Edge Surface Research Articles

Preferential interlayer adsorption sites in phyllosilicate clay edge models by molecular dynamics simulation

Phyllosilicate clay minerals have been proposed as a possible buffer material to be used in deep geological repositories containing high-level waste and used nuclear fuel. This work precisely characterizes ion interactions with two types of adsorption sites present in these clays: MgAl’ substitutions and undercoordinated edge surface atoms. A number of unique structural models were considered to represent the diverse local environments that ions in these systems are likely to encounter. Using molecular dynamics simulation with the CLAYFF potential, the spatial distribution, interlayer composition, and residence times of Na+ and Cl− ions as radionuclide analogs in pyrophyllite and montmorillonite clay models were investigated to identify the most favorable conditions for sequestration. The most significant factor impacting ion adsorption was found to be the localization of charge density at substitution sites. In a montmorillonite system in which substitution sites were distributed evenly to produce a low charge density, sequestration performance was found to be comparable to pyrophyllite.

Nodal precession of a hot Jupiter transiting the edge of a late A-type star TOI-1518

Abstract TOI-1518b, a hot Jupiter around a late A-type star, is one of the few planetary systems that transit the edge of the stellar surface (the impact parameter b ∼ 0.9) among hot Jupiters around hot stars (Cabot et al. 2021, AJ, 162, 218). The high rotation speed of the host star (∼85 km s−1) and the nearly polar orbit of the planet (∼120○) may cause a nodal precession. In this study, we report the nodal precession undergone by TOI-1518 b. This system is the fourth planetary system in which nodal precession is detected. We investigate the time change in b from the photometric data of TOI-1518 acquired in 2019 and 2022 with TESS and from the spectral transit data of TOI-1518b obtained in 2020 with two high-dispersion spectrographs; CARMENES and EXPRES. We find that the value of b is decreasing with db$/$dt = −0.0116 ± 0.0036 yr−1, indicating that the transit trajectory is moving toward the center of the stellar surface. We also estimate the minimum value of the quadrupole mass moment of TOI-1518, J2,min = 4.41 × 10−5, and the logarithm of the Love number of TOI-1518, log k2 = −2.17 ± 0.33, from the nodal precession.

Effect of the leading-edge vortex generator on the performance of the linear cascade

In this paper, based on the airflow improvement mechanism of dragonfly wing veins, a vortex generator is designed at the leading edge of the suction surface to improve the flow condition of compressor cascades. The influence of the placement positions and geometric dimensions of the vortex generators on the flow field structure and aerodynamic performance is investigated by numerical simulation. The research reveals that vortex generators at the leading edge of the suction surface can generate induced vortices near the end wall, suppressing the accumulation of low-energy fluid in the corner region. This results in a backward shift of the separation initiation point, a reduction in the corner separation region along the pitch direction, and a reduction in flow loss. The vortex generators exhibit favorable characteristics with positive incidence angles. However, when the incidence angle is below the minimum loss incidence angle, the vortex generators increase the flow losses of the cascade. Optimum performance is achieved when the vortex generators are positioned at the start of the corner separation. The flow control influence initially increases and then decreases as the height of the vortex generators increases. Similarly, the control impact is enhanced and then weakened as the placement position moves away from the suction surface. The flow losses decrease by 10.3% when the vortex generators are placed at the junction between the end wall recirculation and the mainstream region at a height equal to 2% of the blade height.

Research on the Overall Influence of Magnus Cylinders on Airfoil Structures and Structural Optimization

With the coupling effect of Magnus cylinder and symmetric airfoil as the research object, the numerical analysis method is used to study the influence of Magnus cylinder layout position and protruding height ratio on the aerodynamic characteristics of the airfoil. Based on the aerodynamic law of Magnus airfoil and Optistruct deformer optimisation method, the optimisation model of Magnus airfoil structure is proposed. Results reveal that the placement of the Magnus cylinder near the leading edge of the upper surface and the trailing edge of the lower surface significantly impacts the aerodynamic characteristics of the Magnus airfoil. Moreover, as the protruding height ratio increases, the aerodynamic performance of the airfoil experiences an initial enhancement followed by a reduction. Under the conditions of an 8° angle of attack and a Reynolds number of 9.5×105, the optimized aerodynamic performance of the Magnus airfoil demonstrates a remarkable increase of 17.5% compared to the baseline airfoil, accompanied by a significant reduction of 28.1% in stress concentration.

Topological Quantum Switching Enabled Neuroelectronic Synaptic Modulators for Brain Computer Interface.

Aging and genetic-related disorders in the human brain lead to impairment of daily cognitive functions. Due to their neural synaptic complexity and the current limits of knowledge, reversing these disorders remains a substantial challenge for brain-computer interfaces (BCI). In this work, a solution is provided to potentially override aging and neurological disorder-related cognitive function loss in the human brain through the application of the authors' quantum synaptic device. To illustrate this point, a quantum topological insulator (QTI) Bi2Se2Te-based synaptic neuroelectronic device, where the electric field-induced tunable topological surface edge states and quantum switching properties make them a premier option for establishing artificial synaptic neuromodulation approaches, is designed and developed. Leveraging these unique quantum synaptic properties, the developed synaptic device provides the capability to neuromodulate distorted neural signals, leading to the reversal of age-related disorders via BCI. With the synaptic neuroelectronic characteristics of this device, excellent efficacy in treating cognitive neural dysfunctions through modulated neuromorphic stimuli is demonstrated. As a proof of concept, real-time neuromodulation of electroencephalogram (EEG) deduced distorted event-related potentials (ERP) is demonstrated by modulation of the synaptic device array.

Head surface strain measurement based wireless bolt sensor with self temperature compensating

Bolt loosening detection is crucial for ensuring the safe operation of equipment. Loosened bolts are hard to detect, and if left undetected, it can lead to catastrophic failures, especially for numerous bolts in large-scale structures. Therefore, the development of distributed bolt monitoring method and related sensors is highly necessary. In this paper, a novel bolt preload sensor with self-temperature compensation is proposed, based on the strain distribution of the bolt head end face. This study enhances previous research by conducting a detailed analysis of strain distribution at the edge of the bolt head surface. The finite element analysis results show that the bolt preload has almost no effect on the circumferential strain in the edge region of bolt head surface. Based on this feature, the strain gauge is applied circumferentially along the edge of the bolt head face as a temperature compensation gauge. In this way, the measuring strain gauge and the temperature compensation gauge can be integrated on the surface of the bolt head, thus achieving self-temperature compensation for the sensor. An experimental device has been established and the experimental results show that the designed sensor has excellent linearity to the bolt preload and effective temperature compensation. For the monitoring of numerous bolts with a wide distribution, a wireless sensing network utilizing the proposed sensor has been designed. The proposed wireless bolt sensor is easy to install and replace, without redesigning or changing the existing structure, thus providing a simple and effective way to monitor large number of bolts with wide distribution.

Effect of AC Electric Field Polishing on Motion of Slurry and Tool Edge Surface

Effect of AC Electric Field Polishing on Motion of Slurry and Tool Edge Surface

Numerical studies on shock wave and boundary layer interaction in the high-load turbine rotor cascades

Design of transonic high-load turbine is the essential approach to improve thrust-to-weight ratio of gas turbine engines. The shock wave and boundary layer interaction (SWBLI) in high-load turbine is one of the important unsteady sources and the main source of loss in turbine stages. In order to study mechanism of SWBLI in high-load turbine, rotor blades with loading coefficients range from 1.6 to 2 were designed and Delayed Detached Eddy Simulations (DDES) were carried out. The influences of loading coefficient, exit isentropic Mach number and incidence angle on characteristics of shock wave, SWBLI as well as flow details in the blade passages were compared. Results indicated the shock wave was generated and enhanced as exit isentropic Mach numbers increased leading to the increase of 2.8% in the total pressure loss coefficient. There was not significant difference in the total pressure loss coefficient as loading coefficient increased, however the shock wave was stronger and the separation bubble was longer at the loading coefficient of 1.6. Meanwhile, the influence of strong separation near the leading edge of suction surface induced by variation of incidence angles on the characteristics of the shock wave and the loss was also obvious.

Enhancing the photothermal efficiency of MoS2 through ultraviolet-ozone exposure for improved solar evaporation

MoS2 has been explored as a photothermal layer for solar-driven water evaporators to produce clean water. However, there have been no reports studying the effects of ultraviolet-ozone (UVO) exposure on the photothermal properties of MoS2. This study investigates the impact of UVO exposure (10, 20, and 30 minutes) on bulk 2H-MoS2 synthesized via a hydrothermal method at 200°C for 16 hours. The freshly prepared MoS2 contained high concentrations of molybdenum oxide phases, which significantly diminished after 10 minutes of UVO exposure, indicating improved purity of MoS2. The increased purity of UVO-exposed MoS2 led to a rise in layer temperature to 47.37°C, surpassing the 43.40°C temperature of MoS2 without UVO exposure. Extending the UVO exposure to 30 minutes further increased the number of surface edge sites, thereby enhancing the wettability of MoS2 due to the increased binding sites for polar water molecules. Consequently, MoS2 exposed to UVO for 30 minutes demonstrated the highest evaporation rate of 1.83 kg m−2 h−1, achieving a photothermal efficiency of 94%, a high salt rejection rate of 99.98%, and a high heavy metal ion rejection rate of 91.84%. Therefore, the application of UVO-exposed MoS2 serves as an effective photothermal layer for sustainable and eco-friendly clean water production technologies.

Analysis of unsteady flow and pressure pulsation of multistage centrifugal pump based on actual size

In this paper, the unsteady flow and pressure pulsation in 11-stage centrifugal pump were analyzed based on large eddy simulation. The performances from the numerical simulation agreed with the ones from the experiment. The numerical results show that large pressure gradient area appears on trailing edge of blade pressure surface, and large vorticity intensity area appears on blade suction surface and trailing edge. The vortexes in the impeller passage decrease obviously with the increase of flow rate from 0.4 Q to 1.2 Q. As the stage increase, there is a local high pressure area at the tongue and it affects the fluid backflow. The main frequency of the pulsation at the impeller inlet is the blade passing frequency ( fBPF), and the main frequency at the impeller outlet and the interface is 2 fBPF. Due to interstage interference, the main frequency of the second impeller includes blade passing frequency of the first stage impeller (5 fn) and its own blade passing frequency (7 fn). With the increase of the stages, the rule of pulsation gradually tends to be consistent.

Water thin films on kaolinite gibbsite and edge surfaces and their effects on surface wettability in relation to geological carbon sequestration

Geological carbon sequestration (GCS) is a promising method to alleviate CO2 emission, while CO2 structural trapping is one of main GCS mechanisms, in which the storage capacity is strongly dependent on CO2-water–rock contact angle. Although CO2-water-kaolite contact angle on basal surfaces has been studied, the knowledge about kaolinite edge surface wettability remains unknown. In this work, we use molecular dynamics (MD) simulations to study CO2-water-kaolinite contact angle on kaolinite gibbsite and edge surfaces under a typical GCS condition (330 K and 200 bar). The common belief is that surface wettability in presence of water is determined by surface hydroxyl (–OH) group density. While the surface –OH group density of kaolinite edge surface is much lower than that of gibbsite surface, both gibbsite and edge surfaces are strongly water-wet. Edge surface is better hydrated than gibbsite surface as both silanol and aluminol groups can form hydrogen bonding with water molecules thanks to large effective water accessible volume around them, while pocket water can further anchor water film. Therefore, the atomic-level surface characteristics dictate interfacial water structures which determine CO2-water-kaolinite contact angle. Our study provides important insights into the effect of surface heterogeneity on interfacial water structures, and kaolinite gibbsite and edge surface wettability which is crucial to the optimization of GCS processes.

Molecular Mechanisms of Sorbed Ion Effects during Boehmite Particle Aggregation.

Classical theories of particle aggregation, such as Derjaguin-Landau-Verwey-Overbeek (DLVO), do not explain recent observations of ion-specific effects or the complex concentration dependence for aggregation. Thus, here, we probe the molecular mechanisms by which selected alkali nitrate ions (Na+, K+, and NO3-) influence aggregation of the mineral boehmite (γ-AlOOH) nanoparticles. Nanoparticle aggregation was analyzed using classical molecular dynamics (CMD) simulations coupled with the metadynamics rare event approach for stoichiometric surface terminations of two boehmite crystal faces. Calculated free energy landscapes reveal how electrolyte ions alter aggregation on different crystal faces relative to pure water. Consistent with experimental observations, we find that adding an electrolyte significantly reduces the energy barrier for particle aggregation (∼3-4×). However, in this work, we show this is due to the ions disrupting interstitial water networks, and that aggregation between stoichiometric (010) basal-basal surfaces is more favorable than between (001) edge-edge surfaces (∼5-6×) due to the higher interfacial water densities on edge surfaces. The interfacial distances in the interlayer between aggregated particles with electrolytes (∼5-10 Å) are larger than those in pure water (a few Ångströms). Together, aggregation/disaggregation in salt solutions is predicted to be more reversible due to these lower energy barriers, but there is uncertainty on the magnitudes of the energies that lead to aggregation at the molecular scale. By analyzing the peak water densities of the first monolayer of interstitial water as a proxy for solvent ordering, we find that the extent of solvent ordering likely determines the structures of aggregated states as well as the energy barriers to move between them. The results suggest a path for developing a molecular-level basis to predict the synergies between ions and crystal faces that facilitate aggregation under given solution conditions. Such fundamental understanding could be applied extensively to the aggregation and precipitation utilization in the biological, pharmaceutical, materials design, environmental remediation, and geological regimes.

Evaluation of Suitability of High-Speed Drag Finishing Machine Prototype Utilization for Workpiece Modification

The purpose of the experimental results evaluated in this paper is to verify the viability of using a prototype drag finishing machine for the modification of machined workpieces. The workpieces used in the experiments had a cylindrical shape and were manufactured by turning. Three different workpiece materials were tested, and three workpieces for each material were machined with different cutting parameters. Multiple aspects of the drag-finishing process influence were kept track of—surface roughness, dimensional accuracy, and edge burr shape change. The parameters of the drag finishing were kept constant for all workpieces, and the development of each aforementioned observed aspect was recorded. The workpieces were periodically removed from the process and measured using a coordinate measuring machine with a touch probe, a surface roughness measuring machine, and an optical microscope. Based on the gathered data, it can be concluded that the usage of a prototype drag finishing machine designed primarily for cemented carbide tool microgeometry modification is viable for workpiece finishing as well. The parameters of the drag-finishing process need to be adjusted depending on the workpiece material and initial surface roughness. Additionally, the medium used for the drag finishing should be considered with respect to the desired output quality of the workpiece. Experimental work shows that having one multi-purpose machine for precise modification of wide range of materials and shapes can be an effective approach from the standpoint of economy and productivity when it comes to small numbers of workpieces requiring surface finishing.

Investigation on heat transfer enhancement of supercritical hydrocarbon fuel in rotating channel interpolated with spiral wire

Hypersonic vehicles carry their hydrocarbon fuels as the only regenerative fluid because the existing air-cooled turbine blades cannot meet the stringent heat transfer requirements, including aerodynamic heating in overload environments. In this study, supercritical-pressure n-decane was used as the working medium, and a spiral wire with a wire diameter and pitch of 0.1 and 10 mm was inserted into a smooth circular tube (inner diameter = 2 mm; length = 200 mm) for studying the convective heat transfer characteristics under different rotating speeds, mass flow rates, inlet temperatures, and heat fluxes and investigating the enhanced heat transfer effect of the spiral wire. Experimental results indicate that the overall heat transfer performance of the spiral-wire structure tube was improved by more than 1.3 times compared to that of the smooth tube. Further, at the trailing edge surface at 300 rpm, the Nusselt number increases by an average of two times; in the meanwhile, the PEC value for the reinforced tube is obtained as 1.25–1.68, indicating a better enhanced heat transfer capability in the rotating channel. The experimental results are compared and verified using a computational fluid dynamics method with SST k-ω turbulence model, revealing the maximum relative deviation to be within 13.56 %. The numerical simulation results explain the mechanism of the temperature differences between the leading- and trailing-edge surfaces within the centrifugal section and the reinforcing effect of the interpolated spiral wire. This study provides a novel orientation towards the application of aviation fuel for turbine blade cooling and the efficient heat transfer performance of cooling channels under accelerated conditions.

A study on effects of curing and machining conditions in post-processing of SLA additive manufactured polymer

Stereolithography (SLA) is a promising additive manufacturing technology in terms of versatility and functionality. However, SLA-printed products lack mechanical properties and accuracy, so post-processing is essential. This study comprehensively contributes to a deeper understanding of influences of two types of post-processing [ultraviolet (UV) treatment and machining] and interactions between them. The effect of UV treatment was first investigated by evaluating properties of SLA specimens before and after UV curing. The UV curing greatly increased hardness by rearranging the molecular chains. The higher curing temperature, the denser and more uniform network was created; the surface hardness of the specimen cured at 80 °C increased by 208.30 % compared to the uncured specimen. Then, the interactions were analyzed by machining SLA specimens cured under different conditions. The pre-curing increased the hardness, molecular bonding, and brittleness. Thus, small surface roughness on the machined surface and small exit edge chipping were observed under the non-pre-curing conditions; the pre-curing increased the exit edge chipping size up to 48.21 %.

Revolutionizing CO2 Electrolysis: Fluent Gas Transportation within Hydrophobic Porous Cu2O.

The success of electrochemical CO2 reduction at high current densities hinges on precise interfacial transportation and the local concentration of gaseous CO2. However, the creation of efficient CO2 transportation channels remains an unexplored frontier. In this study, we design and synthesize hydrophobic porous Cu2O spheres with varying pore sizes to unveil the nanoporous channel's impact on gas transfer and triple-phase interfaces. The hydrophobic channels not only facilitate rapid CO2 transportation but also trap compressed CO2 bubbles to form abundant and stable triple-phase interfaces, which are crucial for high-current-density electrocatalysis. In CO2 electrolysis, in situ spectroscopy and density functional theory results reveal that atomic edges of concave surfaces promote C-C coupling via an energetically favorable OC-COH pathway, leading to overwhelming CO2-to-C2+ conversion. Leveraging optimal gas transportation and active site exposure, the hydrophobic porous Cu2O with a 240 nm pore size (P-Cu2O-240) stands out among all the samples and exhibits the best CO2-to-C2+ productivity with remarkable Faradaic efficiency and formation rate up to 75.3 ± 3.1% and 2518.2 ± 8.1 μmol h-1 cm-2, respectively. This study introduces a novel paradigm for efficient electrocatalysts that concurrently addresses active site design and gas-transfer challenges.

On the evolution and formation of discharge morphology in pulsed dielectric barrier discharge

The discharge morphology of pulsed dielectric barrier discharge (PDBD) plays important roles in its applications. Here, we systematically investigated the effects of the voltage amplitude, discharge gap, and O2 content on the PDBD morphology, and revealed the possible underlying mechanism of the U-shaped formation. First, the morphological evolution under different conditions was recorded. A unique U-shaped region appears in the middle edge region when the gap is larger than 2 mm, while the entire discharge region remains columnar under a 2 mm gap in He PDBD. The width of the discharge and the U-shaped region increase with the increase in voltage, and decrease with the increase of the gap and O2 content. To explain this phenomenon, a two-dimensional symmetric model was developed to simulate the spatiotemporal evolution of different species and calculate the electric thrust. The discharge morphology evolution directly corresponds to the excited-state atomic reduction process. The electric thrust on the charged particles mainly determines the reaction region and strongly influences the U-shaped formation. When the gap is less than 2 mm, the electric thrust is homogeneous throughout the entire region, resulting in a columnar shape. However, when the gap is larger than 2 mm or O2 is added, the electric thrust in the edge region becomes greater than that in the middle, leading to the U-shaped formation. Furthermore, in He PDBD, the charged particles generating electric thrust are mainly electrons and helium ions, while in He/O2 PDBD those that generate electric thrust at the outer edge of the electrode surface are mainly various oxygen-containing ions.

Study on Wear Characteristics of a Guide Vane Centrifugal Pump Based on CFD–DEM

Guide vane submersible centrifugal pumps are a kind of submersible pump, and the fluid inside the pump is often mixed with gravel and other impurities during operation, affecting the pump’s operating efficiency and life expectancy. However, past studies on solid–liquid two-phase flow (STF) and wear characteristics in guided vane centrifugal pumps have been limited to the particle trajectory and wear region distribution. These studies have lacked research on the effect of particles on the fluid flow and the specific amount of wear on the overflow components. Additionally, most of them have used the DPM discrete-phase model, which does not consider the particle–particle and particle–wall interactions. This paper is based on the CFD–DEM method, combined with the Archard wear model. A solid–liquid two-phase flow simulation is carried out for pumps with different particle sizes and particle shapes to analyze the particle movement inside the pump, the wear distribution and average wear amount of the overflow components, and the effect of particles on the turbulent kinetic energy of the fluid. The results show that the particles mainly collide with the leading and trailing edges of the impeller blades and the leading edge of the guide vane blades and form a buildup at the trailing edge of the concave surface of the guide vane blades, resulting in the wear being mainly distributed in these regions. With an increase in particle size and a decrease in sphericity, the average wear on the overflow components increases. The change of particle size directly affects the resistance of the fluid and the structure of the flow field, which has a large impact on the fluid flow pattern and generates large turbulent kinetic energy fluctuations. The shape of the particles only changes the structure of the local flow field, which has a small impact on the fluid flow pattern.

Investigation of the influence mechanism of hypersonic flow field environment on thermionic emission efficiency

Electron Transpiration Cooling (ETC) is a novel thermal management method that utilizes thermionic emission to cool the leading edge surface of a hypersonic vehicle. Establishing a thermionic emission model that accounts for the hypersonic flow field environment is imperative for accurately predicting the thermal protection efficiency of ETC. A thermionic emission dual-sheath model was established, considering the impact of hypersonic non-equilibrium flow field particle parameters on thermal electron emission. The virtual cathode threshold was obtained through numerical analysis, considering the influence of particles parameters and surface thermoelectric material parameters in a non-equilibrium flow field. Distribution of sheath potential and particle number density in plasma sheath region were performed at a range of conditions. Thermionic emission efficiency approached 80 % as the plasma ion density was 5 × 20 m−3 and the work function was 2 eV. The results showed that plasma ions have different degrees of neutralization effect on thermal emission electrons depending on the flow field and surface material characteristics, ultimately causing varying surface thermionic emission efficiency.

Моделирование скругления острых кромок наклонных охлаждающих отверстий лопаток турбин методом электроэрозионного фрезерования на многоосевых станках с ЧПУ

The article views efficiency improving issues, quality and accuracy of sharp edge smoothing for numerous angular fans in the turbine blades of gas turbine engines made of heat-resistant nickel alloys and used in modern growing passenger aviation transport based on the development of ED milling new technology for modern multi-axis CNC machines with a rotating hollow electrode and a high-pressure fluidsupply of a special flush through the electrode body. An automated process for sharp edge machining has been developed for the production of more than 200 differently placed angular fans with a diameter of 0,45…0,6 mm in one blade instead of labor-intensive manual benchwork, where various needles, abrasive and metal rotary files are used. It is found that modeling and the development of special software resulted in a uniform radius of smoothing with high accuracy due to automatic ED milling operation along the entire trailing edge of each angular hole in the turbine blades at a multi-axis machining electro discharge center. The use of a rounded edge of the outlet ports provides more efficient cooling of the turbine blades and higher performance of gas turbine engines. At the same time, it is found that with a significant efficiency improving in blade sharp edge machining, a higher quality of the rounded edge surfaces in the holes is ensured. The results of the conducted research are recommended for the adoption of technologies in the aircraft engine industry.