Incremental Thickness Research Articles

The Influence of Additively Manufactured Specimen Thickness on Laser-Induced Ultrasonic Signals

Selective laser melting (SLM) technology, employed in metal additive manufacturing, is widely utilised to fabricate components with precise dimensions and excellent mechanical properties by melting powder layer by layer. Laser ultrasonic testing is anticipated to be an efficient method for in-line monitoring in the additive manufacturing (AM) process. The conversion of specimens from thin to thick during the SLM manufacturing process has an impact on the ultrasonic signals. This paper focuses on the influence of AM specimen thickness changes on ultrasonic signals. In the finite element analysis, the incremental specimen thickness was maintained at 0.2 mm, which was the initial value. As the specimen thickness increased sequentially, ultrasonic signals were obtained from different specimens. The results demonstrate that Lamb waves are generated when the specimen is thin, and the dispersive characteristics weaken as the thickness increases. The dispersive phenomenon diminishes significantly once the specimen thickness exceeds 1 mm. By employing the f-k method, calculated dispersion curves for various specimen thicknesses were obtained. After fitting the derived dispersion curve, a mapping relationship is established with respect to the specimen thickness. Consequently, the fitting coefficient of the dispersion curve can therefore be utilized to characterize the thickness of the additive manufactured thin specimen.

Influence of Layer Thickness and Shade on the Transmission of Light through Contemporary Resin Composites.

Material-dependent parameters have an important impact on the efficiency of light polymerization. The present in vitro study aimed to investigate the influence of the increment thickness and shade of nano- and nanohybrid resin composites on the transmission of curing light. Three contemporary resin composites were evaluated: Tetric EvoCeram® (TEC); Venus Diamond® (VD); and Filtek Supreme XTE® (FS XTE). Light transmission (LT) was recorded in accordance with the sample thickness (0.5 to 2.7 mm) and the shade. Polymerized samples were irradiated for 10 s each using the high-power LED curing light Celalux 2 (1900 mW/cm2). LT was simultaneously recorded using the MARC Patient Simulator (MARC-PS). LT was strongly influenced by the composite layer thickness. For 0.5 mm-thick samples, a mean power density of 735 mW/cm2 was recorded at the bottom side. For the 2.7 mm samples, a mean power density of 107 mW/cm2 was measured. Only LT was markedly reduced in the case of darker shades. From A1 to A4, LT decreased by 39.3% for FS XTE and 50.8% for TEC. Dentin shades of FS XTE and TEC (A2, A4) showed the lowest LT. The thickness and shade of resin composite increments strongly influences the transmission of curing light. More precise information about these parameters should be included in the manufacture manual.

Influence of Light-Curing Time and Increment Thickness on the Properties of Bulk Fill Composite Resins With Distinct Application Systems.

The objective of this study was to evaluate the influence of light-curing time and increment thickness on the microhardness and degree of conversion (DC) of bulk fill composite resins with different application systems. Translucency parameter (TP) was also measured. Specimens of resin composites were prepared in a circular matrix using a single increment with different thicknesses (2, 4, and 6 mm) and light-cured with distinct times (10, 20, and 40 s). The materials tested (n = 5 pergroup) were Filtek One (FO) bulk fill, Tetric N-Ceram (TC) bulk fill, SonicFill 3 (SF), VisCalor (VC) bulk. After 24 h, Knoop microhardness (KN) was measured, and the bottom/top ratio (B/Tratio) was calculated. The DC was measured using Fourier transformed infrared (FTIR) spectroscopy. The TP was assessed in additional specimens with 1 mm thick (n = 5). The data were statistically analyzed with analysis of variance (ANOVA) and Tukey's tests (5%). Significant differences were observed for all factors, for both B/Tratio and DC (p < 0.05). The higher increment thickness and the lower curing times resulted in lower B/Tratio and DC means. The VC and TC resins exhibited the overall higher B/Tratio, and the highest TP. SF presented the lowest values of B/Tratio and DC, with compromised polymerization at 6 mm depth. TP (means ± SD) were FO (12.85 ± 1.0)1, SF (15.62 ± 0.73)2, TC (20.32 ± 0.49)3, and VC (20.53 ± 0.73)3. We concluded that the greater the thickness of the increment, the lower the DC. Higher light curing times resulted on increased DC of the tested composites. The higher translucent materials VC and TC showed the greater B/Tratio; and FO resin exhibited the higher DC values.

Effective lane width analysis for autonomous trucks

Lateral wander of autonomous truck can be further improved by optimizing the uniform wander. Increase in available lane width for the autonomous trucks can increase the performance efficiency of this mode. This research is based on finding the optimum, combination of lane width increment and asphalt layer thickness reduction among different scenarios. Therefore, In this research with assumed maximum lane width of 4.35 m, difference combination of lane width and asphalt layer thickness scenarios have been analyzed using finite element modelling in ABAQUS. Considering the base pavement width of 3.75 m, increment for each scenario is 15 cm and reduction in asphalt layer thickness is at 2 cm. Performance efficiency of each scenario is conducted while considering the initial construction costs and damage assessment for each scenario. Moreover, life cycle cost analysis (LCCA) is conducted for the base scenario and selected optimum scenario. Results show that increase in pavement width beyond 4.2 m, renders the scenarios uneconomical and thus, the scenario consisting of 4.2 m lane width and 16 cm asphalt layer thickness yield a maximum performance efficiency of 20% among all other alternatives. LCCA analysis shows that a difference in salvage value of 42 million Euros exists when compared with the base scenario. By selecting the optimum lane width of 4.2 m and asphalt layer thickness of 16 cm, Pavement lifetime can be further increased by 13 years with full depth reclamation used as maintenance intervention.

Technical note: Water-equivalent thickness of Superflab bolus material at diagnostic x-ray energies.

The purpose of this work was to determine the water-equivalent thickness of Superflab bolus material for narrow and broad field-of-view (FOV) x-ray geometries at diagnostic x-ray energies. Transmission measurements were performed for incremental thicknesses of Superflab bolus material and water in narrow and broad FOV x-ray geometries. The transmission data was fit to a non-linear model for x-ray transmission - the Archer model. Water-equivalent thickness of Superflab was calculated based upon fitting parameters to transmission curves for 75, 95, and 115kV x-ray tube voltages. Measured x-ray transmission factors for water and Superflab were used to determine the water equivalence of Superflab. For all x-ray tube voltages and geometries, the water equivalence of Superflab was greater than one, indicating that Superflab is more attenuating than water. This effect was stronger for broad FOV geometries. At 95kV, 30cm of Superflab corresponded to 32.0cm of water in the narrow FOV geometry, and 34.3cm of water in the broad FOV geometry. The Archer model fitting parameters and Superflab water equivalence are reported for all x-ray beam conditions explored in this work. Superflab bolus material is more attenuating than water at diagnostic x-ray energies. The Archer model and its respective fitting parameters reported in this work may be used to estimate the water-equivalent thickness of Superflab for diagnostic x-ray spectra.

Ion transport facilitation through template based optimization of corrugation geometry over membrane surface

The resistance at the diffusion boundary layer limits ion transport through membrane (counter-ionic) in electro-electrodialysis (EED), which are addressed through novel design of flow promoter (spacer), but increased pressure drop in the flow channel and power consumption are major rudiments. This report investigates casting of template based micro molded membranes containing cylinder, square-pillar, and rectangular-pillar corrugations and their application in EED setup without spacer. Square-pillar showed higher ion transport relative to rectangular-pillar and cylinder, which was supported by increased surface area, and reduced boundary layer thickness. For height optimization of square pillar corrugation, corrugated membranes containing pillars of five different heights: 50, 75, 100, 125 and 150 μm were synthesized and tested for using EED setup, where 100 μm height showed better ion transport. Limited ion transport with corrugation height above 100 μm resulted lower concentration of NaOH requiring higher energy. Corrugated membrane with two different arrangements of square pillars: linear and staggered were tested keeping their height same (100 μm), where staggered arrangement showed better ion transport. Direction of applied current facing flat and corrugated performed differently in ion transport, and the latter performed better due to reduced boundary layer resistance. All EED experiments were conducted with industrial green liquor feed to obtain NaOH (mol·L−1) as product, where current density, flowrate and duration were kept unchanged. NaOH recovery, Current efficiency, and energy consumption estimates with each configuration was supported through velocity profiles obtained by solving equation of motion and continuity using COMSOL multiphysics software. Combine effect of turbulence creations due to corrugation, surface area increment and boundary layer thickness control the ion transport.

Layered nonwoven filter embodied with packing density gradient measured by X-ray computed tomography for enhanced filtration performance

This research explores the possibility of tuning the structure of needle-punched nonwoven fabrics by incorporating layers of differently oriented fibres. The fibre orientation in carded batts is regulated with the help of carding parameters viz. feeder, cylinder, and doffer speeds. The carding parameters were optimized by using response surface methodology to obtain carded batts of differently oriented fibers, which were then placed distinctly to form composite layered nonwoven fabrics. The physical, mechanical, and functional properties of layered fabrics were evaluated. X-ray computed tomography technique was used for comprehensive evaluation of the packing densities at incremental thickness of layered fabrics. The obtained trends of packing density were found to be in good agreement with the measured properties of nonwoven fabrics. The creation of an inverse gradient of packing density in a layered nonwoven fabrics displayed close to highest filtration efficiency and close to lowest pressure drop.

Effect of copper donor material-assisted friction stir welding of AA6061-T6 alloy on downward force, microstructure, and mechanical properties

In this research, copper (Cu) donor material-assisted friction stir welding (FSW) of AA6061-T6 alloy was studied. Cu-assisted FSW joints of AA6061-T6 alloy were prepared at a constant tool rotational rate of 1400 rpm and various welding speeds at 1 mm/s and 3 mm/s. The Cu donor material of different thickness (i.e., 20%, 40%, and 60%) with respect to the workpiece thickness was selected to assist the FSW joining at the plunge stage. It is observed that the downward force generated in the FSW process was gradually decreased after introducing Cu donor material with incremental thicknesses with respect to workpiece at the plunge stage. Post-weld analysis was characterized in terms of microstructure and mechanical properties. The results of microstructure analysis at the stir zone (SZ) show the formation of finer grains due to dynamic recrystallization and plastic deformation. Micro-hardness tests reveal that the hardness decreased from the base metal (BM) to the SZ across the heat-affected zone (HAZ) and thermo-mechanically affected zone (TMAZ). The lowest value of hardness appeared in the TMAZ and HAZ where tensile failure occurs. With increasing welding speed, the average hardness in the SZ decreased due to lower heat input and faster cooling rate. Tensile test plots show no significant change in ultimate tensile strength with or without Cu donor material. Fractography of tensile tested samples shows both ductile and brittle like structure for given welding parameters. This proposed work of FSW with Cu donor material is promising to increase tool life due to the decrement of the downforce during plunge and throughout the welding stage. Meanwhile, the inclusion of donor material did not compromise the weld quality in terms of the mechanical properties and micro-hardness.

Effect of extended light activation and increment thickness on physical properties of conventional and bulk-filled resin-based composites.

To evaluate the biaxial flexural strength (BFS), flexural modulus (BFM), and Knoop microhardness (KHN) of incremental and bulk-filled resin-based composites (RBCs) using extended curing exposure times. Disc specimens (n = 8; 6-mm diameter) were fabricated using three stacked molds (0.5-mm thick for the top and bottom molds, and a 1-mm-thick center mold for the conventional and 3-mm thick for the bulk-fill RBCs). Conventional (Tetric EvoCeram/TCE and Filtek Z250/FIZ) and bulk-fill RBCs (Tetric EvoCeram Bulk Fill/TBF and Filtek One Bulk Fill Restorative/FOB) were evaluated. The stacked RBC-filled molds were light-cured for (1) the manufacturer-recommended exposure (MRE) duration; (2) 50%, and (3) 100% extension of the MRE. The BFS, BFM, and KHN of the top and bottom discs were measured. BFS and BFM were analyzed by three-way ANOVA (material*curing time*depth) and Tukey's post hoc (α = 0.05). KHN was analyzed by two-way ANOVA (curing time*depth) and Tukey's post hoc (α = 0.05). Extending the exposure duration did not change the BFS and BFM on the top of the RBCs, but the BFS and KHN increased at the bottom of bulk-fill RBCs. For the conventional RBCs, TCE showed the highest increase on BFS at the bottom, going from 53.6MPa at T1 to 69.9 at T3. Among the bulk-fill RBCs, FOB presented the highest increase on the bottom BFS (T1: 101.0 ± 19.9MPa, T3: 147.6 ± 12.9MPa). For all RBCs and exposure times, BFS and KHN were lower at the bottom. Only FIZ and FOB reached a bottom-to-top hardness ratio of 80%, at T3 and T2. A significant increase on the BFS and KHN on the bottom of bulk-fill RBCs can be observed when the time of exposure to the curing light is double the MRE. However, extended exposure does not eliminate differences on the BFS and KHN between the shallow and deep regions of RBCs. TCE and TBF failed to reach an acceptable B/T hardness ratio at all evaluated exposure times. Mechanical properties of RBCs can be affected by insufficient polymerization, specially at deeper regions of the increment. Therefore, clinicians should consider applying twice the MRE to curing-light to polymerize the maximal increment thickness of bulk-fill RBCs.

Influence of increment thickness on microhardness and bond strength in composite resins

The aim of this study was to evaluate the Knoop microhardness and the microtensile bond strength of a second-generation of bulk-fill (BF) and a nanohybrid composite resins (NH) in different thicknesses of increments. For this, ninety disks of composite resin were made for Knoop microhardness, being divided into six groups (n = 15). The Knoop microhardness obtained in each millimeter of the internal face. For microtensile bond strength, ninety restored in third molars were used, divided into six groups (n = 15). For Knoop microhardness, the Wilcoxon and Friedman test was used. For the microtensile bond strength were used the Two-way Anova test and Tukey's post-test (p &lt;0.05). The NH resin showed higher Knoop micro hardness than BF and it was observed that hardness value decreases as increases the thickness of the resin. There was no significant difference in microtensile bond strength comparing NH and BF. However, there was a significant difference between G2 and G4 for the NH groups, with the highest and lowest bond strength values, respectively. Thus, the new generation of the bulk-fill composite resin provided lower microhardness values as the thickness of the increments increases in comparison with the nanohybrid composite resin. The microtensile bond strength does not appear to have been influenced by the type of resin, or the thickness of the increment.

Effect of Operator Experience on Ability to Place Sequential, 2-mm-thick Increments of Composite.

To measure and compare the effect of operator experience in their ability to place composite in increments that are 2 mm thick. Fifteen volunteers from each class of freshmen, sophomores, juniors, and senior dental students and 15 clinical faculty (total number of volunteers = 75) were asked to restore a Class I preparation that was 5 mm in diameter and 8 mm deep from the cusp tips using three increments of composite that were each to be 2 mm thick. Once completed, the models were sectioned, and the thickness of each increment was measured. A repeated-measures analysis of variance (pre-set α=0.05) was used to compare the mean increment thickness with respect to operator experience level and increment sequence number. In addition, the proportion of operators placing clinically acceptable increments (between 1.75 and 2.25 mm thick), as well as the proportions from each group who placed increments that either were thinner or thicker than this range, was determined using nonparametric analyses. Overall, there was an increasing trend for groups with a higher experience level to provide mean incremental thickness values close to 2 mm. However, the likelihood of placing an increment that was thicker or thinner than the manufacturer-recommended thickness was not significantly different. Regardless of the increment value, only about one-third of the increments placed fell within the desired range of 1.75 to 2.25 mm. Operator experience had no overwhelming significant influence on the ability to place increments of composite that were between 1.75 and 2.25 mm thick. An operator has only about one chance out of three to place a composite increment within this clinically acceptable range when using no external measurement system.

Photon-Counting Multienergy Computed Tomography With Spectrally Optimized Contrast Media for Plaque Removal and Stenosis Assessment.

The aim of this study was to systematically evaluate the potential to combine investigational contrast media with spectrally optimized energy-thresholding of photon-counting detector computed tomography (PCCT) for subtraction of calcified plaques in a coronary artery stenosis phantom. A small vessel phantom containing 3 fillable tubes (diameter, 3 mm each) with calcified plaques was placed into an anthropomorphic chest phantom. The plaques had incremental thicknesses ranging from 0.3 to 2.7 mm, simulating vessel stenoses ranging from 10% to 90% of the lumen diameter. The phantom was filled with 5 different investigational contrast media (iodine, bismuth, hafnium, holmium, and tungsten) at equal mass concentrations (15 mg/mL) and was imaged on a prototype PCCT at 140 kVp using optimized, contrast media-dependent energy thresholds. Contrast maps (CMs) were reconstructed for each contrast medium by applying a linear 2-material decomposition algorithm. Image noise magnitude and noise texture of CM were compared among the contrast media using the noise power spectrum. Two blinded readers independently rated the vessel lumen visualization on short-axis and the overall subjective image quality on long-axis CM relative to iodine as the reference standard. Four readers determined the highest degree of stenosis that could be assessed with high diagnostic confidence on long-axis CM. Average image noise on CM was lower for tungsten (49 HU) and hafnium (62 HU) and higher for bismuth (81 HU) and holmium (165 HU) compared with iodine (78 HU). Noise texture of CM was similar among the contrast media. Interreader agreement for vessel lumen visualization on short-axis CM ranged from moderate to excellent (k = 0.567-0.814). Compared with iodine, lumen visualization of each reader was improved using tungsten (P < 0.001 for both readers), similar to improved using hafnium (P = 0.008, P = 0.29), similar using bismuth (P = 0.38, P = 0.69), and decreased using holmium (both, P < 0.001). Overall subjective image quality was similar for holmium and superior for tungsten, hafnium, and bismuth as compared with iodine. Higher-degree stenoses were evaluable with high confidence using tungsten (mean, 70%; interquartile range, 70%-70%), bismuth (70%; 60%-70%), and hafnium (75%; 70%-80%) compared with iodine (50%; 50%-60%) and holmium (50%; 50%-60%). Spectral optimization in PCCT combined with investigational contrast media can improve calcium subtraction and stenosis assessment in small vessels. Contrast maps of tungsten and, to a lesser extent, hafnium as contrast media yielded superior image noise properties and improved vessel lumen visualization, along with a higher subjective image quality compared with the reference standard iodine.

Flexure strength of methacrylate- and ormocer-based bulk fill resin composites: effect of material thickness and distance to photo-polymerization device

This study evaluated the effect of thickness and photo-polymerization distance on flexure strength of two bulk fill resin composites. In total, 96 rectangular-shaped resin composite bars were divided into eight experimental groups (n = 12/group) according to the three experimental factors; Factor 1: Material (X-tra fil and Admira Fusion X-tra), Factor 2: Thickness (2 mm and 4 mm) and Factor 3: photo-polymerization distance (2 mm and 8 mm). The bars were prepared with fixed 2 mm width and 2 mm length but differed in thickness (2 mm or 4 mm). The bars were light cured either at 2 mm or 8 mm distances. Flexure strength test was run at a crosshead speed of 0.5 mm/min. Data were analyzed using 3-Way ANOVA/Student t-test. Methacrylate-based resin composite exhibited significant higher flexure strength (p < 0.001). At 2 mm distance, there was no significant difference between 2 mm and 4 mm thicknesses for X-tra fil and Admira Fusion X-tra (p = 0.726 and p = 0.486, respectively). At 8 mm distance, both materials showed significantly higher flexure strength with 4 mm thickness compared to 2 mm thickness (p ˂ 0.001). Only X-tra fil with 2 mm thickness had no statistically significant difference on the flexure strength at 2 mm and 8 mm distances (p = 0.437). X-tra fil in 2 mm thickness cured at 8 mm distance and Admira Fusion X-tra in 4 mm thickness cured at 2 mm distance revealed the highest reliability. Methacrylate-based resin composite tested in this study had superior flexure strength compared to ormocer-based resin composite, regardless of the increment thickness and photo-polymerization distance.

Synthesis of model Al-Al2O3 multilayer systems with monolayer oxide thickness control by circumventing native oxidation

A hybrid thin film deposition system was built by combining physical vapor deposition (PVD) with atomic layer deposition (ALD) without breaking high vacuum, which was achieved by a chamber-in-chamber design. The vacuum is better than 1 × 10−5 Pa during the entire sample transfer process between the ALD and PVD chambers. The Al-Al2O3 multilayers synthesized by the PVD-ALD integrated system consist of ALD Al2O3 sublayers between pure PVD Al sublayers. The Al2O3 sublayers, with incremental thickness of 1 nm from 1 to 10 nm, effectively interrupted the grain growth of the ~250 nm thick Al sublayers. Native surface oxide formation on the PVD deposited pure Al sublayers was circumvented by keeping the substrate in high vacuum between processing steps. The pure Al sublayers are constituted of equiaxed grains with no epitaxial or texture relationship with the neighboring layers. The Al grain boundaries are parallel to the film growth direction and extend the height of each Al sublayer, to form a brick-and-mortar type microstructure. In this system, ALD allows precise control of the thickness of each ultrathin Al2O3 layer, to thicknesses below the native surface oxide thickness of pure Al, and avoids further natural oxidation through the low-oxygen environment of the PVD-ALD system.

Tribological study of HAp/CTS coatings produced by electrodeposition process on 316L stainless steel

Chitosan (CTS) is a biocompatible, bio-degradable, and bacterial copolymer that, combined with synthetic hydroxyapatite (HAp), is a good material option for orthopedic applications. In this regard, this work presents the tribological studies of three CTS/HAp composite coatings produced by an electrodeposition process at 15, 22.5, and 30 min of deposition time on 316L SS substrate. The coatings were formed by a CTS matrix with HAp particles with similar morphology for all the samples with incremental thickness as a function of deposition time. The coating presented a similar crystalline structure and the main vibrational mode of the CTS and HAp. The 30 min coating showed the best tribological properties, with a coefficient of friction value of 0.15 at 0.5 N and more stable friction force performance at 1 and 1.5 N load. Although this coating exhibited fractures, abrasion marks, and adhesion failure by the sliding-contact tests at 1 and 1.5 N, there is no remotion of the coating, thus protecting the substrate surfaces during all the test.

In-depth analysis of defects in TiO2 compact electron transport layers and impact on performance and hysteresis of planar perovskite devices at low light

Properties of the electron transport layer (ETL) are known to influence the performance of lead halide perovskite solar cells (PSCs). But so far very little emphasis has been given on the increased impact of this layer at low light. In this work we compare the effect of thickness and coverage of a TiO2 compact layer on the performance and hysteresis of methyl ammonium lead iodide planar devices tested under 200 lux vs. 1 sun illumination. Standard TiO2 layers are produced with incremental thickness and coverage using sequential spray pyrolysis of a Ti-acetylacetonate precursor (0–50 sprays, 1 spray ~ 1 nm TiO2). Thorough materials characterisation combining FEG-SEM, XPS, and cyclic voltammetry shows that a crystalline, nearly pin-hole free TiO2 layer is achieved by deposition of ≥15 sprays over small to large areas (0.2 mm2–1 cm2). Device performance is affected by two main parameters, namely the coverage yield and thickness of the TiO2 layer, especially under 200 lux illumination. A 25 vs. 50 sprays-TiO2 layer is found to provide the best compromise between coverage and thickness and avoid charge recombination at the TiO2/perovskite interface whilst minimizing resistive losses with 11.7% average PCE at 200 lux vs 7.8% under 1 sun. Finally, the analysis of I/V forward vs. reverse scans and open circuit voltage decay data suggests that hysteresis is greatly affected by the capacitive properties of the ETL at low light, whilst other phenomena such as ion migrations may dominate under 1 sun.

CHOROIDAL NEVUS TRANSFORMATION INTO MELANOMA PER MILLIMETER INCREMENT IN THICKNESS USING MULTIMODAL IMAGING IN 2355 CASES: The 2019 Wendell L. Hughes Lecture.

To analyze risk of nevus transformation into melanoma per millimeter increment. Retrospective analysis of 3,806 choroidal nevi for transformation into melanoma per incremental millimeter thickness (flat [≤1.0 mm], thin [1.1-2.0 mm], thicker [2.1-3.0 mm], and thickest [>3.0 mm]) RESULTS:: The median nevus thickness was 1.4 mm, and nevi were categorized (flat, thin, thicker, and thickest) in 1,140 (30%), 2052 (54%), 555 (15%), and 59 (<1%), respectively. There were differences in tumor diameter (2.5, 4.8, 7.5, and 9.3 mm; P < 0.01), optical coherence tomography detection of overlying subretinal fluid (<1, 4, 15, and 11%; P < 0.01), overlying retinal edema (<1, 3, 14, and 25%; P < 0.01), overlying drusen (23, 49, 64, and 64%; P < 0.01), overlying retinal pigment epithelial detachment (1, 4, 4, and 9%; P < 0.01), and overlying lipofuscin hyperautofluoresence (<1, 3, 6, and 7%; P < 0.01). Choroidal nevus transformation into melanoma (n = 90/2,355 cases, 3.8%) was found by Kaplan-Meier 7-year estimates (2.2, 6.1, 31.7, and 34.5%; P < 0.0001) and by hazard ratio (HR) compared with nevus ≤1.0 mm (not available, 4.7 [P = 0.01], 35.7 [P < 0.0001], and 52.0 [P < 0.0001]). For all thicknesses, those with growth displayed increase in mean basal diameter of 2.4 mm and thickness of 1.1 mm, optical coherence tomography increase in subretinal fluid (65%), autofluorescence increase in lipofuscin (40%), and ultrasonography increase in hollowness (30%). Multivariable risk factors, recalled by the mnemonic "To Find Small Ocular Melanoma Doing IMaging" (TFSOM-DIM) representing Thickness >2 mm (ultrasonography), Fluid subretinal (optical coherence tomography), Symptom vision loss (Va), Orange pigment (autofluorescence), Melanoma hollow (ultrasonography), and DIaMeter >5 mm, revealed factors per incremental thickness category (compared with flat) including thin (Fluid overlying, HR 6.1; DIaMeter >5 mm, HR 3.3), thicker (Fluid subretinal ≤3 mm from nevus, HR 5.7; Melanoma acoustic hollowness, HR 2.7), and thickest (Orange pigment, HR 9.1). Each incremental increase in choroidal nevus thickness demonstrated risk of growth into melanoma with HR (compared with flat) 4.7 for thin, 35.7 for thicker, and 52.0 for thickest. The increase from ≤2.0 mm to >2.0 mm thickness conferred the greatest rise for transformation.

The effect of curing lights and modes on dentin bond strength of bulk-fill composites applied in different thickness

To investigate shear bond strength (SBS) to dentin of a conventional and three bulk-fill composites applied in different increment thickness and cured by mono- and multi-wave LED LCUs. Two hundred and fifty-two extracted sound human molars were prepared for SBS test. The teeth were divided into four groups according to the resin composites used. Conventional composite: Tetric N-Ceram (control); high-viscosity bulk-fills: Tetric N-Ceram Bulk Fill, X-tra Fil, and SonicFill. Each group was subdivided (n = 7) according to increment thickness (2, 4, and 6 mm) and cured by standard mode of a mono-wave LED or two different modes (standard and xtra power) of a multi-wave LED. The failure mode was stereomicroscopically determined at 40× magnification. Data were analyzed using Three-way ANOVA and further comparisons were assessed by Bonferroni’s multiple comparison test. There were no significant differences within X-tra fil and Tetric N-Ceram Bulk Fill groups for any of the variables (p > 0.05). A significant decrease in SBS values with increase of layer thickness was observed for SonicFill and control groups. Also, curing mode had a significant effect on both composites at 6 mm thickness and standard mode of multi-wave LED caused the highest SBS value (p ˂ 0.05). Adhesive failure was the most common fracture pattern especially at 6 mm thickness applications. Based on the results of this study, the bulk-fill composites can be safely applied in one-step with 4 mm increments, although the examined composites performed better at 2 mm thickness. The performance of the composites at 6 mm increment may show differences related to the curing lights and modes.

Mechanical properties of bulk-fill versus nanohybrid composites: effect of layer thickness and application protocols

Objective: The objective of this study was to evaluate the compressive strength, flexural strength and flexural modulus of high-viscosity, low-viscosity bulk-fill, and conventional nano-hybrid resin composite materials alone and when covered with nano-hybrid resin composite at different incremental thicknesses on the bulk-fill composites. Materials and Methods: Specimens (N=60) were fabricated from the following materials or their combinations (n=10 per group): a) conventional nano-hybrid composite Z550 (FK), b) high-viscosity bulk-fill composite (Tetric N Ceram-TBF), c) low-viscosity bulk-fill composite SDR (SDR), d) Sonicfill (SF), e) SDR (2 mm)+FK (2 mm), f) SDR (4 mm)+FK (4 mm). After 24 h water storage, compressive strength was measured in a universal testing machine (1 mm/min). Additional specimens (N=40) (25x2x2 mm3) were made from FK, TBF, SDR and SF in order to determine the flexural strength and the flexural modulus, (n=10) and subjected to three-point bending test (0.5 mm/min). Data were analyzed using one-way ANOVA and Tamhane’s T2 post-hoc tests (p&lt;0.05). Results: The mean compressive strength (MPa) of the nano-hybrid composite (FK) was significantly higher (223.8±41.3) than those of the other groups (123±27 - 170±24) (p&lt;0.001). SDR (4 mm)+FK (2 mm) showed significantly higher compressive strength than when covered with 4 mm (143±30) or when used alone (146±11) (p&lt;0.05). The mean flexural strength (159±31) and the flexural modulus of FK (34±7) was significantly higher than that of the high- or low-viscosity bulk-fill composites (p&lt;0.001). The mean flexural strength of SF (132±20) was significantly higher compared to TBF (95±25) (p&lt;0.05). Conclusion: Bulk-fill resin composites demonstrated poorer mechanical properties compared to nano-hybrid composite but similar to that of SF. Increasing the thickness of low-viscosity bulk-fill composite (SDR) from 2 to 4 mm underneath the nano-hybrid composite (FK) can improve the mechanical properties of the bulk-fill composites. KeywordsBulk-fill composites; Compressive strength; Flexural modulus; Flexural strength; Mechanical properties.

Numerical investigation of design parameters for optimization of the in-situ ultrasonic fouling removal technique for pipelines

Fouling build-up in engineering assets is a known problem and, as a solution, the application of power ultrasonic for in-situ fouling removal has gained much attention from the industry. Current state-of-the-art fouling removal includes the use of hydraulic, chemical and manual techniques. Much research has been conducted to advance the knowledge on the potential uses of ultrasonics across different fouling applications, primarily in reverse osmosis membranes and heat exchangers. However, the optimization of in-situ ultrasonic fouling removal has not yet been investigated and is still in its infancy. The present study uses a previously experimentally-validated numerical model to conduct a parametric study in order to optimize the technique. Focus was given to the adoption of ultrasonics for large diameter pipes. Therefore, this investigation was conducted on a 6 in. schedule 40-carbon steel pipe. Parameters investigated include: optimum number of transducers to remove fouling in long pipes from a single transducer location; performance at elevated temperature; different fluid domains; optimum voltage; variety of input signals and incremental thickness of fouling. Depending on the particular studied conditions, the possible fouling removal of up to +/−3 m from a single transducer location is demonstrated in a 6 in. schedule 40 carbon steel pipe.