Journal of Engineering

Many mechanical systems are exposed to undesired vibrations, so designing an active vibration control (AVC) system is important in engineering decisions to reduce this vibration. Smart structure technology is used for vibration reduction. Therefore, the cantilever beam is embedded by a piezoelectric (PZT) as an actuator. The optimal LQR controller is designed to reduce the vibration of the smart beam by using a PZT element. In this study, the main part is to change the length of the aluminum cantilever beam, keeping the control gains, the excitation, the actuation voltage, and mechanical properties of the aluminum beam for each length of the smart cantilever beam, and observe the behavior and effect of changing the length of the smart cantilever beam. A cantilever beam with piezoelectric is modeled in Mechanical APDL ANSYS version 15.0 and verified by using experimental work. The AVC was tested on a smart beam under different control gains in experimental work and chose the best control gain depending on FEM results for each length of the smart beam. The response of the smart beam is noticed to be different for every length and the reduction percentage for settling time was different for every length.

Desalination is a process where fresh water is produced from high salinity solutions. One of the most important processes for this purpose is membrane distillation (MD). Direct contact membrane distillation (DCMD) is considered the most prominent type of MD due to its ease of design and operation. This study examines the efficiency of using DCMD for desalination brine with different concentrations (1.75%, 3.5%, 5% NaCl). A frame and plate cell was used with a flat sheet PTFE hydrophobic membrane. The study proves that MD is an effective process for desalination brines with feed temperatures less than 60°C, especially for feed with low TDS. The feed temperatures used in the study were 37°C, 47°C, and 57°C, and the permeate temperatures were 17°C, 22°C, and 27°C. The results showed that the flux increases with increasing feed temperature and flow rate, and decreases with increasing feed concentration, experiment time, and permeate temperature.

ZSM-5 zeolite was synthesized under hydrothermal conditions at 175°C. The synthesis parameters were investigated to find the optimum synthesis method. The crystallization time was studied to determine the optimum time, and the ageing time was also examined. The morphology, structure, and composition of the synthesized ZSM-5 zeolite were characterized using scanning electron microscopy (SEM), pH meter, viscometer, and X-ray powder diffraction (XRD). The bulk Si/Al ratio of ZSM-5 zeolite was in the range of 9.5—11.7. The synthesized ZSM-5 zeolite with appropriate ageing time could adjust crystal size and degree of crystallinity. The crystal size of ZSM-5 zeolite obtained at an ageing time of 24 hours was around 2.0 μm. The suitable aging time was 24 hours, and the relative crystallinity of ZSM-5 zeolite could reach up to 100% after crystallization for 48 hours at 175°C.

In this study, nano TiO₂ was prepared with titanium isopropoxide (TTIP) as a resource to titanium oxide. The catalyst was synthesized using phosphotungstic acid (PTA) and stearyl trimethyl ammonium bromide (STAB) as the structure-directing material. Characterization of the product was done by X-ray diffraction (XRD), X-ray fluorescent spectroscopy (XRF), nitrogen adsorption/desorption measurements, Atomic Force Microscope (AFM), and Fourier transform infrared (FTIR) spectra. The TiO₂ nanomaterials were prepared in three crystalline forms (amorphous, anatase, anatase-rutile). The results showed that the nanoparticles of anatase TiO₂ have good catalytic oxidative activity, achieving 100% conversion within 90 seconds from 300 ppm of dibenzothiophene. This is compared to conversion rates for anatase–rutile nanoparticles and amorphous nanoparticles, which reached 52% and 31%, respectively. The influence of the reaction temperature, catalyst amount, H₂O₂ concentration, and initial DBT concentration on the oxidation of DBT was investigated

The aim of this study is to propose reliable equations to estimate the in-situ concrete compressive strength from non-destructive tests. Three equations were proposed: the first equation considers the number of rebound hummer only, the second equation considers the ultrasonic pulse velocity only, and the third equation combines the number of rebound hummer and the ultrasonic pulse velocity. The proposed equations were derived from non-linear regression analysis and calibrated with the test results of 372 concrete specimens compiled from the literature. The performance of the proposed equations was tested by comparing their strength estimations with those of related existing equations from the literature. Comparisons revealed that the proposed ultrasonic pulse velocity and combined equations achieved better agreements with the test results than the related existing equations, whereas the proposed and the existing rebound hummer equations were inconsistent.

This research investigated the importance and priorities of the project overhead costs in Iraq via a questionnaire using the fuzzy analytic hierarchy process technique (FAHP). Using this technique is very important in the uncertain circumstances as in our country. The researcher reached to frame an equation through the results of the priorities of weights include the percentages of each of the main items of the project overhead costs. The researcher tested this equation by applying it to one of the completed projects and the results showed suitability for the application. The percentages of the (salaries, grants, and incentives) and (fieldwork requirements) in equation represent approximately two-thirds of project overhead costs. So the contractors should deal with the project overhead costs carefully during estimate the bid.

A good performance of reinforced concrete structures is ensured by the bond between steel and concrete, which makes the materials work together, forming a part of solidarity. The behavior of the bond between the reinforcing bar and the surrounding concrete is significant to evaluate the cracking control in serviceability limit state and load capacity in the ultimate limit state. In this investigation, the bond stresses between reinforcing bar and reactive powder concrete (RPC) was considered to compare it with that of normal strength concrete (NSC). The push-out test with short embedment length is considered in this study to evaluate the bond strength, bond stress-slip relationship, and bond stress-crack width relationship for reactive powder concrete members. The compressive strength of concrete, the nominal diameter of reinforcement, concrete cover, and amount of steel fibers and embedded length of reinforcement were considered as variables in this study. The test results show that the ultimate bond stress increased with increasing of the compressive strength of concrete, decreasing the nominal diameter of the reinforcing bar, increasing the concrete cover and increasing steel fiber content. In a bond stress-slip relationship, the NSC specimen shows a very short softening zone after reaching the peak point in comparisons with RPC specimen. In RPC, bond stress-slip relationship shows stiffer behavior when the steel fiber content was increased. RPC shows stepper softening zone due to the presence of steel fiber, and the absence of steel fiber cause push-out failure without descending part after peak point. Using NSC instead of RPC in anchorage between reinforcement and concrete, decrease the crack width produced due to radial tensile stresses through the push-out of reinforcing bar. In RPC, the absence of steel fiber, decrease the nominal diameter of the reinforcing bar, increase the concrete cover, decrease the embedded length of reinforcing bar cause push-out failure and vice versa cause splitting failure.

This study evaluates the accuracy of the Stonex X-300 laser scanner cameras, which are used in close-range photogrammetry. The evaluation was necessary because the device manual did not provide sufficient information about the cameras. The study involved comparing the Root Mean Square Error (RMSE) of checkpoints obtained using the laser scanner cameras with those obtained using a digital camera (NIKON 5200D). The results showed that the RMSE in the X direction was 58.9 mm, in the Y direction was 10.5 mm, and in the Z direction was 0.09 mm. The study concluded that the Stonex X-300 laser scanner cameras have good accuracy for close-range photogrammetry applications.