Home About us Contact
|
Home About us Contact | ||
|
|
||
Generation Models (generation + models)
Selected AbstractsSecond Generation Models of Currency CrisesJOURNAL OF ECONOMIC SURVEYS, Issue 5 2001Jesper Rangvid Until the beginning of the 1990s, currency crises were typically analyzed within the framework of a generation of models that assumed that the foreign exchange reserves of a country that was running a fixed exchange rate policy were falling (because the government was running a deficit on its budget that was financed by printing money). When the foreign exchange reserves reached a lower bound, a speculative attack on the fixed exchange rate was launched. Today, this theory is no longer the benchmark when explaining the occurrence of a currency crisis. Actually, a new generation of models that seeks to take explicitly into account the costs and benefits associated with the maintenance of a fixed exchange rate has emerged. This paper surveys these ,second generation models of currency crises'. This generation of models emphasizes that it is an endogenous decision if a government chooses to abandon a policy of fixed exchange rates. The survey pays special attention to the fact that the second generation of currency crises models often generates multiple equilibria for the rate of devaluation given one state of the economic fundamentals. A currency crisis can thus occur even if no secular trend in economic fundamentals can be identified, as in recent currency crises. [source] Altruism and Determinacy of Equilibria in Overlapping Generations Models with ExternalitiesTHE JAPANESE ECONOMIC REVIEW, Issue 2 2003Alain Venditti This paper deals with an OLG model with production and a single commodity, in which agents are assumed altruistic and the aggregate production function contains external effects. I prove that, if the technology satisfies a minor assumption, which encompasses positive and negative externalities, some curvature conditions on the utility function ensure local determinacy of stationary and period 2 equilibria. I prove that non-separable, strictly concave preferences are a fundamental ingredient for the occurrence of indeterminate equilibria. Finally, considering the case of unbounded growth, I establish that for any utility and production functions a unique balanced growth path is globally determinate. JEL Classification Numbers: C62, E32 [source] Emergency service systems: The use of the hypercube queueing model in the solution of probabilistic location problemsINTERNATIONAL TRANSACTIONS IN OPERATIONAL RESEARCH, Issue 5 2008Roberto D. Galvão Abstract Probabilistic location problems are surveyed from the perspective of their use in the design of emergency service systems, with special emphasis on emergency medical systems. Pioneering probabilistic models were defined in the 1980s, as a natural extension of deterministic covering models (first generation models) and backup models (second generation). These probabilistic models, however, adopted simplifying assumptions that in many cases do not correspond to real-world situations, where servers usually cooperate and have specific individual workloads. Thus the idea of embedding the hypercube queueing model into these formulations is to make them more adherent to the real world. The hypercube model and its extensions are initially presented in some detail, which is followed by a brief review of exact and approximate methods for its solution. Probabilistic models for the design of emergency service systems are then reviewed. The pioneering models of Daskin and ReVelle and Hogan are extended by embedding the hypercube model into them. Solution methods for these models are surveyed next, with comments on specialized models for the design of emergency medical systems for urban areas and highways. [source] Second Generation Models of Currency CrisesJOURNAL OF ECONOMIC SURVEYS, Issue 5 2001Jesper Rangvid Until the beginning of the 1990s, currency crises were typically analyzed within the framework of a generation of models that assumed that the foreign exchange reserves of a country that was running a fixed exchange rate policy were falling (because the government was running a deficit on its budget that was financed by printing money). When the foreign exchange reserves reached a lower bound, a speculative attack on the fixed exchange rate was launched. Today, this theory is no longer the benchmark when explaining the occurrence of a currency crisis. Actually, a new generation of models that seeks to take explicitly into account the costs and benefits associated with the maintenance of a fixed exchange rate has emerged. This paper surveys these ,second generation models of currency crises'. This generation of models emphasizes that it is an endogenous decision if a government chooses to abandon a policy of fixed exchange rates. The survey pays special attention to the fact that the second generation of currency crises models often generates multiple equilibria for the rate of devaluation given one state of the economic fundamentals. A currency crisis can thus occur even if no secular trend in economic fundamentals can be identified, as in recent currency crises. [source] VARIATIONS IN COMPOSITION, PETROLEUM POTENTIAL AND KINETICS OF ORDOVICIAN , MIOCENE TYPE I AND TYPE I-II SOURCE ROCKS (OIL SHALES): IMPLICATIONS FOR HYDROCARBON GENERATION CHARACTERISTICSJOURNAL OF PETROLEUM GEOLOGY, Issue 1 2010H. I. Petersen Lacustrine and marine oil shales with Type I and Type I-II kerogen constitute significant petroleum source rocks around the world. Contrary to common belief, such rocks show considerable compositional variability which influences their hydrocarbon generation characteristics. A global set of 23 Ordovician , Miocene freshwater and brackish water lacustrine and marine oil shales has been studied with regard to their organic composition, petroleum potential and generation kinetics. In addition their petroleum generation characteristics have been modelled. The oil shales can be classified as lacosite, torbanite, tasmanite and kukersite. They are thermally immature. Most of the shales contain >10 wt% TOC and the highest sulphur contents are recorded in the brackish water and marine oil shales. The kerogen is sapropelic and is principally composed of a complex of algal-derived organic matter in the form of: (i) telalginite (Botryococcus-, Prasinophyte- (Tasmanites?) or Gloeocapsomorpha-type); (ii) lamalginite (laminated, filamentous or network structure derived from Pediastrum- or Tetraedron-type algae, from dinoflagellate/acritarch cysts or from thin-walled Prasinophyte-type algae); (iii) fluorescing amorphous organic matter (AOM) and (iv) liptodetrinite. High atomic H/C ratios reflect the hydrogen-rich Type I and Type I-II kerogen, and Hydrogen Index values generally >300 mg HC/g TOC and reaching nearly 800 mg HC/g TOC emphasise the oil-prone nature of the oil shales. The kerogen type and source rock quality appear not to be related to age, depositional environment or oil shale type. Therefore, a unique, global activation energy (Ea) distribution and frequency factor (A) for these source rocks cannot be expected. The differences in kerogen composition result in considerable variations in Ea -distributions and A-factors. Generation modelling using custom kinetics and the known subsidence history of the Malay-Cho Thu Basin (Gulf of Thailand/South China Sea), combined with established and hypothetical temperature histories, show that the oil shales decompose at different rates during maturation. At a maximum temperature of ,120°C reached during burial, only limited kerogen conversion has taken place. However, oil shales characterised by broader Ea -distributions with low Ea -values (and a single approximated A-factor) show increased decomposition rates. Where more deeply buried (maximum temperature ,150°C), some of the brackish water and marine oil shales have realised the major part of their generation potential, whereas the freshwater oil shales and other brackish water oil shales are only ,30,40% converted. At still higher temperatures between ,165°C and 180°C all oil shales reach 90% conversion. Most hydrocarbons from these source rocks will be generated within narrow oil windows (,20,80% kerogen conversion). Although the brackish water and marine oil shales appear to decompose faster than the freshwater oil shales, this suggests that with increasing heatflow the influence of kerogen heterogeneity on modelling of hydrocarbon generation declines. It may thus be critical to understand the organic facies of Type I and Type I-II source rocks, particularly in basins with moderate heatflows and restricted burial depths. Measurement of custom kinetics is recommended, if possible, to increase the accuracy of any computed hydrocarbon generation models. [source] ORDINARY LEAST SQUARES LEARNING AND NONLINEARITIES IN MACROECONOMICSJOURNAL OF ECONOMIC SURVEYS, Issue 1 2010Orlando Gomes Abstract The paper reviews the literature on adaptive learning in macroeconomic settings where the formation of expectations is particularly relevant. Special attention will be given to simple two-period overlapping generations models with a unique fixed point perfect foresight equilibrium; in this kind of scenario, eventual long-term periodic and a-periodic cycles are exclusively the result of the process of learning. The outcome that high rates of money growth have a potentially destabilizing effect generating periodic fluctuations and chaos is emphasized. The persistence of systematic forecast errors in a scenario where agents are supposed to act rationally is relevant in this context and it will be thoroughly discussed resorting to the notions of self-fulfilling mistakes, consistent expectations equilibria and beliefs equilibria. [source] | ||||||||||