High Angle Research Articles

Numerical investigation into effects of slot control on flow around wind turbine blades

This paper investigates the effects of slots on wind turbine blade sections on the reduction of fluid loads on the airfoil in turbulent flows. The governing conversation equations were discretized using the finite volume method (FVM), numerically simulating an unsteady flow with a turbulent regime. It was found that slots at ΨA70° and high angles of attack (AOAs) improved the aerodynamic performance of the airfoil and delayed the stall by 2°. The Cl-Cd ratio was 31.49%, 79.22%, and 29.66% higher in the slotted airfoil than in the non-slotted one at an AOA of 18°, 20°, and 22°, respectively. Furthermore, slots with ΨA70° at AOAs of 20° and 22° substantially reduced lift and drag variations on the airfoil.

Clustering technical approaches of elite and world-class pole vaulters based on 10 years of measurement during competitions

ABSTRACT Recently, a variety of technical approaches in world-class pole-vaulters’ behaviour have been observed. The aim of this study was to investigate the presence of subgroups using different technical approaches and to compare biomechanical performance differences. Biomechanical analysis of performances over 5.00 metres from 99 athletes were clustered with K-means methodology based on the relative position of the top hand at take-off and the direction of the top of the pole from take-off to the maximal pole bending. Analysis revealed four subgroups that were distinguished by higher and lower direction angle and relative position values. Despite differences in technique, the analysis did not reveal significant differences between these four groups in performance, take-off speed, or athlete anthropometrics. Nevertheless, these clusters showcased variations in pole–athlete interactions and pole bending, suggesting different strategies and physical requirements associated with each approach. Cluster 2 characterised the classical technique with a high direction angle and a take-off position close to the vertical plane. Cluster 4 displayed a technique with a low take-off angle, suggesting the influence of athletes like Lavillenie, in deviating from the conventional model. Understanding and categorising athletes based on their preferred technique can aid coaches in providing tailored instructions, leading to performance improvements.

One-step fabrication of multifunctional superhydrophobic copper surfaces via laser-assisted ablation PDMS solution

The super-hydrophobic surfaces have been greatly restricted in multi-functional applications because of the poor surface durability and multi-step processes such as preparing rough structures and low surface energy modification. In this work, a multifunctional wear-resistant super-hydrophobic surface (SHS) was primarily developed by one step laser etching polydimethylsiloxane (PDMS) i.e. the uncured PDMS layer was laser-ablated just after it was coated on the surface of copper. The wettability, morphology and chemical composition of the surfaces were characterized by a contact Angle measuring instrument, scanning electron microscope (SEM) and Fourier transform infrared spectrometer (FTIR). The results show that the developed SHS has the high contact angle (WCA) of 156.8° and low sliding angle (WSA) of 4.6°; which presents a regular linear grating array and a large number of coral-like rough structures, and the developed SHS can withstand at least 120 tape stripping tests, 40 sandpaper friction abrasion tests, 60 h of high temperature treatment (100 °C∼300 °C) or 240 h of ultraviolet light exposure tests, respectively. The self-cleaning rate and anti-fouling rate of the SHS were 94.2 % and 91.8 %, respectively, and the freezing time of droplets on the SHS is 162 s longer than that on the original copper surface, and almost 3 times longer than that on the smooth surface. In all, the non-polluting wear-resistant multifunctional SHS was primarily developed by laser ablation of metals and polymers, which has strong potential usage in the fields of anti-fouling of industrial pipeline systems and anti-icing of outdoor power transmission systems.

Solar radiation on naturally ventilated double skin facade in real climates: the impact of solar incidence angle

Although the angular dependence of optical properties has long been recognised in transparent glazing facades, the impact of such dependence on natural ventilation between glazing has not been widely studied, especially in building facades with high solar incident angles. To better cope with such properties with the prevailing implementation of transparent building envelopes, this study investigated the effects of high solar incidence angles for vertical building facades through theoretical and numerical methods. The theoretical model validates the features of the optical properties simulated by the numerical model, supporting the numerical model’s capability of revealing the radiation reflection, absorption, and transmission when multi-reflection is present. Then, such angular impact is studied with typical seasonal data in three cities, namely Shanghai, Melbourne and Chicago. Results firstly revealed the discrepancies between considering or ignoring multi-reflection between two glazing facades at varying incidence angles. Due to the opposite variation trend in reflectivity and transmissivity over angles, there is a critical solar incidence angle at 75˚ when multi-reflection’s impact on natural ventilation reaches its highest. After that, the influence is reduced to its minimum. Identifying this angle helped highlight the enhanced natural flow due to realistic angular-dependent reflections between transparent panes, namely, under-estimation occurs if the angular dependence is not considered in the setting of optical properties. The analysis in three cities also revealed the climatic and locational impact of the angular impacts on ventilation rates. By addressing the impact on the optical and thermal performance of transparent facades, the dynamic variation of solar conditions can be more accurately integrated into passive building designs.

Association between dietary variety status and sarcopenia as defined by the Asian Working Group for Sarcopenia 2019 consensus in older outpatients at a hospital specializing in geriatric medicine: A cross‑sectional study with baseline data of prospective cohort study (JUSTICE‑TOKYO study).

To the best of our knowledge, little is known about the association between dietary variety status and sarcopenia in university-affiliated geriatric hospital in elderly. The present study aimed to investigate, in a multidisciplinary setting, the prevalence of sarcopenia and association between dietary variety status and sarcopenia in older outpatients at Juntendo Tokyo Koto Geriatric Medical Center (Tokyo, Japan). Between October 2020 and December 2021, a cross-sectional study of outpatients aged ≥65 years [458 male (44%) and 584 female (56%); mean age, 78.2±6.1 years] was conducted to assess prevalence of sarcopenia, according to Asian Working Group for Sarcopenia 2019 criteria, and the relationship between dietary variety status and sarcopenia. Patient profile, comorbidities, drug use, neuropsychological data, abdominal symptoms, pulmonary function and dietary variety status were collected. Of 1,042 subjects, there were 223 (21.4%) with [142 male (63.7%) and 81 female (36.3%); mean age, 80.6±6.3 years] and 819 (78.6%) without sarcopenia [316 male (38.6%) and 503 female (61.4%); mean age, 77.6±5.8]. In multivariate analysis, older age, male sex, low body mass index, high Brinkman Index and phase angle, low quality of life, history of daycare use, diabetes mellitus, osteoporosis and low Mini-Mental State Examination and Dietary Variety Score were related to sarcopenia. The prevalence of sarcopenia was higher in than in community-dwelling individuals. Dietary variety status was associated with sarcopenia.

Effect of physicochemical properties on critical sinking and attachment of respirable coal mine dust impacting on a water surface

Respirable coal mine dust (RCMD) inhalation is identified as the main cause of the resurgence of coal worker’s pneumoconiosis (CWP) since the mid-1990s. At present, the predominant dust control technology is the water spray system. However, in practice, the capture efficiency of RCMD by this technology is relatively low. To understand the capturing mechanism and develop improvement strategies, this research is focused on the surface chemistry study of RCMD and its impact on a water surface using a dynamic model. Proximate analysis, chemical, and mineral composition of a run-of-mine (ROM) coal sample from Appalachian region were analyzed using a proximate analyzer, Inductively Coupled Plasma Mass Spectrometry (ICP-MS), and X-ray Diffraction (XRD), respectively. Contact angles were measured by capillary rise test using the Washburn equation. Based on the dynamic model, the effects of particle size, density, contact angle, and surface tension on the critical sinking were investigated. It was pointed out in this work that reducing surface tension, in turn, decreases contact angle, which has been neglected in the literature. Regime maps for different minerals were created and showed that organic matter has the highest critical velocity due to its low density and high contact angle. Reducing water surface tension to the critical solid surface tension of coal around 30 mN/m could maximize the attachment efficiency. Scaling laws, constructed by force balance, led to the criteria of critical sinking: Ucr61-cosθ2D+1γlvρlR, i.e., Wecr121-cosθ2D+1. A semi-empirical formula for critical velocity was obtained by fitting the simulation data, Ucr=1.0961-cosθ2D+1γlvρlR. Attachment efficiency was defined and formulated as Pa=U02Ucr2=We0Wecr, establishing relationships between attachment efficiency and the physicochemical properties of RCMD and water droplets

Relationship between microstructure and mechanical properties of V-N microalloyed high strength ship plate steel

V-N microalloying treatment is an important way to improve the service performance of non-quenched and tempered ship plate steel. Herein, the influence of V(C, N) on the evolution of microstructure and improvement of mechanical properties was studied. In addition, the relationship between microstructure and mechanical properties of V-N microalloyed high strength ship plate steel was revealed. The results showed that the composite addition of V and N not only formed a fine dispersed precipitated phase, but more importantly, significantly refined the ferrite/pearlite microstructure, promoted the formation of intragranular acicular ferrite, increased the proportion of high angle grain boundaries, and decreased the kernel average misorientation value. The optimization of microstructure brought about by V-N microalloying achieved synchronous improvement of strength and cryogenic toughness. The impact energy of V-N microalloying ship plate steel increased from 97 J of V-N-free ship plate steel to 239 J at −40 °C, and the impact fracture mode changed from brittle quasi-cleavage fracture to microvoid coalescence fracture with a large number of equiaxial dimples.

CFD study of the effect of leading-edge tubercles on the aerodynamic characteristics of a small UAV based on eppler 186 airfoils

A numerical analysis is carried out to evaluate the aerodynamic characteristics of a small Unmanned Aerial Vehicle (UAV) whose wings are modified to incorporate sinusoidal leading edges (tubercles). This UAV has a rectangular wing composed of Eppler 186 airfoils. The aerodynamic characteristics of four UAV configurations varying the wavelength and amplitude along the wingspan are evaluated using Computational Fluid Dynamics (CFD). Results are compared with the baseline case, that is, without leading-edge tubercles. The wing configurations with tubercles exhibited increased lift at high angles of attack and delayed stall. The configuration with maximum amplitude (a=0.05c) and minium wavelength (λ=0.25c) achieved an increase up to 17 % in the maximum lift coefficient and delayed the stall up to the angle of attack of 20° compared to the baseline case.

On the texture and strength of a 316L steel processed by powder bed fusion

The developed microstructures and textures and their effect on the tensile behavior of a 316L austenitic stainless steel produced by powder bed fusion (PBF) were studied. The material printed with one set of printing parameters was tensile tested in three different directions. The microstructural analysis was conducted using electron microscopy. Referring to the build direction (BD) and the side direction (SD), which are parallel/crosswise to the laser scanning direction, the texture can be characterized by two strong components of <011>//BD and <001>//SD. The obtained steel samples exhibit the yield strength of 550 MPa–590 MPa depending on the tensile direction. The strengthening contributors to the PBF material were considered separately. Considering the microstructural grain size between the high angle boundaries and taking the dislocations of cellular structure as a part of dislocation density, the dislocation density is considered being the main strength contributor while the Taylor factor variety from about 2.9 to 3.2 for different directions revealed the strength anisotropy as an attribute of the texture.

Investigation of physico-mechanical, thermal, morphological, and antibacterial effects of bio-based epoxidized soybean oil plasticizer on PLA-ZnO nanocomposites as flexible food packaging

Polylactic acid (PLA) has attracted considerable attention because of its excellent properties compared to petroleum-based materials. However, improving its toughness, crystallization, and functionalities is challenging. Using a laboratory internal batch mixer, we produced unique blended nanocomposites comprising polylactic acid (PLA) as the host matrix, epoxidized soybean oil (ESO) as the plasticizer, and zinc oxide nanoparticles (ZnO NPs) as the reinforcements. The SEM-EDS test showed that neat PLA had a smooth surface, but the PLA-ZnO nanocomposite had rough micrographs and a uniform dispersion state of the nanoparticles. It was also found that adding ESO to the blend nanocomposites created a matrix droplet structure, and the size of the oil domains decreased as the ZnO content increased. All results derived from FTIR, XRD, and DSC tests were consistent with the morphological features in which ZnO NPs acted as the blend’s compatibilizer and heterogeneous nucleating agent. Our team observed that adding ESO decreased the PLA-ZnO nanocomposites’ glass transition temperature (Tg) by an average of 2 °C and increased the crystallization rate. It was also confirmed that the presence of ESO improved the flexibility and reduced the strength of the PLA. The tensile strength was further enhanced by incorporating ZnO into the blend. Adding 5 wt% of ZnO NPs increased the tensile strength of the PLA containing 10 wt% ESO by approximately 3.5 MPa. Furthermore, the tensile modulus was predicted using theoretical models; for example, the Paul model fitted with experimental findings. The addition of ESO increased the overall surface free energy of the nanocomposites. On the other hand, increasing ZnO content resulted in high contact angles and antibacterial properties of the blended nanocomposites. The favorable characteristics of the resulting films emphasized the potential use of these nanocomposite films as a promising choice for food packaging materials.

A comprehensive guide to milling techniques for smoothing the surfaces of 3D-printed thermoplastic parts

Purpose This study aims to thoroughly examine the milling process applied to fused filament fabrication (FFF) parts. The primary objective is to identify the key variables in creating smooth surfaces on FFF specimens and establish trends about specific parameters. Design/methodology/approach In this study, PLA and ABS samples fabricated by FFF are subjected to side milling in several experiments. Achievable surface quality is studied in relation to material properties, milling parameters, tooling and macrostructure. The surface finish is quantified using profile measurements of the processed surfaces. The study classifies the created chips into categories that can be used as criteria for the anticipated quality. Spectral analysis is used to examine the various surface formation modes. Thermal monitoring is used to track chip formation and surface temperature changes during the milling process. Findings This study reveals that effective heat dissipation through proper chip formation is vital for maintaining high surface quality. Recommended methodology demands using a tool with a substantial flute volume, using high positive rake and clearance angles and optimizing the feed-per-tooth and cutting speed. Disregarding these guidelines may cause the surface temperature to surpass the material’s glass transition, resulting in inferior quality characterized by viscous folding. For FFF thermoplastics, optimal milling can bring the average surface roughness down to the micron level. Originality/value This research contributes to the field by providing valuable guidance for achieving superior results in milling FFF parts. This study includes a concise summary of the theoretically relevant insights, presents verification of the key factors by qualitative analysis and offers optimal milling parameters for 3D-printed thermoplastics based on systematic experiments.

Effect of shot peening on surface characteristics and high-temperature corrosion behaviour of super 13Cr martensitic stainless steel

Super 13Cr, as an economy stainless steel (SS) for oil country tubular goods, needs stable corrosion resistance in high-pressure and high-temperature (HPHT) downhole medium. Severe plastic deformation (SPD) are the surface modification technology to improve mechanical properties, fatigue behavior and corrosion resistance of metals, and shot peening (SP) has been the most widely used SPD process. However, there are quite limited studies about the microsutructure evolution, residual stress, and high-temperature corrosion behavior of SP treated martensitic SS. In this study, super 13Cr martensitic SS was treated by shot peening with various air pressures and nozzle speeds. The surface characteristics and high-temperature corrosion behaviour in 3.17 mol/L K2HPO4 solution was investigated through finite element model analysis, characterization of residual stress and microstructure, as well as electrochemical and stress corrosion cracking (SCC) tests at 160 °C and 10 MPa. The results showed that SP treated super 13Cr could generate high-level compressive residual stress and SPD microstucture, including nano-sized equiaxed grains, gradient lamellar structure and fragmented carbides. Increasing air pressure contributed to achieve uniform nanocrystalline, but tended to generate high dislocation density and surface defects. The improving effect of SP treatment at low air pressure of 0.15 MPa on passivation ability was limited, and high air pressure adversely impacted corrosion resistance. SP treated specimens showed high SCC susceptibility, due to the introduction of more surface defects, high angle grain boundaries, and dislocations.

Modification and strengthening of recycled Al-Mg-Si-based alloy upon continuous rheological extrusion (CRE) forming

With global warming and resource scarcity, it is crucial to devise a simple, energy-efficient, and low-emission recycling method for aluminum alloys. In the recycled Al-Mg-Si-based alloy, the coarse α-Al dendrites, the long plate-like β-Al5FeSi phase and bulk Mg2Si phase significantly impair the microstructure and mechanical properties of the alloys. In this works, combined the continuous rheological extrusion (CRE) technology with the addition of CRE Al-5.0Ti-1.0B (wt%) refiner, the recycled Al-Mg-Si-based alloy wires at extrusion ratios (ER) of 3, 5 and 7 were prepared. The refinement of Mg2Si and β-Al5FeSi phases and the grain refinement caused by the continuous dynamic recrystallization (CDRX) behavior in the CRE process were discussed. The strengthening mechanism of recycled Al-Mg-Si-based alloy was revealed. The results showed that, CRE technology and CRE Al-5.0Ti-1.0B (wt%) refiner can effectively refine Mg2Si and β-Al5FeSi phases, and even to the nanometer level. At the same time, the increase of ER and the addition of CRE Al-5.0Ti-1.0B (wt%) can promote the transformation of low angle grain boundaries (LAGBs) to high angle grain boundaries (HAGBs), thereby promoting the occurrence of CDRX. In addition, the increase of dislocations and nanophases caused by the increase of ER and the addition of CRE Al-5.0Ti-1.0B can effectively refine CDRX grains. When 0.2 wt% CRE Al-5.0Ti-1.0B (wt%) refiner was added at ER of 7, the ultimate tensile strength (UTS), yield strength (YS) and elongation (EL) of recycled Al-Mg-Si-based alloy were 259.40 MPa, 140.80 MPa and 18.20%, respectively. Grain boundary strengthening and dislocation strengthening were the primary mechanisms in enhancing the YS of the recycled Al-Mg-Si-based alloy.

Evaluation of Slurry-Eroded Rubber Surface Using Gloss Measurement

Slurry erosion testing is essential for evaluating the durability of materials under erosive conditions. This study examines the slurry erosion behaviours of chloroprene rubber (CR) under varying impact conditions to assess its durability. Traditional mass loss methods and qualitative techniques, including microscopy, SEM, and AFM, were employed to analyse eroded CR samples. Results indicate that cumulative material loss in CR increases linearly with sand impingement after approximately 60 kg of sand and correlates with an impact energy of about 30 kJ. The highest erosion rate was found at an impact angle of 15°. Erosion mechanisms vary with impact angle, affecting surface topography from cutting and ploughing at lower angles to deformation and crater formation at higher angles. Despite their efficacy, these methods are time-intensive and costly. This paper presents a novel approach utilising gloss measurement for continuous, non-destructive monitoring of eroded rubber surfaces. Gloss measurements are 24 times faster than traditional mass loss methods. Correlating gloss values with cumulative material loss, steady-state erosion, and impact energy offers significant time savings and an enhanced understanding of the erosion process. Experimental results demonstrate the effectiveness of gloss measurement as a reliable tool in slurry erosion testing of rubbers. The quantitative output from gloss measurements could support proactive maintenance strategies to extend service life and optimise operational efficiency in industrial applications, particularly in the mining industry.

Omniphobic PTFE based Hollow Fiber Membrane with ZnO Nanoparticles Deposition via Universal Spray Technique

This investigation aimed to enhance the hydrophobicity of a polytetrafluoroethylene (PTFE) hollow fiber membrane, transforming it into an omniphobic surface. This was achieved by coating the membrane with a mixture of zinc oxide nanoparticles (ZnO-NPs) and polyvinylidene fluoride-cohexafluoropropylene (PVDF-HFP) using the universal spray technique. The membrane's morphology and performance were evaluated based on the number of spray cycles, which influenced the coating thickness on the membrane surface. The spraying process was varied up to 4 cycles to determine the membrane with the most effective deposition of ZnO NPs in terms of water contact angle and liquid entry pressure (LEPw). Results indicated that the membrane spray-coated up to 4 cycles, denoted as PTFE-4, exhibited a rough hierarchical re-entrant morphology, imparting omniphobic characteristics. The optimized membrane demonstrated a high water contact angle of 170° and a liquid entry pressure of 2.6 bar. Fourier-transform infrared (FTIR) and energy dispersive analysis of X-rays (EDX) confirmed the successful chemical integration of ZnO NPs onto the commercial membrane. This research holds significance for the future of membrane distillation in treating wastewater containing low surface tension pollutants.

Microstructure and performance of AlCoCrFeNiCu(CeO2)X high-entropy alloy coatings by plasma cladding

AlCoCrFeNiCu(CeO2)X (x=0 wt%, 0.3 wt%, 0.6 wt%, 0.9 wt%, and 1.2 wt%) HEA coatings were applied via plasma cladding technology to a 35CrMo steel surface in this investigation. Electron back-scattering diffraction (EBSD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to analyze the phase composition and microstructure of the coatings. A microhardness meter, a nanoindenter, a wear test machine, and an electrochemical station were used to assess the coating performance. The findings demonstrate that the phase composition of the coatings is unaffected by the addition of CeO2, with all coatings consisting of FCC and BCC phases. CeO2 was added to the coatings to refine their grain size and increase their proportion of high angle grain boundaries (HAGBs), BCC phase content, and geometrically necessary dislocation (GND) density. These improvements led to significant increases in the microhardness and wear resistance of the coatings. The 0.3 wt% CeO2 coating has the best corrosion resistance, which is caused by a number of factors including the element distribution, grain size, content of each phase, and phase distribution of the coatings. The corrosion resistance of the coating increases and then decreases nonlinearly with increasing CeO2 content.

Effect of grain structure on the magnetic properties of AlNiCo 8 alloys

AlNiCo alloy has gained popularity again in recent years due to its good corrosion resistance, affordability, and superior performance at high temperature. However, the lower magnetic properties of AlNiCo limit its wide variety of applications. Directional solidification process is a key process that affects the properties of AlNiCo alloy. During the solidification process, grains with various structures are formed due to the difference of cooling rate at different positions of the ingot. As the cooling rate slows down, the average grain size gradually increases, and orientation degree of the grains becomes better, resulting in the increase of coercivity (Hc) and remanence (Br). Therefore, the top sample has the best Hc and Br, the bottom is the worst, and the middle is between the two. It is found that when the average grain size increases, the percentage of transverse grain boundaries and high angle grain boundaries (HAGBs) decrease, the truncated α1 phase decreases, and the Hc rises, whereas the magnetic moment along the easy-axis direction is not affected by the external magnetic field when the grain orientation coincides, and the Br value increases, and the Br value increases. Large and highly oriented grains are associated with excellent performance, providing a new method to enhancing magnetic properties by regulating the grain structure.

Quantitative and qualitative evaluation of high-quality hepatobiliary phase imaging with shortened timing and utility in patients with compromised liver function.

To compare high flip angle (FA) hepatobiliary-phase (hHBP) imaging with variable time intervals to conventional HBP (cHBP) to assess the impact of increased FA on image quality in shortened HBP imaging. Data from 218 patients, divided into normal liver group (n = 184) and decompensated liver group (n = 34), who underwent liver magnetic resonance imaging (MRI) including 10-min, 15-min, 20-min hHBP, and cHBP were analyzed. Signal-to-noise ratio (SNR), contrast-ratio (CR), contrast-to-noise ratio (CNR), signal intensity ratios (SIRs), and relative enhancement (RE) of the liver were calculated for quantitative analysis. Sharpness, noise, and artifacts of the image, contrast media visibility, overall image quality, and lesion conspicuity were evaluated by two abdominal radiologists. Quantitative analysis showed that SNR, RE, SIR for liver/muscle, liver/spleen, and CR of all hHBP images demonstrated a significantly higher value compared to cHBP images in the normal liver group (p < 0.001). These values were also superior in the normal liver group compared to the decompensated liver group (p < 0.01). In qualitative analysis, both normal and decompensated liver groups exhibited significantly superior image sharpness in all hHBP images compared to cHBP images and the overall image quality of the 15-min and 20-min hHBP did not show significant difference compared to cHBP. All values tended to be better in the normal liver group than the decompensated liver group with statistical significance except for lesion conspicuity (p < 0.01). High-FA HBP has proven to be a valuable image acquisition method, potentially shortening liver MR imaging time while maintaining acceptable image quality.

Prediction of the maximum tooth root stress for fatigue analysis of highly crowned spherical gear couplings working at high misaligned conditions

Spherical gear couplings efficiently transfer power between highly misaligned rotating shafts, featuring high longitudinal crowning in their design. At high misalignment angles, the contact point shifts across the face width, reducing the number of teeth in contact and increasing the risk of tooth root fatigue failure.While gear coupling fatigue sizing standards typically address misalignment angles above one degree as special cases, many applications involve misalignment angles exceeding 3°. This paper proposes a surrogate modeling approach to predict maximum tooth root stress for fatigue analysis of spherical gear couplings operating under misaligned conditions. Results indicate that this cannot be predicted in an independent manner from the number of teeth in contact or the effective face width. Consequently, demonstrates that using a single coefficient to account for the effect of the misalignment on load distribution yields optimal results. This research validates the suitability of the presented methodology for predicting tooth root stresses in spherical gear couplings prone to tooth root fatigue failure under high misalignment conditions with a mean error of 0.4%, while it serves as a valuable fast tool for engineers during the design phase.

Twist angle-dependent transport properties of twisted bilayer graphene

Twisted bilayer graphene (tBLG) with small twist angles has attracted significant attention because of its unique electronic properties arising from the formation of a moiré superlattice. In this study, we systematically characterized the twist-angle-dependent electronic and transport properties of tBLG grown via chemical vapor deposition. This characterization included parameters such as the charge-neutral point voltage, carrier concentration, resistance, and mobility, covering a wide range of twist angles from 0° to 30°. We experimentally demonstrated that these parameters exhibited twist-angle-dependent moiré period trends, with high twist angles exceeding 9°, revealing more practically useful features, including improved mobilities compared to those of single-layer graphene. In addition, we demonstrated that the doping states and work functions were weakly dependent on the twist angles, as confirmed by additional first-principles calculations. This study provides valuable insights into the transport properties of tBLG and its potential for practical applications in the emerging field of twistronics.