numOSL (version 1.3)

fastED: Estimating a fast-component equivalent dose

Description

A number of decay curves obtained through a single aliquot regenerative (SAR) protocol (Murray and Wintle, 2000) are decomposed and fast-component decaying signals are extracted (if possible) to build a dose response curve to estimate a fast-component equivalent dose.

Usage

fastED(Sigdata, Redose, ncomp = 2, constant=TRUE,  
       control.args = list(), typ = "cw", nstart = 100, upb = 1, 
       ErrorMethod = c("mc", "sp"), model = NULL, origin = NULL)

Arguments

Sigdata

data.frame(required): a number of decay curves obtained with the SAR method, the first column should be the time values

Redose

vector(required): the regenerative dose values (redose1, redose2, etc)

ncomp

numeric(with default): the number of components used to decompose a decay curve, which should be an integer in the space [2,4]

constant

logical(with default): subtract a constant component when fitting the curve or not, see decompc

control.args

list(with default): some further arguments used in the differential evolution algorithm, see decomp

typ

character(with default): the type of an OSL decay curve, only type of "CW" is available currently

nstart

numeric(with default): the allowed maximum number of attempts that used to initialize parameters during the fitting of a growth curve, see calED

upb

numeric(with default): the upper limit on b value, see calED

ErrorMethod

character(with default): a method ("sp" or "mc") for assessing the standard error of an equivalent dose. Default ErrorMethod="mc". See calED

model

character(optional): the fitting model ("line", "exp", or "line+exp"). See calED

origin

logical(optional): force the fitting to pass the origin (x=0,y=0) or not, see calED

Value

• Return a list containing following elements:
• pars
  the estimated parameters and standard errors for each decay curve
• decayRate
  a summarized list for decay rates of decay curves (except the decay curve that corresponds to the 0-regenerative dose and its test dose)
• Curvedata
  data used to build the fast-component dose response curve, see calED
• Ltx
  the estimated standardised natural OSLs and their standard error, see calED
• model
  the model used for fitting the dose-response curve, which is chosen automatically between "line", "exp" and "line+exp" with the principle of the minimum of the sum of squared residuals if model=NULL
• LMpars
  the estimated characteristic parameters and standard errors of the growth curve
• value
  the sum of squared residuals for the fitted growth curve
• ED
  the estimated fast-component equivalent dose (and its standard error)
• RecyclingRatio
  the estimated fast-component recycling ratio
• Recuperation
  the estimated fast-component recuperation

Details

Function fastED() is used to estimated a fast-component equivalent dose with data obtained by the SAR protocol (Murray and Wintle, 2000), only CW-OSL data can be analyzed currently. The routine trys to decompose a series of decay curves to a specified number of components, then the fast-component signal from each decay curve is extracted to build a dose response curve, from which a fast-component equivalent dose can be obtained.

References

Murray, A.S., Wintle, A.G., 2000. Luminescence dating of quartz using improved single-aliquot regenerative-dose protocol. Radiation Measurements, 32, pp.57-73.

Li, S.H., Li, B., 2006. Dose measurement using the fast component of LM-OSL signals from quartz. Radiation Measurements, 41, pp.534-541.

See Also

calED; decomp; decompc

Examples

data(Signaldata)
# Calculating a fast-component equivalent dose with 3 components (decay curves that
# correspond to the 0-regenerative dose (12th) and its test-dose (13th) are removed)
 fastED(Signaldata$cw[,c(-12,-13)],Redose=c(80,160,240,320,80)*0.13,
        ncomp=3,constant=FALSE)