Tip Geometry Research Articles

Preparation of Polymer Nanopillar Arrays with Controlled Tip Shapes and Their Application to Hydrophobic and Oleophobic Surfaces.

Ordered arrays of nanopillars with controlled tip shapes were fabricated by a template formation process using anodic porous alumina with controlled pore shapes. Although various studies have been reported on the preparation of nanopillar arrays using anodic porous alumina as a template, there have been no reports on the formation of nanopillar arrays with precisely controlled tip shapes. Re-anodization of anodized samples in a neutral electrolyte can flatten the bottom of pores. The use of the resulting anodic porous alumina as a template enabled the fabrication of ordered nanopillar arrays with a flattened tip. The formation of overhanging nanopillar arrays was also possible by using anodic porous alumina with a controlled pore shape as a template, which was fabricated by a combination of anodization, TiO2 coating by atomic layer deposition, and pore-widening treatment. The contact angles of water and oil droplets were measured using the obtained polymer nanopillar arrays with controlled tip shapes. The contact angle of water droplets did not change regardless of the tip shape of the nanopillars, whereas the contact angle of oil droplets changed depending on the tip shape of the nanopillars. This indicates that liquids with high surface tension are not affected by the nanopillar tip shape, whereas liquids with low surface tension are greatly affected by the nanopillar tip shape. Among the nanopillar arrays fabricated in this study, it was confirmed that the overhanging nanopillar array with many edge structures that have the pinning effect of suppressing the wetting spread of the solution exhibited the highest oil repellency. The method reported here can be used to fabricate nanopillar arrays with a precisely controlled tip geometry, and it is expected that optimization of the geometry will further improve the water- and oil-repellent properties.

Study of Injector Geometry and Parcel Injection Location on Spray Simulation of the Engine Combustion Network Spray G Injector

Abstract Parcel-based simulations are the most common method to simulate fuel sprays, especially for reacting conditions, due to their lower computational cost compared to more highly resolved simulations. It is important, however, to understand how spray boundary conditions are used to initialize the parcels that represent the atomizing fluid affect downstream conditions and overall simulation performance. Traditionally, when parcel simulations are used, the injector tip geometry is either significantly simplified or removed altogether due to resolution limits. Recent advances in computational power and numerical methods, however, have made it possible to resolve flow through these features. Previous work has shown some potential effects of even simple injector tip geometries, and this study investigates the effect of very detailed nozzle geometries on parcel-based simulations that have typically ignored these details. Four different parameters were investigated: whether a simulation includes a detailed injector tip geometry or a flat surface; whether parcels are initialized at the counterbore exit, which is more common, or at the nozzle exit; the use of an experimentally derived rate of injection or one-way coupling with a separate internal nozzle volume of fluid (VOF) simulation; the use of nominal or measured injector geometry. Simulations were compared using both global penetrations as well as local data near the injector. Spray penetration and other global measures showed limited sensitivity to boundary conditions/initialization procedure, but local data such as the local liquid volume fraction showed greater variation between the conditions, which may have an impact on mixing and combustion predictions in engine applications.

Aspects of molar form and dietary proclivities of African colobines

This study investigates aspects of molar form in three African colobine species: Colobus polykomos, Colobus angolensis, and Piliocolobus badius. Our samples of C. polykomos and P. badius are from the Taï Forest, Ivory Coast; our sample of C. angolensis is from Diani, Kenya. To the extent that protective layers surrounding seeds are hard, we predicted that molar features related to hard-object feeding would be more pronounced in Colobus than they are Piliocolobus, as seed-eating generally occurs at higher frequencies in species of the former. We further predicted that among the colobines we studied, these features would be most pronounced in Taï Forest C. polykomos, which feeds on Pentaclethra macrophylla seeds encased within hard and tough seed pods. We compared overall enamel thickness, enamel thickness distribution, absolute crown strength, cusp tip geometry, and flare among molar samples. Sample sizes per species and molar type varied per comparison. We predicted differences in all variables except overall enamel thickness, which we expected would be invariant among colobines as a result of selection for thin enamel in these folivorous species. Of the variables we examined, only molar flare differed significantly between Colobus and Piliocolobus. Our findings suggest that molar flare, an ancient feature of cercopithecoid molars, was retained in Colobus but not in Piliocolobus, perhaps as a result of differences in the seed-eating proclivities of the two genera. Contrary to predictions, none of the aspects of molar form we investigated tracked current dietary differences in seed-eating between the two Colobus species. Finally, we explored the possibility that molar flare and absolute crown strength, when analyzed together, might afford greater differentiation among these colobine species. A multivariate t test of molar flare and absolute crown strength differentiated C. polykomos and P. badius, possibly reflecting known niche divergence between these two sympatric Taï Forest species.

Quantifying and correcting tilt-related positioning errors in microcantilever-based microelectromechanical systems probes

The impact of tilt-related errors on the positioning of microcantilever-based microelectromechanical systems (MEMS) on-wafer electrical probes, having multiple contact pads, is quantified and investigated here. A tilt error associated with probe roll results in the probe contact pads not being parallel to the approaching surface as a downward overtravel is imposed—this leads to one probe pad making contact with the surface before the others. In a MEMS-based probe, the analysis of the impact of roll error angle must consider both the bending and the torsion of the flexible cantilever as the overtravel is increased—something which eventually results in all pads being in contact with the surface, but not with the same contact force. An original mathematical description of the problem is presented. By making some assumptions, the analytical modeling enables the derivation of elegant equations relating the roll error angle and the cantilever deflection to achieve planarity of the cantilever apex with the underlying surface. The modeling predicts probe tip planarity for rectangular and trapezoidal shaped probes. The predictions of the modeling are tested by using macroscopic cantilevers—excellent agreement between modeling and experiment is demonstrated. The macroscopic experimental setup reveals interesting behavior concerning a bending/twisting, tilted cantilever in contact with—and skating across—an underlying surface. The experimental findings also indicate the pertinence of the modeling for the potential use with understanding the behavior of microscopic cantilevers—such as MEMS-based probes—similarly in contact with a surface. A flexible microcantilever enables a torsional compensation of the roll error angle. It also enables a protocol where the roll error angle can be corrected. The design geometry of the probe tip will determine which approach is best suited. In principle, the modeling is scalable to MEMS probes composed of silicon-based cantilevers.

CPT-based design method for helical piles in sand

Helical piles are used extensively for low and medium rise developments and are a popular foundation solution in cases where resistance to significant uplift loads is required. The ability to re-use helical piles and recent interest in their use as foundations in offshore wind and solar energy applications has renewed interest in improving existing design methods. This paper presents the results from field investigations in medium dense and dense sand that examine effects on the axial tension and compression capacity of varying the helix pitch, shaft diameter, advancement ratio and shaft tip geometry. The results from the 20 pile tests conducted (many of which included instrumentation) indicate low sensitivity to a range of the investigated parameters and a strong correlation of the capacity to the cone penetration test resistance. A design method based on these findings is proposed for typical helical pile geometries and is shown to provide predictions that are generally within 10 to 15% of the axial capacities reported for 30 other well documented pile tests reported in the literature. The method, referred to as UWASP-22, incorporates a simple means of estimating the load-displacement response of a helical pile as well as a formulation enabling prediction of the installation torque which is a common quality control measure for helical piles.

Fiber-based optrode with microstructured fiber tips for controlled light delivery in optogenetics

Objective. Optogenetic modulation of neuronal activity requires precise and flexible light delivery to deep brain regions. Flat cleaved optical fibers combined with electrodes are widely used in implantable optogenetic devices for light delivery and electrical monitoring of neural activity. However, the flat fiber tip geometry induces serious tissue damage upon insertion, and makes it difficult to adjust and control the spatial extent of illumination within the brain. With their strongly increased tissue-compatibility and the possibility of spatial illumination control, tapered fibers outperform cleaved fibers in targeted neural photo-stimulation. Approach. In this work, we describe our device concept, and present a novel approach for reproducible fabrication of tapered fiber tips via grinding. Furthermore, we characterize recording electrodes by commenting data obtained from electrochemical impedance spectroscopy (EIS). We also investigate the impact of different cone angles (14°, 30°, 60°, and 90°) on the illumination profile and optical throughput. Main results. We fabricated a fiber-based optrode with cone tip and two deposited electrodes. Custom grinding setup for fabrication of tapered fiber tips with various cone angles is developed as a part of our research. Microscope images showed very good optical quality of cone tips. The results of transmitted optical power measurements performed with integrating sphere suggest that, compared to the flat cleaved optical fiber, transmitted power decreases exponentially with cone angle reduction. Obtained emission profiles (as induced fluorescence in Rhodamine 6G water solution) indicate very strong effect of cone angle on shape and size of illumination volume. Results obtained from EIS show the effect of electrode size on its recording capability. Significance. Compared to optrodes with flat cleaved optical fiber, the demonstrated fiber-based optrode with cone tip allows controlled light delivery with reduced invasiveness. The possibility to fabricate reproducible fiber tips with various cone angles enables control of light delivery in optogenetic experiment. The results presented here give neuroscientists the possibility to choose the appropriate tissue-compatible cone geometry depending on their stimulation requirements.

Influence of cantilever tip geometry and contact model on AFM elasticity measurement of cells.

We have measured the elastic properties of live cells by Atomic Force Microscope (AFM) using different tip geometries commonly used in AFM studies. Soft 4-sided pyramidal probes (spring constant = 12 mN/m and 30 mN/m, radius 20 nm), 3-sided pyramidal probes (spring constant = 100 mN/m, radius of curvature 65-75 nm), flat (circular) probes (spring constant = 63 mN/m, radius 290 nm) and spherical probes (spring constant = 43 mN/m, radius 5 μm) have been used. Cells (3T3 fibroblasts) having elastic moduli around 0.5 kPa were investigated. We found that cell measured stiffness shows a systematic dependence on tip geometry: the sharper the tip, the higher the average modulus values. We hypothesize that the blunter the tip, the larger the contact area over which the mechanical response is measured or averaged. If there are small-scale stiffer areas (like actin bundles) they will be easier to pick up by a sharp probe. This effect can be seen in the wider distribution of the histograms of the measured elastic moduli on cells. Furthermore, non-linear responses of cells may be present due to the high average pressures applied by sharp probes, which would lead to an overestimation of the Young's modulus. Pressure versus contact radius simulations for the different tip geometries for a 0.5 kPa sample suggested similar average pressure for Bio-MLCTs, PFQNM and cut tips, except spherical tips that showed much lower average pressure at the same 400 nm indentation. However, real data of the cells suggested different results. Using the same indentation depth (400 nm) PFQNM and Bio-MLCTs showed similar average pressure and it decreased for cut and spherical tips. The calculated contact area at 400 nm cell indentation, using the obtained apparent Young's modulus for each tip geometry, showed the following distribution: Bio-MLCTs < PFQNM < cut << spherical. In summary, tip geometry as well as average pressure and tip-sample contact area are important parameters to take into account when measuring mechanical properties of soft samples. The larger the tip radius, the larger the contact area that will lead to a more evenly distribution of the applied pressure.

Multimethod analysis of three rotary instruments produced by electric discharge machining technology.

This study aimed to compare three rotary instruments produced by the EDM process with the heat-treated ProTaper Gold system regarding design, metallurgy, mechanical properties and shaping ability. HyFlex EDM (25/~), Neoniti (25/.06), EDMax (25/.06) and ProTaper Gold (25/.08v) instruments (n = 58 per group) were compared regarding design, metallurgy and mechanical performance. Unprepared canal areas were calculated for each system after preparation of mesiobuccal, mesiolingual and distal canals of mandibular molars (15 canals per group) using micro-CT technology. Statistical analyses were performed using One-way anova post-hoc Tukey and Kruskal-Wallis post-hoc Dunn's tests (α = 5%). All instruments had asymmetrical blades, no radial lands, no major defects and almost equiatomic nickel/titanium ratios, but different cross-section designs, tip geometries and surface appearances. Although instruments had distinct transformation temperature curves, they showed crystallographic martensitic arrangement at 21°C and mixed austenite plus R-phase at body temperature. Neoniti and HyFlex EDM showed similar results in all mechanical tests (p > .05), while EDMax and ProTaper Gold had similar time to fracture (p = .841), maximum bending load (p = .729), and cutting ability (p = .985). ProTaper Gold showed the highest torque to failure (p < .001) and HyFlex EDM had the lowest buckling resistance (p < .001). Mean percentages of unprepared canal areas ranged from 20.4% to 25.7% in the mesial canals, and from 20.8% to 26.2% in the distal canal, with no statistical differences among systems (p > .05). Instruments' geometry and phase transformation temperatures influenced the results of the mechanical tests, but not their shaping ability.

Wind Turbine Blade-Tip Optimization: A Systemic Computational Approach

Curved bladelets on wind turbine blades play an important role in improving the performance and efficiency of wind turbines. Implementing such features on the tip of wind turbine blades can improve their overall aerodynamic characteristics by reducing turbulence and loading without hindering lift generation and overall efficiency, thus leading to increased energy capture and reduced costs over the life of the turbine. Subjecting the integrated blade tip to optimization procedures can maximize its beneficial contribution to the assembly in general. Within this context, a systemic workflow is proposed for the optimization of a curved bladelet implemented on a wind turbine blade. The approach receives input in the form of an initial tip geometry and performs improvements in two distinct stages. Firstly, shape optimization is performed directly on the outer shape to enhance its aerodynamic properties. Subsequently, the topology of its interior structure is refined to decrease its mass while retaining its improved airflow characteristics. The proposed workflow aims to approach blade tip optimization holistically, both in terms of aerodynamic performance and structural capabilities; is computationally validated via fluid dynamics studies and finite element analysis to evaluate the performance augmentation achieved through it; and is further coupled with additive manufacturing for the production of prototype parts, benefiting from the manufacturing flexibility offered by digital fabrication technologies. The optimized bladelet model presented an approximate 30% improvement in the torque generated on it, while maintaining only 70% of its original mass, effectively contributing to a 0.81% increase to the total torque generated by the blade, consequently confirming the effectiveness of the proposed methodology.

Investigation of the Interaction Between Tip Leakage and Main Annulus Flow in the Large Scale Turbine Rig: Comparison of Different Rotor Tip Geometries

Abstract Shroudless rotor blades are state-of-the-art in modern high pressure turbines. Tip leakage flow has a crucial impact on turbine efficiency. Specific blade tip designs are a key factor to handle tip leakage losses by controlling tip leakage flow and its re-entry into the rotor passage. Comparative measurements of a cavity squealer type tip and a notch type tip have been conducted at the Large Scale Turbine Rig at Technical University of Darmstadt. The test rig has been operated at the blade tips design point. Experimental data have been acquired at rotor inlet and outlet as well as within the rotor passage. For cavity squealer tips, a tip leakage vortex develops at the suction side as the tip leakage flow is rolled-up and further mixed with main annulus flow. The tip leakage vortex determines the blockage of main annulus flow at the blade tip. The design of the suction side of the notch tip benefits a jet-like re-entry of tip leakage flow into the passage. Results are a tip leakage vortex system with smaller sized vortices and a more homogeneous mass flow redistribution in the outer annulus of the rotor. The zone of affected main annulus flow at the blade tip increases through the dominant tip leakage jet.

Javelin use among Ethiopia’s last indigenous hunters: Variability and further constraints on tip cross-sectional geometry

Ethnographically known weapon systems are crucial for the functional interpretation of pertinent archaeological materials. The tip cross-sectional geometries of North American ethnographic projectiles are particularly widely used as standards against which the probable functions of archaeological stone points are assessed. While their known weapon-delivery mechanisms make these North American samples ideal references for archaeological investigations, their applicability to Afro-Eurasian assemblages is contestable. Using metric and contextual data from contemporary hunting javelins in southwestern Ethiopia, we expand on recent efforts to recalibrate such reference datasets. We find that overall javelin size and tip geometry are governed by factors ranging from the hunter’s age and physical competence to prey type and the intended hunting (e.g., startling, diverting, wounding, killing), and even symbolic/ceremonial, tasks. We argue that such dynamics may explain the great variation in the tip cross-sectional geometries of stone points in the archaeological record. Comparisons of our tip cross-sectional values with relevant published data provide further metric constraints and highlight the need for cautious interpretations of prehistoric weapon-delivery mechanisms where the role of symbolism and of children in the making of the archaeological record should also be considered.

Cathodic discharge plasma in electrochemical jet machining: Phenomena, mechanism and characteristics

An ultrahigh voltage is frequently required in electrochemical jet machining (EJM) to produce extreme current densities (>900 A/cm2 for this study) to achieve maximum dissolution rates. However, such a high electric field easily induces a cathodic discharge at the nozzle, and the generation mechanism and characteristics remain unexplored. For the first time, this study shows a direct visualisation of the hydrogen evolution and cathodic discharge in EJM using high-speed photography. An in-depth analysis of the discharge behaviour was carried out based on electrical monitoring, temperature measurement, and characterisation of the resulting changes in the electrode surface. It was revealed that the current density threshold determines the discharge ignition. Discharge occurs preferentially at the inner edge of the nozzle end face, which can cause nozzle wear and reduce localisation of anode workpiece dissolution. The discharge intensity can be controlled by varying the applied voltage and pulse frequency. The electrolyte flow velocity and gap distance influence the discharge behaviour. With appropriate process control, cathodic plasma can enhance the EJM performance while minimising its negative impact. Furthermore, cathodic discharge can be significantly suppressed by designing the geometry of the nozzle tip to avoid local electric field concentration.

Penetration performance of protective materials from crossbow attack: a preliminary study

Crossbow-related injuries resulting in serious and mortal consequences have increased in recent years, and although significant research exists for both injury and fatality on the human body, limited data exists on the lethality of the bolt and the failure modes of protective materials. This paper concerns itself with the experimental validation of four differing crossbow bolt geometries, their effects on material failure and potentially lethality. During this study, four different types of crossbow bolt geometries were tested against two protection mechanisms that differed in mechanical properties, geometry, mass and size. The results show that at 67 ms−1, ogive, field and combo tips do not provide lethal effect at 10-m range, whilst a broadhead tip will perforate both the para-aramid and a reinforced area of polycarbonate material consisting of two 3-mm plates at 63–66 ms−1. Although perforation was apparent with a more honed tip geometry, the chain mail layering within the para-aramid protection and friction caused by polycarbonate petalling on the arrow body reduced the velocity enough to demonstrate the materials under test are effective at withstanding crossbow attack. Subsequent calculation of the maximum velocity that arrows could achieve if fired from the crossbow within this study shows results close to the overmatch value of each material and therefore a requirement to advance the knowledge in this field to influence the development of more effective armour protection mechanisms.

Modeling and Analysis of the Capillary Force for Interactions of Different Tip/Substrate in AFM Based on the Energy Method.

This paper presents a simple and robust model to describe the wet adhesion of the AFM tip and substrate joined by a liquid bridge. The effects of contact angles, wetting circle radius, the volume of a liquid bridge, the gap between the AFM tip and substrate, environmental humidity, and tip geometry on the capillary force are studied. To model capillary forces, while a circular approximation for the meniscus of the bridge is assumed, the combination of the capillary adhesion due to the pressure difference across the free surface and the vertical component of the surface tension forces acting tangentially to the interface along the contact line is utilized. Finally, the validity of the proposed theoretical model is verified using numerical analysis and available experimental measurements. The results of this study can provide a basis to model the hydrophobic and hydrophilic tip/surfaces and study their effect on adhesion force between the AFM tip and the substrate.

Effects of the Electrodes’ Shape and Graphite Quality on the Arc Stability During Hydrogen Plasma Smelting Reduction of Iron Ores

Reducing greenhouse gases (GHG), especially CO2, is necessary to counteract climate change. The European steel industry currently corresponds to 5.7% of the total EU emissions and must therefore minimize their GHG fractions in the future. One of the most promising technologies to eliminate CO2 emissions while directly reducing iron ore to steel in a single step is the hydrogen plasma smelting reduction. The stability of the plasma arc, which is determined by the properties and geometry of the graphite electrode, has a substantial impact on the process’ economic feasibility. To study the arc stability concerning the graphite quality, tip geometry, and electrode gap, a series of experiments is conducted. The results are evaluated to create stability maps and fields to identify stable process parameters. The geometry of the graphite cathode shows the primary influence on arc stability. Tips with a flat end (standard version) offering the most unstable and a machined step on the graphite cathode providing the most stable conditions. However, an additional coating to prevent side arcing leads to the deterioration of the arc. The two graphite grades tested, with different maximum grain sizes and price classes, show no great relevance to the stability of the arc.

Synthesis and characterization of metal carbides for nanoindentation tip applications

Instrumented indentation experiments at elevated temperatures require careful attention to a myriad of experimental details. Not the least of these is the choice of the indenter tip material. Traditional room-temperature indenters, e.g., diamond and sapphire, can break down, react, and wear excessively at elevated temperatures. In this work, rf-induction heating float-zone and high-temperature solution single-crystal growth techniques have been used to prepare a suite of bulk refractory carbide specimens (i.e., ZrC, VC0.86, NbC, TiC0.95, WC). These potential indenter tip materials were subsequently characterized using nanoindentation testing techniques to determine their single-crystal elastic modulus, hardness, and fracture toughness in order to evaluate their potential for use as elevated-temperature nanoindentation tips. Additionally, subject carbide crystal characteristics were compared to those of single-crystal sapphire and polycrystalline WC-Co. The cumulative results show that single-crystal WC is a promising candidate for indenter tip material based on a combination of its high elastic modulus, hardness, and resistance to cracking—in addition to being crystallographically favorable for fabrication in the frequently used three-sided pyramidal indenter tip geometries.

Experimental Investigation of a High-Speed Turbine With Rainbow Rotor and Rim Seal Purge Flow

AbstractThe present paper addresses the experimental and numerical study of the unsteady flow established in a high-pressure turbine stage with rim seal purge. The HPT test section, operated at engine-relevant flow conditions in the high-speed turbine rig of the von Karman Institute, is heavily instrumented for high-resolution, high-bandwidth aerothermal measurements. A rainbow rotor setup allows the simultaneous testing of six different sectors, each hosting a specific tip and platform geometry optimized for enhanced aerodynamic performance. This paper focuses on the flow over the baseline sector, equipped with an axisymmetric hub platform and a squealer tip, with a purge flowrate matching 1.74% and 1% of the stage mass flow. The numerical study relies on Reynolds-averaged Navier–Stokes (RANS) computations with test-calibrated boundary conditions. Unsteady pressure and heat transfer measurements are performed at the rotor shroud. The maximum heat transfer is achieved along the front pressure side rim, whereas the squealer cavity generates a region of uniformly low static pressure and heat flux. The experimental adiabatic wall temperature is derived to quantify the thermal contribution to the global heat flux, demonstrating an increase in over-tip gas temperature up to 1.2 T01 above the pressure side rim. A Euler-based model is proposed to evaluate the temperature-driving work-exchange mechanism in the tip gap. The peak in casing heat transfer coefficient (750 W/m2K) is found at the tip leading edge. Time-resolved measurements of outlet total pressure, Mach number, and flow angle confirm the predicted phase and intensity of the tip leakage and upper passage vortex in the near-casing region. At 20% hr, the total pressure minimum is highly underpredicted by the RANS, indicating an inaccurate modeling of the interaction between rim seal purge and main flow. The measured impact of the purge flow variation is more significant than predicted by the RANS computations, with a negative offset of about 0.5% P01 in the lower 50% hr at lower purge flowrate.

A new blade tip geometry to improve aerodynamic performance and acoustic noise of helicopter blade in hovering flight

The goal of the present study is to improve aerodynamic performance of the helicopter main rotor by geometric redesign of its blades' tips. In this process, the generated noise is examined as well to ensure that it is not increased by the new tip geometry. Three-dimensional flow field around the blades is numerically simulated by the solution of the compressible unsteady Reynolds averaged Navier-Stokes (URANS) equations to calculate torque and thrust coefficients of CQ and CT, and the figure of merit (FoM) ratio. The turbulence model used in this study is “SST k-ω”. To check both the thickness noise and the high-speed impulsive (HSI) noise on the rotor plane, the Ffowcs Williams-Hawking (FW-H) equation is solved to obtain the sound pressure level at certain points in the flow field. Following the noticeable aerodynamic improvements that anhedral and dihedral winglets made on the fixed-wings, aerodynamic performance of the blade tip geometries composed of anhedral and dihedral winglets or a combination of them are investigated on the helicopter blades in present research. Redesign of blade tips minimizes the geometric changes needed for a new blade design. Flow fields around blades with nine different tip geometries are three-dimensionally simulated and analyzed in detail at crucial rotational speeds of 1250 rpm and 2540 rpm in hovering flight. To determine the amount of improvement, results obtained for different tip geometries are compared with the reference results of the rectangular blade. Among all of the different tip geometries, it was concluded that Eagle and Anhedral-Eagle make maximum improvements in aerodynamic and aeroacoustic of the main rotor blades. The FoM ratios of these two tip geometries have increased even up to 17% and 21%, respectively. Also, their noise levels of them have decreased by about 4.5% and 1%.

A feasibility study towards traceable calibration of size and form of microspheres by stitching AFM images using ICP point-to-plane algorithm

We present a new method for traceable calibration of size and form error of microspheres, which was realised by stitching a series of atomic force microscopic (AFM) images measured at different orientations of microspheres using the metrological large range AFM of the PTB. The stitching algorithm is achieved using an iterative closest point point-to-plane algorithm. As the AFM tip geometry is one of the most significant error sources for the developed method, it was traceably calibrated to a line width standard (type IVPS100-PTB), whose feature geometry was calibrated with a traceable route to the lattice constant of crystal silicon. Measurement setup, scan strategy, and data evaluation processes have been detailed in the paper. Measurement results show high stability and robustness of the developed method. For instance, the standard deviation of four repeated measurements reaches 5 nm, indicating promising performance.

Parametric study on the internal geometry affecting agricultural air induction nozzle performance

With recent advances in agricultural engineering, precision spraying has become of prime interest to avoid chemical drift or rebound and to minimize water and soil pollution. Air induction nozzles are reliable alternatives for conventional nozzles to overcome these challenges. A parametric study was designed both experimentally and numerically to investigate the effect of each design parameter on the performance of an air induction nozzle. A number of components were designed, manufactured, and tested. The spray structure was captured using a planer Mie scattering imaging system. The mean droplet size was measured using a Malvern particle sizer based on a laser diffraction technique. The results indicated the influence of each geometrical component on the resultant behavior. The internal geometry of the nozzle was found to significantly impact the stability and structure of the spray such as the fluid behavior inside the nozzles and the air-to-liquid mass flow ratio, as well as spray angle, droplet size, and uniformity. The key findings of this study indicate that pre-orifice inlet diameter primarily controls the flow behavior, air, and liquid inlet diameters of the ejector section impact mainly on the air-to-liquid mass flow ratio, the geometry of the mixing chamber mainly controls the stability of the resulting spray, and the geometry of the flat-fan tip essentially controls the spray angle and droplet size. The results can help nozzle designers optimize the design target, enhance atomization efficiency, and understand the effect of the various design parameters on the internal flow behavior of air induction nozzles.