Hot flow forming(HFF)is a promising forming technology to manufacture thin-walled cylindrical part with longitudinal inner ribs(CPLIRs)made of magnesium(Mg)alloys,which has wide applications in the aerospace field.How...Hot flow forming(HFF)is a promising forming technology to manufacture thin-walled cylindrical part with longitudinal inner ribs(CPLIRs)made of magnesium(Mg)alloys,which has wide applications in the aerospace field.However,due to the thermo-mechanical coupling effect and the existence of stiffened structure,complex microstructure evolution and uneven microstructure occur easily at the cylindrical wall(CW)and inner rib(IR)of Mg alloy thin-walled CPLIRs during the HFF.In this paper,a modified cellular automaton(CA)model of Mg alloy considering the effects of deformation conditions on material parameters was developed using the artificial neural network(ANN)method.It is found that the ANN-modified CA model exhibits better predictability for the microstructure of hot deformation than the conventional CA model.Furthermore,the microstructure evolution of ZK61 alloy CPLIRs during the HFF was analyzed by coupling the modified CA model and finite element analysis(FEA).The results show that compared with the microstructure at the same layer of the IR,more refined grains and less sufficient DRX resulted from larger strain and strain rate occur at that of the CW;various differences of strain and strain rate in the wall-thickness exist between the CW and IR,which leads to the inhomogeneity of microstructure rising firstly and declining from the inside layer to outside layer;the obtained Hall-Petch relationship between the measured microhardness and predicted grain sizes at the CW and the IR indicates the reliability of the coupled FEA-CA simulation results.展开更多
This study deals with base pressure management in a duct for various values of the Mach number(M),namely,Mach number corresponding to sonic and four supersonic conditions.In addition to the Mach number,the nozzle pres...This study deals with base pressure management in a duct for various values of the Mach number(M),namely,Mach number corresponding to sonic and four supersonic conditions.In addition to the Mach number,the nozzle pressure ratio(NPR),the area ratio,the rib dimension,and the duct length are influential parameters.The following specific values are examined at M=1,1.36,1.64,and 2,and NPRs between 1.5 and 10.The base pressure is determined by positioning ribs of varying heights at predetermined intervals throughout the length of the square duct.When the level of expansion is varied,it is seen that the base pressure initially drops for overexpanded flows and increases for under-expanded flows.When ribs are present,the flow field in the duct and pressure inside the duct fluctuate as the base pressure rises.Under-expanded flows can achieve a base pressure value that is suitably high without experiencing excessive changes in the duct flow in terms of static pressure if a rib height around 10%of the duct height close to the nozzle exit is considered.Rectangular rib passive control does not negatively affect the duct’s flow field.展开更多
Thoraco-brachial outlet syndrome (TDSD) or cervical rib brings together all the clinical symptoms (arterial, neurological and/or venous) due to extrinsic, intermittent or permanent compression of the vascular-nervous ...Thoraco-brachial outlet syndrome (TDSD) or cervical rib brings together all the clinical symptoms (arterial, neurological and/or venous) due to extrinsic, intermittent or permanent compression of the vascular-nervous elements of the root of the upper limb during cervico-thoraco-brachial crossing syndrome. This pathology is relatively common but often overlooked;it affects women more often (between 4/1 and 2/1) and is rare in children. We report the case of a 59-year-old female patient seen in the department for paresthesia and muscular weakness of the upper limbs rated 3/5 on the right and 4/5 on the left progressively evolving over 39 years, electromyography (EMG) showed indicated compression of the brachial plexus and the CT scan confirmed the presence of bilateral cervical ribs fused with the first on the left. She benefited from physiotherapy while awaiting her surgery, and unfortunately, she died of a stroke in the traumatology department. This pathology is the first in our department to be supported by a review of the literature.展开更多
In order to study the residual stress distribution law of welded joints of arch ribs of large-span steel pipe concrete arch bridges,numerical simulation of temperature,stress and strain fields based on ABAQUS for weld...In order to study the residual stress distribution law of welded joints of arch ribs of large-span steel pipe concrete arch bridges,numerical simulation of temperature,stress and strain fields based on ABAQUS for welded joints of arch-ribbed steel tubes using 7-,8-and 9-layer welds is carried out and its accuracy is demonstrated.The steel pipe welding temperature changes,residual stress distribution,different processes residual stress changes in the law,the prediction of post-weld residual stress distribution and deformation are studied in this paper.The results show that the temperature field values and test results are more consistent with the accuracy of numerical simulation of welding,the welding process is mainly in the form of heat transfer;Residual high stresses are predominantly distributed in the Fusion zone(FZ)and Heat-affected zone(HAZ),with residual stress levels tending to decrease from the center of the weld along the axial path,the maximum stress appears in the FZ and HAZ junction;The number of welding layers has an effect on the residual stress distribution,the number of welding layers increases,the residual stress tends to decrease,while the FZ and HAZ high stress area range shrinks;Increasing the number of plies will increase the amount of residual distortion.展开更多
Tapered ring with thin wall and three high ribs(TRTWTHR),showing complicated geometry(wall thickness is less than 4 mm and rib height exceeds 20 mm),is extensively utilized to fabricate the critical structural parts o...Tapered ring with thin wall and three high ribs(TRTWTHR),showing complicated geometry(wall thickness is less than 4 mm and rib height exceeds 20 mm),is extensively utilized to fabricate the critical structural parts of aerospace equipment such as spacecraft cabin,rocket body and fuel tank because of light weight and high carrying capacity.How to fabricate TRTWTHR with high performance is a critical problem that aerospace area needs to solve.In this work,constraining ring rolling(CRR)technique is first adopted to form TRTWTHR.However.unreasonable metal streamlines(UMS)and uncoordinated growth of three ribs easily occur in CRR of TRTWTHR,which makes the forming quality of TRTWTHR difficult to be controlled.Faced with this difficulty,an analytical model that can predict UMS and the height of three ribs in CRR of TRTWTHR is established so as to guide the process design of CRR.Subsequently,the reliability of the established analytical model and the feasibility of CRR of TRTWTHR are confirmed by FE simulation and experiment.Then,using the established analytical model,the window of UMS occurring relevant to the tapered angle of TRTWTHR and the location of the rib of middle end is developed.Finally,three uncoordinated growth modes among three ribs are found when the width of three ribs is identical and UMS do not occur,and the mechanisms of three uncoordinated growth modes are revealed.展开更多
Conical rings with thin sterna and high ribs(CRTSHR)are key bearing-load parts of aerospace equipment,which are required to be manufactured with high performance and efficiency.Traditional ring rolling is the most pre...Conical rings with thin sterna and high ribs(CRTSHR)are key bearing-load parts of aerospace equipment,which are required to be manufactured with high performance and efficiency.Traditional ring rolling is the most preferred method for manufacturing high-performance ring parts,but it can hardly achieve the forming of CRTSHR due to the extreme geometry of CRTSHR.To solve this difficulty,an innovative constraining ring rolling process(CRR)is proposed in this paper to manufacture CRTSHR.To evaluate the proposed CRR and reveal its deformation behaviors,a thermomechanical coupled FE model for CRR of CRTSHR is established.Then,the experiment for CRR of CRTSHR is performed on a modified ring rolling machine,which proves that CRR of CRTSHR is feasible and the established FE model is reliable.Based on the reliable FE model,the metal flow mode in deformed CRTSHR is analyzed,and the deformation characteristics such as the stress state,strain distribution and the evolution of power parameters in CRR of CRTSHR are revealed.Finally,the influences of key parameters such as the friction factor between ring and molds,the diameter of idle roll and the feed velocity of idle roll on CRR of CRTSHR are investigated by FE simulation.展开更多
The aim of this paper is to report an exceptional case of multiple internal exostoses of the ribs in a young patient affected by multiple hereditary exostoses(MHE) coming to our observation for chest pain as the only ...The aim of this paper is to report an exceptional case of multiple internal exostoses of the ribs in a young patient affected by multiple hereditary exostoses(MHE) coming to our observation for chest pain as the only symptom of an intra-thoracic localization. A 16 years old patient with familiar history of MHE came to our observation complaining a left-sided chest pain. This pain had increased in the last months with no correlation to a traumatic event. The computed tomography(CT) scan revealed the presence of three exostoses located on the left third, fourth and sixth ribs, all protruding into the thoracic cavity, directly in contact with visceral pleura. Moreover, the apex of the one located on the sixth rib revealed to be only 12 mm away from pericardium. Patient underwent video-assisted thoracoscopy with an additional 4-cm mini toracotomy approach. At the last 1-year followup, patient was very satisfied and no signs of recurrence or major complication had occured. In conclusion, chest pain could be the only symptom of an intra-thoracic exostoses localization, possibly leading to serious complications. Thoracic localization in MHE must be suspected when patients complain chest pain. A chest CT scan is indicated to confirm exostoses and to clarify relationship with surrounding structures. Video-assisted thoracoscopic surgery can be considered a valuable option for exostoses removal, alone or in addiction to a mini-thoracotomy approach, in order to reduce thoracotomy morbidity.展开更多
Cylindrical rings with thin wall and high web ribs(CRTWHWR)are widely used as the key load bearing structures such as rocket body and space station cabin in aerospace field.However,it is still difficult to efficiently...Cylindrical rings with thin wall and high web ribs(CRTWHWR)are widely used as the key load bearing structures such as rocket body and space station cabin in aerospace field.However,it is still difficult to efficiently manufacture CRTWHWR with high performance because of their extreme geometry with thin-walled skins,high web ribs and large size.In this paper,a novel radial envelope forming process is put forward to efficiently achieve the plastic forming of CRTWHWR with high performance.Firstly,the principle of radial envelope forming process is clarified.Then,an efficient design method for the tool motion and geometry is proposed based on the reverse envelope principle,i.e.,CRTWHWR is adopted to reversely envelope the tool and thus the tool which does not interfere with CRTWHWR can be efficiently obtained in a single operation.Finally,a reasonable 3D FE model of the radial envelope forming process of CRTWHWR is established and the radial envelope forming mechanism of CRTWHWR is comprehensively revealed.Through the FE simulation and experiments with material of plastic mud,a typical CRTWHWR with diameter of 300 mm,axial height of 192 mm,the maximum rib height of 25 mm,the minimum rib thickness of 3 mm and skin thickness of 5 mm is radial envelope formed,i.e.,the ratio of the maximum rib height to the minimum rib thickness reaches 8.33,the ratio of the maximum rib height to skin thickness reaches 5 and the ratio of diameter to the minimum rib thickness reaches 100.The above results verify that the proposed radial envelope forming process has great potentials in efficiently manufacturing CRTWHWR with extreme geometry.展开更多
BACKGROUND： With the development of internal fixation materials, simple operation with internal fixation has become a tendency. Ni-Ti shape memory alloy embracing fixator has such advantages as slight injury, easy op...BACKGROUND： With the development of internal fixation materials, simple operation with internal fixation has become a tendency. Ni-Ti shape memory alloy embracing fixator has such advantages as slight injury, easy operation, security, reliable fixation, and better histocompatibility. The present study was to explore curative effect and postoperative results of Ti-Ni shape memory alloy embracing ？ xator in patients with multiple fractured ribs and ？ ail chest.METHODS： The curative effect and long-term follow-up results were observed after internal ？ xation with a shape memory alloy embracing ？ xator in patients with multiple fractured ribs and ？ ail chest from January 2006 to December 2009.RESULTS： All patients were cured with an average hospital stay of 10.31±3.14 days. Post-operative pain was less severe than preoperative pain （P=0.02）.The rate of postoperative complications such as atelectasis, pulmonary infection, etc was 17.65%. There were fewer long-term complications and less in？ uence on daily work and life.CONCLUSIONS： It is practical to perform an operation for fracture of multiple ribs using a Ti-Ni shape memory alloy embracing ？ xator. The ？ xator, which is less traumatic, simple, safe, and reliable, has a good-histocompatibility and fewer postoperative complications.展开更多
A numerical investigation has been carried out to examine turbulent flow and heat transfer characteristics in a three-dimensional ribbed square channels. Fluent 6.3 CFD code has been used. The governing equations are ...A numerical investigation has been carried out to examine turbulent flow and heat transfer characteristics in a three-dimensional ribbed square channels. Fluent 6.3 CFD code has been used. The governing equations are discretized by the second order upwind differencing scheme, decoupling with the SIMPLE (semi-implicit method for pressure linked equations) algorithm and are solved using a finite volume approach. The fluid flow and heat transfer characteristics are presented for the Reynolds numbers based on the channel hydraulic diameter ranging from 104 to 4 ′ 104. The effects of rib shape and orientation on heat transfer and pressure drop in the channel are investigated for six different rib configurations. Rib arrays of 45° inclined and 45° V-shaped are mounted in inline and staggered arrangements on the lower and upper walls of the channel. In addition, the performance of these ribs is also compared with the 90° transverse ribs.展开更多
Closed-cell type barrier ribs such as meander, honeycomb, SDR, and waffle types were produced using capillary molding process. Sintering of the ribs revealed that the ribs with asymmetric geometry such as meander and ...Closed-cell type barrier ribs such as meander, honeycomb, SDR, and waffle types were produced using capillary molding process. Sintering of the ribs revealed that the ribs with asymmetric geometry such as meander and SDR type became distorted severely by the sintering process, but the ribs with symmetric geometry such as honeycomb and waffle type maintained their green state morphology. After sintering, the ribs were coated with green phosphor using osmosis coating process and its luminance characteristics were evaluated. The results indicated that the luminance and its efficiency is improved by using closed-cell type ribs with the new phosphor forming technology.展开更多
Experimental and numerical investigations have been conducted to study turbulent flow of water and heat transfer characteristics in a rectangular channel with discontinuous crossed ribs and grooves.The tests investiga...Experimental and numerical investigations have been conducted to study turbulent flow of water and heat transfer characteristics in a rectangular channel with discontinuous crossed ribs and grooves.The tests investigated the overall heat transfer performance and friction factor in ribbed and ribbed-grooved channels with rib angle of 30°.The experimental results show that the overall thermo-hydraulic performance for ribbed-grooved channel is increased by 10%-13.6% when compared to ribbed channel.The investigation on the effects of different rib angles and rib pitches on heat transfer characteristics and friction factor in ribbed-grooved channel was carried out using Fluent with SST(shear-stress transport) k-ω turbulence model.The numerical results indicate that the case for rib angle of 45° shows the best overall thermo-hydraulic performance,about 18%-36% higher than the case for rib angle of 0°.In addition,the flow patterns and local heat transfer characteristics for ribbed and ribbed-grooved channels based on the numerical simulation were also analyzed to reveal the mechanism of heat transfer enhancement.展开更多
Research on microforming of fine-grained superplastic Zn-AI22 alloy was carried out in this paper by means of superplastic forming. With the selected material, microformability tests have been carried out with the spe...Research on microforming of fine-grained superplastic Zn-AI22 alloy was carried out in this paper by means of superplastic forming. With the selected material, microformability tests have been carried out with the specially developed evaluation method by using two kinds of stainless steel dies. With these dies, micro-extrusion tests have been carried out and the characteristics of microformability of the material have been clarified. Effects of processing parameters and die structure on forming have been analyzed. SEM and metallographic microscope have been used to analyze the formed specimens. Through analysis of flow lines of the formed specimen, behavior of material could be understood well.展开更多
The influence of ribs on the train aerodynamic performance was computed using detached eddy simulation(DES), and the transient iteration was solved by the dual-time step lower-upper symmetric Gauss-Seidel(LU-SGS) meth...The influence of ribs on the train aerodynamic performance was computed using detached eddy simulation(DES), and the transient iteration was solved by the dual-time step lower-upper symmetric Gauss-Seidel(LU-SGS) method. The results show that the ribs installed on the roof have a great effect on the train aerodynamic performance. Compared with trains without ribs, the lift force coefficient of the train with convex ribs changes from negative to positive, while the side force coefficient increases by 110%and 88%, respectively. Due to the combined effect of the lift force and side force, the overturning moment of the train with convex ribs and cutting ribs increases by 140% and 106%, respectively. There is larger negative pressure on the roof of the train without ribs than that with ribs. The ribs on the train would disturb the flow structure and contribute to the air separation, so the separation starts from the roof, while there is no air separation on the roof of the train without ribs. The ribs can also slow down the flow speed above the roof and make the air easily sucked back to the train surface. The vortices at the leeward side of the train without ribs are small and messy compared with those of the train with convex or cutting ribs.展开更多
The Large-size Conical Cylinders with Inner Transverse High Ribs(LCCWITHR) can reduce the weight of the parts while maintaining high rigidity and strength. Radially Loading Rotary Extrusion(RLRE) forming technology ca...The Large-size Conical Cylinders with Inner Transverse High Ribs(LCCWITHR) can reduce the weight of the parts while maintaining high rigidity and strength. Radially Loading Rotary Extrusion(RLRE) forming technology can achieve integral forming of LCCWITHR through the synergy of radial and rotary movements of dies. The flow law of the material during the forming process is the key to forming large-size inner ribs. At present, there is no unified understanding of the metal flow law of RLRE forming technology. An analytical expression was derived to predict the Radial Direction(RD) deformation loads. The FE simulation and process experiment were carried out to investigate the effects of the inclination angle, thickness factor and transition arc radius of the split top dies on the spacing of the metal diversion plane, the metal flow velocity of the rib area and the final radius of the inner rib. The influence of the split top dies loading distance and the bottom die rotation angle of each pass on the inner radius of the inner rib was verified. And the optimal combination of dies shape parameters and loading paths which can make the metal flow orderly was obtained: the inclination angle is 140°, the thickness factor is 3.64, the transition arc radius is 16 mm;the top dies loading distance is 15 mm, the bottom die rotation angle is 45°.The FE simulation results have been found to be in close agreement with physics experiment.The research results reveal the metal flow law of rib growth in the RLRE of LCCWITHR, which lays a theoretical foundation for subsequent thorough research and process optimization.展开更多
We used the spheroidal beam equation to calculate the sound field created by focusing a transducer with a wide aperture angle to obtain the heat deposition, and then we used the Pennes bioheat equation to calculate th...We used the spheroidal beam equation to calculate the sound field created by focusing a transducer with a wide aperture angle to obtain the heat deposition, and then we used the Pennes bioheat equation to calculate the temperature field in biological tissue with ribs and to ascertain the effects of rib parameters on the temperature field. The results show that the location and the gap width between the ribs have a great influence on the axial and radial temperature rise of multilayer biological tissue. With a decreasing gap width, the location of the maximum temperature rise moves forward; as the ribs are closer to the transducer surface, the sound energy that passes through the gap between the ribs at the focus decreases, the maximum temperature rise decreases, and the location of the maximum temperature rise moves forward with the ribs.展开更多
Researchers from the National Institute for Occupational Safety and Health(NIOSH)are developing a coal pillar rib rating(CPRR)technique to measure the integrity of coal ribs.The CPRR characterizes the rib composition ...Researchers from the National Institute for Occupational Safety and Health(NIOSH)are developing a coal pillar rib rating(CPRR)technique to measure the integrity of coal ribs.The CPRR characterizes the rib composition and evaluates its impact on the inherent stability of the coal ribs.The CPRR utilizes four parameters:rib homogeneity,bedding condition,face cleat orientation with respect to entry direction,and rib height.All these parameters are measurable in the field.A rib data collecting procedure and a simple sheet to calculate the CPRR were developed.The developed CPRR can be used as a rib quality mapping tool in underground coal mines and to determine the potential of local rib instabilities and support requirements associated with overburden depth.CPRR calculations were conducted for 22 surveyed solid coal ribs,mainly composed of coal units.Based on this study,the rib performance was classified into four categories.A preliminary minimum primary rib support density(PRSD)line was obtained from these surveyed cases.Two sample cases are presented that illustrate the data collection form and CPRR calculations.展开更多
In this work, the photosensitive paste was prepared. It was comprised of inorganic particles and a photosensitive organic component. The inorganic panicles included glass, ceramics, and metals. The organic component s...In this work, the photosensitive paste was prepared. It was comprised of inorganic particles and a photosensitive organic component. The inorganic panicles included glass, ceramics, and metals. The organic component should contain at least the following photosensitive materials： photosensitive monomers, photoreactive copolymer and photopolymerization initiators. The photoreactive copolymer played a role of an adhesive in the photosensitive paste. Meanwhile in the development stage, the carboxyl groups of the copolymer reacted with the alkalescent developer. Following this, the unexposed part must be removed and an excellent pattern can be formed. A series of three-component acrylic copolymers （MAA/St/MMA） were designed, and then synthesized via free radical polymerization. Subsequently glycidyl methacrylate （GMA） was employed to modify the prepared copolymers through ring-opening reactions between the carboxyl groups and the epoxide groups. Eventually the photosensitive copolymers were obtained and used to form the barrier ribs of PDPs. The chemical structure, glass transition temperature, acid value and molecular weight of photosensitive copolymers had different effects on the structure and pattern of PDP barrier ribs. Through analyzing effects of different polymer performance parameters on the patterns of barrier ribs, the optimal photosensitive copolymer was acquired.展开更多
SCRamjet is exposed to severe thermal environments during hypersonic flights,which poses a serious challenge to the engine cooling technology.Regenerative cooling with hydrocarbon fuel is considered promising,in which...SCRamjet is exposed to severe thermal environments during hypersonic flights,which poses a serious challenge to the engine cooling technology.Regenerative cooling with hydrocarbon fuel is considered promising,in which the hydrocarbon fuel flows through micro channels(200μm-3 mm)to absorb the combustion heat release.With strictly limited hydrocarbon fuel onboard,heat transfer deterioration and over-temperature are highly possible.In this paper,micro ribs with staggered side gaps are introduced and numerically studied to enhance the heat transfer.Compared with the straight channel and channel with straight micro ribs,the staggered side gaps alleviate the local low velocity zone and intensify the longitudinal and transverse vortexes.The heat transfer is obviously enhanced.Larger rib height enhances the heat transfer by stronger side gap effects at the cost of larger pressure loss.The best overall heat transfer factorηis achieved in the case of h_(rib)/H=0.1,which increases by 204.5%comparing to the straight channel.When the rib interval is too small or too large,it approaches to the straight channel.The best overall heat transfer factorηis achieved in the case of L/p_(rib)=100,which increases by212.9%comparing to the straight channel.It is known the improvement in the geometry of the ribs,i.e.,the staggered-side-gap micro ribs,induces extra transverse vortex and improves the heat transfer performance more effectively.The research of this paper provides support for the cooling design of the SCRamjet.展开更多
基金supported by the National Nat-ural Science Foundation of China(Grant Nos.51775194 and 52090043).
文摘Hot flow forming(HFF)is a promising forming technology to manufacture thin-walled cylindrical part with longitudinal inner ribs(CPLIRs)made of magnesium(Mg)alloys,which has wide applications in the aerospace field.However,due to the thermo-mechanical coupling effect and the existence of stiffened structure,complex microstructure evolution and uneven microstructure occur easily at the cylindrical wall(CW)and inner rib(IR)of Mg alloy thin-walled CPLIRs during the HFF.In this paper,a modified cellular automaton(CA)model of Mg alloy considering the effects of deformation conditions on material parameters was developed using the artificial neural network(ANN)method.It is found that the ANN-modified CA model exhibits better predictability for the microstructure of hot deformation than the conventional CA model.Furthermore,the microstructure evolution of ZK61 alloy CPLIRs during the HFF was analyzed by coupling the modified CA model and finite element analysis(FEA).The results show that compared with the microstructure at the same layer of the IR,more refined grains and less sufficient DRX resulted from larger strain and strain rate occur at that of the CW;various differences of strain and strain rate in the wall-thickness exist between the CW and IR,which leads to the inhomogeneity of microstructure rising firstly and declining from the inside layer to outside layer;the obtained Hall-Petch relationship between the measured microhardness and predicted grain sizes at the CW and the IR indicates the reliability of the coupled FEA-CA simulation results.
文摘This study deals with base pressure management in a duct for various values of the Mach number(M),namely,Mach number corresponding to sonic and four supersonic conditions.In addition to the Mach number,the nozzle pressure ratio(NPR),the area ratio,the rib dimension,and the duct length are influential parameters.The following specific values are examined at M=1,1.36,1.64,and 2,and NPRs between 1.5 and 10.The base pressure is determined by positioning ribs of varying heights at predetermined intervals throughout the length of the square duct.When the level of expansion is varied,it is seen that the base pressure initially drops for overexpanded flows and increases for under-expanded flows.When ribs are present,the flow field in the duct and pressure inside the duct fluctuate as the base pressure rises.Under-expanded flows can achieve a base pressure value that is suitably high without experiencing excessive changes in the duct flow in terms of static pressure if a rib height around 10%of the duct height close to the nozzle exit is considered.Rectangular rib passive control does not negatively affect the duct’s flow field.
文摘Thoraco-brachial outlet syndrome (TDSD) or cervical rib brings together all the clinical symptoms (arterial, neurological and/or venous) due to extrinsic, intermittent or permanent compression of the vascular-nervous elements of the root of the upper limb during cervico-thoraco-brachial crossing syndrome. This pathology is relatively common but often overlooked;it affects women more often (between 4/1 and 2/1) and is rare in children. We report the case of a 59-year-old female patient seen in the department for paresthesia and muscular weakness of the upper limbs rated 3/5 on the right and 4/5 on the left progressively evolving over 39 years, electromyography (EMG) showed indicated compression of the brachial plexus and the CT scan confirmed the presence of bilateral cervical ribs fused with the first on the left. She benefited from physiotherapy while awaiting her surgery, and unfortunately, she died of a stroke in the traumatology department. This pathology is the first in our department to be supported by a review of the literature.
基金Sponsored by the National Natural Science Foundation of China(Grant No.52268048)the Guangxi Key Technology Research and Development Program(Grant No.GUI-KEAB23026101)the Guangxi Science and Technology Major Special Project(Grant No.GUI-KEAA22068066).
文摘In order to study the residual stress distribution law of welded joints of arch ribs of large-span steel pipe concrete arch bridges,numerical simulation of temperature,stress and strain fields based on ABAQUS for welded joints of arch-ribbed steel tubes using 7-,8-and 9-layer welds is carried out and its accuracy is demonstrated.The steel pipe welding temperature changes,residual stress distribution,different processes residual stress changes in the law,the prediction of post-weld residual stress distribution and deformation are studied in this paper.The results show that the temperature field values and test results are more consistent with the accuracy of numerical simulation of welding,the welding process is mainly in the form of heat transfer;Residual high stresses are predominantly distributed in the Fusion zone(FZ)and Heat-affected zone(HAZ),with residual stress levels tending to decrease from the center of the weld along the axial path,the maximum stress appears in the FZ and HAZ junction;The number of welding layers has an effect on the residual stress distribution,the number of welding layers increases,the residual stress tends to decrease,while the FZ and HAZ high stress area range shrinks;Increasing the number of plies will increase the amount of residual distortion.
基金the National Natural Science Foundation of China (No. U2037204)the 111 Project (No. B17034)+1 种基金Innovative Research Team Development Program of Ministry of Education of China (No. IRT17R83)the National Natural Science Foundation of China (No. 52005375)
文摘Tapered ring with thin wall and three high ribs(TRTWTHR),showing complicated geometry(wall thickness is less than 4 mm and rib height exceeds 20 mm),is extensively utilized to fabricate the critical structural parts of aerospace equipment such as spacecraft cabin,rocket body and fuel tank because of light weight and high carrying capacity.How to fabricate TRTWTHR with high performance is a critical problem that aerospace area needs to solve.In this work,constraining ring rolling(CRR)technique is first adopted to form TRTWTHR.However.unreasonable metal streamlines(UMS)and uncoordinated growth of three ribs easily occur in CRR of TRTWTHR,which makes the forming quality of TRTWTHR difficult to be controlled.Faced with this difficulty,an analytical model that can predict UMS and the height of three ribs in CRR of TRTWTHR is established so as to guide the process design of CRR.Subsequently,the reliability of the established analytical model and the feasibility of CRR of TRTWTHR are confirmed by FE simulation and experiment.Then,using the established analytical model,the window of UMS occurring relevant to the tapered angle of TRTWTHR and the location of the rib of middle end is developed.Finally,three uncoordinated growth modes among three ribs are found when the width of three ribs is identical and UMS do not occur,and the mechanisms of three uncoordinated growth modes are revealed.
基金the National Natural Science Foundation of China(No.U2037204)the Natural Science Foundation of Hubei Province(No.2019CFA041)+1 种基金the National Key Research and Development Program of China(No.2019YFB1704502)the Fundamental Research Funds for the Central Universities(No.2019-YB-016)for the support。
文摘Conical rings with thin sterna and high ribs(CRTSHR)are key bearing-load parts of aerospace equipment,which are required to be manufactured with high performance and efficiency.Traditional ring rolling is the most preferred method for manufacturing high-performance ring parts,but it can hardly achieve the forming of CRTSHR due to the extreme geometry of CRTSHR.To solve this difficulty,an innovative constraining ring rolling process(CRR)is proposed in this paper to manufacture CRTSHR.To evaluate the proposed CRR and reveal its deformation behaviors,a thermomechanical coupled FE model for CRR of CRTSHR is established.Then,the experiment for CRR of CRTSHR is performed on a modified ring rolling machine,which proves that CRR of CRTSHR is feasible and the established FE model is reliable.Based on the reliable FE model,the metal flow mode in deformed CRTSHR is analyzed,and the deformation characteristics such as the stress state,strain distribution and the evolution of power parameters in CRR of CRTSHR are revealed.Finally,the influences of key parameters such as the friction factor between ring and molds,the diameter of idle roll and the feed velocity of idle roll on CRR of CRTSHR are investigated by FE simulation.
文摘The aim of this paper is to report an exceptional case of multiple internal exostoses of the ribs in a young patient affected by multiple hereditary exostoses(MHE) coming to our observation for chest pain as the only symptom of an intra-thoracic localization. A 16 years old patient with familiar history of MHE came to our observation complaining a left-sided chest pain. This pain had increased in the last months with no correlation to a traumatic event. The computed tomography(CT) scan revealed the presence of three exostoses located on the left third, fourth and sixth ribs, all protruding into the thoracic cavity, directly in contact with visceral pleura. Moreover, the apex of the one located on the sixth rib revealed to be only 12 mm away from pericardium. Patient underwent video-assisted thoracoscopy with an additional 4-cm mini toracotomy approach. At the last 1-year followup, patient was very satisfied and no signs of recurrence or major complication had occured. In conclusion, chest pain could be the only symptom of an intra-thoracic exostoses localization, possibly leading to serious complications. Thoracic localization in MHE must be suspected when patients complain chest pain. A chest CT scan is indicated to confirm exostoses and to clarify relationship with surrounding structures. Video-assisted thoracoscopic surgery can be considered a valuable option for exostoses removal, alone or in addiction to a mini-thoracotomy approach, in order to reduce thoracotomy morbidity.
基金the National Natural Science Foundation of China(No.U2037204)the 111 Project(B17034)+1 种基金Innovative Research Team Development Program of Ministry of Education of China(No.IRT17R83)the National Natural Science Foundation of China(No.52005375)for the support given to this research。
文摘Cylindrical rings with thin wall and high web ribs(CRTWHWR)are widely used as the key load bearing structures such as rocket body and space station cabin in aerospace field.However,it is still difficult to efficiently manufacture CRTWHWR with high performance because of their extreme geometry with thin-walled skins,high web ribs and large size.In this paper,a novel radial envelope forming process is put forward to efficiently achieve the plastic forming of CRTWHWR with high performance.Firstly,the principle of radial envelope forming process is clarified.Then,an efficient design method for the tool motion and geometry is proposed based on the reverse envelope principle,i.e.,CRTWHWR is adopted to reversely envelope the tool and thus the tool which does not interfere with CRTWHWR can be efficiently obtained in a single operation.Finally,a reasonable 3D FE model of the radial envelope forming process of CRTWHWR is established and the radial envelope forming mechanism of CRTWHWR is comprehensively revealed.Through the FE simulation and experiments with material of plastic mud,a typical CRTWHWR with diameter of 300 mm,axial height of 192 mm,the maximum rib height of 25 mm,the minimum rib thickness of 3 mm and skin thickness of 5 mm is radial envelope formed,i.e.,the ratio of the maximum rib height to the minimum rib thickness reaches 8.33,the ratio of the maximum rib height to skin thickness reaches 5 and the ratio of diameter to the minimum rib thickness reaches 100.The above results verify that the proposed radial envelope forming process has great potentials in efficiently manufacturing CRTWHWR with extreme geometry.
文摘BACKGROUND： With the development of internal fixation materials, simple operation with internal fixation has become a tendency. Ni-Ti shape memory alloy embracing fixator has such advantages as slight injury, easy operation, security, reliable fixation, and better histocompatibility. The present study was to explore curative effect and postoperative results of Ti-Ni shape memory alloy embracing ？ xator in patients with multiple fractured ribs and ？ ail chest.METHODS： The curative effect and long-term follow-up results were observed after internal ？ xation with a shape memory alloy embracing ？ xator in patients with multiple fractured ribs and ？ ail chest from January 2006 to December 2009.RESULTS： All patients were cured with an average hospital stay of 10.31±3.14 days. Post-operative pain was less severe than preoperative pain （P=0.02）.The rate of postoperative complications such as atelectasis, pulmonary infection, etc was 17.65%. There were fewer long-term complications and less in？ uence on daily work and life.CONCLUSIONS： It is practical to perform an operation for fracture of multiple ribs using a Ti-Ni shape memory alloy embracing ？ xator. The ？ xator, which is less traumatic, simple, safe, and reliable, has a good-histocompatibility and fewer postoperative complications.
文摘A numerical investigation has been carried out to examine turbulent flow and heat transfer characteristics in a three-dimensional ribbed square channels. Fluent 6.3 CFD code has been used. The governing equations are discretized by the second order upwind differencing scheme, decoupling with the SIMPLE (semi-implicit method for pressure linked equations) algorithm and are solved using a finite volume approach. The fluid flow and heat transfer characteristics are presented for the Reynolds numbers based on the channel hydraulic diameter ranging from 104 to 4 ′ 104. The effects of rib shape and orientation on heat transfer and pressure drop in the channel are investigated for six different rib configurations. Rib arrays of 45° inclined and 45° V-shaped are mounted in inline and staggered arrangements on the lower and upper walls of the channel. In addition, the performance of these ribs is also compared with the 90° transverse ribs.
文摘Closed-cell type barrier ribs such as meander, honeycomb, SDR, and waffle types were produced using capillary molding process. Sintering of the ribs revealed that the ribs with asymmetric geometry such as meander and SDR type became distorted severely by the sintering process, but the ribs with symmetric geometry such as honeycomb and waffle type maintained their green state morphology. After sintering, the ribs were coated with green phosphor using osmosis coating process and its luminance characteristics were evaluated. The results indicated that the luminance and its efficiency is improved by using closed-cell type ribs with the new phosphor forming technology.
基金Supported by the Guangdong Science and Technology Project (2008A01070003)
文摘Experimental and numerical investigations have been conducted to study turbulent flow of water and heat transfer characteristics in a rectangular channel with discontinuous crossed ribs and grooves.The tests investigated the overall heat transfer performance and friction factor in ribbed and ribbed-grooved channels with rib angle of 30°.The experimental results show that the overall thermo-hydraulic performance for ribbed-grooved channel is increased by 10%-13.6% when compared to ribbed channel.The investigation on the effects of different rib angles and rib pitches on heat transfer characteristics and friction factor in ribbed-grooved channel was carried out using Fluent with SST(shear-stress transport) k-ω turbulence model.The numerical results indicate that the case for rib angle of 45° shows the best overall thermo-hydraulic performance,about 18%-36% higher than the case for rib angle of 0°.In addition,the flow patterns and local heat transfer characteristics for ribbed and ribbed-grooved channels based on the numerical simulation were also analyzed to reveal the mechanism of heat transfer enhancement.
文摘Research on microforming of fine-grained superplastic Zn-AI22 alloy was carried out in this paper by means of superplastic forming. With the selected material, microformability tests have been carried out with the specially developed evaluation method by using two kinds of stainless steel dies. With these dies, micro-extrusion tests have been carried out and the characteristics of microformability of the material have been clarified. Effects of processing parameters and die structure on forming have been analyzed. SEM and metallographic microscope have been used to analyze the formed specimens. Through analysis of flow lines of the formed specimen, behavior of material could be understood well.
基金Projects(51075401,U1134203,U1334205)supported by the National Natural Science Foundation of ChinaProject(NCET-10-083)supported by the Program for New Century Excellent Talents in University of Ministry of Education,ChinaProject(2013J004-8)supported by the Science and Technology Research and Development Program of China Railway Corporation
文摘The influence of ribs on the train aerodynamic performance was computed using detached eddy simulation(DES), and the transient iteration was solved by the dual-time step lower-upper symmetric Gauss-Seidel(LU-SGS) method. The results show that the ribs installed on the roof have a great effect on the train aerodynamic performance. Compared with trains without ribs, the lift force coefficient of the train with convex ribs changes from negative to positive, while the side force coefficient increases by 110%and 88%, respectively. Due to the combined effect of the lift force and side force, the overturning moment of the train with convex ribs and cutting ribs increases by 140% and 106%, respectively. There is larger negative pressure on the roof of the train without ribs than that with ribs. The ribs on the train would disturb the flow structure and contribute to the air separation, so the separation starts from the roof, while there is no air separation on the roof of the train without ribs. The ribs can also slow down the flow speed above the roof and make the air easily sucked back to the train surface. The vortices at the leeward side of the train without ribs are small and messy compared with those of the train with convex or cutting ribs.
基金co-supported by the National Natural Science Foundation of China(No.52075501)the Fundamental Research Program of Shanxi Province,China(No.20210302124206).
文摘The Large-size Conical Cylinders with Inner Transverse High Ribs(LCCWITHR) can reduce the weight of the parts while maintaining high rigidity and strength. Radially Loading Rotary Extrusion(RLRE) forming technology can achieve integral forming of LCCWITHR through the synergy of radial and rotary movements of dies. The flow law of the material during the forming process is the key to forming large-size inner ribs. At present, there is no unified understanding of the metal flow law of RLRE forming technology. An analytical expression was derived to predict the Radial Direction(RD) deformation loads. The FE simulation and process experiment were carried out to investigate the effects of the inclination angle, thickness factor and transition arc radius of the split top dies on the spacing of the metal diversion plane, the metal flow velocity of the rib area and the final radius of the inner rib. The influence of the split top dies loading distance and the bottom die rotation angle of each pass on the inner radius of the inner rib was verified. And the optimal combination of dies shape parameters and loading paths which can make the metal flow orderly was obtained: the inclination angle is 140°, the thickness factor is 3.64, the transition arc radius is 16 mm;the top dies loading distance is 15 mm, the bottom die rotation angle is 45°.The FE simulation results have been found to be in close agreement with physics experiment.The research results reveal the metal flow law of rib growth in the RLRE of LCCWITHR, which lays a theoretical foundation for subsequent thorough research and process optimization.
基金supported by the National Basic Research Program of China(Grant Nos.2012CB921504 and 2011CB707902)the National Natural Science Foundation of China(Grant No.11274166)+4 种基金the Fundamental Research Funds for the Central Universities,China(Grant No.020414380001)the Fund from State Key Laboratory of AcousticsChinese Academy of Sciences(Grant No.SKLA201401)China Postdoctoral Science Foundation(Grant No.2013M531313)the Priority Academic Program Development of Jiangsu Higher Education Institutions and SRF for ROCS,SEM
文摘We used the spheroidal beam equation to calculate the sound field created by focusing a transducer with a wide aperture angle to obtain the heat deposition, and then we used the Pennes bioheat equation to calculate the temperature field in biological tissue with ribs and to ascertain the effects of rib parameters on the temperature field. The results show that the location and the gap width between the ribs have a great influence on the axial and radial temperature rise of multilayer biological tissue. With a decreasing gap width, the location of the maximum temperature rise moves forward; as the ribs are closer to the transducer surface, the sound energy that passes through the gap between the ribs at the focus decreases, the maximum temperature rise decreases, and the location of the maximum temperature rise moves forward with the ribs.
文摘Researchers from the National Institute for Occupational Safety and Health(NIOSH)are developing a coal pillar rib rating(CPRR)technique to measure the integrity of coal ribs.The CPRR characterizes the rib composition and evaluates its impact on the inherent stability of the coal ribs.The CPRR utilizes four parameters:rib homogeneity,bedding condition,face cleat orientation with respect to entry direction,and rib height.All these parameters are measurable in the field.A rib data collecting procedure and a simple sheet to calculate the CPRR were developed.The developed CPRR can be used as a rib quality mapping tool in underground coal mines and to determine the potential of local rib instabilities and support requirements associated with overburden depth.CPRR calculations were conducted for 22 surveyed solid coal ribs,mainly composed of coal units.Based on this study,the rib performance was classified into four categories.A preliminary minimum primary rib support density(PRSD)line was obtained from these surveyed cases.Two sample cases are presented that illustrate the data collection form and CPRR calculations.
基金financially supported by Beijing Municipal Natural Science Foundation (No.2102035)National Natural Science Foundation of China (No.51173013)
文摘In this work, the photosensitive paste was prepared. It was comprised of inorganic particles and a photosensitive organic component. The inorganic panicles included glass, ceramics, and metals. The organic component should contain at least the following photosensitive materials： photosensitive monomers, photoreactive copolymer and photopolymerization initiators. The photoreactive copolymer played a role of an adhesive in the photosensitive paste. Meanwhile in the development stage, the carboxyl groups of the copolymer reacted with the alkalescent developer. Following this, the unexposed part must be removed and an excellent pattern can be formed. A series of three-component acrylic copolymers （MAA/St/MMA） were designed, and then synthesized via free radical polymerization. Subsequently glycidyl methacrylate （GMA） was employed to modify the prepared copolymers through ring-opening reactions between the carboxyl groups and the epoxide groups. Eventually the photosensitive copolymers were obtained and used to form the barrier ribs of PDPs. The chemical structure, glass transition temperature, acid value and molecular weight of photosensitive copolymers had different effects on the structure and pattern of PDP barrier ribs. Through analyzing effects of different polymer performance parameters on the patterns of barrier ribs, the optimal photosensitive copolymer was acquired.
基金sponsored by the National Natural Science Foundation of China(No.51906207,No.U22B2091)the Young Elite Scientists Sponsorship Program by CAST(2021QNRC001)Technical Field Foundation(2021-JCJQ-JJ-0342)。
文摘SCRamjet is exposed to severe thermal environments during hypersonic flights,which poses a serious challenge to the engine cooling technology.Regenerative cooling with hydrocarbon fuel is considered promising,in which the hydrocarbon fuel flows through micro channels(200μm-3 mm)to absorb the combustion heat release.With strictly limited hydrocarbon fuel onboard,heat transfer deterioration and over-temperature are highly possible.In this paper,micro ribs with staggered side gaps are introduced and numerically studied to enhance the heat transfer.Compared with the straight channel and channel with straight micro ribs,the staggered side gaps alleviate the local low velocity zone and intensify the longitudinal and transverse vortexes.The heat transfer is obviously enhanced.Larger rib height enhances the heat transfer by stronger side gap effects at the cost of larger pressure loss.The best overall heat transfer factorηis achieved in the case of h_(rib)/H=0.1,which increases by 204.5%comparing to the straight channel.When the rib interval is too small or too large,it approaches to the straight channel.The best overall heat transfer factorηis achieved in the case of L/p_(rib)=100,which increases by212.9%comparing to the straight channel.It is known the improvement in the geometry of the ribs,i.e.,the staggered-side-gap micro ribs,induces extra transverse vortex and improves the heat transfer performance more effectively.The research of this paper provides support for the cooling design of the SCRamjet.
