Straight Edge Research Articles

A Ritornello Pedagogy: Troubling School Art Orthodoxies

AbstractIn the studio, there are routines and rituals to be observed. One of those is making gesso. The quantities change each time and the ingredients vary, but the mechanical process remains the same: soak rabbit skin glue for 3 hours, double burner melt the glue, sieve in champagne chalk whiting, stir slowly, and tap the sides to remove air bubbles. Brush on first layer. Dry. Sand. Repeat × 10. Out of repetition each new territory is unique with its own lumps, drips and curves on a straight edge board. Making gesso is a kind of ritornello. Drawing on Deleuze and Guattari, a ritornello is a repetition leading to a transformation; it is a methodical kind of time that is rhythmic, local and spatiotemporal. It contravenes the idea of a universal, overarching time to consider heterogeneous, plural experiences of time in the art classroom. Ritornellos exist in both the studio and the art classroom, but in the art classroom, they often sediment into endless repetitions without rupture: tonal scales, colour wheels, drawing grids and pastiche. We apply the concept of ritornello to pedagogy in Secondary Art and Design education to think about school art orthodoxies and how they can be reterritorialised.

Design of bi-axial piezoelectric MEMS micro mirror with gimbal actuator for dynamic decoupling

Abstract This study presents a novel structural design of a bi-axial piezoelectric micro-electro-mechanical-systems scanning mirror aimed at preventing the dynamic coupling between the two scanning axes and avoiding distortion of the scanning pattern. In the proposed design, the gimbal actuator, constrained by torsional springs at both ends, not only serves as the torque generation component for the actuation of one axis but also acts as a pivot to prevent structural interference between the two axes during scanning. This approach achieves the advantages of decoupling and compactness simultaneously. Simulations indicate that the gimbal actuator experiences very small displacement during y-axis actuation, thus realizing the dynamic decoupling from the x-axis scanning unit. To evaluate the proposed designs, fabrication processes were adopted on a silicon-on-insulator wafer with a lead zirconium titanate film. The miniaturized scanners, featuring a mirror with a 1.2 mm diameter, were realized on a compact 5 × 5 mm2 chip. Measurements indicate that the resonant frequencies of x-axis and y-axis scanning are 2.69 kHz and 4.29 kHz, respectively, and the optical scanning angles reach 33° and 21° under an 8 Vpp driving voltage. Additionally, measurements show that the displacement ratio between the central mirror and the gimbal actuator can reach up to 17 during y-axis actuation, verifying the concept of dynamic decoupling. The bi-axial Lissajous scanning pattern with straight edges also demonstrates the effective decoupling by the proposed gimbal actuator design.

Ceracis luci sp. nov., the first Ciidae species (Coleoptera: Tenebrionoidea) from the Caatinga biome

Ceracis luci sp. nov., the first Ciidae species from the Caatinga biome, is described based on individuals collected in Licínio de Almeida, in the state of Bahia, Northeast Brazil. The species is recognizable mainly by the following characteristics: antennae with 8 antennomeres and subseriate elytral punctation; male anterocephalic edge produced forward and slightly elevated upward forming a wide lamina with a straight edge (when seen from above); male anterior edge of pronotum produced forward as a plate deeply emarginate at middle forming two horns, almost parallel to each other and with rounded apices; and female ovipositor lacking gonostyli. Ceracis luci sp. nov. is morphologically similar to Ceracis pullulus (Casey), for which we provide information on the morphology of the abdominal terminalia of males and females and new geographic distribution records.

FACE: Feature-preserving CAD model surface reconstruction

Feature lines play a pivotal role in the reconstruction of CAD models. Currently, there is a lack of a robust explicit reconstruction algorithm capable of achieving sharp feature reconstruction in point clouds with noise and non-uniformity. In this paper, we propose a feature-preserving CAD model surface reconstruction algorithm, named FACE. The algorithm initiates with preprocessing the point cloud through denoising and resampling steps, resulting in a high-quality point cloud that is devoid of noise and uniformly distributed. Then, it employs discrete optimal transport to detect feature regions and subsequently generates dense points along potential feature lines to enhance features. Finally, the advancing-front surface reconstruction method, based on normal vector directions, is applied to reconstruct the enhanced point cloud. Extensive experiments demonstrate that, for contaminated point clouds, this algorithm excels not only in reconstructing straight edges and corner points but also in handling curved edges and surfaces, surpassing existing methods.

Roof plane parsing towards LoD-2.2 building reconstruction based on joint learning using remote sensing images

Building models are important for urban studies. Remote sensing multi-spectral (MS) images are widely used for its rich semantic information. The lack of geometry features is fulfilled by introducing photogrammetry derived digital surface models (DSMs), resulting in pairs of DSMs and MS images. Utilizing such pairs and a convolutional neural network, level of detail (LoD) 2.2 building models, which contain roof planes and major roof elements (e.g. dormers), are reconstructed in this work. Leveraging both raster and vector predictions, 3-D building models with straight edges and sharp corners are obtained. The proposed two-stage method first extracts vectorized roof lines from pairs of DSMs and RGB images, followed by generation of detailed 2-D and 3-D polygonal building models. We conducted our experiments based on two datasets: a custom dataset in Landsberg am Lech in Germany, and an open dataset named Roof3D. For the custom dataset, our proposed model achieved mean average precision (mAP) for building roof vertices of 64.3% and for building roof lines of 54.5% at highest. Mean precision and recall for reconstructed 2-D building roof plane polygons are 52.2% and 54.7% respectively. For the Roof3D dataset, mAP is reported to be 25.3% and 12.4% for the extracted building roof lines and roof plane polygons respectively.

The starting vortices generated by bodies with sharp and straight edges in a viscous fluid

A two-dimensional body that moves suddenly in a viscous fluid can instantly generate vortices at its sharp edges. Recent work using inviscid flow theory, based on the Birkhoff–Rott equation and the Kutta condition, predicts that the ‘starting vortices’ generated by the sharp and straight edges of a body – i.e. the vortices formed immediately after motion begins – can be one of three distinct self-similar types. We explore the existence of these starting vortices for a flat plate and two symmetric Joukowski aerofoils immersed in a viscous fluid, using high-fidelity direct numerical simulations (DNS) of the Navier–Stokes equations. A lattice Green's function method is employed and simulations are performed for chord Reynolds numbers ranging from 5040 to 45 255. Vortices generated at the leading and trailing edges of the flat plate show agreement with the derived inviscid theory, for which a detailed assessment is reported. Agreement is also observed for the two symmetric Joukowski aerofoils, demonstrating the utility of the inviscid theory for arbitrary bodies. While this inviscid theory predicts an abrupt transition between the starting-vortex types, DNS shows a smooth transition. This behaviour occurs for all Reynolds numbers and is related to finite-time effects – there is a maximal time for which the (self-similar) starting vortices exist. We confirm the inviscid prediction that the leading-edge starting vortex of a flat plate can be suppressed dynamically. This has implications for the performance of low-speed aircraft such as model aeroplanes, micro air vehicles and unmanned air vehicles.

Robotic Grasping of Unknown Objects Based on Deep Learning-Based Feature Detection.

In recent years, the integration of deep learning into robotic grasping algorithms has led to significant advancements in this field. However, one of the challenges faced by many existing deep learning-based grasping algorithms is their reliance on extensive training data, which makes them less effective when encountering unknown objects not present in the training dataset. This paper presents a simple and effective grasping algorithm that addresses this challenge through the utilization of a deep learning-based object detector, focusing on oriented detection of key features shared among most objects, namely straight edges and corners. By integrating these features with information obtained through image segmentation, the proposed algorithm can logically deduce a grasping pose without being limited by the size of the training dataset. Experimental results on actual robotic grasping of unknown objects over 400 trials show that the proposed method can achieve a higher grasp success rate of 98.25% compared to existing methods.

PerfectTailor: Scale-Preserving 2-D Pattern Adjustment Driven by 3-D Garment Editing.

We address the problem of modifying a given well-designed 2-D sewing pattern to accommodate garment edits in the 3-D space. Existing methods usually adjust the sewing pattern by applying uniform flattening to the 3-D garment. The problems are twofold: first, it ignores local scaling of the 2-D sewing pattern such as shrinking ribs of cuffs; second, it does not respect the implicit design rules and conventions of the industry, such as the use of straight edges for simplicity and precision in sewing. To address those problems, we present a pattern adjustment method that considers the nonuniform local scaling of the 2-D sewing pattern by utilizing the intrinsic scale matrix. In addition, we preserve the original boundary shape by an as-original-as-possible geometric constraint when desirable. We build a prototype with a set of commonly used alteration operations and showcase the capability of our method via a number of alteration examples throughout the article.

Design, optimization and analysis of a modified Savonius hydro-kinetic turbine (MSHT) with curved winglet and straight blade

The pico-scale power generation in remote locations is now very promising due to small-scale power requirements. The major challenge is harnessing the same from the run-off river streams or canals that have low free-stream flow-speed (less than 1 m/s). Savonius hydro-kinetic turbine can self-start in such flow streams, but it exhibits poor efficiency. This study proposes a novel airfoil-shaped curved winglet that can enhance the functionality of this turbine. The popular semi-circular blade is replaced with a hybrid blade profile consisting of a curved winglet at the front-edge, which is tore out from NACA 63415 airfoil, followed by a straight blade section up to the trailing edge, thereby resulting in a modified Savonius hydro-kinetic turbine. The curved winglet minimizes negative torque effect on the rotor, while the long straight edge offers a greater moment-arm and gap-flow. The research is performed in two stages. In the first stage, three different models of the turbine with various combinations of blade overlapping, side clearance, and winglet offset are designed. Transient Computational Fluid Dynamics (CFD) simulations are run to assess and compare the model performances under different low flow-speeds. Taguchi optimization is then performed to obtain a combination of best design and operating conditions for higher performance. In the second stage, two more design variables of the winglet, namely winglet arc angle and cut-out arc section are introduced on the previous best model and detail analysis is done to further improve the turbine performance. Finally, the two best models are compared to obtain important performance insights of the turbine. Results show that winglet parameters with best cut-out arc section and offset improve performance more than the performance with traditional overlapping or side clearance design considerations. The maximum Cp and CT of 0.36 and 0.75 are obtained for the best model at the best winglet arc angle (a1) of 30° for flow-speed 0.4 m/s, and TSR 0.7 with combinations of 20 % blade overlapping, 6.14 % side clearance, and 15 mm winglet offset. The performance parameters of the turbine is also compared with the existing modified Savonius-turbine designs to emphasize the essential improvement of the current design.

Improved British pendulum test using curved slider

ABSTRACT The conventional British pendulum tester (BPT) utilises a cuboid rubber slider and measures the skid resistance between its front slider edge and a test surface. This standard test method is known to produce erroneous skid resistance measurements on grooved pavements, owing to impacts between the straight slider edge of BPT and the vertical walls of pavement grooves. To overcome the problem, this study replaced the cuboid slider with a curved slider having an external radius of 100 mm, constructed of the same rubber material as the standard BPT rubber slider. The ability of the proposed improved device to eliminate the vertical-wall impact problem and provide correct skid resistance measurements of a grooved surface was verified experimentally and numerically. A full-scale prototype was fabricated for this purpose. Experimental validation tests involving the standard cuboid-slider BPT and the curved-slider BPT were conducted, and the test results were analysed with the aid of finite-element numerical models. The results confirmed that the proposed curved-slider BPT can provide more consistent and accurate skid resistance measurements compared to the standard BPT, for both grooved and ungrooved pavements.

REVISITING THE CRETACEOUS LUNGFISH <em>ATLANTOCERATODUS IHERINGI</em> (AMEGHINO 1898) FROM THE MATA AMARILLA FORMATION (ARGENTINA) WITH COMMENTS ON TOOTH PLATES HISTOLOGY

Atlantoceratodus iheringi (Ameghino 1898) from Argentine territory is restudied based on its known tooth plates and newly discovered material, which includes previously unknown skull roof bones and vomerine tooth plates. The latter represent the first records of such elements from the Mesozoic era in South America. The comparative morphological analysis reveals its distinctiveness from other dipnoans, and offers valuable data for future systematic and phylogenetic research. The pterygopalatine tooth plates display narrow-based first denticulations and lack anterior wear facets, with the inner angle positioned at the level of the second denticulation. Similarly, the prearticular tooth plates feature straight mediolingual edges, and a wide-based first denticulation without sinuosities at the tip. Histological sections are performed and analyzed in detail for the first time. A. iheringi presents in this aspect distinctive features such as: large-lumen denteons tending to cluster together, circumdenteonal dentine arranged in a double band (an inner birefringent and an outer monorefringent), and a disordered interdenteonal dentine, with birefringence surrounding denteons and areas with monorefringence. A. iheringi exhibits histological structure closer to Mesozoic and Cenozoic dipnoans than Paleozoic, especially resembling the disposition observed in the Upper Cretaceous Patagonian species Metaceratodus baibianorum. The wide distribution of features designated as diagnostic for Atlantoceratodus is discussed.

Constructible Sandwich Cut

In mathematical measure theory, the “Ham-Sandwich” theorem states that any n objects in an n-dimensional Euclidean space can be simultaneously divided in half with a single cut by an (n-1)-dimensional hyperplane. While it guarantees its existence, the theorem does not provide a way of finding this halving hyperplane, as it is only an existence result. In this paper, we look at the problem in dimension 2, more in the style of Euclid and the antique Greeks, that is from a constructible point of view, with straight edge and compass. For two arbitrary regions in the plane, there is certainly no hope for constructing the halving line by straight edge and compass. At the opposite end, for two circles the problem is very easy, as the halving line is simply the line which passes through the centers of both circles. It turns out that for the case of two equilateral triangles the problem is already interesting and challenging from a constructible point of view, and this is the main goal of our paper. We will investigate the “deltoid” of a triangle, that is, three hyperbolas which form an “envelope” of all halving lines of a given triangle, and how to construct halving lines with certain given properties.

Low-Level Visual Features of Window Views Contribute to Perceived Naturalness and Mental Health Outcomes.

Previous studies have shown that natural window views are beneficial for mental health, but it is still unclear which specific features constitute a 'natural' window view. On the other hand, studies on image analysis found that low-level visual features (LLVFs) are associated with perceived naturalness, but mainly conducted experiments with brief stimulus presentations. In this study, research on the effects of window views on mental health was combined with the detailed analysis of LLVFs. Healthy adults rated window views from their home and sent in photographs of those views for analysis. Content validity of the 'ecological' view assessment was evaluated by checking correlations of LLVFs with window view ratings. Afterwards, it was explored which of the LLVFs best explained variance in perceived percentage of nature and man-made elements, and in ratings of view quality. Criterion validity was tested by investigating which variables were associated with negative affect and impulsive decision-making. The objective and subjective assessments of nature/sky in the view were aligned but objective brightness was unreliable. The perceived percentage of nature was significantly explained by green pixel ratio, while view quality was associated with fractals, saturation, sky pixel ratio and straight edge density. The higher subjective brightness of rooms was associated with a lower negative affect, whereas results for impulsive decision-making were inconsistent. The research highlights the validity to apply LLVFs analysis to ecological window views. For affect, subjective brightness seemed to be more relevant than LLVFs. For impulsive decision-making, performance context needs to be controlled in future studies.

Precision Modulation and the Shadow Blister Phenomenon in Optical Diffraction Using Straight-Edge Apertures

The shadow blister effect, depicting the distortion of shadows when two objects overlap, is an optical phenomenon observable in sunlight without requiring specialized lab equipment. Despite its seemingly straightforward nature, this effect challenges explanation through ray theory and the Fresnel diffraction equation in certain regions. Conversely, the shadow blister effect exhibits both linear and nonlinear behavior corresponding to the steady variation of the transverse distance between the two unplanar straight edges along the optical axis. This article explores the shadow blister effect alongside the diffraction of a straight edge, revealing fundamental aspects of the diffraction phenomenon. The experimental study introduces a diffraction model adept at elucidating the shadow blister effect. This model relies on an inhomogeneous fractal space, potentially generated by objects near their surfaces, including the edges of barriers.

Research on the Sealing Mechanism of Split-Liner High-Pressure Hydrogen Storage Cylinders

Hydrogen storage is a crucial factor that limits the development of hydrogen energy. This paper proposes using a split liner for the inner structure of a hydrogen storage cylinder. A self-tightening seal is employed to address the sealing problem between the head and the barrel. The feasibility of this structure is demonstrated through hydraulic pressure experiments. The influence laws of the O-ring compression rate, the distance from the straight edge section of the head to the sealing groove, and the thickness of the head on the sealing performance of gas cylinders in this sealing structure are revealed using finite elements analysis. The results show that when the gas cylinder is subjected to medium internal pressure, the maximum contact stress on the O-ring extrusion deformation sealing surface is greater than the medium pressure. There is sufficient contact width, that is, the arc length of the part where the stress on the O-ring contact surface is greater than the medium pressure, so that it can form a good sealing condition. At the same time, increasing the compression ratio of the O-ring and the head’s thickness will help improve the sealing performance, and reducing the distance from the straight edge section of the head to the sealing groove will also improve the sealing performance.

Composite control of airfoil broadband noise based on the combination of porous material and serrated trailing edges

Improving the noise reduction capability of airfoil broadband noise through serrated trailing edge design is a challenging task. To address this, we propose a novel porous-serrated trailing edge design where the gaps between the serrations are filled with porous media. Implicit large eddy simulations were conducted at Mach number Ma=0.1631 and Reynolds number Re=96 000 under a zero incidence angle. In addition to straight trailing edges and conventional serrated trailing edges, cutting-type porous-serrated (CPS) and insert-type porous-serrated (IPS) trailing edges with different porosities were designed. The flow in the porous media is described by Darcy's law, which is related to the pressure and velocity. The results indicate that the CPS trailing edges offer limited noise reduction compared to conventional serrated trailing edges, while IPS trailing edges achieve a significant noise reduction of approximately 5.21 dB. However, the drag force increases by 8.0% in the IPS case with maximum noise reduction. The composite control mainly affects flow structures near the trailing edges, especially inducing the flow penetration across the porous surface. To investigate the noise reduction mechanism, dynamic mode decomposition was conducted to show that both the CPS and IPS designs promote energy transferring significantly from the energetic mode to the modes at other frequencies, which would partly explain the difference in the noise reduction performance to some extent. Furthermore, the analysis of the wall pressure fluctuations reveals that the reduced convection velocity on the porous surface and enhanced destructive interference between the porous and the solid surfaces in IPS cases could be identified as the key factors contributing to lower noise radiation efficiency.

Geometrically nonlinear bending of stiffened composite skewed cylindrical shells under transverse pressure

The literature review on relative performances of laminated composite skewed shells confirms that research reports on bending performances of moderately thin, stiffened, laminated composite skewed cylindrical panels, using the geometrically nonlinear approach, are not available. This paper aims to fill that deficiency and proposes a finite element code combining eight-noded, doubly curved elements with modified Sanders’ first approximation theory for thin shells and von Kármán-type nonlinear strains. Correctness of the proposed geometrically nonlinear bending formulation for skewed shells are verified through solutions of benchmark problems. The deflections, force, and moment resultants are reported for different skew angles, laminations, stacking sequences, radius of curvature, plan dimension ratios, and stiffener properties like orientations, numbers, and eccentric positions. The results are discussed critically which reveals that shells having curved edges free and straight edges clamped fabricated using 0°/90°/0° laminate offer the best performances. The biaxial stiffeners, nx = 7, ny = 7, show the minimum deflections and stress resultants. The skewed shells offer greater deflections and hence, must be avoided in industrial practices.

Research and exploration on cymatics in sound visualization

The article reveals the connection between kinematics and music. Cymatics is a process by which sound can be visualized on a physical substance, and then captured in a photograph. For example, a kinematic image can be tracked through the impact of the speaker on the sand scattered on the plate. Thus, a fluctuating frequency expressed in Hertz will show an unusual result on the plate. The sound that propagates from the speaker in the environment provokes the mobility of sand on the plate, moreover, quite peculiar. Sand, as it travels from the area of the vibrating sections of the plate to places where the vibration does not reach, creates interesting forms of a symmetrical nature (lines, ovals, waveforms, ellipses and even straight edges). Those areas of the plate in which the vibration does not fall are called nodal points and lines.

Welding of 20 mm thick EH40 steel by means of a single-pass hybrid laser-arc welding technique

In the naval applications, as well as for infrastructure and construction sectors, welding of thick steel plates (>15 mm) has become of crucial importance. Nowadays, the common techniques involve several passes of traditional Gas Metal Arc Welding (GMAW) to fill a gap with a precise geometry. These techniques are, inevitably, time consuming due to the necessity of multiple passes, material consuming because of the volume of the gap which needs to be filled, and complicated due to the precise preparation of the joints. To overcome these drawbacks, we propose here a Hybrid Laser-Arc Welding (HLAW) technique in a configuration which allowed us to achieve a sound weld of two plates, 20 mm thick, of naval steel EH40 in a single pass. The goal has been obtained with a 15 kW fiber laser and a welding speed of 1500 mm/min. The most important result of this research is that the welds have been performed in a simple butt configuration, with straight edges of the plates and without any chamfer or additional preparation. Moreover, the length of the weld seam, 1 meter, guarantees the stability and the solidity of the process, its scalability over longer plates, and thus, an easy implementation on an industrial machine for massive production.

A Modern Approach to the Complicated Line Integrals in Linear Elastic Dislocation Theory

The standard textbook analysis of dislocations is generally limited to the case of infinitely straight screw or edge dislocations, which do not exist. This is due to the complexity of the formulas for arbitrary dislocation loops, i.e., Burger’s equation for the displacement field, the Peach-Köhler equation for the stress field and Blin’s equation for the interaction energy, which involve line integrals along the dislocation loop. The integrands are complex, and integration often involves non-elementary functions. Elaboration of the integrands with symbolic mathematical software produces tensor formulas which can be reused at will. By formulating convenient parametric expressions for the configuration studied and using superposition, mathematical software can be used to perform the integrations for arbitrary Burgers vectors. Often, the resulting expressions for the tensorial fields are very long, but they can be easily incorporated as user-defined formulas for plotting, parametric analysis, and incorporation into routines for energy minimisation or the non-linear equations for force equilibrium. The effectiveness of this approach will be illustrated by the example of short straight dislocations, circular dislocations, the interaction between a pileup and dissociated dislocations in the grain boundary, and the nucleation of dislocations at grain boundaries.