Line Structure Research Articles

Study on the influence of crack depth on the safety of tunnel lining structure

In order to study the mechanism of the influence of crack depth on the bearing capacity and stability of tunnel lining structure, the calculation model of internal force of lining with cracks is established based on the theory of fracture mechanics, and the variation of stability coefficient of lining structure with Ⅰ-Ⅱ composite cracks is analyzed. With the increase of the crack depth of the vault, the bending moment of the vault gradually decreases, the stress intensity factor increases, and the stability factor f gradually decreases. The critical depth of tensile and compressive crack instability propagation is 54.38% and 74.01% of the lining thickness, respectively. The relationship between load and displacement, internal force and contact pressure, crack propagation depth and time, and strain variation of the secondary lining vault during the loading process of cracks at different depths are analyzed. It is found that cracks have a significant impact on the bearing capacity of the secondary lining, and the deeper the cracks, the lower the bearing capacity and stability. When the crack depth is large, the tensile stress peaks in a short time, and applying smaller loads can also cause the crack to expand. When the crack depth is 0.9d (d is the thickness of the secondary lining), the bearing capacity of the structure decreases by 72.57%. The research results can provide certain theoretical guidance for the prediction and prevention of lining crack propagation during tunnel operation.

A new artificial lateral line attitude perception method based on mixed activation function-multilayer perceptron (MAF-MLP)

Attitude perception is significant for state recognition and navigation of underwater applications. However, few studies have combined pressure sensors with gyroscopes for attitude sensing alone, and even fewer have addressed how to obtain the pitch angle, roll angle and travel speed at the same time. To make up for these shortcomings, an artificial lateral line attitude perception method based on mixed activation function-multilayer perceptron (MAF-MLP) model was proposed to recognize various attitudes of underwater vehicles. The artificial lateral line carrier model is created based on the lateral line structure of fish, and its surface pressure distribution characteristics are obtained by simulation analysis. The artificial lateral line (ALL) system and the data collection board equipped with a gyroscope module are used to conduct underwater experiments, and the gyroscope is used to collect the carrier attitude information in real-time to improve model prediction accuracy. Finally, the experimental data agree with the theoretical analysis results, and the MAF-MLP model is used as the data source to predict the carrier attitude. The results show that the MAF-MLP model can accurately predict the pitch angle, roll angle and travel speed, which provides a theoretical basis for realizing the state identification and navigation of the underwater vehicle.

Comparative Analysis and Safety Evaluation of Shield Segment Structure Model under Surcharge Loading.

In shield tunneling projects, the selection of an accurate model to calculate the mechanical response of segment structure plays a crucial role in the design and cost of the project. The shell-spring and beam-spring models are two widely used methods for this purpose. However, it is still not clear how accurate and different these models are in calculation results under surcharge load. Therefore, to accurately calculate the internal forces and deformation of the segment structure and clarify the difference between the two models' results, the shell-spring and beam-spring models were established based on a subway shield tunnel project in Zhengzhou city. The reliability of the models was verified by comparing and analyzing the differences in deformation results between the models and field measurements. Furthermore, the safety of the segment structure was evaluated according to the ultimate bearing capacity of the normal section. The results declare that: (1) In the shell-spring model, the internal force gradually reduces from the edges towards the center of the segment width, and the shield segment exhibits a prominent non-plane strain state. (2) The internal force of the beam-spring model is larger than that of the shell-spring model. The axial force difference between the two models is relatively small; meanwhile, there is a larger disparity in the bending moment. However, with an increase in surcharge loading, the discrepancy in internal forces between the two models gradually decreases. (3) The calculation results of the shell-spring model are close to the field-measured values and the shield tunnel model test values, which verifies the accuracy and reliability of the shell-spring model. Therefore, it is more reasonable to use the shell-spring model to calculate the mechanical response of the segment structure. (4) With an increase in surcharge loading, the safety of the shield tunnel decreases gradually. Therefore, surcharge loading above the shield tunnel should be reasonably controlled to meet the requirements of the normal use of the shield segment. This manuscript aims to provide a reference for the future design and optimization of the shield tunnels' lining structure.

Robust Wideband Adaptive Beamforming by Convolutional Neural Network Structures in an Array System

The structure of arrays capable of receiving wideband signals differs from arrays which can only receive narrowband signals. These arrays should be capable of receiving several GHz instant bandwidth signals over the entire operating frequency, like High Resolution Radars or Terahertz in 6G communication systems. In these arrays, the number of beamformer coefficients increase due to using a time delay line structure, hence leading to a high computational complexity. This is one of the challenges of beamforming in wideband systems. Additionally, there are other factors in classic Wideband beamformers. These factors include poor performance against input DOA (direction of arrival) error, array calibration error, and too many snapshots to reach the steady state of the beamformer. Therefore, this paper focuses on the robustness of beamforming using deep learning technique, which has not been discussed before. The basis of network design is convolutional layers. Two different proposed approaches have been proposed to obtain optimal structure. In the first approach, appropriate values of hyperparameters are estimated, whereas the network model is selected in the second approach. Also, the network training method is done to become more robust against the mentioned factors. In the proposed structures, the constraints of the previous methods have been evaluated. The proposed structure is shown to have a superior performance when compared with other existing algorithms. In addition, the matrix of signal samples is replaced with the covariance matrix at the network's input, so the calculation time is significantly improved compared to the previous methods.

Adaptive responses of neuronal cells to chronic endoplasmic reticulum (ER) stress

Accumulation of misfolded proteins or perturbation of calcium homeostasis leads to endoplasmic reticulum (ER) stress and is linked to the pathogenesis of neurodegenerative diseases. Hence, understanding the ability of neuronal cells to cope with chronic ER stress is of fundamental interest. Interestingly, several brain areas uphold functions that enable them to resist challenges associated with neurodegeneration. Here, we established novel clonal mouse hippocampal (HT22) cell lines that are resistant to prolonged (chronic) ER stress induced by thapsigargin (TgR) or tunicamycin (TmR) as in vitro models to study the adaption to ER stress. Morphologically, we observed a significant increase in vesicular und autophagosomal structures in both resistant lines and ‘giant lysosomes’, especially striking in TgR cells. While autophagic activity increased under ER stress, lysosomal function appeared slightly impaired; in both cell lines, we observed enhanced ER-phagy. However, proteomic analyses revealed that various protein clusters and signaling pathways were differentially regulated in TgR versus TmR cells in response to chronic ER stress. Additionally, bioenergetic analyses in both resistant cell lines showed a shift toward aerobic glycolysis (‘Warburg effect’) and a defective complex I of the oxidative phosphorylation (OXPHOS) machinery. Furthermore, ER stress-resistant cells differentially activated the unfolded protein response (UPR) comprising IRE1α and ATF6 pathways. These findings display the wide portfolio of adaptive responses of neuronal cells to chronic ER stress. ER stress-resistant neuronal cells could be the basis to uncover molecular modulators of adaptation, resistance, and neuroprotection as potential pharmacological targets for preventing neurodegeneration.

Genetic diversity and population structure of maize inbred lines using phenotypic traits and single nucleotide polymorphism (SNP) markers

Understanding germplasm’s genetic diversity is essential for developing new and improved cultivars with stable yields under diverse environments. The objective of this study was to determine the genetic diversity and population structure of 128 maize inbred lines sourced from the International Institute of Tropical Agriculture (IITA), the International Maize and Wheat Improvement Centre (CIMMYT), and the University of KwaZulu-Natal (UKZN) using 11,450 informative single nucleotide polymorphism (SNP) markers. The inbred lines revealed highly significant (p < 0.001) levels of variability for the key phenotypic traits. The SNP markers had a mean gene diversity (GD) and polymorphic information content (PIC) of 0.40 and 0.31, respectively, indicating the existence of substantial genetic variation across the germplasm panel. The model-based population structure analysis identified three subpopulations (K = 3) among the inbred lines. This corroborated the phylogenetic analysis using phenotypic traits and molecular markers which classified the inbred lines into three groups. The findings of this study identified considerable genetic diversity for the selection of inbred lines with favourable alleles for multiple traits and could be useful to initiate marker-assisted selection (MAS) to identify significant loci associated with agronomic performance and multiple-stress tolerance.

Radio frequency designed a quadrature hybrid divider for the load-tolerant ICRF system on EAST

A quadrature power divider designed for EAST uses a metal plate and coaxial line structure and operates at frequencies ranging from 27 to 45 MHz. The key parameters for the power divider, including central frequency, transmission coefficient, and phase dependence of output ports, are obtained through radio frequency simulation by CST MWS and optimized to achieve reflection and isolation levels below −24 dB with a bandwidth of 20 MHz. The power divider is tested at low power levels, confirming its reliability, and demonstrating a ±10 degree tolerance for phase management during synthesis. With its simple structure, excellent RF performance, and water cooling capability, the power divider is an important component for improving the stability of the ion cyclotron heating system.

Insulation design of -800 kV gas insulation transmission line for negative ion based neutral beam injector

The high-voltage transmission line carries electricity, water, and gas for the high-potential components in the NNBI system. High voltage transmission lines used in -800 kV acceleration grade NNBI systems require the transmission of multiple high voltages of different voltage levels. Its insulation design not only guarantees the reliability of insulation but also requires a small occupation volume. The FEA method is used for insulation design of multi-conductor transmission lines. In the design of -800 kV transmission line, coaxial and non-coaxial structures are mainly considered. In the case of SF6 filling space, conductor radius and conductor position are the main factors affecting insulation strength. Both structures can make its insulation strength meet the requirements. However, it is found that the coaxial transmission line is more compact and concise when it meets the insulation requirements, but it is difficult to install and maintain.

Experimental study on performance of spring damping support structure system for large deformation tunnel in soft rock

According to the convergence confinement theory, it is an effective measure to control the large deformation of high ground stress in fractured soft rock tunnels by using yielding support. The yielding support can be classified as either radial or circumferential yielding support. Circumferential yielding support is achieved by transforming radial displacement into circumferential tangential closure without compromising the support capacity of the primary lining support structure. Based on this, and inspired by the design principle of dampers, a yielding support structure system with spring damping elements as its core was developed, based on the connection characteristics of steel arches in highway tunnel, which can provide increasing support resistance in the yielding deformation section. Then the mechanical properties of spring damping elements were obtained through indoor axial pressure and flexural tests. In addition, according to these results with numerical calculations, the yielding support structure system with embedded spring damping elements can reduce the internal force of the support structure by approximately 10% and increase the area of the plastic zone of the surrounding rock by 11.23%, which can fully utilize the self-bearing capacity of surrounding rock and verify the effectiveness of circumferential yielding support. Finally, the spring damping support structure system was designed with reference to the construction process of the tunnel excavated by drilling and blasting method, and the transformation of the spring damping element to spring damping support structure was achieved. Based on field test results, surrounding ground pressure for the yielding support optimization scheme was reduced by 40% and more evenly distributed, resulting in the successful application and a reduction in the construction cost of large deformation tunnels in soft rock.

Interactions Between Flow Fields Induced by Surface Dielectric Barrier Discharge Arrays

This study investigates the flow field induced by a surface dielectric barrier discharge (SDBD) system, known for its efficient pollution remediation of volatile organic compounds (VOCs). We aim to understand the flow dynamics that contribute to the high conversion observed in similar systems using this specific SDBD design. Examining how the surface discharge affects the gas mixing in chemical processes is important for both understanding the fundamentals and for potential industrial applications. Experimental techniques, including schlieren imaging and particle image velocimetry (PIV), applied with high temporal resolution, were used to analyse the flow field. Complementary, fluid simulations are employed to investigate the coupling between streamer and gas dynamics. Results show distinct fluid field behaviours for different electrode configurations, which differ in geometric complexity. The fluid field analysis of the most basic electrode design revealed behaviours commonly observed in actuator studies. The simulation results indicate the local information about the electron density as well as different temporal phases of the fluid flow velocity field containing the development of the experimental found vortex structure, its direction and speed of rotation. The electrode design with mostly parallel grid line structures exhibits confined vortices near the surface. In contrast, an electrode design also used in previous studies, is shown to promote strong gas transport through extended vortex structures, enhancing gas mixing and potentially explaining the high conversion observed.

Retracted: On Chemical Invariants of Semitotal-Point Graph and Its Line Structure of the Acyclic Kragujevac Network: A Novel Mathematical Analysis

Retracted: On Chemical Invariants of Semitotal-Point Graph and Its Line Structure of the Acyclic Kragujevac Network: A Novel Mathematical Analysis

Experimental study on the high water pressure erosion mechanism and its influence on the submarine shield tunnel concrete segments

This study investigated a high water pressure erosion mechanism and its influence on the mechanical performance deterioration of submarine shield tunnel concrete segments using a series of tests. First, a chloride ion pressure penetration test was conducted to reveal the impermeability performance and chloride ion permeability of the tunnel lining concrete. Then, given the environmental and mechanical characteristics of the lining segment structure of a submarine shield tunnel, a cofferdam-type electrochemically accelerated corrosion method was proposed to simulate the simultaneous application of unilateral water pressure and compression-bending loads on the segment. The effects of water pressure on the strain, deformation, crack propagation, and failure mode of the segment components were investigated. In addition, the damage caused by high water pressure on the segment components was explored using acoustic emission. This study lays the foundation for further research on the durability of shield tunnel structures under high water pressures.

Flow–solid coupling analysis of underground reinforced concrete forked pipe enclosing rock and structure

The stability of the surrounding rock for the construction excavation and the reinforcement of the lining structure during operation in the water-rich area is a difficult problem for the design of high-head underground turnout pipes. Firstly, according to the mechanism of excavation load release and surrounding rock damage evolution, the seepage effect of excavation in the construction of the forked caves is coupled to the surrounding rock stress damage, and an iterative method of numerical simulation of the coupled mutual feedback effect of excavation surrounding rock stress and seepage is proposed. Then, based on the cracking characteristics of the high internal water pressure reinforced concrete turnpike lining, a numerical analysis method of the coupling interaction between lining cracking and internal water seepage is proposed by coupling internal water seepage to stress damage in the lining by cracking the forked pipe structure. Applying the aforementioned method to a forked pipe project, the results show that: during the construction period, there is a significant increase in the damage zone, stress, and displacement of the rock around the cavern after considering the coupled iterations; during the operation period, with the increase in internal water pressure, the lining structure accelerates cracking due to the external infiltration of internal water; after the internal water is applied, the surrounding rock bears the main internal water pressure and the reinforcement bears only part of the circumferential force. The method provides theoretical support for the analysis and calculation of the reinforcement of similar underground high-pressure tunnels for rock support and lining structures and has certain theoretical and engineering significance.

Numerical studies of plasma edge in W7-X with 3D FINDIF code

Abstract Modelling of the plasma transport for inherently three-dimensional (3D) problems as in stellarators requires dedicated complex codes. FINDIF is a 3D multifluid plasma edge transport code that has been previously successfully used for the analysis of energy transport in the TEXTOR-DED tokamak [1], where 3D perturbations led to an ergodic structure of field lines in the plasma edge. The ongoing efforts to apply it meaningfully to Wendelstein 7-X (W7-X) plasma problems resulted in advancements in the main model and accompanying tools for mesh generation and post-processing. In order to verify the applicability of the code and to compare with the reported simulation (EMC3-EIRENE) and experimental (OP1.1) results, a series of simulations for varying plasma density, temperature and anomalous transport coefficients as well as for fixed input power were performed. The connection length pattern of FINDIF traced magnetic field lines on the limiter was reproduced and its impact on heat loads was confirmed. An increase in the peak heat load on the limiter with a rise in plasma density, temperature and anomalous plasma transport coefficients was observed. The decay lengths of density, electron temperature and heat flux did not change with density, and were decreasing with temperature and increasing with anomalous plasma transport coefficient, which was compared to the simple scrape-off layer (SOL) model.

Impact of the Physical Cellular Microenvironment on the Structure and Function of a Model Hepatocyte Cell Line for Drug Toxicity Applications.

It is widely recognised that cells respond to their microenvironment, which has implications for cell culture practices. Growth cues provided by 2D cell culture substrates are far removed from native 3D tissue structure in vivo. Geometry is one of many factors that differs between in vitro culture and in vivo cellular environments. Cultured cells are far removed from their native counterparts and lose some of their predictive capability and reliability. In this study, we examine the cellular processes that occur when a cell is cultured on 2D or 3D surfaces for a short period of 8 days prior to its use in functional assays, which we term: "priming". We follow the process of mechanotransduction from cytoskeletal alterations, to changes to nuclear structure, leading to alterations in gene expression, protein expression and improved functional capabilities. In this study, we utilise HepG2 cells as a hepatocyte model cell line, due to their robustness for drug toxicity screening. Here, we demonstrate enhanced functionality and improved drug toxicity profiles that better reflect the in vivo clinical response. However, findings more broadly reflect in vitro cell culture practises across many areas of cell biology, demonstrating the fundamental impact of mechanotransduction in bioengineering and cell biology.

High-frequency signal transmission in a coplanar waveguide structure with different surface finishes

Continuous pursuits for higher data rate, larger network capacity, low-latency communication, and better energy efficiency have motivated the development of the fifth generation (5 G) mobile communication technologies in recent years. Under a high-frequency transmission, the alternating electric current (AC) tends to distribute to the outer of a conductor due to the so-called “skin effect”; therefore, the surface coatings of Cu interconnect becomes an indispensable factor of the signal transmission characteristics. The focus of this study is to deeply probe into the effect of surface coatings on the high-frequency signal transmission (1–100 GHz) of Cu interconnects. We investigated six different surface finishes over a coplanar waveguide (CPW) transmission line structure, including immersion tin (ImSn), immersion silver (ImAg), immersion gold (IG), electroless palladium/immersion gold (EPIG), immersion gold/electroless palladium/immersion gold (IGEPIG), and ultrathin-Ni(P)-type ENEPIG. The high-frequency signal performance of the CPW transmission line was analyzed through the finite element analysis (FEA) method by using a 3D electromagnetic simulation software. Furthermore, experimental measurements were conducted by using a vector network analyzer (VNA) to characterize the signal loss arising from different surface finishes, so as to validate the numerical simulation results. The FEA and VNA results showed that a noticeable current redistribution might be induced by a high conductivity/permeability of surface coating(s), i.e., ImSn and ultrathin-Ni(P)-type ENEPIG, which significantly increases the signal insertion loss at high frequencies. Thus, an appropriate surface coating over Cu interconnects was necessary for enhancing the high-frequency signal transmission performance.

Altitude Correction Method for Audible Noise of ± 800 kV UHVdc Overhead Transmission Line and its Engineering Application

With the improvement of the voltage level of DC overhead transmission lines (OHTLs), the audible noise (AN) caused by the corona discharge of conductors is an increasingly serious problem. AN has become a critical parameter that determines the selection of conductors, line structures and specifications for UHVdc OHTLs in high-altitude areas. To study the altitude correction method of AN for UHVdc OHTLs, we erected 6 × 720 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 6 × 900 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> conductors on DC full-scale test lines located at altitudes of 4,300 m and 50 m, respectively. We carried out an experimental study on AN over a long period and obtained its distribution law at high and low altitudes and its altitude-related increment. At the same time, on four DC reduced-scale test lines located at 4,300 m, 3,400 m, 1,700 m and 50 m above sea level, 6 × 95 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> conductors were erected for experiments. The law that the AN of the DC OHTL shows a nonlinear change with increasing altitude is obtained. Based on the combination of full-scale and reduced-scale tests, an altitude correction method of AN for UHVdc OHTLs considering the influences of both altitude and electric field strength on the conductor surface is proposed. From 0 to 4,300 m above sea level, when the maximum electric field strength on the conductor surface is 19 kV/cm, the increase in AN calculated with the formula suggested by this article is only 55% of the value calculated with the method recommended by the EPRI. The altitude correction formula of AN proposed herein is applicable to the design of UHVdc OHTLs in high-altitude areas, which can greatly save line investment while meeting the requirements of environmental protection.

Building fraction magnitude knowledge with number lines: Partitioning versus analogy.

Understanding fraction magnitudes is foundational for later math achievement. To represent a fraction x/y, children are often taught to use partitioning: Break the whole into y parts and shade in x parts. Past research has shown that partitioning on number lines supports children's fraction magnitude knowledge more than partitioning on area models. However, partitioning may not take full advantage of children's prior knowledge or the structure of the number line. We tested an alternative fraction number line lesson that leveraged children's preexisting whole number knowledge using a domain-general learning tool: analogy. In a preregistered online experiment, second and third graders (N = 84, M = 8.83 years) were randomly assigned to an analogy lesson (e.g., if I know how big 3 is on a 0-4 line, I know how big ¾ is on a 0-1 line), a partitioning lesson on number lines, or a control lesson using square area models. Results showed that the analogy lesson was more effective for promoting fraction magnitude understanding than the control lesson, and it was at least as effective as the partitioning lesson. The analogy group, but not the partitioning group, significantly outperformed the control group with large-denominator fractions at retention (i.e., 1-week delayed posttest) and on transfer tests (i.e., fraction comparison). We also replicated past findings that fraction partitioning lessons are more effective on number lines than on area models, and this advantage was partially sustained after a 1-week delay. Overall, these findings highlight the power of domain-general analogy to support mathematical development. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Contact Failure Characteristic Test and Overheating Analysis of UHV GIL Electrical Connection Structure

As the key component of the conductor of the gas-insulated power transmission equipment, the electrical connection structure bears high current, high stress and high temperature for a long time. Electrical contact failures become an important issue, while it’s failure characteristics and mechanisms are ambiguous so far. In this paper, based on complex electrical connection structures of gas-insulated transmission line (GIL), equivalent tests were conducted on the contact failure characteristics of such structure. Result shows that poor contact of the such electrical connection structure will cause two types of situations: micro-gap discharge and contact overheating. The causes of both are different. Firstly, micro slip is a kind of cause of discharge faults despite the separation gap is small. The current transfer area (b) of such contact structure is the main position where the arc starts. The contact stability at that location should be fully considered in the layout of such electrical connection structure. Secondly, combined with the surface morphology and element distribution, the mechanism of contact discharge and the source of metal particles are further explained by the occurrence of coating peeling and material transfer behavior. Finally, the difference in contact state is the main reason for a few contacts overheating. There is a significant temperature difference between contacts in different contact state. The temperature rises nonlinearly with the increase of the current under the condition of uneven current carrying. The above research can provide a practical basis for fault analysis and prevention of such electric contact structures in the UHV gas-insulated power transmission equipment.

High-Efficiency Circularly Polarized Phased Array Based on 5 μm-Thick Nematic Liquid Crystals: Design, Over-The-Air Calibration, and Experimental Validation

This paper presents a systematic investigation and demonstration of a K-band circularly polarized liquid-crystal-based phased array (LCPA), including the design, over-the-air (OTA) in-array calibration, and experimental validation. The LCPA contains 16 phase-shifting radiating channels, each consisting of a circularly polarized stacked patch antenna and a liquid-crystal-based phase shifter (LCPS) based on a loaded differential line structure. Thanks to its slow-wave properties, the LCPS exhibits a maximum phase-shifting range of more than 360° with a figure of merit of 78.3(° )·dB−1 based on a liquid crystal layer with a thickness of only 5 μm. Furthermore, an automatic OTA calibration based on a state ergodic method is proposed, which enables the extraction of the phase–voltage curve of every individual LCPA channel. The proposed LCPA is manufactured and characterized with a total profile of only 1.76 mm, experimentally demonstrating a scanned circularly polarized beam from −40° to +40° with a measured peak gain of 12.5 dBic and a scanning loss of less than 2.5 dB. The bandwidth of the LCPA, which satisfies the requirements of port reflection (|S11|) < −15 dB, an axial ratio (AR) < 3 dB, beam squinting < 3°, and a gain variation < 2.2 dB, spans from 25.5 to 26.0 GHz. The total efficiency is about 34%, which represents a new state of the art. The use of the demonstrated low-profile LCPA to support circularly polarized scanning beams, along with the systematic design and calibration methodology, holds potential promise for a variety of millimeter-wave applications.