unit_definitions.py

#!/bin/env python
"""
Module simtk.unit.unit_definitions

"""

from __future__ import division

__author__ = "Christopher M. Bruns"
__version__ = "0.6"

from baseunit import BaseUnit
from standard_dimensions import *
from unit import Unit, ScaledUnit, UnitSystem, dimensionless
from unit_operators import * ; # needed for manipulation of units
from prefix import *
import math
import sys

#####################
### DIMENSIONLESS ###
#####################

# dimensionless = Unit({}); # defined in unit.py

##############
### LENGTH ###
##############

meter_base_unit = BaseUnit(length_dimension, "meter", "m")
meters = meter = Unit({meter_base_unit: 1.0})
define_prefixed_units(meter_base_unit, module = sys.modules[__name__])

angstrom_base_unit = BaseUnit(length_dimension, "angstrom", "A")
angstrom_base_unit.define_conversion_factor_to(meter_base_unit, 1e-10)
angstroms = angstrom = Unit({angstrom_base_unit: 1.0})

planck_length_base_unit = BaseUnit(length_dimension, "Planck length", "l_P")
planck_length_base_unit.define_conversion_factor_to(meter_base_unit, 1.61625281e-35)

inch_base_unit = BaseUnit(length_dimension, "inch", "in")
inch_base_unit.define_conversion_factor_to(centimeter_base_unit, 2.5400)
inch = inches = Unit({inch_base_unit: 1.0})

foot_base_unit = BaseUnit(length_dimension, "foot", "ft")
foot_base_unit.define_conversion_factor_to(inch_base_unit, 12.0)
foot = feet = Unit({foot_base_unit: 1.0})

yard_base_unit = BaseUnit(length_dimension, "yard", "yd")
yard_base_unit.define_conversion_factor_to(foot_base_unit, 3.0)
yard = yards = Unit({yard_base_unit: 1.0})

furlongs = furlong = yard.create_unit(scale=220.0, name="furlong", symbol="furlong")
miles = mile = furlong.create_unit(scale=8.0, name="mile", symbol="mi")

############
### MASS ###
############

gram_base_unit = BaseUnit(mass_dimension, "gram", "g")
grams = gram = Unit({gram_base_unit: 1.0})

define_prefixed_units(gram_base_unit, module = sys.modules[__name__])

planck_mass_base_unit = BaseUnit(mass_dimension, "Planck mass", "m_P")
planck_mass_base_unit.define_conversion_factor_to(kilogram_base_unit, 2.1764411e-8)

# pound can be mass, force, or currency
pound_mass_base_unit = BaseUnit(mass_dimension, "pound", "lb")
pound_mass_base_unit.define_conversion_factor_to(kilogram_base_unit, 0.3732)
pound_mass = pounds_mass = Unit({pound_mass_base_unit: 1.0})

stone_base_unit = BaseUnit(mass_dimension, "stone", "stone")
stone_base_unit.define_conversion_factor_to(pound_mass_base_unit, 14.0)
stone = stones = Unit({stone_base_unit: 1.0})

############
### TIME ###
############

second_base_unit = BaseUnit(time_dimension, "second", "s")
seconds = second = Unit({second_base_unit: 1.0})

define_prefixed_units(second_base_unit, module = sys.modules[__name__])

planck_time_base_unit = BaseUnit(time_dimension, "Planck time", "t_P")
planck_time_base_unit.define_conversion_factor_to(second_base_unit, 5.3912427e-44)

minutes = minute = second.create_unit(scale=60.0, name="minute", symbol="min")
hours = hour = minute.create_unit(scale=60.0, name="hour", symbol="hr")
days = day = hour.create_unit(scale=24.0, name="day", symbol="day")
weeks = week = day.create_unit(scale=7.0, name="week", symbol="week")
years = year = day.create_unit(scale=365.25, name="julian year", symbol="a")
centuries = centurys = century = year.create_unit(scale=100.0, name="century", symbol="century")
millenia = milleniums = millenium = century.create_unit(scale=10.0, name="millenium", symbol="ka")

fortnights = fortnight = day.create_unit(scale=14.0, name="fortnight", symbol="fortnight")

###################
### TEMPERATURE ###
###################

kelvin_base_unit = BaseUnit(temperature_dimension, "kelvin", "K")
kelvins = kelvin = Unit({kelvin_base_unit: 1.0})

planck_temperature_base_unit = BaseUnit(temperature_dimension, "Planck temperature", "T_p")
planck_temperature_base_unit.define_conversion_factor_to(kelvin_base_unit, 1.41678571e32)

##############
### CHARGE ###
##############

elementary_charge_base_unit = BaseUnit(charge_dimension, "elementary charge", "e")
elementary_charges = elementary_charge = Unit({elementary_charge_base_unit: 1.0})

coulomb_base_unit = BaseUnit(charge_dimension, "coulomb", "C")
# Exact conversion factor
coulomb_base_unit.define_conversion_factor_to(elementary_charge_base_unit, 6.24150962915265e18)
coulombs = coulomb = Unit({coulomb_base_unit: 1.0})

planck_charge_base_unit = BaseUnit(charge_dimension, "Planck charge", "q_P")
planck_charge_base_unit.define_conversion_factor_to(elementary_charge_base_unit, 11.706237639840)

##############
### AMOUNT ###
##############

mole_base_unit = BaseUnit(amount_dimension, "mole", "mol")
moles = mole = Unit({mole_base_unit: 1.0})

single_item_amount_base_unit = BaseUnit(amount_dimension, "item", "")
mole_base_unit.define_conversion_factor_to(single_item_amount_base_unit, 6.0221417930e23)
items = item = Unit({single_item_amount_base_unit: 1.0})

##########################
### Luminous Intensity ###
##########################

candela_base_unit = BaseUnit(luminous_intensity_dimension, "candela", "cd")
candelas = candela = Unit({candela_base_unit: 1.0})

#############
### ANGLE ###
#############

radian_base_unit = BaseUnit(angle_dimension, "radian", "rad")
radians = radian = Unit({radian_base_unit: 1.0})

degree_base_unit = BaseUnit(angle_dimension, "degree", "deg")
degree_base_unit.define_conversion_factor_to(radian_base_unit, math.pi/180.0)
degrees = degree = Unit({degree_base_unit: 1.0})

arcminutes = arcminute = degree.create_unit(scale=1.0/60.0, name="arcminute", symbol="'")
arcseconds = arcsecond = arcminute.create_unit(scale=1.0/60.0, name="arcsecond", symbol='"')

###################
### INFORMATION ###
###################

bit_base_unit = BaseUnit(information_dimension, "bit", "bit")
bits = bit = Unit({bit_base_unit: 1.0})

byte_base_unit = BaseUnit(information_dimension, "byte", "B")
byte_base_unit.define_conversion_factor_to(bit_base_unit, 8.0)
bytes = byte = Unit({byte_base_unit: 1.0})

nat_base_unit = BaseUnit(information_dimension, "nat", "nat")
nat_base_unit.define_conversion_factor_to(bit_base_unit, 1.0/math.log(2.0))
nats = nat = nits = nit = nepits = nepit = Unit({nat_base_unit: 1.0})

ban_base_unit = BaseUnit(information_dimension, "ban", "ban")
ban_base_unit.define_conversion_factor_to(bit_base_unit, math.log(10.0, 2.0))
bans = ban = hartleys = hartley = dits = dit = Unit({ban_base_unit: 1.0})


###############
### DERIVED ###
###############

# Molar mass
# daltons = dalton = grams / mole
daltons = dalton = Unit({ScaledUnit(1.0, gram/mole, "dalton", "Da"): 1.0})
amus = amu = dalton
atom_mass_units = atomic_mass_unit = dalton

# Volume
liter_base_unit = ScaledUnit(1.0, decimeter**3, "liter", "L")
liter = liters = litre = litres = Unit({liter_base_unit: 1.0})
define_prefixed_units(liter_base_unit, module = sys.modules[__name__])

# Concentration
molar_base_unit = ScaledUnit(1.0, mole/liter, "molar", "M")
molar = molal = Unit({molar_base_unit: 1.0})
define_prefixed_units(molar_base_unit, module = sys.modules[__name__])

# Force
newton_base_unit = ScaledUnit(1.0, kilogram * meter / second / second, "newton", "N")
newtons = newton = Unit({newton_base_unit: 1.0})
define_prefixed_units(newton_base_unit, module = sys.modules[__name__])
# pound can be mass, force, or currency
pound_force_base_unit = ScaledUnit(4.448, newton, "pound", "lb")
pound_force = pounds_force = Unit({pound_force_base_unit: 1.0})
dyne_base_unit = ScaledUnit(1.0, gram * centimeter / second**2, "dyne", "dyn")
dyne = dynes = Unit({dyne_base_unit: 1.0})

# Energy
joule_base_unit = ScaledUnit(1.0, newton * meter, "joule", "J")
joules = joule = Unit({joule_base_unit: 1.0})
define_prefixed_units(joule_base_unit, module = sys.modules[__name__])
erg_base_unit = ScaledUnit(1.0, dyne * centimeter, "erg", "erg")
erg = ergs = Unit({erg_base_unit: 1.0})

# In molecular simulations, "kilojoules" are in microscopic units
# And you really only want to use kilojoules/mole.
md_kilojoule_raw = gram * nanometer**2 / picosecond**2
md_kilojoules = md_kilojoule = Unit({ScaledUnit(1.0, md_kilojoule_raw, "kilojoule", "kJ"): 1.0})
kilojoules_per_mole = kilojoule_per_mole = md_kilojoule / mole

calorie_base_unit = ScaledUnit(4.184, joule, "calorie", "cal")
calories = calorie = Unit({calorie_base_unit: 1.0})
define_prefixed_units(calorie_base_unit, module = sys.modules[__name__])
md_kilocalories = md_kilocalorie = Unit({ScaledUnit(4.184, md_kilojoule, "kilocalorie", "kcal"): 1.0})
kilocalories_per_mole = kilocalorie_per_mole = md_kilocalorie / mole

# Power
watt_base_unit = ScaledUnit(1.0, joule / second, "watt", "W")
watt = watts = Unit({watt_base_unit: 1.0})

# Current
ampere_base_unit = ScaledUnit(1.0, coulomb / second, "ampere", "A")
ampere = amperes = amp = amps = Unit({ampere_base_unit: 1.0})

# Electrical potential
volt_base_unit = ScaledUnit(1.0, watt / ampere, "volt", "V")
volt = volts = Unit({volt_base_unit: 1.0})

# Magnetic field
tesla_base_unit = ScaledUnit(1.0, newton / (ampere * meter), "tesla", "T")
tesla = teslas = Unit({tesla_base_unit: 1.0})
gauss_base_unit = ScaledUnit(10.0**-4, tesla, "gauss", "G")
gauss = Unit({gauss_base_unit: 1.0})

# Electrical resistance
ohm_base_unit = ScaledUnit(1.0, volt / ampere, "ohm", "O")
ohm = ohms = Unit({ohm_base_unit: 1.0})

# Capacitance
farad_base_unit = ScaledUnit(1.0, coulomb / volt, "farad", "F")
farad = farads = Unit({farad_base_unit: 1.0})

# Inductance
henry_base_unit = ScaledUnit(1.0, volt * second / ampere, "henry", "H")
henry = henries = henrys = Unit({henry_base_unit: 1.0})

# Pressure
pascal_base_unit = ScaledUnit(1.0, newton / (meter**2), "pascal", "Pa")
pascals = pascal = Unit({pascal_base_unit: 1.0})
define_prefixed_units(pascal_base_unit, module = sys.modules[__name__])
psi_base_unit = ScaledUnit(1.0, pound_force / (inch**2), "psi", "psi")
psi = Unit({psi_base_unit: 1.0})
bar_base_unit = ScaledUnit(10.0**5, pascal, "bar", "bar")
bar = bars = Unit({bar_base_unit: 1.0})
atmosphere_base_unit = ScaledUnit(101325.0, pascal, "atmosphere", "atm")
atmosphere = atmospheres = Unit({atmosphere_base_unit: 1.0})
torr_base_unit = ScaledUnit(1.0/760.0, atmosphere, "torr", "Torr")
torr = Unit({torr_base_unit: 1.0})
mmHg_base_unit = ScaledUnit(133.322, pascal, "mmHg", "mmHg")
mmHg = Unit({mmHg_base_unit: 1.0})

####################
### Unit Systems ###
####################

ampere_base_unit = ScaledUnit(1.0, coulomb/second, "ampere", "A")

si_unit_system = UnitSystem([\
        meter_base_unit,\
        kilogram_base_unit,\
        second_base_unit,\
        ampere_base_unit,
        kelvin_base_unit,
        mole_base_unit,
        candela_base_unit,
        radian_base_unit])

cgs_unit_system = UnitSystem([\
        centimeter_base_unit,\
        gram_base_unit,\
        second_base_unit,\
        ampere_base_unit,
        kelvin_base_unit,
        mole_base_unit,
        radian_base_unit])

dalton_base_unit = ScaledUnit(1.0, gram/mole, "dalton", "Da")

md_unit_system = UnitSystem([\
        nanometer_base_unit,\
        dalton_base_unit,
        picosecond_base_unit,\
        elementary_charge_base_unit,
        kelvin_base_unit,
        mole_base_unit,
        radian_base_unit])

planck_unit_system = UnitSystem([\
        planck_length_base_unit,
        planck_mass_base_unit,
        planck_time_base_unit,
        planck_charge_base_unit,
        planck_temperature_base_unit,
        single_item_amount_base_unit,
        radian_base_unit])

########################
### TESTING/EXAMPLES ###
########################

# run module directly for testing
if __name__=='__main__':
    # Test the examples in the docstrings
    import doctest, sys
    doctest.testmod(sys.modules[__name__])