Synthesis of three-dimensional light fields with binary spatial light modulators

Computation of a binary spatial light modulator (SLM) pattern that generates a desired light field is a challenging quantization problem for which several algorithms have been proposed, mainly for far-field or Fourier plane reconstructions. We study this problem assuming that the desired light field is synthesized within a volumetric region in the non-far-field range after free space propagation from the SLM plane. We use Fresnel and Rayleigh-Sommerfeld scalar diffraction theories for propagation of light. We show that, when the desired field is confined to a sufficiently narrow region of space, the ideal gray-level complex-valued SLM pattern generating it becomes sufficiently low pass (oversampled) so it can be successfully halftoned into a binary SLM pattern by solving two decoupled real-valued constrained halftoning problems. Our simulation results indicate that, when the synthesis region is considered, the binary SLM is indistinguishable from a lower resolution full complex gray-level SLM. In our approach, free space propagation related computations are done only once at the beginning, and the rest of the computation time is spent on carrying out standard image halftoning.     

Thermal,morphological, and spectral changes after Er,Cr:YSGG laser irradiation at low fluences on primary teeth for caries prevention

The aim of this study was to determine the temperature increase in the pulp chamber and possible thermal effects on molecular structure of primary teeth during the irradiation with Er,Cr:YSGG laser. Primary central incisors were divided into three groups (n = 20). Labial surfaces in each group were irradiated by Er,Cr:YSGG laser within different power and frequencies as following groups: I: 0.25 W, 20 Hz, II: 0.50 W, 20 Hz, III: 0.75 W, 20 Hz. A thermocouple was placed inside the pulp chamber so that the temperature increments were recorded during the enamel irradiation. Morphological changes of enamel surfaces were experimentally evaluated by SEM. Fourier‐transform infrared spectroscopy and RAMAN analyses were carried out to determine the differentiations in the molecular structure. The experimental results obtained were analyzed statistically by means of one‐way analysis of variance. Statistically significant differences were detected between groups (p < .05). Group III exhibited the highest values for the temperature parameters. Besides, the conical craters, cracks, and formation of ablation areas were observed for all the groups. Also, it was obtained that the hydroxyapatite lost the hydroxyl ions due to the thermal effect of the laser. Temperature rise throughout the Er,Cr:YSGG laser irradiation for prevention of primary enamel demineralization presented a positive correlation with the laser output power level. The formations of adverse morphological and spectral changes were detected on the surface of teeth after the laser application. On this basis, the Er,Cr:YSGG laser applications should be treated with much more caution considering enamel surface and pulpal tissues in primary teeth.     

Biological activities and chemical composition of three honeys of different types from Anatolia

In this study, we investigated and compared some chemical properties and in vitro biological activities of three different types of Turkish honey. The first two honey samples were monofloral from chestnut and rhododendron flowers, collected from the east Black Sea region, and the third sample was the heterofloral form of astragalus (Astragalus microcephalus Willd.), thyme (Thymus vulgaris) and other several mountain flowers, collected from Erzincan in Eastern Anatolia. The chemical properties of the honey samples, such as total moisture, ash, total protein, sucrose, invert sugar, diastase activity, hydroxymethylfurfural content and acidity, were determined. Total phenolics, superoxide radical- and peroxynitrite-scavenging activities, and ferric reducing/antioxidant power measurements were used as antioxidant capacity determinants with ±-catechin, butylated hydroxytoluene, ascorbic acid, and trolox^® used as reference. The antimicrobial activity was studied by the agar diffusion method, using eight bacteria and two yeasts. The mineral contents were also determined by an AAS method. The chestnut flower honey had the highest phenolic content, superoxide radical-scavenging activity and reducing power, while the heterofloral honey sample exhibited the highest peroxynitrite-scavenging activity. The antioxidant activities were also found to be related to the sample concentrations. The mineral content of the chestnut honey was much higher than the others. The samples showed moderate antimicrobial activity against some microorganisms, especially Helicobacter pylori ATCC 49503, Staphylococcus aureus ATCC 25923, Bacillus subtilis ATCC 6633, Candida tropicalis ATCC 13803 and Candida albicans ATCC 10231. The honey samples studied proved to be a good source of antioxidants and antimicrobial agents that might serve to protect health and fight against several diseases.     

High temperature wear and friction properties of duplex surface treated bearing steels

Duplex treatments by thermo reactive diffusion (TRD) chromizing and puls plasma nitriding were carried out on AISI 52100 and 8620 bearing steels. Tribological behaviors of TRD chromized and duplex treated bearing steels were investigated against Al₂O₃ ball in ball-on-disc system at room temperature and 500 °C. The samples were pack chromized in a furnace at temperature of 1000 °C for 5 h. After chromizing, the samples were puls plasma nitrided for 5 h at 500 °C. The coated steels were characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), scratch and microhardness testing. Plasma nitriding of chromized steels increased the total thickness of the compound layer. The subsequent plasma nitriding increased the surface hardness to 2135 HK_0.025 due to the formation of CrN and Cr₂N. The surface hardness and scratch resistance of coating can be increased with duplex treatment of chromizing followed by plasma nitriding, resulting in high wear resistance. Tribological tests indicated that puls plasma nitriding process decreased the coefficient of friction values and wear rate of the chromized steels at room temperature and 500 °C. Also, examination of the worn surface of the samples showed that particularly at high temperature, the oxidized compact layer occurs and tribo-oxidation played an important role in oxidation behaviour of the steels after the duplex treatment.     

Xanthan gum production of Xanthomonas spp. Isolated from different plants

Xanthan gum were produced from the following Xanthomonas strains; standard strain Xanthomonas campestris NRRL B-1459 and isolated strains Xanthomonas arbicola pv. juglandis, Xanthomonas axonopodis pv. vesicatoria, Xanthomonas axonopodis pv. begonia, Xanthomonas axonopodis pv. dieffenbachia. The viscosity features of the xanthan gums obtained were determined at 25–80°C with different pH values and were compared to commercial xanthan gum. Our results indicate that X. arbicola pv. juglandis showed the highest productivity (8.22±1.52 g/L gum). This was followed by X. axonopodis pv. begonia (7.74±1.30 g/L gum), and the control bacterial strain X. campestris NRRL B-1459 (7.46±0.28 g/L gum). X. axonopodis pv. vesicatoria showed the lowest productivity (6.40±0.55 g/L gum). No xanthan gum could be obtained from X. axonopodis pv. dieffenbachia. Xanthan gum produced by X. axonopodis pv. vesicatoria showed the highest viscosity value (428 mPa·sec at 1% solution) in all Xanthomonas strains isolated from plants.     

Investigation of performance and emission characteristics of waste cooking oil as biodiesel in a diesel engine

Biodiesel is one of the most popular prospective alternative fuels and can be obtained from a variety of sources. Waste frying oil is one such source along with the various raw vegetable oils. However, some specific technical treatments are required to improve certain fuel properties such as viscosity and calorific value of the biodiesel being obtained from waste cooking oil methyl ester (WCOME). Various treatments are applied depending on the source and therefore the composition of the cooking oil. This research investigated the performance of WCOME as an alternative biofuel in a four-stroke direct injection diesel engine. An 8-mode test was undertaken with diesel fuel and five WCOME blends. The best compromise blend in terms of performance and emissions was identified. Results showed that energy utilization factors of the blends were similar within the range of the operational parameters (speed, load and WCOME content). Increasing biodiesel content produced slightly more smoke and NOx for a great majority of test points, while the CO and THC emissions were lower.     

Adaptive path selective fuzzy decorrelating detector under impulsive noise for multipath fading CDMA systems

This letter proposes a novel adaptive path selective fuzzy decorrelating (APSFD) detector for direct-sequence code- division multiple-access (DS-CDMA), systems with time-varying multipath fading channels under impulsive noise. The proposed detector combines adaptive path selective decorrelating (APSD) detector with a fuzzy median filter which is based on fuzzy rank ordering of samples to eliminate the effect of impulsive noise. Simulation results clearly show that the proposed detector eliminates the effect of impulsive noise and improves the performance of APSD detector under high impulsive noise.     

Combination of Different Size Distributions for Mineral Particles by Applying Experimentally Determined Apparent Mean Shape Factor

As is well known, the behavior of systems of fine particles is strongly dependent on the size of the individual particles, and the size effects become increasingly important as the particles become progressively smaller. This study covers two different size analysis techniques, sieving and laser diffraction measurement, and constructs whole size distribution for different mill (ball and rod) products of some industrial minerals: barite and quartz minerals. A smooth overlap of corrected laser diffraction size distribution and sieve size distribution was obtained by applying the particle size with the apparent mean shape factor shifting to the right side of the curve for the rod-milled barite and ball- and rod-milled quartz. The apparent mean shape factors determined from the corrected particle size distributions were found to be 1.02 and 1.39 for ball- and rod-milled barite and 1.29 and 1.25 for ball- and rod-milled quartz, respectively. The results indicate that the ball-milled products of barite mineral have more regular (rounder in shape) particles than those of rod-milled barite, but there are not significant differences between the shape factors of ball- and rod-milled products of quartz mineral, i.e., both of them have irregular particles that deviate from spherical shape, as evident from the SEM pictures taken.