Investigation of Corrosion Behavior of Borided Gear Steels

In this study, corrosion behaviors of GS18NiMoCr36 (GS 18) and GS32NiCrMo6.4 (GS 32) gear steels borided in Ekabor-II powder at the temperature of 950 °C for 2 and 6 h were investigated in a 6 % M HCI acid solution. The boride layer was characterized by optical microscopy, X-ray diffraction technique and the Micro-Vickers hardness tester. X-ray diffraction analysis of boride layers on the surface of the steels revealed the existence of FeB, Fe₂B, CrB and Cr₂B compounds. The thickness of the boride layer increases by increasing boriding time for gear steels. The hardness of the boride compounds formed on the surface of the steels GS 18 and GS 32 ranged from 1,728 to 1,905 HV_0,05 and 1,815 to 2,034 HV_0,05 respectively, whereas Vickers hardness values of the untreated steels GS 18 and GS 32 were 335 HV_0,05 and 411 HV_0,05, respectively. The corrosion resistance of borided gear steels is higher compared with that of unborided steels. The boride layer increased the corrosion resistances of gear steels 4–6-fold.     

Textural fabric defect detection using statistical texture transformations and gradient search

The inspection of the fabric defects is an important problem, which highly affects both the quality and the cost in the textile industry. Because of consistency and accuracy problems, the inspection of the fabric defect by human experts is neither feasible nor efficient. This requires development and use of automated inspection techniques. Thus, in this study, a texture analysis method, which uses sum and difference histograms (SDH) conjointly with co-occurrence matrices, is proposed to introduce an objective criterion for defect detection. To accomplish the detection task with high accuracy, several features were extracted from SDH and then, a defect search technique, which was developed in the context of this study, was applied. Moreover, several experiments and parameter analysis were performed to carry out detection at feasible computation time and memory storage. The developed method was applied to 28 kinds of raw woven fabric defects and 27 of them (i.e. 93.1%) were successfully recognized by the proposed detection system. The quantitative results and qualitative discussions show the effectiveness of the developed strategy.     

CHARACTERIZATION OF CERIUM OXIDE AND CARBON SUPPORTED Ag-Cu ELECTRO-CATALYSTS FOR ANODE ELECTRODE IN DIRECT ETHANOL FUEL CELLS

In this study, electrochemical and spectroscopic characterization of home-made CeO₂, activated carbon-based Ag-Cu electro-catalysts, and preliminary anode polarization results in a direct ethanol fuel cell test system were presented. Ag-Cu transition metal couples were impregnated onto carbon and cerium oxide supports by wet impregnation, ion exchange, and co-precipitation techniques. Wet impregnation technique was selected for further spectroscopic analysis and fuel cell testing due to its easy metal loading advantage and highest peak currents in ethanol-containing electrolyte environment. When Ag and Cu were loaded 37.5 and 12.5 wt.% onto carbon and cerium oxide by wet impregnation technique, XPS analysis indicated an appreciable amount of Ag and Ag₂O and a high amount of CuO. In cerium oxide-based samples atomic percentage of oxygen fits well with the stoichiometry of CuO/CeO₂. Preliminary results show that BET surface area and the current peaks exhibit a close resemblance (highest BET surface area indicates highest anodic dissolution current), which is thought to be due to the high accessibility of copper layers impregnated onto cerium oxide and activated carbon in H₂SO₄ electrolyte environment. Hydrogen reduction of CeO₂-based samples prepared by wet impregnation at 750°C greatly improved anode polarization and onset oxidation potential.     

Deterioration Assessment and Rehabilitation Design of Existing Steel Bridge

Diagnostic truck-load tests and microstructural analysis were applied for structural deterioration assessment of a steel truss bridge and its rehabilitation design. The feasibility and potential benefits of using advanced field experimental techniques within a structural-identification framework have been demonstrated. Experimental information, coupled with visual inspection, engineering experience, and intuition, increased the level of confidence in the results of the condition-assessment process, permitting a more rational and cost-effective rehabilitation design. Based on the condition assessment, a two-step rehabilitation is recommended for the bridge: Restoration for a safe service life of 5–7 years, and a subsequent effort for preservation beyond.     

Double Carbonylation Reactions of Enynols and Thiols to Form Thioester Substituted 6‐Membered Ring Lactones

The double carbonylation reaction of enynols with thiols affords functionalized 6‐membered ring lactones. Two kinds of 6‐membered ring lactones were obtained by the use of different palladium complexes with added phosphine ligands.     

Rhodium Complexed C2‐PAMAM Dendrimers Supported on Large Pore Davisil Silica as Catalysts for the Hydroformylation of Olefins

Polyamidoamine (PAMAM) dendrimers up to the third generation were grown for the first time on the surface of a large‐pore (18 nm) Davisil silica support. The supported dendrimers of generations 0, 1, 2 and 3 were phosphinomethylated and complexed with rhodium. All the generations were found to be very active for the hydroformylation of olefins. The hydroformylation of 1‐octene was accomplished with a turnover frequency of 1700 h⁻¹ at 70 °C. The G(1) material was found to be the most active when the different generations were compared at 50% conversion at 70 °C     

Effect of wastewater composition on archaeal population diversity

Distribution and occurrence of Archaea and methanogenic activity in a laboratory scale, completely mixed anaerobic reactor treating pharmaceutical wastewaters were investigated and associated with reactor performance. The reactor was initially seeded with anaerobic digester sludge from an alcohol distillery wastewater treatment plant and was subjected to a three step feeding strategy. The feeding procedure involved gradual transition from a glucose containing feed to a solvent stripped pharmaceutical wastewater and then raw pharmaceutical wastewater. During the start-up period, over 90% COD removal efficiency at an organic loading rate (OLR) of 6 kg COD m(-3)d(-1) was achieved with glucose feeding, and acetoclastic methanogenic activity was 336 ml CH4 gTVS(-1)d(-1). At the end of the primary loading, when the feed contained solvent stripped pharmaceutical wastewater at full composition, 71% soluble COD removal efficiency was obtained and acetoclastic methanogenic activity decreased to half of the rate under glucose feed (166 ml CH4 gTVS(-1)d(-1)). At the end of secondary loading with 60% (w/v) raw pharmaceutical wastewater, COD removal dropped to zero and acetoclastic methanogenic activity fell to less than 10 ml CH4 gTVS(-1)d(-1). Throughout the course of the experiment, microbial community structure was monitored by DGGE analysis of 16S rRNA gene fragments. Five different archaeal taxa were identified and the predominant archaeal sequences belonged to methanogenic Archaea. Two of these showed greatest sequence identity with Methanobacterium formicicum and Methanosaeta concilii. The types of Archaea present changed little in response to changing feed composition but the relative contribution of different organisms identified in the archaeal DGGE profiles did change.     

A simulated annealing algorithm based approach for balancing and sequencing of mixed-model U-lines

It is known that two interrelated problems called as line balancing and model sequencing should be solved simultaneously for an efficient implementation of a mixed-model U-shape assembly line in a JIT (Just in Time) environment. On the other hand, three versions of assembly line balancing problem can be identified: Type I, Type II, and Type E. There are only two articles ( Kara, Ozcan, & Peker, 2007a and Hamzadayi & Yildiz, 2012) related to simultaneous balancing and sequencing of mixed-model U-lines for minimizing the number of stations (Type 1 problem) by ignoring the fixed model sequence in the current literature. In this paper, a simulated annealing algorithm is proposed for solving a problem of type 1 by ignoring the fixed model sequence. Accordingly, simulated annealing based fitness evaluation approach proposed by Hamzadayi and Yildiz (2012) is enhanced by adding the tabu list, and inserted into the proposed algorithm. Implementation difficulties experienced in meta-heuristics based on solution modification for solving these types of problems are demonstrated. ‘Absolute deviation of workloads’ (ADW) is quite frequently used as performance criteria in the literature. It is found that ADW is an insufficient performance criterion for evaluating the performance of the solutions, and this is showed by means of an illustrative example. The parameters of the proposed algorithm are reviewed for calibrating the algorithm by means of Taguchi design of experiments. Performance of the proposed approach is tested through a set of test problems. The results of computational experiments indicate that the proposed approach is an effective method in solving simultaneous line balancing/model sequencing problems for mixed-model U-lines for minimizing the number of stations.     

High temperature bending creep behavior of a multi-cation doped α/β-SiAlON composite

SiAlON ceramics with high hardness and high toughness can be made through designing α/β-SiAlON composites. An important advantage of α-SiAlON phase is that the amount of intergranular phase is reduced by the transient liquid phase being absorbed into the matrix of α-SiAlON phase during sintering. But, the thermal stability of the α-SiAlON phase is an important concern for α/β-SiAlON composites especially at high temperatures. The use of different types of single or multiple cations during fabrication directly affects resultant microstructures and mechanical behavior of α/β-SiAlON composites. In this study, the creep behavior of a multi-cation (Y, Sm and Ca) doped α/β-SiAlON composite, in which aluminum-containing nitrogen melilite solid solution phase was designed as intergranular phase, was investigated by four-point bending creep tests under stresses from 50 to 150 MPa and at temperatures from 1300 °C to 1400 °C in air. The stress exponent was determined to be 1.6 ± 0.13 at 1400 °C and the creep activation energy was calculated to be 692 ± 37 kJ/mol⁻¹. Grain boundary sliding coupled with diffusion was identified as the rate-controlling creep mechanism for the α/β-SiAlON composite.     

Synthesis,structural characterization,and antiproliferative/cytotoxic effects of a novel modified poly(maleic anhydride-co-vinyl acetate)/doxorubicin conjugate

Polymer Bulletin - Drug carrier, poly(maleic anhydride-co-vinyl acetate) (MAVA or poly[MA-co-VA]) copolymer, was traditionally synthesized by free radical chain polymerization reaction, in methyl...