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Due to high cost and embodied energy of synthetic fibers, their use in engineered cementitious composites (ECCs) is a barrier against the practical applications of ECC. This study investigated the length effects of fibers obtained from polyethylene-based selvage, the edges of woven fabrics that are normally discarded, on fresh, fiber dispersion, and tensile properties of ECC. Three ECC mixtures were designed with selvage fibers with lengths of 5, 10, and 15 mm. Mini-slump and mechanical tests were performed, and fiber dispersion was evaluated. Test results showed that flowability increased as the length of selvage fibers decreased. On the other hand, compressive strength, tensile strength, and tensile strain capacity increased as the length of selvage fibers increased. It was observed that the length of selvage fibers had little influence on fiber dispersion. The tensile properties of F-5 mixture, showing minimum performance, were superior to those of recycled fiber-reinforced ECCs. [ABSTRACT FROM AUTHOR]

In this paper, the concept of a novel optical FM/PM demodulator which can be designed from low-cost passive optical components and can have peak-to-peak bandwidth in the GHz region has been described. The bandwidth can be increased by reducing the single mode fiber length incorporated in the design, which is followed by a corresponding fall in frequency sensitivity of the device. The bandwidth and frequency sensitivity can be traded-off keeping their product a constant. The crossover wavelength can be tuned by changing the length of the optical delay line and the length of the single mode fiber (SMF). The Figure of Merit (FOM) of the demodulator, defined as the bandwidth sensitivity product, has a value of π which is greater than that of a passive hybrid Tee microwave discriminator and those of Mach-Zehnder interferometer-based designs. Calculated third harmonic distortion (3HD) of the demodulated optical FM signal increases with the increase in FM index and with the increase in SMF length for a given modulation frequency. Typical 3HD for the device with SMF length of 1 cm is calculated to be −39.9 dB for FM index = 2 and a modulation frequency of 400 MHz. [ABSTRACT FROM AUTHOR]

Bamboo fiber is a natural fiber that is ecologically beneficial and one of the best materials to replace lignin fiber for roads, which is still difficult to utilize properly in asphalt mixtures owing to its poor adherence, dispersion, and hydrophilicity. Previous research has discovered that alkali treatment, as an effective treatment approach, may effectively lower the hydrophilicity of plant fibers and improve their compatibility with the matrix. As a result, it is vital to investigate the effect of alkali treatment on bamboo fibers used in asphalt mixtures. The composition and microstructure of bamboo fibers treated with alkali were investigated using SEM and FTIR methods, while the adhesion between the bamboo fiber and asphalt before and after alkali treatment was tested using the fiber pull-out test. In addition, the dispersion rate of bamboo fibers in asphalt mixture was determined by developing a connection equation using the Schellenberg binder drainage test. The performance of bamboo fiber asphalt mixtures was then evaluated using rutting tests, beam bending tests, immersion Marshall tests, freeze-thaw splitting tests, and cyclic fatigue testing. The results showed that the alkali treatment successfully eliminated impurities in the outer layer of the bamboo fibers and reduced their hydrophilicity, which enhanced the asphalt-bamboo fiber interactions as well as the asphalt mixture's water damage resistance, specifically manifested as the residual stability of ABM was enhanced by 7.8% and the splitting tensile strength of ABM was raised by 12.2%. Furthermore, the surface polarity of the bamboo fibers was reduced, which weakened the agglomeration phenomenon and increases the dispersion rate of bamboo fibers in the mixture by 9%, efficiently improving the low-temperature cracking resistance and fatigue performance of asphalt mixtures. [ABSTRACT FROM AUTHOR]

3D concrete printing (3DCP) presents unique challenges in optimizing rheological properties of concrete mixture, while tailoring the rheology of Engineered Cementitious Composites (ECC) for 3D printing (3DP-ECC) is more intricate due to the added complexity of fiber dispersion. This study proposes an innovative printability evaluation method specifically designed for 3DP-ECC, which takes into account the impact of fiber dispersion while also emphasizing cost-effectiveness and efficiency. Additionally, the proposed method enables the calculation of the printable open time, thus adjusting the mixing time of the ECC paste. The feasibility of the proposed method was verified through actual printing test and rheological test, and experimental results showed good agreement with theoretical results. The tensile performance of 3DP-ECC was also investigated, providing further validation for the proposed methodology.

In this work, a pulsating extensional stress induced melt mixer was developed. The compositions, structure, working principle, and melt mixing process of the device were introduced in detail. The mixer generated a full-process pulsating extension deformation effect on materials by the eccentric vane units and arc-shaped flow channels, which greatly promoted the dispersion and mixing of the materials. Polypropylene/carbon fibers (PP/CFs) composites were prepared by the new mixer, and the effects of different rotational speeds and mixing time on the properties of the composites were studied. The results showed that proper rotational speed and mixing time effectively promoted the dispersion of CFs in PP matrix, while the fibers still had long remaining lengths. As a result, the overall properties, especially the mechanical properties of the PP/CFs composites improved. When the CFs content was 30 wt.%, at the process parameters of 20 r/min and 2 min, compared with pure PP, the tensile strength (58.46 MPa) and modulus (1962 MPa) of the PP/CFs composite were increased by 78.6% and 263.3%, respectively. [ABSTRACT FROM AUTHOR]

Carbon fibres are widely recognised as reinforcement materials that effectively control cracks in concrete structures. Nonetheless, these fibres do not disperse uniformly inside the cement matrix, disrupting the mixture homogeneity. To address this concern, this study investigated two distinct mixing sequences of cement composites with carbon fibres. Two mixing sequences were investigated including the addition of fibres after cement (AC-CF) and the addition of fibres before cement (BC-CF). The surface topography of carbon fibres and the engineering properties of the cement paste were also examined. Consequently, carbon fibres in cement composite produced lower flowability due to the surface roughness. The AC-CF specimen demonstrated the highest hardened density at 28 days with 2679.22 kg/m3 followed by BC-CF and the control specimen with 2386.08 kg/m3 and 2278.36 kg/3, respectively. The AC-CF specimen also had the highest compressive strength at 28 days with 69.91 MPa, followed by BC-CF and the control specimen with 65.92 MPa and 63.20 MPa, respectively. Further, the flexural strength of the AC-CF specimen exhibited the highest strength with 10.86 MPa, followed by BC-CF and the control specimen with 9.35 MPa and 9.17, respectively. The fibre dispersion in AC-CF was also superior to BC-CF. Therefore, it can be concluded that the best mixing sequence is the addition of fibre after cement (AC-CF) because it had better fibre dispersion and engineering properties compared to the addition of fibre before cement (BC-CF). ABSTRAK: Gentian karbon lebih dikenali sebagai bahan bantuan yang berkesan dalam mengawal keretakan pada struktur konkrit. Walau bagaimanapun, gentian ini tidak tersebar secara seragam di dalam matrik simen dan akan mengganggu kehomogenan campuran. Bagi mengatasi masalah ini, kajian ini mengkaji tentang dua susunan campuran berbeza simen komposit dengan gentian karbon. Dua susunan campuran ini adalah melalui penambahan gentian selepas simen (AC-CF) dan penambahan gentian sebelum simen (BC-CF). Permukaan topografi gentian karbon dan sifat kejuruteraan pes simen turut diperiksa. Kajian mendapati bahawa gentian karbon dalam komposit simen mengurangkan kebolehaliran pes simen disebabkan oleh kekasaran pada permukaan gentian. Spesimen AC-CF menunjukkan ketumpatan pengerasan tertinggi pada hari ke-28 dengan 2679.22 kg/m3 diikuti spesimen BC-CF dan spesimen kawalan sebanyak 2386.08 kg/m3 dan 2278.36 kg/m3, masing-masing. Spesimen AC-CF juga mempunyai kekuatan mampatan tertinggi pada hari ke-28 dengan 69.91 MPa, diikuti oleh spesimen BC-CF dan spesimen kawalan sebanyak 65.92 MPa dan 63.20 MPa, masing-masing. Seterusnya, kekuatan lenturan spesimen AC-CF menunjukkan kekuatan tertinggi dengan 10.86 MPa, diikuti spesimen BC-CF and spesimen kawalan dengan 9.35 MPa dan 9.17 MPa, masing-masing. Penyebaran gentian dalam AC-CF juga lebih baik daripada BC-CF. Oleh itu, kajian ini merumuskan bahawa susunan campuran terbaik adalah dengan penambahan gentian selepas simen (AC-CF) kerana ia mempunyai kekuatan lenturan gentian terbaik dan sifat kejuruteraan berbanding penambahan gentian sebelum simen (BC-CF).

This paper focuses on studying the influences of thickener (hydroxypropyl methyl cellulose, HPMC) on ECC performance, with the adding dosages of 0%−0.1% by mass of the reference mix. The tensile properties (including the tensile strength, the tensile strain capacity, and the cracking characteristics) and the compressive strength were thoroughly evaluated. Particularly, the matrix toughness and the fiber-matrix bridging behaviors were further studied by a varies of so-called meso-scale experiments. Meanwhile, the fibers dispersions in the mixes with HPMC were analyzed. The results showed that, both the tensile strength and the tensile strain first increased and then decreased, with the largest values at the 0.05% HPMC (the strain value was up to 8%); while the compressive strength gradually declined according to the HPMC contents. After adding 0.05% HPMC, the crack numbers reached a stable level of around 100 with the average crack width of approximately 60 µm, and the dispersion coefficient of fibers tended to a higher level of around 0.35. The variation trends of the matrix fracture toughness and the maximum fiber bridging stress were almost agreement with that of the compressive strength and the tensile properties, respectively. Therefore, no more than 0.05% HPMC was recommended to be used into ECC (or 3D printing ECC).

Understanding the mechanics of fiber attrition during the extrusion process is highly important in predicting the strength of long fiber-reinforced thermoplastic composites. However, little work has been done to investigate the mechanics of fiber dispersion and its effects on fiber attrition. This study aims at investigating fiber dispersion in simple shear flows for long fiber-reinforced thermoplastic pellets. Depending on the fabrication process, fiber bundles display distinct levels of compaction within the pellets. Studies have shown that morphological differences can lead to differences in dispersion mechanics; therefore, using a Couette rheometer and a sliding plate rheometer, coated and pultruded pellets were subjected to simple shear deformation, and the amount of dispersion was quantified. Additionally, a new image-based analysis method is presented in this study to measure fiber dispersion for a multi-pellet-filled system. Results from the single-pellet dispersion study showed a small amount of correlation between the dimensionless morphological parameter and the dispersion measurement. Pultruded and coated pellets were both found to have similar dispersion rates in a multi-pellet system. However, pultruded pellets were found to have a higher dispersion value at all levels when compared with coated pellets in both dispersion studies. [ABSTRACT FROM AUTHOR]

Recycled carbon fiber, as a novel form of regenerated fiber, exhibits exceptional properties such as high strength, high modulus, excellent electrical conductivity, and corrosion resistance. Consequently, it has garnered significant attention in recent years, owing to its potential to confer unique intelligent characteristics to cement-based materials. However, the dispersion of recycled carbon fiber remains an inevitable concern. Building upon existing research, this paper meticulously categorizes different types of recycled carbon fiber based on their mechanical properties and surface characteristics, while also exploring the impact of additives on fiber dispersion. Furthermore, a thorough evaluation of fiber dispersion methods is provided, considering the dimensions of stability, uniformity, and morphology at various stages, including fiber suspension, fresh mixture, and hardened matrix. Additionally, this paper offers a comprehensive summary and comparison of fiber dispersion methods, taking into account fiber pretreatment and preparation processes. Extensive literature reviews unequivocally support the notion that achieving a uniform dispersion of recycled carbon fiber serves as a fundamental requirement for enhancing and optimizing the properties of composites. Consequently, the utilization of dispersion and evaluation methods based on carbon fiber enables the exploration of appropriate dispersion methods tailored to different types of recycled carbon fiber in cement-based materials.

We demonstrate the damage-free delivery of nearly diffraction-limited picosecond laser pulses at 1064 nm with a maximum peak power of 3.5 MW in a 5 m air-filled anti-resonant hollow-core fiber (AR-HCF). In the air-filled AR-HCF, the transmission efficiency of picosecond pulses is degraded due to stimulated Raman scattering for the incident peak power above 3.59 MW. The temporal compression of pulses is also observed in the air-filled AR-HCF, where the self-phase modulation plays a key role in the anomalous dispersion region. By vacuuming the air in the core, a nearly constant coupling efficiency of 77% is achieved through the 5 m AR-HCF free of nonlinear effects, with M2 of the output beam less than 1.17. [ABSTRACT FROM AUTHOR]

Analog-to-digital converter (ADC) is indispensable components in modern information systems, and photonic technologies have emerged as promising avenues for overcoming bottlenecks in ADC performance. This paper introduces a novel approach: a photonic sampled ADC integrated with a neural network that combines Convolutional Neural Networks (CNNs) and Transformers for data recovery. The proposed system utilizes a multi-wavelength optical sampling pulse train interleaved in the time domain through fiber dispersion. Sampled signals are quantified in parallel channels by electronic ADC (EADC). Through supervised training, the hybrid deep neural network extracts both local and global features of photonic system defects, enabling the recovery of distorted data. Experimental validation showcases the effectiveness of this architecture, achieving successful reconstruction of radio frequency (RF) signals at a sampling rate of 12 Giga-samples per second (Gs/s) with an effective number of bits (ENOB) of 7.13. The results underscore the potential of the proposed architecture in achieving high conversion accuracy in multi-channel photonic sampled ADCs. • The accuracy of multi-channel photonic sampled ADC is limited by nonlinearity errors and mismatch errors. • Neural networks contribute to the mitigation of errors. • The hybrid networks perform better when facing complex input analog signals. • The proposed architecture showcases potential for high conversion accuracy with improvements in SINAD and ENOB. [ABSTRACT FROM AUTHOR]

Quartz fiber has good high-temperature resistance, but the poor dispersion of quartz fiber in water limits the application of quartz paper in thermal insulation materials. As a technique that can solve the problem of fiber flocculation, foam forming provides a new approach to the formation of quartz fibers. This paper investigated the influence of fiber characteristics on foam properties and the dispersing effect of different foam systems on quartz fiber. Eventually, we constructed an evaluation model for the evenness of foam-formed quartz paper, and the foam forming mechanisms of quartz fibers were analyzed. The results show that quartz fiber with a hydrophobic surface has a stronger ability to refine the bubble sizes, and the half-life time of the foam system generally increases as the bubble size becomes smaller. The dodecyl dimethyl amine oxide (OB-2) foam system is the most suitable one for the foam forming of quartz fiber. When the forming concentration reaches 1.6%, the formation index of the quartz paper (fiber length 6 mm) is less than 150. It is found that with fiber length increasing to 48 mm, quartz paper (forming a concentration of 0.6%) still has excellent uniformity. Under the suitable turbulence effect of aqueous foam and the physical barrier effect of bubbles, the foam-formed quartz paper has a good formation. [ABSTRACT FROM AUTHOR]

No doubt, composite technology is fast growing with an increase in research efforts around the world and with many academic interests consisting of breath-taking innovations in polymer science. Herein, the primary determinants of fiber/filler-matrix/composite properties are discussed viz-a-viz dispersion of reinforcing fibers, interfacial adhesion between matrix/fibers, and surface treatment methods for fibers in composite fabrication. Both thermoplastic and thermoset composites are discussed with much-focused discussion on the biodegradable and environmentally friendly PLA polymer matrix adhesion with filler/fibers. Since achieving enhanced mechanical properties of both thermoset and thermoplastic matrices involves reinforcement with both micro and nanofiller and, in many cases, with natural fibers, addressing the major issue of compatibilising the hydrophilic fiber with the hydrophobic polymer becomes more imperative. Beginning the discussion with a brief on adhesion and its mechanisms with polymer/matrix interaction, it further looked at key surface modification techniques with organic acids to promote dispersion in organic solvents and hydrophobic polymers to enhance interfacial adhesion. The last section offered recommendations with regards to 100% green composite system, with the possibility of achieving fiber/matrix compatibility with zero chemical consumption and fabrication of new materials whose properties are compatible without coupling and surface treatment of reinforcing fibers. [ABSTRACT FROM AUTHOR]

The present study was conducted to investigate the tensile strength characteristics of polypropylene (PP) fiber reinforced soil with different fiber dispersion, content and aspect ratio. In order to investigate this, the experimental programme was comprised by the test with a wide range of fiber content (0.35%, 0.60%, 0.85%), fiber aspect ratio (150, 225, 350), and mix patterns (discrete or random distribution). The results indicated that increases in fiber content caused an increment in the tensile strength whether discrete or random distribution. The increasing extent of tensile strength was different with increase of fiber aspect ratio under different fiber mix patterns. From experimental data, a genetic programming (GP) model was proposed for analyzing tensile strength contrast of the two mix patterns. In addition, the sensitive analysis of three inputs showed that aspect ratio has the greatest influence on the forecasting model. The effectiveness of the GP model was validated by the test results, and the robust model developed would provide a theoretical support for roadbase designing and construction which were reinforced with PP fibers.

Fiber dispersion was one of the crucial factors, which influenced the mechanical properties of fiber reinforced metal matrix composites (FR-MMCs). The incomprehension of fiber dispersion mechanisms and the lack of control methods limited the developments and further applications of the 3D printed FR-MMCs. In this work, the tensile properties and microstructures of continuous carbon fiber reinforced SnPb matrix composites, which were fabricated by the double-layer printing head 3D printing process (DPP), were measured and observed. The dual mechanisms of capillarity pressure driving and nonuniform interface reaction driving in fiber dispersion were proposed. Besides, the dynamic of fiber dispersion was discussed. It was found that improving wicking performance could increase the dispersion of fibers. This research filled in the blank of fiber dispersion mechanisms of 3D printed FR-MMCs, and provided the methodological supports for further improving the performances of composites.

It is critical to understand the interaction mechanism of fiber-bubble before the foam-forming technique is used to disperse the long fiber and tailor the material microporous structure. Herein, the adhesion behavior of ionic and nonionic surfactants with different concentrations on five fibers was investigated, and the effect of electrostatic force and adhesion driving force on the interaction between fibers and bubbles was analyzed. In addition, the fiber dispersion mechanisms and the response mechanism of the fiber orientation and tensile strength of foam-formed paper on the interaction strength between fiber and bubble were clarified. The results show that the adhesion ability between hydrophobic fibers with weak surface polarity and cationic and amphoteric surfactants is more obvious. Though electrostatic repulsion weakens the interaction strength of fibers with anionic surfactants, the adhesion ability can exist when the adhesion driving force is larger than 6.6 mN/m. Furthermore, the bridge effect between ethoxylated surfactant headgroups with the acylamino on the aramid fiber surface also propels the adhesion behavior of bubble-fiber. The fiber dispersion mechanisms were proposed based on the adhesion effect of the fiber-bubble, electrostatic elimination, and high-viscosity (≥95 mPa∙s) properties of the "foam-fiber" slurry. Eventually, under the gradually decreased interaction strength between fibers and bubbles, the fiber orientation in the Z direction of foam-formed NBSKP fiber paper turned from −20°-20° to −60°-40°, and the tensile strength decreased from 693 KPa to 537 KPa. This work has implications for improving the long fiber dispersion and regulating the structure of foam-formed fiber composites. [Display omitted] • The interaction between fibers and bubbles was elucidated. • Adhesion existence when the adhesion driving force is larger than 6.6 mN/m. • Interaction strength is a key parameter affecting fiber dispersion. • Electrostatic elimination and high viscosity are key fiber dispersion mechanisms. • Interaction strength can be used to regulate fiber orientation and paper strength. [ABSTRACT FROM AUTHOR]

Many soft tissue materials consist of an isotropic ground matrix which is reinforced by fibers that are dispersed about a mean orientation. In this work, we attempt to examine how fiber dispersion affects the mechanical response of a base Neo-Hookean material subjected to a few simple deformations. We find that the composite which consists of a highly dispersed fiber assembly exhibits large resistance to compressive loads along the mean fiber direction. It is an established fact that for a unidirectionally reinforced base material, fiber compression leads to material instability and loss of ellipticity of governing equations primarily due to fiber kinking. We observe that reinforcement by means of dispersed fibers improves material stability against kinking in planar deformations. We present results for two particular fiber strain energy densities, namely, the standard reinforcing model and the exponential model and employ the rotationally symmetric von-Mises distribution function to incorporate fiber dispersion. It is expected that the results qualitatively depict the general response of a Neo-Hookean solid that is reinforced by fibers with a convex strain energy function and which are dispersed with rotational symmetry about a preferred direction. [ABSTRACT FROM AUTHOR]

Fiber-feedback optical parametric oscillators (OPOs) incorporate intracavity fibers to provide a compact high-energy wavelength-tunable laser platform; however, dispersive effects can limit operation to the sub-picosecond regime. In this research article, we modeled pulse propagation through systems of cascaded fibers, incorporating SMF-28 and ultra-high numerical aperture (UHNA) fibers with complementary second-order dispersion coefficients. We found that the pulse duration upon exiting the fiber system is dominated by uncompensated third-order effects, with UHNA7 presenting the best opportunity to realise a cascaded-fiber-feedback OPO.

In this work we experimentally demonstrate the compensation of nonlinearities introduced by a semiconductor optical amplifier (SOA) operating as a power booster in a field-modulated direct detection fiber-optic system transmitter. We show that a combination of digital pre-compensation to deal with SOA nonlinearities, and digital post-compensation after Kramers-Kronig receiver for mitigating the impacts of chromatic dispersion and signal-signal beat interference (SSBI) is an effective scheme to gain ∼3dB in ROSNR in presence of SOA nonlinearity at 3dB of gain compression.

Skin tissue is a complex heterogeneous material abundant with fibers. Various models capturing its anisotropy, nonlinearity, and viscoelasticity have been developed. However, the existence of multiple fiber families and their differences have been largely ignored. Furthermore, inhomogeneous deformation over the thickness is observed in the skin under shear deformation, which the traditional skin models do not predict. In this paper, we propose that two fiber families with distinct mechanical and structural properties exist in the skin within the framework of a general structure tensor-based constitutive strain energy model. Our constitutive model considers fiber families' distinct properties and the consequent inhomogeneous deformation in the skin, showing good agreement with in vivo measurements of human face skin. [ABSTRACT FROM AUTHOR]

Limestone calcined clay cement (LC3) is successfully used to fabricate engineered cementitious composites (ECC) exhibiting tensile strength σtu of 9.55 ± 0.59 MPa or tensile strain capacity εtu of 8.53 ± 0.30%. The high tensile strength of the composites is closely related to the improvement of fiber/matrix interfacial bond strength, and the high ductility is attributed to the enhancement of fiber dispersion homogeneity. For the case of ECC incorporating 50% LC3, the reduction of initial cracking stress σtc that favors the growth of the crack in a controlled manner also contributes to the improvement of strain hardening behavior. The composition analysis indicates that carboaluminates and additional hydration products including C-(A)-S-H and ettringite are generated, which contributes to the densification of the microstructure of the ECC matrix. The pore structure is thus remarkably refined. Besides, when ordinary Portland cement (OPC) is partly replaced by LC3, the consumed energy and equivalent CO2 emission decrease, especially the equivalent CO2 emission with the reduction ratio attaining 40.31%. It is found that ECC using 35% LC3 exhibits the highest mechanical resistance and ECC incorporating 50% LC3 shows the highest ductility from the environmental point of view. [ABSTRACT FROM AUTHOR]

Cracking is one of the most common distresses in asphalt pavement. Because asphalt concrete is relatively weak in tension, synthetic fibers have shown to increase its tensile strength and, therefore, reduce the chance of cracking. An approach was used in this study with the aim of evaluating the interaction between fibers and asphalt mastic and the fiber distribution in asphalt concrete. Three types of aramid fibers and two types of nylon fibers were used. A pullout test was used to determine the typical shear bond strength between fibers and the asphalt mastic. The bond strength obtained from the pullout test was then used to calculate the minimum fiber embedded length on each side of the crack in order for the fiber to reach its full capacity before being pulled out. Of course, increasing fiber length increases the chance of bridging cracks considering the random distribution of fibers in fiber-reinforced asphalt concrete (FRAC) and the random orientation of fibers relative to cracks. On the other hand, increasing fiber length may result in uneven distribution of fibers in the FRAC. Fiber extraction and recovery tests were then used to determine the dispersion of aramid fibers in the FRAC with different fiber lengths. The study showed that aramid fibers in the order of 20 mm would provide a good bond with the asphalt mastic and result in reasonable dispersion in the FRAC. The uniaxial fatigue test and flow number test were also performed on FRAC with different aramid fiber lengths. The 19-mm fibers also showed better performance test results than the 10- and 38-mm fibers. A similar length is recommended for the Nylon 1 fibers based on the bond properties only. Longer Nylon 2 fibers are recommended, but caution needs to be taken to avoid uneven fiber dispersion in the FRAC. [ABSTRACT FROM AUTHOR]

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Fiber-reinforced asphalt concrete (FRAC) was tested using limestone, PG 64-22 binder, and 20% reclaimed asphalt pavement (RAP). After mixing fibers with different lengths and dosages, they were extracted and recovered to evaluate their dispersion in the FRAC. The uniaxial fatigue test, IDEAL CT test, and flow number test were performed on FRAC with different fiber lengths and asphalt contents. The balanced mix design (BMD) approach was then used to analyze the uniaxial and flow number test results in order to evaluate the effect of aramid fibers on fatigue and rutting resistance of the pavement. The dispersion test showed that the 19 mm and 10 mm aramid fibers at a dosage rate of 0.5 g/kg provided the best dispersion. The 19 mm fibers showed better performance test results than the 10 mm and 38 mm fibers. The BMD approach provided ranges of asphalt contents to produce mixes with certain resistances to fatigue and rutting. The BMD approach also demonstrated the effect of fibers with different lengths on increasing the resistance to fatigue and rutting. The study concluded that the 19 mm fibers with a dosage of 0.5 g/kg produce best results. The BMD approach is a good tool that can be used to refine the mix ingredients, including additives such as fibers, in order to optimize pavement resistance to various distresses such as fatigue cracking and rutting. [ABSTRACT FROM AUTHOR]

The traditional theoretical model is not suitable for the simulation of the oil particle filtration process of a composite filter due to its huge difference in fiber diameter. In this paper, the concept of fiber dispersion σ was introduced into a mathematical model for describing the dynamic filtration process of a composite filter. The results show that the model is in good agreement with the experimental data. As the packing density is constant, the higher the fiber dispersion, the better performance is. In addition, the effect of different factors on the efficiency of different mechanisms was discussed. For fine particles (1 μm), the inertia impaction mechanism dominates the filtration efficiency. The fiber diameter has a significant effect on the inertia impaction mechanism. The single-fiber efficiency by inertia impaction mechanism is obviously affected by filtration velocity. The packing density has an effect on all mechanisms except for the diffusion mechanism. Moreover, such a model would contribute to an accurate prediction of the dynamic filtration performance of composite filters with polydisperse fiber diameter and improve performance by adjusting parameters reasonably.

We demonstrate the damage-free delivery of nearly diffraction-limited picosecond laser pulses at 1064 nm with a maximum peak power of 3.5 MW in a 5 m air-filled anti-resonant hollow-core fiber (AR-HCF). In the air-filled AR-HCF, the transmission efficiency of picosecond pulses is degraded due to stimulated Raman scattering for the incident peak power above 3.59 MW. The temporal compression of pulses is also observed in the air-filled AR-HCF, where the self-phase modulation plays a key role in the anomalous dispersion region. By vacuuming the air in the core, a nearly constant coupling efficiency of 77% is achieved through the 5 m AR-HCF free of nonlinear effects, with M2 of the output beam less than 1.17.

A diffusion tensor imaging (DTI) -based statistical micromechanical model was developed to study the effect of axonal fiber architecture on the inter- and intra-regional mechanical heterogeneity of the white matter. Three characteristic regions within the white matter, i.e., corpus callosum, brain stem, and corona radiata, were studied considering the previous observations of locations of diffuse axonal injury. The embedded element technique was used to create a fiber-reinforced model, where the fiber was characterized by a Holzapfel hyperelastic material model with variable dispersion of axonal orientations. A relationship between the fractional anisotropy and the dispersion parameter of the hyperelastic model was used to introduce the statistical DTI data into the representative volume element. The FA-informed statistical micromechanical models of three characteristic regions of white matter were developed by deriving the corresponding probabilistic measures of FA variations. Comparison of the model predictions and experimental data indicated a good agreement, suggesting that the model could reasonably capture the inter-regional heterogeneity of white matter. Moreover, the standard deviations of experimental results correlated well with the model predictions, suggesting that the model could capture the intra-regional mechanical heterogeneity for different regions of white matter. [ABSTRACT FROM AUTHOR]

In this work we experimentally demonstrate the compensation of nonlinearities introduced by a semiconductor optical amplifier (SOA) operating as a power booster in a field-modulated direct detection fiber-optic system transmitter. We show that a combination of digital pre-compensation to deal with SOA nonlinearities, and digital post-compensation after Kramers-Kronig receiver for mitigating the impacts of chromatic dispersion and signal-signal beat interference (SSBI) is an effective scheme to gain ∼3dB in ROSNR in presence of SOA nonlinearity at 3dB of gain compression. [ABSTRACT FROM AUTHOR]

The use of fibers as additives to increase the strength of investment casting shell has yielded some significant results. Here, polypropylene fiber of length 6 mm was added to the shell by airflow placement fiber method, and the three different processes [the conventional method, preimmersion silica sol method, and preimmersion slurry method (PSM)] were used to prepare fiber-reinforced shell based on better fiber dispersion; the strength of shell with 0.2–1.0 wt% fiber addition was tested and compared. The experimental results show that the green strength and fired strength of shell with 0.4–0.6 wt% fiber addition reached the maximum in the three processes. The shell prepared by PSM exhibited a higher strength than the other two methods with the same amount of fiber addition; the maximum green strength was 36.9% higher than the strength of fiber-free shell. Combined with the surface morphology of placement fiber and fracture surface morphology of shell, the factors affecting shell strength and interface bonding characteristics were analyzed. [ABSTRACT FROM AUTHOR]

Single-mode VCSEL technology has advanced significantly in the past few years. The advantages of single-mode VCSELs lie primarily on the narrower linewidth, lower numerical aperture, and smaller spot size compared to multimode VCSELs. They are suitable for transmitting over both multimode fibers and few-mode fibers. For multimode fiber systems, the narrow linewidth can reduce the chromatic dispersion penalty and increase the system reach. A single-mode VCSEL also allows the coupling into graded-index single-mode fiber, which is few-mode around 850 nm with high bandwidth, for few-mode transmission. We review recent progress and present new experimental results and modeling analyses of single-mode VCSEL transmission over both types of fibers. The experiments and analyses shed new light on how single-mode VCSELs can be used with multimode fibers and graded-index single-mode fibers and relative merits between 850 nm single-mode VCSELs versus 980 nm and 1060 nm single-mode VCSELs to address the needs of various applications. [ABSTRACT FROM AUTHOR]

Nowadays, glass fiber (GF) reinforced polyamide 66 (PA66) composites have attracted strong interests in commercial and engineering applications due to many advantages, such as corrosion resistance, high potential of integration, self‐lubricating, and high toughness. However, it is very difficult for traditional plastic molding equipment to concurrently obtain the increase of fiber retention length and the improvement of fiber dispersion during the PA66/GF composites manufacturing, which greatly limit the widespread application of such composites. An innovative twin eccentric rotor volume pulsating plasticizing transportation equipment (TERE) based on series explosion effects, is applied to prepare PA66/GF composites at different rotor speeds and fiber loadings. Inside the PA66/GF30 composite prepared by TERE, the fibers are evenly dispersed in polymer matrix and the average fiber length increases by 3.2 times when compared to that of twin‐screw plasticizing transportation equipment (TSE). The Charpy impact strength of PA66/GF composites prepared by TERE is nearly twice that of TSE at all fiber contents. The fatigue properties, thermal oxygen aging properties, and creep properties of the TERE composites exhibit better effects than the TSE composites, indicating that the TERE can ensure longer fiber length and better dispersion effect simultaneously. [ABSTRACT FROM AUTHOR]

A novel photonic microwave and millimeter-wave (mm-wave) mixer with simultaneous third-order intermodulation distortion (IMD3) suppression and dispersion-induced power fading compensation is proposed and experimentally demonstrated. In our proposed scheme, a dual-polarization quadrature phase shift-keying (DP-QPSK) modulator is used to modulate RF/IF and LO signals. The bias voltages of the main modulators are adjusted to compensate dispersion-induced power fading. When the polarization state of the modulated signal and the attenuation of the RF signal are properly adjusted, IMD3 distortion can be suppressed. In the experiment, relatively flat microwave and mm-wave signals from 11 to 35 GHz are obtained through 4- and 50-km fiber transmission, while the measured spurious free dynamic range (SFDR) is $112.9~{\mathrm {dB}} \cdot \text{Hz} ^{4/5}$. In addition, an up-converted 16 quadrature amplitude modulation (16 QAM) vector signal with a carrier frequency of 19.3 GHz is obtained and the measured constellation diagrams and error vector magnitudes are given after transmission over different fiber lengths (back to back, 4 and 50 km). [ABSTRACT FROM AUTHOR]

As a type of high performance inorganic fiber, basalt fiber exhibits excellent strength properties? high/low temperature resistance and chemical stability，which can be widely used in the field of construction and building materials, heat insulation and filtration. However,the poor dispersibility and paper strength of paper made of basalt fiber limit its ap­plication in paper industry. In this work，iltrafine basalt fiber was employed as material to in­vestigate the effect of pH of fiber suspension on fiber dispersion. In addition,the influence of the ratio of basalt fiber and unbleached electric insulation pulp on paper properties was also investigated. Results showed that the optimal fiber dispersion can be obtained when fiber suspension pH was 4. 38. And paper physical testing showed that the apparent density, tensile index and breakdown strength of basalt fiber/cellulosic fiber composite paper decreased with increasing basaltfibercontent.Whenbasaltfibercontentwaslower than 50 % ,the tensile strength of paper can satisfy the requirement of manufacturing. Therefore, the addition a­mount of basalt fiber depends on the requirement of paper properties and its application. [ABSTRACT FROM AUTHOR]

In this work, a new composite for microwave absorption applications, especially for anechoic chambers, is studied. We propose to substitute carbon black loaded polyurethane foam, currently used in commercial absorbers, by epoxy foam filled with carbon fibers. The purpose of the present paper is to study the influence of three dispersion methods (spatula, shear mixer and ultrasound probe) and four fiber lengths (1 mm, 3 mm, 6 mm and 12 mm) on the homogeneity and dielectric properties (permittivity ε′ and dielectric losses tanδ) of achieved composites. Long fibers dispersed with spatula have shown higher dielectric properties than short fibers. However, such a soft dispersion method was revealed to be inefficient to disperse properly the long fibers. Although a homogenous dispersion was obtained with the shear mixer (mechanical dispersion), we noticed an important degradation of the fibers which lead to a decrease of the dielectric properties. Dispersion with ultrasounds appears to be a good compromise between homogeneity and dielectric properties of composites. Finally, electromagnetic simulation predicted a high absorption performance for pyramidal absorber made with the 12 mm-carbon fibers loaded composite with reflection loss lower than − 50 dB for frequencies ranging between 8 GHz and 18 GHz. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA) fiber with high elastic modulus and toughness can act as a reinforcing material to improve the brittleness of cement-based materials. However, the difficulty of fiber dispersion in the matrix is correspondingly increased due to its bending and clustering. Poor fiber dispersion not only deteriorates the mechanical properties of PVA fiber-reinforced cementitious composites (PVA-FRCCs) but also increases the difficulty in determining the relationship between fiber dispersion and hardening properties. Rheology, as a vital method to supervise the mixture properties, can improve the fiber distribution and optimize the hardening performance. This paper investigated rheological performance, fiber dispersion, and strengths of three types of PVA-FRCCs and discussed the effect of different fiber factors on the materials properties. Results showed that the rheology of a mixture can affect fiber dispersion and uniform fiber dispersion can be achieved through the experimental design of PVA-FRCCs. Besides, the quantitative relationship between fiber distribution parameters and flexural strengths of PVA-FRCCs was proposed, which showed a superior reliability than the composites theory formula and other traditional fitting equations. However, the relationship between fiber dispersion and compressive strengths was hardly founded due to the deterioration in compressive strength caused by the addition of PVA fibers. [ABSTRACT FROM AUTHOR]

Photonic techniques have potential to overcome the limitations of electronic digital-to-analog conversion. A serial optical DAC, using fiber dispersion with optical weighted wavelength multiplexing, is proposed and demonstrated. Serial Digital codes are overlapped regularly in time domain due to dispersion-based delays. Intensity information for the conversion is extracted by synchronous gating pulse train. The system is operated with a high precision time control. Performance of the ODAC is experimentally investigated by establishing a 4-b 12.5 Gb/s system. The linear transfer function is described and an ENOB of 3.55 is obtained. The proposed architecture could be easily modified for better performance.

This paper investigates on the relationship between the arrangement of collagen fibers within soft tissues and parameters of constitutive models. Starting from numerical experiments based on biaxial loading conditions, the study addresses both the direct (from structure to mechanics) and the inverse (from mechanics to structure) problems, solved introducing optimization problems for model calibration and regression analysis. A campaign of parametric analyses is conducted in order to consider fibers distributions with different main orientation and angular dispersion. Different anisotropic constitutive models are employed, accounting for fibers dispersion either with a generalized structural approach or with an increasing number of strain energy terms. Benchmark data sets, toward which constitutive models are fitted, are built by employing a multiscale description of fiber nonlinearities and accounting for fibers dispersion with an angular integration method. Results show how the optimal values of constitutive parameters obtained from model calibration vary as a function of fibers arrangement and testing protocol. Moreover, the fitting capabilities of constitutive models are discussed. A novel strategy for model calibration is also proposed, in order to obtain a robust accuracy with respect to different loading conditions starting from a low number of mechanical tests. Furthermore, novel results useful for the inverse determination of the mean angle and the variance of fibers distribution are obtained. Therefore, the study contributes: to better design procedures for model calibration; to account for mechanical alterations due to remodeling mechanisms; and to gain structural information in a nondestructive way. [ABSTRACT FROM AUTHOR]

Highlights • FBG-AOTF is used to optimize the OCSR of OSSB signal. • The RZ pulse is chosen as the data transmitting pulse. • Data are only modulated on the optical carrier of the OSSB signal to reduce the influence of fiber dispersion. • Both the receiving sensitivity and stability of the RoF-OSSB link can be improved. Abstract An improved OSSB modulation scheme is proposed in this paper. The improvements are realized by three aspects. Firstly, the fiber Bragg grating based acousto-optic tunable filter (FBG-AOTF) is introduced to tune the Optical Carrier-to-Sideband Ratio (OCSR). Secondly, the Return-to-Zero (RZ) pulse is chosen as the data transmitting pulse. In the end, the OSSB signal with optimized OCSR is separated, and only the optical carrier is modulated by the data. When the transmission distance is within 360 km, the receiving sensitivity of the link in the improved scheme is relatively stable in the range of (−23.6 dBm, −24.1 dBm) with the increase of the distance. While for the original OSSB modulation, under the same condition, the receiving sensitivity is only about −20.0 dBm when the fiber length is 200 km. Not only the OCSR of the OSSB can be optimized, but also the problem of time shift of code edges caused by the fiber dispersion can be eliminated. As a result, both the performance and the stability of the OSSB system can be upgraded in the improved scheme. Two complete simulation systems are built by using the characteristic of the experimentally made FBG-AOTF. And the increased receiving sensitivity of 2.6 dB in the improved scheme further verifies the conclusion. [ABSTRACT FROM AUTHOR]

Abstract In this work, the performance of a point-to-point fiber communication system that use a directly modulated (DML) VCSEL have been studied at 2.5, 10, and 40 Gb/s. We have demonstrated that a low-cost error-free transmission is possible by the appropriate choice of the shape of the driving electric pulse, the extinction ratio (ER) and the On-Off Keying (OOK) signal code (Non Return to Zero-NRZ and Return to Zero-RZ). Additionally, a theoretical model is developed to research and simulate the behavior of chirped signal transmission in dispersive media such as an optical fiber. Thus, the VCSEL-DML generated frequency chirp can be handled in order to avoid the effects of the interaction of laser chirp with fiber dispersion. The transmission performance of a 40 Gb/s optical link over Standard Single-Mode Fiber (SSMF) and over Negative Non-Zero Dispersion Shifted Fiber (NZDSF (−)) is researched by simulation. [ABSTRACT FROM AUTHOR]