Horizontal And Vertical Research Articles

Seismic design parameters of double-layer diamatic domes

The effect of past earthquakes (e.g., the 1995 Kobe and 2016 Kumamoto earthquakes) on the space structures revealed the fact that the assumption of the invulnerability of these structures is incorrect despite their light self-weight and high degree of redundancy, and space structures may suffer severe damage during strong ground motions. Therefore, special attention should be paid to the design of this type of structure in high seismic-risk regions. Nevertheless, the existing seismic design codes have not provided the seismic design parameters (i.e., the seismic response modification factors), including the behavior factor, R, and the displacement amplification factor, Cd for space structures. This research aims to extract the seismic design parameters of double-layer diamatic domes (DLDDs) to answer the challenges that structural engineers face in the design of this type of structure. For this purpose, 16 DLDD models with different rise-to-span ratios (RSRs) and span lengths were considered. After designing the models and performing the nonlinear time history analysis using the simultaneous effect of the three transitional components of ground motions, the target displacement at the control node was determined. Then, the pushover analysis was carried out to derive the capacity curve of the structures and calculate the seismic response modification factors in both horizontal and vertical directions. The results indicate that the domes with RSRs of 1/7 and 1/5 should be designed such that they remain in the elastic state in the horizontal direction. Then, with the growth of RSR, the value of R increases and reaches 1.792. Finally, equations were presented in this study for the period, behavior factor, and displacement amplification factor of DLDD structures in both horizontal and vertical directions using the nonlinear regression analysis.

Visualizing plasmons and ultrafast kinetic instabilities in laser-driven solids using X-ray scattering

Ultra-intense lasers that ionize atoms and accelerate electrons in solids to near the speed of light can lead to kinetic instabilities that alter the laser absorption and subsequent electron transport, isochoric heating, and ion acceleration. These instabilities can be difficult to characterize, but X-ray scattering at keV photon energies allows for their visualization with femtosecond temporal resolution on the few nanometer mesoscale. Here, we perform such experiment on laser-driven flat silicon membranes that shows the development of structure with a dominant scale of 60 nm in the plane of the laser axis and laser polarization, and 95 nm in the vertical direction with a growth rate faster than 0.1 fs−1. Combining the XFEL experiments with simulations provides a complete picture of the structural evolution of ultra-fast laser-induced plasma density development, indicating the excitation of plasmons and a filamentation instability. Particle-in-cell simulations confirm that these signals are due to an oblique two-stream filamentation instability. These findings provide new insight into ultra-fast instability and heating processes in solids under extreme conditions at the nanometer level with possible implications for laser particle acceleration, inertial confinement fusion, and laboratory astrophysics.

Effects of lorazepam on saccadic eye movements - evidence from prosaccade and free viewing tasks.

Peak velocities of saccadic eye movements are reduced after benzodiazepine administration. Even though this is an established effect, past research has only examined it in horizontal prosaccade tasks. The spectrum of saccadic eye movements, however, is much larger. Therefore, we aimed to make a first attempt at filling this research gap by testing benzodiazepine effects on saccades under different experimental task conditions. 1mg lorazepam or placebo was administered (within-subjects, double-blind, in randomised order) to n = 30 healthy adults. Participants performed an extended version of the prosaccade task, including vertical saccade directions and different stimulus eccentricities, as well as a free viewing task. Results from the prosaccade task confirmed established effects of benzodiazepines as well as saccade direction on saccadic parameters but additionally showed that the drug effect on peak velocity was independent of saccade direction. Remarkably, in the free viewing task peak velocities as well as other saccade parameters were unaffected by lorazepam. Furthermore, exploration patterns during free viewing did not change under lorazepam. Overall, our findings further consolidate the peak velocity of prosaccades as a biomarker of sedation. Additionally, we suggest that sedative effects of low doses of benzodiazepines may be compensated in tasks that more closely resemble natural eye movement behaviour, possibly due to the lack of time constraints or via neurophysiological processes related to volition.

Writing direction influences the spatial representations of past- and future-tense forms: Evidence from eye tracking.

The present study tests the hypothesis that the directionality of reading habits (left-to-right or right-to-left) impacts individuals' representation of nonspatial events. Using the blank screen paradigm, we examine whether eye movements reflect culture-specific spatial biases in processing temporal information, specifically, grammatical tense in Russian and Hebrew. Sixty-two native speakers of Russian (a language with a left-to-right reading and writing system) and 62 native speakers of Hebrew (a language with a right-to-left reading and writing system) listened to verbs in the past or future tense while their spontaneous gaze positions were recorded. Following the verb, a visual spatial probe appeared in one of the five locations of the screen, and participants responded manually to indicate its position. While participants' response latencies to the spatial probe revealed no significant effects, their gaze positions along the horizontal axis for past- and future-tensed verbs aligned with the reading and writing direction in their language. These results provide novel evidence that eye movements during auditory processing of grammatical tense are influenced by culturally specific reading and writing conventions, shifting leftward or rightward on the horizontal plane depending on the stimuli's time reference (past or future) and the participants' language (Russian or Hebrew). This spatial bias indicates a common underlying cognitive mechanism that uses spatial dimensions to represent temporal constructs.

Cost-effective gaze tracking system based on polymer fiber specklegrams.

Gaze tracking technology has a wide range of applications in the fields of VR/AR glasses. In this paper, a plastic optical fiber (POF) is used as a light transmission waveguide to transmit the light reflected from the eye to the outside of the device for processing, thereby eliminating the need for in-device camera installations. By processing two fan-shaped surfaces on the POF at a 45° angle relative to the vertical direction, the POF gains the ability to couple light from the side. The reflected light of the eye can be transmitted to the outside of the device through the POF. The specklegram corresponding to 76 different gaze directions is classified by SE-Resnet18, and the accuracy reached 96.9%. The gaze tracking system is low cost and simple in structure and has potential application in fields such as AR glasses, human-computer interaction (HCI), and medical diagnosis.

Evaluation of plasticity and determination of deformation index of 3D-printed composite cement-based materials

ABSTRACT Given the current situation that the evaluation system of the deformation and instability failure of 3DPC is immature, this study was devoted to shaping the performance of 3DPC to provide new ideas and ways for exploring the stable forming of 3DPC. The relationship between the deformation in different directions and the number of layers was analysed. The deformation regulation of 3DPC was revealed, and the controllable index was determined. Results show that the vertical and horizontal deformation in the plastic state is correlated to evaluate the overall deformation by considering only the lateral deformation. The horizontal and vertical deformation of each layer decreases as the number of layers increases, forming a trapezoidal shape. The relationship between the horizontal deformation and the number of layers varies with the shape of the printed component. This relationship follows a linear pattern in the vertical direction and remains independent of the printing shape. The deformation process of 3DPC can be divided into three stages: linear deformation, elastoplastic, and plastic failure. The elastoplastic stage is identified as the primary stage, and the horizontal deformation begins here. Comparatively, the horizontal strain is more suitable for evaluating the plasticity of 3DPC than the vertical strain.

Synthesis and Anisotropic Memristive Behavior of Borophene Nanosheets

Neuromorphic computing, marked by its parallel computational abilities and low power usage, has become pivotal in advancing artificial intelligence. However, the advancement of neuromorphic computing has faced significant obstacles due to the performance limitations of traditional memory devices struggling with high power consumption and limited reliability. Two‐dimensional (2D) materials have been extensively investigated as high‐performance memristive materials, but they are often restricted by fixed memristive properties, which complicate circuit design and limit flexibility. Here, we report that multilayer borophene nanosheets represent a breakthrough material, displaying anisotropic variable memristive properties. The nanosheets, comprising semiconductor α’‐4H‐borophene sheets and metal β12‐borophene sheets, have been synthesized on aluminum foil surface through chemical vapor deposition (CVD) method. The multilayer borophene nanosheets exhibit volatile memory behavior in the vertical direction and non‐volatile memory behavior in the planar direction. This innovative class of 2D nanosheets not only overcomes the limitations of conventional memory devices but also expands the potential applications of borophene‐based memories in information storage and in‐memory computing.

Synthesis and Anisotropic Memristive Behavior of Borophene Nanosheets.

Neuromorphic computing, marked by its parallel computational abilities and low power usage, has become pivotal in advancing artificial intelligence. However, the advancement of neuromorphic computing has faced significant obstacles due to the performance limitations of traditional memory devices struggling with high power consumption and limited reliability. Two-dimensional (2D) materials have been extensively investigated as high-performance memristive materials, but they are often restricted by fixed memristive properties, which complicate circuit design and limit flexibility. Here, we report that multilayer borophene nanosheets represent a breakthrough material, displaying anisotropic variable memristive properties. The nanosheets, comprising semiconductor α'-4H-borophene sheets and metal β12-borophene sheets, have been synthesized on aluminum foil surface through chemical vapor deposition (CVD) method. The multilayer borophene nanosheets exhibit volatile memory behavior in the vertical direction and non-volatile memory behavior in the planar direction. This innovative class of 2D nanosheets not only overcomes the limitations of conventional memory devices but also expands the potential applications of borophene-based memories in information storage and in-memory computing.

Establishment of an Animal Model of Oral Squamous Cell Carcinoma Invading the Mandible.

To establish an animal model of oral squamous cell carcinoma invading the mandible through multi-sample experiments that verified the stability, repeatability, tumorigenicity and mandible destruction rate of the model. Oral squamous cell carcinoma cell suspension was injected into the outer side of the mandible through the anterior edge of the masseter muscle of naked mice to observe the tumourforming process. Then, the anatomical, histological and imaging examinations were carried out to determine whether the tumour had invaded the mandible. By comparing the tumour growth of multiple groups of various squamous cell carcinoma cells (CAL27, HN6 and HN30 cells), the changes in body weight and characteristics of tumour formation were compared, and the experience was summarised to further verify the stability, repeatability, tumour formation rate and arch damage rate of the model. The subsequent specimens of tumour-bearing nude mice were validated once the model had been established. In vitro, tumour tissue wrapped around the mandible's tumour-bearing side, and the local texture was tough with no resistance to acupuncture. Haematoxylin and eosin staining revealed that squamous cells were infiltrating the mandible in both the horizontal and sagittal planes. Microcomputed tomography results showed that the mandible on the tumour-bearing side displayed obvious erosion damage. Cell lines with various passage rates clearly had diverse tumour-bearing life cycles. This study successfully established an animal model of oral squamous cell carcinoma invasion of the mandible. The model has excellent biological stability, repeatability, tumorigenesis rate and mandible destruction rate.

SELECTION OF GAS MIXER PARAMETERS FOR DIESEL CONVERSION GENERATOR MOTOR IN GAS DIESEL

According to literary sources, options for converting diesel engines into dual-fuel engines for operation on any fuel, in particular, natural gas (NG), were analyzed. The conversion method with external mixture formation and an ignition dose of liquid fuel involves the preparation of a gas-air mixture of the required composition in a special device. The methodology for choosing the design parameters of the gas mixer for the organization of the work process of a V-shaped diesel engine type 12Ch 15/17.5, converted into a gas diesel, which works as part of a motor-generator unit of backup power supply, is given. The basic design of the diesel motor-generator was analyzed. A comparative calculation of the working processes of diesel and gas-diesel variants of execution (with an ignition dose of diesel fuel of 10%) was carried out. The requirements for the design and location of the gas mixer have been formed. In the work, using 3D modeling technologies, the geometry of the gas mixer and its flow part were formed. Using the method of finite volumes, the calculation grid was synthesized and its adaptation near solid walls was carried out. Next, a series of numerical experiments was conducted in a three-dimensional setting to evaluate the throughput and quality of mixing network methane with air (when the robot is operating at typical operating modes). The distribution of flow velocities in the vertical and horizontal planes of the flow part of the gas mixer was evaluated, the change in pressure along the height of the gas mixer and the distribution of the mass fraction of methane in the flow part of the engine intake tract were analyzed, and scientific and practical recommendations were developed to ensure the efficient operation of gas diesel as part of a motor-generator installation. It is shown that the proposed design of the gas mixer allows effective mixing of methane with air when operating in the entire power range of the considered engine. The use of 3D modeling technologies, with the use of modern numerical methods, allows you to assess the operating conditions of the mixture by macro indicators and in local sub-regions, which allows, in the future, to develop recommendations for increasing the efficiency of the process of preparing the fuel-air mixture.

Method for defining the horizontal plane in fluoroscopic kinematic analysis

PurposeIn vivo kinematics of skeletal joints and prostheses is affected by gravity; therefore, absolute tilt must be taken into account. However, current fluoroscopic kinematic analysis cannot measure the tilt. This study introduces and validates a method for defining the horizontal plane in fluoroscopy systems to measure the tilt of an object. MethodsA rectangular metal plate (200 ​× ​200 ​× ​10 ​mm) with a flatness of 0.03/100 ​mm was horizontally adjusted using a leveler (sensitivity of 0.02° and accuracy of ±0.06°), and its three-dimensional coordinate was calculated from a two-dimensional fluoroscopic image. A coordinate calculation formula was developed, with precision and accuracy assessed via computer simulations. Actual fluoroscopic tests included four aspects: accuracy under the same condition; accuracy under different X-ray tube height; reproducibility when changing X-ray tube height; and reproducibility when the flat panel was tilted and returned. ResultsThe theoretical measurement error indicated by the computer simulations was 0.0 ​± ​0.2° on the xy-plane and 0.0 ​± ​0.0° on the yz-plane. The actual experimental results showed that the horizontal plane tilt was measured to be −0.2 ​± ​0.1° tilt on the xy-plane and 0.3 ​± ​0.0° tilt on the yz-plane for the device used in this study. The F-test showed no significant differences between the computer simulations and the actual experiments. There were no significant differences between the four actual tests. ConclusionsThis method enables the horizontal plane to be defined and the tilt of an object to be measured in fluoroscopic kinematic analysis.

Fuel mixing and diffusion behind the unswept ramp injector with lobed nozzle at combustor of scramjet engine

-The use of 2-lobe nozzle for efficient fuel mixing behind the ramp injector nozzle is comprehensively investigated in this article. Computational fluid dynamic is applied for the evaluation of the three-dimensional flow behind the strut with annular 2-lobe nozzle at supersonic combustion chamber. In this work, the Mach number of free steam air flow and fuel jet are 2 and 1, respectively. The usage of internal air jet for the fuel mixing improvement is also analysed to disclose the critical features which improve the fuel diffusion in the combustor. The Mach contour on the horizontal and vertical planes in both injection model is compared to show how induced vortex pair is created and extended behind the strut. The result of computational study shows that the injection of the air jet increases the number of vortex pairs behind the strut and the interaction of the fuel with air jet is increased. However, the circulation strength is decreased by inner air jet. Use of inner jet enhances the fuel mixing more than two times behind the nozzle. Our findings show that the fuel mixing is heightened downstream of strut by coupling inner air jet with annular fuel jet.

Comparison of 1- and 3-piece directly 3-dimensional printed indirect bonding trays: An in vitro study

This study aimed to compare the transfer accuracy of indirect bonding trays of different thicknesses and numbers of pieces. Digital indirect bonding was performed on 56 printed resin models, divided into 4 groups with 14 models in each: 1-mm 1-piece tray (OPT), 2-mm OPT, 1-mm 3-piece tray (TPT), and 2-mm TPT. The trays were designed using Appliance Designer (3Shape A/S, Copenhagen, Denmark). Angular (torque, tip, or angulation) and linear (mesiodistal, buccolingual, occlusogingival, or vertical) differences were compared by using open-source GOM Inspect software (GOM GmbH, Braunschweig, Germany). In the buccolingual direction, the 1-mm TPT (0.180 ± 0.041 mm) was significantly more accurate than the 1-mm OPT (0.240 ± 0.032 mm). In the vertical direction, significant differences were seen between the 1-mm and 2-mm OPTs (1-mm OPT: 0.220 ± 0.043 mm; 2-mm OPT: 0.428 ± 0.143 mm; P= 0.003) and between the 1-mm and 2-mm TPTs (1-mm TPT: 0.210 ± 0.072 mm; 2-mm TPT: 0.340 ± 0.062 mm; P= 0.004) in the total region. In the tip angle, significant differences were seen between the 1-mm and 2-mm OPTs and between the 1-mm OPT and TPT. In the torque angle, a significant difference was seen between the 1-mm TPT (2.815°±0.350°)and 2-mmTPT (2.368° ± 0.245°; P= 0.017). Both the thickness and the splitting of the trays impacted the bracket bonding accuracy. The 1-mm trays were more accurate than the 2-mm trays. Despite a few statistically significant differences between the 1-mm OPT and TPT, the 1-mm OPT was recommended for clinical use, considering the designing and placing of the trays.

Recurrence quantification analysis of uterine vectormyometriogram reveals differences between normal-weight and overweight parturient women

Objective.This study aims to use recurrence quantification analysis (RQA) of uterine vectormyometriogram (VMG) created from the slow wave (SW) and high wave (HW) bands of electrohysterogram (EHG) signals and assess the directionality of the EHG activity (horizontal orX, vertical orY) in normal-weight (NW) and overweight (OW) women during the first stage of labor.Approach. The study involved 41 parturient women (NW = 21 and OW = 20) during the first stage of labor, all of whom were attended at the Gynecology and Obstetrics Hospital of the Maternal and Child Institute of the State of Mexico in Toluca, Mexico. Twenty-minute EHG signals were analyzed in horizontal and vertical directions. Linear and nonlinear indices such as dominant frequency (Dom), Sample Entropy (SampEn), and RQA measures of VMG were computed for SW and HW bands.Main results. Significant differences in SampEn and Dom were observed in the SW band between NW and OW in bothXandYdirections, indicating more regular dynamics of electrical uterine activity and a higher Dom in NW parturient women compared to OW women. Additionally, the RQA indices calculated from the VMG of SW were consistent and revealed that NW women exhibit more regular dynamics compared to OW women.Significance. The study demonstrates that RQA of VMG signals and EHG directionality differentiate uterine activity between NW and OW women during the first stage of labor. These findings suggest that the uterine vector may become more periodic, predictable, and stable in NW women compared to OW women. This highlights the importance of tailored clinical strategies for managing labor in OW women to improve maternal and infant outcomes.

Anisotropic microstructure and tensile property of laser powder bed fusion fabricated Al–Mn–Mg–Sc–Zr alloy built at different layer thickness

Laser powder bed fusion (LPBF) fabricated Al-Mn-Mg-Sc-Zr alloy generally possesses a bi-modal microstructure of columnar grains and equiaxed grains. Such an anisotropic microstructure would introduce varied tensile performance in different orientations. To date, few study on the microstructure and tensile property anisotropy have been reported for LPBF fabricated Al-Mn-Mg-Sc-Zr alloys built at different layer thicknesses, which limits the exploration in mechanical property optimization. In this work, the microstructure anisotropy and room-temperature tensile properties of LPBF produced and peak-aged Al-Mn-Mg-Sc-Zr alloys built at 30 and 60 μm layer thicknesses were systematically investigated by scanning electron microscope, transmission electron microscope, and tensile testing. A higher layer thickness of 60 μm resulted in coarser grains with the precipitates size remained similarly compared to the 30 μm specimens. This led to a reduced yield strength in 60 μm specimens (492 - 509 MPa) comparing to those in 30 μm specimens at 502 MPa - 510 MPa. In addition, the existence of columnar grains within melt pools contributed to a larger effective slip length in the vertical direction than that in the horizontal orientation. Such difference in effective slip length in the loading direction contributed to a lower strength in vertical orientations. For ductility, the slightly higher defect level in 60 μm specimens (0.58%) resulted in reduced elongations of 3% - 6% compared to those of 30 μm specimens (0.10%). The ductility anisotropy was attributed to the preferential distribution of gas pores and keyhole defects at melt pool boundaries.

Outburst flood events since the last glacial maximum in the Hutiao Gorge of Jinsha River: Geomorphological evidence from eddy gravel bars

Breaching of natural dams in the Hutiao Gorge of the Jinsha River across the Yulong-Haba Mountains is one of the major geomorphological events in the largest river of Asia. Catastrophic flood events have an important influence on the geomorphological evolution of the First Bend of the Yangtze River since the Last Glacial Maximum (LGM). However, detailed geomorphological evidence, ages, and depositional phases of outburst flooding remain unclear. In this paper, large-scale gravel bars overlying the river terraces and dammed lakes are analyzed within the Daju Basin. The macroscopic geomorphological characteristics of megaflood landforms with large thickness and uniform gravel bars are similar to those of Missoula and Altai megafloods. Morphological analysis shows that eddy gravel bars (EGBs) with rhythmic structure are characterized by a dome-shaped protrusion in the cross section and a gravel mound in the longitudinal section. Each bar with oblique, parallel and massive bedding was analyzed from the horizontal and vertical directions. Three dome-shaped bars clearly show at least three palaeoflood phases. Quartz grain surface macrotextures are mainly V-shaped pits and conchoidal fractures, which exhibits a high-energy environment during the flood. The stratigraphic sequence model of EGBs is dominated by coarse sand and fine gravel rhythmic bedding in high-energy eddy environments and suspended sand deposits in low-energy backwater environments. Such phenomenon reveals megaflood fluctuates, which is also confirmed by geochemical difference. The episode of natural dam break floods triggered by tectonic activity and glacier fluctuation was dated to 20–17 ka during the LGM. Sedimentary pattern of EGBs offers fresh insights into understanding the megaflood geomorphological characteristics of the upper Yangtze River and better identification similar high-energy palaeoflood landforms in the southeast Tibetan Plateau.

Development of piezo-actuated x-ray deformable mirror for vertical focussing of synchrotron radiation at Indus-2

Piezo-actuated x-ray deformable mirrors (PXDMs) can effectively control the surface profile with sub-nanometre accuracy for adaptive focusing and, correct the wavefront distortion generated due to imperfections in optical components or other extraneous effects like heat load, minor misalignments of synchrotron radiation beamline. Generating and controlling the desired shape of PXDMs with sub-nanometre accuracy is very challenging due to the presence of a large number of actuators and constraints related to nonlinearity of piezoactuator, boundary conditions, fabrication related limitations and the requirement for ex-situ as well as in-situ characterization of PXDM. To accomplish this, a PXDM of zerodur with multiple electrodes on a piezoactuator has been developed for vertical focusing of synchrotron x-rays for the first time in India. The PXDM has been fabricated and characterized by in-house developed technologies. The iterative piezo response function-based optimization technique is used to optimize the electric fields of individual piezoactuators in order to achieve the desired parabolic shape of the PXDM. The ex-situ characterization showed that the PXDM can achieve the target parabolic profile with 42 nm root-mean-square error. Furthermore, in-situ characterization at a beamline, BL-12, of Indus-2 synchrotron radiation source using PXDM has confirmed the focusing of collimated x-ray beam in the vertical direction from FWHM 235 μm to FWHM 83 μm.

DEM study on the force chain evolution of biaxial compression of pebble bed

Li4SiO4 and Li2TiO3 are granular materials in the pebble bed of fusion reactors, and their physical parameters and mechanical properties directly affect the working status and structural design of the pebble bed. The force chain can be employed to intuitively describe the mechanical properties of the pebble bed in the particle aggregate. Based on the discrete element method, we conducted a numerical study on the evolution characteristics of the force chain of Li4SiO4 and Li2TiO3 pebble beds under biaxial compression and explored the friction coefficient and pebble bed effect of the aspect ratio on the force chain distribution. The results revealed that as the particle friction coefficient increased, the force chain tended to be isotropically distributed, indicating that the friction mechanism was more conducive to a uniform distribution of the force chain. During compression, the average coordination number of the pebble bed increased with the friction coefficient. The Li2TiO3 particles had larger gravity than the Li4SiO4 pebble bed therefore, the Li2TiO3 pebble bed accounted for more force chains in the vertical direction. When the aspect ratio of the pebble bed was less than 0.5 or greater than 2.5, the distribution of force chains exhibited strong anisotropy. Conversely, when the pebble bed aspect ratio ranged between 0.5 and 2.5, the distribution of force chains tended towards an isotropic trend. Moreover, the number of force chains in each direction varied with changes in the aspect ratio of the pebble bed, characterized by a high concentration at the edges and a lower concentration in the middle. The results can provide an in-depth understanding of the force chain distribution and evolution characteristics in the pebble bed and provide a theoretical basis for designing and analyzing tritium breeding pebble beds.

Additively manufactured Nb-Ti-Si based alloy: As-built and heat-treated conditions

This work aims to fully characterise the Nb-Ti-Si based alloy (Nb-26Ti-16Si-2.2Al-2Cr), processed by the electron-beam powder-bed-fusion in both as-built and heat-treated conditions, to elucidate the microstructure-property relationships. The as-built condition has [001]-oriented columnar grains of the Nb3Si phase with the Nbss phase dispersed throughout the microstructure. The microhardness is 645.2 ± 6.7 HV0.5, and the indentation fracture toughness shows distinct directionality: 7.7 MPa·m1/2 in the horizontal direction compared to 5.3 MPa·m1/2 in the vertical direction. Both properties are comparable to the cast version. The directionality is attributed to the underlying mechanisms such as crack bridging, arrest, and micro-crack formation. By contrast, in the heat-treated condition, the alloy exhibits a dual-phase microstructure (Nbss and Nb5Si3 phases) with near-equiaxed grain shape due to the Nb3Si phase decomposition. The fracture toughness increases to 12.1 MPa·m1/2, at the expense of a reduced microhardness of 564.4 ± 15.0 HV0.5.

Enhancing dynamic stability of HTS maglev systems with preloading method

High temperature superconducting (HTS) bulks have strong flux pinning capabilities and are widely used in various fields. Their self-stabilizing characteristics also provide new ideas for ultra-high-speed rail transit. For HTS maglev systems, operational stability, curve negotiation and safety when subjected to external forces are very important. Due to the hysteresis effect of superconducting bulks, they do not always return to their initial positions after deviating from the levitated position in an alternative external magnetic field. In some cases, the levitation system can be destroyed. Studies have shown that preloading can enhance quasi-static levitation performance. Therefore, this paper conducts a detailed analysis of the quasi-static levitation and guidance forces of HTS bulks above a Halbach permanent magnet guideway (PMG) under conditions with and without preloading. Additionally, the dynamic responses of the HTS bulks under lateral or vertical pulsed excitations are studied, with a particular focus on the final equilibrium position offset after disturbance. The results indicate that preloading can suppress the attenuation of the levitation force, enhance the guidance performance, and raise stiffness in both lateral and vertical directions. It also effectively suppresses position deviation from disturbance and increases the maximum excitation force threshold for system instability. This study provides practical insights for HTS maglev applications.