Grooving corrosion is a major form of corrosion and is prone to occur when high-frequency electric resistance welded （HFW） pipes are being used. Therefore,grooving corrosion is one of the performance indexes of HFW ...Grooving corrosion is a major form of corrosion and is prone to occur when high-frequency electric resistance welded （HFW） pipes are being used. Therefore,grooving corrosion is one of the performance indexes of HFW products. Grooving corrosion usually occurs along the welding fusion line, resulting in one or more corrosion grooves. The main factors affecting grooving corrosion include the contents of alloying elements and impurities （especially sulphur） in the steel,the microstructure of the welds and the steel substrate, welding parameters and the service environment as well. In this study, the existing methods for assessing grooving corrosion were systematically reviewed, improvements and new methods were proposed and developed to overcome the shortcomings of the existing methods, such as inaccuracy and excessive research time. By comparison with the existing methods, the operational procedures and the characteristics of the new methods are introduced, and issues regarding the behavior of grooving corrosion and their assessment methods, which both need further research,are discussed in this study.展开更多
Grooving method can restrain the deformation and destruction of surrounding rock by transferring the maximum stress to deep rock,bringing about the effective control for floor heave in soft rock roadway. Based on this...Grooving method can restrain the deformation and destruction of surrounding rock by transferring the maximum stress to deep rock,bringing about the effective control for floor heave in soft rock roadway. Based on this important effect,and to discuss the relationship between cutting parameters and pressurerelief effect,this paper carried out a numerical simulation of grooving along bottom slab and two sides of gateway with finite difference software FLAC^（2D）.The results show that the control effect on floor heave in soft rock tunnel can be improved by selecting appropriate cutting parameters.Appropriately increasing the crevice depth in the middle of the floor can improve the stress state of bottom slab by stress transfer. So the floor heave can be more effectively controlled.To lengthen the crevice in the corners of roadway can simultaneously transfer the maximum stresses of bottom slab and two sides to deep rock,and promote the pressure-relief effect.Extending the crevice length and crevice width on both sides within a certain range can decrease the stress concentration in the corners of roadway,and reduce the deformation of two sides.The cutting position beneficial to restrain the floor heave is close to the bottom slab.展开更多
In order to investigate the CO2 corrosion behavior and the grooving corrosion susceptibility of electric resistance welded tubes of the Q125 grade, the high temperature and high pressure autoclave was employed to cond...In order to investigate the CO2 corrosion behavior and the grooving corrosion susceptibility of electric resistance welded tubes of the Q125 grade, the high temperature and high pressure autoclave was employed to conduct CO2 corrosion experiments for the welded joint. The mechanisms of grooving corrosion and the factors influencing grooving corrosion susceptibility were identified by electrochemical measurement, microstructure observation, residual stress examination, micro-region composition and orientation analysis. The CO2 corrosion results show that the corrosion resistance of the base material is the best, followed by heataffected zone and the welded seam is the worst. The grooving corrosion occurred in the welded seam, and the grooving corrosion susceptibility of welded seam is relativity high. The dominated reason for the grooving corrosion of the electric resistance welded joint is the notable inclusions consisting of MnS as the main content in the welded seam. The proportion of high-angle grain boundaries in the welding zone is higher than that of base metal and the heat affected zone, which plays an important role in the corrosion behavior of the welded seam.展开更多
Although it is usually latent on citrus, apple, and pear, apple stem grooving virus(ASGV) poses a great risk to many sensitive cultivars. Since severe leaf yellow mottle mosaic(LYMM) symptoms have been observed on Hua...Although it is usually latent on citrus, apple, and pear, apple stem grooving virus(ASGV) poses a great risk to many sensitive cultivars. Since severe leaf yellow mottle mosaic(LYMM) symptoms have been observed on Huangjinmiyou(HJY) pummelos(Citrus grandis cv. Huangjinmiyou), a commercial variety that is widely cultivated in South China, high throughput sequencing(HTS) was used to find potential pathogens and only three divergent ASGV variants were identified. The three ASGV variants shared 81.03–82.34% genome-wide pairwise identities with each other, and were separately closest to other ASGV variants from different hosts and/or geographical regions, as indicated by viral phylogenies. However, these new variants may have developed from viral interstrain interactions, based on the results of recombination analysis. A large-scale survey using reverse transcription-PCR(RT-PCR) protocols designed for the three ASGV variants revealed a high incidence(92.7–100%) of ASGV in symptomatic HJY trees from 11 major citrusproducing regions in China. None of ASGV were detected in asymptomatic trees. Temperature treatments applied to the symptomatic HJY plants showed that ASGV is sensitive to high temperatures(30–35°C), at which not only the plants recovered, but also the viruses were not detected by RT-PCR, while at low temperatures(20–24°C), both the symptoms and viruses remained detectable. These data show that ASGV is associated with the LYMM disease prevalent on HJY in China, and this is the significant basis especially of taking appropriate measures timely to manage the disease.展开更多
BACKGROUND Groove pancreatitis(GP)is a rare focal chronic pancreatitis of the pancreaticoduodenal groove that is usually diagnosed in chronic alcoholics.However,it is often difficult to differentiate from pancreatic o...BACKGROUND Groove pancreatitis(GP)is a rare focal chronic pancreatitis of the pancreaticoduodenal groove that is usually diagnosed in chronic alcoholics.However,it is often difficult to differentiate from pancreatic or periampullary cancers.In this study,we report a case of GP with the rare symptom of severe gastric outlet obstruction.CASE SUMMARY A 68-year-old man presented to our institution with severe gastric outlet obstruction accompanied by vomiting persisted for 3 days,severe electrolyte imbalance,and altered mental status with cardiac arrest.Differential diagnosis of cancers of the ampulla of Vater or duodenum was difficult due to discordant findings from preoperative imaging and an endoscopic biopsy of the lesion.In addition,the gastric outlet obstruction did not improve with conservative treatment;therefore,pancreatoduodenectomy was performed.Postoperatively,the histological findings revealed multiple cystic lesions in the duodenal wall that were collectively diagnosed as GP.The patient underwent a follow-up 3 years postoperatively and was found to have no postoperative sequelae.CONCLUSION In this case of GP,pancreatoduodenectomy safely treated severe gastric outlet obstruction when a cancer diagnosis could not be excluded.展开更多
Taking the NACA0012 airfoil as the research object,the bio-inspired herringbone groove array,a new passive control method,is applied to relieve the flow separation under the large angle-of-attack conditions,and its ef...Taking the NACA0012 airfoil as the research object,the bio-inspired herringbone groove array,a new passive control method,is applied to relieve the flow separation under the large angle-of-attack conditions,and its effectiveness and mechanism in delaying airfoil stall are investigated by numerical simulations.The herringbone groove array is placed on the airfoil's upper surface near the trailing edge,and the effects of groove depth and yaw angle on the control effect are investigated.The results demonstrate that different designs of herringbone groove array can effectively broaden the stable operating range of the airfoil,and the application of herringbone groove array with a depth of only 0.00135 times the chord length and a yaw angle of 45°can result in a28.57%increase in the stable operating range.The flow details indicate that a pair of induced vortices with the same strength and opposite direction are formed near the converging line under the combined action of the accumulation effect of small-scale vortices in the grooves and the spanwise migration flow above the grooves.The induced vortices increase the mixing between the main flow and the boundary layer,allowing the boundary layer to gain sufficient energy to withstand the adverse pressure gradient at high angles of attack,effectively delaying airfoil stall.展开更多
Grooved tuning forks with hierarchical structures have become some of the most widely used piezoelectric quartz microelectromechanical system devices;however,fabricating these devices requires multi-step processes due...Grooved tuning forks with hierarchical structures have become some of the most widely used piezoelectric quartz microelectromechanical system devices;however,fabricating these devices requires multi-step processes due to the complexity of etching of quartz,particularly in specific orientations of the crystal lattice.This paper proposes a one-step fabrication strategy that can form a complete hierarchical structure with only a single etching process using novel lithography patterns.The core principle of this strategy is based on the effect of the size of the groove patterns on quartz etching,whereby trenches of varying depths can be created in a fixed etching time by adjusting the width of the hard mask.Specifically,the device outline and grooved structure can be completed using a seamlessly designed etching pattern and optimized time.Furthermore,the etching structure itself influences the etching results.It was found that dividing a wide trench by including a wall to separate it into two narrow trenches significantly reduces the etching rate,allowing for predictable tuning of the etching rate for wider grooves.This effectively increases the usability and flexibility of the one-step strategy.This was applied to the manufacture of an ultra-small quartz grooved tuning fork resonator with a frequency of 32.768 kHz in a single step,increasing production efficiency by almost 45%and reducing costs by almost 30%compared to current methods.This has great potential for improving the productivity of grooved tuning fork devices.It can also be extended to the fabrication of other quartz crystal devices requiring hierarchical structures.展开更多
Repairing the Ni-based superalloy component remains challenging due to the limited understanding of the role of the defect’s morphology on microstructure and related deformation responses.To address this issue,GH4099...Repairing the Ni-based superalloy component remains challenging due to the limited understanding of the role of the defect’s morphology on microstructure and related deformation responses.To address this issue,GH4099 Ni-based superalloy plate with U-shaped and V-shaped grooves was prepared and repaired by laser-directed energy deposition method using GH4099 powders.Both grooves exhibit three similar regions at the repaired interphase,which are the base metal region with equiaxed grains,repaired region with columnar or elongated equiaxed grains,and a transition region in between.High-temperature gradient in the repaired region induced a high density of substructures,and the repaired region in U-shaped grooves has an even higher temperature gradient due to fewer passes of the melted metal,which induces more metallic carbides in the subgrain boundaries and improves the tensile strength of the repaired samples.However,due to the steep side walls,local vortex might form at the bottom corner of the U-shaped groove,leaving macroscale holes and micro-cracks there.Such defects will decrease the alloy’s ductility.The relationship among groove morphology-macro-and microstructure-mechanical properties is then established,which suggesting the preferred V-shaped groove considering the flatter sidewall and more passes induced near equilibrium microstructure.展开更多
Metal micro-nano grating has received much attention due to its ability to provide high-efficiency light absorption.However,the current research scales of these metal gratings are focused on subwavelengths,and little ...Metal micro-nano grating has received much attention due to its ability to provide high-efficiency light absorption.However,the current research scales of these metal gratings are focused on subwavelengths,and little attention has been paid to the absorption properties of metal gratings at other scales.We investigate the absorption properties of metal gratings based on surface plasmon resonance(SPR)across the scales from superwavelength to subwavelength.Under grazing incidence,we observe continuous strong absorption phenomena from superwavelength to subwavelength Al triangle-groove gratings(TGGs).Perfect absorption is realized at the subwavelength scale,whereas the maximum absorption at all other scales exceeds 74%.The electric field distribution gives the mechanism of the strong absorption phenomenon attributed to SPR on the surface of Al TGGs at different scales.In particular,subwavelength Al TGGs have perfectly symmetric absorption properties for different blaze angles,and the symmetry is gradually broken as the grating period’s scale increases.Furthermore,taking Al gratings with varying groove shapes for example,we extend the equivalence rule of grating grooves to subwavelength from near-wavelength and explain the symmetric absorption properties in Al TGGs.We unify the research of metal grating absorbers outside the subwavelength scale to a certain extent,and these findings also open new perspectives for the design of metal gratings in the future.展开更多
The aim of the study is to investigate the impact of the buffer groove structure on the pressure of continuous rotation electro-hydraulic servo motor.The mathematical model of the motor valve plate with triangular gro...The aim of the study is to investigate the impact of the buffer groove structure on the pressure of continuous rotation electro-hydraulic servo motor.The mathematical model of the motor valve plate with triangular groove and U-groove structure is established firstly,and the structure size of the two buffer grooves with better pressure drop effect is obtained by Matlab.Secondly,an established pressure gradient model is developed for the sealed canisters for electric motors using a combined groove structure.The bird swarm optimization algorithm is used to obtain the optimal dimensions for the combined depth and angle of the pressure groove.The flow field in the motor seal chamber is simulated and calculated by Fluent.This study compared the pressure field distributions in the motors sealing chamber using triangular and combined groove structures.It investigated the combined grooves effect on the pressure impact during the commutation of a continuously rotating electro-hydraulic servo motor.It is found that the combined groove structure has a positive impact on reducing the pressure impact.The results indicate that the combined groove structure significantly enhances the efficiency of mitigating pressure shocks when the motor switches between high-and low-pressure chambers.展开更多
Metamorphic mechanism has the advantages of variable topology and variable degrees of freedom, which can realize the requirements of multi-conditions and multi-tasks, and has a good application prospect. The configura...Metamorphic mechanism has the advantages of variable topology and variable degrees of freedom, which can realize the requirements of multi-conditions and multi-tasks, and has a good application prospect. The configuration transformation is prominent feature of the metamorphic mechanism. The number of constraints or properties of the kinematic pairs provided by the metamorphic kinematic pairs will change under certain conditions, its dynamic performance is much more complex than that of traditional kinematic pairs with immutable constraints. However, the clearance model about traditional kinematic pairs with immutable constraints established by long-term research is difficult to be directly applied to the metachromatic kinematic pairs. Referring to the experience of the traditional kinematic pairs with immutable constraints, the continuous contact model of Metamorphic Groove pin pair with clearance is established. According to the traditional continuous contact model of the kinematic pairs with immutable constraints, the forces between the elements of kinematic pair of the mechanism with clearance and the ideal mechanism without clearance are regarded as the same, and the inertia force and inertia moment of the components are also calculated according to the acceleration of the ideal mechanism. The clearance is regarded as a massless virtual bar with length r. For the rotating pair part, the massless virtual bar length r is the difference between the radius of the shaft and the hole, and for the sliding pair part, the massless virtual bar length r is half of the difference between the height of the slider and the guide groove. According to the new mechanism without gap after adding the imaginary bar, kinetic energy and potential energy of the system are calculated for the two configurations of mechanism with metamorphic Groove pin pair with clearance. The kinetic energy and potential energy of the system are calculated according to the new mechanism without clearance after adding the massless virtual bar. The kinetic energy, potential energy and generalized force are substituted into the Lagrangian equation to obtain the motion equation of the metamorphic mechanism, which lays the foundation for the dynamic performance study of the mechanism with metamorphic groove pin pair with clearance.展开更多
Hydrogen separation through oxygen transport membranes(OTMs)has attracted much attention.Asymmetric membranes with thin dense layers provide low bulk diffusion resistances and high overall hydrogen separation performa...Hydrogen separation through oxygen transport membranes(OTMs)has attracted much attention.Asymmetric membranes with thin dense layers provide low bulk diffusion resistances and high overall hydrogen separation performances.However,the resistance in the porous support layer(PSL)limits the overall separation performance significantly.Engineering the structure of the PSL is an appropriate way to enable fast gas transport and increase the separation performance.There is no relevant research on studying the influence of the PSL on hydrogen separation performance so far.Herein,we prepared Ce0.85Sm0.15O1.925–Sm0.6Sr0.4Cr0.3Fe0.7O3-δ(SDC-SSCF)asymmetric membranes with straight grooves in PSL by tape-casting and laser grooving.A~30%improvement in the hydrogen separation rate was achieved by grooving in the PSLs.It indicates that the grooves may reduce the concentration polarization resistance in PSL for the hydrogen separation process.This work provides a straight evidence on optimizing the structures of PSL for improving the hydrogen separation performance of the membrane reactors.展开更多
Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while exte...Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while extending their lifespan.This paper explores the application of laser-assisted water jet technology in constructing high-quality micro-trap structures on 316L stainless steel,a key material in accelerator manufacturing.The study systematically analyzes the impact of various parameters such as laser repetition frequency,pulse duration,average power,water jet pressure,repeat times,nozzle offset,focal position,offset distance between grooves,and processing speed on the surface morphology of stainless steel.The findings reveal that micro-groove depth increases with higher laser power but decreases with increasing water jet pressure and processing speed.Interestingly,repeat times have minimal effect on depth.On the other hand,micro-groove width increases with higher laser power and repeat times but decreases with processing speed.By optimizing these parameters,the researchers achieved high-quality pound sign-shaped trap structure with consistent dimensions.We tested the secondary electron emission coefficient of the"well"structure.The coefficient is reduced by 0.5 at most compared to before processing,effectively suppressing secondary electron emission.These results offer indispensable insights for the fabrication of micro-trap structures on material surfaces.Laser-assisted water jet technology demonstrates considerable potential in mitigating SEE on metal surfaces.展开更多
Thin-walled metal parts with functional micro-featured surface have broad application prospects in the fields of resistance reduction,noise reduction,etc.In this study,a novel micro-rolling&incremental sheet formi...Thin-walled metal parts with functional micro-featured surface have broad application prospects in the fields of resistance reduction,noise reduction,etc.In this study,a novel micro-rolling&incremental sheet forming hybrid process(μR-ISF)is proposed to fabricate thin-walled metal parts with microgroove arrays.An analytical model which relates the rolling force and microgroove depth in the micro-rolling stage was first established.Then,the formation mechanism of microgroove morphology during both micro-rolling stage and macro-shape forming stage are investigated.After the micro-grooved sheet being incrementally formed,a significant reduction(between 21%to nearly 60%)is occurred in the depth of both transverse and longitudinal grooves compared to the flat sheet.Meanwhile,the width of transverse grooves decreases slightly by about 10%on average,while the width of longitudinal microgrooves increases significantly by more than 30%on average.After micro-rolling,85°{102}tensile twins appear on the micro-grooved sheet and the percentage of 65°{112}compressive twins increases.After incremental forming,the percentage of low-angle grain boundaries and the density of geometrically necessary dislocations in the formed part increase significantly,and the grain size distribution becomes more uniform.The present work provides a new strategy for the fabrication of 3D metal thin-walled components with surface micro-features.展开更多
It is well known that femtosecond laser pulses can easily spontaneously induce deep-subwavelength periodic surface structures on transparent dielectrics but not on non-transparent semiconductors.Nevertheless,in this s...It is well known that femtosecond laser pulses can easily spontaneously induce deep-subwavelength periodic surface structures on transparent dielectrics but not on non-transparent semiconductors.Nevertheless,in this study,we demonstrate that using high-numerical-aperture 800 nm femtosecond laser direct writing with controlled pulse energy and scanning speed in the near-damage-threshold regime,polarization-dependent deep-subwavelength single grooves with linewidths of~180 nm can be controllably prepared on Si.Generally,the single-groove linewidth increases slightly with increase in the pulse energy and decrease in the scanning speed,whereas the single-groove depth significantly increases from~300 nm to~600 nm with decrease in the scanning speed,or even to over 1μm with multi-processing,indicating the characteristics of transverse clamping and longitudinal growth of such deep-subwavelength single grooves.Energy dispersive spectroscopy composition analysis of the near-groove region confirms that single-groove formation tends to be an ultrafast,non-thermal ablation process,and the oxidized deposits near the grooves are easy to clean up.Furthermore,the results,showing both the strong dependence of groove orientation on laser polarization and the occurrence of double-groove structures due to the interference of pre-formed orthogonal grooves,indicate that the extraordinary field enhancement of strong polarization sensitivity in the deep-subwavelength groove plays an important role in single-groove growth with high stability and collimation.展开更多
Airport pavement engineers are required to maintain pavement skid resistance at a satisfactory level to minimize the likelihood of runway excursions.Runway overruns and skidding along rapid exit taxiways are the two m...Airport pavement engineers are required to maintain pavement skid resistance at a satisfactory level to minimize the likelihood of runway excursions.Runway overruns and skidding along rapid exit taxiways are the two most frequently encountered forms of runway excursion accidents.Currently only empirical statistical models based on historical accident data are available to predict the risks of runway excursions.All such models fail to account for the impacts of pavement skid resistance properties.Mechanistic solutions of the tire-fluid-pavement interaction problem are now available,and the impacts of pavement skid resistance properties on runway excursion accidents can now be quantitatively evaluated.This paper presents a state-of-the-art review of recent research developments on the topic.It highlights the Concept of Pavement Skid Resistance State which provides(i)a logical theoretical framework for mechanistic representation of tire-pavement skid resistance,and(ii)an approach for modeling of the physical process of aircraft skidding and hydroplaning.Next,runway excursion risk prediction models are presented for risk evaluation of aircraft hydroplaning,runway overruns,and rapid exit taxiway excursions.Also examined in detail mechanistically is the effectiveness of pavement grooving in reducing the risks of runway excursions.The review clearly confirms the capability of mechanistic approach in analyzing runway excursions for the purpose of enhancing safe aircraft operations on airport runways.展开更多
Traditional descriptions of liver anatomy refer to a smooth,convex surface contacting the diaphragm.Surface depressions are recognized anatomic variants.There are many theories to explain the cause of the depressions....Traditional descriptions of liver anatomy refer to a smooth,convex surface contacting the diaphragm.Surface depressions are recognized anatomic variants.There are many theories to explain the cause of the depressions.We discuss the theory that these are caused by hypertrophic muscular bands in the diaphragm.展开更多
The dynamics model of a 2-degree-of-freedom deep groove ball bearing is established by incorporating the raceway surface waviness model comprising multiple sinusoidal functions superposition.The model is solved using ...The dynamics model of a 2-degree-of-freedom deep groove ball bearing is established by incorporating the raceway surface waviness model comprising multiple sinusoidal functions superposition.The model is solved using the fourth-order Runge-Kutta method to obtain the vibration characteristics including displacement,velocity,acceleration,and frequency of the bearing.Validation of the model is accomplished through comparison with theoretical vibration frequencies.The influence of the amplitude of waviness of the inner and outer ring raceway surfaces of deep groove ball bearings on the vibration displacement,peak-to-peak vibration displacement and root-mean-square vibration acceleration is analyzed,and the results show that as the amplitude of the inner and outer ring raceway surfaces waviness increases,all the vibration characteristic indexes increase,indicating that the vibration amplitude of the bearings as well as the energy of the waviness-induced shock waveforms increase with the increase of the amplitude of the waviness.展开更多
Objective: To explore the application value of disposable grooved negative pressure drainage tubes in rib fracture incision and internal fixation. Methods: Seventy-five patients admitted to our Department of Trauma Su...Objective: To explore the application value of disposable grooved negative pressure drainage tubes in rib fracture incision and internal fixation. Methods: Seventy-five patients admitted to our Department of Trauma Surgery from June 2022 to April 2024 who underwent rib fracture osteotomy and internal fixation were selected. According to the types of drainage tubes left in the patients after the operation, they were divided into the observation group (35 cases who were left with disposable grooved negative pressure drainage tubes) and the control group (40 cases who were left with closed silicone thoracic drainage tubes). Comparison of chest drainage, pain, postoperative complications, secondary chest penetration rate, drain placement time, hospitalization time, and treatment costs were compared between the two groups. Results: The total postoperative chest drainage volume of the observation group was less than that of the control group (P < 0.05);the degree of pain, the incidence of postoperative complications, and the rate of secondary chest puncture in the observation group were lower than that of the control group three days after the operation (P < 0.05);and the time of drain placement in the observation group was shorter than that of the control group (P < 0.05). Conclusion: The application of disposable grooved negative pressure drainage tubes in rib fracture incision and internal fixation can significantly improve patients’ postoperative pain and discomfort, reduce complications, lower the rate of secondary chest penetration, promote patients’ postoperative recovery, decrease the amount of postoperative chest drainage, and shorten the time of drain placement, which is worthy of clinical promotion and application.展开更多
A novel grooving method for eliminating the bending-induced collapse of hexagonal honeycombs has been proposed,which lies in determining the appropriate grooving parameters,including the grooving spacing,angle,and dep...A novel grooving method for eliminating the bending-induced collapse of hexagonal honeycombs has been proposed,which lies in determining the appropriate grooving parameters,including the grooving spacing,angle,and depth.To this end,a framework built upon the experiment-based,machine learning approach for grooving parameters prediction was presented.The continuously grooved honeycomb bending experiments with various radii,honeycomb types,and thicknesses were carried out,and then the deformation level of honeycombs at different grooving spacing was quantitatively evaluated.A criterion for determining the grooving spacing was proposed by setting an appropriate tolerance for the out-of-plane compression strength.It was found that as the curvature increases,the grooving spacing increases due to the deformation level of honeycombs being more severe at a smaller bending radius.Besides,the grooving spacing drops as the honeycomb thickness increases,and the cell size has a positive effect on the grooving spacing,while the relative density has a negative effect on the grooving spacing.Furthermore,the data-driven Gaussian Process(GP)was trained from the collected data to predict the grooving spacing efficiently.The grooving angle and depth were calculated using the geometrical relationship of honeycombs before and after bending.Finally,the grooving parameters design and verification of a honeycomb sandwich fairing part were conducted based on the proposed grooving method.展开更多
文摘Grooving corrosion is a major form of corrosion and is prone to occur when high-frequency electric resistance welded （HFW） pipes are being used. Therefore,grooving corrosion is one of the performance indexes of HFW products. Grooving corrosion usually occurs along the welding fusion line, resulting in one or more corrosion grooves. The main factors affecting grooving corrosion include the contents of alloying elements and impurities （especially sulphur） in the steel,the microstructure of the welds and the steel substrate, welding parameters and the service environment as well. In this study, the existing methods for assessing grooving corrosion were systematically reviewed, improvements and new methods were proposed and developed to overcome the shortcomings of the existing methods, such as inaccuracy and excessive research time. By comparison with the existing methods, the operational procedures and the characteristics of the new methods are introduced, and issues regarding the behavior of grooving corrosion and their assessment methods, which both need further research,are discussed in this study.
文摘Grooving method can restrain the deformation and destruction of surrounding rock by transferring the maximum stress to deep rock,bringing about the effective control for floor heave in soft rock roadway. Based on this important effect,and to discuss the relationship between cutting parameters and pressurerelief effect,this paper carried out a numerical simulation of grooving along bottom slab and two sides of gateway with finite difference software FLAC^（2D）.The results show that the control effect on floor heave in soft rock tunnel can be improved by selecting appropriate cutting parameters.Appropriately increasing the crevice depth in the middle of the floor can improve the stress state of bottom slab by stress transfer. So the floor heave can be more effectively controlled.To lengthen the crevice in the corners of roadway can simultaneously transfer the maximum stresses of bottom slab and two sides to deep rock,and promote the pressure-relief effect.Extending the crevice length and crevice width on both sides within a certain range can decrease the stress concentration in the corners of roadway,and reduce the deformation of two sides.The cutting position beneficial to restrain the floor heave is close to the bottom slab.
文摘In order to investigate the CO2 corrosion behavior and the grooving corrosion susceptibility of electric resistance welded tubes of the Q125 grade, the high temperature and high pressure autoclave was employed to conduct CO2 corrosion experiments for the welded joint. The mechanisms of grooving corrosion and the factors influencing grooving corrosion susceptibility were identified by electrochemical measurement, microstructure observation, residual stress examination, micro-region composition and orientation analysis. The CO2 corrosion results show that the corrosion resistance of the base material is the best, followed by heataffected zone and the welded seam is the worst. The grooving corrosion occurred in the welded seam, and the grooving corrosion susceptibility of welded seam is relativity high. The dominated reason for the grooving corrosion of the electric resistance welded joint is the notable inclusions consisting of MnS as the main content in the welded seam. The proportion of high-angle grain boundaries in the welding zone is higher than that of base metal and the heat affected zone, which plays an important role in the corrosion behavior of the welded seam.
基金supported by the National Key R&D Program of China(2019YFD1001800)the National Natural Science Foundation of China(32072389)+1 种基金the Innovation Program for Chongqing’s Overseas Returnees(cx2019013)111 Project(B18044)from Ministry of Education(China)。
文摘Although it is usually latent on citrus, apple, and pear, apple stem grooving virus(ASGV) poses a great risk to many sensitive cultivars. Since severe leaf yellow mottle mosaic(LYMM) symptoms have been observed on Huangjinmiyou(HJY) pummelos(Citrus grandis cv. Huangjinmiyou), a commercial variety that is widely cultivated in South China, high throughput sequencing(HTS) was used to find potential pathogens and only three divergent ASGV variants were identified. The three ASGV variants shared 81.03–82.34% genome-wide pairwise identities with each other, and were separately closest to other ASGV variants from different hosts and/or geographical regions, as indicated by viral phylogenies. However, these new variants may have developed from viral interstrain interactions, based on the results of recombination analysis. A large-scale survey using reverse transcription-PCR(RT-PCR) protocols designed for the three ASGV variants revealed a high incidence(92.7–100%) of ASGV in symptomatic HJY trees from 11 major citrusproducing regions in China. None of ASGV were detected in asymptomatic trees. Temperature treatments applied to the symptomatic HJY plants showed that ASGV is sensitive to high temperatures(30–35°C), at which not only the plants recovered, but also the viruses were not detected by RT-PCR, while at low temperatures(20–24°C), both the symptoms and viruses remained detectable. These data show that ASGV is associated with the LYMM disease prevalent on HJY in China, and this is the significant basis especially of taking appropriate measures timely to manage the disease.
文摘BACKGROUND Groove pancreatitis(GP)is a rare focal chronic pancreatitis of the pancreaticoduodenal groove that is usually diagnosed in chronic alcoholics.However,it is often difficult to differentiate from pancreatic or periampullary cancers.In this study,we report a case of GP with the rare symptom of severe gastric outlet obstruction.CASE SUMMARY A 68-year-old man presented to our institution with severe gastric outlet obstruction accompanied by vomiting persisted for 3 days,severe electrolyte imbalance,and altered mental status with cardiac arrest.Differential diagnosis of cancers of the ampulla of Vater or duodenum was difficult due to discordant findings from preoperative imaging and an endoscopic biopsy of the lesion.In addition,the gastric outlet obstruction did not improve with conservative treatment;therefore,pancreatoduodenectomy was performed.Postoperatively,the histological findings revealed multiple cystic lesions in the duodenal wall that were collectively diagnosed as GP.The patient underwent a follow-up 3 years postoperatively and was found to have no postoperative sequelae.CONCLUSION In this case of GP,pancreatoduodenectomy safely treated severe gastric outlet obstruction when a cancer diagnosis could not be excluded.
基金supported by the National Natural Science Foundation of China(No.52306058)the Natural Science Foundation of Tianjin Municipal Science and Technology Commission,China(No.22JCQNJC00050)。
文摘Taking the NACA0012 airfoil as the research object,the bio-inspired herringbone groove array,a new passive control method,is applied to relieve the flow separation under the large angle-of-attack conditions,and its effectiveness and mechanism in delaying airfoil stall are investigated by numerical simulations.The herringbone groove array is placed on the airfoil's upper surface near the trailing edge,and the effects of groove depth and yaw angle on the control effect are investigated.The results demonstrate that different designs of herringbone groove array can effectively broaden the stable operating range of the airfoil,and the application of herringbone groove array with a depth of only 0.00135 times the chord length and a yaw angle of 45°can result in a28.57%increase in the stable operating range.The flow details indicate that a pair of induced vortices with the same strength and opposite direction are formed near the converging line under the combined action of the accumulation effect of small-scale vortices in the grooves and the spanwise migration flow above the grooves.The induced vortices increase the mixing between the main flow and the boundary layer,allowing the boundary layer to gain sufficient energy to withstand the adverse pressure gradient at high angles of attack,effectively delaying airfoil stall.
文摘Grooved tuning forks with hierarchical structures have become some of the most widely used piezoelectric quartz microelectromechanical system devices;however,fabricating these devices requires multi-step processes due to the complexity of etching of quartz,particularly in specific orientations of the crystal lattice.This paper proposes a one-step fabrication strategy that can form a complete hierarchical structure with only a single etching process using novel lithography patterns.The core principle of this strategy is based on the effect of the size of the groove patterns on quartz etching,whereby trenches of varying depths can be created in a fixed etching time by adjusting the width of the hard mask.Specifically,the device outline and grooved structure can be completed using a seamlessly designed etching pattern and optimized time.Furthermore,the etching structure itself influences the etching results.It was found that dividing a wide trench by including a wall to separate it into two narrow trenches significantly reduces the etching rate,allowing for predictable tuning of the etching rate for wider grooves.This effectively increases the usability and flexibility of the one-step strategy.This was applied to the manufacture of an ultra-small quartz grooved tuning fork resonator with a frequency of 32.768 kHz in a single step,increasing production efficiency by almost 45%and reducing costs by almost 30%compared to current methods.This has great potential for improving the productivity of grooved tuning fork devices.It can also be extended to the fabrication of other quartz crystal devices requiring hierarchical structures.
基金support of the Mount Taishan Industrial Leading Talent Project.
文摘Repairing the Ni-based superalloy component remains challenging due to the limited understanding of the role of the defect’s morphology on microstructure and related deformation responses.To address this issue,GH4099 Ni-based superalloy plate with U-shaped and V-shaped grooves was prepared and repaired by laser-directed energy deposition method using GH4099 powders.Both grooves exhibit three similar regions at the repaired interphase,which are the base metal region with equiaxed grains,repaired region with columnar or elongated equiaxed grains,and a transition region in between.High-temperature gradient in the repaired region induced a high density of substructures,and the repaired region in U-shaped grooves has an even higher temperature gradient due to fewer passes of the melted metal,which induces more metallic carbides in the subgrain boundaries and improves the tensile strength of the repaired samples.However,due to the steep side walls,local vortex might form at the bottom corner of the U-shaped groove,leaving macroscale holes and micro-cracks there.Such defects will decrease the alloy’s ductility.The relationship among groove morphology-macro-and microstructure-mechanical properties is then established,which suggesting the preferred V-shaped groove considering the flatter sidewall and more passes induced near equilibrium microstructure.
基金upported by the Guangdong Provincial Pearl River Talents Program(Grant No.2019ZT08Z779)the National Natural Science Foundation of China(Grant Nos.U21A20509 and 62205124).
文摘Metal micro-nano grating has received much attention due to its ability to provide high-efficiency light absorption.However,the current research scales of these metal gratings are focused on subwavelengths,and little attention has been paid to the absorption properties of metal gratings at other scales.We investigate the absorption properties of metal gratings based on surface plasmon resonance(SPR)across the scales from superwavelength to subwavelength.Under grazing incidence,we observe continuous strong absorption phenomena from superwavelength to subwavelength Al triangle-groove gratings(TGGs).Perfect absorption is realized at the subwavelength scale,whereas the maximum absorption at all other scales exceeds 74%.The electric field distribution gives the mechanism of the strong absorption phenomenon attributed to SPR on the surface of Al TGGs at different scales.In particular,subwavelength Al TGGs have perfectly symmetric absorption properties for different blaze angles,and the symmetry is gradually broken as the grating period’s scale increases.Furthermore,taking Al gratings with varying groove shapes for example,we extend the equivalence rule of grating grooves to subwavelength from near-wavelength and explain the symmetric absorption properties in Al TGGs.We unify the research of metal grating absorbers outside the subwavelength scale to a certain extent,and these findings also open new perspectives for the design of metal gratings in the future.
基金Supported by the National Natural Science Foundation of China(No.52375037)the Masters Innovation Project of Beijing University of Civil Engineering and Architecture(No.PG2024142)+1 种基金the Outstanding Youth of Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture(No.GDRC20220801)the Breeding Program Funding of Beijing University of Civil Engineering and Architecture(No.X24026).
文摘The aim of the study is to investigate the impact of the buffer groove structure on the pressure of continuous rotation electro-hydraulic servo motor.The mathematical model of the motor valve plate with triangular groove and U-groove structure is established firstly,and the structure size of the two buffer grooves with better pressure drop effect is obtained by Matlab.Secondly,an established pressure gradient model is developed for the sealed canisters for electric motors using a combined groove structure.The bird swarm optimization algorithm is used to obtain the optimal dimensions for the combined depth and angle of the pressure groove.The flow field in the motor seal chamber is simulated and calculated by Fluent.This study compared the pressure field distributions in the motors sealing chamber using triangular and combined groove structures.It investigated the combined grooves effect on the pressure impact during the commutation of a continuously rotating electro-hydraulic servo motor.It is found that the combined groove structure has a positive impact on reducing the pressure impact.The results indicate that the combined groove structure significantly enhances the efficiency of mitigating pressure shocks when the motor switches between high-and low-pressure chambers.
文摘Metamorphic mechanism has the advantages of variable topology and variable degrees of freedom, which can realize the requirements of multi-conditions and multi-tasks, and has a good application prospect. The configuration transformation is prominent feature of the metamorphic mechanism. The number of constraints or properties of the kinematic pairs provided by the metamorphic kinematic pairs will change under certain conditions, its dynamic performance is much more complex than that of traditional kinematic pairs with immutable constraints. However, the clearance model about traditional kinematic pairs with immutable constraints established by long-term research is difficult to be directly applied to the metachromatic kinematic pairs. Referring to the experience of the traditional kinematic pairs with immutable constraints, the continuous contact model of Metamorphic Groove pin pair with clearance is established. According to the traditional continuous contact model of the kinematic pairs with immutable constraints, the forces between the elements of kinematic pair of the mechanism with clearance and the ideal mechanism without clearance are regarded as the same, and the inertia force and inertia moment of the components are also calculated according to the acceleration of the ideal mechanism. The clearance is regarded as a massless virtual bar with length r. For the rotating pair part, the massless virtual bar length r is the difference between the radius of the shaft and the hole, and for the sliding pair part, the massless virtual bar length r is half of the difference between the height of the slider and the guide groove. According to the new mechanism without gap after adding the imaginary bar, kinetic energy and potential energy of the system are calculated for the two configurations of mechanism with metamorphic Groove pin pair with clearance. The kinetic energy and potential energy of the system are calculated according to the new mechanism without clearance after adding the massless virtual bar. The kinetic energy, potential energy and generalized force are substituted into the Lagrangian equation to obtain the motion equation of the metamorphic mechanism, which lays the foundation for the dynamic performance study of the mechanism with metamorphic groove pin pair with clearance.
基金the National Natural Science Foundation of China(22008231 and 21776267)grants of Dalian National Laboratory for Clean Energy(DNL)(DNL180203)+1 种基金the LiaoNing Revitalization Talents Program(XLYC1801004)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Y201829).
文摘Hydrogen separation through oxygen transport membranes(OTMs)has attracted much attention.Asymmetric membranes with thin dense layers provide low bulk diffusion resistances and high overall hydrogen separation performances.However,the resistance in the porous support layer(PSL)limits the overall separation performance significantly.Engineering the structure of the PSL is an appropriate way to enable fast gas transport and increase the separation performance.There is no relevant research on studying the influence of the PSL on hydrogen separation performance so far.Herein,we prepared Ce0.85Sm0.15O1.925–Sm0.6Sr0.4Cr0.3Fe0.7O3-δ(SDC-SSCF)asymmetric membranes with straight grooves in PSL by tape-casting and laser grooving.A~30%improvement in the hydrogen separation rate was achieved by grooving in the PSLs.It indicates that the grooves may reduce the concentration polarization resistance in PSL for the hydrogen separation process.This work provides a straight evidence on optimizing the structures of PSL for improving the hydrogen separation performance of the membrane reactors.
文摘Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while extending their lifespan.This paper explores the application of laser-assisted water jet technology in constructing high-quality micro-trap structures on 316L stainless steel,a key material in accelerator manufacturing.The study systematically analyzes the impact of various parameters such as laser repetition frequency,pulse duration,average power,water jet pressure,repeat times,nozzle offset,focal position,offset distance between grooves,and processing speed on the surface morphology of stainless steel.The findings reveal that micro-groove depth increases with higher laser power but decreases with increasing water jet pressure and processing speed.Interestingly,repeat times have minimal effect on depth.On the other hand,micro-groove width increases with higher laser power and repeat times but decreases with processing speed.By optimizing these parameters,the researchers achieved high-quality pound sign-shaped trap structure with consistent dimensions.We tested the secondary electron emission coefficient of the"well"structure.The coefficient is reduced by 0.5 at most compared to before processing,effectively suppressing secondary electron emission.These results offer indispensable insights for the fabrication of micro-trap structures on material surfaces.Laser-assisted water jet technology demonstrates considerable potential in mitigating SEE on metal surfaces.
基金This work is supported by the National Natural Science Foundation of China(Nos.51975328,52275348)Taishan Scholar Project of Shandong Province(No.tsqn202306006)Youth Innovation Technology Support Program of Shandong Provincial Universities(No.2022KJ041).
文摘Thin-walled metal parts with functional micro-featured surface have broad application prospects in the fields of resistance reduction,noise reduction,etc.In this study,a novel micro-rolling&incremental sheet forming hybrid process(μR-ISF)is proposed to fabricate thin-walled metal parts with microgroove arrays.An analytical model which relates the rolling force and microgroove depth in the micro-rolling stage was first established.Then,the formation mechanism of microgroove morphology during both micro-rolling stage and macro-shape forming stage are investigated.After the micro-grooved sheet being incrementally formed,a significant reduction(between 21%to nearly 60%)is occurred in the depth of both transverse and longitudinal grooves compared to the flat sheet.Meanwhile,the width of transverse grooves decreases slightly by about 10%on average,while the width of longitudinal microgrooves increases significantly by more than 30%on average.After micro-rolling,85°{102}tensile twins appear on the micro-grooved sheet and the percentage of 65°{112}compressive twins increases.After incremental forming,the percentage of low-angle grain boundaries and the density of geometrically necessary dislocations in the formed part increase significantly,and the grain size distribution becomes more uniform.The present work provides a new strategy for the fabrication of 3D metal thin-walled components with surface micro-features.
基金Project supported by the Natural Science Foundation of Guangdong Province (Grant No.2021A1515012335)the National Natural Science Foundation of China (Grant No.11274400)+2 种基金Pearl River S&T Nova Program of Guangzhou (Grant No.201506010059)State Key Laboratory of High Field Laser Physics (Shanghai Institute of Optics and Fine Mechanics)State Key Laboratory of Optoelectronic Materials and Technologies (Sun Yat-Sen University)。
文摘It is well known that femtosecond laser pulses can easily spontaneously induce deep-subwavelength periodic surface structures on transparent dielectrics but not on non-transparent semiconductors.Nevertheless,in this study,we demonstrate that using high-numerical-aperture 800 nm femtosecond laser direct writing with controlled pulse energy and scanning speed in the near-damage-threshold regime,polarization-dependent deep-subwavelength single grooves with linewidths of~180 nm can be controllably prepared on Si.Generally,the single-groove linewidth increases slightly with increase in the pulse energy and decrease in the scanning speed,whereas the single-groove depth significantly increases from~300 nm to~600 nm with decrease in the scanning speed,or even to over 1μm with multi-processing,indicating the characteristics of transverse clamping and longitudinal growth of such deep-subwavelength single grooves.Energy dispersive spectroscopy composition analysis of the near-groove region confirms that single-groove formation tends to be an ultrafast,non-thermal ablation process,and the oxidized deposits near the grooves are easy to clean up.Furthermore,the results,showing both the strong dependence of groove orientation on laser polarization and the occurrence of double-groove structures due to the interference of pre-formed orthogonal grooves,indicate that the extraordinary field enhancement of strong polarization sensitivity in the deep-subwavelength groove plays an important role in single-groove growth with high stability and collimation.
文摘Airport pavement engineers are required to maintain pavement skid resistance at a satisfactory level to minimize the likelihood of runway excursions.Runway overruns and skidding along rapid exit taxiways are the two most frequently encountered forms of runway excursion accidents.Currently only empirical statistical models based on historical accident data are available to predict the risks of runway excursions.All such models fail to account for the impacts of pavement skid resistance properties.Mechanistic solutions of the tire-fluid-pavement interaction problem are now available,and the impacts of pavement skid resistance properties on runway excursion accidents can now be quantitatively evaluated.This paper presents a state-of-the-art review of recent research developments on the topic.It highlights the Concept of Pavement Skid Resistance State which provides(i)a logical theoretical framework for mechanistic representation of tire-pavement skid resistance,and(ii)an approach for modeling of the physical process of aircraft skidding and hydroplaning.Next,runway excursion risk prediction models are presented for risk evaluation of aircraft hydroplaning,runway overruns,and rapid exit taxiway excursions.Also examined in detail mechanistically is the effectiveness of pavement grooving in reducing the risks of runway excursions.The review clearly confirms the capability of mechanistic approach in analyzing runway excursions for the purpose of enhancing safe aircraft operations on airport runways.
文摘Traditional descriptions of liver anatomy refer to a smooth,convex surface contacting the diaphragm.Surface depressions are recognized anatomic variants.There are many theories to explain the cause of the depressions.We discuss the theory that these are caused by hypertrophic muscular bands in the diaphragm.
文摘The dynamics model of a 2-degree-of-freedom deep groove ball bearing is established by incorporating the raceway surface waviness model comprising multiple sinusoidal functions superposition.The model is solved using the fourth-order Runge-Kutta method to obtain the vibration characteristics including displacement,velocity,acceleration,and frequency of the bearing.Validation of the model is accomplished through comparison with theoretical vibration frequencies.The influence of the amplitude of waviness of the inner and outer ring raceway surfaces of deep groove ball bearings on the vibration displacement,peak-to-peak vibration displacement and root-mean-square vibration acceleration is analyzed,and the results show that as the amplitude of the inner and outer ring raceway surfaces waviness increases,all the vibration characteristic indexes increase,indicating that the vibration amplitude of the bearings as well as the energy of the waviness-induced shock waveforms increase with the increase of the amplitude of the waviness.
文摘Objective: To explore the application value of disposable grooved negative pressure drainage tubes in rib fracture incision and internal fixation. Methods: Seventy-five patients admitted to our Department of Trauma Surgery from June 2022 to April 2024 who underwent rib fracture osteotomy and internal fixation were selected. According to the types of drainage tubes left in the patients after the operation, they were divided into the observation group (35 cases who were left with disposable grooved negative pressure drainage tubes) and the control group (40 cases who were left with closed silicone thoracic drainage tubes). Comparison of chest drainage, pain, postoperative complications, secondary chest penetration rate, drain placement time, hospitalization time, and treatment costs were compared between the two groups. Results: The total postoperative chest drainage volume of the observation group was less than that of the control group (P < 0.05);the degree of pain, the incidence of postoperative complications, and the rate of secondary chest puncture in the observation group were lower than that of the control group three days after the operation (P < 0.05);and the time of drain placement in the observation group was shorter than that of the control group (P < 0.05). Conclusion: The application of disposable grooved negative pressure drainage tubes in rib fracture incision and internal fixation can significantly improve patients’ postoperative pain and discomfort, reduce complications, lower the rate of secondary chest penetration, promote patients’ postoperative recovery, decrease the amount of postoperative chest drainage, and shorten the time of drain placement, which is worthy of clinical promotion and application.
基金the National Natural Science Foundation of China(No.11902256)the Natural Science Basic Research Program of Shaanxi,China(No.2019JQ-479).
文摘A novel grooving method for eliminating the bending-induced collapse of hexagonal honeycombs has been proposed,which lies in determining the appropriate grooving parameters,including the grooving spacing,angle,and depth.To this end,a framework built upon the experiment-based,machine learning approach for grooving parameters prediction was presented.The continuously grooved honeycomb bending experiments with various radii,honeycomb types,and thicknesses were carried out,and then the deformation level of honeycombs at different grooving spacing was quantitatively evaluated.A criterion for determining the grooving spacing was proposed by setting an appropriate tolerance for the out-of-plane compression strength.It was found that as the curvature increases,the grooving spacing increases due to the deformation level of honeycombs being more severe at a smaller bending radius.Besides,the grooving spacing drops as the honeycomb thickness increases,and the cell size has a positive effect on the grooving spacing,while the relative density has a negative effect on the grooving spacing.Furthermore,the data-driven Gaussian Process(GP)was trained from the collected data to predict the grooving spacing efficiently.The grooving angle and depth were calculated using the geometrical relationship of honeycombs before and after bending.Finally,the grooving parameters design and verification of a honeycomb sandwich fairing part were conducted based on the proposed grooving method.
