Polymerization of pyrrole derivatives on polyacrylonitrile matrix,FTIR–ATR and dielectric spectroscopic characterization of composite thin films

Oxidative polymerization of acrylonitrile (AN) initiated by Ce(IV)–oxalic acid redox system in the aqueous medium was performed and polyacrylonitrile (PAN)/polypyrrole (PPy) composite thin films were prepared by polymerization of pyrrole on polyacrylonitrile matrix. Effect of concentration of pyrrole derivatives on the resulting polymeric film properties was investigated. The influence of the pyrrole derivative type and content on the dielectric permittivity, dielectric loss and electrical properties of the composite films were analyzed in the frequency range from 0.05 Hz to 10 MHz. For a selected concentration of 200 μl of composite films at 10⁷ Hz, the conductivity was found to be in the following order: PAN–PPy < PAN–PNMPy < PAN–PNPhPy. Dielectric constant increase of the composite films was more obvious when the quantity of n-phenyl pyrrole was increased. A linear relationship was observed between the absorbances (FTIR–ATR) and conductivities (dielectric spectroscopy).     

Lateral load response of steel fiber reinforced concrete model piles in cohesionless soil

It has been long recognized that piles could be damaged under major lateral loading environments. Precautions such as increasing pile dimensions or reinforcement to avoid damages were often proved to be inadequate for satisfactory pile design especially against heavy lateral loads. This fact necessitated research for piles that are more resistant to lateral forces. Recent debate for better lateral load performance has been about the design and construction of ductile piles. In this respect, steel fiber reinforced concrete (SFRC) can be considered as a contemporary material being able to provide desired additional ductility to conventional reinforced concrete (RC) piles. The lateral load carrying mechanisms of SFRC piles and their interaction with surrounding soil have not been fully studied yet. In this study an investigation for lateral load carrying capacity of SFRC piles in cohesionless soils has been undertaken. A model study involving instrumented model piles, a testing pool and a monotonic loading mechanism has been planned and pursued. Three different steel fiber ratios by volume were utilized in the production of model piles. Performances of these piles were compared with that of the conventional concrete pile. The goal was to observe the influence of steel fibers on ductile pile behavior by isolating them from other reinforcement components (i.e. bending and shear reinforcement). It has been found that SFRC model piles with steel fiber reinforcement ratios of 1% and 1.5% are capable of providing more ductility and higher lateral load carrying capacity while taking lower bending moments compared with the concrete model pile.     

The effects of exploration strategies and communication models on the performance of cooperative exploration

Exploration with mobile robots is utilized in a wide range of applications including search and rescue missions, planetary exploration, homeland security, surveillance, and reconnaissance. Cooperative exploration offers the potential of exploring an unknown zone more quickly and robustly than single-robot case. However, coordinating multiple robots is a challenging task due to heterogeneous processing and communication requirements, and the complexities of exploration algorithms. This paper presents a comparison of different cooperative exploration strategies, such as frontier-based exploration, market-driven exploration, and role-based exploration, based on their exploration performances and processing time requirements. To show the effect of CPU power on the processing time of the exploration algorithms, two notebooks and a netbook with different specifications have been extensively used. Comparative simulation results of our own application developed in Java show that the processing time requirements are consistent with the computational complexities of the exploration strategies. The results we obtained are consistent with the CPU power tests of independent organizations, and show that higher processing power reduces processing time accordingly.     

Determination of textural deterioration in fish meat processed with electrospun nanofibers

Nano-applications are named as one of the novel methods, which provide many advantages like a larger contact area on the surface of fish fillets with less material. The goal of the study was to reveal the textural profile changes correlated with TPB growth of fish fillets coated with nanofibers having 2.47 ± 0.68 mV zeta potential value and 172 nm diameter. The difference of TPB count between control (CS) and the fish fillets treated with nanofibers (NG) reached 3.45 log CFU/g (p < .05) on the sixth day. The hardness value of CS was decreased (p < .05) (the decline: 68%) while the hardness of NG was found to be much more stable (the change: 42%). The highest change in springiness for CS and NG samples was determined as ~24 and ~15%, respectively, for 12 days. Cohesiveness values of CS were slightly increased, but those of the fish fillets coated with nanofibers were remarkably decreased. The coefficient of correlation analysis between TPB count and cohesiveness values was determined as “r = −.026 and r = .796” for CS and NG, respectively. Chewiness values of CS were significantly decreased (p < .05). However, chewiness values of the fish fillets coated with nanofibers were found as much more stable (p > .05). The results revealed that nanofiber coating limited the increase of TPB in fish fillets; it also better kept the textural profile of fish fillets as compared to CS stored at 4°C. The study could play a guiding role in further food nanotechnology applications in the industry and food science.     

Fatigue behaviour of welded joints from magnesium alloy (AZ31) according to the local strain concept

In the present study, the results of fatigue tests with the magnesium alloy AZ31 (ISO‐MgAl3Zn1) in the material states base metal, heat affected zone and weld metal obtained under strain control at room temperature within a range from 2·10² to 5·10⁶ cycles are presented. The fatigue behaviour was characterized by the Coffin–Manson–Basquin equations and the stress – strain behaviour by the Ramberg–Osgood equation. The data can be used to assess welded magnesium joints according to the local strain concept.     

An experimental and computational approach to the heat transfer mechanism in the cooling channel of a texturing process

An experimental and computational investigation of the cooling process during the heat set previous to the texturing has been presented. Different yarn speed values between 600 and 1400 m/min and inlet temperature values with two different channel material (austenite and ferrite steel) and fiber type (polyester and polyamide) have been compared. The convective heat transfer coefficients have been computed iteratively based on the measured values. To reach a reasonable relationship between the geometrical parameters, materials type and the heat transfer values, three-dimensional numerical simulations of the convective flow along the cooling channel were performed.