#### Traffic Gridlock

In studying traffic flow in a large city grid, the following questions arise. Is there a largest traffic density that permits free flow? Is there a density above which gridlock is inevitable? In 1992 Biham, Middleton and Levine introduced a simplified model for the study of these questions, called the BML model. This simplified model proved to be surprisingly complex – in a series of papers...

#### Improved Electron Gun Design

Electron beams are employed in vacuum devices to generate very high power microwaves for many critical applications, including amplifiers in communications, television, radar guns and computer monitors, and high energy accelerators. The quality of these electron beams directly impacts the output power and efficiency that can be achieved. In a SAMSI workshop, a group of graduate students was...

#### Shedding Light on Blackouts

The control of communication and power networks through regulation and deregulated market mechanisms presents tremendous challenges and affects almost every citizen of the United States. Theoretical understanding in this area is built on the mathematical field called stochastic networks, a field whose growth has been closely tied to the Institute for Mathematics and its Applications (IMA). In...

#### An Eye for Aphids

Soybeans are a key livestock feed in the US, an important human food source in many parts of the world, and–in the form of biodiesel fuel–a promising source of renewable energy. Informed pest management increases yield and reduces pesticide application: farmers use population estimates obtained by counting the aphids on sample soybean leaves in planning their crop dusting schedules. However,...

#### Expander Graphs

A central computational theme is “parallel processing”: allowing a large number to processors to work simultaneously and thus potentially speed up computation. A major issue for this development is the architecture of the communication network among these processors. The problem of how to design such a network is translated into a mathematical problem of finding graphs called “expanders” which...