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A model prediction controller (MPC) based on radial basis function (RBF) neural network is designed to counter the model uncertainty and multiple constraints of the autonomous underwater vehicle (AUV). On this basis of path following control with MPC, the RBF neural network is trained online with real-time measurement data to compensate for the AUV's model uncertainty, thus suppressing the interference of model uncertainty on the MPC and reducing its overshoot and tracking error. Simulation results show that the path following algorithm based on RBF-MPC has better transient and steady-state performance compared with the classical MPC algorithm.

A kind of nitrile rubber (NBR) with high bound acrylonitrile content was prepared by low-temperature emulsion-polymerization and the sequence structure of the polymer was characterized by proton nuclear magnetic resonance spectroscopy, and the effects of different coagulants on the coagulation behavior and physico-mechanical properties of the polymer were studied. The results showed that the BAA sequence structure appeared in NBR with high bound acrylonitrile content, and the content of BAA, BAB, and ABA sequence structures increased gradually and that of BBB and BBA sequence structures decreased gradually with the increase in bound acrylonitrile content; the coagulation efficiency of CaCl2 and Al2(SO4)3 was much higher than those of NaCl and H2SO4, and the coagulation efficiency of the first two both reached about 98%; Al2(SO4)3 could improve the hardness, tensile strength, modulus, and elongation at break of NBR, and the elongation at break of NBR prepared from Al2(SO4)3 was 566%.

To investigate the effect of group gliding formation on the hydrodynamic performance of manta rays, numerical simulations were used to investigate the drag, the lift and pressure distribution of multiple manta rays in tandem, triangular and diamond-shaped arrangements. The simulation results show that the leader manta ray at the head of the group always suffers the least drag, and in most cases, the companion manta ray at the tail of the group suffers the most drag. The pressure distribution in the flow field shows that the drag reduction effect mainly comes from the distribution of high pressure and low pressure zones among the individual rays in the cluster, the high pressure zone is beneficial to the manta rays at the front of the group, and under certain circumstances, the presence of low pressure zone generates forward suction to reduce the drag of the manta rays at the end of the group. It is found that when manta rays glide in "two in front and one at the back", four-body diamond, six-body tandem and six-body diamond arrangement, the average drag of the system can be reduced, which provides theoretical guidance for the formation of bionic vehicle groups.

A pre-swirl pumpjet propeller(PJP) is widely used in the new generation of quiet submarines all over the world, although the experimental study of its hydrodynamic performances is still rare. This paper carries out experimental tests of the pre-swirl PJP with a 9-blade stator and a 7-blade rotor in a cavitation water tunnel. The thrust coefficient and torque coefficient of the pre-swirl PJP in open water are tested with a force measurement device, and the wake flow field of the pre-swirl PJP is tested with a laser particle velocimetry system. The experimental results show that the rotor thrust coefficient, stator-duct thrust coefficient and rotor torque coefficient of the pre-swirl PJP decrease with increasing the advance coefficient J, but the absolute value of the torque coefficient of the stator-duct thrust increases with increasing J. The open water efficiency of the pre-swirl PJP reaches the maximum when J=1.0, being 61.91%. The thrust of the pre-swirl PJP is mainly provided by the rotor. In addition, the wake flow field of the pre-swirl PJP is composed of jet acceleration zone, hub low-speed zone and mixed zone. The transient velocity and average velocity in the wake flow field under different working conditions are obtained.

Flow-induced noise hybrid prediction method based on sound wave boundary condition is an effective numerical method to deal with a flow-induced noise problems of complex configuration. This method can not only finely simulate the sound source, but also analyze the noise propagation characteristics. In this paper, numerical methods such as space-time discrete scheme and boundary conditions involved in discrete solution of acoustic perturbation equations(APE) are developed, and strategies such as adding buffer layer are proposed to improve divergence caused by numerical discontinuity at the junction of sound source region and propagation region, so as to establish a high-precision flow-induced noise hybrid method. In order to study the rationality of flow-induced noise hybrid method, the numerical simulation of acoustic radiation at the trailing edge of NACA0012 airfoil in BANC experiment was carried out. Compared with the results of sound field solved by large eddy simulation method, the analysis shows that the high-precision flow-induced noise hybrid method based on sound wave boundary conditions can predict the spatial sound field distribution with high precision and directly reflect the interaction between sound waves. Compared with the results of large eddy simulation, the error of sound pressure level is less than 2 dB, and the noise directional distribution trend is consistent.

Objective To share our experience of percutaneous or transthoracic closure of atrial septal defect (ASD) and ventricular septal defect (VSD) supported by echocardiography guidance. Methods From December 2010 to September 2019, 54 patients of congenital heart disease (30 cases of isolated atrial septal defect, 24 cases of ventricular septal defect) were treated with surgical operation by occluder under guidance of echocardiography closed without cardiopulmonary bypass. Fourteen cases of ASD were performed device closure through a small right sternal margin thoracotomy incision at the forth intercostal space, 16 cases of ASD underwent percutaneous occlusion surgery, and 24 cases of VSD were closed through small incision under the xiphoid process. Results The operations were successful in the 24 cases of VSD. One of the cases with minimally incision ASD occlusion was displaced 7 hours after operation, the occluder was taken out and ASD was repaired under cardiopulmonary bypass in emergency. There were 13 cases of successful occlusion and 3 cases of failure in percutaneous ASD closure patients. Among three cases, 2 cases underwent ASD closed through transthoracic closure and 1 case underwent open surgery under cardiopulmonary bypass successfully. The 46 cases were followed up for 3-103 months, with an average of (21.3±16.2)months. No occluder displacement, shedding, significant residual shunt were observed. Conclusions Echocardiography-guided percutaneous atrial septal defect and ventricular septal defect is safe and effective without radiation and CPB. Percutaneous closure of atrial septal defect is suitable for children over 3 years. Atrial septal defect and ventricular septal defect occlusion through small thoracic incision is feasible and easy to operate in other healthcare institutions.

Underwater Bionic Robot swarm has the advantages of high redundancy, flexible mobility and wide range of task execution, which can be applied to underwater environment monitoring, underwater target monitoring, resource exploration and other fields. For a long time, the problem of energy consumption is the focus on the application of Underwater Bionic Robot swarm engineering. This article draws on the sports advantages of biological clusters, from the perspective of hydrodynamic analysis, summarizes the domestic and foreign research status of key energy-saving technologies of underwater bionic robot clusters. The main content includes a summary on the development status of the three key technologies of biological cluster movement energy saving mechanism, underwater bionic robot vortex field information perception and cluster cooperative control, and analysis and summary of the development trend of key energy-saving technologies of underwater bionic robot cluster.

In order to obtain the influence of water entry angle and speed on the cavitation and impact load characteristics of supercavitating vehicle, a high-speed water entry numerical model of supercavitating vehicle based on VOF model is established, and the accuracy of the model is verified by relative experiments. Through simulation, the cavitation evolution process, cavitation size, impact load change and surface pressure distribution of supercavitating vehicle entering water at different angles and velocities are obtained and compared. The results show that with the increase of water entry velocity, the depth of cavitation closing position increases, the cavitation size increases, the peak value of axial load increases and the surface pressure of vehicle increases; With the increase of water entry angle, the bubble closing time remains unchanged, the bubble size decreases, the axial load peak increases, and the asymmetry of pressure distribution decreases. The pressure on the upstream surface of the cavitator increases along the radius to the center of the circle, but the asymmetry decreases when it enters the water obliquely.

In order to explore the mechanism of bionic propulsion and bionic robots, to make up for the limitations of traditional propulsion with a uniform incoming flow, numerical methods are used to couple fluid dynamics and flapping foil motions, and a flapping-fluid coupling self-propulsion calculation model is established in this paper. K is used as the waveform adjustment parameter to change the waveform from triangle wave to sine wave and square wave. The self-propulsion performances of non-sinusoidal heave motion under two frequency-heaving amplitude combinations are numerically simulated to study the influence of different motion waveforms on self-propulsion velocity, efficiency and flow field structure in still water. The results show that the non-sinusoidal waveform has a great influence on the self-propulsion. With the increase of K, the closer to the square wave, the more violent the speed oscillation, the faster the starting acceleration, the greater the forward displacement and the average speed, as K decreases, self-propulsion efficiency and energy utilization continue to increase. The results of this study have certain guiding significance for the design of bionic underwater vehicles.

When a resistance test of an underwater vehicle model is conducted in a towing tank, the blockage effect will inevitably occur, particularly since the experimental model is relatively large. This paper investigates the estimation of resistance coefficients for an Axisymmetrical Rotary Body Underwater Vehicle (ARBUV) and a Blended Wing Body Underwater Vehicle (BWBUV). The Computational Fluid Dynamics (CFD) method is employed to predict the resistance of Autonomous Underwater Vehicles (AUVs). In order to quantify the blockage effect on the resistance coefficients of AUVs with different configurations, the resistance coefficients of AUVs are calculated in the infinite domain and finite domain under various blockage ratios. Through analysis of the resistance results, velocity distribution, and pressure distribution, the action law of the blockage effect is provided. It indicates that blockage effects have a greater influence on the pressure resistance for ARBUV. Surprisingly, the resistance coefficients of BWBUV are less affected, though it is closer to the sidewalls. It suggests that the blockage ratio of ARBUV and BWBUV should be separately smaller than 0.375% and 2.5% in the towing tank test. The towing tank experiments satisfy the blocking ratio with a Reynolds number greater than 107, which saturates the blocking effect and further reduces the effect on the drag coefficient. [ABSTRACT FROM AUTHOR]

To address the significance of enhancing myelination for functional recovery after white matter injury (WMI) in preterm infants, we characterized hypomyelination associated with chronic hypoxia and identified structural and functional deficits of excitatory cortical synapses with a prolonged motor deficit. We demonstrate that genetically delaying myelination phenocopies the synaptic and functional deficits observed in mice after hypoxia, suggesting that myelination may possibly facilitate excitatory presynaptic innervation. As a gain-of-function experiment, we specifically ablated the muscarinic receptor 1 (M1R), a negative regulator of oligodendrocyte differentiation in oligodendrocyte precursor cells. Genetically enhancing oligodendrocyte differentiation and myelination rescued the synaptic loss after chronic hypoxia and promoted functional recovery. As a proof of concept, drug-based myelination therapies also resulted in accelerated differentiation and myelination with functional recovery after chronic hypoxia. Together, our data indicate that myelination-enhancing strategies in preterm infants may represent a promising therapeutic approach for structural/functional recovery after hypoxic WMI.

Different nose shape can cause a significant influence on the water entry trajectory and cavity. In order to study the evolution characteristics of cavity and trajectory of asymmetric nose in the process of water entry, based on the high-speed photography technology, the low-speed water entry comparative experiments were carried out for three different cut-angle nose types of 35°, 40° and 45° under different water entry angles. Through digital image processing technology, the contour of the water entry cavity and motion attitude information of the vehicle at different times are extracted, and the law of influence of the cut angle and entry angle on the cavity and trajectory is obtained. The experimental results show that: the cut angle side of the asymmetric nose can effectively promote the expansion of the cavity, thus forming the asymmetric water entry cavity; the expansion scale of the cavity is positively related to the initial horizontal expansion speed of the cavity and the area of the section of the head; the water entry trajectory of the asymmetric head will deflect to the cut angle side; the smaller the water entry angle is, the shorter the trajectory leveling time is, and the deeper the leveling depth is However, the change of attitude angle is almost independent of the entry angle.

In order to solve the underwater noise pollution and improve the acoustic stealth performance of underwater vehicles, NACA0020 was bionically modified according to the structure of the leading edge tubercles of humpback fin. The flow field and noise characteristics of the hydrofoil-turbulent interaction model before and after the modification were studied by using the large eddy simulation and the FW-H equation. The results show that the wavy leading edge can effectively reduce the turbulence interaction noise of the hydrofoil, especially the broadband noise after 89.55 Hz. The overall sound pressure level(OASPL) directivity of the wavy leading edge hydrofoil are the same as the original hydrofoil, and both have dipole characteristics, but the noise value in all directions is reduced to a certain extent. The OASPL is calculated and analyzed in different frequency bands. The results show that the OASPL has a best reduction in 1 000-5 000 Hz frequency band, and the noise can be reduced up to 12.6 dB. Through the analysis of flow field, it is concluded that the noise reduction effect of wavy leading edge mainly relates to the decrease in pressure fluctuation at leading edge and the decrease in coherence of vortex in spanwise direction caused by the enhancement of spanwise flow.

The pump-jet propulsor(PJP) performances under various rotational speeds (20~50 r/s) are analyzed for further studying the influence of the Reynolds number (Re) on the hydrodynamics of PJP, before this, the calculation model is verified by using the experiment data, it proves the present numerical method is proper to make a further study. The results indicate both the hydrodynamic coefficients of PJP and PJP components and the contours with dimensionless variables are present high similarity, yet the Re has the slight effect on the components performance, among which, the force coefficient of rotor is the least affected, with a relative error no more than 1%. Followed is the force coefficient of rotor stator, the maximum error is 2.1%, since the force of duct and stator is so low that has the slight effect on PJP, the total force error is less than 2%. However, the torque coefficient error is bigger with a value of about 3%. Besides, it is found that all hydrodynamic coefficients vary monotonically with rotating speed, the higher Re caused by increasing the rotational speed will contribute to enhance the work ability of rotor, thus cause a lower pressure at vortex core, and change the trajectory of TLV.

Objective To investigate the expression of HIF-1 α, PAR-1 and VEGF in breast cancer tissues from patients with type 2 diabetes and the effect of hypoxia microenvironment on the invasion and proliferation of human breast cancer cell line (MCF-7). Methods Thirty-seven specimens of breast cancer from patients with complicated with type 2 diabetes mellitus were examined by surgical resection. The expression of HIF-1α, PAR-1, VEGF and microvessel density (MVD) in breast cancer and paracancerous tissues were examined by immunohistochemistry. MCF-7 cells were divided into control group (5.6 mmol/L glucose), high glucose group (30 mmol/L glucose), hypoxia group (1% O2 5% CO2 94% N2) and high glucose plus hypoxia group. The cell morphology was observed by microscoped, the cell proliferation was detected by CCK-8 method, the invasive ability of cells was detected by Transwell chamber test, and the expression of HIF-1α, PAR-1, VEGF mRNA and protein were detected by RT-qPCR and Western blot. Results The expression of HIF-1α, PAR-1, VEGF and MVD count in breast cancer tissues were higher than those in periaracancerous tissues(P＜0.05); the number of cells passing through the basement membrane and the cell survival rate of MCF-7 in the high glucose hypoxia group were significantly higher than those in the control group (P＜0.01); and the expressions of HIF-1α, PAR-1, VEGF mRNA and protein in the hypoxia group and hypoxia high glucose group were significantly higher than those in the control group(P＜0.05). Conclusions Hypoxia and high glucose can promote the proliferation and invasion and the expression of HIF-1α, PAR-1, VEGF of MCF-7 cells, which is a potential target for clinical detection and treatment of breast cancer of patients with type 2 diabetes.

Underwater vehicles heavily depend on the integration of inertial navigation with Doppler Velocity Log (DVL) for fusion-based localization. Given the constraints imposed by sensor costs, ensuring the optimization ability and robustness of fusion algorithms is of paramount importance. While filtering-based techniques such as Extended Kalman Filter (EKF) offer mature solutions to nonlinear problems, their reliance on linearization approximation may compromise final accuracy. Recently, Invariant EKF (IEKF) methods based on the concept of smooth manifolds have emerged to address this limitation. However, the optimization by matrix Lie groups must satisfy the "group affine" property to ensure state independence, which constrains the applicability of IEKF to high-precision positioning of underwater multi-sensor fusion. In this study, an alternative state-independent underwater fusion invariant filtering approach based on a two-frame group utilizing DVL, Inertial Measurement Unit (IMU), and Earth-Centered Earth-Fixed (ECEF) configuration is proposed. This methodology circumvents the necessity for group affine in the presence of biases. We account for inertial biases and DVL pole-arm effects, achieving convergence in an imperfect IEKF by either fixed observation or body observation information. Through simulations and real datasets that are time-synchronized, we demonstrate the effectiveness and robustness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Side-scan sonar plays a crucial role in underwater exploration, and the autonomous detection of side-scan sonar images is vital for detecting unknown underwater environments. However, due to the complexity of the underwater environment, the presence of a few highlighted areas on the targets, blurred feature details, and difficulty in collecting data from side-scan sonar, achieving high-precision autonomous target recognition in side-scan sonar images is challenging. This article addresses this problem by improving the You Only Look Once v7 (YOLOv7) model to achieve high-precision object detection in side-scan sonar images. Firstly, given that side-scan sonar images contain large areas of irrelevant information, this paper introduces the Swin-Transformer for dynamic attention and global modeling, which enhances the model's focus on the target regions. Secondly, the Convolutional Block Attention Module (CBAM) is utilized to further improve feature representation and enhance the neural network model's accuracy. Lastly, to address the uncertainty of geometric features in side-scan sonar target features, this paper innovatively incorporates a feature scaling factor into the YOLOv7 model. The experiment initially verified the necessity of attention mechanisms in the public dataset. Subsequently, experiments on our side-scan sonar (SSS) image dataset show that the improved YOLOv7 model has 87.9% and 49.23% in its average accuracy ( m A P 0.5 ) and ( m A P 0.5:0.95), respectively. These results are 9.28% and 8.41% higher than the YOLOv7 model. The improved YOLOv7 algorithm proposed in this paper has great potential for object detection and the recognition of side-scan sonar images. [ABSTRACT FROM AUTHOR]