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Roque Calvo,Emilio Gómez,Rosario Domingo 한국정밀공학회 2014 International Journal of Precision Engineering and Vol. No.
Flatness and planar straightness are fundamental form tolerances in engineering design and its materialization through manufacturing processes. Minimum zone tolerance is a preferred approach of flatness and straightness for widely accepted ISO and ANSI standards. In this paper, we propose a novel accurate method of minimum zone tolerance based on vectorial calculus of point coordinates. The non-linear minimax formulation of the original flatness or straightness problem is transformed into a set of linear problems. Next, the optimal solution of the envelop planes or lines is reached through vectorial calculus for both flatness and planar straightness. Then, the developed algorithms are compared to a selection of methods with published tests in recent and classic literature on the topic, reaching the best attained accuracies or outperforming them in the trials. Finally, we propose a new decomposition of the uncertainty contributions for analysis and the improvement of sampling strategy. We conclude remarking the practical contributions of the proposals.
Selective Migration and Economic Growth in México
Jaime Lara Lara,Bernardo Garza Gómez,Dania Monárrez Barrón,Emilio Mátar Zambrano,Gustavo Vázquez García 중앙대학교 경제연구소 2023 Journal of Economic Development Vol.48 No.1
The objective of this study is to determine the impact of selective internal migration on regional economic growth in Mexico. The net skilled migration rate has no significant impact on growth. The net migration rate is positively correlated with economic growth, but has no effect when endogeneity is solved. Together, the results indicate that there is no significant and robust causal impact of migration on growth. These results sustain even when we consider the negative effect that population growth rate have on regional economies.