Search Results (67)

Background/Objectives: Triboelectrification in fluid systems, and specifically in hydrofluorocarbon (HFC)-based propellants, used in pressurised metered-dose inhalers (pMDIs) remains understudied despite its impact on aerosol behaviour and does delivery. This study investigates how ethanol concentration affects charge generation and dissipation in HFC-152a (1,1-difluoroethane; R152a) flowing through low-density polyethylene (LDPE) tubing, a common valve-stem material in pMDIs. Methods: Controlled experiments measured electrical current, charge accumulation, and flow stability for HFC-152a with varying ethanol concentrations in LDPE tubing. Statistical analysis (two-way ANOVA, p < 0.05) assessed the effects of the propellant and material. Comparative tests include R134a (1,1,1,2-tetrafluoroethane) and R227ea (1,1,1,2,3,3,3-heptafluoropropane), and the tubing materials are polybutylene terephthalate (PBT), polyvinyl chloride (VINYL), polyoxymethylene (POM), and LDPE. Results: Increasing ethanol concentration produced larger measured currents, reduced net charge accumulation, and improved flow stability; these effects are attributed to ethanol’s higher dielectric constant and conductivity enhancing charge mobility and dissipation. Significant propellant x material interactions were found (p < 0.05): R152a generated the largest responses with PBT and VINYL (~16 nA and ~5.6 nA, respectively), R227ea showed higher responses with POM and LDPE (~8 nA), and R134a delivered the highest flow rates across materials but exhibited limited electrical responsiveness. Conclusions: Ethanol addition mitigates undesirable electrostatic effects in HFC-based propellants by promoting charge dissipation. The results demonstrate the strong material dependence of triboelectric behaviour and underline the importance of optimising propellant–polymer pairings to minimise the electrostatic adhesion of aerosolised particles and improve pMDI drug delivery performance. Full article

This study investigates the sealing performance of marine vent valves in low-temperature environments (−30 °C to −40 °C) via thermo-mechanical coupling analysis. Polytetrafluoroethylene (PTFE) was selected as the sealing material for its excellent cryogenic toughness, corrosion resistance, and cost-effectiveness. The total minimum specific sealing pressure ($q_{total}$) of PTFE, corrected for marine vibrations (15–60 Hz), was 3.702 MPa. Using ANSYS Workbench 2022, finite element simulations of a DN200 globe valve showed that low temperatures caused non-uniform thermal contraction, reducing the gasket-poppet contact width (2.5 mm to 1.75 mm) and maximum specific pressure (16.967 MPa to 13.352 MPa), leading to leakage risks. Optimizing the stem preload to 36,000 N restored effective sealing: the maximum specific pressure rebounded to 16.601 MPa, with no pressure below 3.702 MPa. This research provides a method for evaluating low-temperature sealing performance and supports safe vessel operation in cold waters. Full article

To address the problem of flow-induced resonance in the valve core assembly of a pilot-operated molten salt regulating valve in a concentrated solar thermal power generation molten salt energy storage system under high pressure differential and high flow rate conditions, the flow-induced vibration characteristics of the pilot-operated molten salt regulating valve were analyzed using computational fluid dynamics (CFD) and fluid–structure interaction modal analysis. The vibration characteristics of the valve core assembly under the excitation force of the molten salt medium were analyzed using the harmonic response method, and the influence of different parameters on the valve core assembly’s vibration characteristics was studied. The results show that under typical operating openings, the first six modal frequencies of the valve core motion assembly are not close to the fluid excitation frequency, indicating that flow-induced resonance does not occur. The maximum vibration stress and displacement of the valve core assembly decrease with increasing damping ratio. With increasing pressure differential, the maximum stress and maximum amplitude of the valve core assembly increase. By changing the valve stem constraint conditions, the vibration stress of the valve core assembly can be reduced. This study provides a reference for the design of flow-induced vibration suppression for pilot-operated molten salt regulating valves and provides guidance for the safe operation of concentrated solar thermal power generation molten salt regulating valves under high pressure differential and high flow rate conditions. Full article

To address the data acquisition limitations of traditional flow balance methods that stem from insufficient flow rate measurements, this study establishes a pipeline flow calculation model based on the pressure data and proposes a pipeline leak identification approach for product oil pipelines. Firstly, field leak tests are designed and conducted on a product oil pipeline in East China by discharging oil in a valve chamber to simulate the leak process. Subsequently, combining the Bernoulli equation with the Leapienzon formula, a calculation model is established for flow rate prediction using the pressure data monitored at the stations and valve chambers along the pipeline. By analyzing the instantaneous flow rate changes at each pipeline section and pressure drops at each station and valve chamber, a dual-parameter collaborative threshold is set based on the flow balance principle, and leaks are identified when both parameters exceed the threshold simultaneously. Finally, the proposed flow rate calculation model and leak identification method are validated with respect to the field test data. The results show that the flow rate model yields a relative error as low as 0.48%, and the leak identification method accurately captured all six leak events in the field test, indicating very good stability and accuracy, with great potential for leak identification and alarm systems for product oil pipelines in engineering applications. Full article

Pathologies of the heart (e.g., ischemic disease, valve fibrosis and calcification, progressive myocardial fibrosis, heart failure, and arrhythmogenic disorders) stem from the irreversible deterioration of cardiac tissues, leading to severe clinical consequences. The limited regenerative capacity of the adult myocardium and the architectural complexity of the heart present major challenges for tissue engineering. However, recent advances in biomaterials and biofabrication techniques have opened new avenues for recreating functional cardiac tissues. Particularly relevant in this context is the integration of biomimetic design principles, such as structural anisotropy, mechanical and electrical responsiveness, and tissue-specific composition, into 3D bioprinting platforms. This review aims to provide a comprehensive overview of current approaches in cardiac bioprinting, with a focus on how structural and functional biomimicry can be achieved using advanced hydrogels, bioprinting techniques, and post-fabrication stimulation. By critically evaluating materials, methods, and applications such as patches, vasculature, valves, and chamber models, we define the state of the art and highlight opportunities for developing next-generation bioengineered cardiac constructs. Full article

Control valves in nuclear systems operate under high-pressure differentials generating intense transient fluid forces that induce destructive structural vibrations, risking resonance and the valve stem fracture. In this study, computational fluid dynamics (CFD) was employed to characterize the internal flow dynamics of the valve, supported by experiment validation of the fluid model. To account for nonlinear structural effects such as contact and damping, a coupled fluid–structure interaction approach incorporating nonlinear perturbation analysis was applied to evaluate the dynamic response of the valve core assembly under fluid excitation. The results indicate that flow separation, re-circulation, and vortex shedding within the throttling region are primary contributors to structural vibrations. A comparative analysis of stability coefficients, modal damping ratios, and logarithmic decrements under different valve openings revealed that the valve core assembly remains relatively stable overall. However, critical stability risks were identified in the lower-order modal frequency range at 50% and 70% openings. Notably, at a 70% opening, the first-order modal frequency of the valve core assembly closely aligns with the frequency of fluid excitation, indicating a potential for critical resonance. This research provides important insights for evaluating and enhancing the vibration stability and operational safety of control valves under complex flow conditions. Full article

Aortic stenosis (AS), the most common valvular heart disease, is traditionally graded based on several echocardiographic quantitative parameters, such as aortic valve area (AVA), mean pressure gradient (MPG), and peak jet velocity (Vmax). This systematic review evaluates the clinical significance and prognostic implications of discordant high-gradient AS (DHG-AS), a distinct hemodynamic phenotype characterized by elevated MPG despite a preserved AVA (>1.0 cm²). Although often overlooked, DHG-AS presents unique diagnostic and therapeutic challenges, as high gradients remain a strong predictor of adverse outcomes despite moderately reduced AVA. Sixty-three studies were included following rigorous selection and quality assessment of the key studies. Prognostic outcomes across five key studies were discrepant: some showed better survival in DHG-AS compared to concordant high-gradient AS (CHG-AS), while others reported similar or worse outcomes. For instance, a retrospective observational study including 3209 patients with AS found higher mortality in CHG-AS (unadjusted HR: 1.4; 95% CI: 1.1 to 1.7), whereas another retrospective multicenter study including 2724 patients with AS observed worse outcomes in DHG-AS (adjusted HR: 1.59; 95% CI: 1.04 to 2.56). These discrepancies may stem from delays in intervention or heterogeneity in study populations. Despite the diagnostic ambiguity, the presence of high gradients warrants careful evaluation, aggressive risk stratification, and timely management. Current guidelines recommend a multimodal approach combining echocardiography, computed tomography (CT) calcium scoring, transesophageal echocardiography (TEE) planimetry, and, when needed, catheterization. Anatomic AVA assessment by TEE, CT, and cardiac magnetic resonance imaging (CMR) can improve diagnostic accuracy by directly visualizing valve morphology and planimetry-based AVA, helping to clarify the true severity in discordant cases. However, these modalities are limited by factors such as image quality (especially with TEE), radiation exposure and contrast use (in CT), and availability or contraindications (in CMR). Management remains largely based on CHG-AS protocols, with intervention primarily guided by transvalvular gradient and symptom burden. The variability among the different guidelines in defining severity and therapeutic thresholds highlights the need for tailored approaches in DHG-AS. DHG-AS is clinically relevant and associated with substantial prognostic uncertainty. Timely recognition and individualized treatment could improve outcomes in this complex subgroup. Full article

The integration of new technologies in Industry 4.0 has modernised agriculture, fostering the concept of smart agriculture (Agriculture 4.0). Higher education institutions are incorporating digital technologies into agricultural curricula, equipping students in agriculture, agronomy, and engineering with essential skills. The implementation of targeted STEM activities has the potential to enhance the teaching of Agriculture 4.0 through the utilisation of practical applications that stimulate student interest, thereby facilitating more accessible and effective teaching. In this context, this study presents a system comprising retrofitted real-scale components that facilitate the understanding of digital technologies and automations in agriculture. The specific system utilises a typical centrifugal electric pump and a water tank and adds logic to it, so that its flow follows various user-defined setpoints, given and monitored via a smartphone application, despite the in-purpose disturbances invoked via intermediating valves. This setup aims for students to gain familiarity with concepts such as closed-loop systems and PID controllers. Going further, fertile ground is provided for experimentation on the efficiency of the PID controller via testing different algorithmic variants incorporating non-linear methods as well. Feedback collected from the participating students via a corresponding survey highlights the importance of integrating similar hands-on interdisciplinary activities into university curricula to foster engineering education. Full article

Laver fluffy is an indispensable link in the processing of laver products. After fluffing, the laver acquires an appealing color, which is conducive to better marketability. During the primary mechanical processing of laver, a valve capable of rapid opening and closing is required to ensure that the laver’s surface becomes fluffy and lustrous post-processing. However, valve products that can meet the specific requirements of laver fluffing are scarce. This study proposes a novel principle for a high-speed switching control valve. This valve can quickly turn on or cut off the high-pressure gas path during laver processing while also taking into account the response speed and service life. The structure and principle of the new control valve were introduced. Different flow field models in the valve were designed, and their flow characteristics and flow field performance under various schemes were compared and discussed by using Fluent. Subsequently, an optimized control valve structure model was proposed. Based on this, a strength analysis of the control valve was conducted via fluid–structure interaction, revealing the response characteristics of the valve under the working state. The results indicate that, when different cone angles and bell shapes were selected for the upper chamber inlet of the control valve, the number and intensity of vortices in the upper chamber can be reduced. The height of the upper chamber affected the formation of the throttle between the top and bottom surfaces of the upper chamber. When the height of the upper chamber was 32 mm, the energy loss in the upper chamber remains basically stable. Simultaneously changing the inlet shape and height of the upper chamber can effectively prevent the throttle formed by the height of the upper chamber, which was conducive to increasing the valve outlet flow rate. Through the analysis of the flow field with different valve chamber structures, the improved control valve adopted the bell-shaped inlet, with an upper chamber height of 32 mm and curved transition for the internal flow channel. Compared to the original fluid domain, when the opening was 100%, the outlet flow rate of the 10° conical tube and bell-shaped inlet increased by 12.77% and 12.59%, respectively. The outlet flow rate at the curved transition position rose by 15.35%, and the outlet flow of the improved control valve increased by 32.70%. When the control valve was operating under a preload pressure of 1 MPa, at 20% opening, the maximum equivalent stress of the valve body was 52.51 MPa, and the total deformation was 12.56 microns. When the preload pressure exceeded 1.5 MPa, the equivalent stress and total deformation of the control valve body and T-shaped valve stem exhibited an upward trend with further increases in the preload pressure. Full article

The valve stem made of 20CrMo1V1A has low surface resistance and high susceptibility to corrosion, significantly curtailing its service life. To address these issues, a high-quality ultrasonic rolling (USR) technology was applied to the 20CrMo1V1A stainless steel valve stem to enhance its corrosion resistance and mechanical properties. Subsequently, fatigue and corrosion tests were conducted on the valve stem. The results indicate that USR produces surfaces with a roughness average (Ra) of 0.3 μm and a gradient nanostructure on the valve stem surface. This unique microstructural modification resulted in a 27% improvement in surface hardness and nearly a three-fold grain size reduction. Additionally, the friction coefficient and electrochemical corrosion rate dropped by 47% and 32%, respectively. Therefore, USR was applicable for enhancing multiple properties of valve components as an additional final processing step for achieving high-performance valve stems. Full article

Current trends in the development of technology are linked inextricably to the increasing level of automation in technological processes and production systems. In this regard, the development of systems for supplying working fluids with adjustable pumps that have high performance characteristics, an increased service life and low operating costs is an important scientific and technical task. A primary challenge in the development of such systems lies in achieving low fluid flow rates while maintaining stable operating characteristics. This challenge stems from the fact that currently available controlled hydraulic pumps exhibit either a high cost or suboptimal life and efficiency parameters. This work focuses on the development of a plunger hydraulic pump with a small working volume. A mathematical model has been developed to investigate the characteristics, optimize the design of this pump and further expand the size range of such pumps. The solution was implemented on a computer using the dynamic modelling environment MATLAB/Simulink. In order to verify the mathematical model’s adequacy, a plunger pump prototype was built and integrated with a test bench featuring a measurement system. The test results showed higher pump efficiency and a significant reduction in hydraulic losses. An analysis of the obtained data shows that the pump is characterized by increased efficiency due to optimal flow distribution and reduced internal leakage, which makes it promising for use in hydraulic systems requiring improved operating characteristics. The developed pump has more rational characteristics compared to existing alternatives for use in water supply systems for induction superheaters. The experimental external characteristics of the developed pump are 10% higher than the external characteristics of the ULKA EX5 pump selected as an analogue, and the pressure characteristics are 65% higher. It offers production costs that are several times lower compared to existing cam-type plunger or diaphragm pumps with oil sumps and precision valve mechanisms. Additionally, it has significantly better operating characteristics and a longer service life compared to vibrating plunger pumps. Full article

Cardiovascular diseases resulting from myocardial infarction (MI) remain a leading cause of death worldwide, imposing a substantial burden on global health systems. Current MI treatments, primarily pharmacological and surgical, do not regenerate lost myocardium, leaving patients at high risk for heart failure. Engineered heart tissue (EHT) offers a promising solution for MI and related cardiac conditions by replenishing myocardial loss. However, challenges like immune rejection, inadequate vascularization, limited mechanical strength, and incomplete tissue maturation hinder clinical application. The discovery of human-induced pluripotent stem cells (hiPSCs) has transformed the EHT field, enabling new bioengineering innovations. This review explores recent advancements and future directions in hiPSC-derived EHTs, focusing on innovative materials and fabrication methods like bioprinting and decellularization, and assessing their therapeutic potential through preclinical and clinical studies. Achieving functional integration of EHTs in the heart remains challenging due to the need for synchronized contraction, sufficient vascularization, and mechanical compatibility. Solutions such as genome editing, personalized medicine, and AI technologies offer promising strategies to address these translational barriers. Beyond MI, EHTs also show potential in treating ischemic cardiomyopathy, heart valve engineering, and drug screening, underscoring their promise in cardiovascular regenerative medicine. Full article

In the valve hall of the converter station of a UHV transmission project at high altitudes, the shielding sphere and the wall/floor form a large-size sphere–plane long air gap. Burr defects on the surface of the shielding sphere can affect its discharge characteristics. The streamer-to-leader transition is a key process in the discharge of the long air gap. The existing research is limited to the discharge characteristics of small-size electrodes at low altitudes and cannot be directly extended to those of large-size electrodes at high altitudes. Therefore, this paper constructs a discharge test platform with optical–electrical synchronous detection at an altitude of 2200 m. The instantaneous optical power, electric field intensity, high potential current, and other physical parameters during the discharge in the long air gap of a 1.3 m diameter sphere–plane system were collected for both a sphere electrode with burrs and one without burrs. The injection current of the initial streamer was used as the input variable and substituted into Gallimberti’s model to analyse the transformation process of the streamer stem’s vibrational energy into translational energy. A modified model that is more suitable for high altitudes was developed by taking into account convective diffusion and the thermal expansion of the streamer, and the influence of burr defects on the characteristics of the transition from streamer to leader was analysed and compared with the experimental results. Overall, burr defects reduced the duration of the streamer-to-leader transition and facilitated discharge. The analysis results generally agree with the experimental results. The research results are of great significance for the design of the valve hall insulation in converter stations at high altitudes. Full article

Inflammatory cytokines, including interleukin 6 (IL6), are associated with ion channel remodeling and enhance the propensity to alterations in cardiac rhythm generation and propagation, in which the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels play a crucial role. Hence, we investigated the consequences of exposure to IL6 on HCN channels in cell models and human atrial biopsies. In murine atrial HL1 cells and in cardiomyocytes derived from human induced pluripotent stem cells (hiPS-CMs), IL6 elicited STAT3 phosphorylation, a receptor-mediated downstream signaling. Downregulation of HCN1,2,4 by IL6 was observed after 24–48 h; in hiPS-CMs, this effect was reverted by 24 h of application of tocilizumab, a human IL6 receptor antagonist. In parallel, hiPS-CM action potentials (APs) showed a reduced spontaneous frequency. Moreover, we assessed IL6 and HCN expression in dilated left atrial samples from patients with mitral valve disease, an AF-prone condition. IL6 levels were increased in dilated atria compared to controls and positively correlated with echocardiographic atrial dimensions. Interestingly, the highest IL6 transcript levels and the lowest HCN4 and HCN2 expression were in these samples. In conclusion, our data uncovered a novel link between IL6 and cardiac HCN channels, potentially contributing to atrial electrical disturbances and a higher risk of dysrhythmias in conditions with elevated IL6 levels. Full article

Background: Mitral annulus calcification is a chronic degenerative condition affecting the fibrous base of the mitral valve. Historically viewed as an age-related phenomenon, recent studies suggest it is driven by active mechanisms involving systemic inflammation, hemodynamic stress, abnormal calcium-phosphorus metabolism, and lipid accumulation. Despite often being asymptomatic and incidentally detected, its clinical relevance stems from its strong association with increased cardiovascular disease risk, higher cardiovascular mortality, and elevated overall mortality. Methods: This article investigates the complexities and controversies surrounding mitral annular calcification as a potential embolic source, focusing on its diagnosis, its relationship with systemic inflammation, and its links to metabolic and chronic disorders. Results: The findings highlight that mitral annular calcification is not merely a passive marker of aging but an active indicator of atherosclerotic burden with significant implications for cardiovascular health. Conclusion: Mitral annulus calcification should be recognized as an important factor in cardiovascular risk assessment, offering insight into systemic inflammatory processes and metabolic dysregulation. Full article