Confinement Model Research Articles

A Mesoscale Study on the Dilation of Actively Confined Concrete under Axial Compression.

The confinement of concrete enhances its strength and ductility by restraining lateral dilation. The accuracy of a confinement model depends on how well it captures the dilation of concrete. In the current paper, a mesoscale model is established to study the dilation properties of concrete in active confinement, where the heterogeneity of concrete is considered. The stress–strain and lateral–axial strain curves of concrete in active confinement were used to demonstrate the validity of the mesoscale model. Subsequently, the distribution of lateral strain and the influences of the strength grade and confinement ratio on the dilation of concrete were investigated in a simulation. The results show that the distribution of the lateral strain along the radial or longitudinal directions is not uniform on the specimen when compressive failure occurs. The confinement ratio has a more significant influence on the concrete’s transverse dilation than the strength grade. Finally, an expression of the lateral–axial strain relationship of concrete in active confinement is proposed. The proposed formula can reflect the simulation results of the mesoscale model and is in good agreement with the prediction of existing formulas.

Application of Group Method of Data Handling on the Ultimate Conditions' Prediction of FRP-Confined Concrete Cylinders.

Fiber-reinforced polymer (FRP) is widely used in the field of structural engineering, for example, as a confining material for concrete. The ultimate conditions (i.e., compressive strength and ultimate axial strain) are key factors that need to be considered in the practical applications of FRP-confined concrete cylinders. However, the prediction accuracy of existing confinement models is low and cannot provide an effective reference for practical applications. In this paper, a database containing experimental data of 221 FRP-confined normal concrete cylinder specimens was collected from the available literature, and eleven parameters such as the confining stress, stiffness ratio and strain ratio were selected as the input parameters. Then, a promising machine learning algorithm, i.e., group method of data handling (GMDH), was applied to establish a confinement model. The GMDH model was compared with nine existing models, and the prediction results of these models were evaluated by five comprehensive indicators. The results indicated that the GMDH model had higher prediction accuracy and better stability than existing confinement models, with determination coefficients of 0.97 (compressive strength) and 0.91 (ultimate axial strain). Finally, a convenient graphical user interface (GUI) was developed, which can provide a quick and efficient reference for engineering design and is freely available.

Nucleation of stem cell domains in a bistable activator–inhibitor model of the shoot apical meristem

Shoot apical meristems (SAMs) give rise to all above-ground tissues of a plant. Expansion of meristematic tissue is derived from the growth and division of stem cells that reside in a central zone of the SAM. This reservoir of stem cells is maintained by expression of a transcription factor WUSCHEL that is responsible for the development of stem cells in the central zone. WUSCHEL expression is self-activating and downregulated by a signaling pathway initiated by CLAVATA proteins, which are upregulated by WUSCHEL. This classic activator-inhibitor network can generate localized patterns of WUSCHEL activity by a Turing instability provided certain constraints on reaction rates and diffusion constants of WUSCHEL and CLAVATA are satisfied, and most existing mathematical models of nucleation and confinement of stem cells in the SAM rely on Turing's mechanism. However, Turing patterns have certain properties that are inconsistent with observed patterns of stem cell differentiation in the SAM. As an alternative mechanism, we propose a model for stem cell confinement based on a bistable-switch in WUSCHEL-CLAVATA interactions. We study the bistable-switch mechanism for pattern formation in a spatially continuous domain and in a discrete cellularized tissue in the presence of a non-uniform field of a rapidly diffusing hormone. By comparing domain formation by Turing and bistable-switch mechanisms in these contexts, we show that bistable switching provides a superior account of nucleation and confinement of the stem cell domain under reasonable assumptions on reaction rates and diffusion constants.

Behaviour of Confined and Unconfined Clay with or without Openings of Brick Masonry Columns

Masonry components are frequently limited to increase structural capacity. Concrete confinement models are commonly used to develop generalised approaches for assessing the behaviour of confined masonry columns. Concrete and masonry, on the other hand, differ significantly in terms of physical and mechanical qualities. Recent scientific studies on the experimental behaviour of constrained masonry columns have supplied useful knowledge.When two confined and unconfined masonry columns were exposed to vertical loads, an experimental study was conducted to compare their seismic behaviour. The first wall turned into built with conventional clay brick units, at the same time as the second one wall turned into built with modern concrete units. Both types of bricks have been synthetic at factories. The simple masonry homes have been decided via way of means of trying out 4 prisms of every brick kind beneathneath axial compression plus 4 small partitions subjected to diagonal compression, in addition to the unit homes, the one-of-a-kind mortars used for laying the bricks, and the obvious masonry homes received via way of means of trying out 4 prisms of every brick kind beneathneath axial compression plus 4 small partitions subjected to diagonal compression. The purpose of this study is to conduct an experimental analysis of brick masonry columns in order to assess the strength of specimens after 28 days. Clay substance that is both contained and unconfined.

The effects of deposition manner and rate on structure and morphology of porous ZnSe nanolayers: Modification of Phonon Confinement Model for resonant Raman conditions

Nanolayers of porous ZnSe with thickness of ∼50 nm were prepared by thermal vacuum evaporation, applying continuous and periodically interrupted deposition at different deposition rates. The surface morphology and film composition are studied by SEM and EDS methods. The XRD and Raman scattering measurements are used to confirm zinc blende ZnSe crystal structure. The Phonon confinement model is modified to analyze the Raman spectra excited by different laser lines both in non-resonant and near-resonant conditions. This analysis provides more profound insight in the ZnSe layers composition, nanocrystallite size and crystal lattice strain. The Raman results are also supported by the spectroscopic ellipsometry regarding the energy gap and porous properties of ZnSe layers. This study shows that both manner and rate of deposition significantly affect the nanolayers structure, morphology and optical properties and provide preparation of films with properties suitable for application which requires specific porous parameters important for the films chemical sensitivity.

Analytical study and design approach of the axial and flexural response of reinforced masonry columns confined with FRP jackets

Using fiber-reinforced polymer (FRP) wraps has proven to be an effective and optimized confinement technique to upgrade the axial and flexural capacity of reinforced concrete (RC) and reinforced masonry (RM) columns. The axial capacity of FRP-confined masonry depends on both the compressive strength of masonry before strengthening and the confinement pressure provided by the FRP jacket. This study proposes a simplified methodology to design and analyze prismatic fully grouted reinforced masonry columns (RMCs) strengthened with FRP Jackets. The proposed design methodology included an analytical confinement model to predict the compressive strength gain in RMCs due to the effective confinement pressure provided by FRP jackets. The proposed procedure was also designed to predict the nominal capacity of RMCs for practical design applications, with columns subjected to both axial loading and bending moment. The essential parameters to perform detailed section analysis were established, and suggested expressions were proposed to obtain the parameter values. Practical values for the equivalent rectangular stress block parameters were proposed. The theoretical axial force-moment interaction diagrams obtained by the proposed procedure were compared with available experimental data. The experimental test results were in good agreement with the analytical predictions by a reasonable marginal error. Furthermore, the effect of five design variables on the axial-flexural interaction of FRP-wrapped RMCs was investigated. The variables considered in the parametric study were the number of FRP layers, radius of the corners, stiffness of the FRP composite, cross-sectional aspect ratio, and masonry compressive strength. The results showed that increasing the FRP layers, corner radius, and FRP jacket stiffness significantly enhanced the axial capacity of the FRP-confined RMCs. However, the increase in the masonry compressive strength and cross-sectional aspect ratio negatively affected the axial capacity gain ratio of FRP-strengthened RMCs.

Cybernetic Approach to Health Assessment

The exploration of orbital space served as a prerequisite for the creation of a new direction of medical science in relation to the very extreme conditions of life of spacecraft crews. Space medicine, relying on the most modern research methods and approaches, thanks to the development of new medical devices and the use of unique data analysis algorithms, has made a significant contribution to the development of telemedicine, medical cybernetics, and prenosological principles for assessing the state of human health. The review reflects the main stages in the development of medical cybernetics and prenosological diagnostics based on the assessment of the regulatory components of the cardiovascular system. Discussed the aspects of the application of the method of mathematical analysis of the heart rhythm in relation to the assessment and forecast of the working capacity of cosmonauts, at the simulating model of microgravity and confinement. Shown the useful methodically apply for the healthcare of manufacture teams at the plants, passenger bus driver’s employments. As the part of appliance of the new advance tools of children and adolescents public health during the educating process at schools. The created system for analyzing the current functional state of human health and mathematical models that make it possible to predict its negative changes make it possible to predetermine the vector of development of medicine in the future. The foundations of knowledge gained over the period of more than 70 years of scientific activity of Professor R.M. Bavsky are reflected in promising areas of cardiology research using computer technologies - such as Cardiometry technologies.

Performance and modeling of FRP-steel dually confined reinforced concrete under cyclic axial loading

Fiber-reinforced polymer (FRP)-steel tubed reinforced concrete (FSTRC) columns present promising engineering applications due to the reasonable integration of three constituent materials. Compared with the numerous studies on their performance under monotonic loading, relatively few studies have focused on their cyclic axial behavior. Moreover, the available models for plain concrete solely confined by FRP might be incapable of estimating the confined concrete behavior in cyclically loaded FSTRC due to the possible effect induced by the steel reinforcement in concrete, the additional steel tube confinement, and the girth gaps at column ends. To this end, this paper investigated circular FSTRC stub columns under monotonic and cyclic axial loading. The test results confirmed that the inclusion of reinforcement had noticeable effects on the unloading path since the tensile axial stresses in longitudinal steel bars slowed down the stiffness degradation of the inner concrete during unloading. For envelope cycles, the increase of the additional steel confinement level had a negligible impact on the plastic strain and the stress deterioration of the inner concrete. A confinement model was developed to estimate the full-range behavior of the FRP-steel dually confined reinforced concrete under cyclic axial loading with favorable accuracy.

Behavior and design of axially loaded high-strength concrete-filled circular aluminum tubular short columns

Concrete-filled aluminum tubular (CFAT) columns inherit superior mechanical performance in terms of strength and ductility and offer excellent corrosion resistance. However, due to the limited investigation, the performance of CFAT columns has not been fully understood yet. This paper presents a new fiber element (FBE) model for nonlinear analysis of axially loaded high-strength CFAT short columns with circular sections. The accurate constitutive material models of aluminum and confined concrete utilized in the FBE model are presented. On the basis of test results, a novel lateral confinement model is developed to determine the confinement effect of outer aluminum tubes on core concrete in circular CFAT columns. A new strength degradation factor for quantitatively determining the post-peak behavior of the confined concrete in CFAT circular columns is also proposed and incorporated into the FBE model. The proposed FBE model is validated through comparisons with test results compiled from published literature, predictions by three-dimensional finite element (3D FE) modeling and the existing lateral pressure model of CFAT columns proposed by another researcher. Parametric studies are implemented to ascertain the influences of key variables on the performance of the CFAT columns. The experimental and numerical data are utilized to examine the applicability of current design standards for the design of conventional concrete-filled steel tubular (CFST) columns in designing CFAT columns. A new strength design formula is proposed to predict the compressive ultimate strengths of CFAT columns and validated by comparing with test results and the ones obtained from FBE analyses. Overall, it is found that the proposed FBE model and design formula can predict well the axial responses of high-strength CFAT short columns with circular cross-sections.

Nonparaxial interference and diffraction under 3D spatial coherence.

The nonparaxial interference and diffraction by a planar array of emitters have been recently described in terms of the light energy confinement in Lorentzian wells, which are spatially structured by the geometric potential, activated in turn by the two-point correlation prepared at the array plane. Nevertheless, the use of nonplanar arrays of light emitters is of increasing interest in optical technology. Therefore, we extend the confinement model to include spatially structured Lorentzian wells by geometric potentials associated with nonplanar distributions of points. Such geometric potentials are activated by two-point correlations with 3D supports prepared at the nonplanar array. The theoretical analysis is supported and illustrated by numerical simulations.

Performance improvement of ballasted railway tracks using three-dimensional cellular geoinclusions

Three-dimensional (3D) cellular inclusions such as geocells and scrap rubber tyres improve the engineering properties of the infill materials by providing all-around confinement. Although the 3D geoinclusions possess immense potential in the railway industry, their application is still limited due to a lack of adequate techniques to evaluate the magnitude of improvement provided by these artificial inclusions. This article presents an innovative computational approach to evaluate the effectiveness of 3D cellular geoinclusions in improving the performance of ballasted railway tracks. The proposed method is an integrated approach that combines the additional confinement model with the geotechnical rheological model for a railway track. The methodology is applied to an open track-bridge transition, and the results revealed that the geoinclusions substantially reduce the differential settlement. However, the magnitude of improvement depends on the opening size, placement location within the track and material used to manufacture the cellular inclusions. Moreover, the magnitude of settlement reduction also depends on the axle load and subgrade soil properties. The proposed methodology can assist the railway engineers in assessing the efficacy of 3D inclusions in improving the performance of railway tracks and help select the most appropriate material, size, and location of reinforcement for deriving maximum benefits.

A Comparative Study on the Confinement Models of High-Strength Steel Fiber Concrete

Since the last four decades, the behavior of concrete contains of steel fiber, or often called steel fiber concrete, with a wide range of compressive strength has been carried out. Generally, the results of the experimental program produced a material which has a more ductile compared with normal concrete or concrete without fiber. Due to the ductility properties of the material, it is very suitable for use as an earthquake-resistant structural material. At the same time, the behavior of high-strength steel-fiber concrete has also investigated, one of which is about confined high-strength steel-fiber concrete. Analytical models of confined high-strength steel fiber concrete have been developed in various preliminary studies, with their characteristics derived based on the experimental results. Therefore, this research evaluated the models of confined high-strength steel-fiber concrete proposed by Mansur et al., Hsu and Hsu, and Paultre et al. The evaluation includes stress-strain behavior, strength enhancement of confined concrete (f'cc/f'co) or K value, the increase in confined concrete strain (ε'cc/ε'co), and strain of confined concrete when the stress has dropped by 50 percent against its unconfined strain (εcc50/εc50). The comparison method was carried out using a statistical approach and stress-strain simulation. Evaluation results showed significant predictive differences in confinement models in terms of post-peak behavior and parameters ε'cc/ε’co and εcc50/εc50. Prediction of confinement models on the value of f'cc/f’co to the experimental results has a coefficient of variation above 10%. The result further showed that a modified model of confined high-strength steel-fiber concrete was proposed and able to simulate the stress-strain behavior.

Proton diffusion and hydrolysis enzymatic reaction in 100 nm scale biomimetic nanochannels.

Liquids in 10-100 nm spaces are expected to play an important role in biological systems. However, the liquid properties and their influence on biological activity have been obscured due to the difficulty in nanoscale measurements, either in vivo or in vitro. In this study, an in vitro analytical platform for biological systems is established. The nanochannels were modified with lipid bilayers, thereby serving as a model for biological confinement, e.g., the intercellular or intracellular space. As a representative property, the proton diffusion coefficient was measured by a nanofluidic circuit using fluorescein as a pH probe. It was verified that proton conduction was enhanced for channel widths less than 330 nm. A proton-related enzymatic reaction, the hydrolysis reaction, was also investigated, and a large confinement effect was observed.

Effect of Confinement on Detonation Velocity and Plate Dent Test Results for ANFO Explosive

The detonation properties of nonideal explosives are highly dependent on charge diameter and existence and properties of confinement. In this study, the effect of different confinements on the detonation velocity of ANFO explosives was experimentally determined along with the results of the plate dent test. ANFO explosive was selected as one of the most commonly used nonideal explosives. Following the measurement results, we found that the detonation velocity increased with increasing wall thickness, and the velocity increase was different for different confinement materials. A strong correlation existed between the ratio of the mass of confiner and explosive (M/C) and the detonation velocity (R = 0.995), and between (M/C) and the depth of the dent (δ) (R = 0.975). The data presented in this paper represent preliminary findings in developing a confinement model required for reliable numerical modeling of nonideal explosives.

Design and Applications of Integrated Transducers in Commercial CMOS Technology

Monolithic integration of Microelectromechanical Systems (MEMS) directly within CMOS technology offers enhanced functionality for integrated circuits (IC) and the potential improvement of system-level performance for MEMS devices in close proximity to biasing and sense circuits. While the bulk of CMOS-MEMS solutions involve post-processing of CMOS chips to define freely-suspended MEMS structures, there are key applications and conditions under which a solid, unreleased acoustic structure composed of the CMOS stack is preferred. Unreleased CMOS-MEMS devices benefit from lower barrier-to-entry with no post-processing of the CMOS chip, simplified packaging, robustness under acceleration and shock, stress gradient insensitivity, and opportunities for frequency scaling. This paper provides a review of advances in unreleased CMOS-MEMS devices over the past decade, with focus on dispersion engineering of guided waves in CMOS, acoustic confinement, CMOS-MEMS transducers, and large signal modeling. We discuss performance limits with standard capacitive transduction, with emphasis on performance boost with emerging CMOS materials including ferroelectrics under development for memory.

Longitudinal dynamics for mesons on the light cone

We survey a set of proposed light-front models for confinement in the valence quark sector of the mesons and portray similarities as well as differences. We present the spectroscopies for the light mesons that result from a selection of longitudinal confinement forms. We note that the Sturm-Liouville theory provides a unifying framework for many elements of this comparison.

Optogeometric study of multimode TiO[formula omitted] waveguide thin films elaborated by reactive magnetron sputtering

TiO2 thin films were deposited by reactive magnetron sputtering with increasing thickness T1, T2, T3 and T4. The μ-Raman spectra showed the presence of anatase TiO2 in all films. The phonon confinement model revealed the crystallite size ranging between 5.1 and 6.1 nm. The optical gap energy was found to decrease from 3.45 eV to 3.37 eV. Scanning electron microscopy and energy dispersive X-ray spectroscopy analysis showed enhancement of crystallinity and stoichiometry over the films’ thickness in accordance with the μ-Raman measurements. The m-lines spectroscopy confirmed the normal behavior of the films as multimode waveguides by the increase of propagation modes’ number with the films’ thickness for each transverse electric and transverse magnetic polarization. Both ordinary and extraordinary refractive indices decreased over the films’ thickness. The birefringence however had an opposite behavior. The cut-off thickness experienced an increment as a function of thickness. In comparison, m-lines and Swanepoel’s method were relatively compatible.

Charmonium radiative decays within the covariant confined quark model

We have studied the dominant one-photon radiative transitions of the charmonium ground and orbitally excited states within an analytic confinement model. Along with two fixed basic model parameters (mc and the cutoff value λ), we introduced only one adjustable parameter common to charmonium states: ηc, J/ψ, χc0, χc1, hc and χc2 to parameterize the quark distribution inside the hadron. Our estimates are in good agreement with the latest data.

Numerical investigations of the vortex feature-based vorticity confinement models for the assessment in three-dimensional vortex-dominated flows

In order to improve the vortex resolution in aerodynamic wakes, a locally normalized vortex feature-based vorticity confinement method is implemented into the multi-block, structured computational fluid dynamics solver (ROSITA). In this method, the second vorticity confinement (VC2) scheme with two well-known vortex feature detection methods (non-dimensional Q criterion, non-dimensional lambda _2 criterion) is employed to counterbalance the truncation error introduced by the numerical discretization of the convective term. The flow field of two benchmark three-dimensional steady vortex-dominated cases, the NACA0015 wing and the Caradonna–Tung hovering rotor, is simulated with the implemented method. The improvements in aerodynamics prediction, vorticity preservation, computational stability, and efficiency are demonstrated. From the numerical results, the vortex feature-based confinement models significantly improve the computational stability, the aerodynamic loads prediction and vorticity preservation capability, especially for the lambda _2–based VC2 model. In addition, it allows the use of higher confinement parameters on a coarse grid with a relatively higher computational efficiency to obtain better results than those of a finer grid.

Numerical analysis of processes for the formation of moonlets confining the arcs of Neptune

ABSTRACT The arcs of Neptune – Fraternité, Egalité, Liberté, and Courage – are four incomplete rings immersed in the Adams ring. A recent confinement model for the arcs proposes that the structures are azimuthally confined by four co-orbital moonlets. In this work, we intend to approach some points related to the dynamics of co-orbital moonlets and suggest a model for their formation. We study the equilibrium configurations for 1+N co-orbital satellites under the 42:43 Lindblad resonance with Galatea. We obtained three distinct configurations with 1+3 and 1+4 moonlets able to confine and reproduce the location of the arcs. The moonlets’ formation is analysed by the disruption of an ancient body at a Lagrangian point of a moon. The disruption fragments spread out in horseshoe orbits and collide to form moonlets, which reach an equilibrium configuration due to a non-conservative effect. In such a scenario, the arcs likely formed through a mixture of different processes, with impacts between disruption outcomes and meteoroid impacts with the moonlets being possibilities.