Yi Chen

A space tether is a long cable used to couple satellites, probes or spacecrafts to each other or to other masses, such as a spent booster rocket, space station, or an asteroid. The motorised momentum exchange tether (MMET) was first proposed by Cartmell in 1996 and published in 1998. The system comprises a specially designed tether connecting two payload modules, with a central launcher motor. The models in this book have shown that including axial, torsional and pendular elasticity, the MMET systems have a significant bearing on overall performance and that this effect should not be ignored in future, particularly for control studies. This book provides the following points: introduction to space tethers and space tethers control, the motorised momentum exchange tether(MMET), hybrid fuzzy sliding mode control for spin-up of the MMET. The studies should help shed some light on the tether systems and hybrid control for the tether spin-up, and should be especially useful to professionals in reospace/mechanical/control engineering, or anyone else who may be of interest in utilising intelligent control for dynamical behaviors of the space tethers.

Dynamical Modelling of Space Tether

Dynamical Modelling of a Flexible Motorised Momentum Exchange Tether and Hybrid Fuzzy Sliding Mode Control for Spin-up

Yun Li

Computational Intelligence Assisted Design framework mobilises computational resources, makes use of multiple Computational Intelligence (CI) algorithms and reduces computational costs. This book provides examples of real-world applications of technology. Case studies have been used to show the integration of services, cloud, big data technology and space missions. It focuses on computational modelling of biological and natural intelligent systems, encompassing swarm intelligence, fuzzy systems, artificial neutral networks, artificial immune systems and evolutionary computation. This book provides readers with wide-scale information on CI paradigms and algorithms, inviting readers to implement and problem solve real-world, complex problems within the CI development framework. This implementation framework will enable readers to tackle new problems without difficulty through a few tested MATLAB source codes

In Industrial Revolution 4.0

Computational Intelligence Assisted Design

My dissertation attempts to provide new theoretical explanations of some long-standing international macro-finance puzzles, including the consumption-real exchange rate anomaly (i.e. the Backus-Smith puzzle), the consumption correlation puzzle, the real exchange rate volatility puzzle, the equity home bias puzzle and the exchange rate disconnect puzzle, with a particular emphasis on the possible role(s) played by news shocks and / or recursive preferences à la Epstein and Zin (1989). News shocks, defined in a broad sense as shocks to the market's expectations about future changes in driving forces, can have dramatically different impacts on the model dynamics in contrast to traditional unanticipated shocks to the driving forces. Epstein-Zin preferences, by breaking two independent aspects of preferences (attitude toward risks and willingness to substitute consumptions over time), make consumers more sensitive to long-run risks and as a result amplify the impacts of news shocks. Both features have become increasingly popular in the recent closed-economy macro-finance literature. My dissertation is among the first few to use these features to explain a long list of international macro-finance puzzles. Chapter 1 deals with the consumption-real exchange rate anomaly, the consumption correlation puzzle and the real exchange rate volatility puzzle. Data show that real exchange rates are negatively correlated with cross-country relative consumptions; consumptions are less correlated internationally than outputs; and real exchange rates are much more volatile than consumptions. Chapter 1 argues that these facts don't necessarily point to a "lack of risk sharing across countries" or a "low degree of international goods market integration", as are widely thought to be responsible for the above phenomena. The idea is formalized in a frictionless endowment-driven two-country two-good model featuring long-run news, i.e. slowly-moving signals that change the market's expectations about future output growth, and Epstein-Zin preferences. The model predicts that (1) news has opposite effects on the relative consumption and real exchange rate, so the two can be negatively correlated; (2) news has opposite effects on the home and foreign consumptions, so the cross-country consumption correlation can be low; (3) news makes the inter-temporal marginal rate of substitution (IMRS) excessively volatile relative to consumption growth, so the real exchange rate-consumption volatility ratio can be high. Intuitively, prediction (1) is true because news shocks behave as a demand shifter in the short run. Unlike unanticipated supply shocks, news shocks disturb the relative demand curve and trace out an upward-sloping relative supply curve. Prediction (2) can be justified by the fact that news does not materialize on impact (Christmas hasn't come yet), meaning that responses of consumptions to news are essentially a "zero-sum game" in the short run. Prediction (3) can be understood by noticing that news generates a dynamic wedge between the IMRS and the contemporaneous consumption growth. Calibrated through a structural vector auto-regression (SVAR) exercise, the model quantitatively replicates all the puzzling facts mentioned above. I also investigate the plausibility of two alternative explanations of the puzzles. Neither an incomplete-market model nor a trade-cost model can jointly account for all the facts. Chapter 2 incorporates EZ preferences in an otherwise standard open-macro model and shows that EZ preferences play a role of raising the home bias in equities, i.e. the bias of equity portfolios toward home assets, relative to the standard constant-relative-risk-aversion (CRRA) preferences. This happens because EZ preferences generate a long-run risk hedging demand that contributes to a positive covariance between the relative expenditure and the excess equity return. As a result the domestic equity is more likely a good asset as it pays off more whenever investors are willing to spend more. Additional main findings can be summarized as follows. First, using least structural information, we show that the degree of equity home bias depends on the conditional covariance-variance ratio between the relative expenditure and the excess equity return, which is in contrast to the CRRA models' counterfactual prediction that the degree of equity home bias relies on the conditional covariance-variance ratio between the real exchange rate and the excess equity return. Second, we solve for the optimal portfolio as an explicit function of the structural parameters using Devereux and Sutherland (2011)'s approach. Analytical solutions clearly show that EZ models tilt optimal portfolios toward local equities for a wide range of parameterizations relative to CRRA models. Third, the decomposition of equity home bias into two terms indicates that the relative contribution of the consumption covariance term and the portfolio covariance term to the rise in home bias relies on the persistence of endowment shocks. Chapter 3 looks into the exchange rate disconnect puzzle. Exchange rates seem to be disconnected from macro fundamentals: current and past macro fundamentals have a hard time accounting for the movements in nominal exchange rates (also known as the Meese-Rogoff puzzle); both nominal and real exchange rates appear excessively volatile relative to macro fundamentals; exchange rates don't seem to follow the strong cyclical patterns implied by most standard models. Chapter 3 argues that allowing for news about future money supply in a sticky-price open-economy model can shed light on the disconnect puzzle. News shocks, unlike unanticipated shocks, can affect exchange rates on impact but have muted effects on the contemporaneous macro variables. Two additional assumptions are made to make the mechanism work. First, only a fraction of households have access to the international financial markets while the rest leads a hand-to-mouth life. As news shocks have opposite impacts on the consumptions of two types of households, the aggregate consumption is less responsive. Second, export prices are denominated in local currencies. This assumption helps eliminate the spending-switching effects of nominal exchange rate movements. Overall the model is shown to move things in right directions both qualitatively and quantitatively.

Yi Chen

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