The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Dirk Reheul - One of the best experts on this subject based on the ideXlab platform.
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Feasibility of isolation Perimeters for genetically modified maize
Agronomy for Sustainable Development, 2008Co-Authors: Yann Devos, Olivier Thas, Eva M. Clercq, Mathias Cougnon, Karl Cordemans, Dirk ReheulAbstract:Using geographic information system datasets and Monte Carlo simulations, this study investigates to what extent the intra-regional variability in maize share and field distribution affects the feasibility of implementing isolation Perimeters between genetically modified (GM) and non-GM maize fields. More specifically, five scenarios differing in shares and spatial distributions of GM maize were tested for various isolation Perimeters in six agricultural areas in Flanders (Belgium). Proportions of non-GM maize fields and farmers having at least one non-GM maize field occurring within isolation Perimeters were calculated to assess how spatial co-existence measures would affect the freedom of choice of neighbouring farmers to grow non-GM maize on their fields. Irrespective of the scenario tested, our results demonstrated that the proportions of non-GM maize fields and their corresponding farmers falling within the isolation Perimeters are approximately two to eight times higher in areas with the highest maize share than in areas with the lowest maize share. The higher the share of GM maize and the wider the imposed isolation Perimeter, the lower the intra-regional differences became. Hence, those findings confirm that farmers will not be equally affected by isolation Perimeters, indicating the importance of considering intra-regional differences in the choice of appropriate spatial co-existence measures. Since uniform and wide isolation Perimeters tend to be difficult to implement in practice and hardly reflect the diversity of the agricultural landscape, relying on flexible or combining various co-existence measures is worthwhile considering. As an alternative to single co-existence measures for limiting the GM input from cross-fertilisations between neighbouring maize fields, the appropriateness of other on-farm co-existence measures is discussed for Flemish agricultural conditions. Proposing the most appropriate co-existence measures on a case-by-case basis may be one step forward in reaching proportionate, fair and consistent co-existence at the regional and landscape level.
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Implementing isolation Perimeters around genetically modified maize fields
Agronomy for Sustainable Development, 2007Co-Authors: Yann Devos, Dirk Reheul, Olivier Thas, Eva M. Clercq, Mathias Cougnon, Karl CordemansAbstract:Due to the growing cultivation area of genetically modified (GM) maize and the rising number of GM maize varieties commercially available to European farmers, the co-existence between GM and non-GM maize is becoming a burning issue in some European regions. Hence, Member States are imposing or discussing specific co-existence measures to keep the adventitious presence of GM material in non-GM produces below the established labelling threshold. As maize is a cross-pollinated crop that uses wind for the dispersal of its pollen, on-farm co-existence measures may rely on the spatial isolation of GM and non-GM maize fields. In this study, we developed an approach that combines geographic information system (GIS) datasets with Monte Carlo simulations to assess the feasibility of implementing isolation Perimeters around GM maize fields, since its practical implementation is rarely addressed in the co-existence debate. More specifically, five scenarios differing in shares and spatial distributions of GM maize were tested for various isolation Perimeters in two agricultural areas in Flanders (Belgium). The GIS analyses emphasised the small size of maize fields and their scattered distribution throughout the cropped area. The feasibility of implementing isolation Perimeters was largely affected by the (GM) maize share, the spatial distribution of GM maize, and the width of isolation Perimeters. The higher the (GM) maize share and the wider the isolation Perimeter, the higher the proportions of farmers with non-GM maize fields occurring within the implemented isolation Perimeter. Compared with randomly distributed GM maize fields, the clustering of GM maize fields on a larger scale and at the farm level increased the feasibility of implementing isolation Perimeters. The approach developed proved to be a valuable tool to quantify the feasibility of implementing isolation Perimeters under real agricultural conditions.
Karl Cordemans - One of the best experts on this subject based on the ideXlab platform.
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Feasibility of isolation Perimeters for genetically modified maize
Agronomy for Sustainable Development, 2008Co-Authors: Yann Devos, Olivier Thas, Eva M. Clercq, Mathias Cougnon, Karl Cordemans, Dirk ReheulAbstract:Using geographic information system datasets and Monte Carlo simulations, this study investigates to what extent the intra-regional variability in maize share and field distribution affects the feasibility of implementing isolation Perimeters between genetically modified (GM) and non-GM maize fields. More specifically, five scenarios differing in shares and spatial distributions of GM maize were tested for various isolation Perimeters in six agricultural areas in Flanders (Belgium). Proportions of non-GM maize fields and farmers having at least one non-GM maize field occurring within isolation Perimeters were calculated to assess how spatial co-existence measures would affect the freedom of choice of neighbouring farmers to grow non-GM maize on their fields. Irrespective of the scenario tested, our results demonstrated that the proportions of non-GM maize fields and their corresponding farmers falling within the isolation Perimeters are approximately two to eight times higher in areas with the highest maize share than in areas with the lowest maize share. The higher the share of GM maize and the wider the imposed isolation Perimeter, the lower the intra-regional differences became. Hence, those findings confirm that farmers will not be equally affected by isolation Perimeters, indicating the importance of considering intra-regional differences in the choice of appropriate spatial co-existence measures. Since uniform and wide isolation Perimeters tend to be difficult to implement in practice and hardly reflect the diversity of the agricultural landscape, relying on flexible or combining various co-existence measures is worthwhile considering. As an alternative to single co-existence measures for limiting the GM input from cross-fertilisations between neighbouring maize fields, the appropriateness of other on-farm co-existence measures is discussed for Flemish agricultural conditions. Proposing the most appropriate co-existence measures on a case-by-case basis may be one step forward in reaching proportionate, fair and consistent co-existence at the regional and landscape level.
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Implementing isolation Perimeters around genetically modified maize fields
Agronomy for Sustainable Development, 2007Co-Authors: Yann Devos, Dirk Reheul, Olivier Thas, Eva M. Clercq, Mathias Cougnon, Karl CordemansAbstract:Due to the growing cultivation area of genetically modified (GM) maize and the rising number of GM maize varieties commercially available to European farmers, the co-existence between GM and non-GM maize is becoming a burning issue in some European regions. Hence, Member States are imposing or discussing specific co-existence measures to keep the adventitious presence of GM material in non-GM produces below the established labelling threshold. As maize is a cross-pollinated crop that uses wind for the dispersal of its pollen, on-farm co-existence measures may rely on the spatial isolation of GM and non-GM maize fields. In this study, we developed an approach that combines geographic information system (GIS) datasets with Monte Carlo simulations to assess the feasibility of implementing isolation Perimeters around GM maize fields, since its practical implementation is rarely addressed in the co-existence debate. More specifically, five scenarios differing in shares and spatial distributions of GM maize were tested for various isolation Perimeters in two agricultural areas in Flanders (Belgium). The GIS analyses emphasised the small size of maize fields and their scattered distribution throughout the cropped area. The feasibility of implementing isolation Perimeters was largely affected by the (GM) maize share, the spatial distribution of GM maize, and the width of isolation Perimeters. The higher the (GM) maize share and the wider the isolation Perimeter, the higher the proportions of farmers with non-GM maize fields occurring within the implemented isolation Perimeter. Compared with randomly distributed GM maize fields, the clustering of GM maize fields on a larger scale and at the farm level increased the feasibility of implementing isolation Perimeters. The approach developed proved to be a valuable tool to quantify the feasibility of implementing isolation Perimeters under real agricultural conditions.
Yann Devos - One of the best experts on this subject based on the ideXlab platform.
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Feasibility of isolation Perimeters for genetically modified maize
Agronomy for Sustainable Development, 2008Co-Authors: Yann Devos, Olivier Thas, Eva M. Clercq, Mathias Cougnon, Karl Cordemans, Dirk ReheulAbstract:Using geographic information system datasets and Monte Carlo simulations, this study investigates to what extent the intra-regional variability in maize share and field distribution affects the feasibility of implementing isolation Perimeters between genetically modified (GM) and non-GM maize fields. More specifically, five scenarios differing in shares and spatial distributions of GM maize were tested for various isolation Perimeters in six agricultural areas in Flanders (Belgium). Proportions of non-GM maize fields and farmers having at least one non-GM maize field occurring within isolation Perimeters were calculated to assess how spatial co-existence measures would affect the freedom of choice of neighbouring farmers to grow non-GM maize on their fields. Irrespective of the scenario tested, our results demonstrated that the proportions of non-GM maize fields and their corresponding farmers falling within the isolation Perimeters are approximately two to eight times higher in areas with the highest maize share than in areas with the lowest maize share. The higher the share of GM maize and the wider the imposed isolation Perimeter, the lower the intra-regional differences became. Hence, those findings confirm that farmers will not be equally affected by isolation Perimeters, indicating the importance of considering intra-regional differences in the choice of appropriate spatial co-existence measures. Since uniform and wide isolation Perimeters tend to be difficult to implement in practice and hardly reflect the diversity of the agricultural landscape, relying on flexible or combining various co-existence measures is worthwhile considering. As an alternative to single co-existence measures for limiting the GM input from cross-fertilisations between neighbouring maize fields, the appropriateness of other on-farm co-existence measures is discussed for Flemish agricultural conditions. Proposing the most appropriate co-existence measures on a case-by-case basis may be one step forward in reaching proportionate, fair and consistent co-existence at the regional and landscape level.
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Implementing isolation Perimeters around genetically modified maize fields
Agronomy for Sustainable Development, 2007Co-Authors: Yann Devos, Dirk Reheul, Olivier Thas, Eva M. Clercq, Mathias Cougnon, Karl CordemansAbstract:Due to the growing cultivation area of genetically modified (GM) maize and the rising number of GM maize varieties commercially available to European farmers, the co-existence between GM and non-GM maize is becoming a burning issue in some European regions. Hence, Member States are imposing or discussing specific co-existence measures to keep the adventitious presence of GM material in non-GM produces below the established labelling threshold. As maize is a cross-pollinated crop that uses wind for the dispersal of its pollen, on-farm co-existence measures may rely on the spatial isolation of GM and non-GM maize fields. In this study, we developed an approach that combines geographic information system (GIS) datasets with Monte Carlo simulations to assess the feasibility of implementing isolation Perimeters around GM maize fields, since its practical implementation is rarely addressed in the co-existence debate. More specifically, five scenarios differing in shares and spatial distributions of GM maize were tested for various isolation Perimeters in two agricultural areas in Flanders (Belgium). The GIS analyses emphasised the small size of maize fields and their scattered distribution throughout the cropped area. The feasibility of implementing isolation Perimeters was largely affected by the (GM) maize share, the spatial distribution of GM maize, and the width of isolation Perimeters. The higher the (GM) maize share and the wider the isolation Perimeter, the higher the proportions of farmers with non-GM maize fields occurring within the implemented isolation Perimeter. Compared with randomly distributed GM maize fields, the clustering of GM maize fields on a larger scale and at the farm level increased the feasibility of implementing isolation Perimeters. The approach developed proved to be a valuable tool to quantify the feasibility of implementing isolation Perimeters under real agricultural conditions.
Yves Robert - One of the best experts on this subject based on the ideXlab platform.
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partitioning a square into rectangles np completeness and approximation algorithms
Algorithmica, 2002Co-Authors: Olivier Beaumont, Vincent Boudet, Fabrice Rastello, Yves RobertAbstract:In this paper we deal with two geometric problems arising from heterogeneous parallel computing: how to partition the unit square into p rectangles of given area s 1 , s 2 , . . . ,s p (such that Σ i=1 p s i = 1 ), so as to minimize either (i) the sum of the p Perimeters of the rectangles or (ii) the largest Perimeter of the p rectangles? For both problems, we prove NP-completeness and we introduce a 7/4 -approximation algorithm for (i) and a $$(2/\sqrt{3})$$ -approximation algorithm for (ii).
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heterogeneous matrix matrix multiplication or partitioning a square into rectangles np completeness and approximation algorithms
Euromicro Workshop on Parallel and Distributed Processing, 2001Co-Authors: Olivier Beaumont, Vincent Boudet, Fabrice Rastello, Arnaud Legrand, Yves RobertAbstract:In this paper, we deal with two geometric problems arising from heterogeneous parallel computing: how to partition the unit square into p rectangles of given area s/sub 1/, s/sub 2/, ..., s/sub p/ (such that /spl Sigma//sub i=1//sup p/ s/sub i/=1), so as to minimize (i) either the sum of the p Perimeters of the rectangles (ii) or the largest Perimeter of the p rectangles. For both problems, we prove NP-completeness and we introduce approximation algorithms.
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Partitioning a Square into Rectangles: NP-Completeness and Approximation Algorithms
2000Co-Authors: Olivier Beaumont, Vincent Boudet, Fabrice Rastello, Yves RobertAbstract:In this paper, we deal with two geometric problems arising from heterogeneous parallel computing: how to partition the unit square into p rectangles of given area s_1, s_2,..., s_p (such that the sum of the s_i is equal to 1), so as to minimize (i) either the sum of the p Perimeters of the rectangles (ii) or the largest Perimeter of the p rectangles. For both problems, we prove NP-completeness and we introduce approximation algorithms.
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Heterogeneous Matrix-Matrix Multiplication or Partitioning a Square into Rectangles: NP-Completeness and Approximation Algorithms
2000Co-Authors: Olivier Beaumont, Vincent Boudet, Fabrice Rastello, Yves RobertAbstract:In this paper, we deal with two geometric problems arising from heterogeneous parallel computing: how to partition the unit square into p rectangles of given area s₁, s₂,..., sₚ (such that the sum of the s_i is equal to 1), so as to minimize (i) either the sum of the p Perimeters of the rectangles (ii) or the largest Perimeter of the p rectangles. For both problems, we prove NP-completeness and we introduce approximation algorithms.
Mathias Cougnon - One of the best experts on this subject based on the ideXlab platform.
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Feasibility of isolation Perimeters for genetically modified maize
Agronomy for Sustainable Development, 2008Co-Authors: Yann Devos, Olivier Thas, Eva M. Clercq, Mathias Cougnon, Karl Cordemans, Dirk ReheulAbstract:Using geographic information system datasets and Monte Carlo simulations, this study investigates to what extent the intra-regional variability in maize share and field distribution affects the feasibility of implementing isolation Perimeters between genetically modified (GM) and non-GM maize fields. More specifically, five scenarios differing in shares and spatial distributions of GM maize were tested for various isolation Perimeters in six agricultural areas in Flanders (Belgium). Proportions of non-GM maize fields and farmers having at least one non-GM maize field occurring within isolation Perimeters were calculated to assess how spatial co-existence measures would affect the freedom of choice of neighbouring farmers to grow non-GM maize on their fields. Irrespective of the scenario tested, our results demonstrated that the proportions of non-GM maize fields and their corresponding farmers falling within the isolation Perimeters are approximately two to eight times higher in areas with the highest maize share than in areas with the lowest maize share. The higher the share of GM maize and the wider the imposed isolation Perimeter, the lower the intra-regional differences became. Hence, those findings confirm that farmers will not be equally affected by isolation Perimeters, indicating the importance of considering intra-regional differences in the choice of appropriate spatial co-existence measures. Since uniform and wide isolation Perimeters tend to be difficult to implement in practice and hardly reflect the diversity of the agricultural landscape, relying on flexible or combining various co-existence measures is worthwhile considering. As an alternative to single co-existence measures for limiting the GM input from cross-fertilisations between neighbouring maize fields, the appropriateness of other on-farm co-existence measures is discussed for Flemish agricultural conditions. Proposing the most appropriate co-existence measures on a case-by-case basis may be one step forward in reaching proportionate, fair and consistent co-existence at the regional and landscape level.
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Implementing isolation Perimeters around genetically modified maize fields
Agronomy for Sustainable Development, 2007Co-Authors: Yann Devos, Dirk Reheul, Olivier Thas, Eva M. Clercq, Mathias Cougnon, Karl CordemansAbstract:Due to the growing cultivation area of genetically modified (GM) maize and the rising number of GM maize varieties commercially available to European farmers, the co-existence between GM and non-GM maize is becoming a burning issue in some European regions. Hence, Member States are imposing or discussing specific co-existence measures to keep the adventitious presence of GM material in non-GM produces below the established labelling threshold. As maize is a cross-pollinated crop that uses wind for the dispersal of its pollen, on-farm co-existence measures may rely on the spatial isolation of GM and non-GM maize fields. In this study, we developed an approach that combines geographic information system (GIS) datasets with Monte Carlo simulations to assess the feasibility of implementing isolation Perimeters around GM maize fields, since its practical implementation is rarely addressed in the co-existence debate. More specifically, five scenarios differing in shares and spatial distributions of GM maize were tested for various isolation Perimeters in two agricultural areas in Flanders (Belgium). The GIS analyses emphasised the small size of maize fields and their scattered distribution throughout the cropped area. The feasibility of implementing isolation Perimeters was largely affected by the (GM) maize share, the spatial distribution of GM maize, and the width of isolation Perimeters. The higher the (GM) maize share and the wider the isolation Perimeter, the higher the proportions of farmers with non-GM maize fields occurring within the implemented isolation Perimeter. Compared with randomly distributed GM maize fields, the clustering of GM maize fields on a larger scale and at the farm level increased the feasibility of implementing isolation Perimeters. The approach developed proved to be a valuable tool to quantify the feasibility of implementing isolation Perimeters under real agricultural conditions.
