An Intelligent Methodology for Railways Monitoring Using Ultrasonic Guided Waves

It is far from trivial to inspect railways for defections. In particular, for the foot area of the rail non destructive testing methods are known to be difficult to apply. In this paper, an ultrasonic guided wave method is considered along with classification methods for automated rail foot defect detection. In effect, given a set of gathered ultrasonic signals, multiple features are extracted from time-, frequency- and time–frequency domains. Next, a robust feature selection method is performed, to collect a small set of complementary features. The classification task is accomplished by means of a kernel-based support vector machine. To demonstrate the performance capabilities of our approach, an extensive experimental setup is designed under representative environmental and operational conditions. The sensitivity and the resolution of the proposed defect detection system are reported. A study on the influence of rail fastening on the proposed method is also reported where robust defect detection rates, greater than 93 %, are achieved assuming that a compact feature subset is considered. However, it is evident in experiments that even in the case of large defects, changes in the environmental conditions (temperature and humidity) increase the interpretation of the acquired signals, thus making the detection task more difficult.     

The Effect of Boron Application on Chemical Characterization and Volatile Compounds of Virgin Olive Oil of Ayvalik Olive Cultivar

In this study, the Ayvalik olive variety, an important and widely grown olive variety in Turkey, was chosen. A month prior to blooming and 2 months prior to harvesting in 2011 and 2012, three different concentrations of boron (100, 150 and 250 ppm) were applied to the olive leaves with or without boron deficiencies. After the application, quality criteria, fatty acid composition, total phenol contents and major volatile compounds of olive oil that was obtained from the harvested olives were investigated. Boron application to the olive trees with boron deficiencies has improved both the amount and the olive oil quality. Experimental results show the significance of boron for olive farming. Application of boron in 150 ppm led to a better olive oil quality by improving fatty acid composition [oleic acid (76.03 %), linoleic acid (9.68 %), linolenic acid (0.56 %), monounsaturated fatty acid (77.24 %)], total phenol content (422.94 ppm) and major volatile compounds [E‐2‐hexenal (43.12 ppm), hexanal (3.02 ppm), Z‐3‐hexenol (1.13 ppm)] in both harvest seasons (2011–2012) and in both olive orchards with or without boron deficiencies.     

Role of chromium in Cr–Fe oxide catalysts for high temperature water-gas shift reaction – A DFT study

Carcinogenic hexavalent Cr in the current iron oxide-based catalysts of high temperature water-gas shift (HT-WGS) reaction is great environmental concern. Interpreting the role of the Cr in this important industrial catalyst system is required. In the present study, we investigated substitution of Cr atoms into the most stable termination of Fe₃O₄ (111) slab surface by spin-polarized periodic DFT approach to comprehend the role of Cr. We applied the projector augmented-wave (PAW) method within the Perdew-Wang 1991 (PW91) form of the generalized gradient approximation (GGA) on the Vienna Ab-initio Simulation Package (VASP). The calculations point out that Cr atoms choose being below the surface FeO₆ sites. Cr slightly affects the dissociative H₂O adsorption. There is no effect on the CO adsorption. Oxygen vacancy is favored to form on the topmost layer with less vacancy formation energy. Substitution of Cr into the structure increases the oxygen vacancy formation energy. This indicates that Cr does not act as a chemical promoter and does not affect the catalytic activity positively, which is experimentally confirmed by the previous studies.     

Numerical study on photovoltaic/thermal systems with extended surfaces

The current study presents a novel and straightforward approach for simulating photovoltaic/thermal (PV/T) systems using the commercial computational fluid dynamics (CFD) solver ANSYS‐FLUENT. Instead of resolving the natural convection within the air gap between the PV and the glass cover, the effective thermal conductivity approach is implemented. Moreover, the solar radiation incident on the PV layer is directly included in the energy equation of the PV domain to evaluate the resultant power output and heat generation. The validity of these implications is proven by comparing predicted data with experimental data from the literature. Comparative results reveal a root‐mean‐square error of 7% and 2% for the PV temperature and the outlet air temperature, respectively. A comprehensive numerical analysis is also conducted for a PV/T system with and without finned surfaces. In the parametric study, the impacts of varying a number of design parameters, operating conditions, and weather data over a wide range are assessed. Results reveal that channel height and air velocity have the greatest impact on the overall efficiency and outlet air temperature of a PV/T system. An optimization study is also conducted using the response surface methodology to obtain optimal values of design parameters and operating conditions for this system. The highest overall efficiencies and outlet air temperatures are achieved in PV/T systems comprising narrow channel geometries, regardless of the operating conditions or weather data considered. Optimal conditions are achieved for a collector with a collector length of 1.5 m, a channel height of 1 cm, and an air velocity of 2.3 m/s. For the optimal design, overall efficiency and outlet temperature values are evaluated as 53.4% and 310.9 K, respectively. Sensitivity analyses also observe the impact of adding fins to the air channel, and it is concluded that the addition of fins improves the overall efficiency of the PV/T system by up to 19%. However, adding fins does not significantly affect the outlet air temperature; nor does it improve the overall efficiency of the PV/T system beyond a critical channel height.     

Process coordination,project attributes and project performance in offshore-outsourced service projects

Interfirm process coordination is pivotal for offshore outsourced service project success. Via knowledge-based and organizational learning view, this study explores the effectiveness of process coordination in the dyadic client-provider relationship. We investigate the influence of interactive and implicit coordination on project performance under contingencies of project modularity and complexity, which determine interfirm interdependencies from the top down and from the bottom up. The objectives are to comprehend the two approaches to coordinating and integrating partners' endeavors during project implementation and to unveil their interactions with project context. Our theoretical and empirical analyses show how the effectiveness of process coordination depends on project attributes individually and jointly.     

Thermo-Chemical Modelling Strategies for the Pultrusion Process

In the present study, three dimensional (3D) numerical modeling strategies of a thermosetting pultrusion process are investigated considering both transient and steady state approaches. For the transient solution, an unconditionally stable alternating direction implicit Douglas-Gunn (ADI-DG) scheme is implemented as a first contribution of its kind in this specific field of application. The corresponding results are compared with the results obtained from the transient fully implicit scheme, the straightforward extension of the 2D ADI and the steady state approach. The implementation of the proposed approach is described in detail. The calculated temperature and cure degree profiles at steady state are found to agree well with results obtained from similar analyses in the literature. Detailed case studies are carried out investigating the computational accuracy and the efficiency of the 3D ADI-DG solver. It is found that the steady state approach is much faster than the transient approach in terms of the computational time and the number of iteration loops to obtain converged results for reaching the steady state. Hence, it is highly suitable for automatic process optimization which often involves many design evaluations. On the other hand sometimes the transient regime may be of interest and here the proposed ADI-DG method shows to be considerably faster than the transient fully implicit method which is generally used by the general purpose commercial finite element solvers. Finally, using the proposed steady-state approach, a design of experiments is carried out for the curing characteristic of the product based on pulling speed and part thickness.     

The Use of Oxalic Acid as a Chelating Agent in the Dissolution Reaction of Calcium Molybdate

In this study, the dissolution behavior of calcium molybdate (CaMoO₄) was investigated in oxalic acid (H₂C₂O₄) solution. The effects of stirring speed, temperature, H₂C₂O₄ concentration, and particle size on the dissolution reaction of CaMoO₄ were determined. The dissolved quantities of molybdenum and calcium were analyzed quantitatively by ICP-OES. Fractional conversion of CaMoO₄ vs time and concentration of calcium vs time diagrams were plotted. It was observed that at constant temperatures and lower H₂C₂O₄ concentrations, the dissolution increased by increasing H₂C₂O₄ concentration, but at higher H₂C₂O₄ concentrations, the effect of H₂C₂O₄ concentrations was negligible. The dissolution reaction of CaMoO₄ in H₂C₂O₄ solution was performed in two steps as series–parallel type reaction. In the first step, CaMoO₄ reacted with H₂C₂O₄ to form the water-soluble calcium aqua oxalato molybdate (Ca[MoO₃(C₂O₄)(H₂O)]) intermediate chelate product. In the second step, the intermediate chelate, Ca[MoO₃(C₂O₄)(H₂O)], reacted with the reactant, H₂C₂O₄, to yield water-soluble hydrogen oxalato dimolybdate chelate (H₂[(MoO₃)₂(C₂O₄)]) and insoluble CaC₂O₄H₂O as final products. It was found that 500 rpm was enough to eliminate the resistance of liquid film layer that surrounds the solid particles. It was concluded that the optimum temperature was 313 K (40 °C) and the optimum concentration of H₂C₂O₄ was 1 kmol m^?3 to obtain high conversion during the dissolution of CaMoO₄.     

Aqueous Phase Glycerol Reforming by PtMo Bimetallic Nano-Particle Catalyst: Product Selectivity and Structural Characterization

A carbon supported PtMo aqueous phase reforming catalyst for producing hydrogen from glycerol was characterized by analysis of the reaction products and pathway, TEM, XPS and XAS spectroscopy. Operando X-ray absorption spectroscopy (XAS) indicates the catalyst consists of bimetallic nano-particles with a Pt rich core and a Mo rich surface. XAS of adsorbed CO indicates that approximately 25% of the surface atoms are Pt. X-ray photoelectron spectroscopy indicates that there is unreduced and partially reduced Mo oxide (MoO₃ and MoO₂), and Pt-rich PtMo bimetallic nano-particles. The average size measured by transmission electron microscopy of the fresh PtMo nano-particles is about 2?nm, which increases in size to 5?nm after 30?days of glycerol reforming at 31?bar and 503?K. The catalyst structure differs from the most energetically stable structure predicted by density functional theory (DFT) calculations for metallic Pt and Mo atoms. However, DFT indicates that for nano-particles composed of metallic Pt and Mo oxide, the Mo oxide is at the particle surface. Subsequent reduction would lead to the experimentally observed structure. The aqueous phase reforming reaction products and intermediates are consistent with both C?CC and C?COH bond cleavage to generate H₂/CO₂ or the side product CH₄. While the H₂ selectivity at low conversion is about 75%, cleavage of C?COH bonds leads to liquid products with saturated carbon atoms. At high conversions (to gas), these will produced additional CH₄ reducing the H₂ yield and selectivity.     

Quantum computation with write-only memory

In classical computation, a “write-only memory” (WOM) is little more than an oxymoron, and the addition of WOM to a (deterministic or probabilistic) classical computer brings no advantage. We prove that quantum computers that are augmented with WOM can solve problems that neither a classical computer with WOM nor a quantum computer without WOM can solve, when all other resource bounds are equal. We focus on realtime quantum finite automata, and examine the increase in their power effected by the addition of WOMs with different access modes and capacities. Some problems that are unsolvable by two-way probabilistic Turing machines using sublogarithmic amounts of read/write memory are shown to be solvable by these enhanced automata.