Roughness Patterns Research Articles

Roughness and structural modification of PbI2 thin films by isopropanol treatment to improve methylammonium lead halide formation and solar cell efficiency

Perovskite thin films can be prepared by two-step spin coating technique, in which lead iodide (PbI2) is first deposited followed by methylammonium halide. The addition of isopropanol (IPA) in the first deposition leads to more porous and less crystalline PbI2 thin films. To understand the effect of IPA treatment, we study the surface morphology parameters of PbI2 thin films by using statistical fractal analysis on their Atomic Force Microscopy images at different image scales. We found that the surface roughness of IPA-treated PbI2 layer (r-PbI2) is almost twice than that of the PbI2 layer without such treatment (c-PbI2). Moreover, the surface of r-PbI2 thin films shows a self-similar characteristic, which means that the roughness pattern may repeat at different scales. This is confirmed by perfilometry measurement, showing a uniform roughness pattern of r-PbI2 samples in a millimeter scale. Furthermore, larger grain size and crystallinity of perovskite thin films are obtained with r-PbI2, independent of the partial substitution of iodide by chloride or bromide. The perovskite solar cells based on r-PbI2 exhibit average power conversion efficiency (PCE) of 10.27% over 127 cell samples, whereas those fabricated with c-PbI2 films show a lower average PCE of 7.20% over 107 samples.

Synthesis of a novel compound based on chitosan and ammonium polyphosphate for flame retardancy applications

In this investigation, a novel compound (NCSAPP) based on chitosan (CS) and ammonium polyphosphate (APP) was synthesized by employing solutions of chitosan and ammonium polyphosphate. The synthesized compound was characterized using FTIR, PXRD, XPS, FESEM, EDX, TGA and a Micro Calorimeter. Finally, NCSAPP was inserted into vinyl ester resin and study the thermal and flammable properties. The FTIR spectrum of NCSAPP suggested the reaction between chitosan and APP and that formation of –NH3+–O−P– bonds with the –NH3+ peak at 1533 cm−1. The XPS spectrum showed a characteristic peak at 401.36 eV corresponding to the N1s of –NH3+. PXRD suggested the amorphous nature of NCSAPP. FESEM coupled with EDX depicted a rough morphological pattern for NCSAPP with C, N, O and P. The thermal decomposition of NCSAPP was observed to be active at lower temperatures. However, at elevated temperatures (> 315 °C), a slow degradation rate with significantly higher thermal stability than that of CS was observed. The peak release rate (16.9 w/g) and total heat release (0.9 kJ/g) were significantly lower than those of CS. Besides, vinyl ester composite of NCSAPP obtained superior fire-retardant properties than vinyl ester composites of CS and APP. The obtained results indicate that NCSAPP can be applied in thermal applications operating at high temperatures.

Conjugate approach for hypoid gears frictional loss comparison between different roughness patterns under mixed elastohydrodynamic lubrication regime

Abstract This paper compares the frictional loss of hypoid gears between three different tooth surface roughness patterns under the mixed elastohydrodynamic lubrication regime, namely the striated, the isotropic and the less roughed. Conjugate approach contact model for such purpose is proposed, which aids in determination of the parameters input for the lubrication model and construction of wanted tooth surface roughness patterns, by integrating the digital tooth surface technique, the conjugate approach teeth contact analysis and a particular contact search algorithm into a fully integrated contact model. The frictional losses are computed from the upper to the down boundary defined by the load share portion between the film and the asperity in the regime with the varying λ ratio by continuously adding the rotational speed on the geared system. The simulation finds that the frictional loss of the case striated is less than the case isotropic, and the case less roughed has the smallest frictional loss. It also finds that the rotational speed has a significant influence on the film thickness, on the load share, and thus on the frictional loss. Merits are exhibited with this integrated contact model, including good compatibility with lubrication model in passing data, good accuracy and less computation time.

On the Sixth Generation: Preliminary Speculations about Chinese Politics after Xi

ABSTRACT Contrary to the current tendency to extrapolate China’s future trajectory from its current retrenchment, it is argued that China has changed substantially in the past and is likely to continue to change in the future. While change has always been strife-torn and radically contingent, it may be seen in retrospect to fit a rough pattern as occasioned by generational as well as ideological and developmental factors. Can we find clues in this pattern of change that provide some basis for speculation about China’s future? A definition of ‘generation,’ is followed by a review of the past pattern of China’s generational evolution and by a theory of generational change to account for it. The essay concludes with a discussion of China’s path-dependent cyclical future evolution.

Spatial variability of soil roughness in persimmon plantations: A new combined ISUM (improved stock unearthing method) approach

Abstract Soil roughness (SR) is an ecological indicator that describes the distribution of soil surface accumulations and ponds in a terrain, which allows understanding the connectivity of the flows as they act as sinks and sources of water and sediments. There is a set of methods that allows investigating the SR, and we test the use of the improved stock unearthing method (ISUM) as an easy-to-apply and low-cost approach. The ISUM has been initially tested in vineyards using the graft union and measures in the inter-row areas to assess the current soil surface level and estimate soil mobilization. In this research, we present an innovative application of ISUM for persimmons plantations (Diospyros kaki Linn.) to further analyze the microtopographical changes. We chose a persimmon plantation because of the existence of grafted parts in such species, which is a common characteristic in other plantations such as vineyards. To achieve this goal, we calculated the Roughness Index (RI) and the Transect Length Index (TLI) using the dataset generated by means of ISUM. The study was conducted in a conventional persimmon plantation in Eastern Spain. We performed a total of 2130 measures in an experimental plot of 490 m2 taking measures in each paired-plant with intervals of 100 mm. We detected that the studied area is predominantly slightly depressed (occurrence of this category in 69% of the plot) and the soil surface of the studied area presented in 95.5% of the studied area a pattern of roughness characterized as random-oriented. We argue that the ISUM was successfully employed also in a persimmons plantation because of the botanic characteristics of the trees that allowed us creating a feasible database generated to assess soil roughness and mobilization. Hence, we conclude that the ISUM is a method that can provide alternatives of analysis of soil roughness to allow including improvements in actions of restoration or conservation in cultivated soils.

Quantifying Topographic Characteristics of Wetlandscapes

Topography underpins natural processes ranging from incident solar radiation to overland flow and water pooling. Despite the influence of topography on natural processes, especially in wetland ecosystems reliant on uplands for water inputs, topography has not been adequately incorporated into reclamation planning. Instead, wetland reclamation projects are typically guided by height-to-length ratios that produce little resemblance to natural wetlands. We present a methodology to quantify the topographic characteristics in landscapes with an abundance of wetlands to guide the reclamation of naturally appearing and self-sustaining wetlandscapes. Topographic characteristics in over 3000 sample landscapes were quantified using terrain roughness and landform element composition and configuration. A large set of metrics was reduced to a statistically independent subset that was applied and compared across three natural regions and a gradient of disturbance. Our results showed that surface roughness and landform element patterns significantly differ among natural regions and that high disturbance landscapes significantly differ from other disturbance levels. To ensure reclaimed wetlandscapes are naturally appearing and self-sustaining, they should replicate the topographic characteristics found within the distribution of surrounding natural landscapes by applying topographic characteristic benchmarks to reclamation design. The presented methodology can be used as a step towards achieving this goal.

EXPERIMENTAL STUDIES OF ROUGHNESS BY SURFACE PLASTIC DEFORMATION ON FLAT SURFACES

The article presents experimental studies of the roughness by surface plastic deformation (SPD) on flat surfaces of steel 45. A dispersion analysis was used to study the influence of various factors on the surface quality. From the experimental studies and the dispersion analysis made, a graphical interpretation of the main effects was obtained. Graphical visualizations of the roughness pattern after SPD on the processed surfaces were obtained. Overlapping sinusoidal movements of the deforming spherical element were realized.

Heat transfer during dropwise condensation of steam over a mirror polished sol-gel coated aluminum substrate

Dropwise condensation (DWC) is a promising heat transfer mechanism in new trends of thermal management and power generation systems to enhance the heat transfer during condensation. Creation of surfaces which can promote dropwise condensation is one of the main issues. For this purpose, a heat transfer surface that can maintain stable dropwise condensation, using hybrid organic-inorganic sol-gel silica coatings functionalized with methyl groups over an aluminum substrate, is developed and tested. This coating displays mildly hydrophilic behavior. Condensation of steam flowing on this surface occurs in dropwise mode with heat transfer coefficient values equal to 150–180 kW m−2 K−1 in the heat flux range between 150 and 510 kW m−2. The importance of the coating thermal resistance is discussed in the paper. The measured heat transfer coefficient is high compared to previous studies of DWC on metallic – and in particular aluminum - substrates. This type of surfaces paves the way to a cheap and green route to promote stable DWC on aluminum substrates without using fluorocarbons or controlled roughness patterns.

A detailed review on various V-shaped ribs roughened solar air heater

Solar air heater (SAH) is a popular and economical device which collects the solar energy and is employed for space heating, drying of agricultural products, food items, and leather, seasoning of timber, etc. Attachment of artificial roughness on the absorber surface is an appropriate method to augment the heat transfer from the heated surface to the air flowing through SAH duct. Use of artificial roughness has been an area of great interest for researchers as far as the cooling of turbine blades, and combustion chambers are concerned. This technique is effective in enhancing the heat transfer in a micro-channel heating/cooling system. Present paper holistically furnishes concise information about various kinds of V-shaped roughness geometries used in SAHs for improving its performance covering experimental, analytical, numerical and computational fluid dynamics (CFD) approaches. In this paper, 124 research articles have been referred, which provide a detailed comprehensive and comparative study revealing the effect of various geometrical parameters and different V-shaped roughness patterns on the performance of SAH. This article also brings in the information about the correlation developed by researchers for heat transfer and friction factor. This comprehensive review will be quite useful for technical persons and researchers working in the area of SAH.

Direct Assembly of Silica Nanospheres on Halloysite Nanotubes for “Green” Ultrahydrophobic Cotton Fabrics

AbstractThis paper presents a sustainable biomimetic approach to create ultrahydrophobic cotton fabrics. Cotton fabrics are modified using biobased raw materials to create multiple scale roughness and low surface energy on their surfaces. Naturally occurring halloysite nanotubes (HNT) are modified by silanization and direct assembly of silica (SiO2) nanospheres on the surface of HNTs. HNTs “decorated” with SiO2 nanospheres are covalently bonded onto the surface of cotton fabrics, creating a durable multiple scale surface roughness. Surface modified cotton fabrics are further grafted with fatty acid without using any solvent, via esterification. The combination of the hierarchical roughness pattern created on the surface through modified HNT, and fatty acid treatment results in ultrahydrophobic fabrics with water contact angles (WCAs) above 150°. Surface topographies of modified HNT particles and chemical changes are fully characterized. Attenuated total reflectance Fourier‐transform infrared and WCA studies are used to confirm the grafting of modified HNT particles and aliphatic fatty chains on surface of fabrics. The ultrahydrophobic cotton fabrics washed for five standard laundry cycles (25 home washings) show that the ultrahydrophobicity is durable. Moreover, the ultrahydrophobic fabrics are oleophilic, making them suitable for use in oil–water separation, anti‐biofouling and packaging, and other applications apart from water repellent clothing.

SAR-Mode Altimetry Observations of Internal Solitary Waves in the Tropical Ocean Part 2: A Method of Detection

It is demonstrated that the synthetic aperture radar altimeter (SRAL) on board of the Sentinel-3A can detect short-period internal solitary waves (ISWs) with scales of the order of a kilometer. A variety of signatures owing to the surface manifestations of the ISWs are apparent in the SRAL Level-2 products over the ocean. These signatures are identified in several geophysical parameters, such as radar backscatter ( σ 0 ) and sea level anomaly (SLA). Radar backscatter is the primary parameter in which ISWs can be identified owing to the measurable sea surface roughness perturbations in the along-track direction resulting from the sharpened SRAL footprint. The SRAL footprint is sufficiently small (300 m in the along-track direction) to capture radar power fluctuations over successive wave crests and troughs, which produce rough and slick surface patterns arrayed in parallel bands with scales of a few kilometers along-track. Furthermore, it was possible to calculate the mean square slope ( s 2 ¯ ) for the dual-band (Ku and C bands) altimeter of Sentinel-3, which made the ISW signatures unambiguously identified because of the large s 2 ¯ variations in exact synergy with ocean and land color instrument (OLCI) images. Hence, the detection method is validated in cloud-free sun glint OLCI images. It is shown that both σ 0 and SLA yield realistic estimates for routine observation of ISWs with the SRAL. The detection method that is used relies on the parameter s 2 ¯ which is calculated from σ 0 . This is a significant improvement from previous observations recently reported for conventional pulse-limited altimeters (Jason-2). An algorithm is developed to be used in any ocean region. Wavelets were applied for a first analysis of the s 2 ¯ variations because ISWs can be readily identified in high-frequency signals. Other geophysical parameters such as SLA were used to exclude phenomena that are unlikely to be ISWs.

Thermo-hydraulic performance of rectangular channel roughened with combined semi-circular and triangular ribs

Ribs of different geometrical shapes are used on the surface for heat transfer enhancement. However, the combination of different shapes of ribs on the heat transfer surface is found less in literature. The objective of the present investigation is to design ribs roughness pattern of semi-circular, triangular, and hybrid ribs (combined semicircular and triangular ribs) on the bottom heated surface of the channel. Then, find optimum configuration and geometry of ribs pattern that has highest thermo-hydraulic performance. This combination of different shape of ribs pattern may be used for cooling of the heated channel such as in gas turbine blade, and high-temperature gas cooled reactors, etc. The rib pitch to rib height ratio (p/e) is considered in the range from 6.6 to 53.3 and Reynolds number in the range from 12,640 to 52,410. Turbulence model used for analysis is shear stress transport (SST) k-ω model. The effect of different geometry and configuration of ribs pattern on Nusselt number and friction factor are investigated and compared with that of the smooth channel. It is found that the Nusselt number (Nu) is maximum at p/e of 13.3 and friction factor (f) is maximum at p/e of 6.6 for all geometry of ribs pattern considered. Furthermore, Thermal enhancement factor (TEF) is determined for all geometry and configurations of ribs pattern. It is found that Thermal enhancement factor is maximum for hybrid ribs (1.34) at p/e of 13.3 and Reynolds number of 12,640 from the geometry and configuration of ribs pattern considered.

Application of projection lithography using a gradient-index lens array and wet etching to texturing for control of the hydrophobic properties of stainless-steel plates

The effectiveness of line-and-space (L&S) textures grooved onto stainless-steel SUS 304 plates for improving hydrophobic properties was investigated. The textures were grooved using a scan-projection exposure system with a gradient-index lens array as a projection lens and wet chemical etching in ferric chloride aqueous solution. The lithography system was applied because it was developed for printing rough patterns of larger than 15 μm in a large exposure field of 50 mm square. On the other hand, it was expected that textured protrusions with considerably sharper peaks might be formed by the undercut phenomenon during wet etching. When the contact angles of 2 μl pure-water droplets which had been dropped down onto 20 μm L&S textures were measured, it was found that contact angles measured by observing a droplet from the L&S direction were larger than those measured from the direction perpendicular to the L&S, and contact angles were changeable by grooving textures of different sizes.

Microgrooves and Microrugosities in Titanium Implant Surfaces: An In Vitro and In Vivo Evaluation.

The physical characteristics of an implant surface can determine and/or facilitate osseointegration processes. In this sense, a new implant surface with microgrooves associated with plus double acid treatment to generate roughness was evaluated and compared in vitro and in vivo with a non-treated (smooth) and double acid surface treatment. Thirty disks and thirty-six conical implants manufactured from commercially pure titanium (grade IV) were prepared for this study. Three groups were determined, as described below: Group 1 (G1), where the samples were only machined; group 2 (G2), where the samples were machined and had their surface treated to generate roughness; and test group 3 (G3), where the samples were machined with microgrooves and the surface was treated to generate the roughness. For the in vitro analysis, the samples were submitted to scanning microscopy (SEM), surface profilometry, the atomic force microscope (MFA) and the surface energy test. For the in vivo analyses, thirty-six implants were placed in the tibia of 9 New Zealand rabbits in a randomized manner, after histological and histomorphometric analysis, to determine the level of contact between the bone and implant (BIC%) and the bone area fraction occupancy (BAFO%) inside of the threads. The data collected were statistically analyzed between groups (p < 0.05). The in vitro evaluations showed different roughness patterns between the groups, and the G3 group had the highest values. In vivo evaluations of the BIC% showed 50.45 ± 9.57% for the G1 group, 55.32 ± 10.31% for the G2 group and 68.65 ± 9.98% for the G3 group, with significant statistical difference between the groups (p < 0.0001). In the BAFO% values, the G1 group presented 54.97 ± 9.56%, the G2 group 59.09 ± 10.13% and the G3 group 70.12 ± 11.07%, with statistical difference between the groups (p < 0.001). The results obtained in the evaluations show that the surface with microgrooves stimulates the process of osseointegration, accelerating the healing process, increasing the contact between the bone and the implant and the area of new bone formation.

Investigation of free-surface dynamics in an open-channel flow

ABSTRACT Space–time variation of the free-surface roughness pattern, due to sub-surface turbulence, is one of the most important features of turbulent open-channel flows. Despite its importance, the free-surface dynamics is not fully understood, especially regarding the advection and propagation features of surface variations. In this study, a direct numerical simulation of a smooth-wall turbulent open-channel flow allowing free-surface deformation was performed to investigate the dependence of the free-surface features on Reynolds and Froude numbers. The results show that the key features of the free surface are due to surface waves and turbulence, and one or another may prevail depending on the Froude number. While the turbulence is dominant in subcritical flow at low Froude number, the surface waves propagating upstream become more dominant at high Froude number when flow becomes supercritical. Furthermore, it was found that the advection velocity of the roughness patterns becomes slower than the mean surface velocity in the flow where the surface waves become dominant.

Novel Parameterized Utility Function on Dual Hesitant Fuzzy Rough Sets and Its Application in Pattern Recognition

Based on comparative studies on correlation coefficient theory and utility theory, a series of rules that utility functions on dual hesitant fuzzy rough sets (DHFRSs) should satisfy, and a kind of novel utility function on DHFRSs are proposed. The characteristic of the introduced utility function is a parameter, which is determined by decision-makers according to their experiences. By using the proposed utility function on DHFRSs, a novel dual hesitant fuzzy rough pattern recognition method is also proposed. Furthermore, this study also points out that the classical dual tool is suitable to cope with dynamic data in exploratory data analysis situations, while the newly proposed one is suitable to cope with static data in confirmatory data analysis situations. Finally, a medical diagnosis and a traffic engineering example are introduced to reveal the effectiveness of the newly proposed utility functions on DHFRSs.

Application of image edge detection methods for precise estimation of the standard surface roughness parameters: Polypropylene/ethylene-propylene-diene-monomer blend as a case study

Material surface roughness is an important property in different fields of science and its precise measurement is still a serious concern. Roughness measurement is commonly implemented using stylus profilometer. Although it suffers from some drawbacks such as low speed and destructive nature. Optical methods, such as machine vision coupled with image texture analysis have shown promising capability for noncontact/nondestructive roughness measurement. In the present study, a roughness evaluation method is proposed based on image edge detection algorithms. The method was applied to investigate the surface roughness of polypropylene/ethylene-propylene-diene-monomer (PP/EPDM) blend as an important engineering plastic. Different roughness patterns were created on PP/EPDM sheets employing hot press processing. Images of the roughened samples were captured with 10 different resolutions. In the proposed method, the performance of five different edge detectors including Roberts, Prewitt, Sobel, Laplacian of Gaussian (LoG), and Canny were examined. The results showed that LoG method in the images with 200 dpi resolution effectively evaluates PP/EPDM surface roughness. Linear correlation coefficients (R2) between LoG results and Stylus profilometry results was greater than 0.98. Moreover, some mathematical models were developed for evaluation of the roughness parameters based on LoG edge frequency. The models’ results showed 6.7% deviation from stylus profilometry results in the worst case. The proposed method can be used as a feasible solution for roughness evaluation of polymeric materials in online inspections.

Learning about learning: patterns of sharing of research knowledge among Education, Border, and Cognitive Science fields

This study explores the patterns of exchange of research knowledge among Education Research, Cognitive Science, and what we call “Border Fields.” We analyze a set of 32,121 articles from 177 selected journals, drawn from five sample years between 1994 and 2014. We profile the references that those articles cite, and the papers that cite them. We characterize connections among the fields in sources indexed by Web of Science (WoS) (e.g., peer-reviewed journal articles and proceedings), and connections in sources that are not (e.g., conference talks, chapters, books, and reports). We note five findings—first, over time the percentage of Education Research papers that extensively cite Cognitive Science has increased, but the reverse is not true. Second, a high percentage of Border Field papers extensively cite and are cited by the other fields. Border Field authors’ most cited papers overlap those most cited by Education Research and Cognitive Science. There are fewer commonalities between Educational research and Cognitive Science most cited papers. This is consistent with Border Fields being a bridge between fields. Third, over time the Border Fields have moved closer to Education Research than to Cognitive Science, and their publications increasingly cite, and are cited by, other Border Field publications. Fourth, Education Research is especially strongly represented in the literature published outside those WoS-indexed publications. Fifth, the rough patterns observed among these three fields when using a more restricted dataset drawn from the WoS are similar to those observed with the dataset lying outside the WoS, but Education Research shows a far heavier influence than would be indicated by looking at WoS records alone.

Introduction of Multiscaled Longitudinal Vortices by Fractal-Patterned Surface Roughness

To determine the type of surface roughness pattern that is suitable for adaptive suppression of the drag of an obstacle, we observed flow structures introduced by such obstacles. Several roughness patterns were tested: geometric patterns, fractal patterns, reptile-skin patterns, and patterns of circular cylinders arranged in a lattice and in a zigzag manner. A suitable pattern for adaptive control of flow is one that generates longitudinal vortices with nonconstant distances. The preferred instability mode of a laminar boundary layer is expected to be selected automatically from fluctuations involving many frequencies and caused by fractal patterns. Snake- and reptile-skin patterns may have a similar ability as fractal patterns because they consist of multiscale patterns. The longitudinal vortices generated from peculiar positions and concave corners in patterns were observed. The distance between these vortices is not constant because the onset of vortices is at concave corners in fractal patterns. These vortices have differing strengths and easily cause nonlinear interactions, so they can disturb a laminar boundary layer with several higher-harmonic frequencies. The velocity profiles of the laminar boundary-layer flow over the fractal patterns were measured by using hydrogen bubbles. The results show the down-wash flow between the longitudinal vortices, which means that the vortices may effectively suppress the boundary layer separation in an adverse pressure gradient.

Analysis of Squeeze Films Between Rough Circular Plates Lubricated with Rabinowitsch Fluids

The present theoretical work investigates the combined impacts of non-Newtonian (pseudoplastic and dilatant) lubricants and surface roughness on the performance of squeeze films lubrication between two rough circular plates. The modified Reynolds equation has been derived on the basis of Christensen’s stochastic theory of hydrodynamic lubrication for rough surfaces. The lubricant model adopted for the analysis is Rabinowitsch fluid model – an experimentally verified fluid model for lubricated bearing systems. Two types of one-dimensional roughness patterns (radial and azimuthal) have been considered in the analysis. An asymptotic solution for squeeze film pressure, load carrying capacity and squeeze film time are obtained. The numerical results for dimensionless film pressure, load carrying capacity and film squeezing time have been calculated for various values of fluid and operating parameters. The results for dimensionless film pressure, load capacity and squeezing time of the lubricant film have been discussed with clear graphical presentation for different values of parameters of pseudoplasticity and roughness. It was observed that the radial roughness decreases the film pressure, load capacity and squeezing time of lubricant, while increased values of these properties were observed for azimuthal roughness. It was also observed that the pseudoplastic lubricants decrease the film pressure and load capacity, while the dilatant lubricants increase these properties. Also, the variations in these results are highly significant.