Pressure Valve Research Articles

Study of the Relationship between Pulmonary Artery Pressure and Heart Valve Vibration Sound Based on Mock Loop.

The vibration of the heart valves' closure is an important component of the heart sound and contains important information about the mechanical activity of a heart. Stenosis of the distal pulmonary artery can lead to pulmonary hypertension (PH). Therefore, in this paper, the relationship between the vibration sound of heart valves and the pulmonary artery blood pressure was investigated to contribute to the noninvasive detection of PH. In this paper, a lumped parameter circuit platform of pulmonary circulation was first set to guide the establishment of a mock loop of circulation. By adjusting the distal vascular resistance of the pulmonary artery, six different pulmonary arterial pressure states were achieved. In the experiment, pulmonary artery blood pressure, right ventricular blood pressure, and the vibration sound of the pulmonary valve and tricuspid valve were measured synchronously. Features of the time domain and frequency domain of two valves' vibration sound were extracted. By conducting a significance analysis of the inter-group features, it was found that the amplitude, energy and frequency features of vibration sounds changed significantly. Finally, the continuously varied pulmonary arterial blood pressure and valves' vibration sound were obtained by continuously adjusting the resistance of the distal pulmonary artery. A backward propagation neural network and deep learning model were used, respectively, to estimate the features of pulmonary arterial blood pressure, pulmonary artery systolic blood pressure, the maximum rising rate of pulmonary artery blood pressure and the maximum falling rate of pulmonary artery blood pressure by the vibration sound of the pulmonary and tricuspid valves. The results showed that the pulmonary artery pressure parameters can be well estimated by valve vibration sounds.

Design and research of a valve-based piezoelectric pump with low forward resistance and high reverse shutoff

This paper proposes, designs, manufactures and experimentally studies a wedge valve piezoelectric pump driven by a double displacement amplifier vibrator (DDAV). A novel wedge valve is designed, manufactured and analyzed, and the static performance of the wedge valve is tested. The test results show that it has less forward resistance and high reverse shutoff. The DDAV and pump body are designed, and the test experimental platform is built. Results indicate that the static opening pressure of the wedge valve is 0.27 kPa, and the reverse shutoff pressure can reach 200 kPa. When the driving voltage is 700 Vpp and the driving frequency is 425 Hz, the maximum flow rate is 491.2 ml min−1 and the maximum output pressure is 160 kPa.

Programmable Versus Differential Pressure Ventriculoperitoneal Shunts for Pediatric Hydrocephalus: A 20-Year Single-Center Experience From Saudi Arabia.

Background Shunt malfunction is the most common complication after ventriculoperitoneal shunt (VPS) insertion for pediatric hydrocephalus. The incidence of shunt malfunction and the need for VPS revision may be related to the type of valve used in the shunt. Therefore, we aimed to compare the outcome of VPS in the pediatric age group stratified by differential pressure valves (DPV) and programmable shunt valves (PSV). Materials and methods This ethics-approved retrospective study was conducted at a tertiary care hospital in Saudi Arabia. We included 175 children with congenital hydrocephalus who underwent a shunt insertion or revision between 2003 and 2018 and followed them up to December 2022. The VPS complication and revision rates were compared with the patient's demographics and shunt valve types. The Kaplan-Meier method, log-rank test, and univariate and multivariate Cox proportional hazards regression were used to analyze several variables and subsequent shunt revisions. Results Females represented 52% of the study participants, and the mean age of the patients was 21.7 ± 38.4 months. The main indication for VPS was congenital hydrocephalus due to aqueductal stenosis (40%). The differential shunt valve was used in 78.9% and the PSVin 21.1% of the patients. Surgical complications occurred in 33.7% of the patients. Shunt malfunction and infection occurred in 16% and 11.4% of the patients, respectively. The VPS revision rate was significantly lower when PSV was used (odds ratio = 0.39, P < 0.05). Conclusion Overall, one-third of the studied pediatric cohort required shunt revision at some point during the 15-year follow-up. However, children with PSV had fewer revision rate-related complications compared to children with DPV during the first five years of follow-up.

Knockdown of the TRPM4 channel alters cardiac electrophysiology and hemodynamics in a sex- and age-dependent manner in mice.

TRPM4 is a calcium-activated, voltage-modulated, nonselective ion channel widely expressed in various cells and tissues. TRPM4 regulates the influx of sodium ions, thus playing a role in regulating the membrane potential. In the heart, TRPM4 is expressed in both cardiomyocytes and cells of the conductive pathways. Clinical studies have linked TRPM4 mutations to several cardiac disorders. While data from experimental studies have demonstrated TRPM4's functional significance in cardiac physiology, its exact roles in the heart have remained unclear. In this study, we investigated the role of TRPM4 in cardiac physiology in a newly generated Trpm4 knockdown mouse model. Male and female Trpm4 knockdown (Trpm4-/- ) and wild-type mice of different ages (5- to 12- week-old (young) and 24-week-old or more (adult)) were characterized using a multimodal approach, encompassing surface electrocardiograms (ECG), echocardiography recordings, ex vivo ECGs in isolated heart, endocardial mappings, Western blots, and mRNA quantifications. The assessment of cardiac electrophysiology by surface ECGs revealed no significant differences between wild-type and Trpm4-/- young (5- to 12-week-old) mice of either sex. Above 24 weeks of age, adult male Trpm4-/- mice showed reduced heart rate and increased heart rate variability. Echocardiography revealed that only adult male Trpm4-/- mice exhibited slight left ventricular hypertrophic alterations compared to controls, illustrated by alterations of the mitral valve pressure halftime, the mitral valve E/A ratio, the isovolumetric relaxation time, and the mitral valve deceleration. In addition, an assessment of the right ventricular systolic function by scanning the pulmonary valve highlighted an alteration in pulmonary valve peak velocity and pressure in adult male Trpm4-/- mice. Endocardial mapping recordings showed that applying 5 μM of the new TRPM4 inhibitor NBA triggered a third-degree atrioventricular block on 40% of wild-type hearts. These results confirm the key role of TRPM4 in the proper structure and electrical function of the heart. It also reveals differences between male and female animals that have never been reported. In addition, the investigation of the effects of NBA on heart function confirms the role of TRPM4 in atrioventricular conduction.

Obstructive Sleep Apnea.

Obstructive sleep apnea (OSA) is the most common type of sleep-disordered breathing. This article describes advances in the diagnosis, testing, treatment, and monitoring of OSA. Home sleep apnea testing and in-laboratory polysomnography are the most commonly used diagnostic tools in the identification and monitoring of OSA, but new methods for diagnosis and at-home monitoring of treatment response are being developed and validated. While the apnea-hypopnea index is regularly used to define OSA severity, recognition is increasing of its inability to risk-stratify patients. Other sleep study data including arousal threshold, hypoxic burden, and pulse rate variability as well as clinical characteristics can help with risk stratification. The most effective treatment is continuous positive airway pressure (CPAP), which can be limited by adherence and tolerance in some patients. Newer masks and comfort features including heated tubing and expiratory pressure relief may improve tolerance to positive airway pressure (PAP) therapy. Additional treatment options include other PAP modalities, mandibular advancement devices, tongue stimulation therapy, negative inspiratory pressure, nasal expiratory pressure valves, nasal congestion treatments, upper airway surgeries including hypoglossal nerve stimulation, and medications. OSA is a common disorder that causes sleep and daytime symptoms and increases the risk of neurologic and medical complications. Neurologists should be aware of atypical presentations and understand the diagnostic and treatment options.

Aortic Valve Area and Strain Measurements by Cardiac MRI and Transthoracic Echocardiography in Severe Aortic Stenosis with Normal Left Ventricular Function.

Transthoracic echocardiography (TTE) is the recommended imaging technique for the evaluation of patients with aortic stenosis (AS). However, in cases with inconclusive findings, cardiac magnetic resonance (CMR) planimetry is used to grade AS severity. This study aimed to compare the results derived from TTE and CMR in patients with severe AS with normal left ventricular (LV) function. In a prospective study, 20 patients with severe AS were recruited and data derived from TTE and CMR modalities were compared with the archived records of 28 age- and sex-matched healthy controls. The data included aortic valve area (AVA), MRI-derived biventricular global strains, and TTE-derived global longitudinal strain (GLS). SPSS software was used to analyze the data with independent samples t test, intraclass correlation coefficient (ICC), and Pearson correlation. P<0.05 was considered statistically significant. An excellent agreement was found in AVA values derived from CMR and TTE with an average ICC of 0.932 (95% CI=0.829-0.973). There was a significant difference in LV-GLS, LV global radial strain (GRS), right ventricular (RV) GRS, and RV global circumferential strain between the groups. A good correlation was found between CMR- and TTE-derived GLS with an average ICC of 0.721 (95% C=0.255-0.896). The mean aortic valve pressure gradient in TTE had a significant inverse linear correlation with LV-GRS in CMR (r=-0.537). All P values were <0.05. There was a good agreement between AVA and strain values derived from cardiac MRI and TTE. The myocardial strain was impaired in patients with severe AS and normal LV function and correlated with disease severity.

Mobile Crane for Workshop

Abstract: In material handling, the cranes play a vital role in modern manufacturing industries. In our project we aim to fabricate a hydraulic operated floor crane for handling various kinds of materials. The hydraulic floor crane consists of mast, boom, base, lift cylinder, hand lever, hook and wheels. The hydraulic cylinder is pumped with the help of hand lever at the same time the material with the help of hook and hydraulic cylinder released to the pressure valve so the material is unloaded. The material from one place goes to the other place with the help of hydraulic floor crane. The crane reduces the worker’s fatigue and increases the overall efficiency of production process with good safety. The crane is fabricated with complete clear front, small compact frame, good reach, high lift. The crane has the capacity of lifting 250kg to half ton with wide spread application in the shop floor. Thus the floor crane would serve as a safe and versatile model for material handling operations.

Shot-to-Shot Deviation of a Common Rail Injection System Operating with Cooking-Oil-Residue Biodiesel

&lt;div&gt;The shot-to-shot variations in common rail injection systems are primarily caused by pressure wave oscillations in the rail, pipes, and injector body. These oscillations are influenced by fuel physical properties, injector needle movement, and pressure and suction control valve activations. The pressure waves are generated by pump actuation and injector needle movement, and their frequency and amplitude are determined by fluid properties and flow path geometry. These variations can result in cycle-to-cycle engine fluctuations. In multi-injection and split-injection strategies, the pressure oscillation from the first shot can impact the hydraulic characteristics of subsequent shots, resulting in variations in injection rate and amount. This is particularly significant when using alternative fuels such as biodiesel, which aim to reduce emissions while maintaining fuel atomization quality. This study examines the shot-to-shot variations in a second-generation common rail system using cooking-oil-residue biodiesel. The results demonstrate that biodiesel properties impact pressure wave oscillation, shot-to-shot variation, and total injection rate. The study also finds that dwell time has a significant effect on the hydraulic characteristics of the second shot, with minimal influence up to a certain value. However, beyond a certain dwell time value (e.g., 0.8 ms in this study), the impact of dwell time on the pressure fluctuation generated by the second shot is limited. Conducting further research could help deepen our understanding of the influence of shot-to-shot deviations. This could involve exploring biodiesel spray characteristics using techniques such as shadowgraph imaging and studying the effect of these deviations on flame propagation and emission formation. Examining engine performance could also provide valuable insights into the effectiveness of the split-injection strategy and biodiesel blends. Additionally, characterizing biodiesel spray using the double-shot technique to examine spray penetration, cone angle, and/or spray impingement and combustion characteristics could be useful in linking it with the shot-to-shot variation investigated in this study. Such research can contribute to advancing the state-of-the-art knowledge on this topic.&lt;/div&gt;

Left atrial function assessed by speckle tracking echocardiography as a marker of atrial reverse remodeling in patients with mitral regurgitation treated with transcatheter edge-to-edge repair

Abstract Funding Acknowledgements Type of funding sources: None. Background Left atrial reverse remodeling has been defined relying on changes in left atrial volume following specific procedures. Little is known about functional assessment of the left atrium by left atrial strain and left atrial emptying fraction (LAEF) following edge-to-edge mitral repair. Purpose The aim of this study is to assess left atrial function by speckle tracking echocardiography and changes in LAEF, as markers of atrial reverse remodeling, in patient with mitral regurgitation treated with edge-to-edge repair technique. Methods A total of 35 patients diagnosed with severe functional or organic mitral regurgitation who underwent trans-catheter edge-to-edge mitral valve repair were selected. Demographic, clinical and echocardiographic data were collected at the time of enrollment and after a minimum follow-up of six months. The primary endpoint was to assess if left atrial speckle tracking echocardiographic parameters (LASr, LAScd, LASct) and changes in LAEF were reliable indicators of left atrial reverse remodeling, defined as a reduction in indexed left atrial volume ≥ 15% with respect to basal assessment. Collaterally, we tried to identify clinical and standard echocardiographic parameters significantly related to atrial reverse remodeling. Changes between baseline and follow-up parameters were assessed using paired t-test. Results LASr, LASct and LAEF improved significantly in patients with left atrial remodeling during follow-up (LASr: 15,8%±8,43 vs 19,7%±12,22 - P 0,047; LASct: −6,4%±6,21 vs − 9,9%±8,52 - P 0,036; LAEF: 35,5%±14,17 vs 44,1%±15,17 - P 0,003). Collaterally, among all demographics, clinical and echocardiographic data, the absence of coronary artery disease, a systolic dominant pulmonary vein flow, as assessed with pulse-wave-Doppler after the repair, therapy with ACEi/ARB, lower increases in mitral valve pressure gradient after the procedure and lower pulmonary artery systolic pressure at discharge significantly correlated with reverse atrial remodeling. Conclusions In patients with mitral regurgitation treated with edge-to-edge repair, the assessment of left atrial function by speckle tracking echocardiography and left atrial emptying fraction correlates with atrial reverse remodeling, after a minimum follow-up of six months from the procedure. Further studies are needed to better clarify the impact of left atrial remodeling on strong clinical outcomes in patient with mitral regurgitation treated with edge-to-edge repair technique and the role of functional parameters in the definition of the optimal candidate and timing for the repair.

Evaluation of Overshunting between Low and Medium Pressure Ventriculoperitoneal Shunts in Dogs with Severe Hydrocephalus Using Frameless Stereotactic Ventricular Shunt Placement

Hydrocephalus is a neurological disorder characterized by an abnormal accumulation of cerebrospinal fluid (CSF) within the ventricular system of the brain, leading to cerebral ventricular dilation, brain parenchyma compression, and neuronal cell loss. Surgery is an effective method of draining excessive amounts of CSF. Ventriculoperitoneal shunt (VPS) allows excess CSF to divert into the abdomen; this device is the most commonly used in the treatment of hydrocephalus both in veterinary and human patients. This study aims to describe the application of two types of VPS, low-pressure valve and medium-pressure valve, using a frameless stereotactic neuronavigational system in eight severe hydrocephalus in dogs and, in particular, analyze the prevalence of postoperative overshunting. Non-communicating hydrocephalus was found in seven dogs, whereas the rest of them had communicating hydrocephalus caused by traumatic brain injury with a skull fracture. The criteria for pressure valve selection depended on the intraoperative intraventricular pressure (IVP) that was determined by the adaptive manometer, according to the human protocol. Low-pressure valve placement was performed in five dogs, and the others received medium-pressure valve placement. The follow-up period was 2 weeks, 4–12 weeks, and 12 weeks to 12 months. Pre- and postoperative information including neurological signs, CT-Scan or MRI, medical treatment, complications, and ventricular volume were compared in all dogs. Seven dogs showed neurological improvement within 2 weeks after surgery. Overshunting was seen in four dogs who received low-pressure valve placement. Three of them had shunt infections within 4 to 6 weeks after surgery. One dog underwent shunt revision from a low-pressure valve to a medium-pressure valve caused by severe overshunting and progressive neurological signs. In addition, cognitive and learning improvements were evaluated based on the owners’ feedback, and neurological signs were examined during the follow-up period in two dogs that received low-pressure valve placement. We conclude that a medium-pressure valve is recommended for overshunting prevention. However, low-pressure valve placement seems to improve cognitive function and learning ability, which is related to an increase in the brain parenchyma observed during long-term monitoring. Moreover, we also report our experience and surgical procedure for frameless stereotactic ventricular shunt placement (FSVSP) in VPS surgery in dogs affected by hydrocephalus.

Helmet Continuous Positive Airway Pressure in the Emergency Department: A Practical Guide

Helmet continuous positive airway pressure is a simple, noninvasive respiratory support strategy to treat several forms of acute respiratory failure, such as cardiogenic pulmonary edema and pneumonia. Recently, it has been largely used worldwide during the COVID-19 pandemic. Given the increased use of helmet continuous positive airway pressure in the emergency department, we aimed to provide an updated practical guide for nurses and clinicians based on the latest available evidence. We focus our attention on how to set the respiratory circuit. Moreover, we discuss the interactions between flow generators, filters, and positive end-expiratory pressure valves and the consequences regarding the delivered gas flow, fraction of inspired oxygen, positive end-expiratory pressure, and noise level.

An air supply system regulation method for PEMFCs based on disturbance observation and MPC control

The optimal tracking control of air pressure and air flow is an important guarantee to improve the output characteristics of fuel cells. However, under the load disturbances scenario, the optimal control effect is difficult to guarantee. In order to solve this problem, this paper proposes a new control method based on real-time disturbances observation and MPC optimal control. The decoupling of air pressure and air flow is realized by feedback linearization, and then an extended state observer is designed to achieve accurate estimation of load disturbances. Based on the principle of optimal output power of the fuel cell system, the reference trajectory of air pressure and air flow is obtained. Based on this, the optimal MPC controller is designed to achieve accurate tracking of air pressure and air flow by controlling the motor voltage of the air compressor and the opening of the back pressure valve. Under load disturbances, compared with feedback linearization control, improved tracking and robust performances of the proposed strategy can be exhibited through offline and online tests, the net power of PEMFCs is increased by 3%.

Stepwise Add-on and Endotype-informed Targeted Combination Therapy to Treat Obstructive Sleep Apnea: A Proof-of-Concept Study.

Oral appliance therapy (OAT) is an effective treatment for many people with obstructive sleep apnea (OSA). However, OSA pathogenesis is heterogenous and in ~50% of cases, OAT does not fully control OSA. This study aimed to control OSA in individuals with an incomplete response to OAT alone by using additional targeted therapies informed by OSA endotype characterization. Twenty-three people with OSA (apnea-hypopnea index (AHI): 41+19 events/h) not fully resolved (AHI>10 events/h) with oral appliance therapy alone were prospectively recruited. OSA endotypes were characterized pre-therapy during a detailed physiology study night. Initially, an expiratory positive airway pressure valve (EPAP) and supine-avoidance device therapy were added to target the impaired anatomical endotype. Those with residual OSA (AHI>10 events/h) then received one or more non-anatomical interventions based on endotype characterization. This included O2 (4L/min) to reduce high loop gain (unstable respiratory control) and 80/5mg atomoxetine-oxybutynin to increase pharyngeal muscle activity. Finally, if required, OAT was combined with EPAP and CPAP therapy. Twenty participants completed the study. OSA was successfully controlled (AHI<10 events/h) with combination therapy in all but one participant (17/20 without CPAP). OAT plus EPAP and supine-avoidance therapy treated OSA in 10 (50%) participants. OSA was controlled in five (25%) participants with the addition of O2 therapy, one with atomoxetine-oxybutynin and one required O2 plus atomoxetine-oxybutynin. Two participants required CPAP for their OSA, another was CPAP intolerant. These novel prospective findings highlight the potential of precision medicine to inform targeted combination therapy to treat OSA. Clinical trial registered with Australian New Zealand Clinical Trials Registry (ACTRN12618001995268).

Influencing factors of prognosis in children with pulmonary atresia with intact ventricle septum after transthoracic balloon dilation of pulmonary valve and construction of a nomograph prediction model

ABSTRACT This study aimed to identify factors that affect the prognosis of children with pulmonary valve atresia and intact ventricular septum treated with transthoracic balloon dilation of the pulmonary valve. The study included 148 participants who were followed up for 5 years. Of these, 10 died, while 138 survived. Independent sample t-test and χ2 test were used to analyze clinical data of children in the death and survival groups. It was found that height, weight, body surface area, arterial oxygen saturation, degree of tricuspid regurgitation, pulmonary valve cross valve pressure difference, ICU length of stay, length of stay, reoperation intervention, and complications were statistically significant (P<0.05). ROC curve analysis of the measurement indicators with statistically significant differences showed that height, weight, body surface area, arterial oxygen saturation, ICU length of stay, and length of stay had AUCs ranging from 0.723 to 0.870. Logistic regression analysis revealed that the degree of tricuspid regurgitation, pulmonary valve cross valvular pressure difference, ICU length of stay, reoperation intervention, and complications were independent risk factors that affect the prognosis of patients with PA/IVS undergoing transthoracic balloon dilation of pulmonary valve. The study proposed a nomogram prediction model using R language software 4.0 ”rms” package, which was validated using calibration curve and decision curve. The model had a C-index of 0.667 (95% CI: 0.643-0.786) and high degree of fit. This study provides clinicians with a prediction model to identify children with poor prognosis after treatment with transpulmonary valve balloon dilatation.

Multifunctional bypass valve for water management and surge protection in a proton-exchange membrane fuel cell supply-air system

A multifunctional valve for air supply was placed downstream of the compressor in a fuel cell system to manage cathode air characteristics under different load changes and configurations. The advantages of using the four-way valve, with different ports for cathode flow, throttling, and bypassing, were analyzed through modeling and simulation. The model focused on the air supply system, which included a centrifugal compressor, intercooler, membrane humidifier, valve, and mixer. The simulation demonstrated that placing the valve right after the compressor was more effective in controlling the compressor surge than a traditional back pressure valve. During compressor surge, opening the throttling port at 18° could suppress the surge and stabilize the cathode flow. The balance between surge protection and stack performance under transient conditions was also discussed, and an optimal valve opening for throttle flow was presented. Furthermore, bypassing the humidifier by 20% of the supply air reduced the cathode inlet relative humidity by the same percentage, contributing to water management in the stack, particularly under flooding conditions.

Transcatheter Aortic Valve Replacement Prognostication with Augmented Mean Arterial Pressure.

Post-transcatheter aortic valve replacement (TAVR) patient outcome is an important research topic. To accurately assess post-TAVR mortality, we examined a family of new echo parameters (augmented systolic blood pressure (AugSBP) and arterial mean pressure (AugMAP)) derived from blood pressure and aortic valve gradients. Patients in the Mayo Clinic National Cardiovascular Diseases Registry-TAVR database who underwent TAVR between 1 January 2012 and 30 June 2017 were identified to retrieve baseline clinical, echocardiographic and mortality data. AugSBP, AugMAP and valvulo-arterial impedance (Zva) (Zva) were evaluated using Cox regression. Receiver operating characteristic curve analysis and the c-index were used to assess the model performance against the Society of Thoracic Surgeons (STS) risk score. The final cohort contained 974 patients with a mean age of 81.4 ± 8.3 years old, and 56.6% were male. The mean STS risk score was 8.2 ± 5.2. The median follow-up duration was 354 days, and the one-year all-cause mortality rate was 14.2%. Both univariate and multivariate Cox regression showed that AugSBP and AugMAP parameters were independent predictors for intermediate-term post-TAVR mortality (all p < 0.0001). AugMAP1 < 102.5 mmHg was associated with a 3-fold-increased risk of all-cause mortality 1-year post-TAVR (hazard ratio 3.0, 95%confidence interval 2.0-4.5, p < 0.0001). A univariate model of AugMAP1 surpassed the STS score model in predicting intermediate-term post-TAVR mortality (area under the curve: 0.700 vs. 0.587, p = 0.005; c-index: 0.681 vs. 0.585, p = 0.001). Augmented mean arterial pressure provides clinicians with a simple but effective approach to quickly identify patients at risk and potentially improve post-TAVR prognosis.

Computational fluid dynamics as a novel method to predict haemodynamic changes and guide transcatheter edge-to-edge repair.

A 78-year-old female with severe mitral regurgitation (MR) presented with heart failure. Due to the high risk of surgery, transcatheter mitral valve edge-to-edge repair (TEER) was introduced. Computational fluid dynamics (CFD) has been widely used for cardiac function assessment. Here, we investigated the haemodynamic changes by using CFD and its predictive values in TEER. The left heart system (LHS) was constructed from computed tomography and transoesophageal echocardiographic (TEE) images (Mimics 19.0, Leuven, Belgium; 3D Slicer software). The haemodynamics of LHS was calculated and visualized by 3D streamlines using the finite volume method and the combination of pressure-Implicit with splitting of operators and semi-Implicit method for pressure linked equations (PIMPLE) algorithm (OpenFOAM software) before the procedure, indicating perfect matching with the TEE view (Panel A). The reverse flow could be observed in the left atrium, and the MR fraction (MRF) calculated by CFD was 52%, similar to the echocardiographic diagnosis (MR 4+). The CFD-simulated mean mitral valve pressure gradient (MVPG) was 1.77 mmHg, consistent with echocardiography (2 mmHg).

TUBING HANGER INVESTIGATION OF LOADING

In this article, the failures of tube hangers made from UNS N07718 are discussed. An arrangement known as a tubing hanger may be found in wells that produce either oil or gas. It is positioned in the upper tubing head’s bowl after it has been installed. The tubing is held in place by this, and a main annulus seal is created between tubing also the production casing. This holds the tubing in place, and at the same time, it creates a primary annulus seal between tubing also production casing. When compared to odd component in wellhead system, tubing hangers are available in a broader range of styles and sizes than any other option. Tubing hangers made of UNS N07718 are often used in the installation process of sour service oil and gas wells that operate under high pressure and also high temperatures. Afterwards more than 10 years of service, it was only recently found that the tubing hanger made of UNS N07718 had failed in sour wells. Failures of the tubing hanger will inference in substantial production delays as well as high workover expenses. The purpose of this research is to demonstrate the failure mechanism of tubing hanger furthermore its ramifications on existing wells that were erected with material that is comparable to what was used here. In order to establish what caused the failure, each and every exposure that was brought on by well intervention efforts was evaluated. The manner of failure of stringer head suspension was researched, as was its influence on already existing wells that had been erected with materials that were comparable. Keywords: tubing head, tubing hanger, tubing thread, back pressure valve profile, landing shoulder, snap ring, running thread,

Association between coronary flow and aortic stenosis during transcatheter aortic valve implantation.

In patients with aortic stenosis (AS), the coronary flow reserve decreases even in the absence of epicardial coronary artery stenosis. Systolic coronary flow reversal (SFR) reflecting reduced coronary microcirculation, often seen in patients with severe AS, has a potential negative impact on the pathogenesis of cardiac dysfunction. However, there are limited data on the relationship between the severity of AS and SFR, as well as on the benefits of transcatheter aortic valve implantation (TAVI). The aim of this study was to evaluate the relationship between the severity of AS and efficacy of TAVI in improving SFR. Consecutive patients with AS who had undergone TAVI using transoesophageal echocardiography (TEE) from November 2020 to February 2022 were prospectively enrolled. Coronary flow in the left anterior descending artery as well as the aortic valve peak velocities, and the mean aortic valve pressure gradients (AVPGs), indicating the severity of AS, were measured using intraprocedural TEE before and after TAVI. The following parameters were measured as coronary flow: systolic and diastolic peak velocity (cm/s) and systolic and diastolic velocity-time integral (VTI) (cm). SFR was defined as the presence of a reversal coronary flow component in systole. The enrolled patients were classified into two groups according to the presence or absence of SFR before TAVI. A total of 25 patients were included: 13 had SFR and 12 who had no SFR, before TAVI. Patients with SFR had significantly higher aortic valve peak velocities (451.1±45.9 vs. 372.1±52.1cm/s; P<0.001) and mean AVPGs (49.2±14.5 vs. 30.3±11.6mmHg; P=0.002) than those without. The optimal binary cut-off aortic valve peak velocity values and the mean AVPG associated with the presence of SFR before TAVI were >410.0cm/s (specificity, 75.0%; sensitivity, 92.3%) and >37.4mmHg (specificity, 83.3%; sensitivity, 92.3%), respectively. After TAVI, SFR immediately disappeared in 11 of 13 patients with SFR (84.6%). Overall, the systolic coronary VTI significantly increased after TAVI (2.0±4.7 vs. 6.4±3.2cm, P<0.001), and this increase was greater in patients with SFR than in those without SFR before TAVI (interaction P=0.035). SFR was found to be associated with the severity of AS and with a greater increase in systolic coronary flow immediately after TAVI.

Fault diagnosis and analysis of hydraulic brake based on friction vibration signal

The friction vibration signal corresponding to different fault types of brakes is significantly different, thus a hydraulic disc brake fault diagnosis and judgment scheme based on vibration signal detection was proposed and validated in the paper. According to the composition and electric control principle of hydraulic brake, the vibration signal detection and brake pressure control strategies were established. The key hardware and isolation circuit of the detection system were designed, which can effectively improve the stability and anti-interference ability in the process of vibration data acquisition and transmission with SPI and CAN bus communication scheme. In order to eliminate noise interference in friction vibration signal and improve the accuracy of fault diagnosis with advantage, wavelet threshold denoising method was applied to brake disc vibration signal processing. The denoised signal can be obtained by inverting the selected wavelet coefficients to separate the useful components of the signal from the invalid noise. For the research on the correlation between fault types and vibration signal characteristics, a friction vibration test bench for hydraulic braking system was built to obtain and process the output signal from vibration sensor. The frequency spectrum response laws of vibration signals were compared and analyzed when the brake disc was normal and had surface defects, including microcracks, excessive wear and fatigue peeling. The external parameters such as brake pressure and spindle speed were keeping constant, thus eliminating the influence of working factors on vibration characteristics. In order to study the influence of brake pressure failure on friction vibration, the variation law of vibration signal is compared and analyzed under the condition of hydraulic valve leakage and pressure maintaining failure. The results show that the friction vibration signal can be used as an effective basis for judging the surface defects and brake pressure faults of brake discs. Under the condition of wavelet threshold denoising, accurate and effective vibration parameters can be obtained, which is of great significance to the safety and reliability of the braking system.