Velocity Analysis Research Articles

Velocity analysis of moving objects in earth observation satellite images using multi-spectral push broom scanning

ABSTRACT In this study, we present a method for detecting and analysing the velocities of moving objects in Earth observation satellite images, specifically using data from Planet Labs’ push broom scanning satellites. By exploiting the sequential acquisition of multi-spectral images, we estimate the relative differences in acquisition times between spectral bands. This allows us to determine the velocities of moving objects, such as aircraft, even without precise timestamp information from the image archive. We validate our method by comparing the velocities of aircraft observed in satellite images with those reported by onboard ADS-B transponders and find an accuracy of ∼ 4 %. The results demonstrate the potential, despite challenges posed by the limitations of proprietary data, of a new application of commercial satellite data originally intended as an ongoing, once-daily survey of single images covering the entire land-area of the Earth. Our approach extends the applicability of satellite survey imagery for dynamic object tracking and contributes to the broader use of commercial satellite data in scientific research.

Research on the material removal mechanism of vibration-assisted nano-scratch on single-crystal GaN by molecular dynamics.

Single-crystal gallium nitride (GaN) is a semiconductor material known for its hardness and brittleness. This research aims to reveal the differences in the micro-mechanisms of material removal during traditional grinding and ultrasonic vibration-assisted grinding and to provide guidance for the high-efficiency, high-quality planarization processing of single-crystal GaN. To achieve this purpose, molecular dynamics (MD) simulation methods were used to establish a model (30nm × 40nm × 15nm) of single-crystal GaN being scratched by a single abrasive grain with and without ultrasonic vibration assistance. The differences in the surface morphology and subsurface damage formation mechanisms of single-crystal GaN under conditions with and without ultrasonic assistance were compared. The results indicate that, compared to traditional grinding, the periodic ultrasonic vibrations reduce the normal force and result in a more uniform distribution of stress and temperature, thereby mitigating local stress concentration and thermal accumulation effects. Ultrasonic vibration alters the motion of the abrasive grain, expanding the material removal range from 7.384 to 10.315nm, decreasing the number of residual atoms in the machining area, and lowering the chip pileup height at the leading edge of the abrasive grain from 2.063 to 1.528nm. Additionally, the micro-shear deformation induced by ultrasonic vibrations helps to suppress brittle fracturing caused by excessive local stress, thus reducing the thickness of the damaged subsurface. At a scratch depth of 2nm, the total length of dislocation lines in the ultrasonic-assisted scratch is reduced from 185.256 to 33.315 nm compared to traditional scratching. These findings offer new insights into the microscopic mechanisms of material removal in high-efficiency, high-quality grinding processes of single-crystal GaN. This study adopts LAMMPS software for MD simulations to investigate the physical behavior of GaN during the grinding process. The simulation results are then visualized and analyzed using OVITO software to elucidate microstructural changes in the material. During the simulation, the temperature of the Newtonian layer is calculated based on the statistical analysis of atomic velocities under the NVE ensemble. The grinding force applied to the GaN workpiece is determined by differentiating the atomic potential energy. Von Mises stress analysis is adopted to ascertain the stress distribution during the scratching process. Finally, the changes in the crystal structure during scratching are identified and classified using analysis of identified defect structures.

Experimental and Numerical Investigation of Spray Scrubber Dust Collection Efficiency

Spray scrubbers are widely used in gas purification applications and allow fulfillment of the demands of air quality norms introduced all over the world. They effectively remove harmful gases like sulfur dioxide (SO2), nitrogen oxides (NOx), and particulate matter from industrial emissions, reducing their impact on air quality. Moreover, by capturing greenhouse gases such as carbon dioxide (CO2) in certain applications, spray scrubbers contribute to efforts to reduce climate change. Optimization of scrubber internal elements leads to reduced energy usage and lowered water mass flow while maintaining high pollutant removal efficiency. This makes them cost-effective in the long term. The demister is an additional device which is often used in scrubbing systems, and its main task is to prevent the water droplets from escaping through the upper part of the scrubbing chamber. In this article, the pollution (MgO particles) is introduced to the system upstream the scrubber inlet, the working fluid is air under atmospheric pressure, and water droplets are generated by a single nozzle placed inside the scrubber. Before the experimental part, a preliminary numerical analysis of gas velocity inside scrubber is performed and expectations of particle behavior are indicated. Then, the authors present the spray scrubber laboratory stand designed by them and carry out experimental research on it. Each element of the test stand is described in the article including the self-designed fluidizer, which effectively mixes MgO powder with air. The authors investigate the effect of their innovative construction of demister on separation efficiency and compare the results to the case without demister. The impact of water mass flow rate generated by the nozzle and gas inlet velocity on separation efficiency is presented for several investigated cases. The results show that demisters significantly improve the separation efficiency at lower water mass flow rates and successfully prevent water droplets from reaching the scrubber outlet. The measured separation efficiency was in the range of 80% for lower water mass flow rates up to 97% for the highest water flows.

Graphene origami with enhanced impact resistance and energy absorption performance

The ancient art of origami has recently shown its potential in engineering intricate three-dimensional graphene structures with unique properties. This study employs molecular dynamics simulations to investigate the dynamic mechanical behavior of graphene origami structures (GOS) under hypervelocity ballistic impact. The analysis of residual velocity, kinetic energy loss, and specific penetration energy shows that GOS exhibit superior impact resistance and energy absorption performance compared with pristine graphene. One reason for the enhancements is that highly flexible GOS can unfold to produce a conical impact zone with larger out-of-plane deformation. Another reason is that three-dimensional folded regions possess more mass, enabling them to dissipate more kinetic energy from the projectile. The impact behavior of GOS is further analyzed concerning projectile size, impact position, and surface roughness. It is found that the impact resistance and energy absorption capacity of GOS can be adjusted by altering the surface roughness, specifically the folding degree and pattern geometry. This GOS holds promise for diverse applications in impact protection, such as combat armor and spacecraft shields.

Motion Path Study Based on Isometric Solenoids and Discrete Simulation

This paper focuses on the position, speed change and collision detection problems during the traveling process of the bench dragon from both physical and mathematical perspectives. Firstly, based on the equidistance solenoid equation and the mechanical arm model, this paper iteratively recursively starts from the dragon head and sequentially solves the position of each section of the bench in the traveling process. Secondly, this paper combines the velocity analysis of the rigid rod and the nature of isometric solenoid, and also solves the position of each section of the bench in the traveling process sequentially in the form of iterative recursion. Finally, this paper discretizes the disk-in trajectory and carries out collision detection, so as to obtain the time, position, velocity and other information at the termination moment. The study shows that the model can effectively solve the complex optimization problem in the marching process of the dragon dance team.

Effects of mineral mode and textural variation on the seismic anisotropy in lithospheric mantle: an example from Horoman peridotites

We performed a numerical analysis of seismic velocities in mantle peridotite using the elastic constants and crystallographic preferred orientations (CPOs) of olivine, orthopyroxene, and clinopyroxene. Proportions of olivine in the samples ranged from 50 to 100% mechanically, whereas the two pyroxenes ranged from 0 to 50%. We utilized three lherzolite samples from the Horoman peridotite complex for this study. As the quantity of pyroxene increased, the P-wave velocities in the X-direction (8.35–9.14 km/s) and P-wave anisotropies (5.51–14.50%) decreased in all samples. However, the S1-wave velocities remained relatively consistent, with Vs1 ranging from 4.79 to 5.15 km/s and Vs2 from 4.55 to 4.92 km/s. The maximum S-wave anisotropies decreased as orthopyroxene contents increased. As a consequence, non-negligible effects of pyroxenes resulted in the variation of seismic velocities, suggesting the orthopyroxene/clinopyroxene contents and their CPOs could be one of critical factors for evaluating seismic anisotropy within the upper mantle.Graphical abstract

Effect of fine aggregate replacement with limestone Slurry Waste in Self Compacting Concrete: A Microstructural Approach

The stone processing generated Dimensional Limestone Slurry Waste (DLSW) was used in Self-Compacting Concrete (SCC) to evaluate the compressive strength and analyze microstructure. X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) analysis of DLSW was carried out, and its results revealed the presence of CaO (38.93 %) and SiO2 (24.33 %), which was associated with calcite and quartz. The rough, angular shape of particles, fineness, and presence of calcite of DLSW help to get optimum density and enhanced compressive strength at 28 days in modified SCC up to a 45 % replacement level. The Mercury Intrusion Porosimetry (MIP), Scanning Electron Microscopy (SEM), Energy Dispersive Spectrometer (EDS) and Ultrasonic Pulse Velocity (UPV) analysis results support the improvement of compressive strength claims.

Evaluating the mechanical and durability properties of sustainable lightweight concrete incorporating the various proportions of waste pumice aggregate

Traditional waste management faces significant environmental, social, and economic challenges, while concrete's high resource consumption highlights the need for improved, low-density alternatives. Consequently, lightweight concrete (LWC) has emerged as a favored solution. Recent interest in using pumice aggregate in concrete arises from its advantageous properties, such as low unit weight, which enables the construction of lighter buildings and reduces the load on structural elements. This study aimed to create lightweight, sustainable concrete using underutilized waste pumice aggregate (WPA). Concrete specimens with waste pumice aggregate ratios of 20 %, 40 %, 60 %, 80 %, and 100 % were analyzed at 7 and 28 days, with results contrasted against the virgin sample. The testing protocol encompassed detailed laboratory evaluations of concrete properties, including workability, density, strength, impact energy, ultrasonic velocity, water absorption, and cost analysis. Experimental results indicated that the inclusion of Waste pumice aggregate as a lightweight aggregate in concrete, in contrast to conventional aggregates, results in reduced workability, density, and strength metrics, as well as heightened water absorption, diminished impact energy, and lower ultrasonic pulse velocity. Sustainable or green concrete from M-20 to M-60 along strength ≥17 MPa is for load-bearing applications, while M-80 and M-100 whose strength is <17 MPa are for non-load-bearing uses.

Investigating biological nitrogen fixation via single-cell transcriptomics.

The extensive use of nitrogen fertilizers has detrimental environmental consequences, and it is fundamental for society to explore sustainable alternatives. One promising avenue is engineering root nodule symbiosis, a naturally occurring process in certain plant species within the nitrogen-fixing clade, into non-leguminous crops. Advancements in single-cell transcriptomics provide unprecedented opportunities to dissect the molecular mechanisms underlying root nodule symbiosis at the cellular level. This review summarizes key findings from single-cell studies in Medicago truncatula, Lotus japonicus, and Glycine max. We highlight how these studies address fundamental questions about the development of root nodule symbiosis, including the following findings: Single-cell transcriptomics has revealed a conserved transcriptional program in root hair and cortical cells during rhizobial infection, suggesting a common infection pathway across legume species. Characterization of determinate and indeterminate nodules using single-cell technologies supports the compartmentalization of nitrogen fixation, assimilation, and transport into distinct cell populations. Single-cell transcriptomics data has enabled the identification of novel root nodule symbiosis genes and provided new approaches for prioritizing candidate genes for functional characterization. Trajectory inference and RNA velocity analyses of single-cell transcriptomics data have allowed the reconstruction of cellular lineages and dynamic transcriptional states during root nodule symbiosis.

Imaging Moveout in Acoustic Factorized Orthorhombic Media

Summary In velocity model building using full waveform inversion, diving waves are a source of the low-frequency information needed to update the low- to intermediate wavenumber components in the velocity model. Because full waveform inversion is a highly non-linear optimization problem attempting to fit the information from the whole wavefield, it is prone to get stuck in local minimums and experience cycle skipping if the initial model does not contain accurate enough information about the low-wavenumbers to constrain the kinematics. Such initial velocity models will typically be estimated using alternative inversion methods that only apply information from parts of the wavefield in the forward modelling and recorded data. In migration velocity analysis, the unfocusing of the image, caused by inconsistency in the kinematics of reflected waves, is measured and is used to update the velocity model by applying differential semblance optimization. The same concept is applicable when using information from diving waves. For diving waves, little is known about the focusing behaviour, also known as imaging moveout, especially in the presence of azimuthal anisotropy, such as orthorhombic anisotropy, which is a good approximation for volcanic plains and sedimentary basins. Obtaining more knowledge about the focusing behaviour of diving waves for this type of anisotropy may help when choosing parameters to invert during inversion that yield a low trade-off between the parameters. Here, we derive approximate series-based equations describing the imaging moveout of diving qP-waves in acoustic factorized orthorhombic anisotropic media. Due to the complexity of the analytical solutions for diving wave properties in such models, we find a vertical transverse isotropic type of simplification that manages to conserve the curvature and horizontal velocity of the diving qP-wave. The accuracy of the simplified expressions is compared to the exact form and found to yield small errors. To verify the validity of the derived equations for imaging moveout, we compare the generated surfaces with images containing the shape of the unfocusing obtained using reverse time migration, showing a good fit. Of the anisotropic parameters defining the acoustic factorized orthorhombic model, the ε1 and ε2 parameters have the largest influence on the shape of the surface. The anelliptical parameters are shown only to induce minimal changes. Our method to obtain the series expressions describing the imaging moveout in the acoustic factorized orthorhombic model is also applicable to higher symmetry special cases of orthorhombic anisotropy by setting appropriate conditions. Here, this is demonstrated by additionally finding an approximate series expression describing the imaging moveout in acoustic factorized vertical transversely isotropic media, yielding a good match with the image obtained from reverse time migration.

The role of the Andaman Nicobar fault (ANF) in shaping Narcondam offshore: Insights from high-resolution reflection seismic data

The study investigates the Andaman Nicobar Fault (ANF) and its role in the evolution of a volcano-supported basin adjacent to Narcondam Island, using three high-resolution 2D seismic reflection profiles. Migrated images show a fluid zone, determined through velocity and polarity analyses, with mean 1/Q values ranging from 0.0165 to 0.0096 for Lines 1 to 3. Additionally, polygonal faults are imaged, with varying thicknesses (0.1–0.4 km) of Miocene age, positioned above the fluid saturated zone. The migrated sections further show the branches of the ANF to be conduits for fluid migration and accumulation within the basinal deposits. The study finally highlights a shift in depocenter during the Neogene period, indicating fluctuations in sediment supply from the Irrawaddy River and the evolution of the ANF branch.

Role of the complexity factor and Karmarkar condition in constructing new wormhole models in dRGT gravity

This study delves into the distinctive characteristics of wormhole models in the context of de Rham-Gabadadze-Tolley (dRGT) massive gravity, providing insights into their theoretical behavior and stability. We use a null zero complexity factor to find the wormhole shape function for Model I. Additionally, we solve analytically the modified field equations describing wormhole for a given choice of logarithmic redshift function, exploiting the Karmarkar condition for embedding class one metrics for Model II. To achieve this, we analyze the wormhole geometry in a static spherical spacetime with an anisotropic matter configuration. The study investigates a number of parameters, including density, energy conditions, equation of state parameter, adiabatic sound velocity, and equilibrium condition. The solution shows a traversable wormhole that violates the null energy criterion and equilibrium state for certain ranges of free parameters. We employ adiabatic sound velocity analysis to concentrate on the stability of the wormhole. Furthermore, by using the equation of state parameter (ω), we conclude that both models end up in the phantom dark energy region. Finally, our findings highlight distinct photon deflection behaviors in dRTG massive gravity, with Model II showing negative angles indicative of repulsive gravity, while Model I exhibits positive angles, underscoring significant differences in gravitational dynamics.

Velocity-independent NMO correction based on multi-scale dynamic time warping

Normal moveout (NMO) correction is one of the common steps of seismic data processing. Conventional NMO correction is generally based on a velocity function, but velocity analysis is considered time-consuming and labor-intensive. Moreover, the field seismic data observed in complex areas can have low signal-to-noise ratio (SNR), resulting in inaccurate picked up velocity parameters and poor NMO correction. The conventional NMO correction has stretching issues, most significantly at shallow and large offset areas. To address these problems, a new multi-scale dynamic time warping (MSD) algorithm for velocity-independent stretch-free NMO correction is investigated. This algorithm has higher accuracy and stronger noise resistance, as our comparisons with other applications of DTW show. In our algorithm, the original seismic data is decomposed into multiple morphological scales (using mathematical morphology theory), and alignment errors are calculated separately at each scale, followed by further adaptive weighted summation. Accumulation and backtracking operations based on alignment errors produce time shift sequences for automatic flattening of the gathers. The effectiveness of the presented approach is tested on both synthetic and field data. The results demonstrate that compared with traditional velocity-based NMO correction methods, the proposed method can accurately flatten seismic gathers without the NMO stretch and is robust to strong noise.

Volumetric drag coefficients for generic urban configurations: Insights from canopy flow analysis

Alternative drag approaches for representing unresolved buildings were proposed in literature for computational fluid dynamics (CFD) simulation of macroscopic urban airflow. As a contribution, the present work derives the volumetric drag coefficient (Cd*) through canopy drag and velocity analysis and provides appropriate correlations for Cd*against urban morphological parameters. A total of 72 cases across various urban configurations are investigated, categorized by building typology, horizontal layout, height variability, and plan area density (λp, from 0.0625 to 0.57). Reynolds-Averaged Navier-Stokes (RANS) simulations with periodic boundary conditions are performed to model fully developed flows. Results for the normalized drag force and superficial velocity and their relations with λp are evaluated. Subsequent evaluation of the profiles for the sectional coefficients (Cd*(Z)) reveals four distinct types with variations in uniform-height cases and combinations in varying-height cases. A throughout correlations analysis, facilitated by data transformation, identifies the straightforward relations between Cd* and frontal area density (λf) and tortuosity (τ). The followed stepwise regression provides a recommended formula for Cd*, demonstrating a proper fit with the simulated values. These findings facilitate the understanding and appropriate estimation of Cd* and Cd*(Z), promoting the application of macroscopic turbulence models, for neighborhood-scale wind and air quality studies.

Numerical Analysis and Validation of Horizontal and Vertical Displacements of a Floating Body for Different Wave Periods

This study concentrates on numerically evaluating the behavior of a floating body with a box format. Although research on floating objects has been conducted, the numerical modeling of Wave Energy Converter (WEC) devices, considering the effects of fluctuations, remains underexplored. Therefore, this research intends to facilitate the analysis of floating devices. First, the experimental data served as a benchmark for evaluating the motion paths of the floating box’s centroid. Second, the effects of various wave periods and heights on the floating body’s movement were analyzed. The Volume of Fluid (VOF) multiphase model was applied to simulate the interactions between phases. The computational model involved solving governing equations of mass conservation, volumetric fraction transport, and momentum, employing the Finite Volume Method (FVM). The validation demonstrated that the Normalized Root Mean Square Error (NRMSE) for the x/h ratio was 3.3% for a wave height of 0.04 m and 4.4% for a wave height of 0.1 m. Moreover, the NRMSE for the z-coordinate to the depth of water (z/h) was higher, at 5% for a wave height of 0.04 m and 5.8% for a wave height of 0.1 m. The overall NRMSE remained within acceptable ranges, indicating the reliability of the numerical solutions. Additionally, the analysis of horizontal and vertical velocities at different wave periods and heights showed that for H = 0.04 m, the wave periods had a minimal impact on the amplitude, but the oscillation frequency varied. At H = 0.1 m, both velocities exhibited significantly larger amplitudes, especially for T = 1.2 s and T = 2.0 s, indicating stronger motion with higher wave heights.

Laminar burning characteristics of ammonia and hydrogen blends at elevated initial pressures up to 2.5 MPa

Ammonia is a highly promising alternative fuel, and blending it with hydrogen can mitigate its poor combustion performance. However, the combustion mechanism of ammonia-hydrogen mixtures requires further validation through measurements of laminar burning velocity, particularly under high-pressure conditions relevant to practical combustors. Experimental data at high initial pressures (>1.0 MPa) are notably scarce. In this study, experiments were conducted using an outwardly propagating spherical flame in a high-pressure, high-temperature, constant-volume combustion chamber to determine the laminar burning velocities of ammonia-hydrogen blends at elevated initial pressures. The effects of different equivalence ratios (0.6 ∼ 1.4), volumetric hydrogen ratios (0.1 ∼ 0.6), and initial pressures (0.1 ∼ 2.5 MPa) were evaluated. Chemical kinetics of ammonia and hydrogen combustion was investigated at high pressures. The experimental results were compared with the simulation results under a wide range of conditions using several existing mechanisms to evaluate their applicability. The results show that the laminar burning velocity increases first and then decreases as the equivalence ratio (ϕ) increases and reaches a maximum value around ϕ of 1.1. The laminar burning velocity increases non-linearly with the volumetric hydrogen ratio, with more pronounced acceleration at higher hydrogen ratios. In contrast, the laminar burning velocity decreases non-linearly with the increasing initial pressure, and this reduction becomes progressively slower as the initial pressure rises. The predictive performance of the mechanisms by Okafor et al. and Gotama et al. is relatively satisfactory under certain conditions, but further optimization based on experimental data is necessary. Additionally, reaction pathway analysis of ammonia-hydrogen combustion indicates that introducing hydrogen increases the concentration of active radicals such as OH, O, and H, thereby enhancing ammonia combustion. Sensitivity analysis of the laminar burning velocity identified the critical elementary reactions across varying pressures, providing strong support for optimizing ammonia-hydrogen chemical kinetics models and developing simulation models for practical combustion systems.

Bouncing dynamics of binary equal-sized high-viscosity molten glass droplets in head-on collisions

Despite extensive research on head-on droplet collisions over the past decades, detailed investigations into the bouncing behavior of high-viscosity droplets, such as molten glass droplets, are still scarce. In this study, a volume-of-fluid method coupled with dual marker functions is employed to simulate the collision dynamics of molten glass droplets. The results show good agreement with experimental observations in both spatial and temporal dimensions. Theoretical analysis reveals a critical Weber number of 22 for bouncing and coalescence of molten glass droplets with a diameter of 100 μm. Below this threshold, we examine the bouncing behavior across various Weber numbers, categorizing the process into four distinct stages: mutual proximity, radial expansion, suction separation, and reverse separation, and providing a detailed analysis of velocity, pressure, and energy at each stage. As the Weber number increases, vortices sequentially emerge at 4, 8, 12, and 16, suggesting a strong correlation between droplet deformation and vortex generation. At lower Weber numbers, the air film pressure between droplets transitions smoothly between radial expansion and suction separation. However, between Weber numbers 9 and 22, a distinct concave pressure phenomenon is observed during suction separation. Pressure chattering occurs at the beginning of radial expansion and the end of suction separation. Furthermore, the results indicate that the cumulative viscous dissipation energy consistently approaches half of the initial kinetic energy, irrespective of the Weber and Ohnesorge numbers.

Investigation on flow–acoustic resonance behaviors inside ducts with tandem cavities using a high-order spectral/hp element method

This study numerically investigates the flow–acoustic resonance behaviors inside ducts with tandem cavities, containing the flow-excited acoustic eigenmodes and elevated flow dynamics under self-sustained acoustic forcing. An advanced high-order spectral/hp element method integrated with implicit large-eddy simulations was utilized to solve the nonlinear compressible Navier–Stokes equations, which effectively identified the fully coupled self-sustained flow–acoustic resonance fields. The benchmark shallow cavity configuration with a length-to-depth (L/D) ratios of 2 was motivated by the experimental findings from Shaaban and Ziada [“Fully developed building unit cavity source for long multiple shallow cavity configurations,” Phys. Fluids 30, 086105 (2018)], in which the intensive flow–acoustic resonance was occurred at a Reynolds number of 1.3×105, and we further investigated three deeper cavity configurations with L/D of 1, 2/3, and 1/2 for numerical validation and further comparison. Subsequently, aeroacoustic characteristics were assessed by analyzing the wall pressure fluctuations, indicating broader resonance regions and augmented pressure pulsation amplitudes extending from main duct to local cavity volumes with larger cavity depths. As feedback, the intensified acoustic forcing can modulate the cavity flow dynamics into stronger fluctuation levels. Furthermore, the spectral proper orthogonal decomposition analysis was conducted on the pressure fields and velocity fields, respectively. The significant fluctuations in acoustic pressure were linked to transitional acoustic modes that were present as global modes in the main duct and local modes in tandem cavities. As for velocity analysis, coherent vortex structures were extracted along the cavity entrances. These vortex structures caused progressively amplified velocity fluctuations and classified the shear layers into two dynamic motions, i.e., a flapping motion in shallow cavities and a rolling-up motion in deep cavities.

High-Fidelity OC-Seislet Stacking Method for Low-SNR Seismic Data

Seismic stacking is a core technique in seismic data processing, aimed at enhancing the signal-to-noise ratio (SNR) of data by utilizing seismic data acquisition with multifold geometry. Traditional stacking methods always have certain limitations, such as the reliance on the accuracy of velocity analysis for dip moveout (DMO) in common midpoint (CMP) stacking. The seislet transform, a compression technique tailored to nonstationary seismic data, can compress and stack along the prediction direction of seismic data, which provides a new technical idea for high-fidelity seismic imaging based on the effectiveness of the compression. This paper introduces a high-order OC-seislet stacking method for low-SNR seismic data, capable of achieving the high-fidelity stacking of reflection and diffraction waves simultaneously. With the multi-scale analysis advantages of the seislet transform, this method addresses the dependency of DMO stacking on velocity analysis accuracy. In the frequency–wavenumber–scale domain, the correction compensation of the high-order CDF 9/7 basis function is used to obtain the compression coefficients of the high-order OC-seislet transform. This approach simultaneously stacks frequency–wavenumber information of reflection and diffraction waves with high fidelity while implementing DMO processing. After normalizing the weighting coefficients and applying soft thresholding for denoising, the final result is transformed back to the original time–space domain, yielding high-fidelity stacking sections. The results of applying this method to both synthetic and field data show that, compared with conventional DMO stacking methods, the high-order OC-seislet stacking technique reasonably represents dipping layers and fault amplitudes, and it can achieve a balance of a high SNR and high fidelity in stacked profiles.

Design of ION Thruster

Ion thrusters represent a significant advancement in electric propulsion, enhancing fuel efficiency by accelerating ions for thrust generation. These systems, demonstrated in missions such as Deep Space 1 and Dawn, facilitate substantial velocity changes with minimal propellant, making them suitable for long-duration space missions. This paper outlines the design of an ion thruster aimed at achieving a thrust of 0.2 Newton, focusing on the use of xenon as the propellant and employing highvoltage grids for ion acceleration. Key design aspects include an efficient power supply delivering at least 26 W, effective thermal management, and the integration of control systems. Performance metrics target a specific impulse of 3,000 seconds and a thrust-to-power efficiency ratio greater than 0.5. Through detailed calculations, including arc distance, flow configuration and velocity analyses and testing using different materials, this study identifies optimal configurations for thrust generation. The developed ion thruster is tailored for small satellites (700-800 kg) to enhance trajectory control and station-keeping, underscoring the importance of ion propulsion in modern space exploration