The Tradeoff Between Bit Error Rate and Optical Link Distance Using Laser Phase Noise Fixing Process in Coherent Optical OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is a suitable solution thanks to its many advantages known in wireless communications. On the other hand, optical communications is also used as a backbone to transmit and receive large data rates with economical and good performance. Recently, fiber optical communication and OFDM method have been combined to obtain both advantages in a communication link called Coherent Optical OFDM (CO-OFDM). In this study, Bit error rate (BER) versus distance variations are investigated for a constant signal to noise ratio in CO-OFDM systems. Results also show the performance of the CO-OFDM system at different data rates and distances for one RF carrier and one optical carrier. So far, the Telecommunication Standardization Sector standards have suggested 81 channels between 192.1 and 196.1 THz in C band. Extending the number of channels using 111 more channels between 185.9 and 191.4 THz in L band where optical amplifiers and laser sources are available, the total number of channels reaches up to 192. In this research, CO-OFDM technique is modeled and simulated designing a Monte Carlo simulation. Dense wavelength division multiplexing (DWDM) is the key factor to obtain 3 Tb/s (192*16 Gb/s) utilizing only one optical cable by covering whole C and L bands. To the best of our knowledge, this work shows the first BER versus Distance variations in a CO-OFDM communication link for 3 Tb/s.     

Dynamic modeling of a horizontal washing machine and optimization of vibration characteristics using Genetic Algorithms

In this work, a 2D dynamic model of a horizontal axis washing machine is derived regarding the rotation plane in order to examine the vibration characteristics of the spin-cycle and improve the design proposing a new optimization scheme based on Genetic Algorithms (GA). The dynamic model is numerically simulated and the outputs are validated using experimental vibration data acquired from a test-rig including the drum and the motor of a horizontal-axis washing machine. The measurements are performed using piezo-transducers and a novel measurement scheme is used to obtain displacement values from acceleration data as well as estimating the instantaneous frequency of the rotation with appropriate signal processing. This study has two main contributions: (i) a new method for design improvement applying GA to optimization of vibration characteristics for the horizontal-axis washing machines, and (ii) a novel measurement method yielding the displacement in 2D and instantaneous frequency of vibration from acceleration data. While the GA is contributing to passive improvement methods in the field, the novel measurement method opens the way for low-cost diagnosis and active-vibration control of washing machines.     

Synthesis,characterisation and electrochemical investigation of phthalocyanines with pendant 4‐{2‐[2‐(4‐tert‐butylphenoxy)ethoxy]ethoxy} substituents

In this study, a novel metal‐free phthalocyanine and three metallophthalocyanines carrying four 2‐[2‐(4‐tert‐butylphenoxy)ethoxy groups on the periphery were prepared by cyclotetramerisation of a dinitrile derivative in the presence of the corresponding divalent metal salts [zinc(ii ), cobalt(ii ), copper(ii )]. These new phthalocyanine compounds have been characterised by infrared, ¹H and ¹³C nuclear magnetic resonance and electrospray mass spectroscopies and elemental analysis. The electrochemical properties of the metal‐free, zinc(ii ) and cobalt(ii ) phthalocyanines were investigated by cyclic voltammetry and differential pulse voltammetry methods. The cobalt complex showed a metal‐based reduction process, while the metal‐free and zinc(ii ) phthalocyanines showed ligand‐based electron transfer processes. It has been found that the absorption spectra substantially depend on concentration. It has been shown that these changes are attributable to the association of the phthalocyanine molecule. The number of molecules in the associates and the equilibrium constants for this association are determined.     

A Photoluminescent Polymeric 2D Silver(I) Complex Exhibits a Fishbone-like 1D Silver Cluster and New Coordination Mode of the Pyridine-2,3-Dicarboxylate

In this study, a novel organic–inorganic hybrid compound with AgNO₃ and 2,3-pyridinedicarboxylic acid (H₂pydc), [Ag₂(μ₆-pydc)]_n (1) has been synthesized. The molecular structure of complex has been determined by the single crystal X-ray diffraction. The complex has been observed to crystallize in the monoclinic space group P2₁/c. The asymmetric unit of compound consists of two crystallographically different Ag(I) centers and one pydc ligand. The Ag1 and Ag2 adopt tetrahedral and T-shaped geometries, respectively. At the same time, the silver(I) compound consists of a fish bone similar to the 1D silver cluster. Furthermore, novel coordination mode shown by H₂pydc indicates that the crystal exhibits photoluminescence in the solid state at room temperature.     

Determination of optical band gap of ZnO:ZnAl2O4 composite semiconductor nanopowder materials by optical reflectance method

ZnO:ZnAl₂O₄ composite semiconductor nanopowder materials were synthesized by sol gel method. X-ray diffraction results reveal that Al doped ZnO samples have a polycrystalline hexagonal structure with a?=?3.2506 Å, c?=?5.2079 Å lattice parameters. The crystallite size of the ZnO samples is decreased with increasing Al content. Atomic force microscope results indicate the presence of micro/nanohexagons with different sizes from 128 to 166 nm. Optical band gap of the ZnO samples is decreased and reaches a low value of 2.82 eV for 20 % Al. The electrical conductivity dependence of temperature confirms that ZnO:ZnAl₂O₄ composite semiconductor nanopowder materials exhibit semiconductor behavior.     

Viscous-dissipation effects on the heat transfer in a Poiseuille flow

In this study, laminar heat-convection in a Poiseuille flow of a Newtonian fluid with constant properties is analyzed by taking the viscous dissipation into account. At first, both hydrodynamically and thermally fully-developed flow case is investigated. Then, consideration is given to thermally-developed laminar forced-convection. The axial heat-conduction in the fluid is neglected. Two different thermal boundary-conditions are considered: the constant heat-flux and the constant wall-temperature. Both the hot-wall and the cold-wall cases are considered. In the literature, the viscous-dissipation effect is commonly represented by the Brinkman number. Several different definitions of the Brinkman number arise depending on the thermal boundary conditions. Either for the thermally fully-developed case or the thermally-developing case (the Graetz problem), temperature distributions and the Nusselt numbers are analytically determined as functions of the Brinkman number.     

Effect of replacing beef fat with olive oil on quality characteristics of Turkish soudjouk (sucuk)

Four formulation of Turkish soudjouks were produced in three replicates by traditional methods as follows; one control (C) using 85% beef and 15% beef fat and three treatments by replacing 20, 40 and 60% of beef fat with virgin olive oil incorporated as pre-emulsified fat (PEF) with soy protein isolate (SPI), respectively. It was found that the moisture content and pH decreased while fat and ash content increased on the 21st day of fermentation and in the ripening period. Cholesterol content decreased depending on the amount of incorporated olive oil to the formulation, which shows the addition of olive oil in soudjouks reduces the cholesterol content (P<0.05). TBA values were affected by the amount of incorporated olive oil and the highest TBA value was found for with the 60% olive oil replacement. Oleic and linoleic acid contents were high while other fatty acid contents were low for the 40 and 60% olive oil samples compared with controls. Sausages with 40% olive oil received high evaluation from the panel for appearance and texture but there was no significant difference (P>0.05) between samples in the terms of color and general acceptability. It is concluded that replacement of beef fat with olive oil had a positive effect on sensory quality and on reducing the cholesterol content of soudjouks.     

Investigation of surface roughness values of various restorative materials after brushing with blue covarine containing whitening toothpaste by two different methods: AFM and profilometer

The aim of this study is to evaluate the effect of whitening toothpaste on the surface roughness of resin-based restorative materials by different measurement methods. Twenty four specimens from each of human enamel, a microhybrid composite and two nanohybrid composites discs (8.0 diameter × 4.0 mm thick) were divided into two groups (n = 12) according to toothbrushing solutıon and subjected to simulation toothbrushing (30,000 cycles) with both distilled water and whitening toothpaste containing blue covarine. Surface roughness was examined using atomic force microscopy (AFM), profilometer, and scanning electron microscopy (SEM), and the data obtained were subjected to analysis. Ra values of Tescera (TES) were significantly higher than Sonicfill 2 (SF2) when brushing both toothbrushing solutions for initial or 30,000 cycles. Roughness increased for SF2 and TES when brushed for 30,000 cycles and was higher than enamel and Herculite XRV Ultra (HXU). Human enamel was obtained lower surface roughness values brushed with toothpaste compared with distilled water. Evaluation of the surface roughness of control groups using the AFM revealed no statistically significant difference between the groups, but significant differences were found using a profilometer. The use of abrasive whitening toothpaste containing blue covarine and the number of brushing cycles affect the surface properties of human enamel and the restorative material, and also, the clinical success of the restoration. Toothbrushing for 30,000 cycles increased the surface roughness of all materials. The type of toothbrushing solution partially has affected surface roughness.