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Fibers, Volume 5, Issue 2 (June 2017)

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Research

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Open AccessArticle Preparation and Characterization of Polymeric-Hybrid PES/TiO2 Hollow Fiber Membranes for Potential Applications in Water Treatment
Fibers 2017, 5(2), 14; doi:10.3390/fib5020014
Received: 15 January 2017 / Revised: 21 March 2017 / Accepted: 29 March 2017 / Published: 4 April 2017
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Abstract
In this work, poly(ethersulfone) (PES) ultrafiltration (UF) hollow fibers (HF) were modified by introducing TiO2 nanoparticles (TiO2-NPs) in the polymeric dope, to endow them with photocatalytic properties. Different dope compositions and spinning conditions for producing “blank” PES UF fibers with
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In this work, poly(ethersulfone) (PES) ultrafiltration (UF) hollow fibers (HF) were modified by introducing TiO2 nanoparticles (TiO2-NPs) in the polymeric dope, to endow them with photocatalytic properties. Different dope compositions and spinning conditions for producing “blank” PES UF fibers with suitable properties were investigated. PEO–PPO–PEO (Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol, Pluronic® (Sigma-Aldrich, Milan, Italy) was finally selected as the additive and a suitable dope composition was identified. After the detection of an appropriate dope composition and the optimization of the spinning parameters, PES-TiO2 HF was produced. The optimized composition was employed for preparing the mixed matrix HF loaded with TiO2 NPs. The effect of different TiO2 NP (0.3–1 wt %) concentrations and bore fluid compositions on the fiber morphology and properties were explored. The morphology of the produced fibers was analyzed by Scanning Electron Microscopy (SEM). Fibers were further characterized by measuring: pore size diameters and thickness, porosity, and pure water permeability (PWP). The photocatalytic activity of the new membranes was also tested by UV light irradiation. The model “foulant” methylene blue (MB) was used in order to prove the efficiency of the novel UF membrane for dye photo-degradation. Full article
(This article belongs to the Special Issue Hollow Fiber Membrane)
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Open AccessArticle Luminescent Properties of Oxazine 170 Perchlorate Doped PMMA Fiber
Fibers 2017, 5(2), 15; doi:10.3390/fib5020015
Received: 3 February 2017 / Revised: 11 March 2017 / Accepted: 10 April 2017 / Published: 19 April 2017
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Abstract
The article presents fabrication and luminescent properties of poly(methyl methacrylate) (PMMA) fiber doped by Oxazine 170 perchlorate. The bright fluorescence of polymeric fiber (at molar fluorescent organic dye concentration 4.3 × 10−5) was characterized in terms of spectrum and signal attenuation
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The article presents fabrication and luminescent properties of poly(methyl methacrylate) (PMMA) fiber doped by Oxazine 170 perchlorate. The bright fluorescence of polymeric fiber (at molar fluorescent organic dye concentration 4.3 × 10−5) was characterized in terms of spectrum and signal attenuation vs. the fiber length. The significant changes in fluorescence spectrum (λmax red shift average slope 4.6 nm/cm and Full Width at Half Maximum (FWHM) increasing slope 6.7 nm/cm) have been noticed for the length of the fiber (0.02–0.08 m) which corresponds to a high overlapping region of absorption and emission spectra of used dye. The red shift of λmax (c.a. 80 nm) was presented in fabricated polymeric fiber at distance 0.85 m. The obtained characteristics can be used for luminescent properties optimization of fluorescent organic-dye-doped PMMA fiber. Full article
(This article belongs to the Special Issue Advances in Optical Fibers II)
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Open AccessArticle Investigation on Strengthening Approaches Adopted for Poorly Detailed RC Corbels
Fibers 2017, 5(2), 16; doi:10.3390/fib5020016
Received: 19 February 2017 / Revised: 10 April 2017 / Accepted: 21 April 2017 / Published: 1 May 2017
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Abstract
Poor detailing of the position of bearing pad over reinforced concrete (RC) corbel may lead to premature failure, which is undesired and structurally vulnerable. An appropriate retrofitting solution is necessary to ensure the functionality of such RC corbels. Considering the growing popularity of
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Poor detailing of the position of bearing pad over reinforced concrete (RC) corbel may lead to premature failure, which is undesired and structurally vulnerable. An appropriate retrofitting solution is necessary to ensure the functionality of such RC corbels. Considering the growing popularity of external carbon fiber-reinforced polymer (CFRP) in retrofitting, this research examines the effectiveness of an externally wrapped unidirectional CFRP sheet and compares its performance against traditional retrofitting methods. Moreover, it is intended to fulfill the lack of extensive research on external CFRP application for corbel strengthening. A total of eight medium-scale corbel specimens were tested on vertical load. Observed premature failure due to placing the bearing pad near the edge of corbel was verified and the effectiveness of the proposed structural strengthening solutions was studied. Experimental results show that although the loading capacity of the damaged corbel due to the poor detailing of bearing pad position could not be fully recovered, the external CFRP wrapping method demonstrated superior performance over RC jacketing and was able to prevent localized failure. Further study based on non-linear 3D finite element analysis (FEA) was carried out to identify the governing parameters of each retrofitting solution. Numerical studies suggested important parameters of various retrofitting alternatives for higher capacity assurance. Full article
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Open AccessArticle Exploration of Wave Development during Yarn Transverse Impact
Fibers 2017, 5(2), 17; doi:10.3390/fib5020017
Received: 5 December 2016 / Revised: 28 February 2017 / Accepted: 24 April 2017 / Published: 16 May 2017
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Abstract
Single yarns have been impacted in a transverse fashion so as to probe the characteristics of resulting wave development. Longitudinal wave speeds were tracked in efforts to directly measure the yarn tensile stiffness, resulting in a slight increase in the modulus of Kevlar
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Single yarns have been impacted in a transverse fashion so as to probe the characteristics of resulting wave development. Longitudinal wave speeds were tracked in efforts to directly measure the yarn tensile stiffness, resulting in a slight increase in the modulus of Kevlar® KM2 and Dyneema® SK76. Additionally, the load developed in AuTx® and Kevlar® KM2 yarns behind the longitudinal wave front has been recorded, providing additional verification for the Smith relations. Further effort to bolster the Smith equations has been successfully performed via tracking transverse wave speeds in AuTx® yarns over a range of impacting velocities. Additional emphasis has been placed at understanding the transverse wave development around the yarn critical velocity, demonstrating that there is a velocity zone where partial yarn failure is detected. Above the critical velocity, measurement of early time transverse wave speeds also agrees with the Smith solution, though the wave speed quickly reduces in value due to the drop in tensile stresses resulting from filament rupture. Finally, the Smith equations have been simplified and are compared to the Cunniff equation, which bear a striking resemblance. Due to such a resemblance, it is suggested that yarn critical velocity experiments can be performed on trial yarn material, and the effect of modifying yarn mechanical properties is discussed. Full article
(This article belongs to the Special Issue Polymer Fibers)
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Open AccessArticle Experimental and Analytical Modeling of GFRP Strengthened Grouted Mortarless Masonry Prisms
Fibers 2017, 5(2), 18; doi:10.3390/fib5020018
Received: 16 February 2017 / Revised: 8 May 2017 / Accepted: 10 May 2017 / Published: 12 May 2017
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Abstract
The compressive performance of grouted mortarless masonry prisms strengthened with glass fiber-reinforced polymer (GFRP) composites was investigated in this study. A total of 18 grouted mortarless masonry specimens, i.e., nine strengthened with GFRP (called G-GMM) and nine without GFRP (called GMM), were tested
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The compressive performance of grouted mortarless masonry prisms strengthened with glass fiber-reinforced polymer (GFRP) composites was investigated in this study. A total of 18 grouted mortarless masonry specimens, i.e., nine strengthened with GFRP (called G-GMM) and nine without GFRP (called GMM), were tested under uniaxial compression. The effect of grout strength on the compressive strength of the prisms was discussed. Moreover, the effect of GFRP on the cracking load, modulus of elasticity, ultimate bearing capacity, failure modes, compressive stress–strain behavior, and deformation behavior of the specimens was analyzed. The test results indicated that GFRP strengthening increased the ratio of initial cracking load and ultimate load bearing capacity of mortarless masonry to a great extent, i.e., the ratio is 50–80% for G-GMM and 40–65% for GMM. In addition, GFRP clearly improved the deformation capability of the GMM. The tested experimental data were in good agreement with the predicted values using classic expressions. Full article
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Open AccessArticle Fourier-Transform Imaging of Cotton and Botanical and Field Trash Mixtures
Fibers 2017, 5(2), 20; doi:10.3390/fib5020020
Received: 27 September 2016 / Revised: 8 May 2017 / Accepted: 18 May 2017 / Published: 23 May 2017
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Abstract
Botanical and field cotton trash comingled with Upland cotton lint can greatly reduce the marketability and quality of cotton. Trash found comingled with cotton lint during harvesting, ginning, and processing is of interest to the textile community. In the current study attenuated total
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Botanical and field cotton trash comingled with Upland cotton lint can greatly reduce the marketability and quality of cotton. Trash found comingled with cotton lint during harvesting, ginning, and processing is of interest to the textile community. In the current study attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopic imaging was employed as an analytical technique to analyze cotton trash. Some benefits of this technique were its non-destructive nature and lack of required sample preparation. The technique used in this study, specifically ATR-FTIR spectroscopic chemical imaging, allows for three-dimensional spectral and spatial data to be obtained. In the current study, cotton in mixtures with botanical and field trash types have been identified spectrally and spatially using ATR-FTIR imaging. Botanical trash types (trash derived from the cotton plant) were evaluated and identified independently from cotton, even though both contained cellulose. The field trash types were easily identified from cotton due to their differences in chemical composition. This study can complement current cotton qualitative studies by adding spectral and spatial information to sample analysis. Full article
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Open AccessArticle Compact Narrow Linewidth Actively Q-Switched Er–Yb Double-Clad Fiber Laser
Fibers 2017, 5(2), 21; doi:10.3390/fib5020021
Received: 30 March 2017 / Revised: 13 May 2017 / Accepted: 29 May 2017 / Published: 3 June 2017
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Abstract
Actively Q-switched laser operation of a narrow linewidth compact fiber laser based on an Er–Yb double-clad fiber is presented. The laser linewidth as a function of the repetition rate and the Q-switched pulses characteristics for different pump powers are experimentally analyzed. Stable Q-switched
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Actively Q-switched laser operation of a narrow linewidth compact fiber laser based on an Er–Yb double-clad fiber is presented. The laser linewidth as a function of the repetition rate and the Q-switched pulses characteristics for different pump powers are experimentally analyzed. Stable Q-switched laser operation with spectral laser linewidth of 73 pm in a repetition rate range from 90 to 270 kHz is obtained. The minimum pulse duration of 178 ns, maximum peak power of 30.5 W, and maximum pulse energy of 5.4 µJ are observed. The maximum average power reached is 1.1 W. Full article
(This article belongs to the Special Issue Advances in Optical Fibers II)
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Open AccessArticle Effect of Calcination Temperature on NO–CO Decomposition by Pd Catalyst Nanoparticles Supported on Alumina Nanofibers
Fibers 2017, 5(2), 22; doi:10.3390/fib5020022
Received: 28 April 2017 / Revised: 25 May 2017 / Accepted: 6 June 2017 / Published: 8 June 2017
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Abstract
In this work, palladium (Pd) nanoparticles were blended into a solution of a sacrificial polymer and an aluminum sol gel precursor to form alumina fibers containing the palladium particles. The polymer solution was electrospun into template submicron fibers. These fibers were calcined at
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In this work, palladium (Pd) nanoparticles were blended into a solution of a sacrificial polymer and an aluminum sol gel precursor to form alumina fibers containing the palladium particles. The polymer solution was electrospun into template submicron fibers. These fibers were calcined at temperatures between 650 °C and 1150 °C to remove the polymer and oxidize the aluminum. The internal crystalline morphologies of the calcined fibers transformed with change in the calcination temperature. The calcined fibers were formed into fibrous mats and further tested for their catalytic performances. The Pd particles had a size ranging from 5–20 nm and appeared randomly distributed within and near the surfaces of the alumina fibers. The final metal loading of all Pd/Al2O3 samples ranged from 4.7 wt % to 5.1 wt %. As calcination temperature increased the alumina crystal structure changed from amorphous at 650 °C to alpha crystal structure at 1150 °C. With the increase of calcination temperature, the average fiber diameters and specific surface areas decreased. The catalyst supported fiber media had good conversion of NO and CO gases. Higher calcination temperatures led to higher reaction temperatures from 250 to about 450 °C for total conversion, indicating the effective reactivity of the fiber-supported catalysts decreased with increase in calcination temperature. The fibers formed at the 650 °C calcination temperature had the highest reaction activity. Full article
(This article belongs to the Special Issue Nanofibers)
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Review

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Open AccessReview Advances in Mid-IR Fiber Lasers: Tellurite, Fluoride and Chalcogenide
Fibers 2017, 5(2), 23; doi:10.3390/fib5020023
Received: 28 March 2017 / Revised: 30 May 2017 / Accepted: 13 June 2017 / Published: 15 June 2017
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Abstract
A review on the recent progress in modeling and fabrication of medium infrared (Mid-IR) fiber lasers is reported. The main objective is to illustrate some recent examples of continuous wave optical sources at wavelengths longer than those commonly employed in telecom applications and
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A review on the recent progress in modeling and fabrication of medium infrared (Mid-IR) fiber lasers is reported. The main objective is to illustrate some recent examples of continuous wave optical sources at wavelengths longer than those commonly employed in telecom applications and allowing high beam quality. A small number of Mid-IR lasers, among the large variety of schemes, glasses, dopants and pumping schemes reported in literature, is selected on the basis of their slope efficiency and threshold pump power. In particular, tellurite, fluoride and chalcogenide fiber lasers are considered. More details are given with reference to the novel pumping schemes. Full article
(This article belongs to the Special Issue Advances in Optical Fibers II)
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