Horizontal And Vertical Research Articles

A broadband hybrid blue energy nanogenerator for smart ocean IoT network

Blue energy represents a crucial renewable energy resource; however, its development has been limited by the low and variable frequency characteristics of sea waves. In this study, we present a novel approach, wherein a spring pendulum coupled hybrid energy harvester (SPC-HEH) is employed to address these limitations. The SPC-HEH integrates two electromagnetic generators (EMG), two piezoelectric nanogenerators (PENGs), and two multilayer‐structured triboelectric nanogenerators (TENGs) into a vessel, enabling efficient wave energy harvesting. Notably, the integration of the lightweight PENG and TENG with the heavy EMG not only enhances the water wave energy harvesting capability of SPC-HEH but also optimizes its spatial utilization efficiency. Additionally, owing to the spring pendulum, the SPC-HEH is capable of simultaneously harnessing the wave kinetic energy of horizontal and vertical directions and realize the decoupling of vertical energy capture from horizontal energy capture. Remarkably, owing to its precise geometric design and efficient space utilization, the SPC-HEH achieves an impressive peak power density of 82.4 Wm-3. Finally, we demonstrate the practical applicability of the SPC-HEH by integrating it with a circuit as a self-powered ocean buoy for real-time monitoring of ocean temperature, wave frequency, ocean turbidity and other information. The remarkable potential of this system for integration into self-powered smart ocean IoT networks holds significant promise for advancing marine research and environmental monitoring capabilities.

Test and simulation of emergency flotation system buoy anti-overturning method

The helicopter emergency flotation system can provide flotation capability after the helicopter accidentally falls into the water. During a test of a helicopter float in a submerged state, it was found that the vertical distance between the highest point of the contact point of the float and the aircraft and the lowest point of the cabin door was 0.59 m, which seriously hindered the entry and exit of the crew from the cabin door. To reduce the adverse effects of the pontoon flipping up on the occupants entering and exiting the hatch, it is envisaged to use restraint belts, add anti-rollover airbags, and design the anti-rollover airbags into triangles and saddle shapes respectively. Through theoretical analysis, the simulation method eliminated the triangle method for the connecting belt and the anti-rollover airbag and selected the saddle-shaped anti-rollover airbag for floating and immersion tests. The test results met expectations. The highest point of the contact point between the float and the aircraft was the lowest point of the cabin door. The points did not interfere in the vertical direction, and this method was finally chosen to be applied to the buoy to suppress the upturn of the buoy.

Underground Diagnosis Based on GPR and Learning in the Model Space.

Ground Penetrating Radar (GPR) has been widely used in pipeline detection and underground diagnosis. In practical applications, the characteristics of the GPR data of the detected area and the likely underground anomalous structures could be rarely acknowledged before fully analyzing the obtained GPR data, causing challenges to identify the underground structures or anomalies automatically. In this article, a GPR B-scan image diagnosis method based on learning in the model space is proposed. The idea of learning in the model space is to use models fitted on parts of data as more stable and parsimonious representations of the data. For the GPR image, 2-Direction Echo State Network (2D-ESN) is proposed to fit the image segments through the next item prediction. By building the connections between the points on the image in both the horizontal and vertical directions, the 2D-ESN regards the GPR image segment as a whole and could effectively capture the dynamic characteristics of the GPR image. And then, semi-supervised and supervised learning methods could be further implemented on the 2D-ESN models for underground diagnosis. Experiments on real-world datasets are conducted, and the results demonstrate the effectiveness of the proposed model.

Predicting the deformation of compacted loess used for land creation based on the field monitoring with fiber-optic technology

Deformation Prediction of compacted loess is important for the constructions on the land created with such soil. In this study, in-situ fiber-optic monitoring was employed through a 77 m-deep borehole to obtain the variations of deformation and water content in both compacted and natural loess. The monitoring results were analysed together with the sampled soil properties. Initial field studies indicated that natural loess experienced much smaller deformation than compacted loess because of its cementation and different structure. Further analysis showed that the variations of stress and water content increment are the most significant factors in compacted loess, exhibiting a logarithmic relationship with loess deformation. Dry density is also important but needs to be considered in conjunction with stress in the vertical direction, while initial volumetric water content and clay-size fraction exhibit insignificant effects on the time-dependent deformation of compacted loess. Based on the analysis of these factors, a time-dependent model was developed, allowing the compacted loess deformation to be estimated. The proposed model was further verified by a numerical analysis using the artificial neural network (ANN) method, showing the relevance of the factors identified from the field data analysis and adopted in the proposed model.

The ecological risk and fate of microplastics in the environmental matrices of marine ranching area in coastal water

The debate surrounding "source" and "sink" of microplastics (MPs) in coastal water has persisted for decades. While the transportation of MPs is influenced by surface runoff and currents, the precise transport patterns remain inadequately defined. In this study, the typical coastal habitat – marine ranching in Haizhou Bay (Jiangsu Province, China) were selected as a case study to assess the ecological risk of MPs. An enhanced framework was employed to assess the entire community characteristics of MPs in various environmental compartments, including surface water (SW), middle water (MW), bottom water (BW), sea bottom sediment (SS), and intertidal sediment (IS). The results of the assessment showed a low risk in the water column and a high risk in the sediment. PERMANOVA based on size and polymer of MPs revealed significant differences between IS and other compartments (SW, MW, BW, and SS) (P<0.001). The co–occurrence network analysis for MP size indicated that most sites occupied central positions, while the analysis for MP polymer suggested that sites near the marine ranching area held more central positions, with sites in MW, BW, and SS being somewhat related to IS. Generalized additive model (GAM) demonstrated that MP concentration in the water correlated with Chla and nutrients, whereas MPs in sediment exhibited greater susceptibility to dissolved oxygen (DO) and salinity. We believe that except for the natural sedimentation and re–suspension of MPs in the vertical direction, MPs in bottom water may migrate to the surface water due to upwelling mediated by artificial reefs. Additionally, under the combined influence of surface runoff, currents, and tides, MPs may migrate horizontally, primarily occurring between middle and bottom water and sediments. The study recommends limiting and reducing wastewater and sewage discharge, as well as regulating fishing and aquaculture activities to control the sources and sinks of MPs in coastal water. Moreover, it advocates the implementation and strengthening of marine monitoring activities to gain a better understanding of the factors driving MP pollution in marine ranching area.

Mechanical properties of an improved flexible auxetic metamaterial and its application in self-expanding vascular stents

Auxetic metamaterials have shown great significance in the field of cardiovascular stents, but improving their applicability remains an issue. Here, we develop a type of improved auxetic metamaterial called the Re-entrant-Arrow-Snake (RAS) structure by adding arrow-shaped and snake-shaped structures to the Re-entrant (RE) structure. We first systematically study its in-plane elastic properties and compression behaviors. It is observed that the RAS structure exhibits improved vertical stiffness, horizontal flexibility, and clear auxetic effect in the vertical direction. The influence of the additional structures on the deformation pattern and the stability is also discussed by the in-plane compression analysis. Furthermore, we propose a new self-expanding (SE) vascular stent named RAS-SE based on the RAS structure. Numerical analysis demonstrates that the RAS-SE stent possesses enhanced dual-plateau radial force, negative foreshortening behavior, and improved bending flexibility, indicating better deployment performance and support in clinical applications. Biomechanical studies also show that axial deformation caused by the auxetic effect of the RAS-SE stent only slightly increases stress damage to plaque without affecting stress damage of the intima. This study further expands the application of metamaterials in SE vascular stents, and the proposed RAS structure shows high applicability on the SE stent, thus warranting further attention.

Impact dynamics of droplets on circular bodies: Exploring the influence of wettability, viscosity, and body dimensions using the lattice Boltzmann method

This study used the multi-relaxation time pseudopotential lattice Boltzmann method to examine the impact dynamics of droplets on circular bodies, focusing on the influence of the surface wettability, the viscosity of droplets by choosing three distinct Reynolds numbers (Re = 100, 300, and 500), and the body diameters. Initially, the study examined impact behavior under non-wetting and wetting conditions, revealing distinct behaviors characterized by dimensional stretch lengths in horizontal and vertical directions. Furthermore, the study evaluated the impact of viscosity by varying the Reynolds number, providing a better understanding of droplet behavior on the solid body. In addition, the effect of changing the diameter of the circular body was examined. This research underlines the importance of surface wettability in the dynamics of contact with the droplets impinging on it. In particular, higher wettability correlates with a monotonic increase in viscosity by acting on the Reynolds number. In addition, the droplet profile responds to changes in Reynolds number, albeit with relatively limited deformation, even in the case of intense interaction with the wetting surface. These results highlight the complex interplay between wettability, droplet dynamics, viscosity, body dimensions, and surface interactions during impact processes.

Soft-sensor model for indoor temperature prediction under heating conditions

Temperature information is important in everyday life. However, the local temperature at a certain point cannot be determined directly without using a physical thermometer, which can often disturb activity at that point and consume additional energy. Moreover, it would be costly to equip a room with many thermometers simply to measure local temperature. To overcome this problem, this study developed a model for prediction of local indoor temperature under heating conditions based on the heat transfer process mechanism using the soft-sensing method. To simulate the heating of air conditioning in winter, water at temperature of 30/50 °C was fed into water at 10 °C in an acrylic box. The soft-sensor model was trained and validated with transient temperature data and the multiple linear regression method. The particle image velocimetry method was used to obtain the velocity field. Temperature inhomogeneity in the vertical direction was evident for the feed temperature of 50 °C. The temperature variation in the bottom layer was divided into the dead time, rising, and settling periods, which was caused by variation of flow state. Multiple evaluation indicators suggested that the model performed with acceptable accuracy for different feed temperatures and locations. The bottom layer model at 50 °C required correction for the dead time, and model accuracy was improved by separately modeling the rising and settling periods. This soft sensor could be installed in air-conditioning systems to achieve optimal control, provide user comfort, and save energy.

Generation and Life Cycle of Solar Spicules

The physical mechanism for the creation of solar spicules is proposed with three stages of their life cycle. It is assumed that at stage I the density hump is formed locally in the x-y plane in the lower chromosphere in the presence of temperature gradients of electrons and ions along the z-axis (the vertical direction). In this region, the density structure of quasi-neutral (n i ≃ n e = n) plasma after taking birth is accelerated in the vertical direction owing to the thermal force F th ∝ ∇n(x, y, t) × (∇T e + ∇T i ). The exact time-dependent analytical solution of two-fluid plasma equations is presented assuming that density is maximum at the center of the density structure and decays away from it gradually. The 2D density structure is created as a step function H(t) in time at the bottom of the chromosphere, and consequently, the vertical plasma velocity turns out to be the ramp function of time R(t) = tH(t), whereas the source term S(x, y, t) for the density follows the delta function δ(t) form. The upward acceleration a=a(x,y)zˆ produced in this density structure is greater than the downward constant solar acceleration − g ⊙ in the chromosphere. In the transition region, the temperature gradients are steeper; therefore, the upward acceleration increases in magnitude g ⊙ ≪ a and the density hump spends less time there. This is stage II of its life cycle. In stage III, the density structure enters into the corona, where the gradients of temperatures vanish and the structure decelerates to zero velocity under the action of the solar gravitational force.

Research on fusion and deformation analysis of decade' HLS-II control network surveying data

To ensure the long-term stability of the beam and further construction needs, it is necessary to re-measure the particle accelerator regularly. Since 2013, we have been measuring the HLS-II control network with laser trackers and the level for 10 years. Taking HLS-II as the object of study, we introduced the data acquisition strategy for the period of 2013–2023. We analyzed the horizontal and vertical deformation trends of each control point. In the vertical direction, we fused the geometric level and elevation data of the laser tracker network by using MC-GMM (a Gauss-Markov model which considers the uncertainty of Monte Carlo simulation). The analysis results show that, after the HLS upgrade, the annual average settlement of the ground control network tends to be stable. The settlement and horizontal variation of the device are all within a reasonable and controllable range. To ensure stability, accuracy, and efficiency in the measurement, we recommend employing the laser tracker for the re-measurement of the HLS-II storage ring. The data processing flow and methods mentioned in the article can provide a reference for deformation analysis of the upcoming construction of the Hefei Advanced Light Facility (HALF) and other large-scale metrology projects.

10-mJ 300-fs 1-kHz cryogenically cooled Yb:CaF2 regenerative amplifier

In this paper, we report on a cw-pumped cryogenically cooled Yb:CaF2 laser crystal regenerative amplifier that can produce >10.3 mJ, <285 fs laser pulses at 1034-nm and repetition rate of 1-kHz. We achieve record high optical pump to optical amplified compressed output efficiency at >14%. Using a symmetric cavity design to compensate thermal lensing effect, we were able to achieve excellent beam quality with measured M2 at 1.19 and 1.16 at horizontal and vertical directions, respectively.

Research on longitudinal control technology in the transition section of tilt-rotor aircraft based on linear active disturbance rejection control

To solve the problem of strong coupling and control redundancy in the transition section of the tilt-rotor, this paper presents a longitudinal control method based on linear active disturbance rejection control (LADRC), verified by simulation. Firstly, the nonlinear dynamics model of tilt-rotor aircraft based on the mechanism method is established, and the model’s accuracy is verified by comparing the trim result with the generic tilt-rotor aircraft simulation (GTRS) model verified by flight test in XV-15. Then, the control and redundant rudder surface assignment strategies for tilt-rotor aircraft are proposed. Then, the vertical and vertical control law of tilt-rotor aircraft is designed, the linear expansion state observer (LESO) model is analyzed and derived, and the linear active disturbance rejection controller suitable for attitude loop control of tilt-rotor is designed. The altitude and velocity loops are controlled. Finally, the proposed linear active disturbance rejection control (LADRC) controller is verified by simulation, and the whole process of tilting transition is simulated. The results show that the proposed control strategy and the controller designed in this paper have strong anti-disturbance ability, fast response speed, and high control precision and can be used in the transition section of tilt-rotor aircraft. The vertical direction shall be well controlled.

Relativistic Jet Ejections from Slim Disks

A mechanism for the ejection of relativistic jets from slim disks is studied. Since radiation pressure is dominant in the slim disk, radiative energy flows along the pressure gradient in the vertical direction. The divergence of the radiative flux tells us that the flow of radiative energy from a bottom layer near the equatorial plane is absorbed by another layer above the boundary surface. The absorbed energy accumulates in the upper layer as the matter advances inward, and calculations show that the specific energy of the flow in the upper layer can be as large as ∼c 2 near the black hole when the accretion rate through the upper layer is relatively low. Since the specific energy ∼c 2 is much larger than the gravitational energy, the height of the upper layer could significantly increase then. Hence, the innermost part of the upper layer after almost all the angular momentum has been removed could have a much greater height than the size of the black hole, and the flow could collide with itself around the central axis of the disk, bouncing back from the axis while simultaneously expanding along it. The flow is expected to go outward along the central axis and to become supersonic due to the change in its cross section, finally producing relativistic jets.

Optimal strategy of the asymmetric wave energy converter survival in extreme waves

Enhancing the survival performance of wave energy converters (WECs) in extreme wave conditions is crucial, and reducing wave loads is a key aspect of this. Placing the device underwater has been recognized as a beneficial strategy, yet the determination of the optimal submerged depth and the effects of varying wave conditions remain ambiguous. To address this, the study numerically analyzes the total forces in both horizontal and vertical directions, along with their harmonic components, across different wave configurations. A computational fluid dynamics method is employed to investigate a triangular-baffle bottom-shaped oscillating floater, which is known for its high energy conversion efficiency. The findings indicate that submerging the device to a depth equivalent to half the actual focused amplitude (1/2Ab) is the most effective strategy in the given sea state, offering superior wave force reduction vertically and robust performance horizontally. The analysis of harmonics reveals the significant contribution of high-order components to the total wave forces. Additionally, the study examines the impact of focused wave amplitudes and peak frequencies, showing that although force reductions are lessened in more extreme conditions, the optimal submerged depth of 1/2Ab still yields near 30% reduction in total vertical force and 22% in total horizontal force. This research provides theoretical insight that can guide the enhancement of WECs' survival capabilities in practical engineering applications.

Surface wrinkling of a hyperelastic half-space coated by a liquid crystal elastomer film

We consider the stability of a hyperelastic substrate coated by a liquid crystal elastomer film and subjected to compressive forces. In this problem, the liquid crystal elastomer directors are free to evolve and this possible variation needs to be included in the stability analysis. We consider the case where the initial directors are aligned either in the horizontal or in the vertical direction and obtain an exact bifurcation condition for surface wrinkling. We show that director reorientation increases both the critical compressive strain and the critical wavenumber, hence stabilizing the material. In the small wavenumber limit we carry out an asymptotic analysis and obtain analytical solutions for the critical stretch and the critical wavenumber, which can be useful in applications.

Tuning anisotropic properties of epoxy/multi-walled carbon nanotube composites via two-step foaming

Epoxy (EP) composite foams with 1 wt% of multi-walled carbon nanotube (MWCNT) were prepared through a two-step foaming process, which involved first limited foaming the prepreg in a mold and then foaming the resultant foam again. The evolution of nanotubes’ arrangement and cell morphology during different second-step foaming (free-foaming or limited-foaming) process and its effect on compressive, electrical and electromagnetic interference (EMI) shielding properties of EP/MWCNT foams in both vertical and horizontal directions were carefully investigated. Differently interesting combination of anisotropy and isotropy in compressive strength, electrical resistivity, permittivity and EMI SE were facilely realized. For example, Limited-Free foam with a density of 0.401 g/cm3 exhibited a significant anisotropy in electrical resistivity (ρ∥/ρ⊥ = 2.93×10−3) but an isotropy in compressive strength (σ⊥/σ∥ = 1), permittivity (ε′∥/ε′⊥ = 1) and EMI shielding effectiveness (SE∥/SE⊥ = 1), while Limited-Limited foam with a density of 0.304 g/cm3 showed an isotropy in electrical resistivity (ρ∥/ρ⊥ = 0.96), permittivity (ε′∥/ε′⊥ = 0.99) and EMI SE (SE∥/SE⊥ = 0.99) but an obvious anisotropy in compressive strength (σ⊥/σ∥ = 0.74). In addition, the relationship between microsturcture and properties of composite foams was established and the mechanism of tuning anisotropic properties was also investigated. This study paves a way to the development of conductive composite foams with designed isotropic/anisotropic properties.

Microstructures and properties of 7075 aluminum alloy and CP780 steel resistance spot welded joint assisted by magnetic field

Joining steel and aluminum is vital for lightweight automobile but still challenging due to their different physical properties. Herein, resistance spot welding tests were performed on CP780 high-strength steel (thickness 1 mm) and 7075 aluminum alloy (thickness 1.5 mm) dissimilar metals under steady-state magnetic field. The influences of magnetic field (B = 40 mT) on the structure of welded joints, the phase composition/content of intermetallic compounds, and tensile properties of welded joints were analyzed under different welding current conditions (I = 9 kA,10 kA, 11 kA, and 12 kA). At the same welding current, the Lorentz force generated by the additional magnetic field promoted the outward circumferential movement of the molten metal in the weld along the horizontal surface , as well as increased the diameter of the Fe/Al contact interface in the weld nugget along the horizontal direction, conducive to the effective utilization of heat of the resistance spot welding. Except under (11 kA-0 mT) and (11 kA-40 mT), welded joints under other welding parameters displayed a few welding defects, such as incomplete fusion and shrinkage cavity formed at the cross-section of the welded joints. Therefore, the synergism between the magnetic field and appropriate welding current held important roles in the formation of welded joints without obvious welding defects. The intermetallic compounds of all the welds were mainly composed of (Fe, Si)Al2 and (Fe, Si)Al5. Meanwhile, the thickness and content of the intermetallic compounds layer reduced under a magnetic field at the same welding current, significantly improving the tensile properties of the welded joints. The comprehensive properties of welded joints were the best under 11 kA-40 mT, with an average shear force increase from 3.02 kN to 3.49 kN (15.56%) and an average displacement increase from 1.01 mm to 1.22 mm (20.79%). Overall, the proposed dissimilar aluminum/steel resistance spot welded joint assisted by magnetic field looks promising for lightweight automobile use.

Microstructure and mechanical properties of 7075/5356 aluminum alloy laminated composite fabricated by wire arc additive manufacturing

A 7075/5356 aluminum alloy laminated composite was fabricated by alternately depositing a 7075 wire and a 5356 wire layer by layer using wire arc additive manufacturing (WAAM). The microstructure and mechanical properties of the produced components under as-deposited and heat-treated conditions were investigated. The results revealed that the grain morphology of the specimen was mainly composed of equiaxed grains in each layer, while the grain size of the interlayer region was reduced due to the heterogeneous nucleation relying on the partially remelted previous layer. Moreover, a reduced amount of second phase was observed due to decreased Zn and Cu alloying elements content in this region, which resulted in a gradient change in microhardness distribution. The tensile strength and elongation of the heat-treated samples in vertical and horizontal directions were 321 MPa, 10.12 %, and 377 MPa, 9.72 %, respectively. The results indicated good comprehensive mechanical properties, which is promising for further application of WAAM fabricated laminated metal composite.

Bidirectional Multi-Spectral Vibration Control: Insights from Automotive Engine Mounting Systems in Two-Dimensional Structures with a Damaged Vertical Active Element

Active mounting systems have become more prevalent in recent years to effectively mitigate structure-induced vibration across the automobile chassis. This trend is particularly evident in engine mounts. Considerable research has been dedicated to this approach owing to its potential to enhance the quietness and travel comfort of automobiles. However, prior research has concentrated on a limited spectrum of specific vibrations and noise control or has been restricted to vertical vibration control. This article describes the modeling, analysis, and control of a source structure employing a multidirectional active mounting system designed to closely simulate the position and direction of an actual automobile engine mount. A piezoelectric stack actuator is connected in series to an elastic (rubber) mount to form an active mount. The calculation of the secondary force required for each active mount is achieved through the application of harmonic excitation forces. The control signal can also reduce vibrations caused by destructive interference with the input signal. Furthermore, horizontal oscillations can be mitigated by manipulating the parameters via dynamic interconnections of the source structure. We specifically examined the level of vibration reduction performance in the absence of a vertical active element operation and determined whether the control is feasible. Simulation outcomes demonstrate that this active mount, which operates in both the vertical and horizontal directions, effectively mitigates excitation vibrations. Furthermore, a simulation was conducted to mitigate the vibrations caused by complex signals (AM and FM signals) and noise. This was achieved by monitoring the system response using an adaptive filter NLMS algorithm. Adaptive filter simulations demonstrate that the control efficacy degrades in response to complex signals and noise, although the overall relaxation trend remains unchanged.

Wall-modeled large eddy simulation of a tandem wing configuration in transonic flow

In this study, the interaction between a turbulent wake and the boundary layer of a horizontal tail plane (HTP) in the transonic flow regime is investigated. The setup considered corresponds to a generic tandem wing configuration with an OAT15A airfoil as the main wing and a National Advisory Committee for Aeronautics (NACA) 64A-110 as an HTP. Due to the transonic flow, the suction side of the OAT15A exhibits buffet. The numerical approach consists of a two-stage procedure in which a detached eddy simulation (DES) provides unsteady inflow conditions for a subsequent zonal high-fidelity large eddy simulation (LES) performed for the HTP region only; the turbulent boundary layer is modeled using scale-resolved wall-modeled LES (WMLES). The study mainly pursues two objectives: first, to discuss the influence of wake turbulence on the flow characteristics of the NACA airfoil; and second, to evaluate the capability of WMLES as a low-cost but high-resolution numerical approach in challenging flow conditions. Essentially, the study confirms the expected result that the outer part of the HTP's boundary layer is dominated by the wake of the main wing. Mainly based on a discussion of turbulence spectra, the study further demonstrates the advantage of WMLES over DES, proving that WMLES is able to capture the effects of wake turbulence on boundary layer dynamics, and thus validates the WMLES approach as a cost-effective, high-resolution turbulence modeling approach. On a superordinate level, the study further sketches a possible way on how a flow problem with such a strongly unsteady behavior could be systematically evaluated.