Successive Boronizing and Austempering for GGG-40 Grade Ductile Iron

Boronizing and austempering were successively applied to a GGG-40 grade ductile iron in order to combine the advantages of both process in a single treatment. This new procedure formed a 30 μm thick boride layer on the surface with subsurface matrix structure consisted of acicular ferrite and retained austenite. Reciprocating wear tests showed that successive boronizing and austempering exhibited considerably higher wear resistance than conventional boronizing having a subsurface matrix structure consisting of ferrite and pearlite.     

Antibacterial effect of dental cements evaluated using agar diffusion test

Purpose: Secondary caries can occur around the restoration, fixed prosthesis, and orthodontic band margins because of cariogenic bacteria. Long-lasting antibacterial effectiveness of dental cements used contemporarily can reduce this phenomenon. The purpose of this study was to examine the antibacterial activities of nine dental cements (BisCem^®, Super-Bond C&B, Rely X^TM, Panavia^TM F 2.0, Variolink^® II, Unitek^TM Multi Cure, Multilink^® Automix, Clearfil^TM Esthetic Cement, Transbond^TM LR) using agar diffusion test. Materials and methods: The test materials were inserted into the wells of Muller Hinton agar plates inoculated with Streptococcus mutans and Streptococcus salivarious. The diameters of the inhibition zones produced around the materials were measured after 24 h of incubation. Two-Way ANOVA, the Kruskal-Wallis, and the Mann–Whitney U tests at a significance level of p < 0.05 were analyzed for the results. Results: Unitek Multi Cure cement exhibited a significant difference from the control group against both S. mutans and S. salivarious (p < 0.05). While the zone of inhibition of Unitek Multi Cure cement was shorter (8.50 ± 1.77) than the control group (12.63 ± 1.30), Unitek Multi Cure had antibacterial effect against S. mutans and S. salivarious (p < 0.05). S. mutans displayed a significantly lower resistance to Unitek Multi Cure, BisCem, and Superbond C&B than S. salivarious (p < 0.05). Conclusion: Conventional glass ionomer cement, Unitek Multi Cure, exhibited greatest in vitro antibacterial activity against both S. mutans and S. salivarious. Formation of dental caries had been suppressed by the fluoride-releasing GICs.     

Irradiation effect in WO3 thin films

Tungsten oxide (WO₃) films were prepared on indium tin oxide coated glass substrates and Corning glass substrates by sol–gel deposition. The samples coated on the glass substrates have been irradiated to approximately 0.93–21.1 kGy dose using Co-60 gamma radioisotope. Co-60 radioisotope changed the color of the WO₃ films on samples after the irradiation. Their color turned to brownish color tones depending on the applied dose. Optical and structural properties of the samples are examined for both gamma irradiated and unirradiated coated samples. To compare the effect of the irradiation on the electrochromic properties, additional measurements were done with WO₃ coated on ITO substrates irradiated by gamma rays, separately. The coated films were characterized by atomic-force microscopy, NKD-analyzer and cyclic voltammograms. The influence of irradiation on the spectra of transmittance and on the surface structure has been investigated. These showed that the surface texture was changed dramatically by the irradiation. The electrochemical insertion and removal of lithium and proton ions was carried-out using 1 M LiClO₄ propylene carbonate (PC) electrolyte and 1 M KCl in aqueous solutions,respectively.     

Integration of GIS with USLE in Assessment of Soil Erosion

A Geographic Information System (GIS) has been integrated with the USLE (Universal Soil Loss Equation) model in identification of rainfall-based erosion and the transport of nonpoint source pollution loads to the Gediz River, which discharges into the Aegean Sea along the western coast of Turkey. The purpose of the study is to identify the gross erosion, sediment loads, and organic N loads within a small region of the Gediz River basin. Similar studies are available in literature, ranging from those that use a simple model such as USLE to others of a more sophisticated nature. The study presented here reflects the difficulties in applying the methodology when the required data on soil properties, land use and vegetation are deficient in both quantity and quality, as the case is with most developing countries.     

Improvement of thermal stability and gamma-ray absorption in microwave absorbable poly(methyl methacrylate)/graphene nanoplatelets nanocomposite

The graphene nanofiller (2 wt%) was dispersed in poly(methyl methacrylate) by in situ polymerization method. The optimum high frequency (microwave) absorption was evaluated at X-band due to changes in the scattering parameters (determined by using a vector network analyzer). The slight improvement has been attained in gamma attenuation coefficient of the polymer nanocomposite by using gamma transmission technique. The addition of graphene nanoplatelets (2 wt%) resulted in a thermal improvement from 196.73 to 243.00°C (with 5% weight loss) in TGA analysis. The graphene nanoplatelets provided an optimum decrease in scattering of the microwaves due to the elimination of the defects and the prevention of the agglomeration of the graphene nanoplates. The improvement of microwave absorption (between 8 and 12 GHz) suggested that the nanocomposite was a suitable candidate as a microwave absorbing material. This multipurpose nanocomposite has provided thermal stability and it has ensured the optimum gamma-ray and microwave absorption depending on the development of the structural properties. The development of these physical characteristics has enabled to improve the electrical conductivity as a result of the progress in the structural properties.     

Effect of annealing temperature on ZnO:Al/p-Si heterojunctions

Al-doped, zinc oxide (ZnO:Al) films with a 1.2 at.% Al concentration were deposited on p-type silicon wafers using a sol-gel dip coating technique to produce a ZnO:Al/p-Si heterojunction. Following deposition and subsequent drying processes, the films were annealed in vacuum at five different temperatures between 550 and 900 °C for 1 h. The resistivity of the films decreased with increasing annealing temperature, and an annealing temperature of 700 °C provided controlled current flow through the ZnO:Al/p-Si heterojunction up to 20 V. The ZnO:Al film deposited on a p-type silicon wafer with 1.2 at.% Al concentration was concluded to have the potential for use in electronic devices as a diode after annealing at 700 °C.     

ANN modeling of the bremsstrahlung photon flux in tantalum target

Bremsstrahlung photons produced by 15 MeV electron beam are simulated using the Monte Carlo code of FLUKA. Tantalum foils have been chosen as a target material in the simulation, and the obtained photon spectrum has been analyzed with artificial neural network (ANN) technique. In the training ANN model, the thicknesses and energy values of bremsstrahlung photons for the Ta target have been used as input. In this study, we observed that the trained ANN model is consistent with simulation results.     

Remote sensing of tea plantations using an SVM classifier and pattern-based accuracy assessment technique

Tea (Camellia sp.) and its plantation are very important on a worldwide scale as it is the second-most consumed beverage after water. Therefore, it becomes necessary to map the widely distributed tea plantations under various geographies and conditions. Remote-sensing techniques are effective tools to map and monitor the impact of tea plantation on land-use/land-cover (LULC). Remote sensing of tea plantations suffers from spectral mixing as these plantation areas are generally surrounded by similar types of green vegetation such as orchards and bushes. This problem is mainly tied to planting style, topography, and spectral characteristics of tea plantations, and the side effects are observed as low classification accuracies after the classification process. In this study, to overcome this problem, a three-step approach was proposed and implemented on a test area with high slope. As a first step, spectral and multi-scale textural features based on Gabor filters were extracted from high resolution multispectral digital aerial images. Similarly, based on the wavelength range of the sensor, a modified normalized difference vegetation index (MNDVI) was applied to distinguish the green vegetation cover from other LULCs. The second step involves the classification of multidimensional textural and spectral feature combinations using a support vector machine (SVM) algorithm. As a final step, two different techniques were applied for evaluating classification accuracy. The first one is a traditional site-specific accuracy assessment based on a confusion matrix calculating statistical metrics for different feature combinations. The overall accuracy and kappa values were calculated as 93.68% and 0.92, 93.82% and 0.92, and 97.40% and 0.97 for LULC maps produced by red, green, and blue (RGB), RGB + MNDVI, and RGB + MNDVI + Gabor features, respectively. The second accuracy assessment technique was the pattern-based accuracy assessment. The technique involves polygon-based fuzzy local matching. Three comparison maps showing local matching indices were obtained and used to compute the global matching index (g) for LULC maps of each feature set combination. The g values were g_(RGB) (0.745), g_(RGB+MNDVI) (0.745), and g_{(RGB+MNDVI+Gabor)} (0.765) for comparison maps. Finally, based on accuracy assessment metrics, the study area was successfully classified and tea plantation features were extracted with high accuracy.     

Thermal Oxidation of Cold Sprayed Titanium-Based Coating Deposited on Co-Cr Alloy

This study focuses on the surface modification of a medical grade Co-Cr alloy via combining cold spray and thermal oxidation processes. After deposition of a Ti96-Al4 (wt.%) coating, samples were oxidized at 600 °C for 60 h in air. Oxidation transformed the coating into a dual-layered structure comprising an outer oxide layer (mainly rutile) with a diffusion layer (mainly oxygen enriched titanium and Ti-Al intermetallics) beneath it. Formation of new phases made the diffusion layer brittle and prone to fracture during pull out tests. Scratch and Rockwell-C tests confirmed good adhesion between the oxide and underlying diffusion layers, having average hardness as 1297 HV and 387 HV, respectively. The dual-layer coating exhibited excellent wear performance in a 0.9 wt.% NaCl solution against sliding action of alumina ball as compared to Co-Cr substrate, especially at contact pressures?<?1200 MPa, while the maximum in vivo contact pressure is?<?15 MPa for load-bearing orthopedic implants. Furthermore, the release of the aluminum from the dual-layer coating into 0.9 wt.% NaCl solution is lower than the permissible limit stated by the International Agency for Research on Cancer.