Flat Ring Research Articles

Probing the Disk Kinematics of M31 with DESI

M31’s stellar rotation curve and disk line-of-sight dispersion is presented using kinematic data from a novel DESI M31 survey in combination with similar datasets. After removing the foreground, the disk region is isolated and the velocity field deprojected. A flat ring model is fit to the velocity field of M31 out to 30 kpc using a maximum-likelihood routine. The stellar rotation curve is found to flatten to ∼220 km/s, and a disk line-of-sight velocity dispersion of ∼60 km/s is derived. The results extend M31’s rotation curve to 30 kpc and support the picture in which M31 has thicker disk than the Milky Way.

Hypervalent Iodine‐Mediated Regioselective Dearomatization of Non‐Activated Arenes

AbstractThe dearomatizations of non‐activated arenes, particularly those under mild reaction conditions, are highly desired transformations in organic synthesis due to their power in converting flat aromatic rings into three‐dimensional frameworks. Although hypervalent iodine (HVI)‐mediated dearomatization of phenol derivatives has developed rapidly, HVI‐mediated dearomatization of non‐activated arenes remains an urgent and challenging task. To fulfil this task, in this work, we established an HVI‐mediated oxidative dearomatization of non‐activated arenes by using biphenylureas and N‐ or O‐nucleophiles as reactants. This electrophilic dearomatization (DEAr) process is highly regioselective, which enabled different N‐ and O‐nucleophiles to react at the distal C4‐position of the phenyl ring, thus generating dearomative spiro‐products in a single step under mild conditions with wide substrate scope (43 examples, 22%–76% yield). This approach not only provides a successful example for dearomatization of non‐activated arenes under mild reaction conditions, but also has overcome the challenges in HVI‐mediated dearomatization of non‐activated arenes, which will enrich the chemistry of dearomatization.

Topology and curvature effects in the photonics of ring – split ring – cuboid transitions

Topological transitions in various materials are actively being studied, including topological quantum phase transitions, going beyond the Landau theory and the concept of the order parameter. Here we propose the concept of a transition between two structures with different topology using the example of the transition between a flat dielectric ring and a split ring and its further unbending into a rectangular Fabry-Pérot resonator. Experimentally and theoretically, we discovered the lifting of the degeneracy of the CW-CCW photonic modes of the ring and the formation of two families: topological, which acquire an additional phase π, equal to the Berry phase in a thin Möbius strip, and ordinary ones, which do not acquire an additional phase. Topological modes arise due to the gradual “cutting” of one antinode of the field by a gap into two antinodes as the angular size of the gap increases from zero to one degree. Thus, using a topological Fabry-Pérot resonator with variable curvature and fixed length, resonant modes with an arbitrary non-integer number of waves are realized and a new generation of resonators is created with the prospect of unique classical and quantum applications.

Numerical Simulation as a Tool for the Study, Development, and Optimization of Rolling Processes: A Review

Rolling is one of the most important processes in the metallurgical industry due to its versatility. Despite its inherent advantages, design and manufacturing by rolling still rely on trial-and-error-based optimizations, which reduces its efficiency. To minimize the cost and time spent on the development of new rolling schedules, various analytical and numerical methods have been used in recent years. Among other alternatives, simulations based on the finite element method (FEM) are the most widely used. This allows for the analysis of the feasibility of new rolling schedules considering metal alloys with different characteristics, process conditions, or the creation of new operations, as well as the optimization of existing ones. This paper presents a literature review including the latest developments in the field of numerical simulation of rolling processes, which have been classified according to the type of rolling into the following categories: flat rolling, shape rolling, ring rolling, cross-wedge rolling, skew rolling, and tube piercing.

Chainmail inspired metamaterials for use in protective sports equipment

Contact sports and action sports require intense performance yet also include a high risk of injury. Subsequently, protective equipment for those sports usually must trade flexibility for protection and vice versa. Chainmail inspired mechanical metamaterials could be a solution to this dilemma. Chainmail is a type of body armour, consisting of a structured fabric made up of thousands of interlocking metallic rings. Chainmail inspired materials have recently been made from connected 3D shapes, rather than the typical 2D (flat) rings. This chainmail inspired material is flexible when relaxed but stiff when the chains are compressed together. This ability to control the material’s stiffness means chainmail is a type of mechanical metamaterial. Mechanical metamaterials are engineered structures which derive their properties from the structure of the material, not the material itself. In relation to protective equipment, this means that these chainmail materials or fabrics, can be flexible during normal use but stiffen when indented or impacted. The flexibility of these materials can be influenced by changing the size and shape of the connecting chains but to what extent and the effect this has on their stiffness is unknown. This type of structure could improve sporting protective equipment, where (as stated before) there are various trade-offs. The aim of this project was to develop a chainmail inspired material and test the effect of varying cell sizes has on the flexibility and indentation resistance of the material. Additive manufacturing was used to create the chainmail materials and a range of indenters were used to test them, the results of which indicate that as cell size decreases and number of cells increase; their flexibility and formability increases while also maintaining a good degree of indentation resistance, when compared to larger cell sizes. Based on this work, these structures could be tailored to different sporting protective equipment where flexibility, support, and stiffness requirements may vary between normal use and collisions or falls. These chainmail inspired materials could have various applications in contact sports such as rugby, American football and ice hockey where protection for players is key to reduce the severity of injuries. Similarly, action sports such as mountain biking, skateboarding, skiing and snowboarding also necessitate a high degree of protection. An Alternative application for these materials could be as a first aid device, where the material would be formed around the injury site as a brace and stiffened with compression, such as a vacuum pack.

On the Fundamentals of Reverse Ring Rolling: A Numerical Proof of Concept.

Ring Rolling is a near-net manufacturing process with some measurable dimensional inaccuracies in its products. This fact is exaggerated even more under the scope of high-precision manufacturing, where these imprecisions render such products unfitting for the strict dimensional requirements of high-precision applications (e.g., bearings, casings for turbojets, etc.). In order to remedy some of the dimensional inaccuracies of Ring Rolling, the novel approach of Reverse Ring Rolling is proposed and investigated in the current analysis. The conducted research was based on a numerical simulation of a flat Ring Rolling process, previously presented by the authors. Since the final dimensions of the ring from the authors' previous work diverged from those initially expected, the simulation of a subsequent Reverse Ring Rolling process was performed to reach the target dimensions. The calculated deformational results revealed a great agreement in at least two of the three crucial dimensions. Additionally, the evaluation of the calculated stress, strain, temperature and load results revealed key aspects of the mechanisms that occur during the proposed process. Overall, it was concluded that Reverse Ring Rolling can effectively function as a corrective process, which can increase the dimensional accuracy of a seamless ring product with little additional post-processing and cost.

Pseudoconiocessia xishuangbannaensis gen. et sp. nov. in Coniocessiaceae, Xylariales from Coffea liberica in China

During a survey of saprobic fungi on coffee samples in Yunnan Province, China, in 2020 and 2022, fungal fruiting bodies on decaying Liberian coffee twigs were collected and isolated. Maximum likelihood and Bayesian analyses of combined ITS, LSU, and RPB2 genes showed that the two isolated fungal strains belonged to a distinct species in Coniocessiaceae and were well separated from closely related genera with 73% ML and 0.92 PP statistical support. Morphologically, this distinct species can be differentiated from other genera in Coniocessiaceae by aseptate hamathecium, 4–8-spored asci with a flat apical ring, and fusiform ascospores, conical at the lower end. Based on morphology and phylogenetic analyses, the two fungal strains are described as a distinct new genus Pseudoconiocessia, within Coniocessiaceae. Pseudoconiocessia is introduced here with Pseudoconiocessia xishuangbannaensis as the type species.

High-strength preload indicator inner washer forward design method

The preload indicator bolt assembly is a fastener that achieves the desired preload effect by simply tightening the preload nut within a specified range without additional measuring tools. The inner washer is a critical component in this assembly, with its outer diameter and height serving as crucial design parameters. In this paper, an equivalent mechanical model is established for the preload indicator bolt assembly. Utilizing this model, an iterative search process is developed to determine the optimal outer diameter and height of the inner washer. The analytical relationship between the bolt preload force and nut displacement is compared and validated against finite element analysis and experimental results, yielding favorable agreement. Notably, the nut tightening angle can vary within the range of 187°–242°, while the preload force exhibits a minimal variation of only ±2% for type 10-0A bolt connection (Bolt diameter and bolt pitch are φ16 mm and 1.41 mm, respectively. The material of bolt, inner ring, and flat ring are GH4169, 40CrNiMoA, and 30CrMo, respectively). This feature significantly simplifies the installation process of the preload indicator bolt assembly in real-world applications, offering great convenience. The increment in tension force on preloaded bolts under external loads exhibits an almost identical trend for both connection methods. Under the same preload force and the same eccentric working load conditions, the thickness of the connected components follows the same trend as their contact area.

Simulation Study on Dynamic Characteristics of the Chain Drive System for Mining Scraper Conveyor Driven by the Permanent Magnet Synchronous Motor

The chain drive system represents a critical subsystem within the scraper conveyor. This paper proposes a joint simulation model for the drive system of the scraper conveyor, driven by the permanent magnet synchronous motor, in order to conduct a comprehensive analysis of the dynamic characteristics of the chain drive system during the operational process. Firstly, the dynamic simulation model for the mining scraper conveyor’s chain drive system was established in ADAMS, taking into account its structural characteristics. Then, the mathematical model of the permanent magnet synchronous motor was established using the coordinate transformation theory, and the speed controller based on vector control was designed by using the theory related to sliding mode control. The coupling relationship between the chain drive system of the scraper conveyor and the permanent magnet synchronous motor drive system was investigated. Finally, a joint simulation model of the mechanical system and motor control system was created using ADAMS (View 2019) and MATLAB/Simulink (2020a). The dynamic characteristics of the chain drive system were analyzed, and the three typical working conditions of no load, half load, and rated load were considered. The results show that the contact force between the flat ring and the sprocket undergoes an initial increase, followed by a decrease, and finally another increase. As the load increases from no load to full load, there is a marked increase in the contact force between the loaded side chainrings. Due to the polygon effect, both the speed curve of the permanent magnet drive motor and the contact force curve between the ring chains exhibit periodic fluctuations. The research in this paper provides an idea for the coupling analysis of the scraper conveyor electromechanical system.

Investigation on crack resistance of full aeolian sand high-performance concrete synergistically modified by supplementary cementitious materials and superabsorbent polymer

The development of full aeolian sand high-performance concrete (FA-HPC) can alleviate the dilemma of river sand shortage. However, the high cracking potential appears due to the characteristic of low water-to-binder ratio and high cementitious materials content. Herein, supplementary cementitious materials (SCMs), i.e., fly ash and silica fume, and superabsorbent polymer (SAP) are used to optimize the crack resistance synergistically. The crack resistance in plasticity and hardening stages are investigated based on flat plate cracking and ring restrained cracking combined with chloride ions penetration, respectively. Meanwhile, capillary pressure, mechanical strength, and internal temperature field were also involved. Additionally, the modification mechanism of SCMs and SAP is analyzed from a microscopic perspective via hydration heat, phase analysis, and microstructure. The results showed that whether single use or binary mixing, fly ash and silica fume significantly improved the crack resistance of FA-HPC. Moreover, it was further enhanced by the SAP, presenting a 63.39% and 96.96% increase in crack resistance at plasticity stage and hardening stage respectively as well as a 78.31% reduction in chloride ions penetration. Contrary to silica fume, fly ash hindered early hydration leading to a decrease in capillary pressure, strength, and internal temperature field with content dependence. Besides, the most intense volcanic ash reaction was observed in binary mixing. Although SAP delayed the early hydration, the later hydration degree was improved obtaining more hydration products at 28d since the internal curing effect. Thereby, the more refined microstructure was achieved for more optimized crack resistance. This study provides an available strategy for reducing the cracking risk of FA-HPC to promote wide application in engineering.

Dearomative syn-Dihydroxylation of Naphthalenes with a Biomimetic Iron Catalyst.

Arenes are interesting feedstocks for organic synthesis because of their natural abundance. However, the stability conferred by aromaticity severely limits their reactivity, mostly to reactions where aromaticity is retained. Methods for oxidative dearomatization of unactivated arenes are exceedingly rare but particularly valuable because the introduction of Csp3-O bonds transforms the flat aromatic ring in 3D skeletons and confers the oxygenated molecules with a very rich chemistry suitable for diversification. Mimicking the activity of naphthalene dioxygenase (NDO), a non-heme iron-dependent bacterial enzyme, herein we describe the catalytic syn-dihydroxylation of naphthalenes with hydrogen peroxide, employing a sterically encumbered and exceedingly reactive yet chemoselective iron catalyst. The high electrophilicity of hypervalent iron oxo species is devised as a key to enabling overcoming the aromatically promoted kinetic stability. Interestingly, the first dihydroxylation of the arene renders a reactive olefinic site ready for further dihydroxylation. Sequential bis-dihydroxylation of a broad range of naphthalenes provides valuable tetrahydroxylated products in preparative yields, amenable for rapid diversification.

Analytical calculation model for radial-axial coordinated feed strategy in large-scale flat ring rolling based on ultimate bending moment

Analytical calculation model for radial-axial coordinated feed strategy in large-scale flat ring rolling based on ultimate bending moment

Polystemma stevensii (Apocynaceae, Asclepiadoideae), a new species from Michoacán, Mexico

Polystemma stevensii, a new species from Michoacán, Mexico, is described and illustrated. It grows in tropical deciduous forest in the Balsas Depression at elevations from 350 to 750 m. Polystemma stevensii is similar to P. viridiflorum but differs by having a gynostegial corona with five lobes fused at the base to form a discontinuous flat ring (vs. not forming a discontinuous flat ring), an internal corona with two deltate lobes (vs. with one ligulate lobe), and globose style head (vs. flat style head). A distribution map of the new species and a key to determine the Polystemma species of Michoacán are provided. Following IUCN Red List guidelines, it is assigned a preliminary category of endangered, EN B1ab(i,ii,iii)+2ab(i,ii,iii). Polystemma now includes eight species, of which five are endemic to Mexico.

Preparation of 3,5-Methanobenzo[b]azepines: An sp3-Rich Quinolone Isostere.

The replacement of the aromatic ring in bioactive compounds with saturated bioisosteres has become a popular tactic to obtain novel structures with improved physicochemical profiles. In this paper, we describe an efficient synthesis of 3,5-methanobenzo[b]azepine analogues and suggest them as isosteres of quinolones. Quinolones are heteroaromatic, flat rings and considered as privileged scaffolds. An isosteric version of this scaffold with more 3D character would offer new options to expand their use.

On the ideal avoidance property

In this article, we investigate the avoidance property of ideals and rings. Among the main results, a general version of the avoidance lemma is formulated. It is shown that every idempotent ideal (and hence every pure ideal) has avoidance. The avoidance property of arbitrary direct products of avoidance rings is characterized. It is shown that every overing of an avoidance domain is an avoidance domain. Next, we show that every avoidance N-graded ring whose base subring is a finite field is a PIR. It is also proved that the avoidance property is preserved under flat ring epimorphisms. Dually, we formulate a notion of strong avoidance, and show that it is reflected by pure morphisms.

Critical dehydrogenation steps of perhydro-[formula omitted]-ethylcarbazole on Ru(0001) surface

Understanding of the critical atomistic steps during the dehydrogenation process of liquid organic hydrogen carriers (LOHCs) is important to the design of cost-efficient, high-performance LOHC catalysts. Based on the density functional theory (DFT) we studied the thermodynamics and kinetics of the complete dehydrogenation path of perhydro-N-ethylcarbazole (12H-NEC) on Ru(0001) surface, involving the adsorption of 12H-NEC, the discharge of H ions onto Ru surface, and the desorption of H2 and hydrogen-lean NEC. It was found that the bonding of nH-NEC is significantly strengthened for n≤4 because of the flat aromatic ring. Although the whole dehydrogenation process is endothermic, the release of H from nH-NEC, with H adsorbed onto the Ru surface, was found to be exothermic. The desorption of flat, hydrogen-lean NEC, which costs ∼255 kJ/mol, was identified as the most energy demanding step. In addition, the effect of surface morphology on adsorption was studied based on an amorphous surface model. Overall, the results imply more efficient dehydrogenation could be achieved from relatively weak bonding of NEC to catalysts, either through engineering catalyst surface (such as surface defects or smaller catalyst particles) or different catalyst materials. Our calculations also revealed possible dealkylation at elevated temperatures.

Staircase penetration of magnetic flux into a superconducting flat ring

Staircase penetration of magnetic flux into a superconducting flat ring

Radial–axial feeding process design for large-scale flat ring by quantitative estimation of ring roundness error

Due to the large size and thin wall characteristics, the large-scale ring is prone to plastic instability, resulting in loss of ring roundness. An analytical calculation model of roundness error is proposed to design the feeding process. This model is established by analytically deriving the relationships between feeding process, ring geometry, contact arc length, rolling force, ring vibration angle, ring bending angle, contact arc length increment and ring roundness error at different rolling stages. Compared with numerical calculation and production trial, the analytical model can predict the roundness error with reasonable accuracy and high efficiency and guide feeding process design.

Construction of a flat workpiece for manufacturing a turn of the right helicoid

In technology, a common helical surface is a right closed helicoid (auger). It is formed by a helical movement of a horizontal segment, provided that the axis of the auger crosses at one of its ends. The formation of the surface of an open helicoid is similar but the segment must intersect the axis and be located at a constant distance from it. It is known from differential geometry that the helical surface can be transformed by bending to the surface of rotation. This fact is taken as the basis for calculating the geometric shape of a flat workpiece. The surface of the open helicoid is non-disjointed, so the shape of the workpiece must be found in such a way as to minimize plastic deformations during surface formation. Parametric equations of continuous flexion of the turn of an open helicoid into the section of a single-cavity hyperboloid of rotation have been derived. Continuous bending can be represented as a gradual deformation of the turn while reducing its step. The meridian of hyperboloid rotation is the corresponding area of hyperbola. The hyperboloid section is proposed to be approximated by the surface of the truncated cone. This approximation will be more accurate in the area of the hyperbole where it asymptotically approaches the segment of the right line. After selecting a cone, it becomes possible to determine its size and build its exact sweep since the cone is a unfolding surface. The sweep is constructed in the form of a flat ring with a cut sector and will be the desired flat workpiece to form a turn of the auger from it. Most accurately, the surface of the turn of the open helicoid can be made by stamping the workpiece of the resulting form. For small-scale production of the helical surface of an open helicoid, it is advisable to weld flat rings together and, during installation, stretch along the shaft while twisting around its axis. The accuracy of the obtained surface will depend on the accuracy of the approximation of the hyperboloid section of rotation with a truncated cone, which is the topic of this work.

3D Printing and processing of miniaturized transducers with near-pristine piezoelectric ceramics for localized cavitation

The performance of ultrasonic transducers is largely determined by the piezoelectric properties and geometries of their active elements. Due to the brittle nature of piezoceramics, existing processing tools for piezoelectric elements only achieve simple geometries, including flat disks, cylinders, cubes and rings. While advances in additive manufacturing give rise to free-form fabrication of piezoceramics, the resultant transducers suffer from high porosity, weak piezoelectric responses, and limited geometrical flexibility. We introduce optimized piezoceramic printing and processing strategies to produce highly responsive piezoelectric microtransducers that operate at ultrasonic frequencies. The 3D printed dense piezoelectric elements achieve high piezoelectric coefficients and complex architectures. The resulting piezoelectric charge constant, d33, and coupling factor, kt, of the 3D printed piezoceramic reach 583 pC/N and 0.57, approaching the properties of pristine ceramics. The integrated printing of transducer packaging materials and 3D printed piezoceramics with microarchitectures create opportunities for miniaturized piezoelectric ultrasound transducers capable of acoustic focusing and localized cavitation within millimeter-sized channels, leading to miniaturized ultrasonic devices that enable a wide range of biomedical applications.