Opening Width Research Articles

Investigation on Tribological Performance of Lubricating Film with Chevron Texture

The optimization of texture parameters is of great significance to promote the tribological characteristics of a lubricating film. In this article, the mathematical model of a lubricating oil film on a textured surface considering cavitation is established and verified by wear experiments at different rotation speeds and loads. The influence of chevron texture parameters including opening angle, depth, width, and area proportion on the tribological performance of the lubricating film are investigated. The results show that the chevron texture design parameters that affect the tribological characteristics of the lubricating film are opening angle, width, area proportion, and depth. The influence of the opening angle of chevron texture on the tribological performance of the oil film mainly depends on the load-carrying capacity; meanwhile, the other parameters are affected by the viscous drag and the load-carrying capacity of oil film. The tribological characteristics of the chevron texture could be improved through the design and optimization of parameters.

Numerical simulation of hydraulic fracturing with consideration of the pore pressure distribution based on the unified pipe-interface element model

Understanding hydraulic fracture propagation behaviours is vital for optimizing fracturing design in oil and gas production. It has been observed that the stress and pore pressure distribution are much more complex during fracturing treatment as a result of long-term fluid injection and production in the reservoir. When rock is subjected to internal hydraulic pressure and external mechanical loading, the closing, opening, or other interactions of pre-existing weaknesses or induced new fractures will be altered. In this paper, a number of hydraulic simulation scenarios are performed to investigate the effect of pore pressure distribution on fracture initiation and propagation using the unified pipe-interface element method (UP-IEM). The proposed method for predicting the hydraulic fracture path in the permeable porous medium with non-uniform pore pressure field is validated with experimental results. Considering the arrangement of well patterns and natural fractures in the rock, the problems of hydraulic fracture propagation behaviours with wellbore interaction and pore pressure induced natural fracture activation are simulated. The influence of pore pressure saturation and the injection sequence of wellbores on hydraulic fracturing are researched. A sensitivity analysis is carried out to investigate the parameter effects on pre-existing fracture tortuosity, opening width and breakdown pressure under pore pressure. These numerical examples provide guidance to engineers to estimate the probability of danger or possibilities to improve the injection and production of wells.

Survivability of reinforced concrete frames of multi-storey buildings with complex stress elements

Experimental determination of the parameters of the force resistance of reinforced concrete structures aimed at protecting them from emergency beyond design impacts is an important direction in improving the safety of buildings and structures. In this connection, the purpose of the study was an experimental assessment of the deformation parameters in the complexly stressed elements of reinforced concrete frames under special impact in the form of a sudden column removal. Experimental studies were carried out for two frames, one of which was tested when removing the middle column, the second - when removing the extreme. Experimental two-span structures of reinforced concrete frames are designed with three floors in height, reinforcement was made with spatial reinforcing cages that provide resistance to torsion with bending. The results of experimental and theoretical studies of reinforced concrete frame structures under special influences and an assessment of displacements, cracking and destruction of the considered complex-stressed structural elements under such influences are presented. It is established that the type of stress state, the formation and width of crack opening significantly affect the dissipative properties of the structural system.

Reliability-Based Robust Design Optimization for Maximizing the Output Torque of Brushless Direct Current (BLDC) Motors Considering Manufacturing Uncertainty

In recent years, the deterministic design optimization method has been widely used to improve the output performance of brushless direct current (BLDC) motors. However, it does not contribute to reducing the failure rate and performance variation of products because it cannot determine the manufacturing uncertainty. In this study, we proposed reliability-based robust design optimization to improve the output torque of a BLDC motor while reducing the failure rate and performance variation. We calculated the output torque and vibration response of the BLDC motor using the electromagnetic–structural coupled analysis. We selected the tooth thickness, slot opening width, slot radius, slot depth, tooth width, magnet thickness, and magnet length as the design variables related to the shape of the stator and rotor that affect the output torque. We considered the distribution of design variables with manufacturing tolerances. We performed a reliability analysis of the BLDC motor considering the distribution of design variables with manufacturing tolerances. Using the reliability analysis results, we performed reliability-based robust design optimization (RBRDO) to maximize the output torque; consequently, the output torque increased by 8.8% compared to the initial BLDC motor, the standard deviation in output performance decreased by 46.9% with improved robustness, and the failure rate decreased by 99.2% with enhanced reliability. The proposed reliability-based robust design optimization is considered to be useful in the actual product design field because it can evaluate both the reliability and robustness of the product and improve its performance in the design stage.

Model Experiment Exploration of the Kinetic Dissipation Effect on the Slit Dam with Baffles Tilted in the Downstream Direction

Slit dams can eliminate the risk of particle overload accumulation, which can be safer in controlling debris flow compared with a completely closed dam. In attempting to better use the energy dissipation effect of particle collision and reduce the impact of the dam body, referring to the traditional slit dam, this paper proposed one with tilted baffles in the downstream direction. Discrete element simulation and several flume model experiments were carried out herein to verify the advantages and explore the applicable conditions of this tilted baffle slit dam, in which the particle trapping efficiency and the change law of impact force of the tilted baffles under the conditions of different inclined angles, opening sizes, and particle sizes were studied. The results show that: 1. when the inclination angle is 30° ≤ θ ≤ 45°, the tilted baffles can dissipate more particle kinetic energy than the transverse baffles; 2. the maximum impact force and trapping efficiency of the tilted baffles decrease with the increase in the width diameter ratio b/d, with the opening width b of the slit to the particle diameter d; 3. with the given particle size of 6 mm ≤ d ≤ 14 mm, the range that the tilted baffles can effectively intercept the particles flowing down is 0 ≤ b/d ≤ 4, and it reaches the ideal interception state near 1 ≤ b/d ≤ 2, where, relatively, the impact force is weak, and the interception efficiency is high.

Finite-element modelling of RC beams with carbon FRP strengthened web openings

Web openings are commonly used in reinforced concrete (RC) beams to accommodate pipes, ducts, and utilities. The expected reduction in strength can be compensated by locally strengthening the beam opening with carbon fibre-reinforced polymer (CFRP). In this paper, a robust non-linear finite-element model (FEM) is developed to simulate the behavior of RC beams with/without openings. The model can simulate the strengthening of the beam opening with CFRP sheets. The developed FEM is validated using seven simply supported RC beams that were previously tested under monotonic two concentrated loads. The crack pattern and load-deflection relationship, from the FEM, were compared to those obtained from the experiments. The developed FEM was utilised to conduct a parametric study on 32 beams to investigate the behavior of RC beams with CFRP strengthened openings. The parametric study showed that the opening width did not significantly affect the load at failure. However, both the opening depth and distance from support had a clear effect on the failure load. Increasing the stirrups diameter from 8 to 10 mm increased the shear capacity of RC beams by 3–16%. The failure loads obtained from the proposed FEM were compared to those obtained from international design codes.

Numerical model of a tidal current acceleration structure

Advancements in technology have led to a rapid rise in the use of renewable energy sources in the past 25 years. The current work focuses on the potential of a novel hydraulic technology to contribute toward sustainable energy production. The tidal current acceleration structure is a simple structure that uses the basic principle of the Venturi effect in low-speed tides and rivers to accelerate the flow and, in turn, extract energy using turbines. The primary aim of the present study is to understand to what extent this newly proposed tidal flow structure is suitable for real applications. The shear stress transport k–ω model was utilized, and the parametric analysis based on angle variation, Froude number, and bed roughness was undertaken to optimize the performance of the structure. The potential power that could be extracted by an in-stream turbine was then estimated using actuator disk theory. The performance of the structure significantly increased for the configuration having the ratio of the opening and contraction width of 2.66.

Analysis of a Triple-Stator Axial-Flux Spoke-Type Permanent Magnet Vernier Machine

In this article, an axial-flux permanent-magnet (PM) Vernier machine with the triple-stator, spoke-type PM rotor, and toroidal winding wound on the innerstator is proposed. Benefited from the flux focusing spoke-type PM rotor and short end length toroidal winding, the proposed machine has a high torque density and the improved power factor. Based on the air-gap permeance function, the analytical expression of the proposed machine is derived to qualitatively analyze the machine's performance. The quasi-three-dimensional (3-D) finite element analysis (FEA) is adopted to optimize the design parameters, such as innerstator diameter, PM thickness, and slot opening width. The quasi-3-D FEA results match well with the 3-D FEA. The 3-D FEA results show the torque densities of the proposed machine reach 49.4 Nm/L and 11.4 Nm/kg, respectively, under the 232 A/cm average electrical loading. The performances, such as overload capacity, PM demagnetization, and PM and core losses, are also analyzed by 3-D FEA. The comparison with the other axial-flux PM Vernier machine is conducted, and the results reveal that the proposed machine has the great advantages of the torque density and power factor. Since the prototype is not built, in this article, the assembly scheme and thermal behavior of the proposed machine are discussed.

Trench topography in subduction zones: A reflection of the plate decoupling depth

Subduction of lithospheric plates produces narrow, linear troughs (trench) in front of the overriding plates at the convergent boundaries. The trenches show a wide variation in their topographic characteristics, such as width, vertical depth, and bounding surface slopes. Benchmarking their controlling factors is thus a crucial step in the analysis of trench morphology. This article identifies the mechanical coupling between the subducting and overriding plates as a leading factor in modulating the topographic evolution of a trench. The maximum depth of decoupling (MDD) is used to express the degree of decoupling at the plate interface. We simulate subduction zones in computational fluid dynamic (CFD) models to show the topographic elements (maximum negative relative relief: D; fore- and hinter-wall slopes: θF and θH; opening width: W) of trenches as a function of the MDD within a range of 30–120 km. Both D and θ strongly depend on the MDD, whereas W is found to be relatively less sensitive to the MDD, implying that the narrow/broad width of a trench can change little with the plate decoupling factor. We also show that the MDD critically controls the fore-arc stress fields of a trench, switching a compressive to tensile stress transition with increasing MDD. This study finally validates the model findings with well-constrained natural trench topography.

Web-post buckling prediction resistance of steel beams with elliptically-based web openings using Artificial Neural Networks (ANN)

This paper aims to propose an Artificial Neural Network (ANN) model that predicts accurately web-post buckling resistance and failure mode of steel beams with elliptically-based openings. A total of 4,344 and 5,400 geometrical models, were developed by finite element method (FEM) and used to train, validate and test the ANN model for the web-post resistance and failure mode classification, respectively. It was concluded that five neurons model were sufficient to predict the web-post buckling resistance and the failure mode with high level of accuracy. The height and the web thickness of the beams had positive impact of the capacity while the web openings height, width and radius of the elliptically-based web opening were the geometric parameters that had negative impact of the capacity. At last, an ANN-based formula was proposed and compared with previous analytical model for web-post buckling resistance of elliptically-based openings, which considered the web-post as a truss model. The ANN-based formula showed high accuracy, since the Regression (R2), Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Average (FEM/Predicted), Standard Deviation and Variation were 0.9989, 26.03 kN, 15.0 kN, 1.00, 4% and 0.12%, respectively. Consequently, the ANN-based formula for web-post buckling resistance of steel beams with elliptically-based openings can be safely adopted for design purposes.

Bearing Capacity of Reinforced Concrete Beams with Initial Cracks Reinforced with Polymer Composite Materials.

The use of polymer-composite materials for strengthening the reinforcing of concrete structures represents a current scientific trend. The article is devoted to experimental studies of the strength of inclined sections of bent concrete elements, reinforced with transverse polymer reinforcement with initial inclined cracks, with different shear spans and transverse reinforcement options. The characteristics of reinforced concrete specimens with initial inclined cracks and the test results of 22 experimental beams, each of which was tested twice, are given. A significant influence of all eight variable factors was established: three spans of the section, equal to 1.5 ; 2 and 2.5 ; two types of compound clamps and their layout; and opening width of oblique cracks from 0.6 to 0.9 mm. It is shown that the strengthening of the beams supporting sections with external polymer reinforcement using three-sided U-shaped and vertical double-sided stirrups significantly changes their stress-strain state (SSS) and the form of destruction. SSS transforms from the classical destruction of the compressed zone above the end of the inclined crack to the destruction of the beam zone of average height at α = 2.0 and brittle crushing of concrete in the tension zone. Unfavorable combinations of force and geometric factors are revealed. Recommendations are proposed that can be used for structures operated in all weather conditions.

Performance analysis of a novel personalized air curtain for preventing inhalation of particulate matters in industrial environments

Personalized air curtains promise to reduce respiratory exposure in industrial environments. This work explored the performance of normal safe helmets equipped with air curtains to prevent workers from particulate matters via computational fluid dynamics (CFD) method. The impact of human body heat, breathing modes (nose and mouth inhalation), and air curtain characters (opening angle, tilt angle, and opening width) on protective efficiency were analyzed under different air supply velocities. Results showed that the interaction between the downward jet supplied by the air curtain helmet and the free convection flow generated by the thermal human body significantly affects respiratory exposure. There is a critical air supply velocity, i.e., when the jet velocity is greater than this value, the flow field in the breathing zone was dominated by the downward jet; otherwise, it is dominated by free convection flow. Both human body heat and breathing modes have significant effects on the protective effect of the air curtain. The opening angle of 180o, the tilt angle of 0o, the opening width of 3 cm, and the air supply velocity of 0.5 m/s are recommended due to a high protection effect of around 1. This study can provide effective and intuitive guidance in applying personalized air curtains for respiratory protection in highly contaminated industrial environments.

An Improved Model for Five-Phase Induction Motor Based on Magnetic Noise Reduction Part I: Slot Opening Width

Based on the winding function considering the slot width and the air-gap permeability considering the slot opening width, the main radial electromagnetic force wave expressions of the induction motor are determined. The electromagnetic force-vibration prediction model of the induction motor is established. The natural frequency and acoustic radiation model of a finite-length cylindrical shell with two ends clamped is deduced. On this basis, an improved magnetic noise prediction model of cage induction motor is improved, which can calculate the combined effects of electromagnetic force on the axis and circumferential modes of the stator system. Aiming at two different noise reduction targets, an optimization method is proposed to reduce the overall electromagnetic noise of the motor without sacrificing efficiency and output torque. The feasibility of the model for electromagnetic noise prediction is verified by finite element simulation and experiments. For a 30/26 slots five-phase induction motor, low-noise analysis and optimization schemes of the opening width for two different targets are given. The results show that the larger slot opening scheme can also result in less magnetic noise for the right selection, which is contrary to the common design rule that recommends minimizing slot opening to reduce magnetic noise.

Kinematic diagram of the mechanism and algorithm for controlling the width of the indoor structure exhaust opening

The results of theoretical studies of the possibility of reducing the lack and excess of heat in the cultivation structure by substantiating the parameters and algorithm of the mechanism of real-time control width of the exhaust opening are presented. A kinematic diagram of a flat lever mechanism for controlling the width of the draft opening with a drive from an electric linear actuator has been developed. Dependences of the angle of inclination of the leading link of the mechanism and the width of the exhaust opening on the stroke of the actuator rod are determined. The maximum travel of the actuator rod is 225 mm, which allows you to change the width of the exhaust opening from 0 to 900 mm. In this case, the angle of the axis of the master link position sensor varies from 0 to 90 degrees. Based on the analysis of the operation process of the mechanism and the requirements of the plants to the ambient air temperature, an algorithm for controlling the width of the opening was developed, providing for three possible situations. As long as the air temperature meets the biological requirements of the plants, the width of the exhaust opening does not change. If the air temperature exceeds the upper limit, the width of the opening is increased by the value determined by the angle change step of the mechanism driving link. If the air temperature is less than the lower limit, the controller turns on the linear actuator to reduce the opening width. This ensures that the tilt angle of the master link changes by the step dA, which is set during the programming. Logic operators compare the current value of the angle of inclination of the master link with the calculated value and switch the actuator on and off. Thus, the proposed algorithm consistently approximates the state of the system to the optimum zone and reacts to the changes in external conditions.

Research on cogging torque characteristics of permanent magnet synchronous machines with the same number of poles and slots

This paper presents a new permanent magnet synchronous machine with the same number of poles and slots by combining two unit machines. The machine is designed by the magnetomotive force star diagram, and the performance of the machine is demonstrated by finite element simulation. Since the number of poles of the two unit machines is different, the number of periods of the machine cogging torque is solved based on the energy method. In addition, all slots are divided into four parts according to the size of the slots, and the analytical model of cogging torque is established by the superposition technique. Based on the analytical model, the combination of the unit machine and the slot opening width are optimized to further reduce the cogging torque. Finite element simulations were used to verify the validity of the theoretical derivation and to further validate the lower cogging torque of the permanent magnet machine with same number of poles and slots when the slot opening width is the same.

Mechanical Behaviors of Existing Large-Diameter Tunnel Induced by Horseshoe-Shaped Undercrossing Twin Tunnels in Gravel

This article investigates and presents a case study on the Beijing Subway Line 12 excavation beneath the existing Qinghuayuan Tunnel. The composite pre-reinforcement technique was used in conjunction with the shallow tunneling method to control the distortion of the existing large-diameter tunnel. When building twin tunnels underneath, this strategy considerably decreased the impact on the existing large-diameter tunnel. To systematically study the mechanical response of the existing large-diameter tunnel, a variety of sensors was embedded in the prefabricated segments just above the new twin tunnels. During the undercrossing twin tunnels procedure, the earth pressure, tunnel crown settlement, opening width of the segment joint, and the circumferential strain of the large-diameter existing tunnel were all measured. The settlement development of the existing large-diameter tunnel was categorized under six stages: (1) sedimentation, (2) heave, (3) second sedimentation, (4) second heave, (5) third sedimentation, and (6) steady state. The joint opening of the existing large-diameter tunnel changed sharply during the new undercrossing twin tunnels. The earth pressure and concrete stress of the linings rapidly increased during the new undercrossing twin tunnels. The majority of the reinforcement and concrete stresses were compressive and far lower than the yield strength, indicating that the tunnel was in a safe working condition.

Moving model test on the aerodynamic pressure of bilateral inverted-L-shaped noise barriers caused by high-speed trains

With the increasing speed of high-speed trains, the aerodynamic impact of trains on high-speed railway noise barriers has gradually become a focus of attention. Compared with traditional vertical noise barriers, the bilateral inverted-L-shaped noise barrier (BILSNB) has better noise insulation performance, but its aerodynamic impact may be more prominent. In this research, a moving train-BILSNB test system with a scale ratio of 1:16.8 is established, and the influence of train speed and the opening width on the aerodynamic pressure is analysed and discussed. The large eddy simulation is applied to investigate the influence mechanism of flow field on the aerodynamic performance of the BILSNB. The main conclusions are as follows. (1) The pressure amplitude caused by the passing of the train head is 36.67% greater than that generated by the passing of the train tail on average. (2) The maximum pressure of the BILSNB appears at the bottom area. When the height of the measuring point increases from 0.5H to 1.6H, the pressure coefficient of peak positive pressure, peak negative pressure and pressure amplitude decrease by 29.0%, 17.0% and 15.5%, respectively. (3) The aerodynamic pressure in the BILSNB has a longitudinal end effect: the pressure coefficient of positive peak pressure and pressure amplitude at the inlet section are 27.6% and 17.5% higher than the corresponding average value of all middle sections, respectively. (4) The pressure amplitude of the BILSNB is approximately proportional to 2.15 power of the train speed. The pressure coefficient of the BILSNB is approximately a power function of the opening width, and the value range of the index is about (−0.26, −0.30). (5) The mechanism of the longitudinal end effect is as follows: When the train arrives at the inlet section, the high-speed airflow in front of the train head cannot flow around in time resulting in the impact effect of the airflow on the inlet section becomes greater than that on the middle section. The influence mechanism of the opening width is as follows: The narrower the opening width is, the more intense the airflow inside the BILSNB is compressed, and the impact effect of the airflow on the noise barrier is more significant.

Diagnostic value of mouth opening width in patients with temporomandibular disorders

Introduction: mouth opening amplitude allows the evaluation of joint and muscle function, constituting a valuable tool to diagnose alterations in the stomatognathic system. Objective: to characterize the buccal opening amplitude of patients who attended the temporomandibular disorders consultation of the Clinical Surgical “Dr. Miguel Enriquez” Teaching Hospital, in the period January 2017-January 2020. Method: a retrospective observational descriptive study was carried out in the period January 2017-January 2020, forming a database from the information obtained directly from the medical records. Literature review and synthesis was performed and descriptive statistics were used for data analysis by means of absolute frequency distribution expressed in percentages. Results: normal mouth opening width predominated in 61 % of the cases. Severe mouth opening restrictions below 20 mm affected 7 % of the females and 21 % of the males. Twenty-three percent of the 30-39-year-old group presented severe limitations below 20 mm, while 19 % of the 19-29-year-old group presented hypermobility. 65 % of the patients who attended before 1 month of symptom onset recorded limitation of mouth opening. Conclusions: in patients diagnosed with temporomandibular disorders, normal mouth opening amplitude predominated, so the ability of the individual to perform this movement within the established range is not necessarily an indicator of absence of joint and/or muscle damage

Investigation of PM Loss in Spoke-Type Permanent Magnet Vernier Motors With Different Stator Topologies for In-Wheel Direct Drive

In this article, the permanent magnet (PM) loss in spoke-type permanent magnet vernier motors (ST-PMVM) with different stator topologies is investigated and compared for in-wheel direct drive. First, four ST-PMVM with split-pole and open-slot stators are designed for the in-wheel limited requirements. Besides, based on the PM loss model, the dominant influences of both slot and subharmonics on PM loss are highlighted. Then, the quantitative contributions of the air-gap magnetic field harmonics on torque and PM loss are investigated, which embodies the inherent characteristic of larger PM loss in PMVM. Furthermore, the stator tooth parameters, the slot opening width, and auxiliary slot depth on torque and PM loss are described, and then a parameter titled as the slot opening ratio is introduced to evaluate the relationship of various slot opening width combinations. It shows that there exists an irreconcilable contradiction between the torque and PM loss in PMVM, especially in split-pole types. Finally, a prototype was manufactured, and the theoretical results and finite-element analysis results match well with the experimental results.

Some Hatchery Parameters of Three Species of Groupers: Tiger Grouper (Epinephelus fuscoguttatus), Humpback Grouper (Cromileptes altivelis), and Leopard Coral Grouper (Plectropomus leopardus)

Three species of groupers, including tiger grouper (Epinephelus fuscoguttatus), humpback grouper (Cromileptes altivelis), and leopard coral grouper (Plectropomus leopardus), have been successfully cultivated. However, the constraints on larviculture that have been described still arise in the hatchery. This study compares several hatchery parameters in these three grouper species representing three different genera (Epinephelus, Cromileptes, and Plectropomus). The egg incubation and larval rearing were carried out in a concrete tank (3 x 3 x 1.2 m3) filled with 6-7 m3 seawater. Eggs were stocked with a density of 100,000 eggs/tank. The grouper larvae were reared until they became juvenile. The eggs were incubated until they were hatched in the same container and media as larval rearing. Larvae were reared until 60 dah (days after hatching), and data were taken from the rearing for three cycle's larval culture. Management of grouper larval rearing follows the Good Fish Hatchery Method (Cara Pembenihan Ikan yang Baik/CPIB) based on Indonesian National Standard (Standar Nasional Indonesia/SNI). The experimental parameters were egg diameter, hatching rate, larvae mouth opening width, survival activity index (SAI), larvae development, and total body length growth. The several hatchery parameters in three grouper fish species are significantly different. The tiger grouper has the best larval performance.