Elaboration of Al2O3/PTFE icephobic coatings for protecting aluminum surfaces

In order to protect aluminum ground wires and phase conductors of overhead power lines against ice adhesion and excessive accretion, for ensuring safe and reliable power transmission during winter periods, a new coating with icephobic characteristics and satisfactory mechanical properties was developed. The method consisted in depositing an extremely adherent poly(tetrafluoroethylene) or PTFE coating on an Al₂O₃ underlayer produced by anodisation in either a phosphoric or an oxalic acid electrolyte. PTFE impregnation was carried out at low temperature (320 °C) and coating adhesion was assessed using tape and bend tests. These treatments resulted in highly hydrophobic surfaces with water contact angles lying between 130° and 140°. Ice shear stress was reduced by almost 2.5 times, and the PTFE coatings remained active after several ice shedding events. Morphologies and chemical compositions were studied using scanning electron microscopy, energy dispersive X-Ray analysis, as well as Fourier Transform Infra Red and X-Ray photoelectron spectroscopy.     

Practical methods for evaluating the accuracy of the eigenelements of a symmetric matrix

The results of the Householder and QL algorithms for determining the eigenelements of a symmetric matrix, provided by a computer, always contain the errors resulting from floating-point arithmetic round-off error propagation. The Permutation-Perturbation method is a very efficient practical method for evaluating these errors and consequently for estimating the exact significant figures of the eigenelements. But, in the cases of: eigenvalues very close to zero, eigenvalues of widely varying range, and multiple eigenvalues, the Permutation-Perturbation method is not complete. In this paper we propose an algorithm which is able to complete this method.     

Potential Development of Value-Added Fishery Products in Underutilized and Commercial Fish Species: Comparative Study of Lipid Quality Indicators

In this study, proximate and fatty acid composition in the edible flesh of eight underutilized and five commercial freshwater fish species were compared in order to evaluate the potential of these fish for development of functional value-added fishery products. The lipid content (% dry weight basis) of investigated fish species ranged from 3.44 to 9.25 in underutilized and 3.73–7.68 in commercial species. In comparison with underutilized fish species, commercial species had higher levels of protein (P < 0.05). The high proportion of EPA+DHA was found with Goldfish (524 mg/100 g flesh), Wels (422 mg/100 g flesh), and Crucian carp (354 mg/100 g flesh), all of which belonged to underutilized group. All studied fish (save Lenkoran) showed values higher than the minimum recommended DHA/EPA value (0.45). The ratios of n-6/n-3 found in this study were much lower (save Goatfish) than those cited as a harmful value (4.0 as the maximum value). The PUFA/SFA value of the present fish samples was higher at 1.57 for Goatfish, 1.02 for Lenkoran, 0.68 for Wels, all of these fish belonging to the underutilized group. The highest atherogenic and thrombogenicity index values were generally obtained for commercial species. It seems in respect of comparability of these lipid quality indicators, the underutilized fish species could be highly recommended as an important source of polyunsaturated fatty acids and Max-EPA products for humans consumption.     

Cometabolic degradation of para-nitrophenol and phenol by Ralstonia eutropha in a Kissiris-immobilized cell bioreactor

Ralstonia eutropha was able to degrade p-nitrophenol (PNP) at concentrations ranging from 5 to 15mg l ^?1 in the presence of phenol which was kept at the constant concentration of 200 mg l ^?1. More than 90% of phenol was degraded within 30 h and in the absence of PNP. While in this time period and in the presence of 15 mg l ^?1 less than 30% of phenol was degraded and PNP removal ability of the test bacterium was about 20%. Kissiris as a natural source of silicon dioxide having a very rigid structure with many micropores irregularly distributed throughout its surface was used to evaluate effectiveness of the cell immobilization using a Kissiris-immobilized cell bioreactor [ICB]. By applying phenol-feeding regime in the ICB operated in a batch recycling mode, simultaneous degradation of phenol in total amount of 1,000 mg l ^?1 with 15 mg l ^?1 PNP was achieved within 40 h.     

Compressive and flexural properties of novel polylactic acid/hydroxyapatite/yttria-stabilized zirconia hybrid nanocomposite scaffold

The mechanical property is a crucial factor in the design of bone tissue engineering scaffolds. In the current study, novel PLLA (Poly-L-lactic acid)–Hydroxyapatite (HA)–yttria-stabilized zirconia (YSZ) nanocomposite scaffold with various compositions was prepared and characterized. The effect of HA and YSZ contents on the mechanical behavior of the resultant composites was investigated. TEM micrograph revealed that HA particles are needle-like in shape and nano in size. Scanning electron microscopy (SEM) micrograph also showed that YSZ powder is in granule form and submicron size. SEM disclosed that all scaffolds had a highly interconnected porous structure and X-ray diffractometry revealed that there were some molecular interactions between PLA (Polylactic acid), HA, and YSZ in the composites. The results depicted that introducing YSZ to the nanocomposite leads to a significant increase in compressive strength, modulus, and densification strain. In addition, flexural strength and modulus showed an upward trend by adding YSZ particles to scaffolds. It should be noted that PLA–20%HA–20%YSZ indicates the highest strength and modulus in both compression and bending tests, though, it did not demonstrate the proper strain compared to other scaffolds. Thus, PLA–15%HA–15%YSZ has been reported as the best candidate due to appropriate strength and strain. Also, energy absorption in nanocomposites showed an upward trend by increasing the amount of YSZ particles. It was found that the strength of samples was declined after being soaked in simulated body fluid. However, scaffolds with HA underwent more decrease in strength compared to samples containing YSZ.     

Estimation of stresses in atmospheric ice during aeolian vibration of power transmission lines

Aeolian vibration in bare and iced cable was simulated using the theory of cable vibration. High frequency vibration creates stresses in the cable and consequently in the ice covering that cable, which may result in ice failure and eventually ice shedding. These stresses were estimated in this study. Displacement of the cable during vibration was determined; furthermore, instantaneous wind loads in vertical and transverse directions, additional stresses induced by the motion in the cable and in the atmospheric ice, as well as torque due to cable springback were calculated. In order to simulate the loading conditions of a chunk of atmospheric ice in the middle of a span, a new model was developed using ABAQUS. Results from this model show in spite of high frequency vibration, the resulting level of stress in atmospheric ice is far less than its failure limit. In other words, the atmospheric ice under the condition assumed in this investigation does not shed due to aeolian vibration.     

A generalised optimal linear quadratic tracker with universal applications – part 1: continuous-time systems

This paper presents a generalised optimal linear quadratic analog tracker (LQAT) with universal applications for the continuous-time (CT) systems. This includes: (1) a generalised optimal LQAT design for the system with the pre-specified trajectories of the output and the control input and additionally with both the input-to-output direct-feedthrough term and known/estimated system disturbances or extra input/output signals; (2) a new optimal filter-shaped proportional plus integral state-feedback LQAT design for non-square non-minimum phase CT systems to achieve a minimum phase-like tracking performance; (3) a new approach for computing the control zeros of the given non-square CT system; and (4) a one-learning-epoch input-constrained iterative learning LQAT design for the repetitive CT system.     

Effects of temperature and impurities on the DC conductivity of snow

Several major parameters affecting the electrical behavior of natural snow, namely volume conductivity and density, liquid water content and conductivity of water melted from snow, are crucial for the characterization of the electrical performance of snow-covered HV insulators. However, little study has been devoted to this subject, despite of its importance. These parameters are found to vary significantly with snow composition and purity as well as with other parameters, such as temperature, airborne pollutants, electric field strength and polarity. From laboratory experiments carried out on a large number of snow samples, it was found that DC conductivity of snow shows a peak at about -2degC. This apparently curious behavior near the melting temperature is attributed to important changes to the microstructure of snow. A correlation between DC conductivity and snow temperature was established     

Influence of plasma treatment on CNT absorption of cotton fabric and its electrical conductivity and antibacterial activity

In this study, effect of plasma pretreatment on the absorption of carboxilated carbon nanotubes (CNTs) on the surface of cotton fabrics was investigated. Treated samples were characterised using a Raman spectrophotometer. Also, the morphological properties of samples were studied using a scanning electron microscope. Electrical resistance and interactions between CNTs and plasma-treated cotton functional groups at the surface were also evaluated. Antibacterial activity of cotton fabric when modified by low temperature plasma and stabilised with CNTs was also investigated. Results showed a uniform coating of CNTs on the plasma-treated cotton fabric and it was found that the plasma treatment is effective on improving CNTs absorption by cotton fabric. Generally, cotton fabric characterisation, such as antibacterial activity and electrical conductivity, after plasma treatment and loading CNT are improved.     

Multi-objective discrete urban road network design

This paper addresses the problem of designing urban road networks in a multi-objective decision making framework. Given a base network with only two-way links, and the candidate lane addition and link construction projects, the problem is to find the optimal combination of one-way and two-way links, the optimal selection of network capacity expansion projects, and the optimal lane allocations on two-way links to optimize the reserve capacity of the network, and two new travel time related performance measures. The problem is considered in two variations; in the first scenario, two-way links may have different numbers of lanes in each direction and in the second scenario, two-way links must have equal number of lanes in each direction. The proposed variations are formulated as mixed-integer programming problems with equilibrium constraints. A hybrid genetic algorithm, an evolutionary simulated annealing, and a hybrid artificial bee colony algorithm are proposed to solve these two new problems. A new measure is also proposed to evaluate the effectiveness of the three algorithms. Computational results for both problems are presented.