Jean-Marie Constant Duhamel (February 5, 1797 – April 29, 1872) was a noted French

French people

The French are a nation that share a common French culture and speak the French language as a mother tongue. Historically, the French population are descended from peoples of Celtic, Latin and Germanic origin, and are today a mixture of several ethnic groups...

 mathematician

Mathematician

A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....

 and physicist

Physicist

A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

. His studies were affected by troubles of the Napoleonic era

Napoleonic Era

The Napoleonic Era is a period in the history of France and Europe. It is generally classified as including the fourth and final stage of the French Revolution, the first being the National Assembly, the second being the Legislative Assembly, and the third being the Directory...

. He went on to form his own school École Sainte-Barbe. Duhamel's principle

Duhamel's principle

In mathematics, and more specifically in partial differential equations, Duhamel's principle is a general method for obtaining solutions to inhomogeneous linear evolution equations like the heat equation, wave equation, and vibrating plate equation...

 is named for him. He was primarily a mathematician but did studies on the mathematics of heat

Heat

In physics and thermodynamics, heat is energy transferred from one body, region, or thermodynamic system to another due to thermal contact or thermal radiation when the systems are at different temperatures. It is often described as one of the fundamental processes of energy transfer between...

, mechanics

Mechanics

Mechanics is the branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment....

, and acoustics

Acoustics

Acoustics is the interdisciplinary science that deals with the study of all mechanical waves in gases, liquids, and solids including vibration, sound, ultrasound and infrasound. A scientist who works in the field of acoustics is an acoustician while someone working in the field of acoustics...

. He also did work in calculus using infinitesimals. Duhamel's theorem for infinitesimals says that the sum of a series of infinitesimals is unchanged by replacing the infinitesimal with its principal part.