A common problem that most contractors are faced with in slab-bridges’ construction is to predict camber of pre-tensioned or post-tensioned corrugated skew slabs due to prestressing force. It is an important factor to achieve bridge design finished levels without any unforeseen construction cost. Presence of skewedness in bridges makes analysis and design of bridge decks intricate. In this paper, three 3100 mm long post-tensioned corrugated slabs with overall height of 200 mm and 50 mm thickness for both inclined and top parts of specimens, and thickness of 77 mm in the bottom part were studied. Corrugation angle of tested slabs was 60 and skew angle was 20. Specimens are prestressed by two 15.25 mm diameter strands. Camber measurements were carried out during tests by means of measuring the differences of slab bottom levels. Numerical calculation is done utilizing the Finite Element Analysis Program; ANSYS, taking into consideration initial prestress losses. ANSYS program provides a three- dimensional element (Solid 65) with nonlinear model of brittle materials similar to concrete material. Three-dimensional spar element was used for modeling reinforcement and prestressed strands. Comparison between experimental and numerical results is made. Numerical results showed good agreement with experimental results.

Synchronous motors when fed from a power system polluted with harmonic voltages will exhibit harmonic rotating fluxes. The speed of each harmonic flux will correspond to the harmonic voltage frequency, and the direction of rotation will depend on the harmonic voltages sequence. The backward rotating fluxes (produced by the negative sequence harmonic voltages) produce braking torques. Harmonic voltages and the associated currents and fluxes result in additional copper and iron losses. Therefore, the motors, which are fed from polluted-voltage supply, should be derated otherwise the motor temperature would exceed its rated value. This endangers the windings, insulation and bearings of the motor, hence shortening its life span. In the present paper, the proper derating factors for the synchronous motors are determined when fed from polluted supply to avoid thermal stresses.

This paper investigates the principle of direct torque control when applied to single-phase induction motor drive. The presented direct torque control is based on hysteresis band strategy. The proposed control scheme utilizes voltage source inverter consisting of a single-phase rectifier cascaded with a four-switch inverter that provides nine voltage vectors and divided the dq plane into eight sectors. A modified switching pattern has been discussed to improve the performance of the drive. Simulation results have been provided to illustrate the system operation. A comparison between the presented scheme and another direct torque control drive scheme has been held.

The effect of iron substitution on the bioactivity of hydroxyapatite (HAp) under the physiological conditions was investigated. Five samples of iron doped hydroxyapatite (FeHAp) with different iron concentrations (0, 0.05, 0.1, 0.2, and 0.3 mol %) were synthesized by wet chemical method. The formation of bone like apatite layer on the surface of the samples was detected using X-ray diffraction (XRD) and Fourier transforms infrared (FTIR). The changes of the pH of SBF (simulated body fluid medium) were measured at pre-determined time intervals using a pH meter. The dissolution of calcium, phosphorus and iron ions in SBF medium was determined by single beam scanning spectrophotometer. XRD and FTIR results exhibit the formation of carbonate apatite layer on the surface of the immersed samples, which increased with the increase of iron content. The solubility and dissolution tests revealed that iron doped HAp samples had a higher solubility and dissolution rat than pure sample, which indicate that iron increase the bioactivity of HAp in vitro.