Ring Type Research Articles

A novel method of suppressing machining vibration in robotic milling using magneto-rheological foam damper

Owing to their remarkable flexibility and favorable cost-effectiveness, industrial robots have found extensive applications to cutting of materials across sophisticated manufacturing fields. However, the structurally low rigidity of these robots renders the tool tip prone to substantial oscillations during machining processes, significantly impacting product fabrication quality. The objective of this study is to present a novel methodology employing magnetorheological dampers for mitigating vibrations during robotic milling operations. Specifically, a new type of ring nested Magneto-Rheological Foam Damper (MRFD) working in the squeeze mode is developed. Firstly, the MRFD's structure is designed considering the vibrational characteristics of robotic milling. Subsequently, a damping force model of the MRFD is derived. The feasibility of the MRFD’s structural design is validated by the finite element analyses, which is instrumental in comprehending the influence of structural parameters on the electromagnetic characteristics of the MRFD. Next, a prototype of the MRFD is fabricated selecting appropriate parameters. Finally, a series of excitation and milling experiments are conducted on a KUKA KR500 robot. The outcomes demonstrate a substantial reduction (37%-69%) in radial vibration amplitude at the tool tip during robotic milling, highlighting the effectiveness of the developed MRFD. This research endeavor has introduced a pioneering avenue and framework for vibration control in robotic milling, offering a novel paradigm for enhancing the precision of robotic machining.

Design and analysis of 7-stage MOS current mode logic power gated MOSFETs in current starved voltage-controlled oscillator for the phase locked loop application

This paper presents a new process, voltage and temperature (PVT) tolerant 7-stage ring type current starved voltage-controlled oscillator (CS-VCO). In this, a 7-stage ring VCO is proposed using power gated technique for phase locked loop (PLL) application. PLL plays a major role in clock and data recovery, Global Positioning System (GPS) system and satellite communications. For the high-speed application of PLL it is designed using 7-stage inverter delay cell with MOS current mode logic (MCML) technique. The circuit undergoes process, voltage and temperature variations with different parameters such as average power, oscillation frequency, phase noise, tuning range and output noise. The Monte-Carlo analysis justifies the proposed design provides better results. The circuit is simulated under 45 nm CMOS technology using cadence virtuoso. The average power consumption of the proposed circuit is 29.368 µW with the oscillation frequency of 3.06 GHz. The output noise and the phase noise of the proposed VCO are -161.55 dB and -125.92 dBc/Hz respectively. It achieves the frequency tuning range (FTR) of 95.09%. The obtained simulation results are highly robust with PVT making the circuit suitable for PLL application.

Structural aspects of Pt(η3-X1N1X2)(PL) (X1,2 = O, C, or Se) and Pt(η3-N1N2X1)(PL) (X1 = C, S, or Se) derivatives

Abstract This article covers 26 Pt(ii) complexes of compositions Pt(η3-X1N1X2)(PL) (X1,2 = O, C, or Se) and Pt(η3-N1N2X1)(PL) (X1 = C, S, or Se). These complexes crystallized in two crystal classes: monoclinic (14 examples) and triclinic (12 examples). The heterotridentate ligand with monodentate PL builds up a distorted square-planar geometry around each Pt(ii) atom. Each heterotridentate ligand Pt(η3-X1N1X2)(PL) creates two metallocyclic rings with a common N1 atom of the O1C2N1C3O2, O1C3N1C3O2, O1C2NN1C3O2, C1C2N1C2C2, and Se1C2N1NC2Se2 types. In Pt(η3-N1N2X1)(PL) complexes, the tridentate ligand with a common N2 atom forms the following types of metallocyclic rings: N1C2N2C2C1, N1C2N2NCS1, and N1CNN2NCSe1. The total mean values of τ4 for respective complexes as it grows in the sequence: 0.056 (Pt(η3-O1N1O2)(PL)) < 0.091 (Pt(η3-Se1N1Se2)(PL)) < 0.161 (Pt(η3-N1N2S1)(PL)) < 0.174 (Pt(η3-N1N2Se1)(PL)) < 0.188 (Pt(η3-C1N1C2)(PL)) < 0.211 (Pt(η3-N1N2C1)(PL)). The distortion of the square-planar geometry increases in the given sequences. The structural data (Pt–L, L–Pt–L) are analyzed and discussed with attention to the distortion of a square-planar geometry about the Pt(ii) atoms as well as of trans-influence.

Couple-close construction of polycyclic rings from diradicals.

Heteroarenes are ubiquitous motifs in bioactive molecules, conferring favourable physical properties when compared to their arene counterparts1-3. In particular, semisaturated heteroarenes possess attractive solubility properties and a higher fraction of sp3 carbons, which can improve binding affinity and specificity. However, these desirable structures remain rare owing to limitations in current synthetic methods4-6. Indeed, semisaturated heterocycles are laboriously prepared by means of non-modular fit-for-purpose syntheses, which decrease throughput, limit chemical diversity and preclude their inclusion in many hit-to-lead campaigns7-10. Herein, we describe a more intuitive and modular couple-close approach to build semisaturated ring systems from dual radical precursors. This platform merges metallaphotoredox C(sp2)-C(sp3) cross-coupling with intramolecular Minisci-type radical cyclization to fuse abundant heteroaryl halides with simple bifunctional feedstocks, which serve as the diradical synthons, to rapidly assemble a variety of spirocyclic, bridged and substituted saturated ring types that would be extremely difficult to make by conventional methods. The broad availability of the requisite feedstock materials allows sampling of regions of underexplored chemical space. Reagent-controlled radical generation leads to a highly regioselective and stereospecific annulation that can be used for the late-stage functionalization of pharmaceutical scaffolds, replacing lengthy de novo syntheses.

"Polymerization" of Bimerons in Quasi-Two-Dimensional Chiral Magnets with Easy-Plane Anisotropy.

We re-examine the internal structure of bimerons, which are stabilized in easy-plane chiral magnets and represent coupled states of two merons with the same topological charge |1/2| but with opposite vorticity and the polarity. We find that, in addition to the vortices and antivortices, bimerons feature circular regions which are located behind the anti-vortices and bear the rotational sense opposite to the rotational sense chosen by the Dzyaloshinskii-Moriya interaction. In an attempt to eliminate these wrong-twist regions with an excess of positive energy density, bimerons assemble into chains, and as such exhibit an attracting interaction potential. As an alternative to chains, we demonstrate the existence of ring-shaped bimeron clusters of several varieties. In some rings, bimeron dipoles are oriented along the circle and swirl clockwise and/or counterclockwise (dubbed "roundabouts"). Moreover, a central meron encircled by the outer bimerons may possess either positive or negative polarity. In other rings, the bimeron dipoles point towards the center of a ring and consequently couple to the central meron (dubbed "crossings"). We point out that the ringlike solutions for baryons obtained within the Skyrme model of pions, although driven by the same tendency of the energy reduction, yield only one type of bimeron rings. The conditions of stability applied to the described bimeron rings are additionally extended to bimeron networks when bimerons fill the whole space of two-dimensional samples and exhibit combinations of rings and chains dispersed with different spatial density (dubbed bimeron "polymers"). In particular, bimeron crystals with hexagonal and the square bimeron orderings are possible when the sides of the unit cells represent chains of bimerons joined in intersections with three or four bimerons, respectively; otherwise, bimeron networks represent disordered bimeron structures. Moreover, we scrutinize the inter-transformations between hexagonal Skyrmion lattices and disordered bimeron polymers occuring via nucleation and mutual annihilation of merons within the cell boundaries. Our theory provides clear directions for experimental studies of bimeron orderings in different condensed-matter systems with quasi-two-dimensional geometries.

Acoustic Whispering Gallery Modes in a Split Ring Resonator

In this work the Finite Element Method was used to numerically investigate the resonant frequencies for the acoustic Whispering Gallery Modes in a split ring type resonator. This is the case where a defect is considered in the ring resonator and the study was focused on how the resonant frequencies are affected by the presence of the defect in the ring. The findings of this study show that a kind of degeneration appears on the modes of the ring due to the insertion of the defect. The Acoustic Quality factors of the resonances were also calculated and were found to have high values proving a strong enhancement of the field. The strong enhancement of the field is also followed by the observation of intense localization of it into the defect. The results of our study show strong evidence that the proposed structure could be a very promising candidate for applications based on acoustic signals such as sensors and filters.

Contemporary outcomes for resected type 1-3 gastroesophageal junction adenocarcinoma: a single-center experience

BackgroundSurgical resection remains the mainstay of treatment for tumors of the gastroesophageal junction (GEJ). However, contemporary analyses of the Western experience for GEJ adenocarcinoma are sparsely reported. MethodsPatients with GEJ adenocarcinoma undergoing resection between 2012 and 2022 at a single institution were grouped based on Siewert subtype and analyzed. Pathologic and treatment related variables were assessed with relation to outcomes. ResultsA total of 302 patients underwent resection: 161 (53.3%) with type I, 116 (38.4%) with type II, and 25 (8.3%) with type III tumors. Most patients received neoadjuvant therapy (86.4%); 86% of cases were performed in a minimally invasive fashion. Anastomotic leak occurred in 6.0% and 30-day mortality in only 0.7%. The rate of grade 3+ morbidity was lower for the last 5 years of the study than for the first 5 years (27.5% vs 49.3%, P < .001), as was median length of stay (7 vs 8 days, P < .001). There was a significantly greater number of signet ring type tumors among type III tumors (44.0%) than type I/II tumors (11.2/12.9%, P < .001). Otherwise, there was no difference in the distribution of pathologic features among Siewert subtypes. Notably, there was a significant difference in 3-year overall survival based on Siewert classification: type I 60.0%, type II 77.2%, and type III 86.3% (P = .011). Siewert type I remained independently associated with worse survival on multivariable analysis (hazard ratio, 4.5; P = .023). ConclusionsIn this large, single-institutional series, operative outcomes for patients with resected GEJ adenocarcinoma improved over time. On multivariable analysis, type I tumors were an independent predictor of poor survival.

Towards Amplified Probing of Weak Intermolecular Interactions on the External Surfaces of Molecular Capsules.

We report a sensitive method for comparing weak interactions between aryl rings located on the external surfaces of equilibrating homo- and heterodimeric capsules. Two identical self-complementary resorcin[4]arene tetrabenzoate molecules and one tetramethylammonium cation form in CDCl3 hydrogen-bonded homodimeric capsules whose exteriors are decorated with four tight pairs of weakly interacting aryl rings. The pair wise mixing of six different homodimers establishes their equilibria with the corresponding heterodimeric species in which two types of aryl rings exert on each other some gentle forces. This equilibrium is significantly shifted either towards homo- or heterodimers depending on the nature and location of the substituents in the weakly interacting aryl rings. The thermodynamic favorability or disadvantage of the heterodimerization is determined by stronger or weaker aryl-aryl attractions in the hetero- or homodimeric capsules, respectively. The four-fold amplification of weak aryl-aryl interactions on the external surfaces of the equilibrating capsules is responsible for high sensitiveness of our approach.

Hydrophilic Reduction-Resistant Spin Labels of Pyrrolidine and Pyrroline Series from 3,4-Bis-hydroxymethyl-2,2,5,5-tetraethylpyrrolidine-1-oxyl.

Highly resistant to reduction nitroxides open new opportunities for structural studies of biological macromolecules in their native environment inside living cells and for functional imaging of pH and thiols, enzymatic activity and redox status in living animals. 3,4-Disubstituted nitroxides of 2,2,5,5-tetraethylpyrrolidine and pyrroline series with a functional group for binding to biomolecules and a polar moiety for higher solubility in water and for more rigid attachment via additional coordination to polar sites were designed and synthesized. The EPR spectra, lipophilicities, kinetics of the reduction in ascorbate-containing systems and the decay rates in liver homogenates were measured. The EPR spectra of all 3,4-disubstituted pyrrolidine nitroxides showed additional large splitting on methylene hydrogens of the ethyl groups, while the spectra of similar pyrroline nitroxides were represented with a simple triplet with narrow lines and hyperfine structure of the nitrogen manifolds resolved in oxygen-free conditions. Both pyrrolidine and pyrroline nitroxides demonstrated low rates of reduction with ascorbate, pyrrolidines being a bit more stable than similar pyrrolines. The decay of positively charged nitroxides in the rat liver homogenate was faster than that of neutral and negatively charged radicals, with lipophilicity, rate of reduction with ascorbate and the ring type playing minor role. The EPR spectra of N,N-dimethyl-3,4-bis-(aminomethyl)-2,2,5,5-tetraethylpyrrolidine-1-oxyl showed dependence on pH with pKa = 3, ΔaN = 0.055 mT and ΔaH = 0.075 mT.

The Aharonov–Bohm effect in quadratic Gauss quantum rings

We outline a theory for the Aharonov–Bohm effect in a novel type of quantum ring, namely the quadratic Gauss quantum ring, here for brevity called the Gauss ring. A Gauss ring is a one-dimensional nonperiodic lattice with sites at z = z j = j n d with j ∈ {0, 1, 2, ⋯ , s + 1} (), n ≥ 2 (), and d the underlying period wrapped into a ring-shaped geometry. Here we discuss the electronic spectrum of quadratic Gauss rings (n = 2, s ∈ {0, 1, 2, ⋯ , 5, 6, 7}), and show that the spectrum can be described using theoretical tools recently devised to provide an understanding of the Gauss chain [D S Citrin (2023) Phys. Rev. B 107, 235 144]. We then consider the effect on the electronic states of a magnetic flux Φ threading the Gauss ring and show that the effect of the flux is to select specific electronic states from a periodic chain whose supercells are finite-length Gauss chains thus relating the states in the Gauss quantum ring with those in a periodic Gauss chain.

Polarization-controlled ultrasmall single photon emitter combining a quantum dot and an elliptical split ring metamaterial element

We propose a polarization-controlled ultrasmall single-photon emitter that combines a single photon source and an elliptical split ring (SR) type metamaterial element. Simulations using the finite difference time domain method showed that in elliptical metamaterial elements, the annular mode is suppressed and axial electric field oscillations occur preferentially, resulting in upward light emission from the photon source with controlled polarization. We fabricated prototype devices by focused ion beam lithography and PbS quantum dots. Evaluation of the optical properties of the devices revealed that the emission spectrum width was narrower and the emission lifetime was shorter than those of quantum dot ensemble, and that the polarization was controlled along the minor axis of ellipse. These suggested that the quantum dot emission and the metamaterial element resonated as expected. The combination of a single quantum dot and a single elliptical SR-type metamaterial element was shown to have the potential to operate as a polarization-controlled single-photon emitter.

Heat pipes for passive solar heating systems

In the presented research work, heat pipes of gravitational and ring type were investigated. Two types of heat pipes were fabricated and tested under natural conditions for the study. According to the results of experiments, depending on the materials and dimensions of the heat pipes under study, the average value of the temperature difference in the gravitational heat pipe is 1.7 times higher, and the thermal resistance is 1.3 times lower.

Fairy circles and temporal periodic patterns in the delayed plant-sulfide feedback model.

Incorporating the self-regulatory mechanism with time delay to a plant-sulfide feedback system for intertidal salt marshes, we proposed and studied a functional reaction-diffusion model. We analyzed the stability of the positive steady state of the system, and derived the sufficient conditions for the occurrence of Hopf bifurcations. By deriving the normal form on the center manifold, we obtained the formulas determining the properties of the Hopf bifurcations. Our analysis showed that there is a critical value of time delay. When the time delay is greater than the critical value, the system will show asymptotical temporal periodic patterns while the system will display asymptotical spatial homogeneous patterns when the time delay is smaller than the critical value. Our numerical study showed that there are transient fairy circles for any time delay while there are different types of fairy circles and rings in the system. Our results enhance the concept that transient fairy circle patterns in intertidal salt marshes can infer the underlying ecological mechanisms and provide a measure of ecological resilience when the self-regulatory mechanism with time delay is considered.

Desempenho de discos e anéis de semeadoras submetidos a temperaturas crescentes

Abstract The objective of this work was to evaluate the effect of temperature on disks and rings for seeders and the consequences for the performance of seed distribution. The treatments consisted of the heating of three types of disks and rings for seeders at 30, 40, 50, 60, 70, 80, 90, and 100°C, with four replicates. The evaluated variables were: fitting to the base of the seeder, thickness, diameter, and quality of seed distribution (failed, multiple, and acceptable spacings). There is no significant deformation in the disks and rings for the analyzed variables, and the performance of the longitudinal seed distribution is maintained at all temperatures.

Miniscrew-assisted rapid palatal expansion (MARPE): Factors influencing planning.

This cross-sectional study evaluated the bone thickness on mini-implants insertion site, the factors that influence the digital planning of MARPE appliance (miniscrew-assisted rapid palatal expansion), and its different designs. A total of 135 plannings were assessed regarding the size of the expander screw used, the positioning and the type of the mini-implant rings, and their location in relation to the teeth. Bone thickness measurements were assessed in the region of the mini-implants' trajectory. Differences between the sexes was verified using the ANOVA test (5% significance). 73 cases were planned with 4 mini-implants and 62 cases, with 6 mini-implants. In 90% of cases, teeth #16 and #26 were used as supports, and the most used expander screw was 13mm (64.1% of cases). The anterior mini-implants of conventional MARPE showed more pronounced insertion in bone in males (5.9 ± 2mm; p= 0.025). The extra mini-implants (anterior region) were inserted with greater bone thickness in males (11.1 ± 2.3mm) compared to females (9.9 ± 1.8mm; p=0.041). A greater bone thickness was observed in males (10.1 ± 2.1 mm) when using mini-implants in the paramedian region. Additional rings allow more pronounced bone insertion. Male patients had greater bone thickness, which may be related to greater difficulty in opening the sutures. The alveolar process region seems to be a satisfactory site for mini-implants to those patients with reduced bone thickness in the paramedian posterior region. MARPE appliance must be customized for each patient, due to bone thickness and anatomical variations.

UV absorption enhanced polydopamine coating.

Mussel-inspired polydopamine (PDA) coatings have gained significant attention in various fields, including biomedicine, energy, detection, and UV protection, owing to their versatile and promising properties. Among these properties, UV shielding stands out as a key feature of PDA coatings. Nevertheless, the current methods for tuning the UV-shielding properties of PDA coatings are quite limited, and only rely on thickness adjustment, which might involve additional issues like color and visible light transmittance to the coating layer. In this study, we propose a facile and modular approach to enhance the UV absorption of PDA coatings by incorporating thiol-heterocycle (TH) derivatives. Both pre- and post-modification strategies can effectively impede the formation of conjugated structures within PDA, leading to enhanced UV absorption within the PDA layers. More importantly, these strategies can improve the UV absorption of PDA coatings while reducing the visible light absorption. Furthermore, this method enabled efficient regulation of the UV absorption of PDA coatings by altering the ring type (benzene ring or pyridine ring) and substituent on the ring (methoxyl group or hydrogen atom). These PDA coatings with enhanced UV absorption demonstrate great promise for applications in UV protection, antibacterial activity, wound healing and dye degradation.

STRUCTURE OF A RING IN WHICH EVERY ELEMENT IS SUM OF 3, 4 OR 5 COMMUTING TRIPOTENTS

In this paper we show if $R$ be a ring in which every element is sum of three commuting tripotents then for every $k\in R$ we have $(k-3)(k-2)^2(k-1)^2k^2(k+1)^2(k+2)^2(k+3)=0$, if every element of $R$ is sum of four commuting tripotents then for every $k\in R$ we have $(k-4)(k-3)(k-2)^2(k-1)^2k^4(k+1)^2(k+2)^2(k+3)(k+4)=0$, if every element of $R$ is sum of five commuting tripotents then for every $k\in R$ we have $(k-5)(k-4)(k-3)^2(k-2)^3(k-1)^3k^4(k+1)^3(k+2)^3(k+3)^2(k+4)(k+5)=0$. Then we discuss the properties of these type of ring. Finally we find the general structure of a ring in which every element is sum of $n$ commuting tripotents and discuss the properties of it.

The Predictors and Outcomes of Functional Mitral Stenosis following Surgical Mitral Valve Repair: A Retrospective Analysis.

To optimize mitral valve repair outcomes, it is crucial to comprehend the predictors of functional mitral valve stenosis (FMS), to enhance preoperative assessments, and to adapt intraoperative treatment strategies. This study aimed to identify FMS risk factors, contributing valuable insights for refining surgical techniques. Among 228 selected patients, 215 underwent postoperative echocardiography follow-ups, and 36 met the FMS criteria based on a mean trans-mitral pressure gradient of >5 mmHg. Patients with FMS exhibited higher pulmonary systolic arterial pressure and increased late mortality during the follow-up. Univariable logistic regression analysis identified several risk factors for FMS, including end-stage renal disease, anterior leaflet lesion, concomitant aortic valve replacement, smaller ring size, ring type, and neochordae implantation. Conversely, resection alone and resection combined with neochordae implantation had protective effects against FMS. Multivariable logistic regression analysis revealed that smaller ring sizes and patch repair independently predicted FMS. When focusing on degenerative mitral regurgitation, the neochordae implantation without resection in leaflet repair, emerged as an independent predictor of FMS. Surgeons should weigh the substantial impact of surgical procedures on postoperative trans-mitral pressure gradients, emphasizing preoperative evaluation and techniques such as precise ring size assessment and effective leaflet management.

Process based modelling of plants–fungus interactions explains fairy ring types and dynamics

Many mushroom-forming fungi can develop circular colonies affecting the vegetation in a phenomenon named fairy rings. Since the nineteenth century, several hypotheses have been proposed to explain how fairy ring fungi form ring-like shapes instead of disks and why they produce negative or positive effects on the surrounding vegetation. In this context, we present a novel process-based mathematical model aimed at reproducing the mycelial spatial configuration of fairy rings and test different literature-supported hypotheses explaining the suppressive and stimulating effects of fungi on plants. Simulations successfully reproduced the shape of fairy rings through the accumulation of fungal self-inhibitory compounds. Moreover, regarding the negative effects of fungi on vegetation, results suggest that fungal-induced soil hydrophobicity is sufficient to reproduce all observed types of fairy rings, while the potential production of phytotoxins is not. In relation to the positive effects of fungi on plants, results show that the release of phytostimulants is needed to reproduce the vegetation patterns associated to some fairy ring types. Model outputs can guide future experiments and field work to corroborate the considered hypotheses and provide more information for further model improvements.

Wideband hybrid metamaterial absorber via compound design of multiple mechanisms

Broadband and high efficiency are the two core indexes of absorption research, which usually requires a balance between them. Therefore, how to take into account both and achieve broadband and efficient absorption is a hot topic in current research. In this paper, by the compound design of multiple mechanisms, a kind of wideband hybrid metamaterial absorber (HMA) is proposed. The overall structure consists of a layer of patterned resistive film and a layer of magnetic absorbing material (MAM) separated by the air. The resistive layer is designed as square ring type to regulate the local magnetic field, which results in significant magnetic field enhancement within the MAM layer, and this mechanism provides a prerequisite for wideband and high-efficiency absorption in the low frequency band. Furthermore, due to the electrical losses of the resistive film, another absorption band is additionally excited in the high frequency band. Thanks to the multiple mechanisms, the absorption efficiency above 90% in the 3.2–22.0 GHz frequency band can be realized, and the thickness of the overall structure is 7.0 mm that is 0.07 of the wavelengths at the lowest frequency point. To demonstrate this method, a prototype is designed, fabricated and measured. Both the simulation and experiment results verify the effectiveness of the proposed method. This work provides a new method to design wideband and high-efficiency electromagnetic absorption structures and may find potential applications in multi-functional planar or conformal structures.