Abstract Accurate perception of the movement and appearance of vehicles depends on the robustness and reliability of the extrinsic parameters calibration in a multi-sensor fusion scenario. However, conventional calibration methods require manual acquisition of prior information, leading to high labor costs and low calibration accuracy. Therefore, we proposed an automatic coarse-to-fine calibration method for roadside radar and camera sensors to lower costs and improve accuracy. Next, an association strategy based on fluctuating traffic volumes was also developed to assist in robust target matching during the coarse-to-fine calibration process. Finally, extrinsic parameters between the radar coordinate system and camera coordinate system were calibrated through double rotations of the position vectors obtained from each system. To verify the proposed method, an experiment was conducted on a pedestrian bridge using an uncalibrated 4D millimeter-wave radar and a traffic monocular camera. The results showed that our proposed method reduced the interquartile range of the roll angle by 41.5% compared to a state-of-the-art neural network method. It also outperformed the manual calibration method by 2.47% in terms of the average reprojection error.
Mountainous vegetation recovery after major earthquakes has been significant for preventing post-seismic soil erosion and geo-hazards. Magnitude 7.9 Wenchuan earthquake struck western Sichuan, China in 2008, caused salient number of geological hazards and caused major vegetation damage. This recovery process could be a very long and fluctuating. And Remote sensing has been an important method of vegetation restoration monitoring. This study aims to use remote sensing technology data to analyze the post-seismic vegetation damage and recovery situation of the 2008 Wenchuan earthquake over years to 2020, and find the relevant factors affecting the restoration of ecological vegetation. This paper examined the vegetation recovery processes following the 2008 Wenchuan earthquake using 16-day interval MODIS normalized difference vegetation index time series from 2000 to 2020. It has been found that the vegetation recovery rate generally increased by years, the entire study area has recovered 49.89% by 2020. In addition, by combining remote sensing imagery and geographic information data, we also found that the heavily affected vegetation areas are mainly located along the southern part of the earthquake surface rupture, where have a very high slope which mainly over 60 degrees. It makes this part having higher probabilities to experiences secondary natural hazards and a fluctuating vegetation recovery rate. Through this research, it can be concluded that remote sensing is an effective method for monitoring vegetation dynamics in a long series. For soil and soil retention and ecological vegetation protection of landslides after the earthquake, it should be more concerned about the areas where have steep slope that over 60 degrees.
To investigate the effect of corn—alfalfa intercropping on maintaining soil fertility and improving crop yields,soil nutrients and crop yield in both corn—alfalfa intercropping and corn monocropping(CK) lands were studied on different slopes(5°,10°and 15°).The results indicate that,soil nutrients showed little difference between corn—alfalfa intercropping and corn monocropping land before sowing,but significant changes were showed after harvest,as nutrient losses of intercropping were less than monocropping.Difference in contents of organic matter,total N,total phosphorus,nitrate,ammonium nitrogen,available phosphorus and available potassium between intercropping and monocropping were 0.04g/kg,0.05g/kg,0.01 g/kg,1.6mg/kg,1.2mg/kg,0.1mg/kg,3.2mg/kg.Soil nutrients at lower slopes were higher than that at upper slopes under both crop patterns,while this nutrients differences among slopes were less in intercropping than monocropping.And the differences on contents of organic matter,total N,total phosphorus,nitrate,ammonium nitrogen,available phosphorus and available potassium were 0.13g/kg,0.05g/kg,0.01g/kg,0.5mg/kg,0.3mg/kg,0.2mg/kg and 0.4mg/kg between lower slope and upper slope.Corn yields of intercropping were higher than corn yields of monocropping.From 5°to 15°,corn yields of intercropping were 7 426.3,7 280.3and 6 802.5kg/hm2,which was higher by 1.35%,0.92%and 0.89%,respectively,compared to corn yields of monocropping.Moreover,alfalfa yield of intercropping reached the local level,which indicated that the pattern of corn—alfalfa intercropping was feasible in Weibei dryland.
Five forage grass species, 24 varieties in total, Which introduced from USA were evaluated for their adaptation in Hangzhou, Zhejiang province, from October 1997 to June 1999. Annual ryegrass showed both high forage yield and good nutritive value in winter sowing. Perennial ryegrass and tall festuca had good heat tolerance, aftermath growth and persistence. Cocksfoot was adapted to the environmental conditions, but relatively low in forage yield. Bromegrass was heat sensitive and should be utilized by winter sowing. Annual ryegrass cv. Surrey and perennial ryegrass cv. Bison were recommended as the most promising varieties for winter sowing and permanent pasture establishing, respectively.
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