Quantum Spin Liquid Phase in the Shastry–Sutherland Model Detected by an Improved Level Spectroscopic Method

We study the spin-1/2 two-dimensional Shastry–Sutherland spin model by exact diagonalization of clusters with periodic boundary conditions, developing an improved level spectroscopic technique using energy gaps between states with different quantum numbers. The crossing points of some of the relative(composite) gaps have much weaker finite-size drifts than the normally used gaps defined only with respect to the ground state, thus allowing precise determination of quantum critical points even with small clusters. Our results support the picture of a spin liquid phase intervening between the well-known plaquette-singlet and antiferromagnetic ground states, with phase boundaries in almost perfect agreement with a recent density matrix renormalization group study, where much larger cylindrical lattices were used [J. Yang et al., Phys. Rev. B 105, L060409(2022)]. The method of using composite low-energy gaps to reduce scaling corrections has potentially broad applications in numerical studies of quantum critical phenomena.

Spatio-temporal Dynamics of Urbanization in China Using DMSP/OLS Nighttime Light Data from 1992–2013

Understanding the dynamics of urbanization is essential to the sustainable development of cities. Meanwhile the analysis of urban development can also provide scientifically and effective information for decision-making. With the long-term Defense Meteorological Satellite Program’s Operational Linescan System(DMSP/OLS) nighttime light images, a pixel level assessment of urbanization of China from 1992 to 2013 was conducted in this study, and the spatio-temporal dynamics and future trends of urban development were fully detected. The results showed that the urbanization and urban dynamics of China experienced drastic fluctuations from 1992 to 2013, especially for those in the coastal and metropolitan areas. From a regional perspective, it was found that the urban dynamics and increasing trends in North Coast China, East Coast China and South Coast China were much more stable and significant than that in other regions. Moreover, with the sustainability estimating of nighttime light dynamics, the regional agglomeration trends of urban regions were also detected. The light intensity in nearly 50% of lighted pixels may continuously decrease in the future, indicating a severe situation of urbanization within these regions. In this study, The results revealed in this study can provided a new insight in long time urbanization detecting and is thus beneficial to the better understanding of trends and dynamics of urban development.

Remnant fertilizer monitoring system for maize fertilizer applicators

A remnant fertilizer monitoring system utilizing three-dimensional(3D)reconstruction was proposed to detect the amount of remaining fertilizer in the applicator’s tank.Bench tests were carried out to compare the performance of four algorithms to estimate the remnant fertilizer amount:fertilizer remnant monitoring biharmonic spline algorithm(V4),natural nearest-neighbor algorithm(Natural),linear algorithm(Linear),cubic algorithm(Cubic).The average relative error for remnant fertilizer monitoring is 7.33%for the Linear algorithm,7.30%for the Natural algorithm,5.18%for the Cubic algorithm,and 4.30%for the V4 algorithm.Field tests are conducted at three fertilization rates to compare the performances of the V4 and Cubic algorithms.The average relative error for discharged fertilizer monitoring is 8.64%for the Cubic algorithm,which is 1.91%lower than that of the V4 algorithm.The results show that the Cubic algorithm has the best performance for remnant fertilizer monitoring.The average relative error of remnant fertilizer monitoring is 2.42%for the Cubic algorithm,which is 0.43%lower than that of the V4 algorithm.The response time of the remnant fertilizer monitoring system is 0.26 s.The results demonstrate that the proposed remnant fertilizer monitoring system is highly accurate and suitable for real-time applications.