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.

Many researchers had experimentally investigated the parameters influencing the reinforced concrete corbel behavior and shear capacity. The main parameters studied in these researches were the influence of concrete compressive strength (f_c^'), shear span to effective depth ratio (a_v/d), longitudinal reinforcement percentage (ρ_s), horizontal reinforcement ratio (ρ_h), and effective depth (d). All specimens were tested under monotonic vertical load up to failure. Shear strength of corbels is essentially based on empirical or semi-empirical ‎equations. ‎In this work, a total of (47) tests of reinforced concrete corbels from the available in the literature and covered the main parameters are adopted to predict a proposal formula for the nominal shear strength of the corbel. This proposal is compared with ACI-318M- 2019 provisions and with the expressions proposed by other researchers. For the present proposed equation, the coefficient of variation (COV%) factor, which equals to 29.75% for the ultimate load, is the least (COV%) factor compared with other proposed equations. It was also found that the shear span to the effective depth ratio (a_v/d), the amount of horizontal reinforcement (stirrups) (ρ_h), the amount of main reinforcement (ρ_s), the compressive strength of concrete (f_c^') have a significant effect on the nominal strength of reinforced concrete corbels.

Some medicinal particles are poorly soluble in highly acidic solutions, particularly those subjected to various production processes. Therefore, the present research investigated the kinetics and mechanisms of the drug release rate of newly formulated solid pills in a low pH medium. Three pills were prepared: one from a non-moisturized powder mixture (PILD) and the other two, PILC and PILM, from the dried powder mixtures, which were dried using hot-air heating and microwave radiation, respectively. These pills were subjected to drug release tests, and the outcomes were considered in the kinetics investigation using various models. Zero-order, Hixson–Crowell, First-order, Higuchi, Hopfenberg, Korsmeyer-Peppas, Logistic, and Peppas-Sahlin were the kinetic models used to inspect the release rate mechanism of these tablets. It was found that the Peppas-Sahlin and zero-order were the most reliable models to represent the drug release profile of all prepared pills with very high accuracy, estimated by R^2>0.99. The Hixon and first-order models were the weakest to characterize this work outcome. This work also applied these models to describe the controlling mechanism of the drug release for each prepared pill. It is detected that the non-Fickian diffusion and polymer chain relaxation control the PILC’s release behavior. However, case II transport and super case II transport with erosions is the dominant mechanism for PILD and PILM pills, respectively. Additionally, new semi-empirical models were modified to describe the kinetics of the solid release of those tablets with greater accuracy.

Radial heat sinks are often employed as heat transfer enhancers because they increase the heat transfer surface area. Novel shapes of fins are used to enhance thermal heat performance under free convection heat transfer. The present experimental study investigates a new-fin shape effect on the thermal behavior of a radial heat sink with a circular base. The objective is to select the best reference model by comparing the three heat sink models, I, II, and III. The study was conducted for the heat-supplied rates of 20.16, 66.03, 105.30, 157.62, and 196.08 W. The present results showed that the fin in case I configurations dissipated heat transfer up to 12.07% and 30% compared to cases II and III, respectively, at high Rayleigh numbers. The thermal resistance in case III reduced to 13.91% and 16.23% compared to case I and case II, respectively, at the maximum Rayleigh number value. Then, based on experimental data, a correlation was suggested to estimate the Nusselt number for free convection from radial heat sink with vertically oriented double triangular fins.

This research experimentally studied the performance of laced reinforced concrete (LRC) beams with different ratios of glass fiber subjected to bending loads. These beams were reinforced by innovatively welding longitudinal bending reinforcement with shear stirrups at an angle of 45º. First, the effect of different glass fiber ratios on concrete properties, such as compressive and tensile strength, was studied. Then, four beams, a plain concrete beam, an LRC beam, and two LRC beams with 0.5% and 1% glass fiber were tested under bending. All beams had cross sections of 150×150 mm and a length of 1050 mm. The load deflection, stiffness, ductility, and crack width between these beams were compared. The experimental results showed good performance in terms of load and deflection curves for all LRC beams. The maximum load of the LRC beam was 34 kN with ductile behavior. LRC beams with glass fiber ratios had a maximum load of 35 kN; however, they were stiffer than LRC beams without fiber. Also, the LRC beam, compared to the plain concrete beam, showed an increase in strength about two times while the ductility improved about 1.6 to 2 times. Meanwhile, adding glass fiber to LRC beams had approximately the same strength and ductility as the LRC beams; however, it reduced the crack width from 2.63 mm to 0.92 mm.

Radio-over-fiber is emerging as a progressively significant technology within the wireless in-building market. Identifying dynamic range requirements and determining the optimal laser option is crucial for this particular application. Hence, this study introduces a revolutionary architecture for the array waveguide grating multiplexer (AWG) that utilizes switched radio over fiber technology, offering significant system design, installation, and operation advantages. Prospective developments encompass applying AWG-RoF conveyance to facilitate expected pivotal technologies for future mobile systems, including millimeter-wave transmission and enormous MIMO. The output power ranged between (19.983dBm) and (12.431dBm), the average received noise power (dBm) was (17.117), and the average received power was (17.2425dBm). The simulation demonstrated favorable outcomes, including enhanced bandwidth and transmission range, while experiencing negligible losses.

Adhesive bonding is one of the essential methods applied in wide fields, mainly automotive and aerospace, because the adhesive can be used with various materials, weighs less compared to other methods, is easy to work with, and does not require many tools. The present research focuses on determining and predicting the ultimate tensile values for single-lap adhesive joints. The mathematical models and artificial neural network (ANN) method predict the tensile strength values. Two variables were used: the surface roughness and the bonding area. To determine tensile test values, ten samples were used with different surface roughness and an overlap distance of 25 and 40 mm. The results showed that the bonding distance had more effect than the surface roughness on the ultimate tensile load. Also, the predicted error values through mathematical models did not exceed 3.209% for the samples, while the ANN samples' error values did not exceed 8.312.

Many industrial applications require lightweight, low cost and high- performance materials. This work created a bimetal (Al-Cu) using the compound casting technique (Squeeze casting). Nickel-electro coating of copper substrates was used before casting; the copper inserted was a cylindrical rod into a carbon steel die, then melted aluminum at (700˚C). The liquid to-solid ratio influenced the formation of the interface (transition region between the two metals). Also the mechanical characteristics of the bimetal (Al-Cu) were studied. The intermetallic compounds were discovered as (Al_2 Cu,AlCu_4,AlCu,Al_4 Cu_(9,) and Cu_4 Al_3). The nickel coating significantly enhanced and strengthened the bimetal (Al-Cu) interconnection by percentages (17% and 3.5%). Many tests and examinations were conducted, such as examining the microstructure with an optical microscope, scanning electron microscope and X-ray diffraction, hardness and interconnection strength examinations due to restricting the formation of intermetallic compounds. The results also showed that the interface had a thickness and good properties at a ratio of liquid to solids of 17% because the large thermal content increased the interface thickness between the two metals. The effect of this ratio was evident through the tests’ results, as the interconnection strength reached 15.5 MPa. The copper and aluminum interfaces' hardness were is 168, 92, and 38 HV, respectively. While the intermetallic compounds were more diverse at a liquid to- solid ratio of 17%.

Hematite is one of the iron ores, and its chemical formula is (Fe2O3). The present research studies the hematite processing and the effect of grinding factors on it. Hematite ore is considered a low-grade iron ore due to its low iron percentage. The hematite comprised Fe (30.36%), Fe2O3 (43.41%), and other minerals, such as (CaO, SiO2, and Al2O3). It is essential to clean the valuable metal from impurities by making its closed components intertwined with impurities liberated through processing and grinding processes to increase its surface area, which is the research goal. The research methodology included collecting a sample of hematite ore from the Al-Hussainiyat area in (Anbar-Iraq). The hematite ore sample was crushed and ground. Then, samples were sieved using a vibrating sieve to analyze the raw particles based on their particle size distribution. Weight, time, and rotational speed were investigated to obtain the right balance between the input weight, grinding time, and mill speed to get the required particle size. The present research also aims to reduce the ore's particle size to less than 75 m and grind it to maximize its surface area. The findings of the milling process showed that the particle size reduced with increasing speed and duration. Also, it was found that the laboratory ball mill produced raw materials with a size of 20 microns and a maximum weight of 21.6 grams. These gains were achieved when a weight of 50 grams was added to 4 balls, a suitable number of balls, and the mixture was left inside for 30 minutes. The maximum weight achieved at 500 rpm for 10 minutes was 41 grams, with an internal weight of 100 grams and a particle size of 150 microns.

Conventional flexible pavements are released to different types of failure in the initial phases of their service life due to high traffic density, high speeds, heavy loads, and harsh climates. To eliminate pavement damage and failure early, the present search investigates the impact of adding glass, steel, and basalt fibers in the asphalt mixtures. Also, the study evaluates these materials characteristics compared to the mixtures without fibers. The Marshall test and tensile strength ratio test (TSR) were utilized to evaluate the asphalt mixture's performance. A set of specimens were produced by incorporating glass fiber (GF), steel fiber (SF), and basalt fiber (BF) at (0.10%, 0.15%, 0.20%), (0.25%, 0.35%, 0.45%), and (0.15%, 0.35%, 0.50%), respectively. When using these fibers, the findings showed an improvement in Marshall stability, flow, volumetric properties, and TSR value. The highest improvement in Marshall stability and TSR value was obtained at 0.10% of GF by 14% and 11.5%, at 0.25% of SF by 16% and 10%, and at 0.15% BF by 8% and 14.1%, respectively, compared to the control mixture. Therefore, fibers can be used as a convenient modifier for asphalt mixtures to improve the performance of flexible pavement with an optimal addition of 0.1% GF, 0.25% SF, and 0.15% BF to the total mass of the mix.

Three-phase induction motors (IMs) are generally used in commercial, industrial, and domestic applications due to their advantages, such as good self-starting ability, simplicity, high reliability, cost-effectiveness, low maintenance, and ruggedness in construction. The IMs are exposed to different internal and external faults; one of the most popular external faults is unbalanced supply voltages. Unbalanced supply voltage is a popular and worldwide phenomenon that effectively decreases the characteristics of IMs. The present work shows the adverse effect of unbalanced supply voltages on the steady-state characteristics of all NEMA (National Electrical Manufacturers Association) designs of 20hp squirrel cage IMs (SCIMs). A symmetrical component is used to determine the performance of each NEMA design operating in different unbalanced supply voltage situations. The importance of this paper is that it likens different NEMA designs regarding torque-speed characteristics, efficiency, power factor, stator currents, rotor currents, torque pulsation, a ripple in rotor speed, and starting-up performances when subjected to over and under-unbalanced supply voltage conditions. Also, the MATLAB and Simulink environments have been utilized concurrently for simulation purposes.

Gypseous soil is one type of collapsible soil. It is well known in Iraq for causing structural distress to many engineering facilities. It is characterized as having high strength properties as being dry, but when wetted with water, it experiences rapid collapse settlement. The present laboratory study evaluates the collapse settlement for several polygons and non-common footing shapes and compares them. In some structural facilities, such problems may arise when using polygon footing shapes due to reasons regarding non-uniform spacing left for footing, restrictions due to property lines or sanitary works. For this purpose, a large laboratory tank model had lateral dimensions of 0.8× 1.0m and a depth of 0.8m. The studied gypseous soil, with 63% gypsum content, was from Tikrit City, about 200km north of Baghdad/ Iraq. It is compacted to a dry unit weight of 14.82kN/m3 in the model. The used shapes of footings were a square, circular, equilateral triangle, rectangular, plane strain, trapezoidal, and isosceles triangle. All footings were (100 cm2) and bear the same applied pressure (40kN/m2). Both dry and then soaking stages for soil were conducted. The experiments were conducted, such as one test for each tank. The test results revealed that the maximum collapse settlement recorded was in the case of the isosceles triangle, i.e., (settlement/equivalent width) ratio Δs/B is 0.24. The least collapse settlement was for the case of square footing with a Δs/B of 0.15. The settlement measured when the soil dried was about 1-1.3 mm for all footing shapes, i.e., Δs/B=0.01-0.013. The collapse settlement stopped after 5-7 days, while the dry condition settlement took less than one hour to level off and end.

In arid and semi-arid regions like the Middle East, where water scarcity is a significant concern, utilizing treated industrial effluent for irrigation purposes is a common practice. The present study aims to assess the quality and suitability of effluent wastewater from the North Refineries Company (NRC) in Baiji, Iraq, for agricultural use using the irrigation water quality index (IWQI) technique. Bimonthly samples were collected from the treated effluent of NRC between November 2011 and mid-February 2012. These samples underwent testing to calculate an average of 17 physical and chemical parameters, including electrical conductivity (EC), pH, sodium, calcium, magnesium, bicarbonate, chloride, nitrate, aluminum, arsenic, copper, iron, lead, manganese, nickel, and zinc. Selecting these parameters is to comprehensively assess water quality and address environmental and health concerns. A salinity hazard was determined by the water’s electric conductivity (EC), which ranged between 600 and 850 mg/L and is highly suitable for irrigation. An adsorption ratio for sodium was calculated, which ranged from 0.0034-0.12. CL-, HCO3-, and NO3- all had high ratings and suitability except for NO3-, which varied from medium-high in suitability for irrigation at (40-47.5) mg/L, 30–62 mg/Las CaCO3, and 0.2–7.2 mg/L, respectively. In this case, the concentrations of Mn and Cu ions were (0.79-0.04 mg/L and 5.6-0.4 mg/L), respectively, which made the water (moderate in suitability) for irrigation. The values of IWQIs ranged between 39.5 and 40.75, and their classifications fell within the first class (High). As a result, the treated wastewater (NRC) can be used for irrigation. However, it is recommended to implement measures such as establishing a proper drainage system to prevent the accumulation of heavy metals or salinity in the soil.

This paper aims to address the issue of water pollution in the Tigris River in Mosul city through continuous water quality monitoring. The proposed solution involves the use of LoRa-WAN wireless technology. Wireless sensor nodes would be placed at various stations along the river in Mosul, transmitting data to a LoRa gateway at the Nineveh Water Directorate. This gateway would then communicate with a server via a Cloud platform on the internet. The study utilized the OMNET++ program to simulate data transfer from sensor nodes to the LoRa gateway. Two main contributions are highlighted: an environmental contribution in providing data on water pollution levels and a technological contribution in utilizing the LoRa network for water quality monitoring. Thirteen parameters were measured at nine river stations. The sensor nodes will send notifications to the LoRa-WAN network if any parameter exceeds a predetermined value. The simulations analyzed the received signal strength indicator and packet delivery ratio with 117 sensor nodes managed by one LoRa gateway, covering a 20km area. The LoRa-WAN technology demonstrated satisfactory results in the simulated scenarios, improving network performance by studying the impact of increasing distance between sensor nodes and the gateway on RSSI values for different transmitting power levels (2-14 dBm).

In the present study, eight reinforced concrete slabs divided into four groups with two slabs per group were fabricated and tested under impact load, replacing their aggregate with 0%, 4%, 8%, and 16% of polyethylene terephthalate) PET). During the preparation process, PET materials increased the workability of fresh concrete by up to 16% and decreased the density by 9%. The compressive strength decreased by about 11.7%, 15.7%, and 19.9% using 4%, 8%, and 16% of PET, respectively. Splitting strength decreased by 7.2%, 17.4%, and 20.3% using 4%, 8%, and 16% of PET, respectively. Failure mode and deflection amplitude results showed that PET delayed the first cracks and reduced the crack lengths and width and crack spreading at failure. Also, impact resistance enhanced at the first crack and ultimate load stages when PET was used compared to normal concrete. The maximal and minimal displacement decreased with increasing PET proportion to 8% and 16%. The slabs were modeled using the finite element program SAP2000 with 4-node shell elements. The finite element (FE) analysis showed a similar deflection response as those experimentally obtained for all slabs. The deflection obtained by FE was less, about 15.5% and 19%, compared with all slabs experimentally tested except slab G2-2, which showed a higher deflection of about 16.3%.