Temperature insensitivity of an all-fiber quarter-wave plate device fabricated with a high-birefringence fiber

A high-birefringence fiber,Tb:YAG crystal-derived silica fiber(TYDSF),was fabricated by CO_(2)laser-heating drawing technique.Its linear birefringence was 2.99×10^(-5),and it was used to fabricate an all-fiber quarter-wave plate(QWP)device.The polarization extinction ratio(PER)of the device was 0.29 dB,and its ellipticity was 44.26°at 25℃.In the temperature range of-5℃to 200℃,its PER was always less than 0.80 dB,and the fluctuation of PER and ellipticity was also small.Compared with QWPs fabricated with PANDA-type polarization-maintaining fiber(PMF)and elliptical-core PMF,the performance of TYDSF QWP was least sensitive to temperature.Furthermore,the TYDSF QWP was used in a high-power laser system,still maintaining good circular polarization state,and the nonlinear effects were suppressed in the system.The experimental results are of great significance to high-power lasers,fiber-optic current sensors,etc.,in harsh environments.

Giving Food a Fiber Boost: Adding High Beta-Glucan Ingredient from Barley to Everyday Foods

Lack of dietary fiber contributes to many health issues, particularly chronic vascular diseases. Mixed linkage β-1.3 - 1.4 beta-glucan (beta-glucan, in this paper) is a confirmed beneficial ingredient for the human diet through reduction of cholesterol and the glycemic index. Barley contains the highest beta-glucan content of all the grains, and in this study, a percentage of flour from two high beta glucan lines was, each, added to an array of wheat-based food products to measure how it impacted total dietary fiber. Results showed that beta-glucan content was higher in all the products containing the added high beta-glucan flour, along with increased total dietary fiber content. Protein content in the food products is also increased with the higher protein in the barley flours added. Beta-glucan content in the barley-added products increased to 1.2% - 4.0% versus 0.2% - 0.5% in the pure wheat products, while the dietary fibers increased to 3.5% - 24.4% versus 2.1% - 9.1% in pure wheat product controls. This research provided experimental evidence that using a high beta-glucan barley ingredient in food can increase dietary fiber to benefit health.

Study on High Strength Concrete Confined by Continuous Carbon Fiber Sheet

Eight high strength concrete (HSC) prisms strengthened with continuous carbon fiber sheet(CFS)were tested.As a result of the confinement provided by CFS,the concrete would fail at a greater strain than the unconfined and then a significant increase in ductility can be achieved.The lateral pressure exerted by CFS would increase the compressive strength of the concrete,resulting in higher load bearing capacity.This paper proposes the stress strain curve of this kind of hybrid specimen,which agrees well with the test results.Based on the stress strain relationship and the assumptions proposed in this paper,a computer program was developed to analyze HSC columns,confined by CFS,which were subjected to axial compression and biaxial bending.The results shown in this paper indicate that the ductility of HSC column is significantly improved and the strength is also increased by some degree.

High Brightness,High Power Density Fiber Coupling of High Power Laser Diode

The output radiation from the 100μm×1μm aperture of a high power Laser Diode (LD) is efficiently coupled into a 50μm multimode optical fiber.The fiber output of the high power LD with high brightness and high power density is achieved.The power density is up to 3 6×104W/cm2 and the coupling efficiency is 70%.The extreme divergence and the astigmatism of high power LDs require the optics with complex lens structures and high performance.A double-curved lens with two crossed cylindrical lenses structured on both sides of the glass substrate is used in the coupling system.

Study on the Flame-retardant Properties of High Flame-retardant Acrylic Fiber Knitted Fabrics

This paper involved five kinds of weft-knitted fabrics made from high flame-retardant acrylic/cotton(0/100,30/70,50/50,70/30,100/0).The article adopted the vertical burning method,limiting oxygen index method and Cone Calorimeter test method for testing fabric flame retardant property.By comparison with these five fabrics,the effects on the properties of high flame-retardant acrylic fiber knitted fabrics due to the content of high flame-retardant acrylic fiber were analyzed.

Experimental evaluation on high temperature rheological properties of various fiber modified asphalt binders

High temperature rheological properties of fiber modified asphalt binders and impact of the type and content on such properties were studied.Three types of fiber,including polyester(PET),polyacrylonitrile(PAN) and cellulose(CEL),a control content(0%) and four levels of fiber content(2%,4%,6% and 8% by total asphalt binder mass) were used with asphalt binders.The high temperature rheological properties,consisting of complex modulus(G*) and phase angle δ,were measured using SHRP's dynamic shear rheometer(DSR) between 46-82 ℃.Experimental results indicate that the changes of G* and tan δ of fiber modified asphalt binders with the increase of test temperature tend to slow down,and the temperature susceptibility is improved obviously compared to that of original asphalt binder.Fiber modification results in the increase of rutting parameter(G*/sin δ) at high temperatures,the decrease of temperature susceptibility,and further improved high temperature performance of asphalt binder.An excellent correlation exhibits between fiber content and high temperature performance of asphalt binder.Moreover,fiber type also has different influences on the improvement of G*/sin δ,G*/sin δ of PET and PAN fiber asphalt binders are both higher than that of CEL fiber,but G*/sin δ of CEL fiber is still higher than that of original asphalt.However,there is a critical fiber content when fibers start to interact with each other.Therefore,based on the critical fiber content and economic consideration,the optimum fiber contents for various fiber-modified asphalt binders are obtained.

OBSERVATIONS ON DEFORMATION BEHAVIOR OF HIGH PERFORMANCE FIBERS BY POLARIZING OPTICAL MICROSCOPY

By means of polarizing optical microscopy (POM), deformation behavior of four kinds of fibers, i.e, ultra high molecular weight polyethylene (UHMW-PE) fiber, polyvinyl alcohol (PVA) fiber, polyethylene terephthalate (PET) fiber, and wholly aromatic (rho-hydroxybenzoic acid/2-hydroxy-6-naphthoic acid) copolyester [P(HBA/HNA)]/PET (ACPET blend) fiber, in axial compression, axial impacting, and bending was observed. In compression, kink bands formed at an angle of 55-60 degrees ro the fiber axis in 10-times-drawn UHMW-PE fiber, 75-80 degrees in 40-times-drawn sample, 80 degrees in PVA fiber, and 90 degrees in the ACPET blend fiber. In impacting and bending, band angles of UHMW-PE, PVA and PET fibers are nearly the same as those formed in compression, indicating that slip systems do not change. For any of the four kinds of fiber, band spacing exhibits great differences in compression, in impacting, and in bending, which may be attributed to the differences in the degrees of strain or stress concentration.

Stability of fiber laser-MIG hybrid welding of high strength aluminum alloy

The effect of fiber laser on MIG arc was investigated with 8 mm 7075-T6 high strength aluminum alloy as base material.The arc shape,droplet transfer form and electrical signal in the process of MIG welding and laser-MIG hybrid welding were analyzed.The stability of the hybrid welding process was evaluated by standard deviation analysis.The results show that with the increase of laser power,a large number of laser-induced plasma enters the arc column area,providing more conductive channels,which makes the heat of MIG arc more concentrated and the short circuit transition disappear.Due to the continuous effect of laser,the keyhole becomes a continuous electron emission source,and a stable cathode spot will be formed near the keyhole,which enhances the stability of MIG arc at the base current state.By using the method of standard deviation analysis,the voltage standard deviation of single MIG welding arc and laser-MIG hybrid arc within 4 seconds was calculated.The standard deviation of single MIG arc voltage was 1.05,and the standard deviation of MIG arc voltage in laser-MIG hybrid welding was 0.71–0.86,so the hybrid welding process was more stable.

Experimental investigation of axially loaded steel fiber reinforced high strength concrete-filled steel tube columns

An experimental study on the compressive behavior of steel fiber reinforced concrete-filled steel tube columns is presented. Specimens were tested to investigate the effects of the concrete strength, the thickness of steel tube and the steel fiber volume fraction on the ultimate strength and the ductility. The experimental results indicate that the addition of steel fibers in concrete can significantly improve the ductility and the energy dissipation capacity of the concrete-filled steel tube columns and delay the local buckling of the steel tube, but has no obvious effect on the failure mode. It has also been found that the addition of steel fibers is a more effective method than using thicker steel tube in enhancing the ductility, and more advantageous in the case of higher strength concrete. An analytical model to estimate the load capacity is proposed for steel tube columns filled with both plain concrete and steel fiber reinforced concrete. The predicted results are in good agreement with the experimental ones obtained in this work and literatures.

Charactersitics of Stress-strain Curve of High Strength Steel Fiber Reinforced Concrete under Uniaxial Tension

A whole of 110 specimens divided into 22 groups were tested with varying the volume fraction of steel fibers and the matrix strength of these specimens. The stress-strain behaviors of four types of steel fiber reinforced concrete （SFRC） under uniaxial tension were studied experimentally. When the matrix strength and the fiber content increase, the tensile stress and tensile strain vary differently according to the fiber type. The mechanisms of reinforcing effect for different types of fiber were analyzed and the stress-strain curves of the specimens were plotted. Some experimental factors for stress or strain of SFRC were given. A tensile toughness modulus Re0.5 was introduced to evaluate the toughness characters of SFRC under uniaxial tension. Moreover, the formula of the tensile stress-strain curve of SFRC was regressed. The theoretical curve and the experimental ones fit well, which can be used for references in construction.

A novel one-step reaction sodium-sulfur battery with high areal sulfur loading on hierarchical porous carbon fiber

Room temperature sodium-sulfur(RT Na-S)batteries are gaining extensive attention as attractive alternatives for large-scale energy storage,due to low cost and high abundancy of sodium and sulfur in nature.However,the dilemmas regarding soluble polysulfides(Na_(2)Sn,4<n<8)and the inferior reaction kinetics limit their practical application.To address these issues,we report the activated porous carbon fibers(APCF)with small sulfur molecules(S2-4)confined in ultramicropores,to achieve a reversible single-step reaction in RT Na-S batteries.The mechanism is investigated by the in situ UV/vis spectroscopy,which demonstrates Na2S is the only product during the whole discharge process.Moreover,the hierarchical carbon structure can enhance areal sulfur loading without sacrificing the capacity due to thorough contact between electrolyte and sulfur electrode.As a consequence,the APCF electrode with 38 wt%sulfur(APCF-38S)delivers a high initial reversible specific capacity of 1412 mAh g^(-1) and 10.6mAh cm^(-2)(avg.areal sulfur loading:7.5 mg cm^(-2))at 0.1 C(1C=1675 mA g^(-1)),revealing high degree of sulfur utilization.This study provides a new strategy for the development of high areal capacity RT Na-S batteries.

Bond Behavior between BFRP Bars and Hybrid Fiber Recycled Aggregate Concrete after High Temperature

The aim of this study is to improve the bond performance of basalt fiber reinforced polymer(BFRP)bars and recycled aggregate concrete(RAC)after being exposed to high temperatures.The bond behavior(failure modes,bond strength,bond stress-slip curves)between BFRP bars and hybrid fiber recycled aggregate concrete(HFRAC)after being exposed to temperatures ranging from 20℃up to 500℃was studied by using pull-out tests.The effect of high temperatures on mechanical properties of concrete(compressive strength,splitting tensile strength)and tensile strength of BFRP bars was also investigated.The bond strength decreased as the temperature increased and the drop of bond strength between RAC and BFRP bar was larger than that between HFRAC and BFRP bar.As the temperature rises,the key factor affecting the bond strength was gradually transformed from concrete strength to BFRP bar strength.The relationship between bond stress and slip in the dimensionless bond stress-slip ascending section was established,which was in good agreement with the experimental results.

Characterization of diamond MWCNTs composite fiber synthesized under high pressure and high temperature

A regrown composite fiber was synthesized during the sintering of diamond under high pressure 5.8 GPa and high temperature 1500℃for 1 min,using 3wt%MWCNTs as additive.SEM observation of the fiber after alkali and acid treatment revealed that the outer layer of the fiber is composed of nano-polycrystalline diamond.EDS,XPS,XRD and Raman spectrum analysis further identified that the fiber is composed of MWCNTs in the inner part and nano-polycrystalline diamond in the out layer.It is proposed that the untransformed MWCNTs may act as a template for the regrown outer layer of nano diamond fiber under high pressure and high temperature.

Structural Behavior of Continuous Prestressed Steel Fiber Reinforced High Strength Concrete Beam

The flexural behaviors of continuous fully and partially prestressed steel fiber reinforced high strength concrete beams are studied by experiment and nonlinear finite element analysis. Three levels of partial prestress ratio （PPR） are considered, and three pairs of two-span continuous beams with box sections varying in size are designed. The major parameters involved in the study include the PPR and the fiber location. It is concluded that the prestressed high strength concrete beam exhibits satisfactory ductility; the influences of steel fiber on the crack behaviors for partially prestressed beams are not as obvious as those for fully prestressed ones; steel fibers can improve the structural stiffness after cracking for fully prestressed high strength concrete beams; the moment redistribution from mid-span to intermediate support in the first stage should be mainly considered in practical design.

Fabrication of Tm-Doped Fibers for High Power and 121W Output All-Fiber Tm-Doped Fiber Laser

We fabricate the Tm-doped double cladding silica fiber by using the vapor-solution hybrid-doping method, then build up an all-fiber Tin-doped fiber laser which can provide the output power of up to 121 W, corresponding to a slope efficiency of 51% and an optical-optical efficiency of 48%. By using the domestic Tin-doped fiber, it is the first time a hundred-watt level output at 1915nm has been achieved, to the best of our knowledge. The thermal effect of Tm-doped fiber laser is also analyzed.

Experimental study of weld position detection based on keyhole infrared image during high power fiber laser welding

Keyhole is one of the important phenomena in high-power laser welding process. By studying the keyhole characteristic and detecting the seam offset during high-power fiber laser welding, an infrared sensitive high-speed camera arranged off-axis orientation of laser beam was applied to capture the dynamic thermal images of a molten pool. The 304 austenitic stainless steel plate butt joint welding experiment with laser power 10 kW was carried out. Through analyzing the keyhole infrared image, the weld position was calculated. Least squares method was used to determine the actual weld position. Image filtering technique was used to process the keyhole image, and the keyhole centroid coordinate were calculated. Also, least squares method was used to fit the keyhole centroid curve equation and establish a nonlinear continuous model which described the deviation between keyhole centroid and weld seam. The heat accumulation effect affected by the infrared radiation was analyzed to determine whether the laser beam focus spot deviated from the desired welding seam. Experimental results showed that the keyhole centroid has related to the seam offset, and can reflect the welding quality.

Effect of fiber type on the bending and uniaxial tensile properties of high-strength high-ductility cementitious composites

To investigate the effect of fiber types on bending and tensile properties of high-strength,high-ductility cementitious composites( HS-HDCCs), ultra-high-molecular-weight polyethylene( PE) fibers,polyvinyl alcohol( PVA) fibers,and copper-plated micro steel fibers were selected as the reinforcement materials. The bending and tensile properties of HS-HDCCs with different fibers with a volume fraction of 2% were studied. The results indicate that PE,PVA,micro steel,and PVA-PE hybrid fibers impart varying degrees of toughening and improve the tensile strength. During the tensile and bending processes,HS-HDCCs with micro steel fibers exhibit a strain-softening phenomenon. HS-HDCCs with PVA fibers or with PVA-PE hybrid fibers can achieve multiple cracking behaviors and strain hardening phenomenon to a certain extent and show slight high-ductility characteristics. HS-HDCCs with PE fibers exhibit multiple cracking behavior and strain hardening phenomenon and show significant high-ductility characteristics. The test results can provide a basis for selecting fibers suitable for HS-HDCCs reinforcement.

Highly active Fe_(7)S_(8) encapsulated in N-doped hollow carbon nanofibers for high-rate sodium-ion batteries

Nanostructured iron sulfides are regarded as a potential anode material for sodium-ion batteries in virtue of the rich natural abundance and remarkable theoretical capacity.However,poor rate performance and inferior cycling stability caused by sluggish kinetics and volume swelling represent two main obstacles at present. The previous research mainly focuses on nanostructure design and/or hybridizing with conductive materials.Further boosting the property by adjusting Fe/S atomic ratio in iron sulfides is rarely reported.In this work,Fe_7 S_8 and FeS_2 encapsulated in N-doped hollow carbon fibers(NHCFs/Fe_7 S_8 and NHCFs/FeS_2) are constructed by a combined chemical bath deposition and subsequent sulfidation treatment.The well-designed NHCFs/Fe_(7) S_(8) electrode displays a remarkable capacity of 517 mAh g^(-1) at 2 A g^(-1)after 1000 cycles and a superb rate capability with a capability of 444 mAh g^(-1) even at 20 A g^(-1) in etherbased electrolyte.Additionally,the rate capability of NHCFs/Fe_(7) S_(8) is superior to that of the contrast NHCFs/FeS_(2) electrode and also much better than the values of the most previously reported iron sulfide-based anodes.The in-depth mechanism explanation is explained by further experimental analysis and theoretical calculation,revealing Fe_(7) S_(8) displays improved intrinsic electronic conductivity and faster Na^(+) diffusion coefficient as well as higher reaction reversibility.

Highly sensitive and stable probe refractometer based on configurable plasmonic resonance with nano-modified fiber core

A dispersion model is developed to provide a generic tool for configuring plasmonic resonance spectral characteristics.The customized design of the resonance curve aiming at specific detection requirements can be achieved.According to the model,a probe-type nano-modified fiber optic configurable plasmonic resonance(NMF-CPR)sensor with tip hot spot enhancement is demonstrated for the measurement of the refractive index in the range of 1.3332-1.3432 corresponding to the low-concentration biomarker solution.The new-type sensing structure avoids excessive broadening and redshift of the resonance dip,which provides more possibilities for the surface modification of other functional nanomaterials.The tip hot spots in nanogaps between the Au layer and Au nanostars(AuNSs),the tip electric field enhancement of AuNSs,and the high carrier mobility of the WSe_(2)layer synergistically and significantly enhance the sensitivity of the sensor.Ex-perimental results show that the sensitivity and the figure of merit of the tip hot spot enhanced fiber NMF-CPR sensor can achieve up to 2995.70 nm/RIU and 25.04 RIU^(−1),respectively,which are 1.68 times and 1.29 times higher than those of the conventional fiber plasmonic resonance sensor.The results achieve good agreements with numerical simulations,demonstrate a better level compared to similar reported studies,and verify the correctness of the dispersion model.The detection resolution of the sensor reaches up to 2.00×10^(−5)RIU,which is obviously higher than that of the conventional side-polished fiber plasmonic resonance sensor.This indicates a high detection accuracy of the sensor.The dense Au layer effectively prevents the intermediate nanomaterials from shedding and chemical degradation,which enables the sensor with high stability.Furthermore,the terminal reflective sensing structure can be used as a practical probe and can allow a more convenient operation.

Diagnostic capability of peripapillary retinal nerve fiber layer parameters in time-domain versus spectral-domain optical coherence tomography for assessing glaucoma in high myopia

AIM： To evaluate and compare the diagnostic capabilities of peripapillary retinal nerve fiber layer（p-RNFL） parameters of Spectralis optical coherence tomography（OCT） versus Stratus OCT to detect glaucoma in patients with high myopia. METHODS： This is a retrospective, cross-sectional study. Sixty highly myopic eyes of 60 patients were enrolled, with 30 eyes in the glaucoma group and 30 eyes in the control group. All eyes received peripapillary imaging of the optic disc using Stratus and Spectralis OCT. Areas under the receiver operating characteristic curve（AUROC） and the sensitivity at specificity of 〉80% and 〉95% for p-RNFL parameters obtained using the two devices to diagnose glaucoma were analysed and compared. RESULTS： In Spectralis OCT, p-RNFL thickness parameters with the largest AUROC were the temporal-inferior sector（0.974） and the inferior quadrant（0.951）, whereas in Stratus OCT, the best parameters were the 7-o＇clock sector（0.918） and the inferior quadrant（0.918）. Compared to the Stratus OCT parameters, the Spectralis OCT parameters demonstrated generally higher AUROC; however, the difference was not statistically significant. CONCLUSION： The best p-RNFL parameters for diagnosing glaucoma in patients with high myopia were the temporal-inferior sector on Spectralis OCT and the 7-o＇clock sector on Stratus OCT. There were no significant differences between the AUROCs for Spectralis OCT and Stratus OCT, which suggest that the glaucoma diagnostic capabilities of these two devices in patients with high myopia are similar.