Search

Since hydrate resources play a part of the stratigraphic framework structure in sediments, establishing a safe and economic method for hydrates exploitation remains the primary challenge to this day. Among the proposed methods, the spontaneous displacement of CH4 from hydrate cages by CO2 seems to be a perfect mechanism to address gas production and CO2 storage, especially in today's strong demand for carbon reduction and replacing clean energy. After extensive lab researches, in the past decade, injecting a mixture of CO2 and small molecule gas has become a key means to enhance displacement efficiency and has great potential for application. However, there is a lack of in-depth research on gas flow in the reservoir, while the injected gas always passes through low-saturated hydrate areas with high permeability and then occurs gas channel in a short term, finally resulting in the decreases in gas production efficiency and produced gas quality. Therefore, we explored a new injection-production mode of alternate injection of N2 and CO2 in order to fully coordinate the advantages of N2 in enhanced hydrate decomposition and CO2 in solid storage and heat compensation. These alternate "taking" and "storing" processes perfectly repair the problem of the gas channel, achieving self-regulation effect of CH4 recovery and CO2 storage. The 3-D experimental results show that compared to the mixed gas injection, CH4 recovery is increased by >50% and CO2 storage is increased by >70%. Additionally, this alternate injection mode presented a better performance in CH4 concentration of produced gas and showed outstanding N2 utilization efficiency. Further, we analyzed its self-adaptive gas flow mechanism and proposed an application model of "one injection and multiple production". We look forward to this study accelerating the application of CO2-CH4 replacement technology. [ABSTRACT FROM AUTHOR]

Adenomyosis (AM) is a common gynecological disorder characterized by the presence of endometrial glands and stroma within the uterinemyometrium. It is associated with abnormal uterine bleeding (AUB), dysmenorrhea, and infertility. Although several mechanisms have been proposed to elucidate AM, the exact cause and development of the condition remain unclear. Recent studies have highlighted the significance of macrophage polarization in the microenvironment,which plays a crucial role in AMinitiation and progression. However, a comprehensive review regarding the role and regulatory mechanism of macrophage polarization in AM is currently lacking. Therefore, this review aims to summarize the phenotype and function of macrophage polarization and the phenomenon of the polarization of adenomyosis-associated macrophages (AAMs). It also elaborates on the role and regulatory mechanism ofAAMpolarization in invasion/migration, fibrosis, angiogenesis, dysmenorrhea, and infertility. Furthermore, this review explores the underlying molecular mechanisms of AAM polarization and suggests future research directions. In conclusion, this review provides a new perspective on understanding the pathogenesis of AM and provides a theoretical foundation for developing targeted drugs through the regulation of AAM polarization. [ABSTRACT FROM AUTHOR]

China's rural revitalization strategy has expanded non-agricultural employment opportunities for rural residents. This has directly raised farmers' incomes and household expenditures, which in turn has contributed to the upgrading of industrial structure. Using provincial data for 2012–2021, our study investigates how this employment transition affects industrial development. The effect of rural residents' consumption expenditures on this relationship is also explored through a linkage model to help measure the extent of the impact. This study further explores the regional differences in this effect and its robustness. The findings suggest that non-farm employment significantly contributes to industrial structural upgrading. However, this effect is not consistent across regions. Moreover, rural residents' consumption plays a pivotal role in this relationship. Governments should therefore encourage more non-farm jobs, stimulate domestic demand and use rural consumption as a key growth catalyst, especially after the demographic dividend disappears. It is also important to take into account regional nuances in policy formulation and make adjustments to cater for these differences to prevent any potential imbalances. [ABSTRACT FROM AUTHOR]

The article focuses on addressing the unfair exposure issue in session-based recommender systems (SRSs) which provide short-term and dynamic recommendations to users based on their current session. Topics include the introduction of new fairness metrics for item exposure and recommendation quality, the development of a dynamic Fairness-Assurance Strategy for session-based recommender systems (FASTER), and the results demonstrating its ability to improve exposure fairness.

[Display omitted] • Bone repair scaffolds with different filling pattern. • The 90°angle is suitable for long bone repair. • The 60°angle is suitable for bone repair with complex appearance. • The 30°angle is suitable for cancellous bone repair. 3D printing technology can control the shape and filling pattern of the scaffold very well and has been widely used in the preparation of bone repair scaffolds. Modifying the filling pattern of scaffolds to alter their mechanical properties and cellular adhesion holds immense significance. In this study, 3D-printed polylactic acid (PLA) scaffolds with different fibre angles (15°-90°) were prepared. The 90° scaffold showed the best mechanical properties and was suitable for repairing long bones. The 60° scaffold has balanced mechanical properties and is suitable for maxillofacial bone repair. The scaffold with a 30° angle was the best for cell adhesion and proliferation and was suitable for cancellous bone repair. [ABSTRACT FROM AUTHOR]

Laser polishing (LP) provides a fast and efficient way of remelting part surfaces manufactured by additive manufacturing to alter both their geometric as well as physical properties. Depending on the laser parameters, remelted surfaces with different properties are achieved, with a majority exhibiting lower surface roughness compared to the original surface. In this study, a high-power continuous fiber laser is used to polish Inconel 718 (IN718) surfaces produced by depositing a single layer of clads on a steel substrate by the powder-blown directed energy deposition (DED) process. Polishing was performed under different sets of parameters, namely, laser power, beam diameter, feed rate or feed, hatch spacing, and the number of polishing passes. Their effects on the surface roughness profiles and the microstructural properties of the sample cross section were analyzed after one and two polishing passes. Optical microscopic images of the sample's cross sections show the presence of supersaturated γ γ' + γ" phase particles, precipitates, Laves phases, and δ phase needles. The combined effect of high-temperature gradients and lower solidification rates in certain regions within the cross section results in undercooled regions and pseudo-heat treatment of unmelted regions close to the undercooled regions. These results are corroborated by indenting the various regions of the IN718 sample cross section with a pyramidal diamond indenter in the form of a grid, resulting in different micro-hardness values due to different densities of precipitate and phase transformed particles. [ABSTRACT FROM AUTHOR]

The impact of anthropogenic global warming on tropical cyclone (TC) frequency remains a challenging issue, partly due to a relatively short period of reliable observational TC records and inconsistencies in climate model simulations. Using TC detection from 20 CMIP6 historical simulations, we show that the majority (75%) of these models show a decrease in global-scale TC frequency from 1850 to 2014. We demonstrated that this result is largely explained by weakened mid-tropospheric upward motion in CMIP6 models over the Pacific and Atlantic main development regions. The reduced upward motion is due to a zonal circulation adjustment and shifts in Intertropical Convergence Zone in response to global warming. In the South Indian Ocean, reduced TC frequency is mainly due to the decreased survival rate of TC seeds because of an increased saturation deficit in a warming climate. Our analysis highlights global warming's potential impact on the historical decrease in global TC frequency. [ABSTRACT FROM AUTHOR]

The process parameters of Directed Energy Deposition (DED) have been widely studied including laser power, powder flow rate, and scanning speed. These parameters affect clad dimension and melt pool temperature, which are directly related to part quality. However, laser/powder profiles and their alignment have obtained less attention due to the cumbersome characterization process, although they can be directly associated with local energy density for melt pool formation. This study examines the impact of the alignment between the laser beam and powder flow distributions in DED on clad dimension and melt pool temperature. The laser beam and powder profiles are characterized by measuring their respective 2D Gaussian profiles for a given standoff distance. Aligned and misaligned laser-powder profiles are then used to build single-clad square geometries. It was found that a 500-µm offset between the centers of the laser and powder profiles causes up to a 20% change in both the width and the height of a single clad as well as an average temperature increase of 100 K. To understand the interaction between powder flow, energy flux, and local temperature, the local specific energy density distribution was plotted in 2D. These results suggest that laser-powder misalignment may significantly alter the thermal history and shape of deposited clads, possibly preventing DED-manufactured parts from meeting design properties and causing build failures. [ABSTRACT FROM AUTHOR]

The process parameters of Directed Energy Deposition (DED) have been widely studied including laser power, powder flow rate, and scanning speed. These parameters affect clad dimension and melt pool temperature, which are directly related to part quality. However, laser/powder profiles and their alignment have obtained less attention due to the cumbersome characterization process, although they can be directly associated with local energy density for melt pool formation. This study examines the impact of the alignment between the laser beam and powder flow distributions in DED on clad dimension and melt pool temperature. The laser beam and powder profiles are characterized by measuring their respective 2D Gaussian profiles for a given standoff distance. Aligned and misaligned laser-powder profiles are then used to build single-clad square geometries. It was found that a 500-µm offset between the centers of the laser and powder profiles causes up to a 20% change in both the width and the height of a single clad as well as an average temperature increase of 100 K. To understand the interaction between powder flow, energy flux, and local temperature, the local specific energy density distribution was plotted in 2D. These results suggest that laser-powder misalignment may significantly alter the thermal history and shape of deposited clads, possibly preventing DED-manufactured parts from meeting design properties and causing build failures. [ABSTRACT FROM AUTHOR]

• In response to the challenge of maintaining stable and accurate relative positioning information for USVs and UAVs in unpredictable maritime weather conditions, this article introduces the UWB positioning system for the inaugural application in measuring the relative position of UAV landing on USVs. It also performs a quantitative analysis of the UWB positioning array's error, taking into account the impact of short deck baseline length and wave swaying, and proposes an adaptive filter solution. • A novel "surfing" roll and pitch stability control method for USV is proposed. This adjustment effectively minimizes the rolling and pitching response of the USV, consequently facilitating the smooth landing of the UAV. Simultaneously, the UAV evaluates its relative speed, position, and heading deviation in relation to the USV, and dynamically adjusts the expected docking control inputs and motion parameters using a fuzzy working condition table. Multiple autonomous landing experiments at sea have demonstrated the UAV's high landing accuracy and stability during the docking phase. • A task allocation method for efficient sea surface inspection using a heterogeneous unmanned system is proposed. Simulation tests of a USV equipped with four UAVs conducting sea surface inspection tasks are conducted in UE4 and Simulink. Within a 2km × 2km sea area, the surrounding inspection operation covers 74 % of the sea area and can be completed within 10 minutes. This method holds reference value for large-scale maritime search missions conducted by heterogeneous unmanned systems operating in sea and air environments. The incorporation of Unmanned Aerial Vehicles (UAVs) into sea surface inspection and complex water navigation tasks performed by Unmanned Surface Vessels (USVs) enhances the operational capabilities and task efficiency of heterogeneous systems. The autonomous docking of USV by UAV at sea serves as a foundational and vital element for facilitating collaborative tasks among unmanned systems. Faced with the problem that the UAV visual positioning USV deck is susceptible to interference from maritime meteorological conditions and the positioning accuracy of GPS is poor, this paper introduces the UWB positioning system and analyzes and solves the error disturbance term of its positioning array under the influence of sea sway for the first time. At the same time, due to the error problem caused by the small baseline of UWB installed on the deck, an adaptive Kalman filter that combines GPS speed information and UWB positioning data is proposed to reduce error. In light of the destabilizing effects resulting from the swaying of the USV deck during UAV docking, this study proposes a USV roll and pitch stability control strategy that incorporates environmental wind and wave data. Additionally, a UAV docking controller utilizing a fuzzy PID approach has been developed to facilitate secure and stable UAV takeoff and docking operations at sea. The effectiveness of the proposed algorithm was verified through sea docking experiments under various working conditions. Finally, in the context of the multi-target maritime inspection mission of heterogeneous unmanned systems, an exploratory improved VRP algorithm is proposed, allowing UAVs to quickly and efficiently complete sea surface inspection operations.The feasibility and operational efficiency of the cooperative mission system are tested through joint simulation using Simulink and UE4 in a high-fidelity environment. This provides a reference solution for future applications of heterogeneous unmanned systems in real maritime environments. [ABSTRACT FROM AUTHOR]