Tikrit Journal of Engineering Sciences

The present paper presents the design of a foldable quadrotor that can adapt its morphology in the presence of sudden external disturbances such as wind. It focuses on solving the problem of tracking a specific trajectory of the foldable quadrotor in the presence of external disturbances. Therefore, robust controllers were designed to ensure better tracking under sudden turbulence, such as wind, considering the inertia change due to the rotating arms. An architectural console for foldable quadrotors was introduced under a gust of conservative winds. A dual loop control strategy was used in which the movements in the X and Y axes were managed by a nonlinear PID controller in the outer loop. In addition, a sliding mode controller was added to the inner loop to regulate the attitude and height in the Z direction, where the mechanical model of the aircraft was combined with the conservative wind gust model. When a conservative wind gust hit the foldable quadrotor for a certain period, a slight deviation from the proposed path at the beginning and end of the disturbance existed with an overshoot (7.468×10^(-3)) for the x-axis and (8.069×10^(-2)) for the z-axis at the beginning of the disturbance, while at the end of disturbance on the z-axis appears undershoot in its value (6.725×10^(-2)). Therefore, the quadrotor maintained its stability with an accuracy of 98%.

A prepared Aluminum Oxide AL2O3 nanoparticle loaded on Aloe vera Barbadensis Gum Activated Carbon (ABGAC) using the sol-gel method to increase the surface area is employed for phosphate removal from synthetic aqueous solutions. The operating parameters in this study are pH 3-9, adsorbent dose of AL2O3/ABGAC 20-100 mg per 1-liter solution, contact time (CT) 5-105 minutes, magnetic field strength (MFS) 300-600 mTesla, wavelength of light is halogen lamp (white, green, red, yellow, blue, and sunlight), and initial phosphate concentration (Ci) 3.7-10.7 mg/L. The results indicated that phosphate can be removed efficiently with the highest removal efficiency of 85.52% under the following operating conditions: pH= 5, CT= 105 min, Dose= 60 mg, MFS= 600 mTesla, red light, and Ci = 7.6 mg/L. It has been proved that the Langmuir model significantly fits the experimental data. The obtained adsorption capacity range was 63.24 - 969.38 mg/g.

Dynamic stiffness and damping of the soil under the base of the foundation of the retaining wall and the backfill soil behind it play the main role in estimating vibrating displacement during seismic loading. The purpose of the present study is to investigate the effect of dimensionless frequency (ao) on the horizontal, vertical, and rocking dynamic stiffness and dynamic damping of rigid retaining walls. On the other hand, the effect of (ao) and height of the retaining wall on the stiffness and damping for backfill soil behind the rigid retaining wall was also investigated in the cases of active and passive dynamic sliding and dynamic rocking. The study demonstrated that the dynamic stiffness and damping of the soil under the base of the rigid retaining wall increased with the soil shear modulus. While the dynamic stiffness and damping of the backfill soil behind the retaining wall increased with the wall height. The percentage of increment generally varied between (42.1 – 113.2)% when the height of the retaining wall rose from (4 to 6) m. The maximum horizontal, rocking, and vertical dynamic stiffness of the soil under the base of the foundation of the retaining wall occurred at high, low, and intermediate values of (ao), respectively, i.e., at high, low, and intermediate values of angular frequencies (ω) for constant values of soil properties and retaining wall height. It can be also noted that the values of dynamic sliding damping and dynamic rocking damping of the backfill soil decreased and increased with increasing the (ao) or (ω), respectively. The percentages of decrement and increment were (37.5)% and (183.3)% when (ao) increased from (0.19 to 1.35), respectively.

Image compression is one of the most important processes in image processing. It has numerous applications and plays a significant role in increasing transmission efficiency by reducing image size to just a few bytes, enabling the transmission of images without compromising their quality. The present study's proposed method focuses on reducing the size of an image through a compression technique. This technique involves extracting the essential information from the original image, which is represented by the low-frequency coefficients obtained through the discrete wavelet transform (DWT). By discarding the high-frequency coefficients, it can effectively preserve only the important details while significantly reducing the image size. In our approach, we employ the bi-cubic zoom-out method to resize the low-frequency coefficients, resulting in a high compression ratio. Finally, these high-frequency data are reduced by the Minimize-Final-Data method to produce compressed data (a stream of bits). Importantly, this zoomed-out image does not affect the overall image quality. We compared this proposed algorithm with both JPEG and JPEG2000 based on image quality and compression ratio. When applied to the Lena image, the proposed method achieved a PSNR of 40 dB and a compression size of 13.8 KB. However, when compared to the JPEG2000 method, the PSNR increased to 41.1 dB while maintaining a smaller compression size of 13.3 KB.