Line Segments Research Articles

Analysis the Mechanical Response of Tunnels Under the Action of Vertical Jacking in Shield Construction and Research on Reinforcement

This research examines the effects of vertical jacking construction on the mechanical behavior of shield tunnels. Model tests simulating vertical jacking were performed utilizing a purpose-built apparatus to quantify the reaction forces generated by the diffusion block during the jacking operation. A systematic analysis was conducted on the mechanical responses of shield tunnel lining segments and their interconnecting joints. Utilizing Particle Flow Code (PFC) methodology, a deformation prediction model specifically tailored for vertical jacking conditions was formulated. Correlating simulation results with experimental measurements quantified the sensitivity of tunnel deformation to grouting reinforcement, enabling the identification of an optimal reinforcement zone. Key findings reveal that the jacking reaction force distribution exhibits pronounced nonlinearity: a substantial increase precedes failure, followed by rapid post-failure reduction and eventual stabilization in advanced jacking stages. Tunnel convergence deformation evolves through four distinct phases: significant growth, rapid attenuation, gradual diminution, and final stabilization. The primary zone of influence encompasses the opening ring and its two adjacent rings. Jacking induces longitudinal bending deformation, with maximum joint opening occurring at the opening ring. Abrupt longitudinal load fluctuations cause dislocation between the opening ring and neighboring rings. Internal segment stresses exhibit initial tensile and compressive increases followed by subsequent relaxation. Externally applied grouting reinforcement effectively attenuates jacking-induced tunnel deformation. An optimal reinforcement range was determined at the 60° position relative to the segment springline, substantially lowering resource consumption and construction risks compared to conventional reinforcement strategies. These outcomes furnish theoretical underpinnings and technical benchmarks for optimizing engineering design and facilitating the implementation of vertical jacking technology.

Classical and Parameterized Complexity of Covering Problems in Line Segment Arrangements

ABSTRACT Given a line segment arrangement, defined as the geometric structure induced by a set of n line segments in a plane, we study the complexity of two covering problems - Cell Cover for Segments (CCS) and Guarding a Set of Segments (GSS) - by modeling the arrangements as its underlying planar graphs. In Cell Cover for Segments (CCS) problem, the input is an arrangement of line segments and our aim is to cover all the segments with minimum number of cells. We prove that the decision version of CCS is NP-complete. Guarding a Set of Segments (GSS) Problem, which is known to be NP complete [5], asks to cover all the line segments with minimum number of vertices in the input arrangement. We propose a O ∗(k 2k ) FPT algorithm for solving GSS, where k is the solution size. We also show that the special case of GSS, where the underlying planar graph induced by the arrangement is outerplanar, can be solved in O ∗(4 k ). We also define a structural parameter called face density (d) of the arrangement, and provide a O ∗(dk ) FPT algorithm for the GSS problem.

Mechanics of longitudinal joints in segmental tunnel linings: Role of connecting bolts

Mechanics of longitudinal joints in segmental tunnel linings: Role of connecting bolts

Quantum Scattering by Multiple Slits—A Lippmann–Schwinger Approach

We investigate the non-relativistic scattering of a plane wave by a vertical segment formulating the problem in terms of the Lippmann–Schwinger equation in two spatial dimensions. Adjusting the coupling strength function we show how to implement the scattering by a system of multiple slits and by a Cantor set. We present detailed calculations of the scattered wave function for the line segment, as well as for the single, double, and multiple slits. We define reflection and transmission functions that are position-dependent in a defined region. From these results, we obtain the probability densities and differential and total cross-sections for these problems.

Carbon-friendly design method of tunnel lining segments based on Pareto optimal analysis

Carbon-friendly design method of tunnel lining segments based on Pareto optimal analysis

Study on mechanical and damage characteristics of segment lining under the squeezing action of shield shell

Study on mechanical and damage characteristics of segment lining under the squeezing action of shield shell

Experimental investigation on heat transfer performance and thermal stress of segment lining in a heating power energy tunnel

Experimental investigation on heat transfer performance and thermal stress of segment lining in a heating power energy tunnel

Fast Tip Tracking via Needle Detection and Estimation during Ultrasound-guided Prostate Biopsy.

Accurate and real-time needle tip tracking is critical in image-guided prostate biopsy procedures. Ultrasound (US)-based tracking methods, though, are afflicted by suboptimal image quality, low needle visibility, and dynamic, variable appearance of the needle tip. Therefore, this task requires a lightweight and robust approach, capable of handling complex US environments in real-time. We propose a Needle Detection and Estimation (NDE) framework for US-guided needle-tip tracking in real time. Instead of directly detecting the needle tip, we first detect the more consistently represented needle axis using a lightweight line detection model. The needle tip is then estimated as one of the endpoints of such a detected axis. A Kalman-filter-based needle estimation module is added to take advantage of the last detection to improve and guide the current detection, which is particularly helpful within frames where the needle is not visible. Segment of Line (SoL) and Copy-Paste object augmentation strategies are used to increase robustness while reducing dependency on large training datasets. Experiments demonstrate that our method outperforms existing tracking techniques, achieving success rates of 95.27% and 95.62%, and average tracking errors of 1.94 mm and 2.53 mm for the In vitro and In vivo datasets, respectively. Furthermore, our method achieves a tracking speed of 102.13 FPS, making it suitable for real-time scenarios. Our NDE framework can significantly enhance the reliability and efficiency of needle tip tracking during image-guided prostate biopsy. The proposed method shows the potential to improve both clinical diagnosis and therapy for prostate cancer.

High-precision space camera self-calibration via structural priors and intelligent optimization

During long-term on-orbit operation, space cameras are subjected to extreme thermal cycles, high vacuum, intense radiation, and complex mechanical loads, which cause drift in the geometric parameters of the imaging system. To improve the on-orbit camera’s imaging quality without altering the optical system, existing calibration methods are insufficient. Therefore, this study proposes, to our knowledge, a novel on-orbit autonomous calibration method based on the structural features of the spacecraft. Unlike traditional ground-based calibration methods and satellite-based reference object-dependent approaches, this method innovatively utilizes the spacecraft’s inherent solar panels as the calibration reference source and constructs a line feature detection model based on space–frequency domain collaborative analysis. By employing a dual-domain fusion strategy, sub-pixel-level extraction of the solar panel’s structural line features is achieved. The optimal vanishing point is trained using abundant feature line segments, and a final error function is constructed. An intelligent optimization algorithm is then proposed to iteratively solve this optimization problem. Simulations and real-world experiments demonstrate that this method provides excellent stability and accuracy.

Shortest Paths of Mutually Visible Robots

Given a set of [Formula: see text] point robots inside a simple polygon [Formula: see text], the task is to move the robots from their starting positions to their target positions along their shortest paths, while the mutual visibility of these robots is preserved. Previous work only considered two robots. In this paper, we present an [Formula: see text] time algorithm, where [Formula: see text] is the complexity of the polygon, when all the starting positions lie on a line segment [Formula: see text], all the target positions lie on a line segment [Formula: see text], and [Formula: see text] and [Formula: see text] do not intersect. We also argue that there is no polynomial-time algorithm, whose running time depends only on [Formula: see text] and [Formula: see text], that uses a single strategy for the case where [Formula: see text] and [Formula: see text] intersect.

Construction Scheme and Influence Analysis of Horizontal Small-Clear-Distance Shield Tunnel

Based on the construction project of Guangzhou Metro Line 13, this paper explores the special construction scheme for the safety of horizontal small-clear-distance shield tunnel construction, which adopts the construction of a tunnel first and a station later in the actual project to reduce the impact on the tunnel segment and the existing bridge piles. At the same time, the MIDAS GTS(2022R1) geotechnical and structural finite element analysis software is used to simulate and analyze the shield excavation process by using the stratum–structure modeling method, and the effect of grouting reinforcement in the tunnel is compared and analyzed. Through the research and analysis of the displacement and deformation of the model, the rationality and effectiveness of grouting reinforcement are explored to ensure the smooth implementation of the special construction scheme. The test results show that the implementation of grouting reinforcement measures in the tunnel can effectively control the horizontal deformation of the existing bridge piles and the horizontal deformation of the left line segment of the small-clear-distance section, and the above two deformation indexes are reduced by 67.7% and 72.1%, respectively, compared with the non-reinforcement condition. The settlement deformation of the segment and the surrounding existing bridge piles meets the requirements of the code, so the construction scheme is basically feasible.

Multilayered Railway Passenger Demand Estimation Considering Nested Choices: A Computational Graph-based Learning Framework

Abstract This paper attempts to develop a systematic and theoretically consistent machine learning model to quantify and estimate multi-level railway passenger demand, capturing overall demand patterns. This includes estimating boarding and alighting passengers at stations along a corridor, origin–destination trips between stations, and passenger flows loaded onto train lines and corresponding train line segments. Observations are transformed into loss functions and mapped onto a hierarchical flow network to simultaneously estimate these multilayered demand variables. By incorporating a Nested Logit model into the hierarchical flow network, the learning model can further calibrate a series of interpretable parameters associated with key attributes in rail line planning (e.g., line frequency, fare levels, and travel time), enabling policy-sensitive analyses. Unlike pure discrete choice models, the proposed estimation model is constrained by line-based capacity constraints to prevent passenger flow overload on specific train lines and address inconsistencies between different observations. The nonlinear estimation model is reformulated as a computational graph and solved using backpropagation algorithms with off-the-shelf machine learning solvers (e.g., TensorFlow). To validate the applicability of our approach, we conduct a real-world case study on the Beijing–Shanghai high-speed rail corridor. The evolution of multiple loss functions in the case study demonstrates the accuracy and convergence of the method. Fourteen days of ticket sales data (10 days for training and 4 days for validation) are utilized to demonstrate the applicability of the proposed method.

DataMatrix Code Recognition Method Based on Coarse Positioning of Images

A DataMatrix (DM) code is an automatic identification barcode based on a combination of coding and image processing. Traditional DM code sampling methods are mostly based on simple segmentation and sampling of a DM code. However, the obtained DM code images often have problems such as wear, corrosion, geometric distortion, and strong background interference in practical scenarios. To improve decoding ability in complex environments, a DM code recognition method based on coarse positioning of images is proposed. The two-dimensional barcode is first converted into a one-dimensional waveform using a projection algorithm. Then, the spacing between segmentation lines is predicted and corrected using an exponential weighted moving average model for adaptive grid division. Finally, the local outlier factor algorithm and local weighted linear regression algorithm are applied to predict and binarize the gray level values, converting the DM code image into a data matrix. The experimental results show that this method effectively handles problems like blurring, wear, corrosion, distortion, and background interference. Compared to popular DM decoding libraries like libdmtx and zxing, it demonstrates better resolution, noise resistance, and distortion tolerance.

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In the present paper, in a certain finite mixed domain for the equation (signy)jyjmuxx + uyy + α0 jyj1− m2 ux + βy0uy = 0 we study the problem with a nonlocal condition pointwise connecting the value of the unknown function on the boundary and parallel to it internal characteristic, using the fractional order differentiation operator in the sense of Riemann-Liouville. On the segment of the degeneration line, a general conjugation condition and an analogue of the Frankl condition type are specified. The uniqueness of the solution to the problem is proved using the extremum principle of A.V. Bitsadze. The existence of a solution to the problem is proved using the theory of singular integral equations, Wiener-Hopf equations and Fredholm equations of the second kind.

Damage investigation of segmental lining in underwater pipeline tunnels based on plastic hinge theory

For the small-diameter underwater shield tunnel, its failure process and control standard of structural damage have not been clearly defined. In this work, the local and overall failure criteria for the segmental lining were established based on the plastic hinge method. The failure process of two types of segmental lining with straight-joint assembly structure (STRJS) and staggered-joint assembly structure (STGJS) was discussed through fine numerical simulation, and the influence of lateral pressure coefficient, external water pressure and subgrade reaction coefficient on them was analysed. Then, an assessment method for determining the damage state of the underwater shield tunnel segmental lining was established using the ellipticity damage index. The results indicate that the failure process of the segmental lining can be divided into elastic stage, crack development stage, plastic hinge formation stage and failure stage. The plastic hinge formation stage of STRJS is longer than that of STGJS, and it has a higher load-bearing capacity. Increasing the lateral pressure coefficient, external water pressure and subgrade reaction coefficient can enhance the load-bearing performance of the segmental lining. This study is of great significance for promoting the extensive application of trenchless technology in river-crossing shield engineering in the oil and gas pipeline industry.

Strip loading in reinforced concrete: Mechanical modeling and experimental validation

Abstract Strip loading of reinforced concrete is a common problem in engineering practice. The concrete compressive strength at the load introduction can be several times higher than the uniaxial concrete compressive strength, which can be attributed to geometrical and passive confining stresses caused by load dispersion and reinforcement, respectively. However, current design provisions do not allow combining these two confining effects, leading to overly conservative designs. Furthermore, experimental data on strip‐loaded concrete members with pronounced passive confinement and moderate load concentration ratios, common, for example, in longitudinal joints of segmental tunnel linings, are scarce. This article presents different models for strip loading as well as an experimental campaign of 15 concrete blocks subjected to strip loading. The test parameters included (i) the reinforcement ratio and type, (ii) the width and position of the loaded area, and (iii) the concrete strength. Digital image correlation was applied to determine the crack widths. The experimental results give insight into the mechanical behavior and were used to compare the different model approaches for strip loading, including the recently published Dual‐Wedge stress field and a simplification of the same. The models are presented in detail and adjusted for strip loading with moderate load concentration ratios where required. Furthermore, it is discussed how passive confinement can be accounted for with regular and irregular reinforcement spacings. The bearing capacity predictions of models accounting for the combined effect of load dispersion and passive confinement are in good agreement with the tests and allow for an efficient and safe design, whereas the simplification stands out for its ease of use and lowest coefficient of variation.

Margun A. A. Fast decentralized control for uniform distribution of mobile robots

The problem of synthesizing a fast decentralized control algorithm for uniform distribution of a group of mobile robots making up a multi-agent system, over a given straight line segment is considered. The aim of the study is to synthesize a group finite control algorithm to achieve distributed consensus and subsequently test it experimentally. The method used is based on the homogeneity theory and the implicit Lyapunov function method. The stability criteria for a multi-agent system are specified as a solution to a system of linear matrix inequalities. Unlike the existing method, the proposed approach allows weakening the stability criteria, simplifying the setup and application of the algorithm, as well as effectively analyzing the system dynamics and guaranteeing consensus in a finite time. The theoretical results are experimentally confirmed using an IP camera and 4 wheeled robots. The experiments demonstrated high efficiency of the proposed approach, which confirms its applicability to control problems in real conditions.

The Initial Attitude Estimation of an Electromagnetic Projectile in the High-Temperature Flow Field Based on Mask R-CNN and the Multi-Constraints Genetic Algorithm

During the launching process of electromagnetic projectiles, radiated noise, smoke, and debris will interfere with the line of sight and affect the accuracy of initial attitude estimation. To address this issue, an enhanced method that integrates Mask R-CNN and a multi-constraint genetic algorithm was proposed. First, Mask R-CNN was utilized to perform pixel-level edge segmentation of the original image, followed by the Canny algorithm to extract the edge image. This edge image was then processed using the line segment detector (LSD) algorithm to identify the main structural components, characterized by line segments. An enhanced genetic algorithm was employed to restore the occluded edge image. A fitness function, constructed with Hamming distance (HD) constraints alongside initial parameter constraints defined by centroid displacement, was applied to boost convergence speed and avoid local optimization. The optimized search strategy minimized the HD constraint between the repaired stereo images to obtain accurate attitude output. An electromagnetic simulation device was utilized for the experiment. The proposed method was 13 times faster than the Structural Similarity Index (SSIM) method. In a single launch, the target with 70% occlusion was successfully recovered, achieving average deviations of 0.76°, 0.72°, and 0.44° in pitch, roll, and yaw angles, respectively.

Strain-based design for segmental tunnel lining under thrust jack load

A strain-based design approach is proposed to assess precast concrete tunnel lining (PCTL) under thrust jack load exerted by a tunnel boring machine (TBM). This approach is intended to provide service-level PCTL thrust jack load capacities to mitigate TBM thrust-induced cracking. The stress-based methods currently adopted by design guides neglect compression-induced tensile strain and cracking by Poisson’s effect. Hence, when concrete tensile strength is used as design criteria, stress-based approaches significantly overestimate service-level strength. A strain-based design approach is therefore developed via parametric examination of stress distributions in PCTL under thrust jack load, which can be used as an alternative or supplement to finite element analyses (FEA) in practice and consists of design charts accounting for variations in: (1) Poisson’s ratios, (2) contact area between pads and segments, (3) number of pads and (4) segment geometries. The design approach was validated against FEA and full-scale experiments. The sensitivity to eccentric loading and segment curvature were also examined. Loading eccentricity induces higher radial bursting strain due to reduced contact between pads and segments, resulting in higher transverse bursting strain on the eccentricity side of the segment. Tunnel curvature has no significant effect on stress or strain induced by thrust jack loading.

Spleen as an Alternative Tissue for Estimating Tetracapsuloides bryosalmonae Load, Prevalence and Its Relationship With Proliferative Kidney Disease in Brown Trout.

Accurate pathogen detection is essential in fish health management and disease prevention. Pathogens often target different host tissues, and monitoring alternative target organs can provide important insights into disease progression. We evaluated the spleen as an alternative to the kidney for estimating the load and prevalence of the myxozoan parasite Tetracapsuloides bryosalmonae (Tb) and its relationships with proliferative kidney disease (PKD) in juvenile brown trout. We sampled 238 brown trout across nine rivers and quantified parasite load in both tissues using qPCR. Parasite load showed a strong positive correlation between the two tissues for both raw and log10-transformed data (Pearson's r = 0.60-0.71, Spearman's ρ = 0.78), with the spleen exhibiting, on average, 4.1-fold lower parasite load compared to the kidney. Tb was found in 191 specimens, consisting of 167 spleen and 190 kidney detections. The relationships between parasite load and PKD symptoms (renal hyperplasia and anaemia) were comparable for both tissues, and segmented regression line analysis indicated that health parameters deteriorate faster after exceeding a certain parasite load threshold. In conclusion, these results suggest that the spleen may serve as a viable alternative to the kidney for Tb monitoring, providing useful insights into Tb presence, load, and PKD progression in salmonids.