Tikrit Journal of Engineering Sciences

The separation of air by carbon molecular sieve (CMS) adsorption was studied in this work over a range of adsorption pressure of (2–8) bar. Breakthrough curves showed no significant effect of the pressure on product nitrogen purity and adsorbent capacity above 4 bar. Maximum purity of about 98% is observed for time up to 60 s. Adsorbent capacity obtained is in agreement with multicomponent Langmuir isotherm up to 4 bar. Maximum constant adsorbent capacity of about 0.1 mol O2/kg CMS is obtained for pressure above 4 bar.
For PSA two columns 6-steps process, no significant effect of the pressure on the product purity above 4 bar. The purity increases with decreasing the productivity. Maximum purity of 97.6% is obtained at productivity of 156 lit/kg CMS.hr, cycle time of 100 s, and purge flowrate of 1 lit/min. The productivity of 606 lit/kg CMS.hr is obtained at purity of 94%, cycle time of 60s, and purge flowrate of 4 lit/min.

A theoretical study had been conducted to detect the effect of using a porous medium in sunspace to reduce heating load and overcoming coldness of winter in the cold regions. In this work, the heat transferred and stored in the storage wall was investigated. The mathematical model was unsteady, heat conduction equation with nonlinear boundary conditions was solved by using finite difference method and the solution technique of heat conduction had based on the Crank Nicholson method. The results had adopted on the aspect ratio (H/L=30), Darcy number (Da=10-3), porosity (φ=0.35) and particle to fluid thermal conductivity ratio (kp/kf=38.5). The results showed that using the porous medium had enhanced the heat transferred and stored in the storage wall. For the outside storage wall temperature, an increase of 19.7% was achieved by using the porous medium instead of the air, while it was 20.3% for the inside storage wall temperature.

A 13 bit Sigma-Delta ADC for a signal band of 40K Hz is designed in MATLAB Simulink and then implemented using Xilinx system generator tool. The first order Sigma-Delta modulator is designed to work at a signal band of 40 KHz at an oversampling ratio (OSR) of 256 with a sampling frequency of 20.48 MHz. The proposed decimation filter design is consists of a second order Cascaded Integrator Comb filter (CIC) followed by two finite impulse response (FIR) filters. This architecture reduces the need for multiplication which is need very large area. This architecture implements a decimation ratio of 256 and allows a maximum resolution of 13 bits in the output of the filter. The decimation filter was designed and tested in Xilinx system generator tool which reduces the design cycle by directly generating efficient VHDL code. The results obtained show that the overall Sigma-Delta ADC is able to achieve an ENOB (Effective Number Of Bit) of 13.71 bits and SNR of 84.3 dB.

Fresh and hardened properties of high strength steel fibrous self-compacted concrete were studied in this investigation. One reference high strength self-compacted concrete mix is used, with five percent (by weight of cement) silica fume and eight percent of the cement replaced by limestone powder. Three steel fibres percentages by volume of concrete are used (0.4, 0.8, and 1.2). The used steel fibres were a shelled Harex type with irregular cross-section, equivalent diameter of 0.9278 mm, and 32 mm long. Super plasticizer was used to improve the workability and flow ability of the mixes. The test results showed that the presence of steel fibres decrease the flow ability, and increase the time of spreading, segregation, and passing ability of the fresh concrete. For the fibres percentages used, the fresh properties were within the recommended specifications for the self-compacted concrete. The test results showed an early strength development rate more than that for plain normal concrete due to the presence of the fine materials. As for normal concrete, the test results showed also that the increase in the splitting strength is more than the increase in the compressive strength due to the presence of the steel fibres. The brittle mode of failure of the plain unreinforced specimens changed to a ductile one due to the presence of the steel fibres.

In the current research an experimental study was done to show the effect of pulse flow on the
effectiveness of shell and tube type heat exchanger. the study was in the case of steady and pulse
flows with a changing mass flow rate of hot water flowing inside the pipes of the heat exchanger for
the range between (0.0273-0.0819 kg / s) at fix mass flow rate of cold water that flows through the
shell and on the outer surface of the pipes when (0.0416 kg / s), to obtain pulsing a used was
solenoid valve. The research aims to measure the percentage effect of independent factors which
were presenting the mass flow rate of hot water, flow type and the surrounding environment
conditions of the experimental side upon shell and tube type heat exchanger performance using
experimental design technique at the significant level (0.05).The results derived from the
experimental tests showed that pulse flow leads to increase internal heat transfer coefficient (hi)
comparing with its value in the steady flow and the highest increase was by (9.75%) at a mass flow
rate of hot water (0.0416 kg / s) and increases the overall heat transfer coefficient (U), where the
highest percentage was by )4.68%) at a mass flow rate of hot water (0.0416kg/s). The results also
showed increasing both the number of transmitted units (NTU) and the effectiveness of the shell
and tube type heat exchanger ( ) in the case of pulse flow of its value in the steady flow and the
highest percentage of increase occurring was (4.75%) and (1.85%), respectively, and at the mass
flow rate of hot water (0.0416 kg / s). Percentage effect of mass flow rate of hot water was (97%,
97.42%, 95.5%, 99.48%) and the percentage effect of each flow type and the errors were (2.8%,
2.25%, 2.44%, 0.4%) and (0. 2, 0.33%, 2.06%, 0.12) respectively.

In the present work, the drag reduction effectiveness of water soluble Carboxyl methyl cellulose (CMC) was studied as a function of polymer concentration and flow rate. Drag reduction results were assessed by measuring pressure drop over a one meter test section from the selected pipe. The effect of additives concentration was investigated over a range of 0 – 85 wppm, the solvent (water) flow conditions that were studied included higher flow rates. The experimental work was performed in a constructed re–circulating closed loop system. Maximum drag reduction percent (MDR%) of 17.3 % was obtained by using 85 wppm of CMC. The friction factor was calculated from experimental data with an acceptable average absolute percent Deviation. Correlation equation for fanning friction factor was suggested as a function of Re. The drag reduction results have been correlated based on a modification of a theoretical model available in the literature. The functional form of the model requires knowledge of the velocity profile, ratio of mixing length, friction factor, and the additive concentration as dependent variables.

Large areas of BASHEQA region haven't any source of surface water, at the same time, there are large quantities of olives trees and crops depend in its irrigating on Ground Water (GW) as a main source. So it is important to evaluate its (GW) for different uses. In this study the (GW) of 32 wells had been examined in the college of environmental science and technology laboratories to assess its Water Quality (WQ) for drinking, irrigation, and livestock purposes. Average twelve parameters (pH, Ca, Mg, Na, HCO3, SO4, Cl, NO3, EC, TDS, SAR, TH) data in the period 2008-2009 had been applied in three methods through computing Water Quality Indices (WQIS). The first method was the Weighted Average (WAV). The second one was that adopted by Ministry of Nature and Environment (MNE) of Mongolia, while the last one was the Canadian Council of Ministers of the Environment (CCME). The (WQIs) of the three methods results had been compared to assess the suitability of the best one. Although the statistical analysis indicated that there are no significant differences between both (CCME) and (WAV) methods, the (WAV) data had been used in this study as it gave more restrictive control. The analysis of (WQIs) using (WAM) method indicated that (25, 69, 88)% of (GW) are good for drinking, irrigation, and livestock purposes respectively.

This paper illustrates the performance of lightweight concrete using various amounts of expanded polystyrene beads (EPS) and different amounts of foam agent to produce lightweight concrete. The objective of this paper is to produce lightweight concrete with good workability and strength, by different mix proportion of foam agent (0.4, 0.6, 0.8, 1, 1.2 kg/m3) and varying water cement ratio (w/c) depending on the flow. Besides, various proportions using different percentages of EPS in order of volume fractions are used. The flow range used in the study is 110-130%. Each mix proportion is tested for compressive strength, modulus of rupture, density and voids ratio. The results gives acceptable ranges of strength for lightweight concrete produced by the inclusions of EPS beads and foam concrete. Therefore, the lightweight concrete produced in this work can be used for structural applications like multistory building frames, floors, bridges and prestressed or precast elements.

This paper introduces the design and realization of multiple blocks ciphering techniques on the FPGA (Field Programmable Gate Arrays). A back propagation neural networks have been built for substitution, permutation and XOR blocks ciphering using Neural Network Toolbox in MATLAB program. They are trained to encrypt the data, after obtaining the suitable weights, biases, activation function and layout. Afterward, they are described using VHDL and implemented using Xilinx Spartan-3E FPGA using two approaches: serial and parallel versions. The simulation results obtained with Xilinx ISE 9.2i software. The numerical precision is chosen carefully when implementing the Neural Network on FPGA. Obtained results from the hardware designs show accurate numeric values to cipher the data. As expected, the synthesis results indicate that the serial version requires less area resources than the parallel version. As, the data throughput in parallel version is higher than the serial version in rang between (1.13-1.5) times. Also, a slight difference can be observed in the maximum frequency.

Two types of Portland Cement Clinker "PCC" were used in this study: high fineness grinded and low fineness grinded , and after grinding of PCC, hydrated lime was used in 5%,10% and 15%; by weight, as a replacement of the blend cement with a constant 3% addition of gypsum by the blend weight. The importance of this study is to show the influences of different fineness on the physical properties of the blended cement, and to find the probability of using hydrated lime (that could be a by-product) in cement and declare its effects on the blend, so the solid waste "lime" and air pollutant of cement factories will reduce. In this research, the low fineness blend exhibited about 87% from compressive strength of high fineness blend at 28 days age. The results show that the using of hydrated lime up to 10%; by weight, as a replacement of cement will give good compressive strength and workability, and will reduce moderately the setting time, but the use of hydrated lime by more than 10% will reduce the compressive strength and increase the unsoundness of the blend (from 3mm expansion at 10% hydrated lime to 29mm expansion at 15% hydrated lime).

This paper involved the design and analysis of multi-threshold voltage CMOS (MTCMOS) current sense amplifier focusing on optimizing power and time delay. In this work the basic 6T SRAM structure was chosen and the simulation is implemented using ADS programs. The key to low power operation in the SRAM data path is to reduce the signal swings on the bit lines and the data lines. The power dissipation and delay of the sense amplifier circuit can be further reduced by using several low power and high speed techniques like MTCMOS. This technique can be used for solving the leakage power dissipation problem in the higher technology design. Simulated results show the current mode sense amplifier with MTCMOS technology has 0.82ns time delay and 0.395μW power dissipation. The designs and simulations in 0.25μm CMOS technology with supply voltage equal to 1.8 V have been carried out to evaluate the efficiency of the current mode sense amplifier with MTCMOS technique proposed.

The memory cells has become one of the computer basics electronic components, especially nonvolatile ion-dependent growth of filament or so called Conductive Bridge Random Access Memory (CBRAM) type. The memory cells in this work is focused on using copper sulfide as ionic compound Cu2S, the model proposed to identify the behavior of the cell in terms of voltage and current. The model cell is then simulated in order to extract the variables that affect the behavior of the cell and the factors which can be identify the optimal dimensions and specifications in terms of their small size and minimum power dissipation as possible at the same time. The simulation results show that the best thickness of the cell is about 20 nm with a radius equal to 10 nm, These dimensions of the cell has a resistance ratio of high resistance state HRS to low resistance state LRS(Roff / Ron) which correspond to different logic is about 1014 .