A hollow-core fiber with nested anti-resonant node-free cladding tubes suitable for broadband THz guidance with low transmission losses is proposed. It is shown that the tube separation and tube ...thickness of the inner elements have a significant effect on the confinement loss and effective material loss of the fiber in the THz band. Using TOPAS copolymer, the proposed fiber was optimized for operation at 1 THz and it is predicted from numerical simulations that loss can be reduced to as low as 0.05 dB/m with a 0.6 THz wide dispersion flattened bandwidth.
Abstract This study has demonstrated the multimode parabolic index fibers integrated with spatiotemporal VCSEL sources for the optical fiber system improvement. Average radial intensity is clarified ...against fiber radius variations with 0.1 % refractive difference index step. The Max base band Q factor form is demonstrated against the fiber refractive index step variations. The Max base band Q factor form variations are demonstrated against VCSEL diode bias current variations. The Max base band Q factor form variations are clarified against the fiber core radius variations. The Max base band Q factor form is simulated against the fiber cladding thickness variations. Multimode fiber calculation report at the wavelength 1550 nm for the light source (Pol. X = VCSEL LP 0,1) is reported. The Max lighted base optical band form power is clarified versus time after parabolic index multimode fiber with 0.1 % refractive difference index step. The Max optical lighted base band power form is demonstrated against wavelength after parabolic index multimode fiber with 0.1 % refractive difference index step. The Max base Q band form factor is simulated after spatial APD photodetector receiver with 0.1 % refractive difference index step. The fiber base band mode form intensity in x and d directions is demonstrated within the fiber with 0.1 % refractive difference index step. The fiber base band encircled flux form is studied and simulated versus fiber radius variations with 0.1 % refractive difference index step.
Even though the structural behavior steel fiber reinforced concrete (SFRC) has been extensively researched, structural applications are still limited. One barrier to its implementation is the lack of ...mechanical models that describe the behaviour of SFRC members failing in shear. This paper reviews the effect of steel fibers on the different mechanisms of shear transfer and combines the observations from the literature regarding the parameters that affect the shear capacity of SFRC. Additionally, a selection of currently available expressions for the shear capacity of SFRC is presented. This paper reviews the current state-of-the-art on the shear capacity of SFRC elements without shear reinforcement, shows the lacks in our current understanding on the shear behaviour of SFRC elements without shear reinforcement, and outlines the steps necessary to address these lacks. The presented work aims to be a framework for (experimental) efforts addressing the shear capacity of SFRC members without shear reinforcement.
•The presented model considers the effect of steel fibers on all shear-carrying mechanisms in SFRC beams failing in shear.•The model performs satisfactorily when compared to a database of SFRC beams ...failing in shear.•The model does not contain any new empirical elements and is fully based on theory.•The paper identifies ways forward to improve this model based on targeted experiments.
One of the barriers to implementation of steel fiber reinforced concrete (SFRC) into structural applications is the lack of understanding of the shear behaviour of SFRC members. This paper proposes a theoretical model for the shear capacity of SFRC members with mild steel reinforcement based on the shear-carrying mechanisms and sectional analysis. The model is derived completely theoretically, based on concepts from the literature, and does not include new empirical aspects. The approach is then compared to 323 experiments from the literature of beams with slender, rectangular cross-sections failing in shear. It is found that the model is slightly conservative, and experimental research necessary to further develop the model is described. The presented theory aims to be a framework for a fully theoretical description of the shear capacity of SFRC members with longitudinal reinforcement and without shear reinforcement.
Greenhouse gas emissions and environmental impacts of petroleum-based fuels and materials have necessitated the development of renewable resource-based alternatives. In the process to extract ...cellulose for converting it to bioethanol (bio-based gasoline) large quantities of lignin are produced as the main byproduct-making it useful for further processing application for sustainable materials. Lignin is the second abundant source of renewable carbon with an aromatic structure which makes it a potential candidate for carbon fiber production. Since lignin can be dissolved in a variety of organic and non-organic solvents, electrospinning has been used to produce precursor fibers for carbon nanofiber production. These carbon nanofibers have been tested as a potentially sustainable alternative for the current non-renewable electrodes in energy storage and conversion devices such as supercapacitors. Using lignin by-products from the fuel energy sector in making devices for electrical energy sector provides a great opportunity for promoting a circular economy from sustainable materials while also contributing to researching alternative sustainable materials in light of a global pandemic. This review presents a summary of the processing conditions for electrospinning different varieties of lignin, characterization of the electrospun fibers and the carbonization conditions for converting fibers. Different techniques that of the structural properties of the precursor fibers, characteristics of carbon nanofibers and their performance in energy storage devices are discussed. Compared to the other published reviews in this field, this review aims to present the current knowledge on material-processing-lignin-carbon fibers properties relationship.
To utilize both ferronickel slag and its sensible heat, the melting and viscosity-temperature behaviors of the B2O3 modified slags were studied first. Results show that the initial melting ...temperature reduces from 1612 K (1339 °C) to 1534 K (1261 °C), and the complete melting temperatures decreases from 1744 K (1471 °C) to 1696 K (1423 °C) with the increase of B2O3 from 3 to 9 wt%. However, the temperature span of the viscosity ranging in 0.5–2.5 Pa s increases from 10 K (°C) to 39 K (°C) with increasing B2O3. Then, the characterizations of the slag fibers prepared by the modified slags suggest that the addition of B2O3 decreases the mean diameter of the slag fibers from 5.6 ± 0.45 μm to 3.4 ± 0.27 μm, whereas increases their tensile strength from 1724 ± 80 MPa to 2114 ± 136 MPa. Moreover, both the glass transition temperature (Tg) and crystallization temperature (Tc) are delayed by the addition of B2O3 since boron works as network former in the slag melt structure.
Cotton breeding in Bulgaria is mainly aimed at improving the earliness, productivity and fiber quality of modern varieties. The creation of new genetic diversity is one of the basic prerequisites for ...the success of breeding programs. The aim of the study was to evaluate cotton lines obtained by intraspecific and remote hybridization combined with backcross technology, with a view to their most effective usage in selection. Twenty-three lines were included in competitive variety trials conducted during the 2014-2017 period. The averaged results showed that lines 550, 639, 641, obtained by remote hybridization, appeared to be very promising. These three lines were distinguished by the best combination of productivity, fiber length and fiber lint percentage, and by these three indicators they exceeded the standard variety Chirpan-539. A new cotton variety Aida (No. 457) was approved, which in seed cotton yield and fiber yield, and technological fiber properties surpassed the standard varieties Chirpan-539 for earliness and productivity and Avangard-264 for fiber quality. The candidate variety 535 continued the state variety testing. Two new candidate cotton varieties No. 550 and No. 553 were released. In the state variety testing the three candidate varieties confirmed their qualities. The obtained lines, distinguished by one trait or by a complex of qualities, enriched the gene pool of Bulgarian cotton.
We present experimental and simulation results of the zero-dispersion shift in photonics crystal fibers infiltrated with water–ethanol mixture. The fiber based on the fused silica glass with a ...hexagonal lattice consists of seven rings of air-holes filled by liquid. We show that it is possible to shift the zero-dispersion wavelength by 35 ps/nm/km when changing the temperature by 60 °C, and by 42 ps/nm/km when changing the concentration of ethanol from 0 to 100%. The results also show that for the optical fiber filed with pure ethanol the flattened part of the dispersion shifts from anomalous to the normal regime at temperatures below −70 °C.
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