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By analyzing the microbial diversity of the fillers in the multi-layer percolation system and using high-throughput sequencing technology, this paper conducted a detailed analysis of the microbial community structure of the multi-layer percolation system, revealing its role in pollutant removal. It was found that the microorganisms of specific bacterophyla played a key role in the pollutant removal process. It provides the microbiological basis for further optimization of multilayer percolation system.

The study found that the number of empty nesters in China will increase to more than 200 million in 2030. It accounts for 90% of the total number of elderly people, and the elderly in China will have an “empty nesting” situation. In the era when empty nesters are becoming more and more serious, the mental health of empty nesters is becoming increasingly prominent, which has become a key topic of concern in the whole society. In order to better develop the physical and mental health of the elderly, in the context of Internet+, this article uses SWOT method to analyze the issue of family care services for empty nesters. During the discussion, it was found that there are promotion problems, platform security problems, page operation problems and personnel needs problems in the family care service. From these four aspects, the article gives four suggestions of “increasing publicity, strengthening and improving network security, improving the service function of the platform and paying attention to personnel needs”.

In this study, high performance liquid chromatography (HPLC) was used to analysis the content of citric acid and D-isoascorbic acid in beverages. The samples were separated by C18 chromatography column, 0.1 % phosphoric acid solution was used as the mobile phase with the flow rate of 0.5 mL/min, the column temperature was 35 °C, and the detection wavelength was 210 nm. The results showed that the content of citric acid and D-isoascorbic acid has a good linear correlation (r>0.99) within the range of 50 μg to 200 μg. The selectivity, recovery and precision of citric acid and D-isoascorbic acid were suitable. Meanwhile, this method could be used to detect the content of citric acid and D-isoascorbic acid in beverages.

The resilience assessment method of hybrid AC-DC distribution grid is the key and basis of measuring the tolerance of the distribution network in face of extreme events and testing the effect of the resilience improvement strategy of the distribution network. This paper fully considers the characteristics of different extreme natural disasters and proposes a targeted resilience assessment method. For natural disasters, the fault rate model of the line under the influence of the disaster is constructed, and the fault set is generated based on Monte Carlo sampling. According to the operating characteristics, a set of evaluation indicators focusing on the core characteristics of resilience, including capability of strain, defense and recoverability, is constructed. The objective weight of each indicator and the comprehensive assessment results are obtained based relatively on the entropy weight method and the approximate ideal solution sorting method.

Route guidance is an efficient method to improve the capacity and efficiency of traffic system. This paper proposes an advanced ecorouting guidance strategy based on the real-time feedback information of both fuel consumption and travel time under the background of intelligent transportation system. Compared with the geographical shortest path strategy (GSP) and the time shortest path strategy (TSP), simulation experiment results show that the new strategy can help save fuel consumption and traffic cost by less detours. The distribution of travel cost among the roads is also provided, which is consistent with analysis. The implementation of the strategy in real cities might greatly reduce the energy consumption for transportation.

With the development of the Internet era, urban logistics distribution increases. At the same time, the state vigorously promotes the development of the new energy automobile industry and the continuous strengthening of people’s awareness of environmental protection, new energy vehicles began to be favored by logistics enterprises. From the analysis of the national support policy for new energy vehicles, the development of new energy vehicles in recent years and the TCO calculation of their cost advantages, this paper clarifies that new energy vehicles will occupy the mainstream position in urban logistics distribution.

In order to effectively monitor important sea areas, one of the key issues is the detection of small dynamic targets such as ships. Besides monitoring the hull itself, the monitoring of small targets can also be achieved by detecting ship wakes, which means the sea image with clear texture feature is required. This paper firstly reviews the multiscale retinex (MSR) method, commonly used to enhance the image contrast. Then, it proposes a novel contrast enhancement algorithm base on the subband-decomposed multiscale retinex (SDMSR) method. Experimental results show that our proposed method can make a remarkable enhancement effect for ocean remote sensing images with clouds and whitecap, etc.

As the technical basis of Bitcoin, block chain has the characteristics of decentralization ， openness and transparency. In order to promote the development of security and openness of power trading system and solve the trust problem among participants in power market，a new research direction of power trading method based on block chain is proposed. Therefore，this paper outlines the block chain，explains the definition and characteristics of block chain in detail，discusses the application of block chain in power trading system，and summarizes the challenges faced by block chain technology in power trading system.

In order to provide reference for the engineering design in the area with large wind, water flow and other horizontal loads, the experimental study on the horizontal bearing capacity of composite foundation under three different working conditions was carried out in this paper, which includes cap-single pile, cap-9 piles and enlarged cap-9 piles. The results show that under the condition of cap-9 piles, the group pile effect coefficient is 1.17, and the load sharing ratio of the back piles is the largest, and the middle and front piless decrease sequentially. Also, with the increase of horizontal load, the load sharing ratio of the back pile increases while the middle and front piless is decremented. Under the condition of enlarged cap-9 piles, the group pile effect coefficient is 1.36, which is 16.24% higher than that of the cap-9 piles, which means the horizontal resistance is obviously enhanced. At the same time, compared with the cap-9 piles, the load sharing ratio of the back pile is reduced while the middle and front piless is increased, which means the stress of pile body tends to be more uniform.

As an important equipment of power transmission, power cable has been required better performance on cable line loss and current ampacity to achieve its high reliability. This paper proposes an advanced application of superconducting transmission technology in power grid, namely tri-axial high-temperature superconducting (HTS) cable. The corresponding simplified model is established for multi-physical field analysis, and the size of each structure is determined through structural design. The temperature distribution of the cable body is analyzed according to multi-physical field coupling, and the influence of flow rate, size and other factors on the stability of the system is studied. In this paper, it is found that increasing liquid nitrogen volume and flow rate have saturation limit for lowering cable body temperature, and the axial temperature rise rate of cable body tends to be stable when it is greater than 4m. Multi-physical field analysis provides a basis for the design of HTS cable length without having system quench or liquid nitrogen gasification.

In this paper, a multiaxial fatigue life prediction model is proposed under general multiaxial random loadings. First, a brief review for existing multiaxial fatigue models is given and special focus is on the LiuMahadevan critical plane concept, which can be applied to both brittle and ductile materials. Next, new model development based on the Liu-Mahadevan critical plane concept for random loading is presented. The key concept is to use two-steps to identify the critical plane: identify the maximum damage plane due to normal stress and calculate the critical plane orientation with respect to the maximum damage plane due to normal stress. Multiaxial rain-flow cycle counting method with mean stress correction is used to estimate the damage on the critical plane. Equivalent stress transformation is proposed to convert the multiaxial random load spectrum to an equivalent constant amplitude spectrum. The equivalent stress is used for fatigue life prediction. Following this, experimental design and testing is performed for Al 7075-T6 under various different random uniaxial and multiaxial spectrums. The developed model is validated with both literature and in-house testing data. Very good agreement is observed for the investigated material. Finally, conclusion and future work is given based on the proposed study.

About one-third of the crude oil is trapped inside the pores of the carbonate and sandstone after the primary and secondary oil recovery, various methods have been used for the flooding of the trapped crude oil. Due to the opaque nature of the sandstone and shale, the visualization of the fluid flow inside the porous structure conventionally involved the use of very sophisticated equipment like X-ray computed microtomography. In this approach, a low-cost method for the mimic of porous structure for the enhanced oil recovery is proposed using the polymethyl methacrylate (PMMA)-based microfluidic devices with the laser ablated microstructures, where the microstructure is the replica of a real rock fracture. Since the PMMA is optically clear in the visible range, the detailed fluid flow inside the porous structure could be obtained for a better understanding of the liquid front propagation and rheology in the pore-scale. The effect of water flooding is also tested with the proposed microfluidic devices under various flooding rates for the demonstration of oil recovery enhancement with the proposed technology.

According to the demand of new measuring AC high-voltage technology based on the development of power network, this paper proposes an AC high -voltage measuring system using high voltage standard capacitor based on the analysis of the existing AC high-voltage measuring technology, the working principle of the AC high-voltage measuring system is analyzed in detail, and the experimental research on the steady state characteristic and frequency characteristic of the AC high-voltage measuring system is made, at the same time, the possible errors are analyzed in detail. The AC high-voltage measuring system meets the technical requirements of high-voltage signal acquisition in the power system, at the same time, meets the requirements of AC high voltage measurement when the frequency is not more than 2500Hz, and has certain practical value..

This paper describes the basic structure of the current comparator used for high voltage insulation measurements. Further applications for the current comparator in high voltage insulation are investigated and developed. A measuring system for the measurement of harmonics in the loss current of water tree aged insulation is described, as well as the principles to measure partial discharges with the current comparator bridge. A new system for the measurement of the DC component in the leakage current of insulation is de1veloped and presented. The results of experiments on XLPE cable insulation are also given.

Competing Interests: Déclaration de conflit d’intérêts Les chercheurs déclarent n’avoir aucun conflit d’intérêts.