Development of a model-based transient calibration process for diesel engine electronic control module tables – Part 2: modelling and optimization

This is the second part of a study investigating a model-based transient calibration process for diesel engines. The first part addressed the data requirements and data processing required for empirical transient emission and torque models. The current work focuses on modelling and optimization. The unexpected result of this investigation is that when trained on transient data, simple regression models perform better than more powerful methods such as neural networks or localized regression. This result has been attributed to extrapolation over data that have estimated rather than measured transient air-handling parameters. The challenges of detecting and preventing extrapolation using statistical methods that work well with steady-state data have been explained. The concept of constraining the distribution of statistical leverage relative to the distribution of the starting solution to prevent extrapolation during the optimization process has been proposed and demonstrated. Separate from the issue of extrapolation is preventing the search from being quasi-static. Second-order linear dynamic constraint models have been proposed to prevent the search from returning solutions that are feasible if each point were run at steady state, but which are unrealistic in a transient sense. Dynamic constraint models translate commanded parameters to actually achieved parameters that then feed into the transient emission and torque models. Combined model inaccuracies have been used to adjust the optimized solutions. To frame the optimization problem within reasonable dimensionality, the coefficients of commanded surfaces that approximate engine tables are adjusted during search iterations, each of which involves simulating the entire transient cycle. The resulting strategy, different from the corresponding manual calibration strategy and resulting in lower emissions and efficiency, is intended to improve rather than replace the manual calibration process.

Democratization, Education Reform, and the Mexican Teachers' Union

This study examines the effect of democratization on a key education reform across three Mexican states. Previous scholarship has found a positive effect of electoral competition on social spending, as leaders seek to improve their reelection prospects by delivering services to voters. However, the evidence presented here indicates that more money has not meant better educational outcomes in Mexico. Rather, new and vulnerable elected leaders are especially susceptible to the demands of powerful interest groups at the expense of accountability to constituents. In this case, the dominant teachers' union has used its leverage to exact greater control over the country's resource-rich merit pay program for teachers. It has exploited this control to increase salaries and decrease standards for advancement up the remuneration ladder. The evidence suggests that increased electoral competition has led to the empowerment of entrenched interests rather than voters, with an overall negative effect on education.