1,452 research outputs found
A study on certain periodic Schrödinger equations
No full textSubmission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2015-09-29 without embargo termsThe student, Seckin Demirbas, accepted the attached license on 2015-06-25 at 21:24.The student, Seckin Demirbas, submitted this Dissertation for approval on 2015-06-25 at 21:49.This Dissertation was approved for publication on 2015-06-29 at 14:01.DSpace SAF Submission Ingestion Package generated from Vireo submission #8313 on 2015-09-29 at 13:21:39Made available in DSpace on 2015-09-29T20:37:49Z (GMT). No. of bitstreams: 2
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Previous issue date: 2015-06-2
Prof. Dr. Ayhan Demirbas' scientometric biography
No full textIt is well established fact that Turkish scientists have increasingly contributed to the literature on the bio-energy in recent years. However, there has not been any biographic study of these scientists as well as scientists working in the field of bio-energy. Therefore, as a first-ever case study of Turkish scientists, this paper presents a scientometric biography of Prof. Dr. Ayhan Demirbas working in the area of bio-energy since 1980s. He produced 454 articles and reviews in the interdisciplinary areas relating to the bio-energy between 1984 and 2010 where 379 of them were indexed by the SCI or the SSCI. He received 7,309 citations for his 454 papers giving a ratio for the "Average Citations per Item" as 16.1 and "H-index" over 39 as of July 2011, suggesting that the scientific impact of his research on the relevant literature has been significant. This paper suggests that scientometric methods are useful for the evaluation of individual researchers and for publicizing their scientific achievement
Effect of Ag concentration on structure and wear behaviour of coatings formed by micro-arc oxidation on Ti6Al4 V Alloy
No full textMicro-arc oxidation (MAO) coating was prepared on Ti6Al4 V alloy in the electrolyte based on different ratios of calcium acetate and a fixed ratio of sodium phosphate with/without Ag additive. The surface, elemental and phase compositions, and dry wear tests of the MAO coating were analysed. The X-ray diffraction results presented that the MAO coating formed rutile, anatase and hydroxyapatite. The results show that the coating performance was improved when Ag additives were included. The wear resistance of the MAO coatings was increased by the addition of Ag
EFFECTS OF AN Al2O3 NANO-ADDITIVE ON THE PERFORMANCE OF CERAMIC COATINGS PREPARED WITH MICRO-ARC OXIDATION ON A TITANIUM ALLOY
No full textIn this research, nano-sized Al2O3 particles were added to silicate-based coatings and the effect of these particles on the microstructure, composition and properties of the coatings was investigated. The effects of the nano-additive on the structure, phase composition and hardness of the micro-arc oxidation (MAO) coatings were analysed using scanning electron microscopy (SEM), X-ray diffraction and micro-hardness testing. The SEM showed that the coatings with a nano-additive have lower porosities than those without a nano-additive. XRD results showed that the coatings with nano-additives contain more oxide when compared to those without nano-additives. The results showed that the nanoparticle additions improve the hardness of the MAO coatings
Optimizing wavelet neural networks using modified cuckoo search for multi-step ahead chaotic time series prediction
No full textDetermining the optimal number of hidden nodes and their proper initial locations are essentially crucial before the wavelet neural networks (WNNs) start their learning process. In this paper, a novel strategy known as the modified cuckoo search algorithm (MCSA), is proposed for WNNs initialization in order to improve its generalization performance. The MCSA begins with an initial population of cuckoo eggs, which represent the translation vectors of the wavelet hidden nodes, and subsequently refines their locations by imitating the breeding mechanism of cuckoos. The resulting solutions from the MCSA are then used as the initial translation vectors for the WNNs. The feasibility of the proposed method is evaluated by forecasting a benchmark chaotic time series, and its superior prediction accuracy compared with that of conventional WNNs demonstrates its potential benefit
The influence of Nano-TiO2 and Nano-Al2O3 Particles in Silicate Based Electrolytes on Microstructure and Mechanical Properties of Micro Arc Coated Ti6Al4V Alloy
No full textCeramic oxide coatings were fabricated on Ti6A14V alloy by micro arc oxidation (MAO) in silicate electrolytes, with nano-TiO2 and nano-Al2O3 and without nano-additives Effects of nano additives on the structural and mechanical properties of the MAO coatings were analysed The MAO coatings were investigated by scanning electron microscopy (SEM), Energy-Dispersive spectroscopy (EDS) micro-hardness and linear wear test Results show that the surface morphology and tribological properties of MAO coatings are greatly influenced by nano additives in electrolytes After the coating treatment the surface hardness values increased from 300 HV0.1 to 635 HV0.1. The hardness tests show that nano-Al2O3 additition coating has higher microhardness values than those without any additives The results indicated that TiO2 and A1(2)O(3) nanoparticles into the coatings make harder and denser surface and increase the wear resistance The wear resistance of the nano-TiO2 and nano-Al2O3 additives coatings was enhanced about 5 times than without nano additives coating
A common tortoise tick, Hyalomma aegyptium Linne 1758 (Acari: Ixodidae), identified on eastern hedgehog (Erinaceus concolor Martin 1838) in Central Anatolia
No full textDemirbas, Yasin/0000-0002-3264-3444; GAZYAGCI, SERKAL/0000-0002-0043-6942Ticks are obligate blood sucker arthropods that infect animals and humans. A common tortoise tick, Hyalomma aegyptium, was collected from a young and an adult male hedgehog, Erinaceus concolor, from Central Anatolia in July 2008. More ticks were determined on the young one. This is the second record of tortoise tick that parasitizes a hedgehog
Microstructure-property relaltionship in silicon carbide armor ceramics
No full textDefects are one of the factors that show a negative effect on the ballistic performance. Uniform microstructures with a low percentage of well distributed porosity could possibly demonstrate high ballistic strength; therefore, it is of interest to estimate the parameters that define the spatial arrangement of defects. This aspect of microstructures was investigated in a variety of silicon carbide ceramics ranging from off-density sintered samples to high density hot-pressed armor grade samples.
The spatial distribution of defects was examined by various techniques including nearest neighbor distance distributions, tessellation analysis, and pair correlation functions. Random distributions were observed for most of the samples with some degree of clustering. Hardness was selected as a mechanical property to correlate with microstructural findings. Hardness contour maps were constructed by indenting samples with a statistically significant number of indents per load to see the variation in terms of location. The large number of indents allowed for Weibull analysis to be used to examine the spread in the data and to test spatial variability. A high degree of correlation was obtained between microstructural parameters and hardness/Weibull modulus values. Smaller defect sizes and homogenous distribution of defects were shown to provide higher hardness values.
A sintered SiC tile was examined using ultrasound to determine high and low amplitude regions in C-scan image maps. Serial sectioning was performed on diced samples from these two regions. Although no significant difference was observed in terms of density and average defect size, statistical tests showed that the difference in the largest defect size detected in low amplitude and high amplitude regions was significant. Clusters of defects were also identified in the samples from the low amplitude regions. The signal loss that was observed in C-scans maps could partially be attributed to these results.
A particularly high degree of correlation was shown between average defect size, spatial distribution parameters and hardness data. These findings exhibit the strong effect of microstructure on the quasi-static properties and may affect ballistic performance.Ph.D.Includes bibliographical references (p. 210-219)
Analysis of Bounds on Hybrid Vector Clocks
No full textHybrid vector clocks (HVC) implement vector clocks (VC) in a space-efficient manner by exploiting the availability of loosely-synchronized physical clocks at each node. In this paper, we develop a model for determining the bounds on the size of HVC. Our model uses four parameters, epsilon: uncertainty window, delta: minimum message delay, alpha: communication frequency and n: number of nodes in the system. We derive the size of HVC in terms of a differential equation, and show that the size predicted by our model is almost identical to the results obtained by simulation. We also identify closed form solutions that provide tight lower and upper bounds for useful special cases.
Our model and simulations show the HVC size is a sigmoid function with respect to increasing epsilon; it has a slow start but it grows exponentially after a phase transition. We present equations to identify the phase transition point and show that for many practical applications and deployment environments, the size of HVC remains only as a couple entries and substantially less than n. We also find that, in a model with random unicast message transmissions, increasing n actually helps for reducing HVC size
Transport and energy in India. Energy used by Indian transport systems and consequent emissions: the need for quantitative analyses (Well-to-Wheel, Lifecycle)
No full textThe purpose of this work is, at first, a general overview on the state-of-art of the transportation system in India outlining the related energy consumption, for the different transport modes, with consequent estimated emissions. These elements are essential for the preparation of a high-level strategic transport planning on the whole energy issue, to help India in the choices of most suitable transportation systems, according to the well-to-wheel analysis (WTW). Pursuing a WTW global index for India that takes into account both the energy and environmental aspects on a uniform basis is an important aim: it allows the best choices to be made as well as enabling the comparison between some of the most important powertrain and fuel options on the Indian market, the results are discussed from three different points of view: energy, environmental and economic impac
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