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In this article, the free vibration of functionally graded porous (FGP) circular plate with various boundary conditions are investigated by means of the differential quadrature method (DQM) based on Reddy's theory. Performance of the materials varies continuously in the whole thickness and two cosine forms of nonuniform porosity distribution along its thickness are considered. Hamilton's principle is adopted to derive the governing equation of the system, which effectively considers the effects of thermal stress. It is worth noting that due to the introduction of physics neutral surface, reducing stretching-bending coupling effect, so the complex governing equations have been appropriately simplified. Then, using the DQ method, the natural frequencies of free vibration of FGP circular plates subjected to thermal environments with various boundary conditions were obtained. Convergence and comparative research are performed to prove the convergence, reliability, and accuracy of the DQ method. The effects of various factors such as porosity coefficient, porosity distribution pattern, temperature rise, thickness-diameter ratio, and boundary conditions on the natural frequencies are discussed in detail. HIGHLIGHTS: For the first time, the free vibration control equation of the graded porous circular plate in a thermal environment under the Reddy third-order shear theory is established. Introducing the concept of physics neutral surface, we simplify the very complex governing equations. The DQM is used to solve the controlling differential equation with the higher order vibration term caused by the higher order theory, and the vibration frequency of each order under three boundary conditions is given. The influence of porosity distribution on natural frequencies is highlighted. The effects of uniform and nonuniform heating on the dimensionless frequency are analyzed, and the effects of porosity coefficient, thickness-to-diameter ratio, and boundary conditions on frequency are discussed. [ABSTRACT FROM AUTHOR]

The phenomenon of a water droplet impact on a free surface is studied to understand the physics of free surface bubble entrainment. Particle image velocimetry (PIV) and high-speed image system are used to analyse the flow structure evolutions in the droplet impact cavity period and bubble entrainment cavity period, respectively. The photographic results show that the entrapped surface of the impact cavity remains intact and continuous, and individual bubble entrainment occurs during the secondary entrainment cavity evolution. The instantaneous distributions of velocity fields in the longitudinal and lateral directions are uniform and independent of the approaching impact velocity. For the entrainment cavity evolution, the transverse diffusion intensity is higher than that for the impact cavity period. An individual bubble forms during the transverse velocity penetration across the droplet impact area. Consequently, for the droplet impact on a water surface, the present study implies the presence of a mechanism by which the interior flow field plays a key role in the bubble entrainment. [ABSTRACT FROM AUTHOR]

Dust grains play a central role in the physics and chemistry of cosmic environments. They influence the optical and thermal properties of the medium due to their interaction with stellar radiation; provide surfaces for the chemical reactions that are responsible for the synthesis of a significant fraction of key astronomical molecules; and they are building blocks of pebbles, comets, asteroids, planetesimals, and planets. In this paper, we review experimental studies of physical and chemical processes, such as adsorption, desorption, diffusion and reactions forming molecules, on the surface of reliable cosmic dust grain analogues as related to processes in diffuse, translucent, and dense interstellar clouds, protostellar envelopes, planet-forming disks, and planetary atmospheres. The information that such experiments reveal should be flexible enough to be used in many different environments. In addition, we provide a forward look discussing new ideas, experimental approaches, and research directions. [ABSTRACT FROM AUTHOR]

Mechanical energy harvesting technology converting mechanical energy wasted in our surroundings to electrical energy has been regarded as one of the critical technologies for self-powered sensor network and Internet of Things (IoT). Although triboelectric energy harvesters based on contact electrification have attracted considerable attention due to their various advantages compared to other technologies, a further improvement of the output performance is still required for practical applications in next-generation IoT devices. In recent years, numerous studies have been carried out to enhance the output power of triboelectric energy harvesters. The previous research approaches for enhancing the triboelectric charges can be classified into three categories: i) materials type, ii) device structure, and iii) surface modification. In this review article, we focus on various mechanisms and methods through the surface modification beyond the limitations of structural parameters and materials, such as surficial texturing/patterning, functionalization, dielectric engineering, surface charge doping and 2D material processing. This perspective study is a cornerstone for establishing next-generation energy applications consisting of triboelectric energy harvesters from portable devices to power industries. [ABSTRACT FROM AUTHOR]

Edge-chipping, surface roughness and dimensional accuracy are crucial quality aspects of drilled holes in hard-to-cut material such as glass, ceramics and carbon fiber reinforced plastics. In this article, an experimental study was conducted to investigate the quality measures of holes produced by rotary ultrasonic drilling (RUD) and conventional drilling. Edge-chipping width at tool exit side, the surface roughness (Ra and Rz), out-of-roundness, cylindricity error and hole conicity were the main responses when drilling soda glass using diamond abrasive tools and a cutting fluid. Statistically designed experiments were carried out for rotary ultrasonic and conventional drilling (CD) at two levels of tool feed rate (0.6 and 6 mm/min), spindle speed (3,000 and 8,000 rpm) and tool particles-concentration. Analysis of variance was used to define the significant factors and their interactions and build models for predicting the responses. The results showed that reducing the chipping, surface roughness and roundness error. The normal tool concentration showed a substantial effect in improving the surface quality and reducing the hole-geometrical errors. [ABSTRACT FROM AUTHOR]

Land surface temperature (LST) is a key parameter in the physics of land surface processes on a regional and global scale, as it combines the results of all surface-atmospheric interactions and energy fluxes between the atmosphere and the ground. Due to discrepancies in retrieval methods, input parameters, and sensor characteristics, various LST products are different from each other. As one of the important LST contributors, the operational LST product from the visible and infrared radiometer (VIRR) onboard Feng Yun 3C satellite (denoted as VIRR LST1) has not been comprehensively assessed, and the detailed LST retrieval accuracy is still unknown to the public. Taking this into consideration, a new group of VIRR LST (denoted as VIRR LST2) was derived using a generalized split-window method for operational use. Therefore, this study aimed to evaluate the consistency between VIRR LST1 and VIRR LST2 in detail using the LSTs derived from the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Spinning Enhanced Visible and Infrared Imager (SEVIRI) data over the study area (from 11° W to 2° E and 32° N to 44° N). Several LST images in different seasons were used and registered in space, viewing time, and viewing geometry. After that, the LST differences in day-variation, land-cover types, and viewing zenith angles (VZAs) were also investigated. The results indicate that the differences between VIRR LST1 (or VIRR LST2) and MODIS LST were within 2.80 K, and the corresponding values between VIRR LST1 (or VIRR LST2) and SEVIRI LST were within 3.30 K. The VIRR LST1 was always underestimated, and VIRR LST2 was overestimated during the exuberant vegetation day. Furthermore, the mean differences between VIRR LST1 (or VIRR LST2) and MODIS LST for bare soil were larger than those for vegetation since the land surface emissivity for bare soil was often not well produced. On the other hand, the variation was not pronounced when comparing VIRR LST1 (or VIRR LST2) and SEVIRI LST, which could be caused by many more mixed pixels in the SEVIRI data set. In addition, the LST differences seemed to VZA dependent. [ABSTRACT FROM AUTHOR]

To reduce angular and spatial discretization error of the method of characteristics with a coarse calculation condition, the regionwise even-parity discontinuity factor (EPDF) for transport calculations is evaluated through an iterative procedure using only the regionwise scalar flux, i.e., without the odd-parity angular flux, the partial current, or the net current at the region boundary. The regionwise EPDF is evaluated in a single-assembly geometry with the reflective boundary condition. The evaluated EPDF is applied to a 2 × 2 colorset assembly and core configurations, and the performance is compared to that of the conventional superhomogenization (SPH) method. The calculation results indicate that (1) no convergence issue is observed during the iteration process to estimate the EPDF, (2) the performance of the regionwise EPDF is better than that of the conventional SPH method, and (3) the normalization of the EPDF is necessary to incorporate different surface scalar flux levels among different types of fuel assemblies. [ABSTRACT FROM AUTHOR]

Mechanical energy harvesting technology converting mechanical energy wasted in our surroundings to electrical energy has been regarded as one of the critical technologies for self-powered sensor network and Internet of Things (IoT). Although triboelectric energy harvesters based on contact electrification have attracted considerable attention due to their various advantages compared to other technologies, a further improvement of the output performance is still required for practical applications in next-generation IoT devices. In recent years, numerous studies have been carried out to enhance the output power of triboelectric energy harvesters. The previous research approaches for enhancing the triboelectric charges can be classified into three categories: i) materials type, ii) device structure, and iii) surface modification. In this review article, we focus on various mechanisms and methods through the surface modification beyond the limitations of structural parameters and materials, such as surficial texturing/patterning, functionalization, dielectric engineering, surface charge doping and 2D material processing. This perspective study is a cornerstone for establishing next-generation energy applications consisting of triboelectric energy harvesters from portable devices to power industries. [ABSTRACT FROM AUTHOR]

This article presents a simulation model that can be used to generate a two-dimensional surface profile which is statistically similar to the actual measured profile in both directions of asperities, amplitudes, and mean line of the profile. The model uses the Ra, AMS, and RMSS values to regenerate the actual surface profile. The generated segments represent samples from the population of profiles which could have been produced under the same machining conditions of the specimen. So, the study of the relation between profiles of surfaces in contact can be made simpler and the variability of results can be evaluated by considering several samples of simulated profiles. Qualitative and quantitative comparison of the parameters and characteristics of simulation with experimental profiles did not detect any significant difference. [ABSTRACT FROM AUTHOR]

Response surface methodology is used to develop an equation to predict the effect of feed, speed, point angle and nominal relief angle on the life of an 0.625 in. diameter, two-flute, jobber series twist-drill when drilling a cold-rolled, manganese steel to specification K1045.
Important aspects of the experimental design, method and analysis are discussed and the variability about the mean drill life is established. [ABSTRACT FROM AUTHOR]

This paper describes research performed to determine the effect of cutting fluid on first cut surface finish in single point turning. A measure of cutting fluid lubricity was used as an independent variable as well as cutting speed, tool feed, depth of cut and replications. The dependent variable was surface roughness. Though cutting medium was not a significant main factor, it was highly significant in several interactions with the other variables. [ABSTRACT FROM AUTHOR]

The excellent properties exhibited by thermoplastic composites at much reduced weight have attracted attention in the development of products in different sectors. Thermoplastic (TP) composites, because of their distinctive properties as well as ease of manufacturing, have emerged as a competitor against the conventional thermoset resin-based composites. Depending on the application, these composites may undergo impact events at various velocities and often fail in many complex modes. Hence, the development of TP composites having high energy-dissipation at (the desired) much-reduced weight has become a challenging task, but it is a problem which may be alleviated through the appropriate selection of materials and fabrication processes. Furthermore, fibre surface modification has been shown to increase fibre-matrix interfacial adhesion, which can lead to improved impact resistance. Textile preforms are helpful in acting as a structural backbone in the composites since they offer a relatively free hand to the composite designer to tailor its properties to suit a specific application. Additionally, hybrid textile composite structures may help in achieving the desired properties at much lower weight. Simulation software can play a significant role in the evaluation of composites without damaging physical samples. Once the simulation result has been validated with actual experimental results, it should be possible to predict the test outcomes for different composites, with different characteristics, at different energy levels without conducting further physical tests. Various numerical models have been developed which have to be incorporated into these software tools for better prediction of the result. In the current issue of Textile Progress, the effects of various materials and test parameters on impact behaviour are critically analyzed. The effect of incorporating high-performance fibres and natural fibres or their hybrid combination on the impact properties of TP composites are also discussed and the essential properties of TP polymers are briefly explained. The effects of fibre and matrix hybridization, environmental factors, various textile preform structures and fibre surface modification treatments on the impact properties of thermoplastic composites are examined in detail. Various numerical models used for impact analysis are discussed and the potential applications of TP composites in automobile, aerospace and medical sectors are highlighted. [ABSTRACT FROM AUTHOR]

Improved magnetorheological honing process is developed for nanofinishing of variable cylindrical internal surfaces with better surface integrity. In the present work, finishing performance of existing magnetorheological honing process is enhanced. The present improved process consists magnetorheological honing tool having curved permanent magnet end surfaces. When magnetic field is analyzed using Ansoft Maxwell, the improved magnetorheological honing process results in uniform and higher magnitude of magnetic flux density over its magnetic tool curved end surfaces as compared to the tool having magnetic flat end surfaces. Therefore, an improved magnetorheological honing process has been developed with tool having curved permanent magnet end surfaces. During experimentation, surface roughness values Ra, Rq, and Rz get decreased by 76.28%, 76.67%, and 75.20%, respectively, with improved magnetorheological honing tool having curved end magnetic surfaces, while 47.97%, 46.24%, and 47.08% decreased with tool having flat end magnetic surfaces in same 60 minutes of finishing time. This results in enhancement of finishing performance of the present improved magnetorheological honing process in terms of reduced finishing time and ability to produce good surface integrity. Hence, the present improved magnetorheological honing process performance with tool having curved end magnetic surfaces is found as comparatively better than the finishing tool having flat end permanent magnetic surfaces. [ABSTRACT FROM AUTHOR]

In today’s industries, the internal surface finishing of cylindrical objects is highly demanded to improve their functional performance in various engineering applications. During the traditional honing operation, the finishing forces produced by abrasives on the workpiece surface are not easily controllable and also produce various surface defects. Therefore, to further improve the surface integrity of the traditionally cylindrical honed surface made of ferromagnetic or non-ferromagnetic materials, a new magnetorheological (MR) finishing process has been used with a controlled magnetic field. The experimentation is performed on the honed surface made of gray cast iron, which is generally used as a cylinder liner. The percentage change in surface roughness values, i.e., Ra, Rq and Rz, reduced by 77.44%, 70.16% and 72.16%, respectively, with better improvement in surface after 90 minutes of finishing. The experimental results demonstrated the effectiveness of present process for improving the functional applications of ferromagnetic cylindrical honed surface after removing the various surface defects such as deeper grooves, honing grooves with shaper edges, torn and folded metals, and cavities or holes. The applications of new MR finishing process can also be useful in the internal finishing of injection barrel of a molding machine, cylindrical molds and dies, hydraulic cylinder, etc. [ABSTRACT FROM AUTHOR]

A compact soft surface is proposed to improve an isolation of circularly polarized patch antennas in this article. The soft surface is generally made up of a periodically alternating perfect electric conductor and perfect magnetic conductor. The perfect magnetic conductor is implemented by the corrugation with a depth of quarter wavelength. The proposed compact soft surface is designed by a folded corrugation with a length of a quarter wavelength and the folded part is located below perfect electric conductor plane. Thus, the compact soft surface can be designed without any additional area above the ground plane. To verify its feasibility, mutual coupling and axial ratio of two circularly polarized antenna elements without and with the compact soft surface have been compared. This improved isolation results in small active reflection coefficient and wide beamwidth of active element pattern which would help to design wide scanning angle array. [ABSTRACT FROM AUTHOR]

Fused deposition modeling (FDM) has emerged as one of the most utilized 3D printing technique. However, the surface properties of the FDM built parts lacks integrity due to layer by layer manufacturing technique. Therefore, post treatment is done on FDM printed parts. In the present research work, an effort has been made to improve the surface properties of the 3D printed parts by surface modification via chemical/nanoparticles. Nanoclay and dimethyl ketone were utilized for the surface modification of acrylonitrile butadiene styrene specimens. Parameters namely nanoclay content, immersion time, heat treatment and layer thickness were investigated to study their effect on surface roughness, surface hardness and dimensions. Also, the effect of nanoclay on UV absorbance of 3D printed parts was observed. Structural and morphological analysis was performed to characterize the surface of the 3D printed specimens after surface modification process. The results show that the surface roughness was reduced by 94.9%, surface hardness was increased by 9.7% while maintaining minimum dimensional deviation of −0.03 and +0.07 mm. Also, UV absorbance was increased in 350-380 nm range. The results of the present study highlight the capability of the surface modification process for improving the surface properties of FDM parts. [ABSTRACT FROM AUTHOR]

Surface alloying is necessary to enhance the surface features of machine elements. In the present study, feasibility of micro-electric discharge machining (micro-EDM) process for surface alloying has been investigated. Experiments are conducted on Nickel sheets using tool of Ti6Al4V with EDM oil and kerosene as dielectric. The surface modification takes place by spark discharges on localized regions of the work piece and the tool surface causing melting of tool and work piece, disassociation of dielectric, alloying, and quenching in the electrolyte. The samples were analyzed by field emission scanning electron microscope equipped with energy-dispersive X-ray spectroscopy, microhardness testing machine, and X-ray diffraction. Recast layers obtained have distinct structure and composition as compared to the work piece. Average recast layer thickness varied from 10.72 to 69.8 µm in case of EDM oil and from 13.5 to 31.6 µm in case of kerosene by varying voltage, pulse duration (on time) and frequency during the experiment. The microhardness of the machined surfaces was obtained in a wide range of 161.61-338.25 HV whereas the microhardness of unaffected base metal was 132.25 HV. Titanium carbide (TiC) was deposited and consequently there was improvement in the hardness of the work piece. [ABSTRACT FROM AUTHOR]

An efficient approach to analyze the electromagnetic (EM) scattering from coated objects above a three-dimensional (3-D) dielectric random rough surface is proposed in this paper. The electric and magnetic current densities on the sea surface are analytically realized using the semi-deterministic facet scattering model (SDFSM). Considering Fresnel reflection coefficient, a scheme combining the shooting and bouncing rays (SBR) and the physical theory of diffraction (PTD) is developed to calculate the scattering of the coated objects. Simulation results obtained with the combined method are verified by comparison with exact simulations using the multilevel fast multiple method (MLFMM). Scattering of large coated objects over sea surface composite model are too large and complex to be calculated using exact methods. With the asymptotic approach in this paper, the scattering performance can be analyzed with rather moderate computational efforts. Numerical results of composite scattering from an electric large three-dimensional model, e.g. an airplane target over a randomly rough surface with Pierson Moskowitz (PM) spectrum are presented and discussed. [ABSTRACT FROM AUTHOR]

The optimization of manufacturing processes and the investigation of polymer materials during their life cycle imply an extended knowledge of the physical and chemical properties of the material. To obtain colocalized chemical, morphological, and thermomechanical information on the same sample area, we have developed an innovative colocalized atomic force microscopy (AFM)-Raman setup and a sample preparation strategy using cryoultramicrotomy. The developed technique allows perfect crosssectioning of thin membranes (10-300 µm) without embedding avoiding chemical contamination. The opened surface is characteristic of the material's bulk properties and allows spectroscopic and near-field measurements without sample artifacts. Additionally, thin sections can be collected for complementary transmission electron microscopy. [ABSTRACT FROM AUTHOR]

This work is concerned with the size-dependent wave propagation of coupled double-walled boron nitride nanotubes (DWBNNTs) conveying nanoflow-systems based on Timoshenko beam theory. The two DWBNNTs are coupled by an enclosing visco-Pasternak medium. The small-scale effects are captured applying different surface piezoelasticity theories, including stress gradient, strain gradient, and strain inertia gradient. An analytical method is proposed to obtain phase velocity, cut-off, and escape frequencies of the system. Three cases of in-phase wave propagation, out-of-phase wave propagation, and wave propagation with one DWBNNT fixed are considered. Results indicate that ignoring surface and small-scale effects lead to inaccurate results. [ABSTRACT FROM AUTHOR]

Reflection and transmission properties of a planar interface of two non-integer dimensional (NID) half spaces are studied. It is assumed that dimensions of both half spaces normal to the interface are non-integer. Both half spaces are distinguished from each other by non integer dimensions rather than wavenumbers. A plane wave has been taken as source of excitation. It is observed that non integer dimensions are also the factors controlling the reflection and transmission properties of the interface. Special cases are also considered when one or neither of the two half-spaces are NID. [ABSTRACT FROM PUBLISHER]

Large-scale handling of particulate solids can cause severe wear on bulk solids handling equipment surfaces. Wear reduces equipment life span and increases maintenance cost. Examples of traditional methods to reduce wear of bulk solids handling equipment include optimizing transport operations and utilizing resistant materials. To our knowledge, the so-called bionic design has not been utilized. Bionic design is the application of biological models, systems, or elements to modern engineering. Bionic design has promoted significant progress on the development of engineering products and systems. In order to use bionic design for wear reduction of bulk solids handling equipment surfaces, this paper introduces bionic design to bulk solids handling on the basis of analogies between biology and bulk solids handling. In addition, a bionic design methodology for the wear reduction of bulk solids handling equipment surfaces is formulated. Based on the bionic design methodology, two bionic models used for abrasive and erosive wear reduction of bulk solids handling equipment surfaces are proposed. [ABSTRACT FROM AUTHOR]

Toolpath generation is the crucial task of free-form surface machining, and the quality of toolpath affects the final machining precision and efficiency. In conventional method, machining efficiency is approximately evaluated by the length of toolpaths. However, due to the curvature of toolpath distributing irregularly, the axis drive has to accelerate or decelerate to avoid exceeding its limits. For this reason, interpolation situation would affect toolpath quality as well, which is not taken into consideration in the traditional toolpaths generation mechanism. This paper proposes a toolpath generation method to plan toolpath with time-optimal, which has bidirectional information flow between CAM system and CNC system. This architecture is called inverse evaluation mechanism. By this mechanism, an offline simulation interpolation module is integrated into the CNC system; with this module, the feed sensitive zones are inspected by CNC system and the surface is divided into normal zones and low-velocity zones. The low-velocity zones are transmitted to CAM system as the feedback information. This paper gives the whole architecture of inverse evaluation mechanism and the details of how it works. The proposed method is verified with simulation examples; the result shows that this method can automatically find the low-velocity zones and modify the toolpaths. [ABSTRACT FROM PUBLISHER]

We report rheological studies on the liquid-crystal colloids prepared by dispersing silica microparticles with homeotropic surface anchoring in 8CB liquid crystal. In nematic colloids, a shear-thickening behaviour is observed in low shear rate region. The apparent yield stress of both the nematic and smectic-A (SmA) phases increases with increasing volume fraction of particles. The critical strain amplitude (, i.e., crossover ofand) in SmA colloids decreases significantly with increasing. The frequency-dependent storage modulus of SmA colloids show a power-law behaviourand the loss modulusexhibits a shallow minimum. The optical rheomicroscopy shows that the nematic colloids form a network structure which are stretched and broken at high shear rate. When the temperature is decreased to SmA phase, the networks collapse showing regions of high-density particles. The variation of storage modulus withindicates that the SmA colloids response is dominated by defects. [ABSTRACT FROM PUBLISHER]

Various plastic products such as bottles’ plastic caps are manufactured through casting using permanent molds. To obtain the smooth surface on plastic caps during manufacturing, the required permanent mold die punch surface should be defect free and its roughness values in nanometer range. Two different magnetorheological (MR) fluid-based finishing processes are used for nano-surface-finishing of die punch. The MR ball end with solid rotating tool core is used to finish the flat surface, and a turning type MR finishing process is used for external circular surface of the present mold die punch. The material of the present permanent mold punch is P20 tool steel with hardness of 431 VHN. The final roughness values of flat and external circular surfaces of the present die punch are obtained as 30 nm and 80 nm from the initial values of 1080 nm and 630 nm in 120 min of finishing. The change in topography of the surface is observed using metallurgical microscope and mirror image test. The reduction in surface roughness at the nanolevel and microscopic improvement on the die punch surface have demonstrated the feasibility of present finishing processes to be useful in industries for manufacturing the smooth surface of bottles’ plastic caps. [ABSTRACT FROM AUTHOR]

Drilling of polymer composites by means of traditional tools does cause a significant amount of damage to the surface. The forces generated during drilling are the major factors that exert an influence on hole quality. This makes the design and development of the drill geometries an area of paramount importance. Over the years, several tools have been developed and commercialized to minimize the damage induced by drilling. In this technical paper, we presented and discussed about an innovative tool point geometry that was designed, developed, and implemented for the purpose of investigating the drilling performance of composite laminates. The performance of the developed drill bit is compared with extensively used twist drill bit in reference to the drilling induced forces and damage. The input parameters considered are tool point geometry, speed, and feed. Results of this investigation reveal that both forces and damage are significantly reduced when holes are produced using the developed drill bit. [ABSTRACT FROM AUTHOR]

In the first part of this article, we outline Rene Descartes' (1637/1965) list of cues for perceiving distance. We show that this list has essentially persisted up to the present. What began, however, as a heterogeneous list of ways of perceiving distance was reified by David Marr into a set of modular processes instantiated in the visual system. We suggest that this modular approach does not conform well to what is now known about visual space perception. We show that Marr, although strongly influenced by Gibson, did not adopt the view of visual space perception developed in The Senses Considered as Perceptual Systems (Gibson, 1966). In the second part of this article, we show that there is considerable non-modular structure in the optic array that is used to perceive spatial layout. We describe, with examples from the literature, 5 major forms of structure, all of which cut across different forms of information pickup. These are (a) surfaces as references, (b) local and non-local processing, (c) compression and shear, (d) analogous geometrical structures, and (e) boundaries and surfaces. [ABSTRACT FROM AUTHOR]

The wettability of floc has a large effect on the selective flocculation flotation process of fine coal separation. The changes of thermodynamic characterization of coal and kaolinite have been investigated by Washburn dynamic method and Fourier transform infrared spectroscopy (FTIR) before and after the adsorption of anionic polyacrylamide. Lipophilic hydrophilic ratio (LHR), surface free energy, and its components were calculated by Washburn equation combined with Van Oss–Chaudhury–Good theory according to the wetting curves of coal and kaolinite samples wetted by n-hexane, α-bromonaphthalene, formamide, and water. After PAM A401 adsorption, the peaks of hydrophilic functional groups of coal (the amide group, free-NH2, secondary amide N–H, C–N) were increased, while the peaks of the hydrophobic functional group, including methyl (-CH3) and methylene (–CH2–), was decreased. The LHR value of coal decreased from 9.23 to 7.28. The polar components of coal were increased, the non-polar components were decreased, and the surface free energy was increased from 39.92 to 40.43 mN m−1. The coal surface became more hydrophilic. For kaolinite, both hydrophilic and hydrophobic functional groups were increased, while its LHR values increased from 1.44 to 1.65. The polar component was decreased from 58.27 to 55.05 mN m−2. Results of FTIR were corresponding to the surface property. [ABSTRACT FROM AUTHOR]

This paper describes improvements in the considered parameters of micro-geometry: flank surface topology and finishing productivity of 20MnCr5 alloy steel straight bevel gears through their finishing by pulsed electrochemical honing (PECH) process. Effects of three most important parameters of PECH process, namely applied voltage, electrolyte composition, and electrolyte concentration were investigated to identify their optimum values. Pre-identified values of other PECH parameters and an aqueous mixture of NaCl and NaNO3as an electrolyte were used in the present work. Errors in pitch (i.e., single pitch error, adjacent pitch error, and cumulative pitch error) and runout were used to evaluate micro-geometry of the straight bevel gears while volumetric material removal rate was used to judge the finishing productivity of the PECH process. Topology of the gear tooth flank surface and microstructure of the best-finished bevel gears were also studied. The results revealed considerable improvements in the micro-geometry, flank surface topology, and microstructure of the bevel gears finished by PECH. Applied voltage of 8 V, electrolyte composition of 75 wt.% NaCl + 25 wt.% NaNO3,and electrolyte concentration of 7.5 wt.% were identified as the optimum values to achieve simultaneous improvement in all the considered responses. [ABSTRACT FROM AUTHOR]

A general theoretical formulation is done to calculate the field scattered by perfect electromagnetic conductor (PEMC) cylinder coated with anisotropic plasma material. It is buried below a slightly rough surface. Spectral plane wave representation of fields and small perturbation method are used to calculate multiple reflections between coated cylinder and rough surface. To validate the present formulation, scattered field from a PEMC cylinder coated with double negative (DNG) material is obtained from the present formulation. Scattering pattern of non coated PEC/PEMC cylinder or coated with isotropic material can also be obtained by the proper selection of physical parameters such as anisotropy, admittance of PEMC cylinder and permittivity of hosting medium. Analytical expressions of scattered field for a sinusoidal rough surface are given along with their physical interpretation to get a good insight. Effect of geometrical and physical parameters on scattering pattern is observed. [ABSTRACT FROM AUTHOR]

Gas–solid erosive wear is a phenomenon in which serious mechanical damage is caused by the impact of solid particles on a wall. In this study, we investigated the erosive wear characteristics and mechanism of biomimetic groove surfaces in gas–solid erosive wear. Orthogonal experimental results showed that the order of the factors that influenced the erosive wear of the biomimetic groove surface was morphology > space > feature size. The V-shaped groove surface exhibited the best erosive wear resistance over the smooth, square, and U-shaped groove surfaces. The surface microstrain calculated by X-ray diffraction lines was used to study the mechanism of erosive wear resistance enhancement of the biomimetic surface. The microstructure of the eroded surface was analyzed by scanning electron microscopy. The appearance of ribs on the biomimetic groove surface increased the erosive wear of the surface in a distal position with respect to the ribs themselves. This article shows more opportunities for bionic application in improving the anti-erosion performance of moving parts that work under dirt and sand particle environments. [ABSTRACT FROM AUTHOR]

This work presents studies on the antiwear, antifriction, and extreme pressure properties of motor oil dispersed with MoS2nanoparticles. Commercial oil (SAE 20W-40 grade) is dispersed with stabilized MoS2nanoparticles in 0.25, 0.5, 0.75, and 1 wt%. The test oils are tested for antiwear, antifriction, and extreme pressure properties on a four-ball wear tester. The wear and friction offered by nanolubricants has decreased remarkably compared to the commercial base oil. The weld load and load wear index of oils dispersed with nanoparticles were improved substantially compared to the commercial base oil. Metallographic studies conducted on the wear balls from the extreme pressure test show that nanoparticles are deposited on the worn area along with additives in the oil, thereby preventing welding of the surfaces. An optimum weight fraction is arrived at for best performance. A synergy between the additives in the oil and dispersed nanoparticles has been observed, resulting in less dispersion for best results. It is found that beyond an optimum weight percentage of nanoparticles, the trends tend to reverse, resulting in greater wear and friction. [ABSTRACT FROM PUBLISHER]

A detailed numerical study on the film cooling of a corrugated surface through a single slot has been presented in this paper. The effects of the blowing ratio, density ratio (DR), and injection angle on the film cooling of the corrugated surface are discussed. Numerical simulations are carried out over a wide range of DRs ranging from 0.2 to 5.0 at a fixed mainstream Reynolds number of 1.5 × 105, three blowing ratios of 1, 2, and 3, and five injection angles ranging from 30° to 90°. Results show that the velocity profile on a corrugated surface is strongly influenced by the injection of the secondary fluid. It is observed that the film cooling effectiveness of the corrugated surface increases monotonically with an increase in the blowing ratio. The density ratio and injection angle also have a strong influence on the film cooling. [ABSTRACT FROM PUBLISHER]

In electrical impedance tomography (EIT), two- or three-dimensional (2D or 3D) distribution of the electrical conductivity is reconstructed based on potential measurements from the surface of the object. In many industrial and medical applications of EIT, the conductivity distribution is discontinuous – due to, e.g. phase or tissue boundaries. Previous studies have shown that such features in the conductivity can be preserved by using total variation (TV) prior model in the EIT image reconstruction. Recently, both 2D and 3D TV models have been utilized in EIT simulation studies. This far, however, EIT reconstructions with TV models have been evaluated experimentally only in 2D cases or translationally invariant 3D cases. In this paper, an experimental study of EIT with a TV prior in a 3D geometry is presented. In addition, we propose the selection of the prior parameters in the TV model based on the prior information of materials in the target, and their conductivity ranges. The results demonstrate the robustness of the proposed parameter selection strategy, and verify that the use of the TV prior yields sharp reconstructions in 3D EIT. [ABSTRACT FROM PUBLISHER]

In this paper, we study the inverse scattering of tapered waves from sound soft surfaces or horizontally polarized electromagnetic waves from perfectly conducting surfaces. By the related Fréchet derivative with respect to a given surface of the solution of direct scattering problems, an efficient algorithm is proposed to reconstruct the parameters of unbounded rough surfaces from a set of scattered field measurements. Tapered wave is introduced to realize the asymptotic truncation for unbounded fractal rough surface. In order to improve the results of reconstruction, multi-angle and multi-frequency incidence strategy has been used. The numerical results show that the method yields satisfactory reconstructions for some rough surface profiles. [ABSTRACT FROM PUBLISHER]

The results of a study that helps understand the mechanisms of adsorption of polyelectrolytes on particles, using numerical simulation methods, specifically the one known as dissipative particle dynamics are reported here. The adsorption of cationic polyelectrolytes of two different polymerisation degrees interacting with two types of surfaces, one made of gold and the other of silica, is predicted and compared. We find that a more negatively charged wall does not necessarily adsorb more cationic polyelectrolytes because the electrostatic repulsion between the wall and the polyelectrolytes is stronger. Additionally, intra-chain repulsion plays an important role, because the largest polyelectrolyte chains have larger excluded volume than the shorter ones. In regard to the adsorption dependence on the polyelectrolyte polymerisation degree, we find that the excluded volume drives the adsorption throughout the intra-chain electrostatic repulsion, because the SiO2surface is strongly negative. These results are expected to be useful for several nanotechnological applications of current interest, such as in gene therapy and in the improvement of drug delivering mechanisms. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results from laboratory repeated plate load tests on unreinforced and reinforced model sections of unpaved road constructed in a steel test tank. Different types of geosynthetics, namely, geotextile, two types of biaxial geogrids and geocells were used to reinforce the road sections in different tests. The effect of type and form of reinforcement on the stress-strain hysteresis of unpaved road sections is discussed in the light of experimental results. Model tests were also conducted with varying heights and positions of geocell layer to study the effect of these parameters on deformations and surface profiles. It was observed that at higher settlements, the reinforced systems developed less permanent settlements and more elastic settlements compared to unreinforced systems. Increasing the height of the geocell layer resulted in improved performance up to a certain height, beyond which, further increase in the height reduced the load resistance because of the inadequate granular overlay thickness. [ABSTRACT FROM AUTHOR]

A spherical particle lies on a sinusoidal surface under the force of adhesion. Both the sphere and the wavy body are considered to be elastic. Because the radius of curvature of the surface varies with position, the composite radius of curvature of the sphere and the surface also varies with position. The total energy of the system, which includes the adhesion energy, decreases as the composite radius of curvature increases. As a consequence, it is energetically favorable for the sphere to move away from the surface peaks and toward the valleys. The existence of this adhesion–energy-induced driving force is demonstrated theoretically and its value is determined for a range of sphere positions. Linear theory predicts that it can be as large as ∼ 2% of the pull-off force. The inclusion of nonlinear effects would be expected to increase this driving force. [ABSTRACT FROM AUTHOR]

An interference friction causes tear and wear in metal-on-metal (MoM) hip joint. The purpose of this research is to examine the optimization of pit embedded in the acetabular cup using a spark discharge machine. Tribology tests on cup with 8, 21, and 40 pits embedded produced promising results. A modified pin-on-disk tribometer was used to measure the effects of the coefficient of friction and wear on a 28-mm-diameter acetabular cup. Microscopy image analysis was used to examine particle debris and surface disfigurement. This study revealed that the more pits were produced in the hemispherical or curvature cup, the more lubricant was confined inside the pits, and the easier the contact was for MoM. The results also show that the curvature surface modification with pits can positively influence friction and wear and stability optimization of MoM implants. [ABSTRACT FROM PUBLISHER]

Aerodynamically alleviated marine vehicle (AAMV) is a high speed craft equipped with aerodynamic surfaces that operating in ground effect zone provides this craft with the ability to achieve much higher cruising speeds. Reducing the take-off mode of an AAMV is highly desirable. Additionally, it is seen where there is a considerable reserve thrust take-off can occur in the lower get-away speeds that shorten the take-off run and, therefore, is favourable. Accordingly, in this study an attempt has been made to develop a nonlinear mathematical model for an AAMV to simulate accelerations in take-off and landing phases, using semi-empirical equations mainly proposed for mono-hull high-speed craft, which concurrently take into account the hydrostatic, hydrodynamic, aerodynamic and thrust forces. The developed model of dynamics has been well validated against the existing experimental data of an AAMV model test calm water resistance. Finally, the effects of various hydrodynamic and aerodynamic parameters on accelerations and thus total resistance and get-away speed of an AAMV in take-off phase have been investigated. This model has the ability to provide the designers with the valuable data on influence of various hydrodynamic and aerodynamic factors on accelerations of an AAMV in take-off phase, which can be usefully employed to lessen the get-away speed and take-off run. [ABSTRACT FROM PUBLISHER]

This experimental study was carried out to investigate the turbulent shallow wake generated by a vertical sharp-edged flat plate suspended in a shallow channel flow with a gap near the bed. The objective of this study is to understand the effect of the gap flow on the wake by studying two different gap heights between the channel bed and the bottom edge of the bluff body. These two cases will be compared to the no-gap case which is considered as a reference case. The maximum flow velocity was 0.45 m/s and the Reynolds number based on the water depth was 45,000. Extensive measurements of the flow field in the vertical mid-plane and in the horizontal near-bed, mid-depth, and near-surface planes were made using particle image velocimetry. This paper is part of an extensive study to characterise the gap-flow effects and is primarily concerned with the mean velocity fields, while a companion paper discusses the turbulence characteristics. The size of the wake identified in the horizontal planes is found to vary in the three planes, where the gap flow enhances the entrainment in the near-wake region in the near-bed velocity field. The results also revealed that, if the gap flow is weak, it is engulfed by the recirculation zone formed just behind the bluff body whose axis is perpendicular to the vertical mid-plane. On the other hand, if the gap flow is relatively strong, it penetrates in the downstream direction and only a portion of it is diverted upward to feed the recirculation zone. [ABSTRACT FROM PUBLISHER]

The article discusses the work on definitive screening designs and reason of its success including traditional screening experiments, which do not allow detection and estimation of quadratic effects. The article also mentions the standard designs lacking in usefulness and justification of Taylor series expansion in response to surface methodology. The focus of the article is involvement models in 21st century accessing advance technology.

Mechanism of biomimetic adhesive pad and animal's pad are generally alike in stability and be independent of environment, including wet adhesion and seta adhesion. Biomimetic wet adhesive pad has an advantage over creeping on wet surface because of perfect ability of copy surface shape. The processes of adsorbing wall and peeling wall rapidly carry through alternate, so the ability of getting over the wet adhesion force in peeling and the ability of producing the force are equal of importance. This study focus on the problem of peeling from the wall of biomimetic wet adhesive pads, and a new adhesive pad with variable cross-sections microstructures is proposed. The experiments of adhesion force and peeling force of the proposed pads have been investigated, the result shows the validity of the variable cross-section surface microstructures. [ABSTRACT FROM AUTHOR]

The absorption mechanisms of collector and mineral surface structures play important roles in studies of lepidolite flotation. In this work, quantum mechanics (QM) and hybrid quantum mechanics/molecular mechanics (MM) methods were implemented to investigate the flotation mechanisms of lepidolite from muscovite, quartz and albite. The crystal structures, electron density distributions, bonds and the densities of states of lepidolite were calculated and compared with those of muscovite. The adsorption structures and energies of monomer dodecylammonium (DDA) on the three different minerals were also calculated. The headgroup of the DDA cation was found to adsorb on the surface of minerals, with its hydrophobic tail stretching into the vacuum slab, approximately perpendicular to the surface. Simulation results indicate that the purity of fine lepidolite is limited by the existence of muscovite, due to their similarities in surficial structure and properties. Other gangues were found to be removed efficiently with the use of acidic conditions. The results are in good agreement with other experiments. Compared with simple MM simulations, the use of the QM/MM methods to investigate the adsorption on minerals without specific forcefield parameters was concluded to be a more accurate method to attain monomer surfactant–mineral adsorption energies. [ABSTRACT FROM PUBLISHER]

In order to quantitatively evaluate the geomaterial surface characteristics, the surface roughness was divided into two kinds according to texture scale: micro-roughness at a micrometre or millimetre level and macro-roughness at a centimetre or decimetre level. The definition of surface macro-roughness was given. Four evaluation methods, digital survey method, contour line elongation method, roughness elements average height method and projected area ratio of platform and slope surface method, were put forward to evaluate the roughness of regular steps, inclined plane of different gradients and curved slope surfaces. Through analysing and comparing the merits and defects of the four evaluation methods, it is shown that digital survey method and roughness elements average height method are suitable for evaluating the surface macro-roughness of these three categories. To simply and conveniently evaluate the surface macro-roughness, the roughness elements' average height method is recommended. [ABSTRACT FROM AUTHOR]

This study assesses the hypothesis of incomplete similarity for a plane turbulent wall jet on smooth and transitionally rough surfaces. Typically, a wall jet is considered to consist of two regions: an inner layer and an outer layer. The degree to which these two regions reach equilibrium with each other and interact to produce the property of self-similarity remains an open question. In this study, the analysis of the outer and inner regions indicates that each region is characterised by a half-width which exhibits its own distinct dependence on the streamwise distancexfrom the slot, and a single self-similar structure for both regions does not exist. More specifically, the inner and outer layers of the wall jet exhibit different scaling laws, which results in two self-similar mean velocity profiles, both of which retain a dependence on the slot heightH. As such, incomplete similarity of the wall jet on smooth and transitionally rough surfaces is confirmed by this study. In addition, comparison of the experimental results for the transitionally rough surface with the smooth wall case indicates that the surface roughness modifies the development of the mean velocity profile in both the inner and outer regions, although the effect on the outer region is relatively small and close to the experimental uncertainty. [ABSTRACT FROM AUTHOR]

We present the results on the modelling of structural changes in pentagonal small particles (PSPs) during their growth. We prove that after a certain critical size it becomes energetically favourable for a PSP to form a subsurface layer free of twin boundaries (TBs), which are only typical structural elements for smaller size PSPs. In this layer, the low-angle dislocation boundaries (DBs) are formed. Our calculations of the energy stored in the transformed PSP are based on the disclination model of a PSP, in which the TB junctions, as well as TB–DB junctions are treated as wedge disclinations. [ABSTRACT FROM PUBLISHER]

Due to climate change a slowly increasing annual temperature may be experienced by structures. Relative humidity (RH) fluctuations affect the equiibrium moisture content of materials. Repeated RH cycling leads to mechanical failure and may endanger an object's structural integrity. Preventive conservation is based on adopting measures that will prevent fracture. Real-time interferometry allows the acquisition of sequential high-resolution full-field surface images from hygroscopic materials used in cultural heritage by recording during cycles of changing RH. The differential images allow the development of a preventive methodology directly through surface responses. Indications of the natural onset of degradation can be followed and traced before visible damage occurs, allowing preventive measures to be taken in advance. An ongoing study (Climate for Culture European project (FP7-ENV-2008-1 CfC no. 226973)) aims to experimentally classify structural deterioration as a function of acclimatization and confirm the hypothesis that surface responses before deformation can indicate deformation threshold values as reference points for the onset of RH-induced deterioration. [ABSTRACT FROM AUTHOR]

Electromagnetic scattering from a topological insulator (TI) cylinder buried beneath a rough surface is considered. To account for the interactions of the scattered field and the rough surface, spectral plane wave representation of fields is used along with small perturbation method. Both time-reversal symmetry TI cylinder and time-reversal symmetry broken TI cylinder are considered to evaluate the scattered-transmitted field above the rough surface for different values of the periods of the rough surface and the size of the object. It is observed that co- and cross-polarized field components show a maximum before the time-reversal symmetry is broken. The co-polarized component remains almost constant while the cross-polarized component decreases for time-reversal symmetry broken case. [ABSTRACT FROM AUTHOR]

Macerals are the smallest components of coal recognizable on the microscopic scale and, even when optically homogeneous, they may have variable elemental and molecular chemistry not only across different coal ranks but also in iso-rank coals. These variations in maceral chemistry may have significant impact on the behavior of the coal during processing and may also complicate predictions of this behavior. Flotation is one of the processes that is impacted by intermaceral variations. Flotation is used as a main process to upgrade the fines of higher rank coals. It depends on the surface properties of coal particles, hence their chemical composition. Most of the minerals associated with coal, with the exception of a few (elemental sulfur or some pyrites), are hydrophilic and can easily be separated if liberated from coal by flotation. The organic matter (macerals) possesses different degrees of hydrophobicity, and its response to flotation can vary depending on the surface properties that result from chemical composition of macerals and their associations with each other and minerals. This article addresses research progress in the area of chemistry of macerals and their hydrophobicity with a special reference to achieving selectivity in coal flotation. [ABSTRACT FROM AUTHOR]