Africa has been experiencing a rapid urbanization process, which may lead to an increase in unsustainable land use and urban poverty. Assessing the spatiotemporal characteristics of urbanization dynamics is especially important and needed for the sustainable development of Africa. Satellite-based nighttime light (NTL) data are widely used to monitor the dynamics of urban growth from global to local scales. In this study, urban growth patterns across Africa were analyzed and discussed using stable nighttime light datasets obtained from DMSP/OLS (the Defense Meteorological Satellite Program’s Operational Line-scan System) spanning from 1992 to 2013. We partitioned the nighttime lighting areas into three types (low, medium, and high) using thresholds derived from the Brightness Gradient (BG) method. Our results indicated that built-up areas in Africa have increased rapidly, particularly those areas with low nighttime lighting types. Countries with higher urbanization levels in Africa, like South Africa, Algeria, Egypt, Nigeria, and Libya, were leading the brightening trend. The distribution of nighttime lighting types was consistent with the characteristics of urban development, with high nighttime lighting types showed up at the urban center, whereas medium and low nighttime lighting types appeared in the urban-rural transition zone and rural areas respectively. The impacts of these findings on the future of African cities will be further proposed.

The Dongsha Shoal is one of the largest shoals in the South Yellow Sea and has important marine ecological value. The shoal extends in a south–north direction and is controlled by the regional dominating tidal currents. Recently, due to human activities and some natural factors, the geomorphic dynamics of the Dongsha Shoal has undergone drastic changes. However, few people have proposed quantitative research on the changes of tidal flat morphology, let alone the long-term sequence analysis of sand ridge lines. Hence, we attempt to take the Dongsha Shoal in the Radial Sand Ridges as the research area, and analyze the trends of the long-term morphological evolution of the sand ridge lines over the period 1973–2016 based on a high-density time series of medium-resolution satellite images. The sand ridge line generally moves from southeast to northwest, and the position distribution of the sand ridge line from north to south has gradually changed from compact to scattered. We also found that the geomorphological dynamics at different positions of the sand ridge line are inconsistent. The north and south wings are eroded on the west side, while the central area is eroded on the east side. Most of the sand ridge line is moving eastward. In addition, the change of sand ridge line is affected by multiple factors such as sediment supply, typhoon, reclamation and laver cultivation.

In view of the vertical deformation of CRTS III slab ballastless track of high-speed railways under the action of ambient temperature, a simulation model of the temperature field and vertical deformation of CRTS III slab ballastless track was developed and verified by a field test. The main conclusions are as follows: When the temperature gradient is positive, the central part of the slab track deforms upward. The edge of the slab track deforms downward. The displacement in the central part of the slab track is the largest, and the elliptical region is formed in the middle. The more outward the displacement is, the smaller the displacement is. When the temperature gradient is negative, the downward displacement in the middle of the slab track is the largest, an elliptical region is formed in the middle, and the outward displacement gradually changes from downward to upward. The model developed in this study can accurately reflect the temperature field inside the slab track and the vertical displacement of the slab track at the macro level. In practical application, the technical data can be provided for the maintenance of CRTS III slab tracks according to the simulation results. The temperature field distribution and possible deformation of the slab track can be obtained by adding simulated working conditions according to the climatic conditions. These predictions can be used to focus on targeted maintenance and repair to reduce the investment of human, material, and financial resources, and to achieve the purpose of “green maintenance”.