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A non-cavitating tip vortex generated by an elliptical hydrofoil is investigated utilizing tomographic particle image velocimetry (TPIV). Focus is placed on its three-dimensional evolution over a relatively large streamwise region, as well as the transport process of turbulent kinetic energy (TKE). Based on the variations in vortex structure and related vortex properties, three main stages of tip vortex evolution can be identified: formation stage, persistence stage, and decay stage. The boundary between the formation and persistence stages is the position where tip vortex cavitation (TVC) is more prone to incept, attributed to the rapid growth in vortex circulation and vortex-center axial velocity, along with high turbulent fluctuations. During the tip vortex evolution, its swirling momentum significantly influences the axial flow pattern, likely by altering the pressure gradient along the vortex path. TKE transport equation is employed to analyze the turbulent properties of the tip vortex. Flow near the hydrofoil tip is highly turbulent and unsteady, with the local TKE at an excessive level. The local high TKE tends to diffuse into surrounding flow rather than being concentrated within the tip vortex as it moves downstream. TKE is mainly produced on the suction side of hydrofoil, potentially due to local boundary-layer behaviors, and is subsequently transported into the vortex core. As the tip vortex propagates further downstream, the in-core TKE exhibits a decreasing trend, and a relaminarization process appears to occur in far wake region. The flow topology of the tip vortex is examined with the invariants of velocity gradient tensor, providing insights into the topological features during the vortex evolution. [ABSTRACT FROM AUTHOR]

Based on additive manufacturing via photopolymerization, this study combines polymer-dispersed liquid crystal (PDLC) technology with 3D printing technology to produce tunable micro-optical components with switchable diffraction or focusing characteristics. The diffraction grating and Fresnel zone plate are the research targets. Their structures are designed and simulated to achieve expected optical functions. A liquid crystal display (LCD) 3D printer is used to produce structures on transparent conductive substrates. The printed structures are filled with PDLCs and covered with transparent conductive substrates to achieve tunable functions. The proposed configurations are implemented and verified. The experimental results show that the diffraction efficiency of the 0th order increases from 15% to 50% for the diffraction grating and the focusing spot intensity decreases from 74% to 12% after the application of an electric field. These results demonstrate the feasibility of the proposed tunable optical component configurations. [ABSTRACT FROM AUTHOR]

The acoustic, velocity, and surface pressure fields of vertical jet impingement are studied utilizing pressure sensors, particle image velocimetry, and pressure sensitive paint measurements in parallel. Experiments are carried out at Mach numbers of 1.1 and 1.2, with corresponding Reynolds number of 5.8 × 10 5 and 6.2 × 10 5 , respectively. The focus is placed on the understanding of the relationships between noise generation mechanisms within these fields. Features of fluctuation and pulsation of velocity and surface pressure are analyzed using proper orthogonal decomposition and Fourier transformation. Different types of acoustic tones are found corresponding to unique patterns in the decomposition of velocity and pressure fields. Large-scale coherent structures in the velocity field and monopoles in the surface pressure field are correlated with pure tones due to the shedding of coherent structures. Corresponding velocity fluctuations can be detected throughout the jet, reflecting the global effect of aeroacoustic resonance. Near-plate coherent flow structures and dipoles of surface pressure pulsation are associated with impingement tones. These structures account for a smaller portion of the total kinetic energy and act as a local effect near the plate. Additionally, broadband noise is presented as quadrupoles of surface pressure pulsation. The dominant modes of surface pressure exhibit morphological similarity and consistent spectral characteristics with the acoustic poles in the Lighthill analogy. [ABSTRACT FROM AUTHOR]

This paper presents an effective three-dimensional (3D) surface reconstruction technique aimed at profiling composite surfaces with both specular and diffuse reflectance. Three-dimensional measurements based on fringe projection techniques perform well on diffuse reflective surfaces; however, when the measurement targets contain both specular and diffuse components, the efficiency of fringe projection decreases. To address this issue, the proposed technique integrates digital holography into the fringe projection setup, enabling the simultaneous capture of both specular and diffuse reflected light in the same optical path for full-field surface profilometry. Experimental results demonstrate that this technique effectively detects and accurately reconstructs the 3D profiles of specular and diffuse reflectance, with fringe analysis providing the absolute phase of composite surfaces. The experiments validate the effectiveness of this technique in the 3D surface measurement of integrated circuit carrier boards with chips exhibiting composite surfaces. [ABSTRACT FROM AUTHOR]

During heavy oil recovery in the Bohai Oilfield, substantial emulsification of oil and water occurred, primarily forming water-in-oil emulsions. This phenomenon could alter fluid dynamics within the subsurface porous media, potentially impacting well production performance. To elucidate the properties of water-in-oil emulsions and their associated liquid resistance effects, this study conducted a series of rheological tests, microscopic examinations, and injection experiments. The results show that the droplet size and distribution of water-in-oil emulsions were primarily influenced by shear rate and water content, which in turn modified emulsion viscosity. The stability of water-in-oil emulsions was reduced when they flowed through porous media. The increase in emulsion viscosity and the liquid resistance effect collectively enhanced the seepage resistance of water-in-oil emulsions flowing through porous media. Notably, when the emulsion droplet size exceeded the pore throat size, over 90% of the total seepage resistance was attributable to the liquid resistance effect. Conversely, when the majority of the emulsion droplets were smaller than the pore throat, the viscosity accounted for more than 60% of the seepage resistance. Water-in-oil emulsions flowed through cores with permeabilities ranging from 50 to 100 mD, exhibiting threshold pressure gradients between 35 and 43 MPa/m. At a core permeability of 300 mD, the threshold pressure gradient was significantly reduced to 1 MPa/m. The presence of a water-in-oil emulsion in the reservoir could result in a production pressure differential falling below the threshold pressure, thereby reducing reservoir productivity. [ABSTRACT FROM AUTHOR]

Chondritic meteorites are made of primitive components that record the first steps of formation of solids in our Solar System. Chondrules are the major component of chondrites, yet little is known about their formation mechanisms and history within the solar protoplanetary disk (SPD). We use the reconstructed concentrations of short-lived (26)Al in chondrules to constrain the timing of formation of their precursors in the SPD. High-precision bulk magnesium isotopic measurements of 14 chondrules from the Allende chondrite define a (26)Al isochron with (26)Al/(27)Al = 1.2(±0.2) × 10(-5) for this subset of Allende chondrules. This can be considered to be the minimum bulk chondrule (26)Al isochron because all chondrules analyzed so far with high precision (∼50 chondrules from CV and ordinary chondrites) have an inferred minimum bulk initial ((26)Al/(27)Al) ≥ 1.2 × 10(-5). In addition, mineral (26)Al isochrons determined on the same chondrules show that their formation (i.e., fusion of their precursors by energetic events) took place from 0 Myr to ∼2 Myr after the formation of their precursors, thus showing in some cases a clear decoupling in time between the two events. The finding of a minimum bulk chondrule (26)Al isochron is used to constrain the astrophysical settings for chondrule formation. Either the temperature of the condensation zone dropped below the condensation temperature of chondrule precursors at ∼1.5 My after the start of the Solar System or the transport of precursors from the condensation zone to potential storage sites stopped after 1.5 My, possibly due to a drop in the disk accretion rate.

A labeled multi‐Bernoulli filter is used to obtain estimates of the identities and states of targets in complex environments. However, when tracking multiple targets in dense clutters, the computational complexity of the traditional labeled multi‐Bernoulli filter will increase exponentially. A labeled multi‐Bernoulli tracking algorithm based on maximum likelihood recursive update is proposed, which can reduce the computational scale while maintaining tracking accuracy. Specifically, when performing posterior estimation, a maximum likelihood recursive update method is proposed to replace the complete enumeration, truncated enumeration, or sampling enumeration methods used in many traditional methods. Furthermore, combined with the Gaussian mixture technique, a maximum likelihood recursive updating labeled multi‐Bernoulli tracking algorithm is constructed. Simulation results demonstrated that the proposed filter obtained a good balance between the tracking accuracy and computational efficiency. [ABSTRACT FROM AUTHOR]

The non-cavitating tip vortex in the near field of an elliptical hydrofoil is studied utilizing tomographic particle image velocimetry. Both the instantaneous and time-averaged flow fields are analyzed to elucidate the flow characteristics of the near-field tip vortex. The tip vortex is mainly formed on the suction side of hydrofoil and exhibits a tube-like shape. The turbulence intensity is at a relatively high level around the hydrofoil tip due to the roll-up process of the separated shear layers from the pressure side. With increasing angle of attack, the initiating position of the tip vortex moves upstream along the hydrofoil outline. In the near field, the axial flow within the tip vortex manifests a jet-like profile at higher angles of attack (α ≥ 10 °), and the majority of the vorticity is contained within the vortex core. A special position is identified during the streamwise evolution of the tip vortex, where the vortex circulation reaches its local maximum for the first time and the tip vortex cavitation is more prone to incept. In the vicinity of this crucial position, the pressure–velocity relation is derived along the vortex centerline by combining the three-dimensional measured velocity fields with the governing equations. It is revealed that the mean static pressure is directly related to the local mean axial velocity, adhering to the form of Bernoulli's equation. Conversely, corresponding pressure fluctuation depends on both the mean and fluctuating parts of the local axial velocity. [ABSTRACT FROM AUTHOR]

The shedding-scheme transition of hemispherical wake is investigated with time-resolved tomographic particle image velocimetry. Experiments are carried out with Reynolds numbers based on the hemisphere radius R in the range of R e r = 924 – 2315 , crossing the critical value of R e r ≈ 2000. The variation of the hemispherical wake across the critical Reynolds number is carefully studied, and a detailed mechanism of the shedding-scheme transition is explored. A singular-shedding pattern of hairpin vortices at a low Rer is replaced by a pairing-shedding pattern at a moderate Rer, and finally, a less ordered wake and an unstable shedding pattern are observed at Rer > 2000. The onset of the pairing-shedding pattern is due to a streamwise modulation caused by the varicose modes, which is related to the Kelvin–Helmholtz (K–H) instability. Consequently, the pseudo-periodicity induced by the K–H instability is observed in the wake. When Rer > 2000, the stronger sinuous modulation intensifies interactions among the hairpin vortices, leading to frequent absorption and annihilation of those coherent structures, which further makes the dominant frequency of main hairpin vortices halved downstream. [ABSTRACT FROM AUTHOR]

Since 2006, with the development of an optimized methodology for silicon purification based on alkaline fusion followed by cation-exchange chromatography, silicon isotopes have been widely measured across diverse sample types. Nevertheless, this technique does not remove anions and dissolved organic carbon (DOC), leading to potential matrix effects. Notably, under dry plasma conditions, several studies have reported offset in the δ30Si value up to +1.4‰ when [S]/[Si] > 0.02 (wt/wt) and +0.65‰ when [DOC]/[Si] > 1.75. Here, we examine the matrix effects induced by chloride, sulfate and dissolved organic carbon under wet plasma conditions. To achieve this, we doped the NBS-28 (NIST® RM 8546) solution, with varying amounts of sulfate and chloride and measured the δ30Si value in the doped solutions. To investigate the DOC matrix effect, we used the UV photolysis method to decompose the DOC within natural samples and then compared the resulting δ30Si values with those of untreated samples. Importantly, we did not observe any significant δ30Si offset outside the range of our long-term analytical precision (±0.11‰, 2SD) attributed to chloride, sulfate, or DOC across a range of [Cl−]/[Si] = 0.09 to 5.65, [SO42−]/[Si] = 0.09 to 5.65 and [DOC]/[Si] = 0.08 to 6.38. Even though no offset in δ30Si value is observed for DOC-contaminated samples, we recommend removal of DOC. We suggest that the matrix effect observed under dry plasma conditions can be primarily attributed to the use of introduction systems with desolvating membranes, followed by differences in the operating parameters and the absolute quantity of anions introduced into the plasma. Our study indicates that precise and accurate measurements (<0.11‰, 2SD) can be reached for stable Si isotope ratios by MC-ICP-MS in wet plasma, with a larger tolerance to sample based-matrix effect induced by anion contamination compared to dry plasma. [ABSTRACT FROM AUTHOR]

This paper considers the problem of robust bearing-only source localization in impulsive noise with symmetric α-stable distribution based on the Lp-norm minimization criterion. The existing Iteratively Reweighted Pseudolinear Least-Squares (IRPLS) method can be used to solve the least LP-norm optimization problem. However, the IRPLS algorithm cannot reduce the bias attributed to the correlation between system matrices and noise vectors. To reduce this kind of bias, a Total Lp-norm Optimization (TLPO) method is proposed by minimizing the errors in all elements of system matrix and data vector based on the minimum dispersion criterion. Subsequently, an equivalent form of TLPO is obtained, and two algorithms are developed to solve the TLPO problem by using Iterative Generalized Eigenvalue Decomposition (IGED) and Generalized Lagrange Multiplier (GLM), respectively. Numerical examples demonstrate the performance advantage of the IGED and GLM algorithms over the IRPLS algorithm.