The phrase "a defined time" is correct and usable in written English.
It can be used when referring to a specific, clearly established point in time or duration.
Example: "The project must be completed within a defined time to meet the client's expectations."
Alternatives: "a specified time" or "a set time".
The trays were irradiated once using a circulating array of microwave radiators for a defined time.
During the injection, the sample is brought through one of them and is injected electrokinetically for a defined time.
An ecosystem is sustainable if when you affect it -- perhaps through harvesting or humans' hiking through it -- it can still sustain itself through a defined time period.
A natural resource like a forest is sustainable if it can regrow at the same rate that you harvest it, for a defined time period.
In the case of the United States, that has meant the imposition of quota systems and legal statutes that mandate overfishing's end within a defined time frame.
Misalignment usually occurs when companies have developed, tested, and rolled out initiatives ad hoc, without any high-level planning or a defined time horizon.
Three different PEDOT composites (PEDOT Cl, PEDOT:Heparin and PEDOT:DBS) were produced by electropolymerization, applying an electrical current for a defined time in specific polymerization solutions.
A sort of hybrid between a mutual fund and a stock, a unit investment trust holds a fixed portfolio of bonds or stocks for a defined time.
Higher eukaryotic genomes contain both housekeeping genes and genes of which the expression is restricted to a defined time and space.
For a defined time period, reactors are closed systems to some extent, although well-insulated reactors frequently exchange heat with their surroundings.
It consists in exposing humid products to high steam pressure, reached within 1 s, for a defined time followed by a rapid decompression to the vacuum.
