The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase s...The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase step when outlet valve or inlet valve opens, but is more gently in other time; The volume efficiency is influenced by the output pressure slightly, and decreases as the working rotational speed increases; When the inherent frequency of the valves is integer multiple of the working frequency, the volume efficiency of system will decrease evidently.展开更多
In modem four-stroke engine technology,variable valve timing and lift control offers potential benefits for making a high-performance engine.A novel electro-hydraulic fully variable valve train for four-stroke automot...In modem four-stroke engine technology,variable valve timing and lift control offers potential benefits for making a high-performance engine.A novel electro-hydraulic fully variable valve train for four-stroke automotive engines is introduced.The construction of the nonlinear mathematic model of the valve train system and its dynamic analysis are also presented.Experimental and simulation results show that the novel electro-hydraulic valve train can achieve fully variable valve timing and lift control.Consequently the engine performance on different loads and speeds will be significantly increased.The technology also permits the elimination of the traditional throttle valve in the gasoline engines and increases engine design flexibility.展开更多
Electro-hydraulic servo valve is a typical complicated multi-domain system constituted by mechanical, electric, hydraulic and magnetic components, which is widely used in electro-hydraulic servo systems such as constr...Electro-hydraulic servo valve is a typical complicated multi-domain system constituted by mechanical, electric, hydraulic and magnetic components, which is widely used in electro-hydraulic servo systems such as construction machinery, heavy equipment, weapon and so forth. The traditional method of modeling and simulation of servo valve is based on block diagram or signal flow, which cannot describe the servo valve system from components level nor be used in modeling and simulation of overall servo systems. In the procedure of traditional method, computational causality must be involved in modeling of servo valve, which is inconvenient to execute modification on components or parameters. Modelica is an object-oriented modeling language which is suited for large, complex, heterogeneous and multi-domain systems. The key features of Modelica are multi-domain, object-oriented and non-causal, which are suitable for modeling of servo valve and make the model readable, reusable, and easy to modify. The simulation results show similar curves with traditional method. This new servo valve modeling and simulation method can provide the engineers a more efficient way to design and optimize a servo valve and an overall servo system.展开更多
BACKGROUND The management of severe symptomatic aortic stenosis has been revolutionized by transcatheter aortic valve replacement(TAVR),offering a minimally invasive alternative to surgical aortic valve replacement(SA...BACKGROUND The management of severe symptomatic aortic stenosis has been revolutionized by transcatheter aortic valve replacement(TAVR),offering a minimally invasive alternative to surgical aortic valve replacement(SAVR).However,the compara-tive safety and efficacy of these interventions remain subjects of ongoing investigation.AIM To compare the clinical outcomes and safety of TAVR vs SAVR in patients with severe symptomatic aortic stenosis.METHODS A systematic review and meta-analysis were conducted according to PRISMA guidelines.Randomized controlled trials(RCTs)comparing TAVR and SAVR were identified from databases including PubMed,Scopus,and Web of Science up to May 31,2024.Data were extracted on clinical outcomes,including mortality,procedural compli-cations,and post-procedure adverse events.Risk ratios(RRs)with 95%CIs were calculated using a random-effects model.RESULTS A total of 10 RCTs were included.TAVR demonstrated a significantly lower risk of acute kidney injury(RR:0.33;95%CI:0.25–0.44),major bleeding(RR:0.37;95%CI:0.30–0.46),and new-onset atrial fibrillation(RR:0.44;95%CI:0.34–0.57)compared to SAVR.However,TAVR was associated with higher risks of new permanent pacemaker implantation(RR:3.49;95%CI:2.77–4.39),major vascular complications(RR:2.47;95%CI:1.91–3.21),and paraval-vular leaks(RR:4.15;95%CI:3.14–5.48).Mortality at 30 days was comparable(RR:0.95;95%CI:0.78–1.15),but long-term mortality was slightly higher with TAVR in some analyses(RR:1.23;95%CI:1.01–1.49).Rates of stroke(RR:0.97;95%CI:0.81–1.17)and myocardial infarction(RR:0.91;95%CI:0.67–1.24)were similar between the groups.CONCLUSION TAVR offers a less invasive option with significant benefits in reducing acute kidney injury,major bleeding,and new-onset atrial fibrillation,making it particularly advantageous for high-risk surgical candidates.However,higher risks of permanent pacemaker implantation,vascular complications,and paravalvular leaks highlight the need for individualized patient selection and shared decision-making to optimize outcomes.展开更多
Thermosyphon loops are widely used in cooling systems.However,such distributed thermal management systems lack the ability to actively control the coolant flow in each parallel branch.An effective method for addressin...Thermosyphon loops are widely used in cooling systems.However,such distributed thermal management systems lack the ability to actively control the coolant flow in each parallel branch.An effective method for addressing this is to control the coolant flow in each branch using a solenoid valve.However,the existing valves do not satisfy the requirements for fast switching,low power,low pressure loss,and miniaturization.Therefore,in this study,a low-power-consumption miniature solenoid valve(LMSV)is proposed for use in thermal management systems.The key novelty is that the valve is designed with a suitably sized permanent magnet(PM)to allow the spool to continue working without consuming electrical energy.To achieve low flow resistance,a straight-through design is employed in the valve with the electromagnetic actuator located inside the valve shell.Multiphysical coupling analysis is performed to investigate its performance.The influence of the PM dimensions and current on the magnetic field distribution and electromagnetic force is studied.The effects of these key parameters on the flow field and pressure loss are also analyzed.Because the LMSV is sensitive to temperature,the switching time and energy consumption at different working temperatures are investigated.Experimental test platforms are constructed.A valve switching time of as short as 3 ms,pressure loss of 200 Pa at 0.92 L/min,and energy consumption of approximately 1.55 J during the opening and closing processes are achieved.The novel solenoid valve proposed in this study offers fast switching,low power consumption,low pressure loss,and miniaturization to meet the requirements of thermal management systems.展开更多
Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibra...Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibration.An active damping device(ADD)is used to the vibration of the pump valve pipeline system to apply the control force,to achieve the active control of the pipeline vibration.A pump-valve pipeline vibration test bench was built to compare the control effect of active damping device on pipeline vibration under different pump valve working conditions,and the results show that applying ADD control could effectively suppress the vibration of the pump valve pipeline and enhance the stability of the equipment during operation.At different pump operating rotation frequencies,the vibration amplitude of the pump valve pipeline in working frequency and its multiple frequencies are also effectively suppressed,with the maximum amplitude reduction of more than 60%.For the valve vibration caused by different operating openings,the vibration of the highest reduction of 68%,and the centrifugal pump drive shaft vi-bration reduced by up to 73%,which provides a new idea for vibration control of pump valve pipeline system.展开更多
Hydraulic control valves, positioned at the terminus of pipe networks, are critical for regulatingflow and pressure, thereby ensuring the operational safety and efficiency of pipeline systems. However,conventional val...Hydraulic control valves, positioned at the terminus of pipe networks, are critical for regulatingflow and pressure, thereby ensuring the operational safety and efficiency of pipeline systems. However,conventional valve designs often struggle to maintain effective regulation across a wide range of systempressures. To address this limitation, this study introduces a novel Pilot hydraulic valves specificallyengineered for enhanced dynamic performance and precise regulation under variable pressure conditions.Building upon prior experimental findings, the proposed design integrates a high-fidelity simulationframework and a surrogate model-based optimization strategy. The study begins by formulating acomprehensive mathematical model of the pipeline system using electro-hydraulic simulation techniques,capturing the dynamic behavior of both the pilot valve and the broader urban water distribution network. Acoupled simulation platform is then developed, leveraging both one-dimensional (1D) and three-dimensional(3D) software tools to accurately analyze the valve’s transient response and operational characteristics. Toachieve optimal valve performance, a multi-objective optimization approach is proposed. This approachemploys a Levy-based Improved Tuna-InspiredWake-Up Optimization Algorithm (L-TIWOA) to refine aBackpropagation (BP) neural network, thereby constructing a highly accurate surrogate model. Compared tothe conventional BP neural network, the improved model demonstrates significantly reduced mean absoluteerror (MAE) and mean squared error (MSE), underscoring its superior predictive capability. The surrogatemodel serves as the objective function within an Improved Multi-Objective Mother Lode OptimizationAlgorithm (IMOMLOA), which is then used to fine-tune the key design parameters of the control valve.Validation through experimental testing reveals that the optimized valve achieves a maximum flow deviationof just 1.11 t/h, corresponding to a control accuracy of 3.7%, at a target flow rate of 30 t/h. Moreover,substantial improvements in dynamic response are observed, confirming the effectiveness of the proposeddesign and optimization strategy.展开更多
Published proof test coverage(PTC)estimates for emergency shutdown valves(ESDVs)show only moderate agreement and are predominantly opinion-based.A Failure Modes,Effects,and Diagnostics Analysis(FMEDA)was undertaken us...Published proof test coverage(PTC)estimates for emergency shutdown valves(ESDVs)show only moderate agreement and are predominantly opinion-based.A Failure Modes,Effects,and Diagnostics Analysis(FMEDA)was undertaken using component failure rate data to predict PTC for a full stroke test and a partial stroke test.Given the subjective and uncertain aspects of the FMEDA approach,specifically the selection of component failure rates and the determination of the probability of detecting failure modes,a Fuzzy Inference System(FIS)was proposed to manage the data,addressing the inherent uncertainties.Fuzzy inference systems have been used previously for various FMEA type assessments,but this is the first time an FIS has been employed for use with FMEDA.ESDV PTC values were generated from both the standard FMEDA and the fuzzy-FMEDA approaches using data provided by FMEDA experts.This work demonstrates that fuzzy inference systems can address the subjectivity inherent in FMEDA data,enabling reliable estimates of ESDV proof test coverage for both full and partial stroke tests.This facilitates optimized maintenance planning while ensuring safety is not compromised.展开更多
A method of combining the valve system program with the engine cycle modeling software to form a full set of working process modeling is submitted,not only considering the system as an independent part,but also as a p...A method of combining the valve system program with the engine cycle modeling software to form a full set of working process modeling is submitted,not only considering the system as an independent part,but also as a part of working process to evaluate comprehensively and indicate directly if the design is good or not.The designers can optimize the design by changing the engine structure,operation and the basic parameters of the cam on condition that the sysem should be stable so as to save large amounts of time and cost.Practical examples show that such a software package is an effective tool in optimizing the valve systems and performance of the machine.展开更多
The theory of multibody system dynamics is used to simulate valve trains' kinematics and dynamics characteristics, and the methods of establishing and analyzing the multibody system dynamics model for valve trains...The theory of multibody system dynamics is used to simulate valve trains' kinematics and dynamics characteristics, and the methods of establishing and analyzing the multibody system dynamics model for valve trains are discussed. Since most of the flexible bodies of a valve train are slender parts, the finite segment method is used to build their models. Other parts such as cams, valve heads etc., are built as rigid bodies. After applying the constraints, forces and motions, the establishing of the whole system is accomplished, and the Lagrange's multiplier method can be used to obtain its dynamics constitutive equations. As an example, a valve trains multibody system model of 4100QB engine made by the Yunnan Internal Combustion Engine Limited Liability Company is established, and the analysis results obtained show that its working performance is generally good except that the air pass ability and the lubrication effect of the cam and the tappet have to be improved.展开更多
Computational Fluid Dynamics (CFD) simulations of cavitating flow through water hydraulic poppet valves were performed using advanced RNG k-epsilon turbulence model. The flow was turbulent, incompressible and unsteady...Computational Fluid Dynamics (CFD) simulations of cavitating flow through water hydraulic poppet valves were performed using advanced RNG k-epsilon turbulence model. The flow was turbulent, incompressible and unsteady, for Reynolds numbers greater than 43 000. The working fluid was water, and the structure of the valve was simplified as a two dimensional axisymmetric geometrical model. Flow field visualization was numerically achieved. The effects of inlet velocity, outlet pressure, opening size as well as poppet angle on cavitation intensity in the poppet valve were numerically investigated. Experimental flow visualization was conducted to capture cavitation images near the orifice in the poppet valve with 30° poppet angle using high speed video camera. The binary cavitating flow field distribution obtained from digital processing of the original cavitation image showed a good agreement with the numerical result.展开更多
Synthesis characteristics of the electro-hydraulic servo valve are key factors to determine eligibility of the hydraulic production.Testing all synthesis characteristics of the electro-hydraulic servo valve after asse...Synthesis characteristics of the electro-hydraulic servo valve are key factors to determine eligibility of the hydraulic production.Testing all synthesis characteristics of the electro-hydraulic servo valve after assembling leads to high repair rate and reject rate,so accurate prediction for the synthesis characteristics in the industrial production is particular important in decreasing the repair rate and the reject rate of the product.However,the research in forecasting synthesis characteristics of the electro-hydraulic servo valve is rare.In this work,a hybrid prediction method was proposed based on rough set(RS)and adaptive neuro-fuzzy inference system(ANFIS)in order to predict synthesis characteristics of electro-hydraulic servo valve.Since the geometric factors affecting the synthesis characteristics of the electro-hydraulic servo valve are from workers'experience,the inputs of the prediction method are uncertain.RS-based attributes reduction was used as the preprocessor,and then the exact geometric factors affecting the synthesis characteristics of the electro-hydraulic servo valve were obtained.On the basis of the exact geometric factors,ANFIS was used to build the final prediction model.A typical electro-hydraulic servo valve production was used to demonstrate the proposed prediction method.The prediction results showed that the proposed prediction method was more applicable than the artificial neural networks(ANN)in predicting the synthesis characteristics of electro-hydraulic servo valve,and the proposed prediction method was a powerful tool to predict synthesis characteristics of the electro-hydraulic servo valve.Moreover,with the use of the advantages of RS and ANFIS,the highly effective forecasting framework in this study can also be applied to other problems involving synthesis characteristics forecasting.展开更多
The simulation model of a valve control hydraulic system with long pipe isestablished in Simulink4.0, and then the step responses of the systems with difference pipeparameters are investigated by simulation. Simulatio...The simulation model of a valve control hydraulic system with long pipe isestablished in Simulink4.0, and then the step responses of the systems with difference pipeparameters are investigated by simulation. Simulation results show that the long pipes will slowdown the step response of system and make it fluctuate periodically. The results of simulationconform to the results of experiment on the whole, which proves the mathematic model is correct.展开更多
Nowadays, a highly integrated valve?controlled cylinder(HIVC) is applied to drive the joints of legged robots. Although the adoption of HIVC has resulted in high?performance robot control, the hydraulic force system s...Nowadays, a highly integrated valve?controlled cylinder(HIVC) is applied to drive the joints of legged robots. Although the adoption of HIVC has resulted in high?performance robot control, the hydraulic force system still has problems, such as strong nonlinearity, and time?varying parameters. This makes HIVC force control very diffcult and complex. How to improve the control performance of the HIVC force control system and find the influence rule of the system parameters on the control performance is very significant. Firstly, the mathematical model of HIVC force control system is established. Then the mathematical expression for parameter sensitivity matrix is obtained by applying matrix sensitivity analysis(PSM). Then, aimed at the sinusoidal response under(three factors and three levels) working conditions, the simulation and the experiment are conducted. While the error between the simulation and experiment can’t be avoided. Therefore, combined with the range analysis, the error in the two performance indexes of sinusoidal response under the whole working condition is analyzed. Besides, the sensitivity variation pattern for each system parameter under the whole working condition is figured out. Then the two sensitivity indexes for the three system parameters, which are supply pressure, proportional gain and initial displacement of piston, are proved experimentally. The proposed method significantly reveals the sensitivity characteristics of HIVC force control system, which can make the contribution to improve the control performance.展开更多
Transcatheter mitral valve replacement(TMVR)has become an alternative to surgical mitral valve replacement for the treatment of patients with severe mitral insufficiency(MI)who are at very high or prohibitive surgical...Transcatheter mitral valve replacement(TMVR)has become an alternative to surgical mitral valve replacement for the treatment of patients with severe mitral insufficiency(MI)who are at very high or prohibitive surgical risk.[1]Because of impaired left ventricular dysfunction and previous cardiac surgery,some aged patients with degenerated bioprosthetic mitral valve and mitral regurgitation were refused to redo surgery.[2]Increasing demand are required for minimally invasive treatment of these patients.Hundreds of patients worldwide have been treated with a transcatheter mitral valve-in-ring or valve-in-valve procedure using transcatheter aortic valve.[3]However,rare case of transcatheter mitral valve-in-valve/ring replacement using transcatheter mitral valve system was reported.Here,we reported a successfully case of transcatheter mitral“valve-in-valve”replacement for the treatment of bioprosthetic mitral valve degeneration and severe regurgitation with domestic Mithos^TM valve.展开更多
Previous studies have confirmed that an active suspension system with high speed ON/OFF solenoid valves could provide the same vibration isolation efficiency as that of system with pressure proportional valve. In this...Previous studies have confirmed that an active suspension system with high speed ON/OFF solenoid valves could provide the same vibration isolation efficiency as that of system with pressure proportional valve. In this study, by using Linear-quadratic optimization technique and Kalman filter method, an optimal regulator controller with a state observer was designed for the proposed system. Simulation and experimental research was conducted on a quarter car model. The simulation analysis of the system frequency characteristic suggested that the peak value of magnitude response curve in the case of system with an optimal controller would be lowered significantly, and the experiment results also showed that an improvement in the vibration isolation effect was obtained in using the designed optimal controller over the sky hook damper controller.展开更多
To study the dynamic behavior of pipeline systems installed with large-mass valves within nuclear power plants during earthquakes,seismic simulation tests are carried out on a pipeline system equipped with a DN80 gate...To study the dynamic behavior of pipeline systems installed with large-mass valves within nuclear power plants during earthquakes,seismic simulation tests are carried out on a pipeline system equipped with a DN80 gate valve,and the FEM updating technique is used to identify the stiffness distribution of the valve.By conducting tests and a numerical analysis,the following conclusions are obtained:After a large-mass valve is installed in the pipeline,the system shows higher sensitivity to intermediate and high frequency components in the earthquake than low frequency components.It is possible for the intermediate frequency components to be amplified by the valve in the horizontal direction,while the pipes tend to amplify the high frequency components in horizontal and vertical directions.Changes in the high-order modes of the system depend on valve stiffness distribution.Since the existence of a valve makes pipeline system damping distribute with an obvious non-proportional feature,when the response spectrum method is used to calculate the response of the pipeline system,it could result in an underestimation of low-damping positions and overestimation of high-damping positions.展开更多
Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its de...Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its design and operation processes all depend on finite element method.However,in engineering practice,there is always deviations between the theoretical and the measured responses due to the inaccurate value of the structural parameters in the model.The structure parameters identification of VPS within NPP is still an unexplored domain to a large extent.In this paper,the initial 2D-finite element model(FEM)for VPS with a DN80 gate valve was updated by utilizing seismic response.The objective function used in the model updating procedure is the vibration control equation error of the VPS.The experimental results show that the updated 2D-FEM can accurately predict the original dynamic characteristic of the VPS.It was also found the Rayleigh damping coefficients corresponding to the VPS vary slightly with the change in seismic excitation amplitude.The research displayed the complete procedure of updating the complex structured initial FEM by utilizing seismic response,and the results show that the parameters can be accurately identified even if the seismic response used for updating merely contained the fundamental frequency information of the structure.展开更多
The natural frequency of the electrohydraulic system in mobile machinery is always very low,which brings difficulties to the controller design.To improve the tracking performance of the hydraulic system,mathematical m...The natural frequency of the electrohydraulic system in mobile machinery is always very low,which brings difficulties to the controller design.To improve the tracking performance of the hydraulic system,mathematical modeling of the electrohydraulic lifting system and the rubber hose was accomplished according to an electrohydraulic lifting test rig built in the laboratory.Then,valve compensation strategy,including spool opening compensation (SOC) and dead zone compensation (DZC),was designed based on the flow-pressure characteristic of a closed-centered proportional valve.Comparative experiments on point-to-point trajectory tracking between a proportional controller with the proposed compensations and a traditional PI controller were conducted.Experiment results show that the maximal absolute values of the tracking error are reduced from 0.039 m to 0.019 m for the slow point-to-point motion trajectory and from 0.085 m to 0.054 m for the fast point-to-point motion trajectory with the proposed compensations.Moreover,tracking error of the proposed controller was analyzed and corresponding suggestions to reduce the tracking error were put forward.展开更多
Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems res...Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.展开更多
基金This project is supported by National Natural Science Foundation of China(No.10342003).
文摘The dynamics differential equations are constructed, and the initial conditions are also given. Simulation shows the following conclusions： The water pressure in cylinder has great instantaneous pulsation and phase step when outlet valve or inlet valve opens, but is more gently in other time; The volume efficiency is influenced by the output pressure slightly, and decreases as the working rotational speed increases; When the inherent frequency of the valves is integer multiple of the working frequency, the volume efficiency of system will decrease evidently.
文摘In modem four-stroke engine technology,variable valve timing and lift control offers potential benefits for making a high-performance engine.A novel electro-hydraulic fully variable valve train for four-stroke automotive engines is introduced.The construction of the nonlinear mathematic model of the valve train system and its dynamic analysis are also presented.Experimental and simulation results show that the novel electro-hydraulic valve train can achieve fully variable valve timing and lift control.Consequently the engine performance on different loads and speeds will be significantly increased.The technology also permits the elimination of the traditional throttle valve in the gasoline engines and increases engine design flexibility.
基金supported by the National High Technology Research and Development Foundation of China(2009AA044501)the National Basic Research Program of China (2011CB706502)
文摘Electro-hydraulic servo valve is a typical complicated multi-domain system constituted by mechanical, electric, hydraulic and magnetic components, which is widely used in electro-hydraulic servo systems such as construction machinery, heavy equipment, weapon and so forth. The traditional method of modeling and simulation of servo valve is based on block diagram or signal flow, which cannot describe the servo valve system from components level nor be used in modeling and simulation of overall servo systems. In the procedure of traditional method, computational causality must be involved in modeling of servo valve, which is inconvenient to execute modification on components or parameters. Modelica is an object-oriented modeling language which is suited for large, complex, heterogeneous and multi-domain systems. The key features of Modelica are multi-domain, object-oriented and non-causal, which are suitable for modeling of servo valve and make the model readable, reusable, and easy to modify. The simulation results show similar curves with traditional method. This new servo valve modeling and simulation method can provide the engineers a more efficient way to design and optimize a servo valve and an overall servo system.
文摘BACKGROUND The management of severe symptomatic aortic stenosis has been revolutionized by transcatheter aortic valve replacement(TAVR),offering a minimally invasive alternative to surgical aortic valve replacement(SAVR).However,the compara-tive safety and efficacy of these interventions remain subjects of ongoing investigation.AIM To compare the clinical outcomes and safety of TAVR vs SAVR in patients with severe symptomatic aortic stenosis.METHODS A systematic review and meta-analysis were conducted according to PRISMA guidelines.Randomized controlled trials(RCTs)comparing TAVR and SAVR were identified from databases including PubMed,Scopus,and Web of Science up to May 31,2024.Data were extracted on clinical outcomes,including mortality,procedural compli-cations,and post-procedure adverse events.Risk ratios(RRs)with 95%CIs were calculated using a random-effects model.RESULTS A total of 10 RCTs were included.TAVR demonstrated a significantly lower risk of acute kidney injury(RR:0.33;95%CI:0.25–0.44),major bleeding(RR:0.37;95%CI:0.30–0.46),and new-onset atrial fibrillation(RR:0.44;95%CI:0.34–0.57)compared to SAVR.However,TAVR was associated with higher risks of new permanent pacemaker implantation(RR:3.49;95%CI:2.77–4.39),major vascular complications(RR:2.47;95%CI:1.91–3.21),and paraval-vular leaks(RR:4.15;95%CI:3.14–5.48).Mortality at 30 days was comparable(RR:0.95;95%CI:0.78–1.15),but long-term mortality was slightly higher with TAVR in some analyses(RR:1.23;95%CI:1.01–1.49).Rates of stroke(RR:0.97;95%CI:0.81–1.17)and myocardial infarction(RR:0.91;95%CI:0.67–1.24)were similar between the groups.CONCLUSION TAVR offers a less invasive option with significant benefits in reducing acute kidney injury,major bleeding,and new-onset atrial fibrillation,making it particularly advantageous for high-risk surgical candidates.However,higher risks of permanent pacemaker implantation,vascular complications,and paravalvular leaks highlight the need for individualized patient selection and shared decision-making to optimize outcomes.
基金Supported by National Key Research and Development Program of China(Grant No.2022YFC2805703)National Natural Science Foundation of China(Grant Nos.52305073,51975507).
文摘Thermosyphon loops are widely used in cooling systems.However,such distributed thermal management systems lack the ability to actively control the coolant flow in each parallel branch.An effective method for addressing this is to control the coolant flow in each branch using a solenoid valve.However,the existing valves do not satisfy the requirements for fast switching,low power,low pressure loss,and miniaturization.Therefore,in this study,a low-power-consumption miniature solenoid valve(LMSV)is proposed for use in thermal management systems.The key novelty is that the valve is designed with a suitably sized permanent magnet(PM)to allow the spool to continue working without consuming electrical energy.To achieve low flow resistance,a straight-through design is employed in the valve with the electromagnetic actuator located inside the valve shell.Multiphysical coupling analysis is performed to investigate its performance.The influence of the PM dimensions and current on the magnetic field distribution and electromagnetic force is studied.The effects of these key parameters on the flow field and pressure loss are also analyzed.Because the LMSV is sensitive to temperature,the switching time and energy consumption at different working temperatures are investigated.Experimental test platforms are constructed.A valve switching time of as short as 3 ms,pressure loss of 200 Pa at 0.92 L/min,and energy consumption of approximately 1.55 J during the opening and closing processes are achieved.The novel solenoid valve proposed in this study offers fast switching,low power consumption,low pressure loss,and miniaturization to meet the requirements of thermal management systems.
基金The Fundamental Research Funds for the Central Universities(JD2423)。
文摘Pump valve pipeline vibration brings serious safety hazards to the operation of the equipment,for the pump valve system in the process of variable flow,variable speed,variable openings lead to excessive pipeline vibration.An active damping device(ADD)is used to the vibration of the pump valve pipeline system to apply the control force,to achieve the active control of the pipeline vibration.A pump-valve pipeline vibration test bench was built to compare the control effect of active damping device on pipeline vibration under different pump valve working conditions,and the results show that applying ADD control could effectively suppress the vibration of the pump valve pipeline and enhance the stability of the equipment during operation.At different pump operating rotation frequencies,the vibration amplitude of the pump valve pipeline in working frequency and its multiple frequencies are also effectively suppressed,with the maximum amplitude reduction of more than 60%.For the valve vibration caused by different operating openings,the vibration of the highest reduction of 68%,and the centrifugal pump drive shaft vi-bration reduced by up to 73%,which provides a new idea for vibration control of pump valve pipeline system.
基金Gansu Provincial Department of Education(Industrial Support Plan Project:202CYZC-048).
文摘Hydraulic control valves, positioned at the terminus of pipe networks, are critical for regulatingflow and pressure, thereby ensuring the operational safety and efficiency of pipeline systems. However,conventional valve designs often struggle to maintain effective regulation across a wide range of systempressures. To address this limitation, this study introduces a novel Pilot hydraulic valves specificallyengineered for enhanced dynamic performance and precise regulation under variable pressure conditions.Building upon prior experimental findings, the proposed design integrates a high-fidelity simulationframework and a surrogate model-based optimization strategy. The study begins by formulating acomprehensive mathematical model of the pipeline system using electro-hydraulic simulation techniques,capturing the dynamic behavior of both the pilot valve and the broader urban water distribution network. Acoupled simulation platform is then developed, leveraging both one-dimensional (1D) and three-dimensional(3D) software tools to accurately analyze the valve’s transient response and operational characteristics. Toachieve optimal valve performance, a multi-objective optimization approach is proposed. This approachemploys a Levy-based Improved Tuna-InspiredWake-Up Optimization Algorithm (L-TIWOA) to refine aBackpropagation (BP) neural network, thereby constructing a highly accurate surrogate model. Compared tothe conventional BP neural network, the improved model demonstrates significantly reduced mean absoluteerror (MAE) and mean squared error (MSE), underscoring its superior predictive capability. The surrogatemodel serves as the objective function within an Improved Multi-Objective Mother Lode OptimizationAlgorithm (IMOMLOA), which is then used to fine-tune the key design parameters of the control valve.Validation through experimental testing reveals that the optimized valve achieves a maximum flow deviationof just 1.11 t/h, corresponding to a control accuracy of 3.7%, at a target flow rate of 30 t/h. Moreover,substantial improvements in dynamic response are observed, confirming the effectiveness of the proposeddesign and optimization strategy.
文摘Published proof test coverage(PTC)estimates for emergency shutdown valves(ESDVs)show only moderate agreement and are predominantly opinion-based.A Failure Modes,Effects,and Diagnostics Analysis(FMEDA)was undertaken using component failure rate data to predict PTC for a full stroke test and a partial stroke test.Given the subjective and uncertain aspects of the FMEDA approach,specifically the selection of component failure rates and the determination of the probability of detecting failure modes,a Fuzzy Inference System(FIS)was proposed to manage the data,addressing the inherent uncertainties.Fuzzy inference systems have been used previously for various FMEA type assessments,but this is the first time an FIS has been employed for use with FMEDA.ESDV PTC values were generated from both the standard FMEDA and the fuzzy-FMEDA approaches using data provided by FMEDA experts.This work demonstrates that fuzzy inference systems can address the subjectivity inherent in FMEDA data,enabling reliable estimates of ESDV proof test coverage for both full and partial stroke tests.This facilitates optimized maintenance planning while ensuring safety is not compromised.
文摘A method of combining the valve system program with the engine cycle modeling software to form a full set of working process modeling is submitted,not only considering the system as an independent part,but also as a part of working process to evaluate comprehensively and indicate directly if the design is good or not.The designers can optimize the design by changing the engine structure,operation and the basic parameters of the cam on condition that the sysem should be stable so as to save large amounts of time and cost.Practical examples show that such a software package is an effective tool in optimizing the valve systems and performance of the machine.
文摘The theory of multibody system dynamics is used to simulate valve trains' kinematics and dynamics characteristics, and the methods of establishing and analyzing the multibody system dynamics model for valve trains are discussed. Since most of the flexible bodies of a valve train are slender parts, the finite segment method is used to build their models. Other parts such as cams, valve heads etc., are built as rigid bodies. After applying the constraints, forces and motions, the establishing of the whole system is accomplished, and the Lagrange's multiplier method can be used to obtain its dynamics constitutive equations. As an example, a valve trains multibody system model of 4100QB engine made by the Yunnan Internal Combustion Engine Limited Liability Company is established, and the analysis results obtained show that its working performance is generally good except that the air pass ability and the lubrication effect of the cam and the tappet have to be improved.
文摘Computational Fluid Dynamics (CFD) simulations of cavitating flow through water hydraulic poppet valves were performed using advanced RNG k-epsilon turbulence model. The flow was turbulent, incompressible and unsteady, for Reynolds numbers greater than 43 000. The working fluid was water, and the structure of the valve was simplified as a two dimensional axisymmetric geometrical model. Flow field visualization was numerically achieved. The effects of inlet velocity, outlet pressure, opening size as well as poppet angle on cavitation intensity in the poppet valve were numerically investigated. Experimental flow visualization was conducted to capture cavitation images near the orifice in the poppet valve with 30° poppet angle using high speed video camera. The binary cavitating flow field distribution obtained from digital processing of the original cavitation image showed a good agreement with the numerical result.
基金supported by National Natural Science Foundation of China(Grant No.50835001)Research and Innovation Teams Foundation Project of Ministry of Education of China(Grant No.IRT0610)Liaoning Provincial Key Laboratory Foundation Project of China(Grant No.20060132)
文摘Synthesis characteristics of the electro-hydraulic servo valve are key factors to determine eligibility of the hydraulic production.Testing all synthesis characteristics of the electro-hydraulic servo valve after assembling leads to high repair rate and reject rate,so accurate prediction for the synthesis characteristics in the industrial production is particular important in decreasing the repair rate and the reject rate of the product.However,the research in forecasting synthesis characteristics of the electro-hydraulic servo valve is rare.In this work,a hybrid prediction method was proposed based on rough set(RS)and adaptive neuro-fuzzy inference system(ANFIS)in order to predict synthesis characteristics of electro-hydraulic servo valve.Since the geometric factors affecting the synthesis characteristics of the electro-hydraulic servo valve are from workers'experience,the inputs of the prediction method are uncertain.RS-based attributes reduction was used as the preprocessor,and then the exact geometric factors affecting the synthesis characteristics of the electro-hydraulic servo valve were obtained.On the basis of the exact geometric factors,ANFIS was used to build the final prediction model.A typical electro-hydraulic servo valve production was used to demonstrate the proposed prediction method.The prediction results showed that the proposed prediction method was more applicable than the artificial neural networks(ANN)in predicting the synthesis characteristics of electro-hydraulic servo valve,and the proposed prediction method was a powerful tool to predict synthesis characteristics of the electro-hydraulic servo valve.Moreover,with the use of the advantages of RS and ANFIS,the highly effective forecasting framework in this study can also be applied to other problems involving synthesis characteristics forecasting.
基金This project is supported by National Natural Science Foundation of China(No.59875076).
文摘The simulation model of a valve control hydraulic system with long pipe isestablished in Simulink4.0, and then the step responses of the systems with difference pipeparameters are investigated by simulation. Simulation results show that the long pipes will slowdown the step response of system and make it fluctuate periodically. The results of simulationconform to the results of experiment on the whole, which proves the mathematic model is correct.
基金Supported by National Natural Science Foundation of China(Grant No.51605417)Key Project of Hebei Provincial Natural Science Foundation,China(Grant No.E2016203264)State Key Laboratory of Fluid Power and Mechatronic Systems(Zhejiang University)Open Fund Project(Grant No.GZKF-201502)
文摘Nowadays, a highly integrated valve?controlled cylinder(HIVC) is applied to drive the joints of legged robots. Although the adoption of HIVC has resulted in high?performance robot control, the hydraulic force system still has problems, such as strong nonlinearity, and time?varying parameters. This makes HIVC force control very diffcult and complex. How to improve the control performance of the HIVC force control system and find the influence rule of the system parameters on the control performance is very significant. Firstly, the mathematical model of HIVC force control system is established. Then the mathematical expression for parameter sensitivity matrix is obtained by applying matrix sensitivity analysis(PSM). Then, aimed at the sinusoidal response under(three factors and three levels) working conditions, the simulation and the experiment are conducted. While the error between the simulation and experiment can’t be avoided. Therefore, combined with the range analysis, the error in the two performance indexes of sinusoidal response under the whole working condition is analyzed. Besides, the sensitivity variation pattern for each system parameter under the whole working condition is figured out. Then the two sensitivity indexes for the three system parameters, which are supply pressure, proportional gain and initial displacement of piston, are proved experimentally. The proposed method significantly reveals the sensitivity characteristics of HIVC force control system, which can make the contribution to improve the control performance.
基金supported by the National Natural Science Foundation of China(81600240)the Science Foundation for Distinguished Young Scholars of Shaanxi Natural Science Basic Research Program(2018JC-015).
文摘Transcatheter mitral valve replacement(TMVR)has become an alternative to surgical mitral valve replacement for the treatment of patients with severe mitral insufficiency(MI)who are at very high or prohibitive surgical risk.[1]Because of impaired left ventricular dysfunction and previous cardiac surgery,some aged patients with degenerated bioprosthetic mitral valve and mitral regurgitation were refused to redo surgery.[2]Increasing demand are required for minimally invasive treatment of these patients.Hundreds of patients worldwide have been treated with a transcatheter mitral valve-in-ring or valve-in-valve procedure using transcatheter aortic valve.[3]However,rare case of transcatheter mitral valve-in-valve/ring replacement using transcatheter mitral valve system was reported.Here,we reported a successfully case of transcatheter mitral“valve-in-valve”replacement for the treatment of bioprosthetic mitral valve degeneration and severe regurgitation with domestic Mithos^TM valve.
文摘Previous studies have confirmed that an active suspension system with high speed ON/OFF solenoid valves could provide the same vibration isolation efficiency as that of system with pressure proportional valve. In this study, by using Linear-quadratic optimization technique and Kalman filter method, an optimal regulator controller with a state observer was designed for the proposed system. Simulation and experimental research was conducted on a quarter car model. The simulation analysis of the system frequency characteristic suggested that the peak value of magnitude response curve in the case of system with an optimal controller would be lowered significantly, and the experiment results also showed that an improvement in the vibration isolation effect was obtained in using the designed optimal controller over the sky hook damper controller.
文摘To study the dynamic behavior of pipeline systems installed with large-mass valves within nuclear power plants during earthquakes,seismic simulation tests are carried out on a pipeline system equipped with a DN80 gate valve,and the FEM updating technique is used to identify the stiffness distribution of the valve.By conducting tests and a numerical analysis,the following conclusions are obtained:After a large-mass valve is installed in the pipeline,the system shows higher sensitivity to intermediate and high frequency components in the earthquake than low frequency components.It is possible for the intermediate frequency components to be amplified by the valve in the horizontal direction,while the pipes tend to amplify the high frequency components in horizontal and vertical directions.Changes in the high-order modes of the system depend on valve stiffness distribution.Since the existence of a valve makes pipeline system damping distribute with an obvious non-proportional feature,when the response spectrum method is used to calculate the response of the pipeline system,it could result in an underestimation of low-damping positions and overestimation of high-damping positions.
文摘Nuclear power plants(NPP)contain plenty of valve piping systems(VPS’s)which are categorized into high anti-seismic grades.Tasks such as seismic qualification,health monitoring and damage diagnosis of VPS’s in its design and operation processes all depend on finite element method.However,in engineering practice,there is always deviations between the theoretical and the measured responses due to the inaccurate value of the structural parameters in the model.The structure parameters identification of VPS within NPP is still an unexplored domain to a large extent.In this paper,the initial 2D-finite element model(FEM)for VPS with a DN80 gate valve was updated by utilizing seismic response.The objective function used in the model updating procedure is the vibration control equation error of the VPS.The experimental results show that the updated 2D-FEM can accurately predict the original dynamic characteristic of the VPS.It was also found the Rayleigh damping coefficients corresponding to the VPS vary slightly with the change in seismic excitation amplitude.The research displayed the complete procedure of updating the complex structured initial FEM by utilizing seismic response,and the results show that the parameters can be accurately identified even if the seismic response used for updating merely contained the fundamental frequency information of the structure.
基金Project(2006CB705400)supported by the National Basic Research Program of China
文摘The natural frequency of the electrohydraulic system in mobile machinery is always very low,which brings difficulties to the controller design.To improve the tracking performance of the hydraulic system,mathematical modeling of the electrohydraulic lifting system and the rubber hose was accomplished according to an electrohydraulic lifting test rig built in the laboratory.Then,valve compensation strategy,including spool opening compensation (SOC) and dead zone compensation (DZC),was designed based on the flow-pressure characteristic of a closed-centered proportional valve.Comparative experiments on point-to-point trajectory tracking between a proportional controller with the proposed compensations and a traditional PI controller were conducted.Experiment results show that the maximal absolute values of the tracking error are reduced from 0.039 m to 0.019 m for the slow point-to-point motion trajectory and from 0.085 m to 0.054 m for the fast point-to-point motion trajectory with the proposed compensations.Moreover,tracking error of the proposed controller was analyzed and corresponding suggestions to reduce the tracking error were put forward.
文摘Hydraulic butterfly valves have been widely applied in marine engineering because of their large switching torque, low pressure loss and suitability for large and medium diameter pipelines. Due to control problems resulting from switching angular speeds of the hydraulic butterfly valve, a throttle-governing control mode has been widely adopted, and detailed analysis has been carried out worldwide on the structural principle concerning speed-regulation and the load torque on the shaft while opening or closing a hydraulic butterfly valve. However relevant reports have yet been published on the change law, the error and the influencing factors of the rotational angular velocity of the hydraulic butterfly valve while opening and closing. In this article, research was based on some common specifications of a hydraulic butterfly valve with a symmetrical valve flap existing in a marine environment. The throttle governing system supplied by the accumulator to achieve the switching of the hydraulic control valve was adopted, and the mathematical models of the system were established in the actual conditions while the numerical simulations took place. The simulation results and analysis show that the rotational angular velocity and the error of the hydraulic butterfly valve while switching is influenced greatly by the drainage amount of the accumulator, resulting in pressure loss in the pipeline, the temperature of hydraulic medium and the load of the hydraulic butterfly valve. The simulation results and analysis provide a theoretical basis for the choice of the total capacity of the accumulator and pipeline diameters in a throttle governing system with a hydraulic butterfly valve.It also determines the type and specification of the hydraulic butterfly valve and the design of motion parameters of the transported fluid.
