Convex Sidewall Research Articles

Research on defect detection of bottle cap interior based on low-angle and large divergence angle vision system.

During the machine vision inspection of the inner section of bottle caps within pharmaceutical packaging, the unique conca bottom and convex side walls often create obstructions to the illumination. Consequently, this results in challenges such as irregular background and diminished feature contrast in the image, ultimately leading to the misidentification of defects. As a solution, a vision system characterized by a Low-Angle and Large Divergence Angle (LALDA) is presented in this paper. Using the large divergence angle of LED, combined with low-angle illumination, a uniform image of the side wall region with bright-field characteristics and a uniform image of inner circle region at the bottom with dark-field characteristics are obtained, thus solving the problems of light being obscured and brightness overexposure of the background. Based on the imaging characteristics of LALDA, a multi-channel segmentation (MCS) algorithm is designed. The HSV color space has been transformed, and the image is automatically segmented into multiple sub-regions by mutual calculation of different channels. Further, image homogenization and enhancement are used to eliminate fluctuations in the background and to enhance the contrast of defects. In addition, a variety of defect extraction methods are designed based on the imaging characteristics of different sub-regions, which can avoid the problem of over-segmentation in detection. In this paper, the LALDA is applied to the defect detection inside the cap of capsule medicine bottle, the detection speed is better than 400 pcs/min and the detection accuracy is better than 95%, which can meet the actual production line capacity and detection requirements.

Axial segregation characteristics and size-induced flow behavior of particles in a novel rotary drum with curved sidewalls

Particle mixing and segregation are common phenomena in rotary drums, which are challenging to be controlled and driven artificially in powder technology. In this work, the discrete element method (DEM) was applied to construct the novel rotary drum composed of different shaped curved sidewalls. By varying the operation parameters of particle and sidewall shapes as well as the length-to-diameter (L/D) ratio of drums, the axial mixing and segregation processes of binary size-induced particles were investigated. The results show that the axial flow velocity of the particle mixtures is noticeably weakened once the particle angularity increases, making the non-spherical particles to mix better in rotary drums compared to the spherical particles. Besides, in the short drums with size-induced spherical particles, the axial segregation characteristics are significantly enhanced by the convex sidewalls while suppressed by the concave sidewalls. However, for size-induced non-spherical particles, the axial segregation structure can be present in rotary drums with plane and concave sidewalls while not in drums with convex sidewalls. Moreover, the axial segregation band structure of spherical particles eventually increases proportionally with the increased drum L/D ratios. In contrast, the non-spherical particles cannot form obvious multi-proportional segregation bands.

Implementation of light extraction improvements of GaN-based light-emitting diodes with specific textured sidewalls

Textured-sidewall GaN-based light-emitting diodes (LEDs) with various sidewall angles (15–90°) and convex or concave sidewalls prepared using an inductively-coupled-plasma approach are comprehensively fabricated and studied. The device with 45° sidewalls (Device F) and that with convex sidewalls (Device B) show significant improvements in optical properties. Experiments show that, at an injection current of 350 mA, the light output power, external quantum efficiency, wall-plug efficiency, and luminous flux of Device F (Device B) are greatly improved by 18.3% (18.2%), 18.2% (18.2%), 17.3% (19.8%), and 16.6% (18.4%), respectively, compared to those of a conventional LED with flat sidewalls. In addition, negligible degradation in electrical properties is found. The enhanced optical performance is mainly attributed to increased light extraction in the horizontal direction due to a significant reduction in total internal reflection at the textured sidewalls. Therefore, the reported specific textured-sidewall structures (Devices B and F) are promising for high-power GaN-based LED applications.

Effects of shielding coatings on the anode shaping process during counter-rotating electrochemical machining

Electrochemical machining (ECM) has been widely used in the aerospace, automotive, defense and medical industries for its many advantages over traditional machining methods. However, the machining accuracy in ECM is to a great extent limited by the stray corrosion of the unwanted material removal. Many attempts have been made to improve the ECM accuracy, such as the use of a pulse power, passivating electrolytes and auxiliary electrodes. However, they are sometimes insufficient for the reduction of the stray removal and have their limitations in many cases. To solve the stray corrosion problem in CRECM, insulating and conductive coatings are respectively used. The different implement processes of the two kinds of coatings are introduced. The effects of the two kinds of shielding coatings on the anode shaping process are investigated. Numerical simulations and experiments are conducted for the comparison of the two coatings. The simulation and experimental results show that both the two kinds of coatings are valid for the reduction of stray corrosion on the top surface of the convex structure. However, for insulating coating, the convex sidewall becomes concave when the height of the convex structure is over 1.26 mm. In addition, it is easy to peel off by the high-speed electrolyte. In contrast, the conductive coating has a strong adhesion, and can be well reserved during the whole machining process. The convex structure fabricated by using a conductive iron coating layer presents a favorable sidewall profile. It is concluded that the conductive coating is more effective for the improvement of the machining quality in CRECM. The proposed shielding coatings can also be employed to reduce the stray corrosion in other schemes of ECM.

Investigating surface metrology of curved wall surface during milling of SS304 with different tool path strategies

Curved mating surfaces that exist in complex engine parts such as turbine blades play a critical role in part fitting and assembly and, thus, system performance. Control of precise surface metrology (e.g., form error, surface roughness) during machining of such surfaces is highly challenging, especially when processing super alloys like hardened steels. This work aims to experimentally investigate surface metrology of a 12.70-mm-thick curved plate platform (with S-shaped sidewall) of AISI SS304 material during milling on a vertical three-axis milling machine with three different tool path strategies: ramp, contour, and peripheral. Experiments are performed to study surface location error (SLE) and roughness during upward and downward feeding of tool on both concave and convex sidewall surfaces at different spindle speed and feed combinations. SLE values that are estimated as undercut or overcut with respect to the desired surface are found to be minimum with ramp (15.05 μm), followed by contour (18.63 μm), and maximum with peripheral (24.12 μm) milling paths. However, peripheral milling may be preferable in terms of surface roughness (improved about 40 %) and overall machining time (six times faster than ramp milling). The findings are analyzed based on the associated cutting mechanics and cutting forces.

Experimental study of co-annular jet subjected to transverse disturbances

The results of an investigation of the flow field of two coaxially aligned jets consisting of an inner primary jet and a co-annular outer jet issuing from a nozzle with convex sidewalls are reported. A transverse flow injection into the co-annular jet was used to shape the co-annular jet flow. In the region between the exits of the two jets, a recirculating toroidal eddy is formed due to opposing pressure gradients. In the presence of transverse injection, the eddy bifurcates into two lobes with radially emanating flow structures that substantially increase the decay of axial velocity and the spread rate to twice the values when compared to the characteristics of the primary jet alone. Measurements of mean velocities and Reynolds stresses were made at the jet Reynolds number of 16,000 with the help of a specially designed two-component Laser-Doppler-Velocimetry system. Topology of the resulting complex flow in view of the measurements is presented and discussed.

Wetting States on Circular Micropillars with Convex Sidewalls after Liquids Contact Groove Base

It is considered that the Cassie-Baxter wetting state should be transitioned to that of the Wenzel state if a water drop has contact with the base of a roughness groove. However, in recent tests on the leaf surfaces of three lotus varieties, we found that the transition did not occur. To explore the reason behind this, in this work we model the corresponding surface structures as circular micropillars with convex sidewalls, and derive an angle inequality for judging transition from Cassie-Baxter to Wenzel States. We also consider the transition on spherical microparticles, as well as that on circular micropillars with straight sidewalls. Finally, we validate the angle inequality through pressing tests on three lotus varieties and spherical microballs.

Patterned growth on high-index GaAs (311)A substrates

The selectivity of growth on patterned GaAs (311)A substrates qualitatively differs from that on low-index (100) and (111) substrates. During molecular beam epitaxy (MBE) of (AlGa)As, [01−1] oriented mesa stripes develop a fast-growing convex sidewall. For shallow mesa height, this new growth mechanism produces quasi-planar quantum wires with excellent optical properties. Nanometer-scale self-faceting in atomic hydrogen-assisted MBE transforms these sidewall quantum wires into a linear array of quantum dots with minimized size fluctuations. Upon rotating the mesa stripe from [01−1], a continuous transition occurs from the fast-growing sidewall to the slow-growing sidewall along the perpendicular [−233] direction. This allows their systematic combination at the corner or edge of intersecting mesa stripes appropriately inclined from [01−1], thus offering a novel degree of flexibility for the design of lateral functional semiconductor nanostructures.

Surfaces and Interfaces of (Al, Ga) As Heterostructures on Unpatterned and Patterned GaAs Substrates

The correlation between surface morphology and interface properties of (Al, Ga)As quantum wells (Qwell) grown by molecular-beam epitaxy on GaAs (100) and patterned GaAs (311)Ga substrates is investigated by atomic force and scanning electron microscopy in comparison with spectrally and spatially resolved cathodoluminescence (CL), as well as micro-photoluminescence spectroscopy. On unpatterned GaAs (100) substrates, both the surfaces and Qwell interfaces exhibit at least two roughness components with correlation length on a nanometer and micrometer scale. On GaAs (311)Ga substrates patterned with mesastripes along the [011] direction, one side of the mesastripe develops a fast-growing, convex sidewall with thicker Qwell regions below, which are suitable to act as quantum wires. For a zigzag-shaped mesastripe, the growth results in wire branches with dotlike regions between them. The latter are electronically coupled with the wire branches.

Patterned growth on GaAs (311)A substrates: Engineering of growth selectivity for lateral semiconductor nanostructures

The growth selectivity on patterned GaAs (311)A substrates differs qualitatively from that on low-index (100) and (111) substrates. During molecular beam epitaxy of (Al,Ga)As, [01-1] oriented mesa stripes develop a fast growing convex sidewall. A continuous transition occurs towards the slow growing concave sidewall upon turning the mesa along the perpendicular [-233] direction without breaking up the growth front into microfacets. This allows their systematic combination at the corner or edge of intersecting mesa stripes appropriately inclined from [01-1] among which we highlight those involving fast growing sidewalls. The scenario, which is unique for patterned GaAs (311)A substrates, offers a novel degree of flexibility for the design of lateral functional semiconductor nanostructures.

Hexagonal facet laser with optical waveguides grown by flow-rate modulation epitaxy

In selective MOVPE growth on a (111)B plane, the use of the flow-rate modulation epitaxy (FME) method reduces the growth temperature by more than 100°C and drastically improves not only the selectivity but also the shape controllability compared to the conventional simultaneous-flow method. Especially, no polycrystalline deposition occurs on the SiO2 masked area even in the AlAs growth. In addition, intricate structures consisting of concave and convex sidewall facets can be grown in the shapes just like mask patterns. These superior characteristics of FME are used to grow various hexagonal prism-shaped GaAsAlGaAs lasers with rectangular optical waveguides and, as a result, the grown structures consist of sharp facets having the same shape as the mask pattern. The thresholds of these lasers are extremely low compared with those grown by conventional MOVPE, because of the precise control of the facet shape. It is also found that the lasing light output can be efficiently extracted from the points of waveguides in all laser structures.

The use of graded InGaAs layers and patterned substrates to remove threading dislocations from GaAs on Si

We have investigated threading dislocation (TD) removal from GaAs films on Si by introduction of additional InGaAs graded strain layers in combination with growth on patterned substrates. The substrate patterns consisted of mesas with 10–34 μm widths. The mesa sidewalls were either overhanging (concave), leading to free sidewalls for the film on the mesas, or outward sloping (convex) sidewalls with {111} orientation. The dislocation structure was studied using transmission electron microscopy. It was found that the graded strained layers led to a reduction of dislocation density by a factor of ∼5 in films grown both on mesas with concave sidewalls and on unpatterned substrates. This reduction was due to dislocation reactions leading to annihilation of TDs. For films with graded strained layers on mesas with convex sidewalls, an additional factor of ∼3 reduction in TD density was observed in the part of the film that was grown on top of the mesas. In this case all mobile TDs (TDs associated with 60° misfit dislocations, i.e., TDs that could glide to relieve misfit stress) were removed from the film on top of the mesas to the regions above the sidewalls and only TDs associated with 90° misfit dislocations remained. We suggest that this is due to pinning of the TDs associated with 60° misfit dislocations at the mesa edges and we have presented an explanation for this pinning in terms of the stress conditions at the {111} oriented mesa edges. In addition, this leads us to suggest that in order to obtain minimum TD density it is imperative to prevent formation of 90° misfit dislocation during lattice mismatched heteroepitaxial growth.

Switching Dynamics of Bistable Fluidic Amplifiers With Low Setbacks

The transient switching of a model bistable fluidic amplifier with low setbacks and variable configuration has been studied. The amplifier was of conventional design with straight and convex side-walls, cusped and pointed splitters, and variable control port width. Water was used as the fluid and the element was operated at different Reynolds numbers. Effect of loading, inertia of the fluid in the output legs, bias flows from the inactive control port, and geometric changes on the transient switching times were determined. The flow field was made visible by generating hydrogen bubbles in the power nozzle and at the power nozzle exit. Using visual studies of the switching process as a guide, an analysis has been developed to predict the switching times approximately.