Atsushi Yamagishi

Application of evolutionary programming to shape design

Designing the shapes of products is the primary activity of the design process. In this paper, we propose a new model representing free form shape features with the aim of making the system capable of holding and manipulating the shape features after synthesis in order to support the designer early in the design process. The key concept of this study is the shape feature generating process model (SFGP model) which consists of numerous sets of rules using the classifier system (CS). Finally, a computer program was developed to evaluate the model by combining two existing shapes to verify that the shape features of each shape are preserved in the combined shape. It was demonstrated that the model can produce a variety of combined shapes with original, often exaggerated, features.

Do Supermajority Rules Really Deter Extremism? The Role of Electoral Competition

This study investigates how supermajority rules in a legislature affect electoral competition. To this end, we construct a probabilistic voting model and show that supermajority rules magnify the divergence of policy platforms generated by aggregate uncertainty about the electoral outcome. Thus, supermajority rules involve an important trade-off: they induce the convergence of policies for non-commitment issues, while also causing the divergence of policies for commitment issues. In addition, we show that the effect of aggregate uncertainty on the optimal voting rule depends on whether its source is a large district-specific shock or a small number of competitive districts.