Position Of Surface Research Articles

Solar Wind Ion Sputtering from Airless Planetary Bodies: New Insights into the Surface Binding Energies for Elements in Plagioclase Feldspars

Our understanding of the ion-sputtering contribution to the formation of exospheres on airless bodies has been hindered by the lack of accurate surface binding energies (SBEs) of the elements in the various mineral and amorphous compounds expected to be on the surfaces of these bodies. The SBE for a given element controls the predicted sputtering yield and energy distribution of the ejecta. Here, we use molecular dynamics computations to provide SBE data for the range of elements sputtered from plagioclase feldspar crystalline end members, albite and anorthite, which are expected to be important mineral components on the surfaces of the Moon and Mercury. Results show that the SBE is dependent on the crystal orientation and the element’s coordination, meaning multiple SBEs are possible for a given element. Variation in the SBEs among the different surface positions has a significant effect on the predicted yield and energy distribution of the ejecta. We then consider sputtering by H, He, and a solar wind mixture of 96% H and 4% He. For each of these cases, we derive best-fit elemental SBE values to predict the ejecta energy distribution from each of the (001), (010), and (011) cleavage planes. We demonstrate that the He contribution to the sputtering yield cannot be accounted for by multiplying the 100% H results by some factor. Lastly, we average our results over all three possible lattice orientations and provide best-fit elemental SBE values that can be easily incorporated into sputtering yield models.

Is it safe to use sand surface during rehab when training basic skills in early stages? How sand surface and inertial sensor position affect Drop Jump landing's G-forces and it's application in injury recovery

In sports, the use of sand surface as a tool in the injury recovery process has received very good acceptance and an increased attention in recent years. Unfortunately, the number of studies in this area continues being scarce. Therefore, this study analyzes the existence of possible differences in the magnitude of the impact generated during a 45 cm Drop Jump (DJ), depending on the body area analyzed, the contact surface (sand or grass) and the height (thoracic spine and ankle) at which a jump is placed. To that purpose, 6 participants were analyzed by wearing 3 IMU sensors (WIMU PRO™) to measure G foreces in the landing phase of the DJ. The results suggest the existence of statistically significant differences when comparing surfaces (sand vs. grass), body area (ankle and lumbar) and location of device placement (thoracic area vs. ankle).

Numerical investigation of local scour around a 2-degree of freedom vibrating subsea pipeline in steady flow under sagging condition

Numerical simulations are conducted to investigate the local scour below a sagging subsea pipeline vibrating in two degrees of freedom (2-DOF), covering a sagging ratio from −0.3 to 0 and a wide range of reduced velocities from 0.5 to 15. A negative sagging ratio means that the static balance position of the bottom surface of the pipeline is below the sand surface. The combined effects of the sagging and 2-DOF vibration of the pipeline on the scour are investigated. The maximum scour depth of the 2-DOF vibrating pipeline in the lock-in range of the vibration increases by 10% compared to the 1-DOF; however, the reduced velocity where the maximum scour depth occurs changes from 5 to 6. The variations of the vibration amplitude with the reduced velocity for all the sagging ratios follow a similar trend. For embedment ratios of −0.4 to −0.3, initial condition of scour simulation affects the equilibrium scour depth and vibration amplitudes. Simulations with a flat sand surface as initial condition prevent full scour development because the pipeline reaches its static balance position due to weak flow through the pipeline-to-bed gap. However, if the simulation starts with a sufficiently large initial scour depth, scour can reach its equilibrium.

A TÁJHASZNÁLAT ÉS TÁJGAZDÁLKODÁS VÁLTOZÁSA A MAROSSZÖGBEN (18– 19. SZÁZAD)

Nowadays, 35 independent settlements are located on the Marosszög floodplain, exploiting the opportunities provided by the microrelief. The region’s ecological properties and resources available to society, which change over time, and its natural and landscape characteristics were markedly different from the historical counties of Csongrád and Csanád, and in certain elements the Bánság and also from other regions of the former Torontál county. Marosszö can be divided into several parts from a landscape-geographical point of view, and as a result of the surface development, it has a threefold geomorphological division. The highest areas (88–96 m) are late pleistocene loess-sand free areas. The old holocene high flood plain is located in a lower surface position (82–87 m), while the new holocene low flood plain is located at the deepest level (77–81 m). Starting from the 18th century, in the reorganization process of economic life, mixed (polyculture) farming became dominant, characteristic of the settlement group as a whole. Until the start of the integrated environmental transformation works, society adapted, and its landscape-shaping and environment-transforming activities were only at the local level. The integrated environmental transformation works strongly changed the geographical foundations of social production and the ecological conditions, the former floodplain habitats, floodplain landscapes and habitats, which corresponded to the way of life of livestock keepers and farmers, disappeared. The use of landscape and resources changed and developed significantly, arable farming became dominant. The nature of agricultural activity has shifted towards crop production in fields and animal husbandry in stables.

Internal energy consumption analysis of counter-rotating axial-flow compressor based on entropy production theory

Counter-rotating wet gas compressor is an ideal equipment for pressurizing natural gas in offshore gas fields. It has a compact structure, a wide range of operating conditions, and a certain liquid tolerance in the process of gas pressurization. However, due to the opposite rotation of the adjacent rotors, and the characteristics of the flow containing liquid, it is also easy to lead to flow separation in its interior and then produce obvious energy dissipation. In this paper, the numerical simulation of the internal flow field of counter-rotating axial-flow compressor under dry and wet conditions is carried out. The entropy production theory based on the second law of thermodynamics is introduced to analyze the energy consumption of the compressor, and the high energy consumption area in the internal flow field of the compressor is accurately located. Then, the energy consumption of this area is evaluated quantitatively and qualitatively. The entropy production and its proportion of each component under different working conditions, the distribution of the entropy production of each rotor along the flow direction, and the radial distribution under the near-stall state are obtained. The calculation results show that the entropy production of upstream rotor and downstream rotor in the total entropy production is 29.19%–31.41% and 59.48%–62.61% under dry gas conditions, respectively. Under wet conditions, the proportions are 28.20%–30.67% and 60.02%–63.33%, respectively. The wet gas droplets can increase the momentum input to the low energy region of 0.7–0.9 relative position of the suction surface of the upstream rotor and improve the flow field in this region. However, it can also exacerbate flow separation in the front middle of the downstream rotor, causing additional energy loss.

Interaction law between mining stress and fault activation and the effect of fault dip angle in longwall working face

Study of the interaction between fault activation and mining stress evolution in the longwall working face is helpful to provide a targeted area for fault type heavy mine pressure disaster control. Combining theoretical analysis, physical and numerical simulation, the mechanical mechanism of fault activation is analyzed, the interaction law between mining stress and fault activation is studied, and the influence of fault dip angle on the evolution of fault activation and mining stress is discussed. The minimum critical dip angles α of normal and reverse fault activation are π/4 + φ/2 and π/4-φ/2, respectively. During the mining process, the activation position of the fault surface, the peak values of stress and displacement gradually increase and transfer from the high position of the fault to the low position, and the peak value of the advance abutment pressure reaches the maximum at the fault. The advancing distance of the working face required for fault activation gradually decreases with the decrease of the fault dip angle, and the peak elevation area of the working face gradually increases with the decrease of the fault dip angle. Combined with the on-site microseismic monitoring results, it can be seen that when the working face is about 20 m away from the fault, the stress and energy increase sharply, which is the main control area of the impact disaster.

An Advanced DEM-FEM Method for Herringbone Gear in Shot Peening

Introduction: The complex geometry of herringbone gear can lead to uneven surface strengthening, which affects the overall effect of treatment. Methods: A discrete element model (DEM) of shot peening for herringbone gears was developed, incorporating accurate gear surface parameters to study impact characteristics along the tooth profile. A finite element model (FEM) was created for small local units of the gear surface to calculate the residual stress and roughness. Results: There are a large number of low-velocity shots at the root of the gear, and the closer to the top of the gear, the higher the impact velocity of the shots, but the number of impacts also decreases. The surface roughness Sa near the root of the tooth is the smallest, the Sa at the pitch circle is the largest, and the Sa at the top of the tooth is intermediate. However, the residual stress levels at different positions of the tooth surface are not significantly different. Conclusion: The difference in tooth surface roughness of herringbone gear is the synergistic effect of shot impact velocity and shot frequency, but this synergistic effect has no significant effect on the stress after shot peening.

Research on the position of the neutral surface of the space lightweight mirror with a two-axis bipod flexible mount.

This study offers a theoretical solution for the neutral surface position of a space lightweight mirror employing two-axis bipod flexible mounts (TABFM) evenly distributed at three locations along the circumference. To maximize the surface shape accuracy of the mirror (SSAM) under the influence of radial gravity, it is typically necessary that the center of rotation of the TABFM coincides with the position of the neutral surface of the mirror (PNSM). Departing from the PNSM, the SSAM will be substantially deteriorated. In this paper, the compliance matrix of the TABFM utilized for space lightweight mirrors is initially solved. Subsequently, based on the compliance matrix, the analytical formulas and solution approaches for the PNSM under the action of 1g gravity are derived when the support structure of the mirror is symmetrically arranged horizontally and vertically. Additionally, a sensitivity analysis of the PNSM is also conducted. Finally, it is verified through the finite element simulation method. The results indicate that when the support structure of the mirror is uniformly distributed along the circumference and symmetrically arranged horizontally, the PNSM is solely related to the flexibility of the support structure, and the error between the theoretical calculation results and the finite element simulation results is merely 3.2‰; when the mirror support structure is uniformly distributed along the circumference and symmetrically arranged vertically, the PNSM is determined by the flexibility of the support structure and the mass characteristics of the mirror, and the error between the theoretical calculation results and the finite element simulation results is 2.1%. The proposed solution method of PNSM has been implemented in practical engineering projects. The method proposed in this paper can rapidly solve the PNSM and significantly enhance the efficiency and accuracy of integrated simulation optimization. Additionally, the method applies not only to the TABFM investigated in this paper but also to tripod mounts or other symmetric side support structures.

Research on Surface Defect Positioning Method of Air Rudder Based on Camera Mapping Model

(1) Background: Air rudders are used to control the flight attitude of aircraft, and their surface quality directly affects flight accuracy and safety. (2) Method: Traditional positioning methods can only obtain defect location information at the image level but cannot determine the defect’s physical surface position on the air rudder, which lacks guidance for subsequent defect repair. We propose a defect physical surface positioning method based on a camera mapping model. (3) Results: Repeated positioning experiments were conducted on three typical surface defects of the air rudder, with a maximum absolute error of 0.53 mm and a maximum uncertainty of 0.26 mm. Through hardware systems and software development, the real-time positioning function for surface defects on the air rudder was realized, with the maximum axial positioning error for real-time defect positioning being 0.38 mm. (4) Conclusions: The proposed defect positioning method meets the required accuracy, providing a basis for surface defect repair in the air rudder manufacturing process. It also offers a new approach for surface defect positioning in similar products, with engineering application value.

Hydraulic and axial force characteristics of large axial flow pumps under different flow conditions

Abstract Axial flow pumps often experience uneven distribution of axial force on the blades when deviating from design conditions, which can easily lead to local damage to the pump blades. In response to this issue, this article conducts a detailed study on the hydraulic and axial force characteristics of large vertical axial flow pumping stations in China based on constant and non-constant numerical simulation research methods. Research has found that under biased operating conditions, due to the angle between the water flow direction inside the impeller and the impeller blades, the water body collides with the blades, resulting in concentrated pressure distribution on both sides of the inlet side of the impeller blades. Under low flow conditions, the high axial force area of the impeller blade is concentrated in the middle and rear position of the suction surface, while under high flow conditions, the high axial force area is widely distributed. Under the conditions of 0.8 Q to 1.4 Q, the fluctuation of axial force on the impeller blades is mainly affected by the rotation of the impeller blades. However, under low flow conditions, due to the turbulence of the flow state, there is no obvious pattern of axial force variation on the impeller blades. In addition, under different flow conditions, there is no obvious pattern in the fluctuation of axial force on the guide vanes. This also proves that there are problems such as uneven axial force distribution and no periodic changes in the impeller blades under low flow conditions, which can easily lead to damage to the impeller blades. The above analysis can provide some reference for the design of impeller blades.

Design and Verification of Thermal Control System of Communication Satellite

The multiple working modes, complex working conditions, frequent changes in external heat flux, and high power consumption of communication satellites all pose great difficulties to their thermal design. This paper mainly describes the design of a thermal control system for high-power communication satellites. Firstly, new efficient heat transfer technologies and thermal control materials for spacecraft are introduced. Secondly, the structure and internal heat source of the satellite are introduced. Thirdly, the external heat fluxes are analyzed, and the position of the heat dissipation surface and extreme conditions are confirmed. Then, a thermal control system is designed around the difficulties of thermal control. With heat pipes, the temperature uniformity of +Y deck, −Y deck, and +Z deck increased by 8 °C, 9.9 °C, and 34.2 °C, respectively. Furthermore, the maximum temperature of the power controller, secondary power supply, bidirectional frequency converter, and solid discharge decreased by 32.5 °C, 22.0 °C, 14.0 °C, and 164 °C, respectively. Finally, a thermal balance test is performed. The test results show that the temperatures of the solid-state power amplifier, on-board computer, power controller, secondary power supply, and bidirectional frequency converter meet the requirements of the thermal control indices. In addition, the temperature of thermal-sensitive components such as batteries and the storage tank also meets the requirements. The thermal design scheme is reasonable and feasible, and the thermal balance test verifies the correctness of the thermal design.

Improving the dynamic positioning accuracy of the electro-hydraulic drive

Research is focused on improving the dynamic accuracy of control surface positioning during the switching of hydraulic actuator modes and studying the processes and phenomena that cause control surface overshoot. Existing studies on the dynamic accuracy of hydraulic actuators have been analyzed. Transitional processes occurring in the " electromagnetic recirculation valve – electronic control unit" loop during changes in hydraulic actuator operating modes have been examined. The features of processes and physical phenomena leading to increased activation time of the hydraulic actuator have been identified. Solutions and electrical connection schemes for connecting the hydraulic actuator recirculation valve to the electronic control unit have been proposed to meet the accuracy positioning and activation time requirements. Experimental studies have been conducted to simulate the operational mode of hydraulic actuators, and failure situations modes under various load forces have been identified. Based on the results, principles for designing connection schemes for the electromagnetic recirculation valve of the hydraulic-mechanical actuator to the electronic control unit, which enhance system positioning accuracy at the structural level, have been formulated. Technical solutions aimed at achieving the specified accuracy and activation time for the hydraulic actuator have been developed and practically tested. The effectiveness and suitability of the proposed solutions for operational use, considering external factors, have been experimentally confirmed.

Hydrogen evolution reaction on Ag12M icosahedrons: A DFT study

The hydrogen evolution reaction (HER) in Ag12M clusters with first-row 3d metal (M) dopants is evaluated by means of density functional theory (DFT). The results show that the M dopants favor the highest coordination positions, except for M = Zn, favoring the surface position. The findings indicate that Ag12Ti and Ag12Cu clusters are suitable catalysts for HER applications, according to the adsorption energy and Gibbs free energy parameters. The interactions of the clusters with H can be explained by density of states analyses. The obtained results suggest that atomically precise doped Ag clusters are suitable targets as relevant candidates for HER applications.

Noncontact Measurements of Resonance of Small Round Liquid Surfaces Using Sound Wave to Determine Surface Tension.

Various methods have been developed for measuring the surface tension of liquids, and the present study proposes a new method for measuring the surface tension of liquids. A small (9 mm diameter) round liquid surface was excited by sound waves with a common speaker. Nine liquids possessing various physical properties and functional groups were employed, and three resonance frequencies (frs) were observed for each liquid in a frequency range of 20-180 Hz. The resonances were analyzed with a forced oscillation model. In addition, the amplitudes and phases of the resonance oscillations at various positions of the liquid surface were measured, and the total deformations of the liquid surface were determined. The deformation was compared with the Bessel functions, and the oscillation modes and boundary conditions were decided. Finally, proportional relationships between frs and σ0.5ρ-0.5 (σ: surface tension, ρ: density) with high correlations were obtained, which were supported by a new theoretical equation using hydrodynamics.

Indirect optical geometry measurements with a stream of particles as micro probes

The manufacturing of micro-structured components with varying geometries and materials requires precise and versatile applicable geometry measurement techniques. Optical measurement approaches enable high-precision measurements, but they rely on cooperative surfaces. To overcome the dependency on the optical surface response, the surface of a measured object is determined indirectly using an aerosol flow with fluorescent particles and a confocal fluorescence microscope. To precisely extract the surface position from the scanned fluorescence signal of the particles in the surrounding air, a model-based signal processing is proposed. To assess the measurement capabilities and the influence of the aerosol supply flow, geometry and flow measurements are performed on a flat plate geometry and a step geometry. As a result, a measurement uncertainty of ▪ with no systematic error was achieved for the flat plate experiment, despite the different boundary layer flows at the different measurement positions. In contrast to this, a significant systematic measurement error occurred in the wake flow region of the step geometry because of flow separation and, thus, no detectable particles directly behind the step. In summary, the findings clarify an in principle achievable sub-micrometre resolution with improved optics and a large number of detected particles, but also emphasise the necessity of a sufficient particle supply for enabling indirect optical geometry measurements.

Reconstruction of nonstationary sound field based on group sparsity time domain equivalent source method

To improve the accuracy and stability of reconstruction of nonstationary sound field, a novel time domain equivalent source method based on non-convex overlapping group sparsity (NOGS-TESM) is proposed. In the proposed NOGS-TESM, the time-varying pressure in the near field is first modeled by a set of equivalent sources positioned inside the vibrating structure. Then, the NOGS regularization is applied for solving the inverse problem, and a novel algorithm derived on the basis of Majorize-Minimization theory is utilized to obtain the optimal solution of equivalent sources strengths. Finally, the optimal equivalent sources strengths at all times are substituted into a time-domain convolution to calculate the time-varying pressure of reconstruction surface. The proposed NOGS-TESM enriches the prior information by considering the group sparsity of spatial pressure distribution, and enhances the accuracy of estimated equivalent sources strength via its alternative calculation of l0−norm. A vibrating plate to produce a nonstationary sound field, which is designed as a numerical simulation, and the time-varying pressures of measurement surface are input into the proposed NOGS-TESM. The quantitative and qualitative comparisons confirm that the proposed NOGS-TESM can greatly reconstruct the non-stationary sound field in time–space domains, and its reconstruction accuracy is higher than that of TESM with Tikhonov regularization (TR-TESM). Meanwhile, several parameters, for example, the noise and position of equivalent source surface, are discussed in detail, and the superiorities of the proposed NOGS-TESM in terms of stability and robustness are proved by comparing to TR-TESM. The predominance of the proposed NOGS-TESM is further validated by conducting one experiment on the vibrating steel plate.

Impact of porosity distribution and grading parameters on free vibration of functionally graded beams

This study focuses on investigating the free vibration of porous functionally graded (FG) beams based on neutral surface position and the impact of porosity distribution on the properties and performance of materials. To achieve this, the study assumes that the beam’s material characteristics vary continuously along its thickness direction. The volume fraction of constituents is specified using the modified rule of the mixture, which includes porosity volume fraction with changed porosity patterns across the cross-section. The study uses the parabolic shear deformation theory without shear correction factors to derive the equations of motion by applying Hamilton’s principle. The study employs Navier’s method to obtain analytical results for the free vibration of porous FG beams. To verify the proposed formulation, the study compares the results with relevant findings from the literature. The study also examines the relationship between frequency of vibration and grading parameter in homogeneous porosity distributions, as well as the frequency of vibration in beam structures with different porosity patterns. Additionally, numerical examples are provided to investigate the impact of parameters like power-law index, span to depth ratio, porosity distribution pattern, and porosity volume fraction on the natural frequencies of FG beams.

Entanglement island and Page curve for one-sided charged black hole

In this paper, we extend the method of calculating the entanglement entropy of Hawking radiation of black holes using the “in” vacuum state, which describes one-sided asymptotically flat neutral black hole formed by gravitational collapse, to dynamic charged black holes. We explore the influence of charge on the position of the boundary of island ∂I and the Page time. Due to their distinct geometric structures, we discuss non-extremal and extremal charged black holes separately. In non-extremal cases, the emergence of island saves the bound of entropy at late times, and the entanglement entropy of Hawking radiation satisfies the Page curve. Moreover, we also find that the position of the boundary of island ∂I depends on the position of the cutoff surface (observers), differing from the behavior in eternal charged black holes. In extremal black holes, when the island exists, the entanglement entropy is approximately equal to the Bekenstein-Hawking entropy, while the entanglement entropy becomes ill-defined when island is absent. Our analysis underscores how different geometric configurations significantly influence the behavior of entropy.

Optic Nerve Head Morphology and Macula Ganglion Cell Inner Plexiform Layer Thickness in Axially Anisometropic Rhesus Monkeys.

The purpose of this study was to determine the effects of axial elongation on optic nerve head morphology and macula inner retinal thickness in young rhesus monkeys. Both eyes of 26 anisometropic, 1-year-old rhesus monkeys were imaged using optical coherence tomography (OCT). Before imaging, the animals were sedated, their eyes were dilated, and axial length was measured using an optical biometer. OCT imaging included a 20 degrees, 24-line radial scan centered on the optic nerve head (ONH) and two 20 degrees × 20 degrees raster scans, one centered on the ONH and the other on the macula. Radial scans were analyzed using programs written in MATLAB to quantify the Bruch's membrane opening (BMO) area and position, minimum rim width (MRW), anterior lamina cribrosa surface (ALCS) position, size of any scleral crescent, circumpapillary retinal nerve fiber layer (RNFL), and choroid thickness (pCh). Macula total retinal thickness (mTRT) and ganglion cell inner plexiform layer (GCIPL) thicknesses were quantified from macula scans. Linear least square regression was determined for OCT measures and axial length of the right eye, and for inter-eye differences. Animals were 341 ± 18days old at the time of imaging. BMO area (R2 = 0.38), ALCS position (R2 = 0.45), scleral crescent area (R2 = 0.35), pCh thickness (R2 = 0.21), mTRT (R2 = 0.24), and GCIPL thickness (R2 = 0.16) were correlated with the axial length (all P < 0.05). For each of these parameters, the right-eye regression slope did not differ from the slope of the interocular difference (P > 0.57). There are posterior segment morphological differences in anisometropic rhesus monkeys related to axial length. Whether these differences increase the risk of pathology remains to be investigated.

Understanding intermediates adsorption in oxygen reduction/evolution reactions from the local aromaticities of catalyst sites

The adsorption behaviors of active sites for various adsorbates in reactions determine the performance of a catalyst, and different surface positions usually exhibit diverse adsorption strengths for the same species. Herein, density functional theory calculations were conducted to study the adsorptions of all oxygen-containing intermediates in oxygen reduction/evolution reactions (ORR/OER) on the surfaces of various graphene-based electrocatalysts with varied heteroatoms and coordination environments. By using the local aromaticity concept, we found a direct correlation between the adsorption strength of a metal/nonmetal site and its NICS(1)ZZ (perpendicular tensor of the nucleus-independent chemical shift at 1 Å above plane) value: positive (antiaromatic) and negative (aromatic) values basically correspond to stronger and weaker adsorptions, respectively. Consistently, the linear relationship between aromatic characteristics and adsorption behavior can be obtained from the magnetic induced ring currents at the surface sites as well. The stronger adsorptions at the antiaromatic sites may because these catalysts always tend to maximumly preserve their global aromaticities and structural stabilities. Our work not only demonstrates that local aromaticity can serve as a useful indicator for predicting/evaluating the adsorption abilities of various catalyst sites, but also provides a novel understanding of the complex heterocatalytic process from the magnetic response properties of catalysts.