Continuum robots have been a hot topic in recent years due to their intrinsic features of agility,flexibility,and safety.To successfully deploy continuum robots in practical applications,further enhancements in variab...Continuum robots have been a hot topic in recent years due to their intrinsic features of agility,flexibility,and safety.To successfully deploy continuum robots in practical applications,further enhancements in variable stiffness,decoupled motion,and embedded sensing are highly desirable.Since continuum robots are usually composed of multiple joints assembled in series,their mechanical properties and performance will certainly rely on the connected joints.This paper proposes a motion-decoupled variable stiffness-decoupled pneumatic rigid-flexible hybrid joint(RFHJ),which is modular designed and integrated with a rigid hinge,a stiffness-tuning module,and soft actuators.The soft pneumatic muscle actuators are pre-stretched during assembly,ensuring the stable initial state of RFHJ.A novel musculature-mounting configuration is also presented,which enables RFHJs to achieve independent motions in two orthogonal planes.Furthermore,the variable stiffness module is embedded in the RFHJ’s structure to offer real-time and independent stiffness tunability across multiple scales in two perpendicular directions.The proposed RFHJ makes most of the advantages of soft continuum robots and conventional rigid serial robots by introducing a hybrid structure to provide both safe human-robot interaction(HRI),accurate control and reliable stiffness variation,presenting promising potentials for robotic systems,which have been theoretically proved and experimentally verified on the physical prototype.The experimental results also indicate that the developed RFHJ can work with variable stiffness ranging in[1.2,49.9]N·m/rad.A variable stiffness rigid-flexible hybrid continuum arm(RFHA)is designed with three RFHJs in series.Primary tests on the developed RFHA prototype demonstrate that it has the characteristics of decoupled driving,bidirectional stiffness tunability and self-stability.展开更多
Experiments of dense-phase pneumatic conveying of pulverized coal using nitrogen are carded out in an experimental test facility with the conveying pressure up to 4. 0 MPa and the gas-solid ratio up to 450 kg/m^3. The...Experiments of dense-phase pneumatic conveying of pulverized coal using nitrogen are carded out in an experimental test facility with the conveying pressure up to 4. 0 MPa and the gas-solid ratio up to 450 kg/m^3. The influences of different conveying differential pressures, coal moisture contents, gas volume flow rates and superficial velocities on the solid-gas ratios are investigated. Shannon entropy analysis of pressure fluctuation time series is developed to reveal the flow characteristics. Through investigation of the distribution of the Shannon entropy under different conditions, the flow stability and the evolutional tendency of the Shannon entropy in different regimes and regime transition processes are discovered, and the relationship between the Shannon entropy and the flow regimes is also established. The results indicate that the solid-gas ratio and the Shannon entropy rise with the increase in conveying differential pressure. The solid-gas ratio and the Shannon entropy reveal preferable regularity with gas volume flow rates. The Shannon entropy is different for different flow regimes, and can be used to identify the flow regimes. Both mass flow rate and the Shannon entropy decrease with the increase in moisture contents. The Shannon entropy analysis is a feasible approach for researching the characteristics of flow regimes, flow stability and flow regime transitions in dense-phase pneumatic conveying under high pressure.展开更多
The process of DTH（down-the-hole） hammer drilling has been characterized as a very complex phenomenon due to its high nonlinearity,large deformation and damage behaviors.Taking brittle materials（concrete,granite an...The process of DTH（down-the-hole） hammer drilling has been characterized as a very complex phenomenon due to its high nonlinearity,large deformation and damage behaviors.Taking brittle materials（concrete,granite and sandstone） as impact specimens,the explicit time integration nonlinear finite element code LS-DYNA was employed to analyze the impact process and the penetration boundary conditions of DTH hammer percussive drilling system.Compared with previous studies,the present model contains several new features.One is that the 3D effects of DTH hammer drilling system were considered.Another important feature is that it took the coupling effects of brittle materials into account to the bit-specimen boundary of the drilling system.This distinguishes it from the traditional approaches to the bit-rock intersection,in which nonlinear spring models are usually imposed.The impact forces,bit insert penetrations and force-penetration curves of concrete,granite and sandstone under DTH hammer impact have been recorded;the formation of craters and fractures has been also investigated.The impact loads of piston-bit interaction appear to be relatively sensitive to piston impact velocity.The impact between piston-bit interaction occurs at two times larger forces,whereas the duration of the first impact doesn＇t change with respect to the piston velocity.The material properties of impact specimen do not affect the first impact process between the piston and bit.However,the period between the two impacts and the magnitudes of the second impact forces greatly depend on the specimen material properties.It is found that the penetration depth of specimen is dependent on the impact force magnitude and the macro-mechanical properties of the brittle materials.展开更多
A mathematic model is built up to analyze the influences of a pilot valve'sleakage on the performances of pneumatic pressure proportional valve, and the performances aresimulated by using MATLAB. The results indic...A mathematic model is built up to analyze the influences of a pilot valve'sleakage on the performances of pneumatic pressure proportional valve, and the performances aresimulated by using MATLAB. The results indicate that using slide pilot valve in the valve system isfeasible, but the leakage's influences can not be neglected, especially it may induce instability ina low output pressure situation. A pilot valve using too large throttle window will cause the valveoscillate. To improve the working condition of pilot valve, a method adopting different widths oftwo throttle window is proposed. According to our simulation, this method balances the pressure dropbetween the two stage throttle ports, and reduces the influences of pilot valve's leakage.展开更多
The high pressure pneumatic system has been applied to special industries. It may cause errors when we analyze high pressure pneumatics under ideal gas assumption. However, the real gas effect on the performances of h...The high pressure pneumatic system has been applied to special industries. It may cause errors when we analyze high pressure pneumatics under ideal gas assumption. However, the real gas effect on the performances of high pressure pneumatics is seldom investigated. In this paper, the real gas effects on air enthalpy and internal energy are estimated firstly to study the real gas effect on the energy conversion. Under ideal gas assumption, enthalpy and internal energy are solely related to air temperature. The estimation result indicates that the pressure enthalpy and pressure internal energy of real pneumatic air obviously decrease the values of enthalpy and internal energy for high pressure pneumatics, and the values of pressure enthalpy and pressure internal energy are close. Based on the relationship among pressure, enthalpy and internal energy, the real gas effects on charging and discharging processes of high pressure pneumatics are estimated, which indicates that the real gas effect accelerates the temperature and pressure decreasing rates during discharging process, and decelerates their increasing rates during charging process. According to the above analysis, and for the inconvenience in building the simulation model for real gas and the difficulty of measuring the detail thermal capacities of pneumatics, a method to compensate the real gas effect under ideal gas assumption is proposed by modulating the thermal capacity of the pneumatic container in simulation. The experiments of switching expansion reduction （SER） for high pressure pneumatics are used to verify this compensating method. SER includes the discharging process of supply tanks and the charging process of expansion tank. The simulated and experimental results of SER are highly consistent. The proposed compensation method provides a convenient way to obtain more realistic simulation results for high pressure pneumatics.展开更多
Structural stabilization by a pressurized fluid is very common in nature, however hardly found in technology. Car tires, hot air balloons, airships and airhouses are among the few technical exceptions, which are stab...Structural stabilization by a pressurized fluid is very common in nature, however hardly found in technology. Car tires, hot air balloons, airships and airhouses are among the few technical exceptions, which are stabilized by a compressed medium, typically air. Restricted by simple geometries and a very limited load bearing capacity these pneumatic structures could succeed only in very specialized applications. Nevertheless, prospective concepts ag has systematically investigated pneumatic structures during the last few years. As a major result, it was demonstrated that almost any shape can be made with pneumatic structures and that astonishing structures such as the pneumatic airplane Stingray can be realized even with low air pressure. On top of that, Airlight Ltd. in close collaboration with prospective concepts ag has recently developed the fundamental new structural concept Tensairity. The synergetic combination of an inflated structure with conventional structural elements such as cables and struts yields pneumatic light-weight structures with the load bearing capacity of steel girders. Thus, complex forms and high strength open up many new opportunities for pressure induced stability in technology. An overview of these recent developments is presented and the close relationship of pneumatic structures with biology is outlined.展开更多
The pneumatic pressure control systems have been used in some fields. However, the researches on pneumatic pressure control mainly focus on constant pressure regulation. Poor dynamic characteristics and strong nonline...The pneumatic pressure control systems have been used in some fields. However, the researches on pneumatic pressure control mainly focus on constant pressure regulation. Poor dynamic characteristics and strong nonlinearity of such systems limit its application in the field of pressure tracking control. In order to meet the demand of generating dynamic pressure signal in the application of the hardware-in-the-loop simulation of aerospace engineering, a positive and negative pneumatic pressure servo system is provided to implement dynamic adjustment of sealed chamber pressure. A mathematical model is established with simulation and experiment being implemented afterwards to discuss the characteristics of the system, which shows serious asymmetry in the process of charging and discharging. Based on the analysis of the system dynamics, a fuzzy proportional integral derivative （PID） controller with asymmetric fuzzy compensator is proposed. Different from conventional adjusting mecha- nisms employing the error and change in error of the controlled variable as input parameters, the current cham- ber pressure and charging or discharging state are chosen as inputs of the compensator, which improves adaptability. To verify the effectiveness and performance of the pro- posed controller, the comparison experiments tracking sinusoidal and square wave commands are conducted. Experimental results show that the proposed controller can obtain better dynamic performance and relatively consis- tent control performance across the scope of work （2-140 kPa）. The research proposes a fuzzy control method to overcome asymmetry and enhance adaptability for the positive and negative pneumatic pressure servo system.展开更多
BACKGROUND:To investigate the clinical effectiveness of a pneumatic compression device(PCD)combined with low-molecular-weight heparin(LMWH)for the prevention and treatment of deep vein thrombosis(DVT)in trauma patient...BACKGROUND:To investigate the clinical effectiveness of a pneumatic compression device(PCD)combined with low-molecular-weight heparin(LMWH)for the prevention and treatment of deep vein thrombosis(DVT)in trauma patients.METHODS:This study retrospectively analyzed 286 patients with mild craniocerebral injury and clavicular fractures admitted to our department from January 2016 to February 2020.Patients treated with only LMWH served as the control group,and patients treated with a PCD combined with LMWH as the observation group.The incidence of DVT,postoperative changes in the visual analogue scale(VAS)score,and coagulation function were observed and compared between the two groups.Excluding the influence of other single factors,binary logistic regression analysis was used to evaluate the use of a PCD in the patient’s postoperative coagulation function.RESULTS:After excluding 34 patients who did not meet the inclusion criteria,252 patients were were included.The incidence of DVT in the observation group was significantly lower than that in the control group(5.6%vs.15.1%,χ^(2)=4.605,P<0.05).The postoperative VAS scores of the two groups were lower than those before surgery(P<0.05).The coagulation function of the observation group was significantly higher than that of the control group,with a better combined anticoagulant effect(P<0.05).There were no significant differences between the two groups in preoperative or postoperative Glasgow Coma Scale scores,intraoperative blood loss,postoperative infection rate,or length of hospital stay(P>0.05).According to logistic regression analysis,the postoperative risk of DVT in patients who received LMWH alone was 1.764 times that of patients who received LMWH+PCD(P<0.05).The area under the receiver operating characteristic(AUROC)curve of partial thromboplastin time(APTT)and platelet(PLT)were greater than 0.5,indicating that they were the influence indicators of adding PCD to prevent DVT.Excluding the influence of other variables,LMWH+PCD effectively improved the coagulation function of patients.CONCLUSIONS:Compared with LMWH alone,LMWH+PCD could improve blood rheology and coagulation function in patients with traumatic brain injury and clavicular fracture,reduce the incidence of DVT,shorten the length of hospital stay,and improve the clinical effectiveness of treatment.展开更多
Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,espe...Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,especially in the biological fermentation and energy chemical industry,due to their low shear stress,good mixing,perfect mass-/heat-transfer properties,and relatively low costs.To further improve the performance of slurry reactors(i.e.,mixing and mass/heat transfer)and to satisfy industrial require-ments(e.g.,temperature control,reduction of back-mixing,and product separation),the process intensi-fication of slurry reactors is essential.This article starts by reviewing the latest advancements in the intensification of mixing and mass/heat transfer in these two types of reactors.It then summarizes process-intensification methods for mixing and separation that allow continuous production in these slurry reactors.Process-intensification technology that integrates directional flow in an ALR with simple solid-liquid separation in a hydrocyclone is recommended for its high efficiency and low costs.This arti-cle also systematically addresses vital considerations and challenges,including flow regime discrimina-tion,gas spargers,solid particle effects,and other concerns in slurry reactors.It introduces the progress of numerical simulation using computational fluid dynamics(CFD)for the rational design of slurry reactors and discusses difficulties in modeling.Finally,it presents conclusions and perspectives on the design of industrial slurry reactors.展开更多
Pseudoachalasia is a difficult condition for the clinician to differentiate from idiopathic achalasia even by manometry, radiological studies or endoscopy. Its etiology is usually associated with tumors. In most cases...Pseudoachalasia is a difficult condition for the clinician to differentiate from idiopathic achalasia even by manometry, radiological studies or endoscopy. Its etiology is usually associated with tumors. In most cases, the diagnosis is made after surgical explorations. The proposed pathogenesis of the disease is considered as mechanical obstruction of the distal esophagus or infiltration of the malignancy that affects the inhibitory neurons of the meyenteric plexus in the majority of cases. Surgery has been reported as a cause of pseudoachalasia. We report a 70-year-old man who suffered from deglutination disorder caused by pseudo-achalasia after truncal vagotomy. The patient was symptom-free after a nine-year follow-up and complete recovery of esophageal motility status from pseudoachalasia after pneumatic dilations. We also reviewed the literature of pseudoachalasia.展开更多
A novel miniature pressure regulator is fabricated and studied. The regulator can easily be integrated into portable mechatronics or miniature robotic applications because of its lightweight and compact size. An espec...A novel miniature pressure regulator is fabricated and studied. The regulator can easily be integrated into portable mechatronics or miniature robotic applications because of its lightweight and compact size. An especial poppet is designed to minimize its size and to withstand high-pressure. The pressure regulator is designed for a hopping robot which is powered by a combustion system. The hopping robot has great moving capacities such as jumping over big obstacles, wails and dit- ches. The regulator helps the hopping robot to decrease size and weight, and to sustain high pres- sure of oxygen and fuel tank. It will maintain constant output pressure to obtain suitable proportion of oxygen and fuel in the combustion cylinder. Dynamic simulation of the miniature pneumatic pres- sure regulator is performed. Experiments on prototype of miniature pneumatic pressure regulator are also carried out to validate the performance and satisfied performance is obtained.展开更多
The article considers the movement of a mixture of air and raw cotton through a pipeline with a variable cross-section as a multi-speed heterogeneous medium. The regularities of the movement of components inside the p...The article considers the movement of a mixture of air and raw cotton through a pipeline with a variable cross-section as a multi-speed heterogeneous medium. The regularities of the movement of components inside the pipeline, the equation of change in the porosity of cotton, air pressure and component velocities in time and along the transportation line are obtained. It was found that in the initial 20 - 25 m part of the pneumatic transport pipe there is a sharp decrease in pressure and air flow velocity, while the speed of cotton increases rapidly due to which there is a strong deformation of cotton stretching under the influence of aerodynamic force, which occurs due to the difference in the velocities of the components of the mixture, as a result of which the cotton loosens, and its porosity increases intensively.展开更多
Prognosis is a key technology to improve reliability,safety and maintainability of products,a lot of researchers have been devoted to this technology.But to improve the predict accuracy of remaining life of products h...Prognosis is a key technology to improve reliability,safety and maintainability of products,a lot of researchers have been devoted to this technology.But to improve the predict accuracy of remaining life of products has been difficult.To predict the lifetime specification of pneumatic cylinders with high reliability and long lifetime and small specimen,this paper put forward the prognosis algorithm based on the path classification and estimation（PACE） model.PACE model is based entirely on failure data instead of failure threshold.Pneumatic cylinders normally characterize with failure mechanism wear and tear.Since the minimum working pressure increases with the number of working cycles,the minimum working pressure is chosen as degradation signal.PACE model is fundamentally composed of two operations：path classification and remaining useful life（RUL） estimation.Path classification is to classify a current degradation path as belonging to one or more of previously collected exemplary degradation paths.RUL estimation is to use the resulting memberships to estimate the remaining useful life.In order for verification and validation of PACE prognostic method,six pneumatic cylinders are tested.The test data is analyzed by PACE prognostics.It is found that the PACE based prognosis method has higher prediction accuracy and smaller variance and PACE model is significantly outperform population based prognostics especially for small specimen condition.PACE model based method solved the problem of prediction accuracy for small specimen pneumatic cylinders＇ prognosis.展开更多
The structure and working principle of a self-deigned high pressure electronic pneumatic pressure reducing valve (EPPRV) with slide pilot are introduced.The resistance value formulas and the relationship between the r...The structure and working principle of a self-deigned high pressure electronic pneumatic pressure reducing valve (EPPRV) with slide pilot are introduced.The resistance value formulas and the relationship between the resistance and pressure of three typical pneumatic resistances are obtained.Then,the method of static characteristics analysis only considering pneumatic resistances is proposed,the resistance network from gas supply to load is built up,and the mathematical model is derived from the flow rate formulas and flow conservation equations,with the compressibility of high pressure gas and temperature drop during the expansion considered in the model.Finally,the pilot spool displacement of 1.5 mm at an output pressure of 15MPa and the enlarging operating stroke of the pilot spool are taken as optimization targets,and the optimization is carried out based on genetic algorithm and the model mentioned above.The results show that the static characteristics of the EPPRV are significantly improved.The idea of static characteristics analysis and optimization based on pneumatic resistance network is valuable for the design of pneumatic components or system.展开更多
基金Supported by Shenzhen Municipal Natural Science Foundation of China(Grant No.U2013212)National Key R&D Program of China(Grant No.2020YFB1313001)National Natural Science Foundation of China(Grant No.U23 A20328).
文摘Continuum robots have been a hot topic in recent years due to their intrinsic features of agility,flexibility,and safety.To successfully deploy continuum robots in practical applications,further enhancements in variable stiffness,decoupled motion,and embedded sensing are highly desirable.Since continuum robots are usually composed of multiple joints assembled in series,their mechanical properties and performance will certainly rely on the connected joints.This paper proposes a motion-decoupled variable stiffness-decoupled pneumatic rigid-flexible hybrid joint(RFHJ),which is modular designed and integrated with a rigid hinge,a stiffness-tuning module,and soft actuators.The soft pneumatic muscle actuators are pre-stretched during assembly,ensuring the stable initial state of RFHJ.A novel musculature-mounting configuration is also presented,which enables RFHJs to achieve independent motions in two orthogonal planes.Furthermore,the variable stiffness module is embedded in the RFHJ’s structure to offer real-time and independent stiffness tunability across multiple scales in two perpendicular directions.The proposed RFHJ makes most of the advantages of soft continuum robots and conventional rigid serial robots by introducing a hybrid structure to provide both safe human-robot interaction(HRI),accurate control and reliable stiffness variation,presenting promising potentials for robotic systems,which have been theoretically proved and experimentally verified on the physical prototype.The experimental results also indicate that the developed RFHJ can work with variable stiffness ranging in[1.2,49.9]N·m/rad.A variable stiffness rigid-flexible hybrid continuum arm(RFHA)is designed with three RFHJs in series.Primary tests on the developed RFHA prototype demonstrate that it has the characteristics of decoupled driving,bidirectional stiffness tunability and self-stability.
基金The National Basic Research Program of China(973 Program) (No2004CB217702-01)the Foundation of ExcellentPhDThesis of Southeast University
文摘Experiments of dense-phase pneumatic conveying of pulverized coal using nitrogen are carded out in an experimental test facility with the conveying pressure up to 4. 0 MPa and the gas-solid ratio up to 450 kg/m^3. The influences of different conveying differential pressures, coal moisture contents, gas volume flow rates and superficial velocities on the solid-gas ratios are investigated. Shannon entropy analysis of pressure fluctuation time series is developed to reveal the flow characteristics. Through investigation of the distribution of the Shannon entropy under different conditions, the flow stability and the evolutional tendency of the Shannon entropy in different regimes and regime transition processes are discovered, and the relationship between the Shannon entropy and the flow regimes is also established. The results indicate that the solid-gas ratio and the Shannon entropy rise with the increase in conveying differential pressure. The solid-gas ratio and the Shannon entropy reveal preferable regularity with gas volume flow rates. The Shannon entropy is different for different flow regimes, and can be used to identify the flow regimes. Both mass flow rate and the Shannon entropy decrease with the increase in moisture contents. The Shannon entropy analysis is a feasible approach for researching the characteristics of flow regimes, flow stability and flow regime transitions in dense-phase pneumatic conveying under high pressure.
基金supported by the National Natural Science Foundation of China (No. 50475056)
文摘The process of DTH（down-the-hole） hammer drilling has been characterized as a very complex phenomenon due to its high nonlinearity,large deformation and damage behaviors.Taking brittle materials（concrete,granite and sandstone） as impact specimens,the explicit time integration nonlinear finite element code LS-DYNA was employed to analyze the impact process and the penetration boundary conditions of DTH hammer percussive drilling system.Compared with previous studies,the present model contains several new features.One is that the 3D effects of DTH hammer drilling system were considered.Another important feature is that it took the coupling effects of brittle materials into account to the bit-specimen boundary of the drilling system.This distinguishes it from the traditional approaches to the bit-rock intersection,in which nonlinear spring models are usually imposed.The impact forces,bit insert penetrations and force-penetration curves of concrete,granite and sandstone under DTH hammer impact have been recorded;the formation of craters and fractures has been also investigated.The impact loads of piston-bit interaction appear to be relatively sensitive to piston impact velocity.The impact between piston-bit interaction occurs at two times larger forces,whereas the duration of the first impact doesn＇t change with respect to the piston velocity.The material properties of impact specimen do not affect the first impact process between the piston and bit.However,the period between the two impacts and the magnitudes of the second impact forces greatly depend on the specimen material properties.It is found that the penetration depth of specimen is dependent on the impact force magnitude and the macro-mechanical properties of the brittle materials.
基金This project is supported by National Natural Science Foundation of China (No.50122115)the National 10th Five Years Plan Special Research Programs of China(No.2003BA408B14).
文摘A mathematic model is built up to analyze the influences of a pilot valve'sleakage on the performances of pneumatic pressure proportional valve, and the performances aresimulated by using MATLAB. The results indicate that using slide pilot valve in the valve system isfeasible, but the leakage's influences can not be neglected, especially it may induce instability ina low output pressure situation. A pilot valve using too large throttle window will cause the valveoscillate. To improve the working condition of pilot valve, a method adopting different widths oftwo throttle window is proposed. According to our simulation, this method balances the pressure dropbetween the two stage throttle ports, and reduces the influences of pilot valve's leakage.
基金supported by National Natural Science Foundation of China (Grant No. 50575202)
文摘The high pressure pneumatic system has been applied to special industries. It may cause errors when we analyze high pressure pneumatics under ideal gas assumption. However, the real gas effect on the performances of high pressure pneumatics is seldom investigated. In this paper, the real gas effects on air enthalpy and internal energy are estimated firstly to study the real gas effect on the energy conversion. Under ideal gas assumption, enthalpy and internal energy are solely related to air temperature. The estimation result indicates that the pressure enthalpy and pressure internal energy of real pneumatic air obviously decrease the values of enthalpy and internal energy for high pressure pneumatics, and the values of pressure enthalpy and pressure internal energy are close. Based on the relationship among pressure, enthalpy and internal energy, the real gas effects on charging and discharging processes of high pressure pneumatics are estimated, which indicates that the real gas effect accelerates the temperature and pressure decreasing rates during discharging process, and decelerates their increasing rates during charging process. According to the above analysis, and for the inconvenience in building the simulation model for real gas and the difficulty of measuring the detail thermal capacities of pneumatics, a method to compensate the real gas effect under ideal gas assumption is proposed by modulating the thermal capacity of the pneumatic container in simulation. The experiments of switching expansion reduction （SER） for high pressure pneumatics are used to verify this compensating method. SER includes the discharging process of supply tanks and the charging process of expansion tank. The simulated and experimental results of SER are highly consistent. The proposed compensation method provides a convenient way to obtain more realistic simulation results for high pressure pneumatics.
文摘Structural stabilization by a pressurized fluid is very common in nature, however hardly found in technology. Car tires, hot air balloons, airships and airhouses are among the few technical exceptions, which are stabilized by a compressed medium, typically air. Restricted by simple geometries and a very limited load bearing capacity these pneumatic structures could succeed only in very specialized applications. Nevertheless, prospective concepts ag has systematically investigated pneumatic structures during the last few years. As a major result, it was demonstrated that almost any shape can be made with pneumatic structures and that astonishing structures such as the pneumatic airplane Stingray can be realized even with low air pressure. On top of that, Airlight Ltd. in close collaboration with prospective concepts ag has recently developed the fundamental new structural concept Tensairity. The synergetic combination of an inflated structure with conventional structural elements such as cables and struts yields pneumatic light-weight structures with the load bearing capacity of steel girders. Thus, complex forms and high strength open up many new opportunities for pressure induced stability in technology. An overview of these recent developments is presented and the close relationship of pneumatic structures with biology is outlined.
基金Supported by National Natural Science Foundation of China(Grant No.51575199)
文摘The pneumatic pressure control systems have been used in some fields. However, the researches on pneumatic pressure control mainly focus on constant pressure regulation. Poor dynamic characteristics and strong nonlinearity of such systems limit its application in the field of pressure tracking control. In order to meet the demand of generating dynamic pressure signal in the application of the hardware-in-the-loop simulation of aerospace engineering, a positive and negative pneumatic pressure servo system is provided to implement dynamic adjustment of sealed chamber pressure. A mathematical model is established with simulation and experiment being implemented afterwards to discuss the characteristics of the system, which shows serious asymmetry in the process of charging and discharging. Based on the analysis of the system dynamics, a fuzzy proportional integral derivative （PID） controller with asymmetric fuzzy compensator is proposed. Different from conventional adjusting mecha- nisms employing the error and change in error of the controlled variable as input parameters, the current cham- ber pressure and charging or discharging state are chosen as inputs of the compensator, which improves adaptability. To verify the effectiveness and performance of the pro- posed controller, the comparison experiments tracking sinusoidal and square wave commands are conducted. Experimental results show that the proposed controller can obtain better dynamic performance and relatively consis- tent control performance across the scope of work （2-140 kPa）. The research proposes a fuzzy control method to overcome asymmetry and enhance adaptability for the positive and negative pneumatic pressure servo system.
文摘BACKGROUND:To investigate the clinical effectiveness of a pneumatic compression device(PCD)combined with low-molecular-weight heparin(LMWH)for the prevention and treatment of deep vein thrombosis(DVT)in trauma patients.METHODS:This study retrospectively analyzed 286 patients with mild craniocerebral injury and clavicular fractures admitted to our department from January 2016 to February 2020.Patients treated with only LMWH served as the control group,and patients treated with a PCD combined with LMWH as the observation group.The incidence of DVT,postoperative changes in the visual analogue scale(VAS)score,and coagulation function were observed and compared between the two groups.Excluding the influence of other single factors,binary logistic regression analysis was used to evaluate the use of a PCD in the patient’s postoperative coagulation function.RESULTS:After excluding 34 patients who did not meet the inclusion criteria,252 patients were were included.The incidence of DVT in the observation group was significantly lower than that in the control group(5.6%vs.15.1%,χ^(2)=4.605,P<0.05).The postoperative VAS scores of the two groups were lower than those before surgery(P<0.05).The coagulation function of the observation group was significantly higher than that of the control group,with a better combined anticoagulant effect(P<0.05).There were no significant differences between the two groups in preoperative or postoperative Glasgow Coma Scale scores,intraoperative blood loss,postoperative infection rate,or length of hospital stay(P>0.05).According to logistic regression analysis,the postoperative risk of DVT in patients who received LMWH alone was 1.764 times that of patients who received LMWH+PCD(P<0.05).The area under the receiver operating characteristic(AUROC)curve of partial thromboplastin time(APTT)and platelet(PLT)were greater than 0.5,indicating that they were the influence indicators of adding PCD to prevent DVT.Excluding the influence of other variables,LMWH+PCD effectively improved the coagulation function of patients.CONCLUSIONS:Compared with LMWH alone,LMWH+PCD could improve blood rheology and coagulation function in patients with traumatic brain injury and clavicular fracture,reduce the incidence of DVT,shorten the length of hospital stay,and improve the clinical effectiveness of treatment.
基金supported by the National Key Research and Development Program of China(2016YFB0301701)the National Natural Science Foundation of China(21808234,21878318,and 21938009)+3 种基金the DNL Cooperation Fund,Chinese Academy of Sciences(CAS)(DNL201902)the Strategic Priority Research Program of the CAS(XDA21060400)the QIBEBT and Dalian National Laboratory for Clean Energy of the CAS(QIBEBT ZZBS201803 and QIBEBT I201907)the CAS Key Technology Talent Program.
文摘Pneumatically agitated slurry reactors,including bubble column reactors and airlift loop reactors(ALRs),are important gas-liquid-solid multiphase reactors.These reactors have been widely applied in many processes,especially in the biological fermentation and energy chemical industry,due to their low shear stress,good mixing,perfect mass-/heat-transfer properties,and relatively low costs.To further improve the performance of slurry reactors(i.e.,mixing and mass/heat transfer)and to satisfy industrial require-ments(e.g.,temperature control,reduction of back-mixing,and product separation),the process intensi-fication of slurry reactors is essential.This article starts by reviewing the latest advancements in the intensification of mixing and mass/heat transfer in these two types of reactors.It then summarizes process-intensification methods for mixing and separation that allow continuous production in these slurry reactors.Process-intensification technology that integrates directional flow in an ALR with simple solid-liquid separation in a hydrocyclone is recommended for its high efficiency and low costs.This arti-cle also systematically addresses vital considerations and challenges,including flow regime discrimina-tion,gas spargers,solid particle effects,and other concerns in slurry reactors.It introduces the progress of numerical simulation using computational fluid dynamics(CFD)for the rational design of slurry reactors and discusses difficulties in modeling.Finally,it presents conclusions and perspectives on the design of industrial slurry reactors.
文摘Pseudoachalasia is a difficult condition for the clinician to differentiate from idiopathic achalasia even by manometry, radiological studies or endoscopy. Its etiology is usually associated with tumors. In most cases, the diagnosis is made after surgical explorations. The proposed pathogenesis of the disease is considered as mechanical obstruction of the distal esophagus or infiltration of the malignancy that affects the inhibitory neurons of the meyenteric plexus in the majority of cases. Surgery has been reported as a cause of pseudoachalasia. We report a 70-year-old man who suffered from deglutination disorder caused by pseudo-achalasia after truncal vagotomy. The patient was symptom-free after a nine-year follow-up and complete recovery of esophageal motility status from pseudoachalasia after pneumatic dilations. We also reviewed the literature of pseudoachalasia.
文摘A novel miniature pressure regulator is fabricated and studied. The regulator can easily be integrated into portable mechatronics or miniature robotic applications because of its lightweight and compact size. An especial poppet is designed to minimize its size and to withstand high-pressure. The pressure regulator is designed for a hopping robot which is powered by a combustion system. The hopping robot has great moving capacities such as jumping over big obstacles, wails and dit- ches. The regulator helps the hopping robot to decrease size and weight, and to sustain high pres- sure of oxygen and fuel tank. It will maintain constant output pressure to obtain suitable proportion of oxygen and fuel in the combustion cylinder. Dynamic simulation of the miniature pneumatic pres- sure regulator is performed. Experiments on prototype of miniature pneumatic pressure regulator are also carried out to validate the performance and satisfied performance is obtained.
文摘The article considers the movement of a mixture of air and raw cotton through a pipeline with a variable cross-section as a multi-speed heterogeneous medium. The regularities of the movement of components inside the pipeline, the equation of change in the porosity of cotton, air pressure and component velocities in time and along the transportation line are obtained. It was found that in the initial 20 - 25 m part of the pneumatic transport pipe there is a sharp decrease in pressure and air flow velocity, while the speed of cotton increases rapidly due to which there is a strong deformation of cotton stretching under the influence of aerodynamic force, which occurs due to the difference in the velocities of the components of the mixture, as a result of which the cotton loosens, and its porosity increases intensively.
基金supported by the Laboratory of Aviation Safety Technical Analysis and Appraisal of China Academy of Civil Aviation Science and Technology(Grant No. 2009-02)
文摘Prognosis is a key technology to improve reliability,safety and maintainability of products,a lot of researchers have been devoted to this technology.But to improve the predict accuracy of remaining life of products has been difficult.To predict the lifetime specification of pneumatic cylinders with high reliability and long lifetime and small specimen,this paper put forward the prognosis algorithm based on the path classification and estimation（PACE） model.PACE model is based entirely on failure data instead of failure threshold.Pneumatic cylinders normally characterize with failure mechanism wear and tear.Since the minimum working pressure increases with the number of working cycles,the minimum working pressure is chosen as degradation signal.PACE model is fundamentally composed of two operations：path classification and remaining useful life（RUL） estimation.Path classification is to classify a current degradation path as belonging to one or more of previously collected exemplary degradation paths.RUL estimation is to use the resulting memberships to estimate the remaining useful life.In order for verification and validation of PACE prognostic method,six pneumatic cylinders are tested.The test data is analyzed by PACE prognostics.It is found that the PACE based prognosis method has higher prediction accuracy and smaller variance and PACE model is significantly outperform population based prognostics especially for small specimen condition.PACE model based method solved the problem of prediction accuracy for small specimen pneumatic cylinders＇ prognosis.
基金Project(50575202) supported by the National Natural Science Foundation of China
文摘The structure and working principle of a self-deigned high pressure electronic pneumatic pressure reducing valve (EPPRV) with slide pilot are introduced.The resistance value formulas and the relationship between the resistance and pressure of three typical pneumatic resistances are obtained.Then,the method of static characteristics analysis only considering pneumatic resistances is proposed,the resistance network from gas supply to load is built up,and the mathematical model is derived from the flow rate formulas and flow conservation equations,with the compressibility of high pressure gas and temperature drop during the expansion considered in the model.Finally,the pilot spool displacement of 1.5 mm at an output pressure of 15MPa and the enlarging operating stroke of the pilot spool are taken as optimization targets,and the optimization is carried out based on genetic algorithm and the model mentioned above.The results show that the static characteristics of the EPPRV are significantly improved.The idea of static characteristics analysis and optimization based on pneumatic resistance network is valuable for the design of pneumatic components or system.
