RESUMO
Rock-mineral spectrum is a mixture of varied mineral spectra, through which we can obtain information about its components quickly and conveniently without any damage to the sample. Empirical mode decomposition (EMD) cannot directly decompose source signals from information of the mixture, and independent component analysis (ICA) requires the number of mixed signals to be no less than the number of source signals. Combining these two methods, mixed signals can be decomposed using EMD method to obtain intrinsic mode function (IMF), while certain IMFs together with mixed signals can be used as input data matrix of ICA to obtain the source signals. This method overcomes the shortcomings of IMF and ICA. Studies have shown that, the higher content of source signals contained in the mixed signal, the better estimation can be obtained through EMD and ICA. The number of IMFs that participate in ICA decomposition determines the number of approximation of source signals. The accuracy of source signal estimation increases with the correlation coefficient between IMF and mixed signals. By applying this method to quantitative analysis of rock-mineral spectrum, information of the component minerals in rock-mineral can be obtained, which improves the efficiency of component analysis in detecting rock-minerals outside.
RESUMO
Core scan is the instrument used for core spectrum and pictures detection that has been developed in recent years. Cores' data can be digitized with this equipment, then automatic core catalog can be achieved, which provides basis for geological research, mineral deposit study and peripheral deposit prospecting. Meanwhile, an online database of cores can be established by the means of core digitalization to solve the cost problem caused by core preservation and share resources. Quality of core data measurement directly affects the mineral identification, reliability of parameter inversion results. Therefore it's very important to quasi-manage the assessment of data quality with the instrument before cores' spectrum testing services. Combined with the independent R&D of CSD350A type core scan, and on the basis of spectroscopy basic theory, spectrum analysis methods, core spectrum analysis requirements, key issues such as data quality assessment methods, evaluation criteria and target parameters has been discussed in depth, and comprehensive assessment of independent R&D of core scan has been conducted, which indicates the reliability and validity of spectrum measurements of the instrument. Experimental tests show that the methods including test parameters and items can perfectly response the measurements of reflectance spectrum, wavelength accuracy, repeatability and signal to noise ratio with the instrument. Thus the quality of core scan data can be evaluated correctly, and the foundation of data quality for commercial services can be provided. In the case of the current lack of relevant assessment criteria, the method this study proposes for the assessment has great value in the work of core spectrum measurements.
RESUMO
To meet the requirements of outdoor field mineral analysis and remote sensing ground verification spectral analysis, the wide-range fiber spectral instrument covering 400 nm-2 500 nm was developed. The present article illustrates the design of the optical, mechanical and electrical parts of the instrument. The optical system utilizes grating horizontal-reflecting light route to implement the full coverage of the spectrum. Three line-array sensors are intercrossed in three directions on the spectrum surface to sense different spectrum ranges. CPLD device generates the sampling and driving temporal logic signals to the three line-array photoelectrical devices. Fourteen bits high speed AD converts the analog signals into digital ones. USB 2.0 is used for communication. The final results demonstrate that while implementing the measurement of wide spectrum, the instrument is improved in size, spectrum resolving power, signal quality and measuring speed. Ideal spectrum data were acquired.