Economic Development Zones have been proven to be an economic success and have been pursued by many governments around the world over the past several decades, but there is still a research gap on their impact on the environment. This paper documents the effect of national-level EDZs on the environmental performance of firms. Combining rich firm and administrative data in China from 1998–2012, we exploit the relationship between the foundation of EDZs and firms’ pollution emissions with a multi-period differences-in-differences model. We find that the establishment of national EDZs can effectively reduce the pollution emission intensity of firms within it. Moreover, this pollution reduction effects vary across industries, firms, and EDZs types. We also find that the establishment of EDZs can improve firm environmental performance by improving energy efficiency, optimizing the business environment, and upgrading technology.
In this work, we propose a new crack image detection and segmentation method for addressing the issues regarding the poor detection of crack structures in certain complex background conditions, such as the light and shadow, and the easy-to-lose details in segmentation. This method can be categorized into two phases, where the first one is the coding phase. In this phase, the channel attention mechanism and crack characteristics, using the correlation channel with different scales increasing the network robustness and ability of feature extraction, have been introduced to decouple the channel dimension and space dimension. It also avoids underfitting caused by information redundancy during the jumping connection. In the second stage, i.e., the decoding stage, the spatial attention mechanism has been introduced to capture the crack edge information through the global maximum pooling and global average pooling of the high-dimensional features. Then, the correlation between the space and channel has been recovered through multiscale image information fusion to achieve accurate crack positioning. Furthermore, the Dice loss function has been employed to solve the problem of pixel imbalance between the categories. Finally, the proposed method has been tested and compared with existing methods. The experimental results illustrate that our method has a higher crack segmentation accuracy than existing methods. Furthermore, the mean intersection over the union ratio reaches 87.2% on the public dataset and 83.9% on the self-built dataset, and it has a better segmentation effect and richer details. It can solve the problem of crack image detection and segmentation under a complex background.
Abstract. A method was proposed for the determination of copper, iron, nickel, cobalt, gold and silver in industrial wastewater by ICP-AES. Working conditions of the instrument and selection of analytical spectral lines were tested and optimized. The detection limit was 0.002,0.003,0.002,0.008,0.008,0.002mg/L. The effects of inhalation rate and the spectral intensity in nitric acid, hydrochloric acid, perchloric acid and sulfuric acid solution were tested. Nitrate acid with low viscosity, low surface tension and high atomization efficiency was selected. The accuracy and precision of this method were tested, and the relative error was less than 0.8%, relative standard deviation was less than 5.4%.It was accord with national standard. It proved that the determination of Copper, iron, nickel, cobalt, gold, and silver in industrial wastewater by ICP-AES was feasible.
Process mineralogy of a uranium ore which had U (0.22%) and F (1.04%) was investigated by modern SEM-based mineral liberation analysis (MLA) system and traditional process mineralogy research methods. The results indicate that traces of uranium minerals are mainly pitchblende, small amount of coffinite and brannerite in this ore. Pitchblende, coffinite and brannerite are fine and mainly embedded in quartz, muscovite and calcite. The content of pyrite and fluorite are 0.436% and 2.177% respectively. Fluorine minerals are mainly fluorite which is harmful to bioleaching. The content of quartz is 64.9%, which is the main gangue in this ore. The characteristic of this ore is low content and fine particle size of pitchblende, low sulfide and high fluorine. Bioleaching won't have obvious advantages compare with conventional acid-leaching.
Abstract. This paper determined calcium and magnesium in bioleaching solution of uranium ore by optimized EDTA method. This method used acid chrome blue K-naphthol green B mixed indicator after adding reducing agent hydroxylamine hydrochloride, masking agent triethanolamine and masking agent L-cysteine. This method required the concentration of calcium and magnesium more than 0.50g/L, respectively. Thus, coexisting ions did not interfere with the determination, and the titration end point was obvious. The results show that the standard addition recovery rate of calcium and magnesium is 99.15%~101.40% and 99.26%~101.18%, respectively. The relative standard deviation of calcium and magnesium is less than 3.5% with good accuracy and precision. This method is simple and fast to determine calcium and magnesium in bioleaching solution of uranium ore, and the results are accurate and reliable.
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