In the application of cycle-to-cycle control to manufacturing processes, the model of the process reduces to a gain matrix and a pure delay. For a general multiple input – multiple output process, this matrix shows the degree of influence each input has on each output. For a system of high order, determining this gain matrix requires excessive numbers of experiments to be performed, and thus a simplified, but non-ideal form for the gain matrix must be developed. In this paper, the model takes the form of a Gaussian distribution with experimentally determined standard deviation and scaling coefficients. Discrete die sheet metal forming, a multiple input-multiple output process with high dimensionality, is chosen as a test application. Results of the prediction capabilities of the Gaussian model, as well as those of two previously existing models, are presented. It is shown that the Gaussian distribution model does the best job of predicting the output for a given input. The model’s invariance over a set of different formed parts is also presented. However, as shown in the companion paper on cycle-to-cycle control, the errors inherent in this model will cause non-ideal performance of the resulting control system. However, this model appears to be the best form for this problem, given the limit of minimal experimentation. / Singapore-MIT Alliance (SMA)

This thesis contributes to the knowledge and the characterization of scroll machines and their systems. It is based on experimental and modeling works carried out on: a) A hermetic scroll compressor used inside an air-cooled water chiller. b) An oil-free open-drive scroll expander integrated into an Organic Rankine Cycle (ORC) power system. c) Open-drive scroll compressor and expander used in a Liquid Flooded Ericsson Cycle Cooler (LFEC). Such a system uses the liquid flooding of the compressor and of the expander to approach isothermal compression and expansion processes. New semi-empirical models of the scroll compressor and expander were proposed and existing models improved. A deterministic model of the scroll expander was established. The model associates a geometrical description of the machine with a thermodynamic description of the expansion process. This model was validated for the two expanders investigated experimentally. The model validation revealed that the performance of the expanders is mainly affected by the supply pressure drop and by the internal leakages. Using the validated model, parametric studies were carried out to investigate the variation of the performance of both expanders with modification of their design and with the operating parameters. The thesis also investigated the scroll machines from the point of view of their integration into thermal systems. A first experimental investigation was carried out on an air-cooled chiller. The scroll compressor semi-empirical model, with its parameters identified on the basis of published manufacturer data, was used as a refrigerant flow meter. The analysis of the experimental data allowed a better understanding of the chiller operation and a better identification of its model parameters (such as the fan and the hot gas bypass control models). A second experimental investigation was carried out on an ORC power system, working with R123. In order to select the most appropriate fluid, the performances achieved with four different fluids were compared by simulation. The experimental study confirmed that the scroll expander is a good candidate for an ORC system: the tested prototype presented a good performance (the maximum global isentropic effectiveness achieved was 68%). Using an ORC simulation model, parametric studies were carried out to investigate the effects of the expander characteristics and operating conditions on the cycle performance. The latter is mainly affected by the expander internal leakage and by the liquid subcooling at the condenser exhaust. A third experimental investigation was performed on a LFEC working with nitrogen as refrigerant and alkyl-benzene oil as flooding liquid. Experimental data was used to identify the parameters of the scroll compressor and expander semi-empirical models. Parametric studies were performed to identify the different factors affecting their performance. One of the undesirable features of the machines is the increase of the supply and exhaust pressure drops with the increase of oil quantity.

Generally speaking, business cycle could be discussed as a short-term fluctuation of business cycle and long-term economic growth. In this research, we will confer what impact factors might have affected the business cycle of correlations (BCCs) across countries in a period of short time. Many empirical analysis have pointed out the temporary factors to the business cycle mainly come from the transferred factors of economic aspect. This is called ¡§Transmission Mechanisms.¡¨ What is ¡§Transmission Mechanisms?¡¨ Economists often try to substitute it in good markets, financial markets, and the coordination of monetary policies. However, in this duration of the empirical analysis, using only these proxy variables to explain BCCs between two countries seems too limited. According to this situation, we believe if the BCCs can be explained by using proxy factors of non-economic variable, the result can be utilized by making up the defect. We attempt to find new factors in political approach and combine with the ¡§Transmission Mechanisms¡¨ that we have introduced earlier. After that, we expect to comprehend the BCCs among G7 countries from the inputs of the two completed different variables. To analyze further economic implication in our research, five conclusions have been summarized below: Firstly, increasing bilateral trade has significantly provided positive effect to BCCs among G7 countries from 1980 to 2002. Because the empirical result of Single Country is insignificant, we then use a two-stage method. First, we estimate ¡§Trade¡¨ from endogenous variable to exogenous one. Secondly, we use Panel method to expand its matrix. Finally, we improve the empirical estimators of insignificant statistics before. In other words, the important variables of the correlation of bilateral trade are whether or not the two countries speak the same language; the border problem, and the distance between the two are the same, etc. So, when we talk about the relations between BCCs and good and service markets, we must consider these exogenous factors. Eventually, we will receive more detailed results. Secondly, although to trade in financial markets can increase the BCCs between two countries, the statistic report is insignificant -0.0019 (0.0012). About this empirical result, we can obtain reasonable explanations from the researches (for instance: Imbs, 2004 or Kose et al, 2003), they point out that financial markets are bound excessively by globalization. Therefore, this will aggravatingly make each country to focus on its specialization. Finally, this situation will make the BCCs getting collapsed among these countries. This also explains that the specialization among these countries will reduce the positive effect from the BBCs to financial markets. Thirdly, in this empirical research of Single-Country, we use three proxy estimators of economics to substitute common properties of the monetary policy. At this point, there are no identical correlations of corresponding among other countries except some significantly negative trends shown to the member countries of European Union. According to this situation, we believe it may be the consequence to all the member countries under some ERM restrictions, which is Treaty of Maastricht. Also, because of the rules form this treaty, the monetary policies are getting to be accordant, and the BCCs among the countries will soon appear in obviously positive trend. Fourthly, in the model, the difference of the inflation rate between two countries is not significant with BCCs; therefore, an identical correlation is hardly shown. Moreover, the coefficient symbol is not in our expecting direction, so we think maybe some policies are neglected to the influence of this variable. After all these, we believe if we can control some relative policy effect to inflation rate when discussing the relationship between this variable and the BCCs, we should be able to find out the real effect of this substitutive variable to BCCs Lastly, in the research, the statistics effect of the party variables and business cycle of correlations are very significant. This also indicates the political factor will play an important role for many sources of the fluctuation tread of BCCs. In other words, when we discuss the issue of BCCs if miss the contribution of political factors to the BCCs. Then, this might cause the omitted variable biased, and finally cause the whole computation become inefficient. In addition, we can have further discussion by an input of a factor: to conserve the joint benefit of all the member countries in an economic organization, these countries need to be ruled by the same ideal political party. Otherwise, the institute will never reach its essential result. Combining all the conclusions we have shown above, we can find out the BCCs among G7 countries from 1980-2002. Besides the influence of the ¡§Transmission Mechanisms,¡¨ the result will be varied by the political factors. In conclusion, we need to consider the contribution of the political party variables to the BCCs when talking about this issue, therefore; the original theoretical model can be more persuasive. According to a statistics of IMF, the BCCs among those industrial countries are falling little by little in recent years. Therefore, consolidating trade cooperation is essential for what we believe to improve the BCCs among G7. At the same time, pass through a strong integrate monetary policy can move forward all the incumbent parties from all the countries to agree among themselves, and even reach more substantial effect. From the example like this, we might find evidence from BCCs issues by discussing the integration process in European Monetary Union.

Thèse d'exercice : Médecine : Nancy 1 : 2009. / Titre provenant de l'écran-titre.

This thesis is a collection of three essays in which the behaviour of unemployment is studied in different dynamic environments. Throughout, unemployment is understood to be involuntary, arising due to the uncoordinated nature of trade in the labour market as viewed from the perspective of the Diamond-Mortensen-Pissarides equilibrium matching model. It goes without saying that the fundamental motivation for pursuing this line of research is provided by the untold consequences, both human and economic, of otherwise capable people remaining involuntarily idle. An attempt, therefore, is made to contribute to the understanding of how various aspects of macroeconomic policy can influence unemployment outcomes. The approach maintained throughout is to combine general equilibrium modelling with simulation techniques in order to provide not only qualitative inferences but also quantitative descriptions of equilibrium dynamics. The dynamic environments considered cover both the business cycle (the first two chapters) and the life cycle (the third chapter). In the first chapter, Structural Tax Reform and the Cyclical Behaviour of the Labour Market, we build a real business cycle model with frictional unemployment and distortionary tax rates which are increasing in individual taxable labour income. The cyclical aspects of tax reform that are addressed in this chapter are distinct from the stationary state distributional issues that have garnered most of the attention in the existing literature on structural tax reform. Estimating the tax code parameters from federal income tax return data for the U.S., we find that a reduction in the progressivity of the tax system is associated with a significant increase in the volatility of hours per worker. The intuition is simply that the greater the extent to which marginal tax rates fluctuate in response to shocks, the smaller the incentive to adjust working hours. But in a frictional labour market in which it is costly for forms to issue vacancies, the behaviour of hours - i.e. intensive adjustment, or adjustment in the intensive margin - is a determining factor of job creation - i.e. extensive adjustment. We then explain how the dynamic behaviour of hours along the adjustment path to an aggregate productivity shock generates o¤setting incentives for job creation, with the result that tax reform has little impact on unemployment fluctuations. The welfare cost of the business cycle is also computed under different tax regimes. It is found that although business cycles are more costly under a flat tax, the overall welfare implications are quantitatively negligible regardless of the tax system. Having described the effects of the tax system on equilibrium dynamics when perturbed by a productivity disturbance, we then consider business cycle adjustment to an aggregate demand shock in the form of fiscal stimulus. In light of recent fiscal developments in the U.S. and Europe, the ability of expansionary fiscal policy to stimulate output has gained renewed interest in the business cycle literature. We contribute to the analysis by assessing whether the efficacy of government expenditure in reducing unemployment depends on the structure of the tax system. It is demonstrated that a less progressive tax policy increases the ability of expansionary fiscal policy to stimulate output due to a larger response in hours, but this comes at the cost of a smaller unemployment multiplier. Tax reform therefore causes a compositional shift in labour market adjustment in response to aggregate demand shocks, with relatively more adjustment occurring in the intensive margin and less adjustment in the extensive margin the flatter the tax schedule is. The reason why this compositional shift occurs for a demand shock but not a supply shock is that the adjustment path of hours is qualitatively dependent on the type of disturbance. In particular, we describe how equilibrium undershooting in hours occurs only in response to an aggregate productivity (supply) shock, whereas the negative wealth effects arising from increased government expenditure exert sustained upward pressure on hours along the entire adjustment path, thus providing a significant incentive for firms to substitute away from job creation. The second chapter, Monetary Policy and Job Creation in a New Keynesian Model, is motivated by the work of Cooley and Quadrini (1999) and Krause and Lubik (2007). These studies indicate that a typical monetary business cycle model with frictional unemployment and endogenous job destruction tends to encounter difficulty in generating a rise in job creation in response to expansionary monetary policy, rendering the model inconsistent with the downward sloping Beveridge curve that appears in the data and implying only a limited policy role for inflationary job creation. Matching frictions in the labour market congest the job creation process so that firms tend to skew adjustment to shocks towards the job destruction margin. In recognition of the assertion put forth but unpursued by Cooley and Quadrini (1999) that fluctuations in the size of the labour force may ease labour market congestion and therefore amplify cyclical job creation, in Chapter II we extend a New Keynesian model with unemployment to feature an endogenous labour market participation decision. However, a baseline model with a standard degree of risk aversion tends to exhibit countercyclical labour force participation, which is inconsistent with the data. In order to address this issue, we propose the notion of labour market participation as a social consideration, which we demonstrate to be capable of generating procyclical participation incentives. The basic idea is that agents will tend not to exit the labour force during booms in order to "keep up with the Joneses". We then find that plausible fluctuations in the size of the labour force do not exert a quantitatively significant effect on job creation. In light of this result, we search for alternative mechanisms which may overturn the conclusion that inflationary policy is incapable of incentivising job creation. The approach taken involves switching focus to the characteristics of aggregate demand dynamics along the adjustment path to a monetary shock. It is well known that standard New Keynesian models fail to deliver the gradual, hump-shaped adjustment path to monetary policy shocks that is observed in the data. We argue that if aggregate demand experiences a persistent increase in response to a monetary shock instead of peaking on impact, the incentive for firms to create jobs becomes amplified. The intuition is that, since the job creation decision is forward-looking due to the presence of matching frictions, aggregate demand must rise persistently even after the shock takes place so that firms anticipate a further increase in aggregate demand in order for the time consuming process of issuing a vacancy to be justified. To demonstrate this, it is shown that, by altering the dynamics of aggregate demand, time-inseparability in the utility function can significantly improve the ability of expansionary monetary policy to increase job creation, allowing the model to generate a downward sloping Beveridge curve conditional on monetary shocks. In the appendix to Chapter II, we lend further credence to this hypothesis by describing how the manner in which monetary policy it- self is specified may give rise to hump-shaped adjustment dynamics and, consequently, amplify inflationary job creation. Finally, in Chapter III on Equilibrium Matching and Age Discrimination Policy, we abstract from business cycle issues and concentrate instead on the life cycle. Federal legislation prohibiting the discrimination of workers on the basis of age has been in place in the United States since the 1967 Age Discrimination in Employment Act.

The National Aeronautics and Space Agency NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) platform carried by Terra and Aqua satellites, is providing systematic measurements summarized in high quality, consistent and well-calibrated satellite images and datasets ranging from reflectance in the visible and near infrared bands to estimates of leaf area index, vegetation indices and biome productivity. The objective of this research was to relate the spectral responses and derived MODIS products of ecosystems, to biogeochemical processes and trends in their physiological variables. When different sources of data were compared, discrepancies between the MODIS variables and the corresponding ground measurements were evident. Uncertainties in the input variables of MODIS products algorithms, effects of cloud cover at the studied pixel, estimation algorithm, and local variation in land cover type are considered as the cause. A simple "continuous field" model based on a physiologically-driven spectral index using two ocean-color bands of MODIS satellite sensor showed great potential to track seasonally changing photosynthetic light use efficiency and stress-induced reduction in net primary productivity of terrestrial vegetation. The model explained 88% of the variability in Flux tower-based daily Net Primary Productivity. Also a high correlation between midday gross CO2 exchange with both daily and 8-day mean gross CO2 exchange, consistent across all the studied vegetation types, was found. Although it may not be possible to estimate 8-day mean Light Use Efficiency reliably from satellite data, Light Use Efficiency models may still be useful for estimation of midday values of gross CO2 exchange which could then be related to longer term means of CO2 exchange. In addition, the MODIS enhanced vegetation index shows a high potential for estimation of ecosystem gross primary production, using respiration values from MODIS surface temperature, providing truly per-pixel estimates. / Department of Natural Resources and Environmental Management

Thesis (Ph.D.). / Written for the Dept. of Geography. Title from title page of PDF (viewed 2008/08/04). Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 173-191). Also available on the World Wide Web.

Th.--Sci.--Orléans, 1984.