Reliability of Equilibrium Gasification Models for Selected Biomass Types and Compositions: An Overview

In this paper, the authors present an overview of biomass gasification modeling approaches with the aim of evaluating their effectiveness as a modeling tool for the design and optimization of polygeneration plants based on biomass gasification. In fact, the necessity to build plant operating maps for efficiency optimization requires a significant number of simulations, and non-stoichiometry equilibrium models may allow fast computations thanks to their relative simplicity. The main objective consists of the assessment of thermodynamic equilibrium models performance as a function of biomass type and composition to better understand in which conditions of practical interest such models can be applied with acceptable reliability. To this aim, the authors developed two equilibrium models using both a commercial software (referred as Aspen model) and a simulation tool implemented in a non-commercial script (referred as analytical model). To assess their advantages and disadvantages, the two models were applied to the gasification simulation of different biomasses, employing experimental data available from the scientific literature. The obtained results highlighted strengths and limitations of using equilibrium models as a function of biomass type and composition. For example, they showed that the analytical model predicted syngas composition with better accuracy for biomass types characterized by a low ash content, whereas the Aspen model appeared to fairly predict the syngas composition at different conditions of ER; however, its accuracy might be reduced if the properties of the treated biomass changed.

Models of binary neutron star remnants with tabulated equations of state

The emergence of novel differential rotation laws that can reproduce the rotational profile of binary neutron star merger remnants has opened the way for the construction of equilibrium models with properties that resemble those of remnants in numerical simulations. We construct models of merger remnants, using a recently introduced 4-parameter differential rotation law and three tabulated, zero-temperature equations of state. The models have angular momenta that are determined by empirical relations, constructed through numerical simulations. After a systematic exploration of the parameter space of merger remnant equilibrium sequences, which includes the determination of turning points along constant angular momentum sequences, we find that a particular rotation law can reproduce the threshold mass to prompt collapse to a black hole with a relative difference of only $\sim 1\%$ with respect to numerical simulations, in all cases considered. Furthermore, our results indicate a possible correlation between the compactness of equilibrium models of remnants at the threshold mass and the compactness of maximum-mass nonrotating models. Another key prediction of binary neutron star merger simulations is a relatively slowly rotating inner region, where the angular velocity Ω (as measured by an observer at infinity) is mostly due to the frame dragging angular velocity ω. In our investigation of the parameter space of the adopted differential rotation law, we naturally find quasi-spherical (Type A) remnant models with this property. Our investigation clarifies the impact of the differential rotation law and of the equation of state on key properties of binary neutron star remnants and lays the groundwork for including thermal effects in future studies.

Evaluating the budget's distributive influence on household incomes

<p>Many budget measures have been introduced by governments with the stated aim of transferring resources to particular groups - in general, the groups which are seen to receive lower incomes. An evaluative method is required to assess the extent to which resources are actually redistributed to households by the budget. This thesis suggests a taxonomy for assessing whether a measure of household income that takes account of central government budget activities is distributed differently from household earnings (market income). The taxonomy for evaluating the budget's distributive influence has four stages. Each stage progresses from observable household market income data to a more comprehensive income measure. Stage One is basically an accounting concept. Household market income is compared with an income measure which takes account of those central government budget transactions which have an obvious or direct effect on the sources and uses of household income. Stage Two is similar to studies of the influence of the budget on income distribution, such as those by Gillespie and Musgrave, which are referred to as quantitative studies. Quantitative studies are not based on structured models of economic activity, but use the results of other incidence analysis to approximate the economic effects of budget receipts and expenditures on household incomes. Stages Three and Four require structured general equilibrium models to take consistent account of the behavioural relationships important to the analysis of the economic effects of the budget by household income. The Harberger-Mieskowki-McLure (HMM) two-sector general equilibrium models specify both factor and product price changes, incorporating theories about the short-run macroeconomic effects of budget measures. Conclusions about budget incidence based on the HMM approach, however, relate to aggregate factor (capital and labour) income. Multi-sector models pioneered by Shoven, Whalley and Fullerton focus on the analysis of tax incidence by household income groups. Given the current state of the art, it is not possible to analyse the distributional effects of the entire budget on household income distribution using general equilibrium models. This thesis provides a clearer definition of some of the issues involved. A quantitative study of the money-income effects of the 1981/82 government budget is carried out as part of this thesis. The government budget is defined as the national income account of the central government's current income and outlays. Work by the New Zealand Department of Statistics based on a tax modelling system called ASSET provides the foundation for manipulating the massive data requirements of this thesis topic. The results are expressed by 10 household income groups (deciles) and 10 household types and represents the entire population residing in private dwellings. A major contribution of this thesis is that it analyses the distribution of government expenditures by household income and household type. It is found that the 1981/82 budget does redistribute money-income from households in the higher income groups to those in the lower-income groups. The personal income tax is shown to be the most important redistributive force, based on the assumption that households' actual tax payments are the same as their statutory liability for the tax. The household types which are estimated to receive the greatest net benefit from the 1981/82 central government non-market budget are one-adult and two-adult national-superannuitant household. According to the results, government expenditures tend, on average, to be consumed in greater proportion by childless household than by households with children. Comparison of the results using the Stage One and Stage Two approaches, as well as a rough approximation of a Stage Three initial income base, suggests that the more theoretically comprehensive the evaluative approach, the less redistributive is the budget. Piggott (1980b) has shown that a feature of the SWF general equilibrium models that makes them attractive for policymakers interested in social policy is that the model can be used to evaluate both the distributional and efficiency consequences of a budget change in terms of household incomes. This, and the above comparison, are powerful arguments in favour of further development of SWF models so that the incidence of the budget can be assessed in a theoretically-consistent fashion.</p>

Evaluating the budget's distributive influence on household incomes

<p>Many budget measures have been introduced by governments with the stated aim of transferring resources to particular groups - in general, the groups which are seen to receive lower incomes. An evaluative method is required to assess the extent to which resources are actually redistributed to households by the budget. This thesis suggests a taxonomy for assessing whether a measure of household income that takes account of central government budget activities is distributed differently from household earnings (market income). The taxonomy for evaluating the budget's distributive influence has four stages. Each stage progresses from observable household market income data to a more comprehensive income measure. Stage One is basically an accounting concept. Household market income is compared with an income measure which takes account of those central government budget transactions which have an obvious or direct effect on the sources and uses of household income. Stage Two is similar to studies of the influence of the budget on income distribution, such as those by Gillespie and Musgrave, which are referred to as quantitative studies. Quantitative studies are not based on structured models of economic activity, but use the results of other incidence analysis to approximate the economic effects of budget receipts and expenditures on household incomes. Stages Three and Four require structured general equilibrium models to take consistent account of the behavioural relationships important to the analysis of the economic effects of the budget by household income. The Harberger-Mieskowki-McLure (HMM) two-sector general equilibrium models specify both factor and product price changes, incorporating theories about the short-run macroeconomic effects of budget measures. Conclusions about budget incidence based on the HMM approach, however, relate to aggregate factor (capital and labour) income. Multi-sector models pioneered by Shoven, Whalley and Fullerton focus on the analysis of tax incidence by household income groups. Given the current state of the art, it is not possible to analyse the distributional effects of the entire budget on household income distribution using general equilibrium models. This thesis provides a clearer definition of some of the issues involved. A quantitative study of the money-income effects of the 1981/82 government budget is carried out as part of this thesis. The government budget is defined as the national income account of the central government's current income and outlays. Work by the New Zealand Department of Statistics based on a tax modelling system called ASSET provides the foundation for manipulating the massive data requirements of this thesis topic. The results are expressed by 10 household income groups (deciles) and 10 household types and represents the entire population residing in private dwellings. A major contribution of this thesis is that it analyses the distribution of government expenditures by household income and household type. It is found that the 1981/82 budget does redistribute money-income from households in the higher income groups to those in the lower-income groups. The personal income tax is shown to be the most important redistributive force, based on the assumption that households' actual tax payments are the same as their statutory liability for the tax. The household types which are estimated to receive the greatest net benefit from the 1981/82 central government non-market budget are one-adult and two-adult national-superannuitant household. According to the results, government expenditures tend, on average, to be consumed in greater proportion by childless household than by households with children. Comparison of the results using the Stage One and Stage Two approaches, as well as a rough approximation of a Stage Three initial income base, suggests that the more theoretically comprehensive the evaluative approach, the less redistributive is the budget. Piggott (1980b) has shown that a feature of the SWF general equilibrium models that makes them attractive for policymakers interested in social policy is that the model can be used to evaluate both the distributional and efficiency consequences of a budget change in terms of household incomes. This, and the above comparison, are powerful arguments in favour of further development of SWF models so that the incidence of the budget can be assessed in a theoretically-consistent fashion.</p>

Development and Application of a New Zealand General Equilibrium Model

<p>Whether a country gains or loses from dismantling protection is a question which has received much attention in overseas studies; studies which deal both with the relevant theory and with actual measurement. The topic has not been well analysed in the New Zealand context. Discussion amongst economists and other interested parties has certainly occurred but this has been based more on philosophical and political considerations than on applied economic research. Since questions of protection reform affect the whole economy it is inappropriate to study such problems in a partial or selective framework which cannot capture the interdependencies between each and every sector in the economy. A multi-sectoral general equilibrium model overcomes this deficiency. This thesis is concerned with the development and application of such a model. The model (named JULIANNE) is a medium term policy model designed to answer 'what if' type questions, particularly questions about trade and structure. It is not a forecasting model. Its role is rather like that of a laboratory in the natural sciences, where experiments can be conducted in a situation where certain aspects of the (economic) environment can be controlled by the researcher so that it is possible to measure the relationships between the variables of interest. The closer the environment is to the 'real world' the easier it is to apply deductions from the experiment to reality. But even quite artificial experiments can yield useful insights. The thesis comprises eleven chapters, the first three of which introduce and develop the model, examining some of the overseas general equilibrium models and assessing some of the problems which need to be addressed when constructing such a model for New Zealand; a model with an emphasis on trade and structure. The following three chapters present the JULIANNE model including its equations, a detailed explanation of its features and routines, and its method of solution, which for general equilibrium models is a most important consideration as it distinguishes the purely abstract Walrasian model from a model which is actually computable. Chapters 7 and 8 apply the model to various problems, especially to protection reform, but also to other interesting topics such as export subsidisation, relative occupational wage rates and medium term projections. The issue of model validation (in a general sense) is also covered. In Chapter 9 the model is extended from a single period snapshot model into a multi-period dynamic model, essentially introducing another variable; time, that can be controlled by the experimenter. Some of the results from Chapters 7 and 8 are then reassessed with the extended model, as described in Chapter 10. Results from the application of the model to questions about the effects of changes in protection enabled one to conclude that under flexible factor prices with fixed factor employment, the gains from freer trade vary directly with the values of the export price elasticities of demand, with the potential for economies of scale arising from specialization, and with the time horizon under consideration. They vary inversely with the values of the elasticities of substitution both between domestic and imported goods of a given type, and between goods of different types. Under a different labour market asumption, namely fixed real wage rates and flexible employment, the case for free trade is much stronger (that is, for a given set of parameter values). The profile of protection across sectors can also be important with the not improbable chance that a low uniform level of protection is superior to complete free trade, again depending on parameter values and the characteristics of the labour market. In this connection the observed uniformity of the current protection regime is very dependent on the degree of sectoral disaggregation identified in the model. As the degree of disaggregation increases, the potential for specialization also increases, as does the potential for substitution between different commodity types. Just how important these issues are, is a question for future research.</p>