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Pultrusion is a highly efficient continuous process to manufacture advanced fiber-reinforced composites. The injection pultrusion variant permits a higher control of the resin flow, enabling the manufacturing of a high reinforcement volume fraction. Moreover, it reduces the emission of volatile compounds that are dangerous for the operators and for the working environment. The present study proposes an experimental analysis of injection pultrusion in three different operative conditions. In particular, the activity focused on the effects of the temperature setup on the thermochemical and rheological behaviors of the resin system and on the interaction between the processed materials and the pultrusion die wall. The setup of the parameters was selected to evidence the behavior of the viscous interaction during the thermoset transition to the solid state, which is particularly challenging due to the localization of high adhesive forces related to the sharp increase in resin viscosity. Microscope observations of the cross-sections were performed to discuss the effects of the process parameters. [ABSTRACT FROM AUTHOR]

A theoretical foundation for implementing surface self-cleaning can be provided by analyzing the motion of adhering droplets in airflow. When driving in rainy circumstances, self-cleaning windshield technology can efficiently guarantee driver safety. In this study, the CLSVOF method is employed to simulate a three-dimensional wind tunnel model, enabling an investigation into the dynamics of droplets adhering to a windshield under the influence of airflow. Subsequent analysis mainly focuses on the impacts of wind velocity and droplet size on the motion patterns and morphological characteristics of the droplets. The temporal evolution of the forces acting on the droplets is examined, along with a comparative analysis of the predominant forces driving droplet motion against other forms of resistance. The results demonstrate that the motion patterns of the droplets can be broadly categorized into three phases: accelerated decline, forces equilibrium, and accelerated climb. As wind speed increases, there is a noticeable reduction in the wetting length Ld, while the height of the droplets H and the dominant force influencing their motion shift from gravitational component Fgsinα to wind traction force Fwind. Moreover, an increase in droplet size accentuates the lag in changes to wetting length, droplet height, and the contact angle. [ABSTRACT FROM AUTHOR]

The 6-DOF Stewart parallel elevation platform serves as the platform for mounting the tea-picking robotic arm, significantly impacting the operational scope, velocity, and harvesting precision of the robotic arm. Utilizing the Stewart setup, a parallel elevation platform with automated lifting and leveling capabilities was devised, ensuring precise halts at designated elevations for seamless harvesting operations. The effectiveness of the platform parameter configuration and the reasonableness of the posture changes were verified. Firstly, the planting mode and growth characteristics of Yunnan large-leaf tea trees were analyzed to determine the preset path, posture changes, and mechanism stroke of the Stewart parallel lifting platform, thereby determining the basic design specifications of the platform. Secondly, a 3D model was established using SolidWorks, a robust adaptive PD control model was built using MATLAB for simulation, and dynamic calculations were carried out through data interaction in Simulink and ADAMS. Finally, the rationality of the lifting platform design requirements was determined based on simulation data, a 6-DOF Stewart parallel lifting platform was manufactured, and a motion control system was built for experimental verification according to the design specifications and simulation data. The results showed that the maximum deviation angle around the X, Y, and Z axes was 10°, the maximum lifting distance was 15 cm, the maximum load capacity was 60 kg, the platform response error was within ±0.1 mm, and the stable motion characteristics reached below the millimeter level, which can meet the requirements of automated operation of the auxiliary picking robotic arm. [ABSTRACT FROM AUTHOR]

This article proposes a new method for optimizing tooth profile modification amounts of cycloidal reducers. By optimizing transmission error and transmission ratio fluctuation, the objective optimization function is determined, and the influence of optimized modification amount on various transmission performances is studied. In addition, this article also conducted mechanical analysis on the cycloidal reducer and obtained the results of tooth contact force. The mathematical model for the mechanical analysis of the cycloidal reducer was established, and the variation law of force distribution between the internal and external gears of the cycloidal reducer was calculated. The results indicate that the needle tooth force, bearing force, transmission ratio, and transmission error obtained through the mechanical analysis model using optimized modification quantities tend to stabilize and exhibit periodic changes, which corresponds to the actual scenario. [ABSTRACT FROM AUTHOR]

Immersion cooling is widely used for thermal management of servers. The two-phase immersion cooling, which transfers heat by boiling, possesses efficient temperature control ability under intensive heat generation. In the process of temperature control through boiling, the generation and transportation of bubbles play a crucial role in calculating the heat-transfer capacity. Therefore, it holds immense significance to obtain a profound understanding of the mechanisms underlying bubble formation and detachment. Currently, numerous mechanistic explanations and empirical correlations have been proposed to elucidate the various parameters of bubbles during the boiling process. These findings were considered to be valuable references when selecting appropriate boiling media and designing efficient heating surfaces. To comprehensively present the progress of bubble formation and heat transfer in the boiling system, the forces exerted on the bubbles are highlighted in this article. A meticulous review of bubble-force analysis and correlation formulae pertaining to various relevant parameters (e.g., nucleation sites density, bubble growth rate, bubble growth period, and detachment frequency) was conducted. This review article was also expected to provide a novel foundation for further exploration of enhanced boiling heat transfer. [ABSTRACT FROM AUTHOR]

Urban overpasses, being long-span linear projects, are inevitably affected by ground fissure activities. This study focused on the three-span continuous overpass, and used the MIDAS GTS NX finite element simulation software to establish the model of an urban overpass crossing active ground fissures with different straddling ground fissure positions and hanging wall settlements. This study analyzed the deformation and stress characteristics of soil and bridges induced by ground fissures under different working conditions. The results demonstrate that the soil's displacement response is mainly concentrated near the ground fissures, and the displacement changes decrease with increasing ground fissures. Ground fissure activities redistribute the stress inside the beam and pier, resulting in the tilting of the pier. When the fissure activity is small, the use of multi-span beams to straddle the ground fissures can effectively reduce the influence of ground fissure activities on bridge deformation. However, when the fissure activity is significant, the bridge may be damaged, and excessive deformation of the bridge and piers may not meet code requirements. In such cases, the multi-span beam structure type should be changed to adapt to the ground fissure activity. The research results provide significant reference value for urban traffic planning and overpass design. [ABSTRACT FROM AUTHOR]

In submarine oil and gas pipelines, the movement of a differential pressure multisection pipeline robot mainly relies on the front and rear driving pressure difference of the fluid and the friction between the cup and the pipe wall. The passability of the pipeline is a key point to guarantee success in scanning and detecting the inner wall of a pipeline by robot. When the multisection pipeline robot moves, the force of the internode connection points changes the degree of freedom of the robot. The existence of the connection points causes speed fluctuations in the robot during the movement process which, in turn, affects the detection accuracy of the pipeline. Consequently, a systematic analysis of the connection point movement is of great importance. In this paper, a rigid–flexible, coupled, multibody, dynamic motion system is established, where a multisection micro pipeline robot is built. The cup of the robot is set as a flexible body. The motion law of the differential pressure multisection pipeline robot is analyzed through simulation, and the robot's motion speed and internode stress of the different cabin sections are explored jointly in practice. Taking the transportation of an oil and gas pipeline into full consideration, the motion law and force of the multisection pipeline robot are analyzed by changing the bulge and turning the radius of the inner wall of the pipeline. A corresponding experimental bench is built to explore the effects of different numbers of cups and lengths of the cabin sections on the turning characteristics of the robot. Simulations and experiments results are highly similar and within the error range. To this end, the presented work provides significant information for the model selection of multisection micro pipeline robots in the fields of submarine oil and gas pipelines. [ABSTRACT FROM AUTHOR]

The cave dwelling is one of the most typical traditional dwellings and green building forms in the Loess Plateau of Northern Shaanxi. The construction of the cave dwelling was built only based on the experience passed down by predecessors, without the guidance of formal design theories and calculation methods, and the overall safety of the cave-dwelling structure needs to be solved urgently. To make the mechanical analysis model closer to the actual force of the masonry cave dwelling, it is proposed to simplify the arch ring in the masonry cave-dwelling structure into an unhinged arch mechanical calculation model. Applying the theory of elastic center to the force method calculation in structural mechanics, the force of the cave-dwelling structure is analyzed and compared with the force results of the three-hinged arch calculation model, so as to determine the correctness and reliability of the calculation diagram of the unhinged arch. The conclusions indicate it is correct and reliable to use the unhinged arch calculation model, which is closer to the actual force situation, to calculate the forces of the arch rings in masonry cave dwellings, and both the three-hinged arch and unhinged arch models are feasible to be applied to the mechanical analysis of the arch rings. The unhinged arch calculation model is more reliable and safer in the design and calculation of the cave-dwelling leg components compared with the three-hinged arch calculation model because it considers the bending moment at the arch foot support. The research results can be used to improve the structural design data of the cave dwelling and provide theoretical guidance for the construction, repair, and protection of the cave dwelling. [ABSTRACT FROM AUTHOR]

With the synergistic effect of laser and arc heat sources, laser-arc hybrid welding (LAHW) technology can improve welding speed and penetration depth, and enhance gap-bridging ability. This review describes the fundamental concepts and characteristics of droplet transfer behavior in LAHW. Emphasis was placed on the physical interaction between the laser and arc and the effect of the combined laser/arc heat sources on the welding process. However, the physical understanding of these multivariable and complex interactions is still evolving. Through numerous research findings and summary, it is found that there are several critical factors, including the laser-to-arc distance, heat source leading mode, shielding gas composition, and laser power, affecting the droplet transfer characteristics. This review critically interprets the latest development in the basic understanding of LAHW. It lays great stress on the coupling effect of laser and arc in droplet transfer dynamic process of LAHW, and offers a direction for the future study and progress of LAHW. Significant fields for future research are also confirmed. [ABSTRACT FROM AUTHOR]

The collection of Camellia oleifera flowers is a key foundation of Camellia oleifera flower pollen extraction. Due to the current problems of low efficiency, high labor intensity and the high cost of manual collection of Camellia oleifera flowers, a harvesting actuator was designed. By analyzing the inherent characteristics of the Camellia oleifera flower and the harvesting method, a harvesting structure using a combination of friction roller twisting harvesting and pipeline pneumatic conveying was designed. The geometric model of the Camellia oleifera flower was established and the motion analysis of the flower was carried out, which indicated that the Camellia oleifera flower would tend to a stable state for easy picking after entering the actuator. Using Automatic Dynamic Analysis of Mechanical Systems 2015 software (ADAMS, MSC. Software Corporation, Santa Ana, CA, USA) to simulate the process of Camellia oleifera flower picking, a mechanical analysis was performed in the contact plane to prove the theoretical feasibility of friction roller picking these flowers, and the main influencing factor was obtained as the speed of the friction roller. The test prototype for Camellia oleifera flower picking was built, and the picking experiment was implemented to study the effect of motor speed on the picking time of single Camellia oleifera flowers and the effect of the success rate of the flower picking. The test results show that when the motor speed is 400 r/min, the picking success rate is 96%, the picking time of a single flower is 1.2 s, and the speed of the machine collection of Camellia oleifera flowers is 2.3 times that of manual collection, which proves the realistic feasibility of this picking actuator. This paper provides an important reference and basis for the research and development of a flower harvesting actuator. [ABSTRACT FROM AUTHOR]

Bubble lift-off diameter is characterized as the size of a bubble rising from a wall, which is vital in the boundary condition of heat transfer model and interfacial area transport equation. In this paper, mechanistic force analysis was conducted to explore a predictive model for bubble lift-off diameter in a vertical channel of subcooled boiling flow. Specifically, the component of growth force normal to the wall and the shear lift force lead to the lift-off of a bubble on the vertical surface. Through force analysis, we found that bubble lift-off diameter is arranged to be related to wall superheat, latent heat, liquid velocity, fluid properties, bulk liquid subcooling, etc. To account for the contribution of the influencing factors, the dimensionless bubble lift-off diameter was correlated with dimensionless parameters, including the Prandtl number, the Reynolds number, the Jacob number, and dimensionless subcooling. The proposed correlation was assessed according to experimental data and the predictions showed good agreement with the data. [ABSTRACT FROM AUTHOR]

Currently, energy demand is more significant than ever due to population growth and advances in recent technologies. In order to supply more energy while maintaining a healthy environment, renewable energy resources are employed. This paper proposes a novel solar-driven shape memory alloy thermomechanical actuator as an eco-friendly solution for solar thermal applications. The proposed actuator was assessed numerically and experimentally. The numerical tests showed that the designed actuation mechanism's inner temperature has a minimum variation per day of about 14 °C and a temperature variation of 19 °C for most days of the year, which allows for proper activation and deactivation of the actuator. As for the experimental tests, the presented actuation mechanism achieved a bi-directional force of over 150 N, where the inner temperatures of the actuator were recorded at about 70.5 °C while pushing forces and 28.9 °C while pulling forces. Additionally, a displacement of about 127 mm was achieved as the internal temperature of the actuator reached 70.4 °C. The work presented adds to the body of knowledge of a novel solar-based self-driven actuation mechanism that facilitates various applications for solar thermal systems. [ABSTRACT FROM AUTHOR]

Nut fasteners are produced by machines working around the clock. Companies generally operate with a run-to-failure or planned maintenance approach. Even with a planned maintenance schedule, however, undetected damage to the dies and non-die parts occurring between maintenance periods can cause considerable downtime and pervasive damage to the machine. To address this shortcoming, force data from the fourth and sixth dies of a six-die nut manufacturing machine were analysed using correlation to the best health condition on the force profile and on the force shock response spectrum profile. Fault features such as quality adjustments and damage to both die and non-die parts were detectable prior to required maintenance or machine failure. This detection was facilitated by the determination of health thresholds, whereby the force SRS profile generated a longer warning period prior to failure. The analytical approach could benefit the industry by identifying damage that would normally go undetected by operators, thereby reducing downtime, extending die life, enabling "as needed" maintenance, and optimising machine operation. [ABSTRACT FROM AUTHOR]

Featured Application: Authors are encouraged to provide a concise description of the specific application or a potential application of the work. This section is not mandatory. An accurate description of the transition corridor is of great significance for the flight process of the vertical take-off and landing (VTOL) fixed-wing unmanned aerial vehicle (UAV). To study the transition flight process of vertical take-off and landing fixed-wing UAVs, the dynamic model and transition corridor model of this type of UAV are established in the current article. The method for establishing the model is based on a reasonable match of the power and aerodynamic force of this type of UAV. From the perspective of flight dynamics, the ducted lift-increasing system's deflection angle–speed envelope is studied with the maximum lift coefficient of the wing and the system's available power. The influence of the overall parameters and energy parameters of the UAV on the deflection angle–speed envelope of the ducted lift-increasing system is analyzed, and a method is proposed to expand the vertical take-off and landing fixed-wing UAV's transition corridor. Taking the UAV as the object, using the established model, the transition flight corridor of the UAV is obtained, the influence of the control parameters on the transition flight is studied, and the appropriate transition flight control strategy is determined. At the same time, the influence of the overall parameters and energy parameters on the transition corridor is calculated. According to the calculation results, the effect of expanding the flight corridor of the UAV is more obvious when increasing the available power than when increasing the aerodynamic parameters by the same proportion. [ABSTRACT FROM AUTHOR]

To investigate the impact of polymer viscoelasticity on microscopic remaining oil production, this study used microscopic oil displacement visualisation technology, numerical simulations in PolyFlow software, and core seepage experiments to study the viscoelasticity of polymers and their elastic effects in porous media. We analysed the forces affecting the microscopic remaining oil in different directions, and the influence of polymer viscoelasticity on the displacement efficiency of microscopic remaining oil. The results demonstrated that the greater the viscosity of the polymer, the greater the deformation and the higher the elasticity proportion. In addition, during the creep recovery experiment at low speed, the polymer solution was mainly viscous, while at high speed it was mainly elastic. When the polymer viscosity reached 125 mPa·s, the core effective permeability reached 100 × 10−3 μm2, and the equivalent shear rate exceeded 1000 s−1, the polymer exhibited an elastic effect in the porous medium and the viscosity curve displayed an 'upward' phenomenon. Moreover, the difference in the normal deviatoric stress and horizontal stress acting on the microscopic remaining oil increased exponentially as the viscosity of the polymer increased. The greater the viscosity of the polymer, the greater the remaining oil deformation. During the microscopic visualisation flooding experiment, the viscosity of the polymer, the scope of the mainstream line, and the recovery factor all increased. The scope of spread in the shunt line area significantly increased, but the recovery factor was significantly lower than that in the mainstream line. The amount of remaining oil in the unaffected microscopic area also decreased. [ABSTRACT FROM AUTHOR]

To investigate the microphysics mechanism and the factors that influence arc development along a polluted surface, the arc was considered as a plasma fluid. Based on the image method and the collision ionization theory, the electric field of the arc needed to maintain movement with different degrees of pollution was calculated. According to the force of the charged particle in an arc plasma stressed under an electric field, a calculation model of arc velocity, which is dependent on the electric field of the arc head that incorporated the effects of airflow around the electrode and air resistance is presented. An experiment was carried out to measure the arc velocity, which was then compared with the calculated value. The results of the experiment indicated that the lighter the pollution is, the larger the electric field of the arc head and arc velocity is; when the pollution is heavy, the effect of thermal buoyancy that hinders arc movement increases, which greatly reduces the arc velocity. [ABSTRACT FROM AUTHOR]

Patient transfer has always been a difficult problem in the hospital. For medical staff, there are problems including high risk of infection, heavy physical labor and low efficiency of transfer; for patients, there are problems including poor comfort and secondary injury. In this paper, a novel bilateral patient transfer robot is investigated and designed. The following tasks are conducted: (1) Based on the process of patient transfer, a transfer model, which consists of two degrees of freedom, is proposed, and the working principle of bilateral patient transfer robot is obtained and analyzed in detail. (2) Force analysis of the patient transfer robot is conducted. The corresponding relationship between the patient comfort and the insertion angle is proposed, and the optimal sizes of mechanical structure are obtained. (3) Based on the theoretical analysis, the mechanical structure and the control system of the robot are designed, and the prototype is manufactured. (4) Experimental research is conducted. The results show that the prototype can complete the required motion performance with a carrying capacity up to 150 kg and patient comfort is excellent. The results of this paper prove that this kind of patient transfer robot has good performance, it can also reduce the burden on medical staff. [ABSTRACT FROM AUTHOR]

The slippage of cable clamps during the long-term operation of suspension bridges is a common and detrimental phenomenon. From an experimental point of view, the cable clamp slippage of a suspension bridge was investigated to reveal the effect of this sliding on the force acting on the full bridge. The forces acting on the bridge before and after the slippage were analyzed using a finite element model. The calculation results showed that the cable clamp slippage directly affects the cable forces of the hangers. The hanger cable force decreased by 19.2% when the slippage reached 10.2 cm, while the maximum increase in the cable force of adjacent hangers was 147.7 kN, an increase of 7.25%. The variation of forces in the hanger cable disrupted the force balance of the main girder, thereby producing a torque effect at the corresponding position in the girder, i.e., increased torque. Meanwhile, the slippage affected the axial tension in the main cable and the main girder. The impact of the tower internal force was less than 1%. Hence, the study concluded that the effect of cable clamp slippage is better understood, ensuring the safety of the suspension bridge. [ABSTRACT FROM AUTHOR]

Experiments with a cam-type clamp tool were carried out to overcome the difficulty of transporting and installing large-diameter mono-piles for offshore wind turbines. Using the experiments method to design a small wedge-type clamping mechanism and using cam teeth made of 40Cr material resulted in the maximum friction for the mechanism. A single clamping design was created for the cam-type clamp tool to hoist mono-piles for offshore wind turbines. Through force analysis and Automatic Dynamics Analysis of Mechanical System (ADAMS) dynamic simulation of the lifting tool, it was calculated that the clamping force of the lifting tool meets application requirements. A prototype was built in order to carry out an experiment in which the lifting tool hoisted a mono-pile. It was concluded from the experiment that the proposed design of the lifting tool is feasible in practical applications. [ABSTRACT FROM AUTHOR]

Since many studies on axial piston pumps aim at enhancing their high power-weight ratio, many researchers have focused on the generated mechanical losses by the three friction pairs in such pumps and attempted to diminish them through abundant and new structural designs of the pump's components. In this paper, a high-speed 2D piston pump is introduced and its architecture is specifically described. Afterward, a mathematical model is established to study the pump's mechanical efficiency, including the mechanical losses caused by the viscosity and stirring oil. Additionally, in this study the influences of the rotational speed, the different load pressures, and the rolling friction coefficient between the cone roller and the guiding rail are considered and discussed. By building a test rig, a series of experiments were carried out to prove that the mechanical efficiency was accurately predicted by this model at low load pressures. However, there was an increasing difference between the test results and the analytical outcomes at high pressures. Nevertheless, it is still reasonable to conclude that the rolling friction coefficient changes as the load pressure increases, which leads to a major decrease in the mechanical efficiency in experiments. [ABSTRACT FROM AUTHOR]

The automatic charging of electric vehicles is an important but challenging problem. Recently, various charging robots are proposed for electric vehicles. Most previous researches do not pay enough attention to the robots' load capacities. Actually, providing the charging connector with adequate pushing and/or pulling forces is vital to guarantee a reliable electrical connection, which is a key issue for charging robot design. In this paper, we present a novel serial-parallel robot for the automatic charging of electric vehicles. This robot is based on the 3 universal-prismatic-universal (3UPU) parallel mechanism and featured by high-load capacity. We firstly address the kinematic and static models of the proposed robot, then analyze its load capacity. It is shown that the robot's maximum load capacity depends not only on the driving ability of the prismatic joints, but also on the robot's structural parameters and the robot's configuration. Finally, optimizations are made and results show that the robot's load capacity along the desired trajectory has more than doubled. Results of this paper could be useful for the development of automatic electric-vehicle-charging devices. [ABSTRACT FROM AUTHOR]

In melt blowing, microfibrous nonwoven material is manufactured by using high-speed air to attenuate polymer melt. The melt-blown air jet determines the process of polymer attenuation and fiber formation. In this work, the importance of lateral velocity on the fiber was first theoretical verified. The lateral diffused characteristic of the air flow field in slot-die melt blowing was researched by measuring the velocity direction using a dual-wire probe hot-wire anemometer. Meanwhile, the fiber path was captured by high-speed photography. Results showed that there existed a critical boundary of the lateral diffusion, however, air jets in the x–z plane are a completely diffused field. This work indicates that the lateral velocity in the y–z plane is one of the crucial factors for initiating fiber whipping and fiber distribution. [ABSTRACT FROM AUTHOR]

As there are significant variations of cell elasticity among individual cells, measuring the elasticity of batch cells is required for obtaining statistical results of cell elasticity. At present, the micropipette aspiration (MA) technique is the most widely used cell elasticity measurement method. Due to a lack of effective cell storage and delivery methods, the existing manual and robotic MA methods are only capable of measuring a single cell at a time, making the MA of batch cells low efficiency. To address this problem, we developed a robotic MA system capable of storing multiple cells with a feeder micropipette (FM), picking up cells one-by-one to measure their elasticity with a measurement micropipette (MM). This system involved the following key techniques: Maximum permissible tilt angle of MM and FM determination, automated cell adhesion detection and cell adhesion break, and automated cell aspiration. The experimental results demonstrated that our system was able to continuously measure more than 20 cells with a manipulation speed quadrupled in comparison to existing methods. With the batch cell measurement ability, cell elasticity of pig ovum cultured in different environmental conditions was measured to find optimized culturing protocols for oocyte maturation. [ABSTRACT FROM AUTHOR]

Experimental and numerical investigations of force analysis acted on single circular cylinder in the T pipe junction with the effect of vanes are reported in this paper. Experiments are carried on in a small wind tunnel at five different velocity ratios (R) from 0.117 to 0.614. The mean pressure data acted on the cylinder are obtained and in turn the drag and lift. Vanes are installed at the junction to change the secondary flow in the suction duct and the angle is in the range of 90° ≤ φ ≤ 130°. Numerical studies which are validated by the experimental data help understand the flow structure for the analysis. It is found that in the T shape junction without vanes, the cylinder presents different surface mean pressure distributions at the different positions in the suction duct. As the increase of the distance from the junction to the cylinder center, the surface mean pressure distributions recover to the benchmark gradually which performs in the straight duct beforehand. Four feature points including the front/rear stagnation points and the separation points and the corresponding three divisions of flow region are analyzed in detail with the auxiliary numerical simulation of flow structure. Effect of the vanes with different angle is also discussed. Finally, the drag and lift coefficients acted on the cylinder with or without vanes are performed. [ABSTRACT FROM AUTHOR]