical modelling of deep bed filtration

Numerous mathematical models have been developed to evaluate both initial and transient stage removal efficiency of deep bed filters. Microscopic models either using trajectory analysis or convective-diffusion equations were used to compute the initial removal efficiency. These models predicted the removal efficiency under favorable filtration conditions quantitatively, but failed to predict the removal efficiency under unfavorable conditions. They underestimated the removal efficiency under unfavorable conditions. Thus, semi-empirical formulations were developed to compute initial removal efficiencies under unfavorable conditions. Also, correction for the adhesion of particles onto filter grains improved the results obtained for removal efficiency from the trajectory analysis. Macroscopic models were used to predict the transient stage removal efficiency of deep bed filters. O’Melia and Ali’s model assumed that the particle removal is due to filter grains as well as the particles that are already deposited onto the filter grain. Thus, semi-empirical models were used to predict the ripening of filtration. Several modifications were made to the model developed by O’Melia and Ali to predict the deterioration of particle removal during the transient stages of filtration. Models considering the removal of particles under favorable conditions and the accumulation of charges on the filter grains during the transient stages were also developed. This paper evaluates those models and their applicability under different operating conditions of filtration.

Low-frequency volatility of yen interest rate swap market in relation to macroeconomic risk

Using ‘low-frequency’ volatility extracted from aggregate volatility shocks in interest rate swap (hereafter, IRS) market, this paper investigates whether Japanese yen IRS volatility can be explained by macroeconomic risks. The analysis suggests that this low-frequency yen IRS volatility has strong and positive association with most of the macroeconomic risk proxies (e.g., volatility of consumer price index, industrial production volatility, foreign exchange volatility, slope of the term structure and money supply) with the exception of the unemployment rate, which is negatively related to IRS volatility. This finding is fairly consistent with the argument that the greater the macroeconomic risk the greater is the use of derivative instruments to hedge or speculate. The relationship between the macroeconomic risks and IRS volatility varies slightly across the different swap maturities but is robust to alternative volatility specifications. This linkage between swap market and macroeconomy has practical implications since market makers and hedgers use the swap rate as benchmark for pricing long-term interest rates, corporate bonds and various other securities.

Mathematical modelling for Singapore primary classrooms : from a teacher’s lens

Limited Singapore research indicated a lack of exposure of modelling tasks at primary levels. Teacher reflection is used as a tool in design research cycles exploring the potentials of modelling tasks in a Singapore primary five classroom. Findings reveal that the teacher identified three potentials of a modelling task on children’s mathematisation process: the task provided a platform for children to (a) identify variables and form relationships between them, (b) relate school-based math learning to real-world experiences, and (c) justify their mathematical models. Implications on the promotion of modelling tasks at primary schools as well as teacher education are drawn.

Credit cycle dependent spread determinants in emerging sovereign debt markets

We address credit cycle dependent sovereign credit risk determinants. In our model, the spread determinants' magnitude is conditional on an unobservable endogenous sovereign credit cycle as represented by the underlying state of a Markov regime switching process. Our explanatory variables are motivated in the tradition of structural credit risk models and include changes in asset prices, interest rates, implied market volatility, gold price changes and foreign exchange rates. We examine daily frequency variations of U.S. dollar denominated Eurobond credit spreads of four major Latin American sovereign bond issuers (Brazil, Colombia, Mexico and Venezuela) with liquid bond markets during March 2000 to June 2011. We find that spread determinants are statistically significant and consistent with theory, while their magnitude remarkably varies with the state of the credit cycle. Crisis states are characterized by high spread change uncertainty and high sensitivities with respect to the spread change determinants. We further document that not only changes of local currencies, but also changes of the Euro with respect to the U.S. dollar are significant spread drivers and argue that this is consistent with the sovereigns' ability to pay.

Expert systems modeling for assessing climate change impacts and adaptation in agricultural systems at regional level

Australian agriculture is very susceptible to the adverse impacts of climate change, with major shifts in temperature and rainfall projected. In this context, this paper describes a research methodology for assessing potential climate change impacts on, and formulating adaptation options for, agriculture at regional level. The methodology was developed and applied in the analysis of climate change impacts on key horticultural commodities—pome fruits (apples and pears), stone fruits (peaches and nectarines) and wine grapes—in the Goulburn Broken catchment management region, State of Victoria, Australia. Core components of the methodology are mathematical models that enable to spatially represent the degree of biophysical land suitability for the growth of agricultural commodities in the region of interest given current and future climatic conditions. The methodology provides a sound analytic approach to 1) recognise regions under threat of declines in agricultural production due to unfolding climatic changes; 2) identify alternative agricultural systems better adapted to likely future climatic conditions and 3) investigate incremental and transformational adaptation actions to improve the problem situations that are being created by climate change.

A panel vector error correction approach to forecasting demand in regional construction markets

Reliable forecasting as to the level of aggregate demand for construction is of vital importance to developers, builders and policymakers. Previous construction demand forecasting studies mainly focused on temporal estimating using national aggregate data. The construction market can be better represented by a group of interconnected regions or local markets rather than a national aggregate, and yet regional forecasting techniques have rarely been applied. Furthermore, limited research has applied regional variations in construction markets to construction demand modelling and forecasting. A new comprehensive method is used, a panel vector error correction approach, to forecast regional construction demand using Australia’s state-level data. The links between regional construction demand and general economic indicators are investigated by panel cointegration and causality analysis. The empirical results suggest that both long-run and causal links are found between regional construction demand and construction price, state income, population, unemployment rates and interest rates. The panel vector error correction model can provide reliable and robust forecasting with less than 10% of the mean absolute percentage error for a medium-term trend of regional construction demand and outperforms the conventional forecasting models (panel multiple regression and time series multiple regression model). The key macroeconomic factors of construction demand variations across regions in Australia are also presented. The findings and robust econometric techniques used are valuable to construction economists in examining future construction markets at a regional level.

Panel cointegration tests of the Fisher hypothesis

Recent empirical studies suggest that the Fisher hypothesis, stating that inflation and nominal interest rates should cointegrate with a unit parameter on inflation, does not hold, a finding at odds with many theoretical models. This paper argues that these results can be explained in part by the low power inherent in univariate cointegration tests and that the use of panel data should generate more powerful tests. In doing so, we propose two new panel cointegration tests, which are shown by simulation to be more powerful than other existing tests. Applying these tests to a panel of monthly data covering the period 1980:1 to 1999:12 on 14 OECD countries, we find evidence supportive of the Fisher hypothesis.

Boron carbide reinforced aluminium matrix composite : physical, mechanical characterization and mathematical modelling

This paper investigates the manufacturing of aluminium-boron carbide composites using the stir casting method. Mechanical and physical properties tests to obtain hardness, ultimate tensile strength (UTS) and density are performed after solidification of specimens. The results show that hardness and tensile strength of aluminium based composite are higher than monolithic metal. Increasing the volume fraction of B4C, enhances the tensile strength and hardness of the composite; however over-loading of B4C caused particle agglomeration, rejection from molten metal and migration to slag. This phenomenon decreases the tensile strength and hardness of the aluminium based composite samples cast at 800 °C. For Al-15 vol% B4C samples, the ultimate tensile strength and Vickers hardness of the samples that were cast at 1000 °C, are the highest among all composites. To predict the mechanical properties of aluminium matrix composites, two key prediction modelling methods including Neural Network learned by Levenberg-Marquardt Algorithm (NN-LMA) and Thin Plate Spline (TPS) models are constructed based on experimental data. Although the results revealed that both mathematical models of mechanical properties of Al-B4C are reliable with a high level of accuracy, the TPS models predict the hardness and tensile strength values with less error compared to NN-LMA models.

Migration, unemployment and trade

Migration, Unemployment and Trade focuses on the issues of migration, welfare and unemployment in a trade and development framework. Several chapters of the book analyze the implications of internal labor mobility in a model designed to highlight its implications for regional welfare, urban unemployment, rural-urban dichotomy and structural adjustment. An important innovation in this work is the disaggregation of the economy and the use of separate utility functions to highlight non-homogeneity of preferences. The book also deals with international mobility of factors in different frameworks. In particular it concentrates on the highly emotive issue of legal and illegal migration. Thus this work incorporates interesting and important features of labor economics and factor mobility into trade and distortion theory.

Modelling of fabric energy storage systems - a review

Fabric energy storage (FES) systems have gained in popularity in the recent years in response to the demand for energy efficient buildings. The dynamic heat transfer mechanisms of an FES require specialised techniques to predict its thermal performance. This requirement has been one of the barriers to the wider use of FES systems. Based on the research literature, this paper presents a critical review of the published mathematical models of FES systems. The paper discusses the usefulness of these models based on the following criteria: the inputs required; the accuracy of predictions; the ability to link with commercially available simulation software: and the degree of difficulty in using the models. The review found that the currently available mathematical models are either not able to predict the thermal behaviour of a building space with an FES system reliably or the models are too complicated and/or require too much specialised knowledge to make them useful.

Building capacity in an indigenous nonprofit artistic enterprise

Growth in Indigenous artistic enterprises has attracted government funding, cultural tourists, and arts managers with a strong interest in cultural democracy and, more recently, an interest in business models for these artists. This paper documents a case study of Arilla Paper, an artistic enterprise in Queensland, Australia, where a group of Aboriginal women, worked on making paper from natural materials, to create a sustainable non-profit arts business. Sections of the business manual developed for these women, together with primary and secondary data supporting the Indigenous creative industries, are presented. The paper concludes that success in such ventures requires a social entrepreneurship model of funding that recognises the challenges of Indigenous cultural ownership and capacity building in business practice.

Is money targeting an option for Bank Indonesia?

In this paper, using the cash-in-advance model, we estimate Indonesia's money demand function for the period 1970–2005. We find the real M1 and real M2 are cointegrated with their determinants, namely real income, real exchange rate and short-term domestic and foreign interest rates. The long-run elasticities, except for the relationship between M2 and domestic interest rate, are plausible. Interestingly, we find a negative relationship between real exchange rate and real money demand, suggesting evidence of currency substitution. We test for causal relationships and find that in the short-run only the real exchange rate Granger causes real M1 and real M2. Finally, we find that Indonesia's money demand functions are unstable. We conclude that money targeting is not an option for Bank Indonesian and that currency substitution should be curbed in order to ensure macroeconomic sustainability.

Fundamental determinants of the Australian price-earnings multiple

This paper is the first attempt to investigate the factors fundamental to the setting of the price–earnings (P–E) multiple for the Australian stock market. The quarterly P–E ratio for the ASX 200 index is used as a measure of the market wide P–E multiple. It is demonstrated that a large portion of the variation in the P–E multiple can be explained by the dividend payout ratio, interest rates and GDP growth rates. In addition, consumers' confidence—a leading indicator of future growth opportunities, the Australian–US exchange rate—a key determinant of the competitiveness of domestic companies, and volatility of domestic market returns—a risk factor, have incremental explanatory power.

Investigating the determinants of the decision to engage in a corporate hedging strategy

This paper investigates the decision to engage in a comprehensive corporate hedging strategy for Australian listed companies. Specifically the pursuit of a comprehensive hedging strategy is gauged by jointly investigating the corporate use of foreign currency derivatives; interest rate derivatives; commodity derivatives and foreign debt. The results show that firm size, leverage, dividend yield and block holdings are incentive factors to the comprehensive hedging decision, while executive shares is a disincentive factor. Consistent with hedging theory, the significance of the leverage variables supports the financial distress cost hypothesis. Support is also found for the dividend decision is a substitute for corporate hedging.

Design of a distributed power system stabiliser

A new design method for a distributed power system stabiliser for interconnected power systems is introduced in this paper. The stabiliser is of a low order, dynamic and robust. To generate the required local control signals, each local stabiliser requires information about either the rotor speed or the load angle of the other subsystems. A simple MATLAB based design algorithm is given and used on a three-machine unstable power system. The resulting stabiliser is simulated and sample results are presented.