As a core power device in strategic industries such as new energy power generation and electric vehicles,the thermal reliability of IGBT modules directly determines the performance and lifetime of the whole system.A s...As a core power device in strategic industries such as new energy power generation and electric vehicles,the thermal reliability of IGBT modules directly determines the performance and lifetime of the whole system.A synergistic optimization structure of“inlet plate-channel spoiler columns”is proposed for the local hot spot problem during the operation of Insulated Gate Bipolar Transistor(IGBT),combined with the inherent defect of uneven flow distribution of the traditional U-type liquid cooling plate in this paper.The influences of the shape,height(H),and spacing from the spoiler column(b)of the plate on the comprehensive heat dissipation performance of the liquid cooling plate are analyzed at different Reynolds numbers,A dual heat source strategy is introduced and the effect of the optimized structure is evaluated by the temperature inhomogeneity coefficient(Φ).The results show that the optimum effect is achieved when the shape of the plate is square,H=4.5 mm,b=2 mm,and u=0.05 m/s,at which the HTPE=1.09 and Φ are reduced by 40%.In contrast,the maximum temperatures of the IGBT and the FWD(Free Wheeling Diode)chips are reduced by 8.7 and 8.4 K,respectively,and ΔP rises by only 1.58 Pa while keeping ΔT not significantly increased.This optimized configuration achieves a significant reduction in the critical chip temperature and optimization of the flow field uniformity with almost no change in the system flow resistance.It breaks through the limitation of single structure optimization of the traditional liquid cooling plate and effectively solves the problem of uneven flow in the U-shaped cooling plate,which provides a new solution with important engineering value for the thermal management of IGBT modules.展开更多
Human pose estimation is a critical research area in the field of computer vision,playing a significant role in applications such as human-computer interaction,behavior analysis,and action recognition.In this paper,we...Human pose estimation is a critical research area in the field of computer vision,playing a significant role in applications such as human-computer interaction,behavior analysis,and action recognition.In this paper,we propose a U-shaped keypoint detection network(DAUNet)based on an improved ResNet subsampling structure and spatial grouping mechanism.This network addresses key challenges in traditional methods,such as information loss,large network redundancy,and insufficient sensitivity to low-resolution features.DAUNet is composed of three main components.First,we introduce an improved BottleNeck block that employs partial convolution and strip pooling to reduce computational load and mitigate feature loss.Second,after upsampling,the network eliminates redundant features,improving the overall efficiency.Finally,a lightweight spatial grouping attention mechanism is applied to enhance low-resolution semantic features within the feature map,allowing for better restoration of the original image size and higher accuracy.Experimental results demonstrate that DAUNet achieves superior accuracy compared to most existing keypoint detection models,with a mean PCKh@0.5 score of 91.6%on the MPII dataset and an AP of 76.1%on the COCO dataset.Moreover,real-world experiments further validate the robustness and generalizability of DAUNet for detecting human bodies in unknown environments,highlighting its potential for broader applications.展开更多
Chinese named entity recognition(CNER)has received widespread attention as an important task of Chinese information extraction.Most previous research has focused on individually studying flat CNER,overlapped CNER,or d...Chinese named entity recognition(CNER)has received widespread attention as an important task of Chinese information extraction.Most previous research has focused on individually studying flat CNER,overlapped CNER,or discontinuous CNER.However,a unified CNER is often needed in real-world scenarios.Recent studies have shown that grid tagging-based methods based on character-pair relationship classification hold great potential for achieving unified NER.Nevertheless,how to enrich Chinese character-pair grid representations and capture deeper dependencies between character pairs to improve entity recognition performance remains an unresolved challenge.In this study,we enhance the character-pair grid representation by incorporating both local and global information.Significantly,we introduce a new approach by considering the character-pair grid representation matrix as a specialized image,converting the classification of character-pair relationships into a pixel-level semantic segmentation task.We devise a U-shaped network to extract multi-scale and deeper semantic information from the grid image,allowing for a more comprehensive understanding of associative features between character pairs.This approach leads to improved accuracy in predicting their relationships,ultimately enhancing entity recognition performance.We conducted experiments on two public CNER datasets in the biomedical domain,namely CMeEE-V2 and Diakg.The results demonstrate the effectiveness of our approach,which achieves F1-score improvements of 7.29 percentage points and 1.64 percentage points compared to the current state-of-the-art(SOTA)models,respectively.展开更多
U-shaped sacral fractures are rare and often difficult to diagnose primarily due to the difficulty in obtaining adequate imaging and the severe associated injuries. These fractures are highly unstable and frequently c...U-shaped sacral fractures are rare and often difficult to diagnose primarily due to the difficulty in obtaining adequate imaging and the severe associated injuries. These fractures are highly unstable and frequently cause neurological deficits. The majority of surgeons have limited experience in management of U-shaped sacral fractures. No standard treatment protocol for U-shaped sacral fractures has been available till now. This study aimed to examine the management of U-shaped sacral fractures and the early outcomes. Clinical data of 15 consecutive patients with U-shaped sacral fracture who were admitted to our trauma center between 2009 and 2014 were retrospectively analyzed. Demographics, fracture classification, mechanism of injury and operative treatment and deformity angle were assessed. All the patients were treated with lumbopelvic fixation or （and） sacral decompression. EQ-5d score was applied to evaluate the patients＇ quality of life. Of the 15 consecutive patients with U-shaped sacral fracture, the mean age was 28.8 years （range： 15-55 years） at the time of injury. There were 6 females and 9 males. The mean follow- up time was 22.7 months （range： 9-47 months） and mean full weight-bearing time was 9.9 weeks （range： 8-14 weeks）. Ten patients received lumbopelvic fixation and sacral decompression, one lombosacral fixation, and 4 merely sacral decompression due to delayed diagnosis or surgery. The post-operation deformity angle （mean 27.87°, and range： 8°-90°） of the sacrum was smaller than that pre-operation （mean 35.67; range： 15-90） with no significance difference noted. At the latest follow-up, all patients obtained neurological recovery with different extents. Visual analogue score （VAS） was reduced from preoperative 7.07 （range： 5-9） to postoperetive 1.93 （range： 1-3）. All patients could walk without any aid after treatment. Eight patients were able to care for themselves and undertook some daily activities. Five patients had returned to work full time. In conclusion, lumbopelvic fixation is an effective method for stabilization of U-shaped sacral fractures with fewer complications developed. Effective reduction and firm fixation are the prerequisite of early mobilization and neurological recovery. Sacral decompression effectively promotes neurological recovery even in patients with old U-shaped sacral fractures.展开更多
Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape not...Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape notch on the spool, such as mass flow rates, flow coefficients, effiux angles and steady state flow forces under different operating conditions. At last, the reliability of the mathematical model of the flow area for the sloping U-shape notch orifice on the spool was demonstrated by the comparison between the orifice area curve derived and the corresponding experimental data provided by the test. It is presented that the bottom arc of sloping U-shape notch （ABU） should not be omitted when it is required to accurately calculate the orifice area of ABU. Although the theoretical flow area of plain bottom sloping U-shape notch （PBU） is larger than that of ABU at the same opening, the simulated mass flow and experimental flow area of ABU are both larger than these of PBU at the same opening, while the simulated flow force of PBU is larger than that of ABU at the same opening. Therefore, it should be prior to adapt the ABU when designing the spool with proportional character.展开更多
Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming,the stress concentration and defects such as wrinkling and fracture may easily occur.It is a key to reveal the defo...Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming,the stress concentration and defects such as wrinkling and fracture may easily occur.It is a key to reveal the deformation behaviors in order to obtain a sound product.Based on the ABAQUS platform,a 3 D-FE model of the four-layered U-shaped metallic bellow hydroforming process is established and validated by experiment.The stress and strain distributions,wall thickness variations and bellow profiles of each layer in the whole process,including bulging,folding and springback stages,are studied.Then deformation behaviors of bellows under different forming conditions are discussed.It is found that the wall thinning degrees of different layer vary after hydroforming,and is the largest for the inner layer and smallest for the outer layer.At folding stage,the wall thinning degree of the crown point increases lineally,and the difference among layers increases as the process going.The displacements of the crown point decrease from the inner layer to the outer layer.After springback,the U-shaped cross section changes to a tongue shape,the change of convolution pitch is much larger than the change of convolution height,and the springback values of the inner layer are smaller than the outer layer.An increase in the internal pressure and die spacing cause the maximum wall thinning degree and springback increase.With changing of process parameters,bellows with deep convolution are easily encountered wall thinning during hydroforming and convolution distortion after springback.This research is helpful for precision forming of multi-layered bellows.展开更多
The formulae for stresses and angular displacements of U-shaped bellows overall bending in a meridian plane under pure bending moments are presented based on the general solution for slender ring shells proposed by Zh...The formulae for stresses and angular displacements of U-shaped bellows overall bending in a meridian plane under pure bending moments are presented based on the general solution for slender ring shells proposed by Zhu Weiping, et al. and the solution for ring plates. The results evaluated in this paper are compared with those on EJMA (standards of the expansion joint manufacturers association) and of the experiment given by Li Tingxilz, et al.展开更多
Open U-shaped steel arch supports are commonly used in large-section static-pressure roadways in coal mines that are more than 900 m deep;however,it is very difficult to control floor heave of roadways.In this paper,a...Open U-shaped steel arch supports are commonly used in large-section static-pressure roadways in coal mines that are more than 900 m deep;however,it is very difficult to control floor heave of roadways.In this paper,a U-shaped steel closed support with an inverted U-shaped steel arch in the floor is proposed as a method for improving the support effect of the surrounding rock during the process of floor heaving.This research established a mechanical model for the U-shaped steel closed support,and determined the reaction forces at the connection of a camber angle.Using the limit load method calculated the critical buckling load of the inverted U-shaped steel arch,and use of a strength check method tested the strength of the U-shaped steel material.A numerical simulation was conducted using the finite difference software FLAC3 D.The simulation results show that the U-shaped steel closed support is able to control the floor heave of roadways,which is successfully used in the West 11-2 development roadway of the Zhuji Mine in the Huainan mining area in China.The cumulative floor heave over two years was less than50 mm.展开更多
U-shaped micro-nanochannels can generate significant flow disturbance as well as locally amplified electric field, which gives itself potential to be microfluidic mixers, electrokinetic pumps,and even cell lysis proce...U-shaped micro-nanochannels can generate significant flow disturbance as well as locally amplified electric field, which gives itself potential to be microfluidic mixers, electrokinetic pumps,and even cell lysis process. Numerical simulation is utilized in this work to study the hidden characteristics of the U-shaped micro-nanochannel system, and the effects of key controlling parameters(the external voltage and pressure) on the device output metrics(current, maximum values of electric field, shear stress and flow velocity) were evaluated. A large portion of current flowing through the whole system goes through the nanochannels, rather than the middle part of the microchannel, with its value increasing linearly with the increase of voltage. Due to the local ion depletion near micro-nanofluidic junction, significantly enhanced electric field(as much as 15 fold at V=1 V and P_0=0) as well as strong shear stress(leading to electrokinetic flow) is generated.With increasing external pressure, both electric field and shear stress can be increased initially(due to shortening of depletion region length), but are suppressed eventually at higher pressure due to the destruction of ion depletion layer. Insights gained from this study could be useful for designing nonlinear electrokinetic pumps and other systems.展开更多
To get a full understanding of hot extrusion,solid solution treatment and aging process on the Al−0.56Mg−0.63Si alloy,the microstructure and mechanical properties of a U-shaped profile were studied through optical mic...To get a full understanding of hot extrusion,solid solution treatment and aging process on the Al−0.56Mg−0.63Si alloy,the microstructure and mechanical properties of a U-shaped profile were studied through optical microscopy,scanning electrical microscopy,transmission electrical microscopy,hardness,and tensile tests.The coarse equiaxed grains existed near the profile edge as a result of the dynamic recrystallization nucleation and exceeding growth during hot extrusion.The fibrous deformed and sub-structured grains located between the two coarse grain layers,due to the occurrence of work-hardening and dynamic recovery.Perpendicular needle β′′precipitates were distributed inside the grain,and obvious precipitates-free zone appeared after aging treatment.The tensile strength,yield strength and elongation of the aged Al−Mg−Si alloy U-shaped profile were no less than 279.4 MPa,258.6 MPa,and 21.6%,respectively.The fracture morphology showed dimple rupture characteristics.The precipitates and grain boundaries played key role in the strengthening contribution.展开更多
Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was...Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was established. Using parametric programming language, finite element calculation modules considering climate conditions, bridge site, structure dimension and material thermophysical properties were compiled. Six standard day cycles with the strongest yearly radiation among the bridge sites were selected for sectional solar temperature field calculation and temperature distributions under different temperature-sensitive parameters were compared. The results show that under the influence of sunshine, U-shape section of the beam shows obvious nonlinear distribution characteristics and the maximum cross-section temperature difference is more than 21℃; the ballast significantly reduces sunshine temperature difference of the beam and temperature peak of the bottom margin lags with the increase of ballast thickness; the maximum cross-section vertical temperature gradient appears in summer while large transverse temperature difference appears in winter.展开更多
This study proposes a novel U-shaped 65Mn steel bumper as the displacement restraining device for base-isolated structures with laminated elastomeric rubber bearings.A series of bumpers with different geometric parame...This study proposes a novel U-shaped 65Mn steel bumper as the displacement restraining device for base-isolated structures with laminated elastomeric rubber bearings.A series of bumpers with different geometric parameters were designed and tested under monotonic and cyclic quasi-static loading protocols.The experimental results from a total of 232 specimens were analyzed to develop an analytical model to calculate the backbone curve and the maximum elastic restoring force for U-shaped 65Mn bumpers.Thus,the analytical equations to calculate the elastic,hardening,and unloading stiffness of U-shaped 65Mn bumpers,as well as their maximum elastic restoring force,are validated by using an additional ten groups of bumpers with varying radiuses.These analytical equations can accurately predict the mechanical parameters of U-shaped 65Mn steel bumpers for a design purpose.展开更多
This paper follows the work of[1,2].There are some progress in dealing with moderately small rotations(the squares of rotation angles are the order of magnitude of strains)of middle surface normals of inside and outsi...This paper follows the work of[1,2].There are some progress in dealing with moderately small rotations(the squares of rotation angles are the order of magnitude of strains)of middle surface normals of inside and outside ring shells and compressed angle of bellows.Calculation results agree with experiments well.To bellow design,the method given in this paper is of practical value and the discussion of the influence of compressed angle on characteristic relation is helpful.展开更多
In view of the problems of multi-scale changes of segmentation targets,noise interference,rough segmentation results and slow training process faced by medical image semantic segmentation,a multi-scale residual aggreg...In view of the problems of multi-scale changes of segmentation targets,noise interference,rough segmentation results and slow training process faced by medical image semantic segmentation,a multi-scale residual aggregation U-shaped attention network structure of MAAUNet(MultiRes aggregation attention UNet)is proposed based on MultiResUNet.Firstly,aggregate connection is introduced from the original feature aggregation at the same level.Skip connection is redesigned to aggregate features of different semantic scales at the decoder subnet,and the problem of semantic gaps is further solved that may exist between skip connections.Secondly,after the multi-scale convolution module,a convolution block attention module is added to focus and integrate features in the two attention directions of channel and space to adaptively optimize the intermediate feature map.Finally,the original convolution block is improved.The convolution channels are expanded with a series convolution structure to complement each other and extract richer spatial features.Residual connections are retained and the convolution block is turned into a multi-channel convolution block.The model is made to extract multi-scale spatial features.The experimental results show that MAAUNet has strong competitiveness in challenging datasets,and shows good segmentation performance and stability in dealing with multi-scale input and noise interference.展开更多
On the basis of paper[1],assuming the logarithm of thickness at arbitrary point on a U-shaped bellows meridian is linear with the logarithm of distance between that point and axis of symmetry,perturbation solutions of...On the basis of paper[1],assuming the logarithm of thickness at arbitrary point on a U-shaped bellows meridian is linear with the logarithm of distance between that point and axis of symmetry,perturbation solutions of the corresponding problems of large axisymmetrical deflection are given.The effects of thickness distribution variation,which result from technology factors,on stiffness of bellows are discussed.展开更多
An ultra-low specific on-resistance （Ron,sp） oxide trench-type silicon-on-insulator （SOI） lateral double-diffusion metal-oxide semiconductor （LDMOS） with an enhanced breakdown voltage （BV） is proposed and inve...An ultra-low specific on-resistance （Ron,sp） oxide trench-type silicon-on-insulator （SOI） lateral double-diffusion metal-oxide semiconductor （LDMOS） with an enhanced breakdown voltage （BV） is proposed and investigated by simulation. There are two key features in the proposed device： one is a U-shaped gate around the oxide trench, which extends from source to drain （UG LDMOS）; the other is an N pillar and P pillar located in the trench sidewall. In the on-state, electrons accumulate along the U-shaped gate, providing a continuous low resistance current path from source to drain. The Ron,sp is thus greatly reduced and almost independent of the drift region doping concentration. In the off-state, the N and P pillars not only enhance the electric field （E-field） strength of the trench oxide, but also improve the E-field distribution in the drift region, leading to a significant improvement in the BV. The BV of 662 V and Ron,sp of 12.4 mΩ.cm2 are achieved for the proposed UG LDMOS. The BV is increased by 88.6% and the Ron,sp is reduced by 96.4%, compared with those of the conventional trench LDMOS （CT LDMOS）, realizing the state-of-the-art trade-off between BV and Ron,sp.展开更多
A novel optical fiber sensor with a U-shaped micro-groove structure ablated by femtosecond laser on single-mode fiber for measuring air relative humidity(RH)is reported in this paper.In order to improve the accuracy o...A novel optical fiber sensor with a U-shaped micro-groove structure ablated by femtosecond laser on single-mode fiber for measuring air relative humidity(RH)is reported in this paper.In order to improve the accuracy of sensor,a graphene oxide(GO)/polyvinyl alcohol(PVA)composite film is coated on the surface of micro-groove structure.In the U-shaped micro-groove structure,the remaining core and micro-cavity in the micro-groove make up two major optical propagation paths,forming a Mach-Zehnder interferometer(MZI).The sensor has a good linear response within the RH range of 30%—85%,and the maximum sensitivity can reach 0.638 1 nm/%RH.The effect of temperature on the overall performance of the humidity sensor is also investigated.As a new type of all-fiber device,the sensor shows excellent sensitivity and stability.展开更多
In this work,we report a novel octa-nuclear uranyl(U8)motif[(UO2)8O4(μ3-OH)2(μ2-OH)2]4+embedded in a uranyl-oxalate coordination polymer(compound 1)based on a U-shaped linker with extra-long xylylene chains for stab...In this work,we report a novel octa-nuclear uranyl(U8)motif[(UO2)8O4(μ3-OH)2(μ2-OH)2]4+embedded in a uranyl-oxalate coordination polymer(compound 1)based on a U-shaped linker with extra-long xylylene chains for stabilizing the resulting high-nuclear motif through additional cross-linking connectivity.A comparison with dimeric and monomeric uranyl compounds obtained at different pH value from the same hydrothermal system reveals that,solution pH plays a vital role in formation of this octa-nuclear uranyl motif by promoting hydrolysis of uranyl source.Since high similarity of eight uranium centers in this nearly planar U8 motif here,overlapping and broadening of signals in fluorescence,infra-red(IR)and Raman spectra can be found.展开更多
Temperature has an important impact on the corrosion resistance of mold with cooling channels prepared by casting method.The effect of preheating temperature of the mold and the carbon fiber core on the roughness and ...Temperature has an important impact on the corrosion resistance of mold with cooling channels prepared by casting method.The effect of preheating temperature of the mold and the carbon fiber core on the roughness and corrosion resistance of U-shaped cooling channels made of Al-12Si alloy was examined in depth.The experimental results suggest that as the preheating temperature increased from 273 K to 573 K,the roughness of the inner wall of the cooling channel reduced from 96.6μm to 77.0μm.When the preheating temperature continued to increase to 723 K,the roughness increased to 85.3μm.The wetting between the Al melt and the carbon fiber will reduce micro bubbles and waves on the channel wall as the preheating temperature rises,thereby reducing the roughness.However,with the further increase of preheating temperature,it will increase the solidification time of the Al melt.At this time,the carbon fiber and Al melt will take more time to react,which increases the roughness of the channel wall to a certain extent.The results of exfoliation corrosion show that the larger roughness will aggravate exfoliation corrosion.The prolongation of high temperature reaction time between the carbon fiber and the Al melt will lead to the segregation of Si,which is easy to cause intergranular corrosion.Therefore,reasonable preheating temperature has an important impact on the roughness and corrosion resistance of U-shaped cooling channels.展开更多
An ultralow specific on-resistance （Ron,sp） trench metal-oxide-semiconductor field effect transistor （MOSFET） with an improved off-state breakdown voltage （BV） is proposed. It features a U-shaped gate around the...An ultralow specific on-resistance （Ron,sp） trench metal-oxide-semiconductor field effect transistor （MOSFET） with an improved off-state breakdown voltage （BV） is proposed. It features a U-shaped gate around the drift region and an oxide trench inserted in the drift region （UG MOSFET）. In the on-state, the U-shaped gate induces a high density electron accumulation layer along its sidewall, which provides a low-resistance current path from the source to the drain, realizing an ultralow Ron,sp. The value of Ron,sp is almost independent of the drift doping concentration, and thus the UG MOSFET breaks through the contradiction relationship between R p and the off-state BV. Moreover, the oxide trench folds the drift region, enabling the UG MOSFET to support a high BV with a shortened cell pitch. The UG MOSFET achieves an Ron,sp of 2 mΩ·cm^2 and an improved BV of 216 V, superior to the best existing state-of-the-art transistors at the same BV level展开更多
基金supported by Tianjin Science and Technology Planning Project(22YDTPJC0020).
文摘As a core power device in strategic industries such as new energy power generation and electric vehicles,the thermal reliability of IGBT modules directly determines the performance and lifetime of the whole system.A synergistic optimization structure of“inlet plate-channel spoiler columns”is proposed for the local hot spot problem during the operation of Insulated Gate Bipolar Transistor(IGBT),combined with the inherent defect of uneven flow distribution of the traditional U-type liquid cooling plate in this paper.The influences of the shape,height(H),and spacing from the spoiler column(b)of the plate on the comprehensive heat dissipation performance of the liquid cooling plate are analyzed at different Reynolds numbers,A dual heat source strategy is introduced and the effect of the optimized structure is evaluated by the temperature inhomogeneity coefficient(Φ).The results show that the optimum effect is achieved when the shape of the plate is square,H=4.5 mm,b=2 mm,and u=0.05 m/s,at which the HTPE=1.09 and Φ are reduced by 40%.In contrast,the maximum temperatures of the IGBT and the FWD(Free Wheeling Diode)chips are reduced by 8.7 and 8.4 K,respectively,and ΔP rises by only 1.58 Pa while keeping ΔT not significantly increased.This optimized configuration achieves a significant reduction in the critical chip temperature and optimization of the flow field uniformity with almost no change in the system flow resistance.It breaks through the limitation of single structure optimization of the traditional liquid cooling plate and effectively solves the problem of uneven flow in the U-shaped cooling plate,which provides a new solution with important engineering value for the thermal management of IGBT modules.
基金supported by the Natural Science Foundation of Hubei Province of China under grant number 2022CFB536the National Natural Science Foundation of China under grant number 62367006the 15th Graduate Education Innovation Fund of Wuhan Institute of Technology under grant number CX2023579.
文摘Human pose estimation is a critical research area in the field of computer vision,playing a significant role in applications such as human-computer interaction,behavior analysis,and action recognition.In this paper,we propose a U-shaped keypoint detection network(DAUNet)based on an improved ResNet subsampling structure and spatial grouping mechanism.This network addresses key challenges in traditional methods,such as information loss,large network redundancy,and insufficient sensitivity to low-resolution features.DAUNet is composed of three main components.First,we introduce an improved BottleNeck block that employs partial convolution and strip pooling to reduce computational load and mitigate feature loss.Second,after upsampling,the network eliminates redundant features,improving the overall efficiency.Finally,a lightweight spatial grouping attention mechanism is applied to enhance low-resolution semantic features within the feature map,allowing for better restoration of the original image size and higher accuracy.Experimental results demonstrate that DAUNet achieves superior accuracy compared to most existing keypoint detection models,with a mean PCKh@0.5 score of 91.6%on the MPII dataset and an AP of 76.1%on the COCO dataset.Moreover,real-world experiments further validate the robustness and generalizability of DAUNet for detecting human bodies in unknown environments,highlighting its potential for broader applications.
基金supported by Yunnan Provincial Major Science and Technology Special Plan Projects(Grant Nos.202202AD080003,202202AE090008,202202AD080004,202302AD080003)National Natural Science Foundation of China(Grant Nos.U21B2027,62266027,62266028,62266025)Yunnan Province Young and Middle-Aged Academic and Technical Leaders Reserve Talent Program(Grant No.202305AC160063).
文摘Chinese named entity recognition(CNER)has received widespread attention as an important task of Chinese information extraction.Most previous research has focused on individually studying flat CNER,overlapped CNER,or discontinuous CNER.However,a unified CNER is often needed in real-world scenarios.Recent studies have shown that grid tagging-based methods based on character-pair relationship classification hold great potential for achieving unified NER.Nevertheless,how to enrich Chinese character-pair grid representations and capture deeper dependencies between character pairs to improve entity recognition performance remains an unresolved challenge.In this study,we enhance the character-pair grid representation by incorporating both local and global information.Significantly,we introduce a new approach by considering the character-pair grid representation matrix as a specialized image,converting the classification of character-pair relationships into a pixel-level semantic segmentation task.We devise a U-shaped network to extract multi-scale and deeper semantic information from the grid image,allowing for a more comprehensive understanding of associative features between character pairs.This approach leads to improved accuracy in predicting their relationships,ultimately enhancing entity recognition performance.We conducted experiments on two public CNER datasets in the biomedical domain,namely CMeEE-V2 and Diakg.The results demonstrate the effectiveness of our approach,which achieves F1-score improvements of 7.29 percentage points and 1.64 percentage points compared to the current state-of-the-art(SOTA)models,respectively.
文摘U-shaped sacral fractures are rare and often difficult to diagnose primarily due to the difficulty in obtaining adequate imaging and the severe associated injuries. These fractures are highly unstable and frequently cause neurological deficits. The majority of surgeons have limited experience in management of U-shaped sacral fractures. No standard treatment protocol for U-shaped sacral fractures has been available till now. This study aimed to examine the management of U-shaped sacral fractures and the early outcomes. Clinical data of 15 consecutive patients with U-shaped sacral fracture who were admitted to our trauma center between 2009 and 2014 were retrospectively analyzed. Demographics, fracture classification, mechanism of injury and operative treatment and deformity angle were assessed. All the patients were treated with lumbopelvic fixation or （and） sacral decompression. EQ-5d score was applied to evaluate the patients＇ quality of life. Of the 15 consecutive patients with U-shaped sacral fracture, the mean age was 28.8 years （range： 15-55 years） at the time of injury. There were 6 females and 9 males. The mean follow- up time was 22.7 months （range： 9-47 months） and mean full weight-bearing time was 9.9 weeks （range： 8-14 weeks）. Ten patients received lumbopelvic fixation and sacral decompression, one lombosacral fixation, and 4 merely sacral decompression due to delayed diagnosis or surgery. The post-operation deformity angle （mean 27.87°, and range： 8°-90°） of the sacrum was smaller than that pre-operation （mean 35.67; range： 15-90） with no significance difference noted. At the latest follow-up, all patients obtained neurological recovery with different extents. Visual analogue score （VAS） was reduced from preoperative 7.07 （range： 5-9） to postoperetive 1.93 （range： 1-3）. All patients could walk without any aid after treatment. Eight patients were able to care for themselves and undertook some daily activities. Five patients had returned to work full time. In conclusion, lumbopelvic fixation is an effective method for stabilization of U-shaped sacral fractures with fewer complications developed. Effective reduction and firm fixation are the prerequisite of early mobilization and neurological recovery. Sacral decompression effectively promotes neurological recovery even in patients with old U-shaped sacral fractures.
基金Project(51004085)supported by the National Natural Science Foundation of China
文摘Precise function expression of the flow area for the sloping U-shape notch orifice versus the spool stroke was derived. The computational fluid dynamics was used to analyze the flow features of the sloping U-shape notch on the spool, such as mass flow rates, flow coefficients, effiux angles and steady state flow forces under different operating conditions. At last, the reliability of the mathematical model of the flow area for the sloping U-shape notch orifice on the spool was demonstrated by the comparison between the orifice area curve derived and the corresponding experimental data provided by the test. It is presented that the bottom arc of sloping U-shape notch （ABU） should not be omitted when it is required to accurately calculate the orifice area of ABU. Although the theoretical flow area of plain bottom sloping U-shape notch （PBU） is larger than that of ABU at the same opening, the simulated mass flow and experimental flow area of ABU are both larger than these of PBU at the same opening, while the simulated flow force of PBU is larger than that of ABU at the same opening. Therefore, it should be prior to adapt the ABU when designing the spool with proportional character.
基金the funds of the National Natural Science Foundation of China(No.51875456)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2019JM-450)+3 种基金the Young Talent fund of University Association for Science and Technology in Shaanxi,China(No.20170518)the Key Laboratory of Advanced Manufacture Technology for Automobile Parts(Chongqing University of Technology),Ministry of Education(No.2018KLMT03)Materials Science and Engineering provincial-level superior discipline funding project of Xi'an Shiyou Universitythe Program for Young Innovative Research Team in Xi'an Shiyou University(No.2015QNKYCXTD02)。
文摘Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming,the stress concentration and defects such as wrinkling and fracture may easily occur.It is a key to reveal the deformation behaviors in order to obtain a sound product.Based on the ABAQUS platform,a 3 D-FE model of the four-layered U-shaped metallic bellow hydroforming process is established and validated by experiment.The stress and strain distributions,wall thickness variations and bellow profiles of each layer in the whole process,including bulging,folding and springback stages,are studied.Then deformation behaviors of bellows under different forming conditions are discussed.It is found that the wall thinning degrees of different layer vary after hydroforming,and is the largest for the inner layer and smallest for the outer layer.At folding stage,the wall thinning degree of the crown point increases lineally,and the difference among layers increases as the process going.The displacements of the crown point decrease from the inner layer to the outer layer.After springback,the U-shaped cross section changes to a tongue shape,the change of convolution pitch is much larger than the change of convolution height,and the springback values of the inner layer are smaller than the outer layer.An increase in the internal pressure and die spacing cause the maximum wall thinning degree and springback increase.With changing of process parameters,bellows with deep convolution are easily encountered wall thinning during hydroforming and convolution distortion after springback.This research is helpful for precision forming of multi-layered bellows.
文摘The formulae for stresses and angular displacements of U-shaped bellows overall bending in a meridian plane under pure bending moments are presented based on the general solution for slender ring shells proposed by Zhu Weiping, et al. and the solution for ring plates. The results evaluated in this paper are compared with those on EJMA (standards of the expansion joint manufacturers association) and of the experiment given by Li Tingxilz, et al.
基金provided by the National Natural Science Foundation of China(No.51404256)the National Basic Research Program of China(No.2013CB227900)Fundamental Research Funds for the Central Universities of China(No. 2014QNA51)
文摘Open U-shaped steel arch supports are commonly used in large-section static-pressure roadways in coal mines that are more than 900 m deep;however,it is very difficult to control floor heave of roadways.In this paper,a U-shaped steel closed support with an inverted U-shaped steel arch in the floor is proposed as a method for improving the support effect of the surrounding rock during the process of floor heaving.This research established a mechanical model for the U-shaped steel closed support,and determined the reaction forces at the connection of a camber angle.Using the limit load method calculated the critical buckling load of the inverted U-shaped steel arch,and use of a strength check method tested the strength of the U-shaped steel material.A numerical simulation was conducted using the finite difference software FLAC3 D.The simulation results show that the U-shaped steel closed support is able to control the floor heave of roadways,which is successfully used in the West 11-2 development roadway of the Zhuji Mine in the Huainan mining area in China.The cumulative floor heave over two years was less than50 mm.
基金supported by the Intergovernmental International Science,Technology and Innovation Cooperation Key Project of the National Key R&D Programme(2016YFE0105900)the National Natural Science Foundation of China(21576130and 11372229)Kuwait Foundation for the Advancement of Sciences(Kuwait-MIT signature project,Project code:P31475EC01)
文摘U-shaped micro-nanochannels can generate significant flow disturbance as well as locally amplified electric field, which gives itself potential to be microfluidic mixers, electrokinetic pumps,and even cell lysis process. Numerical simulation is utilized in this work to study the hidden characteristics of the U-shaped micro-nanochannel system, and the effects of key controlling parameters(the external voltage and pressure) on the device output metrics(current, maximum values of electric field, shear stress and flow velocity) were evaluated. A large portion of current flowing through the whole system goes through the nanochannels, rather than the middle part of the microchannel, with its value increasing linearly with the increase of voltage. Due to the local ion depletion near micro-nanofluidic junction, significantly enhanced electric field(as much as 15 fold at V=1 V and P_0=0) as well as strong shear stress(leading to electrokinetic flow) is generated.With increasing external pressure, both electric field and shear stress can be increased initially(due to shortening of depletion region length), but are suppressed eventually at higher pressure due to the destruction of ion depletion layer. Insights gained from this study could be useful for designing nonlinear electrokinetic pumps and other systems.
基金financial support of project on reliability and life research of typical components in rail trains (K10TZ20P0500) of CRRC Zhuzhou Electric Locomotive Research Institute.
文摘To get a full understanding of hot extrusion,solid solution treatment and aging process on the Al−0.56Mg−0.63Si alloy,the microstructure and mechanical properties of a U-shaped profile were studied through optical microscopy,scanning electrical microscopy,transmission electrical microscopy,hardness,and tensile tests.The coarse equiaxed grains existed near the profile edge as a result of the dynamic recrystallization nucleation and exceeding growth during hot extrusion.The fibrous deformed and sub-structured grains located between the two coarse grain layers,due to the occurrence of work-hardening and dynamic recovery.Perpendicular needle β′′precipitates were distributed inside the grain,and obvious precipitates-free zone appeared after aging treatment.The tensile strength,yield strength and elongation of the aged Al−Mg−Si alloy U-shaped profile were no less than 279.4 MPa,258.6 MPa,and 21.6%,respectively.The fracture morphology showed dimple rupture characteristics.The precipitates and grain boundaries played key role in the strengthening contribution.
基金Project(51378503)supported by the National Natural Science Foundation of ChinaProject(2010G018-A-3)supported by Technology Research and Development Program of the Ministry of Railways,China
文摘Based on transient temperature field theory of heat conduction, the solar temperature field calculation model of U-shape sectioned high-speed railway cable-stayed bridge under actions of concrete beams and ballast was established. Using parametric programming language, finite element calculation modules considering climate conditions, bridge site, structure dimension and material thermophysical properties were compiled. Six standard day cycles with the strongest yearly radiation among the bridge sites were selected for sectional solar temperature field calculation and temperature distributions under different temperature-sensitive parameters were compared. The results show that under the influence of sunshine, U-shape section of the beam shows obvious nonlinear distribution characteristics and the maximum cross-section temperature difference is more than 21℃; the ballast significantly reduces sunshine temperature difference of the beam and temperature peak of the bottom margin lags with the increase of ballast thickness; the maximum cross-section vertical temperature gradient appears in summer while large transverse temperature difference appears in winter.
基金National Science Foundation of China for the Financial Support for This Research under Grant Nos.51378047 and 51408027。
文摘This study proposes a novel U-shaped 65Mn steel bumper as the displacement restraining device for base-isolated structures with laminated elastomeric rubber bearings.A series of bumpers with different geometric parameters were designed and tested under monotonic and cyclic quasi-static loading protocols.The experimental results from a total of 232 specimens were analyzed to develop an analytical model to calculate the backbone curve and the maximum elastic restoring force for U-shaped 65Mn bumpers.Thus,the analytical equations to calculate the elastic,hardening,and unloading stiffness of U-shaped 65Mn bumpers,as well as their maximum elastic restoring force,are validated by using an additional ten groups of bumpers with varying radiuses.These analytical equations can accurately predict the mechanical parameters of U-shaped 65Mn steel bumpers for a design purpose.
文摘This paper follows the work of[1,2].There are some progress in dealing with moderately small rotations(the squares of rotation angles are the order of magnitude of strains)of middle surface normals of inside and outside ring shells and compressed angle of bellows.Calculation results agree with experiments well.To bellow design,the method given in this paper is of practical value and the discussion of the influence of compressed angle on characteristic relation is helpful.
基金National Natural Science Foundation of China(No.61806006)Jiangsu University Superior Discipline Construction Project。
文摘In view of the problems of multi-scale changes of segmentation targets,noise interference,rough segmentation results and slow training process faced by medical image semantic segmentation,a multi-scale residual aggregation U-shaped attention network structure of MAAUNet(MultiRes aggregation attention UNet)is proposed based on MultiResUNet.Firstly,aggregate connection is introduced from the original feature aggregation at the same level.Skip connection is redesigned to aggregate features of different semantic scales at the decoder subnet,and the problem of semantic gaps is further solved that may exist between skip connections.Secondly,after the multi-scale convolution module,a convolution block attention module is added to focus and integrate features in the two attention directions of channel and space to adaptively optimize the intermediate feature map.Finally,the original convolution block is improved.The convolution channels are expanded with a series convolution structure to complement each other and extract richer spatial features.Residual connections are retained and the convolution block is turned into a multi-channel convolution block.The model is made to extract multi-scale spatial features.The experimental results show that MAAUNet has strong competitiveness in challenging datasets,and shows good segmentation performance and stability in dealing with multi-scale input and noise interference.
文摘On the basis of paper[1],assuming the logarithm of thickness at arbitrary point on a U-shaped bellows meridian is linear with the logarithm of distance between that point and axis of symmetry,perturbation solutions of the corresponding problems of large axisymmetrical deflection are given.The effects of thickness distribution variation,which result from technology factors,on stiffness of bellows are discussed.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61176069 and 61376079)the Program for New Century Excellent Talents at the University of Ministry of Education of China(Grant No.NCET-11-0062)
文摘An ultra-low specific on-resistance （Ron,sp） oxide trench-type silicon-on-insulator （SOI） lateral double-diffusion metal-oxide semiconductor （LDMOS） with an enhanced breakdown voltage （BV） is proposed and investigated by simulation. There are two key features in the proposed device： one is a U-shaped gate around the oxide trench, which extends from source to drain （UG LDMOS）; the other is an N pillar and P pillar located in the trench sidewall. In the on-state, electrons accumulate along the U-shaped gate, providing a continuous low resistance current path from source to drain. The Ron,sp is thus greatly reduced and almost independent of the drift region doping concentration. In the off-state, the N and P pillars not only enhance the electric field （E-field） strength of the trench oxide, but also improve the E-field distribution in the drift region, leading to a significant improvement in the BV. The BV of 662 V and Ron,sp of 12.4 mΩ.cm2 are achieved for the proposed UG LDMOS. The BV is increased by 88.6% and the Ron,sp is reduced by 96.4%, compared with those of the conventional trench LDMOS （CT LDMOS）, realizing the state-of-the-art trade-off between BV and Ron,sp.
基金supported by the National Natural Science Foundation of China(No.11104162)the Shandong Province Young and Middle-Aged Scientists Research Awards Fund(No.2011BSB01110)
文摘A novel optical fiber sensor with a U-shaped micro-groove structure ablated by femtosecond laser on single-mode fiber for measuring air relative humidity(RH)is reported in this paper.In order to improve the accuracy of sensor,a graphene oxide(GO)/polyvinyl alcohol(PVA)composite film is coated on the surface of micro-groove structure.In the U-shaped micro-groove structure,the remaining core and micro-cavity in the micro-groove make up two major optical propagation paths,forming a Mach-Zehnder interferometer(MZI).The sensor has a good linear response within the RH range of 30%—85%,and the maximum sensitivity can reach 0.638 1 nm/%RH.The effect of temperature on the overall performance of the humidity sensor is also investigated.As a new type of all-fiber device,the sensor shows excellent sensitivity and stability.
基金National Natural Science Foundation of China(21671191,21577144,11405186)。
文摘In this work,we report a novel octa-nuclear uranyl(U8)motif[(UO2)8O4(μ3-OH)2(μ2-OH)2]4+embedded in a uranyl-oxalate coordination polymer(compound 1)based on a U-shaped linker with extra-long xylylene chains for stabilizing the resulting high-nuclear motif through additional cross-linking connectivity.A comparison with dimeric and monomeric uranyl compounds obtained at different pH value from the same hydrothermal system reveals that,solution pH plays a vital role in formation of this octa-nuclear uranyl motif by promoting hydrolysis of uranyl source.Since high similarity of eight uranium centers in this nearly planar U8 motif here,overlapping and broadening of signals in fluorescence,infra-red(IR)and Raman spectra can be found.
基金financially supported by the National Natural Science Foundation of China(No.51775353)the National Key Research and Development Program of China(No.2019YFB2006501)+2 种基金the Program for Natural Science Foundation of Liaoning Province(No.2021-BS-150)Science and Technology Program of Liaoning Provincial Department of Education(LJKZ0116)Hebei Key Laboratory of Dielectric and Electrolyte Functional Material,Northeastern University at Qinhuangdao(HKDEFM2021204)。
文摘Temperature has an important impact on the corrosion resistance of mold with cooling channels prepared by casting method.The effect of preheating temperature of the mold and the carbon fiber core on the roughness and corrosion resistance of U-shaped cooling channels made of Al-12Si alloy was examined in depth.The experimental results suggest that as the preheating temperature increased from 273 K to 573 K,the roughness of the inner wall of the cooling channel reduced from 96.6μm to 77.0μm.When the preheating temperature continued to increase to 723 K,the roughness increased to 85.3μm.The wetting between the Al melt and the carbon fiber will reduce micro bubbles and waves on the channel wall as the preheating temperature rises,thereby reducing the roughness.However,with the further increase of preheating temperature,it will increase the solidification time of the Al melt.At this time,the carbon fiber and Al melt will take more time to react,which increases the roughness of the channel wall to a certain extent.The results of exfoliation corrosion show that the larger roughness will aggravate exfoliation corrosion.The prolongation of high temperature reaction time between the carbon fiber and the Al melt will lead to the segregation of Si,which is easy to cause intergranular corrosion.Therefore,reasonable preheating temperature has an important impact on the roughness and corrosion resistance of U-shaped cooling channels.
基金Supported by the National Natural Science Foundation of China under Grant No 61376079the Fundamental Research Funds for the Central Universities under Grant No ZYGX2013J043
文摘An ultralow specific on-resistance （Ron,sp） trench metal-oxide-semiconductor field effect transistor （MOSFET） with an improved off-state breakdown voltage （BV） is proposed. It features a U-shaped gate around the drift region and an oxide trench inserted in the drift region （UG MOSFET）. In the on-state, the U-shaped gate induces a high density electron accumulation layer along its sidewall, which provides a low-resistance current path from the source to the drain, realizing an ultralow Ron,sp. The value of Ron,sp is almost independent of the drift doping concentration, and thus the UG MOSFET breaks through the contradiction relationship between R p and the off-state BV. Moreover, the oxide trench folds the drift region, enabling the UG MOSFET to support a high BV with a shortened cell pitch. The UG MOSFET achieves an Ron,sp of 2 mΩ·cm^2 and an improved BV of 216 V, superior to the best existing state-of-the-art transistors at the same BV level
