Symbolic Dynamics and Chaotic Synchronization in Coupled Duffing Oscillators

In this work we discuss the complete synchronization of two identical double-well Duffing oscillators unidirectionally coupled, from the point of view of symbolic dynamics. Working with Poincar´e cross-sections and the return maps associated, the synchronization of the two oscillators, in terms of the coupling strength, is characterized. We obtained analytically the threshold value of the coupling parameter for the synchronization of two unimodal and two bimodal piecewise linear maps, which by semi-conjugacy, under certain conditions, gives us information about the synchronization of the Duffing oscillators

Endogenous fisheries management in a stochastic model: Why do fishery agencies use TAC

The aim of this paper is to explain under which circumstances using TACs as instrument to manage a fishery along with fishing periods may be interesting from a regulatory point of view. In order to do this, the deterministic analysis of Homans and Wilen (1997)and Anderson (2000) is extended to a stochastic scenario where the resource cannot be measured accurately. The resulting endogenous stochastic model is numerically solved for finding the optimal control rules in the Iberian sardine stock. Three relevant conclusions can be highligted from simulations. First, the higher the uncertainty about the state of the stock is, the lower the probability of closing the fishery is. Second, the use of TACs as management instrument in fisheries already regulated with fishing periods leads to: i) An increase of the optimal season length and harvests, especially for medium and high number of licences, ii) An improvement of the biological and economic variables when the size of the fleet is large; and iii) Eliminate the extinction risk for the resource. And third, the regulator would rather select the number of licences and do not restrict the season length.TAC, season lengths, fisheries management, stock uncertainty

Why Economists Reject Long-Term Fisheries Management Plans?

Most fisheries agencies conduct biological and economic assessments independently. This independent conduct may lead to situations in which economists reject management plans proposed by biologists. The objective of this study is to show how to find optimal strategies that may satisfy biologists and economists' conditions. In particular we characterize optimal fishing trajectories that maximize the present value of a discounted economic indicator taking into account the age-structure of the population as in stock assessment methodologies. This approach is applied to the Northern Stock of Hake. Our main empirical findings are: i) Optimal policy may be far away from any of the classical scenarios proposed by biologists, ii) The more the future is discounted, the higher the likelihood of finding contradictions among scenarios proposed by biologists and conclusions from economic analysis, iii) Optimal management reduces the risk of the stock falling under precautionary levels, especially if the future is not discounted to much, and iv) Optimal stationary fishing rate may be very different depending on the economic indicator used as reference.fisheries management, age-structured models, discounting, Fmsy, Fmax, northern stock of hake

Lessons from the northern hake long-term management plan: Could the economic assessment have accepted it?

An economic expert working group (STECF/SGBRE-07-05) was convened in 2007 for evaluating the potential economic consequences of a Long-Term Management Plan for the northern hake. Analyzing all the scenarios proposed by biological assessment, they found that keeping the F in the status quo level was the best policy in terms of net present values for both yield and profits. This result is counter intuitive because it may indicate that effort costs do no affect the economic reference points. However, it is well accepted that the inclusion of costs affects negatively the economic reference points. In this paper, applying a dynamic agestructured model to the northern hake, we show that the optimal fishing mortality that maximizes the net present value of profits is lower than Fmax.northern hake, economic assessment, age-structured models, fishery management optimization, net present value of profits

Spatial Cournot Oligopoly with Vertical Linkages

This paper examines the equilibrium of location of N vertically-linked firms. In a spatial economy composed of two regions, a monopolist firm supplies an input to N consumer goods firms that compete in quantities. It was concluded that, when there are increases in the transport cost of the input, downstream firms prefer to agglomerate in the region where the upstream firm is located, in order to obtain savings in the production cost. On the other hand, increases in the general transport cost or in the number of downstream firms lead to a dispersion of these firms, in order to reduce competition and locate closer to the final consumer.Agglomeration; Intermediate Goods; Spatial Oligopoly.

The Optimality of the Common Fisheries Policy: the Northern Stock of Hake

We evaluate the management of the Northern Stock of Hake during 1986-2001. A stochastic bioeconomic model is calibrated to match the main features of this fishing ground. We show how catches, biomass stock and profits would have been if the optimal Common Fisheries Policy (CFP) consistent with the target biomass implied by the Fischler’s Recovery Plan had been implemented. The main finding are: i) an optimal CFP would have generated profits of more than 667 millions euros, ii) if side-payments are allowed (implemented by ITQ’s, for example) these profits increase 26%.common fisheries policy, fishing regulation, fischler recovery plan

Endogenous Fishing Mortalities: a State-Space Bioeconomic Model

A methodology that endogenously determines catchability functions that link fi shing mortality with contemporaneous stock abundance is presented. We consider a stochastic age-structured model for a fishery composed by a number of fi shing units (fleets, vessels or métiers) that optimally select the level of fishing effort to be applied considering total mortalities as given. The introduction of a balance constrain which guarantees that total mortality is equal to the sum of individual fi shing mortalities optimally selected, enables total fishing mortality to be determined as a combination of contemporaneous abundance and stochastic processes affecting the fishery. In this way, future abundance can be projected as a dynamic system that depends on contemporaneous abundance. The model is generic and can be applied to several issues of fisheries management. In particular, we illustrate how to apply the methodology to assess the floating band target management regime for controlling fishing mortalities which is inspired in the new multi-annual plans. Our results support this management regime for the Mediterranean demersal fishery in Northern Spain.This work was funded by the European Commission as part of the MINOUW project (H2020-SFS-2014-2, number 634495) and the Spanish Ministry of Economy, Industry and Competitiveness (ECO2016-78819-R, AEI/FEDER, UE

Pulse vs. Optimal Stationary Fishing: The Northern Stock of Hake

Pulse fishing may be a global optimal strategy in multicohort fisheries. In this article we compare the pulse fishing solutions obtained by using global numerical methods with the analytical stationary optimal solution. This allows us to quantify the potential benefits associated with the use of periodic fishing in the Northern Stock of hake. Results show that: first, management plans based exclusively on traditional reference targets as Fmsy may drive fishery economic results far from the optimal; second, global optimal solutions would imply, in a cyclical manner, the closure of the fishery for some periods and third, second best stationary policies with stable employment only reduce optimal present value of discounted profit in a 2%.optimal fisheries, management optimization in age-structured models, pulse fishing

Estudo sobre métodos de estimação de F(t) para o cálculo dos parâmetros de distribuições de Weibull com a aplicação em uma análise de falhas de garrafas PET

TCC(graduação) - Universidade Federal de Santa Catarina. Campus Joinville. Bacharelado Interdisciplinar em Mobilidade.A distribuição de Weibull, desenvolvida inicialmente durante as décadas de 1920 a 1950, ficou famosa com um trabalho publicado por W. Weibull (1951) sobre a tensão de escoamento de aços. Neste presente estudo, será analisado a aplicação de diferentes métodos para se estimar F(t) para o cálculo dos parâmetros de uma distribuição Weibull, aplicando-os em resultados experimentais de testes de fadiga com Garrafas PET. Os ensaios de fadiga foram realizados em amostras de garrafas PET de 1 litro, feitas com preformas de 48g, com 1 litro de água alcalina (pH 12), escolhidas aleatoriamente e colocadas em um dispositivo de testes para realizar ciclos de pressurização a 600 kPa (6 bar). Os resultados obtidos mostram valores muito próximos, porém ao serem aplicados em cálculos de probabilidade os resultados podem divergir em até 10%. Logo, nota-se a importância de validar o método de estimação antes que seja aplicado em análises de confiabilidade