1,721,444 research outputs found
Aggregation of Linear Dynamic Microeconomic Models
No full textWe survey a number of important results concerning aggregation of dynamic, stochastic relations. We do not aim at a comprehensive review; instead, we focus heavily on the results collected in Forni and Lippi [Forni, M., Lippi, M., 1997. Aggregation and the Microfoundations of Dynamic Macroeconomics. Oxford University Press, Oxford]. We argue that the representative-agent assumption is misleading and the microfoundation of dynamic macroeconomics should be based on explicit modeling of heterogeneity across agents. An unpleasant aspect of this modeling strategy is that macroeconomic implications of micro theory are difficult to obtain. However, difficulties are reduced by large number results. Moreover, puzzling implications of existing theories could be reconciled with empirical evidence on macro data. © 1999 Elsevier Science S.A. All rights reserve
Aggregation and the Microfoundations of Dynamic Macroeconomics
No full textThis book argues that modern macroeconomics has completely overlooked the aggregate nature of the data. Standard models start with intertemporally maximizing agents and obtain dynamic equations linking economic variables like consumption, income, investment, interest rates and employment. Such equations exhibit testable properties like cointegration, definite patterns of Granger causality, and restrictions on the parameters. The usual simplification that agents are identical leads to testing these properties directly on aggregate data. Here this simplification is systematically questioned. In Part I the homogeneity assumption is tested using disaggregate data and strongly rejected. As shown in Part II, the consequence of introducing heterogeneity is that, apart from flukes, cointegration, unidirectional Granger causality and restrictions on the parameters do not survive aggregation: thus the claim that modern macroeconomics has solid microfoundations is unwarranted. However, it is argued in Part III that aggregation is not necessarily bad. Some important theory-based models that do not fit aggregate data well in their representative-agent version can be reconciled with aggregate data by introducing heterogeneity
Highly dynamic 1D coordination polymers for adsorption and separation applications
No full textOne-dimensional (1D) coordination polymers (CPs) are a class of materials with intriguing specific properties which however have been significantly overlooked, partially due to the monumental growth of research activities on their three-dimensional analogues, considered more robust and useful for applications. Here, we highlight the main advances on the use of 1D CPs for adsorption and separation purposes, focusing on larger guest molecules rather than common gaseous species (such as N2, CO2, etc...), also including CP systems capable to adsorb charged dyes or ions from aqueous solutions. Overall, in most cases, the adsorption processes here described induce quite significant structural changes in the CPs framework, which we were able to play up given the extensive X-ray characterization available. We aim to show how the dynamic properties of this class of compounds, in terms on their aptitude to respond to external chemical stimuli, is inherent with their structural features, for they are composed by robust chain-like arrays hold together by weak inter-chain interactions
Human multi-robot safe interaction: A trajectory scaling approach based on safety assessment
No full textNowadays, industrial robotics requires that robots and humans share the same workspace and collaborate to a certain extent. In such a scenario, the safety is the minimum requirement and, for this reason, many off-the-shelf collaborative robots are now available on the market which, basically, are able to limit the contact forces in the case of impact. Differently from many different works, this article presents a solution to human multi-robot safe interaction in which multiple mobile manipulators are in charge of performing a cooperative task in a workspace shared with human operators. The safety of the interaction is assessed by a safety field that considers the whole system and is general enough concerning its expression. Based on the value of this field, the cooperative task trajectory is properly modified so as to ensure a safe interaction while trying to preserve as much as possible the nominal task, which is instead completely aborted whenever the safety of the interaction cannot be guaranteed. The solution is first designed within a centralized architecture and, then, upon this, a distributed implementation is presented, which, in general, aims to exhibit the same performance as the centralized counterpart. Finally, both simulations and experiments on real industrial robots corroborate the designed solution
Leontodon villarsii and L. Rosani: nomenclatural, palynological, caryological and micromorphological aspects
No full textSafety in human-multi robot collaborative scenarios: a trajectory scaling approach
No full textIn this paper, a strategy to handle the human safety in a multi-robot scenario is devised. In the presented framework, it is foreseen that robots are in charge of performing any cooperative manipulation task which is parameterized by a proper task function. The devised architecture answers to the increasing demand of strict cooperation between humans and robots, since it equips a general multi-robot cell with the feature of making robots and human working together. The human safety is properly handled by defining a safety index which depends both on the relative position and velocity of the human operator and robots. Then, the multi-robot task trajectory is properly scaled in order to ensure that the human safety never falls below a given threshold which can be set in worst conditions according to a minimum allowed distance. Simulations results are presented in order to prove the effectiveness of the approach
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