In this paper, based on the Science and Technology Statistics in Beijing Statistical Yearbook, grey theory is used to study the relationship among S&T (Science and Technology) activities personnel, R&D (resear...In this paper, based on the Science and Technology Statistics in Beijing Statistical Yearbook, grey theory is used to study the relationship among S&T (Science and Technology) activities personnel, R&D (research and development) personnel FTE (Full Time Equivalent), intramural expenditure for R&D and Patent Application Amount. According to the grey correlation coefficient, screening of grey GM(1,N) prediction variables, the grey prediction model is established. Meanwhile, time series model and GM(1,1) model are established for patent applications and R&D personnel equivalent FTE. By comparing the simulating results with the real data, the absolute relative error of prediction models is less than 10%. The results of the prediction model are tested. In order to improve the prediction accuracy, the mean values of the predicted values of the two models are brought into the GM(1,N) model to predict the number of scientific and technical personnel in Beijing during 2015-2025. Forecast results show that the number of science and technology personnel in Beijing will grow with exponential growth trend in the next ten years, which has a certain reference value for predicting the science and technology activities and formulating the policy in Beijing.展开更多
The self-reinforced Si_3N_4 ceramics which contain Y_2O_3 and La_2O_3 additives have been prepared by hot-pressing. Under the optimum processing conditions, this material has the flexural strength of 960～1050MPa and ...The self-reinforced Si_3N_4 ceramics which contain Y_2O_3 and La_2O_3 additives have been prepared by hot-pressing. Under the optimum processing conditions, this material has the flexural strength of 960～1050MPa and the fracture toughness of 11.17～12.74MPa·m^(1/2) at room-temperature, and 720～780MPa and 22～24MPa·m^(1/2) at 1350℃. The effects of heat ing rate, sintering temperature, and holding time on the microstructures and mechanical properties are investigated. The experimental results show that an appropriate β-Si_3N_4 grain size and homogeneous microstructure can be obtained under the conditions of a heating rate of 10℃/min, sintering temperature of 1800℃, and holding time of 1h, which are advantageous to enhancing the mechanical properties. Crack deflection in large rodlike β-Si_3N_4 grains is a principle source of toughening.展开更多
文摘In this paper, based on the Science and Technology Statistics in Beijing Statistical Yearbook, grey theory is used to study the relationship among S&T (Science and Technology) activities personnel, R&D (research and development) personnel FTE (Full Time Equivalent), intramural expenditure for R&D and Patent Application Amount. According to the grey correlation coefficient, screening of grey GM(1,N) prediction variables, the grey prediction model is established. Meanwhile, time series model and GM(1,1) model are established for patent applications and R&D personnel equivalent FTE. By comparing the simulating results with the real data, the absolute relative error of prediction models is less than 10%. The results of the prediction model are tested. In order to improve the prediction accuracy, the mean values of the predicted values of the two models are brought into the GM(1,N) model to predict the number of scientific and technical personnel in Beijing during 2015-2025. Forecast results show that the number of science and technology personnel in Beijing will grow with exponential growth trend in the next ten years, which has a certain reference value for predicting the science and technology activities and formulating the policy in Beijing.
基金Supported by China Postdoctoral Science Foundation
文摘The self-reinforced Si_3N_4 ceramics which contain Y_2O_3 and La_2O_3 additives have been prepared by hot-pressing. Under the optimum processing conditions, this material has the flexural strength of 960～1050MPa and the fracture toughness of 11.17～12.74MPa·m^(1/2) at room-temperature, and 720～780MPa and 22～24MPa·m^(1/2) at 1350℃. The effects of heat ing rate, sintering temperature, and holding time on the microstructures and mechanical properties are investigated. The experimental results show that an appropriate β-Si_3N_4 grain size and homogeneous microstructure can be obtained under the conditions of a heating rate of 10℃/min, sintering temperature of 1800℃, and holding time of 1h, which are advantageous to enhancing the mechanical properties. Crack deflection in large rodlike β-Si_3N_4 grains is a principle source of toughening.
