Topological One-Way Edge States in an Air-Hole Honeycomb Gyromagnetic Photonic Crystal

Topological one-way edge states have attracted increasing attention because of their intriguing fundamental physics and potential applications, particularly in the realm of photonics. In this paper, we present a theoretical and numerical demonstration of topological one-way edge states in an air-hole honeycomb gyromagnetic photonic crystal biased by an external magnetic field. Localized horizontally to the edge and confined in vertical direction by two parallel metallic plates, these unique states possess robust one-way propagation characteristics. They are strongly robust against various types of defects, imperfections and sharp corners on the path, and even can unidirectionally transport along the irregular edges of arbitrary geometries. We further utilize the one-way property of edge states to overcome entirely the issue of back-reflections and show the design of topological leaky wave antennas. Our results open a new door towards the observation of nontrivial edge states in air-hole topological photonic crystal systems, and offer useful prototype of robust topological photonic devices, such as geometry-independent topological energy flux loops and topological leaky wave antennas.

Prediction of Flow Path Pressure Drops in Curved Galleries for Additively Manufactured Hydraulic Manifolds

Hydraulic manifolds are traditionally manufactured using externally drilled intersecting galleries. This results in undesirable artefacts in the flow path such as sharp corners, and dead oil volumes, and requires additional plugs to blank redundant holes. These artefacts affect flow separation, aggravate pressure-drop and reduce hydraulic stiffness. Recent advancements in additive manufacturing (AM) technology have enabled the development of additively manufactured components which provide greater freedom in channel design and routing. Galleries can provide flow paths which are smoothly curved in 3 dimensions. AM manifold geometry can be optimized to reduce size and weight. In this research, analytical expressions are sought to approximate pressure drops in complex curved flow paths, which can subsequently be used for manifold optimization. The curved flow paths are defined by polynomial splines which are then fragmented into a series of segments each defined by a bend angle and bend radius. This paper uses approximations to Computational Fluid Dynamics (CFD) results to form pressure-drop models over a range of segment bend radii and angles. These models are then used to predict the pressure drops for curved galleries used in AM manifolds. The method is applied to four example curved galleries, and provides a reasonably accurate pressure-drop prediction in each case.

Dark topological valley Hall edge solitons

Topological edge solitons propagating along the edge of a photonic topological insulator are localized self-sustained hybrid states that are immune to defects/disorders due to the protection of the edge states stemming from the nontrivial topology of the system. Here, we predict that exceptionally robust dark valley Hall edge solitons may form at the domain walls between two honeycomb lattices with broken inversion symmetry. The underlying structure can be created with femtosecond laser inscription, it possesses a large bandgap where well-localized dark edge solitons form, and in contrast to systems with broken time-reversal symmetry, it does not require external magnetic fields or complex longitudinal waveguide modulations for the realization of the topological phase. We present the envelope equation allowing constructing dark valley Hall edge solitons analytically. Such solitons propagate without radiation into the bulk of the lattice and can circumvent sharp corners, which allows observing their persistent circulation along the closed triangular domain wall boundary. They survive over huge distances even in the presence of disorder in the underlying lattice. We also investigate interactions of closely located dark topological valley Hall edge solitons and show that they are repulsive and lead to the formation of two gray edge solitons, moving with different group velocities departing from group velocity of the linear edge state on which initial dark solitons were constructed. Our results illustrate that nonlinear valley Hall systems can support a rich variety of new self-sustained topological states and may inspire their investigation in other nonlinear systems, such as atomic vapors and polariton condensates.

On the Milling Strategy in Machining Curved Surfaces Based on Minimum Stress Concentration by a 3-axis Machining Center

3-axis computer numerical control machining centers are used in machining due to their simple operation. When machining curved surfaces, the 3-axis CNC machining centers use interpolation lines segment to fit the curved surfaces. The quality of the machined surface is affected by the length of the interpolation line segment. Sharp corners are formed at the junction of straight segments. The appearance of sharp corners will lead to increased stress concentration. To study the relationship between surface quality and interpolation straight line in surface processing, this paper establishes the mathematical model of surface topography in 3-axis ball-end milling curved surfaces based on the acceleration and deceleration control. Based on the surface topography model, the surfaces stress concentration factor analysis is carried out in machining curved surfaces with variable curvatures with different lengths of interpolation lines. The results show that when the length of interpolation lines and the radius of curvature are kept constant, the stress concentration factor decreases with the increase of the central angle. When the length of the interpolation lines and the central angle are kept constant, the stress concentration factor decreases with the increase of the radius of curvature. When the radius of curvature and the central angle are kept constant, the stress concentration factor increases as the length of the interpolation lines increases. A method of selecting the length of interpolation lines based on the surface’s stress concentration is proposed. Through the optimization of the tool path, the quality of the machined surfaces can be improved.

A novel p-harmonic descent approach applied to fluid dynamic shape optimization

We introduce a novel method for the implementation of shape optimization for non-parameterized shapes in fluid dynamics applications, where we propose to use the shape derivative to determine deformation fields with the help of the $$p-$$ p - Laplacian for $$p > 2$$ p > 2 . This approach is closely related to the computation of steepest descent directions of the shape functional in the $$W^{1,\infty }-$$ W 1 , ∞ - topology and refers to the recent publication Deckelnick et al. (A novel $$W^{1,\infty}$$ W 1 , ∞ approach to shape optimisation with Lipschitz domains, 2021), where this idea is proposed. Our approach is demonstrated for shape optimization related to drag-minimal free floating bodies. The method is validated against existing approaches with respect to convergence of the optimization algorithm, the obtained shape, and regarding the quality of the computational grid after large deformations. Our numerical results strongly indicate that shape optimization related to the $$W^{1,\infty }$$ W 1 , ∞ -topology—though numerically more demanding—seems to be superior over the classical approaches invoking Hilbert space methods, concerning the convergence, the obtained shapes and the mesh quality after large deformations, in particular when the optimal shape features sharp corners.

Effect of Mixer Type on Particle Coating by Magnesium Stearate for Friction and Adhesion Modification

Glidants and lubricants are often used to modify interparticle friction and adhesion in order to improve powder characteristics, such as flowability and compactability. Magnesium stearate (MgSt) powder is widely used as a lubricant. Shear straining causes MgSt particles to break, delaminate, and adhere to the surfaces of the host particles. In this work, a comparison is made of the effect of three mixer types on the lubricating role of MgSt particles. The flow behaviour of α-lactose monohydrate, coated with MgSt at different mass percentages of 0.2, 0.5, 1, and 5 is characterised. The mixing and coating process is carried out by dry blending using Turbula, ProCepT, and Mechanofusion. Measures have been taken to operate under equivalent mixing conditions, as reported in the literature. The flow resistance of the coated samples is measured using the FT4 rheometer. The results indicate that the flow characteristics of the processed powders are remarkably similar in the cases of samples treated by Turbula and Mechanofusion, despite extreme conditions of shear strain rate. The least flow resistance of samples is observed in the case of samples treated by the ProCepT mixer. High-velocity collisions of particles round off the sharp corners and edges, making them less resistant to flow. The optimal percentage of magnesium stearate is found to be approximately 1% by weight for all mixer types, as the addition of higher amounts of lubricant does not further improve the flowability of the material.

Fatigue Life and Stress Analysis of the Crankshaft of a Single Cylinder Diesel Engine under Variable Forces and Speeds

In this paper, a single cylinder crankshaft manufactured with C45 steel was used to investigate variation in stress, deformation, and fatigue life and safety factor at critical locations of the crankshaft. For this purpose, numerical analyses using ANSYS/Workbench software were performed under different operating conditions. Additionally, low cycle fatigue analyses were conducted experimentally for the validation of the numerical results in terms of the failure characteristics of the crankshaft. It was concluded that chamfers at sharp corners of the crankshaft on the flywheel side showed critical regions, indicating that the experimental and numerical results were consistent. These results suggested that critical regions of the crankshaft could be optimized for the improvement of sustainability in long life service.

Free Vibrations of Anisotropic Nano-Objects with Rounded or Sharp Corners

An extension of the Rayleigh–Ritz variational method to objects with superquadric and superellipsoid shapes and cylinders with cross-sections delimited by a superellipse is presented. It enables the quick calculation of the frequencies and displacements for shapes commonly observed in nano-objects. Original smooth shape variations between objects with plane, convex, and concave faces are presented. The validity of frequently used isotropic approximations for experimentally relevant vibrations is discussed. This extension is expected to facilitate the assignment of features observed with vibrational spectroscopies, in particular in the case of single-nanoparticle measurements.

Time-optimal Feedrate Scheduling with Actuator Constraints for 5-axis Machining

Cycle time minimization is one of the major goals that many manufacturers are eager to achieve. Maximizing feedrate is the direct solution, however, physical motions need to be under the specified motion limits to avoid high-frequency vibration, causing machining error. In this paper, a time-optimal feedrate scheduling approach for 5-axis G1 toolpath is presented for 5-axis machining. A quintic B-spline corner smoothing method is utilized to smoothen sharp corners in the toolpath. Then, the S-shape feedrate profile of each block is optimized under the actuator motion constraints, with the objective of minimizing the cycle time. Particle swarm optimization (PSO) is used to provide the optimized solution. Experiments are conducted to validate the proposed approach and the results are compared with two other existing approaches. It is found that the proposed method can achieve shorter cycle time and less contour errors, showing the effectiveness of the proposed approach.

Design and Development of Roll Cage and Steering System of Go-Kart

Go-kart is a one of the motor sport which is played globally. This racing does not require any professional drivers or greater speed. It is a light weight and cheaper vehicle which does not require suspension and differential. In this paper we are concentrating on Roll cage and steering system of Go-kart. While keeping it light weight, chassis material is selected as AISI 1018 which give more tensile strength, machinability, and can sustain maximum load. For designing and analysis CATIA and ANSYS soft wares were used. Whereas in steering system the Ackermann steering mechanism is used for attaining maximum cornering speed, without the slippage of tires. This also gives us minimum turning radius, helping us to take sharp turns when the driver has to take sharp corners.