scholarly journals Print Email The Godley–Tobin memorial lecture

2021 ◽  
Vol 9 (1) ◽  
pp. 1-10
Author(s):  
Robert J. Shiller ◽  
Keyword(s):  
Driving Force ◽  
Dynamic Models ◽  
Economic Modeling ◽  
Memorial Lecture ◽  
Animal Spirits ◽  
Business Fluctuations ◽  
Economic Decisions ◽  
Transmission Of Disease ◽  
Ambiguous Situations

John Maynard Keynes's (1936) concept of ‘animal spirits’ or ‘spontaneous optimism’ as a major driving force in business fluctuations was motivated in part by his and his contemporaries' observations of human reactions to ambiguous situations where probabilities couldn't be quantified. We can add that in such ambiguous situations there is evidence that people let contagious popular narratives and the emotions they generate influence their economic decisions. These popular narratives are typically remote from factual bases, just contagious. Macroeconomic dynamic models must have a theory that is related to models of the transmission of disease in epidemiology. We need to take the contagion of narratives seriously in economic modeling if we are to improve our understanding of animal spirits and their impact on the economy.

A Tail-Payoff Puzzle in Dynamic Pollution Control

2011 ◽  
Vol 11 (1) ◽  
Author(s):  
Antti Iho ◽  
Mitri Kitti
Keyword(s):  
Pollution Control ◽  
Driving Force ◽  
Crop Production ◽  
Social Welfare Function ◽  
Dynamic Models ◽  
Dynamic Problems ◽  
Negative Externalities ◽  
Input Use ◽  
Optimal Policies ◽  
Phosphorus Losses

Abstract We analyze dynamic models with negative externalities occurring from production capital and input use. We uncover a puzzle related to such models: evaluated with a social welfare function, the steady-state outcome of a socially optimal policy, and thus the tail of the corresponding payoff sequence, may yield a smaller social payoff than a market outcome. The main questions we address are under what conditions this phenomenon arises and how general it is. We show that there are always Pareto-optimal policies which lead to the puzzle when the discount rate is fixed. In addition to discounting, the driving force of our results is that the periodic pollution and profits are linked to production capital. We demonstrate the puzzle with a model for controlling phosphorus losses from crop production. We argue that the puzzle should be taken into account in the policy analysis of dynamic problems, including negative externalities.

Driving force analysis for the secondary adjustable system in FAST

Robotica ◽  
2011 ◽  
Vol 29 (6) ◽  
pp. 903-915 ◽  
Author(s):  
Zhu-Feng Shao ◽  
Xiaoqiang Tang ◽  
Xu Chen ◽  
Li-Ping Wang
Keyword(s):  
Trajectory Optimization ◽  
Driving Force ◽  
Dynamic Models ◽  
Inverse Dynamics ◽  
Driving Forces ◽  
Euler Method ◽  
Central Component ◽  
Force Analysis ◽  
Inverse Dynamic ◽  
Driving Force Analysis

SUMMARYThe Secondary Adjustable System (SAS) addressed here is a central component of the Five-hundred-meter Aperture Spherical radio Telescope (FAST). It is a 6-degree-of-freedom rigid Stewart manipulator, in which one platform (the end-effector) should be controlled to track-desired trajectory when another platform (denoted as the base) is moving. Driving force analysis of the SAS is the basis for selecting rational servomotors and guaranteeing the dynamic performance, which will affect the terminal pose accuracy of the FAST. In order to determine the driving forces of the SAS, using the Newton–Euler method, the inverse dynamics of the Stewart manipulator is modeled by considering the motion of the base. Compared with the traditional dynamic models, the inverse dynamic model introduced here possesses an inherent wider application range. By adopting the kinematic and dynamic parameters of the FAST prototype, the driving force analysis of the SAS is carried out, and the driving force optimization strategies are proposed. Calculation and analysis presented in the paper reveal that there are three main factors affecting the driving forces of the SAS. In addition, the driving force analysis of this paper lays out guidelines for the design and control of the FAST prototype, as well as the structure and trajectory optimization.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

The nucleation of cavities at grain boundaries

1987 ◽  
Vol 45 ◽  
pp. 288-291
Author(s):  
P. J. Goodhew
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Grain Boundaries ◽  
Radiation Damage ◽  
Impurity Concentration ◽  
Driving Force ◽  
Nucleation And Growth ◽  
Phase Boundaries ◽  
Cavity Nucleation ◽  
Spherical Bubble

Cavity nucleation and growth at grain and phase boundaries is of concern because it can lead to failure during creep and can lead to embrittlement as a result of radiation damage. Two major types of cavity are usually distinguished: The term bubble is applied to a cavity which contains gas at a pressure which is at least sufficient to support the surface tension (2g/r for a spherical bubble of radius r and surface energy g). The term void is generally applied to any cavity which contains less gas than this, but is not necessarily empty of gas. A void would therefore tend to shrink in the absence of any imposed driving force for growth, whereas a bubble would be stable or would tend to grow. It is widely considered that cavity nucleation always requires the presence of one or more gas atoms. However since it is extremely difficult to prepare experimental materials with a gas impurity concentration lower than their eventual cavity concentration there is little to be gained by debating this point.

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