This paper develops a new model with heterogeneous firms under perfect competition in a Heckscher-Ohlin-Samuelson setting. We show that trade need not make selection in the comparative advantage sector stricter as suggested by earlier work. Selection is driven by the capital intensity in entry...

In social networks, social foci are physical or virtual entities around which social individuals organize joint activities, for example, places and products (physical form) or opinions and services (virtual form). Forecasting which social foci will diffuse to more social individuals is important...

The bike rebalancing problem is one of the major operational challenges in the urban bike-sharing system which involves the redistribution of bikes to prevent stations from being empty or overloaded. This paper investigates a new bike rebalancing problem, which considers the collection of broken...