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The purpose of this paper is to study the multi-phase flow behaviors in solid fluidization exploitation of natural gas hydrate (NGH) and its effect on the engineering safety.

In this paper, a multi-phase flow model considering the endothermic decomposition of hydrate is established and finite difference method is used to solve the mathematical model. The model is validated by reproducing the field test data of a well in Shenhu Sea area. Besides, optimization of design parameters is presented to ensure engineering safety during the solid fluidization exploitation of NGH in South China Sea.

To ensure the engineering safety during solid fluidization exploitation of marine NGH, taking the test well as an example, a drilling flow rate range of 40–50 L/s, drilling fluid density range of 1.2–1.23 g/cm3 and rate of penetration (ROP) range of 10–20 m/h should be recommended. Besides, pre-cooled drilling fluid is also helpful for inhibiting hydrate decomposition.

Systematic research on the effect of multiphase flow behaviors on the engineering safety is scare, especially for the solid fluidization exploitation of NGH in South China Sea. With the growing demand for energy, it is of great significance to ensure the engineering safety before the large-scale extraction of commercial gas from hydrate deposits. The result of this study can provide profound theoretical bases and valuable technical guidance for the commercial solid fluidization exploitation of NGH in South China Sea.

This paper aims to carry out tribological experiments to explore the applications of femtosecond laser surface texturing technology on rock bit sliding bearing to enhance the lifetime and working performance of rock bit sliding bearing under high temperature and heavy load conditions.

Surface textures on beryllium bronze specimen were fabricated by femtosecond laser ablation (800 nm wavelength, 40 fs pulse duration, 1 kHz pulse repetition frequency), and then the tribological behaviors of pin-on-disc configuration of rock bit bearing were performed with 20CrNiMo/beryllium bronze tribo-pairs under non-Newtonian lubrication of rock bit grease.

The results showed that the surface texture on beryllium bronze specimens with specific geometrical features can be achieved by optimizing femtosecond laser processing via adjusting laser peak power and exposure time; more than 52 per cent of friction reduction was obtained from surface texture with a depth-to-diameter ratio of 0.165 and area ratio of 5 per cent at a shear rate of 1301 s−1 under the heavy load of 20 MPa and high temperature of 120°C, and the lubrication regime of rock bit bearing unit tribo-pairs was improved from boundary to mixed lubrication, which indicated that femtosecond laser ablation technique showed great potential in promoting service life and working performance of rock bit bearing.

Femtosecond laser-irradiated surface texture has the potential possibility for application in rock bit sliding bearing to improve the lubrication performance. Because proper micro dimples showed good lubrication and wear resistance performance for unit tribo-pairs of rock bit sliding bearing under high temperature, heavy load and non-Newtonian lubrication conditions, which is very important to improve the efficiency of breaking rock and accelerate the development of deep-water oil and gas resources.

Live streaming sales (LSS) is an emerging and flourishing practice in the retail industry. While its implementation has been pervasively attempted, there is a lack of systematic and academic exploration of the practice. Therefore, the aim of this study was to investigate the LSS ecosystem and its development through a literature review and an industry analysis. Moreover, by pinpointing the pitfalls in current practices, this paper presents the practical implications of LSS and provides recommendations and directions for future academic exploration.

The aim of the present study was to investigate the developing trajectory, exclusive elements (such as multi-channel networks (MCNs) and live streamers) and other critical components of the LSS ecosystem using a mixed-methods approach that comprises content analysis of newspaper articles and press releases, literature view and industry analysis.

The results of the analyses indicate the presence of several nonfungible modular components in the LSS ecosystem, including upstream suppliers, MCNs, live streamers and platforms. It was also found that inequalities and hierarchies are inherent to the LSS ecosystem as it currently exists: low-end participants in the LSS industry and small- and medium-sized enterprise owners, who constitute the majority of LSS practitioners, cannot reach the break-even point via LSS hosted by top-level live streamers or others (low-level live streamers, employees, etc.).

This article discusses the LSS ecosystem based on the nature of the nonfungible modules within it. In addition, it discusses the modules (roles) and relationships among them based on the theory of ecosystem developed by previous studies. Furthermore, drawing from an analysis of the pitfalls in the LSS ecosystem, this article highlights strategies for two critical e-commerce processes: 1) choosing which type of LSS to apply based on the factors of brands, products and consumers and 2) integrating LSS to optimize post-sale service and appeal to the sustainability of development.