Search Results (92)

Plasma electrolytic oxidation (PEO) is an electrochemical surface modification technique for producing dense oxide layers on valve metals. This review compiles the various modifications to the PEO process that have been used to improve the produced coatings and make them suitable for specific applications, with a focus on examples of aluminum, magnesium, and titanium substrates. An overview of the PEO process is given, highlighting the various process parameters and their effects on the final surface. The challenges with light metals that motivate the use of surface modifications are summarized, along with some of the other modifications that attempt to overcome them. Two broad categories of modifications to the PEO process are presented: in situ modifications, influencing the properties of the coating during its formation, and ex situ modifications, augmenting the properties of an already-formed coating. Finally, specific examples of applications for modified PEO processes are discussed, including battery, biomedical, water treatment, and energy production applications. Full article

Converter stations are pivotal in high-voltage direct current (HVDC) systems, enabling power conversion between an alternating current (AC) and a direct current (DC) while ensuring efficient and stable energy transmission. Fault detection in converter stations is crucial for maintaining their reliability and operational safety. This paper focuses on image-based detection of five common faults: metal corrosion, discoloration of desiccant in breathers, insulator breakage, hanging foreign objects, and valve cooling water leakage. Despite advancements in deep learning, existing detection methods face two major challenges: limited model generalization due to diverse and complex backgrounds in converter station environments and sparse supervision signals caused by the high cost of collecting labeled images for certain faults. To overcome these issues, we propose InvMOE, a novel fault detection algorithm with two core components: (1) invariant representation learning, which captures task-relevant features and mitigates background noise interference, and (2) multi-task training using a mixture of experts (MOE) framework to adaptively optimize feature learning across tasks and address label sparsity. Experimental results on real-world datasets demonstrate that InvMOE achieves superior generalization performance and significantly improves detection accuracy for tasks with limited samples, such as valve cooling water leakage. This work provides a robust and scalable approach for enhancing fault detection in converter stations. Full article

The sealing performance of metal seals in all-metal angle valves significantly affects their reliability and the safety of the entire fluid system. This study investigates a DN40 all-metal angle valve, analyzing the contact characteristics between the sealing ring and valve head cone surface, focusing on microscopic surface morphology. Finite element analysis and laboratory experiments were conducted on sealing rings with surface roughness values of 1.6 μm, 0.4 μm, and 0.2 μm. Additionally, leakage rates were measured experimentally to verify the model’s accuracy. The results show that reducing surface roughness to 0.2 μm lowers the valve’s leakage rate to 1.28 × 10⁻¹¹ Pa·m³/s, meeting ultra-high vacuum requirements. Compared to 0.4 μm, the leakage rate of 0.2 μm was reduced by 45.9%. The sealing performance of the 1.6 μm metal sealing ring was relatively poor and failed to meet ultra-high vacuum requirements. These findings align well with theoretical predictions. Further analysis revealed that lower surface roughness increases the effective contact area between the sealing ring and valve head cone, reducing leakage and improving overall sealing efficiency. These results suggest that optimizing surface roughness in sealing ring design can enhance valve performance, improving reliability and efficiency in industrial applications, particularly in vacuum systems and high-performance fluid control. Full article

Background: Endoscopic self-expandable metallic stent (SEMS) placement is a widely accepted treatment for malignant left-sided colorectal obstruction (LSO) because of its lower invasiveness and quicker symptomatic relief compared to surgery. However, SEMS placement for ileocecal valve obstruction (ICVO) has not been established due to its technical difficulties. Methods: This single-center retrospective study compared the clinical outcomes of patients who underwent SEMS placement for ICVO (ICVO group, n = 13) and LSO (LSO group, n = 146). Particularly in cases with severe small-intestine dilation, we applied a “Two-Step Strategy”, which involved long intestinal tube insertion followed by SEMS placement to ensure safety and overcome technical challenges. Results: Patients in the ICVO group were significantly more likely to undergo SEMS placement with the Two-Step Strategy compared to those in the LSO group (76.9% vs. 6.9%, p < 0.001). Both groups achieved similarly high technical and clinical success rates (100% vs. 98.6%, p = 1.000; 92.3% vs. 88.4%, p = 1.000), and the incidence of adverse events also showed no significant difference between the groups (7.7% vs. 13.0%; p = 1.000). Furthermore, the median time to recurrent colorectal obstruction and survival time after SEMS placement did not differ between patients with palliative stenting for ICVO and LSO (not reached vs. 430 days, p = 0.586; 119 days vs. 200 days, p = 0.303). Conclusions: SEMS placement for malignant ICVO is as safe and effective as it is for malignant LSO, and the Two-Step Strategy might be useful in ICVO cases. Full article

Objective: Stuck prosthetic valves, often resulting from pannus formation or thrombus accumulation, represent a critical complication in prosthetic valve management, carrying significant risks for morbidity and mortality. This study aims to identify factors associated with stuck valve development and assess the effectiveness of interventions in restoring normal valve function. Methods: A total of 27 patients with stuck valves were analyzed, including mitral, aortic, and tricuspid valve cases. Metallic valves were initially implanted in all patients. Interventions included pannus cleaning in suitable cases and valve replacement when necessary, with the replacement being either metallic and biological based on clinical indications. Preoperative and postoperative ECG rhythms, left ventricular ejection fraction (LVEF) values, and gradient measurements were evaluated across patient groups. Results: No significant difference was found in time since initial surgery across valve types (p = 0.67), except in mitral valves, where time was longer in the replacement group (p = 0.02). Maximum gradients were higher in the pannus cleaning group for mitral valves (p = 0.03), while overall gradient values showed no significant differences. Postoperative left ventricular ejection fraction improved significantly in all groups (p < 0.001). Conclusions: The findings highlight the importance of timely intervention in managing stuck prosthetic valves, which are associated with severe hemodynamic compromise and embolic risk. Pannus cleaning emerged as a viable alternative in selected cases where the obstruction was localized, with the valve structure otherwise intact. Biological valve replacements demonstrated superior rhythm stabilization in this study, although definitive conclusions are constrained by the minimal sample size (n = 2). Future research should focus on expanding sample sizes and incorporating comprehensive preoperative analyses to better inform surgical and clinical management strategies. Full article

Plasma electrolytic oxidation (PEO) is often used to improve the physical and mechanical properties of valve metals. This method allows for the formation of thicker and denser metal oxide coatings, which helps to improve physical and mechanical properties, especially the wear and corrosion resistance of the surface. The PEO process is widely used in areas such as mechanical engineering, aerospace, biomedical, and others. This review aims to summarize and explain the fundamental principles of the PEO process, with a focus on the influence of waveform types and their parameters on the properties of PEO coatings. This study found that a sinusoidal waveform promotes the generation of more stable discharges compared to a rectangular waveform, thereby enhancing the corrosion resistance of the coatings. Furthermore, it was demonstrated that using a rectangular waveform with adjustable parameters enables the production of thicker and more wear-resistant coatings. Meanwhile, the application of sawtooth and trapezoidal waveforms reduces sharp current spikes during the onset of discharges, minimizing defect formation and positively influencing the coating formation process. In addition, bipolar and unipolar modes are analyzed, and the promising future directions are discussed. Full article

Hydrogen fuel cell-based UAM (urban air mobility) systems are gaining significant attention due to their advantages of higher energy density and longer flight durations compared to conventional battery-based UAM systems. To further improve the flight times of current UAM systems, various hydrogen storage methods, such as liquid hydrogen and hydrogen metal hydrides, are being utilized. Among these, hydrogen metal hydrides offer the advantage of high safety, as they do not require the additional technologies needed for high-pressure gaseous hydrogen storage or the maintenance of cryogenic temperatures for liquid hydrogen. Furthermore, because of the relatively slower dynamic response of hydrogen fuel cell systems compared to batteries, they are often integrated into hybrid configurations with batteries, necessitating an efficient power management system. In this study, a UAM system was developed by integrating a hydrogen fuel cell system with hydrogen metal hydrides and batteries in a hybrid configuration. Additionally, a state machine control approach was applied to a distribution valve for the endothermic reaction required for hydrogen desorption from the hydrogen metal hydrides. This design utilized waste heat generated by the fuel cell stack to facilitate hydrogen release. Furthermore, a fuzzy logic control-based power management system was implemented to ensure efficient power distribution during flight. The results show that approximately 43% of the waste heat generated by the stack was recovered through the tank system. Full article

This paper presents the results of a hot-fire test campaign aimed at characterizing a newly developed ignition system for nitromethane-based green monopropellants. Nitromethane-based propellants are a cost-effective replacement for hydrazine and energetic ionic liquid hydrazine alternatives such as LMP-103S and ASCENT. The developed system uses a glow plug as the ignition source. Additionally, gaseous oxygen is injected simultaneously into the combustion chamber at the beginning of a firing. After closing the oxygen valve, a pure monopropellant operation follows. Three test series were carried out using NMP-001, a previously characterized nitromethane-based monopropellant. During the first test series, the required ROF for ignition was identified to be above 0.3. In the second test series, the low-pressure combustion limit was shown to be 13.9 bar, which is significantly lower than the 30 bar limit of heritage nitromethane-based monopropellants. In the third test series, the oxygen injection timing was optimized to minimize the required amount of oxygen for successful ignition to 1.5 g per ignition in this test setup. This approach to ignition is more cost effective than the catalytic initiation used for other monopropellants because neither costly precious-metal catalytic materials nor lengthy preheating procedures are required. Full article

A flat-plate unglazed solar water heater (SWH) with a polymer thermal absorber was developed and experimented with. Polymer thermal absorbers could be a viable alternative to metal thermal absorbers for SWH systems. The performance of this polymer SWH system was measured based on inlet and outlet water temperature, water flow rate, ambient air temperature and solar irradiance. The polymer thermal absorbers were hollow Polyvinyl Chloride (PVC) tubes with a 20 mm external diameter and 3 mm thickness and were painted black to enhance radiation absorption. The pipes are arranged in a rectangular spiral inward–outward alternating-flow (RSioaf) pattern. The collector pipes were placed in a 1 m × 1 m enclosure with bottom insulation and a reflective surface for maximized radiation absorption. Water circulated through a closed loop with an uninsulated 16 L storage tank, driven by a pump and controlled by two valves to maintain a mass flow rate of 0.0031 to 0.0034 kg·s⁻¹. The test was conducted under a partially clouded sky from 9 a.m. to 5 p.m., with solar irradiance between 105 and 1003 W·m⁻² and an ambient air temperature of 27–36 °C. This SWH system produced outlet hot water at 65 °C by midday and maintained the storage temperature at 63 °C until the end of the test period. Photothermal energy conversion was recorded, showing a maximum value of 23%. Results indicate that a flat-plate solar water heater with a polymer thermal absorber in an RSioaf design can be an effective alternative to an SWH with a metal thermal absorber. Its performance can be improved with glazing and optimized tube sizing. Full article

Contaminated water has remained an unsolved problem for decades, particularly when the contamination derived from heavy metals. A possible solution is to mix the contaminated water with magnetic nanoparticles so that an adsorption process can take place. In that frame, Tesla valve micromixer and ${\mathrm{Fe}}_3{\mathrm{O}}_4$ magnetic nanoparticles were selected to perform simulations for encounter maximum mixing efficiency. These simulations focus on inlet velocities ratios between contaminated water and nanoparticles and inlet rates of nanoparticles. The maximum mixing efficiency was 44% for the inverse double Tesla micromixer found for the combination of ${\mathrm{Fe}}_3{\mathrm{O}}_4$ nanoparticles as the inlet rate and with inlet velocity ratios of ${\displaystyle \frac{V_p}{V_c}}=10$. Full article

Background: Since laparoscopic surgery became the gold standard for colorectal procedures, specific skills are required to achieve good outcomes. The best way to acquire basic and advanced skills and reach the learning curve plateau is by using dedicated simulators: box-trainers, video-trainers and virtual reality simulators. Laparoscopic skills training outside the operating room is cost-beneficial, faster and safer, and does not harm the patient. When compared to box-trainers, virtual reality simulators and cadaver models have no additional benefits. Several laparoscopic trainers available on the market as well as homemade box and video-trainers, most of them using plastic boxes and standard webcams, were described in the literature. The majority of them involve training on a flat surface without any anatomical environment. In addition to their demonstrated benefits, box-trainers which add anatomic details can improve the training quality and skills development of surgeons. Methods: We created a 3D-printed anatomic pelvi-trainer which offers a real-size narrow pelvic space environment for training. The model was created starting with a CT-scan performed on a female pelvis from the Anatomy Museum (Cluj-Napoca University of Medicine and Pharmacy, Romania), using Invesalius 3 software (Centro de Tecnologia da informação Renato Archer CTI, InVesalius open-source software, Campinas, Brazil) for segmentation, Fusion 360 with Netfabb software (Autodesk software company, Fusion 360 with Netfabb, San Francisco, CA, USA) for 3D modeling and a FDM technology 3D printer (Stratasys 3D printing company, Fortus 380mc 3D printer, Minneapolis, MN, USA). In addition, a metal mold for casting silicone valves was made for camera and endoscopic instruments ports. The trainer was tested and compared using a laparoscopic camera, a standard full HD webcam and “V-Box” (INTECH—Innovative Training Technologies, Milano, Italia), a dedicated hard paper box. The pelvi-trainer was tested by 33 surgeons with different qualifications and expertise. Results: We made a complete box-trainer with a versatile 3D-printed pelvi-trainer inside, designed for a wide range of basic and advanced laparoscopic skills training in the narrow pelvic space. We assessed the feedback of 33 surgeons regarding their experience using the anatomic 3D-printed pelvi-trainer for laparoscopic surgery training in the narrow pelvic space. Each surgeon tested the pelvi-trainer in three different setups: using a laparoscopic camera, using a webcam connected to a laptop and a “V-BOX” hard paper box. In the experiments that were performed, each participant completed a questionnaire regarding his/her experience using the pelvi-trainer. The results were positive, validating the device as a valid tool for training. Conclusions: We validated the anatomic pelvi-trainer designed by our team as a valuable alternative for basic and advanced laparoscopic surgery training outside the operating room for pelvic organs procedures, proving that it supports a much faster learning curve for colorectal procedures without harming the patients. Full article

The greatest losses during gas transportation occur in the elements of shut-off valves, the operating parameters of which, among other things, depend on the thickness and hardness of the protective coating of the ball plugs. The study of the parameters of nickel–phosphorus and chrome coatings on ball plugs of serially produced shut-off valves, including control of their thickness and hardness, was carried out. Based on the test results, deviations in the actual parameters of coatings from the requirements of technological documentation were revealed, the necessity of their complex control was substantiated, recommendations on the choice of methods and equipment were formulated, and the main provisions of the test methodology were developed. Full article

The seal and weight of the Type IV hydrogen storage vessel are the key problems restricting the safety and driving range of fuel cell vehicles. The boss, as a metal medium connecting the inner liner of the Type IV hydrogen storage vessel with the external pipeline, affects the sealing performance of the Type IV hydrogen storage vessel, and there is no academic research on the weight of the boss. Therefore, according to the force characteristics of the boss, this paper divides the upper and lower areas (valve column and plate). The valve column with seal optimization and light weight is manufactured with a 3D printing additive, while the plate bearing and transferring the internal pressure load is manufactured by forging. Firstly, a two-dimensional axisymmetric simulation model of the sealing ring was established, and the effects of different compression rates on its seal performance were analyzed. Then, the size and position of the sealing groove were sampled, simulated, and optimized based on the Latin Hypercube method, and the reliability of the optimal seal structure was verified by experiments. Finally, the Solid Isotropic Material with Penalization (SIMP) topology method was used to optimize the weight of the boss with optimal sealing structure, and the reconstructed model was checked and analyzed. The results show that the weight of the optimized boss is reduced by 9.6%. Full article

At present, the methods for sulfur solubility testing of high-sulfur natural gas generally use laboratory proportioning gas samples and then connect equipment to test the sulfur solubility of the gas samples based on the adsorption deposition mechanism. However, these testing methods generally have the following problems: (1) The equipment used in these test methods has safety hazards such as leakage at pipe and valve connections. (2) The sulfur solubility of real gas samples cannot be measured directly. (3) The equipment is difficult to clean, and it is especially difficult to clean the sulfur deposited at pipe elbows and valve connections. This will lead to low sulfur solubility test results. (4) The thermal insulation performance during the test process is not good, and temperature changes have a great impact on gas volume measurement. In order to solve the above problems, a testing method and comprehensive experimental device for the solubility of elemental sulfur in high-sulfur natural gas were established. This test method wraps the entire experimental device with a metal shell, which has good safety and thermal insulation performance, and it uses customized pipeline connections, which have high flushing efficiency, less sulfur deposition, and more accurate experimental results. The upgraded filtration system can directly measure the sulfur dissolution of real gas samples, and a CS₂ solution recovery process is added to reduce the risk of leakage and environmental pollution. This method and equipment were used to test the elemental sulfur solubility determination of real gas samples from a high-sulfur gas well. The research results show that the solubility of elemental sulfur is related to temperature, pressure, and H₂S concentration and increases with the increase in temperature, pressure, and H₂S concentration. Compared with the previous method, this method has less residual sulfur during the test process, the measured sulfur solubility is 2.13% greater, and the test results are more accurate and reliable. This research result provides important basic data support for accurately measuring the elemental sulfur solubility of real gas samples in high-sulfur gas reservoirs and dealing with sulfur deposition problems. Full article

Diesel engine combustion is dependent mainly on the fuel injection characteristics, particularly the injection pressure and rate, which directly affect the engine efficiency and emissions. Herein, an electrically controlled supercharger is added to a traditional high-pressure common rail system to form an ultrahigh-pressure common rail system. Then, the variations in the spray, combustion, and emission characteristics of a diesel engine with a variable fuel injection rate are analyzed. Moreover, a simulation model for a diesel engine combustion chamber is built and verified by experimental results for numerical analysis. The results reveal that the injection rate can be flexibly adjusted via regulation when the solenoid valves are opened on the electrically controlled supercharger. Specifically, (1) the boot-shaped injection rate has greater potential than the traditional rectangular injection rate in terms of combustion and emission; (2) the main injection advance angle at the boot-shaped injection rate can be properly increased to improve combustion; and (3) the pilot injection quantity and advance angle are strongly coupled with the boot-shaped injection rate, potentially enhancing the mixing efficiency of fuel and air in the cylinder to achieve favorable emission results. This paper provides good guidance for the reliable design and optimization of noble-metal-based diesel engines. Full article