Tikrit Journal of Engineering Sciences

Calcium carbonate deposition is generally predominant in cooling water-circulating system. For the control of calcium carbonate, scale formation two types of polymeric scale inhibitors were used Polyamino polyether methylene phosphonate (PAPEMP) and polyacrylaminde (PAA).Model of cooling tower system have been built up in laboratory scale. Experiments were carried out using different inhibitor concentrations (0.5, 1, 1.5, 2, 3) ppm, at water temperature of 40oC and flow rate of 150 l/hr. It was found that Polyamino polyether methylene phosphonate more effective than polyacryle amide’ as scale inhibitor in all used concentrations and the best inhibition efficiency (95%) was at (2.5) ppm of Polyamino polyether methylene phosphonate and (85%) with polyacryle amide at concentrations of (3) ppm.
The performance of the polymeric scale inhibitors was compared with a method used to control heavy calcium carbonate scale forming by the deposition of sufficiently thin protective calcium carbonate scale using sulfuric acid and depending on Ryznar stability index controlling method.

The Cyclic Prefix (CP) technique is widely used in Orthogonal Frequency Division Multiplexing (OFDM) systems. A CP of length greater than the channel order guarantees the orthogonality of the consecutive OFDM symbols. Therefore, the effects of Inter Symbol Interference (ISI) and Inter Carrier Interference (ICI) are cancelled. On the other hand, CP reduces the transmission efficiency.
Conventional OFDM systems use constant length CP. For time varying channels, CP length may become shorter than channel order resulting in considerable loss in orthogonality and performance degradation. Otherwise, when CP length becomes much greater than channel order it results with time and power wasting, and hence decreasing transmission efficiency.
This paper proposes the usage of a multipath delay-tracking module to provide the OFDM system with the actual channel order and accordingly the suitable CP length will be determined. Computer simulations show that the proposed system saves about 47.6% of the time and power spent by the same constant length CP OFDM system tested under the same conditions.

There are more concerns about possible health effects related to electromagnetic fields from computer monitors and other video display terminals because of the widespread using of computers in laboratories, offices and internet halls. This research aims to detect the effect of electromagnetic field radiations in these halls and laboratories and study the successful ways of minimizing its negative health effect on human health. The research has been performed on both the mathematical calculations and practical measurements. The obtaining results show that the practical measurements are consistent with the mathematical calculations results. Comparison of these results with the safety standard guideline limits shows that they are within the acceptable espousing limits recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and that means there is no health risk from exposure to these fields if the exposure is within the acceptable limits

This paper aims at establishing a model in OPNET (Optimized Network Engineering Tool) simulator for the University of Mosul computer network. The proposed network model was made up of two routers (Cisco 2600), core switch (Cisco6509), two servers, ip 32 cloud and 37 VLANs. These VLANs were connected to the core switch using fiber optic cables (1000BaseX). Three applications were added to test the network model. These applications were FTP (File Transfer Protocol), HTTP (Hyper Text Transfer Protocol) and VoIP (Voice over Internet Protocol). The results showed that the proposed model had a positive efficiency on designing and managing the targeted network and can be used to view the data flow in it. Also, the simulation results showed that the maximum number of VoIP service users could be raised up to 5000 users when working under IP Telephony. This means that the ability to utilize VoIP service in this network can be maintained and is better when subjected to IP telephony scheme

In This search, the phenomena of resonance in series piping systems with oscillating valve have been studied. The one-dimensional flow, unsteady state flow, and partial differential equations have been solved by using transfer matrix method.
The details of the transfer matrix method, the derivation of the field matrices and point matrices, and procedures for determining the natural frequencies and frequency response of piping system are then presented. A computer program (Resonance) was developed to calculate the pressure and discharge oscillations at the valve, the phase angle between the pressure head and relative gate opening of the valve, the phase angle between the discharge and the relative gate opening of the valve and the pressure and discharge oscillations at certain sections of the pipes. To verify the transfer matrix method, the results have been compared with impedance method and agreement has been found.

In this work the effect of spark timing on the spark ignition engines is investigated by computer simulation and experimental test for speeds of (1500,2000,2500,3000 and 3500)rpm at spark timing of (20o,30o,40o,50o and 60o) before TDC for each speed. This is done in order to find a suitable mathematical expression for spark ignition advancing with respect to the speed of the engine to predict the correct ignition advance as in real engines .The results showed that the method of using a mathematical expression is more realistic and reasonable comparing with the results obtained by other workers.

Sometimes in a manufacturing environment, a robotic arm is wanted to move in a straight path such as welding, painting and assembling. This straight path causes the manipulator to actuate all or most of its joints in the same time to track the path. Along this path, the manipulator may reach a specific singular configuration in its workspace at which one or more joints are in their limits, or a part of the path lies outside the workspace. These conditions make the arm’s movement be unsmooth and may cause damage to the manufacturing process. In this paper, the singularities inside the workspace of a 4-DOF spherical manipulator are indicated and a method is presented for finding the arm configurations (assuming that all joints are actuated at the same time) along a straight path between an initial and a goal configurations. All joint limits are presented and if a part of the path lies outside the workspace, the model processes this condition by introducing a new initial configuration through changing the third joint’s (q3) position only. A smooth straight path is generated between any two configurations using the parametric equations of the line connecting them. Unlike the analytical inverse kinematics, which needs a (4 x 4) homogeneous transformations convention matrix (DH) to find the joint variables, this method needs only the initial configuration, goal configuration, link lengths and the corresponding Cartesian coordinates of the path. It always gives the correct solution for the under taken path.

Efficient image compression approaches can provide the best solutions to the recent growth of the data intensive and multimedia based applications. As presented in many papers the Haar matrix–based methods and wavelet analysis can be used in various areas of image processing such as edge detection, preserving, smoothing or filtering. In this paper, color image compression analysis and synthesis based on Haar and modified Haar is presented. The standard Haar wavelet transformation with N=2 is composed of a sequence of low-pass and high-pass filters, known as a filter bank, the vertical and horizontal Haar filters are composed to construct four 2-dimensional filters, such filters applied directly to the image to speed up the implementation of the Haar wavelet transform. Modified Haar technique is studied and implemented for odd based numbers i.e. (N=3 & N=5) to generate many solution sets, these sets are tested using the energy function or numerical method to get the optimum one.
The Haar transform is simple, efficient in memory usage due to high zero value spread (it can use sparse principle), and exactly reversible without the edge effects as compared to DCT (Discrete Cosine Transform). The implemented Matlab simulation results prove the effectiveness of DWT (Discrete Wave Transform) algorithms based on Haar and Modified Haar techniques in attaining an efficient compression ratio (C.R), achieving higher peak signal to noise ratio (PSNR), and the resulting images are of much smoother as compared to standard JPEG especially for high C.R.
A comparison between standard JPEG, Haar, and Modified Haar techniques is done finally, which approves the highest capability of Modified Haar between others

Under drip irrigation , the plant's root is concentrated inside the wetted bulb (region). Thus, the development of these roots and the plant production are greatly affected by the wetting pattern. Therefore, the wetting pattern of soil under drip irrigation must be taken into consideration in the design of drip irrigation system for both single dripping source or multi-overlapping wetting patterns of dripping water sources.
The aim of this study is to evaluate the effect of initial water content of the soil and spacing between two adjacent dripping sources with different flow rate on the movement of the wetting front.
This study included 16 tests for monitoring the advancement of the wetting front with time during and after the water application phase. The water advance and water distribution measurement are carried out for two cases of the soil profile: for the first case with initial volumetric water content of 4.08% and for the second case with initial volumetric water content of 12.24%. Two spacing between the emitter were tested 25cm and 50 cm using application flow rates of 0.606, 1.212, 1.818, and 2.424 cm3 /min/cm to show the combined effect of spacing and flow rate on the performance of two adjacent emitter.
The study proposed a method for determining the spacing between the two emitting sources , the water application rate and watering time. The proposed method depends on a wetted zone whose depth is equal to the root zone depth with a values equals to the maximum vertical advance of the wetting front underneath the drip line at time when this depth is equal to the depth of wetting at midpoint between the drip line. the study revealed that both the vertical water advance in soil underneath the emitter and the horizontal advance of the wetting front is larger than those in the case of single emitter.
Furthermore, the vertical water advance increases with the decrease spacing between the two drip lines. Also, the horizontal advance of the wetting front is not affected by varying this spacing for both studied cases of initial water content.

Most of the current studies of Arabic Islamic architecture indicates different theoretical bases, whether in its definition or analyses, between different thinkers and researchers, dependable on the cultural, thoughtful and ideological bases of related references; thus, we can find Arabic Islamic architecture, both in urban planning and architectural point of view, in the light of deferent visions of: western thinkers, as an artistic forms and compositions, Arab national pioneers, analyzing its components on Arab society values, declined from its establishment of Arab desert and its impact on its rural culture; and radical Muslims thinkers restricting it on certain historical period, trying to reform it according to blocked theoretical rules, giving up its capability to development, sustainability and renewal.
The reason of all these problems is the ambiguity of the comprehensive emphasizes of one the most effective bases of Arabic Islamic architecture, which is the balance between the poles of spirit-material dualism; so that, some thinkers stood on one pole of this dualism, trying to study it through this defect point of view; meanwhile others stand on the other pole; without conscious or preconscious of the other pole, consequently the result of this hard shortage in identifying the bases of Arabic Islamic architecture in most of these studies.
This research concludes an example of Arabic Islamic cities, Samarra City, which passed on different ages, lasting from Abbasid age to modern age, reflecting different spiritual and materialistic changes according to change in political, economic, social and cultural regimes; all these indicated by the vital ruins, obviously translating these changes, where it appoints the importance of the balance between both poles of this dualism, to illustrate vision of Arabic Islamic City, through these ages.

The main objective of this study is to compare the performance of three alternative materials used to improve dewatering of sludge produced from secondary settling tank of Mosul medical city wastewater treatment plant; those materials are Kaolin, Limestone and Clay stone.
Six dry weight percentages for each alternative are used (2, 4, 6, 8, 10, 12) % from dry weight of sludge. The specific resistance to filtration (SRF) was used as a criterion to compare the studied materials.
Experimental results showed that SRF is 4.1×1012, 5.9×1012, 5.8×1012 m/kg when 8% additional dose were used for each of Kaolin, Limestone and Clay stone respectively, this study showed that the best alternative material studied is kaolin which achieve decreasing efficiency in SRF more than 70%.

In this research a laboratory study was carried out to investigate the scour phenomenon in sandy soil beds downstream different shapes of culverts, Four shapes of culverts such as circular, ellipse, rectangular and square were used. So, a best hydraulic section was used in rectangular and ellipse shapes. The study includes the measurement and comparison of maximum scour depth and length of scour hole downstream these different shapes of culverts. Also, the distribution of soil parts was studied. It was used five discharges for each one of culvert.
Laboratory results of this study showed that the minimum depth of scour in the same discharge occurred downstream ellipse culvert and then rectangular culvert and then square culvert and the last circular culvert.