ALBERT

Description: The Global Navigation Satellite Systems (GNSS) becomes the primary choice for device localization in outdoor situations. At the same time, many applications do not require precise absolute Earth coordinates, but instead, inferring the geometric configuration information of the constituent nodes in the system by relative positioning. The Real-Time Kinematic (RTK) technique shows its efficiency and accuracy in calculating the relative position. However, when the cycle slips occur, the RTK method may take a long time to obtain a fixed ambiguity value, and the positioning result will be a “float” solution with a low meter accuracy. The novel method presented in this paper is based on the Relative GNSS Tracking Algorithm (Regtrack). It calculates the changes in the relative baseline between two receivers without an ambiguity estimation. The dead reckoning method is used to give out the relative baseline solution while a parallel running Extended Kalman Filter (EKF) method reinitiates the relative baseline when too many validation failures happen. We conducted both static and kinematic tests to assess the performance of the new methodology. The experimental results show that the proposed strategy can give accurate millimeter-scale solutions of relative motion vectors in adjacent two epochs. The relative baseline solution can be sub-decimeter level with or without the base station is holding static. In the meantime, when the initial tracking point and base station coordinates are precisely obtained, the tracking result error can be only 40 cm away from the ground truth after a 25 min drive test in an urban environment. The efficiency test shows that the proposed method can be a real-time method, the time that calculates one epoch of measurement data is no more than 80 ms and is less than 10 ms for best results. The novel method can be used as a more robust and accurate ambiguity free tracking approach for outdoor applications.

Description: Excess phosphorus (P) accumulation in the soil can change the bioavailability of P and increase the leaching risks, but the quantitative evaluation of these responses in acidic red soil is lacking. This study aimed to investigate the composition of soil P fractions under different phosphorus apparent balances (PAB) in acidic red soil and the bioavailability and the leaching change-points of different P fractions. Five phosphorus (P) fertilization rates were applied (0, 16.38, 32.75, 65.50, 131.00 kg P·ha−1) in every sweet corn cultivation from the field experiment, and the treatments were marked as P0, P1, P2, P3, and P4, respectively. The PAB showed negative values in P0 and P1 which were −49.0 and −15.0 kg P·ha–1 in two years, respectively. In contrast, PAB in P2 as well as in P3 and P4 were positive, the content ranging from 40.2 to 424.3 kg P·ha−1 in two years. Per 100 kg ha−1 P accumulate in the soil, the total P increased by 44.36 and 10.41 mg kg−1 in the surface (0–20 cm) and subsurface (20–40 cm) soil, respectively. The content of inorganic P fractions, including solution phosphate (Sol-P), aluminum phosphate (Al-P), iron phosphate (Fe-P), reduction phosphate (Red-P), and calcium phosphate (Ca-P), significantly increased by 0.25, 16.22, 22.08, 2.04, and 5.08 mg kg−1, respectively, in surface soil per 100 kg ha−1 P accumulated in the soil. Path analysis showed that the most important soil P fractions contributing to Olsen-P were Sol-P and Al-P, which can directly affect Olsen-P, and their coefficients were 0.24 and 0.73, respectively. Furthermore, the incubation experiments were conducted in the laboratory to investigate the leaching risk of different P fractions, and they showed Sol-P was a potential source of leaching, and the leaching change-points of Al-P and Fe-P were 74.70 and 78.34 mg·kg–1, respectively. Continuous P that accumulated in soil changed the composition of P fractions, and the bioavailability as well as the leaching risks increased. This is important in optimizing soil P fertilization management in agricultural ecosystems based on the bioavailability and critical levels for leaching of P fractions.

Description: Based on the motion principle of bionic earthworms, we designed and fabricated a novel crawling robot driven by pneumatic power. Its structure is divided into four segments, and its motion process is periodic with high stability. Due to the pneumatic suction cups mounted on its feet, it is able to crawl on smooth horizontal, inclined, or vertical walls. On this basis, we designed a novel underactuated steering mechanism. Through the tendons on both sides and the springs installed on the side of the robot, we accurately controlled the steering motion of the robot. We analyzed the steering process in detail, calculated the influence of external parameters on the steering process of the robot, and simulated the trajectory of the robot in the steering process. The experimental results validated our analysis. In addition, we calculate the maximum thrust that each segment of the robot can provide, and determine the maximum load that the robot can bear during climbing motions.

Description: The prime objective of biochar production is to contribute to nutrients recycling, reducing waste and converting useful bio-wastes into carbon rich products in the environment. The present study was intended to systematically evaluate the effect of pyrolysis conditions and characteristics of feedstock influencing the generation of biochar. The study revealed the nutritional importance of waste mushroom substrate (WMS) biochar which may elevate soil nutritional status and soil quality. The results showed that the yields and properties of WMS biochar depended principally on the applied temperature where pyrolysis at higher temperatures, that is, 600 °C and 700 °C produced biochar having high ash, P and K contents. Moreover, numerous useful macro and micro nutrients such as Ca, Mg, Fe and Zn were observed to positively correlate with the increase in temperature. The WMS biochar in our study is highly alkaline which can be used to rectify acidic soil pH. Overall our results suggest that WMS biochar being a rich source of nutrients can be the best remedy to maintain and further enhance the soil nutritional status. Thus by interpreting biochar feedstock characteristics and pyrolysis conditions, the regulation of tailored WMS biochar manufacturing and application in soil can be facilitated.

Description: The solution of carrier phase ambiguity is essential for precise global navigation satellite system (GNSS) positioning. Methods of searching in the coordinate domain show their advantage over the methods based on ambiguity fixing, for example, immune to cycle slips, far fewer epochs taken for obtaining the precise solution. However, there are still some drawbacks via using the Ambiguity Function Method (AFM), such as low computation efficiency and the existence of a false global optimum. The false global optimum is a situation where the Least Square (LS) criterion achieves minimum in another place than the point of the actual position, which restricts the application of this method to single-frequency receivers. The numerical search approach derived in this paper is based on the Modified Ambiguity Function Approach (MAFA). It focuses on eliminating the false optimum solution and reducing the computation load by utilizing single-frequency receivers without solving the ambiguity fixing problem. An improved segmented simulated annealing method is used to decrease the computation load while the Kernel Density Estimator (KDE) method is used to filter out the false optimum candidates. Static experiments were carried out to evaluate the performance of the new approach. It is shown that a precise result can be obtained by handling two epochs of data with z coordinate fixed to the referenced value. Meanwhile, the new approach can achieve a millimeter level of position accuracy after dealing with nineteen epochs of observations data when searching in x , y , z domain. The new approach shows its robustness even if the search region is broad, and the prior position is several meters away from the referenced value.