Curvature analysis is frequently employed in shape interrogation. Umbilical points are of particular interest in curvature analysis because of their identical normal curvatures in all tangential ...directions. Locating the umbilical points is the basis of geometric analysis. On the one hand, as singularities, umbilical points severely hinder the analysis (e.g., in nets of curvature lines). On the other hand, they provide qualitative information about the intrinsic shape of a surface and are therefore desirable quantities in some applications. In this study, we develop a straightforward and effective method to detect generic umbilical points on triangular meshes. This method is applicable to any type of admissible parametrization. We propose two local parametrization schemes–orthogonal projection and conformal transformation–to be used with the proposed method. Furthermore, we systematically analyze our method and prove its convergence behavior. The algorithm used in our approach is flexible and straightforward to implement for triangular meshes of arbitrary topology.
•A method to find umbilical points over a mesh by using shape operators is proposed.•The mathematical methods upon which the method is based are presented in detail.•It is shown to be flexible and easier to implement.
We propose a stabilization method for linear tetrahedral finite elements, suitable for the implicit time integration of the equations of nearly and fully incompressible nonlinear elastodynamics. In ...particular, we derive and discuss a generalized framework for stabilization and implicit time integration that can comprehensively be applied to the class of all isotropic hyperelastic models. In this sense the presented development can be considered an important extension and complement to the stabilization approach proposed by the authors in previous work, which was instead focused on explicit time integration and simple neo-Hookean models for nearly-incompressible elasticity. With the goal of computational efficiency, we also present a two-step block Gauss–Seidel strategy for the time update of displacements, velocities and pressures. Specifically, a mixed system of equations for the velocity and pressure is updated implicitly in a first stage, and the displacements are updated explicitly in a second stage. The proposed mixed formulation is then embedded in Newton-type strategies for the nonlinear solution of the equations of motion. Various implicit time integration strategies are considered, and, particularly, we focus on high-frequency dissipation time integrators, which are preferable in transient mechanics applications. An extensive set of numerical computations with linear tetrahedral elements is presented to demonstrate the performance of the proposed approach.
BACKGROUND AND AIMS: During the fallow period, non-legume cover crop species can capture mineral nitrogen (N) and thus decrease nitrate leaching, whereas legume cover crop species can provide a green ...manuring service that increases N availability for the subsequent crop. The aim of our study was to investigate the ability of bispecific mixtures to simultaneously produce these two services of N management in relation to their interspecific interactions. METHODS: Three field experiments were conducted at contrasting sites from summer to autumn to evaluate 25 mixtures and 10 sole crops. We measured biomass, N acquisition, C:N ratio and soil mineral N. Ecosystem services were assessed using both experimental data and simulation model predictions. RESULTS: Overall, prediction of N mineralized from cover crop residues was significantly higher for mixtures than for non-legume sole crops. Predictions of nitrate leached after mixtures did not differ significantly from those after non-legume sole crops and remained significantly lower than those under bare soil, especially for mixtures with turnip rape which benefitted greatly from being in mixtures. CONCLUSIONS: Some of the mixtures provided a choice of compromises between the two ecosystem services, which helps define solutions for adapting mixture choice according to the site’s soil and climate characteristics and to fallow period management.
In this paper, we discuss the similarity between two trajectories using the Needleman Wunsch algorithm. The calculation steps are interpolating the trajectory, calculating the distance between the ...trajectory coordinates, identifying the equivalent length, transforming trajectories into a sequence of alphabetic letters, aligning the sequences, and measuring the magnitude of the similarity based on the alignment results. The similarity obtained is compared directly to the length of the trajectories shared by the two lines. The calculation results show that the accuracy of the alignment method reaches more than 90%. Abstrak: Dalam tulisan ini dibahas cara perhitungan persentase kesamaan dari dua buah lintasan menggunakan algoritma Needleman Wunsch dan perhitungan secara manual berdasarkan irisan dari lintasan-lintasan tersebut. Pada perhitungan menggunakan algoritma Needleman Wunsch, tahapan-tahapan yang dilakukan adalah menginterpolasi lintasan, menghitung jarak antara titik-titik koordinat dari kedua lintasan, mengidentifikasi jarak yang ekivalen, mengubah lintasan menjadi sekuens huruf alfabet, menyejajarkan sekuens, dan menentukan besarnya kesamaan berdasarkan hasil penyejajaran. Kesamaan yang diperoleh dari metode penyejajaran dibandingkan secara langsung dengan panjang jalur yang dilalui bersama oleh kedua lintasan, hasil perhitungan menunjukkan bahwa akurasi metode penyejajaran mencapai lebih dari 90%.
This article aims to solve multiple problems associated with attitude estimation; the complexity of Kalman filter (KF) calculations in the attitude and heading reference system (AHRS), the ...interference sensitivity of magnetic, angular rate, and gravity (MARG) sensors, and the low accuracy of the factored quaternion algorithm (FQA). It presents a two-layer linear KF using MARG sensors to obtain attitude estimation in quaternions. First, data from a triaxial accelerometer and magnetometer is processed by a novel algorithm, which fuses the quaternion estimator (QUEST) algorithm and FQA by the linear interpolation (LERP) to obtain an observation model. Second, the process model in the two-layer KF was obtained by using LERP to fuse an optimum quaternion obtained from a gyroscope and FQA. The LERP can eliminate gyro bias drift, and integral error, and compensate for unexpected conditions, such as fast rotation and temporary strong magnetic disturbances. The proposed algorithm presents higher accuracy and lower computational load than QUEST or FQA used with a KF alone. The performance of the proposed algorithm is verified through simulation and experiments.
Fillet welds by intermittent welding are widely used in the welding of centrifugal fans, such as attaching a fan blade to the rear plate. The intermittent welding method transforms the full-length ...continuous weld into multiple short welds to minimize distortion by reducing the total heat input for a welded joint to control welding distortion. An infinite number of short welds are created during this process. However, depending on the complexity of the model, the computational cost of predicting welding distortion based on full-scale modeling is considerable. These numerous short welds undoubtedly complicate modeling and computations, limiting rapid distortion prediction for large and complex structures. This study develops an equivalent deformation calculation approach based on a local-to-global technique and applies it to predict distortion of a fillet joint welded specimen. The approach consists of two steps. First, the welding-induced structural deformation is calculated for a two-dimensional (2D) weld and a 2D heat-affected zone (local calculation). Second, the 2D structural deformation is applied to the full-scale welded structure using a nearest-point spatial interpolation algorithm to acquire the three-dimensional (3D) equivalent deformation (global calculation). Note that the weld shape was considered in both local and global calculations. In addition, welding tests were performed, and the coordinates of the key points were measured. The geometric parameters of the welds used in the numerical simulations were obtained from experimental observations. Finally, the key point coordinates obtained by the proposed approach were compared with experimental measurements. Furthermore, the distribution of out-of-plane distortion caused by the new approach was compared with the simulation results of the thermo-elastic-plastic method performed on a full-scale welded structure. The proposed approach can be verified by both comparisons.
Wear is directly related to rough surface contact, and the accuracy of a wear prediction model depends on the accurate determination of contact pressure. In this work, a numerical model with high ...computational accuracy for rough surface contact is developed and applied to the wear prediction of spur gears. To acquire contact pressure, the integral equation that contact pressure should satisfy is discretized into a set of linear equations by piecewise linear interpolating contact pressure. Then, a gear wear model including rough surface contact is established. The proposed contact model is verified by comparing with smooth and rough surface contact, and the wear depths of a spur gear drive with geometry and pressure updates are analyzed. Result shows that a small roughness value among contact surfaces may cause a large change in contact pressure. The effects of main design parameters on gear wear are subsequently investigated. Gear wear is found to decrease with increased module and pressure angle but increases with increased transmission ratio and input torque. These findings indicate that reasonable parameter matching is beneficial to improving gear wear resistance.
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•A novel contact model for rough surfaces is developed.•A wear model for spur gears including rough surfaces contact is presented.•Wear depths of spur gears with or without geometry and pressure updates are analyzed.•Rational parameters matching in gear design is beneficial for wear resistance.
Irrigation with wastewater is an increasing practice around the world triggered by the large needs of water for agriculture. Many times this source of water is added by flooding to the fields, ...creating short temporal oxygen-depleted environments, where nitrous oxide (N2O) emissions are promoted. Agriculture is responsible for up to 60% of the global annual emissions of this gas, and its emission factors (EF) must be reported. During 21 months, we installed closed chambers to measure the N2O emissions from a wastewater irrigated plot in the Mezquital Valley. Here, alfalfa, rye grass, and maize were grown in succession, receiving mainly organic N contained in the untreated wastewater and the residues of the previous crop; only maize received extra mineral fertilization of 100 kg of N ha−1. We obtained a time series where the gaps were filled by linear interpolation. EF and N2O direct emissions were estimated by the Tier 1 approach of the IPCC. We found that the alfalfa and rye grass, which only receive organic nitrogen, produced minor N2O emissions, that reflected in lower EF (0.004 and 0.001, respectively), compared with the default value of the IPCC (0.01). In contrast, maize, which receives organic and inorganic N, lost 1% of this N input as N2O, the same as the default value (0.01). It seems that the form of N, the crop age and type influence greatly the N dynamics in this wastewater irrigated land-use system. Therefore, the Tier I approach of the IPCC seems to underestimate the N efficiency of this agroecosystem and overestimates the N2O direct emissions from alfalfa and rye grass.
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•Wastewater reuse for agricultural purposes is an increasing practice around the world.•Flooding irrigation promotes the anaerobic transformation of N, releasing N2O to the atmosphere.•The time series of N2O emissions were filled by linear interpolation.•Addition of mineral fertilizer to wastewater irrigated crops increases N2O emissions.•The IPCC default value seems to underestimate the N efficiency of wastewater irrigated agroecosystems.
•An enhanced absolute nodal coordinate formulation (ANCF) is proposed.•The enhanced formulation use smaller coordinates to accurately and efficiently model long cable dynamics.•Linear interpolation ...technique is applied for rotational DOFs and the formulation is simplified.•The results of illustrative example solutions show the excellent performance of the enhanced formulation.
Long cable structures can be accurately modeled in the absolute nodal coordinate formulation (ANCF), but often at the expense of using too many degrees of freedom (DOFs). This research refines the section of node coordinates and configuration description of the element and forms an enhanced ANCF that required modeling DOFs are greatly reduced. In this formulation, the cable is treated as an elastic line and discretized with two-node elements. The gradients of all nodes and the absolute positions of only head node are selected as generalized coordinates. The gradient field of the element is linearly interpolated in nodal gradients. Unlike the traditional ANCFs, the absolute position vector of an arbitrary point of the element is calculated by evaluating an integral of the element gradient over the element length plus the position vector of the starting node of the element, instead of cubic polynomial interpolation of nodal position and gradient vectors of the element. This leads to considerable DOFs saving. Governing motion equations of the cable are derived. Benchmark examples are used to show the performance of the enhanced formulation against with the classical ANCF cable element. Comparative studies show the validity and the efficiency of the enhanced formulation.
This paper aims to promote the integration of animation design and cultural and creative industries. The shape gradient algorithm is used to analyze the features of the animated shapes. The ...corresponding interval distance of anime shapes is determined by calculating the curve sampling points of anime feature points. The deformation framework is created, and a sequence of anime shapes is generated using the linear interpolation method. In the deformation of anime design, the role of three algorithms, namely image segmentation module, association map of attributes, and mathematical description of EMD, on its generation is focused on the analysis. The results show that anime users from post-00 and post-10 are more inclined to anime peripherals, accounting for 30% and 35%, respectively. The annual growth rate of anime peripheral is 90.2%, and the annual growth rate of the overseas anime market is also gradually increasing, reaching a growth rate of 103.1%. A successful anime IP will certainly influence the development of its anime and cultural creation industry. The research in this paper is conducive to promoting better integration of animation design and cultural and creative industries and promoting the development of an innovation economy.
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