Ring Curvature Research Articles

Three-Dimensional Piston Ring–Cylinder Bore Contact Modeling

Increasing durability, preventing knocking combustion, improving fuel efficiency, and reducing pollutant emission characterize the needs for modern internal combustion engine design. These factors are highly influenced by the power cylinder system design. In particular, the piston ring to cylinder bore contact force distribution around the circumference of the piston rings must be optimized under all running conditions. To accomplish this, the ring manufacturers make the ring curvature nonconstant along the circumference. Most existing analytical tools are not able to simulate the variation along the ring circumference. In order to improve the understanding of this contact distribution and provide a high-fidelity ring design tool, a three-dimensional finite element piston ring model was developed to accomplish this variation. The modeling procedure and results are presented in this work. Experiments using a commercially available ring with negative ovality were conducted to validate the model. The ring free-shape profile and the ring cross section geometries were used as inputs to the model. Typical piston ring groove and cylinder wall temperatures were also model inputs to characterize thermal influences on the ring/bore interface forces. The ring/bore conformability was analyzed as a function of the ring radial displacements, cylinder bore constraint forces and thermal load changes to the ring. The model output showed radially separation gaps between the ring front face and the bore. This analysis provides an insight to evaluate the piston ring design. Together with an optimizer, the model can be used as a ring design tool to predict the ring free shape with a specified constraint force distribution pattern. Examples are given to demonstrate the capabilities of this numerical analytical tool. In addition, the 3D ring model can be used to improve the accuracy of existing lubrication, friction, and wear analysis tools and therefore improve the entire internal combustion engine power cylinder system design.

Controlling the ring curvature, solution assembly, and reactivity of gigantic molybdenum blue wheels.

We describe the synthesis, structure, self-assembly, solution chemistry, and mass spectrometry of two new gigantic decameric molybdenum blue wheels, {Mo200Ce12} (1) and {Mo100Ce6} (2), by building block rearrangement of the tetradecameric {Mo154} framework archetype and control of the architecture's curvature in solution from the addition of Ce(III). The assembly of 1 and 2 could be directed accordingly by adjusting the ionic strength and acidity of the reaction mixture. Alternatively, the dimeric cluster {Mo200Ce12} could be transformed directly to the monomeric species {Mo100Ce6} upon addition of a potassium salt. ESI-ion mobility mass spectra were successfully obtained for both {Mo200Ce12} and {Mo100Ce6}, which is the first report in molybdenum blue chemistry thereby confirming that the gigantic clusters are stable in solution and that ion mobility measurements can be used to characterize nanoscale inorganic molecules.

Gaussian semiflexible rings under angular and dihedral restrictions.

Semiflexible polymer rings whose bonds obey both angular and dihedral restrictions [M. Dolgushev and A. Blumen, J. Chem. Phys. 138, 204902 (2013)], are treated under exact closure constraints. This allows us to obtain semianalytic results for their dynamics, based on sets of Langevin equations. The dihedral restrictions clearly manifest themselves in the behavior of the mean-square monomer displacement. The determination of the equilibrium ring conformations shows that the dihedral constraints influence the ring curvature, leading to compact folded structures. The method for imposing such constraints in Gaussian systems is very general and it allows to account for heterogeneous (site-dependent) restrictions. We show it by considering rings in which one site differs from the others.

Semiautomatic morphometric land surface segmentation of an arid mountainous area using DEM and self-organizing maps

In this study, the land surface in an arid mountainous area in southwestern Iran, Jooyom, was segmented by self-organizing maps, using an unsupervised method. The classification was performed using a digital elevation model with 10-m resolution and window size of 17 × 17. Twenty-two morphometric layers were calculated using elevation derivatives with first, second, and third orders. The morphometric layers then were ranked and the optimum numbers of parameters and classes were selected with an optimum index factor and Davies–Bouldin index methods. It was found that the most effective parameters in classification of the area were differential curvature, slope insolation, rotor, aspect, cross-sectional curvature, total ring curvature, extreme curvature, vertical curvature, and unsphericity. The study area was segmented into six classes of negative contact, pitty-thalweg valley, gently eastward and westward sloping transversely concave and convex plains, sloping or slopy pass, and peaky ridges. The average parameters of each class confirmed their gravity, debris, and wash behavior of the surface slopes. The relative coverage percent of each formation in each class showed that the Asmari formation with highest coverage of classes 5 and 6 and Mole member marl limestone with the highest coverage of class 1 have the smallest maturity and highest maturity between formations, respectively. The maturities of each formation based on coverage percentages of different classes agreed with their corresponding hypsometric integral indexes. Furthermore, the distribution of classes in watersheds on mountain flanks confirmed the existence of tectonic tilting in this area.

The rotating black hole in renormalizable quantum gravity: The three-dimensional Hořava gravity case

Recently Hořava proposed a renormalizable quantum gravity, without the ghost problem, by abandoning Einsteinʼs equal-footing treatment of space and time through the anisotropic scaling dimensions. Since then various interesting aspects, including the exact black hole solutions have been studied but no rotating black hole solutions have been found yet, except some limiting cases. In order to fill the gap, I consider a simpler three-dimensional set-up with z=2 and obtain the exact rotating black hole solution. This solution has a ring curvature singularity inside the outer horizon, like the four-dimensional Kerr black hole in Einstein gravity, as well as a curvature singularity at the origin. The usual mass bound works also here but in a modified form. Moreover, it is shown that the conventional first law of thermodynamics with the usual Hawking temperature and chemical potential does not work, which seems to be the genuine effect of Lorentz-violating gravity due to lack of the absolute horizon.

Long-range hydrodynamic correlations in quasi-one-dimensional circular and straight geometries

We report the results of studies of the collective and pair diffusion coefficients of particles in two quasi-one-dimensional geometries: straight 2-mm-long channels and rings with radii between 3 and 35 μm. We find a contribution to the packing fraction dependence of the collective diffusion coefficient that confirms the behavior predicted by Frydel and Diamant [D. Frydel and H. Diamant, Phys. Rev. Lett. 104, 248302 (2010)], indicative of long-range hydrodynamic coupling resulting from collective motion of particles in periodic quasi-one-dimensional geometries. Specifically, we find a proportionality constant of 0.19 ± 0.01 μm(2)/s between the residual collective diffusion coefficient (defined as the collective diffusion coefficient less the mean self-diffusion coefficient of colloids) and the packing fraction for the ring geometries, independent of ring curvature, and a proportionality constant of 0.14 ± 0.01 μm(2)/s for 2-mm straight channels. Both of these values, for circular geometries in particular, are significantly larger than predicted when only ensemble averaging over particle positions is accounted for, which strongly suggests the presence of additional hydrodynamic coupling. These findings are signficant because they imply that the global geometry of the confined suspension influences collective colloidal diffusion even when single file motion of colloids is maintained.

Numerical Analysis of Laser-Textured Piston-Rings in the Hydrodynamic Lubrication Regime

In this work, the performance of barrel-shaped laser-textured piston rings is numerically investigated. The surface texture, parameterized by the dimple density, dimple depth, and dimple distribution pattern, is optimized to minimize the friction coefficient for piston rings of variable curvature. We consider fully textured as well as partially textured piston rings with two different dimple distributions patterns: a central dimple distribution, and a distribution along the piston ring edges. Finally, the sensitivity of the optimal surface parameters to the piston ring curvature is assessed.

Characterizing perpendicular-to-grain compression (C⊥) behavior in wood construction

Abstract Current compression perpendicular-to-grain (C⊥) design values for wood members are based on mean stress obtained from ASTM D143 specimen. The standard ASTM test with metal on wood bearing has limited applicability in modern construction assemblies with C⊥ loading scenarios. Previous work has shown that end-bearing conditions and wood-on-wood C⊥ bearing is a more severe case as opposed to load applied over central area and metal-on-wood bearing. This study evaluated C⊥ behavior of typical assemblies used in construction, in which members experience C⊥ stresses near their longitudinal-end through wood-on-wood contact. These included assembly of the bottom chord of a truss bearing on the top plate of a wall (BC assembly) and assembly of the compression chord of a shear wall bearing on the bottom plate (BP assembly) of a wall. Three different BC assemblies were tested with varying aspect ratios (height/width) of the bottom chord (B.C.) member. For each test assembly, paired ASTM tests of the main member (bottom chord member in BC tests, and bottom plate member in BP tests) were conducted. The assembly stresses at 1 mm deflection were always lower than the corresponding ASTM stresses at the same deflection. Due to varying assembly depths, 1 mm deflection was a poor criterion for determining C⊥ stress values. For B.C. members, when loaded tangentially, they buckle in the direction of annual ring curvature. High aspect ratios accentuate this effect. Expectedly, the tendency to buckle and the probability of total failure in the assembly increase with increasing aspect ratio. This behavior was not observed in the ASTM tests.

The influence of material properties on the amount of twist of spruce wood during kiln drying

The development of twist in Norway spruce boards (Picea abies Karst.) during normal temperature kiln drying was researched. Tangentially oriented boards were sawn from diametrical radial planks, from which the basic wood properties, i.e. linear shrinkage and grain angle, were determined. The unrestrained boards were kiln dried using a selected drying schedule. During the controlled drying process the moisture content (MC) and twist of the boards were measured. Twist was generally induced by the shrinkage of wood below the fibre saturation point, and increased in proportional to the decrease in MC. The earlier appearance of twist, with regard to MC and drying time, was confirmed in the case of boards sawn from the central part of logs. The final twist amounted to between 10 and 20°/m in the case of boards close to the pith, and decreased to less than 4°/m in the case of boards sawn at a radius of 70 mm from the centre of the logs. Ring curvature had the highest impact on the final twist of the dried boards, followed by grain angle and tangential shrinkage.

One-Dimensional Coupling of Gold Nanoparticle Plasmons in Self-Assembled Ring Superstructures

Plasmon coupling in ordered metal nanoparticle assemblies leads to tunable collective surface plasmon resonances that strongly depend on the interparticle distance. Here we report on the surface plasmon scattering of polystyrene-functionalized 40 nm gold nanoparticles self-assembled into close-packed rings. Using single particle dark-field scattering spectroscopy, we observed strong near-field coupling between neighboring nanoparticles, which results in red-shifted multipolar plasmon modes highly polarized along the ring circumference. Correlated optical spectroscopy and scanning electron microscopy of individual rings with different diameters revealed that the plasmon coupling is independent of ring curvature and mostly insensitive to the local nanoparticle arrangement. Our results further suggest that a one-dimensional gold nanoparticle assembly yields long-range collective plasmonic properties similar to those of metallic nanowires.

The single cube apparatus for shear testing – Full-field strain data and finite element analysis of wood in transverse shear

The design and analysis of wood structures require accurate data for shear properties, where transverse shear in particular has been neglected in the past. The single cube apparatus (SCA) was applied to transverse shear of Norway spruce ( Picea abies), due to the importance of this species in wood structures, such as glulam, and also its allegedly low value of G RT . Full-field strain data and FEA were used to analyze the potential of the method. The presence of a large central region of homogeneous and close to pure shear strain was confirmed. The SCA method is therefore a strong candidate for improved shear test procedures in wood and other materials, where porosity (gripping problems), heterogeneity on mm-scale and polar orthotropy (annual ring curvature) may cause particular difficulties. In contrast to many other shear test studies, the accuracy of the present G RT data is supported by documented large and homogeneous specimen stress- and strain-fields in almost pure shear, direct measurements of strain-field, and careful stress analysis based on FEA.

Application of the crack compliance method to long axial cracks in pipes with allowance for geometrical nonlinearity and shape imperfections (dents)

Application of the crack compliance method to the analysis of thin-walled rings with a radial crack has two features: a crack is considered as a concentrated angular compliance and the deformation of all other sections of the rings is calculated as for a curvilinear beam. The latter can be most conveniently found by the method of initial parameters where the values of generalized forces and displacements at the end of some zone are determined as a linear combination of their values at the beginning of the zone. The goal of the study is to derive and apply the method of initial parameters equations taking into account the influence of circumferential stresses on the ring curvature. As far as the authors know, this is the first time that the stress intensity factor has been derived for an elastic thin-walled pipe with a radial crack in a geometrically nonlinear formulation. Here, an increase in pressure leads to a somewhat slowed increase in the stress intensity factor. In addition, a number of problems for dents are considered. The effect of the dent shape on the stress–strain state is analyzed. An expression for the stress intensity factor for a complex defect, a crack emanating from the dent apex, is presented.

A numerical study of the transverse modulus of wood as a function of grain orientation and properties

Abstract Finite element analysis was used to study the effective transverse modulus of solid wood for all possible end-grain patterns. The calculations accounted for cylindrical anisotropy of wood within rectangular specimens and explicitly modeled wood as a composite of earlywood and latewood. The effective modulus was significantly reduced by growth ring curvature or off-axis loading, The large changes were attributed to the low transverse shear modulus of wood. The explicit, or heterogeneous, model was compared to prior numerical methods that homogenized properties in the transverse plane. The two models gave similar effective modulus results, but a heterogeneous model was required to capture details in modulus calculations or to realistically model stress concentrations. Various numerical methods for modeling transverse stresses in wood are discussed.

Charcoal analysis and dendrology: data from archaeological sites in north-western France

During the last 15 years, charcoal analysis of archaeological sites in north-western France has been carried out in conjunction with systematic and detailed dendrological examination. By considering these extrinsic criteria in association with the analytical results, palaeo-ethnographic and palaeo-environmental information can be obtained. The charcoals are classically identified under the microscope on the basis of their cellular structure. This examination is associated with an observation of the ligneous structure on transverse sections using a binocular lens. When charcoal fragments are large enough, the growth ring widths are measured. Tree ring curvature is also noted. Finally, alteration by fusion or radial cracks, the presence of fungal hyphae, and insect degradation are also recorded. Results are thus obtained on the nature of fuel used in domestic fireplaces and kilns. The selection of timbers and their catchment areas are also revealed. The average width of the growth rings in oak charcoal from domestic hearths coming from about forty sites in north-western France shows a significant increase from 6000 to 2000 BP. There is a similar increase in the number of heliophilic taxa used from the Neolithic to the Iron Age. This implies that the environment became more and more open because of use by society. The interpretation of the dendrology results applied to charcoal analyses is obtained through a convergence of criteria. Thus, charcoal analysis can provide more than just an identification of the species used, and can yield fundamental information on the interaction of society with the environment.

Effect of growth conditions on wood density of Spanish Pinus nigra

The natural forests of Laricio Pine (Pinus nigra Subsp. salzmannii) cover in Spain an area of 353,000 ha, producing annually 310,000 m3 of roundwood. This species is considered as the fourth, most important Spanish conifer, being its timber frequently used in construction. The natural area of distribution of Laricio pine in Spain is officially divided into ten different regions of provenance, being only four of them considered as productive. The present study on the influence of growth conditions on extracted wood basic density (EBD) is carried out on 89 P. nigra trees, sampled from the two most productive Spanish regions of provenance (R.7 and R.8) in seven different sites. Cross-sectional disks were cut at 3 m (in 89 trees) and every 3 m height (in 18 trees) from the butt up to 15 m. For assessing the pattern of radial variation of the properties, 20×20×20 mm3 wood samples were taken radially from every cross-sectional disk. In every 20×20×20 mm3 wood sample, age and distance to the pith of the central annual ring was recorded, together with the average growth rate. Extractive content and EBD were measured in every sample. The results lead to the conclusion that there is not a significant relationship between EBD and provenance or growth rate. On the contrary, a significant relationship has been found between EBD and site quality or cambial age. The results also demonstrate that in a tree EBD tends to diminish from the base to the top and from the pith outwards. The main result of the present study is related with the observation that for the same cambial age, annual ring width has no significant influence on EBD, confirming that its utility as a predictor of the quality of timber is highly questionable, at least if the ring curvature is not considered.

Comparison between HT-dried and LT-dried spruce timber in terms of shape and dimensional stability

Abstract The performance of timber studs from Norway spruce (Picea abies) in terms of shape and dimensional stability was evaluated. The shape stability studied included three modes of distortion, i.e. twist, bow and spring. The dimensional stability was assessed by measuring longitudinal shrinkage and swelling properties. The study comprised 96 studs measuring 45 mm×70 mm×2500 mm from 15 butt logs. Half the studs from each log were dried using a high-temperature method (HT) at 115°C, while the other half were dried using a conventional low-temperature method (LT) at 70°C. Distortion in the studs was measured at moisture contents of 14% and 9%. The HT-dried timber had significantly lower distortion values than the LT-dried timber. As a result, 80% of the high-temperature-dried studs were able to pass the limits for distortion, while only 60% of the low-temperature-dried studs passed the same limit. Studs cut close to the pith displayed the largest twist, independent of the drying method. A simple model for predicting twist that was used in previous studies was also valid for HT-dried timber. The most important parameters in this model for both HT- and LT-dried timber were grain angle, annual ring curvature and tangential shrinkage.

The dynamics of ring dark soliton in inhomogeneous Bose-Einstein condensates

The dynamics of the ring dark soliton in an inhomogeneous Bose-Einstein condensates (BEC) with thin disk-shaped potential trapping is investigated analytically and numerically. Analytical result shows that the ring dark soliton is governed by a variable coefficients Korteweg-de Vries (KdV) equation. The effect of the ring curvature (nonplanar geometry) and the inhomogeneous of the background on soliton amplitude and the emitted radiation profiles are obtained analytically. The theoretical results are confirmed by the direct numerical results.

Artificial Lineaments in Digital Terrain Modelling: Can Operators of Topographic Variables Cause Them?

Digital terrain modeling is widely used in geological studies. In some cases, orthogonal and diagonal linear patterns appear on maps of local topographic variables. These patterns may be both portrayals of geological structures and artefacts. Some researchers speculated that possible anisotropy of operators of local topographic variables might be a cause of these artefacts. Using a principle for testing derivative operators in image processing, we gave proof to isotropy (rotation invariability) of operators of a majority of local topographic attributes of the complete system of curvatures (i.e., slope gradient, horizontal curvature, vertical curvature, mean curvature, Gaussian curvature, accumulation curvature, ring curvature, unsphericity curvature, difference curvature, minimum curvature, maximum curvature, horizontal excess curvature, and vertical excess curvature). Rotating an elevation function about z-axis and then applying these operators cannot lead to variations in both values of the topographic variables and patterns in their maps, comparing with results of applying these operators to an unrotated elevation function. This demonstrates that linear artefacts with preferable directions in maps of the topographic attributes specified cannot be caused by intrinsic properties of their operators. Other possible sources for false linear patterns in maps of topographic variables are briefly discussed: (a) errors in the compilation of digital elevation models (DEMs), (b) grid geometry of digital terrain models (DTMs), (c) errors in DEM interpolation, (d) imperfection of algorithms for DTM derivation, and (e) aliasing errors.

Electronic eigenstates in quantum rings: Asymptotics and numerics

The electronic eigenstates of quantum rings of constant width and arbitrary shapes are studied in the two-dimensional infinite hard-wall potential approximation. An asymptotic method is developed to evaluate the eigenenergies and eigenfunctions under the assumption that the ratio of ring half-width to a typical radius of curvature is small, and this provides a significant improvement over a more conventional zero-curvature approximation. A direct numerical scheme based on spectral methods is also developed and this is free of the small curvature limitation. To illustrate the versatility and accuracy of our general formulas we also treat a specific illustrative case, a pseudoelliptic annulus, and the two methods are compared. The asymptotic model is demonstrated to be very accurate while being orders of magnitude faster than the direct numerics. The effects of varying ring curvature on spectral and transport properties of quantum rings are studied. In particular, the existence and structure of eigenstates localized at the regions of maximal curvature is investigated.

Taming ring morphology in 2D Co(OH)2 Liesegang patterns

We present here novel expermients on the formation of Liesegang rings in 2D. We consider the system of propagating Co(OH)2 bands studied extensively in 1D, from the viewpoint of a large number of considerations. In this paper, we focus on morphological aspects and, in the first part, we seek to steer the appearance of the pattern to achieve a pre-determined morphology. We aim at attaining three main features: minimizing the re-dissolution of Co(OH)2 at the back of the propagating pattern, clearing the fuzzy precipitate region lagging behind, and increasing the ring spacing. We vary three experimental parameters to achieve that threefold purpose: 1. decreasing the concentration of the diffusing (outer) electrolyte (NH4OH), 2. applying a constant electric field radially across the circular pattern, and, 3. increasing the gel concentration to a moderately high value. The best pattern was obtained under the conditions: 9% gelatin, [NH4OH]0 = 1.33 M, and applied potential V = 4.0 V, for a 0.100 M CoCl2 taken as constant throughout the whole set of experiments performed. The observations are discussed in relation to the effects that cause them, and the known properties of Liesegang patterns. In the second part of the study, we monitor distortions of the ring pattern from circular symmetry, by applying a constant linear electric field across the circular medium. Elliptical distortions are obtained, which become notably important as the applied potential increases through 1.75 V. The variation of the ring curvature with applied potential is quantified and discussed.