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We demonstrate a L-band all-fibre erbium-doped laser mode-locked by nonlinear polarisation rotation. The use of a single gain segment with appropriate length and dispersion and a L-band optimised Brewster fibre grating as an in-fibre polariser enables the generation of 64-fs pulses at 1.59µm.

BACKGROUND Online weight-loss communities (OWCs) have been becoming increasingly popular for weight management, which enable individuals to monitor (i.e. self-monitoring) and discuss (i.e. social interaction) their weight-loss experiences. However, there has been limited understanding of the role of individuals’ prior weight-loss experiences in subsequent weight-loss success, especially in online settings. OBJECTIVE To address the significant literature gap, this study investigates the relationship between prior weight-loss experiences (success or failure), online social support and subsequent weight-loss success in the contexts of OWCs based on self-determination theory. METHODS The data of 1650 users from one popular OWC is collected using a python crawler procedure, including individuals’ characteristics (e.g. gender, age, friends, posts, membership duration) and weight-loss diary information. Two logit regression models are deployed to estimate the effects of prior weight-loss experiences and social support on subsequent weight-loss success, as well as the moderation effect of social support. RESULTS The results reveal that prior successful weight-loss experiences are positively related to subsequent weight-loss success (β=0.376,p0.1). CONCLUSIONS This study contributes to literature on prior experiences and online social support in the context of OWCs, and provides valuable insights for OWCs’ designs to improve users’ engagement and their weight-loss success.

Ba0.7Sr0.3TiO3 ceramic fibers were synthesized via the precursor linear self-assembly nonhydrolytic sol-gel (NHSG) method, taking TiCl4 as the titanium source, anhydrous barium acetate and strontium acetate as the barium source and strontium source, anhydrous ethanol and glycol as the oxygen donor and solvent, respectively. The NHSG method promotes the formation of Ba–O–Ti and Sr–O–Ti through heterogeneous condensation. The bimolecular association structure of the reaction intermediate (chlorotitanium ethoxide) between ethanol and titanium tetrachloride facilitates the self-linear assembly of precursors. It also enables linear colloidal particle formation and excellent spinnability of the sol. The novel Ba0.7Sr0.3TiO3 ceramic fibers would promote the flexibility of electronic products.

A wearable device based on an alignment-free photonic chip (AFPC) which consists of optical microfiber and flexible liquid chip for precise human health monitoring was developed. High-fidelity physiological signals and vital signs were detected and extracted for cardiovascular health accessment.

Environmental degradation sourced by conventional energy sources is not only a major factor behind climate change but also poses an adverse impact on human health. Undoubtedly, fossil fuels are major drivers of economic growth; however, their detrimental environmental impacts are of global scope, affecting the inhabitants of the whole world. In the literature, there is no comprehensive empirical evidence on the linkage between different energy sources and CO2 emissions in Russia which is among the top five CO2 emitting nations. Thus, this paper aims to quantify the relationships between oil consumption, natural gas consumption, coal consumption, and CO2 emission controlling economic growth in Russia. The findings indicate that CO2 emissions in Russia are cointegrated with oil, gas, coal, and economic growth. The long-run outcomes unfold that Russian economic growth is not directly harmful to environmental quality; however, the consumption of oil, gas, and coal upsurge the level of CO2 emissions. In addition, we conducted Granger causality tests for causal interaction analysis. The findings on the Russian data confirm the existence of both long and short-term causal connections with the country’s economic growth, disaggregated fossil fuel consumption, and CO2 emissions. In conclusion, we directed several policy recommendations to address the challenges and threats posed by energy-related emissions without adversely impacting economic growth in Russia. These policies could also be advantageous to other countries, especially those with close Russian links.

Environmental degradation stemming from the combustion of conventional energy sources is not only a major factor behind climate change but it also poses an adverse impact on human health. Undoubtedly, fossil fuels are major drivers of economic growth; however, their detrimental environmental impacts are of global concern. In the literature, there is no comprehensive empirical evidence on the linkage between the use of different energy sources and carbon dioxide emissions in the context of Russia, a nation that is ranked third in the list of the top carbon dioxide-emitting global countries. Hence, this paper aims to scrutinize the relationships between oil consumption, natural gas consumption, coal consumption, and carbon dioxide emissions controlling economic growth for Russia over the 1990–2016 period. The findings from the econometric analysis indicate that carbon dioxide emissions in Russia have long-run associations with economic growth and consumption of oil, gas, and coal. The long-run elasticity estimates reveal that economic growth is not directly harming Russia’s environmental quality. However, higher oil, gas, and coal consumption degrades environmental quality by boosting the level of carbon dioxide emissions in Russia. In addition, the results from the Granger causality analysis confirm the existence of both long and short-term causal connections among the variables of concern. In line with these findings, several policy recommendations to address the environmental challenges in Russia are put forward.

We report on the multi-state soliton generation in a chirped fiber Bragg grating (CFBG) based bidirectional mode-locked fiber laser. In particular, a $\theta $ -shape associate cavity is designed to introduce reverse dispersion distributions in counter-propagation directions through incorporating the bidirectional reflection of the CFBG into the lasing oscillator. With a relatively compact cavity configuration, the clockwise (CW) and counterclockwise (CCW) directions are managed into large anomalous and normal dispersion regimes, respectively. Consequently, conventional solitons (CSs) and dissipative solitons (DSs) can be emitted from the counter-propagation directions. To the best of our knowledge, it is the first report of CS/DS generation in a CFBG based bidirectional fiber laser. This investigation can contribute to research community of multiplexed ultrafast fiber lasers.

A simple all-fiber Solc filter (AFSF), which consists of two 45°-tilted fiber gratings (45°-TFGs) UV-inscribed in the polarization-maintaining fiber (PMF) and a series of PMF cavities, is proposed and demonstrated. The performance of the proposed filter has been theoretically simulated and experimentally verified. Both the simulated and experimental results show that the bandwidth of the filter could be tuned by the PMF sub-cavity length and the number of PMF cavities. And the free spectral range (FSR) only depends on the sub-cavity length. As a proof of that, the bandwidths of AFSF with different number of PMF sub-cavity (N=2, N=3, N=4) and the same PMF sub-cavity length of 30cm are 4 nm, 2.6nm, and 2nm, respectively. The FSRs of 3-stage AFSF with different PMF sub-cavity length (L=20 cm and L=40 cm) are 15.3 nm and 7.97 nm, respectively. Furthermore, we have also investigated the tunability of the AFSF by controlling the temperature of PMF cavity with a tuning sensitivity around 1.205 nm°/c. Compared with existing fiber-optic Solc filters, the AFSF with prominent advantages such as extremely simple and robust structure, thermal tunability in wavelength, and low cost will bring a bright future for applications in optical communication and sensing systems.

We present a passively mode-locked Erbium-doped fiber laser with tunable parameters including central wavelength, 3-dB bandwidth, and pulse duration. The mode-locking mechanism of the laser is realized by using single-walled carbon nanotubes (SWCNTs) polyvinyl alcohol composite film as a saturable absorber. The tunable operation is implemented via a fiber birefringence filter consisting of a polarization maintaining (PM) fiber and a Brewster fiber grating. The laser achieves a maximum spectral tuning range of 36 nm with 8-cm PM fiber. The maximum spectral width variation of 5.19 nm is acquired when the PM fiber is 12 cm. Simultaneously, the spectral widths of pulses at different central wavelengths are also adjustable. Furthermore, the total cavity length is 8.28 m, which is the shortest cavity length to obtain such wide tuning range in an Erbium-doped fiber laser based on SWCNTs.

In this paper, we report a high-resolution and precision acceleration sensor network with potential large sensing capacity, which is based on distributed Bragg reflector fiber lasers. To start with, a transducer based on a T-shaped cantilever beam and an adjustable bearing is theoretically designed and experimentally employed to achieve high sensitivity and wideband frequency response. Second, the beat frequency interrogation system that utilizes super-heterodyne receiver and digital orthogonal phase identifying technology is developed to improve the resolution of the sensors. In addition, assisted with the wavelength/time division multiplexing technology, hundreds of sensing units could be potentially multiplexed in the prototype system. A proof-of-concept sensing network with three acceleration sensor units is established for experimental validation. The sensor network demonstrates a sensitivity of 1.16064 GHz/g with a flat frequency response region from 20 to 200 Hz, corresponding to a noise equivalent acceleration of $\text{17.99}\,{\text{ng/}}\surd {\rm{Hz}}$ at 90 Hz. In particular, the measurement precision of the prototype system has been calibrated as high as 1.305 μ g. The proposed acceleration sensor network could benefit potential applications in smart unmanned platforms and seismic monitoring.

Experiments were conducted to simultaneously remove NO and SO2 from simulated exhaust gas by cyclic scrubbing and online supplementing pH-buffered NaClO2 solutions in a bench-scale reactor. The eff...

We report here Fe3O4 quantum dots embedded Fe 3O4@C electrode materials via a facile micelle-colloid template method for pushing forward the Li-ion battery technology. To improve uniform dispersion of Fe3O4 quantum dots (5–10 nm) and create macropores in the carbon matrix, ferric micelle colloids of CTA+X−1 Fe3+ with chelate adsorption of ferric colloids on CTAB micelle corona by electrostatic attraction has been developed in a resin layer. Thus, nanocrystalline Fe3O4 and graphitic carbon matrix are mutually formed from the same texture during the pyrolysis process, resulting in a tightly tangled carbon-Fe3O4 hybrids. The conformable embedment of Fe3O4 quantum dots in carbon matrix can effectively prevent its loss and alleviate local tension stress for volume variation during change-discharge process. The well structure-designed Fe3O4@C electrode materials deliver a stable capacity of 601 mA h g−1 at 2 A g−1 even after 800 cycles. This work provides a new strategy for design of transition-metal-oxide based electrode materials for long-life lithium-ion batteries.

Microstructured optical fiber based distributed pressure sensor is proposed and demonstrated for high resolution manometry (HRM), which adopts the hybrid wavelength and frequency division multiplexing architecture, and hyperelastic packaging. The microstructure acting as a sensing element is composed of two identical and closely spaced ultrashort fiber Bragg gratings with the reflectivity of only 1%. In theory, 243 microstructures can be multiplexed along one single fiber with an interval of 10 mm beneficial from the compact structure, hybrid encoding feature, and low insertion loss. Homogeneous elastic packaging is explored to protect the fiber and greatly enhance the lateral pressure sensitivity of the sensor. Moreover, a mechanical model is established through the finite element method to analyze the sensitizing effect of the packaging. A prototype system is built and experimentally demonstrated the distributed pressure measurement with the spatial resolution of 10 mm and the pressure sensitivity up to 2.2 Nm/mPa. Due to the advantage of high spatial resolution, high multiplexing capacity, and high pressure sensitivity, the proposed sensor is suitable for HRM in medical application.

Purpose Although the use of instant messaging (IM) at work has been studied in the IS field, its effective use and impact on performance have not been adequately addressed. The purpose of this paper is to explore the antecedents and consequences of the effective use of IM at work by adapting Burton-Jones and Grange’s theory of effective use. Design/methodology/approach The authors introduce “Comprehensive IM policy” as a facilitator of adaptation and learning actions to improve the effective use of IM, which will improve communication quality and productivity. The impact of IM competence on effective use is also discussed. Based on a survey of 215 managers, this study applies the partial least square technique to test the research model. Findings The results indicate that comprehensive IM policy encourages adaptation and learning actions, which improve the effective use of IM and thereafter improve communication quality and productivity. Meanwhile, IM competence has a substitutive interaction effect with IM reconfiguration and self-learning on effective use. Originality/value The results refine the general theory of effective use and provide managers with an approach to leverage IM use at work for performance gains.

Via using an L-band optimized in-fiber polarizing grating device, a GHz L-band femtosecond passively harmonic mode-locked Er-doped fiber laser based on nonlinear polarization rotation is first demonstrated. In total, 4.22 GHz pulses with the duration of 810 fs and super-mode suppression ratio (SMSR) of 32 dB are obtained under the pump power of 712 mW corresponding to 215th harmonic order. The central wavelength of 4.22 GHz pulses is 1581.7 nm with 10.1 nm 3 dB bandwidth. Furthermore, under this fixed pump power, higher harmonic orders can also be attained by rotating the polarization controllers properly. The highest repetition rate we obtained is 7.41 GHz with the SMSR of 20.7 dB.

A data processing method for correcting the frequency sweeping nonlinearity of a tunable laser in an optical frequency domain reflectometry system is presented. The proposed method calibrates the positions of all the data points by the time-scale factor determined by the zero-crossing points of the auxiliary interferometer. Then, the signal of the main interferometer is interpolated with the calibrated results. In experiments, a spatial resolution of 0.17 mm over a measurable range of 155 m has been obtained even when the optical path difference of the auxiliary interferometer is shorter than that of the main interferometer. This method could resolve the problem that measurable range is limited by the length of delay fiber in the auxiliary interferometer and significantly decrease the requirement of sampling rate.

In order to suppress the noise of the coherent fiber distributed acoustic sensing (DAS) system, the spatio-temporal joint oversampling-downsampling technique is proposed. The spatial oversampling is used for artificially dense sampling, whose spacing is far less than the target spatial resolution. Then the spatial downsampling performed by the average of multiple differential sub-vectors is utilized to reduce the influence of noise vectors, which could completely eliminate the interfere fading without increasing any system complexity and introducing any crosstalk. Meanwhile, the temporal oversampling-downsampling is analyzed from the perspective of theory and simulation, demonstrating that the noise floor will decrease with the increase of downsampling coefficient. The temporal oversampling is carried out to expand the noise distribution bandwidth and ensure the correct quantization of the noise frequency. Then the temporal downsampling of differential phase reconstruction is utilized to recover the target bandwidth and reduce the out-of-band noise. The experimental results prove that the noise floor is inversely correlated with the spatiotemporal downsampling factors. The strain resolution of the DAS system with the proposed scheme can reach 2.58pε/√Hz@100Hz-500Hz and 9.47pε/√Hz@10Hz under the condition of DC-500Hz target bandwidth, as well as the probability of the large-noise sensing channels is greatly reduced from 44.32% to 0%. Moreover, the demodulated SNR of dynamic signal is improved by 20.8dB compared with the traditional method. Without any crosstalk, the noise floor is optimized 8dB lower than the averaging technique. Based on the proposed method, the high-performance DAS system has significant competitiveness in the applications with the demand of high-precision and high-sensitivity, such as passive-source seismic imaging and VSP exploration.

A multi-channel parallel ultrasound detection system based on a photothermal tunable fiber optic sensor array is proposed. The resonant wavelength of the ultrasound sensor has a quadratic relationship with the power of a 980-nm heating laser. The maximum tuning range is larger than 15 nm. Through photothermal tuning, the inconsistent operating wavelengths of the Fabry–Perot (FP) sensor array can be solved, and then a multiplexing capacity of up to 53 can be theoretically realized, which could greatly reduce the time required for data acquisition. Then, a fixed wavelength laser with ultra-narrow linewidth is used to interrogate the sensor array. The interrogation system demonstrates a noise equivalent pressure (NEP) as low as 0.12 kPa, which is 5.5-times lower than the commercial hydrophone. Furthermore, a prototype of a four-channel ultrasound detection system is built to demonstrate the parallel detection capability. Compared with the independent detection, the SNR of parallel detection does not deteriorate, proving that the parallel detection system and the sensor array own very low cross talk characteristics. The parallel detection technique paves a way for real-time photoacoustic/ultrasound imaging.

A wavelength-tunable noise-like pulse (NLP) erbium-doped fiber laser incorporating PbS quantum dot (QD) polystyrene (PS) composite film as a saturable absorber (SA) is experimentally demonstrated. The wavelength tuning is implemented via a Lyot filter consisting of a segment of polarization-maintaining fiber (PMF) and a 45° tilted fiber grating. By adjusting the polarization state of the ring cavity, the laser can deliver NLP with a continuous wavelength-tunable range from 1550.21 to 1560.64 nm. During continuous wavelength tuning, the output power varies between a range of 30.88–48.8 mW. Worthwhile noting is that the output power of 48.8 mW is the reported highest output power for wavelength-tunable NLP operation in an erbium-doped fiber laser using composite film as a saturable absorber.

Liquid level sensor with large sensing range and high-resolution is essential for the application of industry monitoring. In this work, a distributed optical fiber liquid level sensor is proposed and demonstrated based on phase-sensitive optical time domain reflectometry (φ-OTDR). In the basic of the thermal optic effect, the temperature change will induce the fluctuation of the effective refractive indexes of the fiber core, as well as the fluctuation of the optical path of the light transmitting in the fiber. Therefore, the φ-OTDR can detect the liquid level with a large measurement range by interrogating the phase information along the fiber due to the temperature difference between the liquid and air. Further, the scattering enhanced optical fiber (SEOF) is used as the sensing fiber to improve the signal to noise ratio (SNR) of the phase signal. Moreover, a high sensitivity liquid level sensing head by wrapping the SEOF on a heat conductive cylinder is designed and optimized to improve the sensing resolution. In the experiment, the proposed distributed liquid level sensor presents a high sensitivity of 73.4 rad/mm, corresponding to a competitive liquid level resolution of 142μm based on the noise floor of 10.4 rad within 160 s. The field test validates a large sensing range of 20 cm which is limited by the cylinder length, while a potential sensing range could reach 320 m with the sensing fiber of 40 km, proving a dynamic range of 127.1 dB. The proposed liquid level sensor with large dynamic range and high sensing resolution can benefit potential application in smart industry platforms and biomedicine monitoring.

We have witnessed an increasing number of mergers and acquisitions (M&A) between two-sided digital platforms, generally involving a unidirectional resource transfer policy from the acquired to the acquiring platform. This scenario may incur an asymmetric network effect that has not been explored in the extant literature. Using a unique dataset from Dianping and Meituan, two digital platforms similar to Yelp, we explore whether and how the unidirectional data integration policy causes a positive network effect, as reflected by the increments of user engagement on each side of the M&A. We measure user engagement in two dimensions, namely, quantity measures (e.g., number of total reviews) and quality measures (e.g., number of reviews with pictures and length of review). The results show that the policy enhances both measures of user engagement for the acquired and acquiring platforms but that its effects on user engagement on the acquiring platform are larger than those on the acquired platform. We propose three mechanisms: the network size effect, self-image management effect, and social learning effect to explain the possible impacts of platform integration on user engagement, and we conduct single-group interrupted time-series analyses to test the effects. We further conduct three sets of supplementary analyses. We find that, first, the policy not only expands its user base but also boosts the contribution enthusiasm of current users. Second, we clarify how the benefits of platform integration are shaped by merchant features such as per capita consumption and whether a merchant has chain stores. Third, we focus on the multi-homing phenomenon of merchants and find that multi-homing merchants benefit more from platform integration. The findings of this study deepen our understanding of the connections between unidirectional resource transfer and the asymmetric network effect in the context of the integration of two digital platforms.

We review the wavelength selective switch (WSS) for ultra-broadband transmission and spatial division multiplexing. We also discuss and present experimental results of WSS components with high spectral resolution and compactness.

A microfiber probe-based wearable sensor is proposed and demonstrated. Based on the flexibility and high sensitivity of microfiber, the sensor can measure the joint motion and the pulse wave for health monitoring.

In the past decades, space missions to small bodies (Galileo, OSIRIS‐REx, Hayabusa, Hayabusa2, Chang'e 2, Rosetta, etc.) have enriched us greatly with voluminous new knowledge on our solar system. In situ observations by these missions have revealed the extreme complexity and remarkable diversity of the spatial environment around their target asteroids. A study on the motion of objects in such complex environments is of great importance for understanding the evolution history of surface/subsurface materials on the asteroids. Establishing a reasonable dynamic model is obviously a crucial step. This paper proposes a method for tracking the motion of an object near the surface of an arbitrary asteroid. This method combines the irregular shape, an unlimited rotational state and asymmetric gravitational field, which are three key factors that dominate the complex movement of an object on and off the asteroid's surface. The gravitational attraction and potential are computed using the polyhedral method with corrections for the possible singularities. The asteroid's surface is then approximated using a continuous and differentiable surface, and the parametric representation forms of the body are derived based on polynomial series. An event‐driven scheme is designed, so that the orbital motion and surface motion are processed separately by checking the triggering events. The algorithm was implemented using C++. Benchmarking tests are organized on a local cluster, showing a satisfactory performance in both accuracy and efficiency. This method was further applied to improve the control accuracy of the landing spot of an asteroid surface lander.

A spatio-temporal oversampling-downsampling fiber DAS system is proposed and demonstrated. Without increasing the complexity and cost of the system, the demodulated SNR can be increased by 15dB, and the fading noise can be completely eliminated.

A tunnel steel loop reinforcement invalidation monitoring technology based on optical fiber distributed acoustic sensing (DAS) is proposed and demonstrated. Assisted with machine learning, the identification accuracy rate of invalid degree is up to 97.8%.

E-healthcare platforms start to integrate medical services across online and offline channels, where providers can perform online consultations, schedule patients’ offline visits, synchronize relevant medical records, and finally, answer online inquiries regarding follow-up and recovery anytime and anywhere within one operations management function (i.e., online-offline service integration). In this study, we seek to quantify the effects of online-offline service integration on the e-healthcare providers’ demand and reputational outcomes, noting that it is not altogether clear how the service integration function will affect the providers who adopt such a function in e-healthcare platforms. Leveraging a quasi-natural experiment on an e-healthcare platform, we conducted difference-in-differences analyses in tandem with a variety of matching strategies, including propensity score matching and look-ahead propensity score matching. Further, we explored the moderating roles of provider-specific characteristics. Our results reveal a set of robust and interesting findings: i) e-healthcare providers, on average, experience increases in online demand and decreases in offline demand post online-offline service integration; ii) the service integration function also improves the professional reputation of participating providers; iii) the impact of channel integration on the outcomes are weaker for providers with lower (vs. higher) professional titles; and iv) the providers who specialize in treating chronic (vs. acute) diseases experience greater increases in online demand and reputational outcomes, yet insignificant changes in offline demand. This work contributes to related prior literatures on healthcare operations management, e-healthcare, and online-offline channel integration, offering design implications for the service operations of e-healthcare platforms.

A method for disturbance positioning in noisy environment is introduced. By the partitioning algorithm and a well-trained B-P neural network classifier, an average locating accuracy of 95% was demonstrated in the field test.

We design a lightweight fiber optical hydrophone cable based on scattering enhanced fiber. Combined with distributed acoustic sensing technology, it realizes fully distributed hydroacoustic sensing with an ultra-high sensitivity up to −127dB (re rad/μPa).

Background. Patients with stable chronic obstructive pulmonary disease (COPD) have been observed to benefit from tiotropium bromide. However, there are few studies of tiotropium bromide on sputum and sputum viscosity. To evaluate the effect of tiotropium bromide on mucus hypersecretion, a randomized, double-blind controlled trial was performed. Methods. 120 cases of patients with pulmonary function grade II were divided into two groups, which include the treatment group given tiotropium bromide powder inhalation (18 μg, inhalation, QD) and the control group given formoterol fumarate powder inhalation (12 μg, inhalation, BID) plus ambroxol hydrochloride tablets (60 mg, oral, TID). After 3 months of treatment, the pulmonary function and α1-acid glycoprotein (α1-AGP) in sputum were detected, and the changes of glycoprotein and Ca2+ content were evaluated by Miller classification. Results. Three patients (2 cases in the treatment group and 1 case in the control group) were dropped due to loss of follow-up, and 117 cases of patients were enrolled in this study. After 3 months of treatment, the sputum character score, α1-acid glycoprotein, Ca2+ content, and lung function of the two groups were significantly improved; group comparison analyses revealed that there was no significant difference in the content of α1-AGP, Ca2+ in sputum, and lung function between the two groups ( P > 0.05 ), but the improvement of sputum properties was significant ( P < 0.05 ), and the treatment group was better than the control group ( t = − 2.77 ; P = 0.007 ). Conclusions. Inhaled tiotropium bromide can effectively inhibit the mucus hypersecretion in stable COPD patients, improve the sputum properties and lung function of patients, and improve the quality of life of patients.

A dual-stage-recognition network combined with the fiber optic DAS system is designed to realize a high accuracy intrusion pattern recognition in practical complicated environments. Field test is performed to verify an average recognition accuracy rate of 97.04% for five typical events including animals, human and mechanical movement.

An intrusion recognition method based on the combination of one-dimensional convolution neural network (1-D CNN) and DenseNet network is proposed and demonstrated. Assisted with fiber optic distributed acoustic sensing (DAS) system, the average recognition accuracy of 98.4% for six types of events and 2ms processing time were achieved in the field test.