Force Characteristics Research Articles

Diazotrophic community in the sediments of Poyang Lake in response to water level fluctuations.

Water level fluctuations (WLFs) are typical characteristic of floodplain lakes and dominant forces regulating the structure and function of lacustrine ecosystems. The sediment diazotrophs play important roles in contributing bioavailable nitrogen to the aquatic environment. However, the relationship between the diazotrophic community and WLFs in floodplain lakes is unknown. In this paper, we carried out a comprehensive investigation on the alpha diversity, abundance, composition and co-occurrence network of the sediment diazotrophs during different water level phases in Poyang Lake. There were no regular variation patterns in the alpha diversity and abundance of the sediment diazotrophs with the water level phase transitions. The relative abundance of some diazotrophic phyla (including Alphaproteobacteria, Deltaproteobacteri, Euryarchaeota, and Firmicutes) and genera (including Geobacter, Deferrisoma, Desulfuromonas, Rivicola, Paraburkholderia, Methylophilus, Methanothrix, Methanobacterium, and Clostridium) was found to change with the water level phase transitions. The results of ANOSIM, PerMANOVA, and DCA at the OTU level showed that the diazotrophic community structure in the low water level phase was significantly different from that in the two high water level phases, while there was no significant difference between the two high water level phases. These results indicated that the diazotrophic community was affected by the declining water level in terms of the composition, while the rising water level contributed to the recoveries of the diazotrophic community. The diazotrophs co-occurrence network was disrupted by the declining water level, but it was strengthened by the rising water level. Moreover, redundancy analysis showed that the variation of the diazotrophic community composition was mostly related to sediment total nitrogen (TN) and total phosphorous (TP). Interestingly, the levels of sediment TN and TP were also found to vary with the water level phase transitions. Therefore, it might be speculated that the WLFs may influence the sediment TN and TP, and in turn influence the diazotrophic community composition. These data can contribute to broadening our understanding of the ecological impacts of WLFs and the nitrogen fixation process in floodplain lakes.

Large eddy simulation of end effects on a cylinder rotor

Due to the limited length of cylinders, their use in practical engineering inevitably involves end effects, which results in three-dimensional flows at the ends of cylinders. These flow fields are the main factor influencing the aerodynamic and flow field characteristics of cylinders. Regarding a finite-length cylinder rotor, a specific pattern of tip vortices will form under the action of rotation, resulting in notable differences in the aerodynamic characteristics between an ideal two-dimensional cylinder and a finite-length cylindrical rotor. In the present study, the large eddy simulation method is used to systematically investigate cylinder rotors with various aspect ratios. By analyzing the sectional aerodynamic and flow field characteristics, the variation laws of the aerodynamic force, wind pressure, and flow field characteristics of cylinder rotors under the influence of end effects were summarized. The results show that the influence range and intensity of the tip vortices on the rotor flow field and sectional aerodynamic characteristics are dominated by the dimensionless rotating speed, which in turn affects the range of the end effects. The development trend of the tip vortices is analyzed and discussed from multiple aspects, including sectional aerodynamics, the pressure coefficient, and the flow correlation, and an attempt is made to explain changes in the phenomenon.

Research status and prospect of flexible optimization design methodology of propeller CNC polishing machines.

Among the components of high-tech ships, the structural complexity of the propeller profile requires a high degree of flexibility in the CNC polishing machine. In addressing this requirement, the study formulates the flexible optimization problem pertaining to research on the propeller CNC polishing machine. A comprehensive analysis is undertaken to scrutinize the geometric features of the propeller and the phenomenon of polished contact. The propeller profile-polishing head dynamic contact mechanism is revealed, and the contact force characteristics of propeller polishing are obtained. It is suggested that the propeller configuration-process-polishing machine structure coupling mechanism be explored under the influence of polishing contact force. Subsequently, a dynamic model of the propeller CNC polishing process is formulated. Based on the above model, a simulation of the motion personification and structural flexibility of the propeller CNC polishing machine is proposed to obtain dynamic personification and flexibility rules. Integrating polishing contact force characteristics with dynamic personification and flexibility rules, the dynamic flexible collaborative optimization principle of the propeller CNC polishing machine is revealed. On this basis, multi-objective optimization modeling and solving are carried out, forming a new method for the flexible optimization design of propeller CNC polishing machines.

Experimental and numerical study on buffeting force characteristics of the π -shaped bridge deck

In this study, a π-shaped main beam with typical geometric characteristic parameters was selected for conducting wind tunnel tests, and the characteristics of the buffeting force were measured. Based on the measured results, numerical expansion research was conducted using the narrowband synthetic random flow generation (NSRFG) turbulent inlet method, and a grid strategy was provided. By changing the geometric characteristic parameters of the π-shaped girder, a comparative study was conducted using proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) methods, revealing the influence of cross-sectional geometric characteristic parameters on the buffeting force characteristics and analyzing their mechanism of action. The results indicate that the inlet wind parameters of the NSRFG need to be adapted to the grid size. The grid filter size at the front end of the model should be smaller than 0.193 of the along-wind turbulence integral scale, which can then be used to solve for 80% of the turbulent kinetic energy. The smaller the aspect ratio is, the larger the buffeting force spectrum is, and the smaller the opening ratio is, the smaller the buffeting force spectrum is. The opening ratio strongly influences the buffeting lift spectrum, and the aspect ratio strongly influences the buffeting drag spectrum. The POD decomposition indicates that the geometric characteristic parameters affect the shape, strength, position, and direction of vortices at the section opening. DMD decomposition indicates that geometric feature parameters affect the frequency and growth rate of dominant modes as well as the directionality and regularity of vortex distribution.

Analysis of electromagnetic vibration of submerged tubular linear motors based on wave propagation approach

This paper presents the properties of electromagnetic vibration in a submerged tubular linear induction motor through an analytical model. Firstly, the spatial and temporal characteristics of electromagnetic force acting in the stator are analyzed. Subsequently, based on the wave propagation approach, an analytical model is established to calculate the vibration response of the stator, which is simplified as a finite-length cylindrical shell. The accuracy of the proposed model is verified by comparing natural frequencies of axial breathing modes and frequency response with the finite element method. Finally, the effects of the position of electromagnetic force, the spatial distribution of electromagnetic force, radial static pressure and structure parameters on vibration response are investigated and discussed. Some conclusions are outlined, which is of great importance to reduce electromagnetic vibrations by optimizing the structure design of the motor.

Design of Household Cognitive Level Assessment System Based on Grip Force and Finger Force Distribution.

In this paper we designed a household cognitive level assessment system based on finger force distribution. The system evaluates the user's current cognitive level according to the degree of matching between the characteristics of user's grip force and finger force distribution data and the characteristics in the database. The system based on finger force distribution will greatly reduce the space and economic cost of household cognitive level assessment.

Research on fatigue damage correction coefficient of main truss members of railway suspension bridges

Steel truss girder suspension bridges are gradually applied to long-span railway bridges. The fatigue damage correction factor is an important parameter for fatigue calculation, however the research on the coefficient is limited to small-span bridges. This paper analyzes force characteristics of main truss members, calculates the fatigue damage correction coefficient of truss members, and studies the influences of train loading length, annual traffic level of fatigue damage correction coefficient. The main conclusions are as follows: (1) The influence line and fatigue stress characteristics of the main truss members were studied; the stress range of members under tension or mainly under tension is analyzed, and the stress ranges and ratios between dead and live loads in main truss members are investigated. The results show that the maximum stress range of the bottom chord is 182 MPa, the ratios of dead to live loads of about 90 % of bottom chords and diagonal web members exceed the current specifications, and stress ratios of about 10 % of bottom chords and diagonal web members exceed the current specifications. (2) The fatigue damage correction coefficients of main truss members under different train loading lengths and annual traffic levels are calculated and recommended. The research results provide a basis for updating and supplementing the railway steel bridge code.

Research on the energy transfer and efficiency performance of an electro-hydrostatic actuator for wheel-legged robot joint

Intelligence and electrification stimulate the development of wheel-legged robots (WLRs), providing excellent environmental adaptability and mobility. This paper investigates a novel electro-hydrostatic actuator (EHA) with a four-quadrant working principle, two models of electro-hydraulic drive and energy recovery integrated into WLR joints. The range and stability of WLRs will be dramatically improved by utilizing highly efficient EHAs with a high force-to-weight ratio. Mathematical models depending on the force and velocity characteristics are developed and analyzed to explore the energy conversion mechanism. Furthermore, experiments and parameter identification are performed to verify the feasibility and obtain unknown parameters, including torque, leakage, and damping coefficients. The analysis results indicate that the presented EHA is highly efficient, achieving a drive efficiency of up to 87 % and an energy recovery efficiency of up to 88 %. The primary concentration of loss is pressure reduction within the hydraulic circuit. Practical solutions to promote the work and the average efficiency are given in the last. The research will provide theoretical guidance, aiding further structural optimization and control strategies.

Experimental and Numerical Modeling of the Freeze–thaw Response of U-Shaped Channel Lining on Sulfate Saline Soil Foundation

Under the influence of seasonal freeze-thaw cycles, the concrete lining of channels situated on saline soil foundations is highly vulnerable to an array of deleterious phenomena, such as frost heave, salt expansion, and corrosion. To investigate the synergistic interplay among saline soil substrates, U-shaped channel lining structures, and ambient temperatures during freeze-thaw cycles, a novel Hydraulic-Thermal-Salt-Mechanical (HTSM) model is established in this study. The HTSM model elucidates the migration of moisture and salt solute, ice-water phase transitions, and sodium sulfate crystallization within unsaturated saline soils throughout the freeze-thaw cycles. It considers the variations in volume and pore solution volume before and after the phase transition of sodium sulfate. Temperature and salt frost heaving force measurements obtained from outdoor freeze-thaw cycles are compared with numerical simulation results to validate the efficacy of the HTSM model and investigate the distribution patterns of salt frost heaving force (frost swelling force) along the channel. The results showed that the frost swelling force and depth exhibit a great linear relationship and the maximum stress of the U-shaped channel appears at the bottom of the channel, highlighting the good arching force characteristics of the U-shaped structure which prove that bottom of the channel is also the most prone to fracture. Significantly, the initial water content significantly impacts the frost swelling force—it increases by 4% while the frost swelling force increases by 76%. Comparing the numerical simulation results of temperature variations, moisture changes, and salt-frost heaving forces with the outdoor experimental data, it is evident that the proposed HTSM model effectively simulates the salt-frost heaving patterns observed in U-shaped channel linings.

Forced resonance of a buckled beam flexibly restrained at the inner point

Restraints along slender structures, such as pipes conveying fluid and beams, play important roles in enhancing their bending stiffness. The current work investigates the influence of the midpoint restraint on the buckled axial force and dynamic characteristics for the first time. A continuous model is introduced by treating the midpoint restraint force as a concentrated force using Dirac function. The influence of the midpoint restraint is discussed based on modal expansion, and a partitioned model is proposed for validation. The conclusion is that the continuous model has good accuracy. Based on this model, it finds out two stable buckled states changing with the midpoint stiffness. The first stable buckled state occurs under weak midpoint restraint and has a cambered shape. The zero- and double frequency components occur in symmetric modal shapes and the response is softened along the whole beam. However, in the second stable buckled state, it turns into a whole sine function shape. The zero- and double frequency components just occur in the second modal shape, and the soften phenomenon doesn’t occur at the midpoint. With increasing excitation amplitude, a bubble appears on the primary resonance peak while another resonance peak emerges nearby it. This work explains the influence of midpoint stiffness on nonlinear resonance and enhances the study of the nonlinear behavior of buckled slender structures.

Inertial and kinematic demands of isolated pile-supported wharves in liquefiable soils: Centrifuge tests

Pile-supported wharves in liquefiable soils are prone to severe damage during earthquakes. This study employs seismic isolation techniques to adapt for wharf construction, evaluating their seismic performance under lateral ground deformation due to liquefaction. Experimental and numerical analyses are necessary for confirming the efficiency of the isolation in decreasing the requirements for pile-supported wharves. The study initially tests two pile-supported wharves under geotechnical centrifuge conditions, one reinforced by isolation bearings and the other without. The objective is to simulate the force characteristics of isolated pile-supported wharves in liquefiable soils and to analyze the impact of isolation on reducing the seismic response of these wharves. Subsequent analysis delves into the interaction between inertia and kinematics for two types of pile-supported wharves, providing crucial insights. The development of plastic hinges for two kinds of pile-supported wharves under inertia and kinematics is also analyzed. Quantifiable thresholds are established to study the influence of isolation on the resistance of wharves to seismic disruptions, thus preventing pile-supported wharves damage.

Calculation of force parameters of workpiece machining process with end mill cutters

The aim is to develop and validate an operational methodology for calculating the force parameters and characteristics of the tool and the process of milling structural materials with end milling cutters. The structural schemes of machining and force models of oblique cutting processes in the modes of axial tool feed and continuous plastic deformation of the processed material were used when developing the method of preliminary calculation of the total axial force working on the cutting edge of end milling cutters. The rotating tool tests were conducted on a Hermle UWF 1202 H 3-axis machining center supplemented with a Kistler piezoelectric dynamometer (model 9272). Authors suggested, developed and tested the preliminary calculation method applied to the force characteristics of the machining process of workpieces by end milling cutters, considering how the energy power of ductile fracture of the machined material affects the process. Contact friction arising on the front and rear surfaces of the cutting tool does not reach the limiting value being subject to the Coulomb – Amonton law, that is, it is estimated by the dependence directly proportional to the normal pressure. After calculations, we defined the materials of the workpiece for milling, that is 45 steel (AISI 1045), and the end two-tooth cutter, uncoated T14K8 alloy, which was used to produce samples. The following milling modes were established: 4 mm boring depth; 50, 100 and 150 m/min cutting speeds; 0.05 and 0.1 mm/rev cutting tool feed. Deviation of the measured values of axial cutting force from the calculated values in the range of changing values of tool feed rate was found to be no more than 11%, and in the range of changing values of cutting speed no more than 15%. The developed calculation and analytical methodology for estimating force parameters of the machining process by end milling cutters provides an increase in the efficiency and reliability of the preliminary prognostic calculation of operating parameters and characteristics of cutting elements of end milling cutters.

Innovative multi-dimensional learning algorithm and experiment design for human-robot cooperation

This paper proposed a learning algorithm for human-robot skill transfer based on dynamic movement primitive. Through the establishment of Transmission Control Protocol communication, the position trajectory and force characteristic of the human demonstrator while demonstrating the robot were recorded as the training data of the dynamic movement primitive model. The demonstrated skill/motion reproduction and generalization were successfully achieved through adjusting the parameters of the dynamic movement primitive model. The impedance control system investigated in this paper improved the compliance of the robot trajectory reproduction and skill generalization, and improved the robustness of robot control system in different environments. In addition, for the problem of inverse solution of redundant robots, this paper improved the dimension of constraint equations in the inverse solution of robots by training multiple dynamic movement primitive models, which guaranteed the constraints of inverse solutions of redundant robots. The proposed algorithm had been validated on a simulated robot platform using MATLAB and a ROKAE xMate robot platform, respectively.

Explicit hybrid MPC for the lateral stabilization of electric vehicle system

This paper presents a hybrid Model Predictive Control (hMPC) approach to improve Electric Vehicle (EV) stability when cornering or in high-risk driving conditions. By using approximations of tire force characteristics, the EV system proposed in this study is considered as a Piecewise Affine (PWA) system which is a class of Hybrid Dynamical Systems (HDSs). First, a hybrid modeling of the studied system is developed within the PWA framework. Then, the synthesis of an explicit hybrid MPC law, based on the integration of the Active Front-wheel Steering control method (AFS) and Direct Yaw moment Control method (DYC), can be established. The purpose of the PWA-MPC is to force the yaw rate and sideslip angle of the EV system to follow the given references to guarantee lateral stability. The calculation of the control laws of this proposed approach is performed offline using multiparametric programming. Finally, this paper investigates the effectiveness of the designed controller by performing a set of simulations to analyze the efficiency and robustness of the proposed approach. A comparative study is addressed in this work to demonstrate the efficiency of the proposed hybrid MPC controller compared to the conventional MPC approach which considers the linear model of the system. Another simulations are carried out to assess the robustness of the proposed control, important disturbances and uncertainties were incorporated such as the change of the additional mass, the change of terrain and the high velocity. The simulation results show that the PWA EV system model with the designed controller is able to ensure lateral stability by keeping the sideslip angle and yaw rate tracking the ideal values.

Optimal lane-changing and collision avoidance strategy for intelligent vehicles in high-speed driving environments

This paper proposes an optimal lane-changing and control strategy to solve the collision avoidance of intelligent vehicles in highway driving. A quintic polynomial lane-changing trajectory model is established in the Frenet frame, and the trajectory planning problem is transformed into the optimisation problem of lane-changing target coordinates. To consider the multiple environmental factors on vehicle lane-changing, the feasible region of the lane-changing target point was generated based on the lateral acceleration limitation and the safe distance constraints. The performance evaluation indexes were established, considering efficiency, comfort, lateral slip, and lane offset. The multi-objective optimisation problem is solved in the feasible region, and the optimisation results were applied to the collision detection process. In addition, considering the nonlinear characteristics of tire force caused by sudden lateral movements of vehicles at high-speed, a vehicle dynamics model based on the Magic Formula is established, and Model Predictive Control is applied to track the expected trajectory. Simulation results show that this strategy can plan suitable lane-changing trajectories in high-speed working conditions and achieve vehicle collision avoidance.

Dynamic characteristics analysis and valve core optimization for second stage hydrogen pressure reducer of hydrogen decompression valve

As an important component of pressure management system, hydrogen decompression valve (HDV) is used in hydrogen fuel cell vehicles, hydrogen refueling stations, etc. The high-pressure difference causes severe pressure fluctuation. Thus, the HDV is composed of multi-stage pressure reducers. Specially, the outlet pressure from the HDV highly affects the pressure of fuel cell. The service life and operation condition of fuel cell is affected significantly by the HDV. This paper conducted the research of the second stage hydrogen pressure reducer (SHPR) of on-boarding hydrogen decompression valve. The force and dynamic characteristics of the valve core are obtained and the flow characteristic is analyzed through the steady and transient flow model. The results are shown that the fluid force and combined force on the valve core exhibit linear increase with inlet pressure and throttling area. The flow characteristics in the throttling gap exhibit similar distribution law under different throttling lengths and inlet pressures. The pressure-drop at entrance and exit of the throttling gap is drastic. Besides, the spring stiffness has a significant impact on the dynamic characteristics of the valve core. With the increase of spring stiffness, the dynamic characteristics change from unstable-state to stable-state under the sudden increase of inlet pressure. The larger spring stiffness initially causes displacement fluctuation of the valve core and then the valve core maintains a stable opening under the stable state. Finally, the optimized structure of valve core is proposed and the better stability of SHPR has been achieved. Meanwhile, there is no significant difference in flow performance but the dynamic characteristics are improved.

Foot force characteristics when using foot-controlled isometric device and operating method based on them

Foot force characteristics when using foot-controlled isometric device and operating method based on them

The Logic and Pathway of Green Finance in Advancing the Development of New Quality Productivity

Against the dual backdrop of economic globalization and ecological environmental crisis, green finance has become a key force in driving the development of new quality productive forces. This paper first defines the concept, constituent elements, and characteristics of new quality productive forces, and then explores the promotional role of green finance in their development through theoretical analysis. The research finds that green finance can effectively promote the development of new quality productive forces by mechanisms such as providing financial support, guiding technological innovation, and optimizing industrial structure. The paper specifically outlines the pathways through which green finance can drive the development of new quality productive forces and proposes strategic recommendations on how to enhance the functions of green finance and stimulate the vitality of new quality productive forces. The study emphasizes that constructing an effective green finance system can promote the development of new quality productive forces and achieve sustainable development.

Study of postoperative laryngopharyngeal discomfort: protocol for a single-centre cohort study

IntroductionPostoperative laryngopharyngeal discomfort after extubation can lead to severe throat pain, dysphagia, or postoperative tongue oedema. Possible mechanisms include increased oral pressure, obstruction of venous and lymphatic return in the...

Vibro-Inertance Matrix Supported OCF Characteristics Analysis of PMSM Under Multiple Operating Conditions for EV

Vibration analysis of converter-fed motor for electric powertrain is a much-needed technology for electric vehicle industry, which plays an important role in the noise, vibration, harshness (NVH) optimization design, fatigue monitor, fault diagnosis, and life prediction. The characteristics of the internal operating condition force (OCF) for the propulsion motor of electric vehicles under multiple operating conditions (MOC) were investigated by using the proposed vibro-inertance matrix theory (VIMT) in this paper. The complete analytical expansion of vibro-inertance matrix ofthe statorcomponentwas firstly derived, and a mathematical analytical testing model of OCF was established. The OCF of the 21kW prototype was measured under MOC, and the spectra of the mechanical and electromagnetic OCF of the prototype were fully secured via Brüel & Kjær 4520 3D acceleration sensors and Brüel & Kjær multi-purpose input modules. The vibration and fatigue sources under MOC were revealed through the source path contribution (SPC) analysis method. Finally, the proposed VIMT measurement and analysis method of OCF were verified by both finite element simulation and experimental verification.