Tikrit Journal of Engineering Sciences

The present paper deals with studying the dynamic model and control of absorption column by implementing two types of control strategies for CO2 gas and NaOH solution. The control methods in this study are PID, fuzzy with five membership function. The results showed that a good improvement for CO2/Air-NaOH system with chemical reaction is achieved when the fuzzy logic with five membership function because these methods have more suitable, lower over shoot, less offset value and less integral absolute error.

It is important step to use a new technology for collaborative learning. The aim of this research is to facilitate collaborative learning group, increase a skill of learning, extending the knowledge of wiki in building online web collaborative learning activities system of computer science departments, by development a standards learning using free collaborative Wikispaces. The built system is called ComWiki. The ComWiki is an online collaborative system for learning. Includes delegation and Coordinate of responsibilities between group of members and share their opinions and ideas. The responsibilities such as exchange of views and important information, experiences of different professors with interaction between them. This work is published in http://ccomwiki.wikispaces.com. ComWiki is used mechanism for adding a trust more than others by enhancing online cooperative and collaborative education in using a non-open source Wikispaces application. ComWiki support a protection media for all information to prevent changing by web users and ease of use. ComWiki has a different media of learning like pictures, videos, text, chatting.

In this research, Flow-3D software uses to study the energy dissipation for stepped spillways with different end sills. The study is bases on three models. The first model contains rectangular end sills in all steppes. The second model contains rectangular end sills between one step and another. The third model contains triangular end sills in all steppes. For each of these models, three different variables are adopt, slope, height of the spillway and a number of steppes, and four different discharges value, carrying the total number of experiments to (324) tests.
Analytical results show that the model (3) is the highest energy dissipation for all discharges value. Empirical equations extraction to find the energy dissipation for each of these models. The artificial neural network is also adopt to prove the accuracy and efficiency of the analytical results which are at high rates of compatibility with the values of the coefficient of determination for (model 1), (model 2) and (model 3) equal to (93.47%), (88.20%) and (86.00%) respectively. Also, artificial neural network identifies the most influential factors on the energy dissipation, the friction Froude number is the highest impact on the energy dissipation for models (1) and (2), while the parameter (b/ks) for the model (1).

Ride comfort is one of the important requirement which cars manufactures is try to achieved it because its directly effect on the sales rate, so it was to be tacking the factors that effect on the comfort degree of car users , in this field it has been concentrating on the driver comfort because of his responsibility on the car drive and on passengers safety as well as to focus on the road and see the obstacles, this is achieved by isolating the vehicle body from the vibrations results due to irregularly by use suitable suspension system . In order to obtain accurate results, we study the non - linear disposition of system parts by taking into account the most prominent source of non-linearity represented by large angle of swing and non-linearity of spring and damper behavior, appropriate model was chosen by taking non-linear half truck vehicle model with four degree of freedom and by considering rigid vehicle body using two types of excitation half sin wave and trapezoidal obstacles as an expression of road irregularly. A Fortran computer program for simulation the results represented by displacement, velocity and acceleration in the center of gravity of vehicle body (C.G) , then comparison with recently published research was doing and it shown an acceptable compliance degree, to find out the improvement extent when taking into account the system non - linearity we compare with linear halve truck vehicle model and found that the adopting of non – linearity leads to improve the results, then an investigation to the driver comfort subject been carried out to know what we have achieved in this field by choose Ride Comfort Level (RCL) as comfortable criteria then the results have been used to determine the maximum speed that keeps the vehicle within comfort limit using three types of obstacles . It was found that the adopting of non-linearity in the accounts gives more speed range. Thus it can be say that we have achieved the goal of this research.

This work presents the analysis and modeling of communication network used for data transmission with multi-protocols in campus network. The designed network is based on the geographical location of communication nodes. (Colleges and centers). Network optimal backbone is first designed by Kruskal algorithm. It will be subject to reliability improvement by links addition. Tie-sets method is used to evaluate the network reliability. Communication nodes are modeled using local area network (LAN), server, links, router, switch, and Firewall. Intranet will be used as communication backbone mainly to connect different communication nodes with the Principal Communication Center (PCC) where the System Server (SS) is located. The connection of Intranet to the Internet is mad via the front-end system server (SS). Tikrit University Intranet (TUI) is taking as case study in the present research. Tikrit University sites are grouped into master communication nodes. Each node is composed from several colleges, centers, and administrative sections.

The effect of rust of the reinforcement bars on the bond and slip behavior between the rebars and the surrounding concrete is still under research judgement. This paper, investigated the effect of ranges of rebar rusting (0, 30-50% and 70-90%) of the limits of losing in mass that specified in the ASTM standard (6% of bar nominal mass) combined with other main parameters that affect the bond and slip behavior. A number of 72 pullout prepared specimens were tested. The studied parameters were using normal and high strength concrete (31 MPa and 76 MPa), different bars diameters (12, 16 and 25 mm), the change of embedment length (150 and 300 mm) and the using of bond epoxy coating for embedded length of reinforcing bars. The results showed that the rust within certain amount of permissible losing of mass (about 50%) led to increase the bond strength and decrease the slip between reinforcement bars and concrete. However, increasing rusting above 50% but within the permissible losing in mass would slightly decrease the bond strength and increase the slip comparing with zero rusting case for all tested bar sizes with and without using the bond improvement factors. The main recommendation of the study is to use the same criterion of acceptance of losing in mass specified by ASTM as the acceptance criterion of the amount of rust in the reinforcement bars
and using one of the studied improvement factors when the rust amount exceed 50% of the permissible limit of losing in mass.

A sample of sunflower oil, produced from Homs Sugar Company, was used in this study to fry local potato by frying under air at household conditions, and frying under pressure (at 150-180ºC, pressure 10-15kg/cm²) for 12 continuous hours without adding new oil. The results were estimated statistically by using Minitab program version 17.0 at level 0.01. The results showed, in both cases of frying, an increase in the physical properties (density, viscosity, refractive index, and coloring degree) of used oil by increasing frying time. A decrease Iodine Number, increase Peroxide Number, increase the percentage of free fatty acids, increase of C16:0 and C18:1 acids percentage, and decrease of C18:2 and C18:3 acids percentage, associated by increasing frying time. But when frying under pressure we noticed that these changes were slow because of the unadequated oxygen presence during frying under pressure. So we can say that the oil was still usable for frying for a long time when frying under pressure more than when frying under air with the vessel is open.

Flat tubes are vital components of various technical applications including modern heat exchangers, thermal power plants, and automotive radiators. This paper presents the hybridization of computational fluid dynamic (CFD) and artificial neural network (ANN) approach to predict the thermal-hydraulic characteristics of in-line flat tubes heat exchangers. A 2D steady state and an incompressible laminar flow in a tube configuration are considered for numerical analysis. Finite volume technique and body-fitted coordinate system are used to solve the Navier–Stokes and energy equations. The Reynolds number based on outer hydraulic diameter varies between 10 and 320. Heat transfer coefficient and friction are analyzed for various tube configurations including transverse and longitudinal pitches. The numerical results from CFD analysis are used in the training and testing of the ANN for predicting thermal characteristics and friction factors. The predicted results revealed a satisfactory performance, with the mean relative error ranging from 0.39% to 5.57%, the root-mean-square error ranging from 0.00367 to 0.219, and the correlation coefficient (R2) ranging from 99.505% to 99.947%. Thus, this study verifies the effectiveness of using ANN in predicting the performance of thermal-hydraulic systems in engineering applications such as heat transfer modeling and fluid flow in tube bank heat exchangers.

The main structural problem in construction on gypseous soils is due to the melting of the gypsum when exposed to water. This may be creating voids in the soil leading to rearrangement of the soil structure and moving the soil particles to more stable positions. This can cause excessive settlement which directly affects superstructures. This study, investigates the influence of gypsum removing on granular soil classification. Four gypsum soil specimens were taken from Al-Qadisiyah district in Tikrit at different depths from the natural ground surface. The depths adopted were 0.75, 1.10, 2.00 and 3.30 m. The corresponding gypsum content was 42.23%, 32.50%, 8.75% and 19.82%, respectively. The EDTA solution was used to disassemble and remove the gypsum particles by washing using distilled water. The results showed that EDTA solution and washing with distilled water was an effective method to remove gypsum from granular soils. Gypsum ratio was reduced to less than 2% in all tested specimens. The percentage of organic matter was not affected, and the specific gravity of the specimens increased between 2% and 12%. The gypsum removal process affected the granular distribution curves of the soil specimens and led to a decrease in the rate of soil grain diameters. In general, classification process of the soil before and after the washing of gypsum from the soil was not affected.

An experimental work on heat transfer enhancement in a shell and tube heat exchanger by insertion of helical coiled wires into the tube bundle was conducted. Four different pitch sizes were used (4.8, 6.4, 8.0, 9.6) mm. The working fluid for both shell and tube sides of the exchanger was water. Flow arrangement used was parallel and laminar for both sides with a Reynolds number for the tube inside ranging (100-920). Variables were taken into account, including; convection heat transfer coefficient, number of heat transfer units, thermal effectiveness, and pressure drop. CFD analysis was done in order to validate the experimental results. The study results showed an increase in heat transfer coefficient on the tube side by 54% due to the use of 9.6 mm pitched inserts. Highest thermal effectiveness obtained was in the case of 9.6 mm pitch inserts. Pressure drop rose up to 260% due to inserts.