Open University of Cyprus

This paper introduces a novel model-free fractional-order composite control methodology specifically designed for precision positioning in permanent magnet synchronous motor (PMSM) drives. The proposed framework ingeniously combines a composite control architecture, featuring a super twisting double fractional-order differential sliding mode controller (STDFDSMC) synergistically integrated with a complementary extended state observer (CESO). The STDFDSMC incorporates an innovative fractional-order double differential sliding mode surface, engineered to deliver superior robustness, enhanced flexibility, and accelerated convergence rates, while simultaneously addressing potential singularity issues. The CESO is implemented to achieve precise estimation and compensation of both intrinsic and extrinsic disturbances affecting PMSM drive systems. Through rigorous application of Lyapunov stability theory, we provide a comprehensive theoretical validation of the closed-loop system’s convergence stability under the proposed control paradigm. Extensive comparative analyses with conventional control methodologies are conducted to substantiate the efficacy of our approach. The comparative results conclusively demonstrate that the proposed control method represents a significant advancement in PMSM drive performance optimization, offering substantial improvements over existing control strategies.

The Gaussian sum cubature Kalman filter (GSCKF) based on Gaussian mixture model (GMM) is a critical nonlinear non-Gaussian filter for data fusion of global navigation satellite system/strapdown inertial navigation systems (GNSS/SINS) tightly coupled integrated navigation system. However, the stochastic model of non-Gaussian noise in practical operating environments is not static, but rather time-varying. So if the GMM of GSCKF cannot be adjusted adaptively, it will lead to a decrease in estimation accuracy. To address this issue, we propose a novel adaptive GSCKF (AGSCKF) based on the dynamic adjustment of GMM. By analyzing the impact of GMM displacement parameter on the fitting accuracy of non-Gaussian noise, a novel algorithm for GMM displacement parameter adaptive adjustment is proposed using a cost function. Then this novel algorithm is applied to overcome the limitations of GSCKF under time-varying non-Gaussian noise environment, thereby improving the filtering performance. The simulation and experimental results indicate that the proposed AGSCKF exhibits significant advantage in changeable environments affected by time-varying non-Gaussian noise, which is applied to GNSS/SINS tightly coupled integrated navigation system data fusion can improve estimation accuracy and adaptability without sacrificing significant computational complexity.

AbstractThis study employs first‐principles methods to investigate the ORR catalytic activity of As‐doped and AsN co‐doped graphene. As atoms, as catalytic active sites, exhibit excellent catalytic activity. Due to the strong interaction between As and N, the stability of the As−N co‐doped substrate is enhanced. In particular, As−N4 co‐doped graphene not only demonstrates the best thermodynamic and kinetic stability, but also has an ORR overpotential of only 0.53 V. We also propose a method to predict the Gibbs free energy change of the system by calculating the adsorption energies of the adsorbates. This approach can streamline the process by eliminating the need to calculate the Gibbs free energy of the ORR system, making it highly advantageous for future studies on the ORR catalytic activity of multi‐impurity co‐doped graphene.

ABSTRACTThis paper discusses the asynchronous control problem for discrete‐time singular Markov jump systems (SMJSs) with incomplete transition probabilities (TPs) and actuator saturation. A hidden Markov model (HMM) is employed to characterize the asynchronization behavior between the system and the controller, and the TPs of the system and the controller are not completely known. A convex hull approach is constructed to deal with the saturated non‐linearity. Firstly, some sufficient conditions to ensure the system is stochastically admissible (SA) with desired performance are obtained. Secondly, a novel approach is given to design the special structural controllers. Thirdly, the domain of attraction of the system is estimated. Finally, the effectiveness of the proposed approach is illustrated by simulations.

AbstractA novel and efficient strategy for the direct synthesis of 3‐arylthioquinoline derivatives via radical induced tandem cyclization of propargylamines with diaryl disulfides was developed. This protocol undergoes a cascade sulfuration/ cyclization/ oxidation/ aromatization pathway to afford the desired products in a broad substrate scope using readily available starting materials under mild conditions. Based on this strategy, we further modified 3‐arylquinolines to obtain two novel deep blue fluorescent molecules, QLSCz and QLSTCz, with good optical properties through two‐step synthesis by oxidation and electron donor modification.

In this study, we explored the growth of incongruently melting crystals in a starting solution with flux to better understand the role of flux in crystal growth mechanisms. We recorded the spectrum of BaBPO5 crystals across a 200–1400 cm−1 range for detailed Raman spectroscopic analysis. The observed Raman bands corresponded to the vibrations of PO4 and BO4 units. These units link with B–O–P bonds via common corners to form PBO7 groups that serve as basic structural units of the crystal. Notably, these PBO7 structures remain stable at high temperatures up to the crystal melting point, at which the isolated PO4 groups predominantly exist in the melt, as revealed by high-temperature Raman spectroscopy. Further investigations into the Raman spectra of the starting solution enriched with BPO4 self-flux indicate that PBO7 groups are crucial for crystal growth. The addition of PBO4 flux aids in the formation of these PBO7 units. This research paves the way for expanding our understanding to other systems, which will help elucidate the mechanisms behind crystal growth.

New ten tetrakis(benzoxazine) calix[4]resorcinarenes modified by organic amine through Mannich reaction were obtained in this paper. Compounds 2 ~ 11 were characterized by infrared spectroscopies, nuclear magnetic resonance spectroscopies. The structure of compounds 2, 10 and 11 was characterized by single crystal X-ray diffraction. Compound 7 possesses a MIC value of 3.13 μg/mL against S. Aureus, demonstrating a favorable inhibitory effect, and a MIC value of 6.25 μg/mL against E. Coli, likewise showing a good inhibitory effect. The UV and 1H NMR titration experiments were conducted to explore the host–guest chemistry between compound 10 and acetonitrile molecules, indicating that compound 10 exhibited encapsulation behavior towards acetonitrile molecules through hydrogen bonding interactions. Then Hirshfeld surface analysis showed that H⋅⋅⋅H, C − H⋅⋅⋅O, C − H⋅⋅⋅π, O − H⋅⋅⋅O played an important role in the crystal accumulation of compounds 2, 10 and 11.

A common approach for analyzing slope stability in normally consolidated or lightly overconsolidated clays assumes a linear variation of undrained shear strength with depth. However, the undrained shear strength of soil (cu) varies not only in the vertical direction, but also in the horizontal direction. An upper bound limit analysis method was presented to investigates the stability of cracked embankment slope fill on soil ground with spatial varying shear strength. The undrained shear strength of the foundation soil is assumed to increase linearly with depth and vary concurrently with horizontal distance. Based on the upper bound theorem of limit analysis, a rotational failure mechanism which combines log-spiral and circular arc failure surface is adopted in this paper. In addition, an analytical method is provided for calculating the critical height, minimum safety factor, and critical sliding surface, facilitating a quick assessment of stability in embankments with cracks. It is shown that a positive ‘i’ suggests greater undrained shear strength around the slope toe, enhancing the embankment’s stability. An increase in the undrained shear strength ratio M increases the stability of the embankment slope, with the most significant impact observed at lower values of M. Cracks at the top require a lower critical slope height for stability.

Abstract Combining buildings with photovoltaic (PV) is very promising, whether a building-integrated photovoltaic (BIPV) or building-attached PV (BAPV) program. In this paper, we take a home building as an example to design a feasible energy management scheme; we classify the home loads into dispatchable and nondispatchable loads and optimize the operating hours of dispatchable loads to obtain lower electricity bills and higher PV consumption rates. We perform a detailed analysis of the proposed strategy and fully validate it, and the proposed plan has been proven to perform better.

The continuous evolution of information technology underscores the growing emphasis on data security. In the realm of medical imaging, various diagnostic images represent the privacy of individuals, and the potential repercussions of their unauthorized disclosure are substantial. Therefore, this study introduces a novel chaotic system (TLCMCML) and employs it to propose a multi-image medical image encryption algorithm. To simultaneously augment security and optimize encryption efficiency, we undertake a dual-pronged approach. Firstly, we identify the regions of interest (ROIs) within individual medical images, subsequently applying an independent scrambling technique based on an odd-even interleaving configuration. Secondly, we integrate all medical images through horizontal concatenation, forming a comprehensive large-scale image, upon which we implement a synchronized bit-level permutation-diffusion encryption mechanism. Following extensive testing, enhancements were verified across various metrics including information entropy analysis, adjacent pixel correlation examination, differential attack simulations, and robustness assessments, thereby attesting to the exceptional encryption efficacy of the proposed algorithm.

ABSTRACTTraditional Oncomelania hupensis detection relies on human eye observation, which results in reduced efficiency due to easy fatigue of the human eye and limited individual cognition, an improved YOLOv8 O. hupensis detection algorithm, YOLOv8‐ESW(expectation–maximization attention [EMA], Small Target Detection Layer, and Wise‐IoU), is proposed. The original dataset is augmented using the OpenCV library. To imitate image blur caused by motion jitter, salt and pepper, and Gaussian noise were added to the dataset; to imitate images from different angles captured by the camera in an instant, affine, translation, flip, and other transformations were performed on the original data, resulting in a total of 6000 images after data enhancement. Considering the insufficient feature fusion problem caused by lightweight convolution, We present the expectation–EMA module (E), which innovatively incorporates a coordinate attention mechanism and convolutional layers to introduce a specialized layer for small target detection (S). This design significantly improves the network's ability to synergize information from both superficial and deeper layers, better focusing on small target O. hupensis and occluded O. hupensis. To tackle the challenge of quality imbalance among O. hupensis samples, we employ the Wise‐IoU (WIoU) loss function (W). This approach uses a gradient gain distribution strategy and improves the model convergence speed and regression accuracy. The YOLOv8‐ESW model, with 16.8 million parameters and requiring 98.4 GFLOPS for computations, achieved a mAP of 92.74% when tested on the O. hupensis dataset, marking a 4.09% improvement over the baseline model. Comprehensive testing confirms the enhanced network's efficacy, significantly elevating O. hupensis detection precision, minimizing both missed and false detections, and fulfilling real‐time processing criteria. Compared with the current mainstream models, it has certain advantages in detection accuracy and has reference value for subsequent research in actual detection.

Due to its low stiffness, the gas diffusion layer (GDL) exhibits significant deformation under a compression service condition, thereby exerting a nonlinear and strong coupling influence on fuel cells’ performance. Therefore, it is of great practical significance to study the structural characteristics evolution of GDLs. The microstructure of the GDLs was obtained using micro-X-ray computed tomography in this study, and their structural properties were analyzed comprehensively and quantitatively. The morphology of GDLs exhibited significant variations across manufacturers due to disparities in the materials and manufacturing processes. The distribution of the pore equivalent diameter and sphericity in GDLs conformed to a normal distribution, with irregular shapes. The fiber length distribution in the unit followed a Gamma distribution, showing a random and uneven distribution in the XY plane. When compressed, the average fiber length was reduced, and a substantial increase in isolated pores was observed. However, the quantity of long fibers and connected and isolated pores decreased after acidification treatment.