An air cycle machine (ACM) is the refrigeration unit of the environmental control system (ECS) used in pressurized gas turbine-powered aircraft. Normally an aircraft has two or three of these ACM. Each ACM and its components are often referred as an air conditioning pack. The air cycle cooling process uses air instead of a phase changing material such as Freon in the gas cycle. No condensation or evaporation of a refrigerant is involved, and the cooled air output from the process is used directly for cabin ventilation or for cooling electronic equipment.

Air cycle machines were first developed in the 19th century for providing chilling on ships. The technique is a reverse Brayton cycle (the thermodynamic cycle of a gas turbine engine) and is also known as a Bell Coleman cycle or "Air-Standard Refrigeration Cycle".

The usual compression, cooling and expansion seen in any refrigeration cycle is accomplished in the ACM by a centrifugal compressor, two air-to-air heat exchangers and an expansion turbine.

Ray Dalio (born in 1949 in Jackson Heights, Queens, New York, United States) is an American businessman and founder of Bridgewater Associates.

The son of a jazz musician, Dalio began investing at age 12 when he bought shares of Northeast Airlines for $300 and tripled his investment after the airline merged with another company.

Dalio received a BA from Long Island University and an MBA from Harvard Business School.

After completing his education, Dalio worked on the floor of the New York Stock Exchange and invested in commodity futures. He later worked as the Director of Commodities at Dominick & Dominick LLC. In 1974, he became a futures trader and broker at Shearson Hayden Stone. In 1975, he founded the investment management firm, Bridgewater Associates. As of January 2012, the company is the largest hedge fund in the world with nearly $120 billion under management.

Ray Dalio has written a pdf called "Principles" to share his life and business management principles with his employees.

Dalio is a practitioner of the Transcendental Meditation technique and resides with his wife in Greenwich, CT. According to Forbes he is the 44th richest person in America and the 88th richest person in the world with a net worth of $10 billion as of March 2012. Dalio has been labeled as the Steve Jobs of investing.