Characterization of thermal flame sprayed coatings prepared from FeCr mechanically milled powder

This paper discusses augmenting a thermal flame spray process with a mechanically milled feedstock to deposit low porosity FeCr coatings onto a steel substrate. A variety of tests were performed to assess the quality of the coatings obtained: microstructural and chemical analyses using X-ray diffraction (XRD) and optical and scanning electron microscopy (SEM) coupled with energy dispersive spectrometry (EDS). The microscopy studies showed that the coatings displayed a lamellar structure with two distinct darker phases and contained unmelted particles; moreover, oxides and micro-cracks were observed at the surface. A lower level of porosity was observed compared to that reported in the literature, and the chromium concentration was found to increase with decreasing coating thickness. The mechanical properties of the coatings were characterized using micro-hardness, adhesion and residual stress tests. The results show a cohesive fracture mode for all samples, whatever the coating thickness. Electrochemical tests were carried out using open circuit potential (OCP), potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) measurements. The best electrochemical properties were observed for coatings in which the voids were sealed with a polymeric substance and those fabricated with a Ni-based bond coating. However, the thinner coatings show higher chromium concentrations, lower porosity, and better mechanical and electrochemical properties than the thicker coatings.     

Analytic study on linear systems of fractional differential equations

An analytic study on linear systems of fractional differential equations with constant coefficients is presented. We briefly describe the issues of existence, uniqueness and stability of the solutions for two classes of linear fractional differential systems. This paper deals with systems of differential equations of fractional order, where the orders are equal to real number or rational numbers between zero and one. Exact solutions for initial value problems of linear fractional differential systems are analytically derived. Existence and uniqueness results are proved for two classes. The presented results are illustrated by analyzing some examples to demonstrate the effectiveness of the presented analytical approaches.     

Qualitative evaluation of the germination frequency in Zr–Fe binary alloy

Major thermo-physical properties data are of fundamental importance to accurate and reliable design of melting and casting processes. In this paper, we show that we can control the germination process using thermodynamics data. These data must be known for the entire period of time and temperature range of interest in any given condition. In addition, a kinetic approach is employed to predict the microstructure of alloys. Viscosity data for Zr₇₆Fe₂₄, are fitted with an empirical relation. The best fit allows to estimate, through the resistance to germination factor, thermodynamic proprieties of interest (i.e., namely the enthalpy of fusion, the surface tension, the molar volume and the glass temperature). From the values of these quantities, the parameters (T, t) can be estimated. The temperature T is found between 930 K and 1194 K and the time t can be derived from the plateau of the germination frequency–temperature profile.     

Detection of Magnetic Fields Highly Attenuated by the Skin Effect Through a Ferrous Steel Boundary Using a Super Narrow-Band Digital Filter

A complete instrumentation system is described that is capable of launching alternating magnetic fields through a large mild steel plate that is 2 mm in thickness and detecting them on the face opposite from the transmitter with remarkable signal-to-noise ratios. Results for signal frequencies ranging between 4.5 and 13 kHz are reported. The skin depth at 9 kHz for the steel used is approximately 137 mum. The detection of the minute fields arriving at the receiving coil is made possible by the use of digitally synthesized input signals, low-noise amplification, and, in particular, the use of a powerful real-time digital signal processing system that isolates the signal of interest using a super narrow-band filter and very high levels of distortion-free gain. Although traditional methods of weak signal detection, such as lock-in amplification, may also be applied in this context, the digital approach discussed here is both more cost effective and flexible, allowing the simultaneous detection of multiple frequencies.     

Dual-frequency and broad-band antennas with stacked quarterwavelength elements

Original lightweight, low-cost, and compact air-filled planar antennas with short-circuited elements, fed by a coaxial probe, for dual-frequency (S-antenna) and wide-band applications (E-antenna) are investigated. The two-band frequency antenna is formed of two stacked quarter-wavelength elements, short-circuited along diametrically opposed planes. This structure offers two modes with different radiation characteristics. The ratio between the two frequencies can be closely controlled within a range varying from 1.3-2. A bandwidth of 30% for a VSWR <2 is demonstrated using two stacked quarter-wavelength elements short-circuited along the same plane. Numerical simulation results are compared with experiments and a very good agreement is observed. Radiation patterns and input impedance of both structures are measured and the effects of various physical parameters are presented     

Extracting dimensional information from steel reinforcing bars in concrete using neural networks trained on data from an inductive sensor

A new method is presented for extracting dimensional information from steel bars using images generated by an inductive sensor. The technique is based on the application of two feedforward backpropagation neural networks; one to estimate bar depth and the other to estimate bar diameter. Both of the networks have been trained on a set of data that consists of the peak parameters of six different bars scanned at 41 different bar depths. These input and target data must be pre-processed to obtain a good network generalisation. By testing the two networks with a completely different set of data, accurate performance has been obtained. Real, two-dimensional scan data have then been applied to both of the networks and the bar dimensional parameters have been extracted successfully. The advantage of the neural network method for extracting information is that it continues to operate reliably for very deep bars, for which the signal strength is severely attenuated and manifests a poor signal-to-noise ratio. Depth and diameter measurements have been obtained for bars located down to 58 mm, with errors that satisfy the requirements of the BS 1881 standard. At a depth of 40 mm, these measurements yield an error of ±4%, and this decreases as the depth reduces; in other words, the extracted bar diameter is within the requirements of the DIN 488 standard.     

Interleukin-8 in chronic renal failure and dialysis patients

A total of 105 patients participated in this study, including 10 with chronic glomerulonephritis with normal renal function (CGN patients), 36 uraemic patients (CRF patients), 19 continuous ambulatory peritoneal dialysis patients (CAPD) without peritonitis, three CAPD patients with peritonitis, 37 patients undergoing chronic haemodialysis (HD) divided into short-term HD, 15 patients; medium-term HD, 12 patients; and long-term HD, 10 patients. IL-8 and two other proinflammatory cytokines, IL-6 and TNF alpha were tested using a specific immunoassay. IL-8, IL-6, and TNF alpha serum levels were significantly increased in patients with chronic renal failure compared to their levels in normal individuals (P < 0.0001, P < 0.05 and P < 0.0001 respectively). The most pronounced increment in IL-8, IL-6 and TNF alpha serum levels was observed in CAPD patients (P < 0.0001). CAPD patients without peritonitis showed relatively low levels of IL-8 or IL-6 in peritoneal dialysate effluents (PDE), whereas PDE-TNF alpha were not detectable in almost all patients tested. Patients with peritonitis showed very high serum and PDE levels of IL-8, IL-6 and TNF alpha. The clinical recovery from peritonitis was characterized by a rapid fall in IL-8, IL-6 and TNF alpha in serum and dialysate. HD patients showed a significant increase in serum levels of IL-8 and also IL-6 and TNF alpha compared to normal individuals (P < 0.05, P < 0.05 and P < 0.01 respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

Wind speed and wind energy potential of Jordan

Routine wind data from 11 stations in Jordan have been analysed. Monthly average, and seasonal wind speed and average power density distributions were determined for each station. The monthly average wind speed for the two most potential sites Ras Muneef (RA) and Mafraq (MF) ranged from 3.0 to 7.4 m/sec and the average power density for these two sites ranged from 110 to 370 W/m² at RA and from 105 to 470 W/m² at MF. An application of wind power as supplementary power supply is suggested and cost analysis is given.