Search Results (366)

Topographic slope is a key parameter for characterizing landscape geomorphology. The Ice, Cloud, and Land Elevation Satellite-2 (ICESat-2) offers high-resolution along-track slopes based on the ground profiles generated by dense signal photons. However, the across-track slopes are typically derived using the ground photon geolocations from the weak-beam and strong-beam pair, limiting the retrieval accuracy and losing valid results over rugged terrains. The goal of this study is to propose a new method to derive the across-track slope merely using single-track photon data of a strong beam based on the theoretical formula of the received signal pulse width. Based on the ICESat-2 photon data over the Walker Lake area, the specific purposes are to (1) extract the along-track slope and surface roughness from the signal photon data on the ground; (2) generate an elevation frequency histogram (EFH) and calculate its root mean square (RMS) width; and (3) derive the across-track slope from the RMS width of the EFH and evaluate the retrieval accuracy against the across-track slope from the ICESat-2 product and plane fitting method. The results show that the mean absolute error (MAE) obtained by our method is 11.45°, which is comparable to the ICESat-2 method (11.61°) and the plane fitting method (12.51°). Our method produces the least invalid data proportion of ~2.5%, significantly outperforming both the plane fitting method (10.29%) and the ICESat-2 method (32.32%). Specifically, when the reference across-track slope exceeds 30°, our method can consistently yield the optimal across-track slopes, where the absolute median, inter quartile range, and whisker range of the across-track slope residuals have reductions greater than 4.44°, 1.31°, and 0.10°, respectively. Overall, our method is well-suited for the across-track slope estimation over rugged terrains and can provide higher-precision, higher-resolution, and more valid across-track slopes. Full article

Harbor seals (Phoca vitulina) have excellent perception of water disturbances and can still sense targets as far as 180 m away, even when they lose their vision and hearing. This exceptional capability is attributed to the undulating structure of its vibrissae. These specialized whiskers not only effectively suppress vortex-induced vibrations (VIVs) during locomotion but also amplify the vortex street signals generated by the wake of a target, thereby enhancing the signal-to-noise ratio (SNR). In recent years, researchers in fluid mechanics, bionics, and sensory biology have focused on analyzing the hydrodynamic characteristics of seal vibrissae. Based on bionic principles, various underwater biomimetic seal whisker sensors have been developed that mimic this unique geometry. This review comprehensively discusses research on the hydrodynamic properties of seal whiskers, the construction of three-dimensional geometric models, the theoretical foundations of fluid–structure interactions, the advantages and engineering applications of seal whisker structures in suppressing VIVs, and the design of sensors inspired by bionic principles. Full article

The improvement of densification and fracture toughness in high-entropy ceramics is important to realizing their practical applications. In this study, SiC whiskers and metal Ni additions were incorporated to solve these problems of high-entropy boride ceramics. The influence of sintering temperatures (1450–1650 °C) on the densification, microstructure, hardness, fracture toughness, and bending strength of (M_0.2Ti_0.2Ta_0.2V_0.2Nb_0.2)B₂-SiC_w-Ni (M=Hf, Zr, or Cr) composites prepared by hot-pressing technology were studied. Results showed that when SiC whiskers and metal Ni additions were used as additives, increasing sintering temperatures from 1450 to 1600 °C promoted the densification of high-entropy boride ceramics. This was mainly attributed to the high sintering driving force. However, when the temperature further increased to 1650 °C, their densification behavior decreased. At a sintering temperature of 1600 °C, these high-entropy borides ceramics all had the highest densification behavior, leading to their high hardness and fracture toughness. The highest relative density was 96.3%, the highest hardness was 22.02 GPa, and the highest fracture toughness was 13.25 MPa·m^1/2, which was improved by the co-function of SiC whiskers and plastic metal Ni. Meanwhile, in the adopted sintering temperature range of 1450 to 1650 °C, the highest bending strength at room temperature of these high-entropy boride ceramics could reach 320.8 MPa. Therefore, this research offers an effective densification, strengthening, and toughening method for high-entropy boride composites at a low sintering temperature. Full article

Three-dimensional printing techniques can prepare complex bioceramic parts and scaffolds with high precision and accuracy, low cost, and customized geometry, which greatly broadens their application of 3D-printed bioceramics and bioceramic matrix composites in the clinical field. Nevertheless, the inadequate mechanical properties of 3D-printed bioceramic scaffolds, such as compressive strength, wear resistance, flexural strength, fracture toughness, and other properties, are a bottleneck problem and severely limit their application, which are overcome by introducing reinforcements. Three-dimensional printing techniques and the mechanical property of bioceramics and bioceramic matrix composites with different reinforcements, as well as their potential applications for bone tissue engineering, are discussed. In addition, the biological performance of 3D-printed bioceramics and scaffolds and their applications are presented. To address the challenges of insufficient mechanical strength and mismatched biological performance in bioceramic scaffolds, we summarize current solutions, including the advantages and strengthening effects of fiber, particle, whisker, and ion doping. The effectiveness of these methods is analyzed. Finally, the limitations and challenges in 3D printing of bioceramics and bioceramic matrix composites are discussed to encourage future research in this field. Our work offers a helpful guide to research and medical applications, especially application in the tissue engineering fields of bioceramics and bioceramic matrix composites. Full article

Accurate imaging methods are important for understanding electrodeposition phenomena in metal batteries. Among the suitable imaging methods for this task is magnetic resonance imaging (MRI), which is a very powerful radiological diagnostic method. In this study, MR microscopy was used to image electroplating in a lithium symmetric cell, which was used as a model for a lithium-metal battery. Lithium electrodeposition in this cell was studied by sequential 3D ¹H MRI of 1 M LiPF₆ in EC/DMC electrolyte under different charging conditions, which resulted in different dynamics of the amount of electroplated lithium and its structure. The acquired images depicted the electrolyte distribution, so that the images of deposited lithium that did not give a detectable signal corresponded to the negatives of these images. With this indirect MRI, phenomena such as the transition from a mossy to a dendritic structure at Sand’s time, the growth of whiskers, the growth of dendrites with arborescent structure, the formation of dead lithium, and the formation of gas due to electrolyte decomposition were observed. In addition, the effect of charge and discharge cycles on electrodeposition was also studied. It was found that it is difficult to correctly predict the occurrence of these phenomena based on charging conditions alone, as seemingly identical conditions resulted in different results. Full article

The world’s largest mangrove, Sundarbans, Bangladesh, is the habitat of the euryhaline catfish Nona Tengra (Mystus gulio). This study aimed to assess the stock status of M. gulio and provide reference points for sustainable fisheries’ management. One-year length–frequency (LF) data were collected from the Sundarbans region of Bangladesh and analyzed using the Length-Based Bayesian Biomass (LBB) method and the Length-Based Spawning Potential Ratio (LBSPR) model. The findings showed healthy biomass (B/B_MSY = 1.2), with 57% of the wild stock of this species being harvested (B/B₀ = 0.43). The calculated fishing mortality ratio indicated the underfishing conditions (F/M = 0.9). Safe exploitation (E = 0.46) was depicted, as E was smaller than the permitted level of 0.5. The value of capture length (L_c = 12.8 cm) was larger than the optimum capture length (L_{c_opt} = 10.0 cm) and the optimum length for maximum yield per recruit (L_opt = 12.0 cm) and larger than the maturity length (L_m = 9.16 cm), indicating the capture of mature individuals. The calculated Spawning Potential Ratio (SPR = 48%) was higher than the target reference points (SPR = 40%). This research evaluated the sustainable stock status. Although the margin between L_{c_opt} and L_m is very narrow, setting the minimum capture size at L_opt would be a conservative buffer to ensure long-term sustainability. The recommended minimum harvest size is 12 cm for M. gulio. Current fishing gear selectivity can ensure the sustainability of M. gulio in Sundarbans, Bangladesh; however, maintaining current fishing practice through careful management is suggested. Further assessments with length-based and other low-data methods should be conducted to refine exploitation estimates and trends. Full article

Choosing the appropriate cutting tool material is essential for enhancing machining processes because it directly affects product quality, surface finish, dimensional accuracy, tool longevity, and overall efficiency. Different materials are used for cutting tools, i.e., for cutting inserts. Due to their high hardness and high temperature resistance, ceramics cutting inserts allow for increased cutting speeds, resulting in shorter manufacturing times and reduced costs, despite being pricier than traditional cemented carbide and facing certain technical challenges due to their brittleness. Alumina-based ceramics dominate the market, accounting for about two-thirds of usage, followed by silicon nitride and zirconia. This paper provides a comprehensive overview of recent advances in alumina ceramic materials used as cutting inserts, focusing on research conducted in the last five years to optimize static and dynamic mechanical and thermal properties, wear resistance, density, etc. They ways in which the properties are altered through the incorporation of whiskers, nanoparticles, or nanotubes; the modification of the structure; the optimization of sintering parameters; and the application of advanced sintering techniques are demonstrated. The paper also addresses sustainability, environmental impact, and the management of critical raw materials associated with cutting inserts, which pertains to the future development of cutting insert materials. Full article

Incorporating a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide-based derivative (1,4-bis(diphenoxyphosphoryl)piperazine, DIDOPO) in combination with modified calcium sulfate whiskers (MCSWs) improved the flame retardancy, thermal stability, and rheological properties of a polyethylene oxide (PEO) composite. The synergistic flame-retardant effect of DIDOPO and MCSW on the PEO system was investigated. After introducing 5 wt.% MCSW and 10 wt.% DIDOPO into PEO, the UL-94 rating of the composite reached V-0, and the limiting oxygen index was increased to 26.5%. Additionally, the peak and average heat release rates and total heat release of the PEO/10% DIDOPO/5% MCSW composite decreased by 38.9%, 22%, and 20.07%, respectively. The results of a thermogravimetric analysis (TGA) revealed that PEO/10% DIDOPO/5% MCSW displayed an improved initial thermal stability and rate of char formation compared to those of the PEO matrix. The results of TGA/Fourier transform infrared analysis indicated that the composites exhibited phosphorus-containing groups during thermal degradation, based on the characteristic absorption peaks, and increased amounts of gas-phase volatiles. The morphologies and structures of the residues indicated that the PEO/10% DIDOPO/5% MCSW blend was less stable than PEO during combustion. The MCSW mixture formed a denser, more continuous carbon layer on the composite surface during combustion. The rheological behavior indicated that the high complex viscosity and moduli of PEO/10% DIDOPO/5% MCSW promoted the cross-linking network structure of the condensed phase during combustion. MCSW exhibited an excellent flame retardancy and improved thermal stability, which are potentially promising for use in fire safety applications. Full article

This study conducts water channel experiments to measure and compare the lift forces experienced by the seal whisker-shaped sensor and the circular cylinder sensor in both no vortex generator and the wake of two types of circular cylinders. Particle Image Velocimetry (PIV) is employed to capture the velocity fields of the cylinder wake and the surrounding flow of the seal whisker-shaped cylinders. Spectral analysis of the lift signals reveals that both cylinder types exhibit a primary peak close to the vortex shedding frequency of the upstream circular cylinder. However, seal whisker-shaped cylinders demonstrate relatively weaker components in their lift signals that do not align with the primary frequency, indicating a stronger sensing capability of the upstream cylinder’s wake. Modal analysis using Spectral Proper Orthogonal Decomposition (SPOD) on the PIV-measured velocity fields shows that the lift signals of both cylinder types are primarily induced by the vortices in the upstream cylinder’s wake. Full article

While gut microbiota-derived short-chain fatty acids (SCFAs) are recognized to modulate pathological pain by decreasing inflammation, the neurophysiological basis for SCFAs, butyrate’s ability to reduce hyperexcitability in nociceptive primary neurons during inflammatory conditions is still unknown. The objective of this study was to determine, using in vivo conditions, whether systemic butyrate administration attenuates inflammation-induced hyperexcitability of trigeminal ganglion (TG) primary neurons and the concomitant mechanical inflammatory hyperalgesia. Rats received complete Freund’s adjuvant (CFA) injections in their whisker pads to induce inflammation. CFA-inflamed rats showed a significantly lower mechanical stimulation-induced escape threshold compared to naïve rats. Systemic butyrate administration restored the mechanical threshold to levels comparable to naïve rats within four days. Four days of butyrate administration significantly decreased the mean increased discharge frequency of TG neurons to both non-noxious and noxious mechanical stimuli in inflamed rats. The increased mean spontaneous discharge of TG neurons in inflamed rats significantly decreased four days after butyrate administration. Collectively, our findings indicate that butyrate reduces inflammatory hyperexcitability in nociceptive primary TG neurons, thereby alleviating inflammatory hyperalgesia. These results suggest that butyrate may serve as a promising therapeutic approach for the prevention of trigeminal inflammatory mechanical hyperalgesia and its clinical manifestations. Full article

This study investigates the mechanical and impact resistance properties of high-performance cementitious composites (HPCCs) incorporating hybrid fibers under a low water-to-binder ratio, with a focus on the multi-scale synergistic effects of different fiber types. Aramid fibers (AFs), basalt fibers (BFs), and calcium sulfate whiskers (CSWs) contribute to reinforcement at the macro, meso, and micro levels, respectively. Experimental results reveal that hybrid fiber systems significantly outperform single-fiber composites in terms of both impact resistance and crack suppression. The optimal mix design—comprising 3% CSW, 0.067% AF, and 0.033% BF—achieved a remarkable 233.3% increase in impact energy absorption compared to the control group. This enhancement is attributed to the complementary roles of the three fibers: CSWs refine the pore structure and mitigate microcrack propagation; AFs effectively restrain the development of macrocracks due to their high tensile strength and aspect ratio; and BFs contribute to energy dissipation through crack bridging and mechanical interlocking. Statistical analysis using the two-parameter Weibull distribution accurately characterized the variability and reliability of the impact resistance data, while pore structure analysis confirmed a reduction in average pore diameter and a more favorable pore size distribution. These findings underscore the effectiveness of fiber hybridization in improving the mechanical behavior and dynamic load resistance of cement-based composites, offering valuable insights for their application in demanding engineering scenarios. Full article

Modern aero-engines need alloys that sustain both strength and ductility at high temperatures. However, conventional titanium alloys face inherent trade-offs between strength and ductility. In situ TiB-reinforced titanium matrix composites could fill this gap, but their texture evolution and hot-working mechanics are still poorly understood. In this study, TiB-reinforced IMI834 titanium matrix composites were synthesized using in situ technology in a remelting furnace. Meanwhile, the evolution of microstructure and texture in the hot-rolled titanium matrix composites was examined through both Abaqus simulations and experimental observations. Results indicate that dynamic recrystallization occurred in the microstructure of the composites at a deformation level of 95%. Due to the specific orientation relationship between the TiB whiskers and Ti matrix, the hot-rolled composites developed a pronounced [11-20]_Ti // rolling direction fiber texture. TiB whiskers rotated toward the rolling direction, enhancing the intensity of the [11-20]_Ti // rolling direction fiber texture, consistent with the predictions from numerical simulations. Tensile tests revealed that the combined effects of grain refinement and the rotation of TiB whiskers along the rolling direction increased the yield strength of the hot-rolled composite to 1153 MPa, while simultaneously raising the elongation to 10%. Full article

To improve the tribological performance of poly(ether ether ketone) (PEEK), a potassium titanate whisker/graphene multi-dimensional hybrid filler was proposed. Hybrid fillers with one-dimensional (1D) potassium titanate whiskers and two-dimensional (2D) graphene nanosheets in different ratios were fabricated using direct mixing and grafting methods. The potassium titanate whiskers and graphene nanosheets are an excellent combination, as confirmed by SEM and FTIR. Furthermore, PEEK/hybrid filler composites with different mass percentages of fillers were prepared and investigated systematically. It was found that introducing multi-dimensional hybrid PTWs–GNPs (volume ratio 1:3) fillers led to the wear rate being as low as 3.214 × 10⁻⁶ mm³N⁻¹m⁻¹, reduced by 60% compared with pure PEEK. In addition, the wear mechanism of PEEK composites was also investigated. The results demonstrate the superior tribological properties of the PEEK composites with multi-dimensional hybrid PTWs–GNPs fillers. Full article

In this study, high-performance SiC whisker (SiCw)-reinforced Cu matrix functionally graded materials (FGMs) were achieved through the synergy of numerical simulation and co-electrodeposition and then successfully applied as the interface of Cu and Si. A comprehensive numerical simulation framework was developed to investigate the influence of gradient transition modes and the maximum volume fraction of SiCw on the thermal–mechanical properties in the different gradient structures. The optimized FGMs via numerical simulation were fabricated using a co-electrodeposition technique, producing a 100 μm thick coating with a SiCw volume fraction gradient ranging from 0% to 40%. The interface of Cu and SiC was void free in the FGMs and the SiCw was coated by nano-scale Cu grains during the electroplating process. The coefficient of thermal expansion in FGMs was higher than 9.78 × 10⁻⁶ K⁻¹, which was the coefficient of thermal expansion in the Cu-40% vol. SiCw, and lower than 16.4 × 10⁻⁶ K⁻¹, which was the coefficient of thermal expansion in pure Cu. Notably, the bonding interface area between the Cu/Si joint with the gradient-structured FGMs was more than twice that of non-graded materials. The enhanced thermal–mechanical performance was attributed to the synergistic effects of the nano-scale grain-reinforced SiCw-Cu interface and an optimized stress distribution achieved by the gradient structure. Full article

This article is used to reconstruct mechanical parts with highly reflective surfaces. Three-dimensional reconstruction based on Phase Measuring Profilometry (PMP) is a key technology in non-contact optical measurement and is widely applied in the intelligent inspection of mechanical components. Due to the high reflectivity of metallic parts, direct utilization of the captured high-dynamic-range images often results in significant information loss in the oversaturated areas and excessive noise in the dark regions, leading to geometric defects and reduced accuracy in the reconstructed point clouds. Many image-fusion-based solutions have been proposed to solve these problems. However, unknown geometric structures and reflection characteristics of mechanical parts lead to the lack of effective guidance for the design of important imaging parameters. Therefore, an adaptive high-precision 3D reconstruction method of highly reflective mechanical parts based on optimization of exposure time and projection intensity is proposed in this article. The projection intensity is optimized to adapt the captured images to the linear dynamic range of the hardware. Image sequence under the obtained optimal intensities is fused using an integration of Genetic Algorithm and Stochastic Adam optimizer to maximize the image information entropy. Then, histogram-based analysis is employed to segment regions with similar reflective properties and determine the optimal exposure time. Experimental validation was carried out on three sets of typical mechanical components with diverse geometric characteristics and varying complexity. Compared with both non-saturated single-exposure techniques and conventional image fusion methods employing fixed attenuation steps, the proposed method reduced the average whisker range of reconstruction error by 51.18% and 25.09%, and decreased the median error by 42.48% and 25.42%, respectively. These experimental results verified the effectiveness and precision performance of the proposed method. Full article