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The authors have investigated the potential of a plant-based natural surfactant in the modification of various bubble parameters. Bubble dynamics at the orifice were studied in natural surfactant solutions extracted from the plant Sapindus mukorossi at concentrations below and above its critical micellar concentration (CMC). The results were compared to the ones obtained with Sodium Dodecyl Sulfate solutions. The CMC values of Sapindus mukorossi and Sodium Dodecyl Sulfate are 7.5 × 10−3 g/cc and 2.39 × 10−3 g/cc, respectively. A photographic method was employed to observe bubble formation at the orifice. The results show that biosurfactants, like chemical surfactants, have a comparable effect on bubble density, size, and rise velocity. Experimentally determined bubble radius, volume, and radial velocity were used to calculate various forces contributing to the bubble dynamics. The buoyancy, pressure, and surface tension forces were significantly stronger in magnitude in comparison to the gas momentum, viscous drag, and added mass forces. Our findings suggest that the significance of various dynamic forces involved in bubble growth dynamics varies according to the bubble generation frequency regimes. We report for the first time the potential of Sapindus mukorossi in altering bubble properties and surface forces at the orifice and its usage in various bubble-related industrial applications. [ABSTRACT FROM AUTHOR]

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An analytical method is presented for force analysis of plain lever mechanisms with one degree of freedom, based on the vector method. Using the example of a two-drive structural group, a method is outlined for finding reaction vectors in all its kinematic pairs, while maintaining the clarity and consistency of the solution inherent in the graphic-analytical method of diagrams of component forces. An original analytical description is given for finding the vectors of tangential and normal components of reactions in kinematic pairs. Application of the proposed method of force analysis makes it possisble to find reaction vectors in kinematic pairs without compiling and solving complex systems of equilibrium equations or graphical construction. Adaptation of the proposed force analysis in modern mathematical packages allows for the study of plain lever mechanisms with one degree of freedom in a short time and with high accuracy.

The friction loss caused by the oil-free operation of miniature oil-free rolling piston compressor can not be ignored. Therefore, it is important to know how to reduce the friction loss of miniature oil-free rolling piston compressor. For this purpose, a study was conducted on the friction power consumption of the main friction pairs of miniature oil-free rolling piston compressor under varying operating conditions and structures. Firstly, a mathematical model for the dynamic analysis of miniature oil-free rolling piston compressor was established. Then, the force characteristics of the main components of the miniature oil-free rolling piston compressor were analyzed, and the variation law of the friction power consumption of the main friction pair with the spindle angle was calculated. Finally, the influence of exhaust pressure, slide thickness, eccentricity, and relative cylinder length on the friction power consumption and proportion of the main friction pairs in miniature oil-free rolling piston compressor were analyzed. The research results show that the discharge pressure of the miniature oil-free rolling piston compressor increase from 1 100 kPa to 1 800 kPa, and the total friction power consumption increase by 67. 7%, while the total friction power consumption only increase by 32. 8% . The eccentricity of the miniature oil-free rolling piston compressor increases from 0. 06 to 0. 2, and the total friction power consumption increase by 121. 5% . The relative cylinder length of the miniature oil-free rolling piston compressor increases from 0. 25 to 0. 6, and the total friction power consumption increase by 31. 9% . According to the analysis results, the most suitable eccentricity value for the miniature oil-free rolling piston compressor is around 0. 14. The optimized eccentricity has the most significant effect on improving the friction loss of the miniature oil-free rolling piston compressor followed by changing the thickness of the sliding plate, and finally changing the length of the corresponding cylinder. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The underactuated manipulator has the advantages of simple structure, low cost, easy control and strong adaptive ability. However, the underactuated manipulator relies on mechanical limit and spring constraint to complete the grasp, resulting in poor grasping stability and inability to output greater fingertip grasping forces. Accordingly, a new underactuated three‑finger manipulator with fingertip self‑locking is proposed. The distal knuckle and middle knuckle can self‑lock when grasping, which increases the grasping stability. At the same time, the D-H kinematic model of the single finger is established, the working space of the manipulator is analyzed by MATLAB, the finger is analyzed by statics, the manipulator is simulated by ADAMS software, and finally the grasping test is carried out. The results show that the self‑locking manipulator can output greater grasping forces. Thus, the rationality and feasibility of the structure of the self‑locking manipulator are verified. [ABSTRACT FROM AUTHOR]

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]

Traditional methods for characterizing friction in mechanical systems can be challenging, and the fitting accuracy often proves unsatisfactory. In contrast to conventional friction identification and numerical fitting approaches, we explore friction by analytically determining the normal forces emerging at contact surfaces. The associated joints are modeled as dual-mass systems with elastic transmission elements, which account for the effects of viscous damping and friction. When a joint experiences a constraint, the corresponding constraint force is computed as the solution to the Udwadia-Kalaba (U-K) equation. Employing a normal force, a closed-form expression for the friction torque is derived using the Stribeck friction model. This expression encompasses the magnitude at any instant of time without the need for auxiliary variables. A comparison between experimental and simulation results demonstrates that the friction analysis method proposed offers a reasonable and effective description. [ABSTRACT FROM AUTHOR]

Copyright of Guangdong Architecture Civil Engineering is the property of Guangdong Architecture Civil Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of the research is to substantiate the critical rotation speed of a rotor with bent blades based on force analysis and modeling the movement of mixture particles in a horizontal loader of a circulation mixer. The research method[1]ology included the substantiation of the highest rotation frequency of the loader blade rotor based on a force analysis of moving particles of forces when they were moved by the bent blades of the loader and compliance with the conditions for the entry of flying particles into the tray. The numerical analysis performed on the basis of the obtained expressions using the Mathcad mathematical package made it possible to establish the critical values of the rotation speed of the rotor-loader with bent blades based on the condition of the material coming off the blade and the condition of the flight of particles from the blade into the receiving tray. With radial blades, the limitation is the entry of particles into the receiving tray at a critical frequency of 43 min-1 , then for a blade bend of 30° – about 60 min-1 , for a blade bend of 45° – about 70 min-1, for a blade bend of 60° – about 80 min-1. The lowest critical values of the rotor-loader rotation frequency from the condition of particle movement along the blade correspond to the blade bend angle of 27–60° and are determined by the friction coefficient of the material, amounting to 83–78 min-1. With an increase in material friction, the critical values of the rotor rotation speed from the condition of material coming off the blade decrease slightly, and the bend angle for the rotation speed extremum increases. The highest rotation speed of the rotor - loader with a radius of 0.12 m is limited to 78 min-1 at a blade bending angle of the order of 30–60°, determined by the friction of the material on the blade.

Two-dimensional particle-in-cell simulations are performed to study the coupling between ion and electron motions in collisionless magnetic reconnection. The electron diffusion region (EDR), where the electron motions are demagnetized, is found to have a two-layer structure: an inner EDR near the reconnection site and an outer EDR that is elongated to nearly 10 ion inertial lengths in the outflow direction. In the inner EDR, the speed of the electron outflow increases when the electrons move away from the X line. In the outer EDR, the speed of the electron outflow first increases and then decreases until the electrons reach the boundary of the outer EDR. In the boundary of the outer EDR, the magnetic field piles up and forms a depolarization front. From the perspective of the fluid, a force analysis on the formation of electron and ion outflows has also been investigated. Around the X line, the electrons are accelerated by the reconnection electric field in the out-of-plane direction. When the electrons move away from the X line, we find that the Lorentz force converts the direction of the accelerated electrons to the x direction, forming an electron outflow. Both electric field forces and electron gradient forces tend to drag the electron outflow. Ion acceleration along the x direction is caused by the Lorentz force, whereas the pressure gradient force tends to decelerate the ion outflow. Although these two terms are important, their effects on ions are almost offset. The Hall electric field force does positive work on ions and is not negligible. The ions are continuously accelerated, and the ion and electron outflow velocities are almost the same near the depolarization front.

Based on the complexity and metrological requirements of temperature calibration within the rotor of a medical low-temperature centrifuge, a wireless temperature calibration device for medical centrifuges has been designed and developed. The temperature probe is integrated into the centrifuge tube, and the entire device can be placed inside the rotor of the centrifuge, allowing for the measurement and analysis of the actual temperature of the test solution inside the centrifuge tube under dynamic rotation conditions. Furthermore, the force situation during dynamic calibration is analyzed and performance tested. The calibration device can consistently and dependably achieve dynamic temperature data acquisition under high-speed conditions of medical low-temperature centrifuges, facilitating dynamic temperature calibration within the centrifuge rotor and offering support for centrifuge temperature control processes.

This paper systematically investigates a soft-rigid hybrid pneumatic actuator (SRHPA), which consists of a rigid-foldable twisting skeleton capable of a large range of helical motion and a soft bellows muscle with high linear driving force. Considering the unique varying-pitch helical motion of the foldable skeleton, the analytical model mapping the input force generated by the bellows muscle and output forces of the actuator is revealed and verified with a simulation of the force analysis. Prototypes of the actuator are developed by fabricating the twisting skeleton with multilayered aluminum composite panels and 3D-printing the bellows muscle with thermoplastic polyurethane (TPU) 95A filament. The static and dynamic performances of the prototypes are tested to validate the analytical modeling of output forces. Using the actuator as a module, a novel bipedal inchworm robot with four modules is developed and tested to demonstrate its adaptability in confined space by switching between the going-straight, the turning-around, and the rotating gaits. The hybrid actuator and the inchworm robot with zero onboard electronics have the potential to be deployed in extreme environments where pneumatically actuated systems are preferred over electrical machines and drives, such as in nuclear and explosive environments. [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]

Cement slurry solidification process is an important part of cementing engineering, cement slurry solidification directly affects the quality of cementing, and then affects the whole drilling engineering and cost problems. In the process of cement slurry solidification, the decrease of slurry column pressure will increase the pull of upper casing, which is also the main reason for oil, gas, water channeling and early casing damage. In the process of cement slurry gelling, hydration will cause it to heat up, and then lose weight, and the combination of temperature and pressure will cause great deformation of the casing string. With the solidification of cement, this deformation will also be consolidated in the cement-sealed section. With the change of temperature and pressure under the injection-production condition, the casing in the sealed section may be under serious stress and strain, and may become an important factor affecting the service life of the casing. However, previous research on casing damage only focused on the completion of cementing. After cementing, due to the influence of formation high temperature and high pressure, construction and other factors in the later stage of oilfield production, people's attention mainly focused on the mechanical and chemical effects, and rarely considered the change of casing state during the cement slurry gaging process. Therefore, it is necessary to study the stress and deformation rule of casing string during the weight loss of cement cement gel. This paper simulates the casing force and change under different working conditions under the influence of factors such as cement slurry density, cement ring length, admixtures and formation environment. It is found that the axial tension of casing increases step by step with the cement slurry setting time and tends to decline at last. The research of casing damage in the later period provides a reference. [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]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Disassembly is a crucial step in remanufacturing and is currently mainly performed by humans. Automating disassembly can reduce labour costs and make remanufacturing more economically attractive. This paper focuses on identifying and characterizing a common disassembly task, dual peg-hole disassembly, with the aim of building a robotic disassembly system for this task. We enumerate the possible contact states and their geometric conditions during the extraction of two studs in a dual peg-hole. This paper focuses on jamming in the extraction and conducts geometrical and quasi-static analyses to determine the boundary conditions of jamming. Based on the analyses, this paper also investigates the role of active compliance as a solution to avoid jamming. We also simulate critical variables and examine key parameters such as the degree of compliance, the location of the compliance centre and initial position errors. Finally, we conduct experimental studies on dual peg-hole extraction with different compliance centres obtained using active compliance. [ABSTRACT FROM AUTHOR]

Copyright of Railway Investigation & Surveying is the property of Railway Investigation & Surveying Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of Nanjing University of Aeronautics & Astronautics is the property of Editorial Department of Journal of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Objective Through reducing the total mass of the main container of LNG film tank, the development and market expansion of LNG storage facilities are promoted. Methods The basic geometric parameters of the main container of the film tank are designed, and the mathematical model of the tank and the required objective function are established. The stress of the tank in the full tank state is analyzed and calculated, and the basic geometric data is parameterized and the thickness of the tank wall is optimized by ANSYS software. The mathematical model of the dome is solved by using particle swarm optimization algorithm and MATLAB software programming. Results The optimal curvature radius of the dome is 28 000 mm, the minimum thickness of the tank wall is reduced by 0.50 mm, the total mass of the tank roof is reduced by 103 t, and the maximum thickness of the tank wall is reduced by 0.62 mm. Conclusions The optimized calculation results are qualified after the air pressure test, which has important reference value for the lightweight research and cost reduction of LNG film tank. [ABSTRACT FROM AUTHOR]

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.

The productivity of the wood grinding process can be increased by using abrasive wheels with spherical corundum grains. They also expand the area of application of rigid abrasive instruments by reducing soiling and eliminating burns on the treated surface. The studies revealed several advantages of the abrasive wheels over sanding paper: very precise processing, achievement of the desired grade of the treated surface, high durability of the instrument, and low cost. A force analysis of a grinding surface with micro-cuttings made of spherical corundum grains was performed depending on the degree of its wear. The results revealed that chip removal by the spherical corundum grains was possible only under certain conditions when the cutting edges of the grains were exposed. Besides, the theoretical dependencies of forces in micro-cutting were obtained from every principal condition for the process of grinding wood and wooden materials: properties of the spheres, treatment modes, and material-related factors. The special properties were analyzed by the chip formation process and self-sharpening conditions of the spherical corundum wheels. The grain size had the greatest influence on the thickness of chips which were cut by one grain. The grain content and bonding, like other properties of the internal volumetric structure, had a less substantial impact. The abrasive tool characteristics must complement the processed material, such as grain size, hardness, and structure. On the other hand, spherical corundum has optimal physical and mechanical properties for grinding, particularly the thickness of the grain’s edges, which primarily determine the material’s tensile strength. The grinding depth and feed rate mostly define the parameters of the grinding performance of wood and wood-based materials. An increase in those leads to a rise in cutting forces, roughness of the ground surface, a reduction in the grinding length over the period of the wheel’s durability, and the grinding coefficient. If the grinding depth and feed rate are constant, the performance can be improved by increasing the cutting rate. For citation: Sergeevichev A.V., Sokolova V.A., Mikhailova A.E., Ovcharova E.O., Voinash S.A. Force Analysis of a Single Grain Cutting Process in Wood Grinding Using Spherical Corundum. Lesnoy Zhurnal = Russian Forestry Journal, 2023, no. 3, pp. 140–154. (In Russ.). https://doi.org/10.37482/0536-1036-2023-3-140-154

[Display omitted] Despite the flourishing studies of Leidenfrost droplet motion in its boiling regime, the droplet motion across different boiling regimes has rarely been focused on, where bubbles are generated at the solid–liquid interface. These bubbles are probable to dramatically alter the dynamics of Leidenfrost droplets, creating some intriguing phenomena of droplet motion. Hydrophilic, hydrophobic, and superhydrophobic substrates with a temperature gradient are designed, and Leidenfrost droplets with diverse fluid types, volumes, and velocities travel from the hot end to the cold end of the substrate. The behaviors of droplet motion across different boiling regimes are recorded and depicted in a phase diagram. A special phenomenon of Leidenfrost droplets that resembles a jet engine is witnessed on a hydrophilic substrate with a temperature gradient: the droplet traveling across boiling regimes repulsing itself backward. The mechanism of repulsive motion is the reverse thrust from fierce bubble ejection when droplets meet nucleate boiling regime, which cannot take place on hydrophobic and superhydrophobic substrates. We further demonstrate that conflicting droplet motions can occur in similar conditions, and a model is developed to predict the occurring criteria of this phenomenon for droplets in diverse working conditions, which agrees well with the experimental data. [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]

Copyright of Machine Tool & Hydraulics is the property of Guangzhou Mechanical Engineering Research Institute (GMERI) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, a new over-constrained parallel driving mechanism (PDM) with planar sub-closed chains is proposed. First, the number of over-constraints on the PDM is calculated. Then, an analysis is conducted as to the kinematics of the hybrid manipulator, including positions, velocities, and accelerations of all bodies. Furthermore, the Newton–Euler approach is taken to deduce the kinematic formula of each link and the formula of inertial force at the center of mass. However, it remains difficult to solve the equation since the number of equations is smaller than that of unknown variables. To solve this problem, the screw theory is applied in the present study to analyze the cause of over-constraints, with the link's elastic deformation introduced as the supplement of deformation compatibility equations. Moreover, the actuation forces and constrained forces/moments are calculated simultaneously. Finally, the dynamic model is verified through simulation and experimentation. The proposed modeling approach provides a fundamental basis for the structural optimization and friction force computation of the over-constrained PDM. [ABSTRACT FROM AUTHOR]

At present, the main structural form of sprocket body generally adopts the integral structure at home and abroad, which is difficult to reverse and maintain. The split sprocket shaft group has great advantages in maintenance cost and convenience compared with the integral sprocket shaft group. According to the classical theoretical mechanics, the force analysis of the split sprocket body with new structure is carried out. It is combined with the results of finite element analysis, and then the calculation method of the split sprocket body connection structure design is obtained. This research provides the research method of force analysis of the split sprocket, which can provide necessary loads and constraints for design calculation and finite element analysis. When the split sprocket body is connected by connecting screws, cylindrical pins are set between the upper and lower sprocket bodies to transmit torque, which can ensure the connection reliability of the scraper sprocket of the existing high-power heavy scraper under the conditions of limited installation space and limited number of connecting bolts. Thus it can provide reference and theoretical guidance for the design of similar sprocket bodies in the future.

Abstract Background Occlusal analysis is essential in the dental clinical practice. However, the traditional occlusal analysis performed on the two-dimensional level can not directly correspond to the tooth surface with three-dimensional profile, therefore the clinical guidance value is limited. Methods By combining the 3D digital dental models and quantitative data from 2D occlusal contact analysis, this study constructed a novel digital occlusal analysis method. The validity and reliability of DP and SA were verified by comparing the results of occlusal analysis of 22 participants. ICC values for occlusal contact area (OCA) and occlusal contact number (OCN) were tested. Results Results confirmed the reliability of the two occlusal analysis methods with ICC values of 0.909 for SAOCA, 0.906 for DPOCA, 0.929 for SAOCN and 0.904 for DPOCN. The Bland-Altman plot, paired t-test (tOCN = 0.691, P > 0.05) and Pearson correlation analysis results (R = 0.68, p

【Objective】 Bidirectional shaft tubular pump is a device commonly used in hydraulic projects. The aim of this paper is to study the impact of guide vane numbers on the force imposed to the pump when it is under different working conditions. 【Method】 The investigation was based on computational fluid dynamics (CFD) and experiments conducted in a real engineering project. Water flow in the pump was turbulent and described by the RNG k-ε turbulence model. The experimental data was used to calibrate the model, and the validated model was then used to analyze the impact of guide vane numbers on the pump under different working conditions. 【Result】 Under back and forth operation condition, the average axial force imposed to the pump by different guide vane numbers was comparable. Making the ratio of guide vane numbers to blade numbers an integer increased the peak axial force pulsation significantly, risking pump operation. The radial force imposed to the impeller was minimal and can be neglected in design. It was also found that setting the number of guide vanes even can reduce the radial force imposed to the pump by the guide vane. 【Conclusion】 The number of guide vanes and the number of blades combined to affect the force imposed to the pump. Our results indicated that design should avoid the ratio of the guide vane numbers to the blade numbers being an integer.

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.

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.

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

A vane-type separator has been successfully applied to gas-liquid and liquid-liquid separation. In order to evaluate the separation performance of the separator, a theoretical model for calculating the particle motion trajectory in the vane-type separator was developed. Firstly, the simplified steady incompressible Navier-Stokes equations were derived to acquire the equations of tangential velocity and axial velocity of continuous phase flow field. Then, the coefficients were determined by fitting the CFD results and it can be used to obtain the velocity at different swirler structure conditions. Further, the force analysis on the particle was conducted to develop the motion governing equations to predict the trajectory. The predicted separation lengths at different geometric swirl number conditions show a good agreement with the experimental results and its relative error is smaller than 3%. Besides, the effects of the key parameters including density difference, particle size and viscosity of the continuous phase on the separation length were investigated. • The velocity field in the swirl chamber was derived from Navier-Stokes equations. • A prediction model for the particle trajectory was developed. • The effects of the key parameters on the particle trajectory were studied. [ABSTRACT FROM AUTHOR]

In view of the problems of untimely opening and pressure relief of the traditional explosion-proof door and the low degree of automatic operation of the latch device, from the perspective of mechanics, the stress of the explosion-proof door under the two states of normal operation and reverse air operation of the fan is analyzed in detail. The application of the new electromagnetic latch technology to the explosion-proof door pressure relief and backdraft process was studied on the basis of the traditional latch, the required suction force of the new electromagnetic latch under different operating conditions of the fan was calculated and the design of the automatic explosion-proof door pressure relief was further proposed based on the electromagnetic latch technology. The results show that the explosion-proof door can be opened only when the explosion power is large, and there may be air leakage in the process of reverse wind. In order to prevent the above situations, in the proposed automatic pressure relief design of the explosion-proof door, the counterweight of the explosion-proof door is increased to the natural state, the explosion-proof door is pulled down, and the new electromagnetic latch is used to provide sufficient suction to meet the requirements of pressure relief and anti wind work of the explosion-proof door. The calculation shows that when the counterweight is 114 484 N to ensure the balance state of the explosion-proof door, the electromagnetic latch provides at least 166 169 N suction to ensure the smooth operation of the explosion-proof door in different working states of the fan. In addition, using the new electromagnetic latch and high-performance sensor technology, under the condition that the counterweight of the explosion-proof door is greater than the combined force of the gravity, positive(negative) pressure and friction of the explosion-proof door cover, the rapid pressure relief under any explosion power can be realized when the distance between the explosion position and the explosion-proof door is greater than the distance that the explosion shock wave has propagated when the latch is powered off. Through theoretical calculation, it is concluded that the safe distance between the explosion position and the explosion-proof door in the automatic pressure relief design of the explosion-proof door is about 326 m.

Multi-bridge centralized drive wheel loaders can produce parasitic power to waste energy and aggravate tire wear. Distributed Electric Wheel Loader(DEWL) is a new structure with two drive motors that can be controlled independently or in concert. Hence, this study investigates the mechanical characteristics of DEWL in its shoveling condition. Firstly, for the DEWL, dynamic models are established including running and shoveling conditions, on the basis of automobile theory. Secondly, a simplified structural model of DEWL is used to construct the mechanical equations, and the theoretical derivation is utilized to analyze the forces on wheels during different driving modes of running and shoveling conditions. Finally, the free shoveling of dry sands and gravel materials is tested by a ZL50GV-EV DEWL, and the drive forces of three drive modes on horizontal concrete pavement are tested. The results show that the parasitic power is generated when the driving motor has a larger speed than that of the other motor, which is caused by the movement of the loader's center of gravity. The driving torques generated by the motors are basically the same when the DEWL is in front-drive mode and rear-drive mode at the setting speed of 600rpm, whether it is running forward or backward, with a torque fluctuation of 0.16%-1.28% and a power fluctuation of 0.02%-1.29%. The DEWL consumes more power in dual-drive mode than in single drive if it is controlled in speed-target mode. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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]

Background: Occlusal analysis is essential in the dental clinical practice. However, the traditional occlusal analysis performed on the two-dimensional level can not directly correspond to the tooth surface with three-dimensional profile, therefore the clinical guidance value is limited. Methods: By combining the 3D digital dental models and quantitative data from 2D occlusal contact analysis, this study constructed a novel digital occlusal analysis method. The validity and reliability of DP and SA were verified by comparing the results of occlusal analysis of 22 participants. ICC values for occlusal contact area (OCA) and occlusal contact number (OCN) were tested. Results: Results confirmed the reliability of the two occlusal analysis methods with ICC values of 0.909 for SAOCA, 0.906 for DPOCA, 0.929 for SAOCN and 0.904 for DPOCN. The Bland-Altman plot, paired t-test (tOCN = 0.691, P > 0.05) and Pearson correlation analysis results (R = 0.68, p < 0.001) verified the validity between SA and DP. Then a novel digital occlusal analysis method was constructed, which not only can locate the occlusion contact and provide the quantitative analysis, but also provide a comprehensive description of the resultant force of each tooth and the component forces on the x-, y- and z-axis. Conclusions: This new occlusal analysis method can obtain quantitative analysis of occlusal contact including contact area and force information simultaneously, which will provide new impetus and greater help for clinical dental treatment and scientific research. [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]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Trapped air bubbles in pipelines significantly affect the safety and efficiency of water supply systems, potentially inducing water hammer and leading to pipeline explosions and interruptions. This study investigates the sweeping velocity of air bubbles in horizontal pipelines by analyzing the forces acting on a single air bubble and deriving a theoretical expression for calculating the sweeping velocity. Physical model experiments and numerical simulations are conducted to examine the variations in sweeping velocity with respect to bubble volume and dimensionless bubble volume. Results indicate that the sweeping velocity increases with bubble volume, and the diameter of the pipeline significantly affects the movement of air bubbles. These findings contribute to a better understanding of air bubble behavior in horizontal pipelines and can inform strategies for mitigating risks associated with trapped air bubbles, ultimately improving the safety and reliability of water supply systems.

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.

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]

Our research group has been developing an automated modularized rail structure construction system. Our system provides robot's locomotion and operational infrastructure in hazardous environments where manned work is difficult. In previous studies, various modules and robots have been developed, and stable transfer of modules between robots in multiple postures has been achieved. However, 3-D construction is not yet realized. In this study, the relationship between the contact force and posture of the constructor robot's (C-robot) end-effector is estimated through force balance calculation and deformation analysis is performed based on the finite element method. The results of construction experiment showed that pushing motion and improvement of the stiffness of the C-robot's grasping part increase the success rate of module construction in the vertically downward direction, which is the most difficult condition. Finally, this study proved that 3-D construction of a modularized rail structure is feasible in various posture condition. [ABSTRACT FROM AUTHOR]