The dynamic characteristics of the track system can directly affect its service performance and failure process.To explore the load characteristics and dynamic response of the track system under the dynamic loads from...The dynamic characteristics of the track system can directly affect its service performance and failure process.To explore the load characteristics and dynamic response of the track system under the dynamic loads from the rack vehicle in traction conditions,a systematic test of the track subsystem was carried out on a large-slope test line.In the test,the bending stress of the rack teeth,the wheel-rail forces,and the acceleration of crucial components in the track system were measured.Subsequently,a detailed analysis was conducted on the tested signals of the rack railway track system in the time domain and the time-frequency domains.The test results indicate that the traction force significantly affects the rack tooth bending stress and the wheel-rail forces.The vibrations of the track system under the traction conditions are mainly caused by the impacts generated from the gear-rack engagement,which are then transferred to the sleepers,the rails,and the ballast beds.Furthermore,both the maximum stress on the racks and the wheel-rail forces measured on the rails remain below their allowable values.This experimental study evaluates the load characteristics and reveals the vibration characteristics of the rack railway track system under the vehicle’s ultimate load,which is very important for the load-strengthening design of the key components such as racks and the vibration and noise reduction of the track system.展开更多
Vascular smooth muscle cells (VSMCs) in the arterial walls play important roles in regulating vascular contraction and dilation. VSMCs actively remodel the arterial walls and dedifferentiate from the contractile to th...Vascular smooth muscle cells (VSMCs) in the arterial walls play important roles in regulating vascular contraction and dilation. VSMCs actively remodel the arterial walls and dedifferentiate from the contractile to the synthetic phenotype under pathological conditions. The mechanism underlying phenotypic transition of VSMCs is important for understanding its role in the pathophysiology of disease. Although numerous studies have reported various biochemical pathways that stimulate the phenotypic transition of VSMCs, very little is known about relation between their phenotypic transition and cellular traction force, which affects many cellular functions. In this study, we induced the differentiation of cultured VSMCs from the synthetic to the contractile phenotype by a low-serum cultivation and investigated changes in the cell traction forces using traction force microscopy technique. The expression of α-SMA, a contractile phenotype marker protein, was significantly upregulated with maturation of actin stress fibers in the low-serum culture, indicating VSMC differentiation was promoted in our experiments. The cells changed their morphology to an elongated bipolar shape, and the direction of the cell traction forces tended to align in the direction of the cell’s major axis. Despite the promotion of contractile differentiation in VSMCs, the overall cell traction forces were significantly reduced, indicating that excessive cell mechanical tension, which might induce cell proliferation and migration, was suppressed during contractile differentiation. These results suggest that suppression of cell traction force and enhanced force polarity might be key factors in VSMC differentiation induced by low serum culture.展开更多
[Objectives]To investigate the clinical efficacy of Cyclic Flexion Traction(CFT)in treating Lumbar Disc Herniation(LDH)and its effects on lumbocrural pain relief,functional improvement,and nerve root decompression.[Me...[Objectives]To investigate the clinical efficacy of Cyclic Flexion Traction(CFT)in treating Lumbar Disc Herniation(LDH)and its effects on lumbocrural pain relief,functional improvement,and nerve root decompression.[Methods]Seventy LDH patients treated at the orthopedic rehabilitation outpatient and inpatient departments of Shiyan Taihe Hospital from June 2022 to December 2024 were randomly divided into a treatment group(CFT therapy,n=35)and a control group(traditional traction,n=35).The treatment group received cyclic flexion traction(traction force of 30%-50%body weight with a cycle of 60-30-30 sec),while the control group received supine position linear traction.Both groups underwent 4 weeks of treatment,with assessments including visual analog scale(VAS),Oswestry Disability Index(ODI),and straight leg raising test(SLRT)angles.[Results]The treatment group showed a significantly greater reduction in VAS scores(from 6.97 to 2.31)compared to the control group(from 6.89 to 3.74)(P<0.05).Similarly,ODI improvement(41.62→15.73 compared with 40.98→22.84)and SLRT angle increase(41.23°→76.47°compared with 42.09°→64.19°)were more pronounced in the treatment group(all P<0.05).[Conclusions]Through dynamic decompression mechanisms,CFT therapy demonstrates superior efficacy to traditional traction in pain relief,functional recovery,and nerve root decompression(effective rate 94.29%compared with 77.14%,P<0.05),representing a superior non-surgical treatment option.展开更多
Replacing the energy density and convenience of diesel fuel for all forms of fossil fuel-powered trains presents significant challenges.Unlike the traditional evolutions of rail which has largely self-optimised to dif...Replacing the energy density and convenience of diesel fuel for all forms of fossil fuel-powered trains presents significant challenges.Unlike the traditional evolutions of rail which has largely self-optimised to different fuels and cost structures over 150 years,the challenges now present with a timeline of just a few decades.Fortunately,unlike the mid-1800s,simulation and modelling tools are now quite advanced and a full range of scenarios of operations and train trips can be simulated before new traction systems are designed.Full trip simulations of large heavy haul trains or high speed passenger trains are routinely completed controlled by emulations of human drivers or automated control systems providing controls of the“virtual train”.Recent developments in digital twins can be used to develop flexible and dynamic models of passenger and freight rail systems to support the new complexities of decarbonisation efforts.Interactions between many different traction components and the train multibody system can be considered as a system of systems.Adopting this multi-modelling paradigm enables the secure and integrated interfacing of diverse models.This paper demonstrates the application of the multi-modelling approach to develop digital twins for rail decarbonisation traction and it presents physics-based multi-models that include key components required for studying rail decarbonisation problems.Specifically,the challenge of evaluating zero-emission options is addressed by adding further layers of modelling to the existing fully detailed multibody dynamics simulations.The additional layers detail control options,energy storage,the alternate traction system components and energy management systems.These traction system components may include both electrical system and inertia dynamics models to accurately represent the driveline and control systems.This paper presents case study examples of full trip scenarios of both long haul freight trains and higher speed passenger trains.These results demonstrate the many complex scenarios that are difficult to anticipate.Flowing on from this,risks can be assessed and practical designs of zero-emission systems can be proposed along with the required recharging or refuelling systems.展开更多
BACKGROUND Gastrointestinal submucosal tumors(SMTs)mostly grew in the lumen,but also some of the lesions were extraluminal,in which the stomach was the most co-mmon site.Gastrointestinal stromal tumor account for a la...BACKGROUND Gastrointestinal submucosal tumors(SMTs)mostly grew in the lumen,but also some of the lesions were extraluminal,in which the stomach was the most co-mmon site.Gastrointestinal stromal tumor account for a large proportion of SMT.Due to the deep lesion location of gastric SMT,endoscopic submucosal dissection related techniques are difficult to operate,while endoscopic full-thickness rese-ction(EFTR)has been widely used in clinical practice because it is less invasive and can preserve the physiological structure and function of the stomach.Ho-wever,complete closure of the gastrectomy site after EFTR is critical.If the closure is incomplete,it may cause peritonitis,late perforation and other conditions,and even require further surgical intervention.Although there are currently a number of suture devices and techniques that can be used to promote closure,they have the problem of requiring additional equipment or being inconvenient to use.Although metal clips are widely used,their effectiveness depends on the size and tension of the defect.Therefore,an effective and convenient endoscopic closure technique is urgently needed to solve the closure problem of gastric SMTs after treatment.AIM To investigate the effect of combined application of the preclosure technique and dental floss traction in gastric wound closure following EFTR.METHODS In this study,the data of 94 patients treated for gastric SMTs at the Gastrointestinal Endoscopy Center of the Affiliated Union Hospital of Fujian Medical University from April 2022 to May 2023 were retrospectively analyzed.The patients were divided into a preclosure group(54 patients)and a non-preclosure group(40 patients)on the basis of the timing of wound closure with titanium clips after dental floss traction-assisted EFTR.Each patient in the preclosure group had their wounds preclosed with titanium clips after subtotal lesion resection,whereas each patient in the non-preclosure group had their wounds closed with titanium clips after total lesion resection.The lesion size,wound closure time,number of titanium clips used,incidence of postoperative complications,and postoperative hospitalization time were compared between the two groups.RESULTS The wound closure time was significantly shorter in the preclosure group than in the non-preclosure group(6.69±2.109 minutes vs 11.65±3.786 minutes,P<0.001).The number of titanium clips used was significantly lower in the preclosure group(8.93±2.231)than in the non-preclosure group(12.05±4.495)(P<0.001).There was no sig-nificant difference between the two groups in terms of the need for an indwelling gastric tube or the length of postoperative hospital stay(6.41±1.31 vs 6.13±1.06 days).For all patients in the preclosure group and the non-preclosure group,resection was completed successfully without bleeding,abdominal pain,abdominal distension,or other postoperative complications.CONCLUSION Application of the preclosure technique combined with dental floss traction can be used intraoperatively to effectively close the surgical wound in patients undergoing EFTR,reliably preventing the tumor from falling into the peritoneal cavity.展开更多
The variation of the nonlinear contact stiffness induced by the elastic wheel-holding effect between the aircraft and tractor has an important effect on the vibration characteristics of an airfield towbarless traction...The variation of the nonlinear contact stiffness induced by the elastic wheel-holding effect between the aircraft and tractor has an important effect on the vibration characteristics of an airfield towbarless traction system,making it essential for ensuring the safety of this emerging towing-out mode.In this paper,the frequency evolutionary tendency of the traction system is studied and obtained considering the variation of nonlinear contact stiffness for the first time.A novel modal analysis method,based on a derived nonlinear contact relationship,is proposed to investigate the vibration characteristics for mechanical system.Frequency veering and mode exchange phenomena in the low-order modes are observed due to the variation of nonlinear contact stiffness.These findings are further validated by the experimental results of a scaled-down model.In addition,it is also found that the veering critical point will be shifted with the external loads.The study provides valuable insights into the vibration characteristics and frequency veering behavior of similar mechanism-based systems,such as towbarless traction system,and has important implications for improving their design and operational performance.展开更多
The identification of the traction acting on a portion of the surface of an anisotropic solid is very important in structural health monitoring and optimal design of structures. The traction can be determined using in...The identification of the traction acting on a portion of the surface of an anisotropic solid is very important in structural health monitoring and optimal design of structures. The traction can be determined using inverse methods in which displacement or strain measurements are taken at several points on the body. This paper presents an inverse method based on the method of fundamental solutions for the traction identification problem in two-dimensional anisotropic elasticity. The method of fundamental solutions is an efficient boundary-type meshless method widely used for analyzing various problems. Since the problem is linear, the sensitivity analysis is simply performed by solving the corresponding direct problem several times with different loads. The effects of important parameters such as the number of measurement data, the position of the measurement points, the amount of measurement error, and the type of measurement, i.e., displacement or strain, on the results are also investigated. The results obtained show that the presented inverse method is suitable for the problem of traction identification. It can be concluded from the results that the use of strain measurements in the inverse analysis leads to more accurate results than the use of displacement measurements. It is also found that measurement points closer to the boundary with unknown traction provide more reliable solutions. Additionally, it is found that increasing the number of measurement points increases the accuracy of the inverse solution. However, in cases with a large number of measurement points, further increasing the number of measurement data has little effect on the results.展开更多
The surgical treatment of severe scoliosis and kyphoscoliosis in the pediatric population is complicated and has high morbidity and mortality risks.Severe scoliosis has traditionally been defined by a coronal Cobb ang...The surgical treatment of severe scoliosis and kyphoscoliosis in the pediatric population is complicated and has high morbidity and mortality risks.Severe scoliosis has traditionally been defined by a coronal Cobb angle of greater than 90°or 100°.The usual corrective methods for these patients have been anterior or posterior release and osteotomies using a combined anterior-posterior or posterior-only approach.Many of these patients have pre-existing pulmonary compromise;therefore,an anterior approach is often not reasonable or possible.Acute correction of a deformity may also cause neurologic injury.Halo gravity traction(HGT)allows for progressive,gradual,and sustained correction of the spinal deformity in the coronal,sagittal,and axial planes,leading to a decrease in the amount of correction needed at definitive posterior fusion.This relates to decreased postoperative neurologic deficit and improved pulmonary function.Preoperative HGT has evolved to be the surgical adjunct in the treatment of severe spinal deformity.Indications for HGT,best protocols of application,and optimal duration of traction still lack uniformity;thus,a review of the literature remains relevant and necessary.This review summarizes the existing literature on HGT,including its indications,applications,duration of traction,and associated complications.展开更多
Objective: To analyze the therapeutic effect of combining dental arch splint intermaxillary traction with rigid internal fixation for the treatment of facial comminuted fractures. Methods: Sixty patients with facial c...Objective: To analyze the therapeutic effect of combining dental arch splint intermaxillary traction with rigid internal fixation for the treatment of facial comminuted fractures. Methods: Sixty patients with facial comminuted fractures admitted for treatment between July 2023 and December 2024 were selected. Using a random number table method, 30 patients were assigned to the observation group, where moderate traction using a dental arch splint combined with rigid internal fixation was applied. Another 30 patients were assigned to the control group and only received dental arch splint traction treatment. The total effective rate, postoperative recovery indicators, periodontal status, complication rate, and quality of life scores were compared between the two groups. Results: The total effective rate in the observation group was higher than that in the control group. The postoperative recovery indicators and periodontal status in the observation group were superior to those in the control group. The complication rate and quality of life score were lower in the observation group compared to the control group, with P < 0.05. Conclusion: Combining dental arch splint intermaxillary traction with rigid internal fixation can improve the periodontal status and quality of life of patients with facial comminuted fractures, shorten postoperative recovery time, reduce various complications, and enhance surgical efficacy.展开更多
Critical for metering and protection in electric railway traction power supply systems(TPSSs),the measurement performance of voltage transformers(VTs)must be timely and reliably monitored.This paper outlines a three-s...Critical for metering and protection in electric railway traction power supply systems(TPSSs),the measurement performance of voltage transformers(VTs)must be timely and reliably monitored.This paper outlines a three-step,RMS data only method for evaluating VTs in TPSSs.First,a kernel principal component analysis approach is used to diagnose the VT exhibiting significant measurement deviations over time,mitigating the influence of stochastic fluctuations in traction loads.Second,a back propagation neural network is employed to continuously estimate the measurement deviations of the targeted VT.Third,a trend analysis method is developed to assess the evolution of the measurement performance of VTs.Case studies conducted on field data from an operational TPSS demonstrate the effectiveness of the proposed method in detecting VTs with measurement deviations exceeding 1%relative to their original accuracy levels.Additionally,the method accurately tracks deviation trends,enabling the identification of potential early-stage faults in VTs and helping prevent significant economic losses in TPSS operations.展开更多
Modern electric traction networks(ETN)are equipped with automated systems for commercial accounting of power consumption(ASCAPC),which allows solving properly the problems of enhancing the energy efficiency of transpo...Modern electric traction networks(ETN)are equipped with automated systems for commercial accounting of power consumption(ASCAPC),which allows solving properly the problems of enhancing the energy efficiency of transportation processes.Energy efficiency of ETNs is defined as the amount of power losses in ETN components:overhead catenary systems and traction transformers.Due to the instability of traction loads and changes in their location in space,the electric traction network is different from the general network.It is necessary to develop an approach for loss analysis in traction networks and in transformers of traction substations.To solve this prob-lem,a balance-based technique for power loss calculation in traction networks based on ASCAPC data is proposed.First,the balance-based technique presented here breaks down the power consumption of the train by source.Then,calculates technical power losses in 25 and 225 kV traction networks as well as in traction transformers.Last,the technique is implemented in the form of an algorithm tested on real-life data and it is ready for practical use.展开更多
在实现“双碳”目标的背景下,城市轨道交通需要实现节能低碳运行。现有牵引供电系统(traction power supply system,TPSS)采用下垂控制策略存在再生制动能量利用率低、缺乏对系统潮流主动有效控制及优化手段等问题。该文分析双向变流器...在实现“双碳”目标的背景下,城市轨道交通需要实现节能低碳运行。现有牵引供电系统(traction power supply system,TPSS)采用下垂控制策略存在再生制动能量利用率低、缺乏对系统潮流主动有效控制及优化手段等问题。该文分析双向变流器的下垂参数对系统用电量的影响,进而提出一种实现牵引负荷功率最优分配的协同控制方法,该方法对双向变流器的下垂参数实时优化和调整,促进机车再生制动能量的流动,有效提高再生制动能量利用率,显著提升系统协同控制性能。经仿真计算,采用该方法可年节约0.17亿k W·h电量,有效助力城市轨道交通牵引供电系统安全、经济运行。展开更多
基金supported by the National Natural Science Foundation of China(No.52388102)the Sichuan Science and Technology Program(No.2024NSFTD0011)the Fundamental Research Funds for the State Key Laboratory of Rail Transit Vehicle System of Southwest Jiaotong University(No.2023TPL-T11).
文摘The dynamic characteristics of the track system can directly affect its service performance and failure process.To explore the load characteristics and dynamic response of the track system under the dynamic loads from the rack vehicle in traction conditions,a systematic test of the track subsystem was carried out on a large-slope test line.In the test,the bending stress of the rack teeth,the wheel-rail forces,and the acceleration of crucial components in the track system were measured.Subsequently,a detailed analysis was conducted on the tested signals of the rack railway track system in the time domain and the time-frequency domains.The test results indicate that the traction force significantly affects the rack tooth bending stress and the wheel-rail forces.The vibrations of the track system under the traction conditions are mainly caused by the impacts generated from the gear-rack engagement,which are then transferred to the sleepers,the rails,and the ballast beds.Furthermore,both the maximum stress on the racks and the wheel-rail forces measured on the rails remain below their allowable values.This experimental study evaluates the load characteristics and reveals the vibration characteristics of the rack railway track system under the vehicle’s ultimate load,which is very important for the load-strengthening design of the key components such as racks and the vibration and noise reduction of the track system.
文摘Vascular smooth muscle cells (VSMCs) in the arterial walls play important roles in regulating vascular contraction and dilation. VSMCs actively remodel the arterial walls and dedifferentiate from the contractile to the synthetic phenotype under pathological conditions. The mechanism underlying phenotypic transition of VSMCs is important for understanding its role in the pathophysiology of disease. Although numerous studies have reported various biochemical pathways that stimulate the phenotypic transition of VSMCs, very little is known about relation between their phenotypic transition and cellular traction force, which affects many cellular functions. In this study, we induced the differentiation of cultured VSMCs from the synthetic to the contractile phenotype by a low-serum cultivation and investigated changes in the cell traction forces using traction force microscopy technique. The expression of α-SMA, a contractile phenotype marker protein, was significantly upregulated with maturation of actin stress fibers in the low-serum culture, indicating VSMC differentiation was promoted in our experiments. The cells changed their morphology to an elongated bipolar shape, and the direction of the cell traction forces tended to align in the direction of the cell’s major axis. Despite the promotion of contractile differentiation in VSMCs, the overall cell traction forces were significantly reduced, indicating that excessive cell mechanical tension, which might induce cell proliferation and migration, was suppressed during contractile differentiation. These results suggest that suppression of cell traction force and enhanced force polarity might be key factors in VSMC differentiation induced by low serum culture.
基金Supported by the Hospital-level Program of Shiyan Taihe Hospital(2022JJXM144).
文摘[Objectives]To investigate the clinical efficacy of Cyclic Flexion Traction(CFT)in treating Lumbar Disc Herniation(LDH)and its effects on lumbocrural pain relief,functional improvement,and nerve root decompression.[Methods]Seventy LDH patients treated at the orthopedic rehabilitation outpatient and inpatient departments of Shiyan Taihe Hospital from June 2022 to December 2024 were randomly divided into a treatment group(CFT therapy,n=35)and a control group(traditional traction,n=35).The treatment group received cyclic flexion traction(traction force of 30%-50%body weight with a cycle of 60-30-30 sec),while the control group received supine position linear traction.Both groups underwent 4 weeks of treatment,with assessments including visual analog scale(VAS),Oswestry Disability Index(ODI),and straight leg raising test(SLRT)angles.[Results]The treatment group showed a significantly greater reduction in VAS scores(from 6.97 to 2.31)compared to the control group(from 6.89 to 3.74)(P<0.05).Similarly,ODI improvement(41.62→15.73 compared with 40.98→22.84)and SLRT angle increase(41.23°→76.47°compared with 42.09°→64.19°)were more pronounced in the treatment group(all P<0.05).[Conclusions]Through dynamic decompression mechanisms,CFT therapy demonstrates superior efficacy to traditional traction in pain relief,functional recovery,and nerve root decompression(effective rate 94.29%compared with 77.14%,P<0.05),representing a superior non-surgical treatment option.
文摘Replacing the energy density and convenience of diesel fuel for all forms of fossil fuel-powered trains presents significant challenges.Unlike the traditional evolutions of rail which has largely self-optimised to different fuels and cost structures over 150 years,the challenges now present with a timeline of just a few decades.Fortunately,unlike the mid-1800s,simulation and modelling tools are now quite advanced and a full range of scenarios of operations and train trips can be simulated before new traction systems are designed.Full trip simulations of large heavy haul trains or high speed passenger trains are routinely completed controlled by emulations of human drivers or automated control systems providing controls of the“virtual train”.Recent developments in digital twins can be used to develop flexible and dynamic models of passenger and freight rail systems to support the new complexities of decarbonisation efforts.Interactions between many different traction components and the train multibody system can be considered as a system of systems.Adopting this multi-modelling paradigm enables the secure and integrated interfacing of diverse models.This paper demonstrates the application of the multi-modelling approach to develop digital twins for rail decarbonisation traction and it presents physics-based multi-models that include key components required for studying rail decarbonisation problems.Specifically,the challenge of evaluating zero-emission options is addressed by adding further layers of modelling to the existing fully detailed multibody dynamics simulations.The additional layers detail control options,energy storage,the alternate traction system components and energy management systems.These traction system components may include both electrical system and inertia dynamics models to accurately represent the driveline and control systems.This paper presents case study examples of full trip scenarios of both long haul freight trains and higher speed passenger trains.These results demonstrate the many complex scenarios that are difficult to anticipate.Flowing on from this,risks can be assessed and practical designs of zero-emission systems can be proposed along with the required recharging or refuelling systems.
文摘BACKGROUND Gastrointestinal submucosal tumors(SMTs)mostly grew in the lumen,but also some of the lesions were extraluminal,in which the stomach was the most co-mmon site.Gastrointestinal stromal tumor account for a large proportion of SMT.Due to the deep lesion location of gastric SMT,endoscopic submucosal dissection related techniques are difficult to operate,while endoscopic full-thickness rese-ction(EFTR)has been widely used in clinical practice because it is less invasive and can preserve the physiological structure and function of the stomach.Ho-wever,complete closure of the gastrectomy site after EFTR is critical.If the closure is incomplete,it may cause peritonitis,late perforation and other conditions,and even require further surgical intervention.Although there are currently a number of suture devices and techniques that can be used to promote closure,they have the problem of requiring additional equipment or being inconvenient to use.Although metal clips are widely used,their effectiveness depends on the size and tension of the defect.Therefore,an effective and convenient endoscopic closure technique is urgently needed to solve the closure problem of gastric SMTs after treatment.AIM To investigate the effect of combined application of the preclosure technique and dental floss traction in gastric wound closure following EFTR.METHODS In this study,the data of 94 patients treated for gastric SMTs at the Gastrointestinal Endoscopy Center of the Affiliated Union Hospital of Fujian Medical University from April 2022 to May 2023 were retrospectively analyzed.The patients were divided into a preclosure group(54 patients)and a non-preclosure group(40 patients)on the basis of the timing of wound closure with titanium clips after dental floss traction-assisted EFTR.Each patient in the preclosure group had their wounds preclosed with titanium clips after subtotal lesion resection,whereas each patient in the non-preclosure group had their wounds closed with titanium clips after total lesion resection.The lesion size,wound closure time,number of titanium clips used,incidence of postoperative complications,and postoperative hospitalization time were compared between the two groups.RESULTS The wound closure time was significantly shorter in the preclosure group than in the non-preclosure group(6.69±2.109 minutes vs 11.65±3.786 minutes,P<0.001).The number of titanium clips used was significantly lower in the preclosure group(8.93±2.231)than in the non-preclosure group(12.05±4.495)(P<0.001).There was no sig-nificant difference between the two groups in terms of the need for an indwelling gastric tube or the length of postoperative hospital stay(6.41±1.31 vs 6.13±1.06 days).For all patients in the preclosure group and the non-preclosure group,resection was completed successfully without bleeding,abdominal pain,abdominal distension,or other postoperative complications.CONCLUSION Application of the preclosure technique combined with dental floss traction can be used intraoperatively to effectively close the surgical wound in patients undergoing EFTR,reliably preventing the tumor from falling into the peritoneal cavity.
基金co-supported by the Key Projects of the Civil Aviation Joint Fund of the National Natural Science Foundation of China(No.U2033208)。
文摘The variation of the nonlinear contact stiffness induced by the elastic wheel-holding effect between the aircraft and tractor has an important effect on the vibration characteristics of an airfield towbarless traction system,making it essential for ensuring the safety of this emerging towing-out mode.In this paper,the frequency evolutionary tendency of the traction system is studied and obtained considering the variation of nonlinear contact stiffness for the first time.A novel modal analysis method,based on a derived nonlinear contact relationship,is proposed to investigate the vibration characteristics for mechanical system.Frequency veering and mode exchange phenomena in the low-order modes are observed due to the variation of nonlinear contact stiffness.These findings are further validated by the experimental results of a scaled-down model.In addition,it is also found that the veering critical point will be shifted with the external loads.The study provides valuable insights into the vibration characteristics and frequency veering behavior of similar mechanism-based systems,such as towbarless traction system,and has important implications for improving their design and operational performance.
基金funded by Vice Chancellor of Research at Shiraz University(grant 3GFU2M1820).
文摘The identification of the traction acting on a portion of the surface of an anisotropic solid is very important in structural health monitoring and optimal design of structures. The traction can be determined using inverse methods in which displacement or strain measurements are taken at several points on the body. This paper presents an inverse method based on the method of fundamental solutions for the traction identification problem in two-dimensional anisotropic elasticity. The method of fundamental solutions is an efficient boundary-type meshless method widely used for analyzing various problems. Since the problem is linear, the sensitivity analysis is simply performed by solving the corresponding direct problem several times with different loads. The effects of important parameters such as the number of measurement data, the position of the measurement points, the amount of measurement error, and the type of measurement, i.e., displacement or strain, on the results are also investigated. The results obtained show that the presented inverse method is suitable for the problem of traction identification. It can be concluded from the results that the use of strain measurements in the inverse analysis leads to more accurate results than the use of displacement measurements. It is also found that measurement points closer to the boundary with unknown traction provide more reliable solutions. Additionally, it is found that increasing the number of measurement points increases the accuracy of the inverse solution. However, in cases with a large number of measurement points, further increasing the number of measurement data has little effect on the results.
文摘The surgical treatment of severe scoliosis and kyphoscoliosis in the pediatric population is complicated and has high morbidity and mortality risks.Severe scoliosis has traditionally been defined by a coronal Cobb angle of greater than 90°or 100°.The usual corrective methods for these patients have been anterior or posterior release and osteotomies using a combined anterior-posterior or posterior-only approach.Many of these patients have pre-existing pulmonary compromise;therefore,an anterior approach is often not reasonable or possible.Acute correction of a deformity may also cause neurologic injury.Halo gravity traction(HGT)allows for progressive,gradual,and sustained correction of the spinal deformity in the coronal,sagittal,and axial planes,leading to a decrease in the amount of correction needed at definitive posterior fusion.This relates to decreased postoperative neurologic deficit and improved pulmonary function.Preoperative HGT has evolved to be the surgical adjunct in the treatment of severe spinal deformity.Indications for HGT,best protocols of application,and optimal duration of traction still lack uniformity;thus,a review of the literature remains relevant and necessary.This review summarizes the existing literature on HGT,including its indications,applications,duration of traction,and associated complications.
基金Special Support Program for Scientific and Technological Talent“Application and Impact of Dental Arch Splint Intermaxillary Traction Combined with Rigid Internal Fixation on Oral Health in Patients with Facial Fractures”(DX2023BR18)。
文摘Objective: To analyze the therapeutic effect of combining dental arch splint intermaxillary traction with rigid internal fixation for the treatment of facial comminuted fractures. Methods: Sixty patients with facial comminuted fractures admitted for treatment between July 2023 and December 2024 were selected. Using a random number table method, 30 patients were assigned to the observation group, where moderate traction using a dental arch splint combined with rigid internal fixation was applied. Another 30 patients were assigned to the control group and only received dental arch splint traction treatment. The total effective rate, postoperative recovery indicators, periodontal status, complication rate, and quality of life scores were compared between the two groups. Results: The total effective rate in the observation group was higher than that in the control group. The postoperative recovery indicators and periodontal status in the observation group were superior to those in the control group. The complication rate and quality of life score were lower in the observation group compared to the control group, with P < 0.05. Conclusion: Combining dental arch splint intermaxillary traction with rigid internal fixation can improve the periodontal status and quality of life of patients with facial comminuted fractures, shorten postoperative recovery time, reduce various complications, and enhance surgical efficacy.
基金supported by the National Natural Science Foundation of China(No.52107125)Applied Basic Research Project of Sichuan Province(No.2022NSFSC0250)Chengdu Guojia Electrical Engineering Co.,Ltd.(No.KYL202312-0043).
文摘Critical for metering and protection in electric railway traction power supply systems(TPSSs),the measurement performance of voltage transformers(VTs)must be timely and reliably monitored.This paper outlines a three-step,RMS data only method for evaluating VTs in TPSSs.First,a kernel principal component analysis approach is used to diagnose the VT exhibiting significant measurement deviations over time,mitigating the influence of stochastic fluctuations in traction loads.Second,a back propagation neural network is employed to continuously estimate the measurement deviations of the targeted VT.Third,a trend analysis method is developed to assess the evolution of the measurement performance of VTs.Case studies conducted on field data from an operational TPSS demonstrate the effectiveness of the proposed method in detecting VTs with measurement deviations exceeding 1%relative to their original accuracy levels.Additionally,the method accurately tracks deviation trends,enabling the identification of potential early-stage faults in VTs and helping prevent significant economic losses in TPSS operations.
基金the state assign-ment of Ministry of Science and Higher Education of the Russian Federation(theme No 123102000012-2“Compre-hensive study of aerodynamic characteristics of plasma systems of thermochemical fuel preparation”,agreement No 075-03-2023-028/1 of 05.10.2023).
文摘Modern electric traction networks(ETN)are equipped with automated systems for commercial accounting of power consumption(ASCAPC),which allows solving properly the problems of enhancing the energy efficiency of transportation processes.Energy efficiency of ETNs is defined as the amount of power losses in ETN components:overhead catenary systems and traction transformers.Due to the instability of traction loads and changes in their location in space,the electric traction network is different from the general network.It is necessary to develop an approach for loss analysis in traction networks and in transformers of traction substations.To solve this prob-lem,a balance-based technique for power loss calculation in traction networks based on ASCAPC data is proposed.First,the balance-based technique presented here breaks down the power consumption of the train by source.Then,calculates technical power losses in 25 and 225 kV traction networks as well as in traction transformers.Last,the technique is implemented in the form of an algorithm tested on real-life data and it is ready for practical use.
文摘在实现“双碳”目标的背景下,城市轨道交通需要实现节能低碳运行。现有牵引供电系统(traction power supply system,TPSS)采用下垂控制策略存在再生制动能量利用率低、缺乏对系统潮流主动有效控制及优化手段等问题。该文分析双向变流器的下垂参数对系统用电量的影响,进而提出一种实现牵引负荷功率最优分配的协同控制方法,该方法对双向变流器的下垂参数实时优化和调整,促进机车再生制动能量的流动,有效提高再生制动能量利用率,显著提升系统协同控制性能。经仿真计算,采用该方法可年节约0.17亿k W·h电量,有效助力城市轨道交通牵引供电系统安全、经济运行。
