Triangular Surface Research Articles

Multi-spectral radiation thermometry based on an Alpha spectrum-LM algorithm under the background of high temperature and intense reflection.

In order to meet the needs of multi-spectral radiation temperature measurement under high temperature background, this paper studies the problems of reflected radiation interference and spectral emissivity difficult to obtain in high temperature and intense reflection environment. First, using discrete triangular surface elements and radiation angle coefficients, an analysis model of high temperature background reflected radiation is constructed to describe the variation characteristics of high temperature background reflected radiation. Secondly, the least squares support vector machine (LSSVM) is optimized by particle swarm optimization (PSO) algorithm, and an emissivity model identification algorithm based on Alpha spectrum-Levenberg Marquarelt (LM) algorithm is proposed, which has stronger applicability and accuracy than existing emissivity model identification methods. Finally, the high temperature background radiation and the emissivity model are combined to construct and solve the multi-spectral target equation, so as to realize the reflected radiation error correction and radiation temperature measurement under the high temperature and intense reflection background. The simulation and experimental comparison with the existing methods show that the temperature measurement error of the radiation temperature measurement method proposed in this paper is below 9.5K, which can effectively correct the reflected radiation error and further improve the temperature measurement accuracy.

Improving the prediction of the thermohydraulic performance of secondary surfaces and its application in heat recovery processes

Accurate prediction of heat transfer and friction performance is a key issue in the design of heat exchangers. This is particularly important in technologies that use secondary surfaces such as the plate and fin exchanger, where the number of surfaces available for design is large. Sets of experimental thermohydraulic data are available for most surfaces, but its use in sizing methodologies requires the development of generalised correlations. Some of the available correlations cover a limited Reynolds number interval as fitting these expressions to the whole range, causes prediction errors to increase. This work looks at the development of simple generalised correlations for surfaces such as louvered, rectangular, and triangular fins. The predictions extend from the laminar to the turbulent regime. Compared to experimental data, the average absolute errors of predictions for louvered surfaces are between 4% and 12% for Colburn and between 3% and 8% for the friction factor. For rectangular and triangular surfaces, the error is 5% on both parameters. Use of these correlations in design gives maximum volume prediction errors of 4.78%, while the use of other published generalised correlations results in volume errors in the order of 91.85%.

On the construction of polynomial minimal surfaces with Pythagorean normals

A novel approach to constructing polynomial minimal surfaces (surfaces of zero mean curvature) with isothermal parameterization from Pythagorean triples of complex polynomials is presented, and it is shown that they are Pythagorean normal (PN) surfaces, i.e., their unit normal vectors have a rational dependence on the surface parameters. This construction generalizes a prior approach based on Pythagorean triples of real polynomials, and yields more free shape parameters for surfaces of a specified degree. Moreover, when one of the complex polynomials is just a constant, the minimal surfaces have the Pythagorean–hodograph (PH) preserving property — a planar PH curve in the parameter domain is mapped to a spatial PH curve on the surface. Cubic, quartic and quintic examples of these minimal PN surfaces are presented, including examples of solutions to the Plateau problem, with boundaries generated by planar PH curve segments in the parameter domain. The construction is also generalized to the case of minimal surfaces with non–isothermal parameterizations. Finally, an application to the problem of interpolating three given points in R3 as the corners of a triangular cubic minimal surface patch, such that the three patch sides have prescribed lengths, is addressed.

Extracting Skeletons of Two-Manifold Triangular Mesh Surface for Planning Skeleton-Guided Five-Axis Surface Inspection Path

Abstract Skeleton curve-guided five-axis sweep scanning is an emerging surface inspection technique with marvelous inspection efficiency. The precondition of applying such a technique to a complex surface is to extract the skeleton curves of a two-manifold surface associated with partitioning the surface into compact surfaces. However, the work on extracting skeletons of two-manifold triangle mesh surfaces is scarce, as existing skeletonization methods mostly focus on either 2D planar shapes or 3D solid shapes. In this paper, we present a new approach to extract the skeletons on a two-manifold triangle mesh with boundaries. The skeletons are formed in the most intuitive manner of wave front propagation which is based on computing the initial value problem of geodesics on a triangle mesh. The step-length of wave front propagation is adaptively controlled to guarantee the appropriate density of skeleton points for having good connectivity. Experiments show that, as a direct application of the proposed skeleton generation and its associated surface partitioning result, the five-axis sweep scanning path of complex free-form surface can be generated conveniently. Experimental results also validate that the computation of our proposed approach is simpler and faster than the state-of-the-art geodesic Voronoi diagram (GVD) method when most of the two-manifold triangle mesh is nearly planar. Additionally, the augmented parameter used for tracing the wave front’s geodesic propagation information is helpful for the skeleton-based surface partition, which is necessary for skeleton curve-guided five-axis sweep scanning.

New practical discrete non-spherical N-body method: Validation with the Brazil nut effect

This paper presents an implementation of the contact dynamics method for discrete non-spherical particles. The algorithm can handle particles with a wide range of geometries as long as they are described in triangular surface meshes. The contact detection between particles is organized into two phases: coarse-grained and fine-grained contact detection. Specifically, different hierarchies of grids are utilized to perform fast contact detection: (a) A spatial sorting method is utilized for coarse-grained contact detection, where each non-spherical particle is represented with a corresponding bounding-sphere (b) The Polygonal Contact Method is introduced into the fine-grained contact detection phase to accurately determine the active contact areas between the interacting particles. These techniques solve the difficulties of determining the action point(s) of contact force and torque between non-spherical particles. The smooth (force-based) method is employed to calculate the contact force and torque, which is generally regarded as conforming to the actual physical process. Particularly, the non-linear Hertz and Mindlin-Deresiewicz theories are adopted to calculate the normal and tangential forces. The non-spherical Brazil nut effect under the shear vibration mode is simulated as validation by comparing with the existing experimental results. The simulation results confirmed that the convection and percolation mechanism mutually affect the nut heap's behavior and finally drive the rise of the Brazil nut from the bottom to the top layer.

Mixed Convection in a Lid‐Driven Cavity with Triangular Corrugations and Built‐in Triangular Block

The influence of triangular surface corrugations on the mixed convection characteristics in a tall lid-driven cavity for non-Newtonian power-law fluids is reported. In particular, numerical experimentations are executed for a range of parameters, such as aspect ratio of cavity, number of triangular corrugations, Richardson numbers, Prandtl numbers (Pr), power-law indexes, and at a constant Grashof number. The corrugation number seems to be the maximum impact for higher Prandtl number fluids. For taller cavities, higher Nusselt number values were obtained for Pr = 100. Triangular corrugations showed a modest change in the heat transfer augmentation in most of the considered parameters.

Simulation of the evolution of rough surfaces by sputtering using the binary collision approximation

The evolution of triangular surface structures with different sizes, the roughening of initially smooth surfaces, and the smoothing of initially rough surfaces were studied by computer simulations for sputtering by 5 keV argon on copper at normal incidence as a function of incident fluence. The program SDTrimSP-2D was used in binary collision approximation, diffusion was neglected. As already predicted by Sigmund [J. Mater. Sci. 1973, 8, 1545], a triangular ridge is relatively stable under bombardment at low fluences. However, at fluences above a critical fluence, it eventually flattens out and finally disappears. Initially smooth surfaces get rougher during bombardment, the roughness increases as the square root of incident fluence. This effect is more pronounced for larger metaparticle sizes. Initially rough surfaces get smoother by sputtering, the final smoothness depends on the initial degree of roughness. The smoothing process follows a characteristic pattern with smaller-scale roughness disappearing first and larger-scale roughness remaining stable until higher fluences. This effect gets visible in the Fourier-spectrum of the rough surface as damping of higher frequencies.

The Effect of Scanning Strategy on Intraoral Scanner's Accuracy.

The purpose of the present study was to examine the impact of scanning strategy on trueness and precision of the impression acquired from an intraoral scanner. Fifteen complete-arch, mandibular, post-orthodontic treatment casts were scanned with a laboratory scanner (Identica SE 3D, Medit) as the gold standard, and with an intraoral scanner (i500 Medit) following three different paths of the scanning head over the arch (scanning strategies A, B, and C). The hand scans were performed twice by one examiner and repeated by a second examiner, resulting in 180 triangular mesh surfaces (digital casts). The meshes were superimposed on the gold standards using the Viewbox 4 software. The closest distances between the meshes were computed and trueness and precision were evaluated using a General Linear Model. An interaction was found among the examiner and strategy. The accuracy of complete-arch impressions was affected by the scanning strategy; the manufacturer’s recommended strategy (A) was statistically significantly better (p < 0.05) than B and C, which were similar. An average accuracy below 50 μm, which is clinically acceptable in most orthodontic procedures, was achieved with all the examined scanning strategies.

A high-efficiency preparation method of super wear-resistant superhydrophobic surface with hierarchical structure using wire electrical discharge machining

Superhydrophobic surface has extensive application prosperity for in aerospace, shipping, armament and other fields due to its excellent performance, such as anti-icing, self-cleaning, metal corrosion resistance, oil/water separation. However, because of complex preparation process and wear resistance, the engineering application of superhydrophobic surfaces is limited. To address this issue, this paper proposes a high-efficiency preparation method of super wear-resistant superhydrophobic surface with hierarchical structure using wire electrical discharge machining (WEDM). Firstly, the single-step preparation principle of hierarchical structure using WEDM is introduced, which is consists of micron-grade discharge morphology and submillimeter-grade surface texture. Secondly, the preparation process of micron-grade discharge morphology is investigated to obtain the maximum apparent contact angle (ACA). It was found that the micron-grade discharge morphology and the absorbed organics can increase apparent contact angle from 75.5° to 121°. Additionally, the preparation process of submillimeter-grade surface texture is studied to obtain the best triangular surface texture. A gas-liquid-solid contact angle (CA) simulation model is established to analyze the effect of the surface texture size on the contact angle. The experimental results show that the maximum contact angle can be up to 156.5° through combining the maximum apparent contact angle with the best triangular surface texture. The simulation data of contact angle shows a good agreement with experimental data. Finally, the prepared superhydrophobic surface is proved to be of excellent time durability and wear resistance. This study can provide some guiding value for preparing super wear-resistant superhydrophobic surface.

Jewelry Art Modeling Design Method Based on Computer-Aided Technology

In order to improve the effect of jewelry art modeling design, this paper applies computer-aided technology to jewelry art modeling design. Moreover, in order to solve the situation that the given data points do not form a topological rectangular grid, an interpolation algorithm based on triangular BB surfaces is specially studied in this paper. The algorithm automatically triangulates the given scattered data points to establish the topological relationship between the data points, and modified and optimized the triangulation algorithm according to the requirements of jewelry art modeling design. In addition, the improved algorithm can handle the triangulation problem of spatial data points well, and the triangulation speed is fast. The experimental verification shows that the jewelry art modeling design method based on computer-aided technology proposed in this paper can effectively improve the effect of jewelry art modeling design.

Directional transport of droplets impacting on superhydrophobic opening triangular groove surfaces

Directional droplet transport is of great importance to various processes including heat transfer, water harvesting and microfluidics. Here, a facile superhydrophobic opening triangular groove surface was proposed, and the directional transport behavior of droplets impacting on the surface was observed. The results show that the essence of the directional transport on the opening triangular groove surface can be attributed to the interaction between the impinging droplet and the groove sidewall, and the directional transport distance is regulated by the contact area during the interaction. Further, by controlling the depth of triangular groove, the triangular opening angle, the impacting point position and the Weber number, the contact area between the droplet and the groove sidewall during the interaction can be changed, leading to the variation of directional transport distance. This study provides a new method for directional droplet transport on superhydrophobic surfaces and offers more options for the manipulation of droplet behavior.

AUTOMATIC TEXTURE MAPPING METHOD FOR 3D MODELS TO CIRCUMVENT OCCLUSION THROUGH 3D SPATIAL THROUGH-VIEW RELATIONSHIPS BETWEEN IMAGES,MODELS, AND POINT CLOUDS

Abstract. Photorealistic 3D models play an important role in various applications related to smart cities. Texture mapping plays a crucial role as the last step of 3D reconstruction. The texture of the model directly reflects the visualization and realism of the model. In complex city scenes, objects often have varying degrees of occlusion from one another. Traditional methods to circumvent occlusion by image or model data are not very effective. In this paper, we propose an automatic texture mapping method for 3D models to circumvent occlusion through 3D spatial through-view relationships between images, models, and point clouds. First of all, calculate the density and voxel resolution of the point clouds, the point clouds here can be either dense matching point clouds or laser point clouds. Voxelization is based on point clouds, voxels generated by voxelization can reflect the spatial location of the point clouds. Secondly, to determine whether there is an occlusion of voxels between the image and the model vertices based on the spatial through-view relationship between the image, the model, and the voxels, and filter out the unobstructed images. Finally, by optimizing the data items of the Markov random field, the shading function is added to the original data items for evaluating the shading condition, based on which the most suitable image is selected for texture mapping of a triangular surface of the model. Loop computation to complete the unobstructed texture mapping of the entire model. In this paper, the public test datasets released by the International Society for Photogrammetry and Remote Sensing (ISPRS) and several urban area datasets collected by ourselves are incorporated to test the performance of the proposed method. Both qualitative and quantitative cross-sectional comparisons with existing texture mapping algorithms are conducted and presented. Experimental results indicate that our method can effectively circumvent occlusion for automated texture mapping, and generate 3D models with fewer obstructed textures, which largely improves the visual quality and realism of the models.

An Intelligent Identification and Repair Method for Annular Holes in 3D Printing.

With the popularization of 3D printing in the consumer goods field, there is a specific type of hole named annular hole in the narrow features, surface bumps, or folded parts of products. The traditional triangular mesh repair method is not effective for such holes. The structural characteristics of the annular hole are analyzed in this research, and the definition and identification method for annular holes is presented through the shape and position relationship of two closed hole lines. To improve the repair efficiency and the applicability of the algorithm, the traditional hole repair method and process are ameliorated. A repair strategy of hole boundary stitching and filling, triangulation optimization, implicit surface construction based on Radial Basis Function, and surface integral deformation is adopted to achieve a smooth joint of the repaired hole surface with the original triangular mesh surface. The method can ensure surface smoothness and accuracy. Finally, two experiments are carried out to verify the repair quality and efficiency of our method. Compared with Geomagic software, the proposed method can automatically identify and repair annular holes with fewer defects and similar efficiency. Compared with a traditional hole repair method, the evaluation results demonstrate that the proposed method is much faster, and the repair quality is higher without the influences of human operations. It is shown that our method can be applied to annular hole repair of 3D printing models without the participation of technicians.

Feature sensitive geometrically faithful highly regular direct triangular isotropic surface remeshing

Feature sensitive geometrically faithful highly regular direct triangular isotropic surface remeshing

Ray Tracing Acceleration Algorithm Based on FaceMap

Raster method and ray tracing are two important algorithms in computer graphics. The former, raster method, marked by high speed and efficiency, has the disadvantage of an unrealistic rendering effect. By contrast, ray tracing requires considerable computing resources and time despite its advantages of high fidelity and simple structure, thus only suitable for offline rendering. Given such limitations, a ray-tracing acceleration algorithm that combines the raster method and ray tracing is proposed in this study based on FaceMap, a two-dimensional data structure that stores surface distribution under point light or the view of a camera. Firstly, all triangular surfaces of the 3D model are rasterized by linear surface projection to form the surface distribution of a spherical panorama. Secondly, the structure of FaceMap is adopted to store the distribution information of all the surfaces in the scene. Thirdly, the data on the intersecting surfaces in this direction are collected by projecting the ray onto FaceMap in the ray-tracing process, thus reducing the intersection and propagation operations and improving the efficiency. Four object models including chessboard, grass patch, bust, and typewriter are selected for comparative rendering experiments. Our proposed method is used to compare with Rhino and VRay rendering software, respectively. The results show that our proposed method obtained better rendering effects within greatly reduced rendering time (© 2018Optical Society of America).

Stability Analysis of “Support-Surrounding Rock” System for Fully Mechanized Longwall Mining in Steeply Dipping Coal Seams

The key to safe and efficient longwall mining of steeply dipping seams lies in the stability control of the “support-surrounding rock” system. This study analyzes the difficulties encountered when controlling the stability of the support during the longwall mining process of steeply dipping coal seams in terms of the characteristics of the nonuniform filled-in gob using a combination of physical tests, theoretical analyzes, and field measurements. Considering the floor as an elastic foundation, we built a “support-surrounding rock” mechanical model using data obtained on support-surrounding rock systems in different regions and the laws of support motion under different load conditions. Our findings are summarized as follows: first, depending on the angle of the coal seam, the caving gangue rolls (slide) downward along the inclined direction, resulting in the formation of a nonuniform filling zone in the deep gob where the lower, middle, and upper sections are filled, half-filled, and empty, respectively. In addition, an inverted triangular hollow surface is formed on the floor of the gob in the middle and upper sections behind the support. Furthermore, as the angle of the coal seam, length of the working face, and mining height increase, the characteristics of the nonuniform filled-in gob are enhanced. Second, we found that because of the gangue support, the “support-surrounding rock” system is relatively stable in the lower part of the working face; however, in the middle and upper sections of the working face, the contact method and loading characteristics of the support are more complicated, making stability control difficult. Third, the magnitude and direction of the load, action point, and mining height affect the stability of the support to varying degrees, with the tangential load and action position of the roof load having the most significant impacts on the stability of the support. Under loading by the roof, rotation and subsidence of the support inevitably occur, with gradually increasing amplitudes and effects on the intersupport and sliding forces. Finally, we found that overall stability can be achieved by adopting measures involving “sliding advancement of supports” and applying a “down-up” removal order. These research results serve as a significant reference and guidance for longwall mining applications.

Development of Square and Triangle Surface Area Pocket Books as Learning Media for Junior High Schools

This study was conducted at SMP Negeri 8 Lhokseumawe about the development of rectangular and triangular pocket books against the background of the lack of availability of textbooks in schools, coupled with inadequate learning media that supports students to study independently, thus causing low learning motivation of students. and learning outcomes have not increased. The aims of this study: (1) To determine the validity of the development of rectangular and triangular surface area pocket books as learning media for junior high schools, (2) to determine the feasibility of developing square and triangular surface area pocket books as learning media for junior high schools, (3) to find out responses teachers and students on the development of rectangular and triangular surface area pocket books as learning media for junior high schools. The design of this research is research and development called Research and Development (R D) using the Borg and Gall model modified into 7 stages according to Sugiyono. Data collection techniques using validation sheets and questionnaires. The results obtained from the validation of media experts obtained a percentage of 91.48% and material experts obtained a percentage of 83.52% with a very valid category. The results of the feasibility of pocket books obtained a percentage of 84.69% with a very decent category, and teacher responses to pocket books obtained a percentage of 89.52% in a very good category, and students' responses to pocket books obtained a percentage of 80% in a good category. So it can be concluded that pocket books can be well received at SMP Negeri 8 Lhokseumawe. Recommendations from the research are expected to schools, institutions related to educational practitioners to conduct trials on a broad group so that the level of effectiveness can be known to support learning.

A Statistical Shape Model of the Morphological Variation of the Infrarenal Abdominal Aortic Aneurysm Neck.

Hostile aortic neck characteristics, such as short length and large diameter, have been associated with type Ia endoleaks and reintervention after endovascular aneurysm repair (EVAR). However, such characteristics partially describe the complex aortic neck morphology. A more comprehensive quantitative description of 3D neck shape might lead to new insights into the relationship between aortic neck morphology and EVAR outcomes in individual patients. This study identifies the 3D morphological shape components that describe the infrarenal aortic neck through a statistical shape model (SSM). Pre-EVAR CT scans of 97 patients were used to develop the SSM. Parameterization of the morphology was based on the center lumen line reconstruction, a triangular surface mesh of the aortic lumen, 3D coordinates of the renal arteries, and the distal end of the aortic neck. A principal component analysis of the parametrization of the aortic neck coordinates was used as input for the SSM. The SSM consisted of 96 principal components (PCs) that each described a unique shape feature. The first five PCs represented 95% of the total morphological variation in the dataset. The SSM is an objective model that provides a quantitative description of the neck morphology of an individual patient.

Morphological correlates of distal fibular morphology with locomotion in great apes, humans, and Australopithecus afarensis.

ObjectivesRecent studies highlighted the importance of the fibula to further our understanding of locomotor adaptations in fossil hominins. In this study, we present a three‐dimensional geometric morphometric (3D‐GM) investigation of the distal fibula in extant hominids and Australopithecus afarensis with the aim of pointing out morphological correlations to arboreal behavior.MethodsThree‐dimensional surface meshes of the distal fibula were obtained using computer tomography for 40 extant hominid specimens and laser scanner for five A. afarensis specimens. Distal fibula morphology was quantified positioning 11 fixed landmarks, 40 curve semilandmarks, and 20 surface landmarks on each specimen. A generalized Procrustes analysis (GPA) was carried out on all landmark coordinates followed by Procrustes ANOVA. Principal component analysis (PCA) was performed on the GPA‐aligned shape coordinates. Kruskal‐Wallis tests and Mann–Whitney test were performed on scores along PCs.ResultsGreat apes are characterized by a shorter subcutaneous triangular surface (STS), more downward facing fibulotalar articular facets, more anteriorly facing lateral malleolus and wider/deeper malleolar fossa than humans. Within great apes, orangutans are characterized by more medially facing fibulotalar articular facets. Australopithecus afarensis shows a unique distal fibular morphology with several traits that are generally associated more to arboreality and less to bipedalism such as a short STS, a more anteriorly facing, laterally pointing malleolus and deeper and larger malleolar fossa.ConclusionsThe distal fibula morphology is indicative of locomotor patterns within extant hominids. The 3D‐GM method presented here can be successfully used to further our understanding of arboreal adaptations in fossil hominins.

Numerical analysis of thermoacoustically driven thermoacoustic refrigerator with a stack of parallel plates having corrugated surfaces

Most numerical research on thermoacoustic devices with a stack made of parallel plates has considered a rectangular form for the plate. However, a variety of plate shapes can improve the heat transfer and performance of the stack. In this paper, a 2D numerical model based on computational fluid dynamics (CFD) analysis is used to examine the efficiency of thermoacoustic couples using a diversity of plate surfaces. For this investigation, flat plates and others profiles with corrugated surfaces (rounded and triangular surfaces) were tested to compare their performances and the effect of plate form on thermoacoustic systems. The efficiency of the thermoacoustic engine (TAE) is measured in terms of the generated acoustic pressure and the performance of the thermoacoustic refrigerator (TAR) is considered in terms of the temperature gradient along the refrigeration stack. The results showed that plates profile with irregular surfaces improves the generated acoustic pressure due to the increase of the stack porosity known as the blockage ratio (BR). The triangular shape performed better with a 10% gain than using a flat plate, followed by rounded ripples with a 5.2% increase in pressure amplitude compared to flat surfaces. Unlike in TAR, it was revealed that the stack made of flatform could produce a higher temperature difference (∆T) among the refrigeration stack extremities. By using rounded ripples, ∆T undergoes a reduction up to 52%, and 65% if using triangular ripples compared to flatform. From this investigation, it is observed that the stack with corrugated plates is the most suitable for TAE; however, the flat plates generate a higher temperature difference in TAR.