Search Results (9,247)

It is challenging to manufacture complex and intricate shapes and geometries with desired surface characteristics using a single manufacturing process. Parts often need to undergo post-processing and must be transported from one machine into another between steps. This makes the whole process cumbersome, time-consuming, and inaccurate. These shortcomings play a major role during the manufacturing of micro and nano products. Hybrid manufacturing (HM) has emerged as a favorable solution for these issues. It is a flexible process that combines two or more manufacturing processes, such as additive manufacturing (AM) and subtractive manufacturing (SM), into a single setup. HM works synergistically to produce complex, composite, and customized components. It makes the process more time efficient and accurate and can prevent unnecessary transportation of parts. There are still challenges ahead regarding implementing and integrating sensors that allow the machine to detect defects and repair or customize parts according to needs. Even though modern hybrid machines forecast an exciting future in the manufacturing world, they still lack features such as real-time adaptive manufacturing based on sensors and artificial intelligence (AI). Earlier reviews do not profoundly elaborate on the types of laser HM machines available. Laser technology resolutely handles additive and subtractive manufacturing and is capable of producing groundbreaking parts using a wide scope of materials. This review focuses on HM and presents a compendious overview of the types of hybrid machines and setups used in the scientific community and industry. The study is unique in the sense that it covers different HM setups based on machine axes, materials, and processing parameters. We hope this study proves helpful to process, plan, and impart productivity to HM processes for the betterment of material utilization and efficiency. Full article

With the increase in contamination by microbial agents (bacteria, viruses, etc.) in the fields of agri-food, healthcare, and environment, it is necessary to detect and quantify these biological elements present in complex fluids in a short time with high selectivity, high sensitivity, and, if possible, moderate cost. Acoustic wave biosensors, based on immuno-detection, appear to meet a certain number of these criteria. In this context, we are developing a generic antibody-based biointerface that can detect a wide range of pathogenic bacterial agents using a specific bioreceptor. Based on the silane–oxide chemistry, the process is transferable to any kind of surface that can be either oxidized in surface or activated with O₂-plasma, for instance. For this proof of concept, we have chosen to develop our biointerface on titanium and lithium niobate surfaces. The development of the biointerface consists of grafting antibodies via a self-assembled monolayer (SAM) composed of an aminopropyltriethoxysilane (APTES) and a linker (phenylene diisothiocyanate, PDITC). Two functionalization routes were tested for grafting APTES: in anhydrous toluene followed by a heating step at 110 °C or in chloroform at room temperature. The results obtained on titanium show comparable grafting efficiency between these two routes, allowing us to consider the transposition of the route at room temperature on lithium niobate. The latest route was chosen for fragile materials that do not require the heating steps necessary when using toluene for grafting aminopropyltriethoxysilane. Different surface characterization techniques were used, such as IR spectroscopy (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), and contact angle (WCA), to verify the successful grafting of each layer. Biodetection experiments in static conditions were also carried out to demonstrate the specificity of pathogenic detection, testing an ideal medium with solely bacteria, with no other food sampling nutrients. This paper demonstrates the successful elaboration of a biointerface using APTES as the first anchoring layer, with chloroform as a mild solvent. The process is easily transferable to any kind of fragile surface. Moreover, following anti-L. monocytogenes antibodies, our biointerface shows a specificity of capture in static mode (at a concentration of 10⁷ CFU/mL for an incubation time of 4 h at 37 °C) of up to 98% compared to a species negative control (E. coli) and up to 85% in terms of strain specificity (L. innocua). Full article

This study investigates hyperpolishing of Zerodur^® substrates via chemical-mechanical polishing (CMP) using silica (SiO₂) and ceria (CeO₂) nanoparticles as controlled nano-abrasives. A pre-polishing stress-mirror stage was combined with systematic use of nanoparticles of variable size to evaluate surface-state evolution via optical rugosimeter, HRSEM, cross-sectional HRTEM, and XPS. A set of hexagonal mirrors with a circumscribed diameter of 30 mm was polished for one hour with each nanoparticle type. All tested slurries significantly improved surface quality, with both the smallest (37 nm) and largest (209 nm) SiO₂ particles achieving similar final roughness, though larger particles showed a slight performance advantage that could be offset by longer polishing with smaller particles. CeO₂ nanoparticles (30 nm) produced even better process efficiency and surface finishes than 37 nm SiO₂, demonstrating higher chemical-mechanical polishing efficiency with CeO₂. Sequential polishing strategies, first with 209 nm SiO₂, then with 37 nm SiO₂ and 30 nm CeO₂, also enhanced surface quality, confirming trends from single-particle trials. One of the most effective protocols was adapted and scaled up to 135 mm Zerodur^® mirrors with spherical and plano geometries, representative of precision optical components. The strategic approach adopted to achieve a high-quality surface finish in a reduced processing time relies on the sequential use of nanoparticles acting as complementary nano-abrasives. Indeed, applying two hours of polishing with 209 nm SiO₂ followed by two hours with 37 nm SiO₂ yielded exceptional results, with area roughness (Sa) values of 1 Å for spherical and 0.9 Å for plano surfaces. These results demonstrate the capability of nanoparticle-assisted CMP to produce sub-nanometric surface finishes and offer a robust, scalable approach for high-end optical manufacturing. Full article

Accurate stockpile volume estimation is essential for industries that manage bulk materials across various stages of production. Conventional ground-based methods such as walking wheels, total stations, Global Navigation Satellite Systems (GNSSs), and Terrestrial Laser Scanners (TLSs) have been widely used, but often involve significant safety risks, particularly when accessing hard-to-reach or hazardous areas. Unmanned Aerial Systems (UASs) provide a safer and more efficient alternative for surveying irregularly shaped stockpiles. This study evaluates UAS-based methods for estimating the volume of coal stockpiles at a storage facility near Cadiz, Ohio. Two sensor platforms were deployed: a Freefly Alta X quadcopter equipped with a Real-Time Kinematic (RTK) Light Detection and Ranging (LiDAR, active sensor) and a WingtraOne UAS with Post-Processed Kinematic (PPK) multispectral imaging (optical, passive sensor). Three approaches were compared: (1) LiDAR; (2) Structure-from-Motion (SfM) photogrammetry with a Digital Surface Model (DSM) and Digital Terrain Model (DTM) (SfM–DTM); and (3) an SfM-derived DSM combined with a kriging-interpolated DTM (SfM–intDTM). An automated boundary detection workflow was developed, integrating slope thresholding, Near-Infrared (NIR) spectral filtering, and Canny edge detection. Volume estimates from SfM–DTM and SfM–intDTM closely matched LiDAR-based reference estimates, with Root Mean Square Error (RMSE) values of 147.51 m³ and 146.18 m³, respectively. The SfM–intDTM approach achieved a Mean Absolute Percentage Error (MAPE) of ~2%, indicating strong agreement with LiDAR and improved accuracy compared to prior studies. A sensitivity analysis further highlighted the role of spatial resolution in volume estimation. While RMSE values remained consistent (141–162 m³) and the MAPE below 2.5% for resolutions between 0.06 m and 5 m, accuracy declined at coarser resolutions, with the MAPE rising to 11.76% at 10 m. This emphasizes the need to balance the resolution with the study objectives, geographic extent, and computational costs when selecting elevation data for volume estimation. Overall, UAS-based SfM photogrammetry combined with interpolated DTMs and automated boundary extraction offers a scalable, cost-effective, and accurate approach for stockpile volume estimation. The methodology is well-suited for both the high-precision monitoring of individual stockpiles and broader regional-scale assessments and can be readily adapted to other domains such as quarrying, agricultural storage, and forestry operations. Full article

The interaction between DNA and two-dimensional materials, such as graphene oxide (GO), has aroused significant research interest due to its potential applications, including biosensors, drug delivery, and gene therapy. However, the difference in interaction between DNA and oxygen functional groups on GO remains unclear, and direct observation at the experimental level is still challenging. In this work, we investigated the adsorption process of a single-stranded DNA (ssDNA) onto GO exhibiting a series of oxidation degrees by molecular dynamics simulations. We found that the ssDNA preferentially binds to hydroxyl groups (-OH) over epoxy groups (-O-) on the GO surface. This preferential adsorption feature may be attributed to the stronger tendency of ssDNA to form hydrogen bonds (HBs) with hydroxyl groups compared to epoxy groups in aqueous solutions. Further analysis indicates that the affinity interaction between ssDNA and hydroxyl groups presumably increases the oxidation degree of GO, thus suggesting a better binding between ssDNA and GO. This work is not only expected to provide the underlying mechanism of ssDNA onto graphene-based interfaces but also offers a deeper understanding of the structures of DNA-two-dimensional complexes, which may potentially contribute to designing new molecular structures for bio-sensing-related nano-devices and nanostructures. Full article

In support of sustainable agricultural practices and soil conservation in black soil regions, the accurate modeling of soil–machine interactions is essential for optimizing tillage operations and minimizing environmental impacts. To achieve the precise calibration of interaction parameters between black soil and soil-engaging components, this paper proposes an innovative segmented calibration method to determine the discrete element parameters for interactions between black soil and agricultural machinery parts. The Hertz–Mindlin with Johnson–Kendall–Roberts (JKR) Cohesion contact model in the discrete element method (DEM) software was employed, using a two-stage calibration process. In the first stage, soil particle contact parameters were optimized by combining physical pile angle tests with multi-factor simulations guided by Design-Expert, resulting in the optimal parameter set (JKR surface energy 0.46 J/m², restitution coefficient 0.51, static friction coefficient 0.65, rolling friction coefficient 0.13). In the second stage, based on validated soil parameters, the soil–65Mn steel interaction parameters were precisely calibrated (JKR surface energy 0.29 J/m², restitution coefficient 0.55, static friction coefficient 0.64, rolling friction coefficient 0.07). Simulation results showed that the error between simulated and measured pile angles was less than 0.5%. Additionally, verification through rotary tillage operation tests comparing simulated and measured power consumption demonstrated that within the cutter roller speed range of 150–350 r·min⁻¹, the power error remained below 0.5 kW. Ground surface flatness was introduced as a supplementary validation indicator, and the differences between simulated and measured values were small, further confirming the accuracy of the DEM model in capturing soil–tool interaction and predicting tillage quality. This paper not only enhances the accuracy of DEM-based modeling in agricultural engineering but also contributes to the development of eco-efficient tillage tools, promoting sustainable land management and soil resource protection. Full article

This paper presents an optimisation study to determine the best centre of gravity (CoG) position to improve seakeeping performance. Two varied parameters used in this study were the longitudinal and vertical centre of gravity (LCG and VCG). The Radius Gyration in the y-axis ($R_y$) is introduced as a novel single-objective function to be minimised, avoiding the complexity of the conventional seakeeping optimisation process. The quality of the seakeeping performance was evaluated by response amplitude operators (RAOs) of the heave, pitch, and vertical motion. Two different hull forms are compared to investigate the applicability of the $R_y$ as the objective function in seakeeping optimisation. The patrol boat and S-60 hull form are selected as representatives of a planing hull type and a displacement hull type. The optimisation was carried out by using the Central Composite Design (CCD) and response surface methodology (RSM) to model the relationship between the CoG and $R_y$ from large and small vessels, with the objective function minimising the $R_y$. The finding shows that minimising the $R_y$ is more sensitive to the planing hull type compared to the displacement hull type in reducing the vertical motion in different Froude numbers and wave headings. Full article

The electronic transport behavior in ferromagnetic thin films critically dictates the functionality and efficiency of devices in spintronics and modern materials science. This work characterizes terahertz (THz) responses and nonlinear conductivities of Fe ultrathin films under high-field THz excitation. We demonstrated that different nonlinearities are present for two different thickness samples. For a 2 nm thick Fe film, as the peak THz electric field was increased to 369 kV/cm, the THz transmittance of Fe films generally decreased. However, for the 4 nm thick Fe film, the THz transmittance is almost field strength independent. This result is correlated with the conductivity variations induced by carrier transport processes. The real part of the complex conductivity for the 2 nm thick film increased significantly with the THz electric field, while the 4 nm thick film showed negligible dependence. In addition, we extracted the frequency-domain complex conductivity of the Fe thin films and used the Drude or Drude–Smith model to explain the distinct behaviors between the two thickness samples under intense THz fields, mainly associated with the surface morphology. This work aims to elucidate the transport properties of Fe films in the THz frequency range. Our findings lay a crucial foundation for the design and development of future high-performance THz spintronic functional devices. Full article

Traditional non-destructive measurement of surface roughness exploits complete data of bidirectional reflective distribution function (BRDF). The instrument is normally bulky and the process should be conducted off-line, hence it is time-consuming. If only a part of BRDF data can be sufficient to determine the surface roughness, both the measurement equipment and processing time can be significantly reduced. This paper proposes a compact device capable of detecting multiple angular intensities of reflective scattering with different incident angles from different spatial points of the target object at the same time. It is used to evaluate the surface roughness of a standard specimen with arithmetic mean roughness (Ra) values ranging from 0.13 µm to 2.1 µm. The case of measuring two spatial points of the specimen is used for illustrating the calibration procedure of the device and how the data were searched and processed to increase the reliability and robustness for evaluating the surface roughness with reduced data of BRDF. Similar methodologies can be applicable for other real-time detection methods based on the scattering process. Full article

The optimization of polymer extrusion processes is crucial for improving product quality and manufacturing efficiency in plastic industries. This study aims to investigate the viscoelastic flow behavior of high-density polyethylene (HDPE) through an extrusion die with an internal mandrel, focusing on the effects of die geometry and flow parameters. A two-dimensional (2D) numerical model is developed in COMSOL Multiphysics using the Oldroyd-B constitutive equation, solved using the Galerkin/least-square finite element method. The simulation results indicate that the Weissenberg number (Wi) and die geometry significantly influence the dimensionless drag coefficient (Cd) and viscoelastic stress distribution along the die wall. Furthermore, filleting sharp edges of the die wall surface effectively reduces stress oscillations, enhancing flow uniformity. These findings provide valuable insights for optimizing die design and improving polymer extrusion efficiency. Full article

The article presents a mathematical description of the thermal phenomena occurring both inside and on the surfaces of a homogeneous plate subjected to an external heat flux on one side. Analytical formulae for thermal excitation, with a given duration and constant power, are derived, enabling the determination of temperature increases on both the heated and unheated surfaces of the plate under specific heat transfer conditions to the surroundings. Convective heat transfer, with individual heat transfer coefficients on both sides of the slab, is considered; however, radiative heat loss can also be included. The solution of the problem obtained using two methods is presented: the method of separation of variables (MSV) and the Laplace transform (LT). The advantages and disadvantages of both analytical formulae, as well as the impact of various factors on the accuracy of the solution, are discussed. Among others, the MSV solution works well for a sufficiently long time, whereas the LT solution is better for a sufficiently short time. The theoretical considerations are illustrated with diagrams for several configurations, each representing various heat transfer conditions on both sides of the plate. The presented solution can serve as a starting point for further analysis of more complex geometries or multilayered structures, e.g., in non-destructive testing using active thermography. The developed theoretical model is verified for a determination of the thermal diffusivity of a reference material. The model can be useful for analyzing the method’s sensitivity to various factors occurring during the measurement process, or the method can be adapted to a pulse of known duration and constant power, which is much easier to implement technically than a very short impulse (Dirac) with high energy. Full article

Purpose: We aimed to systematically review the current literature on the bond strength between custom tray materials and impression materials, including the various parameters affecting the strength. Methods: Four electronic databases were used: Ovid, Web of Science, PubMed, and Scopus. Relevant studies were chosen based on their eligibility, determined through inclusion and exclusion criteria. This review followed the PRISMA strategy. A risk of bias assessment was produced to evaluate the validity of each study. Results: There were 173 initial relevant studies identified, and after the screening process, this was reduced to seven. Two additional studies were also included from hand searching, resulting in total nine studies to be included in the review. Four of the nine evaluated studies concerned additively manufactured (AM) materials, including acrylonitrile butadiene styrene (ABS), polyethylene terephthalate glycol polyester (PETG), high-impact polystyrene (HIPS), and polylactic acid (PLA). Five studies evaluated an auto-polymerizing resin and one a thermoplastic material. All studies used polyvinyl siloxane impression materials and an adhesive selection following manufacturers’ recommendations. Three studies used scanning electron microscopy (SEM) to analyze their specimens. All studies reported a low risk of bias. Conclusions: Surface roughening was shown to reduce the strength of the bonding interface, whereas combining chemical and mechanical retention was shown to increase the bond strength. Inconsistent results exist in determining if AMed (3D-printed) tray materials are comparable or perform better than the conventional tray materials, highlighting the need for further study. Clinical Significance: The bond strength of the custom tray to the dental impression material is critical as it affects the model produced and therefore the final prosthesis. It is therefore invaluable to use materials with high bond strength for the construction of custom trays. Full article

The paper aims to investigate the failure modes induced by the Rockwell indentation test on Diamond-Like Carbon (DLC)-based and AlCrN coatings deposited on rolled and additively manufactured Ti6Al4V substrates with different surface finishes and subjected to two distinct post-process heat treatments, and the possible correlations with scratch tests. At the magnification required to capture the entire Rockwell imprint, the adhesion class of the investigated DLC-based and AlCrN coatings could be incorrectly classified as HF1. However, higher-magnification observations revealed numerous radial cracks and non-uniformly distributed small delamination areas, changing the adhesion class to HF3. Additionally, roughness values higher than 1 μm hid the presence of radial cracks, which aligned parallel to the deep dales and high peaks of the roughness profile, as investigated by SEM. Likewise, in the scratch test, the rough surface also made the smallest cracks, formed at the critical load L_C1, undetectable. The critical loads for spallation of the coating in the scratch test (L_C2, L_C3) did not show significant correlation with the number of radial cracks formed during Rockwell indentations. Consequently, a quick Rockwell indentation cannot predict the scratch test results. Finally, both DLC-based and the AlCrN coatings exhibited good adhesion to Ti6Al4V substrates, regardless of the microstructure and surface finish of the titanium substrates. SEM-FIB observations revealed that the cracks formed during Rockwell indentation and scratch tests were deflected longitudinally within the underlying layers of the DLC-based coating and in the bottom part of the AlCrN coating, where the N concentration was higher. Full article

Squall lines are some of the most common types of mesoscale cloud systems in tropical and subtropical regions. Thunderstorms associated with these systems are among the major causes of weather-related disasters and socio-economic losses in many regions across the world. This study investigates the capability of the Weather Research and Forecasting (WRF) model in simulating squall line features over the South African Highveld region. Two squall line cases were selected based on the availability of South African Weather Service (SAWS) weather radar data: 21 October 2017 (early austral summer) and 31 January–1 February 2018 (late austral summer). The European Centre for Medium-Range Weather Forecasts ERA5 datasets were used as observational proxies to analyze squall line features and compare them with WRF simulations. Mid-tropospheric perturbations were observed along westerly waves in both cases. These perturbations were coupled with surface troughs over central interior together with the high-pressure systems to the south and southeast of the country creating strong pressure gradients over the plateau, which also transports relative humidity onshore and extending to the Highveld region. The 2018 case also had a zonal structured ridging High, which was responsible for driving moisture from the southwest Indian Ocean towards the eastern parts of South Africa. Both ERA5 and WRF captured onshore near surface (800 hPa) winds and high-moisture contents over the eastern parts of the Highveld. A well-defined dryline was observed and well simulated for the 2017 event, while both ERA5 and WRF did not show any dryline for the 2018 case that was triggered by orography. While WRF successfully reproduced the synoptic-scale processes of these extreme weather events, the simulated rainfall over the area of interest exhibited a broader spatial distribution, with large-scale precipitation overestimated and convective rainfall underestimated. Our study shows that models are able to capture these systems but with some shortcomings, highlighting the need for further improvement in forecasts. Full article

Chatter vibration in machining operations has been identified as one of the major obstacles to improving surface quality and productivity. Therefore, efficiently and accurately predicting stable cutting regions is becoming increasingly important, especially in high-speed milling processes. In this study, on the basis of a predictor–corrector scheme, the following three error correction methods are developed for milling stability analysis: the Correction Hamming–Milne-based method (CHM), the Correction Adams–Milne-based method (CAM) and the Predictor–Corrector Hamming–Adams–Milne-based method (PCHAM). Firstly, we employ the periodic delay differential equations (DDEs), which are usually adopted to describe mathematical models of milling dynamics, and the time period of the coefficient matrix is divided into two unequal subintervals based on an analysis of the vibration modes. Then, the Hamming method and the fourth-order implicit Adams–Moulton method are separately utilized to predict the state term, and the Milne method is adopted to correct the state term. Based on local truncation error, combining the Hamming and Milne methods creates a CHM that can more precisely approximate the state term. Similarly, combining the fourth-order implicit Adams–Moulton method and the Milne method creates a CAM that can more accurately approximate the state term. More importantly, the CHM and the CAM are employed together to acquire the state transition matrix. Thereafter, the effectiveness and applicability of the three error correction methods are verified by comparing them with three existing methods. The results demonstrate that the three error correction methods achieve higher prediction accuracy without sacrificing computational efficiency. Compared with the 2nd SDM, the calculation times of the CHM, CAM and PCHAM are reduced by around 56%, 56% and 58%, respectively. Finally, verification experiments are carried out using a CNC machine (EMV650) to further validate the reliability of the proposed methods, where ten groups of cutting tests illustrate that the stability lobes predicted by the three error correction methods exhibit better agreement with the experimental results. Full article