Geometric Surface Research Articles

Automated Model-Based 3D Scan Planning for Prefabricated Building Components

Modular construction can improve construction performance (i.e., cost, schedule, and safety) by prefabricating modules at an off-site facility and installing them at a construction site. However, when defects of modules are not easily repairable on the construction site, they cause additional cost overruns and delays due to long lead times of refabrication and reshipment. Thus, quality assessment of modular components at the fabrication facility before shipment is very important. The current inspection practices rely on manual measurement, which can be imprecise, labor-intensive, and time-consuming. To address this issue, some research efforts are made on the module inspection techniques (e.g., estimates of geometric properties and surface quality) using laser-scanned data. The accuracy of these techniques relies on the quality (i.e., coverage and resolution) of the scan data. However, ensuring the consistent quality of data is a major challenge as there is little to no research on optimal scan planning for modular components. Therefore, this paper proposes a model-based 3D scan planning method for modular components that ensures user-specified scan quality. Given a 3D computer-aided design (CAD) or building information modeling (BIM) model, scanner property, and user’s quality requirement, this method automatically computes the input parameters for the laser scanner (i.e., angular step and field of view) and optimal scan positions. It also predicts the scan quality and shows the areas that will not meet the user requirement due to geometric constraints (i.e., self-occluded surfaces). This study was validated through two case studies using two modular-sized structures in a fabrication facility. The results showed that the scan planner is able to accurately predict the scanning quality and ensure that the output scan will meet the user quality requirement.

Dynamic biomass char porosity during gasification: Model compared with data

This investigation presents a new biomass char porosity model as a function of char conversion during gasification and compares it with entrained-flow data from poplar, corn stover and switchgrass particles reacting with H2O, CO2, and combinations of both at temperatures of 1050–1350 °C. The experimental data include particle temperature, mass, size, and shape combined with porosity, BET surface area, geometric specific surface area and SEM images of char vascular structure. The new theoretical model describes char porosity changes during char conversion and the model indicates that porosity increases monotonically, consistent with the data. The vascular char structure remains intact even at the highest conversions and this structure effectively transports reactants and products through the particle, with reactions occurring on the walls of these vascular vessels, referred to here as vascules. The investigation shows that char porosity most strongly depends on average vascule diameter which, in turn, increases with increasing conversion. This investigation extends current understanding of the mechanism of heterogeneous biomass char reactions (gasification and oxidation) under kinetically controlled conditions. This work concludes that (1) kinetically controlled biomass gasification involves reactions on the walls of vascules with small contributions from the nanopores or even mesopores; (2) char porosity increases monotonically with increasing char conversion in the kinetically and internal transport-controlled regimes; and (3) observed porosity behaviors correspond the predicted behaviors.

Determination of selected engineering properties of cashew nut (Anacardium Occidentale) related to the design of cashew nut processing equipments

Cashew plant is a tree in the family Anacardiaceous. Cashew with botanical name Anacardium occidentale is extensively cultivated in the tropics mainly for its apples and nuts. This study aims at investigating the interactions of physical properties of the cashew nuts and its moisture content. The size and shape were described in relation to its surface area and sphericity, geometric mean diameter and arithmetic mean diameter. They were characterized using established procedure. Density was described on the basis of its true and bulk density which resulted to the porosity of the nuts. They were determined with reference using water displacement method. The frictional characteristics which are angle of repose and coefficient of friction were determined on three different structural surfaces plastic, metal and plywood on an inclined plane. Result obtained revealed that the mean value for the nuts major diameter, intermediate diameter, minor diameter, arithmetic mean diameter, geometric mean diameter, sphericity, surface area, mass, volume, true density, bulk density and porosity were 31.58±0.75 mm, 24.25±0.40 mm, 17.23±0.55 mm, 24.35±0.51 mm, 23.63±0.51 mm, 0.75±0.01 mm, 1754.20±75.14 mm2, 7.75±0.72 g, 7.65±0.52 cm3, 1.01±0.03 g/cm3, 0.58±0.03 g/cm3 and 42.53±0.04 % respectively at a moisture content ranging between 5 % to 8 % wet basis. The mean value for coefficient of friction for wood, plastic and metal structural surface was 0.068±0.01, 0.102±0.033 and 0.100±0.037 respectively at a moisture content ranging between 5 % to 8 % wet basis. The mean value for angle of repose for metal, plastic and plywood structural surface were 31.5±1.73°, 25.5±1.29° and 26.25±4.35° respectively. The effect of moisture content on the physical properties considered was significant, the results were expressed graphically.

Determining the Geometric Surface Area of Mesoporous Materials

Specific surface area is an important property of porous materials and a crucial index in multiple disciplines, which is mainly measured using nitrogen isotherms and the Brunauer–Emmett-Teller (BET) equation. The BET surface area is remarkably higher than the geometric surface area, which is defined as the surface area of the crystal geometry structure. However, many studies directly use the BET surface area as the geometric surface area. We proposed a simple, general, and accurate method that only needs the nitrogen adsorption isotherm as the input to calculate the geometric surface area of mesoporous materials. The proposed method considers the adsorptive potential influences and the physical state of adsorbed nitrogen in estimating the surface area. We utilized 18 isotherms generated by molecular simulations and actual experiments to cover a wide range of materials, including minerals, catalysts, and carbon-based tubes, and validate the effectiveness of the proposed method. Our results showed that the surface area determined by the proposed method is almost identical to the referenced geometric area. The surface area obtained by the proposed method can be typically considered a geometric surface area.

Synergistically enhanced flexibility, mechanical strength and microwave absorption performances of TPE-based hybrid films via thermally assisted homogeneous separation technology

With the ever-growing electromagnetic (EM) wave pollution and the rising demand of flexible absorbing materials pasted onto the surfaces of different geometric surfaces, it is urgent to develop high-efficiency EM wave absorption films with good flexibility and mechanical strength. Traditional processing methods endow the film superior features that can be adapted to targeted geometric surfaces and complex conditions, however, the durability is not satisfactory. Confronted with the tough problem, in this work, optimized thermally assisted homogeneous separation technology was proposed to fabricate the thermoplastic elastomer-based magnetic/dielectric two-phase mixed EM wave absorption films, which can achieve good flexibility, machinability, mechanical strength, as well as excellent EM wave absorption performances due to the uniform filling of elastoplastic skeletons and chain-bridge effect between chains and particles. Benefitting from these merits, the as-prepared films exhibit good flexibility and fine mechanical properties, like good deformability (300% of the deformation compared to its original length) and low elastic coefficient (323.8 Pa). Moreover, good EM wave absorption performances can also be balanced, for example, broad effective bandwidth (>14 GHz) and tunable frequency response from high frequency to low frequency. In all, this work opens up a new pathway to realize the integration of strong EM response, good flexibility, and fine mechanical properties, and the obtained films exhibit great potentials as flexible EM wave absorption materials that can be pasted on or peeled off the targeted surfaces at any time.

Twisted intramolecular charge transfer, nonlinear optical, antibacterial activity, and DFT analysis of ultrasound processed (E)-N′-(4-isopropylbenzylidene)nicotinohydrazide

Hydrazones have attracted considerable interest for their antimicrobial and nonlinear optical (NLO) applications. In the present work, a new hydrazone (E)-N′-(4-isopropylbenzylidene)nicotinohydrazide (INH) was synthesized by a condensation reaction of cuminaldehyde with nicotinic hydrazide via ultrasonication. The hydrazone was characterized by FT-IR spectroscopy, mass spectrometry, NMR (1H, 13C, HOMO-COSY, HSQC, and DEPT-135), elemental analysis, and FESEM analyses. Phase-pure and non-existent isomorphic phase transition in INH was demonstrated by X-ray diffraction and thermogravimetric analysis. The absorption maximum of INH in an aqueous solution was red-shifted compared to that of the reactant molecules, indicating that the CN bond formation efficiently enhances the resonance interaction towards the pyridine ring. Fluorescence emission of INH at a shorter wavelength is caused by a locally excited state. A longer wavelength band is caused by intramolecular proton transfer in nonpolar/aprotic solvents, while it is caused by TICT emission in protic solvents. The direct and indirect bandgaps of the INH crystals were assessed using Tauc plots and the Kubelka–Munk algorithm. The efficacy of INH for the inactivation of E. coli and B. subtilis were examined through a plate colony counting assay, and the inactivation was 62.7 ± 0.2 % and 98.3 ± 0.4 %, respectively. The geometrical structure, Mulliken, MEP surface, and electronic properties of INH are theoretically optimized using density functional theory (DFT) at the B3LYP/6-31G(d,p) level and showed good concurrence with the experimentally defined structure. The INH displays higher NLO properties compared to urea as a reference, as determined by molecular hyperpolarizability analysis. The frontier molecular orbitals and global reactivity descriptors showed that INH is more reactive and reasonably stable.

A cuboidal open cell model for constitutive modeling of surface effects in fluid-saturated porous materials

Fluid-saturated porous elastic materials, made up of connected networks of solid ligaments and characteristically having open pores, are commonly found in geological, biological and engineering materials. Surface effects can affect significantly the mechanical performance of such porous materials at macro scale, especially when the solid ligaments and the pores have micro or nano scale sizes. In the present study, in order to explicitly link pore-level geometrical parameters and surface effects with effective poroelastic properties as well as constitutive equations governing poroelastic deformation, we combine the top-down homogenization approach presented a previous study (Chen et al., 2021) with the bottom-up micromechanics approach. Inspired by the Gibson-Ashby cubic cell model for open-cell foams and the cellular networks typically found in fluid-saturated porous materials, we propose a cuboidal open cell model, with surface effects and fluid compressibility accounted for. For two limiting cases, i.e., the undrained state and the drained state, we demonstrate that both the surface moduli and residual surface stress (i.e., surface tension) prevent the deformation of solid ligaments, thus stiffening the porous material with enlarged effective Young's moduli. Further, we reveal that the two surface effect parameters (i.e., residual surface stress versus surface moduli) exhibit a coupling effect on effective moduli: when one parameter is large enough, the variation of the other affects significantly the effective moduli. As applications of the proposed model, we characterize mechanical behaviors of the porous material under typical loadings (e.g., uniaxial and non-proportional multiaxial tension) in both undrained and drained states; we also describe, for the first time, the stress concentration of a compressible liquid inclusion (e.g., a cell) with surface tension embedded in a fluid-saturated porous material with surface effects. Results of this study are beneficial for understanding and investigating how surface effects influence the poroelastic parameters of fluid-saturated porous materials having sufficiently small open pores.

Specific Capacitance of RuO2(110) Depends Sensitively on Surface Order

We report the specific capacitance, Cs, of variously ordered RuO2(110) surfaces measured in a 1 M H2SO4 electrolyte with unprecedented precision. Employing ∼10 nm thick, atomically flat epitaxial RuO2 films along with a geometric surface area-controlled electrochemical cell, we determine an upper limit of Cs = (35.35 ± 0.53) μFcm–2 of the idealized, i.e., well-ordered and stoichiometric RuO2(110) surface by electrochemical impedance spectroscopy (EIS) and scan-rate-dependent cyclic voltammetry. We demonstrate, however, that a slight decrease in surface quality immediately translates into pronounced cyclo-voltammetric differences and a significant increase of Cs. This needs to be considered when determining electrochemically active surface areas (ECSAs) of geometrically ill-defined RuO2 catalysts─a benchmark to measure electrochemical performance─from their measured double-layer capacitance.

Screen Printed Polarization Independent Microwave Absorber for Wideband RCS Reduction

Designing and deploying a broadband microwave absorber that provides wide bandwidth radar cross section (RCS) reduction for planar and curved surfaces is challenging. We present a resistive ink-based multilayered wideband absorber using a low-priced FR4 substrate to cope with the challenge. The reflection coefficient response of the structure lies beneath −10 dB reference over the frequency span of 1.3–18.6 GHz for the normally incident electromagnetic waves. The multilayered structure incorporates the entire microwave radar frequency span with a relative fractional bandwidth of 173.86%. Moreover, to examine the applicability of the structure for a nonplanar geometrical surface, we further design the structure on a very thin FR4 substrate that can be bent easily. We performed an RCS analysis of the redesigned structure under monostatic and bistatic conditions. The structure thereby exhibits novelty in terms of wider stealth and electromagnetic compatibility applications and also a good counterbalance among different design attributes comprising thickness, bandwidth, and periodicity, unlike the earlier reported work. The proposed prototypes are fabricated and experimentally validated for planar and curved surfaces, respectively. The experimental results depict a good concurrence with the simulated results.

The dissolution rates of naturally altered basalts at pH 3 and 120 °C: Implications for the in-situ mineralization of CO2 injected into the subsurface

Due to their widespread distribution in the Earth's crust, it seems likely that altered basalts could be targeted for CO2 storage via subsurface carbon mineralization. To assess the potential efficiency of this approach, the steady state release rates of major elements from a suite of altered basalts have been measured at pH 3, 120 °C, and far from equilibrium conditions. The altered basalt samples have chemical compositions close to that of fresh basalt, but their mineralogy varies due to their alteration either at the Earth's surface or hydrothermal conditions at temperatures up to 250 °C. The studied altered basalts contain variable amounts of primary plagioclase and pyroxene, and substantial secondary phases including quartz, zeolites, epidote, chlorites and clay minerals. Despite their differing mineralogy, the steady-state element release rates of all the altered basalts are similar to each other when normalized to geometric surface area. These rates, however, are one to three orders of magnitude slower than corresponding release rates of basaltic glass and fresh crystalline basalt, depending on the element and on whether the rates are normalized to initial BET or geometric surface area. If present in small amounts in the altered basalts, calcite dissolves rapidly in the acidic reactive fluids, and does not contribute to the measured steady-state calcium release rates. Taken together, the results of this study indicate that altered basalt formations can provide sufficient divalent cations for subsurface carbon mineralization. As the element release rates of these altered basalts are lower than those of basaltic glass or fresh crystalline basalt, efforts to carbonate subsurface altered basalts may be best targeted at systems having temperatures in excess of 100 °C to compensate for the lower reactivity of these rocks.

Design, Fabrication, and Experimental Validation of Microfluidic Devices for the Investigation of Pore-Scale Phenomena in Underground Gas Storage Systems

The understanding of multiphase flow phenomena occurring in porous media at the pore scale is fundamental in a significant number of fields, from life science to geo and environmental engineering. However, because of the optical opacity and the geometrical complexity of natural porous media, detailed visual characterization is not possible or is limited and requires powerful and expensive imaging techniques. As a consequence, the understanding of micro-scale behavior is based on the interpretation of macro-scale parameters and indirect measurements. Microfluidic devices are transparent and synthetic tools that reproduce the porous network on a 2D plane, enabling the direct visualization of the fluid dynamics. Moreover, microfluidic patterns (also called micromodels) can be specifically designed according to research interests by tuning their geometrical features and surface properties. In this work we design, fabricate and test two different micromodels for the visualization and analysis of the gas-brine fluid flow, occurring during gas injection and withdrawal in underground storage systems. In particular, we compare two different designs: a regular grid and a real rock-like pattern reconstructed from a thin section of a sample of Hostun rock. We characterize the two media in terms of porosity, tortuosity and pore size distribution using the A* algorithm and CFD simulation. We fabricate PDMS-glass devices via soft lithography, and we perform preliminary air-water displacement tests at different capillary numbers to observe the impact of the design on the fluid dynamics. This preliminary work serves as a validation of design and fabrication procedures and opens the way to further investigations.

Texture-Mapping Error Removal Based on the BRIEF Operator in Image-Based Three-Dimensional Reconstruction

In image-based three-dimensional (3D) reconstruction, texture-mapping techniques can give the model realistic textures. When the geometric surface in some regions is not reconstructed, such as for moving cars, powerlines, and telegraph poles, the textures in the corresponding image are textured to other regions, resulting in errors. To solve this problem, this letter proposes an image consistency detection method based on the Binary Robust Independent Elementary Features (BRIEF) descriptor. The method is composed of two parts. First, each triangle in the mesh and its neighboring triangles are sampled uniformly to obtain sampling points. Then, these sampled points are projected into the visible image of the triangle, and the corresponding sampled points and their RGB color values are obtained on the corresponding image. Based on the sampled points on these images, a BRIEF descriptor is calculated for each image corresponding to that triangle. In the second step, the Hamming distance between these BRIEF descriptors is calculated, outliers are removed according to the method, and noisy images are also removed. In addition, we propose adding semantic information to Markov energy optimization to reduce errors further. The two methods effectively reduced errors in texture mapping caused by objects not reconstructed, improving the texture quality of 3D models.

Design of a Compliant Robotic End-Effector Tool for Normal Contact Estimation

The use of industrial robots for machining operations such as polishing is gaining popularity these days. However, maintaining constant normal contact on unknown geometrical surfaces still remains a challenge. In order to cope with the issue, this research has developed a unique compliant robotic end-effector that can measure the depth and angles deviation of the robot from the normal complex surfaces in real-time without any prior geometric model of the workpiece. The indigenously developed compliant robotic end-effector is made up of three main components: a novel three-axis force/torque sensor, a compliant contact pin, and a data acquisition (DAQ) board. Initially, the three-axis force/torque sensor has been validated with both simulation and testing. The advantage of being able to take measurements in real-time is provided by the DAQ’s automatic weight compensation feature. Additionally, the pose correction algorithm receives the estimated contact force as feedback during robot surface tracking in order to assess depth and angles and determine the proper distance and perpendicular relationship between the surface and the end-effector. The proposed scheme is then evaluated using a six-axis industrial robot. The experimental results show that the maximum average depth and angle errors are 0.13 mm and 0.64°, respectively. The developed system has achieved significant improvement in contact-based robot surface measuring.

How Loading of Co3O4-Cs on an Open-Cell Foam Influences N2O Decomposition

Co3O4 modified with Cs was deposited on an α-Al2O3 open-cell foam, characterized by X-ray diffraction (XRD), N2 physisorption, temperature-programmed reduction by hydrogen (TPR-H2), and scanning electron microscopy-energy-dispersive X-ray analysis (SEM-EDAX) and tested for the low-temperature decomposition of N2O. The aim was to study the effect of the amount of active phase on N2O conversion. Three different approaches were used: (i) the application of foam supports with different cell sizes, (ii) influencing catalyst loading using impregnation solutions with different precursor concentrations, and (iii) deposition of the active phase precursor by repeated immersion–calcination cycles. Increasing the geometric surface area of the support, and thus catalyst loading, was successfully done using the support with higher pore densities. A higher loading was also achieved by increasing the nitrate precursor concentration in the impregnation solution. In both cases, the catalyst activity increased with an increase in the amount of the active phase. Compared to that, a repeated impregnation procedure can ensure the deposition of a higher amount of active phase in comparison to that obtained with one-step impregnation, but only the last layer is used in the reaction and the rest of the active phase remains unutilized, which makes this type of preparation unfavorable. The high catalytic activity was preserved at 450 °C even in the presence of O2, H2O, and NO.

Mechanical Behavior of Al-Si10-Mg P-TPMS Structure Fabricated by Selective Laser Melting and a Unified Mathematical Model with Geometrical Parameter.

Compared with the traditional lattice structure, the triply periodic minimal surface (TPMS) structure can avoid stress concentration effectively. Here, it is promising in the fields of lightweight and energy absorption. However, the number of structural parameters and mechanical properties of the TPMS structure is plentiful, and the relationship between them is unclassified. In this paper, for the first time, a unified mathematical model was proposed to establish the relationship between TPMS structural design parameters and mechanical properties. Fifteen primitive models were designed by changing the structural parameters (level-set value C and thickness T) and manufacturing by selective laser melting. The geometric defects and surface quality of the structures were explored by optical microscope and scanning electron microscopy (SEM). The mechanical properties were investigated by quasi-static compression test and finite element simulation. The influence of building direction on structural mechanical behavior (failure mode, stress-strain curve) was studied. The real mechanical properties (Young's modulus and plateau stress) of the structure could be predicted according to different C and T combinations. Finally, the energy absorption characteristics were explored. The results showed that when the C value is 0.6 in the range of 0-0.6, the energy absorption performance of the structure is at the maximum level.

Toward an Improved Surface Roughness Parameterization Model for Soil Moisture Retrieval in Road Construction

In passive microwave remote sensing, the estimation of the surface roughness parameter is a significant obstacle for soil moisture (SM) retrieval. For a given SM content, the geometric soil surface roughness has been shown to have a large impact on the surface emission at L-band frequency, which affects the SM retrieval success when using the information observed from the radiometer and is represented through the so-called the surface roughness parameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{R}$ </tex-math></inline-formula> ). Moreover, no previous study has examined the effect of this factor in the context of road construction, where the geometric soil surface roughness is affected by the compaction process, resulting in a substantial change in roughness before and after compaction. Accordingly, a series of experiments at various compaction levels and SM contents was performed for a sand subgrade material in order to identify their effects on <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{R}$ </tex-math></inline-formula> . The soil brightness temperature (TB) was measured using an L-band radiometer at different incidence angles and a laser profiler was used to measure the surface roughness standard deviation ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sigma$ </tex-math></inline-formula> ) before and after compaction. The results of this article have demonstrated that the incidence angle ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta$ </tex-math></inline-formula> ) and SM both affect <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{R}$ </tex-math></inline-formula> and its relation to the geometric soil surface roughness. Importantly, these factors are not accounted for by existing models. Consequently, a modified surface roughness parameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{R}$ </tex-math></inline-formula> ) model, based on the traditional Choudhury model, was developed to include the contribution of these two factors, and its impact on the accuracy of SM retrieval results tested. Specifically, it was shown that it is possible to obtain SM retrieval results with an accuracy of 0.04 cm3/cm3 at almost all incidence angles using either dual-polarization [both horizontal (H) and vertical polarization (V)] or only vertical polarization observations. The modified surface roughness parameter ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$H_{R}$ </tex-math></inline-formula> ) model has improved the performance of the SM retrieval model to achieve an accuracy of 0.04 cm3/cm3, whereas the traditional Choudhury model achieved an accuracy of only 0.05 cm3/cm3.

Evaluation of geometrical precision and surface roughness quality for the additively manufactured radio frequency quadrupole prototype

A multidisciplinary collaboration within the I.FAST project teamed-up to develop additive manufacturing (AM) technology solutions for accelerators. The first prototype of an AM pure-copper Radio Frequency Quadrupole (RFQ) has been produced, corresponding to ¼ of a 4-vane RFQ. It was optimised for production with state-of-the-art laser powder bed fusion technology. Geometrical precision and roughness of the critical surfaces were measured. Although the obtained values were beyond standard RFQ specifications, these first results are promising and confirmed the feasibility of AM manufactured complex copper accelerator cavities. Therefore, further post-processing trials have been conducted with the sample RFQ to improve surface roughness. Algorithms for the AM technological processes have also been improved, allowing for higher geometrical precision. This resulted in the design of a full 4-vane RFQ prototype. At the time of the paper submission the full-size RFQ is being manufactured and will undergo through the stringent surface quality measurements. This paper is discussing novel technological developments, is providing an evaluation of the obtained surface roughness and geometrical precision as well as outlining the potential post-processing scenarios along with future tests plans.

Optimization of fast tool servo diamond turning for enhancing geometrical accuracy and surface quality of freeform optics

Optimization of fast tool servo diamond turning for enhancing geometrical accuracy and surface quality of freeform optics

Atomic reconstruction and oxygen adsorption behavior of the pyrite (100) surface: a DFT study.

The analysis of the surface chemical behavior of pyrite is highly crucial in the fields of environmental conservation, metal extraction, and flotation separation. In this paper, the mechanism of atomic reconstruction on the pyrite surface and the adsorption behavior of O2 on a reconstructed surface are calculated by density functional theory (DFT). Different reconstruction surfaces were constructed by deleting S and Fe atoms on the (100) surface of pyrite. In addition, the geometric configuration, formation energy, binding energy, cohesion energy, and surface electronic properties of the reconstruction surface were calculated. The adsorption energies and geometric configurations of O2 on different reconstructed surfaces were also determined. The results show that under Fe-poor conditions, the charge of Fe atoms increases, and S atoms form Sn on the reconstructed surface. The binding energy between the Sn and the substrate (ideal surface) is lower, which is similar to the Sn adsorption on the substrate surface with the Fe atom as the site. Sn has high cohesive energy and is resistant to being attacked by oxidants, which leads to structural collapse, and a low affinity for O2. Under S-poor conditions, the -[Fe-S]n- plane structure formed on the reconstructed surface. The -[Fe-S]n- structure stably bonds to the substrate by an Fe-S bond, and exhibits strong binding energy. However, the -[Fe-S]n- structure has low cohesive energy and exhibits thermodynamic instability. In contrast, O2 shows a strong affinity for the -[Fe-S]n- structure, indicating that the deficiency of the S atom promotes the surface oxidation reaction. The mechanism of atomic reconstruction on the surface of pyrite is of utmost importance for understanding its surface chemical behavior.

Hybrid offline-online optimization, monitoring and control of milling processes

A hybrid offline-online optimization, monitoring and control (HOMC) system was developed for milling processes. Safe cutting regions (SCRs) are defined based on offline analysis considering process dynamic stability, tool deflection and machined part geometric accuracy and surface quality. Near-optimum cutting conditions are defined offline using the cutter-workpiece contact information along the toolpath. A deep-learning tool condition monitoring approach is developed to detect the wear state in real-time using minimal learning efforts. The HOMC monitors the machining power signals and adaptively controls the feedrate within SCR using online predictions. Validation tests proved better process productivity, part quality and extended tool life.