Tikrit Journal of Engineering Sciences

The digester geometry significantly enhances household batch digesters' performance, especially the internal surface area. The present study investigates the impact of different extended surface areas augmented around inside digesters on anaerobic digestion performance. Four batch digesters were used, i.e., A, B, C, and D, with no extended surfaces, with four horizontal circular extended surfaces of width 2, 4, and 6 cm, respectively. Cow dung was used as a substrate in those digesters under mesophilic conditions. Experimental results show that the highest peak of methane contents were 70.78, 72.61, 73.82, and 74.22 %. High daily biogas production volumes were 18.4, 19.4, 19.5, and 20.8 L, and high accumulative biogas production volumes were 354.1, 425.3, 471.4, and 509 L for digesters A, B, C, and D, respectively. During the experiment start-up phase, pH values dropped to 6.5, 6.4, 6.2, and 6.1 for digesters A, B, C, and D, respectively. The four digesters' methane (CH4) content values increased in the first days of the anaerobic digestion (AD) process. Favored performance and better biogas production outlined with digester D had a high interior extended surface area. The future work, organic loading rate (OLR), and temperature at different reactors to demonstrate its potential use in industrial applications. Co-digestion of STW with multiple organic wastes originating from a significant quantity of biogas at a single point can be investigated further.

The torsional behavior of twelve concrete-filled steel tube (CFST) specimens was experimentally investigated. CFST specimens were reinforced by internal cross-rods with different spacing (0, 50, 100, 150, 200, and 250) mm, different thicknesses of the steel tube (1.5 and 2) mm, and a compressive strength of 65 MPa (high strength concrete). Each sample was tested, and the results were examined. According to the results, the infill concrete prevented buckling failure in CFST specimens. The steel tube and concrete worked together since cutting steel tubes caused diagonal cracks in the infill concrete of CFST specimens. The results also showed that the CFST's torsional moment capacity increased due to the concrete infill, further aiding the steel tubes' performance. Internal stiffening in the steel tubes and concrete infill improved the failure mode, mechanical properties, and CFST specimens’ behavior under torsion.

Sustainability principles are considered one of the vital challenges facing developing countries (including Iraq), which are trying vigorously to implement sustainable development in most of their development projects. The projects of constructing educational buildings, such as schools and universities, are among the most important development projects to be established in Iraq. This study aims to develop standards to help improve the understanding of the sustainability requirements of educational buildings in Iraq. Through a series of studies, this study has developed a system that can be used to measure the sustainability of these buildings. First, information about sustainability assessment systems was gathered from the literature and references. Second, personal interviews with specialists, field questionnaires, and the software Analytical Hierarchal Process (AHP) to identify the weights of the main categories and factors for sustainable educational buildings. The results showed that the criteria of Energy Efficiency received the greatest weight (29.6%). On the other hand, less weight was obtained from the Precious Water and Waste (3.6%). Finally, the study developed a rating system model, "Educational Building Sustainability Rate (EBSR)," under Iraqi environmental conditions.

A spillway is an essential hydraulic structure that discharges excessive water, especially during floods from upstream to downstream of the dam. A shaft spillway is sometimes used when a limited area is available. This study used four physical models of vertical shaft spillways with different edge shapes to study the flow characteristics. Each case was based on three tailwater heights: free, semi, and submerged. The results showed that two flow cases at the entrance depended on the water depth upstream; the weir flow happened at low discharge when the ratio of water depth to shaft diameter H/D was less than 0.5, and orifice flow when the proportion H/D was greater than 0.5. In the weir flow regime for submerged conditions, the water depth upstream (H) decreased by (6%) more than free flow. When replacing inlet shapes, the upstream depth (H) decreased by (40%) in the weir flow and (13%) in the orifice flow. In weir flow, the discharge coefficient values decreased with crest length, and larger values were obtained at the submerged state. While in orifice flow, Cd values increased with crest length, and higher values occurred at semi-submerged. Spillway discharge increased with entrance edge shape length in submerged condition.

Suspended sediment loads (SSL) transported from the watershed of the Diyala River (WODR) are the most important and dangerous forms of sediment as they drift to the stream flow of the Diyala River and are then transferred to the reservoirs of Hemren Dam (HD) and Derbendikhan Dam (DD), which are located in the study area, affecting the capacity storage of the reservoirs and reducing electrical energy production. Therefore, it is necessary to apply a hydrological model that can simulate the SSL distribution in the WODR to enable decision-makers to develop an appropriate plan to solve the sediment problem. In WODR, the data of SSL are very rare, as sediment measurements have not been conducted for more than 40 years. Due to the lack of historical data for sediment values for the study area and the need to reduce uncertainty, sediment measurements were conducted from November 2022 to April 2023. The motivation of the present study is to study and address the limitations imposed on the Soil and Water Assessment Tool (SWAT) model during the estimation of SSL in the WODR that have scarce data and whose quality is inaccurate. The observed monthly flow data from two gauging stations, HD and DD, from January 2000 to April 2023 and suspended sediment concentration, which was measured in the field from November 2022 to April 2023, were used for calibration and validation of the model, respectively, using the Sequential Uncertainty Fitting Version 2 (SUFI-2) algorithm and SWAT-Calibration Uncertainty Procedures (CUP). Statistically, using the coefficient of determination (R2), Nash-Sutcliffe efficiency (NSE), and percent of bias (Pbias) the performance of the model was evaluated, with good agreement between observed and simulated values for both stream flow and SSL. The results showed that the values of the SSL in the WODR from January 2000 to April 2023 were equal to 115.240 t/ha/yr. Sub-basins 5 and 12 have the highest SSL values of 15.125 t/ha/yr and 9.098 t/ha/yr, respectively, and the most important factor in SSL formation is the slope of the land, with a correlation coefficient (R2=0.94).

This study proposes enhancing induction motor (IM) drive systems by developing a DTC-MC with SVPWM integration to reduce ripple. DTC-MC is effective for precise torque control in AC drives, offering high control accuracy by isolating stator flux and torque. The method excels in sensor-less speed control, maintaining unity input power factor at low speeds, and constant switching frequency for rapid torque adjustments. Combining DTC-MC with SVPWM improves simplicity, dynamic behavior, and torque response. The DTC-SVM approach further refines the torque response by correcting flux and torque discrepancies. MATLAB/SIMULINK simulations validated the approach, showing a robust dynamic response and significantly reduced motor torque ripple and control of speed.