Tikrit Journal of Engineering Sciences

Depolymerization reaction is considered one of the most significant ways of converting waste polyethylene terephthalate in to terephthalic acid. The water polyethylene terephthalate bottle waste was collected from different places in Baghdad. The collection step shows that there is plenty amount of polyethylene terephthalate suitable to be an important source of terephthalic acid production.
PET plastic waste conversion to terephthalic acid by depolymerization process was examined. The effect of ethylene glycol amount, reaction time (up to 90 minutes) and reaction temperature (from 70 to 170° C) on the polyethylene terephthalate conversion was obtained.
The kinetic study shows that the ordination of the depolymerization reaction of PET is first order irreversible reaction with 31103.5 J/mole activation energy.
A 97.9 % terephthalic acid purity has been obtained by purification with N, N-dimethylformamide.

In this work, an experimental study has been conducted to investigate the behavior of high strength self-compacted concrete hollow beams under pure torsion.
In this work, the beams were implemented and tested under pure torsion load. A total of six beams were tested. All beams were of the same cross section, the same length, the same concrete mixture and quality control. All beams were of external dimensions (300x300mm) and the hollow dimensions (180 x180mm) and all the concrete beams have the same number of main reinforcement 4Ф12 at the top and 4Ф12 at the bottom, the main variable is the stirrups spacing to investigate the effect of stirrups amount on improving of hollow reinforced concrete beams resistance against torsional moments.
The six beams were subjected to pure torsion by using fabricated test machine to enable the application of the mentioned pure torsion load.
Experimental results showed that, many structural properties of the beams are improved, by decreasing the stirrups spacing. Highest improvement achieved for ultimate torsional moment (Tu) followed by cracking torsional moment (Tcr) and then by angle of twist (Ø) while the improvement of beam's concrete strain (ε) came at last.
The percentage of improvements of the mechanical properties of the beams due to decrease of the stirrups spacing according to the reference beam is:
 For Tu ranges between (25.7-254.3) %.
 For Tcr ranges between (25-200) %.
 For Ø ranges between (23.3-76.0) %.
 For ε (29.0-50.2) %.
The considerable increase in Ø and ε before failure makes the increase of stirrups preferable for safe life and attaining attention.

Artificial neural network in MATLAB simulator is used to model Baiji crude oil distillation unit based on data generated from aspen-HYSYS simulator. Thirteen inputs, six outputs and over 1487 data set are used to model the actual unit. Nonlinear autoregressive network with exogenous inputs (NARX) and back propagation algorithm are used for training. Seventy percent of data are used for training the network while the remaining thirty percent are used for testing and validating the network to determine its prediction accuracy. One hidden layer and 34 hidden neurons are used for the proposed network with MSE of 0.25 is obtained. The number of neuron are selected based on less MSE for the network. The model founded to predict the optimal operating conditions for different objective functions within the training limit since ANN models are poor extrapolators. They are usually only reliable within the range of data that they had been trained for.

Iraq being one of the developing countries of the world considers energy efficiency and the impact of its generation on the environment an imperative process in improvement of its power generation policies. Iraq bearing high temperatures all year long results in reduction of air density, therefore, Inlet air Cooling and Steam Injection Gas Turbines are a striking addition to the regenerative gas turbines. Regenerating Gas turbines tend to have a high back work ratio and a high exhaust temperature, thus, it leads to a low efficiency in power generation in hotter climate. Moreover, STIG and IAC through fog cooling have known to be the best retrofitting methods available in the industry which improve the efficiency of generation from 30.5 to 43% and increase the power output from 22MW to 33.5MW as the outcomes of computer simulations reveal. Additionally, this happens without bringing about much extensive change to original features of the power generation cycle. Furthermore, STIG and spray coolers have also resulted in power boosting and exceeding generation efficiency of gas turbine power plant.

The dynamic characteristics such as speed and torque as well as voltages and currents of pwm brushless DC motor inverter are analyzed with a MATLAB model. The contribution of external load torque and friction torque is monitored. The switching function technique is adopted for the current control of the embedded three phase inverter that drives the brushless DC motor. In switching functions the power conversions circuits can be modeled according to their functions rather than circuit topologies. Therefore, it can achieve simplification of the overall power conversion functions. The trapezoidal type (back emf) is used in the model as it has lower switching loss compared with sinusoidal type (back emf). Results show reliable time analysis for speed, torque, phase and line voltages and currents and the effect of current commutation is clearly observed.

The consideration of novel response spectrum analysis to check the reinforced concrete RC buildings resistance towards the seismic risks in Iraq has not been investigated so far. Due to the increasing of frequent earthquakes with moderate intensity in north of Iraq, caution should be taken into account in building design especially with considering the design codes. Where, there are no specific Iraqi standards of earthquake for building design. Thus, the proposing of new response spectrum relationship matching the properties of Kurdistan region (north of Iraq) soil is considered essential with considering of novel stiffness or inertia reduction factors for concrete sections. Present endeavor is devoted to develop new design spectra dynamic analysis of RC multistory building located in Duhok city-Iraq. Influence of proposed concrete section reduction factors on the analysis outcomes has been investigated also. Great role has been observed for introducing of stiffness reduction factors in present seismic analysis represent in magnifying of lateral deformation of building of more than 50%. Proper matching was obtained between current proposed spectrum design outputs and that for other analytical approaches.

The achievement of life cycle assessments of energy systems with both maximum power output and economical profits is considered as the main objective of operations management. This paper aimed to evaluate both of the performance of a gas turbine using an inlet air cooling system as well as its life cycle cost. Accordingly, a thermodynamic model and an economic model are developed respectively to derive an analytical formula for calculating the cooling loads and life cycle cost. The major results show that, the output power of gas turbines power plant with a cooling system is (120MWh) which is higher than that of gas turbines power plant without the cooling system (96.6 MWh) at peak condition; while the life cycle cost is lower in the case of gas turbines power plant with cooling system. Thus, the proposed methods show a potential cost reduction and achievable through changing the structure of the system.

The present drying beds of Al-Dubaiee waste water treatment station is not enough, thus, the present study is performed. In this work, many experiments have been made in order to find out the optimum thickness of the drying bed and to find suitable filtration agents from local materials. Moreover the effect of flocculent agents is tested. The results show that optimum thickness is 30 cm of brick and 25 cm of sand. Ferric concentration of 100 mg/l gives the best results. It is also found that drying efficiency is improved with reducing specific filtration resistance. The effluent waste water is found suitable for agriculture purpose concerned heavy metal concentration. Special drying bed (handy slop towards center) is constructed and it is found that the required area is reduced by 50%.

A reinforced concrete hollow core one-way slab is one of the types of slabs used widely around the world in residential and industrial buildings to take advantage of them Economic and thermal insulation as well as to reduce the self-weight of the construction. The aim of the present study is to examine the structural behavior of the reinforced concrete hollow core one-way slabs reduce failure using the normal concrete and fibrous concrete and then strengthened using carbon fiber(CFRP)
This study include molding of ( 6) specimens differ in terms of the voids volume (Vv) , volumetric percentage of steel fibers (