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In this study, a novel composite speed controller combining a sliding-mode speed controller with a disturbance observer is proposed for the vector-controlled synchronous reluctance motor (SynRM) drive system. The proposed composite speed controller employs the generalized super-twisting sliding-mode (GSTSM) algorithm to construct both the speed controller and the disturbance observer. The GSTSM speed controller is utilized to stabilize the speed tracking error dynamics in finite time, while the GSTSM disturbance observer compensates for the total disturbance in the speed tracking error dynamics, which includes external disturbances and parametric uncertainties. Under the framework of the constant direct-axis current component vector control strategy for the SynRM drive system, comparative simulation studies are conducted among the standard STSM speed controller, the GSTSM speed controller, the composite speed controller using a GSTSM speed controller and a standard STSM disturbance observer, and the proposed composite speed controller. The effectiveness and superiority of the proposed composite speed controller are verified through simulation results.

This paper proposes a novel composite position controller for the field-oriented control (FOC) strategy of permanent-magnet synchronous motor (PMSM) servo systems. The proposed composite position controller integrates a position controller with a disturbance observer, with each designed based on a specific second-order sliding-mode algorithm. Specifically, the continuous twisting algorithm (CTA) is employed to develop the position controller for achieving rotor position tracking, while the modified super-twisting algorithm (STA) is used to construct the disturbance observer for compensating the total disturbance in the rotor position tracking error dynamics to enhance the dynamic performance. Comparative simulation tests, conducted within an FOC strategy of PMSM servo systems, contrast the performance of the CTA-based position controller, the composite position controller using a CTA-based position controller and a standard STA-based disturbance observer, and the proposed composite position controller. The simulation results validate the proposed position controller’s effectiveness and its superiority over comparable position controllers.

Cable termination serves as a crucial carrier for high-speed train power transmission and a weak part of the cable insulation system. Partial discharge detection plays a significant role in evaluating insulation status. However, field testing signals are often contaminated by external corona interference, which affects detection accuracy. This paper proposes a classification model based on wavelet transform (WT) and deep belief network (DBN) to accurately and rapidly identify corona discharge in the partial discharge signals of vehicle-mounted cable terminals. The method utilizes wavelet transform for noise reduction, employing the sigmoid activation function and analyzing the impact of WT on DBN classification performance. Research indicates that this method can achieve an accuracy of over 89% even with limited training samples. Finally, the reliability of the proposed classification model is verified using measured mixed signals.

This paper presents a comprehensive review of advanced control methods specifically designed for floating offshore wind turbines (FOWTs) above the rated wind speed. Focusing on primary control objectives, including power regulation at rated values, platform pitch mitigation, and structural load reduction, this paper begins by outlining the requirements and challenges inherent in FOWT control systems. It delves into the fundamental aspects of the FOWT system control framework, thereby highlighting challenges, control objectives, and conventional methods derived from bottom-fixed wind turbines. Our review then categorizes advanced control methods above the rated wind speed into three distinct approaches: model-based control, data-driven model-based control, and data-driven model-free control. Each approach is examined in terms of its specific strengths and weaknesses in practical application. The insights provided in this review contribute to a deeper understanding of the dynamic landscape of control strategies for FOWTs, thus offering guidance for researchers and practitioners in the field.

Partial discharge detection is considered a crucial technique for evaluating insulation performance and identifying defect types in cable terminals of high-speed electric multiple units (EMUs). In this study, terminal samples exhibiting four typical defects were prepared from high-speed EMUs. A cable discharge testing system, utilizing high-frequency current sensing, was developed to collect discharge signals, and datasets corresponding to these defects were established. This study proposes the use of the convolutional neural network (CNN) for the classification of discharge signals associated with specific defects, comparing this method with two existing neural network (NN)-based classification models that employ the back-propagation NN and the radial basis function NN, respectively. The comparative results demonstrate that the CNN-based model excels in accurately identifying signals from various defect types in the cable terminals of high-speed EMUs, surpassing the two existing NN-based classification models.

Face morphing attacks have become increasingly complex, and existing methods exhibit certain limitations in capturing fine-grained texture and detail changes. To overcome these limitation, in this study, a detection method based on high-frequency features and progressive enhancement learning was proposed. Specifically, in this method, first, high-frequency information are extracted from the three color channels of the image to accurately capture the details and texture changes. Next, a progressive enhancement learning framework was designed to fuse high-frequency information with RGB information. This framework includes self-enhancement and interactive-enhancement modules that progressively enhance features to capture subtle morphing traces. Experiments conducted on the standard database and compared with nine classical technologies revealed that the proposed approach achieved excellent performance.

Objective To explore the feasibility and effect of electrocorticography (ECoG) for intraoperative mapping of motor cortex. Methods Eight patients with brain lesions near motor areas were operated under awake craniotomy from June 2017 to June 2019. The motor⁃related cortices were detected by intraoperative direct electrical stimulation (DES). The ECoG signals including μ rhythm and slow cortical potential (SCP) were collected intraoperatively and analyzed by wavelet analysis from patients at rest and hand⁃moving state (grasp and extension motion). The changes of event⁃related desynchronization (ERD) of different rhythms were analyzed by wavelet analysis before and after hand grasping. The threshold values of μ rhythm, SCP and different pattern recognition in combination were compared by using DES as "gold standard". The receiver operating characteristic (ROC) area under the curve (AUC) and the sensitivity and specificity were evaluated. Results When the threshold of ERD of the μ rhythm was chosen as 40%, the sensitivity and specificity of ECoG mapping of motor cortex were 81.08% (30/37) and 83.33% (25/30). The ERD threshold of the SCP was chosen as 1.6, the sensitivity and specificity were 83.78% (31/37) and 80% (24/30) respectively. Combined μ rhythm with SCP mapping revealed high sensitivity (97.29%, 36/37) and moderate specificity (80%, 24/30) as compared with DES when D mode (sensitive priority mode) was chosen, that was either μ rhythm or SCP positive was defined as the motor cortex. Conclusions The ECoG analysis has a higher sensitivity to locate the motor cortex without stimulating the brain. It is expected as a new adjuvant to DES for intraoperative mapping of eloquent cortex. DOI:10.3969/j.issn.1672⁃6731.2020.11.005

This article proposes a review of the modeling approaches for floating offshore wind turbines (FOWTs) for nonlinear control design. The aerodynamic, hydrodynamic and mooring line dynamic modules for the FOWT have been reviewed to provide an overview of several modeling approaches with their respective features. Next, three control-oriented models from the literature are revisited by presenting their methodological approaches to modeling and identification. These three models cover the three most popular types of FOWTs. Then, the performances of these models are validated with the open fatigue, aerodynamics, structures, and turbulence (OpenFAST) code, and their performances are evaluated according to several criteria. Finally, one of the three models is used to illustrate a nonlinear second-order sliding mode control based on the twisting algorithm to optimize the performance of the FOWT in terms of energy extraction and reduction in the platform pitch oscillation.

This study proposes a speed estimation scheme for the sensorless-vector-controlled linear induction motor (LIM) drives for medium-low-speed maglev applications, which is composed of two parts: (i) a sliding mode model reference adaptive system observer for speed estimation; and (ii) a parallel secondary resistance online identification for achieving the improvements of the proposed speed estimation scheme performance. The sliding mode observer (SMO) is established on the basis of the state space-vector model of the LIM considering the dynamic end effect. Based on SMO, both speed and secondary resistance estimation algorithms are obtained by utilising Popov's hyperstability theory. Moreover, the Lyapunov stability theory is adopted for the stability analysis of the proposed speed estimation scheme. The effectiveness of the proposed speed estimation algorithm has been verified and compared with the performance of the conventional speed estimation scheme based on single-manifold SMO by the simulation and hardware-in-the-loop tests. [ABSTRACT FROM AUTHOR]

Vascular endothelial cell growth factor (VEGF)-C promotes tumorigenesis by allowing lymph node metastasis and lymphangiogenesis, among other actions. RNA interference (RNAi) is a novel technique for suppressing target gene expression and may increase the effectiveness of cancer treatments. The present study assessed the influence of VEGF-C RNAi on the apoptosis and proliferation of mouse breast cancer cells in vitro and in vivo. A total of three pairs of small interfering RNA (siRNA) targeting mouse VEGF-C were designed and synthesized prior to transfection into 4T1 cells via a liposomal approach. Reverse transcription polymerase chain reaction, western blot analysis, a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, Hoechst 33258 staining and flow cytometry were performed in vitro to analyze VEGF-C expression, cleaved caspase-3 protein expression and 4T1 cell proliferation and apoptosis. Experiments were also conducted in vivo on BALB/c mice with breast cancer. Tumor weight and volume were measured and the number of apoptotic cells in tumor tissues was assessed by a TUNEL assay. Immunohistochemical assays and an enzyme-linked immunosorbent assay were used to measure the expression of VEGF-C in tumor tissues. The results demonstrated that the three pairs of siRNA, particularly siV2, significantly reduced VEGF-C mRNA and protein levels in 4T1 cells. siV2 was deemed to be the most efficient siRNA and therefore was selected to be used in subsequent experiments. Furthermore, in vitro studies indicated that VEGF-C RNAi significantly decreased cell growth, induced apoptosis and upregulated the expression of cleaved caspase-3 protein. Tumor weight and volume in breast cancer in vivo models was reduced by the intratumoral injection of siV2. Antitumor efficacy was associated with decreased VEGF-C expression and increased induction of apoptosis. The present study therefore indicated that VEGF-C RNAi inhibited mouse breast cancer growth in vitro and in vivo and that it may be a novel targeted therapy for breast cancer. [ABSTRACT FROM AUTHOR]

Metastasis constantly occurs in the majority of cases of primary breast cancer at late stage or following surgical treatment. Survivin, a member of the inhibitor of apoptosis protein family, has long been recognized as a promising anticancer target, but its antitumor effects remain largely unexplored. In order to elucidate the role of survivin in breast cancer metastasis, short interfering RNA (siRNA) was used in the present study to specifically downregulate survivin expression in the murine breast cancer cell line 4T1. The results demonstrated that blocking the expression of survivin by siRNA inhibited the proliferation, migration and invasion abilities of murine breast cancer cells in vitro. Vascular endothelial growth factor (VEGF)-C is a lymphatic endothelial cell-stimulating factor that may lead to the formation of lymphatic vessels in lymph nodes. In the present study, the inhibition of survivin by siRNA was able to reduce the overexpression of VEGF-C in 4T1 cells. Furthermore, intratumoral injections of the survivin-siRNA significantly inhibited the growth of orthotopically transplanted 4T1 tumors in vivo. In addition, the number of pulmonary metastases and the microlymphatic vessel density were significantly reduced in vivo, following transfection with survivin-siRNA. The results of the present study suggested that the Akt/hypoxia-inducible factor-1α signaling pathway participates in the survivin-mediated downregulation of VEGF-C expression observed in breast cancer cells treated with survivin-siRNA. Therefore, the use of siRNA specifically targeting survivin may be a potential anticancer method in the future. [ABSTRACT FROM AUTHOR]

Abstract  A novel polyoxotungstate H5[Cu(en)2H2O]{Cu(en)2[P2W19O69(H2O)]} · 2.5H2en · 8H2O (1) has been synthesized under hydrothermal conditions and characterized by IR spectroscopy, elemental analysis, and single crystal X-ray structural analysis. Crystal data for 1: Triclinic, P-1, a = 12.673(6) Å, b = 20.147(10) Å, c = 20.514(11) Å, α = 110.432(7)°, β = 90.171(5)°, γ = 97.502(6)°, V = 4859(4) Å3, Z = 2. Compound 1 exhibits a 1D linear structure, in which the [Cu(en)2]2+ ions act as the linkages of {P 2 W 19 } lacunary units. Graphical Abstract  A novel polyoxotungstate H5[Cu(en)2H2O]{Cu(en)2[P2W19O69(H2O)]} · 2.5H2en · 8H2O has been made under hydrothermal conditions. Compound 1 exhibits a 1D linear structure based on the {P 2 W 19 } lacunary units linked by the [Cu(en)2]2+ bridging groups. [ABSTRACT FROM AUTHOR]

The relationship between common-mode voltages (CMVs) and switching states in the post-fault reconfigured topology of the three-level neutral-point-clamped inverter with open-circuit fault in a leg, which is named eight-switch three-phase inverter (ESTPI), is revealed, and based on that, two modified space vector pulse-width modulation (M-SVPWM) algorithms for the CMV reduction in the ESTPI are proposed. The maximum CMV of the ESTPI with two proposed M-SVPWM algorithms is only half of that with two conventional SVPWM algorithms. Experimental results have shown the effectiveness of two proposed M-SVPWM algorithms. [ABSTRACT FROM AUTHOR]

A model predictive current control scheme with dc-link capacitor voltages fluctuation suppression for the four-switch three-phase rectifier (FSTPR) in balanced grids is presented. The proposed control scheme is a type of the finite-control-set model predictive control scheme and is based on the discrete-time model of the system. From this model, the values of input currents and dc-link capacitor voltages are predicted for all switching states of the FSTPR. On the basis of a predefined cost function, the switching state, which minimises the errors between input currents and their references as well as the difference between two dc-link capacitor voltages at the next sampling instant, is selected. Simulation results are presented to confirm the effectiveness of the proposed control scheme. [ABSTRACT FROM AUTHOR]

Based on analysing the load currents, a current sensor fault diagnosis method for three-phase voltage source inverters in high-speed railway electrical traction drive system is presented. Then, a faulttolerant algorithm is applied to reconstruct the three-phase currents. This fault diagnosis and tolerant control approach is an extension of the normalised average currents method, which requires no additional hardware and permits much more robust diagnostics. Experimental results confirm the effectiveness and accuracy of the proposed algorithm. It is shown that such diagnosis method can locate the faulty sensor, identify the fault modes, and recover the drive system in a fundamental period which is important to avoid catastrophic consequences. [ABSTRACT FROM AUTHOR]

On the basis of sampling theory, an online open-switch fault diagnosis and location method for single-phase pulse-width modulation rectifiers applied in electric railway traction is presented. First, on the basis of analysing the features of the post-fault line current under instantaneous current control strategy at low switching frequency, two specific pulse sequences for sampling line current are generated via the modulation. Then, the DC component of the sampled signal, which is easy to use for diagnostic decision, is obtained through filters. Experimental results are presented to illustrate the validity of the proposed scheme. [ABSTRACT FROM AUTHOR]

Space-vector pulse-width modulation (SVPWM) and carrier-based PWM (CBPWM) of eight-switch three-phase inverters (ESTPIs) which are the post-fault reconfigured topologies for the three-level neutral-point-clamped inverter with an open-circuit fault in a leg are introduced. On the basis of the PWM regular sampling method, the modulating functions of CBPWM which are equivalent to SVPWM of ESTPIs are derived, therefore the relationship between SVPWM and CBPWM of ESTPIs is revealed. The validity of the theoretical analysis is verified by experimental results. [ABSTRACT FROM AUTHOR]

Four-switch three-phase inverters (FSTPIs) are post-fault reconfigured topologies for a two-level inverter with failure of a power switch or a leg, and space vector pulse-width modulation (SVPWM) strategies have been used to control FSTPIs. However, different faulty legs correspond to different topologies of FSTPIs which are controlled by different SVPWM strategies; therefore, three SVPWM strategies need to be prepared for three FSTPIs, respectively, which takes up lots of memory space in the controller and increases the complexity of the control strategy. To overcome these disadvantages, a general SVPWM strategy that can be used to control three FSTPIs is proposed. Experimental results have shown the validity and feasibility of the proposed strategy. [ABSTRACT FROM AUTHOR]