Search Results (134)

With growing reliance on hydraulic fracturing to develop tight oil and gas reservoirs characterized by low porosity and permeability, optimizing proppant transport and placement has become critical to sustaining fracture conductivity and production. However, how fracture geometry influences proppant distribution under varying field conditions remains insufficiently understood. This study employed computational fluid dynamics to investigate proppant transport and placement in hydraulic fractures of which the aperture tapers linearly along their length. Four taper rate models (δ = 0, 1/1500, 1/750, and 1/500) were analyzed under a range of operational parameters: injection velocities (1.38–3.24 m/s), sand concentrations (2–8%), proppant particle sizes (0.21–0.85 mm), and proppant densities (1760–3200 kg/m³). Equilibrium proppant pack height was adopted as the key metric for pack morphology. The results show that increasing injection rate and taper rate both serve to lower pack heights and enhance downstream transport, while a higher sand concentration, larger particle size, and greater density tend to raise pack heights and promote more stable pack geometries. In tapering fractures, higher δ values amplify flow acceleration and turbulence, yielding flatter, “table-top” proppant distributions and extended placement lengths. Fine, low-density proppants more readily penetrate to the fracture tip, whereas coarse or dense particles form taller inlet packs but can still be carried farther under high taper conditions. These findings offer quantitative guidance for optimizing fracture geometry, injection parameters, and proppant design to improve conductivity and reduce sand-plugging risk in tight formations. These insights address the challenge of achieving effective proppant placement in complex fractures and provide quantitative guidance for tailoring fracture geometry, injection parameters, and proppant properties to improve conductivity and mitigate sand plugging risks in tight formations. Full article

For crop protection, electrostatic spraying technology significantly improves deposition uniformity and pesticide utilization through the “wraparound-adsorption” effect of charged droplets. However, existing electrostatic nozzles using hydraulic atomization suffer from low charge-to-mass ratios due to unclear principles for optimizing electrode parameters. To this end, this study designs and evaluates a novel air-assisted hydraulic-atomization hollow-cone electrostatic nozzle. First, the air-assisted hollow-cone nozzle was designed. High-speed imaging was then employed to obtain morphological parameters of the liquid film (length: 2.14 mm; width: 1.96 mm; and spray angle: 49.25°). Based on these parameters, an electric field simulation model of the electrostatic nozzle was established to analyze the influence of electrode parameters on the charging performance and identify the optimal parameter combination. Finally, feasibility and efficiency evaluation experiments were conducted on the designed electrostatic nozzle. The experimental results demonstrate that cross-sectional dimensions of the electrode exhibit a positive correlation with the surface charge density of the pesticide liquid film. In addition, optimal charging performance is obtained when the electrode plane coincides with the tangent plane of the liquid film leading edge. Based on these charging laws, the optimal electrode parameters were determined as follows: 2.0 × 2.0 mm cross-section with an electrode-to-nozzle tip distance of 3.8 mm. With these parameters, the nozzle achieved a droplet charge-to-mass ratio of 4.9 mC/kg at a charging voltage of 3.0 kV. These charged droplets achieved deposition coverages of 12.19%, 5.72%, and 5.91% on abaxial leaf surfaces in the upper, middle, and lower soybean canopies, respectively, which is a significant improvement in deposition uniformity. This study designed a novel air-assisted hollow-cone electrostatic nozzle, elucidated the optimization principles for annular induction electrodes, and achieved improved spraying performance. The findings contribute to enhanced pesticide application efficiency in crops, providing valuable theoretical guidance and technical references for electrostatic nozzle design and application. Full article

In response to the high cost and environmental impact of backfill materials in Xinjiang mines, an eco-friendly, large-volume composite was developed by bonding desert-sand mortar to waste concrete. A rock-filled concrete process produced a highly flowable mortar from desert sand, cement, and fly ash. Waste concrete blocks served as coarse aggregate. Specimens were cured for 28 days, then subjected to uniaxial compression tests on a mining rock-mechanics system using water-to-binder ratios of 0.30, 0.35, and 0.40 and aggregate sizes of 30–40 mm, 40–50 mm, and 50–60 mm. Mechanical performance—failure modes, stress–strain response, and related properties—was systematically evaluated. Crack propagation was tracked via digital image correlation (DIC) and acoustic emission (AE) techniques. Failure patterns indicated that the pure-mortar specimens exhibited classic brittle fractures with through-going cracks. Aggregate-containing specimens showed mixed-mode failure, with cracks flowing around aggregates and secondary branches forming non-through-going damage networks. Optimization identified a 0.30 water-to-binder ratio (Groups 3 and 6) as optimal, yielding an average strength of 25 MPa. Among the aggregate sizes, 40–50 mm (Group 7) performed best, with 22.58 MPa. The AE data revealed a three-stage evolution—linear-elastic, nonlinear crack growth, and critical failure—with signal density positively correlating to fracture energy. DIC maps showed unidirectional energy release in pure-mortar specimens, whereas aggregate-containing specimens displayed chaotic energy patterns. This confirms that aggregates alter stress fields at crack tips and redirect energy-dissipation paths, shifting failure from single-crack propagation to a multi-scale damage network. These results provide a theoretical basis and technical support for the resource-efficient use of mining waste and advance green backfill technology, thereby contributing to the sustainable development of mining operations. Full article

Atmospheric turbulence introduces distortions to the wavefront of propagating optical radiation. It causes image resolution degradation in astronomical telescopes and significantly reduces the power density of radiation on the target in focusing applications. The impact of turbulence fluctuations on the wavefront can be investigated under laboratory conditions using either a fan heater (roughly tuned), a phase plate, or a deformable mirror (finely tuned) as a turbulence-generation device and a wavefront sensor as a wavefront-distortion measurement device. We designed and developed a software simulator and an experimental setup for the reconstruction of atmospheric turbulence-phase fluctuations as well as an adaptive optical system for the compensation of induced aberrations. Both systems use two 60 mm, 92-channel, bimorph deformable mirrors and two tip-tilt correctors. The wavefront is measured using a high-speed Shack–Hartmann wavefront sensor based on an industrial CMOS camera. The system was able to achieve a 500 Hz correction frame rate, and the amplitude of aberrations decreased from 2.6 μm to 0.3 μm during the correction procedure. The use of the tip-tilt corrector allowed a decrease in the focal spot centroid jitter range of 2–3 times from ±26.5 μm and ±24 μm up to ±11.5 μm and ±5.5 μm. Full article

The present research compared the design, metallurgical properties, and mechanical characteristics of the ProTaper Ultimate instruments with five multifile systems. A total of 469 new nickel–titanium rotary finishing instruments, all 25 mm in length but varying in size, taper, and metal alloy composition, from six different multifile systems (ProTaper Ultimate, ProTaper Next, ProFile, Mtwo, EndoSequence, and GT Series X), were inspected for irregularities and analyzed for their spiral density (spirals per millimetre), blade design, surface finishing, alloy composition, phase transformation temperatures, and mechanical performance (microhardness, torsional, and bending resistance tests). Group comparisons were performed using Kruskal–Wallis and one-way ANOVA with post hoc Tukey’s tests (α = 5%). ProFile instruments exhibited a greater number of spirals and a higher density of spirals per millimetre compared to the other systems. Microscopic analysis revealed distinct tip geometries and blade designs among tested instruments. All of them displayed parallel marks from the machining process, but the EndoSequence system had the smoothest surface finish. The alloys of all instruments consisted of an almost equiatomic ratio of nickel to titanium. At the testing temperature, the ProTaper Ultimate system exhibited a complete R-phase crystallographic arrangement, while the ProFile and Mtwo systems were fully austenitic. The ProTaper Ultimate F2, F3, and FX instruments demonstrated the highest maximum torque values (1.40, 1.45, and 3.55 N.cm, respectively) and the lowest maximum bending loads (202.7, 254.9, and 408.4 gf, respectively). EndoSequence instruments showed the highest angles of rotation, while the highest microhardness values were recorded for GT Series X (407.1 HVN) and ProTaper Next (425.0 HVN) instruments. The ProTaper Ultimate system showed a high spiral density per millimetre and a complete R-phase crystallographic arrangement at room temperature, which significantly contributed to its superior flexibility and torsional strength when compared to the other tested systems. Full article

It is estimated that over 60% of known tailed phages are siphophages, which are characterized by a long, flexible, and non-contractile tail. Nevertheless, entire high-resolution structures of siphophages remain scarce. Using cryo-EM, we resolved the structures of T-series siphophage T1, encompassing its head, connector complex, tail tube, and tail tip, at near-atomic resolution. The density maps enabled us to build the atomic models for the majority of T1 proteins. The T1 head comprises 415 copies of the major capsid protein gp47, arranged into an icosahedron with a triangulation number of seven, decorated with 80 homologous trimers and 60 heterotrimers along the threefold and quasi-threefold axes of the icosahedron. The T1 connector complex is composed of two dodecamers (a portal and an adaptor) and two hexamers (a stopper and a tail terminator). The flexible tail tube comprises approximately 34 hexameric rings of tail tube. The extensive disulfide bond network along the successive tail rings may mediate the flexible bending. The distal tip of T1, which is cone-shaped and assembled by proteins gp33, gp34, gp36, gp37, and gp38, displays structural similarity to that of phage lambda. In conjunction with previous studies of lambda-like siphophages, our structure will facilitate further exploration of the structural and mechanistic aspects of lambda-like siphophages. Full article

The article presents basic information about the induction heating of gears, which are widely used in various industries. This article presents the methodology and results of a coupled FEM simulation of a circuit model for a power electronics converter connected to an inductor-charged heating system. The induction heating of gears was performed using a high-frequency inverter with SiC MOSFET transistors. A prototype inverter was built using a full-bridge structure with a series-parallel resonant circuit. The operating frequency was 350 kHz, the output power of the inverter was 3.5 kW, and the drain efficiency was equal to 96%. Coupled simulation was performed for a charge in the form of a gear made of 42CrMo4 steel (material parameters are provided in the article) for two types of heating: with and without a magnetic field concentrator. In addition, the article presents the results of co-simulation studies in the following form: a distribution of magnetic induction in the gear, energy density in the gear, the characteristics of energy density in a single tooth on the 8 mm length and the temperature of the tooth tip for two types of induction heating. Full article

In this study, a single zirconium carbide (ZrC) nanoneedle structure oriented in the <100> direction was fabricated by a dual-beam focused ion beam (FIB-SEM) system, and its field emission characteristics and emission current stability were evaluated. Benefiting from controlled fabrication with real-time observation, the ZrC nanoneedle has a smooth surface and a tip with a radius of curvature smaller than 20 nm and a length greater than 2 μm. Due to its low work function and well-controlled morphology, the ZrC nanoneedle emitter, positioned in a high-vacuum chamber, was able to generate a single and collimated electron beam with a current of 1.2 nA at a turn-on voltage of 210 V, and the current increased to 100 nA when the applied voltage reached 325 V. After the treatment of the nanoneedle tip, the field emission exhibited a stable emission for 150 min with a fluctuation of 1.4% and an emission current density as high as 1.4 × 10¹⁰ A m⁻². This work presents an efficient and controllable method for fabricating nanostructures, and this method is applicable to the transition metal compound ZrC as a field emission emitter, demonstrating its potential as an electron source for electron-beam devices. Full article

In granular media for perpendicular magnetic recording, zigzag-shaped magnetic domain boundaries form between magnetic grains isolated by a non-magnetic grain boundary phase. They are the main source of jitter noise caused by the position fluctuation of magnetic bit transitions. The imaging of zigzag boundaries thus becomes an important task to increase recording density with decreasing bit size, when the zigzag and bit sizes become comparable. We visualized the zigzag boundaries of magnetic domains in as-sputtered granular media with a spatial resolution of less than 3 nm using our developed Alternating Magnetic Force Microscopy (A-MFM). We used a soft magnetic amorphous FeCoB tip with high saturation magnetization, which further enhances the spatial resolution through the inverse magnetostrictive effect. The zigzag size ranged from 2 to 8 nm in media with an estimated grain size of around 5 nm. Additionally, we observed zigzag bit boundaries in commercially recorded granular media with a recording density of 500 kfci. Full article

Lodging of soybean (Glycine max (L.) Merril.) significantly reduces seed yield and quality, particularly in high-yielding environments. This phenomenon occurs when stems weaken under the weight of the plants, complicating harvesting. This study investigated the relationship between soybean stem chemical composition, physical traits, and lodging resistance to improve yield and resilience. We found that as plant density increased, stem hardness decreased, and the elasticity increased, heightening the risk of lodging. Conversely, high temperature (28 °C) boosted lignin, cellulose and pectin content in the stem cell walls, enhancing the lodging resistance. Additionally, after excluding differences in phylogenetic relationships through cluster analysis, we mapped environment-stable genes linked to lodging resistance and identified new QTLs on Chr3 and Chr16. Candidate genes associated with these QTLs were confirmed using qRT–PCR and hormone treatments across diverse soybean varieties. It was found that the expression of stem tip genes was closely related to stem node diameter. These findings provide a theoretical foundation for breeding high-yielding soybean varieties with improved lodging resistance, and advance efforts to develop resilient soybean cultivars. Full article

As the global demand for high-quality tea increases, adopting sustainable agricultural practices is crucial to maintaining environmental health and improving crop productivity. Employing organic fertilizers has the potential to boost agricultural output and improve soil health, as well as curb the spread of pests and diseases. The purpose of this survey was to determine the impact of a range of organic fertilizer mixtures on both tea plants and rhizosphere soil characteristics in tea plantations. This study investigated the response of Jin Guanyin tea (Camellia sinensis L.) plants to various organic fertilizer ratios: 2/3 chemical fertilizer + 1/3 organic fertilizer (JTC), 1/2 chemical fertilizer + 1/2 organic fertilizer (JHOC), 1/3 chemical fertilizer + 2/3 organic fertilizer (JTO), and organic fertilizer only (JOF), with chemical fertilizer alone (JCF) as the control. The experiment was conducted in Xingcun Town, Wuyishan, Fujian Province, China, on 13 October 2021. Key metrics measured included tea plant growth indicators, soil physicochemical properties, enzyme activities, and microbial functional diversity. Results show that JTC and JTO produce the largest leaf area and bud weight, significantly surpassing those in JCF. JCF demonstrated the longest new tip length and highest bud density, while JHOC achieved the highest chlorophyll content, significantly exceeding JCF. Soil analysis revealed that total nitrogen, available nitrogen, organic matter, and pH were highest in JOF, significantly overtaking JCF. Conversely, total phosphorus, available potassium, and available phosphorus levels were highest in JCF. JHOC also had the highest total potassium content compared to JCF. Soil enzyme activity assessments showed that polyphenol oxidase and urease activities peaked in JTC, significantly exceeding those in JCF. JHOC exhibited the highest acid phosphatase activity, while JTO exhibited the highest protease activity. Catalase activity was highest in JOF, both significantly surpassing JCF. Microbial functional diversity analysis indicated that combined organic fertilization improved soil microorganisms’ utilization of carbon sources, significantly enhancing the Shannon diversity index and evenness. Key carbon sources identified included $\mathsf{\alpha }$-cyclodextrin, D-galacturonic acid, and 4-hydroxy benzoic acid. Overall, JHOC emerged as the optimal fertilization strategy, yielding superior growth indicators, enhanced soil physicochemical properties, increased enzyme activity, and improved microbial functional diversity compared to JCF. This study has important value for guiding the rational application of fertilizers in tea gardens, improving the soil environment of tea gardens, enhancing the quality of tea leaves, and achieving sustainable tea production. Full article

In the Afrotropic biogeographic realm, with its diverse and high-density mammal population, early humans may have been hunting with stone-tipped weapons since ~500,000 years ago. Being able to hunt effectively from a distance has several important adaptive advantages. Yet, until now, African long-range javelin hunting remained unexplored as intermediate between short/medium-range, hand-delivered and long-range, mechanically projected weapons. Insights gained from a new Afrotropic comparative dataset with 950 weapon tips of known use—including several javelin types—provide a contextually appropriate middle-range tool for assessing the probable effective hunting ranges of Middle Stone Age points. We use a novel application of the ballistically relevant tip cross-sectional area (TCSA) statistic to define contact, short-, medium-, long- and maximum-range hunting and discuss the adaptive advantages for each. The approach is applied to suggest developments and variations in the best-fit hunting ranges of 5597 stone points from 62 Middle Stone Age Afrotropic assemblages. By aligning our results with the Marine Isotope Stage (MIS) record we hypothesize that effective long-range (~20–30 m) hunting with stone-tipped weapons was probably not practiced by ≥MIS 8, and that experimentation with long-range javelins—similar to those used by contemporary Ethiopian hunters—over these distances may have started during MIS 6, becoming part of the everyday Afrotropic hunting arsenal by the end of MIS 5. Full article

This work aimed to evaluate the fatigue limit of the zirconia ceramic composite stabilized with yttria and ceria reinforced with alumina platelets (ZrO₂CeYAl₂O₃) and characterize the mechanical properties of sintered specimens. Bar-shaped specimens were compacted by uniaxial pressing in a rigid die and sintered at 1500 °C-2 h. Subsequent characterizations included quantitative phase analysis by X-ray diffractometry, determination of density, modulus of elasticity, microhardness, fracture toughness, four-point flexural strength, and fatigue limit. Observations of fracture mechanisms were carried out using confocal and scanning electron microscopy (SEM). The sintered samples presented values above 98% of relative density. Complex microstructures with equiaxed, homogeneously distributed submicrometer grains and planar alumina platelets were observed by SEM. The composite samples showed high values of fracture toughness due to the transformation, during the test, from the tetragonal to monoclinic phase, causing an increase in volume and creating compression zones around the crack, making it difficult to propagate. The average flexural strength reached 445.55 MPa, with a Weibull modulus (m = 16.8), revealing low flexural rupture stress data dispersion. In the composite evaluated in this work, the occurrence of the tetragonal → monoclinic transformation that occurs in the Ce-TZP present at the triple points and grain boundaries during cyclic loading produces “crack tip shielding”, that is, a restricted elastic zone (zone shielding) that surrounds the crack tip. This phenomenon leads to a reduction in the stress intensity factor at the tip of the crack and slows down its growth, generating an increase in the fatigue resistance of the composite. Full article

We present a data-driven, in situ proximal multi-sensor digital soil mapping approach to develop digital twins for multiple agricultural fields. A novel Digital Soil Core^TM (DSC) Probe was engineered that contains seven sensors, each of a distinct modality, including sleeve friction, tip force, dielectric permittivity, electrical resistivity, soil imagery, acoustics, and visible and near-infrared spectroscopy. The DSC System integrates the DSC Probe, DSC software (v2023.10), and deployment equipment components to sense soil characteristics at a high vertical spatial resolution (mm scale) along in situ soil profiles up to a depth of 120 cm in about 60 s. The DSC Probe in situ proximal data are harmonized into a data cube providing vertical high-density knowledge associated with physical–chemical–biological soil conditions. In contrast, conventional ex situ soil samples derived from soil cores, soil pits, or surface samples analyzed using laboratory and other methods are bound by a substantially coarser spatial resolution and multiple compounding errors. Our objective was to investigate the effects of the mismatched scale between high-resolution in situ proximal sensor data and coarser-resolution ex situ soil laboratory measurements to develop soil prediction models. Our study was conducted in central California soil in almond orchards. We collected DSC sensor data and spatially co-located soil cores that were sliced into narrow layers for laboratory-based soil measurements. Partial Least Squares Regression (PLSR) cross-validation was used to compare the results of testing four data integration methods. Method A reduced the high-resolution sensor data to discrete values paired with layer-based soil laboratory measurements. Method B used stochastic distributions of sensor data paired with layer-based soil laboratory measurements. Method C allocated the same soil analytical data to each one of the high-resolution multi-sensor data within a soil layer. Method D linked the high-density multi-sensor soil data directly to crop responses (crop performance and behavior metrics), bypassing costly laboratory soil analysis. Overall, the soil models derived from Method C outperformed Methods A and B. Soil predictions derived using Method D were the most cost-effective for directly assessing soil–crop relationships, making this method well suited for industrial-scale precision agriculture applications. Full article

The <100> oriented single-crystalline Zirconium Carbide (ZrC) nanowires were controllably synthesized on a graphite substrate by chemical vapor deposition (CVD) with optimized growth parameters involving Zirconium tetrachloride (ZrCl₄), flow of methane (CH₄), and growth temperature. The length of nanowires is above 10 µm while the diameter is smaller than 100 nm. A single ZrC nanowire was picked up and fixed on a tungsten tip for field emission measurement. After surface pretreatments, a sharpened and cleaned ZrC nanowire emitter showed a high emission current density of 1.1 × 10¹⁰ A m⁻² at a low turn-on voltage of 440 V. The field emission is stable for 150 min with a fluctuation of 1.77%. This work provides an effective method for synthesizing and stabilizing single-crystalline ZrC nanowire emitters as an electron source for electron-beam applications. Full article