Showing papers by "Wei Jin published in 2023"

Broadband all-fiber optical phase modulator based on photo-thermal effect in a gas-filled hollow-core fiber

Abstract: We report broadband all-fiber optical phase modulation based on the photo-thermal effect in a gas-filled hollow-core fiber. The phase modulation dynamics are studied by multi-physics simulation. A phase modulator is fabricated using a 5.6-cm-long anti-resonant hollow-core fiber with pure acetylene filling. It has a half-wave optical power of 289 mW at 100 kHz and an average insertion loss 0.6 dB over a broad wavelength range from 1450 to 1650 nm. The rise and fall time constants are 3.5 and 3.7 μs, respectively, 2–3 orders of magnitude better than the previously reported microfiber-based photo-thermal phase modulators. The gas-filled hollow-core waveguide configuration is promising for optical phase modulation from ultraviolet to mid-infrared which is challenging to achieve with solid optical fibers.

Utilization of Li-Rich Phases in Aluminum Anodes for Improved Cycling Performance through Strategic Thermal Control

Abstract: Lithium-ion batteries with aluminum anodes had appeared to resolve critical dendrite issues of lithium metal cells in the 1970s. However, the poor cycling performance attributed to aluminum anodes would lead to their obsolescence. In this work, we demonstrate how strategic thermal control in cycling aluminum anodes circumvents the problematic α/β phase transformations that yield poor cycling life. Instead, electrochemical formation of the Li3Al2 and Li2–xAl phases necessitates temperatures slightly above ambient, as the Li3Al2 and Li2–xAl phases are key enablers for high capacity and stable cycling. While delivering a competitive capacity level (ca. 1 Ah kg–1-Al), cycling among those higher-order phases is found to be significantly improved, from several cycles to 100 cycles with ca. 67% capacity retention. Importantly, because modern battery charging is likely to occur above room temperature due to ohmic heating, the thermal conditions explored here are expected to be realized in a variety of applications. Furthermore, we show that elevated temperature is not necessary for aluminum anode delithiation, thus creating additional synergies with many practical scenarios.

Research on Performance Degradation Estimation of Key Components of High-Speed Train Bogie Based on Multi-Task Learning

Abstract: The safe and comfortable operation of high-speed trains has attracted extensive attention. With the operation of the train, the performance of high-speed train bogie components inevitably degrades and eventually leads to failures. At present, it is a common method to achieve performance degradation estimation of bogie components by processing high-speed train vibration signals and analyzing the information contained in the signals. In the face of complex signals, the usage of information theory, such as information entropy, to achieve performance degradation estimations is not satisfactory, and recent studies have more often used deep learning methods instead of traditional methods, such as information theory or signal processing, to obtain higher estimation accuracy. However, current research is more focused on the estimation for a certain component of the bogie and does not consider the bogie as a whole system to accomplish the performance degradation estimation task for several key components at the same time. In this paper, based on soft parameter sharing multi-task deep learning, a multi-task and multi-scale convolutional neural network is proposed to realize performance degradation state estimations of key components of a high-speed train bogie. Firstly, the structure takes into account the multi-scale characteristics of high-speed train vibration signals and uses a multi-scale convolution structure to better extract the key features of the signal. Secondly, considering that the vibration signal of high-speed trains contains the information of all components, the soft parameter sharing method is adopted to realize feature sharing in the depth structure and improve the utilization of information. The effectiveness and superiority of the structure proposed by the experiment is a feasible scheme for improving the performance degradation estimation of a high-speed train bogie.

Dispersion turning point-enhanced photothermal interferometry gas sensor with an optical microfiber interferometer

Abstract: Photothermal interferometry (PTI) spectroscopy is a background-free and ultrasensitive gas or chemical sensing method. To date, most works have focused on applying different techniques to improve the sensitivity of PTI gas sensors via enhancing the photothermal (PT) phase modulation. Herein, we develop an all-fiber dispersion turning point (DTP)-enhanced PTI gas sensor with a taper-based mode interferometer in which the PT phase detection sensitivity of the interferometer is enhanced in a millimeter-long single fiber PTI configuration, which has not been studied yet. The design is demonstrated by conducting the measurement of acetylene with a 3-mm-long, 2.29-μm-diamter microfiber interferometer. A lower detection limit of 965 parts per billion (ppb) acetylene is achieved when the probe wavelength is operating near DTP, showing 16 times enhancement. Besides, theoretical analysis shows that the sensitivity of phase detection would be enormously enhanced when the dispersion factor approaching zero. By optimal design of the taper-based mode interferometer, together with thinner fiber diameter and longer fiber length, gas detection may be further improved by double enhancement of both PT phase generation and phase detection. With advantages of high sensitivity, compact size and low cost, the proposed all-fiber DTP-enhanced PTI gas sensor is potentially promising for ultra-sensitive trace chemical or biochemical sensing.

Lubrication Film Generation with Limited Lubricant Supply and Its Tuned Oil Replenishment in a Cylinder-on-Disc Contact

Abstract: Limited lubricant supply (LLS) with tuned dosage is an emerging approach to reduce friction and energy consumption. However, LLS can cause severe starvation when the oil supply is insufficient. Therefore, how to effectively replenish oil to the lubricated contact in LLS operation is very important. Using a custom-made optical slider bearing test rig, this work experimentally revealed some characteristics of LLS lubrication in a cylinder-on-disc contact, and proposed two wettability gradient patterns, namely stripe wettability and interlaced wettability, to regulate the lubricant supply to improve the lubricating properties of LLS. The effect of these two wettability patterns was evaluated experimentally according to the lubricating film thickness. The interferograms of the bearing contact under LLS show that the two patterns can augment the oil replenishment through unidirectional lubricant transport by the unbalanced interfacial force via the wettability gradient. Moreover, the interlaced wettability pattern is more effective due to the discontinuous distribution of lubricant from its hydrophilic/hydrophobic region intervals and the transfer of the hydrophobic film to the hydrophilic regions.

Direct single-cell antimicrobial susceptibility testing of Escherichia coli in urine using a ready-to-use 3D microwell array chip.

Abstract: Empirical antibiotic therapies are prescribed for treating uncomplicated urinary tract infections (UTIs) due to the long turnaround time of conventional antimicrobial susceptibility testing (AST), leading to the prevalence of multi-drug resistant pathogens. We present a ready-to-use 3D microwell array chip to directly conduct comprehensive AST of pathogenic agents in urine at the single-cell level. The developed device features a highly integrated 3D microwell array, offering a dynamic range from 102 to 107 CFU mL-1, and a capillary valve-based flow distributor for flow equidistribution in dispensing channels and uniform sample distribution. The chip with pre-loaded reagents and negative pressure inside only requires the user to initiate AST by loading samples (∼3 s) and can work independently. We demonstrate an accessible sample-to-result workflow, including syringe filter-based bacteria separation and rapid single-cell AST on chip, which enables us to bypass the time-consuming bacteria isolation and pre-culture, speeding up the AST in ∼3 h from 2 days of conventional methods. Moreover, the bacterial concentration and AST with minimum inhibitory concentrations can be assessed simultaneously to provide comprehensive information on infections. With further development for multiple antibiotic conditions, the Dsc-AST assay could contribute to timely prescription of targeted drugs for better patient outcomes and mitigation of the threat of drug-resistant bacteria.

A Point-to-Multipoint Flexible Transceiver for Inherently Hub-and-Spoke IMDD Optical Access Networks

Abstract: Point-to-multipoint (P2MP) transceivers offer a promising solution to transform present point-to-point optical access networks into scalable and flexible P2MP networks capable of dynamically meeting, in a cost-effective and high energy consumption efficiency manner, the requirements associated with 5G-Advance and beyond networks, including large signal transmission capacity, fast and dense connection, high network flexibility/adaptability and low latency. However, the previously reported P2MP optical transceivers based on either coherent XR optics or IMDD digital filter multiplexing (DFM) techniques are not suitable for implementing in low-latency and highly cost-sensitive IMDD-dominated optical access networks. This paper proposes, experimentally demonstrates and optimises a novel P2MP flexible transceiver incorporating a new cascaded IFFT/FFT-based multi-channel aggregation/de-aggregation technique and an orthogonal digital filtering technique. The performances of the proposed technique are extensively evaluated experimentally in an upstream 55.3 Gb/s @25 km IMDD PON. It is shown that in comparison with the conventional DFM transceivers, the proposed transceivers can reduce the transmitter DSP complexity by a factor that approximates to aggregated channel count, and simultaneously offer additional physical layer network security, without requiring long digital filter lengths and greatly compromising upstream transmission performances/spectral efficiencies as well as differential ONU launch power dynamic ranges.

Ultrafast Selective Enrichment of Ammonia Nitrogen from Water Using Sulfonated Covalent Organic Frameworks Bearing Single Cu Sites

Abstract: Abundant and diverse functional groups of adsorbents are essential for their adsorption performances. Herein, we report a strategy to construct highly efficient ammonia nitrogen adsorbents by installing multiple ion-exchange complexation coordination-hydrogen bonding sites onto covalent organic frameworks (COFs). As a proof of concept, we prepared a COF (TpPa-SO3H) via a modified mechanical grinding synthetic method and then obtained a sulfonated COF bearing single Cu sites (TpPa-SO3Cu0.5) by post-loading. Benefiting from the highly exposed active sites and ordered COF channels, TpPa-SO3Cu0.5 exhibited the highest adsorption kinetics among reported ammonia nitrogen adsorbents proven by the highest pseudo-second-order adsorption rate constant (k2) of 8.97 g mg–1 min–1 with its maximum adsorption capacity (30.45 mg N g–1) higher than most adsorbents (<0.001–0.994 g mg–1 min–1 and 0–25 mg N g–1). Furthermore, TpPa-SO3Cu0.5 exhibited excellent adsorption selectivity with its selective coefficient 328 times as high as that of TpPa-SO3H in real water (10 mg N L–1, pH = 10). It also showed good stability and recyclability with a high ammonia recycle ratio (95.1%) after 5 adsorption–regeneration cycles. These findings pave a new way to develop unique COFs as platforms for ultrafast and selective pollutants in water and wastewater treatment.

Photonic Millimeter Wave Generation and Stabilization in Optically Injected Discrete-mode Semiconductor Lasers subject to Photonic Filter Feedback

Abstract: Photonic millimeter wave signal generation and stabilization based on nonlinear dynamics of optically injected discrete-mode semiconductor lasers with photonic filter feedback are experimentally and numerically studied. The photonic filter is constructed by jointing two ports of a 2×2 optical coupler to form a ring cavity recirculation and is modelled as an infinite impulse response filter. The results show that >30GHz photonic millimeter wave signals can be obtained after optical to electrical conversion of the period-one oscillation output of the optically injected discrete-mode semiconductor laser. More importantly, the linewidth, side peak suppression ratio, as well as the stability of the generated millimeter wave, can be optimized using the photonic filter feedback. A fair comparison of the photonic filter feedback scheme and the single/double optical feedback schemes in terms of optimization performance has been made. The corresponding results demonstrate that the photonic filter feedback scheme has obvious superiority in millimeter wave side peak suppression and stability. The effect of the coupling coefficient as well as the phase variables in the ring cavity has also been discussed in the simulation work and the results qualitatively agree with the experimental observations.

Estimating Continuous Muscle Fatigue For Multi-Muscle Coordinated Exercise: A Pilot Study

Abstract: Assessing the progression of muscle fatigue for daily exercises provides vital indicators for precise rehabilitation, personalized training dose, especially under the context of Metaverse. Assessing fatigue of multi-muscle coordination-involved daily exercises requires the neuromuscular features that represent the fatigue-induced characteristics of spatiotemporal adaptions of multiple muscles and the estimator that captures the time-evolving progression of fatigue. In this paper, we propose to depict fatigue by the features of muscle compensation and spinal module activation changes and estimate continuous fatigue by a physiological rationale model. First, we extract muscle synergy fractionation and the variance of spinal module spikings as features inspired by the prior of fatigue-induced neuromuscular adaptations. Second, we treat the features as observations and develop a Bayesian Gaussian process to capture the time-evolving progression. Third, we solve the issue of lacking supervision information by mathematically formulating the time-evolving characteristics of fatigue as the loss function. Finally, we adapt the metrics that follow the physiological principles of fatigue to quantitatively evaluate the performance. Our extensive experiments present a 0.99 similarity between days, a over 0.7 similarity with other views of fatigue and a nearly 1 weak monotonicity, which outperform other methods. This study would aim the objective assessment of muscle fatigue.

Ultrahigh-resolution and ultra-simple fiber-optic sensor with resonant Sagnac interferometer.

Abstract: The resonant fiber-optic sensor (RFOS) is well known for its high sensing resolution but usually suffers from high cost and system complexity. In this Letter, we propose an ultra-simple white-light-driven RFOS with a resonant Sagnac interferometer. By superimposing the output of multiple equivalent Sagnac interferometers, the strain signal is amplified during the resonance. A 3 × 3 coupler is employed for demodulation, by which the signal under test can be read out directly without any modulation. With 1 km delay fiber and ultra-simple configuration, a strain resolution of 28f ε/Hz at 5 kHz is demonstrated in the experiment, which is among the highest, to the best of our knowledge, resolution optical fiber strain sensors.

Ultra-low loss and large effective area G.654.E fiber in non-relay ultra-long haul optical transmission

Abstract: In this paper, the properties of ultra-low loss and large effective area G.654.E fiber were studied, including the optical properties and cabling performance. Based on the tests of the transmission performances of different optical fibers in nonrelay ultra-long haul optical transmission system, practical suggestions for optical fiber selection of electric communication construction were proposed. G.654.E fiber was utilized in practical engineering, verifying the theoretical research and identifying optimal direction and methods. 467 km non-relay ultra-long haul optical transmission was realized, creating a new record in electric communication network.

Photothermally Induced Birefringence in an Optical Nanofiber for All‐Optical Polarization Manipulation

Abstract: This study reports the experimental observation of photothermally induced birefringence (PIB) in an optical nanofiber (NF). The PIB originates from the interaction between the azimuthally asymmetric evanescent field of a guided pump beam in HE11$H{E_{11}}$ mode and the gas molecules surrounding the NF. Light absorption of gas molecules results in azimuthal inhomogeneity in gas density, which induces birefringence of the NF waveguide. The swift heat transfer and molecular transportation in sub‐micrometer scale accounts for the fast response of the PIB with a measured rising and falling time within 9 and 70 ns, respectively. With a 12‐mm‐long NF, phase retardance as large as 3π is achieved. A theoretical model based on the rate equation is also developed for studying the photothermal dynamics and gas kinetics in PIB generation. This novel model is well consolidated by the numerical simulations, with the results agreeing well with the experiments. In consideration of the extremely low insertion loss, fast response, and reconfigurable principal axes of birefringence, the PIB can be used for all‐optical polarization manipulation. In addition, NF with PIB can also be an interesting platform for studies of gas–surface interaction, light–sound interaction controlling, sub‐micrometer scale heat and mass transfer, and molecular spectroscopy.

Adaptive Hybrid Iterative Linearization Algorithms for IM/DD Optical Transmission Systems

Abstract: For optical field recovery and linear dispersion compensation, we propose a performance-enhanced linearization algorithm, termed adaptive hybrid multi-constraint iteration algorithm (MCIA), which does not require any physical modifications to standard configurations of intensity-modulation and direct-detection (IM/DD) transmission systems. To improve the sensitivity to the residual inter-symbol interference (ISI) effect, we introduce, after fiber backward-propagation, a linear feed-forward equalizer (FFE) pair into the proposed algorithm. To improve the sensitivity to fiber dispersion estimation errors, we utilize a two-stage dispersion estimator coupled with the G-S iteration. After 100-Gb/s PAM-4 signal transmissions over 400-km fibers, the simulation results show that the MCIA offers a 1.5-dB optical signal-to-noise ratio (OSNR) gain and a 1-dB optical power budget improvement compared with the decision-directed data-aided iterative algorithm (DD-DIA), for highly dispersive IM/DD transmissions. By performing adaptive dispersion estimation, the MCIA has higher tolerance to estimation errors in fiber length. Moreover, for cases subject to large dispersion, the usage of the embedded FFE pair not only desensitizes the MCIA on the limited bandwidth effect, but also accelerates the convergence performance for reaching lower BERs. We experimentally demonstrate that the proposed algorithm can support 150-Gb/s PAM-4 transmissions over 25-km standard single mode fibers (SSMF), where just a 7-tap FFE-pair is required. For 150 Gb/s transmissions, the tolerance to fiber length estimation error is increased from 0.9 km to 20 km.

Creep Characterization of Concrete Suffering Initial Damage

Abstract: This work studies the creep characteristics of concrete sustaining initial damage by considering both the initial damage to concrete and the damage caused by crack growth in the creep process. The damage state of concrete is characterized by the characteristics of the amplitude of ultrasonic waves. Creep tests on concrete prisms with different degrees of initial damage were carried out at loads of 40%, 50%, and 60% compressive strength. The results show that the initial damage to concrete significantly impacts its creep behavior. The modified creep curve of concrete, including the initial damage variable, is consistent with the creep curve of undamaged concrete at different stress levels, proving the applicability of the damage variable.

Amplified Photothermal Phase Modulation for Carbon Dioxide Detection by Operating a Dual-Mode Interferometer at Destructive Interference.

Abstract: Photothermal interferometry is a highly sensitive spectroscopic technique for trace gas detection. However, the performance of the state-of-the-art laser spectroscopic sensors is still insufficient for some high-precision applications. Here, we demonstrate optical phase-modulation amplification by operating a dual-mode optical fiber interferometer at destructive interference for ultrasensitive carbon dioxide detection. With a 50 cm long dual-mode hollow-core fiber, amplification of photothermal phase modulation by a factor of nearly 20 is achieved, which enables carbon dioxide detection down to 1 parts-per-billion with a dynamic range of over 7 orders of magnitude. This technique could be readily used to improve the sensitivity of phase modulation-based sensors with a compact and simple configuration.

Laser damage threshold of vanadium dioxide film

Abstract: Vanadium dioxide film can be used to anti-laser interference infrared detector. If the laser energy is strong enough, the film may also be damaged under laser irradiation. VO2 thin films were prepared on sapphire substrates by molecular beam epitaxy. The laser damage threshold test of VO2 film was designed. VO2 film was irradiated with 1064 nm laser, and the damage characteristics of the film were observed by metallographic microscope. The damage threshold of the film was determined according to the damage morphology. The experimental equipment of laser pretreatment to enhance the film damage threshold was set up, and the laser energy of 20%-90% of the film damage threshold was used to pretreat the film. It is found that there is an optimal pretreatment energy for raising the damage threshold of vanadium dioxide films by laser pretreatment, and the optimal pretreatment energy is 60% of the damage threshold energy. The damage threshold of vanadium dioxide films pretreated with this energy was increased by about 31%.