Learning the stress function pattern of ordered weighted average aggregation using DBSCAN clustering

Ordered weighted average (OWA) operator provides a parameterized class of mean type operators between the minimum and the maximum. It is an important tool that can reflect the strategy of a decision maker for decision-making problems. In this study, the idea of obtaining the stress function from OWA weights has been put forward to generalize and characterize OWA weights. The main idea in this paper is mainly constructed on the basis that, generally, stress functions can be constructed using a mixture of constant and linear components. So, we can consider the stress function as a piecewise linear function. For obtaining stress functions as piecewise linear functions, we present a clustering-based approach for OWA weight generalization. This generalization is made using the DBSCAN algorithm as the learning method of a stress function associated with known OWA weights. In the learning process, the whole data set is divided into clusters, and then linear functions are obtained via a least squares estimator.     

Multimodal concept detection in broadcast media: KavTan

Concept detection stands as an important problem for efficient indexing and retrieval in large video archives. In this work, the KavTan System, which performs high-level semantic classification in one of the largest TV archives of Turkey, is presented. In this system, concept detection is performed using generalized visual and audio concept detection modules that are supported by video text detection, audio keyword spotting and specialized audio-visual semantic detection components. The performance of the presented framework was assessed objectively over a wide range of semantic concepts (5 high-level, 14 visual, 9 audio, 2 supplementary) by using a significant amount of precisely labeled ground truth data. KavTan System achieves successful high-level concept detection performance in unconstrained TV broadcast by efficiently utilizing multimodal information that is systematically extracted from both spatial and temporal extent of multimedia data.     

Microbial corrosion of Ni–Cu alloys by Aeromonas eucrenophila bacterium

The corrosion behavior of Ni–Cu alloy in Nutrient Broth medium (peptone from meat 5.0 g, meat extract (N source) 3.0 g, and sodium chloride 6.0 g in 1 L) and in the presence of Aeromonas eucrenophila, isolated from water treatment system, has been studied using electrochemical techniques. Results showed that the polarization curves exhibiting a cathodic shift of the corrosion potential confirmed the increase in the corrosion rates. According to EIS data lower Q_CPE value for 5 h indicates surface inhomogeneity resulting from surface metal roughening, which is the likely cause of the enhanced dissolution of the metal also observed in SEM micrographs. In addition, the pH values of the medium did not change throughout the experiment; however, after immersion the pH value decreased to acidic value and caused corrosion.     

Effects of process variables for biodiesel production by transesterification

In this study, biodiesel production from various vegetable oils by transesterification was studied, to determine the optimum conditions. Experiments were carried out by using different kinds of catalysts (sodium hydroxide, potassium hydroxide, barium hydroxide, pyrolitic coke and wood ash) and feedstocks (corn oil, sunflower oil, soybean oil, olive pomace oil and cottonseed oil) at 65 °C and an agitation speed of 1000 rpm. The neutralization step with controlled pH was performed by treatment with phosphoric acid. An experimental design was used to evaluate the effects of the parameters such as types of vegetable oils, kinds of catalysts, reaction time, alcohol/oil volumetric ratio and amount of catalyst, on the methyl ester conversion. Using response surface methodology, a quadratic polynomial equation was obtained by multiple regression analysis. It was found that catalyst concentration was the most effective parameter. Sodium hydroxide and potassium hydroxide exhibited a superior catalytic behavior, whereas pyrolitic coke and wood ash had to be used in excess amount or for prolonged reaction times. Moreover, the properties such as viscosity, density, calorific value, acid value, and refractive index of the biodiesel were measured. The tri‐, di‐, monoacylglycerols and glycerol residuals in the methyl esters produced were also quantified by GC analysis.     

Assessing the Tribocorrosion Performance of Three Different Nickel-Based Superalloys

Tribocorrosion, which is a material deterioration caused by the synergistic effect of corrosion and wear acting together, is encountered in many engineering applications. Ni-based superalloys, which are widely used in chemical, petrochemical and nuclear power industries as well as in hot sections of turbine engines, owing to their excellent corrosion resistance, high strength and capability to retain hardness at elevated temperatures, are subjected to corrosive wear in service conditions. Therefore, an understanding of the tribocorrosion behavior of these superalloys allows choosing the right material for specified applications and predicting the material damage. In this study, the tribocorrosion behavior of Hastelloy C2000, Hastelloy G35 and Haynes 625 was studied using different electrochemical test techniques including open circuit potential (OCP) measurement, potentiodynamic and potentiostatic polarization tests under sliding contact in 3.5 wt% NaCl solution. Scanning electron microscopy (SEM) was employed in order to characterize corrosive-wear damage, and the surface profiles of wear tracks were obtained using a high-resolution surface profilometer for calculating wear loss. Also the metal dissolution caused by corrosive wear was detected using an inductively coupled plasma optical emission spectrometer (ICP-OES). Test results indicated that the tribocorrosion performance of superalloys is affected by their elemental composition and microstructural characteristics, which induce changes in mechanical properties. Haynes 625, which has the highest hardness value owing to decreasing grain size, showed less material volume loss than other superalloys in all tests. However, the protective oxide film on Haynes 625 especially thickened in potentiodynamic tests provided inhibition of excessive metal dissolution. Cathodic protection resulted in decreasing material loss, but on the other hand hydrogen intake was observed on cathodically polarized specimens.     

Determining Hounsfield Unit values of mortar constituents by computerized tomography

Computerized tomography was first developed in mid-1970 for medical purposes to non-destructively monitor the conditions of human tissues and bones. The idea was to detect the transmitted X-ray radiation emitted from multiple angles and to reconstruct the data as a tomographic image in an arbitrary unit known as Hounsfield Unit (HU) emerged in data processing phase. In this study, the same methodology was employed to obtain the HU values of sand and cement, which are two main components of mortar and concrete. Ranges of HU values were calculated for cement powder, hardened cement paste the sand in both dry and wet conditions.     

Comparison of two palladium catalysts on different supports during hydrogenation

Soybean oil was hydrogenated using two different palladium-based catalysts, 5% palladium on carbon (Pd/C) and 10% palladium on alumina (Pd/A), at various ratios in a 4-L reactor under constant conditions (165°C, 2 bar H₂, and 500 rpm stirring rate). Reaction rate, trans isomer formation, selectivity ratios, and melting behaviors of the samples were monitored. Activity of Pd/C was about 10 times higher than that of Pd/A, and the reaction rate showed a strong dependency on the support material. Increases in the concentrations of both Pd catalysts did not have considerable effect on trans formation, which is slightly dependent on support material. Oleate selectivity (S ₂₁) for all runs varied between 2.48 and 30.34, and type of support material did not have an effect on selectivity. Melting behaviors of the samples were mainly dependent on reaction rates.     

Comparison of Seed Oil Composition of Nigella sativa L. and N. damascena L. During Seed Maturation Stages

Nigella sativa and N. damascena are major spices and aromatic plants that are cultivated commonly in Turkey. The fatty acid compositions of full maturated seeds in the species were compared in the research. Variations in the fatty acid composition of the oil in the species were also examined during the four maturation stages of seeds, immature, premature, mature, and delayed mature. Quantitative variation in the fatty acid compositions were significantly (p < 0.01) different between the species. Linoleic and palmitic acid contents were higher statistically (p < 0.01) in N. sativa with 57.0 and 12.5 %, respectively while the oleic acid content was higher in N. damascena with 32.2 %. During the maturation stages, linoleic acid—the main fatty acid in both species—contents decreased regularly from 57 to 51 % during maturation stages in both species. On the other hand, the oleic acid amount (the main saturated fatty acid in both species), increased from immature stages to delayed mature stages and were found to be 20.0 and 27.2 %, respectively. According to the results, it can be concluded that harvesting from fully mature stages is preferable than other stages. This is due not only to the significant difference in fatty acid content of immature and premature stages but also the harvesting loss of the delayed maturation stages.     

Solvent-impregnated resins (SIRs) – Methods of preparation and their applications

Interest in the development of solvent-impregnated resins (SIRs) and their applications for the separation of metal ions and organic compounds from water in the form of a hybrid polymeric adsorbent material has intensified over the past thirty years. SIRs are particulate adsorbers that possess a combination of the advantageous features of both liquid–liquid extraction and ion exchange and this renders them applicable to a wide range of potential liquid–solid separation and recovery processes. This paper reviews the extensive published literature on methods of synthesis of SIRs, attempts to stabilize hybrid solvent-impregnated resins and various applications of SIRs.