The Best possible Time resolution: How precise could a Radiocarbon dating method be?

ABSTRACTToday, accelerator mass spectrometry (AMS) technology enables us to carry out very precise measurements of radiocarbon (14C). Unfortunately, due to fluctuations in the 14C calibration curve, the resulting calibrated time intervals vary from decades up to centuries in calibrated age. Within a time scale of several decades, we can find several time intervals on the 14C calibration curve which correspond with periods of rapid increases in atmospheric 14CO2 activity. Some of these “high slope” parts of the calibration curve could be used for fine time resolution for radiocarbon dating of individual samples. Nevertheless, there are certain limitations owing to the properties of the samples measured. We have prepared a time-resolution curve for the 14C dating method, applying calibration curve IntCal13 and assuming an uncertainty of 14C analyses ±15 yr BP (for recent samples). Our curve of the time resolution covers the last 50 ka. We found several time intervals with time resolution below 50 yr BP for the last 3 ka. Several time intervals which can enable substantially better time resolution compared to neighboring parts of the calibration curve were also found for periods older than 3 ka.

Wavelet-Based Tool Path Generation for Contour NC Machining

The high resolution curves could be transformed to low resolution curves by wavelet analysis. A new method for boundary preserving of the low resolution curve by modify the knot vector and the control points is represented. The definition of the deviation curve is proposed, and the discrete deviation curve method is represented to estimate the deviation between the low and high resolution curves. Wavelet-based tool path is generated for the contour NC machining by using the low resolution curves as the references. The experimental results demonstrate that the wavelet-based tool path has less information and is smoother than the traditional method’s. So it could reduce the calculating amount and improve the machining efficiency.

STUDY OF MODIS-AQUA DATA FOR MAPPING TOTAL SUSPENDED MATTER (TSM) IN COASTAL WATERS

The MODIS-Aqua data have been studied to map TSM distribution in coastal waters. TSM algorithm model for MODIS data with spatial resolution of 250 m, 500 m and 1000 m was developed by correlating the TSM derived from spectral values of MODIS and the TSM derived from Landsat-7 ETM data using the calibrated algorithm. Statistical test was conducted to see normality of data and level of influence from both parameters. Analysis was conducted to see the change of spectral value from bands of MODIS data with resolution of 1000 m towards the change of level of TSM concentration. The results shows that the TSM algorithm model is in the form of power (Xa) with the highest correlation coefficient is obtained from the correlation between the Landsat TSM value with the quantification of band 1 and band 2 of MODIS data for spatial resolution 250 m, ratio of band 4 and band 3 for spatial resolution 500 m, and ratio of band 13 and 11 for spatial resolution 1000 m. The pattern of TSM distribution in coastal waters can be identified in more accurate using MODIS data with resolution of 250 m and 500 m. The analysis result of the curve of MODIS spectral value data with resolution 1000 m shows that the change of TSM concentration influences significantly to the form of curve of spectral value, especially for band 11 - 16 ( visible green, red and NIR). Keywords : MODIS-Aqua, Landsat, TSM algorithm model, spatial resolution, curve of spectral value

Evaluation of substructure parameters by peak profile analysis of high-resolution neutron diffraction spectra

The peak profile shape analysis has been preferentially used in the evaluation of X-ray and synchrotron powder diffraction pattern. However, neutron diffraction facilities of new generation frequently offer the instrumental resolution high enough to efficiently study the effects of broadening of neutron diffraction profiles. The present paper describes the procedure for a detailed evaluation of Bragg peak shape based on the method of transformed model fitting (TMF) which has been recently developed particularly for the treatment of neutron diffraction profiles. Microstructure modeling is performed in the reciprocal space and the convolution of the model with the instrumental resolution curve is fitted to the profiles recorded in the diffraction experiment.