Search Results (48)

This paper addresses the critical multiple-uncertainty challenge in laser link acquisition for space gravitational wave detection missions—a key bottleneck where spacecraft attitude alignment for laser link establishment is perturbed by inherent random disturbances in such missions, while also needing to balance ultra-high attitude precision, fuel efficiency, and compliance with engineering constraints. To tackle this, a convex optimization-based attitude control strategy integrating covariance control and free terminal time optimization is proposed. Specifically, a stochastic attitude dynamics model is first established to explicitly incorporate the aforementioned random disturbances. Subsequently, an objective function is designed to simultaneously minimize terminal state error and fuel consumption, with three key constraints (covariance constraints, pointing constraints, and torque saturation constraints) integrated into the convex optimization framework. Furthermore, to resolve non-convex terms in chance constraints, this study employs a hierarchical convexification method that combines Schur’s complementary theorem, second-order cone relaxation, and Taylor expansion techniques. This approach ensures lossless relaxation, renders the optimization problem computationally tractable without sacrificing solution accuracy, and overcomes the shortcomings of traditional convexification methods in handling chance constraints. Finally, numerical simulations demonstrate that the proposed method adheres to engineering constraints while maintaining spacecraft attitude errors below 1 μrad under environmental uncertainties. This study provides a convex optimization solution for laser link acquisition in space gravitational wave detection missions considering uncertainty conditions, and its framework can be extended to the optimal design of other stochastically uncertain systems. Full article

Melt electrowriting (MEW) is an advanced additive manufacturing technology that can produce micro- or nano-scale fibres, achieving accurate fibre deposition, and is suitable for manufacturing high-precision, miniature products. This review introduces the key principles and parameters that influence the performance of melt electrowriting and explores the current mathematical modelling under four stages: (1) heating and extrusion system, (2) formation of the Taylor cone, (3) formation and injection of the melt jet, and (4) deposition of the melt jet. In addition, current applications of melt electrowriting in emerging areas, such as tissue engineering, energy, filtration, and bioengineering, are introduced while discussing its combination with other additive manufacturing technologies. Finally, recent challenges, including production time, cost, and precision are covered, while the future research directions are to improve technology and introduce new materials. Full article

El Malpais National Monument in New Mexico, USA, is a landscape of significant cultural and geological importance, characterized by extensive lava flows, caves, and cinder cones. Despite its harsh terrain, El Malpais holds deep cultural and spiritual meanings for Native American communities, including the Acoma, Zuni, Laguna, and Navajo tribes, whose cosmologies and histories are interwoven with this landscape. Employing a mixed-methods approach combining ethnographic fieldwork with comparative literature studies, this paper documents how these Indigenous groups perceive and interpret interconnected geological features as sacred and meaningful parts of their ancestral heritage. The findings reveal that volcanic landscapes are central not only to cultural origin narratives but also to ongoing rituals, resource use, and pilgrimage practices. This interconnectedness is exemplified by the cultural links between El Malpais and adjacent Mount Taylor, highlighting how geological features form a unified sacred geography. This study positions El Malpais as a culturally animated landscape, where Indigenous epistemologies and spiritual relationships with volcanic landforms challenge conventional notions of geoheritage and call for relational, community-informed approaches to heritage management. Full article

In this work, the effect of the palladium precursor on the Oxygen Reduction Reaction (ORR) performance of lignin-based electrospun carbon fibers was studied. The fibers were spun from a lignin-ethanol solution free of any binder, where different Pd salts were added at two concentration levels. The system implemented to perform the spinning was a coaxial setup in which the internal flow contains the precursor dispersion with the metallic precursor, and ethanol was used as external flow to help fiber formation and prevent drying before generating the Taylor cone. The obtained cloths were thermostabilized in air at 200 °C and carbonized in nitrogen at 900 °C. The resulting carbon fibers were characterized by physicochemical and electrochemical techniques. The palladium precursor significantly affects nanoparticle distribution and size, fiber diameter, pore distribution, surface area and electrochemical behavior. The fibers prepared with palladium acetylacetonate at high Pd loading and carbonized at 900 °C under a CO₂ atmosphere showed high mechanical stability and the best ORR activity, showing near total selectivity towards the 4-electron path. These features are comparable to those of the commercial Pt/C catalyst but much lower metal loading (10.6 wt.% vs. 20 wt.%). The most promising fibers have been evaluated as cathodes in a zinc–air battery, delivering astonishing stability results that surpassed the performance of commercial Pt/C materials in both charging and discharging processes. Full article

Serial crystallography is a rapidly advancing experimental technology that has seen significant development in recent years. This technique enables the continuous delivery of a series of protein crystal samples to the X-ray beam, allowing for the collection of diffraction data from a large number of crystals at ambient temperature. Despite its advancements, serial crystallography still possesses considerable potential for further development within synchrotron radiation platforms. Currently, several challenges hinder the progress of this technology, including the preparation of numerous microcrystal samples, methods for sample delivery, data acquisition efficiency, and data processing techniques. The device introduced in this paper is designed to facilitate serial crystallographic experiments at the synchrotron radiation station, employing electrospinning in the vacuum cavity to reduce the average flux, mitigate the effects of air ionization on the Taylor cone, and enhance the stability of Taylor cone during the data acquisition process. The diffraction pattern of lysozyme crystals was successfully acquired with this device at the beamlines of the Shanghai Synchrotron Radiation Facility (SSRF). Full article

The present study reported, for the first time, the fabrication and characterization of electrospun nanofibers based on arabinoxylans (AXs) alone. The Fourier transform infrared spectrum of ferulated water-extractable AXs recovered from wheat endosperm confirmed the molecule identity. The carbon and oxygen signals in X-ray photoelectron spectrometry (XPS) were recorded for this molecule. The AXs had weight-average molar mass, intrinsic viscosity, radius of gyration, and hydrodynamic radius values of 769 kDa, 4.51 dL/g, 55 nm, and 31 nm, respectively. The calculated AX characteristic ratio and persistence length were 10.7 and 3.2 nm, respectively, while the Mark–Houwink–Sakurada α and K constants were 0.31 and 9.4, respectively. These macromolecular characteristics indicate a molecular random coil structure in the polysaccharide. Using aqueous acetic acid 50% (v/v) as a solvent favored the Taylor cone establishment and the fabrication of electrospun nanofibers. The morphology of nanofibers was revealed by scanning electron microscopy images. Atomic force microscopy analysis of AX nanofibers exposed the material deposition in layers; these nanofibers had an average diameter of 177 nm. These nanofibers could be used as advanced biomaterials for biomedical applications such as wound dressing. Full article

A multi-vane and multi-slit electrospinning nozzle for diversion was proposed to respond to the issues of easiness of clogging, existing End Effect among needles in current multi-needle electrospinning, and uncontrollable Taylor cone position in needleless electrospinning. The upper part of the novel nozzle is a cylindrical straight pipe, and the lower part is a flow channel expansion structure composed of multiple vane components that spread outward at an angle. Ansys software was used to study the effect of different opening angles of the vanes on the spreading of the electrospinning solution. In the fluid simulation, for the novel nozzle with a central slit and a support structure, when the vanes have an opening angle of 35° and a length of 11 mm, the droplet holding time is 16 s, twice as long as the nozzle without support (8 s). This result corresponds to the subsequent droplet holding experiment, showing that the support structure aids droplet holding and enhances electrospinning stability. Comsol Multiphysics software was used to investigate the effect of the vanes’ parameters on the uniformity of the electric field. The results indicate that when the vanes of the new electrospinning nozzle are set at an opening angle of 35°, with four vanes each 11 mm in length, a receiving distance of 200 mm, and a voltage of 30 kV, the novel nozzle achieves an average electric field intensity of 5.26 × 10⁶ V/m with a CV value of 6.93%. Metal 3D printing was used to create a new nozzle for electrospinning, which successfully produced stable multiple jets and increased nanofiber output. Full article

Electrosprays have garnered significant interest across various fields, from automotive painting to aerospace propulsion, due to their versatility and precision. This study aims to explore the formation and behavior of the Taylor cone in electrospray systems through the observation of the different characteristics of the produced droplets, in a way to enhance the control of the electrohydrodynamic jet. To obtain these results, the SpraySpy equipment was used, based on the phase Doppler technique, obtaining several characteristics of the droplets, such as velocity, size and distribution for a single liquid, acetone. These characteristics were acquired by varying parameters, namely the distance between the emitter and the collector, the liquid flow rate and the diameter of the emitter. Additionally, a high-speed camera was used to capture the cone angle, in the same operating conditions. The findings revealed a considerable decrease in particle velocity with an increase in the flow rate, while droplet size exhibited a noticeable tendency to grow under the increase in the emitter diameter. These insights aim to provide a deeper understanding of the relationship between these operational parameters and droplet behavior, contributing to the improvement of electrospray applications. Full article

Electrically charged flows were investigated using experimental techniques. These flows were visualized and recorded employing high-speed video, which allowed the study of the formation of electrically charged filaments, focusing on the flow characteristics at meniscus rupture and the flow downstream of the atomization region. Experiments were performed following the design-of-experiments methodology, which provided information on the effect of the main factors and their combinations on the response variables, such as spray angle, size distribution, and particle number. Meniscus formation and its rupture were analyzed as a function of competition between forces. Furthermore, the different rupture modes were determined as a function of the electric field intensity (electric Bond number, $B{o}_e$). The findings reveal that the best atomization condition is defined by a stable Taylor cone jet (at meniscus rupture). However, the results differ downstream of the atomization, since stable jet atomization is characterized by poor particle dispersion. To improve such conditions, it was found that flows with oscillation around the vertical axis and particle detachment (controlled instability) lead to better atomization. This is because a greater dissemination of particles is promoted, and greater homogeneity of the product and smaller particle sizes are generated. A secondary atomization process causes such conditions after the rupture of the meniscus, which is known as Coulomb fission. Full article

The influence of solvent properties on ion generation by swab spray ionization was investigated. The ability of a variety of solvents of different relative permittivity, surface tension, and viscosity to form a stable and reproducible electrospray was examined. It is demonstrated that in swab spray ionization, a crucial balance between solvent composition, applied potential, and the solvent flow fed to the swab head must be maintained. The solvent composition was found to significantly affect the shape of the Taylor cone and the emerging cone jet, which eventually have an impact on the resulting ion yield. The results indicate that the relative permittivity of solvents measured under standard conditions is the main factor governing jet shaping, and consequently, the ionization efficacy. Short jets, which are required for maximum ion yield, were observed for solvents with relative permittivity ε_r higher than 25. Solvents exhibiting lower relative permittivity required the addition of 20% to 60% methanol to limit the jet length and to avoid the ineffective dripping pulsation. The observed effects were compared to conventional electrospray ionization and paper spray ionization. Full article

In this study, we investigate and propose an improved theoretical method to more accurately predict the performance of a field-emission electric propulsion (FEEP) thruster with its complex configuration. We identify critical flaws in the previous theoretical methods and derive corrected equations. Additionally, we define and implement the overall half angle of the Taylor cone to account for variations in the Taylor cone’s half angle depending on the applied voltage. Next, we also establish an improved method of the electric filed simulation in a three-dimensional domain to accurately predict a trajectory of extracted ions and a resulting spatial beam distribution of the FEEP thruster by incorporating a configuration of the Taylor cone with the estimated overall half angle from the results of the present theoretical method. Through comparison with the experimental measurements, we found that the present improved methods for theoretical and electric field simulations can yield more accurate predictions than those of the previous methods, especially for higher V and I_em regimes, which correspond to the actual operating conditions of the FEEP thruster. Consequently, we anticipate that the proposed methods can enhance the reliability and efficiency of the design process by accurately predicting performance when developing the new FEEP thruster with its non-symmetric complex configuration to match specific thrust or spatial beam requirements. Full article

Current progress in numerical simulations and machine learning allows one to apply complex loading conditions for the identification of parameters in plasticity models. This possibility expands the spectrum of examined deformed states and makes the identified model more consistent with engineering practice. A combined experimental-numerical approach to identify the model parameters and study the dynamic plasticity of metals is developed and applied to the case of cold-rolled OFHC copper. In the experimental part, profiled projectiles (reduced cylinders or cones in the head part) are proposed for the Taylor impact problem for the first time for material characterization. These projectiles allow us to reach large plastic deformations with true strains up to 1.3 at strain rates up to 10⁵ s⁻¹ at impact velocities below 130 m/s. The experimental results are used for the optimization of parameters of the dislocation plasticity model implemented in 3D with the numerical scheme of smoothed particle hydrodynamics (SPH). A Bayesian statistical method in combination with a trained artificial neural network as an SPH emulator is applied to optimize the parameters of the dislocation plasticity model. It is shown that classical Taylor cylinders are not enough for a univocal selection of the model parameters, while the profiled cylinders provide better optimization even if used separately. The combination of different shapes and an increase in the number of experiments increase the quality of optimization. The optimized numerical model is successfully validated by the experimental data about the shock wave profiles in flyer plate experiments from the literature. In total, a cheap, simple, but efficient route for optimizing a dynamic plasticity model is proposed. The dislocation plasticity model is extended to estimate grain refinement and volume fractions of weakened areas in comparison with experimental observations. Full article

This paper develops a new time difference of arrival (TDOA) emitter localization algorithm in the 3D space, employing conic approximations of hyperboloids associated with TDOA measurements. TDOA measurements are first converted to 1D angle of arrival (1D-AOA) measurements that define TDOA cones centred about axes connecting the corresponding TDOA sensor pairs. Then, the emitter location is calculated from the triangulation of 1D-AOAs, which is formulated as a system of nonlinear equations and solved by a low-complexity two-stage estimation algorithm composed of an iterative weighted least squares (IWLS) estimator and a Taylor series estimator aimed at refining the IWLS estimate. Important conclusions are reached about the optimality of sensor–emitter and sensor array geometries. The approximate efficiency of the IWLS estimator is also established under mild conditions. The new two-stage estimator is shown to be capable of outperforming the maximum likelihood estimator while performing very close to the Cramer Rao lower bound in poor sensor–emitter geometries and large noise by way of numerical simulations. Full article

The sporadic cone production of longleaf pine (Pinus palustris Mill.) challenges the restoration of the longleaf pine ecosystem. While much has been learned about longleaf pine cone production at the stand level, little information exists at the tree level regarding cone production and energy allocational strategy. This study aims to analyze cone production and diameter growth of approximately ten sampled longleaf pine trees at seven sites across the southeastern USA over the past twenty years. The results indicate that three-year cycles dominated the cone production dynamics, but longer cycles (four years and more) also occurred. The dynamics of entropy in cone production varied among trees. Taylor’s law, which describes the correlation between average and variance, existed in cone production for the majority of trees. Lagged cone production at one and two years was not autocorrelated among trees across sites. No significant relationships existed between tree diameter (or basal area) growth and cone production among trees across sites. This study provides new information on cone production at the individual tree level and narrows down the possible mechanisms. The results will be helpful in developing strategies for the management and modeling of longleaf pine cone production. Full article

The present study focused on the design of geothermal energy piles based on cone penetration test (CPT) data, which was obtained from the Perniö test site in Finland. The geothermal piles are heat-capacity systems that provide both a supply of energy and structural support to civil engineering structures. In geotechnical engineering, it is necessary to provide an efficient, reliable, and precise method for calculating the group capacity of the energy piles. In this research, the first aim is to determine the most significant variables required to calculate the energy pile capacity, i.e., the pile length (L), pile diameter (D), average cone resistance ($q_{c0}$), minimum cone resistance ($q_{c1}$), average of minimum cone resistance ($q_{c2}$), cone resistance ($q_c$), Young’s modulus ($E$), coefficient of thermal expansion (${\alpha }_c$), and temperature change ($\Delta T$). The values of q_c0, q_c1, q_c2, q_c, and E are then employed as model inputs in soft computing algorithms, which includes random forest (RF), the support vector machine (SVM), the gradient boosting machine (GBM), and extreme gradient boosting (XGB) in order to predict the pile group capacity. The developed soft computing models were then evaluated by using several statistical criteria, and the lowest system error with the best performance was attained by the GBM technique. The performance parameters, such as the coefficient of determination (R²), root mean square error (RMSE), mean absolute error (MAE), mean biased error (MBE), median absolute deviation (MAD), weighted mean absolute percentage error (WMAPE), expanded uncertainty (U₉₅), global performance indicator (GPI), Theil’s inequality index (TIC), and the index of agreement (IA) values of the testing data for the GBM models are 0.80, 0.10, 0.08, −0.01, 0.06, 0.21, 0.28, −0.00, 0.11, and 0.94, respectively, demonstrating the strength and capacity of this soft computing algorithm in evaluating the pile’s group capacity for the energy pile. Rank analysis, error matrix, Taylor’s diagram, and the reliability index have all been developed to compare the proposed model’s accuracy. The results of this research also show that the GBM model developed is better at estimating the group capacity of energy piles than the other soft computing models. Full article