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
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
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
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
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 o...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
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...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
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
The interaction of U-shaped rings used for power transmission hardware with a wind-sand field is simulated numerically.A standard kturbulence model is used in synergy with an Eulerian-Lagrangian approach.The results...The interaction of U-shaped rings used for power transmission hardware with a wind-sand field is simulated numerically.A standard kturbulence model is used in synergy with an Eulerian-Lagrangian approach.The results show that the wind pressure on the windward side of the U-shaped ring is the highest,a negative pressure zone appears on both sides of the U-shaped ring,while a Kármán Vortex Street is created on its leeward side.There are three possible regimes of motion for the sand grains in the wind field.Sand grains with size below 0.125 mm can follow the airflow directly into the contact area of two U-shaped rings.When the sand size is about 0.1 mm,the number of sand grains that are blown into the contact area attains a maximum.Through the simulation of U-shaped rings in the wind-sand field,the dynamics of such processes are explained in detail,thereby providing relevant information for the subsequent protection and design of connecting hardware used for power transmission.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
In human life,water resources are inseparable.In recent years,China’s population growth has accelerated,and the industrial level has been continuously improved,resulting in the rapid use and waste of water resources....In human life,water resources are inseparable.In recent years,China’s population growth has accelerated,and the industrial level has been continuously improved,resulting in the rapid use and waste of water resources.The protection and rational distribution of water resources are the most pressing issue in China’s water resources.At present,the water measuring facilities of the U-shaped channel mainly include a straight wall measuring pool,a parabolic throat measuring pool,and a long throat measuring pool.In view of the problems in irrigation measurement,the empirical water measurement of basic open-channel and automatic flow measurement system in irrigation district is summarized to improve the accuracy,fairness,and rationality of water measurement,and promote irrigation district management to a higher level.展开更多
The design of a seven-band stacked patch antenna for the C, X and Ku band is presented. The antenna consists of an H-slot loaded fed patch, stacked with dual U-slot loaded rectangular patch to generate the seven frequ...The design of a seven-band stacked patch antenna for the C, X and Ku band is presented. The antenna consists of an H-slot loaded fed patch, stacked with dual U-slot loaded rectangular patch to generate the seven frequency bands. The total size of the antenna is 39.25 × 29.25 mm2. The multiband stacked patch antenna is studied and designed using IE3D simulator. For verification of simulation results, the antenna is analyzed by circuit theory concept. The simulated return loss, radiation pattern and gain are presented. Simulated results show that the antenna can be designed to cover the frequency bands from (4.24 GHz to 4.50 GHz, 5.02 GHz to 5.25 GHz) in C-band application, (7.84 GHz to 8.23 GHz) in X-band and (12.16 GHz to 12.35 GHz, 14.25 GHz to 14.76 GHz, 15.25 GHz to 15.51 GHz, 17.52 GHz to 17.86 GHz) in Ku band applications. The bandwidths of each band of the proposed antenna are 5.9%, 4.5%, 4.83%, 2.36%, 3.53%, 1.68% and 1.91%. Similarly the gains of the proposed band are 2.80 dBi, 4.39 dBi, 4.54 dBi, 10.26 dBi, 8.36 dBi and 9.91 dBi, respectively.展开更多
The U-shaped crushed rock embankment(UCRE),of which widely utilized in the permafrost regions along the Qinghai-Tibet Railway,has the capability to rapidly reduce the ground temperature of the underlying permafrost.Ho...The U-shaped crushed rock embankment(UCRE),of which widely utilized in the permafrost regions along the Qinghai-Tibet Railway,has the capability to rapidly reduce the ground temperature of the underlying permafrost.However,there remains uncertainty regarding the adaptation of UCRE to climate change and its long-term cooling trend.This study focuses on nine UCRE monitoring sites along the Qinghai-Tibet Railway to analyze the dynamic variations of the ground temperature underlying permafrost from 2006 to 2020.The efficiency of UCRE in stabilizing permafrost temperature in different permafrost zones is evaluated by considering the permafrost table,ground temperature,and MAGT,as well as the temperature difference between the top and bottom of the crushed rock layer and the ground temperature variation index(GTVI).The results show that UCRE is suitable for application in extremely unstable warm permafrost regions where the MAGT is higher than-0.5℃.Moreover,UCRE effectively diminishes the disparity in permafrost thermal stability between the sunny and shaded shoulders of the embankment.The short-term and long-term effect of cooling permafrost is experiencing a change related with permafrost stability.Notably,in stable cold permafrost regions with MAGT lower than-1.5℃,the long-term cooling effect of UCRE on permafrost seems to gradually di-minishes,but UCRE continues to fulfill the role of stabilizing the underlying permafrost thermal state over the long-term.These results show that UCRE can quickly restore and stabilize the thermal state of permafrost in the early stages of construction,and adapt to the influence of future climate change.The findings provide important guidance for understanding the variations of permafrost thermal stability beneath the embankment in permafrost regions,as well as for improving the embankment stability and operational safety of the Qinghai-Tibet Railway.展开更多
Convolutional neural networks(CNN)based on U-shaped structures and skip connections play a pivotal role in various image segmentation tasks.Recently,Transformer starts to lead new trends in the image segmentation task...Convolutional neural networks(CNN)based on U-shaped structures and skip connections play a pivotal role in various image segmentation tasks.Recently,Transformer starts to lead new trends in the image segmentation task.Transformer layer can construct the relationship between all pixels,and the two parties can complement each other well.On the basis of these characteristics,we try to combine Transformer pipeline and convolutional neural network pipeline to gain the advantages of both.The image is put into the U-shaped encoder-decoder architecture based on empirical combination of self-attention and convolution,in which skip connections are utilized for localglobal semantic feature learning.At the same time,the image is also put into the convolutional neural network architecture.The final segmentation result will be formed by Mix block which combines both.The mixture model of the convolutional neural network and the Transformer network for road segmentation(MCTNet)can achieve effective segmentation results on KITTI dataset and Unstructured Road Scene(URS)dataset built by ourselves.Codes,self-built datasets and trainable models will be available on https://github.com/xflxfl1992/MCTNet.展开更多
Magnetic data has been widely applied in the tectonic division.High-resolution magnetic data were used to analyze the geotectonic zoning of the South China Sea.Based on the newly compilated magnetic data,the processin...Magnetic data has been widely applied in the tectonic division.High-resolution magnetic data were used to analyze the geotectonic zoning of the South China Sea.Based on the newly compilated magnetic data,the processing results and the distribution of known faults,we consider that the U-shaped line approximately along the South China Sea national boundary of China shown in the magnetic map is a significant geological and geophysical boundary.We first described the linear characteristics of the magnetic data and then applied pseudo-gravity,Euler deconvolution,tilt derivatives,and the texture segmentation method to process the data.Results show that the dividing line between the South China Sea and the surrounding blocks is approximately along this U-shaped line.The dividing line between the South China domain and the South China Sea domain is along with the Dongsha Islands to Xisha Trough,which is different from the previous geophysical zoning results.Our results are almost consistent with those of the gravity data indicating roughly the tectonic zonation along the U-shaped line.展开更多
The orderly transfer of the manufacturing industry is a major action in China’s industrial restructuring.From the perspective of industrial transfer,we used the concentration ratio to depict the trend of the industri...The orderly transfer of the manufacturing industry is a major action in China’s industrial restructuring.From the perspective of industrial transfer,we used the concentration ratio to depict the trend of the industrial transfer of energy-intensive manufacturing in the eastern,central,and western regions since the policy of large-scale development of western China was implemented.We measured the total factor productivity(TFP)of western China using the DEAMalmquist index method.We conducted a regression analysis to measure the effect of western China’s undertaking of the transfer of the energy-intensive manufacturing industry.The findings of this study show that during 2000–2019,eleven provinces(as well as autonomous regions and municipalities)in western China undertook the transfer of the energy-intensive manufacturing industry from the eastern and central regions to varying degrees,exhibiting significant phase features regarding the rate and scale of transfers.Further investigation also demonstrated that the transfer of energy-intensive manufacturing industries has a U-shaped enabling effect on TFP in western China with the scale effect greater than the technology effect.Therefore,it is necessary to transition from“extensive industrial transfer”at the cost of the labor force,land,and resources to“modern industrial transfer”featured by technology and efficiency improvements to contribute to industrial restructuring in western China effectively.展开更多
In this paper,the flow and heat transfer characteristics in U-shaped channel with three different turn shapes are studied.The rotation number ranges from 0~0.251,Reynolds number are 11500,23000,34500,respectively.The ...In this paper,the flow and heat transfer characteristics in U-shaped channel with three different turn shapes are studied.The rotation number ranges from 0~0.251,Reynolds number are 11500,23000,34500,respectively.The results show that the flow separation and reattachment in the turning section are the key factors affecting the local heat transfer and pressure loss of U-shaped channel.The square turn will generate corner vortices at the outside of the turning section,and the size of the inner separation vortex and reattachment vortex is larger than that of the other two turn shapes.The existence of vortex system will increase the mixing and enhance heat transfer,but increase the pressure loss,so its relative Nusselt number and pressure loss are the largest.There are corner vortices on the outside of the turning section of the channel with a inner circle turn and outer square turn,but the arc-shaped inner edge makes its separation delay and the separation vortex decrease,and the size of the reattachment vortex also decreases.The arc shaped outer edge of the channel with circle turn in both inner and outer further inhibits the generation of corner vortices,so its relative Nusselt number and pressure loss are the lowest.Rotation will cause the fluid to deflect under the influence of Coriolis force,strengthen the heat transfer on the trailing surface of radial outflow and the leading surface of radial internal flow,and generate secondary flow and separation vortex in the turning section,resulting in the change of vortex structure in the turning section.With the increase of rotation number,the Nusselt number of the three types of turning section structures increases.The thermal performance factor of the three channels increases with the increase of rotating speed,and the channel with a inner circle turn and outer square turn is the highest,which is 9.6%higher than the channel with circle turn in both inner and outer on average,and 17.8%higher than the channel with square turn in both inner and outer.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
To achieve complete poverty alleviation,the improvement of infrastructure and living conditions is fundamental.Promoting the flow of factors through infrastructure investment,thereby reducing the income gap among resi...To achieve complete poverty alleviation,the improvement of infrastructure and living conditions is fundamental.Promoting the flow of factors through infrastructure investment,thereby reducing the income gap among residents,has become an important focus of poverty alleviation.Because of the high amount of investment in transportation infrastructure,greater attention has been paid to the income distribution effect it brings,but few studies have analysed the effect of rural highways on the income gap of farmers.Based on the panel data pertaining to 30 provinces in China from 1993 to 2013,this paper uses a fixed-effect model to test the impact of rural highways supply on the income gap of farmers.The empirical results show that:(1)The effect of Chinese rural highways on the farmers'income gap among provinces is"U-shaped".(2)Chinese national and provincial trunk highways are helpful in narrowing the farmers'income gap among provinces.(3)The level of education,household productive fixed assets investment,level of urbanization,and level of regional economic development have multiple effects on the farmers'income gap among provinces.Then,based on the empirical analysis,the paper analyzes the mechanism of rural highways affecting the income gap of farmers from a theoretical perspective and focuses on the causes of the"U-shaped"relationship between rural highways supply and farmers'income gap.展开更多
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.
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.
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.
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National Natural Science Foundation of China(51865055)Tianshan Talents Plan of Xinjiang Autonomous Region of China(201720025)。
文摘The interaction of U-shaped rings used for power transmission hardware with a wind-sand field is simulated numerically.A standard kturbulence model is used in synergy with an Eulerian-Lagrangian approach.The results show that the wind pressure on the windward side of the U-shaped ring is the highest,a negative pressure zone appears on both sides of the U-shaped ring,while a Kármán Vortex Street is created on its leeward side.There are three possible regimes of motion for the sand grains in the wind field.Sand grains with size below 0.125 mm can follow the airflow directly into the contact area of two U-shaped rings.When the sand size is about 0.1 mm,the number of sand grains that are blown into the contact area attains a maximum.Through the simulation of U-shaped rings in the wind-sand field,the dynamics of such processes are explained in detail,thereby providing relevant information for the subsequent protection and design of connecting hardware used for power transmission.
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
文摘In human life,water resources are inseparable.In recent years,China’s population growth has accelerated,and the industrial level has been continuously improved,resulting in the rapid use and waste of water resources.The protection and rational distribution of water resources are the most pressing issue in China’s water resources.At present,the water measuring facilities of the U-shaped channel mainly include a straight wall measuring pool,a parabolic throat measuring pool,and a long throat measuring pool.In view of the problems in irrigation measurement,the empirical water measurement of basic open-channel and automatic flow measurement system in irrigation district is summarized to improve the accuracy,fairness,and rationality of water measurement,and promote irrigation district management to a higher level.
文摘The design of a seven-band stacked patch antenna for the C, X and Ku band is presented. The antenna consists of an H-slot loaded fed patch, stacked with dual U-slot loaded rectangular patch to generate the seven frequency bands. The total size of the antenna is 39.25 × 29.25 mm2. The multiband stacked patch antenna is studied and designed using IE3D simulator. For verification of simulation results, the antenna is analyzed by circuit theory concept. The simulated return loss, radiation pattern and gain are presented. Simulated results show that the antenna can be designed to cover the frequency bands from (4.24 GHz to 4.50 GHz, 5.02 GHz to 5.25 GHz) in C-band application, (7.84 GHz to 8.23 GHz) in X-band and (12.16 GHz to 12.35 GHz, 14.25 GHz to 14.76 GHz, 15.25 GHz to 15.51 GHz, 17.52 GHz to 17.86 GHz) in Ku band applications. The bandwidths of each band of the proposed antenna are 5.9%, 4.5%, 4.83%, 2.36%, 3.53%, 1.68% and 1.91%. Similarly the gains of the proposed band are 2.80 dBi, 4.39 dBi, 4.54 dBi, 10.26 dBi, 8.36 dBi and 9.91 dBi, respectively.
基金supported by the Second Tibetan Plateau ScientificExpeditionand Research Program (STEP) (2021QZKK0205)the Systematic Major Project of the China Railway (P2021G047).
文摘The U-shaped crushed rock embankment(UCRE),of which widely utilized in the permafrost regions along the Qinghai-Tibet Railway,has the capability to rapidly reduce the ground temperature of the underlying permafrost.However,there remains uncertainty regarding the adaptation of UCRE to climate change and its long-term cooling trend.This study focuses on nine UCRE monitoring sites along the Qinghai-Tibet Railway to analyze the dynamic variations of the ground temperature underlying permafrost from 2006 to 2020.The efficiency of UCRE in stabilizing permafrost temperature in different permafrost zones is evaluated by considering the permafrost table,ground temperature,and MAGT,as well as the temperature difference between the top and bottom of the crushed rock layer and the ground temperature variation index(GTVI).The results show that UCRE is suitable for application in extremely unstable warm permafrost regions where the MAGT is higher than-0.5℃.Moreover,UCRE effectively diminishes the disparity in permafrost thermal stability between the sunny and shaded shoulders of the embankment.The short-term and long-term effect of cooling permafrost is experiencing a change related with permafrost stability.Notably,in stable cold permafrost regions with MAGT lower than-1.5℃,the long-term cooling effect of UCRE on permafrost seems to gradually di-minishes,but UCRE continues to fulfill the role of stabilizing the underlying permafrost thermal state over the long-term.These results show that UCRE can quickly restore and stabilize the thermal state of permafrost in the early stages of construction,and adapt to the influence of future climate change.The findings provide important guidance for understanding the variations of permafrost thermal stability beneath the embankment in permafrost regions,as well as for improving the embankment stability and operational safety of the Qinghai-Tibet Railway.
基金supported by the Postgraduate Research&Practice Innovation Program of Jiangsu Province (SJCX21_1427)General Program of Natural Science Research in Jiangsu Universities (21KJB520019).
文摘Convolutional neural networks(CNN)based on U-shaped structures and skip connections play a pivotal role in various image segmentation tasks.Recently,Transformer starts to lead new trends in the image segmentation task.Transformer layer can construct the relationship between all pixels,and the two parties can complement each other well.On the basis of these characteristics,we try to combine Transformer pipeline and convolutional neural network pipeline to gain the advantages of both.The image is put into the U-shaped encoder-decoder architecture based on empirical combination of self-attention and convolution,in which skip connections are utilized for localglobal semantic feature learning.At the same time,the image is also put into the convolutional neural network architecture.The final segmentation result will be formed by Mix block which combines both.The mixture model of the convolutional neural network and the Transformer network for road segmentation(MCTNet)can achieve effective segmentation results on KITTI dataset and Unstructured Road Scene(URS)dataset built by ourselves.Codes,self-built datasets and trainable models will be available on https://github.com/xflxfl1992/MCTNet.
基金Supported by the Geological Survey Project of China(Nos.DD20191001,DD20191004,DD20189410)the National Key R&D Program of China(No.2017YFC0602000)。
文摘Magnetic data has been widely applied in the tectonic division.High-resolution magnetic data were used to analyze the geotectonic zoning of the South China Sea.Based on the newly compilated magnetic data,the processing results and the distribution of known faults,we consider that the U-shaped line approximately along the South China Sea national boundary of China shown in the magnetic map is a significant geological and geophysical boundary.We first described the linear characteristics of the magnetic data and then applied pseudo-gravity,Euler deconvolution,tilt derivatives,and the texture segmentation method to process the data.Results show that the dividing line between the South China Sea and the surrounding blocks is approximately along this U-shaped line.The dividing line between the South China domain and the South China Sea domain is along with the Dongsha Islands to Xisha Trough,which is different from the previous geophysical zoning results.Our results are almost consistent with those of the gravity data indicating roughly the tectonic zonation along the U-shaped line.
文摘The orderly transfer of the manufacturing industry is a major action in China’s industrial restructuring.From the perspective of industrial transfer,we used the concentration ratio to depict the trend of the industrial transfer of energy-intensive manufacturing in the eastern,central,and western regions since the policy of large-scale development of western China was implemented.We measured the total factor productivity(TFP)of western China using the DEAMalmquist index method.We conducted a regression analysis to measure the effect of western China’s undertaking of the transfer of the energy-intensive manufacturing industry.The findings of this study show that during 2000–2019,eleven provinces(as well as autonomous regions and municipalities)in western China undertook the transfer of the energy-intensive manufacturing industry from the eastern and central regions to varying degrees,exhibiting significant phase features regarding the rate and scale of transfers.Further investigation also demonstrated that the transfer of energy-intensive manufacturing industries has a U-shaped enabling effect on TFP in western China with the scale effect greater than the technology effect.Therefore,it is necessary to transition from“extensive industrial transfer”at the cost of the labor force,land,and resources to“modern industrial transfer”featured by technology and efficiency improvements to contribute to industrial restructuring in western China effectively.
基金National Natural Science Foundation of China(51906008)。
文摘In this paper,the flow and heat transfer characteristics in U-shaped channel with three different turn shapes are studied.The rotation number ranges from 0~0.251,Reynolds number are 11500,23000,34500,respectively.The results show that the flow separation and reattachment in the turning section are the key factors affecting the local heat transfer and pressure loss of U-shaped channel.The square turn will generate corner vortices at the outside of the turning section,and the size of the inner separation vortex and reattachment vortex is larger than that of the other two turn shapes.The existence of vortex system will increase the mixing and enhance heat transfer,but increase the pressure loss,so its relative Nusselt number and pressure loss are the largest.There are corner vortices on the outside of the turning section of the channel with a inner circle turn and outer square turn,but the arc-shaped inner edge makes its separation delay and the separation vortex decrease,and the size of the reattachment vortex also decreases.The arc shaped outer edge of the channel with circle turn in both inner and outer further inhibits the generation of corner vortices,so its relative Nusselt number and pressure loss are the lowest.Rotation will cause the fluid to deflect under the influence of Coriolis force,strengthen the heat transfer on the trailing surface of radial outflow and the leading surface of radial internal flow,and generate secondary flow and separation vortex in the turning section,resulting in the change of vortex structure in the turning section.With the increase of rotation number,the Nusselt number of the three types of turning section structures increases.The thermal performance factor of the three channels increases with the increase of rotating speed,and the channel with a inner circle turn and outer square turn is the highest,which is 9.6%higher than the channel with circle turn in both inner and outer on average,and 17.8%higher than the channel with square turn in both inner and outer.
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.
基金supports from the Transport Strategic Planning Policy Foundation of the Ministry of Transport of China(2019-4-1)the Humanities and Social Sciences Project Funded by the Ministry of Education of China(20YJC790005)。
文摘To achieve complete poverty alleviation,the improvement of infrastructure and living conditions is fundamental.Promoting the flow of factors through infrastructure investment,thereby reducing the income gap among residents,has become an important focus of poverty alleviation.Because of the high amount of investment in transportation infrastructure,greater attention has been paid to the income distribution effect it brings,but few studies have analysed the effect of rural highways on the income gap of farmers.Based on the panel data pertaining to 30 provinces in China from 1993 to 2013,this paper uses a fixed-effect model to test the impact of rural highways supply on the income gap of farmers.The empirical results show that:(1)The effect of Chinese rural highways on the farmers'income gap among provinces is"U-shaped".(2)Chinese national and provincial trunk highways are helpful in narrowing the farmers'income gap among provinces.(3)The level of education,household productive fixed assets investment,level of urbanization,and level of regional economic development have multiple effects on the farmers'income gap among provinces.Then,based on the empirical analysis,the paper analyzes the mechanism of rural highways affecting the income gap of farmers from a theoretical perspective and focuses on the causes of the"U-shaped"relationship between rural highways supply and farmers'income gap.