Types Of Roughness Research Articles

Skeleton Runner Roughness and Surface Contact Area Influence on Sliding Ability: Field Experiments

Scientists and sport athletes are constantly seeking for the methods which could improve surface sliding ability on ice. Modifications of contact area and surface roughness are relatively easy but not yet fully understood methods for sliding ability improvements. This research contains information of how one can perform on-field experiments with skeleton sleigh to determine the influence of surface contact area and roughness on sliding ability. Two types of surface roughness i.e. polished (3000 grain sandpaper) and scratched (600 grain sandpaper) are compared using three different contact areas. Obtained data showed that rougher surfaces tend to slide faster if contact area is larger but the effect reverses if contact area is reduced.

Turbulent convection and large scale circulation in a cube with rough horizontal surfaces.

Large-eddy simulations of thermal convection are presented and discussed for a cube with rough horizontal surfaces. Two types of roughness are considered: uniformly placed pyramids, and grooves aligned parallel to one set of sidewalls. The Rayleigh number is 10^{8}, the Prandtl number 0.7, and the aspect ratio 1, as in a previous study [N. Foroozani, J. J. Niemela, V. Armenio, and K. R. Sreenivasan, Phys. Rev. E 95, 033107 (2017)10.1103/PhysRevE.95.033107], except that the meshes here are finer. When the thermal boundary layers are sufficiently large relative to the characteristic roughness height, i.e., for hydrodynamically smooth conditions, the mean properties of the large scale circulation (LSC) are qualitatively similar to the case of smooth surfaces. In particular, the LSC is always aligned along one of the diagonals of the cube. When the boundaries are hydrodynamically rough, the same result holds true only for the case of pyramidal structures; for grooved surfaces, the LSC is forced to be parallel to the sidewalls on average, alternating rapidly between the two diagonals of the cube with a mean period of the order 10 turnover times. Our analysis suggests that the difference from the pyramidal case is due to the breaking of the horizontal x-z symmetry under conditions of hydrodynamical roughness, and the corresponding directional concentration of plume emission along the grooves, from which the LSC is generated, providing a strong restoring force. Furthermore, in this study we observed a small reduction in heat transport for both roughness configurations which is in good agreement with past studies.

Process Understanding of Plasma Electrolytic Polishing through Multiphysics Simulation and Inline Metrology.

Currently, the demand for surface treatment methods like plasma electrolytic polishing (PeP)—a special case of electrochemical machining—is increasing. This paper provides a literature review on the fundamental mechanisms of the plasma electrolytic polishing process and discusses simulated and experimental results. The simulation shows and describes a modelling approach of the polishing effect during the PeP process. Based on the simulation results, it can be assumed that PeP can be simulated as an electrochemical machining process and that the simulation can be used for roughness and processing time predictions. The simulation results exhibit correlations with the experimentally-achieved approximation for roughness decrease. The experimental part demonstrates the results of the PeP processing for different times. The results for different types of roughness show that roughness decreases exponentially. Additionally, a current efficiency calculation was made. Based on the experimental results, it can be assumed that PeP is a special electrochemical machining process with low passivation.

Surface roughness effect on Mo physical sputtering and re-deposition in the linear plasma device PSI-2 predicted by ERO2.0

Abstract Surface morphology and its evolution during the plasma irradiation is known to have a large influence on the erosion and resulting lifetime of plasma-facing components as well as tritium retention. For instance, surface roughness can affect physical sputtering, re-deposition, as well as angular distributions of the sputtered species. In this study the effect of surface roughness is implemented into the 3D Monte-Carlo code ERO2.0. First modelling results for molybdenum (Mo) irradiated with deuterium (D) in the conditions foreseen for the planned experiments at the linear plasma device PSI-2 are presented. Using the constructed examples of surfaces with various (regular and fractal) roughness types it is shown that the effective sputtering yield decreases for rough surfaces in comparison to smooth ones. The angular distribution of particles escaping from the rough surface collimates with the increase of the surface structure's aspect ratio. Moreover, the modelling predicts flattening of the surface during the plasma irradiation due to the preferable re-deposition in the “valleys” and sputtering of the peak tops.

Does Implant-Abutment Interface affect Marginal Bone Levels around Implants?

Objective The use of dental implants with different types of surface roughness and implant-abutment interface has brought about a situation of marginal bone loss. Therefore, the aim of this study was to analyze and compare marginal bone levels of different types of osseointegrated dental implants with platform switch (Group A: Ankylos, Mannheim, Germany) and platform match (Group B: Dentsply Xive, Mannheim, Germany, and Group C: MIS Implant Technologies, Karmiel, Israel). Materials and Methods One hundred and seven patients (52 men and 55 women) with a mean age of 54.79 (standard deviation ± 12.35) years and a total of 321 dental implants (Group A, n = 198; Group B, n = 58; and Group C, n = 65) placed in a private practice between April 2006 and May 2015 were retrospectively analyzed. In addition to demographic information and implant characteristics, marginal bone levels were evaluated by Image J (Wayne Rasband, National Institute of Health, Maryland) program. Results The mean age of all patients was 54.79 ± 12.35 years, and 51.5% of them were women. Implants supporting fixed bridge were most commonly used in all groups (65%), whereas only 20% were restored with a single crown and 15% with overdentures. In total, 47.5% of all implants showed no marginal bone loss. Mean bone loss in Group A was significantly lower (0.81 ± 1.60 mm) as compared to Group B (1.58 ± 1.59 mm) and Group C (1.18 ± 1.36) ( p < 0.005). Conclusion Among different types of dental implants, platform switch seems to preserve marginal bone levels and increase the long-term success of dental implants.

Phagosome Escape of Rough Mycobacterium abscessus Strains in Murine Macrophage via Phagosomal Rupture Can Lead to Type I Interferon Production and Their Cell-To-Cell Spread.

Mycobacterium abscessus complex (MAB) is a rapidly growing mycobacterium(RGM) whose clinical significance as an emerging human pathogen has been increasing worldwide. It has two types of colony morphology, a smooth (S) type, producing high glycopeptidolipid (GPL) content, and a rough (R) type, which produces low levels of GPLs and is associated with increased virulence. However, the mechanism responsible for their difference in virulence is poorly known. By ultrastructural examination of murine macrophages infected, we found that MAB-R strains could replicate more actively in the macrophage phagosome than the S variants and that they could escape into cytosol via phagosomal rupture. The cytosolic access of MAB-R strains via phagosomal rupture led to enhanced Type I interferon (IFN) production and cell death, which resulted in their cell-to-cell spreading. This behavior can provide an additional niche for the survival of MAB-R strains. In addition, we found that their enhancement of cell death mediated cell spreading are dependent on Type I IFN signaling via comparison of wild-type and IFNAR1 knockout mice. In conclusion, our data indicated that a transition of MAB-S strains into MAB-R variants increased their virulence via enhanced Type I IFN production, which led to enhanced survival in infected macrophage via cell death mediated cell-to-cell spreading. This result provides not only a novel insight into the difference in virulence between MAB-R and -S variants but also hints to their treatment strategy.

Pressure generation in rough conical bearing using non-Newtonian Rabinowitsch fluid with variable viscosity

PurposeThis paper aims to investigate the effect of surface roughness (radial and azimuthal) and viscosity variation on a squeeze film of a conical bearing with a non-Newtonian lubricant by using Rabinowitsch fluid model.Design/methodology/approachThe main objective is to determine the stochastic nonlinear modified Reynolds equation for rough conical bearing. Later, first-order closed-form solutions are obtained using a small perturbation method and are numerically solved using the Gauss quadrature method.FindingsThe findings of this paper, numerical calculations, are analyzed for pressure, load carrying capacity and response time. The simulated results indicate that the influence of surface roughness increases the pressure, load carrying capacity and response time, whereas the viscosity variation factor decreases the pressure, load and response time.Originality/valueAccording to both types of surface roughness with viscosity variation, the performance of a squeeze film rough conical bearing was improved by using Rabinowitsch fluid model. As it is inevitable to consider viscosity variation for bearing designer, it leads to a long life period of conical bearing.

Local well-posedness and blow-up for the half Ginzburg-Landau-Kuramoto equation with rough coefficients and potential

We study the Cauchy problem for the half Ginzburg-Landau-Kuramoto (hGLK) equation with the second order elliptic operator having rough coefficients and potential type perturbation. The blow-up of solutions for hGLK equation with non-positive nonlinearity is shown by an ODE argument. The key tools in the proof are appropriate commutator estimates and the essential self-adjointness of the symmetric uniformly elliptic operator with rough metric and potential type perturbation.

Point Mutations Lead to Increased Levels of c-di-GMP and Phenotypic Changes to the Colony Biofilm Morphology in &lt;i&gt;Alcanivorax borkumensis&lt;/i&gt; SK2

Alcanivorax borkumensis is a ubiquitous marine bacterium that utilizes alkanes as a sole carbon source. We observed two phenotypes in the A. borkumensis SK2 type strain: rough (R) and smooth (S) types. The S type exhibited lower motility and higher polysaccharide production than the R type. Full genome sequencing revealed a mutation in the S type involved in cyclic-di-GMP production. The present results suggest that higher c-di-GMP levels in the S type control the biofilm forming behavior of this bacterium in a manner commensurate with other Gram-negative bacteria.

Design and modification of horizontal-flow roughing filter as water treatment at UGM retention pond

UGM Retention Pond as flood controller has its water supply from Belik River. Based on water quality monitoring results by the Environment Agency (BLH) of DIY in 2012–2016, the water status at the upstream area of Belik river has already contaminated before it flows to the retention pond. This study aims to make UGM Retention Pond not only as flood control, but also as a water treatment. The function can be fulfilled with the innovation of rough filter water type applied to horizontal flow, i.e. Horizontal-flow Roughing Filter. Mass balance analysis on the retention pond was calculated based on the assumption of the pond as a complete-mix reactor with BOD5 of 20.9 mg/L and TSS of 102 mg/L with discharge (Q) of 2.54 m3/s. The maximum target output produced for BOD5 was 3 mg/L and TSS was 50 mg/L so the target of filtering efficiency was 94 %. The analysis results showed the most optimal Horizontal-flow Roughing Filter was elongated beam-shaped design with length dimensions of 44.6 m, width of 2.5 m, and height of 1.7 m. Filter media used in the form of pebble (gravel) with the size of 24–16 mm and assumed to have permeability coefficient k = 0.1 m/s.

On the Behaviors of Rough Fractional Type Sublinear Operators on Vanishing Generalized Weighted Morrey Spaces

The aim of this paper is to get the boundedness of rough sublinear operators generated by fractional integral operators on vanishing generalized weighted Morrey spaces under generic size conditions which are satisfied by most of the operators in harmonic analysis. Also, rough fractional integral operator and a related rough fractional maximal operator which satisfy the conditions of our main result can be considered as some examples.

HCF Failure Modes and Mechanisms of Dissimilar Welds of Martensite/Austenite Metals at Elevated Temperature

In this paper, the high cycle fatigue (HCF) behavior and failure mechanism of welded joint for martensite/austenite dissimilar metals were systematically investigated at elevated temperature. The HCF tests were performed at different elevated temperatures of 550, 600 and 630°C with stress ratio of -1. Most tested specimens failed in the heat affected zone (HAZ) of martensite metal, while minor failure occurred on the weld metal (WM) with comparatively more scattered fatigue life. Fatigue crack in the WM initiated from welding defects like porosities and non-metallic inclusions. For failures in the 10Cr-HAZ, fatigue cracks nucleated from the interior matrix of HAZ, which possessed lower hardness. The initiation of cracks was divided into facet type crack origin (FTCO) and rough type crack origin (RTCO). FTCO was observed for specimens tested at high stress amplitude with fatigue life below 107 cycles. Micro-cracks were observed at prior austenite grain boundaries (PAGBs) at high stress level. Micro-cracks preferred to form at martensite lath boundaries and coalesced into macro-crack leading to the formation of RTCO under the condition of lower stress.

Shear-induced Permeability Evolution of Sandstone Fractures

In underground coal mines, shear-induced changes in regional fluid flow are a major factor causing water inrushes from faults into working faces. Shear slip along preexisting fractures tends to be activated during hydraulic fracturing, and this movement can either enhance or diminish hydraulic fracturing efficiency. To prevent water inrush disasters and further hydraulic fracturing, understanding the evolution of shear-induced permeability in fractures in sedimentary rock is very important. In this study, the evolution of shear-induced permeability in saw-cut sandstone fractures with three different types of surface roughness was investigated by conducting triaxial shear tests and examining the 3-D topography of the unsheared and sheared fracture surfaces. The results allow several important conclusions to be drawn. (1) The permeability of fractures follows a three-stage shear-displacement-dependent evolution. The permeability remains unchanged in the first stable stage. After that, permeability decreases sharply with increasing shear displacement. Finally, the permeability enters a second stable stage. (2) The shear stress versus shear-displacement curves can also be divided into three stages, namely, a stress adjustment stage, a stage of increasing stress, and a stable stage. During the experiments, the fractures always experienced stick-slip shear in the stable stage. The oscillations of the shear stress in the stick-slip stage had a higher frequency for fractures with rougher surfaces. In addition, the rougher surfaces exhibited a greater permeability drop after shearing than that shown by smoother fracture surfaces. (3) The 3-D scanning results imply that the coupled effects of grinding (plus scraping) and sealing lead to decreased permeability. During shearing, the fracture walls grind and scrape against each other resulting in partial flattening of the fracture surface and the production of fault gouge in the fracture. This leads in turn to the flow pathways being partially sealed by crushed mineral grains.

Stability of Low-Reynolds-Number Separated Flow Around an Airfoil Near a Wavy Ground

In this numerical–theoretical study, a linear BiGlobal stability analysis of the steady massively separated flow around a NACA 4415 airfoil was performed at a low Reynolds number () and a high angle of attack () close to a wavy ground, with a focus on the effect of three different types of stationary roughness: 1) a perfectly flat ground, 2) a wavy ground with small-amplitude undulations, and 3) a wavy ground with large-amplitude undulations. On increasing the undulation amplitude of the ground but keeping the mean ground clearance constant, it was found that the lift coefficient increased owing to an increase in the static pressure under the airfoil, which is reminiscent of the conventional ground effect over a flat surface. However, it was also found that the leading flow perturbation was the three-dimensional stationary global mode and not the two-dimensional traveling Kelvin–Helmholtz mode, contrary to the results of previous analogous studies of linear global instability of massively separated flow away from the ground. This study provides new insight into the stability of airfoil–ground flow systems at a low Reynolds number and a high angle of attack, contributing to a better understanding of the ground-effect aerodynamics of small insects and micro air vehicles flying over rough waters or complex terrain.

Pseudo-photometric distances of 30 open clusters

Aims. We demonstrate that reliable photometric distances of stellar clusters, and more generally of stars, can be obtained using pseudomagnitudes and rough spectral type without having to correct for visual absorption. Methods. We determine the mean absolute pseudomagnitude of all spectral (sub)types between B and K. Distances are computed from the difference between the star’s observed pseudomagnitude and its spectral type’s absolute pseudomagnitude. We compare the distances of 30 open clusters thus derived against the distances derived from TGAS parallaxes. Results. Our computed distances, up to distance modulus 12, agree within 0.1 mag rms with those obtained from TGAS parallaxes, proving excellent distance estimates. We show additionally that there are actually two markedly different distances in the cluster NGC 2264. Conclusions. We suggest that the pseudomagnitude distance estimation method, which is easy to perform, can be routinely used in all large-scale surveys where statistical distances on a set of stars, such as an open cluster, are required.

Study of the transition position on blunted bodies with roughness at M = 6

The paper presents the data of the effect of distributed and single roughness on a blunted nose of a cone on the position of the laminar-turbulent transition and the development of perturbations in the boundary layer. The experiments were performed at M = 5.95, stagnation temperature T0 = 360 ÷ 418 K and stagnation pressure P0 = 3.5÷ 46 atm. Unit Reynolds number varied in the range (4.2 ÷ 69,7)×106 m−1. The study was carried out in the boundary layer of a cone with half-angle of 7º with different zones of applying a single and distributed roughness on blunted nose-tip of radii 2 and 5 mm. For all types of roughness, the effective Reynolds numbers corresponding to transition on the model’s nose are obtained. The effect of surface roughness on the growth of perturbations in the boundary layer is studied experimentally.

Fatigue life prognostic for medium-carbon steel based S-N curve computation and deep autoencoder

Medium-carbon steel is widely used in architecture, rail, machinable steel and so on. So, there is a huge significance in the analysis and research of its fatigue life. In this paper, the fatigue experiment with different surface roughness was set up. In the experiment, there were three type of roughness and a total of 75 experiments were performed. Then a deep autoencoder to model the relationship of roughness (R), stress (S), and fatigue life (N). It has been found that the method can automatically extract the features which can be used to effectively model the relationship of R, S and N. Finally, the approach presented was compared with the existing model based on Tanaka-Mura theory and got an unexpected better result.

Influence of Roughness on Shear Bonding Performance of CFRP-Concrete Interface.

The potential of Fiber Reinforced Polymer (FRP) in the reinforcement of concrete structures has been shown in many studies and practical applications. However, few works have focused systematically on the development of quantitative criteria to measure surface roughness and relate this parameter to the bonding mechanical property. Moreover, some researchers have declared that, if the concrete interface is rougher, the bond performance between FRP and concrete will be increase, However, there is no answer to how rough the surface is. There are limited application standards for engineers to conduct in FRP reinforcement projects. This work evaluated several concrete specimens with three different strengths and six types of interface roughness. A single shear test was conducted to study the influence of surface roughness on the interfacial bonding performance of a carbon fiber-reinforced composite (CFRP)-concrete beam. The results show that, among the six interfaces, a concrete interface with the roughness of 0.44 has the best interfacial bonding performance. An interfacial appearance with the cement mortar almost cleaned away, and almost one fifth of the single coarse aggregate bared will get the best bond performance. Roughness parameters significantly influenced the effective bond length. The effective bond length of the six interfaces experienced an overall decreasing trend as the roughness increased. The bond–slip curves of concrete interfaces with roughness of 0.25–0.44 did not significantly change the rigidity within the brittle region. The rougher the interface was, the shorter the brittle region was. After entering a plasticity stage, the bond–slip curves for the six types of interfaces all declined with different slopes, and the max slip values were 0.04–0.35 mm when debonding failure occurred.

Time-resolved PIV measurement of influence of upstream roughness on separated and reattached turbulent flows over a forward-facing step

This study reports an experimental investigation of the effects of upstream roughness on a low Reynolds number turbulent boundary layer over a forward-facing step. Two types of upstream roughness were investigated, including a transitionally rough 16-grit sandpaper (ks+ ≈ 69) and fully rough staggered cubes (ks+ ≈ 500). A two-dimensional two-component time-resolved particle image velocimetry (2D-2C TR-PIV) method was used to measure the time-averaged mean velocities, Reynolds stresses, temporal auto-correlations and frequency spectra of the flow field to quantify the influence of upstream roughness on the downstream evolution of the turbulence over the step. The results indicate that upstream roughness decreased the vortex shedding frequency. Roughness also decreased the reattachment length by enhancing the streamwise turbulence intensity level, reducing the magnitude of backflow and suppressing the vortex shedding frequency in comparison to the smooth wall. In the recirculation region, upstream roughness reduced the mean streamwise velocity only in the outer layer. The Reynolds stresses remained relatively unchanged by the sandpaper roughness but were significantly modified by the cube roughness. Downstream of the leading edge, the staggered cubes increased the streamwise Reynolds stress both near the wall and outside the shear layer but decreased the wall-normal Reynolds stress and Reynolds shear stress within the shear layer. These modifications are inversely proportional to distance in the recirculation region. The life times of the streamwise and wall-normal velocity fluctuations increase with streamwise distance and are much longer in the redevelopment region than in the recirculation region. Quadrant decomposition and joint probability density functions of the velocity fluctuations were also measured to characterize upstream roughness effects on the downstream evolution of the dominant motions producing the Reynolds shear stress.

Antimicrobial resistance and molecular characterisation of E. coli from poultry in Eastern India.

In this study 252 poultry samples comprised of poultry meat (n = 228) and poultry eggs (n = 24) were screened for the isolation of Escherichia coli (E. coli). A total of 62 E. coli isolates were recovered from poultry meat. The E. coli isolates belonged to different serogroups based on ‘O’ serotyping of the isolates viz O29 (10.8%), O8 (7.7%), O40 (6.15%), O2 (4.61%), O60 (3.08%), O106 (3.08%), 42 (1.54%), O 87 (1.54%), and 01 serotypes of O1, O7, O30, O45, O59, O66, O105, O1116, O136, O141, O147, O148, O166, and O172. Sixteen (24.62%) of the isolates were UT (untypable) and 6 (9.23 %) were rough types. Molecular characterisation of the isolates was performed, targeting stx1 and stx2 virulence gene fragment. Out of 62 E. coli isolates, 10 (16.12%) were carrying virulence gene stx2, whereas none of the isolate was carrying stx1 gene. The E. coli isolates showed wide variation in resistance pattern against the antimicrobial agents that we used (9-90%). Among E. coli isolates, maximum resistance was observed against cefuroxime (89.1%) and penicillin (89.4%), followed by ampicillin (80.43%), vancomycin (74.1%), co-trimoxazole (73.1%), cephalothin (60.8%), ceftriaxone (28.2%), tetracycline (17.4%), gentamicin (13%), amikacin (13.04%), ofloxacin (13%), and ciprofloxacin (6.5%). A high degree of susceptibility was observed against amikacin (84.7%) and ciprofloxacin (76%) followed by gentamicin (71.73) and ofloxacin (60.86%). High multiple antibiotic resistances were observed and a total of 34 resistance patterns were identified.