Geometric Surface Research Articles

Improvement of Part Accuracy by Combination of Pulsed Wave (PW) and Continuous Wave (CW) Laser Powder Bed Fusion

In this paper, a processing strategy is investigated to increase the geometric accuracy of parts fabricated by laser powder bed fusion (LPBF). Pulsed wave emission (pw) is used for contour exposure in combination with a continuous wave (cw) emission for bulk volume exposure. With the goal of discrete solidification of adjacent melt pools, process parameters of laser power PL, scanning speed vs, and relative pulse overlap ∆xo are developed for contour exposure. Samples with variable contour angles are fabricated to investigate the effect of the pw contour exposure on excessive melting in critical areas of the part prone to overheating. Geometric accuracy and surface roughness are evaluated using SEM images of surface topography and optical surface roughness measurements, respectively. It is observed that excessive melting can be suppressed by using pw contour exposure and usage of modified process parameters. Due to the discretized energy input in pw emission mode, smaller melt pools with lower melt pool fluctuation and powder erosion are produced. The maximum applicable scanning speed is limited by the solidification time of the melt pool and is significantly lower compared to conventional cw contour exposure parameters. Therefore, a combination of cw volume exposure with high process productivity and pw contour exposure for high geometric accuracy is beneficial to limit productivity losses and increase accuracy in part building.

FEATURES OF GEOMETRIC SURFACES AND METHODS OF THEIR COMPUTER MODELING

This paper is devoted to the topical issue of studying the shapes of geometric surfaces in terms of descriptive geometry and their computer modeling. Definitions of algebraic and geometric surfaces are given. The analysis of features and parameters of surfaces for their classification into the main groups that are most common in practice is performed. The main methods of setting surfaces used in practice, depending on the shape of the surface and the task are given. Analytical, kinematic and frame methods of setting surfaces have been studied. The analytical method is presented on the basis of a conical surface of rotation; the canonical equation of the surface is analyzed, its correspondence for the upper and lower cone cavities is shown. The conical surface is graphically displayed in the AutoCAD graphics system. The peculiarities of the kinematic method of surface formation, which is presented on the example of the surface of rotation, made in the graphics system AutoCAD, and the surface of a straight hyperboloid, the drawing of which is made in the system COMPASS-3D. Examples of practical use of simulated surfaces are given. Enough attention is paid to the study of frame surfaces. A complex drawing of the surface of a cylinder given by a linear framework is given. The three-line frame of the ship's surface, which is formed by waterlines, frames and buttocks, is presented in detail. Simulated frame surface of an axial gas turbine blade is presented in the AutoCAD system. Algorithms and methods of geometric modeling of surfaces in graphic systems AutoCAD and KOMPAS-3D are given. Geometric models of some surfaces have been developed: straight helicoid, single-cavity hyperboloid, hyperbolic paraboloid, surface with return edge, etc. Examples of practical implementation of simulated surfaces are given.

Rapid and reversible Na deposition onto Al nanosheet arrays

Sodium metal battery (SMB) is regarded as a promising candidate for next-generation high-energy battery due to high theoretical capacity and abundant natural resources. However, the growth of sodium dendrites and large volume expansion during the processes of sodium plating and stripping seriously restrict the practical application of SMBs. Here, a three-dimensional skeleton of aluminum nanosheet arrays (Al NSARs) is constructed by a facile etching approach to achieve rapid and reversible Na plating/stripping. The Al NSARs with large geometric specific surface and plentiful cavities can provide rich active nucleation sites, reduce local current density and accommodate Na volume change, which lead to uniform deposition of sodium with dendrite-free morphology. As a result, Na plating/stripping on Al NSARs can stably operate over 650 cycles at 2 mA cm−2/2 mAh cm−2 with average Coulombic efficiency (CE) of 100.0% and low potential polarization of 27 mV. Moreover, the full cell of Na3V2(PO4)3‖Al NSARs@Na can run for over 1800 cycles at a high rate of 20C. These superior properties, combined with relatively low cost and weight of Al, enable our Al NSARs to be great prospect for practical applications.

New optical Heisenberg model with timelike optical de Sitter flux density

In this manuscript, we construct new model for de Sitter magnetic Lorentz flux for timelike magnetic T− fiber by de Sitter frame in S12. Then, we present new optical illustrations of timelike magnetic T− fiber by using polarized wave beam fields. Thus, we determine spherical geometric flux surface by spherical flux density. Also, we present new construction for timelike magnetic T−fiber by Heisenberg Sitter ferromagnetic model. Finally, we demonstrate some illustrations of the geometric optical phases in physical optics.

Strong bulk-surface interaction dominated in-plane anisotropy of electronic structure in GaTe

Recently, intriguing physical properties have been unraveled in anisotropic layered semiconductors, in which the in-plane electronic band structure anisotropy often originates from the low crystallographic symmetry and thus a thickness-independent character emerges. Here, we apply high-resolution angle-resolved photoemission spectroscopy to directly image the in-plane anisotropic energy bands in monoclinic gallium telluride (GaTe). Our first-principles calculations reveal the in-plane anisotropic energy band structure of GaTe measured experimentally is dominated by a strong bulk-surface interaction rather than geometric factors, surface effect and quantum confinement effect. Furthermore, accompanied by the thickness of GaTe increasing from mono- to few-layers, the strong interlayer coupling of GaTe induces direct-indirect-direct band gap transition and the in-plane anisotropy of hole effective mass is reversed. Our results shed light on the physical origins of in-plane anisotropy of electronic structure in GaTe, providing guidance to further improving the performance of electronic and optoelectronic devices based on the layered anisotropic semiconductors.

Hybrid microfabrication of 3D pyrolytic carbon electrodes by photolithography and additive manufacturing

We report a novel hybrid method for fabricating high aspect ratio 3D pyrolytic carbon electrodes combining UV photolithography and additive manufacturing with commercially available SLA 3D printers and materials. By using a 3D printed chip holder, aligned 3D printing on a patterned silicon chip was possible. This allowed for the fabrication of cylindrical polymer micropillars with a height of 2173 ± 26 μm and a width of 316 ± 11 μm on SU-8 precursor structures defining the leads, contact pads and underlying 2D electrode prepared using UV lithography. Microfabrication of 3D structures with these dimensions is impossible to achieve with SU-8 photolithography alone. The hybrid polymer structures were converted into 3D carbon electrodes with high structural integrity using a 3-step pyrolysis process optimized for the specific 3D print resin. During this process, the micropillars shrunk to 30 ± 3% in height and 35 ± 1% in width of the polymer precursor structures, while maintaining the macroscopic shape and microscopic surface roughness. Electrochemical experiments confirmed that the pyrolytic carbon formed a monolithic conductive 3D electrode. The surface roughness contributed to a 17 ± 5% increase in electroactive surface area compared to the geometrical surface area of the micropillars. • · 3D polymer microstructures fabricated by a novel hybrid process combining SU-8 photolithography and additive manufacturing • Optimization of a pyrolysis process converting the 3D polymer structures into 3D pyrolytic carbon electrodes • Electrochemical characterization demonstrating monolithic integration and increased surface area of the 3D electrodes

Upscaling calcite dissolution rates in a tight reservoir sandstone

Calcite is a highly abundant mineral in the Earth’s crust and occurs as a cement phase in numerous siliciclastic sediments, where it often represents the most reactive component when a fluid percolates through the rock. Hence, the objective of this study is to derive calcite dissolution rates on different scales in a reservoir sandstone using mineral surface experiments combined with vertical scanning interferometry (VSI) and two types of core plug experiments. The 3D geometry of the calcite cement phase inside the rock cores was characterized by X-ray micro-computed tomography (µXCT) and was used to attempt dissolution rate upscaling from the mineral surface to the core scale. Initially (without upscaling), our comparison of the far-from-equilibrium dissolution rates at the mineral surface (µm-mm-scale, low fluid residence time) and the surface normalized dissolution rates obtained from the core experiments (cm-scale, high fluid residence time) revealed differences of 0.5–2 orders of magnitude. The µXCT geometric surface area connected to the open pore space left( {GSA_{{Cc,{text{open}}}} } right) considers the fluid accessibility of the heterogeneously distributed calcite cement that can largely vary between individual samples, but greatly affects the effective dissolution rates. Using this parameter to upscale the rates from the µm- to the cm-scale, the deviation of the upscaled total dissolution rates from the measured total dissolution rates was less than one order of magnitude for all investigated rock cores. Thus, GSA_{{Cc,{text{open}}}} showed to be reasonably suitable for upscaling the mineral surface rates to the core scale.

Establishment of a corrective geoid surface by spline approximation of Iranian GNSS/levelling network

The performance of the gravimetric geoid models is usually evaluated by comparison of geoid heights with the GNSS/levelling derived geoid. But the GNSS/levelling network can be infected by significant systematic biases and random errors, especially in large and uneven areas. This contribution addresses the challenging problem of the corrector surface development along with the elimination of biases. To this end, fitting an appropriate geometric surface to the GNSS/levelling geoid heights is required, which is accomplished by applying the least squares B-spline approximation theory to the GNSS/levelling data. In addition, the 3D affine transformation is used to detect systematic effects of the GNSS/levelling network compared to a global geoid model. This strategy is applied to the adjustment of the Iranian GNSS/levelling network. A significant tilt is observed across the country ranging from −0.35 m to 0.04 m. The entire study area is divided into four zones and the corrector surfaces are obtained in each zone. The accuracy of three global geoid models, EGM2008, EIGEN-6C4 and SGG-UGM-1, along with that of the Iranian regional geoid model IRG2016, are then investigated based on the raw GNSS/levelling heights and the corrector surfaces. The evaluations show the reliable results regarding the corrector surfaces against the raw data set. All geoid models show their maximum RMSE values of discrepancies in the mountainous zones and their minimum RMSEs in the zones having lower variety in topography. This indicates that the irregular topographies are not well detected by the global models over the study area.

Kawabata Analysis of Cotton Denim Fabrics Treated with Industrial Washing Techniques

ABSTRACT Garment washing of denim fabrics is essential for fading of color, aesthetic effects, vintage look and improvement in handle properties of resulting garments. Denim fabrics of two types, one standard fabric (non-stretch) and other with 2% elastane fiber (stretch), are washed with different industrial washing techniques on Tonello sampling machine. The objective evaluation of handle and mechanical properties of the washed samples are carried out on Kawabata evaluation system (KES-F). Five main characteristics of fabrics are evaluated on KES-F system. The mechanical properties like tensile energy, extensibility and compression energy have increased for both stretch and non-stretch fabrics, while bending stiffness and bending hysteresis have decreased for both types of washed fabrics. The geometrical surface roughness and coefficient of friction have slightly increased after employed washing techniques. The optical microscope is used to investigate the surface changes of the fabric after the employed washing techniques.

带状耕作对种床秸秆清除率和土壤扰动的仿真与试验

Strip-tillage is an effective option for proper seedbed preparation because it ensures the suitable conditions for seed germination and has been widely implemented. This study developed a strip-tillage of corn planter row cleaner using bionic vertical rotary blades to remove seedbed straw and ideal soil for no tillage sowing can be created. Through the qualitative analysis of the serrated arrangement contour of the praying mantis foreleg tip, the characteristic curve of the praying mantis foreleg tip was extracted and fitted, and the bionic geometric structure surface of the vertical rotary blade was constructed. The model and interaction system were established in EDEM 2.6 simulation environment, and their physical properties were calibrated with the real properties of lime concretion black soil and wheat straw. According to theoretical design to set simulation parameters, the radius of the cutter head was set to 120 mm, the driving speed of the cutter shaft was set to 500 r/min, and the depth of the cutting edge was set to 10 mm, the operating velocity of the active anti-blocking device was set to 5 km/h. The experiment results show that when the moving speed ratio is increased from 2.8 to 4.5, compared with the traditional vertical rotary blades, the straw removal rate and soil uniformity of seed bed are increased by 6.4% and 9.3%, and the average torque of the rotary tiller has been reduced by 12.3% respectively, the process effect and sowing quality being effectively improved. The study can provide theoretical reference for realization of no-tillage sowing vertical rotary tillage blade to reduce resistance and consumption and improve the quality.

Hydrolysis of Argyrodite Sulfide-Based Separator Sheets for Industrial All-Solid-State Battery Production.

Researchers have been working for many years to find new material and cell systems that can be used as potential post-lithium-ion batteries. Among these, the all-solid-state battery is considered a promising candidate, with sulfide-based materials having essential advantages over other solid electrolyte materials, particularly in terms of their high ionic conductivity. A great challenge, however, is their high reactivity in contact with water, where harmful hydrogen sulfide (H2S) is formed. Since H2S formation has implications for both worker safety and material quality, it is important to quantify its impact. For this reason, this paper examines the relationship between the product properties and the H2S formation as well as influences resulting from the production environment. Exemplary material states along the process chain of a wet coating process route are analyzed for the steps of storage, mixing, coating, drying, and densifying with Li6PS5Cl (LPSCl) as a solid electrolyte material. By determining the H2S formation rate for sulfide-based separator sheets, it is shown that the water content in the surrounding atmosphere has the highest impact, while other investigated parameters are negligibly small in comparison. Among the product properties, the geometric surface and pore surface have a great influence. These results demonstrate the need for a controlled atmosphere in the production facilities at dew points of -40 to -50 °C. At those moisture levels, occupational safety and product quality are ensured for the investigated solid electrolyte sheets of LPSCl. This study is the first to provide quantitative data from the point of view of the production environment on the formation of H2S gas when using solid sulfide electrolytes and can therefore serve as a guideline for equipment, material, and cell manufacturers.

Enhanced Hydrophobicity of Polymers for Protective Gloves Achieved by Geometric, Chemical and Plasma-Surface Modification.

Gloves are one of the most important elements of personal protective equipment (PPE). To improve gloves properties, a lot of different methods of surface modifications are used. In this work, the application of geometric, chemical, and plasma surface modifications to improve the hydrophobicity of butyl (IIR) and silicone (MVQ) rubber are described. To characterise surface properties contact angle measurements, FT-IR spectroscopy and scanning electron microscopy were used. This study showed that when the chemical modification applied, the contact angle value increases compared to non-modified samples. In addition, plasma modification raised the contact angle value and smoothed the surface morphology. An increase in the polymer surfaces hydrophobicity was the observed effect of the three modifications of rubber.

Multipass double-sided incremental forming method for improving geometric accuracy and forming quality

Double-sided incremental forming (DSIF) has been extensively researched due to its high flexibility, good formability, and low cost when performed in small batches, and it enables the production of personalized sheet parts. However, the influences of process parameters on the geometric accuracy, thickness distribution, and forming quality are not well understood. In this paper, a multipass DSIF method is proposed. Based on the law of sines, the distance between the closest surface of the hemispherical forming tool and the supporting hemispherical tool is given, and a series of experiments are conducted. The influences of process parameters such as the toolpath strategy, incremental depth, and squeeze factor on the quality metrics in multipass DSIF, such as the geometric error, thickness distribution, and forming quality are investigated and compared to those formed by DSIF, accumulative double-sided incremental forming, and mixed double-sided incremental forming. The results show that multipass DSIF can effectively improve the geometric accuracy, thickness distribution, and surface quality. The thinning of the material increases slightly with the squeeze factor of the first D-pass decreases, and the different incremental depths have little effect on the thickness distribution. The multipass DSIF method provides some significant engineering advancements for improving geometric accuracy and forming quality.

Role of multiple reflections in identifying street canyons in microscale urban spaces

In this work, geometric acoustic numerical modeling of sound propagation in a micro-scale urban spaces is presented. The resultant sound propagation demonstrates an amplification of sound and increased reverberation time, due to the multiple reflections in the micro-scale urban spaces. Comparative analysis of the sound field acoustic parameters for various length and width between geometric boundaries can differentiate street canyons from other urban micro-scale spaces. Specifically, sound pressure level results are strongly influenced by the geometric configuration and material properties of the geometric boundary surfaces. The results and limitations of the geometric numerical method for predicting sound propagation in urban environments are discussed.

Simulated transit vibration effects on the postharvest quality of persimmon during storage

The mechanical damage of fresh fruit due to postharvest transport vibration is a major problem in the agricultural industry that dramatically impacts product quality. The quality loss is mainly affected by vibration frequency. In this study, the effects of different simulated vibration frequencies (5, 10, and 15 Hz) on the postharvest quality of persimmons were assessed. Changes in physical properties (weight, geometric mean diameter, surface area and volume), mechanical properties (firmness and rupture force) and chemical properties (pH and total soluble solids) were measured during 4 days of shelf life at 20 °C. Transport vibration contributed to the deterioration of the quality of persimmons during storage, resulting in increased weight loss, pH and total soluble solids, and decreased geometric mean diameter, surface area, volume, firmness and rupture force. After 4 days of shelf life, persimmons subjected to vibration frequencies of 5, 10 and 15 Hz exhibited weight losses of 2.12 %, 2.63 % and 3.26 %, respectively, in comparison to 0.83% on the samples without vibration stress (control). The average values of firmness for the control samples decreased 18%, while these changes for samples subjected to vibration frequencies of 5, 10 and 15 Hz, were 34 %, 56 % and 52 %, respectively. The corresponding mean values for the rupture force were 11 %, 19 %, 38 % and 31 %, respectively. The average pH value of the control samples was 5.72 on the first day, which was increased to 6.16 on the fourth day of storage, at a rate of about 7 %, while the increasing rates for the vibration stressed samples with frequencies of 5, 10 and 15 Hz were about 21 %, 33% and 30 %, respectively. Vibration with a frequency of 10 Hz caused the most severe mechanical damage in persimmons.

Remote sensing applied to classification of local climate zones

Monitoring of representative intra-urban thermal features is a difficult task due to the complexity of urban terrain (OKE, 2004). The characteristics of urbanized areas can be quantified using different methods, including the classification system of Local Climate Zones (LCZs), which describes the local-scale physical conditions of a given area. It is applied with universal and relatively easy standardization based on geometric, thermal, and radiative surface properties. This study aims to characterize the urban and rural areas of the municipality of Campo Grande (Midwest region, Brazil) using an adaptation of the LCZ method. Results from the modeling detected the following six built types: 2 - compact midrise, 3 - compact low-rise, 4 - open high-rise, 6 - open low-rise, 8 - large low-rise, 9 - sparsely built. This method can be used in any urban area if the required input data is available.

Flexible metallic mold based precision compression molding for replication of micro-optical components onto non-planar surfaces

Replication of micro/nano-scale optical components onto non-planar substrates is considered technically challenging and excessively expensive via existing manufacturing approaches. A low-cost, large-volume and high-precision fabrication approach is thus highly desirable. In this paper, a novel precision compression molding approach that enables large-volume and high-resolution replication of micro/nano-scale optical features from planar to non-planar substrates is proposed. A micro-lens array is demonstrated to be transferred from a planar master mold to a non-planar substrate. In such process, a micro-lens array mold is initially fabricated by single-point diamond turning on a planar mold surface and then replicated by micro-injection molding. After that, the optical structures are transferred from micro-injected polymeric samples to a nickel foil by electro-plating, which is employed as a critical transition medium. To obtain sufficient flexibility with considerable strength, the thickness of the electro-plating mold is controlled to be around 75 μm, which is further integrated with precision molding tools to replicate micro/nano-scale optical features onto cylindrical substrates. Geometrical profile and surface roughness of the fabricated optical components in each processing step are characterized experimentally. The results indicate that the replication of the micro-lens array successfully demonstrates the process to transfer micro-optical components from planar surfaces to non-planar thermo-plastic polymeric substrates with high fidelity and optical-level surface quality. Compared with conventional precision compression molding, this novel proposed method in this research could achieve much higher flexibility and comparable fidelity with low cost on transferring optical structures from planar to non-planar surfaces. The application of this method might be widely extended to numerous replication methods, such as precision glass molding, roll-to-roll and roll-to-plane imprinting.

Assessing 3D vs. 2D habitat metrics in a Mediterranean ecosystem for a wiser wildlife management

Although many ecological studies recognize the importance of the three-dimensional complexity of the landscape, only a small number of investigations incorporate it into their methods. Through an empirical study we assess the extent to which habitat metric patterns vary measured by 3D versus 2D methods, and whether it is possible that variations are associated with scale, topographic complexity or specific animal behavior. We analyze areas and potential animals where the use of 3D approaches is most influential for reliable results in ecological studies. This study was carried out in southern Spain, focusing on game estates covering an area of about 2.241 km2. The topographical features of the areas were obtained from a digital terrain model (DTM) and a scalable terrain model (STM) generated from Lidar data. The estates were categorized according to a preliminary 3D vs. 2D surface increment index (SI index). Then an experimental repeated measures design was carried out to compare three nested scales from 1 to 4 km square plots. The influence of plot topography on the SI index was analyzed statistically. Plots were also compared pair-wise through a post hoc comparison analysis. In order to establish how 3D affects the metrics of the trajectories travelled by different animal species, we simulated movements of Oryctolagus cunniculus, Cervus elaphus, Canis lupus and Lynx pardinus, which move and behave differently in the study area. We simulated 15 replicate paths per specie, assuming 24 fixes per path. Variations in animal trajectories were analyzed by fitting general linear models (GLMs), which also provide a basic method for estimating the potential errors produced by a simple 2D analysis. We obtained significant differences between the projected and geometric surface areas, with an increase of up to 11.15% and an increase in animal paths length up to 5% using 3D approaches. Landscape complexity, rather than species type, is related to animal path metrics differences. However, in species such as deer and lynx the 3D spatial component is basic for an accurate estimate of path length, especially in heterogeneous landscapes. Altitude and slope range are determining factors for considering the 3D approaches as advisable. Our results confirm that ecological studies ignoring three-dimensional (3D) components run the risk of misinterpretation due to the fact that the bi-dimensional (2D) approach underestimates distances and landscape area. The use of 3D methods provides more accurate results than with 2D approaches, with far-reaching implications for a wiser wildlife management and conservation in Mediterranean ecosystems.

Introduction of the developable surface concept in fibrous composite materials

Composite sheet forming, especially thermo-forming, has been well researched over the last few decades. However, the concept of developable surfaces has not been implemented for the fibrous composites. These surfaces form critical and lucrative aspects in geometric designs, surface analyses and structural applications, with their roots being strongly established in origami and various shape designs around the world. The current work aims to analytically derive and determine developable (de) curvatures on a flat sheet, based on established theories on lines of curvature. The theoretically derived de curves are then validated by metallic sheet forming before implementing them for the first time on both multi-layered wood veneers and short flax-fibre reinforced polypropylene composites. The work is a novel application of the established developable surface generation in the case of composite sheet forming, the success of which can expand its usage in various consumer goods and structural components.

Comparative evaluation of Ru-coated fecralloy and SiC monolithic catalysts in catalytic partial oxidation of natural gas for hydrogen production

The catalytic activity of structured catalysts comprising Fecralloy and SiC monoliths coated with Ru/Mg-Al oxide by deposition–precipitation was evaluated in the partial oxidation of natural gas and compared with that of a conventional pellet catalyst. The geometric surface area (GSA) of the Fecralloy and SiC monolithic catalysts were 377.0 × 10-4 and 118.5 × 10-4 m2, respectively; significantly larger than that of the 0.5% Ru/Al2O3 pellet catalyst (89.6 × 10-4 m2). Owing to the high GSA of the structured catalysts, a small amount of Ru (0.070–0.12 wt%) resulted in highly dispersed uniform loading. Thus, the structured catalysts exhibited higher performance for catalytic partial oxidation at varying C/O2 ratio, inlet temperature, and gas hourly space velocity (GHSV) than the pellet catalyst. However, in a stability test at high GHSV (50,000 h−1), the CH4 conversion of the Fecralloy monolithic catalyst decreased rapidly from 90% to less than 70% in 150 min. In addition, the Mg-Al oxide layer of the Fecralloy monolithic catalyst was damaged owing to material deterioration, resulting in a loss of Ru particles. In contrast, CH4 conversion catalyzed by the SiC monolithic catalysts remained above 85% even after 1000 min, and the material or support layer was not damaged even under severe conditions.