For more details see Prof. Womersley's web page:


The inverse square law is also known as “Coulomb's law.” It describes how the strength of the force acting between two electrically charged particles varies as the distance between them changes: For example, when the distance between two particles doubles, the force between them drops to one quarter its previous strength.


The inverse square law corresponds to the value s=1.


For more details see Prof. Womersley's web page:

Undergraduate played key role in developing the synchronized calling network

By Ximena Lavender
Published: December 17, 2004

Photo by Steve Green  
Efosa Ojomo

Standing up in front of a room full of the nation's top experts and presenting the results of your recent research—and then defending by responding to probing questions from the audience—is a prospect that can make even veteran presenters nervous. But not Efosa Ojomo, a Vanderbilt senior who has yet to receive his bachelor's degree in computer engineering.

In November the supremely self-confident young engineer presented a summary of the research that he conducted this past summer at the annual meeting of the Acoustical Society of America in San Diego, California.He reported on the successful creation of an electronic network that can mimic the synchronous calling behavior of a number of different animals, including cicadas and frogs, with amazing fidelity. His presentation was one that the conference press officer highlighted for the media covering the meeting.

“I was intimidated at first,” Ojomo acknowledges, “and I was the first one after lunch, but it felt good being able to stand your ground in front of an older, more experienced audience.”

“I was impressed with his self-confidence,” says Kenneth D. Frampton, the assistant professor of mechanical engineering who supervised the project. “He even had some fun and cracked a few jokes.”

Photo by Daniel Dubois
Kenneth Frampton holds up network node

The research project was part of a summer internship program for under-represented minority students from the southeastern United States.Called the Vanderbilt Summer Internship Program in Hybrid and Embedded Software Research or SIPHER, the program focuses on hybrid systems—frequently called smart devices—that combine computers with electrical and mechanical components. These systems are becoming increasingly commonplace in everything from toys to telephones, from automobiles to airplanes. The program is funded by the National Science Foundation. (See Engineering undergrads encounter “real life” problem solving).

To create the synchronous calling network, Frampton had Ojomo start with an off-the-shelf, distributed networking system. Each node consisted of a radio transceiver that allows the nodes to communicate with each other and an onboard microprocessor that can be programmed to control the node's behavior. The nodes are designed so that additional sensors and devices can be added.

For the summer, Ojomo was paired up with another undergraduate, Praveen Mudindi from Alabama A&M University, and they worked under the supervision of graduate students Stephen Williams and Isaac Amundson. The students added sensitive microphones and buzzers to the nodes and wrote the programs that controlled each node's behavior. At the end of the summer, Mudindi returned to Alabama while Ojomo continued to work on getting the bugs out of the system.

Ojomo worked specifically on programming the devices and on developing a louder buzzer, when they found that the buzzers they were using weren't loud enough for their application. He acknowledges that he “got a lot of help from Stephen and Isaac.”

Photo by Daniel Dubois  
Close up on one of the synchronous calling nodes
Through his participation in Vanderbilt's summer internship program, Ojomo says he has learned that an important part of a successful research career “is to get your name, your lab's name and Vanderbilt's name out there.” The way to do that is to prepare papers on the research that are good enough for publication and to present your work at major conferences, such as the ASA meeting in San Diego, he adds.

According to Ojomo, his talk went “really well” overall. His presentation included a demonstration. He distributed a number of nodes to members of the audience. Then the Vanderbilt researchers turned on the network and the audience were able to hear first-hand how the devices went in and out of synchronization.

Photo by Neil Brake
Arthur Overholser

“The audience loved the simulation,” says Ojomo. “But it didn't work as well as it did in the lab, because the presentation room was acoustically dead.” The walls in the laboratory reflect sound more efficiently, allowing the sensors to detect the calls from other modes more readily.

Ojomo credits Senior Associate Dean Arthur Overholser at the School of Engineering with convincing him to transfer to Vanderbilt from Fisk University,which he attended for three years. At Fisk Ojomo was a computer science major, but changed to computer engineering when he entered Vanderbilt.

The next step in Ojomo's scientific career will be moving to Austin,Texas to accept a job at National Instruments. Eventually, he would like to go back to graduate school to obtain an advanced degree.


Ximena Lavender is a major in the interdisciplinary Communication of Science & Technology program


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