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Segmental tunnel is widely adopted in the urban transportation system, thereby its seismic resilience is a cornerstone for resilient cities. The segmental tunnel is an assembly of reinforced concrete segments, bolts, gaskets, gaps, etc., and exhibits highly nonlinear behavior when subjected to external loadings. Yet, in practice, its seismic response is generally estimated via a holistic modeling approach where the segmental tunnel is represented by a homogeneous beam or shell element with equivalent stiffness. Here, a multi-contact joint-based model is developed for a segmental tunnel, incorporating the nonlinearities embedded in the assembly with acceptable computational costs. The reinforced concrete segment is represented as the displacement-based fiber beam element, whereas the complex interaction among the configurations of the joint, i.e. bolt, gasket, and contacting concrete, is modeled via the zero-length section element. The proposed model's accuracy is validated via a series of experimental data under three loading scenarios. A sensitivity analysis demonstrates that the mechanical response of segmental tunnels highly relies on the assembly configurations. The proposed model is implemented to investigate the seismic response of a typical segmental tunnel under various ground motions, demonstrating its applicability in seismic safety assessments, particularly in capturing the nonlinear response of segmental tunnels under high-intensity earthquakes. [ABSTRACT FROM AUTHOR]

During the century-long mining process of the Fushun west open pit, slope slippage and deformation caused varying degrees of horizontal deformation, uneven settlement, and ground cracks on the surface of the urban areas, which caused a certain degree of damage to buildings and infrastructure and affected the livings of residents in the surrounding communities. In this study, a set of building reinforcement and community resilience enhancement methods that can resist slope deformation was proposed to improve the ability of urban areas to cope with slope geological hazards and emergency response. The main research contents included: Firstly, this paper systematically analyzed the deformation mechanism of the dip sloping and the inverse dip sloping section of the open pit mine, which was based on the field measured data and simulation calculation results. In other words, the horizontal deformation of the stratum in the dip sloping section was dominant, while the stratum in the inverse dip sloping section was prone to ground cracks and uneven settlement. In view of this, three surface deformation characteristic subdivisions of the surrounding urban area were proposed. In addition, a study on the damage characteristics of buildings with different types of foundations and structures under the influence of side slope deformation were carried out, and the anti-deformation reinforcement measures for load-bearing members mainly based on steel fiber concrete, carbon fiber materials and profile steel were proposed. Finally, a three-level disaster emergency setting system for urban areas around open pit mine was established, and the disaster prevention and resilience enhancement strategy for build and unbuilt the communities around the side slopes was constructed. The study aims to provide technical support to the overall resilience and response of the urban communities adjacent to open-pit mine slopes against consequent geological hazards and emergencies, thereby promoting sustainable urban development.

A two-axis semi-strapdown stabilized platform is a device designed to eliminate aircraft disturbances and ensure the stability of the sensor's orientation. A traditional two-axis semi-strapdown stabilization platform for aircraft can effectively control disturbance in pitch and yaw channel, but it cannot achieve ideal disturbance control in the roll channel. In order to solve this problem, an adaptive control method based on disturbance transformation and LWOA-PID is proposed. Disturbance transformation is the process of integrating the angular position disturbance of the roll from the previous moment into the combined disturbance of the pitch and yaw at the current moment. This is followed by decoupling the combined disturbance of the pitch and yaw at the current moment, thereby eliminating the disturbance caused by the roll from the previous moment. This process is repeated to achieve the goal of eliminating roll channel disturbances. To ensure the line of sight (LOS) pointing accuracy stability in the two-axis semi-strapdown stabilized platform system for aircraft, a whale optimization adaptive proportional–integral–derivative (LWOA-PID) controller based on Latin hypercube sampling is designed. It is then compared with the classical PID controller in Matlab/Simulink. The simulation results indicate that the disturbance conversion module proposed in this paper can eliminate the impact of roll axis disturbances on the LOS pointing accuracy of the two-axis semi-strapdown stabilized platform for aircraft. Compared to the classical PID controller, the LWOA-PID controller reduces tracking errors for step and sinusoidal signals by 50% and 75%, respectively. It also shortens optimization time by 37.5% compared to the WOA-PID while maintaining the same level of accuracy. Furthermore, when combined with the conversion module, the tracking error is reduced by an additional order of magnitude. [ABSTRACT FROM AUTHOR]

A two-axis stabilizing gimbal is a device that ensures a sensor is working properly on a moving platform. When classical mechanics (Newton–Euler and Lagrange) is employed to model a two-axis stable gimbal, its limitations can complicate the modeling process. To address this issue, a method for establishing a dynamic model for a two-axis stabilizing platform based on the Kane method is proposed in this paper. The Kane method offers the advantage of a simple model structure and computational efficiency. Initially, utilizing a generalized coordinate system, expressions of the generalized velocities, deflection velocities and angular velocities are derived. Subsequently, the generalized active forces and inertial forces acting on the two-axis stabilized gimbal are analyzed. Finally, by combining force and velocity with the Kane equation, the dynamic model of the two-axis stable platform is obtained, demonstrating the validity of the Kane method for establishing the two-axis stable platform model. To ensure the pointing accuracy stability of the two-axis stabilizing platform, a Novel Particle Swarm Optimization Proportion Integration Differentiation (NPSO-PID) controller is designed using the PSO algorithm. It is then simulated in MATLAB/Simulink and compared with a classical PID controller. Simulation results demonstrate that NPSO-PID exhibits superior object tracking performance compared to classical PID controllers and better optimization of control parameters compared to traditional PSO-PID controllers. [ABSTRACT FROM AUTHOR]

Human settlement environment is space places closely related to human production and life, and also surface spaces inseparable from human activities. As a coastal city in the east of China, Qingdao has a relatively high level of urbanization. However, it also along with many urban problems at the same time, among which the problem of human settlement environment has attracted more and more general attention from people. According to the characteristics of human settlement environment in Qingdao, the research constructs an index system with 10 index factors from natural factors and humanity factors, and proposes a comprehensive evaluation model. Evaluate and grade suitability of human settlement environment in Qingdao, explore the spatial aggregation and differentiation of the quality of human settlement environment, and reveal the internal connection of spatial evolution. The results indicate that the overall livability of Qingdao is relatively good, showing a multi-center and radial driving development. The distribution of livability is uneven, showing a decreasing spatial distribution law from the coast to the inland, and the quality of human settlement environment in Jiaozhou Bay and the coastal areas is relatively high. Qingdao is mainly based on natural livability, supplemented by humanity livability, compared with natural suitability, the spatio-temporal evolution characteristics of humanity livability have experienced three stages: rising-contradictory rising-harmonious rising. The quality of human settlement environment has obvious spatial correlation and is positively correlated with the degree of agglomeration, and the agglomeration of blocks with a higher quality of human settlement environment is higher than that of blocks with a lower level. The rule of human settlement environment changing over time is that areas with high quality of human settlement environment begin to shift from the city center to the north and the south, transforming into multi-point development, and overall environmental suitability has been improved. According to the results of the comprehensive evaluation, combined with its local development status and policies, the research puts forward developmental suggestions for the construction of human settlement environment in Qingdao, and provides decision-making basis for relevant departments to solve the problem of deterioration of human settlement environment.

High-precision collaborative observation is urgently needed due to the increasing demands of space science missions. Based on a conventional DFP (disturbance-free-payload) configuration, this paper presents a novel DFP that has great potential to deal with collaborative observation missions. The novel DFP system is developed, in which two or more payloads are installed via a non-contact unit and installed parallel configuration. Thus, the novel design is a multibody dynamics system. With the incorporation of the dynamics of the flexible umbilical between the PMs (payload modules) and SM (support module), the six-degrees-of-freedom multibody rigid–flexible dynamics of the whole system are derived. To verify the effectiveness of the novel DFP design in a collaborative observation mission, a multi-loop controller is designed for an inertial Earth collaborative observation mission. Simulation studies are conducted, which indicate that the proposed design can complete collaborative observation and achieve high precision. [ABSTRACT FROM AUTHOR]

• Re effect leads to higher frequency and stronger circumferential momentum of compressor tip leakage flow. • Impact of tip leakage flow decreases from leading edge to mid-chord, but increases from mid-chord to trailing edge at low RNI condition. • Flow instability, identified by DMD, shows growth of low-frequency stall modes and weakening of blade-passing modes. • High RNI condition exhibits non-uniform high-pressure region due to shock-TLV (tip leakage vortex) interaction, leading to delayed flow field response to blade passing. • Low RNI condition results in uniform high-pressure region due to enhanced circumferentia momentum of tip leakage flow, leading to secondary leakage formation. With the continuous increase in aircraft flight altitude, low Reynolds number effects in high-altitude environments significantly impact the stability of compressor operation. In this study, dynamic mode decomposition (DMD) of the flow field at various time instances near stall conditions in a transonic compressor was performed to investigate the influence of Reynolds number (Re) effects on critical flow characteristics and instability mechanisms. The results indicate that under different Reynolds number index (RNI) conditions near stall conditions, the frequency of tip leakage flow varies. Under high RNI condition, the influence of tip leakage flow is concentrated mainly from the leading edge to the mid-chord. The stall mode is primarily caused by the interaction of shock with the Tip Leakage Vortex, resulting in the breakdown of the vortex. The development of vortex structures inside the passage leads to a delay in the flow field response to blade passing. Under low RNI condition, the tip clearance leakage flow is stronger, with a relatively reduced influence from the leading edge to the mid-chord and an increased impact from the mid-chord to the trailing edge. The main cause of the stall mode is the circumferential movement of vortex structures, causing secondary leakage over adjacent blade tip clearances. The blockage formed by vortex structures within the passage is weaker, and the flow field response to blade passing remains consistent with the blade passing frequency. However, as stall develops further, the flow field response significantly decreases. [ABSTRACT FROM AUTHOR]

Aimed at the shortcomings of traditional piston seal of hydraulic cylinder, such as contact seal and gap seal, a combination of contact seal and gap seal in the prior art was proposed to form a new type of tandem combination seal for a hydraulic cylinder. A numerical analysis model of the structure was established, and the flow field pressure distribution, seal deformation and internal leakage characteristics, as well as the influence of structural parameters on the sealing performance were obtained via numerical simulation. The results show that under the same inlet and outlet pressure, compared with the contact seal, the pressure loss in the internal structure of combination seal greater, and the pressure and impact on the seal ring are smaller, which is conducive to reducing the deformation of the seal. The gap seal at the end of the combination seal structure blocks the oil, weakens the oil impact and pressure on the middle seal ring, and thus the seal ring deformation is smaller. The multi-stage sealing structure of combination seal can better shield leakage and improve sealing performance. The leakage in the combination seal is affected by the gap seal length, seal gap and oil pressure, and increasing the gap seal length and reducing the seal gap and oil pressure can reduce the leakage. The internal leakage physical experiments further shows that the proposed combination seal can effectively reduce internal leakage and hence improve sealing performance, and can still restrain or reduce the internal leakage to a great extent and improve the sealing effect and reliability in case of damage failure of the sealing ring. [ABSTRACT FROM AUTHOR]

Mn2SiO4/CNT composite, which is constructed with polyhedron-shaped particles embedded in the carbon nanotube (CNT) network, has been synthesized by a sol-gel method. The as-prepared Mn2SiO4 presented a well-developed orthorhombic crystal structure, and after modified with CNT, the compound exhibited excellent rate capability and cyclic performance as anode materials for lithium ion batteries. Galvanostatic charge-discharge measurements demonstrated outstanding initial charge and discharge capacity of 664.8 and 392.1 mA h g−1 at the current density of 100 mA g−1, respectively, and stable reversible capacity of 466.9 mA h g−1 was retained after 40 cycles. Even at a high current density of 2000 mA g−1, Mn2SiO4/CNT can deliver the specific capacity of 205.8 mA h g−1. Also, the reaction mechanism of this material is speculated including the formation of Li2SiO3, MnO and Mn. In addition, the significant change of charge transfer resistance compared with pristine Mn2SiO4 confirmed by electrochemical impedance spectroscopy illustrated the fast Li ions intercalation kinetics and reduced electrochemical polarization via CNT modification, suggesting Mn2SiO4/CNT to be promising anode materials for high performance lithium ion batteries. [ABSTRACT FROM AUTHOR]