U-shaped Groove Research Articles

Simulation analysis and optimization of pilot type electro-hydraulic proportional directional valve based on multi field coupling

The pilot-operated electro-hydraulic proportional directional valve is widely used in complex and precision engineering fields. Its operational stability and reliability determine the overall performance of the hydraulic system. During the working process of the pilot-operated electro-hydraulic proportional directional valve, the spool is deformed due to the influence of pressure and temperature, resulting in problems such as clamping or stagnation. In order to solve this problem, this study uses the fluid-solid-thermal coupling simulation method to analyze the flow field characteristics and thermal deformation of the spool with different structural throttling grooves, and optimizes the U-shaped throttling groove structure. The results indicate that as the valve opening increases, the front section of the throttling groove becomes the primary region where the maximum radial deformation of the spool occurs. In this paper, the steady-state flow force of the valve core is taken as the measurement standard, the constraint range of the structural parameters is determined, and the radial thermal deformation is included in the optimization analysis of the structural size. It’s verified that the optimized flow characteristics are improved by about 32 % compared with that before optimization, and the maximum steady-state flow force after considering thermal deformation is reduced by about 4N compared with that before optimization. This provides an important design basis and reference for the structural design and optimization of the pilot electro-hydraulic proportional directional valve.

Micro–Computed Tomographic Analysis of Radicular Dentin Thickness in Mandibular Second Molars Across Diverse Anatomic Root Variations: Identifying Potential Danger Zones

IntroductionThis study aimed to investigate radicular dentin thicknesses in mandibular second molars (MSMs), considering variations in root configuration and the morphology of the pulp chamber floor (PCF). The types of radicular grooves and potential danger zones were also identified. MethodsA total of 149 MSMs were scanned with micro–computed tomographic imaging and classified into 4 groups according to root fusion and PCF morphology as follows: (1) 45 with fused roots and C-shaped PCFs, (2) 45 with fused roots and non–C-shaped PCFs, (3) 14 with a single canal, and (4) 45 with separated roots. The first 2 groups were subdivided into Ω-shaped, U-shaped, and V-shaped radicular groove subgroups. Measurements included minimum and mean dentin thickness from the start of the radicular groove or root bifurcation extending 5 mm apically, the ratio of outer to inner dentin thickness, and the distribution of dentin thickness. ResultsΩ-shaped and U-shaped subgroups showed significant thinner minimum inner wall thickness than V-shaped subgroups at 2–5 mm from the starting point of the radicular groove in both C-shaped and non–C-shaped pulp floor categories (P < .05). The mesial roots of separated rooted MSMs showed significant thinner dentin than a non–C-shaped floor regarding minimum and mean inner thickness and mean outer thickness (P < .05). Teeth with a single canal had significantly thicker walls compared with the other 3 groups. ConclusionsIn MSMs, caution must be exercised, especially in the presence of Ω-shaped and U-shaped grooves in C-shaped roots and around the root furcation of separated roots.

Modeling test study on influence mechanism of large-span double-arch tunnels in proximity to existing tracks

This paper aims to study the influence mechanism of the large-span double-arch tunnels in proximity to existing tracks using 1 g model test. A novel non-contact device able to measure settlements automatically is developed to improve the test accuracy. During the test, the strata settlement, surrounding rock stress and track deformation induced by tunnel excavation are measured simultaneously. The results show that: (1) The excavation of the double-arch tunnel induces an asymmetric “W”-shaped horizontal surface settlement. The horizontal surface settlement near the centerline of the first excavation side is the largest. (2) The U-shaped groove structure exhibits an “M”-shaped deformation, while its structure produces bulges near the maximum horizontal surface settlement. (3) After excavation, the longitudinal surface settlement gradually decreases along the excavation direction, which causes the tilting or bottom voids of the U-shaped groove structure. The U-shaped groove structure may experience torsional shear damage under the load imposed by the train.

A PCF-SPR sensor for dual-polarization and wide refractive index detection range

In this paper, we design a novel H-shaped photonic crystal fiber (PCF) surface plasmon resonance (SPR) sensor, which is composed of a dual-sided U-shaped groove and an Ag–MoS2 coating. The proposed sensor exhibits an asymmetrical structure with birefringence, which provides a possible way to detect the refractive index (RI) of analytes with dual-polarization. Based on the finite element method (FEM) simulations, the influences of the structural parameters on the sensing performances are discussed. For y-polarization, the proposed sensor detects the changes of RI from 1.37 to 1.41 with a maximum wavelength sensitivity of 11,700 nm/RIU, while for x-polarization, RI changes from 1.29 to 1.35 with a maximum sensitivity of 7800 nm/RIU. Thus, a PCF-SPR sensor with dual-polarization and wide RI detection range is achieved, which holds significant promise for applications in biology, medicine, and food safety.

Research on flow, heat transfer, and solidification characteristics of flow distribution process in the twin-roll casting

Twin-roll casting (TRC) has seen a significant interest in recent years due to its short process, low energy consumption, and low emission. The research included both numerical simulation and experimental validation to examine the flow and temperature field distribution of the TRC process. The “U-shaped” buffer groove is identified as beneficial for maintaining a stable liquid level distribution in the molten pool through comparison with various flow distributor structures. The solidified billet shell dispersion around the casting roller in the molten pool is observed to undergo three distinct stages: stable growth, thickness fluctuation, and rapid growth. The inclusion of two circular side outlets, each with a diameter ranging from 8 to 10 mm, proves advantageous in maintaining a stable distribution of the liquid level within the molten pool. The edge outlet size ranges from 7 to 9 mm, and ensuring a U-shaped buffer groove width/flow distribution of 1.25–1.58 aids in enhancing casting stability.

Study on the segregation effect of pyrite and brass ore particles under combined pendulum vibration

This article uses a combined pendulum mode to study the segregation behavior of spherical particles of pyrite and brass ore with different diameters using the discrete element method. The numerical simulation program includes extensive oscillation tests on binary mixed particles of pyrite and brass ore spherical particles in different steel U-shaped oscillation grooves, different oscillation frequencies, oscillation angles, and particle sizes. The dispersion coefficient γ calculated from the Lacey mixing index M is used to characterize the segregation behavior of binary mixed particles and track the evolution of segregation. Numerical simulation shows that the oscillation frequency is 8 Hz, the oscillation amplitude is 14°, and the dispersion coefficient γ of the first group with protrusions reaches 0.8, which is about 19.4% higher than the dispersion coefficient 0.67 of the first group with light grooves. The dispersion coefficient γ of the second group with added protrusions reached 0.69, which is about 16.95% higher than the dispersion coefficient 0.59 of the second group when using a light groove. The addition of protrusions improved the particle layering effect. The oscillation amplitude is taken as 14°, and the oscillation frequencies are taken as 6Hz, 8Hz, 10Hz, and 12Hz, respectively. As the oscillation frequency increases, collisions between particles become more intense, and the dispersion coefficient γ between particles increases to a certain extent when it changes from 6Hz to 8Hz. Then, as the oscillation frequency increases, the dispersion coefficient γ decreases in severe fluctuations, and the particle stratification effect actually deteriorates. The oscillation frequency is taken as 8Hz, and the oscillation amplitude is taken as 10°, 14°, and 18°, respectively. After the oscillation amplitude increases to 14°, the dispersion coefficient γ of the particles remains basically stable, and changing the oscillation amplitude has almost no effect on the particle stratification effect. The oscillation frequency is 8Hz, and the oscillation amplitude is 14°. When adding protrusions to the steel U-shaped oscillation groove, the average relative errors of both experimental schemes are less than 1%, and the correlation coefficients are close to 1. The data points are very close to the 45° line. It indicates that the experimental data and simulation values have high consistency, and the discrete element method is feasible and reliable as a method for studying mineral particulate matter. The in-depth study of the separation and stratification behavior of ore particles under combined oscillation is of great scientific significance for the development of new combined vibration equipment.

River valley-inspired, high-sensitivity, and rapid-response capacitive three-dimensional force tactile sensor based on U-shaped groove structure

High-performance three-dimensional force (3D-force) tactile sensors with the capability of distinguishing normal and tangential forces in sync play a vital role in emerging wearable devices and smart electronics. And there is an urgent need for 3D-force tactile sensors with fast response and high flexibility. Herein, we design a capacitive 3D-force tactile sensors inspired by the U-shaped river valley surface morphology, which has satisfactory performance in terms of rapid response/recovery time (∼36 ms/∼ 36 ms), low hysteresis (4.2%), and high sensitivity (0.487 N−1). A theoretical model of general value for congener sensors is also proposed, obtaining a higher sensitivity through optimizing parameters. To verify the application potential of our device in actual scenarios, the robustness testing and gripping gamepad application were carried out. And it can recognize different motions in humans. Furthermore, principal component analysis is also conducted to demonstrate the distinct classification of different motions. Therefore, our work is eligible for the applications in wearable electronics, human–machine interaction, and soft intelligent robots.

Complementary hydrophobic interaction of the redox enzyme maturation protein NarJ with the signal peptide of the respiratory nitrate reductase NarG

In bacteria, NarJ plays an essential role as a redox enzyme maturation protein in the assembly of the nitrate reductase NarGHI by interacting with the N-terminal signal peptide of NarG to facilitate cofactor incorporation into NarG. The purpose of our research was to elucidate the exact mechanism of NarG signal peptide recognition by NarJ. We determined the structures of NarJ alone and in complex with the signal peptide of NarG via X-ray crystallography and verified the NarJ-NarG interaction through mutational, binding, and molecular dynamics simulation studies. NarJ adopts a curved α-helix bundle structure with a U-shaped hydrophobic groove on its concave side. This groove accommodates the signal peptide of NarG via a dual binding mode in which the left and right parts of the NarJ groove each interact with two consecutive hydrophobic residues from the N- and C-terminal regions of the NarG signal peptide, respectively, through shape and chemical complementarity. This binding is accompanied by unwinding of the helical structure of the NarG signal peptide and by stabilization of the NarG-binding loop of NarJ. We conclude that NarJ recognizes the NarG signal peptide through a complementary hydrophobic interaction mechanism that mediates a structural rearrangement.

Settlement rule of underpass railway model in shield tunnel and influence of nanomaterials on slurry performance during construction

In the shield tunnel, the phenomenon of structure penetration occurs frequently. Therefore, strict control of ground subsidence is imperative during the construction phase. In addition, other variables may be influence the performance of the slurry during the grouting procedure. This study aims to investigate and analyze the impact of nanomaterials on the properties of slurry used in construction, with the goal of determining the optimal construction route for the shield, ensuring quality construction of a U-shaped section, and meeting settlement control requirements. Firstly, the impact of double line spacing on the subsidence of U-shaped grooves is analyzed. Subsequently, the influence of common nanomaterials on slurry properties is examined through compressive strength testing. Among these nanomaterials, micro-silica powder exhibits the most significant enhancement effect on construction slurry performance with an optimal content of 5%. If the content of silica powder reaches 5%, the initial strength and later strength of the cement slurry will increase by 35% and 25% respectively, thereby promoting the enhanced performance of the slurry. In this study, the settlement of a U-shaped groove on the surface and subgrade is controlled by the settlement of a shield tunnel underpass railway model based on the distance between shield construction lines, providing valuable insights for future constructions with similar characteristics.

Effect of U-shaped stress relief groove on crack initiation life of fretting fatigue

A U-shaped stress relief groove was developed to enhance fretting fatigue strength. The effects of the groove on crack initiation location and life were evaluated using the finite element method and the critical plane method. The results demonstrated that by varying the geometry parameters of the groove, the crack initiation location was altered between the contact zone and the groove. When the damage in both the contact zone and the groove was comparable, the life of fretting crack initiation was increased by up to 3.5 times compared with that of the non-grooved specimen. These findings were expected to propose a potential strategy for enhancing the material's resistance to fretting fatigue by designing a groove near the contact zone and to provide insights into the development of components with improved fatigue resistance.

Experimental investigation on biaxial mechanical properties of laminated rock and floor heave mechanism of tunnel based on DIC

Floor heave at the bottom of a tunnel is a common defect during tunnel service. To study the deformation behavior and failure characteristics of the floor, laminated sandstone specimens with precracked U-shaped grooves were prepared, and a series of biaxial compression tests were carried out in the laboratory. Two typical floor structures of a tunnel (with and without inverts) and four lateral stress levels (σ2 = 0, 5, 10 and 15 MPa) were considered. The effects of lateral stress and inverted structure on the deformation and failure characteristics of the floor were investigated. The displacement, strain evolution and failure extent of the floor were analyzed based on the digital image correlation (DIC) technique. The testing results show that the stress concentration at the U-shaped grooves of the specimens can be effectively reduced by the inverted structure. The specimen with an invert can bear more axial deformation and axial stress than that without an invert. The V-shaped notch failure behavior occurred near the tunnel sidewalls for the specimen without an invert, and it occurred in the middle of the tunnel floor for the specimen with an invert. The failure intensity of the V-shaped notch was positively related to the lateral stresses. With the increasing of axial stress, the heave displacement at the tunnel floor gradually increased, while the settlement displacement of the sidewall showed a trend of first increasing and then decreasing. The tensile strain concentration area of the floor undergoes a process of increasing and then decreasing and finally transforms to compressive strain. The failure characteristics of the sandstone specimen observed in the laboratory tests are consistent with the phenomena in real tunnel engineering. In addition, the deformation and failure mechanism of the tunnel floor was analyzed. The key points for the treatment of tunnel floor heave are put forward based on the testing results.

Design and analysis of marine permanent magnet synchronous motor based on Motor-cad

In the marine electric propulsion system, the motor is an important part to ensure safe navigation, which should have the characteristics of low noise, low vibration, high performance protection level, etc. The permanent magnet synchronous motor (PMSM) has the advantages of rapid dynamic response, stable operation, strong overload capacity, high efficiency and small size, which is especially suitable for electric propulsion systems in marine environments. According to the performance requirements of marine motors and the permanent magnet synchronous motor structural characteristics, an electromagnetic design and simulation of a 120kW marine permanent magnet synchronous motor is completed in this paper. Meanwhile, the stator skewed slot is used to reduce the amplitude of harmonic distortion and the additional torque caused by tooth harmonic. At same time, the rotor structure with U-shaped magnetic steel groove is used to enhance the density of power and overload capacity of the motor, expand the scope of motor constant power operation effectively. A prototype with high efficiency, reliability and a small volume has been developed. According to the simulation results, the marine permanent magnet synchronous motor designed in this paper fully meets the design requirements.

Throttling characteristics prediction methodology for combined grooves in directional spool valves under variable flow rates

There is a contradiction between the calculation accuracy and cost when computing the pressure and flow rate. A throttling characteristics prediction methodology for directional spool valve was proposed to balance the contradiction. The throttling characteristics were represented by the flow-number, defined as the product of the flow coefficient and the orifice area, to reveal simultaneously the mapping relationships of the two versus the spool geometry, stroke and flow rate. The pressure and flow rate characteristics at different strokes were obtained through the computational fluid dynamic (CFD) simulations that were validated through bench testing. The concept of saturated flow-number theory was introduced to describe the effects of the flow rate on the flow-number. Models for the saturated flow-number and critical flow rate were established using the U-shape groove, a typical throttling structure, as an example to illustrate the effects of groove structure and opening. The throttling characteristics of the directional spool valve could be predicted by the flow-numbers of the combined grooves. The simulated and experimental results demonstrate that the prediction methodology achieves high calculation accuracy while incurring minimal costs. This methodology holds significant implications for the forward design of valve spool throttling structures.

Flatband λ-Ti3O5 towards extraordinary solar steam generation.

Solar steam interfacial evaporation represents a promising strategy for seawater desalination and wastewater purification owing to its environmentally friendly character1-3. To improve the solar-to-steam generation, most previous efforts havefocused on effectively harvesting solar energy over the full solar spectrum4-7. However, the importance of tuning joint densities of states in enhancing solar absorption of photothermal materials is less emphasized. Here we propose a route to greatly elevate joint densities of states by introducing a flat-band electronic structure. Our study reveals that metallic λ-Ti3O5 powders show a high solar absorptivity of 96.4% due to Ti-Ti dimer-induced flat bands around the Fermi level. By incorporating them into three-dimensional porous hydrogel-based evaporators with a conical cavity, an unprecedentedly high evaporation rate of roughly 6.09 kilograms per square metre per hour is achieved for 3.5 weight percent saline water under 1 sun of irradiation without salt precipitation. Fundamentally, the Ti-Ti dimers and U-shaped groove structure exposed on the λ-Ti3O5 surface facilitate the dissociation of adsorbed water molecules and benefit the interfacial water evaporation in the form of small clusters. The present work highlights the crucial roles of Ti-Ti dimer-induced flat bands in enchaining solar absorption and peculiar U-shaped grooves in promoting water dissociation, offering insights into access to cost-effective solar-to-steam generation.

Gold film effect on temperature compensation of a POF sensor with different structures.

In this paper, temperature compensation of plastic optical fiber (POF) is studied and gold absorbability is utilized. Gold film is modified on the surface of POF by magnetron sputtering. The temperature output characteristics of different structures such as ordinary (POF-N), side-polished (POF-SP), U-shaped (POF-U), and narrow groove structure (POF-NGS) are tested, and the effects of gold film thickness, polishing area, and sputtering sequence on the temperature output characteristics are also investigated. The power change of the sensor at different temperatures is recorded. The experimental results show that when the temperature is between 25°C and 50°C and the sputtering gold film thickness is 50nm, the temperature stabilities of POF-N, POF-U, POF-SP, and POF-NGS are 1.02µW/°C, 0.77µW/°C, 0.18µW/°C, and 0.35µW/°C, respectively. The compensation effect is enhanced as the gold film thickness increases. When the thickness is 100nm, the temperature stability of POF-NGS is 0.06µW/°C. The proposed temperature compensation method is competitive and straightforward.

A Slow Wave Folded Ridge HMSIW Using Spoof Surface Plasmon Polaritons Structure and Its Application in Coupler Design

In this article, a folded ridge half-mode substrate integrated waveguide (FRHMSIW) combined with the novel spoof surface plasmon polaritons (SSPP) is proposed to reduce both the lateral size and the longitudinal size. The SSPP structure consisting of sub-wavelength U-shaped grooves, metal patches and metal blind holes is loaded into the FRHMSIW. Firstly, the SSPP increases the effective permeability and permittivity in the waveguide, which can decrease the cutoff frequency and hence reduce the lateral size. Secondly, the SSPP has slow-wave effect, which can reduce the longitudinal size of the waveguide. Analytical formulas of the effective permeability and permittivity are derived based on anisotropic media theory, which are verified by comparing the calculation results with full wave simulation results. According to the derived analytical formulas, a prototype of the proposed FRHMSIW-SSPP waveguide is designed and fabricated using the PCB process. The measurement results show that the proposed waveguide reduces lateral width by 78.7% and the longitudinal dimension by more than 74% compared with the classical SIW with the same cutoff frequency. Subsequently, the FRHMSIW-SSPP structure is applied to design a 3-dB coupler. Results show that the coupler based on the FRHMSIW-SSPP can reduce the surface area by 92.5% compared with the classical SIW coupler.

Research on Dynamic Modeling Measurement and Control of Cable Traction Devices for Electro-Optical Unmanned Systems

In order to realize the high-precision variable direction cable control of the electro-optical unmanned system in non-electromagnetic remote control, a cable traction device measurement and control with characteristics of variable direction traction, rapid installation, and lightweight portability were proposed. Fan-shaped connect rod mechanism and U-shaped groove fixed pulley group were added to it, which can realize multi-direction traction without derailment on the basis of the cable limit and alleviate the cable fracture caused by mechanical wear. Introducing Euler transformation and analyzing the dynamics of the cable, the whole operation process, and the tension detection model was established. A Kalman Filter traction planning method was proposed to solve the problems of inertia delay and emergency stop of the unmanned vehicles after a sudden direction change. In order to verify the effectiveness, an experimental platform for the cable traction system of a 50kg wheeled and 150kg tracked unmanned system was built for simulation and experimental testing. The results show that the cable system has good dynamic variable traction, which can meet the multi-terrain control ability of an electro-optical unmanned system in a complex field environment.

Initial stages of growth of the GaN(11\=22) layer on a nano-structured Si(113) substrate

Scanning electron microscopy was used to study of the initial stages of the formation of a semipolar GaN(1122) layer during Metalorganic Chemical Vapor Deposition on Si(113) substrates, on the surface of which U-shaped grooves with element sizes &amp;lt;100 nm (NP-Si(113)) were formed. It was found that NP-Si(113) substrates with a buffer AlN layer stimulate the formation of islands faceted by the planes m-GaN, c-GaN. It is shown that there is a predominant growth of the m-GaN facet in comparison with c-GaN.The experimental results correspond to the Gibbs--Curie--Wolff selection principle, but taking into account elastic stresses in the c-GaN plane. Keywords: semipolar gallium nitride, nano-structured substrate, silicon.

Characteristics Analysis of the Pilot-Operated Proportional Directional Valve by Experimental and Numerical Investigation

The main valve spool structure of the pilot-operated proportional directional valve is diverse and has a direct impact on the flow field. To improve the valve’s performance, this work studied the characteristics of four types of spool structures with the following throttling groove arrangements: no throttling groove, a U-shaped groove, a triangle groove, and a combined groove. This study analyzed the flow field simulation of four spool structures under the same opening degree and different pressures to study the flow field cavitation characteristics and pressure distribution in the valve. According to the simulation results, the necessity of opening throttling grooves for the pilot proportional directional valve and the advantages of combined grooves over U-shaped and triangular grooves were verified. Then, the proportional valve with a combined groove structure was simulated and analyzed to study its throttling characteristics, steady flow characteristics, and flow and load differential pressure characteristics, and further explore the advantages of a combined groove. Finally, the experimental results are compared with the simulation results, which can provide a theoretical reference for the selection of the throttle groove of the proportional valve and the structural design of the slide valve.

Flow Field Analysis of Lubricating Air Film in Aerostatic Restrictor with Double U-Shaped Pressure-Equalizing Grooves

Flow Field Analysis of Lubricating Air Film in Aerostatic Restrictor with Double U-Shaped Pressure-Equalizing Grooves