Surface Elements Research Articles

Рейтинги легкових автомобілів за аеродинамічними властивостями та сучасні підходи 3D-моделювання зовнішніх форм кузовів

The work is devoted to the development of passenger car aerodynamics, which began at the beginning of the 20th century. Radical changes to the shape of the body are not enough, the main attention is focused on the surface elements, their optimization is being carried out while preserving the overall shape determined by the design concept. Much attention has always been paid to the improvement of car aerodynamics, especially to the study of frontal drag - the most important factor affecting the traction and operational qualities of a car. During this time, it was possible to significantly reduce the coefficient of aerodynamic resistance Sh. When developing the external shape of the body, the designers strive to give it such contours that the air flows around it as smoothly as possible, without swirls and disruptions of the flow, i.e., that the surface is visually attractive with the correct shapes and with the most streamlined silhouette.
 The relevance of the problem is reduced to the improvement of the external forms of the car, therefore, during development, five components of the overall aerodynamic resistance of the car are taken into account: the resistance of the form; inductive; superficial; interference resistance and resistance of internal flows. The share of each of these components varies depending on the type of car, but, usually, shape resistance accounts for 60...70% of the total aerodynamic resistance, inductive - 7...12% (large values are typical for passenger cars), surface - about 5 ...8%, internal flow resistance - 8...11%.
 The purpose of the work is to analyze the influence of the components of the overall aerodynamic resistance Cx on the operational properties of passenger cars (speed, fuel consumption, safety, convenience and comfort during driving) with the formation of a general rating assessment.
 In general, it is shown that cars of the last period are characterized mainly by wedge-shaped shapes, to which almost all automobile companies in the world have switched. From the point of view of improved aerodynamic properties, these are cars of small and medium classes (classes B, C and E). On the basis of significant research in this field, the improvement of automotive technologies, aimed primarily at improving fuel economy and dynamic properties, manufacturers managed to achieve relatively low drag. At present, the best representatives of this class have closely approached the value of Сх = 0,29 ... 0,30, which is the limit for the current level of technology. Further efforts of researchers are aimed at reducing the resistance created under the hood, reducing pollution and improving acoustic characteristics.

On the Blackbody Spectrum of Kilonovae

The early spectra of the kilonova AT2017gfo have a remarkably smooth blackbody continuum, which reveals information on the thermal properties and radioactive heating within the ejecta. However, the widespread use of a single-temperature blackbody to fit kilonova data is theoretically invalid, because (1) the significant travel-time delays for a rapidly cooling surface result in a broad distribution of temperatures and (2) the relativistic Doppler correction varies across different surface elements. Thus, the observed spectrum should be a modified blackbody with a range of temperatures over the surface. In this paper we quantify the impact of these effects and illustrate the typical wavelength-dependent spectral corrections. We apply the multitemperature blackbody framework to the first-epoch X-shooter AT2017gfo spectrum, to deconvolve the underlying physical temperature at the photosphere from the relativistic Doppler shift. We show that the cooling and Doppler effects individually result in a variation of temperatures over the photosphere of up to 30%, but in combination these effects nearly cancel and produce the single-temperature blackbody observed. Finally, we show that fitting the UV, optical, or near-infrared separately yields blackbody temperatures consistent at the percent level, which puts stringent limits on any proposed modification of the spectral continuum.

Simulation of the atomic structure near spherical void in aluminum and the calculation of the anisotropy of the void growth rate

We simulate structure in the vicinity of different size nanovoids using a new variant of the Molecular Statics, wherein atomic structure in the vicinity of nanovoids and the parameters that define the displacements of atoms placed in elastic continuum around main computation cell are determined in a self-consistent manner. Then, the previously obtained kinetic equations are applied to calculate the shifting rate of the elements of the void surface in certain crystallographic directions. These equations take into account the dependence of the vacancy flux on the deformation fields. The displacement rates in different crystallographic directions for bcc and fcc metals are significantly different. The results show that the effects studied by computer simulation can lead to a change in the shape of initially spherical nanopores and cause their transformation into cuboidal pores in metals with a cubic structure under irradiation.

Digitalization of bridge inventory via automated analysis of point clouds for generation of BIM models

AbstractBuilding Information Modelling (BIM) is becoming increasingly prevalent in infrastructure asset management, as it facilitates current management practices. This includes the construction of BIM models for roads, rails, bridges, tunnels etc. Bridges are particularly challenging to digitalize due to their complex geometry. The manual construction of bridge BIM models based on 2D plans is hardly feasible due to the related workload. Given the recent advancements in the field of 3D surveying and artificial intelligence, new possibilities emerge for an automated generation of as‐is bridge BIM models.This paper presents a novel, modular framework for the automatic processing of point clouds into as‐is BIM models, based on a fusion of artificial intelligence and heuristic algorithms. Representative bridge element datasets were provided to train neural network. Trained neural network can identify elements of a bridge, which are further processed using geometric algorithms into surface and solid bridge elements. This result can be additionally enriched with semantic information from existing databases. The final BIM models are exported in the standardized vendor‐free Industry Foundation Classes (IFC) format.

Self-cleaning SiO2/TiO2/PMMA nanocomposite films fabricated by spin coating technique: Effect of different spin speed and film layers

This research aims to develop the self-cleaning efficiency of silicon dioxide/titanium dioxide/methyl methacrylate (SiO2/TiO2/PMMA) nanocomposite films proved by optical and structural properties. The SiO2/TiO2/PMMA nanocomposite films were prepared by spin coating technique with the crucial parameters of spin speed and film layers. The ratio of SiO2:TiO2 in SiO2/TiO2 nanocomposite was conducted at 1:1 by sonochemical process and loading at 1 wt.% in PMMA matrix. Spin speed of SiO2/TiO2/PMMA nanocomposite films in coating process was conducted at 1000, 2000, and 3000 rpm with film growth at 2 layers. Meanwhile, the different film layers of the nanocomposite film were selected as other crucial parameter in spin coating technique and studied at 1, 2, and 3 layers with spin speed 2000 rpm. Surface morphologies, cross-section and element contents of SiO2/TiO2/PMMA nanocomposite films with different spinning speed and film layers were monitored by the photographs, field emission scanning electron microscope (FE-SEM) and energy dispersive X-ray spectroscopy (EDS). Moreover, optical property in transmission mode of SiO2/TiO2/PMMA nanocomposite films was characterized by UV-VIS spectrophotometer. Furthermore, the contact angle measurement o f SiO2/TiO2/PMMA nanocomposite films can identify to hydrophilic properties on the film surface. Therefore, the improvement of self-cleaning property on SiO2/TiO2/PMMA nanocomposite film was occurred by the optimized conditions of spinning speed at 2000 rpm and film growth at 2 layers by spin coat technique.

Research on Remote Sensing Geochemical Modeling Based on Surface to Surface Model

Remote sensing geochemistry is a simple, fast and economical advanced prospecting method, which carries out inversion and prediction of surface element content using the empirical model by regression or machine learning. The key problem faced by quantitative remote sensing is the low inversion accuracy of the model due to the mismatch of “point surface” information. How to overcome this problem? This paper proposes a “surface to surface” modeling method, which converts point data into surface data through Kriging interpolation to solve this problem. This paper uses geochemical interpolation data of Cu elements at different scales in the Qishitan gold mine area, Xinjiang, and ASTER remote sensing data to conduct geochemical modeling. In order to test the effect of Kriging on decreasing the scale effect, five sets of experiments were designed for comparison. The first four sets of sample data were interpolated according to different cell sizes, and the last set of data was not interpolated. The results show that the Kriging interpolation based on the ground resolution of the remote sensing image can effectively improve the accuracy of the remote sensing quantitative inversion model. When the square interpolation is close to the ground resolution of the used remote sensing data, the modeling accuracy gets the best value. This paper provides a new idea for improving the accuracy of remote sensing geochemical modeling.

Microstructure and Mechanical Properties of Ti/Al-SiC/Ti Clad Plates Prepared via the Powder-in-Tube Method.

SiC particle-reinforced Ti/Al/Ti clad plates were successfully fabricated by the powder-in-tube method. The surface micrography, element diffusion, peeling strength and tensile property of clad plates were studied after annealing and cold rolling. The experimental results show that 6 wt.% is optimal. The presence of SiC particles has been seen to significantly enhance the diffusion of Ti and Al elements. Additionally, it has been observed that the diffusion width of the intermetallic compound (IMC) increases as the size of SiC particles grows. However, it is worth noting that the average of Ti/Al-SiC/Ti clad plates initially increases and subsequently falls. The optimized diffusion thickness of the Ti/Al-SiC/Ti clad plate's IMC layer determined via the powder-in-tube method is approximately 4.5 μm. The 1 μm SiC-reinforced Ti/Al/Ti clad plate can obtain the best mechanical properties after annealing at 500 °C and further hot rolling, and the peeling strength, ultimate tensile strength and elongation are 31.5 N/mm, 305 MPa and 26%, respectively. The efficacy of Ti/Al-SiC/Ti clad plates in delivering exceptional performance is substantiated by the analysis of peeling surfaces, peeling tests and tensile testing, which collectively demonstrate the presence of compact and homogenous intermetallic compounds.

Preparation and Superhydrophobicity of Nano-Al-Coated Wood by Magnetron Sputtering Based on Glow-Discharge Plasma

A superhydrophobic coating on wood can effectively improve the hydrophobicity and service life of wood. In this study, an Al superhydrophobic nano-coating was constructed on the transversal section of poplar wood by magnetron sputtering based on glow-discharge plasma. The structure, microscopic morphology, surface elements, and hydrophobic properties were characterized and tested. When coated for 20 s, the water contact angle on the sample surface can reach 148.9°. When coated for 30 min, the Al-coated wood had a contact angle of 157.3°, which could maintain excellent superhydrophobic properties for 300 s. The sputtered Al nanoparticles were uniformly distributed on the wood surface and formed nanoclusters. Plenty of voids between the clusters can trap air and block contact between water droplets and the coating, making the coating obtain superhydrophobic properties. When the coating time was 60 min, the characteristic peak of the Al (111) crystal plane appeared at 38.4°, while the intensities of (101), (002), and (040) peaks of cellulose were reduced. In conclusion, magnetron sputtering was used to deposit a superhydrophobic coating on wood without low surface free energy agents. Furthermore, this research provides new inspirations for the physical modification of wood and the construction of superhydrophobic coatings on wood.

Hydrodynamic performance assessment of photocatalytic reactor with baffles and roughness in the flow path: A modelling approach with experimental validation

Purification of wastewater is essential for human being as well as for the flora and fauna, and sustainable environment. Photocatalytic reactor with TiO2 coated layer can be used to degrade the pollutants but without proper pollutant mass transfer in the reactive surface, photocatalytic reactor decreases its effectiveness. The baffles and rough surface in the flow path can improve the fluid mixing to enhance pollutant mass transfer to improve the reactor's performance. In this study, a computational fluid dynamics (CFD) model has been developed to investigate the effect of four top baffles and three rough surfaces (semi-circular, triangle, and rectangle) on pressure drops, mass transfer and the hydrodynamic performance of the reactor. The experimental investigation was carried out using Formic Acid (FA) as pollutant in feed water for model validation. The simulated result varies only within 5% with the experimental data of FA concentration versus feed flow rate and fluid velocity. The model was run at fluid velocity of 0.15 m/s and 0.5 m/s (Reynolds number of 2150 (laminar flow) and 7500 (turbulent flow), respectively. The simulation result shows that the addition of baffles and roughness on the reactive surfaces increases the turbulent kinetic energy (minimum increase 8%) and consequently increases the mass transfer (maximum increase 37%) of the pollutant. The highest wall shear was observed to be 40 Pa when both square and triangular elements were used as roughness elements at turbulent flow condition. The results also shows that the highest pressure-drop of 8 kPa was found when the square roughness element was used at turbulent flow condition. Overall, the photocatalytic reactor performance is significantly enhanced by the application of combined baffles and roughness elements in the reactive surface.

Research on Classified Treatment of Electrolytic Zn Anode Slime Based on μ-XRF and Cluster Heatmap

The purpose of this research is to have a clearer understanding of the resource value of electrolytic Zn anode slime, explore its fine structure and treat it in a classified manner. In this paper, the composition, content and distribution of Pb, Mn and Zn in electrolytic Zn anode slime during one production cycle were studied under typical working conditions of enterprises, by using the method of μ-XRF combined with mm-XRF. Based on heatmap and cluster analysis, the resource value of anode slime at different points in the electrolytic Zn silting area and the conventional area was evaluated. The research results were as follows: (1) There were two different areas of electrolytic Zn anode slime: the silting area and conventional area. Between these, the silting area accounted for approximately 15% of the total number of anode plates, and there were significant differences between these areas in terms of surface element content, surface morphology, slime thickness and water content. (2) In the silting area, 3.9 mm away from the Pb-based anode plate surface, there were lumps with fluorescence counting intensity that was close to that of pure Pb. (3) Anode slime at a thickness of 0.1 mm in the silting area could be classified as a type of resource. The resource attributes were categorized using a complete-linkage algorithm and the actual demand of Zn hydrometallurgy enterprises for recycling anode slime from the leaching process, for those with ≥45% Mn content and <20% Pb content. High-Pb resources include 0–1.5 mm (CAP), 0–1.4 mm (SAP) and 6.3–7.0 mm (SAP). A low-Pb, high-Mn and high-Zn resource was identified at 2.9–6.0 mm (SAP). Low-Pb, high-Mn and low-Zn resources include 1.6–6.0 (CAP), 1.5–2.8 mm (SAP) and 6.1–6.2 mm (SAP).

(Keynote) Interplay between Physicochemical Properties of Precursors and “Core-Shell” Hierarchical Carbon Nitride Electrocatalysts for the Oxygen Reduction Reaction

The oxygen reduction reaction (ORR) is a major bottleneck in the operation of proton-exchange membrane fuel cells (PEMFCs) since it introduces large overpotentials (no less than 250-300 mV), which degrade significantly the energy conversion efficiency of the device. In addition, the electrocatalysts (ECs) yielding the lowest ORR overpotentials in the acidic environment found at the PEMFC cathode are based on Pt, a very scarce critical raw material (CRM). Pt raises concerns as it might trigger serious supply bottlenecks in the event of a practical widespread implementation of PEMFCs in the framework of today’s energy transition. Hence, the development of high-performing and durable ECs for the ORR is a major stepping stone towards the large-scale rollout of PEMFCs.In our research group a new breakthrough approach has been devised for the synthesis of ORR ECs, that is completely different form the preparation routes that are commonly adopted in the state of the art [1, 2]. Briefly, the approach consists in the pyrolysis and subsequent treatment of a precursor obtained by coupling suitable carbon species/sacrificial supports with a zeolitic inorganic-organic polymer electrolyte (Z-IOPE). The latter comprises anionic complexes including the Pt “catalyst” and other “co-catalysts”, which are bridged by organic binders [1,2].On one hand, the proposed approach has already shown its potential to yield ECs exhibiting a performance and durability improved with respect to Pt/C benchmark ECs. On the other hand, the proposed approach is extremely flexible, especially with respect to the synthesis of the initial EC precursor. In principle, it is possible to modulate a number of crucial features of such EC precursor, with a particular reference to: (i) the chemical composition (e.g., in terms of Pt, other “co-catalysts” and N; the latter plays a crucial role to stabilize the active sites into “coordination nests” on the EC surface, raising durability); and (ii) the morphology, that can be “templated” on suitable species (e.g., carbon species, sacrificial supports). The very flexibility of the proposed synthetic process needs to be leveraged appropriately to maximize the performance of the final ORR ECs, at the same time minimizing the efforts wasted on approaches with a low development potential.Herein it is elucidated how the modulation in the parameters involved in the synthesis of the EC precursor (e.g., the binder and the approaches to couple the Z-IOPE with the support) impact the physicochemical and electrochemical properties of the final ECs, with a particular reference to the chemical composition, morphology and distribution of the ORR active sites. An extensive characterization of the final ECs is carried out. Inductively-coupled plasma atomic emission spectroscopy (ICP-AES) and microanalysis are adopted to determine the bulk chemical composition. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is used to elucidate the surface chemical composition and the chemical states of the surface elements. Ultra-high resolution scanning electron microscopy (UHR-SEM) and transmission electron microscopy (TEM) allow for the elucidation of EC morphology. The porosimetric features are probed by automatic gas adsorption instrumentations. Wide-angle X-ray diffraction (WAXD) is crucial to resolve the crystal structure. Cyclic voltammetry with the rotating ring-disk electrode method (CV-TF-RRDE) is used to clarify the “ex-situ” electrochemical performance and ORR reaction mechanism. Finally, the most promising ECs are used in the fabrication of single PEMFCs, that are tested as a function of the operating conditions.It is revealed that, in comparison with the Pt/C benchamark, some ECs are characterized by a much higher intrinsic kinetic performance due to the electronic and bifunctional effects bestowed by the carbon nitride support and the «co-catalysts». Finally, the binder has a marked effect on the stoichiometry, size, and distribution of the PtMx aggregates bearing the active sites.

In Situ Growth of High-Performance ZnAl-Layered Double Hydroxides/Al2O3 Composite Coatings on Aluminum Alloy

In this research, high-performance ZnAl-layered double hydroxides (ZnAl-LDHs) with different Zn2+ concentrations were prepared on the surface of an anodized 1060 aluminum alloy using the in situ growth method, and the influence of Zn2+ concentration on corrosion resistance and tribological behavior was further explored. The surface morphology, element distribution, phase composition, and mechanical performance of ZnAl-LDHs/anodic aluminum oxide (AAO) composite coatings were tested and analyzed. Subsequently, the investigation of the anti-corrosion properties and tribological behavior of as-prepared composite coatings and AAO were conducted experimentally. The results show that with the increase in Zn2+ concentration, the thickness and bonding strength of the coatings gradually increase, and the hardness progressively decreases. The ZnAl-LDHs/AAO composite coating with a Zn2+ concentration of 0.3 mol/L exhibits the best anti-corrosion ability, which has the minimum corrosion current density of 2.435 × 10−9 A/cm2. This can be attributed to the uniform and compact ZnAl-LDH films where the porous structure of the AAO is well sealed. Moreover, the excellent friction-reduction and anti-wear properties of ZnAl-LDHs/AAO composite coatings with larger Zn2+ concentrations are verified using a ball-on-disc rotating wear tester under dry wear. A reasonable mechanism for improving tribological properties of resulting ZnAl-LDHs/AAO composite coatings is proposed.

Перспективи застосування електрохімічного полірування зразків скеффолд, виготовлених за адитивною технологією

In recent years, the actual production of metal products directly from electronic data according to a three-dimensional model based on layer-by-layer manufacturing has evolved from rapid prototyping to additive manufacturing. As the quality of additively manufactured metal products continues to increase and their manufacturing processes improve and develop, the demand for additive manufacturing is increasing. Additive manufacturing technology, also known as 3D printing, has become increasingly popular recently. Using additive manufacturing, almost any complex geometry can be manufactured with high degree of precision. After the production of parts using the SLM technology from metal powder, post-processing is applied, in particular electrochemical polishing, the main purpose of which is to reduce surface roughness, increase the gloss of surface elements, and remove metal powder that has partially melted onto the outer surface of the product at the point of contact between the molten metal and the border of the part and the powder, which is located next to the melt. This is especially important for inclined surfaces, internal channels and cellular structures with developed outer surface. For research, samples were made using SLM technology from AISI 316L austenitic steel powder. The samples have a cube shape with a base of 10 mm, a height of 10 mm, and a thickness of 10 mm, with cell widths of 4 mm and 2 mm. The main body of both samples was printed using the same modes at a laser power of 220 W, a scanning speed of 1000 mm/s and a distance between laser passes of 0.14 mm. Samples were printed on Alfa-280 3D printer manufactured by ALT Ukraine LLC. Electropolishing was carried out in a solution of orthophosphoric acid (H3PO4) with glycerol (C3H8O3) by immersing the test samples in the electrolytic solution at a voltage of 17 V and a current density of 3 A/cm2. The control of weight and geometric parameters was carried out with the help of ADV-2000 analytical balances and MKC-25 micrometer. The electropolishing of the experimental samples took place in four stages: 1) visual - optical inspection with fixation, weight control before the start of the process; 2) electropolishing for 3 minutes, visual - optical inspection with photo fixation; weight control after 3 min. polishing process; 3) electropolishing of the same samples for another 3 minutes, visual – optical inspection with photo fixation, weight control after 6 minutes. polishing; 4) electropolishing of the same samples for another 3 minutes, visual - optical inspection with photo fixation; weight control after 9 min. electropolishing process. At each stage, a real current-voltage curve was recorded using an oscilloscope. As a result of weight control before and after the test, it was established that the samples lost approximately the same weight in the range of 6.9...7.1 % relative to the initial one. Based on the analysis of the obtained results, it was established that at a current density of 3 A/cm2 and at a voltage of 17 V, effective active uniform polishing of the surface of samples with a cellular structure of scaffold type with a variable cell size from 4 to 2 mm is realized.

Alkali-thermal activated persulfate treatment of tetrabromobisphenol A in soil: Parameter optimization, mechanism, degradation pathway and toxicity evaluation

The continued accumulation of halogenated organic pollutants in soil posed a potential threat to ecosystems and human health. In this study, tetrabromobisphenol A (TBBPA) was used as a typical representative of halogenated organic pollutants in soil, for alkali-thermal activated persulfate (PS) treatment. The results of response surface methodology (RSM) showed a optimal debromination efficiency of TBBPA was 88.99 % under the optimum reaction conditions. Quenching experiments and electron paramagnetic resonance (EPR) confirmed that SO4−•, HO•, O2−• and 1O2 existed simultaneously in the oxidation process. SO4−• played a major role in the initial stage of the reaction, and O2−• played a major role in the the last stage. Based on density functional theory (DFT) and intermediate products, two degradation pathways were proposed, including debromination reaction and β bond scission. Moreover, the basic physical and chemical properties of the soil were affected to a certain extent, while the soil surface structure, elements and functional group composition rarely changed. In addition, the T.E.S.T. analysis and biotoxicity tests proved that alkali-thermal activated PS can effectively reduce the toxicity of TBBPA-contaminated soil, which is conducive to the subsequent safe secondary utilization of soil.

Machining of ZrO2 using wire EDM: an experiment based investigation via assisted electrode

ABSTRACT Machining of electrically insulating ceramic materials has been a challenging task for ceramic industries. Assisted electrode method (AEM) based wire electrical discharge machining (WEDM) process emerged as an advanced option to machine insulating ceramics. This study deals with the machining of yttrium (Y2O3) stabilised zirconia (ZrO2) ceramic using copper (Cu) and stainless steel (SS) assisted electrode (AE) in presence of alumina (Al2O3) powder, ethylene glycol and demineralised water mixed dielectric fluid. The effect of different AE materials, pulse on time (TON), peak current (IP) on length of cut (LC), surface roughness (Ra), and average micro-hardness (MH) were investigated. Further, the comparison was made between minimum and maximum LC, and Ra (case-(i) and case-(ii)), respectively. SEM and EDS were carried out to analyse the surface characteristics and distribution of elements of the machined surface. Experimental results show that machining with SS AE at high levels of TON and IP provides high spark energy that results in higher value of LC (1300.910 µm), Ra (24.520 µm) and MH (1401.713 HV). Increasing TON and IP significantly increases the LC and Ra. Moreover, hardness near the lower junction was higher than the hardness near the upper junction and middle region of the machined surface.

Surface Quality of Al2O3 Ceramic and Tool Wear in Diamond Wire Sawing Combined with Oil Film-Assisted Electrochemical Discharge Machining

Diamond wire sawing is one of the most widely used methods of cutting Al2O3 ceramic because it has good machining accuracy and causes less surface damage. However, its material removal rate (MRR) needs to be improved with the increasing demand for Al2O3 ceramic parts. In this paper, spark discharges are generated around the diamond wire based on the electrochemical discharge machining (ECDM) process. An oil film-assisted ECDM process is applied to solve the difficulty of generating spark discharges when the thickness of the workpiece exceeds 5.0 mm due to the difficulty of forming a hydrogen gas film. Experimental results show that the combination of oil film-assisted ECDM and diamond wire sawing improved the MRR of Al2O3 ceramic. Oil film-assisted ECDM may improve the surface quality of machined parts and reduce the wear on diamond wire. Therefore, this research focuses on the surface quality of Al2O3 ceramic and tool wear in diamond wire sawing combined with oil film-assisted ECDM. Surface roughness and topography, recast layer, and elements of the machined surface are analyzed. The tool wear is studied using SEM images of diamond wire. The results provide a valuable basis for application of diamond wire sawing combined with oil film-assisted ECDM.

Synergy mechanism of biochar and petcoke co-combustion based on potassium migration and transformation

Co-combustion of biochar and pet-coke can reduce environmental pollution, provide fuel energy supply and improve fuel reaction characteristics. In this study, the co-combustion characteristics and synergistic behavior of rice straw char (BC) and petcoke (PC) were analyzed based on thermogravimetric analysis and kinetic analysis. The combustion corroborative experiments were conducted based on a fixed bed reactor, and the contents of different forms of potassium (K) during combustion of semi-char were characterized. Raman spectroscopy and X-ray photoelectron spectroscopy were used to characterize the carbon structure order and surface elements distribution characteristics of the semi-char after the combustion. The results showed that the co-combustion reactivity improved with the temperature and the BC blended ratio increase. Moreover, the synergistic effect increased with the temperature decrease and the BC blended ratio increase. The synergistic effect was confirmed to be related to the K migration and transformation, and its behavior was varied with active K content adsorbed by PC. The H2O-soluble K would be transformed into -COOK during PC combustion. -COOK would reduce the order of PC and increase the content of amorphous carbon during combustion.

The Effects of a Multifunctional Rust Inhibitor on the Rust Resistance Mechanism of Carbon Steel and the Properties of Concrete

To address rebar corrosion in existing concrete structures, a multifunctional compound rust inhibitor was developed. This study investigates the impact of this inhibitor on carbon steel rust resistance, as well as the mechanical properties and durability of concrete. The results demonstrate a significant reduction in weight loss of carbon steel when using a multifunctional rust inhibitor, with a rust inhibition efficiency of 82.6%. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were employed to observe and analyze the surface elements of carbon steel, both with and without the presence of a rust inhibitor. The findings indicate that the use of a rust inhibitor leads to a smoother and more stable surface film. The results of the experiments on compressive strength, chloride ion electromobility, and the rapid carbonation test of concrete with varying rust inhibitor contents indicate that increasing the amount of rust inhibitor can improve the compressive performance of concrete and can regulate the mobility of chloride ions. Specifically, when the rust inhibitor content reaches 4%, it has a notable positive impact on the performance of concrete, and further increases in content lead to smoother results.

Preparation of 2024-T351 aluminum alloy superhydrophobic surface by laser peening without absorption layer and without confinement layer

The purpose of this study was to investigate the preparation of superhydrophobic surfaces on 2024-T351 aluminum alloy by laser peening without absorption layer and without confinement layer (LPwAC). The wettability, residual stress and microhardness of the treated specimens were measured. The surface morphology of the specimen was characterized by scanning electron microscopy, and the surface elements and crystal orientation were analyzed. The experimental results showed that the micro-nanoporous structure appeared on specimen surface after LPwAC treatment. The superhydrophobic state was observed after chemical modification reduced the surface energy. Additionally, the crystallinity of the surface was increased, the hardness was improved, and residual compressive stress was generated inside the material. LPwAC is an effective process for the preparation of stable 2024-T351 aluminum alloy superhydrophobic surfaces.

A Multirobot System for 3-D Surface Reconstruction With Centralized and Distributed Architectures

In this article, we propose an original solution to the problem of surface reconstruction of large-scale unknown environments, with multiple cooperative robots. As they progress through the 3-D environment, the robots rely on volumetric maps obtained via a TSDF representation to extract discrete incomplete surface elements (ISEs), and a list of candidate viewpoints is generated to cover them. A next-best-view planning approach, which approximately solves a traveling salesman problem (TSP) via greedy allocation, is then used to iteratively assign these viewpoints to the robots. Two multiagent architectures, a centralized one (TSP-Greedy Allocation or TSGA) and a distributed one (dist-TSGA), in which the robots locally compute their maps and share them, are developed and compared. Extensive numerical and real-world experiments with multiple aerial and ground robots in challenging 3-D environments show the flexibility and effectiveness of our surface representation of a volumetric map. The experiments also shed light on the nexus between reconstruction accuracy and surface completeness, and between total distance traveled and execution time.