Al-Khwarizmi Engineering Journal

This paper has investigated experimentally the dynamic buckling behavior of AISI 303 stainless steel Aluminized and as received long columns. These columns, hot-dip aluminized and as received, are tested under dynamic buckling, 22 specimens, without aluminizing (type 1), and 50 specimens, with hot-dip aluminizing at different aluminizing conditions of dipping temperature and dipping time (type 2), are tested under dynamic compression loading and under dynamic combined loading (compression and bending) by using a rotating buckling test machine. The experimental results are compared with Perry Robertson interaction formula that used for long columns. Greenhill formula is used to get a mathematical model that descripts the buckling behavior of the specimens of type (1) under dynamic compression loading. The experimental results obtained show an advantageous influence of hot-dip aluminizing treatment on dynamic buckling behavior of AISI 303 stainless steel long columns. The improvement based on the average value of critical buckling stress, are as follow: (64.8 %) for long columns type (2), compared with columns type (1), under dynamic compression loading, and (56.6 %) for long columns type (2), compared with columns type (1), under dynamic combined loading, and (33.3 %) for long columns type (2) compared with Perry Robertson critical buckling stress.

The design, construction and investigation of experimental study of two compound parabolic concentrators (CPCs) with tubular absorber have been presented. The performance of CPCs have been evaluated by using outdoor experimental measurements including the instantaneous thermal efficiency. The two CPCs are tested instantly by holding them on a common structure. Many tests are conducted in the present work by truncating one of them in three different levels. For each truncation the acceptance half angle (θc) was changed. Geometrically, the acceptance half angle for standard CPC is (26o). For the truncation levels for the other CPC 1, 2 and 3 the acceptance half angle were 20o, 26o and 59o, consequently. A significant difference between the instantaneous thermal efficiency of 3.86× CPC (θc=20o) and 2.32× CPC (θc=26o), and between that for 3.61× CPC (θc=26o) and 2.32× CPC (θc=26o). It's noticed that the difference between the instantaneous thermal efficiency of 2.32× CPC (θc=59o) and 2.32× CPC (θc=26o) is small compared with the difference of the first and second cases, the instantaneous thermal efficiency of 2.32× CPC (26o) was higher than those for other three CPCs. The experimental results show that the maximum thermal efficiency of the full 2.32×CPC (26o) is 0.708, the maximum thermal efficiency of the 3.93×CPC (15o), when it's truncated to 3.84× CPC (20o), 3.61× CPC (26o) and 2.32× CPC (59o) are 0.51, 0.52 and 0.66, respectively. As the concentration ratio decreases from (3.93× to 1×), the thermal efficiency, energy losses and optical efficiency increase from (0.47 to 63), (1.58 to 7.2 K.m2/W) and (0.494 to 0.797), respectively.

The performance of a condenser in a domestic refrigerator system without wires and a condenser with a novel design consisted of number of loops as elliptical shape is investigated experimentally in this work. The experiment was conducted with a refrigerator designed to work with HFC134a, under no load and with loads of (1.5,3 and 12 liters of water). In particular, the effects of shape change of the condenser were very important in heat transfer enhancement and reduce of the frictional loss as a result of reducing the pressure drop in the condenser. The results shown that compressor work decreases with elliptical condenser about (8.6% to 11.3%), and then the power consumption decreases also. The performance of household refrigerator with an elliptical condenser without fins was better than that of the conventional condenser without fins. Therefore, the elliptical condenser can be used instead of the conventional air cooled condenser in a domestic refrigeration system.

In this paper the use of a circular array antenna with adaptive system in conjunction with modified Linearly Constrained Minimum Variance Beam forming (LCMVB) algorithm is proposed to meet the requirement of Angle of Arrival (AOA) estimation in 2-D as well as the Signal to Noise Ratio (SNR) of estimated sources (Three Dimensional 3-D estimation), rather than interference cancelation as it is used for. The proposed system was simulated, tested and compared with the modified Multiple Signal Classification (MUSIC) technique for 2-D estimation. The results show the system has exhibited astonishing results for simultaneously estimating 3-D parameters with accuracy approximately equivalent to the MUSIC technique (for estimating elevation and azimuth angles), and it has privilege to estimate SNR for sources which are under the estimation process.Finally, the proposed system needs less computational time and hardware complexity when it is compared with Eigen value decomposition techniques used by MUSIC technique. Also, it has cost effectiveness with respect to (3-D) active detecting means such as radars.

The paper present design of a control structure that enables integration of a Kinematic neural controller for trajectory tracking of a nonholonomic differential two wheeled mobile robot, then proposes a Kinematic neural controller to direct a National Instrument mobile robot (NI Mobile Robot). The controller is to make the actual velocity of the wheeled mobile robot close the required velocity by guarantees that the trajectory tracking mean squire error converges at minimum tracking error. The proposed tracking control system consists of two layers; The first layer is a multi-layer perceptron neural network system that controls the mobile robot to track the required path , The second layer is an optimization layer ,which is implemented based on hybrid Crossoved Firefly Algorithm with Artificial Bee Colony (CFA-ABC) to tune the controller's parameters to achieve the optimal path. The performance of the hybrid optimization algorithm is verified by various benchmark functions. The simulation results show that the utilizing of CFA and (CFA-ABC ) are better than the original Firefly Algorithm. A simulation example is given to indicate the effectiveness of the proposed algorithm, the results have been done using MATLAB (R2013b), and all trajectory tracking results with two reference trajectories (circular and lemniscates ) are presented.

The aim of human lower limb rehabilitation robot is to regain the ability of motion and to strengthen the weak muscles. This paper proposes the design of a force-position control for a four Degree Of Freedom (4-DOF) lower limb wearable rehabilitation robot. This robot consists of a hip, knee and ankle joints to enable the patient for motion and turn in both directions. The joints are actuated by Pneumatic Muscles Actuators (PMAs). The PMAs have very great potential in medical applications because the similarity to biological muscles. Force-Position control incorporating a Takagi-Sugeno-Kang- three- Proportional-Derivative like Fuzzy Logic (TSK-3-PD) Controllers for position control and three-Proportional (3-P) controllers for force control. They are designed and simulated to improve the desired joints position specifications such as minimum overshoot, minimum oscillation, minimum steady state error, and disturbance rejection during tracking the desired position medical trajectory. Ant Colony Optimization (ACO) is used to tune the gains of position and force parts of the Force-Position controllers to get the desired position trajectory according to the required specification. A comparison between the force-position controllers tuned manually and tuned by ACO shows an enhancement in the results of the second type as compared with the first one with an average of 39%.

In order to select the optimal tracking of fast time variation of multipath fast time variation Rayleigh fading channel, this paper focuses on the recursive least-squares (RLS) and Extended recursive least-squares (E-RLS) algorithms and reaches the conclusion that E-RLS is more feasible according to the comparison output of the simulation program from tracking performance and mean square error over five fast time variation of Rayleigh fading channels and more than one time (send/receive) reach to 100 times to make sure from efficiency of these algorithms.

Worldwide attention is being focused on nanocrystalline zeolites and they are replacing conventional ones due to their pronounced potential in many fields. In this study, NaY zeolite has been prepared hydrothermally using sol –gel method and modified to the proton type by ion –exchange process. Characterization is made using X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), Atomic force microscopy (AFM), Brunauer –Emmet- Teller (BET) nitrogen adsorption method, Ammonia Temperature programmed desorption (NH3-TPD) and Scanning electron microscopy( SEM). The effect of aging time, silica to alumina ratio is studied and the results show well defined crystalline structure with nano particle size (70 and 81nm) with surface area of 499m2/gm.

Airlift reactors are widely used in the chemical and biochemical applications as effective contactors for mass and heat transfer. The main advantages of airlift contactor compared with simple bubble column are ease of construction, low shear rate, high capacity, good mixing and liquid circulation without mechanical agitators and circulating pumps.In this work, growth characteristics of Chlorella vulgaris microalgae were studied in an internal loop airlift photobioreactor for biomass production. The bioreactor operated under batch and semi-continuous culture mode using commercially available 20:20:20+TE NPK fertilizer as nutrients. The experiments were conducted to evaluate the growth rate and biomass productivity of Chlorella vulgaris microalgae as affected by several factors such as nutrients concentration (20-80 mg/L), inlet air flow rate (2-8 LPM), and harvesting ratio (10-30 vol.%). The growth rate and biomass productivity of Chlorella vulgaris was determined as changes in optical density using UV-spectrophotometer. The results of batch operation showed that the growth rate of Chlorella vulgaris microalgae was increase with increasing of NPK nutrient concentration used but the access to the stationary phase of growth was delayed. The rate of growth was also increase with the increase in air flowrate to a limit then decrease. On the other hand the airlift photobioreactor can be operated in semi- continuous mode successfully by choosing the optimum conditions from the batch step which was 40 mg/L NPK nutrients concentration and 6 LPM and air flowrate. Several ratios of reactor content were harvested and the maximum biomass productivity was 0.142 g/L.day when harvested 10 vol.% every two days.

The aim of present study is to determine the optimum parameters of friction stir welding process and known the most important parameter along with percentage contribution of each parameter which effect on tensile strength and joint efficiency of FS welded joint of dissimilar aluminum alloys AA2024-T3 and AA7075-T73 of 3 mm thick plates by applied specific number of experiments using Taguchi method .AA2024 was placed on the advancing side and AA7075 on the retreating side. FSW was achieved under three different rotation speeds (898, 1200 and 1710) rpm, three different welding speeds (20, 45 and 69) mmmin , three different pin profiles (cylindrical, threaded cylindrical and cone) and tool tilt angle 2◦. Taguchi method was proposed the orthogonal array of L9 based on the three number of process parameters and the three levels of variation for each parameter , SN ratio and ANOVA analysis of robust design were applied to the results.The result of SN ratio analysis were obtained to find the parameters optimization, which has been of rotation speed equal to 898 rpm, welding speed 45 mmmin, and threaded cylindrical pin profile with joint efficiency (76%). The tensile strength result shows that the welding speed was the most important parameter with a percentage contribution of 66.05 % over the other process parameters.

In this study many specimen s were prepared from 2024-T3 Aluminum alloy for corrosion test by the dimensions of (15*15*3) mm according to ASTM G71-31 and then subjected to shot peening process at different time (15, 30, 45) minutes using steel ball having a diameter of 2.75 mm and Rockwell Hardness of 55RC to induce compressive residual stress which were measured using X-Ray diffraction method, surface roughness and hardness were tested before and after peening. Electrochemical corrosion test by Tafel extrapolation method was carried out in an environment of 3 .5% NaCl solutions (sea water) where Corrosion rate calculated using Tafle equation.The obtained results show a favorable influence of SP treatment on improving corrosion resistance as induced compressive residual stresses and hardened surface layer, the best corrosion resistance was at SP time of 30 minutes since compressive stress was the highest.

Random throwing of industrial waste has a significant impact on the environment unless it takes into account the conditions of engineered destroying and/or re-used. Taking the advantage of re-using waste materials in engineering projects represents a well-planned project in order to resolve a lot of engineering problems for some difficult soils. The objective of this study was to evaluate the capability and effects of Rubber Shreds (RS) from scrap torn belts towards improving the shear strength of soft clay. A direct shear tests were conducted on soft clay-RS mixture. The following parameters were investigated to study the influence of RS content, water content, normal stress, and dilation ratio. From experimental test results it was found that previous parameters affecting the shear strength of soft clay. Increasing RS content was found effective in improving the shear strength of soft clay when the normal stress increases provided that fixed water content used in the mixture. Cohesion, c and angle of friction,  were increased by ratio of (1.4-2.3) and (1.5-2) respectively. However, it was revealed that RS content mustn’t exceed the liquid limit level of soft soil. If the water content increases and exceeding the liquid limit level of soft clay, shear strength, cohesion and angle of friction will begin to decrease by reduction percentage of (15%-55%) and (20%-45%) respectively in spite of 30% rubber inclusion. The dilation ratio was highly affected by water content increment; disturbed path of dilation ratio were observed with increasing water content in soil mixture.