Lateral Mode Research Articles

Numerical analysis on the effect of graded porosity in closed-cell metal foams/PCM composites

The porous metal foams are potential to integrate phase change materials (PCMs) to form the shape-stabilized composited PCMs for the applications of thermal energy management and temperature regulation. However, the effect of porosity distribution of foam keeps challenging in designing such PCM-based composites. In this work, the closed-cell graded porosity foams (GPFs) involving various gradient directions and gradient differences of porosity are engineered by shrinking Voronoi tessellations to achieve precisely tunable microstructure. Then the GPF/PW composite is formed by integrating paraffin wax (PW) in each pore and its melting performance is investigated by the computational model, which is validated by the melting experiment of a specific sample. The investigations on the gradient configurations of foams reveal that the gradient direction and gradient difference of porosity have significant influences on the pore-scale melting behavior, liquid fraction variation in time and overall energy storage efficiency of PW. The positive gradient variation along the direction of heating source and the moderate gradient difference, i.e. 20% or 30%, are beneficial to improve the melting behavior of graded models. In contrast to the uniform model, the complete melting time of the graded models can maximum shorten by 5.6%, 3.8% and 3.7% for the bottom, lateral and top heating modes, respectively.

Study on dynamic performance of 140 km/h metro vehicles with rubber stack traction structure: rolling vibration test and simulation

This paper analyzes whether the rubber stack traction structure can be applied to 140 km/h metro vehicles from the perspective of vehicle dynamics. The rolling vibration test results indicate that the vehicle Ride Index exceeds the standard limit, the low-frequency vibration of the car body is significantly greater than that of the frame and axle box, and the lateral motion mode of the car body reaches 2.0 Hz. Through the stiffness test, it is found that when the displacement is less than 5.93 mm, the additional stiffness of the rubber stack traction structure exceeds 0.55 MN/m, which is far greater than the stiffness exhibited by the Z-shaped traction rod at the same displacement. The simulation results demonstrate that the excessive additional stiffness of the traction rubber stack is the primary factor for the car body abnormal vibration and does not effectively improve the vehicle stability. It is recommended that this type of metro shall use a rubber stack traction structure with small additional stiffness or Z-shaped traction rod to improve the car body vibration characteristics at 140 km/h. Furthermore, the recommended maximum operating speed for the bogie with the studied rubber stack traction structure is 80 km/h.

Computational fluid dynamic simulation of packed bed drying process: impact of particle properties, drying conditions, and lateral edge heating modes on drying kinetics

In this work, a two-dimensional computational fluid dynamic (CFD) model is developed to describe the drying process of a packed bed made of spherical particles. The volumetrical evaporation rate inside the bed is computed from the pressure difference between the particle surface and the airflow. By using the thermal equilibrium assumption, the heat conservation equation is derived. The CFD model is solved in the COMSOL Multiphysics environment. The obtained results indicate remarkable maldistributions of temperature and moisture content. These maldistributions can be explained by the impact of lateral edges on thermo-hydraulic behavior. Additionally, the impact of particle diameter, air velocity, and bed width on the spatial-temporal moisture content and temperature distribution is investigated. It shows that the CFD model can be simplified to the receding front drying model for a bed made of small particles. Furthermore, by changing the thermal boundary conditions at the lateral edges, the influence of the heating mode at the lateral edges on the drying behavior is explored. The results indicate that contact heating at the bed wall can help to accelerate the drying process significantly.

Mechanical properties of rock under uniaxial compression tests of different control modes and loading rates

To study the influence of control mode and loading rate on mechanical property of rock, uniaxial compression tests of four types of rocks (gray sandstone, red sandstone, mudstone and granite) are carried out under axial strain control mode and lateral strain control mode respectively. The characteristics of complete stress and strain curves, strength, brittleness and failure modes are analyzed. The results show that control mode has little influence on the pre-peak deformation, stress thresholds, while it has a greater impact on post-peak stress and strain curve, which makes the post-peak deformation stable and controllable, and shows the feature of Class II behavior. With lateral loading rates decrease, post-peak stress and strain curves appear more and more obvious fluctuations in the post-peak stage, and the time required for rock failure increases sharply, but the lateral control rate has little effect on the brittleness of rock. The failure mode of rock samples under axial strain control mode is mainly splitting failure, while that under lateral strain control is gradually changed to shear failure. The smaller the lateral loading control rate is, the more obvious the characteristics of shear failure is. Compared with uniaxial compression tests, under high confining pressure, the lateral dilation deformation is restricted, so peak strength is larger and stress redistribution can be better adjusted and stress fluctuation reduced accordingly in post-peak stage. The research results are an effective supplement to rate-dependent property of rocks and can provide some reference for deformation and strength characteristics research of brittle rock under lateral control mode.

Transmissible topological edge states based on Su–Schrieffer–Heeger photonic crystals with defect cavities

Abstract Topological photonic crystals have great potential in the application of on-chip integrated optical communication devices. Here, we successfully construct the on-chip transmissible topological edge states using one-dimensional Su–Schrieffer–Heeger (SSH) photonic crystals with defect cavities on silicon-on-insulator slab. Different coupling strengths between the lateral modes and diagonal modes in photonic crystal defect cavities are used to construct the SSH model. Furthermore, two photonic SSH-cavity configurations, called α and β configurations, are designed to demonstrate the topological edge states. Leveraging the capabilities of photonic crystal transverse electric modes with on-chip transmission, we introduced a waveguide to excite a boundary defect cavity and found that the transmission peak of light, corresponding to the topological edge state, can be received in another boundary defect cavity, which is caused by the tunnel effect. Moreover, the position of this peak experiences a blue shift as the defect cavity size increases. Therefore, by tuning the size of the SSH defect cavity, on-chip wavelength division multiplexing function can be achieved, which is demonstrated in experiments. The ultrafast response time of one operation can be less than 20 fs. This work harmonizes the simplicity of one-dimensional SSH model with the transmissibility of two-dimensional photonic crystals, realizing transmissible on-chip zero-dimensional topological edge states. Since transmission peaks are highly sensitive to defect cavity size, this configuration can also serve as a wavelength sensor and a reconfigurable optical device, which is of substantial practical value to on-chip applications of topological photonics.

High-β lasing in photonic-defect semiconductor-dielectric hybrid microresonators with embedded InGaAs quantum dots

We report an easy-to-fabricate microcavity design to produce optically pumped high-β quantum dot microlasers. Our cavity concept is based on a buried photonic-defect for tight lateral mode confinement in a quasi-planar microcavity system, which includes an upper dielectric distributed Bragg reflector (DBR) as a promising alternative to conventional III–V semiconductor DBRs. The cavities show distinct emission features with a characteristic photonic-defect size-dependent mode separation and Q-factors up to 17 000. Comprehensive investigations further reveal lasing operation with a systematic increase (decrease) of the β-factor (threshold pump power) with the number of mirror pairs in the upper dielectric DBR. Notably, due to the quasi-planar device geometry, the microlasers show high temperature stability, evidenced by the absence of temperature-induced redshift of emission energy and linewidth broadening typically observed for nano- and microlasers at high excitation powers. The device exhibits remarkable lasing performance, maintaining efficacy even under elevated temperatures of up to 260 K.

Design, preparation and electromechanical characteristics analysis of piezoelectric 1-3-type composites with sandwich polymer structures

Aiming at the shortcomings of the traditional 200 kHz 1–3 piezoelectric composites with a thickness of 7.5 mm, which have a lower electromechanical coupling coefficient, lower resolution and larger acoustic impedance, a piezoelectric 1–3-type composites with sandwich polymer structures with higher electromechanical coupling coefficient and lower acoustic impedance was designed in this paper. First, the piezoelectric composites with different volume fractions of piezoelectric ceramics and silicone rubber were simulated by COMSOL software, and the optimal volume fractions of piezoelectric ceramics and silicone rubber were obtained. Second, the first and second lateral mode frequencies of the piezoelectric 1–3-type composites with sandwich polymer structures with different kerf widths were calculated. Then, based on the electromechanical equivalent circuit, the electromechanical characteristics of the piezoelectric 1–3-type composites with sandwich polymer structures were analyzed, and the equivalent performance parameters of the piezoelectric composite were obtained. Compared with other 7.5 mm thickness 1–3 piezoelectric composites, it was found that the electromechanical coupling coefficient of the piezoelectric 1–3-type composites with sandwich polymer structures is significantly increased, and the acoustic impedance is significantly decreased. Therefore, the piezoelectric 1–3-type composites with sandwich polymer structures has great potential advantages in the preparation of high-performance piezoelectric ultrasonic transducers.

Fracture Disaster Assessment of Model Concrete Piles in Loess Slope Engineering under Non-Uniform Lateral Loading

Existing model tests for reinforcing loess slopes with stabilizing piles are often challenged by simulation inaccuracies in lateral loading modes and scaling. Addressing these concerns, this study conducts model tests and numerical simulations to scrutinize the damage characteristics of concrete piles in two varying loess slope conditions under non-uniform lateral loading. The tests were designed to strictly maintain the similarity ratio of the concrete piles. The results reveal a no table 20% reduction in lateral bearing capacity due to the penetration of a potential sliding surface, exacerbating the stress on the piles. Furthermore, compared to uniform loess slopes, the presence of a sliding surface leads to a 38.4% increase in the height of the stress concentration point, resulting in earlier crack formation in the piles. These findings offer substantial theoretical and practical insights, highlighting the critical need for accurate model simulation in slope stabilization research and providing a basis for improving engineering practices.

Comparison of Resonance Modes in Two-Dimensional and Three-Dimensional Microsphere Structures

In this article, we have investigated the performance of a resonator in 2D, in an asymmetric form using the physical method and using the Matlab software, we have analyzed it in 3D. According to the simulation results, in asymmetric 2D and 3D structures, whispering gallery modes, or resonances appeared at similar wavelengths for the same radial and polar mode number. Also, the results obtained from the simulations indicated that the resonances of the asymmetric 2D structure would occur at wavelengths close to the wavelengths of 3D structure and the resonance wavelengths for transverse electric (TE) and while transverse magnetic (TM) modes would not change by altering the lateral mode number. Accordingly, 2D structures can be used to obtain resonance wavelengths in microsphere resonators. Achieving results with high accuracy, as well as faster speed offered by smaller meshing volume is one of the advantages of 2D structures in the physical method.

Influence of environment-induced bridge vibration on high-speed train’s driving performance

When railways traverse densely populated industrial areas, the periodic operation of large-scale factory equipment can produce consistent and regular environmental excitation on bridge structures. This excitation, if resonant with the structure, may cause significant vibration of the bridge, posing a threat to trains’ running safety. For the first time, this paper tackles this practical concern by combining field measurements with an analysis of how environment-induced bridge vibrations impact the operational performance of high-speed trains. The environmental vibration was equivalently incorporated into the analysis of the train-bridge coupled vibration system, examining the effects of structural vibration amplitude, frequency, and environmental influence range. The effect of bridge vibration on the driving performance of high-speed trains was evaluated from the spatial frequency domain properties of dynamic irregularity of track and the trains’ performance sensitivity to different parameters. The field measurements reveal that the environment-induced bridge vibration results in a translational motion of the beam driven by the transverse bending of the pier, resonating at approximately 1.5 Hz with an amplitude of 1.33 mm. The CRH series train, characterized by a prominent lateral mode close to 1.5 Hz (i.e., the wavelength sensitive to the train’s lateral running stability predominantly falls within the 30 m–100 m range at speed of 200∼350 km/h), exhibits a high susceptibility to vibrations induced by the environment in bridges. Among the examined parameters, the amplitude of bridge vibration has the most pronounced impact on the train’s acceleration, showing a linear correlation. The combined effect of bridge vibration and track static irregularity resulted in the lateral acceleration of the car body reaching 0.9 m/s2, which is close to the regulatory limit of 1.0 m/s2. Through parameter analysis, the maximum amplitude of the bridge that can be sustained while ensuring driving stability can be determined.

Designing MEMS accelerometer for enhanced sensitivity and reduced cross-sensitivity in landslide monitoring

MEMS accelerometers capable of detecting weak motions are required in measuring landslide movements. The sensor’s sensitivity and its independent readings of various acceleration modes are crucial factors in the design of these sensors. In addition, it is highly desired to fabricate these sensors with low-cost and flexible manufacturing technologies such as surface micromachining. This paper presents an advanced topology optimization approach to design the suspended structure for the maximum level of sensitivity and for a low cross-sensitivity in the reading of principal and lateral modes, while it is manufacturable with a low-cost surface micromachining process. The effect of inertial forces as a variable loading condition and mode switch prevention is applied using a meta-heuristic topology optimization method with simulated annealing. Considering the unique results of this topology optimization, PolyMUMPs surface micromachining is employed to manufacture the developed sensor. The fabricated sensor is subjected to measurement and subsequent comparison with analogous designs from the literature. The outcomes reveal a sensitivity of 0.3pF/g and cross-axis sensitivity of 0.048%, signifying a noteworthy advancement for surface micromachined accelerometers. Notably, this design, coupled with the devised topology optimization methodology, holds the potential for adoption by sensor manufacturers for diverse commercial applications.

Precise mode control of mid-infrared high-power laser diodes using on-chip advanced sawtooth waveguide designs

Abstract Power scaling in conventional broad-area (BA) lasers often leads to the operation of higher-order lateral modes, resulting in a multiple-lobe far-field profile with large divergence. Here, we report an advanced sawtooth waveguide (ASW) structure integrated onto a wide ridge waveguide. It strategically enhances the loss difference between higher-order modes and the fundamental mode, thereby facilitating high-power narrow-beam emission. Both optical simulations and experimental results illustrate the significant increase in additional scattering loss of the higher-order modes. The optimized ASW lasers achieve an impressive output power of 1.1 W at 4.6 A at room temperature, accompanied by a minimal full width at half maximum lateral divergence angle of 4.91°. Notably, the far-field divergence is reduced from 19.61° to 11.39° at the saturation current, showcasing a remarkable 42% improvement compared to conventional BA lasers. Moreover, the current dependence of divergence has been effectively improved by 38%, further confirming the consistent and effective lateral mode control capability offered by our design.

Investigating Dynamic Behavior and Control Systems of the F-16 Aircraft: Mathematical Modelling and Autopilot Design

The development of control systems for aerial vehicles necessitates a meticulous examination of their dynamic behavior. This research delves into an in-depth investigation of the dynamic behavior of the F-16 aircraft, employing refined mathematical models to analyze both its longitudinal and lateral motions, as well as their corresponding modes. These mathematical models are formulated in two conventional representations: state space equations and transfer functions. By utilizing these mathematical representations, two displacement autopilots have been developed, consisting of a pitch attitude autopilot based on the longitudinal equations and a roll attitude autopilot designed using the lateral equations. Proportional Integral Derivative (PID) controllers, encompassing inner loops, as well as Linear Quadratic Controllers (LQR), have been recruited as control system units. The control structures have undergone analysis utilizing Simulink models. The analyses have yielded favorable damping characteristics and faster responses in both longitudinal and lateral movements and modes.

Rules and design criterion of airship stability and modes

In this paper, the rules and design criterion of airship stability, modes and aerodynamic parameters are studied by varying the hull and fin parameters using systematic modeling. The exposed airship fin surface area is demonstrated to be a critical factor affecting the change of the airship stability and mode states. Based on this factor, the design criterion of stability is confirmed and updated. It is demonstrated that when the normalized exposed airship fin surface area exceeds 0.08, the airship becomes stable. It is also discovered that the necessary exposed fin area required to maintain stability could be reduced by placing the fins farther rearward. Additionally, as the exposed fin area increases, there exists a qualitative change of modes wherein the two lateral exponential modes of the airship may converge into one oscillatory mode. Lastly, attention is also given to two aerodynamic parameters. Because it is found that the stability boundary falls in relatively fixed ranges of the two parameters, they can also be used to estimate airship stability states, whereas the qualitative change boundary of the modes falls in a varying range and a similar conclusion cannot be drawn.

Dynamic analysis of a pedestrian timber truss bridge at three construction stages

This article investigates the dynamic behaviour of a single span pedestrian timber truss bridge by in situ testing and numerical modelling. The in situ dynamic tests were performed at three different construction stages: (1) on only the truss structure, (2) on the finished bridge without the asphalt layer and (3) on the finished bridge with the asphalt layer. The objective is to better understand how the different parts of the bridge contribute to the overall dynamic properties. The experimental results show that the damping ratios increased significantly for the first lateral mode (from 1.0 to 3.8%) and the first torsional mode (from 1.2 to 3.5%) between stage 2 and stage 3 due to the asphalt layer. The damping ratio is around 1.6% for the first bending mode for the finished bridge. The experimental and numerical results indicate that the stiffness of the asphalt layer is important to consider at stage 3 (10 °C) for the first lateral and torsional mode, but not for the first bending mode. Finally, it was concluded that longitudinal springs must be applied at the pot bearings in order to get agreement with the experimental results at all the three stages.

Flight Dynamic Characteristics of Wide-Body Aircraft with Wind Gust and Turbulence

In this research, a wide-body aircraft was analyzed with critical monitoring of its states, a function of several control inputs (wind gust, turbulence, and microburst). The aerodynamic and stability coefficients of a Boeing 747-200 were obtained from previously published works and 6- DOF equations were formulated. Simulations were conducted for various control inputs to determine the aircraft’s free response, as well as the forced response. In order to understand the nature of the atmosphere, three different models were incorporated, including (i) the Dryden Model, (ii) wind gust, and (iii) microburst. The aircraft was found to be stable in the longitudinal and lateral flight modes, with trim conditions agreeing with published data. For a vertical wind gust of −10 ft/s, the AoA and pitch rate were observed to oscillate sinusoidally and became stable with new trim conditions. These states were found to regain trim conditions once the gust was removed. In the case of 3D gust, it was found that the longitudinal modes achieved a new trim condition through Phugoid oscillations, whereas the lateral modes underwent short-period oscillations. For the case of turbulence, random fluctuations were observed for trim conditions with no unstable behavior. When considering the microburst case, it was found that the aircraft initially gained altitude in the region of the headwind; this was followed by a sharp descent under the influence of a vertical velocity component.

A Study on the Lateral Ultimate Strength and Collapse Modes of Doubly Curved Stiffened Plates

Bows and stems are often subjected to wave slamming loads. Stiffened plates with curvatures in both longitudinal and transversal directions are the basic members of these structures. As a result, it is important to investigate the lateral ultimate strength of the doubly curved stiffened plates. In this study, the non-linear finite element method (NFEM) is selected to investigate the collapse modes and lateral ultimate strengths of the doubly curved stiffened plates. Additionally, the influences of curvature and geometrical properties on the collapse modes and ultimate strengths of doubly curved stiffened plates are investigated. In the NFEM analysis, a series of numerical simulations, covering different aspect ratios, curvatures, and structural scantlings are performed. Different collapse modes of doubly curved stiffened plates under lateral loading cases are observed. The relationships between the collapse modes and the geometrical properties are then discussed based on the numerical results. Moreover, the results also show that larger curvatures along the stiffeners and stronger stiffeners contribute more to the lateral ultimate strengths. Subsequently, an empirical formula is derived and verified for predicting the lateral ultimate strength of the doubly curved stiffened plates. The results of the empirical formula match well with numerical calculations.

Sustained connectivity correlates of motor function in Alzheimer’s disease

AbstractBackgroundIn addition to cognitive deficits, issues with motor control are present across the dementia spectrum. Traditional functional connectivity measures synchrony of intrinsic activity between brain regions and is altered in patients with Alzheimer’s disease in regions supporting motor function; however, less is known regarding the temporal stability of that synchrony. Sustained connectivity uses the width of cross correlation curves of BOLD time series to reflect the relative duration of synchronous activity between brain regions. This study investigates sustained connectivity across the dementia spectrum in motor regions.Method109 participants were included in this analysis and included 32 individuals with mild cognitive impairment (MCI) (18 F, 73.84 ± 5.14), 30 with Alzheimer’s disease (AD) (19 F, 77.37 ± 6.45), and 47 control individuals (29 F, mean age 72.13 ± 4.68). All study participants completed MP2RAGE structural imaging and two 15‐minute resting fMRI scans. Preprocessing steps included segmentation, motion realignment, registration to MNI space, and regression of motion parameters. Sustained connectivity values were averaged across both scans and only participants with more than 50% volumes remaining after censoring were included in analysis. A 17 resting‐state network parcellation was used to evaluate sustained connectivity across the brain with each network treated as a single ROI. A linear regression analysis was used to compare sustained connectivity across groups controlling for mean head motion, age, and sex. T statistics and p‐values are reported for across group sustained connectivity values.ResultAcross all three groups, sustained connectivity with the dorsal and ventral somatomotor networks was significantly increased across a number of resting‐state networks including the central visual, anterior ventral attention, and lateral temporal default mode network (DMN; all dorsal) and the somatomotor association, anterior ventral attention, medial frontoparietal, lateral temporal and lateral DMN (all ventral; Figure 1; pFDR < .05).ConclusionThese data suggest sustained connectivity may be a potential metric for assessing progressive cognitive decline in dementia. Our results indicate that sustained connectivity may be used to track changes in the temporal duration of functional connectivity in motor networks in individuals with intact cognition, mild cognitive impairment, and Alzheimer’s disease.

Enhancing the compressive properties of re-entrant honeycombs by line defects with insight from nature

Three novel heterogenous re-entrant honeycombs with possible applicability in the construction and automotive industries are designed with insight from geometric defects in cellular structures of nature (beehives and graphene). The honeycombs that are composed of geometric defect channels and the geometrically perfect honeycomb are produced via fused deposition modeling 3D printing method. The structures are tested via experimental and numerical methods and their behavior is assessed in terms of specific energy absorption (SEA), effective Young’s modulus (Ee), and deformation mechanism under compression. Each innovative structure outperforms the benchmark model in terms of Ee, owning a stiffer response to loading. Two of the defective honeycombs exhibit superior performance to the benchmark in terms of SEA, with about 100% and 157% higher specific energy absorption, due to having better stability and different lateral buckling modes under compression. Unlike the benchmark model, the defective honeycombs’ auxeticity is maintained under compression. Also, one of the parametric studies proves that the novel honeycombs have promising potential in applications where structures are subjected to inclined loads, due to having roughly 148% higher SEA than the benchmark under inclined compression.

Ratiometric electrochemical biosensor based on lateral movement of multi-pedal DNA tetrahedron machine on biomimetic interface

In this work, a lateral moving multi-pedal DNA tetrahedron machine (MTM) is designed and coupled with dual-signal output system to construct a biomimetic electrochemical ratiometric strategy for ultrasensitive target DNA analysis. The tetrahedral structure provided rigid support for the pedal, ensuring efficient replacement of the rail chain modified with ferrocene. By conjugating cholesterol molecules to one vertex of MTM, it is decorated on a lipid bilayer. This molecular architecture confers lateral movement of MTM on an electrode surface while prevents its detachment from the system. The methylene blue tagged hairpin probe provides constant power to support MTM swim on lipid bilayer. Compared with the conventional motion mode, the lateral moving mechanism has the fastest reaction rate and the highest signal-to-noise ratio. Additionally, the dual-signal reporting system further improves the accuracy of target detection on the basis of ensuring motion efficiency. The work improved movement efficiency and shortened time fragment. A linear relationship between the ratio value of two reporters and target DNA concentration was observed from 0.5 fM to 50 pM with a detection limit of 28 aM. The lateral motion mode of DNA machine coalescing with ratiometric system made this sensing platform ultrasensitive and accurate, which holds new avenue of early diagnosis.