KUFA JOURNAL OF ENGINEERING

This paper proposes a new algorithm termed Quad Tree-Discrete Cosine Transform (QT-DCT). QT-DCT is a low complexity algorithm that combines the good energy compaction ability and the simplicity of the DCT used by the Joint Photographic Expert Group (JPEG) image compression standard, and the global and embedding properties of Subband Coding (SBC) systems. The proposed QT-DCT reorders the DCT coefficients into subbands. Then these subbands are coded using quad-tree decomposition method. The main contribution of the proposed QT-DCT algorithm is that it has better PSNR and lower complexity than JPEG image compression standard and some existing algorithms that have about the same complexity. In addition, QT-DCT produces an embedded compressed bit-stream which is able to achieve any compression bit-rate very easily. This is a very desirable feature for the modern requirements represented by the Internet.

Xanthan gum is a nontoxic polysaccharide with a good gelling, thickening and stabilizing attributes, and used widely in food and cosmetic industries. Effect of temperature on the viscosity and density of various solutions of xanthan gum (0.1 ,0.2,0.3,0.4 and 0.5 w/v %) were studied experimentally with temperatures range of 30 to 60 C. The experimental tests were performed using DV-II+Pro viscometer at different speeds (50, 100 and 150rpm). It has been noticed by measuring the viscosity changes, that efficiency of higher polymer concentrations , lower speeds and lower temperatures also. The density increase by increasing concentration and decrease with temperatures

The effect of aspect ratio on the forced convection heat transfer is studied experimentally by construction a device formed mainly from an air duct with sliding surfaces to up or down directions and from a copper tube represents a heat generation source placed inside the air duct. The aspect ratio considered the ratio of the distance between the upper and lower surfaces of the air duct to diameter of the copper tube. The experimental results which obtained from this study show that the Nusselt number decreases with increase of the aspect ratio for Reynolds number range equals to (500 < Re < 3000). From the experimental results, a correlation for Nusselt number calculation is presented that depending on the effect of Reynolds number, Prandtl number, and aspect ratio with an accuracy of ±8%.

Cutting tests were conducted to longitudinally turn low carbon steel using HSS tools with cutting fluid. The experimental design used was based on response surface methodology (RSM) using a central composite rotatable (CCD) design. The primary cutting tests confirmed the use of proper specimen design with length to diameter ratio (L/D) of 2 in the subsequent cutting tests of this research. Further cutting tests were carried out to turn low carbon steel with L/D=2 to determine the effect of using different cutting conditions on the surface roughness and roundness error (out of roundness) of the machined surfaces. At the end of each cutting test, the surface roughness and roundness error measurements were taken and analyzed using “DESIGN EXPERT 8” experimental design software. Mathematical models of responses (surface roughness and roundness error) as functions of the conditions (cutting speed, feed, and depth of cut) were obtained and studied. A quadratic predicted model for surface roughness showed that the feed, cutting speed and their squares and interactions were more effective than the depth of cut because of its little influence on the surface roughness. Also, the resultant two-factor interaction (2FI) model for roundness error exhibited that cutting speed, feed and the interaction of feed and speed were significant parameters, while the depth of cut had no effect. The predicted models indicated that at higher cutting speed and various feed levels, both responses decreased, resulting in a smooth machined surface with lower roundness error. But, both models exhibited that at lower cutting speed and higher feeds, the surface roughness and roundness error increased, producing a rough machined surface with higher out of roundness error.

The aim of this paper was to study microbiologically influenced corrosion of aluminum alloy in the presence Pseudomnas aeruginosa bacteria. Control medium tap water (absence of Pseudomnas aeruginosa bacteria ) and medium with presence Pseudomnas aeruginosa bacteria used in this study. Tafel extrapolation ,weight loss method ,microstructure examination and surface roughness test were carried out to determine the microbiologically influenced corrosion behavior of aluminum alloy. Microbiological analyses, isolation and identification by using appearance factors and biochemical test for biofilm of corrosion product used in this study. Tafel extrapolation and weight loss method of aluminum alloy showed that the presence Pseudomnas aeruginosa bacteria caused corrosion and increasing corrosion current and rate of corrosion. Microstructure examination and surface roughness test showed that the presence Pseudomnas aeruginosa bacteria caused pitting corrosion. Microbiological analyses showed that biofilm are formed as micro colonies, which subsequently caused corrosion and shows the role of Pseudomnas aeruginosa bacteria in acceleration corrosion on aluminum alloy.

Scour is defined as the erosion of streambed sediment around an obstruction in a flow field. Bridge pier scouring is a significant problem in the safety estimation of bridges. In this study, the use of rectangular collar for reducing the effect of local scour at a circular pier in a laboratory flume was presented. The study was conducted using 6.6 m laboratory flume in length and 0.4 m in width. Experiments were conducted for various sizes of rectangular collars fitted at the bed elevation on the scour depth at the circular pier with clear-water scour condition. The time development of scour depth at the circular pier with and without a collar of circular installed was conducted. In collars observed that size of a collar plate increases, the scour decreases. Results showed that the maximum reduction in scour depth equal to 100% (no scour hole). Dimensional analysis technique was used, and from the experimental data an empirical formula was derived. It was found that the predicated scour depth from the formula performs well as compared to the observed scour depth.

Cellular or aerated autoclaved concrete blocks ( called Thermostone in Iraq ) may undergoes several problems during and after manufacturing ,these problems cost both time and money. The present work aims to determine the main types and causes of failure occurred in cellular concrete blocks (Thermostone) during and after production process. Physical and mechanical tests, chemical analysis, as well as X-ray diffraction technique were conducted to investigate the main causes of failures and to suggest solutions. The results showed that the complete reaction (Hydrogen bubbles formation) between lime (CaO) , water ,and Aluminum powder always occurs when the minimum reaction temperature is 43 oC or more, No observed reaction took place when the hydration temperature was less than 40 oC . Aluminum powder diameter of (50-100) µm was found to be suitable for best product properties. X- Ray diffraction results showed a presence of detrimental components causing moisture spots and excessive expansion in both green and autoclaved products. Controlling raw materials, increasing autoclaving period from 10 to 14 hours or adding up to 5% limestone aggregate are essential to get a product fulfills the specifications requirements

The piled raft is a geotechnical composite construction consisting of three elements: piles,raft and soil. It is suitable as a foundation for large buildings. This paper presents an analysis of piled raft foundation, included material nonlinearity and soil structure interaction. An efficient computer program in FORTRAN 9Ois developed for this analysis. A 20 node disoparametric brick element has been used to model pile, raft, soil and interface materials. Thin layer interface element has been used to model the contact zone between the pile and soil, and between raft and soil. The behavior of the piled raft material is simulated by using a linear elastic model. However, the behavior of soil and interface materials is simulated by an elasto-plastic model by the use of Mohr Coulomb failure criterion. Some of the variables of piled-raft system, related to settlement and differential settlement in sandy soil, have been studied, where the length of piles and distance between piles an effective role in reducing both settlement and differential settlement of foundation system. Also increasing the thickness of raft foundation reduces the effectiveness of additional piles for the purpose of reducing differential settlement.

Experimental result are presented for the preparation of zinc metal from Zinc Sulphate solution using electrochemical process. Laboratory cell which equipped with lead anode and aluminum cathode, was designed and utilized to obtain experimental result which was necessary for proceeding of the designated objective of this work. In the present experiment about 121 gm.-Zn / L solution was electrolyzed batch-wise at a current density rang 0.03-0.1 Amp./cm2 at a temperature of 40 to 45 ◦C. The effect of electrolytes concentration and the final concentration of zinc ions and sulphuric acid formed were also tested. The current efficiency of about 92% was obtained for 75% zinc ions conversion, at optimum condition mainly current density of 0.08 Amp./cm2 ,temperature of about 40 ◦C. The above current efficiency is similar to that reported in related studies.

This paper has been carried out to study the precipitate dust particles in residential area at Al-Najaf Al- Ashraf city, with special site of Alsaad quarter. It also studied the impact of the most important climatic characteristics ( such as temperatures, wind speed, humidity and evaporation, and rain) with rate affecting the collection the dust particles and to identify the levels of generation at the city. Also the climatic properties of city had been analyzed that resulted in Knowing the range of dust collected. And to identify the environmental impact of the collecting precipitate dust particles, samples were taken at Alsaad quarter by using metal cylinder, for three years from 2007 until 2009, at monthly rate for each sample. The most important results of this paper are the seasonal changes of the climate with anthropogenic activities accompanied by seasonal changes in dust quantities. Finally, the conclusions and recommendations which help the reducing of the risks of this important problem were presented.