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The leaching and reusability problem of the catalyst in the catalytic transesterification for biodiesel production led to the poor sustainability and high posttreatment cost. Herein, a reusable magnetic Ca2Fe2O5/CaO@MgFe2O4-Fe2O3 catalyst with high textural stability and good catalytic activity was prepared in this study, and its catalytic performance toward transesterification of five different oil feedstocks was evaluated. Catalyst preparation conditions were optimized and characterizations including scanning electron microscope (SEM), X-ray diffraction analysis (XRD), and so on, were also conducted to investigate the catalytic behaviors. The results demonstrated that the catalyst has good ferromagnetism for magnetic separation, and the presence of synergistic interaction enhanced catalytic activity with all of > 90% biodiesel yield and improved the reusability with > 75% biodiesel yields at the 10th cycle. In addition, the biodiesel yield reached the maximum under the transesterification reaction parameters were optimized, and at the 15/1 methanol/oil molar ratio, 2.5 wt% catalyst dosage, 70°C for 120 min. Further, for biodiesel from five different oil feedstocks, the same composition, all of > 90% yield and the quality that met the American Society of Testing Materials (ASTM) standards demonstrated the strong oil feedstocks applicability and application potential of catalysts.

The GRACE and GRACE-FO gravity satellite data were used to retrieve the glacier quality changes in the Nyainqentanglha Mountains from August 2002 to April 2020, and combined with remote sensing technology to estimate the glacier area and reserves changes in the western Nyainqentanglha. The main conclusions are as follows:①The glaciers in the Nyainqentanglha Mountains showed an overall retreat trend during the study period, and there was an accelerated melting trend after 2013. ②The correlation between temperature changes and glacier melting curves can be found by comparing with summer temperature changes and precipitation anomalies better, the precipitation continued to decrease during the study period, indicating that the increase in temperature and the decrease in precipitation are the main reasons for the continuous decrease in the mass of glaciers in the Nyainqentanglha. ③The glacier area of the West Nyainqentanglha Mountains decreased by 72.30 km2 from 2003 to 2017, with an average annual decrease rate of 5.16 km2/a. The glacier area retreats most obviously in the altitude range of 5600~5800 m. ④The coordinated application of satellite gravity and optical remote sensing technology can complement each other's advantages. It can not only estimate changes in glacier quality, but also detect changes in glacier area and elevation. At present, there are still some shortcomings in the joint application of the two technologies, which need to be further studied.

The GF-7 satellite is carrying the Chinese first dual-beam laser altimeter system for earth observation, aimed at assisting stereo optical cameras to realize 1∶10 000 mapping. Due to the influence of the vibration of the satellite during launch and the difference of environment between space and ground, the calibration values of the altimetry parameters on ground are deviated from the actual values in space. In order to improve the altimetry, a two-step on-orbit geometric calibration scheme from coarse to fine is proposed for the GF-7 dual-beam laser altimeter. Firstly, a single beam laser on-orbit geometric calibration model is constructed to estimate the location of the laser footprints based on the typical waveform analysis, so as to realize the single beam laser rough calibration. Secondly, based on the geometric calibration model of single beam laser, the geometric calibration model of dual-beam laser is constructed. Considering the factors such as atmospheric delay and tidal correction, the spot is captured by ground detector array as the ground control point, and realize the joint precision calibration of dual-beam laser. Finally, the relative and absolute elevation measurement accuracy after calibration was verified by using the laser altimeters data on the calm lake surface and the ground control data. The experimental results show that the relative accuracy of laser elevation measurement of GF-7 satellite is better than 0.06 m (1σ), and the absolute accuracy of laser elevation measurement in flat areas is up to 0.10 m (1σ).

The ZiYuan3 ( ZY3 ) is a civilian stereo surveying and mapping satellite from China operating under the framework of the Earth resources satellite series, and its objective is to fulfill 1:50,000 mapping and update largerscale fundamental geographic information products. This article introduces the ZY3-03 satellite's mission and payload specifications as well as its data utilization and distribution policy. In the future, the ZY3-03 will realize the demands of China's national economic and social development and play an important role in the fields of Earth observation and environmental protection.

Non-noble metal (NNM) catalysts have recently attracted intensive interest for their high catalytic performance towards oxygen reduction reaction (ORR) at low cost. Herein, a novel NNM catalyst was synthesized by the simple pyrolysis of carbon black, urea and a Fe-containing precursor, which exhibits excellent ORR catalytic activity, superior durability and methanol tolerance versus the Pt/C catalyst in both alkaline and acidic solutions. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) characterizations demonstrate that the product is a nitrogen-doped hybrid of graphite encapsulated Fe/Fe3C nanoparticles and carbon black. X-ray photoelectron spectrum (XPS) and electrochemical analyses indicate that the catalytic performance and chemical stability correlate closely with a nitrogen-rich layer on the Fe/Fe3C nanoparticle after pyrolysis with presence of urea, leading to the same four-electron pathway towards ORR as the Pt/C catalyst. The hybrid is prospective to be an efficient ORR electrocatalyst for direct methanol fuel cells with high catalytic performance at low cost.

The ground gravity anomalies can be used to calibrate and validate the satellite gravity gradiometry data. In this study, an upward continuation method of ground gravity data based on spherical harmonic analysis is proposed, which can be applied to the calibration of satellite observations from the European Space Agency's Gravity Field and Steady-State Ocean Circulation Explorer (GOCE). Here, the following process was conducted to apply this method. The accuracy of the upward continuation method based on spherical harmonic analysis was verified using simulated ground gravity anomalies. The DTU13 global gravity anomaly data were used to determine the calibration parameters of the GOCE gravitational gradients based on the spherical harmonic analysis method. The trace and the tensor invariants I2, I3 of the gravitational gradients were used to verify the calibration results. The results revealed that the upward continuation errors based on spherical harmonic analysis were much smaller than the noise level in the measurement bandwidth of the GOCE gravity gradiometer. The scale factors of the Vxx, Vyy, Vzz, and Vyz components were determined at an order of magnitude of approximately 10−2, the Vxz component was approximately 10−3, and the Vxy component was approximately 10−1. The traces of gravitational gradients after calibration were improved when compared with the traces before calibration and were slightly better than the EGG_TRF_2 data released by the European Space Agency (ESA). In addition, the relative errors of the tensor invariants I2, I3 of the gravitational gradients after calibration were significantly better than those before calibration. In conclusion, the upward continuation method based on spherical harmonic analysis could meet the external calibration accuracy requirements of the gradiometer.

The theory and methods of the determination of an ultra-high gravity field model by combination of satellite observation data and gravity anomaly data are studied.And an ultra-high gravity field model named SGG-UGM-1 is computed using EGM2008 derived gravity anomaly and GOCE observation data.The block-diagonal least squares (BDLS) method for quickly estimating an ultra-high gravity field model is researched and the corresponding software module is validated by numerical experiments.OpenMP technique is introduced into the BDLS program,which improves computing efficiency dramatically.An ultra-high gravity model SGG-UGM-1 complete to degree and order 2159 is derived using the proposed calculation strategies.The fully occupied normal equation system up to degree and order 220 formed by GOCE satellite data and the block-diagonal normal equation system up to degree and order 2159 formed by EGM2008 gravity anomaly data are used for the combination.Comparison among the models SGG-UGM-1 and EGM2008,EIGEN-6C2,EIGEN-6C4,GOSG-EGM in frequency domain has been done,which shows that SGG-UGM-1 is close to the reference models and that the coefficients lower than degree 220 of SGG-UGM-1 are more accurate than that of EGM2008.The models are also validated by GPS-leveling data in China and America and airborne gravity data in Maowusu surveying area.The results show that in China the accuracy level of SGG-UGM-1 derived geoid is between EIGEN-6C2 and EIGEN-6C4,and better than GOSG-EGM and EGM2008,while in America they are almost the same.In Maowusu area the accuracy level of SGG-UGM-1 derived gravity disturbance is almost at the same accuracy level with EGM2008 and EIGEN-6C4 and better than GOSG-EGM and EIGEN-6C2.