Search Results (2,184)

When a beam twists, localized flexural deformation in the plate occurs at the connection between the corrugated plate and the beam, resulting in a reduction in the bracing stiffness of the corrugated plate. To accurately assess the bracing stiffness of a beam with a connected corrugated plate, it is essential to independently determine the bending stiffness of the corrugated plate and the rotational stiffness of the plate–beam joint. This study conducts bending experiments on corrugated plates subjected to in-plane bending to elucidate the stress mechanisms within the plates. The influence of the width-to-thickness ratio on the bending load and bending stiffness of the corrugated plates is examined using the width-to-thickness ratio regulations of various countries. The findings revealed that when the width-to-thickness ratio of the corrugated plates used in this study was lower than the threshold specified in the Eurocode, the bending load at the onset of stiffness degradation was approximately 80% of the maximum bending load, and the initial bending stiffness corresponded closely to the theoretical value. Conversely, when the web width-to-thickness ratio of the corrugated plates exceeded the limit prescribed in the Eurocode, it was demonstrated that the maximum bending load decreased to approximately 50% of the yield load, and the initial bending stiffness was reduced to about 95% of the theoretical value. Full article

Stainless steels have many practical applications requiring various mechanical or chemical demands in the working environment. By optimizing a device used in mechanical experiments for torsional loading, several cylindrical samples were tested (both ends twisted with the same torque value in opposite directions) of 316L stainless steel (SS) to evaluate changes in the structural, chemical, and mechanical characteristics. Initially, the experimental samples were pre-loaded by tension in the elastic range (6%) and then subjected to torsion (772°) at different rates: 5, 10, and 20 mm/min. The experimental sequence consisted of a combined loading protocol with an initial tensile test followed by a subsequent torsional test. Two reference tests were performed by fracturing the samples in both torsion and tension to determine the mechanical strength parameters. The macro- and microstructural evolution of the samples as a function of the torsional degree was followed by scanning electron microscopy. The microhardness modification of the material was observed because of the strain (the microhardness variation from the center of the disk sample to the edge was also monitored). Structurally, all samples showed grain size changes because of torsional/compressive deformation zones and an increase in the degree of grain boundary misorientation. From the tensile and torsional behaviors of 316L SS and the structural results obtained, it was concluded that these materials are suitable for complex stress states in the elasto-plastic range through tensile and torsion. A reduction in Young’s modulus of up to four times the initial value at medium and high stress rates was observed when complex stresses were applied. Full article

Jute fibers are renewable, light, and strong, allowing them to be considered as attractive materials in composite manufacturing. In the present work, a simple and effective method for preparing continuous pre-preg tapes from short jute fiber bundles (without twist) is developed and its application in winding forming is evaluated. Linear low-density polyethylene film (LLDPE) with good flexibility and weather resistance was used as the thermoplastic matrix; jute fiber bundles were first spread parallel to each other on an LLDPE film and then rolled up to form a pre-roll. The pre-roll enclosing fiber bundles was hot-pressed in a designed mold to form a pre-preg tape, where the fiber bundles were more parallel to the tape than the fibers in twine. Although the untwisted structure exhibited a lower tensile strength for the fiber bundle, it could be processed into a continuous pre-preg with higher tensile strength than the jute twine-impregnated pre-preg. This is based on the good impregnation of the short fiber bundle and its unidirectional, uniform strengthening in the continuous pre-preg. The tensile strength and modulus of the fiber bundle-reinforced pre-preg increased by 16.70% and 257.14%, respectively, compared with jute twine-reinforced pre-preg (within the fiber proportion of 40.wt%). When applied to winding, the fiber bundle-reinforced pre-preg showed advantages of interlayer fusion, surface flatness, and ring stiffness. In contrast, the twisted continuous structure did not retain its advantage in pre-preg. The development of pre-preg tapes by discontinuous fibers might be a good way for utilizing natural fibers in the field of green engineering due to its diverse secondary processing. Full article

We investigate the spontaneous emission of a quantum emitter (QE) placed near the twisted hyperbolic metasurfaces (HMTSs) made of graphene strips. We demonstrate that the spontaneous emission can be enhanced distinctly due to the existence of moiré hyperbolic plasmon polaritons (HPPs) supported by the twisted HMTSs. Moreover, the spontaneous emission decay rate can be efficiently modulated by the chemical potential of graphene, the thickness of the dielectric spacer, and the twist angle between two HMTSs. The maximum spontaneous emission is achieved when topological transition occurs. The spontaneous emission will be enhanced as the thickness of the dielectric spacer increases for most cases. In particular, the twisted HMTSs make it possible to flexibly modify the spontaneous emission through the external field. The findings in this work not only extend past studies of twisted photonic structures but also have important applications in optical sensing and integrated photonics. Full article

Background: Duchenne Muscular Dystrophy (DMD) is a prevalent fatal genetic disorder, and heart failure is the leading cause of mortality. Peak left ventricular (LV) circumferential strain (E_cc), twist, and circumferential-longitudinal shear angle (θ_CL) are promising biomarkers for the improved and early diagnosis of incipient heart failure. Our goals were as follows: 1) to characterize a spectrum of functional and rotational LV biomarkers in boys with DMD compared with healthy age-matched controls; and 2) to identify LV biomarkers of early cardiomyopathy in the absence of abnormal LVEF or LGE. Methods: Boys with DMD (N = 43) and age-matched healthy volunteers (N = 16) were prospectively enrolled and underwent a 3T CMR exam after obtaining informed consent. Breath-held MRI tagging was used to estimate left ventricular E_cc at the mid-ventricular level as well as the twist, torsion, and θ_CL between basal and apical LV short-axis slices. A two-tailed t-test with unequal variance was used to test group-wise differences. Multiple comparisons were performed with Holm–Sidak post hoc correction. Multiple-regression analysis was used to test for correlations among biomarkers. A binomial logistic regression model assessed each biomarker’s ability to distinguish the following: (1) healthy volunteers vs. DMD patients, (2) healthy volunteers vs. LGE(−) DMD patients, and (3) LGE(−) DMD patients vs. LGE(+) DMD patients. Results: There was a significant impairment in the peak mid-wall E_cc [−17.0 ± 4.2% vs. −19.5 ± 1.9%, p < 7.8 × 10⁻³], peak LV twist (10.4 ± 4.3° vs. 15.6 ± 3.1°, p < 8.1 × 10⁻⁴), and peak LV torsion (2.03 ± 0.82°/mm vs. 2.8 ± 0.5°/mm, p < 2.6 × 10⁻³) of LGE(−) DMD patients when compared to healthy volunteers. There was a further significant reduction in the E_cc, twist, torsion, and θ_CL for LGE(+) DMD patients when compared to LGE(−) DMD patients. In the LGE(+) DMD patients, age significantly correlated with LVEF (r² = 0.42, p = 9 × 10⁻³), peak mid-wall E_cc (r² = 0.27, p = 0.046), peak LV Twist (r² = 0.24, p = 0.06), peak LV torsion (r² = 0.28, p = 0.04), and peak LV θ_CL (r² = 0.23, p = 0.07). In the LGE(−) DMD patients, only the peak mid-wall E_cc was significantly correlated with age (r² = 0.25, p = 0.006). The peak LV twist outperformed the peak mid-wall LV E_cc and EF in distinguishing DMD patients from healthy volunteer groups (AUC = 0.88, 0.80, and 0.72), as well as in distinguishing LGE(−) DMD patients from healthy volunteers (AUC = 0.83, 0.74, and 0.62). The peak LV twist and peak mid-wall LV E_cc performed similarly in distinguishing the LGE(−) and LGE(+) DMD cohorts (AUC = 0.74, 0.77, and 0.79). Conclusions: The peak mid-wall LV E_cc, peak LV twist, peak LV torsion, and peak LV θ_CL were significantly impaired in advance of the decreased LVEF and the development of focal myocardial fibrosis in boys with DMD and therefore were apparent prior to significant irreversible injury. Full article

This review provides an analysis of advancements in the design and performance assessment of Darrieus wind turbines over the past decade, with a focus on the contributions of computational fluid dynamics (CFD) to this field. The primary objective is to present insights from studies conducted between 2014 and 2024, emphasizing the enhancement of Darrieus wind turbine performance through various technological innovations. The research methodology employed for this review includes a critical analysis of published articles related to Darrieus turbines. The focus on the period from 2014 to 2024 was considered to highlight recent parametric CFD studies on Darrieus turbines, avoiding overlap with previously published reviews and maintaining originality relative to existing review works in the literature. By synthesizing a collection of articles, the review discusses a wide range of recent investigations utilizing CFD modeling techniques, including both 2D and 3D simulations. These studies predominantly utilize the “Ansys-Fluent” V12.0 and “STAR CCM+” V9.02 solvers to evaluate the aerodynamic performance of Darrieus rotors. Technological advancements focus on modifying the geometry of Darrieus, including alterations to blade profiles, chord length, rotor diameter, number of blades, turbine height, rotor solidity, and the integration of multiple rotors in various configurations. Additionally, the incorporation of flow deflectors, the use of advanced blade shapes, such as V-shaped or twisted blades, and the application of an opening ratio on the blades are explored to enhance rotor efficiency. The review highlights the significant impact of these geometric modifications on key performance metrics, particularly the moment and power coefficients. A dedicated section presents CFD-derived visualizations, including vorticity fields, turbulence contours illustrated through the Q-criterion, velocity vectors, and dynamic pressure contours. These visualizations provide a description of the flow structures around the modified Darrieus rotors. Moreover, the review includes an analysis of the dynamic performance curves of Darrieus, which show improvements resulting from the modifications of the baseline design. This analysis covers the evolution of pressure coefficients, moment coefficients, and the increased power output of Darrieus. Full article

Liquid–liquid mass transfer is crucial in chemical processes like extraction and desulfurization. Traditional tube-in-tube millireactors often overlook internal flow dynamics, focusing instead on entry modifications. This study explores mass transfer enhancement through structured inserts (twisted tapes, multi-blades) and inlet designs (multi-hole injectors, T-mixers). Using high-speed imaging and water–succinic acid–butanol experiments, flow patterns and mass transfer rates were analyzed. Results show annular and dispersion flows dominate under tested conditions with structured inserts lowering the threshold for dispersion flow. Multi-hole injectors improved mass transfer by over 40% compared to T-mixers in plain tubes, while C-tape inserts achieved the highest volumetric mass transfer coefficient (2.43 s⁻¹) due to increased interfacial area and droplet breakup from energy dissipation. This approach offers scalable solutions to enhance tube-in-tube millireactor performance for industrial applications. Full article

Epithelial-to-mesenchymal transition (EMT) is a critical process in malignant ovarian cancer metastasis. EMT involves the conversion of epithelial cells to mesenchymal cells, conferring enhanced migratory and invasive capabilities. Glioblastoma multiforme (GBM) is the most common malignant primary brain tumor and exhibits an aggressive invasive phenotype that mimics some steps of EMT but does not undergo true metastasis, i.e., the invasion of other organ systems. This study conducts a comparative genomic analysis of EMT in ovarian cancer and invasion in GBM—two malignancies characterized by poor prognosis and limited therapies. Investigating the molecular biology in ovarian cancer and GBM demonstrates shared mechanisms of tumor progression, such as similar genetic and molecular pathways influencing cell plasticity, invasion, and resistance to therapy. The comparative analysis reveals commonalities and differences in the regulatory networks and gene expression profiles associated with EMT and invasion in these cancers. Key findings include the identification of core EMT regulators, such as TWIST1, SNAIL, and ZEB1, which are upregulated in both ovarian cancer and GBM, promoting mesenchymal phenotypes and metastasis. Additionally, the analysis uncovers EMT-related pathways, such as the PI3K/AKT and TGF-β signaling, which are critical in both cancers but exhibit distinct regulatory dynamics. Understanding the intricacies of EMT in ovarian cancer and invasion in GBM provides valuable insights into their aggressive behavior and identifies potential common therapeutic targets. The findings stress the importance of targeting EMT/invasion transitions to develop effective treatments to halt progression and improve patient outcomes in these malignancies. Full article

We report the first homologous series of methylene-linked cyanobiphenyl- and cyanoterphenyl-based liquid crystal (LC) dimers (CBnCT). To induce the heliconical twist-bend nematic (N_TB) phase through bent molecular shapes, the CBnCT homologs have an odd-numbered flexible alkylene spacer (n) ranging from 1 to 17. Polarized optical microscopy and differential scanning calorimetry are used to identify phases and analyze the phase-transition behavior. Except for n = 1, all the CBnCT homologs exhibit the conventional nematic (N) and N_TB phases. The CBnCT dimers with n = 3 and 5 show a monotropic N_TB phase, while those with n = 7, 9, 11, 13, 15, and 17 demonstrate an enantiotropic N_TB phase below the conventional N phase temperature. The N_TB phases of the CBnCT dimers (n = 7, 9, and 11) remain stable down to room temperature and vitrify without crystallization. Compared with cyanobiphenyl-based LC dimer homologs (CBnCB), the CBnCT dimers show significantly broader N and N_TB phase temperature ranges with higher isotropic and N_TB–N phase-transition temperatures. The N_TB phase temperature ranges of CBnCT (n = 7, 9, 11, and 13) are over 100 °C. Additionally, more CBnCT homologs exhibit the enantiotropic N_TB phase than the CBnCB ones. These enhancements result from increased π-conjugation and asymmetric molecular structures. Furthermore, CB9CT exhibits higher birefringence than CB9CB owing to its longer π-conjugated terphenyl moiety. Full article

In response to the chattering issue inherent in sliding mode observers during rotor position estimation and to enhance the stability and robustness of sensorless control systems for surface-mounted permanent magnet synchronous motors (SPMSM), this study proposes a rotor position estimation algorithm for SPMSM based on an improved super-twisting sliding mode observer (ISTSMO) and a second-order generalized integrator (SOGI) structure. Firstly, the super-twisting algorithm is introduced to design the observer, which effectively attenuates the sliding mode chattering by using continuous control signals. Secondly, SOGI is introduced in the filtering stage, which not only effectively addresses the time delay issues caused by traditional low-pass filters but also enables the observer to extract rotor position information by monitoring only the back electromotive force (back-EMF) signal of the $\alpha$-phase, thereby simplifying the observer structure. Finally, the proposed scheme is experimentally compared with the traditional sliding mode observer on the YXMBD-TE1000 platform. The experimental results showed that during motor acceleration and deceleration tests, the average speed estimation error was reduced from 141 r/min to 40 r/min, and the maximum position estimation error was reduced from 0.74 rad to 0.29 rad. In load disturbance experiments, the speed variation decreased from 781 r/min to 451 r/min, and the steady-state speed fluctuation was significantly reduced. These results confirm that the proposed observer exhibits superior stability and robustness. Full article

The rapid advancement of quadrotor systems has introduced significant challenges across multiple disciplines. Among these, fault tolerance and trajectory tracking in complex environments have long been recognized as critical challenges in quadrotor control research. To address issues such as rotor performance degradation and external disturbances, a novel position-attitude control system was developed, aimed to achieve precise position and attitude tracking. Initially, a dynamic model of the quadrotor was formulated, serving as the foundation for the controller design. Super-twisting algorithm terminal sliding-mode control (STATSMC) was then employed within the position loop to suppress chattering by the super-twisting algorithm. Subsequently, a new super-twisting algorithm beckstepping adaptive terminal sliding-mode control (STABATSMC) was proposed to mitigate the controller output and merge enable adherence to the desired Euler angles in case of failure. This approach enables the quadrotor to accurately follow position commands and achieve the desired attitude angles. The introduction of terminal sliding-mode control enhances convergence speed and tracking precision, while the super-twisting algorithm mitigates chattering and smoothens the control output. Finally, a series of simulation experiments were conducted within the Simulink environment to validate the proposed control system. The experimental results are compared with the state-of-art terminal sliding-mode control method, demonstrating the superior performance and effectiveness of the proposed method. Full article

Present studies are specifically aimed at investigating the sensitivity of different dynamic stall models when exposed to various excitation frequencies. The investigations are targeted at blade edgewise vibrations. This is carried out on a modified version of the IEA 15 MW reference wind turbine employing a wind turbine design tool, DNV Bladed. State-of-the-art dynamic stall models for wind turbine applications, such as the Øye model, Beddoes–Leishman (BL) model and the newly developed IAG model, are evaluated. The beginning of the research work starts by evaluating different dynamic stall models on rigid blade section forces against known airfoil datasets. Then, the blade flexibility is considered to enable systematic evaluations of the blade flexibility influences in comparison to the rigid blade cases. It is observed that the range of the angle of attack grows depending on the excitation frequency and the adopted dynamic stall model. The critical excitation frequency range and the effects of twist distribution are then identified from the studies, which can be useful as a rough guidance when designing wind turbine blades. Full article

This study addresses the challenge of evaluating circularity within the procurement-to-waste system boundaries, using the example of single-use in-flight drinking cups provided by SWISS International Air Lines Ltd., the national airline of Switzerland. A comprehensive review of the academic literature, market-based tools, and political regulations highlights the absence of adequate methodologies for assessing circularity within these specific system boundaries. Existing approaches, primarily designed at the product level, are often either excessively complex or focused solely on waste management. To address this gap, the research proposes an extension to the Circular Material Use rate (CMU), currently implemented at the European Union level. The traditional CMU rate does not account for circular inflow, thereby neglecting procurement decisions. In response, this study introduces an extended version of the CMU, expressed as CMU Extended = (Circular Inflow + Circular Outflow)/(2 × Total Material). This modification enables a more holistic evaluation of circularity by incorporating both inflows and outflows of materials in relation to total material use. Empirical testing demonstrated the applicability of this extended CMU in the context of SWISS, allowing for an efficient assessment of circularity for single-use in-flight drinking cups. From these initial results, we hypothesize that this ratio is expected to be broadly applicable beyond the airline industry, providing a valuable tool for businesses seeking to measure circularity within similar system boundaries. Full article

This article presents a circular polarized enclosed dielectric resonator antenna (DRA), operating at 5.8 GHz. The design consists of a twist DRA, which is enclosed in a box to give stability to the structure. The circular polarization of the antenna depends on the sense of twisting the top with respect to its base to achieve Left Hand Circular Polarization (LHCP) or Right Hand Circular Polarization (RHCP). The antenna was manufactured using 3D printing and low-loss dielectric filament. The measurement results show the two resonance frequencies and an axial ratio below 3 dB at the operational frequency, while exhibiting a bandwidth and gain compatible for unmanned aerial vehicle (UAV) applications. Full article

Longitudinal motion control is a critical aspect of autonomous vehicle area, requiring a well-designed controller to ensure optimal system performance, safety, and comfort under varying driving conditions. Previous control methods often face challenges such as chattering effects, and model uncertainties. To address such challenges, in this paper, we propose the application of an optimized super-twisting sliding mode control (OST-SMC) for the longitudinal motion control of autonomous vehicles. The motivation is to enhance the robustness and efficiency of the control system while minimizing the chattering problem. The proposed system’s mathematical modeling and control design are presented in detail with stability analyzed using Lyapunov theory. To enhance the controller’s performance, uncertain parameters are optimized using the gradient descent method, a linear regression-based technique. The OST-SMC algorithm shows enhanced robustness against disturbances and parameter uncertainties compared to conventional sliding mode controllers. Simulations in MATLAB/Simulink and CarMaker validate the proposed method, demonstrating strong performance even on downhill roads. The OST-SMC reduces chattering more effectively than traditional SMCs, achieving smooth tracking and consistent robustness under varying road conditions. Full article