Isogeometric Analysis of Hyperelastic Material Characteristics for Calcified Aortic Valve

This study explores the implementation of computed tomography(CT)reconstruction and simulation techniques for patient-specific valves,aiming to dissect the mechanical attributes of calcified valves within transcatheter heart valve replacement(TAVR)procedures.In order to facilitate this exploration,it derives pertinent formulas for 3D multi-material isogeometric hyperelastic analysis based on Hounsfield unit(HU)values,thereby unlocking foundational capabilities for isogeometric analysis in calcified aortic valves.A series of uniaxial and biaxial tensile tests is executed to obtain an accurate constitutive model for calcified active valves.To mitigate discretization errors,methodologies for reconstructing volumetric parametric models,integrating both geometric and material attributes,are introduced.Applying these analytical formulas,constitutive models,and precise analytical models to isogeometric analyses of calcified valves,the research ascertains their close alignment with experimental results through the close fit in displacement-stress curves,compellingly validating the accuracy and reliability of the method.This study presents a step-by-step approach to analyzing themechanical characteristics of patient-specific valves obtained fromCT images,holding significant clinical implications and assisting in the selection of treatment strategies and surgical intervention approaches in TAVR procedures.

Predictive value of preoperative cardiopulmonary exercise testing on early outcomes of pulmonary valve replacement after repair of Tetralogy of Fallot

Objective Cardiopulmonary exercise testing(CPET)is helpful to identify right ventriclar(RV)dysfunction in patients with rapair of Tetralogy of Fallot(rTOF),but its predictive value on early outcomes of pulmonary valve replacement(PVR)of these patients is unclear when similar preoperative ventricular size and function in cardiovascular magnetic resonance(CMR)exist.The aim of this study is to evaluate whether CPET is useful to predict the early outcomes of rTOF patients after PVR.

General Consideration of Measuring System for Operational Test of Thyristor Valves of Ultra High Voltage DC Power Transmission

Thyristor valve is one of the key equipments for ultra high voltage direct current(UHVDC) power transmission projects.Before being installed on site,they need to be tested in a laboratory in order to verify their operational performance to satisfy the technical specification of project related.Test facilities for operational tests of thyristor valves are supposed to enable to undertake more severe electrical stresses than those being applied in the thyristor valves under test(test objects).On the other hand,the stresses applied into the test objects are neither higher nor lower than specified by the specification,because inappropriate stresses applied would result in incorrect evaluation of performance on the test objects,more seriously,would cuase the damage of test objects with expensive cost losing.Generally,the process of operational tests is complicated and performed in a complex synthetic test circuit(hereafter as STC),where there are a lot of sensors used for measuring,monitoring and protection on line to ensure that the test circuit functions in good condition.Therefore,the measuring systems embedded play a core role in STC,acting like "eyes".Based on the first project of building up a STC in China,experience of planning measuring systems is summarized so as to be referenced by related engineers.

TEST METHOD OF HIGH-SPEED ON-OFF VALVE DYNAMIC CHARACTERISTICS

According to the valve port features of high speed on-off valve and its actions, the valve port can be simplified into an a-type half bridge construction. A method that tests the dynamic characteristics of the high speed on-off valve by the output pressure signal of the a-type half bridge is proposed. Having analyzed the factors related to the dynamic characteristics of an a-type half bridge, a rule for designing the outlet chamber＇s volume is worked out. According to the rule, a test stand is built to test the self-developed high-speed on-off valve. From the test results, it can be seen that with the outlet chamber＇s volume controlled by the rule the rise time of the pressure signals driven by signals with different frequencies changes very little. The test results conform to the simulation results, which nroves the correctness of the method.

Properties analysis of a large flow-rate safety valve test device

In order to solve the problem of property test of large flow-rate safety, the property parameter of safety valve test system was analyzed, and a device for property oflarge flow-rate safety valve test was designed.The device used accumulators as power source and a united function cylinder, which can realized the large flow-rate output for the test system.Analyzed the test data and made a particular research on the test device by testing different flow-rate safety valves;it verifies that the test device can be used tode-sign larger flow-rate safety valve test system and can make the flow-rate test and analysis and dynamic characteristics for the large-flow safety valve.

Ileocecal valve dysfunction in small intestinal bacterial overgrowth: A pilot study

AIM: To explore whether patients with a defective ileocecal valve (ICV)/cecal distension reflex have small intestinal bacterial overgrowth. METHODS: Using a colonoscope, under conscious sedation, the ICV was intubated and the colonoscope was placed within the terminal ileum (TI). A manometry catheter with 4 pressure channels, spaced 1 cm apart, was passed through the biopsy channel of the colonoscope into the TI. The colonoscope was slowly withdrawn from the TI while the manometry catheter was advanced. The catheter was placed across the ICV so that at least one pressure port was within the TI, ICV and the cecum respectively. Pressures were continuously measured during air insufflation into the cecum, under direct endoscopic visualization, in 19 volunteers. Air was insufflated to a maximum of 40 mmHg to prevent barotrauma. All subjects underwent lactulose breath testing one month after the colonoscopy. The results of the breath tests were compared with the results of the pressures within the ICV during air insufflation. RESULTS: Nineteen subjects underwent colonoscopy with measurements of the ICV pressures after intubation of the ICV with a colonoscope. Initial baseline readings showed no statistical difference in the pressures of the TI and ICV, between subjects with positive lactulose breath tests and normal lactulose breath tests. The average peak ICV pressure during air insufflation into the cecum in subjects with normal lactu-lose breath tests was significantly higher than cecal pressures during air insufflation (49.33 ± 7.99 mmHg vs 16.40 ± 2.14 mmHg, P = 0.0011). The average percentage difference of the area under the pressure curve of the ICV from the cecum during air insufflations in subjects with normal lactulose breath tests was significantly higher (280.72% ± 43.29% vs 100% ± 0%, P = 0.0006). The average peak ICV pressure during air insufflation into the cecum in subjects with positive lactulose breath tests was not significantly different than cecal pressures during air insufflation 21.23 ± 3.52 mmHg vs 16.10 ± 3.39 mmHg. The average percentage difference of the area under the pressure curve of the ICV from the cecum during air insufflation was not significantly different 101.08% ± 7.96% vs 100% ± 0%. The total symptom score for subjects with normal lactulose breath tests and subjects with positive lactu-lose breath tests was not statistically different (13.30 ± 4.09 vs 24.14 ± 6.58). The ICV peak pressures during air insufflations were significantly higher in subjects with normal lactulose breath tests than in subjects with positive lactulose breath tests (P = 0.005). The average percent difference of the area under the pressure curve in the ICV from cecum was significantly higher in subjects with normal lactulose breath tests than in subjects with positive lactulose breath tests (P = 0.0012). Individuals with positive lactulose breath tests demonstrated symptom scores which were significantly higher for the following symptoms: not able to finish normal sized meal, feeling excessively full after meals, loss of appetite and bloating. CONCLUSION: Compared to normal, subjects with a positive lactulose breath test have a defective ICV cecal distension reflex. These subjects also more commonly have higher symptom scores.

An Operational Test Method for VSC-HVDC Valves Based on Modular Multi-level Converters

为给基于模块化多电平换流器（modular multi-levelconverter,MMC）的电压源换流器高压直流输电（voltagesourced converter HVDC,VSC-HVDC）换流阀提供有效的检验手段,以验证其设计的正确性及其运行可靠性,对换流阀的运行特性和关键应力进行分析,提出基于原理等效的MMC阀运行试验方法,设计试验电路并阐明其运行机理。搭建的PSCAD电磁暂态仿真模型和实际的试验验证证明了试验方法的正确性和有效性。

In vitro bench testing using patient-specific 3D models for percutaneous pulmonary valve implantation with Venus P-valve

Background:Due to the wide variety of morphology,size,and dynamics,selecting an optimal valve size and location poses great difficulty in percutaneous pulmonary valve implantation(PPVI).This study aimed to report our experience with in vitro bench testing using patient-specific three-dimensional(3D)-printed models for planning PPVI with the Venus P-valve.Methods:Patient-specific 3D soft models were generated using PolyJet printing with a compliant synthetic material in 15 patients scheduled to undergo PPVI between July 2018 and July 2020 in Central China Fuwai Hospital of Zhengzhou University.Results:3D model bench testing altered treatment strategy in all patients(100%).One patient was referred for surgery because testing revealed that even the largest Venus P-valve would not anchor properly.In the remaining 14 patients,valve size and/or implantation location was altered to avoid valve migration and/or compression coronary artery.In four patients,it was decided to change the point anchoring because of inverted cone-shaped right ventricular outflow tract(RVOT)(n=2)or risk of compression coronary artery(n=2).Concerning sizing,we found that an oversize of 2-5 mm suffices.Anchoring of the valve was dictated by the flaring of the in-and outflow portion in the pulmonary artery.PPVI was successful in all 14 patients(absence of valve migration,no coronary compression,and none-to-mild residual pulmonary regurgitation[PR]).The diameter of the Venus P-valve in the 3D simulation group was significantly smaller than that of the conventional planning group(36[2]vs.32[4],Z=-3.77,P<0.001).Conclusions:In vitro testing indicated no need to oversize the Venus P-valve to the degree recommended by the balloon-sizing technique,as 2-5 mm sufficed.

Investigation into Equivalency of Synthetic Test Circuit Used for Operational Tests of Thyristor Valves for UHVDC

With the growth of capacity of high voltage direct current(HVDC) transmission lines,the ratings of thyristor valves,which are one of the most critical equipments,are getting higher and higher.Verification of performance of thyristor valves particularly designed for HVDC project plays an important role in the handover of products between the manufacturer and the client.Conventional test facilities based on philosophy of direct test cannot meet the requirements for modern thyristor valves.New test facilities with high ratings are necessarily built based on philosophy of synthetic test.Over the conventional direct test circuit,the later is an economical and feasible solution with less financial investment and higher test capability.However,the equivalency between the synthetic test and the direct test should be analyzed technically in order to make sure that the condition of verification test in a synthetic test circuit should satisfy the actual operation condition of thyristor valves existing in a real HVDC project,just as in a direct test circuit.Equivalency analysis is focused in this paper,covering the scope of thyristor valves' steady state,and transient state.On the basis of the results achieved,a synthetic test circuit of 6 500 A/50 kV for operational tests of thyristor valves used for up to UHVDC project has newly been set up and already put into service in Xi'an High Voltage Apparatus Research Institute Co.,Ltd.(XIHARI),China.Some of the results have been adopted also by a new national standard of China.

Parameters Sensitivity Characteristics of Highly Integrated Valve-Controlled Cylinder Force Control System

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.

Simulation of semisolid diecasting process of four-way valve of HPb59-1 alloy for air-conditioner

There exist many problems in producing four-way valve of HPb59-1 alloy for an air-conditioner by traditional solid state hot forging,i.e.larger forming loads,lower material utilization,larger subsequent machining allowance and nonuniform microstructure.For this reason,based on the orthogonal test,the semisolid diecasting process of a certain type of four-way valve was simulated with FLOW-3D.The simulation results show that the optimized process parameters are:the pouring temperature of 897.25 ?C,the shot velocity of 2.0 m/s and the preheated die temperature of 260 C.The simulation results demonstrate that the cavity can be filled smoothly and completely,the surface defects are small,the temperature field and the pressure field are uniform,and the casting quality is satisfactory.The effectiveness and availability of applying this technology are well verified by the numerical simulation.

Theoretical analysis and experimental study on the dynamic behavior of a valve pipeline system during an earthquake

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.

An experimental study on flowrate and stability for 600MW supercritical steam-turbine control valve

An experimental study on flowrate and stability of a type of control valve of 600MW supercritical steam-turbine was presented by measuring instruments of static, dynamic pressure and vibration in self-designed test rig. The investigation shows that flow coefficient is 30% up more than that of the control valve of GX-1 type used widely in domestic power plants now, as small-medium lifts. If the relative lift (h/D) is less than 20%, the valve can always work steadily in all the pressure ratios. When the h/D is between 20% to 24%, big vibration of valve stem occurs if the pressure ratio is between 0.7 to 0.8. When h/D is more than 25%, relatively great vibration happens in a wide range of pressure ratios of 0.4 to 0.85.

Mechanism of change in cardiac function after mitral valve replacement

Left ventricular contractility was measured using Doppler echocardiography in 37 pa-tients with rheumatic mitral valve disease.Myocardial pathological lesions were studied quanti-tatively by means of the image analysis system and light microscopic examination.The resultsshowed that attenuated cardiac function is due to pathological change of the mitral valve andpathological lesions of the left ventrieular myocardium including increased interstitial fibrosis,thickened intramyocardial arterial wall leading to concentric narrowing of the lumen,hyper-trophic myocardial fiber and endocardial proliferation.Since mitral valve replacement can notcorrect the irreversible myocardial pathological lesions,perioperative protection of the my-ocardium should be emphasized,and intraoperative injury to the myocardium should be mini-mized as far as possible.

The Characterization of Aortic Valve Calcification at Different Stage of Disease

Cardiac valve calcification is a common disease,especially among the elderly.Calcification can affect valve function and cause heart failure and sudden death(Adler et al.,2002).Aortic valve calcification is alsorelated to arteriosclerosis and coronary heart disease(Rashedi et al.,2015).However,the origin of valve calcification is still unclear.This study characterized the

Isolated Rheumatic Pulmonary Valve Disease—Case Reports

Rheumatic heart disease (RHD) is the most common cause of acquired heart disease in children and young adults worldwide and particularly developing countries continuing to experience a high incidence of this disease. The unexpected increase in the incidence of the disease in certain areas may explain the clinical and epidemiological characteristics of this disease. The key manifestation of RHD is the cardiac valvular abnormalities characterized principally by deforming the layered and avascular leaflet architecture due to inflammation and subsequent diffuse fibrosis. Mitral valve is mostly involved and pulmonary valve is rarely affected. Background of these case reports highlighted the increased incidence of rheumatic pulmonary valve disease in Thoothukudi region of India in Tamil Nadu state.

伺服阀旋转直驱超声电机机理与特性

针对某旋转直驱式伺服阀对驱动电机小长径比紧凑型结构形式的设计要求,从伺服阀功率级200 Hz动态响应需求出发,设计了一款环形行波型超声电机。分析了超声电机的基本工作原理并建立了超声电机定子转子摩擦传动模型,搭建了超声电机特性测试实验台并进行了转矩-转速测试,实验结果与仿真结果一致,验证了电机设计的合理性。在此基础上,进行了超声电机驱动频率和驱动电压的影响特性分析,结果表明超声电机在49.8 kHz的驱动频率下具有最大的工作效率,驱动电压大于110 V时可以满足伺服阀转速与转矩工作需求,并且在49.8 Hz的驱动频率和110 V驱动电压条件下可以接近最大的工作效率。

机械反馈式伺服阀流量测试动态缸参数选用分析

相比电反馈伺服阀动态特性可直接通过阀芯位移响应测试获得,机械反馈式流量伺服阀的动态特性,通常需利用动态缸作为流量传感器间接测量获得。测试结果受动态缸泄漏、阻尼、质量惯性等固有非理想化因素的影响,通常无法准确表达伺服阀本身的性能指标。基于一套实际阀控缸系统,建立Matlab-Simulink仿真模型,解析获得的频带宽结果相比实测结果误差小于0.5%,由此建立了可准确表达阀与缸性能特性的仿真模型。在此基础上,理论给出了伺服阀本身的频率特性指标,即无泄漏无阻尼及无限刚度动态缸条件下的系统频率特性。以此为依据,分析了实际动态缸活塞质量、活塞粘性阻尼以及泄漏变化情况下,阀控缸系统频率特性偏离理想条件的变化规律。

隔爆型电磁铁力-行程特性的优化分析及验证

防爆阀是石油勘探等井下液压设备常用的核心控制元件。现有防爆阀常采用的隔爆型电磁铁体积相对较大,难以充分发挥液压元件及系统功重比大的优势。基于防爆阀可靠性的要求,在不增大矿用防爆阀外形尺寸的前提下,分别研究了衔铁高径比、隔磁环位置、上端隔磁角对隔爆型电磁铁力-行程特性的影响。基于L_(9)(3^(4))正交试验,采用极差分析法获得了试验因素影响程度大小以及选择范围内最佳的结构参数组合。结果表明:当隔爆型电磁铁结构参数衔铁高径比为2.03,隔磁环位置距参考点位置下移0.5 mm,上端隔磁角30°时电磁力-行程特性曲线最佳,为隔爆型电磁铁的结构参数优化提供了指导,并通过对比试验验证了隔爆型电磁铁结构设计的合理性和可行性。

经导管缘对缘修复二尖瓣的体外流体力学性能评价

目的建立一套适用于离体二尖瓣体外测试的方法,定量评价国产经导管缘对缘修复术(TEER)对功能性二尖瓣反流(FMR;非A2-P2反流)的修复效果。方法本研究通过对离体猪二尖瓣瓣环扩张和乳头肌非对称移位建立模拟真实解剖结构的FMR病理模型(非A2-P2反流)。使用离体二尖瓣脉动流测试系统,测试6个FMR病理瓣膜经国产TEER器械修复前、后,不同生理和病理条件下的流体力学特征。结果病理瓣膜由修复前的中-重度及重度反流下降到修复后的轻度及轻-中度反流[反流分数(60.2±17.5)%比(34.7±12.0)%,P<0.001],差异有统计学意义。表征瓣膜正向流性能的EOA[(3.8±1.6)cm^(2)比(2.2±0.5)cm^(2),P<0.001]和正向跨瓣压差[(1.8±1.3)mmHg比(3.8±1.8)mmHg,P<0.001]修复前、后比较,差异均有统计学意义。修复带来一定程度上的瓣膜狭窄,有效孔口面积降低约40%,正向跨瓣压差升高约110%,但瓣膜正向流性能仍处于正常生理范围内,未造成医源性狭窄。结论证实国产TEER器械对于治疗FMR(非A2-P2反流)具有良好的修复效果。本研究为TEER器械的设计、优化及可靠性和有效性的验证、评价提供了全面的数据和有效的测试方法,同时也为该类产品测试相关标准的制订提供了可参考的资料。