BACKGROUND Aortic root dilation,linked to bicuspid aortic valve(BAV)or tricuspid aortic valve(TAV),risks aneurysm and dissection.Valve-sparing aortic root replacement(VSARR)preserves native valves,avoiding prosthetic ...BACKGROUND Aortic root dilation,linked to bicuspid aortic valve(BAV)or tricuspid aortic valve(TAV),risks aneurysm and dissection.Valve-sparing aortic root replacement(VSARR)preserves native valves,avoiding prosthetic valve complications.Longterm VSARR durability,especially in BAV patients,is debated.We hypothesize that VSARR outcomes differ between BAV and TAV patients in short-term and long-term settings.AIM To investigate short-term and long-term outcomes of VSARR in BAV vs TAV patients.METHODS This Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant meta-analysis included observational studies comparing VSARR in adult BAV vs TAV patients.PubMed,ScienceDirect,and EMBASE were searched from inception to June 2025.Outcomes included mortality,reintervention,and procedural times.Pooled relative risk(RR)and mean differences(MD)with 95%CI were calculated.Risk of bias was assessed using Risk of Bias in Non-randomized Studies of Interventions;evidence certainty via GRADE.RESULTS Thirteen observational studies involving 1419 BAV and 2349 TAV patients were included.In-hospital mortality(RR=0.34,95%CI:0.10-1.14,P=0.08)and reoperation(RR=1.04,95%CI:0.64-1.69,P=0.87)showed no significant differences.All-cause mortality risk was significantly lower in BAV patients(RR=0.34,95%CI:0.13-0.86,P=0.02).Overall reintervention risk was significantly greater in BAV patients(RR=2.64,95%CI:1.96-3.55,P<0.00001).Aortic cross-clamp(MD=3.35 minutes,95%CI:-5.06 to 11.76,P=0.43)and cardiopulmonary bypass times(MD=3.96 minutes,95%CI:-10.26 to 18.18,P=0.59)showed no significant differences but substantial heterogeneity.The certainty of evidence was moderate for reintervention,low for mortality risk and in-hospital reoperation,and very low for procedural times.CONCLUSION VSARR demonstrates comparable short-term safety between BAV and TAV patients.However,BAV patients face a significantly higher long-term reintervention risk,highlighting the need for tailored strategies and further research.展开更多
BACKGROUND Neoadjuvant therapy(NAT)for pancreatic cancer(PC)is becoming standardized,with neoadjuvant chemoradiotherapy(NACRT)showing proven effectiveness.However,the optimal endoscopic biliary drainage approach durin...BACKGROUND Neoadjuvant therapy(NAT)for pancreatic cancer(PC)is becoming standardized,with neoadjuvant chemoradiotherapy(NACRT)showing proven effectiveness.However,the optimal endoscopic biliary drainage approach during NAT remains controversial.In this single-center retrospective case series,we report the use of a novel multi-hole self-expandable metallic stent(MH-SEMS)for preoperative biliary drainage during NACRT in patients with PC.AIM To assess the feasibility of endoscopic biliary drainage using MH-SEMS during NACRT in patients with malignant distal biliary obstruction secondary to resectable and borderline resectable PC.METHODS We included 14 patients—10 with resectable,2 with borderline resectable,and 2 with unresectable locally advanced disease—who had undergone surgery after biliary drainage using MH-SEMS(diameter:10 mm).Clinical and technical success was achieved in all patients,with a median interval of 105 days between stent placement and surgery.RESULTS A partial response was observed in five patients(35.7%),whereas nine patients(64.3%)exhibited stable disease.Only one patient(7.1%)developed moderate cholangitis from recurrent biliary obstruction caused by sludge 337 days after stent placement during systemic chemotherapy,requiring MH-SEMS replacement.Pathological examination of postoperative specimens revealed tumor shrinkage in many cases,and no stent migration was observed.Adverse events included mild pancreatitis in two patients(14.3%)and moderate pancreatitis in one patient(7.1%),as defined by the Tokyo Criteria 2024.CONCLUSION No cases of cholecystitis,liver abscess,or hemorrhage were reported.No disadvantages in surgical procedures or postoperative complications related to MH-SEMS placement were observed.展开更多
Owing to their excellent biocompatibility and potential for durability enhancement,polymeric heart valves(PHVs)are emerging as a promising alternative to traditional prostheses.Unlike conventional materials,PHVs can b...Owing to their excellent biocompatibility and potential for durability enhancement,polymeric heart valves(PHVs)are emerging as a promising alternative to traditional prostheses.Unlike conventional materials,PHVs can be manufactured under precise design criteria,enabling targeted performance improvements.This study introduces a geometric optimization strategy for enhancing the durability of PHVs.The finite element method(FEM)is combined with a dip-molding technique to develop a novel polymeric aortic valve with improved mechanical properties.The tri-leaflet geometry is parameterized using B-spline curves,and the maximum stress in the valve is reduced from 2.4802 to 1.7773 MPa using a multiobjective optimization algorithm NSGA-II(non-dominated sorting genetic algorithm II).Pre-optimized and optimized valve prototypes were fabricated via dip-molding and evaluated during pulsatile-flow tests and accelerated wear tests.The optimized design meets the ISO 5840 standards,with an effective orifice area of 2.019 cm^(2),a regurgitant fraction of 5.693%,and a transvalvular pressure gradient of 7.576 mmHg.Moreover,the optimized valve maintained its structural integrity and functionality over 14 million cycles of the accelerated wear test,whereas the unoptimized valve failed after two million cycles.These findings confirm that the FEM-based geometric optimization method enhances both the mechanical performance and durability of PHVs.展开更多
Purpose–Type-120 relief valves are critical components of locomotive braking systems,and they rapidly discharge the air pressure during brake release to enable swift pressure relief.In order to develop type-120 relie...Purpose–Type-120 relief valves are critical components of locomotive braking systems,and they rapidly discharge the air pressure during brake release to enable swift pressure relief.In order to develop type-120 relief valve rubber diaphragms with long life and high performance,the damaged faulty samples were analyzed and studied.Design/methodology/approach–Finite element analysis(FEA)was used to investigate the stress distribution and failure mechanism of the rubber diaphragms within the type-120 relief valves under dynamic loading conditions.The Ogden hyperelastic constitutive model was used to fit the diaphragm data obtained from the uniaxial tensile tests,and its suitability for the modeling of large deformations was confirmed.Findings–The FEA results indicated that,when the rubber diaphragms reached their maximum deformation,the peak stress on their upper surfaces was 5.44 MPa.Thus,this region is highly susceptible to fatigue damage.The service life of the rubber diaphragms could be extended by using rubber compounds with high tensile moduli or a fabric-reinforced rubber diaphragm.Originality/value–This study provides valuable data and experience for the development of the rubber diaphragms in the type-120 valves and other long-life rubber products in the railway field.展开更多
The conventional Shear Stress Transport(SST)k–ωturbulence model often exhibits substantial inaccu-racies when applied to the prediction of flow behavior in complex regions within axial flow control valves.To enhance...The conventional Shear Stress Transport(SST)k–ωturbulence model often exhibits substantial inaccu-racies when applied to the prediction of flow behavior in complex regions within axial flow control valves.To enhance its predictive fidelity for internal flow fields,this study introduces a novel calibration framework that integrates an artificial neural network(ANN)surrogate model with a particle swarm optimization(PSO)algorithm.In particular,an optimal Latin hypercube sampling strategy was employed to generate representative sample points across the empirical parameter space.For each sample,numerical simulations using ANSYS Fluent were conducted to evaluate the flow characteristics,with empirical turbulence model parameters as inputs and flow rate as the target output.These data were used to construct the high-fidelity ANN surrogate model.The PSO algorithm was then applied to this surrogate to identify the optimal set of empirical parameters tailored specifically to axial flow control valve configurations.A revealed by the presented results,the calibrated SST k–ωmodel significantly improves prediction accuracy:deviations from large eddy simulation(LES)benchmarks at small valve openings were reduced from 7.6%to under 3%.Furthermore,the refined model maintains the computational efficiency characteristic of Reynolds-averaged Navier-Stokes(RANS)simulations while substantially enhancing the accuracy of both pressure and velocity field predictions.Overall,the proposed methodology effectively reconciles the trade-off between computational cost and predictive accuracy,offering a robust and scalable approach for turbulence model calibration in complex internal flow scenarios.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
Background The effective orifice area(EOA)is utilized to characterize the hemodynamic performance of the transcatheter heart valve(THV).However,there is no consensus on EOA measurement of self-expanding THV.We aimed t...Background The effective orifice area(EOA)is utilized to characterize the hemodynamic performance of the transcatheter heart valve(THV).However,there is no consensus on EOA measurement of self-expanding THV.We aimed to compare two echocardiographic methods for EOA measurement following transcatheter self-expanding aortic valve implantation.Methods EOA was calculated according to the continuity equation.Two methods were constructed.In Method 1 and Method 2,the left ventricular outflow tract diameter(LVOTd)was measured at the entry of the prosthesis(from trailing-to-leading edge)and proximal to the prosthetic valve leaflets(from trailing-toleading edge),respectively.The velocity-time integral(VTI)of the LVOT(VTILVOT)was recorded by pulsed-wave Doppler(PW)from apical windows.The region of the PW sampling should match that of the LVOTd measurement with precise localization.The mean transvalvular pressure gradient(MG)and VTI of THV was measured by Continuous wave Doppler.Results A total of 113 consecutive patients were recruited.The mean age was 77.2±5.5 years,and 72 patients(63.7%)were male.EOA1 with the use of Method 1 was larger than EOA2(1.56±0.39 cm2 vs.1.48±0.41 cm2,P=0.001).MG correlated better with the indexed EOA1(EOAI1)(r=-0.701,P<0.001)than EOAI2(r=-0.645,P<0.001).According to EOAI(EOAI≤0.65 cm2/m2,respectively),the proportion of sever prosthesis-patient mismatch with the use of EOA1 was lower than EOA2(12.4%vs.21.2%,P<0.05).Compared with EOA2,EOA1 had lower interobserver and intra-observer variability(intra:0.5%±17%vs.3.8%±22%,P<0.001;inter:1.0%±9%vs.3.5%±11%,P<0.001).Conclusions For transcatheter self-expanding valve EOA measurement,LVOTd should be measured in the entry of the prosthesis stent(from trailing-to-leading edge),and VTILVOT should match that of the LVOTd measurement with precise localization.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
Background:The Venus-P valve was the first self-expanding valve used world-wide for transcatheter pulmonary valve replacement(TPVR)in patients with severe pulmonary regurgitation(PR).We intended to report the extended...Background:The Venus-P valve was the first self-expanding valve used world-wide for transcatheter pulmonary valve replacement(TPVR)in patients with severe pulmonary regurgitation(PR).We intended to report the extended follow-up results from the prospective trial(No.NCT02590679).Methods:A total of 38 patients with severe PR(mean age 24.2±13.2)were included.Follow-up data were obtained after implanted at 1,6,and 12 months and yearly after.The frame geometry was assessed on post-implant computer tomography(CT)scanning by calculating the non-circularity[circularity ratio(minimum diameter/maximum diameter)<0.9]and under-expansion[expansion ratio(derived external valve area/nominal external valve area)<0.9).Adverse events(all-cause mortality,reintervention,valve dysfunction,stent fracture and endocarditis)were recorded.Results:All valves were implanted successfully with normal function at discharge.Geometric CT analysis showed underexpanded valve was detected in 22 patients(63%)and non-circular valve was seen in 16 patients(46%).During a median follow-up of 4.8 years(range 0.3-8.1),there were 1 death and 1 surgical explant,both resulting from endocarditis.Five-year freedom from valve dysfunction and stent fracture were 84.8%(95%CI 74.8-94.7)and 83.5%(95%CI 73.8-93.2).Endocarditis occurred in 3 patients at a median time of 7 months.Stent fracture was more common in patients with non-circularity stents.Conclusion:TPVR using Venus-P valve is associated with favorable outcomes at 5 years.Non-circular shapes in the valve level may have a higher risk of stent fracture.展开更多
High-speed on-off valves are widey used in PWM electropneumatic servo sys- tems and their characteristics are generally described by their on and off delay time. This paper focuses on establishing the relationships be...High-speed on-off valves are widey used in PWM electropneumatic servo sys- tems and their characteristics are generally described by their on and off delay time. This paper focuses on establishing the relationships between their on-off switching behaviors and their frequency response characteristics. A method is proposed by which the frequency response characteristics of an analog PWM high-speed on-off valve can be calculated for inputs whose periods are certain multiples of the carrier period, based on its switching be- haviors. Thus, a simple and direct describing function for a PWM high-speed on-off valve is established.展开更多
Background: The introduction of transcatheter aortic valve implantation (TAVI) for the treatment of severe aortic stenosis (SAS) has expanded the therapeutic possibilities for successfully managing SAS in cases with i...Background: The introduction of transcatheter aortic valve implantation (TAVI) for the treatment of severe aortic stenosis (SAS) has expanded the therapeutic possibilities for successfully managing SAS in cases with intermediate and high surgical risks. However, the complications and outcomes of new devices have not been studied enough. Hence, the purpose of this study is to evaluate the midterm results of the Core Valve and Evolute R self-expandable (SE) devices versus the Edwards SAPIEN balloon-expandable (BE) devices. Methods and Material: This was a quasi-experimental study conducted in Tehran, Iran, from May 2012 to June 2017. SAS patients who were not ideal candidates for surgery were randomly assigned to either SE or BE groups. For each patient, a questionnaire, including four sections comprised of Basic characteristics, echocardiographic, angiographic, and Computed Tomography (CT) scan data was filled. TAVI was followed by echocardiography a week later and after three months they were reevaluated by another questionnaire. Results: The total number of patients was 60. The mean ages of patients undergoing the procedure with SE or BE devices were 81.2 ± 8 and 79.8 ± 7, respectively. Mortality occurred in 20% of the patients (5 cases in the SE group and 7 cases in the BE);mortality causes were 66.6 % cardiac and 33% non-cardiac. Moderate to severe Paravalvular leakage in both groups did not differ significantly. The mortality rate was 5 (41.6%) in the SE group versus 7 (58.3%) in the BE group (P > 0.05). Conclusion: In conclusion, the BE group did not experience fewer paravalvular leaks in comparison with the SE. Morbidity and mortality between the BE and the SE groups did not differ significantly.展开更多
Natural properties of high speed on-off valves can be described through their on-off behavior and spool movement (static and oscillating) characteristics. High speed on-off valves can be combined with actuators in sys...Natural properties of high speed on-off valves can be described through their on-off behavior and spool movement (static and oscillating) characteristics. High speed on-off valves can be combined with actuators in systems into four typical types of composite valves whose static characteristics are related not only to the structures of the single valves and the composite ones, but also to the PWM control modes. It is proved that the composite valves have similar features as those of servo valves. The nonlinear specific properties of single valves composited can be completely compensated by the suitable PWM control modes.展开更多
Investment and suction casting （ISC） represents an economic and promising process route to fabricate auto-motive exhaust valves of γ-TiAI based alloys, but information available on the metal flow and the temperatur...Investment and suction casting （ISC） represents an economic and promising process route to fabricate auto-motive exhaust valves of γ-TiAI based alloys, but information available on the metal flow and the temperature changeseduring mould filling and solidification process for the ISC process is meager. A sequentially coupled mathematical flow-thermal model, based on the commercial finite-volume/finite-difference code FLOW-3D and the finite-element code PROCAST, has been developed to investigate the ISC process. In term of calcu-lating the flow and temperature fields during the filling and solidification stages, potential defects including the gas bubbles and the surface air entrainment occurred in the mould filling process and the shrinkage porosities formed in the solidification process are predicted and the reasons for the formation of these defects are also analyzed. The effects of filling pressure difference control methods and moulds on gas bubble and surface air entrainment behavior are presented. It is found that by changing the filling pressure difference control methods from general suction casting to ＂air leakage＂ suction casting and reducing air leakage flow rates, the gas bubbles are eliminated effectively, and the surface air entrainment attenuate dramatically. With resort to a mould with a tetragonal runner, the surface air entrainment decrease to the lowest level. Finally, the water analogue and suction casting experiments of exhaust valves are implemented for further validation of the simulation results.展开更多
Leakage due to wear is one of the main failure modes of aero-hydraulic spool valves. This paper established a practical coupling wear model for aero-hydraulic spool valves based on dynamic system modelling theory. Fir...Leakage due to wear is one of the main failure modes of aero-hydraulic spool valves. This paper established a practical coupling wear model for aero-hydraulic spool valves based on dynamic system modelling theory. Firstly, the experiment for wear mechanism verification proved that adhesive wear and abrasive wear did coexist during the working process of spool valves. Secondly coupling behavior of each wear mechanism was characterized by analyzing actual time-variation of model parameters during wear evolution process. Meanwhile, Archard model and three-body abrasive wear model were utilized for adhesive wear and abrasive wear, respectively. Furthermore, their coupling wear model was established by calculating the actual wear volume. Finally, from the result of formal test, all the required parameters for our model were obtained. The relative error between model prediction and data of pre-test was also presented to verify the accuracy of model, which demonstrated that our model was useful for providing accurate prediction of spool valve's wear life. (C) 2016 The Authors. Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.展开更多
The flow characteristics and cavitation effects of water passing throughsmall sharp-edged cylindrical orifices and valves of different shapes in water hydraulics areinvestigated. The test results using orifices with d...The flow characteristics and cavitation effects of water passing throughsmall sharp-edged cylindrical orifices and valves of different shapes in water hydraulics areinvestigated. The test results using orifices with different aspect ratios and different diametersshow that the flow coefficients in the case of non-cavitating flow are larger than that of flow inthe case of cavitation occurrence. The flow coefficients of flow with cavitation initially decreaseas Reynolds number increases and ultimately tend to be of constant values close to contractioncoefficient. Large aspect ratio has an effect of suppressing cavitation. The experimental resultsabout disc valves illustrate that the valves with sharp edge at large opening are less affected bycavitation than that at small opening. Throttle with triangle notch has better anti-cavitationability than that with square notch. The flowrate of the throttle with square notch is significantlyaffected by the flow direction or the flow passage shape.展开更多
Valves are widely used in various working conditions for their flow control functions,and the cavitation inside valves has been investigated owing to its harm to the valve itself and the connecting downstream parts.Th...Valves are widely used in various working conditions for their flow control functions,and the cavitation inside valves has been investigated owing to its harm to the valve itself and the connecting downstream parts.This paper presents a comprehensive review of the progress that has been achieved in the past years about cavitation in valves including both mechanical heart valves and control valves.The review is divided in the following parts,namely the location where there is a high possibility of the occurrence of cavitation,the parameters that affect cavitation intensity,and the methods to minimize cavitation intensity.It should be noticed that although simulation has been widely used,advanced experiments are still needed in order to obtain accurate analysis of cavitation in valves and the cavitation model still needs to be improved.展开更多
AIM:To investigate the clinical advantages of the stent-laparoscopy approach to treat colorectal cancer(CRC)patients with acute colorectal obstruction(ACO).METHODS:From April 2008 to April 2012,surgeryrelated paramete...AIM:To investigate the clinical advantages of the stent-laparoscopy approach to treat colorectal cancer(CRC)patients with acute colorectal obstruction(ACO).METHODS:From April 2008 to April 2012,surgeryrelated parameters,complications,overall survival(OS),and disease-free survival(DFS)of 74 consecutive patients with left-sided CRC presented with ACO who underwent self-expandable metallic stent(SEMS)placement followed by one-stage open(n=58)or laparoscopic resection(n=16)were evaluated retrospectively.The stent-laparoscopy group was also compared with a control group of 96 CRC patients who underwent regular laparoscopy without ACO between January 2010 and December 2011 to explore whether SEMS placement influenced the laparoscopic procedure or reduced long-term survival by influencing CRC oncological characteristics.RESULTS:The characteristics of patients among these groups were comparable.The rate of conversion to open surgery was 12.5%in the stent-laparoscopy group.Bowel function recovery and postoperative hospital stay were significantly shorter(3.3±0.9 d vs 4.2±1.5 d and 6.7±1.1 d vs 9.5±6.7 d,P=0.016 and P=0.005),and surgical time was significantly longer(152.1±44.4 min vs 127.4±38.4 min,P=0.045)in the stent-laparoscopy group than in the stent-open group.Surgery-related complications and the rate of admission to the intensive care unit were lower in the stent-laparoscopy group.There were no significant differences in the interval between stenting and surgery,intraoperative blood loss,OS,and DFS between the two stent groups.Compared with those in the stentlaparoscopy group,all surgery-related parameters,complications,OS,and DFS in the control group were comparable.CONCLUSION:The stent-laparoscopy approach is a feasible,rapid,and minimally invasive option for patients with ACO caused by left-sided CRC and can achieve a favorable long-term prognosis.展开更多
Pseudo spin valves（SVs） exhibiting perpendicular magnetic anisotropy were prepared by magnetron sputtering. Magnetization measurements of the Co/Pt multilayers were performed to select the reference and free layers....Pseudo spin valves（SVs） exhibiting perpendicular magnetic anisotropy were prepared by magnetron sputtering. Magnetization measurements of the Co/Pt multilayers were performed to select the reference and free layers. The selection criteria are square magnetic hysteresis loops, weaker current shunting effect, and proper coercivity. The optimal reference layer and free layer are Pt（5.0 nm）/[Co（0.4 nm）/Pt（0.6 nm）]3/Co（0.4 nm）/Cu（3.0 nm）and Cu（3.0 nm）/[Co（0.4 nm）/Pt（1.5 nm）]4, respectively.The resulting pseudo SV exhibits two well-separated hysteresis loops when the field is applied perpendicular to the film plane. The minor hysteresis loop corresponding to the free layer shifts toward negative direction of the magnetic field axis, indicating ferromagnetic interlayer exchange coupling between the two magnetic layers. The coupling also enhances the coercivity（HC） of both layers. The perpendicular giant magnetoresistance（GMR） of 2.7 % is achieved with current in plane measurement. The GMR first increases when Pt seed layer is thickened, reaches a maximum of 3.0 % at 4 nm and then decreases with the further increase of thickness. But thicker Cu spacer layer always lowers the GMR of the SV.展开更多
文摘BACKGROUND Aortic root dilation,linked to bicuspid aortic valve(BAV)or tricuspid aortic valve(TAV),risks aneurysm and dissection.Valve-sparing aortic root replacement(VSARR)preserves native valves,avoiding prosthetic valve complications.Longterm VSARR durability,especially in BAV patients,is debated.We hypothesize that VSARR outcomes differ between BAV and TAV patients in short-term and long-term settings.AIM To investigate short-term and long-term outcomes of VSARR in BAV vs TAV patients.METHODS This Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant meta-analysis included observational studies comparing VSARR in adult BAV vs TAV patients.PubMed,ScienceDirect,and EMBASE were searched from inception to June 2025.Outcomes included mortality,reintervention,and procedural times.Pooled relative risk(RR)and mean differences(MD)with 95%CI were calculated.Risk of bias was assessed using Risk of Bias in Non-randomized Studies of Interventions;evidence certainty via GRADE.RESULTS Thirteen observational studies involving 1419 BAV and 2349 TAV patients were included.In-hospital mortality(RR=0.34,95%CI:0.10-1.14,P=0.08)and reoperation(RR=1.04,95%CI:0.64-1.69,P=0.87)showed no significant differences.All-cause mortality risk was significantly lower in BAV patients(RR=0.34,95%CI:0.13-0.86,P=0.02).Overall reintervention risk was significantly greater in BAV patients(RR=2.64,95%CI:1.96-3.55,P<0.00001).Aortic cross-clamp(MD=3.35 minutes,95%CI:-5.06 to 11.76,P=0.43)and cardiopulmonary bypass times(MD=3.96 minutes,95%CI:-10.26 to 18.18,P=0.59)showed no significant differences but substantial heterogeneity.The certainty of evidence was moderate for reintervention,low for mortality risk and in-hospital reoperation,and very low for procedural times.CONCLUSION VSARR demonstrates comparable short-term safety between BAV and TAV patients.However,BAV patients face a significantly higher long-term reintervention risk,highlighting the need for tailored strategies and further research.
文摘BACKGROUND Neoadjuvant therapy(NAT)for pancreatic cancer(PC)is becoming standardized,with neoadjuvant chemoradiotherapy(NACRT)showing proven effectiveness.However,the optimal endoscopic biliary drainage approach during NAT remains controversial.In this single-center retrospective case series,we report the use of a novel multi-hole self-expandable metallic stent(MH-SEMS)for preoperative biliary drainage during NACRT in patients with PC.AIM To assess the feasibility of endoscopic biliary drainage using MH-SEMS during NACRT in patients with malignant distal biliary obstruction secondary to resectable and borderline resectable PC.METHODS We included 14 patients—10 with resectable,2 with borderline resectable,and 2 with unresectable locally advanced disease—who had undergone surgery after biliary drainage using MH-SEMS(diameter:10 mm).Clinical and technical success was achieved in all patients,with a median interval of 105 days between stent placement and surgery.RESULTS A partial response was observed in five patients(35.7%),whereas nine patients(64.3%)exhibited stable disease.Only one patient(7.1%)developed moderate cholangitis from recurrent biliary obstruction caused by sludge 337 days after stent placement during systemic chemotherapy,requiring MH-SEMS replacement.Pathological examination of postoperative specimens revealed tumor shrinkage in many cases,and no stent migration was observed.Adverse events included mild pancreatitis in two patients(14.3%)and moderate pancreatitis in one patient(7.1%),as defined by the Tokyo Criteria 2024.CONCLUSION No cases of cholecystitis,liver abscess,or hemorrhage were reported.No disadvantages in surgical procedures or postoperative complications related to MH-SEMS placement were observed.
基金funded by the National Natural Science Foundation of China(No.82400370)the Interdisciplinary Innovation Team Incubation Project of Children’s Hospital of Fudan University(No.EKYX202416).
文摘Owing to their excellent biocompatibility and potential for durability enhancement,polymeric heart valves(PHVs)are emerging as a promising alternative to traditional prostheses.Unlike conventional materials,PHVs can be manufactured under precise design criteria,enabling targeted performance improvements.This study introduces a geometric optimization strategy for enhancing the durability of PHVs.The finite element method(FEM)is combined with a dip-molding technique to develop a novel polymeric aortic valve with improved mechanical properties.The tri-leaflet geometry is parameterized using B-spline curves,and the maximum stress in the valve is reduced from 2.4802 to 1.7773 MPa using a multiobjective optimization algorithm NSGA-II(non-dominated sorting genetic algorithm II).Pre-optimized and optimized valve prototypes were fabricated via dip-molding and evaluated during pulsatile-flow tests and accelerated wear tests.The optimized design meets the ISO 5840 standards,with an effective orifice area of 2.019 cm^(2),a regurgitant fraction of 5.693%,and a transvalvular pressure gradient of 7.576 mmHg.Moreover,the optimized valve maintained its structural integrity and functionality over 14 million cycles of the accelerated wear test,whereas the unoptimized valve failed after two million cycles.These findings confirm that the FEM-based geometric optimization method enhances both the mechanical performance and durability of PHVs.
基金supported by the Science and Technology Research and Development Plan of the China State Railway Group Company Limited(Grant No.N2023J053).
文摘Purpose–Type-120 relief valves are critical components of locomotive braking systems,and they rapidly discharge the air pressure during brake release to enable swift pressure relief.In order to develop type-120 relief valve rubber diaphragms with long life and high performance,the damaged faulty samples were analyzed and studied.Design/methodology/approach–Finite element analysis(FEA)was used to investigate the stress distribution and failure mechanism of the rubber diaphragms within the type-120 relief valves under dynamic loading conditions.The Ogden hyperelastic constitutive model was used to fit the diaphragm data obtained from the uniaxial tensile tests,and its suitability for the modeling of large deformations was confirmed.Findings–The FEA results indicated that,when the rubber diaphragms reached their maximum deformation,the peak stress on their upper surfaces was 5.44 MPa.Thus,this region is highly susceptible to fatigue damage.The service life of the rubber diaphragms could be extended by using rubber compounds with high tensile moduli or a fabric-reinforced rubber diaphragm.Originality/value–This study provides valuable data and experience for the development of the rubber diaphragms in the type-120 valves and other long-life rubber products in the railway field.
基金funded by Gansu Provincial Department of Education(Industrial Support Plan Project:2025CYZC-048).
文摘The conventional Shear Stress Transport(SST)k–ωturbulence model often exhibits substantial inaccu-racies when applied to the prediction of flow behavior in complex regions within axial flow control valves.To enhance its predictive fidelity for internal flow fields,this study introduces a novel calibration framework that integrates an artificial neural network(ANN)surrogate model with a particle swarm optimization(PSO)algorithm.In particular,an optimal Latin hypercube sampling strategy was employed to generate representative sample points across the empirical parameter space.For each sample,numerical simulations using ANSYS Fluent were conducted to evaluate the flow characteristics,with empirical turbulence model parameters as inputs and flow rate as the target output.These data were used to construct the high-fidelity ANN surrogate model.The PSO algorithm was then applied to this surrogate to identify the optimal set of empirical parameters tailored specifically to axial flow control valve configurations.A revealed by the presented results,the calibrated SST k–ωmodel significantly improves prediction accuracy:deviations from large eddy simulation(LES)benchmarks at small valve openings were reduced from 7.6%to under 3%.Furthermore,the refined model maintains the computational efficiency characteristic of Reynolds-averaged Navier-Stokes(RANS)simulations while substantially enhancing the accuracy of both pressure and velocity field predictions.Overall,the proposed methodology effectively reconciles the trade-off between computational cost and predictive accuracy,offering a robust and scalable approach for turbulence model calibration in complex internal flow scenarios.
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Background The effective orifice area(EOA)is utilized to characterize the hemodynamic performance of the transcatheter heart valve(THV).However,there is no consensus on EOA measurement of self-expanding THV.We aimed to compare two echocardiographic methods for EOA measurement following transcatheter self-expanding aortic valve implantation.Methods EOA was calculated according to the continuity equation.Two methods were constructed.In Method 1 and Method 2,the left ventricular outflow tract diameter(LVOTd)was measured at the entry of the prosthesis(from trailing-to-leading edge)and proximal to the prosthetic valve leaflets(from trailing-toleading edge),respectively.The velocity-time integral(VTI)of the LVOT(VTILVOT)was recorded by pulsed-wave Doppler(PW)from apical windows.The region of the PW sampling should match that of the LVOTd measurement with precise localization.The mean transvalvular pressure gradient(MG)and VTI of THV was measured by Continuous wave Doppler.Results A total of 113 consecutive patients were recruited.The mean age was 77.2±5.5 years,and 72 patients(63.7%)were male.EOA1 with the use of Method 1 was larger than EOA2(1.56±0.39 cm2 vs.1.48±0.41 cm2,P=0.001).MG correlated better with the indexed EOA1(EOAI1)(r=-0.701,P<0.001)than EOAI2(r=-0.645,P<0.001).According to EOAI(EOAI≤0.65 cm2/m2,respectively),the proportion of sever prosthesis-patient mismatch with the use of EOA1 was lower than EOA2(12.4%vs.21.2%,P<0.05).Compared with EOA2,EOA1 had lower interobserver and intra-observer variability(intra:0.5%±17%vs.3.8%±22%,P<0.001;inter:1.0%±9%vs.3.5%±11%,P<0.001).Conclusions For transcatheter self-expanding valve EOA measurement,LVOTd should be measured in the entry of the prosthesis stent(from trailing-to-leading edge),and VTILVOT should match that of the LVOTd measurement with precise localization.
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Background:The Venus-P valve was the first self-expanding valve used world-wide for transcatheter pulmonary valve replacement(TPVR)in patients with severe pulmonary regurgitation(PR).We intended to report the extended follow-up results from the prospective trial(No.NCT02590679).Methods:A total of 38 patients with severe PR(mean age 24.2±13.2)were included.Follow-up data were obtained after implanted at 1,6,and 12 months and yearly after.The frame geometry was assessed on post-implant computer tomography(CT)scanning by calculating the non-circularity[circularity ratio(minimum diameter/maximum diameter)<0.9]and under-expansion[expansion ratio(derived external valve area/nominal external valve area)<0.9).Adverse events(all-cause mortality,reintervention,valve dysfunction,stent fracture and endocarditis)were recorded.Results:All valves were implanted successfully with normal function at discharge.Geometric CT analysis showed underexpanded valve was detected in 22 patients(63%)and non-circular valve was seen in 16 patients(46%).During a median follow-up of 4.8 years(range 0.3-8.1),there were 1 death and 1 surgical explant,both resulting from endocarditis.Five-year freedom from valve dysfunction and stent fracture were 84.8%(95%CI 74.8-94.7)and 83.5%(95%CI 73.8-93.2).Endocarditis occurred in 3 patients at a median time of 7 months.Stent fracture was more common in patients with non-circularity stents.Conclusion:TPVR using Venus-P valve is associated with favorable outcomes at 5 years.Non-circular shapes in the valve level may have a higher risk of stent fracture.
文摘High-speed on-off valves are widey used in PWM electropneumatic servo sys- tems and their characteristics are generally described by their on and off delay time. This paper focuses on establishing the relationships between their on-off switching behaviors and their frequency response characteristics. A method is proposed by which the frequency response characteristics of an analog PWM high-speed on-off valve can be calculated for inputs whose periods are certain multiples of the carrier period, based on its switching be- haviors. Thus, a simple and direct describing function for a PWM high-speed on-off valve is established.
文摘Background: The introduction of transcatheter aortic valve implantation (TAVI) for the treatment of severe aortic stenosis (SAS) has expanded the therapeutic possibilities for successfully managing SAS in cases with intermediate and high surgical risks. However, the complications and outcomes of new devices have not been studied enough. Hence, the purpose of this study is to evaluate the midterm results of the Core Valve and Evolute R self-expandable (SE) devices versus the Edwards SAPIEN balloon-expandable (BE) devices. Methods and Material: This was a quasi-experimental study conducted in Tehran, Iran, from May 2012 to June 2017. SAS patients who were not ideal candidates for surgery were randomly assigned to either SE or BE groups. For each patient, a questionnaire, including four sections comprised of Basic characteristics, echocardiographic, angiographic, and Computed Tomography (CT) scan data was filled. TAVI was followed by echocardiography a week later and after three months they were reevaluated by another questionnaire. Results: The total number of patients was 60. The mean ages of patients undergoing the procedure with SE or BE devices were 81.2 ± 8 and 79.8 ± 7, respectively. Mortality occurred in 20% of the patients (5 cases in the SE group and 7 cases in the BE);mortality causes were 66.6 % cardiac and 33% non-cardiac. Moderate to severe Paravalvular leakage in both groups did not differ significantly. The mortality rate was 5 (41.6%) in the SE group versus 7 (58.3%) in the BE group (P > 0.05). Conclusion: In conclusion, the BE group did not experience fewer paravalvular leaks in comparison with the SE. Morbidity and mortality between the BE and the SE groups did not differ significantly.
文摘Natural properties of high speed on-off valves can be described through their on-off behavior and spool movement (static and oscillating) characteristics. High speed on-off valves can be combined with actuators in systems into four typical types of composite valves whose static characteristics are related not only to the structures of the single valves and the composite ones, but also to the PWM control modes. It is proved that the composite valves have similar features as those of servo valves. The nonlinear specific properties of single valves composited can be completely compensated by the suitable PWM control modes.
文摘Investment and suction casting （ISC） represents an economic and promising process route to fabricate auto-motive exhaust valves of γ-TiAI based alloys, but information available on the metal flow and the temperature changeseduring mould filling and solidification process for the ISC process is meager. A sequentially coupled mathematical flow-thermal model, based on the commercial finite-volume/finite-difference code FLOW-3D and the finite-element code PROCAST, has been developed to investigate the ISC process. In term of calcu-lating the flow and temperature fields during the filling and solidification stages, potential defects including the gas bubbles and the surface air entrainment occurred in the mould filling process and the shrinkage porosities formed in the solidification process are predicted and the reasons for the formation of these defects are also analyzed. The effects of filling pressure difference control methods and moulds on gas bubble and surface air entrainment behavior are presented. It is found that by changing the filling pressure difference control methods from general suction casting to ＂air leakage＂ suction casting and reducing air leakage flow rates, the gas bubbles are eliminated effectively, and the surface air entrainment attenuate dramatically. With resort to a mould with a tetragonal runner, the surface air entrainment decrease to the lowest level. Finally, the water analogue and suction casting experiments of exhaust valves are implemented for further validation of the simulation results.
文摘Leakage due to wear is one of the main failure modes of aero-hydraulic spool valves. This paper established a practical coupling wear model for aero-hydraulic spool valves based on dynamic system modelling theory. Firstly, the experiment for wear mechanism verification proved that adhesive wear and abrasive wear did coexist during the working process of spool valves. Secondly coupling behavior of each wear mechanism was characterized by analyzing actual time-variation of model parameters during wear evolution process. Meanwhile, Archard model and three-body abrasive wear model were utilized for adhesive wear and abrasive wear, respectively. Furthermore, their coupling wear model was established by calculating the actual wear volume. Finally, from the result of formal test, all the required parameters for our model were obtained. The relative error between model prediction and data of pre-test was also presented to verify the accuracy of model, which demonstrated that our model was useful for providing accurate prediction of spool valve's wear life. (C) 2016 The Authors. Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.
基金This project is supported by National Natural Science Foundation of China(No.59975031).
文摘The flow characteristics and cavitation effects of water passing throughsmall sharp-edged cylindrical orifices and valves of different shapes in water hydraulics areinvestigated. The test results using orifices with different aspect ratios and different diametersshow that the flow coefficients in the case of non-cavitating flow are larger than that of flow inthe case of cavitation occurrence. The flow coefficients of flow with cavitation initially decreaseas Reynolds number increases and ultimately tend to be of constant values close to contractioncoefficient. Large aspect ratio has an effect of suppressing cavitation. The experimental resultsabout disc valves illustrate that the valves with sharp edge at large opening are less affected bycavitation than that at small opening. Throttle with triangle notch has better anti-cavitationability than that with square notch. The flowrate of the throttle with square notch is significantlyaffected by the flow direction or the flow passage shape.
基金the National Natural Science Foundation of China through Grant No.51805470the Fundamental Research Funds for the Central Universities through Grant No.2018QNA4013the Youth Funds of the State Key Laboratory of Fluid Power and Mechatronic Systems(Zhejiang University)through Grant No.SKLoFP-QN-1801.
文摘Valves are widely used in various working conditions for their flow control functions,and the cavitation inside valves has been investigated owing to its harm to the valve itself and the connecting downstream parts.This paper presents a comprehensive review of the progress that has been achieved in the past years about cavitation in valves including both mechanical heart valves and control valves.The review is divided in the following parts,namely the location where there is a high possibility of the occurrence of cavitation,the parameters that affect cavitation intensity,and the methods to minimize cavitation intensity.It should be noticed that although simulation has been widely used,advanced experiments are still needed in order to obtain accurate analysis of cavitation in valves and the cavitation model still needs to be improved.
基金Supported by National Natural Science Funds of ChinaNo.81101566+4 种基金Scientific Funds of Shanghai Government11DZ228040012QA1400600XYQ201101711411950500
文摘AIM:To investigate the clinical advantages of the stent-laparoscopy approach to treat colorectal cancer(CRC)patients with acute colorectal obstruction(ACO).METHODS:From April 2008 to April 2012,surgeryrelated parameters,complications,overall survival(OS),and disease-free survival(DFS)of 74 consecutive patients with left-sided CRC presented with ACO who underwent self-expandable metallic stent(SEMS)placement followed by one-stage open(n=58)or laparoscopic resection(n=16)were evaluated retrospectively.The stent-laparoscopy group was also compared with a control group of 96 CRC patients who underwent regular laparoscopy without ACO between January 2010 and December 2011 to explore whether SEMS placement influenced the laparoscopic procedure or reduced long-term survival by influencing CRC oncological characteristics.RESULTS:The characteristics of patients among these groups were comparable.The rate of conversion to open surgery was 12.5%in the stent-laparoscopy group.Bowel function recovery and postoperative hospital stay were significantly shorter(3.3±0.9 d vs 4.2±1.5 d and 6.7±1.1 d vs 9.5±6.7 d,P=0.016 and P=0.005),and surgical time was significantly longer(152.1±44.4 min vs 127.4±38.4 min,P=0.045)in the stent-laparoscopy group than in the stent-open group.Surgery-related complications and the rate of admission to the intensive care unit were lower in the stent-laparoscopy group.There were no significant differences in the interval between stenting and surgery,intraoperative blood loss,OS,and DFS between the two stent groups.Compared with those in the stentlaparoscopy group,all surgery-related parameters,complications,OS,and DFS in the control group were comparable.CONCLUSION:The stent-laparoscopy approach is a feasible,rapid,and minimally invasive option for patients with ACO caused by left-sided CRC and can achieve a favorable long-term prognosis.
基金financially supported by the National Natural Science Foundation of China (Nos. 11174020, 51331002, and 51371027)the Fundamental Research Funds for the Central Universities FRF-SD-12-011A
文摘Pseudo spin valves（SVs） exhibiting perpendicular magnetic anisotropy were prepared by magnetron sputtering. Magnetization measurements of the Co/Pt multilayers were performed to select the reference and free layers. The selection criteria are square magnetic hysteresis loops, weaker current shunting effect, and proper coercivity. The optimal reference layer and free layer are Pt（5.0 nm）/[Co（0.4 nm）/Pt（0.6 nm）]3/Co（0.4 nm）/Cu（3.0 nm）and Cu（3.0 nm）/[Co（0.4 nm）/Pt（1.5 nm）]4, respectively.The resulting pseudo SV exhibits two well-separated hysteresis loops when the field is applied perpendicular to the film plane. The minor hysteresis loop corresponding to the free layer shifts toward negative direction of the magnetic field axis, indicating ferromagnetic interlayer exchange coupling between the two magnetic layers. The coupling also enhances the coercivity（HC） of both layers. The perpendicular giant magnetoresistance（GMR） of 2.7 % is achieved with current in plane measurement. The GMR first increases when Pt seed layer is thickened, reaches a maximum of 3.0 % at 4 nm and then decreases with the further increase of thickness. But thicker Cu spacer layer always lowers the GMR of the SV.
