On the Convergence Acceleration of Slowly Convergent Sums Involving Oscillating Terms

In this paper, an acceleration technique based on a Kummer’s transformation method is developed for some slowly convergent series. The original series is decomposed into two parts; one part being rapidly convergent and the other part being slowly convergent. Then the series in the slowly convergent part is expressed as integrals of some auxiliary functions and subsequently they are written in terms of polynomials whose coefficients are given by the zeta functions. The given method is computationally oriented and does not involve much analytic effort. A numerical example is provided to illustrate the usage and the efficiency of the method.     

Electrochemical synthesis of polyaniline films on zinc-cobalt alloy deposited carbon steel surface in sodium oxalate

Polyaniline (PANI) coatings were electropolymerized on zinc-cobalt alloy deposited carbon steel (CS/ZnCo) electrode from an aqueous sodium oxalate solution using three different scan rates in cyclic voltammetric technique. Scanning electron microscopy (SEM) was used to analyze the surface morphology of the polymer film. The SEM images showed that the increase in scan rate induced an increase in grain size of the PANI film. The corrosion behavior of CS/ZnCo electrodes with and without PANI film in 3.5% NaCl solution were investigated through electrochemical impedance spectroscopy (EIS) and anodic polarization studies. The results of the study showed that the PANI coatings provided significant and effective protection for the CS/ZnCo electrode, in preventing corrosion. In addition, the PANI film that was synthesized at a high scan rate, exhibited the best anti-corrosive performance due to the formation of protective oxide layers through its catalytic efficiency.     

Energy policies of Turkey during the period 1923–2003

Turkey has been developing since the foundation of the Republic of Turkey in 1923. Turkish Government played a leading role in energy production and in energy use, as well as in other fields, and implemented several policies to increase electricity production. By 1950s, thermal power plants were used commonly in electricity production. In the following years, hydroelectric power plants were put into operation in order to use the considerable amount of water resources of the country. Coal-fired power plants using national resources accounted for 70–80% of the thermal electricity production. After 1960s, oil, an imported resource, was replaced with national resources due to two petroleum crises. Therefore, the proportion of use of lignite in the energy field increased. By 1980s, energy production lead by the government went on. Afterwards, applications of liberal economy policies resulted in implementation of different energy production methods, and the country had a increasing tendency to meet energy demand by imports as a result of improvement in international economic relations. Natural gas became prevalent in the country as well as all over the world and accounted for 45% of the electricity production in 2003. In this paper, implemented policies in the energy field during different periods since the foundation of the Republic of Turkey in 1923 was investigated.     

Scattering characteristics of FSSs with triangular conducting elements

In this paper, scattering characteristics of dielectric backed frequency selective surfaces (FSSs) having triangular conducting elements are investigated for both transverse magnetic and transverse electric incident plane waves. Since triangular conducting elements are etched periodically on such a surface, incident and scattered fields are expressed as Floquet modes. Using Floquet’s theorem and satisfying the required boundary conditions an integral equation is obtained for the induced current density on the surface of a triangular conducting element in one periodic cell. This induced current density is expressed as a finite sum of piecewise triangular basis functions having unknown coefficients. The resulting integral equation is then converted to a linear matrix equation by using the Method of Moments. Taking the inverse transform of the matrix equation yields the unknown current coefficients which are finally used to compute the reflection and transmission coefficients. Since there are no theoretical or experimental results for FSSs comprising of triangular conductors, verification of the algorithm developed is carried out by comparing the numerical results obtained using this algorithm with the experimental and theoretical results in the literature for FSSs composed of strips and L-shaped conductors. For this, in the algorithm, appropriate arms of the triangles are removed to conform them into strips or L-shaped conductors. Results obtained for strips and L-shaped apertures by using this algorithm are in excellent agreement with the results in the literature.     

The illumination intensity and applied bias voltage on dielectric properties of au/polyvinyl alcohol (Co,Zn‐doped)/n‐Si Schottky barrier diodes

The Au/polyvinyl alcohol (PVA) (Co, Zn‐doped)/n‐Si Schottky barrier diodes (SBDs) were exposed to various illumination intensities. Illumination effect on the dielectric properties has been investigated by using capacitance–voltage (C–V) and conductance–voltage (G/ω–V) characteristics at 1 MHz and room temperature. The values of dielectric constant (ε′), dielectric loss (ε″), loss tangent (tanδ), electric modulus (M′ and M″), and AC electrical conductivity (σ_AC) were found strongly intensity dependent on both the illumination levels and applied bias voltage especially in depletion and accumulation regions. Such bias and illumination dependency of these parameters can be explained on the basis of Maxwell–Wagner interfacial polarization and restructuring and reordering of charges at interface states. In addition, the ε′–V plots also show an intersection feature at ～ 2.8 V and such behavior of the ε′–V plots appears as an abnormality compared with the conventional behavior of an ideal SBD. The obtained results revealed that illumination intensity enhances the conductivity of Au/PVA(Co, Zn‐doped)/n‐Si SBD. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

A Novel Approach to the Synthesis of Alloy: PEG400 Containing ZnNi and ZnNiCr Alloy Coatings and Their Anticorrosion Performance

Metallurgical and Materials Transactions A - ZnNi and ZnNiCr alloy coatings were electrochemically deposited onto carbon steel (CS) in the presence of PEG400 for the first time. Scanning electron...     

Pure YbB6 nanocrystals: First time synthesis via mechanochemical method

The present report provides a new insight into the high purity synthesis of rare-earth ytterbium hexaboride, YbB₆ nanocrystals, without using a solid state reaction or metathesis reaction methods. Single phase YbB₆ nanocrystals were synthesized for the first time by direct and dry milling of Yb₂O₃, B₂O₃ and Mg starting powders. The effects of milling period on the formation and crystallite size of milled nanoparticles have been investigated. Single phase Rietveld refinement confirmed the cubic structure in Pm-3m space group with the lattice parameters a?=?b?=?c?=?3.1444(2)?Å, and 68?nm particle size of YbB₆ phase. The YbB₆ nanocrystals revealed a weak ferromagnetism and plus paramagnetic behavior. The ferromagnetic and paramagnetic behavior of the YbB₆ are correlated to the large surface-to-volume ratio of ball-milled nanocrystals, and the presence of boron-rich and boron-deficient phases.     

Radiation from a Current Filament Located inside a Cylindrical Frequency Selective Surface

We consider electromagnetic field radiation properties of a current filament placed at the origin of a cylindrical frequency selective surface (CFSS). The CFSS consists of free standing metal strips with two‐dimensional periodicity. The analysis is based on a cylindrical Floquet mode wave expansion technique. We observed that near the half wavelength resonance frequencies, there exist some specific frequencies at which the surface becomes totally transparent.     

An improved convergence acceleration method for the strip grating cylindrical surface problem

Modal solutions of circular cylindrical structure problems sometimes involve products of Bessel functions under infinite summations that are slowly convergent. In this paper, we give a convergence acceleration method for an infinite summation arising from the numerical solution of a scattering problem. The philosophy of the method could be extended or modified for the computation of other complicated circular cylindrical structure problems.