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In this work we study a non-flat Friedmann-Robertson-Walker universe filled with a pressure-less dark matter (DM) and Barrow holographic dark energy (BHDE) whose IR cutoff is the apparent horizon. Among various DE models, (BHDE) model shows the dynamical enthusiasm to discuss the universe's transition phase. According to the new research, the universe transitioned smoothly from a decelerated to an accelerated period of expansion in the recent past. We exhibit that the development of $q$ relies upon the type of spatial curvature. Here we study the equation of state (EoS) parameter for the BHDE model to determine the cosmological evolution for the non-flat universe. The (EoS) parameter and the deceleration parameter (DP) shows a satisfactory behaviour, it does not cross the the phantom line. We also plot the statefinder diagram to characterize the properties of the BHDE model by taking distinct values of barrow exponent $\triangle$. Moreover, we likewise noticed the BHDE model in the $(\omega_{D}-\omega_{D}^{'})$ plane, which can furnish us with a valuable, powerful finding to the mathematical determination of the statefinder. In the statefinder trajectory, this model was found to be able to reach the $\Lambda CDM$ fixed point., Comment: 19 pages, 21 figures

The underlying intention of this study is to oversee the flow, heat, and mass transport of hybrid nanofluid (Casson, micropolar, silica, alumina, and Water), Casson, and micropolar fluid flow across a curved stretching sheet. The influence of radiation, cross-diffusion and the applied magnetic field is also looked into. The total entropy rate of the Casson, micropolar and hybrid fluid is discussed. A curvilinear coordinate system models the flow equation. Appropriate similarity transformations are applied to modify the governing nonlinear PDEqns into ODEqns.The proposed system is numerically solved with R-K 4th order based shooting procedure. Outcomes are explained by preparing graphs and tables—comparative studies of obtained results with previously published results discourse. The main outcomes of this study are (a) Hybrid nanofluid has a higher temperature profile than micropolar and Casson fluid. (b) Entropy generation is maximum for larger values of Curvature, temperature difference, diffusion parameter, Dufour and Brinkman number. (c) The micropolar fluid shows higher entropy generation compared to Casson and hybrid nanofluid. (d) Fluid velocity augments with larger magnetic field and Curvature parameter. (e) Casson fluid shows a higher velocity field compared with micropolar and hybrid nanofluid.

The demands towards high precision and surface quality of ultra-thin glass for curved screens are continuously rising in the field of smart mobile terminals. Although the ultra-thin glass molding process (UTGMP) has the advantage of the shorter production cycle and higher efficiency, there are still typical forming defects in the molding process, namely crack, shape deviation, and large surface roughness. This paper aimed to investigate the influence mechanism of UTGMP molding temperature and pressure on the shape deviation, crack area, and surface quality of ultra-thin glass. In this study, a finite element model (FEM) was established to study typical forming defects of curved surfaces, and the effects of molding temperature and pressure on the shape deviation and crack area for ultra-thin glass were studied by the FEM simulation method. The simulation results revealed the molding temperature has a significant effect on the shape deviation, crack area and surface quality, while the molding pressure is only strongly correlated with shape deviation and crack area. In addition, the reliability of the model was verified by a series of five-level single factor experiments, and the shape deviation and crack area of ultra-thin glass were discussed in detail. Under the appropriate molding pressure and temperature range (0.45 MPa, 802–806 °C), the accuracy of curvature was improved by 33%, the roughness was reduced by 21%, and the probability of crack was also reduced. Thus, this study contributes to improving UTGMP's molding accuracy and reducing molding defects, and plays a positive role in reducing production costs and improving production efficiency.

Wave energy converter hull shapes have been optimised in the past to find the most suitable design to maximise mean annual power production and minimise costs. However, costs are generally considered through proxies based on the device's size. When using an optimisation process capable of generating very diverse shapes, more complex objective functions may be required to ensure that resulting shapes truly minimise the levelised cost of energy. For this purpose, relevant cost factors with an effect on geometry, such as manufacturability and materials considerations, should be included in the optimisation process. To address this challenge, different strategies for incorporating manufacturability considerations in a wave energy converter optimisation process with an adaptable geometry definition are discussed here. The resulting optimal shapes are compared to the shapes obtained when these additional constraints are not included. The results show that it is possible to generate wave energy converter shapes designed for a particular manufacturing process, as well as in general with improved manufacturability characteristics - based on the shapes maximum curvature. The proposed approaches can be used in future wave energy converter design studies to generate novel and improved shapes while considering their manufacturability.

We construct a generalisation of Bakry-Emery curvature to prove twisted intertwining relations for Markov semigroups. These relations are applied to Brascamp–Lieb type inequalities and spectral gap results. It extends the method of Arnaudon, Bonnefont and Joulin, to Riemannian manifolds and to a wider class of twists. These results are illustrated with several examples.

The motion of blood conveying gold nanoparticles on a curved surface when suction, thermal radiation, and Lorentz force are significant is explored in this report with the aim to announce the increasing effects of Williamson fluid parameter, volume fraction, radius of curvature, thermal radiation, and Lorentz force on such a transport phenomenon. This report was designed to explore the upper and lower solutions of the model suitable to study the enhancement of the aforementioned variables. The similarity solution of the dimensional governing equation was sought for using the appropriate similarity variables. These dimensionless forms of ODEs are numerically solved using the 3-stage Lobatto formula, also known as bvp4c. The validation of the numerical scheme was considered. The drag force decelerated and then upsurges owing to the volume fraction of nanoparticles in the corresponding UBS and reduces in LBS, while the rate of heat transfer drastically decreases. The temperature and velocity gradient escalate and decelerate, respectively for both branches of results owing to the effect of higher curvature parameter. The temperature distribution decelerates in both outcomes due to the strengthened of mass suction while the velocity weakened in the lower branch solution (LBS) and augments in the upper branch solution (UBS).

The concave-wall jet was formed in the vertical cylinder separator with inlet baffle component. The effect of curvature of radial baffle on the jet flow in the separator was investigated by the experiment of concentration and the numerical simulation of species transport. The results show that the concave-wall jet was confined within the narrow region near the concave-wall and the flow disturbance in the center of separator was weakened. The distribution of concentration and the flow region of wall jet depended on the curvature of radial baffle (K). Compared with the turbulent intensity of the plate baffle (K = 0), that of concave baffle (K = 2) reduced by 6.1% and the turbulent intensity of convex baffle (K = -2) increased by 13.5%. The best flow stability was obtained by the concave baffle because the baffle outlet was similar to convergent nozzle. The outlet convergent angle was between 0° and 19.5° when 0 ≤ K ≤ 2. The secondary vortices were caused by the tangential velocity irregularity on the cross-section of two axial baffles in the separator with convex baffle. The baffle with K ≥ 0 was more suitable in separator inlet than that with K

To pursue high efficiency for wind turbine and harness more energy from wind, the wind power generation system has been designed larger and larger. With length scale increasing, the natural frequency of blade will be lower and changing dramatically with rotational speed, which will threaten the stability of the blade and turbine. However, in the previous research, the parametric, analytical, and quantitative study of centrifugal stiffening effect is rare to see. As a result, the current research has comprehensively studied the centrifugal stiffening effect on the structural characteristics of large wind turbine blade. Specifically, the equivalent rotating wedge beam model has been proposed for composite wind turbine blade. Based on the proposed wedge beam model and Rayleigh-Ritz method, the natural frequency variation curve has been derived and verified by ANSYS 3D simulation results. The parameters, including blade length, stiffness-mass ratio, and aspect ratio, affecting the natural frequency curve have been uncovered and analysed. It was found that the centrifugal stiffening effect has a great impact on the fundamental frequency of blade, e.g. 10% for NREL 5 MW, while it has less impact on other modal frequencies. The variation curve of fundamental natural frequency can be approximated by parabola. The product of the parabola curvature and fundamental frequency is found to be approximately constant for both NREL 5 MW and WindPACT 1.5 MW turbine blades. This research will provide guidelines for the resonance avoidance design of large wind turbine blade in the future.

Micromechanical systems (MEMS) based on electrostatic actuators are commonly involved in driving and actuating high-speed micro-structures. For this to be efficient, these micro-actuators must produce sufficient actuating force in order to achieve the required large strokes for such operations (usually in the order of tens of microns). However, this larger amount of displacement will require high actuation electrostatic voltages (typically in the order of hundreds of volts) or larger actuator dimensions, resulting in a bulky and inefficient design. To overcome these challenges, this paper examines the possible use of the snap-through instability in an electrostatically actuated and initially curved (shallow arch) clamped-clamped microbeam actuator arrangement. An extended version of the variational Hamilton principle is applied to derive nonlinear equations governing the steady-state behavior of the structure under step DC load. These equations are solved by effectiveness meshless numerical Galerkin decomposition technique. A convergence study is performed to show the effectiveness and advantages of the applied numerical approach to the formulated nonlinear problem. The investigation inspects different initial curvature profiles (first three symmetric buckled modes: first, third, and fifth modes) for the shallow arch. It was reported that the presence of the snap-through instability, for all investigated initial profiles, in the structural behavior of the micro-actuator produces a non-trivial order of magnitude increase in its resultant displacement as compared to the classical parallel-plate actuator with identical geometrical dimensions and operating conditions. In addition, out of the assumed first three symmetric buckled modes to outline the initial curvature of the shallow arch microbeam, only the first and fifth modes showed a strong impact on the micro-actuator performances.

The inverse problem of determining how to shot peen a plate such that it deforms into the desired target shape is a challenge in the peen forming industry. While peening thick plates uniformly on one side results in a spherical shape, with the same curvature in all directions, complex peening patterns are required to form other shapes, such as cylinders and saddles found on fuselages and wing skin panels. In this study, we present an optimization procedure to automatically compute shot peening patterns. This procedure relies on an idealized model of the peen forming process, where the effect of the treatment is modeled by in-plane expansion of the peened areas, and on an off-the-shelf optimization algorithm. For validation purposes, we peen formed three 305 × 305 × 4.9 mm and two 762 × 762 × 4.9 mm 2024–T3 aluminium alloy plates into cylindrical and saddle shapes using the same peening treatment. The obtained shapes qualitatively match simulations. For 305 × 305 × 4.9 mm plates, the relative differences had the same distribution and were of the same order of magnitude as initial out-of-plane deviations measured on the as-received plates.

The reconstruction of individual geometries from medical imaging is quite a standard in the framework of patient-specific medicine. A major drawback in such a context is represented by noise inherent to the data acquisition. Low signal-to-noise ratios can negatively impact extraction algorithms, and result in artefacts or poor quality of the reconstructed meshes. Direct application of numerical methods on such meshes can yield misleading results. Indeed, artefacts and badly shaped elements may corrupt numerical simulations or induce relevant errors in the computation of meaningful geometrical quantities, such as the curvature or the geodesic surface distance. In this paper, we propose a denoising procedure to remove artefacts from a triangular mesh of a three-dimensional closed surface which represents a brain cortex. For this purpose, we combine a smoothing technique (i.e., the Taubin or the HC-Laplacian smoothing) with an edge-flipping algorithm. To control the denoising procedure, we introduce a stopping criterion that takes into account both the improvement of the mesh quality and the loss of volume enclosed by the surface. On a brain cortical surface reconstructed from Magnetic Resonance Imaging (MRI) data, we first perform a tuning analysis of the parameters involved in the smoothing algorithm, then we investigate the effectiveness of the denoising procedure. Finally, as an example of relevant geometrical feature, we study the improvement generated by the proposed algorithm on the computation of the cortical curvature.

This analysis reports an unsteady and incompressible flow of Williamson nanoliquid in presence of variable thermal characteristics are persuaded by a permeable stretching cylinder. The flow field investigation is established with the effect of mixed convection and non-uniform heat source/sink on flow and heat transfer. On the cylinder surface, the analysis is inspected with utilization of zero mass flux constraints. By using the appropriate similarity variables, the framed equations for the energy, momentum and mass is converted into non-linear ODEs. The numerical communication of the boundary value problem is successfully implemented using a computer algorithm programmed into the fifth Runge-Kutta scheme. Additionally, the wall shear factor and rate of heat transfer are calculated in two different cases namely, with curvature and without curvature. In addition, the results obtained are confirmed by making comparisons with previously published articles and we found an excellent match that guarantees the indemnity of current communication. A comprehensive change in velocity, temperature and concentration is examined for involved parameters like local Weissenberg number, space dependent heat source constant, magnetic number, curvature constant, thermophoretic parameter, buoyancy parameter, Brownian motion parameter, Prandtl number, Schmidt number, unsteadiness parameter, reaction rate parameter, activation energy parameter and temperature difference parameter. A reduction in velocity is observed for unsteady parameter and buoyancy constant. An enhanced nanofluid temperature is noted for space dependent heat source parameter, time dependent heat source parameter and unsteady parameter. Moreover, the nanofluid concentration is increases for temperature difference parameter while reverse observations are noticed for chemical reaction rate.

In this paper we study the Neumann problem for a type of fully nonlinear second order elliptic partial differential equations on domains in C n without any curvature assumptions on the domain.

The present investigation illustrates the parametric instability of damped functionally graded carbon nanotube (CNT) reinforced composite cylindrical panel subjected to periodic in-plane excitations and thermal environment. The Rayleigh damping is taken into consideration to incorporate the damping in the present formulation. The shell panel model accounts for the shear deformation theory of higher-order and geometric nonlinearity of the von-Karman type. The functional properties of the material for carbon nanotube reinforced composite (CNTRC) panels are considered to be temperature-dependent. The governing partial differential equations (PDE) are transformed into ordinary differential equations (ODE) through Galerkin’s approach. The dynamic instability regions are obtained for the periods T and 2T as suggested by Bolotin, and the time history responses are evaluated following Newmark’s integration technique. Numerical investigation examined the influence of damping on the parametric instability of CNTRC shell panels. In addition to this, the present analysis also explores the effect of CNT distribution, volume fraction, curvature effect, thermal environment, and static pre-loading on the instability responses of the shell panels.

The use of Ultra-High Performance Concrete (UHPC) has been growing rapidly in the past two decades because of its superior mechanical and durability properties compared to conventional concrete (CC). Flexural strength prediction models of CC components underestimate the flexural strength of non-prestressed UHPC components as they ignore the tensile strength of concrete and assume different stress–strain relationships and failure mode from those of UHPC. The objective of this paper is to evaluate the current flexural strength prediction models of non-prestressed UHPC components using test data collected from the literature and validate them using experimental data of a UHPC ribbed slab tested in flexure. Measured and predicted flexural strengths are compared at different curvatures. Evaluation results indicated that neglecting the tensile strength of UHPC significantly underestimates the flexural strength of non-prestressed UHPC components. Peak moment curvature of non-prestressed UHPC components is significantly smaller than ultimate moment curvature. In addition, the differences among idealized stress–strain relationships of UHPC in compression and tension do not have significant effect on the predicted flexural strength.

We review progress in active hydrodynamic descriptions of flowing media on curved and deformable manifolds: the state-of-the-art in continuum descriptions of single-layers of epithelial and/or other tissues during development. First, after a brief overview of activity, flows and hydrodynamic descriptions, we highlight the generic challenge of identifying the dependence on dynamical variables of so-called active kinetic coefficients -- active counterparts to dissipative Onsager coefficients. We go on to describe some of the subtleties concerning how curvature and active flows interact, and the issues that arise when surfaces are deformable. We finish with a broad discussion around the utility of such theories in developmental biology. This includes limitations to analytical techniques, challenges associated with numerical integration, fitting-to-data and inference, and potential tools for the future, such as discrete differential geometry., Comment: 12 pages, 3 figures

A nonlinear nonideal generalized magnetohydrodynamic (MHD) model is developed to explore the evolutionary dynamics of nonlinear wave-structural patterns naturalistically excitable in inhomogeneous protoplanetary disks (PPDs). A local nonlinear perturbation theory (multiscale analysis) over the magnetohydrostatic homogeneous equilibrium of the axisymmetric disk yields a second-order nonlinear partial differential equation in the perturbed gravitational potential curvature with a unique set of multiparametric coefficients. A numerical illustrative platform demonstrates the excitation of nonlinear coherent structures in the form of solitary lump waves (SLWs). The atypical SLW-characteristics are explored geometrically with the phase space trajectories. The SLW amplitude increases in magnitude with the Alfvenic Mach number, and vice-versa. It is interestingly inferred that the Mach number (reference frame velocity and density) acts as a destabilizing (stabilizing) agency to the PPD-dynamics against the nonlocal self-gravity effects, and so forth. It enlightens the long-standing gravitational Laplace 1796 conjecture having a real astronomic significance. At the last, the nontrivial applicability of our findings in the SLW-driven bounded planetary structure formation in varied astroenvirons is actualized.

22 pages, 30 réf.; We illustrate with several new applications the power and elegance of the Bendixson–Dulac theorem to obtain upper bounds of the number of limit cycles for several families of planar vector fields. In some cases we propose to use a function related with the curvature of the orbits of the vector field as a Dulac function. We get some general results for Li´enard type equations and for rigid planar systems. We also present a remarkable phenomenon: for each integer m ≥ 2, we provide a simple 1-parametric differential system for which we prove that it has limit cycles only for the values of the parameter in a subset of an interval of length smaller that 3√2(3/m)m/2 that decreases exponentially when m grows. One of the strengths of the results presented in this work is that although they are obtained with simple calculations, that can be easily checked by hand, they improve and extend previous studies. Another one is that, for certain systems, it is possible to reduce the question of the number of limit cycles to the study of the shape of a planar curve and the sign of an associated function in one or two variables.

The dominant structural systems used for high-rise buildings are tube-type systems. Tall tube-type structures act as a cantilever box girder and become prone to the shear lag phenomenon. This phenomenon causes nonlinear stress along the side of the tubular structures, while the beam theory assumes the stress to be linear. This mechanism reduces the efficiency of tube-type structural systems to resist lateral loads. This study explains a detailed discussion of the shear lag effect and the cause of its existence in two cases, positive and negative, through simple numerical analyses. To this end, the impact of lateral deformation on the shear lag effect was investigated in three tube-type structural systems: framed tube, diagrid, and hexagrid with different heights of 50-, 80-, and 110- story buildings subjected to wind load. The lateral deformation of the model structures was compared with the planer deformation (shear and bending deformation) of the cantilever box girder as the benched mark. Analysis results illustrated that the tube type structural system configuration affected the shear and bending deformation portions and the shear lag effect. Based on the results, the direction of the shear flow was changed according to the slope direction of the tangent line of the deflection curve (first deviation) and caused two cases, positive and negative ones. From the numerical results of candidate models, when the tangent line's angle became zero, the shear lag became minimum. When the curvature of the deflection curve (second deviation) was changed (upward into inward), the shear lag became maximum.

The layer approach is a simple tool to predict the moment–curvature behaviour of steel fibre reinforced concrete (SFRC) beams. The material stress–strain response of compressive concrete and tensile reinforcement is simple, as for ordinary RC structures, whereas the residual stress–strain relation for SFRC in tension determines the accuracy of the deformation analysis and is difficult to establish. The common practice is to construct a residual stress–strain relation based on standard bending tests. While the residual stresses obtained from such tests represent the softening behaviour of SFRC, the response of the tensile zone of structural members with longitudinal reinforcement is more complex due to the interaction between the residual softening stresses and tension stiffening stresses. This study aims to investigate the adequacy of the RILEM residual stress modelling approach. The residual stress–strain relations are derived from the results of standard notched beams and are compared to the stress–strain diagrams inversely obtained from the experimental moment–curvature response of SFRC beams. An experimental study of 8 full-scale SFRC beams with longitudinal reinforcement including the tests of standard notched beams was carried out. The variables were the volume levels of fibres and reinforcement ratio. To produce accurate moment–curvature diagrams, beams were tested in four-point bending with strains measured at four levels throughout the constant bending zone. The predicted curvatures of SFRC beams following the RILEM recommendations were compared to the tests. A limited curvature analysis was also performed using Model Code 2010 and the Australian Bridge Code. Similarly, the residual stress - strain relations inversely derived from the structural tests were compared to the specifications of the codes mentioned above.

This study aimed to compare ProGlider (Dentsply Sirona, Ballaigues, Switzerland) and R-Pilot (VDW, Munich, Germany) instruments in terms of their cyclic fatigue resistance using an artificial stainless steel canal showing an abrupt apical curvature, torsional resistance according to the ISO specification, and topographic changes on the instrument surface after glide path management in mesial canals of mandibular first molars with the abrupt curvature selected based on their micro-computed tomographic examination.Eighty instruments were used: 40 ProGlider (size 0.16, .02v taper) and 40 R-Pilot (size 0.125, .04 taper) instruments. The cyclic fatigue resistance was tested in a static test model using an artificial canal with an abrupt apical curvature (angle of curvature of 90° and radius of curvature of 2 mm). The torsional resistance test was performed according to ISO 3630-1 specifications. To determine surface topography of the unused and used instruments, mesial root canals of mandibular molars with an abrupt apical curvature were selected to prepare a glide path with either the ProGlider or R-Pilot instrument. An optical profilometer and scanning electron microscopy were used to determine the surface properties. Normally distributed torsional and cyclic resistance data were analyzed using the Student t test, whereas quantitative data obtained by the optical profilometer were analyzed with the Kruskal-Wallis H test with a 5% significance threshold.The R-Pilot showed significantly higher cyclic fatigue and torsional resistance than the ProGlider (P .05). Angular deflection values were similar between instruments (P .05). Measurements made from the blade area showed that the surface roughness values of the ProGlider were larger. Cutting blade measurements showed that unused instruments had significantly greater roughness values than used ones (P .05). Although there was a 14% increase between the blade edge radii of the used and unused R-Pilot instruments, this difference was determined as 61% in ProGlider instruments.The R-Pilot exhibited greater cyclic fatigue strength than the ProGlider when tested in an artificial canal with an inner diameter of 1.0 mm and an abrupt apical curvature. Torsional resistance of the R-Pilot was higher than the ProGlider, but the angular deflection values were similar. Glide path preparation in a mesial root canal with an abrupt apical curvature did not increase the surface roughness of both instruments but resulted in a greater blade edge radius.

The round window membrane (RWM) covers an opening between the perilymph fluid-filled inner ear space and the air-filled middle ear space. As the only non-osseous barrier between these two spaces, the RWM is an ideal candidate for aspiration of perilymph for diagnostics purposes and delivery of medication for treatment of inner ear disorders. Routine access across the RWM requires the development of new surgical tools whose design can only be optimized with a thorough understanding of the RWM's structure and properties. The RWM possesses a layer of collagen and elastic fibers so characterization of the distribution and orientation of these fibers is essential. Confocal and two-photon microscopy were conducted on intact RWMs in a guinea pig model to characterize the distribution of collagen and elastic fibers. The fibers were imaged via second-harmonic-generation, autofluorescence, and Rhodamine B staining. Quantitative analyses of both fiber orientation and geometrical properties of the RWM uncovered a significant correlation between mean fiber orientations and directions of zero curvature in some portions of the RWM, with an even more significant correlation between the mean fiber orientations and linear distance along the RWM in a direction approximately parallel to the cochlear axis. The measured mean fiber directions and dispersions can be incorporated into a generalized structure tensor for use in the development of continuum anisotropic mechanical constitutive models that in turn will enable optimization of surgical tools to access the cochlea. STATEMENT OF SIGNIFICANCE: The Round Window Membrane (RWM) is the only non-osseous barrier separating the middle and inner ear spaces, and thus is an ideal portal for medical access to the cochlea. An understanding of RWM structure and mechanical response is necessary to optimize the design of surgical tools for this purpose. The RWM geometry and the connective fiber orientation and dispersion are measured via confocal and 2-photon microscopy. A region of the RWM geometry is characterized as a hyperbolic paraboloid and another region as a tapered parabolic cylinder. Predominant fiber directions correlate well with directions of zero curvature in the hyperbolic paraboloid region. Overall fiber directions correlate well with position along a line approximately parallel to the central axis of the cochlea's spiral.

Answering a question by M. Struwe [26] related to the blow-up behavior in the Nirenberg problem, we show that the prescribed Q-curvature equation Δ 2 u = ( 1 − | x | p ) e 4 u in R 4 , Λ : = ∫ R 4 ( 1 − | x | p ) e 4 u d x ∞ has normal solutions (namely solutions which can be written in integral form, and hence satisfy Δ u ( x ) = O ( | x | − 2 ) as | x | → ∞ ) if and only if p ∈ ( 0 , 4 ) and ( 1 + p 4 ) 8 π 2 ≤ Λ 16 π 2 . We also prove existence and non-existence results for the positive curvature case, namely for Δ 2 u = ( 1 + | x | p ) e 4 u in R 4 , and discuss some open questions.

Underestimation of customized shortwall mining parameters of deep extra-thick coal seams (namely, mining height, mining width, and pillar width) may result in coal pillar instability, surface subsidence, and mining structure failure, while their overestimation would cause a waste of coal resources. This study proposes a new method for optimizing these parameters, whose main purpose is to achieve the maximum coal recovery rate while satisfying surface deformation and coal pillar stability requirements. A case study of an extra-thick coal seam in Eastern China with one km-overburden depth and a thickness of 10 m was analyzed. First, a new method for predicting surface deformation under deep customized shortwall mining based on surface deformation data from fully caving mining was proposed. The variation pattern of the extreme values of surface deformation parameters (including surface subsidence, tilt, curvature, and horizontal strain) versus the area-based recovery rate and mining width was analyzed. After that, the evolution law of the surface deformation with the changing mining height and area-based recovery rate was simulated using the FLAC3D software. The maximum recovery rate and the corresponding mining height, the area-based recovery rate were preliminarily determined, while the surface deformation fell within the allowable range. Simulations of evolutions of the plastic zone width, elastic core ratio, and vertical stress of coal pillars with varying coal pillar width under the maximum recovery rate were performed. The optimal mining scheme had a mining height of 10, a mining width of 100, a coal pillar width of 122 m. It ensured the coal pillar’s long-term stability with the surface deformation within the allowable range and achieved the maximum coal recovery rate of 45%. These findings are considered instrumental in the customized shortwall mining of extra-thick coal seams under buildings, in particular, under Eastern China mining and geological conditions.

This study develops an atomistic simulation-based methodology for studying the dispersed droplet phase in immiscible alloy. The methodology is applied to the immiscible Al–Pb alloy liquid droplet system to study the temperature and curvature effects on the droplet radial distributions of thermodynamic properties, the mutual miscibilities within the spherical droplets, and the pressure differences across the curved liquid–liquid interfaces. The pressure tensor components profiles along radial direction are computed by the Irving–Kirkwood method coupling the spherical coordination and providing the inner droplet pressure data with sufficient statistical precision to validate the generalized Laplace equation in a liquid immiscible alloy system (both Al-rich convex droplet interface and Pb-rich concave droplet interface). Noticeable changes in mutual miscibilities in the droplet phases are seen, which correspond to the shifts of the solvus lines toward lower solubilities as temperature increases or the droplet size decreases. Compared with spherical droplets under the same temperature, cylindrical droplets with the same radii own the same Laplace pressure dependence of the mutual miscibilities but a weaker capability to tune the nano-alloy droplet phase diagram. Current findings contradict the miscibility changes in the two-complexion equilibria within the monoatomic layer at the Al(111)–Pb(liquid) interface [Acta Mater 2018;143:329]. The combined simulation-characterization methodology proposed in this study applies to broader types of immiscible alloy. The calculated data could provide guides to design well-dispersed droplet phases in the immiscible alloys and their manufacturing processes, facilitate the development of the thermodynamic theory/modeling of the nano-sized alloy phase diagram.

The influence of the shear-thinning properties on tear dynamics is analyzed using 2D numerical simulations. The simulations were conducted in conditions close to those of the actual tear film dynamics. The paper deals with the spreading of the shear-thinning tear film on a spherical cornea with blinking. The shear-thinning properties are described using Cross’s rheological model, known as the model that describes well shear-thinning properties of actual tears. We solved the continuity and the momentum equations using the mono-fluid formulation and the volume of fluid (VOF) method. We have examined the influence of rheological properties namely, the time constant, the zero shear viscosity, and the flow behavior index on the tear film profile. The results confirm that the curvature delays the risk of film rupture. The results also indicate that the values of the shear-thinning parameters within the range of the values measured in-vivo are the ones that delay tear-film breakup. These values provide quasi-uniform thin tear film and ensure a low wall shear stress lubrication between the moving eyelid and the cornea surface. The suggested values for the shear-thinning parameters can serve as a starting point for designing efficient artificial tears to alleviate moderate symptoms of dry eye syndrome.

A range of influences, including solar insolation, temperature, shading, deterioration, incompatibility losses, dirtying, etc., all have an impact on the solar cells' performance and reliability. Shading, whether total or fractional, can also have a substantial influence on power output, including things in the PV-array, shading trends, and the presence of bypass diodes encapsulated in the PV segment configuration. It's indeed important to determine the significant impacts of shading, mostly on P-V and I-V curvature, to obtain the desired energy from a PV array.

Free-form surfaces have been widely used in aerospace, automotive and other fields. Due to its complex geometry, free-form surface inspection is generally conducted by touch-trigger or measuring probe-based Coordinate Measurement Machines or On-machine Measurement. Sampling strategy plays a decisive role in improving both measurement accuracy and efficiency, which is determined by sample size and distribution of sample points. However, it is difficult to simultaneously take the surface curvature, sampling density and approximation error into account, considering the complexity of surface geometry. In this paper, triangle mesh simplification is innovatively adopted in sampling planning to achieve multi-geometric constraints. As triangle mesh has outstanding advantages in representing the surface features, strong stability and is easy to modify its structure, free-form surface is converted to a dense triangle mesh. Triangle mesh simplification is implemented by iteratively contracting triangle edges. An improved quadric error metric is established to decide contraction order and optimal target vertices under discrete curvature constraint. Sampling density is controlled by limiting the triangle edge length. Detailed adaptive sampling algorithm under multi-geometric constraints is then developed. Both simulation and experiment are conducted to validate feasibility and robustness of the proposed method. The results are compared with uniform sampling and existing adaptive sampling strategy to show that the proposed method can prominently reduce sampling error when sample size is small.

This paper aims to discuss the viable and analytic solution of the spherically symmetric gravastar model under the influence of modification of Gauss–Bonnet gravity, i.e., f(G) gravity, where G is the Gauss–Bonnet curvature term. For this purpose, we evaluate the field equations in corresponding theory and conservation equation with the help of an effective energy–momentum tensor. A mathematical formalism of the gravastar’s three regions, i.e., interior de-Sitter region, thin shell, and the exterior Schwarzschild vacuum region have been discussed. We, then analyze different realistic features, in particular energy, entropy, and length of the shell. The viability of these physical features is then examined through the graphical representations separately. Within the framework of an alternative theory, we have obtained the exact and singularity free model of gravastar.

A universal method of grinding force modeling in arbitrary 2D freeform grinding is proposed, which is based on the infinitesimal approach. The main idea of this method is to discretize the freeform surface into a group of surfaces with very small widths along the profile of the surface cross section, which can be considered as flat surfaces inclined at different angles. The form grinding process can be considered as a series of inclined flat surface grinding, where the normal grinding force of each flat inclined surface is divided into portions along specific directions. The process of inclined flat surface grinding at certain angle is equivalently converted to flat surface grinding in terms of the same abrasive wheel peripheral velocity and workpiece velocity but different cutting depth and contacting curvature in inclined view plane. A mathematical model of grinding force in flat surface grinding (FSG) is established, where the sliding stage, plowing stage and chip formation stage are considered respectively with 9 coefficients which are determined with linear regression from the grinding experiments. The forces in form grinding are then obtained by summing the individual inclined surfaces grinding forces, which are verified via rail form grinding (RFG). The algorithm was validated by means of the grinding experiments with average relative percentage errors of 6.08% and 7.01% respectively on tangential grinding force and normal grinding force in FSG and average relative percentage errors of 8.47% and 10.37% respectively on longitudinal grinding force and vertical grinding force in RFG.

Ridge-valley features are important elements of a model. To recognize these features from point cloud, this paper introduces a new criterion named Extremal Point Distance (EPD) to greatly reduce the number of potential feature points and locate feature position more accurately. On this basis, a feature enhancement algorithm is proposed. The algorithm adjusts the coordinates of feature regions by minimizing a linear objective function consisting of expected position and normal, which can ensure the accurate sampling of feature position. We also present a parameterization method to eliminate the lateral sliding of feature points and reduce the number of unknowns in the objective function. Since the EPD criterion only depends on the changing trend, rather than the absolute value of the curvature, our algorithm can infer the expected position and normal with a large neighborhood radius, which makes it robust to noise. Experiments show that our algorithm can adjust the feature amplitude and sharpness freely, and achieve satisfactory results in feature recognition, feature enhancement and sharp feature restoration.

In this paper, an innovative column reinforced with HRB 600 MPa reinforcements and ultrahigh-strength (UHS) steel bars with low bond strength was proposed. To study the cyclic behavior of the proposed column, three square cantilever columns were designed and tested under constant axial load and cyclic lateral load. The main parameter was the area proportion of the UHS longitudinal bars in the column section. Under the principle of equal area design, three proportions of 35%, 65% and 100% were selected. As the test results showed, with the increase in the UHS reinforcement area proportion, the columns had an improvement in reducing the residual displacement. Employing the UHS steel bars in the column can make the lateral deformation distribution of the column more uniform in the plastic hinge zone, which means a lower deformation curvature and mitigated concrete damage, thus leading to a corresponding small damage index. Numerical models were established and verified by comparison with the experimental hysteretic response of the three columns under cyclic loading. Additionally, parametric studies consisting of the axial load ratio (ALR) and stirrup arrangement (SA) were conducted. The effects of these parameters on the seismic behavior of the proposed columns were further investigated.

In this study, the applicability and conservativeness of current Eurocode 8 (2004) provisions for the design of ductile reinforced concrete (R/C) shear walls are evaluated. Apart from adequate strength supply, a successful design also requires that the provided section curvature ductility should satisfy the respective demand. The Code, striving to maintain a balance between ease of application and accuracy, provides practical directives to facilitate the required ductility supply. However, at the end of the design there is no tangible verification whether the provided ductility satisfies the requirement. To provide insight regarding the applicability of these Code provisions, an extensive series of rectangular wall cases is analyzed, and various design approaches adopted by engineering practice are evaluated. Moment-curvature analysis including confinement effects is performed on all wall configurations for verification purposes. It is found that simplified Code approaches cannot always guarantee an acceptable design; in this regard, a few alternatives are presented, favoring conservativeness and accelerating the design workflow. The paper concludes with an evaluation of the current design practice, under the light of the upcoming Code revision.

Background Previous descriptions of the sagittal geometry of the tibia and talus have involved single radius curves. The purpose of this investigation was to: determine if the sagittal curvature of the medial and lateral sides of the talus and tibia can be described by dividing the condyles into anterior and posterior regions, determine tibiotalar congruency, and categorize the morphological configurations of the talus and tibia. Methods Eighteen subjects underwent weightbearing CT scans and the osseous curvature was analyzed. Results For the talus, the medial anterior radius was smaller than the lateral anterior radius. For the distal tibia, the lateral posterior radius was smaller than the medial posterior radius. Tibiotalar congruency varied by region. The most common geometric configuration was two cones, one anterior and one posterior, pointed in opposite directions. Conclusion The sagittal profiles of the tibia and talus can be more accurately described using a bi-radial approach as compared to a single radius.

Recent development in research and practice for curved cross-laminated timber (CLT) opens up novel and interesting possibilities for applications of slender surface-active shell structures in architecture. Such typologies provide advantageous structural behaviour allowing for efficient and lightweight structures while simultaneously determine the envelope and space of a building. The high degree of prefabrication combined with a sustainable and renewable building material makes CLT an ecological and economic solution for future construction. This paper presents the design development and construction of the Urbach Tower for the Remstal Gartenschau 2019: a structure made from high curvature CLT components on a building scale. This research contribution illustrates a sophisticated integrative design to construction process emphasizing computational and structural design, fabrication and detailing for curved timber components in complex spatial structures. The authors further explore the structural potential of self-shaped curved CLT investigating the influence of curvature radius on the load-bearing behaviour of the tower structure. The Urbach Tower translates these technical developments into practice arising at the intersection of digital innovation and scientific research.

The steel sections are subjected to instability and buckling failure due to the rapid degradation of flexural rigidity under fire-loading conditions. The behavior of monosymmetric hot-rolled steel I-section beams are studied in this paper under uniform and non-uniform moment conditions. Validated finite element models in ABAQUS is used for parametric study, considering 1500 linear and non-linear simply supported beam models. Behavior of monosymmetric I-beams is analyzed under different uniform temperature conditions having shorter, intermediate, and longer spans with a height-to-width ratio greater than two (h/b > 2). The collapse of beams with longer span is not much affected by the non-linear material behavior. Only up to 17% increase from elastic capacity is observed for such beam under inelastic capacity. The interaction curves for the degree of monosymmetry and moment gradient are provided that can be used for estimating inelastic lateral-torsional buckling (LTB) capacities. Further, statistical analysis and comparison of FE-results with design predictions from Eurocode 3 part 1.2 showed that a single design buckling curve is insufficient in predicting the collapse capacity of hot-rolled beams under different loading conditions at elevated temperatures. Eurocode 3 part 1.2 generally provide highly conservative predictions at higher temperatures for beams under single curvature; however, it may provide unsafe results under double curvature for intermediate to shorter span beams.

In this paper, we study the generalized submodular maximization problem with a non-negative monotone submodular set function as the objective function and subject to a matroid constraint. The problem is generalized through the curvature parameter α ∈ [ 0 , 1 ] which measures how far a set function deviates from linearity to submodularity. We propose a deterministic approximation algorithm which uses the approximation algorithm proposed by Buchbinder et al. [2] as a building block and inherits the approximation guarantee for α = 1 . For general value of the curvature parameter α ∈ [ 0 , 1 ] , we present an approximation algorithm with a factor of 1 + h α ( y ) + Δ ⋅ [ 3 + α − ( 2 + α ) y − ( 1 + α ) h α ( y ) ] 2 + α + ( 1 + α ) ( 1 − y ) , where y ∈ [ 0 , 1 ] is a predefined parameter for tuning the ratio. In particular, when α = 1 we obtain a ratio 0.5008 when setting y = 0.9 , coinciding with the renowned state-of-art approximate ratio; when α = 0 that the object is a linear function, the approximation factor equals one and our algorithm is indeed an exact algorithm that always produces optimum solutions.

Three-dimensional (3D) direct numerical simulations (DNS) of the viscous incompressible fluid flow through a helical pipe with circular cross section were performed. The flow is governed by three parameters: the Dean number (or the Reynolds number), curvature, and torsion. First, we obtained steady solutions by steady 3D calculations, where dual solutions were found, one was uniform in the pipe axial direction and the other varied very slowly, if torsion exceeded a critical value. Then, the instability of the steady solutions obtained was studied by unsteady 3D calculations. We obtained critical Reynolds numbers of steady to unsteady transition by observing the behaviors of the unsteady solutions. The present results of the critical Reynolds number nearly agreed with those by the 2D linear stability analysis (Yamamoto et al. [9] ) except for the lowest critical Reynolds number region, where the present study gave the critical Reynolds number much less than that obtained by the 2D linear stability analysis. We found the vortical structures in the form of a standing wave slightly above the marginal instability state, which is a trigger of explosive 3D instability.

This paper examines the interface elasticity between an elastic half-space and a spherical nanoinhomogeneity subjected to a unidirectional far-field tension that is parallel to the half-space plane boundary. The spherical interface is modeled by the full version of Steigmann–Ogden interface theory. Due to their marginal significance, the effects of half-space plane boundary are neglected. The problem is solved by decomposing the unidirectional load into an all-around and an equal-but-opposite traction field. Benefitting from the property of axial symmetry, the former subproblem is solved by the sole use of Boussinesq displacement potentials. The latter condition is addressed by six harmonic functions extracting from Boussinesq, Papkovich–Neuber and Dougall displacement potentials. The relations between cylindrical and spherical harmonic functions are employed to clear the tractions along the half-space plane boundary and to satisfy the nonclassical traction equilibrium conditions across the matrix/nanoinhomogeneity interface. Truncating the resultant infinite series and equating the coefficients preceding Legendre polynomials, associated Legendre functions as well as their derivatives lead to a system of algebraic equations with respect to the dimensionless unknown parameters in displacement potentials. Extensive parametric studies are further performed in order to analyze the importance of interface tension, interface Lame constants, interface flexural rigidities, shear moduli ratio and nanoinhomogeneity radius-to-depth ratio on stress distributions and stress concentrations. Comparisons against both the classical and the Gurtin–Murdoch solutions help to clarify the separate effects of individual interface material properties. Stresses inside a soft nanoinhomogeneity is most affected by the additional incorporation of interface flexural rigidities. In addition, the deviatoric component of the interface curvature change tensor is found to be more important than the mean part for the proposed nanoinhomogeneity problem.

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG [Abstract] Deployable bar structures are especially useful for emergency buildings. These structures require simplicity and ease of assembly and their performance can be improve by using reciprocal linkage at their bars ends. This reciprocal configuration determines singular constructive conditions that allow all types of cylindrical vaults. This article develops this new system, from a previously theoretical analysis to a test campaign that allows verifying the validity of the proposal. Comparing these results with those resulting from construction systems with straight scissor-like elements or imposed curvature, shows the adequacy of this new proposal, verifying the advantages of the reciprocal joints in cylindrical vaults configurations. This study is part of the research project “Deployable and modular constructions for situations of humanitarian catastrophe”, funded by the Ministry of Economy and Competitiveness of the Kingdom of Spain with reference BIA2016-79459-R. Funding for open access charge: Universidade da Coruña/CISUG

Understanding the effect of curvature and topological frustration on self-assembly yields insight into the mechanistic details of the ordering of identical subunits in curved spaces, such as the assembly of viral capsids, growth of solid domains on vesicles, and the self-assembly of molecular monolayers. However, the self-assembly of nanoparticles with anisotropic surface topology and compartmentalization on curved surfaces remains elusive. By combining large-scale molecular simulations as well as theoretical analysis, we demonstrate here that the interplay among anisotropy, curvature, and chain conformation induces tethered Janus nanoparticles to self-assemble into diverse novel structures on a sphere, including binary nanocluster (CB), trinary nanocluster (CT), nanoribbon (RN) and hexagon with centered reverse (HR), which are mapped on a phase diagram related to the length asymmetry of tethered chains and Janus balance of the nanoparticles. The dynamical mechanism for the formation of these structure states is analyzed by examining the detailed kinetic pathways as well as free energy. We also show that the centered-reverse state is more prone to emerging around the topological defects, indicating the defect-enhanced entropy effect on a curved surface. Finally, the analytical model that rationalizes the regimes of these structure states is developed and fits simulations reasonably well, resulting in a mechanistic interpretation based on the order through entropy. Our findings shed light on curvature engineering as a versatile strategy to tailor the superstructures formed by anisotropic building blocks toward unique properties.

This study aimed to compare the torque generated by 4 different files in root canals with 4 different curvature angles.Four brands of nickel-titanium (NiTi) endodontic files were selected: WaveOne Primary (Dentsply Sirona, Ballaigues, Switzerland), WaveOne Gold Primary (Dentsply Sirona), ProTaper Universal F2 (Dentsply Sirona), and ProTaper Next X2 (Dentsply Sirona). A tempered steel block containing artificial canals with 4 different canal curvatures (15°, 25°, 35°, and 45°) was constructed. Each file was used according to the manufacturer's instructions in the dynamic model, with an added 15 axial up-and-down movements of 4 mm at the end of the canal. The generated torque was recorded, and the total and maximum torque values were measured. Two-way analysis of variance and the Duncan post hoc comparison test were performed at a significance level of 95%.A significant correlation between the curvature angle and the type of file system was observed (P .05). As the degree of canal curvature increased, the generated total and maximum torque increased. At 15° and 25°, the NiTi files with reciprocating motion generated a higher total and maximum torque than files with continuous rotation. ProTaper Universal of conventional NiTi alloy showed the steepest increase in the generated total and maximum torque with the increasing curvature angle. The ProTaper Next file had the lowest torque values at the higher canal angles of 35° and 45° (P .05).Despite the study limitations, it can be concluded that root canal curvature, design, and heat treatment of NiTi files and file kinematics affect the generated torque during instrumentation.

The prediction of the flattening pattern of carbon fiber woven composite material is crucial in preforming processing for composite component manufacturing. However, the variable curvature of component mold surface challenges the prediction, resulting in expensive material waste and difficulty in following manual or automated laying-up processing. A surface flattening model for carbon fiber plain-woven composite preforming processing is presented to solve the above problem. The flattening model for the saddle-like non-developable surface based on woven material characteristics is proved with simulating and material forming tests. The results show that, compared with the simple mass-spring unfolding model, the new model can adapt to the variety of fiber angles, and the prediction accuracy of the near-net shape is high: The margin of the 45°/135°formed prepreg predicted by the new model is reduced by 53%. And the margin of the 0°/90° prepreg is reduced by 76%, and there is no material shortage defect.

Introduction Separated endodontic instruments may adversely affect the outcome of endodontic treatment. The combination of ultrasonic techniques and dental operating microscopes appears to be effective in the removal of separated instruments compared with more randomized techniques. This study evaluated the roles of root canal curvature and separated instrument length on the time needed to loosen and retrieve the instrument fragments. Methods The retrieval procedures of 128 separated instruments referred to a private endodontic practice for retreatment by general practitioners were evaluated in patients who were monitored for a minimum of 6 months. Preoperative cone-beam computed tomographic images were used to measure separated instrument lengths in relation to the degrees of canal curvatures. Ultrasonic instruments were used in the initial phase to remove the tooth structure and to loosen the fractured instrument. In the second phase, ultrasonic instruments, wire loops, or XP Shapers (FKG Dentaire SA, La Chaux-de-Fonds, Switzerland) were used for fragment removal. The time periods for all procedures were recorded. Statistical analysis was completed applying log-normal regression, structural equation modeling, and linear regression using Stata Version 14.2 software (StataCorp LLC, College Station, TX). Results All separated instruments were successfully retrieved. Using the protocol in this study, 89.8% of the instruments were removed using ultrasonic instruments alone with a mean time of 221 seconds. The instrument removal time was dependent on both the instrument length and the root canal curvature. Additionally, preparation times were proportionately longer with increasing separated instrument lengths when the loop device was required. Conclusions The preparation phase appears to have an important role in the retrieval of separated instruments. Preparation times for both non-loop and loop groups demonstrate that length and curvature are independent predictors of the log-transformed time. Generally, procedure times were extended with increasing file lengths and higher degrees of canal curvature.

An experimental study together with numerical simulation was conducted to investigate the formation mechanisms and control methods for stray grains at melt-back of seed in this paper. The numerical simulation results showed that the convex solid/liquid (S/L) interface changed very slowly into a concave interface during the initial solidification stage and the undercooling was slightly affected by the S/L curvature change. The formation of stray grains below melt-back interface at seed perimeter could be suppressed with the decrease of clearance between the seed and mold. However when the clearance was further decreased to 0, an orientation deviation layer formed originated from the deformation of un-melted seed caused by different expend coefficient between the seed and mold. The nucleation of stray grains above the melt-back interface at the seed perimeter could be suppressed using the mold with small surface roughness. The isolated un-melted dendrite stem at semi-solid mushy of the seed with the large original primary dendrite spacing transfer to complex network structure, suppressing the formation of the stray grains, when the primary dendrite spacing of seed decreased or the seed underwent solution heat treatment. Then, the formation mechanisms of the stray grains at the melt-back region are discussed based on above results, and a method is proposed to suppress the formation of the stray grains for preparing single crystal components by re-used seed.

Machining distortion is extensively observed in the milling of multi-frame components due to residual stress and low rigidity. Therefore, it is critical to accurately predict the distortion and develop corresponding reduction technology in the milling of multi-frame components. In this paper, a novel analytical model to predict the machining distortion of multi-frame components was established based on the energy method. The influence of bulk residual stress inner the material, machining induced residual stress and the characteristics of workpiece structure were taken into account in this theoretical model. Milling experiments were performed on two classical multi-frame components including rib, web and hole to verify the proposed model. Measurement results of 3D and 2D distortions of the components were compared with prediction results. Fine consistency between the two results demonstrated the accuracy of the established theoretical model. According to the theoretical results, a new parameter with general consideration of the influence of bending curvature in x- and y-direction was formulated as distortion coefficient and further applied to adjust the processing parameters to reduce the distortion. Furthermore, the corn starch suspension with shear thickening property was also successively employed to reduce the machining distortion at the mean time. Milling experiment results successfully proved the effectiveness of the proposed methods in this work, and the machining distortion can be reduced nearly by 20%.

The structure-induced regulation mechanism of that regulates the participation of radicals and nonradicals involved in the activation of the peroxymonosulfate (PMS) reaction pathway is important for the metal-free catalytic degradation of water pollutants. Here, an N-doped carbon material with a hollow structure (SiM) was constructed by a template self-assembly method, which provides a unique spatially confined configuration that activates PMS to oxidize bisphenol A (BPA). The results of a systematic study showed that the curvature of the hollow structure controls the proportion of carbon sp3/sp2 hybridization and the transition of persistent free radicals (PFR), thereby triggering the mechanism of nonradicals and radicals conversion. The content of the N species was varied to obtain mathematical relationship between the N species content and the nonradical reaction rate. The results of this study provide new insights into the controlled pathways and types of reaction in carbon-catalyzed peroxymonosulfate activation.

Providing accurate constitutive stress–strain relationships for confined concrete can increase the reliability of the moment curvature (MC) analyses in the displacement-based seismic design of reinforced concrete (RC) columns. This paper presents a new stress–strain model for high-strength concrete (HSC) tied square columns which exhibit a more brittle behavior than normal strength concrete (NSC) members. Introducing the concept of least confined volume in the damage localization zone at the middle of the concrete core, a new approach is developed for the confinement stress distribution of lateral ties. In order to determine the lateral stresses acting on the vertical surfaces of the least confined volume, the effective confinement stresses are reduced considering the tie configuration. The peak strength and the ductility of the column should therefore be calculated for the confined concrete in this region. A concrete failure criterion applicable to multi-axial compression due to the reduced confinement stresses in two orthogonal directions, is then used to determine the ultimate strength of HSC columns. Moreover, plotting the compression meridian of the failure criterion, a simple and design-oriented formula is proposed for the ultimate strength of HSC tied columns. The validity of the proposed approach and the performances of two well-known analytical models are verified against the test results of eighty-six HSC columns from five different experimental studies for both the axial stress–strain behavior and the ultimate strength. Besides, the implementation of the concept of the reduced confinement stress in the Mander’s model leads to a significant improvement in its capability of predicting the triaxial strength of HSC.

Using the endosomal sorting complex required for transport (ESCRT)-III membrane remodeling complex as an example, we analyze three popular coarse-grained models (the regular MARTINI, polarizable MARTINI (POL-MARTINI), and big multipole water MARTINI (BMW-MARTINI)) for the description of membrane curvature sensing and generation activities of peripheral proteins. Although the three variants of the MARTINI model provide consistent descriptions for the protein-protein interface in a linear filament model of ESCRT-III, they differ considerably in terms of protein-membrane interface and therefore membrane curvature sensing and generation behaviors. In particular, BMW-MARTINI provides the most consistent description of the protein-membrane interface as compared to all-atom simulations, whereas the regular MARTINI is most consistent with atomistic simulations in terms of the qualitative sign of membrane curvature sensing and generation. With POL-MARTINI, the ESCRT-III model interacts weakly with the membrane and therefore does not exhibit any curvature-sensitive activities. Analysis suggests that the incorrect membrane curvature activities predicted by BMW-MARTINI are due to overestimated insertion depth of an amphipathic helix and incorrect sign for the spontaneous curvature of anionic lipids. These results not only point to ways that coarse-grained models can be improved but also explicitly highlight local lipid composition and insertion depth of protein motifs as essential regulatory factors for membrane curvature sensing and generation.

Dasgupta (2015) has recently put forward a novel argument, which he calls the ‘curvature argument’, that aims to show that Galilean spacetime is not an ideal setting for our classical theory of motion. This paper examines the curvature argument and argues that it is not sound. The discussion yields a remark about the conditions under which a ‘symmetry argument’ demonstrates that a particular spacetime is a non-ideal setting for our theory of motion.