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Search Results for Mahmood Al-Obaidi

Article
Extending the mechanical-durability performance of hot mix asphalt modified with waste aluminum scrape powder

Mahmood Al-Obaidi, Alaa H. Abed

Pages: 35-46

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Abstract

Moisture damage in terms of stripping; and aging surface in terms of raveling and abrasion are among the primary distresses that lead to the deterioration of asphalt pavement, diminishing the overall quality and functionality of road surfaces. This study investigates the impact of using low-cost and locally available waste aluminum scrape powder (WASP) with a particle size ranging from sieves No.8 to No.200. WASP exhibits a high bulk specific gravity and melting point temperature on HMA mixtures, which could also potentially enhance the density and stiffness of modified mixtures. Five quantities of additives 0.5, 1.0, 1.5, 2.0, and 2.5% have been used to enhance the mechanical-durability features. The aggregate sources of AlDoz and AlNibaa'e were chosen, and different mixtures were produced utilizing Marshall and Roller compaction methods. The study's findings indicated that WASP enhanced mechanical-durability characteristics and reduced the asphalt mixture's sensitivity to abrasion, moisture damage, and aging. The optimal amount of WASP was determined to be 1.5%. In addition, based on the influence of the aggregate source and compaction technique, it is visible that the AlNibaa'e source and roller compaction mode provide superior outcomes compared to the AlDoz aggregate source and the Marshall method.

Article
Channel Estimation for Mixed-Analog to Digital Converters Architecture in Massive MIMO Architecture Using Approximate Conjugate Gradient Pursuit Algorithm

Yaseen A. Mohammed Obaidi, Anas L. Mahmood

Pages: 296-303

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Abstract

Millimeter Wave (mmWave) Massive Multiple Input Multiple Out (MIMO) system is a key technology for future wireless transmission. The system's architecture can differ based on the type of Analog-to-Digital Converters (ADCs) used at the receiver, whether they are all low-resolution or a mix of different resolutions (Mixed-ADCs).  Mixed-ADCs is a promising solution to achieve better performance than low-resolution ADC-only architectures by leveraging high-resolution ADCs to capture critical signal components while maintaining energy efficiency through low-resolution ADCs. In this paper, the problem of channel estimation for this system architecture is taken into consideration. A novel compressive-sensing based algorithm, that is called Approximate Conjugate Gradient Pursuit (ACGP), is proposed to estimate the channel coefficients. The performance of the proposed algorithm is investigated under varying system parameters, including different Signal-to-Noise Ratios (SNR), Radio Frequency (RF) chains, ADC resolutions, and numbers of observation frames. Matlab software was used to perform numerical simulations. The results demonstrated that mixed-ADCs architecture outperforms low resolutions only in performance. It was found that ACGP achieves lower Minimum Mean Squared Error (MMSE) compared to Orthogonal Matching Pursuit (OMP) and Least Square (LS), particularly in low SNR conditions showcasing its robustness and efficiency in signal reconstruction, achieving an average enhancement of 30% to 50% at moderate SNR levels. While OMP exhibited faster computation times under various number of observation frames, ACGP maintained stable computational performance, with a slight increase in computation time. For applications where accurate channel estimation is required under noisy environment, the proposed algorithm is an effective choice to meet such requirements. 

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