Study on the correlation between river network patterns and topography in the Haihe River basin

In recent decades, the river network patterns (RNPs) in China’s Haihe River basin have changed dramatically, and the topology of the river network has become increasingly complex. It is important to quantitatively study the correlation between river network patterns and topography (CRNPT) and the changes in the correlation. In this paper, the Haihe River basin was spatially gridded (4 km × 4 km), and different geomorphological areas were extracted for a multiarea study. We selected topographic and river network indicators and proposed new indicators to characterize regional topographic ‘stressfulness’ and then used redundancy analysis for correlation studies. The results showed that the variance of RNP explained by topography was 53.39%. The combined contribution of the topographic wetness index (TWI) and topographic wetness stress index (TSI) ranged from 35.66% to 78.29% in multiple areas, and the TSI showed stronger explanatory power. The regional effect of the CRNPT was significant, with mountains and transition areas having higher effects than plain areas. Compared to the natural river network, the CRNPT of the current river network was significantly lower. Among the RNP indicators, the artificial channel proportion (Pac) had the highest proportion of variance, and the CRNPT was strongly influenced by artificial channels. Artificial channels changed the consistency of topography with the RNP and reduced the topographic interpretation of the RNP, which may weaken the stability and hydrological connectivity of the river network. The variation in interpretation was related to the distribution of artificial channels, which showed a logarithmic function relationship between them

Solution-Processed Nanoparticle Super-Float-Gated Organic Field-Effect Transistor as Un-cooled Ultraviolet and Infrared Photon Counter

High sensitivity photodetectors in ultraviolet (UV) and infrared (IR) range have broad civilian and military applications. Here we report on an un-cooled solution-processed UV-IR photon counter based on modified organic field-effect transistors. This type of UV detectors have light absorbing zinc oxide nanoparticles (NPs) sandwiched between two gate dielectric layers as a floating gate. The photon-generated charges on the floating gate cause high resistance regions in the transistor channel and tune the source-drain output current. This ‘‘super-float-gating’’ mechanism enables very high sensitivity photodetectors with a minimum detectable ultraviolet light intensity of 2.6 photons/µm2s at room temperature as well as photon counting capability. Based on same mechansim, infrared photodetectors with lead sulfide NPs as light absorbing materials have also been demonstrated

Solution-Processed Nanoparticle Super-Float-Gated Organic Field-Effect Transistor as Un-cooled Ultraviolet and Infrared Photon Counter

High sensitivity photodetectors in ultraviolet (UV) and infrared (IR) range have broad civilian and military applications. Here we report on an un-cooled solution-processed UV-IR photon counter based on modified organic field-effect transistors. This type of UV detectors have light absorbing zinc oxide nanoparticles (NPs) sandwiched between two gate dielectric layers as a floating gate. The photon-generated charges on the floating gate cause high resistance regions in the transistor channel and tune the source-drain output current. This ‘‘super-float-gating’’ mechanism enables very high sensitivity photodetectors with a minimum detectable ultraviolet light intensity of 2.6 photons/µm2s at room temperature as well as photon counting capability. Based on same mechansim, infrared photodetectors with lead sulfide NPs as light absorbing materials have also been demonstrated

Impact of changes in river network structure on hydrological connectivity of watersheds

River network connectivity is a key factor affecting watershed ecosystems and an important criterion for evaluating the health of river. The river network structure of the basin has changed dramatically in recent years due to human activity, but the response of connectivity to changes in physical structure is still poorly understood. In this paper, a dynamic index (connectivity index) based on daily-scale flow and probability density function is proposed to characterize the connectivity capacity of river networks. The Haihe River basin in China is selected as the study area, and a graphic model is constructed to assess the evolutionary structure of the river network. The 54 sections were classified into Low human impact (LHI) and High human impact (HHI), and the trends and causes of connectivity changes of the sections with the evolution of the network were analyzed. The results reveal that the river network degree and clustering coefficient keep increasing, the path length decreases and becomes more dense downstream, and the river network gradually evolves into a “small-world” network. The “small-world” characteristics improve the potential efficiency and specific functionality of the river network, but make the physical structure mismatch with the hydraulic gradient, and the network flow disperses severely, leading to a significant decrease in connectivity (HHI connectivity index is lower than LHI 52.1%). Moreover, the structural changes enhance the spatial and temporal differences in hydrological connectivity, which further restricts the function of the river system. “Small-world” and connectivity indicators (duration, start time, and intermittency) show strong correlations. Therefore, physical structure is an important factor influencing connectivity capacity of river networks. The planning and management of the watershed should consider the changes in hydrological connectivity caused by the structural modifications of the river network

Spatial production or sustainable development? An empirical research on the urbanization of less-developed regions based on the case of Hexi Corridor in China.

The relationships between spatial production, urbanization and sustainable development are becoming a focus of the international academic cycle. Urbanization dominated by spatial production driven by capital and power often produces and enlarges uneven development, which leads to multiple eco-environmental problems. Thus, the key to development lies in whether the pattern of urbanization is in harmony with the ecological environment. However, previous researches mainly concentrate on spatial production in developed countries or regions. The urbanization and sustainable development of less-developed regions, with complex and fragile ecological environments, are often overlooked. It is a new idea to explain the relationships and interactions between spatial production, urbanization and sustainable development based on less-developed regions by the theory of spatial production. The paper chooses the Hexi Corridor as a typical case, puts forward a conceptual framework and explores the process of spatial production from 2000 to 2017. The results reveal that urbanization in the Hexi Corridor is a multidimensional socio-spatial process: power and capital gave birth to a higher urbanization and accelerated the process of urbanization, however, the urban-rural gap between regions has not narrowed accordingly. Driven by comprehensive interests, local governments often take some extreme measures to forcefully promote the urbanization process, thereby violating the goals and requirements of sustainable development. At present, there is an urgent need to coordinate the relationship between urban and rural regions on different scales and transform the urbanization model from traditional spatial production to a new-type of urbanization with people-oriented and sustainable development

Impact of Human Activities on Red-crowned Crane Nest-sites Based on Voronoi Diagram

Based on the data investigated into Red-crowned Crane nest-sites in the Zhalong National Nature Reserve in 1996 and the period from 2003 to 2007, the characteristics of the spatial distribution of the nest-sites were analyzed, and the topological index (Voronoi Diagram Area) was calculated. The statistics showed that the spatial distribution of Red-crowned Crane nest-sites featured in the form of spatial clustering. The objects include the nest-sites, residential area, national highways and railways in the Zhalong National Nature Reserve in 2006, and then constructed the Voronoi diagrams to analyze their influence each other. The findings indicated that human activities made a great impact on the spatial distribution of nest-sites and played an important role in protecting the habitat of Red-crowned Crane. It constituted an effective tool that combined spatial data to describe and analyse interactions while providing support for decisions makers. Similarly, an objective quantitative analysis provided a rational basis for management decisions incorporating impact on species habitat