When will China's total water consumption reach the turning point? EKC simulation and influencing factors.

The turning point of China's total water consumption is very important for the understanding of the evolution trend of total water consumption and the formulation of water conservation policies. Based on the environmental Kuznets curve (EKC) model, this paper verifies the shape of water consumption Kuznets curve. Scenario analysis and Monte Carlo simulation are combined for the first time to predict water consumption Kuznets curve. The LMDI model is used to decompose the driving factors of the evolution of total water consumption, and the STIRPAT model is expanded to explore the influence mechanism of total water consumption. The results show the following: (1) The theoretical water consumption Kuznets curve exists, and the turning point is 26,448 yuan RMB (in around 2013). (2) Based on the multiple driving factors (water intensity, per capita GDP, and population) and multiple scenarios (baseline scenario, target scenario, and 2 adjusted scenarios), 32 scenarios are designed in this paper; in the S1-S8, the turning point still appeared near 2013; the curves under the S11-S14, S16, and S25-S32 were inverted U-shaped, and the turning point was 48,728 yuan RMB (in around 2025); and in the S9, S10, and S15, the curve shows an upward trend; in the S17-S24, the curve has a rising-falling-rising characteristic. (3) Domestic effect and ecological effect both play a role in promoting the total water consumption, while the production effect is in an inverted N-shaped. Economic growth has always promoted the increase in industrial and agricultural water consumption, and the role of population size is relatively weak. The intensity of production water consumption has always promoted reduction in industrial and agricultural water consumption. Industrial water intensity and industrial structure are the primary and secondary factors that promote the decline of production intensity. (4) The per capita GDP has the largest contribution to total water consumption, followed by the water intensity, and the industrial structure has the least impact. The population has a negative impact. Based on this, a number of policy implications are obtained.

Investigation of Weld Root Defects in High-Power Full-Penetration Laser Welding of High-Strength Steel.

The currently available high-power laser shows promising opportunities for the welding of thick plates in a single pass. However, weld-root defect frequently occurs when a high-power laser is used to join thick plates in a full-penetration mode, which has a significantly adverse effect on the serviceability of the weld joint. The purpose of this work is to understand the defect formation mechanism and reduce these defects through controlling welding parameters. In this study, the characteristics of weld root defects were investigated using a 10 kW fiber laser using a program of experiment and theoretical analysis. The corresponding defect formation mechanisms were discussed based on the bottom molten pool behaviors observed by the high-speed camera. The results showed that there were four types of weld-root appearances as follows with an increase of linear heat input from 300 J/mm to 1000 J/mm: weld-root humping (30 mm/s), sound weld (25 mm/s), weld sagging (20 mm/s) and excessive weld sagging. The remedies for reducing weld-root defects were also presented to obtain sound weld bead by optimizing welding parameters. Weld-root humping was formed due to the quasi-full-penetration keyhole. Weld sagging resulted from the imbalance of the hydrostatic pressure and surface tension in the condition of a through keyhole. It was also found that the sound weld was formed when a through keyhole and a proper molten pool size were obtained. Thus, the state of the keyhole and molten pool geometry were the major factors that affect weld-root defects.

Penalized maximum-likelihood reconstruction for improving limited-angle artifacts in a dedicated head and neck PET system.

Positron emission tomography (PET) suffers from limited spatial resolution in current head and neck cancer management. We are building a dual-panel high-resolution PET system to aid the detection of tumor involvement in small lymph nodes ([Formula: see text]10 mm in diameter). The system is based on cadmium zinc telluride (CZT) detectors with cross-strip electrode readout (1 mm anode pitch and 5 mm cathode pitch). One challenge of the dual-panel system is that the limited angular coverage of the imaging volume leads to artifacts in reconstructed images, such as the elongation of lesions. In this work, we leverage a penalized maximum-likelihood (PML) reconstruction for the limited-angle PET system. The dissimilarity between the image to be reconstructed and a prior image from a low-resolution whole-body scanner is penalized. An image-based resolution model is incorporated into the regularization. Computer simulations were used to evaluate the performance of the method. Results demonstrate that the elongation of the 6-mm and 8-mm diameter hot spheres is eliminated with the regularization strength γ being 0.02 or larger. The PML reconstruction yields higher contrast recovery coefficient (CRC) of hot spheres compared to the maximum-likelihood reconstruction, as well as the low-resolution whole-body image, across all hot sphere sizes tested (3, 4, 6, and 8 mm). The method studied in this work provides a way to mitigate the limited-angle artifacts in the reconstruction from limited-angle PET data, making the high-resolution dual-panel dedicated head and neck PET system promising for head and neck cancer management.