The presence of heteroskedasticity in a considered regression model may bias the standard deviations of parameters obtained by the Ordinary Least Square (OLS) method. In this case, several hypothesis tests on the mode...The presence of heteroskedasticity in a considered regression model may bias the standard deviations of parameters obtained by the Ordinary Least Square (OLS) method. In this case, several hypothesis tests on the model under consideration may be biased, for example, CHOW’s coefficient stability test (or structural change test), Student’s t-test and Fisher’s F-test. Most of the heteroscedasticity tests in the literature are based on the comparison of variances. Despite the multiplication of equality tests of coefficients of variation (CVs) that have appeared in the literature, to our knowledge, the first and only use of the coefficient of variation in the detection of heteroskedasticity was offered by Li and Yao in 2017. Thus, this paper offers an approach to determine the existence of heteroskedasticity by a test of equality of coefficients of variation. We verify by a Monte Carlo robustness and performance test that our method seems even better than some tests in the literature. The results of this study contribute to the exploitation of the statistical measurement of CV dispersion. They help technicians economists to better verify their hypotheses before making a scientific decision when making a necessary forecast, in order to contribute effectively to the economic and sustainable development of a company or enterprise.展开更多
Calibration coefficients validation is the foundation for ascertaining the sensor performance and carrying out the quantitative application.Based on the analysis of the differences between the calibration and validati...Calibration coefficients validation is the foundation for ascertaining the sensor performance and carrying out the quantitative application.Based on the analysis of the differences between the calibration and validation,two calibration coefficients validation methods were introduced in this paper.Taking the HJ-1A satellite CCD1 camera as an example,the uncertainties of calibration coefficients validation were analyzed.The calibration coefficients validation errors were simulated based on the measured data at an Inner Mongolia test site.The result showed that in the large view angle,the ground directional reflectance variation and the atmospheric path variation were the main error sources in calibration coefficients validation.The ground directional reflectance correction and atmospheric observation angle normalization should be carried out to improve the validation accuracy of calibration coefficients.展开更多
Connotation of land competitiveness is expatiated from both the narrow sense and broad sense. Evaluation index system of land competitiveness is established according to the 2008 China Statistical Yearbook and 2008 Ch...Connotation of land competitiveness is expatiated from both the narrow sense and broad sense. Evaluation index system of land competitiveness is established according to the 2008 China Statistical Yearbook and 2008 China Land Resources Statistical Yearbook. Efficiency Coefficient Method and Principal Component Analysis Method are used to evaluate the land competitiveness of 31 provincial units in China. Result shows that in the year 2007, land competitiveness gradually decreases from southeast to northwest. The land competitiveness and GDP per unit land have significant negative correlation. The rank of approved new construction land has low positive correlation with the rank of land competitiveness in China. This indicates that there is little correlation between the allocation of regional new construction land and the land use efficiency. Therefore, it is suggested that regional allocation of new construction land should be treated differently based on the evaluation result of land competitiveness.展开更多
文摘The presence of heteroskedasticity in a considered regression model may bias the standard deviations of parameters obtained by the Ordinary Least Square (OLS) method. In this case, several hypothesis tests on the model under consideration may be biased, for example, CHOW’s coefficient stability test (or structural change test), Student’s t-test and Fisher’s F-test. Most of the heteroscedasticity tests in the literature are based on the comparison of variances. Despite the multiplication of equality tests of coefficients of variation (CVs) that have appeared in the literature, to our knowledge, the first and only use of the coefficient of variation in the detection of heteroskedasticity was offered by Li and Yao in 2017. Thus, this paper offers an approach to determine the existence of heteroskedasticity by a test of equality of coefficients of variation. We verify by a Monte Carlo robustness and performance test that our method seems even better than some tests in the literature. The results of this study contribute to the exploitation of the statistical measurement of CV dispersion. They help technicians economists to better verify their hypotheses before making a scientific decision when making a necessary forecast, in order to contribute effectively to the economic and sustainable development of a company or enterprise.
基金supported by the International Science and Technology Cooperation Program of China(Grant No.2008DFA21540)the National Hi-Tech Research and Development Program of China(Grant No.2006AA12Z113)+1 种基金the Chinese Defense Advance Research Program of Science and Technologythe Young Talents Filed Special Project of Institute of Remote Sensing and Application of Chinese Academy of Sciences
文摘Calibration coefficients validation is the foundation for ascertaining the sensor performance and carrying out the quantitative application.Based on the analysis of the differences between the calibration and validation,two calibration coefficients validation methods were introduced in this paper.Taking the HJ-1A satellite CCD1 camera as an example,the uncertainties of calibration coefficients validation were analyzed.The calibration coefficients validation errors were simulated based on the measured data at an Inner Mongolia test site.The result showed that in the large view angle,the ground directional reflectance variation and the atmospheric path variation were the main error sources in calibration coefficients validation.The ground directional reflectance correction and atmospheric observation angle normalization should be carried out to improve the validation accuracy of calibration coefficients.
基金Supported by the Natural Science Foundation of China (70803032)
文摘Connotation of land competitiveness is expatiated from both the narrow sense and broad sense. Evaluation index system of land competitiveness is established according to the 2008 China Statistical Yearbook and 2008 China Land Resources Statistical Yearbook. Efficiency Coefficient Method and Principal Component Analysis Method are used to evaluate the land competitiveness of 31 provincial units in China. Result shows that in the year 2007, land competitiveness gradually decreases from southeast to northwest. The land competitiveness and GDP per unit land have significant negative correlation. The rank of approved new construction land has low positive correlation with the rank of land competitiveness in China. This indicates that there is little correlation between the allocation of regional new construction land and the land use efficiency. Therefore, it is suggested that regional allocation of new construction land should be treated differently based on the evaluation result of land competitiveness.
