Journal of Engineering

The technical development in scientific fields, has an effective influence in developing the possibilities of auditorium design, erection and performance. In the recent years, there was a great demand for flexible spaces, which could accommodare different acting performance and would be economical too.
Therefore technical efforts and facilities can be great help in providing flexibility's in geometrical relations, space configuration, material treatment and surface finishes of multi purpose halls. This research emphasis the importance of technical possibilities in both mechanical and acoustical sides for providing flexibility's in acoustical performance in auditorium by:
1 Theoretical side discussing
a Technical possibilities in multi purpose halls,
b Main acoustical charseters and parameters, which are important for the evaluation of acoustical performance of multi purpose halls
Practical side; uradying an example which in the national theater in Baghdad as study case, and calculating the acoustical parameters mathematically and discussing its technical possibilities and then giving acoustical and technical advice for developing its functional and acoustical performance.

r three-phase converters, the knowledge of the orders and relative amplitudes of lower harmonic components is essential for a filter design. Under unbalanced conditions of the supply voltage, harmonics that are not produced under balanced conditions are generated. The effect of unbalanced- supply conditions on the harmonics generated in the primary of a Transformer feeding a three- phase six- pulse uncontrolled converter is investigated theoretically .The validity of theoretical results is demonstrated practically.

An experimental investigation was made for the study of incompressible flow on a circular disc. It consists of two parts. The first was the determination of the pressure distribution of the front an! rear sides of three samples of discs with diameters 9.73,10.75 and 11.94cm and 3mm thickness. The discs were mounted normal to the flow direction. This part also included the determination of pressure distribution on the front and rear sides of an inclined disc of 10.75 cm diameter it inclination angles of 30, 60, 120, and 150 to the horizontal. The second part of the investigation was the determination of the drag coefficient on a circular disc 10.75 cm in diameter and 3 mm in thickness using two methods. The first using strain gages as sensitive elements. The strain readings were recorded and transformed into drag force by using a transformation system or by using the strain transformation equations. The second using a dial gage whereby the displacement was transformed into drag force. Drag determination was performed for normal and inclined disc. Inclination included 30,60 and 90 to the horizontal. Tests were made using a low speed wind tunnel, at low, medium and high velocities of 4.74, 8.316 and 10.35 m/s respectively. The experimental results compared well with theoretical predications and with available published data

This paper introduces a new class of convolutional codes, which is called Turbo Code. Turbo Code was shown to achieve performance in terms of Bit-Error-Rate (BER), which is near Shannon limit. Turbo Code encoder is built using a parallel concatenation of two Recursive Systematic Convolutional (RSC) codes. In this paper, two solutions to the trellis termination problem are presented. The first solution encoder uses terminated Upper RSC encoder and unterminated Lower RSC encoder. On the other side, the second solution encoder uses terminated Upper and Lower RSC encoders. The performance of the two solutions is tested for different circumstances and the results are interesting.

This paper reports the conversion of a large unsignalised roundabout (HURIYA SQUARI!) relatively close to the University of Baghdad campus to a signalized intersection. The study focused on reduction of vehicle delay and queue length at this intersection area. During the course of this research project, two software packages for the analysis and design of isolated intersection, SIDRA (Akcelik, R.1986 and 1991) and HCS (Transportation Research Board, National Research Council 1994) were available. A trial site selected and the observed data used in the evaluation of the SIDRA and HCS outputs. The evaluation process indicated that SIDRA produce vehicle delay, which is reasonably consistent with the observed vehicle delay. Hence, SIDRA software used in the evaluation of alternative designs of the HURIYA SQUARE intersection. Five proposals of signaling plans and four proposed geometric layouts examined. The first proposal evaluated on site; the other four proposals examined with aid of the SIDRA software. Based on the carried analysis, the intersection geometric layout, signal timing, and phasing plan which result in lower vehicle delay and higher reserved capacity selected.

the present investigation is concerned with thesevaluation of creep behavior of concrete under variable temperature and relative humidity. It includes analytical and experimental parts. In the analytical part, BP-KX creep model is presented. As this model considers temperature and relative humidity to be constant, it was modified through considering them to be variable with time, which is the usual case. Functions for the daily variation of these two parameters, according to Baghdad climate, were developed and substituted in the model. In the experimental part, three series of cylindrical specimens (100mm x 200mm) were prepared for the creep test. In series (1), the temperature was raised and simultaneously the relative humidity was lowered just after loading. Series (2). specimens were loaded at high temperature and low relative humidity followed by low temperature and high relative humidity. Series (3) specimens were loaded at low temperature ard high relative humidity followed by high temperature and low relative humidity.Comparison between the analytical and the experimental work confirmed the need for a correction factor to be included in the proposed modified model. The results revealed that concrete specimens subjected to high temperature and low relative humidity, after the load application, will show higher creep than specimens kept at high temperature and low relative humidity before and after lord application. This indicates that specimens loaded in summer show lower creep than those loaded in winter

Conventional methods of slope analysis are based on the concept of limit equilibrium and enab e only the calculation of the critical height or the minimum factor of safety of a slope. These methods are not usually concerned with the stress distribution within a slope either above or below assumed surfaces of failure. This task can be done through the finite element method. In this paper, this method is used for the analysis of embankments. It was found that a good agreement could be obtained between the simple non-linear elastic-plastic finite element analysis, adopted in this paper, and sophisticated analyses which deal with plastic behavior of soils. This can be done when choosing the appropriate material parameters.

An experimental investigation was conducted to study the various parameters affecting the production of oxalic acid by the action of concentrated nitric acid on carbohydrates. Two feedstocks were studied, viz., dates fruit and dates syrup. The study also covered the effect of the amount of nitric acid and catalyst used in addition to employing two acid concentrations (67 wt.% and 98 wt.% acid). The results showed that when using 67 wt.% nitric acid, dates syrup was best suited as a raw material. And the best amount of nitric acid and V₂O, catalyst were in the ratio of 150 mls: 25 mg per 50 g feedstock. When using 98 wt.% nitric acid, no catalyst was required for the reaction and the reaction proceeded violently with the evolution large amount of the nitrogen oxides

This work covers the investigation of the effects of space environments factors on spacecraft structure. The satellite operates on a low earth orbit at circular (500,500) km, and subjected to different torques in space environments.The purpose of this paper is to develop the satellite structure design and test it to obtain the mechanical behaviour of structure. The satellite used so far is spin - stabilized, and rotating about one axis in 3 rpm. A configuration to the structure is suggested to be hexagonal; the dimension of structure is 110cm in diameter and 85cm high. The general static and dynamics tested of the system are verified, and analyzed to find the stress,strain, and vibration on the structure.

The free solution of the Dirac equation is so important in the modern field of heavy ion atomic physics, determined through Lorentz transformation [W. Greiner 1997]. At high energies one must investigate the relative wave equations. This means equations, which are invariant under Lorenz transformation. The Lorentz transformation is so important, that it needs, to be derived on a more logical basis. Many textbooks and research papers have derived Lorentz transformation by different postulates [Anderson, J.L. 1967][G. Nadean 1962][H.A. Atwater 1974], which are not treated electro-dynamically this paper exhibits a method of finding the Lorentz transformation by exploiting the Maxwell's famous equations of the electromagnetic field equations

Uncoupled behavior of a dam under, earthquake loading is investigated. Three constitutive models are used:. The linear-elastic model where soil properties; shear modulus and damping ratio are strains ar d cycle independent.-The equivalent linear model where soil properties are strain dependent but cycle independert. The shear modulus tends to decrease as the shear strain increases, while the damping ratio tends to increase as the shear strain increases. - A non-linear model where soil properties tend to change not only with shear strain but also with the progression of cycles. In this work, the bounding surface model is used.For these studies, three kinds of umerical integration methods in the time domain are usel. namely, Newmark, Wilson-0 and the a-methods with different damping ratios, In this study, the bounding surface plasticity model visualizes the realistic behaviour of the dam under the dynamic loading rather than the equivalent linear and the elastic linear models

This research is concerned with performance of different shapes (parallel plate, grid, corrugated) and materials (polystyrene, polypropylene, P.V.C, and steel) of packing for an air -water- cooling tower. A Mechanical forced draught counter current flow cooling tower of 300 mm x 300 mm, cross-sectional area and 1.65m height was constructed and studied theoretically and experimentally Air flow rates of 0.533,1.035, and 1.774 kg/m2.s were used in conjunction with water flow rates of 1.686, 2.218, and 2.66 kg/m2.s, and water temperature of 40,45,50 °C. The tower characteristics (KG a Z/L) and the volumetric mass and heat transfer coefficients (Kça, hoa and ha) are found to be a function of the water and air flow rates simultaneously.The work was extended to include the longitudinal and transverse temperature profiles within the tower for different parameters. By employing packed heights of polystyrene, and polypropylene of 120,90,60, and 30 cm, end effect were studied and the tower characteristics (KG a Z/L) corrected for these effects. Least square method was used to correlate the experimental results for (Ko a Z/L) in terms of air flux G and water flux L

The transient performance (acceleration and deceleration) analysis of turbojet gas turbine engine has been carried out in the present work. Transient simulation of the engines is based on the compatibility of flow and rotational speed but not of work. Gas turbine simulation is a general- purpose simulation developed for steady state (matching) study. Matching is achieved by zeroing the difference in mass flow rate of adjacent components, and work of compressor-turbine pairs Steady state is taken as an initial condition for transient simulation of the engine. The factors indicating engine limits such as surge margin, engine maximum temperature, and combustion chamber flameout that affect transient response has been studied. The results show that there is sudden change in the investigated parameters during transient operation, except for the rotational speed and the engine flow rate. Increasing the compressor surge margin and /or maximum turbine inlet temperature improves engine acceleration and decreases the acceleration time. Comparison with previous experimental work showed good agreement.