The Approach of Compensation of Air Refractive Index in Thermal Expansion Coefficients Measurement Based on Laser Feedback Interferometry

We present the thermal expansion coefficient （TEC） measurement technology of compensating for the effect of variations in the refractive index based on a Nd： YA G laser feedback system, the beam frequency is shifted by a pair of aeousto-optic modulators and then the heterodyne phase measurement technique is used. The sample measured is placed in a muffle furnace with two coaxial holes opened on the opposite furnace walls. The measurement beams hit perpendicularly and coaxially on each surface of the sample. The reference beams hit on the reference mirror and the high-refiectivity mirror, respectively. By the heterodyne configuration and computing, the influences of the vibration, distortion of the sample supporter and the effect of variations in the refractive index are measured and largely minimized. For validation, the TECs of aluminum samples are determined in the temperature range of 29-748K, confirming not only the precision within 5 × 10-7 K-1 and the accuracy within 0.4% from 298K to 448K but also the high sensitivity non-contact measurement of the lower reflectivity surface induced by the sample oxidization from 448 K to 748 K.

Input-output efficiency model of urban greenenergy development from the perspective of a low-carbon economy

With the acceleration of urbanization,cities are the main targets for carbon neutrality and urban energy is the terminal of energy consumption and the integration point of various energy systems.Therefore,there is a need to promote the development of urban green energy and achieve low input and high output to achieve a low-carbon economy in cities.Previous studies have not considered the input-output efficiency of urban green-energy development.This study fills this gap.Based on the economic-energy-environmental framework,an input-output efficiency-evaluation index system for urban green-energy development was constructed.Based on improved data-envelopment analysis,a comparative evaluation of the input-output efficiency of green-energy development was carried out in 30 provinces in China in 2019.Considering the differences in regions,the development of urban green energy in different provinces was classified.From the perspective of a low-carbon economy,economic growth factors and environmental constraint factors were set.Together with the generalized Divisia index approach,the input-output efficiency optimization directions of urban green-energy development were obtained.The results showed that the input-output efficiencies of urban green-energy development in Jiangsu,Zhejiang,Fujian,Inner Mongolia,Ningxia and other provinces and cities were relatively high.Provinces with faster economic development and higher environmental carrying capacity have advantages after optimization and will become pilot areas for the development of urban green energy.This research provides a reference for the development of urban green energy in various provinces from the input and output perspective.