The Tarim River is the longest inland river at an arid area in China. Deterioration in its ecohydrological system has received much attention world widely. This study presents quantitative assessment ...of hydrological alterations in the hydrological regime of the Tarim River caused by reservoir irrigation and channel irrigation over a period of over a half century. The improved indicators of hydrologic alteration and range of variability approach were applied to the daily flow rates at the two representative hydrological stations. Our study shows that the annual extreme water conditions (1-, 3-, 7-day annual minimum and extreme low timing) have been altered, compared with the pre-impact period. The average flow rate in July, the 30-day annual maximum flow rates, the date for the maximum rate, the rise rate, and the fall rate show a significant decreasing trend. The improved overall degree of hydrological alteration for the two stations are approximately 68.7% and 61.8%, suggesting a high degree of alteration. This study greatly improved our understanding of impacts of irrigations on the ecohydrological characteristics in the Tarim River.
Understanding contributions of climate change and human activities to changes in streamflow is important for sustainable management of water resources in an arid area. This study presents ...quantitative analysis of climatic and anthropogenic factors to streamflow alteration in the Tarim River Basin (TRB) using the double mass curve method (DMC) and the Budyko methods. The time series (1960~2015) are divided into three periods: the prior impacted period (1960~1972) and the two post impacted periods, 1973~1986 and 1987~2015 with trend analysis. Our results suggest that human activities played a dominant role in deduction in the streamflow in TRB with contribution of 144.6% to 120.68% during the post impacted period I and 228.68% to 140.38% during the post impacted period II. Climatic variables accounted for 20.68%~44.6% of the decrease during the post impacted period I and 40.38% ~128.68% during the post impacted period II. Sensitivity analysis indicates that the streamflow alteration was most sensitive to changes in landscape parameters. The aridity index and all the elasticities showed an obvious increasing trend from the upstream to the downstream in the TRB. Our study suggests that it is important to take effective measures for sustainable development of eco-hydrological and socio-economic systems in the TRB.
The Tarim River Basin (TRB) is an extremely arid area in China, suffering from dry climate and intense human activities, which have brought about significant changes in ecological processes and then, ...led to serious ecological vulnerability (EV). This study proposes an assessment framework to evaluate EV and analyze its dynamic change in the TRB during 2005–2015. An integrated method is developed with the Fuzzy Analytic Hierarchy Process (FAHP) and the Pressure-State-Response (PSR) framework, which highlights impacts of nature and anthropogenic interference on the ecology. Specific management strategies are put forward based on the spatial recognition of ecologically vulnerable areas in the TRB. The EV is divided into four vulnerability levels including Light I, Medium II, Heavy III and Very heavy IV. Results show that the average EV is at Heavy III vulnerability level in the TRB in the last 2005–2015, and there has been an increasing trend in EV, which even has come up to the Very heavy IV vulnerability level in the year 2013–2015. As a whole, the EV displays a high-to-low gradient from east to west during the study period. Heavy III and Very heavy IV vulnerability levels, distributed in the East, mainly in the mainstream areas with characterization of frequent human interferences, tend to increase persistently. In contrast, Light I vulnerability level, mainly in the west source areas, shows a significant decline after 2010. Based on the results, some suggestions targeted at different vulnerable areas were proposed to help restore ecological environments by integrating legal managements with public efforts. The proposed methodology, reflecting the nature and human interaction on the EV is of practical use for the ecological restorations in the TRB.
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•An integrated indicator system for specially assessment of ecological vulnerability (EV) is established.•The EV was largely aggravated in the Tarim River Basin (TRB) during 2005–2015.•The Heavy III level dominates throughout the TRB with a low-to-high spatial distribution from west to east.•Ecological restorations with different use control for different partitions are proposed.
The Tarim River (TR), as the longest inland river at an arid area in China, is a typical regions of vegetation variation research and plays a crucial role in the sustainable development of regional ...ecological environment. In this paper, the newest dataset of MODND1M NDVI, at a resolution of 500m, were applied to calculate vegetation index in growing season during the period 2000-2015. Using a vegetation coverage index, a trend line analysis, and the local spatial autocorrelation analysis, this paper investigated the landscape patterns and spatio-temporal variation of vegetation coverage at regional and pixel scales over mainstream of the Tarim River, Xinjiang. The results showed that (1) The bare land area on both sides of Tarim River appeared to have a fluctuated downward trend and there were two obvious valley values in 2005 and 2012. (2) Spatially, the vegetation coverage improved areas is mostly distributed in upstream and the degraded areas is mainly distributed in the left bank of midstream and the end of Tarim River during 2000-2005. (3) The local spatial auto-correlation analysis revealed that vegetation coverage was spatially positive autocorrelated and spatial concentrated. The high-high self-related areas are mainly distributed in upstream, where vegetation cover are relatively good, and the low-low self-related areas are mostly with lower vegetation cover in the lower reaches of Tarim River.
Landscape ecological characteristics of the urban-rural ecotone of Nanjing City were studied by using remote sensing and geographical information system (GIS) techniques. Two representative study ...regions with the same area were chosen in the eastern and southern part of the city. The urban-rural fringe of both east (URFE) and south region (URFS) can be divided into three zones: fringe-paraurban zone, transition zone and pararural zone. URFE was basically characterized by low landscape diversity, dominance and fragmentation. The forest patches in URFE had larger area and average perimeter, while their average fractal dimension, average stretched index and separated degree were lower. The average area of vegetable land and paddy land was larger than that of south region. URFS showed higher landscape diversity, dominance and fragmentation, more and higher density of patches. The area and the perimeter of water and architectural patches in URFS were also larger than that of URFE. The relationship between patch area and fractal dimension, stretched index and fractal dimension, patch number and area were discussed. The function and contributing factors of each type of patches, especially forestland, and the landscape characteristics and the ecological significance of corridors including road, river, and city wall of urban-rural fringe were also analyzed.
Coordinated Volt-Var control methods have demonstrated their techno-economic feasibility in voltage regulation of photovoltaic (PV) rich distribution systems. However, fast fluctuating PV power and ...imperfect communication networks may significantly challenge the effectiveness of these methods. In this paper, a revised dynamic consensus algorithm is proposed to coordinate distributed inverters for Volt-Var control in real time. With this proposed method, Var saturation and overvoltage issues which tend to occur at downstream buses of PV rich distribution systems are significantly mitigated. To quantitatively analyse the algorithm performance in imperfect communication environments, the information delivery between agents is modelled by stochastic state transition processes among finite numbers of virtual nodes so as to quantitatively depict the random time delay and packet dropout in a discrete way. On this basis, the state transition process of the whole system is further depicted by a series of row- stochastic matrices, and the ergodic theory is used to analytically derive the algorithm tracking error in an imperfect communication environment. Our proposed method can also be extended to more complex applications, where both Var compensation and PV curtailment (or EV dispatch) are available for system voltage control. Simulation results verify the superiority of our method over traditional ones.
Epithelial–mesenchymal transition (EMT) program, which facilitates tumor metastasis, stemness and therapy resistance, is a reversible biological process that is largely orchestrated at the epigenetic ...level under the regulation of different cell signaling pathways. EMT state is often heterogeneous within individual tumors, though the epigenetic drivers underlying such heterogeneity remain elusive. In colon cancer, hyperactivation of the Wnt/β-catenin signaling not only drives tumor initiation, but also promotes metastasis in late stage by promoting EMT program. However, it is unknown whether the intratumorally heterogeneous Wnt activity could directly drive EMT heterogeneity, and, if so, what are the underlying epigenetic driver(s). Here, by analyzing a phenotypically and molecularly heterogeneous colon cancer cell line using single-cell RNA sequencing, we identified two distinct cell populations with positively correlated Wnt activity and EMT state. Integrative multi-omics analysis of these two cell populations revealed RUNX2 as a critical transcription factor epigenetically driving the EMT heterogeneity. Both in vitro and in vivo genetic perturbation assays validated the EMT-enhancing effect of RUNX2, which remodeled chromatin landscape and activated a panel of EMT-associated genes through binding to their promoters and/or potential enhancers. Finally, by exploring the clinical data, we showed that RUNX2 expression is positively correlated with metastasis development and poor survival of colon cancer patients, as well as patients afflicted with other types of cancer. Taken together, our work revealed RUNX2 as a new EMT-promoting epigenetic regulator in colon cancer, which may potentially serve as a prognostic marker for tumor metastasis.
This study analyzed several disadvantages of the servo control method based on discharge probability detection in wire-cut electrical discharge machining (WEDM) for semiconductor processing. Among ...these disadvantages is the reduction in machining quality, cutting efficiency, and shape accuracy caused by a change in feed speed. The relationship between pulse width and discharge probability was analyzed to develop a control method based on pulse width proportional–integral–derivative (PID) control. PID adjustment of the pulse width to control discharge probability was applied to achieve constant discharge probability processing. A constant discharge probability pulse power source for WEDM was designed and constructed and subsequently applied to ordinary WEDM machines. Straight line and arc cutting experiments were carried out to prove the feasibility of the new system. The feasibility of the proposed system was verified by conducting straight line and arc cutting experiments. Process parameters were then optimized through the target probability experiment.
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