Search

• Pulse-width modulation (PWM) is proposed to control subcritical R744 ejectors. • PWM is also proposed to control subcritical R744 ejector motive nozzles. • Subcritical PWM motive nozzle is as effective as a high-pressure expansion valve. • PWM ejector controls the high pressure effectively in transition regime. • PWM ejector increase COP by up to 7.9 % compared to a high-pressure expansion valve. The target of this study is to experimentally compare the performance of three different expansion devices for small-capacity subcritical R744 vapour-compression refrigeration units. The first considered expansion device was the conventional high-pressure expansion valve, which was selected as the baseline. The second assessed expansion device was a two-phase ejector for expansion work recovery whose refrigerant flow was modulated via the pulse-width modulation (PWM) strategy. Finally, the PWM approach was employed for controlling the refrigerant flow of the ejector motive nozzle while the refrigerant was not permitted to be drawn by the ejector suction nozzle. The results showed that the motive nozzle controlled via PWM effect offers similar effectiveness to a conventional high-pressure expansion valve in the subcritical regime. Furthermore, it was observed that the PWM ejector is able to control the high pressure effectively while increasing the coefficient of performance (COP) by up to 5.3 % without and by up to 7.9 % with overfed evaporator compared to the baseline in the transition regime. The results also showed that the installation of the conventional high-pressure expansion valve is not necessary. Finally, the yearly performance of the aforementioned expansion devices was assessed in five different locations, i.e., Athens (Greece), Phoenix (USA), New Delhi (India), Riyadh (Saudi Arabia) and Bangkok (Thailand). The outcomes revealed that the PWM ejector allows for a higher in yearly average COP (COP yearly avg) from 4.9 % (in Athens) to 11.8 % (in Bangkok) over the baseline. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the effects of a decreasing refrigerant charge on the performance and operating conditions of an R513A water-to-water heat pump equipped with a large liquid receiver, an electronic expansion valve, and a vapor accumulator at the compressor inlet. The mass of the refrigerant inside the machine is progressively extracted to simulate refrigerant leakages occurring during the normal operation or in case of failures. The results show that the subcooling is the parameter mostly affected by a refrigerant charge variation since it rapidly collapses to 0 K with the charge reduction. Furthermore, it is possible to identify three different zones in which almost all the properties analyzed (COP, heating capacity, operating pressures and expansion valve opening) exhibit peculiar trends with the charge decrease: subcooling sensitivity zone, constant parameters zone, and compressor failure risk zone. The extension of these zones is determined by the size of the liquid receiver which is installed in the system and, for the heat pump under consideration, is between 100% and 95% of the initial charge for the first zone, between 95% and 40% for the second zone, and below 40% for the third zone. [ABSTRACT FROM AUTHOR]

The novel rotary-baffle curved-channel electronic expansion valve (RBCC-EEV) has appeared in industry to replace a capillary tube as the variable expansion device in household refrigerators. However, due to the structure differences between the RBCC-EEV and the traditional orifice-type EEV, the previous empirical mass flow correlation inapplicable. In this paper, a new empirical correlation is proposed based on the structure and regulation principle of the novel RBCC-EEV, and the effects of different operating conditions on the mass flow rate of R600a flowing through two different RBCC-EEVs are experimentally investigated. The new empirical correlation introduces a centrifugal force coefficient and a variable length coefficient to represent the effect of asymmetric cavitation phenomenon and super-linear mass flow rate characteristics. The experimental results show a rise in the mass flow rate with increasing inlet pressure, inlet subcooling and opening ratio. Under the test range, the flow pattern of R600a flowing through the RBCC-EEV is chocked flow. Moreover, the proposed new empirical mass flow correlation agrees well with the experimental data. For 95.7 % of the prediction value, the relative deviation is below 15 %, while 89.0 % exhibit a relative deviation less than 10 %. The average deviation and standard deviation stand at 6.52 % and 4.56 %, respectively. [ABSTRACT FROM AUTHOR]

The yaw damper is an integral and pivotal component in guaranteeing the carbody hunting stability of high-speed trains (HSTs). However, it is reported that the occurring incidences of low-frequency carbody hunting frequently have been observed in HSTs, a predicament attributed to the degradation of yaw damper performance resulting from the obstruction of the damping valve by foreign particulates. Given these circumstances, the objective of this study is to investigate the impact of yaw damper performance degradation on the intricate phenomenon of carbody hunting motion. A HST dynamic model is developed, incorporating a detailed physical parameter model of the yaw damper, which enables the reproduction of abnormal low-frequency swaying arising from the deterioration in yaw damper performance. The findings of this study demonstrate that the obstruction of the damping valve significantly augments the damping force and dynamic stiffness of the yaw damper, thereby potentially instigating the occurrence of severe low-frequency hunting motion and consequent deterioration in the ride comfort of HSTs. [ABSTRACT FROM AUTHOR]

While the visual estimation of systolic left ventricular function by experienced examiners closely aligns with quantitative methodologies, the accuracy of visual estimation in determining the severity of valvular regurgitation using colour flow Doppler assessment of native heart valves remains largely unexplored. This study analysed the ability of 262 physicians to visually estimate the severity of 12 native valve regurgitations by grading colour Doppler transthoracic echocardiography loops in an online questionnaire. The assessments of the participants were compared to standardized quantitative evaluations conducted by certified echocardiography experts. Of the three valves to assess, evaluations by the participants showed the best correlation (Rs = 0.75, p < 0.0001) and agreement (percent agreement: 66.4%) with those of the experts in mitral valve regurgitation (MR). High agreement was observed for mild regurgitation across all valves (MR 94.5%, AR 80.3% and TR 88.7%), while consensus diminished in moderate (MR 55.9%, AR 49.5% and TR 55.0%) and severe regurgitation (MR 57.6%, AR 67.4%, TR 14.6%). The study underscores the potential utility of visual estimation of valvular regurgitation in clinical settings for identifying clinically relevant regurgitations. However, our findings also highlight the importance of integrating visual estimation with quantitative methods, particularly in moderate and severe cases of regurgitation. [ABSTRACT FROM AUTHOR]

Speaking valves enable tracheostomy patients to speak naturally. However, improper use may cause dangerous overpressure, leading to severe complications or even patient's death. We address this life-threatening issue by creating a biomimetic speaking valve, which incorporates an integrated overpressure valve that automatically opens when reaching critical pressure levels. To enhance safety, we integrated a whistle module to provide an audible alert for medical staff. Fundamental research on the Utricularia vulgaris trapdoor inspired our abstracted valve form. Through a comprehensive analysis using generalized linear mixed-effect models, we examined various membrane parameter effects on the function of the biomimetic overpressure valve. This enabled us to adjust the valve's opening pressure to cater to patient's unique requirements, thus potentially saving lives by applying a solution from nature. [ABSTRACT FROM AUTHOR]

In this work, the influence of plenum and port geometry on the performance of the intake process in a four-stroke spark ignition engine for ultralight aircraft applications is analyzed. Three intake systems are considered: the so-called "standard plenum", with a relatively small plenum volume, the "V1 plenum", with a larger plenum volume, and the "standard plenum" equipped with a large curvature manifold called the "G2 port". Both measurements and 3D CFD simulations, by using Ansys® Academic Fluent, Release 20.2, are performed to characterize and analyze the steady-flow field in the intake system for selected valve lifts. The experimental data and the numerical results are in excellent agreement with each other. The results show that at the maximum valve lift, i.e., 12 mm, the V1 plenum allows an increase in the air mass flow rate of 9.1% and 9.4% compared to the standard plenum and the standard plenum with the "G2 port", respectively. In addition, the volumetric efficiency has been estimated under unsteady-flow conditions for all geometries at relatively high engine rpms. The difference between numerical results and measurements is less than 1% for the standard plenum, thus proving the accuracy of the model, which is then used to study the other configurations. The V1 plenum shows a fairly constant volumetric efficiency as the engine speed increases, although such an efficiency is lower than that of the other two geometries considered in this work. Specifically, the use of the "G2 port" leads to an increase of 1.5% in terms of volumetric efficiency with respect to the configuration with the original manifold. Furthermore, for the "G2 port" configuration, higher turbulent kinetic energy and higher swirl and tumble ratios are observed. This is expected to result in an improvement of air–fuel mixing and flame propagation. [ABSTRACT FROM AUTHOR]

As a commonly used hydraulic control component, the nozzle-flapper servo valve has the advantages of small structure and sensitive dynamic response. Due to the small size and complex structure of the servo valve, the classical control methods based on various feedback information cannot effectively improve its performance. In order to effectively improve the performance of the servo valve, this paper implemented the feedforward control method to suppress the dynamic performance of the armature assembly of the servo valve. The distributed parameters mathematical models of the armature assembly are established and verified which can accurately predict the vibration of the armature assembly. With the mathematical model, the feedforward control signal is calculated based on the real-time velocity, acceleration, and deflection of the armature assembly, respectively. The applicability of different signals is analyzed and the signals calculated by velocity and deflection are verified which can effectively suppress the vibration amplitude of armature assembly. The numerical simulation and experimental methods are implemented to verify the performance of different control signals and the optimal feedforward control signal under different external loads is obtained. [ABSTRACT FROM AUTHOR]

This work presents nonlinear and linear controls ensuring the global stability of a pressure-reducing valve. The global property using both nonlinear and linear controls is very important to guarantee stability even though the pressure-reducing valve operates far from its nominal working point. To this goal, this work develops the mathematical description of a pressure-reducing valve. It is a second-order model, nonlinear, and nonaffine in control implemented with two secondary (solenoid) valves. Due to the nonlinear nature of the system, the Lyapunov theory allows developing the control, which ensures the global stability of the system using one input. In addition, the second control input is modified to enlarge the operating range of the pressure-reducing valve. To implement the control in (nowadays) industrial controllers, a linear proportional-integral (PI) control, ensuring all the stabilizing properties of the nonlinear control, is included as a subset of the nonlinear law. Experimental results demonstrate the good performance of the proposed PI. Practical Applications: The importance of controlling pressures in water distribution systems is widely recognized. This study delves into the analysis of a pressure-reducing valve, beginning with its mathematical model and culminating in its control mechanism. Two secondary (solenoid) valves serve to operate the pressure-reducing valve, acting as the system's control inputs. The research showcases that the achieved control operates effectively across a broader range of operating conditions, a notable distinction from other pressure-reducing valve controls. Furthermore, it demonstrates the feasibility of utilizing only one control input while keeping the other fixed. Additionally, a strategy is proposed to maximize the operational range of the pressure-reducing valve within the constraints of the inputs. Finally, considering implementation in the field using validated hardware, and acknowledging the complexity of the obtained control, this study substitutes the original control with a well-established (PI) control, ensuring the desired properties. Experimental results validate the effectiveness of the proposed control strategy. [ABSTRACT FROM AUTHOR]

Existing analytical flow models for predicting flow rates at microscale seal displacements are limited to two separate domains. The first assumes a small channel length to height aspect ratio at relatively large seal displacements. The second assumes a large channel length to height aspect ratio at relatively small seal displacements. A piecewise analytical model for compressible flow is developed here to enable predicting flow rates in valves with fluid pathways of any aspect ratio. The new model is validated by numerical studies and experiment. The results are applicable to flat valve seals having a cylindrical seal boss feature with fluid passage length to height aspect ratios ranging from 3.3 to 800. The new model is particularly useful for the design of microvalves and macroscale valves with small actuator displacements. [ABSTRACT FROM AUTHOR]

The editorial discusses the importance of power transmission and control in various machinery, including vehicles, airplanes, and ships. The Special Issue focuses on new achievements in hydraulic and pneumatic systems, highlighting advancements in design, analysis, and control strategies. The papers cover topics such as hydraulic system design, pneumatic systems, and analytical models for optimization, aiming to enhance the reliability and efficiency of power transmission systems. Emerging technologies like cybernetic physic systems and artificial intelligence are expected to drive further innovation in fluid power transmission and control. [Extracted from the article]

The article presents a case study of a 17-year-old patient with cystic fibrosis experiencing persistent air leaks and empyema following unresolved pneumonia. Topics discussed include the use of endobronchial valves to reduce airflow through alveolopleural fistulas, the management challenges associated with pleuropulmonary infections, and the effectiveness of nonsurgical interventions like tunneled pleural catheters in minimizing hospital stays and promoting outpatient care.

Key Points Nasal valve treatment with TCRF results in NAO symptom improvement in the presence of septal deviation. Severe septal deviation does not impact the beneficial effect of TCRF nasal valve treatment. Symptoms improve with TCRF nasal valve treatment even if septal deviations involve the nasal valve. [ABSTRACT FROM AUTHOR]

In order to study the influence of regulating valve openings on the dynamic characteristics of the rotor structure of a multistage pump during the transient startup process, a seven-stage pump was selected as the research object. The transient startup of the pump was jointly simulated using Flowmaster and CFX, and the deformation law of the rotor under different valve openings with time was investigated through Workbench. The results showed that the deformation trends of the impellers at each stage were similar under different valve openings during transient startup, and regulating the valve opening had little significant impact on the stability of the rotor structure. The maximum deformation of the pump shaft occurred at the contact surface between the intermediate impeller and the pump shaft under different valve openings. As the valve opening increased, the maximum deformation of the pump shaft decreased slightly. This study reveals the structural characteristics of the multistage pump during the transient startup process under different valve openings, which is of great importance for improving the safety and reliability of multistage pumps during emergency operations. [ABSTRACT FROM AUTHOR]

Introduction: Posterior urethral valve (PUV) is a major cause of congenital bladder dysfunction, often persisting despite treatment. Emerging therapies, including anticholinergics and α-1 blockers, offer potential but lack clear guidelines. This study evaluates their effectiveness in improving bladder function after valve fulguration. Methods: Twenty PUV patients, aged ≥3 years, were randomized into anticholinergic (group A, n = 11) and α-1 adrenergic blocker (group B, n = 9) groups post-fulguration. Follow-up included clinical, radiological, and urodynamic assessments 6 months posttreatment initiation. Results: In group A, the mean maximum detrusor pressure (Pdet) decreased from 30.17 to 23.45 cm H2O (p = 0.033). Two patients normalized from high detrusor pressure (>40 cm H2O). In group B, 1 patient retained high detrusor pressure posttreatment. Group B improved in average urinary flow (Q avg) and maximum flow rate (Q max), with all patients having initially low Q avg (<10 mL/s). Two group B patients showed improved average flow rates posttreatment (p = 0.016); three in group A showed improvement but were not statistically significant (p = 0.197). Q max/flow time ratio was abnormal in all group B patients pretreatment. Two of the nine improved posttreatment, while only one in group A did. Conclusions: Anticholinergic medications positively impact cystometric parameters and are effective for detrusor instability and low compliance bladder. α-Adrenergic blockers influence uroflow parameters and can help treat bladder outflow obstruction. Consideration for a larger study with extended follow-up is warranted. [ABSTRACT FROM AUTHOR]

A methodology for the design calculation of a new design of a hydraulic pulse vibrator with a valve pressure pulse generator of a parametric type has been developed, which allows determining its energy, power and geometric parameters. [ABSTRACT FROM AUTHOR]

Background The ileocecal valve (ICV) is considered to be one of the most difficult locations for endoscopic submucosal dissection (ESD). The objective of this study was to evaluate the efficacy and safety of traction-assisted ESD in this situation. Methods All patients who underwent traction-assisted ESD for an ICV lesion at three centers were identified from a prospective ESD database. En bloc and R0 rates were evaluated. Factors associated with non-R0 resection were explored. Results 106 patients with an ICV lesion were included. The median lesion size was 50 mm (interquartile range 38–60) and 58.5% (62/106) invaded the terminal ileum. The en bloc and R0 resection rates were 94.3% and 76.4%, respectively. Factors associated with non-R0 resection were lesions covering ≥75% of the ICV (odds ratio [OR] 0.21. 95%CI 0.06–0.76; P=0.02), and involving the anal lip (OR 0.36, 95%CI 0.13–0.99; P=0.04) or more than two sites on the ICV (OR 0.27, 95%CI 0.07–0.99; P=0.03). Conclusion Traction-assisted ESD for treatment of ICV lesions was a safe and feasible option. Large lesions and anal lip involvement appeared to be factors predictive of difficulty. [ABSTRACT FROM AUTHOR]

Metacestode infestation of Semibalanus balanoides (L., 1767) and Balanus crenatus Bruguiеre, 1789, collected in the Barents and White Seas and in the northern part of the Sea of Okhotsk in 2020 and 2021, respectively, was studied. A total of 313 S. balanoides from Mogilnaya Bay of Kildin Island (Barents Sea) and isolated mature wrinkled barnacles B. crenatus, two and four specimens from the Pechora Sea and Kandalaksha Bay of the White Sea, respectively, were examined in 2020. Metacestodes Fimbriarioides intermedia (Fuhrmann, 1913) (Cyclophyllidea, Hymenolepididae) were found in 1.0 ± 0.6% of S. balanoides in the Barents Sea with an invasion intensity (I. I.) of 2–5 specimens, and in one of two B. crenatus from the Pechora Sea (I. I. 15 specimens). For the first time, in both B. crenatus from the Pechora Sea, taken from the valves of the mussel Mytilus edulis, metacestodes Microsomacanthus sp. I (I. I. 13 and 20 specimens) with proboscis hooks 38–41 (39.4 ± 0.1) µm long and blades of 9.5–11 (10.7 ± 0.1) µm were obtained. One of four B. crenatus from the Kandalaksha Bay was infected with another Microsomacanthus sp. II (I. I. 19 specimens) with proboscis hooks 44.0–49.5 (45.7 ± 0.5) µm long and blades 14.0–16.0 (14.8 ± 0.07) µm long. A total of 362 S. balanoides were collected and dissected in Gizhiginskaya Bay of the northern part of the Sea of Okhotsk in 2021, of which 8.0 ± 1.4% were infected with F. intermedia metacestodes (I. I. 1–19 specimens). Study results of the infestation of S. balanoides on the Koni-Pyagin coast of the Sea of Okhotsk (according to the collections of 2006–2007) were supplemented and clarified. Description of metacestodes and the taxonomic affiliation of cysticercoids Microsomacanthus spp. are given. [ABSTRACT FROM AUTHOR]

Refrigerants are a critical component of air conditioning and heat pump systems, but their high global warming potential has led to increasing concerns about their environmental impact. This research quantifies leakage from Schrader valves commonly used in air conditioning equipment. These valves serve as access points for refrigerant circuits and are often cited by service technicians as a source of leaks, contributing to greenhouse gas emissions. The study conducted laboratory testing of Schrader valves using an innovative experimental apparatus that tracked pressure and temperature of nitrogen gas contained by the valve over a 64-h test. The study found that 8 out of 61 used Schrader valves tested leaked at rates that would result in substantial refrigerant loss (M = 1,280 g/yr, SD = 3,168 g/yr, range = 9.4 to 9,117 g/yr). Gasketed caps were found to prevent refrigerant loss. Combining a Schrader valve with a gasketed cap significantly reduces the risk of leaks, and their use should be encouraged in air conditioning systems. The methodology developed for estimating leak rates from Schrader valves could be applied to other components in refrigeration systems, contributing to more comprehensive efforts to reduce refrigerant emissions. [ABSTRACT FROM AUTHOR]

The next generation supra-annular, self-expanding Evolut FX transcatheter aortic valve (TAV) system was designed to improve catheter deliverability, provide stable and symmetric valve deployment, and assess commissural alignment during the procedure. The impact of these modifications has not been clinically evaluated. Procedural information was collected by survey in 2 Stages: Stage I comprised 23 centers with extensive experience with Evolut TAV systems, and Stage II comprised an additional 46 centers with a broad range of balloon- and self-expanding system experience. Operators were to compare the experience with the Evolut FX to the predicate Evolut PRO+ system. There were 285 cases during Stage I from June 24 to August 12, 2022, and 254 cases during Stage II from August 15 to September 11, 2022. Overall, the cusp overlap technique was used in 88.6 %, and commissural alignment was achieved in 96.1 % of these cases. Compared to implanter's previous experience with the Evolut PRO+ system, less resistance was noted with the Evolut FX system: in 83.0 % of cases during vascular insertion, in 84.7 % of cases while tracking through the vasculature, in 84.4 % of cases while traversing over the arch, and 76.1 % of cases in advancing across the valve. Better symmetry of valve depth was observed in 423 of 525 cases (80.6 %). Evolut FX system design modifications translated into improvements in catheter deliverability, deployment symmetry and stability, and commissural alignment as assessed by experienced self-expanding and balloon expandable operators. • The Evolut FX was compared to the Evolut PRO+ transcatheter valve in 539 cases. • Data collected from June to September 2022. • Cusp overlap was used in 89 % of patients. • Commissural alignment was achieved in >96 % of patients. • Improved catheter delivery, deployment symmetry & valve stability with Evolut FX. [ABSTRACT FROM AUTHOR]

Aiming at the problem of torque fluctuations and intake pressure fluctuations caused by cycle cylinder deactivation, we introduced a refined control strategy encompassing fixed cycle frequency with fixed deactivation frequency, variable cycle frequency with fixed deactivation frequency, and variable cycle frequency with variable deactivation frequency. The cycle cylinder deactivation rate is determined by controlling the cycle frequency and the cylinder deactivation frequency, which provides a new method for exploring the torque fluctuation of the cycle cylinder deactivation. Furthermore, we introduced an intake compensation method based on the cylinder deactivation compensation coordinate system is proposed. The non-uniformity of the intake air volume of each cylinder of the cycle cylinder deactivation is improved by changing the valve lift. After compensation, the non-uniformity of the intake air volume and the mean indicated pressure of each cylinder are within 2%, and the maximum torque fluctuation is reduced by 52%. It provides a useful reference for enhancing the dynamic smoothness of cylinder deactivation in engines. [ABSTRACT FROM AUTHOR]

This paper presents a novel methodology for the coupled optimization of water distribution network (WDN) pipe sizing and isolation valve placement. The methodology is based on the effective application of biobjective genetic algorithm optimization to simultaneously minimize installation cost and average demand shortfall due to segment isolations, followed by a postprocessing financial analysis including assessment of valve maintenance costs. For speeding up convergence, a constraint is implemented in the optimization to enforce the telescopic property of pipe diameters, which are expected to shrink from source(s) to external parts of the WDN. The methodology is applied to two case studies with different levels of complexity, enabling the results to be compared with the traditional approach based on decoupled least-cost optimization of pipe sizing and placement of isolation valves at all (N_valve rule) or all but one (N-1_valve rule) pipes connected to the generic demand node. The least-cost pipe design equipped with the N_valve rule valve placement is always dominated. The adoption of the N-1_valve rule yields very close results to the optimization, as long as the best among the very numerous possible N-1_valve layouts is suitably identified. However, more beneficial solutions featuring lower valve maintenance costs can be selected from the optimal solutions obtained from the novel methodology. The use of the weighted average demand shortfall as objective function, instead of the simple average demand shortfall, tends to produce a larger variety of solutions. [ABSTRACT FROM AUTHOR]

• A novel degradation process with abrupt jumps caused by operation state transition is proposed. • Analytical reliability solutions of the model are derived in the form of one-dimensional Laplace-Stieltjes transform. • The limit reliability solutions are investigated, as alternative strategy under long-term service. • Analytical solutions regarding statistical characteristics of degradation amount during regeneration epoch are proposed. • The case of spool valve is implemented to verify the effectiveness and the feasibility of the solutions. This paper proposes a novel type of degradation process incorporating continuous degradation and abrupt degradation jump under dynamic operation states. By analyzing the failure mechanism of practical application, the abrupt degradation jump is comprehensively considered, and it is triggered by some certain state switching processes. Then, the reliability solutions of the degradation process (reliability function and moments of lifetime) are derived in the form of Laplace-Stieltjes transform. To a further step, inspired by the advanced equipment with long service span, the reliability solutions in limit region are explored, where an effective calculation method regarding statistical characteristics of degradation amount during regeneration epoch is pioneeringly proposed. To verify the proposed solutions in the form of Laplace-Stieltjes transform and their limit case, the representative example, spool valve, is implemented, and the results show the effectiveness and the feasibility of the solutions. [ABSTRACT FROM AUTHOR]

In order to obtain the transient characteristics of a low-speed centrifugal pump during the start-up and shutdown stages, dedicated experimental tests were conducted with eight different valve opening conditions. The Pearson correlation coefficient was used to reveal the linear correlation between variables. According to the results, the stable rotational speed decreases with increasing valve opening (rotational speed decreases from approximately 1472 to 1453 r/min), while the stable shaft power exhibits an increasing trend (shaft power increases from approximately 0.242 to 0.390 kW). The stable time and zeroing time of each parameter during start-up and shutdown processes vary, with the flow zeroing time significantly increasing with the relative flow, reaching up to 10.468 s, while the shaft power zeroing time is roughly between 1.219 and 1.375 s. The results demonstrate that with increasing valve opening, the stable and zeroing time of flow significantly increase (|r| greater than 0.95), while the stable and zeroing time of rotational speed, power, and head display a smaller sensitivity on the valve opening (|r| less than 0.6). [ABSTRACT FROM AUTHOR]

This contribution explores the development of a digital twin for industrial valves, with a focus on mitigating the costly consequences of valve malfunctions in large-scale industrial environments. Industrial valves are critical components in fluid and gas control systems where unexpected failures can lead to significant downtime and financial loss. Digital twins as virtual replicas of physical systems offer a promising solution as they enable real-time monitoring and predictive maintenance. This paper looks at the creation of a digital twin for a specific valve type (74BS from SchuF Armaturen und Apparatebau GmbH) and considers key aspects such as model development, sensor integration and IT infrastructure. A test bench is constructed to collect the measured values to support the validation of the digital twin. The integration of sensors and the development of an IT system for data processing are also described in detail. Finally, the technically relevant frequencies are identified in an FFT. [ABSTRACT FROM AUTHOR]

Hydraulic spool valves may clamp under the action of sensitive particles when working in hydraulic oils that contain solid particles, which will then bring about a devastating detriment to the machines. According to the failure statistics of hydraulic systems organized by ISO, more than 80% of the operational failures of hydraulic systems are caused by fluid contamination, and particulate contamination is the most important factor causing spool valve stagnation. In this paper, we considered various factors, including the material, size, and concentration of particles and the spool postures, and built a systematic spool clamping mechanical model. A device was designed to measure the spool valve friction under the action of particles. The influence of particle material, concentration, and size on the friction force of spool valves was investigated. By experiments, we measured the spool clamping force under the action of each single factor and then fitted the datum quantity of spool clamping force and the empirical equation of pulsating quantity. The study results demonstrate three types of non-ideal postures of spools in a valve hole, which are off-center, tilting, and off-center with tilting. Those three postures can engender clamping risk zones with different ranges inside the clearance between spool valves, increasing the risk of spool clamping. The kind of particles is found to have a certain but limited impact on the spool clamping force. Usually, particles with a higher elastic modulus can trigger a larger spool clamping force, which is in line with the theoretical equation. Within a certain range, the probability density distribution of particle size tallies with the normal distribution function, where the "sensitive particles" take up 0.7–1 of the clearance between spool valves. A higher particle volume fraction in oils means a greater number of sensitive particles and a larger spool clamping force. For the particles of a similar size with the clearance between spool valves, when their volume concentration tops over the "sensitive concentration", namely 5%, the risk of spool clamping rises in a drastic manner. This study provides a theoretical reference and an empirical equation for the mechanism of spool clamping under the action of particles, as well as a definite quantitative indicator for the prediction and estimation of spool clamping which is of positive significance for the study of the predictive maintenance of hydraulic equipment. [ABSTRACT FROM AUTHOR]

Objective: The ventriculoperitoneal shunt (VPS) is an established approach in treating normal pressure hydrocephalus (NPH). This study aims to examine the long-term effects of VPS regarding clinical and radiological outcomes, to explore interdependencies with comorbidities and medication, and to determine a suitable opening pressure of the programmable valve. Methods: 127 patients with VPS were retrospectively evaluated. The Hakim triad along with Evans index (EI) and callosal angle (CA) were examined preoperatively and postoperatively at various time points up to over thirty-six months. Preexisting comorbidities and medication were considered. Adjustments to valve settings were documented along with symptom development and complications. Wilcoxon and paired-sample t-tests were used to analyze postoperative change. Chi-square, Eta-squared, and Pearson coefficients were used in correlation analyses. Results: Relief from individual symptoms was most prominent within the first 6 months (p < 0.01). EI and CA significantly decreased and increased, respectively (p < 0.05). Postoperative clinical and radiological improvement was largely maintained over the follow-up period. Diabetes mellitus and apoplexy correlated with surgical outcomes (p < 0.05). The median opening pressure as a function of overall symptom management was determined to be 120 mmH2O for women and 140 mmH2O for men. Conclusion: VPS is effective in treating NPH with respect to both clinical and radiological outcomes, although these two components are independent of each other. Improvement is most pronounced in short-term and maintained in the long-term. Comorbidities have significant influence on the course of NPH. The valve setting does not forecast change in radiological findings; consequently, priority should be placed on the patient's clinical condition. [ABSTRACT FROM AUTHOR]

AbstractThis paper presents a one-dimensional model that describes fluid flow in lymphangions, the segments of lymphatic vessels between valves, using quasilinear hyperbolic systems. The model incorporates a phenomenological pressure-cross-sectional area relationship based on existing literature. Numerical solutions of the differential equations align with known results, offering insights into lymphatic flow dynamics. This model enhances the understanding of lymph movement through the lymphatic system, driven by lymphangion contractions. [ABSTRACT FROM AUTHOR]

Summary: Pittosporum beecheyi Tuyama, endemic to the Ogasawara (Bonin) Islands is described and illustrated; the species is known only from the Hahajima Island group. Key characters for the recognition of this species include the hairy ovary, the solitary flowers with curved pedicels, and the pendulous globose fruits that dehisce into three valves. [ABSTRACT FROM AUTHOR]

Consideration is given to problems of calculating the exhaust from the engine cylinder through a "valve–valve pipe" system at all flow modes. It has been shown that there is a need to determine the exhaust parameters precisely in the cross section of the valve pipe outlet and also to clarify the moment of blocking the flow in the valve and at the valve pipe outlet. Based on the idea of analogy with a sudden expansion of the passage section of a conditional channel, relations have been obtained for determining the flow coefficient of the valve system. The results of calculations using these relations are in good agreement with the results of blowdowns of the valve system of a real engine. To simplify flow calculations and visualize the flow modes in the system using the criteria of the similarity theory and gas-dynamic functions, a method has been developed for constructing a universal two-parameter gas-dynamic characteristic (map) of a valve system similar to maps of compressors and turbines. In this case, the values of flow coefficients in all the modes represented by the maps will be almost the same for systems of various scale and having identical parameters of geometric expansion. [ABSTRACT FROM AUTHOR]

Gate valves provide sealing with metal-to-metal friction. When the right interior parts are selected, and the production is not made according to the proper design criteria, internal leaks occur in the valves in the medium term. Considering the ideal pressure, velocity equations and designs suitable for the process can be realized by determining the nominal pressure and velocity curves. This study designed a standard gate valve with 8-inch connection dimensions. Computational Fluid Dynamics (CFD) method investigated split, flexible, and solid wedge types of the designed valve, 0.5, 1, and 2 m/s flow velocities for zero, four and five-degree wedge closing angles and 20 mm, 40 mm, 60 mm, 90 mm, and 120 mm opening wedge positions. Ansys Fluent software was used for the analyses. Mesh optimization was performed for the ideal mesh number and analyzed according to the ideal mesh number. The k-Epsilon turbulence model was used for simulations. The same situations were repeated for a parallel wedge (0-degree wedge seating angle). The lowest pressure distribution and pressure loss occurred in the parallel wedge compared to the opening position of other types of wedges. The best gate type obtained from the analysis results was determined, and an experimental tightness test was performed. It can be said that the soft seat gate valve, designed according to the results of the sealing test, gives approximately 2.5 times more opening-closing life than the metal gate valve, thus reducing the maintenance-repair costs. [ABSTRACT FROM AUTHOR]

A new species of diatom, Amphorotia robusta sp. nov., is described from subaquatic sediments in the Lingding estuary and Pearl River delta, China. It is distinctive in having strongly curved valves, and regularly even-spaced stria arrangement on both ventral and dorsal sides of the valve. This study builds upon previous diatom research conducted in the Pearl River delta and contributes to our understanding of the taxonomy of the genus Amphorotia in southeastern China. Consequently, it highlights this region as one of the most ecologically diverse habitats for the genus Amphorotia in the Southeast Asian region. [ABSTRACT FROM AUTHOR]

Background: Valve-in-Valve (VIV) transcatheter aortic valve replacement (TAVR) is a potential solution for malfunctioning surgical aortic valve prostheses, though limited data exist for its use in Perceval valves. Methods: searches were performed on PubMed and Scopus up to 31 July 2023, focusing on case reports and series addressing VIV replacement for degenerated Perceval bioprostheses. Results: Our analysis included 57 patients from 27 case reports and 6 case series. Most patients (68.4%) were women, with a mean age of 76 ± 4.4 years and a mean STS score of 6.1 ± 4.3%. Follow-up averaged 9.8 ± 8.9 months, the mean gradient reduction was 15 ± 5.9 mmHg at discharge and 13 ± 4.2 mmHg at follow-up. Complications occurred in 15.7% of patients, including atrioventricular block III in four patients (7%), major bleeding or vascular complications in two patients (3.5%), an annular rupture in two patients (3.5%), and mortality in two patients (3.5%). No coronary obstruction was reported. Balloon-expanding valves were used in 61.4% of patients, predominantly the Sapien model. In the self-expanding group (38.6%), no valve migration occurred, with a permanent pacemaker implantation rate of 9%, compared to 5.7% for balloon-expanding valves. Conclusions: VIV-TAVR using both balloon-expanding and self-expanding technologies is feasible after the implantation of Perceval valves; however, it should be performed by experienced operators with experience both in TAVR and VIV procedures. [ABSTRACT FROM AUTHOR]

The optimization of flow channel structures significantly impacts the performance enhancement of proton exchange membrane fuel cells (PEMFCs). In this paper, the influences of the loop radius, inclination angle, and presence of the island in the Tesla valve flow field on the performance of a fuel cell were investigated numerically. The results indicated that increasing the inclination angle and curvature radius of the Tesla valve increased the voltage by 16.3% and 31.1%, respectively, compared to the parallel flow field at 0.8 A/cm2. Elevating the inclination angle amplified the resistance effect exerted by tributaries on the main stream, consequently fostering channel-to-membrane mass transfer. Increasing the curvature radius contributed to a heightened total oxygen concentration, but also led to water accumulation problems. The removal of islands increased the reactant contact area, but also created more dead zones, resulting in an observed improvement compared to the parallel flow field, but only marginal improvements over the basic Tesla flow field. [ABSTRACT FROM AUTHOR]

For the development of a digital valve, modularization, miniaturization, and low-temperature rise are crucial factors that need to be balanced against each other. A digital valve with integrated multiple coils based on a rectangular section magnetic sleeve is proposed to improve performance. To predicate the thermal performance of the proposed digital valve accurately and rapidly, a nonlinear thermal equivalent circuit (NTEC) model was developed. The most significant distinction of this model is its consideration of the changes in convective thermal resistance based on the operating temperature and installation state. This model has been derived and evaluated by simulation and experiments. The experiment results show that the temperature responses of four key test types obtained from the NTEC model have fairly good correspondence with to those from the experiment and the maximum temperature rise deviation is below 17 %. Finally, a comparison study with a C-type sleeve is demonstrated, indicating that the maximum temperature decline of the coil is 26.1 °C under a vertical state. [ABSTRACT FROM AUTHOR]

A previously developed model of a lymphatic vessel as a chain of lymphangions was investigated to determine whether lymphangions of unequal length reduce pumping relative to a similar chain of equal-length ones. The model incorporates passive elastic and active contractile properties taken from ex vivo measurements, and intravascular lymphatic valves as transvalvular pressure-dependent resistances to flow with hysteresis and transmural pressure-dependent bias to the open state as observed experimentally. Coordination of lymphangion contractions is managed by marrying an autonomous transmural pressure-dependent pacemaker for each lymphangion with bidirectional transmission of activation signals between lymphangions, qualitatively matching empirical observations. With eight lymphangions as used here and many nonlinear constraints, the model is capable of complex outcomes. The expected flow-rate advantage conferred by longer lymphangions everywhere was confirmed. However, the anticipated advantage of uniform lymphangions over those of unequal length, compared in chains of equal overall length, was not found. A wide variety of dynamical outcomes was observed, with the most powerful determinant being the adverse pressure difference, rather than the arrangement of long and short lymphangions. This work suggests that the wide variation in lymphangion length which is commonly observed in collecting lymphatic vessels does not confer disadvantage in pumping lymph. [ABSTRACT FROM AUTHOR]

• A novel variable stiffness valve based on PEEK and stainless steel was proposed. • Stress-strain behavior and operational characteristics of novel valve were studied. • Impacts of novel valve on compressor performance and noise experimentally. • Compressor performance improved by 2.6 % and noise reduced by 3–5 dB. Improving valve design is crucial for enhancing the performance of rolling piston type rotary compressor. A novel variable stiffness valve based on PEEK and stainless steel was proposed. The stress-strain behavior of the novel valve was studied, and its operational characteristics, including opening and closing angles and over-compression losses, were analyzed in a compressor. It is shown that opening and closing angle of the new-designed valve were advanced compared to that of the original cylinder by about 2∼3°, leading to a general reduction in over-compression losses, with a maximum decrease of 4.15 W. The impacts of new-designed valve on compressor performance were experimentally investigated. The cooling capacity and coefficient of performance of compressors equipped with new-designed compared to original valve were improved by 1.1–1.7 % and 1.1–2.6 %, respectively. In addition, the input electrical power required for the new valve was observed to be 0.9–1.3 % lower. The incorporation of high-damping material in the new valve design significantly reduced compressor noise by 3–5 dB at the critical frequency bands of 630–1250 Hz. These findings offer valuable insights for enhancing the energy efficiency and noise reduction in rolling piston type rotary compressors. [ABSTRACT FROM AUTHOR]

• Cyclic thermodynamic perfection decreases by 20.3 % when prototype's speed increases from 6000 rpm to 10,800 rpm. • Prototype's vane and roller separate by 0.38 mm at 10,800 rpm. • Double-valve structure decreases over-compression loss by 45.0 % at 10,800 rpm. • Double-valve alleviates separation by 10.5 %. With the trend towards miniaturization of rotary compressors, increasing the speed of compressors and improving performance at high speed have become important research directions. Simultaneously, due to the need for refrigerants with low global warming potential (GWP), R290 has become an important alternative to hydrofluorocarbons (HFCs). Under the same compressor structure size, meeting the cooling/heating demands with R290 necessitates higher operating speed owing to its lower cooling capacity per unit volume. In this paper, the performance loss distribution of an ultra-high-speed R290 rotary compressor has been studied theoretically and experimentally, and the accuracy of theoretical calculation was verified through experiments. According to the calculation, the primary factor influencing the performance of the ultra-high-speed rotary compressor is over-compression loss. Consequently, corresponding solutions to improve the performance of the ultra-high-speed compressor were proposed. The internal parameters of the compressor were measured, thereby validating the conclusions and assessing the efficacy of the proposed solutions. Finally, the structure parameters were further optimized, which was also verified by experiments. It is found that the double-valve structure can effectively reduce the over-compression loss. When operating at 10,800 rpm under the ASHRAE T1, compared with the prototype, the compressor with double-valve structure can reduce the over-compression loss by 45.0 %, and increase the cyclic thermodynamic perfection by 7.85 %. [ABSTRACT FROM AUTHOR]

Using modern high-performance microcontrollers with wireless interfaces, built-in ADCs and low overall consumption, we develop a portable, real-time parametric diagnostic system for marine engines. The system is based on the use of modern Android/iOS gadgets that receive information from sensors via Bluetooth and then carry out the necessary calculations and display charts and data in real time. The system developed here uses a combination of a gas pressure sensor in the working cylinder and a vibroacoustic sensor, which expands the diagnostic capabilities of marine diesel engines under operating conditions. This solution allows for diagnosis of the fuel injection system, the valve train mechanism, and several other engine systems. In order to develop a portable diagnostic system for marine diesel engines, it is first necessary to solve the problem of analytically determining top dead centre (TDC), since such a system does not use special sensors for this. An algorithm for determining TDC is proposed here, based on an analysis of the measured pressure diagram rather than its derivative, which minimises the influence of digital and analogue noise. Our algorithm for determining TDC and subsequent data synchronisation is applicable in the absence of information about the actual compression ratio in the cylinder, which is a typical scenario for modern engines with variable valve timing. The algorithm also works under conditions of only approximate data on the charge air pressure, which are refined during the iteration process. A formula is proposed for determining the initial TDC position. Parameters for irregular operation of the engine are considered, and can be calculated in real time using time diagrams of pressure and vibration. Methods for expressly assessing the stability of the functioning of the main engine systems by monitoring and analysing a number of successive operating cycles are considered. To assess the unevenness of operation of the engine, a dispersion estimate of the deviations in the main parameters is used. To enable a comprehensive assessment of the engine stability in real time, the CII (cycle irregularity index) criterion is developed. The data processing methods described in this article provide an accurate estimate of the indicated power, due to the precise determination of TDC, thereby enabling an analysis of the stability of the operating cycles, optimal tuning of the engine systems, and monitoring of the results during operation. [ABSTRACT FROM AUTHOR]

Several studies have utilized commercial Computational Fluid Dynamics (CFD) software to predict and optimize hood performance in reducing odors. In this study, our objective is to simulate the European standard test using CFD software. To achieve this objective, we modeled a full-scale kitchen and hood-mounted Air Flow Control Valve (AFCV) using Ansys Fluent software. We investigated the impact of hood flow rate and AFCV design on capture efficiency and Methyl Ethyl Ketone (MEK) extraction in detail. The analyzes simulate the capture of the heated water vapor and MEK mixture by the AFCV. The analyzes have been validated with experimental results for different flow rate conditions and have been used with confidence to model the MEK diffusion in a realistic kitchen. Thanks to the innovative AFCV created, an 8% improvement has been achieved in capture performance at a flow rate of 100 m3/h. The experiments have been repeated at different flow rates, when evaluated in terms of system pressure required for flow rate and energy consumption, approximately 27% savings were achieved at 400 m3/h flow. It is great to hear that this study has provided valuable insights for developing high-efficiency ventilation systems (hood) with improved indoor air quality and low energy consumption for central ventilation systems. [ABSTRACT FROM AUTHOR]

Copyright of Informatica (03505596) is the property of Slovene Society Informatika and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The electro-pneumatic braking system with ON/OFF solenoid valves has been widely used in trains due to its advantages and superiority. The undesirable impact of the thermal effect on the electro-pneumatic braking system leads to frequent valve switching, degradation of the pressure tracking performance and sometimes instability. This article presents an adaptive model predictive control approach to solve the pressure control problem under temperature uncertainty based on a switched unscented Kalman filter. First, a nonlinear switched dynamical model with the uncertain temperature parameter is derived for the electro-pneumatic braking system by comprehensively integrating its nonlinear, discontinuous dynamics and thermal effect. Using a switched unscented Kalman filter on the presented model of the system, the temperature parameter is accurately estimated to improve the model's accuracy. Based on the corrected system model and the designed adaptive model predictive control method, the pressure tracking performance and the valves' switchings of the electro-pneumatic braking system are improved, and the stability is guaranteed. The simulations and the experiments conducted for a braking system prototype confirm the performance validity of the proposed method. • A switched UKF is designed to account for the hybrid characteristics of the braking system. • An adaptive hybrid MPC is proposed to achieve optimal pressure tracking performance while minimizing the number of valve switches. • The stability of the closed-loop system is rigorously analyzed using Lyapunov theory. [ABSTRACT FROM AUTHOR]