Greater Surface Roughness Research Articles

Cu and Fe chalcopyrite leach activation energies and the effect of added Fe 3+

The leaching kinetics of chalcopyrite (CuFeS 2) concentrate in sulfuric acid leach media with and without the initial addition of Fe 3+ under carefully controlled solution conditions ( E h 750 mV SHE, pH 1) at various temperatures from 55 to 85 °C were measured. Kinetic analyses by (i) apparent rate (not surface area normalised), and rate dependence using (ii) a shrinking core model and (iii) a shrinking core model in conjunction with Fe 3+ activity, were performed to estimate the activation energies ( E a) for Cu and Fe dissolution. The E a values determined for Cu and Fe leaching in the absence of added Fe 3+ are within experimental error, 80 ± 10 kJ mol −1 and 84 ± 10 kJ mol −1, respectively (type iii analyses E a are quoted unless stated otherwise), and are indicative of a chemical reaction controlled process. On addition of Fe 3+ the initial Cu leach rate (up to 10 h) was increased and Cu was released to solution preferentially over Fe, with the E a value of 21 ± 5 kJ mol −1 (type ii analysis) suggestive of a transport controlled rate determining process. However, the rate of leaching rapidly decreased until it was consistently slower than for the equivalent leaches where Fe 3+ was not added. The resulting E a value for this leach regime of 83 ± 10 kJ mol −1 is within experimental error of that determined in the absence of added Fe 3+. In contrast to Cu release, Fe release to solution was consistent with a chemical reaction controlled leach rate throughout. The Fe release E a of 76 ± 10 kJ mol −1 is also within experimental error of that determined in the absence of added Fe 3+. Where type (ii) and (iii) analyses were both successfully carried out (in all cases except for Cu leaching with added Fe 3+, <10 h) the E a derived are within experimental error. However, the type (iii) analyses of the leaches in the presence of added Fe 3+ (>10 h), as compared to in the absence of added Fe 3+, returned a considerably smaller pre-exponential factors for both Cu and Fe leach analyses commensurate with the considerably slower leach rate, suggestive of a more applicable kinetic analysis. XPS examination of leached chalcopyrite showed that the surface concentration of polysulfide and sulfate was significantly increased when Fe 3+ was added to the leach liquor. Complementary SEM analysis revealed the surface features of chalcopyrite, most likely due to the nature of the polysulfide formed, are subtly different with greater surface roughness upon leaching in the absence of added Fe 3+ as compared to a continuous smooth surface layer formed in the presence of added Fe 3+. These observations suggest that the effect of Fe 3+ addition on the rate of leaching is not due to the change in the chemical reaction controlled mechanism but due to a change in the available surface area for reaction.

One-step controllable fabrication of superhydrophobic surfaces with special composite structure on zinc substrates

Stable superhydrophobic platinum surfaces have been effectively fabricated on the zinc substrates through one-step replacement deposition process without further modification or any other post-treatment procedures. The fabrication process was controllable, which could be testified by various morphologies and hydrophobic properties of different prepared samples. By conducting SEM and water CA analysis, the effects of reaction conditions on the surface morphology and hydrophobicity of the resulting surfaces were carefully studied. The results show that the optimum condition of superhydrophobic surface fabrication depends largely on the positioning of zinc plate and the concentrations of reactants. When the zinc plate was placed vertically and the concentration of PtCl4 solution was 5mmol/L, the zinc substrate would be covered by a novel and interesting composite structure. The structure was composed by microscale hexagonal cavities, densely packed nanoparticles layer and top micro- and nanoscale flower-like structures, which exhibit great surface roughness and porosity contributing to the superhydrophobicity. The maximal CA value of about 171° was obtained under the same reaction condition. The XRD, XPS and EDX results indicate that crystallite pure platinum nanoparticles were aggregated on the zinc substrates in accordance with a free deposition way.

A comparative in vitro study of frictional resistance between lingual brackets and stainless steel archwires

Friction between archwires and labial brackets has received considerable attention; however, information on the frictional behaviour of commercially available lingual brackets is limited. The aim of this study was to investigate the frictional resistance resulting from a combination of lingual orthodontic brackets (7th Generation, STb, Magic, and In-Ovation L) and stainless steel archwires at 0, 5, and 10 degrees of second-order angulation. Each bracket type (n = 30) was tested with three different sizes of archwires. Static and kinetic frictional forces were evaluated with a universal testing machine. Statistical analysis of the data was performed with non-parametric Kruskal-Wallis and Dunn's multiple comparison tests. All tested brackets showed higher frictional forces as the wire size and second-order angulation increased. The lowest friction was found with In-Ovation L brackets and 0.016 inch archwires at 0 degrees angulation, and the greatest friction with a combination of STb brackets and 0.017 × 0.025 inch archwires at 10 degrees angulation. For all combinations, Magic and In-Ovation L brackets showed lower frictional resistance when compared with 7th Generation and STb brackets. The slot width (occluso-gingival dimension) of the brackets, measured using the optics of a microhardness machine, showed that all brackets were oversized and that Magic brackets had the largest slot width. Surface roughness of the brackets investigated using atomic force microscopy and scanning electron microscopy, demonstrated that the 7th Generation brackets had the greatest surface roughness.

Fabrication of superhydrophobic surfaces on zinc substrates

Stable superhydrophobic surfaces were fabricated on the zinc substrates through simple silver replacement deposition process with the modification of octadecyl mercaptan. The effects of reaction conditions on the surface morphology and wettability of the prepared surfaces were carefully studied. The results show that the fabrication of a best superhydrophobic surface depends largely on the moderate reactant concentration. When the concentration of AgNO 3 solution was 2 mmol/L, the zinc substrate was covered by a dendritic outline structure. Aggregated silver nanoparticles were formed on the substrate in accordance with some certain laws, exhibiting great surface roughness. The typical hierarchical micro-nanostructures, flower-like structures and porous structures also could be found from the SEM images. The maximal water contact angle (CA) value of about 161 ± 2°, and the minimal sliding angle (SA) of about 2° were obtained under the same reaction condition.

Influence of size and surface roughness of large lactose carrier particles in dry powder inhaler formulations

The objective of this study was to determine the effect of both carrier particle size and surface roughness on the aerosol performance of dry powder formulations. Two morphologically distinct grades of lactose, anhydrous (AN) and granulated (GR), were fractionated into 11 discreet sizes up to 300 μm, and separately employed as carriers in 2% (w/w) budesonide blends. In vitro deposition studies were performed at 60 L min −1 with an Aerolizer ® DPI. It was found that large carriers can improve dispersion performance, although the effect is more pronounced with greater surface roughness. AN carriers exhibited minimal surface roughness and generally behaved as predicted from the literature, with the smaller carriers outperforming their larger counterparts. In contrast, GR carriers had a high degree of surface roughness, and the dispersion performance of larger carriers exceeded that of the smaller size fractions. Comparing the two lactose grades, AN carriers deposited a greater fraction of the total dose up to the 90–125 μm size range, when they were surpassed in performance by the GR carriers. These results suggest that the mechanism of drug detachment varies with the physical properties of the carrier particle population, where surface roughness can alter the predominant detachment mechanism to favor larger carrier particle diameters.

On the anisotropic wafer curvature of GaN-based heterostructures on Si(1 1 0) substrates grown by MOVPE

We highlight the challenges of GaN growth on (1 1 0)-oriented Si substrates with respect to the substrate-induced anisotropic strain state. A 5:4 lattice matching relationship, which is valid for AlN and Si(1 1 1), is also expected for AlN on Si(1 1 0) along the [1 1 –2 0]AlN/[1 −1 0]Si direction. This reduces the effective lattice mismatch for AlN on Si(1 1 0) along [1 1 –2 0] AlN/[1 −1 0] Si from 23.4% to −1.3% (compressive), while in the [1 −1 0 0] AlN/[0 0 1] Si direction, the mismatch value remains at 0.7% (tensile). The opposite signs of the two mismatch values lead to an anisotropic strain state of the deposited AlN and GaN films, which makes it difficult to balance the tensile strain induced by thermal mismatch. For a simple growth scheme using 1 μm GaN on top of a 40 nm AlN layer, this situation is reflected in an aspherical wafer curvature, anisotropic X-ray diffraction (XRD) Ω scan full width at half maximum (FWHM) values, greater surface roughness and cracking, predominantly occurring parallel to the [1 1 –2 0] direction. The anisotropic XRD FWHM may be explained by a strain-induced anisotropic nucleation mechanism for GaN on AlN. Also, a partial relaxation of the GaN film during growth caused by very high tensile strain along [1 –1 0 0] AlN/[0 0 1] Si is assumed to contribute to the XRD anisotropy. The insertion of an AlN/GaN superlattice structure in between the AlN and GaN films inhibits this relaxation process and leads to a smoother surface morphology with less visible cracks.

On-Line Inspection of the Surface Roughness of Workpiece in Ultraprecision Machining

An in situ technique to determine the surface roughness of ultraprecision machining using optical characteristic effects is fundamental as probes are not used, which prevents contact damage on the surface. Because the plastic lens molding reprints the roughness of the mold core fabricated by machining, tool marks result in the poor surface of the plastic lens. The machined surface can reflect the input light of a green laser with a short wavelength of 532 nm. By varying the feed rate of the ultraprecision machining, several samples of the electrolyte-less nickel with different surface roughness have been examined using the green laser and the photodiode array. The distribution of the optical scattering effect of each sample under the light source of green laser is derived for prediction of the surface roughness. The results show that greater surface roughness produces more expansive distribution of light scattering. In addition, the bidirectional scatter distribution function (BSDF) of the machined surface is found to be proportional to roughness. Using the ratio of the main and the side measuring channels of the photodiode array, a suitable approach to establish the relationship between light scattering and surface roughness can be developed. The laser and the photodiode array are found to efficiently predict the surface roughness of the ultraprecision machined electroless nickel.

Adsorption of polar and nonpolar compounds onto complex nanooxides with silica, alumina, and titania

Adsorption of low-molecular adsorbates (nonpolar hexane, nitrogen, weakly polar acetonitrile, and polar diethylamine, triethylamine, and water) onto individual (silica, alumina, titania), binary (silica/alumina (SA), silica/titania (ST)), and ternary (alumina/silica/titania, AST) fumed oxides was studied to analyse the effects of morphology and surface composition of the materials. Certain aspects of the interfacial phenomena dependent on the structural characteristics of oxides were analysed using calorimetry, 1H NMR, and Raman spectroscopies, XRD, and ab initio quantum-chemical calculations. The specific surface area S BET,X-to- S BET,N 2 ratio (X is an organic adsorbate) changes from 0.68 for hexane adsorbed onto amorphous SA8 (degassed at 200 °C) to 1.85 for acetonitrile adsorbed onto crystalline alumina (degassed at 900 °C). These changes are relatively large because of variations in orientation, lateral interactions, and adsorption compressing of molecules adsorbed onto oxide surfaces. Larger S BET,X/ S BET,N 2 values are observed for mixed oxides with higher crystallinity of titania or/and alumina phases in larger primary nanoparticles with greater surface roughness and hydrophilicity. Polar adsorbates can change the structure of aggregates of oxide nanoparticles that can, in turn, affect the results of adsorption measurements.

WITHDRAWN: Hard and superhard nanolaminate and nanocomposite coatings for machine elements based on Ti6Al4V alloy

Purpose: Verification of a series of hybrid treatments of Ti6Al4V alloy consisting of primary diffusion hardening of the substrate with subsequent deposition of wear resistant coatings. Design/methodology/approach: Different nanolaminate and nanocomposite coatings were deposited with use of four different methods including a newly developed high density gas pulsed plasma MS technique. After deposition the coatings were investigated using OM, SEM, HRTEM, XRD, XPS, nanoindentation, DaimlerBenz, ball-on-plate and scratch tests. Findings: Besides an important increase of Ti6Al4V alloy hardness much greater further increase of hardness was obtained due to coatings deposition up to 53 GPa in case of a nanolaminate coating and to 47 GPa in case of a nanocomposite nc-TiN/a-SiN coating. At the same time the volume wear coefficient decreases several orders of magnitude for all the coatings. Simultaneously the friction coefficient decreased to a great extent except for the nc-TiN/a-SiN coating. Research limitations/implications: High density gas pulsed plasma magnetron sputtering is an effective method for superhard coatings deposition, however the roughness of the deposited nc-TiN/a-SiN coating was greater than after conventional magnetron sputtering. This finding needs further experimental and theoretical investigation. Practical implications: Greater surface roughness and high resistance to wear of the coatings synthesized using the newly developed gas pulsed plasma magnetron sputtering deposition limits their application to wear protection of cutting tools rather than for friction reduction in tribological couples. Originality/value: Applicability of the broad spectrum of nanolaminate and nanocomposite coatings as well as different CVD and PVD techniques for an improvement of tribological properties of Ti6Al4V alloy was analyzed in the paper including a newly developed original high density gas pulsed plasma magnetron sputtering technique.

Research on chemo-mechanical grinding of large size quartz glass substrate

Finishing process of quartz glass substrate is meeting great challenges to fulfill the requirements of photomask for photolithography applications. For the final finishing of the substrate surface, chemical mechanical polishing (CMP) is often utilized. Those free abrasive processes are able to offer a great surface roughness, but sacrifice profile accuracy. On the other hand, the fixed abrasive process or grinding is known as a promising solution to improve accuracy of profile geometry, but always introduces damaged layer. Chemo-mechanical grinding (CMG) is potentially emerging defect-free machining process which combines the advantages of fixed abrasive machining and CMP. In order to simultaneously achieve high surface quality and high profile accuracy, CMG process has been applied into machining of large size quartz glass substrates for photomask use. Reported in this paper are CMG performances in finishing of quartz glass substrates including material removal rate (MRR), surface roughness, flatness and optical characteristics.

Development of chitosan–ellagic acid films as a local drug delivery system to induce apoptotic death of human melanoma cells

This study was designed to develop a local chemotherapy device using chitosan as a local drug carrier and ellagic acid (EA) as an anticancer drug. We fabricated chitosan-ellagic acid (Ch-EA) films with concentrations of 0, 0.05, 0.1, 0.5, and 1% (w/v) of EA and examined the films using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and contact angle measurement. The WM115 human melanoma cell line as a skin cancer model was used to evaluate cell response to the films with the MTS assay and apoptosis assay, and HS68 human newborn fibroblast cell line as a control. With the increase in the concentration of the EA, the composite films exhibit increasing amide and ester groups and diffraction peaks of the crystallized EA and greater surface roughness and hydrophilicity. The chitosan films with 0.5 and 1% (w/v) of EA were found to have a potent antiproliferative effect on the melanoma cells by inducing apoptotic cell death. Localized effect of composites on cell behaviors has been clearly demonstrated. Our study demonstrated that the novel Ch-EA film can be potentially used in local chemotherapy.

Effects of Amine Fluoride on Biofilm Growth and Salivary Pellicles

The amine fluoride (AmF) N′-octadecyltrimethylendiamine-N,N,N′-tris(2-ethanol)-dihydrofluoride is a cationic antimicrobial which can have beneficial effects on plaque formation. Here, we determine changes in pellicle and bacterial cell surface properties of the strains Actinomyces naeslundii HM1, Streptococcus mutans NS, S.mutans ATCC 700610, S. sobrinus HG1025 and S. oralis HM1 upon adsorption of this AmF and accompanying effects on bacterial adhesion and biofilm growth. In vitro pellicles had a zeta potential of –12 mV that became less negative upon adsorption of AmF. The chemical functionalities in which carbon and oxygen were involved changed after AmF adsorption and AmF-treated pellicles had a greater surface roughness than untreated pellicles. Water contact angles in vitro decreased from 56 to 45° upon AmF treatment, which corresponded with water contact angles (44°) measured intraorally on the front incisors of volunteers immediately after using an AmF-containing toothpaste. All bacterial strains were negatively charged and their isoelectric points (IEP) increased upon AmF adsorption. Minimal inhibitory concentrations were smallest for strains exhibiting the largest increase in IEP. Adhesion to salivary pellicles and biofilm growth of the mutans streptococcal strains were significantly reduced after AmF treatment, but not of A. naeslundii or S. oralis. However, regardless of the strain involved, biofilm viability decreased significantly after AmF treatment. The electrostatic interaction between cationic AmF and negatively charged bacterial cell surfaces is pivotal in establishing reduced biofilm formation by AmF through a combination of effects on initial adhesion and killing. The major effect of AmF treatment, however, was a reduction brought about in biofilm viability.

Sensitivity of channel mapping techniques to uncertainty in digital elevation data

Digital elevation data are now commonly used to map channel networks automatically. This paper evaluates the sensitivity of six methods of extracting channel networks from digital elevation models (DEMs) to elevation error. As such, the robustness of channel mapping techniques against noisy data was evaluated and not the accuracy of DEM extracted channel networks. Stochastic simulations were used in combination with a fine‐resolution LiDAR DEM of a small upland catchment to assess the robustness of each of the channel mapping algorithms. Findings showed that the four tested methods that were based on identifying patterns or positions in the surface morphology were more sensitive to elevation error than the two methods that were based on simulating overland flow and channelization processes, particularly at lower error magnitudes. While the morphology‐based channel‐mapping methods were highly sensitive to the degree of spatial autocorrelation in elevation error fields, the channelization based methods were relatively insensitive. Drainage network extent and the geometry of exterior stream channels were both found to be greatly influenced by low to moderate degrees of topographic error. Although LiDAR data were found to provide a sufficient resolution for mapping fine‐scale headwater channels, the greater surface roughness did present challenges for automated channel‐mapping techniques.

Use of electrochemical impedance spectroscopy to characterise the physical properties of ex situ reconstructed sea surface microlayer

The objective of this work was to develop electrochemical impedance spectroscopy (EIS) to characterise the physical properties of the sea surface microlayer ( ssm ). Samples from Lake Rogoznica in Croatia were extracted by n-hexane and dichloromethane (dcm) respectively and transferred to mercury electrodes. The EIS results were compared with those of a model phospholipid, dioleoyl phosphatidylcholine (DOPC) which forms near defect-free monolayers on a mercury surface. The ssm extracts formed inhomogeneous monolayers on the mercury surface and the dcm ssm extract monolayer showed greater surface roughness than the hexane ssm extract. The hexane ssm extract introduced defects and a greater surface roughness into mixed DOPC- ssm extract monolayers than the dcm ssm extract due to the lower compatibility of the non-polar hexane extract with the DOPC than that of the polar ssm extract. In addition, the dcm ssm component in the mixed DOPC- ssm monolayer showed an association with pyrene added to the solution.

Effect of surface roughness and field annealing on interlayer coupling in MnIr-based magnetic tunnel junction

The interlayer coupling field ( H in) and coercivity ( H c) were measured using micro-optical Kerr effect, and the surface roughness was obtained by using atomic force microscopy (AFM) at different points across the patterned tunnel junction. H in and H c increase with greater surface roughness. This result shows that the enhanced coercivity ( H ce) is linearly proportional to H in such as H ce = α H i n . Finally, the propositional constant α has been deduced from the annealing field dependence of H in and H ce as the function of surface magnetization of pinned layer, α = ( M s – M ps ) / M ps . From the results of H in and H ce in magnetic tunnel junction (MTJ) multilayer, we can infer that the surface magnetization of pinned layer is due to the interfacial morphological corrugations.

Fatigue debonding of the roughened stem–cement interface: Effects of surface roughness and stem heating conditions

The aim of this study was to determine the effects of cyclic loading on the debond process of a roughened stem-cement interface used in total hip arthroplasty. The specific goals were to assess the effects of two surgeon-controlled variables (stem heating and degree of stem surface roughness) and to determine if an independent finite element-based fracture mechanics model could be used to predict the debond response. A clamped cantilever beam geometry was used to determine the fatigue debond response of the stem-cement interface and was created using an experimental mold that simulated in vivo cementing conditions. A second experiment was performed using a torsion-loading model representative of the stem-cement-bone composite. For both experiments, two stem heating (room temperature and 50 degrees C) and surface roughness conditions (grit blasted: Ra = 2.3 and 5.1 microm) were used. Finally, a finite element model of the torsion experiment with provision for crack growth was developed and compared with the experimental results. Results from both experiments revealed that neither stem preheating nor use of a stem with a greater surface roughness had a marked effect on the fatigue debond response. There was substantial variability in the debond response for all cases; this may be due to microscopic gaps at the interface for all interface conditions. The debond rate from the finite element simulation (10(-7.31) m/cycle) had a magnitude similar to the experimental torsion model (10(-(6.77 +/- 1.25)) m/cycle). This suggests that within the context of the experimental conditions studied here that the debond response could be assessed using a linear elastic fracture mechanics-type approach.

Effect of different finishing and polishing techniques on the surface roughness of microfilled, hybrid and packable composite resins

This study examined the average surface roughness (Ra, microm) of 2 microfilled (Durafill and Perfection), 1 hybrid (Filtek Z250) and 2 packable composite resins (Surefil and Fill Magic), before (baseline) and after eight different finishing and polishing treatments. The surface roughness was assessed using a profilometer. Ten specimens of each composite resin were randomly subjected to one of the following finishing/polishing techniques: A -- carbide burs; B -- fine/extrafine diamond burs; C -- Sof-Lex aluminum oxide discs; D -- Super-Snap aluminum oxide discs; E -- rubber polishing points + fine/extrafine polishing pastes; F -- diamond burs + rubber polishing points + fine/extrafine polishing pastes; G -- diamond burs + Sof-Lex system; H -- diamond burs + Super-Snap system. Data were analyzed using two-way ANOVA and Tukey's HSD test. Significant differences (p<0.05) were detected among both the resins and the finishing/polishing techniques. For all resins, the use of diamond burs resulted in the greatest surface roughness (Ra: 0.69 to 1.44 microm). The lowest Ra means were obtained for the specimens treated with Sof-Lex discs (Ra: 0.11 to 0.25 microm). The Ra values of Durafill were lower than those of Perfection and Filtek Z250, and these in turn had lower Ra than the packable composite resins. Overall, the smoothest surfaces were obtained with the use the complete sequence of Sof-Lex discs. In areas that could not be reached by the aluminum oxide discs, the carbide burs and the association between rubber points and polishing pastes produced satisfactory surface smoothness for the packable and hybrid composite resins, respectively.

Role of particle size and filler–matrix adhesion on dynamic fracture of glass-filled epoxy. II. Linkage between macro- and micro-measurements

Spherical particles of mean diameter 7–200 μm are used to reinforce epoxy matrix at a constant volume fraction (10%) and two different filler–matrix strengths, weak and strong. Role of particle size and filler–matrix adhesion strength on steady-state dynamic fracture toughness is investigated by linking optical measurements reported in [1] with surface roughness parameters. Crack tilting and twisting appears to dominate when filler is strongly bonded to the matrix while crack front twisting and blunting occur with weakly bonded filler. The weaker filler–matrix interfaces also act as distributed attractors of a propagating crack resulting in greater surface roughness. A linear relationship between fracture toughness and surface roughness is seen when particle size effects and filler–matrix adhesion effects are factored out. The overall surface roughness (Ra) does not correlate with macro-measurements and only a component of Ra, defined as “fracture induced roughness”, Ra f does. A model for calculating Ra f based on volume fraction, particle size, inter-particle spacing and overall surface roughness is introduced. A linear relationship between steady state fracture toughness and the quantity Ra f / D ( D being the average particle diameter) has been found to exist.

Evolution of matt surface topography in aluminium pack rolling. Part II: effect of material properties

A model has been presented in a companion paper [1] to predict the generation of roughness on the matt surface in pack rolling of aluminium foil. The model is based on the finite element method using isotropic plasticity. This model is used in the current paper to investigate the effect of material properties on the generation of surface roughness. There is a large inhomogeneity of strain during deformation, with harder grains generally deforming less than softer ones. It is found that the roughness amplitude is roughly proportional to the standard deviation of the initial grain yield stress distribution, normalised by the initial mean yield stress, so that a wider distribution of the initial yield stress results in greater surface roughness. It is shown that a suitable linear hardening law can be used to approximate the roughening behaviour for real material flow stress curves.

Correlation Study of the Strength of the Color Doppler Twinkling Artifact with the Roughness of the Reflecting Surface and the Doppler Angles

Background The color Doppler twinkling artifact is manifested as a rapidly changing mixture of red and blue colors behind a strongly reflecting structure. The effects of the roughness of the reflecting surface and the Doppler angle on the intensity of the twinkling artifact have never been quantitatively reported before. In this study, a simple in vitro system with reproducible results was established to observe the effects of these two factors on the strength of the twinkling artifact. Materials and Methods Six different grits of water sandpapers were simultaneously scanned in a water bath with a fixed probe. In part 1, the computer calculated the pixels of color Doppler twinkling artifact behind each water sandpaper. In part 2, the signals of twinkling artifacts with different sandpaper sizes and different Doppler angles were recorded and analyzed. Results In part 1, the twinkling artifact was identified persistently and more intensely behind water sandpapers that had greater surface roughness. In part 2, different Doppler angles revealed less obvious effects on the strength of the twinkling artifacts in a certain range of angles, but would drastically decrease the intensity in the steeper angles. Conclusions We have established a simple model system with water sandpapers for the evaluation of the twinkling artifact. Our data confirmed the assumption that the roughness of the reflecting surface is directly related to the strength of the twinkling artifact. In addition, the Doppler angle affects the intensity of the artifact, but only in the steeper angles.