Typically,seat or floor acceleration is used to evaluate the ride comfort of a high-speed train.However,the dynamic performance of the human body significantly differs from that of the floor.Therefore,using the car bo...Typically,seat or floor acceleration is used to evaluate the ride comfort of a high-speed train.However,the dynamic performance of the human body significantly differs from that of the floor.Therefore,using the car body floor and seat accelerations to calculate the ride comfort index of a high-speed train may not reflect the true feelings of passengers.In this study,a 3D human-seat-vehicle-track coupling model was established to investigate the ride comfort of highspeed train passengers.The seated human model,which considers the longitudinal,lateral,vertical,pitching,yawing,and rolling motions,comprises the head,upper torso,lower torso,pelvis,thighs,and shanks.The model parameters were determined using multi-axis excitation measurement data based on a genetic algorithm.Subsequently,the applicability of the small-angle assumption and natural modes of the human model is analyzed.Using the coupling system model,the vibration characteristics of the human-seat interaction surface were analyzed.The ride comfort of the high-speed train and human body dynamic performance were analyzed under normal conditions,track geometric irregularities and train meeting conditions.The results showed that the passenger seats in the front and rear rows adjacent to the window had a higher acceleration value than the others.The human backrest and seat pad connection points have higher vibration amplitudes than the car body floor in the human-sensitive frequency range,indicating that using the acceleration values on the floor may underestimate the discomfort of passengers.The ride comfort of high-speed trains diminishes in the presence of track geometric irregularities and when trains pass each other.When the excitation frequency of track geometry irregularities approached the natural frequency of the human-seat-vehicle system,ride comfort in high-speed trains decreased significantly.Moreover,using seat acceleration to evaluate passenger ride comfort overlooks the vibration characteristics of the human body.The transient aerodynamic force generated when the train meets can cause a larger car body roll and lateral motion at 2 Hz,which,in turn,decreases the passenger ride comfort.This study presents a detailed human-seat-vehicle-track coupling system that can reflect a passenger’s dynamic performance under complex operating conditions.展开更多
Many biodynamic models have been derived using trial and error curve-fitting technique, such that the error between the computed and measured biodynamic response functions is minimum. This study developed a biomechani...Many biodynamic models have been derived using trial and error curve-fitting technique, such that the error between the computed and measured biodynamic response functions is minimum. This study developed a biomechanical model of the human body in a sitting posture without backrest for evaluating the vibration transmissibility and dynamic response to vertical vibration direction. In describing the human body motion, a three biomechanical models are discussed (two models are 4-DOF and one model 7-DOF). Optimization software based on stochastic techniques search methods, Genetic Algorithms (GAs), is employed to determine the human model parameters imposing some limit constraints on the model parameters. In addition, an objective function is formulated comprising the sum of errors between the computed and actual values (experimental data). The studied functions are the driving-point mechanical impedance, apparent mass and seat- to-head transmissibility functions. The optimization process increased the average goodness of fit and the results of studied functions became much closer to the target values (Experimental data). From the optimized model, the resonant frequencies of the driver parts computed on the basis of biodynamic response functions are found to be within close bounds to that expected for the human body.展开更多
Deep-seated catastrophic landslides,particularly rock or debris avalanches,travel extremely rapidly for long distances,causing severe damage over wide areas.This paper summarizes the geological and geomorphological fe...Deep-seated catastrophic landslides,particularly rock or debris avalanches,travel extremely rapidly for long distances,causing severe damage over wide areas.This paper summarizes the geological and geomorphological features of such events,which were induced by earthquakes and rainstorms in Asia,and then uses these features to predict future potential sites of failures.Most of the rock avalanches are preceded by gravitational slope deformation with topographic features,in which small scarps along future head of landslide are the most representative;the scarps can be identified in topographic images made by highresolution airborne LiDAR DEMs and may suggest the instability just before catastrophic failure.展开更多
A comprehensive discussion on the deep seated genesis of gold metallogenic materials and the tectono magmatic controls over gold deposits is given in this paper, which is based on the crustal and upper mantle struct...A comprehensive discussion on the deep seated genesis of gold metallogenic materials and the tectono magmatic controls over gold deposits is given in this paper, which is based on the crustal and upper mantle structural characteristics of the Jiaodong massif, the property, activation history and styles of the Tancheng Lujiang fault zone, as well as a series of accompanying tectono magmatic events. Prediction for further prospecting gold deposits in the area is also made.展开更多
The purpose of this paper is to present the rationale for registration of the Seated Condylar Position (SCP)/Centric Relation (CR) position of the condyles.
The purpose of this paper is to present the technique for registration of the Seated Condylar Position (SCP)/Centric Relation (CR) position of the condyles: a two-piece wax bite registration with deprogramming and no ...The purpose of this paper is to present the technique for registration of the Seated Condylar Position (SCP)/Centric Relation (CR) position of the condyles: a two-piece wax bite registration with deprogramming and no mandibular manipulation.展开更多
Objective:To evaluate the intervention effects of seated Baduanjin exercise on patients undergoing maintenance hemodialysis(MHD).Methods:A total of 108 MHD patients admitted between July 2022 and July 2023 were select...Objective:To evaluate the intervention effects of seated Baduanjin exercise on patients undergoing maintenance hemodialysis(MHD).Methods:A total of 108 MHD patients admitted between July 2022 and July 2023 were selected.They were randomly assigned into two groups:the experimental group,with 55 patients,who received seated Baduanjin exercise combined with leg exercises during dialysis;and the control group,with 53 patients,who only performed leg exercises during dialysis.The psychological state,fatigue symptoms,quality of life,and sleep quality scores were compared between the two groups,and exercise endurance was recorded.Results:After the intervention,the psychological state scores in the experimental group were lower than those in the control group,the fatigue symptom scores were lower,the quality of life scores were higher,the sleep quality scores were lower,and the exercise endurance was higher(P<0.05).Conclusion:Seated Baduanjin exercise can improve the negative psychological state and fatigue symptoms of MHD patients,enhance their quality of life and sleep quality,and effectively increase their exercise endurance.展开更多
Understanding the vibration characteristics of a seated human body is critical for evaluation and improvement of ride comfort of various passenger vehicles. There have been very little publications about the vibration...Understanding the vibration characteristics of a seated human body is critical for evaluation and improvement of ride comfort of various passenger vehicles. There have been very little publications about the vibration characteristics of a seated Chinese human body. By using wide-band white noise excitations and a homemade seat sensor, vertical vibration tests were carried out on 28 volunteers. Apparent masses were obtained for each volunteer at a frequency range of 1-20 Hz for various excitation le-vels. A biodynamic model, which has two degrees of freedom in parallel and includes a frame mass, was chosen to describe the vertical vibration characteristics of the seated human body. The model parameters were identified by means of a Gauss-Newton method with an error function defined in terms of both real and imaginary parts of the apparent mass against frequency. Based on the averaged data of the mass-normalized apparent mass from experiments, the model parameters and corresponding modal parameters were obtained for seated Chinese people at ages of 20-25 with standard weight. The apparent masses predicted by the biodynamic model with identified parameters agree very well with those obtained from experiments. Statistical analysis demonstrates the influence of volunteer’s height and weight on the model parameters for a seated human body.展开更多
Investigation of the vertical vibration characteristics of the seated human body is beneficial for the design and development of vehicle ride comfort.In this study,we first established models of the seated human body ...Investigation of the vertical vibration characteristics of the seated human body is beneficial for the design and development of vehicle ride comfort.In this study,we first established models of the seated human body with two,three and four degrees of freedom(DOF).Then,the vibration characteristics of 30 volunteers were tested under standard conditions with a vibration test rig to obtain data for the apparent mass,driving point mechanical impedance,and seat-to-head transfer function.Based on the experimental data,the parameters of these models are identified and the results show that the four-DOF model can simulate the vertical vibration characteristics of the seated human body more comprehensively.Then,different seated human body models were applied to optimize the damping of shock absorber.The results show that the optimized damping with the four-DOF Chinese seated human body model is 27%more than that with rigid mass and 7%less than that with ISO 5982:2001 seated human body model.展开更多
Background Seated workplaces have greatly increased in China. Many researchers have found that seated work is a risk factor in the development of low-back pain. Backrest can reduce the load on the lower back by transm...Background Seated workplaces have greatly increased in China. Many researchers have found that seated work is a risk factor in the development of low-back pain. Backrest can reduce the load on the lower back by transmitting more of the weight from the upper body to the floor via the backrest so as to prevent low-back pain. To design a suitable chair backrest for seated office work, some backrest parameters must be optimized. In this study, the role of backrest density on lumbar load and comfort were investigated. The goal of the study was to help establish criteria with which backrests that alleviate and prevent low back pain during seated office work can be designed and selected. Methods Twenty volunteers （10 men and 10 women） were seated in three backrest conditions （10 kg/m^3, 25 kg/m^3, and 40 kg/m^3）. Pressure data, including contact pressure （CP）, peak contact pressure （PCP） and contact area were collected during 15-minute trial. Subjective data were collected after each pressure test. Results Backrest density had a significant effect on backrest pressure variables. CP and PCP increased with increasing backrest density. Contact area decreased with increased density. In terms of user preference, the backrest with low density was most highly rated. Conclusions Backrest density plays an important role in lumbar load and comfort during seated work. During designing and selecting backrests, backrest density should be focused on so as to alleviate and prevent low-back pain during seated office work. Backrest density at 10 kg/m^3 got the lowest CP and PCP and largest contact area. Backrest with low density can reduce lumbar pressure and increase support contact area, which could raise comfort feeling. Backrest density at 10 kg/m^3 is better to maintain a balance between providing effective support and alleviating excess lordosis.展开更多
Rationale:Melioidosis is a serious opportunistic infection caused by Burkholderia(B.)pseudomallei,primarily affecting immunocompromised individuals,particularly in endemic regions.Timely diagnosis and appropriate trea...Rationale:Melioidosis is a serious opportunistic infection caused by Burkholderia(B.)pseudomallei,primarily affecting immunocompromised individuals,particularly in endemic regions.Timely diagnosis and appropriate treatment are crucial to prevent fatal outcomes.Patient concerns:Case 1 was a 34-year-old male kidney transplant recipient who presented with a 15-day history of intermittent fever,accompanied by liver and spleen abscesses.Case 2 was a 37-year-old female kidney transplant recipient who presented with acute febrile illness and developed leucopenia.Blood cultures for both patients grew B.pseudomallei.Diagnosis:Both patients were diagnosed with melioidosis caused by B.pseudomallei,with the diagnosis confirmed through pus culture from the liver abscess in Case 1 and blood culture in Case 2.Interventions:Both patients were treated with an intensive regimen of meropenem(renal-adjusted doses),followed by a 3-month course of oral cotrimoxazole for eradication therapy.Outcomes:Case 1 experienced resolution of liver and spleen abscesses after 3 months of treatment and continued to recover well.In Case 2,blood cultures became sterile after 4 weeks,with no further complications observed.Lessons:Melioidosis should be suspected in immunocompromised patients,especially kidney transplant recipients,who present with unexplained fever and sepsis-like symptoms.Early diagnosis through aspiration of abscesses and prompt treatment are critical for preventing relapses and improving patient outcomes.展开更多
A high-temperature and high-pressure valve is the key equipment of a wind tunnel system;it controls the generation of high-temperature and high-pressure gas.To reduce the adverse impact of high-temperature and high-pr...A high-temperature and high-pressure valve is the key equipment of a wind tunnel system;it controls the generation of high-temperature and high-pressure gas.To reduce the adverse impact of high-temperature and high-pressure gas on the strength of the valve body,a cooling structure is set on the valve seat.This can significantly reduce the temperature of the valve body and valve seat.The effects of its structure on the cooling characteristics and stress of the valve seat are studied,and six main parameters that can completely describe the geometry of the cooling structure are proposed.The central composite design method is used to select sample points,and the multi-objective genetic algorithm(MOGA)method is used for optimal structural design.A modification method according to the main parameters for the valve seat is proposed.The results show that the cooling structure weakens the pressure-bearing capability of the valve seat.Among the six main parameters of the valve seat,the distance from the end face of the lower hole to the Z-axis and the distance from the axis of the lower hole to the origin of the coordinates have the most obvious effects on the average stress of the valve seat.An optimum design value is proposed.This work can provide a reference for the design of high-temperature and high-pressure valves.展开更多
In this study,it is aimed to develop a generic model which calculates the trajectory of the ejection seat from the jet aircraft,by taking into account the parameters that will affect the seat movement such as the seat...In this study,it is aimed to develop a generic model which calculates the trajectory of the ejection seat from the jet aircraft,by taking into account the parameters that will affect the seat movement such as the seat’s launch speed,ejection direction,ejection angle,altitude of the aircraft,distance/height from the aircraft rudder and canopy,pilot and ejection seat weight.With the model algorithm proposed,the ejection seat trajectory model was developed on MATLAB.The ejection seat trajectory model is based on point mass trajectory mathematical model.In this study,an analytical study of the problem has been made for modeling the flight trajectory of the ejection seat after it has been ejected.Past studies were used as a basis for validation and simulation.By writing a generic MATLAB code,a user interface was developed and presented to the user as a module.This generic code that has been developed could be used for simulations by users in the future by revising it in accordance with their own job descriptions.展开更多
This study presents the development of a Magnesium Alloy Seat Frame(MASF),supported by case studies from automotive original equipment manufacturers.The process covers integrated design,simulation,manufacturing,and te...This study presents the development of a Magnesium Alloy Seat Frame(MASF),supported by case studies from automotive original equipment manufacturers.The process covers integrated design,simulation,manufacturing,and testing,aiming to boost industry confidence in Mg alloy applications.A novel structural design is developed that integrates the headrest with the backrest,achieving a balance between lightweight performance and safety.Structural optimization is guided by stress–strain simulations under diverse conditions within a complete forward development process.Casting simulations are conducted to analyze process characteristics,resulting in a verified MASF yield rate exceeding 90%.The final 9.88 kg MASF represents a 24.6%(3.23 kg)weight reduction versus a steel seat.This research contributes to advancements in defect control technology for large die casting magnesium alloy parts and has broad implications for their application in automotive manufacturing.展开更多
Seasonal adjustment has been widely used in statistic analyses.Nowadays,the research on seasonal adjustment methods mainly concentrates on X-11,X-12 etc in China,lacking the whole understanding of foreign seasonal adj...Seasonal adjustment has been widely used in statistic analyses.Nowadays,the research on seasonal adjustment methods mainly concentrates on X-11,X-12 etc in China,lacking the whole understanding of foreign seasonal adjustment methods,and the latest progress of seasonal adjustment methods has been less introduced.In this article,various seasonal adjustment methods were introduced,and a comparison of their characteristics and applications was made.It is helpful that statistical organizations can develop appropriate seasonal adjustment methods,concerning different kinds of data.展开更多
基金Supported by National Natural Science Foundation of China(Grant No.U1934203)Research and Development Project of Science and Technology of China Railway Corporation(Grant No.P2023T002)。
文摘Typically,seat or floor acceleration is used to evaluate the ride comfort of a high-speed train.However,the dynamic performance of the human body significantly differs from that of the floor.Therefore,using the car body floor and seat accelerations to calculate the ride comfort index of a high-speed train may not reflect the true feelings of passengers.In this study,a 3D human-seat-vehicle-track coupling model was established to investigate the ride comfort of highspeed train passengers.The seated human model,which considers the longitudinal,lateral,vertical,pitching,yawing,and rolling motions,comprises the head,upper torso,lower torso,pelvis,thighs,and shanks.The model parameters were determined using multi-axis excitation measurement data based on a genetic algorithm.Subsequently,the applicability of the small-angle assumption and natural modes of the human model is analyzed.Using the coupling system model,the vibration characteristics of the human-seat interaction surface were analyzed.The ride comfort of the high-speed train and human body dynamic performance were analyzed under normal conditions,track geometric irregularities and train meeting conditions.The results showed that the passenger seats in the front and rear rows adjacent to the window had a higher acceleration value than the others.The human backrest and seat pad connection points have higher vibration amplitudes than the car body floor in the human-sensitive frequency range,indicating that using the acceleration values on the floor may underestimate the discomfort of passengers.The ride comfort of high-speed trains diminishes in the presence of track geometric irregularities and when trains pass each other.When the excitation frequency of track geometry irregularities approached the natural frequency of the human-seat-vehicle system,ride comfort in high-speed trains decreased significantly.Moreover,using seat acceleration to evaluate passenger ride comfort overlooks the vibration characteristics of the human body.The transient aerodynamic force generated when the train meets can cause a larger car body roll and lateral motion at 2 Hz,which,in turn,decreases the passenger ride comfort.This study presents a detailed human-seat-vehicle-track coupling system that can reflect a passenger’s dynamic performance under complex operating conditions.
文摘Many biodynamic models have been derived using trial and error curve-fitting technique, such that the error between the computed and measured biodynamic response functions is minimum. This study developed a biomechanical model of the human body in a sitting posture without backrest for evaluating the vibration transmissibility and dynamic response to vertical vibration direction. In describing the human body motion, a three biomechanical models are discussed (two models are 4-DOF and one model 7-DOF). Optimization software based on stochastic techniques search methods, Genetic Algorithms (GAs), is employed to determine the human model parameters imposing some limit constraints on the model parameters. In addition, an objective function is formulated comprising the sum of errors between the computed and actual values (experimental data). The studied functions are the driving-point mechanical impedance, apparent mass and seat- to-head transmissibility functions. The optimization process increased the average goodness of fit and the results of studied functions became much closer to the target values (Experimental data). From the optimized model, the resonant frequencies of the driver parts computed on the basis of biodynamic response functions are found to be within close bounds to that expected for the human body.
文摘Deep-seated catastrophic landslides,particularly rock or debris avalanches,travel extremely rapidly for long distances,causing severe damage over wide areas.This paper summarizes the geological and geomorphological features of such events,which were induced by earthquakes and rainstorms in Asia,and then uses these features to predict future potential sites of failures.Most of the rock avalanches are preceded by gravitational slope deformation with topographic features,in which small scarps along future head of landslide are the most representative;the scarps can be identified in topographic images made by highresolution airborne LiDAR DEMs and may suggest the instability just before catastrophic failure.
文摘A comprehensive discussion on the deep seated genesis of gold metallogenic materials and the tectono magmatic controls over gold deposits is given in this paper, which is based on the crustal and upper mantle structural characteristics of the Jiaodong massif, the property, activation history and styles of the Tancheng Lujiang fault zone, as well as a series of accompanying tectono magmatic events. Prediction for further prospecting gold deposits in the area is also made.
文摘The purpose of this paper is to present the rationale for registration of the Seated Condylar Position (SCP)/Centric Relation (CR) position of the condyles.
文摘The purpose of this paper is to present the technique for registration of the Seated Condylar Position (SCP)/Centric Relation (CR) position of the condyles: a two-piece wax bite registration with deprogramming and no mandibular manipulation.
基金Research Project of Sichuan Nursing Vocational College(Project No.2022RZY38)。
文摘Objective:To evaluate the intervention effects of seated Baduanjin exercise on patients undergoing maintenance hemodialysis(MHD).Methods:A total of 108 MHD patients admitted between July 2022 and July 2023 were selected.They were randomly assigned into two groups:the experimental group,with 55 patients,who received seated Baduanjin exercise combined with leg exercises during dialysis;and the control group,with 53 patients,who only performed leg exercises during dialysis.The psychological state,fatigue symptoms,quality of life,and sleep quality scores were compared between the two groups,and exercise endurance was recorded.Results:After the intervention,the psychological state scores in the experimental group were lower than those in the control group,the fatigue symptom scores were lower,the quality of life scores were higher,the sleep quality scores were lower,and the exercise endurance was higher(P<0.05).Conclusion:Seated Baduanjin exercise can improve the negative psychological state and fatigue symptoms of MHD patients,enhance their quality of life and sleep quality,and effectively increase their exercise endurance.
基金supported by the National Natural Science Foundation of China (Grant No. 50675110)the Research Foundation of State Key Laboratory of Automotive Safety and Energy (Grant No. ZZ080082)
文摘Understanding the vibration characteristics of a seated human body is critical for evaluation and improvement of ride comfort of various passenger vehicles. There have been very little publications about the vibration characteristics of a seated Chinese human body. By using wide-band white noise excitations and a homemade seat sensor, vertical vibration tests were carried out on 28 volunteers. Apparent masses were obtained for each volunteer at a frequency range of 1-20 Hz for various excitation le-vels. A biodynamic model, which has two degrees of freedom in parallel and includes a frame mass, was chosen to describe the vertical vibration characteristics of the seated human body. The model parameters were identified by means of a Gauss-Newton method with an error function defined in terms of both real and imaginary parts of the apparent mass against frequency. Based on the averaged data of the mass-normalized apparent mass from experiments, the model parameters and corresponding modal parameters were obtained for seated Chinese people at ages of 20-25 with standard weight. The apparent masses predicted by the biodynamic model with identified parameters agree very well with those obtained from experiments. Statistical analysis demonstrates the influence of volunteer’s height and weight on the model parameters for a seated human body.
文摘Investigation of the vertical vibration characteristics of the seated human body is beneficial for the design and development of vehicle ride comfort.In this study,we first established models of the seated human body with two,three and four degrees of freedom(DOF).Then,the vibration characteristics of 30 volunteers were tested under standard conditions with a vibration test rig to obtain data for the apparent mass,driving point mechanical impedance,and seat-to-head transfer function.Based on the experimental data,the parameters of these models are identified and the results show that the four-DOF model can simulate the vertical vibration characteristics of the seated human body more comprehensively.Then,different seated human body models were applied to optimize the damping of shock absorber.The results show that the optimized damping with the four-DOF Chinese seated human body model is 27%more than that with rigid mass and 7%less than that with ISO 5982:2001 seated human body model.
文摘Background Seated workplaces have greatly increased in China. Many researchers have found that seated work is a risk factor in the development of low-back pain. Backrest can reduce the load on the lower back by transmitting more of the weight from the upper body to the floor via the backrest so as to prevent low-back pain. To design a suitable chair backrest for seated office work, some backrest parameters must be optimized. In this study, the role of backrest density on lumbar load and comfort were investigated. The goal of the study was to help establish criteria with which backrests that alleviate and prevent low back pain during seated office work can be designed and selected. Methods Twenty volunteers （10 men and 10 women） were seated in three backrest conditions （10 kg/m^3, 25 kg/m^3, and 40 kg/m^3）. Pressure data, including contact pressure （CP）, peak contact pressure （PCP） and contact area were collected during 15-minute trial. Subjective data were collected after each pressure test. Results Backrest density had a significant effect on backrest pressure variables. CP and PCP increased with increasing backrest density. Contact area decreased with increased density. In terms of user preference, the backrest with low density was most highly rated. Conclusions Backrest density plays an important role in lumbar load and comfort during seated work. During designing and selecting backrests, backrest density should be focused on so as to alleviate and prevent low-back pain during seated office work. Backrest density at 10 kg/m^3 got the lowest CP and PCP and largest contact area. Backrest with low density can reduce lumbar pressure and increase support contact area, which could raise comfort feeling. Backrest density at 10 kg/m^3 is better to maintain a balance between providing effective support and alleviating excess lordosis.
文摘Rationale:Melioidosis is a serious opportunistic infection caused by Burkholderia(B.)pseudomallei,primarily affecting immunocompromised individuals,particularly in endemic regions.Timely diagnosis and appropriate treatment are crucial to prevent fatal outcomes.Patient concerns:Case 1 was a 34-year-old male kidney transplant recipient who presented with a 15-day history of intermittent fever,accompanied by liver and spleen abscesses.Case 2 was a 37-year-old female kidney transplant recipient who presented with acute febrile illness and developed leucopenia.Blood cultures for both patients grew B.pseudomallei.Diagnosis:Both patients were diagnosed with melioidosis caused by B.pseudomallei,with the diagnosis confirmed through pus culture from the liver abscess in Case 1 and blood culture in Case 2.Interventions:Both patients were treated with an intensive regimen of meropenem(renal-adjusted doses),followed by a 3-month course of oral cotrimoxazole for eradication therapy.Outcomes:Case 1 experienced resolution of liver and spleen abscesses after 3 months of treatment and continued to recover well.In Case 2,blood cultures became sterile after 4 weeks,with no further complications observed.Lessons:Melioidosis should be suspected in immunocompromised patients,especially kidney transplant recipients,who present with unexplained fever and sepsis-like symptoms.Early diagnosis through aspiration of abscesses and prompt treatment are critical for preventing relapses and improving patient outcomes.
基金supported by the National Natural Science Foundation of China(No.52175067)the Zhejiang Key Research&Development Project(No.2021C01021)+1 种基金the Natural Science Foundation of Zhejiang Province(No.LY20E050016)the Postdoctoral Fellowship Program of China Postdoctoral Science Foundation(CPSF)(No.GZC20241478)。
文摘A high-temperature and high-pressure valve is the key equipment of a wind tunnel system;it controls the generation of high-temperature and high-pressure gas.To reduce the adverse impact of high-temperature and high-pressure gas on the strength of the valve body,a cooling structure is set on the valve seat.This can significantly reduce the temperature of the valve body and valve seat.The effects of its structure on the cooling characteristics and stress of the valve seat are studied,and six main parameters that can completely describe the geometry of the cooling structure are proposed.The central composite design method is used to select sample points,and the multi-objective genetic algorithm(MOGA)method is used for optimal structural design.A modification method according to the main parameters for the valve seat is proposed.The results show that the cooling structure weakens the pressure-bearing capability of the valve seat.Among the six main parameters of the valve seat,the distance from the end face of the lower hole to the Z-axis and the distance from the axis of the lower hole to the origin of the coordinates have the most obvious effects on the average stress of the valve seat.An optimum design value is proposed.This work can provide a reference for the design of high-temperature and high-pressure valves.
文摘In this study,it is aimed to develop a generic model which calculates the trajectory of the ejection seat from the jet aircraft,by taking into account the parameters that will affect the seat movement such as the seat’s launch speed,ejection direction,ejection angle,altitude of the aircraft,distance/height from the aircraft rudder and canopy,pilot and ejection seat weight.With the model algorithm proposed,the ejection seat trajectory model was developed on MATLAB.The ejection seat trajectory model is based on point mass trajectory mathematical model.In this study,an analytical study of the problem has been made for modeling the flight trajectory of the ejection seat after it has been ejected.Past studies were used as a basis for validation and simulation.By writing a generic MATLAB code,a user interface was developed and presented to the user as a module.This generic code that has been developed could be used for simulations by users in the future by revising it in accordance with their own job descriptions.
基金supported in part by the project is supported partly by National Key Research and Development Program of China(no.2022YFB2503504)Chongqing Technology Innovation and Application Development Project(no.CSTB2022TIAD-DEX0011)China Scholarship Council.
文摘This study presents the development of a Magnesium Alloy Seat Frame(MASF),supported by case studies from automotive original equipment manufacturers.The process covers integrated design,simulation,manufacturing,and testing,aiming to boost industry confidence in Mg alloy applications.A novel structural design is developed that integrates the headrest with the backrest,achieving a balance between lightweight performance and safety.Structural optimization is guided by stress–strain simulations under diverse conditions within a complete forward development process.Casting simulations are conducted to analyze process characteristics,resulting in a verified MASF yield rate exceeding 90%.The final 9.88 kg MASF represents a 24.6%(3.23 kg)weight reduction versus a steel seat.This research contributes to advancements in defect control technology for large die casting magnesium alloy parts and has broad implications for their application in automotive manufacturing.
文摘Seasonal adjustment has been widely used in statistic analyses.Nowadays,the research on seasonal adjustment methods mainly concentrates on X-11,X-12 etc in China,lacking the whole understanding of foreign seasonal adjustment methods,and the latest progress of seasonal adjustment methods has been less introduced.In this article,various seasonal adjustment methods were introduced,and a comparison of their characteristics and applications was made.It is helpful that statistical organizations can develop appropriate seasonal adjustment methods,concerning different kinds of data.
