The effect of nano-SiO2 and the styrene butadiene styrene polymer on the high-temperature performance of hot mix asphalt

The production of modified asphalt mixtures with appropriate performance in high temperature has always been under the attention of researchers. One of these modifiers is Styrene Butadiene Styrene (SBS) polymer. Since the application of SBS polymer in bitumen and asphalt mixture does not have expected performance of field due to phase separation of bitumen and polymer, oxidation, and aging, the present study tries to not only improve the polymer defects, but also analyzes its high-temperature performance by using nano-SiO₂ and SBS polymer in bitumen modification. According to the study results, adding nano-SiO₂ and SBS polymer with 3 and 4.5 bitumen weight percent, respectively, to bitumen in asphalt mixture leads to an increase of flow number in dynamic creep test at 50°C for 399 times and at 60°C for 1,015 times compared to unmodified asphalt mix. This, in turn, indicates the considerable improvement of asphalt mixture high-temperature performance.     

Efficiency of Hydrothermal Synthesis of Nano/Microsized Copper and Study on In Vitro Antifungal Activity

In this study, the synthesis and characterization of copper nano/microparticles in the presence of (2,2′,2″,2″′-(ethane-1,2-diylbis(azanetriyl))tetraacetohydrazide) as a capping and reducing agent under hydrothermal conditions for use in biological conditions were investigated. The effects of reductant ligand/copper ion, concentration ratios, reaction temperatures, and reaction time on the various morphologies of copper nano/microparticles were studied. The obtained particles have been characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectrum analysis (EDAX), and zeta potential analysis. Further, the formation of particles with different morphologies was confirmed. The biological and antifungal effects of these selected particles were compared with those of the Bordeaux mixture. Experiments were conducted on Alternaria alternata, Alternaria solani, and Fusarium expansum as three types of phytopathogenic fungi and Penicilliums as a non-phytopathogenic fungus. The results obtained showed that not only were the nano/microparticles more effective than Bordeaux mixture in killing phytopathogenic fungi, but also these particles did not have a fungicidal effect on the non-phytopathogenic fungus, Penicillium, which is an advantage of the obtained nano/microparticles.     

Microstructure and phase evolution of alumina-spinel self-flowing refractory castables containing nano-alumina particles

The microstructure and phase composition of alumina-spinel self-flowing refractory castables added with nano-alumina particles at different temperatures are investigated. The physical and mechanical properties of these refractory castables are studied. The results show that the addition of nano-alumina has a great effect on the physical and mechanical properties of these refractory castables. With the increase of nano-alumina content in the castable composition, the mechanical strength is considerably increased at various temperatures. It is shown that nano-alumina particles can affect formed phases after firing. The platy crystals of CA₆ are detected inside the grain boundaries of tabular alumina and spinel grains in samples fired at 1500 °C. CA₆ phase can be formed at lower temperatures (1300 °C) with the addition of nano-alumina particles. As a result of using nanometer-sized alumina particles with high surface area, the solid phase sintering of the nano-sized particles and CA₆ formation can occur at lower temperatures.     

Dynamic job shop scheduling using variable neighbourhood search

In this paper a scheduling method based on variable neighbourhood search (VNS) is introduced to address a dynamic job shop scheduling problem that considers random job arrivals and machine breakdowns. To deal with the dynamic nature of the problem, an event-driven policy is selected. To enhance the efficiency and effectiveness of the scheduling method, an artificial neural network with a back propagation error learning algorithm is used to update parameters of the VNS at any rescheduling point according to the problem condition. The proposed method is compared with some common dispatching rules that have been widely used in the literature for the dynamic job shop scheduling problem. Results illustrate the high efficiency and effectiveness of the proposed method in a variety of shop floor conditions.     

Comparison of transmission and the 90-degree holographic recording geometry

We compare the system performances of two holographic recording geometries using iron-doped lithium niobate: the 90-degree and transmission geometry. We find that transmission geometry is better because the attainable dynamic range (M/#) is much higher. The only drawback of transmission geometry is the buildup of fanning, particularly during readout. Material solutions that reduce fanning such as doubly-doped photerefractive crystals make transmission geometry the clear winner.     

Nonlinearity in Simple and Complex Cells in Early Biological Visual Systems

The nonlinear model put forward in Mahmoodi (J Math Imaging Vis 54(2):138–161, 2016) for early visual systems is investigated in detail in this paper to explain some nonlinear behaviours of complex and some simple cells. Nonlinear cells are modelled as systems with linear–nonlinear structures where the linear sub-unit is constructed by the layers proposed in Mahmoodi (2016) and nonlinear sub-units are the results of an axon (modelled as a transmission line) carrying a series of spikes. In this paper, the nonlinear sub-systems of complex cells are investigated in more detail to show the mechanism by which nonlinear neurons work. Here the nonlinear systems modelling nonlinear sub-units of complex cells are represented by their first- and second-order responses. Our analytical as well as numerical results show good agreements with biological recordings reported in the literature.     

Power management in SMAC-based energy-harvesting wireless sensor networks using queuing analysis

One of the most important constraints in traditional wireless sensor networks is the limited amount of energy available at each sensor node. The energy consumption is mainly determined by the choice of media access mechanism. SMAC is a typical access mechanism that has drawn much attention in recent years. In WSNs, sensors are usually equipped with capacity-limited battery sources that can sustain longer or shorter period, depending on the energy usage pattern and the activeness level of sensor nodes. To extend the lifetime of the sensor networks, ambient energy resources have been recently exploited in WSNs. Even though solar radiation is known as the superior candidate, its density varies over time depending on many factors such as solar intensity and cloud states, which makes it difficult to predict and utilize the energy efficiently. As a result, how to design an efficient MAC in a solar energy harvesting based WSN becomes a challenging problem. In this paper, we first incorporate a solar energy-harvesting model into SMAC and conduct its performance analysis from a theoretical aspect. Our research works provide a fundamental guideline to design efficient MAC for energy harvesting based WSNs. Our major contribution includes three folders: firstly, we model solar energy harvesting in a photovoltaic cell and then derive the throughput of SMAC in the energy-harvesting based WSNs. Second, we develop a new model based on queuing theory to calculate the average number of energy packets in battery in terms of both duty cycle and throughput. Finally, we form an optimization problem to find a suitable range for the duty cycle to satisfy both quality of service (QoS) and network lifetime requirements.     

Dynamic pull-in of thermal cantilever nanoswitches subjected to dispersion and axial forces using nonlocal elasticity theory

Microsystem Technologies - Precise analysis of nanoelectromechanical systems has an outstanding contribution in performance improvement of such systems. In this research, the dynamic...