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Background: This study aimed to investigate the in vitro effect of a charcoal-containing dentifrice with different toothbrush stiffness on enamel. Methods: Four main groups were applied: distilled water, conventional fluoridated toothpaste (Colgate® Total® 12 Clean Mint Toothpaste), charcoal toothpaste (Colgate® Total® Charcoal Toothpaste) and whitening toothpaste (Colgate Total® Advanced Whitening Toothpaste). Three subgroups for each toothpaste were further included according to the toothbrush bristles' stiffness (soft, medium, and hard). Enamel specimens were subjected to 1,250 and 2,500 cycles of brushing using toothbrushing simulation machine. The average surface roughness change (ΔRa) in nanometer (nm) was measured to estimate the changes following the brushing simulation model. Two-way ANOVA and Tukey tests analyzed the data. Results: The type of toothpaste and the bristles' stiffness were determinant factors in increasing the ΔRa value (P = < 0.05). Generally, charcoal and whitening toothpastes with medium and hard bristles yielded higher ΔRa than fluoridated toothpaste and smooth bristles. Following 1,250 cycles of brushing simulation, charcoal toothpaste did not increase the enamel roughness compared to the controls. However, in prolonged brushing via 2,500 cycles of brushing simulation, using bristles with soft stiffness revealed that charcoal toothpaste was associated with increased surface roughness (55.86 ± 41.18 nm), which was statistically significant (P = 0.024) compared to the negative control. Using bristles with medium stiffness showed that the whitening (68.23 ± 48.58 nm) and charcoal (73.62 ± 34.66 nm) toothpastes significantly (P = < 0.05) increased the enamel roughness compared to the conventional toothpaste (36.53 ± 22.56 nm). There was no significant difference among the groups when brushes with hard bristles were used, as all the groups revealed increased enamel roughness. Conclusion: The use of charcoal and whitening toothpastes increased enamel roughness, particularly with long-term use. The effect of bristle stiffness on enamel roughness was found to vary depending on the type of toothpaste used. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the bond strength between PEEK/PEKK and composite resins after various laser treatments and to compare the effectiveness of lasers on these polymers. 130 disc-shaped PEEK and PEKK blocks were obtained (10 mm diameter-4 mm height). One sample from each group (10 in total) was selected for scanning electron microscopy (SEM) analysis. The samples were randomly divided into 5 different surface treatment groups for each material (PEEK and PEKK): Er: YAG laser, Nd: YAG laser, diode laser, femtosecond laser and control (no surface treatment) (n = 12). Baseline and post-treatment surface roughness measurements were performed using a profilometer. The composite resin was bonded and SBS was measured. Comparisons among the groups were conducted via Kruskal–Wallis, one-way ANOVA; Tukey and Dunn tests were used as a post hoc test (p ≤ 0.05). All lasers significantly increased the roughness values of the PEEK and PEKK samples. In terms of shear bond strength; the Er: YAG and femtosecond laser groups had the highest values and the Nd: YAG, diode and control groups had the lowest values of the PEEK samples (p ≤ 0.05). The control group had the highest bond strength values and the femtosecond group had the lowest values for PEKK samples (p ≤ 0.05). All laser treatments increased the surface roughness of the PEEK and PEKK. Lasers increased the bond strength of PEEK to the veneering composite resin and decreased the bond strength values of PEKK. This shows that lasers behave differently in PEEK and PEKK materials. [ABSTRACT FROM AUTHOR]

One of the most chemically adaptable elements is boron which is found in the periodic table between two groups, i.e., metals and nonmetals and may create more than 16 polymorphs that are bulk and made of connected boron polyhedra. Given that boron and carbon are comparable elements, it has been questioned whether two-dimensional (2D) boron could serve as a conceptual starting point for the construction of other boron nanostructures. Using boron as fundamental building blocks, boron nanosheets were synthesized known as borophenes. Borophene is found to be a crystalline form of atomic monolayer boron which was theoretically first predicted in mid-1990s and experimentally synthesized very recently in 2015. In this work, we studied both armchair and zigzag formation of borophene and presented a comparative analysis of their minimum sub-band energy, effective mean free path E n , number of conduction channels N ch , scattering resistance per unit length. The N ch for armchair BNR is 3,2,1 for 22 nm, 13 nm, 7 nm, respectively, which is comparatively more than zigzag BNR. We later proposed Top-Contact BNR (TC-BNR) and Side-Contact BNR (SC-BNR). Our analysis shows that SC-BNR offers 9 6 % less resistance compared to TC-BNR and it is of the order of SC-GNR. Further, if we compare with copper interconnects, BNR is better in terms of performance and copper can be replaced with BNR due to high bulk mean free paths 300 nm and 400 nm compared to copper's 40 nm. Boron, a metalloid, displays remarkable adaptability, giving rise to over sixteen polymorphs, including borophenes—2D boron nano sheets synthesized in 2015. Armchair borophenes demonstrate greater conduction channels (Nch) compared to zigzag counterparts, with Side- Contact BNR (SC-BNR) boasting 96% less resistance than Top-Contact BNR (TC-BNR). These properties position boron nanostructures as competitive alternatives to copper interconnects, offering significantly longer mean free paths (300nm–400nm for BNR versus 40nm for copper). Borophene, akin to graphene in its honeycomb structure, boasts greater strength and flexibility, alongside a slightly reduced mean free path and fourfold higher fermi velocity. Its resistance is comparable to graphene, yet it offers advantages over copper, including excellent superconductivity with results on par with graphene. [ABSTRACT FROM AUTHOR]

In the last decade, the task of developing environmentally friendly and cost-effective methods for obtaining stable superhydrophobic coatings has become topical. In this study, we examined the effect of the concentrations of filler and polymer binder on the hydrophobic properties and surface roughness of composite coatings made from organic–aqueous compositions based on hexyl methacrylate (HMA) and glycidyl methacrylate (GMA) copolymers. Silicon dioxide nanoparticles were used as a filler. A single-stage "all-in-one" aerosol application method was used to form the coatings without additional intermediate steps for attaching the adhesive layer or texturing the substrate surface, as well as pre-modification of the surface of filler nanoparticles. As the ratio of the mass fraction of polymer binder (Wn) to filler (Wp) increases, the coatings show the lowest roll-off angles among the whole range of samples studied. Coatings with an optimal mass fraction ratio (Wn/Wp = 1.2 ÷ 1.6) of the filler to polymer binder maintained superhydrophobic properties for 24 h in contact with a drop of water in a chamber saturated with water vapor and exhibited roll-off angles of 6.1° ± 1°. [ABSTRACT FROM AUTHOR]

This paper presents the experimental and numerical results of a study on producing axisymmetric parts made of the C60-grade steel by skew rolling. The experimental part of this study involved conducting the skew rolling process with varying parameters, including the forming angle α, tool angle θ, chuck velocity Vu, and reduction ratio δ. Their effect on the quality of produced parts was examined and described by the roughness parameter Ra. Numerical calculations involved the use of machine learning models to predict the quality class of produced parts. The highest prediction accuracy of the results was obtained with the random forest and logistic regression models. Metrics such as precision, recall and accuracy were used to evaluate the performance of individual models. Confusion matrices and ROC curves were also employed to illustrate the performance of the classification models. The results of this study will make it possible to prevent the formation of spiral grooves on the circumference of steel parts during the rolling process. [ABSTRACT FROM AUTHOR]

Carbon-based electrodes have recently been most widely used in P-MFC due to their desirable properties such as biocompatibility, chemical stability, affordable price, corrosion resistance, and ease of regeneration. In general, carbon-based electrodes, particularly graphite, are produced using a complex process based on petroleum derivatives at very high temperatures. This study aims to produce electrodes from bio-pitch and charcoal powder as an alternative to graphite electrodes. The carbons used to manufacture the electrodes were obtained by the carbonisation of Robinia pseudoacacia and Azadirachta indica wood. These carbons were pulverised, sieved to 50 µm, and used as the raw materials for electrode manufacturing. The binder used was bio-pitch derived from coconut shells as the raw materials. The density and coking value of the bio-pitch revealed its potential as a good alternative to coal-tar pitch for electrode manufacturing. The electrodes were made by mixing 66.50% of each carbon powder and 33.50% of bio-pitch. The resulting mixture was moulded into a cylindrical tube 8 mm in diameter and 80 mm in length. The raw electrodes obtained were subjected to heat treatment at 800 °C or 1000 °C in an inert medium. The electrical resistivity obtained by the four-point method showed that N1000 has an electrical resistivity at least five times lower than all the electrodes developed and two times higher than that of G. Fourier-transform infrared spectroscopy (FTIR) was used to determine the compositional features of the samples and their surface roughness was characterised by atomic force microscopy (AFM). Charge transfer was determined by electrical impedance spectroscopy (EIS). The FTIR of the electrodes showed that N1000 has a spectrum that is more similar to that of G compared to the others. The EIS showed the high ionic mobility of the ions and therefore that N1000 has a higher charge transfer compared to G and the others. AFM analysis revealed that N1000 had the highest surface roughness in this study. [ABSTRACT FROM AUTHOR]

This paper presents a new approach to determine more robust shear failure criteria, focusing on rough concrete-rock interfaces. The proposed method could also be applied to rock joints. The new approach is based on the distribution and variety of interfaces numerically tested in terms of surface roughness. For this reason, random field simulations are performed using the turning bands method to generate an extensive database of synthetic rough rock surfaces. With this database of synthetic rough rock surfaces, numerical simulations of direct shear tests are carried out. Finally, analytical and neural network models are proposed using the database of shear strength obtained from the finite element simulations to estimate the peak shear strength of concrete-rock interfaces. The performances of the analytical and neural network models in estimating this peak shear strength are evaluated by computing the percentage error and the mean absolute error (MAE) between the predicted and the numerically obtained values. Both models lead to satisfactory predictions. Nevertheless, it is worth noting that the neural network model mildly outperforms the analytical model regarding the magnitude of the error. Furthermore, the neural network model reproduces the possible non-bijective aspect of the correlation roughness-peak shear strength. Highlights: New methodology to investigate the influence of roughness on the shear behavior of interfaces Methodology to generate databases of synthetic rough rock surfaces with controlled roughness values Establishment of numerical simulations as a strategy to perform extensive virtual experimental studies The correlation between interface roughness and shear strength is not bijective. Assessment of artificial neural network modeling as a complementary alternative to failure criteria [ABSTRACT FROM AUTHOR]

Because oil and gas pipelines reside in high-temperature, high-pressure and highly acidic environments for a long time, it is very common for such pipes to experience corrosion thinning. To solve the long-term online monitoring problem of piezoelectric ultrasonic dry coupling of monitored objects with different surface roughnesses, the effects of different thicknesses of silver plates, different surface roughnesses and different coaxial loads on piezoelectric ultrasonic dry coupling were studied here. To improve the low SNR of the acquired signal, a Batworth high-pass filter and zero-phase digital filter are proposed for online ultrasonic monitoring. The effects of three kinds of roughness and axial load on the piezoelectric ultrasonic dry coupling signal are studied, and the relationship between the roughness, thickness of the silver plate and axial load is obtained. The results show that under different roughness conditions, the SNR of the ultrasonic signal increases with increasing axial load. When the axial load reaches a certain magnitude, the SNR of the ultrasonic signal tends to be stable. When the surface roughness is Ra = 1.6 µm and the thickness of the silver plate is 0.05 mm, the SNR of the ultrasonic signal reaches the best value, and the required axial load is minimal. [ABSTRACT FROM AUTHOR]

The roughness of a joint has a significant influence on the physical and mechanical properties of rock mass, and it is a hot and challenging research topic to determine the joint roughness quickly and accurately. In this paper, based on the random field theory and the traditional roughness evaluation index Z2s, a novel three-dimensional (3D) joint roughness evaluation index named Zσ,θd is proposed. The novel index involves three parameters: the standard deviation (SD) and the scales of fluctuation (SOF) of elevation distribution, which are related to the joint shape, and the sampling interval (SI), which is determined by the sampling method. The 3D joint is generated by the random field method, and the variation of Zσ,θd with SD, SOF, and SI is investigated. The results show that the roughness of the 3D joint generated by the random field method has good robustness, with a maximum fluctuation error of 3.87%. The roughness increases linearly with the increase of SD and decreases exponentially with the increase of SOF and SI, and the fitting formula is obtained. On this basis, the normalization method of Zσ,θd is put forward to eliminate the influence of SI on roughness, and the validity of Zσ,θd is verified by the actual joint in the public database. Finally, the application prospect of this method in the preparation of joint specimens is discussed, and the corresponding 3D surfaces are given according to the 10 typical joint profiles provided by Barton. This paper contributes a quantitative roughness evaluation index and a method for generating the 3D joint, which can serve as a basis for model experiments and numerical calculations. [ABSTRACT FROM AUTHOR]

This article explores the surface architecture formation on layered A3B6 semiconductors, such as In4Se3, InSe, and InTe, focusing on kinetics of surface roughness parameters, such as RMS, skewness and kurtosis, and power spectral density (PSD) under indium deposition studied through large-scale 1 × 1 µm2 and 150 × 150 nm2 scanning tunneling microscopy (STM) images analysis. Our findings reveal common kinetics of surface parameters across different crystals, suggesting fundamental similarities in their interface kinetics. Particularly, PSD analysis elucidates the role of low-frequency spatial structures, underscoring their significance in surface roughness kinetics to some extent independent of the specific layered crystal surface structure. [ABSTRACT FROM AUTHOR]

The solar air heater (SAH), which utilizes solar energy to satisfy the building's heating demands, is an important integrated component of the building. However, SAH's performance isn't good enough for it to be used in building. Adding roughness component to the effective zone of heat transfer underneath the absorber plate is the most successful and efficient technique to augment the thermal performance of solar air heater (SAH). In this regards, artificial roughness consisting of several Multiple Open Trapezoidal Rib (MOTR) has been devised with intention of capitalizing on the benefits of secondary flows with regard to the improvement of heat transmission. The geometrical parameters of MOTRs such as relative limb length (L/w = 0.2–1.0), Reynold number (Re = 2000–16000), relative rib height (e/Dh = 0.023–0.054), and relative roughness pitch (p/e = 6–12) have been exploited, while relative width ratio (W/w = 6) and angle of attack (α = 60°) are maintained constant in all the set of experiments. The highest augmentation in Nusselt number (Nu) is observed as 6.07 times as that of smooth absorber plate. In addition, following empirical correlations have been developed for Nu & f with accuracy of average absolute deviation of 5.47% and 5.02%, respectively. [ABSTRACT FROM AUTHOR]

This paper presents the influence of the preparation of the inspected surface on the deviations obtained when measuring the basic roughness parameters using the contact method. The problems described in the article are often encountered in industry when measurements are performed in mass production conditions, where a short measurement time is extremely important. Presented are the measurement results of five samples made of 1.0503 steel after the grinding process, subjected to various methods of preparation for roughness measurement: sample immediately after treatment, sample after treatment and after evaporation of liquid part of the coolant, sample after blowing with compressed air, sample after blowing with compressed air and washing in isopropyl alcohol, and the sample after blowing with compressed air and washing with acetone. The measurement results obtained from the contact profilometer provide the basis for developing recommendations regarding the preparation of surfaces for inter-operational and final measurements in the production process. [ABSTRACT FROM AUTHOR]

This study addresses this issue by exploring the effectiveness of abrasive water jet drilling (AWJD) as an unconventional machining approach for UHMWPE. The research employs a full factorial analysis to examine various hole characteristics, including machining time (MT), surface roughness (Ra), taper angle (TA), material removal rate (MRR), and taper ratio (TR). The study aims to understand the effect of the process features, namely abrasive water jet pressures (p), traverse rates (v), and abrasive mass flow rates (ma), on the geometry and position of the drilled holes. The results show that (v) and (p) affect the drilled hole characteristics of surface morphology, roughness, MT, MRR, TA, and TR. The microstructural characteristics of the drilled-hole surfaces are analyzed by scanning electron microscopy (SEM). It revealed that the smooth surface is attained at the lower v of 150 mm/min and ma of 250 g/min. [ABSTRACT FROM AUTHOR]

Hybrid composites made of natural fibers are replacing composites made of synthetic fibers, which is better for the environment. In this study, a Cotton/Corn Hybrid Composite was prepared using compression moulding and evaluated the Abrasive Water Jet Machining (AWJM) process variables on surface quality. The AWJM investigations were conducted using experimental design approaches, with variables including water pressure, nozzle transfer speed, and standoff distance. Among these variables, it was determined that nozzle transfer speed had the most influential impact on surface quality. The optimal machining parameters P2, s1, and d1 were identified, resulting in a surface roughness of 4.459 μm. This demonstrates that accomplishing better surface quality is attainable through the suitable parameter selection. Further, the prediction model's efficiency was validated by establishing a strong relationship between the experimental, predicted, and validated surface roughness values. This highlights the model's reliability in predicting and optimizing surface quality in the AWJM process. [ABSTRACT FROM AUTHOR]

This paper deals with problems in determining surface roughness values. The process of determining surface roughness values is a relatively difficult task. In this process, it is necessary to set the measurement conditions, which have a huge impact on the measurement uncertainty, and neglecting this process can cause a complete degradation of the measurement and evaluation result. Certain changes in this process are defined by new standards that have been approved to guide this process. The development of the methodology is very necessary in this area in order to obtain reliable data on surface roughness values. [ABSTRACT FROM AUTHOR]

Important technological advances in the mechanical manufacturing industry have increasingly generated good results with the turning of hardened materials, using polycrystalline cubic boron nitride (PCBN) tools, mainly replacing abrasive processes. The ability to meet project requirements without the need for multiple processes translates into cost reduction and increased productivity. Tool steels play varied and essential roles in various industrial applications, such as dies and punches for forming and cutting. Improvements in the performance of cutting tools are crucial to withstand the severe tribological conditions of the turning process of hardened materials. In this context, this work aimed to evaluate the performance of a PCBN tool in turning quenched and tempered AISI D2 steel, both in continuous cutting and interrupted cutting conditions, in the finishing operation with dry machining. The surface roughness was evaluated in the parameters (Ra, Rt, and Rz), the wear suffered by the tools, their mechanisms, and the morphological analysis of the chips. Tests were carried out with different cutting speeds (60, 130, 200, and 240 m/min), maintaining a constant feed rate of 0.15 mm/rev and a cutting depth of 0.2 mm. The results indicated that the most evident wear was crater and flank in the continuous cut, while in the interrupted cut, there was the presence of chipping and catastrophic failure. Wear mechanisms, such as adhesion (attrition), abrasion, and diffusion, were prominently observed. Furthermore, the tests showed that the increase in flank wear did not necessarily result in an increase in surface roughness, and that the wear mechanism changed with the increase in cutting speed. In the continuous cutting condition, the tool achieved more satisfactory performance, especially at higher cutting speeds (130, 200, and 240 m/min). In interrupted cutting, there is a predominance of catastrophic failure mainly in the ranges of 60 and 130 m/min and better performance at 200 m/min within the ranges evaluated. [ABSTRACT FROM AUTHOR]

Cesium lead iodide (CsPbI3) exhibits great potential in developing photovoltaic cells due to suitable optical bandgap and thermal stability. However, the photoactive γ‐phase normally exists at high‐temperatures ≈180 °C, and it is challenging to obtain γ‐phase CsPbI3 at room temperature. Here, it discovers that γ‐phase CsPbI3 is achievable by reducing the underlayer surface roughness to a certain level. This method is universal as demonstrated on the surface of poly(3,4‐ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS), poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] (PTAA), polystyrene (PS), and silicon substrates. Moreover, it is found that lower surface roughness resulted in smaller crystallite size in the CsPbI3 film, which is an important reason for achieving γ‐phase because the decrease in crystallite size will increase grain surface energy to suppress tilting of PbI6 octahedra and lattice distortion. This study offers a universal approach to obtain γ‐phase CsPbI3 for the development of high‐performance all‐inorganic perovskite solar cells and other optoelectronic devices. [ABSTRACT FROM AUTHOR]

The fabrication of pressure-sensitive adhesives (PSA) using liquid crystal elastomers (LCE) that are tolerant to substrate roughness is explored in this work. Traditional soft adhesives are designed by maintaining a balance between their cohesive strength and compliance. However, rough surfaces can significantly affect the adhesion strength of PSAs. Lowering the stiffness of the adhesive by reducing the cross-linking density or using additives can improve contact on rough surfaces. But this also decreases the cohesive strength and affects the overall performance of the adhesive. Additive-free LCE-based adhesives are shown to overcome these challenges due to their unique properties. Soft elasticity of LCE and low cross-link density contribute to their high compliance, while moderate cross-linking provides finite strength. The effect of contact time and substrate roughness on the adhesive performance is evaluated using probe-tack, indentation, lap shear, and static loading experiments. The unique combination of properties offered by LCE can lead to the development of roughness-tolerant adhesives, thereby broadening the application scope of PSAs. [ABSTRACT FROM AUTHOR]

Insects attach to various surfaces that differ, among others, in roughness and wettability. Identifying surface characteristics that allow or prevent insects from attaching are an important research avenue of pest control. Here we take an experimental approach to analyse the attachment of common bed bugs, Cimex lectularius Linnaeus (1758), to Perspex (PMMA) substrates. We construct a reliable centrifuge device that allows the measurement of attachment forces at substrate roughnesses, Ra, between 0.02 and 1.3 μm and at two wettabilities. Our results suggest that bed bug attachment to surfaces is minimal at a substrate roughness of 0.2 and 0.4 μm on normal PMMA, where the lowest attachment force was 0.8 mN and the safety factor 15. At lower and higher roughness, attachment forces were higher and the safety factor increased to a maximum of 133. On PMMA that was made superhydrophobic by spray‐coating, attachment was lowest (0.2 mN) at the lowest roughness and continuously increased with increasing roughness, reaching 2.5 mN and a safety factor of 46. For every roughness, attachment forces were lower on superhydrophobic than on normal PMMA. This knowledge may inspire the development of repelling substrates for bed bug control. [ABSTRACT FROM AUTHOR]

As-built additively manufactured components for heat exchanger applications, suffer from high surface roughness. In this study, a novel ultrasonic-assisted electropolishing setup is designed and tested to reduce the internal surface roughness of a Laser Powder Bed Fusion (L-PBF) additively manufactured copper (GRCop-42) heat exchanger component. In the electropolishing setup, the surface of the as-built heat exchanger is used as the anode while a bulk copper rod is used as the cathode. An electropolishing fluid consisting of CuCl2, HCl, and SiC abrasive particles was used as electrolyte media, along with ultrasonication. The effect of chemical constituents, ultrasonic duration, and abrasive particles on surface roughness reduction was studied. It was observed that the ultrasonic agitation condition assisted with the abrasive particles was beneficial to reduce the surface roughness of the heat exchanger sample (over 50%) through acoustic streaming and scrubbing effect. An addition of 1% bio-based trihexyltetradecyl phosphonium saccharinate ionic liquid improved the corrosion properties for the copper surface. Overall, to reduce the roughness of L-PBF additively manufactured samples of complicated shapes with internal features, this process could be a viable technique, where mechanical polishing is not possible and internal surfaces are not accessible. [ABSTRACT FROM AUTHOR]

Seasonal changes, sea level rise, and global warming make flood events more frequent, which necessitates watershed management and efficient use of water resources. In this context, understanding the hydrodynamic behavior of basins is critical for the development of flood prevention strategies. The contributions of hydrological and hydraulic modeling techniques in this process are among the key determinants of sustainable water resources management. The Filyos Sub-Basin, located in the Western Black Sea Basin, stands out as one of the regions where flood risk assessment is a priority, as it has two important floodplains. This study aims to analyze the flood risk in the Filyos River Sub-Basin with hydraulic modeling methods, and to determine the Manning roughness coefficient. In the study, the parameters affecting the roughness of the river bed were analyzed using the Cowan method, and the effects of vegetation on river bed resistance were evaluated in the laboratory environment. Flood simulations were carried out for four different flow rates (Q1000, Q500, Q100 and Q50) using the HEC-RAS model, and the performance of flood protection structures were analyzed. The findings show that a significant portion of the existing protection structures are unable to meet the potential flood flows, which can cause serious damage to residential and agricultural areas. In basins with limited historical discharge data, such as the Filyos River, these findings provide important contributions to sustainable water resources management and regional planning processes. The results of the study serve as a reference for flood risk assessment, not only for the Filyos River Basin, but also for other basins with similar hydrodynamic characteristics. It is envisaged that future research, supported by larger data sets, can improve the accuracy of flood simulations. Furthermore, the Cowan method and HEC-RAS model used in this study are expected to contribute to strategic planning and engineering solutions to minimize flood risk in other watershed management projects. In future studies, we plan to further develop methodological approaches for determining the roughness coefficient, and to address applications to increase the effectiveness of flood protection structures. [ABSTRACT FROM AUTHOR]

In the modified formula for the cubic law, the roughness correction coefficient C serves as a parameter that indicates the characteristics of the roughness of a rock's surface. In this study, surface data for natural rock samples were acquired through high-precision 3D scanning and combined with publicly accessible CT scan data on rough rock fractures to generate spatial coordinates. The roughness correction coefficient C was calculated and analyzed using both formulaic and numerical methods. The analysis revealed significant effects of scale on the roughness correction coefficient for rock fractures within a size range of 5 to 10 cm (determined based on the actual sample size), with tensile fractures demonstrating greater variations compared to shear fractures. When calculating the roughness correction coefficient on the same fracture surface in different directions, significant directional effects were observed. Furthermore, elliptical fitting demonstrated favorable results. The conclusion drawn was that the roughness correction coefficient for fracture surfaces can be represented effectively using a tensor form, thereby simplifying the expression of directionality. Calculating and analyzing the fractal dimension of a rough surface further confirmed the existence of effects of size on roughness. [ABSTRACT FROM AUTHOR]

Since the internal structure of actual porous media has irregularity and complexity and is rough on the surface, it cannot be characterized accurately by traditional theoretical analytical methods. In this paper, the mathematical formalism of the effective diffusion coefficient of gas on rough porous surfaces is established by employing fractal geometry theory, utilizing the rough capillary tube bundle model, and introducing the penetration correction factor. The effective gas diffusion coefficient is investigated as a function relation of the rough porous media structural parameters and gas parameters. The results show that the effective diffusion coefficient of gas is positively correlated to the porosity, maximum pore diameter, and area fractal dimension of porous media and negatively correlated to the relative roughness, tortuous fractal dimension, the molar mass of gas, and gas density. The correctness and reliability of the present model have been confirmed, by the comparative analysis of the model predictive values in this paper and the available experimental data. [ABSTRACT FROM AUTHOR]

Background: To overcome the color layering procedure, monochromatic resin composites have been introduced. However, little is known about their polishability, gloss and color stability. This study aimed to investigate the surface roughness, gloss, and color change of monochromatic resin composites polished with wheel systems after being immersed in coffee. Materials and methods: Omnichroma, Zenchroma, Essentia Universal, Charisma Diamond One and NeoSpectra ST were used to obtain 120-disc samples of 8 × 2 mm. Only one side of the sample was polished with Twist Dia (TWD) or Nova Twist (NOV). The samples were examined for surface roughness, gloss, and color (ΔE and ΔE00) before and after 7 days of immersion in coffee and subsequent repolishing. The discs were examined via SEM. Surface roughness and gloss values were analyzed using ANOVA, Tukey and Pearson correlation tests. ΔE and ΔE00 values were evaluated using T tests, multivariate ANOVA, and Dunnett's post-hoc tests. Results: For TWD groups, the smoothest material was Omnichroma (p < 0.05), while for NOV groups, it was Omnichroma and Zenchroma. Omnichroma was the glossiest, while Charisma Diamond One was the least glossy. In TWD groups, Charisma Diamond One and Essentia Universal were the most discolored, while Zenchroma and Omnichroma were the least. For NOV groups, Essentia Universal and Charisma Diamond One were the most discolored, while NeoSpectra ST, Omnichroma and Zenchroma were the least. After repolishing, Charisma Diamond One did not reach the level of ΔE < 2, while the other groups showed values below. Color evaluation with the CIELab and CIEDE2000 systems revealed similar results for the TWD groups after post-staining. Conclusions: Smooth and glossy surfaces could be achieved with the wheel system regardless of the composite resin. Repolishing after discoloration ensures that the color recovery is below the acceptable limit. Color evaluations with CIELab and CIEDE2000 yielded similar results. [ABSTRACT FROM AUTHOR]

Aiming at the difficulty in achieving the control of micro uniform grinding force and the profiling finishing for the traction wheel groove of elevator utilizing the traditional grinding processes, a constrained abrasive flow finishing method was proposed, and the process characteristics for the abrasive flow were studied by means of theoretical modeling, simulation analysis and finishing experiment. Firstly, the principle of the constrained abrasive flow finishing was analyzed, and a hydrodynamic model of the abrasive flow was constructed based on the Eulerian multiphase flow theory and the standard k-ε double equation model. Then, the fluid dynamics characteristics of the abrasive flow within the constrained flow passage were calculated and studied, yielding the variation patterns of fluid dynamic pressure and abrasive pressure on the workpiece surface with the key process parameters. Finally, a constrained abrasive flow finishing experimental platform was established, and the comparative experiments of finishing were conducted using ductile iron as the workpiece material to verify the simulation calculation and the processing method. The research results indicate that the abrasive pressure and the dynamic pressure reach their maximum values within the constrained space, which is the effective finishing area. Within the range of 15 to 75 degrees, the smaller the inlet angle of the constrained space, the more uniform the distribution of the abrasive pressure, and the more intense the fluid dynamic pressure. As the height of the constrained space decreases, the dimensionless material removal rate increases exponentially, resulting in higher processing efficiency. [ABSTRACT FROM AUTHOR]

Approximately 75% of the world's and California's shores are rocky. Rocky shores are of biological interest owing to their diverse and productive species assemblages, where waves and currents play a critical role in larval dispersal and recruitment. Surface variability for nearshore (5⪅depth⪅60m) $(5\lessapprox \mathrm{d}\mathrm{e}\mathrm{p}\mathrm{t}\mathrm{h}\lessapprox 60\hspace*{.5em}\mathrm{m})$ rocky bottoms at intermediate wave scale 1/750

A stable attachment between bubbles and solid particles is essential for flotation. Therefore, it is particularly necessary to study the dynamic process that occur in the attachment of bubbles to a solid surface. In this paper, Teflon and plexiglass plates were used as hydrophobic and hydrophilic solid surfaces, respectively, and solid surfaces with roughness of 0.018 μm to 5.33 μm were prepared by polishing with sandpaper. The influence of roughness on the dynamic process in bubble attachment to solid surfaces with different hydrophobicity was studied via a high-speed camera (750 frames per second). It was found that roughness played a positive role in the attachment to the hydrophobic Teflon surface while a negative role in the attachment to the hydrophilic plexiglass surface in terms of the bubble's attachment to the solid plates. For a smooth Teflon surface, the formation of three–phase contact (i.e., the drainage of wetting film) took up to 95 ms, whereas for a very rough Teflon surface it took only 5 milliseconds. On the contrary, the high roughness prevented the bubble from attaching to the hydrophilic plexiglass surface. It was concluded that the increased roughness of Teflon plates was conductive to air entrapment in surface irregularities, inducing the rapid rupture of the wetting film on a very rough Teflon surface, while the increased roughness of the plexiglass plates resulted in "water pockets" in surface grooves, making the wetting film on the plexiglass surface stable. [ABSTRACT FROM AUTHOR]

The paper presents an analysis of the filler's effect on the machining process and on changes in the thermomechanical properties of polymer composites based on aluminum chips. Composite research samples with a polymer matrix in the form of polyamide 6 were made by the pressing method. Comparative studies were carried out on the changes in thermomechanical properties and structure of the obtained molders with different filler contents and different fractions after the machining process. In order to determine the changes in thermal and mechanical properties, analysis was carried out using the differential scanning calorimetry (DSC) method, thermal analysis of dynamic mechanical properties (DMTA) and a detailed stereometric analysis of the surface. After mechanical processing, roughness amplitude parameters and volumetric functional parameters were determined. In order to analyze the structure, tomographic examinations of the manufactured composite were conducted. In relation to the polymer matrix, a significant increase in the storage modulus of the composites was noted in the entire temperature range of the study. An increase in the enthalpy of melting of the matrix was noted in composites with a lower filler content and a shift in the melting range of the crystalline phase. Significant differences were noted in the study of the composite surfaces in the case of using fillers obtained after machining with different fractions. The dependencies of the functional and amplitude parameters of the surfaces after machining of composite samples prove the change in the functional properties of the surface. The use of aluminum chips in the composite significantly changed the surface geometry. [ABSTRACT FROM AUTHOR]

Shear fracture is a significant failure mechanism in particular disaster such as fault slips and rockbursts in deep rock engineering, which frequently involve in-situ stress and disturbance loads from earthquakes or blasting. Studying the dynamic shear fracture behavior of rocks under confining pressure is crucial for disaster prevention. This study performed a series of dynamic mode II fracture tests under different confining pressures using granite short core in compression (SCC) specimens via a modified triaxial split Hopkinson pressure bar (SHPB) system. It is discovered that (1) dynamic mode II fracture toughness increases as loading rate and confining pressure rise; (2) The Linear relationship between dynamic or static fracture toughness and confining pressure is independent of loading rate. An empirical equation was presented to quantify relationship between fracture toughness, confining pressure and loading rate. The final failure degree of SCC specimens aggravates as the loading rate increases or confining pressures reduce. The morphological features of fracture surfaces were quantitatively investigated using fractal and statistical theories. It was observed that roughness in dynamic fracture surfaces decreases with increased in confining pressures and loading rates. Statistical analyses on asperity height h and slope angle α indicate that the undulation of fracture surfaces decreases with confining pressure at a given loading rate, validating the fractal results. A new index, namely the number of dominant intervals (NDI), is proposed to quantify the degree of aspect orientation distribution concentration. Generally, there is a notable trend of reducing NDI with confining pressures and loading rates. Highlights: Conducting dynamic mode II fracture tests on granite short core in compression specimens under different confining pressures. Quantitatively obtaining the relationship between dynamic mode II fracture toughness and the confining pressure, loading rate and axial stress. The roughness of dynamic mode II fracture surface decreases with the increased confining pressures and loading rates. Investigating the morphological features such as asperity height and slope angle of dynamic shear fracture surfaces by using statistical methods. [ABSTRACT FROM AUTHOR]

The present paper gives an overview of the recent modelling activities under NATO-STO AVT-349, focussed on the understanding and modelling of boundary layers for incompressible, high-Reynolds-number flows subject to non-equilibrium conditions such as strong pressure gradients, three-dimensionality, and surface roughness and heterogeneity. For this, we consider simpler cases where the above flow conditions are present separately or in a reduced number of combinations. First, we focus on the effect of roughness on the outer flow and the problems associated to its characterisation and prediction, with a particular emphasis on the conditions necessary for outer-layer similarity to hold. We then focus on how the presence of adverse and favourable pressure gradients affects the effect of roughness, and to what extent the figures used to quantify it are still useful under such conditions. We also consider the effect of surface heterogeneity, the shortcomings when modelling it and how these can be addressed. We then focus on the effect on the outer layer of pressure gradients and non-equilibrium conditions, to what extent similarity holds in those conditions, and how RANS models perform for such flows, identifying routes for their improvement to handle pressure gradients and non-equilibrium. We also discuss the use of data-driven and machine-aided methods in closure models. [ABSTRACT FROM AUTHOR]

Stainless steels 316 and 304 are among the alloys commonly used to make medical equipment, including surgical instruments. These steels, however, do not exhibit properties that control bacterial growth or destroy bacteria upon contact, leading to significant contamination. This problem can be largely mitigated by applying coatings with high antibacterial properties. One such coating that has attracted considerable attention from researchers, in recent years, is Zr-based metallic glass coatings. In this study, after studying the effects of different elements on the antibacterial behavior of coatings, an alloy with the chemical composition of Zr30Cu20Al10Ag10Cr10Si10B10 was designed and produced. A thin layer of this amorphous alloy was then applied to a 316 stainless steel substrate, and its behavior against two common hospital bacteria was studied. After weighing and mixing the selected elements in the required stoichiometric ratios and homogenizing them using a mechanical ball mill, a target with the desired chemical composition was produced using Spark Plasma Sintering (SPS). Structural investigations revealed a uniform distribution of the elements in the produced target. Using this target, thin layers of the alloy with different thicknesses were deposited on the 316 stainless steel substrate. Preliminary investigations showed that the coatings, in addition to forming a good bond with the substrate, possess a glassy and amorphous structure. The antibacterial behavior of the coatings against Escherichia Coli and Staphylococcus Aureus was then investigated. The results showed that the coatings, due to the presence of copper and silver, exhibit high antibacterial properties against these bacteria. Furthermore, the application of the coating, which reduces the roughness of the polished 316 substrate by 50%, can significantly affect the adhesion of human and animal blood platelets, as well as human and animal cancer cells, to surgical instruments made from 316 stainless steel. [ABSTRACT FROM AUTHOR]

Ceramic dental restorative materials have growing popularity, albeit their brittle and stochastic nature are acknowledged shortcomings that impact the prosthesis lifespan. The mechanical performance of ceramics is dominated by the constitutional microstructural and fracture toughness mechanisms, as well as externally applied triggers. Thus, there is ongoing expanding research in the sphere of ceramic material engineering and thermal refinement, addressing concerns regarding toughness, machinability, reliability, stainability, and biodegradation. While the current trend in dental ceramic manufacturing has transitioned from micrometric crystalline sizes to submicrometric and nanometric ranges, there is an unclear understanding of the microstructural implications on ceramic behaviour. Therefore, this review covers the comprehensive characterisation approaches commonly employed in the scientific literature to describe the multifaceted performance aspects as well as clinical-related prerequisites of dental ceramics. Moreover, updated standardised testing parameters and performance thresholds pertaining to ceramic mannerisms are described in an attempt to translate their clinical applicability. [ABSTRACT FROM AUTHOR]

This work investigates the characterization of a cryo-processed AlTiN-coated tool and its turning characteristics for Inconel 600. The microhardness was enhanced by 3.68% under cryo-treatment when compared with the as-received condition of the inserts because of the wear-protective coating formed on the surfaces of the cutting tool. This was confirmed through EDS elemental analysis of carbon element growth and change in chemical composition, as well as XRD phase analysis. Next, this work studied the influence of cryo-treated inserts on roughness and mechanism of wear during turning Inconel 600 using varying cutting velocities (37, 60, and 100 m/min) under dry conditions. The output responses revealed that the use of cryo-treated tools reduced the roughness of the product by 11–27% and the rate of tool wear when compared with the untreated conditions. Due to these enhanced properties with cryo-treated conditions, it remains a suitable cutting tool for a significant contribution to sustainable machining toward dry cutting of aerospace alloys. [ABSTRACT FROM AUTHOR]

Low thermal diffusivity of NiTi-based smart alloy results in concentrated heat accumulation during laser beam machining which rises to adverse thermal effects like heat-affected zones, residual stresses, and alterations in microstructure of shape memory alloy (SMA) system. The addition of Cu and Zr can reduce the thermal hysteresis in the phase transformation of NiTi SMAs. Minimizing thermal hysteresis is desirable in SMA applications where precise control of the phase transformation temperatures is required, such as in actuators, sensors, and medical devices. Therefore, aqua jet integrated laser (AJ-FLBM) machining is a suitable choice for smart materials that need to be machined with high precision and low heat affected zone. In this current research, the NiTiCuZr SMA is machined using AJ-FLBM to investigate the effects of process variables on surface characteristics measured using RSM-BBD approach. The surface quality was enhanced by 68.93% with a gradual decrease in laser power (P), cutting speed (CS), and an increase in frequency (F). Aqua jet integrated FLBM technique may reduce heat affected zone due to the removal of heat in areas near the cutting location. This was confirmed by the DSC test which reveals that optimal machining inputs do not alter shape memory properties. [ABSTRACT FROM AUTHOR]

Currently, the majority of industries rely on turning processes to manufacture mechanical products. The selection of coolant is of paramount importance in the pursuit of sustainable manufacturing. Super duplex steel's machinability during the turning process is the subject of the present investigation. The machining characteristics, such as Flank wear (Fw) and Surface roughness (Ra), were analyzed by varying the control parameters, including cutting velocity (Vs), feed rate (f), and cutting conditions i.e. Dry, Nanofluid + MQL (NMQL), LN2 + MQL (LMQL), through a constant depth of cut (d) using a Taguchi L27 orthogonal array. The results demonstrated that the LMQL approach is more efficient as it reduces the Ra by 77%, 54%, and Fw by 83%, and 93%, respectively, in comparison to the dry and NMQL conditions. Additional research on microstructure revealed that the character of the grains is improved when the surface is machined with LMQL in comparison to other cutting conditions. [ABSTRACT FROM AUTHOR]

This article delves into optimizing and modeling the input parameters for the selective laser melting (SLM) process on Inconel 625. The primary aim is to investigate the microstructure within the interlayer regions post-process optimization. For this study, 100 layers with a thickness of 40 µm each were produced. Utilizing the design of experiments (DOE) methodology and employing the Response Surface Method (RSM), the SLM process was optimized. Input parameters such as laser power (LP) and hatch distance (HD) were considered, while changes in microhardness and roughness, Ra, were taken as the responses. Sample microstructure and surface alterations were assessed via scanning electron microscopy (SEM) analysis to ascertain how many defects and properties of Inconel 625 can be controlled using DOE. Porosity and lack of fusion, which were due to rapid post-powder melting solidification, prompted detailed analysis of the flaws both on the surfaces of and in terms of the internal aspects of the samples. An understanding of the formation of these imperfections can help refine the process for enhanced integrity and performance of Inconel 625 printed material. Even slight directional changes in the columnar dendrite structures are discernible within the layers. The microstructural characteristics observed in these samples are directly related to the parameters of the SLM process. In this study, the bulk samples achieved a microhardness of 452 HV, with the minimum surface roughness recorded at 9.9 µm. The objective of this research was to use the Response Surface Method (RSM) to optimize the parameters to result in the minimum surface roughness and maximum microhardness of the samples. [ABSTRACT FROM AUTHOR]

Machining of metal matrix composites (MMC) is a challenging process as they are difficult to cut and cutting tools get worn out in a short time. In this paper, the performance of two industrial carbide grades and a cubic boron nitride (CBN) tool are assessed when machining of AZ91/SiC composites. Mg-based composites with different volume fractions and particle sizes are machined at various cutting conditions to evaluate the tools wear resistance and finished surface. The surface of the worn-out tools and machined samples are analyzed by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and roughness tester. Results revealed that the tool wear increased for composites reinforced by smaller particles regardless of the tool type. Additionally, tool grade TH1000 resulted in longer tool life when machining of Mg-based composites compared to the CP500 grade so that at a cutting speed of 70 m/min and feed rate of 0.1 mm/rev, tool life improved nearly 250%. CBN tools showed the best performance when machining of Mg-based composites as tools became worn out after 255 s which is considerable compared to carbide tools. Also, the finished surface caused by cemented carbide CP500 indicated the worst quality. [ABSTRACT FROM AUTHOR]

Aim: The study aimed to compare the depth of cure, hardness, surface roughness, and wear resistance of four restorative materials used in pediatric dentistry: FUJI IX GP FAST, RivaSilver, SDR flow+, and Vertise Flow. Materials and Methods: The depth of cure was measured per ISO 4049 standards using a digital caliper, with 15 samples of each material. Hardness was evaluated using a Vickers indenter under a 10 N load for 20 s. Surface roughness was assessed before and after acid exposure using an optical profilometer according to ISO 4288. Brushing wear resistance was analyzed by subjecting samples to 20 and 60 min of brushing, followed by roughness measurements. Statistical analysis was performed using independent sample t-tests to determine the significance of differences between the materials, with p-values < 0.05 considered significant. Results: SDR flow+ exhibited the highest depth of cure with an average of 3.5 mm (±0.2 mm), significantly higher than Vertise Flow at 2.8 mm (±0.3 mm) (p < 0.001). Hardness testing revealed SDR flow+ had the highest average hardness (85 HV ± 4 HV), while Vertise Flow had the lowest (72 HV ± 5 HV) (p < 0.001). Surface roughness increased significantly after acid exposure for RivaSilver (from 1.2 μm ± 0.12 μm to 1.6 μm ± 0.15 μm, p = 0.007) and for SDR flow+ (from 0.85 μm ± 0.08 μm to 1.3 μm ± 0.14 μm, p = 0.001). Brushing wear resistance was highest in RivaSilver (Ra increase from 1.2 μm to 1.4 μm ± 0.11 μm) and lowest in FUJI IX GP FAST (Ra increase from 1.5 μm to 1.9 μm ± 0.15 μm, p < 0.001). Conclusions: The study demonstrates significant differences in performance among the tested materials. SDR flow+ showed a superior depth of cure and hardness, making it suitable for high-stress applications. However, all materials displayed increased surface roughness following acid exposure and brushing, with FUJI IX GP FAST showing the highest wear. These findings highlight the need to select restorative materials based on the specific clinical demands of pediatric patients, considering both their mechanical properties and resistance to wear and acid. [ABSTRACT FROM AUTHOR]

The crystal structure and composition of the Co–Ni–Fe films has been analyzed, and the effect of the deposition rate on the coefficient dB/dH of conversion of a weak magnetic field into the magnetic induction has been established. The presence of oxygen on the film surface indicates the porosity of the Co–Ni–Fe film structure, which is confirmed by the surface roughness. Electrochemical deposition from a chloride electrolyte has demonstrated the possibility of controlling the magnetic properties of the films by improving the deposition technique. The chloride electrolyte with filtration and boric acid, saccharin, and hydrochloric acid additives in a concentration ratio of CCo : CNi : CFe = 1 : 1 : 1 ensures, at a temperature of 70°C, the reproducible electrochemical deposition of the Co–Ni–Fe films with low stresses, a uniform structure, and a high coefficient of conversion of a weak magnetic field into the magnetic induction. [ABSTRACT FROM AUTHOR]

Gyrofinishing is a mass-finishing process used for large and/or complex workpieces. In this process, abrasive media filled in a container are accelerated by rotating the container, impacting the workpiece fixed in it and smoothing the workpiece surface. In this study, the effects of the materials and sizes of the abrasive media on the surface roughness, microstructure, and residual stress on the specimen surface developed by gyrofinishing were revealed. The surface of the gyrofinished specimen was smooth. However, the specimen surface when using the HS medium, consisting of a mixture of ceramic and small abrasive grains, was slightly rougher compared to that finished using the PS medium, consisting of ceramic. An ultra-fine grained structure was formed at the surface after gyrofinishing, regardless of medium. A flow of the microstructure was observed in the specimens gyrofinished with the HS media, indicating that shear stress occurred during gyrofinishing. All the gyrofinished specimens exhibited a significant compressive residual stress near the surface. The residual-stress profile along the depth direction differed depending on the material and size of the media. The small media shallowed the depth of the maximum compressive residual stress (dmax), whereas the medium size hardly affected the maximum compressive residual stress (·max). The measured dmax was significantly smaller than the dmax value estimated based on the Hertz contact theory, which is likely due to the shear stress generated by the rotation or sliding of the media on the specimen surface during gyrofinishing. The specimens gyrofinished using the HS series had a higher ·max than those gyrofinised using the PS series. The rough surface of the HS medium is expected to introduce a high compressive residual stress through the burnishing effect. It can be concluded that gyrofinishing provides the specimen surface with a smooth, ultra-fine grained structure and significant compressive residual stress. [ABSTRACT FROM AUTHOR]

Explant analysis can provide important understanding of how artificial joints perform in the human body. The articulating surfaces of the metacarpal head and the radius cup from a chromium nitride coated metal-on-metal Motec wrist implant were analysed. Due to bone resorption and aseptic loosening, the implant was removed after 6 years in the patient, and metallosis was observed during removal. Visually, some areas of the articulating surfaces appeared polished, others were dulled. A chemical composition analysis of the metacarpal head showed that the polished surfaces were chromium rich, implying this surface was the original chromium nitride coating, whereas the dulled surfaces were cobalt rich, indicating the underlying cobalt chromium substrate. In addition, the underlying cobalt chromium substrate was an order of magnitude rougher than the polished surface, indicating the scale of damage to it. It is speculated that the loss of the coating, and the subsequent damage to the underlying substrate due to a third-body wear process, led to osteolysis and the metallosis seen at revision surgery. [ABSTRACT FROM AUTHOR]

AbstractTitanium alloys are important engineering materials used in various industry areas, such as aviation, aerospace and medical devices. The surface roughness is a significant parameter for assessing the machining quality of titanium alloys. In this study, in order to compare the effects of dry and wet milling conditions on the surface roughness of titanium alloys, we established a test system to obtain the surface roughness, three-dimensional milling vibration and three-dimensional milling force signals. The gray correlation theory was applied to investigate the correlation between surface roughness and milling vibration or milling force under dry and wet milling conditions. Using the least squares method, the prediction models of surface roughness corresponding to dry and wet milling conditions were developed according to the features of vibration or force signals. Furthermore, the combined prediction models of surface roughness that integrate multiple signal features and milling parameters were established. The comparison results revealed that there was a stronger correlation between roughness and milling force, milling vibration in wet milling. Wet milling exhibited significantly lower roughness compared to dry milling under the same machining parameters, with up to a 59% reduction. The correlation coefficient of the wet milling model is as high as 0.95. [ABSTRACT FROM AUTHOR]

Residual stresses and surface roughness have been recognized to play a critical role in the fatigue strength of metal components. Machining processes can induce different roughness and residual stress conditions depending on the parameters used in the process. Therefore, it is essential to develop knowledge that helps to predict the residual stresses and roughness that would be obtained from different machining conditions. Due to the growing interest from the industry in the use of 42CrMo4 steel because of its excellent mechanical properties, the main objective of this work is to establish two phenomenological models to accurately predict the residual stress and roughness values in turned specimens of this material. The models are derived from data of four process variables: (a) insert tip radius; (b) feed rate; (c) cutting speed; and (d) depth of cut. For this purpose, a wide experimental campaign has been developed, which includes the machining of 68 specimens under various cutting scenarios, and their subsequent measurement of residual stresses and roughness. Once the experimental data were obtained, the response surface method based on the central composite design was used to fit the models, obtaining a correlation index R 2 higher than 0.9 in both cases. In this article, it is concluded that feed rate and insert radius have a greater effect on the residual stress and roughness obtained, while cutting speed and depth of cut have a lesser impact on the results. It is hoped that the findings will establish a groundwork for the machining of this material type, ensuring controlled conditions of residual stress and roughness. [ABSTRACT FROM AUTHOR]

This study investigates the tribological properties of graphite foils (GF) with densities of 1.0, 1.3, and 1.6 g/cm3, produced from purified natural graphite of different particle sizes (40–80 μm, 160–200 μm, >500 μm). Surface roughness was measured after cold rolling and friction testing at static (0.001 mm/s) and dynamic conditions (0.1 Hz and 1 Hz). Results showed that static friction tests yielded similar roughness values (Sa ≈ 0.5–0.7 μm, Sq ≈ 0.5–1.0 μm) across all densities and particle sizes. Dynamic friction tests revealed increased roughness (Sa from 0.7 to 3.5 μm, Sq from 1.0 to 6.0–7.0 μm). Friction coefficients (µ) decreased with higher sliding speeds, ranging from 0.22 to 0.13. GF with 40–80 μm particles had the lowest friction coefficient (µ = 0.13–0.15), while 160–200 μm particles had the highest (µ = 0.15–0.22). Density changes had minimal impact on friction for the 40–80 μm fraction but reduced friction for the 160–200 μm fraction. Young's modulus increased with density and decreased with particle size, showing values from 127–274 MPa for 40–80 μm, 104–212 MPa for 160–200 μm, and 82–184 MPa for >500 μm. The stress–strain state in the graphite foil samples was simulated under normal and tangential loads. This makes it possible to investigate the effect of the anisotropy of the material on the stress concentration inside the sample, as well as to estimate the elasticity modulus under normal compression. Structural analyses indicated greater plastic deformation in GF with 40–80 μm particles, reducing coherent-scattering region size from 28 nm to 24 nm. GF samples from 160–200 μm and >500 μm fractions showed similar changes, expanding with density increase from 18 nm to 22 nm. Misorientation angles of GF nanocrystallites decreased from 30° to 27° along the rolling direction (RD). The coherent scattering regions of GF with 40–80 μm particles increased, but no significant changes in the coherent scattering regions were observed for the 160–200 μm and >500 μm fractions during dynamic friction tests. Microstrains and residual macrostresses in GF increased with density for all fractions, expanding under higher friction-induced loads. Higher values of both stresses indicate a higher level of accumulated deformation, which appears to be an additional factor affecting the samples during friction testing. This is reflected in the correlation of the results with the roughness and friction coefficient data of the tested samples. [ABSTRACT FROM AUTHOR]

Infiltration parameters and roughness are essential parameters in the design and management of furrow irrigation. Accurate determination of these parameters is essential for achieving reliable irrigation techniques and improving furrow irrigation performance. Therefore, this study proposed a method combining least squares support vector machines (LSSVM) and genetic algorithm (GA) to invert infiltration parameters and roughness. During the parameters inversion, it is necessary to know the simulated values of advance and recession time to construct the objective function, but the relationship between the furrow irrigation advance, recession time and soil infiltration parameters and roughness is implicit in the zero-inertia model, lacking a direct solution. Manually inputting parameters into WinSRFR for validation would severely hinder the efficiency of parameter estimation. Therefore, this study utilized LSSVM to map the complex nonlinear relationship the furrow irrigation advance, recession times and soil infiltration parameters and roughness. The advance time LSSVM regression model (regularization constant 60, RBF kernel width 35) and recession time LSSVM regression model (regularization constant 70, RBF kernel width 20) were constructed. Results showed that the root mean square error (RMSE) for advance and recession time in training samples ranged from 0.84 to 1.75 min and 2.18 to 3.16 min, respectively. For testing samples, the RMSE values ranged from 0.85 to 1.77 min and 2.41 to 3.62 min, demonstrating high prediction accuracy. This approach reduces the computational burden of manual input in WinSRFR by using LSSVM regression models to simulate advance/recession time, thus facilitating parameter estimation with GA. The key to implementing the LSSVM-GA method lies in the data transfer and iteration between LSSVM and GA when calculating the fitness function. To further verify the reliability of the proposed method, furrow irrigation experiments were conducted on closed-end furrows in cornfields in Shuangzhao Village, Xianyang, Shaanxi Province, China. Two typical furrow lengths were selected, each with two test plots to observe the actual advance and recession times. Each scheme was repeated three times, and the final experimental data were averaged. Multiple nonlinear regression (MNR) and Merriam-Keller post-irrigation volume balance analysis (MK-PIVB) from WinSRFR were also used for comparison. Results indicated that for the advance process simulation, the parameters estimated by MK-PIVB and LSSVM-GA provided similar curves, with RMSE ranging from 1.30 to 2.94 min and coefficient of determination (R²) from 0.97 to 0.99. In contrast, MNR performed slightly worse, particularly for F1, with an RMSE of 5.52 min. Further analysis of the recession process showed that MNR's parameter estimates were not ideal, with RMSE ranging from 4.77 to 6.00 min and R² below 0.60. MK-PIVB's estimates were satisfactory only for F2, but were inaccurate for the other three furrows with RMSE of 4.75, 4.13, and 4.18 minutes and R² of 0.49, 0.70, and 0.54, respectively. The LSSVM-GA method provided improved parameter estimates for both processes, with RMSEs ranging from 1.06 to 2.12 minutes for advance and 2.28 to 3.11 minutes for recession. The LSSVM-GA method effectively combined nonlinear mapping and heuristic algorithms, overcoming the limitations of the other two methods, such as the need for predefined regression functions, reliance on manual experience and judgment, and high computational cost. [ABSTRACT FROM AUTHOR]

The joint effect of rectangular-type roughness and horizontal vibration on two-dimensional (2D) turbulent Rayleigh–Bénard convection (RBC) is investigated by using the thermal lattice Boltzmann method (LBM) in this article. The present work focuses on the Nusselt number and plume dynamics of the convection in the range of dimensionless vibration frequency 0 ≤ ω* ≤ 1000 and the range of dimensionless roughness height 0 ≤ h* ≤ 0.05. The Rayleigh number is 108 and Prandtl number is 4.38. Our numerical results indicate that the relationship between the Nusselt number and roughness height is mostly proportional, and the relationship between the Nusselt number and the vibration frequency is exponential. It is further found that heat transfer enhances by 3.06 times under the joint effect of horizontal vibration and rectangular roughness on turbulent RBC. It provides significant physical insight into the mechanism of cooperative heat transfer enhancement. [ABSTRACT FROM AUTHOR]

Polycrystalline diamond (PCD) is widely used for micro tools due to its high hardness and wear resistance. However, micro PCD tools face challenges in machining with high accuracy and efficiency. Therefore, electrical discharge machining grinding (EDM-grinding) composite machining was proposed. The effects of pulse discharge parameters on surface quality and microhole drilling performance of PCD tool were investigated. The results show that the surface roughness of helix flute and flank face of the fabricated PCD tool were 0.125 µm and 0.158 µm, respectively, as well as the inner wall roughness achieved 0.331 µm after drilling of microhole. The average current displayed a greater effect on the machining quality of PCD tools, with tool breakage in excessive average current. The preferred pulse discharge parameters were determined as an open-circuit voltage of 95 V, an average current of 1400 mA, a pulse width of 400 ns, and a pulse interval of 2000 ns. [ABSTRACT FROM AUTHOR]

Abrasive Flow Machining (AFM) is highly effective for precise surface control and finishing. The process's material removal mechanism significantly impacts surface quality, especially in complex parts. However, little research addresses how initial micro-surface textures affect AFM outcomes. This study prepared four types of initial surface profiles and machined them using various abrasive media particle sizes. The rheology of the abrasive media was analyzed, with a custom guide restricting the fluid domain to create gradient flow changes. Both experimental and simulated one-way and two-way AFM processes were conducted. Results demonstrated that the material removal efficiency improved according to an enhanced version of Preston's equation for flat surfaces. Initial surface textures exerted more influence on material removal than anticipated. All abrasive media sizes yielded uniform surface quality, with surface roughness improvements exceeding 80%. Larger initial surface textures experienced greater material removal. Chemical element analysis confirmed the AFM process is contamination-free. [ABSTRACT FROM AUTHOR]