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At transitional Reynolds numbers, an elastically supported airfoil oscillating in pitch can undergo laminar separation flutter (LSF), which is characterized by self-sustained small-amplitude oscillations. To gain insight into the mechanism of LSF, we conduct wind tunnel tests for [Formula: see text] to investigate the LSF response of a freely rotating NACA0015 airfoil with various structural natural frequencies and positions of the elastic axis. The experimental results show that the dominant mode of flow around the NACA0015 airfoil abruptly changes at [Formula: see text], resulting in a change in the trend of LSF response. Then, an aeroelastic model is constructed to explain how the instability of LSF arises. This model can accurately predict the LSF frequency of airfoils with various structural natural frequencies. Moreover, based on the aeroelastic model, we perform linear stability analysis on the aeroelastic system and propose the instability criterion for LSF as [Formula: see text]. This instability criterion is identical to that for rotational galloping of square cylinder, indicating that LSF and rotational galloping of square cylinder are essentially the same aeroelastic phenomenon that appears in different aerodynamic profiles. This finding identifies the underlying cause for the remarkable similarities between the two phenomena.

Transonic buffet is an aerodynamic phenomenon of self-sustained shock oscillations. The aeroelastic problem caused by it is very complex, including two different dynamic modes: forced vibration and frequency lock-in. The vibration of the structure has a negative influence on the fatigue life of the aircraft. Especially in the region of frequency lock-in, the limit cycle oscillations occur due to the instability of the structural mode. Researchers have accurately predicted the region of frequency lock-in in transonic buffet and have clarified its mechanism by using a linear aerodynamic model. However, the nonlinear aeroelastic modeling and prediction of the transonic buffet remain to be solved. The long short-term memory (LSTM) deep neural network is suitable for predicting the time-delayed effects of unsteady aerodynamics. And it has achieved remarkable results in sequential data modeling. In the present work, a nonlinear model is developed for the aeroelastic system with NACA0012 airfoil in transonic buffeting flow and validated with the coupled computational fluid dynamics/computational structural dynamics (CFD/CSD) simulation. First, the data set and the loss function are specially designed. Then, the reduced-order model (ROM) based on the LSTM of the flow is built by using unsteady Reynolds-averaged Navier–Stokes computations data in a post-buffet state. By coupling the ROM and the single degree-of-freedom equation for the pitching angle, the nonlinear aeroelastic model is finally produced. The results show that the phenomenon of frequency lock-in and the self-sustained buffeting aerodynamics are precisely reconstructed. And the model has a strong generalization ability and can reproduce complex vibrations caused by competition between different modes. In short, the model can replace the CFD/CSD method in the current case with high efficiency and accuracy. The method can be used for modeling and prediction of other various complex aeroelastic systems.

In the field of computational fluid dynamics, stability and convergence problems are often encountered when solving the governing equation. This paper studies the effect of the mode multigrid on the stability and convergence of iterative algorithms. By further analyzing the mechanism for accelerating the convergence of mode multigrid, a new adaptive mode multigrid (AMMG) is proposed, and an adaptive selection criterion is formulated for the parameters of dynamic modal decomposition, which can accurately identify and filter out the unstable modes in the flowfield, thus efficiently obtaining the accurate steady solution. In the cases of laminar flow past circular cylinder and turbulent flow past airfoil, the AMMG significantly improves the stability of the iterative algorithm; in the case of transonic flow past airfoil, the AMMG solves the problem of shock wave shaking during the iteration, and the convergence is significantly improved. In summary, the AMMG method significantly enhances the stability and convergence of the iterative algorithm, and can be used as an effective convergence-preserving computation strategy.

This article is devoted to discussing the problem of global Mittag-Leffler synchronization (GMLS) for the Caputo-type fractional-order fuzzy delayed inertial neural networks (FOFINNs). First of all, both inertial and fuzzy terms are taken into account in the system. For the sake of reducing the influence caused by the inertia term, the order reduction is achieved by the measure of variable substitution. The introduction of fuzzy terms can evade fuzziness or uncertainty as much as possible. Subsequently, a nonlinear delayed controller is designed to achieve GMLS. Utilizing the inequality techniques, Lyapunov’s direct method for functions and Razumikhin theorem, the criteria for interpreting the GMLS of FOFINNs are established. Particularly, two inferences are presented in two special cases. Additionally, the availability of the acquired results are further confirmed by simulations.

This paper proposes a crack detection method for rail joint screw holes based on the ultrasonic nonlinearity. Experimental and numerical studies are conducted to validate the performance of the proposed approach. The ultrasonic signals excited and received at the rail head are processed by spectral analysis and Wavelet Packet Decomposition (WPD). The third harmonic can be clearly observed from the spectrum analysis, which is supposed to be the nonlinearity of structures. Further, WPD is used to decompose the frequency components of the received signals. A damage index (DI) is defined based on the energy percentage of the energy in the WPD node containing the third harmonic with respect to the total energy of the received signal. It is found that the DI relating to the third harmonic increases with an approximately linear relationship when the crack grows bigger. It can provide a basis for the crack detection and quantification for the rail joint screw holes. A finite element model of the experimentally tested rail is also developed and numerical studies are conducted to verify the ultrasonic nonlinearity in the rail structure. Numerical results have the same trend with the experimental results, which verifies the effectiveness of the proposed method for crack detection in rail joints based on the high order ultrasonic nonlinear harmonics.

This paper discusses a class issue of finite-time lag projective synchronization (FTLPS) of delayed fractional-order quaternion-valued neural networks (FOQVNNs) with parameter uncertainties, which is solved by a non-decomposition method. Firstly, a new delayed FOQVNNs model with uncertain parameters is designed. Secondly, two types of feedback controller and adaptive controller without sign functions are designed in the quaternion domain. Based on the Lyapunov analysis method, the non-decomposition method is applied to replace the decomposition method that requires complex calculations, combined with some quaternion inequality techniques, to accurately estimate the settling time of FTLPS. Finally, the correctness of the obtained theoretical results is testified by a numerical simulation example.

Purpose Traditional nondestructive failure localization techniques are increasingly difficult to meet the requirements of high density and integration of system in package (SIP) devices in terms of resolution and accuracy. Time domain reflection (TDR) is recognized as a novel positioning analysis technology gradually being used in the electronics industry because of the good compatibility, high accuracy and high efficiency. However, there are limited reports focus on the application of TDR technology to SiP devices. Design/methodology/approach In this study, the authors used the TDR technique to locate the failure of SiP devices, and the results showed that the TDR technique can accurately locate the cracking of internal solder joints of SiP devices. Findings The measured transmission rate of electromagnetic wave signal was 9.56 × 107 m/s in the experimental SiP devices. In addition, the TDR technique successfully located the failure point, which was mainly caused by the cracking of the solder joint at the edge of the SiP device after 1,500 thermal cycles. Originality/value TDR technology is creatively applied to SiP device failure location, and quantitative analysis is realized.

In the intelligent age, computers are required to help people complete simple daily work. Among them, computer voice databases and systems occupy a very important position in the field due to their wide application. In order to optimize the system design method, the application of IGA algorithm is proposed, and the performance of the model under the algorithm is compared and tested. The algorithm experiment shows that when the IGA objective function value is 34.4, there is no change, and the number of iterations is 100; Compared with the traditional genetic algorithm, the value of the optimal solution is always the minimum. Then the error of the optimal solution under different algorithms is compared and analyzed. It is found that the error of the optimal solution under IGA operation has the minimum value of 0.0079; The experiment of speech recognition efficiency shows that the speech recognition rate under the intervention of IGA algorithm has increased by 8%, and the overall efficiency is higher than 95%. It can be seen from the above results that IGA is helpful to the acquisition of voice database data, and improves the recognition efficiency. The feasibility of the method is high, which is of great significance to the development of China’s intelligent system industry. But at present, the overall progress of the voice system is still limited, so expanding research methods to apply to the field of voice system is still the next research direction that can be explored.

Previous studies have observed that human epidermal growth factor receptor 2 (HER2)-low-positive patients and HER2-zero patients have different prognoses. This study was conducted to investigate whether there are differences in clinicopathological characteristics and the response to neoadjuvant systemic therapy (NST) defined as systemic treatment prior to surgery between HER2-low-positive patients and HER2-zero patients. We retrospectively analyzed the data of patients with HER2-negative breast cancer who received NST at the First Affiliated Hospital of Nanjing Medical University from 2014 to 2021. There were 238 patients with HER2-low-positive status and 198 patients with HER2-zero status. The proportion of hormone receptor (HR)-positive patients in the HER2-low-positive group was significantly higher than that in the HER2-zero group (82.8% vs 52.0%, p

Left bundle branch area pacing (LBBAP) includes left bundle branch pacing (LBBP) and left ventricular (LV) septal myocardial pacing (LVSP).The study aimed to assess resynchronization effects and clinical outcomes by LBBAP in heart failure (HF) patients with cardiac resynchronization therapy (CRT) indications.LBBAP was successfully performed in 29 consecutive patients and further classified as the LBBP-group (N = 15) and LVSP-group (N = 14) based on the LBBP criteria and novel LV conduction time measurement (LV CT, between LBBAP site and LV pacing (LVP) site). AV-interval optimized LBBP or LVSP, or LVSP combined with LVP (LVSP-LVP) was applied. LV electrical and mechanical synchrony and clinical outcomes were assessed.All 15 patients in the LBBP-group received optimized LBBP while 14 patients in the LVSP-group received either optimized LVSP (5) or LVSP-LVP (9). The LV CT during LBBP was significantly faster than that during LVP (p .001), while LV CT during LVSP were similar to LVP (p = .226). The stimulus to peak LV activation time (Stim-LVAT, 71.2 ± 8.3 ms) and LV mechanical synchrony (TSI-SD, 35.3 ± 9.5 ms) during LBBP were significantly shorter than those during LVSP (Stim-LVAT 89.1 ± 19.5 ms, TSI-SD 49.8 ± 14.4 ms, both p .05). Following 17(IQR 8) months of follow-up, the improvement of LVEF (26.0%(IQR 16.0)) in the LBBP-group was significantly greater than that in the LVSP-group (6.0%(IQR 20.8), p = .001).LV activation in LBBP propagated significantly faster than that of LVSP. LBBP generated superior electrical and mechanical resynchronization and better LVEF improvement over LVSP in HF patients with CRT indications.

Observational epidemiologic studies have associated vitamin D deficiency with cholestasis. It has been reported by our laboratory that the vitamin D/vitamin D receptor (VDR) axis activation in cholangiocytes mitigates cholestatic liver injury by remodeling the damaged bile duct. However, the function of VDR in hepatocytes during cholestasis remains unclear.Paricalcitol (VDR agonist, 200 ng/kg) was injected intraperitoneally into bile duct-ligated mice every other day for 5 days. Primary hepatocytes and HepG2 cells were transfected with Vdr short hairpin RNA, control short hairpin RNA, Vdr plasmid, control vector, Atg5 small interfering RNA (siRNA), and control siRNA. Liver histology, cell proliferation, and autophagy were evaluated.Treatment with the VDR agonist paricalcitol improved bile duct-ligated mouse liver injury by up-regulating VDR expression in hepatocytes, which in turn reduced hepatocyte apoptosis by inhibiting reactive oxygen species (ROS) generation via suppressing the Ras-related C3 botulinum toxin substrate 1/reduced nicotinamide adenine dinucleotide phosphate oxidase 1 pathway. Mechanistically, upon exposure to the ROS-inducing compound, Vdr siRNA contributed to apoptosis events, whereas the Vdr plasmid led to apoptosis resistance. Interestingly, up-regulated VDR expression also appeared to increase autophagosome generation and macroautophagic/autophagic flux, which was the underlying mechanism for VDR activation-inhibited apoptosis. Autophagy depletion completely impaired the up-regulated VDR-inhibited apoptosis events, whereas autophagy induction showed a synergistic effect with VDR overexpression. Importantly, up-regulation of VDR promoted autophagy activation by suppressing the activation of the extracellular signal-regulated kinase (ERK)/p38 mitogen-activated protein kinase (p38MAPK) pathway. The p38MAPK inhibitor abrogated the Vdr siRNA-induced decrease in autophagy and the Vdr siRNA-induced increase in apoptosis. In contrast, the MEK/ERK activator prevented the Vdr plasmid-enhanced autophagy and decreased apoptosis. Moreover, the ROS inhibitor NAC blocked Vdr siRNA-enhanced activation of the ERK/p38MAPK pathway.VDR activation mitigated liver cholestatic injury by reducing autophagy-dependent hepatocyte apoptosis and suppressing the activation of the ROS-dependent ERK/p38MAPK pathway. Thus, VDR activation may be a potential target for the treatment of cholestatic liver disease.

All ferromagnetic metal perforated with nanopore arrays with high sensing performance.