Three-dimensional Analysis Method Research Articles

Energy Element Method for Three-Dimensional Vibration Analysis of Stiffened Plates with Complex Geometries

A novel numerical method, the energy element method, is proposed for the three-dimensional vibration analysis of stiffened plates with complex geometries. The problem is modeled in a cuboidal domain, and a cuboidal energy element is developed for the simulation of the structural components. To simulate the energy distribution of the structure, stiffened plates are treated as discrete energy systems, where variable stiffness is used to characterize their energy distribution in a cuboidal domain and a global admissible function is used to approximate their vibrational behavior. With extended interval integral, Gauss quadrature, variable stiffness, and Legendre polynomials used for numerical integration in the cuboidal domain, the cuboidal energy element can offer sufficient precision with sufficient Gauss points for simulating the strain energy of stiffened plates with complex geometries. The Gauss–Legendre quadrature will provide accurate integration results if the integral domain is cuboidal. Otherwise, small cuboidal energy elements are generated with denser Gauss points to capture the geometric boundaries. As the numerical model is constructed on a standard geometric domain, all energy functionals and computational procedures are standard. Three-dimensional vibration problems are investigated for variously shaped stiffened plates with straight or curvilinear stiffeners. The present results are compared with analytical, numerical, and experimental results published in the literature.

Effect of excavations on the bearing capacity of adjacent foundations using three-dimensional upper bound limit analysis method

Effect of excavations on the bearing capacity of adjacent foundations using three-dimensional upper bound limit analysis method

A novel finite element limit equilibrium method and its application in instability analysis for 3-D high core rockfill dams

The safe operation of high rockfill dams is an important issue related to human life and property safety. However, the stability analysis of high core rockfill dams with complex spatial morphology is mostly confined to two-dimensional, and appropriate stability analysis methods are scarce. Therefore, it is necessary to develop the three-dimensional stability analysis method for high core rockfill dams and study the spatial stability mechanism after impoundment. Firstly, a finite element limit equilibrium framework suitable for stability analysis of high rockfill dams is introduced, and the horn-shaped three-dimensional failure mechanism is presented for optimization. Then, according to the statistical results of the actual core rockfill dam above 100 m, 15 high dam models with actual Duncan-Chang parameters between 100 m and 300 m are established to study the three-dimensional instability mechanism. Meanwhile, grey relation analysis (GRA) is used for quantitative analysis of stability sensitive factors. Finally, the stability analysis of the Quxue core rockfill dam (173.2 m) was completed within the established stability framework. The results show that the combined failure mechanism with the horn-shaped is suitable for dam stability analysis, and with the increase of height and slope ratio of dam, the most dangerous sliding surface evolves to shallow layer. In addition, GRA results show that slope ratio is the most sensitive parameter compared to dam height and material parameters. The practical engineering stability results of Quxue show that the research results can provide a reliable reference for the stability of the high core rockfill dam.

Back analysis of the shear strength parameters of 3D landslides with Bayesian approach and reliability theory

To establish an accurate model for determining the shear strength parameters of sliding surfaces while considering the variability and uncertainty of geotechnical parameters, a reliability back analysis method for parameters based on Bayesian theory and a three-dimensional slope stability analysis method are proposed in this paper. First, the prior information of shear strength parameters is updated according to the field test information based on Bayesian theory. Then, combined with the reliability theory, the influences of different two-dimensional and three-dimensional sliding surface shapes on the parameters back analysis are studied. The results show that the uncertainty of parameters decreases with the increase in the amount of test data after introducing the test data to update the mastered parameter information based on Bayesian theory, and it is of great significance to consider the shape and three-dimensional effect of the sliding surface accurately to improve the accuracy of parameter determination and slope stability analysis.

Polynomial expansion method for full wave three-dimensional analysis of dielectric waveguides and periodic structures

In summary, the utilization of Legendre polynomial expansion in the modal analysis of stratified dielectric layers with doubly periodic permittivity profiles offers a departure from conventional methods. This novel approach, grounded in the analytical projection of Maxwell’s equations onto the Hilbert space defined by Legendre polynomials, results in well-behaved algebraic equations. These equations, in turn, facilitate the derivation of propagation constants and electromagnetic field profiles, circumventing issues related to numerical instability and oscillatory behavior. Moreover, the method's adaptability to extend its application to nonperiodic dielectric waveguides through the periodic repetition concept further underscores its versatility and potential impact in electromagnetic field analysis. Finally, to validate the proposed method, we conducted a comparative analysis of three standard test cases against previously reported results in the literature. The comparison showcased a high level of agreement, affirming the accuracy and efficacy of the presented approach.

Improved Jacobian-Torsor model for optimizing mechanical product quality

The quality of an assembly largely depends on the predictive accuracy of the assembly deviation model in the selective assembly process. Presently, three-dimensional deviation analysis methods only offer tolerances that indicate the overall deviation of a part feature. This limitation fails to accurately represent the fit of the parts during the assembly process, resulting in initial inaccuracies in the selective assembly model. To address this issue, an improved Jacobian-Torsor model is proposed that incorporates measured data from part assembly features into the deviation analysis model. Initially, the actual contact state of the assembly is determined by measuring the contact surface of the plane fit and the shaft-hole fit. Next, the Jacobian matrix, representing the transmission path of assembly deviation, is constructed by analyzing the assembly connection diagram. Subsequently, by integrating the actual contact state characterized by small displacement torsor (SDT) into the unified Jacobian-Torsor model, the advantage of high credibility tolerance propagation is provided. Finally, the feasibility of the proposed improved Jacobian-Torsor model is verified using the double-joint manipulator.

Modeling the failure process of rock masses using a 3D nodal-based continuous-discontinuous deformation analysis method

A three-dimensional nodal-based continuous-discontinuous deformation analysis method (3D-NCDDAM) is developed in this study for modeling the failure process of rock masses. In the 3D-NCDDAM, four-node tetrahedral elements which can be automatally generated are used to discretize the problem domain. To reduce computational cost, and effectively model the failure process of rock masses at concerned regions, the problem domain is devided into two types of regions, namely, the “non-destructive region” and “possible destructive region”. The non-destructive region is mainly used to reduce the boundary effects on the numerical results, and is regarded transitional zone in which the failure of rock masses is not considered. For the possible destructive region, artificial joint elements are inserted, and the failure of these joint elements is used to represent fracture initiation and propagation in rock masses. Additionally, the contact potential which is initially proposed in finite-discrete element method (FDEM) is incorporated into the 3D-NCDDAM to simuate the opening and slipping of discontinuous structural planes involved in rock masses’ failure process. Note that the difficultly in determing contact types in the traditional 3D discontinuous deformation analysis (3D-DDA) method is avoided in the 3D-NCDDAM. The proposed 3D-NCDDAM can be treated as a hybrid method, which inherite both the advantage of DDA method and FDEM. To validate the 3D-NCDDAM, seven numerical examples are conducted. The numerical results indicte that the 3D-NCDDAM can effectively model the failure process of rock masses in both experimental scale and engineering scale.

Kinematic Analysis and Research on the "Push Shot" Action of Table Football

In order to reveal the kinematic characteristics of the "push shot" technique in table football, this article analyzes and studies the kinematics of the "push shot" technique in table football using the three-dimensional motion analysis method, conducts experimental measurements of the push shot technique in table football players, and analyzes and studies its kinematic parameters. When completing the entire table football technical movement, the upper limbs need to rotate and cooperate with the vertical axis and coronal axis of the torso, ultimately forming a wrist compression movement to the fingers and wrists. When athletes complete technical movements, whether it is dribbling or shooting, the flexibility of their wrists is extremely high. Therefore, during practice, it is necessary to strengthen the training of the wrist and small muscle groups of the fingers, and pay attention to the practice of instant force application. Both the joints of the upper and lower limbs are very important. Therefore, during athlete training, it is necessary to strengthen the strength of the body's joints.

The effect of climate change on energy generated at hydroelectric power plants: A case of Sakarya river basin in Turkey

In this study, the effect of climate change on energy data produced in HEPPs in Sakarya River basin of Turkey was investigated. Data were analysis by using classical and modern analysis methods. Before applying these methods, serial correlation coefficients of the data were calculated and it was decided whether trend methods would be applied or not. As a result of the study, while a decreasing trend was observed in Mann-Kendall (50 % of data) and Innovative Trend Analysis (ITA) (90 % of data) methods in energy and streamflow data, unstable trends were observed in Three-Dimensional Innovative Trend Analysis (3D-ITA) method (70 % of data). However, a stable decreasing trend was observed in the middle region in energy and streamflow data of Pamukova HEPP. No trend was generally observed in all methods in precipitation data of Sakarya province. Stable trends were observed in the 3D-ITA method (In 67 % of the region). A generally increasing trend was observed in all methods in temperature data of Sakarya province. Stable trends were observed in the 3D-ITA method (In 67 % of the region). The beginning of the trend in Mann-Kendall Rank Correlation method in both energy-streamflow data and precipitation-temperature data showed the second half of 2016.

Bidirectional two-degree-of-freedom grating interferometer with biased Littrow configuration

Traditional grating interferometer with Littrow configuration suffer from low optical subdivision factor and high grating base surface shape error. To solve these problems, a grating interferometer with bidirectional Littrow configuration is proposed. Using a high linear density grating of 1800 gr/mm with quadruple optical subdivision is achieved on the optical path. A three-dimensional contour analysis method is proposed to calculate the influence of surface shape error. The experimental result shows that the error of the 10 mm/2 mm displacement test in the X/Z direction fluctuates in the range of ±25 nm, and the actual resolution in the X and Z direction is all 1.5 nm. In summary, the system has good repeatability and high resolution, and can achieve nanoscale displacement measurement in the X/Z direction, and has broad application prospects in the field of precision machining and manufacturing.

Colon length in pediatric health and constipation measured using magnetic resonance imaging and three dimensional skeletonization.

Recent magnetic resonance imaging (MRI) studies showed that colonic volumes in children are different between health and functional constipation. The length of the colon has however been rarely measured and principally using unphysiological colon preparations or cadaver studies. The main objective of this study was to measure the length of the undisturbed colon in children with functional constipation (FC) and healthy controls. Here, the colon of 19 healthy controls (10-18 years old) and 16 children with FC (7-18 years old) was imaged using MRI. Different regions of the colon (ascending, transverse, descending, and sigmoid-rectum) were first segmented manually on the MRI images. Three-dimensional skeletonization image analysis methods were then used to reduce the regions of interest to a central, measurable line. Total colon length (corrected for body surface area) in healthy controls was 56±2 cm/m2 (mean±SEM). Total colon length was significantly longer in children with FC 69±3 cm/m2 compared to controls (p = 0.0037). The colon regions showing the largest differences between groups were the ascending colon (p = 0.0479) and the sigmoid-rectum (p = 0.0003). In a linear regression model, there was a positive significant correlation between total colon length and age (R = 0.45, p = 0.0064), height (R = 0.49, p = 0.0031), weight (R = 0.46, p = 0.0059) and colon volume (R = 0.4543, p = 0.0061). Our findings showed significant differences in colon lengths between healthy controls and children with constipation. A new objective diagnostic imaging endpoint such as colon length may help to improve knowledge of colon morphology and function and, in turn, understanding of colon functional pathology.

Correlation between microstructure and Young’s modulus of porous ceramics using three-dimensional mesoscale analysis and FIB-SEM reconstruction method

Correlation between microstructure and Young’s modulus of porous ceramics using three-dimensional mesoscale analysis and FIB-SEM reconstruction method

Evaluating Street Character Using the 3D Fractal Analysis Method: Lefkoşa

The aim of this article is to reveal the mathematical dimension behind the complex structure of architectural fabric through a three-dimensional analysis. Given that the architectural character, which has evolved under the influence of various cultures over time, is crucial for urban integrity and sustainability, understanding the mathematical dimension underlying this character is of great importance for new designs and interventions in existing urban fabric. Therefore, streets in the Arabahmet neighbourhood of Lefkoşa Suriçi, which best represents the traditional fabric, were examined using a three-dimensional fractal analysis method. The analyses indicate that, in general, the fractal dimension values of the residential fabric-created streets are above 2.52, demonstrating a high level of character and complexity in these streets. Additionally, the fractal dimension values of these streets are close to each other, supporting the spatial and mass consistency of different streets within the same neighbourhood.

Retracted: Three-Dimensional Image Analysis and Training Method of Action Characteristics of Sanda Whip Leg Technique Based on Wavelet Transform

Retracted: Three-Dimensional Image Analysis and Training Method of Action Characteristics of Sanda Whip Leg Technique Based on Wavelet Transform

Cylinder Liner Velocity Calculation under Dynamic Condition in the Pursuit of Liner Cavitation Investigation of an Internal Combustion Engine

<div>An analytical method for nonlinear three-dimensional (3D) multi-body flexible dynamic time-domain analysis for a single-cylinder internal combustion (IC) engine consisting of piston, connecting rod, crank pin, and liner is developed. This piston is modeled as a 3D piston that collides with the liner as in a real engine. The goal is to investigate the piston slap force and subsequent liner vibration. Liner vibrational velocity is directly responsible for pressure fluctuations in the coolant region resulting in bubble formation and subsequent collapse. If the bubble collapse is closer to the liner surface, cavitation erosion in the liner might occur. The mechanism of liner cavitation is briefly explained, which would take a full computational fluid dynamics (CFD) model to develop, which is out of scope for the present work. However, as a first step, the present method focused on a comprehensive and accurate estimation of the highest inward and outward liner velocities, which are directly related to the bubble formation and collapse, respectively. Sensitivity of liner velocity to different engine-operating conditions (warm and hot, with highest skirt temperatures of 178 and 130°C), piston pin bore offsets (thrust side, anti-thrust side directions in the amounts of 0.6 mm, and the nominal no offset case), and liner thicknesses are determined. Piston thermal growth is considered as part of the analysis resulting in interference condition between piston skirt and liner under the hot operating condition and low minimum clearance under the warm condition. Correlation of liner velocity contour plots with real engine liner cavitation erosion is presented. Analytical model showed a maximum liner inward velocity of 55 mm/s with no piston pin offset under nominal engine-operating configuration. A correlation has been found between location of this highest liner velocity and location of the actual cavitation erosion in the field.</div>

Three-dimensional nonlinear flutter analysis of long-span bridges by multimode and full-mode approaches

Based on amplitude-dependent flutter derivatives (FDs), the present study established three-dimensional (3D) nonlinear flutter analysis methods, including a multimode and a full-mode approach, for long-span bridges. Then, by adopting the proposed methods, the influences of 3D effects, self-excited drag force, and multimode aerodynamic coupling effects on nonlinear flutter response were investigated. Besides, critical structural modes that have a great impact on nonlinear flutter were identified, their contributions were quantified and roles were clarified. The results show that the 3D effects of structural modes can reduce the system stability mainly by increasing the negative uncoupled aerodynamic damping. Thus, if the 3D effects are ignored, the stable amplitude of nonlinear flutter will be underestimated. For long-span bridges whose foundational symmetric torsional mode couples a minor lateral-bending mode shape, the added aerodynamic damping from self-excited drag force, especially the term of FD P1∗∗1, can improve the stability of the system. Thus, it will overestimate the nonlinear flutter response if the self-excited drag force is ignored. Meanwhile, the aerodynamic coupling effect among different structural modes should be considered, otherwise the nonlinear flutter responses of long-span bridges may be misestimated significantly. For the nonlinear flutter dominated by the fundamental symmetric torsional modal branch, the symmetric vertical bending modes with a frequency lower than the fundamental symmetric torsional mode should be considered. Besides, the other higher-order structural mode coupled with relatively significant fundamental symmetric torsional mode shape is also worth being taken into account. The selection of structural modes is an important and experience-based work in the multimode method. Thus, the full-mode method, which can consider the potential higher-order structural modes that may have contributions to the 3D nonlinear flutter, is also needed, especially when the amplitude is large enough. Otherwise, the nonlinear flutter response may be underestimated by the multimode method.

The limestone spheroids of 'Ubeidiya: intentional imposition of symmetric geometry by early hominins?

Spheroids are one of the least understood lithic items yet are one of the most enduring, spanning from the Oldowan to the Middle Palaeolithic. Why and how they were made remains highly debated. We seek to address whether spheroids represent unintentional by-products of percussive tasks or if they were intentionally knapped tools with specific manufacturing goals. We apply novel three-dimensional analysis methods, including spherical harmonics and surface curvature, to 150 limestone spheroids from 'Ubeidiya (ca 1.4 Ma), presently the earliest Acheulean occurrence outside of Africa, to bring a new perspective to these enigmatic artefacts. We reconstruct the spheroid reduction sequence based on trends in their scar facets and geometry, finding that the spheroid makers at 'Ubeidiya followed a premeditated reduction strategy. During their manufacture, the spheroids do not become smoother, but they become markedly more spherical. They approach an ideal sphere, a feat that likely required skilful knapping and a preconceived goal. Acheulean bifaces are currently thought to represent the earliest evidence of hominins imposing a premeditated, symmetrical shape on stone. The intentional production of sphere-like objects at 'Ubeidiya similarly shows evidence of Acheulean hominins desiring and achieving intentional geometry and symmetry in stone.

Three-dimensional singular spectrum analysis for precise land cover classification from UAV-borne hyperspectral benchmark datasets

The precise classification of land covers with hyperspectral imagery (HSI) is a major research-focused topic in remote sensing, especially using unmanned aerial vehicle (UAV) systems as the abundant data sources have brought severe intra-class spectral variability and high spatial heterogeneity challenges, making precise classification difficult. To this end, a novel three-dimensional singular spectrum analysis (3DSSA) method is proposed for the 3D feature extraction of HSI. It aims to construct a low-rank trajectory tensor containing global and local features and extract both spectral discrimination features and spatial contextual features in conjunction with tensor singular value decomposition (t-SVD). To reduce the risk of tensor operations exceeding memory on large-scale HSI data, the extended regional clustering (RC) 3DSSA framework (RC-3DSSA) is proposed for precise HSI classification. RC-3DSSA uses RC processing to alleviate the scale diversity and further applies 3DSSA to tackle issues of intra-class spectral variability and spatial heterogeneity. In order to effectively evaluate the performance of RC-3DSSA, a new challenging classification dataset namely the Qingdao UAV-borne HSI (QUH) dataset was further built. It consists of three sub-datasets: QUH-Tangdaowan, QUH-Qingyun, and QUH-Pingan, which are freely available as benchmarks for precise land cover classification. The experimental results on QUH and two publicly available datasets show that the RC-3DSSA can accurately distinguish ground objects and reliably map their distribution when benchmarked with ten state-of-the-art methods. Specifically, the overall accuracies achieved are 86.62%, 87.51%, and 87.35% under 10% spatially disjoint training samples for the three UAV-borne HSI datasets, respectively, providing the best performance.

A General Framework for the Impact of Shield Tunnel Construction on Existing Tunnel in Soil

During the excavation process of shield tunneling, it is inevitable that the surrounding soil mass is disturbed, which will affect the adjacent structures. This paper proposes a general framework for the impact of shield tunneling construction on existing tunnels. First, the impact partition of shield tunneling construction regarding adjacent tunnels and buildings is established by a three-dimensional numerical analysis method. Then, the displacement of adjacent tunnels and buildings is predicted using fuzzy gray theory. Finally, based on the results of a numerical simulation and experiment, the risk classification standard of adjacent buildings is established. This framework has certain reference significance and value for the deformation prediction and safety evaluation of adjacent buildings.

Finite element analysis of endodontically treated premolars without ferrule restored with one-piece glass fiber post and core in combination with different inner shoulder retention form systems

ObjectiveThe current study was performed to explore the impact of post materials as well as the inner shoulder retention form (ISRF) design on the biomechanical behavior of endodontically treated premolars without ferrule restoration using a method of mathematical three-dimensional (3D) finite element analysis (FEA). MethodsBased on the tooth anatomy and our previous research, eight mandibular second premolar FEA models representing different restorative situations were built: teeth with (a) 2.0 mm height ferrule (DF), (b) no ferrule (NF), (c) 0.5 mm width and 0.5 mm depth ISRF (ISRFW0.5D0.5), (d) 0.5 mm width and 1.0 mm depth ISRF (ISRFW0.5D1.0), (e) 0.5 mm width and 1.5 mm depth ISRF (ISRFW0.5D1.5), (f) 1.0 mm width and 0.5 mm depth ISRF (ISRFW1.0D0.5), (g) 1.0 mm width and 1.0 mm depth ISRF (ISRFW1.0D1.0), (h) 1.0 mm width and 1.5 mm depth ISRF (ISRFW1.0D1.5). All groups were restored with prefabricated glass fiber post and resin composite core (PGF), one-piece glass fiber post-and-core (OGF) and cast Co-Cr alloy (Co-Cr) respectively, and the zirconia crown was restored. Load (180N) was subjected to the buccal cusp at 45° to the tooth's long axis. Stress pattern, maximum principal stress values (MPS), and maximum displacement values on root, post and core, cement layer were calculated for each model. ResultsStress distributions were similar while the values were different among groups. Regardless of restorative approaches, roots restored with PGF showed the highest MPS values, followed by OGF and Co-Cr groups. Regardless of post materials, NF groups resulted in the highest MPS values and maximum displacement values, while ISRF and DF groups exhibited similar results. Compared with PGF groups in association with ISRF, except for OGF with ISRFW0.5D0.5, the remaining OGF groups with ISRF and all Co-Cr groups in association with ISRF presented lower values than that of DF groups. And among different ISRF systems, roots restored with ISRFW1.0D1.0 presented the lowest stress (PGF: 32.96 MPa, OGF: 31.69 MPa, Co-Cr: 29.66 MPa). ConclusionsFor endodontically treated premolars without ferrule, restored with OGF in combination with ISRF preparation could effectively enhanced its load-bearing capacity. Furthermore, the ISRF with a depth and width of 1.0 mm is recommended.