A SWOT-AHP analysis on biodiesel as an alternative future marine fuel

Clean Technologies and Environmental Policy - Alternative fuels especially those produced in a green way are essential for meeting supplying the world's growing energy needs. Biodiesel is...     

Theoretical and experimental investigation of effects of failures on the tensile endurance of elevator ropes

Elevators have an important place in human life just after uprising demands in high rise buildings, skyscraper and luxury residence concepts have surged. Steel wire ropes provide permanent working safety and reliability in the elevator installations. Due to this reason steel wire ropes are one of the vital components of elevators. In this study, effects of discard criteria such as wire breaks, abrasive wear and corrosion where extents of those failures are defined by ISO 4344 standard on the tensile endurance of 6×19 Seale and 8×19 Warrington elevator ropes have been investigated theoretically and experimentally. Tensile endurances of rope samples that have different extents of failure have been determined by using tensile testing machine and comparison is made by undamaged samples for each rope separately. In addition, stress and strain values occurred on the elevator ropes investigated have also been presented. The most critical failure type has been found to be 24 wire breaks for 6×19 Seale rope with fiber core where lifting capacity reduced by 25.99 %. The most critical failure type has been found to be abrasive wear which is 0.1 mm in depth along 100 mm length for 8×19 Warrington rope with independent wire rope core where lifting capacity reduced by 7.93 %.     

Crosstalk between MicroRNA and Oxidative Stress in Primary Open-Angle Glaucoma

Reactive oxygen species (ROS) plays a key role in the pathogenesis of primary open-angle glaucoma (POAG), a chronic neurodegenerative disease that damages the trabecular meshwork (TM) cells, inducing apoptosis of the retinal ganglion cells (RGC), deteriorating the optic nerve head, and leading to blindness. Aqueous humor (AH) outflow resistance and intraocular pressure (IOP) elevation contribute to disease progression. Nevertheless, despite the existence of pharmacological and surgical treatments, there is room for the development of additional treatment approaches. The following review is aimed at investigating the role of different microRNAs (miRNAs) in the expression of genes and proteins involved in the regulation of inflammatory and degenerative processes, focusing on the delicate balance of synthesis and deposition of extracellular matrix (ECM) regulated by chronic oxidative stress in POAG related tissues. The neutralizing activity of a couple of miRNAs was described, suggesting effective downregulation of pro-inflammatory and pro-fibrotic signaling pathways, including nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), transforming growth factor-beta 2 (TGF-β2), Wnt/β-Catenin, and PI3K/AKT. In addition, with regards to the elevated IOP in many POAG patients due to increased outflow resistance, Collagen type I degradation was stimulated by some miRNAs and prevented ECM deposition in TM cells. Mitochondrial dysfunction as a consequence of oxidative stress was suppressed following exposure to different miRNAs. In contrast, increased oxidative damage by inhibiting the mTOR signaling pathway was described as part of the action of selected miRNAs. Summarizing, specific miRNAs may be promising therapeutic targets for lowering or preventing oxidative stress injury in POAG patients.     

The Effects of Thermal Cycles on the Impact Fatigue Properties of Thermoplastic Matrix Composites

The effects of thermal cycles on the impact fatigue properties of unidirectional carbon fibre reinforced polyetherimide (PEI) matrix composites were investigated. During the thermal cycles, samples were immersed into boiling water (100 °C) and subsequently to ice water (0 °C), 50, 200 and 500 times. The changes in viscoelastic properties of the composites were investigated by means of dynamic mechanical thermal analyzer (DMTA). At the second step, thermal cycled composites were subjected to repeated impact loadings, with different impact energies. Instrumented impact test results were presented as a function of force, energy, deformation during the experiments. The scanning electron microscope (SEM) studies were done in order to understand the morphology of fractured samples after impact fatigue loading. The number of thermal cycles and applied impact energy of the hammer are found to have a great importance on the fracture morphology of repeatedly impacted material, as expected.     

Novel ZA27/B4C/Graphite Hybrid Nanocomposite-Bearing Materials with Enhanced Wear and Corrosion Resistance

Metallurgical and Materials Transactions A - In this study, nanosized B4C and graphite-reinforced ZA27 matrix hybrid nanocomposites were produced with mechanical milling followed by hot pressing....     

Effect of fiber orientation on viscoelastic properties of polymer matrix composites subjected to thermal cycles

Fibers in polymer composites can be designed in various orientations for their usage in service life. Various fiber orientated polymer composites, which are used in aeroplane and aerospace applications, are frequently subjected to thermal cycles because of the changes in body temperatures at a range of −60 to 150°C during flights. It is an important subject to investigate the visco‐elastic properties of the thermal cycled polymer composite materials which have various fiber orientations during service life. Continuous fiber reinforced composites with a various fiber orientations are subjected to 1,000 thermal cycles between the temperatures of 0 and 100°C. Dynamic mechanic thermal analysis (DMTA) experiments are carried out by TA Q800 type equipment. The changes in glass transition temperature (T_g), storage modulus (E′), loss modulus (E′′) and loss factor (tan δ) are inspected as a function of thermal cycles for different fiber orientations. It was observed that thermal and dynamic mechanical properties of the polymer composites were remarkably changed by thermal cycles. It was also determined that the composites with [45°/−45°]_s fiber orientation presented the lowest dynamic mechanical properties. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Evaluation of the validity of the scalar approximation in optical wave propagation using a systems approach and an accurate digital electromagnetic model

The cause and amount of error arising from the use of the scalar approximation in monochromatic optical wave propagation are discussed using a signals and systems formulation. Based on Gauss’s Law, the longitudinal component of an electric field is computed from the transverse components by passing the latter through a two input single output linear shift-invariant system. The system is analytically characterized both in the space and frequency domains. For propagating waves, the large response for the frequencies near the limiting wave number indicates the small angle requirement for the validity of the scalar approximation. Also, a discrete simulator is developed to compute the longitudinal component from the transverse components for monochromatic propagating electric fields. The simulator output helps to evaluate the validity of the scalar approximation when the system output cannot be analytically calculated.