Arabian Journal for Science and Engineering

Cooperative spatial multiplexing technique proposed to simplify the transmitting and receiving process on the relay nodes while providing significant energy savings. This paper investigates the performance of constellation rearrangement scheme when used in conjunction with cooperative spatial multiplexing MIMO/SISO relaying networks. During the MIMO relaying process, instead of having a single antenna for relay we have multiple antennas for relay by using additional information from MAC layer. The idea is to use the optimized constellation so that minimum squared Euclidean distance between different branches is maximized. Through extensive numerical search, we obtain the best constellation rearrangement scheme. Maximum likelihood detector is required in the receiver but the computational complexity of the receiver does not change because the proposed constellation will be saved in a table at the transmitter this search done by using arrival information from MAC layer.

With the development of deep mines and deep tunnels, the phenomenon of high temperature is becoming more and more serious. Moreover, high temperature is one of the recognized extreme environments in the application of concrete. High temperature will significantly deteriorate the performance of concrete and shorten the service life of concrete structure. In this paper, firstly, According to the characteristics of temperature distribution, 80 °C was selected to simulate the dry heat environment. By adding organic polyurethane and fly ash into concrete, three types of concrete were prepared, in which polyurethane mainly replaced part of water content. The compressive properties of concrete at different ages under dry heat environment was studied. Then, the hydration products and structure distribution characteristics of three kinds of concrete were analyzed by SEM. Finally, the binding test between organic polyurethane and aggregates was designed under dry heat temperature. The results showed that compressive strength of polyurethane concrete under dry heat environment was higher than that of fly ash concrete and ordinary concrete, and polyurethane concrete had good temperature resistance. However, fly ash concrete had a shrinkage phenomenon at 28 days under dry heat temperature. Through microscopic analysis, the network structure was found between polyurethane and aggregate, the hydration degree of cement in polyurethane concrete was high, and the flocculent structure of polyurethane under dry heat temperature improved the stability of concrete structure. The research results could provide reference for the selection of concrete in tunnels and mines engineering roadway support under high temperature geological environment.

Plant fibers have enormous potential for enhancing concrete's impact resistance due to their exceptional toughness and ductility. Nevertheless, theoretical studies on the impact properties of plant fiber-reinforced concrete (PFRC) are still relatively few. Thus, it is crucial to investigate from a theoretical standpoint how plant fibers affect concrete's impact properties. Based on the modified Griffith fracture theory, this study established the relationship between plant fiber type and strain hysteresis factor. In order to simulate the damage process of PFRC, a micro-spring system was used. Based on this, a dynamic constitutive model considering the influence of plant fibers was proposed by combining the methods of damage mechanics and fracture theory. Parameter fitting and inverse analysis were used to validate the accuracy of the proposed model. Additionally, the mechanical behavior of four types of PFRC (Jute, Flax, Ramie and Sisal Fiber Concrete) under impact loading was simulated by the finite element method (FEM) using the proposed model. The results show that the predictions of the proposed model maintain a good of fit R2 more than 0.98 with the experimental results. The parameter fitting and inversion results also show that the proposed model has a good prediction. Simulation results show that sisal fiber-reinforced concrete exhibited the best performance among the four types of PFRC under identical loading conditions, offering more significant advantages for engineering applications. Theoretical and simulation studies on the impact properties of PFRC were conducted in this paper, and the findings are believed to provide a valuable methodological basis for the engineering application of using less expensive plant fibers to enhance concrete impact properties.

The aim of this study is to enhance the flame retardant property of the glass fiber reinforced polyester composites by using intumescent flame retardants such as ammonium polyphosphate (APP) and/or expandable graphite (EG) in addition to aluminum tri-hydroxide (ATH). Flame retardant properties of the composites were tested by limiting oxygen index and UL-94 tests. Chemical characterization of the materials was done using Fourier transform infrared spectroscopy. Mechanical properties were evaluated by tensile test, and surface morphology analysis was performed by using stereomicroscope and scanning electron microscope. Thermal properties of the composites were characterized by thermogravimetry/differential thermal analyzer. The results showed that the flame retardancy of the composites was significantly improved by the addition of intumescent flame retardants with no considerable adverse effect on the mechanical properties. Thermal analysis data revealed that intumescent flame retardants increased the char yields of the composites. Also, the APP containing formulations yielded lower weight loss rates. To our knowledge, this is the first study investigating the flame retardancy, thermal, and mechanical properties of glass fiber reinforced polyester composite comprising ATH, APP, and EG in dual- or triple-flame retardant formulations.

The aim of this paper is to study warped product manifolds endowed with a semi-symmetric non-metric connection. We find relations between the Levi-Civita connection and the semi-symmetric non-metric connection of the warped product M = M 1 × f M 2. We obtain some results of Einstein warped product manifolds with a semi-symmetric non-metric connection.

Measuring the surface velocity and breach outflow discharge is a challenge in earth dam-break experiments. To solve this problem, large-scale particle image velocimetry (LS-PIV), a non-intrusive approach to measuring surface velocities, was applied in earth dam-break experiments. In this paper, two dam-break experiments were conducted in a large flume, and LS-PIV was used to measure the surface flow velocities of the dam breach. The flume was 50 m long, 4 m wide and 2 m high, and an idealized, non-cohesive, homogeneous earthen dam was placed in the middle of the flume. Three pressure sensors were used to measure the water depth over time. In addition, three high-speed digital cameras and two industrial cameras were used to record the dam breach process. The measured velocities were applied to evaluate the breach outflow discharge. Acceptable agreement was obtained between the discharges estimated with the LS-PIV and water level change methods. The surface velocity field was also obtained, and a dam crest cross section was selected to analyze the process of surface velocity change. Moreover, a convenient and simple formula was introduced to rapidly estimate breach discharge at the dam crest cross section. Finally, based on the Manning formula and surface velocity, the shear stress of the breach bottom was computed and discussed. The findings of this paper validate the accuracy and reliability of the LS-PIV technique for dam-break experiments and suggest that it is a reliable and advantageous technology for dam failure experiments.

This study investigates the successful joining methods of dissimilar metals of AZ31B Mg and AA7075-T6 Al alloys. The specimens were joined by using open-flame heating system and investigated the effect of the friction stir welding (FSW) process parameters on the welding quality, transverse rupture strength (TRS), tensile strength, microhardness, and microstructure of the resulting specimens. The welding experiments were conducted based on the Taguchi mixed-orthogonal-array for tests, L16 (42 × 22), at a constant spindle speed of 500 rpm using a K10 grade carbide mixing tool with two different tilt angles (0° and 3°), and two tool tip geometries (square and triangle). The specimens were successfully welded, and the test results revealed that the welding temperatures and forces had the strongest effect on the welding quality. The achieved maximum tensile strength and TRS were approximately 122.1 MPa and 712.1 MPa, respectively, at a tool travel speed of 20 mm/min, tool offset value of 0.75 mm, tool tilt angle of 3°, and using a triangle tool tip. The microstructural analysis indicated that a dynamically recrystallized and grain refinement structure formed in the welded zone depending on the temperature and on the excessive deformation. The increase in the microhardness values depends on the intermetallic compounds ratio and fine-grained structure in the welded zone.

Vehicular fog computing (VFC) is a technology that enhances vehicular applications by offloading the task of the resource-restricted vehicle to the resourceful fog node (vehicle or static fog node). The mobility of vehicles leads to various challenges in task offloading, i.e., low successful offloading ratio, high response time, etc. Apart from this, the available idle computation resource at the fog node is different at the time of advertisement of computation capability and at the time of task allocation. This change results in less efficient resource utilization and unequal load balance at the fog node. Hence to overcome this, we have proposed an approach based on future mobility and imminent computation awareness (FMICA). The future mobility prediction allows us to offload the task to the fog node, which will be near during task retrieval . Additionally, imminent computation awareness of the available resources (at the imminent time $$\tau $$ ) allows us to efficiently utilize the idle resources through offloading higher deadline tasks at the $$\tau $$ time. FMICA optimizes resources according to various criteria such as offloading delay, load variance, within-range ratio, and successful offloading ratio using a Strength Pareto Evolutionary Algorithm 2 (SPEA2). An order preference by similarity to the ideal solution (TOPSIS) and multiple criteria decision-making (MCDM) technique is used to select the best solution. Through the experimental analysis, we have found that the FMICA has an improvement of 37.64%, 25.57%, 9.96%, and 12.62% in metrics average response time, successful offloading ratio, resource utilization, and average load variance against available approach, respectively.