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A micron is  one-millionth of a meter, also called a micrometer . It is  an SI-derived unit of length that equals 1×10−6 meters.  The nanometer is equivalent to one one-thousandth of a micron or micrometer, or one billionth of a meter (0.000000001 m).

GCV is the full form of gross calorific value.  The calorific value is the amount of heat generated during the combustion of a specified quantity.  The Calorific value  is the total energy  released as heat  when a substance undergoes complete combustion  with oxygen  under standard conditions.  The higher heating value (HHV; gross energy, also known as an upper heating value, or  gross calorific value GCV , or higher calorific value; HCV) indicates the upper limit of the available thermal energy produced by the complete combustion of fuel. It is measured as a unit of energy per unit mass or volume of a substance. Each fuel has a unique GCV, and the cost of fuel is largely determined by the GCV: Credits: Heat of combustion