Small Ratio Research Articles

Modeling of masonry infilled RC frames with different aspect ratios using plastic hinge and equivalent strut

The existence of diverse modeling approaches for masonry-infilled frames causes uncertainty among practicing engineers when seeking a definitive model for their design practice. This paper presents a practical and simple approach to modeling the masonry-infilled frames. The proposed approach models the plasticity in the beams and columns of the reinforced concrete (RC) frames using flexural plastic hinges while modeling the masonry panel as a nonlinear equivalent strut. The implementation of the hinge is based on discretizing the frame cross-section into fibers and utilizing a popular formula to estimate the plastic hinge length specific to masonry-infilled frames. Furthermore, the implemented equivalent strut model employs a trilinear force–displacement backbone curve. The efficiency of this approach was evaluated against the experimental results of four different tested infilled RC frames available in the literature. A conventional approach based on a typical explicit plastic hinge was included for comparison. Unlike the conventional approach, the numerical results obtained from the presented approach better matched the experimental results. Subsequently, the presented approach was utilized to investigate the effect of the aspect ratio of clay masonry infill panels on the behavior of RC frames. The investigation revealed that the panels with larger aspect ratios provided a larger contribution to the ultimate lateral load, despite experiencing lower ultimate axial stresses compared to panels with smaller aspect ratios. However, increasing the thickness of the masonry infill with a small aspect ratio appeared to improve its effectiveness in resisting the lateral force.

The hierarchical three-body problem at $$ \mathcal{O}\left({G}^2\right) $$

The hierarchical three-body problem at $$ \mathcal{O}\left({G}^2\right) $$

Deconvolution Density Estimation with Penalized MLE

Deconvolution is the important problem of estimating the distribution of a quantity of interest from a sample with additive measurement error. Nearly all infinite-dimensional deconvolution methods in the literature use Fourier transformations. These methods are mathematically neat, but unstable, and produce bad estimates when signal-noise ratio or sample size are low. A popular alternative is to maximize penalized likelihood for a finite-dimensional basis expansion of the unknown density. We develop a new method to optimize penalized likelihood over the infinite-dimensional space of all functions. This gives the stability of regularized likelihood methods without restricting the space of solutions. Our method compares favorably with state-of-the-art methods on simulated and real data, particularly for small sample size or low signal-noise ratio. We also provide the first results on the consistency and rate of convergence of penalized maximum likelihood estimates for density deconvolution. Supplementary materials for this article are available online, including a standardized description of the materials available for reproducing the work.

Effect of Aspect Ratio on Asymmetrical Wear of Brake Pads Under High-Speed and Heavy-Load Braking Conditions

This study investigates the influence and mechanisms of friction blocks with varying aspect ratios on the asymmetrical wear of brake pads under high-speed and heavy-load braking conditions. A large megawatt-level wind turbine brake device was used, and the Archard wear model was integrated into the analysis of brake interface wear characteristics through finite element method (FEM) and arbitrary Lagrangian-Eulerian (ALE) technology. A thermal-mechanical-wear coupling model was developed for brake systems with five different aspect ratio friction blocks, and its accuracy was validated through wear tests on an inertial brake test bench. A method for calculating tangential and radial wear is proposed to characterize the degree of asymmetrical wear at the friction interface. The study revealed a non-uniform wear distribution at the contact interface, with greater wear observed at the leading and outer edges of the friction block. A small aspect ratio (L/W < 1.5) predominantly results in radial wear, while a large aspect ratio (L/W > 1.5) leads to tangential wear. An aspect ratio of 2:1 balances radial and tangential wear, indicating improved wear resistance.

Construction of AI scroll profiles for scroll compressors utilizing algebraic spiral and involute

A new type of scroll profile consisting of an algebraic spiral and an involute (AI) is proposed in this paper. To solve the problem of the small built-in volume ratio in the traditional scroll profile and the need to modify the wrap head before use, mathematical equations and geometric models of AI scroll profiles are generated based on the boundary constraints of combined scroll profiles. In addition, the geometrical relationship between scroll profile parameters and the influence of profile parameters on the midline, scroll wrap, and geometrical properties of AI scroll profiles are quantitatively studied. Finally, the stress and deformation of the new AI scroll wrap are compared to those of the involute scroll wrap. The results indicate that the AI scroll profile improves the performance of the scroll compressor and can be used directly without head modification. Under the same scroll wrap profile parameters, the maximum deformation and maximum equivalent stress of AI scroll wrap are 44.61% and 80.12% lower than those of the involute scroll wrap, respectively.

Understanding the Importance of the Small Artery Media-Lumen Ratio: Past and Present.

The media-lumen diameter ratio of small arteries is increased in hypertension, diabetes and obesity. It is likely that both shear stress on the endothelial cells, transmural pressure and smooth muscle cell tone are important for the altered vascular structure. However, the precise interaction and importance of these factors are incompletely understood. At the molecular level transglutaminases, metalloproteinases, integrins, NO and several other factors have been suggested to be important, but our understanding of how the many factors together control vascular structure is surprisingly limited. The media-lumen diameter ratio of the small arteries has prognostic value, which is independent of the classical risk factors for cardiovascular disease. Importantly this is also the case in patients treated pharmacologically for high blood pressure. It is therefore relevant to consider small artery structure as a potential target in relation to prevention of cardiovascular disease.

Resonant capture of stars by black hole binaries: extreme eccentricity excitation

ABSTRACT Massive black hole (MBH) binaries in galactic nuclei are one of the leading sources of ${\sim}$mHz gravitational waves (GWs) for future missions such as Laser Interferometer Space Antenna (LISA). However, the poor sky localization of GW interferometers will make it challenging to identify the host galaxy of MBH mergers absent an electromagnetic counterpart. One such counterpart is the tidal disruption of a star that has been captured into mean motion resonance with the inspiralling binary. Here we investigate the production of tidal disruption events (TDEs) through capture into, and subsequent evolution in, orbital resonance. We examine the full non-linear evolution of planar autoresonance for stars that lock into autoresonance with a shrinking MBH binary. Capture into the 2:1 resonance is guaranteed for any realistic astrophysical parameters (given a relatively small MBH binary mass ratio), and the captured star eventually attains an eccentricity $e\approx 1$, leading to a TDE. Stellar discs can be produced around MBHs following an active galactic nucleus episode, and we estimate the TDE rates from resonant capture produced when a secondary MBH begins inspiralling through such a disc. In some cases, the last resonant TDE can occur within a decade of the eventual LISA signal, helping to localize the GW event.

Study of the motion and interaction of micro-swimmers with different scales in Poiseuille flow

We conducted numerical simulations using the immersed boundary–lattice Boltzmann method to investigate the motion and interaction of microswimmers of different scales in Poiseuille flow. The squirmers self-propelling via generating surface waves were used as the model for microswimmers. The movement of two squirmers with different scale ratios (0.6–1.5), swimming Reynolds numbers (0.1–2.0), swimming strength (1–7), and blockage ratios (0.125–0.25) in Poiseuille flow was studied. Five classical motion patterns were identified: periodic tumbling, steady motion, periodic oscillation, damped oscillation, and chaotic motion modes. Initially, we examined the interaction between a pair of squirmers of the same scale and elucidated the causes of their different motion pattern transitions using the pressure distribution, direction angle, and swimming velocity of the squirmers. We investigated the variation of transport velocity with blockage ratio and swimming strength. A pair of squirmers with small ratios tended to migrate in a stable motion pattern, while those with large ratios showed a high tendency to change their motion patterns. Pushers with an increasing swimming Reynolds number were adsorbed to the wall and migrated stably along the wall.

Finite element analysis and experimental study on the sealing performance of low-phenyl silicone rubber sealing rings

PurposeThe brake pipe system was an essential braking component of the railway freight trains, but the existing E-type sealing rings had problems such as insufficient low-temperature resistance, poor heat stability and short service life. To address these issues, low-phenyl silicone rubber was prepared and tested, and the finite element analysis and experimental studies on the sealing performance of its sealing rings were carried out.Design/methodology/approachThe low-temperature resistance and thermal stability of the prepared low-phenyl silicone rubber were studied using low-temperature tensile testing, differential scanning calorimetry, dynamic thermomechanical analysis and thermogravimetric analysis. The sealing performance of the low-phenyl silicone rubber sealing ring was studied by using finite element analysis software abaqus and experiments.FindingsThe prepared low-phenyl silicone rubber sealing ring possessed excellent low-temperature resistance and thermal stability. According to the finite element analysis results, the finish of the flange sealing surface and groove outer edge should be ensured, and extrusion damage should be avoided. The sealing rings were more susceptible to damage in high compression ratio and/or low-temperature environments. When the sealing effect was ensured, a small compression ratio should be selected, and rubbers with hardness and elasticity less affected by temperature should be selected. The prepared low-phenyl silicone rubber sealing ring had zero leakage at both room temperature (RT) and −50 °C.Originality/valueThe innovation of this study is that it provides valuable data and experience for the future development of the sealing rings used in the brake pipe flange joints of the railway freight cars in China.

Capillary-driven self-assembly of soft ellipsoidal microgels at the air–water interface

The adsorption of ellipsoidal colloidal particles on liquid interfaces induces interfacial deformation, resulting in anisotropic interface-mediated interactions and the formation of superstructures. Soft prolate-shaped microgels at the air-water interface offer an ideal model for studying spontaneous capillary-driven self-assembly due to their tunable aspect ratio, controlled functionality, and softness. These microgels consist of a polystyrene core surrounded by a cross-linked, fluorescently labeled poly([Formula: see text]-isopropylmethylacrylamide) shell. By uniaxially stretching the particles embedded in polyvinyl alcohol films, the aspect ratio [Formula: see text] can be finely adjusted. [Formula: see text] was found to vary from 1 to 8.8 as estimated in their swollen conformation at 20 °C from confocal laser scanning microscopy. The spontaneous interfacial self-assembly at the air-water interface is investigated through fluorescence microscopy, theoretical calculations, and computer simulations. A structural transition occurs from a seemingly random assembly for small aspect ratios to compact clusters, which transform into a side-to-side assembly forming long chains for high aspect ratios. The influence of the poly([Formula: see text]-isopropylmethacrylamide) shell on the assembly indicates a significant [Formula: see text]-dependent microgel deformation. This deformation, in turn, determines the average distance between the particles. Consequently, capillary-driven self-assembly of soft anisotropic colloids becomes a powerful mechanism for structuring interfaces and designing microstructured materials.

Carrier Tunnelings on Ultrashort‐Gate Junction‐Less Field‐Effect Transistor Designs

This study discusses tunneling problems encountered when designing ultrashort‐gate junction‐less field‐effect transistors (FETs). Ultrathin‐body silicon‐on‐insulator (UTB‐SOI) FETs are suitable for nano‐length gate designs owing to the augmented bandgap at channel regions. However, a comprehensive understanding of source‐to‐drain (S/D) and gate‐dielectric (G/D) tunneling is essential to ensure optimal performance and reliability. In this study, numerical simulations of UTB‐SOI FETs are conducted to reveal their effects. First, for S/D tunneling, only a p‐channel FET (PFET) is considered critical, and larger tunneling mass eases this problem. Second, for G/D tunneling, an n‐channel FET (NFET) is considered critical. Therefore, the oxide‐wall UTB‐SOI design is considered for the NFET, enabling a large and small ratios for NFET and PFET. Conversely, the conventional trenched UTB‐SOI is considered suitable for PFET. Moreover, the findings demonstrate that adopting hafnium oxide (HfO) as the oxide material renders good FET characteristics. The optimized FET designs can facilitate the minimum gate length to be 1 nm or shorter, especially for NFETs.

On the Use of Strong Proton Donors as a Tool for Overcoming Line Broadening in NMR: A Comment.

Overcoming line broadening of labile protons and achieving high-resolution NMR spectra is crucial for the structural and conformational analysis of organic molecules. Recently, Ma etal. (Magn. Reson. Chem. 2024, 62, 198-207) demonstrated the effectiveness of 2,2,2-trifluoroacetic acid (TFA) in sharpening NMR signals for nitrogen-containing compounds which exhibit prototropic tautomerization or conformational isomerism using high molar ratio of [acids]/[solute] ~ 5 to 200. In this commentary, we provide an overview of earlier publications and highlight the extensive applications of TFA in enhancing NMR resolution across a variety of organic functional groups, with the use of very small ratios of [acids]/[solute] ~ 10-3 to 10-2. The prospects for the unequivocal structure analysis using labile protons as the starting point will be analyzed.

Ultraviolet Photodissociation of the N,N-Dimethylformamide Cation.

N,N-Dimethylformamide (DMF) provides a useful small-molecule model for studying features of the peptide bond that forms the backbone of proteins. We report results from a comprehensive multimass velocity-map imaging study into the ultraviolet (UV) photolysis of the N,N-dimethylformamide cation (DMF+) at wavelengths of 225, 245, and 280 nm. Electronic structure calculations on DMF and DMF+ were employed to help interpret the experimental results. DMF+ ions are generated by 118 nm single-photon ionization of neutral DMF. Subsequent UV photolysis is found to lead to selective cleavage of the N-CO amide bond. This yields HCO + NC2H6+ as major products, with virtually all of the excess energy released into internal modes of the fragments. The data also indicate a small branching ratio into the HCO+ + NC2H6 product pair, which can be accessed from the 32A' electronic state of DMF+. N-CO bond dissociation can also be accompanied by simultaneous intramolecular hydrogen transfer from the oxygen to the nitrogen end of the amide bond, in which case NCH4+ can be formed efficiently at all three wavelengths. The primary NC2H6+ product is relatively long-lived, but the high degree of internal excitation often results in secondary fragmentation via a variety of pathways to form CH3+, NH4+, NCH2+, and NC2H4+, with secondary dissociation more likely at higher photon energies. The isotropic velocity-map images recorded for the various fragments attest to the long lifetime of NC2H6+ and also imply that dissociation most probably occurs from the same set of electronic states at all wavelengths studied; these are thought to be the 12A' ground state and 22A' first excited state of the DMF+ cation.

Numerical simulation of EFP forming and penetration characteristics for shaped charge with a small aspect ratio

Abstract In this paper, the effects of main charge aspect ratio, liner curvature radius, liner wall thickness, and other factors on the forming characteristics of the explosively formed projectile(EFP) were studied based on the AUTODYN simulation platform. The influence laws of various factors on the forming characteristics of EFP were obtained, and the structure of the shaped charge with a small aspect ratio was optimized. Numerical simulations showed that, in the data range studied in this paper, to obtain the ideal penetration effect, the aspect ratio of the main charge should be selected from 0.65 to 0.8, the wall thickness of the liner should be generally selected from 0.02 to 0.05 times of charge diameter (CD), and the liner curvature radius should be 90 mm to 110 mm. At the same time, the influence law of each factor on armor steel penetration is obtained, which provides a theoretical basis for selecting suitably shaped charge structures under different damage requirements.

Confidence intervals of the relative risk and odds ratio can predict when the optimal information size in a meta-analysis is not met.

We sought to empirically evaluate whether the width of confidence interval (CI) of the relative risk (RR) and odds ratio (OR) can obviate the need for calculating the optimal information size (OIS) when making GRADE imprecision judgments. We analyzed a convenience sample of meta-analyses extracted from the Cochrane Database of Systematic Reviews. From each meta-analysis, we calculated OIS based on relative risk reductions (RRR) of 15%-50% and evaluated the ratio of upper to lower 95% CI boundaries of RR (RR CI ratio) and OR (OR CI ratio). We calculated the positive predictive value (PPV) as the probability that a small CI ratio would correctly identify an OIS that was met, and the negative predictive value (NPV) as the probability that a large CI ratio would correctly identify an OIS that was not met. We analyzed 39,569 meta-analyses (266,877 studies). Analyses across various RRR's demonstrated high NPV's and low PPV's, suggesting that using the CI approach is helpful in identifying when OIS would not be met, but not as helpful in 'ruling in' that OIS would be met. Cutoffs previously proposed for RR CI ratio (>2.5) and OR CI ratio (>3) had very high NPV's (>90%) except when the RRR used to calculate OIS was high (30%-50%) and when the baseline risk or number of included studies increased. This empirical analysis supports using CI ratios of RR and OR to 'rule out' meeting OIS (i.e., to rate down the certainty of evidence due to imprecision). The CI approach is not helpful to 'rule in' meeting OIS and is not helpful when the plausible effect size is >30% RRR.

Rigorous justification of hydrostatic approximation of compressible fluid flow equations

In this paper, we obtain the 3D compressible primitive equations approximation with gravity by taking the small aspect ratio limit to the Navier-Stokes equations. We use the versatile relative entropy inequality to prove rigorously the limit from the compressible Navier-Stokes equations with a pressure law of the form p(ρ) = ρ2 to the compressible primitive equations.

A Simplified Mathematical Model for Cell Proliferation in a Tissue-Engineering Scaffold.

While the effects of external factors like fluid mechanical forces and scaffold geometry on tissue growth have been extensively studied, the influence of cell behavior-particularly nutrient consumption and depletion within the scaffold-has received less attention. Incorporating such factors into mathematical models allows for a more comprehensive understanding of tissue-engineering processes. This work presents a comprehensive continuum model for cell proliferation within two-dimensional tissue-engineering scaffolds. Through mathematical modeling and asymptotic analysis based on the small aspect ratio of the scaffolds, the study aims to reduce computational burdens and solve mathematical models for tissue growth within porous scaffolds. The model incorporates fluid dynamics of nutrient feed flow, nutrient transport, cell concentration, and tissue growth, considering the evolving scaffold porosity due to cell proliferation, with the crux of the work establishing the ideal pore shape for channels within the tissue-engineering scaffold to obtain the maximum tissue growth. We investigate scaffolds with specific two-dimensional initial porosity profiles, and our results show that scaffolds which are uniformly graded in porosity throughout their depth promote more tissue growth.

Significantly improve capacitive properties of alicyclic polyimide dielectrics at high temperatures via hard/soft segment engineering

The demand for high energy storage density and efficiency of polymer film capacitors at high temperatures is urgently increasing in the electronics and electrical field. However, most traditional high temperature resistant polymers exhibit the low bandgap and high conductive loss because of the presence of conjugated aromatic structures, resulting in a significant decrease in the energy storage performance at high temperatures and high fields. In this paper, a series of alicyclic polyimide dielectric films containing hard segment of phenyl imide and soft segment of cyclohexyl imide are designed and prepared. On the one hand, the introduction of non-coplanar alicyclic ring into main-chain of polyimide can break long distance conjugation effect, weaken the intermolecular and intramolecular charge transfer interaction and improve the bandgap. On the other hand, the physical crossing point formed by the soft segments can sharply increase Young's modulus of the polyimide films. As a result, the terpolymer polyimide film (CPI90) with copolymerization ratio of phenyl/cyclohexyl dianhydride of 9:1 achieves a highest discharge energy density (Ud) of 5.59 J cm−3 at 150 °C. Importantly, the CPI90 film can obtain the Ud of 2.74 J cm−3 at 200 °C. In addition, the CPI90 film possesses a good self-healing ability attributing to a small ratio for the carbon to hydrogen and oxygen. This work offers a new strategy for synergistically promoting the bandgap and Young's modulus of polymer dielectrics via molecular and hard/soft segment engineering.

Turbulence distortion and blockage in the induction zone of a horizontal axis turbine

Wind tunnel measurements of the incident turbulent velocity fields and axial forces on a horizontal axis turbine and porous disc analogues are reported. The models were tested in both a simulated atmospheric boundary layer (ABL) and in grid turbulence, allowing for a range of turbulence length scale to rotor diameter ratios to be considered. A theoretical framework to account for the combined effect of distortion and potential flow blocking in the induction zone is presented. In the case of very large length-scale turbulence to diameter ratios, where distortion effects are minimal, a quasi-steady approach is adopted for the effect of blocking. For the small length-scale ratio limit, the method is developed from the classical analyses for rapid distortion of turbulence and blockage from flow through a porous sheet of resistance. For general length-scale ratios, an efficient prediction method based on interpolation between the two length-scale ratio extremes is established. For very large length-scale ratios, a quasi-steady theory without distortion is appropriate for a rotor or disc in a simulated ABL. The small length-scale theory is applicable for tests conducted in grid turbulence. The results of the study can inform the prediction and interpretation of typical measurements of turbulence within the induction zone and the fluctuating loads on a rotor, at both prototype and full scale. This is of particular importance to fatigue load assessments.

Photometric and Spectroscopic Analysis of Eight Totally Eclipsing Contact Binaries with Small Mass Ratios

This paper selected eight totally eclipsing contact binaries for photometric and spectroscopic studies. Spectral data were analyzed by University of Lyon Spectroscopic analysis Software, and photometric data were analyzed using PHOEBE through Markov Chain Monte Carlo (MCMC) sampling. We used two methods to calculate the initial values for running MCMC: one method is a new approach proposed by ourselves to model light curves without spots, while the other method is the genetic algorithm, which can determine physical parameters with spots. The results imply that these eight targets are all contact binary stars with a small mass ratio below 0.25. There are four systems exhibiting the O’Connell effect. By adding a dark spot on the primary component, the ideal fitting can be obtained. Meanwhile, it was found that two systems are shallow contact binaries, while the remaining six are moderate contact binaries. An O − C analysis of the eight eclipsing binary stars revealed that seven of them exhibit long-term changes. Four of them display a long-term decreasing trend in orbital period, while the other three show a long-term increasing trend, and two targets exhibit periodic variations. A decrease in period may be caused by the transfer of matter from the more massive component to the less massive component, while an increase in period may be caused by transfer in the opposite way. The absolute physical parameters, orbital angular momentum, initial masses, and ages of these eight systems were calculated. Additionally, their mass–luminosity and mass–radius distributions were analyzed.