With numerous applications coilable masts in high-precision astronomical observations,such as X-ray source observations,it is important to investigate mast stiffness.To date,there have been many studies on the bending...With numerous applications coilable masts in high-precision astronomical observations,such as X-ray source observations,it is important to investigate mast stiffness.To date,there have been many studies on the bending stiffness of coilable masts,but few studies on their torsional stiffness,especially regarding the nonlinear characteristics of torsional stiffness of coilable masts under large torsional deformation.In this paper,a nonlinear analysis method is presented to examine the torsional stiffness of coilable masts with triangular sections.Based on the second-order bending buckling hypothesis of battens under large torsion deformation,the nonlinear relationship between torsional torque and torsional angle is obtained by analyzing torsional deformation and force of coilable masts.This method is used to analyze the torsional stiffness nonlinearity of a certain type of coilable mast which will be used in a practical application in the future and the results are verified by simulation and testing.The comparison results show that the error is within the acceptable range,which proves the effectiveness of the proposed method.展开更多
Wireless capsule endoscopy(WCE)has the potential to fully replace conventional wired counterparts for its low invasiveness.Recent studies have attempted to expand the functions of capsules toward this goal.However,lim...Wireless capsule endoscopy(WCE)has the potential to fully replace conventional wired counterparts for its low invasiveness.Recent studies have attempted to expand the functions of capsules toward this goal.However,limitations in space and energy supply have resulted in the inability to perform multiple diagnostic and treatment tasks using a single capsule.In this study,we developed a dual-functional capsule robot(DFCR)for drug delivery and tissue biopsy based on magnetic torsion spring technology.The delivery module was shown to rotate the push rod with a thrust of 894 mN to release approximately 0.3 mL of semisolid drug.The biopsy module used a built-in blade to cut tissue with a shear stress of 22.87 MPa,producing a sample of approximately 1.8 mm3.Additionally,a five-degree-of-freedom permanent magnet drive system was developed.By adjusting the strength of the unidirectional magnetic field generated by an external magnet,the capsule can be wirelessly controlled to sequentially trigger the two functions.Ex vivo tests on porcine stomachs confirmed the feasibility of the prototype capsule(12 mm in diameter and 45 mm in length)in active movement,medication,and tissue biopsy.The newly developed DFCR further expands the clinical application prospects of WCE robots in minimally invasive surgery.展开更多
We show that the torsion module Tor_(j)^(R)(R/a,H_(a)^(i)(X))is in a Serre subcategory for the bounded below R-complex X.In addition,we prove the isomorphism Tor_(s-t)^(R)(R/a,X)≅Tor_(s)^(R)(R/a,H_(a)^(t)(X))in some c...We show that the torsion module Tor_(j)^(R)(R/a,H_(a)^(i)(X))is in a Serre subcategory for the bounded below R-complex X.In addition,we prove the isomorphism Tor_(s-t)^(R)(R/a,X)≅Tor_(s)^(R)(R/a,H_(a)^(t)(X))in some case.As an application,the Betti number of a complex X in a prime ideal p can be computed by the Betti number of the local cohomology modules of X in p.展开更多
Degradable metals,represented by magnesium and magnesium alloys,have attracted significant attention as fracture internal fixation and bone defect repairing materials due to their good biocompatibility,suitable elasti...Degradable metals,represented by magnesium and magnesium alloys,have attracted significant attention as fracture internal fixation and bone defect repairing materials due to their good biocompatibility,suitable elastic modulus and degradable properties.The Mg-3Zn-1Ca-0.5Sr(wt%)alloy is considered a competitor in the biomaterial field thanks to its unique composition of essential nutrients and excellent mechanical properties.However,the presence of coarse second-phase particles in the alloy accelerates its degradation rate and causes excessive gas formation during implantation,which restricts the alloy's potential for clinical device applications.In order to further optimize the properties of the alloy,extrusion combined with high-pressure torsion(HPT)was adopted for deformation processing.The results show that by optimizing the material processing means,the grain can be refined and broken,and the second-phase distribution can be improved,thus improving the microstructure,mechanical properties,and corrosion resistance of the alloy.After 15 cycles of HPT processing,the grains of the alloy are significantly refined to the nanometer scale,reaching approximately 98 nm.Additionally,the second-phase distribution is greatly improved,transforming the original streamlined structure into a more dispersed distribution.This change in microstructure leads to a significant strengthening effect on the alloy,with a noticeable increase in hardness from 60.3 HV in the as-extruded state to 98.5 HV.展开更多
Let 0<γ<π be a fixed pythagorean angle. We study the abelian group Hr of primitive integral triangles (a,b,c) for which the angle opposite side c is γ. Addition in Hr is defined by adding the angles β opposi...Let 0<γ<π be a fixed pythagorean angle. We study the abelian group Hr of primitive integral triangles (a,b,c) for which the angle opposite side c is γ. Addition in Hr is defined by adding the angles β opposite side b and modding out by π-γ. The only Hr for which the structure is known is Hπ/2, which is free abelian. We prove that for generalγ, Hr has an element of order two iff 2(1- cosγ) is a rational square, and it has elements of order three iff the cubic (2cosγ)x3-3x2+1=0 has a rational solution 0<x<1. This shows that the set of values ofγ for which Hr has two-torsion is dense in [0, π], and similarly for three-torsion. We also show that there is at most one copy of either Z2 or Z3 in Hr. Finally, we give some examples of higher order torsion elements in Hr.展开更多
The 304 austenitic stainless steel was processed by high-pressure torsion(HPT)at room temperature with 10,20,and 30 rotations under a pressure of 3 GPa and a rotation speed of 1 r/min.The phase transformation and micr...The 304 austenitic stainless steel was processed by high-pressure torsion(HPT)at room temperature with 10,20,and 30 rotations under a pressure of 3 GPa and a rotation speed of 1 r/min.The phase transformation and microstructural evolution of 304 stainless steel after HPT were investigated by X-ray diffraction(XRD)analysis,electron backscatter diffraction(EBSD)analysis,transmission electron microscopy(TEM),nanoindentation test and differential scanning calorimetry(DSC)analysis.The experimental results show that HPT causes elongated nanocrystalline grains of 25 nm width along the torsion direction.After 10 turns of HPT,the deformation-induced martensitic transformation is completed and the hardness increases from 3 GPa to 8.5 GPa at the edge of the disc.However,a local reverse phase transformation from martensite to austenite is observed in the peripheral regions of the sample after 30 turns of HPT,leading to a higher volume fraction of austenite,and the hardness of the sample also decreases accordingly.展开更多
The failure analysis was conducted on unqualified torsion bar spring in automobile suspension system used for light vehicles during engine test.The effects of through hardening,surface induction hardening,quenching an...The failure analysis was conducted on unqualified torsion bar spring in automobile suspension system used for light vehicles during engine test.The effects of through hardening,surface induction hardening,quenching and tempering,and tempering temperature on the microstructure and fatigue life of 45CrNiMoVA steel torsion bars were also investigated.Results showed that only the torsion bar spring after through quenching and tempering is subjected to surface induction quenching and tempering to achieve the fatigue life of the qualified torsion bar.The fatigue life of torsion bar spring reaches 3×10^(5) cycles more than the required 2×10^(5) cycles.This is because the distribution of gradient microstructure was helpful to relieve the applied stress during the fatigue process.The microstructure of the non-hardened region,which consists of tempered sorbite regardless of whether it is tempered at 330 or 430℃,contributes to minimizing the impact of temper brittleness on the fatigue life of the torsion bar.Consequently,the fatigue life of the torsion bar is relatively unaffected by temper brittleness due to the presence of tempered sorbite in its non-hardened regions.And the reason for the unqualified fatigue life was that the depth and hardness of the hardened region did not meet the standard requirements of 5–7 mm and 47–52 HRC,respectively.展开更多
Polyorchidism is a rare anomaly of the male urogenital tract characterized by the presence of one or more extra testes.Supernumerary testes can often present with coexistent conditions,including cryptorchidism,inguina...Polyorchidism is a rare anomaly of the male urogenital tract characterized by the presence of one or more extra testes.Supernumerary testes can often present with coexistent conditions,including cryptorchidism,inguinal hernia,and torsion.We report a case of a pediatric patient with initial concern for intra-scrotal left testicular torsion on ultrasonography who was ultimately found to have torsion of an intra-abdominal supernumerary testis.He underwent scrotal exploration with bilateral orchiopexy and laparoscopic excision of the torsed gonad.This case highlights a unique presentation of polyorchidism with incongruent descent of an ipsilateral supernumerary testis.展开更多
BACKGROUND Point-of-care ultrasound(POCUS)is the use of portable ultrasound devices by trained healthcare professionals to diagnose and monitor medical conditions directly at the patient's bedside,such as in emerg...BACKGROUND Point-of-care ultrasound(POCUS)is the use of portable ultrasound devices by trained healthcare professionals to diagnose and monitor medical conditions directly at the patient's bedside,such as in emergency settings.We described a case where POCUS use,in Pediatric Emergency Department,allowed an early diagnosis and timely management in the surgical department,with a favorable outcome for child.Therefore we write this case because it is desirable to po-pularize ultrasound as the fifth pillar of clinical examination especially in Emer-gency Department CASE SUMMARY A 13-year-old girl with acute gastrointestinal symptoms,such as vomit and abdominal and lumbar pains.Upon physical examination,the patient had lo-calized abdominal pain in the left lower quadrant.Ultrasonography performed at the bedside revealed an enlarged left ovary with an irregular structure containing a 3 cm cyst.These findings raised suspicion of ovarian torsion.The child tran-sferred to Gynecology Surgery Unit,where she was taken emergently to the ope-rating room CONCLUSION It is desirable to spread POCUS in emergency settings where it allows a sig-nificant saving of time in patient management.展开更多
Magnesium(Mg)alloys are usually subjected to torsion deformation during processing or manufacturing.However,the torsional behavior remains underexplored at the atomic level compared to uniaxial deformation.In this wor...Magnesium(Mg)alloys are usually subjected to torsion deformation during processing or manufacturing.However,the torsional behavior remains underexplored at the atomic level compared to uniaxial deformation.In this work,atomistic simulations are employed to understand the deformation mechanism during torsion around <1010>and<1120>axes of Mg.We reveal that the onset of plasticity occurs near the surface due to stress-gradient effect and the deformation mechanisms are highly dependent on torsion axis.Specifically,the prismatic and basal slip dominate torsion around[1120]axis.During torsion around[1010]axis,{1121}twinning can be activated,whereas{1011}twinning is formed due to local stress but detwinned eventually.Moreover,extensive cross slip and interactions between basal and prismatic dislocations are observed and the associated mechanisms are discussed.These novel atomic-scale insights provide deeper understanding of the plastic deformation mechanisms of Mg under torsional loading.展开更多
BACKGROUND Omental torsion(OT)is a rare cause of acute abdomen,it can be difficult to diagnose preoperatively and is frequently misdiagnosed.Computed tomography(CT)is the primary imaging modality for OT.It typically s...BACKGROUND Omental torsion(OT)is a rare cause of acute abdomen,it can be difficult to diagnose preoperatively and is frequently misdiagnosed.Computed tomography(CT)is the primary imaging modality for OT.It typically shows the swirl sign.contrast-enhanced CT can better visualize the central vascular structure of the mass,thus improving the diagnostic accuracy for OT.Surgical resection is the mainstay of treatment for OT.Laparoscopy allows direct visualization of the primary torsion site and comprehensive abdominal exploration,thereby decreasing misdiagnoses.It is a safe and reliable approach for OT treatment,which offers the advantages of minimal trauma,mild postoperative pain,and rapid recovery for stylistic precision.CASE SUMMARY A 48-year-old man was admitted to our hospital due to lower right abdominal pain for the preceding 70 hours.Physical examination revealed lower right abdominal muscle strain,tenderness,and rebound pain,but no mass was palpable.Contrast-enhanced CT revealed a thickened,blurred omentum with swirling changes in the right abdomen.Laparoscopic exploration and omentectomy were performed in the emergency setting.The procedure revealed 50 mL of dark-red bloody ascites in the pelvis and twisting of the right omentum along its longitudinal axis,with a 10 cm×8 cm purple-black necrosis at the distal end.Postsurgical pathology revealed omental hemorrhage,degeneration,and necrosis.The patient had an uneventful recovery and was discharged on the fourth postoperative day.During the subsequent nine-month follow-up,he remained asymptomatic.CONCLUSION OT is a rare disease that lacks specific clinical manifestations.Abdominal contrast-enhanced CT plays a crucial role in diagnosing OT,and laparoscopic surgery is a safe and effective diagnostic and therapeutic approach.展开更多
Testicular torsion is a urological emergency that requires prompt diagnosis and treatment,accounting for 10%-15%of cases of acute scrotum.[1]It occurs most frequently during the perinatal period and adolescence and ca...Testicular torsion is a urological emergency that requires prompt diagnosis and treatment,accounting for 10%-15%of cases of acute scrotum.[1]It occurs most frequently during the perinatal period and adolescence and can occur at any age.[2]The incidence of testicular torsion is 1/4,000 in males under 25 years of age and 1/160 in males over 25 years of age.[3]Unilateral torsion is relatively common,with a higher incidence on the left side.Testicular torsion is typically managed through surgical exploration.Necrotic testes,identified by a black appearance,require orchiectomy.[4]展开更多
The evolution mechanism of the second-order mechanical behaviors under the complex pre-torsion path has not been clarified,which limits its potential application for optimizing precision forming processes of Mg alloy ...The evolution mechanism of the second-order mechanical behaviors under the complex pre-torsion path has not been clarified,which limits its potential application for optimizing precision forming processes of Mg alloy structural components.In this work,the combined loading of reciprocating free-end torsion(FET)and free-rotational tension(FRT)was performed on the extruded AZ31 solid rod with basal fiber texture.The corresponding mechanical response,microstructure evolution,and twinning behaviors were investigated,and the physical mechanism of the second-order behaviors(both the Swift and inverse Swift effects)was discussed.The results indicate that the two-stage deformation of reciprocating torsion is capable of activating tensile twins,effectively refining the surface grains,and thus improving the yield asymmetry.Due to the reverse load,detwinning dominates the deformation of reverse FET(RFET),while detwinning in FRT deformation is caused by the spontaneous rotation of the inverse Swift effect.The twin variants with c-axis tending to extrusion direction(ED)are predisposed to detwinning,and the bimodal texture introduced by FET is degraded.The plastic deformation of RFET is primarily coordinated by basal and prismatic slips.The large strain FRT is dominated by basal slip due to its low SF/CRSS.The interaction between twinning and detwinning dominates the multi-directionality of the Swift effect during reciprocating torsion,and the cumulative effect of strain hardening further enhances the dependence of RFET axial strain on basal slip.The dγ/dεindex successfully captures the evolution of the inverse Swift effect during FRT.The forward rotation of the solid rod is caused by the inversion of the radial residual shear stress field,and the internal stress introduced by the torsional inhomogeneity is compensated.The subsequent reverse rotation is the result of balancing the orientation inhomogeneity and local strain heterogeneity introduced by the shear deformation.The increase in the reverse rotation rate is caused by detwinning.展开更多
This paper proposes a novel idea by integrating a torsion dynamic vibration absorber with a triboelectric energy harvester to realize synchronous torsional vibration suppression and energy harvesting in a rotor system...This paper proposes a novel idea by integrating a torsion dynamic vibration absorber with a triboelectric energy harvester to realize synchronous torsional vibration suppression and energy harvesting in a rotor system.The most fantastic feature of the proposed torsion harvester-absorber system(HAS)is the quasi-zero-stiffness(QZS)characteristic for suppressing and har-vesting low-frequency vibration energy.The QZS characteristic is realized by combining negative stiffness magnet couplings(NSMC)in parallel connection with a pair torsion coil spring.A theoretical model of the NSMC is established based on the equivalent magnetic charge method,and parametric studies are conducted to provide a guideline for the design of the NSMC.Furthermore,the dynamic model of the host oscillator with a torsion QZS HAS is established based on Lagrange’s equation,and then the dynamic amplification factor is obtained using the harmonic balance method.The effects of geometric parameters on both the performances of vibration mitigation and energy harvesting are investigated.Finally,the parameters of the torsion QZS HAS are optimized using H_(∞)optimization method and genetic algorithm,respectively.This enables the torsion QZS HAS to effectively suppress low-frequency vibrations of the rotor system while simultaneously harvesting energy over a wide frequency band.展开更多
An improved understanding of fatigue behavior of a cast aluminum alloy（2-AS5U3G-Y35）in very high cycle regime is developed through the ultrasonic fatigue test in axial and torsion loading.The new developed torsion f...An improved understanding of fatigue behavior of a cast aluminum alloy（2-AS5U3G-Y35）in very high cycle regime is developed through the ultrasonic fatigue test in axial and torsion loading.The new developed torsion fatigue system is presented.The effects of loading condition and frequency on the very high cycle fatigue（VHCF）are investigated.The cyclic loading in axial and torsion at 35 Hz and 20 kHz with stress ratio R=-1 is used respectively to demonstrate the effect of loading condition.S-N curves show that the fatigue failure occurs in the range of 105—1010 cycles in axial or torsion loading and the asymptote of S-N curve is inclined,but no fatigue limit exists under the torsion and axial loading condition.The fatigue fracture surface shows that the fatigue crack initiates from the specimen surface subjected to the cyclic torsion loading.It is different from the fatigue fracture characteristic in axial loading in which fatigue crack initiates from subsurface defect in very high cycle regime.The fatigue initiation is on the maximum shear plane,the overall crack orientation is on a typical spiral 45° to the fracture plane and it is the maximum principle stress plane.The clear shear strip in the torsion fatigue fracture surface shows that the torsion fracture is the shear fracture.展开更多
Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation.The thermal torsion effect,characterized by the reversible untwisting o...Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation.The thermal torsion effect,characterized by the reversible untwisting of twisted fibers as temperature increases due to greater radial than axial thermal expansion,is crucial to the actuation performance of these artificial muscles.This study explores the thermal torsion effect of polymer muscles made of twisted Nylon 6 fibers in experimental and theoretical aspects,focusing on the interplay between material properties and temperature.It is revealed that the thermal torsion effect enhances the actuation performance of the twisted polymer actuator while the thermal softening effect diminishes it.A thermal-mechanical model incorporating both the thermal torsion effect and thermal softening effect is used to predict the recovered torque of the twisted polymer actuators.An optimal bias angle and operating temperature are identified to maximize the recovered torque.Analysis of strain and stress distributions in the cross-section of the twisted polymer fiber shows that the outer layers of the fiber predominantly contribute to the torsional actuation.This work aids in the precise control and structural optimization of the thermally-activated twisted polymer actuators.展开更多
In this paper,we compute sub-Riemannian limits of some important curvature variants associated with the connection with torsion for four dimensional twisted BCV spaces and derive a Gauss-Bonnet theorem for four dimens...In this paper,we compute sub-Riemannian limits of some important curvature variants associated with the connection with torsion for four dimensional twisted BCV spaces and derive a Gauss-Bonnet theorem for four dimensional twisted BCV spaces.展开更多
The torsional low strain integrity test(TLSIT),known for its advantages such as a smaller detection blind zone,improved identification of shallowly buried defects,stable phase velocity for signal interpretation,and be...The torsional low strain integrity test(TLSIT),known for its advantages such as a smaller detection blind zone,improved identification of shallowly buried defects,stable phase velocity for signal interpretation,and better adaptability for existing pile testing.However,it lacks a comprehensive understanding of the authentic three-dimensional(3D)strain wave propagation mechanism,particularly wave reflection and transmission at defects.To address this gap,a novel 3D theoretical framework is introduced in this context to model the authentic 3D wave propagation during the TLSIT.The proposed approach is validated by comparing its results with those obtained from 3D finite element method(FEM)simulations and simplified 1D(one-dimensional)and 3D analytical solutions.Additionally,a parametric study is conducted to enhance insights into the formation mechanism of high-frequency interference observed during the TLSIT.Finally,a defect identification study is performed to provide guidance for interpreting the wave spectrum in terms of defect characteristics.展开更多
Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent ...Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent a key research aspect for morphing aircraft,since they can lead to potential improvements in flight range,maneuverability,load alleviation and airport compatibility.This paper proposes a hinge mechanism design for folding wingtips based on the shape memory alloy torsion tube,aiming to achieve successful folding using the actuation effect of the shape memory alloy.The proposed design employs a shape memory alloy torsion tube as the actuator for the active folding of the wingtip,which is motivated by the characteristics of the tube,enabling a simplified structure for the integration with high energy density.Through numerical simulation and testing of the folding wingtip structure,the concept is verified,which shows its potential as an actuator for folding wingtips.展开更多
文摘With numerous applications coilable masts in high-precision astronomical observations,such as X-ray source observations,it is important to investigate mast stiffness.To date,there have been many studies on the bending stiffness of coilable masts,but few studies on their torsional stiffness,especially regarding the nonlinear characteristics of torsional stiffness of coilable masts under large torsional deformation.In this paper,a nonlinear analysis method is presented to examine the torsional stiffness of coilable masts with triangular sections.Based on the second-order bending buckling hypothesis of battens under large torsion deformation,the nonlinear relationship between torsional torque and torsional angle is obtained by analyzing torsional deformation and force of coilable masts.This method is used to analyze the torsional stiffness nonlinearity of a certain type of coilable mast which will be used in a practical application in the future and the results are verified by simulation and testing.The comparison results show that the error is within the acceptable range,which proves the effectiveness of the proposed method.
基金supported by the National Natural Science Foundation of China(No.52105072)Zhejiang Provincial Natural Science Foundation of China(No.LZ24E050004)+2 种基金Jiangsu Provincial Outstanding Youth Program(No.BK20230072)a grant from Suzhou Industrial Foresight and Key Core Technology Project(No.SYC2022044)grants from Jiangsu Qinglan Project and Jiangsu 333 High-level Talents.
文摘Wireless capsule endoscopy(WCE)has the potential to fully replace conventional wired counterparts for its low invasiveness.Recent studies have attempted to expand the functions of capsules toward this goal.However,limitations in space and energy supply have resulted in the inability to perform multiple diagnostic and treatment tasks using a single capsule.In this study,we developed a dual-functional capsule robot(DFCR)for drug delivery and tissue biopsy based on magnetic torsion spring technology.The delivery module was shown to rotate the push rod with a thrust of 894 mN to release approximately 0.3 mL of semisolid drug.The biopsy module used a built-in blade to cut tissue with a shear stress of 22.87 MPa,producing a sample of approximately 1.8 mm3.Additionally,a five-degree-of-freedom permanent magnet drive system was developed.By adjusting the strength of the unidirectional magnetic field generated by an external magnet,the capsule can be wirelessly controlled to sequentially trigger the two functions.Ex vivo tests on porcine stomachs confirmed the feasibility of the prototype capsule(12 mm in diameter and 45 mm in length)in active movement,medication,and tissue biopsy.The newly developed DFCR further expands the clinical application prospects of WCE robots in minimally invasive surgery.
基金Natural Science Foundation of Gansu Province(23JRRA866)Higher Education Innovation Fund of Gansu Provincial Department of Education(2025A-132)+1 种基金University-level Scientific Research and Innovation Project of Gansu University of Political Science and Law(GZF2024XQN16)Youth Foundation of Lanzhou Jiaotong University(2023023)。
文摘We show that the torsion module Tor_(j)^(R)(R/a,H_(a)^(i)(X))is in a Serre subcategory for the bounded below R-complex X.In addition,we prove the isomorphism Tor_(s-t)^(R)(R/a,X)≅Tor_(s)^(R)(R/a,H_(a)^(t)(X))in some case.As an application,the Betti number of a complex X in a prime ideal p can be computed by the Betti number of the local cohomology modules of X in p.
基金National Key Research and Development Program of China(2021YFB3701004)。
文摘Degradable metals,represented by magnesium and magnesium alloys,have attracted significant attention as fracture internal fixation and bone defect repairing materials due to their good biocompatibility,suitable elastic modulus and degradable properties.The Mg-3Zn-1Ca-0.5Sr(wt%)alloy is considered a competitor in the biomaterial field thanks to its unique composition of essential nutrients and excellent mechanical properties.However,the presence of coarse second-phase particles in the alloy accelerates its degradation rate and causes excessive gas formation during implantation,which restricts the alloy's potential for clinical device applications.In order to further optimize the properties of the alloy,extrusion combined with high-pressure torsion(HPT)was adopted for deformation processing.The results show that by optimizing the material processing means,the grain can be refined and broken,and the second-phase distribution can be improved,thus improving the microstructure,mechanical properties,and corrosion resistance of the alloy.After 15 cycles of HPT processing,the grains of the alloy are significantly refined to the nanometer scale,reaching approximately 98 nm.Additionally,the second-phase distribution is greatly improved,transforming the original streamlined structure into a more dispersed distribution.This change in microstructure leads to a significant strengthening effect on the alloy,with a noticeable increase in hardness from 60.3 HV in the as-extruded state to 98.5 HV.
文摘Let 0<γ<π be a fixed pythagorean angle. We study the abelian group Hr of primitive integral triangles (a,b,c) for which the angle opposite side c is γ. Addition in Hr is defined by adding the angles β opposite side b and modding out by π-γ. The only Hr for which the structure is known is Hπ/2, which is free abelian. We prove that for generalγ, Hr has an element of order two iff 2(1- cosγ) is a rational square, and it has elements of order three iff the cubic (2cosγ)x3-3x2+1=0 has a rational solution 0<x<1. This shows that the set of values ofγ for which Hr has two-torsion is dense in [0, π], and similarly for three-torsion. We also show that there is at most one copy of either Z2 or Z3 in Hr. Finally, we give some examples of higher order torsion elements in Hr.
基金Funded by the National Natural Science Foundation of China(No.51905215)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX231233)。
文摘The 304 austenitic stainless steel was processed by high-pressure torsion(HPT)at room temperature with 10,20,and 30 rotations under a pressure of 3 GPa and a rotation speed of 1 r/min.The phase transformation and microstructural evolution of 304 stainless steel after HPT were investigated by X-ray diffraction(XRD)analysis,electron backscatter diffraction(EBSD)analysis,transmission electron microscopy(TEM),nanoindentation test and differential scanning calorimetry(DSC)analysis.The experimental results show that HPT causes elongated nanocrystalline grains of 25 nm width along the torsion direction.After 10 turns of HPT,the deformation-induced martensitic transformation is completed and the hardness increases from 3 GPa to 8.5 GPa at the edge of the disc.However,a local reverse phase transformation from martensite to austenite is observed in the peripheral regions of the sample after 30 turns of HPT,leading to a higher volume fraction of austenite,and the hardness of the sample also decreases accordingly.
基金support from the National Natural Science Foundation of China(No.52174351).
文摘The failure analysis was conducted on unqualified torsion bar spring in automobile suspension system used for light vehicles during engine test.The effects of through hardening,surface induction hardening,quenching and tempering,and tempering temperature on the microstructure and fatigue life of 45CrNiMoVA steel torsion bars were also investigated.Results showed that only the torsion bar spring after through quenching and tempering is subjected to surface induction quenching and tempering to achieve the fatigue life of the qualified torsion bar.The fatigue life of torsion bar spring reaches 3×10^(5) cycles more than the required 2×10^(5) cycles.This is because the distribution of gradient microstructure was helpful to relieve the applied stress during the fatigue process.The microstructure of the non-hardened region,which consists of tempered sorbite regardless of whether it is tempered at 330 or 430℃,contributes to minimizing the impact of temper brittleness on the fatigue life of the torsion bar.Consequently,the fatigue life of the torsion bar is relatively unaffected by temper brittleness due to the presence of tempered sorbite in its non-hardened regions.And the reason for the unqualified fatigue life was that the depth and hardness of the hardened region did not meet the standard requirements of 5–7 mm and 47–52 HRC,respectively.
文摘Polyorchidism is a rare anomaly of the male urogenital tract characterized by the presence of one or more extra testes.Supernumerary testes can often present with coexistent conditions,including cryptorchidism,inguinal hernia,and torsion.We report a case of a pediatric patient with initial concern for intra-scrotal left testicular torsion on ultrasonography who was ultimately found to have torsion of an intra-abdominal supernumerary testis.He underwent scrotal exploration with bilateral orchiopexy and laparoscopic excision of the torsed gonad.This case highlights a unique presentation of polyorchidism with incongruent descent of an ipsilateral supernumerary testis.
文摘BACKGROUND Point-of-care ultrasound(POCUS)is the use of portable ultrasound devices by trained healthcare professionals to diagnose and monitor medical conditions directly at the patient's bedside,such as in emergency settings.We described a case where POCUS use,in Pediatric Emergency Department,allowed an early diagnosis and timely management in the surgical department,with a favorable outcome for child.Therefore we write this case because it is desirable to po-pularize ultrasound as the fifth pillar of clinical examination especially in Emer-gency Department CASE SUMMARY A 13-year-old girl with acute gastrointestinal symptoms,such as vomit and abdominal and lumbar pains.Upon physical examination,the patient had lo-calized abdominal pain in the left lower quadrant.Ultrasonography performed at the bedside revealed an enlarged left ovary with an irregular structure containing a 3 cm cyst.These findings raised suspicion of ovarian torsion.The child tran-sferred to Gynecology Surgery Unit,where she was taken emergently to the ope-rating room CONCLUSION It is desirable to spread POCUS in emergency settings where it allows a sig-nificant saving of time in patient management.
基金supported by the National Natural Science Foundation of China—Excellent Young Scientists Fund(Overseas)Partial support came from the Fundamental Research Funds for the Central Universities,Jilin University.
文摘Magnesium(Mg)alloys are usually subjected to torsion deformation during processing or manufacturing.However,the torsional behavior remains underexplored at the atomic level compared to uniaxial deformation.In this work,atomistic simulations are employed to understand the deformation mechanism during torsion around <1010>and<1120>axes of Mg.We reveal that the onset of plasticity occurs near the surface due to stress-gradient effect and the deformation mechanisms are highly dependent on torsion axis.Specifically,the prismatic and basal slip dominate torsion around[1120]axis.During torsion around[1010]axis,{1121}twinning can be activated,whereas{1011}twinning is formed due to local stress but detwinned eventually.Moreover,extensive cross slip and interactions between basal and prismatic dislocations are observed and the associated mechanisms are discussed.These novel atomic-scale insights provide deeper understanding of the plastic deformation mechanisms of Mg under torsional loading.
文摘BACKGROUND Omental torsion(OT)is a rare cause of acute abdomen,it can be difficult to diagnose preoperatively and is frequently misdiagnosed.Computed tomography(CT)is the primary imaging modality for OT.It typically shows the swirl sign.contrast-enhanced CT can better visualize the central vascular structure of the mass,thus improving the diagnostic accuracy for OT.Surgical resection is the mainstay of treatment for OT.Laparoscopy allows direct visualization of the primary torsion site and comprehensive abdominal exploration,thereby decreasing misdiagnoses.It is a safe and reliable approach for OT treatment,which offers the advantages of minimal trauma,mild postoperative pain,and rapid recovery for stylistic precision.CASE SUMMARY A 48-year-old man was admitted to our hospital due to lower right abdominal pain for the preceding 70 hours.Physical examination revealed lower right abdominal muscle strain,tenderness,and rebound pain,but no mass was palpable.Contrast-enhanced CT revealed a thickened,blurred omentum with swirling changes in the right abdomen.Laparoscopic exploration and omentectomy were performed in the emergency setting.The procedure revealed 50 mL of dark-red bloody ascites in the pelvis and twisting of the right omentum along its longitudinal axis,with a 10 cm×8 cm purple-black necrosis at the distal end.Postsurgical pathology revealed omental hemorrhage,degeneration,and necrosis.The patient had an uneventful recovery and was discharged on the fourth postoperative day.During the subsequent nine-month follow-up,he remained asymptomatic.CONCLUSION OT is a rare disease that lacks specific clinical manifestations.Abdominal contrast-enhanced CT plays a crucial role in diagnosing OT,and laparoscopic surgery is a safe and effective diagnostic and therapeutic approach.
基金supported by the National Natural Science Foundation of China(82371709).
文摘Testicular torsion is a urological emergency that requires prompt diagnosis and treatment,accounting for 10%-15%of cases of acute scrotum.[1]It occurs most frequently during the perinatal period and adolescence and can occur at any age.[2]The incidence of testicular torsion is 1/4,000 in males under 25 years of age and 1/160 in males over 25 years of age.[3]Unilateral torsion is relatively common,with a higher incidence on the left side.Testicular torsion is typically managed through surgical exploration.Necrotic testes,identified by a black appearance,require orchiectomy.[4]
基金supported by the National Natural Science Foundation of China(Nos.51771166,52225101)Fundamental Research Funds for the Central Universities(No.2023CDJYXTD-002)+1 种基金Cultivation Project for Basic Research and In-novation of Yanshan University(No.2021LGZD002)Project of State Key Laboratory of Materials Processing and Die&Mould Technology(No.P2023-004).
文摘The evolution mechanism of the second-order mechanical behaviors under the complex pre-torsion path has not been clarified,which limits its potential application for optimizing precision forming processes of Mg alloy structural components.In this work,the combined loading of reciprocating free-end torsion(FET)and free-rotational tension(FRT)was performed on the extruded AZ31 solid rod with basal fiber texture.The corresponding mechanical response,microstructure evolution,and twinning behaviors were investigated,and the physical mechanism of the second-order behaviors(both the Swift and inverse Swift effects)was discussed.The results indicate that the two-stage deformation of reciprocating torsion is capable of activating tensile twins,effectively refining the surface grains,and thus improving the yield asymmetry.Due to the reverse load,detwinning dominates the deformation of reverse FET(RFET),while detwinning in FRT deformation is caused by the spontaneous rotation of the inverse Swift effect.The twin variants with c-axis tending to extrusion direction(ED)are predisposed to detwinning,and the bimodal texture introduced by FET is degraded.The plastic deformation of RFET is primarily coordinated by basal and prismatic slips.The large strain FRT is dominated by basal slip due to its low SF/CRSS.The interaction between twinning and detwinning dominates the multi-directionality of the Swift effect during reciprocating torsion,and the cumulative effect of strain hardening further enhances the dependence of RFET axial strain on basal slip.The dγ/dεindex successfully captures the evolution of the inverse Swift effect during FRT.The forward rotation of the solid rod is caused by the inversion of the radial residual shear stress field,and the internal stress introduced by the torsional inhomogeneity is compensated.The subsequent reverse rotation is the result of balancing the orientation inhomogeneity and local strain heterogeneity introduced by the shear deformation.The increase in the reverse rotation rate is caused by detwinning.
基金supported by National Natural Science Foundation of China(Grant Nos.12122206,11972152,12272129)Postgraduate Scientific Research Innovation Project of Hunan Province and the Hong Kong Scholars Program(Grant No.XJ2022012).
文摘This paper proposes a novel idea by integrating a torsion dynamic vibration absorber with a triboelectric energy harvester to realize synchronous torsional vibration suppression and energy harvesting in a rotor system.The most fantastic feature of the proposed torsion harvester-absorber system(HAS)is the quasi-zero-stiffness(QZS)characteristic for suppressing and har-vesting low-frequency vibration energy.The QZS characteristic is realized by combining negative stiffness magnet couplings(NSMC)in parallel connection with a pair torsion coil spring.A theoretical model of the NSMC is established based on the equivalent magnetic charge method,and parametric studies are conducted to provide a guideline for the design of the NSMC.Furthermore,the dynamic model of the host oscillator with a torsion QZS HAS is established based on Lagrange’s equation,and then the dynamic amplification factor is obtained using the harmonic balance method.The effects of geometric parameters on both the performances of vibration mitigation and energy harvesting are investigated.Finally,the parameters of the torsion QZS HAS are optimized using H_(∞)optimization method and genetic algorithm,respectively.This enables the torsion QZS HAS to effectively suppress low-frequency vibrations of the rotor system while simultaneously harvesting energy over a wide frequency band.
基金Supported by the National Natural Science Foundation of China(50775182)the Scientific Research Foundation for the Returned Scholars of the Ministry of Education of China~~
文摘An improved understanding of fatigue behavior of a cast aluminum alloy（2-AS5U3G-Y35）in very high cycle regime is developed through the ultrasonic fatigue test in axial and torsion loading.The new developed torsion fatigue system is presented.The effects of loading condition and frequency on the very high cycle fatigue（VHCF）are investigated.The cyclic loading in axial and torsion at 35 Hz and 20 kHz with stress ratio R=-1 is used respectively to demonstrate the effect of loading condition.S-N curves show that the fatigue failure occurs in the range of 105—1010 cycles in axial or torsion loading and the asymptote of S-N curve is inclined,but no fatigue limit exists under the torsion and axial loading condition.The fatigue fracture surface shows that the fatigue crack initiates from the specimen surface subjected to the cyclic torsion loading.It is different from the fatigue fracture characteristic in axial loading in which fatigue crack initiates from subsurface defect in very high cycle regime.The fatigue initiation is on the maximum shear plane,the overall crack orientation is on a typical spiral 45° to the fracture plane and it is the maximum principle stress plane.The clear shear strip in the torsion fatigue fracture surface shows that the torsion fracture is the shear fracture.
基金support from the National Natural Science Foundation of China(Grant No.12272146)the Fundamental Research Funds for the Central Universities(Grant No.2024BRA009)the Young Top-notch Talent Cultivation Program of Hubei Province,is appreciated.
文摘Twisted polymer artificial muscles activated by thermal heating represent a new class of soft actuators capable of generating torsional actuation.The thermal torsion effect,characterized by the reversible untwisting of twisted fibers as temperature increases due to greater radial than axial thermal expansion,is crucial to the actuation performance of these artificial muscles.This study explores the thermal torsion effect of polymer muscles made of twisted Nylon 6 fibers in experimental and theoretical aspects,focusing on the interplay between material properties and temperature.It is revealed that the thermal torsion effect enhances the actuation performance of the twisted polymer actuator while the thermal softening effect diminishes it.A thermal-mechanical model incorporating both the thermal torsion effect and thermal softening effect is used to predict the recovered torque of the twisted polymer actuators.An optimal bias angle and operating temperature are identified to maximize the recovered torque.Analysis of strain and stress distributions in the cross-section of the twisted polymer fiber shows that the outer layers of the fiber predominantly contribute to the torsional actuation.This work aids in the precise control and structural optimization of the thermally-activated twisted polymer actuators.
基金Supported by National Natural Science Foundation of China(Grant No.11771070).
文摘In this paper,we compute sub-Riemannian limits of some important curvature variants associated with the connection with torsion for four dimensional twisted BCV spaces and derive a Gauss-Bonnet theorem for four dimensional twisted BCV spaces.
基金supported by the National Natural Science Foundation of China(Grant Nos.52408407 and 52478373)the‘CUG Scholar’Scientific Research Funds at China University of Geosciences(Grant No.2023082).
文摘The torsional low strain integrity test(TLSIT),known for its advantages such as a smaller detection blind zone,improved identification of shallowly buried defects,stable phase velocity for signal interpretation,and better adaptability for existing pile testing.However,it lacks a comprehensive understanding of the authentic three-dimensional(3D)strain wave propagation mechanism,particularly wave reflection and transmission at defects.To address this gap,a novel 3D theoretical framework is introduced in this context to model the authentic 3D wave propagation during the TLSIT.The proposed approach is validated by comparing its results with those obtained from 3D finite element method(FEM)simulations and simplified 1D(one-dimensional)and 3D analytical solutions.Additionally,a parametric study is conducted to enhance insights into the formation mechanism of high-frequency interference observed during the TLSIT.Finally,a defect identification study is performed to provide guidance for interpreting the wave spectrum in terms of defect characteristics.
基金supported by the National Natural Science Foundation of China(No.52305262)the Aeronautical Science Foundation of China(No.20230015052002)the Fundamental Research Funds for the Central Universities(No.NT2024001)。
文摘Morphing aircraft are designed to adaptively adjust their shape for changing flight missions,which enables them to improve their flight performance significantly for future applications.The folding wingtips represent a key research aspect for morphing aircraft,since they can lead to potential improvements in flight range,maneuverability,load alleviation and airport compatibility.This paper proposes a hinge mechanism design for folding wingtips based on the shape memory alloy torsion tube,aiming to achieve successful folding using the actuation effect of the shape memory alloy.The proposed design employs a shape memory alloy torsion tube as the actuator for the active folding of the wingtip,which is motivated by the characteristics of the tube,enabling a simplified structure for the integration with high energy density.Through numerical simulation and testing of the folding wingtip structure,the concept is verified,which shows its potential as an actuator for folding wingtips.
