Contour Curve Research Articles

A Unified Solution Method for Free Vibration of Arbitrarily Shaped Plates without or with Cracks

This paper presents a new approach for analyzing the free vibration of thin plates with arbitrary piecewise smooth curvilinear contour under various boundary conditions. It can also be applied to plates with cracks. This approach is based on the transformation of energy integral expressions and the domain decomposition technique. Furthermore, boundary conditions are modeled by using linear springs to restrain the plate edges. For obtaining the expressions of energy integral, the arbitrarily shaped domain of integration is divided into several trapezoid domains with curved sides by a set of parallel lines passing through the intersection points of contour curve segments. Then, Jacobi orthogonal polynomials are introduced as the admissible functions, so that the repeated integrals in the energy expressions are reduced to definite integrals analytically. At this point, the calculation method of the energy functional is determined by the equation forms of the curve segments of the plate contour. When the equations of the curve segments allow the integrands to have analytic primitive functions, the energy functional has an analytical solution. Otherwise, the Gauss–Legendre method is used to obtain the numerical solution. Accordingly, the arbitrarily shaped plate with cracks is decomposed into several arbitrarily shaped subdomains based on the cracks. Each subdomain is handled according to the above procedure. The continuity conditions at the interconnecting interfaces of the subdomains are realized by linear springs. The plate without or with crack is modeled by setting the spring stiffness to infinity or 0. The accuracy of the proposed method is verified by comparing the obtained results with the published results. Furthermore, the vibration characteristics of plates with various shapes, such as astroid-shaped plates and cracked elliptical plates, are investigated. These new results can serve as benchmarks for further studies on the vibration of plates.

Long-range medical image registration through generalized mutual information (GMI): towards a fully automatic volumetric alignment

Objective. Mutual information (MI) is consolidated as a robust similarity metric often used for medical image registration. Although MI provides a robust registration, it usually fails when the transform needed to register an image is too large due to MI local minima traps. This paper proposes and evaluates Generalized MI (GMI), using Tsallis entropy, to improve affine registration. Approach. We assessed the GMI metric output space using separable affine transforms to seek a better gradient space. The range used was 150 mm for translations, 360° for rotations, [0.5, 2] for scaling, and [−1, 1] for skewness. The data were evaluated using 3D visualization of gradient and contour curves. A simulated gradient descent algorithm was also used to calculate the registration capability. The improvements detected were then tested through Monte Carlo simulation of actual registrations with brain T1 and T2 MRI from the HCP dataset. Main results. Results show significantly prolonged registration ranges, without local minima in the metric space, with a registration capability of 100% for translations, 88.2% for rotations, 100% for scaling and 100% for skewness. Tsallis entropy obtained 99.75% success in the Monte Carlo simulation of 2000 translation registrations with 1113 double randomized subjects T1 and T2 brain MRI against 56.5% success for the Shannon entropy. Significance. Tsallis entropy can improve brain MRI MI affine registration with long-range translation registration, lower-cost interpolation, and faster registrations through a better gradient space.

Automatic measurement of LV wall thickness from 2D cardiac echocardiography

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): PIC from European Union"s Horizon 2020 Marie Skłodowska-Curie Actions ITN Background The wall thickness of the left ventricle (LV) is an important parameter in the diagnosis of hypertension and more specifically in hypertrophic cardiomyopathy. A user-dependent manual assessment of distances on 2D echocardiographic images is the current clinical gold-standard. Purpose The automation of LV wall thickness measurements in 2D echocardiography in order to improve robustness and reduce time of clinical reports where wall thickness is required, such as hypertrophy and the presence of Basal Septal Hypertrophy (BSH)(1). Methods A dataset of 4-chamber (4CH) echocardiograms on 118 patients with a diagnosis of hypertension (2) is used for this study. The images were segmented automatically (3) extracting the blood pool and the myocardium. Based on the curvature of the complete myocardial contour, the valve annular regions are removed leaving the endocardial and the epicardial walls as independent structures. The wall thickness along the myocardium is calculated as the distance from each endocardial border pixel to the closest epicardial point (see Figure 1). A high pass gaussian filter was applied to remove high frequency noise. Ultimately, the basal-to-mid septal wall thickness ratio that defines BSH (ratio ≥ 1.4) was computed as the maximal of basal-septal segment divided by minimum of mid-septal segment. In order to validate the method for BSH detection, the wall thickness septal ratio was carefully measured by a clinical expert following the guidelines (2). The statistical agreement was accessed via linear correlation and Bland-Altman analysis. Results The automatic assessment of LV wall thickness along the myocardium is feasible in 2D echocardiography. The septal ratio showed an excellent agreement with manual measurements (R2 = 0.94, bias=-0.01, see Figure 2), leading to a detection of BSH in n = 19 vs the n = 18 detected manually (1 false-negative and 2 false-positives). In comparison to the intra and inter-observer variabilities of 12% and 42% respectively in the manual measurement (4), the automatic method had no variability for a given image acquisition. Conclusions The automatic measurement of myocardial wall thickness from a 2D echocardiographic images is accurate and reproducible. The implementation of the methodology in clinical practise has the potential to improve and automate the assessment of hypertrophic cardiac conditions. Abstract Figure. Pipeline for automatic measurement of WT Abstract Figure. Agreement of BSH WT ratio

Overlapping optimization of hybrid deposited and micro-rolling additive manufacturing

PurposeThis paper aims to summarize the influence law of hybrid deposited and micro-rolling (HDMR) technology on the bead morphology and overlapping coefficient. A better bead topology positively supports the overlapping deposited in multi-beads between layers while actively assisting the subsequent layer's deposition in the wire and arc additive manufacturing (WAAM). Hybrid-deposited and micro-rolling (HDMR) additive manufacturing (AM) technology can smooth the weld bead for improved surface quality. However, the micro-rolling process will change the weld bead profile fitting curve to affect the overlapping coefficient.Design/methodology/approachWeld bead contours for WAAM and HDMR were extracted using line lasers. A comparison of bead profile curves was conducted to determine the influence law of micro-zone rolling on the welding bead contour and fitting curve. Aiming at the optimized overlapping coefficient of weld bead in HDMR AM, the optimal HDMR overlapping coefficient curve was proposed which varies with the reduction based on the best surface flatness. The mathematical model for overlapping in HDMR was checked by comparing the HDMR weld bead contours under different rolling reductions.FindingsA fitting function of the bead forming by HDMR AM was proposed based on the law of conservation of mass. The change rule of the HDMR weld bead overlapping spacing with the degree of weld bead rolling reduction was generated using the flat-top transition calculation for this model. Considering the damming-up impact of the first bead, the overlapping coefficient was examined for its effect on layer surface flatness.Originality/valueUsing the predicted overlapping model, the optimal overlapping coefficients for different rolling reductions can be achieved without experiments. These conclusions can encourage the development of HDMR technology.

Micronutrient requirements and effects on cellular growth of acetic acid bacteria involved in vinegar production

This study aimed to verify the need for minerals and vitamins to increase the production of cell mass by acetic acid bacteria (AAB) isolated from the vinegar industry (086/06) and standard strain (Acetobacter aceti CCT 2565). Five minerals (Mo, B, Zn, Fe, and Mn) and eight vitamins (p-aminobenzoic acid, thiamine, niacin, pantothenic acid, pyridoxine, biotin, cyanocobalamin, and inositol) were tested in a fractional factorial design. To prepare the inoculum, different compositions of MYP (mannitol, yeast, and peptone) medium were tested. The most adequate medium was mannitol 25 g/L, yeast extract 0.625 g/L, and peptone 0.375 g/L. Through contour curves, it was determined that strain 086/06 needed supplementation with minerals Mo, B and Mn and vitamins p-aminobenzoic acid, pyridoxine and cyanocobalamin. Standard strain CCT 2565 needed supplementation of all minerals and vitamins studied, except inositol. The lower requirement of micronutrients for high cell multiplication of the 086/06 strain may be related to the adaptation of strain 086/06 to industrial production conditions.

Research on custom-tailored swimming goggles applied to the internet

Custom-tailored designs have attracted increasing attention from both consumers and manufacturers due to increasingly intense market competition. We propose and verify a method for custom designing swimming goggles that is suitable for use on the Internet. Twenty-five points representing head features were first identified, and the relationship between these points and the size of the goggles were confirmed. The correct position for photography was then experimentally determined, and a camera-position corrector was designed and manufactured. A three-dimensional (3D) scanning model was divided into 18 planes based on the feature points, and the contour curve of the surface on each plane was extracted. Secondly a Hermite interpolation curve was then used to describe the contour curve for the head, and a parametric 3D head model was established. The method of using orthographic photographs with patches to obtain 3D data was summarized to determine the size of the user’s head, and a 3D model of the user’s head and the 3D model of the goggles were established. Lastly, we developed an algorithm for eliminating errors in the photographs. We also produced an operational flowchart for an application (APP) following the research approaches and then determined the page structure of the APP based on the flowchart to verify the validity of our proposed method and ultimately to establish an APP for interactively designing swimming goggles. The entire APP operation process was completed using a volunteer as an experimental subject when a model for custom-tailored goggles was obtained. The model was then processed and applied using 3D printing. The volunteer confirmed the model by declaring that the goggles were comfortable to wear and perfectly positioned on his face, thereby verifying the validity of the method.

Mathematical modelling and analysis of profile meter

The profiler measures the workpiece to reflect the contour curve shape of the surface of the workpiece. When measuring the same workpiece, the drawn contour curve will shift due to the different placement angle and horizontal position. In order to improve the measurement accuracy of the profiler, the paper proposes a new modelling and calculation method for the profiler. This method uses mathematical methods such as vectors and geometric relations to calculate parameters; then completes level correction by changing the coordinate system; finally, uses geometric methods and analogy inference methods to obtain the deviation between the calculated values of each parameter. The research results show that this method can realize the measurement of the profiler more accurately.

ВЛИЯНИЕ ПРОКАТА КОЛЕСА ГРУЗОВОГО ВАГОНА НА КОНТАКТНО-УСТАЛОСТНУЮ ДОЛГОВЕЧНОСТЬ

The authors have analysed and determined curvature and radius of worn contour of a wheel and an inclination angle of a tangent. They have got a dependence of a value of tread surface wear from a mileage. The authors have determined influence of the first-order derivative on curvature radius of the worn contour and refined a formula for that radius. As a result, they have analysed limits of applicability of the formulas that will allow using them in calculations at studying worn tread surface contour.

Influence of Surface Crack Propagation on Ring-Shell Structure

In this paper, the surface cracks of deep-sea ring-shell structures are studied. In this paper, the geometric and physical parameters of 1000m underwater titanium alloy ring shell structure were analyzed. Firstly, the mathematical model of its relevant contour curve was obtained by combining with the parameter equation. Based on the mathematical model, the finite element model was established and the force analysis under static equilibrium condition was carried out. Secondly, the stress maximum point was solved by finite element analysis, and the initial crack was added at the stress maximum point. The stress intensity factor method was used to analyze the stress intensity factor and crack propagation. Finally, according to the physical parameter load, stress ratio, morphology coefficient and different Angle analysis, the influence factors that interfere with crack growth and the dynamic trend of crack morphology were evaluated. Aiming at the study of dynamic performance of cracked ring-shell structure, the crack characteristic curves under different complex working conditions were analyzed to deepen the research in related fields and provide some scientific reference for the study of related ring-shell structure.

Modeling of the Saltwater Intrusion Using the Level Set Method. Application to Henry’s Problem

The salt intrusion phenomenon is caused by overexploitation of aquifers in coastal areas. This physical phenomenon has been the subject of numerous studies and numerous methods have been proposed, with the aim of protecting the quality of the water in these aquifers. This work proposes a two-dimensional saline intrusion model using the sharp interface approach and the level set method. It consists of a parabolic equation modeling the underground flow and a hyperbolic Equation (the level set equation) which makes it possible to track the evolution of the interface. High-order numerical schemes such as the space scheme WENO5 and the third-order time scheme TVD-RK were used for the numerical resolution of the hyperbolic equation. To limit the tightening of the contour curves of the level set function, the redistanciation or reinitialization algorithm proposed by Sussma et al. (1994) was used. To ensure the effectiveness and reliability of the proposed method, two tests relating to the standard Henry problem and the modified Henry problem were performed. Recall that Henry’s problem uses the variable density modeling approach in a confined and homogeneous aquifer. By comparing the results obtained by the level set method with reinitialization (LSMR) and those obtained by Henry (1964), and by Simpson and Clement (2004), we see in the two test cases that the level set method reproduces well the toe, the tip and the behaviour of the interface. These results correspond to the results obtained by Abarca for Henry’s problem with constant dispersion coefficients. The results obtained with LSMR, reproduced the interface with a slight spacing compared to those obtained by Henry. According to Abarca (2006), this spacing is due to the absence of the longitudinal and transversal dispersion coefficients in the model.

Simulation and experimental study on drag reduction and anti-adhesion of subsoiler with bionic surface

A new subsoiler with placoid scale microstructure bionic surface was proposed which mimicked shark skin to reduce tillage resistance and soil adhesion during subsoiling cultivation. The contour curves of placoid scale microstructure on shark skin were fitted, and two kinds of bionic subsoiler with continuous and discontinuous microstructures were designed and fabricated, respectively. The effects of different bionic surfaces on tillage resistance were investigated by finite element simulation and experiment. The results indicated that the bionic subsoiler with discontinuous microstructure reduced the horizontal and vertical force by 21.3% and 24.8%, respectively. The subsoiler with discontinuous microstructure surface can prevent the adhesion between the soil and subsoiler surface more efficiently. Keywords: drag reduction, anti-adhesion, subsoiler, bionic surface, placoid scale microstructure, Finite element simulation DOI: 10.25165/j.ijabe.20221504.6531 Citation: Niu J P, Luo T Y, Xie J Q, Cai H X, Zhou Z K, Chen J, et al. Simulation and experimental study on drag reduction and anti-adhesion of subsoiler with bionic surface. Int J Agric & Biol Eng, 2022; 15(4): 57–64.

Formulation of Novelty and Complexity in Shape and its Application to Design

Design aesthetics is one of the most important factors in the attractiveness of industrial products. In this study, we focused on the theory of aesthetics, which states that moderate novelty and complexity maximize pleasant feelings, and formulated the novelty and complexity perceived from a closed curve contour shape using curvature and Fourier expansion coefficients. Using this formulation, we developed "Hybrid-GAN," a shape generation system that iterates shape generation, feature computation, and shape optimization. The system is capable of generating a variety of shapes of arbitrary novelty and complexity. In a subsequent experiment, subjective evaluations of novelty and complexity, as well as beauty and interest, were obtained for the shape samples generated by the system. The results showed that the novelty and complexity formulations had significant positive correlations with the subjective evaluation, and the sum of novelty and complexity had a strong positive correlation with interestingness. The results of this study are expected to be used to support the design of attractive and long-loved shapes by providing feedback to designers on the degree of novelty and complexity that users find most pleasant.

Liouville Integrability in a Four-Dimensional Model of the Visual Cortex.

We consider a natural extension of the Petitot–Citti–Sarti model of the primary visual cortex. In the extended model, the curvature of contours is taken into account. The occluded contours are completed via sub-Riemannian geodesics in the four-dimensional space M of positions, orientations, and curvatures. Here, models the configuration space of neurons of the visual cortex. We study the problem of sub-Riemannian geodesics on M via methods of geometric control theory. We prove complete controllability of the system and the existence of optimal controls. By application of the Pontryagin maximum principle, we derive a Hamiltonian system that describes the geodesics. We obtain the explicit parametrization of abnormal extremals. In the normal case, we provide three functionally independent first integrals. Numerical simulations indicate the existence of one more first integral that results in Liouville integrability of the system.

Dual-field measurement system for real-time material flow on conveyor belt

In this paper, an innovative dual-field measurement system is proposed for measuring the real-time material flow on the conveyor belt. The system consists of two light sources to illuminate the upper and the lower surface of the conveyor belt, respectively, and two binocular cameras to capture the dual-field contour images. The contour curves are extracted from the images by the contour acquisition algorithm and fitted with linear interpolation functions for the calculation of instantaneous cross-sectional area of material flow. Then the real-time volume of material flow is obtained according to the belt speed. Compared with conventional visual methods, the proposed method is no need to preliminarily acquire the data of the empty belt as well as hardly affected by belt deformation. Some measured objects are prepared for both sectional area and volume measurement. The results show that the accuracy of the proposed system can achieve up to 96.3% and 96.05% for the volume measurement of regular materials and coals, respectively, which is superior to the conventional visual method. The proposed measurement method has strong robustness and low construction cost, which is expected to generalize and apply in the bulk material transport field.

An optimized method for extracting slope length in RUSLE from raster digital elevation

The Universal Soil Loss Equation (USLE) and the Revised Universal Soil Loss Equation (RUSLE) have been widely used for predicting average soil loss. Slope length is an important topographical parameter of the L factor in USLE/RUSLE. Among the widely studied GIS procedures for extracting slope length, the distributed watershed erosion slope length (DWESL) based on the unit contributing area estimation method, which considers two-dimensional runoff process and cutoff factors, is a relatively complete model for calculating slope length. Slope length in the DWESL model is primarily calculated using conventional flow direction algorithms such as D8, Dinf, MS and MFD-md. However, DWESL outputs require further improvement due to the errors in the usual estimates of the uphill contributing area and the effective contour length of discrete elements. Combined with a theoretical differential equation of specific catchment area on hillsides, the calculation of the DWESL model was optimized without estimating the uphill contributing area or the effective contour length for each cell. The proposed integration method based on the topographical features slope line, contour curvature and cutoff factors (ITF method) was used to extract slope length from the raster digital elevation. Slope length extracted using the ITF method had the smallest error in verification of mathematical surfaces (average RRMSE = 0.0573), and its spatial distribution was more consistent with the structure of the terrain surface for all test data, relative to the conventional flow direction algorithms in the original DWESL model. The proposed ITF method could provide a reference for predicting soil erosion using the USLE/RUSLE model.

Biomimetic Rotary Tillage Blade Design for Reduced Torque and Energy Requirement.

A rotary cultivator is a primary cultivating machine in many countries. However, it is always challenged by high operating torque and power requirement. To address this issue, biomimetic rotary tillage blades were designed in this study for reduced torque and energy requirement based on the geometric characteristics (GC) of five fore claws of mole rats, including the contour curves of the five claw tips (GC-1) and the structural characteristics of the multiclaw combination (GC-2). Herein, the optimal blade was selected by considering three factors: (1) the ratio (r) of claw width to lateral spacing, (2) the inclined angle (θ) of the multiclaw combination, and (3) the rotary speed (n) through the soil bin tests. The results showed that the order of influence of factors on torque was n, r, and θ; the optimal combination of factors with the minimal torque was r = 1.25, θ = 60°, and n = 240 rpm. Furthermore, the torque of the optimal blade (BB-1) was studied by comparing with a conventional (CB) and a reported optimal biomimetic blade (BB-2) in the soil bin at the rotary speed from 160 to 320 rpm. Results showed that BB-1 and BB-2 averagely reduced the torque by 13.99% and 3.74% compared with CB, respectively. The field experiment results also showed the excellent soil-cutting performance of BB-1 whose average torques were largely reduced by 17.00%, 16.88%, and 21.80% compared with CB at different rotary speeds, forward velocities, and tillage depths, respectively. It was found that the geometric structure of the five claws of mole rats could not only enhance the penetrating and sliding cutting performance of the cutting edge of BB-1 but also diminish the soil failure wedge for minimizing soil shear resistance of BB-1. Therefore, the GC of five fore claws of mole rats could inspire the development of efficient tillage or digging tools for reducing soil resistance and energy consumption.

Hand measurement and analysis based on image and mark watershed algorithm

PurposeThe purpose of this paper is to propose a method for hand measurement based on image and marker watershed algorithm, and combine the data to analyze the shape and characteristics of the hand.Design/methodology/approachA portable hand image capturing instrument was designed and manufactured, and the hand images and dimensions of 328 young men in Zhejiang area were obtained. The outer contour curve of the hand and the key points of finger root, fingertip, wrist and knuckle position were extracted. Then, the size of each hand part was calculated. The hand data obtained from the two-dimensional image was compared with the manual measurement data. Finally, the hands were classified according to the measurement data, and the relationship between hand control size and hand length, hand width and the relationship between hand length and height were explored.FindingsThe data comparison results show that the two measurement methods have high data consistency and are replaceable. In addition, analyzing the data obtained four major characteristic factors that affect the shape of the hand, divided the hands of young men in Zhejiang into five categories, and obtained the regression equations of basic hand size, hand length and hand width, and obtained the regression equation of hand length and height.Originality/valueThe method proposed in this study to obtain hand size based on the image and mark watershed algorithm has lower requirements on the external environment and testers, conforms to the development trend of applying artificial intelligence to anthropometric engineering and provides a useful reference value for data collection of gloves specification design. In addition, the results of data analysis can provide a valuable reference basis for consumer hand shape predictions, which can be used to guide the research and production of hand instruments, the design of specifications series and the purchase of hand products.

Non-invasive methods of cardiac output measurement and their importance in everyday clinical practice: the current state of knowledge

Cardiac output is an important parameter in the evaluation of the patients’ haemodynamic status which can be measured using a number of methods with varying degrees of invasiveness. These include invasive (such as pulmonary artery catheterization, transpulmonary thermodilution, lithium dilution), minimally invasive (catheter-based arterial pressure curve contour analysis, transoesophageal Doppler) and non-invasive (electrical bioimpedance, transthoracic echocardiography, measurement of exhaled CO2, continuous non-invasive blood pressure measurement) techniques. With advances in medicine, the role of non-invasive methods as an alternative to pulmonary artery catheterization continues to grow. The undoubted advantage of non-invasive methods is their safety for the patients and their wide availability. In contrast, invasive methods are characterized by greater measurement precision. It is up to the physician to choose the most appropriate haemodynamic monitoring method depending on the clinical situation. The aim of this article is to discuss non-invasive cardiac output measurement techniques and their application in everyday clinical practice.

Optimization and synthesis of a cam-linkage mechanism with a swing follower with variable pivot

In this paper, a cam-linkage mechanism with a swing follower with variable pivot has been studied. In this mechanism, the pivot of the swing follower is installed on a slider with an adjustable track direction, the follower performs a complex planar motion, and the motion range of the output angle can be adjusted according to the output requirements. In order to synthesize this mechanism, firstly, the relevant model is established and the basic structural parameters are optimized by considering the assembly conditions and the pressure angle under the limit position of the movement track of the follower mounting slider. Subsequently, the inverse method and the envelope theory are employed to derive the cam contour coordinates. Finally, the corresponding follower motion law is selected, the corresponding cam contour coordinates are calculated, and the entire cam contour curve is obtained using spline interpolation. An automatic design system for cam contours is developed. The processes are carried out through design examples and verified through motion simulations and prototype experiment. The present work can enrich the design theory of cam-linkage mechanisms.

Construction of uncut chip geometry in gear skiving using level contours

In gear skiving, tool-chip contact condition becomes complicated when using multiple radial infeed strategy. We are interested in calculating a precise boundary of the uncut chip geometry to capture its topological variation especially in semi-/finishing-passes. To achieve this, we propose a level contour method to implicitly construct the uncut chip and gear gap geometries with contour curves. By comparing the artificial potential energy defined on the different contours, geometries of uncut chip and gear gap are successfully obtained. In addition, the implicit contour provides an efficient and comprehensive way to express the topology changes of the uncut chip geometry from the I to the U shape. By changing the radial and axial infeed rates, the proposed method is proven can advance the understanding of tool-chip contact area variation with the active contour, which can smoothly present merging, emerging and separation, for the development from single-contact to multiple-contact areas during a single-cut.