Tangential Surface Research Articles

Effect of γ-radiations on the optoelectrical parameters of coumarin-poly vinyl alcohol composite thin films

This work aims to study the effect of γ-radiations on the optoelectrical parameters of coumarin-poly vinyl alcohol composite thin films at room temperature prepared by solution casting method. For these polymer composite films, the various parameters calculated from the refractive index and extinction coefficient were obtained from transmittance and reflectance spectra. The effect of radiations on the optical band gap, Urbach energy, tangent loss factor, volume and surface energy loss functions were studied. The effect of γ-radiations on the optoelectrical parameters like high-frequency dielectric constant, optical carrier concentration, relaxation time, optical mobility and optical resistivity derived from Drude theory were also discussed. Moreover, other parameters of interest under the investigation were optical conductivity, electronic polarizability, optical electronegativity, nonlinear optical susceptibility, optical, and chemical hardness. The impacts of γ-radiations on dispersion parameters like oscillator energy, dispersion energy, oscillator wavelength and oscillator strength were also studied by using Wemple-DiDomeenico single oscillator model.

Hardness Penetration Depth Prediction in the Grind-Hardening Process through a Combined FEM model

The grind-hardening process aims to increase the surface hardness of the material through the dual action of the mechanical and thermal load. A novel approach to model the process and predict the hardness penetration depth was developed based exclusively on the prediction of austenite-martensite transformation. A combined micro and macro scale approach was implemented to forecast the temperature reached in the surface starting from the action of a single grain and using its specific cutting power to design a moving heat source representing the interaction between the grinding wheel and the material. The martensitic transformation temperature considered in this paper takes into consideration the fast heat cycle typical of this process. In order to validate the model, tangential surface grinding tests were performed on 42CrMo4 and microstructural analysis with micro-hardness measurements were performed. This research presents a first step in developing a grinding process simulation that includes multi-grain grinding, real grain geometries, binder effect, and real workpiece-grinding wheel kinematics.

Timber Properties and Cellulose Crystallites Size in Pine Wood Cut in Different Sawing Patterns after Pretreatment with CH3COOH and H2O2 and Densification

One process to improve wood quality is densification or wood surface compression. Our study analyzed the changes in some basic properties of pine wood, including its anatomical structure, density, modulus of elasticity (MOE), and dimensions of cellulose crystallites, after densification following soaking pretreatment in CH3COOH and H2O2 at a concentration of 20%. Samples were sawn in radial and tangential directions for analysis of the wood. The results showed a change in the shape of tracheid cells from hexagonal to oval, as well as damage to the ray cell constituents on the tangential surface. The thickness decrease of the samples was in accordance with the target, which meant that spring-back was short. In general, the tangential boards had a higher density than the radial boards, with a lower MOE and crystallite dimensions. Our findings showed that the densified tangential board was stronger than the radial board.

Huygens' Principle geometric derivation and elimination of the wake and backward wave

Huygens' Principle (1678) implies that every point on a wave front serves as a source of secondary wavelets, and the new wave front is the tangential surface to all the secondary wavelets. But two problems arise: portions of wavelets that exist outside of the new wave front combine to form a wake. Also there are two tangential surfaces so wave fronts are propagated in both the forward and backward directions. These problems have not previously been resolved by using a geometrical theory with impulsive wavelets that are in harmony with Huygens' geometrical description. Doing so would provide deeper understanding of and greater intuition into wave propagation, in addition to providing a new model for wave propagation analysis. The interpretation, developed here, of Huygens' geometrical construction shows Huygens' Principle to be correct: as for the wake, the Huygens' wavelets disappear when combined except where they contact their common tangent surfaces, the new propagating wave fronts. As for the backward wave, a source propagates both a forward wave and a backward wave when it is stationary, but it propagates only the forward wave front when it is advancing with a speed equal to the propagation speed of the wave fronts.

Construction of Developable Surface with Geodesic or Line of Curvature Coordinates

In this paper, a developable surface with geodesic or line of curvature coordinates is constructed in the Euclidean 3-space. A developable surface is coordinated by two families of parametric curves, base curves (directrices) and lines (rulings). Since any part of a straight line on a developable surface is geodesic and line of curvature, we only need to show that the directrices curves are geodesics or lines of curvature to ensure that the developable surface is parameterized by geodesic or line of curvature coordinates. The necessary and sufficient conditions for the directrices curves to be geodesics or lines of curvature are studied. The main results of this paper show that the developable surface with geodesic coordinates is a generalized cylinder, and the developable surface with line of curvature coordinates is a tangent surface.

On the cause of surface tension at a liquid–gas interface

In this paper, a qualitative explanation of the causes of surface tension forces at a liquid–gas interface acting parallel to an interface is presented. None of the common explanations of surface tension given in preliminary physics courses consider the reasons behind the attractive forces between nearest neighbor molecules acting parallel to a surface. The earlier proposed explanations are based on the assumption that there is a concentration gradient at the liquid–gas interface. The analysis is based on considering the anisotropic pressure tensor in the interface layer. Unfortunately, these explanations are difficult to understand in preliminary physics courses. Additionally, they do not pay enough attention to the physical reasons for the formation of a special surface layer with the distance between the nearest neighbors in the direction parallel to the surface greater than in the direction normal to it. In this paper, a simple qualitative explanation of surface tension forces at a liquid–gas interface is provided. The consideration includes the reasons for the formation of a special liquid–gas interface and the reasons for the appearance of tangent surface tension forces. The instability of the liquid–gas interface and the associated fluctuations are also discussed.

Parametric Design of NC Tangency Point in Archimedes spiral Helical surface

This article based on matlab secondary development on the surface of the archimedean spiral cut NC contacts of parametric design. The generation principle of the spiral surface is described, and the processing error that may be caused by the processing method of the spiral surface is analyzed. In the case of meeting the processing requirements, a larger step length and a larger path distance are selected to calculate the tangent contact points of the spiral surface for CNC machining, and the accuracy of the contact points is verified by Matlab. Finally, a parametric design is carried out for the processing of the spiral curved surface tangent contact.

Boundary-Layer Control by Means of Pulsed Jets at Different Inclination Angles

Finite amounts of compressed air are impulsively emitted through a rectangular outlet at an axial velocity of . Their interaction with a steady crossflow with a zero-pressure-gradient turbulent boundary layer is studied on the basis of phase-locked particle image velocimetry measurements for a parameter space that is spanned by the jet inclination angle defined with respect to the surface tangent downstream of the outlet and the ratio between the axial jet velocity and the crossflow velocity . Two types of vortex structures are observed. For , , jets penetrate into the crossflow, and distinct, asymmetrical vortex rings are produced. For , as well as for , , starting jets attach to the wall as leading vortex half-rings are formed. The latter type is better suited to energize the boundary layer as low-momentum fluid is shifted away from the surface and high-momentum fluid from the freestream is entrained into the jet wake. In terms of the overall gain in streamwise momentum, the impulse provided due to overpressure during the rapid jet initiation is of major importance in the present study, and its exploitation may enable a significant enhancement in future flow control applications.

A Local Approach for Computing Smooth B-Spline Surfaces for Arbitrary Quadrilateral Base Meshes

Abstract We present a method for approximating surface data of arbitrary topology by a model of smoothly connected B-spline surfaces. Most of the existing solutions for this problem use constructions with limited degrees-of-freedom or they address smoothness between surfaces in a post-processing step, often leading to undesirable surface behavior in proximity of the boundaries. Our contribution is the design of a local method for the approximation process. We compute a smooth B-spline surface approximation without imposing restrictions on the topology of a quadrilateral base mesh defining the individual B-spline surfaces, the used B-spline knot vectors, or the number of B-spline control points. Exact tangent plane continuity can generally not be achieved for a set of B-spline surfaces for an arbitrary underlying quadrilateral base mesh. Our method generates a set of B-spline surfaces that lead to a nearly tangent plane continuous surface approximation and is watertight, i.e., continuous. The presented examples demonstrate that we can generate B-spline approximations with differences of normal vectors along shared boundary curves of less than one degree. Our approach can also be adapted to locally utilize other approximation methods leading to higher orders of continuity.

Migration of a micro-swimmer in a channel flow

An immersed boundary-lattice Boltzmann (IB-LB) method is employed to investigate the migration of a two-dimensional cylindrical micro-swimmer in a channel flow. The swimming Reynolds numbers (Res), the flow Reynolds numbers (Rep), and the blockage ratios (κ) are respectively set being from 0.05 to 2.0, 40 to 160, and 0.11 to 0.5 in the simulations. A two-dimensional archetypal self-propelled model generating tangential surface waves is employed to mimic a micro-swimmer with different Res swimming in the presence of a channel flow with different Rep and κ, finding four typical locomotion modes, namely, the horizontal mode, the attracted oscillatory mode, the oscillatory mode, and the chaotic mode. At Rep = 100 and κ = 0.25, the squirmer displays an oscillatory motion even though at a lower Res (Res = 0.05), indicating a different migration behavior from that of a passive particle; With increasing Res, the horizontal or the attracted oscillatory mode develops to the oscillatory or the chaotic mode, showing a tendency of motion symmetrical concerning the centreline. On increasing Rep with Res = 0.1 and κ = 0.25, the squirmer with a lower swimming intensity |β| ≤ 1 maintains the attracted oscillatory mode, whereas the pusher (propelled from the rear) with β = −3 and the puller with β = 3 (propelled from the front) develop to the attracted oscillatory mode from the oscillatory and horizontal modes, respectively. At Rep = 100 and Res = 0.1, the squirmers with −3 ≤ β ≤ 0 and the puller with β = 5 respectively maintain the attracted oscillatory and the horizontal modes regardless of κ; On increasing κ, the horizontal mode for the pullers with 1 ≤ β ≤ 3 and the attracted oscillatory mode for the pusher with β = −5 develop to the attracted oscillatory and oscillatory modes, respectively. The transport velocity of the squirmer is also studied with the variations of Res, Rep, and κ, obtaining a maximum value for the neutral squirmer at Res = 1.5, Rep = 100, and κ = 0.25.

Change in the surface roughness and surface free energy of Samama (Anthocephalus macrophyllus) after citric acid impregnation through pre-compression method

This research aims at detecting the hydrophobicity change in Samama (Anthocephalus macrophyllus) wood surface after hydro-thermo-mechanical modification. The modification started by soaking the test piece until water-saturated, followed with pre-compression at 100 °C for an hour. The second stage was impregnation of citric acid 10% using autoclave at pressure 7.5 kg cm−2 for 4 h. The other test piece was only impregnated using distilled water, without citric acid, with the same pressure within the same time. Further, the second compression was conducted on the test piece impregnated only with distilled water and citric acid. It was conducted at 180 °C for 10, 20, 30, 40, 50 and 60 min. The compaction target was 20%. After conditioning for 2 weeks at room temperature (25 °C) and RH 85%, the test piece was soaked in distilled water for 24 h for the spring back test. The surface roughness and surface free energy were tested after the spring back test. The test result shows that the tangential surface of Samama wood impregnated with citric acid and compressed for 50 min (type CA50) has the smoothest tangential surface. The type also has the lowest SFE value of 36.193 mJ m−2. In addition, the dispersive component of densified Samama wood surface seems to increase and, on the contrary, its polar component is reduced. The wood radial surface impregnated with citric acid tends to be rougher with a higher total SFE value than that of the tangential surface.

Surface tension and energy conservation in a moving fluid

The transport of energy in a moving fluid with a simply connected free surface is analyzed, taking into account the contribution of surface tension. This is done by following a "control volume" with arbitrary, specified velocity, independent of the flow velocity, and determining the rates of energy passing through the boundaries, as well as the energy dissipation in the bulk. In particular, a simple conservation equation for the surface area is written down, which clearly shows the contribution of the Laplace pressure at the free surface and the tangential surface tension forces at its boundary. It emerges as the mechanical conservation law for the surface energy in its general form. For a static control volume, all contributions from surface tension disappear, except that the pressure has to be modified by the Laplace contribution.

Micromorphology and fractal evaluation of Dinizia excelsa Ducke wood under three different cut conditions by atomic force microscopy

An advanced characterization on the micromorphology of Dinizia excelsa Ducke was performed on the roughly sanded main wood cutting surfaces, longitudinal radial, longitudinal tangential, and transversal. AFM was applied to obtain 3D topographical images. Morphology and its correlated parameters were studied using MountainsMap software, according to the ISO 25178-2: 2012. Advanced fractal parameters, explicitly, fractal dimension, fractal succolarity, fractal lacunarity, and surface entropy, were obtained and analyzed. Each plan has a unique morphology, and the most significant roughness occurred to the tangential surface. All plans exposed similar asymmetry and kurtosis. Microtextures were similar, although the tangential surface exhibited the least spatial complexity. The fractal parameters H and β confirmed the microtexture similarity, revealing all the surfaces have similar topographic uniformity and textures. Fractal succolarity showed that the surface percolation was significantly different. These results indicate the mathematical tools applied to topographical AFM images can map the wood surface spatial patterns.

Parametric study of a yellow birch surface impregnation process

Wood is a renewable resource that has been used as a material in appearance products for years. Despite its acceptable mechanical resistance, different modification processes were developed to enhance wood’s hardness and make it an even more durable material. Impregnating wood pores with monomers under vacuum-pressure cycle is a common method for that purpose. However, most implemented processes are long and mostly submerge wood into a monomer formulation (Bethell’s full-cell process). For that, they can be considered wasteful on the quantity of materials used, energy consumed and on process duration. The objective of this paper was to evaluate the parameters that influence the penetration of monomers into the tangential surface of Yellow birch (Betula alleghaniensis Brit.) samples. The analyzed factors were the monomer formulation’s viscosity, the surface temperature, the vacuum level applied to the process, the anatomy of samples, and the absorption time. After impregnation, the weight gain of the samples was calculated. Monomer penetration depth was calculated and visualized using density profiles and micro X-ray tomography imaging. Results showed that using a low viscosity monomer formulation allied to a certain level of vacuum and absorption time can considerably increase the impregnation into the wood.

Global mantle flow retrodictions for the early Cenozoic using an adjoint method: evolving dynamic topographies, deep mantle structures, flow trajectories and sublithospheric stresses

SUMMARY During the Cenozoic, the Earth experienced multiple first-order geological events that are likely mantle flow related. These include the termination of large-scale marine inundation in North America in the Palaeocene, the late Tertiary rise of Africa relative to other continents and the long-wavelength tilting of Australia since the late Cretaceous, which occurred when the continent approached the southeast Asia subduction systems on its northward passage from Antartica. Here we explore a suite of eight high-resolution, compressible, global mantle flow retrodictions going back to 50 Ma, using an adoint method with $\approx$670 million finite elements. These retrodictions show for the first time that these events emerge jointly as part of global Cenozoic mantle flow histories. Our retrodictions involve the dynamic effects from an upper mantle low-viscosity zone, assimilate a past plate-motion model for the tangential surface velocity field, probe the influence of two different present-day mantle state estimates derived from seismic tomography, and acknowledge the rheological uncertainties of dynamic Earth models by taking in four different realizations for the radial mantle viscosity profile, two of which were published previously. We find the retrodicted mantle flow histories are sensitive to the present-day mantle state estimate and the rheological properties of the Earth model, meaning that this input information is testable with inferences gleaned from the geological record. For a deep mantle viscosity of $1.7\times 10^{22}$ Pa s and a purely thermal interpretation of seismic structure, lower mantle flow velocities exceed 7 cm yr–1 in some regions, meaning they are difficult to reconcile with the existence of a hotspot reference frame. Conversely, a deep mantle viscosity of $10^{23}$ Pa s yields modest flow velocities (< 3 cm yr–1 ) and stability of deep mantle heterogeneity for much of the retrodiction time, albeit at the expense that African uplift is delayed into the latest Neogene. Retrodictions allow one to track material back in time from any given sampling location, making them potentially useful, for example, to geochemical studies. Our results call for improved estimates on non-isostatic vertical motion of the Earth’s surface—provided, for instance, by basin analysis, seismic stratigraphy, landform studies, thermochronological data or the sedimentation record—to constrain the recent mantle flow history and suggest that mantle flow retrodictions may yield synergies across different Earth science disciplines.

Evaluating basic density calibrations based on NIR spectra recorded on the three wood faces and subject to different mathematical treatments

Background: Near infrared (NIR) spectroscopy has been successfully applied to estimate the chemical, physical and mechanical properties of various biological materials, including wood. This study aimed to evaluate basic density calibrations based on NIR spectra collected from three wood faces and subject to different mathematical treatments. Methods: Diffuse reflectance NIR spectra were recorded using an integrating sphere on the transverse, radial and tangential surfaces of 278 wood specimens of Eucalyptus urophylla x Eucalyptus grandis. Basic density of the wood specimens was determined in the laboratory by the immersion method and correlated with NIR spectra by Partial Least Squares regression. Different statistical treatments were then applied to the data, including Standard Normal Variate, Multiplicative Scatter Correction, First and Second Derivatives, Normalization, Autoscale and MeanCenter transformations. Results: The predictive model based on NIR spectra measured on the transverse surface performed the best (R²cv = 0.85 and RMSE = 25.5 kg/m³) while the model developed from the NIR spectra measured on the tangential surface had the poorest performance (R²cv = 0.53 and RMSE = 46.8 kg/m³). The difference in performance between models based on original (untreated) and mathematically-treated spectra was minimal. Conclusions: Multivariate models fitted to NIR spectra were found to be efficient for predicting the basic density of Eucalyptus wood, especially when based on spectra measured on the transversal surface. For this data set, models based on the original spectra and mathematically treated spectra had similar performance. The reported findings show that mathematical transformations are not always able to extract more information from the spectra in the NIR.

APPLICATION OF RULED SURFACES IN FREEFORM AND GEAR METROLOGY

An application of two ruled surfaces (i.e., surfaces generated by a motion of a straight line), a surface of hyperbolic paraboloid and a tangent surface of a cylindrical helix in freeform and gear metrology is introduced in this paper. Both surfaces have been implemented as the main functional figures in several artefacts – metrological calibration standards intended for testing the freeform capabilities of various measuring technologies (e.g., tactile point-to-point measurement and tactile scanning on coordinate measuring machine, optical scanning, computer tomography). Geometrical and mathematical properties of the surface used are summarised, CAD models of all the developed standards are presented and photos of the manufactured standards are shown.

Magnetic Barkhausen noise: A simulation tool

Non-destructive magnetic controls are increasing in the industrial field. In this domain, the expectation for simulation tools able to anticipate the magnetic signature, improve the understanding and avoid fastidious and uncertain experimental pre-characterizations is high. Among different methods, the magnetic Barkhausen noise (MBN) control is one of the most popular. MBN raw signal is stochastic, not reproducible, and complex to exploit. MBNenergy, which is obtained by integrating the square of the MBN voltage signal with respect to the time axis is a much more stable indicator. Although the so-called MBNenergy is not, strictly speaking, an energy, it is connected to the domain wall motions and to their kinetic energy. By plotting MBNenergy as a function of H (the tangent surface excitation field), hysteresis cycles are observed. After a rescaling step, B(H) and MBNenergy(H) hysteresis cycles can be compared. They look similar for materials with high magnetocrystalline anisotropy (i.e. when the domain wall contribution is dominant over the magnetization rotation one during the magnetization process). In this study, a multiscale model is used to simulate a virtual anhysteretic behavior of a ferromagnetic steel with a magnetization process limited to the domain wall contribution. By using this anhysteretic contribution in the Jiles-Atherton model and running an inverse procedure, a MBN envelop can be obtained. By modulating the amplitude of an alternating, high frequency signal using this envelop, an accurate simulation of the raw Barkhausen noise is obtained.

The Effect of Direction of Load on Bending Strength of <i>Melia compositae</i>

In this paper, empirical study of stiffness (modulus of elasticity-MoE) and Bending strength/flexural strength (modulus of rupture-MoR) in wood, mainly on radial and Tangential surface of <i>Melia compositae</i> wood were evaluated. Here loading in the radial direction means that load is applied to the tangential surface and loading in the tangential direction means that load is applied to the radial surface. The strength properties vary with species to species and also application of direction of load. Loading direction appreciably affects the bending properties remarkably due to the anisotropic /orthotropic nature of timber. It was observed that always MoE and MoR have greater value in Radial surface. The direction of application of load has an appreciable effect on strength properties of wood. While this is generally attributable to the presence of medullary rays in the radial direction. The bending strength of timber when loaded parallel to the direction of load is greater than that of timber loaded perpendicular to the direction of load. The ratio of flexural strength values varied from13% to 14% for <i>Melia composita</i>.

Instability of a tangential discontinuity surface in a three-dimensional compressible medium

Compressible flows appear in many natural and technological processes, for instance, the flow of natural gases in a pipe system. Thus, a detailed study of the stability of tangential velocity discontinuity in compressible media is relevant and necessary. The first early investigation in two-dimensional (2D) media was given more than 70 years ago. In this article, we continue investigating the stability in three-dimensional (3D) media. The idealized statement of this problem in an infinite spatial space was studied by Syrovatskii in 1954. However, the omission of the absolute sign of cos θ with θ being the angle between vectors of velocity and wave number in a certain inequality produced the inaccurate conclusion that the flow is always unstable for entire values of the Mach number M. First, we revisit this case to arrive at the correct conclusion, namely that the discontinuity surface is stabilized for a large Mach number with a given value of the angle θ. Next, we introduce a real finite spatial system such that it is bounded by solid walls along the flow direction. We show that the discontinuity surface is stable if and only if the dispersion relation equation has only real roots, with a large value of the Mach number; otherwise, the surface is always unstable. In particular, we show that a smaller critical value of the Mach number is required to make the flow in a narrow channel stable.