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The curing distortion is a critical determinant of the quality of integrally manufactured composite structures, playing a pivotal role in the design and fabrication of composite. This paper presents two simplified methods in predicting the curing distortion for large-scale composite aircraft structures manufactured through the autoclave process. Firstly, the refined finite element models of the two simplified methods were developed. Then, it was utilized to predict the curing distortion of Ω-shaped composite laminates. The comparative study between the experimental data and numerical results shows that the proposed second simplified method balanced the prediction accuracy and efficiency, which is urgently needed in practice. Finally, using the second simplified method, predictions were conducted for the curing distortion of practical large-scale composite skin structures. The results were in good agreement with the corresponding experiments. This study provides a new solution for the rapid iterative design of large-scale composite structures, as well as the efficient design of frame molds for their manufacturing. [ABSTRACT FROM AUTHOR]

This study is based on a theory for analyzing non-uniform torsion in thin-walled beams made of homogeneous elastic material with arbitrary cross-sections by incorporating the effect of the shear deformation of a cross-section. Utilizing the Finite Element Method (FEM), the proposed numerical approach addresses non-uniform torsion by breaking down a 3D analysis into 2D cross-sectional and 1D modeling components. Initially, the geometric constants of the cross-section were computed using a 9-node isoparametric element in 2D FEM. Subsequently, a 1D FEM employing a linear isoparametric element calculated the twist angle, torsion warping parameters, and stress results. The stress field was determined through a local analysis of the 2D cross-section. Notably, the 2D FEM component aligns with contemporary trends in commercial software, thereby bolstering the potential and practical applicability of the proposed numerical approach. Its verification and validation through numerical analyses using MATLAB underscore the efficacy and reliability of the method in analyzing non-uniform torsion behavior in structural design, particularly under diverse boundary conditions.

Conventional beam elements ignoring distortion may overestimate the lateral resistance of frames and curved beams made of monosymmetric I-sections. This paper introduces two new distortional modes represented by mechanical couples relative to twisting and shearing of the two flanges that are opposite in directions but unequal in magnitudes. A straight beam element with nine degrees of freedom (DOFs) per node, including the conventional three translations, three rotations, warping and the new two distortions, is newly derived. This allows all the DOFs of the connected elements at a common joint to be easily transformed to the global coordinates for stiffness assembly. As a result, the warping–distortion compatibility problem that occurs in frames and curved beams is resolved. In the numerical examples, the results produced by the present beam element is demonstrated to agree excellently with the shell-element solutions for the lateral-distortional deformation of the angled frame and curved beam. It is observed that the cross-sectional distortion effect becomes extremely significant for angled frames of short unbraced length and for curved beams of high curvature. [ABSTRACT FROM AUTHOR]

Background: The use of 3D-printing in medicine requires a context-specific quality assurance program to ensure patient safety. The process of medical 3D-printing involves several steps, each of which might be prone to its own set of errors. The segmentation error (SegE), the digital editing error (DEE) and the printing error (PrE) are the most important partial errors. Approaches to evaluate these have not yet been implemented in a joint concept. Consequently, information on the stability of the overall process is often lacking and possible process optimizations are difficult to implement. In this study, SegE, DEE, and PrE are evaluated individually, and error propagation is used to examine the cumulative effect of the partial errors. Methods: The partial errors were analyzed employing surface deviation analyses. The effects of slice thickness, kernel, threshold, software and printers were investigated. The total error was calculated as the sum of SegE, DEE and PrE. Results: The higher the threshold value was chosen, the smaller were the segmentation results. The deviation values varied more when the CT slices were thicker and when the threshold was more distant from a value of around -400 HU. Bone kernel-based segmentations were prone to artifact formation. The relative reduction in STL file size [as a proy for model complexity] was greater for higher levels of smoothing and thinner slice thickness of the DICOM datasets. The slice thickness had a minor effect on the surface deviation caused by smoothing, but it was affected by the level of smoothing. The PrE was mainly influenced by the adhesion of the printed part to the build plate. Based on the experiments, the total error was calculated for an optimal and a worst-case parameter configuration. Deviations of 0.0093 mm ± 0.2265 mm and 0.3494 mm ± 0.8001 mm were calculated for the total error. Conclusions: Various parameters affecting geometric deviations in medical 3D-printing were analyzed. Especially, soft reconstruction kernels seem to be advantageous for segmentation. The concept of error propagation can contribute to a better understanding of the process specific errors and enable future analytical approaches to calculate the total error based on process parameters. [ABSTRACT FROM AUTHOR]

Thin-walled channel beams such as cold-formed steel purlins are primarily used to withstand wind forces in the roofing and walling systems of buildings. Traditionally, these types of members are usually designed for bending moments, with the effects of torsion ignored. However, the loading on thin-walled channels can be much more complicated than simple bending actions. Because of the position of the shear centre outside the section, channels can undergo bending and torsion when subjected to vertical load on the top flange. The applied torsion may cause significant stresses in the channel, which may need to be accounted for in design. There appears to be no research on quantifying the effects of torsion on thin-walled channels subjected to a uniformly distributed load acting on the top flange. In this paper, a theoretical solution is derived for calculating the longitudinal stresses in thin-walled channels subjected to torsion caused by a uniformly distributed load acting on the top flange. The theory is validated by modelling the channels in a finite-element analysis. The theoretical results include calculations of the twist rotation, bimoment, sectorial coordinate and longitudinal stresses, while the results from the finite-element analysis include the twist rotation and longitudinal stresses. The results show that the longitudinal stresses caused by torsion can significantly exceed those caused by the bending moment. Practical advice is also given for engineers on how to minimize torsion in cold-formed steel purlins. [ABSTRACT FROM AUTHOR]

Together with axial and flexural actions, modern-designed reinforced-concrete walls can also be subjected to torsion during rare loading events, such as large-magnitude earthquakes or strong winds. For certain widely used nonplanar open cross-section geometries, this torque is resisted primarily through warping. In some cases, the longitudinal stresses caused by torsional warping can be of the same order of magnitude as those caused by flexure, which postulates a reduction of the in-plane bending moment capacity of the section. This study explores the reduction of bending moment capacity of open reinforced-concrete U-shaped core walls due to the simultaneous application of flexural, axial, and torsional loading. Initial investigations focused on strain gradients through the wall segments of reinforced-concrete U-shaped walls. Using a refined data set from a recent experimental campaign, the commonly assumed linear strain gradient used in the design of reinforced-concrete walls is challenged. Numerical methods that intrinsically rely on the observed strain gradients are then employed to compute, for a range of torque-to-bending-moment ratios, the ultimate bending moment and torque capacities from combined loading scenarios. The numerical results corroborate existing experimental results, indicating a significant reduction (almost half) in ultimate bending moment capacity when a torque equal to approximately 20% of imposed bending is applied. Interaction diagrams between the ultimate torque and bending moment show that it is possible to derive a simple relationship between the two for the purposes of structural design. These results can help formulate guidelines for future international building codes, which in their current form cannot account for the design of open sections governed by warping torsion. [ABSTRACT FROM AUTHOR]

The clonal materials of Tectona grandis L. f. in fast-growing plantations exhibit faster growth than the seminal materials. Therefore, it is necessary to investigate the differences in wood drying to ensure the quality and yield of the final product. This study evaluated the outdoor drying behavior of three genotypes of teak lumber. Two clonal genotypes (G1 and G2) and one of seminal origin (G3) were assessed. Boards measuring 30 × 150 × 1000 mm (thickness × width × length) were produced from the basal logs. The average moisture content (79.3, 64.9, and 60,1%), final moisture content (10.8, 9.8, and 11.6%), and mean drying rate (1.2, 0.97, and 0.85%.day-1) were observed in the wood from genotypes G1, G2 and G3, respectively. The clonal material crooked and bowed below 5 mm.m-1, which is considered the tolerance limit for both warpings. The seminal material had a greater incidence of splitting. The clonal genotypes G1 and G2 had similar qualities and presented higher drying rates, final moisture contents below 11% and a lower incidence of defects, especially splitting, compared to the naturally seeded material.

One of the main objectives of weaving production is the production of high quality fabrics and the search for ways to increase the productivity of weaving machines in order to improve the economic performance and competitiveness of the enterprise. In the production conditions of RUPTE "Orsha Linenmill" weaving machines Picanol OptiMax 190 are installed for the production of a range of household fabrics from low linear density yarn, most of which are exported. To ensure the quality of pure linen fine fabrics and the production of fine yarn, long flax fibre No. 11–14 and above is required. However, due to a number of reasons, the quality and quantity of incoming domestic raw materials cannot guarantee stable technological efficiency of production preparation and weaving processes, which is provided by the uniformity of flax and flax-containing yarn and its tensile properties. The aim of the research is to reduce warp breakage in weaving by determining rational production parameters on the loom and the choice of the sizing agent in order to increase the productivity of the loom in the production of linen fabrics with low surface density. In the article the properties of wet spinning yarn of 30 tex linear density made of long linen fibre are studied, the features of Karl Mayer SMR-SP-10-1800/800 SMR-SP-10-1800/800 sizing machine and Picanol OptiMax 190 rapier weaving machine are studied, the selection of modern sizing agent was made in order to increase machine productivity and reduce warp breakage during weaving of the most elite and marketable article – linen fabric with surface density of 120 g/m2. The changes in the technology made it possible to reduce the equipment downtime by reducing the number of warp breaks from 0.95 to 0.76 breaks per 1 running meter of fabric, to increase the coefficient of utilisation and to increase the annual volume of fabrics produced.

Within the framework of linear elasticity, we show that any displacement of a straight rod is the sum of a Bernoulli–Navier displacement and two terms, one for shearing and the other for warping. Then, we load a straight rod so that bending and shear contribute the same to the rotations of the cross-section. [ABSTRACT FROM AUTHOR]

Warping not only one of the most important phenomena in steel section it is also considered as the most complicated phenomena. Ductility, bearing capacity and serviceability of steel sections may affect by increasing stress concentration of the normal stresses due to warping. In the present work, simulation of steel beam section under effect of warping is studied. Two cantilevers connected to two columns in opposite sides with a middle steel beam-column connection to create different moments on the beam to investigate the behavior of steel section under warping using building information modeling. It is found that the stress strain relationship has four groups depending on the load intensity and the angle of rotation induced due to warping. [ABSTRACT FROM AUTHOR]

The clonal materials of Tectona grandis L. f. in fast-growing plantations exhibit faster growth than the seminal materials. Therefore, it is necessary to investigate the differences in wood drying to ensure the quality and yield of the final product. This study evaluated the outdoor drying behavior of three genotypes of teak lumber. Two clonal genotypes (G1 and G2) and one of seminal origin (G3) were assessed. Boards measuring 30 × 150 × 1000 mm (thickness × width × length) were produced from the basal logs. The average moisture content (79.3, 64.9, and 60,1%), final moisture content (10.8, 9.8, and 11.6%), and mean drying rate (1.2, 0.97, and 0.85%.day-1) were observed in the wood from genotypes G1, G2 and G3, respectively. The clonal material crooked and bowed below 5 mm.m-1, which is considered the tolerance limit for both warpings. The seminal material had a greater incidence of splitting. The clonal genotypes G1 and G2 had similar qualities and presented higher drying rates, final moisture contents below 11% and a lower incidence of defects, especially splitting, compared to the naturally seeded material. [ABSTRACT FROM AUTHOR]

A problem of restrained torsion of thin-walled beams under the action of an end torque is considered. The asymptotic splitting method is applied to obtain a system of resolving equations that describes combined torsion, tension-compression, and bending of the beam. The example of typical cross sections is used to compare the resulting model with a stress-strain state in the beam, determined in the calculation using the developed model and three-dimensional numerical calculation by the finite element method. The resulting mathematical model is analyzed and its advantages are revealed and compared to the widely used Vlasov theory. It is shown that the developed model does not contain the restrictions imposed by the Vlasov theory hypotheses, such as the nondeformability of the cross-sectional contour and the absence of shear strains on the middle surface. The resulting model makes it possible in many cases to more accurately determine the emerging stress-strain state. In particular, it is shown that the developed model accounts for the presence of a boundary layer near the clamped end, which arises during torsion of angle sections and makes a significant contribution to longitudinal stresses, while the Vlasov theory does not allow for the recovery of the arising longitudinal stresses. [ABSTRACT FROM AUTHOR]

Dispersion is a representative property of low-frequency sound propagation over long distances in shallow-water waveguides, making dispersion curves valuable for geoacoustic inversion. This study focuses on estimating the geoacoustic parameters using the dispersion curves extracted from airgun sounds received in the East Siberian Sea. The seismic survey was conducted in September 2019 by the icebreaking research vessel R/V Araon, operated by the Korea Polar Research Institute. A single hydrophone was moored at the East Siberian Shelf, characterized by nearly range-independent shallow water (<70 m) with a hard bottom. In the spectrogram of the received sounds, the dispersion curves of the first two modes were clearly observed. Utilizing a combination of warping transform and wavelet synchrosqueezing transform these two modes were separated. Then, the geoacoustic parameters, such as sound speed and density in the sediment layer, were estimated by comparing the two modal curves extracted at a source-receiver distance of approximately 18.6 km with the predictions obtained by the KRAKEN normal-mode propagation model. Subsequently, the distances between the airgun and the receiver system in the 18.6 to 121.5 km range were estimated through the comparison between the measured modal curves and the model replicas predicted using the estimated geoacoustic parameters. [ABSTRACT FROM AUTHOR]

How can scalable vector graphics (SVG) data of human faces be transformed to resemble specific animal faces? Since the early $20^{th}$ century, multimedia featuring animals has garnered significant attention, particularly as interest in anthropomorphic animals has grown. In this paper, we survey various anthropomorphic studies. Additionally, we develop a warping system for anthropomorphizing animal characters. Our system enables the automatic generation of anthropomorphized animal characters using SVG datasets. This dataset includes frontal and side views of 60 animal species commonly featured in animations, as well as male and female human characters. Users can create new anthropomorphized animal characters using our dataset and their vector data. Our warping system implements a continuous warping technique between animal and human facial shapes in ten stages, supported by a developed algorithm and an SVG warping program. The code of the warping system and SVG dataset are available at link: https://github.com/jenero05458/SVG_warping

Recent deep learning techniques have enabled simple methods of image editing through textual instructions; however, it remains challenging to perform specific and quantitative editing. In contrast, intuitive image editing methods that use displacement vectors often require the preservation of the original appearance after editing. This study proposes a new method for precisely editing expressions and orientations in facial images. Existing methods that rely on displacement vectors are unable to independently edit facial expressions and orientations. Our method offers separate editing capabilities by introducing multiple displacement vectors with two roles, which are used for transferring three-dimensional (3D) keypoints. These keypoints are then used in image warping to achieve stable deformations. The process involves extracting the movements of 3D keypoints with the images sampled from movies, which are then used to train a deep neural network for expression edits. In addition, the 3D rotation matrix for the keypoints is calculated to handle the change of face orientation. The edited keypoints are passed through a thin-plate spline motion model to warp an input facial image used as an identity. Our method outperforms existing facial image editing and warping methods in preserving face identity by 3.7% in terms of the structural similarity, as demonstrated by quantitative comparisons, and produces more natural results qualitatively.

When designing steel members with nonsymmetric cross sections, it is essential to consider twisting effects when performing stability checks via second-order analysis according to the ANSI/AISC 360-22. Existing line-element formulations for nonsymmetric sections are mostly derived based on thin-walled assumptions, leading to an overestimation of member strength due to the inaccurate prediction of member behavior, especially when the cross sections have moderate wall thickness. This paper proposes an efficient line-element method for second-order analysis of steel members with nonsymmetric thick-walled sections considering the warping degree of freedom (DOF) and the twisting effects along with the transverse shear deformations. Additionally, a two-dimensional (2D) finite-element cross section analysis method employing the constant strain triangle (CST) element is developed to calculate the section properties for arbitrary cross sections, including the Wagner and the shear coefficients. The proposed method is implemented in the educational structural analysis software MASTAN2 and verified through two sets of examples. [ABSTRACT FROM AUTHOR]

To be able to produce ceramic bodies with complex shapes without interlayer delamination and warping through vat photopolymerization‐based 3D printing techniques, photosensitive ceramic slurries should be studied to prepare 3D printed green and sintered bodies. In this study, we developed dual curable acrylate–epoxide ceramic slurries for digital light processing (DLP) 3D ceramic printing. The dual curing process of the slurries is a combination of photo‐radical polymerization of acrylate and thermal cationic polymerization of cyclo‐aliphatic epoxide. The green bodies prepared by dual curing of the slurries showed higher fracture strength and better adhesion between layers and between starting particles and binder polymer in comparison to acrylate‐based green body. These advantages were due to higher crosslinking density of the binder matrix and hydrogen bonding by hydroxyl groups from epoxide ring opening. The green and sintered bodies printed with improved slurry and DLP 3D printer had flat shape without warping unlike those from acrylate‐based bodies. Moreover, the distribution of inter‐particle necking in the sintered body was uniform and the interface boundary between layers was not observed. This is because of excellent uniformity of the dual cured acrylate–epoxide polymer matrix (uniform crosslinking density in layers) in the green body and hydroxyl groups generated by epoxy ring opening. [ABSTRACT FROM AUTHOR]

The warping may become an important factor for the precise transverse vibrations of curved beams. Thus, the first aim of this study is to specify the structural design parameters where the influence of cross-sectional warping becomes great and the first-order shear deformation theory lacks the precision necessary. The out-of-plane vibrations of the first-order shear deformation theory are compared with the warping-included vibrations as the curvature and/or thickness increase for symmetric and asymmetric transversely-functionally graded (TFG) curved beams. The second aim is to determine the influence of design parameters on the vibrations. The circular/exact elliptical beams are formed via curved mixed finite elements (MFEs) based on the exact curvature and length. The stress-free conditions are satisfied on three-dimensional (3D) constitutive equations. The variation of functionally graded (FG) material constituents is considered based on the power-law dependence. The cross-sectional warping deformations are defined over a displacement-type FE formulation. The warping-included MFEs (W-MFEs) provide satisfactory 3D structural characteristics with smaller degrees of freedom (DOFs) compared with the brick FEs. The Newmark method is used for the forced vibrations. [ABSTRACT FROM AUTHOR]

The yield of Eucalyptus regnans logs for lumber production was evaluated. Crack width and length at each log end were measured. Two log-cutting plans were used to obtain sawn lumber. The first plan (PA) considered logs with diameters varying from 28 to 40 cm, and in the second plan (PB), the log diameters ranged from 42 to 56 cm (PB). Lumber yield was determined using two log volume methods: the Japanese Agricultural Standards (JAS) and Smalian's equation. The deformations of E. regnans lumber were measured. The Australian and Chilean standards were used to classify sawn lumber. The results showed that logs had radial cracks at both log ends. Cracks were classified into two groups, considering the crack length. Regarding the lumber deformations, most boards exhibited level B bows and crooks in both cutting plans. Levels A and B twists were prevalent in PA, whereas in PB, level A significantly outnumbered level B. The lumber yield of E. regnans in PB was higher than in PA. The lumber yield determined by Smalian's equation was higher than that determined by the JAS method. This research provides insight into the characterization of E. regnans for lumber production, highlighting its relevance in the forestry industry. [ABSTRACT FROM AUTHOR]

Recent approaches for fast semantic video segmentation have reduced redundancy by warping feature maps across adjacent frames, greatly speeding up the inference phase. However, the accuracy drops seriously owing to the errors incurred by warping. In this paper, we propose a novel framework and design a simple and effective correction stage after warping. Specifically, we build a non-key-frame CNN, fusing warped context features with current spatial details. Based on the feature fusion, our context feature rectification (CFR) module learns the model's difference from a per-frame model to correct the warped features. Furthermore, our residual-guided attention (RGA) module utilizes the residual maps in the compressed domain to help CRF focus on error-prone regions. Results on Cityscapes show that the accuracy significantly increases from 67.3 % to 71.6 % , and the speed edges down from 65.5 FPS to 61.8 FPS at a resolution of 1024 × 2048 . For non-rigid categories, e.g., "human" and "object", the improvements are even higher than 18 percentage points. [ABSTRACT FROM AUTHOR]

This article presents a new beam model that employs a recursive derivation procedure that enables the user to set the order of the governing differential equations as an input parameter, without the need for ad hoc assumptions or methodologies. This article employs a novel system of kinematic variables, section constants, and section functions that facilitate the development of higher-order beam models that retain a clear philosophical link to classical beam models such as Euler–Bernoulli beam theory and Timoshenko beam theory. The present beam model is a type of equivalent single layer beam model, wherein section constants are used to model the global stiffness characteristics of the beam, and section functions are used to recover sectional fields of displacements, strains, and stresses. The present beam model is solved for several example beams, and the results are compared to the results of finite element analyses. It is shown that the present beam model can accurately predict the deformed shapes and stress fields of each of the example beams. This article also reveals an interesting peculiarity of the elastic potential energy that pertains to any unidimensional beam model that is governed by differential equations that are of finite order.

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Laser powder bed fusion (LPBF) includes a few printing techniques widely used, in recent years, concerning the additive manufacturing of Ti6Al4V alloys. These produced parts, typically utilized in sectors such as aerospace and biomedical, are characterized by very high added value. It is therefore fundamental to identify the influence of process parameters typical of LPBF technology on the occurrence of warping leading to process failure. This study deals with the characterization of single-track and "micro-scale" level warping phenomena which may lead to protrusion of material over the powder bed and process failure before normal termination. This phenomenon was investigated as a function of process parameters, referring also to the strength and ductility characteristics of the manufactured samples. With this purpose, several samples were printed using variable process parameters both in terms of line energy density (LED) values and in terms of laser power and speed combinations such as to guarantee constant LED values. For the samples that did not show significant micro-warping phenomena, in addition to the transversal and longitudinal geometric characterization of the single track, tensile tests were performed to determine both the resistance of the material and the ductility characteristics. The single tracks, for given process parameters, were printed on a homogeneous material substrate. For every single track, a microstructural and morphological transverse and longitudinal characterization has been carried out and the measured geometrical features were correlated to the process parameters. The obtained results allowed the identification of a new threshold parameter, indicating the limit operating conditions beyond which significant warping phenomena and process failure occur. [ABSTRACT FROM AUTHOR]

The warping effects may predominate in geometrically nonlinear analysis of open cross-section members. The formulation of conventional beam-column elements incorporating the warping effects is cumbersome due to the method considering the inconsistency between the shear center and centroid. To develop a concise warping element formulation, this paper presents a transformation matrix to integrate the inconsistent effects into the element stiffness matrix. The co-rotational (CR) method used to establish the element equilibrium conditions in the geometrically nonlinear analysis is adopted to simplify the element formulation and improve the efficiency of nonlinear analysis. A new beam-column element explicitly considering the warping deformation and the Wagner effects is derived based on the CR method and the Euler–Bernoulli beam theory. A detailed kinematic description is provided for considering large deflections and rigid body motions. Based on the mechanical characteristic, the coordinate and the rigid body motion transformation matrices are given. The secant relationship is developed to evaluate the element internal forces accurately and effectively in each iteration. Several verification examples are provided to validate the proposed method's reliability and robustness. The verifications demonstrate that the proposed element leads to considerable computational advantages. The results of this paper are useful for future upgrading of frame analysis software with warping degrees-of-freedom (DOFs). [ABSTRACT FROM AUTHOR]

In this paper, a new finite element for 2D non-prismatic (curved and tapered) elastic beams with narrow rectangular cross-section is proposed. The element is geometrically exact, hence capable of handling large displacements and finite rotations, and allows for cross-section arbitrary warping through the inclusion of additional degrees of freedom (DOFs). These additional DOFs make it possible to capture the non-standard shear stress distributions that are developed in tapered members. All expressions required to implement the proposed finite element are derived and written in a simple vector/matrix form. To assess the accuracy and demonstrate the capabilities of the proposed element, several numerical examples are presented. For comparison purposes, results obtained with refined meshes of standard 2D finite elements are also shown. It is concluded that the proposed element leads to very accurate results with a small computational cost. [ABSTRACT FROM AUTHOR]

This article presents a new beam model that employs a recursive derivation procedure that enables the user to set the order of the governing differential equations as an input parameter, without the need for ad hoc assumptions or methodologies. This article employs a novel system of kinematic variables, section constants, and section functions that facilitate the development of higher-order beam models that retain a clear philosophical link to classical beam models such as Euler–Bernoulli beam theory and Timoshenko beam theory. The present beam model is a type of equivalent single layer beam model, wherein section constants are used to model the global stiffness characteristics of the beam, and section functions are used to recover sectional fields of displacements, strains, and stresses. The present beam model is solved for several example beams, and the results are compared to the results of finite element analyses. It is shown that the present beam model can accurately predict the deformed shapes and stress fields of each of the example beams. This article also reveals an interesting peculiarity of the elastic potential energy that pertains to any unidimensional beam model that is governed by differential equations that are of finite order. [ABSTRACT FROM AUTHOR]

Steel thin-walled profiles are the backbone of modern lightweight construction, offering exceptional efficiency in terms of material use and assembly speed. However, their inherent susceptibility to buckling under complex loading conditions, especially bending torsion, has limited their broader application in advanced structural systems. This paper introduces a groundbreaking method for analyzing the bending-torsion behavior of steel thin-walled C-profile beams, specifically focusing on the critical but often overlooked factor of support warping stiffness. Unlike conventional studies that primarily examine local or global buckling resistance, this research pioneers a comprehensive approach that integrates the warping stiffness of supports into the structural analysis. Through the introduction of novel coefficients—warping (0.377–0.484) and bending (0.616–0.672)—this study established a new paradigm in the design and stability analysis of thin-walled beams. Our findings reveal that incorporating support warping stiffness can dramatically increase normal stresses by 2–4 times within the span, a revelation that significantly alters existing design assumptions. The study also demonstrated how sectorial stiffness, a key parameter, directly enhances the warping stiffness of the supports, while the bending stiffness of the beam has negligible impact on the compliance factor. This novel insight provided a substantial leap forward in accurately predicting the complex interaction between bending and torsion in lightweight steel structures. By addressing a critical gap in the literature, this research not only advances the theoretical understanding of thin-walled profiles but also offers practical implications for optimizing the structural design of modern construction systems, enhancing both performance and safety. • A method was developed for determining the bimoment in beams with support warping stiffness. • A method is proposed for determining the actual reference values of the bending moment and bimoment from numerically obtained values of the reference normal stresses. • Range of values of the coefficients are revealed, considering warping and bending finite stiffness of thin-walled profiles, for the case when stud profiles are supported inside track profiles of various thicknesses and high of 150 mm. • With an increase in the sectorial stiffness of the profile, the support warping stiffness increases, while with increase in bending stiffness of the beam, the compliance bending factor of the support changes insignificantly. • Considering the warping stiffness of the support connection leads to an increase in the obtained normal stresses in the span of a thin-walled profile by 2-4 times, depending on the sectorial stiffness of the profile. [ABSTRACT FROM AUTHOR]

Steel beams are susceptible to lateral-torsional buckling (LTB) failure when subjected to bending. Considering the effect of semi-rigid connections, the partial end restraints in torsion and warping can significantly influence the buckling behavior of members. However, these restraints are not properly simulated in the traditional line-finite-element method (LFEM), which may lead to an error in the estimation of member buckling capacity. To fill this gap, this research introduces an improved end-spring model into the formulation of an advanced co-rotational (CR)-LFEM, where the partial restraints in axial, bending, torsion, and warping degree of freedom (DOF) can be considered. A parametric study on the LTB behavior of steel beams is conducted using the modified CR-LFEM, where a series of elastic buckling analyses are conducted. The results show that the stiffness of partial torsion and warping restraints have a significant influence on the LTB capacity. The influence of various cross-section shapes and member slenderness ratios on the LTB behavior is also discussed. Finally, design recommendations are provided for classifying connection stiffness in torsion and warping DOF, offering guidelines for practitioners. In addition, the improved CR-LFEM with end-springs proposed in this study has been implemented into the educational software MSASect2. • Introduced an improved end-spring model into an advanced co-rotational line-finite-element method. • The partial restraints in axial, bending, torsion, and warping degrees of freedom can be directly considered. • Performed parametric studies for the lateral-torsional buckling (LTB) of steel members with partial restraints. • Investigated the influence of member geometry and connection stiffness on the LTB capacity of beams. • Proposed recommendations for classifying connection stiffness in torsion and warping. [ABSTRACT FROM AUTHOR]

The out-of-plane buckling behavior of arches is closely related to the element torsional behavior. The traditional 12-degree-of-freedom second-order element stiffness matrix which uses a simplified element torsional stiffness GJ/ L (where G is the shear modulus, J the St. Venant torsion constant, L the element length) may significantly underestimate the out-of-plane buckling loads of funicular arches. This paper presents a simple and effective exact matrix stiffness method (MSM) for the out-of-plane buckling analysis of funicular arches. The developed MSM uses a 14-degree-of-freedom second-order element stiffness matrix of three-dimensional beam-columns considering both torsion and warping deformations. The out-of-plane buckling analysis of funicular arches is performed by using the global structural stability stiffness matrix, which combines the transformed second-order element stiffness matrices. The proposed MSM with the exact 14-degree-of-freedom second-order element stiffness matrix for the out-of-plane buckling analysis is verified by comparing with some classical solutions of funicular circular and parabolic arches with box sections and I-sections. Further discussions show that the 14-degree-of-freedom second-order element stiffness matrix may be reduced to a simplified 12-degree-of-freedom form only by deriving the exact element torsional stiffnesses, which could be significantly larger than GJ/ L for members with large cross-sectional torsional stiffness parameters (especially open cross-sections). [ABSTRACT FROM AUTHOR]

Virtual view synthesis, which generates novel views similar to the characteristics of actually acquired images, is an essential technical component for delivering an immersive video with realistic binocular disparity and smooth motion parallax. This is typically achieved in sequence by warping the given images to the designated viewing position, blending warped images, and filling the remaining holes. When considering 6DoF use cases with huge motion, the warping method in patch unit is more preferable than other conventional methods running in pixel unit. Regarding the prior case, the quality of synthesized image is highly relevant to the means of blending. Based on such aspect, we proposed a novel blending architecture that exploits the similarity of the directions of rays and the distribution of depth values. By further employing the proposed method, results showed that more enhanced view was synthesized compared with the well-designed synthesizers used within moving picture expert group (MPEG-I). Moreover, we explained the GPU-based implementation synthesizing and rendering views in the level of real time by considering the applicability for immersive video service.

This paper describes the computational aspects of the beam Finite Element formulation recently developed by the authors to simulate the nonlinear response of structural members subjected to shear and torsion, accounting for cross-section warping. The paper focuses on an efficient consistent solution algorithm that by-passes the iterative procedure required in force-based and mixed Finite Elements and makes the model easy to be implemented in a standard code. Moreover, it proposes a new non-iterative technique to condense out the stress components derived by the three-dimensional constitutive response and not directly included in the fiber section formulation. The efficiency and accuracy of the proposed numerical model are validated by simulating the response of steel and reinforced concrete structural members.

Recent approaches for fast semantic video segmentation have reduced redundancy by warping feature maps across adjacent frames, greatly speeding up the inference phase. However, the accuracy drops seriously owing to the errors incurred by warping. In this paper, we propose a novel framework and design a simple and effective correction stage after warping. Specifically, we build a non-key-frame CNN, fusing warped context features with current spatial details. Based on the feature fusion, our context feature rectification (CFR) module learns the model’s difference from a per-frame model to correct the warped features. Furthermore, our residual-guided attention (RGA) module utilizes the residual maps in the compressed domain to help CRF focus on error-prone regions. Results on Cityscapes show that the accuracy significantly increases from 67.3% to 71.6%, and the speed edges down from 65.5 FPS to 61.8 FPS at a resolution of 1024×2048. For non-rigid categories, e.g., “human” and “object”, the improvements are even higher than 18 percentage points.

Multivariate spatial-statistical models are often used when modeling environmental and socio-demographic processes. The most commonly used models for multivariate spatial covariances assume both stationarity and symmetry for the cross-covariances, but these assumptions are rarely tenable in practice. In this article, we introduce a new and highly exible class of nonstationary and asymmetric multivariate spatial covariance models that are constructed by modeling the simpler and more familiar stationary and symmetric multivariate covariances on a warped domain. Inspired by recent developments in the univariate case, we propose modeling the warping function as a composition of a number of simple injective warping functions in a deep-learning framework. Importantly, covariance-model validity is guaranteed by construction. We establish the types of warpings that allow for cross-covariance symmetry and asymmetry, and we use likelihood-based methods for inference that are computationally efficient. The utility of this new class of models is shown through two data illustrations: a simulation study on nonstationary data, and an application to ocean temperatures at two different depths. [ABSTRACT FROM AUTHOR]

The straight-beam approach is a simple and efficient means for analyzing the buckling of curved beams. Although previous researchers showed that the straight-beam approach is capable of simulating the lateral buckling of solid curved beams, the warping effect had been neglected and thus its practical application in engineering was limited. In this study, thin-walled curved I-beams will be dealt with by assuming the warping degrees of freedom (DOFs) to be identical at the common node for non-aligned connected elements. One feature of the present formulation is that the moments induced by initial nodal moments undergoing out-of-plane rotations are duly considered in the geometric stiffness matrix, while the compatibility and equilibrium are enforced for angled joints at the deformed position. With high computational efficiency, the present approach obtains buckling loads that agree well with the theoretical curved-beam solutions or the ones obtained by ABAQUS using shell elements. Compared with the modern curved-beam elements, the straight-beam element is locking free, invariant and simple in formulation, since the effect of curvature is not involved in global assembly. [ABSTRACT FROM AUTHOR]

Abstract Image and video processing based on geometric principles typically changes the rectangular shape of video frames to an irregular shape. This paper presents a warping based approach for rectangling such irregular frame boundaries in space and time, i.e., making them rectangular again. To reduce geometric distortion in the rectangling process, we employ content-preserving deformation of a mesh grid with line structures as constraints to warp the frames. To conform to the original inter-frame motion, we keep feature trajectory distribution as constraints during motion compensation to ensure stability after warping the frames. Such spatially and temporally optimized warps enable the output of regular rectangular boundaries for the video frames with low geometric distortion and jitter. Our experiments demonstrate that our approach can generate plausible video rectangling results in a variety of applications.

Because of the significance of electron microscope tomography in the investigation of biological structure at nanometer scales, ongoing improvement efforts have been continuous over recent years. This is particularly true in the case of software developments. Nevertheless, verification of improvements delivered by new algorithms and software remains difficult. Current analysis tools do not provide adaptable and consistent methods for quality assessment. This is particularly true with images of biological samples, due to image complexity, variability, low contrast and noise. We report an electron tomography (ET) simulator with accurate ray optics modeling of image formation that includes curvilinear trajectories through the sample, warping of the sample and noise. As a demonstration of the utility of our approach, we have concentrated on providing verification of the class of reconstruction methods applicable to wide field images of stained plastic-embedded samples. Accordingly, we have also constructed digital phantoms derived from serial block face scanning electron microscope images. These phantoms are also easily modified to include alignment features to test alignment algorithms. The combination of more realistic phantoms with more faithful simulations facilitates objective comparison of acquisition parameters, alignment and reconstruction algorithms and their range of applicability. With proper phantoms, this approach can also be modified to include more complex optical models, including distance-dependent blurring and phase contrast functions, such as may occur in cryotomography.

Integrating physiology with structural insights of the same neuronal circuit provides a unique approach to understanding how the mammalian brain computes information. However, combining the techniques that provide both streams of data represents an experimental challenge. When studying glomerular column circuits in the mouse olfactory bulb, this approach involves e.g., recording the neuronal activity with in vivo 2-photon (2P) calcium imaging, retrieving the circuit structure with synchrotron X-ray computed tomography with propagation-based phase contrast (SXRT) and/or serial block-face scanning electron microscopy (SBEM) and correlating these datasets. Sample preparation and dataset correlation are two key bottlenecks in this correlative workflow. Here, we first quantify the occurrence of different artefacts when staining tissue slices with heavy metals to generate X-ray or electron contrast. We report improvements in the staining procedure, ultimately achieving perfect staining in ∼67% of the 0.6 mm thick olfactory bulb slices that were previously imaged in vivo with 2P. Secondly, we characterise the accuracy of the spatial correlation between functional and structural datasets. We demonstrate that direct, single-cell precise correlation between in vivo 2P and SXRT tissue volumes is possible and as reliable as correlating between 2P and SBEM. Altogether, these results pave the way for experiments that require retrieving physiology, circuit structure and synaptic signatures in targeted regions. These correlative function-structure studies will bring a more complete understanding of mammalian olfactory processing across spatial scales and time.

Straight elements are a simple tool for tackling the locking problem for curved beams. When a curved I-beam is approximated by chordwise straight elements, the conventional approach is to treat the rate of twisting as the warping degree of freedom (DOF) for the chordwise elements, which involves some confusion. In this article, a new straight element was derived by a mixed formulation by adopting the generalized warping deformation used in the energy composition as the associated nodal DOF based on the Bernoulli-Euler-Vlasov hypothesis. The convergence characteristics of both approaches were theoretically analyzed. The example demonstrated good convergence properties for both the conventional and mixed straight elements, aside from the fact that they are locking-free, unlike some curved elements. The mixed straight element showed a better performance because its treatment of warping deformation is more consistent in energy terms. [ABSTRACT FROM AUTHOR]

Image and video processing based on geometric principles typically changes the rectangular shape of video frames to an irregular shape. This paper presents a warping based approach for rectangling such irregular frame boundaries in space and time, i.e., making them rectangular again. To reduce geometric distortion in the rectangling process, we employ content-preserving deformation of a mesh grid with line structures as constraints to warp the frames. To conform to the original inter-frame motion, we keep feature trajectory distribution as constraints during motion compensation to ensure stability after warping the frames. Such spatially and temporally optimized warps enable the output of regular rectangular boundaries for the video frames with low geometric distortion and jitter. Our experiments demonstrate that our approach can generate plausible video rectangling results in a variety of applications. [ABSTRACT FROM AUTHOR]

YAG wafers are the most host laser crystals used for high-power lasers, which are usually machined by grinding to meet the required accuracy for laser components. Warping deformation induced by the residual stress is one of the main damages for YAG wafers after the grinding process, which will seriously decrease the service accuracy and life of the lasers. Developing theoretical model of warping deformation is of great significance to achieving the ultra-precision machining of YAG wafers. The cutting depth of single abrasive and grinding force in self-rotating grinding were investigated by considering the kinematic trajectory of abrasives, brittle-to-ductile transition, elastic mechanics, elastic deformation of the grinding wheel and strain rate effect. A theoretical model of warping deformation in self-rotating grinding of YAG wafers was developed based on the cutting depth and grinding force. The influence of subsurface damage and residual stress on warping deformation was analyzed based on the theoretical model and finite element simulation. Self-rotating grinding tests of YAG wafers were performed, and the results showed that the warping deformation decreased as the wheel rotational speed increased, and increased as the abrasive size, workpiece rotational speed and feed speed increased. The experimental results agreed well with the simulated results of the theoretical model, indicating that the theoretical model can accurately predict the warping deformation induced by self-rotating grinding process. This work will not only enhance the understanding of the essence of the wafer warping induced by ultra-precision machining, but also provide a guide for optimizing the processing parameters in self-rotating grinding of YAG wafers. [ABSTRACT FROM AUTHOR]

Virtual view synthesis, which generates novel views similar to the characteristics of actually acquired images, is an essential technical component for delivering an immersive video with realistic binocular disparity and smooth motion parallax. This is typically achieved in sequence by warping the given images to the designated viewing position, blending warped images, and filling the remaining holes. When considering 6DoF use cases with huge motion, the warping method in patch unit is more preferable than other conventional methods running in pixel unit. Regarding the prior case, the quality of synthesized image is highly relevant to the means of blending. Based on such aspect, we proposed a novel blending architecture that exploits the similarity of the directions of rays and the distribution of depth values. By further employing the proposed method, results showed that more enhanced view was synthesized compared with the well‐designed synthesizers used within moving picture expert group (MPEG‐I). Moreover, we explained the GPU‐based implementation synthesizing and rendering views in the level of real time by considering the applicability for immersive video service. [ABSTRACT FROM AUTHOR]

Featured Application: The model proposed in this article lays the foundation for cost-efficient in-process measurement of warp in corrugated cardboard manufacturing and, subsequently, improved process control to reduce waste. A model for describing warp—characterized as a systematic, large-scale deviation from the intended flat shape—in corrugated board based on Kirchhoff plate theory is proposed. It is based on established homogenization techniques and only a minimum of model assumptions. This yields general results applicable to any kind of corrugated cardboard. Since the model is intended to be used with industrial data, basic material properties which are usually not measured in practice are summarized to a few parameters. Those parameters can easily be fitted to the measurement data, allowing the user to systematically identify ways to reduce warp in a given situation in practice. In particular, the model can be used both as a filter to separate the warp from other surface effects such as washboarding, and to interpolate between discrete sample points scattered across the surface of a corrugated board sheet. Applying the model only requires height measurements of the corrugated board at several known (not necessarily exactly predetermined) locations across the corrugated board and acts as an interpolation or regression method between those points. These data can be acquired during production in a cost-efficient way and do not require any destructive testing of the board. The principle of an algorithm for fitting measured data to the model is presented and illustrated with examples taken from ongoing measurements. Additionally, the case of warp-free board is analyzed in more detail to deduce additional theoretical conditions necessary to reach this state. [ABSTRACT FROM AUTHOR]

This paper presents the use of a finite element method (FEM) to analyze the shear lag effect due to the flexure of beams with an arbitrary cross-section and homogeneous elastic material. Beams are constrained by the most common types of supports, such as fixed, pinned, and roller. The transverse, concentrated, or distributed loads act on the beams through the shear center of the cross-section. The presented FEM transforms the 3D analysis of the shear lag phenomenon into separated 2D cross-sectional and 1D beam modeling. The characteristics of the cross-section are firstly derived from 2D FEM, which uses a 9-node isoparametric element. Then, a 1D FEM, which uses a linear isoparametric element, is developed to compute the deflection, rotation angle, bending warping parameter, and stress resultants. Finally, the stress field is obtained from the local analysis on the 2D-cross section. A MATLAB program is executed to validate the numerical method. The validation examples have proven the efficiency and reliability of the numerical method for analyzing shear lag flexure, which is a common problem in structural design. [ABSTRACT FROM AUTHOR]

This paper describes the computational aspects of the beam Finite Element formulation recently developed by the authors to simulate the nonlinear response of structural members subjected to shear and torsion, accounting for cross-section warping. The paper focuses on an efficient consistent solution algorithm that by-passes the iterative procedure required in forcebased and mixed Finite Elements and makes the model easy to be implemented in a standard code. Moreover, it proposes a new non-iterative technique to condense out the stress components derived by the three-dimensional constitutive response and not directly included in the fiber section formulation. The efficiency and accuracy of the proposed numerical model are validated by simulating the response of steel and reinforced concrete structural members. [ABSTRACT FROM AUTHOR]