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§ 1066.1005 Symbols, abbreviations, acronyms, and units of measure.
The procedures in this part generally follow either the International System of Units (SI) or the United States customary units, as detailed in NIST Special Publication 811, which we incorporate by reference in § 1066.1010. See 40 CFR 1065.20 for specific provisions related to these conventions. This section summarizes the way we use symbols, units of measure, and other abbreviations.
(a) Symbols for quantities. This part uses the following symbols and units of measure for various quantities:
Table 1 of § 1066.1005—Symbols for Quantities
| Symbol | Quantity | Unit | Unit symbol | Unit in terms of SI base units |
|---|---|---|---|---|
| α | atomic hydrogen to carbon ratio | mole per mole | mol/mol | 1. |
| A | area | square meter | m2 | m2. |
| A | vehicle frictional load | pound force or newton | lbf or N | m·kg·s−2. |
| ag | acceleration of Earth's gravity | meters per second squared | m/s2 | m·s−2. |
| Am | calculated vehicle frictional load | pound force or newton | lbf or N | m·kg·s−2. |
| a0 | intercept of least squares regression. | |||
| a1 | slope of least squares regression. | |||
| a | acceleration | feet per second squared or meters per second squared | ft/s2 or m/s2 | m·s–2. |
| B | vehicle load from drag and rolling resistance | pound force per mile per hour or newton second per meter | lbf/(mi/hr) or N·s/m | kg·s–1. |
| β | ratio of diameters | meter per meter | m/m | 1. |
| β | atomic oxygen to carbon ratio | mole per mole | mol/mol | 1. |
| c | conversion factor. | |||
| C | vehicle-specific aerodynamic effects | pound force per mile per hour squared or newton-second squared per meter squared | lbf/(mi/hr)2 or N·s2/m2 | m–1·kg. |
| C# | number of carbon atoms in a molecule | C# | number of carbon atoms in a molecule | C#. |
| Cd | discharge coefficient. | |||
| CdA | drag area | meter squared | m2 | m2. |
| Cf | flow coefficient. | |||
| Cp | heat capacity at constant pressure | joule per kelvin | J/K | m2·kg·s–2·K–1. |
| Cv | heat capacity at constant volume | joule per kelvin | J/K | m2·kg·s–2·K–1. |
| d | diameter | meters | m | m. |
| D | distance | miles or meters | mi or m | m. |
| D | slope correlation | pound force per mile per hour squared or newton second squared per meter squared | lbf/(mi/hr)2 or N·s2/m2 | m−2·kg. |
| DF | dilution factor. | 1. | ||
| e | mass weighted emission result | grams/mile | g/mi. | |
| F | force | pound force or newton | lbf or N | kg·s−2. |
| ƒ | frequency | hertz | Hz | s−1. |
| ƒn | angular speed (shaft) | revolutions per minute | r/min | π·30·s−1. |
| FC | friction compensation error | horsepower or watt | W | m2·kg·s−3. |
| FR | road-load force | pound force or newton | lbf or N | kg·s−2. |
| γ | ratio of specific heats | (joule per kilogram kelvin) per (joule per kilogram kelvin) | (J/(kg·K))/(J/(kg·K)) | 1. |
| H | ambient humidity | grams water vapor per kilogram dry air | g H2O vapor/kg dry air | g H2O vapor/kg dry air. |
| Δh | change in height | meters | m | m. |
| I | inertia | pound mass or kilogram | lbm or kg | kg. |
| I | current | ampere | A | A. |
| i | indexing variable. | |||
| IR | inertia work rating. | |||
| K | correction factor | 1. | ||
| Kv | calibration coefficient | m4·s·K0.5/kg | m4·kg−1·s·K0.5. | |
| µ | viscosity, dynamic | pascal second | Pa·s | m−1·kg·s−1. |
| M | molar mass | gram per mole | g/mol | 10–3·kg·mol−1. |
| Me | effective mass | kilogram | kg | kg. |
| m | mass | pound mass or kilogram | lbm or kg | kg. |
| N | total number in series. | |||
| n | total number of pulses in a series. | |||
| p | pressure | pascal | Pa | m−1·kg·s−2. |
| Δp | differential static pressure | pascal | Pa | m−1·kg·s−2. |
| pd | saturated vapor pressure at ambient dry bulb temperature | kilopascal | kPa | m−1·kg·s−1. |
| PF | penetration fraction. | |||
| ρ | mass density | kilogram per cubic meter | kg/m3 | m−3·kg. |
| R | dynamometer roll revolutions | revolutions per minute | rpm | π·30−1·s−1. |
| r | ratio of pressures | pascal per pascal | Pa/Pa | 1. |
| r2 | coefficient of determination. | |||
| Re# | Reynolds number. | |||
| RF | response factor. | |||
| RH | relative humidity. | |||
| S | Sutherland constant | kelvin | K | K. |
| SEE | standard error of the estimate. | |||
| SG | specific gravity. | |||
| Δs | distance traveled during measurement interval | meters | m | m. |
| T | absolute temperature | kelvin | K | K. |
| T | Celsius temperature | degree Celsius | °C | K−273.15. |
| T | torque (moment of force) | newton meter | N·m | m2·kg·s–2. |
| t | time | hour or second | hr or s | s. |
| Δt | time interval, period, 1/frequency | second | s | s. |
| U | voltage | volt | V | m2·kg·s–3·A–1. |
| v | speed | miles per hour or meters per second | mi/hr or m/s | m·s–1. |
| V | volume | cubic meter | m3 | m3. |
| V | flow volume rate | cubic feet per minute or cubic meter per second | ft3/min or m3/s | m3·/s−1. |
| VP | volume percent. | |||
| x | concentration of emission over a test interval | part per million | ppm. | |
| y | generic variable. | |||
| Z | compressibility factor. |