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Functional design is an extremely important part in the design and development of complex systems. It is necessary to establish a forward development method to ensure the correctness and completeness of functional design. Therefore, taking the flight control system of civil aircraft as an example, a forward development method for functional design is proposed. First, system modeling language is used to establish the functional requirements relationship model from aircraft level to system level and then to item level. Then, the functional requirements are combined with the safety requirements in SAE ARP4754A aircraft development guide to construct the functional knowledge set of the flight control system. Finally, the functional model of the flight control system is established based on functional unit block diagram and functional integration block diagram. This method can be used as a reference for the functional design of complex systems.

Unmanned underwater vehicles play an important role in ocean observation and exploration; however, they do not have long endurance due to energy limitations. This paper proposes an energy self-sufficient underwater profiling buoy that uses ocean thermal energy for buoyancy propulsion and as a power supply, to enable long-term ocean observations. Based on the principle of operation of the proposed buoy, an energy balance model is established that is used to calculate the energy captured by the heat exchangers and the energy consumption of the devices on board. The energy self-sufficiency rate is defined as an indicator for evaluating the impact of the key configuration parameters of the buoy on the energy self-sufficiency performance, which depends on the diving speed, diving depth, and system pressure of the accumulator. In addition, a buoyancy compensation unit with two accumulators is installed on the buoy to compensate for the impact of variations in seawater density on the buoyancy propulsion performance and to overcome buoyancy loss. When the diving speed of the buoy is around 0.24 m/s and the diving depth is above 900 m, the accumulator has an initial pressure of 10 MPa, a driving pressure of 11.1–17.9 MPa, and a charging pressure of 20 MPa, and the energy self-sufficiency rate of the buoy exceeds 100%. This work provides theoretical guidance for realising energy self-sufficiency for other unmanned underwater vehicles. [ABSTRACT FROM AUTHOR]

Owing to the requirements for high performance and long life, the friction and wear problems of rolling piston type rotary compressors have drawn much attention. Various theoretical models have been developed and improved to reveal the inner state of the compressor and obtain the optimization schemes. However, there remain some disadvantages and research gaps in the corresponding modeling and mixed lubrication analyses, and a comprehensive summary is lacking. To have a better understanding of the research status, this paper reviews the theoretical model development and mixed lubrication analyses of the compressor in the past decades. The determination of compression pressure, the modeling process of moving components, and the key findings are presented in detail. On this basis, some important influencing factors and the problems remaining to be solved are also discussed. This paper provides multifaceted guidance for manufacturers and researchers to conduct further theoretical analysis and optimal design. [ABSTRACT FROM AUTHOR]

In order to address the issue of drill string stick–slip vibration, which leads to drill bit wear and reduces the drilling velocity, we conducted a study on the characteristics of stick–slip vibration using a proportional-integral-derivative (PID) controller. By applying the principles of rigid body mechanics, we established a two-degree-of-freedom torsional dynamics equation and derived the first-order differential dynamics equation for the drill string. Subsequently, we designed a PID controller and obtained an equation for the control of stick–slip vibration. The research findings indicate that variations in the difference between the static and dynamic friction coefficients directly impact the nature of the limit cycles in the phase plane. As this difference decreases, the limit cycle narrows and the stick–slip vibrations weaken progressively. When the static and dynamic friction coefficients are equalized, no stick–slip vibrations occur within the drill string. The implementation of PID control effectively manages stick–slip vibrations in the drill string, with greater efficiency observed in controlling the turntable velocity compared to the drill bit velocity. This research provides valuable insights for the development of control strategies aimed at mitigating stick–slip vibrations in drilling engineering applications, thereby facilitating the efficient and safe extraction of oil and gas resources. [ABSTRACT FROM AUTHOR]

Dietary supplements are currently being used to ameliorate metabolic alterations via maintaining gut microflora balance. Mulberry leaf is known as medicine homologous food for its glucose‐ and lipid‐modulating properties. However, the effects of mulberry leaf polysaccharide (MP) on metabolic dysbiosis and gut microbiota are still poorly understood. After extraction and characterization, the beneficial effects of water‐soluble MP were evaluated in high‐fat diet‐induced obese mice. MP treatment could reduce adipose tissue, improve insulin resistance, and alleviate the pathological lesions in colon. Investigation of the underlying mechanism showed that MP modulated gut microbial community by 16S rRNA analysis and reversed the elevation of lipid indexes by plasma lipidomics analysis. Correlation analysis indicated that the abundance of seven key bacterial species and six lipids were closely associated with the metabolic traits, respectively. Overall, MP could ameliorate metabolic disorders, and modify the gut microbiota and lipids. This would greatly facilitate the utilization of MP as a functional food. [ABSTRACT FROM AUTHOR]