Some Characterization of Spiral Surfaces

In this paper we will study special spiral surfaces in the three dimensional Euclidean space and we give some characterization of these surfaces. More specifically, we investigate the Chang-Yau operator acting on the Gauss map of spiral surfaces. We also give some results about canonical vector field of these surfaces, i.e., we study incomperssibility of canonical vector field in two types of spiral surfaces. Moreover, we give some necessary conditions for a spiral surface to be a Weingarten surface. Existence of umbilical point is another problem that we investigate about it for a special case of spiral surfaces of the first type.

Rapid Prototyping of Bio-Inspired Dielectric Resonator Antennas for Sub-6 GHz Applications

Bio-inspired Dielectric Resonator Antennas (DRAs) are engaging more and more attention from the scientific community due to their exceptional wideband characteristic, which is especially desirable for the implementation of 5G communications. Nonetheless, since these antennas exhibit peculiar geometries in their micro-features, high dimensional accuracy must be accomplished via the selection of the most suitable fabrication process. In this study, the challenges to the manufacturing process presented by the wideband Spiral shell Dielectric Resonator Antenna (SsDRA), based on the Gielis superformula, are addressed. Three prototypes, made of three different photopolymer resins, were manufactured by bottom-up micro-Stereolithography (SLA). This process allows to cope with SsDRA’s fabrication criticalities, especially concerning the wavy features characterizing the thin spiral surface and the micro-features located in close proximity to the spiral origin. The assembly of the SsDRAs with a ground plane and feed probe was also accurately managed in order to guarantee reliable and repeatable measurements. The scattering parameter S11 trends were then measured by means of a Vector Network Analyzer, while the realized gains and 3D radiation diagrams were measured in the anechoic chamber. The experimental results show that all SsDRAs display relevant wideband behavior of 2 GHz at −10 dB in the sub-6 GHz range.

Analysis of features of the design of a screw feeder for the purpose of improving its work

Feeders are an integral part of the modern technological process, they establish and regulate the pace of production, ensure its rhythm, contribute to increased productivity and increase output. The aim of the article is to investigate and analyze the types of feeders, in particular the design features of a screw feeder, to determine its advantages and disadvantages. In order to increase the efficiency of the screw feeder, to propose a way to improve its design based on the modernization of the screw. The types of feeders are considered in the article, and the main attention is paid to the study of the advantages and disadvantages and design features of the screw feeder most common in technological processes of various industries as the simplest in design and often structural features of screw feeders in modern sources, which showed that the issue of the screw configuration screw feeders are not adequately studied in terms of uptime and the factors affecting this aspect indicate relevance. Currently, in the works of modern domestic authors and in the industries of various industries, waste-free screw feeders are considered. The article describes in detail these feeders developed by TechTron in two versions - the gutter and pipe. Today, there are also studies of a screw conveyor with additional blades on the spirals of the screw, in which the relationship between its structural and functional parameters is established. An analysis of the considered design features of existing screw feeders in modern sources has shown that issues of design features, namely the configuration of screws of screw feeders, have not been studied enough in terms of uptime and factors affecting this aspect, indicating the relevance of this issue to solve a specific problem of increasing work efficiency. The advantages of screw (screw) feeders compared to other types of feeders, such as continuity of supply, tightness, simplicity of design, the ability to create excess pressure at the outlet of the screw, the ability to aggregate with other equipment in industrial plants, have led to their widespread use in many industries in various technological processes.The main disadvantage of screw feeders is the low productivity due to the communication of the auger blade of the transported material, not only translational motion, but also rotational, which leads to turning the material together with the auger. Also a disadvantage of screw feeders is the rapid operation of the screw and the loading pipe due to overloads. To increase the efficiency of the screw feeder and eliminate one of its most important shortcomings - sensitivity to overload, resulting in accumulation of material inside the chute, stopping the feeder and reducing its performance and operational reliability, screw configurations were changed. Namely, the advanced screw was divided into two zones A - the loading zone, B - the main zone of the screw. Such a structure has a spiral surface and a cylindrical casing of smaller diameter D1 in the loading zone than the diameter of the spiral surface and a cylindrical casing in the main zone D2 of the screw feeder. The advanced design of the screw feeder works as follows. During loading of the feeder, the bulk material fills the entire space under the loading device with a continuous flow, including the spiral surface D1 of the screw. When the screw is rotated, the material completely filled the cylindrical casing with a diameter of D1, having a fill factor of j1 = 1, moves in a continuous flow through section A. When approaching the material to section B, by increasing the diameter of the spiral surface to D2, the fill coefficient decreases to j2, which ensures the operation of the screw feeder without accumulation of material and increases its operational reliability.

Microliter ultrafast centrifuge platform for size-based particle and cell separation and extraction using novel omnidirectional spiral surface acoustic waves

Asymmetric surface acoustic waves have been shown useful in separating particles and cells in many microfluidics designs, mostly notably sessile microdroplets. However, no one has successfully extracted target particles or...

Research on a lunar mobile spiral surface-soil sampler

This article presents the design of a spiral sampling device to perform lunar soil sampling and packaging, considering the special lunar environment and the physical and mechanical properties of the lunar soil. Combining the mechanical properties of lunar soil and the geometrical characteristics of the sampling device, the contact model between particles and the contact parameters between device and particles were adjusted. Through a discrete element simulation of the sampling process, the particles’ streamline, which is between the screw conveying modules and the sampling bailer, is derived. This result provides a theoretical foundation for the structural optimization of the device. Finally, a sampling experiment in simulated lunar soil verifies the feasibility of the sampling device.