A CUSUM test with sliding reference for ground resonance monitoring

Ground resonance is potentially destructive oscillations that may develop on helicopters rotors when the aircraft is on or near the ground. Therefore, this unstable phenomenon has to be detected before it occurs in order to be avoided by the pilot. To predict the zones of instability, works have generally relayed on off-line modal analysis of the helicopter model. Unfortunately, this off-line analysis is not sufficiently reliable. The subspace-based cumulative sum CUSUM test, able of on-line monitoring, is a good alternative which permits - at once- to avoid the system identification for each flight point and to have more robust detection, with reduced costs. In this paper, we describe an alternative test- with a moving reference this time- in order to kill wrong alarms or premature responses that are observed for fixed-reference tests. Numerical results reported herein are driven from simulation data

Biofuels and climate change mitigation : a CGE analysis incorporating land-use change

The question of whether biofuels help mitigate climate change has attracted much debate in the literature. Using a global computable general equilibrium model that explicitly represents land-use change impacts due to the expansion of biofuels, this study attempts to shed some light on this question. The study shows that if biofuel mandates and targets currently announced by more than 40 countries around the world are implemented by 2020 using crop feedstocks, and if both forests and pasture lands are used to meet the new land demands for biofuel expansion, this would cause a net increase of greenhouse gas emissions released to the atmosphere until 2043, since the cumulative greenhouse gas emissions released through land-use change would exceed the reduction of emissions due to replacement of gasoline and diesel until then. However, if the use of forest lands is avoided by channeling only pasture lands to meet the demand for new lands, a net increase of cumulative greenhouse gas emissions would occur but would cease by 2021, only a year after the assumed full implementation of the mandates and targets. The study also shows, contrary to common perceptions, that the rate of deforestation does not increase with the rate of biofuel expansion; instead, the marginal rate of deforestation and corresponding land-use emissions decrease even if the production of biofuels increases.Climate Change Mitigation and Green House Gases,Climate Change Economics,Energy and Environment,Environment and Energy Efficiency,Climate Change and Environment

A new SSI algorithm for LPTV systems: Application to a hinged-bladed helicopter

Many systems such as turbo-generators, wind turbines and helicopters show intrinsic time-periodic behaviors. Usually, these structures are considered to be faithfully modeled as linear time-invariant (LTI). In some cases where the rotor is anisotropic, this modeling does not hold and the equations of motion lead necessarily to a linear periodically time- varying (referred to as LPTV in the control and digital signal field or LTP in the mechanical and nonlinear dynamics world) model. Classical modal analysis methodologies based on the classical time-invariant eigenstructure (frequencies and damping ratios) of the system no more apply. This is the case in particular for subspace methods. For such time-periodic systems, the modal analysis can be described by characteristic exponents called Floquet multipliers. The aim of this paper is to suggest a new subspace-based algorithm that is able to extract these multipliers and the corresponding frequencies and damping ratios. The algorithm is then tested on a numerical model of a hinged-bladed helicopter on the ground

Modeshapes recognition using Fourier descriptors: a simple SHM example

The main objective of this study is to develop an alternative criterion for modeshape classification, as the currently available one, MAC (Modal Assurance Criteria), is only a vector correlation representing modeshape similarities. This new method is developed to provide a set of features (Fourier Descriptors) for comparing modeshapes with “local” similarities of higher interest than “global” similarities using nodal lines. These lines are able to characterize modeshapes very easily. So when damage occurs, we are able to track the few descriptors changes to localise the damage. We validated our method on a CFCF plate demonstrating the quality of the damage localisation and possible use in a “mode tracking” application (space structure)

Is SAFTA trade creating or trade diverting?: A computable general equilibrium assessment with a focus on Sri Lanka

The Agreement on South Asian Free Trade Area (SAFTA) entered its second phase of implementation in 2008. The creation of a free trade area is expected to affect its participants—Bangladesh, Bhutan, India, the Maldives, Nepal, Pakistan, and Sri Lanka—very differently given their diversity in terms of size, income, and structure of trade and protection. Using the 2004 MAcMapHS6-v2 database on measures of applied protection at the HS6 level and MIRAGE, a computable general equilibrium global model, this study examines the effects of SAFTA on trade and net income in the region. The magnitude of the effects will depend on initial levels of protection in the region and whether the agreement is trade diverting or trade creating. An important component of the SAFTA agreement is the exemption of products (sensitive list) from the trade liberalization process. Because such exclusion can restrict significantly the benefits from the regional trade agreement, we simulate the effects of SAFTA with and without sensitive products. Our findings show that among South Asian countries, Sri Lanka gains the most from the agreement because it initially has relatively low tariffs and faces high tariffs in the region. Exempting sensitive products from the agreement limits gains from trade for the lower-middle-income members of SAFTA but may be welfare enhancing for the least developed economies.South Asian Free Trade Area (SAFTA), trade liberalization, Computable General Equilibrium (CGE) model, welfare, trade, applied protection, income, FTA, Markets, Globalization,

More or less ambition?: modeling the development impact of U.S.–EU agricultural proposals in the Doha Round

"What is at stake in the standoff between the United States and Europe over agriculture in the Doha Round of trade talks at the World Trade Organization (WTO)? What impact would an agreement based on greater or lesser levels of ambition have on developing countries, whose economies depend heavily on agriculture? Two years after the WTO talks broke down in Cancún, reform of the heavily protected and subsidized agricultural sectors of the United States and Europe remains a major impediment to progress. Using the MIRAGE computable general equilibrium model of the global economy, in this policy brief we compare different scenarios for the Doha agriculture negotiations, taking real numbers from the proposals currently on the table from the European Union (EU), the United States, and the G20 group of developing countries." from TextAgricultural subsidies, tariffs, Doha Developmental Round of the World Trade Organization (WTO), Trade reform, Protectionism, trade policies, Trade barriers, exports, International trade, General equilibrium model, Market access,

Searching for an alternative to economic partnership agreements:

"On January 1, 2008, Economic Partnerships Agreements (EPAs), currently being negotiated between the European Union (EU) and nearly 80 African, Caribbean, and Pacific (ACP) countries, are expected to replace the Cotonou Agreement, which has governed trade relations between these countries since 2000. The Cotonou Agreement, implemented through a waiver from the World Trade Organization (WTO), expires on December 31, 2007. At the second EU-Africa summit, held in Lisbon on December 8–9, trade issues have been a major bone of contention, with several African heads of state denouncing the way the negotiation had been led by the European Commission. At the end of the summit, the Commission agreed to continue EPA negotiations in 2008." from textInternational agreements, Trade agreements,

The effects of alternative free trade agreements on Peru: Evidence from a global computable general equilibrium model

"By using a global computable general equilibrium model, this report analyzes the impact of various pending free trade agreements for Peru. In December 2007, a Peru–United States free trade agreement (FTA) was finally ratified by the U.S. Congress, replacing the Andean Trade Promotion and Drug Eradication Act, which awarded Peru and other Andean countries nonreciprocal preferential tariffs. A Peru–European Union (EU27) FTA is also being negotiated in the context of Peru's participation in the integration of the Andean Community (CAN). Finally, as of October 2008 Peru is concluding negotiations for a free trade agreement with China, its third major trading partner after the United States and the EU27. Although these agreements are expected to improve market access, their impact on the economic welfare of the beneficiary countries is dependent on the countries' structure of current tariffs and trade and the extent to which the new agreements result in trade diversion versus trade creation. The analysis shows that specific features of Peru's trade and tariff structures make the country a better candidate for a South-South FTA with China than for North-South FTAs with the United States or the EU27." from authors' abstractWTO, Free Trade Agreement, trade liberalization, CGE Modeling,

Two opportunities to deliver on the Doha Development pledge:

"In this brief, we evaluate the effects of a possible Doha agreement based on proposals currently on the table from the United States, the European Union, and the Group of Twenty (G20)....[The brief presents] two development-oriented alternatives...which demonstrate that more can be accomplished in the Doha Round if these two development-oriented and pro-trade measures are used." from TextAgricultural subsidies, tariffs, Doha Developmental Round of the World Trade Organization (WTO), Trade reform, Protectionism, trade policies, Trade barriers, exports, International trade, Market access, MIRAGE model,

Genetically modified food and international trade: The case of India, Bangladesh, Indonesia, and the Philippines

"Genetically modified (GM) food crops have the potential to raise agricultural productivity in Asian countries, but they are also associated with the risk of market access losses in sensitive importing countries. We study the potential effects of introducing GM food crops in Bangladesh, India, Indonesia, and the Philippines in the presence of trade-related regulations of GM food in major importers. We focus on GM field crops (rice, wheat, maize, soybeans, and cotton) resistant to biotic and abiotic stresses, such as drought-resistant rice, and use a multi-country, multi-sector computable general equilibrium model. We build on previous international simulation models by improving the representation of the productivity shocks associated with GM crops, and by using an improved representation of the world market, accounting for the effects of GM food labeling policies in major importers and the possibility of segregation for non-GM products going toward sensitive importing countries. The results of our simulations first show that the gains associated with the adoption of GM food crops largely exceed any type of potential trade losses these countries may incur. Adopting GM crops also allows net importing countries to greatly reduce their imports. Overall, we find that GM rice is bound to be the most advantageous crop for the four countries. Second, we find that segregation of non-GM crops can help reduce any potential trade loss for GM adopters, such as India, that want to keep export opportunities in sensitive countries, even with a 5 percent segregation cost. Lastly, we find that the opportunity cost of segregation is much larger for sensitive importing countries than for countries adopting new GM crops, which suggests that sensitive importers will have the incentive to invest in separate non-GM marketing channels if exporting countries like India decide to adopt GM food crops." from Authors' AbstractGenetically modified food, International trade, Developing countries, Segregation,