Search

The impact of climate change on the crop water footprint (WF) is highly uncertain, hindering effective agricultural water use in response to climate change. This study proposes a factor sensitivity analysis method, which can screen out statistically significant climatic factors and interactions on crop WF under various uncertainties and determine water resource management measures to mitigate drought for different crops. A special case study was conducted in Heilongjiang Province, China. The results showed that (1) the annual change in crop WF showed a downward trend from 1988 to 2018. The crop WF was dominated by green water footprint (WF green), and the average occupancy rate of WF green in crops was 58.7%–74.1 %; the spatial distribution of WF has latitude zonality. (2) Drought has different effects on WF of different crops, and WF of soybean is susceptible to drought. Wind speed, sunshine hours, and humidity have a greater impact on crop WF in most growth stages. (3) The effect of climatic factors on crop WF varies in different months. The rice WF is mainly affected by the climate in May, and there is an interaction between May humidity and May rain. The WF of maize and soybeans are affected primarily by the climate in July, especially sunshine hours. The proposed approach attempts to analyze that crop WF is affected by not only an individual climatic factor but also their interactions. Crop water management practices should be adjusted based on the results to mitigate the adverse impact of climatic conditions on crop WF during different growing months. [ABSTRACT FROM AUTHOR] more...

Since 2000, the gross domestic product (GDP) of the Pearl River Delta (PRD) has increased by more than eight‐fold. Experiences throughout the world indicate that the impacts of economic development on vegetation are particularly important. This study analyzed the variations in vegetation coverage in the PRD from 2000 to 2016. Moderate resolution imaging spectroradiometer normalized difference vegetation index (NDVI) data were employed, whereas climate data, GDP, and population were also used as influencing factors. Topographic factors were introduced to explain the spatial vegetation patterns, and the impacts of human activities on vegetation were explored. The results revealed (a) the overall vegetation coverage in the PRD showed an increasing trend, and the overall average NDVI increased by 0.0033/a. (b) The spatial pattern did not change greatly, but the high and low NDVI values moved to low elevations and shallow topographic slopes where human activities were prevalent. This trend resulted in increased NDVI values in 38% of the area of the PRD (p < 0.01). (c) There was a positive correlation between NDVI and economic growth (GDP, population), with correlation coefficients greater than 0.8 (p < 0.01). NDVI is influenced by climate change and human activities (such as afforestation, resident lifestyles, and economic development policies). This study reveals that with good policies, both rapid economic development and vegetation coverage improvements can be simultaneously achieved in a region. The findings of this study are crucial for the sustainable development of the mega‐urban agglomerations of the PRD and Guangdong‐Hong Kong‐Macau Grand Bay. [ABSTRACT FROM AUTHOR] more...

The sedimentary record in the Late Palaeoproterozoic‐Neoproterozoic Bayan Obo rift belt can provide critical insight into tectonic evolution of Columbia and the North China Craton. In this study, we present new U–Pb geochronology, Hf isotopic analyses from the Bayan Obo Group, the Mesoproterozoic kimberlite, and gabbro to constrain the depositional age and potential provenance information of the Bayan Obo Group. We show that the Dulahala‐Jianshan, Bilute, and Baiyinbaolage formations were deposited at ca. 1.81–1.7 Ga, ca. 1.58–1.35 Ga, and ca. 1.25–1.0 Ga, respectively. Our data suggest the following potential provenance for sediments within the Bayan Obo Group: (a) The Khondalite Belt, Yinshan Block, and crystalline basement complex of the North China Craton to the south were the most potential provenance of the Dulahala and Jianshan formations during the initial deposition of Bayan Obo Group; (b) The Yinshan Block, and crystalline basement complex of the North China Craton, and local intermediate‐acid igneous rocks were the most potential provenance of the Bilute Formation; and (c) the local gabbro and volcanic rocks were the most potential provenance of the Baiyinbaolage Formation. Based on regional geologic constraints and the sedimentary history, we propose that the Northern Marginal Rift System probably represented several distinct rifting events. Furthermore, the Bayan Obo and Huade rift belts were active more recently than 1.0 Ga, which suggests that these rift systems were not only related to the rifting of the Columbia supercontinent. We propose that the Bayan Obo rift belt also records the rifting related to the breakup of Rodinia with the deposition of Qingbaikou System (Tonian) strata. [ABSTRACT FROM AUTHOR] more...

• The efficiency enhancement method of abrasive water jet slit-assisted shield cutter cutting reinforced concrete was investigated. • Revealed the efficiency enhancement mechanism of abrasive water jet slit-assisted shield cutters. • The main influencing factors affecting the effectiveness of abrasive water jet slit-assisted shield cutters were discussed. To improve the efficiency and safety of shield machines cutting reinforced concrete (RC) obstacles, using an abrasive waterjet (AWJ)-assisted shield cutter to cut RC is considered a feasible solution. To explore the effect of an AWJ on a shell cutter cutting RC, laboratory experiments and numerical simulation methods were used to compare the breaking performance and damage mechanism of a shell cutter cutting RC with and without a slit. The results showed that the waterjet pre-cutting slit could effectively reduce the cutter force of the shell cutter and promote the cutting of steel bars. The reduction rate of the cutter force by the waterjet slit increased and then decreased with an increase in the penetration degree. When the penetration degree was 1.5 mm, the waterjet cutting slit had the best reduction effect on the cutting force. An optimal critical value was found for the waterjet cutting slit of the steel bar; when the waterjet slit was larger than ½ of the diameter of the steel bar, the steel bar was prone to tensile fracture under the cutting action. The waterjet pre-cutting slit reduced the residual cross-sectional area and stress distribution of the steel bar, which promoted the bending and tensile fracture of the steel bar and thus improved the cutting efficiency. Furthermore, construction recommendations for the AWJ-assisted shield cutting of RC obstacles were identified. The findings presented in this paper can provide useful reference information for the design and construction of AWJ shield machines. [ABSTRACT FROM AUTHOR] more...

ABSTRACT Sulfonated poly(phthalazinone ether sulfone ketone) (SPPESK) composite membranes are fabricated through electrostatic layer-by-layer (LbL) self-assembly method with chitosan (CS) and phosphotungstic acid (PWA) to enhance the proton conductivity and stability. The results demonstrate that LbL self-assembly has different effects on the SPPESK membrane substrates with different sulfonation degrees (DSs). It elevates proton conductivity of the SPPESK membrane of lower DS and enhances swelling stability of the SPPESK membrane of higher DS. For instance, at 80°C, proton conductivity of the SPPESK0.74/(CS/PWA)1 membrane (lower DS) increases by 16%-96.49 mS cm−1, and swelling ratio of the SPPESK1.01/(CS/PWA)3 membrane (higher DS) decreases from 58 to 29%. Attribute to the electrostatic interaction and ion cross-linking networks, permeability of the SPPESK0.74/(CS/PWA)3 membrane and the SPPESK1.01/(CS/PWA)5 membrane are reduced by 45 and 30%, respectively. The results indicate that the LbL self-assembly has broadened the available DS range for fuel cell applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 132, 42867. [ABSTRACT FROM AUTHOR] more...

• Relationships between ecosystem services and urbanization were assessed. • Ecosystem services were significantly correlated with urbanization. • Different ecosystem services showed varied responses to urbanization. • Most developed urban areas had the lowest regulating and supporting services. • Relationships between ecosystem services and urbanization remained robust. Research on the relationship between ecosystem services (ESs) and urbanization has been drawing attention in recent years. We analyzed the relationship between ESs and urbanization in the Pearl River Delta (PRD) region, and explored whether and how this relationship changes across temporal and spatial scales. The InVEST model was used for ESs mapping and various urbanization indicators were selected. Correlation analysis and curve estimation were used to detect the linear and nonlinear relationships between ESs and urbanization. Results of the study indicated that regulating and supporting services decreased, while provisioning services increased with urbanization. Significant correlations (p ˂0.05) were found between ESs and urbanization, and mostly presented an increasing trend from 2000 to 2018 and from the grid scale to the county scale. Curve estimation indicated that regulating and supporting services decreased as urbanization increased, and water yield service increased as urbanization increased, while the relationship between food provisioning and urbanization presented an inverse-U shape. Generally, the relationships between ESs and urbanization varied with different ESs but remained relatively robust across time and scale. This study specifies the impact of urbanization on ESs, and highlights the importance of spatial scales in studying the relationship between urbanization and ESs. [ABSTRACT FROM AUTHOR] more...

In order to improve the crushing efficiency of drilling machinery, laser-assisted mechanical rock-breaking technology has gained wide attention in the field of engineering construction. In this method, the weakening effect of the laser on the compressive strength of the rock is a key factor of the technology. To reveal the weakening effect of the laser on the compressive strength of rocks, standard uniaxial compression tests were carried out on irradiated rocks using a uniaxial compression testing machine. The weakening effect of laser power and irradiation time on rock strength and rock failure mode was investigated. The experimental results show that the laser power and irradiation time have similar effects on the mechanical properties of the rocks. With the increase of laser power and irradiation time, the peak stress of the specimens shows a tendency to decrease rapidly and then slowly. At the same time, the rock elastic modulus decreases and peak strain increases, and the behavior eventually transform from brittle damage to plastic damage. Melting pit holes and crack networks are the root cause of the weakness of the compressive strength. On one hand, the vertical melting pit hole provides a conical free surface, which reduces the rock deformation constraint and generates stress concentration at the bottom of the hole, so that it facilitates the splitting-tension damage of the specimen. On the other hand, the axial load induces symmetric tensile cracks in the thermal cracks, and adjacent tensile cracks interpenetrate to create a surface of tensile damage, leading to fragmentation of the specimen in the form of rock blocks, ultimately undermining the rock. This work provides an improved understanding of the effect of lasers on the compressive strength of rocks in engineering applications. Highlights: The effect of laser irradiation on the compressive strength weakening of rock was investigated. Failure modes and strength weakening mechanisms of irradiated rocks were revealed. The advantage parameters of laser-assisted rock breaking were clarified. [ABSTRACT FROM AUTHOR] more...

Purpose: To investigate the optimal threshold for measuring thyroid volume in patients with Grave's hyperthyroidism (GH) by SPECT/CT. Materials and methods: A 53 mL butterfly-shaped hollow container made of two 45-degree transparent elbows was put into a NEMA IEC phantom tank. The butterfly-shaped container and the tank were then filled with Na99mTcO4 of different radioactive concentrations, respectively, which could simulate thyroid gland with GH by different target-to-background ratios (T/B) (200:1, 600:1, 1000:1). The different T/B of planar imaging and SPECT/CT were acquired by a Discovery NM/CT 670 Pro SPECT/CT. With Thyroid software (Version 4.0) of GE-Xeleris workstation, the region of the thyroid gland in planar imaging was delineated. The thyroid area and average long diameter of both lobes were substituted into the Allen formula to calculate the thyroid volume. The calculation error was compared with the actual volume. Q-Metrix software was used to perform CT-based attenuation correction, scatter correction, resolution recovery. Ordered-subsets expectation maximization was used to reconstruct SPECT data. 20%, 25%, 30%, 40%, 50%, 60% thresholds were selected to automatically delineate the volume of interest and compared with the real volume, which determinated the optimal threshold. We measured the thyroid volume of 40 GH patients using the threshold and compared the volumes obtained by planar imaging and ultrasound three-dimensional. The differences of the volumes with different T/B and thresholds were compared by the ANOVA and least significant difference t test. The volumes delineated by SPECT/CT were evaluated using ANOVA, least significant difference t test, correlation analysis and, linear regression and Bland–Altman concordance test plot. The differences and consistency of thyroid volume were compared among the above three methods. Results: There was no significant difference in the results between different T/B models (P > 0.05). The thyroid volume calculated by the planar imaging formula method was higher than the real volume, with an average overestimation of 22.81%. The volumes delineated by SPECT/CT threshold automatically decreased while the threshold increased. There were significant differences between groups with different thresholds (P < 0.001). With an average error of 3.73%, the thyroid volume analyzed by the threshold of 25% was close to the results of ultrasound measurement (P > 0.05). Thyroid volume measured by planar imaging method was significantly higher than ultrasound and SPECT/CT threshold automatic delineation method (P < 0.05). The agreement between the SPECT/CT 25% threshold and ultrasound (r = 0.956, b = 0.961) was better than that between the planar imaging and ultrasound (r = 0.590, b = 0.574). The Bland–Altman plot also showed that the thyroid volume measured by the 25% threshold automatic delineation method was in good agreement with the ultrasound measurement. Conclusions: The T/B has no effect on the measurement of thyroid volume in GH patients; planar imaging method can significantly overestimate thyroid volume in GH patients, and 25% threshold automatic delineation method can obtain more accurate thyroid volume in GH patients. [ABSTRACT FROM AUTHOR] more...

• Improve the performance of TBM in hard rock and extremely hard rock environments. • The method of rock breaking with pre-grooving assisted disc cutter is studied. • As the pre-groove depth increases, the cutting performance of the cutter increases. To improve the tunnelling performance of tunnel boring machines in hard rock and extremely hard rock environments, abrasive water jet assisted rock breaking is a possible solution that has currently attracted considerable attention. In this approach, the depth of the pre-cut groove is a key factor affecting the performance of assisted rock breaking. To study the influence of the pre-groove depth on assisted rock breaking performance, a full-scale linear cutting test of pre-grooved rock was conducted with a disc cutter. The influence of the pre-groove depth on the rock breaking effect under the same-trajectory mode (SM) and different-trajectory mode (DM) of assisted cutting was explored, and the mechanism of assisted rock breaking with different groove depths was revealed. Compared with the complete cutting mode (CM), the results showed that the normal force (F N), rolling force (F R), side force (F s), and specific energy (SE) under SM decrease as the groove depth increase. Under DM, the F N , F R , and SE decrease as the average groove depth on both sides increase, and the F s decreases as the minimum groove depth increases. In SM and DM, the cutting SE first decreased rapidly and then tended to decrease slowly as the groove depth increased, indicating the existence of an optimal groove depth. The rock fracture patterns under SM and DM are more prone to tensile failure, which significantly reduces the rock cutting force and SE of the disc cutter. These results can provide inspiration for the design and construction of new types of tunnel boring machines that are assisted by abrasive water jet pre-grooving. [ABSTRACT FROM AUTHOR] more...

[Display omitted] • Soil silt/clay and nutrients increased with increasing distance from the shelterbelt. • Downslope deposition lead to an increase in plow pan thickness and a decrease in bulk density. • Erosion rate was primarily affected by shelterbelt distance, followed by elevation. • Sites closer to shelterbelt warrant particular attention due to coarse-texture materials. Soil erosion is the most severe form of land degradation globally. Farmland shelterbelts are important for reducing erosion, especially erosion caused by the co-occurrence of water and wind. However, few studies have focused on how the distance from the shelterbelt associated with farmland topography affects the redistribution of soil quality indicators. The aims of this study is to reveal the relative importance of these two factors to soil quality under typical wind and water erosion conditions concurrent with the Songnen Plain, China. Topsoils (0–10 cm) were sampled at seven distances from the shelterbelt with three replicates, where topography heterogeneity was also considered. We found that the silt/clay content and soil nutrients at sites farther from the shelterbelt were significantly greater than those at sites closer to the shelterbelt (P < 0.05). Similarly, deposition was dominant at sites farther from the shelterbelt and downslope positions, while erosion was dominant at sites closer to the shelterbelt and upslope positions. Moreover, we discovered that the relative influence of distance from the shelterbelt and farmland elevation varied with individual soil quality indicators. Soil nutrients increased through the deposition of more fine-textured soil (silt/clay) positions farther from the shelterbelt. The downslope region responds to soil deposition by enhancing the plough pan thickness and lowering the bulk density and pH. Overall, distance from the shelterbelt and farmland elevation had interactive effects on soil quality, and erosion was primarily affected by distance from the shelterbelt (63.4 %), followed by elevation (22.7 %). Furthermore, the sites closer to the shelterbelt (i.e., 20 to 420 m) warrant particular attention due to the deposition of coarse-texture materials here. This work is crucial for an improved understanding of the synergistic effects of long-term water and wind co-occurrence on soil quality evolution. [ABSTRACT FROM AUTHOR] more...