Simulating land use/cover change (LUCC) and determining its transition rules have been a focus of research for several decades. Previous studies used ordinary logistic regression (OLR) to determine transition rules in cellular automata (CA) modeling of LUCC, which often neglected the spatially non-stationary relationships between driving factors and land use/cover categories. We use an integrated geographically weighted logistic regression (GWLR) CA-Markov method to simulate LUCC from 2001–2011 over 29 towns in the Connecticut River Basin. Results are compared with those obtained from the OLR-CA-Markov method, and the sensitivity of LUCC simulated by the GWLR-CA-Markov method to the spatial non-stationarity-based suitability map is investigated. Analysis of residuals indicates better goodness of fit in model calibration for geographically weighted regression (GWR) than OLR. Coefficients of driving factors indicate that GWLR outperforms OLR in depicting the local suitability of land use/cover categories. Kappa statistics of the simulated maps indicate high agreement with observed land use/cover for both OLR-CA-Markov and GWLR-CA-Markov methods. Similarity in simulation accuracy between the methods suggests that the sensitivity of simulated LUCC to suitability inputs is low with respect to spatial non-stationarity. Therefore, this study provides critical insight on the role of spatial non-stationarity throughout the process of LUCC simulation. 相似文献
A series of three-dimensional numerical simulations is carried out to investigate the effect of inclined angle on flow behavior behind two side-by-side inclined cylinders at low Reynolds number Re=100 and small spacing ratio T/D=1.5 (T is the center-to-center distance between two side-by-side cylinders, D is the diameter of cylinder). The instantaneous and time-averaged flow fields, force coefficients and Strouhal numbers are analyzed. Special attention is focused on the axial flow characteristics with variation of the inclined angle. The results show that the inclined angle has a significant effect on the gap flow behaviors behind two inclined cylinders. The vortex shedding behind two cylinders is suppressed with the increase of the inclined angle as well as the flip-flop gap flow. Moreover, the mean drag coefficient, root-mean-square lift coefficient and Strouhal numbers decrease monotonously with the increase of the inclined angle, which follows the independent principle at small inclined angles.
We studied the effects of expected end-of-the-century pCO2 (1000 ppm) on the photosynthetic performance of a coastal marine cyanobacterium Synechococcus sp. PCC7002 during the lag, exponential, and stationary growth phases. Elevated pCO2 significantly stimulated growth, and enhanced the maximum cell density during the stationary phase. Under ambient pCO2 conditions, the lag phase lasted for 6 days, while elevated pCO2 shortened the lag phase to two days and extended the exponential phase by four days. The elevated pCO2 increased photosynthesis levels during the lag and exponential phases, but reduced them during the stationary phase. Moreover, the elevated pCO2 reduced the saturated growth light (Ik) and increased the light utilization efficiency (α) during the exponential and stationary phases, and elevated the phycobilisome:chlorophyll a (Chl a) ratio. Furthermore, the elevated pCO2 reduced the particulate organic carbon (POC):Chl a and particulate organic nitrogen (PON):Chl a ratios during the lag and stationary phases, but enhanced them during the exponential phase. Overall, Synechococcus showed differential physiological responses to elevated pCO2 during different growth phases, thus providing insight into previous studies that focused on only the exponential phase, which may have biased the results relative to the effects of elevated pCO2 in ecology or aquaculture. 相似文献
The interactions among surface water, groundwater and seawater are closely related in the coastal area with complex hydrological conditions. A series of impacts from human activities and climate change are also more significant in this region. In order to understand the key knowledge and research status of surface water and groundwater interaction in coastal area, it is a useful method to analyze literatures in this research scope in the core database of Web of Science by using CiteSpace. The research achievements in this field were systematically sorted and potential research hotspots were explored, which may provide references for subsequent researches. The results show the following. The number of highly cited articles and highly burst articles in this research field has increased significantly since 2010. At present, this field is still in the development stage and has a broad research prospect. The United States, Australia, China and Germany have done plenty of researches on this issue and achieved a lot. At present, the number of research achievements supported by National Natural Science Foundation of China is in the lead over the world. Seawater intrusion, submarine groundwater discharge, the relationship between tide and hydrological conditions are the main research direction in this field. Hydrochemistry and isotopic analysis, and numerical simulation are the most important research methods in this field. The potential development directions and breakthroughs in this field include submarine groundwater discharge, the evolution of coastal mangrove wetlands, the migration and transformation of nutrients, the influences of different hydrological factors on coastal areas, and the impact of climate change on coastal areas. Overall, the future development of surface water and groundwater research in coastal areas is inseparable from the cross-integration of various disciplines, mutual verification of multiple methods and the introduction of new technical means. 相似文献
Polynomial chaos expansions (PCEs) have been widely employed to estimate failure probabilities in geotechnical engineering. However, PCEs suffer from two deficiencies: (a) PCE coefficients are solved by the least-square minimization method which easily causes overfitting issues; (b) building a high order PCE is often computationally expensive. In order to overcome the aforementioned drawbacks, the Bayesian regression technique is employed to evaluate PCE coefficients, which not only provides a sparse solution but also avoids overfitting. With the aid of the predictive means and variances given by Bayesian analysis, a learning function is proposed to sequentially select the most informative samples that are critical to build a PCE. This sequential learning scheme can highly enhance the computational efficiency of PCEs. Besides, importance sampling (IS) is incorporated into the sequential learning (SL)-PCEs to deal with geotechnical problems with small failure probabilities. The proposed method of SL-PCE-IS is applied to three illustrative examples, which shows that the improved PCE method is more effective and efficient than the common PCEs method, leading to accurate estimations of small failure probabilities using fewer training samples. 相似文献