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This paper aims to investigate the contents of heavy metals Cd, Cr, Ni, Cu, Pb and Zn in the soil of vegetable production bases in the Yongnian County of Hebei Province by random sampling.

The environmental quality conditions of these heavy metals were evaluated by both the single quality index and comprehensive quality index methods.

It was concluded that the average heavy metal contents in the soil of protected vegetable fields in the Yongnian County are all under the limit values prescribed by the environmental quality evaluation standard for farmland of greenhouse vegetables production (2007), so the soil’s environmental quality is classified as first class regarding cleanliness. It is fit for the plantation of non-polluted vegetables. It is shown that there is a cumulative trend of heavy metal contents in the soil with age after analysis of a correlation coefficient between heavy metal contents and age in Yongnian’s protected fields and excessive application of fertilizers or organic fertilizers, which is the main factor leading to an increase in heavy metal contents in the soil.

It is suggested that the amount of fertilizer should be properly reduced to prevent the soil’s environmental deterioration, the vegetable planting structure should be improved and the vegetables grown in areas with weaker accumulation of heavy metals should be cultivated.

Hydraulic conductivity is very low in saline-sodic soil, which decreases water infiltration. For saline-sodic soil, increasing infiltration water has a special meaning. Increasing infiltration water not only increases the water in the soil profile but also decreases the salinity of the soil, thus making it suitable for growing crops. This study aims to examine the effect of sand pipes on soil water and salt distribution through laboratory tests with different depths and diameters of sand pipes.

The soil water and salt distribution responses to different sand pipe depths and diameters was investigated. Treatments included sand pipes with diameters of 4 cm, 5cm, 6 cm and the same depth of 4 cm; with depths of 2cm, 6 cm and the same diameter of 5 cm, and a control with no sand pipe (with the diameter of 0 cm and the depth of 0 cm).

The results suggested that the amount of cumulative infiltration water and transport distance of the wetting front could be increased by increasing the depth and diameter of sand pipes. The soil water content in the soil profile decreased under all treatments except for the control, whereas the value of EC increased with increasing distance from the film hole center. Positive relationships were also found among the sand pipe depth, diameter and the zone of low salt content. Furthermore, salt leaching depth increased with sand pipe depth and diameter. Overall, the treatments with and without sand pipes exhibited obvious differences.

The correlation analysis proved that increasing the infiltration area through sand pipes positively affected the amount of infiltration water, wetting scope and salt leaching depth.

In certain latitude areas, fruit growth is determined by the slope between 5° and 20°. According to the designed sunny slope direction and the parallel lines to the slope direction, we take two adjacent rows of the hedge to meet certain condition of the sun light, and draft the chart of shadow top contour based on the solar azimuth angle A and the coefficient of shadow length γ to get crown space of the rectangular cross section in different ground of slopes. Then, the crown section lateral is changed to get mathematical models which determine the crown space of different cross sections in hedgerow orchard.

In the hedgerow orchard of hilly land, the crown height changes with ground slope so as to meet the condition of the sun light. Using astronomical trigonometric formulas, this paper calculates solar position of the 40° north latitude in vernal equinox and autumnal equinox. At the same time, it calculates the shadow length of tree body, determines the shadow length coefficient y and drafts the chart of shadow top contour based on the solar azimuth angle A and the coefficient of shadow length γ. According to the design of the north-south direction, we take two lines of the hedge with the changing figure of the top contour of shadow and crown cross-section to get mathematical models which determine the crown height of different sections in different ground slope.

Coal waste that releases highly acidic, sulfate and metals rich drainage is a serious environmental problem which causes the contamination of surface and ground water as well as soils in coal mining areas in China. In order to study the effect of using fly ash for preventing acid-mine drainage and controlling heavy metals contamination from coal waste, two column leaching tests were conducted to determine if a cover of fly ash could be used for the control of acid-mine drainage from coal waste. We investigated the effect of the cover of fly ash on controlling acid, sulfate and heavy metals contamination from coal waste. The results from the experimental data analyses show that the cover of fly ash can effectively immobilize cadmium, copper, iron, lead and zinc in acid-mine drainage from coal waste, increase the pH value from 2.0 to 7.5 and decrease Eh from 249 mV to 148 mV, EC from 5.22 mS/cm to 1.05 mS/cm and SO₄^2- concentrations from 12911.7 mg/L to 881.4 mg/L of acid-mine drainage from coal waste. The immobilization rate of heavy metals reached 99%. The oxidation of sulfide minerals in coal waste was prevented by the cover of fly ash, which favors the generation of alkalinity, the decrease of the population of Thiobacillus ferrooxidans, the heavy metals immobilization by precipitation inside the column, and the halt of the oxidation process of sulfide through iron coating on the surface of sulfide minerals in coal waste. The cover of fly ash can effectively control acid-mine drainage and heavy metals contamination from coal waste in situ treatment systems.

The influence of calcium nitrite corrosion inhibitor on the durability of Portland cement mortars against sulphate solutions was investigated experimentally in the present research. For this reason, mortar specimens were produced using CEM I 42.5N cement and were immersed in different sulphate and sulphate‐chloride contaminated solutions. Sulphate resistance was evaluated according to the procedure described in ASTM C1012. The properties measured were the specimens' expansion, development of compressive strength, changes in corrosion potential and corrosion current density measurements of steel‐containing specimens.

The sudden COVID-19 epidemic in 2019 has frustrated China's overall economy, and the implementation and development of the National Fitness Program has encountered huge obstacles. At a new historical starting point, in order to realize the dream of becoming a powerful country in sports, it is necessary to transform the successful experience gained since the reform and opening up into regular understanding and systematic theories, so as to make a theoretical response to the new contradictions and challenges faced in development and give full play to the National Fitness has comprehensive values and multiple functions in improving people's health, promoting people's all-round development, promoting economic and social development and demonstrating the country's cultural soft power.

Taking the topic of national fitness as an example, this paper sets out from the three dimensions of knowledge input, knowledge output and knowledge production, using citation analysis, social network analysis, co-word analysis and cluster analysis, to measure the characteristics and knowledge structure of interdisciplinary knowledge exchange.

China's national fitness is still in the primary development stage, and the strong boost of the national top-level policy is the biggest driving force of its development, driven by the policy together with the settlement of many major events, constantly improving and enriching the wings. The main body of knowledge production on the topic of national fitness is mainly colleges and universities, with low participation of government and enterprises, high degree of cooperation among authors, obvious interdisciplinary characteristics and strong application of research themes.

This study provides a strong theoretical basis for the promotion of the Healthy China strategy. Especially under the influence of COVID-19, this paper can contribute to the comprehensive value and multimodal functions of national fitness in improving the health of people, promoting economic and social development and demonstrating the soft power of national culture.

The purpose of this paper is to establish a model to analyze the impacts of economic policy on the demand for electricity in China, including the impacts of fiscal and monetary policies.

With the development of electric reform, the impacts of economic policy on demand for electricity will be more and more obvious. It is difficult to analyze the impacts by a conventional model. CGE model is based on the theory of general equilibrium which is put forward by Walras, it describes the supplying and demanding relationship between the sectors of the economic system, a CGE model can recognize that an exogenous change (in policy or from other source) that affects any one part of the economy can produce repercussions throughout the system, it can also analyze the impacts of economic policy on electric power sector.

A CGE model and a social accounting matrix are established.

Accessibility and availability of data are the main limitations which model will be applied.

A very useful model to study the impacts of economic policy on electric power sector.

The new method to analyze the impacts of economic policy on electric power sector in China. The paper aims at policy makers and the researchers who deal with electric power demand and supply.

Lubricating oil leakage is a common issue in thermal power plant operation sites, requiring prompt equipment maintenance. The real-time detection of leakage occurrences could avoid disruptive consequences caused by the lack of timely maintenance. Currently, inspection operations are mostly carried out manually, resulting in time-consuming processes prone to health and safety hazards. To overcome such issues, this paper proposes a machine vision-based inspection system aimed at automating the oil leakage detection for improving the maintenance procedures.

The approach aims at developing a novel modular-structured automatic inspection system. The image acquisition module collects digital images along a predefined inspection path using a dual-light (i.e. ultraviolet and blue light) illumination system, deploying the fluorescence of the lubricating oil while suppressing unwanted background noise. The image processing module is designed to detect the oil leakage within the digital images minimizing detection errors. A case study is reported to validate the industrial suitability of the proposed inspection system.

On-site experimental results demonstrate the capabilities to complete the automatic inspection procedures of the tested industrial equipment by achieving an oil leakage detection accuracy up to 99.13%.

The proposed inspection system can be adopted in industrial context to detect lubricant leakage ensuring the equipment and the operators safety.

The proposed inspection system adopts a computer vision approach, which deploys the combination of two separate sources of light, to boost the detection capabilities, enabling the application for a variety of particularly hard-to-inspect industrial contexts.