Precision Frequency Measurement of ^(87)Rb 5S_(1/2)(F=2)→5D_(5/2)(F″=4)Two-Photon Transition through a Fiber-Based Optical Frequency Comb

The absolute frequency of 87Rb 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition at 778nm is measured in an accuracy of 44kHz. A home-made erbium-doped fiber laser frequency comb with frequency stability of 5.0 × 10-13@1 s is employed for the light source. By using a periodically poled lithium niobate, the femtosecond pulse operating in 1556 nm is frequency-doubled to 778 nm to obtain the direct two-photon transition spectroscopy of thermal rubidium vapor. Through sweeping the carrier envelope offset frequency （fceo）, the 5S1/2 （F=2）→5D5/2 （F＂ = 4） two-photon transition line is clearly resolved and its absolute frequency is determined via the peak-finding of the fitting curve. After the frequency correction, the measured result agrees well with the previous experiment on this transition. The entire potential candidate of optical frequency standard for system configuration is compact and robust, providing a telecommunication applications.

Combination of hollow fiber-based liquid-phase microextraction with sweeping techniques in micellar electrokinetic chromatography for the determination of Strychnos alkaloids in human urine

A new method for the enrichment of Strychnos alkaloids in biological samples via liquid-phase microextxaodon （LPME） based on porous polypropylene hollow fibers in combination with on-line sweeping in micellar electrokinodc chromatography was developed. The calibration curve was linear over the range of 20-200 ng mL^-1 for both strychnine and brucine in human urine sample. The detection limits （S/N = 3：1） for strychnine and brucine were 1 ng mL^-1 and 2 ng mL^-1, respectively. The LPME-sweeping method has been successfully applied to the analysis of strychnine and brucine in real urine samples.

Attosecond-Resolution Er:Fiber-Based Optical Frequency Comb

Highly stable frequency-controlled optical frequency combs axe key elements of many applications in time- frequency and optical-metrology domains. In this work, we demonstrate a highly stable frequency-controlled erbium-fiber-based optical frequency comb system. Its repetition rate is phase-stabilized to a continuous-wave laser with both an intra-cavity electro-optic modulator and a piezo-transducer; while the carrier-envelope-offset frequency is phase-locked to a radio-frequency signal generator by controlling the pump power. In-loop relative frequency stabilities of the comb are below 1 ×10-16 at I s, and integrate down to low 10-2o level at 104 s. The corresponding timing uncertainties are 100-200 as over the full measurement range.

Recent progress of fiber-based transistors: materials, structures and applications

Wearable electronics on fibers or fabrics assembled with electronic functions provide a platform for sensors,displays,circuitry,and computation.These new conceptual devices are human-friendly and programmable,which makes them indis-pensable for modern electronics.Their unique properties such as being adaptable in daily life,as well as being lightweight and flexible,have enabled many promising applications in robotics,healthcare,and the Internet of Things(IoT).Transistors,one of the fundamental blocks in electronic systems,allow for signal processing and computing.Therefore,study leading to integration of transistors with fabrics has become intensive.Here,several aspects of fiber-based transistors are addressed,including materials,system structures,and their functional devices such as sensory,logical circuitry,memory devices as well as neuromorphic computation.Recently reported advances in development and challenges to realizing fully integrated electronic textile(e-textile)systems are also discussed.

High-Performance Natural Melanin/Poly(vinyl Alcohol-co-ethylene) Nanofibers/PA6 Fiber for Twisted and Coiled Fiber-Based Actuator

Twisted and coiled fiber-based actuators have drawn a great attention because their unique structure can provide mechanical response with the external thermal stimulus.Herein,an ultra-fast and light-weight twisted and coiled fiber-based actuator was designed based on a nature melanin/poly(vinyl alcohol-co-ethylene)(PVA-co-PE)nanofibers/PA6 composite fiber.In brief,PA6 was firstly coated by melanin/PVA-co-PE nanofibers using a spraying method,followed by the twisting and coat-ing the composite fiber to obtain the actuator.The excellent photothermal property of melanin contributed to the superior performance of the actuator,whereas the PVA-co-PE nanofibers was responsible for the uniform distribution of melanin and the enhanced mechanical property of the prepared-actuator.This unique design has led to the high performance of the melanin/NFs/PA6 fiber-based actuator,whose torsion actuation can reach to 14,000 rpm,and maximum tensile actuation was−6.36%at temperature difference of 40℃.In addition,the tensile stress of PA6/NFs/melanin fiber was about four times higher than PA6 filaments.Owing to the simple and environmental-benign preparation method,as well as the excellent effi-ciency of twisted and coiled melanin/NFs/PA6 fiber-based actuator,this study highlights the facile design of the composite fiber for high-performance fiber-based actuators.This fiber-based actuator is promising for application in energy generator.

Switchable dual-wavelength fiber ring laser featuring twin-core photonic crystal fiber-based filter

A simple configuration for the generation of a switchable dual-wavelength fiber ring laser is presented.The proposed configuration employs a short twin-core photonic crystal fiber acting as a Mach–Zehnder interferometer at room temperature.A polarization controller is further utilized to enable switchable dualwavelength operation.

Recent Progress on Fiber-Based Optical Components

The trends of fiber-based optical component technologies are reviewed focusing on fused-taper couplers and fiber Bragg gratings for high bit-rate DWDM transmission systems.

Wavelength-Dependent Transient Characteristics Caused by Gain Saturation in Highly Nonlinear Fiber-Based Raman Amplifiers

We have investigated the transient characteristics of discrete Raman Amplifiers and found that the response time caused by gain saturation is dependent upon the wavelength, which corresponds to the effective length of the pump light.

Fiber-based optical parametric amplifier for 40-Gb/s NRZ-DPSK signal transmission system employing QC-LDPC codes

In this letter, we investigate quasi-cyclic low-density parity-check （QC-LDPC） codes in a 40-Gb/s nonreturn-to-zero differential phase-shift keying （NRZ-DPSK） signal transmission system based on a fiber- based optical parametric amplifier （FOPA）. A constructed algorithm of QC-LDPC codes according to the optimizing set of shift vMues on the circulant permutation matrix （CPM） of the basis matrix is proposed. Simulation results prove that the coding gain in the encoded system can be realized at 10.2 dB under QC- LDPC codes with a code rate of 5/6 when the bit error rate （BER） is 10-9. In addition, the error-floor level originating from the uncoded system is suppressed.

Numerical study of directional heat transfer in composite materials via controllable carbon fiber distribution

Carbon fiber reinforced polyamide 12(CF/PA12),a new material renowned for its excellent mechanical and thermal properties,has drawn significant industry attention.Using the steady-state research to heat transfer,a series of simulations to investigate the heat transfer properties of CF/PA12 were conducted in this study.Firstly,by building two-and three-dimensional models,the effects of the porosity,carbon fiber content,and arrangement on the heat transfer of CF/PA12 were examined.A validation of the simulation model was carried out and the findings were consistent with those of the experiment.Then,the simulation results using the above models showed that within the volume fraction from 0% to 28%,the thermal conductivity of CF/PA12 increased greatly from 0.0242 W/(m·K)to 10.8848 W/(m·K).The increasing porosity had little influence on heat transfer characteristic of CF/PA12.The direction of the carbon fiber arrangement affects the heat transfer impact,and optimal outcomes were achieved when the heat flow direction was parallel to the carbon fiber.This research contributes to improving the production methods and broadening the application scenarios of composite materials.

One-step wet-spinning assembly of twisting-structured graphene/carbon nanotube fiber supercapacitor

Graphene fiber-based supercapacitors hold great promise as flexible energy-storage devices. However, simultaneously achieving high ion-transport ability in electrode and electrolyte layer, which is crucial for realizing the high electrochemical performance, still remains challenging. Here, a facile and effective strategy to solve the problem was proposed by developing a twisting-structured graphene/carbon nanotube(CNT) fiber supercapacitor via one-step wet-spinning process with customized multi-channel spinneret.The remarkable structure features of the resulting fiber supercapacitor with wrinkled and thin electrolyte layer, and well-developed porosity of fiber electrode favored the rapid infiltration and transport of electrolyte ions inside the electrode, as well as between electrode and electrolyte, thus boosting high specific capacitance of 187.6 mF cm^(-2) and energy density of 30.2 μWh cm^(-2), and featuring long cycling life(93%capacitance retention after 10,000 cycles) and excellent flexibility. Moreover, the specific capacitance and energy density could be further improved to 267.2 m F cm^(-2) and 66.8 μWh cm^(-2), respectively, when Mn O2 was incorporated into the fiber.

Chemicals,Energy,and Biomaterials from Agricultural Waste Resources in South China

Owing to its subtropical or tropical environment and climate,South China is home to unique agricultural crops such as sugar cane,pineapple,banana,cassava,and rice,which generate a large amount of lignocellulosic agricultural wastes during agricultural as well as associated industrial processing.The efficient utilization of these wastes will have a significant impact on the economy and sustainable development of South China.This paper reviews the research investigations conducted both in China and elsewhere on the conversion of wastes from these subtropical or tropical agricultural crops into useful chemicals,energy,and biomaterials.The goal of this paper is to promote and summarize the extensive investigations on these agricultural wastes for the development of biorefinery.

Assessment of seismic design response factors of concrete wall buildings

To verify the seismic design response factors of high-rise buildings, five reference structures, varying in height from 20- to 60-stories, were selected and designed according to modern design codes to represent a wide range of concrete wall structures. Verified fiber-based analytical models for inelastic simulation were developed, considering the geometric nonlinearity and material inelasticity of the structural members. The ground motion uncertainty was accounted for by employing 20 earthquake records representing two seismic scenarios, consistent with the latest understanding of the tectonic setting and seismicity of the selected reference region （UAE）. A large number of Inelastic Pushover Analyses （IPAs） and Incremental Dynamic Collapse Analyses （IDCAs） were deployed for the reference structures to estimate the seismic design response factors. It is concluded that the factors adopted by the design code are adequately conservative. The results of this systematic assessment of seismic design response factors apply to a wide variety of contemporary concrete wall buildings with various characteristics.

Functional Fibers and Functional Fiber‑Based Components for High‑Power Lasers

The success of high-power fiber lasers is fueled by maturation of active and passive fibers,combined with the availability of high-power fiber-based components.In this contribution,we first overview the enormous potential of rare-earth doped fibers in spectral coverage and recent developments of key fiber-based components employed in high-power laser systems.Subsequently,the emerging functional active and passive fibers in recent years,which exhibit tremendous advantages in balancing or mitigating parasitic nonlinearities hindering high-power transmission,are outlined from the perspectives of geo-metric and material engineering.Finally,novel functional applications of conventional fiber-based components for nonlinear suppression or spatial mode selection,and correspondingly,the high-power progress of function fiber-based components in power handling are introduced,which suggest more flexible controllability on high-power laser operations.

Efficient Photocatalytic Degradation of the Persistent PET Fiber‑Based Microplastics over Pt Nanoparticles Decorated N‑Doped TiO_(2) Nanoflowers

Fiber-based microplastics(FMPs)are highly persistent and ubiquitously exist in the wastewater of textile industry and urban sewage.It remains challenging to completely remove such newly emerged organic pollutants by the predominant physical techniques.In this work,we investigated a photocatalytic degradation catalyzed by TiO_(2) catalyst to demonstrate the feasibility of implementing efficient chemical protocol to fast degrading polyethylene terephthalate(PET)-FMPs(a major FMP type existing in environment).The result shows that a hydrothermal pretreatment(180℃/12 h)is necessary to induce the initial rough appearance and molecular weight reduction.With the comprehensive action of the nano-flower shaped N doped-TiO_(2) catalyst(Pt@N-TiO_(2)-1.5%)on the relatively low molecular weight intermediates,an approximate 29%weight loss was induced on the pretreated PET-FMPs,which is about 8 times superior to the untreated sample.This work not only achieves a superior degradation effect of PET-FMPs,but also provides a new inspiration for the proposal of reduction strategies in the field of environmental remediation in the future.

MOF-derived ZnCo_2O_4/C wrapped on carbon fiber as anode materials for structural lithium-ion batteries

To meet the requirements for the mechanical and electrochemical performance for carbon fiber-based (CF-based) composites in the structural lithium ion batteries (SLIBs) application, better CF-Based composites are urgently needed. Herein, we report a novel composite metal organic framework (MOF)-derived ZnCo_2 O_4/C@carbon fiber via a facile method and subsequent annealing treatment. In this anode,the nano ZnCo_2 O_4/C coatings wrapped on the surface of CF provide more active sites for electrode reactions and the thin carbon layers give the additional protection. For this material, after 100 cycles, it exhibits excellent cycling stability including high reversible capacity of 463 mAh/g at 50 mA/g, which increases 201% than that of the CF. Thus, this structural anode material exhibits enhanced capacity, high initial columbic efficiency.

Wearable Fiber‑Based Supercapacitors Enabled by Additive‑Free Aqueous MXene Inks for Self‑Powering Healthcare Sensors

Wearable fiber-based electronics have found diverse applications including energy storage,healthcare or thermal management,etc.In particular,additive-free aqueous inks play significant roles in fabrication of wearable fiber-based devices,owning to their nontoxic nature and ease of manufacturing.Herein,wearable carbon fiber-based asymmetric supercapacitors(WASSC)are developed based on additive-free aqueous MXene inks,for self-powering healthcare sensors.The sediments of MXene without further modification are used as inks.Furthermore,combined with additive-free aqueous MXene/polyaniline(MP)inks,WASSC,with a wide voltage window and high capacitance is developed for practical energy supply.Impressively,WASSC has been successfully utilized to power wearable pressure sensors that could monitor motions and pulse signals.This wearable self-powered monitoring system on can accurately monitor the human motions,pronunciation,swallow or wrist pulse,without using the rigid batteries.This advantage realizes a great potential in simple and cost effective monitoring of human health and activities.Besides,self-powered system enables waste recycling of MXene and provides an effective approach for designing wearable and fiber-based self-powered sensors.

Fiber‑Based Materials for Aqueous Zinc Ion Batteries

Neutral aqueous zinc ion batteries(ZIBs)have tremendous potential for grid-level energy storage and portable wearable devices.However,certain performance deficiencies of the components have limited the employment of ZIBs in practical applications.Recently,a range of pristine materials and their composites with fiber-based structures have been used to produce more efficient cathodes,anodes,current collectors,and separators for addressing the current challenges in ZIBs.Numerous functional materials can be manufactured into different fiber forms,which can be subsequently converted into various yarn structures,or interwoven into different 2D and 3D fabric-like constructions to attain various electrochemical performances and mechanical flexibility.In this review,we provide an overview of the concepts and principles of fiber-based materials for ZIBs,after which the application of various materials in fiber-based structures are discussed under different domains of ZIB components.Consequently,the current challenges of these materials,fabrication technologies and corre-sponding future development prospects are addressed.

Hierarchical ferric-cobalt-nickel ternary oxide nanowire arrays supported on graphene fibers as high-performance electrodes for flexible asymmetric supercapacitors

Fiber-based supercapacitors （FSCs） are new members of the energy storage family. They present excellent flexibility and have promising applications in lightweight, flexible, and wearable devices. One of the existing challenges of FSCs is enhancing their energy density while retaining the flexibility. We developed a facile and cost-effective method to fabricate a highly capacitive positive electrode based on hierarchical ferric-cobalt-nickel ternary oxide nanowire arrays/graphene fibers and a negative electrode based on polyaniline-derived carbon nanorods/graphene fibers. The elegant microstructures and excellent electrochemical performances of both electrodes enabled us to construct a high- performance flexible asymmetric graphene fiber-based supercapacitor device with an operating voltage of 1.4 V, a specific capacitance up to 61.58 mF.cm-2, and an energy density reaching 16.76 μW·h·cm-2. Moreover, the optimal device presents an outstanding cycling stability with 87.5% initial capacitance retention after 8,000 cycles, and an excellent flexibility with a capacitance retention of 90.9% after 4,000 cycles of repetitive bending.

Regulating the Electronic Structure of Fe^(3+)‑Doped BiOCl_(x)I_(1-x)Solid Solution by an Amidoxime‑Functionalized Fibrous Support for Efficient Photocatalysis

BiOX(X=Cl,I,Br)has attracted intensive interest as a photocatalyst for environmental remediation,but its limited pho-tocatalytic activity versus visible light irradiation restricts its practical application.Herein,a Fe^(3+)-doped BiOCl_(x)I_(1-x)solid solution(Fe-BiOCl_(x)I_(1-x))was synthesized in situ on an amidoxime-functionalized fibrous support via a one-pot solvothermal approach.Comprehensive characterization and DFT calculations indicate that the robust chelated interaction between ami-doxime groups and Fe^(3+)greatly boosts the crystal growth of nanosized Fe-BiOCl_(x)I_(1–x)on the fibrous surface,simultaneously tunes its electronic structure for improved light harvesting and oxygen vacancy creation,and enables the fibrous support to act as an electron sink for efficient charge separation.These synergistic qualities result in high photocatalytic activity for the degradation of organic contaminants,which outperforms that obtained for unsupported Fe-BiOCl_(x)I_(1-x)and other fibrous samples by several times.Our findings highlight the importance of functionalized support design for the development of efficient BiOX photocatalysts under visible light irradiation.