Comparison of the effect of GFRP and steel reinforcement in concrete members subjected to compressive stress

Composite materials became more popular and commercially available as reinforcement for concrete elements. Fibre Reinforced Polymer (FRP) bar is an excellent thermal and electrical insulator with high tensile strength and low weight. These assumptions make them a possible substitution for steel reinforcement. Moreover, GFRP is not responsible to corrosion for that are suitable for structures with high humidity and unfavorable environment. GFRP is easier to handle due to its low weight. Also, it has electromagnetic neutrality. But it has some disadvantages. It has a low modulus of elasticity and sensitivity to elevated temperatures. Another drawback and uncertainty with designing is the impact of an alkaline environment, which decreases the long-term strength of GFRP bars. This paper describes a pre-experiment study of concrete elements resistance. The analysis is performed for a cross-section of 200x150 mm for a short concrete column with steel and GFRP reinforcement. The study compares P-M diagrams for steel reinforcement and GFRP reinforcement with different reinforcement ratios. Other characteristics such as tensile strength and modulus of elasticity must be considered to design the GFRP reinforced concrete element. The study also considers the contribution of GFRP reinforcement in compression. The analysis has shown, the shape of interaction diagrams of steel and GFRP reinforcement are significantly different.

Improving Characteristic Parameters of Memristor Based on HfO2 Active Layer

The improvement of the characteristic parameters of the memristor depends on the factors such as thickness and surface area of the active layer. These parameters define leakage currents, which is the main disatvantige of the memory storage device and to improve the electrical features the leakage currents must be dropped to the zero in ideal case. In the presented work is described the electrical isolation of the active layer from the substrate by the thin layer of photoresist, which is an electrical insulator. For reducing area was used the new fotomask, which is able to reduce area 100 times. The memristor structures are designed in the form of “crossbars”, which allows us to individually investigate each memristor and create a database with the possibility of incorporating it into the microchip in the future. In this work is presented also research outcomes regarding to selection memristor’s contacts and active layers. As contacts are overviewed tungsten (W), titanium nitride (TiN) and aluminum (Al). Is considered metal and transition metal oxides as active layers WOx, HfO2, WOx +HfO2, HfO2 + HfOx. The oxide electrical and structural properties is defined from I-V, C-V, XRD and XPS characteristics.

Parametric Study of Concrete Members with GFRP Reinforcement Subjected to Bending and Axial Force

The paper deals with the possible replacement of steel reinforcement by GFRP reinforcement for concrete elements subjected to bending moment and compressive axial force. For the last 15 years, Fibre Reinforced Polymer (FRP) bars became more popular and commercially available as reinforcement for concrete elements. Composite FRP materials are still new in construction and many engineers are not familiar with their properties and behaviour. FRP has certain advantages over steel reinforcement. It is a durable material that is not subject to corrosion, does not conduct heat, is an electrical insulator and conducts electrical current, and is non-magnetic. In contrast, FRP also has certain deficiencies such as sensitivity to higher temperatures, alkaline environments, and reduction of mechanical properties at high levels of long-term stress. In the case of FRP reinforcements, the plastic branch is missing in the σ-ε diagrams, what leads to a sudden failure of the reinforced concrete element, either by tensile rupture of the reinforcement or by crushing the concrete. The most used FRP reinforcement is made of glass fibres - GFRP reinforcement. The paper deals with the possible replacement of steel reinforcement by GFRP reinforcement for slab and beam elements. The text describes a parametric study for different reinforcement ratio with GFRP reinforcement and steel reinforcement. The study is performed for a cross-section of 500x500 mm for a column element and a cross-section of 1000x250 mm for a slab element. The effect of longitudinal GFRP reinforcement in elements under compression was investigated. The study contains a comparison of interaction P-M diagrams of concrete elements with steel and GFRP reinforcement. For design of GFRP reinforced concrete elements, it is necessary to consider different material characteristics such as tensile strength and modulus of elasticity. The contribution of the GFRP reinforcement in compression was neglected due to the anisotropic nature of the GFRP reinforcement and the low modulus of elasticity. The main reference basis for the elaboration of a parametric study is the fib Bulletin No. 40.

FEATURES OF PHASE TRANSFORMATIONS IN THE SYNTHESIS OF COMPLEX LITHIUM-CONDUCTING OXIDE MATERIALS

Lithium-ion batteries (LIB`s) are widely used in consumer electronics, mobile phones, personal computers, as well as in hybrid and electric vehicles. Liquid electrolytes, which mainly consist of aprotic organic solvents and lithium-conductive salts, are used for the transfer of lithium ions in LIB`s. However, the application of liquid electrolytes in LIB`s leads to a number of problems, the most significant of which are the risk of battery ignition during operation due to the presence of flammable organic solvents and loss of capacity due to the interaction of liquid electrolyte with electrode materials during cycling. An alternative that can ensure the safety and reliability of lithium batteries is the development of completely so­lid state batteries (SSB`s). SSB`s are not only inherently safer due to the absence of flammable organic components, but also have the potential to increase significantly the energy density. Instead of a porous separator based on polypropylene saturated with a liquid electrolyte, the SSB`s use a solid electrolyte that acts as an electrical insulator and an ionic conductor at the same time. The use of a compact solid electrolyte, which acts as a physical barrier that prevents the growth of lithium dendrites, also allows using lithium metal as the anode material. It is desirable to use oxide systems as the so­lid electrolytes for SSB`s, as they are resistant to moisture and atmospheric air. Among the lithi­um-conducting oxide materials, which exhibit relatively high lithium conductivity at a room temperature and can be used as a solid electrolyte in the completely solid-state batteries, lithium-air batteries and other electrochemical devices, the most promising materials are ones with NASICON, perovskite and garnet-type structures. The phase transformations that occur during the synthesis of complex lithium-conductive oxides, namely Li1.3Al0.3Ti1.7(PO4)3 with the NASICON-type structure, Li0.34La0.56TiO3 with the perovskite-type structure and Li6.5La3Zr1.5Nb0.5O12 with the garnet-type structure by the solid-state reactions method in an air were investigated. The optimal conditions for the synthesis of each of the above-mentioned compounds were determined.

The Effect of Optogenetically Activating Glia on Neuronal Function

Glia, or glial cells, are considered a vital component of the nervous system, serving as an electrical insulator and a protective barrier from the interstitial (extracellular) media. Certain glial cells (i.e., astrocytes, microglia, and oligodendrocytes) within the CNS have been shown to directly affect neural functions, but these properties are challenging to study due to the difficulty involved with selectively-activating specific glia. To overcome this hurdle, we selectively expressed light-sensitive ion channels (i.e., channel rhodopsin, ChR2-XXL) in glia of larvae and adult Drosophila melanogaster. Upon activation of ChR2, both adults and larvae showed a rapid contracture of body wall muscles with the animal remaining in contracture even after the light was turned off. During ChR2-XXL activation, electrophysiological recordings of evoked excitatory junction potentials within body wall muscles of the larvae confirmed a train of motor nerve activity. Additionally, when segmental nerves were transected from the CNS and exposed to light, there were no noted differences in quantal or evoked responses. This suggests that there is not enough expression of ChR2-XXL to influence the segmental axons to detect in our paradigm. Activation of the glia within the CNS is sufficient to excite the motor neurons.

Chromatin remodeling in oligodendrogenesis

Oligodendrocytes are one type of glial cells responsible for myelination and providing trophic support for axons in the central nervous system of vertebrates. Thanks to myelin, the speed of electrical-signal conduction increases several hundred-fold because myelin serves as a kind of electrical insulator of nerve f ibers and allows for quick saltatory conduction of action potentials through Ranvier nodes, which are devoid of myelin. Given that different parts of the central nervous system are myelinated at different stages of development and most regions contain both myelinated and unmyelinated axons, it is obvious that very precise mechanisms must exist to control the myelination of individual axons. As they go through the stages of specification and differentiation – from multipotent neuronal cells in the ventricular zone of the neural tube to mature myelinating oligodendrocytes as well as during migration along blood vessels to their destination – cells undergo dramatic changes in the pattern of gene expression. These changes require precisely spatially and temporally coordinated interactions of various transcription factors and epigenetic events that determine the regulatory landscape of chromatin. Chromatin remodeling substantially affects transcriptional activity of genes. The main component of chromatin is the nucleosome, which, in addition to the structural function, performs a regulatory one and serves as a general repressor of genes. Changes in the type, position, and local density of nucleosomes require the action of specialized ATP-dependent chromatin-remodeling complexes, which use the energy of ATP hydrolysis for their activity. Mutations in the genes encoding proteins of the remodeling complexes are often accompanied by serious disorders at early stages of embryogenesis and are frequently identified in various cancers. According to the domain arrangement of the ATP-hydrolyzing subunit, most of the identified ATP-dependent chromatin-remodeling complexes are classified into four subfamilies: SWI/SNF, CHD, INO80/SWR, and ISWI. In this review, we discuss the roles of these subunits of the different subfamilies at different stages of oligodendrogenesis.

Review on the development of jute polyethylene nanocomposites as a function of fiber chemical treatments

: The research on jute fiber reinforced polymer composites is an emergent concern with the development of new materials due to its significant properties like economical, partially biodegradable and environment friendly. It is wondered that the hydrophilic nature of jute fiber negatively affects the interfacial interaction with hydrophobic polymeric materials in the composite which then affects the resultant mechanical, microstructural and physico-chemical absorption properties. In order to overcome this fact, researchers have been carried out some techniques for fiber surface chemical treatments. On the other hand, due to the low processing costs and design flexibility, thermoplastics deal many benefits over thermoset polymers, and polyethylene shows excellent processing behaviors such as: low density, low cost, considerable flex life, outstanding surface hardness, scratch resistance and good electrical insulator. Beside the traditional thermoplastic and thermosetting polymers, montmorillonite nanoclay are also receiving attention to manufacture fiber polymer nanocomposites for industrial and household applications as well. The review is considered to highlight the progress of jute fiber reinforced polymer nanocomposites. The study also focuses on the several features of juter polymer composites and nanocomposites as a function of fiber chemical treatments.

Usefulness of a Radiofrequency Transseptal Needle in the Second Puncture of Fontan Extracardiac Conduit

We performed a second puncture of the extracardiac conduit in an 11-year-old Fontan patient to assess the patency of the stent previously deployed in the left pulmonary vein. For the first puncture, a mechanical Brockenbrough needle was selected to puncture the Gore-Tex conduit, an electrical insulator. For the second puncture, the location of that previous hole was detected as an indentation covered with atrial tissue, which is an electrical conductor. The second puncture was performed safely using a radiofrequency transseptal needle.

Investigation of Structural, Morphological, Resistivity of Novel Electrical Insulator: Industrial Wastes

In the present study, the effect of china clays on the sintering, strength and dielectric behavior of electrical ceramic fly ash/china clay (FA/CC) composite insulator is investigated. The different composition of samples containing different china clay (CC) contents of 10, 20, 30, 40, and 50 % are prepared using the uniaxial pressure technique applying 10 MPa pressure. At 1200 °C, for the composition having 40 wt% china clays, the maximum resistivity is calculated and is 39.5 × 107 Ωm. The composite is highly competence with china clays-based insulators. Further, the prepared composite is also analysed using different characterization technique such as x-ray diffraction, field emission scanning electron microscopy with energy dispersive analysis, fourier transformation infra-red spectroscopy, dielctric, and thermo gravimetric analysis. Frequency dielectric value of the composite is estimated at room temperature in the frequency range of 1-500 kHz at room temperature. According to the resistivity and dielectric properties, the composite has enormous potential for the electrical insulator application.