Pair Of Rings Research Articles

Multibeam antennas with customized elevation angles based on near-field magnetic field coupling of metamaterials

In this paper, we propose the design of multibeam antennas with customized elevation angles based on near-field magnetic field coupling of metamaterials. The antenna consists of a monopole feed and four identical metamaterial transmission-line (MTL) structures surrounding the feed. The MTL structure is composed of two pairs of broadside-coupled omega rings (BCORs) that are connected by two straight strip-lines. Under such a framework, magnetic fields within the near-field zone of the monopole feed can be coupled efficiently by the inner BCOR, converted to travelling waves along the double strip-lines, guided toward the outer end of the MTL structure, and radiated by the outer BCOR like a loop antenna. Due to travelling wave nature of the MTL structure, there is phase lag along the MTL structure and the radiation main lobes are tilted towards the outward direction. By arranging several MTL structures around the feed monopole, multi-beam directional radiation can be realized. More interestingly, by adjusting structural parameters and pitch angles of the MTL structures, elevation angle of the radiation main lobes can be customized. To validate the design, we simulated, fabricated and measured four prototypes with pitch angles 0°, 15°, 30° and 45°. Both the simulated and measured results verify the design and show that multiple-beam radiation with customized elevation angle can be obtained. This work provides an alternative method of designing multi-beam antennas and may find applications in communication, surveillance, etc.

The effect of $S$-accr on intermediate rings between certain pairs of rings

The rings considered in this article are commutative with identity and the modules are assumed to be unitary. If $R$ is a subring of a ring $T$, then it is assumed that $R$ contains the identity element of $T$. Let $S$ be a multiplicatively closed subset (m.c. subset) of a ring $R$. In this paper, we consider the concept of $S$-accr, the generalization by Hamed and Hizem of the notion of (accr) in module theory given by Lu. We say that $R$ satisfies (accr) if the increasing sequence of residuals of the form $(I:_{R}B)\subseteq (I:_{R}B^{2})\subseteq (I:_{R}B^{3})\subseteq \cdots$ is stationary for any ideal $I$ of $R$ and for any finitely generated ideal $B$ of $R$. Focusing on certain pairs of rings $R\subseteq T$, the aim of this paper is to study whether $S$-accr on each intermediate ring $A$ between $R$ and $T$ for a suitable m.c. subset $S$ of $A$ (depending on $A$) implies that $A$ satisfies (accr) for each such $A$.

CAUSES OF DESTRUCTION DURING OIL STARVING IN THE FRICTION COUPLE "PISTON RING - CYLINDER LINER"

The study deals with the phenomenon of wear in the friction pair of the piston ring -cylinder liner during bench tests on prototypes. The tribological performance of dry frictionsimulating oil starvation was evaluated using the reciprocating motion of the tribometer. Significantwear was observed on the surface of the sleeve, made of gray cast iron, in contact with the chromesteel surface. This can be explained by a significant gradient in the rigidity of the tribopair inconjugation. With a chrome coating that has a noticeable hardness, extrusion and foaming of thesurface are observed along the edge of the sleeve, which indicates a change in wear. The coefficientof friction in dry sliding with stepped load increases showed an unstable state of friction, which isnot appreciated in the operation of any tribological system.Piston rings are used to seal the exhaust outlet gap between the piston and the liner for efficientoperation of the internal combustion engine. The distribution surface of the cylinder liner and pistonring during reciprocating motion is subject to continuous wear due to constant stresses, hightemperatures and intense loads. Thus, the performance and reliability of such heavy-duty enginecomponents depend on the topography of the conjugate surfaces and the associated tribologicalinteractions. Therefore, it is necessary to study the tribological behavior of conjugates of liners -rings that are subject to wear during oil starvation, and designed to effectively prevent exfoliation.This phenomenon leads to new surface coatings and modifications with significant wear propertiesin difficult operating conditions. Under certain conditions of loading, sliding and lubrication, the temperature rises to a criticalstate, the formation of the lubricating film is stopped and any formed lubricating film is destroyed,which leads to a catastrophic increase in friction. This continuous thermal feedback with the contactzone leads to wear of the friction pair of the piston ring - the cylinder liner. Given the changes in thedesign and materials of the engine, despite the fact that engine performance has increasedsignificantly with reduced emissions, it is impossible to exclude increased performance and enginefailure.

Safe physical human-robot interaction: A quasi whole-body sensing method based on novel laser-ranging sensor ring pairs

Non-contact detection is a competitive method for ensuring safety in close human-robot interaction (HRI). However, existing sensor configuration methods have difficulty satisfying the requirements for covering a wide range of sensing zones with fewer spots and a low-cost, low-complexity processing system. In this study, we developed a novel laser-ranging sensor configuration comprising sensors mounted on ring pairs, thereby implementing quasi whole-body sensing and cooperative location with fewer sensors. Each sensor ring pair was composed of double sensor rings mounted at opposite ends of robot arms. Based on the cone detection zone of each laser-ranging sensor, an optimisation of the configuration parameters showed that the maximum sensing volume coverage could be obtained when the laser-ranging sensors on each sensor ring were mounted in a tilted and biased form at certain angles. According to detection data and robot arm kinematics, a cooperative location model was also established to estimate the intervention position. Furthermore, we presented a self-occlusion geometric detection method for the robot, so as to identify cases in which the robot body entered the detection zone of the sensor ring pairs. To validate the efficacy of the proposed methods, experiments on quasi whole-body sensing, cooperative location, and self-occlusion detection were conducted with a UR10 robot. The experimental results show that the proposed sensor ring pair and detection method can effectively detect an approaching human and effectively estimate the intervention position and self-occlusion, allowing for efficient and safe cooperative performance with humans.

Interventional Microbubble Enhanced Sonothrombolysis on Left Ventricular Assist Devices

The left ventricular assist device (LVAD) is often used in the treatment of heart failure. However, 4% to 9% implanted LVAD will have thrombosis problem in one year, which is fatal to the patient's life. In this work, an interventional sonothrombolysis (IST) method is developed to realize the thrombolysis on LVAD. A pair of ultrasound transducer rings is installed on the shell of LVAD, and drug‐loaded microbubbles are injected into the LVAD through the interventional method. The microbubbles are adhere on the thrombus with the coated thrombus‐targeted drugs, and the thrombolytic drugs carried by the bubbles are brought into the thrombus by the cavitation of bubbles under the ultrasound. In a proof‐of‐concept experiment in a live sheep model, the thrombus on LVAD is dissolved in 30 min, without damages on LVADs and organs. This IST exhibits to be more efficient and safer compared with other thrombolysis methods on LVAD.

An active geophone with an adjustable electromagnetic negative stiffness for low-frequency vibration measurement

The low-frequency performance of an active vibration isolation system depends on the low-frequency measurement ability of inertial sensors such as geophones. Reducing the stiffness of the interior mechanical spring may serve as an effective way to improve the low-frequency performance of a geophone. But unfortunately, this approach may lead to a nonlinear response and a stability problem. This paper develops an active geophone with an adjustable electromagnetic negative stiffness (AENS). The AENS of the proposed geophone consists of two pairs of magnet rings and coil winds and adopts a concentric nested configuration. The AENS neutralizes the positive stiffness of mechanical spring and provides a low linear composite stiffness in a stroke range of ± 4.4 mm without affecting the high-frequencies stability of the active geophone. Besides, the “drift” phenomenon caused by an initial installation misalignment of the AENS is discussed. The analyzed result shows that once the misalignment happens, the deviation from the initial position will aggravate further. Therefore, by combining the AENS with active control of a drift suppression and a force-balance, the nonlinearity and misalignment problems caused by the AENS are addressed to guarantee an improved low-frequency performance. The performance of the prototype is analyzed and validated by experiments. The results have shown that the measurable bandwidth of the prototype is 0.1 Hz ∼ 25 Hz, and the sensitivity is 275 V/(m/s).

Extended Conjugation Attenuates the Quenching of Aggregation-Induced Emitters by Photocyclization Pathways.

Herein, we expose how the antagonistic relationship between solid‐state luminescence and photocyclization of oligoaryl alkene chromophores is modulated by the conjugation length of their alkenyl backbones. Heptaaryl cycloheptatriene molecular rotors exhibit aggregation‐induced emission characteristics. We show that their emission is turned off upon breaking the conjugation of the cycloheptatriene by epoxide formation. While this modification is deleterious to photoluminescence, it enables formation of extended polycyclic frameworks by Mallory reactions. We exploit this dichotomy (i) to manipulate emission properties in a controlled manner and (ii) as a synthetic tool to link together pairs of phenyl rings in a specific sequence. This method to alter the tendency of oligoaryl alkenes to undergo photocyclization can inform the design of solid‐state emitters that avoid this quenching mechanism, while also allowing selective cyclization in syntheses of polycyclic aromatic hydrocarbons.

Extended Conjugation Attenuates the Quenching of Aggregation‐Induced Emitters by Photocyclization Pathways

AbstractHerein, we expose how the antagonistic relationship between solid‐state luminescence and photocyclization of oligoaryl alkene chromophores is modulated by the conjugation length of their alkenyl backbones. Heptaaryl cycloheptatriene molecular rotors exhibit aggregation‐induced emission characteristics. We show that their emission is turned off upon breaking the conjugation of the cycloheptatriene by epoxide formation. While this modification is deleterious to photoluminescence, it enables formation of extended polycyclic frameworks by Mallory reactions. We exploit this dichotomy (i) to manipulate emission properties in a controlled manner and (ii) as a synthetic tool to link together pairs of phenyl rings in a specific sequence. This method to alter the tendency of oligoaryl alkenes to undergo photocyclization can inform the design of solid‐state emitters that avoid this quenching mechanism, while also allowing selective cyclization in syntheses of polycyclic aromatic hydrocarbons.

A note on pairs of rings with the same prime ideals

We study the ring extensions $R \subseteq T$ having the same set of prime ideals provided $\mathrm{Nil}(R)$ is a divided prime ideal. Some conditions are given under which no such $T$ exists properly containing $R$. Using idealization theory, the examples are also discussed to strengthen the results.

Numerical Investigation of Jet Control Using Two Pulsed Jets under Different Amplitudes

A turbulent jet with a Reynolds number of 71,000, controlled by a pair of pulsed jets operating 180° out of phase, is investigated by large-eddy simulation. The effect of the forcing amplitude on jet development and generated coherent structures is investigated through six cases: an unforced case and five cases at different amplitudes. With this forcing mode, the jet bifurcates in the far field that promotes the spread of the shear layer. It was found that the jet yields the largest bifurcation angle at medium amplitude, while the bifurcation is restrained at lower or higher amplitudes. As the amplitude increases, the streamwise vortex pair generated by the control jet is stronger and penetrates deeper into primary jet. This phenomenon reduces the inclination of vortex ring when mutual interaction between vortex ring and streamwise vortex pair occurs. Meanwhile, at higher amplitudes, the inclined vortex ring is stronger and unevenly distributed, prompting the jet bifurcation. In order to investigate the coupling effect of amplitude and frequency, different forcing frequencies were also simulated. The results demonstrated that the optimal frequency based on centerline velocity decay rate decreases with increasing amplitude; however, it eventually saturates around StD = 0.1.

Second-Order Real Nodal-Line Semimetal in Three-Dimensional Graphdiyne.

Real topological phases featuring real Chern numbers and second-order boundary modes have been a focus of current research, but finding their material realization remains a challenge. Here, based on first-principles calculations and theoretical analysis, we reveal the already experimentally synthesized three-dimensional (3D) graphdiyne as the first realistic example of the recently proposed second-order real nodal-line semimetal. We show that the material hosts a pair of real nodal rings, each protected by two topological charges: a real Chern number and a 1D winding number. The two charges generate distinct topological boundary modes at distinct boundaries. The real Chern number leads to a pair of hinge Fermi arcs, whereas the winding number protects a double drumhead surface bands. We develop a low-energy model for 3D graphdiyne which captures the essential topological physics. Experimental aspects and possible topological transition to a 3D real Chern insulator phase are discussed.

Characterizations of Pairs of Rings with Few Non‐Dedekind Intermediary Rings

We determine the Dedekind domain pairs of rings; that is, pairs of rings R ⊂ S such that each intermediary ring in between R and S is a Dedekind domain. We also establish that if R ⊂ S is an extension of rings having only one non‐Dedekind intermediary ring, then necessarily R is not Dedekind and so R is a maximal non‐Dedekind domain subring of S. Maximal non‐Dedekind domain subrings R of S are identified in the following cases: (1) R is not integrally closed, (2) R is integrally closed and either |Supp(S/R)| < ∞ or |Max(R)| < ∞, (3) S is a field, (4) R is a valuation domain, and (5) R ⊂ S is an integral extension. We also provide some classifications of pairs of rings having exactly two non‐Dedekind domain intermediary rings.

Vortex Ring Formed by a Butterfly Wing and Dynamic Forces

Butterfly generates unsteady dynamic fluid force with a pair of vortex rings. In order to elucidate the flight mechanism of butterflies, it is necessary not only to clarify the vortex rings formed around the wings but also elucidate the characteristics of the unsteady fluid force generated by the flapping motion. By applying the momentum theory to the vortex rings formed during flapping motion, it is possible to estimate the force generated by flapping motion. In this study, we reconstruct a pair of vortex rings formed by flapping motion based on a small number of visualization results and elucidate dynamic fluid force characteristics. A part of estimation result of Lift estimated by the rough shape vortex rings generated by downstroke and upstroke do not match with the direct measurement result. But not only the peak value of estimation result of Lift is near with the direct measurement result quantitatively but also the value of estimation result between upstroke is a small negative as well as the direct measurement result. Although there is a phase difference between the estimation result and direct measurement result, there is a qualitative and quantitative agreement between estimation results and direct measurement result. From those results, butterfly generate the unsteady dynamic Lift between downstroke, especially at butterfly spread wing maximum (t/T = 0.40). After that, the unsteady dynamic Lift decrease and become 0 at upstroke.

Linking and link complexity of geometrically constrained pairs of rings

We investigate and compare the effects of two different constraints on the geometrical properties and linking of pairs of polygons on the simple cubic lattice, using Monte Carlo methods. One constraint is to insist that the centres of mass of the two polygons are less than distance d apart, and the other is to insist that the radius of gyration of the pair of polygons is less than R. The second constraint results in links that are quite spherically symmetric, especially at small values of R, while the first constraint gives much less spherically symmetric pairs, prolate at large d and becoming more oblate at smaller d. These effects have an influence on the observed values of the linking probability and link spectrum.

Influence of honing angle on tribological behaviour of cylinder liner–piston ring pair: Experimental investigation

Research conducted on the influence of honing angle on the cylinder liner surface lacks consensus on the numerical value of the honing angle for the desired performance of the liner-ring tribosystem. The paper presents the results of experimental work performed on the cylinder liner samples honed at different angles (20° −100°) to explore the influence of honing angles under boundary lubrication conditions. Experiments conducted at two distinct sliding conditions (0.2 m/s and 0.3 m/s) using a linear reciprocating tribometer indicated 40° as the optimum honing angle based on the evaluation of tribological characteristics such as the coefficient of friction and the wear.

Adhesive anastomosis for organ transplantation

The recent development of tough tissue adhesives has stimulated intense interests among material scientists and medical doctors. However, these adhesives have seldom been tested in clinically demanding surgeries. Here we demonstrate adhesive anastomosis in organ transplantation. Anastomosis is commonly conducted by dense sutures and takes a long time, during which all the vessels are occluded. Prolonged occlusion may damage organs and even cause death. We formulate a tough, biocompatible, bioabsorbable adhesive that can sustain tissue tension and pressurized flow. We expose the endothelial surface of vessels onto a gasket, press two endothelial surfaces to the adhesive using a pair of magnetic rings, and reopen the bloodstream immediately. The time for adhesive anastomosis is shortened compared to the time for sutured anastomosis. We have achieved adhesive anastomosis of a great vein in transplanting the liver of a pig. After the surgery, the adhesive is absorbed, the vein heals, and the pig lives for over one month.

Development of sliding contact resistance testing equipment for carbon brush confluence ring

A carbon brush and a confluence ring form a pair of sliding electrical contacts. To reduce the contact resistance between the carbon brush and the confluence ring, the time for the running-in wear of the carbon brush increased during the machining process to increase the actual contact area. As a result, the welding and ablation failure between the carbon brush and the confluence ring happened under the impact of high current during service. To explore the effect of carbon brush wear on sliding electrical contact performance, it is necessary to monitor the dynamic contact resistance of the carbon brush and the confluence ring. In this paper, a set of 8-channel contact resistance testing equipment is developed. The device uses a relay array to achieve 1-8 channel gating and uses a data acquisition card to detect the contact resistance of each carbon brush and confluence ring pair combining with a four-point method. Based on the Labview software, it realizes the selection of acquisition channels, data acquisition card driving, real-time data processing, displaying, and storage. The range of contact resistance that this set of equipment can detect is 10mΩ ∼2Ω, and the accuracy can reach 1% of the full scale. Finally, the simulation experiments show that the testing equipment meets the technical requirements, and the continuous test runs stably and reliably. It can be used for the testing and research of the sliding contact resistance between the carbon brush and the confluence ring during the running-in wear process.

TWISTS, CROSSED PRODUCTS AND INVERSE SEMIGROUP COHOMOLOGY

AbstractTwisted étale groupoid algebras have recently been studied in the algebraic setting by several authors in connection with an abstract theory of Cartan pairs of rings. In this paper we show that extensions of ample groupoids correspond in a precise manner to extensions of Boolean inverse semigroups. In particular, discrete twists over ample groupoids correspond to certain abelian extensions of Boolean inverse semigroups, and we show that they are classified by Lausch’s second cohomology group of an inverse semigroup. The cohomology group structure corresponds to the Baer sum operation on twists.We also define a novel notion of inverse semigroup crossed product, generalizing skew inverse semigroup rings, and prove that twisted Steinberg algebras of Hausdorff ample groupoids are instances of inverse semigroup crossed products. The cocycle defining the crossed product is the same cocycle that classifies the twist in Lausch cohomology.

Modulation of the optical properties of soluble N-alkylated 4-pyridyl diketopyrrolopyrrole derivatives

The absorption and fluorescence properties of N-alkylated 3,6-di (pyridin-4-yl)-2,5-dihydropyrrolo [3,4-c]pyrrole-1,4-dione (PyrDPP NH) derivatives in solution and the solid state are reported, along with the modulation of these properties under varying acidity or basicity. The compounds with hexyl (PyrDPP N-Hex) and methoxy ethoxy ethyl (PyrDPP N-MEE) chains were synthesised from PyrDPP NH giving highly soluble dyes. In addition, the mono-substituted derivatives were also isolated. A range of solvents was explored to provide understanding regarding their potential use in applications ranging from organic electronics to sensors. Optically the dyes are highly fluorescent and, as a result of N-alkylation breaking the hydrogen bond network, emissive in the solid state with large Stokes shifts. The nature of the chain dictates the π interactions and packing of the materials, resulting in modulation of the solid-state absorption spectra and theoretical mobility predicted from the crystal structures. The methoxy ethoxy ethyl chain twists out of the plane and bends to allow considerable molecular overlap and small interchromophore displacement with strikingly similar π interactions to the parent PyrDPP NH, resulting in a contribution of H-type aggregation to the absorption band and an order of magnitude improvement in theoretical mobility compared with the hexyl analogue. In contrast, PyrDPP N-Hex possesses a distorted CH-π interaction between pyridyl and lactam units, with greater molecular displacement manifesting in dominant J -aggregation contribution to absorption band and moderate mobility. The results emphasise the potential for sidechain modification and show structural evidence for the potential benefits of the flexible polar chains. The nitrogen lone pair of the pyridyl ring can be protonated in acidic environment to produce a photometric response suggesting potential as a proton sensor. The mono-substituted compounds are responsive to both base and acid, making them interesting for molecular logic applications.

Targeted particle delivery via vortex ring reconnection

A conceptual model for targeted particle delivery is proposed using controlled vortex ring reconnection. Entrained particles can be efficiently transported within the core of vortex rings which advect via self-induction. A pair of these particle-transporting vortex rings traveling in the streamwise direction along parallel trajectories will mutually interact, resulting in a pair of vortex reconnection events. The reconnection causes a topological change to the vortex ring which is accompanied by a rapid repulsion in a perpendicular plane to the direction of travel, effectively transporting the particles toward the desired location on the sidewalls of a ducted flow. In addition to proposing this conceptual model, we show the dominant physics of the process and the considerations for targeted delivery.