The Mellin non-uniformly distributed moving blade method was adopted to conduct CFD numerical analysis and sample experimental tests on the axial-flow turbines before and after optimization using the uniformly distributed and non-uniformly distributed design methods, respectively. In the original design, five blades were evenly distributed in the 360° circumferential direction, and the non-uniformly distributed angles were 46°, 102°, 46°, 83°, and 83°. CFD numerical analysis shows that due to the low rotational speed of the turbine and the absence of a sealing structure at the blade tip, factors such as tip noise leakage and backflow have little impact, and the flow field pulsation is mainly caused by the blades themselves. The non-uniformly distributed design can significantly enhance the work-doing capacity of the blades. At 90% of the blade height, the torque can be increased by up to 60%, but at the same time, the axial force on the blades also increases accordingly. Near 80% - 90% of the blade height, the axial force increases by 33%. The flow rate performance of the non-uniformly distributed design is slightly inferior to that of the uniformly distributed design, but the overall noise is better than that of the uniformly distributed design, with maximum optimization of 0.48 dB (A); the maximum values of the first three orders of discrete noise are significantly improved, with a maximum improvement of 0.75 dB (A), and the discrete noise orders of the non-uniformly distributed turbine can avoid blade - related factors and disperse the energy to nearby orders.

This study presents a hydrodynamic analysis of an optimised heaving buoy for a single-body point absorber wave energy converter (WEC). A conventional deep-draft cylindrical buoy is modified into a composite single-body configuration consisting of three rigidly coupled sections to improve frequency-dependent hydrodynamic performance while reducing structural volume. The proposed buoy is compared with a reference cylindrical buoy adapted from Ruezga (2019). The governing equations are formulated considering added mass, radiation damping, and hydrostatic restoring forces. Numerical simulations are performed in Ansys AQWA under both frequency-domain and time-domain conditions using regular and irregular wave analyses. The results show that the proposed buoy increases peak absorbed power to 58.4 kW, achieving a 6.8% improvement over the reference buoy, together with a 15% broader operational frequency bandwidth. These improvements are achieved with approximately 10% reduction in structural volume while maintaining a simple oscillating system configuration. The findings demonstrate the effectiveness of geometry-based optimisation for improving the hydrodynamic performance of point absorber WECs.

The push for higher energy density in electric vehicles has resulted in large-sized lithium-ion batteries, but their geometric upscaling exacts a heavy thermal price. Under high-rate discharge, these massive cells become heat traps, risking thermal runaway. To tame this instability, this paper engineered a hybrid management strategy fusing liquid cooling, Phase Change Materials (PCMs), and flow deflectors. With a primary focus on the structural optimization of the cooling channel, a three-dimensional numerical model, calibrated using experimentally determined thermophysical properties, was developed to overcome the thermal bottlenecks of conventional cooling architectures. Results indicated that the initial channel optimization effectively reduced the maximum temperature to 327.7 K, but it still remained near the safety threshold. Integrating PCM radically altered the thermal landscape, slashing the outlet temperature differential by 41.67% (from 2.76 K to 1.61 K) compared to pure liquid cooling and blunting peak thermal spikes. Furthermore, to overcome laminar stagnation, strategic deflector baffles were introduced to agitate the coolant, enhancing heat dissipation. Specifically, the optimal half-coverage (L = 1/2) baffle configuration successfully lowered the maximum temperature to 322.42 K while substantially reducing the system pressure drop from 948.16 Pa to 627.57 Pa, achieving a 33.33% reduction compared to the full-coverage scheme. Finally, a multi-variable sensitivity analysis confirmed the extraordinary engineering robustness of the optimized configuration, demonstrating a negligible maximum temperature fluctuation of less than 0.5% despite +/- 10% operational and material uncertainties. This synergistic system actively stabilizes the thermal envelope, offering a robust engineering blueprint for next-generation high-power battery packs.

This study investigates an aerodynamic optimization framework inspired by marine biological morphology, utilizing the sailfish profile as a basis for airfoil configuration. Through Latin hypercube experimental design combined with optimization algorithms, four key geometric variables governing the airfoil’s hydrodynamic characteristics were systematically analyzed. Parametric studies revealed that pivotal factors including installation angle significantly influenced the fluid dynamic performance metrics of lift generation and pressure drag. Response surface methodology was employed to establish predictive models for these critical performance indicators, effectively reducing computational resource consumption and experimental validation costs. The refined bio-inspired configuration demonstrated multi-objective performance improvements compared to the baseline configuration, validating the computational framework’s effectiveness for hydrodynamic profile optimization studies. Furthermore, a coaxial dual-rotor vertical axis turbine configuration was developed, integrating centrifugal and axial-flow energy conversion mechanisms through a shared drivetrain system. The centrifugal rotor component harnessed tidal current kinetic energy while the axial-flow rotor module captured wave-induced potential energy. Transient numerical simulations employing dynamic mesh techniques and user-defined functions within the Fluent environment were conducted to analyze rotor interactions. Results indicated the centrifugal subsystem demonstrated peak hydrodynamic efficiency at a 25° installation angle, whereas the axial-flow module achieves optimal performance at 35° blade orientation. Parametric optimization revealed maximum energy extraction efficiency for the centrifugal rotor occurs at λ = 1.25 tip-speed ratio under Re = 1.3 × 105 flow conditions, while the axial-flow counterpart attained optimal performance at λ = 1.5 with Re = 5.5 × 104. This synergistic configuration demonstrated complementary operational characteristics under marine energy conversion scenarios.

In this study, the dynamic mechanical properties of C60 concrete under biaxial confinement were systematically investigated through experiments and numerical simulations. The experimental investigation employed a triaxial Split Hopkinson pressure bar to study the dynamic response of C60 concrete under various confining pressures (0 MPa, 5 MPa, 7.5 MPa, and 10 MPa) and high strain rates (60 s-1, 90 s-1, and 110 s-1). The numerical simulation results were consistent with the experimental data, thereby confirming the reliability of the numerical model. The results indicated that the confinement and strain rates exerted a notable synergistic effect on the dynamic strength and damage characteristics of C60 concrete. A higher confining pressure significantly enhanced the load-bearing capacity, whereas increased strain rates further improved the dynamic performance. Energy dissipation analysis revealed a saturation effect regarding the regulation of wave propagation by the confining pressure. These findings provide essential insights into the effective application of prestressed concrete in protective structures.

The vertical axis hydrokinetic turbine is increasingly being used as a renewable energy device to harness tidal energy. In coastal regions with low tidal flow velocities, vertical-axis hydrokinetic turbines often exhibit low energy conversion efficiency, limiting their engineering applications. However, research in this field lacks systematic reviews and reliable solutions for improving efficiency. The paper, based on the traditional vertical axis hydrokinetic turbines, utilized numerical calculations and experimental methods to investigate the effects of blade helicity and airfoil curvature on the energy conversion efficiency of vertical axis hydrokinetic turbines in low flow velocity conditions. Additionally, an improved vertical-axis turbine model is proposed to enhance energy conversion efficiency in low-flow environments. The results indicate that increasing the blade helical angle and airfoil curvature can better optimize the flow conditions around the turbine, significantly improving the energy conversion efficiency of vertical axis turbines. The airfoil blade with a 20% curvature performs best at blade angle, with its power coefficient curve reaching higher peak values at several azimuth angles. At this point, the maximum efficiency reaches 24.42%. Compared to the conventional straight-blade design, the improved turbine model exhibits 6.13% increase in average energy capture efficiency, 3.70% increase in average dynamic torque, and 11.1% improvement in self-starting performance. Comparative analysis reveals that vertical-axis helical blade turbines exhibit superior hydrodynamic performance under low-flow conditions, effectively overcoming the limitations of conventional straight-blade turbines, including poor self-starting capability and low efficiency. This research provides valuable insights into improving the performance of vertical-axis turbines in low-flow environments and suggests innovative solutions for optimizing turbine design.

This article uses the sailfish outline as an airfoil profile to create a dual vertical-axis water turbine model for capturing wave and tidal current energy. A parametric water turbine model is built with the shape function perturbation and characteristic parameter description methods. Optimized by the multi-island genetic algorithm on the Isight platform, a CNC sample of the optimized model is made. Its torque and pressure are measured in a wind tunnel and compared with CFD numerical analysis results. The results show small differences between the numerical and experimental results. Both indicate that the relevant performance parameters of the turbine improved after optimization. During constant flow velocity measurement, the optimized axial-flow turbine has a pressure increase of 55% and a torque increase of 40%, while for the centrifugal turbine, the pressure increases by 60% and the torque by 12.5%. During constant rotational speed measurement, the axial-flow turbine’s pressure increases by 16.7%, with an unobvious torque increase. The Q-criterion diagram shows more vortices after optimization. This proves the method can quickly and effectively optimize the dual vertical-axis water turbine.

Abstract This article adopts a biomimetic approach and uses the profile of the fastest sailfish in the ocean as the airfoil profile of a water turbine. Integrating centrifugal and axial flow turbines on one drive shaft can effectively integrate wave and current energy (wave current integration). The wake of a centrifugal turbine flows into the flow field of an axial flow turbine, and based on the Kantar effect, the energy harvesting coefficient of the axial flow turbine is improved. The five blades of the axial flow turbine and centrifugal turbine are subjected to uneven forces, resulting in torsional and radial forces on the drive shaft, causing periodic series motion of the turbine and reducing the overall lifespan of the machine.

This article takes the outline of the sailfish as an airfoil profile and establishes a dual vertical axis water turbine model. The centrifugal and axial flow water turbines share a common drive shaft, which is connected to the generator. The centrifugal water turbine utilizes tidal energy, while the axial flow water turbine utilizes wave potential energy. Based on Fluent UDF and sliding grid, numerical simulation of hydraulic turbines was conducted, and it was found that the centrifugal turbine had the highest energy harvesting coefficient at an attack angle of 25 degrees, while the axial flow turbine had the highest energy harvesting coefficient at an attack angle of 35 degrees. The centrifugal turbine has the highest energy gain when the tip speed ratio is 1.25 and the Reynolds number is 1.3e (boolean AND) 5. The axial flow turbine has the highest energy gain when the tip speed ratio is 1.5 and the Reynolds number is 5.5e (boolean AND) 4. The downstream turbine impeller utilizes the Kantar effect to perform work, but the boundary layer separation is severe and vortex shedding is obvious, which seriously affects the energy harvesting efficiency of the turbine.

By combining computational fluid dynamics (CFD) and surrogate model method (SMM), the relationship between turbine performance and airfoil shape and flow characteristics at low flow rate is revealed. In this paper, the flow velocity tidal energy airfoil model is designed based on the Kriging model, and the original airfoil with a relative thickness of 12% and a relative curvature of 2.5% is obtained. The parameter optimization is carried out by setting the 4th CST equations through the surrogate model; the maximum lift-drag ratio is the optimization goal, the optimization design variable is 10, the maximum number of iterations is 100, and the maximum number of sub-optimization iterations is 200. The results show that the hydrodynamic performance of the airfoil with thinner thickness and more curvature is better, the maximum thickness part is shifted forward by 4.58%, and the lift-drag ratio is improved by 4.03%. The flow field and the efficiency are more stable, which provides an engineering reference for the optimal design of hydraulic turbine airfoils under low flow velocity. It supplements the research on the performance of turbine blades in low velocity.

The spontaneous growth and evolution mechanism of metal whiskers have long been scientific problems. With the development of the integration of electronic and electrical productions, short circuits and system failures are raised by metal whiskers continuously. In the meantime, the related theories and mechanisms of whiskering problem are still vague, leading to a deficiency in the studies of environmental factors influencing the whisker phenomenon. Besides, the extreme environments such as aerospace, have been proven the accelerators to the formation of metal whiskers, resulting in a severe threaten to equipment and devices working in such environments including satellite and military equipment. To establish a comprehensive understanding to the whiskering process associated with their applicable control strategies, this study analyzes the growth phenomenon, influencing factors, formation process and evolution mechanism of metal whiskers in extreme service environments, puts forward the corresponding controlling strategies, offers a reference for the establishment of Chinese extreme aerospace strategic environment, and improves the reliability of aerospace systems.

针对应用于海上多无人艇目标搜索任务的经典深度强化学习模型难以收敛且训练耗时长的问题,提出一种基于优先经验回放的异步确定性策略梯度模型.为提升模型收敛效果,引入一种基于优先级的经验回放机制,该机制可以有效提高高价值经验的利用率,从而避免算法收敛困难的问题.为进一步减少模型训练耗时长,引入异步学习的训练框架,该框架通过多子线程的同步训练参数更新主进程网络,有效提高了模型训练效率.在MPE仿真环境对提出的PA-MADDPG算法与MADDPG、MAPPO和PER-MADDPG算法进行对比实验,结果表明:提出模型在1 000～1 200 回合就达到收敛,经过1 000 回合左右训练智能体总碰撞次数就趋于0,相较于其他算法任务成功率提高了5%～10%.

The hulls of marine vehicles are generally very effective at attenuating airborne acoustic noise generated by their powertrains. However, conventional hull designs are generally not very effective at attenuating wide-band low-frequency noise. Meta-structure concepts offer an opportunity for the design of laminated hull structures tailored to address this concern. This research proposes a novel meta-structure laminar hull concept using periodic layered Phononic crystals to optimize the sound insolation performance on the air–solid side of the hull structure. The acoustic transmission performance is evaluated using the transfer matrix, the acoustic transmittance, and the tunneling frequencies. The theoretical and numerical models for a proposed thin solid-air sandwiched meta-structure hull indicate ultra-low transmission within a 50-to-800 Hz frequency band and with two predicted sharp tunneling peaks. The corresponding 3D-printed sample experimentally validates the tunneling peaks at 189 Hz and 538 Hz, with 0.38 and 0.56 transmission magnitudes, respectively, with the frequency band between those values showing wide-band mitigation. The simplicity of this meta-structure design provides a convenient way to achieve acoustic band filtering of low frequencies for marine engineering equipment and, accordingly, an effective technique for low-frequency acoustic mitigation.

We propose a multi-band acoustic metalens that achieves 18–26 λ long beam focusing and with narrow FWHM of 4–5 λ across multiple frequency bands, utilizing principles of multiple scattering theory. The metalens sample was meticulously fabricated using quadrilateral lattice scatterers in the cross section, and its experimental acoustic field tests showed focused sound beams with a length of 0.78–1.07 m falling within the frequency bands of 5800–6100 Hz, 8500–8700 Hz, and 9700-9900 Hz. This study holds potential applications in acoustic directional projection, signal enhancement, and acoustic power collection.

非接触磁浮机构是航空、航天、高铁设备的重要控制元件.而对磁浮机构中的组成部分——线圈及磁缸相互作用产生的弱洛伦兹力的检测,从而指导线圈和磁缸的优化则显得极为重要.针对传统检测系统多维测量精度低、波动大、操作困难等问题,设计了一种磁浮机构弱磁力多维检测系统.该系统采用稳定可靠的双输出可编程电流源、三维位移电动平台、光栅尺、上位机、工控机等设备,实现了非接触磁浮机构洛伦兹力多自由度检测.该系统配合了先进成熟的控制及检测技术,达到了有效的降振降噪处理,实测结果证明,非接触磁浮机构弱磁力检测系统运行稳定、可靠性高、检测精度满足要求.

The widespread heavy metal contamination in soil induced by extensive human disturbance has been a global significant issue because of its chronic toxic effects on human health. However, the establishment of effective monitoring and assessing methods for heavy metal content in the soil remain a long-term challenge due to the intrinsic limitation of the current multi-band remote sensing technology and field measurement methods. Prompted by this significant technique gap, we represent an implementation of remote-sensing inversion models based on hyperspectral imagery to reconstruct soil heavy metal contents within an experimental farmland located in Mianzhu city, Sichuan, China. We collected soil samples at the pre-defined sites, and measured soil heavy metal contents and soil spectrum in the laboratory condition. Meanwhile, we obtained Orbita Hyper -spectral Satellites (OHS) imagery and quantified the associated vegetation indexes. The measured soil spectrum, bands of OHS, and the generated vegetation indexes were mathematically transformed to better represent their relations with soil heavy metal contents. Consequently, the most sensitive variables were selected as potent predictors of soil heavy metal contents in the inversion models. After evaluating the optimal inversion models for each heavy metal element, we implemented them to reconstruct the spatial patterns of soil heavy metal contents over the study landscape. We found obvious benefits of the remote sensing inversion model in predicting the spatial heterogeneity of heavy metal content within this small landscape patch. Specifically, the inversion model unraveled a normal distribution of heavy metal contents within the landscape, while the traditional spatial interpolation based on field measurements may suggest a largely skewed distribution. Compared with airborne -based studies, this study represents an application of spaceborne satellite data, which can be easily applied to a large spatial scale and long-term monitoring.

Floating offshore wind turbines (FOWTs) are located in complex ocean environments; therefore, they typically exhibit more significant dynamic responses than land-based wind turbines. Examples from the marine and offshore industries have shown that mooring line systems may fail under mild to severe sea conditions during their life cycle, possibly changing the global responses of the FOWTs and affecting their internal drivetrain dynamics. Therefore, this paper considered an OC4 DeepCwind semisubmersible FOWT as a representative model to investigate the influence of one broken mooring line on the steady-state and transient responses of the system, as well as on the internal drivetrain responses when the turbine operated normally. A fully coupled wind turbine model was constructed to analyze the global response, and then a decoupled method was applied to analyze the internal drivetrain responses. Furthermore, a set of load cases were considered to perform the simulations. The results showed that accidental fracture of the upwind line significantly affected platform motions, turbine structural loads, and tensions in the remaining lines. However, the effects of upwind line failure on the electrical power output and the internal gearbox dynamics were relatively small due to the almost unaffected nacelle yaw errors and the actions of pitch-torque control.

为研究浪流联合环境对于浮式潮流能水轮机性能的影响,对均匀来流环境下施加波浪激励下的水平轴获能叶轮进行水动力分析.结合ANSYS-Fluent流体仿真软件并对其进行二次开发,采用重叠网格法建立均匀来流时浮式获能叶轮受迫运动的水动力分析模型,模拟S型双向潮流能叶轮在不同幅值的纵荡运动时的水动力性能,并结合实际水槽试验对计算结果的准确性进行验证.分析结果显示:纵荡激励使获能叶轮周边的流场速度产生明显的瞬时波动,且获能叶轮受力载荷的波动幅值会因纵荡激励作用的增强而升高;叶轮尾流场的流速变化和流线的变化伴随纵荡幅值的增大而增大,但流场的均匀度伴随纵荡幅值的增大而降低.

双向直驱式潮流发电系统的输出功率的大小受到水流速度和发电机转速的直接影响,只有在速尖比为某以固定值(即最优速尖比)时该系统才能输出该流速下的最大功率.通过对发电机转矩平衡关系的分析,因为水流所产生的转矩为被动量,所以对电磁转矩的控制成为该论文实现最大功率跟踪的关键.将在对该发电系统的理论分析基础上,通过对BUCK-BOOST电路占空比的控制实现对发电机电磁转矩的控制.换句话说,通过对占空比的控制实现对发电机转速的控制使得速尖比达到最优速尖比即可实现最大功率跟踪的控制的目标.所以是基于对BUCK-BOOST电路占空比的最大功率跟踪控制.主要是通过分析潮流发电系统中发电机的转矩平衡来提出功率跟踪的控制算法,然后在仿真MATLAB/Simulink仿真平台验证控制策略的有效性和正确性.

Whiskering has been a reemerging problem affecting the reliability of lead-free electronics. Although the in-layer strain has long been considered one of the major driving forces for whisker growth, the quantitative understanding of the relationship between stress and Sn whiskering is still limited. To fill this technological gap, we develop an analytical model to express the contribution of strain accumulation to the formation of whiskers. The model predicts the average whisker length by calculating the volume of Sn material reallocated by strain in a single whisker site. We apply this model to analyze strain generation (via thermal expansion mismatch, applied forces, and dynamic recrystallization (DRX) process) and strain relaxation processes (creep-law plasticity and material diffusion). The simulated average whisker length is in good agreement with multiple previous experimental data, and $R^{2}$ reaches 0.80 after reliable calibration. The sensitivity and uncertainty are conducted to evaluate the reliability of the model in response to variations in external input, including deposition thickness and whisker density. The amount of DRX strain is estimated based on the model results. The application and limitations of the model are theoretically analyzed and discussed.