Contour Curve Research Articles

Energy optimization method for variable curvature contour machining

Energy optimization method for variable curvature contour machining

Dazzling Evaluation of the Impact of a High-Repetition-Rate CO2 Pulsed Laser on Infrared Imaging Systems.

This article utilizes the Canny edge extraction algorithm based on contour curvature and the cross-correlation template matching algorithm to extensively study the impact of a high-repetition-rate CO2 pulsed laser on the target extraction and tracking performance of an infrared imaging detector. It establishes a quantified dazzling pattern for lasers on infrared imaging systems. By conducting laser dazzling and damage experiments, a detailed analysis of the normalized correlation between the target and the dazzling images is performed to quantitatively describe the laser dazzling effects. Simultaneously, an evaluation system, including target distance and laser power evaluation factors, is established to determine the dazzling level and whether the target is recognizable. The research results reveal that the laser power and target position are crucial factors affecting the detection performance of infrared imaging detector systems under laser dazzling. Different laser powers are required to successfully interfere with the recognition algorithm of the infrared imaging detector at different distances. And laser dazzling produces a considerable quantity of false edge information, which seriously affects the performance of the pattern recognition algorithm. In laser damage experiments, the detector experienced functional damage, with a quarter of the image displaying as completely black. The energy density threshold required for the functional damage of the detector is approximately 3 J/cm2. The dazzling assessment conclusions also apply to the evaluation of the damage results. Finally, the proposed evaluation formula aligns with the experimental results, objectively reflecting the actual impact of laser dazzling on the target extraction and the tracking performance of infrared imaging systems. This study provides an in-depth and accurate analysis for understanding the influence of lasers on the performance of infrared imaging detectors.

Analysis of factors related to the morphological evolution of Lingnan export mugs in the 18th-20th centuries in the context of one belt and one road.

As a significant trade item on the ancient Silk Road, the evolution of mug shapes represents a confluence of Eastern and Western economic history and cultural-artistic exchanges, also reflecting the flourishing export culture of Guangzhou. This paper analyzes the functional and social factors influencing the morphological changes of Lingnan mugs from 1616 to 1949 from the perspective of quantitative typological analysis. The overall design trend of these mugs transitioned from complex to simple, enhancing user comfort, while variations in mug scale reflect the diversity of consumer classes and regional drinking cultures. Among the 30 mugs analyzed, the average capacity was 356ml, with a range of 1588ml. Common shapes included cylindrical bodies and ear-shaped handles. Morphologically, the belly of the mugs transformed from arc-barrel bodies (emphasizing heat retention) to bulbous bodies, and eventually to cylindrical bodies (combining heat retention, practicality, and economy), with handles also showing signs of East-West integration. The analysis of the mug body' s inclination, with handle-side junction angles ranging from 34° to 53° and wall-side junction angles from 50° to 90°, indicates that these features are associated with stability in placement, aesthetic design, and practicality in liquid containment. These morphological evolutions reflect genuine responses to market demands and advancements in production technology, manifesting as products of market orientation and societal needs. By measuring changes in morphology, scale, volume, and external contour curves, this paper addresses how social factors shape material morphology in an academic context.

ANALYSIS OF NATURAL FREQUENCIES FOR EARLY DAMAGE DETECTION IN CFRP SHAFTS USING RSM-BASED FREQUENCY CONTOUR PLOTS

This study explores early damage detection in carbon fiber-reinforced polymer shafts by analyzing natural frequencies. Modern engineering components often face increased flexibility and high stress levels, leading to cracks in rotating parts, which can result in premature failures. To address this issue, modal analysis, specifically natural frequency analysis, is employed to identify deviations caused by cracks. Cracks alter stiffness and mass distribution, leading to shifts in natural frequencies. The study employs finite element models to simulate various crack locations and depths, normalizing them with respect to shaft diameter and length. A cantilever shaft configuration is utilized with refined mesh structures near the transverse crack. The analysis leverages the frequency contour method with response surface methodology to visualize how crack depth and location influence normalized natural frequencies. Results indicate that crack depth has a significant impact on natural frequencies, while crack location has a subtler effect. Combining depth and location produces the most pronounced frequency variations. The corresponding R² values for the normalized first and third natural frequencies are 95.69% and 96.32%, while for the normalized second natural frequency this value is 75.70%. The study also demonstrates the use of frequency contour curves for accurate crack detection, with the 1st and 3rd natural frequencies being reliable indicators.

Three-Dimensional Profiling of Drilled Shafts Based on Four-Point Ultrasonic Measurement

Drilled piles are one of the most important foundation systems, and the shapes of the shafts prior to casting have a significant impact on their quality. In order to better obtain geometrical information on the shafts, this study proposes a profiling approach based on four-point ultrasonic measurement. First, data from horizontal sections are fitted using least squares to obtain sectional contour curves. Vertical contours are generated by iterative fitting to ensure the smoothness of the curves. Data-processing software is then used to merge the horizontal sectional curves and the vertical curves into a three-dimensional image that approximates the actual contours of the shaft.

DECISION ANALYSIS FOR OPTIMAL CONCEPTUAL DESIGN OF CONCURRENT BRAKE ACTUATOR

Enhanced capabilities and customization in designs demand a thorough conceptual design phase for products or equipment. To ensure favorable outcomes, a comprehensive analysis of multiple design concepts is vital. This paper aims to conduct a decision analysis to determine the most suitable design for a concurrent brake actuator (CBA) among a range of alternative design concepts. It presents the development of the conceptual design of the CBA mechanism, which serves as a foundational mechanism design for future CBA development. Four mechanism design concepts were generated by utilizing the expanding curvature contour design, linear contour design, tilted position linear slope, and the nonlinear radius profile of the cam roller. The assessment of potential failures in the CBA concept design was performed by employing the risk priority number (RPN) within the framework of Design Failure Mode and Effects Analysis (DFMEA). The data obtained from DFMEA was utilized to conduct thorough analyses of motion and stress performance for each conceptual design using commercial software. Subsequently, the most optimal concept design for the CBA was chosen. This decision was reached by selecting the CBA concept design that achieved the highest score during the evaluation process, which employed a weighted decision matrix. According to the findings, the optimal CBA concept design was determined to be CBA Design B with the highest total score of 102 based on an RPN score is 32 and maximum stress of 3.647 x 104 N/m2. Its expanding linear contour design effectively distributes nonlinear brake force while minimizing failure risk, forming the foundational framework for future CBA development.

Research on Simulation of Coating Fusion and Solidification Process in Electro-Spark Deposition

As a surface-strengthening technology, electro-spark deposition (ESD) is widely used in the strengthening and repair of key components of high-end equipment. In this paper, a fusion and solidification model of ESD coating is established. The method of heat–fluid–solid interaction is adopted to simulate the material’s flow and fusion process in the droplet dropping into the molten pool. The distribution law of the coating-matrix material inside the coating was studied. Through the heat transfer between the molten material and the matrix material, the condensation and solidification process of the coating-matrix material is simulated, the temperature change in the coating area during the solidification process is analyzed, and the solidification law of the molten material is studied. The results show that the deposition time reaches 80 μs, and the content of electrode material at the bottom of the molten pool reaches 4.5%. The content of electrode material in the upper region of the material gushing out of the molten pool is higher than that in the bottom region. The material outside the molten pool solidifies first, and the molten material in the molten pool gradually solidifies from the bottom up; the shape of the solidification interface is similar to the boundary of the molten pool. Through the single-point deposition experiment of electro-spark deposition, the surface morphology of the deposition point was observed. The depth of the concave part of the contour can reach 16 μm. The difference between the two contour curves in the horizontal direction is not much; the error of the diameter is about 4%. The element distribution of the surface and the section of the deposition point are analyzed. The diffusion distance in the depth direction of the coating is about 4μm, and the transverse diffusion distance inside the coating is 364 μm. The error is 7.6% compared with the experimental results. The cross-section structure of the deposition point was observed, and the error between the experimental results and the simulation results in diameter is about 11%. It was found that the material distribution in the sedimentary area is basically consistent with the simulation results, and the simulation results are verified from the side.

Distribution of local curvature values as a structural feature for off-line handwritten signature verification

In the paper, a new feature for describing a digital image of a handwritten signature based on the frequency distribution of the values of the local curvature of the signature contours, is proposed. The calculation of this feature on the binary image of a signature is described in detail. A normalized histogram of distributions of local curvature values for 40 bins is formed. The frequency values recorded as a 40-dimensional vector are called the local curvature code of the signature.During verification, the proximity of signature pairs is determined by correlation between curvature codes and LBP codes described by the authors in [23]. To perform the signature verification procedure, a two-dimensional feature space is constructed containing images of the proximity of signature pairs. When verifying a signature with N authentic signatures of the same person, N(N-1)/2 patterns of the proximity of pairs of genuine signatures and N images of pairs of proximity of the analyzed signature with genuine signatures are presented in the feature space. The Support Vector Machine (SVM) is used as a classifier.Experimental studies were carried out on digitized images of genuine and fake signatures from two databases. The accuracy of automatic verification of signatures on the publicly available CEDAR database was 99,77 % and on TUIT was 88,62 %.

The mid-level vision toolbox for computing structural properties of real-world images

Mid-level vision is the intermediate visual processing stage for generating representations of shapes and partial geometries of objects. Our mechanistic understanding of these operations is limited, in part, by a lack of computational tools for analyzing image properties at these levels of representation. We introduce the Mid-Level Vision (MLV) Toolbox, an open-source software that automatically processes low- and mid-level contour features and perceptual grouping cues from real-world images. The MLV toolbox takes vectorized line drawings of scenes as input and extracts structural contour properties. We also include tools for contour detection and tracing for the automatic generation of vectorized line drawings from photographs. Various statistical properties of the contours are computed: the distributions of orientations, contour curvature, and contour lengths, as well as counts and types of contour junctions. The toolbox includes an efficient algorithm for computing the medial axis transform of contour drawings and photographs. Based on the medial axis transform, we compute several scores for local mirror symmetry, local parallelism, and local contour separation. All properties are summarized in histograms that can serve as input into statistical models to relate image properties to human behavioral measures, such as esthetic pleasure, memorability, affective processing, and scene categorization. In addition to measuring contour properties, we include functions for manipulating drawings by separating contours according to their statistical properties, randomly shifting contours, or rotating drawings behind a circular aperture. Finally, the MLV Toolbox offers visualization functions for contour orientations, lengths, curvature, junctions, and medial axis properties on computer-generated and artist-generated line drawings. We include artist-generated vectorized drawings of the Toronto Scenes image set, the International Affective Picture System, and the Snodgrass and Vanderwart object images, as well as automatically traced vectorized drawings of set architectural scenes and the Open Affective Standardized Image Set (OASIS).

Efficient active contours with optical physical parameters for shoreline extraction: a general method and novel framework

ABSTRACT Accurate shoreline extraction is important for global climate change, land-sea interactions, and ocean dynamics. However, many current shoreline extraction methods have limitations in accuracy and efficiency when applied to different data, resulting from either empirical model parameters or limited image types. Considering the advantages of active contour in applying variational ideas to solve energy generalizations and the universal adaptability of optical physical parameters, an active contours with optical physical parameters (ACOPP) method that rapidly converges for shoreline extraction is proposed in this study. This model uses active contours to calculate the pixel-level energy generalization function of the image and combines the energy of the optical physical parameters to accelerate the process of contour curve approximation to the target edge by energy confrontation through iterative fitting, and improve the accuracy and efficiency of the target curves. Different images with multiple time phases in different regions were selected as experimental data, including GF2, SPOT-5, Sentinel-2, and Landsat-8, to demonstrate the accuracy, efficiency, and universality, while shoreline complexity coefficient was proposed for the study area division, which was used for shoreline extraction by ACOPP. Finally, the extraction results were analysed and validated, and the conclusions are as follows: ACOPP has a faster convergence speed in the extraction process than traditional methods, and the extraction results have a higher spatial resolution. The extraction results were highly accurate, and the mean absolute error (MAE) compared with the validation sets was < 2 pixels. The model is applicable to remote sensing images in which the normalized difference water index (NDWI) can be calculated, that is, optical remote sensing images containing green and near-infrared (or mid-infrared) bands. The experimental results prove the feasibility of ACOPP and a novel framework that combines ACOPP to extract target feature edge information for remote sensing images is proposed, the feasible and extensible of the frame have been verified.

Improving concave point detection to better segment overlapped objects in images

This study presents a method to improve state-of-the-art concave point detection methods as the first step towards effectively segmenting overlapping objects in images. The approach relies on analysing the curvature of the object contour. This method comprises three main steps. First, the original image is preprocessed to obtain the curvature value at each contour point. Second, the regions with higher curvatures are selected and a recursive algorithm is applied to refine previously selected regions. Finally, a concave point is obtained for each region by analysing the relative position of their neighbourhood. Furthermore, the experimental results indicate that improving the detection of concave points leads to better division of clusters. To evaluate the quality of the concave point detection algorithm, a synthetic dataset was constructed to simulate the presence of overlapping objects. This dataset includes the precise location of concave points, which serve as the ground truth for evaluation. As a case study, the performance of a well-known application, such as the splitting of overlapping cells in images of peripheral blood smears samples from patients with sickle cell anaemia, was evaluated. We used the proposed method to detect concave points in cell clusters and then separated these clusters by ellipse fitting.

The Grass Square Latch Paving Agency Based on the Bionic Spinning Knife

To better solve the problem of land desertification, this paper designed a portable grass grid-laying robot to lay grass squares to prevent wind and sand fixation. Among them, the ploughing module was proposed to use a bionic rotary tillage knife to improve soil cutting efficiency. By analyzing the characteristics of the forefoot claw contour curve of the groundhog, the point cloud data of the claw toe profile curve was obtained by reverse engineering technique, and then the Gaussian equation of the contour curve was fitted by MATLAB and the toe tip profile fitting curve was obtained. The BT model of the obtained fitting curve was applied to the national standard rotary tillage knife to design a preliminary bionic rotary tillage knife. When W0 was 50 mm and θ was 35°, the resistance of the rotary tillage knife was the least and the cutting performance was the best, and the final bionic rotary tillage knife was designed. In the field test, the data pointed out that compared with the traditional national standard rotary tillage knife, the maximum stress of the bionic rotary tillage knife was only 32.21 MPA, the average torque decreased by 10.16% compared with the national standard rotary tillage knife, the average power decreased by 7.68% to 71.4 KW, the tool quality was reduced by 8.26%, and the crushing rate was greatly improved. This study can provide some reference for the design of grass grid laying machines and rotary tillage knives to reduce resistance and consumption.

Designing the working surfaces of rotary planetary mechanisms

Purpose. To design a method for smoothing the working surfaces of stator and rotor with the use of computer simulation to eliminate the impact of the rotor on the stator when they interact. Methodology. Special and general methods of research have been used: interpolation of the point series – to determine the contour nodes of the rotor and the stator of the rotary-planetary machine; formation of B-splines – to construct a point series whose coordinates are structurally determined; technology of automated formation of curves in CAD-system SolidWorks – for modelling of functional surfaces of a planetary-rotary compressor. Findings. Algorithms for formation of the contours representing curves defined analytically or constructively with a given accuracy have been developed. The obtained contours are used in the CAD system as linear elements of the surface model. The developed method has been tested in the simulation of functional surfaces of a planetary-rotary compressor. Optimization of the body shape and rotor profiles in order to increase the productivity of the rotary-planetary machine has been carried out. Originality. The developed algorithms make it possible to determine the original point series belonging to any curve and provide a given interpolation accuracy when forming a B-spline contour or second-order curve arcs. Computer models of the body surfaces of the rotor are formed on the basis of the gear ratio of the planetary-rotary mechanism and the rotor dimensions. In order to increase the performance of the compressor, the working surfaces of the rotor have been optimized. The maximum volume of the working chamber was increased by increasing the radius of the moving gear of the planetary-rotary mechanism. In order to prevent the rotor from jamming during compressor operation, the rotor contour was changed. Practical value. The method for modelling the surfaces of complex shape in CAD-system has been developed on the basis of creating contours which with given accuracy represent lines from the surface determinant. This method makes it possible to form computer models of complex surfaces on the basis of a framework consisting of curves absent in CAD libraries.

Diverse optical solitons to the Radhakrishnan–Kundu–Lakshmanan equation for the light pulses

In this paper, we study the Radhakrishnan–Kundu–Lakshmanan equation (RKLE) that plays a key role in modeling the nonlinear propagation of the light pulses. Two novel methods namely Wang’s Bäcklund transformation-based method and Wang’s direct mapping method are employed to construct the diverse exact optical soliton solutions. Abundant exact solutions like the bright soliton solution, dark soliton solutions, singular soliton solutions, algebraic solitary wave solutions and the singular periodic wave solutions expressed in the form of the rational function type, double-exp function type, Sin-Cos function type, Tan function type, Cot function type, Sinh-Cosh function type, Tanh function type, Coth function type, Sech function type, Csch function type, Sec function type and Csc function type are obtained. The dynamics of the different exact solutions are presented through the 3D plot, contour and 2D curve, and the corresponding physical interpretations are elaborated in detail. It is confirmed that the proposed methods are effective and powerful, and can be adopted to construct the optical solitons of the other PDEs arising in the optical physics.

Free vibration of arbitrarily shaped plates with complex cutouts

In this paper, an exact model for free vibration analysis of arbitrarily shaped plates with various cutouts under general elastic boundary conditions is established. It combines the artificial connecting spring technique with the domain segmentation integral method (DSIM) proposed by the author. The arbitrarily shaped plate with cutouts is decomposed into several arbitrarily shaped subdomains based on the cutouts. The continuity conditions at the interconnecting interfaces of the subdomains are realized by artificial coupling springs. The energy expressions of the free vibration of the subdomain with arbitrary shape is calculated analytically or semi-analytically by using the DSIM. That is, in order to simplify the energy expressions into definite integrals, the arbitrarily shaped integration domain of the energy integrals is divided into several trapezoid domains with curved sides, and then the penalty method and Gram–Schmidt orthogonalization process are combined to generate the admissible functions for calculation. When the contour curve equations of the plate enable the energy integrals to be analytically calculated, the model can obtain the exact solution of free vibration of an arbitrarily shaped plate with various cutouts under general elastic boundary conditions; otherwise, the semi-analytic results can be obtained by combining Gauss–Legendre method. The convergence and accuracy of the proposed model are verified by comparing the numerical examples with results available in the literatures. The vibration characteristics of several complex shaped plates with various cutouts are studied. Taking elliptical plates with a rhombic cutout as examples, the effects of cutout size and position on the vibration characteristics of the plate are discussed. These new results can serve as benchmarks for further research.

Novel design of variable Mach number nozzle operated by a single jack

The increasing demand for the wide-range aircraft technique requires the ground test facilities with continuous variation of the Mach number. Owing to the rigorous aerodynamic foundation and simple operation, the single-jack flexible nozzle is widely used. However, there are still some problems in the original single-jack flexible nozzle, such as low Mach number and insufficient flow uniformity. This paper presents a novel design of the single-jack flexible nozzle with high flow uniformity and continuous variable Mach number, adopting flow field inverse design and elasticity inverse design. The new nozzle adopts a three-order transonic asymptotic solution and a B-spline axial velocity distribution, designed by the method of characteristics. By comparing with the original nozzle, the new nozzle no longer requires the conical flow assumption, and the flow fields are more uniform. Another improvement is the continuous contour curvature to ensure the coincidence of the aerodynamic profile and the elastic profile, avoiding the negative Mach waves generated by the curvature discontinuity. In addition, the new nozzle has the advantage of two Mach number design points. Similar to the squeeze theorem, the flow fields are uniform at the non-design points between two design points. The numerical results show that the new nozzle eliminates the Mach waves at different Mach number cases. Within the design range of Mach 2.0–4.0, the flow angle's maximum deviations do not exceed 0.2°, and the average deviations do not exceed 0.1°, meeting the national standard of 0.3°. The Mach number's maximum deviations are around 0.5% of Ma¯, the average deviations are less than 0.2% of Ma¯, and the standard deviations meet the national advanced standard. Even at Mach 1.5 and Mach 4.5 outside the design range, the new nozzle still performs well. The evaluation results validate the feasibility of the novel design, supporting the future construction of the variable Mach number facility.

Optimization with manufacturing constraints for composite laminates reinforced by curvilinear fibers through a parametric level set method

This paper presents the design optimization with manufacturing constraints for composite laminates reinforced by curvilinear fibers by using a parametric level set method. In each layer of the composite laminate, a level set function is defined by using the compactly supported radial basis functions (CS-RBFs), and the iso-contours of each level set function represent the fiber paths in one layer of the laminate. By this means, the fiber orientation at an arbitrary point in a layer can be computed by the orientation of the tangent vector of the iso-contour passing through this point. To avoid structure defects (such as gap/overlap, wrinkling and delamination) that would arise if the fiber paths are not parallel or their curvature is too large, the gradient norm and contour curvature radius of the level set functions are considered as constraints in the design optimization. The p-norm method is used to aggregate the constraints to improve the optimization efficiency. The coefficients of CS-RBFs are considered as design variables. Several numerical examples of compliance minimization and eigen-frequency maximization are investigated to verify the proposed method.

Multi-Tooth Cutting Method and Bionic Cutter Design for Broccoli Xylem (Brassica oleracea L. var. Italica Plenck)

During the harvesting of cut-stem vegetables, the structural parameters of cutters have an important influence on the harvesting effect. Structural parameters of stalks directly affect the cutting effect of the cutter. The thickness of the stalk xylem has a strong influence on the cutting stability and cutting surface effect of the cutter. In this paper, the effect of the broccoli stalk xylem on conventional toothless cutters was investigated using broccoli stalks as the cutting object. It was found that a thicker xylem leads to shear force fluctuations, which in turn affects the smooth operation of the cutting device. Taking locust mouthparts as the research object, a bionic multi-tooth cutting method is proposed in this paper to obtain the contour curve based on the locust upper jaw cutting tooth lobe. By establishing the regression equation, the contour curve of the cutting teeth is fitted accurately. The cutter edge is designed with the locust’s maxillary incisive lobe as the bionic object. ANSYS software was used to simulate the cutting of a double disc cutter and broccoli stalk. The effect of each factor was analyzed by response-surface regression to determine the optimal cutter speed, machine forward speed, cutting inclination, blade overlap, and optimal cutting position. The cutting test is verified via broccoli stalks and a cutting test bench to further determine the cutting device operating parameters. The optimal operating parameters of the cutting device were 0.239 m/s forward speed, 30.974-degree cutting edge angle, 10.066 mm blade overlap, and 467.511 rpm.

Image cognition using contour curvature statistics

Drawing on elementary invariance principles, we propose that a statistical geometric object, the probability distribution of the normalized contour curvatures (NCC) in the intensity field of a planar image has the potential to categorize objects. We show that NCC is sufficient for discriminating between cognitive categories such as animacy, size and type, and demonstrate the robustness of this metric to variation in illumination and viewpoint, consistent with psychological experiments. A generative model for producing artificial images with the observed NCC distributions highlights the key features that our metric captures, and those that it does not. More broadly, our study points to the need for statistical geometric approaches to cognition that build in both the statistics and the natural invariances of the visual world.

Automatically Extracting Rubber Tree Stem Shape from Point Cloud Data Acquisition Using a B-Spline Fitting Program

Natural rubber is an important and strategic raw material, used in tires, gloves, and insulating products, that is mainly obtained by cutting the bark of rubber trees. However, the complex contour curve of the rubber tree trunk is hard to fit using a tapping machine. Thus, a trunk contour curve collection would be useful for the development of tapping machines. In this study, an acquisition system based on laser-ranging technology was proposed to collect the point cloud data of rubber tree trunks, and a B-spline fitting program was compiled in Matrix Laboratory (MATLAB) to extract the trunks’ contour curves. The acquisition system is composed of power, a controller, a driver, a laser range finder, and data transmission modules. An automatic extraction experiment on the contour curves of rubber tree trunks was carried out to verify the feasibility and accuracy of using the acquisition system. The results showed that the degree of rubber tree trunk characteristic recognition reached 94.67%, which means that the successful extraction of the rubber tree trunk contour curves and the B-spline fitting program are suitable for the extraction of irregular curves of rubber tree trunks. The coefficient of variation of repeated collection was 0.04%, which indicates that changes in relative positions and acquisition directions have little influence on the extraction and the accuracy of the acquisition system, which are high and stable. Therefore, it was unnecessary to adjust the position of the acquisition device before the collecting process, which helped to improve the efficiency of acquisition considerably. The acquisition system proposed in this study is meaningful to the practical production and application of agroforestry and can not only improve the precision of the rubber tapping process by combining with an automatic rubber tapping machine but can also provide technical support for the prediction of rubber wood volume and the development of ring-cutting equipment for other fruit trees.