Print ISSN: 1814-6120

Online ISSN: 2311-8385

Volume 6, Issue 1

Volume 6, Issue 1, Autumn 2006, Page 1-109


Characterizing and Modelling of Indoor Radio Propagation Channel at ISM Band

Yessar Ezze; din; Abdulkareem S. Abdallah

Basrah Journal for Engineering Science, Volume 6, Issue 1, Pages 1-10

The investigation of the indoor electromagnetic propagation has been performed at the unlicensed industrial, scientific, and medical (ISM) band, which has gained increased attention recently due to high data rate communication systems developed to operate in it. The effect of. the incidence angle and materials thicknesses on the reflection coefficients for both horizontal and vertical polarization has been studied. Two-dimensional ray-tracing model has been suggested to simulate the influence of buildings electromagnetic properties on indoor radio channel characteristics, such as signal level, rms delay spread, and coherence bandwidth. Results show that the influence of the permittivity is more important than the influence of the order of reflection considered for the ray- tracing model. It is also shown that, compared with power level, rms delay spread is more sensitive to the building dielectric parameters. Maximum rms delay spread is dependent mainly on the reflectivity of the walls which dependent on the dielectric parameters.

NOVEL SYNTHESIS METHODOLOGY FOR CONTROLLING ZERO-CURRENT ZERO-V0LTGE TRANSITION DC/DC BOOST CONVERTER

Elaf J. Majeed; Ramzy .S. Ali; R. H. Thejel

Basrah Journal for Engineering Science, Volume 6, Issue 1, Pages 11-26

Among the soft-switching techniques, the Zero-Current Zero-Voltage Transition (ZCZVT) technique is used in this paper. It is based on the Resonant Transition Mechanism requirements, which permit newcomers to perceive the Resonant Transition techniques as a whole instead of dissimilar soft-switching techniques. The open loop operation of the power circuit (DC/DC Boost Converter) and control circuit have been implemented and tested with MatLab software. The simulation test facility and the analytical development tools being used are described. The derivation of closed loop control strategy based on fuzzy logic control with nonlinear fuzzy sets for input and output variables is described in detail. The closed loop simulation results that describe the performance of the proposed converter with this control strategy due to different effects are also included.

Synchronization of chaotic Semiconductor Lasers with Optoelectronic Feedback and its Applications to Encoded Communications

Fadil Rahma Tahir

Basrah Journal for Engineering Science, Volume 6, Issue 1, Pages 27-39

The theoretical study of synchronization of two coupled single — mode semiconductor lasers is achieved. The transmitter is laser subject to optoelectronic feedback that operates in a chaotic regime. The receiver can also operate in a chaotic regime similar to the transmitter. The effects of parameter mismatch on the synchronization of two lasers with optoelectronic feedback are determined, with mismatch in delay time, with mismatch in feedback strength, and with coupling strength between two systems. The synchronization is sensitive to mismatch in the delay time for the transmitter and receiver feedback loops. An open — loop receiver configuration does not have the problem of delay time mismatch and shows the highest synchronization. The synchronization phenomena that appear in the two-coupled semiconductor lasers can be used in communications systems. Finally, an encoding and decoding of message on the chaotic carrier is demonstrated.

Optimal Design for LCL-SRC Type

Adel M. Dakhee

Basrah Journal for Engineering Science, Volume 6, Issue 1, Pages 40-47

The LCL Series Resonant Converter (LCL-SRC) type offer nearly load- independent output voltage under some operating conditions. By this way the output voltage can be regulated against a wide load and line variations with a small variation of switching frequency.
In this paper a simple method for optimization of LCL-SRC is presented. This method takes the stored energy as a theoretical index to obtain the minimal size of the converter inductors L1 and L2 which contribute significantly to the converter size and weight.
The R0-method for the analysis of resonant converter is discussed. This method was found fairly accurate for operation above resonant frequency.

BOCST DC/DC CONVERTER CONTROL BASED ON FUZZY LOGIC

Ali Fathel; Ramzy S. Ali; Jawad Radhi

Basrah Journal for Engineering Science, Volume 6, Issue 1, Pages 48-61

This paper proposes a fuzzy logic based controller for boost type DC/DC converter. It forms an improvement to the dynamic performances of the well known P1 like fuzzy controller which uses the output voltage error & its rate of change as an inputs.
The proposed controller generates a duty ratio control signal through the addition of a weighted part of the input voltage and of the low pass filtered signal of the inductor current to that of the fuzzy controller which is fed by voltage error and a signal representing the differences of the output voltage from its low pass filtered version.
The controlled boost DC/DC converter exhibited excellent performances under small and larger disturbances of the input voltage and output load resistance and also showed good reference tracking ability.

Exact Stiffness Matrices for Piles in Nonhomogeneous Elastic Foundation .

Mohamad Jawad K. Essa

Basrah Journal for Engineering Science, Volume 6, Issue 1, Pages 62-73

This paper presents an exact solution for the load — settlement relationship of axially loaded piles embedded in nonhomogeneous elastic foundation. The governing differential equation is reduced to modified Bessel equation of order v. The solution is represented by Bessel’s functions of the first kind of order v. The stiffness coefficients are then derived from the exact solution. Numerical comparison with approximate solutions of special cases verify’ the accuracy and efficiency of the adopted method

Dynamic Analysis of Offshore Structures with. the Effect of Soil-Structure Interaction

Mohamad J. K. Essai; Anis A. Mohamad All; Mr Samoel M. Saleh

Basrah Journal for Engineering Science, Volume 6, Issue 1, Pages 74-86

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

MODELLING OF VAPOUR-GAS BUBBLE OSCILLATION UŠING LINEAR WAVE EQUATION

Abbas Z. AI-Asady

Basrah Journal for Engineering Science, Volume 6, Issue 1, Pages 87-101

By using linear wave equation a new model of bubble dynamics in acoustic field is constructed including effects of thermal conduction both inside and outside a bubble, and non-equilibrium evaporation and condensation of water vapour at bubble wall. The liquid temperature at bubble wall is numerically calculated by solving the heat conduction equation (without assuming a profile of liquid temperature). It is including effect of the latent heat of non-equilibrium evaporation and condensation at bubble wall. It is concluded that the liquid temperature increases to the same order of magnitude with that of the maximum temperature attained in the bubble at strong collapses. It is caused by the latent heat of intense vapour condensation and by the thermal conduction from the heated interior of the bubble to the surrounding liquid. The intense vapour condensation takes place at strong collapses because the pressure inside the bubble increases. The comparison is given between the calculated result and the experimental data of radius-time curve for one acoustic cycle. The calculated result fits well with the experimental data.

ESTIMATION OF FAILURE TEMPERATURE IN THE RISER TUBES OF BOILER FURNACES

Haider .M. Mohammed

Basrah Journal for Engineering Science, Volume 6, Issue 1, Pages 102-109

In this research, the temperature of failure and surface temperature was determined using theoretical and experimental works. Stress rupture occurs due to overheating, thick layer of deposits in water-side, and erosion in the fire-side were studied. The mechanical properties such as yield strength, ultimate strength, and yield strain are taken experimentally from tensile-test data of the riser tubes of boiler furnaces of Petrochemical Industry in Basrah. The experimental values are used in calculation of stress rupture. Heat transfer relations are used to calculate the temperature of the wall tube. Also, pressure to rupture required for causing plastic flow (rupture) was derived by using failure criterion. Pressure to rupture compared to the stress rupture to find the value of failure temperature. A computer program was used to obtain the results as curves that are gives the value of failure and surface temperature and to show the effect of erosion and presence of deposits on the failure of tubes.