Basrah Journal for Engineering Sciences

Mathematical programming techniques have been used to minimize the cost of the reinforced concrete T-beam floors. The floor system consists of a one-way continuous slab and simply supported T-beams. The study presents a formulation based on elastic analysis followed by the ultimate strength method of design with the consideration of serviceability constraints as per the ACI Code. The formulation of the optimization problem has been made by utilizing the interior penalty function method as an optimization method to minimize the objective function representing the cost of the one-meter length of the floor system. The cost includes the cost of concrete reinforcement and formwork. The design variables considered in this study are the dimensions and the amounts of reinforcement for the slab and beams, in addition to the spacing of the beams. Many examples are solved to show the effect of these design variables on the optimum solution of the floor system. The effect on the optimum design of the compressive strength of concrete, yield strength of steel, concrete cost ratios, and formwork cost ratios has also been studied.

This research has been conducted in order to evaluate the compression index of gypsiferous soil. A series of consolidation experimental tests with different percentages between 5% - 20% of gypsum added to the soil have been performed. From the results, it had been seen that, with an increasing percentage of gypsum, the compression index increased, with a maximum percentage of 30.4%.

In the present study, the dynamic analysis of jacket-type offshore structures under the action of sea wave is carried out. The finite element method is adopted for the solution to the problem. The effect of soil-structure interaction on the dynamic behaviour of the offshore structure is taken into account due to the deformation of the soil caused by the motion of the structure, which in turn modifies the response of the structure. The supporting elastic foundation is represented by the Winkler-type model having normal and tangential modules of sub-grade reaction. These modules may be constant or vary linearly or non-linearly along the embedded length of the pile that supports the offshore structure. The pile tip condition is also considered. A time-domain solution is recommended. The generalized Morison's equation is used to calculate the wave force and Aliys linear theory is to describe the flow characteristics. Both free and forced vibration analysis are studied. The dynamic response has been obtained by model analysis in conjunction with the Wilson method. For example, a modified model of an actual jacket-type offshore platform is analyzed under the action of sea waves.

This paper presents PWM AC/DC buck converter circuits incorporating a frontend rectifier followed by AC/DC converter. Two Transistors are used as a main and auxiliary switch. The proposed circuit provides zero-current (2C) turn ON and zero-current/ zero-voltage (ZCZV) turn off to the two transistors, besides zero-voltage turn ON to two diodes. Numerical methods are used to analyze and determine the performance of the converter system. A feed-forward technique is employed to improve the performance of the converter over a range or output Power.

This paper considers the neural network-based PID controller. The learning and generalization properties of neural networks are utilized in improving the performance of a conventional PID controller. Two different schemes are introduced. Both schemes are studied and their performance is comparatively evaluated on an example of an uncertain system.

The influence of time delay on the statistical behavior of the first-order phase-locked-loop is investigated in VHF and UHF synchronous communication systems. The Fokker-Plank equation has been proposed to estimate the probability density function (pdf) of phase fluctuations as well as the average time to loss lock in the presence of noise. The result reveals that the degradation in the loop performance occurs under various conditions of detuning when the inherent time delay is present.

The use of fiber-optic links as the connecting media in wireless microcellular networks can provide uniform radio coverage to spatially distributed mobile users in a cost-effective manner. This paper investigates theoretically the performance of a fiber distribution system for a mobile phone network that uses a single high-power Nd: YAG laser in the base station and is shared by many microcells. Analytical expressions are derived for the bit-error-rate (BER) floor characteristics and optimum operating conditions. The results indicate clearly that the laser power can be reduced significantly when the modulation index is optimized.

The main object of this investigation is to obtain convenient expressions for the estimation of discharge coefficient for submerge flow over concave and convex semicircle shape crested weirs. Sixteen weir models were constructed and tested, these models were classified into four groups. The first and second groups were of single cycles having concave and convex shapes, respectively, with a curvature radius of 15 cm. The third and fourth groups were of double cycle having concave and convex shapes, respectively, with a curvature radius of 7.5 cm. In each group, the weir height p was varied four times 10 cm, 7.5 cm, 5 cm, and 2.5 cm. Based on the results of this study it was found that for constant weir radius, R, the discharge coefficient Cd, increases with the increase in the relative upstream head, h/p, while, for the constant upstream head, weirs of mall heights give a higher discharge coefficient than those of large height. Two general expressions were obtained for the estimation of Cd as a function of relative upstream head h/p, and relative radius R/P, one expression for single and double-cycle concave submerged weirs and the other for convex submerged weirs.

This study concerns the improvement of soils in the Basrah area. Two types of soil have been selected, the first from the Garmatt Ali place and the second type from the Abu Al-Khasseeb place. Natural (palm) fibers are used in the stabilization of these soils. These fibers were added by different percentages (0, 1, 2, and 3%) by weight of dry soil to improve soil properties. The selected soil is subjected to different tests, such as liquid and plastic limit, specific gravity, unconfined compressive strength, and compaction test. It was found that the addition of fibers to the soil affects compaction characteristics by decreasing maximum dry density and increasing optimum moisture content for both types of soils. The unconfined compressive strength increased with more addition of fibers. The effect of fiber content on swelling, the swelling percent reduced, especially during the first days of the test.